• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.12 no.1
• /
• pp.88-93
• /
• 1999

This paper describes the electron transport characteristics in $SiH_4$ gas calculated for the range of E/n:0.5~300(Td) and Pressure:0.5, 1, 2.5(Torr) by the Monte carlo simulation and Boltzmann equation method using a set of electron collision cross sections determined by the reported results. The motion has been calculated to give swarm parameters for the electron drift velocity, longitudinal and transverse diffusion coefficients, the electron ionization coefficients, characteristics energy and the electron energy distribution function. The electron energy distributions function has been analysed in $SiH_4$ at E/N: 30, 50(Td)for a case of the equilibrium region in the mean electron energy and respective set of electron collision cross sections. The results of Monte carlo simulation and Boltzmann equation have been compared with experimental data by ohmori ad Pollock.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.578-580
• /
• 2005

Energy distribution function for electrons in SF6-Ar mixtures gas used by MCS-BEq algorithm has been analysed over the E/N range 30~300[Td] by a two term Boltzmann equation and by a Monte Carlo Simulation using a set of electron cross sections determined by other authors, experimentally the electron swarm parameters for 0.2[%] and 0.5[%] $SF_6$-Ar mixtures were measured by TOF method, The results show that the deduced electron drift velocities, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients and mean energy agree reasonably well with theoretical for a rang of E/N values. The results obtained from Boltzmann equation method and Monte Carlo simulation have been compared with present and previously obtained data and respective set of electron collision cross sections of the molecules.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2014.04a
• /
• pp.753-756
• /
• 2014

파킨슨병은 도파민계 신경이 파괴되는 질병으로 알츠하이머병과 함께 대표적인 퇴행성 뇌 질환으로 병의 진행을 완화시킬 수 있는 치료법이 존재하기 때문에 병의 진단이 굉장히 중요하다. 파킨슨병을 진단하기 위한 과거의 연구는 대부분 단일 생체지표를 이용하는 것이었지만 이러한 방법에는 한계성이 존재한다. 따라서 본 연구에서는 생화학적 생체지표인 뇌척수액 내의 ${\alpha}-synuclein$ 단백질 수치와 영상학적 생체지표인 확산 텐서 영상의 여러 모수들을 결합한 융합 생체지표를 특징으로 사용하는 파킨슨병 진단 모델을 개발하고 성능을 평가하였다. 10-fold cross validation 에서 모든 성능지표에 대해 최고 100%를 보였으며, cross validation 의 과적합을 감안하더라도 파킨슨병의 조기진단에 유용하게 사용될 수 있는 가능성을 제시하였다.

• Nuclear Engineering and Technology
• /
• v.54 no.11
• /
• pp.4280-4295
• /
• 2022

In this paper, a new multi-group neutron-gamma transport calculation code system STRAUM-MATXST for complicated geometrical problems is introduced and its development status including numerical tests is presented. In this code system, the MATXST (MATXS-based Cross Section Processor for S_N Transport) code generates multi-group neutron and gamma cross sections by processing MATXS format libraries generated using NJOY and the STRAUM (S_N Transport for Radiation Analysis with Unstructured Meshes) code performs multi-group neutron-gamma coupled transport calculation using tetrahedral meshes. In particular, this work presents the recent implementation and its test results of the Krylov subspace methods (i.e., Bi-CGSTAB and GMRES(m)) with preconditioners using DSA (Diffusion Synthetic Acceleration) and TSA (Transport Synthetic Acceleration). In addition, the Krylov subspace methods for accelerating the energy-group coupling iteration through thermal up-scatterings are implemented with new multi-group block DSA and TSA preconditioners in STRAUM.

• SUVANNABHUMI
• /
• v.11 no.2
• /
• pp.159-186
• /
• 2019

Southeast Asia accounts for nearly a tenth of total worldwide cross-border movements of migrant workers. Cambodia, Indonesia, Laos, Myanmar, and Philippines make up the sending countries while Malaysia, Singapore, and Thailand are the major destinations. Migrant worker movements are predominantly in production process and low- to medium-skilled sectors. It is not unusual for irregular or undocumented movements to take place. In not a few instances, migrants work under harsh and exploitative conditions. In recent years, however, ASEAN has taken steps to manage labor migration at the regional level. The paper argues that ASEAN has not managed these cross-border labor flows as well as it should particularly in terms of protecting and promoting the human rights of migrants. It will be difficult to establish the genuine building blocks for a regional human rights mechanism unless there is a diffusion of alternative universal norms and standards to what ASEAN already embodies. As long as states resist any attempt to weaken or question or deligitimize their capacity to determine who gets to enter, stay, and leave their jurisdictions, it will be difficult to establish an effective migrant rights framework for the region.

• Proceedings of the Technology Innovation Conference
• /
• 2003.02a
• /
• pp.173-190
• /
• 2003

Demand forecasting is essential in establishing national and corporate strategy as well as the management of their resource. We forecast demand for multi-generation product using discrete choice model combining diffusion model The discrete choice model generally captures consumers'valuation of the product's qualify in the framework of a cross-sectional analysis. We incorporate diffusion effects into a discrete choice model in order to capture the dynamics of demand for multi-generation products. As an empirical application, we forecast demand for worldwide DRAM (dynamic random access memory) and each of its generations from 1999 to 2005. In so doing, we use the method of 'Technological Forecasting'for DRAM Density and Price of the generations based on the Moore's law and learning by doing, respectively. Since we perform our analysis at the market level, we adopt the inversion routine in using the discrete choice model and find that our model performs well in explaining the current market situation, and also in forecasting new product diffusion in multi-generation product markets.

• Tunnel and Underground Space
• /
• v.25 no.1
• /
• pp.46-55
• /
• 2015

A water tube with detonating cord was devised to control the blast dust. Water diffusion experiments with different detonating cord positions were conducted during the series of experiments to optimize the design parameters of the tube. Images from high speed camera were analyzed to evaluate the results. AUTODYN program was adopted to simulate the diffusion process of water and compared with the images. Diffusion of water shows cross flow in case of external charge while the internal case shows radial flow. A bubble ring was formed during the numerical analysis of internal charge case as occurred in underwater blast. An additional bubble ring was formed by the reflection pressure from the ground. And the Weber number was determined as sufficient for spray atomization performance of the water tube.

• Journal of Korea Water Resources Association
• /
• v.34 no.5
• /
• pp.499-509
• /
• 2001

2-D transport model based on a discrete probability distribution for a particle displacement was developed too solve advection-diffusion problems in natural stream. In this proposed model, the probabilities expressed as an average and variance function were used to predict the mass transfer between cells in one time step. The proposed model produces solutions without numerical dispersion for constant velocity, diffusion coefficient, and cross-sectional area. When the stability and positivity restrictions were satisfied, the model produced excellent results compared to analytical solutions and other finite difference methods. The proposed model is tested against the dispersion data collected in the Grand River, Canada. The simulation results show that the proposed model can properly describe the two-dimensional mixing phenomena in the natural stream.

• Journal of Environmental Health Sciences
• /
• v.35 no.6
• /
• pp.500-509
• /
• 2009

Passive samplers have been used for many years for the sampling of organic vapors in work environment atmospheres. Currently, all passive samplers used in domestic occupational monitoring are foreign products. This study was performed to evaluate variable parameters for the development of passive organic samplers, which include the geometry of the device and diffusive length for the sampler design. Four prototype diffusive lengths; A-1(4.5 mm), A-2(7.0 mm), A-3(9.5 mm), A-4(12.0 mm) were tested for adsorption performances to a chemical mixture (benzene, toluene, trichloroethylene, and n-hexane) according to the US-OSHA's evaluation protocol. A dynamic vapor exposure chamber developed and verified by related research was used for this study. The results of study are as follows. The results in terms of sampling rate and recommended sampling time test indicate that the most suitable model was A-3 (9.5 mm diffusive lengths on both sides) for passive sampler design in time weighted average (TWA) assessment. Sampling rates of this A-3 model were 45.8, 41.5, 41.4, and 40.3 ml/min for benzene, toluene, trichloroethylene, and n-hexane, respectively. The A-3 models were tested on reverse diffusion and conditions of low humidity air (35% RH) and low concentrations (0.2 times of TLV). These conditions had no affect on the diffusion capacity of samplers. In conclusion, the most suitable design parameters of passive sampler are: 1) Geometry and structure - 25 mm diameter and 490 $mm^2$ cross sectional area of diffusion face with cylindrical form of two-sided opposite diffusion direction; 2) Diffusive length - 9.5 mm in both faces; 3) Amount of adsorbent - 300 mg of coconut shell charcoal; 4) Wind screen - using nylon net filters (11 ${\mu}m$ pore size).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.5
• /
• pp.644-654
• /
• 2003

An analytical solution for a vertically stratified viscous flow in a microchannel with a rectangular cross-section is constructed, assuming fully developed laminar flow where the interfaces between the fluid layers are flat. Although the solution is for n-layer flow, restricted results to symmetrical three-layer flow are presented to investigate the effects of the viscosity and thickness ratios of the fluid layers and the aspect ratio of the microchannel on the flow field. Relations between the flow rate and thickness ratios of the fluid layers with varying viscosity distributions are found, considering the cross -sectional velocity profiles which vary noticeably with the three parameters and differ significantly from the velocity profiles of the flow between infinite parallel plates. Interfacial instability induced by the viscosity stratification in the microchannel is discussed referring to previous studies on the instability analysis for plane multilayer flow. Exact solution derived in the present study can be used for examining a diffusion process and three -dimensional stability analysis. More works are needed to formulate the equations including the effects of interfacial' tension between immiscible liquids and surface wettability which are important in microscale transport phenomena.