• 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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.325-334
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• 2008

The standard prestressed concrete I-girder bridge (PSC I-girder bridge) is one of the most prevalent types for small and medium bridges in Korea. When determining the member forces in a section to assess the safety of girder in this type of bridge, the general practice is to use the simplified practical equations or the live load distribution factors proposed in design standards rather than the precise analysis through the finite element method or so. Meanwhile, the live load distribution factors currently used in Korean design practice are just a reflection of overseas research results or design standards without alterations. Therefore, it is necessary to develop an equation of the live load distribution factors fit for the design conditions of Korea, considering the standardized section of standard PSC I-girder bridges and the design strength of concrete. In this study, to develop an equation of the live load distribution factors, a parametric analysis and sensitivity analysis were carried out on the parameters such as width of bridge, span length, girder spacing, width of traffic lane, etc. As a result, the major variables to determine the size of distribution factors were girder spacing, overhang length and span length in case of external girders. For internal adjacent girders, the determinant factors were girder spacing, overhang length, span length and width of bridge. For internal girders, the factors were girder spacing, width of bridge and span length. Then, an equation of live load distribution factors was developed through the multiple linear regression analysis on the results of parametric analysis. When the actual practice engineers design a bridge with the equation of live load distribution factors developed here, they will determine the design of member forces ensuring the appropriate safety rate more easily. Moreover, in the preliminary design, this model is expected to save much time for the repetitive design to improve the structural efficiency of PSC I-girder bridges.

• Korean Journal of Veterinary Research
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• v.37 no.1
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• pp.71-78
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• 1997

This study was designed to investigate the number of the growing and mature follicles following gonadotrophin treatments for superovulation in mature rats. Eighteen mature rats (Sprague-Duwely, initially 190~230gm) were randomly alloted into 3 groups. One group was control group, another FSH-treated group was injected intramuscularly with 0.5 units of follicular stimulating hormone (FSH) / rat, and third PMS and HCG-treated group was intramuscularly injected with 20~25IU of pregnant mare serum (PMS) / rat and then at the 48 hrs later, with 20~25IU of human chorionic gonadotrophin (HCG) / rat. The uteri and ovaries of rats were collected and then were observed grossly and serial sections of paraffin embedding ovaries were stained with H-E. Number of ovarian follicles by following 3 grades of large, middle and small follicles from secondary and tertiary follicles were investigated by LM photography of preparations. Small follicles were classified as secondary follicles of preantral follicles with more than 2 layers of granulosa cells surrounding the oocyte and middle follicles were classified as secondary follicles with early signs of antral cavity or with more than one small cavity on either side of the oocytes and large follicles were classified as tertiary follicles with a single medium sized antral cavity or large well-formed antral cavity. In gross findings, the uteri were slightly swelling in FSH-treated group and markedly swelling or filled with fluid in the uterine lumen in PMS and HCG-treated group. In histological findings, the shape and size of the follicles were diverse in middle and large follicles of FSH-treated group and PMS and HCG-treated group, and proportion of atretic follicles was increased in FSH-treated group and PMS and HCG-treated group than those in control group. The uteri of FSH-treated group and PMS and HCG-treated group were hypertropied or filled with fluid in the lumens and walls of uteri. The wall tissue layers were flattened and their blood and lymph vessels were dilated. The mean number of follicle per ovary in control group were appeared to be $17.1{\pm}5.6$($14.0%{\pm}4.6%$), $37.8{\pm}9.1$($30.9{\pm}7.4%$) and $67.6{\pm}30.1$($55.2{\pm}24.6%$) respectively at large, middle and small follicles and total number of these 3 grade follicles were appeared to be $122.5{\pm}40.0$. The mean number of follicle per ovary in FSH-treated group were appeared to be $22.8{\pm}7.0$($17.4%{\pm}5.3%$), $43.4{\pm}6.6$($33.2{\pm}5.1%$) and $64.5{\pm}13.0$($49.3{\pm}9.9%$) respectively at large, middle and small follicles and total number of these 3 grade follicles were appeared to be $130.7{\pm}16.6$. The mean number of follicle per ovary in PMS and HCG-treated group were appeared to be $29.7{\pm}11.0$($16.3%{\pm}6.0%$), $61.9{\pm}17.2$($33.9{\pm}9.4%$) and $91.1{\pm}28.2$($49.9{\pm}15.4%$) respectively at large, middle and small follicles and total number of these 3 grade follicles were appeared to be $182.6{\pm}32.7$. The above findings reveal that large follicles were increased 29.8% in FSH-treated group and 73.7% in PMS and HCG-treated group than those in control group and in histologic findings, proportion of atretic follicles were more increased in ovaries with more number of more developing follicles.

• Journal of the Korean association of regional geographers
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• v.5 no.2
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• pp.1-14
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• 1999

In the course of modernization and globalization, each region in Korea has experienced deep subordination to the center of Seoul and the increase of colonization possibility by world capital. In order to overcome the current situation, above all, the strategies should be developed focusing on daily life and life space. The basis for the development of strategies is the establishment of regional identity on life space. It is because of the reason that life space, or small-scale region has drawn wide attention in the research of geography in recent years. Especially, humanistic geography and new regional geography have developed the concerning theory and methodology, and kept going on the research of small-scale regions. Generally speaking, there have been quite large amount of theoretical discussions on small-scale region in recent years in the field of geography. Empirical researches focusing on a particular small-scale region, however, have been rarely made. It seems related to the deficiency of data materials and the obscurity of research framework of small-scale regional geography. A community paper must be very helpful for the geographic research on small-scale region. As community paper is published based on county('gun'), small or mid-size city('si'), or district of large city('gu'), it deals with small news and daily life information closely attached to the region. Accordingly, it functions as a medium of the formation of regional identity. It is also a valuable source material for the validation of regional identity and for the analysis of identity-shaping mechanism. The geographic interests in community paper, first of all, should be taken shape by the work on the geographical distribution and the periodic change of publication situation of community papers in Korea. Another research subject on community paper is the examination of characteristics of the region by analyzing the news and the advertisements. The news in community paper must be a valuable data source of regional studies in geography. Also, the regional identification process of community people through the community paper could be and should be explored, and how the regional centrality, or self-generation based on the identity is achieved will be an important subject.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.285-293
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• 2018

This study aimed to evaluate the effect of height suppression of cucumber and tomato plug seedlings as affected by mechanical stimulus using brushing as environment-friendly method. Cucumber (Cucumis sativus L. 'Joeunbaekdadagi') and tomato (Solanum lycopersicum L. 'Mini Chal') seeds were sown in 40-cell plug trays ($54{\times}27.5{\times}5cm$) filled with growing medium on Oct. 9, 2017. The cultivation environment in a venlo-type glasshouse was maintained as cultivation temperature range of $15-25^{\circ}C$ and the relative humidity of $50{\pm}10%$. Nontreatment and diniconazole ($7.5mg{\cdot}L^{-1}$) application at 15 days after sowing were used as the control. In addition, brushing treatments in cucumber and tomato were applied interval of 2, 4 or 6 hrs for 15 and 20 days, respectively. Plant height, hypocotyl length, and internode length were inhibited for cucumber and tomato in the diniconazole treatment than in the control. The leaf size was reduced, both cucumber and tomato, while the SPAD increased under the diniconazole treatment. However, stem diameter of cucumber was the thickest in the 2 hrs brushing interval treatment. Fresh weights of shoot and root were the significantly lowest in the diniconazole treatment. Application of brushing improved seedlings quality by promoting dry weights of shoot and root, and compactness of tomato seedlings. The chlorophyll fluorescence of tomato seedlings drastically decreased with 2 hrs treatment, indicating that mechanical stress by brushing treatment. The relative growth rate of tomato seedlings was significantly lower in the diniconazole treatment, but cucumber seedlings were not significantly different in all treatments. As a results, height suppression of cucumber and tomato seedlings was best achievement in the diniconazole treatment by the chemical as growth regulator. In an environment-friendly point of view, however, it is considered that 2 hrs brushing interval treatment can be the applicability for replacing the chemical methods in plug seedling growth of cucumber and tomato.

• Journal of Preventive Medicine and Public Health
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• v.25 no.3 s.39
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• pp.312-329
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• 1992

The purpose of this study is to estimate cesarean section rate in Korea and analyze the socioeconomic variables and health resources which affect regional variation in the rate. Samples were drawn from the record of vaginal and cesarean section deliveries based upon insurance claim bills which have been submitted to the National Federation of Medical Insurance for the first three months, January through March, 1991. The results are obtained as follows : It was found that. cesarean section rate was increasing rapidly up to 23.1% in 1991. Cesarean section per 10 thousand insured people was 4.8 and the number of cesarean section per 10 thousand insured eligible($15{\sim}49$ years old) female was 7.6. The fee for normal delivery was 109,489 won and that for cesarean section was 390,024 won. The average days of hospitalization in normal delivery was 2.3 days, and those in cesarean section was 7.6 days. On the average cesarean section has a longer of stay as much as by 4.3 days and cost 3.6 times more than normal deliveries. Cesarean section rates vary among medical facilities 19.8% at clinics 37.6% in small-scale hospitals, and 29.1% in general hospitals. The regional variation of cesarean section rates was also fairly prominent. The South Cheju Gun has the highest rate of cesarean section, 56.2%. Meanwhile no cesarean section cases has been reported in Sunchang Gun during the period of this study. The variation is noted among provinces. The rate for Cheju province has been 3.4 times higher than that for Chunnam. The number of cesarean section per 10 thousand insured people vary greatly among regions, too. This study has found that there exists significant regional variations among various geographic units in terms of average length of stay, average cost, number of obsretricians and number of beds. Multiple regression analysis was done to identify factors explaining the regional variance of various cesarean section rates : In the urban areas, no significant explaining variables were noted except the number of beds for the dependent variable of cesarean section cases per 10 thousand insured eligible females. The smaller the number of bed, the more cases of cesarean section was noted for an urban area. The is mostly because the rate of cesarean section is higher in medium-size hospitals than in large general hospitals. In the rural areas, the factor of education has been found significant for all three deplendent variables. The higher the educational level, the rate of cesarean section is most likely to rise. An income variable measured by the amount of monthly insurance contribution has been identified a powerful predictor in explaining the valiance of cesarean section rates. The same has been noted for the number of obstetricians. Similar findings are observed for the country as a whole. The income level has veen found as the most powerful explaining factor in the regional variance of cesarean section rates. In general the rate is higher in the urban areas, and lower in the area with more small hospitals. As this is the initial attempt to identify the factors relevant to the regional difference in the rates of cesarean section, more elaborated study is urgently required.

• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.367-375
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• 2010

Understanding the interactions between earth materials and fluids is essential for studying the diverse geological processes in the Earth's surface and interior. In order to better understand the interactions between earth materials and fluids, we explore the effect of specific surface area and porosity on structural parameters of pore structures. We obtained 3D pore structures, using random packing simulations of porous media composed of single sized spheres with varying the particle size and porosity, and then we analyzed configurational entropy for 2D cross sections of porous media and cube counting fractal dimension for 3D porous networks. The results of the configurational entropy analysis show that the entropy length decreases from 0.8 to 0.2 with increasing specific surface area from 2.4 to $8.3mm^2/mm^3$, and the maximum configurational entropy increases from 0.94 to 0.99 with increasing porosity from 0.33 to 0.46. On the basis of the strong correlation between the liquid volume fraction (i.e., porosity) and configurational entropy, we suggest that elastic properties and viscosity of mantle melts can be expressed using configurational entropy. The results of the cube counting fractal dimension analysis show that cube counting fractal dimension increases with increasing porosity at constant specific surface area, and increases from 2.65 to 2.98 with increasing specific surface area from 2.4 to $8.3mm^2/mm^3$. On the basis of the strong correlation among cube counting fractal dimension, specific surface area, and porosity, we suggest that seismic wave attenuation and structural disorder in fluid-rock-melt composites can be described using cube counting fractal dimension.

• Journal of Intelligence and Information Systems
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• v.21 no.3
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• pp.79-99
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• 2015

The prediction of bankruptcy has been extensively studied in the accounting and finance field. It can have an important impact on lending decisions and the profitability of financial institutions in terms of risk management. Many researchers have focused on constructing a more robust bankruptcy prediction model. Early studies primarily used statistical techniques such as multiple discriminant analysis (MDA) and logit analysis for bankruptcy prediction. However, many studies have demonstrated that artificial intelligence (AI) approaches, such as artificial neural networks (ANN), decision trees, case-based reasoning (CBR), and support vector machine (SVM), have been outperforming statistical techniques since 1990s for business classification problems because statistical methods have some rigid assumptions in their application. In previous studies on corporate bankruptcy, many researchers have focused on developing a bankruptcy prediction model using financial ratios. However, there are few studies that suggest the specific types of bankruptcy. Previous bankruptcy prediction models have generally been interested in predicting whether or not firms will become bankrupt. Most of the studies on bankruptcy types have focused on reviewing the previous literature or performing a case study. Thus, this study develops a model using data mining techniques for predicting the specific types of bankruptcy as well as the occurrence of bankruptcy in Korean small- and medium-sized construction firms in terms of profitability, stability, and activity index. Thus, firms will be able to prevent it from occurring in advance. We propose a hybrid approach using two artificial neural networks (ANNs) for the prediction of bankruptcy types. The first is a back-propagation neural network (BPN) model using supervised learning for bankruptcy prediction and the second is a self-organizing map (SOM) model using unsupervised learning to classify bankruptcy data into several types. Based on the constructed model, we predict the bankruptcy of companies by applying the BPN model to a validation set that was not utilized in the development of the model. This allows for identifying the specific types of bankruptcy by using bankruptcy data predicted by the BPN model. We calculated the average of selected input variables through statistical test for each cluster to interpret characteristics of the derived clusters in the SOM model. Each cluster represents bankruptcy type classified through data of bankruptcy firms, and input variables indicate financial ratios in interpreting the meaning of each cluster. The experimental result shows that each of five bankruptcy types has different characteristics according to financial ratios. Type 1 (severe bankruptcy) has inferior financial statements except for EBITDA (earnings before interest, taxes, depreciation, and amortization) to sales based on the clustering results. Type 2 (lack of stability) has a low quick ratio, low stockholder's equity to total assets, and high total borrowings to total assets. Type 3 (lack of activity) has a slightly low total asset turnover and fixed asset turnover. Type 4 (lack of profitability) has low retained earnings to total assets and EBITDA to sales which represent the indices of profitability. Type 5 (recoverable bankruptcy) includes firms that have a relatively good financial condition as compared to other bankruptcy types even though they are bankrupt. Based on the findings, researchers and practitioners engaged in the credit evaluation field can obtain more useful information about the types of corporate bankruptcy. In this paper, we utilized the financial ratios of firms to classify bankruptcy types. It is important to select the input variables that correctly predict bankruptcy and meaningfully classify the type of bankruptcy. In a further study, we will include non-financial factors such as size, industry, and age of the firms. Thus, we can obtain realistic clustering results for bankruptcy types by combining qualitative factors and reflecting the domain knowledge of experts.

• Journal of radiological science and technology
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• v.35 no.2
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• pp.157-164
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• 2012

The purpose of this study is to analyze the dose distribution when wedge filter is used in the various tissue electron density materials. The dose distribution was assessed that the enhanced dynamic wedge filter and physical wedge filter were used in the solid water phantom, cork phantom, and air cavity. The film dosimetry was suitable simple to measure 2D dose distribution. Therefore, the radiochromic films (Gafchromic EBT2, ISP, NJ, USA) were selected to measure and to analyze the dose distributions. A linear accelerator using 6 MV photon were irradiated to field size of $10{\times}10cm^2$ with 400 MUs. The dose distributions of EBT2 films were analyzed the in-field area and penumbra regions by using dose analysis program. In the dose distributions of wedge field, the dose from a physical wedge was higher than that from a dynamic wedge at the same electron density materials. A dose distributions of wedge type in the solid water phantom and the cork phantom were in agreements with 2%. However, the dose distribution in air cavity showed the large difference with those in the solid water phantom or cork phantom dose distributions. Dose distribution of wedge field in air cavity was not shown the wedge effect. The penumbra width, out of the field of thick and thin, was observed larger from 1 cm to 2 cm at the thick end. The penumbra of physical wedge filter was much larger average 6% than the dynamic wedge filter. If the physical wedge filter is used, the dose was increased to effect the scatter that interacted with photon and physical wedge. In the case of difference in electron like the soft tissue, lung, and air, the transmission, absorption, and scattering were changed in the medium at high energy photon. Therefore, the treatment at the difference electron density should be inhomogeneity correction in treatment planning system.

• Land and Housing Review
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• v.2 no.4
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• pp.559-568
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• 2011

This study aims at listing up those manufacturing activities sensitive to regional characteristics by analyzing locational hierarchy designed on the urban rank-size rule. This locational hierarchy by manufacturing activities is expected to provide a ground for the proper supply of an industrial complex. The analysis of the locational hierarchy by manufacturing activities can work as a method of observing the characteristics of the distribution of location for each economic activity by analyzing the trend in the change of manufacturing location. Consequently, it can be used to determine the appropriate manufacturing activities for the industrial complex of a particular region. Here, the locational hierarchy is analyzed depending on the base of the basic local government such as Gun(district level) and Si(city level), and manufacturing activities are categorized by Korea Standard Industry Code. Those activities demonstrating growth pattern are Manufacture of Electronic Equipment(KSIC 26), Manufacture of Medical Precision Optical Instruments Watch(KSIC 27), Manufacture of Motor Vehicles (KSIC 30, 31), etc. With proper infrastructures, these activities can be located everywhere. Those sectors on the decline pattern in the locational hierarchy can be summarized as Manufacture of Tobacco Products(KSIC 12), Manufacture of wearing apparel Fur Articles(KSIC 14), etc. Those sectors scattered widely in the locational hierarchy are Manufacture of Food Products(KSIC 10), Manufacture of Coke Petroleum Products(KSIC 19), Manufacture of Chemical Products(KSIC 20), Manufacture of Electronic Equipment(KSIC 26). These particular manufacturing activities can be operated in those regions in a sufficient supply of unskilled workers regardless of proper infrastructures. Those activities that have a tendency to reconcentrate on larger cities are Manufacture of Textiles(KSIC 13), Manufacture of Wearing Apparel Clothing Fur Articles(KSIC 14), Manufacture of Other Transport Equiptmen(KSIC 31). In most cases, these sectors tend to favor their existing agglomerated areas and concentrate around large cities. Therefore, it is inefficient to promote these sectors in small or medium-sized cities or underdeveloped regions. The establishment of developmental strategies of an industrial complex can gain greater competitiveness by observing such characteristics of the locational hierarchy.