• Proceedings of the KSME Conference
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• 2005.11a
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• pp.32.2-32.2
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• 2005

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.759-766
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• 2011

Recently, noise reduction in room air conditioners has been one of the important issues as well as cooling efficiency. The rotary compressor is the dominant noise source in an air conditioner. A number of studies have been conducted on reducing compressor noise through improving muffler and resonator design. However the noise from the accumulator, a noise delivering path between compressor and air conditioner, is not fully taken into consideration. The accumulator contains a large inner cavity, and usually generates additional resonance noise during operation. This paper aims to conduct an optimal design for reducing accumulator noise by maximizing the transmission loss within the target frequency range that represents high-order nonlinearity. Design of experiments and radial basis function neural network are used in the context of approximate meta-models, and genetic algorithm is used as an optimization tool.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.984-991
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• 2006

The applications of multi air-conditioners into multiplex and high-rise buildings have been increased by replacing central air-conditioning systems. The pipe length and altitude difference between the indoor and outdoor units can be increased based on installation conditions, which may increase the possibility of flash gas generation at the expansion device inlet. The flash gas generation causes rapid reduction of refrigerant flow rate passing through the expansion device, yielding lower system efficiency. Accumulator heat exchangers have been widely used in multi air-conditioners in order to minimize flash gas generation and obtain system reliability. However, the studies on the heat transfer characteristics and pressure drops of accumulator heat exchangers are very limited in open literature. In this study, the heat transfer rates and pressure drops of accumulator heat exchangers were measured with refrigerant flow rate and operating conditions by using R-22. The heat transfer rate increased with the increase of refrigerant flow rate, while subcooling decreased. The heat transfer rate enhanced with the reduction of inlet superheat and subcooling due to the increased temperature difference between the accumulator and inner heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.418-425
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• 2006

An AHX (Accumulator Heat exchanger) consists of a commercial accumulator and an inner heat exchanger located inside of the accumulator. The AHX is used in multi air-conditioners to assure that liquid-phase refrigerant enters into the expansion device. This purpose is achieved by heat transfer between the refrigerant leaving the evaporator and the refrigerant leaving the condenser. In this study, the effects of AHX on the performance of a refrigeration system using R-22 were measured and the test results were analyzed. The operating characteristics of the refrigeration system with the AHX are considerably different from those without the AHX. Therefore, it is required to determine optimum refrigerant charge and optimum operating conditions when the AHX is used in the refrigeration system having a constant flow-area expansion device such as capillary tube.

• Journal of Power System Engineering
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• v.5 no.4
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• pp.31-37
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• 2001

Pressure propagation and attenuation characteristics in a hydraulic pipeline with a bellows type accumulator was investigated by theoretical analyses and experiments. In the first stage of the study, equations to evaluate the amount of oil volume charged into the bellows together with nitrogen gas were proposed. In the next stage, the authors suggested a mathematical model based on transfer matrix method to describe the dynamic characteristics of the pipe element with a metal bellows type accumulator. Through comparisons and considerations of the experimental and the numerical data shown in frequency domain, the validity of the mathematical model was confirmed.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.227-230
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• 2003

본 논문은 공개된 네트워크를 통해 교환되는 기밀정보의 무결성과 인증을 위해 사용되는 공기키 인증서에 대한 새로운 인증방법을 제안한다. 제안된 새로운 방법은 인증된 딕셔너리［1］기반하에 RSA 일방향 어큐뮬레이터를 이용하여 인증서 폐기목록(CRL： Certificate Revocation List) 원소들의 존재 유무에 대한 증거값들을 미리 생성하고 사용자가 인증서의 유효성을 알아보기 위해 해당 원소에 대한 질의를 보내게 되면 미리 계산되어진 증거값을 바로 제시해줌으로써 계산시간이나 전송용량의 효율성을 극대화시켰다. 또한 파라미터값을 주어 CRL을 여러개의 부분집합으로 나눔으로써 계산량을 동적으로 분산시켜 사용자가 소형기기나 무선 네트워크 환경에 있더라도 활용이 가능하도록 하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.183-184
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• 2007

• Elastomers and Composites
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• v.35 no.1
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• pp.4-11
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• 2000

A rubber diaphragm is a critical element of accumulators. The material of a diaphragm is nitrile rubber so as to recover and adjust the large deformation under external pressure fluctuation. The performance of accumulators is influenced by the deformation behaviors of the diaphragm. A large deformation behavior of the diaphragm has been investigated using the commercial finite element program MARC K7.1. The several elastic moduli have been used in linear analysis and Ogden's coefficients have been used in non-linear analysis. As a result, it has been shown that the deformation behavior with a elastic modulus of $0.3 kg/mm^2$ is similar to the behavior of non-linear analysis. And, the modified diaphragm shape to reduce the stress concentration has been proposed.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.433-438
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• 2005

An AHX(Accumulator Heat eXchanger) consists of a commercial accumulator and an inner heat exchanger located inside of the accumulator. The AHX is used in multi air-conditioners to assure the liquid-phase refrigerant entering into the expansion device. This purpose is achieved by heat transfer between the refrigerant leaving the evaporator and the refrigerant leaving the condenser. In this study, the effects of AHX on the performance of a refrigeration system using H-22 were measured and the test results were analyzed. The operating characteristics of the refrigeration system with the installation of AHX were quite different from those without the installation of AHX. Therefore, it is required to find an optimum refrigerant charging amount and optimum operating conditions, when AHX is installed in the refrigeration system with an fixed area expansion device such as a capillary tube.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.651-660
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• 2008

The widespread use of public networks, such as the Internet, for the exchange of sensitive data that need a severe security, like legally valid documents and business transactions. At the same time public-key certificates used for sensitive data interchange form the viewpoint of data integrity and authentication. But there are some weakness of data transfer capacity and security in public key infrastructure(PKI) environment. This paper use the RSA one-way accumulator to realize an efficient and dynamic authenticated dictionary, where untrusted directories provide cryptographically verifiable answers to membership queries on a set maintained by a trusted source.