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- Handal, M, et al.
(författare)
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Opioid maintenance treatment of pregnant women in the Scandinavian countries
- 2020
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Ingår i: Nordisk alkohol- & narkotikatidskrift : NAT. - : SAGE Publications. - 1458-6126. ; 37:3, s. 298-312
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Tidskriftsartikel (refereegranskat)abstract
- WHO guidelines emphasise the need for descriptions of clinical practice and observational studies on risk and benefits of pharmacotherapies in pregnancy. The aims of the present study were to: (1) Describe opioid maintenance treatment (OMT) in the Scandinavian countries in general, and specifically for pregnant women, (2) Describe a project which utilises a new approach using registry-linkage data to examine associations between prenatal exposure to OMT and child outcomes: a Scandinavian cohort study of pregnant women in OMT during pregnancy (ScopeOMT). Data: Guidelines describing the treatment of persons with opioid use disorders in general, and specifically for pregnant women. Scandinavian registry-linkage data from ScopeOMT. Results: Registry data show that approximately 800 pregnant women received OMT during pregnancy in the period of the ScopeOMT study. Similarities across the Scandinavian countries include access to free healthcare and treatment; multidisciplinary teams trained to support pregnant women in OMT; buprenorphine as the recommended drug when initiating therapy; and a holistic focus on the patients’ lives. An important difference is that Norwegian women who use illegal substances that may harm the foetus may be admitted – voluntarily, or against their will – for parts of, or the remainder of the pregnancy to inpatient treatment at specialised clinics. Conclusion: Many similarities in the treatment provided to opioid-dependent persons in the Scandinavian countries place this area in an excellent position to combine the efforts and carry out observational studies concerning the safety of OMT during pregnancy.
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- Naim, M.M., et al.
(författare)
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A net present value assessment of make-to-order and make-to-stock manufacturing systems
- 2007
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Ingår i: Omega. - : Elsevier BV. - 0305-0483 .- 1873-5274. ; 35:5, s. 524-532
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Tidskriftsartikel (refereegranskat)abstract
- This paper shows the impact of using the net present value (NPV) on parameter selection in the ordering policy of a production planning and control system. Using a well understood and documented model, the net present value is used as an objective function to determine the discounted future variance costs resulting from the model's dynamics. The NPV of the variance (NPVv) is defined and applied to the model under make-to-order and make-to-stock conditions. We show that the cost structure of the manufacturing system defines the NPVv and hence aids in identifying the most appropriate control strategy to apply. © 2005 Elsevier Ltd. All rights reserved.
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| 10. |
- SHELDON, RW, et al.
(författare)
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NANOPLANKTON AND PICOPLANKTON GROWTH AND PRODUCTION IN THE BAY OF VILLEFRANCHE-SUR-MER (NW MEDITERRANEAN)
- 1992
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 241:2, s. 91-106
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Tidskriftsartikel (refereegranskat)abstract
- Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 mum) flagellates but towards the end it was more or less equally divided between the nano- and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nano- or picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.
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| 11. |
- Spiegler, Virginia L M, et al.
(författare)
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A control engineering approach to the assessment of supply chain resilience
- 2012
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Ingår i: International Journal of Production Research. - : Taylor and Francis. - 0020-7543 .- 1366-588X. ; 50:21, s. 6162-6187
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Tidskriftsartikel (refereegranskat)abstract
- There is no consensus on the supply chain management definition of resilience. To aid in evaluating the dynamic behaviour of such systems we need to establish clearly elucidated performance criteria that encapsulate the attributes of resilience. A literature review establishes the latter as readiness, responsiveness and recovery. We also identify robustness as a necessary condition that would complement resilience. We find that the Integral of the Time Absolute Error (ITAE) is an appropriate control engineering measure of resilience when it is applied to inventory levels and shipment rates. We use the ITAE to evaluate an often used benchmark model of make-to-stock supply chains consisting of three decision parameters. We use both linear and nonlinear forms of the model in our evaluation. Our findings suggest that optimum solutions for resilience do not yield a system that is robust to uncertainties in lead-time. Hence supply chains will experience drastic changes in their resilience performance when lead-time changes.
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| 12. |
- Spiegler, Virginia L. M., et al.
(författare)
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A technique to develop simplified and linearised models of complex dynamic supply chain systems
- 2016
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Ingår i: European Journal of Operational Research. - : ELSEVIER SCIENCE BV. - 0377-2217 .- 1872-6860. ; 251:3, s. 888-903
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Tidskriftsartikel (refereegranskat)abstract
- There is a need to identify and categorise different types of nonlinearities that commonly appear in supply chain dynamics models, as well as establishing suitable methods for linearising and analysing each type of nonlinearity. In this paper simplification methods to reduce model complexity and to assist in gaining system dynamics insights are suggested. Hence, an outcome is the development of more accurate simplified linear representations of complex nonlinear supply chain models. We use the highly cited Forrester production-distribution model as a benchmark supply chain system to study nonlinear control structures and apply appropriate analytical control theory methods. We then compare performances of the linearised model with numerical solutions of the original nonlinear model and with other previous research on the same model. Findings suggest that more accurate linear approximations can be found. These simplified and linearised models enhance the understanding of the system dynamics and transient responses, especially for inventory and shipment responses. A systematic method is provided for the rigorous analysis and design of nonlinear supply chain dynamics models, especially when overly simplistic linear relationship assumptions are not possible or appropriate. This is a precursor to robust control system optimisation. (C) 2015 Elsevier B.V. All rights reserved.
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| 13. |
- Wikner, Joakim, et al.
(författare)
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IOBPCS based models and decoupling thinking
- 2017
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Ingår i: International Journal of Production Economics. - : ELSEVIER SCIENCE BV. - 0925-5273 .- 1873-7579. ; 194, s. 153-166
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Tidskriftsartikel (refereegranskat)abstract
- The inventory and order based production control system (IOBPCS) is mainly a model of a forecast driven production system where the production decision is based on the forecast in combination with the deviation between target inventory and actual inventory. The model has been extended in various directions by including e.g. WIP feedback but also by interpreting the inventory as an order book and hence representing a customer order driven system. In practice a system usually consists of one forecast driven subsystem in tandem with a customer order driven subsystem and the interface between the two subsystems is represented by information flows and a stock point associated with the customer order decoupling point (CODP). The CODP may be positioned late in the flow, as in make to stock systems, or early, as in make to order systems, but in any case the model should be able to capture the properties of both subsystems in combination. A challenge in separating forecast driven from customer order driven is that neither the inventory nor the order book should be allowed to take on negative values, and hence non-linearities are introduced making the model more difficult to solve analytically unless the model is first linearized. In summary the model presented here is based on two derivatives of IOBPCS that are in tandem, and interfaces between them related to where the demand information flow is decoupled and the position of the CODP.
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| 16. |
- Grubisic, Lorena M., et al.
(författare)
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Effects of stratification depth and dissolved organic matter on brackish bacterioplankton communities
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 453, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- Bacterioplankton growth is often directly or indirectly controlled by external energy subsidies via organic matter inputs or solar radiation. We carried out a mesocosm experiment to assess how bacterioplankton communities responded to elevated levels of dissolved organic matter (DOM) and experimentally controlled stratification depth. The month-long experiment consisted of 2500 l mesocosms subjected to 4 experimental manipulations in triplicate: the stratification depth was set to either 1.5 or 3.5 m, with or without experimental addition of ambient levels of chromophoric DOM. DOM addition had a significant effect on bacterial community composition as assessed by terminal restriction fragment length polymorphism of amplified 16S rRNA genes. In contrast, there were no effects of the DOM amendment on bacterial biomass or production. Mixing depth and the coupled effective light climate in the photic zone also had a significant effect on bacterial community composition. Furthermore, shallow mixing depth was associated with enhanced primary production, whereas DOM addition had a negative effect on phyto plankton biomass and productivity. Our results suggest that bacterial community composition is coupled to primary production under the studied coastal nutrient regime, and point to a key role of DOM quality in controlling bacterioplankton communities.
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| 17. |
- Jalili, Armin, et al.
(författare)
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A nonlinearity error calibration technique for pipelined ADCs
- 2011
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Ingår i: Integration. - Amsterdam, The Netherlands : Elsevier. - 0167-9260 .- 1872-7522. ; 44:3, s. 229-241
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a digital background calibration technique that measures and cancels offset, linear and nonlinear errors in each stage of a pipelined analog to digital converter (ADC) using a single algorithm. A simple two-step subranging ADC architecture is used as an extra ADC in order to extract the data points of the stage-under-calibration and perform correction process without imposing any changes on the main ADC architecture which is the main trend of the current work. Contrary to the conventional calibration methods that use high resolution reference ADCs, averaging and chopping concepts are used in this work to allow the resolution of the extra ADC to be lower than that of the main ADC.
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| 18. |
- Jalili, Armin, et al.
(författare)
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Calibration of high-resolution flash ADCS based on histogram test methods
- 2010
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Ingår i: Electronics, Circuits, and Systems (ICECS), 2010 17th IEEE International Conference on. - : IEEE. - 9781424481552 ; , s. 114-117
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper a calibration technique for high-resolution, flash analog- to-digital converters (ADCs) based on histogram test methods is proposed. A probability density function, PDF, generator circuit is utilized to generate a triangular signal with a constant PDF, i.e., uniform distribution, as a test signal. In the proposed technique both offset estimation and trimming are performed without imposing any changes on the comparator structure in the ADC. The proposed algorithm estimates the offset values and stores them in a RAM. The trimming circuit uses the stored values and performs the trimming by adjusting the reference voltages to the comparators. An 8-bit flash ADC with a 1-V reference voltage, a comparator offset distribution with σos ≈ 30 mV, and a 10-bit test signal with about 3% nonlinearity are used in the simulations. The results show that the calibration improves the DNL and INL from about 3.6/3.9 LSB to about 0.9/0.75 LSB, respectively.
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| 19. |
- Jalili, Armin, et al.
(författare)
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Calibration of sigma-delta analog-to-digital converters based on histogram test methods
- 2010
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Ingår i: NORCHIP, 2010. - : IEEE. - 9781424489725 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a calibration technique for sigma-delta analog-to-digital converters (ΣΔADC) in which highspeed, low-resolution flash subADCs are used. The calibration technique as such is mainly targeting calibration of the flash subADC, but we also study how the correction depends on where in the ΣΔ modulator the calibration signals are applied. It is shown that the calibration technique can cope with errors that occur in the feedback digital-to-analog converter (DAC) and the input accumulator. Behavioral-level simulation results show an improvement of in effective number of bits (ENOB) from 6.6 to 11.3. Fairly large offset and gain errors have been introduced which illustrates a robust calibration technique.
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| 22. |
- Muelbert, Jose H., et al.
(författare)
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ILTER : The International Long-Term Ecological Research Network as a Platform for Global Coastal and Ocean Observation
- 2019
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Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 6
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Forskningsöversikt (refereegranskat)abstract
- Understanding the threats to global biodiversity and ecosystem services posed by human impacts on coastal and marine environments requires the establishment and maintenance of ecological observatories that integrate the biological, physical, geological, and biogeochemical aspects of ecosystems. This is crucial to provide scientists and stakeholders with the support and knowledge necessary to quantify environmental change and its impact on the sustainable use of the seas and coasts. In this paper, we explore the potential for the coastal and marine components of the International Long-Term Ecological Research Network (ILTER) to fill this need for integrated global observation, and highlight how ecological observations are necessary to address the challenges posed by climate change and evolving human needs and stressors within the coastal zone. The ILTER is a global network encompassing 44 countries and 700 research sites in a variety of ecosystems across the planet, more than 100 of which are located in coastal and marine environments (ILTER-CMS). While most of the ILTER-CMS were established after the year 2000, in some cases they date back to the early 1900s. At ILTER sites, a broad variety of abiotic and biotic variables are measured, which may feed into other global initiatives. The ILTER community has produced tools to harmonize and compare measurements and methods, allowing for data integration workflows and analyses between and within individual ILTER sites. After a brief historical overview of ILTER, with emphasis on the marine component, we analyze the potential contribution of the ILTER-CMS to global coastal and ocean observation, adopting the "Strength, Weakness, Opportunity and Threats (SWOT)" approach. We also identify ways in which the in situ parameters collected at ILTER sites currently fit within the Essential Ocean Variables framework (as proposed by the Framework for Ocean Observation recommendations) and provide insights on the use of new technology in long-term studies. Final recommendations point at the need to further develop observational activities at LTER sites and improve coordination among them and with external related initiatives in order to maximize their exploitation and address present and future challenges in ocean observations.
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| 23. |
- Naim, Mohamed M., et al.
(författare)
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Identifying the causes of the bullwhip effect by exploiting control block diagram manipulation with analogical reasoning
- 2017
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Ingår i: European Journal of Operational Research. - : Elsevier. - 0377-2217 .- 1872-6860. ; 263:1, s. 240-246
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Tidskriftsartikel (refereegranskat)abstract
- Senior managers when solving problems commonly use analogical reasoning, allowing a current ‘target problem’ situation to be compared to a valid previous experienced ‘source problem’ from which a potential set of ‘candidate solutions’ may be identified. We use a single-echelon of the often-quoted Forrester (1961) production-distribution system as a case ‘target model’ of a complex production and inventory control system that exhibits bullwhip. Initial analogical reasoning based on ‘surface similarity’ would presuppose a classic control engineering ‘source model’ consisting of a phase-lag feedback system for which it is difficult to derive the transfer function. Simulation alone would have to be relied on to mitigate the bullwhip effect. By using z-transform block diagram manipulation, the model for a single-echelon, consisting of 17 difference equations with five feedback loops is shown to have exact analogy to Burns and Sivazlian's (1978) second order system that has no feedback. Therefore, this more appropriate ‘source model’ is based on a deeper understanding of the ‘behavioral similarities’ which indicates that the bullwhip effect is not in the case of the ‘target model’ due to feedback control but due to a first-order derivative, ‘phase advance’, term in the feed forward numerator path. Hence a more appropriate ‘candidate solution’ can be found via the use of a ‘recovery’ filter. An interdisciplinary framework for exploiting control engineering block diagram manipulation, utilizing analogical reasoning, in a practical setting is presented, as is an example in a contemporary supply chain situation.
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