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충돌분무의 액적 거동에 미치는 비등방성 난류특성의 영향에 대한 수치해석 연구
고권현(G. H. Ko),유홍선(H. S. Ryou) 한국전산유체공학회 2003 한국전산유체공학회지 Vol.8 No.4
It is an aim of this study to perform extensive numerical study for analyzing the anisotropic turbulence effects on spatial and temporal behaviors of droplet for impinging sprays. The turbulence model of Durbin is used for comparisons with the k-E model. The turbulence-induced dispersions of droplets are consider to describe the anisotropy of turbulence effectively and spray/wall interactions are simulated using the model of Lee and Ryou. Present study investigates the overall and the internal structures of impinging diesel sprays such as spray shapes, radius and height of wall sprays, Sauter mean diameter (SMD), local droplet velocity, and local gas velocity and compared the results with experimental data by two adopted turbulence models. When the anisotropy effect of turbulence is included, better predictions for both gas and droplet tangential velocities are obtained, compared to the k-ε model. It is concluded that anisotropic effect of turbulence should be considered for simulating impinging diesel sprays.
Host People's Kindness and Migrant Workers' Cultural Adaptation: Evidence from South Korea
Jihyun Ryou(Jihyun Ryou),Sang-Yeon Kim(Sang-Yeon Kim) 한국학술연구원 2022 Korea Observer Vol.53 No.4
This study purports to determine the predictors of migrant workers' cultural adaptation in South Korea. In the main, we examined the extent to which the level of inter-/intracultural socializing, exposure to local/native media, and host culture receptivity affect the level of cultural adaptation in cognitive, affective, behavioral domains. Potential impacts of demographic factors (e.g., age, sex, ethnicity, marital status, living alone vs. with family, education level, residency in years, perceived cultural similarity) were also explored. To find answers to the research questions, a total of 634 migrant workers from 37 different nations were reached using a snowball sampling. Surveys were collected in 12 districts of Seoul, the capital of South Korea, and 21 adjacent metropolitan areas. Results indicate that intercultural interaction with host people and media exposure to local contents tend to help improve their knowledge about South Korea (e.g., language, culture). With all else equal, migrant workers treated kindly by Koreans at the workplace and in service sectors, and those living with family, compared to those who live alone, tended to enjoy a greater satisfaction with work and life in South Korea and were more willing to stay. Practical implications for Korean policymakers include encouraging competent migrant workers to move together with the family, making administrative efforts to further simplify the documentation process, and initiating public campaigns to raise host culture receptivity among Korean citizens.
Ryou, Hong-Sun,Lee, Seong-Hyuk,Ko, Gwon-Hyun,Hong, Ki-Bae The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.7
The present article presents an extension to the computational model for spray/wall interaction and liquid film processes that has been dealt with in the earlier studies (Lee and Ryou, 2000a). The extensions incorporate film spread due to impingement forces and dynamic motion induced by film inertia to predict the dynamic characteristics of wall films effectively. The film model includes the impingement pressure of droplets, tangential momentum transfer due to the impinging droplets on the film surface and the gas shear force at the film surface. Validation of the spray/wall interaction model and the film model was carried out for non-evaporative diesel sprays against several sources of experimental data. The computational model for spray/wall interactions was in good agreement with experimental data for both spray radius and height. The film model in the present work was better than the previous static film model, indicating that the dynamic effects of film motion should be considered for wall films. On the overall the present film model was acceptable for predication of the film radius and thickness.
A State Table Design for Load Balancing in distributed Computing System
Ryou, Jea-Cheol 충남대학교 자연과학연구소 1992 忠南科學硏究誌 Vol.19 No.1
분산시스템에서 부하균형이란 과부하상태인 프로세서로부터 부하가 적은 프로세서에게로 테스크들을 이동시킴으로써 평균응답시간을 줄일 수 있는 하나의 테스크 스케쥴링 방법이다. 테스크의 이동을 위해서는 각 프로세서의 부하상태에 대한 정보가 필요한데 분산시스템에서 정보를 얻는데 많은 메세지가 필요하게된다. 본 논문에서는 각 프로세서에게 송신집합을 부여하고 이 집합에 속해있는 프로세서에게만 부하정보를 보내는 방법을 사용한 결과, 부하정보를 얻는데 필요한 메세지 수가 줄어들게 되었다. 그러나 송신집합이 적절하게 선택되어야 하는데, 그렇지 않을 경우에는 일부의 프로세서간에는 서로의 부하정보를 알지못하여 부하균형이 이루어지지 않을 수가 있다. 또한 부적절한 송신집합은 특정 프로세서에게 부하균형 제어권을 주게되는 결과를 초래한다. 이에 본 논문에서는 어떤 프로세서간에도 부하균형이 이루어지며, 부하균형 제어권이 모든 프로세서에게 균등히 배분될 수 있는 송신집합을 구하여, 프로세서의 갯수가 N일때 메세지 수가 √N으로 줄어들 수 있음을 보였다. Load balancing is a task scheduling scheme for distributed computing system that transfers tasks from heavily-loaded processors to lightly-loaded or idle processors to balance workload so that average response time can be reduced. Maintaining workload information is needed in making task migration decisions. However, it may incur large message overhead. In this paper, we adapt a strategy that assigns a sending set to each processor so that load information of a processor is sent only to the processors in the sending set. Symmetrically, each processor receives load information only from a set of processors called receiving set. As a result, the size of load table can be reduced substantially. Maintaining a reduced load table requies fewer messages and less local processing time. However, sending set have to be chosen properly, otherwise load balancing may not occur between some pair of processors due to lack of load information in their load tables. Also, improper sending sets may put extra burden on some processors and leads to an uneven distribution of load balancing control. We propose an algorithm based on balanced sending sets with which load balancing can occur between any pair of processors and load balancing control is evenly distributed among participating processors. With balanced sending sets, number of messages required for each update can be reduced to the square root of the number of processors in the system. Evaluation of load balancing schemes with balanced sending sets is also presented in this paper.
Task Allocation in an N-Cube Multiprocessor System
Ryou, Jea-Cheol 충남대학교 자연과학연구소 1992 忠南科學硏究誌 Vol.19 No.2
하이퍼큐브 다중프로세서는 그들의 상호연결특징에 의하여 이상적인 병렬구조로 알려지고있다. 하이퍼큐브에서 하나의 테스크를 수행하기 위해서는 다중프로세서들 중에서 한 서브큐브에 테스크를 할당해야 하는데, 이러한 할당문제는 시스템성능에 중요한 영향을 미치고 있다. 본 논문에서는 테스크를 할당하기 위하여 하나의 서브큐브를 탐색하는 알고리즘을 제시하고자 한다. 전체 하이퍼큐브가 어느 테스크에게도 할당되지 않은 자유로운 상태라면, 어떤 크기의 서브큐브라도 쉽게 탐색할수 있지만, 일부의 프로세서가 어느 테스크에 할당이 되어 있으면 이러한 문제는 NP-Complete이다. 제시하고자하는 알고리즘의 기본방향은 일단 하이퍼큐브를 2차원의 격자구조로 변환하여 서브큐브를 이루는 프로세서들을 결정론적으로 탐색하는 것이다. 이 알고리즘이 지금까지 알려진 방법들보다 향상된 서브큐브 인지능력이 있음을 보였다. The n-dimensional hypercube multiprocessor is considered as ideal parallel architectures for their powerful interconnection features. A task arriving at a hypercube must be assigned to a subcube in the multiprocessor for execution. Efficient allocation of processors in a hypercube is a key to its performance and utilization. The purpose of this paper is to study how to find a free subcube to allocate an incoming task. When the entire hypercube is free, subcubes of arbitrary dimension can be imbedded in it. But if some processors have been assigned to other tasks, then the general mapping problem is NP-complete. The idea of the proposed algorithm is to map a hypercube to a two-dimensional grid structure and then deterministically find a set of free processor which form a subcube. We show that the proposed algorithm has enhanced subcube recognition capability than any existing algorithms.
Ryou, Myung-Hyun,Lee, Dong-Jin,Lee, Je-Nam,Lee, Hong-Kyeong,Seo, Myung-Won,Lee, Hye-Won,Shin, Weon-Ho,Lee, Yong-Min,Choi, Jang-Wook,Park, Jung-Ki The Korean Electrochemical Society 2011 Journal of electrochemical science and technology Vol.2 No.4
A polymer electrolyte was prepared by using polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) or poly(ethylene glycol) dimethacrylate (PEGDMA) as polymer matrices, succinonitrile as an additive, and lithium perchlorate as a lithium salt. Compared to the polymer electrolyte employing PVdF-HFP, the PEGDMA-based polymer electrolyte exhibits substantially superior thermal stability when exposed to high temperatures. Nonetheless, the ionic conductivity of the PEGDMA-based polymer electrolyte was preserved in a wide temperature range between $-20^{\circ}C$ and $80^{\circ}C$.