• 콘크리트학회논문집
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• 제17권3호
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• pp.445-454
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• 2005

프리스트레스트 콘크리트 구조는 압축강도에 비해 낮은 인장강도로 인하여 콘크리트의 균열이 발생되고, 구조물의 강성이 저하되며, 과도한 처짐으로 인한 구조물의 기능이 저하된다. 주 연구에서는 이러한 단점을 보완하기 위해 인장부 일부분의 고성능 강섬유 보강 콘크리트와 압축부의 보통강도 콘크리트의 합성으로 이루어진 새로운 구조형식의 프리스트레스트 이중 콘크리트 보가 제안되었고, 3개의 프리스트레스트 이중 콘크리트 보와 2개의 프리스트레스트 콘크리트 보가 제작되었다 프리스트레스트 이중 콘크리트 보의 쉽 거동 분석을 위해 각 구간별(precracking stage, postcracking stage, ultimate stage) 해석적 모델이 제안되었고, 해석 결과와 실험 결과가 비교적 잘 일치되었다. 프리스트레스트 이중 콘크리트 보는 인장부 일부분에 적용된 고성능 강섬유 보강 콘크리트에 의해 균열의 생성과 성장이 억제되었고, 초기균열 및 한계사용하중이 증가되었으며, 내하력 및 쵱 강성이 확연하게 증가되었다.

• 한국산학기술학회논문지
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• 제10권4호
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• pp.857-864
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• 2009

본 연구에서는 겨울철 수온강하, 여름철 우천시 표류수 중의 고탁도 물질 및 봄, 가을철의 조류성장 시기 등을 고려하여 기존의 급속모래여과시스템을 이단 이층 복합여과시스템으로 개량하는 기술을 개발하는 것을 목표로 하였다. 본 기술은 기존 여과지의 개량 또는 신설 여과지 설계시 또 다른 부지의 확장 없이 기존 모래여과지를 대체하는 기술로서 하부집수장치 상부에 모래 + 활성탄 층을 두고 활성탄 층 상부에 일정한 간격의 역세 팽창층을 두고 전 처리의 개념으로 중간집수장치 위에 모래층을 두는 이단 이층 복합여과시스템을 말한다. 본 연구에서는 이단이층 복합여과시스템을 경기도 S 정수장에 소규모 파일롯 플랜트를 설치하였으며, 탁도는 INTU 이하로 안정하게 유지되었고, TOC, THMFP, HAAFP는 약 90%정도 제거되어 S정수장에 비해 약 2배 정도 높았으며, 이는 본 시스템의 하단에 충전된 활성탄층에서의 흡착 및 생물분해 효과에 기인된 것으로 판단된다.

• 한국정밀공학회지
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• 제22권5호
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• pp.103-112
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• 2005

This paper presents one-axis high precision scanning system and illustrates the design of modified $X-Y-{\theta}$ stage as a tracker using VCM and commercialized air bearings for it. The scanning system for 100nm resolution is composed of the 3-axis stage and one axis long stroke linear motor stage as a follower. In this study a previous proposed and presented structure of VCM for the fine stage is modified. The tracker has 3 DOF($X-Y-{\theta}$ motions by four VCM actuators which are located on the same plane. So 4 actuating forces are suggested and designed to create least pitch and roll motions. This article will show about the design especially about optimal design. The design focus of this fine stage is to have high acceleration to accomplish high throughput. The optimal design of maximizing acceleration is performed in restrained size. The most sensitive constraint of this optimal design is heat dissipation of coil. There are 5 design variables. Because the relationship between design variables and system parameters are quite complicated, it is very difficult to set design variables manually. Due to it, computer based optimal design procedure using MATLAB is used. Then, this paper also describes the procedures of selecting design variables for the optimal design and a mathematical formulation of the optimization problem. Based on the solution of the optimization problem, the final design of the stage is also presented. The results can be verified by MAXWELL. The designed stage has the acceleration of about 5 $m/s^{2}$ with 40kg total mass including wafer chuck and interferometer mirror. And the temperature of coil is increased $50^{\circ}C$. In addition, the tracker is controlled by high precision controller system with HP interferometer for it and linear scaler for the follower. At that time, the scanning system has high precision resolution about 5nm and scanning resolution about 40nm in 25mm/s constant speed

• International Journal of Air-Conditioning and Refrigeration
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• 제17권3호
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• pp.107-113
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• 2009

The objective of this study is to investigate performance characteristics of a household refrigerator using a two-stage compression cycle. The performance of the two-stage compression cycle was measured by varying the compressor speed, condensing temperature, and evaporating temperature. The COP of the two-stage compression cycle was analyzed and then compared with that of the single-stage compression cycle. The optimum combination of compressor speeds for a low- and a high-stage was determined. The COP of the two-stage compression cycle using a PTC (parallel two-stage compression) method was 5.85% higher than that of a STC (serial two-stage compression) method at optimum operating conditions.

• ETRI Journal
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• 제26권6호
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• pp.555-559
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• 2004

We propose an efficient digital IF down converter architecture for dual-mode WCDMA/cdma2000 based on the concept of software defined radio. Multi-rate digital filters and fractional frequency conversion techniques are adopted to implement the front end of a dual-mode receiver for WCDMA and cdma2000. A sub-sampled digital IF stage was proposed to support both WCDMA and cdma2000 while lowering the sampling frequency. Use of a CIC filter and ISOP filter combined with proper arrangement of multi-rate filters and common filter blocks resulted in optimized hardware implementation of the front end block in 292k logic gates.

• 전기전자학회논문지
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• 제13권2호
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• pp.220-223
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• 2009

A simple measurement system is built to estimate the dual-antenna diversity gain at 2.4GHz easily in open lab environment. To obtain multipath fading propagation channel, the system consists of two transmission horn that placed on opposite direction and a rotating stage mechanically changing the position of test dual-antenna with time over distance greater than one wavelength. Estimated diversity is nearly same as theoretical value such that measured diversity gain of 30mm separated is about 6dB similar to theoretical value of 5.7dB and increases monotonically with the increasing separation distance as predicted by the theory. Proposed measurement system that is simple enough to fit in a small space can evaluate the performance of various dual-antennas with a reasonable accuracy with lower 5% difference between the ten sets of measured waveform distribution and theoretical Rayleigh cumulative distribution.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.103-106
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• 2014

The effects of hydrogen ($H_2$) ratio on combustion and emission characteristics in a $H_2/diesel$ dual-fuel engine were investigated. Dual-fuel strategy was applied to improve the control of combustion phasing. The combustion phasing was retarded with increasing $H_2$ fraction. This can be explained by both reduced diesel concentration and chemical effect of $H_2$, which reduce the heat release rate during the low temperature reaction stage. Hydrocarbon and carbon monoxide emissions of the engine were decreased drastically when $H_2$ ratio was increased.

• 가정과삶의질연구
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• 제22권5호
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• pp.265-281
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• 2004

This study aims at studying dual-earner couple's household work time and life satisfaction in modern times. To reach this goal, dual-earner couple's variable of society and population, income for working hours, attitude of sex's role and working hours time were classified as individual variable of study model. In the end of 2000, positive analysis was completed through dual-earner couples' frequencies, percentage, means, paired-samples T Test, one-way ANOVA, duncan test, multiple regression and path analysis to 112 Korean couples in 'Research material for comparative analysis of family's time use in Korea and in the United States' performed by Lee, Ki-young, along with 3 person in the end of 2000. The time of household work performance at home at this stage is about 30 hours. 90% of 30 hours was given by housewife who was working for another job. In the aspect of dual-earner couple's life satisfaction, the life satisfaction is a little over the level of average. In variables couple's life satisfaction, wife's life satisfaction was additionally influenced by variable of wife's profession, age difference of couple, wife's household work time husband's household work time and wife's sex-role attitudes in oder. Husband's life satisfaction was perfectly influenced by his level of education, his household work time and wife's sex-role attitudes.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.356-362
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• 2017

This paper presents a robust position controller for a one degree-of-freedom (DOF) mechanical system using only position measurement. In order to alleviate the performance degradation owing to various uncertainties, a two-stage design method is studied by employing a proportional integral observer (PIO). In the first stage, a baseline backstepping controller is designed for a nominal system without accounting for uncertainties. The PIO is developed for estimating both the velocity information for the backstepping controller and an equivalent input disturbance for a feedforward compensation using the estimated uncertainty. It is shown that the estimation errors with the proposed PIO can be made arbitrarily small in a finite time. If the system suffers from undesirable actuator nonlinearities, however, it might be necessary to estimate the velocity and the disturbance with different rates of convergence. The proposed method combines the predesigned backstepping controller and dual PIOs to reduce mechanical vibrations as well as steady-state errors. The performance of the proposed method is tested through comparative computer simulations and experiments using a laboratory prototype.

• 연구논문집
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• 통권25호
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• pp.91-98
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• 1995

Recently, improving the energy efficiency of a pneumatic system and reducing the consumption of compressed air were a concern of scholars at domestic and abroad. The using fields of a pneumatic system are widely used in factory automation of manufacturing line, chemical factories with explosiveness danger and petroleum industries etc. In particular, pneumatic cylinder is applied to feeding work of workpiece. jig tools and press mechanism, reciprocation and rotary motion with rack and pinion. In this study, the experimental apparatus consisted to pneumatic cylinder, dual supply pressure regulator and solenoid valve. The dual supply pressure regulator connected to outlet port of solenoid valve. The supply pressure($4.5kg_f/cm^2$) of compressed air goes into the rodless chamber 1 to drive the piston rod forward which is named working stage. The supply pressure ($2kg_f/cm^2$) of compressed air goes into the rod chamber 2 to drive the piston rod backward which is named no-working stage. Accordingly, the research results of this study can be obtained to Energy-Saving Effects of the compressed air about 35%.