• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.10-18
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• 2007

A tested micro axial-type turbine consists of two stages and its mean radius of rotor flow passage is 8.4 mm. This turbine could be applied to a driver of micro power system, and its rotational speed in the unloaded state reaches to 100,000 RPM. The performance of this system is sensitive depending on the blade angles of the rotor and stator because it is operated in a low partial admission rate, so a performance test is conducted through measuring the specific output power and the net specific output torque with various blade angles on the nozzle, stator and rotor. The experimental results show that the net specific output torque is varied by 15% by changing the rotor blade angle, and the optimal incidence angle is about $10.3^{\circ}$.

• Journal of Korea Game Society
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• v.9 no.2
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• pp.105-113
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• 2009

The most important service of the online game is the stability. However, in online games, the increase in the number of users burdens the server as thousands of users connect to the server at the same time. While various techniques to reduce the load on the server are studied, the study is limited only to the server part like an improvement of server algorithms. In this paper, a program to handle the largest load of the server, the message synchronization of both the server and client, is designed and implemented.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.75-82
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• 1997

기술의 발달로 인하여 인간이 사용하는 많은 공구들은 전동화되어 사용의 간편함과 아울러 작 업성능의 획기적인 변화를 이루었다. 그러나 이는 반대로 누적외상병이나 VWF(Viberation induced Whiter Finger)와 같은 새로운 문제점과 함께 중량의 증가로 인체에 더 많은 부하를 안겨 주는 부작용도 초래하고 있다. 현대의 많은 수공구들은 그 중량과 반발력을 지탱하기 위하여 대 부분 양손으로 작동하도록 설계되어 있느며, 제품의 성능의 향상에만 그 초점이 맞추어져 왔고 사용자의 안전과 편이성은 상대적으로 무시되어 왔다. 이에 본 연구에서는 이러한 양손공구의 인 간공학적 설계를 위한 체계적인 접근방식을 제시함으로써 산업디자인에 활용됨과 함께 유사한 제 품의 디자인에도 응용될 수 있는 바탕을 마련하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.40-42
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• 2001

본 논문에서는 공유 저장장치 기반 클러스터 시스템의 평균 서비스 시간을 줄이기 위해서 클러스터 시스템의 연선 종류와 부하량에 따라 재구성 시점을 결정하는 적응적 자료 재구성 방식(Adaptive Data Reorganization)을 제안한다. 또한 클러스터 시스템에서 처리해야할 서비스가 없고 서비스 요청도 없을 때 자료 재구성을 수행하는 지연 재구성 방식(Deferred Reorganization)을 채택하였다. 자료 재구성 방식은 전체적인 자료 재구성과 부분적인 자료 재구성으로 나누어 실행된다. 또한 적응적 자료 재구성 방식을 통한 공유 저장장치 기반 클러스터 시스템의 성능 평가를 위해 마르코프 모델(Markov Model)을 사용한다.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.200-204
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• 1998

인간공학 분야는 작업부하로 인한 육체적.정신적인 피로와 주어진 작업에서의 성능 저하, 주위 집중의 저하 등 객관화 가능한 부분을 주로 다루어 왔다. 그러나 최근의 연구들에서는 작업의 환경 등으로 인한 정서상태의 변화에 대한 특정이나, 작업부하로서의 정신부하와 작업환경의 변화 등으로 인한 정서적 반응을 구별하여 이에 대한 활발한 연구가 진행 중이다. 최근 쾌적환경의 연 구들이 여러 분야에서 행하여지고 있고 특히 인간공학 분야에서 작업의 효율성과 작업수행도에 미치는 영향 및 기준들이 제시되고 있다. 그러나 인간이 느끼는 쾌적감이 이러한 환경 기준들 내에서 일정하게 유지되는 것인가, 혹은 단지 쾌적감이라는 명목 하에서의 환경기준이 작업의 효율성에 있어서 최적인가 하는 것이다. 따라서 인간요소 중심에서 쾌적감이란 무엇인가를 정 리해 볼 필요가 있다고 여겨진다. 그럼으로써 쾌적환경의 접근방법에 있어 인간을 주체로하는, 즉 인간특성에 맞는 환경을 고려한다는 관점의 변화를 시도해 보고자 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1730-1738
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• 2001

This paper presents an overview of testing and analyzing field performance of a centrifugal chiller which has a rated capacity of 200 RT(703 kW). Field data of a chiller installed in the cleanroom research building of KIST has been collected far performance analysis. The operating data included start-up, shut-down, and quasi-static state where cooling capacity and compressor power consumption varied cyclically. It was found that the steady-state thermodynamic model could be applied to relate the cooling capacity and COP under quasi-static conditions. The results led to finding the required cooling load pattern and a possible energy saving method. This study provides a method of evaluating performance of a large capacity centrifugal chiller in which field test is necessary.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.482-490
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• 2002

This paper presents modelling and analyzing method of centrifugal chiller which has a rated capacity of 200 RT(703 kW) through on-site performance test. Field performance data of a chiller installed in a research building of KIST have been collected. Simple models were developed for predicting the heat exchanger and system performances by regression of chiller operation data during 5 days in August. The models proposed here account for the effect of variations of cooling capacity, temperatures and flew rates of secondary fluids. The proposed models can predict the actual performance data from June to September within $\pm$ 5% error. The COP of centrifugal chiller are estimated under the standard rating conditions and reduced mass flow rates of chilled and cooling water.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.130-135
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• 2002

Bypass air conditioning systems are divided into three types; outdoor air bypass, mixed air bypass and return air bypass system. Among bypass air conditioning systems, a return air bypass system is more effective than other two systems because it doesn't induce unconditioned outdoor air into conditioned room. The numerical study on the bypass air conditioning system shows this system can maintain indoor RH(Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. A simulator was built to compare results of a numerical experiment and those of a simulator experiment. The results of the simulator experiment was nearly same as those of the numerical experiment; when a design sensible load (the ratio of sensible load to total sensible load) was 70 percent (at this time, RSHF=0.7), indoor relative humidity (in case of both numerical experiments and simulator experiments) was maintained below 60% specified by ASHRAE STANDARD 62-1999. The bypass air conditioning system is expected to be applied to many buildings where the Percentage of latent loads or air change tate is high.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4197-4203
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• 2013

In order to investigate the heating performance of multi-heat pump applying an inverter compressor, the experiment on heat pump with 3 indoor units was performed under the heating standard and heating low-temperature conditions. The performance data of heat pump with 3 indoor units were measured by the multi-psychrometric calorimeter. The operation characteristics and the behavior of the refrigerant cycle of the heat pump with 3 indoor units were understood from the heating capacity, heating COP, and P-h diagram by indoor-unit combination. The present experimental results show that the operating load and performance of the multi-heat pump depends on the indoor-unit combination. The heating capacity and heating COP of the low temperature condition were smaller than those of the standard one. Also the refrigerant cycles on indoor-unit combination were analyzed by using P-h diagram.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.61-70
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• 2000

The performance simulation program on the turboprop engine(PT6A-62), which is a main engine of the first trainer KT-1 in republic of Korea, was developed. Characteristics of engine components were required for the steady-state performance analysis including on and off design point analysis. In most cases, these were substituted for what scaled from well known engine components characteristics with the scaling law. The developed program was compared with CASTURB program which is well known for the simulation performance analysis, such as analysis results of mass flow rate, compressor pressure ratio, fuel flow rate, power, specific fuel consumption ratio and turbine inlet temperature in the following four cases, to evaluate whether the developed program is acceptable or not. The first case was the sea level static standard condition and other cases were considered with various flight Mach numbers, altitudes. After verifying the developed program, the partload performance analysis was carried out. Transient performance analysis for various fuel schedules were performed. When the fuel step increase of 0.1sec was performed, the overshoot of the compressor turbine inlet temperature occurred. However, the fuel ramp increase for longer than 0.1sec time was performed, the overshoot could be eliminated.