• Journal of electromagnetic engineering and science
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• 제1권1호
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• pp.30-36
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• 2001

Whereas it is well known that microwave propagation around corners of urban area is estimated well by the uniform geometrical theory of diffraction (UTD), it is not clear how much depolarization occurs at a given receiver position and how much transmission through walls affects to total path loss. This paper presents the results of the ray tracing simulation to answer these questions. Simulations of microwave propagation around corners were performed for various line-of-sight (LOS) and out-of-sight(OOS) positions of a receiver, by summing the electrical fields of reflected, diffracted and transmitted rays coherently. Since height difference between transmitter and receiver, as well as ground plane, causes depolarization, the ray tracing simulation estimates the cross-polarization coupling. It was found that the cross-polarization coupling decreases as receiver moves away from transmitter. Another part of the study focused on the signal transmitted through building walls of the corner. It was found that the transmitted field is dominant at OOS region when the conductivity of the walls is low (for example, lower than 0.0l S/m). The simulation results of the ray tracing technique in this study agreed well with an experimental measurement around corners.

• Journal of Power Electronics
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• 제6권2호
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• pp.104-113
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• 2006

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; $(1^{st})$ paying attention to details, and $(2^{nd})$ handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application. This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

• Asia pacific journal of information systems
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• 제20권1호
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• pp.101-125
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• 2010

This paper uses the status inconsistency theory to identify factors related to team members' (dis)satisfaction with the composition of virtual IT project teams in order to predict their turnover intentions. Our approach is based on the premise that virtual teams, although increasingly popular among global organizations, create an environment replete with cultural and functional diversity. Yet, a paradox exists: increasing diversity in virtual teams maximizes the creation and use of organizational knowledge while simultaneously increasing dissatisfaction and turnover. This is a critical issue in the formation and management of virtual teams. Therefore, we investigate how team members' perceptions of differences among themselves (i.e. foreignness) impact the stability of team membership, leading to what we describe as a 'liability of foreignness.' Findings indicate that a member's perception of foreignness has a detrimental effect on satisfaction with his or her team members while satisfaction is likely to decrease turnover intention. This may be an implication that managers need to maintain a balance in order to discourage member turnover and the loss of key players.

• The Journal of Asian Finance, Economics and Business
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• 제8권5호
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• pp.863-872
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• 2021

The main goal of this research is to understand how small and medium enterprises (SMEs) owners in Oman perceive the factors that drive or impede their growth and sustainability. Based on survey data of 395 SMEs in Oman, factor analysis was conducted to check if all the items load as one factor in each of the constructs. The results show that all the items measuring motivators and barriers loaded significantly for the respective scales, with high reliability (Cronbach alpha for Motivators = 0.991 and Barriers = 0.995). Relationships between the demographic factors of entrepreneurs and firm characteristics were tested and it was found that all the four variables: age of the entrepreneur (p = 0.00), qualification of the entrepreneur (p = 0.00), SME sector (p = 0.00), and age of the firm (p = 0.00) have a significant relationship with both the Motivators and the Barriers. The findings of this study could have significant implications for policymakers in Oman and other Middle Eastern countries. Since SMEs face similar problems and are given priority around the world, the findings could be applicable to other countries, as well. The findings also add important results to the empirical literature on SMEs.

• Structural Engineering and Mechanics
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• 제84권2호
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• pp.285-293
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• 2022

Lumped damage mechanics (LDM) is a recent nonlinear theory with several applications to civil engineering structures, such as reinforced concrete and steel buildings. LDM apply key concepts of classic fracture and damage mechanics on plastic hinges. Therefore, the lumped damage models are quite successful in reproduce actual structural behaviour using concepts well-known by engineers in practice, such as ultimate moment and first cracking moment of reinforced concrete elements. So far, lumped damage models are based in the strain energy equivalence hypothesis, which is one of the fictitious states where the intact material behaviour depends on a damage variable. However, there are other possibilities, such as the energy equivalence hypothesis. Such possibilities should be explored, in order to pursue unique advantages as well as extend the LDM framework. Therewith, a lumped damage model based on the energy equivalence hypothesis is proposed in this paper. The proposed model was idealised for reinforced concrete structures, where a damage variable accounts for concrete cracking and the plastic rotation represents reinforcement yielding. The obtained results show that the proposed model is quite accurate compared to experimental responses.

• 사상체질의학회지
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• 제8권2호
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• pp.41-68
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• 1996

This thesis is a try for examining the historical characteristics of Constiutional medicine. For this purpose, I have examined their theory, and made a comparison carefully. Through this study, I have obtained several results as following. Both Chang and Lee lived in the time of change, which was unstable and uncertain. Under the condition, they both rejected following the existing trends of learned circles, and developed new thoughts and clinical techniques. They rejected superstitious beliefs and fatalism, and conducted the pursuit of experimental knowledge and rationale idea. Clinical experience was the very base of their study. They both criticized the bad habits of abuse of tonifing medication and health seeking. Especially Lee regarded control of emotion and regulation of a way of life as the best way for preservation of one's health. Chang regarded pathogenic factors as the ultimate factor of diseases, and strived for eliminating pathogenic factors, but L brought to a conclusion that the final factor of diseases was what is called "heart" itself, and emotional changes were the most essential causes of disease. It can be said that the pathogenesis insisted by Chang can be called The insistence that pathologic factors are the very etiology of all the disease (邪氣致病論), or all the diseases result from pathologic factors. And his whole remedy can be summarized as following, A study on the method of eliminating pathogenic factors. But the purpose of Constitutional medicine is to correct imbalance intrinsic to one's internal organs. In this aspect, Constitutional medicine is a "regulatory medicine". Depending on the classification of six vital substances, Chang classified all disease into six categories. These were based on symptoms and sings represented. While classification of diseases made by Lee was likely to rely upon constitutional characteristics. Chang thought that the three remedies made up of perspiration, purgation, vomiting were the most efficient way of eliminating pathogenic factors. Lee, however, thought those weren't methods of eliminating pathogenic factors but the best ways restoring one's self-regulation power. Chang thought that all the febrile disease essentially has a tendency in properties to belong to "heat", but Lee pointed out that pathologic processes are variable in accordance with constitutional features. They both regarded pathogenesis of diabetes as fire. That is to say, fire is the most essential factor of diabetes. And there are many risk factors such as inappropriate foods, drugs, climate, etc., but Lee thought what is most important is heart. Putting all accounts together, medical characteristics of Chang are similar to those of T aiyinjen and Shaoyangjen, and have no relation to those of those of Shaoyinjen. Therefore we can conclude that Chang understood pathologic processes of disease of T aiyinjen and Shaoyangjen, whether he knew about constitutional features or not.

• 디자인학연구
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• 제18권3호
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• pp.209-218
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• 2005

영상 제작의 창작과정에서 제작자들은 의식적으로 혹은 무의식적으로 다양한 미적표현의 선:l을 하게 된다. 이러한 선택을 위해 공감될 수 있는 보편적인 미학적 원리가 제시될 수 있다면 제작 과정의 시행착오를 줄일 수 있는 심미적 판단의 기준이 될 수 있을 것이다. 본 논문은 3D 애니메이션 제작환경에 맞는 카메라 기법의 미학적 기준을 정립하여 애니매이션 제작과정에서 최적의 화면 구성을 하기 위한 이론적 접근을 시도했다. 허버트 제틀(Herbert Zettl)의 영상 미학의 구성원리 중 카메라와 관련이 있는 힘과 구도의 2차원, 깊이와 입체의 3차원, 시간과 동작의 4차원 영역으로 나누어 고찰하였다. 이러한 이론접근을 위해 일반 영화영상을 위한 카메라와 3D 애니메이션에서 카메라 기법을 비교하여 분석하였다. 2차원 영역은 종횡비에 따른 여백 및 크기, 방향에 따른 힘의 논리, 힘의 상호작용과 샷(shot)의 크기를 중심으로, 3차원 영역은 심도와 관련한 Z-축의 축소와 확장, 깊이감 표현을 중심으로, 4차원 영역은 피사체와의 이동방향에 따른 시간, 주관적시간, 피사체 시점, 동작 등을 중심으로 3D 애니메이션 제작환경에 맞는 원리로 재구성하였다. 이러한 전통적 카메라 기법의 영상미학 원리들이 3D 애니메이션에서의 카메라를 이용한 화면 구성에 적용될 때 효율적 제작 진행을 위해 활용될 수 있다. 또한 이를 기반으로 다양한 조형언어들과의 상호 관련성을 연구한다면 3D애니메이션 제작을 위한 더욱 창의적인 화면구성 기법들이 정립될 수 있을 것이다.

• 한국철학논집
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• 제38호
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• pp.189-220
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• 2013

본고에서는 음양가(陰陽家)의 등장 과정과 아울러 묵가(墨家)의 음양오행론(陰陽五行論)을 제가(諸家)와의 비교를 통해서 살펴보았다. 사마천(司馬遷)이 열전(列傳)에서 시사한 바대로 추연(鄒衍)으로 대표되는 음양가는 당시 유가(儒家)와도 일정한 관련이 있었던 것으로 보인다. 음양 관념은 본래 햇빛과 관련이 있었지만 전국 중기 이후 기(氣), 혹은 도(道) 관념과 연계되면서 점점 추상화되었다. 오행 관념 또한 본래 일상생활에 필수적인 오재(五材) 관념에서 출발하여 인간과 자연의 모든 것을 포괄하는 분류 기준으로 발전하였다. 오덕종시설(五德終始說)로 대표되는 추연을 비롯한 음양가 혹은 음양오행가의 사상은 근본적으로 왕조 교체의 법칙성을 도출하기 위한 것이었다. 그러나 이러한 관점은 전국말에 이르기까지 백가쟁명의 주제로서 부각되지 못하였다. 비록 제가에서 공통적으로 음양오행론에 대한 기본적인 이해를 전제로 그것을 활용하고 있는 것은 사실이지만 각각의 사상체계에 연계되지 못하였다. 묵가 또한 음양오행 관념을 수용하고 군사학 방면에 활용하면서도 일관되게 합리적인 관점을 유지하고 있다. 이것은 제가의 현실인식과 역사관의 차이에서 근본적인 원인을 찾을 수 있을 것이다.

• 한국전산유체공학회지
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• 제19권3호
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• pp.91-97
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• 2014

A high resolution numerical method aimed at solving cavitating flow was proposed and applied to gas-liquid two-phase shock tube problem with arbitrary void fraction. The present method with compressibility effects employs a finite-difference 4th-order Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL TVD scheme. The Jacobian matrix from the inviscid flux of constitute equation is diagonalized analytically and the speed of sound for the two-phase media is derived by eigenvalues. So that the present method is appropriate for the extension of high order upwind schemes based on the characteristic theory. By this method, a Riemann problem for Euler equations of one dimensional shock tube was computed. Numerical results of high speed flow phenomena such as detailed observations of shock and expansion wave propagations through the gas-liquid two-phase media and some data related to computational efficiency are made. Comparisons of predicted results and solutions at isothermal condition are provided and discussed.

• 대한의용생체공학회:의공학회지
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• 제20권4호
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• pp.435-442
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• 1999

본 연구에서는 PVC를 분류하기 위하여 웨이브렛 계수를 기반으로 하는 fuzzy-ART 네트워크를 설계하였다. 설계된 네트워크는 feature를 추출하는 부분과 fuzzy-ART 네트워크를 학습시키는 부분으로 구성된다. 우선 feature의 문턱치 구간을 설정하기 위하여 심전도 신호의 QRS를 검출하였고, 검출된 QRS는 Haar 웨이브렛을 이용한 웨이브렛 변환에 의해 주파수 분할하였다. 분할된 주파수 중에서 입력 feature를 추출하기 위하여 저주파 영역의 6번째 계수(D6)만을 선택하였다. D6신호는 입력 feature를 구성하기 위한 문턱치를 적용하여 fuzzy-ART 네트워크의 2진수 입력 feature로 전환하였고, PVC를 분류하기 위하여 fuzzy-ART네트워크를 학습시켰다. 본 연구의 성능을 평가하기 위하여 PVC가 포함된 MIT/BIH 데이터 베이스가 사용되었으며, fuzzy-ART 네트워크의 분류성능은 96.25%이었다.