2025-04-22 2008, Volume 14 Issue 1

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  • Xinhua Ji , Xinwei Yang , Jinlong Chen

    In this paper, white light digital image analysis in frequency domination area for measuring 3D displacement is put forward. The measuring system has the characteristics of whole-field, non-contact and omni-bearing measurement. It is simple and the coherent light is not demanded. Gray images before and after deformation are recorded using two CCDs at two different shooting angles, then digitalized and analyzed by frequency domination correlation arithmetic. The 2D displacement obtained is used to formulate 3D displacement via mathematical transformation. The experimental plate is 40 mm in length, 30 mm in width and 10 mm in height. The definite displacement is given using a 3D precise adjusting frame. The 3D displacement is calculated and compared with the definite displacement. The error is 4%–11% and the availability of this method was certified. Using this method, the compression deformation of a thin-wall cylinder with 140 mm in height, 64 mm in inner diameter and 64.6 mm in external diameter, was also measured. This method is proper to measure dynamic deformation.

  • Yitong Zhang , Jian Gao , Jiafu Xu

    A new representation of the Maxwell relation for phase transformation is given, which is expressed in simpler form and has more direct physical meaning than the original Maxwell relation. It is shown that the physical conjecture for the so-called “lock-up” condition suggested by Jensen (1999) is correct, but the equation for the “lock-up” condition suggested by Jensen (1999) is not. Numerical examples also demonstrate that the application of the new representation of Maxwell relation gives exactly the same solutions as the ones with application of the original Maxwell relation and, however, application of the “lock-up” condition gives no real solutions.

  • Nan Ge , Jun Zhang

    The stress and the elastic deflection of internal ring gear in high-speed spur planetary gear units are investigated. A rim thickness parameter is defined as the flexibility of internal ring gear. Six evenly spaced linear springs are used to describe the fitting status between internal ring gear and the gearcase. The finite element model of the whole internal ring gear is established by means of Pro/E and ANSYS. The loads on meshing teeth of internal ring gear are applied according to the contact ratio and the load-sharing coefficient. With the finite element analysis (FEA), the influences of flexibility and fitting status on the stress and elastic deflection of internal ring gear are predicted. The simulation reveals that the principal stress and deflection increase with the decrease of rim thickness of internal ring gear. Moreover, larger spring stiffness helps to reduce the stress and deflection of internal ring gear. Therefore, the flexibility of internal ring gear must be considered during the design of high-speed planetary gear transmissions.

  • Dong Ming , Chengwei Gu , Wenya Nan , Shuangchi Liu , Wei Song , Longlong Cheng , Baikun Wan

    A new measurement and analysis method was proposed to investigate the changes in elbow joint moments that occur with the use of a front-wheeled walker. A strain gauge-based walker instrumentation system was developed to monitor the hand loads during walker-assisted walking and integrated with an upper extremity biomechanical model. Preliminary system data were collected for 12 subjects following informed consent. Bilateral upper extremity kinematic data were acquired with a six-camera motion analysis system. Internal joint moments at the elbow were determined in the three clinical planes using the inverse dynamics method. Results showed that during a walker-assisted gait elbow joint moments mainly distributed in the walker stance period. There was a noted demand on the elbow extensor in the sagittal plane with the greatest record as 0.381 N·m/(kg·m). An interesting “bare phase” of mean elbow joint moments was also found in phase angle −240°–340° of gait cycle. Complete description of elbow joint moments of walker-assisted gait may provide insight into walker use parameters and rehabilitative strategies.

  • Weidi Dai , Wenjun Wang , Yuexian Hou , Ying Wang , Lu Zhang

    This paper focuses on document clustering by clustering algorithm based on a DEnsityTree (CABDET) to improve the accuracy of clustering. The CABDET method constructs a density-based treestructure for every potential cluster by dynamically adjusting the radius of neighborhood according to local density. It avoids density-based spatial clustering of applications with noise (DBSCAN)’s global density parameters and reduces input parameters to one. The results of experiment on real document show that CABDET achieves better accuracy of clustering than DBSCAN method. The CABDET algorithm obtains the max F-measure value 0.347 with the root node’s radius of neighborhood 0.80, which is higher than 0.332 of DBSCAN with the radius of neighborhood 0.65 and the minimum number of objects 6.

  • Chengang Lü , Zhixiong Hu , Peng Zu , Chunfeng Ge , Xing Wu

    A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm–1 575 nm, and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.

  • Guojun Dong , Jufeng Dai

    Based on five scheduling types and their QoS requirements defined in IEEE 802.16e specification, this paper proposes a new scheduling algorithm for non-real-time or real-time multimedia services. Taking the performances of efficiency, fairness and complexity into consideration, the proposed algorithm enhances the efficiency of air interface resource at the expense of the short-time unfairness, but ensures the long-time fairness. Moreover, the proposed algorithm introduces an efficient QoS assurance mechanism, which implements the functions of congestion control, queuing management and traffic management. The simulation results based on a simplified traffic model show that the proposed algorithm guarantees better performances of efficiency and fairness than conventional algorithms, without increasing the algorithm complexity. Especially on the occasion of heavy-traffic requirement, the performance of efficiency and fairness can be improved by 50% at most.

  • Baoyun Xu , Xueming Zheng , Weijiang Zhang , Xuemei Zhang , Zhiyong Zhang , Huijian Shang

    The kinetics of esterification of 2-keto-L-gulonic acid with methanol in the liquid phase catalyzed by cation exchange resin, D001, was studied. The experiments were carried out in a stirred batch reactor at 318, 323, 328, 333, 338, 341 K under atmospheric pressure. It is found that the speed of rotating rate has no effect on the esterification rate in the range of 300–500 r/min and the effect of internal mass transfer resistance is not obvious. The effects of temperature and catalyst loading on the reaction rate were researched under the condition of eliminating the effect of diffusion. The rate was found to increase with the increase of the temperature and catalyst loading. The experimental data were correlated with a kinetic model based on the pseudo-homogeneous catalysis. The kinetic equation for describing the reaction catalyzed by cation exchange resin was developed. The experimental data are in good agreement with the model.

  • Yufu Ning , Wansheng Tang , Changyou Guo

    In order to solve three kinds of fuzzy programming models, i.e. fuzzy expected value model, fuzzy chance-constrained programming model, and fuzzy dependent-chance programming model, a simultaneous perturbation stochastic approximation algorithm is proposed by integrating neural network with fuzzy simulation. At first, fuzzy simulation is used to generate a set of input-output data. Then a neural network is trained according to the set. Finally, the trained neural network is embedded in simultaneous perturbation stochastic approximation algorithm. Simultaneous perturbation stochastic approximation algorithm is used to search the optimal solution. Two numerical examples are presented to illustrate the effectiveness of the proposed algorithm.

  • Jing Liu , Daoji Shi , Xinrong Wu

    This paper puts forward a Poisson-generalized Pareto (Poisson-GP) distribution. This new form of compound extreme value distribution expands the existing application of compound extreme value distribution, and can be applied to predicting financial risk, large insurance settlement and high-grade earthquake, etc. Compared with the maximum likelihood estimation (MLE) and compound moment estimation (CME), probability-weighted moment estimation (PWME) is used to estimate the parameters of the distribution function. The specific formulas are presented. Through Monte Carlo simulation with sample sizes 10, 20, 50, 100, 1 000, it is concluded that PWME is an efficient method and it behaves steadily. The mean square errors (MSE) of estimators by PWME are much smaller than those of estimators by CME, and there is no significant difference between PWME and MLE. Finally, an example of foreign exchange rate is given. For Dollar/Pound exchange rates from 1990-01-02 to 2006-12-29, this paper formulates the distribution function of the largest loss among the investment losses exceeding a certain threshold by Poisson-GP compound extreme value distribution, and obtains predictive values at different confidence levels.

  • Xianling Ren , Huizhao Liu

    Impulsive neutral differential inclusions play an important role in characterizing many social, physical and engineering problems, and the existence of solutions for the initial value problem in Banach spaces has been extensively studied. However, in most cases, the nonlinear term on the right-hand side of differential inclusions has to satisfy the compact or continuous assumptions. The object of this paper is to study the existence of solutions to the initial value problems of the first and second order impulsive neutral functional differential inclusions in Banach spaces under some weaker conditions, where the nonlinear term on the right-hand side does not necessarily satisfy the compact and continuous assumptions. Based on a fixed point theorem for discontinuous multivalued increasing operators, the results are obtained by means of the partial ordering method and measure of noncompactness.

  • Lihe Yang , Yong Zhu , Guochen Fan , Yude Sun , Shiwen Xie

    Using carbon tetrachloride (CCl4) as extraction agent, the activated sludge from Tianjin Jizhuangzi Sewage Treatment Plant as inoculum, the test study on biodegradability of lubricants was carried out. The test flasks containing the mineral medium, the test oil and the inoculum were placed in incubation together with flasks containing poisoned blanks for periods of 0 and 21 days, respectively. Flasks containing the reference materials in place of the test oil were run in parallel. At the end of the incubation period, the contents of the flasks were subjected to sonic vibration, and were acidified and extracted by using CCl4. The extracts were then analysed by infra-red (IR) spectrometer to measure the maximum absorption of the C-H stretch of CH2-CH3 band at wavelength of 2 930 cm−1. The absorption values were used to calculate the residual oil contents of the poisoned and test flasks. Consequently the biodegradability of the test oil was calculated. The test results indicate that the differences in the biodegradability of test materials in different tests are within 5.5%, and consistent with the data described in Coordinating European Council (CEC) L-33-A-93. The biodegradability of lubricants can be evaluated by this method effectively.

  • Fangwei Wang , Yunkai Zhang , Jianfeng Ma

    Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly analyzes and obtains the average delay for all peers in the whole transmitting process due to the limitation of network throughput, and then proposes a mathematical model for the propagation of passive worms over the unstructured P2P networks. The model mainly takes the effect of the network throughput into account, and applies a new healthy files dissemination-based defense strategy according to the file popularity which follows the Zipf distribution. The simulation results show that the propagation of passive worms is mainly governed by the number of hops, initially infected files and uninfected files. The larger the number of hops, the more rapidly the passive worms propagate. If the number of the initially infected files is increased by the attackers, the propagation speed of passive worms increases obviously. A larger size of the uninfected file results in a better attack performance. However, the number of files generated by passive worms is not an important factor governing the propagation of passive worms. The effectiveness of healthy files dissemination strategy is verified. This model can provide a guideline in the control of unstructured P2P networks as well as passive worm defense.

  • Changxiu Han , Jili Ren , Baogui Zhang

    A new supported amorphous catalyst CoP/TiO2 was prepared by chemical reduction and characterized by ICP, XRD, TEM, BET and DSC. Its application in decomposing PH3 to high purity phosphor and its catalytic activity were studied. The decomposition rate is over 95% at 450 °C. For comparison, unsupported CoP amorphous catalyst was prepared by the same method. The result suggests that CoP/TiO2 exhibits higher thermal stability and catalytic activity than CoP, which is attributed to the high dispersion of CoP alloy particles on the support-TiO2.