• 유기물자원화
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• 제12권2호
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• pp.72-81
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• 2004

전체 유기성폐기물 가운데 약 30%가량을 차지하는 음식물쓰레기는 높은 염분과 함수율로 인해 적정 처리 방안의 부재라는 상황에서 기존의 처리방법들에 비해 보다 환경친화적인 지렁이를 이용한 퇴비화 방안은 최근 들어 관심이 집중되고 있다. 그러나 지렁이 이용기술은 도입초기의 운영방법 및 기술이 현재에도 적용되고 있으며 자료부족과 경험부족으로 인해 효율성이 떨어진다고 볼 수 있다. 지렁이를 이용한 음식물쓰레기 자원화 단계에서 높은 수분, 염분, 그리고 유기물 함량은 지렁이의 생육에 큰 저해 원인이 되는 것으로 알려지고 있으며, 이러한 영향을 최소화하기 위하여 전처리 단계에서 가능한 한 수분의 양을 줄이고 유기물을 1차적으로 분해하여 이용하도록 유도하고 있다. 본 연구에서는 지렁이를 이용한 음식물쓰레기 자원화에 있어 음식물쓰레기의 염분농도와 급이되는 음식물쓰레기의 부숙정도 그리고 혼합비에 따른 지렁이의 영향정도를 관찰하기 위하여 실시되었다. 실험 결과, 지렁이 생육과 관련된 최적의 함수율은 약 55%로 한계 염분 농도는 0.5%로 조사되었다. 음식물쓰레기의 높은 염분농도와 유기물 분해에 따른 발열 및 유기산 생성등의 부하를 줄이기 위한 분변토와의 혼합은 필수적 이었으며, 유기물 감량이 목적인 부숙과정은 결과적으로 음식물쓰레기의 염분농도를 증가 시키는 것으로 조사되었다. 따라서 가급적 부숙과정은 피하고 분변토와의 적절한 혼합을 통한 유기물감량이 요구되며, 결과적으로 음식물쓰레기와 분변토와의 혼합비는 모든 조건등을 고려했을 때 부숙되지 않은 음식물쓰레기와 분변토와의 3:7 혼합비가 가장 적절하다고 사료된다.

• 한국물환경학회지
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• 제32권5호
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• pp.419-432
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• 2016

이 연구의 목적은 응천에서 채집한 담수 붕어(Carassius auratus)의 산화적 스트레스와 조직병리학적 손상을 분석하여 하수처리장 방류수의 영향을 평가하는 것이다. 방류수 혼합 지점과 하류 지점에서 채집한 붕어의 아가미, 간, 콩팥의 과산화수소 분해효소(catalase)의 활동도는 상류 지점과 비교하여 더 높은 것으로 나타났다. 또한, 혼합 지점의 아가미와 간의 글루타치온 S-전이효소(glutathione-S-transferase)의 활동도는 상류 지점과 비교하여 유의하게 높았으며(p < 0.05), 상류 지점보다 유의하게 더 증가된 간의 지질 과산화(lipid peroxidation)가 혼합 지점에서 관찰되었다. 붕어의 조직병리학적 손상의 정도는 간 > 콩팥 > 아가미순으로 나타났다. 이 결과는 간이 방류수의 영향을 가장 크게 받는다는 것을 의미한다. 붕어의 조직 손상도(degree of tissue changes)는 혼합 지점에서 채집한 시료(30.98 ± 5.40)에서 가장 컸으며, 그 다음은 하류 지점 시료(19.28 ± 4.31)이고 가장 낮은 것은 상류 지점 시료(4.83 ± 2.67)로 나타났다. 이러한 결과는 혼합 지점에서 채집한 붕어가 방류수에 가장 큰 영향을 받았다는 것을 의미하며, 산화적 스트레스와 조직병리학적 지표들이 방류수로 오염된 하천을 모니터링하는데 유용하다는 것을 나타낸다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.75-78
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• 2004

Various jet engines (Turbine engine family and RAM Jet engine) have been developed for high speed aircrafts. but their application to hypersonic flight is restricted by principle problems such as increase of total pressure loss and thermal stress. Therefore, the development of next generation propulsion system for hypersonic aircraft is a very important subject in the aerospace engineering field, SCRAM Jet engine based on a key technology, Supersonic Combustion. is supposed as the best choice for the hypersonic flight. Since Supersonic Combustion requires both rapid ignition and stable flame holding within supersonic air stream, much attention have to be given on the mixing state between air stream and fuel flow. However. the wider diffusion of fuel is expected with less total pressure loss in the supersonic air stream. So. in this study the direction of fuel injection is inclined 30 degree to downstream and the total pressure of jet is controlled for lower penetration height than thickness of boundary layer. Under these flow configuration both streams, fuel and supersonic air stream, would not mix enough. To spread fuel wider into supersonic air an aerodynamic force, baroclinic torque, is adopted. Baroclinic torque is generated by a spatial misalignment between pressure gradient (shock wave plane) and density gradient (mixing layer). A wedge is installed in downstream of injector orifice to induce an oblique shock. The schlieren optical visualization from side transparent wall and the total pressure measurement at exit cross section of combustor estimate how mixing is enhanced by the incidence of shock wave into supersonic boundary layer composed by fuel and air. In this study non-combustionable helium gas is injected with total pressure 0.66㎫ instead of flammable fuel to clarify mixing process. Mach number 1.8. total pressure O.5㎫, total temperature 288K are set up for supersonic air stream.

• Clinical and Experimental Reproductive Medicine
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• 제24권3호
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• pp.369-375
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• 1997

Studies were conducted to determine the efficiency of decondensation protocols. Sperm obtained from seven normal donors was immediately washed after liquefaction and then decondensed using the method of West et al. (1989) and my original protocol. My optimized protocol entailed mixing 1 ml aliquots of semen with 4 ml phosphate buffered saline (PBS). Following centrifugation, pellets were resuspended in 1 ml PBS containing 6 mM EDTA. After centrifugation, pellets were resuspended in 1 ml PBS containing 2 mM dithiothreitol at $37^{\circ}C$ for 45 min. Following mixing with 2 ml PBS and centrifugation, pellets were resuspended by vortexing. While vortexing, 5 ml of fixative were gently added. Slide preparation was accomplished using the smear method and it was stored at $4^{\circ}C$. When comparing these protocols, the degree of sperm decondensation and head swelling was monitored by measuring nuclear length, area, perimeter, and degree of roundness using FISH analysis software. Apparent copy number for chromosome 1 and, separately, for the sex chromosomes was determined by FISH using satellite DNA probes for loci DIZ1, DXZ1 and DYZ3. Sperm treated by my decondensation protocol showed significant increases (p<0.05) in length, area, perimeter, and degree of roundness. There was a significant decrease (p<0.05) in the frequency of nuclei displaying no signal but no change in the frequency of nuclei with two signals in samples decondensed by my protocol. My data suggested that decondensation using my original protocol may lower the frequency of cells with spurious "nullisomy" due to hybridization failure without inducing spurious "disomy" resulting from increased distances between split signals.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.274-277
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• 2004

ATR 엔진 연소기 내부에서의 연료와 공기의 혼합성능은 연소 안정성이나 효율에 지배적인 요인이 된다. 본 연구에서는 ATR 모델 연소기에서의 혼합성능을 비교하기 위하여 두 유체의 속도 비$(r=v_a/v_f)$를 변화시키면서 연료분포를 측정하였다. 측정 방법으로는 2차원 연료분포를 얻기 위하여 널리 이용되는 평면레이저 유도형광기법과 화상처리 기법을 사용하여 연료분포 이미지를 얻었다. 측정된 연료분포 화상으로부터 공기속도/연료속도 비가 1에 가까울수록 연료 혼합성능이 떨어지는 특성을 관찰하였다.

• Carbon letters
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• 제15권4호
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• pp.282-289
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• 2014

Blends of poly(vinyl alcohol) (PVA), polyethyleneimine (PEI), and graphene oxide (GO) were prepared by solution casting method. Calorimetric thermal properties of the blends were investigated. The $T_gs$ of PVA/PEI blends were higher than the $T_gs$ of either of the component polymers at low concentrations of PEI. These abnormal increases of $T_gs$ may be due to the negative entropy of mixing which is associated with strong hydrogen bonding between PVA and PEI. The degree of depression of $T^0_ms$ was not reduced by the negative entropy of mixing, since strong hydrogen bonding also causes an increase in the magnitude of negative ${\chi}$ between PVA and PEI. The $T_g$ of PVA was increased significantly by adding 0.7 wt.% GO into PVA. The magnitude of negative ${\chi}$ was increased by adding GO into the blends of PVA and PEI.

• 반도체디스플레이기술학회지
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• 제12권3호
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• pp.1-6
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• 2013

In many technical fields including electronics and display manufacturing processes, properties of coating liquids could be greatly enhanced by adding nanopowders and it requires efficient mixing techniques to achieve uniform dispersion of nanoparticles in liquids. This paper presents the three-dimensional CFD simulations on the flowfields of a highly viscous liquid in the large scale industrial mixer of impeller type. The effects of several important design and operation parameters such as impeller geometry, rotational speed, and degree of liquid viscosity are investigated to appreciate the mixing performance by examining the computational results for flow pattern of rotationally stirred liquid of high viscosity in the mixer.

• Korea-Australia Rheology Journal
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• 제14권3호
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• pp.121-128
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• 2002

A series of thermoplastic polymers and their blends were melt-processed with high intensity ultrasonic wave in an intensive mixer. For the effective transfer of ultrasonic energy, an experimental apparatus was specially designed so that polymer melt can directly contact with ultrasonic horn. It was observed that significant variations in the rheological properties of polymers occur due to the unique action of ultrasonic wave without any aid of chemical additives. It was also found that the direct sonication on immiscible polymer blends in melt state reduces the domain sizes considerably and stabilizes the phase morphology of the blends. The degree of compatibilization was strongly affected by viscosity ratio of the components and the morphology was stable after annealing in properly compatibilized blends. It is suggested that ultrasound assisted melt mixing can lead to in-situ copolymer formation between the components and consequently provide an effective route to compatibilize immiscible polymer blends.

• Corrosion Science and Technology
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• 제3권6호
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• pp.257-261
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• 2004

Leaking of fuel gas in a building creates flammable atmosphere and gives rise to explosion. Observations from accidents suggest that some explosions are caused by quantity of gas significantly less than the lower explosion limit amount required to fill the whole confined space, which might be attributed to inhomogeneous mixing of the leaked gas. The minimum amount of leaked gas for explosion is highly dependent on the degree of mixing in the building. This paper proposes a method for estimating minimum amount of flammable gas for explosion assuming Gaussian distribution of flammable gas.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.657-664
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• 2004

In this study, a fundamental experiment was carried out to investigate the frost formation on a cryogenic flat plate with/without temperature distribution from 230K to 160K under the convective flow. The effects of mixing ethanol as a condensable substance were also researched. From the test results, when surface temperature at the upstream is 230K, mass flux is high. On the other hand, when surface temperature at the downstream is 160K, mass flux is low. The degree of improvement to restrain frost formation by ethanol mixing is relatively larger at the upstream than at the downstream.