• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.199-210
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• 2003

The development of strain localization within shear zones is frequently observed during soil deformation. In fact, the phenomenon appears to be more often the norm rather than the exception. Conceptually, any soil condition that renders negative work increment is prone to localization. In this study, a broad range of soil and loading conditions are investigated to test this criterion, including: dilative soil subjected to drained shear (standard case), contractive soil sheared under undrained conditions, cavitation in dilative soil in undrained shear, inhomogeneous soils, particle alignment in contractive soils made of platy particles, soils that experience particle crushing, and the shear of low-moisture and/or lightly cemented loose soils. Unique specimens and test procedures are designed to separately test each of these soil conditions in the laboratory According to experimental test results, soil specimens with post-peak strain softening behavior are prone to progressive failure, localization of deformations, and shear banding. The state of stress, the soil density, inherent mechanical and geometrical properties of soil particles, low water content, and heterogeneity can contribute to triggering strain localization. Considering all possible cases of localization, the best method to obtain the critical state line in the laboratory is to use contractive homogeneous specimens subjected to drained shear.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.2 s.150
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• pp.207-220
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• 2006

The purpose of the study is to develop the basic pattern of casual jacket for men aged between 25 and 34. Compared to the tailored jackets, casual jackets are designed much more diverse form depending on the target customer, price range and moreover fashion trend. Therefore in order to reduce the cost and time of developing new style, pattern draft from the basic pattern is better approach rather than develop each style form the measurements every time. For men's casual jacket pattern draft, the basic pattern of fit and comfort was developed through following research procedures. 173 men were surveyed about their habit of buying and wearing of casual jackets. MDs and pattern designers of 10 casual wear brands for men were interviewed. As a starting point, 3 different basic patterns were selected. 2 patterns were from the 2 interviewed brands and the last one was the pattern of ESMOD. The 3 patterns were studied by means of comparing measurements and general styling. As a results it was found that the pattern of S brand is featuring I silhouette, the pattern of K brand is featuring H silhouette and the pattern of ESMOD is featuring Y silhouette. The results of wearing test showed that the pattern of S brand is the best among the three. They were to add ease around the chest line and waist line, to relocate the waist line and the break point, to increase the jacket length and upper arm width. The improved pattern was made of polyester for the wearing test. The wearing test showed developed pattern was improved significantly. To verify the use of developed basic pattern, two buttoned single jacket was made.

• Computers and Concrete
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• v.19 no.4
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• pp.357-363
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• 2017

This paper conveys the effects of fly ash and silica fume incorporated in concrete at various replacement ratios on the durability properties of concretes. It is quite well known that concrete durability is as much important as strength and permeability is the key to durability. Permeability is closely associated with the voids system of concrete. Concrete, with less and disconnected voids, is assumed to be impermeable. The void system in concrete is straightly related to the mix proportions, placing, compaction, and curing procedures of concrete. Reinforced concrete structures, particularly those of subjected to water, are at the risk of various harmful agents such as chlorides and sulfate since the ingress of such agents through concrete becomes easy and accelerates as the permeability of concrete increases. Eventually, both strength and durability of concrete reduce as the time moves on, in turn; the service life of the concrete structures shortens. Mineral additives have been proven to be very effective in reducing permeability. The tests performed to accomplish the aim of the study are the rapid chloride permeability test, pressurized water depth test, capillarity test and compressive strength test. The results derived from these tests indicated that the durability properties of concretes incorporated fly ash and silica fume have improved substantially compared to that of without mineral additives regardless of the binder content used. Overall, the improvement becomes more evident as the replacement ratio of fly ash and silica fume have increased. With regard to permeability, silica fume is found to be superior to fly ash. Moreover, at least a 30% fly ash replacement and/or a replacement ratio of 5% to 10% silica fume have been found to be highly beneficial as far as sustainability is concerned, particularly for concretes subjected to chloride bearing environments.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.1
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• pp.95-104
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• 2012

The purpose of this study is to examine what effects the experiment class to stress discussion of small groups in scientific experiment class of the elementary school has on scientific achievement and attitude on the science of the students comparing to the usual scientific experiment class. For that purpose, this study has divided 49 students at the 6th grade of the M elementary school in P City into test groups of 24 students and control groups of 25 students. Classes have been progressed by giving sufficient time to the test groups for discussion by each small groups after experiment while by allowing the control groups to finish the experiment with arrangement of the experiment results. Conclusions of this study include: First, the more familiar the experiment materials are and the easier the experiment procedures are to be operated by the students, the more actively the small group discussion activities have been deployed. It shows that the students need a certain level of background knowledge before experiment for vital discussing activities. Second, it is appeared that the test groups given the scientific experiment class stressing small group discussing activity have significantly high scores comparing to the control groups given the existing scientific experiment class. It shows that the small group discussing activities have effects on promoting understanding of the students on the scientific achievement for the scientific experiment class. Third, it is appeared that the test groups given the scientific experiment class stressing small group discussing activity significantly high scores on attitude about the science comparing to the control groups given the existing scientific experiment class. It is considered that the students could have opportunities to compare their own thoughts with others and to have reflective thought to change their thoughts through the small group discussing activity. As shown above, it shows that the experiment class to stress discussing activities is more effective to increase scientific achievement and attitude about the science than the scientific experiment class to get and arrange the experiment results from the existing experiment classes.

• Journal of Digital Convergence
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• v.14 no.2
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• pp.501-507
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• 2016

We obtained medical test data of 150 male from National Health Insurance Corporation, that included physique, blood chemistry, and lifestyle. ${\chi}^2-test$ and logistic regression, and multiple regression were done to verify how CAD risks and/or lifestyle are different between obese and non-obese person. SPSS(version 18) was used for statistical procedures and p-value of .05 was regarded as good through. ${\chi}^2-test$ showed the frequency of hypertension, htperglycemia, hyperlipidemia were higher in obese person than in non-obese This result told us that lifestyle modification could be a key to prevent cardiovascular disease by controlling and managing body composition, especially abdominal obesity.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.739-750
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• 1997

Treatment of root perforation elicits special considerations due to its blood-contaminated circumstances. It is known that conventional dental restorative materials are all leaking. Calcium sulfate is the material which react with water to become chemically set. This study, therefore, was performed to develop a new compound containing calcium sulfate and to evaluate its physical and biological characteristics. Three materials were used, IRM, calcium sulfate, calcium sulfate-hydroxyapatite compound. The composition of the calcium sulfate-hydroxyapatite compound was basically 50 % of calcium sulfate and 50 % of hydroxyapatite mixed with guajacol. The materials were mixed in conventional way and underwent four physical test procedures, setting time, solubility test, compressive strength, and marginal leakage test. All materials were evaluated under the scanning electron microscope to examine the marginal sealing ability. Animal experiment was also performed to test the materials' tissue response. Twenty-four dog's premolars were tested with either furcation perforations or apical retro-fillings. From the results, we found that calcium sulfate possess the good marginal sealing ability. However, calcium sulfate creates many voids which is caused by crystal thrusting action when it reacts with water. It seemed that the voids caused disintegration of the material which eventually lead to tissue reaction. By compounding calcium sulfate and hydroxyapatite, we were able to obtain the better physical properties but it showed larger marginal gap between the material and the root surface. Within the six weeks observation period, both IRM and calcium sulfate-hydroxyapatite compound showed good tissue responses in animal experiment. It is concluded that calcium sulfate would be the material of choice in root perforation repair, but the physical property needs to be further improved.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.279-286
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• 2011

The aging degradation and lifetime assessment of a domestic class 1E Ethylene-Propylene-Diene-Monomer (EPDM), which is a popular insulating elastomer for electrical cables in the nuclear power plants, were studied for equipment qualification verification under the Loss of Coolant Accident (LOCA) conditions. The specimens were acceleratively aged, underwent a LOCA environment, as well as tested mechanically, thermo-gravimetrically, and spectroscopically according to the American Society of the Testing of Materials (ASTM) procedures. The tensile test results revealed that the elongation at break gradually decreased with an increasing aging temperature. The lifetime of EPDM aged isothermally at $140^{\circ}C$ was 1,316 hours and reduced to 1,120 hours after experiencing the severe accident test. The activation energies of the elongation reduction were $1.10{\pm}0.196$ eV and $0.93{\pm}0.191$ eV before and after the LOCA condition, respectively. The TGA test results also showed that the activation energy of the aging decomposition decreased from 1.35 eV to 1.02 eV after undergoing the LOCA environment. Although the mechanical property changes were discernibly observed during the aging process, along with the LOCA simulation, the FT-IR analysis showed that the spectroscopic peaks and their intensities did not alter significantly. Therefore, it can be concluded that the degradation of the domestic class 1E EPDM due to aging can be tolerable, even in severe accident conditions such as LOCA, and thus it qualifies as a suitable insulating material for electrical cables in the nuclear power plants.

• Fire Science and Engineering
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• v.30 no.5
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• pp.124-129
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• 2016

According to the current law, on-site flame resistant-treated interior decorations should pass the flame resistant performance test through a 45 degree combustion test from the district fire department. Although a 45 degree combustion test is the most accurate method for determining the flame resistant performance, it can be unreliable when tested on unauthorized samples. To avoid unauthorized sampling, this study suggests on-site flame resistant inspection by X-ray fluorescence spectrometer. Ten types of flame resistant paint were spread on plywoods and MDFs and the components were analyzed by X-ray fluorescence spectrometer. As a result, due to a difference amounts of substances in each paint, each flame resistant paints showed its own characteristic spectrum and the contents of each substance could be determined. On-site flame resistant inspections can be used efficiently when institutional procedures are created.

• Korean Journal of Child Studies
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• v.9 no.2
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• pp.1-28
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• 1988

The purpose of this study was to develop a behavior rating scale for the evaluation of children's development for utilization by preschool teachers. The procedures for the study included content validation, pilot test, and main study. A total of 97 items were retained after the content validation and pilot test. The items of the scale were grouped into five areas (physical, language, cognitive, emotional, and social development) and 11 sub-areas. The resulting "Behavior Rating Scale for Preschool Children" was administered to 479 boys and girls, 3-6 through 6-5 years of age, selected from 10 different kindergartens and early education centers in Seoul, Pusan, and Chonju. The analysis of data was done with SPSS computer programs, including item analysis, Cronbach's ${\alpha}$ for reliability, factor analysis to test construct validity, two-way ANOVA to test age and sex differences, and percentile norms. The 97 items of the scale were found to be satisfactory in terms of item discrimination with indices ranging from .31 to .73. Cronbach's ${\alpha}$ was .98 for the total scale and ranged from .87 to .93 in specific domains, which was considered satisfactory. The factors extracted from each area were consistent with the educational objectives of the Yonsei Open Education Program except for emotional development. The intercorrelations among the domains were relatively high, ranging from .56 to .81. Age differences were significant in cognitive, physical, and language development, but not significant in social and emotional development. Sex differences were significant in all areas with girls higher on the average than the boys. Percentile ranks were drived from the total score for each age group and quartiles were calculated for sub-scores in each domain.

• Journal of Ocean Engineering and Technology
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• v.29 no.6
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• pp.445-453
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• 2015

The stress triaxiality and lode angle are known to be most dominant fracture parameters in ductile materials. This paper proposes a three-dimensional failure strain surface for a ductile steel, called a low-temperature high-tensile steel (EH36), using average stress triaxiality and average normalized lode parameter, along with briefly introducing their theoretical background. It is an extension of previous works by Choung et al. (2011; 2012; 2014a; 2014b) and Choung and Nam (2013), in which a two-dimensional failure strain locus was presented. A series of tests for specially designed specimens that were expected to fail in the shear mode, shear-tension mode, and compression mode was conducted to develop a three-dimensional fracture surface covering wide ranges for the two parameters. This paper discusses the test procedures for three different tests in detail. The tensile force versus stroke data are presented as the results of these tests and will be used for the verification of numerical simulations and fracture identifications in Part II.