• KSBB Journal
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• v.10 no.1
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• pp.55-62
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• 1995

The functional relationship between the initial cell concentration and the ethanol productivity was investigated in the repeated batch fermentation of Sacharomyces cerevisiae ATCC 24858. The repeated batch fermentations were performed in the range of 60 to $150g/\ell$ of initial sugar concentration and 17.5g/$\ell$ to $53.1g/\ell$ of initial cell concentration. The time of one batch fermentation was 1 or 2 hours and the batch fermentation was repeated ten times in every repeated formentaction. The functional relationship showed that the productivity increased non-linearly according to the increase of initial cell concentration regardless of initial sugar concentration. When the initial concentration of sugar was $60g/\ell$ and that of biomass was $34.5g/\ell$, the fermentation was completed within one hour and its ethanol productivity was $26.7g/\ell$.hr, the latter including the times of cell separation, pouring the new substrate into a flask and sampling. When the initial sugar concentration was $120g/\ell$ and the initial cell concentration $50.3g/\ell$, the fermentation was also finished within one hour and its productivity was $45.8g/\ell$$.$hr, The maximum ethanol productivity for eight different repealed fermentations in this work was $53g/\ell$.hr.

• Journal of the Korean Society for information Management
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• v.17 no.1
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• pp.129-148
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• 2000

Experiments were performed on three subsets of a Korean test collection in order to determine whether 2-Poisson model's Z value is a good measure for selecting subject words from a document to be indexed. It was found that subject word selection based on the Z value was effective for only one subset with short texts, i.e., the Science and Technology subset. Correlation analyses between 2-Poisson model's Z and TF.IDF weight for the three subsets showed that the correlation was relatively high for two test subsets with short texts, i.e., the Science and Technology subset and the Newspaper subset.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.123-131
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• 2001

The objective of this study is to investigate the criteria of the width-to-thickness ratio and to evaluate the buckling strength of high strength steel beam-columns and to compare their buckling strength with design codes, which are the Limit State Design code and the Allowable Stress Desogn code(drift). SM520TMC and SM570Q class steels are used for high strength steels. The coupon test and the stub column test were carried out to investigate the properties of high strength steels and the stress-strain curves of stub columns. The buckling strength of high strength steel beam-columns are assessed by numerical analysis used axial force, moment and curvature relationships.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.371-378
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• 1995

YBCO 산화물 초전도체의 초소성 변형에 대한 최적 변형조건을 파악하고자 80$0^{\circ}C$~93$0^{\circ}C$의 온도범위에서 1.0 $\times$ $10^{-3}$s^{-1}$!1.0 $\times$ $10^{-7}$s^{-1}$의 초기변형속도로 압축시험을 수행하였다. 변형속도 민감지수는 m=0.50 $\pm$ 0.1로 나타났다. 이는 결정립계 미끄러지\ulcornerㄹ 주 변형기구로 하는 초소성임을 의미한다. 결정립크기에 따른 유동응력과의 관계는 $\sigma$\propto$d^{1.8 $\pm$ 0.3}$의 지수함수식을 이루고 있으며 Nabarro-Hering 크\ulcorner과 상응하는 격자확산이 확산경로임을 보였다. 초소성 변형에 대한 활성화에너지는 Q=571 $\pm$ 30 kJ/mole이었다. 본 실험온도 구간에서 압축 변형시 변형속도, 변형응력 및 결정립크기에 따른 고온 변형거동 관계식은 $\varepsilon$=A$\sigma$^{2.00 $\pm$ 0.04 - 1.8 $\pm$ 0.3}$ exp(-571 $\pm$ 30kJ/RT)와 같이 유도 되었다. 본 실험조건에서 최적 초소성 변형조건은 86$0^{\circ}C$ 부금, 초기변형속도 ~1.0 $\times$ $10^{-4}$S^{-1}$이었다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.258-261
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• 2012

풀화재에서 화염화염진동은 주위공기와의 밀도차에 의한 부력효과에 기인하여 주로 발생한다. 본 연구는 풀화재의 화염불안정성에 대해 산화제 유속 및 농도 변화에 따른 효과를 검토하기 위하여 컵버너 실험을 수행하였다. 실험결과는 산화제의 농도를 변화시켰을 경우에는 산화제의 불활성기체의 농도가 증가할수록 청염의 길이가 길어지고 컵버너 끝단으로부터 부상되는 것이 관찰된다. 한편, 산화제의 유속이 증가함에 따른 진동주파수가 감소함을 보인다. 이는 무차원 변수로 표현되는 주파수와 부력의 관계로 도시하였을 때 다양한 속도스케일을 사용할 수 있었지만, 연료와 산화제의 유속차로 정의되는 특성속도인 경우에 정지되어 있는 공기중에서의 풀화재 진동과 일치하는 관계식을 얻을 수 있었다. 그리고 진동주파수는 산화제 희석율과는 특정한 관계를 보이지 않는데 이는 국부적 화염구조와 연관성을 가지기 때문으로 판단된다.

• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.741-749
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• 1999

This study is to develop a method of measuring the soil water concentration by using TDR, which is based on the relationships between the bulk soil electrical conductivity of soil and the reflected wave of TDR. The proposed monitoring method is combined with two important relationships. One is that between the bulk soil electrical conductivity and the solute concentration, which is known to be linear at a constant volumetric soil water content and the other is that between the relative bulk soil electrical conductivity and the water content at a constant concentration. Some formulas have been proposed to solve the second relationship, but a new formula and the critical water content are proposed to improve the accuracy of measurement. This proposed formula estimates the relative bulk soil electrical conductivity for water contents which is divided to two regions, linear and nonlinear, by the critical water content. As the result of the comparison with other formulas, the proposed formula is proved to be superior to other formulas and to be an available method to apply to the unsaturated transient solute transport.

• Journal of the Korean Geotechnical Society
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• v.17 no.2
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• pp.21-30
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• 2001

통계적 절리모델링에서 가장 불확실성이 큰 부분이 절리의 길이분포를 추정하는 것이다. 절리선 길이 분포의 추정에서 이제까지는 주로 조사선 조사(scanline survey)를 통한 절리선 반길이 분포를 이용하여 왔다. 이 연구에서는 포이송 디스크 절리모델에 대하여 보다 정밀도가 높은 절리선 길이 분포 추정방법을 찾기 위하여 조사창 조사를 이용하였다. 직사각형 및 원형 조사창에 대하여 양쪽 끝이 조사창 내부에 존재하는 절리선인 양끝내포선의 길이 분포와 한쪽 끝만이 존재하는 한끝내포선의 길이 분포를 이용, 절리선 분포를 추정하는 4개의 관계식을 각각 유도하고 컴퓨터 모의실험을 통하여 유도식의 타당성을 검증한 후 각 유도식을 이용한 절리선 분포의 추정오차를 비교하였다. 또한 절리선 분포로부터 절리직경분포를 계산하는 수치적 해를 유도하고 컴퓨터 모의시험을 통해 수치적 해에 대한 타당성을 검증하였다. 이 연구에서 제시한 조사창 조사를 이용한 절리 길이의 추정방법은 앞으로 절리모델링 분야에서 적용성이 높을 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1153-1163
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• 2013

Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance based on being bonded together, both for the overlay layer and the existing pavement which perform as one monolithic layer. Therefore, it is important to have a suitable bond strength criteria for long term performance of bonded concrete overlay. This study aimed to investigate the affecting of bond strength on various bond characteristics, and to compare the bond strength between direct tensile test and indirect tensile test due to various conditions such as overlay materials, compressive and flexure strength of existing pavement, and deterioration status of existing pavement. As a result of this study, bond strength occurred by both of direct and indirect tensile test due to monotonic load is highly correlated such as coefficient of determination of 0.75 and P-value of 0.002. However, bond strength by indirect tensile test was relatively higher than bond strength by direct tensile test. It was known that correlation between direct and indirect tensile test was possible to use the characteristics analysis of bond fatigue behavior based on bond strength due to cyclic load which can simulate real field behavior of bonded concrete overlay.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.205-213
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• 2007

Strength relationships are presented through experimental data from the concrete strength tests in this study. Various strength tests such as the compressive, flexural, and splitting tensile strength and the modulus of elasticity are included. An experimental work was performed to determine the various strength characteristics for various mix designs. Three different coarse aggregates such as granite, limestone, sandstone were used and included were fine aggregates such as natural sand, washed sand and crushed sand. Also included was cement amount as experimental variable. It was confirmed that each strength value with respect to curing time is to follow a typical strength development curve. With this somewhat reliable test results various strength relationships such as flexural strength-compressive strength, splitting tensile strength-compressive strength, modulus of elasticity-compressive strength, splitting tensile strength-flexural strength were analyzed through statistics. Experimental data were well fitted to the 0.5-power relationship of flexural strength and compressive strength which has been commonly accepted. The splitting tensile strength is expected to be best in the linear relationship from the flexural strength data. Finally splitting tensile strength was found to be proportional to the 0.87 power of the cylindrical compressive strength.

• Journal of the Korea Convergence Society
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• v.10 no.4
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• pp.139-145
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• 2019

This paper investigated the strength and stiffness of composite truss unit structures. The model used is a core-filled model combining the Kagome model and the cube truss model. The material properties used for the analysis are 304 stainless steel with elastic modulus of 193 GPa and yield stress of 215 MPa. The theoretical equation is derived from the relative elasticity relation of Gibson - Ashby ratio, the analysis was performed using Deform 3D, a commercial tool. In conclusion, the relative elasticity for this unit model correlates with 1.25 times the relative density and constant coefficient, elasticity is inversely proportional to pore size. The relative compressive strength has a correlation with relative density of 1.25 times. Proof of this is a real experiment, the derived theoretical relationship should further consider mechanical behavior such as bending and buckling. In the future, it is hoped that the research on the elasticity and the stress according to the structure of the three-dimensional space will be continued.