• 열처리공학회지
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• 제30권6호
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• pp.258-263
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• 2017

The effect of cooling rate on the damping capacity of pure Mg was studied. Two Mg samples with different cooling rates were prepared by heat treatment at 873 K for 24 h, followed by water quenching and by furnace cooling to room temperature, respectively. The average grain sizes of the Mg samples were almost identical regardless of the cooling rate, but more twins were observed in the sample with faster cooling rate. The calculated vacancy fraction was higher in the fast cooling sample than the slow cooling one. It is noted that the fast cooling sample exhibited lower damping capacity both in the strain-amplitude independent and strain-amplitude dependent regions. Higher values of vacancy concentration and number density of twins in the fast cooling sample are considered to be responsible for the deteriorated damping capacity in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• 한국지반공학회지:지반
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• 제12권2호
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• pp.85-94
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• 1996

말뚝직경이 개단말뚝의 폐색정도와 지지력에 미치는 영향을 규명하기 위하여 응력상태와 상대밀도의 조절이 가능한 토조와 직경이 다른 세개의 모형말뚝을 이용하여 모형말뚝실험을 수행하였다. 모형말뚝은 말뚝의 지지력 성분을 분리측정하기 위하여 직경이 다른 두개의 파이프로 만들어졌다. 실험결과에 의하면 말뚝이 완전폐색 상태로 되는 관입깊이는 말뚝직경과 지반의 상대밀도가 증가할수록 커지는 것을 알 수 있었으며, 관입비와 관내토 증분비가 동일하더라도 단위 관내토 지지력은 말뚝의 직경이 커질수록 감소하는 경향을 보였다. 그러나 기존의 지지력 산정식은 말뚝의 관입비나 폐색정도가 동일한 상태에 대하여 관내토 지지력은 말뚝의 직영에 관계없이 일정하거나 직경이 증가할수록 커지는 결과를 주고 있다. 이는 본 연구의 실험결과와 상반되는 것으로서 관내토 지지력의 산정시 말뚝의 폐색정도 뿐만 아니라 크기효과도 고려하는 것이 필요한 것으로 밝혀졌다.

• 한국엔터테인먼트산업학회논문지
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• 제14권8호
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• pp.197-202
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• 2020

본 연구에서는 20대 여성의 카페인 중독이 심장호흡기계 능력에 미치는 영향을 조사하였다. 본 연구의 대상자는 G 광역시 소재의 H 대학교 여학생 35명을 카페인 중독자(n=17)과 카페인 비중독자(n=18)가 참여하였다. 심장능력을 평가하기 위해 사이클 에르고미터를 사용하여 최대산소섭취량, 최대에너지소비량, METs를 측정하였으며, 호흡기계 능력은 파워브리드 K5를 사용하여 최대들숨압, 평균들숨압, 최대들숨유속, 평균들숨유속, 최대들숨량, 평균들숨량을 측정하였다. 본 연구의 결과는 심장능력에서 카페인 중독군은 카페인 비중독군에 비해 최대산소섭취량과 METs에서 통계학적으로 유의한 감소를 보였으며, 호흡기계 능력에서는 카페인 중독군이 비중독군에 비해 최대들숨압, 평균들숨압, 최대들숨유속, 평균들숨유속에서 통계학적으로 유의한 감소를 보였다. 본 연구의 결과를 종합하면, 카페인 중독은 20대 여성의 심장호흡기계 능력의 감소를 보였다. 따라서 본 연구의 결과는 20대 여성의 카페인 중독예방을 위한 기초자료로 활용할 수 있을 것이다.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.461-472
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• 2017

The dynamic tests of recycled aggregate concrete (RAC) are carried out, the rate-dependent mechanical models of RAC are proposed. The dynamic mechanical behaviors of RAC frame structure are investigated by adopting the numerical simulation method of the finite element. It is indicated that the lateral stiffness and the hysteresis loops of RAC frame structure obtained from the numerical simulation agree well with the test results, more so for the numerical simulation which is considered the strain rate effect than for the numerical simulation with strain rate excluded. The natural vibration frequency and the lateral stiffness increase with the increase of the strain rate. The dynamic model of the lateral stiffness is proposed, which is reasonably applied to describe the effect of the strain rate on the lateral stiffness of RAC frame structure. The effect of the strain rate on the structural deformation and capacity of RAC is analyzed. The analyses show that the inter-story drift decreases with the increase of the strain rate. However, with the increasing strain rate, the structural capacity increases. The dynamic models of the base shear coefficient and the overturning moment of RAC frame structure are developed. The dynamic models are important and can be used to evaluate the strength deterioration of RAC structure under dynamic loading.

• 생명과학회지
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• 제10권6호
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• pp.598-604
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• 2000

This study was conducted to investigate the effect of simulated acid rain (SAR) on germination, growth, acid buffering capacity and nutrient leaching in Impatiens balsamina L. and Tagetes patula L.. In both species, germination was not inhibited at pH 4.0, but the germination rate decreased at the lower pH of 3.0, showing higher rate in Inpatiens balsamina L. than Tagetes patula L.. As the pH decreases, the growth of radicle was markedly decreased than that of hypocotyl in both species. The plant height, root length, leaf area, total dry weight, relative growth rate and net assimilation rate were inhibited by SAR. The acid buffering capacity in the leaves were increased at pH 4.0, on the other hand, it was shown a tendency to decrease at pH 2.0 in both species. As the pH levels decreased from 5.6 to 2.0, the nutrient leaching from leaves was significantly increased in both species. Based on the results, there are a great difference in the responses to SAR between the two species. In general, Tagetes patula L. represented a higher tolerance to SAR than Impatiens balsamina L.. These results suggested that interspecific variation in the acid buffering capacity and nutrient leaching from leaves may be responsible for the interspecific susceptibility to SAR.

• Geomechanics and Engineering
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• 제8권2호
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• pp.221-235
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• 2015

A series of laboratory model tests were conducted to investigate the effects of buried pipes location on the bearing capacity of strip footing in cohesionless soil. The variables examined in the testing program include relative density of the sand, loading rate of tests, burial depths of pipe and horizontal distance of pipe to footing. The test results showed a significant increase in bearing capacities when embedment ratio of pipe and horizontal distance of pipe to footing were increased. Based on the test results, it can be concluded that the location of pipes and relative density of sand are main parameters that affect the bearing capacity of strip footing. However, loading rate has not considerable effect on bearing capacity.

• 설비공학논문집
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• 제15권12호
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• pp.1043-1048
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• 2003

An experimental investigation was executed to determine the capacity degradation due to non-uniform refrigerant distribution in a multi-path evaporator. In addition, the possibility of recovering the capacity reduction by controlling the refrigerant distribution among refrigerant paths was assessed. The finned-tube evaporator, which had a three-path and three-depth-row, was tested by controlling inlet quality, exit pressure, and exit superheat for each refrigerant path. The capacity reduction due to superheat unbalance between each path was as much as 30%, even when the overall evaporator superheat was kept at a target value of 5.6$^{\circ}C$. It may indicate that the internal heat transfer within the evaporator assembly caused the partial capacity drop. For the evaporator having air mal-distributions, the maximum capacity reduction was found to be 8.7%. A 4.5% capacity recovery was obtained by controlling refrigerant distribution to obtain the target superheat at the outlet of each path.

• 한국전기전자재료학회논문지
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• 제21권3호
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• pp.249-254
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• 2008

Ag doping effect on $Li[Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ cathode material was studied. Specially, we focused on rate performance of Ag doped samples. The $Li[Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ powder was prepared by simple combustion method and the Ag was doped using $AgNO_3$ during gelation process. Based on X-ray diffraction analysis, there was no structural change by Ag doping, but the 'metallic' form of Ag was included in the doped powder. Both bare and Ag 1 wt.% doped sample showed similar discharge capacity of 242 mAh/g at 0.2C rate. However, as the increase of charge-discharge rate to 3C, Ag 1 wt.% doped sample showed higher discharge capacity (172 mAh/g) and better cyclic performance than those of bare sample. The discharge capacity of Ag 5 wt.% doped sample was relatively low at all rate condition. However it displayed better rate performance than other samples.

• 상하수도학회지
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• 제26권2호
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• pp.191-199
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• 2012

Rainwater harvesting systems (RWHS), one of measures for on site rainwater management, have been promoted by laws, regulations and guidelines and have been increased. However, more evaluation of economic feasibility on RWHS is still needed due to seasonal imbalance of rainfall and little experiences and analysis on design and operation of RWHS. In this study, we investigated tank capacity of RWHS to secure economic validity considering catchment area and water demand, which is affected by building scale. Moreover, sensitivity analysis was performed to examine the effect of design factors, cost items and increase rate of water service charge on economic feasibility. The BCR (benefit cost ratio) is proportional to the increase in tank capacity. It is increased steeply in small tank capacity due to the effect of cost and, since then, gently in middle and large tank capacity. In case of 0.05 in the rate of tank volume to catchment area and 0.005 in water demand to catchment area, BCR was over one from the tank capacity of 160 $m^{3}$ taking into account of private benefits and from the tank capacity of 100 $m^{3}$ taking into account of private and public benefits. Sensitivity analysis shows that increase of water demand can improve BCR values with little cost so that it is needed to extend application of rainwater use and select a proper range of design factor. Decrease of construction and maintenance cost reduced the tank volume to secure economic validity. Finally, increase rate of water service charge had considerable impact on economic feasibility.

• Steel and Composite Structures
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• 제1권2호
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• pp.201-212
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• 2001

In order to investigate the effect of the loading rate on the mechanical behavior of SRC shearwalls, we conducted the lateral loading tests on the 1/3 scale model shearwalls whose edge columns were reinforced by H-shaped steel. The specimens were subjected to the reversed cyclic lateral load under a variable axial load. The two types of loading rate, 0.01 cm/sec for the static loading and 1 cm/sec for the dynamic loading were adopted. The failure mode in all specimens was the sliding shear of the in-filled wall panel. The edge columns did not fail in shear. The initial lateral stiffness and lateral load carrying capacity of the shearwalls subjected to the dynamic loading were about 10% larger than those subjected to the static loading. The effects of the arrangement of the H-shaped steel on the lateral load carrying capacity and the lateral load-displacement hysteresis response were not significant.