• Journal of Biomedical Engineering Research
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• v.21 no.6
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• pp.551-558
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• 2000

이 연구의 목적은 시각의 유도운동을 기반으로 하는 새로운 현기증 진단 방법을 제시하는데 있다. 시각의 유도운동은 주위환경이 움직임에 따라 고정된 물체도 움직이는 것처럼 느끼는 현상이다. 실험은 방음실에서 수행되었으며, 전체적인 시스템은 PC, 조이스틱, 프로젝터 그리고 스크린으로 구성되어졌다. 현기증의 크기를 정량적으로 측정하기 위하여 세 가지의 다른 주수온도(1$0^{\circ}C$, 2$0^{\circ}C$,3$0^{\circ}C$)를 사용하는 온도자극법에 의해 현기증이 유도되어졌다. 또한, 색의 변화에 의하여 유발되어지는 COP(center of pressure)의 변동을 찾기 위해 여섯 가지색이 유도운동에 사용되어졌다. 그 결과, 유도운동이 현기증과 높은 연관성이 있다는 것과 색의 변화가 인체의 균형에 영향을 미친다는 것을 알 수 있었다. 그렇지만, 색 자체의 변화보다는 집중도와 선명도가 뛰어난 색의 조합으로 구성된 유도운동 시스템이 필요하다는 것도 알 수 있었다. 결론적으로 시각의 유도운동이 현기증의 정량적인 측정에 유용함을 알 수 있었고 이 연구가 현기증 진단 시스템의 개발에 확장되어 쓰여질 수 있을 것이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.247-258
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• 1994

In this study, experimental investigations to find cold energy storage performance have been made for two different temperatures at condenser. Temperatures at inlet and outlet of condenser were measured to calculate global heat transfer coefficient of direct contact method in our cold energy storage system. Also storage performance by direct contact method was compared with that of Ice-On-Coil type ice storage which was calculated by analytic solution. Results show that, in the case of $-8.0^{\circ}C$ at condenser inlet, heat transfer coefficient of direct contact method is 3.25 times higher than that of conventional method and COP of system is improved by using R141b as refrigerant which produces gas hydrate and has higher phase change temperature than $0.0^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.5
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• pp.269-276
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• 2015

Single-effect $CH_3OH-LiI-ZnBr_2$ and $C_2H_5OH-LiI$ absorption heat pumps are simulated to evaluate feasibility as heating device. These systems are predicted to give higher heating COPs in wide operating ranges compared to conventional systems. Among the two systems, the $C_2H_5OH-LiI$ system is found to be more advantageous for operating in extremely cold weather due to the large solubility of Lil in $C_2H_5OH$.

• Journal of Biosystems Engineering
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• v.23 no.2
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• pp.147-156
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• 1998

It is desirable to use the renewable energy for the greenhouse heating in winter season, it make possible not only to save fossil fuel and conserve green environment but also to promote the quality of agricultural products and reduce the agricultural production cost. In this study the heat pump - PCM latent heat storage system has been developed to use the natural energy as much as possible for the thermal environment control of greenhouse. The coefficient of performance (COP) of the heat pump system was 3~4 with the ambient temperature ranging from 8$^{\circ}C$ to -8$^{\circ}C$, and greenhouse heating effect of the heat pump-PCM latent heat storage system on the basis of the ambient temperature was about 12-15$^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.127-133
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• 2002

The objectives of this paper are to develop an advanced GAX cycle named HGAX (Hybrid Generator Absorber heat exchanger) cycle, and to study the effect of key parameters on the cycle performance and the hot-water temperature from the condenser. New types of the HGAX cycle are developed by adding a compressor between the generator and the condenser- Type C (performance improvement and reduction of the generator temperature) and Type D (Hot-water temperature application). The solution temperature in the generator outlet is reduced to 168$^{\circ}C$ with the COP improvement of 19% compared to the standard GAX cycle. The hot-water temperature from the condenser is raised to 106$^{\circ}C$ for panel heating (Ondol heating) application.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.1
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• pp.7-13
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• 2006

Because the usage of CFC and HCFC based refrigerants are restricted due to the depletion of ozone layer, the $NH_3$ gas, in the experiment is evaluated to the performance characteristics for the superheat control to improve the energy efficiency. The experiment is carried out about the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa through the degree of superheat from 0 to $10^{\circ}C$ at each condensing pressure. As a result, in the case of shell and tube type of heat exchanger, the COP is more efficient than other cases at the degree of superheat $1^{\circ}C$ at each condensing pressure. In the case of shell and disk type of heat exchanger, the COP is the most efficient at the degree of superheat 0.

• Journal of Biosystems Engineering
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• v.27 no.6
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• pp.565-572
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• 2002

In order to control the root-zone temperature of greenhouse crops in the hydroponics at hot and cold season, heat pump system for cooling and heating was built and tested in this work. The system was air-to-water type and vapour compression type. The heating and cooling mode was selected by the four way valve. Capacity of the compressor was 3.75㎾ and heat transfer area of the evaporator and the condenser were 3.05㎡ and 0.6㎡, respectively. According to the performance test, it could supply heat of 42,360 to 64,372kJ/h depending on the water circulation rate of 600 to 1,500ℓ/h, respectively, when indoor air temperature was 10∼20$\^{C}$. COP of heat pump system was 3.0 to 4.0 in the heating mode. But, COP of the cooling mode was 1.3 to 2.1 at indoor temperature of 20∼35$\^{C}$. The feasibility test in the greenhouse the developed heating and cooling system was installed, showed that the heating cost of the developed system was only about 13% of that of the conventional heating system. The heating cost of the developed system was 367won/day(electric consumption 9.7㎾h/day), while that of the conventional system was 2,803won/day(oil consumption 7.7ℓ/day) at the same heating mode.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2165-2170
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• 2008

The cooling load in winter season is significant in many commercial buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Therefore, the development of a multi-heat pump which can cover heating and cooling simultaneously for each indoor unit is required. In this study, the characteristics and performance of a simultaneous heating and cooling heat pump in the cooling-only and cooling-main operating mode was investigated experimentally with a variation of indoor air dry bulb temperature which is from $21^{\circ}C$ to $35^{\circ}C$. EEV opening was adjusted from 20% to 24% during the tests. When the indoor air temperature varied, the performance in the cooling-only mode was more sensitive to the temperature than in the cooling-main mode. The total capacity and COP were increased by 53.8% and 48.1%, respectively, in the cooling-main, while those were increased by 19.6% and 19.3% in the cooling-only mode. The performance differences between the two operating modes became larger at lower temperatures, especially for the COP.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.592-598
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• 2015

In this study, we experimentally investigate the performance characteristics of a high-performance summer-cooling heat pump for an R410A by applying an air-cooled-type vapor-injection (VI) cycle. The devices used for the experiment consist of a VI compressor, condenser, oil separator, plate-type heat-exchanger, economizer, evaporator, and re-cooler. The experimental conditions employed for the cooling performance were divided into three cycles. First, in Cycle A, we apply a VI cycle and with no heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant in the re-cooler. For Cycle B, there is heat exchange, and for Cycle C, there is neither a VI cycle nor heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant. From the analysis results, we observe that the performance was highest in the VI cycle with heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant (Cycle B), while it was lowest in Cycle C without application of the VI cycle. Moreover, the cooling coefficient of Performance ($COP_C$) averaged 3.5 in Cycle B, which was 8.6% higher than the corresponding value in Cycle A, and 33% higher than that in Cycle C.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.4
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• pp.11-20
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• 1998

Fault simulatior has been used to compute exact fault coverages of test vectors for digial circuits. But it is time consuming because execution time is proportional to square of circuit size. Recently, several algorithms for testability analysis have been published to cope with these problems. COP is very fast and accurate but cannot be used for sequential circuits, while STAFAN can be used for sequential circuits but needs vast amount of execution time due to good circuit simulation. We proposed EXTASEC which gave fast and accurate fault coverage. But it shows noticeable errors for a few sequential circuits. In this paper, it is shown that the inaccuracy is due to uninitializble flipflops, and we propose ITEM to improve the EXTASEC algorithm. ITEM is an improved evaluation method of fault coverage by analysis of backward lines and uninitializable flipflops. It is expected to perform efficiently for very large circuits where execution time is critical.