• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.58-72
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• 2006

In recent years, not only the occurrences but the magnitude of earthquakes in Korea are on an increasing trend and other sources of dynamic events including large-scale construction, operation of hi띤-speed railway and explosives blasting have been increasing. Besides, the probability of exposure fir rock joints to free faces gets higher as the scale of rock mass structures becomes larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, a shaking table test system was set up and a series of dynamic test was carried out to examine the dynamic frictional behavior of rock joints. In addition, a computer program was developed, which calculated the acceleration and deformation of the sliding block theoretically based on Newmark sliding block procedure. The static friction angle was back-calculated by measuring yield acceleration at the onset of slide. The dynamic friction angle was estimated by closely approximating the experimental results to the program-simulated responses. As a result of dynamic testing, the static friction angle at the onset of slide as well as the dynamic friction angle during sliding were estimated to be significantly lower than tilt angle. The difference between the tilt angle and the static friction angle was $4.5\~8.2^{\circ}$ and the difference between the tilt angle and the dynamic friction angle was $2.0\~7.5^{\circ}$. The decreasing trend was influenced by the magnitude of the base acceleration and inclination angle. A DEM program was used to simulate the shaking table test and the result well simulated the experimental behavior. Friction angles obtained by shaking table test were significantly lower than basic friction angle by direct shear test.

• Journal of the Korean association of regional geographers
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• v.11 no.1
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• pp.19-28
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• 2005

Although Dokdo, small and dependent islands of Ulleung County, can be considered critical in terms of both geo-politics and physical geography, it is clear that Korean geographers have been too silent tn study Dokdo. In the author's view, such tendency is partly due to difficulties in access to Dokdo. In this sense this study would be meaningful for inquiring into the regional geomorphology of Dokdo regardless of only three-day field work. The major findings of the study are as follows. Firstly, the geology of Dokdo is composed of 8 rock units. Secondly, in a slope analysis of Dokdo volcano using GIS tool, steep slopes over $26^{\circ}$ account for 79.1% of whole slopes and even free faces, defined as slopes over $40^{\circ}$, account for 65.4%. Thirdly, the main landforms of Dokdo constitute volcanic landform, coastal landform and the others, such as talus, dyke, tafoni and erosional hollow. Fourthly, it turns out that advanced landform classification map of Dokdo can be designed by taking an approach tn regional geomorphology. Finally, based on a detailed review of the latest geological literature, I argue that part of landforms of East Dokdo(dongdo) is closer tn an erosional hollow than a small crater.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.2
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• pp.149-162
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• 2005

This paper suggest a way to detect a specific wanted figure in public places such as subway stations and banks by comparing color face images extracted from the real time CCTV with the face images of designated specific figures. Assuming that the characteristic of the surveillance camera allows the face information in screens to change arbitrarily and to contain information on numerous faces, the accurate detection of the face area was focused. To solve this problem, the normalization work using subsampling with $20{\times}20$ pixels on arbitrary face images, which is based on the Perceptron Neural Network model suggested by R. Rosenblatt, created the effect of recogning the whole face. The optimal linear filter and the histogram shaper technique were employed to minimize the outside interference such as lightings and light. The addition operation of the egg-shaped masks was added to the pre-treatment process to minimize unnecessary work. The images finished with the pre-treatment process were divided into three reception fields and the information on the specific location of eyes, nose, and mouths was determined through the neural network. Furthermore, the precision of results was improved by constructing the three single-set network system with different initial values in a row.

• Tunnel and Underground Space
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• v.16 no.2 s.61
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• pp.166-178
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• 2006

Recently, the frequency of occurring dynamic events such as earthquakes, explosives blasting and other types of vibration has been increasing. Besides, the chances of exposure for rock discontinuities to free faces get higher as the scale of rock mass structures become larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, artificially fractured rock joint specimens were prepared in order to examine the dynamic frictional behavior of rough rock joint. Roughness of each specimen was characterized by measuring surface topography using a laser profilometer and a series of shaking table tests was carried out. For mated joints, the static friction angle back-calculated ken the yield acceleration was $2.7^{\circ}$ lower than the tilt angle on average. The averaged dynamic friction angle for unmated joints was $1.8^{\circ}$ lower than the tilt angle. Displacement patterns of sliding block were classified into 4 types and proved to be related to the first order asperity of rock joint. The tilt angle and the static friction angle for mated joints seem to be correlated to micro average inclination angle which represents the second order asperity. The tilt angle and the dynamic friction angle for unmated Joints, however, have no correlation with roughness parameters. Friction angles obtained by shaking table test were lower than those by direct shear test.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.121-131
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• 2007

Recently, the probability of rock joints being exposed to free faces is getting higher for the scale of rock mass structures gets larger. Also, the frequency of occurring dynamic events such as earthquakes and blasting has been increasing. Thus, the shear behavior of rock joints under different conditions needs to be investigated. In this study, a series of direct shear tests were carried out under various conditions to examine the velocity-dependent shear behavior of saw-cut rock joints. Two types of direct shear test were carried out. The first was to examine the velocity-dependent shear behavior of saw-cut rock joints at seven different shear velocities, each with three different normal stresses. The second was to examine the shear behavior of saw-cut rock joints when three different instantaneous shear velocities changed. As a result, the coefficient of friction was affected by normal stress. The breakpoint velocity, the point when the change of shear velocity starts to affect the frictional behavior, became lower as normal stress increased. Also, as the shear velocity became lower, the degree of stress-drop on stick-slip behavior became larger. As a result of examining the changes of friction coefficient, velocity weakening (decrease of friction coefficient) was observed. The decrement of friction coefficient due to the changes of shear velocity under slow shear velocity was larger than that under fast shear velocity.

• Advances in Energy Research
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• v.1 no.2
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• pp.147-163
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• 2013

The world faces several issues of energy crisis and environmental deterioration due to over-dependence on single source of which is fossil fuel. Though, fuel is needed as ingredients for industrial development and growth of any country, however the fossil fuel which is a major source of energy for this purpose has always been terrifying thus the need for alternative and renewable energy sources. The search for alternative energy sources resulted into the acceptance of a biofuel as a reliable alternative energy source. This work presents the study of optimization of process of transesterification of vegetable oil to biodiesel using NaOH as catalyst. A $2^4$ factorial design method was employed to investigate the influence of ratio of oil to methanol, temperature, NaOH concentration, and transesterification time on the yield of biodiesel from vegetable oil. Low and high levels of the key factors considered were 4:1 and 6:1 mole ratio, 30 and $60^{\circ}C$ temperatures, 0.5 and 1.0 wt% catalyst concentration, and 30 and 60 min reaction time. Results obtained revealed that oil to methanol molar ratio of 6:1, tranesetrification temperature of $60^{\circ}C$, catalyst concentration of 1.0wt % and reaction time of 30 min are the best operating conditions for the optimum yield of biofuel from vegetable oil, with optimum yield of 95.8%. Results obtained on the characterizzation of the produced biodiesel indicate that the specific gravity, cloud point, flash point, sulphur content, viscosity, diesel index, centane number, acid value, free glycerine, total glycerine and total recovery are 0.8899, 4, 13, 0.0087%, 4.83, 25, 54.6. 0.228mgKOH/g, 0.018, 0.23% and 96% respectively. Results also indicate that the qualities of the biodiesel tested for are in conformity with the set standard. A model equation was developed based on the results obtained using a statistical tool. Analysis of variance (ANOVA) of data shows that mole ratio of ground nut oil to methanol and transesterification time have the most pronounced effect on the biodiesel yield with contributions of 55.06% and 9.22% respectively. It can be inferred from the results various conducted that vegetable oil locally produced from groundnut oil can be utilized as a feedstock for biodiesel production.

• Applied Microscopy
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• v.25 no.2
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• pp.53-64
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• 1995

This study was designed to investigate the morphological alterations of zonula occludens, macula adherences and gap junctions between the hepatocytes in the fasting conditions. Animals (Sprague Dawley, $250{\sim}280g$) were divided into two groups: normal and fasting. The latter were fasted for eight days prior to sampling. Liver tissues were sectioned and replicated after freeze fracturing for the transmission electron microscopy. In the normal rat liver, the interhepatocellular space at the area of some zonula occludens appeared to be widened in thin sections. On the freeze fracture replicas., the zonula occludens appeared as an anastomosing network of $2{\sim}4$ strands or grooves on P or E faces. Free ends and fragments of the strands were observed. In the rat fasted for eight days, the hepatocytes were diminished in size and the organelles were decreased in number and size. The intercellular space was wide at many areas of zonula occludens in thin section. On the freeze fracture replicas, the zonula occludens showed diminution or disappearence of anastomosing network of strands or grooves. Free ends and small fragments of the strands or grooves were frequently encountered. The macula adherens was markedly increased in number in thin sections, although they could not be found on the freeze fracture replicas. The gap junctions were increased in number in thin sections. Small aggregations of the intramembranous particles appeared with larger ones on the freeze fracture replica. The evidences may suggest the followings: (1) The disassembly of zonula occludens in the fasting states is led from the diminished mechanical stress on the luminal surface of bile canaliculus with the impaired secretion of bile components from the hepatocytes. (2) The increase of macula adherens is necessary to maintain the liver parenchyma integrity in the fasting state which leads the hepatocyte to be diminished and finally the intercellular space to be separated. (3) The rise in both number and size of gap junctions is owing to the need of increasing intercellular communication between the hepatocytes during the fasting. (4) The alteration of zonula occludens is easily led by the physiological condition of hepatocytes even in the normal ones.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.19-26
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• 2023

Hydrogen, a clean energy source free of COx emissions, is poised to replace fossil fuels, with its usage on the rise. Despite its high energy content per unit mass, hydrogen faces limitations in storage and transportation due to its low storage density and challenges in long-term storage. In contrast, ammonia offers a high storage capacity per unit volume and is relatively easy to liquefy, making it an attractive option for storing and transporting large volumes of hydrogen. While NH₃ decomposition is an endothermic reaction, achieving excellent low-temperature catalytic activity is essential for process efficiency and cost-effectiveness. The study examined the effects of different zeolite types (5A, NaY, ZSM5) on NH₃ decomposition activity, considering differences in pore structure, cations, and Si/Al-ratio. Notably, the 5A zeolite facilitated the high dispersion of Ni across the surface, inside pores, and within the structure. Its low Si/Al ratio contributed to abundant acidity, enhancing ammonia adsorption. Additionally, the presence of Na and Ca cations in the support created medium basic sites that improved N₂ desorption rates. As a result, among the prepared catalysts, the 15 wt%Ni/5A catalyst exhibited the highest NH₃ conversion and a high H₂ formation rate of 23.5 mmol/g_cat·min (30,000 mL/g_cat·h, 600 ℃). This performance was attributed to the strong metal-support interaction and the enhancement of N₂ desorption rates through the presence of medium basic sites.

• Korean Security Journal
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• no.22
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• pp.169-196
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• 2010

Although more priority is given to politicians from the aspect that they represent people and decide the future of country, the current situation is that politicians are not free from terrorism because of insufficient guard-concerned law, negative social recognition and increased crime and terrorism. The measure for politician terrorism shall be handled from the aspect of national security rather than public peace. For the purpose, basic legal foundation shall be prepared and specialized guard technique considering specialty of politician shall be established. Basic solution shall be established by reinforcing law against politician terrorism and establishing new law from the national viewpoint. The guard for politician has two faces that both of safety of guard target and voting intention of voter shall be met at the same time. Although special guard technique is required for guarding politician, current situation is that it is not researched professionally. In relation to the measure to develop the system of protection for politician, First, the study suggested legal foundation for politician guard. Although the 17th National Assembly proposed revised legal plan to protect politician from terrorism, it is suspended, expired and abolished now. The legal plan presented by members of the National Assembly was simply restricted to the scope of public guard. The study divided establishment of legal foundation into two things. The first one is the dispatch type of effective public guard and the second one is the transfer to private guard. Second, the study suggested environmental development method of politician guard. in the environment of politician guard, the study suggested improvement and development method by analyzing social recognition, politician's mind and voter's mind psychologically. After the beginning of human society, if human race is continued, political activity won't disappear. It is obvious that the safety of political leader is very important issue for human race because he plays the role to decide the future of human. In the future, more specialized, effective law shall be prepared and deeper study of scholar shall be performed.

• Management & Information Systems Review
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• v.37 no.3
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• pp.27-47
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• 2018

In this study, we examine how land use zoning affects the land price controlling other variables such as road-facing condition of the land, land form, land age after its development and land size. We employ geographically weighted regression analysis which reflects spatial dependency as methodology with a data sample of land transaction price data of Jangyu, a new town, in Korea. The results of our empirical analysis show that the respective coefficients of traditional regression and geographically weighted regression are not significantly different. However, after calculating Moran's Index with residuals of both OLS and GWR models, we find that Moran's Index of GWR decreases around 26% compared to that of OLS model, thus improving the problem of spatial autoregression of residuals considerably. Unlike our expectation, though, in both traditional regression and geographically weighted regression where residential exclusive area is used as a reference variable, the dummy variable of the residential land for both housing and shops shows a negative sign. This may be because the residential land for both housing and shops is usually located in the level area while the residential exclusive area is located at the foot of a mountain or on a gentle hill where the residents can have good quality air and scenery. Although the utility of the residential land for both housing and shops is higher than its counterpart's since it has higher floor area ratio, amenity which can be explained as high quality of air and scenery in this study seems to have higher impact in purchase of land for housing. On the other hand, land for neighbourhood living facility seems to be valued higher than any other land zonings used in this research since it has much higher floor area ratio than the two land zonings above and can have a building with up to 5 stories constructed on it. With regard to road-facing condition, land buyers seem to prefer land which faces a medium-width road as expected. Land facing a wide-width road may have some disadvantage in that it can be exposed to noise and exhaust gas from cars and that entrance may not be easy due to the high speed traffic of the road. In contrast, land facing a narrow road can be free of noise or fume from cars and have privacy protected while it has some inconvenience in that entrance may be blocked by cars parked in both sides of the narrow road. Finally, land age variable shows a negative sign, which means that the price of land declines over time. This may be because decline of the land price of Jangyu was bigger than that of other regions in Gimhae where Jangyu, a new town, also belong, during the global financial crisis of 2008.