• 제목/요약/키워드: Surface Expansion

검색결과 1,001건 처리시간 0.028초

유한 요소법을 이용한 자동차용 디스크 브레이크의 열간 저더 해석 (Analysis of Hot Judder of Disc Brakes for Automotives by Using Finite Element Method)

  • 정성필;박태원;정원선
    • 대한기계학회논문집A
    • /
    • 제35권4호
    • /
    • pp.425-431
    • /
    • 2011
  • 차량 제동시 디스크와 패드사이의 미끄럼 접촉에 의해 발생하는 마찰열은 재질의 열 탄성 변형을 일으키고, 이는 접촉면의 압력 분포에 영향을 끼친다. 이러한 열탄성 불안정성 (Thermo-Elastic Instability, TEI)은 디스크의 고유 진동모드와 결합되어 열섬 현상 및 열간 저더 진동을 발생시킨다. 본 연구에서는 상용 유한 요소 해석 프로그램인 SAMCEF 를 이용하여 자동차용 통풍식 디스크에 대한 3 차원 열간 저더 해석을 수행하였다. Staggered approach 에 의거한 중간 처리기를 이용하여 구조-동역학 해석 결과와 열 전달 해석 결과를 교환하였다. 디스크 표면에 열섬이 발생하는 것을 확인하였고, 이를 디스크 고유 진동 모드와 비교함으로써 모드 형상과 열섬 분포의 관계를 분석하였다.

유채단백질의 Proteolysis에 의한 기능성 변화 (Functionality Changes of Rapeseed Protein upon Proteolysis)

  • 김충희;김효선;이장순
    • 한국식품영양과학회지
    • /
    • 제21권5호
    • /
    • pp.519-524
    • /
    • 1992
  • 탈지유채박(Brassica napus var. Youngsan)으로부터 추출, 정제하여 얻어진 유채단백질을 가수분해하여 가수분해물의 이화학적 및 기능적 특성을 조사하였다. 가수분해물의 UN 및 고유형광 스펙트럼은 각각 274nm, 360nm에서 최대치를 나타내었다. 황색도는 약간 감소한 반면 표면 소수성은 약 4배 감소하였다. SDS-PAGE 분석 결과 상당부분이 1.4~$1.2{\times}10^4$ dalton의 분자량을 가진 band로 나타났으며, pH별 용해도는 산성부근에서 10~15% 정도 증가하였고, 수분 및 유흡수성, 거품 팽창성, 에멀젼 안정성은 증가한 반면 절대 점도, 열 및 칼슘 응고성, 거품 안정성, 에멀젼 활성지수는 감소하였다.

  • PDF

CD40L 발현 K562 세포주를 이용한 시험관내 B 세포 증식과 항원제공능 증가 (Enhancement of Proliferation and Antigen Presentation of Human B Cells in Vitro by K562 Cells Expressing CD40L)

  • 박정용;윤성희;김은경;윤선옥;손현정;김태규
    • IMMUNE NETWORK
    • /
    • 제7권2호
    • /
    • pp.80-86
    • /
    • 2007
  • Background: CD40-activated B (CD40-B) cells might be an attractive source of autologous antigen-presenting cells (APCs) for immunotherapy due to the convenience to obtain from peripheral blood and expand in vitro. Moreover, CD40-B cells were found to be comparable with DCs in their capacity to raise antigen-specific CD8+ T cells. Here, we have established K562 cells expressing CD40L to expand CD40-activated B cells used for APCs. Methods: After activation of B cell by K562/CD40L, CD40-B cells were examined by counting B cell numbers. Surface expression of CD54, CD80, CD86 and HLA class II was measured by flow cytometry. The CD40-B cells were tested for its function as APC by mixed lymphocyte reactions (MLR) and by induction of T cell responses specific for pp65 peptide in vitro. Results: The expansion of B cells by K562/CD40L increased about 6-folds compared with anti-CD40 or K562. Furthermore, the expression of CD54, CD80, CD86 and HLA class II was up-regulated by K562/CD40L. B cells by K562/CD40L showed comparable antigen presentation activity with mature DCs as shown in MLR, INF-${\gamma}$ ELISPOT assay. Conclusion: These results suggest that K562/CD40L could be used to generate activated B cells as potent APCs which could be useful for cellular vaccination and adoptive immunotherapy.

CH4공기 제트 확산화염에서 CO2 첨가에 따른 단일 와동의 동적거동에 관한 연구 (An Investigation on Dynamic Behaviors of Single Vortex with CO2 Dilution in a CH4-Air Jet Diffusion Flame)

  • 황철홍;오창보;이대엽;이창언
    • 대한기계학회논문집B
    • /
    • 제27권9호
    • /
    • pp.1209-1219
    • /
    • 2003
  • The dynamic behaviors of the single vortex interacting with $CH_4-Air$ jet diffusion flame are investigated numerically. The numerical method is based on a predict-corrector scheme for a low Mach number flow. A two-step global reaction mechanism is adopted as a combustion model. Studies are conducted in fixed initial velocities for the three cases according as where $CO_2$ is added; (1) without dilution, (2) dilution in fuel stream and (3) dilution in oxidizer stream. A single vortex is generated by an axisymmetric jet, which is made by an impulse of a cold fuel when a flame is developed entirely in a computational domain. The simulation shows that $CO_2$ dilution in fuel stream results in somewhat larger vortex radius, and greater amount of entrainment of surrounding fluid than in other cases. Thus, the dilution of $CO_2$ in fuel stream enhances the mixing in single vortex and increases the stretching of the flame surface. The budgets of the vorticity transport equation are examined to reveal the mechanism of vortex formation when $CO_2$ is added. It is found that, in the case of $CO_2$ dilution in fuel stream, the vortex destruction due to volumetric expansion and the vortex production due to baroclinic torque are more dominant than in other cases.

정지기상위성 자료를 이용한 정량적 황사지수 개발 연구 (The Study on the Quantitative Dust Index Using Geostationary Satellite)

  • 김미자;김윤재;손은하;김금란;안명환
    • 대기
    • /
    • 제18권4호
    • /
    • pp.267-277
    • /
    • 2008
  • The occurrence and strength of the Asian Dust over the Korea Peninsular have been increased by the expansion of the desert area. For the continuous monitoring of the Asian Dust event, the geostationary satellites provide useful information by detecting the outbreak of the event as well as the long-range transportation of dust. The Infrared Optical Depth Index (IODI) derived from the MTSAT-1R data, indicating a quantitative index of the dust intensity, has been produced in real-time at Korea Meteorological Administration (KMA) since spring of 2007 for the forecast of Asian dust. The data processing algorithm for IODI consists of mainly two steps. The first step is to detect dust area by using brightness temperature difference between two thermal window channels which are influenced with different extinction coefficients by dust. Here we use dynamic threshold values based on the change of surface temperature. In the second step, the IODI is calculated using the ratio between current IR1 brightness temperature and the maximum brightness temperature of the last 10 days which we assume the clear sky. Validation with AOD retrieved from MODIS shows a good agreement over the ocean. Comparison of IODI with the ground based PM10 observation network in Korea shows distinct characteristics depending on the altitude of dust layer estimated from the Lidar data. In the case that the altitude of dust layer is relatively high, the intensity of IODI is larger than that of PM10. On the other hand, when the altitude of dust layer is lower, IODI seems to be relatively small comparing with PM10 measurement.

2단 응축 히트펌프 온수시스템의 사이클 해석 및 성능분석 (Performance of Heat Pump Water Heater with Dual Condenser)

  • 유영선;김영중;강금춘;백이;윤진하;강연구;이형모
    • Journal of Biosystems Engineering
    • /
    • 제31권5호
    • /
    • pp.423-429
    • /
    • 2006
  • The heat pump water heater developed in this research consisted of one evaporator, one compressor, 1st condenser, 2nd condenser, one expansion valve, one water tank, one recirculation circuit and etc. The performance of heat pump water heater was tested and analyzed. The quantities of output water changed linearly from 2380 to $660{\ell}/h$, and the output water temperature changed curvedly from 29.9 to $44.5^{\circ}C$ when the opening rate of recirculation valve changed from 0 to 100%. The COP of heat pump water heater increased from 3.0 to 3.8 when the quantities of output water changed from 660 to $2380{\ell}/h$. When the temperature distributions of water tank were measured during 50 minutes after turning on the heat pump, the temperature stratification by the level appeared apparently. When the inlet water temperature changed from 30 to$50^{\circ}C$, the output energy of heat pump hardly changed. The surface area of double pipe heat exchanger changed from 0.429 to $6.254m^2$ when the compressor capacity increased from 1.0 to 50.0 PS.

노즐 탭과 노즐 내부 낮은 돌출부가 초음속 제트유동장에 미치는 영향에 관한 연구 (An Experimental Study on the Effects of Tabs and Small Proturbances Inside Nozzle on Supersonic Jet Flowfield)

  • 진원진;조창권;이열;윤웅섭
    • 한국항공우주학회지
    • /
    • 제30권5호
    • /
    • pp.24-31
    • /
    • 2002
  • 축 대칭 원형노즐 출구에 삼각형 형태의 작은 탭이나 얇은 테이프가 부착되었을 때 나타나는 초음속 제트유동장의 변화에 관한 연구가 쉴리렌 영상과 피토압력 측정을 통하여 수행되었다. 노즐 출구면적의 1 %에 해당하는 작은 탭에서 나타나는 유동방향 와류에 의한 제트유동 변화는 유동이 과소팽창 될 때 완전팽창과 과대팽창의 경우에 비하여 더 크게 나타나며 이로 인한 유동유입이 더 크게 나타남을 알 수 있었다. 탭의 설치각도 변화에 의한 영향도 평가되었으며, 유동이 과대팽창 될 때 노즐 안으로 구부러진 탭의 설치가 충격파의 간섭강도를 약화시키고 이로 인한 마하디스크의 소멸현상을 관찰할 수 있었다. 아울러 노즐내부 낮은 높이의 돌출부가 후방 유동장의 원주방향으로 압력변화를 나타내고, 이러한 압력변화는 유동의 팽창 정도에 영향을 받음을 알 수 있었다.

고추 (Capsicum annum L.)식물체 및 배양세포의 Capsidiol 생산 유도 (Elicitation of Seedlings and Cultured Cells for the Production of Capsidiol in Capsicum annum L.)

  • 권순태;정은아;박해영;손건호
    • 식물조직배양학회지
    • /
    • 제28권5호
    • /
    • pp.249-254
    • /
    • 2001
  • 고추 (Capsicum annum L.)의 잎, 과실 및 배양세포를 대상으로 capsidiol의 생산을 유도하기 위해 자외선, cellulase 및 jasmonic acid (JA)의 영향을 구명하였다. 배양세포는 cellulase 0.05 mg/L나 JA 0.1 mg/L처리로 세포의 capsidiol 생산을 위한 유도가 가능하였다. Elicitor를 처리한 배양세포는 자체 생성한 capsidiol의 독성에 의해 활력이 급격히 감소하여 48시간 이후에는 세포활력을 거의 잃어버리는 것으로 나타났다. 자외선 스트레스의 처리는 48시간의 처리로 고추 잎의 capsidiol의 함량을 최고 45.4배까지 증가시켰다. Cellulase 0.05 mg/L또는 JA 1.0mg/L를 식물의 잎 표면이나 과실의 기부에 미세주사기로 주입하면, 잎은 elicitor를 주입한 부위로부터 합성된 capsidiol의 독성으로 병반이 확대되어 가는 것을 관찰할 수 있었으며, 과실에서도 elicitor의 주입에 의해 병반이 확산되며 elicitor를 주입한 과실에서 capsidiol의 생성이 확인되었다.

  • PDF

Strain-induced enhancement of thermal stability of Ag metallization with Ni/Ag multi-layer structure

  • 손준호;송양희;김범준;이종람
    • 한국진공학회:학술대회논문집
    • /
    • 한국진공학회 2010년도 제39회 하계학술대회 초록집
    • /
    • pp.157-157
    • /
    • 2010
  • Vertical-structure light-emitting diodes (V-LEDs) by laser lift-off (LLO) have been exploited for high-efficiency GaN-based LEDs of solid-state lightings. In V-LEDs, emitted light from active regions is reflected-up from reflective ohmic contacts on p-GaN. Therefore, silver (Ag) is very suitable for reflective contacts due to its high reflectance (>95%) and surface plasmon coupling to visible light emissions. In addition, low contact resistivity has been obtained from Ag-based ohmic contacts annealed in oxygen ambient. However, annealing in oxygen ambient causes Ag to be oxidized and/or agglomerated, leading to degradation in both electrical and optical properties. Therefore, preventing Ag from oxidation and/or agglomeration is a key aspect for high-performance V-LEDs. In this work, we demonstrate the enhanced thermal stability of Ag-based Ohmic contact to p-GaN by reducing the thermal compressive stress. The thermal compressive stress due to the large difference in CTE between GaN ($5.6{\times}10^{-6}/^{\circ}C$) and Ag ($18.9{\times}10^{-6}/^{\circ}C$) accelerate the diffusion of Ag atoms, leading to Ag agglomeration. Therefore, by increasing the additional residual tensile stress in Ag film, the thermal compressive stress could be reduced, resulting in the enhancement of Ag agglomeration resistance. We employ the thin Ni layer in Ag film to form Ni/Ag mutli-layer structure, because the lattice constant of NiO ($4.176\;{\AA}$ is larger than that of Ag ($4.086\;{\AA}$). High-resolution symmetric and asymmetric X-ray diffraction was used to measure the in-plane strain of Ag films. Due to the expansion of lattice constant by oxidation of Ni into NiO layer, Ag layer in Ni/Ag multi-layer structure was tensilely strained after annealing. Based on experimental results, it could be concluded that the reduction of thermal compressive stress by additional tensile stress in Ag film plays a critical role to enhance the thermal stability of Ag-based Ohmic contact to p-GaN.

  • PDF

차륜 답면의 열손상에 대한 잔류응력 평가 (Evaluation of Residual Stress for Thermal Damage of Railway Wheel Tread)

  • 권석진;서정원;이동형;함영삼
    • 한국정밀공학회지
    • /
    • 제28권5호
    • /
    • pp.537-542
    • /
    • 2011
  • The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.