• 자원리싸이클링
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• 제32권2호
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• pp.33-42
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• 2023

금속 에멀젼(metal emulsion)은 제강 공정의 효율성을 높이는 방법으로 수십 년 동안 연구되어 왔습니다. 본 연구는 육안으로 관찰하기 어려운 고온 실험의 단점을 보완하기 위해 상온에서 관찰 가능한 수모델을 이용하여 수행하였다. 슬래그 내 금속 에멀젼의 대신하여 증류수를 실리콘 오일에 적하하여 운동량 균형 방정식에 의한 계산 결과와 비교하는 실험을 하였다. 물방울의 하강 속도는 물방울의 직경과 유체(실리콘 오일)의 점도가 증가함에 따라 감소하였다. 교반 조건에서 실리콘 오일에서 물방울의 하강 속도를 시뮬레이션하기 위해 유체(실리콘 오일)의 유속을 입자 이미지 속도계(PIV) 방법으로 측정하였다. 물방울의 하강 속도 계산은 점성 실리콘 오일을 교반하거나 교반하지 않고 측정된 값과 잘 일치하였다.

• 생물환경조절학회지
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• 제24권3호
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• pp.147-152
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• 2015

온실의 냉방부하 산정방법 개발을 위하여 열수지 방법에 기초한 냉방부하 산정식을 구성하고, 포그냉방 온실에서 냉방부하를 실측하여 검증하였다. 포그냉방 온실의 냉각열량은 포그분사에 의한 증발수량에 물의 증발잠열을 곱하여 구할 수 있다. 여기서, 증발수량은 포그 분사량에 증발효율을 곱하면 구할 수 있으며, 즉 분무수량을 계측하고 포그시스템의 증발효율을 알면 온실의 냉방부하를 실측할 수 있다. 따라서 온실의 냉방부하 실측을 위하여 실험온실에서 포그시스템의 증발효율을 실험하고, 실험온실의 열환경 계측과 더불어 포그 분사량을 계측하여 냉방부하 산정방법을 검토하였다. 먼저 냉방부하 산정식의 환기전열량을 검토하기 위하여 냉방을 실시하지 않은 상태에서 환기량 실측 실험을 통해 비교한 결과 열수지식을 이용한 환기전열량 예측은 비교적 양호한 결과를 보이는 것으로 나타났다. 이류체 포그시스템의 증발효율은 0.3~0.94의 범위를 보였으며 평균 0.67로 나타났고, 환기율이 증가함에 따라 커지는 것으로 나타났다. 포그냉방을 실시하면서 온실의 환경을 계측하여 열수지식으로 냉방부하를 계산하고, 분무량 실측치로부터 증발 냉각열량을 구하여 비교한 결과 냉방부하 계산치와 실측치는 대체로 유사한 경향을 보이는 것으로 나타났다. 냉방부하가 낮은 경우에는 실측치에 비하여 약간 크게 예측되었고, 냉방부하가 높은 경우에는 실측치보다 작게 예측되었다. 온실의 냉방시스템 설계 시에는 최대냉방부하를 이용하여 냉방설비의 용량을 결정하게 된다. 따라서 냉방부하가 큰 쪽에서 실측치보다 작게 예측되는 부분은 검토가 필요하지만 설비용량 산정시의 안전계수를 고려하면 본 연구에서 제시한 냉방부하 산정방법은 온실의 환경설계에 적용할 수 있는 것으로 판단된다.

• Asian-Australasian Journal of Animal Sciences
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• 제20권9호
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• pp.1367-1373
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• 2007

The aim of this study was to determine the feeding value to sheep of Acacia saligna grown under temperate conditions. Pen trials were undertaken to determine the effects of feeding A. saligna, which had been grown in a Mediterranean environment, on feed intake, nitrogen balance and rumen metabolism in sheep. Sheep were given ad libitum access to A. saligna with or without supplementation with PEG 4,000 or PEG 6,000. PEG 4000 appears to be the major detannification agent used in trials involving high tannin feed despite the fact that PEG 6000 has been shown to be more effective, in vitro. For this reason it was of interest to compare the two, in vivo. Dry matter intake was greater (p<0.05) in sheep supplemented with either PEG 4,000 or PEG 6,000 compared to the control. There was no difference, however, in intake between those supplemented with either PEG 4,000 or 6,000. Although animals were not weighed throughout the trial, a loss in body condition was obvious, in particular in the control group. Intake of N was greater (p<0.05) in sheep supplemented with either PEG 4,000 or PEG 6,000 than in the control. There was no difference in N intake between those supplemented with either PEG 4,000 or PEG 6,000. There were no significant differences in either the faecal or urinary N output between any of the treatment groups and all treatment groups were in negative N balance. Neither the average nor maximum pH of ruminal fluid of the control group was different to those supplemented with PEG. The minimum pH for the control group, however, was significantly higher (p<0.05) than for either of the PEG treatments. The average and the maximum ammonia levels were lower (p<0.05) in the control group compared with those in either of the PEG treatment groups. For all dietary treatments ruminal ammonia levels were well below the threshold for maximal microbial growth. Feeding A. saligna, without PEG, had a definite defaunating effect on the rumen. For all dietary treatments ruminal ammonia levels were well below the threshold for maximal microbial growth. It was concluded that A. saligna was inadequate as the sole source of nutrients for sheep, even with the addition of PEG 4,000 or PEG 6,000. The anti-nutritional effects on the animals were largely attributed to the excessive biological activity of the phenolics in the A. saligna leaves. There is a need to determine other supplements that may be complimentary with PEG to enhance the nutritive value of A. saligna to maintain a minimum of animal maintenance.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.170-170
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• 2010

The energy conversion from the temperature difference between hot and cold source like ocean thermal energy conversion (OTEC), requires a long and large-diameter pipe (about 1000 to 10,000 meters long) to reach the deep water. The pipe diameter ranges from 2.8 meter for proposed early test systems, to 5 meter for large, commercial power generation systems. The pipe must be designed to resist collapsing pressures produced by water temperature and density differences, and the reduced pressure required to induce flow up the pipe. Other design considerations include the external-drag effect on the pipe due to ocean currents, and the wave-induced motions of the platform to which the pipe is attached. Various approaches to the pipe construction have been proposed, including aluminum, steel, concrete, and fiberglass. More recently, a flexible pipe construction involving the use of fiberglass reinforced plastic has been proposed. This report presents the results of a scaled fixed cold water pipe (CWP) model test program performed by EES(Engineering Equation Solver) to demonstrate the feasibility of this pipe approach.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.59-62
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• 2014

Predicting coal combustion by computational fluid dynamics (CFD) requires a combination of complicated flow and reaction models for turbulence, radiation, particle flows, heterogeneous combustion, and gaseous reactions. There are various levels of models available for each of the phenomena, but the use of advanced models are significantly restricted in a large-scale boiler due to the computational costs and the balance of accuracy between adopted models. In this study, the influence of coal devolatilization model and turbulent mixing rate was assessed in CFD for a commercial boiler at 500 MWe capacity. For coal devolatilization, two models were compared: i) a simple model assuming single volatile compound based on proximate analysis and ii) advanced model of FLASHCHAIN with multiple volatile species. It was found out that the influence of the model was observed near the flames but the overall gas temperature and heat transfer rate to the boiler were very similar. The devolatilization rate was found not significant since the difference in near-flame temperature became noticeable when it was multiplied by 10 or 0.1. In contrast, the influence of turbulent mixing rate (constant A in the Magnussen model) was found very large. Considering the heat transfer rate and flame temperature, a value of 1.0 was recommended for the rate constant.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.151-158
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• 1998

The screw compressor is first invented by a Swedish engineer, Alf Lysholm in 1934. Since then, the development of the screw compressor idea for industrial applications has been continued by the Swedish research organization Svenska Rotor Maskiner, often identified by its initials SRM. The first industrial application of the machine was marketed as an air compressor in the 1950s. The screw compressor which is a positive displacement type compressor compresses gases by the rotation of a pair of mating rotors. The operation of this compressor is entirely rotary and dynamically in balance. Also there is no need for any valve mechanism and there exists less mechanical wear between the parts compared to the conventional reciprocating compressors. Due to these prominent features, the screw compressor has been rapidly spread into the air compressor market replacing the conventional reciprocating compressors and begun to be applied as a refrigerant compressor since the 1960s. In this work, the operation principle of the screw compressor is described in brief and the major design parameters affecting the compressor performance are classified. The international research trend in screw compressor development is introduced and the current situation in our country is described.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.175-185
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• 2004

Rotating disks are used in various machines such as data storage device, gyroscope, circular saw, etc. Transverse vibration of a rotating disk is very important for the performance of these machines. This work proposes a method to suppress transverse vibration of a very flexible rotating disk in non-contacting manner. A system considered in this study is a very flexible rotating disk with a thrust bearing pad which is located underneath the rotating disk. The pressure force generated in the gap between the rotating disk and the thrust pad pushes the rotating disk in the direction of axis of rotation while the centrifugal force and the elastic recovery force push the rotating disk in reverse direction. The balance between these forces suppresses the transverse vibration of the rotating disk. A coupled disk-fluid system is analyzed numerically. The finite element method is used to compute the pressure distribution between the thrust pad and the rotating disk while the finite difference method is used to compute the transverse vibration of a rotating disk. Results show that the transverse vibration of the rotating disk can be suppressed effectively for certain combination of air bearing and operating parameters.

• Journal of Chest Surgery
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• 제23권6호
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• pp.1152-1157
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• 1990

Colloid solution is commonly used to increase the oncotic pressures of priming solutions used in the cardiopulmonary bypass circuit. To study the effectiveness of this practice, we retrospectively evaluated 24 patients undergoing cardiac operations to receive isoelectric solution plus 50 gm of albumin[group A], isoelectric solution plus 25 gm of albumin[group B] and isoelectric solution without albumin[group C] as the prime solution for the bypass circuit. Various clinical parameters related to the perioperative fluid balance, cardiopulmonary function, and renal function were studied. There were no differences between the three groups with regard to postoperative clinical parameter of cardiopulmonary, liver function and renal function. But at the previous report by Cho et al. [38], there was a significant difference between groups with regard to hematologic property, especially in crenated red blood cells. These hematologic events did not affect the clinical outcome but thorough evaluations are needed in order to prove the clinical effect of crenated red blood cell. We conclude that there is no clinically detectable advantage for the routinely supplementing of albumin to the priming solution of bypass circuit in cardiac operations. Whether this practice can be of value in selected cases needs to be further studied.

• 한국진공학회지
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• 제9권2호
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• pp.172-178
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• 2000

반도체 제조공정 중 플라즈마 반응기 내에서 입자오염을 유발하는 입자들의 거동과 성장을 모델식을 사용하여 이론적으로 고찰하였다. 플라즈마 반응기 내에서 입자 거동에 영향을 미치는 힘들로 유체 대류, 입자 확산 및 외부힘 (ion drag force, electrostatic force, 중력) 등을 고려하였다. 플라즈마 벌크 영역에서 전하를 가진 입자들간의 충돌에 의한 입자 성장을 고려하기 위해 모델식에 입자 전하 분포를 고려하였다. 대부분의 입자들은 ion drag force와 electrostatic force가 균형을 이루고 있는 두 sheath 경계 영역에 존재하였으며 두 sheath 영역과 벌크 플라즈마에서의 입자 농도는 0에 접근하였다. 시간이 지남에 따라 입자 충돌로 인한 입자들의 크기는 증가하였으며 입자가 성장함에 따라 입자 표면적의 증가와 더불어 입자가 가지는 평균 전하량도 증가하였다.

• 대한본초학회지
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• 제27권4호
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• pp.17-23
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• 2012

Objectives : Schisandrae Fructus (SF) has traditionally been used to balance level of body fluid and to strengthen kidney function. It has been reported that the SF extract has antioxidant, hepatoprotective, neuroprotective and anticancer effects. This study investigated an antiproliferative effect of SF extract on PC-3 human prostate cancer cells and analyzed active ingredients of SF extract qualitatively and quantitatively. Methods : We examined the antiproliferative effect of SF extract with MTT assay, DAPI staining and annexin-V/7-AAD double staining. The active ingredients of SF extract were identified by using HPTLC and HPLC/DAD system. Results : SF-chloroform fraction inhibited growth of PC-3 cells and changed the morphology of nucleus in a dose dependent manner. A dose-dependent apoptotic cell death was also measured by flow cytometry analysis. It was analyzed that SF-chloroform fraction contained more schizandrin than other fractions by using HPTLC and HPLC/DAD system. Conclusions : These results suggest that SF extract and schizandrin may be a potential chemotherapeutic agent for the control of PC-3 human prostate cancer cells.