最新刊期
卷 44 ， 期 4 ， 2012
- 摘要：Abstract:A new and promising strategy of CO2 capture and utilization (CCU) based on analysis of the costs and potential geological risks of application of CCS technique was presented.It is believed that,in addition to enormous energy expenditure and costs, application of CCS faces a few geological risks such as leakage of CO2, destruction of saline,ground upheaval and triggering earthquake. CCU, meaning that CO2 being captured and used as raw material to produce high-value chemical products (or related by-products), thereby reducing CO2 emissions with low energy expenditure and costs, is more attractive than CCS as the best currently available technology. This study, for the first time, shows several promising methods to mineralize CO2 and simultaneously produce valuable products, such as employing MgCl2·6H2O to mineralize CO2 and to recover hydrochloric acid and magnesium carbonate,and using phosphogypsum to mineralize CO2 and produce Sulphur-based compound fertilizer and calcium carbonate as well. It is shown that within the scope of human use (about 5 km underground),if 1% of calcium and magnesium ions of the total amount of the earth’s crust were used for mineralization of CO2 with a conversion rate of 50%, it could theoretically sequestrate 2.56×10^6 billion tons of CO2. According to a report by the International Energy Agency, global CO2 emission in 2010 was expected to reach 30.06 billion tons. Potentially, in theory, the natural sources could mineralize as much as 85 thousand years of global CO2 emissions. Besides, if the magnesium ions of approximate 50 million tons of phosphogypsum wastes annually produced in China were used for mineralization, it could theoretically sequestrate 12.5 million tons of CO2 per year. By producing value-added product compensating the costs of handling CO2, the proposed CCU strategy provides a feasible and economic way to fulfill commercial application of techniques for reducing global CO2 emission.关键词：Carbon Dioxide Reduction;CCU;CCS
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- 44
发布时间：2023-11-14 - 摘要：Abstract:The shield construction safety in soft soil is always an important issue in engineering field. Based on the seepage-stress coupling theory, the evolution of soil permeability, the time-dependent stiffness and permeability of the grout material were modeled through second development on the platform of ABAQUS. The influence of cover depth, ground water level and soil properties on the ground settlement was investigated numerically. The results showed that the influence of time-dependent stiffness and permeability of grout material on ground settlement is more obvious than that of strain-dependent permeability of soil. Cover depth, ground water level and soil properties have an impact on ground settlement, and the influence of elastic modulus of soil is the greatest among them.关键词：shield tunneling;soft soil;the evolution of permeability;time-dependent;cover depth;ground water level;soil properties;seepage-stress coupling
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发布时间：2023-11-14 - 摘要：Abstract:Natural clays have their structure caused by inhomogeneity of the cementation. In order to provide theoretical bases for finite element method of structural soils,based on the theoretical framework of breakage mechanics,the weakly form of elastoplastic constitutive of binary medium for soils was given by Eshelby eigenstrain self-consistent method with the consideration of the compatibility for strain and the continuity for stress between bonding elements and frictional elements.A typical example showed that mechanical properties of bonding elements and frictional elements,breakage laws of bonding elements,loading histories,loading modes and states of stress have a great effect on the mechanical property of binary medium for soils, and the constitutive relationship could take it into account.关键词：binary medium model;Eshelby tensor;eigenstrain;self-consistent method;elastoplastic constitutive
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that for general composite frame consisting of concrete-filled steel tubular (CFT) columns and steel-concrete composite beams (CB), the method to achieve strong column-weak beam behavior is not available in China code, GB 50011—2010, Pushover method was applied to study the damage mechanism of the CB-concrete-filled square steel tubular (CFST) column frame. The influence of ultimate moment ratio (column to beam) and beam-column line stiffness ratio on the structural yield mechanism was discussed. The analysis results showed that the method by adjusting the elastic inner force for RC frame can not give a guarantee to fulfill the strong column-weak beam yield mechanism. Furthermore the design formula to make sure the strong column-weak beam mechanism of CB-CFT column frames was preliminarily suggested, which could offer some valuable references in design of composite frame structures.关键词：composite frame;strong column-weak beam;ultimate moment ratio;line stiffness ratio
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发布时间：2023-11-14 - 摘要：Abstract:The issues of choosing proper intercepted range of dynamic analysis model and its artificial boundary setting were discussed. Based on the distribution characteristics of seismic wave field of underground caverns, the setting method for artificial boundary used in time history analysis of underground caverns was presented, which allowed the free surface not to be covered by analysis model. The wave field reflected by free surface was calculated using analytical method and then incident into analysis model through artificial boundary. Based on wave field separation principle, artificial boundary surrounding the analysis model could well absorb outgoing scattered wave to guarantee the accuracy of computation. The theoretical test and practical case calculation indicated that the presented method is sufficiently accurate and able to meet the requirements of time history analysis of underground caverns. Meanwhile, the amount of computation can be considerably reduced and the time-consuming is lowered accordingly.关键词：underground caverns;dynamic time-history;artificial boundary
- 2696
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发布时间：2023-11-14 - 摘要：Abstract:The method for the concentration calculation of observation point was developed and verified. A pollution cloud’s spatial reconstruction model based on the backward probability density function was proposed, and the direct scanning method was used to search the optimal solution. The solution obtained by this method was the global optimal solution in the discrete solution space. The discussion of two cases showed that the model has excellent reliability and accuracy, when the quantity of observation points is two or more.关键词：backward probability density function;pollution cloud;spatial reconstruction
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problems of designing flood for the current reclamation of data scarce small to medium scale river basins, the method of estimating flood from rainfall data observed in river basins was proposed. Two approaches of US Rational Formula and “Zhongtie Method” were investigated in a case study of Zishui River basin for its adaptability. The estimation equations were established by adjacent river basins with similar catchment scales and observed hydrological data. Results indicated that design floods obtained by Zhongtie method are much more accurate than those by US Rational Formula. Therefore, Zhongtie method is a suitable approach for the design flood estimation in the small to medium scale catchments in China.关键词：small to medium scale rivers;comprehensive reclamation;design flood;peak flow;Zishui River
- 3026
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发布时间：2023-11-14 - 摘要：Abstract:In order to reduce the adverse influence of The Three Gorges reservoir operation on ecological system, the problem of four major Chinese carps spawning was studied. Combined with the hydrological data, eco-hydrological events of spawning period were analyzed and calculated by using environment flow components calculation algorithm. With the statistical result of the ecological event parameters, the ecological flow process, which can meet the spawning demand, was proposed and improved by ecological operation. The results indicated that the four major Chinese carps spawning process is composed of low flow event and high-flow pulse event, the proposed flow process can meet its spawning demand of flood pulse. The ecological operation is beneficial to four major Chinese carps spawning and ecological system restoration.关键词：ecological operation;ecological flow process;environment flow components;ecological flood;four major Chinese carps
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- 10
发布时间：2023-11-14 - 摘要：Abstract:In order to study the hydraulic characteristics of unsaturated flow in single fracture, a method for generating the distribution of fracture aperture using Weierstrass-Mandelbrot function was proposed according to fractal dimension,dislocation value and contact area of fracture surface.Based on the assumption that a parallel-plate approximation can stand in the subregion of the fracture,a numerical model for simulating unsaturated flow in single fracture considering the quasi-static water exchange between fracture and matrix was built up.The simulated relationships between capillary pressure and saturation and between unsaturated hydraulic conductivity and capillary pressure of fracture could be used to describe the hysteresis during drainage and imbibition and figure out the air-entry value and the residual water saturation during drainage.The qualitative comparison of simulated results and experimental results showed that the proposed model is feasible and reliable in modeling the unsaturated flow in single fracture considering the water exchange between fracture and matrix.Finally,comparisons of relation curve between unsaturated hydraulic conductivity and capillary pressure by taking water exchange into account or not was conducted.The result showed that the fracture-matrix exchange is negligible under high capillary pressure (low saturation).关键词：water exchange;single fracture;unsaturated flow;numerical simulation
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发布时间：2023-11-14 - 摘要：Abstract:Considering uncertain factors in multi-objective flood operation,some risk indexes in flood control operation were extracted,the interval number based multi-attribute decision making with fuzzy trade-off method was proposed to solve the optimum seeking problem in archive set,and multi-attribute decision matrix was established to avoid the vagueness and uncertainty of candidate schemes.Considering possibility degree matrix with subjective weights,positive ideal scheme and negative ideal scheme were selected from candidate schemes. These candidate schemes were sorted by the difference degree and closeness degree of ideal schemes,and finally the satisfactory multi-attribute decision scheme was obtained by the proposed interval number based multi-attribute decision making with fuzzy trade-off method.关键词：multi-objective schemes;interval potential energy;fuzzy trade-off;interval possibility matrix;closeness degree;difference degree
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发布时间：2023-11-14 - 摘要：Abstract:A field investigation of Gengda-Yingxiu reach of Yuzixi River, a tributary of the Minjiang River, found that the river was always either squeezed by natural dams,resulting in river bending or broadening laterally,or the river was uplift strongly,or developed into step-like riverbed. Considering the limitations of field investigation,the dynamic characteristics of peak discharge of dammed lakes cascade failure were explored by field flume experiments. The amplified scale of peak discharge intensified the degree of erosion and deposition along the flume, which could be conducive to forming the step-like riverbed.关键词：Wenchuan earthquake;dammed lakes;cascade failure;channel evolution;field flume experiments
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发布时间：2023-11-14 - 摘要：Abstract:The finite element method combined with the analytical method was employed to systematically analyze the stress intensity factor for the cracked flattened Brazilian disk under combined mode loading condition. The calculations showed that within certain range of the load distribution angle, the formula of the stress intensity factor for the cracked Brazilian disk subjected to pressure can be directly used to calculate the stress intensity factors for the cracked flattened Brazilian disk under combined mode loading condition. In addition, the analyzed result also confirmed that the Saint-Venant’s principle is still valid in fracture mechanics. Based on the analyzed result, a cracked flattened Brazilian disk with a load distribution angle 7.25° was recommended to be used in the cracked flattened Brazilian disk test.关键词：cracked flattened Brazilian disk(CFBD);stress intensity factor(SIF);combined mode;central crack;numerical analysis
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发布时间：2023-11-14 - 摘要：Abstract:To overcome the difficulty in the convergence of hysteretic analysis on numerical calculation by available models for concrete, an incompatible D-P model was proposed to simulate concrete based on the classical Drucker-Prager(D-P for short) model with modified cap yield criterion. A large amount of trial calculation was implemented to reveal the rational range of incompatible parameters αandk. The proposed model was used to simulate the mechanical behavior of a reinforced concrete specimen under monotonic load at mid-span, as well as hysteretic behavior of a reinforced concrete specimen and a steel reinforced specimen under low cyclic loading separately. By comparing with the experimental results, the adaptability of the model was verified adequately, and the restoring force model of concrete specimen under low cyclic loading could be obtained through numerical calculation.关键词：concrete member;nonlinear analysis;incompatible Drucker-Prager model;numerical simulation;hysteretic curves;restoring force model
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发布时间：2023-11-14 - 摘要：Abstract:In order to research the eccentric compression performances of hooping technique strengthening member, mechanical behavior testings of 22 specimens were completed to investigate the influence of 7 different factors on the failure pattern and bearing capacity of the member. Test results indicated that the failure mode of hooping strengthening member was similar to that of common reinforced concrete member. The actual test strains of midsection before cracking basically complied with the plane section assumption, which showed that the young-old concrete can work together. By analyzing the relationship curve of test load and strain, it was inferred that the new-old reinforcement and concrete are able to reach its design strength in the calculation of carrying capacity. Based on the basic design principles of RC structure, and combined with the existing strengthening technical specifications, the formula for the bearing capacity of hooping strengthening member considered various influence factors was proposed. Then, the formula was duly simplified in the light of the actual situation of the test. The comparison between the simplified theoretical calculation results and test results verified the correctness and reliability of the proposed formula.关键词：reinforced concrete;eccentric compression member;Strengthening;compression testing;mechanical behavior;bearing capacity
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发布时间：2023-11-14 - 摘要：Abstract:Based on the fact that concrete undergoes autogenous deformation and temperature deformation during its hydration advancement, which is closely linked with the durability of concrete and is concerned by engineering construction parties, two stress-free meters that were located on different places around the cooling pipe in a southwest concrete extra-high arch dam construction site were used to monitor the total deformations, and a new method with the consideration of concrete temperature history was adopted for decoupling the monitored deformations. This method could avoid the dependence on taking thermal expansion coefficient of early age concrete as a constant value, thus, the curve of thermal expansion coefficient vs. equivalent age was got and finally temperature deformation and autogenous deformation were separated from the data. Test results showed that the method could consider temperature history, separate the thermal expansion coefficient and autogenous deformation of concrete at early age more precisely and easily, and provide guidance for the site concrete curing and anti-crack constructions.关键词：temperature history;maturity theory;concrete at early age;separation of autogenous deformation;field test
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发布时间：2023-11-14 - 摘要：Abstract:In order to simplify the device configuration, reduce the cost, improve the instrument stability and anti-interference ability, a new type of double-line flow-injection ion-selective electrode method was proposed, and determination conditions of the method, such as the carrier composition and flow rate, acidity adjusting liquid composition and flow rate, and reaction coil length were optimized. The method was successfully used in simultaneous determinations of K+、Na+、Cl-、Ca2+in serums. Linear ranges of the method were in 2.0~24.0 mmol·L^-1for K+, 102~252 mmol·L^-1for Na+, 20~300 mmol·L^-1for Cl- and 0.7~8.0 mmol·L^-1 for Ca2+, respectively. The relative standard deviation was less than 1.3% (n=11), the recoveries obtained by adding K+,Na+,Cl- and Ca2+in serum samples were in range 96%~104%, the analysis speed was 480 detections/h, and the consumption of the sample was only 45 μL per time. These determination ranges were in normal ranges of human serum’s electrolyte concentrations.关键词：blood;electrolyte;simultaneous determination;negative pressure;flow-injection;flow-through microelectrode
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发布时间：2023-11-14 - 摘要：Abstract:In view of the shortcomings of artificial neural network, such as slow convergence, easily falling into local optimum, based on ANN and GA, a method was put forward to establish a model which could achieve fast analysis of Polydatin and Resveratrol in the extracting process of Rhizoma Polygoni Cuspidati by near infrared spectroscopy(NIR) . The method was proved to be convenient, rapid, accurate and reliable. It has the better precision of prediction and applicability compared with PLS, and provides a promising application for pharmaceutical production process and quality control.关键词：polydatin;resveratrol;artificial neural network(ANN);Genetic algorithm;partial least square(PLS)
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发布时间：2023-11-14 - 摘要：Abstract:Theoretical analysis of the adiabatical evaporation process from the free surface of a continuous falling liquid cylindrical column was carried out. The axial distribution of temperature on the vpaor-liquid interface and evaporation flux were obtained numerically. It was shown that the rate of this non-equilibrium surface evaporation accountes for only 20% of the theoretical maximum calculated under thermodynamic equilibrium. The evaporation rate is controlled by heat transfer from the inner of the liquid cylindrical column. The evaporation rate attenuates rapidly along the flow direction. When x/L=0.5, the evaporation progress ηx is only around 0.25, which means that the evaporation is coming to the end. It revealed that the refreshment on the surface of liquid is the key to intensify the surface evaporation process. The simulation results of this model were verified by the experimental data of the adiabatic vacuum evaporation from the free surface of a continuous falling liquid cylindrical column, with an error within 10%.关键词：simulation;falling liquid cylindrical column;free surface;adiabatic evaporation;non-equilibrium
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发布时间：2023-11-14 - 摘要：Abstract:The silica sand-water two-phase suspension in an unbaffled stirred tank agitated by a standard Rushton turbine was experimentally studied using the PC-6D particle concentration measuring instrument.The critical suspension speeds under different impeller off-bottom clearance and impeller-to-tank diameter ratios were measured and compared with those in the baffled stirred tank.The solids concentration and power profiles under different operating conditions were analyzed.Results showed that the critical suspension speed and power number for the unbaffled stirred tank are smaller than those in the baffled stirred tank.Both of them were found to increase with increase of the off-bottom clearance and decrease with increase of the impeller size at constant tank diameter.For the unbaffled suspension operation, the suspension is the best with impeller off-bottom clearance C=T/5、and impeller-to-tank diameter ratio D=T/3.There is no help to improve the suspension uniformity by increasing the impeller-to-tank diameter ratio or the impeller rotational speed.关键词：unbaffled stirred tank;solid-liquid suspension;critical suspension speed;concentration distribution;power consumption
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发布时间：2023-11-14 - 摘要：Abstract:Based on HSC, a computational chemistry software, the thermodynamic analysis and equilibrium composition calculation were carried out for vacuum carbothermal reduction of a multi-component and multi-phase complex system composed of vanadium-titanium magnetite and reductant. The result of thermodynamic analysis showed that Fe is the ultimate stable phase for carbothermal reduction of ferriferous oxides, the reaction Gibbs energy of producing TiC is the lowest among all possible carbothermal reduction of titanium oxides above 1 600 K, whereas the reaction Gibbs energy of producing VO2 is the lowest among the carbothermal reduction of V2O5 between 600 K and 1 600 K, and VC can be obtained only above 1 348 K. High temperature can facilitate the production of VC. The equilibrium composition calculation showed that under the pressure of 2 Pa, the stable existing temperature of Fe is between 400 ℃ and 1 300 ℃, the stable existing temperature of TiC is between 900 ℃ and 1 300 ℃, and the stable existing temperature of VC is between 800 ℃ and 1 300 ℃.关键词：magnetite;in situ processing;carbothermal reduction;thermodynamics;metallic matrix composites
- 2778
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发布时间：2023-11-14 - 摘要：Abstract:The reactive process of silicon carbide in Al2(SO4)3-Na2SO4 molten salts system was studied. The surface morphology and phase transition were studied by X-ray diffraction(XRD), infrared spectroscopy(IR), transmission electron microscope(TEM), scanning electronic microscope(SEM), and energy dispersive spectrometer(EDS), respectively. XRD and IR results show that silicon carbide could be completely transform into mullite whiskers. TEM result showed that the mullite crystals grew along ［111］ crystal plane firstly and developed into fibrous microstructure. An oxidation-dissolution mechanism was proposed for the explanation of the reaction of SiC powders in mixture molten salts.关键词：silicon carbide;molten salts method;mullite;whisker
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发布时间：2023-11-14 - 摘要：Abstract:Poly(para-dioxanone)(PPDO)-based composites was prepared by blending PPDO with three different types of CaCO3 particles, nano-CaCO3, CaCO3 whisker, and silane-coated CaCO3 whisker. The effects of particle size and composition on thermal properties and crystalline structure of the composites were investigated using differential scanning calorimetry(DSC), polarizing optical microscopy（POM）and X-ray diffraction(XRD). DSC revealed that the CaCO3 particles acted as a nucleating agent and promoted the crystallinity of PPDO. The decrease of particle size led to the increase of crystallinity, due to the greater nucleating efficiency of the smaller particles.关键词：poly(para-dioxanone),PPDO;CaCO3;composites;crystallization behaviour
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of frame images’ non-synchronization due to the imbalance overload of different rendering nodes, two synchronization algorithms were proposed which were the feedback verification and dead reckoning algorithm (FVDR) and texture image cutting algorithm (TICA). Feedback verification, maximum related waiting time and dead reckoning mechanisms were used to achieve synchronization for the FVDR algorithm. And the TICA algorithm firstly got a large texture image, and then cut the image and assigned to every visual client. The derivation of the two algorithms and their program implementations based on Visual C++ and OpenGL were given in a three-channel tiled display system. Contrast experimental results showed that both of the two proposed algorithms could achieve better synchronal effect on improving visual images’ timeliness and consistency.关键词：multi-projector tiled display;rendering synchronization;feedback verification;dead reckoning;texture image cutting
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发布时间：2023-11-14 - 摘要：Abstract:A self-adaptive weighted mean algorithm is proposed for filtering the salt-pepper noise in images. The algorithm detects the noise pixel with minimum-maximum inspection, and then replaces the noise pixel with weighted mean value, where the weight of each pixel in neighborhood is set based on its correlation with the center pixel. The algorithm adapts itself to different noise densities by rectifying the filtering window according to the number of non-extremum pixels in neighborhood. Simulation results showed that, compared with other methods, the proposed algorithm achieves more satisfactory images while it gives better Signal-to-Noise Ratio(SNR) and Mean Squared Error(MSE), and exhibits more excellent in scenarios where the image is highly corrupted.关键词：correlation weights;grayscale difference value;weighted mean filtering;salt-pepper noise
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发布时间：2023-11-14 - 摘要：Abstract:Horizon detection plays a vital role in the control system of an aircraft during approach and landing. A new horizon detection algorithm based on virtual and actual information fusion was proposed. Firstly, position and pose data were extracted from GPS/AHRS guidance system, and then the exact slope and estimated equation of horizon were calculated with the help of virtual model. Furthermore, the variance of the region above the horizon was acquired. Finally, precise equation of the horizon was determined using region growing and estimation algorithms. Experiment and visual measurement showed this algorithm can effectively detect horizon under low visibility conditions, and provide much auxiliary information to pilots during approach and landing.关键词：virtual and actual fusion;low visibility;horizon detection;region growing
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发布时间：2023-11-14 - 摘要：Abstract:To solve the partial correct problem of loop program, an algorithm was presented to generate non-linear loop invariant by computing Dixon resultant based on algebraic transition system and constraint system. The loop program was firstly transformed to an algebraic transition system, then a polynomial set was constructed from algebraic transition relation and invariant template, and a constraint system w.r.t template variable was obtained by computing Dixon resultant. Finally the constraint system was resolved to get invariant. The algorithm was effective to whether single-path or multi-path programs through case study.关键词：loop invariant;Dixon resultant;template;constraints
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发布时间：2023-11-14 - 摘要：Abstract:A fast algorithm for the classification of high dimensional vectors was proposed. A special nonlinear feature function was used to reshape training sample sets of multi classes to low dimensional and orthogonal feature sub-spaces. Then the principle components of each feature sub-space were calculated. By projecting a new coming vector on each feature sub-space the projection residuals was calculated. The new vector was regarded as a sample of the feature sub-space with the smallest residual. This algorithm can distinguish high dimensional vectors of multi classes by one comparison and has good accuracy. Furthermore, manifold learning theory was added to the feature function to keep the accuracy and greatly reduce the dimensionality of feature sub-spaces.关键词：kernel method;feature sub-space;projection residual;manifold learning
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发布时间：2023-11-14 - 摘要：Abstract:The goal of node ID assignment scheme was set firstly, and a non-certificate signature scheme without trusted third party was proposed based secret sharing and non-certificate cryptography without paring. Based on that, a reliable node ID assignment protocol was presented for distributed structured P2P systems. Analysis showed that this protocol is more secure, efficient and scalable than the conventional ones.关键词：secret sharing;non-certificate signature without trusted center;reliable node ID assignment
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发布时间：2023-11-14 - 摘要：Abstract:Based on non-certificate public key cryptography, a new mobile IP(MIP) registration protocol was proposed to minimize the registration time and enhance registration performance. The protocol could realize the authentication between HA and FA by using a short non-certificate signature scheme without bilinear pairings. Protocol parameters between HA and MN could be kept synchronised by reusing the initial values in the MIP registration. User anonymity could be achieved via a temporary identity transmitted by a mobile user, instead of its true identity. Random values were added to the registration messages of the mobile entity to prevent a possible replay attack. Compared with the exist protocols, the protocol could minimize the amount of calculation of HA and FA and shorten the length of the message. Moreover, it could guarantee the mutual authentications of each node, the secure distribution of secret keys and the integrity of the message.关键词：protocol;digital signature;certificateless public key cryptography;mobile IP
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发布时间：2023-11-14 - 摘要：Abstract:Besides the typical characteristics of scale-free network, the indispensable features of social networking services and microblog can not be described by existing models completely and accurately. Based on comparison and analysis of network data, a hybrid model was put forward to describe the features of formation and evolution of generalized social network. Average-field equations were constructed, and its solution showed that the degree distribution follows the translated and stretched power-law. The simulation results showed that the model can describe the overall characteristics of social network. Finally, several models, including this model, were compared, and reasons were given for the differences of features among the models.关键词：complex networks;social networking services;cluster;power-law distribution
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发布时间：2023-11-14 - 摘要：Abstract:Based on image energy correlation, a novel second-order prediction algorithm was proposed to solve the low coding efficiency caused by inaccurate prediction and no detailed analysis of the correlation between the pixels. By analyzing the statistical properties between intra residual and inter residual, the energy correlation between pixels was defined. Then, the statistics of the energy correlation and first-order inter residual curve were applied to filter out second intra prediction reference pixels dynamically and the second order prediction became more accurate which makes a bitrate reduction and the coded image quality improvement. Experimental results showed that the bitrate and the quality of image are significantly improved. Especially for high-resolution video with complex movement, this algorithm achieves significant PSNR increment and bit rate reduce on average. The rate-distortion optimization has a significantly improvement.关键词：H.264/AVC;second-order prediction;the distance of pixel correlation;energy correlation;threshold;high-resolution video
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发布时间：2023-11-14 - 摘要：Abstract:An anisotropic left ventricular (LV) model was composed by non-linear finite element method to relate regional ischemic effect of the LV to the global cardiovascular system. Several parameters from LV model were used to drive the circulatory model updating the LV model at each time step. A compound three-dimensional LV model was built to mimic regional myocardial ischemic pathological with myocardial fiber structure built in the element of the LV model. A ventricular wall tissue fiber structure was innovatively applied in the cardiovascular system model. It provided a unique platform for medicine predictions. The validity of the model system was given by the good agreement with statistical data.关键词：finite element method;analog model;cardiovascular;heart model;numerical integration
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发布时间：2023-11-14 - 摘要：Abstract:There are large amount of calculation using continuation method to search the Bogdanov-Takens bifurcation point in power systems, and the traditional direct method requires accurate initial value, as its feature vector norm has uncertainty. In view of this problems, a improved direct method was put forward. This method used the constraint features of vector and it’s transposed, improved expansion equations feature vector constraint. The method could converge to the Bogdanov-Takens bifurcation point in the larger range of initial values, improved the effectiveness of the proposed algorithm. Simulation of power system through the model verified its correctness.关键词：Bogdanov-Takens bifurcation;improved direct method;expansion equation
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发布时间：2023-11-14 - 摘要：Abstract:Active power filter(APF) usually appears unstable and it is quite difficult to determine its exact mathematical model , when the load and parameters are changing. In order to treat this problem, fuzzy proportional-integral(PI) controller and Lyapunov-based stability theory were introduced into the direct current(DC) side voltage control and current control of APF to guarantee the precision and stability of APF. Through fuzzification, fuzzy inference and defuzzifier, fuzzy PI controller adjusted the parameters of the PI controller according to the error and error varying rate of the DC side voltage. After testing on four different control methods with Matlab/Simulink, the distinctive effectiveness of the proposed method was therefore confirmed. The results showed that, when the load and parameter change abruptly, compared with PI and hysteresis controllers, the total harmonic distortion(THD) of source current after applying the proposed method is decreased obviously.When the load is time-varying and parameter changes abruptly, both the THD of source current and overshoot of the DC capacitor voltage are much smaller in the proposed method, while the APF runs unsteadily after applying PI and hysteresis controllers.关键词：active power filter;fuzzy control;Lyapunov methods;power quality;stability
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发布时间：2023-11-14 - 摘要：Abstract:It is difficult to obtain critical values of pressure vessel defect cracks accurately. In order to solve this problem, the safety evaluation simulation system for the failure rate and paths of the crack on the aerodynamic pressure vessel was used to find the inflection point of the failure rate in safety critical region and the threshold of aN.The ray method or parallel method did not reflect the real level of dynamic security, but the defects along the failure path which reaches safety critical distance and this distance really reflected the remaining number of cyclic fatigue defects, and a new theory criterion for pressure vessel residual life prediction was established.关键词：pressure vessel;safety assessment;failure simulation;safety margin;residual life
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发布时间：2023-11-14 - 摘要：Abstract:Voigt model based ultrasound vibrometry method can be utilized to measure shear mechanical properties of materials or biological tissue quantitatively and invasively. But Voigt model cannot describe stress relaxation of medium. In order treat this problem, a more generalized model, Zener model, was used to represent complex viscoelastic behavior of isotropic and incompressible viscoelastic medium. Based on Zener model, the shear wave propagation velocity was derived from the wave equation and the constitutive relation of Zener model. The shear modulus was estimated from velocity by mathematical method. Shear wave velocities in gelatin and rubber were obtained.Voigt and Zener model were utilized to fit the velocities, respectively, and the results demonstrated that Zener model is better for characterization.关键词：ultrasound vibrometry;viscoelasticity;Zener model
- 3696
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- 18
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- 0
发布时间：2023-11-14 - 摘要：Abstract:A new method of model order reduction for impact-contact dynamics simulation of space robotic manipulator was proposed.The impact-contact dynamics model of space robotic manipulator was constructed through the rigid body approximation method and Herz impact-contact force model.The corresponding state space equation of the space robotic manipulator was obtained by the linearization to the impact-contact dynamics model at the reference point.Then the eigenvalues of this linearized state space equation were solved to deal with the model order reduction of the system in which the eigenvalues with larger negative real part were disregarded because these eigenvalues usually represent the rapidly decayed modal responses with high frequencies.An example of 3-DOF planar robotic manipulator conducting contact manipulation was presented to verify the feasibility and efficiency of the proposed model order reduction method.关键词：space robotic manipulator;impact-contact;dynamics model;model order reduction
- 2773
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- 0
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- 1
发布时间：2023-11-14 - 摘要：Abstract:To eliminate the backlash and improve the precision and efficiency of enveloping worm, by analyzing the shortcomings in the existing non-backlash worm gear sets,non-parallel double-roller enveloping hourglass worm gearing was proposed based on the research of non-backlash double-roller enveloping hourglass worm gearing.Two rows of rollers were assigned to misplace and there was a certain defection angle between the roller axis and the radial.The working principle was introduced. According to the theories of differential geometry and space engagement theory, the dynamic and static coordinate system based on worm gear pair and the moving coordinate system based on the contacting point were established. The tooth surface equations of worm and contacting line equations of worm gear were deduced. The formulas of meshing limit function, induced normal curvature, lubrication angle and rotation angle of the non-parallel double-roller enveloping hourglass worm gearing were derived by means of the theory of differential geometry. The simulation was conducted using MATLAB software,c2,Rand γ, which impacted the engagement performance of this transmission, were analyzed. The numerical example showed that c2 should not be more than 10 cm,Rshould be controlled within 8 to 15 cm, and should be controlled within 28° to 50°, for effectively improving the meshing performance of the non-parallel double-roller enveloping hourglass worm gearing.关键词：non-parallel;double-roller;hourglass worm gearing;meshing performance
- 2702
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- 2
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- 9
发布时间：2023-11-14 - 摘要：Abstract:To solve the interactive issues during semiconductor assembly and test production planning, the multi-agent technology was applied to separate the semiconductor assembly and test production planning into several modules. The traditional contract net protocol(CNP) was improved with “capacity registered matrix” to build the multi-agent negotiation model, and the announce-bid-award process between agents interaction was discussed. Subsequently, the heuristic algorithm was employed to optimize the capacity equilibrium during bidding process. The presented method was implemented into S company production planning and compared with the traditional MRP Ⅱ method. The results showed that the integrated ameliorated CNP and heuristic algorithm has the better response close rate and correlation coefficient matrix for the production planning arrangement and capacity equilibrium.关键词：contract net;multi-agent;production planning;heuristic algorithm
- 2495
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- 0
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- 0
发布时间：2023-11-14
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