• Journal of Industrial Technology
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• v.22 no.A
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• pp.161-168
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• 2002

Latex modified concrete is governed by both cement hydration and polymer film formation processes in its binder phase. Such the reactions are expected to improve the polymer-cement co-matrixes themselves and the bond between the cement hydrates and aggregates, and to improve the properties of hardened latex-modified concrete. The purpose of this study was to study the strength and chemical resistance of Rapid-setting latex modified concrete(RSLMC) with the main experimental variables such as latex content(0, 5, 10, 15, 20%) and water-cement ratio(36, 38, 40%) at latex content 15%. Water absorption test was earned out to estimate water permeability resistance. Chemical resistance test was carried out to measure the weight change and to observe the appearance of RSLMC immersion in hydrochloric acid, sulfuric acid, and calcium choloride.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.3
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• pp.127-135
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• 2002

Shore hardness test was developed in 1906 to overcome the limit of Brinell hardness test. However, the detailed requirements on the tester was not clearly specified except the scale, i.e., 100 HS for high carbon steel and 10 HS for soft brass. As a result, the shore hardness was used for quite long time without well established standards. For the establishment of hardness standards, standard tester, standard procedure, and standard hardness block must be provided. So far the standard of Shore hardness was maintained by correlating Shore hardness scale to Vickers hardness through converting equation. This is the so called converted Shore hardness and it is not the true Shore hardness standard strictly. In this paper, the possibility of establishing Shore hardness standard based on the Shore standard hardness tester is reported.

• Microbiology and Biotechnology Letters
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• v.25 no.4
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• pp.396-402
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• 1997

Biocontrol of plant pathogens provides an alternative means of reducing the incidence of plant diseases without the negative aspects of chemical pesticides. Nowdays, as the resistant fungi about the chemical fungicides have revealed and the concern of environment has increased, the biological control of phytopathogenic fungi by the antagonistic microorganisms is very much indispensable. For the selection of strong antagonistic bacterium for biological control agent of rice leafblast and cucumber gray mold rot, the antifungal strain KL-3 strain was selected among 120 strains isolated from the rhizosphere soils. And the strain was identified to be a species of Bacillus subtilis or closely related strain. In several biochemical and in vitro antibiosis tests, antifungal substances of Bacillus sp. KL-3 were presumed heat stable, micromolecular antibiotic substances. In vivo test and vinyl house field test, the antifungal substances of Bacillus sp. KL-3 represented excellent biocontrol ability aganist Alternaria mali, Phyricularia oryzae, and Alternaria kikuchiana as well as broad spectrum of other fungi. In particular, Bacillus sp. KL-3 strain showed more predominant activity than some chemical fungicides against fungi shown to resist chemcal fungicides.

• The Korean Journal of Ecology
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• v.14 no.2
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• pp.149-157
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• 1991

To find out allelopathic potential of naturally occurring substances emitted form pinus korairnsis, water extracts and volatile sudstances of the tree materials werw provided and used for tests such as seed germination and seedling growth test. In general, the more was the concentration of the extracts and essential oils, the worse was growth effects of the selected species. The germination an the growth were inversely proportional to the concentration of the extracts and the essential oils of p. koraiensis. in other words, the chemical substances had the biological toxic activity. gc and gc/ms methods were employed for analysis and identification of phytotoxic substances from the tree leaves. Sixteen chemical compounds were identified from water extracts and nineteen from essential oils of p. koraiensis leaves. Through the experiment on germination and seedling growth test, the chemical substances naturally occurring from p. koraiensis seemed to be responsible for the allelopathic potential in this study.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.543-552
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• 2014

A quantitative structure activity relationship (QSAR) study is performed for modeling and prediction of oral bioavailabilities of 216 diverse set of drugs. After calculation and screening of molecular descriptors, linear and nonlinear models were developed by using multiple linear regression (MLR), artificial neural network (ANN), support vector machine (SVM) and random forest (RF) techniques. Comparison between statistical parameters of these models indicates the suitability of SVM over other models. The root mean square errors of SVM model were 5.933 and 4.934 for training and test sets, respectively. Robustness and reliability of the developed SVM model was evaluated by performing of leave many out cross validation test, which produces the statistic of $Q^2_{SVM}=0.603$ and SPRESS = 7.902. Moreover, the chemical applicability domains of model were determined via leverage approach. The results of this study revealed the applicability of QSAR approach by using SVM in prediction of oral bioavailability of drugs.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.47-52
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• 2000

Recently, it is very necessary the development of the manufacturing techniques for high strength concrete(HSC) for the large-scale size and good quality of civil structure. But, the manufacture and quality control of HSC of which shrinkage, heat of hydration and workability at construction filed are considered, is very difficult due to its low water-cement ratio and high quantity of unit cement content. In the present study, we tried to know and assess the influences of chemical and physical properties of cement on the material properties of HSC. We analyzed basic properties of 4 kinds of cement whose chemical and physical properties are different each other through various tests such as chemical analysis and mortal test. Also, we performed the assessment of the material properties of HSC for each dement by the test for the conditions of same mix design and similar compressive strength. From the results in the study, the assessment of the important quality factors of cement influencing the properties of HSC may be utilized to quality control of applied cement to manufacture the HSC of high quality.

• Journal of the Korea Institute of Building Construction
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• v.4 no.2
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• pp.81-88
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• 2004

The purpose of this study is to investigate the chemical shrinkage and autogenous shrinkage of high strength cement paste and silica fume and fly ash and sand to cement ratio by the method of volumetric tests, and also investigate the autogenous shrinkage of high measurement method, and compare the results of volumetric test and linear length measurement test. A series of cement paste which have W/C ratio of 25%, 35%, 45% respectively were planed to study the effect of the W/C ratio to the shrinkages, and a series of cement paste which were replaced the cement by the silica fume and fly ash with 5%, 10%, 15% as the mass of cement respectively were planed to investigate the effects of poazolana to the shrinkages. A series of mortar which have a C/S ratio of 1:1, 1:1.5, 1:2 respectively were planed to investigate the shrinkage resistant effect of aggregate.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.334-341
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• 2001

The chemical and geometric effects of weld on flow-accelerated corrosion (FAC) of SA106 Gr.C low alloy steel pipe in 3.5wt% NaCl and simulated feedwater of nuclear power plant have been investigated by using rotating cylinder electrode. Polarization test and weight loss test were conducted and compared at rotating speed of 2000rpm (3.14m/s) with the variables of chemical and geometric parameters. The results showed that the chemical effects were relatively larger than the geometric effects, and the welded parts were the local anode and preferentially corroded, which could be explained by the differences between microstructural and compositional parameters. On the other hand, under active corrosion conditions, the heat affected zone were severely corroded and microstructural effects became the important role in the whole process.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.111-118
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• 2001

Tungsten probe is the most important part of a probe card, which is widely used for the performance test of wafer chips. Electro chemical etching becomes an exclusive choice for mass production of the tungsten probes. In the mass production, not only the shape of the probe but also the shape distribution of machined probes is important. A new method is proposed for the mass production of the tungsten probes. Tungsten wires are separated by a distance, and dipped into electrolyte. The dipping rate is controlled to shape the probes. Several experimental tests are performed to study the machining characteristics. From the test results, machining parameters including electrical conditions and anode position showed significant influences on the shape, repeatability, precision and quality of sharp tips.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.953-956
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• 2010

본 연구에서는 건축자재로 널리 사용되는 PVC바닥상재 표면에 내오염성과 항균성을 증가시키기 위한 광경화형 코팅액 개발에 관한 것이다. PVC 바닥상재용으로 사용되는 우레탄-아크릴 수지에 수용성 대전방지제와 항균제를 배합하여 오염 및 정전기로부터 보호하고 미생물에 의한 전염성질환을 예방할 수 있는 광경화형 내오염/항균 코팅액에 관한 실험을 수행하였다. 연구결과, 수지에 수용성대전방지제 15%와 항균제 1%를 혼합하여 제조한 코팅액을 Bar-coater No.12로 코팅한 표면이 전기저항($10^9\Omega/cm^2$), 내오염도(매직 Test, 먼지부착 Test) 및 부착력(100%) 양호, 항균성(99.99%)로 가장 좋은 물성을 보였다.