Free vibration analysis of spherical caps by the pseudospectral method

The pseudospectral method is applied to the axisymmetric and asymmetric free vibration analysis of spherical caps. The displacements and the rotations are expressed by Chebyshev polynomials and Fourier series, and the collocated equations of motion are obtained in terms of the circumferential wave number. Numerical examples are provided for clamped, hinged and free boundary conditions. The results show good agreement with those of existing literature. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Jinhee Lee received B.S. and M.S. degrees from Seoul National University and KAIST in 1982 and 1984, respectively. He received his Ph.D. degree from University of Michigan in 1992 and joined Dept. of Mechano-Informatics of Hongik University in Choongnam, Korea. His research interests include inverse problems, pseudospectral method, vibration and dynamic systems.     

Pseudospectral analysis of buckling and free vibration of rectangular Mindlin plates

A study of buckling and free vibration of rectangular Mindlin plates is presented. The analysis is based on the pseudospectral method, which uses basis functions that satisfy the boundary conditions. The equations of motion are collocated to yield a set of algebraic equations that are solved for the critical buckling load and for the natural frequencies in the presence of the in-plane loads. Numerical examples of rectangular plates with SS-C-SS-C boundary conditions are provided for various aspect ratios and thickness ratios, which show good agreement with those of the classical plate theory when the thickness ratio is very small. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Jinhee Lee received B.S. and M.S. degrees from Seoul National University and KAIST in 1982 and 1984, respectively. He received his Ph.D. degree from the University of Michigan, Ann Arbor in 1992 and joined the Dept. of Mechanical and Design Engineering of Hongik University in Choongnam, Korea. His research interests include inverse problems, pseudospectral method, vibration and dynamic systems.     

Computational study on aerodynamics of long-span bridges

A numerical procedure for aerodynamic load analysis of long span bridges is presented. The preconditioned Reynolds averaged Navier-Stokes equations are adopted to compute flows over the bridges. To capture the turbulent characteristics of the flows, two equation turbulence models, Coakley’s q − ω model and Menter’s k − ω SST model, are used to compute the turbulent viscosity. A dual time stepping method in conjunction with the AF-ADI method is used to advance the solution in time. A loosely coupled method of the preconditioned RANS equations with the turbulence model equations is employed for fast computation without losing numerical stability. The numerical method for the aerodynamic load analysis is verified against well-known benchmark problems. Aerodynamic loads of two real bridges are computed with the method to demonstrate the usefulness of the method. This paper was recommended for publication in revised form by Associate Editor Kyung-Soo Yang Ilyong Yoo is a Ph.D. candidate in Aerodynamic Analysis and Design Laboratory at Inha University. He received his B.S. and M.S. degrees in Aerospace Engineering from Inha University in 2004 and 2006, respectively. His research area includes computational fluid dynamics, and its application to active flow control using MEMS devices. Einkeun Kwak is a Ph.D. candidate in Aerodynamic Analysis and Design Laboratory at Inha University. He holds B.S. and M.S. degrees in Aerospace Engineering from Inha University. His research area includes computational fluid dynamics, and its application to supersonic inlet analysis and design. Seungsoo Lee is a professor in Aerospace Engineering at Inha University. Prior to joining the faculty at Inha University, he was a senior research engineer at the Agency for Defense Development. He earned his Ph.D. degree from the Pennsylvania State University in 1990. He also holds B.S. and M.S degrees in Aeronautical and Astronautical Engineering from Seoul National University. Dr. Lee’s research interests are in the area of computational fluid dynamics, overset grid method, and applied aerodynamics. Beom Soo Kim received his B.S. and M.S degrees in Aeronautical and Astronautical Engineering from Seoul National University in 1974 and 1977, respectively. He earned his Ph.D. degree from University of Oklahoma in 1983. Dr. Kim is currently a Professor at the Department of Aerospace Engineering at Inha University. Dr. Kim’s research interests are in the area of hypersonic aerodynamics, and wind tunnel testing. Si Hyong Park is a developer in the applied analysis team of MidasIT Co. Ltd, Korea. He received the Bachelor, the Master and the Ph.D degree in Aerospace Engineering from Seoul National University in 1996, in 1998 and in 2003, respectively. His research interest is currently development of CAE software including FEM, CFD and Multi-physics simulation.     

Vibration suppression in ultrasonic machining described by non-linear differential equations

Vibrations are usually undesired phenomena as they may cause damage or destruction of the system. However, sometimes they are desirable, as in ultrasonic machining (USM). In such case, the problem is a complicated one, as it is required to reduce the vibration of the machine head and have reasonable amplitude for the tool. In the present work, the coupling of two non-linear oscillators of the tool holder and tool representing ultrasonic cutting process is investigated. This leads to a two-degree-of-freedom system subjected to multi-external excitation force. The aim of this work is to control the tool holder behavior at simultaneous primary and internal resonance condition and have high amplitude for the tool. Multiple scale perturbation method is applied to obtain a solution up to the second order approximations. Other different resonance cases are reported and studied numerically. The stability of the system is investigated applying both phase-plane and frequency response techniques. The effects of the different parameters of the tool on the system behavior are studied numerically. Comparison with the available published work is reported. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin M. M. Kamel received his B.S. degree in Mathematics from Ain Shams University, EGYPT, in 1979. He then received his M.S.c degrees from Ain Shams University, in 1986 and Ph.D. degrees from Menofia University, in 1994. Dr. M. M. Kamel is currently an Associate Professor of Mathematics at the Department of Engineering Mathematics, Faculty of Electronic Engineering Menofia University, Egypt. Dr. M. M. Kamel research interests include Differential equations, Numerical Analysis, and Vibration control. W. A. A. El-Ganini received her B.S. degree in Mathematics from Ain Shams University, EGYPT, in 1980. She then received her M.S.c and Ph.D. degrees from Suez Canal University, in 1984 and 1989, respectively. Dr. W. A. A. El-Ganini is currently an Assistant Professor of Mathematics at the Department of Engineering Mathematics, Faculty of Electronic Engineering Menofia University, Egypt. Dr. W. A. A. El-Ganaini research interests include Differential equations, Numerical Analysis, and Vibration control. Y. S. Hamed received his B.S. degree in Mathematics from Menofia University, EGYPT, in 1998. He then received his M.S.c and Ph.D. degrees from Menofia University, in 2005 and 2009, respectively. Dr. Y. S. Hamed is currently an Assistant Professor of Pure Mathematics at the Department of Engineering Mathematics, Faculty of Electronic Engineering Menofia University, Egypt. Dr. Y. S. Hamed research interests include Differential equations, Numerical Analysis, and Vibration control.     

A second-order time-accurate finite element method for analysis of conjugate heat transfer between solid and unsteady viscous flow

A fractional four-step finite element method for analyzing conjugate heat transfer between solid and unsteady viscous flow is presented. The second-order semi-implicit Crank-Nicolson scheme is used for time integration and the resulting nonlinear equations are linearized without losing the overall time accuracy. The streamline upwind Petrov-Galerkin method (SUPG) is applied for the weighted formulation of the Navier-Stokes equations. The method uses a three-node triangular element with equal-order interpolation functions for all the variables of the velocity components, the pressure and the temperature. The main advantage of the method presented is to consistently couple heat transfer along the fluid-solid interface. Five test cases, which are the lid-driven cavity flow, natural convection in a square cavity, transient flow over a heated circular cylinder, forced convection cooling across rectangular blocks, and conjugate natural convection in a square cavity with a conducting wall, are selected to evaluate the efficiency of the method presented. This paper was recommended for publication in revised form by Associate Editor Kyung-Soo Yang Atipong Malatip received his B.S. degree in Mechanical Engineering from King Mongkut’s University of Technology North Bangkok, Thailand, in 2002. He then received his M.S. degree in Mechanical Engineering Chulalongkorn University, Thailand, in 2005. He is currently pursuing a Ph.D. degree in Mechanical Engineering at Chulalongkorn University. His research interests include computational fluid dynamics and fluid-thermal-structural interaction. Niphon Wansophark received his B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Chulalongkorn University, Thailand in 1996, 2000, and 2007, respectively. He is an Assistant Professor of Mechanical Engineering at Chulalongkorn University, Bangkok, Thailand. His research interests are numerical methods and finite element method. Pramote Dechaumphai received his B.S. degree in Industrial Engineering from Khon-Kaen University, Thailand, in 1974, M.S. degree in Mechanical Engineering from Youngstown State University, USA in 1977, and Ph.D. in Mechanical Engineering from Old Dominion University, USA in 1982. He is currently a Professor of Mechanical Engineering at Chula-longkorn University, Bangkok, Thailand. His research interests are numerical methods, finite element method for thermal stress and computational fluid dynamics analysis.     

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

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

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.     

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

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

Analytical solutions for bending analysis of rectangular laminated plates with arbitrary lamination and boundary conditions

The intent of the present study is to employ the extended Kantorovich method for semi-analytical solutions of laminated composite plates with arbitrary lamination and boundary conditions subjected to transverse loads. The method based on separation of spatial variables of displacement field components. Within the displacement field of a first-order shear deformation theory, a laminated plate theory is developed. Using the principle of minimum total potential energy, two systems of coupled ordinary differential equations with constant coefficients are obtained. The equations are solved analytically by using the state-space approach. The results obtained are compared with the Levy-type solutions of cross-ply and antisymmetric angle-ply laminates with various admissible boundary conditions to verify the validity and accuracy of the present theory. Also, for other laminations and boundary conditions that there exist no Levy-type solutions the present results are compared with those obtained by other investigators and finite element method. It is found that the present results have very good agreements with those obtained by other methods. This paper was recommended for publication in revised form by Associate Editor Heoung Jae Chun Ali Mohammad Naserian Nik received his M.S. in Mechanical Engineering from Ferdowsi University of Mashhad, Iran, in 2006. Currently, he is a doctoral student at the Department of Mechanical Engineering, Ferdowsi University of Mashhad, Iran. His research interests are in the area of computational mechanics and nanobiotechnology. Masoud Tahani is currently an Associate Professor at the Department of Mechanical Engineering at Ferdowsi University of Mashhad, Iran. He received his B.S. in Mechanical Engineering from Ferdowsi University of Mashhad, Iran, in 1995. He then received his M.S. and Ph.D. degrees from Sharif University of Technology, Iran, in 1997 and 2003, respectively. Dr. Tahani’s research interests include design of structures using advanced composites, mechanics of anisotropic materials, smart materials and structures, mechanics of plates and shells and biomechanics.     

Measurements of the characteristics of spray droplets using in-line digital particle holography

In-line digital particle holography is applied to measure the characteristics of spray droplets. Common reconstruction methods were considered and the best one was selected. Several important parameters at the time of hologram recording, such as the object distance and the region of laser beam used, are discussed. The feasibility of the correlation coefficient (CC) method for focal plane determination of 3-D droplets was verified. A double exposure hologram recording system with synchronization system for time control was established, and two digital spray holograms were obtained in a short time interval. For post-processing of reconstruction images, the two-threshold and the image segmentation methods were used in binary image transformation. Using the CC method and some image processing techniques applied to droplets in each double exposure image, the spatial positions of droplets used to evaluate the three dimensional droplet velocities were easily located, which proved the feasibility of in-line digital particle holographic technology as a good measurement tool for spray droplets. This paper was recommended for publication in revised form by Associate Editor Gihun Son Boseon Kang received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National University in 1986 and 1988, respectively. He then went on to receive his Ph.D. degree from University of Illinois, Chicago in 1995. He is currently Professor at School of Mechanical Systems Engineering, Chonnam National University in Gwangju, Korea. His research interests are in the area of sprays, holographic techniques in thermofluid measurements. Yan Yang received his B.S. degree in Mechanical Engineering from Chongqing Insitute of Technology in 1997, and received his M.S. degree in Mechanics from Chongqing University in 2005. He is doctoral student of Department of Mechanical Systems Engineering, Chonnam National University in Gwangju, Korea. He is also currently Associate Professor at Automobile College, Chongqing University of Technology in Chongqing, China. His research direction is digital holographic techniques     

Modeling and controller design of manta-type unmanned underwater test vehicle

This paper describes the mathematical model and controller design for Manta-type unmanned underwater test vehicle (MUUTV) with 6 DOF nonlinear dynamic equations. The mathematical model contains hydrodynamic forces and moments expressed in terms of a set of hydrodynamic coefficients which were obtained through the PMM (planar motion mechanism) test. Based on the 6 DOF dynamic equations, numerical simulations have been performed to analyze the dynamic performance of the MUUTV. In addition, using the mathematical model PID and sliding mode controller are constructed for the diving and steering maneuver. Simulation results show that the control performance of the MUUTV compared with that of NPS (Naval Postgraduate School) AUV II. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Seung-Keon Lee received the B.S. and M.S. degrees from Pusan National University, in 1982 and 1984, respectively, and the Ph.D. degree from University of Tokyo in 1988. He is currently a Professor in the Department of Naval Architecture and Ocean Engineering, Pusan National University, Busan, Korea. His research interests are about the hydrodynamic force and mathematical model for the motion of surface and underwater vehicles. Joon-Young Kim received the B.S. and M.S. degrees from Inha University, in 1989 and 1993, respectively, and the Ph.D. degree from Hanyang University in 1999. He is currently a Professor in the Department of Ocean System Engineering, Jeju National University, Jeju, Korea. His current research interests are in unmanned underwater vehicle design and control.     

Numerical simulation on soot deposition process in laminar ethylene diffusion flames under a microgravity condition

A numerical study on soot deposition in ethylene diffusion flames has been conducted to elucidate the effect of thermophoresis on soot particles under a microgravity environment. Time-dependent reactive-flow Navier-Stokes equations coupled with the modeling of soot formation have been solved. The model was validated by comparing the simulation results with the previous experimental data for a laminar diffusion flame of ethylene (C₂H₄) with enriched oxygen (35% O₂ + 65% N₂) along a solid wall. In particular, the effect of surrounding air velocity as a major calculation parameter has been investigated. Especially, the soot deposition length defined as the transverse travel distance to the wall in the streamwise direction is introduced as a parameter to evaluate the soot deposition tendency on the wall. The calculation result exhibits that there existed an optimal air velocity for the early deposition of soot on the surface, which was in good agreement with the previous experimental results. The reason has been attributed to the balance between the effects of the thermophoretic force and convective motion. This paper was recommended for publication in revised form by Associate Editor Ohchae Kwon Jae Hyuk Choi received his B.S. and M.S. degrees in Marine System Engineering from Korea Maritime University in 1996 and 2000, respectively. He then went on to receive a Ph.D. degrees from Hokkaido university in 2005. Dr. Choi is currently a BK21 Assistant Professor at the School of Mechanical and Aerospace Engineering at Seoul National University in Seoul, Korea. Dr. Choi’s research interests are in the area of reduction of pollutant emission (Soot and NOx), high temperature combustion, laser diagnostics, alternative fuel and hydrogen production with high temperature electrolysis steam (HTES). Junhong Kim received his B.S., M.S., and Ph. D degrees in Mechanical Engineering from Seoul National University in 1998, 2000, and 2004, respectively. His research interests include lifted flames, edge flames, and numerical simulation. Sang Kyu Choi received his B.S. degree in Mechanical Engineering from Seoul National University in 2004. He is a Ph. D student in the School of Mechanical Engineering, Seoul National University. His research interests include edge flames, oxy-fuel combustion, and numerical simulation. Byoung ho Jeon received his B.S degrees in Mechanical Engineering from kangwon University in 1998, and M.S., Ph. D. degrees in Mechanical Engineering from Hokkaido University in 2002, 2008, respectively. Dr Jeon is working at Korea Aerospace Research Institute from 2007. June. as Gasturbine engine developer. Jeon’s research interests are in the area of reduction of pollutant emission (Soot and Nox), High temperature combustion, combustion system (Furnace, Combine Generation system, IGCC, CTL), and Fire safety in building. Osamu Fujita received his B.S., M.S., and Ph. D. degrees in Mechanical Engineering from Hokkaido University in 1982, 1984, and 1987, respectively. Prof. Fujita is currently a Professor at the division of Mechanical and space Engineering at Hokkaido University in sapporo, Japan. Prof. Fujita’s research interests are in the area of reduction of pollutant emission (Soot and Nox), solid combustion, catalytic combustion, high temperature combustion, alternative fuel and fire safety in space. Suk Ho Chung received his B.S. degree in Mechanical Engineering in 1976 from Seoul National University, and his M.S. and Ph. D. degree in Mechanical Engineering in 1980 and 1983, respectively from Northwestern University. He is a professor since 1984 in the School of Mechanical and Aerospace Engineering, Seoul National University. His research interests cover combustion fundamentals, pollutant formation, and laser diagnostics.     

Hydraulic transport of sand-water mixtures in pipelines Part I. Experiment

The hydraulic transport characteristics of sand-water mixtures in circular and square pipelines are experimentally investigated by changing the Reynolds number and volumetric delivered concentration. The hydraulic gradients are increased along with the Reynolds number. When the mean velocity is larger than the critical velocity, the hydraulic gradient of sand-water mixture in the square duct is larger than that in the circular pipe. The deposition-limit velocity in the square duct is smaller than that in the circular pipe. Thus, it can be concluded that the square duct transports sands more effectively than the circular pipe in a low operating range of velocity. The empirical correlation between the hydraulic gradient and the Reynolds number is obtained. It is believed that the present data and empirical equation can be used to validate the numerical methods developed for the analysis of the transport characteristics of slurry in the circular and square pipelines. This paper was recommended for publication in revised form by Associate Editor Jun Sang Park Chang-Hee Kim received a B.S. degree in Mechanical Engineering from Hanyang University in 1985. He then went on to receive his M.S. degrees from Hanyang University in 1994. Mr. Kim has joined Hyundai Engineering and Construction Company after his degree and is currently working for Oil & Gas Plant as a Procurement Manager. Man-Soo Lee received his M.S. and Ph.D. degrees from civil eng. dept. of Seoul National University in 1992 and 2004, respectively. He has joined Hyundai Engineering and Construction company since 1991 as a research engineer. Recently assisting a big dredging & reclamation project of Hyundai near Incheon Airport in Korea, he is responsible for the geotechnical researching team of civil engineering division at Hyundai Institute of Construction Technology. Cheol-Heui Han received a B.S. degree in Mechanical Engineering from Hanyang University in 1993. He received his M.S. and Ph.D. degrees from Hanyang University. in 1998 and 2003, respectively. Then, he worked as a visiting post-doctoral researcher at the Dept. of Aerospace and Ocean Engineering at Virginia Tech, USA. Dr. Han is currently a Assistant Professor at the Department of Aeronautical and Mechanical Design Engineering. Dr. Han’s research interests are in the area of biomimetics, aircraft and turbomachine design.     

The development of a GUI program for automated generating rotor blade airfoil performance table

A user-friendly, Windows-based Graphic User Interface (GUI) program that automates the generation of the aerodynamic performance tables for comprehensive helicopter load analysis codes was developed. With this program, computational grids are automatically created for the given airfoil surface coordinates, and users can verify the grids immediately. In addition, the program’s post-processing feature can enable the real-time inspection of the interim results of the computation. The aerodynamic performance tables can be generated by performing automated aerodynamic analysis of the airfoil in various angles of attack and Mach numbers by using validated CFD code. The Mixed-Language technique was employed to combine the FORTRAN-based CFD codes to the C++-based GUI program without needing any transformation between these two languages. The MS Access was used to construct the data base of the aerodynamic tables. The real-time inputs of the analysis results of the ODBC Access data base make it easy to retrieve the aerodynamic tables. Of the entire range of the angle of attack (−180° to 180°), the CFD analysis is only performed in the significant angles depending on the Mach number. The aerodynamic data for the other angles were obtained by using an interpolation method; therefore, the tables could be generated quickly. Various aerodynamic information such as drag divergence Mach number and stall angle can be extracted from the computed results stored in the database. This paper was recommended for publication in revised form by Associate Editor Yang Na Taewoo Kim received a B.S. degree in Aerospace Engineering from Pusan National University in 2007. He is currently a M.S. candidate at the graduate school of Aerospace Engineering at Pusan National University in Pusan, Korea. His research interests are in the area of aerodynamics, optimization design, and helicopter aerodynamics. Kwanjung Yee received a B.S. degree in Aerospace Engineering from Seoul National University in 1992. He then went on to receive his M.S. and Ph.D. degrees from Seoul National University in 1992 and 1998, respectively. Dr. Yee is currently an Assistant Professor at the Department of Aerospace Engineering in Pusan National University, Korea. His major research area covers unsteady aerodynamics, rotorcraft flight dynamics and multidisciplinary design optimization. Sejong Oh received his B.S. and M.S. degrees in Aerospace Engineering from Seoul National University in 1979 and 1982 respectively. He finished his Ph.D. degrees from Stanford University in 1988. Prof. Oh is currently a Professor at Department of Aerospace at Pusan National University in Busan, Korea. He is currently a Board Member of Korean Society of Aeronautical and Space Sciences. Prof. Oh’s research interests are in the area of Vortex flow and Rotorcraft aerodynamics. Hee Jung Kang received a B.S. degree in Aerospace Engineering from KAIST in 1994. He then went on to receive his M.S. and Ph.D. degrees from KAIST in 1996 and 2001, respectively. Dr. Kang is currently a senior research engineer at Rotor Department in KARI (Korea Aerospace Research Institute). Dr. Kang’s research interests are in the area of helicopter rotor aerodynamics, CFD (Computational Fluid Dynamics) and simulation of fluid-structure interaction.     

Kinematics, kinetics and muscle activities of the lower extremity during the first four steps from gait initiation to the steady-state walking

In this study, biomechanical characteristics during the whole process of gait initiation for twenty normal healthy volunteers were determined by the motion analysis with six near-infrared cameras, four forceplates, and an EMG system. Gait initiation, a transitional movement phenomenon from quiet stance to steady-state walking, involves a series of muscular activities, GRFs, movements of COP and COM, and joint motions. Results showed that the location of the net COP to be most lateral during double limb stance at the beginning of gait initiation. During gait initiation, changes in anteroposterior components of GRFs were first found and then changes in vertical components followed. Hip and knee motions were found before the ankle joint motion. Walking speed, step length, and stride length gradually increased until the second step. The interaction between the COM and COP is tightly regulated to control the trajectory of the COM and thereby control total body balance. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Sun-Woo Park received a B.S. degree in Biomedical Engineering from Yonsei University in 2006. He is currently a M.S. candidate in the Department of Biomedical Engineering, Yonsei University, Korea. His research interests in the area of Human Movement and detection of gait phase using motion sensors. Hue-Seok Choi received a B.S. degree in Computer Engineering from Daejeon University in 2004. He is currently a P.D. candidate at the Department of Biomedical Engineering at Yonsei University, Korea. His research interests are in the area of Human Movement and Rehabilitation Engineering. Ki-Hong Ryu received a B.S. and M.S. degrees in Biomedical Engineering from Yonsei University in 1998 and 2001, respectively. He is currently a P.D. candidate in the Department of Biomedical Engineering, Yonsei University, Korea. His research interests are in the area of Human Movement and Gait Training System using Functional Electrical Stimulation. Sa-Yup Kim received a B.S. degree in Electrical Engineering from Yeungnam University in 2002 and M.S. degrees in Biomedical Engineering from Yonsei University in 2006. He is currently working from Korea Institute of Industrial Technology in Cheonan, Korea. Young-Ho Kim received a B.S. degree in Mechanical Engineering from Hanyang University in 1982. He then went on to receive his M.S. and Ph.D. degrees from University of Iowa in 1989 and 1991, respectively. He is currently a Professor in the Department of Biomedical Engineering, Yonsei University, Korea. His research interests are in the area of Human Movement, Rehabilitation Engineering, and Biomechanics.     

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.     

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.     

Dynamics modeling and simulation of a new nine-bar press with hybrid-driven mechanism

A novel hybrid-driven mechanical press for precision drawing is presented. This new press is composed of a nine-bar linkage which has two degrees of freedom determined by inputs from a dc constant speed motor and a dc servomotor. Therefore, the generalized coordinates are the angular displacement of two cranks. The kinetic energy, potential energy and generalized torques are analyzed. According to the equivalent circuit of the dc motor and the brushless servomotor, their dynamical model and position negative feedback model are developed separately. Then, a dynamical model for the hybrid-driven press is developed by using Lagrange’s formulation. The dynamical equation is then transformed into a system of first order equations. Six first order differential equations are obtained in the state variables. In the end, the fourth fourth order Runge-Kutta method, an explicit method, is chosen as the integration technique of computer simulation. Two motors’ current, two cranks’ position and two cranks’ angular velocity are treated as unknowns and the time response of the hybrid-driven press is obtained by integrating the system of first order equations through time. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Hui Li received the B.S. degree in mechanical engineering from the Hebei Polytechnic University, Hebei, China, in 1991. He received the M.S. degree in mechanical engineering from the Harbin University of Science and Technology, Heilongjiang, China, in 1994. He received the PhD degree from the School of Mechanical Engineering of Tianjin University, Tianjin, China, in 2003. He is currently a professor in mechanical engineering at Shijiazhuang Institute of Railway Technology, China. His research and teaching interests include hybrid driven mechanism, kinematics and dynamics of machinery, mechatronics, CAD/CAPP, signal processing for machine health monitoring, diagnosis and prognosis.     

A series solution for spatially coupled deflection analysis of thin-walled Timoshenko curved beam with and without elastic foundation

The exact solutions for the spatially coupled deflection and the normal stress at an arbitrary location of a crosssection of the thin-walled Timoshenko curved beam with symmetric and non-symmetric cross-sections with and without two types of elastic foundations are newly presented using series solutions for the displacement parameters. The equilibrium equations and the force-deformation relations are derived from the elastic strain energy including the effects of shear deformation and the axial-flexural-torsional coupling, and the strain energy considering the foundation effects. The explicit expressions for displacement parameters are derived by applying the power series expansions of displacement components to the simultaneous ordinary differential equations. Next, the element stiffness matrix is determined by using the force-deformation relationships. The normal stress at any arbitrary location of the cross-section for a curved beam is evaluated from the stiffness matrix. To verify the validity and the accuracy of this study, the displacements and the normal stresses of curved beams are presented and compared with the analytical solutions, the finite element results using the isoparametric curved beam elements based on the Lagrangian interpolation polynomial, and the detailed three-dimensional analysis results using the shell elements of SAP2000. This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho Nam-Il Kim received his B.S. degree in Civil and Environmental Engineering from Sungkyunkwan University, Korea, in 1996. He then received his M.S. and Ph.D. degrees from Sungkyunkwan University in 1998 and 2004, respectively. Dr. Kim is currently a research professor at Civil and Environmental Engineering at Myongji University in Korea. Dr. Kim’s research interests include stability and vibration of steel and composite structures. Dong Ku Shin received his B.S. and M.S. degrees in Civil Engineering from Seoul National University, Korea, in 1983 and 1985, respectively. He then received his Ph.D. degree from Virginia Tech. at Blacksburg, VA, USA, in 1990. Dr. Shin is currently a professor of Civil and Environmental Engineering Department at Myongji University in Korea. Prof. Shin’s research interests include LRFD design of steel bridges and stability of composite structures.     

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.