最新刊期
卷 46 ， 期 6 ， 2014
- 摘要：Abstract:The existing searchable encryption schemes can neither support semantic fuzzy keyword search nor resist threats from “dishonest-and-curious” data server. In order to solve these problems, a verifiable semantic fuzzy searchable encryption scheme based on hybrid cloud model was proposed. Semantic extension on keywords through WordNet was made and secure index through bloom filter was built. The index and query were dealt with by two rounds mapping of bloom filter so that the privacy of user was guaranteed. In hybrid cloud model, the computation overhead can be reduced at the user terminals. The private cloud server was responsible to build index and verify the results in order to ensure that all matched encrypted files are returned. The public cloud server implemented search operations on secure documents. The efficiency of the suggested scheme was tested through simulation on real data sets.关键词：searchableencryption;cloudcomputingsecurity;bloomfilter;hybridcloudmodel
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发布时间：2023-11-14 - 摘要：Abstract:Aiming at the problem that the traditional anti-virus structure cannot effectively solve malware threats on Windows OS on virtualization platform by using the benefits of virtualization, and traditional anti-virus softwares have to face their own security threats, an agentless online anti-virus technology of processes running on Windows VM based on KVM was proposed. By adding memory reading and writing functions in KVM kernel module and providing interfaces to register hooks in the kernel module of processes handling, the VM’s processes’ information could be resolved. After restoring process’s PE image in memory into disk file before running, the open source antivirus engine ClamAV would be called to scan virus. When results returned to the decision-making module, process handling module would deal with suspicious processes accordingly, and the current process could be scanned and killed without any agent. Analysis and test results showed that the technique could solve the traditional anti-virus frameworks’ resource consumption and security issues by taking advantage of virtualization’s benefits.关键词：KVM;virtualization security;agentless technique;process monitoring;PE image reduction;process killing
- 2535
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发布时间：2023-11-14 - 摘要：Abstract:The existing Android system does not allow customized application permission due to its coarse-grained and inflexible management mechanism. To solve this problem, DroidDefence, a fine-grained Android permission management system was proposed, which was extended on the base of the original Android framework. Users can dynamically allocate application permissions under different scenarios through a light-weight client deployed on mobile device. And safety reports would be released after user data collection and processing based on mobile cloud crowdsourcing. Experimental results showed that DroidDefence can enhance system security and protect user privacy with little system consumption.关键词：Androidsecurity;securitymechanism;permissioncontrol;privacyprotection;crowdsourcing;malware
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发布时间：2023-11-14 - 摘要：Abstract:In order to investigate feasibility and effectiveness of negative selection algorithm (NSA) in credit scoring, a new model named LR & RONSA Based model, which hybridizing Rset optimized negative selection algorithm (RONSA) with logistic regression, was proposed. Firstly, logistic regression selected the most relevant variables with the target variables into the model. Secondly, RONSA used the selected variables as the genes to detect “no-self”. Finally, with experiments on “German Credit set” and ROC curves, it was found that LR and RONSA Based model has better predict effect than the logistic regression model. It can be used as an ideal tool for credit risk prediction.关键词：creditscoring;logisticregression;artificialintelligence
- 2459
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发布时间：2023-11-14 - 摘要：Abstract:The current method of cloud storage data protection for user privacy is lack of the protection for keys. In order to solve this problem, a key management mechanism based on trusted module for cloud storage user was proposed. By introducing the trusted hardware module, a secure and efficient key backup and restore mechanism was established based on the basic principles of cryptography without a certificate to generate and store the user key information. Meanwhile, the efficiency of data protection was improved based on the theory of data segmentation. The implementation of key management based on trusted hardware module was described and detailed analysis focusing on security and efficiency was carried out. The experimental results showed that the mechanism can effectively protect the security of the users’ privacy data.关键词：cloudstorage;dataprivacy;trustedhardware;keymanagement
- 2470
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发布时间：2023-11-14 - 摘要：Abstract:In the wireless sensor network environment, the randomness, fuzziness，and unpredict-ability bring a lot of secure issues to network transactions. In order to treat this problem, by using cloud model theory, the trust model based on cluster structure was proposed. This trust evaluation approach can implement the conversion between qualitative and quantitative of trust attributes. The model simulated LEACH routing protocol, evaluating trust value of the nodes according to their own characters and can identify of selfish nodes accurately. The simulation results showed that the model can accurately and objectively evaluate the nodes, and the cloud trust model proposed here may provide a new promising method for research of trust evaluation in wireless sensor networks environment.关键词：wirelesssensornetwork;clusterstructure;clusterheads;trustmodel;cloudmodel
- 2228
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that the B2C electronic commerce logistics distribution optimization accuracy is not high, a new hybrid differential evolution and particle swarm optimization heuristic optimization algorithm based B2C e-commerce logistics distribution optimization was proposed. Firstly, the particle swarm population was used as auxiliary mutation operator to do the crossover operation with differential evolution algorithm population, resulting new generation that inherits the advantages of characteristics of parents, thus avoiding the single algorithm premature convergence and low convergence rate. Through simulation comparison with the other existing improved algorithm, the algorithm here can effectively escape from local minima, prevent premature convergence, and the convergence is fastest. The simulation showed the designed distribution scheme has the faster calculation speed and better convergence of the target value.关键词：hybriddifferentialparticleswarm;directionalvariation;logisticspathoptimization
- 2573
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发布时间：2023-11-14 - 摘要：Abstract:The embedment depth equations of a rigid retaining wall,which can meet different anti-overturning stability coefficients,was derived by using the unified solution of shear strength in the plane strain condition for the unsaturated soils.The effects of the unsaturated characteristics and the intermediate principal stress on the shear strength were also taken into consideration.Direct use of these equations can plot the influences of the intermediate principal stress,the matric suction,and the stability coefficient on the embedment depth of a rigid retaining wall. The closed-form solutions are an orderly set of new results and these solutions provide more choices and optimizations for the design of foundation pits with different types and features.The results showed that both the intermediate principal stress and the matric suction have obvious influences on the embedment depth of a retaining wall,i.e.,the embedment depth decreases remarkably with the increase of the intermediate principal stress or matric suction.In addition,different failure criteria have an obvious effect on the anti-overturning design of a retaining wall;the greater stability coefficient designed,the greater is the embedment depth,which is also related to the excavation depth of a foundation pit.Finally,the results provide a theoretical basis for the analysis and evaluation about the work performance and the safety reserve of the retaining wall of a foundation pit in the unsaturated soils.关键词：unsaturatedsoils;retainingwalloffoundationpit;anti-overturningstability;embedmentdepth;intermediateprincipalstress;matricsuction
- 2011
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- 5
发布时间：2023-11-14 - 摘要：Abstract:A new model referring to the relation of CSA and CSD was proposed,which was based on the physical mechanism for the origin of river heads.The feasibility of the model was verified by using two watersheds of Duilongqu basin of Lhasa River and Beishuiqu basin of Niyang River in Tibet to calculate the CSA and extract river networks.The comparison results of river networks derived from DEM with real ones indicated that the critical support discharge Qc are (0.002 8 ±0.001) m3/s in Duilongqu and (0.008 5±0.001) m3/s in Beishuiqu,respectively.The CSD can vary with hydro-climate conditions. It was higher in humid region and lower in arid region.Using this method, the optimal critical support discharge Qc of 0.008 5 m3/s in Beishuiqu basin (humid region) was greater than 0.002 8 m3/s for Duilongqu (semi-arid region).The suggested method provided a new application approach that could be used to determine CSD (Qc)in complex geographical regions,and the effect of hydro-climate change could be reflected.关键词：rivernetworkextraction;criticalsupportdischarge;hydro-climateconditions;riverhead
- 1986
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- 8
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发布时间：2023-11-14 - 摘要：Abstract:Aiming at the present shortcoming of strong subjectivity,weak conclusion guiding and not real-time analysis existing in dam safety evaluation,a dynamic dam safety evaluation was put forward,which took the part as object,and the characteristics times as limit.It adopted multi effect quantities to get membership of indicators,combined the information entropy theory and expert evaluating method to determine the weight of index,and got conclusions by clustering method.The method was programed and applied to Shiziping dam safety decision,the evolution process of the key parts along any time period was provided in this method,and the conclusion based on the past safe characters was much easier to use.According to the change of the monitoring data the index weight was adjusted. When the data leveled off,the weight was reduced,on the contrary,it was increased,which conformed to the actual operation.关键词：earth-rockfilldam;safetyevaluation;informationentropy;clusteranalysis
- 1830
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- 3
发布时间：2023-11-14 - 摘要：Abstract:To obtain a successful parameter calibration of conceptual hydrological model,hydrological characteristics of large and small runoff process were chosen for considering different characteristics of generation and concentration.A multi-objective cultural self-adaptive electromagnetism-like mechanism (MOCSEM) algorithm was proposed to solve parameter calibration problem.The MOCSEM was tested,firstly,and applied to multi-objective parameters calibration of Xinanjiang model.After achieving satisfactory performance on parameters calibration problems,the self-identifying parameters combination forecast method was implemented for trying to find a self-identifying parameter combination mode.The results showed that the proposed method can provide more precise forecast results than a single parameter scheme for hydrological forecasters.关键词：conceptualhydrologicalmodel;parametercalibration;multi-objective;parameterscombinationforecast
- 2540
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发布时间：2023-11-14 - 摘要：Abstract:The navigable condition is often worsen by the effect of unsteady flow caused by daily regulation of hydropower station.In order to reduce this kind of phenomenon,the control parameters need to be proposed which can give appropriate safety navigable waterways.According to the results obtained by one-dimensional mathematical model calculation and physical modelling experiment,the propagation characteristics of unsteady flow caused by daily regulation of Xiangjiaba hydropower station under different operating conditions in the dry season were illuminated.Its influences on water level amplitude,velocity,slope and other shipping hydro impact factors were analyzed.The self-propelled ship model test was used for giving the conditions of navigation in key leg upward.The results showed that the peaking and peaking amplitude variability of Xiangjiaba hydropower station should not be too large in a day.The water level downstream hub amplitude does not exceed the maximum hours of 1.5 m/h,and the maximum daily amplitude does not exceed 4.5 m/d, which will have minor impact on navigation of downstream.关键词：dailyregulation;unsteadyflow;mathematicalmodel;physicalmodel;hydraulicfactors;navigationcondition
- 2032
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- 5
发布时间：2023-11-14 -
Study on the Static and Dynamic Bearing Behaviors of Pelton Turbine Distributor and Hydropower House
摘要：Abstract:In order to study the concrete damage characteristic of pelton turbine distributor and its effects on the dynamic behaviors of the hydropower house,nonlinear static analysis of the distributor and powerhouse was carried out using concrete plastic-damage model by finite element method.Based on the concrete damage state,the natural vibration properties and the response to generating unit vibration were calculated subsequently.The results showed that though the concrete surrounding the distributor is poured after steel pipe carrying parts of the internal pressure alone,the concrete in some regions is still apt to damage.These regions include the top of the pipe,the inside waist of pipe and the branch acute angle region.Usually the damage originating from the top and waist of the pipe will extend to the concrete surface.Because of the concrete damage,the steel pipe and rebar take most of the internal pressure especially in the branching region,but the stresses of steel pipe and rebar are still in the allowable range due to the small diameter and large pipe shell thickness. Simultaneously the concrete damage leads to the reduction of local structural stiffness and the increase of uneven uplift and vibration response of unit pedestal. However the effect of damage is local and small,the static and dynamic bearing capacity of the whole structure can be maintained.关键词：hydropower station;impulse turbine;distributor;concrete damage;free vibration characteristic;generating unit vibration- 1920
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发布时间：2023-11-14 - 摘要：Abstract:In order to identify the location and extent of the damage for high flexible cantilever structure,the constrainted flexibility method for damage identification was proposed.The relationships between equivalent bending stiffness and the elements of the flexibility matrix or a first-order modal parameters were deduced,and high flexible cantilever structure was simplified as a curved concentrated mass model based on a first-order modal parameters.By analyzing morbid of flexibility method for damage identification based curved concentrated mass model and introducing constrainted conditions,low morbid equations were established and used to identify damage.The results of numerical example showed that constrainted flexibility method for damage identification has better identifications,and significantly improves the morbid of flexibility method.关键词：cantileverstructure;flexibilitymatrix;damageidentification;modalparameters
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发布时间：2023-11-14 - 摘要：Abstract:In order to get the quantitative description index of cracks and the relation between the index and strength parameter during the study of fractured rock mass, the intact coal was used to obtain the specimens of fractured rock mass through earlier loading,and the point cloud dates which represent the distribution of 3-D cracks could be got after CT scanning on fractured rock mass samples and model rebuilding.Lastly,the uniaxial compressive strength of fractured rock mass after scanning was tested and the relation between the index of quantitative description and strength parameter was analyzed.The results showed that the point cloud which was got after CT scanning could represent the distribution status of 3-D cracks in rock mass well.The 3-D cracks in rock mass,a kind of nature fractal,was self-similar,and it’s fractal dimension could be as a index of quantitative description for fracture rock mass.The relation between the quantitative description index (fractal dimension) and the uniaxial compression strength of fractured rock mass was a logarithmic relation in the statistical sense,and the trend of strength parameter decreased with the increase of the complexity of rock mass.关键词：fracturedrockmass;3-Dcracks;CTscanning;fractaldimension;strengthparameter
- 2709
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发布时间：2023-11-14 - 摘要：Abstract:Aimed at overcoming the disadvantages of the separation between geological information database and 3-D modeling system in hydraulic and hydro-power 3-D geological modeling software,the interactive design method,which combines 3-D geological database and 3-D modeling software,was proposed.And 3-D geological modeling platform,which is appropriate to hydraulic and hydro-power engineering,was developed on CATIA.By using the Microsoft SQL 8.0,3-D geological modeling database,which achieves the functions like data entry,data query,date delete,excel import and export etc,was established.3-D geological modeling platform was built through Visual Basic.net.This platform includes the basic modules like covering layer,geological layer,hydrological layer,and model analysis etc.When 3-D database is embedded into 3-D geological modeling platform, some functions including drill data importing,virtual drilling,and 3-D geological modeling section graphing can be realized.The design idea on the integration of 3-D geological modeling database and 3-D modeling platform comes true.关键词：3-Dgeologicalmodelingplatform;3-Dgeologicaldatabase;hydraulicandhydro-powerengineering
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发布时间：2023-11-14 - 摘要：Abstract:A special form of three-dimensional steel bracket was made by drawing the advantage of large span space grid structure,and its applicability in the supporting of high stressed soft rock roadway was researched.In combination with PanSan typical mine roadway engineering,the laboratory test under the effect of high pressure was carried out,and the stress and deformation laws of three-dimensional steel bracket was researched.Based on the support structure features and laboratory test results,the fully closed three-dimensional steel bracket bolting shotcrete structure on the roadway was designed.Finally,industrial test proved that the structure of three-dimensional steel bracket bolting shotcrete structure was reasonable.It could play the material properties and not only had a high bearing capacity but also had the yielding,which could be satisfied the support request of high stressed soft rock roadway.关键词：soft rock roadway;steel bracket;anchor-sprayed;model test;construction technology
- 1862
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- 2
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发布时间：2023-11-14 - 摘要：Abstract:For the internal threat of cloud, a privilege control framework named Virt-RSBAC was presented to enhance privacy protection for cloud users, and mitigate the policy conflict between the demand of security monitoring of cloud provider and users’ privacy. By adding privilege control and role-based resource isolation rules in the virtual machine monitor (VMM), it implemented the separation of administrative of privileged domain, simplified the management of cloud users, and created a mutually trusted secure virtual machine (SVM) to provide security services for cloud platform providers and users. Finally, a prototype of the Virt-RSBAC framework based Xen was realized. The experiments showed that the framework can prevent malicious administrator to get user privacy and other security functions work well, and its performance payload is restricted whining an acceptable range compare with the original system.
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发布时间：2023-11-14 - 摘要：Abstract:Threshold mismatch of energy detection (ED) under noise power uncertainty (NPU) model was investigated. A threshold optimization algorithm of ED (TO-ED) was proposed based on constant false alarm ratio (CFAR) criterion. Firstly, for optimizing the threshold of robust statistics approach (RSA) under the condition of CFAR, the unique existence of optimal modified factor was proved. Secondly, since the average false alarm probability of RSA is a monotonic function of modified factor, Newton dichotomy was applied to quick search of this optimal factor. Simulations showed that the performance of TO-ED is consistent with theoretical analysis and its robust detection is realized with a lower signal-to-noise ratio(SNR) comparing with RSA.关键词：energydetection(ED);noisepoweruncertainty(NPU);thresholdoptimization;constantfalsealarmratio(CFAR);robuststatisticsapproach(RSA)
- 1954
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- 2
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发布时间：2023-11-14 - 摘要：Abstract:A novel algorithm called double convergence factors FastICA (DCF-FastICA) was proposed to solve the problem that the FastICA algorithm is sensitive to the initial weights.Two FastICA algorithms with different step size factors were combined in this method,and the combination coefficient was adjusted using the gradient algorithm until the optimal separation matrix was obtained.Theoretical analysis and experimental simulation showed that the proposed algorithm can produce better separation result compared with the previous improved algorithms,the problem of initial weights sensitivity could be resolved with almost no loss of separation precision,the average separation speed is improved nearly 70% and the number of iterations reduced nearly 80% compared with the original FastICA algorithm.关键词：FastICA;blindsignalseparation;independentcomponentanalysis
- 1896
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- 2
发布时间：2023-11-14 - 摘要：Abstract:In OFDMA-based wireless cooperative multicast systems,it is impossible to guarantee successful transmission of every data due to instant deep fading. Hence, in order to solve the problem,resource optimization algorithms form frequency and power resource was exploited.A cooperative joint subcarrier and power allocation scheme that minimizes the probability of multicast transmission failure were proposed.Cooperative proportional (CP) subcarrier allocation strategy and iterative power (IP) allocation strategy were proposed to achieve tradeoff between throughput and fairness,and fully utilize the limited power,respectively.Simulation results showed that system performance of the schemes with cooperation is significantly enhanced compared with that without cooperation and the scheme with IP remarkably outperform that without IP.Therefore,the schemes can overcome the effect of instant deep fading,and guarantee the reliable multicast transmission.关键词：multicast;cooperativediversity;OFDMA;resourceoptimization
- 1987
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- 1
发布时间：2023-11-14 -
Two-phaseDrivenTimeGratingDisplacementSensorAngleMeasuringSystem Error ModelingandAnalysis
摘要：Abstract:In order to further expand the scope of applications of the time grating displacement sensor, a novel angle measuring system in view of a two-phase driving type time grating displacement sensor was proposed based on the traditional field type time grating displacement sensor. Position signals from grating sensor with low resolution, low-cost and time signals based on the direct digital frequency synthesizer technique were used to form one novel time traveling wave in the angle measuring system. Under the support of traditional technology from the traditional time grating displacement sensor, the time traveling wave was used to construct a new type angle measuring system. The error model of the angle measuring system was studied and the results showed that the main errors are made up of non-orthogonal grating signals, non-equal amplitude of grating signals and residual DC level. The experimental results showed that the measuring errors of time grating displacement sensor are reduced effectively, and the measuring accuracy of the angle measuring system is improved greatly and the measuring accuracy reaches ±3.2″ through the error model.关键词：timegratingdisplacementsensor;travelingwave;grating;errormodel- 1844
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发布时间：2023-11-14 - 摘要：Abstract:The co-simulation of the electromagnetic-field-and-circuits hybrid system was studied by employing the extended finite-difference time-domain (FDTD) algorithm. The extended FDTD’s principle and its iterative formula reflecting the embedment of lumped devices in the FDTD cells were introduced. As a sample,a microstrip double dipole antenna loaded with a lumped matching circuit at its input port, which was an antenna-and-circuit hybrid system, was simulated by the extended FDTD. In the simulation,S11 of this antenna was obtained by using a technique,which directly inserted the microstrip feeding line into a complex frequency shifted perfectly matched layer(CFS-PML) and executed the FDTD program twice.The loaded antenna was fabricated and measured.Results showed that the measurement agrees well with the simulation,and for the antenna,the lumped matching circuit slightly affects its gain and radiation patterns,but varies its resonant frequency and significantly changed its S11 curve.关键词：extendedFDTD;field-circuitco-simulation;antenna;lumpedmatchingcircuit
- 1755
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发布时间：2023-11-14 - 摘要：Abstract:Due to the peculiarity of mechanical behavior for titanium alloy under impact loading,its thermo viscoplasticity under high strain rate and the quantitative relation of temperature stress reduction and thermo viscoplasticity dissipation cannot be described by the classical Johnson-Cook model perfectly.In order to solve this problem,a modified Johnson-Cook model which expressed the functional relationship of temperature stress reduction about strain rate and thermo viscoplasticity dissipation was proposed,and all the parameters could be easily determined by the local search optimization algorithm taking least squares method as the object function.Finally,by the increment equations of the modified Johnson-Cook model derived under conditions of strain control,the dynamic true stress-strain curves for Ti-6Al-4V titanium alloy under different strain rates and temperatures could be drawn.The results of model analysis were verified by the results of experiments from reference. The modified Johnson-Cook model and the fast simulation method studied have reference value for other titanium materials.关键词：titaniumalloy;thermoviscoplasticity;modifiedJohnson-Cookmodel;localsearch;incrementequation
- 2658
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- 6
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发布时间：2023-11-14 - 摘要：Abstract:A series of parametric study results of fibre metal laminates subjected to low velocity impact using the validated finite element models were firstly presented.Effects of target size,target thickness,projectile size and shape as well as projectile striking angle on the peak load and deflection at the peak load were included in this research.Based on these parametric study results and Timoshenko’s theory,empirical formulas for circular or square plates impacted perpendicularly at the centre by hemi-spherical projectile were developed.The calculated results from the empirical formulas were compared with numerical simulations.Good correlation was obtained in terms of load-displacement traces up to the peak load, the peak load and the maximum deflection.The developed formulas could be used to assist the design of fibre metal laminates subjected to low velocity impact.关键词：fibremetallaminate;empiricalformula;ABAQUS;lowvelocityimpact
- 1856
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- 10
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发布时间：2023-11-14 - 摘要：Abstract:The short-term tensile creep behaviors of EVA cable highly filled with powder under different temperature,material ratio and stress levels were studied through tensile creep test.Burgers model was applied to simulate the creep behaviors of the composites.The results showed that the instantaneous elastic modulus Em,retardant elastic modulus Ek and ηk viscosity were obvious correlative to the temperature and stress levels. When the weight ratio of metal hydroxide and EVA was 3∶2,a synergistic effect between Al(OH)3and Mg(OH)2 was confirmed by improving the ability of the composites deformation.In the short term,the predicted results from Burgers model and Findley power law were in good agreement with the experimental results.In addition,Burgers model clearly showed a better prediction than the one using Findley power law,while the Findley power law was of the good predicting ability over large time scale.The present study can be practically significant to the optimizing formula of special halogen-free flame retardant EVA cable compound,as well as the further study on the short-term tensile creep behaviors of EVA cable highly filled with powder.关键词：EVA cable composites;powder highly filled;creep;Burgers model;Findley power law
- 1511
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发布时间：2023-11-14 - 摘要：Abstract:In order to study the desulfurization performance of activated carbon fibers (ACF) with N-surface modified, surface modified ACF with nitrogen-containing group were prepared by heat-treatment of ACF with urea. Samples were characterized by SEM, XPS, and TG, and the desulfurization activities were tested. The results showed that the sample prepared under the heat treatment temperature of 750 ℃ and the urea concentration of 2.4 mol/L has the best desulfurization activity. The number of nitrogen surface functional groups of ACF were increased by the impregnation of urea and treatment under high temperature, especially pyridine nitrogen increased nearly five times.The ACF modified by nitrogen-functional groups has good desulfurization activity.关键词：flue gas desulfurization;activated carbon fiber;nitrogen-containing functional groups;urea
- 2035
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the servo accuracy of hydraulic quadruped robot electro-hydraulic servo actuators during operation,the equivalent model of electro-hydraulic servo actuators was derived and the load characteristic was analyzed,the compound control strategy including flow compensation and minimal control synthesis was proposed,and the principle of compound control strategy was given.The effect of the external disturbance force and inertia loads on the performance of actuator was inhibited by the flow compensation and the proportion closed-loop,respectively,the accuracy was further improved by the minimal control synthesis controller.The correctness of the co-simulation of MATLAB & AMESim model was verified by experiment.On the condition of inertia load variation and random interference force，the electro-hydraulic position servo experiment was simulated in co-simulation environment,and the simulation results showed that the parameters variation of actuator was inhibited effectively by the compound control strategy, the maximum amplitude attenuation and phase lag was less than 10% and 10°,respectively,and the efficiency of the proposed control strategy was verified.关键词：hydraulicquadrupedrobot;electro-hydraulicpositionservo;minimalcontrolsynthesis;flowcompensation;semi-physicalsimulation
- 2393
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- 6
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发布时间：2023-11-14 - 摘要：Abstract:For clarifying the effect of intermittent multi-body contact state on kiln shell stress and mechanical strength,different shell thicknesses were selected as sample points by the design of experiment method,and the shell stresses and fatigue life were obtained corresponding with the sample points by finite element analysis,then kriging surrogate model was constructed.Taking the fatigue life of support segments,transition segments,and end and middle segments as the optimal goal,and considering shell thicknesses,cross section deformations,and flexibilities as constraints,the improved multi-objective genetic algorithm (MOGA Ⅱ) was applied to conduct a comprehensive search for the optimal results of surrogate model in a given design space,and the optimal shell thicknesses were obtained.The results showed that the minimum fatigue life enhances from 48.4 years to 89.3 years,and the shell lives tend to be equal,even,and the same at support segments,transitional segments,and middle segments,respectively.关键词：shell;intermittentmulti-bodycontact;surrogatemodel;anti-fatigueoptimization
- 1668
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发布时间：2023-11-14 - 摘要：Abstract:The swing problems were studied after finishing the task of capturing the target object which aiming at the space tether-net system, and an in-plane swing damping method was proposed by retrieving tether at the turning points and deploying tether at the equilibrium points. The damping mechanism was explained theoretically and the influence of the changed quantity and rate of tether on the effect of swing damping was researched. The experimental system of swing damping under constant gravity was set up, and the result of ground experiment and simulation showed that the method was very effective in swing damping. The condition of implying the above method to the space tethered system was that the tether should be deployed at the equilibrium points which satisfied the condition of θ•>0 through the orbital dynamics. Lastly, the simulation of swing damping to space tether system was developed, which showed that the method achieved good results.关键词：spacetether-netsystem;swingdamping;dampingmechanism;orbitaldynamics
- 2434
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发布时间：2023-11-14 - 摘要：Abstract:Mechanical seals is operated by a thin fluid film to separate the pair of seal faces for lubricating and sealing,so the film thickness needs to be measured. Because the current technique is not suit for industry,a method for measurement of film thickness of mechanical seals based on acoustic emission technique was presented.Through the direction of direct measurement,a detection model based on acoustic emission signal was built.First,the signal was processed by empirical mode decomposition,and kernel principal component analysis was used to optimize data features.Then,a cascaded decision model based on artificial neural network was presented to estimate the film thickness.The model has better recognition rate than a single neural network, and has a wide industrial prospect.关键词：mechanicalseals;measurementoffilmthickness;dimensionreduction;cascadeddecision
- 1767
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发布时间：2023-11-14
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