• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.357-363
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• 2008

In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a horizontal micro-fin tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($400{\sim}1200\;kg/m^2s$), heat fluxes($10{\sim}30\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$), and PAG oil concentration($0{\sim}5\;wt%$). The variation of the heat transfer coefficient was different in accordance with the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

• Journal of Korean Physical Therapy Science
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• v.12 no.4
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• pp.11-24
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• 2005

대전에 소재하는 C 대학교 병원의 물리치료실에 2003년 5월 9일부터 2004년 10월 20일까지 내원한 환자들 중 견부 통증의 진단으로 치료를 받은 환자 가운데 중추신경계에 손상 병력이 없고, 치료사와 의사소통이 가능한 인지 능력을 가졌으며, 실험에 참가하기로 동의한 환자를 대상으로 내원한 순서에 따라 아로마 초음파군, 아로마군, 초음파군에 각각 30명씩을 배정하여 실험한 결과, 치료의 횟수가 증가함에 따라 통증의 정도를 알아보는 시각적 통증 점수가 감소하였으며(p<0.001), 군 간에 통증 감소의 정도도 차이가 있었다. 사후 검정을 보면 아로마 초음파군과 아로마군의 통증 감소의 정도가 초음파군에 비해 높았다(p<0.001). 또한 치료의 횟수가 증가함에 따라 McGill-Melzac 통증 점수 역시 감소하였으며(p<0.001), 군 간에 차이는 없었지만, 교호작용을 고려하면 아로마를 사용한 군에서 감소 폭이 더 큰 것으로 해석할 수 있다. 압통계의 역치 역시 치료의 횟수가 증가함에 따라 모든 군에서 상승하였으며(p<0.001), 군 간에 역치 증가의 정도에도 차이가 있었는데(p<0.05), 사후 검정을 보면 아로마 초음파군이 아로마군에 비해 역치 증가의 폭이 더 컸다. 따라서 압통계의 역치 증가는 아로마 보다는 초음파에 더 영향을 받는 것으로 생각할 수 있다. 이상의 결과로 볼 때 아로마 오일은 주관적이고, 정서적인 통증을 검사하는 시각적 통증 점수와 McGill-Melzac 점수에 많은 영향을 미치는 반면 조직의 회복에 의해 상승하는 압력 역치를 검사하는 압통계의 수치에는 영향을 적게 미침을 확인할 수 있었으며, 반면 초음파는 주관적, 정서적인 통증의 감소보다는 실제 조직이 회복되면서 감소하는 통증에 더 많은 영향을 미치는 것을 알 수 있었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.6
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• pp.1-10
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• 2019

The wave motion inside the nozzle is known as one of the major damping elements of the rocket's combustion instability by it's aeroacoustic effects that result from the flow passage through the nozzle throat. These effects can be quantitatively evaluated by the nozzle admittance. In this study, one-dimensional linearized Euler equation was adopted to calculate the nozzle admittance, and trend analysis was performed depending on the nozzle's main design variables. As a result, when nozzle converging part shortens, it is verified that the frequency dependency of the nozzle admittance is decreased due to the widened frequency range with lowered longitudinal nozzle admittance. Also, admittance estimation using the short nozzle theory is not appropriate when the first tangential mode of the pressure perturbation arises.

• Polymer(Korea)
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• v.29 no.4
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• pp.369-374
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• 2005

In this work, the calcium alginate microcapsules containing lemon oil were prepared by emulsification-internal gelation and their potential use as aromatherapy was examined by the controlled release system. The lemon oil encapsulated in the alginate was successfully observed by Fourier transform (FT-IR) spectroscopy and differential scanning calorimeter (DSC) measurements. Analysis of the diameters and shapes of microcapsules was conducted by scanning electron microscopy (SEM). The mean diameters ranging from 4 to 7 um and encapsulation yield ranging from 50 to $85\%$ were obtained. The controlled release of the lemon oil at $37^{circ}$ was demonstrated by the infrared moisture determination (IMDB). It was found that the amount of released lemon oil decreased with increasing concentrations of alginate and $CaCl_2$ due to the higher the cross-linking density of the capsules prepared. The oil release from the capsule was measured as a function of physical force. We confirmed that the external factor could control the collapse of capsule wall and the release rate.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.688-693
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• 2014

This study is to increase the utilization of the ozonated water generator to make it easier to take advantage of the ozone water in the world today, there will be to develop a system that operates in one motion. Furthermore, olive oil and ozone is reacted with the wish to apply to the manufacturing technology. In the case of many existing products ozone generator driven mostly non-ozone system. In the case of ozone, but handwriting is implied general way pressure ozone gas leakage risks of suction force to the pump, it is the case of the challenge by using the injector, and limit the generation of ozone and ozone inhalation according to whether the water inlet leakage of existing products risk due to minimized. Despite the disadvantages of the injector system was found the effectiveness of the ozonated water production unit injector system used in this study to maintain the microbiological disinfection performance.

• Journal of the Korean Institute of Gas
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• v.19 no.1
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• pp.12-17
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• 2015

The core of the CNG fueling station is the compressor and most of CNG compressors in Korea require lubrication. Lubrication oil of CNG compressor that can be transferred into the pressure regulators and the engines of fueling system can cause a negative effect on NGV(Nature Gas Vehicle) performance during refueling due to oil Carry-over. In order to avoid the problem, it is necessary to enhance the quality of the compressed natural gas by measuring quantitatively the amount of the transferred oil. In this research, a sampling device and sampling tube were developed, which can be used with a gravimetric method of detection to measure CNG oil Carry-over. In addition, CNG samples were taken at 6 pre-selected CNG fueling stations and analysed for their trace oil Carry-over. The measured total oil Carry-over ranged from 2.569 to 6.509 ppm. This test measurements were compared with those of previous studies to verify the results.

• Clean Technology
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• v.27 no.1
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• pp.69-78
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• 2021

Vegetable oils, such as palm oil and cashew nut shell liquid (CNSL), are used as major raw materials for bio-diesel in transportation and bio-heavy oil in power generation in South Korea. However, due to the high unsaturation degree caused by hydrocarbon double bonds and a high content of oxygen originating from the presence of carboxylic acid, the range of applications as fuel oil is limited. In this study, hydrotreating to saturate unsaturated hydrocarbons and remove oxygen in mixed bio-oil containing 1/1 v/v% palm oil and CNSL on monometallic catalysts (Ni and Cu) and bimetallic catalysts (Ni-Zn, Ni-Fe, Ni-Cu Ni-Co, Ni-Pd, and Ni-Pt) was perform under mild conditions (T = 250 ~ 400 ℃, P = 5 ~ 80 bar and LHSV = 1 h-1). The addition of noble metals and transition metals to Ni showed synergistic effects to improve both hydrogenation (HYD) and hydrodeoxygenation (HDO) activities. The most promising catalyst was Ni-Cu/��-Al2O3, and in the wide range of the Ni/Cu atomic ratio of 9/1~1/4, the conversion for HYD and HDO reactions of the catalysts were 90-93% and 95-99%, respectively. The tendency to exhibit almost constant reaction activity in these catalysts of different Ni/Cu atomic ratios implies a typical structure-insensitive reaction. The refined bio-oil produced by hydrotreating (HDY and HDO) had significantly lower iodine value, acid value, and kinetic viscosity than the raw bio-oil and the higher heating value (HHV) was increased by about 10%.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.157-171
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• 2019

The fracturing by liquid carbon dioxide ($LCO_2$) as a fracking fluid has been an alternative to mitigate the environmental issues often caused by the conventional hydraulic fracking since it facilitates the fluid permeation owing to its low viscosity. This study presents how $LCO_2$ injection influences the breakdown pressure, acoustic emission, and fracture morphology. Three fracturing fluids such as $LCO_2$, water, and oil are injected with different pressurization rate to the synthetic and porous mortar specimens. Also, the shale which has been a major target formation in conventional fracking practices is also tested to examine the failure characteristics. The results show that $LCO_2$ injection induces more tortuous and undulated fractures, and particularly the larger fractures are developed in cases of shale specimen. On the other hand, the relationship between the fracturing fluids and the breakdown pressure shows opposite tendency in the tests of mortar and shale specimens.

• Journal of the Korean GEO-environmental Society
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• v.19 no.10
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• pp.21-26
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• 2018

Soil-water characteristic curve, which is called soil retention curve, is required to explore water flows in unsaturated soils, relative permeability of water in multi-phase fluids flow, and change to stiffness and volume of soils. Thus, the understanding of soil-water characteristic curves of soils help us explore the behavior of soils inclduing fluids. Biopolymers are environmental-friendly materials, which can be completely degraded by microbes and have been believed not to affect the nature. Thus, various biopolymers such as deacetylated power, polyethylene oxide, xanthan gum, alginic acid sodium salt, and polyacrylic acid have been studies for the application to soil remediation, soil improvement, and enhanced oil recovery. PAA (polyacrylic acid) is one of biopolymers, which have shown a great effect in enhanced oil recovery as well as soil remediation because of the improvement of water-flood performance by mobility control. The study on soil-water characteristic curves of sandy soils containing PAA (polyacrylic acid) has been conducted through experimentations and theoretical models. The results show that both capillary entry pressure and residual water saturation dramatically increase according to the increased concentration of PAA (polyacrylic acid). Also, soil-water characteristic curves by theoretical models are quite well consistent with the results by experimental studies. Thus, soil-water characteristic curves of sandy soils containing biopolymers such as PAA (polyacrylic acid) can be estimated using fitting parameters for the theoretical model.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.868-869
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• 2015

지하 매설된 가스배관을 정기적으로 검사하기 위해서 가스 공급 및 용역업체에서는 주로 비피과검사 탐상장비인 MFL(Magnetic Flux Leakage) PIG(Pipeline Inspection Gauge)를 사용한다. 기존의 MFL PIG는 배관 내 유체(가스,오일 등)의 전후차단 압력의 흐름을 이용해 별도의 구동장치 없이 피그를 진행시켜 배관의 결함 유무를 평가하는 시스템이다. 하지만 10기압 이하의 낮은 운영압력과 T 분기관과 같이 급격한 곡관부가 존재하는 직경 16인치 이하의 도시가스 배관에는 기존의 시스템을 적용하기 어렵다. 이처럼 기존 MFL PIG의 적용이 불가한 도시가스 배관(직경 16인치 이하)을 활주하기 위해서는 우선 비파괴검사 시스템을 견인할 수 있는 추진 로봇이 필요하고 추진로봇에 적합한 자기누설 비파괴검사 시스템의 개발이 필요하다. 또한 비파괴검사 장비의 센서 시스템은 결함신호를 탐지하여 결함의 발생유무 및 결함의 형상을 판별하는 성능도 중요하다. 본 논문에서는 16인치 도시가스 배관의 검사를 위한 자기누설 비파괴검사 시스템의 기초설계와 대상 시스템의 자기적 특성을 분석한다. 또한 배관 외벽의 결함 발생 유무에 따른 자기누설 신호의 크기 및 분포변화를 3차원 유한요소법을 이용해 해석하여, 결함 검출 신호의 특성을 분석하는데 초점을 둔다.