Approximate velocity scale for primary and secondary dual-inlet side-dump flows

Effects of the bulk inlet velocity on the characteristics of dual-inlet side-dump flows are numerically investigated. Non-reacting subsonic turbulent flow is solved by a preconditioned Reynolds-averaged Navier-Stokes equation system with low-Reynolds number k − ɛ turbulence model. The numerical method is properly validated with measured velocity distributions in the head dome and the combustor. With substantial increase in the bulk inlet velocity, general profiles of essential primary and secondary flows normalized by the bulk inlet velocity are quantitatively invariant to the changes in the bulk inlet velocity. This paper was recommended for publication in revised form by Associate Editor Do Hyung Lee Seung-chai Jung received his B.S. degree in Mechanical Engineering from Yonsei University, Korea, in 2001. He then received his M.S. degree in Mechanical Engineering from Yonsei University, Korea, in 2005. Mr. Jung is currently a Ph. D. candidate at Yonsei University, where he is majoring in Mechanical Engineering. Mr. Jung’s research interests include propulsion system and particle-surface collision dynamics. Byung-Hoon Park received his B.S. degree in Mechanical Design and Production Engineering from Yonsei University in 2003. He is currently a Ph.D. candidate in Yonsei University in Seoul, Korea. His research interests include performance design of propulsion systems and nu-merical analysis of instability in multiphase turbulent reacting flow-fields. Hyun Ko received his B.S. degree in Aerospace Engineering from Chonbuk National University, Korea, in 1996. He then received his M.S. degree in Mechanical Design from Chonbuk National University, Korea, in 1998. In 2005, he obtained his Ph.D. degree from Yonsei University, where he majored in mechanical engineering. Dr. Ko is currently a Principal Research Engineer of the MicroFriend Co., Ltd. in Seoul, Korea. His research interests include propulsion related systems and computational fluid dynamics. Woong-sup Yoon received his B.S. degree in Mechanical Engineering from Yonsei University, Korea, in 1985. He then received his M.S. degree from University of Missouri-Rolla in 1989. In 1992, he obtained his Ph.D. degree from the University of Alabama in Huntsville, where he majored in mechanical and aerospace engineering. Dr. Yoon is currently a professor at the School of Mechanical Engineering at Yonsei University in Seoul, Korea. His research interests include propulsion system and particle-related environmental/ thermal engineering.     

Application of nonlinear integer programming for vibration reduction optimum design of ship structure

This paper presents a hybrid optimization algorithm which combines an external call type optimization method and a general stochastic iterative algorithm for the nonlinear integer programming with genetic algorithm (GA). GA can rapidly search the approximate global optimum under a complicated design environment such as a ship structure. Meanwhile it can handle optimization problems involving discrete design variables. In addition, there are many parameters that have to be set for GA which greatly affect the accuracy and calculation time of the optimum solution. However, the setting process is difficult for users, and there are no rules to decide these parameters. Therefore, to overcome these difficulties, the optimization of these parameters has been also conducted by using GA itself. It is proven using the trial function that the parameters are optimal. Finally, the verification of validity and usefulness of nonlinear integer programming is performed by applying this method to the compass deck of a ship where the vibration problem is frequently occurs. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin YoungMo Kong received his B.S. degree, M.S. and Ph.D. degrees in Mechanical Engineering from Pukyong National University, Korea, in 1990, 1992 and 2006, respectively. Dr. Kong is currently a Principal Research Engineer at the Vibration & Noise R&D Team at Daewoo Shipbuilding & Marine Engineering Co.LTD, Korea. His research interests include vibration and noise analysis, optimum design of rotating machinery and structure. SuHyun Choi received his B.S. degree and M.S. degrees in Naval Architecture from Seoul National University, Korea, in 1982 and 1984, respectively and Ph.D. in Mechanical Engineering from The University of Michigan, Ann Arbor in the USA in 1992. Dr. Choi is currently a Vice President at the Commercial Ship Business Management at Daewoo Shipbuilding & Marine Engineering Co.LTD, Korea. His research interests include vibration and noise analysis, optimum design of rotating machinery and structure. Jin Dae Song received his B.S. degree and M.S. degree in Mechanical Engineering from Pukyong National University, Korea, in 2000 and 2002, respectively. Mr. Song is currently a candidate for the Ph.D degree in Mechanical Engineering from Pukyong National University. His research interests include vibration analysis and optimum design of rotating machinery. Bo-Suk Yang is a professor at the Pukyong National University in Korea. He received his Ph.D. degree in Mechanical Engineering from Kobe University, Japan in 1985. His main research fields cover machine dynamics and vibration engineering, intelligent optimum design, and condition monitoring and diagnostics in rotating machinery. He has published well over 190 research papers on vibration analysis, intelligent optimum design and diagnosis of rotating machinery. He is listed in Who’s Who in the World, Who’s Who in Science and Engineering, among others. ByeongKeun Choi is an Associate Professor at the Department of Precision Mechanical Engineering at Gyeongsang National University in Korea. He received his Ph.D. degrees in Mechanical Engineering from Pukyong National University, Korea, in 1999. Dr. Choi worked at Arizona State University as an Academic Professional from 1999 to 2002. His research interests include vibration analysis and optimum design of rotating machinery, machine diagnosis and prognosis and acoustic emission. He is listed in Who’s Who in the World, among others.     

Optimal design of a variable stiffness joint in a robot manipulator using the response surface method

The response surface method combined with the design of experiment-based design optimization of a variable stiffness joint (VSJ) is presented in this article. A VSJ used in a manipulator of a robot arm to support 1 kg payload at the end is designed by considering the minimization of the total weight as the objective function. Owing to the requirement of large rotational stiffness of the VSJ, over 10 N · m, ring-type permanent magnets are adopted. First, a model composed of two permanent magnets was initially manufactured and tested for comparison with the analysis results. Then, a three-ring-type permanent magnet-based model is suggested and optimized to increase the torque of VSJ. The finite element method is used as a magnetic field analysis method to substitute for the expensive experimental process. Optimization results decrease the weight from 0.899 kg to 0.538 kg, still satisfying the requirement for the rotational stiffness. This paper was recommended for publication in revised form by Associate Editor Tae Hee Lee Jeonghoon Yoo received his B.S. and M.S. degrees in Mechanical Design and Production Engineering from Seoul National University, in 1989 and 1991, respectively. He then received his Ph.D. degrees from the University of Michigan, Ann Arbor, in 1999. Dr. Yoo is currently a Professor at the School of Mechanical Engineering at Yonsei University in Seoul, Korea. Dr. Yoo’s research interests include analysis and design of electromagnetic field systems. Myung Wook Hyun received his B.S. and M.S. degrees in Mechanical Engineering from Yonsei University, Korea, in 1995 and 1997, respectively. While studying for his M.S. degree, Mr. Hyun also studied variable stiffness unit design. He is now working at Samsung Electronics, Co. Ltd.. Jun Ho Choi received his B.S. and M.S. degrees in Mechanical Design from Hanyang University, Korea and his Ph.D. degree from the University of Michigan, Ann Arbor. He is currently a senior research scientist in the Korea Institute of Science and Technology. His research interests include nonlinear control, manipulator control, and safe-joint design. Sungchul Kang received his B.S., M.S., and Ph.D. degrees in Mechanical Design and Production Engineering from Seoul National University, Korea, in 1989, 1991, and 1998 respectively. Dr. Kang is currently a Principal Research Scientist in the Center for Cognitive Robotics Research, Korea Institute of Science and Technology, in Seoul, Korea. Dr. Kang’s research interests include mobility and manipulation of field and service robots and haptics. Seung-Jong Kim received his B.S. degree in Mechanical Engineering from Seoul University, Korea, in 1989, and his M.S. and Ph.D. degrees from KAIST in 1991 and 1998, respectively. Dr. Kim is currently a Principal Research Scientist at the Korea Institute of Science and Technology in Seoul, Korea. Dr. Kim’s research interests include the design, control, and dynamic analysis of mechatronic systems.     

Experimental study on heat transfer characteristics of internal heat exchangers for CO2 system under cooling condition

This paper presents the heat transfer characteristics of the internal heat exchanger (IHX) for CO₂ heat pump system. The influence on the IHX length, the mass flow rate, the shape of IHX, the operating condition, and the oil concentration was investigated under a cooling condition. Four kinds of IHX with a coaxial type and a micro-channel type, a mass flow meter, a pump, and a measurement system. With increasing of the IHX length, the capacity, the effectiveness, and the pressure drop increased. For the mass flow rate, the capacity of micro-channel IHX are higher about 2 times than those of coaxial IHX. The pressure drop was larger at cold-side than at hot-side. In the transcritical CO₂ cycle, system performance is very sensitive to the IHX design. Design parameters are closely related with the capacity and the pressure drop of CO₂ heat pump system. Along the operating condition, the performance of CO₂ IHXs is different remarkably. For oil concentration 1, 3, 5%, the capacity decreases and the pressure drop increased, as compared with oil concentration 0%. This paper was recommended for publication in revised form by Associate Editor Yong Tae Kang Prof. Young-Chul Kwon received his B.S. degree in Precision Mechanical Engineering from Pusan National University, Korea, in 1989. He then received his M.S. and Ph.D. degrees from POSTECH, in 1991 and 1996, respectively. Dr. Kwon is currently a Professor at the Division of Mechanical Engineering at Sunmoon University in Chungnam, Korea. He serves as a chief of the Institute of Automation and Energy Technology. Dr. Kwon’s research interests include heat exchanger, CO₂ cycle, heat pump, and energy recovery ventilator for HVAC&R. Mr. Dae-Hoon Kim is currently Doctoral student at the Mechanical Engineering from Hanyang University in Seoul, Korea. His research topics include experimental and numerical of CO₂ heatpump system. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Prof. Jae-Heon Lee received his B.S. degree in Mechanical Engineering from Seoul National University, Korea, in 1971. He then received his M.S. and Ph. D. degree from Seoul National University in 1977 and 1980, respectively. Dr. Lee is currently a Professor at the school of Mechanical Engineering at Hanyang University in Seoul, Korea. Dr. Lee is currently a president at the Korea Institute research interests include simulation of thermal fluid and Plant engineering and construction. Dr. Jun-Young Choi received his B.S. degree in Mechanical Engineering from Yonsei University, Republic of Korea, in 1989. He then received his M.S. and Ph. D. degrees from Yonsei University in 1991 and 1999, respectively. Dr. Choi is currently a chief researcher with the 18 years experience on the energy performance testing of HVAC/R product. He is now assigned to the Energy Technology Center at Basic Industry Division at Korea Testing Laboratory. He has been involved in the development of Design and Manufacturing Technology for Air-Conditioner E.E.R. and Performance Testing Equipment for Cooling and Heating System with Non-CFCs, and natural refrigerants. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Dr. Sang Jae Lee received his Ph.D. degree in Mechanical Engineering from Hanyang University, KOREA, in 2008. Dr. Lee is currently a Researcher at the Korea Institute of Industrial Technology in Cheonan, Korea. Dr. Lee’s research interests CO₂ heatpump system, liquid desiccant air conditioning system and Micro heat exchanger.     

Spray formation by like-doublet impinging jets in low speed cross-flows

Breakup and spray formation by impinging liquid jets introduced into a low-speed cross-flow are experimentally investigated. Effects of the cross-flows on the macroscopic and microscopic spray parameters are optically measured in terms of jet Weber number and liquid-to-gas momentum ratio. The liquid stream undergoes Rayleigh jet breakup at lower jet Weber numbers and bag/plume breakup at higher momentum ratio through Kelvin-Helmholtz instability. In particular, the first and the second wind breakup occur at an intermediate jet Weber number. At higher jet Weber numbers, the hydrodynamic impact waves commands and the effect of the convective gas flows is insignificant. The breakup length rises in proportion to the jet Weber number, but starts to decrease when the jet Weber number further rises over 1000. The cross-flow promotes the jet breakup and renders a finer spray in an entire range of injection velocities. This paper was recommended for publication in revised form by Associate Editor Gihun Son Woong-Sup Yoon is a Professor in the School of Mechanical Engineering at Yonsei University. His current research interests are in wave instabilities, unusual spray formation, emission control, and propulsion system modeling. He received a BS degree from the Department of Mechanical Engineering, Yonsei University, in 1985; an MS degree from the Department of Mechanical Engineering, University of Missouri-Rolla, in 1989; and a Ph.D degree from the Department of Mechanical and Aerospace Engineering, the Unversity of Alabama in Huntsville, in 1992. Sang-seung Lee received his B.S. degree in Weapons Engineering from Korea Military Academy, Korea, in 2002. He then received his M.S. degrees from Yonsei University, in 2006. Mr. Lee is currently a Lecturer at the School of Weapons Engineering at Korea Military Academy in Seoul, Korea. He serves as an Editor of the Journal of Mechanical Science and Technology. Mr. Lee’s research interests include Ramjet, Atomization of injector. Won-ho Kim received his B.S. degree in Mechanical Engineering from Yonsei University, Korea, in 2003. Mr. Kim has then gone on to do graduate work at the Ph.D in the School of Mechanical Engineering at Yonsei University in Seoul, Korea. Mr. Kim’s research interests include Atomization of 2phase flow and Dust collection efficiency.     

Reliability design of preventive maintenance scheduling for cumulative fatigue damage

As the cumulative running times of a locomotive truck increases, degradation such as fatigue, wear, and deterioration occur. Particularly the container train and uncovered freight train, their maintenance cost during their lifetime is three times more than the manufacturing cost. Generally, for the freight train, corrective maintenance to repair a bad part after a breakdown is not adapted; however, preventive maintenance that fixes a bad part before a breakdown is. Therefore, it is important and necessary to establish a system of optimal preventive maintenance and exact maintenance period. This study attempts to propose a preventive maintenance procedure that predicts a repair period using reliability function and instantaneous failure rate based on fatigue test and load history data. Additionally, this method is applied to the end beam of an uncovered freight train, which is the brake part, and its usefulness is examined and analyzed. This paper was recommended for publication in revised form by Associate Editor Chongdu Cho Seok-Heum Baek received a B.S. and M.S. degree in Mechanical Engineering from the Dong-A University in 2001 and 2003, respectively. He is currently a Ph.D. student at the School of Mechanical Engineering at Dong-A University in Busan, Korea. Student Baek works on ceramic composite design and robust and reliability-based design, and his research interests are in the areas of trade-off analysis in multicriteria optimization, design under uncertainty with incomplete information, and probabilistic design optimization. Seok-Swoo Cho received a B.S. degree in Mechanical Engineering from Dong-A University in 1991. He then went on to receive his M.S. from Dong-A University in 1993 and Ph.D. degree from Dong-A University in 1997. Dr. Cho is currently a Professor at the Vehicle Engineering at Kangwon National University in Kangwon-do, Korea. Dr. Cho works on crack growth modeling and composite design and optimization, and his research interests are in the areas of structural optimization and inverse and identification problems, and X-ray diffraction, brittle collapse and crack propagation, fatigue fracture phenomena. Hyun-Su Kim received a B.S. degree in Mechanical Engineering from Seoul National University in 1978. He then went on to receive his M.S. from KAIST in 1980 and Ph.D. degree from University of Iowa in 1989. Dr. Kim is currently a Professor at the Mechanical Engineering at Dong-A University in Busan, Korea. His research interests are in the area of high temperature creep fatigue, bio-engineering, design using the finite element method, optimization, and MEMS. Won-Sik Joo received a B.S. degree in Mechanical Engineering from Dong-A University in 1968. He then went on to receive his M.S. from Dong-A University in 1978 and Ph.D. degree from Kookmin University in 1988. Dr. Joo is currently a Professor at the Mechanical Engineering at Dong-A University in Busan, Korea. His research interests are in the area of creep and fatigue in high temperature alloy, fatigue design, and strength evaluation.     

Improved dimension reduction method (DRM) in uncertainty analysis using kriging interpolation

Uncertainty or reliability analysis is to investigate the stochastic behavior of response variables due to the randomness of input parameters, and evaluate the probabilistic values of the responses against the failure, which is known as reliability. While the major research for decades has been made on the most probable point (MPP) search methods, the dimension reduction method (DRM) has recently emerged as a new alternative in this field due to its sensitivity-free nature and efficiency. In the recent implementation of the DRM, however, the method was found to have some drawbacks which counteract its efficiency. It can be inaccurate for strong nonlinear response and is numerically instable when calculating integration points. In this study, the response function is approximated by the Kriging interpolation technique, which is known to be more accurate for nonlinear functions. The integration is carried out with this meta-model to prevent the numerical instability while improving the accuracy. The Kriging based DRM is applied and compared with the other methods in a number of mathematical examples. Effectiveness and accuracy of this method are discussed in comparison with the other existing methods. This paper was recommended for publication in revised form by Associate Editor Tae Hee Lee Junho Won received B.S. and M.S. degree in Mechanical and Aerospace Engineering from Korea Aerospace University in 2004 and 2006, respectively. He is currently a doctoral course at the departments of Mechanical and Aerospace Engineering, Korea Aerospace University in Gyeonggi, Korea. His research interests are in the area of reliability analysis, multidisciplinary design optimization, and fatigue analysis. Changhyun Choi received B.S. and M.S. degree in Mechanical and Aerospace Engineering from Korea Aerospace University in 2006 and 2008, respectively. He is currently researcher at the SFA Engineering Corp. in kyungnam, Korea. His research interests are in the area of computer control system, high reliable product technology, and factory automation system. Jooho Choi received a B.S. degree in Mechanical Engineering from Hanyang University in 1981. He then went on to receive his M.S. and Ph.D. degrees from KAIST in 1983 and 1987, respectively. Dr. Choi is currently a Professor at the School of Mechanical and Aerospace Engineering, Korea Aerospace University in Gyeonggi, Korea. He is currently serving as an Editor of the Journal of Mechanical Science &Technology. Dr. Choi’s research interests are in the area of reliability analysis, multidisciplinary design optimization, and design optimization using automation system integrated with CAD/CAE.     

Optimal operating points of PEM fuel cell model with RSM

The output power efficiency of the fuel cell system mainly depends on the required current, stack temperature, air excess ratio, hydrogen excess ratio, and inlet air humidity. Therefore, the operating conditions should be optimized to get maximum output power efficiency. In this paper, a dynamic model for the fuel cell stack was developed, which is comprised of a mass flow model, a gas diffusion layer model, a membrane hydration, and a stack voltage model. Experiments have been performed to calibrate the dynamic Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack model. To achieve the maximum output power and the minimum use of hydrogen in a certain power condition, optimization was carried out using Response Surface Methodology (RSM) based on the proposed PEMFC stack model. Using the developed method, optimal operating conditions can be effectively selected in order to obtain minimum hydrogen consumption. This paper was recommended for publication in revised form by Associate Editor Tong Seop Kim Dong-Ji Xuan received his B.S. degree in Mechanical Engineering from Harbin Engineering University, China in 2000. He then received his M.S. degree in Mechanical Engineering from Chonnam National University, South Korea in 2006. Currently, he is a Ph.D. candidate of the Department of Mechanical Engineering, Chonnam National University, South Korea. His research interests include control and optimization of PEM fuel cell system, dynamics and control, and mechatronics. Zhen-Zhe Li received his B.S. degree in Mechanical Engineering from Yanbian University, China in 2002. He then received his M.S. degree in Aerospace Engineering from Konkuk University, South Korea in 2005 and his Ph.D. degree in Mechanical Engineering from Chonnam National University, South Korea in 2009. Dr. Li is currently a Researcher of the Department of Mechanical Engineering in Chonnam National University, South Korea. Dr. Li’s research interests include applied heat transfer, fluid mechanics, and optimal design of thermal and fluid systems. Jin-Wan Kim received his B.S. degree in Aerospace Engineering from Chosun University, South Korea in 1990. He then received his M.S. degree in Aerospace and Mechanical Engineering from Korea Aerospace University, South Korea in 2003 and his Ph.D degree in Mechanical Engineering from Chonnam National University, South Korea in 2008. He is currently a Post Doctor of the Department of Mechanical Engineering in Chonnam National University, South Korea. His research interests include control of hydraulic systems, dynamics and control, and mechatronics. Young-Bae Kim received his B.S. degree in Mechanical Design from Seoul National University, South Korea in 1980. He then received his M.S. degree in Mechanical Engineering from the Korean Advanced Institute of Science and Technology (KAIST), South Korea in 1982 and his Ph.D. degree in Mechanical Engineering from Texas A&M University, USA in 1990. Dr. Kim is currently a Professor of the School of Mechanical and Systems Engineering in Chonnam National University, South Korea. Dr. Kim’s research interests include mechatronics, dynamics and control, and fuel cell hybrid electric vehicle (FCHEV) systems.     

A study on cooling efficiency using 1-d analysis code suitable for cooling system of thermoforming

Thermoforming is one of the most versatile and economical processes available for polymer products, but cycle time and production cost must be continuously reduced in order to improve the competitive power of products. In this study, water spray cooling was simulated to apply to a cooling system instead of compressed air cooling in order to shorten the cycle time and reduce the cost of compressed air used in the cooling process. At first, cooling time using compressed air was predicted in order to check the state of mass production. In the following step, the ratio of removed energy by air cooling or water spray cooling among the total removed energy was found by using 1-D analysis code of the cooling system under the condition of checking the possibility of conversion from 2-D to 1-D problem. The analysis results using water spray cooling show that cycle time can be reduced because of high cooling efficiency of water spray, and cost of production caused by using compressed air can be reduced by decreasing the amount of the used compressed air. The 1-D analysis code can be widely used in the design of a thermoforming cooling system, and parameters of the thermoforming process can be modified based on the recommended data suitable for a cooling system of thermoforming. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Zhen-Zhe Li received his B.S. degree in Mechanical Engineering from Yanbian University, China, in 2002. He then received his M.S. degree in Aerospace Engineering from Konkuk University, South Korea, in 2005. He then received his Ph.D. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2009. Dr. Li is currently a Researcher of the Department of Mechanical Engineering, Chonnam National University, South Korea. Dr. Li’s research interests include applied heat transfer, fluid mechanics and optimal design of thermal and fluid systems. Kwang-Su Heo received his B.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 1998. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Chonnam National University, South Korea, in 2003 and 2008, respectively. Dr. Heo is currently a Post-doctorial Researcher of the Department of Mechanical Engineering, KAIST(Korean Advanced Institute of Science and Technology), South Korea. Dr. Heo’s research interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor. Dong-Ji Xuan received his B.S. degree in Mechanical Engineering from Harbin Engineering University, China, in 2000. He then received his M.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2006. He is currently a Ph.D. candidate of the Department of Mechanical Engineering, Chonnam National University, South Korea. His research interests include control & optimization of PEM fuel cell system, dynamics & control, mechatronics. Seoung-Yun Seol received his B.S. degree in Mechanical Design from Seoul National University, South Korea, in 1983. He then received his M.S. degree in Mechanical Engineering from KAIST(Korean Advanced Institute of Science and Technology), South Korea, in 1985. He then received his Ph.D. degree in Mechanical Engineering from Texas Tech University, USA, in 1993. Dr. Seol is currently a Professor of the School of Mechanical and Systems Engineering, Chonnam National University, South Korea. Dr. Seol’s research interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor.     

Mapping of the morphological and the material characteristics on the glenoid and estimation of predominant loading condition on the glenoid through the mapping

The aim of this study was to predict and map the regional distribution of the trabecular architecture and the material properties of the glenoid and to estimate the predominant loading condition on the glenoid through the mapping. The morphological and material characteristics of the glenoid were investigated by analyzing digitized trabecular bone images obtained from twelve cadaver scapula specimens. The morphological and material characteristics computed from the cadaver specimens show that the predominant loading on the glenoid generally occurs during shoulder movement, which produces forces directed toward the posterior aspect of the bare region. This study is innovative in its detailed mapping of the morphological and material characteristics of the glenoid and its pioneering approach used to estimate the loading pattern acting on the glenoid through the mapping. This paper was recommended for publication in revised form by Associate Editor Young Eun Kim Dohyung Lim received B.S. and M.S. degrees in Biomedical Engineering from Inje University, Kimhae, Korea, in 1998 and 2000, respectively. He then went on to receive his Ph.D. degree from School of Biomedical Engineering, Science, & Health Systems, Drexel University, Philadelphia, PA, USA, in 2004. Dr. Lim completed a postdoctoral fellowship in Department of Physical Therapy and Human Movement Science, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA and a Research Professor of Biomedical Engineering, Yonsei University, Wonju, Gangwon, Korea. Dr. Lim is currently a Senior Researcher at the Korea Institute of Industrial Technology in Cheonan, Chungnam, Korea. Han-Sung Kim received B.S. and M.S. degrees in Machine Design and Production Engineering from Hanyang University, Seoul, Korea, in 1989 and 1991, respectively. Dr. Kim received Ph.D. degree in Mechanical Engineering from University of Manchester Institute of Science and Technology, Manchester, UK, in 1999. Dr. Kim is currently an Associated Professor at the Biomedical Engineering at Yonsei University in Wonju, Korea. Jung-Sung Kim received B.S. and M.S. degrees in Biomedical Engineering from Inje University, Kimhae, Korea, in 1996 and 1998, respectively. He is currently in the doctor’s course in Department of Medical Engineering and BK 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea. Rami Seliktar has a BS and MS degree in Mechanical Engineering, from The Technion, IIT, and Ph.D. (BME) from Strathclyde University, Scotland. He has held academic appointments in several institutions worldwide: Strathclyde University (2yrs.); associate professor at the Technion (9yrs.); Texas A&M (on sabbatical leave from the Technion), and twenty seven years as professor of BME and ME at Drexel University in Philadelphia. Concurrently he founded and directed a Biomechanics laboratory at the Loewenstein Rehab. in Israel and consulted to governments, public agencies and industries. Prof. Seliktar has done research on limb prosthetics, human performance, orthopedic and occupational biomechanics, assistive technology for automomobil dynamics. His research has been funded by: The NSF, NIH, the RWJ Foundation, the Easter Seal Foundation, NIDRR, AIduPont, the United Cerebral Palsy and some hospitals. He has published numerous articles in scientific journals, book chapters and conference proceedings. At the present, Rami Seliktar is Professor and Vice Director of the School of Biomedical Engineering, Science and Health Systems of Drexel University. Sung-Jae Lee received B.S. and M.Eng. degrees in Mechanical Engineering from Cornell University, Ithaca, NY, USA, in 1984 and 1985, respectively. He re-ceived Ph.D. degree in Biomedical Engineering from University of Iowa, Iowa City, IA, USA, in 1993 Dr. Lee is currently a Professor at Department of Biomedical Engineering, Inje University, Gimhae, Gyongnam, Korea. He is currently serving as a board member for the Division for Health Care Technology Assessment of International Federation of Medical and Biological Engineering (IFMBE), a executive member of Korean Orthopedic Research Society, director of international relations for the Korean Society for Biomaterials and also for the Korean Society of Biomechanics.     

Two -fluid nonlinear mathematical model for pulsatile blood flow through catheterized arteries

The pulsatile flow of blood through a catheterized artery is analyzed, assuming the blood as a two-fluid model with the suspension of all the erythrocytes in the core region as a Herschel-Bulkley fluid and the peripheral region of plasma as a Newtonian fluid. The resulting system of the nonlinear implicit system of partial differential equations is solved by perturbation method. The expressions for shear stress, velocity, flow rate, wall shear stress and longitudinal impedance are obtained. The variations of these flow quantities with yield stress, catheter radius ratio, amplitude, pulsatile Reynolds number ratio and peripheral layer thickness are discussed. The velocity and flow rate are observed to decrease, and the wall shear stress and resistance to flow increase when the yield stress increases. The plug flow velocity and flow rate decrease, and the longitudinal impedance increases when the catheter radius ratio increases. The velocity and flow rate increase while the wall shear stress and longitudinal impedance decrease with the increase of the peripheral layer thickness. The estimates of the increase in the longitudinal impedance are significantly lower for the present two-fluid model than those of the single-fluid model. This paper was recommended for publication in revised form by Associate Editor Gihun Son Dr. D. S. Sankar received his B. Sc degree in Mathematics from the University of Madras, India, in 1989. He then received his M.Sc, M. Phil and Ph.D. degrees from Anna University, India in 1991, 1992 and 2004, respectively. Dr. D. S. Sankar is currently working at the School of Mathematical Sciences, University Science Malaysia, Malaysia. He serves as a referee for several reputed international journals. Dr. D. S. Sankar’s research interests include Fluid Dynamics, Hemodynamics, Differential Equations and Numerical Analysis. Dr. Usik Lee received his B.S. degree in Mechanical Engineering from Yonsei University, Korea in 1979. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Stanford University, USA in 1982 and 1985, respectively. Dr. Lee is currently a Professor at the Department of Mechanical Engineering at Inha University in Incheon, Korea. He serves as a referee for many reputed international journals. Dr. Lee’s research interests include structural dynamics, biomechanics, and computational mechanics.     

Investigation of variations of lubricating oil diluted by post-injected fuel for the regeneration of CDPF and its effects on engine wear

The purpose of the present study was to investigate the effects of oil diluted by post-injected fuel for CDPF regeneration on engine wear and to find out the characteristic variation of diluted oil according to operating conditions. Experimental studies were made on a 2700 cc, 5 cylinder engine with an after-treatment system. Fuel content in oil increased according to the increase in the duration of post injection. A fuel dilution chart was made to predict the existing fuel content in used oil. The oil analysis method using this chart was validated through the comparison of the results analyzed by GC. The oil contamination by the post-injected fuel caused the quantity of blow-by gas and engine wear to increase and main gallery pressure to decrease. This paper was recommended for publication in revised form by Associate Editor Kyoung Doug Min Bong-Ha Song received a B.S. degree in Mechanical Engineering from Konkuk University in 1999. He received a M.S. degree from Yonsei University in 2002. He then went to Ajou University to get a Ph.D degree. Bong-Ha Song is currently a student at the School of Mechanical Engineering at Ajou University in Suwon, Korea. Yun-Ho Choi received a B.S. degree in Mechanical Engineering from Seoul National University in 1978. He then went on to receive his M.S. and Ph.D. degrees from Pennsylvania State University in 1984 and 1988, respectively. Dr. Choi is currently a professor at the Division of Mechanical Engineering at Ajou University in Suwon, Korea. Dr. Choi’s research interests are in the area of Computational Fluid Dynamics, Thermal Propulsion Systems Modeling and Two Phase Flows.     

Theoretical analysis and experiments of axial flux pm motors with minimized cogging torque

This paper deals with analysis and experiments of an axial flux PM (AFPM) brushless dc motor with minimized cogging torque. Recently, many optimal designs for the AFPM motor have been done by finite element (FE) analysis, but such analysis is time-consuming. In this study, the equation of magnetic flux lines existing between PMs and core is assumed mathematically and the minimum cogging torque is calculated theoretically and geometrically without FE analysis. The form of equation is assumed to be a 2^nd order polynomial. The skew angle that makes the cogging torque minimized is calculated theoretically, and the value of minimum cogging torque is compared with the results obtained by FE analysis and experiments. The maximum cogging torque of a proposed AFPM motor has the smallest value approximately at a skew angle of 4° in both the theoretical and FE analysis. Compared with the non-skewed motor, the cogging torque of the skewed motor can be decreased to over 90%, which has a value of 5% of the rated torque. Two types of stator cores, with the skew angle of 0° and 4°, are analyzed, manufactured, and tested experimentally. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Dong Ho Kim received B.S. and M.S. degrees in Mechanical Engineering from Pusan National University in 1982 and 1984, respectively. He then received his Ph.D. degree from Yonsei University in 2007. Dr. Kim is currently a Professor at the Department of Automation and Robots at Kyonggi Institute of Technology in Gyeonggi, Korea. His research interests are in the area of production automation. Jong Hyun Choi received B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Yonsei University, Seoul, Korea, in 1996, 1998, and 2006, respectively. Dr. Choi is currently a post-doctor at the School of Mechanical Engineering at Yonsei University. His research interests are in the area of electromagnetic actuators and magnetic levitation system. Chang Woo Son received a B.S. from Kyungwon University, Seoul, Korea, in 2006, and his M.S. degree from Yonsei University in 2008, all in mechanical engi-neering. He is currently a research engineer at DA Laboratory of LG Electronics in Seoul, Korea. His research interests are in the area of electromagnetic actuators. Yoon Su Baek received B.S. and M.S. degrees from Yonsei University, Seoul, Korea, in 1979 and 1981, respectively, and M.S. and Ph.D. degrees from Oregon State University in 1986 and 1990, respectively, all in mechanical engineering. He worked for Samsung Heavy Industry Ltd. as head research engineer at Mechatronics Research Center from 1990 to 1993. Dr. Baek is currently a Professor at the School of Mechanical Engineering at Yonsei University. His research interests are motion devices and robotics, especially relating to multi-D.O.F. actuators. He is also interested in magnetic brake and levitation system.     

Analysis of unavoidable geometric errors in the side wall of end-milled parts for corner surface

The location and the size of a geometrically defected region in the side wall of a corner, which is generated during the flat end-milling process, are investigated through experiments and geometrical analysis. A corner with inner and outer surfaces is assumed to be made up of one arc-surface patch and two flat-surface patches. Based on the previous findings that the change of material removal per tooth affects the geometry of the end-milled side wall, it is expected that the geometrically defected regions are located around the corner when the tool is approaching and leaving the arc surface. In this respect, analytic models are proposed to predict the location and the size of a geometrically defected region, which are then validated via comparison with the experimental results. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Kun Sang Lee received his B. S. degree in Mechanical Engineering from Seoul National University, Korea, in 1982. He then received his Dipl.-Ing. and Dr.-Ing. degrees from Technical University of Berlin, Germany, in 1991 and 1993, respectively. Dr. Lee is currently a Professor at the School of Mechanical and Automotive Engineering at Kookmin University in Seoul, Korea. He serves as a Staff of the Korea Engineering Education Research Center. His research interests include precision machining, high energy beam material processing, and creative design methodology. Kang Kim received his B. S. and M. S. degrees in Mechanical Design and Production Engineering from Seoul National University, Korea, in 1982 and 1984, respectively. He then received his Ph.D. degree from Purdue University, USA, in 1992. Dr. Kim is currently a Professor at the School of Mechanical and Automotive Engineering at Kookmin University in Seoul, Korea. His research interests include material removal processes, and concurrent engineering.     

Effects of injection type on slot film cooling for a ramjet combustor

A slot film cooling technique has been used to protect a combustor liner from hot combustion gas. This method has been developed for gas turbine combustors. A ramjet combustor exposed to high temperature can be protected properly with a multi-slot film cooling method. An experimental study has been conducted to investigate the change of the first slot angle under recirculation flow and the influence of wiggle strip within a slot, which affects the film cooling effectiveness. The first slot angle has been changed to understand the effect of the injection angle on the film cooling effectiveness in a recirculation zone. The distribution of dimensionless temperature was obtained by a thermocouple rake to investigate the wiggle strip effect, and the adiabatic film cooling effectiveness on downstream wall was measured by a thermochromic liquid crystal (TLC) method. At the first slot position, the film cooling effectiveness decreases significantly because of the effects of recirculation flow. The lip angle of the first slot affects slightly on the film cooling effectiveness. The wiggle strip reinforces the structure of slot and keeps the uniform open area of slot. However, it induces three dimensional flows and enhances the flow mixing between the main flow and the injected slot flow. Therefore, the wiggle strip decreases slightly the overall film cooling effectiveness. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Kwanghoon Park received his M.S degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2007. He is currently working for an education of an officer as a drillmaster in Army Consolidated Logistics School. Kang Mo Yang joined the Republic of Korea Army in 2004. He is currently working towards the M.S. degree at the Department of Mechanical Engineering, Yonsei University. Keon Woo Lee received his M.S. degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2008. In 2008, he joined the Doosan heavy industries & Construction Co, LTD, where he is a member of the IGCC Business Team. Hyung Hee Cho received his PhD degree in Mechanical Engineering from University of Minnesota, Minneapolis, MN in 1992. In 1995, he joined the Department of Mechanical Engineering, Yonsei University, Seoul, Korea, where he is currently a full professor in the School of Mechanical Engineering. His research interests include heat transfer in turbomachineries, rocket/ramjet cooling as well as nanoscale heat transfer in thin films, and microfabricated thermal sensors. Hee Cheol Ham received his PhD degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2001. In 1984, he joined the Agency for Defense Development, Daejeon, Korea, where he is currently a Principal Researcher. Ki Young Hwang received his Ph.D. degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 1994. In 1979, he joined the Agency for Defense Development, Daejon, Korea, where he is currently a principal researcher in the Airbreathing Propulsion Directorate.     

Topology optimization with displacement-based nonconforming finite elements for incompressible materials

This investigation is concerned with the topology optimization using displacement-based nonconforming finite elements for problems involving incompressible materials. Although the topology optimization with mixed displacement-pressure elements was performed, a displacement-based approach can be an efficient alternative because it interpolates displacement only. After demonstrating the Poisson locking-free characteristics of the employed nonconforming finite elements by a simple patch test, the developed method is applied to solve the design problems of mounts involving incompressible solid or fluid. The numerical performance of the nonconforming elements in topology optimization was examined also with existing incompressible problems. This paper was recommended for publication in revised form by Associate Editor Tae Hee Lee Gang-Won Jang received his M.S. degree in 2000, and Ph.D. degree in 2004, both from the School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, Korea. He is currently an Assistant Professor at the School of Mechanical and Automotive Engineering, Kunsan National University, Jeonbuk, Korea. His current interest concerns topology optimization of multiphysics problems and thin-walled beam analysis. Yoon Young Kim received his B.S. and M.S degrees from Seoul National University, Seoul, Korea, and the Ph.D. degree from Stanford University, Palo Alto, CA, in 1989. He has been on the faculty of the School of Mechanical and Aerospace Engineering, Seoul National University, since 1991. He is also the Director of the National Creative Research Initiatives Center for Multiscale Design. His main research field is the optimal design of multiphysics systems, mechanisms, and transducers. He has served as an editor of several Korean and international journals, and as an organizing committee member of several international conferences.     

Evaluation of elastic modulus for unidirectionally aligned short fiber composites

An analytical approach of to reinforcement for of short fiber reinforced composites has been extended to include the estimation of elastic modulus. The model is based on the theoretical development of shear lag theory developed by Cox for unidirectionally Aligned aligned Short short Fiber fiber Compositescomposites. Thus, the evolution of conventional models is described in detail along with the effect on the modulus of various parameters. Results are shown with experimental data as well as the comparison of other theories. It is found that the present model agrees well with experimental data and resolves some of the discrepancies among the previous models. It is also found that the present model is very accurate yet relatively simple to predict Young’s modulus of discontinuous composites and has the capability to correctly predict the effects of fiber aspect ratio, fiber volume fraction, and fiber/matrix modulus ratio. This paper was recommended for publication in revised form by Associate Editor Chongdu Cho Hong Gun Kim received a B.S. and M.S. degree in Mechanical Engineering from Hanyang University in 1979 and 1984. He then went on to receive his Ph.D. degrees from University of Massachusetts in 1992, respectively. Dr. Kim is currently a Professor at the Department of Mechanical & Automotive Engineering at Jeonju University in jeonju, Korea. He is currently serving as an Editor of the KSAE and KSMTE. Dr. Kim’s research interests are in the area of fuel cell, FEM analysis, mechanical design, and composite mechanics. Lee Ku Kwac received a B.S. degree in Precision Mechanical Engineering from Chosun University in 1999. He then went on to receive his M.S. and Ph.D. degrees from Chosun University in 2001 and 2005, respectively. Dr. Kwac currently a Professor at the Department of Mechanical & Automotive Engineering at Jeonju University in jeonju, Korea. Dr. Kwac’s research interests are in the area of fuel cell, nano-mechanism, and micro-machining.     

Optimization of the industrial guide-way vehicle to improve the running stability

This paper presents an optimization of the industrial guide-way vehicle that aims to improve running stability at increased speeds. A guide-way vehicle was used to transfer products in various manufacturing industries. Using Design Of Experiment(D.O.E.), the design prototype was optimized. The improved design prototype and its design parameters were obtained by a case study determined by the engineering discussion. The computational model for the optimization was validated by correlation with the test results. Through this procedure, the optimization method presented in this paper has been proven to be effective. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Kab-Jin Jun received a B.S. degree in Mechanical Engineering from Ajou University in 2005. He is currently a Ph.D candidate at Ajou University in Suwon, Korea. His research interests are in the area of optimization, vehicle dynamics. Tae Won Park received a B.S. degree in Mechanical Engineering from Seoul University. He then went on to receive his M.S. and Ph.D. degrees from the University of Iowa. Dr. Park is currently a Professor at the School of Mechanical Engineering at Ajou University in Suwon, Korea. Sung Pil Jung is currently a Ph.D candidate at Ajou University in Suwon, Korea. Mr. Jung’s research interests are in the area of multi-body & structural dynamics, optimization and computer aided engineering.     

Micromechanically consistent calculation of rotational stiffness of radial tire

The rotational stiffness of a radial tire is one of the most important structural properties of the sidewall, and it has been evaluated conventionally by using a simplified model. However, in this paper, it is found that the conventional shear modulus used for the calculation of the stiffness is not micromechanically consistent. We examine the conventional shear modulus of the sidewall from the viewpoint of micromechanics, and present a new micromechanically consistent shear modulus for evaluating the rotational stiffness attributed to the shear deformation of sidewall. The developed method is discussed and rationalized through an approximate quantitative analysis. The calculation based on the micromechanically consistent shear modulus is validated by comparing it with experimental stiffness and the conventionally-calculated stiffness. This paper was recommended for publication in revised form by Associate Editor Jeong Sam Han Yong-Woo Kim received his Bachelor degree in Mechanical Engineering from Yonsei University, Seoul, Korea, in 1982, and his Ph.D. degree from Yonsei Graduate School in 1991. Dr. Kim is currently Professor at Department of Mechanical Engineering at Sunchon National University in Sunchon, Korea. Dr. Kim’s research interests include structural analysis, machine design, and tire mechanics.     

Numerical analysis of flow characteristics of fire extinguishing agents in aircraft fire extinguishing systems

If fire breaks out on an airplane, a large amount of fire extinguishing agents should be discharged within a very short time. For effective fire extinguishing, increased discharge velocity of the fire extinguishing agents is required. This can be achieved by using a large-sized vessel in which the fire extinguishing agents are highly pressurized by noncombustible gases. It is important to understand the flow characteristics of a fire extinguishing system for optimal system design. This study reports a numerical analysis of the flow characteristics of an airplane fire extinguishing system using halon-1301 as a fire extinguishing agent. The unsteady flow model was simulated with the general-purpose software package “FLUENT”, to study the flow characteristics of the fire extinguishing agents in the system. The effects of the rupture surface area and tube diameter on the flow characteristics were investigated for optimal system design. From the analysis results, it was clarified that the characteristics of the halon discharge from the end of tube are very sensitive to the rupture surface area and significantly affected by the tube diameter. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Byung-Joon Baek received his B.S. degree in Mechanical Engineering from Seoul National University, KOREA, in 1979. He then received his M.S. and Ph.D. degrees from Seoul National University, KOREA, in 1981 and University of Missouri-Rolla USA, in 1989, respectively. Dr. Baek is currently a Professor at Division of Mechanical System Engineering at Chonbuk National University in Jeonju, Korea. Dr. Baek’s research interests include the thermal control of micro-fluidics. Jee-Keun Lee received his B.S. degree in Precision Mechanical Engineering from Chonbuk National University, KOREA, in 1986. He then received his M.S. and Ph.D. degrees from Chonbuk National University, KOREA, in 1992 and in 1998, respectively. Dr. Lee is currently an associate Professor at Division of Mechanical System Engineering at Chonbuk National University in Jeonju, Korea. Dr. Lee’s research interests include the measurement of a turbulent flow and sprays using the laser diagnostics.