| 1. |
- Bernard, Olivier, et al.
(författare)
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Standardized evaluation system for left ventricular segmentation algorithms in 3D echocardiography.
- 2016
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Ingår i: IEEE Transactions on Medical Imaging. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0062 .- 1558-254X. ; 35:4, s. 967-977
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Tidskriftsartikel (refereegranskat)abstract
- Real-time 3D Echocardiography (RT3DE) has been proven to be an accurate tool for left ventricular (LV) volume assessment. However, identification of the LV endocardium remains a challenging task, mainly because of the low tissue/blood contrast of the images combined with typical artifacts. Several semi and fully automatic algorithms have been proposed for segmenting the endocardium in RT3DE data in order to extract relevant clinical indices, but a systematic and fair comparison between such methods has so far been impossible due to the lack of a publicly available common database. Here, we introduce a standardized evaluation framework to reliably evaluate and compare the performance of the algorithms developed to segment the LV border in RT3DE. A database consisting of 45 multivendor cardiac ultrasound recordings acquired at different centers with corresponding reference measurements from 3 experts are made available. The algorithms from nine research groups were quantitatively evaluated and compared using the proposed online platform. The results showed that the best methods produce promising results with respect to the experts' measurements for the extraction of clinical indices, and that they offer good segmentation precision in terms of mean distance error in the context of the experts' variability range. The platform remains open for new submissions.
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| 2. |
- Ahmadi, K., et al.
(författare)
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Inducing Dzyaloshinskii-Moriya interaction in symmetrical multilayers using post annealing
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial Dzyaloshinskii-Moriya Interaction (iDMI) is an antisymmetric exchange interaction that is induced by the broken inversion symmetry at the interface of, e.g., a ferromagnet/heavy metal. Thus, the presence of iDMI is not expected in symmetrical multilayer stacks of such structures. Here, we use thermal annealing to induce the iDMI in a [Py/Pt](x10) symmetrical multilayer stack. Brillouin light scattering spectroscopy is used to directly evidence the iDMI induction in the annealed sample. Structural characterizations highlight the modified crystallinity as well as a higher surface roughness of the sample after annealing. First principles electronic structure calculations demonstrate a monotonic increase of the iDMI with the interfacial disorder due to the interdiffusion of atoms, depicting the possible origin of the induced iDMI. The presented method can be used to tune the iDMI strength in symmetric multilayers, which are the integral part of racetrack memories, magnonic devices as well as spin-orbitronic elements.
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| 3. |
- Alimadadi, Hossein, 1983, et al.
(författare)
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Corrosion properties of electrodeposited nanocrystalline and amorphous patterned Ni-W alloy
- 2009
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Ingår i: MATERIALS & DESIGN. - : Elsevier BV. - 0261-3069 .- 0264-1275 .- 1873-4197. ; 30:4, s. 1356-1361
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Tidskriftsartikel (refereegranskat)abstract
- Nickel-tungsten with satisfactory corrosion properties is a promising alloy to replace hard chromium. Relatively high adhesion between copper substrate and electrodeposited Ni-W alloy results in patterned morphology due to crack formation. In this work, corrosion resistance of patterned Ni-W alloys comprising 0-26 at.%.W were studied by potentiodynamic polarization and EIS in a medium containing Cl-. It is shown that corrosion resistance of single phase Ni-W is superior to amorphous and dual phase coated layers. It is also found that crack density is the dominant affecting factor on corrosion resistance of amorphous Ni-W alloys.
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| 4. |
- Gaur, A.P.S., et al.
(författare)
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Surface Energy Engineering for Tunable Wettability through Controlled Synthesis of MoS2
- 2014
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:8, s. 4314-4321
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Tidskriftsartikel (refereegranskat)abstract
- MoS2 is an important member of the transition metal dichalcogenides that is emerging as a potential 2D atomically thin layered material for low power electronic and optoelectronic applications. However, for MoS2 a critical fundamental question of significant importance is how the surface energy and hence the wettability is altered at the nanoscale in particular, the role of crystallinity and orientation. This work reports on the synthesis of large area MoS2 thin films on insulating substrates (SiO2/Si and Al2O3) with different surface morphology via vapor phase deposition by varying the growth temperatures. The samples were examined using transmission electron microscopy and Raman spectroscopy. From contact angle measurements, it is possible to correlate the wettability with crystallinity at the nanoscale. The specific surface energy for few layers MoS2 is estimated to be about 46.5 mJ/m2. Moreover a layer thickness-dependent wettability study suggests that the lower the thickness is, the higher the contact angle will be. Our results shed light on the MoS2–water interaction that is important for the development of devices based on MoS2 coated surfaces for microfluidic applications.
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| 5. |
- Ahmadi Achachlouei, Mohammad, 1981-
(författare)
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Exploring the Effects of ICT on Environmental Sustainability: From Life Cycle Assessment to Complex Systems Modeling
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The production and consumption of information and communication technology (ICT) products and services continue to grow worldwide. This trend is accompanied by a corresponding increase in electricity use by ICT, as well as direct environmental impacts of the technology. Yet a more complicated picture of ICT’s effects is emerging. Positive indirect effects on environmental sustainability can be seen in substitution and optimization (enabling effects), and negative indirect effects can be seen in additional demand due to efficiency improvements (rebound effects).A variety of methods can be employed to model and assess these direct and indirect effects of ICT on environmental sustainability. This doctoral thesis explores methods of modeling and assessing environmental effects of ICT, including electronic media. In a series of five studies, three methods were at times applied in case studies and at others analyzed theoretically. These methods include life cycle assessment (LCA) and complex systems modeling approaches, including System Dynamics (SD) and agent-based (AB) modeling.The first two studies employ the LCA approach in a case study of an ICT application, namely, the tablet edition of a Swedish design magazine. The use of tablets has skyrocketed in recent years, and this phenomenon has been little studied to date. Potential environmental impacts of the magazine’s tablet edition were assessed and compared with those of the print edition. The tablet edition’s emerging version (which is marked by a low number of readers and low reading time per copy) resulted in higher potential environmental impacts per reader than did the print edition. However, the mature tablet edition (with a higher number of readers and greater reading time per copy) yielded lower impacts per reader in half the ten impact categories assessed.While previous studies of electronic media have reported that the main life-cycle contributor to environmental impacts is the use phase (which includes operational electricity use as well as the manufacture of the electronic device), the present study did not support those findings in all scenarios studied in this thesis. Rather, this study found that the number of readers played an important role in determining which life-cycle phase had the greatest impacts. For the emerging version, with few readers, content production was the leading driver of environmental impacts. For the mature version, with a higher number of readers, electronic storage and distribution were the major contributors to environmental impacts. Only when there were many readers but low overall use of the tablet device was the use phase the main contributor to environmental impacts of the tablet edition of the magazine.The third study goes beyond direct effects at product- and service-level LCAs, revisiting an SD simulation study originally conducted in 2002 to model indirect environmental effects of ICT in 15 European countries for the period 2000-2020. In the current study, three scenarios of the 2002 study were validated in light of new empirical data from the period 2000–2012. A new scenario was developed to revisit the quantitative and qualitative results of the original study. The results showed, inter alia, that ICT has a stimulating influence on total passenger transport, for it makes it more cost- and time-efficient (rebound effects).The modeling mechanism used to represent this rebound effect is further investigated in the fourth study, which discusses the feedback loops used to model two types of rebound effects in passenger transport (direct economic rebound and time rebound). Finally, the role of systems thinking and modeling in conceptualizing and communicating the dynamics of rebound effects is examined.The aim of the fifth study was to explore the power of systems modeling and simulation to represent nonlinearities of the complex and dynamic systems examined elsewhere in this thesis. That study reviews previous studies that have compared the SD and AB approaches and models, summarizing their purpose, methodology, and results, based on certain criteria for choosing between SD and AB approaches. The transformation procedure used to develop an AB model for purposes of comparison with an SD model is also explored.In conclusion, first-order or direct environmental effects of ICT production, use, and disposal can be assessed employing an LCA method. This method can also be used to assess second-order or enabling effects by comparing ICT applications with conventional alternatives. However, the assessment of enabling effects can benefit from systems modeling methods, which are able to formally describe the drivers of change, as well as the dynamics of complex social, technical, and environmental systems associated with ICT applications. Such systems methods can also be used to model third-order or rebound effects of efficiency improvements by ICT.
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| 6. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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Modeling the Effects of ICT on Environmental Sustainability : Revisiting a System Dynamics Model Developed for the European Commission
- 2015
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Ingår i: ICT Innovations for Sustainability. - Switzerland : Springer Publishing Company. - 9783319092270 - 9783319092287 ; , s. 449-474
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Bokkapitel (refereegranskat)abstract
- This chapter revisits a System Dynamics model developed in 2002 with the aim of exploring the future impacts of Information and Communication Technology (ICT) on environmental sustainability in the EU, which then consisted of 15 countries. The time horizon of the study was 20 years (2000–2020). We analyze the results in light of empirical data that is now available for 2000–2012. None of the three scenarios that were developed by experts to specify the external factors needed to run the model were realistic from today’s point of view. If the model is re-run with more realistic input data for the first half of the simulation period, however, the main results regarding the impact of ICT remain qualitatively the same; they seem to be relatively robust implications of the causal system structure, as it is represented in the model. Overall, the impacts of ICT for mitigating greenhouse gas emissions and other environmental burdens for 2020 tend to be slightly stronger if the simulation is based on the empirical data now available.
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| 7. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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Modelling Rebound Effects in System Dynamics
- 2014
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Ingår i: Proceedings of the 28th Conference on Environmental Informatics - EnviroInfo 2014 - ICT for Energy Efficiency. - Germany : BIS Oldenburg. - 9783814223179
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Konferensbidrag (refereegranskat)abstract
- The induction of demand by increasing the efficiency of a production or consumption process is known as the rebound effect. Feedback loops in System Dynamics can be used to conceptualize the structure of this complex phenomenon and also for communicating model-based insights. In passenger transport, the rebound effect can be induced through increased cost efficiency (direct economic rebound) and/or increase in speed (time rebound). In this paper we review and compare two models on environmental effects of passenger transport—including a model on the role of information and communication technology. We highlight the feedback mechanisms used to deal with the rebound effect (price, efficiency, and time rebound).
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| 8. |
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| 9. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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System Dynamics vs. agent-based modeling—comparing models and approaches : A literature review and a transformation procedure
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Systems modeling and simulation methods such as System Dynamics (SD) and agent-based (AB) modeling have been used to foster a better understanding of the dynamics and complexity of natural, technical, and social systems. System Dynamics provides an aggregate-level perspective, highlighting thinking in feedback loops and employing differential equations to model the causal relations in a system, exploring the system's dynamics by numerically solving the equations. Agent-based modeling, in a bottom-up method, focuses on constituent units (agents) and their interactions to explore the emerging behavior at a system level by means of simulation. Comparing these modeling methods can help us understand their strengths and weaknesses in order to choose the right approach for a given modeling problem. It may also support the analysis of a given system to build multiple models using the different approaches and comparing them, in particular to treat fundamental uncertainties in systems modeling and simulation. In this paper, we review the existing studies comparing the SD and AB approaches and models, investigating the aims, methodology, and results of such comparative studies. We also highlight lessons learned for future model comparisons by examining how the corresponding SD and AB models are built for the purpose of comparison. A procedure for transforming System Dynamics models into agent-based models is presented and discussed using examples from the literature.
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| 10. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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Using Systems Thinking and System Dynamics Modeling to Understand Rebound Effects
- 2016
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Ingår i: Advances And New Trends In Environmental And Energy Informatics. - Cham, Switzerland : Springer Publishing Company. - 9783319234557 - 9783319234540 ; , s. 237-255
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Bokkapitel (refereegranskat)abstract
- Processes leading to an increase of demand for a resource as a consequence of increasing the efficiency of using this resource in production or consumption are known as (direct) rebound effects. Rebound effects at micro and macro levels tend to offset the reduction in resource consumption enabled by progress in efficiency. Systems thinking and modeling instruments such as causal loop diagrams and System Dynamics can be used to conceptualize the structure of this complex phenomenon and also to communicate model-based insights. In passenger transport, the rebound effect can be invoked by increased cost efficiency (direct economic rebound) and/or increase in speed (time rebound). In this paper we review and compare two existing models on passenger transport—including a model on the role of information and communication technology—with regard to the feedback loops used to conceptualize rebound effects.
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