• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.273-297
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• 2005

In construction site, there are some occasions where concrete under initial curing is being affected by nitration from nearby vibration sources. To study these effects, in this paper, strength characteristics of concrete specimens subjected to continuous vibration up to 12 hours in vertical direction after concrete placement were observed. And through the vibration time control experiment where a number of time combinations consisted of times before and after applying vibration during initial curing period were used as experimental parameters, possibility of concrete strength improvement was investigated. From the experimental results, it could be seen that the concrete strengths were mostly decreased due to the increase of vibration velocity during initial curing period. But fluctuation ratio of concrete strength did not have any close correlations with the vibration times. And results of vibration time control experiment showed that if times before applying vibration sustains at least more than 3 hours, subsequent vibrations after that hours do not affect the concrete strength in any unfavorable ways.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.73-81
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• 2017

In this paper, the periods of cold weather concrete and early frost damage depending on each region in South Korea were studied using the climate data from Korea meteorological administration. The specifications of Korea Concrete Institute(KCI) and Architectural Institute of Japan(AIJ) were applied to provide the periods of cold weather concrete. The periods of early frost damage risk(EFD) were calculated by Hasegawa's suggestion depending on 91 cities in Korea. Climate data for 5 years (2008~2012) were used to obtain both of the periods. Existing data from 1971 to 2000 were also used to compare differences in the periods between past and present study. The periods of cold weather concrete by KCI were calculated about 98 days on average. As the latitude goes up and close to mountain areas, the periods tend to be increased. The periods by present study was shown to be reduced compared to that of previous study by 1~2days. The period of EFD was provided with the level of daily lowest temperature from $-5^{\circ}C$, $-2^{\circ}C$ and $0^{\circ}C$. The beginning day of the period of EFD was earlier than the period of cold weather concrete and the finishing day of the period of EFD was later than the period of cold weather concrete.

• KSBB Journal
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• v.22 no.6
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• pp.414-420
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• 2007

Nanomaterials have been applied to various fields due to their advantageous characteristics such as high surface area, rapid diffusion, high specific surface areas, reactivity in liquid or gas phase, and a size close to biomacromolecules. Up to date, increased manufacturing and frequently use of the materials, however, revoke people's concerns on their hazard impact including toxicity the materials. Many research groups have carried out different protocols to evaluate toxic effects of nanomaterilas on different organisms, and consequently, nanomaterials are known to cytotoxicity. In this paper, we reviewed some of the most reports on toxic effects of several nanoparticles specifically on bacteria. There are numbers of reports focused on antibacterial effect of nanoparticles based on bacterial cell viability. Therefore, the application of each nanomaterial should be concerned with its toxicity and its toxic effect should be evaluated in terms of concentrations and sizes of the nanomaterials used, prior to use of a nanomaterial.

• Journal of the Economic Geographical Society of Korea
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• v.12 no.4
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• pp.627-644
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• 2009

In the knowledge-based economy highlighting the importance of human capital, there has been a growing interest in human capital externalities as a fundamental engine of growth and development of a region. The purpose of this study is to analyze human capital externalities using 3-level hierarchical linear model(3-HLM), decomposing determinants of wages into three levels involving workers(level-1) nested within firms(level-2) nested within regions(level-3). This study separately estimates the effect of the average education level on the wages by three different schooling groups on the assumption that the intensity of knowledge spillovers varies with each group's schooling level. The main results are as follows; First, the coefficient of the average education level of a region shows 0.044, indicating that one-year increase in the average level of schooling could increase average individual earnings by 4.4%. Secondly, the external effects of human capital on three different schooling groups are considerably different, raising less than high school graduates' wages by 3.0%, college graduates' wages by 4.7%, and graduate schools' wages by 11.8%, respectively. Thirdly, well educated workers are much more sensitive to the variation of the regional education level than less educated ones when we apply the shares of each schooling group as alternative measures for the average level of education. Such findings of this study draw an implication that local governments could speed up regional economic growth in the knowledge-based economy by not only raising total human capital stock in a region but building the close networks that promote productivity-enhancing human capital external effects.

• Journal of the Institute of Convergence Signal Processing
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• v.17 no.2
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• pp.83-92
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• 2016

In this paper, we introduce the results of the testing and observation systems for performance wideband expansion in the Korean VLBI Network(KVN). The KVN performs VLBI observations to 1024 Mbps data rate, and 8192 Mbps observing for four simultaneous observation is now evaluating for normal operation. The VLBI stations in several world countries developed their own wideband observing systems to observe the celestial objects with high precision and high resolution or are working with several countries. The KVN is planning to introduce a high-speed sampler, OCTAD, for sampling directly up to 2048 MHz bandwidth for RF signal of K/Q/W/D band in the frequency band without conversion. Therefore, as a preliminary study for the performance scalability of the KVN then through the close cooperation with National Astronomical Observatory of Japan (NAOJ), the OCTAD high-speed sampler and OCTADISK2 high-speed recorder were installed in the KVN Yonsei station, and verify the performance through a wideband.

• Journal of the Korean association of regional geographers
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• v.21 no.1
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• pp.176-191
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• 2015

Military Geography is a literature studying the application of geographical elements to military behaviour. The elements of military geography including topography greatly influences on building military art and theory. The military art applied on korean pennisula from the period of ancient three countries(Koguryeo, Shilla, Paekche) has been developed maintaining consistent stream reflecting topographic features. Despite the close relationship between building of military art and military geography's elements, the study for korean military geography has been depressed and the discourses of literature has been insufficient. But, in the western study of military geography, the study vitalization efforts studying military peace keeping and humanitarism activity are ongoing. Based on the current trend of western study and the analysis of existing korean study, this treatise proposes three plans to improve the study and education of korean military geography. The key contents of plans are comprised with the improvement of education curriculum, the construction of council between relevant organism, and the installation of subdivision in relevant geographical society. The possibility shaping up the identity of korean military geography as a common literature can be increased by enhancing the study toward peace and humanitarism and specifying the method for development as noted on this study.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.319-327
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• 1991

Cheju is the biggest island in Korean peninsula, consisted entirely of volcanic rocks and pyroclastic sediments. The topography is characterized by wide basalt plain in the low altitude but at the center of island, basalt volcano rises 1,950m above sea-level. Surface drainage is very poor, therefore water supply has been dependent on ground water and natural springs. There are about 1,650 production wells and most of them yield $1,000{\sim}2,000mm^3/day$. According to increase of ground water use, saline water is intruded in the low altitude of coastal area. Specially in the eastern coastal area, the topography is extensively flat and the level of ground water is very close to sea-level, at which overuse of ground water has brought saline intrusion up to maximum 6km far from the coast. Hydrochemical monitoring on this salt water intrusion is now undertaken on long term base.

• Archives of design research
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• v.19 no.2 s.64
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• pp.283-292
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• 2006

The Plastic material had been developed in the middle of the 19th century as an alternative material. Along with the development of the electrical engineering industry, it cropped up into center stage as an effective material and has increasingly expanded its use. As such, the plastic material has bound deep-seated ties with the design activities of industrial products, coming into the main material for a variety of industrial designs. Despite its dose affinity to design function in terms of its materialistic property, we have rarely seen examples of intensive study on the realtionship between plastics and designs. This study aims to find the importance that the substance affects industrial products in designs along with the development of plastic materials. With the objective in mind, we made a review of the streamline stylishness that had flourished in the twenties and thirties of the 19th century. Through this study, we understand that the plastic material has a close realtionshop with design activities in three different aspects. First, its amorphous state of nature makes it possible to change into any shape one desires in plastic surgery, which feature in turn influences the moulding of any design forms. Second, the plastic material is best suited to mass-manufacture, which induces to reduce the cost of production. Hence, the expansion of design industry. Third, the plastic material allows the multiple variety of colors, sensitivity, gloss and patterns and infinitely large possibility ranging from natural senses to human senses with the result that numberless diversity of designs cdould come into being.

• Journal of Biosystems Engineering
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• v.27 no.2
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• pp.117-124
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• 2002

This research was conducted to develop a method to remove the effect of surface temperature of Shingo pears for sugar content measurement. Sugar content was measured by a near-infrared spectrum analysis technique. Reflected spectrum and sugar content of a pear were used for developing regression models. For the model development, reflected spectrums having wavelengths in the range of 654 to 1,052nm were used. To remove the effect of surface temperature, special sample preparation techniques and partial least square (PLS) regression models were proposed and tested. 71 Shingo pears stored in a cold storage, which had 2$^{\circ}C$ inside temperature, were taken out and left in a room temperature for a while. Temperature and reflected spectrum of each pear was measured. To increase the temperature distribution of samples, temperature and reflected spectrum of each pear was measured four times with one hour twenty minutes interval. During the experiment, temperature of pears increased up to 17 $^{\circ}C$. The total number of measured spectrum was 284. Three groups of spectrum data were formed according to temperature distribution. First group had surface temperature of 14$^{\circ}C$ and total number of 51. Second group consisted of the first and the fourth experiment data which contained the minimum and the maximum temperatures. Third group consisted of 155 data with normal temperature-distribution. The rest data set were used for model evaluation. Results shelved that PLS model I, which was developed by using the first data group, was inadequate for measuring sugar content of pears which had different surface temperatures from 14$^{\circ}C$. After temperature compensation, sugar content predictions became close to the measured values. Since using many data which had wide range of surface temperatures, PLS model II and III were able to predict sugar content of pears without additional temperature compensation. PLS model IV, which included the surface temperatures as an independent variable. showed slightly improved performance(R$^2$=0.73). Performance of the model could be enhanced by using samples with more wide range of temperatures and sugar contents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.594-600
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• 2016

The present study numerically investigated the gas leakage characteristics in a simplified underground combined cycle power plant. The effect of obstacles near a crack location on the gas concentration in the confined space was analyzed by using the lower flammable limit (LFL) of methane gas. When the jet flow was close to the vertical walls, the longitudinal leakage distance increased by about 60% (when an obstacles was present) compared to the case without any obstacle, because these obstacles prevented transverse flows. In addition, when an air filter was installed near to the trajectory of the gas flow, the longitudinal leakage distance was similar to the distance between the crack and obstacle, whereas the transverse leakage distance increased up to 8 times compared to the case without any obstacle. As the jet flow impacts on the obstacle and changes its direction, the gas flows recirculate. Therefore, it is necessary to consider the effect of the structure and facility locations on the trajectory of the jet flow to propose an accident prevention system in confined spaces.