• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.941-944
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• 2005

Asymmetry of rotor systems is an important factor for identification of dynamic characteristics including the stability and response of rotors and for condition monitoring. In this work, asymmetry of rotors is identified by applying curve-fitting method to the directional frequency response functions (dFRFs), which are known as a powerful tool for detecting the presence and degree of asymmetry. This method minimizes least square error between analytical and measured dFRFs by iteratively updating physical parameters associated with rotor asymmetry. The effectiveness of the identification method is demonstrated by experiments with a laboratory test rotor.

• The Korean Journal of Rheology
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• v.8 no.2
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• pp.139-146
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• 1996

2차원 비점성 Euler 방정식의 Stuart 해에 의하여 주어지는 주기적인 유동장, 소위 말하여 Stuart와동장내에 놓여있는 아주 작은 비대칭성 입자의 다양한 부력 변수에 따른 침 강운동을 고찰하엿다. 본 연구에서 사용한 수치방법은 매질의 준전적인 Stokes 방정식과 입 자의 평형방정식을 연계하였다. 다양한 초기 배향각 또는 형상비에 따른 궤적이나 각변화를 예측하기 위하여 힘과 토오크 관계식을 입자의 운동방정식에 적용하였으며 4차 Runge-Kutta 방정식을 이용하여 입자의 운동을 규명하였다.

• Economic Analysis
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• v.24 no.3
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• pp.1-36
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• 2018

When it comes to explaining the relationship between inventory investment and business fluctuations, the production smoothing theory and the stock-out avoidance theory take contradictory stances. Decision-making related to inventory investments of corporations is thought to be influenced by both motives, but the relative sizes or directions of their respective influences can differ depending upon the phase of the business cycle. Against this backdrop, this paper differs from existing studies in that it theoretically tests the relative significances of the production smoothing and stock-out avoidance motives in the inventory investment dynamics, while placing its analytical focus on determining the existence and patterns of the asymmetric dynamics of inventory investment over the business cycle phases. To this end this paper sets up a non-linear model that is expanded from the existing linear inventory investment model, and checks whether its predictive power is better than that of the existing model. The results of analysis confirm the nature of the asymmetric dynamics of inventory investment over the business cycle phases. A stock-out avoidance motive appears but there is no significant production smoothing motive in boom times. In downturns, in contrast, the stock-out avoidance motive is insignificant, but a quality of asymmetric dynamics in which changes in inventory cause the deepening of recessions, due to the non-convexity of production costs proposed by Ramey (1991), is detected. This paper confirms that a model considering the asymmetric dynamics of inventory investment can have better predictive power than one that does not consider it, through within-sample and out-of-sample predictions and various predictive power tests. These research results are expected to be useful for economic forecasting, through their enhancement of the understandings of the inventory investment dynamics and of the nature of its business cycle destabilization.

• International Area Studies Review
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• v.15 no.3
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• pp.55-76
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• 2011

In this paper, we estimate a model that incorporates key features of business cycles, co-movement among economic variables and switching between regimes of expansion and recession, to aggregate quarterly data for the NAFTA region. Two common factors reflecting the permanent and transitory components of the business cycle in the region, along with the turning points from one regime to the other, were extracted from the data by using the Kalman filter and maximum likelihood estimation approach of Kim (1994). Estimation results confirm that a typical aspect of business cycles are also observed (i.e., recessions are steeper and shorter than recoveries) in the region, and that both co-movement and that regime switching are found to be important features of the business cycle. The two common factors produce sensible representations of the trend and cycle, and the estimated turning points are in line with independently determined chronologies. It also turns out that the degree of synchronization between the NAFTA region and Korea, has significantly increased since the entry into force of the NAFTA.

• The korean journal of orthodontics
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• v.35 no.3 s.110
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• pp.163-173
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• 2005

The purpose of this study was to compare the asymmetric degree between maxillofacial hard and soft tissues in individuals with facial asymmetry. Computerized tomographies (CT) of 34 adults (17 male, 17 female) who had facial asymmetry were taken. The CT images were transmitted to personal computers and then reconstructed into three-dimensional (3D) images through the use of computer software. In order to evaluate the degree of facial asymmetry, 6 measurements were constructed as the hard tissue measurements while 6 counterpart measurements were taken as the soft tissue measurements. The means and standard deviations were obtained for each measurement using 3D measure, then t-test was used to investigate the differences between each hard tissue measurement and the corresponding soft tissue measurement All measurements used in the present study showed statistically significant differences between the hard and soft tissues. The degree of soft tissue asymmetry was smaller than that of corresponding hard tissue asymmetry in case of chin deviation, frontal ramal inclination difference, and frontal corpus inclination difference. On the other hand, the degree of soft tissue asymmetry was greater than that of underlying hard tissue asymmetry in the measurement of lip canting and lip cheilion height difference The present study suggests that asymmetric differences of hard and soft tissue is observed nu facial asymmetric subjects and thus soft tissue analysis is needed in addition to hard tissue analysis when making an evaluation of facial asymmetry.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.169-178
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• 2008

The goals of this study were to provide data of 3 dimensional ground reaction force(GRF) parameters during stair ascent and descent on three different stair runs and to investigate variability and asymmetry index of them. 10 healthy adults participated in this study and performed 7 different types of gait with 10 trials each. After data analysis, following results were found. Firstly, stair run did not affect on the pattern of GRF parameters, coefficient of variation and asymmetry index. Secondly, a significant different GRF pattern was found between level walking and stair walking. Especially, ascending stair walking has only large Fz1 and small Fz3 while level walking and descending stair walking have a "M" shape connected by Fz1, Fz2 and Fz3. Thirdly, only vertical GRF parameters of stair walking revealed acceptable coefficient of variation and asymmetry index.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.49.2-49.2
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• 2018

스퍼터링에 의해 증착된 박막 내 기계적 응력 발생 현상을 규명하기 위하여 활발한 이론적, 실험적 접근이 있었으나, 복잡한 플라즈마 증착환경 내에서 다양한 증착 파라미터로 인해 정확한 응력 발생 메커니즘에 대해 아직도 완벽한 규명이 되지 않은 상황이다. 본 연구에서는 몰리브데늄 (Mo)과 텅스텐 (W) 박막을 마그네트론 스퍼터링법을 이용하여 증착 시 발생하는 잔류응력 발생 현상에 대해 논의하겠다. Mo 박막의 경우 증착압력을 2.5 mTorr와 4.1 mTorr로 고정시킨 채 기판 바이어스를 0-250 V 간격으로 변화시킨 결과, 2.5 mTorr에서는 기판바이어스가 증가할수록 압축응력이 증가하는 반면 4.1 mTorr에서는 기판바이어스가 증가할수록 인장응력이 증가하는 것이 확인되었다. 이러한 반대 경향의 잔류응력을 발생시키는 기판 바이어스 효과를 확인하기 위하여 증착 파라미터 변경에 따른 박막 성장 거동 모델을 제시한다. W 박막은 준안정상인 ${\beta}$-상이 증착 초기(2.5 nm)에 형성이 되고, 증착 과정에서 열역학적 안정상인 ${\alpha}$-상으로 상변태 하였다. 상변태에 의한 부피 변화에 따른 잔류응력 발생의 분석을 위하여 X-ray 회절피크의 비대칭성을 분석한 결과 압축응력과 인장응력이 공존하고 있는 것으로 확인되었다. 본 연구결과는 스퍼터링 공정 시 높은 에너지를 가지는 중성화된 Ar과 스퍼터된 원자가 기판과 충돌 시 atomic peening effect에 의해 압축응력이 발생한다는 일반적인 이론과 상충되는 결과로서, Mo 및 W 박막 내 잔류응력 제어를 위한 방안을 제시한다.

• The Journal of the Korea Contents Association
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• v.22 no.3
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• pp.576-585
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• 2022

In determining the cause of dysmenorrhea, it is necessary to investigate postural alignment and balance. The purpose of this study is to compare and analyze whether there is a difference in posture alignment and foot pressure balance according to the dysmenorrhea degree. The subjects were twenty female students in their 20s, who had pain caused by dysmenorrhea. According to the degree of dysmenorrhea, the subjects were divided into mild and severe groups. In the results, there was a significant difference only in shoulder height asymmetry angle between the mild and severe groups (p<0.05), and there was no significant difference in pelvic and knee joint alignment. In the correlation analysis, there was a significant positive correlation between the dysmenorrhea score (MDQ) and shoulder height asymmetry angle was found. These results indicate that dysmenorrhea symptom and asymmetric alignment of shoulder are related. To analyze these factors, further research will need to investigate the correlation between dysmenorrhea and spinal alignment.

• Korean System Dynamics Review
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• v.4 no.2
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• pp.45-69
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• 2003

'비대칭'으로 특징지워지는 이동통신 시장에서의 규제 정책은 찬반 논란속에서 많은 이슈들을 제기하고 있다. 이에 따라 많은 선행 연구들이 이동통신 시장에서의 비대칭 규제에 대한 한계를 지적하고 계선 방안을 제시하고자 노력하였다. 그러나 대부분 개념적으로 설명하여 정책의 실효성을 가시적으로 보여주지 못할 뿐만 아니라 다양한 정부 정책들이 혼합되어 나타날 영향에 대한 고려는 미흡하다. 본 연구는 이러한 한계를 극복하기 위한 하나의 대안으로서 시스템 다이내믹스라는 새로운 접근 방법을 적용하였다. 다양한 변수들간의 인과 관계와 피드백 구조를 중심으로 작성된 인과지도는 이동통신시장과 같이 복잡한 시스템의 특성을 규명하여 문제의 원인을 구조적으로 설명할 수 있으며 이에 기초한 시뮬레이션 모델은 다양한 정책 대안들을 시나리오에 따라 시뮬레이션 함으로써 정부 규제가 이동통신 시장에 미치는 영향을 예측하고 의사결정을 위한 함의를 이끌어내는 데 매우 유용할 수 있다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10a
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• pp.252-254
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• 1999

서버로부터 클라이언트로의 전송 능력이 클라이언트로부터 서버로의 전송 능력보다 월등히 높다는 통신 비대칭성(communication asymmetry)이 여러 유무선 정보 시스템에서 관찰됨에 따라서, 클라이언트가 서버로 데이터에 대한 요청을 보내는 전통적인 클라이언트/서버 통신 방식과는 달리 클라이언트로부터의 직접적인 요청없이도 서버가 클라이언트에 데이터를 전송하는 "푸시(push)"기법 및 일대다(one-to-many) 푸시 기법인 "데이터 전파(data dissemination)" 기법에 대한 연구가 활발히 진행되어 오고 있다. 본 논문은 비균등 선호도 분포(non-uniform popularity distribution)를 가지는 데이터를 단일 브로드캐스트 채널에 효과적으로 전송하기 위해 연구되어온 브로드캐스트 디스크(Broadcast Disks) 기법에서 데이터에 대한 평균 지연 시간을 최소화하기 위해 각 디스크에 대한 주파수를 최적으로 설정하는 문제를 다루고 있다. 본 논문에서는 최적의 주파수 설정과 연관된 조건을 규명하기 위해서 수학적 모델링과 증명을 하였으며, 이러한 접근방식의 정확성을 입증하기 위한 시뮬레이션 결과들을 제시한다. 위한 시뮬레이션 결과들을 제시한다.