Security system architecture for data integrity based on a virtual smart meter overlay in a smart grid system

As an efficient and intelligent system for managing and monitoring electricity usage, the “smart grid” has many useful applications. It supports energy producers and energy consumers efficiently by supporting the estimation and provision of the proper amount of electricity at the proper time. The most serious threat to a smart grid system may be when information is altered or forged by attackers; the system could malfunction and could collapse. In some cases, the attackers could waste system resources on purpose and this could lead to disastrous results. In this paper, we propose security system architecture to provide the secure and reliable smart grid service. It includes a data authentication process to verify the aggregated data and virtual network management to detect a compromised area or node. It detects a false data injection attack and further prevents a denial of service attack efficiently with less overhead for the individual devices comprising the smart grid system.     

Studies of dynamic crack propagation and crack branching with peridynamics

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons. We also analyze the influence of the particular shape of the micro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well as it obtains crack propagation speeds that compare well, qualitatively and quantitatively, with experimental results published in the literature. The branching patterns also correlate remarkably well with tests published in the literature that show several branching levels at higher stress levels reached when the initial notch starts propagating. We notice the strong influence reflecting stress waves from the boundaries have on the shape and structure of the crack paths in dynamic fracture. All these computational solutions are obtained by using the minimum amount of input information: density, elastic stiffness, and constant fracture energy. No special criteria for crack propagation, crack curving, or crack branching are used: dynamic crack propagation is obtained here as part of the solution. We conclude that peridynamics is a reliable formulation for modeling dynamic crack propagation.     

Blood flow interpretation in femoral pseudoaneurysm

A femoral artery pseudoaneurysm is one complication of vascular intervention, and the incidence is increasing. Early management is then needed to avoid potential dangers from it. It differs from a true aneurysm in that it doesn＇t include any component of the vascular wall, and is not studied as much as a true aneurysm. Here, a model of a femoral pseudoaneurysm was made and a Computational Fluid Dynamics（CFD） simulation was verified with PIV experiment. Afterwards, a CFD simulation with two different models was performed to look for any findings which may help in developing new treatment methods.     

Disassembly leveling and lot sizing for multiple product types: a basic model and its extension

We consider two interrelated problems that occurred in disassembly systems: disassembly leveling and lot sizing. Disassembly leveling, one of disassembly process planning decisions, is to determine disassembly structures that specify parts and/or subassemblies to be obtained from disassembling used/end-of-life products, and disassembly lot sizing is the problem of determining the amounts of disassembly operations required to satisfy the demands of their parts and/or subassemblies. Unlike the existing studies, this study considers the two problems at the same time for the objective of minimizing the sum of disassembly setup and operation costs. In particular, we consider a generalized version in which disassembly levels may be different even for products of the same type. Two types of the problem are considered in this study. The first one is the basic problem without parts commonality, i.e., products do not share their parts or subassemblies, for which a polynomial time optimal algorithm is suggested after developing a mathematical programming model. The second one is an extended problem with parts commonality. After developing another mathematical programming model for the extension, we prove that it is NP hard. Then, a heuristic algorithm is suggested together with its computational results.     

An exploration strategy using sonar sensors in corridor environments

We present a novel solution for topological exploration in corridor environments using cheap and error-prone sonar sensors. Topological exploration requires significant location detection and motion planning. To detect nodes (i.e., significant places) robustly, we propose a new measure, the eigenvalue ratio (EVR), which converts geometrical shapes in the environment into quantitative values using principal component analysis. For planning the safe motion of a robot, we propose the circle following (CF) method, which abstracts the geometry of the environment while taking the characteristics of the sonar sensors into consideration. Integrating the EVR with the CF method results in a topological exploration strategy using sonar sensors approach. The practicality of this approach is demonstrated by simulations and real experiments in corridor environments.     

Globally asymptotically stable tracking control for a trailer system

This article addresses a tracking controller design for a trailer system consisting of a steering tractor and a passive trailer linked with a rigid free joint and having nonholonomic constraints. We design the tracking controller using the Lyapunov direct method, for both forward and backward driving of the trailer system. Backward driving is unstable, and thus is more difficult than forward driving. In previous research, we proposed a globally asymptotically stable (GAS) tracking control for forward driving of a trailer system with nonholonomic constraints. In this article, we implement the GAS tracking controller for forward and backward driving, and perform experiments using visual feedback and remote control systems. The experimental results represent stable responses and demonstrate the effectiveness of our method. © 2002 Wiley Periodicals, Inc.     

A new SiO/C anode composition for lithium-ion battery

A new anode composition comprising SiO and graphite(C) is prepared through a high-energy ball milling process. During the first cycle, the anode delivers high discharge and charge capacity values of 1556 and 693 mAh g⁻¹, respectively. The electrode shows a reversible charge capacity value of 688 mAh g⁻¹ at the 30th cycle with 99% Coulombic efficiency. X-ray diffraction analysis reveals that ball milling does not produce any new compound, but only causes a reduction in particle size. The irreversible and reversible capacities appear to be interdependent.