Vehicle health management using adaptive techniques

Automated engine diagnostics using cognitive computing methodologies are investigated. Space shuttle main engine vibrational data is used to test the algorithms

Scylla: a matrix-free fix-propagate-and-project heuristic for mixed-integer optimization

We introduce Scylla, a primal heuristic for mixed-integer optimization problems. It exploits approximate solves of the Linear Programming relaxations through the matrix-free Primal-Dual Hybrid Gradient algorithm with specialized termination criteria, and derives integer-feasible solutions via fix-and-propagate procedures and feasibility-pump-like updates to the objective function. Computational experiments show that the method is particularly suited to instances with hard linear relaxations

Dynamics of Ideological Biases of Social Media Users

Humanity for centuries has perfected skills of interpersonal interactions and evolved patterns that enable people to detect lies and deceiving behavior of others in face-to-face settings. Unprecedented growth of people's access to mobile phones and social media raises an important question: How does this new technology influence people's interactions and support the use of traditional patterns? In this paper, we answer this question for homophily driven patterns in social media. In our previous studies, we found that, on a university campus, changes in student opinions were driven by the desire to hold popular opinions. Here, we demonstrate that the evolution of online platform-wide opinion groups is driven by the same desire. We focus on two social media: Twitter and Parler, on which we tracked the political biases of their users. On Parler, an initially stable group of right-biased users evolved into a permanent right-leaning echo chamber dominating weaker, transient groups of members with opposing political biases. In contrast, on Twitter, the initial presence of two large opposing bias groups led to the evolution of a bimodal bias distribution, with a high degree of polarization. We capture the movement of users from the initial to final bias groups during the tracking period. We also show that user choices are influenced by side-effects of homophily. The users entering the platform attempt to find a sufficiently large group whose members hold political bias within the range sufficiently close to the new user's bias. If successful, they stabilize their bias and become a permanent member of the group. Otherwise, they leave the platform. We believe that the dynamics of users uncovered in this paper create a foundation for technical solutions supporting social groups on social media and socially aware networks.Comment: 7 pages, 4 figures, submitted to IEEE Communications Magazin

Electrophysiology of cortical spreading depression in the rat neocortex

Thesis (M.A.)--Boston UniversityCortical spreading depression (CoSD) is a reaction of the cerebral cortex to injury and neuropathology. It is comprised of self propagating waves of neuronal hyperexcitability, followed by a pronounced and lasting depression of the electrical activity. This depression travels outward from the initiation source across the surface of the brain at a rate of 2-5 mm/min and is accompanied by a shift in the direct current potential. To better understand the mechanism behind CoSD, intra-cortical electrophysiological recording techniques were used to test the hypothesis that CoSD produces a layer-specific effect on the rat cortex. A linear multi-electrode was used to examine coherent neural activity at all levels of the primary visual cortex before, during and after CoSD. In addition, evoked neural activity was assessed by the use of paired pulse stimulation to the contralateral primary visual cortex. The effect of CoSD on the frequency content of the neural signals was also investigated. Finally, current source density analysis of the evoked signal was examined to determine whether CoSD produced alterations in the location or magnitude of where the evoked currents entered (current sinks) and left (current sources) the cortical laminae. CoSD was reliably induced, but the effects were short, only lasting for the first five minutes post initiation. Immediately following the initiation of CoSD, the first peak of the evoked potential was reduced, indicating that the excitability of the cortex was reduced by CoSD. After a period of time passed, the first peak returned to baseline while the second peak increased. The paired pulse index (ratio of the amplitude of the first evoked signal to the amplitude of the second evoked signal) was highly reduced and showed a lasting effect, indicating a reduction in the evoked inhibitory tone. This reduction in inhibitory tone was accompanied by alterations in the evoked gamma and beta bands, and a reduction in the alpha, which likely contributed in part to the reduction of the first peak. The spontaneous measured frequency bands showed a selective decrease in alpha, beta and theta, whereas gamma and delta were unaffected. All these were not specific to individual cortical lamina, but occurred at every laminae. Finally, current source density analysis showed that the CoSD did not induce any immediate or lasting changes in the pattern or magnitude of the current sinks and sources. These findings show that CoSD induces highly specific changes in the cortex, but does so in a uniform manner throughout the cortical width. The paired pulse data in conjunction with the results of the frequency analysis also suggests that CoSD causes a decrease in the efficacy of the cortical inhibitory networks. Frequency analysis further suggests that CoSD is possibly associated with a functional disconnection between the cortex and the thalamus. These data are the first to show the effects of CoSD using intracortical recordings and further the understanding of CoSD

ZnMgTe/ZnTe 導波路の作製と高性能電気光学効果デバイスの開発

早大学位記番号:新7502早稲田大

LOCATION AND ROUTING PROBLEMS: A UNIFIED APPROACH

This thesis is about location and routing problems. We propose a unified algorithmic approach, based on the branch-and-cut-and-price paradigm, for the exact solution of general location and routing problems involving both costs and profits. In particular three different types of N P -hard problems are taken into account: the first is an extension, arising in the context of waste collection management, of the well studied Vehicle Routing Problem. The second is based on the Multi-Depot Vehicle Routing Problem with profits and has applications in the exploration of planetary surfaces. The last problem is about the distribution of drugs in emergency situations. For every problem a detailed description and a mathematical formulation are given. The largest part of the thesis is dedicated to the careful explanation of how our method can be efficiently implemented in every of the problems taken into account. In particular we propose new algorithmic ideas and several modifications and extensions to many procedures already presented in the literature. However, all components of our algorithms are fully presented and analyzed pointing out every methodological and practical issue. Extensive computational experiments and comparisons are carried out to evaluate the performance of our approach and the tractability of the problems addressed