• 한국자동차공학회논문집
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• 제5권1호
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• pp.129-135
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• 1997

Previous studies has shown that the curve of low-cycle fatigue life was not expressed with the single line subjected to Manson-Coffin's law type and bent to short life in low ${\Delta}{\varepsilon}_p$ region. The main cause of this phenomenon has been considered that the localization of plastic strain in the crack initiation process fosters the crack initiation. In this study, the low-cycle fatigue life was investigated for each specimens omitted crack initiation process and it was found that fatigue life curve in log(${\Delta}{\varepsilon}_p$)-log($N_f$)was bent in low ${\Delta}{\varepsilon}_p$ region as ever. Therefore, the main cause of appearance of knee point in fatigue life curve is not found in the crack initiation process but in the crack propagation process. In the crack propagation process, the localization of the plastic strain in the vicinity of crack tip and the influence of test environment on the crack propagation rate were observed and these inclinations were more remarkable in low ${\Delta}{\varepsilon}_p$ region. Hence, it was concluded that these two phenomena in the crack propagation process were proved to the main cause which accelerates the crack propagation in low ${\Delta}{\varepsilon}_p$ region and bent the fatigue life curve in result.

• 설비공학논문집
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• 제26권11호
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• pp.504-511
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• 2014

The objective of this study is to theoretically analyze the performance of an open wet air-cycle refrigeration system, which nowadays is increasingly generating environmental concern. The temperature and relative humidity of the outside air are selected as the most important parameters. As the temperature and relative humidity of the outside air increase, the pressure ratio of the ACM compressor is determined to be nearly constant, the air temperature at the exit of the system increases, and the amount of condensed water, the cooling capacity, the COP, and the total entropy production rate increase overall. The effects of the effectiveness of the heat exchanger and the efficiency of the turbine on the performance are greater than that of the efficiency of the ACM compressor. Also, the performance of the wet air-cycle refrigeration system with two heat exchangers is enhanced, with a high COP and low total entropy production rate, compared to the system with a single heat exchanger.

• 대한기계학회논문집B
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• 제33권2호
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• pp.133-140
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• 2009

A fast-response $CO_2$ analyzer has been developed for measuring the $CO_2$ concentration during transient condition of a SI engine. The analyzer consists of the non-dispersive infrared absorption method, electrical chopping system and water cooling system. The analyzer has good repeatability, linearity and permissible drift characteristic. Besides, it showed 18ms of a response to measure the $CO_2$ concentration. The fast-response $CO_2$ analyzer was applied to a single cylinder SI engine and the $CO_2$ emission was examined during engine start. Simultaneously, the standard exhaust gas analyzer, which has slow response time, was used for confirming the accuracy of the exhaust gas analysis using the fast-response $CO_2$ analyzer. The developed analyzer showed much faster responsive characteristic than that of a standard analyzer and made cycle by cycle exhaust gas analysis possible. The transient engine operating characteristics will be estimated from the $CO_2$ concentration of engine-out emissions and engine operating variables.

• 한국태양에너지학회 논문집
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• 제37권5호
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• pp.27-37
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• 2017

In this study, an artificial solar simulator composed of a 2.5 kW Xe-Arc lamp and mirror reflector was used to carry out the solar thermal two step thermochemical water decomposition cycle which can produce high efficiency continuous hydrogen production. Through various operating conditions, the change of hydrogen production due to the possibility of a dual-zone reactor and heat recovery were experimentally analyzed. Based on the reaction temperature of Thermal-Reduction step and Water-Decomposition step at $1,400^{\circ}C$ and $1,000^{\circ}C$ respectively, the hydrogen production decreased by 23.2% under the power off condition, and as a result of experiments using heat recovery technology, the hydrogen production increased by 33.8%. Therefore, when a thermochemical two-step water decomposition cycle is conducted using a dual-zone reactor with heat recovery, it is expected that the cycle can be operated twice over a certain period of time and the hydrogen production amount is increased by at least 53.5% compared to a single reactor.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2018년도 춘계학술대회
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• pp.59-60
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• 2018

부산신항의 환적화물 처리물량은 지속적으로 늘어나 전체 물동량의 50%를 넘기고 있지만 작업자의 경험에 의존한 작업의 순서 결정에 따라 효율적인 환적화물 운송이 이루어지고 있다고 보기 힘들다. 특히, 외부 트럭이 필요한 경우가 많은 타부두 환적은 작업 상황에 따라 차량 대기로 인한 과도한 혼잡으로 물류비 증가와 사회적 비용이 발생하게 된다. 이 문제를 해결하기 위한 방법 중 하나는 트럭의 단일 운송을 최소화하고 작업을 마친 트럭을 다른 작업에 투입하여 활용하는 듀얼 사이클 운송을 최대화하는 것이다. 이에 따라, 본 연구에서는 컨테이너 터미널간 환적화물의 듀얼 사이클 운송을 위한 방안에 대해 연구하고자 한다.

• International Journal of Computer Science & Network Security
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• 제23권3호
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• pp.31-48
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• 2023

The popularization of smart devices and subsequent optimization of their sensing capacity has resulted in a novel mobile crowdsensing (MCS) pattern, which employs smart devices as sensing nodes by recruiting users to develop a sensing network for multiple-task performance. This technique has garnered much scholarly interest in terms of sensing range, cost, and integration. The MCS is prevalent in various fields, including environmental monitoring, noise monitoring, and road monitoring. A complete MCS life cycle entails task allocation, data collection, and data aggregation. Regardless, specific drawbacks remain unresolved in this study despite extensive research on this life cycle. This article mainly summarizes single-task, multi-task allocation, and space-time multi-task allocation at the task allocation stage. Meanwhile, the quality, safety, and efficiency of data collection are discussed at the data collection stage. Edge computing, which provides a novel development idea to derive data from the MCS system, is also highlighted. Furthermore, data aggregation security and quality are summarized at the data aggregation stage. The novel development of multi-modal data aggregation is also outlined following the diversity of data obtained from MCS. Overall, this article summarizes the three aspects of the MCS life cycle, analyzes the issues underlying this study, and offers developmental directions for future scholars' reference.

• 기술사
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• 제33권4호
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• pp.53-58
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• 2000

Within 10years, it will be possible to integrate 10B transistors on a single chip microprocessor which wilt operate far beyond GHZ, and it will execute about 20-200 instructions per clock cycle from widely variable instruction streams leveraging SMT(Simultaneous Multithreading) technology . Also it will decouple the current legacy X86 binary compatibility by translation layer such as code morphing technology.

• 한국광학회:학술대회논문집
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• 한국광학회 2005년도 제16회 정기총회 및 동계학술발표회
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• pp.146-147
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• 2005

• Journal of the Korean Statistical Society
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• 제25권3호
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• pp.445-456
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• 1996

In this paper, we derive unbiased estimators for the sensitivities of expected performance measures in a Markov renewal process. We restrict our derivation to the performance measures during a busy cycle and apply smoothed perturbation analysis method to find those esti-mators. The results show all the terms in the derived estimators can be obtained from a single sample path.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2003년도 하계학술대회 논문집
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• pp.13-13
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• 2003