• Title/Summary/Keyword: local energy

Search Result 1,966, Processing Time 0.028 seconds

Local Mean Water Layer Thickness in Countercurrent Stratified Two -Phase Fllow (물-증기 역류 성층이상유동에서의 국부 평균 액체층 두께)

  • Kim, Hho-Jung;Kim, Kap
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.10 no.6
    • /
    • pp.947-958
    • /
    • 1986
  • 물-증기 역류 성층이상유동에서의 평균 액체층 두께가 여러가지 경사각과 종횡비에 따라 측정되었다. 난류유동에 있어서 전단응력분포의 선형화와 von Karman의 혼합길이 이론을 근거로 평균 액체층의 두께에 대한 관계식이 제시되었으며 실험결과와 잘 일치하였음을 보였다. 접촉면에서의 조파저항이 고려되지 않은 해석결과는, 수평 성층유동의 경우에, 평균 액체층 두께보다는 오히려 파곡까지의 액체층 두께를 예측하고 있는 것으로 나타났다. 또한 평균 액체층 두께에 대한 실험 상관관계식이 계산시 편의를 위해 쉽게 인지할 수 있는 매개변수들의 항들롤 제시되었다.

Effect of Slit Ventilation System in Sportswear on Physiological Responses (스포츠웨어의 슬릿 벤틸레이션 시스템이 인체 생리반응에 미치는 효과)

  • Yeon, Soo-Min;Kim, Hee-Eun
    • Fashion & Textile Research Journal
    • /
    • v.7 no.1
    • /
    • pp.75-80
    • /
    • 2005
  • The purpose of this study was to investigate the effects of silt ventilation system on physiological responses. We measured rectal temperature, local skin temperature, clothing microclimate, blood pressure, heart rate, energy metabolism, body weight loss and subjective sensation during 70 minute, 50 min exercise period and 20 min rest period. The five women subjects randomly wore sportswear without slit ventilation system(NS sportswear) and sportswear with slit ventilation system(S sportswear) under the environmental condition of $25^{\circ}C$, 50%RH. The results of this study are as follows; Rectal temperature, mean skin temperature, clothing microclimate, blood pressure, heart rate, energy metabolism and body weight loss were significantly lower level in 'S sportswear'. In 'S sportswear', subjects replied less hot, less uncomfortable and less wet. Slit ventilation system can be used for bellow effect which is meaningful device of convection during exercise. We could find out that 'S sportswear' has advantage in physiological function.

DIRECTIONAL FILTER BANK-BASED FINGERPRINT IMAGE ENHANCEMENT USING RIDGE CURVATURE CLASSIFICATION

  • Lee, Joon-Jae;Lee, Byung-Gook;Park, Chul-Hyun
    • Journal of the Korean Society for Industrial and Applied Mathematics
    • /
    • v.11 no.2
    • /
    • pp.49-57
    • /
    • 2007
  • In fingerprints, singular regions including core or delta points have different directional characteristics from non-singular regions. Generally, the ridges of singular regions change more abruptly than those of nonsingular areas, thus in order to effectively enhance fingerprint images regardless of region, local ridge curvature information needs to be used. In this paper, we present an improved Directional Filter Bank (DFB)-based fingerprint image enhancement method that effectively takes advantage of such ridge curvature information. The proposed method first decomposes a fingerprint image into 8 directional subbands using the DFB and then classifies the image into background, low curvature, and high curvature regions using the directional energy estimates calculated from the subbands. Thereafter, the weight values for directional subband processing are determined using classification information and directional energy estimates. Finally, the enhanced image is obtained by synthesizing the processed subbands. The experimental results show that the proposed approach is effective in enhancing both singular and non-singular regions.

  • PDF

Control of Intensity Distribution Profile of Laser Beam using Beam Shaping Mask with Random Array Slits (빔셰이퍼 마스크를 이용한 레이저 빔의 강도 분포 제어)

  • Oh, Jae-Yong;Park, Deog-Su;Shin, Bo-Sung
    • Laser Solutions
    • /
    • v.15 no.2
    • /
    • pp.11-14
    • /
    • 2012
  • In this paper, we have made a proposal concerning the beam shaping mask(BSM) using random-array slits to control intensity distribution profile of laser beam and demonstrated its proprieties experimentally. When a lot of slits are set out irregularly, diffraction patterns of light does not appear but granularity patterns as a bundle of fibers appear. Intensity distribution profile is controlled by densities distribution of circular slits arrayed randomly because the number of slits and its area means amount of light energy through BSM. Namely as the number of slits in high intensity area is increased and that in low intensity area decreased, amount of light energy is same over all local parts. So gaussian intensity distribution could be changed to flat-top.

  • PDF

Electromigration Behavior of Eutectic SnPb Solder (공정 조성의 SnPb 솔더에서의 Electromigration 거동)

  • 최재영;이상수;주영창
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.16 no.1
    • /
    • pp.19-25
    • /
    • 2003
  • Electromigration characteristics of eutectic SnPb solder were studied using thin stripe-type test structures. Significant changes in the microstructure were observed after electromigration test, in which the temperature and the current density were varied from 80 to 100 $^{\circ}C$ and from 4.6${\times}$10$^4$A/$\textrm{cm}^2$ to 8.7${\times}$10$^4$A/$\textrm{cm}^2$. While voids or local thinning were found near the cathode end, hillocks were mainly observed near the anode end. From resistance measurements, it was calculated that the activation energy of the eutectic SnPb solder for electromigration was 0.77 eV. The dominant migrating element along the electron flow at 100$^{\circ}C$ was Pb.

A Study on the Convection Heat Transfer on the Side-wall with a Offset (오프셋이 있는 경우 측벽에서의 대류열전달에 관한연구)

  • Park, Yong-Il
    • Solar Energy
    • /
    • v.8 no.2
    • /
    • pp.57-65
    • /
    • 1988
  • The coefficients of convective heat transfer were investigated when air is jetted to surface of the heated side-wall. The temperature on the side-wall was measured when the offsets changed from 1.5 to 10.5 as 7 steps at the state of fixed Reynolds numbers that were 35000, 29000 and 23000. The experimental results are as follows: 1. The mean Nusselt number is very high on the surface of reattached flow region. 2. The offset and the recirculation flow region decreased, while the mean Nusselt number increased between the outlet of nozzle and the region of reattachment flow. 3. The local Nusselt number is not concerned with Reynolds number on the recirculation flow and on the reattached flow region when the offset decrease. But the Nusselt number increased only when Reynolds numbers on the wall jet flow region increased. 4. The mean and the maximum Nusselt number decreases linearly, and in particular its values rapidly decrease in accordance with changing of the offset from 1.5 to 3 in inverse proportion.

  • PDF

Cyclic Vehavior of composite Beams with Double-Circular Web Openings (쌍원형 개구부를 가진 합성보의 이력거동)

  • 김원기
    • Proceedings of the Earthquake Engineering Society of Korea Conference
    • /
    • 1999.10a
    • /
    • pp.162-169
    • /
    • 1999
  • Intentionally weakened girders near the beam-to-colum connection lead ductile failures at the weakened points prior to potential brittle failure at the connection points subjected to strong earthquake. Recent research investigated cyclic behavior of composite beams with a rectangular web opening and find out ductile failure of such beams due to plastic hinge formation of T-section at the four corners of the rectangular opening. But eventual failures of T-sections are resulted from local buckling of T-section having a narrow stem and a narrow bound of plastic hinge formation. This continuing research proposes double-circular opening instead of rectangular one in ofter to improve energy dissipation capacity as well as composite beam strength, Experimental test of two specimens was carried out and its results are compared with those of nonlinear finite element analyses

  • PDF

A Thermal hydraulic Investigation on ADSR Liquid Lead Target

  • Kim, Ju Y.;Byung G. Huh;Chang H, Chung;Tae Y. song;Park, Won S.
    • Proceedings of the Korean Nuclear Society Conference
    • /
    • 1998.05a
    • /
    • pp.666-671
    • /
    • 1998
  • Computational fluid dynamics(CFD) code FLUENT[11 was used to simulate the thermal hydraulic processes occuring in conceptual design of the accelerator-driven subcritical reactor(ADSR) liquid lead target. The purpose of the analysis is to investigate the thermal hydraulic characteristics of liquid lead as ADSR target material with various target geometries and injection locations of proton beam. In the calculation analysis, the local temperature of the liquid lead target rises to the boiling temperature very rapidly When the proton beam is injected from the bottom of the target system, the duration time to reach the boiling temperature is longer and the temperature distribution is flatter than other cases.

  • PDF

Geometrically Non-Linear Analysis for Shallow Arch using the 3-Dimensional Curved Beam

  • Lee, Dae-Hee;Eum, Se-Yoon
    • Proceedings of the Korean Nuclear Society Conference
    • /
    • 1996.05d
    • /
    • pp.259-266
    • /
    • 1996
  • This paper presents a geometrically non-linear formulation for the general curved beam element based on assumed strain fields and Timoshenko's beam theory. This general curved beam element is formulated from constant strain fields. And this element, designed in a local curvilinear coordinate system, is transformed into a global cartesian system in order to analyze effectively the general curved beam structures located arbitrarly in space. Numerical examples are presented to show the accuracy and efficiency of the present formulation. The results obtained from the present formulation are compared with those available in the literature and analysis by ANSYS.

  • PDF

Numerical Study on Heat Transfer Characteristics in Impinging Air Jet System (충돌분류시스템의 열전달 특성에 관한 수치적 연구)

  • Kum, Sung-Min;Kim, Dong-Choon
    • Journal of the Korean Solar Energy Society
    • /
    • v.23 no.4
    • /
    • pp.55-61
    • /
    • 2003
  • Heat transfer characteristics for an air jet vertically impinging on a flat plate with a set of hybrid rods was investigated numerically using the RNG k-$\varepsilon$turbulent model. A commercial finite-volume code FLUENT is used. The rods had cross sections of half circular and rectangular shapes. The heating surface was heated with a constant heat flux value of $1020W/m^2$. Parameters investigated were the jet Reynolds number, nozzle -to-plate spacing, the rod pitch and rod-to-plate clearance. The local and average Nusselt number were found to be dependent on the rod pitch and the clearance because installing rods disturbed the flow. Higher convective heat transfer rate occurred in the whole plate as well as in the wall jet region.