• 대한토목학회논문집
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• 제31권2B호
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• pp.109-119
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• 2011

본 연구에서는 한강하구의 흐름에 직접적인 영향을 미치는 구조물인 신곡수중보의 하류 이설 후 변형, 그리고 철거 등을 가정하여 이에 따른 수리특성을 평면 2차원 수치모형을 통해 분석하였다. 2차원적 해석은 보 이설이나 변형이 주변 지형, 특히 습지에 어떤 수리학적 영향을 미치는지 확인할 수 있게 하였다. 모의에 사용된 조위 및 유황은 2007년도 자료를 바탕으로 하였으며, 유량은 풍수기와 평수기로 구분하고 조위는 대조기와 소조기를 포괄하였다. 연구대상 영역으로 한강상류는 한강대교, 임진강상류는 통일대교, 하구경계는 유도로 잡았다. 모의결과 수중보 이설 및 변형에 따라 만조시 해수 유입 영향권이 크게 변화하였으며, 주요 지점의 수위는 유량 및 조위 조건에 따라 변동폭이 다양하게 나타났다.

• 간호행정학회지
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• 제11권1호
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• pp.79-88
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• 2005

Purpose: This study was conducted to assess the effects of shift-work on psychological factors in university hospital's nurses. Method: The subjects were 276 nurses who have worked in a university hospital and the nurses were questioned with self-reported questionnaire forms. We investigated psychological factors(anxiety, depression, stress and self-esteem), nurses' general characteristics and shift-work. The data was analyzed by using SAS for Windows 9.13. Results: The frequency of nurses with anxiety, depression and high stress were 56.5%, 44.9% and 19.6%, respectively. The mean score of self-esteem was 30.03. Stress was higher in cases of having shift-work. Immediately after doing shift-work, nurses had higher depression and stress, and lower self-esteem scores. After controlling confounding variables, psychological factors affected by shift-work was stress. An upward tendency in anxiety, depression and stress were found in cases of doing shift-work for more than 5 years. Conclusions: It is necessary to develope a program for reducing psychological disturbance at the early times of shift-work and to plan adequate shift-work intervals.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.10-21
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• 1996

In this study, as a strategy to improve shift characteristics, the authors developed a new style pressure modulator which can reduce shock torque during power shift by modulating the pattern of pressure increase in the cylinder for actuating the clutch. The remarkable merits of this new pressure modulator lie in its structural simplicity and durability, because the modulator is only composed of a poppet type valve and a few orifices. The usefulness of the new pressure modulator is confirmed by experiments and numerical analyses on a clutch control hydraulic system simplified for easy test. Also, the excellency of the transmission with the new pressure modulator is verified by experiments on a test bench for simulating the running power train of an excavator.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.431-437
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• 2013

Measured acoustic signal from operating high speed train contains frequency change called doppler shift due to its motion. To avoid this doppler shift wind tunnel test is required. But scaledown of model can cause change of source characteristics. And measurements using some part of train cannot reproduce real flow condition. The best way to recognize real noise source characteristics is measurement from operating high speed train but doppler shift makes it hard. So, we developed simple dedopplerization technique for one microphone and applied to field test data of high speed train. Through this, we could capture real frequency of noise from operating high speed train.

• 드라이브 ㆍ 컨트롤
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• 제15권3호
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• pp.36-42
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• 2018

Agricultural tractors require frequent shifting to improve operation efficiency, and PST (Powershift Transmission) is considered as a suitable transmission. However, due to the inherent characteristics of the PST, shocks arise during shifting, which imparts a negative effect on the operator. Therefore, in order to improve the transmission performance of the tractor PST, researches on various methods including the hydraulic system circuit, the engine input speed control, and the mechanical system of the transmission are steadily being conducted. In this study, in order to reduce the impact of PST on a shift based on SimulationX software, we analyzed the characteristics of the input signal of PCV (Pressure Control Valve) through sensitivity analysis and verified the simulation model through actual vehicle test. Optimization was performed for minimizing the shift shock for some of the parameters of the input signal at constant temperature and RPM conditions.

• 대한교통학회지
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• 제30권3호
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• pp.17-30
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• 2012

본 연구는 공로에서 철도로의 모달 쉬프트를 활성화 하는데 필요한 기본 특성을 조사하고 분석하였다. 연구의 대상 화물은 국내에서 내륙으로 운송되는 컨테이너이며, 연구의 대상 지점은 모달 쉬프트가 이루어지는 환적노드를 중심으로 하였다. 연구에서 수행한 주요 내용은 다음과 같다. 첫째, 컨테이너 육상운송을 하는 화주가 생각하는 환적노드의 운송환경에 대한 인식을 조사하였다. 그리고 이로부터 공로에서 철도로 모달 쉬프트가 활성화되지 않는 저항요인을 분석하였다. 둘째, 환적노드의 저항요인을 반영한 운송수단 선택모형을 추정하였다. 그리고 이를 활용하여 탄력성을 도출하고 모달 쉬프트 저항 요인별 특성을 분석하였다. 셋째, 연구에서 도출된 결과로부터 컨테이너 운송수단을 공로에서 철도로 모달 쉬프트 시키는 방안을 제시하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권2호
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• pp.69-75
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• 1999

The characteristics of $H_2$ gas detection have been investigated using the Pt-MIS capacitor composed of the LPCVD nitride on the oxide. The flat band voltage shift is measured as 0.1 V in 1,000 ppm $H_2$ gas ambient and to be independent of Pt catalyst thickness. It is found that the flatband voltage shift is proportional to the hydrogen concentrations. The response and recovery time of Pt-MIS capacitor are 5 mins and 25 mins respectively. The samples of 30nm thick Pt revealed much higher sensitivity than that of 150nm samples. The samples of 150nm Pt showed that the flatband voltage shift of the device is due to the formation of the dipole layer of the adsorbed hydrogen atoms at the Pt-insulator interface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.723-729
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• 2001

Electro-hydraulic shift control of a vehicle automatic transmission has been predominantly carried out via an open-loop control based on numerous time-consuming calibrations. Despite remarkable success in practice, the variations of system characteristics inevitably deteriorate the performance of the tuned open-loop controller. As a result, the controller parameters need to be continuously updated in order to maintain satisfactory shift quality. This paper presents a self-learning algorithm for automatic transmission shift control in a construction vehicle during inertia phase. First, an observer reconstructs the turbine acceleration signal (impossible to measure in a construction vehicle) from the readily accessible turbine speed measurement. Then, a control algorithm based on a quadratic function of the turbine acceleration is shown to guarantee the asymptotic convergence (within a specified target bound) of the error between the actual and the desired turbine accelerations. A Lyapunov argument plays a crucial role in deriving adaptive laws for control parameters. The simulation and hardware-in-the-loop simulation (HILS) studies show that the proposed algorithm actually delivers the promise of satisfactory performance despite the system characteristics variations and uncertainties.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.90-98
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• 2005

HMT is a type of continuously variable transmission which has split power flow path characteristics with gear train and hydro static unit. The benefit of improved fuel economy and high power capacity enables it to be a promising application fur large vehicles. This paper presents the analysis results including velocity, static torque, transmission efficiency and dynamic model of the HMT that is developed for city buses. The speeds or gear shafts, the static clutch torque and split power ratio for each mode are detailed here. From the analysis of HMT transmission efficiency considering the power loss in meshed gear and hydraulic unit, we can conclude that minimization of hydraulic power is necessary for improved fuel economy design. Also, the dynamic simulation result for mode shift characteristics shows that little shift shock is observed because of the synchronized rotation speed in clutch.

• Journal of Power Electronics
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• 제16권4호
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• pp.1355-1366
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• 2016

In the present paper, a speed control algorithm with fast response characteristics is proposed to reduce the shift shock of medium/large-sized electric vehicles equipped with a two-speed AMT. Shift shocks, which are closely related with to the vehicles' ride comfort, occur due to the difference between the speed of the motor shaft and the load shaft when the gear is engaged. The proposed speed control method for shift shock reduction can quickly synchronize speeds occurring due to differences in the gear ratios during speed shifts in AMT systems by speed command feed-forward compensation and a state feedback controller. As a result, efficient shift results without any shift shock can be obtained. The proposed speed control method was applied to a 9 m- long medium- sized electric bus to demonstrate the validity through a simulated analysis and experiments.