• 한국농공학회논문집
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• 제51권4호
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• pp.57-66
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• 2009

수학적 모델은 수량과 수질의 예측을 위해 현장 조사의 대안으로 사용되어지며 이러한 모델의 사용과 실측에 불확실성이 존재하게 된다. 불확실성에 대한 많은 연구들이 진행되어 왔으나 시나리오에 의한 모델링 과정에서 발생하는 불확실성에 대한 연구는 미흡한 실정이다. 본 연구에서는 산림이 농경지와 목초지로의 변화에 따른 시나리오를 설계한 후 시나리오 적용에 따른 SWAT (Soil and Water Assessment Tool) 매개변수의 불확실성을 분석하고자 하였다. 몬테카를로 기법 (Monte Carlo simulation)을 이용하여 각 매개변수별 1,000개의 난수를 발생하였으며 앙상블 유량모의 기법을 이용하여 미국 Alabama주 카하바강 상류 (50,967ha)를 대상으로 각 난수별 100개의 유량을 통해 불확실성을 분석하였다. 분석 결과 산림지역이 농경지와 목초지로 변화 되었을 때 유출량이 증가하는 것으로 분석되었으며, 임야가 목초지 보다 농경지로 변화되었을 때 유출량은 더욱 증가하는 것으로 나타났다. 각 시나리오별 SWAT 매개변수의 불확실성은 AWC (Available water capacity), CN (Curve number), GWREVAP (groundwater re-evaporation coeffeicient), REVAPMN (minimum depth of water in shallow aquifer for re-evaporation to occur)순으로 크게 나타났으며, Ksat (Saturated hydraulic conductivity)와 ESCO(Soil evaporation compensation factor)는 유출량의 변화에 큰 영향을 미치지 못하는 것으로 분석되었다. 토지피복별 산림 면적이 클 경우 불확실성이 크게 나타나 산림이 목초지와 농경지로 변함에 따라 불확실성은 감소하는 것으로 나타났다.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.71-80
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• 2002

영구자석형 선형동기전동기(PMLSM)는 고속, 고추력의 직선추진이 가능하므로 산업현장에서 위치결정장치나 물류반송시스템 및 공작기계 등의 선형 서보 시스템에 이용이 되고 있다. 본 논문에서는 PMLSM의 AC 서보화를 위해 동기 프레임상에서 제어구조가 미리 설정된 스위칭 함수에 따라 불연속적으로 변화되는 가변구조 전류제어방식 및 간접 벡터제어이론을 기본으로하여 도달시간을 제거하고, 구동시스템의 추력 이용도를 높이기 위해 파라미터 변동과 한정된 외란에 거의 영향을 받지 않으며 오버슈트가 없는 고속응답을 실현하기 위해 슬라이딩 모드제어 알고리즘을 제안하여 PMLSM의 위치제어에 적용하고자 한다.

• 보건교육건강증진학회지
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• 제15권1호
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• pp.151-163
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• 1998

The purpose of this study is to find options which reduce the job stress and to enhance morale through a variable analysis, and also apply this data in the legal and administration fields. The data for the research was obtained from 217 dental hygienists working in the dental clinics, dental hospitals and university's dental hospitals' in Seoul. The tool used by this study was a Questionnaire measuring on-the-job stress of dental hygienists, was a modified and revised. The Questionnaire version used to measure bank's job stress and used to suggest options by Dae-ha Yoon(1991). Classification of items for measuring job stress was based on Theoretical Study on Job Stress by Dae-hyon Song(1986). The scale used in study was the two points (yes or no in the job stress) scale measuring for variables. The period of data collection was 30 days from December 4, 1995 to January 5, 1996. The methods of data collection were self-writing, direct visit, and postal Questionnaire answering, 224 copies of Questionnaire data were collected, but only 217 copies were used. 7 copies could not be analyzed, were not used for this study. The data analysis was conducted by SPSS after coding the collected raw data. The general characteristics was obtained from real digits and percentages. In order to analyze the difference of sub-variables against the job stress based on general characteristics. Mean, Standard Deviation, and F test (ANDVA) were conducted. The following were the results of job stress variables: 1. Meaningful variable affecting the working organization, is compensation system(p〈0.03). 2. Meaningful variable affecting the working period, is work overload(p〈0.02). 3. Meaningful variable affecting average patients per day, is the career management and payment(p〈0.04, p〈0.01). 4. Meaningful variable affecting number of staff, is the comrade relationship, role conflict among patients, work overload, and job overload(p〈0.000, p〈0.05, p〈0.04, p〈0.01). The comrade relationship is most affected to the number of staffs aides. 5. Meaningful variables affecting job diversion, are the desire and value, the non-role play, and the environment(p〈0.003, p〈0.02, p〈0.005).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.283-286
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• 2003

The electric traction load is quite differ from general power system load which is single-phase, high-speed heavy load receiving power from 3-phase power system and also has variable load characteristics over time and space. Therefore, there are inevitably power quality problems such as steady state or transient voltage drop, voltage imbalance and harmonic distortion. In addition, it is expected that transient voltage sag could affect the safety of feeding system. Thus, in this paper transient analysis and voltage sag compensation of AT(Auto Transformer) feeding system are studied. The fault study of traction network is analysed by using PSCAD/SMTDC simulation tool. In addition, application of DVR in electric traction system is proposed to compensate the voltage sag of traction network which is occurred by the fault of utility source. The results of fault study will be a useful research works for operation and setting of electric traction relay. Also, it can be shown that application of the DVR in electric system is very useful to compensate the voltage sag from the result of related simulated work. The results of study will be a useful research works for management and planning of power quality in electric traction system.

• Smart Structures and Systems
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• 제26권3호
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• pp.373-390
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• 2020

Hybrid simulation (HS) is a versatile tool for structural performance evaluation under dynamic loads. Although real structural responses are often multiple-directional owing to an eccentric mass/stiffness of the structure and/or excitations not along structural major axes, few HS in this field takes into account structural responses in multiple directions. Multi-directional loading is more challenging than uni-directional loading as there is a nonlinear transformation between actuator and specimen coordinate systems, increasing the difficulty of suppressing loading error. Moreover, redundant actuators may exist in multi-directional hybrid simulations of large-scale structures, which requires the loading strategy to contain ineffective loading of multiple actuators. To address these issues, lately a new strategy was conceived for accurate reproduction of desired displacements in bi-directional hybrid simulations (BHS), which is characterized in two features, i.e., iterative displacement command updating based on the Jacobian matrix considering nonlinear geometric relationships, and force-based control for compensating ineffective forces of redundant actuators. This paper performs performance validation and application of this new mixed loading strategy. In particular, virtual BHS considering linear and nonlinear specimen models, and the diversity of actuator properties were carried out. A validation test was implemented with a steel frame specimen. A real application of this strategy to BHS on a full-scale 2-story frame specimen was performed. Studies showed that this strategy exhibited excellent tracking performance for the measured displacements of the control point and remarkable compensation for ineffective forces of the redundant actuator. This strategy was demonstrated to be capable of accurately and effectively reproducing the desired displacements in large-scale BHS.

• 통상정보연구
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• 제14권2호
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• pp.369-387
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• 2012

한미 FTA의 협상 과정에서부터 비준을 걸쳐 발효된 이후까지 끊이지 않는 논쟁의 중심에는 바로 투자자-국가 소송제도인 ISD가 있다. ISD의 본 취지인 외국인 투자자에 대한 보호기능은 국제통상환경에서 없어서는 안 될 보호장치이며 지금까지 수많은 양자투자협정(BIT)에도 적용되어온 제도임에도 ISD에 대한 부정적인 시각은 여전히 존재한다. 그중에서도 가장 큰 우려는 정부의 공공정책이 ISD 때문에 제한될 수 있다는 것이다. 실제로 한미 FTA의 당사국인 미국이 맺은 NAFTA의 경우를 보면 ISD로 인하여 캐나다와 멕시코 정부가 ISD 제소를 당해왔으며, 그로 인하여 공공정책을 추진하면서 제약을 느껴온 것은 사실이다. 그러나 일부의 ISD 사건에서는 일국 정부의 공공정책이 투자자의 이익을 우선한다는 판정부의 결정도 있었다. 그렇다면 한미 FTA가 막 발효된 이 시점에서 우리가 앞으로 일어날 수 있는 우리 정부에 대한 미국기업이나 미국인 투자자의 ISD 제소에 어떻게 대비해야 하며, 정부의 공공정책이 어떻게 해야 ISD 제소의 표적이 되지 아니할지에 대한 분석이 필요하다. 이러한 분석에 가장 효과적인 자료가 미국이 당사국으로 있는 NAFTA의 ISD 사건들이다. NAFTA의 ISD 사건 분석은 판정부가 판정을 함에 있어 어떠한 법리적 해석을 하는지를 알 수 있는 근거자료이며 나아가 우리의 상황에 적용하여 대비하는데 필수적인 도구이기도 하다.

• 대한기계학회논문집A
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• 제41권10호
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• pp.967-974
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• 2017

본 연구에서는 횡가속도 센서 계측 신호 기반의 기준 차량 요레이트 모델을 활용하여 횡경사 유무에 관계 없이 견실한 성능을 보장하는 제동기반 요 모멘트 제어시스템을 개발하였다. 2자유도 single track 모델과 횡가속도 센서 계측 신호를 융합하여 새로운 기준 요레이트 모델을 설계하였고 이를 기반으로 요 모멘트 제어기를 설계하였다. 또한 외란 관측기를 적용하여 요레이트 동역학에 존재하는 차량 파라미터 오차를 보상하고 제어기의 성능을 개선하였다. 다자유도 차량동역학 해석 SW인 CARSIM을 이용하여 평지 및 횡경사 노면을 반영한 다양한 검증 시나리오 조건에서 제안된 제어기를 검증하였다. 그 결과 기준 차량모델에 횡가속도 계측 신호를 반영하고 외란 관측기를 통해 모델 파라미터 오차를 보상하는 것을 특징으로 하는 새롭게 제안된 횡안정성 제어기가 도로 횡경사에 관계없이 다양한 주행상황에서 차량의 횡안정성을 견실하게 유지할 수 있음을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.114-123
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• 2018

Recently, as one of the countermeasures to reduce carbon dioxide($CO_2$) for global warming problems, operation methods in micro-grid systems replacing diesel generator with renewable energy sources including wind power(WP) and photovoltaic(PV) system have been studied and presented in energetic manners. However, it is reported that some operation problems in micro-grid systems without diesel generator for carbon-free island are being occurred when large scaled WP systems are at start-up. To overcome these problems, this paper proposes an operation strategy in micro-grid systems by adapting control devices such as CVCF(constant voltage constant frequency) ESS(energy storage system) for constant frequency and voltage regulation, load control ESS for balancing demand and supply and SVC(static-var compensator) for reactive power compensation. From the simulation results based on the various operation scenarios, it is confirmed that the proposed operation strategy in micro-grid systems without diesel generators is a useful tool to perform a stable operation in micro-grid systems without diesel generator and also make a contribution to reduce carbon dioxide in micro-grid systems.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.106-109
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• 2005

Springback is a common phenomenon in sheet metal forming, caused by the elastic recovery of the internal stresses after removal of the tooling. Recently, advanced high strength steels (AHSS) such as TRIP and DP are finding acceptance in the automotive industry because their superior strength to weight ratio can lead to improved fuel efficiency and assessed crashworthiness of vehicles. The major troubles of the automotive structural members stamped with high strength steel sheets are the tendency of the large amount of springback due to the high yield strength and the tensile strength. The amount of springback is mainly influenced by the type of the yield function and anisotropic model induced by rolling. The discrepancy of the deep drawn product comparing the data of from the product design induced by springback must be compensated at the tool design stage in order to guarantee its function and assembly with other parts. The methodology of compensation of the low shape accuracy induced by large amount of springback is developed by the expert engineer in the industry. Recently, the numerical analysis is introduced in order to predict the amount of springback and to improve the shape accuracy prior to tryout stage of press working. In this paper, the tendency of springback is evaluated with respect to the blank material. The stamping process is analyzed fur the front side member formed with AHSS sheets such as TRIP60 and DP60. The analysis procedure fully covers the binderwrap, stamping, trimming and springback process with the commercial elasto-plastic finite element code LS-DYNA3D.

• 대한지역사회영양학회지
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• 제24권2호
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• pp.117-126
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• 2019

Objectives: This study was conducted to investigate the current difficulties surrounding children's obesity management and evaluate the application of a mobile phone as a tool to overcome such difficulties of obesity management from the perspective of main caregivers of elementary school students. Methods: The qualitative data were collected through 3 focus group interviews including 6 full-time housewives, 7 mothers with overweight children, and 4 working mothers. Data were analyzed using a thematic approach. Results: The limitations of current children's obesity management included difficulty in diet management and exercise as well as challenges of setting goals and lack of support at the household and school levels. Mobile technology may be useful to overcome the current problems by providing real-time knowledge on diet management and physical activity, online compensation scheme according to goal setting, and interactive environmental supports at both household and school levels for promoting overall health. Conclusions: The mobile-based multiple support program may assist in overcoming the current limitations of child obesity management by providing tailored information and by creating a more supportive environment.