• 대한기계학회논문집
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• 제19권1호
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• pp.231-239
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• 1995

This paper describes a computer simulation of the triple effect, water-lithium bromide absorption cooling cycles. The performance of the absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature, the working solution concentrations, the ratio of the amount of the weak solution to the high, middle and low temperature generators, and the temperature difference of each solution heat exchanger. The efficiency of different cycles has been studied and the simulation results show that higher coefficient of performance could be obtained for the parallel cycle of constant solution distribution rate. As a result of this analysis, the optimum designs and operating conditions were determined based on the operating conditions and coefficient of performance.

• Geomechanics and Engineering
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• 제12권4호
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• pp.707-721
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• 2017

The objective of this paper is to experimentally study the consolidation of saturated silty clay subjected to repeated heating-cooling cycles using a modified temperature-controlled triaxial apparatus. Focus is placed on the influence of the water content, confining pressure, and magnitudes and number of thermal loading cycles. The experimental results show that the thermally induced pore pressure increases with increasing water content and magnitude of thermal loading in undrained conditions. After isothermal consolidation at an elevated temperature, the pore pressure continues to decrease and gradually falls below zero during undrained cooling, and the maximum negative pore pressure increases as the water content decreases or the magnitude of thermal loading increases. During isothermal consolidation at ambient temperature after one heating-cooling cycle, the pore pressure begins to rise due to water absorption and finally stabilizes at approximately zero. As the number of thermal loading cycles increases, the thermally induced pore pressure shows a degrading trend, which seems to be more apparent under a higher confining pressure. Overall, the specimens tested show an obvious volume reduction at the completion of a series of heating-cooling cycles, indicating a notable irreversible thermal consolidation deformation.

• 동력기계공학회지
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• 제18권1호
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• pp.51-56
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• 2014

In this paper, the performance of the $CO_2-C_2H_6-N_2$ cascade liquefaction cycle with respect to temperature differences in the LNG heat exchangers is analyzed theoretically using HYSYS software and then compared the COP(coefficient of performance) of the cascade liquefaction cycles using $C_3H_8-C_2H_4-C_1H_4$ and $CO_2-N_2O-N_2$. In comparison of COP of three cycles, the cascade liquefaction cycles using $C_3H_8-C_2H_4-C_1H_4$ showed the highest COP. And the liquefaction cycle using $CO_2-C_2H_6-N_2$ and $CO_2-N_2O-N_2$ presented the second and third highest COP, respectively. In case of COP, the $C_3H_8-C_2H_4-C_1H_4$ cascade liquefaction cycle yields better COP. But, in terms of the environment and maintain, it is confirmed that the cascade liquefaction cycle using $CO_2-C_2H_6-N_2$ provides favorable characteristics.

• 열처리공학회지
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• 제4권3호
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• pp.31-38
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• 1991

Effect of thermal cycling on shape memory effect and stabilization of austenite was investigated in Fe-21%Mn alloy. The thermal cyclic treatment was carried out with two types, room temperature${\leftrightarrow}215^{\circ}C$ and room temperature${\leftrightarrow}260^{\circ}C$. In case of the room temperature${\leftrightarrow}215^{\circ}C$, the SME was rapidly increased up to 3 cycles and maintained nearly constant value regardless of further cycles. In case of the room temperature${\leftrightarrow}260^{\circ}C$, however, the SME was increased with increasing the thermal cycle up to 5 cycles and decreased gradually with further cycle. The variation of the ${\varepsilon}$ martensite volume pet with the thermal cycle was in good agreement with the variation of the SME. Therefore, the change of the SME due to the cyclic treatment was explained with the change of the ${\varepsilon}$ martensite content. As the thermal cycle was increased, the $M_s$ temperature was decreased, and the $A_s$ and $A_f$ temperatures were increased, respectively.

• 한국의류산업학회지
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• 제13권3호
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• pp.425-431
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• 2011

The purpose of this study was to investigate washing effects according to the rinsing conditions and the characteristics of soiled fabrics. In this study rinsing conditions including rinsing cycle, time, temperature, and bath ratio were examined. The foamability of rinsing bath was also examined. The quantity of LAS in the rinsing bath and extracts of test fabrics was analyzed after washing and rinsing, respectively. The results of these experiments were as follows: The washing effects of soiled fabrics were varied from the kinds of soils and rinsing conditions. The removal of soils from fabrics was increased by the first rinsing after washing effectively. The priorities of rinsing conditions were rinsing temperature> rinsing time > rinsing cycles> references. Foamability was result from residual LAS in rinsing bath and fabrics extracts after rinsing. The residual quantity of LAS was references > rinsing cycles> rinsing time> rinsing temperature, which shown rinsing temperature was the most efficient factor of the rinsing performance.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.402-408
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• 2011

Organic Rankine cycles (ORC) can be used to produce power from heat at different temperature levels available as geothermal heat, as biogenic heat from biomass, as solar or as waste heat. In ORC working fluids with relatively low critical temperatures and pressures can be compressed directly to their supercritical pressures and heated before expansion so as to obtain a better thermal match with their heat sources. In this work thermal performance of ORC with and without an internal heat exchanger is comparatively investigated in the range of subcritical and transcritical cycles. R134a is considered as working fluid and special attention is paid to the effect of turbine inlet pressure on the characteristics of the system. Results show that operation with supercritical cycles can provide better performance than subcritical cycles and the internal heat exchanger can improve the thermal efficiency when the temperature of heat source becomes higher.

• Applied Science and Convergence Technology
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• 제24권3호
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• pp.67-71
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• 2015

InP/InGaP quantum structures (QSs) were grown on GaAs (001) substrates by a migration-enhanced molecular beam epitaxy method. Temperature-dependent photoluminescence (PL) and emission wavelength-dependent time-resolved PL (TRPL) were performed to investigate the optical properties of InP/InGaP QSs as a function of migration enhanced epitaxy (MEE) growth cycles from 2 to 8. One cycle for the growth of InP QS consists of 2-s In and 2-s P supply with an interruption time of 10 s after each source supply. As the MEE growth cycle increases from 2 to 8, the PL peak is redshifted and exhibited different (larger, comparable, or smaller) bandgap shrinkages with increasing temperature compared to that of bulk InP. The PL decay becomes faster with increasing MEE cycles while the PL decay time increases with increasing emission wavelength. These PL and TRPL results are attributed to the different QS density and size/shape caused by the MEE repetition cycles. Therefore, the size and density of InP QSs can be controlled by changing the MEE growth cycles.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.89-95
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• 2001

The fretting wear characteristics of Zircaloy-4 tube at room and high temperature were Investigated experimentally. In this study, the number of cycles, slip amplitude and temperature were selected as main factors of fretting wear. The results of this research showed that the wear volume Increased with the Increase of slip amplitudes and the number of cycles but decreased with temperature and the coefficient of friction were observed different tendency between room and high temperature. According to SEM(EDS) only gross slip were observed on the surface of both specimens and compacted oxide were on worn surfaces. XRO patterns showed that the crystallization of ZrO$_2$ were observed on the worn surface at high temperature. The fretting wear were Investigated due to oxidation and accumulation of plastic flow.

• 한국군사과학기술학회지
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• 제10권3호
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• pp.62-70
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• 2007

Most design temperature of environmental test in korea is based on the standard of Department of Defense. There are few studies to establish temperature standard. Besides the representative environmental test guide 'MIL-STD-810F' encourage to tailor to generate the most relevant test data possible and to test to make a match of test environment with operational environment. Under these circumstances, it is irrational to comply with baseless daily cycle. Thus the study about design method of test temperature is essential. So, the daily cycles to be appropriate to the Korean peninsula was presented in this study. And this research shows how to derive two main element, frequency-of-occurrence and daily maximum (minimum) temperature in daily cycles, in case we can not find the daily cycle.

• 융합신호처리학회논문지
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• 제12권4호
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• pp.355-361
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• 2011

기존 발열체의 전력제어는 On-Off 제어, 위상제어, PWM 제어를 사용해왔다. 최근 개발된 PTC 발열체를 기존의 방법으로 전력제어를 하였을 경우, 온도를 정밀하게 제어하지 못하고 인체에 유해한 전자파가 발생한다. 본 논문은 AC Cycles 가변을 이용한 PTC 열선의 전력 제어를 제안한다. 이것은 N개의 교류 cycle을 전력 제어의 단위로 간주하여, 각 cycle 마다 On-Off 여부를 결정하여 N cycles 내의 on-cycle 을 랜덤하게 배치하여 지속적으로 AC전력제어방법이다. 이 때 최소 전력량은 1/N이 되고 최대 전력량은 1이 되며 설정 값에 따라 on cycle의 수를 설정하여 N개의 단계로 일정하게 전력을 제어할 수 있다. PTC 열선과 온도센서를 사용한 발열 시스템에서 제안한 전력제어 방식이 전자파 발생과 온도제어 특성에서 우수함을 MATLAB simulation과 실험 및 측정을 통하여 확인하였다.