• 대한의용생체공학회:의공학회지
• /
• 제34권2호
• /
• pp.80-90
• /
• 2013

Recently, functional insoles of wedge-type it is for the young to raise their height inserted between insole and heel cause foot pain and disease. Additionally, these have a problem with stability and excessively load-bearing during gait like high-heel shoes. In this study, we compared the changes in biomechanical characteristics of foot with different insole thickness then we will utilize for the development of the insole with the purpose of relieving the pain and disease. Subjects(male, n = 6) measured COP(center of pressure) and PCP(peak contact pressure) on the treadmill(140cm/s) using F-scan system and different insole thickness(0~50 mm) between sole and plantar surface during gait. Also, we computed changes of stresses at the foot using finite element model with various insole thickness during toe-off phase. COP moved anterior and medial direction and, PCP was increased at medial forefoot surface, $1^{st}$ and $2^{nd}$ metatarsophalangeal, ($9%{\uparrow}$) with thicker insoles and it was show sensitive increment as the insole thickness was increased from 40 mm to 50 mm. Change of the stress at the soft-tissue of plantar surface, $1^{st}$ metatarsal head represents rapid growth($36%{\uparrow}$). Also, lateral moments were increased over the 100% near the $1^{st}$ metatarsal as the insole thickness was increased from 0 mm to 30 mm. And it is show sensitive increment as the insole thickness changed 10 mm to 20 mm. As a result, it was expected that use of excessively thick insoles might cause unwanted foot pain at the forefoot region. Therefore, insole thickness under 30 mm was selected.

• 한국농공학회지
• /
• 제33권2호
• /
• pp.112-119
• /
• 1991

Some experiments were carried out to investigate the effects of freezing and thawing on the strength and strain characteristics of alluvial silty clay under the different temperatures, loading and moisture conditions. The results were as follows; 1. The soil used was proved to be consisted of silty clay with honey-combed structure, and showed higher dilatancy, frost activity and lower stability in natural state. 2. Soil treated with freezing and thawing cycles showed lower compressive strength compared with the non treated, The strength decreased with incement of freezing and thawing cycles. It's shapes of stress-strain curves were flat and did not formulate a peak while the peak strength of higher moisture content soil decreased with the increment of moisture content. It's decrement ratio was most distinctly shown at the first one cycle of freezing and thawing. 3. The cohesion decreased due to freezing and thawing cycles but internal frcition angle was not changed. 4. The liquid limit decreased with increment of freezing and thawing cycles, and became almost constant after three cycles of freezing and thawing. 5. The strength under simple loading at failure mode was appeared to be higher compared with the cyclic loading after freezing and thawing but initial moisture content effect was not observed. 6. Ice lense was not observed within 50% of ice content ratio but observed over 100%. The higher the ice content ratio, the higher the peak strength. As a matter of fact, it seems that an optimum ice content ratio exists for plastic mode and the least compressive strength.

• Journal of Microbiology and Biotechnology
• /
• 제20권4호
• /
• pp.749-756
• /
• 2010

In many conditions, bacterial surface properties are changed as a result of variation in the growth medium and conditions. This study examined the influence of bile salt concentrations (0-0.1%) on colony morphotype, hydrophobicity, $H_2O_2$ concentration, S-layer protein production, and slpA gene expression in Lactobacillus acidophilus ATCC 4356. It was observed that two types of colonies (R and S) were in the control group and the stress condition. When the bile level increased in the medium, the amount of S type was more than the R type. A stepwise increment in the bile concentration resulted in a stepwise decline in the maximum growth rate. The results showed that hydrophobicity was increased in 0.01%-0.02% bile, but it was decreased in 0.1% bile. Treatment by bile (0.01%-0.1%) profoundly decreased $H_2O_2$ formation. S-Layer protein and slpA gene expression were also altered by the stress condition. S-Protein expression was increased in the stress condition. The slpA gene expression increased in 0.01%-0.05% bile and it decreased in 0.1% bile. However, we found that different bile salt concentrations influenced the morphology and some surface properties of L. acidophilus ATCC 4356. These changes were very different in the 0.1% bile. It appears that the bacteria respond abruptly to 0.1% bile.

• 한국가스학회지
• /
• 제15권3호
• /
• pp.58-66
• /
• 2011

본 연구에서는 건설 현장에 매설된 삼중관이 항타 진동에 노출되었을 경우에 발생하는 동적 거동을 분석하였다. 항타 에너지는 7tonf의 램이 1.2m에서 낙하하였을 경우로 선정하였으며 이격 거리는 5∼30m로 변화하여 연구를 진행 하였다. 관의 길이 방향 중심에서의 진동 속도와 응력을 확인 하였고, 감쇠비를 고려하여 삼중관의 거동을 분석하였다. 매설 심도가 동일한 경우의 진동 속도에 대한 감쇠율은 이격 거리가 증가함에 따라 감소하는 추세를 보이며 내관에서 역시 이격 거리가 증가함에 따라 감소하는 추세를 보인다. 상하부에서 최대 응력값을 보이는 내관과 달리 외관은 불규칙한 응력 분포를 나타내는 것을 확인하였다.

• Journal of Ginseng Research
• /
• 제36권3호
• /
• pp.248-255
• /
• 2012

Potential antioxidant effect of processed ginseng (sun ginseng, SG) on oxidative stress generated by tert-butyl hydroperoxide (t-BHP) was investigated in HepG2 cells. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and lactate dehydrogenase (LDH) leakage test demonstrated that SG dose-dependently prevents a loss of cell viability against t-BHP-induced oxidative stress. Also, SG treatment dose-dependently relieved the increment of activities of hepatic enzymes, such as aspartate aminotrasferase and alanine aminotransferase, and lipid peroxidation mediated by t-BHP treatment in HepG2 cells. SG increased the gene expression of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. However, high dose of SG treatment caused decrease in mRNA level of glutathione peroxidase as compared to low dosage of SG-treated cells. The gene expression of glutathione reductase was found to be slightly increased by SG treatment. In addition, SG extract attributed its hepaprotective effect by inducing the mRNA level of bcl-2 and bcl-xL but reducing that of bax. But, the gene expression of bad showed no significant change in SG-treated HepG2 cells. These findings suggest that SG has hepatoprotective effect by showing reduction of LDH release, activities of hepatic enzymes and lipid peroxidation and regulating the gene expression of antioxidant enzymes and apoptosis-related molecules against oxdative stress caused by t-BHP in HepG2 cells.

• 콘크리트학회지
• /
• 제11권1호
• /
• pp.209-219
• /
• 1999

본 연구와 관련한 이전의 연구에서는 기존연구에서 제시한 설계식 및 현행의 ACI 규준식에 대한 문제점을 분석하고 그 결과에 의해 비부착 긴장재의 극한응력을 평가할 수 있는 새로운 설계식을 제시하였다. 따라서 본 연구에서는 설계식에서 제안된 주요변수가 비부착 긴장재의 응력에 미치는 영향을 분석하기 위하여 총 14개의 실험체를 제작하여 실험을 수행하였다. 실험에 사용된 변수는 유효프리스트레스, 콘크리트 강도, 긴장재 양, 일반철근 양, 작용하중 형태, 스팬/춤 비 등이다. 실험결과에서는 유효프리스트레스가 증가하면 증가할수록, 그리고 긴장재 및 일반철근의 양이 증가할수록 긴장재의 응력증가량은 감소함을 알았다. 그리고 콘크리트 강도 및 작용하중의 형태도 긴장재의 응력에 영향을 미치는 것으로 나타났다. 또한 스팬/춤 비가 높은 경우에 현행의 ACI 규준식과는 상이하게 스팬/춤 비가 긴장재의 응력에 미치는 영향이 미미미한 것으로 나타났다.

• Computers and Concrete
• /
• 제13권6호
• /
• pp.709-737
• /
• 2014

Fibre-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics of hardened concrete as a result of fibre addition. To produce SCC, either the constituent materials or the corresponding mix proportions may notably differ from the conventional concrete (CC). These modifications besides enhance the concrete fresh properties affect the hardened properties of the concrete. Therefore, it is vital to investigate whether all the assumed hypotheses about CC are also valid for SCC structures. In the present paper, the experimental results of short-term flexural load tests on eight reinforced SCC and FRSCC specimens slabs are presented. For this purpose, four SCC mixes - two plain SCC, two steel, two polypropylene, and two hybrid FRSCC slab specimens - are considered in the test program. The tests are conducted to study the development of SCC and FRSCC flexural cracking under increasing short-term loads from first cracking through to flexural failure. The achieved experimental results give the SCC and FRSCC slabs bond shear stresses for short-term crack width calculation. Therefore, the adopted bond shear stress for each mix slab is presented in this study. Crack width, crack patterns, deflections at mid-span, steel strains and concrete surface strains at the steel levels were recorded at each load increment in the post-cracking range.

• 지질공학
• /
• 제18권2호
• /
• pp.207-214
• /
• 2008

점토함량에 따른 미고결 이암의 시간 의존적 변형을 비교하기 위해 측방변형이 구속된 상태에서의 일축압밀시험을 수행하였다. 미고결 이암의 변형은 응력의 증가에 따른 즉각적인 변형과 일정한 응력 하의 크리프 변형으로 구분되었다. 응력 증가분이 동일한 경우에 시간 의존적 변형은 거의 일정한 크기로 발생하였으며 응력 증가분이 증가할수록 크리프변형의 크기도 증가하여 선형점성변형의 특성을 보였다. 점토함량이 증가함에 따라 시간 의존적 변형은 증가하는 경향을 보여 점토가 이암의 시간 의존적 변형 발생에 중요한 역할을 하는 것으로 사료된다. 크리프 변형은 시간에 따라 지수함수 형태를 보여 크립 모델 중 하나인 power-law 모델로 잘 예측될 수 있었다.

• 대한기계학회논문집A
• /
• 제20권4호
• /
• pp.1123-1132
• /
• 1996

It has been reported that high temperature structural components represent the phenomenon of material degradation according to a long term service under high temperature and pressure. Especially, fossile power plant components using the fossil fuel and heavy oil are affected by dewpoint corrosion of $H_2SO_4$produced during a combustion. Therefore, the service materials subjected to high temperature and pressure may occur the stress corrosion cracking. The object of this paper is to investigate SCC susceptibility according to the material degradation of the high temperature structural materials in dewpoint corrosive environment-$H_2SO_4$.The obtained results are summarized as follows : 1) In case of secondary superheater tube, the fractograph of dimple is observed at the concentration of $H_2SO_4$-5%. When the concentration of $H_2SO_4$ is above 10%, the fracture mode is shifted from a transgranular fracture to an quasi-intergranular fracture according to the increment of concentration. 2) In the relationship between [$\Delta$DBTT]$_sp$ and SCC susceptibility, it is confirmed that the greater material degradation degree is, the higher SCC susceptibility is. In addition, it can be known that SP test is useful test method to evaluate SCC susceptibility for high temperature structural components. 3) When [$\Delta$DBTT]$_sp$ is above 17$17^{\circ}C$ the SCC fracture behavior is definitely observed with SCC susceptibility of above 0.4.

• 한국지반공학회논문집
• /
• 제26권10호
• /
• pp.15-25
• /
• 2010

본 연구에서는 정규압밀된 점토지반에서 피에조콘관입시험 (PCPT) 결과를 이용하여 원위치 응력상태를 평가할 수 있는 방법을 제안하였다. 이를 위해 다양한 현장시험과 실내시험 결과를 분석하였으며, 현장시험에서 구해진 PCPT 결과값과 실내시험에서 얻어진 결과를 토대로 이론식을 산정하였다. 제안된 방법에서는 기존 방법에 포함되어 있던 불교란 시료 채취과정과 단위중량 결정을 위한 별도의 실험과정이 요구되지 않으며, PCPT 시험결과를 통해 유효응력의 추정이 가능하기 때문에, 조사과정에서의 비용이나 소요시간을 최소화 할 수 있다. 제안된 방법의 적용성 평가를 위하여 국내의 다양한 점성토 지반에서 수행된 피에조콘관입시험 결과를 수집하였으며, 이를 토대로 제안된 방법에 의한 결과와 기존방법의 결과와의 비교분석을 실시하였다. 분석결과, 예측된 결과는 측정된 결과와 유사함을 확인할 수 있었다.