967 research outputs found
The Swedish crime paradox : A brief on challenges posed by organised crime in Sweden
No full textIn this policy brief, based on published and forthcoming studies, author Amir Rostami outlines the changing nature of crime in Sweden, with a focus on organised crime, specifically lethal violence and fraud. What are the lessons learned from the Swedish crime paradox, namely the rise in organised crime, but not an equivalent rise in general crime, and what needs to be implemented to counter organised crime? The reaction to the question can be divided into two components: local and global.</p
A convex reformulation and an outer approximation for a large class of binary quadratic programs
No full textIn this paper, we propose a general modeling and solving framework for a large class of binary quadratic programs subject to variable partitioning constraints. Problems in this class have a wide range of applications as many binary quadratic programs with linear constraints can be represented in this form. By exploiting the structure of the partitioning constraints, we propose mixed-integer nonlinear programming (MINLP) and mixedinteger linear programming (MILP) reformulations and show the relationship between the two models in terms of the relaxation strength. Our solution methodology relies on a convex reformulation of the proposed MINLP and a branch-and-cut algorithm based on outer approximation cuts, in which the cuts are generated on the fly by efficiently solving separation subproblems. To evaluate the robustness and efficiency of our solution method, we perform extensive computational experiments on various quadratic combinatorial optimization problems. The results show that our approach outperforms the state-of-the-art solver applied to different MILP reformulations of the corresponding problems
Supplemental Material, supporting_information - Insight into the structure of polystyrene-poly(methyl methacrylate) core-shell particles synthesized by seeded suspension polymerization
No full textSupplemental Material, supporting_information for Insight into the structure of polystyrene-poly(methyl methacrylate) core-shell particles synthesized by seeded suspension polymerization by H Rostami, F Abbasi, K Jalili, E Mehravar and M Najafpour in Polymers and Polymer Composites</p
Branch-price-and-cut algorithms for the vehicle routing problem with stochastic and correlated travel times
No full textIn this paper, we consider a version of the capacitated vehicle routing problem (CVRP) where travel times are assumed to be uncertain and statistically correlated (CVRP-SCT). In particular, we suppose that travel times follow a multivariate probability distribution whose first and second moments are known. The main purpose of the CVRPCST is to plan vehicle routes whose travel times are reliable, in the sense that observed travel times are not excessively dispersed with respect to their expected value. To this scope we adopt a mean-variance approach, where routes with high travel time variability are penalized. This leads to a parametric binary quadratic program for which we propose two alternative set partitioning reformulations and show how to exploit the structure of the correlation matrix when there is correlation only between adjacent links. For each model, we develop an exact branch-price-and-cut algorithm, where the quadratic component is dealt with either in the column generation master problem or in its subproblem. We tested our algorithms on a rich collection of instances derived from well-known data sets. Computational results show that our algorithms can efficiently solve problem instances with up to 75 customers. Furthermore, the obtained solutions significantly reduce the time variability when compared with standard CVRP solutions. Copyright
Supporting model data for Paleogeographic controls on the evolution of Late Cretaceous ocean circulation by Ladant, J.-B., et al. in Climate of the Past, doi:10.5194/cp-2019-157.
No full textThe dataset is comprised of CCSM4 model variables required to reproduce the figures shown in the following manuscript:
Ladant, J.-B., C. J. Poulsen, F. Fluteau, C. R. Tabor, K. G. MacLeod, E. E. Martin, S. J. Haynes and M. A. Rostami, Paleogeographic controls on the evolution of Late Cretaceous ocean circulation, Climate of the Past, doi:10.5194/cp-2019-157
Traumatic brain injury in humans and animal models
No full textTraumatic brain injuries (TBI) are receiving increasing attention due to a combination of injuries related to war and sports, as well as to an increasing number of traffic accident survivors. Today the leading cause of death in young adults in industrialized nations is traumatic brain injury and in the population under 35 years, the death rate is 3.5 times that of cancer and heart disease combined. Despite a major improvement in the outcome of TBI in the acute setting, the assessment, therapeutic interventions and prevention of long-term complications remain a challenge. The challenges today are primarily related to a rapid diagnosis, identification of patient’s pathophysiological heterogeneity and to limit the secondary injuries. TBI is a complex condition that can be caused by focal or diffuse primary impacts that may initiate complex secondary neurochemical processes that proceeds over hours and days. The major secondary events include neuronal death, ischemia, excitotoxicity, mitochondrial failure, oxidative stress, oedema and inflammation. In addition, the brain’s restorative capacity involving neurotrophins, in particular brain derived neurotrophic factor (BDNF), is triggered. Animal models are necessary to gain a deeper insight into the events that follow a TBI, and to ultimately apply the findings to the clinical setting.The aim of this thesis was to identify distinct pathological processes in different types of TBI by using animal models that mimic distinct types of TBI found in patients. We investigated alterations in gene expression, serum biomarkers and secondary processes such as inflammatory response involving the complement cascade. In addition we aimed to assess the effects of heterogeneity of TBI patients, based on their genetic background, on the outcome of TBI, with specific focus on BDNF. We used animal models to mimic three major types of TBI; blast wave, penetrating and rotational acceleration TBI. We found distinct profiles of alteration in gene expression in these models. The histological findings in blast and rotational TBI indicated these injuries to be mild. The hallmark of the rotational TBI was axonal injuries found in anatomical locations comparable with clinical findings in diffuse axonal injuries (DAI) in humans. Despite the mild type of injury displayed in the histology and behavioural outcome, significant increases in the serum biomarkers Tau, S100B, NF-H and MBP were observed up to 2 weeks following the injury. The complement cascade was initiated in both penetrating and rotational TBI, detected by C1q and C3. However, the terminal pathway that generates cell death, detected by C5b9, was only activated in the penetrating TBI. This suggests that axonal injuries and secondary axotomy found in the rotational TBI are not complement mediated. In order to investigate whether genetic heterogeneity can be used to predict injury outcome and brain plasticity following TBI, we targeted the ApoE ε4 allele and the BDNF gene. We investigated whether there was an association between the presence of the ApoE ε4 allele and BDNF polymorphisms and cognitive outcome in veterans who had suffered penetrating head injury. We found that the genetic polymorphisms of BDNF predict general intelligence following penetrating TBI. Subsequently we investigated the expression of BDNF and its receptors TrkB-full length, TrkB-truncated and p75NTR, in animals exposed to penetrating TBI. The expression of TrkB truncated and p75NTR was altered in the chronic phase.In summary, these results show the importance of categorizing the different types of TBI, not only through the use of animal models but also in the clinical setting. Each type of TBI shows distinct patterns of gene expression, behavioural outcome, and morphological changes that may be reflected in the release of serum biomarkers. In the clinical setting, the situation is further complicated by the coexistence of different types of injuries. In addition to this, the genetic background of each patient contributes to the heterogeneity of TBI pathology as well as their ability to recover. The use of distinct types of TBI models will provide essential information about the underlying pathology, which can then be applied to the clinical setting. This will contribute to the establishment of better diagnostic tools as well as more individualized treatment approaches.List of scientific papersI. Risling M, Plantman S, Angeria M, Rostami E, Bellander BM, Kirkegaard M, Arborelius U, Davidsson J. Mechanisms of blast induced brain injuries, experimental studies in rats. Neuroimage. 2011 Jan; 54 Suppl 1:S89-97. Epub 2010 May 21. https://doi.org/10.1016/j.neuroimage.2010.05.031 II. Rostami E, Davidsson J, Ng KC, Lu J, Gyorgy A, Wingo D, Walker J, Plantman S, Bellander BM, Agoston D, Risling M. A model for mild traumatic brain injury that induces limited transient memory impairment and increased levels of axon related serum biomarkers. Front Neurol. 2012; 3:115. Epub 2012 Jul 23. https://doi.org/10.3389/fneur.2012.00115 III. Rostami E, Davidsson J, Agoston DV, Gyorgy A, Risling M, Bellander BM. The complement terminal pathway is activated in focal penetrating but not in mild diffuse Traumatic Brain Injury. [Submitted]IV. Rostami E, Krueger F, Zoubak S, Dal Monte O, Raymont V, Pardini M, Hodgkinson CA, Goldman D, Risling M, Grafman J. BDNF polymorphism predicts general intelligence after penetrating traumatic brain injury. PLoS ONE. 2011; 6(11):e27389. Epub 2011 Nov 8. https://doi.org/10.1371/journal.pone.0027389 V. Rostami E, Krueger F, Plantman S, Davidsson J, Agoston DV, Grafman J, Risling M. Alteration in BDNF and its receptors, full-length and truncated TrkB and p75NTR following penetrating traumatic brain injury. [Submitted]</p
Deep reinforcement learning and fuzzy logic controller codesign for energy management of hydrogen fuel cell powered electric vehicles
No full textAbstract Hydrogen-based electric vehicles such as Fuel Cell Electric Vehicles (FCHEVs) play an important role in producing zero carbon emissions and in reducing the pressure from the fuel economy crisis, simultaneously. This paper aims to address the energy management design for various performance metrics, such as power tracking and system accuracy, fuel cell lifetime, battery lifetime, and reduction of transient and peak current on Polymer Electrolyte Membrane Fuel Cell (PEMFC) and Li-ion batteries. The proposed algorithm includes a combination of reinforcement learning algorithms in low-level control loops and high-level supervisory control based on fuzzy logic load sharing, which is implemented in the system under consideration. More specifically, this research paper establishes a power system model with three DC-DC converters, which includes a hierarchical energy management framework employed in a two-layer control strategy. Three loop control strategies for hybrid electric vehicles based on reinforcement learning are designed in the low-level layer control strategy. The Deep Deterministic Policy Gradient with Twin Delayed (DDPG TD3) is used with a network. Three DRL controllers are designed using the hierarchical energy optimization control architecture. The comparative results between the two strategies, Deep Reinforcement Learning and Fuzzy logic supervisory control (DRL-F) and Super-Twisting algorithm and Fuzzy logic supervisory control (STW-F) under the EUDC driving cycle indicate that the proposed model DRL-F can ensure the Root Mean Square Error (RMSE) reduction for 21.05% compared to the STW-F and the Mean Error reduction for 8.31% compared to the STW-F method. The results demonstrate a more robust, accurate and precise system alongside uncertainties and disturbances in the Energy Management System (EMS) of FCHEV based on an advanced learning method
Performance analysis of FAS-aided NOMA-ISAC: a backscattering scenario
No full textThis paper investigates a two-user downlink system for integrated sensing and communication (ISAC) in which the two users deploy a fluid antenna system (FAS) and adopt the non-orthogonal multiple access (NOMA) strategy. Specifically, the integrated sensing and backscatter communication (ISABC) model is considered, where a dual-functional base station (BS) serves to communicate the two users and sense a tag’s surrounding. In contrast to conventional ISAC, the backscattering tag reflects the signals transmitted by the BS to the NOMA users and enhances their communication performance. Furthermore, the BS extracts environmental information from the same backscatter signal in the sensing stage. Firstly, we derive closed-form expressions for both the cumulative distribution function (CDF) and probability density function (PDF) of the equivalent channel at the users utilizing the moment matching method and the Gaussian copula. Then in the communication stage, we obtain closed-form expressions for both the outage probability and for the corresponding asymptotic expressions in the high signal-to-noise ratio (SNR) regime. Moreover, using numerical integration techniques such as the Gauss-Laguerre quadrature (GLQ), we have series-form expressions for the user ergodic communication rates (ECRs). In addition, we get a closed-form expression for the ergodic sensing rate (ESR) using the Cramér-Rao lower bound (CRLB). Finally, the accuracy of our analytical results is validated numerically, and we confirm the superiority of employing FAS over traditional fixed-position antenna systems in both ISAC and ISABC
Fluid antenna-aided rate-splitting multiple access
No full textThis letter considers a fluid antenna system (FAS)-aided rate-splitting multiple access (RSMA) approach for downlink transmission. In particular, a base station (BS) equipped with a single traditional antenna system (TAS) uses RSMA signaling to send information to several mobile users (MUs) each equipped with FAS. To understand the achievable performance, we first present the distribution of the equivalent channel gain based on the joint multivariate t-distribution and then derive a compact analytical expression for the outage probability (OP). Moreover, we obtain the asymptotic OP in the high signal-to-noise ratio(SNR) regime. Numerical results show that combining FAS with RSMA significantly outperforms TAS and conventional multiple access schemes, such as non-orthogonal multiple access (NOMA),in terms of OP. The results also indicate that FAS can be the tool that greatly improves the practicality of RSMA
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