• 수산해양기술연구
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• 제42권4호
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• pp.259-266
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• 2006

In this study, the 2-way condensation system was designed applying air-to-air heat pump to dry a marine product such as squid in the winter. And to be made the drying apparatuses by this system, there are two kinds of type, A type, was set a compressor outside of the drying apparatus, B type, was set a compressor in the drying room. And then the variations of temperature in drying room were measured to compare the heating performance of the drying apparatuses between A type and B type at $-6.5^{\circ}C$, outdoor temperature. The temperature of the drying room for B type was increased to $36^{\circ}C$ but the temperature of the drying room for A type was not increased to $36^{\circ}C$, to be increased to $20^{\circ}C$.

• 대한방사선치료학회지
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• 제33권
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• pp.71-78
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• 2021

목 적: 폐암과 간암 환자에 대해 압력 기반 복부압박장치를 적용하여 입체적 세기변조 회전 방사선치료(VMAT)를 시행하였을 때의 치료 간(interfraction) 위치 재현성과 호흡 재현성을 평가함으로써 그 유용성을 평가하고자 한다. 대상 및 방법: 압력 기반 복부압박장치를 사용해 입체적 세기변조 회전 방사선치료를 받은 6명의 폐암 환자와 3명의 간암 환자를 대상으로 하였다. 치료 간 위치 재현성 평가를 위해 모의치료 CT 영상과 매일 획득한 CBCT 영상 174건을 비교하여 이미지 정합의 이동 값을 비교, 분석하였다. 치료 간 호흡 재현성 평가를 위해 모의치료 4DCT 영상과 매주 획득한 4D CBCT 영상 54건을 비교하여 호흡량 오차를 구하였다. 결 과: 수평수직 세 방향의 3D 벡터값인 전체 위치변화(Overall position variation, Overall VP)값은 폐와 간에서 각각 평균 1.1 ± 1.4 mm, 4.5 ± 2.8 mm로 나타났다. 호흡 변화(respiratory variation, Vr)값은 폐에서 평균 0.7 mm ± 3.4 mm (p=0.195), 간에서 평균 3.6 mm ± 2.6 mm (p<0.05)로 나타났다. 결 론: 흉복부 방사선 치료 시 압력 기반 복부압박장치의 적용은 복부 압박 재현을 통해 치료 간 종양의 호흡 변이뿐만 아니라 위치 변이를 안정적으로 조절하는 데에 유용한 것으로 사료된다. 보다 안정적인 재현성을 위해 치료 계획 시 적절한 PTV 여유가 고려되어야 하고, 매 치료 전 영상 유도에 따른 표적의 위치와 호흡 검증이 필요하다.

• 동력기계공학회지
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• 제17권4호
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• pp.58-63
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• 2013

This paper presents the new cascade liquefaction cycles using $CO_2-C_2H_6-N_2$ and $CO_2-N_2O-N_2$. The performance of the cascade liquefaction cycles with respect to temperature differences in the LNG heat exchangers is analyzed using HYSYS software and then compared the performance of these cycles with phillips optimized cascade liquefaction cycle. The coefficient of performance of the new liquefaction cycles considered in this study decreases with the temperature differences in the LNG heat exchangers, but the compressor work, expander work and heat capacity in the LNG heat exchanger increases, respectively. From the comparison of performance of three cycles, the cascade liquefaction cycles using $CO_2-C_2H_6-N_2$ showed the highest COP. And the cycles using $CO_2-C_2H_6-N_2$ and $CO_2-N_2O-N_2$ presented the second and third highest COP, respectively. In the view of performance, the optimized cascade liquefaction cycle using $C_3H_8-C_2H_4-C_1H_4$ yields much better COP. But, in the environment view, it is found that the cascade liquefaction cycle using $CO_2-C_2H_6-N_2$ shows favorable characteristics.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1635-1646
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• 1998

The present study investigated the effects of geometric parameters considered on the performance of an automotive scroll compressor by assuming ideal, semi-real and real gases for R-134a. The geometric parameters were center thickness of scroll, height of scroll and the size of discharge port. Fourth-order Runge-Kutta method was applied to solve the thermodynamic equations, leaking rate equation and the equation of motion of discharge valve for ideal, semi-real, and real gases. The volumetric and adiabatic efficiencies for semi-real and real gases differed little, but those for ideal gas differed by 18% and 25% compared with those for real gas at 2,000rpm. The volumetric efficiency changed little as the design angle of scroll (${\gamma}$) changed, but the adiabatic efficiency at ${\gamma}$ of $34^{\circ}$ was higher by 2.4% than that of $147^{\circ}$ for 2,000rpm. The volumetric and adiabatic efficiencies at scroll height of 29.8mm were higher by 1.7% and 2.8% than those of 65.8mm. The volumetric efficiency changed little as the size of discharge port changed, but the adiabatic efficiency increased a little as the size of discharge port decreased.

• 한국초전도ㆍ저온공학회논문지
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• 제3권1호
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• pp.64-68
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• 2001

An experimental study on the Joule-Thomson cryocooler with the mixed refrigerant (MR) is described in this paper, J-T refrigeration experiment was performed with a single stage regular air-conditioning compressor The mixed refrigerant in the experiment was composed of 75% mol fraction of $N_2$. 30% moi fraction of CH$_4$. 30% moi fraction of $C_2$H$_{6}$. 10% mot fraction of $C_3$H$_{8}$ and 15% mot fraction of iso-C$_4$H$_{10}$. Oil mist in the MR stream could be eliminated completely by the glass microfiber filter. Since a single stage compressor that had been designed thor R22 is not appropriate for high Pressure ratio of the mixed refrigerant especially during the transient period. two modifications were incorporated to regular J-T refrigeration cycle. First. a Portion of the MR was by-passed at the inlet of the heat exchanger and transferred directly to 7he suction of the compressor in the modified system. Second, a buffer volume was Prepared to change the mass flow rate of refrigerant. The pressure ratio in J-T expansion device was relieved at the beginning of the operation due to the by-Pass scheme. but it gradually decreased during the transient Process as some of the MR component condensed at low temperature. The buffer volume at the suction side was used to increase the MR gas density in the system after the transient cool-down period. Form the experiment with the modified system, the refrigerator could reach the lowest temperature of -152$^{\circ}C$ without cooling load. and about -15$0^{\circ}C$ with 5 W of cooling load . . . .

• 대한전기학회논문지:시스템및제어부문D
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• 제49권6호
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• pp.316-321
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• 2000

In this paper, we proposed MBDD(Modified Binary Decision Diagram) as a multi-level logic synthesis method and a vertex of MBDD to NMOS transistors matching. A vertex in MBDD is matched to a set of NMOS transistors. MBDD structure can be achieved through transformation steps from BDD structure. MBDD can represent the same function with less vertices less number of NMOS transistors, consequently capacitance of the circuit can be reduced. Thus the power dissipation can be reduced. We applied MBDD to a full odder and a 4-2compressor. Comparing the 4-2compressor block with other synthesis logic, 31.2% reduction and 19.9% reduction was achieved in numbers of transistors and power dissipation respectively. In this simulation we used 0.8 ${\mu}{\textrm}{m}$ fabrication parameters.

• 동력기계공학회지
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• 제19권4호
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• pp.69-75
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• 2015

In this study, the characteristics of heating performance of a high-performance air-cooled heat pump with vapor-injection(VI) cycle using re-heater was investigated experimentally. Devices used in the experiment is consist of a VI compressor, condenser, oil separator, refrigerant (economizer outlet refrigerant) re-heater, economizer, evaporator. And R410A was used as a working fluid. The experiment was conducted with two cycles(cycles A and B) for investigating heating performance. In case of cycle B, heat exchange was conducted by re-heater between outlet refrigerant of compressor and suction refrigerant of the VI system(Fig.1, re-heater). But the re-heater was not used in case of cycle A. As a result of this experiment, discharge temperature of refrigerator in compressor was shown higher value, when the cycle B was conducted, because of the heat exchange between suction refrigerant of VI cycle and outlet refrigerant of compressor in the re-heater than cycle A that was not use re-heater. it means that liquid hammer and the decrement of heating performance can be decreased by using re-heater. Also, Heating coefficient of performance(COPh) was shown about 2.98 in Cycle B which was 4% higher than Cycle A and from these results, It was confirmed that the improvement of the heating performance of heat pump with VI cycle can be achieved by applying re-heater.

• 한국추진공학회지
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• 제3권4호
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• pp.93-103
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• 1999

소, 중형 산업용 항공기나 초등 훈련기용으로 많이 이용되고 있는 터보프롭 엔진의 정상상태 성능해석 프로그램을 개발하고 성능진단을 위해 선형 GPA 기법을 적용하였다. 정상상태 성능해석 프로그램의 검증을 위해 상용 정상상태 해석 프로그램인 TURBOMARCH 해석결과와 비교하였다. 지상정지조건에서의 성능 및 비행마하수에 따른 출력 둥을 비교한 결과 각 구성품의 입,출구 온도 및 압력, 출력 등에서는 약 3%이하의 오차율을 보였으며, 마하수 변화에 따른 출력 비교에서도 최대오차율 2.4 % 이내로 프로그램의 신뢰성을 확인하였다. 선형 GPA 기법의 계측변수의 선정에 따른 정확성을 알기 위해 종속변수의 선정을 다르게 하여 오차율을 알아보았다. 성능저하 원인으로는 압축기에만 오염이 발생하였을 경우, 압축기와 압축기 터빈에 각각 오염과 부식이 발생하였을 경우, 압축기 터빈과 동력터빈에 동시에 부식이 발생하였을 경우, 압축기, 압축기 터빈, 동력터빈이 모두 오염과 부식이 발생하였을 경우를 가정하였다. 해석결과 계측기 변수가 많을수록 RMS 오차가 적었으며 같은 수의 계측기 변수라 하더라도 어떠한 변수를 계측하는가에 따라 오차율이 달라짐을 알 수 있었다. 비교적 오차율이 적으면서 경제성이 있는 경우는 8개의 측정변수를 이용한 경우로 최적의 계측기 수 및 계측기 변수 선정이 중요함을 알 수 있었다.

• 한국유체기계학회 논문집
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• 제12권4호
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• pp.23-29
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• 2009

For the purpose of high outlet pressure, compactness and low vibration and noise, 2 stage reciprocating air compressors can have various cylinder arrangement: opposed, in-line, and V type. This paper presents an effective method to calculate the inertia forces and to design counter weight. This method is based on the complex representation for the orbital behavior of the compressor shaft. This method helps to find the optimal balancing rate easily to reduce the inertial force or moment. This paper shows that the residual inertia forces of the single throw shafts and the residual inertia moments of the double throw shafts remain to be imbalanced.

• 대한방사선치료학회지
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• 제25권2호
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• pp.159-165
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• 2013

목적: 복부압박장치를 적용한 정위적방사선치료 시 환자 호흡에 기인하는 내부종양용적의 동적변이 양상을 연구하고자 하였다. 대상 및 방법: 2012년 4월부터 2013년 4월까지 복부압박장치를 이용하여 정위적방사선치료를 받은 폐암 환자 20명(상엽 7명, 중엽 4명, 하엽 9명), 총 67건을 대상으로 하였다. 치료 자세의 변동과 호흡에 의해 움직이는 종양 위치 변동을 알아보기 위해 4차원 cone- beam CT (4D-CBCT)를 사용하여 좌표 이동 값을 얻었다. 각 부위별로 LR (좌우), SI (상하), AP (전후) 방향의 벡터의 95% 신뢰구간(95% Confidence interval, 95% CI), 최대값, 그리고 최소값을 통하여 비교하였으며 자세변동 보정 값과 호흡변동 보정 값 간의 피어슨 곱 상관계수를 통하여 일치도를 분석하였다. 결과: 호흡에 의한 종양용적의 각 부위별로 변동은 폐 상엽에서 1.8~2.9 mm, 중엽과 하엽에서 2.3~5.4 mm, 2.2~4.0 mm로 분석되었다(95%CI, P<0.001). 자세변동 보정 값과 호흡변동 보정 값 간의 일치도($R^2$)를 살펴보면 상엽은 LR방향, SI방향, AP 방향에서 각각 0.75, 0.68, 0.63으로 나타났고, 중엽은 각각 0.82, 0.51, 0.92로 나타났으며, 하엽은 각각 0.63, 0.50, 0.34로 나타났다. 결론: 폐암의 정위적방사선 치료 시 복부압박장치의 사용으로 폐에 위치하는 종양은 환자 호흡에 의해 각 부위별로 각기 다른 양상을 보였다. 따라서 치료 자세에 대한 보정뿐만 아니라 호흡에 의한 변동을 보정해야만 한다. 또한 이러한 각기 다른 동적변이로 인한 오차의 보정 시 4D-CBCT의 사용은 매우 유용한 것으로 사료된다.