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CONTENTS
Volume 1, Number 3, July 2016
 

Abstract
In this work, we extend the split previously developed kinetic energy (dubbed as KEP) method Mineo and Chao (2012) by modifying the mass parameter to include the negative mass. We first show how to separate the total system into the subsystems with 3 attractive delta potentials by using the KEP method. For repulsive delta potentials, we introduce

Key Words
kinetic energy partition; Schrödinger equation; negative mass; zero-range potential

Address
Yu-Hsin Chen and Sheng D. Chao: Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan, R.O.C.

Abstract
We propose a heat jet approach for a two-dimensional square lattice with nearest neighbouring harmonic interaction. First, we design a two-way matching boundary condition that linearly relates the displacement and velocity at atoms near the boundary, and a suitable input in terms of given incoming wave modes. Then a phonon representation for finite temperature lattice motion is adopted. The proposed approach is simple and compact. Numerical tests validate the effectiveness of the boundary condition in reflection suppression for outgoing waves. It maintains target temperature for the lattice, with expected kinetic energy distribution and heat flux. Moreover, its linear nature facilitates reliable finite temperature atomic simulations with a correct description for non-thermal motions.

Key Words
heat jet approach; atomic simulations; finite temperature; square lattice

Address
Baiyili Liu and Shaoqiang Tang: HEDPS, CAPT, and LTCS, College of Engineering, Peking University, Beijing 100871, P.R. China

Abstract
The formation of silicon-on-nothing (SON) structure during an annealing process from the silicon substrate including the trench structures has been considered as an effective technique to construct the structure that has an empty space under the closed flat surface. Previous studies have demonstrated the mechanism of the formation of SON structure, which is based on the surface diffusion driven by the minimization of their surface energy. Also, it has been fragmentarily shown that the morphology of SON structure can be affected by the initial design of trench (e.g., size, number) and the annealing conditions (e.g., temperature, pressure). Based on the previous studies, here, we report a comprehensive study for the design of the cavity-embedded structure (i.e., SON structure). To do this, a dynamic model has been developed with the phase field approach. The simulation results represent that the morphology of SON structures could be detailedly designed, for example the position and thickness of cavity, the thickness of top and bottom layer, according to the design parameters. This study will give us an advantage in the effective design of SON structures.

Key Words
SON structure; morphological design; phase field model; multi-physics analysis

Address
Jihwan Song and Dongchoul Kim:1Department of Mechanical Engineering, Sogang University, Seoul, 121-742, Korea

Linan Zhang: Department of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou, 310018, China

Abstract
This work employed density functional theory to investigate the structural and ferroelectric properties of the Ruddlesden-Popper (RP) phase of lead titanate, Pb2TiO4, as well as its phase transitions with epitaxial strain. A wealth of novel structural instabilities, which are absent in the host PbTiO3material, were identified in the RP phase through phonon soft-mode analysis. Our calculations showed that the ground state of Pb2TiO4 is antiferroelectric,distinct fromthe dominant ferroelectric phase in the corresponding hostmaterial. In addition, applied epitaxial strain was found to play a key role in the interactions among the instabilities. The induction of a sequence of antiferroelectric and antiferrodistortive (AFD) phase transitions by epitaxial strain was demonstrated, in which the ferroic instability andAFDdistortionwere cooperative rather than competitive, as is the case in the host PbTiO3. The RP phase in conjunction with strain engineering thus represents a new approach to creating ferroic orders and modifying the interplay among structural instabilities in the same constituent materials, enabling us to tailor the functionality of perovskite oxides for novel device applications.

Key Words
ferroelectrics; Ruddllesden-Popper phase; antiferroelectricity; strain; first-principles

Address
Tao Xu, Takahiro Shimada and Takayuki Kitamura: Department of Mechanical Engineering and Science, Kyoto University,
Kyoto-Daigaku Katsura, Nishikyo-ku, Kyoto 615-8540, Japan

Jie Wang: Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University,
Zheda Road 38, Xihu District, Hangzhou 310027, China

Abstract
We present relatively simple derivations of theHelfrich energy potential that has been widely adopted in the analysis of lipid membranes without detailed explanations. Through the energy variation methods (within the limit of Helfrich energy potential), we obtained series of analytical solutions in the case when the lipid membranes are excited through their edges. These affordable solutions can be readily applied in the related membrane experiments. In particular, it is shown that, in case of an elliptic cross section of a rigid substrate differing slightly from a circle and subjected to the incremental deformations, exact analytical expressions describing deformed configurations of lipidmembranes can be obtainedwithout the extensive use ofMathieu\'s function.

Key Words
lipid membranes; bilayers; shape equation; substrate-membrane interaction; elliptical contact domain; analytic solution

Address
Chun IL Kim: Department of Mechanical Engineering,University of Alberta, Edmonton, Alberta T6G 2G8, Canada

Abstract
The longitudinal velocity (forward speed) having significant importance in proper running of railway wheelset on track, depends greatly upon the adhesion ratio and creep analysis by implementation of suitable dynamic systemon contamination. The wet track condition causes slip and slide of vehicle on railway tracking, whereas high speedmay also increase slip and skidding to severewear and deterioration ofmechanical parts. The basic aimof this research is to design appropriatemodel aimed estimator that can be used to control railway vehicle forward velocity to avoid slip. For the filtration of disturbance procured during running of vehicle, the kalman filter is applied to estimate the actual signal on preferered samples of creep co-efficient for observing the applied attitude of noise. Thus error level is detected on higher and lower co-efficient of creep to analyze adhesion to avoid slip and sliding. The skidding is usually occurred due to higher forward speed owing to procured disturbance. This paper guides to minimize the noise and error based upon creep coefficient.

Key Words
longitudinal speed; adhesion; creep coefficient; kalman filter; tractive force

Address
Zulfiqar Ali Soomro: Department of Mechanical Engineering, Quaid-e-Awam University of Engg; Science &Tech;
Nawabshah, Pakistan

Abstract
Shape-memory alloys (SMA) have interesting behaviors and important mechanical properties due to the solid–solid phase transformation. These phenomena are dominated by the evolution of microstructures. In recent years, the microstructures in SMAs have been studied extensively and modeled using molecular dynamics (MD) simulations. However, it remains difficult to identify the crystal variants in the simulation results, which consist of large numbers of atoms. In the present work, a method is developed to identify the austenite phase and the monoclinic martensite crystal variants in MD results. The transformation matrix of each lattice is calculated to determine the corresponding crystal variant. Evolution of the volume fraction of the crystal variants and the microstructure in Ni-Ti SMAs under thermal and mechanical boundary conditions are examined. The method is validated by comparing MD-simulated interface normals with theoretical solutions. In addition, the results show that, in certain cases, the interatomic potential used in the current study leads to inconsistent monoclinic lattices compared with crystallographic theory. Thus, a specific modification is applied and the applicability of the potential is discussed.

Key Words
microstructure; molecular dynamics; Ni-Ti shape-memory alloys; phase transition

Address
Jo-Fan Wu and Chuin-Shan Chen: Department of Civil Engineering, National Taiwan University,No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan




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