• Title/Summary/Keyword: Cross effects

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Analysis of Fully Developed Multilayer Flow in Microchannel with a Rectangular Cross Section (직사각형 단면을 갖는 미세채널에서 완전 발달된 다층유동에 관한 해석)

  • Kim, Jung-Kyung;Jung, Chan-Il;Jang, Jun-Keun;Yoo, Jung-Yul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.5
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    • pp.644-654
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    • 2003
  • An analytical solution for a vertically stratified viscous flow in a microchannel with a rectangular cross-section is constructed, assuming fully developed laminar flow where the interfaces between the fluid layers are flat. Although the solution is for n-layer flow, restricted results to symmetrical three-layer flow are presented to investigate the effects of the viscosity and thickness ratios of the fluid layers and the aspect ratio of the microchannel on the flow field. Relations between the flow rate and thickness ratios of the fluid layers with varying viscosity distributions are found, considering the cross -sectional velocity profiles which vary noticeably with the three parameters and differ significantly from the velocity profiles of the flow between infinite parallel plates. Interfacial instability induced by the viscosity stratification in the microchannel is discussed referring to previous studies on the instability analysis for plane multilayer flow. Exact solution derived in the present study can be used for examining a diffusion process and three -dimensional stability analysis. More works are needed to formulate the equations including the effects of interfacial' tension between immiscible liquids and surface wettability which are important in microscale transport phenomena.

The effects of tube bundle geometry on vibration in two-phase cross-flow (2상 횡유동에서 열교환기 관군 배치에 다른 진동특성 고찰)

  • 김범식
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.681-687
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    • 2001
  • Two-phase cross-flow exists in many shell-tube heat exchangers such as steam generators, condensers and reboilers. An understanding of flow-induced vibration excitation mechanism is necessary to avoid problems due to excessive tube vibration. This paper presents the results of a series of experiments done on tube bundles of different geometries subjected to two-phase cross-flow simulated by air-water mixtures. Normal(30$^{\circ}$) and rotated (60$^{\circ}$)triangular, and normal(90$^{\circ}$) and rotated (45$^{\circ}$) square tube bundle configurations of pitch-to-diameter ratio of 1.2 to 1.5 were tested over a range of mass fluxes from 0 to 1,000kg/$m^2$ㆍ s and void fraction from 0 to 100%. The effects of tube bundle geometry on vibration excitation mechanism such as fluidelastic instability and random turbulence, and on dynamic parameters such as damping and hydrodynamic mass are discussed. A lower pitch-to-diameter results in a higher hydrodynamic mass. The effect of tube bundle configurations on damping and random turbulence excitation is minor. The effect of pitch-to-diameter on the fluidelastic instability, however, is significant.

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The Effects of Drawing Conditions on Physical Properties of the Drawn Worsted Yarns (I) (연신공정 조건이 소모연신사의 물성에 미치는 영향 (I))

  • Han, Won-Hee;Kim, Seung-Jin;Kim, Sang-Ryong
    • Textile Coloration and Finishing
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    • v.22 no.1
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    • pp.51-60
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    • 2010
  • This research works on the effects of drawing conditions on the physical properties of the drawn worsted yarns. The drawn worsted yarns were made by the yarn drawing system under various drawing conditions such as concentration of reducing agent, draw ratio, setting time of drawn yarn, and concentration of oxidizing agent. The drawn worsted yarns from 2/80Nm to 2/90Nm were obtained from 2/60Nm worsted yarns, the surface and cross-sectional shapes and tensile properties of these various specimens were measured and discussed with the various drawing conditions. The drawing of worsted yarn made constituent wool fiber scratched and made it changing to polygonal cross-sectional shape. The tenacity and modulus were increased with draw ratio and concentration of reducing agent. And tensile strain was increased with draw ratio, which decreased with concentration of reducing agent.

A Clinical study on Sitting Cross-Legged Patient Diagnosed as Peroneal Neuropathy (압박손상으로 발생한 비골신경마비 환자 치험 1례)

  • Kim, Jung-Ah;Ji, Min-Jung;Won, Je-Hoon;An, Tteul E Bom;Kim, Dong-Chul
    • The Journal of Churna Manual Medicine for Spine and Nerves
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    • v.9 no.1
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    • pp.77-87
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    • 2014
  • Objectives: The Purpose of this study is to report the effects of Korean medical treatment on patient of peroneal neuropathy caused by sitting cross-legged. Methods: The patient diagnosed as peroneal neuropathy was treated by Acupuncture, Bee Venom therapy, Herbal medicine. To evaluate the effects of Korean treatment, we used Range of Motion(ROM) of Ankle, Visual Analog Scale(VAS), Numeric Rating Scale(NRS), Ankle-Hind-foot Scale(AHS), Digital Infrared Thermal Imaging(DITI). Results: After treatment, ROM of Ankle, VAS, NRS, AHS were improved. Temperature Difference(${\Delta}T$) was decreased on DITI. Conclusions: This study suggests that Korean medical treatment might be effective on sitting cross-legged patient diagnosed as Peroneal Neuropathy.

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A finite strip method for elasto-plastic analysis of thin-walled structures under pure bending

  • Cheung, M.S.;Akhras, G.;Li, W.
    • Structural Engineering and Mechanics
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    • v.8 no.3
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    • pp.233-242
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    • 1999
  • In the present study, the elasto-plastic analysis of prismatic plate structures subjected to pure bending is carried out using the finite strip method. The end cross-sections of the structure are assumed to remain plane during deformation, and the compatibility along corner lines is ensured by choosing proper displacement functions. The effects of both the initial geometrical imperfections and residual stresses due to fabrication are included in the combined geometrically and materially nonlinear simulation. The von-Mises yield criterion and the Prandtl-Reuss flow theory of plasticity are applied in modelling the elasto-plastic behavior of material. Newton-Raphson iterations are carried out as the rotation of the end cross sections of the structure is increased step by step. The parameter representing the overall axial strain of structure is adjusted constantly during the iteration process in order to eliminate the resulting overall axial force on any cross-section of the structure in correspondence with the assumption of zero axial force in pure bending. Several numerical examples are presented to validate the present method and to investigate the effects of some material and geometrical parameters.

The Effects of an Overweight Control Exercise Program in Elementary School Students (줄넘기운동과 걷기운동을 통한 소아비만관리 프로그램의 효과)

  • Go, Young-Aie;Baek, Hee-Chong;Hwang, In-Young
    • Research in Community and Public Health Nursing
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    • v.18 no.4
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    • pp.535-542
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    • 2007
  • Purpose: The purpose of this study was to identify the effects of an overweight control exercise program on body composition and blood lipids. Method: This comparative study was conducted at an elementary school in Seoul, Korea. Pre and post body weight, BMI, PBF, and obesity degree as body composition and TC, HDL-C, LDL-C, and TG as blood lipids were tested. The aerobic exercise lasted 12 weeks from April to July, 2006. A total of 168 overweight 3rd grade to 5th grade school children attended and were divided into a walking exercise group (n=68) and a rope jumping exercise group (n=38). Data were analysed using SAS 8.12. Result: At the end of the program, the participation rate was higher in the rope jumping exercise group than in the walking exercise group. Body weight, BMI, PBF, obesity degree, TC, and LDL-C were lower than those before the program, and HDL-C was higher than before the program. Conclusion: The school-based overweight control exercise program was effective. Because of the participation rate was higher in the rope jumping exercise group than in the walking exercise group, rope jumping exercise is recommended for low grade children.

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Optimization of Rheological Properties for the Processing of Omija-pyun(Omija jelly) by Response Surface Methodology (반응표면 분석법을 이용한 오미자편의 물성특성)

  • 정희선;주나미
    • Korean journal of food and cookery science
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    • v.19 no.4
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    • pp.429-438
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    • 2003
  • The optimization of Omija-pyun as a traditional dessert, with the most European taste and year round availability, was studied with regard to its texture. The response surface methodology was used to determine the optimal composition of Omija-pyun as a European style dessert. The texture, including the springiness, gumminess, cohesiveness, adhesiveness, hardness and chewiness, was measured using TPA parameters (TA-HD Texture Analyser, stable micro system, UK). The texture of Omija-pyun was influenced by pectin and sucrose to the first linear order. The properties of springiness and adhesiveness were influenced by pectin x pectin to the second quadratic order. No cross product effects between ingredients were found from the analysis. The maximum springiness was obtained with 42g of pectin, 450g of sucrose, 110g of glucose syrup and 4.8g of tartaric acid. The maximum chewiness was with 55g of pectin, 330g of sucrose, 140g of glucose syrup and 5.7g of tartaric acid. The maximum adhesiveness was achieved using 17g of pectin and 400g of sucrose. The gumminess and hardness increased with increasing pectin content, and a cross product effect was observed(Eds note: you said earlier that no cross product effects between the ingredients was found\ulcorner) between sucrose and glucose syrup.

Turbulence effects on surface pressures of rectangular cylinders

  • Li, Q.S.;Melbourne, W.H.
    • Wind and Structures
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    • v.2 no.4
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    • pp.253-266
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    • 1999
  • This paper presents the effects of free-stream turbulence on streamwise surface pressure fluctuations on two-dimensional rectangular cylinders. Particular attention is given to possible effects of turbulence integral scale on fluctuation and peak pressures. The mean, standard deviation, peak pressure coefficients, spectra and cross-correlation of fluctuating pressures were measured to investigate the nature of the separation and reattachment phenomenon in turbulent flows over a wide range of turbulence intensity and integral scale.

Design of Intermediate Die for Spline Drawing (스플라인형상 인발을 위한 중간패스 단면형상 설계)

  • Lee, T.K.;Lee, J.E.;Lee, S.K.;Kim, B.M.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.337-340
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    • 2008
  • The cross section shape of intermediate die is one of important parameters to obtain dimensional accuracy of final product in shaped drawing process. Until now it has been designed by the experience or trial and error of the expert. In this study, the cross section shape of intermediate die fur spline shape is determined by the electronic field analysis, shape factor method. The result of the electronic field analysis, shape factor method has been compared with that of the present method. The effects of cross section shape on the dimensional accuracy were investigated by using FE analysis. And then the multi-stage shaped drawing experiments were performed to verify the results of FE analysis. As a result, the cross section shape from the electronic field analysis had the good dimensional accuracy. The electronic field analysis can be used for the method to obtain the cross section shape of intermediate die in shaped drawing process.

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Effect of cross-beam on stresses revealed in orthotropic steel bridges

  • Fettahoglu, Abdullah
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.149-163
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    • 2015
  • Orthotropic steel highway bridges exist almost everywhere in world, especially in Europe. The design of these bridges started very early in 20th century and ended with a conventional orthotropic steel bridge structure, which is today specified in DIN FB 103. These bridges were mostly built in 1960's and exhibit damages in steel structural parts. The primary reason of these damages is the high pressure that is induced by wheel- loads and therefore damages develop especially in heavy traffic lanes. Constructive rules are supplied by standards to avoid damages in orthotropic steel structural parts. These rules are first given in detail in the standard DIN 18809 (Steel highway- and pedestrian bridges- design, construction, fabrication) and then in DIN- FB 103 (Steel bridges). Bridges built in the past are today subject to heavier wheel loads and the frequency of loading is also increased. Because the vehicles produced today in 21st century are heavier than before and more people have vehicle in comparison with 20th century. Therefore dimensioning or strengthening of orthotropic steel bridges by using stiffer dimensions and shorter spans is an essence. In the scope of this study the complex geometry of conventional steel orthotropic bridge is generated by FE-Program and the effects of cross beam web thickness and cross beam span on steel bridge are assessed by means of a parameter study. Consequently, dimensional and constructional recommendations in association with cross beam thickness and span will be given by this study.