• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.1-8
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• 2013

A liquid-monopropellant hydrazine thruster has several outstanding advantages such as relatively-simple structure, long/stable propellant storability, clean exhaust products, and so on. Therefore hydrazine thruster has such a wide application as orbit and attitude control system (ACS) for space vehicles. A hydrazine thruster with the medium-level thrust to be used in the ACS of space launch vehicles (SLV) has been developed, and its ground firing test result is presented in terms of thrust, impulse bit, temperature, and chamber pressure. It is verified through the performance test that the response and repeatability of thrust are very excellent, and the thrust efficiencies compared to its ideal requirement are larger than 93%.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.67-73
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• 2017

An analysis of thermal degradation of epoxy based adhesive performed by thermogravimetry tests are presented in this study. Six different heating rates were employed for the weight change measurements. Based on the data, an Arrhenius type modeling equation was developed by calculating activation energies and proportional constants, and $n^{th}$ polynomial function was adopted to predict the weight change rates. The prediction results by the modeling was compared with the data using the average activation energy. It was found that the activation energy at the each heating rate was not same due to the different degradation kinetics, especially at the high heating rate. To overcome this pitfall, a new approach using exponential function series was introduced and employed. The calculation results showed very good agreements with the test data regardless of the heating rates.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.25-32
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• 2005

Seismic load is distributed to modes of a structure through the modal participation factor(MPF). The modal participation factor is essential to analyze structural response under earthquake load. MPF of a real structure differs from that of analytical mathematical model due to the error induced from analytical assumptions and during the construction. In this study, an identification method is proposed to calculate the 1st MPF of real structure based on $H^{\infty}$ optimal model reduction. The MPF is obtained from the relationship between observability and controllability matrices realized from system identification and those of a prototype 2-degree state space model. The proposed method is verified thorough numerical examples.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.72-81
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• 2009

In this paper, we investigate a spectrum sharing scheme based on the interference temperature (IT), that is a recently introduced receiver-centric metric by FCC. We extend the existing frequency sharing procedure for single CR to the one for multiple CRs (or secondary users, SUs). In the proposed interference model, we consider the practical operating characteristics of primary users (PUs), stochastically activated (ON)/deactivated (OFF) at the time axis, and analyze quantitatively the CR user capacity based on the model. We define the instantaneous capacity for idle time-slot channel allocation and the mean capacity averaging this instantaneous capacity and use them for a proper frequency sharing. Apart from existing schemes, the proposed frequency sharing scheme changes the frequency parameters adaptively depending on the channel characteristics and does not need any sensing information from PUs. Through computer simulation, we verify the proposed model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.774-781
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• 2014

The radar measurements are composed of range, Doppler and angles which are expressed as polar-coordinate components. An approach to match the measurements with the states of target dynamics which are modeled in cartesian coordinates is to use the pseudo-measurements or the extended Kalman filter in order to solve the mismatching problem. Another approach is that the states of dynamics are modeled in polar coordinates and measurement equation is linear. However, this approach bears that we have to deal with a time-varying dynamics. In this study, it is proposed that the states of dynamics are expressed as polar-coordinate component and the system matrix of the dynamic equation is modeled as a time-invariant. Nonlinear terms that appear due to the proposed modeling are regarded as a system input. The results of a series of simulation runs indicate that the tracking filter that uses the proposed modeling is viable from the fact that the Doppler measurement is easy to be augmented in the measurement equation.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.476-487
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• 2016

Although the number of adolescents with complicated problems and needs has increased, there has been a limited service for this population. In addition, a traditional social service could not alleviate the problems. In order to provide an alternative to a traditional social service to this population, the wraparound model is reviewed and explored. The study presents a review of literature on wraparound and social work via EBSOCO. By reviewing 12 articles on the subject, the study discovers 3 topics, such as (1) youth with various problems, (2) general characteristics of wraparound, and (3) evidence-based practice and wraparound. Based on 3 topics, the study also discusses the feasibility of wraparound service in Korea.

• Journal of Korea Multimedia Society
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• v.8 no.5
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• pp.641-650
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• 2005

In this parer, curve stopping function based on the CT number of lung parenchyma from CT lung images is proposed to detect lung region in replacement of conventional edge indication function in geodesic active contour model. We showed that the proposed method was able to detect lung region more effectively than conventional method by applying three kinds of measurement numerically. And, we verified the effectiveness of proposed method visually by observing the detection Procedure on actual CT images. Because lung parenchyma region could be precisely detected from actual EBCT (electron beam computer tomography) lung images, we were sure that the Proposed method could aid to early diagnosis of lung disease and local abnormality of function.

• The Journal of the Acoustical Society of Korea
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• v.11 no.4
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• pp.5-13
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• 1992

The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system has direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key-off of a jeep by experiment and computer simulation using a general purpose mechanical system program, DADS. The computer simulation model consists of the engine, body including frame, and front and rear axles and each axle has right and left tires. The force element between body and suspension is modeled as a combination of suspension spring and damper, and the unsprung mass has roll and pitch motion. The body shake obtained from experiment was compared with the result of computer simulation. Parametric study of the body shake on engine key-off is performed with changing the stiffness of engine mount rubber, the engine mount installation angle and position of engine mounts by using the verified computer simulation model.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.447-452
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• 2013

Vessel traffic system uses multiple sea surveillance radars as a primary sensor to obtain maritime traffic information like as ship's position, speed, course. The systematic errors such as the range bias and the azimuth bias of the two-dimensional radar system can significantly degrade the accuracy of the radar image and target tracking information. Therefore, the systematic errors of the radar system should be corrected precisely in order to provide the accurate target information in the vessel traffic system. In this paper, it is proposed that the method compensates the range bias and the azimuth bias using AtoN information installed at VTS coverage. The radar measurement residual error model is derived from the standard error model of two-dimensional radar measurements and the position information of AtoN, and then the linear Kalman filter is designed for estimation of the systematic errors of the radar system. The proposed method is validated via Monte-Carlo runs. Also, the convergence characteristics of the designed filter and the accuracy of the systematic error estimates according to the number of AtoN information are analyzed.

• 한국벤처창업학회:학술대회논문집
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• 2017.11a
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• pp.63-69
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• 2017

2015년 기업생멸 행정통계에 따르면, 우리나라의 최근 5년 동안('2010~2014년) 연평균 창업은 77만개, 폐업은 69만개인 것으로 나타났다. 지난 2015년 한해에만 개인사업자로 106만8313명이 창업을 하고 73만9420명이 폐업을 했다. 이는 하루 평균 3000명이 창업을 하고 2000명이 문을 닫는 셈이다. 실패를 경험한 기업인들은 여러 가지 심리적, 경제적 어려움에 직면하게 된다고 연구 보고되고 있다. 이같은 결과는 사업실패를 경험한 기업인들에 대한 케어의 필요성을 보여준다. 지난 2010년부터 정부가 실패기업인들에 대한 재기지원사업에 나서고는 있으나 재창업지원제도의 효과성에 대해서는 보장하기 어려운 상태다. 일각에서는 재창업지원이 양적인면에서는 활성화됐으나 질적으로는 아직 미흡하다고 지적이 나오고 있다. 이같은 상황에 착안하여 본 연구는 사업실패를 경험한 기업인들이 겪게되는 심리적 특성과 재기를 하고자 할 때 방해요소로 작용하는 감정요인에 초점을 맞추고자 한다. 따라서 선행연구를 통해 사업실패를 경험한 기업인들의 감정메카니즘을 규명한 모델(건강신념 모델:Health Belief Model)을 적용한 창업실패관련 개인평가와 사업실패경험(재무적 손실, 비재무적 손실)이 재창업의도에 어떠한 영향을 미치는지 규명하고자 한다. 감정요인인 창업실패관련 개인평가는 지각된 심각성, 지각된 취약성, 지각된 장애로 구성했다. 또 창업실패관련 개인평가와 재창업의도 사이, 사업실패경험과 재창업의도 사이에 재창업지원정책, 창업자기효능감이 각각 조절작용을 하는지 유의미한 관계성을 알아보고자한다. 연구 대상은 정부 재창업지원 프로그램을 진행하고 있는 중소기업진흥공단, 서울산업진흥원, 재도전지원센터등 기관의 재창업지원을 받은 기업인을 대상으로 설문을 실시하여 이들이 재창업지원서비스를 받기 전과 후에 대한 측정을 통해 실증분석을 하려고 한다.이 연구가 설정한 가설이 맞을 경우, 시사점으로는 정부의 재창업지원 프로그램의 효과성에 대한 검증이 될 것이다. 또 창업실패관련 감정메카니즘 규명으로 사업실패 기업인들의 재기를 도울 수 있는 재창업지원정책의 고도화가 가능해 질 것으로 판단된다.