• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.203-208
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• 1987

Design problem of output feedback controllers for discrete large scale systems using simplified model is investigated. It is shown that neglecting fast modes does not generally guarantee the stability of the closed loop system. In this paper, the design procedure is proposed to stabilize the system by minimizing a quadratic cost function for the simplified model and a measure of stability for the neglected fast model.

• Archives of Plastic Surgery
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• 제42권6호
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• pp.761-768
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• 2015

Background Surgical scars on the palmar surface of the hand may lead to functional and also aesthetic and psychological consequences. The objective of this study was to introduce a new incision technique for periarterial sympathectomy of the hand and to compare the results of the new two-step incision technique with those of a Koman incision by using an objective questionnaire. Methods A total of 40 patients (17 men and 23 women) with intractable Raynaud's disease or syndrome underwent surgery in our hospital, conducted by a single surgeon, between January 2008 and January 2013. Patients who had undergone extended sympathectomy or vessel graft were excluded. Clinical evaluation of postoperative scars was performed in both groups one year after surgery using the patient and observer scar assessment scale (POSAS) and the Wake Forest University rating scale. Results The total patient score was 8.59 (range, 6-15) in the two-step incision group and 9.62 (range, 7-18) in the Koman incision group. A significant difference was found between the groups in the total PS score (P-value=0.034) but not in the total observer score. Our analysis found no significant difference in preoperative and postoperative Wake Forest University rating scale scores between the two-step and Koman incision groups. The time required for recovery prior to returning to work after surgery was shorter in the two-step incision group, with a mean of 29.48 days in the two-step incision group and 34.15 days in the Koman incision group (P=0.03). Conclusions Compared to the Koman incision, the new two-step incision technique provides better aesthetic results, similar symptom improvement, and a reduction in the recovery time required before returning to work. Furthermore, this incision allows the surgeon to access a wide surgical field and a sufficient exposure of anatomical structures.

• Smart Structures and Systems
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• 제22권1호
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• pp.41-55
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• 2018

Damping ratio and frequency have influence on dynamic serviceability or instability such as vortex-induced vibration and displacement amplification due to earthquake and critical flutter velocity, and it is thus important to make determination of damping ratio and frequency accurate. As bridges are getting longer, small scale model test considering similitude law must be conducted to evaluate damping ratio and frequency. Analysis conditions modified by similitude law are applied to experimental test considering different scale ratios. Generally, Nyquist frequency condition based on natural frequency modified by similitude law has been used to determine sampling rate for different scale ratios, and total time length has been determined by users arbitrarily or by considering similitude law with respect to time for different scale ratios. However, Nyquist frequency condition is not suitable for multimode system with noisy signals. In addition, there is no specified criteria for determination of total time length. Those analysis conditions severely affect accuracy of damping ratio. The focus of this study is made on the determination of minimum analysis conditions for different scale ratios. Influence of signal to noise ratio is studied according to the level of noise level. Free initial value problem is proposed to resolve the condition that is difficult to know original initial value for free vibration. Ambient and free vibration tests were used to analyze the dynamic properties of a system using data collected from tests with a two degree-of-freedom section model and performed on full bridge 3D models of cable stayed bridges. The free decay is estimated with the stochastic subspace identification method that uses displacement data to measure damping ratios under noisy conditions, and the iterative least squares method that adopts low pass filtering and fourth order central differencing. Reasonable results were yielded in numerical and experimental tests.

• 웰빙융합연구
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• 제6권1호
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• pp.23-31
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• 2023

Purpose: The purpose of this study is a preliminary study to develop a comprehensive information avoidance scale that includes various search contexts. Research design, data and methodology: This study is a part of exploratory sequential design of mixed method for the development of information avoidance scale. Based on the themes derived from the analysis of the in-depth interview data collected in the qualitative research of the first stage of the study, 45 preliminary items on information search and avoidance were constructed. The factors related to information searching included information recognition, information seeking purpose, and information search expectations. Individual, information, time, and system factors were related to information avoidance. Pearson's correlation analysis was performed for the correlation between factor items, and Cronbach's alpha analysis was performed for the reliability analysis of the items. Exploratory factor analysis was applied to examine the construct validity of 35 items of information avoidance. Results: Among the information avoidance items, one of the less relevant among information purpose items, two information factor items, and one time factor item were excluded. Conclusions: A secondary survey should be conducted to confirm the validity and reliability of the scale composed of adjusted items (35) based on the results of exploratory factor analysis. The strength of this preliminary scale is that it was developed based on vivid qualitative data of ordinary people who had experiences of search and avoidance in various search contexts.

• 대한기계학회논문집
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• 제5권3호
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• pp.159-169
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• 1981

The mixing length theory is extended to close the momentum queations for two-phase turbulent flow at a first-order closure level. It is assumed that the mass fraction of the particles is of the order of unity, that the particle size is so small that the particles are fully suspended is the primary fluid, and that the relaxation time scale of the particles is of the same order as the time scale of the energy containing eddies so that the suspended particles are responsive to the fluctuating turbulent field. The bulk motion of the particles is treated as a secondary fluid with its own coefficient of momentum transport. The proposed closure is uniformly destributed acress the pipe section. Predicted velocity profiles and the friction factors are in good agreement with avaiable experimental data.

• Journal of Species Research
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• 제5권3호
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• pp.517-529
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• 2016

Two scale worms of the family Polynoidae, Arctonoe vittata (Grube, 1855) and Hyperhalosydna striata (Kingberg, 1856) were found for the first time from Korea by SCUBA diving survey. The two species are free-living organisms or associated commensally with a wide variety of other invertebrates. Specimens of A. vittata were collected from the East Sea and were closely associated with asteroids, holothuroids, gastropods and nudibranchs species. Specimens of H. striata were collected from Jeju-do Island, and of these, one specimen was collected in a tube of eunicid species. The two species can be easily distinguished from their congeners by distinct morphological characteristics as follows: (1) A. vittata has pigmented band near segment eight and two kinds of neurochaetae; (2) H. striata has reddish-brown longitudinal striped elytra. The morphological key characteristics of both species agreed well with their original descriptions and redescriptions. In this study, the descriptions, detailed illustrations and ecological photographs of two species based on Korean materials were provided.

• KIEE International Transactions on Power Engineering
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• 제11A권4호
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• pp.33-38
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• 2001

The KEPS(KEPCO＇s Enhanced Power system Simulator) Real Time Digital Simulator(RTDS) is the largest real time power system simulator ever built. A power system which includes 320 (3-phase) buses and 90 generators has been modeled and run in real time. Since such large-scale systems were involved, it was not practical to validate them using non-real time electro-magnetic transient programs such as EMTDC™ or EMTP. Instead, the results of the real time electromagnetic transient simulation were validated by comparing to transient stability simulations run using PTI's PSS/E™ program. The comparison of results from the two programs is very good in almost all cases. However, as expected, some differences did exist and were investigated. The differences in the results were primarily traced to the fact that the electromagnetic transient solution algorithm provides more detail solutions and therefore greater accuracy than the transient stability algorithm. After finding very good comparison of results between RTDS Simulator and PSS/E, and after investigating the discrepancies found, KEPCO gained the necessary confidence to use the large-scale real time simulator to analyze and develop their power system.

• Asian Journal of Business Environment
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• 제7권4호
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• pp.35-41
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• 2017

Purpose - This paper aims to examine several time series models to predict sales of department stores and discount store markets in South Korea, while other previous trial has performed sales of convenience stores and supermarkets. In addition, optimal predicted values on the underlying model can be got and be applied to distribution industry. Research design, data, and methodology - Two retailing types, under investigation, are homogeneous and comparable in size based on 86 realizations sampled from January 2010 to February in 2017. To accomplish the purpose of this research, both ARIMA model and exponential smoothing methods are, simultaneously, utilized. Furthermore, model-fit measures may be exploited as important tools of the optimal model-building. Results - By applying Holt-Winters' additive seasonality method to sales of two large-scale retailing types, persisting increasing trend and fluctuation around the constant level with seasonal pattern, respectively, will be predicted from May in 2017 to February in 2018. Conclusions - Considering 2017-2018 forecasts for sales of two large-scale retailing types, it is important to predict future sales magnitude and to produce the useful information for reforming financial conditions and related policies, so that the impacts of any marketing or management scheme can be compared against the do-nothing scenario.

• Interaction and multiscale mechanics
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• 제5권1호
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• pp.27-40
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• 2012

The two-dimensional incompressible flow of a linear viscoelastic fluid we considered in this research has rapidly oscillating initial conditions which contain both the large scale and small scale information. In order to grasp this double-scale phenomenon of the complex flow, a multiscale analysis method is developed based on the mathematical homogenization theory. For the incompressible flow of a linear viscoelastic Maxwell fluid, a well-posed multiscale system, including averaged equations and cell problems, is derived by employing the appropriate multiple scale asymptotic expansions to approximate the velocity, pressure and stress fields. And then, this multiscale system is solved numerically using the pseudospectral algorithm based on a time-splitting semi-implicit influence matrix method. The comparisons between the multiscale solutions and the direct numerical simulations demonstrate that the multiscale model not only captures large scale features accurately, but also reflects kinetic interactions between the large and small scale of the incompressible flow of a linear viscoelastic fluid.

• 한국수자원학회논문집
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• 제40권1호
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• pp.39-50
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• 2007

본 논문에서는 대수-선형 파손율 모형(log-linear ROCOF)과 와이블 파솔율 모형(Weibull ROCOF)을 이용하여 상수도 주철 배수관로의 파손율을 모형화하고, '수정된 시간 척도'를 이용하여 최적교체시기를 산정할 수 있는 방법이 개발되었다. 두 ROCOF의 모형화를 위하여 개별 관로의 파손시간을 기록한 '파손 시간자료(failure-time data)'와 일정 시간간격 사이에서 발생하는 파손횟수를 기록한 '파손 횟수자료(failure-number data)'를 이용하였고, 최대로그우도 추정값을 이용하여 두 ROCOF의 각 파손자료 유형에 대한 모형화 수행 능력을 검증하였다. 또한 두 ROCOF를 이용한 관로의 최적교체시기 방정식은 ROCOF의 매개변수 추정에 있어서 수렴성을 보장하기 위하여 '수정된 시간 척도'를 적용하여 유도하였다. 연구대상 주철 배수 관로들의 '파손 시간자료'와 '파손 횟수자료'에 두 파손율 모형을 적용시켜 본 결과 파손 시간자료를 이용할 경우 대수-선형 ROCOF가 와이블 ROCOF 보다 적합한 모형인 것으로 나타났다. 또한 두 모형 모두 '파손 시간자료'를 이용하는 것이 '파손 횟수자료'를 이용하는 것보다 모형화 수행 능력이 높아지는 것으로 나타나서, 분석에 사용된 관로의 파손율 모형화와 최적교체시기 산정을 위해서는 일정 시간간격 동안의 관로 파손횟수를 기록하는 것보다 관로의 파손시간을 기록하는 것이 더욱 우수한 모형화 결과를 낳는 것으로 나타났다.