• 전기학회논문지
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• 제58권4호
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• pp.688-693
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• 2009

The response characteristics of power system frequency are determined by generator droop characteristics and load damping properties. The characteristics of governor droops are termed by generators constant, while those of load damping by load constant. In this paper, the generator constant and the load constant are assessed by measured data at the event of generator trips.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.471-477
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• 1999

A new stress, load and displacement controlled direct shear apparatus has recently been developed at the Hyundai Institute of Construction Technology This direct shear apparatus is capable of testing of rock joint under constant normal stiffness, constant normal stress or constant normal load boundary conditions. This paper describes this direct shear apparatus and illustrates results of shear tests at constant normal stress condition, constant normal load condition and constant normal stiffness condition with dental stones which have a same joint roughness and unconfined compressive strength.

• Elastomers and Composites
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• 제44권1호
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• pp.41-46
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• 2009

천연고무의 일정하중 영구압축률에 온도와 가교시스템이 미치는 영향을 고찰하였다. 다양한 가교시스템과 가교밀도의 고무시편을 만들기 위해 여러 가지 함량의 황과 dicumyl peroxide(DCP)를 사용하여 배합하였으며, 가교된 천연고무의 일정변위 조건에서 측정된 영구압축률과 일정하중에서 측정된 영구압축률의 차이를 비교하였다. 일정하중 영구압축률은 일정변위 영구압축률에 비해 가교밀도의 변화에 따라 상대적으로 큰 차이를 보였으며, 이는 영구압축률 측정 시 공급된 변형에너지가 다르기 때문이다. 또한 일정하중 영구압축률 측정에서 황으로 가교시킨 시편의 경우 하중과 온도증가에 따라 영구압축률이 크게 증가하였고, 이에 반해 DCP로 가교시킨 시편의 경우 하중과 온도증가에 큰 영향을 받지 않았다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.14-16
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• 2004

A DC railway system has low feeder voltage, The remote fault current can be smaller than the current of load starting. So it is important to discriminate between the small fault current and the load starting current. The load starting current increases step by step but the fault current increases all at once. As for the load starting current, the time constant of load current at each step is much smaller than that of the fault current. To detect faults in DC railway systems, an algorithm using the time constant calculated by the method of least squares was presented. But, It have a weakness about harmonic to calculate time constant. So in this paper, new protection algorithm for DC railway systems using estimation of time constant based on fourier transform was presented.

• 한국정밀공학회지
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• 제18권5호
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• pp.105-111
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• 2001

The creep crack growth properties in 3.3NiCrMoV steel were investigated at 55$0^{\circ}C$ by using CT specimen under constant load and constant Ct condition that was held during crack growth of Imm distance. Ct lelied on load line displacement rate, C＊usually increased with crack length though load is reduced in order to maintain constant Ct value as crack growth and appeared scatter band. At constant load and Ct region, crack growth slope was 0.900 and 0.844 each, on the other hand C＊ slope was 0.480. Fully coalesced area(FCA) ahead of crack tip increased as Ct increase to the critical value, and after that value FCA decreased. For the tertiary creep stage of crack growth test, the most of displacement was due to the steady state creep, except only small part due to the primary creep and other effects. Therefore, tests were mainly interrupted in the tertiary stage to obtain high value of Ct.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.116-122
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• 2000

This paper presents a simulation method with constant power model for the train load. In power system simulation loads could be modeled as a constant power, constant current, constant Impedance or a function of voltage and frequency. At this time, however, representing a train load as the function is difficult because of the lack of data. Therefore as a first step, simulation method with a constant power model fer a train is studied, and the test result is compared with the simulation result using the constant Impedance model.

• 한국전산유체공학회지
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• 제19권4호
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• pp.1-7
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• 2014

A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under a sinusoidal heat load was conducted. It was found that the time constant is not affected by the maximum heating magnitude of the sinusoidal heat load. However, the time constant increases with low duration of the sinusoidal heating period and low Reynolds number. Moreover, there is a threshold where a heater temperature do not reach to time constant at low thermal diffusivity, low flow rate, and low pulse duration of the sinusoidal heating. The time constant should be considered for transient convective heat transfer under transient sinusoidal heat load in a micro heat sink.

• 설비공학논문집
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• 제21권12호
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• pp.695-702
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• 2009

Dynamic behavior of Libr-water absorption system using low-temperature hot water was investigated numerically. Thermal-hydraulic model of single-effect/double-lift 100 RT chiller was developed by applying transient conservation equations of total mass, Libr mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analysis were performed to quantify the effects of bulk concentration and part-load operation on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum bulk concentration was found to exist, which resulted in the minimum time constant with stable cooling capacity. COP and time constant increased as the load decreased down to 40%, below which the time constant increased abruptly and COP decreased as the load decreased further.

• 대한기계학회논문집
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• 제6권4호
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• pp.323-330
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• 1982

The vibration characteristics of continuous span periodically supported beams with moving loads are determined theoretically and experimentally. Moving loads are assumed to travel at constant acceleration with constant magnitude. Analyses by using the Fourier Transform technique are developed to determine the dynamic performance of moving load interacting with multiple and continuous beam. Equation of motion for the moving load is non-dimensionalized. Non-dimensional deflection proflies of continuous beam are presented in detail for the single concentrated moving load with constant acceleration. Experimental moving load and continuous beam models are developed. The maximum deflections at each midpoints 5,7 and 9 span beam are measured and their non-dimensional maximum deflections are presented. The non-dimensional maximum deflection of continuous beam is compared with measured maximum deflection of 9 span beam and found to agree reasonably well. The deflection of continuous beam due to moving load with acceleration is strongly influenced in the resonance region.

• International Journal of Precision Engineering and Manufacturing
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• 제3권2호
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• pp.95-101
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• 2002

The propagation rate(da/dt) prediction parameter and the microstructure properties of creep crack in domestic 3.3NiCrMov steel were investigated at 550$\^{C}$ by using 0.5" CT specimen under constant load(4090N) and constant Ct(300∼4000N/mhr) condition that was maintained during crack growth of 1mm distance. C＊ usually increased with crack length though load was reduced in order to maintain constant Ct value as crack growth and considerably showed the scatter band, but Ct depended on load line displacement rate and represented a good relation with da/dt. At constant toad and Ct region, crack growth slope was 0.900 and 0.844 each, in the other hand C＊ slope was 0.480. Fully coalesced area(FCA) ahead of crack tip was increased as Ct value increase to the critical value, and after that value FCA decreased. The average diameter ditribution of cavity in FCA showed the greatest value about 1.5 ㎛ when Ct=2000N/mhr. The increasing of Ct in FCA view point enlarged the size of damage area and the size reached to maximum 800 ㎛ when Ct=2000N/mhr.