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.     

Development of dynamic response analysis algorithm for beam structures using transfer of mass coefficient

The authors developed the transfer mass coefficient method (TMCM) in order to compute effectively the dynamic response of a beam structure. In this paper, the algorithm for the dynamic response analysis of a three-dimensional beam structure is formulated. Through the computation results of numerical models, which are plane and space beam structures, obtained by the transfer mass coefficient method and the direct integration method, we verify that the transfer mass coefficient method can remarkably decrease the computation time of the direct integration method without the loss of accuracy in spite of using small computer storage. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Myung-Soo Choi received his B.S. and M.S. degrees from National Fisheries University of Pusan, Korea, in 1992 and 1994, respectively. He then received his Ph.D. degree from Pukyong National University in 1999. Dr. Choi is currently an Assistant Professor at the Department of Maritime Police Science at Chonnam National University in Yeosu, Korea. His research interests include mechanical vibration, structural dynamics, and optimum design. Jung-Joo Suh received his B.S., M.S. and Ph.D. degrees from National Fisheries Uni-versity of Pusan, Korea, in 1972, 1985 and 1995, respec-tively. Dr. Suh is currently a Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. His research interests include internal combustion engines and numerical analysis. Dong-Jun Yeo received his B.S., M.S. and Ph.D. degrees from National Fisheries University of Pusan, Korea, in 1981, 1985 and 1996, respectively. Dr. Yeo is currently a Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. He serves as an Academic Director of the Korean Society for Power System Engineering. His research interests include structural dynamics, vibration, and analytic techniques. Jung-Kyu Yang received his B.S. degree from Pusan Fisherise College, Korea, in 1973. He then received his M.S. and Ph.D. degrees from Chungnam National University in 1985 and 1996, respectively. Dr. Yang is currently a Professor at the Faculty of Marine Technology at Chonnam University in Yeosu, Korea. His research interests include combustion engineering, air flow characteristics, and numerical analysis. Jung-Hwan Byun received his B.S. and M.S. degrees from National Fisheries University of Pusan, Korea, in 1992 and 1995, respectively. He then received his Ph.D. degree from Pukyong National University in 1997. Dr. Byun is currently an Associate Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. His research interests include numerical analysis and synchronous control.     

An enhanced real-time dynamic imbalance correction for precision rotors

Even a moderate mass imbalance of a high-precision rotor produces a significant level of vibration when it spins at high revolutionary speed such as 10,000 rpm or faster. As a result, many attempts have been made for the development of dynamic rotor balancing methods mostly by the precision mechanical system industry; however, intensive studies about the fundamental principles from a theoretical point of view should be carried out further. In the present paper, a new dual axes dynamic imbalance correction method is introduced and tested through simulations. The proposed method is more efficient and effective than its predecessors. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Jung Kwan Lee is currently a masteral student in the School of Mechanical Engineering at Sungkyunkwan University Korea. He received his B.S. degree from Sungkyunkwan University. His primary research interests are rotor design, analysis, and rotor dynamics. Hyungpil Moon received his Ph.D. degree in mechanical engineering from the University of Michigan in 2005. He was a postdoctoral fellow at Carnegie Mellon University. He joined the faculty of the School of Mechanical Engineering at Sungkyunkwan University in 2008. Dongho Oh received his Ph.D. degree from KAIST in 1996. He worked as a Principal En-gineer of Samsung Electronics and SAIT. Dr. Oh is currently an Associate Professor at the Department of Mechanical Engineering at Chungnam National University. Ja Choon Koo is an associate professor of the School of Mechanical Engineering at Sungkyunkwan University Korea. He was an engineer at IBM Corporation, San Jose, California. He received his Ph.D from the University of Texas at Austin. His primary research interests are analysis, and control of dynamic systems, mechatronics, sensors, and actuators.     

Novel scan path generation method based on area division for SFFS

A solid freeform fabrication (SFF) system using selective laser sintering (SLS) is currently recognized as a leading process of fabrication using variable materials, and SLS extends the application to machinery and automobiles. Due to the time delay in the sintering process, shrinkage and warping often occur. Curling also occurs due to laser and scan delays. These problems affect not only the accuracy of the fabricated product but also the total system efficiency. These deficiencies can be overcome by reducing the total processing time of the SFF system. To accomplish this, the laser scanning time, from mark (laser on) to jump (laser off), must be reduced as it contributes the major part of the total processing time. This can be done by employing area division scan path generation, which promotes digital efficiency. A simulation and an experiment was carried out in this study to evaluate the developed scan path method. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Kyung-Hyun Choi received his B.S. and M.S. degrees in Mechanical Engineering from Pusan National University, Korea, in 1983 and 1990,. He then received his M.S. and Ph.D. degrees from University of Ottawa in 1995. Dr. Choi is currently a professor at the School of Mechanical Engineering at Cheju National University, Korea. His research interests include micro-machining, printed Electronics. Hyung-Chan Kim received his B. S. and M. S. degrees in Electronics Engineering from Cheju National University, Korea, in 2006 and 2008, respectively. Mr. Kim is currently a Ph.D. candidate at the School of Electronics Engineering at Cheju National University, Korea. His research interests include RP System, micro-machining, printed Electronics. Yang-Hoi Doh received his B.S. and M.S. degrees in Electronics Engineering from KyungBuk National University, Korea, in 1982 and 1984, respectively. He then received his Ph.D. degree from University of Kyung Buk National University, Korea, in 1988. Dr. Doh is currently a Professor at the School of Electronics Engineering at Cheju National University, Korea. His research interests include micro-machining, Digital signal processing. Dong-Soo Kim received his M.S. and Ph.D. degrees in Mechanical Engineering from Yung Nam University, Korea, in 1991 and 2001, respectively. Dr. Kim is currently the general manager at Nano Mechanical System Research Division at Korea Institute of Machinery & Materials. His research interests include printed Electronics, R2R printing, RP system.     

Dual stage and an image processing-based method for sight stabilization

This paper presents a combined dual stage-based mechanical and image-based stabilization scheme for a three-axis image-tracking sight system. To improve the stabilization and tracking accuracy, a secondary stage actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. For the remaining roll axis stabilization, an electronic digital- image stabilization technique is introduced to estimate and correct roll motions. Experimental results are given to demonstrate the effectiveness of the proposed stabilization system and the image-stabilization scheme. This paper was recommended for publication in revised form by Associate Editor Dong Hwan Kim Joon Lyou received a B.S. degree in Electronics Engineering from Seoul National University in 1978. He then went on to receive M.S. and Ph.D. degrees from KAIST in 1980 and 1984, respectively. Dr. Lyou is currently a professor of the Department of Electronics Engineering at Chungnam National University in Daejeon, Korea. His research interests include industrial control and sensor signal processing, IT based robotics, and navigation systems. MinSig Kang received a B.S. degree from the Department of Mechanical Engineering of Seoul National University in 1980. He then went on to receive M.S. and Ph.D. degrees from KAIST in 1983 and 1987, respectively. He worked for the Agency for Defence Development during 1987–1998. Dr. Kang is currently a professor of the Department of Mechanical and Automotive Engineering at Kyungwon University in Sungnam, Korea. His research interests include dynamic systems measurement and control, industrial robotics, and manufacturing systems. HwyKuen Kwak received a B.S. degree in Electronics Engineering from Chungnam National University in 2005. He is currently working on his M.S. and Ph.D. course at Chungnam National University in Daejeon, Korea. His research areas are image signal processing, sensors and digital control systems. YoungJun Choi received a B.S. and M.S. degree in Mechanical Engineering from Kyungwon University in 2004 and 2006. He is currently a researcher for the Agency for Defence Development in Daejeon, Korea. His research fields are dynamic systems measurement and control, satellite systems, navigation systems and smart materials.     

Receding horizon tracking control for wheeled mobile robots with time-delay

In this paper, a receding horizon (RH) controller is developed for tracking control of wheeled mobile robots (WMRs) subject to nonholonomic constraint in the environments without obstacles. The problem is simplified by neglecting the vehicle dynamics and considering only the steering system. First, the tracking-error kinematic model is linearized at the equilibrium point. And then, it is transferred to an exact discrete form considering the time-delay. The control policy is derived from the optimization of a quadratic cost function, which penalizes the tracking error and control variables in each sampling time. The minimizing problem is solved by using the QP (quadratic programming) method taking the current error state as the initial value and including the velocity constraints. The performance of the control algorithm is verified via the computer simulations with several different predefined trajectories showing that the strategy is feasible. This paper was recommended for publication in revised form by Associate Editor Doo Yong Lee Kil To Chong (M’96) received the Ph.D. degree in mechanical engineering from Texas A&M University, College Station, in 1995. Currently, he is a Professor at the School of Electronics and Information Engineering, Chonbuk National University, Jeonju, Korea, and Head of the Mechatronics Research Center granted from the Korea Science Foundation. His research interests are in the areas of motor fault detection, network system control, time-delay systems, and neural networks. Chang Goo Lee was born in Chonju, South Korea on Dec., 1958. He received the B.S. and M.S., and Dr.Eng. degrees in Electrical Engineering from Chonbuk National University, South Korea, 1981, 1983 and 1990 respectively. He had been with ETRI as a senior researcher from 1983 to 1991. Since 1992, He has been with the School of Electronic and Information Engineering, Chonbuk National University where he is presently a Professor. His research interests include intelligent control, nonlinear control, and home network control. Yu Gao received the master’s degree in Electronics and Information from Chonbuk National University, Korea, in 2008. He got his bachelor’s degree in Physics from Soochow University, China, in 2005. Currently, he is a Ph.D. candidate in the School of Electronics and Information, Chonbuk National University, Korea. His research interests are in the area of the receding horizon control.     

A numerical study on oil retention and migration characteristics in the heat pump system

In HVAC system, the oil circulation is inevitable because the compressor requires the oil for lubrication and sealing. A small portion of the oil circulates with the refrigerant flow through the system components while most of the oil stays or goes back to the compressor. Because oil retention in refrigeration systems can affect system performance and compressor reliability, proper oil management is necessary in order to improve the compressor reliability and increase the overall efficiency of the system. This paper describes a numerical analysis of oil distribution in each component of the commercial air conditioning system including the suction line, discharge line and heat exchanger. In this study, system modeling was conducted for a compressor, discharge line, condenser, expansion valve, evaporator and suction line. Oil separation characteristics of the compressor were taken from the information provided by manufacturer. The working fluid in the system was a mixture of a R-410A refrigerant and PVE oil. When the oil mass fraction (OMF) was assumed, oil mass distribution in each component was obtained under various conditions. The total oil hold-up was also investigated, and the suction line contained the largest oil hold-up per unit length of all components. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Min Soo Kim received his B.S., M.S., and Ph.D. degree at Seoul National University, Korea in 1985, 1987, and 1991, respectively. After Ph.D. degree, Prof. Kim worked at National Institute of Standards and Technology (NIST) in U.S.A. for about three years. He is currently a professor at the School of Mechanical and Aerospace Engineering of Seoul National University, Korea. Jong Won Choi received B.S. degree in Mechanical Engineering from Korea University in Seoul, Korea, in 2004, and then received M.S. degrees from Seoul National University in 2006. He is currently a student in Ph.D. course at the School of Mechanical and Aerospace Engineering of Seoul National University in Seoul, Korea. His research interests include refrigeration system, micro-fluidic devices, and PEM fuel cell as an alternative energy for next generation. Mo Se Kim received B.S. degree in Mechanical and Aerospace Engineering from Seoul National University in Seoul, Korea, in 2007. He is currently a student in M.S. course at the School of Mechanical and Aerospace Engineering of Seoul National University in Seoul, Korea. He had studied on the oil migration in the heat pump system, and now he studies on the refrigeration system using an ejector. Baik-Young Chung received his B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Inha University, Korea in 1984, 1986, and 2001, respectively. He is currently a research fellow of HAC Research Center at LG Electronics. He is responsible for the commercial air conditioner group. Sai-Kee Oh received B.S. degree in Mechanical Engineering from Seoul National University, Korea in 1989, and then received M.S. and Ph.D. degrees from KAIST, Korea in 1991 and 1997, respectively. He is currently a principal research engineer of HAC Research Center at LG Electronics. He is responsible for the residential air conditioner group. Jeong-Seob Shin received B.S. degree in Machine Design and Production Engineering from Hanyang University, Korea in 1988, M.S. degree in Mechanical Engineering from KAIST, Korea in 1991, and Ph.D. degree in Mechanical Engineering from POSTECH, Korea in 2004. He has joined HAC Research Center at LG Electronics since 2006 as a principal research engineer.     

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.     

Investigation of penetration force of living cell using an atomic force microscope

Recently, the manipulation of a single cell has been receiving much attention in transgenesis, in-vitro fertilization, individual cell based diagnosis, and pharmaceutical applications. As these techniques require precise injection and manipulation of cells, issues related to penetration force arise. In this work the penetration force of living cell was studied using an atomic force microscope (AFM). L929, HeLa, 4T1, and TA3 HA II cells were used for the experiments. The results showed that the penetration force was in the range of 2∼22 nN. It was also found that location of cell penetration and stiffness of the AFM cantilever affected the penetration force significantly. Furthermore, double penetration events could be detected, due to the multi-membrane layers of the cell. The findings of this work are expected to aid in the development of precision micro-medical instruments for cell manipulation and treatment. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Keum-Sik Hong Eun-Young Kwon received her B.S. and M.S degrees in Mechanical Engineering from Yonsei University, Korea, in 2005 and 2007, respectively. Ms. Kwon is currently an Engineer at Digital Printing Division of Samsung Electronics. Her research interests include biotribology, tribology, and electrophotography. Young-Tae Kim received his B.S. in Automotive Engineering from Seoul National University of Technology, Korea, in 2003. He then received his M.S. degree from Yonsei University in Seoul, Korea in 2005. Mr. Kim is currently a Ph. D. candidate at the Graduate School of Mechanical Engineering at Yonsei University in Seoul, Korea. His research interests include biotribology, tribology, and biomechanics. Dae-Eun Kim received his B.S. in Mechanical Engineering from Tufts University, USA, in 1984. He then received his M.S. and Ph.D. degrees from M.I.T. in 1986 and 1991, respectively. Dr. Kim is currently a Professor at the School of Mechanical Engi-neering at Yonsei University in Seoul, Korea. His research interests include tribology, functional surfaces, and micromachining.     

Phase of acoustic impedance and performance of standing wave thermoacoustic coolers

Investigations on the relations between the phase angle of the acoustic impedance at the driver piston and the system performance of a standing wave thermoacoustic cooler were performed. The system performance measured at a fixed acoustic power showed that the coefficient of performance of the standing wave thermoacoustic cooler increases as the phase angle increases when the stack temperature span is relatively low. The results were consistent with the simulation results obtained from DELTAE, a computer code based on linear thermoacoustic theory. Analysis on the temperature profiles along the stack showed that the cooling efficiency (COP) of the system could be decreased or increased as the phase angle of the acoustic impedance at the driver piston changes depending on the stack temperature spans. This paper was recommended for publication in revised form by Associate Editor Yeon June Kang Insu Paek received the B.S. degree in Mechatronics Engineering from Kangwon National University, Chuncheon, Korea, in 1997, the M.S. degree in Mechanical Engineering from the University of Texas at Austin, USA, in 2000, and the Ph. D. degree in Mechanical Engineering from Purdue University, West Lafayette, USA, in 2005. He worked as a postdoctoral researcher in Purdue University and McGill University in 2006 and 2007. He is currently a faculty member in the Department of Mechatronics Engineering, Kangwon National University, Chuncheon, Korea. His research interests include thermoacoustic cooling and power generation, solar heat driven absorption cooling., and wind power. Luc Mongeau received the B.S. and M.S. degrees in mechanical engineering from the University of Montreal, QC, Canada, in 1984 and 1986, respectively, and the Ph. D. degree in Acoustics from Pennsylvania State University, University Park, USA, in 1990. He is currently a professor in the Department of Mechanical Engineering at McGill University, Montreal, QC, Canada. He has published over 50 archival journal publications on various topics related to acoustics and noise control. His research activities are in the flow and turbomachinery noise areas, as well as in the areas of voice production, and thermoacoustic refrigeration. James E. Braun received the B.S. degree in Mechanical Engineering from the University of Massachusetts, USA, in 1976, and the M.S. and Ph. D. degrees in Mechanical Engineering from the University of Wisconsin, Madison, USA, in 1980 and 1988, respectively. He is currently a professor in the Department of Mechanical Engineering, Purdue University, West Lafayette, USA. Professor Braun’s research combines the use of computer modeling, optimization, and experiments to study and improve the performance of thermal systems. He has published over 140 papers. Professor Braun is currently an associate editor for the international journal of HVAC&R Research. Shin You Kang received the B.S. and M.S. degrees in the Department of Mechanical Design from Seoul National University, Seoul, Korea, in 1982, and 1986, respectively. He then received the Ph.D. in Mechanical Engineering at the same university in 1992. Professor Kang is currently a professor in the Department of Mechatronics Engineering, Kangwon National University, Chuncheon, Korea. His research interests include mechanical structure design, crash analysis, optimal design, computational structure analysis and evaluation.     

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.     

Nanomechanics of biomolecules: focus on DNA

Nano-mechanical measurements and manipulations at the single-cell and single-molecular levels using the atomic force microscope (AFM) and optical tweezers are presenting fascinating opportunities to the researchers in bioscience and biotechnology. Single molecule biophysics technologies, due to their capability to detect transient states of molecules and biomolecular complexes, are the methods of choice for studies in DNA structure and dynamics, DNA-DNA and DNA-protein interactions, and viral DNA packaging. The aim of this review is to describe the recent developments of scientific tools and the knowledge gained in single molecule DNA mechanics such as DNA elasticity, electrostatics, condensation and interactions of DNA with surrounding fluids during its hydrodynamic flow. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor In-Ha Sung Y. Eugene Pak is currently serving as the Director of Research Planning Team at the Advanced Institute of Convergence Technology in Seoul National University. He received B.S. degree in Mechanical Engineering from the State University of New York at Buffalo in 1980, and M.S. and Ph.D. degrees in Mechanical Engineering from Stanford University in 1982 and 1985, respectively. After obtaining the Ph.D. degree, he worked as Senior Research Scientist at Northrup-Grumman Corporate Research Center. He joined the Samsung Advanced Institute of Technology (SAIT) in 1995 and has since been leading and expanding research programs in MEMS, Nano and Biotechnology. Sanghyo Kim received B.S. degree in Polymer Science and Engineering from Pusan National University in 1986. He then went on to receive his M.S. and Ph.D. degrees from POSTECH in 1992 and1996, respectively. After the Ph.D. degree, he worked as Senior Researcher at University of Sheffield, UK and University of Cincinnati, USA. He joined the Samsung Electronics Ltd. as a principal researcher in 2002. Dr. Kim is currently an Assistant Professor at the College of Bionano Technology, Kyungwon University in Gyeonggi, Korea. His research interest is in the area of pervasive healthcare information technology including ubiquitous healthcare system and cell/tissue based lab-on-a-chip. Mohana Marimuthu received her Bachelor degree in Pharmacy from The TamilNadu Dr. M.G.R Medical University, India, in 2007. She worked as a clinical study coordinator in phase III clinical trials (Asthma and Chronic Obstructive Pulmonary Disease) at pulmonary department in Sri Ramakrishna Hospital and Institute of Health science, India until February 2008. She is currently doing final year M.S degree in Bionanotechnology at Kyungwon University, Korea. Her research interests extend into microfluidics, tissue engineering and drug delivery.     

Transfer alignment considering measurement time delay and ship body flexure

This paper deals with the transfer alignment problem of strap-down inertial navigation systems (SDINS), using electro-magnetic (EM) log velocity information and gyrocompass attitude information of the ship. Major error sources for velocity and attitude matching are lever-arm effect, measurement time-delay, and ship-body flexure (flexibility). To reduce these alignment errors, an error compensation method based on delay state augmentation and DCM (direction cosine matrix) partial matching is devised. A linearized error model for a velocity and attitude matching transfer alignment system is devised by first linearizing the nonlinear measurement equation with respect to its time delay, and augmenting the delay state into conventional linear state equations. DCM partial matching is then properly combined with velocity matching to reduce the effects of a ship’s Y-axis flexure. The simulation results show that this method decreases azimuth alignment errors considerably. This paper was recommended for publication in revised form by Associate Editor Kyongsu Yi Joon Lyou received a B.S. degree in Electronics Engineering from Seoul National University in 1978. He then went on to receive M.S. and Ph.D. degrees from KAIST in 1980 and 1984, respectively. Dr. Lyou is currently a professor of the Department of Electronics Engineering at Chungnam National University in Daejeon, Korea. His research interests include industrial control and sensor signal processing, IT based robotics, and navigation systems. You-Chol Lim received a B.S. degree in Electronics Engineering from Chungnam National University in 1998. He then received his M.S. and Ph.D. degrees from Chungnam National University in 2000 and 2003, respectively. Dr. Lim is currently a senior researcher at Electronics Department KSLV Technology Division at KARI in Daejeon, Korea. Dr. Lim’s research interests are in the area of remote control, digital filter, and navigation 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.     

Improved information fusion approach based on D-S evidence theory

Conventional D-S evidence theory has an unavoidable disadvantage in that it will give counter-intuitive result when fusing high conflict information. This paper proposes an improved method to solve this problem. By reassigning weight factors before fusing, the method can give reasonable results especially when the initial weight factors of conflict evidences are almost equal. It gives an adjustable factor to adjust the reassigning force. An example is given to illustrate these advantages. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Rui Sun, PhD candidate. He received M.E. in mechatronics engineering from University of Electronic Science and Technology of China. He is currently a Ph.D. candidate in School of Mechatronics Engineering, University of Electronic Science and Technology of China. His research interests include system reliability analysis and mechanical fault diagnosis. Hong-Zhong Huang is a full professor and the Dean of the School of Mechanical, Electronic, and Industrial Engineering at the University of Electronic Science and Technology of China, Chengdu, Sichuan, China. He has held visiting appointments at several universities in Canada, USA, and elsewhere in Asia. He received a Ph. D. degree in Reliability Engineering from Shanghai Jiaotong University, China. His current research interests include system reliability analysis, warranty, maintenance planning and optimization, and computational intelligence in product design. Dr. Qiang Miao obtained B.E. and M.S. degrees from Beijing University of Aeronautics and Astronautics and Ph.D. degree from University of Toronto. He is currently an associate professor of the School of Mechanical, Electronic, and Industrial Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, China. His current research interests include machinery condition monitoring, reliability engineering, and maintenance decision-making.     

Elastic stresses and failure of rotating cross-ply laminate disks

Centrifugal force acting on a rotating disk induces in-plane loads in the radial and circumferential directions. An application of fiber-reinforced composite materials to a rotating disk can satisfy the demand for increasing its rotating speed. However, previous researches have been confined to single lamina disks. In this paper, a stress analysis of rotating disks made of multidirectional laminates is performed. The Tsai-Wu failure criterion is applied to the strength analysis of the rotating laminate disks, from which the maximum allowable speeds are obtained. The cross-ply ratios providing the maximum allowable speeds are obtained for the glass/epoxy and carbon/epoxy cross-ply laminate disks with CD geometry. This paper was recommended for publication in revised form by Associate Editor Heoung Jae Chun Kyo-Nam Koo received his B.S. and M.S. degrees in Aerospace Engineering from Seoul National University, Korea, in 1987 and 1989, respectively. He then received his Ph.D. degree from Korea Advanced Institute of Science and Technology in 1994. Dr. Koo had worked with Korea Aerospace Research Institute for seven years after his education. He is currently a Professor at the Department of Aerospace Engineering at University of Ulsan in Korea since 2001. His research interests include composite materials, structural dynamics, finite element analysis, and aeroelasticity.     

Optimization of rapid thermal processing for uniform temperature distribution on wafer surface

An optimization of rapid thermal processing (RTP) was conducted to obtain uniform temperature distribution on a wafer surface by using linear programming and radiative heat transfer modeling. The results show that two heating lamp zones are needed to maintain uniform wafer temperature and the optimal lamp positions are unique for a given geometry and not affected by wafer temperatures. The radii of heating lamps, which were obtained by optimization, are 45 mm and 108 mm. The emissivity and temperature of the chamber wall do not significantly affect the optimal condition. With obtained optimum geometry of the RTP chamber and lamp positions, the wafer surface temperatures were calculated. The uniformity allowance of the wafer surface is less than ±1°C when the mean temperature of the wafer surface is 1000°C. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Hyuck-Keun Oh received the B.S. and M.S degrees in Mechanical & Aerospace Engineering from Seoul National University in 2000 and 2002, respectively. He had experienced mechanical and electrical engineering in the Samsung SDI Corporation on various display devices between 2002 and 2007. He is now pursuing the Ph.D degree in Mechanical & Aerospace engineering at Seoul National University, Korea. His research interests are heat transfer and thermal management with a focus on power generation and energy efficiency. Sae Byul Kang received the B.S degree in Mechanical engineering from Korea University in 1996. He then went on to receive his M.S and Ph.D. degrees from Seoul National University in 1998 and 2003, respectively. Dr. Kang is currently a senior researcher at the Korea Institute of Energy Research in Daejeon, Korea. Dr. Kang’s research interests are development of industrial boiler and burner for bio-mass. Young Ki Choi received the B.S and M.S degrees in Mechanical engineering from Seoul National University in 1978 and 1980, respectively and the Ph.D. de-gree in mechanical engineering from the University of California at Berkeley in 1986. He is currently a professor at the School of Mechanical Engineering, Chung Ang University, Korea. His research interests are in the area of micro/nanoscale energy conversion and transport, computational fluid dynamics, and molecular dynamics simulations. Joon Sik Lee received the B.S and M.S degrees in Mechanical engineering from Seoul National University in 1976 and 1980, respectively and the Ph.D. degree in mechanical engineering from the University of California at Berkeley in 1985. He is currently a professor at the School of Mechanical & Aerospace Engineering, Seoul National University, Korea. He is also the director of Micro Thermal System Research Center. His research interests are in the area of micro/nanoscale energy conversion and transport, thermal management for power generation and energy efficiency, and various convective heat transport phenomena such as pool boiling and nanofluid.     

Efficiency evaluation of micro factory for micro pump manufacture

The micro factory, a miniature manufacturing system, is a means of achieving higher throughput with minimal space, and minimal consumption of energy and resources by downsizing of production processes. Even though, a micro factory is able to perform whole manufacturing processes like the macro factory, the possibility of improving its manufacturing efficiency has not been considered enough. In this paper, an efficiency index is proposed to calculate the efficiency of the micro factory to manufacture a micro pump. The efficiency index has been proposed based on efficiency definition with input and output parameters of the system. Input parameters include cost of system, processing time and energy. Output parameters represent number of product manufactured from the microfactory. Cost of the system has been categorized by micro assembly machine cost, cost of resources, manipulators’ cost, manufacturing space value, and human operators. Processing time has been categorized by assembly time and material handling time. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Murali Subramaniyam received his B.E. and M.Tech. from India in 2003 and 2005, respectively. Currently, he is pursuing his Ph.D. in Me-chanical Design Engineering under Brain Korea 21 program fellowship at CNU (Chungnam National University), Korea. Also he is working as a research associate in LID (Laboratory of Intelligent Design and manufacturing) at CNU, under Professor Sangho Park. His research interests include CAD/CAM (Computer Aided Design/ Computer Aided Manufac-turing), Computer Integrated Manufacturing, Rapid Prototyping and DHM (Digital Human Modeling). Sangho Park is currently a Professor in Mechanical Design Engineering at CNU. He received his B.S., M.S. and Ph.D. from Seoul National University, Korea in 1988, 1990 and 1995 respectively. He was a Senior Research Scientist at ETRI (Electronics and Telecommunications Research Institute), Korea. His areas of expertise and research interest includes CAD/CAM, Virtual Reality, DHM and Micro Assembly. LID (renamed from CAD/CAM) is doing research under his advice. Sung-il Choi received a B.S. form Konyang University in 1995, Korea. He then received an M.S. from CNU in 1997. Currently, he is pursuing his Ph.D. in Mechanical Design Engineering at CNU. He was a researcher at ETRI. His research intersts include the areas of development of CAD interface, virtual simulation, 3D Web solutions, geometric modelling, micro-assembly, and application of distributed environment. Jun-Yeob Song is a Team Leader in the IT Machinery Research Team, Korea Institute of Machinery and Materials, Korea. Also, He is a Chief of National Research Laboratory on Knowledge Evolution based Manufacturing Devices. He received a Ph. D. from the School of Industrial Engineering at Busan National University in 2001. He has extensive experience in design & control of automation and autonomous manufacturing systems, and reliability engineering. In recent years, Dr. Song’s research interests are in the area of micro assembly, bonding, and multi chip packaging (MCP). Jong-Kweon Park received a B.S. degree in Mechanical Engineering from Inha University in 1977. He then received M.S. and Ph.D. degrees in mechanical engineering from Changwon National University in 1993 and 1997. Dr. Park is currently a principal research at Korea Institute of Machinery and Materials in Daejeon, Korea. His current research areas are cutting dynamics and control, structural dynamics and optimization, ultra precision machining systems, micro/nano manufacturing systems, and design and evaluation of machine tool systems. He is currently a project leader for the project, “Development of Microfactory System Technologies for Next Generation.”     

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.     

Evaporation of inkjet printed pico-liter droplet on heated substrates with different thermal conductivity

In this work, the evaporation phenomena of 20–45 picoliter water droplet (i.e. 50–65 μm diameter) on heated substrates with different thermal conductivity are studied experimentally. The effect of thermal conductivity of substrates and inter-distance between jetted droplets on the evaporation is investigated. In addition, the model to predict evaporation rate of the picoliter droplet on different substrates at a heated condition is developed using approximations for picoliter droplet. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Taewoong Lim received his B.S and M.S. degree in mechanical engineering from Korea University, Seoul, Korea in 2007 and 2009, respectively. His thesis topic was the evaporation of inkjet printed pico-liter droplet and He has been working at Hyundai Motor Company. Jaeik Jeong received his B.S. degree in mechanical engineering from Korea University in 2008. He is currently a M.S. candidate in mechanical engineering at Korea University. Jaewon Chung received his B.S. and M.S. degrees in mechanical engineering from Yonsei University, Seoul, Korea in 1995 and 1997, respectively and Ph.D. degree from University of California, Berkley in 2002. He was postdoctoral associate in Engineering System Research Center at University of California, Berkley in 2002–2004 and had worked in the Center of Micro and Nano Technology at Lawrence Livermore National Laboratory as a visiting collaborator. He is a currently an associate professor at the Department of Mechanical Engineering at Korea University in Seoul, Korea. His research interests include direct writing methods including drop on demand inkjet printing, electrohydrodynamic printing and laser material processing for printing electronics. Jin Taek Chung received his B.S. and M.S. degrees in mechanical engineering from Korea University, Seoul, Korea in 1983 and 1985, respectively and Ph. D. degree from University of Minnesota, U.S.A. in 1992. He is a currently a professor at the Department of Mechanical Engineering at Korea University in Seoul, Korea. His research interests are heat transfer and 3-D flow in gas turbines and thermal management of electronic devices.