• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.3
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• pp.120-125
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• Korean Journal of Human Ecology
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• v.18 no.1
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• pp.157-166
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• 2009

This study was conducted to evaluate the differences in external appearances and functional qualities between the slacks which were patterned on existing designs and on a new design in order to improve on their level of comfort of ready-made clothes for abdominally fat women. Five abdominally fat women in their 60's were chosen as experimental participants. Twenty-four external evaluation items, and seven different actions involving six moving parts of the body were investigated with a 5-level scale in the repeated wearing test. The results were analyzed by statistical methods. The newly designed pattern in this study was definitely superior to the other two patterns(L-type and K-type) on the external appearance evaluation. The newly pattern removed a waist belt and a dart from the front part of the garment and gave surplus space around the waist. It prevented superfluous wrinkles at the abdominal region and thighs. The superfluous wrinkles at the side regions also disappeared due to the length (inseam) reduction from waist to crotch. The newly pattern made the center-line of the back side slightly sloped to the main pattern in order to remove the drooped line. The newly pattern showed the highest score in the functional test of several actions. It was due to the reduction of the length from waist to crotch as well as the belt width. It made waist-line movement better, and made it easier and more comfortable to sit down. The newly pattern also showed the highest score in the functional test classified by specific movements of parts of the body for the same purpose. The slacks which were made of elastic materials showed better results than the non-elastic ones on external appearances and functional test items. It showed that the elastic materials played a better role in the increase of functional action of abdominally fat, aged women. This study suggests that the newly designed slacks pattern could give abdominally fat, aged women better external features and a more comfortable fitting sensation. As well, the results were significant as basic data to produce ready-made and/or tailer-made garments.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.59-68
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• 2006

Flow separation of recirculation zone by increasing of flow and change of its direction at confluence results in backwater due to conveyance reduction. The hydraulic characteristics of flow separation are analysed by experimental results of flow ratios of tributary and main streams and approaching angles. The boundary of flow separation by dimensionless length and width is defined by the streamline of zero and this definition agrees well to the existing investigation. Because flow separation doesn't appear in small flow ratio and approaching angle of $30^{\circ}$, the equation of flow separation with flow ratio and approaching angle is provided. In flow separation consideration and comparing with previous results, the existing equations of dimensionless length and width ratios by function of approaching angle, flow ratio, and downstream Froude number are modified and also contraction coefficient and shape factor are analysed. Dimensionless length and width ratios are proportional to the flow ratio and approaching angle. In analysis of water surface profiles, the backwater effects are proportional to the flow ratio and approaching angle and the magnitude at outside wall is greater than that of inside wall of main stream. The length, $X_l$ from the beginning of confluence to downstream of uniform flow, where the depth is equal to uniform depth, is characterized by width of stream, flow ratio, approaching angle, and contraction coefficient. The ratios between maximum water depth by backwater and minimum depth at separation are analysed.

• Restorative Dentistry and Endodontics
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• v.41 no.3
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• pp.210-217
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• 2016

Exposing sound structure of a subgingivally fractured tooth using orthodontic extrusion is considered to be a conservative way to re-establish biologic width without sacrificing esthetics or jeopardizing periodontal support of neighboring teeth. When a misaligned tooth is traumatically involved, a more comprehensive approach combining tooth extrusion and re-alignment may be necessary for a successful restorative outcome. This case report describes a successful esthetic management of a patient with complicated crown-root fracture on the maxillary right central incisor and pre-existing malocclusion in the maxillary anterior region. Forced eruption along with re-alignment of teeth by orthodontic movement seems to allow re-positioning of the fracture line to a favorable position and correction of crowding, providing a better esthetic result.

• The Research Journal of the Costume Culture
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• v.7 no.3
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• pp.134-141
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• 1999

The purpose of this study is to provide new style for fashion illustration fo different image of Korean middle aged women. The research method is as follows. First, we make basic style base on The Korea Industrial Advancement Administration\`s Korean standard stomatype. Second, it give variety to body\`s rate and make each different 8 style. The subject are 144 college students who majoring clothing, fashion design and they have responded to the questionnaires. Questionnaires were taken from April, 1998 to Jan. 1999. Data were analyzes by analysis of variance, ANOVA test, Dunkun test, SPSS. PC/sup +/. As a result of this study, we found this following conclusions, 1. Well-proportion style have the exaggerated shoulder and the extended body at the same rate below waist line than basic style. 2. Reduction and extension need stability and well balanced. 3. Fashion illustration of middle aged women\`s clothing expression is not proper too narrow width, too long length of legs. 4. To making length, it is award well-proportion have too long hand or too long arm.

• The Research Journal of the Costume Culture
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• v.18 no.3
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• pp.541-549
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• 2010

The purposes of this study were to examine the slacks purchases and wearing satisfaction among old-aged women who were highly dissatisfied with their bodies and fit due to physical changes and to provide some basic data needed to develop slacks patterns to meet their needs. A survey was taken among 223 old-aged women aged 60~79 living in Seoul. Using the SPSS 12.0 program, the collected data were analyzed in descriptive statistics, t-test, and crosstab. The result were as follows: the most used place for them to shop slacks was a market(including the Dongdaemun and Namdaemun market), which was followed by a department store and a discount store in the order. As for their preference for slacks according to age, those who were in their sixties most preferred straight-line slacks, while those who were in their seventies semistraight-type slacks. As for fit for each body part according to age, there were significant differences only in crotch length. Those who were in their seventies were more dissatisfied with crotch length than those who were in their sixties, feeling that crotch length was short. As for their experiences of repair after purchasing a pair of slacks, 82.5% said they had such an experience. Most of the repairs with length, waist and slacks width involved in size reduction.

• Korean Journal of Materials Research
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• v.29 no.4
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• pp.252-257
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• 2019

Fabrication of soft magnetic composite powders for the $Fe_2O_3-Ca$ system by mechanical alloying(MA) has been investigated at room temperature. It is found that soft magnetic composite powders in which CaO is dispersed in ${\alpha}-Fe$ matrix are obtained by MA of $Fe_2O_3$ with Ca for 5 hours. Changes in magnetization and coercivity also reflect the details of the solidstate reduction process of hematite by pure metal of Ca during MA. The saturation magnetization of MA powders increases with increasing MA time and reaches a maximum value of 65 emu/g after 7 hours of MA. The average grain size of ${\alpha}-Fe$ in MA powders, estimated by diffraction line-width, gradually decreases with increasing MA time and reaches 52 nm after 5 hours of MA. It can also be seen that the coercivity of the 5-hour MA sample is fairly high at 190 Oe, suggesting that the grain refinement of already-produced ${\alpha}-Fe$ tends to clearly occur during MA.

• Journal of Digital Contents Society
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• v.18 no.5
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• pp.989-994
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• 2017

In this paper, we propose a pothole detection system using 2D LiDAR and a pothole detection algorithm. Conventional pothole detection methods can be divided into vibration-based method, 3D reconstruction method, and vision-based method. Proposed pothole detection system uses two inexpensive 2D LiDARs and improves pothole detection performance. Pothole detection algorithm is divided into preprocessing for noise reduction, clustering and line extraction for visualization, and gradient function for pothole decision. By using gradient of distance data function, we check the existence of a pothole and measure the depth and width of the pothole. The pothole detection system is developed using two LiDARs, and the 3D pothole detection performance is shown by detecting a pothole with moving LiDAR system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1542-1548
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• 2009

This paper describes a size-reduced Wilkinson power divider using substrate integrated artificial dielectric(SIAD). SIAD transmission lines have increased effective refractive index, so the line width and length are reduced from those of standard transmission lines. Therefore the "size-reduction effect" is achieved if SIAD lines are applied to high frequency circuits. An efficient simulation method is proposed for SIAD lines which have an enormous number of via-holes. A 2GHz Wilkinson power divider is designed and measured using SIAD transmission line as an example of application. The size of the fabricated divider is reduced by 32% due to the increased effective refractive index of SIAD, while the performances are maintained similarly.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.428-446
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• 1997

Restorative procedures can lead to weakening tooth due to reduction and alteration of tooth structure. It is essential to prevent fractures to conserve tooth. The resistance to fracture of the restored tooth may be influenced by many factors, among these are the cavity dimension and the physical properties of the restorative material. The placement of direct composite resin restorations has generally been found to have a strengthening effect on the prepared teeth. It is the purpose of this investigation to study the relationship between the cavity isthmus and the fracture resistance of a tooth in composite resin restorations. In this study, MO cavity was prepared on maxillary first premolar. Three dimensional finite element models were made by serial photographic method and isthmus(1/4, 1/3, 1/2 of intercuspal distance) were varied. Two types of model(B and R model) were developed. B model was assumed perfect bonding between the restoration and cavity wall and R model was left unfilled. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as follows : 1. Displacement of buccal cusp in R model occurred and increased as widening of the cavity, and displacement in B model was little and not influenced by cavity width. 2. There was a significant decrease of stress resulting in increase of fracture resistance in B model when compared with R model. 3. With the increase of the isthmus width, B model showed no change in the stress and strain. In R model, the stress and strain increased both in the area of buccal-pulpal line angle and the buccal side of marginal ridge, therefore the possibility of crack increased. 4. The stress and strain were distributed evenly on the tooth in B model, but in R model, were concentrated on the buccal side of the distal marginal ridge and buccal-pulpal line angle, therefore the possibility of fracture increased.