最新刊期
卷 43 ， 期 4 ， 2011
- 摘要：Abstract:To investigate the effect and feasibility of different treatment method in urban flood inundation simulation, four methods of solid wall for building representation, two dimensions topography building representation, local friction based representation of building, and two dimensions shallow water equations with plot ratio were summarized. Then, a simulated urban complex construction example was established. Finally, the results of the four methods were comparied. The results indicated that the effect of solid wall for building representation method is best, but it requires complicated data processing and high computational cost. The reasonable effect could be obtained by the method of two dimensions shallow water equations with plot ratio with simple data processing and low computational cost.关键词：hydrodynamics;finite volume method;numerical simulation;urban flood;shallow water equations
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发布时间：2024-04-19 - 摘要：Abstract:An uncertain positive correlation has been found between uniaxial compressive strength and elastic modulus of rocks. In order to make this kind of uncertainty unambiguous and let rocks’elastic modulus, which is more difficultly achieved,could be estimated with new correlations,based on the research of the differences between the texture and structure of rock samples, testing results derived from over 300 sedimentary rock samples were statistically analyzed.The results showed that the correlative degree between these two mechanical parameters was observably increased with the increase of the particular degree of the structural and textural classification.Hence,while studying the correlations between rocks’mechanical parameters,rock materials shouldn’t be considered as homogeneous materials any more.Accordingly, ten correlations between these two parameters were set up for different textural and structural classifications of sedimentary rock samples. Compared with similar research results in the past, the setting-up foundations of these correlation expressions were more rational.Furthermore,these expressions might be used to estimate the elastic modulus of almost all sedimentary rocks with the uniaxial compressive strength while lacking the essential experimental conditions or during preliminary application.关键词：sedimentary rock;uniaxial compressive strength;elastic modulus;correlation
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发布时间：2024-04-19 - 摘要：Abstract:Geomechanical model tests were performed on wet sand in a glass-walled fault rest box to investigate the relationship between the propagation of fault rupture and the shapes, and the locations of failure surface. Three CCD cameras were used to capture the process of the surface rupture development and to analyze the displacement field by using the digital speckle correlation method. Based on the experiment, it was observed that when the thrust fault moved upward, the sediment layers formed a shear zone. The smaller the angle of faults, the wider of shear zone was formed in the sediment layer. The vertical displacement and the movement velocity of the fault are greater, the deformation of sediment layer is wider, and the deformation of the soil layer is stronger. When the vertical displacement of the fault exceeds 40% of the soil thickness, the deformed soil will form tension crack at the surface of the sediment. For a fixed sediment thickness with a fixed vertical displacement, the width of the deformation bands decreased with the increased fault movement velocity. However, the degree of deformation and failure will become more intense under a faster fault movement. Experimental results of this study on fault angle, fault movement velocity and sediment thickness is an important issue in further studies on ground deformation and failure characteristics of a thrust fault.关键词：reverse faults;geomechanical model test;digital speckle correlation method;propagation of fault rupture;surface rupture characteristic
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发布时间：2024-04-19 - 摘要：Abstract:On the basis of slope stability due to gravity based on strength reduction FEM, temperature driving strength reduction FEM considering deformation parameters modification was proposed for the stability analysis of 3D reservoir intake tower-base complex structure, which was more efficient than traditional strength reduction FEM. Temperature driving strength reduction FEM considering and not considering deformation parameters modification was applied to analyze the reservoir intake tower-base complex structure under the given conditions, respectively, and a comparison with the method of overloading hydraulic pressure was carried out,By getting the curves of currentwise displacement vs. time of nodes in different place, tracing the variation of equivalent plastic strain of the whole structure and the convergence or disvergence of the computation, the factor of safety and the possible factor that may lead the collapse of the structure were gained. The analysis results showed that the calculated results gained from temperature driving strength reduction FEM considering deformation parameters modification was more reasonable, and closed to that from overloading hydraulic pressure method.关键词：temperature driving parameters reduction FEM;φ~ν inequation;limit state;factor of safety;factor of collapse
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发布时间：2024-04-19 - 摘要：Abstract:Pressure runaway analysis of rock salt storage is very important to the operation safety control under extreme conditions.Based on the one-dimensional steady flow theory, the intra-cavity pressure time-varying models were deduced by introducing time variable without the pipeline induced fiction and with fiction in both cases.The analytical solutions of pressure change under the out-of-control blowout condition were obtained using the variable separation method.The calculations were then compared to the experimental data.The results showed that the time travel curve of pressure drop submits an exponential distribution,and the attenuation coefficient is the function of the pipe length,diameter, fiction coefficient, as well as the cavern capacity and the initial state parameters of intra-cavity gas. Further study of the stability of rock salt storage may be based on the above theoretical conclusions.关键词：rock salt storage;pressure drop;steady flow;analytical solution;time travel curve
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发布时间：2024-04-19 - 摘要：Abstract:In the construction of high concrete dam, different concrete pouring placement has different reliability of construction progress and quality, different difficulty degree of construction organizations and different construction cost. In order to determine the optimal concrete pouring placement scheme, ensure the construction progress and quality, and have the best technical and economic comprehensive indicator, by using the parameters obtained by computer simulation, the evaluation index system for the optimization of high concrete dam construction program was set up. Then, by using fuzzy multiple attribute decision making theory, the index values were quantified and the weights were determined. Finally, two high concrete dams’alternative concrete pouring placement options were ranked which can prove the proposed method is effective and easy to operate.关键词：high concrete dam;fuzzy multiple attribute decision;construction scheme optimal selection
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发布时间：2024-04-19 - 摘要：Abstract:In order to investigate the mechanical behavior of multistory masonry structure with structure columns and ring beams under the different vertical load, 1∶4 reduced-scale model of six-storey masonry was tested, and the test parameters and fracture shape of the model under different vertical compression were obtained. The nonlinear finite element analysis results showed good agreement with the experimental results. The effects of structural height, structural column’s space, elasticity modulus and shear strength on the strength and deformation of multi-storey masonry were studied with the nonlinear finite element method, and the formulas of stress of composite wall with structure columns under the different vertical load and the recommended value of vertical drag coefficient were proposed.关键词：masonry structure;cracking;different vertical compression;model testing;nonlinear finite element analysis
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发布时间：2024-04-19 - 摘要：Abstract:In order to study the thermal, shrinkage deformation and crack mechanism of concrete, its temperature, moisture and stress distribution was calculated based on the theory of heat, mass transfer and hydration as well as finite element method. The finite element method was used in space domain, two-point time difference scheme was used in time domain, and the finite element program was coded. With the application of this program, the process of concrete structure poured in different situations was simulated. The result showed that drying shrinkage is a major cause of the deterioration of concrete structures, but proper control measures can decrease the stress of concrete, crack can be prevented.关键词：relative humidity;drying shrinkage;crack prevention
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发布时间：2024-04-19 - 摘要：Abstract:In order to study the effects of gravel contents, confining pressures and stress level on creep properties and laws of clay mixed with gravel, drained triaxial creep tests under different confining pressures and stress level were carried out for clay-gravel mixtures with different mixture proportions. The gravel contents were 30%, 40%, 50% and 70%, respectively. The confining pressures were loaded from 50 to 200 kPa and the stress levels were varied from 0.21 to 1.04. Test results indicated that instantaneous and creep deformation would take place evidently for clay mixed with gravel after being loaded. The creep strain would prone to a stabilizing value finally. The creep strain of clay mixed with gravel decreases with the increase of gravel contents, and increases with the increase of confining pressures and stress level. An empirical creep function including three parameters was presented to describe the stress level-axial strain-time behavior of clay mixed with gravel. The axial strain-time and stress level-axial strain behavior can be denoted with hyperbolic functions. Meanings of parameters in this model were analyzed and the values of parameters for rockfill were determined.关键词：clay;gravel;creep;hyperbolic functions
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发布时间：2024-04-19 - 摘要：Abstract:The uniaxial seven stress levels cyclic loading and unloading test for salt rock and marble were carried out on MTS815 Flex Test GT rock mechanics test system, and the damage unloading modulus were discussed. The loading test wave for low cyclic loading test was sine wave，and its frequency was 1.0 Hz. The maximum of cyclic stress was less than the value of the average intensity of compression, and the cyclic number of every level cyclic stress was 30 cycles. The test showed that the hysteresis loop of the curve of strain and stress was the ribbon for salt rock and tine lobation for marble stone. The salt rock had larger irreversible deformation at reloading and unloading position where corresponding elastic deformation response was slow, but the results for the marble stone were contrary. Because the unloading modulus for salt rock was influenced by test method, the changing tendency of unloading modulus for salt rock during the two test methods was reverse, while the results for marble stone were consistent during the two test methods. The effect on the increment of irreversible deformation for salt rock was more prominent for the condition of the loading stress amplitude than that of the cyclic numbers. The damage variable test results revealed that it was more authentic to describe the damage property through the damage elastic modulus which was tested by the low cyclic loading test method for rock with marked visco-plastic deformation.关键词：damage variable;unloading modulus;visco-plastic deformation;salt rock
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发布时间：2024-04-19 - 摘要：Abstract:The change of the bank slope accumulations’seepage and its stability is a dynamic process during the period of rising or falling of reservoir water level. The combination of the FEM method and equilibrium analysis was applied to analyze the action mechanism and laws of the water level’s rising and falling speed effect on accumulations’seepage and stability. The analysis results showed that the water level’s rising and falling speed can influence the congeries’s transient seepage obviously, and faster rising speed of water level is favorable to the accumulations’stability. But the faster falling speed is unfavorable, and the stability coefficient will reduce by 15%~20% with the falling speed increased from 0.5 to 5 m/d, and the most dangerous water levels are commonly located at one-third to one-fifth of the congeries’s height up the accumulations’ bottom.关键词：rising or falling speed of reservoir water level;seepage;stability;accumulations
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发布时间：2024-04-19 - 摘要：Abstract:In order to study the creep characteristics and the creep parameter change law of Zhangzhou soft clay, a direct shear creep test with different consolidation pressure was carried out, and Chen method was used to process the creep test data. The test results showed that the creep deformation of Zhangzhou soft clay was nonlinear that the stress level was higher, the nonlinear characteristic was more remarkable. The modulus of shearing Gmaximum value and stable value increased along with the increase of consolidation pressure under the same shearing stress, while it increased along with the decrease of shearing stress under the same consolidation pressure. The relation between instantaneous shear modulus G0and the long term shear modulusG∞ could be determined withG0=at-b+G∞. Because the microscopic structure was damaged gradually along with the increase of shearing stress, the viscosity coefficient increased along with the shearing stress and achieved a peak value, and a bigger consolidation pressure made the peak value more obvious. Zhangzhou soft clay’sC∞=6.71 kPa,φ∞=9.66°, Shear modulus coefficientK=(0.424~0.56), long-term strength and instantaneous strength ratio C∞/C =86.3%，φ∞/φ=72.4%.关键词：creep;creep parameters;shear modulus;viscosity coefficient;long-term strength
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发布时间：2024-04-19 - 摘要：Abstract:In order to improve the limitation and lacuna of the traditional damage constitutive models for concrete,by using Hsieh-Ting-Chen four-parameter yield function,which could reflect the different strength characteristics of concrete in tension and compression,a new elasto-plasticity damage constitutive models for concrete was proposed based on the energy dissipation principle.Moreover,numerical test for concrete stress-strain relation under uniaxial tension and compression was given.Compared with other damage constitutive models, the proposed model contained only one unknown parameter and the other parameters could be found in Hsieh-Ting-Chen four-parameter yield function.And the same damage evolution law,which is used for tension and compression,was good for determining stress-strain curves and damage characteristic in complex stress state.关键词：concrete;plasticity;constitutive models;energy dissipation;stress-strain curves
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发布时间：2024-04-19 - 摘要：Abstract:A Partition-Oriented Hierarchical Control and Data Flow Graph (PO-HCDFG) method was proposed to study the hardware/software (HW/SW) partition with the goal of reducing energy consumption under the constraints of time and cost in the functional model of embedded software descript by C language. Firstly, the formal description of PO-HCDFG was made. Then, the transformation method from C program to PO-HCDFG was deeply analyzed, including the configuration of node levels, data dependency analysis, setup of partitioned objects, and rules of granularity conversion. The experimental results showed that the PO-HCDFG modeling method is effective to HW/SW partition.关键词：hardware/software partitioning;control and data flow graph;granularity conversion;energy consumption optimization
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发布时间：2024-04-19 - 摘要：Abstract:A new method for automatic image registration was proposed, which included the scale space projection and feature matching. Based on scale-invariance of Harris-Laplace the scale space projection applied Harris-Laplace detector to extract image feature, then, a feature space on the projection information in the direction of feature main orientation was constructed, making feature space rotation-invariant and resolution-invariant.The feature matching adopted feature space k-d tree distance matching to combine with RANSAC, which implemented feature matching effectively and satisfactorily.The experiments and comparison analyses showed that this method can perform automatic image registration accurately in the different resolutions and rotations.关键词：image registration;Harris;Laplace;scale-invariant
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发布时间：2024-04-19 - 摘要：Abstract:The issue of detecting the status of video scenes was studied. First, Gaussian pyramid algorithm was employed to preprocess input frames. By comparing three consecutive inter-frame difference methods, the method that calculated the inter-frame difference on the gray frame images was adopted. According to the spatial distribution of the difference information as well as the morphological features of high intensity points, a new algorithm named Ratio of Erosion and Dilation per Point (REDP) was proposed to detect status change under different videos, which were captured in different scenes, luminance and weather conditions. The experimental results confirmed the effectiveness of indicating whether there are motions in the video. When the proposed approach was applied to the inter-frames, the detection capability of the algorithm can become more robust under an appropriate frame interval.关键词：intelligent vision;motion analysis;detection status of scenes;ratio of erosion and dilation per point
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发布时间：2024-04-19 - 摘要：Abstract:In order to increase the intelligence of the family service robot, a human action recognition method was put forward. First, the scheme of Motion History Image was used to adaptively update the background model. Then, YCbCr images combined with gray images were used to segment the images to decrease the shadow. At last, space-time interest points based on high entropy changes were brought forward to recognize the human action. Experiments showed that the background model can obtain the family environment background satisfactorily. And the recognition rate of the action recognition scheme combined with the environmental information could reach 95%.关键词：space-time interest points;background modeling;human action recognition;family service
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发布时间：2024-04-19 - 摘要：Abstract:In order to overcome the problems that the existing group proxy signature schemes do not have strong unforgeability and can not resist collusion attack by proxy themselves, a group proxy signature scheme of resisting collusion attack based on key matrix was proposed. Based on CDH problem and bilinear pairings，the traditional secret sharing scheme was improved by using rank of matrix，and its correctness, security and efficiency were analyzed. The scheme enhances intrusion-tolerance of system, has strong unforgeability and non-repudiation, and can resist collusion attack. It is a forward-secure group proxy signature scheme.关键词：proxy signature;key matrix;CDHP;bilinear transformation
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发布时间：2024-04-19 - 摘要：Abstract:In order to solve the problem that emerging and encrypted P2P protocols cannot be classified by traditional methods, a new efficient P2P identification algorithm based on the flow statistical characteristics was proposed. The concept of network protocol feature vector was defined at first, and then the feature subclass was selected using the neighbor distance and genetic algorithm. Due to the role of different attributes, the concept of network protocol feature weighting was proposed and calculated by particle swarm optimization. In order to improve the identification rate, the corresponding feature space was established respectively for TCP and UDP protocols. Experimental results showed that this method could effectively select the subclass from multiple attributes that could most reflect the difference among P2P protocols and also between P2P and non-P2P protocols. The identification rate was improved by feature weighting calculated by particle swarm optimization. In this algorithm, the identification rate of popular P2P protocols reached to 96%.关键词：Network Protocols;feature weighting;Genetic algorithm;particle swarm optimization;KNN
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发布时间：2024-04-19 - 摘要：Abstract:Due to resource constraint and topology dynamism of wireless networks, P2P systems designed for wired networks may not be applicable to wireless networks. Based on semi-direct product of two groups in the algebra group theory, a new structured P2P system, which was the cayley graph with constant degrees, was presented. By using the Cayley-4DHT, different nodes were partitioned into corresponding groups based on nodes’ identifiers, thus, neighbor nodes in the overlay networks were also neighbors in physical networks. Furthermore, by using cross-layer technology of wireless networks in the routing algorithm, the broadcast character of wireless networks was utilized for searching resources in P2P systems. Theory analysis and simulation results showed that the proposed Cayley-4DHT can achieve optimal performance of searching resources in wireless mesh networks.关键词：wireless Mesh networks;cayley graph;peer-to-peer;cross-layer
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发布时间：2024-04-19 - 摘要：Abstract:An efficient interval Newton algorithm for univariate polynomial equation was proposed.This algorithm reduced greatly the number of iterations and computations based on Hansen’s method for univariate polynomial equation. The algorithm was implemented as a Maple program.Compared with the existing algorithm, this algorithm was dramatically fast in some cases.A large number of polynomials generated randomly by Maple were tested and the performance was reported.关键词：interval arithmetic;Newton iteration;root;univariate polynomial equation;Maple procedure
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发布时间：2024-04-19 - 摘要：Abstract:In order to produce a code with high quality and high reliability, a static pointer dereference checking method was presented, and the definition of the finite-state machine for pointer-state transition was given. The point-to information was gotten and the mapping relationship between pointer and memory unit was built through semantic analysis of source codes to judge whether it was legal to use the pointer according to the pointer-state in the finite-state machine. This method not only recorded the scope and pointer sets of the variable, but also analyzed point-to including the definite and the possible. And the method of delayed writing point-to to partial control blocks was applied to increase the efficiency of pointer dereference analysis and to detect the problem of the bad deallocation. Results of experimentation showed that this method can detect invalid pointer dereference and bad deallocation effectively.关键词：finite-state machine;pointer dereference;pointer state;delayed writing;bad deallocation
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发布时间：2024-04-19 - 摘要：Abstract:Signal waveforms of low frequency vibration of external cavity reflective surface were demodulated from self-mixing interference signals that external cavity length was modulated by a high frequency signal. In order to realize high frequency modulation of external cavity length against the low frequency vibration, a scheme of laser source sinusoidal vibration was proposed, in which a laser diode module was mounted on an electromagnetic vibrator with the length and diameter of 23 mm and 13 mm, respectively. The vibrator excited by a sinusoidal signal drives laser source vibration which amplitude and frequency was about a quarter wavelength and 7 kHz respectively. Using Fourier transform and phase unwrapped means, the low frequency vibration signal waveforms were demodulated from the self-mixing interference signals by digital signal process. The amplitude of the smallest waveform ably resolved was about 0.02 wavelengths. Light density or polarization direction of the laser source unchanged with modulation signal, which was superior to a phase modulator plugged in external cavity. From experimental measurement, it was sure that laser source of sinusoidal vibration can realize modulation of external cavity in self-mixing interference.关键词：vibration analysis;laser diode;self-mixing interferometer;external cavity resonators;modulation;Doppler effect;light sources
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发布时间：2024-04-19 - 摘要：Abstract:In order to measure aspherical surfaces more accurately, the influence of test device on measurement error was analyzed. Instead of ronchi grating, sinusoidal grating was used to test aspherical mirrors based on the Ronchi method.By synchronous phase detection technology and geometrical theory, shape deviation gradients of all tested points could be obtained. Then the surface of the tested mirror was reconstructed after restoring shape deviations using area wave-front reconstruction method.The influence of combination fringes, asphericity and grating contrast on reconstructed tested surface were presented.The numerical results showed that both the combination fringes and grating contrast affect the testing accuracy of aspherical surface, and the error of reconstruction increases with asphericity.The results may provide an affective and reliable basis for Ronchi test device.关键词：optical measurement;error analysis;Ronchi test;aspherical mirrors;synchronous phase detection technology
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发布时间：2024-04-19 - 摘要：Abstract:In order to supply the downlink receiver design of practical LTE system with effective prior information, downlink 4×2 high order MIMO antennas configuration was considered. Firstly, the received signal model of downlink hybrid MIMO transmission schemes was presented in LTE systems, and then Minimum Mean Square Error(MMSE) equalizer and Maximal Ratio Combination(MRC) equalizer were designed to suppress the hybrid interferences, respectively. Furthermore, for improving system simulation efficiency, a modified formula of Signal to Interference plus Noise Ratio(SINR) based on modifying factor was deduced from the random perturbation assumption of channel response matrix. Finally, the hybrid MIMO transmission schemes were considered in downlink LTE system simulations, and throughput curves of target user with different scheme were drawn. The results showed that MMSE equalizer performs better than MRC equalizer, and has important reference value for analyzing actual LTE system performance.关键词：communication transmission technique;LTE;MIMO
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发布时间：2024-04-19 - 摘要：Abstract:Catalysts with the loading of cerium oxide on activated carbon prepared by impregnation were used for the selective catalytic reduction (SCR) of NO with C3H6 by temperature programmed reaction (TPR). The different loading of cerium oxides and calcination temperature was investigated, respectively. The catalysts were characterized by N2-specific surface area measurement (BET), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscope (SEM). The results indicated that cerium oxide supported on activated carbon is highly dispersed. The specific surface area of activated carbon decreases with the increase of the loading of cerium oxide, but the NO conversion increases with the increase of the loading of cerium oxide. Ce(0.07)/AC-400 can keep the NO conversion above 70% between 270 ℃ to 330 ℃. It is benefit to NO reduction by getting a better balance between the loading amount and dispersion of cerium oxides on AC. The calcination temperature is important to the conversion of precursor, but the higher temperature may destroy the structure of AC. It was indicated that the catalyst which is calcined at 400 ℃ can achieve wider temperature window.
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发布时间：2024-04-19 - 摘要：Abstract:During the process of oxidizing cyclohexene to produce 1,2-epoxycyclohexane by hydrogen peroxide, many byproducts are generated，including cyclohexanol, cyclohexanone and etc. In oder to obain high purity 1,2-epoxycyclohexane, the byproducts must be removed through rectification. Refining 1,2-epoxycyclohexane through rectification needs the vapor-liquid equilibrium (VLE) data of the relative system, so the VLE data of 1,2-epoxycyclohexane-cyclohexanol system were studied at 101.33 kPa by an improved EC-2 vapor-liquid equilibrium still, and then thermodynamic consistency of the data was tested by Herrington’s method.Very good result was obtained.The VLE data were correlated by Wilson and NRTL equation, using the error sum squares of vapor phase composition as target function.Variations between values from theoretical calculation and experimental data are very minor, which indicatesing that the experiment data are suitable for the engineering design.关键词：vapor-liquid equilibrium;1,2-epoxycyclohexane;cyclohexanol;Wilson equation;NRTL equation
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发布时间：2024-04-19 - 摘要：Abstract:In order to find out the relationship between electricity generation and organics degradation in anaerobic fluidized bed microbial fuel cell, the model of organics degradation based on mass balance and biomass growth was developed. The model of electricity generation based on inflow, external resistance and substrate concentration of influence was also developed. The parameters of the two models were estimated and validated using experimental data obtained in an anaerobic fluidized bed microbial fuel cell used to treat high-strength organic wastewater. The model of organics degradation is q=0.607S/398.82+S and the model of electricity generation is U=96485S/8·Q·(6×10－6S－0.0133)·Rex.关键词：anaerobic fluidized bed;microbial fuel cell;electricity generation;organics;degradation
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发布时间：2024-04-19 - 摘要：Abstract:A novel method was established to separate and quantify simultaneously 11 acidic compounds in traditional Chinese medicine of Conyza blinii levl. and Artemisia annua L. using capillary electrophoresis (CE). Optimized apparatus conditions were given. A fused-silica capillary 50 cm (40 cm to detector)×75 μm i.d. was used.Working voltage of +15 kV was applied at 25 ℃. The buffer(pH=11.42) containing 35.7 mmol phosphate sodium, 2.86×10-5mol/L fluorescein sodium (respondence reagent), and small amount of methanol was used. The hydrodynamic injection of a sample (0.5 psi(3.45 kPa)) during 5 sec was used. Indirect laser induced fluorescence(LIF) detection was applied by LIF detector at wavelength of 488 nm(excitation), 520 nm (detection).The method had a wide linear range, low relative standard deviation, high precision and perfect reproducibility. Real samples assay result was achieved perfectly in this condition.关键词：capillary electrophoresis(CE);indirect laser induced fluoresence detection;acidic constituents;Conyza blinii levl.;Artemisia annua L.
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发布时间：2024-04-19 - 摘要：Abstract:In order to improve the repeatability of HPLC determination of cypermethrin in fungal degradation system, a pre-treatment method for HPLC analysis of cypermethrin in Aspergillus oryzaedegradation system was studied. A suitable pre-treatment method including sampling and extraction of cypermethrin from the A. oryzae degradation system was established. Total sampling could solve the uneven dispersion or distribution of cypermethrin in the degradation system. Acetonitrile extraction assisted with ultrasonic could make cypermethrin in or on the fungal cells be released more sufficiently. The determination of cypermethrin in the pretreated sample by HPLC showed a high precision (RSD=1.14%,n=5) and a good repeatability (RSD=1.70%~2.12%,n=5) as well as a good stability (RSD=1.57%,n=5). This method can provide an important reference for HPLC determination of pyrethroid in microbial degradation systems.关键词：cypermethrin;degradation system;Aspergillus Oryzae;HPLC;pre-treatment method
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发布时间：2024-04-19 - 摘要：Abstract:Deionized water was applied to prepare five kinds of water samples, in which the organics were equivalent in contents, but different in polar components. Ultrafiltration membrane was used to filter the samples. Based on the filter cake and intermediate blocking filtration models, the effect of organic polarity on the membrane filtration performance was analyzed. The results showed that the removal rate of organic matters with different polarities was VHA>SHA>NEU>CHA. At the end of filtration, compared with initial fluxes, the fluxes of sample 1, sample 2, sample 3, sample 4 and sample 5 were 91%, 80%, 69%, 56% and 45%, respectively. The cake layer filtration resistance coefficient denoted by kpand membrane pore adsorption coefficient denoted by kcwere increased with the elevation of hydrophobic organic contents, indicating that both the deposition of hydrophobic organics on membrane surface and the membrane pore adsorption performance were stronger than hydrophilic organics. Hydrophobic organic matters were the major factors causing the organic pollution of ultrafiltration membrane.关键词：ultrafiltration membrane;organic polarity;membrane fouling;filter cake blocking filtration model;intermediate blocking filtration model
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发布时间：2024-04-19 - 摘要：Abstract:The metastable equilibriua of the quaternary system Li+，K+//CO32-，SO42--H2O at 273 K was studied by the isothermal evaporation method. Metastable solubilities and densities of the solution were determined experimentally. Based on the experimental data, the metastable equilibrium phase diagram and water content diagram were plotted, respectively. The phase diagram in the quaternary system had three invariant points, seven univariant curves, and five crystallization fields corresponding to K2SO4·Li2SO4,K2SO4, Li2SO4·H2O,Li2CO3,and K2CO3·3/2H2O. Carbonate potassium (K2CO3) had the biggest solubility and strong salting-out effect on other salts.关键词：salt-water system;metastable equilibrium;solubility;potassium
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发布时间：2024-04-19 - 摘要：Abstract:The Brazilian disk(BD) test was used to investigate the rate dependence of the tensile strength of glass-ceramic Macor. The static measurement was conducted with a servo-controlled material testing machine and the dynamic experiment was carried out with a 6.35 mm diameter split Hopkinson pressure bar(SHPB) system. The pulse-shaping technique was used to achieve dynamic force balance, eliminate the loading inertial effect, and enable quasi-static stress analysis. The experimental results showed that the tensile strength of Macor is loading rate dependent, the tensile strength, as a function of loading rate, increases from 26 MPa to 50 MPa as the loading rate is increased from zero to 5 780 GPa/s.关键词：tensile strength;rate dependence;machinable-glass-ceramic(MACOR);Brazilian disk;Split Hopkinson Pressure Bar(SHPB)
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发布时间：2024-04-19 - 摘要：Abstract:Considering the importance of the mechanical properties of rubber-like material for the water-seal design, different Rivlin models were applied to process experimental data of uniaxial tension test, uniaxial compression test and pure shear test in order to describe the hyper-elastic properties for the material overall. The nonlinear calculation for the free extension of pressure-filled telescopic water seal was done by using the fitting parameters from the models. The comparison between the calculated results and test results was carried out. The results showed that the second rank and five terms Rivlin model was of good application in project and fit well in describing the hyper-elastic properties of rubber-like material. It was more precise to use it in nonlinear finite element calculation, which provided a good reference for the design and calculation of gate water seal structure.关键词：rubber-like material;hyper-elastic properties;nonlinear finite element;Rivlin formula
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- 5
发布时间：2024-04-19 - 摘要：Abstract:The stability of DLG IRC18490 cylindrical lithium-ion batteries(LiCoO2/C) under the conditions of different temperature and different charge currents were investigated. The electrochemical impedance spectroscopy characteristics in different conditions indicated the instability of the lithium-ion batteries. Meanwhile,I0,an important kinetic characteristic of the electron transfer process, was obtained by theoretical calculation. Analysis showed that the growing of electrolyte interface film(Rsei) and charge transfer resistance(Rct) were increased from room temperature to 60 ℃. Noticeably,Rct which was heavily depended upon the battery SoCwas declined considerably with the increase of SoC. The qualitative physical explanation and quantitative theoretical calculation were given on these phenomena above. These results are of great significance to the application of lithium-ion batteries.关键词：lithium-ion batteries;electrochemical impedance spectroscopy;charge
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发布时间：2024-04-19 - 摘要：Abstract:According to the forming process of cold-extruded internal thread，the microstructure at the surface of cold-extruded internal thread was investigated. The corrosion resistance was analyzed from the changing perspective of surface status of cold-extruded internal thread. The results showed that the fibrous structure of the metal surfaces on the root of thread was pressed and refined to distinguish the grains difficultly. The metal structure appeared to be streamline type and distributed along the normal direction of the tooth surface. The hardening layers of cold-extruded internal thread had an adverse effect on corrosion, and it reduced corrosion degree at the surface of the sample in the same corrosive environment, and mostly avoided producing corrosion pits to cause local stress concentration. Cold-extruded internal thread had better corrosion resistance.关键词：thread;cold extrusion;microstructure;corrosion
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发布时间：2024-04-19 - 摘要：Abstract:In order to resolve the problem that circumferential tensile strength of conventional forming pipe is low, a self-made shear-tensile bidirectional combined stress field pipe extrusion equipment was used to engender induced crystallization to produce bidirectional self-reinforcement pipes by adding a small amount of relatively high molecular weight HDPE(HMWPE) to relatively low molecular weight general purpose HDPE. Results of tensile testing showed that the circumferential and axial tensile strength of the system with 6%(wt)HMWPE increases by 49.0% and 6.9%, respectively. Differential scanning calorimetry(DSC), scanning electron microscopy(SEM) and wide-angle X-ray diffraction(WAXD) test showed that macromolecule orientation under a complex stress field and the increase of crystallinity result in the bidirectional self-reinforcement of pipe.关键词：plastic pipe;shear stress;high density polyethylenes(HDPE);induced crystallization;reinforcement
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发布时间：2024-04-19 - 摘要：Abstract:Mo2C has been used in conventional Ti(C,N)-based cermets to improve its wettability between hard phase and binder phase. Recently, some researchers have attempted to develop Ti(C,N)-based cermets free of Mo. To investigate the effect of replacing Mo2C by WC in conventional Ti（C,N）-based cermets, the cutting performance of cermets with the addition of WC and Mo2C was studied, respectively. Wear morphology of cutting tool was observed by SEM, and element distribution of tool surface was analyzed by EDS. The results showed that the cutting tool life of cermets with WC addition was equal to that with Mo2C addition. When the size of the initial WC powder decreased, the cutting tool life could be prolonged, the zonal tangle chip changed to helix chip, and the chip build-up could be reduced. Diffusion wear, oxidation wear accompanied by abrasive wear were considered to be the main wear mechanisms of the cermets.关键词：Ti(C,N)-based cermets;WC;Mo2C;cutting tools
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发布时间：2024-04-19 - 摘要：Abstract:The influence of aging time at 175 ℃ on the tensile strength(σb), elongation(δ) and microstructures of Al-Cu-Mn casting aluminum alloy after (540±5) ℃ solution treatment for 14 h were investigated. The results showed that, the suitable aging time range is from 3 h to 8 h, during which the tensile strength would be greater than 455 Mpa and at the same time the elongation would be greater than 8%, the peak value of σbreaches 480 MPa when the aging time is 5 h, the corresponding elongation is 8.2%. The aging time has a little influence on the tensile strength, because the main strengthening mechanism is the dispersion strengthening of precipitate phase θ′ in matrix and the second T phase in grains. The elongation decreases with the increase of aging time, moreover, when the aging time is greater than 10 h, the elongation would be lowered distinctly and the value is less than 5.0%. The reason could be attributed to the fact that when the aging time is greater than 10 h, the appearance of Grain Precipitates on Boundary(GPB) changes from chain to bulky block, the Precipitation Free Zone(PFZ) is widened excessively, serious segregation of second T phase and blank area happens within grains, the matrix separated by the net-type grain boundary. All of above mentioned microstructures reduce the ductility of Al-Cu-Mn casting aluminum alloy.关键词：aluminum copper alloys;age hardening;tensile strength;elongation;microstructure
- 2650
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发布时间：2024-04-19 - 摘要：Abstract:The crystalline characteristics of poly p-dioxanone(PPDO) with high molecular weights was researched using differential scanning calorimeter(DSC),polarized optical microscopy (POM) and X-Ray Diffraction (XRD).DSC curves of all samples revealed the same crystallization behaviors. The results showed that when the molecular weight of PPDO reaches a certain level (Mw>30 000 g/mol),it will not influence both the crystallization behavior and the glass transition temperature of PPDO. The spherulitic growth rate of PPDO with different molecular weight was investigated using a POM. PPDO-4 (Mw=277 700 g/mol) had the highest molecular weight and the smallest spherulitic growth rate. The results confirmed that the higher the molecular weight and crystallization temperature, the smaller the spherulitic growth rate.关键词：PPDO;molecular weights;crystallization
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发布时间：2024-04-19 - 摘要：Abstract:Aiming at the demand of great dexterity in minimally invasive operation, one minimally invasive surgical robot was designed with hybrid structure. The configuration of the robot was optimized based on results of dexterous workspace. To layout an incision and plan the operation path reasonably, the dexterous workspace was analyzed according to the service sphere and service areas of the end tool. So the flexibility ratio of any point in the workspace was obtained by numerical approach. The dexterity distribution of workspace horizontal section was also mapped out. The results provided operational data for incision layout and operation path planning. The number of points in the workspace horizontal section, whose dexterity degree was greater than 0.85, was taken as the appraise criterion. Therefore, the influence on the dexterity, coming from the wrist joint rotation range and the length of the operation tool,was analyzed quantitatively.It provided computation basis for structure optimization of the minimally invasive surgical hybrid robot. Both the results of simulation and actual motion of model proved that the hybrid robot could satisfy the dexterous requirement of minimally invasive surgical.关键词：minimally invasive surgical robot;kinematics;dexterous workspace;hybrid structure
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发布时间：2024-04-19 - 摘要：Abstract:The calculation of convective heat transfer coefficients is the key problem of machine tools’thermal analysis. Taking the Y directional screw-nut feed system of a Gantry Machining Center as an example, a method for the calculation of convective heat transfer coefficients was proposed based on a neural network and experimental data. A finite element model of the screw-nut feed system was build as this method’s base, and by using this model’s thermal analytical data, a neural network was build to simulate relationships between convective heat transfer coefficients and the temperature field. Importing measured temperatures into the established neural network, the value of convective heat transfer coefficients was computed. Finally, by comparing results of the above method and a method based on similarity theory with experimental data, the accuracy and validity of this method were proved.关键词：convective heat transfer coefficient;thermal analysis;Neural network;gantry machining center
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发布时间：2024-04-19 - 摘要：Abstract:The dynamics of motorized spindle of machine tool was analyzed based on transference matrix (TM), and the numerical calculation of a specific example was executed with MATLAB. The validity of this mathematic model was verified by experimental modal analysis (EMA). The results showed that the tolerance of the first set natural frequency is about 1.2%, but the tolerance of the second set is a little high, because TM is supposed to be the theory of lump mass and after the continuous model was dispersed, the tolerance of higher set natural frequency is considerable. Thus, this model is reliable for calculating the lower set modal parameters. Asymmetry details such as the screw holes and key slots are neglected during simplifying the model when using TM. The natural frequency obtained by TM is less than that by EMA, which means the symmetry modal shape can not be obtained.关键词：motorized spindle of machine tool;dynamics analysis;TM;EMA
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发布时间：2024-04-19 - 摘要：Abstract:The existing machine vision systems acquired the images of the scoured wool with contaminants in the visible lights band by CCD cameras, and then processed the images for the removal of the contaminants from wool. They cannot distinguish the scoured wool from the white contaminants, reducing the quality of the fiber products significantly. In order to overcome this problem, a spectrophotometer was used to measure the diffuse reflection spectrum of scoured wool with nine types of white contaminants in 200~2 600 nm band, the relationship of their diffuse reflection spectrum with the changes of their wavelength was analyzed, and then by constructing an optimal model for band selection, the best band for discriminating white contaminants from wool was calculated. Based on that, the infrared images of scoured wool with the white contaminants were acquired by an infrared camera and analyzed. The experiment indicated that the histograms of the infrared images are bimodal so that their images would be segmented easily. Therefore, this method can be used for detecting write contaminants in scoured wool in a machine vision system.关键词：spectroscopic analysis;wool contaminants;optimal detection band;infrared imaging
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发布时间：2024-04-19
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