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Integration of uniform design and quantum-behaved particle swarm optimization to the robust design for a railway vehicle suspension system under different wheel conicities and wheel rolling radii

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Acta Mechanica sinica 2017年第5期33卷 963-980页

作者： Yung-chang Cheng Cheng-Kang lee Department of Mechanical and Automation Engineering Kaohsiung First University of Science and Technology Department of Industrial Engineering and Management Cheng Shiu University

This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspension system. Based on the new nonlinear creep model derived from combining Hertz contact theory, Kalker's linear theory and a heuristic nonlinear creep model, the modeling and dynamic analysis of a 24 degree-of-freedom railway vehicle system were investigated. The Lyapunov indirect method was used to examine the effects of suspension parameters, wheel conicities and wheel rolling radii on critical hunting speeds. Generally, the critical hunting speeds of a vehicle system resulting from worn wheels with different wheel rolling radii are lower than those of a vehicle system having original wheels without different wheel rolling radii. Because of worn wheels, the critical hunting speed of a running railway vehicle substantially declines over the long term. For safety reasons, it is necessary to design the suspension system parameters to increase the robustness of the system and decrease the sensitive of wheel noises. By applying UD and QPSO, the nominal-the-best signal-to-noise ratio of the system was increased from -48.17 to -34.05 dB. The rate of improvement was 29.31%. This study has demonstrated that the integration of UD and QPSO can successfully reveal the optimal solution of suspension parameters for solving the robust design problem of a railway vehicle suspension system.

关键词： Speed-dependent nonlinear creep model Quantum-behaved particle swarm optimization Uniform design Wheel rolling radius Hunting stability

A Routing Protocol for Urban Vehicular Multi-hop Data Delivery

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Chinese Journal of Electronics 2016年第2期25卷 348-356页

作者： chang Sang-woo lee Sang-sun Department of Electronic Engineering Hanyang University

Vehicular ad-hoc network(VANET) has distinctive environments such as highly dynamic topology, frequently disconnected network, hard delay constraints for safety-related application, and various communications environments based on highway or urban traffic scenarios. Therefore, development of a suitable routing protocol that considers these characteristics of VANET should be needed. In this paper we propose the improved distance-based VANET routing protocol in urban traffic environments. We apply approaches to multi-hop broadcast scheme for reliable packet dissemination in the intersection and stable route decision scheme based on the adaptive waiting time. The performance is evaluated under simulation which is implemented with the Manhattan urban traffic model. The results show the improved performance as compared with other protocols.

关键词： Distance-based routing protocol Vehicle-to-vehicle communication Waiting time Urban traffic environments Vehicular ad-hoc network(VANET)

Radiative life time of an exciton confined in a strained GaN/Ga_(1-x)Al_xN cylindrical dot:built-in electric field effects

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Chinese Physics B 2011年第7期20卷 367-372页

作者： chang Woo lee A.John Peter Department of Chemical Engineering and Green Energy Center College of EngineeringKyung Hee University1 SeochunGihungYonginGyeonggi 446-701Republic of Korea Department of Physics Government Arts and Science CollegeMelur-625106India

The binding energy of an exciton in a wurtzite GaN/GaAlN strained cylindrical quantum dot is investigated theoretically. The strong built-in electric field due to the spontaneous and piezoelectric polarizations of a GaN/GaAlN quantum dot is included. Numerical calculations are performed using a variational procedure within the single band effective mass approximation. Valence-band anisotropy is included in our theoretical model by using different hole masses in different spatial directions. The exciton oscillator strength and the exciton lifetime for radiative recombination each as a function of dot radius have been computed. The result elucidates that the strong built-in electric field influences the oscillator strength and the recombination life time of the exciton. It is observed that the ground state exciton binding energy and the interband emission energy increase when the cylindrical quantum dot height or radius is decreased, and that the exciton binding energy, the oscillator strength and the radiative lifetime each as a function of structural parameters （height and radius） sensitively depend on the strong built-in electric field. The obtained results are useful for the design of some opto-photoelectronic devices.

关键词： quantum dot donor bound excitons oscillator strength

Synthesis of crosslinked polystyrene particles by seeded batch polymerization with monomer absorption

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 153-159页

作者： Ki-chang lee Han-Ah WI Department of Polymer Science and Engineering Engineering Research Institute Gyeongsang National University

A highly crosslinked, monodispersed polystyrene（PS） particle was prepared by a seeded batch dispersion polymerization with a monomer absorption method. Prior to polymerization, 1,9 lam monodispersed PS seed particles were treated under an optimum condition of monomer absorption. The effects of divinylbenzebe（DVB） concentration and polymerization temperature were examined for styrene（in PS seed）/styrene（in the second stage） mass ratio of 1：1 in the medium range of EtOH/water mass ratio of 100/0-80/20 and 2.3 μm uniform crosslinked PS particles containing 15%-20% （mass fraction） DVB were prepared at 60-70 ℃. The results show that monomer absorption before the second stage of polymerization is more effective to prepare highly crosslinked monodispersed PS particles.

关键词： crosslinked polystyrene particle seeded batch dispersion polymerization monomer absorption divinylbenzene (DVB)

Electronic and optical properties of CdS/CdZnS nanocrystals

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Chinese Physics B 2012年第8期21卷 441-448页

作者： A.John Peter chang Woo lee epartment of Chemical Engineering and Green Energy Center College of EngineeringKyung Hee University1 SeochunGihungYonginGyeonggi 446-701S.Korea Department of Physics Govt.Arts CollegeMelurMadurai-62510India Department of Chemical Engineering and Green Energy Center College of EngineeringKyung Hee University1 SeochunGihungYonginGyeonggi 446-701S.Korea

Cd1-xZnxS nanocrystals are prepared by a co-precipitation method with different atomic fractions of Zn. The texture, structural transformation and optical properties with increasing x value in Cd1-xZnxS are studied with scanning electron microscopy, electron diffraction patterning, and absorption spectra respectively. Quantum confinement in a strained CdS/Cd1-xZnxS related nanodot with various Zn content values is investigated theoretically. Binding energies on exciton bound CdS/CdxZn1-xS quantum dot are computed, with consideration of the internal electric field induced by the spontaneous and piezoelectric polarizations, and thereby the interband emission energy is calculated as a function of the dot radius. The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically. Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm. The X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with an increase in Zn content. The lattice constant gradually decreases as the Zn content increases. The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as the Zn content increases. The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for the CdS film and 3.5 eV for the ZnS film. Our numerical results are in good agreement with the experimental results.

关键词： quantum dots quasicrystals semiconductor

Bioinspired Segment Robot with Earthworm-like Plane Locomotion

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Journal of Bionic Engineering 2016年第2期13卷 292-302页

作者： chang-Woo Song Dong-Jun lee Seung-Yop lee Department of Mechanical Engineering Sogang University 1 Shinsu-dong Mapo-gu Seoul 121-742 Republic of Korea

In this paper, a miniaturized segment robot using solenoids is developed to mimic the plane locomotion of earthworms. The bioinspired robot is composed of five segmented bodies, and one segment has two solenoid actuators. This robot can move linearly and it can also turn due to the pair of solenoid actuators that facilitate the earthworm-like peristaltic locomotion. We have designed a miniaturized solenoid with a permanent magnet plunger in order to increase the total electromagnetic force. A theoretical analysis is performed to predict the linear and turning motions of each segment, and the optimal profiles of input signals are obtained for fast locomotion. Experiments are then conducted to determine the linear and turning motions of the segment robot. It takes about 0.5 s for the five segments to complete one cycle of the peristaltic locomotion. In experiments, the segment robot is shown to have the linear and angular velocities of 27.2 mm·s^-1 （0.13 body-length per second） and 2 degrees per second, respectively.

关键词： bioinspired robot earthworm peristaltic locomotion solenoid segmented robot

Velocity Profiles between Two Baffles in a Horizontal Circular Tube

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Journal of Thermal Science 2014年第6期23卷 544-551页

作者： Tae-Hyun chang Hae-Soo lee Keon-Je Oh Doeg Hee Doh chang-Hoan lee Senior Research Fellow of RESEAT Korea Institute of Science and Information Postdoctoral Research Fellow School of Mechanical Engineering of Kyungnam University School of Mechanical Engineering Kyungnam University Division of Mechanical and Energy Systems Engineering Korea Marine and Ocean University Korea Institute of Science and Technology Information

The shell and tube heat exchanger is an essential part of a power plant for recovering heat transfer between the feed water of a boiler and the wasted *** baffles are also an important element inside the heat *** materials influence the flow pattern in the *** influence of baffles in the velocity profiles was observed using a three-dimensional particle image velocimetry around baffles in a horizontal circular *** velocity of the particles was measured before the baffle and between them in the test *** show that the flows near the front baffle flow were parallel to the vertical wall,and then concentrate on the upper opening of the front *** flows circulate in the front and rear *** flow profiles are related to the Reynolds number(Re) or the flow *** velocity profiles at lower Re number showed a complicated mixing,concentrating on the lower opening of the rear baffle as front *** flow was employed in this study,which was produced using tangential velocities at the *** the entrance of the front baffle,the velocity vector profiles with swirl were much different from that without ***,velocities between two baffles are not much different from those without swirl.

关键词： Baffle Shell and tube Tangential inlet Swirl Particle image velocimetry

Design of a long range nano-scale resolution mechanism

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第4期11卷 250-254页

作者： Shuo Hung chang Jen Bon lee Department of Mechanical Engineering National Taiwan University

This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high *** fine stage is arranged in series with a coarse *** key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and *** designed the toggle mechanism for reduction of the displacement to suppress signal *** performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,*** measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.

关键词： Coarse-fine dual stage Nano-scale resolution Piezoelectric (PZT) actuator

Photo-Induced Electron Spin Polarization in a Narrow Band Gap Semiconductor Nanostructure

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Chinese Physics Letters 2012年第11期29卷 186-190页

作者： A.John Peter chang Woo lee Department of Chemical Engineering and Green Energy Center College of EngineeringKyung Hee University1 SeochunGihungYonginGyeonggi 446-701S.Korea

Photo-induced spin dependent electron transmission through a narrow gap InSb/InGa_(x)Sb_(1-x) semiconductor symmetric well is theoretically studied using transfer matrix *** transparency of electron transmission is calculated as a function of electron energy for different concentrations of *** spin-polarized photon assisted resonant tunnelling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level and compressed spin-polarization are *** results show that Dresselhaus spin-orbit coupling is dominant for the photon effect and the computed polarization efficiency increases with the photon effect and the gallium concentration.

关键词： polarization resonant photon