• 한국유체기계학회 논문집
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• 제18권6호
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• pp.12-18
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• 2015

Recently, the development trend of turbomachinery is high capacity and high efficiency. Most of turbomachinery in the market are adopting ball bearings or air foil bearings. However, ball bearings have a limit for high speed product over $2.0{\times}10^6DN$(product of the inner diameter of the bearing in mm (D) and the maximum speed in rpm (N)). Air foil bearings have a limit for high axial load for high power products over 200~300 HP(horse power). Magnetic bearing is one of the solutions to overcome the limits of high speed and high axial load. Because magnetic bearings have no friction between the rotor and the bearings, they can reduce the load of the motor and make it possible to increase the rotating speed up to $5.0{\times}10^6DN$. Moreover, they can have high axial load capacity, because the axial load capacity of magnetic bearing depends on the capacity of the designed electromagnet. In this study, the radial and thrust magnetic bearings are designed to be applied to the 200 HP class turbo blower, and their performance was evaluated by the experiment. Based on the tests up to 26,400 rpm and 21,000 rpm under the no-load and load condition, respectively, it was verified that the magnetic bearings are stably support the rotor of the turbo blower.

• 센서학회지
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• 제17권6호
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• pp.418-424
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• 2008

The PZT based piezoelectric thick films prepared by screen printing method have been mainly used as a functional material for MEMS applications due to their compatibility of MEMS process. However the screen printed thick films generally reveal poor electrical and mechanical properties because of their porous microstructure. To improve microstructure we mixed attrition milled powder with ball milled powder of 0.01Pb$(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3$-$0.35PbTiO_3$-$0.23PbZrO_3$+0.1 wt% ${Y_2}{O_3}$+1.5 wt% ZnO composition. By mixing 25 % of attrition milled powder and 75 % of ball milled powder, the broadest particle size distribution was obtained, leading to a dense thick film with crack-free microstructure and improved dielectric properties. The X-ray diffraction analysis revealed that the film was in wellcrystallized perovskite phase. The remanent polarization was increased from $13.7{\mu}C/cm^2$ to $23.3{\mu}C/cm^2$ at the addition of 25 % attrition milled powder.

• 한국도로학회논문집
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• 제1권2호
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• pp.121-133
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• 1999

본 논문은 국내 정유사에서 생산되는 도로 포장용 아스팔트에 대하여 노화에 따른 거동 특성을 파악하였다. 이를 위해 국내의 5개 정유회사에 생산되는 두가지 등급의 아스팔트 제품(침입도 85-100, 침입도 60-70)을 포함한 총 9종에 대하여 노화 단계별(노화 이전, 단기노화, 장기노화)로 국내 스트레이트 아스팔트의 침입도$(25^{\circ}C)$, 점도$(50^{\circ}C\;135^{\circ}C)$, 연화점, 및 DSR 시험$(-20^{\circ}C\sim30^{\circ}C)$을 수행하여, 아스팔트의 물성 변화 특성을 고찰하였다. 연구 결과, 국내 스트레이트 아스팔트의 거동은 고온($60^{\circ}C$근방) 및 상온$(10-30^{\circ}C)$범위에서 정유사 제품에 따라 상당한 차이를 나타내었으며, 저온의 경우에는 정유사 제품이나 등급에 관계없이 거의 유사한 거동을 나타내었다. 따라서 어느 정유사의 아스팔트를 사용하는가에 따라, 저온에서의 온도 균열에 대한 저항성은 다소 비슷한 수준일 것으로 판단되지만, 소성변형 및 피로 균열에 대한 저항성이 상이하게 나타날 것으로 판단된다.

• 한국정보통신학회논문지
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• 제11권6호
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• pp.1062-1068
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• 2007

유비쿼터스게임을 디자인하고 개발하기 위하여 현실세계과 가상세계와의 자연스럽고 다양한 상호작용이 필요하다. 이는 물리적인측면 뿐 아니라 상황변화에 알맞은 대응 감지기술을 필요로한다. 이를 위하여 가상세계와의 유저인터페이스 모델을 정의하고 이를 구현하기 위하여 텍타일감지 시스템을 제작하였다. 텍타일 데이터는 외부환경에 민감하므로 신호처리방법을 사용하여 잡음을 제거하고 유저인터페이스를 위한 데이터 형태로 외부입력을 분석 추론하였다. 이는 일반적인 게임에서 사용하는 마우스나 키보드에 따른 입력과 전혀 다른 형태의 입력으로 유비쿼터스 환경에서의 플레이어의 상황대응에 대한 중요한 정보를 제공하여준다. 구현한 시스템을 통하여 가상공간상에 존재하는 공에 작용한 힘을 3차원적으로 분석하여 힘의 위치, 크기, 분포, 방향 등을 분석하는 방법을 제시 해보았으며 이 같은 실세계 정보 분석을 통하여 가상공간상에서 3차원적인 자연스러운 반작용이 가능하도록 하는 가능성을 보였다. 이 같은 방법들은 유비쿼터스 게임의 상호작용 개발을 위한 기초자료로 사용될 수 있다.

• 농업생명과학연구
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• 제43권4호
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• pp.33-36
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• 2009

Globose to clavate base-ball sized, pear shaped, fruiting bodies were found under the Himalayan cedar, Cedrus deodora at less fertile and poor sandy poor soil in the campus of Gyeongsang National University in Jinju, Korea. The fruiting body was at first, round to club-shaped, usually with a narrow, rooting base with yellowish rhizomorphs attached to it and lack a volva and a sterile base. The peridium of fruiting body was tough and crusty. The peridioles were white pea-like capsules in a blackish matrix. The color change to darker tints of brown at the top of the exterior peridium reflected the gradual ripening of the interior gleba and peridioles, which proceeded from the top downward to become a mass of spore dust, appearing as cinnamon brown at the apex of the vertical section. At around this stage, the peridium cracked open linearly, exposing the gleba with powdery spores mass released from overmatured peridioles. Spores were more or less round, warty or spiny, 10 to $12{\mu}m$; globose, cinnamon brown in powdery mass, with spines up to $2{\mu}m$ long. The thin peridium ruptured further in response to the disintegration of the peridioles, releasing the powdery spores, which proceeded until whole fruiting body disappeared leaving the dry spore dust coats in the vicinity. The absence of a capillitium is a distinctive characteristic that distinguishes the specimen from other puff-ball fungi and from most of earthballs. Based on the above characteristics, the specimen was identified as Poslithus tinctorius.

• 대한조선학회논문집
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• 제31권3호
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• pp.129-134
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• 1994

레이저 절단기는 고도의 정밀을 요하는 선체구조강판의 가공용으로 최근 조선소에서 사용되게 되었으며, 정밀성 유지를 위해서 이 시스템 자체의 운동으로 인한 변형은 일정한도 내에서 유지되어야 한다. 본 논문에서는 새로 개발된 레이저 절단기의 모드해석 및 구조해석을 이 시스템의 설계요구조건에 부합하는지를 검토하기 위하여 수행하였으며, 이를 위하여 유한 요소 모델링의 효과적인 기법과 가상 질량요소를 분대하는 기법, 가속도장의 변화로 주어지는 외력조건의 구체화 방법등을 제시하였다. 또한 고유진동해석을 수행하여 이 시스템의 동적효과 존재 여부를 검토하였으며 시간영역의 동적해석을 하지 않고 정적해석을 통한 시스템 특성 규명 타당성을 규명하였다. 해석 접근 방법의 유용성이 입증되었으며 결과적으로 본 논문에서 보여 준 해석기법은 유사한 시스템의 특성 규명에 유효하게 적용될 수 있음을 시사하고 있다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.822-823
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• 2014

다시점 디스플레이용 영상은 주로 레퍼런스가 되는 컬러 카메라와 깊이 카메라의 영상을 입력 받아 DIBR (Depth Image Based Rendering) 기법을 활용, 3차원 점 구름 형태로 재구성 한 후 가상 카메라를 여러 시점에서 배치하여 중간 영상을 생성하여 조합하였다. 이렇게 다시점 중간 영상을 생성하면 원래의 시점에서는 구멍이 없었지만 다른 시점에서는 구멍(Hole)이 보이는 현상이 발생한다. 기존에는 틈새 영역을 채우는 알고리즘을 개발하거나 깊이 영상을 보정하여 개선시키는 방법을 연구하였으나 본 논문에서는 점 구름을 메시(Mesh)화 시키는 알고리즘 중 한 가지인 볼 피봇팅(Ball Pivoting) 방법을 적용시켜 중간 영상의 화질 개선 방법을 설명하고 있다. 마이크로소프트사의 발레와 브레이크 댄서 영상에 개발된 개선 방법을 적용시켜 보았고 PSNR로 비교할 때 약 0.18~1.19정도의 향상을 보임을 확인하였다. 본 논문을 통해 개선 방법과 실험방법, 그리고 결과에 대해 설명한다.

• 패션비즈니스
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• 제27권2호
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• pp.39-51
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• 2023

The purpose of this study was to effectively improve the thigh muscles of adult women working from home due to COVID-19. In this study, ten adult women working from home performed 1) an electromyography test, 2) a static balance test on a balance board, and a 3) dynamic balance test by squatting on a Bosu ball four times: before electric muscle stimulation (EMS), after EMS, after high-intensity circuit training (HICT), and after EMS plus HICT. For this test, EMS was attached to a medical knee support to manufacture an EMS knee band that could be easily worn regardless of the location. For the experiment, EMS(electric muscle stimulation) was attached to the medical knee protector to manufacture an EMS knee band that can be easily worn regardless of location, and was measured based on the right foot. The study results confirmed that in all tests (electromyography test, static balance test on the balance board, and dynamic balance test by squatting on a Bosu ball), thigh strength improved in the order of treatment before EMS, after EMS, after HICT, and after EMS plus HICT. The study showed that people working from home or with activity restrictions due to COVID-19 had better exercise effects when wearing the EMS knee band and performing HICT, even in a small space.

• Tribology and Lubricants
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• 제40권4호
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• pp.111-117
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• 2024

Due to global CO₂ emission reductions and fuel efficiency regulations, the trend toward transitioning from internal combustion engine vehicles to electric vehicles (EVs) has accelerated. Consequently, the problem of EV failures has become a focal point of active research. The parasitic capacitance generated during motor-shaft rotation induces voltage that deteriorates the raceway and ball surfaces of bearings, causing electrical damage in EVs. Despite numerous attempts to address this issue, most studies have been conducted under high viscosity lubricant and low load conditions. However, due to factors such as high-speed operation, rapid acceleration and deceleration, motor heating, and motor system-decelerator integration, current EV applications have shown diminished stability in lubrication films of motor bearings, thereby leveraging the investigation to address the risk of electrical damage. This study investigates the electrical damage to rolling bearing elements in EV motor drive systems. The experimental analysis focuses on the effects of electric currents and operational loads on bearing integrity. A test rig is designed to generate high-rate voltage specific to a motor system's parasitic capacitance, and bearing samples are exposed to these currents for specified durations. Component evaluation involves visual inspections and vibration measurements. In addition, a predictive model for electrical failure is developed based on accumulated data, which demonstrates the ability to predict the likelihood of electrical failure relative to the duration and intensity of current exposure. This in turn reduces uncertainties in practical applications regarding electrical erosion modes.

• 한국생활과학회지
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• 제21권2호
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• pp.315-329
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• 2012

The purpose of this study was to examine clothing purchase behavior of sports participants based on outdoor sports types and sports participation motivation. The research was conducted with the use of a self-administered questionnaire. A total of 703 respondents between the ages of 25 and 55 participated in the research through an internet survey. Motivation for participation in particular sports was comprised of four factors: impress others, mental rejuvenation, social interaction, and health maintenance/improvement. Perceived benefits of clothing choice were categorized into three factors: brand/fashion pursuit, positive image pursuit, and practicality pursuit. Outdoor sports activities was categorized into six types, climbing, jogging, cycling, fishing, golf, and others including ball games. Each sports group presented differences in demographics, sports motivation factors, and benefit factors. Four segments were identified based on sports participation motivation: active group, social group, health and revitalization group, and inactive group. The active group considered three clothing benefits and 14 evaluative criteria as being the most important among the four segments, indicating the major target market for outdoor sportswear brands. On the other hand, the members of inactive group showed passive attitudes toward clothing purchasing behaviors. This study discusses the results of this research within the context of the managerial implication for outdoor sports marketers.