Bat echolocation modelling using spike kernels with Support Vector Regression

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Vehicle routing with stochastic time-dependent travel times

Assigning and scheduling vehicle routes in a stochastic time-dependent environment is a crucial management problem. The assumption that in a real-life environment everything goes according to an a priori determined static schedule is unrealistic. Our methodology builds on earlier work in which the traffic congestion is captured in an analytical way using queueing theory. The congestion is then applied to the VRP problem. In this paper, we introduce the variability in traffic flows into the model. This allows for an evaluation of the routes based on the uncertainty involved. Different experiments show that the risk taking behavior of the planner can be taken into account during optimization. As more weight is given to the variability component, the resulting optimal route will take a slightly longer travel time, but will be more reliable. We propose a powerful objective function that is easily implemented and that captures the trade-off between the average travel time and its variance. The evaluation of the solution is done in terms of the 95th-percentile of the travel time distribution (assumed to be lognormal), which reflects well the quality of the solution in this stochastic time-dependent environment

Vehicle routing with stochastic time-dependent travel times

Abstract Assigning and scheduling vehicle routes in a stochastic time-dependent environment is a crucial management problem. The assumption that in a real-life environment everything goes according to an a priori determined static schedule is unrealistic. Our methodology builds on earlier work in which the traffic congestion is captured based on queueing theory in an analytical way and applied to the VRP problem. In this paper, we introduce the variability in the traffic flows into the model. This allows for an evaluation of the routes based on the uncertainty involved. Different experiments show that the risk taking/avoiding behaviour of the planner can be taken into account during optimization. As more weight is contributed to the variability component, the resulting optimal route will be slightly slower, but more reliable. The solution quality in terms of the 95 th -percentile of the travel time distribution (assumed lognormal) will also improve

Communication breakdown: Limits of spectro-temporal resolution for the perception of bat communication calls

During vocal communication, the spectro‑temporal structure of vocalizations conveys important contextual information. Bats excel in the use of sounds for echolocation by meticulous encoding of signals in the temporal domain. We therefore hypothesized that for social communication as well, bats would excel at detecting minute distortions in the spectro‑temporal structure of calls. To test this hypothesis, we systematically introduced spectro‑temporal distortion to communication calls of Phyllostomus discolor bats. We broke down each call into windows of the same length and randomized the phase spectrum inside each window. The overall degree of spectro‑temporal distortion in communication calls increased with window length. Modelling the bat auditory periphery revealed that cochlear mechanisms allow discrimination of fast spectro‑temporal envelopes. We evaluated model predictions with experimental psychophysical and neurophysiological data. We first assessed bats’ performance in discriminating original versions of calls from increasingly distorted versions of the same calls. We further examined cortical responses to determine additional specializations for call discrimination at the cortical level. Psychophysical and cortical responses concurred with model predictions, revealing discrimination thresholds in the range of 8–15 ms randomization‑window length. Our data suggest that specialized cortical areas are not necessary to impart psychophysical resilience to temporal distortion in communication calls

Stochastic vehicle routing with random time dependent travel times subject to perturbations

Assigning and scheduling vehicle routes in a stochastic time dependent environment is a crucial management problem. The assumption that in a real-life environment everything goes according to an a priori determined static schedule is unrealistic, resulting in a planning gap (i.e. difference in performance between planned route and actual route). Our methodology introduces the traffic congestion component based on queueing theory, thereby introducing an analytical expression for the expected travel. In real life travel times are subject to uncertainty, we solve a time dependent vehicle routing problem to find robust solutions, that can potentially absorb such uncertainties. We model uncertainty as perturbations that are randomly inserted on the routes, we optimize the perturbed solutions via Tabu Search. We conduct experiments on a set of 32 cities, and found that the perturbed solutions generally cope better with the uncertainty than the non-perturbed solutions, with a small increase in expected travel times

Vehicle routing with stochastic time-dependent travel times

Abstract Assigning and scheduling vehicle routes in a stochastic timedependent environment is a crucial management problem. The assumption that in a real-life environment everything goes according to an a priori determined static schedule is unrealistic. Our methodology builds on earlier work in which the traffic congestion is captured based on queueing theory in an analytical way and applied to the V RP problem. In this paper, we introduce the variability in the traffic flows into the model. This allows for an evaluation of the routes based on the uncertainty involved. Different experiments show that the risk taking/avoiding behaviour of the planner can be taken into account during optimization. As more weight is contributed to the variability component, the resulting optimal route will take a slightly longer travel time, but be more reliable. We propose to evaluate the solution quality in terms of the 95 th -percentile of the travel time distribution (assumed lognormal) as this measure captures well the trade-off between the average travel time and its variance

Why Iranian married women use withdrawal instead of oral contraceptives? A qualitative study from Iran

<p>Abstract</p> <p>Background</p> <p>Withdrawal as a method of birth control is still used in Iran. The aim of this study was to explore married women's perspectives and attitudes on withdrawal use instead of oral contraceptive (OC) in Tehran, Iran.</p> <p>Methods</p> <p>This was a qualitative study. Participants were 50 married women, not currently pregnant, not desiring pregnancy and who had been using withdrawal for contraception. Face-to face interviews were conducted to collect data. Content analysis was performed to analyze the data.</p> <p>Results</p> <p>Four major themes were extracted from the interviews: advantages, disadvantages, barriers for OC use, and husband-related factors. Advantages of withdrawal use were identified as: easy to use, convenient, ease of access, natural. Even those participants who had experienced unwanted pregnancy while using withdrawal, relied on withdrawal as their contraceptive method. Disadvantages of OC included concerns about side effects. Barriers related to use of OC included the need for medical advice, vaginal examination and daily use. Husband-related factors included: the husband wanted to be the primary decision maker on the number of children and that he preferred withdrawal.</p> <p>Conclusion</p> <p>Health providers should address misunderstandings that exist about OC and highlight the non-contraceptive health benefits of OC to balance the information provided for women. We suggest that not only women but also their spouses be advised in family planning programs.</p