• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.129-138
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• 1993

The shortage of agricultural labour due to industrial growth has greatly induced the mechanization in Korean agriculture. However small and scattered land holdings have been the main constraints in the process of mechanization. This paper describes the interrelationships of farm land structure, machinery selection and machinery operation areas. The sandy silt loam irrigated paddy land having single crop a year was selected as a target areas for this study. Machine operation cost is greatly influenced by operation period, plot geometry and operation area. On the improved geometry plots, optimal machine size increases slowly with increase in operation area. Operable area increases due to increased effective machine capacity on better geometry plot. The difference between the effects of operation period and plot geometry is that in the former case, the cost reduction is caused by delay in increase of machine size, whereas in the latter case timeliness cost is reduced by increase ffective capacity. The effect of farmland consolidation is greater on small plots than that on big plots. Increasing wage rates have induced the adoption of more labor saving machinery. Bigger labor saving machines require enlargement of operation area and larger plots through improvement in farm land structure. Machine cost on poor plot geometry increases more rapidly than that on the good plot geometry and as operation area increases machine cost reduces significantly. It is concluded that the development of agricultural mechanization ion Korea will depend on the improvement in farm land structure and enlargement of operation area.

• The Journal of Society for e-Business Studies
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• v.10 no.2
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• pp.59-88
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• 2005

The recent development of IT, consolidation of communications and multimedia technology have brought enormous changes in many organizations. These changes are enabling the new educational environments such as distance learning and virtual education. Particularly e-Learning has grown rapidly in business training fields. In this regard, the primary purpose of this study is to investigate which factors of e-Learning influence education and training in business organizations through an empirical survey. The results show that most of hypotheses get significant support. Implications of these findings are discussed for researchers and practitioners.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.888-895
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• 2006

In this study, anisotropically consolidated undrained shear(CAU) test was performed to examine the variation of the shear strength according to the stress history. The specimen having 30% relative density was homogeniously prepared, and 200KPa of back pressure was applied to increase the B value more than 0.95. To make NC specimens, the vertical stress was applied on the specimen by 100KPa, 200KPa and 400KPa, and to make OC specimens, the vertical stress was applied upto 400KPa and was reduced to 200KPa and 100KPa resulting in OCR 2 and 4 respectively. The test result indicates the shear strength for the OC specimens are slightly higher then that of the NC specimens at the same confining pressure. The elastic modulus varies according to the confining stress and considerably affected by preconsolidation stress.

• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.701-721
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• 2014

In the assessment of existing RC buildings, the reliable appraisal of the compressive strength of in-situ concrete is a fundamental step. Unfortunately, the data that can be obtained by the available testing methods are typically affected by a high level of uncertainty. Moreover, in order to derive indications about the degradation and ageing of the materials by on site tests, it is necessary to have the proper terms of comparison, that is to say, to know the reference data measured during the construction phases, that are often unavailable when the building is old. In the cases when such a comparison can be done, the in situ strength values typically turn out to be lower than the reference strength values (tests performed on taken samples during the construction). At this point, it is crucial to discern and quantify the specific effect induced by different factors: ageing of the materials; poor quality of the placement, consolidation or cure of the concrete during the construction phases; damage due to drilling. This paper presents a procedure for correlating the destructive compressive tests and non-destructive tests (ultrasonic pulse velocity tests) with the data documenting the compressive strength tested during the construction phases. The research work is aimed at identifying the factors that induce the difference between the in-situ strength and cubes taken from the concrete casting, and providing, so, useful information for the assessment procedure of the building.

• Journal of the Korean Society of Costume
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• v.58 no.5
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• pp.198-210
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• 2008

The purpose of this study is to establish the conservation methods of embroidered textiles and textile works. The conservation of remained textiles is consisting of examination, cleaning, support and consolidation, restoration, and storage and display process. It aims to prevent the damage on textile remains for long time display and storage and to prolong their aesthetics and functionality. The embroidered textiles and textiles works, which are remained by handed down or excavated or included in the Buddhist are embossed with colorful threads on the fabrics: the stitches include embroideries on clothing, bed clothes, wrapping clothes, utensil pouches, panels and Buddhist goods; textile works include hats, ornaments, shoes, attachments of clothes etc. These are composed of mainly fabrics, precious metals, leathers and precious stones, etc., and are fabricated by several techniques such as braiding, twining, sewing as well as weaving. Metal threads were also used to add a decorative effect on these goods. In order to conserve and preserve the remained goods, a special care must be taken on the metal threads, which are the most fragile material among the constituents. Hence, characteristics of metal threads and its cleaning methods, general conservation techniques of a rank badge, which is brocaded and partly attached to Cheogori and Samo(men's hat) from the excavated old tombs are introduced here.

• Geomechanics and Engineering
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• v.23 no.4
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• pp.301-311
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• 2020

In this study, shear strength behavior of fine-grained soils was investigated under unsaturated conditions. The samples in the unsaturated state were subjected to a net normal stress (σ-u_a) of 40 kPa and different matric suctions (u_a-u_w) of 50, 100 and 150 kPa. The matric suction values applied in the triaxial tests were selected according to the bubbling pressures determined from the SWC curves. The study was carried out on prepared re-constituted cylindrical samples by uniaxial consolidation of soil slurries. First, consolidated drained (CD) triaxial compression tests were performed on the saturated samples and the cohesion and angle of internal friction were determined. After that, drained triaxial compression tests under matric suctions were performed on the unsaturated samples. In order to obtain unsaturated test results, cohesion and internal friction angle values of saturated samples were used. The nonlinear surface representing the shear strength surface was approximated consisting of two planes (double planar surface). The reason for the nonlinear behavior of some soils is that the amount of sand content contained in it is relatively high and the bubbling pressure/permanent water content value is relatively low.

• Journal of The Korean Association of Information Education
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• v.11 no.4
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• pp.425-432
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• 2007

Each university runs curriculum for pre-service teachers to improve teaching skills and designing classes and realizing them. Pre-service teachers can have opportunities of designing and realizing charming classes in the course of practice teaching. We can say that if pre-service teachers can practice simulation for effective teaching skills, there can be some advantages: improvement of class environment, consolidation of instructors' abilities, and thus a ripple effect of for those within the whole community. The purpose of this study is to introduce and indicate the direction of simulation for pre-service teachers and beginners alike, thus training and expecting them to improve effective questioning skills through systematic education courses.

• 보존과학연구
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• s.30
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• pp.125-136
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• 2009

Stone cultural heritages in Korea have a severe damages from chemical and biological weathering because most of them have been situated in outdoors without any suitable protection systems, and this in turn causes deformation and structural damage. To counteract these problems and increase durability, various kinds of conservation materials are used in the conservation and restoration treatments. However until now there are not many practical and technological experiments on this subject. This paper attempts quantitative evaluation of effectiveness about chemical of ethylsilicate based resin for sandstone in Yeongyang-gun. It takes a long time to evaluate durability and side effect after conservation materials treatment. So we use artificial weathering through freezing§ thawing experimental method. As a result of this experiment, porosity and absorptance increased, and elastic wave speed, elastic modules, unconfined compression strength and tensile strength decreased more than before. This study plans to make a scientific method study about weathering factor and mechanism, and to deduce correlation between artificial weathering and natural weathering.

• Journal of Conservation Science
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• v.24
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• pp.43-56
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• 2008

When we consolidate the iron artifacts, only we used VM&P Naphtha as solvent of paraloid NAD10. After consolidating the iron artifacts using paraloid NAD10, artifacts were too glossy to exhibit and see. We choose the solvent YK-VMP as solvent of paraloid NAD10 for complementing this defect and examined characterizations of paraloid NAD10 films in each solvent. As a result of evaluation by several surface analysis such as optical microscope, measuring film thickness, adhesive strength, gloss of surface, contact angle, yellowing test and EIS, it is possible to use YK-VMP instead of VM&P Naphtha as solvent of paraloid NAD10, because YK-VMP lowered surface gloss and did not change the effect of consolidation.

• Journal of Powder Materials
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• v.14 no.6
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• pp.362-366
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• 2007

Magnesium and magnesium alloys are promising materials for light weight and high strength applications. In order to obtain homogeneous and high quality products in powder compaction and powder forging processes, it is very important to control density and density distributions in powder compacts. In this study, a model for densification of metallic powder is proposed for pure magnesium. The mode] considers the effect of powder characteristics using a pressure-dependent critical density yield criterion. Also with the new model, it was possible to obtain reasonable physical properties of pure magnesium powder using cold iso-state pressing. The proposed densification model was implemented into the finite element method code. The finite element analysis was applied to simulating die compaction of pure magnesium powders in order to investigate the density and effective strain distributions at room temperature.