Two-stage design process of a frame-panel land vehicle structure employing topology and cross section optimization

A new structural design technology has been recently developed to build a new type of land vehicle in military use. While thick panels are only employed in conventional land vehicle structures, solid frames combined with relatively thin composite panels are employed for the new type of vehicle. The structural integrity of the new vehicle structure type is mainly guaranteed by the solid frames while composite panels are used to protect passengers and equipments of the vehicle. To design such a frame-panel structure, frame design needs to be done first. In this paper, a two-stage design process is proposed employing topology and cross section optimization methods. Overall frame arrangement of the new vehicle structure is obtained by the topology optimization in the first design stage and the detailed dimensions of the frames are obtained by the cross section optimization in the second design stage.     

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

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

Development of enhanced ESP system through vehicle parameter estimation

In this research, an enhanced lateral stability control system has been developed for a vehicle. The system consists of a vehicle parameter estimation part and an enhanced ESP control logic part. The vehicle parameter estimation was conducted by considering the physical relationship among the longitudinal dynamic components. The enhanced ESP logic was designed so that the controller gains change adaptively to the vehicle parameter variation. All the system components were tested in a simulation environment, while the vehicle mass estimation algorithm was also tested in the field. The results indicated that the lateral vehicle stability limit can be improved with the designed ESP system. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Kihong Park received his B.S. degree in Mechanical Design & Production Engineering from Seoul National University in 1986. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Cornell University in 1990 and 1994, respectively. He is currently a professor at the School of Mechanical and Automotive Engineering at Kookmin University in Seoul, Korea. His main research interest is chassis control and intellegent vehicle design.     

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.     

Analysis of the effects of main design parameters variation on the vibration characteristics of a vehicle sub-frame

In the design process of an automobile part, several analysis methods are usually used to evaluate the performance of the part. However, most automobile design engineers do not directly use CAE (computer aided engineering) tools since specific skills are required to obtain practical results. Moreover, CAE requires a huge amount of computation time and cost. To resolve these problems, a new design approach, termed first order analysis (FOA), has been proposed. In this paper, the FOA technique is employed to design a vehicle sub-frame. An equivalent model of the vehicle subframe which only consists of beam elements is proposed and the modal properties obtained with the model are compared to those obtained with a full scale finite element model. The effects of some parameter variations on the modal characteristics of the vehicle sub-frame are investigated by employing the FOA equivalent model. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong Hee Yoo graduated from the Department of Mechanical Design and Production Engineering at Seoul National University in 1980 and received his Master’s degree from the same department in 1982. He received his Ph.D. degree in 1989 from the Department of Mechanical Engineering and Applied Mechanics at the University of Michigan at Ann Arbor, U.S.A. He is currently working as a professor in the School of Mechanical Engineering in Hanyang University, Seoul, Korea.     

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.     

Friction-induced ignition modeling of energetic materials

The heat released during the external frictional motion is a factor responsible for initiating energetic materials under all types of mechanical stimuli including impact, drop, or penetration. We model the friction-induced ignition of cyclotrimethylenetrinitramine (RDX), cyclotetramethylene-tetranitramine (HMX), and ammonium-perchlorate/ hydroxylterminated-polybutadiene (AP/HTPB) propellant using the BAM friction apparatus and one-dimensional time to explosion (ODTX) apparatus whose results are used to validate the friction ignition mechanism and the deflagration kinetics of energetic materials, respectively. A procedure to obtain the time-to-ignition for each energetic sample due to friction is outlined. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Min-cheol Gwak received his B.S. degree in Mechanical Engineering from Korea Aerospace University, Korea, in 2007. Now he is a graduate student of Mechanical and Aerospace Engineering at Seoul National University in Seoul, Korea. His research interests are ignition of high energy material and combustion phenomena. Tae-yong Jung received his B.S. degree in Mechanical and Aerospace Engineering from Seoul National University, Korea, in 2007. Now he is a graduate student of Mechanical and Aerospace Engineering at Seoul National University in Seoul, Korea. His research interests are solid propellant combustion and phase transformation. Professor J. Yoh received his BSME from UC Berkeley in 1992 and MSME from UCLA in 1995. His doctoral degree is in Theoretical & Applied Mechanics from the University of Illinois at Urbana-Champaign, 2001. His research interest is in high energy system design using high power lasers and condensed energetic materials.     

Parameter study for a dimple location in a space grid under the critical impact load

The spacer grid assembly, an interconnected array of slotted grid straps embossed with dimples and springs, is one of the main structural components of a pressurized light-water reactor (PWR). It takes the role of supporting the nuclear fuel rods which experience a severe expansion and contraction caused by harsh operational conditions such as an earthquake. The external load by an earthquake can be mainly represented as a lateral load, and the resistance to it is evaluated in terms of dynamic crush strengths. It has been reported that a dimple location in a space grid has an effect on this strength. In this paper, based on this fact, the effect of a dimple location in a 3×3 support grid on impact strength has been investigated as a preliminary parameter study for a full sized support grid. The optimal location of the dimple, about 3.5 mm from the tip of the strap, has been found and some design guidelines for a support grid such as reducing the spring length and the dimple gap have been provided. This paper was recommended for publication in revised form by Associate Editor Heoung-Jae Chun Keenam Song received his B.S. degree in the department of mechanical engineering from Seoul National University in 1980, then went on to receive his M.S. degree at KAIST in 1982. Since then he has served as a researcher, senior researcher, principal researcher, and project manager at Korea Atomic Energy Research Institute. Soobum Lee is a postdoctoral research associate in the University of Maryland, U.S. He received the B.S. degree in Mechanical Design and Production Engineering from Yonsei University, Seoul, Korea, in 1998, and the M.S. and Ph.D. degree in Mechanical Engineering from KAIST (Korea Advanced Institute of Science and Technology), Korea, in 2000. His main research interests include structural shape and topology optimization, energy harvester design, nuclear plant design for hydrogen production, robust design using Taguchi method, genetic algorithm, automobile part and system design. He received the best paper award from Korean Society of Mechanical Engineering in 2007.     

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.     

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

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

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.     

Numerical study of droplet dynamics in a PEMFC gas channel with multiple pores

The water droplet motion in a PEMFC gas channel with multiple pores, through which water emerges, is studied numerically by solving the equations governing the conservation of mass and momentum. The liquid-gas interface is tracked by a level set method which is based on a sharp-interface representation for accurately imposing the matching conditions at the interface. The method is modified to implement the contact angle conditions on the walls and pores. The dynamic interaction between the droplets growing on multiple pores is investigated by conducting the computations until the droplet growth and sliding motion exhibits a periodic pattern. The numerical results show that the configuration subject to droplet merging is not effective for water removal and that the wettability of channel wall strongly affects water management in the PEMFC gas channel. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Gihun Son received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National University in 1986 and 1988, respectively, and Ph.D. degree in Mechanical Engineering from UCLA in 1996. Dr. Son is currently a professor of Mechanical Engineering at Sogang University in Seoul, Korea. His research interests are in the area of multiphase dynamics, heat transfer, and power system simulation. Jiyoung Choi received a B.S. degree in Mechanical Engineering from Sogang University in 2005. He is a graduate student of Mechanical Engineering at Sogang University in Seoul, Korea. Choi’s research interests are in the area of PEM fuel cell and microfluidics.     

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

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

Tolerance effects on natural frequencies of multibody systems undergoing constant rotational motion

A general multi-body formulation to analyze the tolerance effects on the statistical property variations of natural frequencies of multi-body systems undergoing constant rotational motion is proposed in this paper. To obtain the tolerance effects, Monte-Carlo simulation method is conventionally employed. However, the Monte-Carlo simulation has serious drawbacks; spending too much computation time for the simulation and achieving very slow convergence around some dynamically unstable regions. To resolve such problems, a method employing analytical sensitivity information is suggested in this paper. To obtain the sensitivities of natural frequencies the eigenvalue problem should be differentiated with respect to a design variable. The sensitivities of mass and stiffness matrices should be calculated at the dynamic equilibrium. By employing the sensitivities of natural frequencies along with the tolerance of the design variable, the statistical property variations of the natural frequencies can be calculated. This paper was recommended for publication in revised form by Associate Editor Seockhyun Kim Seung Man Eom graduated from the Department of Mechanical Engineering at Incheon University in 2005 and received his master degree from the Department of Mechanical Engineering at Hanyang University in 2007. He is currently working as a Researcher of Aircraft Development Team in KIAT(Korea Institute of Aerospace Technology, Koreanair), DaejeonDeajeon, Korea. Bum Suk Kim graduated from the School of Mechanical Engineering at Hanyang University in 2006 and received his master degree from the same department in 2008. He is currently working as a Ph.D. student in the School of Mechanical Engineering in Hanyang University, Seoul, Korea. Hong Hee Yoo graduated from the Department of Mechanical Design and Production Engineering at Seoul National University in 1980 and received his master degree from the same department in 1982. He received his Ph.D. degree in 1989 from the Department of Mechanical Engineering and Applied Mechanics in the University of Michigan at Ann Arbor, U.S.A. He is currently working as a professor in the School of Mechanical Engineering in Hanyang University, Seoul, Korea.     

Design and analysis of a twisting-type thermal actuator for micromirrors

This paper reports the design of a novel twisting-type micromirror actuation system. The actuating mechanism for driving the micromirror combines two paralleled bimorph actuators bending in opposite directions for rotational control of the micromirror. Each actuator is structured by gold and silicon dioxide or nickel and silicon nitride thin films with embedded polysilicon line heaters. With a size of only 15μm in width, 1.3μm in thickness, and 100μm in length, two bimorph actuators can result in a vertical displacement of 25μm at 10 volts dc with the span of 120μm, and thus the micromirror can rotate by angles over 20°, which is a significant improvement, compared to conventional tilting-type micromirrors. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Dong Hyun Kim received his B.S. and M.S. degrees in Mechanical Engineering from Hongik University, Korea, in 2005 and 2007, respectively. Mr. Kim is currently graduate student in the department of Mechanical Engineering at Hongik University in Seoul, Korea. His research interests include micro and nanoscale heat transfer and silicon crystallization technologies for displays. Kyung Su Oh received his B.S. and M.S. degrees in Mechanical Engineering from Hongik University, Korea, in 2005 and 2007, respectively. Mr. Oh is currently a research scientist at LG Chem. Ltd. His research interests include nanoscale heat transfer, nanotubes and fuel cells and molecular simulation technology. Seungho Park received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National University, Korea, in 1981 and 1983, respectively. He then received his Ph.D. degree from U.C. Berkeley, U.S.A. in 1989. Dr. Park is currently a Professor at the department of Mechanical and System Design Engineering at Hongik University in Seoul, Korea. He served as a director of general affairs of KSME. Dr. Park’s research interests include micro and nanoscale heat transfer, molecular dynamics simulation and silicon crystallization technologies for displays.     

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.     

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.     

Numerical study of droplet motion in a microchannel with different contact angles

The droplet motion in a microchannel with different contact angles, which is applicable to a typical proton exchange membrane fuel cell (PEMFC), was studied numerically by solving the equations governing the conservation of mass and momentum. The gas-liquid interface or droplet shape was determined by a level set method which was modified to treat the static and dynamic contact angles. The matching conditions at the interface were accurately imposed by incorporating the ghost fluid approach based on a sharp-interface representation. Based on the numerical results, the droplet dynamics including the sliding and detachment of droplets was found to depend significantly on the contact angle. Also, the effects of inlet flow velocity, droplet size and side wall on the droplet motion were investigated. This paper was recommended for publication in revised form by Associate Editor Haecheon Choi Gihun Son received a B.S. and M.S. degree in Mechanical Engineering from Seoul National University in 1986 and 1988, respectively. He then went on to receive his Ph.D. degrees from UCLA in 1996. Dr. Son is currently a Professor of Mechanical Engineering at Sogang University in Seoul, Korea. Dr. Son’s research interests are in the area of multiphase dynamics, heat transfer, and power system simulation. Jiyoung Choi received a B.S. degree in Mechanical Engineering from Sogang University in 2005. He is a graduate student of Mechanical Engineering at Sogang University in Seoul, Korea. Choi’s research interests are in the area of PEM fuel cell and microfluidics.     

Optimal microchannel design using genetic algorithms

This paper presents a novel method of optimizing particle-suspended microfluidic channels using genetic algorithms (GAs). The GAs can be used to generate an optimal microchannel design by varying its geometrical parameters. A heuristic simulation can be useful for simulating the emergent behaviors of particles resulting from their interaction with a virtual microchannel environment. At the same time, fitness evaluation enables us to direct evolutions towards an optimized microchannel design. Specifically, this technique can be used to demonstrate its feasibility by optimizing one commercialized product for clinical applications such as the microchannel-type imaging flow cytometry of human erythrocytes. The resulting channel design can also be fabricated and then compared to its counterpart. This result implies that this approach can be potentially beneficial for developing a complex microchannel design in a controlled manner. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Hyunwoo Bang was born in Korea on June 2, 1978. He received the B.S. degree in mechanical and aerospace engineering from Seoul National University, Seoul, Korea in 2001 and the Ph.D. degree in mechanical and aerospace engineering from Seoul National University in 2007. He did postdoctoral research at University of California Los Angeles, CA that involved the integration of functional biological components into engineered devices with Prof. Jacob J. Schmidt from April 2007 to August 2008. His current research interests include microfluidics based Lab-on-a-chip devices and their design optimization using artificial intelligence. Dong-Chul Han received the B.S. degree from the Department of Mechanical Engineering, Seoul National University, Seoul, Korea, in 1969, and the Dipl.-Ing. and Dr.-Ing. degrees from the Department of Mechanical Engineering, University of Karlsruhe, Karlsruhe, Germany, in 1975 and 1979, respectively. He also received the Habilitation from the Department of Mechanical Engineering, University of Karlsruhe. He had been a professor in the school of Mechanical and Aerospace Engineering at Seoul National University from 1982 to 2008. His research interests include active magnetic bearing systems, mechanical lubrication, Bio-MEMS (MicroElectroMechanical Systems) and nano-fabrication.     

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

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