最新刊期
卷 51 ， 期 4 ， 2017
- 摘要：A new liquid injection and drainage online dynamic balancing method is proposed for reducing the unbalance vibration of the grinding wheel. A new balance device is also designed. The liquid in the balance chamber is controlled by evaluating the injection liquid and calculating the drainage to provide appropriate correction mass. A dynamic liquid injection model is proposed by analyzing the relationship between the centrifugal force and the radius of liquid level in the chamber. The parametric measurement of the short hole throttle valve in drainage is accomplished. A theoretical model for flow controlling is established to calculate the liquid in the balance chamber by analyzing the influence factor of the throttle valve. Balancing experiment shows that the unbalance response is reduced by 89.25% at 2 700 r/min, the effectiveness of the proposed method is also verified. The new balance method with continuous balance ability solves the problem that liquid injection in online dynamic balance chamber loses the balance ability due to full cavity.关键词：grinding wheel;online dynamic balance;liquid injection and drainage;rotor vibration1081|5|24更新时间：2025-07-09
- 摘要：To improve the lubrication performance of artificial joint and to prolong its service life, temperature-sensitive hydrogel is taken as a carrier for releasing lubricants in artificial joint, and the tribological property of the released solution is investigated. The temperature-sensitive hydrogel of polycaprolactone-polyethylene glycol-polycaprolactone(PCEC)copolymer is synthesized by ring-opening polymerization method, and it can undergo the sol-gel transition at simulative body temperature. The release behavior of chitosan(CS)/BSA(bovine serum albumin)mixture carried by temperature-sensitive hydrogel is investigated by Bradford method in vitro. The tribological property of the release solution is measured by friction and wear tests. The concentration of BSA in the release solution is about 1% of the concentration of BSA before release. The friction coefficient of the release solution is about 25% of saline, distilled water or the simulation of body fluids. For Al2O3 ceramic ball and Co-Cr-Mo disc pair, the wear rate with the release solution is about 73% lower than that of the saline solution, about 50% lower than the distilled water and about 20% lower than the simulated body fluid.关键词：artificial joint;temperature-sensitive hydrogel;tribological property;in-vitro release;wear rate832|5|1更新时间：2025-07-09
- 摘要：For the purpose of improving discharge gas pulsation characteristic of twin screw refrigeration compressor, a gas pulsation damping device following the principle of Helmholtz resonator was developed. In consideration of the oil-gas two-phase flow in the compressor discharge chamber, a two-phase sound speed calculation model was established. Then the resonant frequency of damping device can be evaluated. The gas pulsation damping device applied to twin screw refrigeration compressor was developed. Experimental investigation was carried out to analyze the effects of discharge temperature and lubrication oil flow rate on the performance of damping device. And the vibration characteristic of compressor with the damping device was compared with the one without damping device. It is concluded that there exists an optimal sound speed of R134a to achieve the maximum damping ratio when the lubrication oil flow rate keeps constant. With the increasing oil flow rate, the optimal value of R134a sound speed increases. There also exists an optimal sound speed of the two-phase fluid, and optimal value keeps constant but the damping ratio increases as the oil flow rate increases. The vibration acceleration of compressor under-chassis under first-order gas pulsation frequency can be reduced by 36.2% to 40.9% as the compressor is equipped with the damping device.关键词：twin screw refrigeration;compressor;gas pulsation damping device806|6|2更新时间：2025-07-09
- 摘要：To quickly find a path of wireless power transfer networks, which can maximize the transmission efficiency and minimize electrical energy loss, the cellular genetic algorithm(CGA)is chosen to optimize the transfer link. Analyzing the mathematical model of wireless energy transmission network, the objective function of the active injection and the passive injection wireless power transfer networks is established, and the objective function is taken as the fitness function of the cellular genetic algorithm. To heighten the proportion of effective individuals in the population and improve the searching efficiency, a duplicate elimination scheme is proposed to transform infeasible solution into feasible solution. Genetic algorithms and cellular automata are combined by the cellular genetic scheme, a niche thus forms between individuals and their neighbors, the good individuals spread slowly in the population, so the algorithm can effectively break the restriction of local optimal solution and quickly converge to the global optimal solution. Simulation results show that the cellular genetic algorithm can accurately find the optimal path in both the active injection and the passive injection wireless power transfer networks, which verifies the feasibility of this cellular genetic algorithm for path optimization of wireless power transfer networks.关键词：wireless power transfer;wireless power transfer networks;path optimization;cellular genetic algorithm794|5|4更新时间：2025-07-09
- 摘要：According to the phenomenon that higher line trip rate of power system is often caused by lightning strike, an impact coefficient model of ground device of pole and tower for different lightning current amplitude is established to evaluate the impact of lightning current on grounding resistance of the pole and tower, and improve impulse grounding resistance measurement accuracy. X-ray photograph platform is constructed to get the gradual change law of spark discharge in soil along spot-sphere-streamer-arc channel under lightning current. Via field test under different lightning current, the interaction of the effect of inductance effect on the current blocking action and the effect of the spark effect on flow are revealed. The impact resistance of the grounding device is obtained by decoupling the inductive effect and the spark effect. Experiment results show that with the proposed model the impulse characteristic of the ground device under large lightning current can be obtained via measurement under small lightning current. Hence, portable ground impedance tester can be adopted to measure impulse ground impedance, and the error between the calculated impedance and the actual one is less than 3%.关键词：lightning current;ground device of pole and tower;X-ray photograph platform;spark discharge;spark coefficient;inductance coefficient776|5|0更新时间：2025-07-09
- 摘要：Aiming at the noise of photoelectric device and difficulty of threshold setting, an adaptive threshold method is proposed. According to the distribution differences of partial discharge(PD)signals and noises, the sample data are divided into groups and accumulated by multi-cycles in time domain. Sufficiently investigating the power features, the AR spectrum estimation is applied to calculate the power spectrum of the sequence, and three power indexes, i.e., total power, signal power and harmonic ratio, are extracted. Analyzing the indexes, a parameter is defined which can characterize the weighted ratio of signal power to total power, and the adaptive threshold is set in terms of the fluctuation of noise power. Experiments show that the proposed method is able to adapt the threshold according to sample data and realize auto-detection of PD with high sensitivity and without human intervention, especially for early warning and online monitor of electrical equipment.关键词：fluorescent fiber;system noise;phase distribution;power characteristics;evaluation criteria864|5|3更新时间：2025-07-09
- 摘要：An effective method to reduce residual silicon content in reaction-sintered silicon carbide(RSSC)ceramics is presented to solve the problem that traditional RSSC ceramics have low mechanical properties for its high residual silicon content. The method helps to reduce the residual silicon content and to get composite ceramics with excellent mechanical properties by using short carbon fiber as carbon source and boron carbide to promote liquid silicon infiltration. The reaction mechanism of the carbon fiber, the microstructure evolution of the sintered body and the change of the mechanical properties are analyzed. Experimental results show that the carbon fiber reacts with silicon using dissolution-precipitation method to form fiber-like silicon in the sintering body, then the resulting SiC blocks the capillary and the carbon fiber reacts with the silicon by diffusion. Under the dual fuction of the self-supporting interpenetrating network structure of the carbon fiber and the boron carbide, the flexural strength reaches a peak value of(482±12)MPa when 30% volume fraction of carbon fiber is added; while the residual silicon content decreases to 1.6% volume fraction, the silicon size is nanoscale and the fracture toughness reaches a peak value of(5.82±0.37)MPa?m1/2 when 40% of carbon fiber is added.关键词：reaction sintering;carbon fiber;mechanical property;nanoscale644|6|0更新时间：2025-07-09
- 摘要：The three-body engagement consists of three vehicles, which are an evading target, a defending missile launched by the target, and a homing missile. An adaptive collaborative guidance strategy for the target and the defender is proposed to protect the target from the homing missile. Firstly, it is assumed that the perfect information of the homing missile is known. The optimal collaborative guidance laws for the target and defender are derived by using optimal control theory to minimize the missile-defender miss distance and control effort of the target and defender. Then, the real engagement condition with unknown missile's guidance strategy and measurement noise is considered. Adaptive collaborative guidance laws are proposed based on the multiple-model adaptive estimator with square-root cubature Kalman filter(MMAE-SRCKF)and the optimal collaborative guidance laws. MMAE-SRCKF is used to estimate the guidance law and state information of the homing missile. The adaptive collaborative guidance laws are derived by combining each model's optimal collaborative guidance laws. Simulation results show that the defender hits the homing missile with less control effort in the aid of the target by using the proposed optimal collaborative guidance laws, and the miss distance is smaller than 0.1 m. The proposed adaptive collaborative guidance laws estimate the state information of the missile accurately and make the target and defender act as a team to hit the homing missile.关键词：three-body engagement;optimal cooperative guidance law;multiple-model adaptive estimator;adaptive cooperative guidance law590|5|3更新时间：2025-07-09
- 摘要：A method for acquiring and analyzing program resource sensitivity is proposed to deal with the problem that the performances of programs and systems are unstable due to workload consolidation in clusters or data centers. A control group with tunable resources is set up by using Cgroups in Linux, and programs are executed in the control group under various resource conditions. The performance of programs within limited resources is obtained and used for calculating the resource sensitivity. The sensitivity values of programs under restriction of multiple resources form a sensitivity hyperplane to predict the performance of co-running programs. The resources required by a program are reordered according to their importance for cluster scheduling. Experimental results show that the average absolute error between the real sensitivity value and the sensitivity value predicted by the method is 0.093. A comparison with the common least load scheduling strategy shows that the scheduling strategy using resource sensitivity aware improves program performance by 22.2% and enhances both disk I/O and network I/O utilization. It also shows the contribution of program resource sensitivity to workload consolidation.关键词：program resource sensitivity;workload consolidation;cluster scheduling;co-running programs647|5|0更新时间：2025-07-09
- 摘要：An active compliance control strategy based on position impedance control is proposed to solve the problem of flexible hinges with high aspect ratio and the deformation of parallel robot caused by external environment. Based on the equivalent reaction model between a flexible parallel robot and external environment and the position-based impedance control model, this strategy adds an external environment force in its control process. The steady state error of force tracking model is considered and accurately controlled by adjusting the initial reference position based on position control. Then, the external force tracking control is analysed with the position control under accurate environment variables. Lyapunov stability model and Lyapunov energy equation are used under the condition of unknown environment variables, and the adaptive force control is achieved by directly controlling the target position through a force deviation. Experimental results show that the precision of the position-based force control and the adaptive control reaches ±0.05 N and ±0.1 N, respectively, and meets design requirement. The accuracy and effectiveness of the strategy are verified.关键词：flexible parallel robot;impedance control;adaptive control;force control648|5|1更新时间：2025-07-09
- 摘要：A novel influence prediction method is proposed to deal with the social promotion problem on crowdfunding platforms and to investigate the predictability of social influence for fundraising projects. The proposed method gradually predicts future influence growth of each project based on features extracted in different timestamps from data streams of crowdfunding websites and social networks. Experimental results show that features extracted from aggregate data rather than incremental data are better indicators of the social influence growth, and the method has the highest prediction precision 88.31%. Analysis of features also shows that some features such as the statistic of projects and social influence of promoters are consistently significant within the prediction process. These results provide hints for devising better social promotions.关键词：social network;crowdfunding project;social influence;influence prediction778|5|0更新时间：2025-07-09
- 摘要：A new method for data collection and anomaly detection of hosts is proposed to focus on the problems that the methods based on signature matching cannot detect unknown anomaly and data collection agents occupy too many host resources. Intelligent mobile agents are employed to perform data collection so that the number of collection agents is greatly reduced. In order to achieve the goal of online anomaly detection, the principal component analysis method is employed to reduce the dimension of the data, and the clustering method is used to mine the abnormal events. The host anomaly detection method based on continuous time windows is adopted to eliminate the influence of random outliers. Experimental results show that the proposed method has lower computational complexity and higher detection accuracy, and for same number of records the time complexity is reduced by more than 50% and the detection accuracy is above 95%, compared with conventional method. It is concluded that the method is suitable for real-time detection of host anomaly.关键词：anomaly detection;mobile agent;principal component analysis;clustering method1215|5|4更新时间：2025-07-09
- 摘要：A sliding mode switching function with double closed-loop is proposed based on inductance current to deal with the problems that the sliding coefficients are often difficult to determine and the robustness control of a system conflicts with dynamic quality. Benchmark inductor currents are tracked by the output voltage and tracing coefficients are determined by solving the Lyapunov functions, which avoids the difficulties to determine conventional sliding mode coefficients and to measure the benchmark inductor currents. Moreover, the arithmetic builds a nonlinear link on the sliding mode switching function, and derives an adaptive control method of terminal sliding modes with double closed-loop. In order to obtain an optimal control strategy of terminal sliding modes, the present method improves the approach speed and the convergence speed simultaneously by implementing the adaptive selection of terminal sliding modes, effectively suppresses the output voltage impulse in the start-up phase, and improves the transient response and robustness of a system simultaneously. Simulation verifies the applicability of the present method in accurate control of Buck converters.关键词：Buck converter;adaptive terminal sliding mode control;double closed-loop sliding mode control;transient response;robustness784|4|1更新时间：2025-07-09
- 摘要：A state estimation-based model predictive control strategy is proposed to deal with the constraints and the poor robustness problems existing in the system of servo motor driven pump-controlled asymmetric cylinders. A state-space model with input and output constraints is developed according to the principle of pump-controlled cylinder system and the practical requirements. The model predictive control is introduced to avoid the nonlinearity of valve switching and to improve the performance of constrained optimal control. The Kalman filter is combined to compensate the impacts of disturbance and modelling errors and to improve the robustness of the system. Simulation results of the strategy show that offset-free reference tracking is achieved, no over-limit of the input and no overshoot of the output are guaranteed, and model mismatch and disturbance are handled satisfactorily. Experimental results with the strategy show that the position has no overshoot with a relative tracking error of about 0.5% and the effects of disturbance and modelling error are small. Hence, the proposed method is applicable to the real pump-controlled systems, improves the control performance under input and output constraints, and allows for certain disturbance and modelling error.关键词：pump-controlled asymmetric cylinder;constraint;robustness;model predictive control;Kalman filter784|5|5更新时间：2025-07-09
- 摘要：The phenomenon of steam condensation within a horizontal rectangle channel with one-side cooling in multi-channel cylinder dryer is experimentally studied to investigate the characteristics of steam condensing in the multi-channel cylinder dryer, to improve the efficiency and to reduce the energy consumption of paper industry. Experiments are conducted via the visualization method under the quality of 0.2-0.8 and mass flux of 20-50 kg?m-2?s-1. Four flow patterns, including annular, wave, slug and plug flows, are observed. The slug flow, plug flow and wave flow are observed at low mass flux, the wave flow and annular flow are observed at high mass flux with a low steam quality, while the slug and plug flows are not found during the entire condensation process. It is found that the observed flow patterns agree well with Tandon's flow pattern map. The effects of quality and mass flux on condensing heat transfer are analyzed. The experimental results show that the effect of low mass flux(G<35 kg?m-2?s-1)on condensing heat transfer coefficient can be ignored, and the condensing heat transfer coefficient increases obviously with increasing quality and high mass flux. Four kinds of correlations are employed to predict the coefficients of condensing heat transfer, and the result reveals that Cavallini's correlation agrees with the experimental results relatively well.关键词：visualization;flow regime;condensation;heat transfer;multi-channel cylinder dryer708|5|3更新时间：2025-07-09
- 摘要：By employing the unified colored-noise approximation approach and the stochastic averaging method, the first-passage is analyzed for a class of nonlinear damping dynamical systems under colored noise excitation. A backward Kolmogorov(BK)equation for the conditional reliability function and a generalized Pontryagin(GP)equation for the conditional moment of the first-passage time are established. Under the regular boundary conditions and initial conditions for BK and GP equations, the conditional reliability function, probability density function and numerical solution of the first-passage time of the systems are obtained, and the effects of system parameters and external excitation noise on system reliability are discussed via numerical simulation. The results show that the system reliability can be improved by increasing system parameters, and the probability of the first-passage rises and the system reliability lowers with the increasing excitation intensity. Moreover, the influence of noise autocorrelation time on the system reliability is related to the system parameters. The system reliability rises if the noise autocorrelation time for a large system parameter increases, but the system reliability lowers if the noise autocorrelation time for a small system parameter increases.关键词：first-passage;colored noise excitation;dynamical system;nonlinear damping;reliability function648|5|0更新时间：2025-07-09
- 摘要：A restrictive calabash surface structure for the purpose of suppressing the emission of secondary electron and the effect of multipactor is proposed to improve the multipactor phenomenon in microwave devices. Simulation is performed to calculate secondary electron emission with the phenomenological probabilistic model, and to follow tracks of secondary electrons inside the groove with considering electrons multi-generation. Effects of the calabash surfaces on secondary electron yield(SEY)and secondary electron energy spectrum(SES)are simulated. Moreover, the SEY and the multipactor factor in different structures of the calabash surface are calculated. Simulation results show that increasing the half-width of upper calabash structure makes SEY have a trend of increase after first decrease, while the height of the upper calabash structure improves the multipactor factor linearly. In addition, when the half-width of the bottom calabash structure reaches its optimal value, the effects of the SEY suppression are 21.2% better than the effects of SEY of the rectangle structure surface, and the multipactor factor improves by 24.97%.关键词：restrictive surface;secondary electron;multipactor;numerical simulation642|6|3更新时间：2025-07-09
- 摘要：Modelling and multi-response optimization of direct contact membrane distillation for water desalination are studied to search for a balance between high water productivity and low energy consumption and to maximize water productivity and thermal efficiency simultaneously. Response surface methodology and desirability function approach are applied for modeling and multi-response optimization, in which the investigated objectives are water productivity and thermal efficiency. The effects of both operating parameters and configuration parameters of membrane module are investigated. These parameters include inlet temperatures of feed and permeate, flow velocity of feed, module packing density, and length-diameter ratio of module on the objectives. Models for predicting the objectives are developed and statistically validated by analysis of variance. It is found that both objectives are significantly influenced by the interaction effects of these variables. The different binary interaction effects of the variables on the objectives are illustrated. Multi-objective optimization is conducted using the desirability function approach. The optimal conditions are obtained as follows: 70 ℃ in feed inlet temperature, 40 ℃ in permeate inlet temperature, 60 m/min in flow velocity of feed, 50% in module packing density, and 20 in length-diameter ratio of module. Experiments under the optimal conditions obtain water productivity 1.697 kg?h-1 and thermal efficiency 88.2%. This study may provide reference for optimization and scale-up design of membrane distillation process.关键词：direct contact membrane distillation;desalination;water production;thermal efficiency;multi-response optimization710|5|0更新时间：2025-07-09
- 摘要：A design method based on water pinch analysis is presented to design water-using networks with single internal water main quickly and effectively. The water pinch analysis obtains the concentration of initial internal water main and provides water allocation rules flowing in and out internal water main based on directing water-using units to use fresh water or reused water. The internal water main is formed according to water pinch concentration values, then the water-using units are grouped and arranged at different positions in the water-using network. The final structure of the water network is determined through optimizing the water volume of the internal water main. The water pinch analysis provides an initial structure of a water-using network and reduces the scale and difficulty of mathematical optimization. The presented method is simpler and easier for use. The results obtained from two examples and the comparisons with simple water pinch analysis method and the water saving factor method show that the presented method saves fresh water consumption by 2.56% and 7.58%, respectively.关键词：internal water main;water pinch;water-using network685|5|0更新时间：2025-07-09
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