• 한국농공학회지
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• 제15권1호
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• pp.2904-2912
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• 1973

The density of soil is one of the most important of its engineering properties, and many soil-engineering operations directed toward improving the density characteristics of matecal. This report is a study on relationship between density, permiabilty and other physical properties of compacted soil in various desity grades. The results of the study can be summariged as follow: 1. The optimum moisture content of soil increses with increasing of fine particles and a relationship between both parameter is $w_0=0.1765.n$ Where, n is passing percentage from #200 sieve. 2. The porosity of soil increases with increasing of optimum water content as $e=aw_0+b$ without having relation to compaction ratio. 3. The increment of permeability of soil is high when the compaction ratio is increased and the phenomenon is conspicuous in case of course soil and non-plastic soil. 4. The permeability of soil decreases with increasing of optrimum water content and the phenomenon is conspicuous when compaction ratio decreases. And the permeability is almost constant when optimum water content is more than 25 percent, even though compaction ratio changes. 5. The permeablity of soil increanses when the amount of fine particles is very few, the permeability is almost constant as being impervious condition without having relation to compaction ratio when there in more than 90 percent of fine particles(less than #200 sieve).

• Wind and Structures
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• 제16권6호
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• pp.603-616
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• 2013

This study is aimed at formulating an empirical equation for the across-wind fluctuating moment and spectral density coefficient, which are needed to estimate the across-wind dynamic responses of tall buildings, as a function of the side ratios of buildings. In order to estimate an empirical formula, wind tunnel tests were conducted on aero-elastic models of the rectangular prisms with various aspect and side ratios in turbulent boundary layer flows. In this paper, criteria for the across-wind fluctuating moment and spectral density are briefly discussed and the results are analyzed mainly as a function of the side ratios of the buildings. Finally, empirical formulas for the across-wind fluctuating moment coefficient and spectral density coefficient according to variation of the aspect ratio are proposed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.45-46
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• 2023

CLC is used as a filling material for many buildings, and according to energy saving design standards, CLC also requires insulation performance. However, it shows lower insulation performance compared to organic insulation, so additional research is needed. Therefore, in this study, the insulation properties of CLC were analyzed by incorporating EPS beads with high insulation performance into CLC. In this experiment, EPS beads and blast furnace slag were replaced, and W/B was fixed at 33%. The EPS Bead mixing ratio was divided into 5 levels: 0, 0.5, 1.0, 1.5, 2.0 (%), and the experimental items were measured for apparent density and thermal conductivity. As a result of the experiment, the apparent density and thermal conductivity tended to decrease as the mixing ratio of EPS beads increased. It is judged that the density decreased due to the low density and the micropores inside, and the thermal conductivity also decreased.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2001년도 추계학술대회 논문집
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• pp.169-172
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• 2001

There are many people who suffer from simulation sickness when immersing in virtual reality. In this study, we analyzed two photoplethysmogram(PPG) parameters - a second derivative parameter and power spectral density ratios - in order to relate PPG parameters with simulation sickness. 36 young, healthy subjects were participated in the experiment, and each subject was equipped with a PPG electrode during his or her immersion. Simulation sickness section was defined as a 7 - second section which starts from the point where a subject reported simulation sickness, and normal section as a same-length section where no physical stimuli was presented to him or her. We compared the PPG parameters of the simulation sickness sections with the normal sections, - d/a ratio is believed to have lower value during vasodilation and higher value during vasoconstriction, however, we could not find much difference in the parameter between normal and simulation sickness sections. We also compared 1 to 10Hz power spectral density ratios in normal sections with in simulation sickness section, and found that 6 density ratios among them have different value. Therefore, the density ratios might be utilized as parameters to detect simulation sickness of subjects.

• Journal of Preventive Medicine and Public Health
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• 제30권4호
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• pp.729-740
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• 1997

고혈압과 영양소 섭취와의 관계를 분석하기 위하여 춘천시 남면과 사북면의 10개리에 거주하는 30세 이상 성인을 대상으로 1995년 7월$\sim$8월, 1996년 6월에 혈압측정 및 24시간 회상법을 이용한 식이조사를 시행하여 남자 250명, 여자 297명을 대상으로 분석하였다. 혈압과 영양소 섭취와의 관련성을 분석한 결과를 요약하면 아래와 같다. 1. 평균 수축기 혈압과 영양소 섭취와의 상관관계 분석에서 유의한 상관관계를 보인 영양소는 남성에서 단백질 에너지(%)였다$(\gamma=0.16)$. 여성에서는 유의한 상관 관계를 보여주지 않았다. 2. 평균 이완기 혈압과의 상관관계 분석시 남성에서 단백질 밀도와 단백질 에너지(%)가 강한 양의 상관관계를(p<0.01)보여주었으며, 칼슘 밀도(calcium density)와 에너지 보정 단백질도 유의한 양의 상관관계를 보여주었다. 여성에서는 유의한 상관관계를 보인 영양소는 없었다. 3. 탄수화물과 나트륨을 제외한 영양소 섭취량은 전체적으로 고혈압군에서 높았으나 유의한 차이는 보이지 않았다. 4. 다중선형회귀분석(multiple linear regression analysis)에서 남성의 경우 영양소 밀도를 이용한 모델에서는 평균 이완기 혈압만이 단백질 밀도와 유의한 양의 연관성을 보여주었다. 에너지 보정 영양소를 이용한 모델에서는 평균 이완기 혈압과 에너지 보정 단백질만이 유의한 양의 연관성을, 총 열량은 음의 연관성을 보여주었다. 여성의 경우는 평균 수축기 및 이완기 혈압과 유의한 연관성을 보여주는 영양소는 없었다. 5. 고혈압과 영양소와의 관계를 성, 연령, 체질량 지수, 가족력을 보정하고 선형중회귀로짓분석을 이용하여 분석시 영양소 밀도를 이용한 모델에서는 단백질 밀도가 강한 양의 연관성을(Odds ratio=3.18), 지방밀도는 유의한 양의 연관성을(Odds ratio=1.94)을, 나트륨 밀도는 유의한 음의 연관성을 보여주었다(Odds ratio=0.73). 에너지 보정 영양소를 이용한 모델에서는 에너지 보정 단백질이 유의한 양의 연관성을 보여주었다(Odds ratio=1.01). 본 연구는 단면조사를 통하여 혈압과 영양소와의 상관관계 분석과 고혈압군과 정상혈압군의 영양소 섭취의 차이를 분석하여 영양소섭취와 고혈압과의 연관성을 보고자 하였는데 적대적인 영양소 섭취량보다는, 같은 에너지 섭취수준에서 단백질과 지방 섭취가 상대적으로 많은 경우가 양의 연관성을 보였고, 나트륨 섭취가 상대적으로 적은 경우가 음의 연관성을 보였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1458-1465
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• 2010

A lot of dredging and reclaming projects are recently under way in Korea for the efficient use of limiting land space. Saemanguem area is special case of reclaiming by dredged soil. In case of a confined disposal of dredged soils by a pump dredger, generally coarse grained soils are separated from fines with dropping at the near part of the pump dredger. This kind of seperation of fine contents could be a factor of liquefaction by earthquake. In Korea, recently, earthquakes with magnitude of 3.0 or higher are distinctively increasing in 1990. In this study, cyclic shear characterics of Saemanguem Dredged sand depending on fine content were analyzed. A series of undrained cyclic triaxial test with cyclic stress ratio ($\sigma_d/{2\sigma_{{\upsilon}c}}'$) were performed on both isotropic consolidated specimen and sand with fine contents of 0%, 5%, 15%, 30%, 40% under the effective vertical stress of 100kPa and 50% and 60%, 70% of relative density for fine content of 0%, respectively. In the test results, cyclic shear strength increased by increasing of cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) with increasing the relative density at the same number of cyclic under the effective confining pressure of 100kPa. It is almost highest the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10% at fine content of 15% between Cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) value at cyclic number five and fine content. Number of cyclic is 30 under the effective vertical stress of 100kPa, 70% of relative density for fine content of 15%. when the cyclic stress ratio at each relative density was compared at cyclic number five, the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10%, and the pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value were compared; under the relative density of 70% and the effective confining pressure of 100kPa. The pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value showed a similar trend to the double amplitude (DA) 5% line.

• 한국농공학회지
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• 제30권1호
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• pp.73-80
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• 1988

This study was performed to obtain the basic data which can be applied to use of foaming mortars. The results obtained were Summarized as follows; 1.At the mixing ratio of 1:1, the highest bulk densities were showed by foaming mortars, respectively. But, it gradually was decreased in poorer mixing ratio and more addition of foaming agent. The decreasing rates of bulk densities were increased in richer mixing ratio and more addition of foaming agent. 2.The bulk densities were decreased up to 38.8-55.9% by mix-foaming type and 9.7-23.6% by pre-foamed type than cement mortar. 3.At the mixing ratio of 1:1, the lowest absorption rates were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. The increasing rates of absorption rates were increased in richer mixing ratio and more addition of foaming agent. 4.Absorption rates when immersed in 72hours were showed up tp 3.41-5.85 times by mix-foaming type and 1.05- 1.S5times by pre -foamed type than cement mortar, it was significantly higher at the early stage of immersed time than cement mortar. 5.The correlations between bulk density and absorption rate were highly singnificant, respectively. The multiple regression equations of bulk density and absorption rate were computed depending on a fuction of mixing ratio and addition of foaming agent. it was highly significant respectively.

• 한국농공학회지
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• 제34권3호
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• pp.33-42
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• 1992

The shear strength of cohesionless Soils results from particle-to-particle friction and structural resistance by interlocking. And, the shear strength of soils is subjected to vary depending on the internal states and external condtions. If the volume change occurring in the soils and stress-strain relationships under the internal and external changes can accrurately he described, it is possible to predict the behaviors of soils. To accomplish these objectives a series of drained triaxial compression tests and isotropic compression test was performed on the Banwol sand at different relative densities ranging from 20% to 80% and different confining pressures ranging from 0.4kgf/cm$^2$ to l2kgf/cm$^2$. The results and main conclusions of the study are summarized as follows; 1.When the relative density or the confining pressure is increased, the maximum deviator stress is increased. The ratio of the maximum deviator stress and the confining pressure is linearly proportional to the relative density. 2.It is observed that the dilatancy depends not only upon its relative density but also the confining stress, and that the maximum deviator stress is obtained after the diatancy occurs. 3.The volume of sands undergoes initial contraction prior to the dilatancy occurred by strain softening. The dilatancy rate eventually approaches the critical state or a constant volume. 4.At lower strains, Poisson's ratio approaches a certain minimum value regadless of the state of materials. At larger strains, however, the ratio is increased as the relative density is increased. 5.It is observed that the modulus of elasticity is linearly proportional to the relative density and the pressure. 6.When the relative density is increased, the friction angle of sands is linearly increased. 7.When the relative density is increased, the expansion index and the compression index are linearly decreased, and the ratio of the two is about 1/3.

• 전기학회논문지
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• 제66권2호
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• pp.370-378
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• 2017

A fluid model of 2D axis-symmetry based on inductively coupled plasma (ICP) reactor using $N_2/NH_3/SiH_4$ gas mixture has been developed for hydrogenated silicon nitride ($SiN_x:H$) deposition. The model was comprised of 62 species (electron, neutral, ions, and excitation species), 218 chemical reactions, and 45 surface reactions. The pressure (10~40 mTorr) and gas mixture ratio ($N_2$ 80~96 %, $NH_3$ 2~10 %, $SiH_4$ 2~10 %) were considered simulation variables and the input power fixed at 1000 W. Different distributions of electron, ions, and molecules density were observed with pressure. Although ionization rate of $SiH_2{^+}$ is higher than $SiH_3{^+}$ by electron direct reaction with $SiH_4$, the number density of $SiH_3{^+}$ is higher than $SiH_2{^+}$ in over 30 mTorr. Also, number density of $NH^+$ and $NH_4{^+}$ dramatically increased by pressure increase because these species are dominantly generated by gas phase reactions. The change of gas mixture ratio not affected electron density and temperature. With $NH_3$ and $SiH_4$ gases ratio increased, $SiH_x$ and $NH_x$ (except $NH^+$ and $NH_4{^+}$) ions and molecules are linearly increased. Number density of amino-silane molecules ($SiH_x(NH_2)_y$) were detected higher in conditions of high $SiH_x$ and $NH_x$ molecules density.

• 한국농공학회논문집
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• 제48권4호
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• pp.59-66
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• 2006

In this study, construction modulus, void ratio and settlement characteristics of 38 CFRD in domestic and foreign countries were investigated from monitoring data. The effect of field dry density and void ratio to dam body was analyzed. The standard void ratio of CFRD that can be easily used by dam designers and field engineers was proposed from the monitoring data. It was confirmed that we can get the degree of compaction needed for reasonable compaction of dam body by calculating the field dry density from inverse operation of the standard void ratio. It was thought that the void ratio of CFRD depends on shape coefficient and in case of a high shape coefficient, the void ratio was high with its void ratio 0.17 -0.38.