1. |
- Axehill, Daniel, 1978-
(författare)
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Applications of Integer Quadratic Programming in Control and Communication
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main topic of this thesis is integer quadratic programming with applications to problems arising in the areas of automatic control and communication. One of the most widespread modern control principles is the discrete-time method Model Predictive Control (MPC). The main advantage with MPC, compared to most other control principles, is that constraints on control signals and states can easily be handled. In each time step, MPC requires the solution of a Quadratic Programming (QP) problem. To be able to use MPC for large systems, and at high sampling rates, optimization routines tailored for MPC are used. In recent years, the range of application of MPC has been extended from constrained linear systems to so-called hybrid systems. Hybrid systems are systems where continuous dynamics interact with logic. When this extension is made, binary variables are introduced in the problem. As a consequence, the QP problem has to be replaced by a far more challenging Mixed Integer Quadratic Programming (MIQP) problem. Generally, for this type of optimization problems, the computational complexity is exponential in the number of binary optimization variables. In modern communication systems, multiple users share a so-called multi-access channel, where the information sent by different users is separated by using almost orthogonal codes. Since the codes are not completely orthogonal, the decoded information at the receiver is slightly correlated between different users. Further, noise is added during the transmission. To estimate the information originally sent, a maximum likelihood problem involving binary variables is solved. The process of simultaneously estimating the information sent by multiple users is called multiuser detection. In this thesis, the problem to efficiently solve MIQP problems originating from MPC is addressed. Two different algorithms are presented. First, a polynomial complexity preprocessing algorithm for binary quadratic programming problems is presented. By using the algorithm, some, or all, binary variables can be computed efficiently already in the preprocessing phase. In simulations, the algorithm is applied to unconstrained MPC problems with a mixture of real and binary control signals. It has also been applied to the multiuser detection problem, where simulations have shown that the bit error rate can be significantly reduced by using the proposed algorithm as compared to using common suboptimal algorithms. Second, an MIQP algorithm tailored for MPC is presented. The algorithm uses a branch and bound method where the relaxed node problems are solved by a dual active set QP algorithm. In this QP algorithm, the KKT-systems are solved using Riccati recursions in order to decrease the computational complexity. Simulation results show that both the QP solver and the MIQP solver proposed have lower computational complexity than corresponding generic solvers.
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2. |
- Friedrich, Jana, et al.
(författare)
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Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11, s. 1215-1259
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX (“In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies”, www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of watercolumn oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.
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3. |
- Galis, Vasilis, 1978-, et al.
(författare)
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Partisan Scholarship in Technoscientific Controversies : Reflections on Research Experience
- 2012
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Ingår i: Science as Culture. - London : Routledge. - 0950-5431 .- 1470-1189. ; 21:3, s. 335-364
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Tidskriftsartikel (refereegranskat)abstract
- Several academic traditions have addressed epistemological objectivity and/or partisanship in the study of technoscientific controversies. On the one hand, positivist andrelativist scholars agree that the political commitments of the social researcher should notimpinge on scientific enquiry, while on the other hand, feminist and Marxist scholars notonly take stands in diverse technoscientific debates, but even claim their agendas to bemore credible than those of orthodox scientists. Such perspectives stress that all researchis partisan in one way or another because it involves questions of who controls,manipulates, and establishes decisions, facts, and knowledge. With this in mind, it ispossible to identify different forms of partisan research including capture byparticipants, de facto and overt partisanship, and mercenary scholarship. These differentforms of partisan scholarship are characterised by differences in the motives underlyingepistemological choices of research topic and method, personal commitments to thefields studied, use of research findings in controversies, and positioning of results inwider debates. Two examples help to illustrate partisan scholarship: first, a study of newtechnologies for managing climate change (carbon dioxide capture and storage); andsecond, the construction of the new underground metro system in Athens and itsaccommodation of accessibility standards. Both cases entail partisan positions and raisesimilar concerns about the orthodox epistemological assumptions underpinningsociotechnical systems, especially when it comes to technoscientific controversies.Supporting STS partisan scholarship, therefore, enables greater social and democraticengagement with technoscientific development.
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4. |
- Giang, Kok Wai, 1984, et al.
(författare)
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The risk of dementia after coronary artery bypass grafting in relation to age and sex
- 2021
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Ingår i: Alzheimers & Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 17:6, s. 1042-1050
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Tidskriftsartikel (refereegranskat)abstract
- Introduction We examined the long-term risk of dementia after coronary artery bypass grafting (CABG) in relation to age and sex. Methods All CABG patients in Sweden 1992-2015 (n = 111,335), and matched controls (n = 222,396) were included in a population-based study. Adjusted hazard ratios (aHR) for all-cause dementia, vascular dementia, and Alzheimer's disease were calculated. Results There was no difference in the risk for all-cause dementia between CABG patients and control subjects (aHR 0.98 [95% confidence interval 0.95 to 1.02]). CABG patients <65 years and 65 to 74 years had higher risk (aHR 1.29 [1.17-1.42] and 1.08 [1.02-1.13], respectively), and patients >= 75 years had lower risk (aHR 0.76 [0.71-0.81]). The highest risk was observed in women <65 years (aHR 1.64 [1.31-2.05]). Discussion Overall, the long-term risk for all-cause dementia does not differ between CABG patients and the general population. Younger patients have a higher risk, while older patients have a lower risk, compared to controls.
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5. |
- Meier, Markus, et al.
(författare)
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Comparing reconstructed past variations and future projections of the Baltic sea ecosystem first results from multi model ensemble simulations
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:3, s. 034005-
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Tidskriftsartikel (refereegranskat)abstract
- Multi-model ensemble simulations for the marine biogeochemistry and food web of the Baltic Sea were performed for the period 1850-2098, and projected changes in the future climate were compared with the past climate environment. For the past period 1850-2006, atmospheric, hydrological and nutrient forcings were reconstructed, based on historical measurements. For the future period 1961-2098, scenario simulations were driven by regionalized global general circulation model (GCM) data and forced by various future greenhouse gas emission and air-and riverborne nutrient load scenarios (ranging from a pessimistic 'business-as-usual' to the most optimistic case). To estimate uncertainties, different models for the various parts of the Earth system were applied. Assuming the IPCC greenhouse gas emission scenarios A1B or A2, we found that water temperatures at the end of this century may be higher and salinities and oxygen concentrations may be lower than ever measured since 1850. There is also a tendency of increased eutrophication in the future, depending on the nutrient load scenario. Although cod biomass is mainly controlled by fishing mortality, climate change together with eutrophication may result in a biomass decline during the latter part of this century, even when combined with lower fishing pressure. Despite considerable shortcomings of state-of-the-art models, this study suggests that the future Baltic Sea ecosystem may unprecedentedly change compared to the past 150 yr. As stakeholders today pay only little attention to adaptation and mitigation strategies, more information is needed to raise public awareness of the possible impacts of climate change on marine ecosystems.
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6. |
- Nielsen, Susanne, 1969, et al.
(författare)
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Socioeconomic Factors, Secondary Prevention Medication, and Long-Term Survival After Coronary Artery Bypass Grafting: A Population-Based Cohort Study From the SWEDEHEART Registry.
- 2020
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Ingår i: Journal of the American Heart Association. - 2047-9980. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- Background Low income and short education have been found to be independently associated with inferior survival after coronary artery bypass grafting (CABG), whereas the use of secondary prevention medications is associated with improved survival. We investigated whether underusage of secondary prevention medications contributes to the inferior long-term survival in CABG patients with a low income and short education. Methods and Results Patients who underwent CABG in Sweden between 2006 to 2015 and survived at least 6months after discharge (n=28448) were included in a population-based cohort study. Individual patient data from 5 national registries, including the SWEDEHEART (Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) registry, covering dispensing of secondary prevention medications (statins, platelet inhibitors, β-blockers, and RAAS inhibitors), socioeconomic factors, patient characteristics, comorbidity, and long-term mortaity were merged. All-cause mortality risk was estimated using multivariable Cox regression models adjusted for patient characteristics, baseline comorbidities, time-updated secondary prevention medications, and socioeconomic status. Long-term mortality was higher in patients with a low income and short education. Statins and platelet inhibitors were dispensed less often to patients with a low income, both at baseline and after 8years. The decline in dispensing over time was steeper for low-income patients. Short education was not associated with reduced dispensing of any secondary prevention medication. Use of statins (adjusted hazard ratio=0.57 [95% CI, 0.53-0.61]), RAAS inhibitors (adjusted hazard ratio=0.78 [0.73-0.84]), and platelet inhibitors (adjusted hazard ratio=0.74 [0.68-0.80]) were associated with reduced long-term mortality irrespective of socioeconomic status. Conclusions Secondary prevention medications are dispensed less often after CABG to patients with low income. Underusage of secondary prevention medications after CABG is associated with increased mortality risk independently of income and extent of education.
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7. |
- Parvini Ahmadi, Shervin, 1989-
(författare)
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Distributed Optimization for Control and Estimation
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Adopting centralized optimization approaches in order to solve optimization problem arising from analyzing large-scale systems, requires a powerful computational unit. Such units, however, do not always exist. In addition, it is not always possible to form the optimization problem in a centralized manner due to structural constraints or privacy requirements. A possible solution in these cases is to use distributed optimization approaches. Many large-scale systems have inherent structures which can be exploited to develop scalable optimization approaches. In this thesis, chordal graph properties are used in order to design tailored distributed optimization approaches for applications in control and estimation, and especially for model predictive control and localization problems. The first contribution concerns a distributed primal-dual interior-point algorithm for which it is investigated how parallelism can be exploited. In particular, it is shown how the computations of the algorithm can be distributed on different processors so that they can be run in parallel. As a result, the algorithm execution time is accelerated compared to the case where the algorithm is run on a single processor. Simulation studies on linear model predictive control and robust model predictive control confirm the efficiency of the framework. The second contribution is to devise a tailored distributed algorithm for nonlinear least squares with application to a sensor network location problem. It relies on the Levenberg-Marquardt algorithm, in which the computations are distributed using message passing over the computational graph of the problem, which is obtained from what is known as the clique tree of the problem. The results indicate that the algorithm provides not only a good localization accuracy, but also it requires fewer iterations and communications between computational agents in order to converge compared to known first-order methods. The third contribution is a study of extending the message passing idea in order to design tailored distributed algorithm for general non-convex problems. The framework relies on an augmented Lagrangian algorithm in which a primal-dual interior-point method is used for the inner iteration. Application of the framework for general model predictive control of systems with several interconnected sub-systems is extensively investigated. The performance of the framework is then compared with distributed methods based on the alternating direction method of multipliers, where the superiority of the framework is illustrated.
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8. |
- Scaini, Anna, et al.
(författare)
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Pathways from research to sustainable development: Insights from ten research projects in sustainability and resilience
- 2024
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Ingår i: AMBIO. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 53
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Tidskriftsartikel (refereegranskat)abstract
- Drawing on collective experience from ten collaborative research projects focused on the Global South, we identify three major challenges that impede the translation of research on sustainability and resilience into better-informed choices by individuals and policy-makers that in turn can support transformation to a sustainable future. The three challenges comprise: (i) converting knowledge produced during research projects into successful knowledge application; (ii) scaling up knowledge in time when research projects are short-term and potential impacts are long-term; and (iii) scaling up knowledge across space, from local research sites to larger-scale or even global impact. Some potential pathways for funding agencies to overcome these challenges include providing targeted prolonged funding for dissemination and outreach, and facilitating collaboration and coordination across different sites, research teams, and partner organizations. By systematically documenting these challenges, we hope to pave the way for further innovations in the research cycle.
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9. |
- Ternström, Lisa, 1972, et al.
(författare)
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Plasma activity of individual coagulation factors, hemodilution and blood loss after cardiac surgery: a prospective observational study.
- 2010
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Ingår i: Thrombosis research. - : Elsevier BV. - 1879-2472 .- 0049-3848. ; 126:2
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Hemodilution and consumption of coagulation factors during cardiopulmonary bypass has been suggested to contribute to bleeding complications after cardiac surgery. The aim was to describe the activity of individual coagulation factors after CABG in relation to hemodilution and postoperative bleeding. MATERIALS AND METHODS: Plasma concentrations of fibrinogen and plasma activity of FII, FV, FVII, FVIII, FIX, FX, FXI and FXIII adjusted for hemodilution were analysed in 57 CABG patients before, and 2h and 24h after surgery. Postoperative bleeding was registered and correlations to coagulation factor activity were calculated. RESULTS: Adjusted plasma concentration of fibrinogen (-14+/-6%), and plasma activity of FII (-9+/-6%), FV (-13+/-8%), FX (-13+/-7%) and FXIII (-9+/-14%) were reduced two hours after surgery compared to baseline (all p<0.001). FVII (+3+/-12%, p=0.34) and FXI (+1+/-19%, p=0.50) were unchanged, while FVIII (+23+/-44%, p=0.006) and FIX (+23+/-17%, p<0.001) increased. Twenty-four hours after surgery fibrinogen (+45+/-27%), FVIII (+93+/-66%) and FIX (+33+/-26%) were all increased (all p<0.001), while FVII (-37+/-14%, p<0.001), FXI (-4+/-18%, p=0.02) and FXIII (-6+/-15%, p=0.004) were decreased. Median postoperative blood loss was 380 ml/12h. There were significant inverse correlations between postoperative blood loss and fibrinogen concentration 2h after surgery (r=-0.33, p=0.019) and between postoperative blood loss and pre- and postoperative FXIII activity (r=-0.34, p=0.009 and r=-0.41, p=0.003, respectively), but not between blood loss and any of the other factors. CONCLUSIONS: There is a marked dissociation in plasma activity of individual coagulation factors after CABG. Plasma concentration of fibrinogen and factor XIII activity correlates inversely to postoperative blood loss after CABG.
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11. |
- Ahlqvist, E., et al.
(författare)
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Novel subgroups of adult-onset diabetes and their association with outcomes: a data-driven cluster analysis of six variables
- 2018
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Ingår i: Lancet Diabetes & Endocrinology. - : Elsevier BV. - 2213-8587. ; 6:5, s. 361-369
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Tidskriftsartikel (refereegranskat)abstract
- Background Diabetes is presently classified into two main forms, type 1 and type 2 diabetes, but type 2 diabetes in particular is highly heterogeneous. A refined classification could provide a powerful tool to individualise treatment regimens and identify individuals with increased risk of complications at diagnosis. Methods We did data-driven cluster analysis (k-means and hierarchical clustering) in patients with newly diagnosed diabetes (n=8980) from the Swedish All New Diabetics in Scania cohort. Clusters were based on six variables (glutamate decarboxylase antibodies, age at diagnosis, BMI, HbA(1c), and homoeostatic model assessment 2 estimates of beta-cell function and insulin resistance), and were related to prospective data from patient records on development of complications and prescription of medication. Replication was done in three independent cohorts: the Scania Diabetes Registry (n=1466), All New Diabetics in Uppsala (n=844), and Diabetes Registry Vaasa (n=3485). Cox regression and logistic regression were used to compare time to medication, time to reaching the treatment goal, and risk of diabetic complications and genetic associations. Findings We identified five replicable clusters of patients with diabetes, which had significantly different patient characteristics and risk of diabetic complications. In particular, individuals in cluster 3 (most resistant to insulin) had significantly higher risk of diabetic kidney disease than individuals in clusters 4 and 5, but had been prescribed similar diabetes treatment. Cluster 2 (insulin deficient) had the highest risk of retinopathy. In support of the clustering, genetic associations in the clusters differed from those seen in traditional type 2 diabetes. Interpretation We stratified patients into five subgroups with differing disease progression and risk of diabetic complications. This new substratification might eventually help to tailor and target early treatment to patients who would benefit most, thereby representing a first step towards precision medicine in diabetes.
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12. |
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13. |
- Andersson, Malin E, 1978, et al.
(författare)
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Kinesin gene variability may affect tau phosphorylation in early Alzheimer's disease.
- 2007
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Ingår i: International journal of molecular medicine. - 1107-3756 .- 1791-244X. ; 20:2, s. 233-9
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Tidskriftsartikel (refereegranskat)abstract
- Kinesin is a microtubule-associated motor protein that transports Alzheimer-associated amyloid precursor protein (APP) in neurons. In animal models, impaired kinesin-mediated APP transport seems to enhance formation of the neurotoxic 42 amino acid fragment of beta-amyloid (A beta 42). In man, one study suggests that a polymorphism (rs8702, 56,836G>C) in the kinesin light chain 1 gene (KNS2) may affect the risk of Alzheimer's disease (AD). To further assess KNS2 as a susceptibility gene for AD we analyzed 802 patients with sporadic AD and 286 controls, 134 longitudinally followed patients with mild cognitive impairment (MCI) and 39 cognitively stable controls for the rs8702 polymorphism. The rs8702 polymorphism did not influence risk of AD (p=0.46). However, rs8702 interacted with APOE epsilon 4 carrier status in AD (p=0.006) and influenced cerebrospinal fluid levels of hyperphosphorylated tau in MCI patients who converted to AD during follow-up (p=0.018). These findings support earlier indications that genetic variability in the KNS2 gene may play a role during early stages of AD pathogenesis.
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14. |
- Anshelm, Jonas, 1960-, et al.
(författare)
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Battling Promethean dreams and Trojan horses : Revealing the critical discourses of geoengineering
- 2014
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Ingår i: Energy Research & Social Science. - : Elsevier. - 2214-6296 .- 2214-6326. ; 2, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- Geoengineering could counteract climate change by either altering the earth's global energy balance by reflecting sunlight or removing CO2 from the atmosphere. Geoengineering evokes various ethical and political challenges that are increasingly reflected in public debate and deliberation. Via a qualitative textual analysis of 1500 articles, we investigate discursive claims critical of geoengineering, considering what subjects are the most controversial, and what worldviews, values, and problematizations are shared by the actors subscribing to this discourse. We argue that the controversy about geoengineering differs, discursively, from other techno-political conflicts. Geoengineering proponents are described as reluctantly favouring research and deployment and displaying an unusual self-reflexivity, as they are well aware of and seriously consider all the technology's risks. Our analysis demonstrates that the discourse critical of geoengineering differs from and questions the dominant pro-geoengineering discourse in several profound ways with lasting implications for energy scholarship and analysis.
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15. |
- Anshelm, Jonas, 1960-, et al.
(författare)
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Climate change and the convergence between ENGOs and buisness: on the loss of utopian energies
- 2011
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Ingår i: Environmental Values. - : White Horse Press. - 0963-2719 .- 1752-7015. ; 20:1, s. 75-94
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Tidskriftsartikel (refereegranskat)abstract
- The conflicts permeating the environmental debate since the 1960s have mainly involved two actors: multinational companies and international environmental organizations (ENGOs). Today, there are signs that the antagonism is ending with regards to co-operation and strategy. We argue that this convergence is no longer limited to specific joint projects, but is also prevalent at the idea and policy levels. Both actors have begun describing problems in similar terms, articulating the same goals and recommending the same solutions. Such convergence offers advantages in efforts to counteract climate change but also some problems: declining citizen trust in ENGOs, risk of intellectually impoverished environmental and energy debates, and loss of alternate visions and values.
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16. |
- Arnström, Daniel, 1994-
(författare)
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On Complexity Certification of Active-Set QP Methods with Applications to Linear MPC
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In model predictive control (MPC) an optimization problem has to be solved at each time step, which in real-time applications makes it important to solve these efficiently and to have good upper bounds on worst-case solution time. Often for linear MPC problems, the optimization problem in question is a quadratic program (QP) that depends on parameters such as system states and reference signals. A popular class of methods for solving such QPs is active-set methods, where a sequence of linear systems of equations is solved. The primary contribution of this thesis is a method which determines which sequence of subproblems a popular class of such active-set algorithms need to solve, for every possible QP instance that might arise from a given linear MPC problem (i.e, for every possible state and reference signal). By knowing these sequences, worst-case bounds on how many iterations, floating-point operations and, ultimately, the maximum solution time, these active-set algorithms require to compute a solution can be determined, which is of importance when, e.g, linear MPC is used in safety-critical applications. After establishing this complexity certification method, its applicability is extended by showing how it can be used indirectly to certify the complexity of another, efficient, type of active-set QP algorithm which reformulates the QP as a nonnegative least-squares method. Finally, the proposed complexity certification method is extended further to situations when enhancements to the active-set algorithms are used, namely, when they are terminated early (to save computations) and when outer proximal-point iterations are performed (to improve numerical stability).
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17. |
- Arnström, Daniel, 1994-
(författare)
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Real-Time Certified MPC : Reliable Active-Set QP Solvers
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Model Predictive Control (MPC), optimization problems are solved recurrently to produce control actions. When MPC is used in real time to control safety-critical systems, it is important to solve these optimization problems with guarantees on the worst-case execution time. In this thesis, we take aim at such worst-case guarantees through two complementary approaches:(i) By developing methods that determine exact worst-case bounds on the computational complexity and execution time for deployed optimization solvers.(ii) By developing efficient optimization solvers that are tailored for the given application and hardware at hand.We focus on linear MPC, which means that the optimization problems in question are quadratic programs (QPs) that depend on parameters such as system states and reference signals. For solving such QPs, we consider active-set methods: a popular class of optimization algorithms used in real-time applications.The first part of the thesis concerns complexity certification of well-established active-set methods. First, we propose a certification framework that determines the sequence of subproblems that a class of active-set algorithms needs to solve, for every possible QP instance that might arise from a given linear MPC problem (i.e., for every possible state and reference signal). By knowing these sequences, one can exactly bound the number of iterations and/or floating-point operations that are required to compute a solution. In a second contribution, we use this framework to determine the exact worst-case execution time (WCET) for linear MPC. This requires factors such as hardware and software implementation/compilation to be accounted for in the analysis. The framework is further extended in a third contribution by accounting for internal numerical errors in the solver that is certified. In a similar vein, a fourth contribution extends the framework to handle proximal-point iterations, which can be used to improve the numerical stability of QP solvers, furthering their reliability.The second part of the thesis concerns efficient solvers for real-time MPC. We propose an efficient active-set solver that is contained in the above-mentioned complexity-certification framework. In addition to being real-time certifiable, we show that the solver is efficient, simple to implement, can easily be warm-started, and is numerically stable, all of which are important properties for a solver that is used in real-time MPC applications. As a final contribution, we use this solver to exemplify how the proposed complexity-certification framework developed in the first part can be used to tailor active-set solvers for a given linear MPC application. Specifically, we do this by constructing and certifying parameter-varying initializations of the solver.
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18. |
- Assenza, Giacomo, et al.
(författare)
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White Paper on Industry Experiences in Critical Information Infrastructure Security : A Special Session at CRITIS 2019
- 2020
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Ingår i: Critical Information Infrastructures Security14th International Conference, CRITIS 2019. - Cham : Springer. - 9783030376697 - 9783030376703 ; , s. 197-207
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Bokkapitel (refereegranskat)abstract
- The security of critical infrastructures is of paramount importance nowadays due to the growing complexity of components and applications. This paper collects the contributions to the industry dissemination session within the 14th International Conference on Critical Information Infrastructures Security (CRITIS 2019). As such, it provides an overview of recent practical experience reports in the field of critical infrastructure protection (CIP), involving major industry players. The set of cases reported in this paper includes the usage of serious gaming for training infrastructure operators, integrated safety and security management in the chemical/process industry, risks related to the cyber-economy for energy suppliers, smart troubleshooting in the Internet of Things (IoT), as well as intrusion detection in power distribution Supervisory Control And Data Acquisition (SCADA). The session has been organized to stimulate an open scientific discussion about industry challenges, open issues and future opportunities in CIP research.
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19. |
- Axehill, Daniel, 1978-
(författare)
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Integer Quadratic Programming for Control and Communication
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main topic of this thesis is integer quadratic programming with applications to problems arising in the areas of automatic control and communication. One of the most widespread modern control methods is Model Predictive Control (MPC). In each sampling time, MPC requires the solution of a Quadratic Programming (QP) problem. To be able to use MPC for large systems, and at high sampling rates, optimization routines tailored for MPC are used. In recent years, the range of application of MPC has been extended to so-called hybrid systems. Hybrid systems are systems where continuous dynamics interact with logic. When this extension is made, binary variables are introduced in the problem. As a consequence, the QP problem has to be replaced by a far more challenging Mixed Integer Quadratic Programming (MIQP) problem, which is known to have a computational complexity which grows exponentially in the number of binary optimization variables. In modern communication systems, multiple users share a so-called multi-access channel. To estimate the information originally sent, a maximum likelihood problem involving binary variables can be solved. The process of simultaneously estimating the information sent by multiple users is called Multiuser Detection (MUD). In this thesis, the problem to efficiently solve MIQP problems originating from MPC and MUD is addressed. Four different algorithms are presented. First, a polynomial complexity preprocessing algorithm for binary quadratic programming problems is presented. By using the algorithm, some, or all, binary variables can be computed efficiently already in the preprocessing phase. In numerical experiments, the algorithm is applied to unconstrained MPC problems with a mixture of real valued and binary valued control signals, and the result shows that the performance gain can be significant compared to solving the problem using branch and bound. The preprocessing algorithm has also been applied to the MUD problem, where simulations have shown that the bit error rate can be significantly reduced compared to using common suboptimal algorithms. Second, an MIQP algorithm tailored for MPC is presented. The algorithm uses a branch and bound method where the relaxed node problems are solved by a dual active set QP algorithm. In this QP algorithm, the KKT systems are solved using Riccati recursions in order to decrease the computational complexity. Simulation results show that both the proposed QP solver and MIQP solver have lower computational complexity compared to corresponding generic solvers. Third, the dual active set QP algorithm is enhanced using ideas from gradient projection methods. The performance of this enhanced algorithm is shown to be comparable with the existing commercial state-of-the-art QP solver \cplex for some random linear MPC problems. Fourth, an algorithm for efficient computation of the search directions in an SDP solver for a proposed alternative SDP relaxation applicable to MPC problems with binary control signals is presented. The SDP relaxation considered has the potential to give a tighter lower bound on the optimal objective function value compared to the QP relaxation that is traditionally used in branch and bound for these problems, and its computational performance is better than the ordinary SDP relaxation for the problem. Furthermore, the tightness of the different relaxations is investigated both theoretically and in numerical experiments.
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20. |
- Axehill, Daniel, 1978-, et al.
(författare)
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Mixed Integer Predictive Control Using a Tailored Mixed Integer Dual Quadratic Programming Algorithm
- 2006
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Ingår i: Proceedings of Reglermöte 2006.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objective with this work is to derive an MIQP solver tailored for MPC. The MIQP solver is built on the branch and bound method, where QP relaxations of the original problem are solved in the nodes of a binary search tree. The difference between the subproblems is often small and therefore it is interesting to be able to use a previous solution as a starting point in a new subproblem. This is referred to as a warm start of the solver. Because of its good warm start properties, a dual active set QP method was chosen. The method is tailored for MPC by solving a part of the KKT system using a Riccati recursion, which makes the computational complexity of the QP iterations grow linearly with the prediction horizon. Simulation results are presented both for the QP solver itself and when it is incorporated as a part of the MIQP solver. In both cases the computational complexity is significantly reduced compared to if a primal active set solver not utilizing structure is used.
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21. |
- Axehill, Daniel, 1978-, et al.
(författare)
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Parallel implementation of hybrid MPC
- 2014
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Ingår i: Distributed Model Predictive Control Made Easy. - Dordrecht : Springer Netherlands. - 9789400770058 - 9789400770065 ; , s. 375-392
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Bokkapitel (refereegranskat)abstract
- In this chapter parallel implementations of hybrid MPC will be discussed. Different methods for achieving parallelism at different levels of the algorithms will be surveyed. It will be seen that there are many possible ways of obtaining parallelism for hybrid MPC, and it is by no means clear which possibilities that should be utilized to achieve the best possible performance. To answer this question is a challenge for future research.
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22. |
- Axehill, Daniel, 1978-, et al.
(författare)
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Towards Parallel Implementation of Hybrid MPC : A Survey and Directions for Future Research
- 2012
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Ingår i: Distributed decision making and control. - London : Springer London. - 9781447122647 - 9781447122654 ; , s. 313-338
-
Konferensbidrag (refereegranskat)abstract
- In this chapter parallel implementations of hybrid MPC will be discussed. Different methods for achieving parallelism at different levels of the algorithms will be surveyed. It will be seen that there are many possible ways of obtaining parallelism for hybrid MPC, and it is by no means clear which possibilities that should be utilized to achieve the best possible performance. To answer this question is a challenge for future research.
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23. |
- Bellamy, R., et al.
(författare)
-
Incentivising bioenergy with carbon capture and storage (BECCS) responsibly : Comparing stakeholder policy preferences in the United Kingdom and Sweden
- 2021
-
Ingår i: Environmental Science and Policy. - : Elsevier Ltd. - 1462-9011 .- 1873-6416. ; 116, s. 47-55
-
Tidskriftsartikel (refereegranskat)abstract
- Bioenergy with carbon capture and storage (BECCS) plays a central role in scenario pathways that limit global warming in line with the objectives of the Paris Agreement. Yet deliberate policy efforts to incentivise BECCS—whether through amending existing climate policies or introducing entirely new ones—remain rare. In this paper, we contend that BECCS must be incentivised responsibly, through policy-making processes which account for diverse and geographically varying societal values and interests. More specifically, we make the case for responsible incentivisation by undertaking a comparative analysis of stakeholder attitudes to four idealised policy scenarios for BECCS, including representatives of government, business, nongovernmental and academic communities, in the UK and Sweden. The scenarios were: business as usual; international policy reform; national BECCS policy; and national policy for negative emissions technologies. Based on our findings, we recommend that policymakers 1) recognise the need to develop new incentives and make enabling reforms to existing policy instruments; 2) consider the risk of mitigation deterrence in their real world (and not abstracted) contexts; 3) employ multi-instrument approaches to incentivisation that do not overly rely on carbon pricing or 4) force a choice between technology specific or technology neutral policies; and 5) attend to the diversity of stakeholder and wider public perspectives that will ultimately determine the success—or failure—of their policy designs.
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24. |
- Björklund, Erik, et al.
(författare)
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Comparison of Midterm Outcomes Associated With Aspirin and Ticagrelor vs Aspirin Monotherapy After Coronary Artery Bypass Grafting for Acute Coronary Syndrome.
- 2021
-
Ingår i: JAMA network open. - : American Medical Association (AMA). - 2574-3805. ; 4:8
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Tidskriftsartikel (refereegranskat)abstract
- Guidelines recommend dual antiplatelet therapy after coronary artery bypass grafting (CABG) for patients with acute coronary syndrome (ACS). However, the evidence for these recommendations is weak.To compare midterm outcomes after CABG in patients with ACS treated postoperatively with acetylsalicylic acid (ASA) and ticagrelor or with ASA monotherapy.This cohort study used merged data from several national registries of Swedish patients who were diagnosed with ACS and subsequently underwent CABG. All included patients underwent isolated CABG in Sweden between 2012 and 2017 with an ACS diagnosis less than 6 weeks before the procedure, survived 14 days after discharge from hospital, and were treated postoperatively with ASA plus ticagrelor or ASA monotherapy. A multivariable Cox regression model was used for the main analysis, and propensity score-matched models were performed as sensitivity analysis. Data were analyzed between May and September 2020.Postoperative antiplatelet treatment, defined as filled prescriptions, with either ASA and ticagrelor or ASA only.Major adverse cardiovascular events (MACE), defined as all-cause mortality, myocardial infarction, and stroke, and major bleeding, at 12 months and at the end of follow-up.A total of 6558 patients (5281 [80.5%] men; mean [SD] age at surgery, 67.6 [9.3] years) were included; 1813 (27.6%) were treated with ASA plus ticagrelor and 4745 (72.4%) were treated with ASA monotherapy. Crude MACE rate was 3.0 per 100 person years (95% CI, 2.5-3.6 per 100 person years) in the ASA plus ticagrelor group and 3.8 per 100 person years (95% CI, 3.5-4.1 per 100 person years) in the ASA group. After adjustment, there was no significant difference in MACE risk between ASA plus ticagrelor vs ASA only, neither during the first 12 months (adjusted hazard ratio [aHR], 0.84; 95% CI, 0.58-1.21; P=.34) or during total follow-up (aHR, 0.89; 95% CI, 0.71-1.11; P=.29). The use of ASA plus ticagrelor was associated with a significantly increased risk for major bleeding during the first 12 months (aHR, 1.90; 95% CI, 1.16-3.13; P=.011). Sensitivity analyses confirmed the results.In patients with ACS who survived 2 weeks after CABG, no significant difference in the risk of death or ischemic events could be demonstrated between ASA plus ticagrelor and patients treated with ASA only, while the risk for major bleeding was higher in patients treated with ASA plus ticagrelor. Sufficiently powered prospective randomized trials comparing different antiplatelet therapy strategies after CABG are warranted.
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25. |
- Björklund, Erik, et al.
(författare)
-
Postdischarge major bleeding, myocardial infarction, and mortality risk after coronary artery bypass grafting
- 2023
-
Ingår i: HEART. - 1355-6037 .- 1468-201X.
-
Tidskriftsartikel (refereegranskat)abstract
- Objective To investigate the incidence and mortality risk associated with postdischarge major bleeding after coronary artery bypass grafting (CABG), and relate this to the incidence of, and mortality risk from, postdischarge myocardial infarction.Methods All patients undergoing first-time isolated CABG in Sweden in 2006-2017 and surviving 14 days after hospital discharge were included in a cohort study. Individual patient data from the SWEDEHEART Registry and five other mandatory nationwide registries were merged. Piecewise Cox proportional hazards models were used to investigate associations between major bleeding, defined as hospitalisation for bleeding, with subsequent mortality risk. Similar Cox proportional hazards models were used to investigate the association between postdischarge myocardial infarction and mortality risk.Results Among 36 633 patients, 2429 (6.6%) had a major bleeding event and 2231 (6.1%) had a myocardial infarction. Median follow-up was 6.0 (range 0-11) years. Major bleeding was associated with higher mortality risk <30 days (adjusted HR (aHR)=20.2 (95% CI 17.3 to 23.5)), 30-365 days (aHR=3.8 (95% CI 3.4 to 4.3)) and >365 days (aHR=1.8 (95% CI 1.7 to 2.0)) after the event. Myocardial infarction was associated with higher mortality risk <30 days (aHR=20.0 (95% CI 16.7 to 23.8)), 30-365 days (aHR=4.1 (95% CI 3.6 to 4.8)) and >365 days (aHR=1.8 (95% CI 1.7 to 2.0)) after the event.Conclusions The increase in mortality risk associated with a postdischarge major bleeding after CABG is substantial and is similar to the mortality risk associated with a postdischarge myocardial infarction.
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26. |
- Björklund, Erik, et al.
(författare)
-
Secondary prevention medications after coronary artery bypass grafting and long-term survival : a population-based longitudinal study from the SWEDEHEART registry.
- 2019
-
Ingår i: European Heart Journal. - : Oxford University Press. - 0195-668X .- 1522-9645. ; 41:17, s. 1653-1661
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: To evaluate the long-term use of secondary prevention medications [statins, β-blockers, renin-angiotensin-aldosterone system (RAAS) inhibitors, and platelet inhibitors] after coronary artery bypass grafting (CABG) and the association between medication use and mortality.METHODS AND RESULTS: All patients who underwent isolated CABG in Sweden from 2006 to 2015 and survived at least 6 months after discharge were included (n = 28 812). Individual patient data from SWEDEHEART and other mandatory nationwide registries were merged. Multivariable Cox regression models using time-updated data on dispensed prescriptions were used to assess associations between medication use and long-term mortality. Statins were dispensed to 93.9% of the patients 6 months after discharge and to 77.3% 8 years later. Corresponding figures for β-blockers were 91.0% and 76.4%, for RAAS inhibitors 72.9% and 65.9%, and for platelet inhibitors 93.0% and 79.8%. All medications were dispensed less often to patients ≥75 years. Treatment with statins [hazard ratio (HR) 0.56, 95% confidence interval (95% CI) 0.52-0.60], RAAS inhibitors (HR 0.78, 95% CI 0.73-0.84), and platelet inhibitors (HR 0.74, 95% CI 0.69-0.81) were individually associated with lower mortality risk after adjustment for age, gender, comorbidities, and use of other secondary preventive drugs (all P < 0.001). There was no association between β-blockers and mortality risk (HR 0.97, 95% CI 0.90-1.06; P = 0.54).CONCLUSION: The use of secondary prevention medications after CABG was high early after surgery but decreased significantly over time. The results of this observational study, with inherent risk of selection bias, suggest that treatment with statins, RAAS inhibitors, and platelet inhibitors is essential after CABG whereas the routine use of β-blockers may be questioned.
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27. |
- Boman, Antonia, et al.
(författare)
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Antibodies against citrullinated peptides are associated with clinical and radiological outcomes in patients with early rheumatoid arthritis : a prospective longitudinal inception cohort study
- 2019
-
Ingår i: RMD Open. - : BMJ Publishing Group Ltd. - 2056-5933. ; 5:2
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Anticitrullinated peptide antibody (ACPA) responses for 22 citrullinated peptides in patients with early rheumatoid arthritis (RA) were analysed and related to radiological and clinical outcome during the first 2 years in a prospective inception cohort.Methods: The ACPA reactivities were assessed in 1022 patients with early RA (symptoms <12 months) using the custom-made microarray chip (Thermo Fisher Scientific, Uppsala, Sweden) in a prospective longitudinal study of observational assessments of Disease Activity Score (DAS28 and its components) and radiology during the first 24 months, accounting for the treatment.Results: Frequency of ACPA reactivities varied between 13.3% and 63.1%. Of the anticyclic citrullinated peptide-2 (anti-CCP2) antibody-negative patients, ACPA reactivities were positive in 32.6%. Smoking, human leucocyte antigen-shared epitope (HLA-SE), anti-CCP2/rheumatoid factor, protein tyrosine phosphatase non-receptor type 22 (1858C/T) and DAS28 were significantly associated with number of ACPA reactivities. The ACPA reactivities modified differently the development of DAS28 over 24 months (identified using trajectories). Anti-Filaggrin307-324, anti-hnRNP (Peptide)-Z1 and anti-F4-CIT-R antibodies anticipated lower DAS28 values (p<0.01–0.05), while positivity for anti-Fibrinogen(Fib)β62-78(74), and anti-Fibα563-583 predicted higher DAS28 (p<0.01 both). Interaction between anti-Fibß36-52, anti-Pept-5 and anti-Bla-26 antibodies, respectively, and DAS28 during 24 months decreased significantly the DAS28 values (p<0.01–0.05). Corticosteroids and biologicals were related to DAS28-area under the curve and Larsen score 24 months. Anti-vimentin2-17 antibodies remained significantly associated with Larsen score at baseline and 24 months, respectively, and radiological progression, besides biologicals at 24 months adjusted for sex and age.Conclusions: Several ACPA reactivities modified significantly the DAS28 development during the first 24 months and were significantly associated with Larsen score at baseline, 24 months and radiological progression.
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28. |
- Bryngelsson, Mårten, et al.
(författare)
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Energy policy on shaky ground? : A study of CCS-scenarios
- 2009
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; :1, s. 4673-4680
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Tidskriftsartikel (refereegranskat)abstract
- Scenarios play an important role for the societal acceptance of CCS. This paper looks into influential reports containing CCS scenarios and analyses results, key assumptions and drivers for CCS' deployment. Significant uncertainties regarding CCS' development were in several cases excluded or marginalized. Despite these shortcomings, scenarios support a massive deployment of CCS and reflect an undivided optimism. If CCS would fail to meet the high expectations a backlash could follow. Indications were found that new scenarios including uncertainties are needed to balance this over-optimism. So-called unpleasant scenarios are often valuable in helping decision makers develop flexible strategies and policies.
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29. |
- Buhr, Katarina, 1980-, et al.
(författare)
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Capturing the Stories of Corporations : A comparison of media debates on carbon capture and storage in Norway and Sweden
- 2011
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Ingår i: Global Environmental Change. - : Elsevier. - 0959-3780 .- 1872-9495. ; 21:2, s. 336-345
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Tidskriftsartikel (refereegranskat)abstract
- The development and deployment of carbon capture and storage (CCS) are sensitive to public debates that socially frame the technology. This study examines the evolving CCS debates, focusing on the media's framing of firms. Corporations are central CCS actors, and we analyze them in light of the nation-state, which has been emphasized in previous research as the primary context of CCS politics. Empirically, we compare framings of Statoil and Vattenfall in the Norwegian and Swedish media, drawing on a qualitative dataset of news media articles published between 2005 and 2009. We conclude that firms make regular media statements either to foster legitimacy or to respond to criticism of CCS. We also conclude that framing is not necessarily linked to technological success or failure and that interpretations of the technology have different forms depending on whether the related activity occurs in domestic or foreign markets. Finally, we explain the media framings based on the domestic energy situation and politics.
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30. |
- Egecioglu, Emil, 1977, et al.
(författare)
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Hedonic and incentive signals for body weight control.
- 2011
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Ingår i: Reviews in endocrine & metabolic disorders. - : Springer Science and Business Media LLC. - 1573-2606 .- 1389-9155. ; 12:3, s. 141-51
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Forskningsöversikt (refereegranskat)abstract
- Here we review the emerging neurobiological understanding of the role of the brain's reward system in the regulation of body weight in health and in disease. Common obesity is characterized by the over-consumption of palatable/rewarding foods, reflecting an imbalance in the relative importance of hedonic versus homeostatic signals. The popular 'incentive salience theory' of food reward recognises not only a hedonic/pleasure component ('liking') but also an incentive motivation component ('wanting' or 'reward-seeking'). Central to the neurobiology of the reward mechanism is the mesoaccumbal dopamine system that confers incentive motivation not only for natural rewards such as food but also by artificial rewards (eg. addictive drugs). Indeed, this mesoaccumbal dopamine system receives and integrates information about the incentive (rewarding) value of foods with information about metabolic status. Problematic over-eating likely reflects a changing balance in the control exerted by hypothalamic versus reward circuits and/or it could reflect an allostatic shift in the hedonic set point for food reward. Certainly, for obesity to prevail, metabolic satiety signals such as leptin and insulin fail to regain control of appetitive brain networks, including those involved in food reward. On the other hand, metabolic control could reflect increased signalling by the stomach-derived orexigenic hormone, ghrelin. We have shown that ghrelin activates the mesoaccumbal dopamine system and that central ghrelin signalling is required for reward from both chemical drugs (eg alcohol) and also from palatable food. Future therapies for problematic over-eating and obesity may include drugs that interfere with incentive motivation, such as ghrelin antagonists.
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31. |
- Eltigani, Amna, et al.
(författare)
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Exploring lessons from five years of biochar-producing cookstoves in the Kagera region, Tanzania
- 2022
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Ingår i: Energy for Sustainable Development. - : Elsevier BV. - 0973-0826 .- 2352-4669. ; 71, s. 141-150
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Tidskriftsartikel (refereegranskat)abstract
- Biochar-producing cookstoves can supply fuel-efficient heat for cooking in developing countries. The produced biochar can be used as a soil amendment, providing a range of environmental and agronomic benefits and serve to remove carbon dioxide from the atmosphere. Despite these advantages, many stove initiatives have not been sustained in the long term, but very little attention has been devoted to understanding the reasons be-hind this. The present study contributes to filling this knowledge gap, by identifying key factors affecting the level of stove adoption and use, as well as biochar utilization. Based on a follow-up survey of 50 households in north-western Tanzania that received microgasifier stoves in 2015, only 12 still made use of their stove 5 years later. One of the main reasons for this relates to the inadequate quality of stove material. Declining or inconsistent availability of feedstocks was also identified as a major challenge. Furthermore, the households generally did not embrace the idea of amending soils with biochar, due to a combination of local practices and perceptions, and a lack of education and awareness programs. We conclude that, under the conditions of the studied project, three factors are required to scale dissemination: improvement of the stove design, provision of training pro-grams on biochar management and subsidies or microloans that would make more durable stoves affordable. Sustained stove deployment can only be achievable by institutionalizing financing structures that are indepen-dent from short-term grant-based initiatives.
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32. |
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33. |
- Ernest, Baraka, et al.
(författare)
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Evaluation of selected organic fertilizers on conditioning soil health of smallholder households in Karagwe, Northwestern Tanzania
- 2024
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Ingår i: Heliyon. - : Elsevier. - 2405-8440. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Soil management is a strategy for improving soil suffering from problems such as low pH, nutrient deficiency, and erosion. The study evaluated the effects of human urine (HU), biogas slurry (BS), standard compost (StC), animal manure (AM), and synthetic fertilizer (SF) in comparison with no soil fertility management (NFM) on soil pH, cation exchange capacity (CEC), soil organic carbon (SOC), soil moisture content, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) in the Karagwe district, a Northwestern Tanzania. Four household farms representing each soil amendment type were selected for soil sampling. A total of 192 soil samples were collected and air-dried. After laboratory analysis, BS-enriched soil had the highest pH (6.558), CEC (23.945 cmol+/kg), SOC (5.573%), soil moisture (5.573%), N (0.497%), P (247.130 mg/kg), K (3.036 cmol+/kg), Ca (18.983 cmol+/kg), Mg (4.076 cmol+/kg), Na (2.960 cmol+/kg), and Cu (12.548 mg/kg). Similar soil properties were lower in NFM than in the other soils. The soil properties on the chosen farms did not differ significantly depending on the sampling zone for each organic fertilizer. Therefore, the result indicates that all evaluated organic fertilizers improved soil health compared to NFM, but BS and HU fertilizers led to relatively better soil health improvements than StC, AM, and SF.
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34. |
- Forsling, Robin, 1988-, et al.
(författare)
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Conservative Linear Unbiased Estimation Under Partially Known Covariances
- 2022
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 70, s. 3123-3135
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Tidskriftsartikel (refereegranskat)abstract
- Mean square error optimal estimation requires the full correlation structure to be available. Unfortunately, it is not always possible to maintain full knowledge about the correlations. One example is decentralized data fusion where the cross-correlations between estimates are unknown, partly due to information sharing. To avoid underestimating the covariance of an estimate in such situations, conservative estimation is one option. In this paper the conservative linear unbiased estimator is formalized including optimality criteria. Fundamental bounds of the optimal conservative linear unbiased estimator are derived. A main contribution is a general approach for computing the proposed estimator based on robust optimization. Furthermore, it is shown that several existing estimation algorithms are special cases of the optimal conservative linear unbiased estimator. An evaluation verifies the theoretical considerations and shows that the optimization based approach performs better than existing conservative estimation methods in certain cases.
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35. |
- Fridahl, Mathias, 1980-, et al.
(författare)
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Biochar deployment drivers and barriers in least developed countries
- 2021
-
Ingår i: Handbook of climate change management. - Cham : Springer. - 9783030227593 ; , s. 1-30
-
Bokkapitel (refereegranskat)abstract
- Agriculture in the least developed countries (LDCs) is highly vulnerable to the impacts of climate change. Applying biochar to soils has been proposed as a solution, especially in the carbon-depleted and acid sub-Saharan soils. Correctly applied, biochar increases yield capacities, decreases contamination, and promotes resilience. Hope is that biochar will store atmospheric carbon in soils, thus generating negative emissions. Nonetheless, several goal conflicts may arise, for example, between the global aspirations to achieve negative carbon emissions and local sustainability. Using interviews, a survey, and field visits to biochar initiatives in Tanzania, this chapter explores deployment drivers and barriers in LDCs and their implications for biochar carbon removal in local contexts. As such, it seeks to address a gap in the literature on actual, opposed to hypothesized, engagement of biochar practitioners. The chapter concludes that the idea of carbon removal alone is unlikely to motivate widespread biochar deployment in LDCs. Optimization of carbon content and stability must be balanced against maximizing yields with minimum inputs. Tangible results drive deployment among smallholders and agricultural businesses alike, yet developing biochar systems is challenging due to their complexity and long lead times. Thus, while financing and external expertise are vital at the initial stages, education, wareness, and persistent demonstration are key to sustained action.
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36. |
- Fridahl, Mathias, 1980-, et al.
(författare)
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Mapping Multi-Level Policy Incentives for Bioenergy With Carbon Capture and Storage in Sweden
- 2020
-
Ingår i: Frontiers in Climate. - : Frontiers Media S.A.. - 2624-9553. ; 2, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Bioenergy with carbon capture and storage (BECCS) is considered a key mitigation technology in most 1.5–2.0°C compatible climate change mitigation scenarios. Nonetheless, examples of BECCS deployment are lacking internationally. It is widely acknowledged that widespread implementation of this technology requires strong policy enablers, and that such enablers are currently non-existent. However, the literature lacks a more structured assessment of the “incentive gap” between scenarios with substantive BECCS deployment and existing policy enablers to effectuate BECCS deployment. Sweden, a country with progressive climate policies and particularly good preconditions for BECCS, constitutes a relevant locus for such examinations. The paper asks to what extent and how existing UN, EU, and Swedish climate policy instruments incentivize BECCS research, development, demonstration, and deployment in Sweden. The analysis is followed by a tentative discussion of needs for policy reform to improve the effectiveness of climate policy in delivering BECCS. Drawing on a tripartite typology of policy instruments (economic, regulatory, and informational) and the ability of these instruments to create supply-push or demand-pull, the article finds that: (1) no instruments create a demand-pull to cover operational expenditure; (2) economic instruments provide partial support for research and the capital expenditure associated with demonstration, and; (3) regulatory instruments provide partial clarity on environmental safeguards and responsibilities. A few regulatory barriers also continue to counteract deployment. The article concludes that the existing policy mix requires considerable reform if BECCS is to contribute substantially to the Swedish target for net-zero emissions. Continued effort to dismantle regulatory barriers must be complemented with a strong demand-pull instrument that complements the current focus on supply-push incentives. If unreformed, the existing policy mix will most likely lead to substantial public expenditure on BECCS research, development, and demonstration without leading to any substantial deployment and diffusion.
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37. |
- Fridahl, Mathias, 1980-, et al.
(författare)
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Novel carbon dioxide removals techniques must be integrated into the European Union’s climate policies
- 2023
-
Ingår i: Communications Earth & Environment. - Stockholm : Springer Nature. - 2662-4435. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Emissions reductions are crucial to mitigating climate change. However, in the past decade, the world community’s failure to reduce emissions at a sufficient speed to avoid dangerous climate change has become obvious4. This reality acutely necessitates the development of innovative sets of policies to spur the deployment of novel CO2 removals, an urgency that is further underlined by the long lead time for many novel removal methods. Disregarding the potential of novel removals is incommensurate with the scale of the challenge of achieving EU’s commitment to reach net-zero greenhouse gas emissions by 2050.We argue that the current policy framework neither provides Union-wide economic incentives for novel CO2 removals, nor does it encourage EU Member States to develop national policy incentives. Our proposed solutions includes incentivizing removals through a conditional integration into the EU Emissions Trading System (ETS), expanding the portfolio of removal methods in the Land-Use, Land-Use Change and Forestry (LULUCF) Regulation, and to manage anticipations regarding which residual emissions that need to be counterbalanced by removals.
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38. |
- Fridahl, Mathias, 1980-, et al.
(författare)
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Towards Indicators for a Negative Emissions Climate Stabilisation Index : Problems and Prospects
- 2020
-
Ingår i: Climate. - : BioMed Central. - 2225-1154. ; 8:6
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Forskningsöversikt (refereegranskat)abstract
- The incongruence between the United Nations objective to hold global warming well below 2 °C and the rate of global emission reductions has intensified interest in negative emissions. Previous research has explored several pros and cons of individual negative emissions technologies. Systematised approaches to comparing and prioritising among them are, however, largely lacking. In response to this gap in the literature, this article reviews the scientific literature on indicators for designing negative emissions climate stabilisation value indexes. An index typically provides summary measures of several components, often denoted indicators. Utilizing a narrative review methodology, the article derives five categories of indicators underpinned by overlapping and often mutually reinforcing environmental and socio-economic values. A list of 21 indicators are proposed to capture both positive and negative values associated with effectiveness, efficiency, scale, risk, and synergies. While discussing indicators capable of providing guidance on negative emissions is timely, given the emerging shift away from pure emission reduction targets towards net-zero targets, numerous complexities are involved in determining their relative values. The results herein serve to inform policy making on the prioritisation and incentivisation of negative emissions technologies capable of delivering on the new objectives, and the results highlight the many risks and uncertainties involved in such exercises. The article concludes that systematic research on the comparison of NETs is incomplete. An iterative, interdisciplinary research programme exploring such questions has the potential to be extremely rewarding
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39. |
- Gourdon, Pontus Emanuel, 1978, et al.
(författare)
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Optimized in vitro and in vivo expression of proteorhodopsin: A seven-transmembrane proton pump
- 2008
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Ingår i: Protein Expression and Purification. - : Elsevier BV. - 1096-0279 .- 1046-5928. ; 58:1, s. 103-113
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Tidskriftsartikel (refereegranskat)abstract
- Proteorhodopsin is an integral membrane light-harvesting proton pump that is found in bacteria distributed throughout global surface waters. Here, we present a protocol for functional in vitro production of pR using a commercial cell-free synthesis system yielding 1.0 mg purified protein per milliliter of cell lysate. We also present an optimized protocol for in vivo over-expression of pR in Escherichia coli, and a two-step purification yielding 5 mg of essentially pure functional protein per liter of culture. Both approaches are straightforward, rapid, and easily scalable. Thus either may facilitate the exploitation of pR for commercial biotechnological applications. Finally, the implications of some observations of the in vitro synthesis behavior, as well as preliminary results towards a structural determination of pR are discussed.
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40. |
- Haikola, Simon, 1982-, et al.
(författare)
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From polarization to reluctant acceptance : Bioenergy with carbon capture and storage (BECCS) and the post-normalization of the climate debate
- 2019
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Ingår i: Journal of Integrative Environmental Sciences. - : Taylor & Francis. - 1943-815X .- 1943-8168. ; 16:1, s. 45-69
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Tidskriftsartikel (refereegranskat)abstract
- The paper covers the public debate on BECCS (bioenergy with carbon capture and storage) between 2008 and 2018. Through a qualitative analysis of around 800 feature articles, editorials, and opinion pieces published in English, German, Swedish, Danish, and Norwegian in news media and debates sections of scientific media, we highlight conspicuous aspects of the debate and relate them to the theoretical concept of post-normal science. We find that the debate is characterized by an emphasis on values, scientific uncertainty and the integrity of science, premised on a pervading sense of urgency. To a significant extent, the debate can be understood as a “normal” view of science questioning what it perceives to be unscientific model-based climate scenarios, and the scenarios, in turn, can be seen as a response to post-normal circumstances. The urgency permeating the debate provides conditions for open debate about ethical and epistemological uncertainty. The debate goes through a period of polarization – corroborating findings from previous studies on the climate science debate after COP21 – between an intense critique of BECCS inclusion in climate scenarios and reluctant acceptance thereof. Towards the end of the studied period, emphasis shifts towards reluctant acceptance, indicating that post-normal debate may only occur as a temporary state always tending towards new consensus.
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41. |
- Haikola, Simon, 1982-, et al.
(författare)
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Limits to climate action - Narratives of bioenergy with carbon capture and storage
- 2021
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Ingår i: Political Geography. - : Elsevier. - 0962-6298 .- 1873-5096. ; 88
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, bio-energy with carbon capture and storage (BECCS) has been awarded a key role in climate mitigation scenarios explored by integrated assessment models and referenced in reports by the Intergovernmental Panel on Climate Change. Because a majority of scenarios limiting global warming to 2 °C or 1,5 °C include vast deployment of BECCS, a critical discussion has emerged among experts about the moral implications of thus introducing an unproven technology into the policy realm.In this paper, we analyse this discussion as it has played out between 2013 and 2019, with a focus on how expert narratives are constructed in the mass media about the possibilities for decarbonisation within the current political-economic order. We find there are almost no narratives that support massive deployment of BECCS, and that all narratives presuppose limits to decarbonisation imposed by the current political-economic system. The perception of such limits lead some to argue, through deterministic and apolitical narratives, for the necessity of negative emissions technologies, while others argue instead that “degrowth” is the only solution. Thus, there is a distinct lack of positive narratives about how capitalism can bring about decarbonisation.
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42. |
- Haikola, Simon, 1982-, et al.
(författare)
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Map-makers and navigators of politicised terrain : Expert understandings of epistemological uncertainty in integrated assessment modelling of bioenergy with carbon capture and storage
- 2019
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Ingår i: Futures. - : Elsevier. - 0016-3287 .- 1873-6378. ; 114:102472
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Tidskriftsartikel (refereegranskat)abstract
- Bioenergy with carbon capture and storage (BECCS) has recently risen to international prominence due to its modelled potential to allow a mid-term temperature overshoot compensated by large, long-term removal of carbon dioxide from the atmosphere. The technology, however, is far from commercial. Therefore, BECCS is a suitable entry point for exploring how modellers identify, manage and communicate uncertainties. By applying framing analysis to 21 interviews with researchers working directly or closely with integrated assessment models (IAMs), three prevalent cognitive frames are identified: Climate scenarios as (1) talking points to discuss possible futures, (2) fundamentally political prescriptions that foreclose alternatives, and (3) distortions of pure science. The discourse around IAMs has entered a phase of critical reflection about their performative, political dimensions, both inside and outside of the IA modelling community. This phase is marked by modellers grappling with the responsibilities that are perceived to come with simultaneously providing maps of possible futures and standards by which these maps are to be evaluated.
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43. |
- Haikola, Simon, 1982-, et al.
(författare)
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Views of BECCS among modelers and policymakers
- 2018
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Ingår i: Bioenergy with carbon capture and storage. - Brussels : Liberal European Forum. - 9789187379475 ; , s. 17-29
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Bokkapitel (refereegranskat)abstract
- Chapter 3 (“Views of BECCS Among Modelers and Policymakers”) moves from exploring the magnitude of BECCS deployment in climate scenarios to outlining caveats raised by modelers themselves. The chapter addresses how modelers navigate the landscape of political and academic pressures to deliver timely, insightful, and relevant policy advice despite inherent and crucial uncerttainties and increasing model complexity. Based on interviews with modelers, the chapter discusses perspectives on uncertainty, the communication of IAM results, and the models’ relationship to reality. The chapter also discuss views of BECCS among policymakers whom generally want to give relatively low priority to investments in BECCS. Failing to invest in the future delivery of BECCS, combined with today’s lack of mitigation ambition, limits future generations’ maneuvering room to resolve the climate crisis.
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44. |
- Hallberg, David, 1978-, et al.
(författare)
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Constraints of ICT in lifelong learning on disadvantaged women
- 2014
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Ingår i: The Electronic Journal of Information Systems in Developing Countries. - Hongkong : Wiley. - 1681-4835. ; 61:8, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- This paper draws attention to the urgency of taking into consideration women’s genderspecific needs and interests in the implementation of community-based ICT projects in lifelong learning. We set out this research to understand the constraints of information and communications technology (ICT) in lifelong learning on disadvantaged women. National statistics and data from field studies were used. The constraints and their consequences at national level are often a result of national policies and regulations – or lack thereof – while the constraints and their consequences at local/regional level involve everyday-life occurrences that are present in women's immediate surroundings. Hence, an understanding of both levels is critical. This research is valuable for stakeholders delving into issues of development intervention using ICTs, not only in Kenya but in a broader, global perspective.
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45. |
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46. |
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47. |
- Hallgren, Axel, et al.
(författare)
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Conflicting Narratives of Deep Sea Mining
- 2021
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 13:9
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Tidskriftsartikel (refereegranskat)abstract
- As land-based mining industries face increasing complexities, e.g., diminishing return on investments, environmental degradation, and geopolitical tensions, governments are searching for alternatives. Following decades of anticipation, technological innovation, and exploration, deep seabed mining (DSM) in the oceans has, according to the mining industry and other proponents, moved closer to implementation. The DSM industry is currently waiting for international regulations that will guide future exploitation. This paper aims to provide an overview of the current status of DSM and structure ongoing key discussions and tensions prevalent in scientific literature. A narrative review method is applied, and the analysis inductively structures four narratives in the results section: (1) a green economy in a blue world, (2) the sharing of DSM profits, (3) the depths of the unknown, and (4) let the minerals be. The paper concludes that some narratives are conflicting, but the policy path that currently dominates has a preponderance towards Narrative 1—encouraging industrial mining in the near future based on current knowledge—and does not reflect current wider discussions in the literature. The paper suggests that the regulatory process and discussions should be opened up and more perspectives, such as if DSM is morally appropriate (Narrative 4), should be taken into consideration.
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48. |
- Hallgren, Axel, et al.
(författare)
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Deep sea mining
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This brief is based on a literature review conducted by Axel Hallgren at Linköping University that maps ongoing deep sea mining (DSM) research, scientific debates and controversies and synthesizes major narratives in the field. The brief will first contextualize DSM, pinpoint a few significant challenges, and continue with a short description of the targeted mineral resources. The discussion that follows hone in on a few governance challenges that emanate from the aspirations to achieve an equitable distribution of mining revenues and the lack of scientific knowledge, and the inherently unmanageable task to draft a legitimate regulatory system for the governance of the global and currently uncharted deep sea bed in merely a few years. The brief rounds off by highlighting a few avenues for topical social scientific research.
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49. |
- Hamdan, Mohammed, 1978-
(författare)
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Effects of temperature and terrestrial carbon on primary production in lake ecosystems
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Climate warming is predicted to affect northern lake food webs in two ways: (1)directly via changes in water temperature and ice conditions, and (2) indirectlyvia changes in catchment characteristics and processes that influence input ofallochthonous coloured dissolved organic matter (cDOM) and nutrients. Input ofcDOM increases carbon dioxide (CO2) availability, causes brownification andreduced light conditions, and may increase nutrient availability especially forpelagic primary producers. Increased water temperature and light penetrationand longer ice-free periods affect metabolic rates. These changes are expected toinfluence gross primary production (GPP) and growth of higher trophic levels.However, majority of studies focus on pelagic processes and net effects at wholelake scale is not well understood. Consequently, the lack of knowledge of whatfactors control benthic GPP makes predictions of net effects of climate change onwhole-ecosystem GPP spurious. The aim of this thesis was to experimentally testeffects of warming and increased input of allochthonous cDOM on habitatspecific and whole-ecosystem GPP in lakes. First, by manipulating the CO2concentrations in large scale pond ecosystems, we showed that increased CO2stimulated whole-ecosystem GPP. In a separate incubation study with naturallake sediments in a boreal lake, we tested the role of CO2 as a limiting factor forbenthic GPP under different light levels. The results showed that CO2 supplystimulated benthic GPP at high but not at low light availability, suggesting thatbenthic GPP can be CO2-limited. In the same experimental pond ecosystems, thecombined effect of increased allochthonous cDOM and warming (+3.5°C) on GPPwas studied. The results showed that cDOM input decreases whole-ecosystemGPP, mainly as a result of decreased benthic GPP due to light limitation not fullycounteracted by an increase in pelagic GPP under ambient conditions. Warmingon the other caused a hump shaped increase in whole-ecosystem GPP withincreasing cDOM input mainly due to a positive response in pelagic GPP due torelaxed nutrient limitation. Finally, by manipulating the fish consumer biomassin the same experimental pond ecosystems we showed that whole-ecosystem GPPcan be controlled by top-down effects under warm (+ 3.0°C) but not ambienttemperature conditions. The decline in whole-ecosystem GPP was mainlyattributed to a warming-stimulated consumer-driven trophic cascade in thepelagic habitat and top-down control by zooplankton on phytoplankton growth,while no corresponding cascade was evident in the benthic habitat.Taken together, the results suggest that climate change impacts, as increasinginputs of cDOM, warming and changes in food webs, have different effects onhabitat specific GPP and alone or in combination have impacts on whole-lakeGPP. This thesis offers important insights to better understand the factors thatcontrol lake GPP and to predict future lake ecosystem responses to environmentalchange.
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50. |
- Hansson, Anders, 1978-
(författare)
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Ambivalence in calculating the future : the case of re-engineering the world
- 2014
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Ingår i: Journal of Integrative Environmental Sciences. - : Taylor & Francis. - 1943-815X .- 1943-8168. ; 11:2, s. 125-142
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Tidskriftsartikel (refereegranskat)abstract
- Recently, climate engineering and particularly sulphur aerosol injection (SAI) have entered the arena of international climate change politics. The idea behind SAI is very simple: to reflect sunlight and heat back into space by injecting particles into the stratosphere. SAI has the theoretical potential to moderate anthropogenic climate change in a timely fashion and at very low costs but may also cause major environmental harm. Determining the future of SAI will entail dealing with many major uncertainties such as assessing risks, costs and benefits. This paper critically investigates scientific knowledge production under conditions of major uncertainty. It discusses how uncertainty, ethics and social considerations are treated in the SAI literature, which applies techno-economic models. In the simplest studies, important uncertainties are excluded from the models, but the more complex studies include many uncertainties, which may have considerable influence on the results and recommendations. In some cases the modelled results are overshadowed or strengthened by ethical discussions or methodological reflexivity that emphasize uncertainties and model limitations. There seems to be ambivalence between constructing certainty, on one hand, and an awareness of methodological limitations, on the other. Finally, the value of these papers for decision-makers and other concerned groups is discussed.
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