• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1309-1315
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• 2014

The switch for a maglev vehicle should be designed such that the vehicle safely changes its track without touching the guiderail. In particular, a medium-to-low-speed EMS -type maglev train relies heavily on a U-type electromagnet where it generates levitation force and guidance force simultaneously. Therefore, it is necessary to evaluate the safety of the vehicle whenever it passes the switch, as it lacks active control of the guidance force. Furthermore, when the vehicle passes a segmented switch, which is a group of curves made up of connected lines with a small radius of curvature, it may come into mechanical contact with the guiderail owing to the excessive lateral displacement of the electromagnet. The goal of this study is to analyze the influence of a segmented switch on the safety of major design-related variables for achieving improved running safety. We propose a three-dimensional multibody dynamics model composed of two cars with one body. Using the proposed model, we perform a simulation of the lateral air gap, which is one of the measurements of the running safety of the vehicle when it passes the switch. The analyzed design variables are the length between short span girder, the articulation angle, the length between two centers of a fixed girder at its ends, and the number of girders. On the basis of the effects of the considered design variables, we establish an optimized design of a switch with improved safety.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.77-82
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• 2014

Stretchable electrodes are focused due to many demands for soft electronics. One of the candidates, carbon black composites have advantages of low cost, easy processing and decreasing resistivity in a certain range during stretching. However, the electrical conductivity of carbon black composites is not enough for electronic devices. Graphene is 2-dimensional nanostructured carbon based material which shows good electrical properties and flexibility. They may help to improve electrical conductivity of the carbon black composites. In this study, graphene was added to a carbon black electrode to enhance electrical properties and investigated. Electrical resistivity of graphene added carbon electrode decreased comparing with that of carbon black electrode because graphene bridged non-contacting carbon black aggregates to strengthen the conductive network. Also graphene reduced an increase in the resistance of the carbon black electrode applied to strain because they connected gap of separated carbon black aggregates and aligned along the stretching direction at the same time. In conclusion, an addition of graphene to carbon black gives two benefits on the electrical properties of carbon black composite as a stretchable electrode.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.42-47
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• 2017

In this study,we conducted an injection molding analysis of metal powder materials for the development of flanges, which are necessary adapters for optical communication. The metal powder injection molding process is a technique for producing an injection molded article having a complicated shape by mixing ceramic or stainless powder and binders. It is used to produce products which require complex processing technology or for which the productivity is low. The purpose of this study is to minimize the manufacturing processing of products which are manufactured through existing mechanical processing procedures. For the injection molding analysis, we mixed stainless STS316 metal powder with binders at a ratio of 6 to 4 to make molding materials consisting of granular pellets. Then, three-dimensional modeling and meshing were carried out to obtain the optimal injection molding analysis conditions(molding temperature, melting temperature, injection time, injection temperature, injection pressure, packing time and cooling time). As a result of the analysis, it was discovered that the inlet became available 13.29 seconds after the first injection. Also, as the flowing and packing in the melt through the sprue, runner and gate were stable, it is expected that good molds can be manufactured.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.58-63
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• 2010

The glass-ceramics made from the mixture of coal bottom ash, produced from a thermal power plant mixed with $Na_2O$ and $Li_2O$ was fabricated and their crystallization behavior was studied using a non-isothermal analyzing method. The temperature for 50% crystallization was higher than the exothermic peak temperature $T_p$ at DTA curve and the quickest crystallization temperature was much the same as $T_p$ as identified from the relationships of crystallized fraction and crystallization rate with temperature. By using Kissinger equation describing a crystallization behavior, the activation energy (262 kJ/mol), the Avrami constant (1.7) and the frequency ($5.7{\times}10^{16}/s$) for crystallization were calculated from which the nepheline crystal could be expected as showing an 1~2-dimensional surface crystallization behavior mainly with some bulk crystallization tendency at the same time. The actual observation of microstructure using SEM showed the considerable amount of surface crystals of dendrite and the bulk crystals with low fraction, so the prediction by the Kissinger equation was in accord with the crystallization behavior of glass-ceramics fabricated in this study.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.103-107
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• 2005

In order to investigate the velocity structure of the southern part of the Korean peninsula, exploded seismic signals were recorded for 120 s along a 294-km WNW-ESE line and 150 s along a 335-km NNW-SSE line in 2002 and 2004, respectively. Velocity tomograms were derived from inverting first arrival times. One-dimensional velocity models derived by joint analyses of teleseismic receiver functions and surface wave dispersion at several stations near the profiles were uesd to build initial models. The raypaths indicate several midcrust interfaces including ones at approximate depths of 2.0 and 14.9 km with refraction velocities of approximately 6.0 and 7.1 km/s, respectively. The deepest significant interface varies in depth from 30.8 km to 36.1 km. The critically refracting velocity varies from 7.8 to 8.1 km/s along this interface which may correspond to the Moho discontinuity. The velocity tomograms show (1) existence of a low-velocity zone centered at 6-7 km depth under the Okchon fold belt, (2) extension of the Yeongdon fault down to greater than 10 km, and (3) existence of high-velocity materials under the Gyeongsan basin whose thickness is less than 4.2 km.

• Radiation Oncology Journal
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• v.32 no.3
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• pp.187-197
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• 2014

Purpose: We aimed to analyze the treatment outcome and long-term toxicity of 70 Gy hypofractionated intensity-modulated radiotherapy (IMRT) for localized prostate cancer using a customized rectal balloon. Materials and Methods: We reviewed medical records of 86 prostate cancer patients who received curative radiotherapy between January 2004 and December 2011 at our institution. Patients were designated as low (12.8%), intermediate (20.9%), or high risk (66.3%). Thirty patients received a total dose of 70 Gy in 28 fractions over 5 weeks via IMRT (the Hypo-IMRT group); 56 received 70.2 Gy in 39 fractions over 7 weeks via 3-dimensional conformal radiotherapy (the CF-3DRT group, which served as a reference for comparison). A customized rectal balloon was placed in Hypo-IMRT group throughout the entire radiotherapy course. Androgen deprivation therapy was administered to 47 patients (Hypo-IMRT group, 17; CF-3DRT group, 30). Late genitourinary (GU) and gastrointestinal (GI) toxicity were evaluated according to the Radiation Therapy Oncology Group criteria. Results: The median follow-up period was 74.4 months (range, 18.8 to 125.9 months). The 5-year actuarial biochemical relapse-free survival rates for low-, intermediate-, and high-risk patients were 100%, 100%, and 88.5%, respectively, for the Hypo-IMRT group and 80%, 77.8%, and 63.6%, respectively, for the CF-3DRT group (p < 0.046). No patient presented with acute or late GU toxicity ${\geq}$grade 3. Late grade 3 GI toxicity occurred in 2 patients (3.6%) in the CF-3DRT group and 1 patient (3.3%) in the Hypo-IMRT group. Conclusion: Hypo-IMRT with a customized rectal balloon resulted in excellent biochemical control rates with minimal toxicity in localized prostate cancer patients.

• Korean Journal of Environmental Biology
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• v.34 no.3
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• pp.169-176
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• 2016

Although chemical fertilizers have a quick effect and broad applicability to agricultural fields, they have caused many problems like increasing soil acidity or decreasing soil organic matters. Environmental-friendly agriculture has been attempted in various ways such as organic agriculture, natural farming, low input and sustainable agriculture. The common interest of all environmental-friendly systems is to decrease burden to agricultural environment by low input of agricultural labor and materials. This study was conducted to estimate overwintering capacity and genetic distance among Chinese Milk Vetch (Astragalus sinicus, CMV) collections based on morphological characteristics and AFLP (Amplified fragment length polymorphism) analysis. Furthermore, the effect of CMV as green manure was observed in mix-cultured paddy fields with rice, sesame and sweet-potato. An another objective of this study was also to compare the pattern of weed occurrence in paddy fields with or without CMV and different rice transplanting times. The CMV collected from Paju district in central region of Korea was successively occurring through self-reseeding without artificial management. However, there was no noticeable difference in growth habit between Paju native CMV and introduced CMV from China which is currently used in farm fields. On the basis of multi-dimensional scaling and tree analyses, there are no significant difference of agricultural growth characteristics among Paju and chinese collections only excepting leaf angle and root length. The flowering time of Gurye collection was fast for 1 week as compared to other collections. AFLP that was commonly used for plant classfication, was applied to exam the genetic variation of CMV collections. Total 579 PCR products and 336 polymorphic fragments were generated using 8 primer pairs.

• Journal of the Korean Geophysical Society
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• v.8 no.1
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• pp.45-48
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• 2005

In order to investigate the velocity structure of the southern part of the Korean peninsula, exploded seismic signals were recorded for 120 s along a 294-km WNW-ESE line and 150 s along a 335-km NNW-SSE line in 2002 and 2004, respectively. Velocity tomograms were derived from inverting first arrival times. One-dimensional velocity models derived by joint analyses of teleseismic receiver functions and surface wave dispersion at several stations near the profiles were uesd to build initial models. The raypaths indicate several midcrust interfaces including ones at approximate depths of 2.0 and 14.9 km with refraction velocities of approximately 6.0 and 7.1 km/s, respectively. The deepest significant interface varies in depth from 30.8 km to 36.1 km. The critically refracting velocity varies from 7.8 to 8.1 km/s along this interface which may correspond to the Moho discontinuity. The velocity tomograms show (1) existence of a low-velocity zone centered at 6-7 km depth under the Okchon fold belt, (2) extension of the Yeongdon fault down to greater than 10 km, and (3) existence of high-velocity materials under the Gyeongsan basin whose thickness is less than 4.2 km.

• Korean journal of food and cookery science
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• v.19 no.3
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• pp.339-353
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• 2003

The rapid increase in food borne illness outbreaks in Korea has been one of the major threats to the Nation's Health. Foodservice establishments have been identified as the major place for these outbreaks, mainly due to the lack of sanitary management and sanitary facility management practices. The purposes of the study were to develop hospital foodservice facility evaluation tools, based on the general HACCP-based standards and guidelines, for hospital food service establishments, to ensure the safety of these foodservices and to reduce the risk of food home illness. The scope of this study included: 1) an assessment of the current foodservice sanitation practices and managements for 6 general hospitals, with more than 400 beds, and 3 general hospitals, with less than 400 beds; 2) the development of foodservice establishments sanitation evaluation tools and sanitation standards, based on the HACCP system. The survey data showed varied results between the hospitals surveyed. Most of the hospital foodservice operations had many problems with ventilation and the plumbing. The total dimensional mean scores for the hospitals with more than 400 beds and less than 400 beds were 31.5 and 27.0, respectively. The highest dimension scores were for the water supply facility and lighting, with the lowest for insect and rodent control and toxic materials management. The levels of the mean scores were very low, especially for the general hospitals with less than 400 beds. These low mean scores may have arisen from critical problems within the hospital foodservice operations. The most needed facility management items for improvement were: storage shelf should be spaced 6 inches from the floor and walls, the use of three compartment sinks, utility sinks and cleaning facilities, with a floor drain for cleaning mops or liquid wastes, a ventilation hood designed to prevent dripping onto food, cooking facilities should be disassembled for washing and sanitizing, a separated hand washing sink and a sanitized food board for each area should be provided, all toxic material must have warning labels attached, and be stored in an area away from food preparation under padlock. The evaluation tool consisted of 14 dimensions, with 65 check-off items. The results of this study will provide basic facilities' guidelines to regulators, or foodservice industry personnel, wishing to build, or expend, and establish an efficient flow of food. As a result, food borne illnesses will be effectively prevented, and the Nation's health will be promoted for the development of their own sanitation standards, with a checklist for the safe production of foods.

• Korean Journal of Radiology
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• v.20 no.1
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• pp.58-68
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• 2019

Objective: To compare digital breast tomosynthesis (DBT) and conventional full-field digital mammography (FFDM) in the detectability of breast cancers in patients with dense breast tissue, and to determine the influencing factors in the detection of breast cancers using the two techniques. Materials and Methods: Three blinded radiologists independently graded cancer detectability of 300 breast cancers (288 women with dense breasts) on DBT and conventional FFDM images, retrospectively. Hormone status, histologic grade, T stage, and breast cancer subtype were recorded to identify factors affecting cancer detectability. The Wilcoxon signed-rank test was used to compare cancer detectability by DBT and conventional FFDM. Fisher's exact tests were used to determine differences in cancer characteristics between detectability groups. Kruskal-Wallis tests were used to determine whether the detectability score differed according to cancer characteristics. Results: Forty breast cancers (13.3%) were detectable only with DBT; 191 (63.7%) breast cancers were detected with both FFDM and DBT, and 69 (23%) were not detected with either. Cancer detectability scores were significantly higher for DBT than for conventional FFDM (median score, 6; range, 0-6; p < 0.001). The DBT-only cancer group had more invasive lobular-type breast cancers (22.5%) than the other two groups (i.e., cancer detected on both types of image [both-detected group], 5.2%; cancer not detected on either type of image [both-non-detected group], 7.3%), and less detectability of ductal carcinoma in situ (5% vs. 16.8% [both-detected group] vs. 27.5% [both-non-detected group]). Low-grade cancers were more often detected in the DBT-only group than in the both-detected group (22.5% vs. 10%, p = 0.026). Human epidermal growth factor receptor-2 (HER-2)-negative cancers were more often detected in the DBT-only group than in the both-detected group (92.3% vs. 70.5%, p = 0.004). Cancers surrounded by mostly glandular tissue were detected less often in the DBT only group than in the both-non-detected group (10% vs. 31.9%, p = 0.016). DBT cancer detectability scores were significantly associated with cancer type (p = 0.012), histologic grade (p = 0.013), T and N stage (p = 0.001, p = 0.024), proportion of glandular tissue surrounding lesions (p = 0.013), and lesion type (p < 0.001). Conclusion: Invasive lobular, low-grade, or HER-2-negative cancer is more detectable with DBT than with conventional FFDM in patients with dense breasts, but cancers surrounded by mostly glandular tissue might be missed with both techniques.