• 대한기계학회논문집
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• 제14권3호
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• pp.624-635
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• 1990

본 연구에서는 마멸과정을 선형파괴역학적 관점에서 해석하여, 탄성체의 표면 에 산재되어 있는 표면균열의 전파거동을 마멸과정규명의 입장에서 살펴보고자 한다. 우선 마멸거동에 관한 파괴역학적 접근방식에 의한 마멸이론의 확립을 위해서, 표면균 열이 내부균열보다 그 전파 가능성이 높다고 한 Keer등의 주장에 착안하여 Hertz 접촉 압력하의 경사진 표면균열의 전파거동을 선형파괴역학적으로 해석하고자 한다. 이론 해석에 있어서는 표면균열을 인상전립의 연속분포로 치환하고, 전립밀도분포함수에 관 한 특이적분방정식을 유도해서 Erdogangupta의 방법을 이용하여 그 해를 구하였다.

• 대한전자공학회논문지SP
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• 제46권6호
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• pp.1-15
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• 2009

본 논문에서는 이동 중인 철도차량 제륜자의 두께, 편마모 및 제륜자와 차륜 사이의 거리를 자동으로 측정하는 시스템을 제안한다. 철도차량의 제륜자는 촬영 시스템이 설치된 곳을 지날 때 자동으로 촬영되며, 두께 등을 측정하기 위해 가장 먼저 영상 내에서 제륜자의 위치를 검출한다. 이는 제륜자의 위치가 영상 마다 다르기 때문이며 이를 적응적으로 찾기 위해, 제륜자와 차륜 사이에 나타나는 그림자 영역을 이용한다. 그림자 영역의 경계는 9차 다항식을 통해 모델링되며, 그 영역을 지나는 임의의 곡선 (초기 곡선)은 제약 곡선 피팅 방법을 통해 검출된다. 다음은 검출된 초기 곡선과 명암도 변화 정보를 이용하여 제륜자의 앞과 뒤, 차륜 상의 세 곡선 및 제륜자의 수직면을 지나는 직선을 검출한다. 최종적으로, 앞서 구한 곡선과 직선을 이용하여 제륜자의 두께, 편마모 및 제륜자와 차륜 사이의 거리를 측정한다. 실험에서는 제안된 방법을 실제 선로에서 촬영한 영상에 대해 적용해 보았으며, 그 결과 평균 0.654mm의 두께 측정 오차를 나타내었다.

• Tribology and Lubricants
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• 제31권2호
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• pp.50-55
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• 2015

This study investigates the effects of a pattern of 200 μm dimples in a hexagonal array on tribological characteristics. A textured surface might reduce the friction coefficient and wear caused by third-body abrasion and thus improve the tribological performance. There are three friction conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction conditions. In this experiment, we investigate the friction characteristics by carrying out the friction tests at sliding speeds ranging from 0.06 to 0.34 m/s and normal load ranging from 10 to 100 N. We create dimple surfaces for texturing by using the photolithography method. There are three kinds of specimens with different dimple densities ranging from 10% to 30%. The dimple density on the surface area is the one of the important factors affecting friction characteristics. Friction coefficient generally decreases with an increase in the velocity and load, indicating that the lubrication regime changes depending on the load and velocity. The fluid friction regime is fully developed, as indicated by the duty number graph. Fluid friction occurs at a velocity of 0.14-0.26 m/s. The best performance is seen at 10% dimple density and 200 μm dimple circle in the hexagonal array.

• 열처리공학회지
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• 제35권6호
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• pp.303-313
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• 2022

The purpose of this study was to test and analyze the effects of the mechanical properties and structural changes of the austenitized and tempered martensite STS 410 stainless steel containing 11.5~13%Cr and 0.10%C on its temper embrittlement. The STS 410 stainless steel test pieces for each 3 hours at 960℃, 1000℃ and then, tempered them for 2 hours at 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃ and 700℃ known as the intervals vulnerable to temper embrittlement to observe the changes of their structures and mechanical properties. In case autenitizing was insufficient due to lower temperature of thermal treatment for solution, unsolved carbides and ferrites remained in the structure after quenching, which meant that the parts could wear out and corrode to embrittle at the room temperature. Elongation and impact energy changes with Tempering conditions showed minimum results in range of 400~500℃. The decrease in elongation and impact energy at 400~500℃ was the hardening effect of the subgrain due to the precipitation of many M₃C or M₇C₃, M₂₃C₆. And STS 410 stainless steel corrosion tested in 10% NaCl solution at 30℃ after tempering treatment. The degree of corrosion sensitization showed increasing tendency with increase of tempering temperature and Cr carbide precipitation were observed in grain boundary.

• Tribology and Lubricants
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• 제39권3호
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• pp.87-93
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• 2023

Nanofluids are dispersions of particles smaller than 100 nm (nanoparticles) in base fluids. They exhibit high thermal conductivity and are mainly applied in cooling applications. Nanolubricants use nanoparticles in base oils as lubricant additives, and have recently started gathering increased attention owing to their potential to improve the tribological and thermal performances of various machinery. Nanolubricants reduce friction and wear, mainly by the action of nanoparticles; however, only a few studies have considered the rheological properties of lubricants. In this study, we adopt a parallel slider bearing model that does not generate geometrical wedge effects, and conduct thermohydrodynamic (THD) analyses to evaluate the effect of higher thermal conductivity and viscosity, which are the main rheological properties of nanolubricants, on the lubrication performances. We use a commercial computational fluid dynamics code, FLUENT, to numerically analyze the continuity, Navier-Stokes, energy equations with temperature-viscosity-density relations, and thermal conductivity and viscosity models of the nanolubricant. The results show the temperature and pressure distributions, load-carrying capacity (LCC), and friction force for three film-temperature boundary conditions (FTBCs). The effects of the higher thermal conductivity and viscosity of the nanolubricant on the LCC and friction force differ significantly, according to the FTBC. The thermal conductivity increases with temperature, improving the cooling performance, reducing LCC, and slightly increasing the friction. The increase in viscosity increases both the LCC and friction. The analysis method in this study can be applied to develop nanolubricants that can improve the tribological and cooling performances of various equipment; however, additional research is required on this topic.

• 복식
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• 제58권3호
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• pp.63-78
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• 2008

Since 1960, minimalism has been one of the fashion phenomenon and turned out in many different ways. After postmodernism which contains negotiation and pluralism, appeared in 1980, there was a new wave of post minimalism that inherited 1960's minimalism. Minimal style which come out of 60's fashion, is marked by simplicity, minimal expression, and monochrome color, and it shows up simple style with no decoration. It opened up a young fashion period, and we saw minimal style in sports wear which utilized simplicity and function with spread of sports in the 70's. And also since 1980, Post-Modern widely influenced the idea about modern culture as well as complicated clothes getting rid of fixed concept, seeking to break the boundary between culture and life which were seek in fashion and personality as well as various characteristic, Accordingly in different ages, The style and image were borrowed from different culture and natural environment mixing the image, cultural phenomena like these appearing in complexity and expression, variety and possibility of new vision was expanded. Since 1980, Fashion has become more gradually diversity, high classed, required of each individuality. The phenomenon of fashion reappearance which was influenced by minimalism is continued to 2000. The Oriental style fashion is still attracted, so The new term "Ethic Minimalism" has appeared along with the trends which is put together. Therefore the purpose of this study is to search the concept and the characteristics of ethnic minimalism, to consider the relationship between minimalism and ethnic minimalism, and reveal the characteristic of ethnic minimalism happened to modern fashion. The study method went through literature research and practice research. The range of this study is oriental fashion spanning of from 1960 to current day. Photo records from this period show well the spirit of the oriental and the personality of minimalism. The oriental representative designer and western representative designer are centered Consequently, The formative characteristics of ethnic minimalism are simple, pure, unbalanced free style and representing the phenomena of compromise, blending oriental and western fashion. Structually, Elements of space and plane are emphasized, colors are restricted, and materials are composed mainly of natural fiber. So, minimalism based on simplicity combined with a structure of oriental spiritual depth and space, It could be called ethnic minimalism as a rational fashion.

• 복식
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• 제54권3호
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• pp.27-42
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• 2004

Music videos provide for many others images, alluring the audience to fall in another emotional world, while the sexual images shown in them suggest new images of man and woman. Today, men's images are being interpreted from various viewpoints. As interests in men's fashion are visualized through music video clothing, not only juveniles who want to be identified with the music video images but also adults try to imitate them, and proceed to wear the clothing, obliterating the boundary between 'reality' and 'illusion' and creating new images of men. This study is aimed at reviewing the male images shown in the music videos, particular their clothing, produced between 2000 and 2002. The results of this study could be summarized as follows : 1. Since beginning of the human history, men's image has been characterized by patriarchal system, capitalism, bourgeois class which emerged after industrial revolution and other man-dominant socio-cultural phenomena, such male image are shown in the music video as conservative and dominant image. 2. However, due to the post-modern culture, the power began to be decentralized. while feminism and men's liberation movement gain strength. As a result, women or heterosexuals began to regard men as sexual objects, and such a phenomenon is featured as sexual, bisexual or decadent images in the music videos. 3. On the threshold of the 21st century, music videos have begun to creatively describe men's life, their social conflicts, dreams and hopes and death and thereby. feature men's such images as being destroyed in view of existentialism. The numerous creative men's images interpreted in this way are featured in many music video works only to create playful, cyborg or demonic images using the senses. After all, men's images are featured in the music video costumes in diverse ways ranging from the conventional images to acquiescent images. In addition, various male images are combined with the characteristics of the music videos to be re-created anew. The young men in the our modern age tend to imitate or apply such images to create their own images or individualistic styles. All in all, men's image can be fixed no longer but diversified and fragmented in the new age.

• Corrosion Science and Technology
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• 제13권1호
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• pp.28-35
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• 2014

Recently, the fuel oil of diesel engines of marine ships has been increasingly changed to heavy oil of low quality as the oil price is getting higher and higher. Therefore, the spiral gear attached at the motor of the oil purifier which plays an important role to purify the heavy oil is also easy to expose at severe environmental condition due to the purification of the heavy oil in higher temperature. Thus, the material of the spiral gear requires a better mechanical strength, wear and corrosion resistance. In this study, the heat treatment(tempering) with various holding time at temperature of $500^{\circ}C$ was carried out to the alloy of Cu-7Al-2.5Si as centrifugal casting, and the properties of both hardness and corrosion resistance with and without heat treatment were investigated with observation of the microstructure and with electrochemical methods, such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and a.c. impedance. in natural seawater solution. The ${\alpha}$, ${\beta}^{\prime}$ and ${\gamma}_2$ phases were observed in the material in spite of no heat treatment due to quenching effect of a spin mold. However, their phases, that is, ${\beta}^{\prime}$ and ${\gamma}_2$ phases decreased gradually with increasing the holding time at a constant temperature of $500^{\circ}C$. The hardness more or less decreased with heat treatment, however its corrosion resistance was improved with the heat treatment. Furthermore, the longer holding time, the better corrosion resistance. In addition, when the holding time was 48hrs, its corrosion current density showed the lowest value. The pattern of corroded surface was nearly similar to that of the pitting corrosion, and this morphology was greatly observed in the case of no heat treatment. It is considered that ${\gamma}_2$ phase at the grain boundary was corroded preferentially as an anode. However, the pattern of general corrosion exhibited increasingly due to decreasing the ${\gamma}_2$ phase with heat treatment. Consequently, it is suggested that the corrosion resistance of Cu-7Al-2.5Si alloy can be improved with the heat treatment as a holding time for 48 hrs at $500^{\circ}C$.

• 터널과지하공간
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• 제23권3호
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• pp.180-191
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• 2013

본 연구는 백운광산지역에 부존하는 대리석을 효율적으로 채석하고자 새로이 도입한 체인쏘머신(chain saw machine)의 적용성과 작업 효율을 분석함으로써 최적의 채석 방안을 도출하고자 하였다. 절단 효율에 큰 영향을 미치는 채석대상암석의 물리적 특성을 파악한 결과, 국내 타 지역에서 산출되는 대리석의 물성과 유사한 수준을 보이고 있으며 등방적 성질을 지니고 있어 산업용 석재로서 유리한 것으로 나타났다. 부존 대리석이 석재로서 가지는 중장기 품질을 확인하기 위해 내부식성, 마모율 등의 시험을 수행한 결과, pH 5.6의 인공강우를 50회 적용한 이후부터 시험편의 무게와 탄성파속도가 감소하였으며 마모율은 22.67%로 나타났다. 채석장 현장에서 시험운행 중인 체인쏘머신의 작업별 소요시간과 절단속도를 분석하여 단위작업을 9가지로 분류하였고 각 단위작업별 소요시간을 도출하였다. 이를 토대로 현장에 실제 적용 가능한 2가지 작업패턴에 대한 작업소요시간을 비교한 결과 장비 본체이동을 최소화하여 절단순서를 결정한 패턴 B가 원석의 외곽면을 우선 절단하도록 절단순서를 결정한 패턴 A보다 약 6%의 작업시간 단축을 나타내었다. 절단패턴 분석과 함께 백운광산의 광체를 3차원으로 모델링하고 대상암석의 부존조건을 고려한 채석 계획안을 제시하였다.

• 복식
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• 제41권
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• pp.95-105
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• 1998

SOO-BAL(Hair Style) is a method Which match hair style to face and clothes with using hair covering and protecting the head. Also SOO-BAL includes personal ornaments using to avoid one's hair be disheveled. In a standpoint of beauty and spirit, etiquette SOO-BAL is a very important thing as one being dressed up. Until now, since just a form of hair style have been studied, hair styling process is nothing to be known and studied. Time after time, our unique traditional SOO-BAL is forgotten with clothes and then this th-esis will be classified hair styling form follow-ing a form of hair style in royal palace of the C-hosun dynasty. According to the record of HAE DONG HISTORY, it shows the same of attire between Ko-rean and chinese style in ae of the chosun. The reason in that there were no any certain boundary border and the interaction of culture between two countries was happened spontaneously at ancient time like the GOCHO-SUN age. Until the period of the three states, the korean attire be changed had gone with chinese one s-imilarly. The chinese form gave to influence on the EONJIN MEURI·POON-GI-MYEONG MEURI·JJO-CJIN MEURI·MOOK-EUN GOONG-BAL MEURI·OL-LIN MEURI·SSANGSANG-TU ME-URI be drawn wall painting in the KOKUR-YU. And a gold chignon accesso-ry unearthed in a MOO-RYOUNG royal mausoleum is proof of the korean attrire be changed with chinese. In the shilla dynasty at three years after Cjin-Deuk(A.D. 649) reign. It was recorded that the dynasty let women wear the form of chinese attire. Also in the koryo dyn-asty, a rod-like hairpin (BIN-YEU) and DANG-GI employing EON-JIN MEURI was used. The SOO-BAL based on the Confucianism had lots of regulations which limited to use ornaments with classes of society in the CHOSUN dynasty. Until YOUNG CHO and CHUNG CHO period. EONJIN MEURI be decorated GACHAE was announced by dynasty as ind-ulging in luxury. Women of yangban used a rod-like hairpin and a chignon accessory made by jewerly. And 1-owly women weared a rod-like hairpin made of born and wood to perfom EONJIN MEURI with PUNCHAE. Most unmarried women decorated with DDA-AH-NEULIN MEURI, GUI-MIT MEURI, specially in palace with SAE-ANG MEURI. At palace, one put on a full dress with KEUN MEURI, and a simple dress with ER-YEO MEURI be decorated DDERL-JAM The CHOP-JI MEURI manifested social rank, class. Kids at CHO-SUN age had BA-DUK-PANMEURI and JONG-JONG MEURI. The ornament things are GACHE, DDERL JAM with EON-JIN M-EURI, and all kinds of rod-like hairpin and chignon accessory used in JJOK MEURI. IN DANGGE, JE-BI-BURI DANGGI used by ummarried women. DO-TOO-RAK DANGGI and AP DANGGI on a dress suit, and BE-SSI DANGGI used by 3∼4 years ungrown kids etc. were used. And at palace, kinds of CHUPJI used with JJOK MEURI showed social rank. In CHOSUN age, women want to keep shiny hair washed at TA-NO festival day, a treatment of bald hair used a forked remedy. In CHOSUN age, woman Soo-Bal hair style has DAE-SOO·DDEU-KOO-JI MEURI·CHO-P-GI MEURI·EON-JIN MEURI·SAE-ANG MEURI· and so on. We could find out Soo-Bal was developed very well by these variety hair styles. I attatched all of the hair style pictures step by step, and also explained detail my research foll owing these pictures.