Damage detection in beams

Identification of crack location and depth in structural elements such as beams, columns, and slabs, etc., subjected to time varying loads will help them to retrofit before failure thereby its life and structural capabilities can be greatly improved. It is not always possible to detect the initial cracks by visual inspection. Laboratory test results of isotropic simply supported beam and Cantilever beams with different crack location and crack depths data are collected from literatures as in terms of system natural frequencies and crack locations for single crack and multi cracks. Different models are developed for crack detention using Natural frequencies as Input and Crack Depth and locations as Output. At first an attempt made for simply supported beam having a Single crack detection using Artificial Neural Network (ANN) Model. Different ANN models are developed using different training functions and found Levenberg-Marquartd (LM) fits best among others which is evaluated in terms of R-square value. The Comparison has been made between developed ANN models and regression models. It shows that the ANN models can perform well than regression models. Further the simple equation has been presented for evaluation of crack depth based on the performance of the models developed. Secondly, the problem involves detection of multi crack damage in a Cantilever beam using ANN Model and Response Surface Method (RSM). To achieve better results in RSM higher degree equation is used. The final performances of each model are evaluated in terms of R- value. And, it is found that ANN fits the equation reasonably good. Crack Depth and Crack location can be detected using ANN approaches which may be helpful in retrofitting the structures

Optimal Attack against Cyber-Physical Control Systems with Reactive Attack Mitigation

This paper studies the performance and resilience of a cyber-physical control system (CPCS) with attack detection and reactive attack mitigation. It addresses the problem of deriving an optimal sequence of false data injection attacks that maximizes the state estimation error of the system. The results provide basic understanding about the limit of the attack impact. The design of the optimal attack is based on a Markov decision process (MDP) formulation, which is solved efficiently using the value iteration method. Using the proposed framework, we quantify the effect of false positives and mis-detections on the system performance, which can help the joint design of the attack detection and mitigation. To demonstrate the use of the proposed framework in a real-world CPCS, we consider the voltage control system of power grids, and run extensive simulations using PowerWorld, a high-fidelity power system simulator, to validate our analysis. The results show that by carefully designing the attack sequence using our proposed approach, the attacker can cause a large deviation of the bus voltages from the desired setpoint. Further, the results verify the optimality of the derived attack sequence and show that, to cause maximum impact, the attacker must carefully craft his attack to strike a balance between the attack magnitude and stealthiness, due to the simultaneous presence of attack detection and mitigation

Modeling and Detecting False Data Injection Attacks against Railway Traction Power Systems

Modern urban railways extensively use computerized sensing and control technologies to achieve safe, reliable, and well-timed operations. However, the use of these technologies may provide a convenient leverage to cyber-attackers who have bypassed the air gaps and aim at causing safety incidents and service disruptions. In this paper, we study false data injection (FDI) attacks against railways' traction power systems (TPSes). Specifically, we analyze two types of FDI attacks on the train-borne voltage, current, and position sensor measurements - which we call efficiency attack and safety attack -- that (i) maximize the system's total power consumption and (ii) mislead trains' local voltages to exceed given safety-critical thresholds, respectively. To counteract, we develop a global attack detection (GAD) system that serializes a bad data detector and a novel secondary attack detector designed based on unique TPS characteristics. With intact position data of trains, our detection system can effectively detect the FDI attacks on trains' voltage and current measurements even if the attacker has full and accurate knowledge of the TPS, attack detection, and real-time system state. In particular, the GAD system features an adaptive mechanism that ensures low false positive and negative rates in detecting the attacks under noisy system measurements. Extensive simulations driven by realistic running profiles of trains verify that a TPS setup is vulnerable to the FDI attacks, but these attacks can be detected effectively by the proposed GAD while ensuring a low false positive rate.Comment: IEEE/IFIP DSN-2016 and ACM Trans. on Cyber-Physical System

Convex Hulls under Uncertainty

We study the convex-hull problem in a probabilistic setting, motivated by the need to handle data uncertainty inherent in many applications, including sensor databases, location-based services and computer vision. In our framework, the uncertainty of each input site is described by a probability distribution over a finite number of possible locations including a \emph{null} location to account for non-existence of the point. Our results include both exact and approximation algorithms for computing the probability of a query point lying inside the convex hull of the input, time-space tradeoffs for the membership queries, a connection between Tukey depth and membership queries, as well as a new notion of \some-hull that may be a useful representation of uncertain hulls

N=1 Non-Abelian Tensor Multiplet in Four Dimensions

We carry out the N=1 supersymmetrization of a physical non-Abelian tensor with non-trivial consistent couplings in four dimensions. Our system has three multiplets: (i) The usual non-Abelian vector multiplet (VM) (A_\mu{}^I, \lambda^I), (ii) A non-Abelian tensor multiplet (TM) (B_{\mu\nu}{}^I, \chi^I, \varphi^I), and (iii) A compensator vector multiplet (CVM) (C_\mu{}^I, \rho^I). All of these multiplets are in the adjoint representation of a non-Abelian group G. Unlike topological theory, all of our fields are propagating with kinetic terms. The C_\mu{}^I-field plays the role of a Stueckelberg compensator absorbed into the longitudinal component of B_{\mu\nu}{}^I. We give not only the component lagrangian, but also a corresponding superspace reformulation, reconfirming the total consistency of the system. The adjoint representation of the TM and CVM is further generalized to an arbitrary real representation of general SO(N) gauge group. We also couple the globally N=1 supersymmetric system to supergravity, as an additional non-trivial confirmation.Comment: 18 pages, no figur

Hysteresis Models for Steel Members Subjected to Cyclic Buckling or Cyclic End Moments and Buckling (User's Guide for Drain-2d:EL9 and EL10)

https://deepblue.lib.umich.edu/bitstream/2027.42/154132/1/39015094008078.pd

Symbiotic Organisms Search Optimization to Predict Optimal Thread Count for Multi-threaded Applications

Multicore systems have emerged as a cost-effective option for the growing demands for high-performance, low-energy computing. Thread management has long been a source of concern for developers, as overheads associated with it reduce the overall throughput of the multicore processor systems. One of the most complex problems with multicore processors is determining the optimal number of threads for the execution of multithreaded programs. To address this issue, this paper proposes a novel solution based on a modified symbiotic organism search (MSOS) algorithm which is a bio-inspired algorithm used for optimization in various engineering domains. This technique uses mutualism, commensalism and parasitism behaviours seen in organisms for searching the optimal solutions in the available search space. The algorithm is simulated on the NVIDIA DGX Intel-Xeon E5-2698-v4 server with PARSEC 3.0 benchmark suit.  The results show that keeping the thread count equal to the number of processors available in the system is not necessarily the best strategy to get maximum speedup when running multithreaded programs. It was also observed that when programs are run with the optimal thread count, the execution time is substantially decreased, resulting in energy savings due to the use of fewer processors than are available in the system

Cost-Benefit Analysis of Moving-Target Defense in Power Grids

We study moving-target defense (MTD) that actively perturbs transmission line reactances to thwart stealthy false data injection (FDI) attacks against state estimation in a power grid. Prior work on this topic has proposed MTD based on randomly selected reactance perturbations, but these perturbations cannot guarantee effective attack detection. To address the issue, we present formal design criteria to select MTD reactance perturbations that are truly effective. However, based on a key optimal power flow (OPF) formulation, we find that the effective MTD may incur a non-trivial operational cost that has not hitherto received attention. Accordingly, we characterize important tradeoffs between the MTD's detection capability and its associated required cost. Extensive simulations, using the MATPOWER simulator and benchmark IEEE bus systems, verify and illustrate the proposed design approach that for the first time addresses both key aspects of cost and effectiveness of the MTD.Comment: IEEE/IFIP International Conference on Dependable Systems and Networks (DSN) - 201

The hnRNP A1 homolog Hrp36 is essential for normal development, female fecundity, omega speckle formation and stress tolerance in Drosophila melanogaster

Hrp36/Hrb87F is one of the most abundant and well-characterized hnRNP A homolog in Drosophila and is shown to have roles in regulation of alternative splicing, heterochromatin formation, neurodegeneration, etc. Yet, hrp36 null individuals were reported to be viable and without any apparent phenotype, presumably because of overlapping functions provided by Hrp38 and related proteins. Here we show that loss of both copies of hrp36 gene slows down development with significant reduction in adult life span, decreased female fecundity and high sensitivity to starvation and thermal stresses. In the absence of Hrp36, the nucleoplasmic omega speckles are nearly completely disrupted. The levels of nuclear matrix protein Megator and the chromatin remodeller ISWI are significantly elevated in principal cells of larval Malpighian tubules, which also display additional endoreplication cycles and good polytene chromosomes. We suggest that besides the non-coding hsr omega-n transcripts, the Hrp36 protein is also a core constituent of omega speckles. The heat-shock-induced association of other hnRNPs at the hsr omega locus is affected in hrp36 null cells, which may be one of the reasons for their high sensitivity to cell stress. Therefore, in spite of the functional redundancy provided by Hrp38, Hrp36 is essential for normal development and for survival under conditions of stress

Satisfação do cliente em relação aos serviços hoteleiros: uma revisão sistemática e uma agenda de pesquisa

In the highly competitive world, the hotel industry's success depends on the quality of services they provide, which gives wow feelings and high customer satisfaction. Many researchers have tried to assess customer satisfaction towards hotel services by proposing different models. Hence, the present study attempts to identify the influencing factors for determining customer satisfaction towards hotel services by conducting a systematic literature review. During the search process, 457 articles were obtained from the Web of Science database, and after filtration, 91 articles were used for further analysis. The result revealed that the top six influential factors affecting customer satisfaction towards hotel services are empathy, assurance, reliability, responsiveness, tangibility, and green practices. If customers are satisfied, they will be motivated to revisit, spread positive word of mouth, and build loyalty. Moreover, the results identified that the USA, Malaysia, and China are the leading countries in this field. This study provides an extensive literature review, which otherwise is an unexplored area so far, which offers valuable insight for the hotel service providers to improve their services and also to the researchers and academicians to develop and propose new theories.En un mundo altamente competitivo, el éxito de la industria hotelera depende de la calidad de los servicios que brinda, lo que genera sensaciones asombrosas y una alta satisfacción del cliente. Muchos investigadores han intentado evaluar la satisfacción del cliente hacia los servicios hoteleros proponiendo diferentes modelos. Por lo tanto, el presente estudio intenta identificar los factores que influyen en la determinación de la satisfacción del cliente hacia los servicios hoteleros mediante la realización de una revisión sistemática de la literatura. Durante el proceso de búsqueda, se obtuvieron 457 artículos en la base de datos Web of Science y, después de la filtración, se utilizaron 91 artículos para un análisis posterior. El resultado reveló que los seis factores principales que influyen en la satisfacción del cliente hacia los servicios hoteleros son la empatía, la garantía, la confiabilidad, la capacidad de respuesta, la tangibilidad y las prácticas sostenibles. Si los clientes están satisfechos, se motivarán a revisitar, difundir recomendaciones positivas y construir lealtad. Además, los resultados identificaron que Estados Unidos, Malasia y China son los países líderes en este campo. Este estudio proporciona una revisión integral de la literatura, un área hasta ahora poco explorada, ofreciendo ideas valiosas para que los proveedores de servicios hoteleros mejoren sus servicios, así como para que los investigadores y académicos desarrollen y propongan nuevas teorías.Num mundo altamente competitivo, o sucesso da indústria hoteleira depende da qualidade dos serviços que presta, o que proporciona sensações surpreendentes e elevada satisfação do cliente. Muitos pesquisadores têm tentado avaliar a satisfação do cliente em relação aos serviços hoteleiros propondo diferentes modelos. Assim, o presente estudo tenta identificar os fatores que influenciam a determinação da satisfação do cliente em relação aos serviços hoteleiros, através da realização de uma revisão sistemática da literatura. Durante o processo de busca, foram obtidos 457 artigos na base de dados Web of Science e, após filtragem, 91 artigos foram utilizados para posterior análise. O resultado revelou que os seis principais fatores que influenciam a satisfação do cliente em relação aos serviços hoteleiros são empatia, garantia, confiabilidade, capacidade de resposta, tangibilidade e práticas sustentáveis. Se os clientes estiverem satisfeitos, serão motivados a revisitar, propagar recomendações positivas e construir lealdade. Além disso, os resultados identificaram que os Estados Unidos, Malásia e China são os países líderes nesse campo. Este estudo fornece uma revisão abrangente da literatura, uma área até então pouco explorada, oferecendo insights valiosos para os provedores de serviços hoteleiros melhorarem seus serviços, bem como para pesquisadores e acadêmicos desenvolverem e propor novas teorias