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Simple PSF based method for pupil phase mask’s optimization in wavefront coding system
ZHANG Wen-zi, CHEN Yan-ping, ZHAO Ting-yu, YE Zi, YU Fei-hong
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 3-.
https://doi.org/10.1631/jzus.2007.A0180
By applying the wavefront coding technique to an optical system, the depth of focus can be greatly increased. Several complicated methods, such as Fisher Information based method, have already been taken to optimize for the best pupil phase mask in ideal condition. Here one simple point spread function (PSF) based method with only the standard deviation method used to evaluate the PSF stability over the depth of focus is taken to optimize for the best coefficients of pupil phase mask in practical optical systems. Results of imaging simulations for optical systems with and without pupil phase mask are presented, and the sharpness of image is calculated for comparison. The optimized results showed better and much more stable imaging quality over the original system without changing the position of the image plane.
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Metal hydride work pair development and its application on automobile air conditioning systems
QIN Feng, CHEN Jiang-ping, ZHANG Wen-feng, CHEN Zhi-jiu
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 6-.
https://doi.org/10.1631/jzus.2007.A0197
Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26Al0.13/ La0.6Y0.4Ni4.8Mn0.2 was developed working at 393~473 K/293~323 K/263~273 K. Property tests showed that both alloys have flat plateau slopes and small hystereses; system theoretical coefficient of performance (COP) is 0.711. Based on this work pair, a function proving automobile metal hydride refrigeration system was constructed. The equivalent thermal conductivities of the activated reaction beds were merely 1.1~1.6 W/(m∙K), which had not met practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power was 84.6 W at 423 K/303 K/273 K with COP being 0.26. By altering cycling parameters, experiment data showed that cooling power and system COP increase with the growth of heat source temperature as well as pre-heating and regeneration time while decrease with heat sink temperature increment. This study confirms the feasibility of automobile metal hydride refrigeration systems, while heat transfer properties of reaction beds still need to be improved for better performance.
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Experimental observation on a small-scale thermoacoustic prime mover
JIN Tao, ZHANG Bao-sen, TANG Ke, BAO Rui, CHEN Guo-bang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 7-.
https://doi.org/10.1631/jzus.2007.A0205
A miniature thermoacoustic prime mover, consuming heat to radiate sound, may be considered as a potential way of heat management in microcircuits because of its simplicity and stability. A prototype with variable resonant tube length of 10 to 25 cm was built, and experiments were carried out to observe its performance, such as onset temperature, oscillation amplitude and operating frequency. The results with atmospheric air showed that proper structures and operating conditions can make the system start an oscillation at a temperature lower than 100 °C, which proves the feasibility of potential usage in electronic units. The influences of stack position, heat input power or tube inclination on the oscillation amplitude, onset temperature and operating frequency are also presented.
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Advances in research of stress-assisted corrosion fatigue problem
TANG Zhi-bo, LI Qiang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 10-.
https://doi.org/10.1631/jzus.2007.A0221
Ceramic materials are notable for their rigidity, insulation and resistance to hostile environment. Nevertheless, if a stressed ceramic component is exposed to chemical attack, it may suffer from a form of delayed fracture known as static fatigue. From the point of view of a designer, it is clearly desirable to determine the behavior of sub-critical crack growth; the crack path and crack growth rate, as a function of material properties and loading conditions are of particular interest. This paper presents a review of advances in stress assisted corrosion problem in history and its corresponding numerical approaches in the last decades, and finally, comes up with consideration and crucial suggestions for future work.
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An analytical model for predicting sheet springback after V-bending
ZHANG Dong-juan, CUI Zhen-shan, CHEN Zhi-ying, RUAN Xue-yu
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 12-.
https://doi.org/10.1631/jzus.2007.A0237
Springback is caused by the redistribution of stress in sheet material after the tooling is removed. Precise prediction of sheet springback is very important in die design. Based on Hill’s yielding criterion and plane strain condition, an analytical model is proposed in this paper which takes into account the effects of contact pressure, the length of bending arm between the punch and die, transverse stress, neutral surface shifting and sheet thickness thinning on the sheet springback of V-bending. The predicted results by this analytical model indicated that the contact pressure and transverse stress have much effect on the springback when the bending ratio (the ratio of punch radius to sheet thickness) is less than five. The contact pressure declined when the length of bending arm goes up, which means that shorter length of bending arm will result in larger springback. The effect of neutral surface shifting on the springback is less than that of contact pressure and decreases with the bending ratio. However, this research showed that the influence of thickness thinning on the springback can be ignored. Comparison with finite element method (FEM) simulating results shows that the predicted results by the analytical model accord well with simulation results by FEM. In addition to that, the bending ability—the limit bending ratio for a given sheet thickness and material properties was also determined.
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Optimization study of a PEM fuel cell performance using 3D multi-phase computational fluid dynamics model
AL-BAGHDADI Maher A.R. Sadiq, AL-JANABI Haroun A.K. Shahad
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 18-.
https://doi.org/10.1631/jzus.2007.A0285
An optimization study using a comprehensive 3D, multi-phase, non-isothermal model of a PEM (proton exchange membrane) fuel cell that incorporates significant physical processes and key parameters affecting fuel cell performance is presented and discussed in detail. The model accounts for both gas and liquid phase in the same computational domain, and thus allows for the implementation of phase change inside the gas diffusion layers. The model includes the transport of gaseous species, liquid water, protons, energy, and water dissolved in the ion-conducting polymer. Water is assumed to be exchanged among three phases: liquid, vapour, and dissolved, with equilibrium among these phases being assumed. This model also takes into account convection and diffusion of different species in the channels as well as in the porous gas diffusion layer, heat transfer in the solids as well as in the gases, and electrochemical reactions. The results showed that the present multi-phase model is capable of identifying important parameters for the wetting behaviour of the gas diffusion layers and can be used to identify conditions that might lead to the onset of pore plugging, which has a detrimental effect on the fuel cell performance. This model is used to study the effects of several operating, design, and material parameters on fuel cell performance. Detailed analyses of the fuel cell performance under various operating conditions have been conducted and examined.
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A remote control training system for rat navigation in complicated environment
FENG Zhou-yan, CHEN Wei-dong, YE Xue-song, ZHANG Shao-min, ZHENG Xiao-jing, WANG Peng, JIANG Jun, JIN Lin, XU Zhi-jian, LIU Chun-qing, LIU Fu-xin, LUO Jian-hong, ZHUANG Yue-ting, ZHENG Xiao-xiang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 21-.
https://doi.org/10.1631/jzus.2007.A0323
A remote control system has been developed to deliver stimuli into the rat brain through a wireless micro-stimulator for animal behavior training. The system consists of the following main components: an integrated PC control program, a transmitter and a receiver based on Bluetooth (BT) modules, a stimulator controlled by C8051 microprocessor, as well as an operant chamber and an eight-arm radial maze. The micro-stimulator is featured with its changeable amplitude of pulse output for both constant-voltage and constant-current mode, which provides an easy way to set the proper suitable stimulation intensity for different training. The system has been used in behavior experiments for monitoring and recording bar-pressing in the operant chamber, controlling rat roaming in the eight-arm maze, as well as navigating rats through a 3D obstacle route. The results indicated that the system worked stably and that the stimulation was effective for different types of rat behavior controls. In addition, the results showed that stimulation in the whisker barrel region of rat primary somatosensory cortex (SI) acted like a cue. The animals can be trained to take different desired turns upon the association between the SI cue stimulation and the reward stimulation in the medial forebrain bundle (MFB).
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Molecular simulation of the adsorption of linear alkane mixtures in pillared layered materials
LI Wen-zhuo, CHE Yu-liang, LIU Zi-yang, ZHANG Dan
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(2): 22-.
https://doi.org/10.1631/jzus.2007.A0331
The adsorption isotherms of mixtures of linear alkanes, involving n-pentane, n-hexane, and n-heptane in pillared layered materials (PLMs) with three different porosities Ψ=0.98, 0.94 and 0.87, and three pore widths H=1.02, 1.70 and 2.38 nm at temperature T=300 K were simulated by using configurational-bias Monte Carlo (CBMC) techniques in grand canonical ensemble. A grid model was employed to calculate the interaction between a fluid molecule and two layered boards here. For alkane mixtures, the n-heptane, the longest chain component in alkane mixtures, is preferentially adsorbed at low pressures, with its adsorption increasing and then decreasing as the pressure increases continuously while the n-pentane, the shortest chain component in alkane mixtures, is still adsorbed at high pressures; the adsorption of the longest chain component of alkane mixtures increases as the pore width and the porosity of PLMs increase.
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22 articles
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