A dynamic model for road protection against flooding

This paper focuses on the problem of identifying optimal protection strategies to reduce the impact of flooding on a road network. We propose a dynamic mixed-integer programming model that extends the classic concept of road network protection by shifting away from single-arc fortifications to a more general and realistic approach involving protection plans that cover multiple components. We also consider multiple disruption scenarios of varying magnitude. To efficiently solve large problem instances, we introduce a customised GRASP heuristic. Finally, we provide some analysis and insights from a case study of the Hertfordshire road network in the East of England. Results show that optimal protection strategies mainly involve safeguarding against flooding events that are small and likely to occur, whereas implementing higher protection standards are not considered cost-effective

Detection of blood aspiration in deadly head gunshots comparing postmortem computed tomography (PMCT) and autopsy

BACKGROUND: The aim of our study was to analyze the reliability of postmortem computed tomography (PMCT) versus autopsy in detecting signs of blood aspiration in a distinct group of patients following deadly head, mouth or floor of mouth gunshot injuries. METHODS: In this study, in 41 cases PMCT was compared to autopsy reports, the gold standard of postmortem exams, regarding detection of blood aspiration. PMCT was evaluated for the presence and level of typical signs of blood aspiration in the major airways and lung using a semi-quantitative scale ranging from level 0 (no aspiration) to 3 (significant aspiration) also taking density values of the described potential aspiratory changes into account. RESULTS: Overall, in 29 (70.7%) of 41 enrolled cases PMCT and autopsy revealed the same level of aspiration. A difference of one level between PMCT and autopsy resulted for 5 (12.2%) of the remaining 12 cases. More than one level difference between both methods resulted for 7 cases (17.2%). Autopsy described no signs of aspiration in 10 cases, compared to 31 cases with reported blood aspiration. In contrast, PMCT revealed no signs of blood aspiration in 15 cases whereas 26 cases were rated as positive for signs of aspiration in the major airways. In 18 of these 26 cases considered positive for blood aspiration by autopsy and PMCT, clear signs of aspiration signs were also described bilaterally by both methods. CONCLUSIONS: The presented study provides evidence for the assumption that PMCT seems to be helpful in the detection of blood aspiration in cases of deadly head gunshots. In conclusion, it seems reasonable to suggest performing PMCT additionally to traditional postmortem exams in cases of suspected aspiration to rule out false-negative cases and to possibly allow for a more detailed and rather evidence based examination reconnoitering the cause of death. However, the adequate use of PMCT in this context needs further evaluation and the definition of an objective scale for aspiration detection on PMCT needs to be established in future studies

Reliable hub network design: Formulation and solution techniques

In this paper, we investigate the issue of unreliability in hub location planning. A mixed integer nonlinear programming model is formulated for optimally locating p uncapacitated hubs, each of which can fail with a site-specific probability. The objective is to determine the location of hubs and the assignment of demand nodes to hubs in order to minimize expected demand weighted travel cost plus a penalty if all hubs fail. A linear version of the model is developed employing a specialized flow network called a probability lattice to evaluate compound probability terms. A Tabu search algorithm is proposed to find optimal to near optimal solutions for large problem instances. A parallel computing strategy is integrated into the Tabu search process to improve performance. Experimental results carried out on several benchmark instances show the efficiency of our linearized model and heuristic algorithm. Compared to a standard hub median model that disregards the potential for hub failures, our model produces solutions that serve larger numbers of customers and at lower cost per customer

Large scale local search heuristics for the Capacitated Vertex p-Center Problem

This article investigates the application of very large neighborhood search techniques for solving the capacitated vertex p-center problem. We characterize a local search neighborhood in terms of path and cyclic exchanges of customers among facilities, and exploit principles borrowed from network optimization theory to efficiently detect cost-decreasing solutions in such a neighborhood. We complement the multiexchange methodology with a relocation mechanism specifically designed to perform facility location adjustments. The validity of the proposed approach is supported by empirical investigation and performance comparisons with the commercial code CPLEX

Use of OR in earthquake operations management: A review of the literature and roadmap for future research

To reduce human losses and minimize social and economic disruption caused by large-scale earthquakes, effective planning and operational decisions need to be made by responsible agencies and institutions across all pre- and post-disaster stages. Operations Research (OR), which encompasses a broad array of quantitative and analytical methods for systematic decision making, has garnered a considerable amount of attention in the disaster operations management literature over the past few decades. The purpose of this review is to highlight and discuss main lines of research involving the use of OR techniques applied specifically to earthquakes disasters. As part of our review, we identify existing research gaps and propose a roadmap to guide future work and enhance the real-world applicability of OR to earthquake operations management. We emphasize the need for (i) developing models that are specifically tailored to earthquake operation management, including the need to contend with cascading effects and secondary disasters caused by aftershocks; (ii) greater stakeholder involvement in problem identification and methodological approach to enhance realism and adoption of OR models by practitioners; (iii) more holistic planning frameworks that combine decision making across multiple disaster stages; (iv) integration of OR methods with real- and near real-time information systems, while confronting the problem of dealing with missing and incomplete data; (v) greater use of use of multi-methodology and interdisciplinary approaches, including behavioral OR and Soft OR techniques as well as seismology and earthquake engineering expertise; and (vi) improved data generation defined at appropriate scales and better probability estimation of earthquake scenarios

Three-photon excitation of InGaN quantum dots

We demonstrate that semiconductor quantum dots can be excited efficiently in a resonant three-photon process, whilst resonant two-photon excitation is highly suppressed. Time-dependent Floquet theory is used to quantify the strength of the multi-photon processes and model the experimental results. The efficiency of these transitions can be drawn directly from parity considerations in the electron and hole wavefunctions in semiconductor quantum dots. Finally, we exploit this technique to probe intrinsic properties of InGaN quantum dots. In contrast to non-resonant excitation, slow relaxation of charge carriers is avoided which allows us to measure directly the radiative lifetime of the lowest energy exciton states. Since the emission energy is detuned far from the resonant driving laser field, polarization filtering is not required and emission with a greater degree of linear polarization is observed compared to non-resonant excitation

An integrated user-system approach for shelter location and evacuation routing

Disasters are catastrophic events that can severely affect the life conditions of entire communities. Disaster-related issues are usually dealt with according to the Disaster Operations Management framework, which is composed of four phases: mitigation, preparedness, response, and recovery. This work focuses on two crucial operations belonging to the response phase: shelter location and evacuation of endangered populations. Specifically, the ultimate scope of this paper is to present some applications of a scenario-based mixed-integer two-stage linear program which integrates shelter location with two different types of evacuation, self- (or car-based) evacuation and supported- (or bus-based) evacuation, namely the Scenario-Indexed Shelter Location and Evacuation Routing (SISLER) model. The SISLER model is solved using an off-the-shelf optimization software, whose performance is improved through the addition of some valid inequalities which are added at the root node of the solution tree to improve the lower bound. Computational results are reported for both testbed instances and a realistic case study (Sioux Falls network). The analysis of the solutions provides some useful managerial insights for relevant stakeholders working within the shelter location and evacuation planning area, such as emergency management practitioners and public service providers

Postmortem computed tomography (PMCT) and autopsy in deadly gunshot wounds--a comparative study.

Postmortem computed tomography (PMCT) data in gunshot-related death were evaluated by two reader groups and compared to the gold standard autopsy for the determination of forensic pathology criteria. Reader group I consisted of two board-certified radiologists whereas one board-certified radiologist and one board-certified forensic pathologist formed group II. PMCT data of 51 gunshot-related deaths were evaluated for the forensic pathology criteria number of gun shots, localization of gunshot injury, caliber, and direction of the gunshot differentiating between entry and exit wound as well as associated injury to surrounding tissue. The results of both reader groups were compared to the each other and to autopsy findings considered as gold standard. Reader groups I and II and as gold standard the autopsy evaluation showed in general a good correlation between all results. The overall discrepancy rate was 12/51 (23.4%) cases for group I and 8/51 (15.6%) for group II. Ultimately, the designated reader is able to draw the following conclusion from the presented data. At first, physical autopsy is better than PMCT regarding the localization of most gunshot injuries. Second, PMCT presents with better results than physical autopsy in locating fragmented bullets/fragment clouds, and finally, PMCT results of two radiologists were equivalent to the results of one evaluating radiologist and one pathologist with the exception of caliber assessment. However, referring to the pure numbers, the slight but not significant difference in the overall discrepancy rate of both reader groups might indicate the advantage of combining expertise in evaluating imaging in cases of gunshot-related death