• Earthquakes and Structures
• /
• 제22권2호
• /
• pp.147-155
• /
• 2022

Regarding the importance of seismic pounding, the available standards and guidelines specify minimum separation distance between adjacent buildings. However, the rules in this field are generally based on some simple assumptions, and the level of confidence is uncertain. This is attributed to the fact that the relative response of adjacent structures is strongly dependent on the frequency content of the applied records and the Eigen frequencies of the adjacent structures as well. Therefore, this research aims at investigating the separation distance of the buildings through a probabilistic-based algorithm. In order to empower the algorithm, the record-to-record uncertainties, are considered by probabilistic approaches; besides, a wide extent of material nonlinear behaviors can be introduced into the structural model by the implementation of the hysteresis Bouc-Wen model. The algorithm is then simplified by the application of the linearization concept and using the response acceleration spectrum. By implementing the proposed algorithm, the separation distance in a specific probability level can be evaluated without the essential need of performing time-consuming dynamic analyses. Accuracy of the proposed method is evaluated using nonlinear dynamic analyses of adjacent structures.

• 한국항공우주학회지
• /
• 제39권1호
• /
• pp.33-41
• /
• 2011

내삽형 부스터의 분리 운동 수학모델을 소개하였다. 부스터 분리 운동을 시뮬레이션 하기 위하여 3자유도 2물체 운동모델을 정립하였다. 유도탄과 공기중에 노출되는 부스터 영역의 공력모델을 개발하였다. 그리고, 부스터를 밀어내는 가스발생기도 모델링하였다. 이 모델을 시뮬레이션하기 위하여 유도탄이 부스터 분리과정에서 계속 1g 수평비행 조건을 유지한다는 가정을 세우고, 이를 기반으로 유도탄과 부스터간의 작용력을 분리 단계별로 정의 할 수 있었다. 단계 0: 초기, 단계 1: 선형이동, 단계 2: 자유운동. 이 시뮬레이션을 통하여 부스터를 안전하게 분리할 수 있는 유도탄의 마하수 및 고도의 범위를 제안할 수 있었다.

• Advances in nano research
• /
• 제3권3호
• /
• pp.143-168
• /
• 2015

Initiation of crack and its growth simulation requires accurate model of traction - separation law. Accurate modeling of traction-separation law remains always a great challenge. Atomistic simulations based prediction has great potential in arriving at accurate traction-separation law. The present paper is aimed at establishing a method to address the above problem. A method for traction-separation law prediction via utilizing atomistic simulations data has been proposed. In this direction, firstly, a simpler approach of common neighbor analysis (CNA) for the prediction of crack growth has been proposed and results have been compared with previously used approach of threshold potential energy. Next, a scheme for prediction of crack speed has been demonstrated based on the stable crack growth criteria. Also, an algorithm has been proposed that utilizes a variable relaxation time period for the computation of crack growth, accurate stress behavior, and traction-separation atomistic law. An understanding has been established for the generation of smoother traction-separation law (including the effect of free surface) from a huge amount of raw atomistic data. A new curve fit has also been proposed for predicting traction-separation data generated from the molecular dynamics simulations. The proposed traction-separation law has also been compared with the polynomial and exponential model used earlier for the prediction of traction-separation law for the bulk materials.

• Wind and Structures
• /
• 제19권2호
• /
• pp.113-144
• /
• 2014

Separation bubble and conical vortices on a large-span flat roof were observed in this study through the use of flow visualization. The results indicated that separation bubble occurred when the flow was normal to the leading edge of the flat roof. Conical vortices that occur under the cornering flow were observed near the leading edge, and their appearance was influenced by the wind angle. When the wind changed from along the diagonal to deviating from the diagonal of the roof, the conical vortex close to the approaching flow changed from circular to be more oblong shaped. Based on the measured velocities in the conical vortices by flow visualization, a proposed two-dimensional vortex model was improved and validated by simplifying the velocity profile between the vortex and the potential flow region. Through measured velocities and parameters of vortices, the intensities of conical vortices and separation bubble on a large-span flat roof under different wind directions were provided. The quasi-steady theory was corrected by including the effect of vortices. With this improved two-dimensional vortex model and the corrected quasi-steady theory, the mean and peak suction beneath the cores of the conical vortices and separation bubble can be predicted, and these were verified by measured pressures on a larger-scale model of the flat roof.

• 한국농업기계학회:학술대회논문집
• /
• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
• /
• pp.676-685
• /
• 1993

A mathematical model was developed to quantify the separation process of threshed grain-straw mixtures. It was made to predict the separation loss from a separation unit consisted of stationary crimped sieve with rotating inner rotor. Experiments were performed to prove the mathematical model by changing various levels of pertinent variables for rice. Good Agreement between the simulated results and observed data under the various test conditions, such as inclination angle of the separator, vane pitch, rotor speed, MOG/G ratio, feed rate, and crop variety and moisture content, were confirmed.

• 한국해양환경ㆍ에너지학회지
• /
• 제12권3호
• /
• pp.197-201
• /
• 2009

다상유동의 상분리 시뮬레이션 기법으로 Lattice-Boltzmann방법(LBM)을 이용하였다. 기체와 액체상사이의 경계면에서 마이크로한 상호교환을 LBM의 등가함수에서 취급하고 있으며, Van-der-Walls의 free energy를 도입하였다. 표면에너지에 따라 상경계면의 기울기의 변화, 온도에 따른 상분리 특성등을 조사하고, 일정 온도상에서 기체와 액체의 상분리 시뮬레이션을 수행하였다.

• 전기학회논문지
• /
• 제62권1호
• /
• pp.70-75
• /
• 2013

The electrical separation joint as a filter circuit distributes the track circuit frequency. The electrical separation joint is classified into the interval where reinforcing bars are insulated and not insulated through the length of track circuit. In case of incorrectly setting up the length of electrical separation joint, the amplitude of current on the track circuit is not over standard current which is the standard of current on the track circuit and it effects on the close frequency on track circuit. Then, it makes an accident or makes a train not receive information for train control. In this paper, the electrical separation joint model is suggested and parameters are numerically calculated in the model. Moreover, the length of electrical separation joint is analyzed and is demonstrated by uisng Matlab and PSpice program.

• ETRI Journal
• /
• 제45권1호
• /
• pp.138-149
• /
• 2023

In this study, the problem of blind signal separation for coprime planar arrays is investigated. For coprime planar arrays comprising two uniform rectangular subarrays, we link the signal separation to the tensor-based model called coupled canonical polyadic decomposition (CPD) and propose an improved coupled trilinear decomposition approach. The output data of coprime planar arrays are modeled as a coupled tensor set that can be further interpreted as a coupled CPD model, allowing a signal separation to be achieved using coupled trilinear alternating least squares (TALS). Furthermore, in the procedure of the coupled TALS, a Vandermonde structure enforcing approach is explicitly applied, which is shown to ensure fast convergence. The results of Monto Carlo simulations show that our proposed algorithm has the same separation accuracy as the basic coupled TALS but with a faster convergence speed.

• 대한기계학회논문집B
• /
• 제30권2호
• /
• pp.177-185
• /
• 2006

This study aims deriving analysis the flow characteristic of kitchen hood system with using 3-D numerical analysis method and improving the system to expel pollutes more efficiently. To understand the flow characteristics of four models, this study only focuses on velocity field, temperature field, and concentration field varying with followings whether separation plate is set or not and the shapes of separation plates. The quantity of air, speed of exhaust fan and temperature and concentration of heating source are concerned as constant values. The three models having different shapes have one exhaust port and the model which has the vent at the closest position to where pollutes are generated is discovered to be the most efficient model. Compare to the initial model (having no separation plate), it was $1.4-1.9\%$ more efficient at temperature distribution and $9.4-11.9\%$ more at $CO_2$ concentration distribution.

• 한국전산유체공학회지
• /
• 제2권2호
• /
• pp.59-72
• /
• 1997

A numerical model is constructed to simulate the interactions of oblique shock wave / turbulent boundary layer on a strongly heated wall. The heated wall temperature is two times higher than the adiabatic wall temperature and the shock wave is strong enough to induce boundary layer separation. The numerical diffusion in the finite volume method is reduced by the use of a higher order convection scheme(UMIST scheme) which is a TVD version of QUICK scheme. The turbulence model is Chen-Kim two time scale model. The comparison of the wall pressure distribution with the experimental data ensures the validity of this numerical model. The effect of strong wall heating enlarges the separation region upstream and downstream. In order to eliminate the separation, wall suction is applied at the shock foot position. The bleeding slot width is about same as the upstream boundary layer thickness and suction mass flow is 10% of the flow rate in the upstream boundary layer. The final configuration of the shock reflection pattern and the wall pressure distribution approach to the non-viscous value when wall suction is applied.