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.     

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.     

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.     

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.     

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 the modeling and analysis of a helicopter’s occupant seat belt for crashworthiness

Abstrac  In this paper, a method of modeling a seat belt on a crew seat during a dynamic seat testing was studied. The body segments of the occupant were modeled with joints that consisted of various stiffness, damping, and friction. Three types of seat belt restraint systems were investigated and an analysis on the injury assessment of the helicopter’s crew under a drop impact was conducted. The effectiveness of the seat belt system for crashworthiness and safety was likewise evaluated. From the impact analysis results, it was determined that the head, neck, and spine of the crew body can be easily damaged in the vertical direction more than the longitudinal direction. Based on the verified model, the human body’s behavior was studied using three point restraint systems. The displacement and injury level of the 12-point restraint system was the smallest. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Young-Shin Lee received a B.S. degree in Mechanical Engi-neering from Younsei University, Korea in 1972. He received master and Ph.D. degree in Mechanical Engineering from Yonsei University, Korea in 1974 and 1980 respectively. He is currently professor and Dean of Industry Graduate School and Director of BK21 Mechatronics Group at Chungnam National University, Korea. Prof. Lee’s research interests are in area of impact mechanics, optimal design, biomechanical analysis and shell structure analysis. Jung-Hyun Lee received a B.S. degree in Mechanical Design Engineering from Chungnam Na-tional University, Korea in 2007. He received master degree in Mechanical Design Engineering from Chungnam National Uni-versity, Korea in 2009. He is currently researcher of Korea Aerospace Research Institute, Korea. Kyu-Hyun Han received a B.S. degree in Mechanical Design Engineering from Hanbat National University, Korea in 2002. He received master degree in Mechanical Design Engineering from Chungnam National University, Korea in 2004. He is currently researcher of Simuline Inc, Korea.     

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.     

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.”     

A recursive subsystem synthesis method for repeated closed loop structure in multibody dynamics

A recursive subsystem synthesis method has been proposed for efficient analysis for a repeated closed loop structure in multibody dynamics. Virtual work form of equations of motion has been used to reduce subsystem equations of motion. Position, velocity, and acceleration analyses are carried out subsystem by subsystem in the forward recursive fashion. Effective mass matrices and force vectors are computed subsystem by subsystem in the backward recursive fashion. An excavator example is used for a repeated closed loop structure to validate the proposed method. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Sung-Soo Kim received a B.S. degree in Agricultural Engineering from Seoul National University in 1981. He then went on to receive his M.S. and Ph.D. degrees in Mechanical Engineering from the University of Iowa in 1983 and 1988, respectively. Dr. Kim is currently a Professor in the Department of Mechatronics Engineering at Chungnam National University in Daejeon, Korea. His research interests are real-time multibody formulation and its application to the automotive systems and military robot systems.     

Aerodynamic analysis of flapping foils using volume grid deformation code

Nature-inspired flapping foils have attracted interest for their high thrust efficiency, but the large motions of their boundaries need to be considered. It is challenging to develop robust, efficient grid deformation algorithms appropriate for the large motions in three dimensions. In this paper, a volume grid deformation code is developed based on finite macro-element and transfinite interpolation, which successfully interfaces to a structured multi-block Navier-Stokes code. A suitable condition that generates the macro-elements with efficiency and improves the robustness of grid regularity is presented as well. As demonstrated by an airfoil with various motions related to flapping, the numerical results of aerodynamic forces by the developed method are shown to be in good agreement with those of an experimental data or a previous numerical solution. This paper was recommended for publication in revised form by Associate Editor Do Hyung Lee Jin Hwan Ko received his B.S. degree in Mechanical Engineering from KAIST, Korea, in 1995. He then received his M.S. and Ph.D. degrees from KAIST in 1997 and 2004, respectively. Dr. Ko is currently a research professor at the School of Mechanical and Aerospace Engineering at Seoul National University in Seoul, Korea. His research interests include fluid-structure interaction analysis, structural dynamics of a micro-scale resonator, and model order reduction. Soo Hyung Park received his B.S. degree in Aerospace Engineering from KAIST, Korea, in 1996. He then received his M.S. and Ph.D. degrees from KAIST in 1999 and 2003, respectively. Prof. Park is currently an assistant professor at the Dept. of Aerospace Information Engineering at Konkuk University in Seoul, Korea. His research interests include computational fluid dynamics, fluid-structure interaction analysis, rotorcraft aerodynamics, and turbulence modeling.     

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 averaging bidirectional flow tube for measurement of single-phase flow rate in a piping system

A new instrument, an averaging bidirectional flow tube (BDFT), is proposed to measure single-phase flow rates. This averaging BDFT has unique measuring characteristics foremost among which is the capability to measure bidirectional flow and insensitivity of the fluid attack angle. Single phase calibration tests were conducted to demonstrate the performance of the averaging BDFT. Likewise, to enhance the applicability of the averaging BDFT on various flow conditions, flow analyses using CFD code were performed focusing on design optimization of the BDFT. The calibration test results indicated that this averaging BDFT has a linearity within 0.5 % in the Reynolds (Re) number range of above 10,000 where it is meaningful in terms of application. The flow analyses results demonstrate a good linearity of the averaging BDFT with various design features. Therefore, averaging BDFT can be applied for measurement of flow rates within a wide range of flow conditions. This paper was recommended for publication in revised form by Associate Editor Won-Gu Joo Kyoung-Ho Kang received his B.S. and M. S. degrees in Nuclear Engineering from SNU (Seoul National University), KOREA in 1993 and 1995, respectively. He then received his Ph.D. degree in Nuclear and Quantum Engineering from KAIST (Korea Advanced Institute of Science and Technology) in 2009. Dr. Kang is currently a senior researcher at the Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Kang’s research interests include analysis and experiments for the nuclear safety, thermal hydraulics, and experiments and modeling for the severe accidents. Byong-Jo Yun received his B.S. degree in Nuclear Engineering from SNU (Seoul National University), KOREA in 1989. He then received his M.S. and Ph.D. degrees from SNU in 1991 and 1996, respectively. Dr. Yun is currently a principal researcher at the Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Yun’s research interests include analysis and experiments for the nuclear safety, thermal hydraulics, two-phase flow, scaling analysis, and development of instrumentation for two-phase flow. Dong-Jin Euh received his B.S. degree in Nuclear Engineering from Seoul University, Korea, in 1993. He then received his M.S. and Ph.D. degrees from same university in 1995 and 2002, respectively. Dr. Euh is currently a researcher at thermal hydraulic safety research department of Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Euh’s research interests include two-phase thermal hydraulics in the Nuclear Systems and Fundamental Phenomena. Won-Pil Baek has been working at KAERI as the general project manager (director) for development of nuclear thermalhydraulic experiment and analysis technology since 2001. He received his B.S. degree in nuclear engineering from Seoul National University and his M.S. and Ph.D. degrees from KAIST. In 1991–2000, he worked for KAIST as a researcher and research professor. Currently he also serves as an executive editor of the Nuclear Engineering and Technology, an international journal of the Korean Nuclear Society. His research interests include critical heat flux, integral effect tests, modeling, nuclear safety, and advanced reactor development.     

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.     

Development of rapid mixing fuel nozzle for premixed combustion

Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel. This paper was recommended for publication in revised form by Associate Editor Ohchae Kwon Masashi Katsuki received his B.E. degree in Mechanical Engineering from Osaka University, Japan, in 1965. He received his Dr. Eng. from O. U. in 1985. Dr. Katsuki is currently a Visiting Professor at the Department of Environmental Engineering at Hoseo University in Chungnam, Korea. He was a Vice President of the Japan Society of Mechanical Engineers. Dr. Katsuki’s research interests include combustion, computational thermo-fluid dynamics, and molecular dynamics. Jin-Do Chung received his B. S., M.S. and Ph.D. degrees in Mechanical Engineering from Chungnam University, Korea in 1983, 1985 and 1990. He then received another Ph.D. in Environmental Engineering from Kanazawa University, Japan in 1996. After that he worked as Post-doc researcher for 1,6 year at KIMM and Senior researcher for 6years at KEPCO Research Center. Dr. Chung is currently a Professor at the Department of Environmental Engineering at Hoseo University in Asan, Korea. Dr. Chung’s research interests include thermal-fluid and environmental engineering. Jang-Woo Kim received his B. S. degree in Mechanical Engineering from Chungnam University, Korea, in 1990. He then received his M. S. and Ph. D. degrees from Kyushu University, Japan in 1994 and 1998, respectively. Dr. Kim is currently a Professor at the School of Display Engineering at Hoseo University in Asan, Korea. Dr. Kim’s research interests include CFD, aerodynamics, and display equipment technology. Seung-Min Hwang received the Ph.D. degree in Mechanical Engineering at Osaka University in 2005. After that he worked as visiting researcher for 3 years at CRIEPI (central research institute of electric power industry) and Osaka University in Japan. He is currently a Professor at the Graduate School of Venture at Hoseo University in Korea. His major research is thermal-fluid, energy issue and environment. Seung-Mo Kim received his Ph. D. degrees in Mechanical engineering from Osaka University, Japan, in 2004. Dr. Kim is currently a research Professor at Pusan Clean Coal Center at Pusan National University in Pusan, South Korea. Dr. Kim’s research interests include coal combustion, oxy-fuel combustion, coal gasification, coal de-watering, power generation plant system and energy issues. Chul-Ju Ahn received his B.S. degree in Mechanical Engineering from Hanyang University, Korea, in 1998. He then received his M.S. and Ph.D. degrees from Osaka University, Japan, in 2001 and 2006, respectively. Dr. Ahn is currently a Senior Research Engineer at Samsung Techwin CO. LTD. in Changwon, Korea. Dr. Ahn’s research interests include gas turbine engine, biomass gasification, and power system.     

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.     

Prediction of deformations of steel plate by artificial neural network in forming process with induction heating

To control a heat source easily in the forming process of steel plate with heating, the electro-magnetic induction process has been used as a substitute of the flame heating process. However, only few studies have analyzed the deformation of a workpiece in the induction heating process by using a mathematical model. This is mainly due to the difficulty of modeling the heat flux from the inductor traveling on the conductive plate during the induction process. In this study, the heat flux distribution over a steel plate during the induction process is first analyzed by a numerical method with the assumption that the process is in a quasi-stationary state around the inductor and also that the heat flux itself greatly depends on the temperature of the workpiece. With the heat flux, heat flow and thermo-mechanical analyses on the plate to obtain deformations during the heating process are then performed with a commercial FEM program for 34 combinations of heating parameters. An artificial neural network is proposed to build a simplified relationship between deformations and heating parameters that can be easily utilized to predict deformations of steel plate with a wide range of heating parameters in the heating process. After its architecture is optimized, the artificial neural network is trained with the deformations obtained from the FEM analyses as outputs and the related heating parameters as inputs. The predicted outputs from the neural network are compared with those of the experiments and the numerical results. They are in good agreement. This paper was recommended for publication in revised form by Associate Editor Youngseog Lee Truong-Thinh Nguyen received the B.S and M.S degrees from Ho Chi Minh city National University, Viet Nam, in 1997 and 2000, respectively. Now, he is a doctoral candidate in the Department of Mechanical Engineering at Chonnam National University, Korea. His research interests are Induction Heating, Thermal deformations, applications of Neural Network and Fuzzy logic in Industry, intelligent control. Young-Soo Yang received a B.S. degree in Mechanical Engineering from Sungkyunkwan University in 1985. He then went on to receive his M.S. and Ph.D. degrees from KAIST in 1987 and 1991, respectively. Dr. Yang is currently a Professor at the School of Mechanical Engineering at Chonnam National University in Gwangju, Korea. He research interests are in the area of weld structure. Kang-Yul Bae is a Professor of Mechatronics Engineering Department at Jinju National University in Jinju, Korea. He received a B.S. degree in Mechanical Engineering from Busan National University in 1984. He also holds the following degrees of M.S. in Production Engineering and Ph.D. in Mechanical Engineering from KAIST in 1986 and 1994, respectively. He has industrial experience from 1986 to 1998 at Hyundai Heavy Industries, Co. Ltd. as a senior researcher. His teaching and research areas include manufacturing processes, automation, and mechatronics. Sung-Nam Choi received a B.S. and a M.S. degree in Department of Mechanical Engineering from Chonnam National University in 1989 and 1991. He then complete doctor course from the same University in 2006. He is currently a Senior Researcher at Non-Destructive Evaluation Center at Korea Electric Power Research Institute in Daejon, Korea. His research interests are in the area of weld integrity, fracture mechanics, and automated ultrasonic examination.     

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.     

Development of a motion simulator for testing a mobile surveillance robot

A 6-axis motion simulator has been developed, in order to regenerate UGV (unmanned ground vehicle) motion and to test the stabilization system of the mobile surveillance robot that is mounted on the UGV. For developing the 6-axis motion simulator, a simulation-based design procedure was introduced. The 3D geometric model of the motion simulator was created by using 3D CAD modeler ProE. The multibody dynamics model of the motion simulator has also been created by using the general purpose dynamic analysis program ADAMS to validate the design of the motion simulator. Dynamics and control co-simulation model for the motion simulator has been also established for control performance analyses. Actual hardware of the motion simulator has been fabricated based on the proposed simulation based design. Hardware test of the motion simulator has been tried to validate the design. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Oskar Wallrapp was awarded a Ph.D. degree in Mechanical Engineering at the Technical University of Berlin, Germany in 1989. Dr. Wallrapp is currently a Professor in the Department of Precision and Micro Engineering, Muenchen University of Applied Science, Munich, Germany. His research interests are mechanism analysis and design, robotics, and bio-mechanics. Sung-Soo Kim received a Ph.D. degree in Mechanical Engineering from the University of Iowa in 1988. Dr. Kim is currently a Professor in the Department of Mechatronics Engineering at Chungnam National University in Daejeon, Korea. His research interests are real-time multibody formulation and its application to the automotive systems and military robot systems.     

Analysis and design study of LCD transfer robot using dynamic simulation and experiment

Recently, the size of raw glass has been greatly increased in the new generation Liquid Crystal Display (LCD) technology. To handle bigger and heavier glasses, it is necessary to develop a large scale LTR (LCD Transfer Robot) to support various complicated LCD fabrication processes. This adjustment will result in difficult design problems such as vibration, handling accuracy deterioration, and high stress due to heavier dynamic loads. In turn, these will result in inaccurate transfer motion and fatigue cracks. In this paper, the dynamic simulation technique is introduced to validate a baseline design and to propose new and improved designs for the best performance of heavy-scaled LCD transfer robots. The dynamic models and analysis results were verified by real experiments including strain measure test and motor power test. Using the verified simulation model, some dynamic situations such as the robot’s emergency stop and free fall situation, which were not impossible to test using the real proto robot, were analyzed and predicted using the simulation model. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Jong-Hwi Seo received a B.S. M.S. and Ph.D. degrees from Ajou University in 1998, 2000 and 2005, respectively. He is currently a senior engineer in Mechatronics and Manufacturing Technology Center of Samsung Electronics Co. His research interests are in the area of multibody dynamics, robotics and mechanism design. Jae Chul Hwang received a B.S., M.S., and Ph.D. degrees in mechanical engineering from Seoul National University, Korea, in 1996, 1998, and 2002, respectively. He is currently a senior engineer in Mechatronics and Manufacturing Technology Center of Samsung Electronics Co., Ltd. His research interests are in the area of kinematics and dynamics of serial and parallel kinematic robot. Yong-Won Choi received a M.S degree in Mechanical Engineering from Korea University in 1993. He has worked for Samsung Electronics, Ltd from 1993 and is currently a principle engineer at Robot Mechanism Part in Mechatronics and Manufacturing Technology Center of Samsung Electronics Co. He is interest in the area of robotics, control and mechanism design. Hong Jae Yim received B.S. and M.S degrees in mechanical engineering from Seoul National University, Korea, in 1979, and 1983, respectively. He received Ph.D degree from Univ. of Iowa, USA. He is currently a professor in School of Mechanical & Automotive Engineering, Kookmin University. His research interests are in the area of computer aided kinematics and dynamics of mechanical systems.     

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.