• 한국세라믹학회지
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• 제43권12호
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• pp.839-845
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• 2006

Graphite has hexagonal closed packing structure with two bonding characteristics; (1) van der waals bonding between c axis, and (2) covalent bonding in the a and b axis. The weak van der waals bonds cause self-lubricant property, and the strong covalent bonds cause excellent electric and thermal conductivity. Furthermore, graphite is chemically very inert because of the material composed of only carbon elements. Thus, graphite is very useful for mechanical sealing materials. However, Graphite have porous microstructure because starting materials of graphite produce many volatile during the manufacturing processes. This causes low density of graphite, which is unsuitable for the mechanical sealing materials. Thus, further impregnation process is generally needed to enhance the graphite density. In this work, high density graphite is prepared with the principle of densification when coke and pitch binder, prepared from thermal treatment of coal tar pitch, become dehydrogenation during graphitization or carbonization.

• Journal of Magnetics
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• 제20권2호
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• pp.176-185
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• 2015

We present the design optimization of the magnetic pole and slot design options that minimize the cogging torque of permanent-magnet (PM) brushless generators for small wind turbine generators. Most small wind-turbines use direct-driven PM generators which have the characteristics of low speed and high efficiency. Small wind-turbines are usually self-starting and require very simple controls. The cogging torque is an inherent characteristic of PM generators, and is mainly caused by the generator's geometry. The inherent the cogging torque can cause problems during turbine start-up and cut-in in order to start softly and to run a power generator even when there is little wind power during turbine start-up. Thus, to improve the operation of small turbines, it is important to minimize the cogging torque. To determine the effects of the cogging torque reductions, we adjust the slot opening width, slot skewing, mounting method of magnets, magnet shape, and the opening and combinations of different numbers of slots per pole. Of these different methods, we combine the methods and optimized the design variables for the most significant design options affecting the cogging torque. Finally, we apply to the target design model and compare FEA simulation and measured results to validate the design optimization.

• Journal of Gastric Cancer
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• 제16권1호
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• pp.8-13
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• 2016

Purpose: The aim was to verify if changing the Journal of Gastric Cancer (JGC) to only English (starting in December 2010) was successful based on bibliometrics. Materials and Methods: The following indicators were retrieved or calculated from the journal homepage and the Web of Science Core Collection on January 30, 2016: the number of citable articles per year; the number of original articles funded; the national origins of the editorial board members and authors; the total citations; the impact factors; the national origins of authors citing the journal; the source titles of articles citing the journal; and the Hirsch index. Results: From 2011 to 2015, the number of citable articles per year was 40, 41, 39, 39, and 40. The proportion of original articles funded was 39 out of 113 articles (34.5%). The editorial board members were from seven countries. The authors were from 11 countries. The total citations increased from 1 in 2011 to 245 in 2015. From 2013 to 2015, the impact factors (without self-citations) were 1.42, 1.36, and 1.60. In 2014, the value 1.60 corresponded to the ranking of 157 out of 210 oncology journals (74.8%); It was cited from 46 countries. Top-ranking countries of citing authors were China (171), Korea (158), and Japan (75). The number of source titles citing the journal was more than 100. The Hirsch index was 12. Conclusions: The English-only language policy, which started in December 2010, was successful in promoting the JGC to international levels from the perspective of bibliometric analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.964-966
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• 2003

The three-phase induction motor is rugged, reliable, long-lived, self-starting, smooth-running. But it is relatively inexpensive and three-phase power in not available everywhere, so if possible we need single-phase motor with the same characteristics. In fact, single-phase induction motors have excellent characteristics and outnumber the three-phase variety. Most of the small electric motors used in home, farm, or office are single-phase induction motors of one type or another. This electric motors application field need most energy saving type drive according to enlargement of electronic goods and to tend high class. The paper is proposed a various phase control methods for energy saving of single- phase induction motor. The controllers that are embodied by each method can use by various usage according to each performance and it is considered that application may help in the electrical energy saving because is possible to other electrical appliances.

• Structural Engineering and Mechanics
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• 제73권1호
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• pp.65-73
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• 2020

The present work describes a new time marching procedure for structural dynamics analyses. In this novel technique, time integration parameters are automatically evaluated according to the properties of the model. Such parameters are locally defined, allowing the user to input a numerical dissipation property for each element, which defines the amount of numerical dissipation to be introduced. Since the integration parameters are locally defined as a function of the structural element itself, the time marching technique adapts according to the model, providing enhanced accuracy. The new methodology is based on displacement-velocity relations and no computation of accelerations is required. Furthermore, the method is second order accurate, it has guaranteed stability, it is truly self-starting and it allows highly controllable algorithm dissipation in the higher modes. Numerical results are presented and compared to those provided by the Newmark and the Bathe methods, illustrating the good performance of the new time marching procedure.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.331-334
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• 2011

램제트 엔진의 성능은 초음속 흡입구의 성능과 밀접한 연관이 있다. 초음속 흡입구 내부 유동 특성을 관찰하기 위해 실험적/전산해석적 연구를 수행하였다. 자발 시동이 가능한 2차원 실험 모델을 설계 제작하고 마하 2.5 초음속 풍동을 이용한 실험적 연구와 Menter's SST 난류 모델과 RANS 방정식에 기본한 전산해석 결과로부터 내부 유동 특성을 정리하였다. 흡입구의 안정 작동 조건에서의 의사충격파(Pseudo-shock wave)와 불안정 작동 조건의 버즈 현상에 대해 자세한 가시화 결과를 제시하였다.

• Journal of Magnetics
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• 제18권3호
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• pp.311-316
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• 2013

Digital image processing has increasingly been implemented in nanostructural analysis and would be an ideal tool to characterize the morphology and position of self-assembled magnetic nanoparticles for high density recording. In this work, magnetic nanoparticles were synthesized by the modified polyol process using $Fe(acac)_3$ and $Pt(acac)_2$ as starting materials. Transmission electron microscope (TEM) images of as-synthesized products were inspected using an image processing procedure. Grayscale images ($800{\times}800$ pixels, 72 dot per inch) were converted to binary images by using Otsu's thresholding. Each particle was then detected by using the closing algorithm with disk structuring elements of 2 pixels, the Canny edge detection, and edge linking algorithm. Their centroid, diameter and area were subsequently evaluated. The degree of polydispersity of magnetic nanoparticles can then be compared using the size distribution from this image processing procedure.

• 철학연구
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• 제146권
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• pp.25-48
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• 2018

행복이란 필요가 충족된 상태라는 상식적 이해로부터 출발하면서, 이 글은 민주시민이 행복해지기 위해 갖추어야 하는 지성과 덕성을 제안한다. 이를 위해 인간이 가지는 실존적 사실로서 존재, 관계, 그리고 활동을 제시하고, 이러한 사실이 도덕적 가치를 가지기 위해서 각각 독립성, 평등성, 그리고 책임성을 필요로 한다고 설명한다. 나아가 정치영역에서는 시민이 정치권력 앞에서 독립적으로 존재하고 평등하게 관계하고 그리고 책임 있게 활동할 때 행복한 시민이 될 수 있다고 논의한다. 이러한 필요들을 충족시키기 위해 요구되는 것들로서 민주시민의 지성으로서 가치내용의 다원성, 가치형식의 유사성, 그리고 가치실현의 가능성에 대한 이해를 제안하고, 마지막으로 민주시민의 덕성으로서는 자아 존중, 상호 존중, 그리고 법률 존중을 제안한다.

• KEPCO Journal on Electric Power and Energy
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• 제5권2호
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• pp.83-92
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• 2019

Spontaneous combustion propensity of various coals of carbonization grade as a pulverized fuel of coal-fired power plant has been tested from an initial temperature of $25^{\circ}C$ to $600^{\circ}C$ by heating in an oven with air to analyze the self-oxidation starting temperature. These tests produce CPT (Cross Point Temperature), IT (Ignition temperature), and CPS (Cross Point Slope) calculated as the slope of time taken for a rapid exothermic oxidation reaction at CPT base. CPS shows a carbonization rank dependence whereby wood pellet has the highest propensity to spontaneous combustion of $20.995^{\circ}C/min$. A sub-bituminous KIDECO coal shows a CPS value of $15.370^{\circ}C/min$, whereas pet coke has the highest carbonization rank at $2.950^{\circ}C/min$. The nature of this trend is most likely attributable to a concentration of volatile matter and oxygen functional groups of coal surface that governs the available component for oxidation, as well as surface area of fuel char, and constant pressure molar heat.

• International Journal of Knowledge Content Development & Technology
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• 제9권1호
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• pp.57-79
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• 2019

This study attempts to seek a solution, in terms of brain science, to stimulate reading activities of men to whom no attention has been given from the field of reading. In order to do so, brain pattern, reading tendency, reading preference, reading effectiveness and influence of reading were analyzed. As a result of the analysis, first, it showed that respondents' characteristics did not affect brain patterns, but school and social influences on reading were found to affect brain patterns. Second, reading propensity according to gender was observed to be different in terms of personal health, personal self - esteem, and cultural artistry. On the other hand, reading effectiveness was found to be different in terms of reading engagement and the willingness to continue reading whereas reading propensity according to the brain pattern was different in books related to humor and family matters. Third, reading satisfaction, reading engagement and willingness to continue reading all were observed to affect the reading activities of men. Suggesting measures to stimulate reading activities of men based on such findings, first, implementing dynamic reading education programs and finding reading models for men are needed. Second, when selecting books for reading program operations, books should be recommended according to gender rather than being selected en bloc by libraries. Third, since reading education at home shows high influences on both male and male-type brain pattern, the starting point of reading education should be made at homes. In particular, fathers, who can become a role model for men, need a reading role model, and reading education programs for fathers are also required.