Electro-Mechanical Simulation of Switching Characteristics for Nanoelectromechanical Memory

The static switching properties and readout characteristics of proposed high-speed and nonvolatile nanoelectromechanical (NEM) memory devices are investigated By conducting a three-dimensional finite element mechanical simulation combined with an electrostatic analysis, we analyze the electromechanical switching operation of a mechanically bistable NEM floating gate by applying gate voltage. We show that switching voltage can be reduced to less than 10V by reducing the zero-bias displacement of the floating gate and optimizing the cavity structure to improve mechanical symmetry. We also analyze the electrical readout property of the NEM memory devices by combining the electromechanical simulation with a drift-diffusion analysis We demonstrate that the mechanically bistable states of the floating gate can be detected via the changes in drain current with an ON/OFF current ratio of about 3 x 10 (C) 2009 The Japan Society of Applied Physic

A Universal Lifetime Distribution for Multi-Species Systems

Lifetime distributions of social entities, such as enterprises, products, and media contents, are one of the fundamental statistics characterizing the social dynamics. To investigate the lifetime distribution of mutually interacting systems, simple models having a rule for additions and deletions of entities are investigated. We found a quite universal lifetime distribution for various kinds of inter-entity interactions, and it is well fitted by a stretched-exponential function with an exponent close to 1/2. We propose a "modified Red-Queen" hypothesis to explain this distribution. We also review empirical studies on the lifetime distribution of social entities, and discussed the applicability of the model.Comment: 10 pages, 6 figures, Proceedings of Social Modeling and Simulations + Econophysics Colloquium 201

Fabrication and characterization of Si3N4 ceramics without additives by high pressure hot pressing

High pressure hot-pressing of Si3N4 without additives was performed using various kinds of Si3N4 powder as starting materials, and the relation between densification and alpha-beta phase transformation was studied. The temperature dependences of Vickers microhardness and fracture toughness were also examined. Densification of Si3N4 was divided into three stages, and it was found that densification and phase transformation of Si3N4 under pressure were closely associated. The results of the temperature dependence of Vickers microhardness indicated that the high-temperature hardness was strongly influenced not only by the density and microstructure of sintered body but also by the purity of starting powder. The fracture toughness values of Si3N4 bodies without additives were 3.29-4.39 MN/m to the 3/2 power and independent of temperature up to 1400 C

Distribution of Microscopic Energy Flux in Equilibrium State

The distribution function P(j) of the microscopic energy flux, j, in equilibrium state is studied. It is observed that P(j) has a broad peak in small j regime and a stretched-exponential decay for large j. The peak structure originates in a potential advection term and energy transfer term between the particles. The stretched exponential tail comes from the momentum energy advection term.Comment: 5 pages, 2 figure