• Tunnel and Underground Space
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• v.30 no.4
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• pp.320-334
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• 2020

This study presents an application of hydro-mechanical coupled Particle Flow Code 3D (PFC3D) to simulation of fluid injection induced fault slip experiment conducted in Mont Terri Switzerland as a part of a task in an international research project DECOVALEX-2019. We also aimed as identifying the current limitations of the modelling method and issues for further development. A fluid flow algorithm was developed and implemented in a 3D pore-pipe network model in a 3D bonded particle assembly using PFC3D v5, and was applied to Mont Terri Step 2 minor fault activation experiment. The simulated results showed that the injected fluid migrates through the permeable fault zone and induces fault deformation, demonstrating a full hydro-mechanical coupled behavior. The simulated results were, however, partially matching with the field measurement. The simulated pressure build-up at the monitoring location showed linear and progressive increase, whereas the field measurement showed an abrupt increase associated with the fault slip We conclude that such difference between the modelling and the field test is due to the structure of the fault in the model which was represented as a combination of damage zone and core fractures. The modelled fault is likely larger in size than the real fault in Mont Terri site. Therefore, the modelled fault allows several path ways of fluid flow from the injection location to the pressure monitoring location, leading to smooth pressure build-up at the monitoring location while the injection pressure increases, and an early start of pressure decay even before the injection pressure reaches the maximum. We also conclude that the clay filling in the real fault could have acted as a fluid barrier which may have resulted in formation of fluid over-pressurization locally in the fault. Unlike the pressure result, the simulated fault deformations were matching with the field measurements. A better way of modelling a heterogeneous clay-filled fault structure with a narrow zone should be studied further to improve the applicability of the modelling method to fluid injection induced fault activation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.1
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• pp.50-56
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• 2016

Direct seeding of sorghum (Sorghum bicolor L. Moench) has a problem of low yield including poor establishment. This poor establishment results from poor quality seed, poor seedbed preparation, seedling pests, poor sowing technique and high soil temperature. This study sought to establish the age at which sorghum seedlings can be transplanted with minimal effects on grain yield. Transplants were raised in 128 nursery tray pot. Five seedling ages were established by transplanting at 10 (T10), 15 (T15), 20 (T20), 25 (T25) and 30 (T30) days after planting (DAP). The treatment combinations were arranged in a randomized complete block design and replicated three times with an individual plot size of $6{\times}5m^2$. Each plot had five ridges with a planting space of $0.60{\times}0.20m^2$ at one plants per stand. Results showed that seedling age on transplanting significantly affected growths and yields to sorghum after transplanting. Plant heights and diameters of transplants at T15 were longer than the other transplants. Conclusively, The advantages of this practice were better control of crop density and greater yields; either to fill gaps after emerging and thinning of crops or to compensate for a growth period that was too short for a complete crop cycle.

• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.127-135
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• 1998

The Born approximation is widely used for solving the complex scattering problems in electromagnetics. Approximating total internal electric field by the background field is reasonable for small material contrasts as long as scatterer is not too large and the frequency is not too high. However in many geophysical applications, moderate and high conductivity contrasts cause both real and imaginary part of internal electric field to differ greatly from background. In the extended Born approximation, which can improve the accuracy of Born approximation dramatically, the total electric field in the integral over the scattering volume is approximated by the background electric field projected to a depolarization tensor. The finite difference and elements methods are usually used in EM scattering problems with a 2D model and a 3D source, due to their capability for simulating complex subsurface conductivity distributions. The price paid for a 3D source is that many wavenumber domain solutions and their inverse Fourier transform must be computed. In these differential equation methods, all the area including homogeneous region should be discretized, which increases the number of nodes and matrix size. Therefore, the differential equation methods need a lot of computing time and large memory. In this study, EM modeling program for a 2D model and a 3D source is developed, which is based on the extended Born approximation. The solution is very fast and stable. Using the program, crosshole EM responses with a vertical magnetic dipole source are obtained and the results are compared with those of 3D integral equation solutions. The agreement between the integral equation solution and extended Born approximation is remarkable within the entire frequency range, but degrades with the increase of conductivity contrast between anomalous body and background medium. The extended Born approximation is accurate in the case conductivity contrast is lower than 1:10. Therefore, the location and conductivity of the anomalous body can be estimated effectively by the extended Born approximation although the quantitative estimate of conductivity is difficult for the case conductivity contrast is too high.

• Restorative Dentistry and Endodontics
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• v.32 no.6
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• pp.498-513
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• 2007

Since it was reported that incipient enamel caries can be recovered, previous studies have quantitatively evaluated that enamel artificial caries have been, remineralized with fluoride showing simultaneously the increase of width of surface layer and the decrease of width of the body of legion. There is, however, little report which showed that remineralization could occur without fluoride. In addition, the observations on the change of hydroxyapatite crystals also have been scarcely seen. In this study, enamel caries in intact premolars or molars was induced by using lactic acidulated buffering solutions over 2 days. Then decalcified specimens were remineralized by seven groups of solutions using different degree of saturation(0.212, 0.239, 0.301, 0.355) and different pH(5.0, 5.5, 6.0) over 10 days. A qualitative comparison to changes of hydroxyapatite crystals after fracturing teeth was made under SEM(scanning electron microscopy) and AFM(atomic force microscopy). The results were as follows: 1. The size of hydroxyapatite crystals in demineralized area was smaller than the normal ones. While the space among crystals was expanded, it was observed that crystals are arranged irregularly. 2. In remineralized enamel area, the enlarged crystals with various shape were observed when the crystals were fused and new small crystals in intercrystalline spaces were deposited. 3. Group 3 and 4 with higher degree of saturation at same pH showed the formation of large clusters by aggregation of small crystals from the surface layer to the lesion body than group 1 and 2 with relatively low degree of saturation at same pH did. Especially group 4 showed complete remineralization to the body of lesions. Group 5 and 6 with lower pH at similar degree of saturation showed remineralization to the body of lesions while group 7 didn't show it. Unlike in Group 3 and 4, Group 5 and 6 showed that each particle was densely distributed with clear appearance rather than crystals form clusters together.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.35 no.2
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• pp.15-25
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• 2017

The objective of this study is to investigate the value of rock Korean chessboards as a corroborative evidence that go, the play culture naturalized from the past, was also performed under the pavilion of the mountain stream, and the old tree. This study executes analysis on the location and form of rock Korean chessboards, physical environment such as the position of surrounding space, the origin of the nomination, surrounding landscape, and historical significance through the research analysis of comprehensive present conditions, and highlights the position types, landscape significance, and preservation value of the rock Korean chessboards of Korea from diverse angles. The result is as follows. 1. The styles of Korean chess (將棋), which identically propagated in the representative countries of Eastern culture, Korea, China, and Japan, and modified in accordance with each country's idea and native tendency, were organized, and confirmed the Korean Go as a naturalized native culture. 2. Out of 15 rock Korean chessboards confirmed through this study, 9 (60%) were categorized as rock Korean chessboards, and 6 (40%) were categorized as stone Korean chessboards. Also, the average size of the go boards were $51cm{\times}46.6cm$, which demonstrated not much difference with present day universal go boards. The Pearson correlation coefficient between bed rock and go boards were 0.647, demonstrating a relatively high correlation; the research subject of rock go boards have been constructed in consideration of rationality, convenience, and the value of promotion of public welfare. 3. The results of analysis of location patterns of rock Korean chessboard showed that villages (87%), mooring (73%), plains (60%) and mountains (47%). The most frequent location pattern is mooring and village, and these two factors played the most important role in determining the location of the rock Korean chessboard.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.37 no.3
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• pp.37-48
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• 2019

This study, which starting from Yangyang Jukdo's topography formation and questioning revealed in landscape guide and landscape commentary board, is to sort out the characteristics of Jukdo natural landscape through literature research, field observation research and stakeholder interview as part of the proper recognition of Jokdo landscape and search for landscape resources, and pursued a review of nominations and criticism. The results of this study are summarized as follows. Yangyang Jukdo is an island named because it was full of blue bamboo. From before the first half of the 14th Century. to the middle of the 18th Century., there was a Gwanlan-pavilion to see the sea and the bamboo in the west. The time when the original island, the Jukdo, have been a land-tied island connected with the land by the tombolo formed by the erosion of the sand. It is located at the end of the 14th Century. and before the middle of the 18th Century. In Jukdo, colorful weathered terrains, coastal terrain, and structural terrain formed by long-time weathering are found. Among them, the type of weathering, the tafoni style and the gnamma style are the scenic landscapes with the key stories of legend and poetry that are brought to Jukdo. In addition, there are seven kinds of letters caved in the rocks in Jukdo. The rocks found on the coast, basketball cannons, shrines, and sutras are seen as shrouds based on a Taoist hermit motifs and style. In addition, it can be interred from the photography of "jeongssisejeog" that the souvenir of Jukdo was the family of Chogyejeong of mid 18th Century. In terms of observational geography and poetry, Jukdo has been handed down a great deal of missionary color with key motifs such as 'Jukdo-seongoo', 'Jukdo-Dolgooyoo', or 'Stone mortar of Taoist hermit' It is proved that the pearl which is called 'The stone of the Taoist hermit' is a porthole formed in a separate space rather than the topography of the geomorphology in terms of shape, size and function. Currently named Shun-tang is a product of the ridiculous 'naming' of interest. The present landscape guide and commentary is not only incompatible with the place of Jukdo, but also does not match the traditional cultural landscape. Future scenery information such as guide signs and commentary boards should be improved in the direction of positively highlighting the stories and motifs related to the present that are present in order to enhance the landscape identity of Yangyang Jukdo.

• Journal of architectural history
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• v.3 no.1
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• pp.83-99
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• 1994

Ch'ang-Ts'al-Ts'un is a rural Village near Lung-jing City in Yen-pien Korean Autonomous Province of China. It was formed about 100 years ago by Korean Immigrants and has been developed maintaing the characteristics of traditional Korean architecture. Therefore investigating the spatial structure of this village is a meanigful work to confirm and explore one branch of Korean architecture. This study aims at analyzing the spatial structure of the village using direct data collected from the field work and indirect data from books and maps. The field work consists of on-the-site survey of the village layout, interviews of residents, observation notes and photography. Ch'ang-Ts'ai-Ts'un is located 360-370 m high above the sea level and at the side of a long valley. A river flows in the middle of the valley and relatively flat arable land exists at the both sides of the river. The location of the village related to the surrounding river and mountains suggests that the site of the village was chosen according to Feng-Shui, Chinese and Korean traditional architectural theory. The main direction of the house layouts is South-western. The village has been growing gradually until today. Therefore it is meaningful to make the village layout before Liberation(1946 A.D.) because the characteristics of Korean architecture prevailed more in that period. The area of the previous village is limited to the west side of the creek. New houses were later added to the east of the creek, forming a 'New Village'. Previously the village was composed of 3 small villages: Up, Middle and Down. Also the main access roads connecting the village with the neighboring villages were penetrating the village transversely. Presently the main access road comes to the village longitudinally from the main highway located in front of the village. The retrospective layout shows the existence of well-formed Territory, Places and Axes, thus suggesting a coherent Micro-cosmos. The boundary of imaginery territory perceived by present residents could be defined by linking conspicous outside places sorrounding the village such as Five-mountains, Front-mountain, Shin-dong village, Standing-rock, Rear-mountain and Myong-dong village. Inside the territory there are also the important places such as Bus-stop, Memorial tower of patriots, Road-maitenance building and the village itself. And inside it 5 transverse and 1 longitudinal axes exist in the form of river, roads and mountains. The perceived spatial structure of the village formed by Places, Axes and Territory is geometrical and well-balanced and suggests this village is fit for human settlement. The administrative area of the village is about 738 ha, 27 % of which is cultivated land and the rest is mountain area. Initially the village and surrounndings were covered with natural forest But the trees have been gradually cut down for building and warning houses, resulting in the present barren and artificial landscape with bare mountains and cultivated land. At present the area of the village occupied by houses is wedge-shaped, 600 m wide and 220 m deep in its maximum. The total area of the village is $122,175m^{2}$. The area and the rate of each sub-division arc as follow. 116 house-lots $91,465m^{2}$ (74.9 %) Land for public buildings and shops $2,980m^{2}$ (2.4 %) Roads $17,106m^{2}$ (14.0 %) Creek $1,356m^{2}$ (1.1 %) Vacant spaces and others $9,268m^{2}$ (7.6 %) TOTAL $122,175m^{2}$ (100.0 %) Each lot is fenced around with vertical wooden pannels 1.5-1.8 m high and each house is located to the backside of the lot. The open space of a lot is sub-divided into three areas using the same wooden fence: Front yard, Back yard and Access area. Front and back yards are generally used for crop-cultivation, the custom of which is rare in Korea. The number of lots is 116 and the average size of area is $694.7m^{2}$. Outdoor spaces in the village such as roads, vacant spaces, front yard of the cultural hall, front yard of shops and spacse around the creek are good 'behavioral settings' frequently used by residents for play, chatting, drinking and movie-watching. The road system of the village is net-shaped, having T-junctions in intersections. The road could be graded to 4 categories according to their functions: Access roads, Inner trunk roads, Connecting roads and Culs-de-sac. The total length of the road inside the village is 3,709 m and the average width is 4.6 m. The main direction of the road in the village is NNE-SSE and ESE-WNW, crossing with right angles. Conclusively, the spatial structure of Ch'ang-Ts'ai-Ts'un village consists of various components in different dimensions and these components form a coherent structure in each dimension. Therefore the village has a proper spatial structure meaningful and appropriate for human living.

• Journal of the Korean Geographical Society
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• v.31 no.1
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• pp.1-18
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• 1996

This study examines the spatial characteristics of postal office patronage in rural areas. in the light of future possible relocation and closures of the postal facilities. Most of private services have flown out small rural central places due to the decrease of supporting population, and there consequently remain only a few public services including government-run post offices at the Myon seats, the lowest level among rural central places in Korea. The small local population and its further decline undermine the rationale for maintaining such public services in depleted rural areas. For the worse of it, the government recently plans to transform the postal system to a quasi-private, corporational structure. One can fear that the profit-seeking nature of the new postal corporation will inevitably force to close many of such small rural facilities. The study first analysed nation-wide censuses of postal offices for the years of 1986 and 1992. The postal services examined are per capita number of postal stamps and revenue stamps sold, and letters, parcels, telegrams and monetary transactions handled at the post offices. It is found that, while the usage of postal services has increased substantially throughout the nation during the period of 1986-1992, the increment has largely been occurred by urban post offices rather than by those in Gun seats (i.e., rural counties); and that the gap of the service levels between urban and rural post offices is ever widening. The study further examined the service differentials among the post offices within rural counties to find that those post offices adjacent to the county (Gun) seats and larger urban centers rendered less amount of services than remote rural post offices, indicating that rural residents tend to partonize larger centers more and more than local Myon seats. At the second stage of the study, questionnaire surveys were conducted in Muju, Kimpo, and Hongsung-Gun's. These three counties are meant to represent respectively the remote, suburban, and intermediary counties in Korea. The analyses of survey data reveal that the postal hinterlands of the county seats extend to much of nearby Myons, the subdivisions of a Gun. It is also found that the extent of postal hinterlands of the three counties and the magnitude of patronage and quite different from each other depending upon the topography, population density, and the propinquity of the counties to metropolitan centers. The findings suggest to reappraise the current flat allocation scheme of public facilites to each of rural subdivisions throughout the nation. A detailed analysis on the travel behavior of the survey respondents yields that age is the most salient variable to distinguish activity spaces of rural residents. The activity spaces of older respondents tend to be more limited within their Myon, whereas those of younger respondents extend across the Myon boundary, toward the central towns and even distant larger cities. The very existence of several activity spaces in rural areas calls for an attention in the future locational decisions of public facilities. The locational criteria, employed by the Ministry of Communication of Korean government to establish a post office, are the size of hinterland population and the distance from adjacent postal facilities. The present study findings suggest two additional criteria: the order in rural central place hierarchy and the propinquity to the upper-level centers of the central hierarchy. These old and new criteria are complementary each other in that the former criteria are employed to determine new office locations, whereas the latter are appropriate to determine facility relocation and closures.