• Title/Summary/Keyword: Radius Ratio

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

  • Choi, Byong-Soo
    • Journal of Soil and Groundwater Environment
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    • v.13 no.3
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    • pp.15-20
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    • 2008
  • The investigation on the previous paper(Jn. of KoSSGE vol.12, no.3), which proposed three empirical equations for the different aquifers was carried out. To draw out a single equation from the three different equations the mean value of the involution factors was adopted allowing different proportional coefficients for the different aquifers. On the other hand it was found that the square root value of storativity ratio, ${\sqrt{{S_p}/{S_o}}}$ in each well is almost equal to its wellbore radius ratio, ${r_e}/{r_w}$. From this fact, the proportional coefficients can be substituted with assumed aquifer storativity and a generalized empirical equation for the effective wellbore radius has been derived.

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

  • Kang, Hyung-Suk;Choi, Soo-Kun
    • Journal of Industrial Technology
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    • v.28 no.B
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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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Mechanism of Soil Remediation in Contaminated Area Using Vertical Drains (연직배수재(VDs)에 의한 오염지반정화 메커니즘 연구)

  • Lee Haeng Woo;Chang Pyoung Wuck;Kang Byung Yoon;Kim Hyun Tae
    • Journal of The Korean Society of Agricultural Engineers
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    • v.47 no.5
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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.

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

  • 이종선;원종진;홍석주;윤희중
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.5
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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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    • v.55 no.2
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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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    • v.16 no.4
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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.

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

  • 오규동
    • Journal of Astronomy and Space Sciences
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    • v.16 no.1
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    • pp.31-40
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    • 1999
  • With a total 761 contact binary systems in Svechnikov & Kuznetsova(1990)'s catalogue, their physical properties by the mass ratio are investigated - for the early CE type with a common radiative envelope and the late CW type with a common convective envelope. It is found that the early CE type shows a higher temperature difference($\mid$$DeltaT$$\mid$) between the primary and secondary components, and also longer period, than the late CW type. The mass ratio of the CW type are distributed in period, than the late CW type. The mass ratio of the CW type are distributed in smaller ranges, from 0.3 to 0.7, than the CE type. Further, the relation between mass ratio and luminosity for the CW type shows a well-defined linear relation, such as ratio and luminosity for the CW type shows a well-defined linear relation, such as $L_2/L_1$ = 0.01 = 0.89q. In the mass ratio-radii relation, it is confirmed that the physical difference of the CE and CW types is a result of the secondary radius. A new mass ratio-radii relation for the CW type is suggested for both the total radius $({gamma}_1/{gamma}_2$ and the radius ratio $({gamma}_2/{gamma}_1$, respectively.

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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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    • v.35 no.3
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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.

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

  • 강동진
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.6
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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.

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

  • 안수환;손강필
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.6
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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.