• 한국터널지하공간학회 논문집
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• 제20권2호
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• pp.433-452
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• 2018

쉴드 TBM 공법은 터널 굴착으로 인한 터널 굴진면과 굴착면의 변형을 억제하여 지반의 변형을 최소화할 수 있는 공법이다. 이를 위해 쉴드 TBM의 운전 조건들을 적절히 제어하는 것은 매우 중요하다. 쉴드 TBM 공법의 여러 가지 운전 조건 중 굴진면압과 뒤채움주입압은 지반에 직접 압력을 가하는 과정으로 굴착에 인한 지반변위의 억제 뿐만 아니라, 지반 내 유효응력 및 간극수압의 변화에 영향을 미치는 요인이다. 굴진면압과 뒤채움압의 작용에 대한 지반의 반응은 지반의 강성 및 투수성에 따라 상이하다. 특히, 포화된 연약 점성토의 경우 굴진면압과 뒤채움압에 의한 지반 내 응력 변화의 영향이 장시간동안 잔류하므로 이에 대한 반응은 투수성이 큰 지반과 구별되는 거동을 보인다. 따라서 본 논문에서는 유한 요소법을 이용한 응력-간극수압 연계 매개변수해석을 통해 포화 점성토 지반에서 쉴드 TBM 운전 조건과 지반의 강성과 투수성이 지표침하에 미치는 영향에 대한 연구를 수행하였다. 연구 결과, 점성토 지반의 지표침하는 즉시침하와 압밀침하로 구분할 수 있었으며, 특히 압밀침하 거동은 지반의 투수성과 강성의 영향을 크게 받는 것으로 나타났다. 또한, 굴진면압과 뒤채움압의 증가가 항상 지표침하 감소로 이어지지는 않고, 임의 크기의 압력(한계 압력) 이상으로 증가된 굴진면압과 뒤채움압은 역으로 지표침하를 증가시키는 요인으로 작용할 수 있음이 확인되었다.

• 대한임상검사과학회지
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• 제51권2호
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• pp.235-244
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• 2019

본 연구는 배양된 C6 신경교종(glioma) 세포에서 환경오염 원인 황산알루미늄에 의한 신경 독성과 파리풀(PLVAH)추출물의 AS에 의해 유도된 신경 독성에 대한 보호효과를 확인해 보았다. 이를 위해 세포생존력과 전자공여(ED)능, 지질과산화(LP) 저해능 및 과산소음이온라디칼(superoxide anion-radical, SAR) 소거능과 같은 항산화효과를 조사하였다. AS는 용량의존적으로 현저히 세포생존율을 감소시켰고 AS의 $XTT_{50}$ 값은 $120.0{\mu}M$로 측정되었다. AS의 신경 독성은 Borenfreund와 Puerner의 독성 기준에 의해 중간 독성으로 판정되었다. 또한, 항산화제인 catalase (CAT)는 AS의 신경독성에 의해 손상된 세포의 생존력을 현저히 증가시켰다. AS 유발 신경 독성에 대한 PLVAH 추출물의 보호 효과에서, PLVAH 추출물은 ED의 능력, LP의 억제 능력 및 SAR 소거능을 유의하게 증가시켰다. 이러한 결과로부터 산화 스트레스가 AS의 세포독성에 관여하고 있으며, PLVAH 추출물의 항산화 작용에 의해 AS에 의해 유도된 신경 독성을 효과적으로 보호한다는 것을 알 수 있었다. PLVAH 추출물과 같은 천연 성분은 산화스트레스를 만드는 AS와 같은 중금속 화합물로 인한 독성을 치료할 수 있는 잠재적 치료제로 가치가 있다고 사료된다.

• 한국생산제조학회지
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• 제20권5호
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• pp.659-665
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• 2011

Recently, the plastic resin such as PC, ABS are widely used in IT market. Especially, in most cases the keypads mounted on the mobile phone are the dual-injection-plated type. Environmental regulation is based on the quality of injection-molded products and the minimum process steps are required to avoid the plating defects. Various parameters to produce the injection-molded plastic products make it difficult to obtain the desired stability. However, the past experience and the use of CAE analysis make it possible to predict the problems occurred in injection molding process. Especially, the problems of the weld lines such as runner balancing, bending, deformation and forming defects can be solved systematically and minimized by CAE analysis. Through this study, the non-uniform volumetric shrinkage and the difference in temperature distribution induce the deformation and the high value of stress causes the problems such as crack.

• 한국의류산업학회지
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• 제6권3호
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• pp.384-392
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• 2004

The purpose of this study is in development of effective filter-type polymer adsorbent for removal of pollutants from wastewater by UV irradiation graft polymerization. Photografting of acrylic acid (AA) on polypropylene (PP) nonwoven fabric using benzophenone (BP) as a photosensitizer was investigated. Inhibition of homopolymerization was achieved by adding various concentrations of $FeSO_4{\cdot}7H_2O$, $CuSO_4{\cdot}5H_2O$ and Mohr's salt. As AA concentration was increased, the degree of grafting was increased as to a specific value and then decreased, and the effect of BP concentration showed the same tendency. It was also found that the degree of grafting increased with reaction time and reaction temperature. Addition of the polyfunctional monomers and $H_2SO_4$ to the grafting system accelerated the photografting. The melting temperature, molecular weight and breaking stress and breaking strain were decreased with the increase in the degree of grafting.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.114-121
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• 2004

The sensor and measuring instrument that are used for the infrastructure is discussed the reliability problem from the various environment factors. In the domestic infrastructure, the low reliability products are produced, because of lack of the pertinent test methods and equipments. To improve the practical use and accuracy of the sensor, it raises the measurement reliability about the sensor and measurement instrument. In this study, the variance of the displacement value according to temperature was investigated using the LVDT for the infrastructure. The experimental results showed that a sensor is affected by environment factor such as temperature.

• 한국지반환경공학회 논문집
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• 제7권6호
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• pp.67-73
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• 2006

본 연구에서는 하수관거의 기초나 뒷채움재로 많이 사용되고 있는 기존의 모래를 대체할 재료로써 석분의 적용가능성을 평가하기 위하여 석분재료에 대한 기본적인 물리적, 역학적인 특성실험을 실시하였다. 석분의 입도분포는 모래보다 더 좋은 상태를 나타내며, 다짐실험 결과도 모래보다 강도특성이 좋은 것으로 나타났다. 이러한 실험결과로부터 하수관거의 기초 및 뒷채움재로써 석분은 현장적용성이 우수한 것으로 평가되며, 이를 뒷받침하기 위하여 직접전단시험, 삼축압축시험을 실시하여 강도특성을 분석한 결과 모래의 경우와 유사한 경향을 나타내었다. 석분의 경우 일축압축강도 특성은 시간이 지남에 따라 점차 증가하는 경향을 보이지만 6~7일 경과 후에는 거의 일정한 값을 보이는 것을 알 수 있었다. 이와 같은 실험결과로부터 석분도 하수관거의 기초 및 뒷채움재로 충분히 활용할 수 있는 재료로 평가되었다.

• Geomechanics and Engineering
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• 제30권4호
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• pp.373-382
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• 2022

Unsaturated soil at high suctions is widespread. Many civil engineering projects are related to the hydro-mechanical behavior of unsaturated soils at high suctions, particularly in arid and semiarid areas. To investigate water retention behaviors of nine clayey soils (one is classified as fat clay and the others are classified as lean clay according to the unified soil classification system), the high suction (3.29-286.7 MPa) was imposed on the specimens at zero net stress by the vapor equilibrium technique. In this paper, the effect of void ratio on the water retention behavior at high suction was discussed in detail. Validation data showed that soil types, i.e., different mineralogical compositions, are critical in the soil water retention behavior at a high suction range. Second, the hysteresis behavior at a high suction range is mainly related to the clay content and the specific surface area. And the mechanism of water retention and hysteresis behavior at high suctions was discussed. Moreover, the maximum suction is not a unique value, and it is crucial to determine the maximum suction value accurately, especially for the shear strength prediction at high suctions. If the soil consists of hydrophilic minerals such as montmorillonite and illite, the maximum suction will be lower than 10⁶ kPa. Finally, using the area of hysteresis to quantify the degree of hysteresis at a high suction range is proposed. There was a good correlation between the area of hydraulic hysteresis and the specific surface area.

• Asian-Australasian Journal of Animal Sciences
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• 제16권7호
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• pp.988-995
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• 2003

Physiological parameters were measured on six primiparous, non-pregnant Holstein cows prior to peak lactation over a 3-month summer season in southwestern Taiwan. The objectives were to characterize heat stress-induced change in functionality of mammary gland under natural climates of tropical summer and to establish physiological indices applicable to this environment in referring to this change. Environmental and physiological readings, milk and blood samples were taken at 15:00 h biweekly for totally five time points during the study. Climate readings showed that the afternoon humidex value reached the highest (53.5) around mid summer. Rectal temperature of cows taken simultaneously varied between $38.26^{\circ}C$ and $40.02^{\circ}C$ in parallel to humidex. Milk production declined drastically from 29.2 to 22.2 kg/d the first month entering summer but leveled up at end of the summer season suggesting effects exerted by heat stress rather than stages of lactation. Lactose content decreased linearly (p<0.05) with times in summer, from 4.69 to 4.38%. On the other hand, activity of N-acetylglucosaminidase (NAGase) in milk increased linearly to over two folds (p<0.05) during the same intervals. Elevations of fractional constituent of BSA in whey protein and serum cortisol level were also noticed in the course. Measurement of arteriovenous concentration (A-V) difference across the mammary gland demonstrated net uptake of glucose and net release of urea throughout the study period. The amount of urea released from mammary gland increased (p<0.05) progressively from 1.54 to 7.76 mg/dl during summer. It is concluded that gradual regression of mammary gland occurred along the humid tropical summer season. This regression is likely initiated through elevation of body temperature, which is irreversible above certain point. The increased release of urea from mammary gland during heat stress suggests its potential role as an early indicator of suboptimal mammary function.

• Journal of Forest and Environmental Science
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• 제29권4호
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• pp.282-291
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• 2013

Rapid loss in viability of neem (Azadirachta indica A. Juss.) seed is a major problem. Present effort was undertaken for developing a set pattern for assessing of viability and vigour in seed of various mother tree age of neem (Age I-06 years, Age II-15 years, Age III-25 years and Age IV->30 years old). Various viability test viz. triphenyle tetrazolium chloride test, electrical conductivity, excised embryo test, and germination test have been performed on seeds obtained from mother tree age classes. Inconsistency was observed with the TTC and EC test in germination of seed in laboratory as well as nursery. While various vigour tests viz. cold test, chemical stress test (methanol stress test), and accelerated ageing test alongwith ageing index, germination test (G%, MGT and GV) and various seedling growth parameters like seedling length (cm), number of leaves, collar diameter (cm), total biomass (g) alongwith mathematical indices i.e. vigour index, sturdiness quotient, volume index, quality index, root shoot ratio in nursery as well have been taken for study and showed better consistency. On the basis present study results of various viability and vigour test indicated that mother tree age class II performed better in comparison to others and it can be recommended for seed collection. Further it is also recommended that viability of neem seed may be assessed using various laboratory tests like excise embryo test and germination test (G%, MGT and GV) and vigour test may be taken preferably by cold germination test, chemical (methanol) stress test, accelerated ageing test in laboratory and germination alongwith various seedling growth parameters seedling length (cm), number of leaves, collar diameter (cm), total biomass (g) alongwith mathematical indices like Vigour Index, Sturdiness quotient, Volume Index, Quality index, root shoot ratio in nursery as discussed in this study.

• 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.