• Journal of Computational Design and Engineering
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• 제3권2호
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• pp.132-139
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• 2016

In this paper, a minimum time path planning strategy is proposed for multi points manufacturing problems in drilling/spot welding tasks. By optimizing the travelling schedule of the set points and the detailed transfer path between points, the minimum time manufacturing task is realized under fully utilizing the dynamic performance of robotic manipulator. According to the start-stop movement in drilling/spot welding task, the path planning problem can be converted into a traveling salesman problem (TSP) and a series of point to point minimum time transfer path planning problems. Cubic Hermite interpolation polynomial is used to parameterize the transfer path and then the path parameters are optimized to obtain minimum point to point transfer time. A new TSP with minimum time index is constructed by using point-point transfer time as the TSP parameter. The classical genetic algorithm (GA) is applied to obtain the optimal travelling schedule. Several minimum time drilling tasks of a 3-DOF robotic manipulator are used as examples to demonstrate the effectiveness of the proposed approach.

• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.113-123
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• 1998

The present study is to investigate the effect of experimental parameters on the heat transfer characteristics of a spherical capsule storage system using paraffins. N-Tetradecane and mixture of n-Tetradecane 40% and n-Hexadecane 60% were used as paraffins. Water with inorganic material was also tested for the comparison. The experimental parameters were varied for the Reynolds number from 8 to 16 and for the inlet temperature from -7 to 2$^{\circ}C$. Measured local temperatures of spherical capsules in the storage tank were utilized to calculate charging and discharging times, dimensionless thermal storage amount, and the average heat transfer coefficients in the tank. Local charging and discharging times in the storage tank were significantly different. The effect of inlet temperature on charging time was larger than that on discharging time, but the effect of Reynolds number on charging time was smaller than that on discharging time. Charging time of paraffins was faster by 11~72% than that of water with inorganic material, but little difference of discharging time was found among them. The effect of Reynolds number on the dimensionless thermal storage was less during charging process and more during discharging process than the effect of inlet temperature. The effect of the inlet temperature and the Reynolds number on the average heat transfer coefficient of the storage tank was stronger during discharging process than during charging process. The average heat transfer coefficients of the spherical capsule system using paraffins were larger by 40% than those using water.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.113-116
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• 2006

In order to fully utilize the inherent precision that GPS observables could offer, accurate estimation of dynamic and measurement parameters is vital. Among these parameters some are indispensable in virtually every form of GPS processing, while some are limitedly relevant to a particular application. In the context of time transfer by GPS, the transmission-related errors such as ionospheric and tropospheric delays, and the integer ambiguity of the carrier phase observables belong to the former, the atomic clock parameters and data batch-related parameters to the latter. Obviously the atomic clock parameters are of prime importance in GPS time transfer. In this study some of important parameters in conducting time transfer experiments by use of GPS were characterized and their effects on time transfer performance were investigated in detail

• 대한전기학회논문지:전력기술부문A
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• 제54권11호
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• pp.533-539
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• 2005

According to NERC definition, Available Transfer Capability (ATC) is a measure of the transfer capability remaining in the physical transmission network for the future commercial activity. To calculate Available Transfer Capability, accurate and defensible Total Transfer Capability, Capacity Benefit Margin and Transmission Reliability Margin should be calculated in advance. This paper proposes a method to quantify time varying Available Transfer Capability based on probabilistic approach. The uncertainties of power system and market are considered as complex random variables. Total Transfer Capability is determined by optimization technique such as SQP(Sequential Quadratic Programming). Transmission Reliability Margin with the desired probabilistic margin is calculated based on Probabilistic Load Flow analysis, and Capacity Benefit Margin is evaluated using LOLE of the system. Suggested Available Transfer Capability quantification method is verified using IEEE RTS with 72 bus. The proposed method shows efficiency and flexibility for the quantification of Available Transfer Capability.

• 한국컴퓨터산업학회논문지
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• 제2권2호
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• pp.131-140
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• 2001

본 논문은 지상회선과 위성회선의 파일 전송을 위하여 CSDN 접속의 지상회선 모델인 SARA(System ARchitec’ Apprentice)모델에 위성회선을 추가하여 확장된 시뮬레이터를 제안하고 두 회선의 파일전송 효율에 대하여 해석하였다. 위성전송에서 파일전송의 효율을 평가하기 위하여 해석적 방법과 제안된 시뮬레이터로서 파일전송의 시뮬레이션을 수행하였다. 이때 적용된 전송파라미터는 단위 메시지 길이와 파일의 전송시간, 체인 레코드 수와 전송시간으로 하여 위성회선의 최적 메시지 길이를 평가하였다. 평가 결과는 위성회선에서 단위 메시지 길이를 512바이트 보다 짧게 하면 파일 전송시간은 극단적으로 길게 되며,1024바이트로 했을 때 최소로 되고 2048바이트부터 급격하게 증가되었다. 이 결과에서 최적 단위 메시지길이는 1024바이트 부근이라는 것을 확인할 수 있었다.

• Journal of Welding and Joining
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• 제14권5호
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• pp.106-112
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• 1996

The effects of Ti addition in welding wire on the spatter generation and the droplet transfer phenomena were investigated. With increasing Ti content the spattering rate was decreased but the ratio of large size spatter (D $\geq$ 1. 0mm) was increased in both short circuit and globular transfer mode of $CO_2$welding. In short circuit transfer region, the arcing time was increased and the droplet transfer frequency was decreased with increasing Ti content In globular transfer region, the transition current and voltage to globular transfer was lowered and the welding condition region for stable globular transfer was widened with increasing Ti content.

• 한국전산유체공학회지
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• 제17권4호
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• pp.87-92
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• 2012

A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under pulsed heating was conducted. It was found that the time constant is not affected by the pulse heating magnitude at same operating condition. Furthermore, the time constant increases with low substrate thermal diffusivity, low Reynolds number, and large channel diameter. Since the time constant is a dominant parameter to characterize transient heat transfer, it should be considered for transient convective heat transfer coefficient.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.662_663
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• 2009

Motor bus transfer involves the process of transferring a bus that has several critical motors to an alternate source of power when the main normal power source feeding them is interrupted. Bus transfer is a time-critical application in which the transfer progress depends on various parameters such as the type of motor, load on the motor at the time of transfer, inertia of the motor, and the combined open-circuit time constant of various motors present on the bus at the time of transfer. This paper present the result of modeling and simulation of nuclear power motor bus using ETAP(Electrical Transient Analyzing Program) program for motor and motor bus residual voltage decay characteristics.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2409-2413
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• 2007

Time resolved phosphorescence of Dibromobenzophenone (DBBP) choleic acid crystal was observed at 4.2 K as functions of excitation energy and delay time. The experimental results reveal that the energy transfer efficiency is dependent on the excitation energy, i.e. the density of acceptors sites. As the excitation energy or delay time increases, the resonance phosphorescence does not broaden and shift gradually, rather a broad luminescence band develops about 290 cm?1 to lower energy of the resonance phosphorescence. The observation implies that energy transfer from high to low energy sites in this system is controlled by emission of phonons or vibrons. The data of time resolved experiments were analyzed in terms of a mechanism involving direct donor-acceptor excitation transport by exchange coupling. It was concluded that an isotropic twodimensional exchange interaction topology is consistent with energy transfer in this system.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.681-691
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• 2006

Nucleate boiling heat transfer for refrigerants, R113, and R113+wt4% ethanol mixture, an azeotropic mixture under electric field was investigated experimentally in a single-tube shell/ tube heat exchanger. A special electrode configuration which provides a more uniform electric field that produces more higher voltage limit against the dielectric breakdown was used in this study. Experimental study has revealed that the electrical charge relaxation time is an important parameter for the boiling heat transfer enhancement under electric field. Up to 1210% enhancement of boiling heat transfer was obtained for R113+wt4% ethanol mixture which has the electrical charge relaxation time of 0.0053 sec whereas only 280% enhancement obtained for R113 which has relaxation time of 0.97 sec. With artificially machined boiling surface, more enhancement in the heat transfer coefficient in the azeotropic mixture was obtained.