• Title/Summary/Keyword: Lift Off

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Dynamic contact response of a finite beam on a tensionless Pasternak foundation under symmetric and asymmetric loading

  • Coskun, Irfan
    • Structural Engineering and Mechanics
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    • 제34권3호
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    • pp.319-334
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    • 2010
  • The dynamic response of a finite Bernoulli-Euler beam resting on a tensionless Pasternak foundation and subjected to a concentrated harmonic load is investigated in this study. This load may be applied at the center of the beam, or it may be offset from the center. Since the elastic foundation is assumed to be tensionless, the beam may lift off the foundation, resulting in contact and non-contact regions in the system. An analytical/numerical solution is obtained from the governing equations of the contact and non-contact regions to determine the coordinates of the lift-off points. Although there is no nonlinear term in the equations, the problem appears to be nonlinear since the contact regions are not known in advance. Due to that nonlinearity, the essentials of the problem (the coordinates of the lift-off points) are calculated numerically using the Newton-Raphson technique. The results, which represent the symmetric and asymmetric responses of the beam, are presented graphically in this work. They illustrate the effects of the forcing frequency and the beam length on the extent of the contact regions and displacements.

Ti 전극의 Lift-off 공정을 이용한 홀 패턴 형성과 TCO-less 염료감응형 태양전지의 응용 (A Formation of Hole Pattern on Ti Electrode by Lift-off and Its Application to TCO-less Dye-sensitized Solar Cells)

  • 정행윤;기현철;구할본
    • 한국전기전자재료학회논문지
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    • 제28권3호
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    • pp.175-179
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    • 2015
  • In this study, we propose Ti hole pattern structure on the transparent conductive oxide (TCO) less dye-sensitized solar cells (DSSCs) using the lift-off process to improve the low light transmittance and low efficiency caused by opaque Ti electrode. The formation of Ti hole patterns make it possible to move the dye adsorption and electrolyte. The DSSCs with Ti hole patterns showed a higher photoelectric conversion efficiency (PCE) than those with general structure by 11.1%. As a result, The Ti hole pattern structure can be improved to increase the light absorption of the dyes and PCE of the TCO-less DSSCs is also increased.

KSLV-I 외부 음향 하중 예측 및 비행 시험 결과와의 비교 (Prediction of Lift-off Acoustic Loads of KSLV-I and Its Comparison with Flight Measurements)

  • 박순홍;서상현;장영순
    • 항공우주기술
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    • 제10권1호
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    • pp.13-19
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    • 2011
  • 수정된 NASA SP-8072 분포 음원 방법 (Method 2)를 이용하여 KSLV-I의 발사 음향 하중을 예측하고, 이 결과를 비행 시험시의 측정 결과와 비교하였다. 2차 비행 시험시에 케이블 마스트의 4개소에서 발사 음향 하중을 측정하였고, 인터스테이지의 텔레메트리 데이터도 입수하여 비교하였다. 예측된 음향 하중 스펙트럼은 측정 스펙트럼과 유사한 피크 주파수 및 형태를 가지며 약 7dB의 안전 여유를 가지고 예측됨을 알 수 있었다.

Lift-off법에 의한 RTD의 제조 (The fabrication of RTD via Lift-off process)

  • 김종성;원종각
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2000년도 추계학술대회 논문집
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    • pp.299-302
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    • 2000
  • RTD temperature sensor is a thermoresistor which uses the liner dependence of the resistance of the sensing material on the temperature, and has good stability and sensibility, so it can be used in highly precise temperature measurement. In this study RTD sensor was fabricated using Pt thin film. The Pt thin film was deposited on alumina using DC-Sputter, and annealed with various temperature. Through the experiments of XRD, AFM, 4-point probe, the surface structure of the thin film with annealing conditions and their effects on the electrical resistance were investigated. RTD with serpentine pattern was fabricated using Lift-off and resistance-temperature characteristics were studied.

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리프트오프 방식을 이용한 탄성표면파 필터의 제조 (The Preparation of Surface Acoustic Wave Filter using Lift-off method)

  • 이동윤;박재준;윤석진
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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    • pp.242-243
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    • 2005
  • SAW filters were fabricated on $LiNbO_3$ substrates to evaluate frequency response and properties of photolithography. In the both of etch and lift-off methods, lift off method was superior to etch method in fabrication process. Frequency response property was measured by network analyzer. From a measurement of acoustic property, SAW propagation velocity was 3574.9m/sec for $LiNbO_3$ SAW filter.

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로드/언로드 성능향상을 위한 서스팬션의 구조최적화 (Integrated Optimal Design for Suspension to Improve Load/Unload Performance)

  • 김기훈;손석호;박경수;윤상준;박노철;양현석;최동훈;박영필
    • 정보저장시스템학회논문집
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    • 제2권2호
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    • pp.130-137
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    • 2006
  • The HDD(hard disk drive) using Load/unload(L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop(CSS). It has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. The main objects of L/UL are no slider-disk contact or no media damage. For realizing those, we must consider many design parameters in L/UL system. In this paper, we focus on lift-off force. The 'lift-off' force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. To minimize 'lift-off' force we optimizes the slider and suspension using the integrated optimization frame, which automatically integrates the analysis with the optimization and effectively implements the repetitive works between them. In particular, this study is carried out the optimal design considering the process of modes tracking through the entire optimization processes. As a result, we yield the equation which can easily find a lift-off force and structural optimization for suspension.

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음원 분포선 위치가 발사체 이륙 음향하중에 미치는 영향 (Effect of Source Line Location on Lift-off Acoustic Loads of a Launch Vehicle)

  • 최상현;이정권;이익진
    • 한국소음진동공학회논문집
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    • 제25권8호
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    • pp.539-545
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    • 2015
  • Intense acoustic load is generated when a launch vehicle lifts off, causing the damaging vibrations at the launch vehicle or satellite within the fairing. This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. As a test example, the lift-off acoustic load on the Korean launch vehicle, NARO, is predicted by the existing calculation tool, the modified Eldred's second method. Although the acoustic sources, assumed as point sources, are to be located along the center line of the exhaust plume when using the Eldred's prediction method, the exact location of the deflected center line of exhaust gas flow is not usually known. To search for the most appropriate source positions, six models of source line distribution are suggested and the acoustic load prediction results from these models are compared with the actual measurements. It is found that the predicted sound pressure spectrum of the Naro is the most similar to the measured data when the centerline of the turbulent kinetic energy contour is used as the source line.

GIS내에 함유된 자유 도전성 파티클의 거동해석 (A Numerica analysis on the lift-off motion of Free Conducting Particle in GIS)

  • 이방욱;구자윤
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1996년도 하계학술대회 논문집 C
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    • pp.1925-1928
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    • 1996
  • In this work, the behavior of conducting wire type particles existing inside the cylinder type coaxial electrode has been systematically investigated by charge simulation method and electrostatic force analysis from the view point of the acquired charging before being lifted off into the gap under the high ac voltage. Spheroidal charge are adopted as a image charge for the CSM analysis in order to calculate the acquired charges of the particles which are erected on the surface of the outer electrode. For this purpose, different material of the particle and their lengths and diameters have been considered in view to calculate their lift-off field, acquired charge and to understand their effect on the lift-off voltage. The results imply that the particle lengths and diameter have an different influence on the particle behavior in GIS system.

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공기윤활 범프포일 저널 베어링의 내구성 특성에 관한 연구 (A Study on the Durability Characteristics of an Air-lubricated Bump Foil Journal Bearing)

  • 이용복;김태호;김창호;이남수;장건희
    • Tribology and Lubricants
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    • 제18권2호
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    • pp.153-159
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    • 2002
  • This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil Journal bearing. A 52 N weighted bump foil bearing sleeve was lilted off from a rotating Journal at about 3,000 rpm, and produced a load capacity of 500 N at an operating speed of 15,000 rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surfAce were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

공기윤활 범프포일 저널 베어링의 내구성 특성에 관한 연구 (A Study on the Durability Characteristics of an Air-lubricated Bump Foil Journal Bearing)

  • 김태호;이용복;김창호;이남수;장건희
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2001년도 제34회 추계학술대회 개최
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    • pp.212-219
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    • 2001
  • This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil journal bearing. A 52N weighted bump foil bearing sleeve was lifted off from a rotating journal at about 3,000rpm, and produced a load capacity of 500N at an operating speed of 15,000rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surface were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

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