• 제목/요약/키워드: Radius Ratio

검색결과 730건 처리시간 0.024초

유효우물반경 산정 경험공식의 일반화에 대하여 (On the Generalized Empirical Equation for Effective Wellbore Radius)

  • 최병수
    • 한국지하수토양환경학회지:지하수토양환경
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    • 제13권3호
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    • pp.15-20
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    • 2008
  • 지하수토양환경학회지 제12권 3호(2007. 6.)에 게재된 단공시험 관련 논문에서 제시한 유효우물반경 산정을 위한 3개의 경험공식을 단일화 하는 방법에 대하여 검토하였다. 검토의 착안사항은 경험공식들의 누승상수가 허용오차범위내의 비슷한 값을 가지고 있으며, 또한 양수정 및 관측정 저류계수 비의 제곱근 (${\sqrt{{S_p}/{S_o}}}$) 값이 유효우물반경과 우물 반경의 비(${r_e}/{r_w}$)와 거의 일치되게 나타나는 것이다. 이를 기초로 하여 3개의 경험공식을 단일화하고 대수층 조건별 저류계수 대표 값을 추정 적용하여 비례상수 값으로 대체하는 유효우물반경 산정 일반화 공식을 유도 하였다.

고정된 바깥반경에 기준한 pin 핀의 최적화 (Optimization of a Pin Fin Based on Fixed Outer Radius)

  • 강형석;최수근
    • 산업기술연구
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    • 제28권B호
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    • pp.3-7
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    • 2008
  • A cylindrical pin fin with variable fin base thickness is optimized based on fixed outer radius by using the one dimensional analytic method. Heat loss from the pin fin with fixed outer radius is presented as a function of the fin length. The ratio of in length for optimum heat loss to that for the maximum heat loss is listed. The maximum heat loss and effectiveness and the fin length for the optimum heat loss are presented as a function of fin base thickness and outer radius. One of the results presents the maximum effectiveness decreases rapidly first and then decreases slowly as the fin outer radius increases.

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연직배수재(VDs)에 의한 오염지반정화 메커니즘 연구 (Mechanism of Soil Remediation in Contaminated Area Using Vertical Drains)

  • 이행우;장병욱;강병윤;김현태
    • 한국농공학회논문집
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    • 제47권5호
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    • pp.63-71
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    • 2005
  • In-situ soil remediation mechanism through the vertical drains (VDs) is analyzed with numerical model as the error and complementary error function. Results from in-situ test and analysis indicate that the contaminant concentration ratio as initial one ( C/$C_0$) increases as the radius ratio ( r/R) increases from the injection well, and also increases as the depth ratio ( z/ H) increases from the top of contaminated area. The elapse time needed to attain $50\%$ and $90\%$ clean up level ($ t_{50},\;t_{90}$) increases as the radius ratio ( r/R) and the depth ratio ( z/ H) increase. As above results, the procedure of soil flushing in contaminated area using vertical drains makes progress from the top of injection well to the bottom of extraction well.

보강된 복합적층 원통형패널의 좌굴거동 (Buckling Behavior of Stiffened Laminated Composite Cylindrical Panel)

  • 이종선;원종진;홍석주;윤희중
    • 한국공작기계학회논문집
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    • 제12권5호
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    • pp.88-93
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    • 2003
  • Buckling behavior of stiffened laminated composite cylindrical panel was studied using linear and nonlinear deformation theory. Various buckling load factors are obtained for stiffened laminated composite cylindrical panels with rectangular type longitudinal stiffeners and various longitudinal length to radius ratio, which made from Carbon/Epoxy USN150 prepreg and are simply-supported on four edges under uniaxial compression. Buckling behavior design analyses are carried out by the nonlinear search optimizer, ADS.

Buckling analysis of filament wound composite cylindrical shell for considering the filament undulation and crossover

  • Guo, Zhangxin;Han, Xiaoping;Guo, Meiqing;Han, Zhijun
    • Structural Engineering and Mechanics
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    • 제55권2호
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    • pp.399-411
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    • 2015
  • The buckling equations of filament wound composite cylindrical shell are established. The coefficients $K_{ij}$ and $L_{ij}$ of the buckling equations are determined by solving the equations. The geometric analysis and the effective stiffness calculation for the fiber crossover and undulation region are respectively accomplished. Using the effective stiffness of the undulation region, the specific formulas of the coefficients ${K^{\prime}}_{ij}$ and ${L^{\prime}}_{ij}$ of the buckling equations are determined. Numerical examples of the buckling critical loads have been performed for the different winding angles and stacking sequences cylindrical shell designs. It can be concluded that the fiber undulation results in the less effect on the buckling critical loads $P_{cr}$. $P_{cr}$ increases with the thickness-radius ratio. The effect on $P_{cr}$ due to the fiber undulation is more obvious with the thickness-radius ratio. $P_{cr}$ decreases with the length-radius ratio. The effect on $P_{cr}$ due to the fiber undulation can be neglected when the ratio is large.

Determination of an Optimum Orbiting Radius for an Oil-Less Scroll Air Compressor

  • Kim, Hyun-Jin;Lee, Yong-Ho;Kwon, Tae-Hun
    • International Journal of Air-Conditioning and Refrigeration
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    • 제16권4호
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    • pp.124-129
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    • 2008
  • Design practice has been made on an oil-less scroll air compressor as an air supply device for a 2 kW fuel cell system where air pressure of 2 bar and flow rate of 120 liter/min are required. Basic structure of the scroll compressor includes double-sided scroll wrap for the orbiting scroll driven by two crankshafts connected to each other by a timing belt. These features can eliminate thrust surface which otherwise would produce frictional heat and jeopardize reliable operation of the orbiting scroll and the scroll element's deformation as well. This study focuses on optimum scroll wrap design; orbiting radius has been chosen as an independent design parameter. As the orbiting radius changes, scroll sizes such as scroll base plate and discharge port diameters change accordingly. Gas compression-related losses and mechanical loss also change with the orbiting radius. With a scroll base plate diameter of 120mm at most and discharge port of at least 10mm, the orbiting radius should be within the range of 2.5-4.0mm. With this range of the orbiting radius, it was estimated by performance analysis that the compressor efficiency reached to a maximum of ${\eta}_c$=96% at the orbiting radius of $r_s$=3.5mm for the scroll wrap height-to-thickness ratio of h/t=5.

접촉식쌍성의 질량비 분포에 따른 일반적 특성 (GENERAL PROPERTIES OF CONTACT BINARY SYSTEM FOR MASS RATIO DISTRIBUTION)

  • 오규동
    • Journal of Astronomy and Space Sciences
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    • 제16권1호
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    • pp.31-40
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    • 1999
  • Svechnikov & Kuznetsova(1990)의 목록으로부터 761개의 접촉식쌍성을 택하여 그의 물리적 특성에 따라 공통 복사대기층을 갖는 CE형과 공통 대류대기층을 갖는 CW형으로 분류하여 질량비에 따른 그의 특성을 분석하였다. 그 결과 분광형이 조기형인 CE형은 만기형인 CW 형에 비교하여 주성과 반성의 온도차($$\mid${Delta}T$\mid$$)가 크며 주기는 길게 나타났다. 그런데 CW형은 CE형에 비교하여 질량비가 다소 좁은 범위(0.3$L_2/L_1=0.01+0.89q$의 상관 관계를 보였다. 한편, 질량비에 따른 반경과의 관계에서는 CE형과 CWs형의 차이의 원인이 반성의 반경 때문임을 확인하였으며, CW형 접촉식쌍성의 질량비에 따른 두 별의 반경의 합과 반경비와의 새로운 관계를 제시하였다.

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Robust Watermarking Scheme Based on Radius Weight Mean and Feature-Embedding Technique

  • Yang, Ching-Yu
    • ETRI Journal
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    • 제35권3호
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    • pp.512-522
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    • 2013
  • In this paper, the radius weight mean (RWM) and the feature-embedding technique are used to present a novel watermarking scheme for color images. Simulations validate that the stego-images generated by the proposed scheme are robust against most common image-processing operations, such as compression, color quantization, bit truncation, noise addition, cropping, blurring, mosaicking, zigzagging, inversion, (edge) sharpening, and so on. The proposed method possesses outstanding performance in resisting high compression ratio attacks: JPEG2000 and JPEG. Further, to provide extra hiding storage, a steganographic method using the RWM with the least significant bit substitution technique is suggested. Experiment results indicate that the resulting perceived quality is desirable, whereas the peak signal-to-noise ratio is high. The payload generated using the proposed method is also superior to that generated by existing approaches.

단축적방법을 이용한 다단 축류압축기의 설계 (A Design Procedure for a Multi-Stage Axial Compressor Using the Stage-Stacking Method)

  • 강동진
    • 대한기계학회논문집
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    • 제18권6호
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    • pp.1598-1603
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    • 1994
  • A preliminary design procedure for a multi-stage axial compressor is developed, which is based on the stage-stacking method. It determines the flow coefficient which gives rise to the design conditions required such as pressure ratio, mass flow rate and rotational speed for a given specific mass flow rate at inlet to a compressor. With this flow coefficient, blade radii, every stage and compressor performance characterics such as stage pressure ratio, adiabatic efficiency etc. are calculated by stacking each stage performance characteristics. It is shown that there is an optimum number of stage which results in the maximum of compressor overall efficiency for a given specific mass flow rate at inlet to a compressor. A test design was tried for three different geometric design constraints, and comparison with a previous study shows that present procedure could be used reliably in determining the number of compressor stage in preliminary design stage.

거친사각채널에서 왕복운동이 열전달에 미치는 효과 (The Effect of Reciprocating Motion on Heat Transfer in the Roughened Rectangular Channel)

  • 안수환;손강필
    • Journal of Advanced Marine Engineering and Technology
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    • 제26권6호
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    • pp.646-652
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    • 2002
  • The influence of reciprocating frequency and radius on heat transfer in the roughened rectangular channel is experimentally investigated. The aspect ratio (width/height) of the duct is 2.33 and the rib height is one fifteenth of the duct height. And the ratio of rib-to-rib distance to rib height is 10. The discrete ribs were periodically attached to the button wall of the duct with a parallel orientation. The parametric test matrix involves Reynolds number, reciprocating, and reciprocating radius, in the ranges, 1,000∼6,000, 1.7∼2.5 HB and 7∼15cm, respectively. The combined effects of reciprocating frequency and reciprocating radius have considerable influence on the heat transfer due to the modified vortex flow structure.