• 한국수자원학회논문집
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• 제34권5호
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• pp.449-458
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• 2001

단일절리에서 2상유체의 거동을 모의하기 위해 개발된 수치모형의 검증을 위해서 상대투과계수 특성식을 수치모형에 적용하여 가스와 물의 동시거동을 해석한 후, 수치모의 결과를 모형실험결과와 비교하였다. 절리면의 거칠기와 간극의 크기에 댸한 민감도 분석을 실시한 결과, 가스의 이동속도는 절리면의 거칠기와 반비례하였으며, 절리간극의 크기와는 상대투과계수 특성식의 영향으로 단상유체의 흐름에서와 같은 간극크기의 제곱에 비례하는 향상은 보이지 않았다. 수치모형의 현장적용성을 검토하기 위해서 지하 LPG 저장기지에 모형을 적용한 결과, 저장공동에 인접한 단일절리에서의 운영압의 동적변동에 따른 지하수와 프로판가스의 동시거동을 모사할 수 있었다. 절리면이 매끈하고 간극이 작아질수록 운영압과 지하수압의 조절로는 누출된 가스의 이동제어가 불가능해지는 것으로 나타났다.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.448-454
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• 2007

This study was conducted to develop a 100 kPa soil tensiometer mainly consisted of a porous ceramic cup, water-holding tube, and a digital vacuum gauge, through theoretical design analysis and experimental performance evaluation. Major findings were as follows. 1. Theoretical analysis showed that air entry value of a porous media decreased as the maximum effective size of the pore increased, and the maximum diameter of the pores was $2.9\;{\mu}m$ for measuring up a 100 kPa of soil-water tension. 2. Property analysis of tensiometer porous cups supplied in Korean domestic market indicated that main components were $SiO_2$ and $Al_2O_3$ with a porosity range of $33.8{\sim}49.3%$. 3. The porous cup selected through sample fabrication and air-permeability tests showed weight ratios of 87% and 11% for $Al_2O_3$ and $SiO_2$. The analysis of SEM (scanning electron microscope) images showed that the sample was sintered at temperatures of about $1150^{\circ}C$, which consisted of pores with sizes of up to 25% of those for commercial porous cups. 4. The prototype soil tensiometer was fabricated using the developed porous cup and a digital vacuum gauge that could measure water tension with a pressure of 85 kPa in air tests. 5. In-soil tests of the prototype conducted during a period of 25-day drying showed that soil-water tension values measured with the prototype and commercial units were not significantly different, and soil-water characteristic curves could be established for different soils, confirming accuracy and stability of the prototype.

• 한국의류산업학회지
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• 제10권6호
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• pp.1006-1013
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• 2008

This study is basic material for development of a smart girdle. Through the intentionally sampling of 313 consumers from teenagers to the forties who have experienced wearing girdles, lifestyles on consumer's age, attitude to health, favor of warm functional girdle, and possibility to acceptance were surveyed and analyzed by questionnaire. The result of the study are summarized as followed. 1. Analysis about lifestyle with warmth and attitude to health showed that subjects in their thirties and forties have higher than teenagers and the twenties in frequency of distribution. This means people are tend to have more attention to warmth and health as they grow older. 2. In result about analysis of characteristic of wearing girdle, subjects were prefer girdle made of cotton which have superior permeability and hygroscopic property. The reason that wearing girdle is to complement of weak points of body somatotype in the thirties and forties and feel the stability during menstrual period in the twenties and teenagers. The time zone of putting on girdle is mainly winter while one is out wearing one-piece or skirt. 3. When surveyed about the preference to functional warmth girdle and possibility to acceptance, the results were that the subjects in their thirties were first, forty something was second, followed by subjects in their twenties, teenagers. It was shown that over 60% subjects were highly distributed. With regard to necessity of functional warmth girdle, every age groups were shown over 3.6 at average. This result was inferred that subjects had positive possibility to acceptance about functional warmth smart girdle.

• 상하수도학회지
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• 제31권4호
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• pp.303-310
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• 2017

Pressure retarded osmosis(PRO) has attracted much attention as potential technology to reduce the overall energy consumption for reverse osmosis(RO) desalination. The RO/PRO hybrid process is considered as the most logical next step for future desalination. The PRO process aims to harness the osmotic energy difference of two aqueous solutions separated by a semipermeable membrane. By using the concentrated water(RO brine) discharged from existing RO plants, the PRO process can effectively exploit a greater salinity gradient to reduce the energy cost of processing concentrated water. However, in order to use RO brine as the draw solution, PRO membrane must have high water flux and enough mechanical strength to withstand the high operational pressure. This study investigates the development of a thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on the overall power density was studied using the characteristic factors of PRO membranes. Finally, the performance test of an 8-inch spiral wound module was carried out under various operating conditions(i.e. hydraulic pressure, flow rate, temperature). As the flow rate and temperature increased under the same hydraulic pressure, the PRO performance increased due to the growth of water permeability coefficient and osmotic pressure. For a high performance PRO system, in order to optimize the operating conditions, it is highly recommended that the flow pressure be minimized while the flow rate is maintained at a high level.

• 한국농공학회논문집
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• 제62권4호
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• pp.53-61
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• 2020

The laboratory model test was conducted by dividing domestic reclaimed tideland into Sandy Loam (SL) and Silt Clay Loam (SiCL) to estimate soil moisture change and water supply according to soil characteristic when establishing irrigation plan for reclaimed tideland upland crop. In addition, the applicability of each scenario was verified using Van Genuchten model, which is the most widely used mathematical model for analyzing soil moisture characteristics of reclaimed tideland uplands crops. The required water supply according to the target soil moisture tension by reclaimed tideland is as follow. In the case of SL, soil depths of 0~10 cm, 10~20 cm were analyzed as 19 mm, 35 mm to reach the field capacity, and SiCL, 33 mm, 63 mm. The required water supply of SiCL was higher than that of SL. The study compared the simulation results from the scenarios of Van Genuchen model and the measured results from the laboratory model test based on according to the reclaimed tidelands. In the case of parameter, θ_s, θ_r, α, η were analyzed 0.55, 0.18, 0.064, 1.74 in SL and 0.46, 0.22, 0.105, 1.92 in SiCL. In terms of soil characteristics, SL with better water permeability was found to have higher applicability than SiCL. By Soil depth, applicability was found in 0~10 cm directly affected by water supply.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1630-1637
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• 2008

Jeju-do is a island formed by the volcanic activity and has more than 360 volcanic cones distributed widely along the long axis of the elliptically shaped island. The volcanic cones consist mainly of scoria, so called "Song-I" in the local dialect. In this study the chemical and soil mechanical properties of scoria being very different from those of the inland were investigated with the various tests. In the sieve-passing test the particle size of scoria had more than 10 of uniformity coefficient and gradation coefficient of 1 ~ 3, showing relatively homogenous distribution. Based on the uniformity classification, scoria was assorted into GW. In the large scale direct shear tested for measuring the mechanical strength of scoria the internal friction angle of red scoria was $37^{\circ}$ and that of black scoria was $36^{\circ}$. This indicated that there was no difference in the mechanical strength between two types of scoria. On the other hand, red and black scoria had $1.24{\times}10^{-3}$ to $3.55{\times}10^{-2}$ cm/sec of k values for the static water level permeability, thus being classified into a coarse or fine sand as compared with that representing the saturated soil. They also had 1.411 to $1.477\;g/cm^3$ of notably low $r_{dmax}$ values for the compaction test as compared with common soil, which was considered to be due to their low specific gravity and high porosity. In conclusion, the soil mechanic properties of scoria obtained from this study are thought to be very helpful for reducing lots of trial and error happening in the civil engineering construction.

• 멤브레인
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• 제22권1호
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• pp.54-61
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• 2012

VOCs의 분리 및 회수를 위해 PEI 고분자를 이용하여 상분리법으로 중공사 지지체 분리막을 제조하였고 PDMS 고분자를 코팅하여 PEI-PDMS 중공사 복합막을 제조하였다. 제조된 기체 분리막의 특성을 알아보기 위하여 산소와 질소를 이용하여 순수 기체 투과도를 측정하였으며, xylene, ethyl benzene, toluene, cyclohexane을 이용하여 stage cut과 feed 농도 변화에 따른 투과성능을 측정하였다. 또한 VOCs에 대한 내용매성을 알아보기 위하여 DMA을 이용하여 용매 함침 시간에 따른 stress-strain 특성을 알아보았다. 산소와 질소의 순수 투과도는 각각 63 GPU와 30 GPU를 나타내었고, stage cut이 증가할수록 permeate VOCs 농도는 감소하는 경향을 나타내었다. Recovery efficiency의 경우 permeate 농도와는 반대로 state cut이 증가할수록 증가하는 경향을 나타내었다. DMA 인장 테스트 결과 stress는 11.93 MPa, strain은 13.52%로 측정되었다.

• 한국토양비료학회지
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• 제35권4호
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• pp.197-206
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• 2002

토양수분 이동에 대한 토양 특성과 경운의 영향을 구명하기 위하여 3년 동안 일리노이 중부지방의 몇 개 토양통이 다른 옥수수 포장에서 토양 수분함량을 조사하였다. 경작 기간중의 무경운과 경운된 포장에서 30 cm 간격으로 깊이 150 cm 까지 Neutron Scattering 기술에 의하여 수분함량을 측정하였다. 토양 경작층에서의 수분함량은 경운이나 강우에 의해 수분함량의 영향을 받은 반면 심토에서는 토성에 의해 영향을 받았다. 토양수분은 점토 함량이 상대적으로 낮은 Saybrook통이나 Catlin통에서 점토 함량이 높아 수분 보유능이 높은 Drummer통, Flanagan통, 및 Ipava통보다 빠르게 이동하였다. 이들 Drummer통, Flanagan통, Ipava통의 높은 유기물 함량은 수분 보유능을 증가시키는 또 다른 이유가 될 수 있다. 또한 옥수수 경작층에서의 수분함량은 경운 포장에서 무경운 포장보다 높았다.

• Journal of Yeungnam Medical Science
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• 제36권3호
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• pp.231-240
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• 2019

Background: We sought to determine the value of combining diffusion-weighted (DW) and perfusion-weighted (PW) sequences with a conventional magnetic resonance (MR) sequence to assess solid components of borderline ovarian tumors (BOTs) and stage I carcinomas. Methods: Conventional, DW, and PW sequences in the tumor imaging studies of 70 patients (BOTs, n=38; stage I carcinomas, n=32) who underwent surgery with pathologic correlation were assessed. Two independent radiologists calculated the parameters apparent diffusion coefficient (ADC), $K^{trans}$ (vessel permeability), and $V_e$ (cell density) for the solid components. The distribution on conventional MR sequence and mean, standard deviation, and 95% confidence interval of each DW and PW parameter were calculated. The inter-observer agreement among the two radiologists was assessed. Area under the receiver operating characteristic curve (AUC) and multivariate logistic regression were performed to compare the effectiveness of DW and PW sequences for average values and to characterize the diagnostic performance of combined DW and PW sequences. Results: There were excellent agreements for DW and PW parameters between radiologists. The distributions of ADC, $K^{trans}$, and $V_e$ values were significantly different between BOTs and stage I carcinomas, yielding AUCs of 0.58 and 0.68, 0.78 and 0.82, and 0.70 and 0.72, respectively, with ADC yielding the lowest diagnostic performance. The AUCs of the DW, PW, and combined PW and DW sequences were $0.71{\pm}0.05$, $0.80{\pm}0.05$, and $0.85{\pm}0.05$, respectively. Conclusion: Combining PW and DW sequences to a conventional sequence potentially improves the diagnostic accuracy in the differentiation of BOTs and stage I carcinomas.

• 한국지반공학회논문집
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• 제24권10호
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• pp.45-55
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• 2008

현장실험의 경우 규모에 따라 시간이나 비용 등의 측면에서 많은 제약과 어려움이 따르지만, 실내모형실험은 현장 실험에 비해 매개변수에 따라 다양한 실험을 실시할 수 있다. 본 연구에서는 축소된 모형을 사용하여 경제적으로 현장 원형구조물의 지반공학적 거동을 재현하기 위하여 인위적으로 원심력을 가하여 현장의 응력상태를 재현시킬 수 있는 원심모형실험기법을 실시하여 준설지반의 압밀거동을 예측하고 분석하는데 이용하였다. 자중압밀단계의 간극비-유효응력-투수계수의 관계를 유추하기 위하여 저응력 침투압밀 시험을 실시한 결과를 Curve fitting 결과 누승함수 형태의 구성관계를 얻을 수 있었다. 구성관계식을 이용하여 대표단면을 프로그램으로 수치해석 한 결과 최종침하량은 원심모형 실험에 의한 자중압밀 실험결과와 유사한 경향의 결과를 보이고 있었으나 원심모형실험 결과보다 다소 작게 산정되었다.