• International Journal of Air-Conditioning and Refrigeration
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• 제8권1호
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• pp.50-61
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• 2000

The effects of an inserted coil on flow . patterns and heat transfer performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low rpm(less than 1,000rpm), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing rpm. The pumping effects for RHP with an inserted coil resulted in the enhancement in both condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher rpm(above 1,000-1,200) with the transition of flow regime to annular flow.

• 설비공학논문집
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• 제12권3호
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• pp.284-291
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• 2000

A basic pulse tube refrigerator has been constructed with extensive instrumentation to study the characteristics of the heat exchanger experimentally under the oscillating pressure and the oscillating flow. This paper describes the sequential experiments with the basic pulse tube refrigerator. The experiments were performed for various cycle frequencies under the square pressure wave forms. First, the heat flux was measured through the cycle at the both cold and warm end heat exchangers without the regenerator. In order to enhance the thermal communication capability of the heat exchanger with the gas at low operating frequencies, a unique design of the triangular shape radial fin concept was applied to the heat exchangers. For the fin heat exchanger, the measured heat flux and the calculated heat flux from the two well-known oscillating heat transfer correlations were compared and discussed. Second, the regenerator was added to the pulse tube to make a basic pulse tube refrigerator configuration. The experiment showed the great impact of the regenerator on the temperature and the heat flux profiles. At the warm-end, the cyclic averaged heat flux had its maximum value at the specific operating frequency. The paper presents the explanation of the surface heat pumping effect as well as the experimental data.

• Geomechanics and Engineering
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• 제35권6호
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• pp.627-636
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• 2023

The essence of subgrade mud pumping under train load is the migration of fine particles in subgrade soil. The migration of fine particles will change the pore structure of overlying ballast, thus affecting the mechanical properties and hydraulic properties of ballast layer. It is of great theoretical significance and engineering value to study the effect of fine particle migration on the pore structure of ballast layer under cyclic loading. In this paper, a tailor-made subgrade mud pumping test model and an X-ray computed tomography (CT) scanning equipment were used to study the influence of migration of fine particles in subgrade soil on the pore parameters (plane porosity, volume porosity, pore distribution and pore connectivity) of overlying ballast under cyclic loading. The results show that the compression of ballast pores and the blockage of migrated fine particles make the porosity of ballast layer decreases gradually. And the percentage of small pores in ballast layer increases, while the percentage of large pores decreases; the connectivity of pores also gradually decreases. Based on the test results, an empirical model of ballast porosity evolution under cyclic loading is established and verified.

• Journal of information and communication convergence engineering
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• 제5권4호
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• pp.374-376
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• 2007

The output characteristics of HF and DF lasers were compared theoretically. The simulation code shows the good agreement with the experimental results well. As results, the effect of chain termination reaction in $F_2$ rich mixture is larger than that of $SF_6$ rich mixture in HF and DF lasers.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2013년도 자성 및 자성재료 국제학술대회
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• pp.131-132
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• 2013

• Environmental Engineering Research
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• 제10권1호
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• pp.22-30
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• 2005

Nitrite accumulation is not unusual in batch processes such as sequencing batch reactor (SBR) with high-strength of ammonium or nitrate wastewaters. A possible mechanism of nitrite inhibition on Acinetobacter was depicted in a biochemical model, which the protonated species, nitrous acid form of nitrite, affects proton relating transport at the proton-pumping site crossing the cell membrane under unlimited carbon and phosphorus conditions. This effect exerts inhibition of phosphorylation under aerobic condition and yields low APT/ADP ratio, consequently decrease poly-P synthesis and phosphorus uptake from outside the cell in the model.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.250-251
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• 2000

The photoisomerization of the crosslinked and uncrosslinked polymer-pair with azo linkages was studied by the photoinduced birefringence. The amount of photoinduced birefringence of crosslinked polymer system was much smaller than that of uncrosslinked polymer system, even when varying pumping laser power, so the photoisomerization of an azo chromophores could be controlled by crosslinking process. (omitted)

• Current Optics and Photonics
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• 제3권5호
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• pp.458-465
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• 2019

The thermal effect and the light output of a laser crystal under different pumping depths were reported., Based on the thermal model of a single-ended pumped Tm:YAP crystal, the thermal stress coupled model used Comsol to theoretically calculate the effect of changing the pump spot size and pump depth on crystal heat distribution and stress distribution. The experimental results showed that the laser output power first increased and then decreased with increasing pump spot size. As the depth of focus increased, the laser output power first increased and then decreased. The experimental results were consistent with the theoretical simulation results. The theory of pump spot radius and depth of focus in this paper provided an effective simulation method for mitigating thermal effects, and provided theoretical supports for laser crystals to obtain higher laser output power.

• 자원환경지질
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• 제43권2호
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• pp.149-162
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• 2010

K-1 유류비축기지는 인위적 지하 공동을 이용하기 때문에 주변 지하수계의 안정이 중요하다. 기지 주변의 지하수계 특성을 이해하기 위해 광역적 지하수 유동특성, 기지내 공간적 지하수위 분포 양상을 파악하였으며, 지하수 유동에 영향을 미치는 지질 요소를 검토하였다. 연구지역에서 지히수 유동에 크게 영향을 미칠 수 있는 지질구조적 특성은 2가지로서, 편마암-화강암 관입경계를 따라 재활성된 부분과 산성 암맥을 따라 발달한 단열 및 단층이다. 기지 내 4개 관측공들의 수위변동 양상을 검토한 결과, 대부분 강우와 지표수 유입 혹은 공동내 주입수에 의해 지하수위 변동이 영향을 받고 있는 것으로 나타났다. 이 연구에서는 기지 남쪽에 위치한 관정으로부터의 양수가 기지의 지하수위 변동에 미치는 영향에 대해 검토하였다. 산성 암맥을 따라 기지로부터 1.2km 남쪽에 위치한 지점에서의 양수작업은 관측 당시에 기지내 지하수위 변동에 영향을 미치지 않았으나, 모델링 결과에 의하면 $250\;m^3$/day 이상의 양수량으로 지속적인 양수작업이 진행되는 경우 지하수 시스템 안정을 위해 주의가 요구된다.

• 지질공학
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• 제13권4호
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• pp.457-474
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• 2003

본 연구에서는 창원시 대산면 강변여과수 취수장 부지의 지하수위 변동 특성을 분석하였다. 지하수위 및 하천수위 변동과 하천-대수층간의 상호작용은 장기적으로 취수정의 적정양수량을 평가하는데 중요하다. 2003년 2월부터 2003년 10월까지의 지하수위 분포를 보면 지하수위는 대체로 배후지쪽에서 낙동강 쪽으로 갈수록 낮아지는 경향성을 보이고 있으며, 수두경사는 0.008 정도를 나타낸다. 그러나, 취수정의 양수와 강수량에 의한 낙동강 수위 상승에 의해 일시적으로 유동방향이 역전되기도 한다. 낙동강 수위는 강수량 변화에 따라 해수면 기준으로 0 ∼ 10m를 보인다. 6개 지하수 관측공(DS1, DS2. DS3, DS4, DS6, DS7)에 대해서 자기상관분석을 실시한 결과, 세 개의 그룹으로 분류되었다. 1그룹(DS1호공과 DS3호공)은 강한 선형성과 기억효과를 보여주고, 2그룹(DS2호공과 DS6호공)은 중간정도의 선형성과 기억효과를 나타내며. 3그룹(DS4호공과 DS7호공)은 가장 약한 선형성과 기억효과를 보였다. 1그룹은 낙동강 수위변화의 영향을 상대적으로 많이 받고, 2그룹은 낙동강수위와 취수량의 영향을 동시에 받으며. 3그룹은 취수량의 영향을 가장 많이 받는 것으로 분석되었다.