最新刊期
卷 43 ， 期 1 ， 2011
- 摘要：Abstract:The hydraulic concrete structure is mostly be in tensile or shear stress states, which induce the tensile and shear damage. In view of the characteristic of stress and damage states of hydro-structures, tensile and shear damage variables are introduced to describe the influence of micro-crack on the degradation of micromechanical properties. A novel plastic-damage constitutive model that employs a yield criterion based on Mohr-Coulomb criterion with Rankine is proposed. The nonassociated flow rule is assumed and the Drucker-Parager function is adopted. This paper employs implicit backward Euler integration algorithm to update stress. A subroutine in ABAQUS is developed for the validation of the damaged-plasticity model and well agreement is achieved between the analytical and numerical results.关键词：concrete damage;plasticity;Composite yield criterion;Rankine;Mohr-Coulomb;Implicit Backward-Euler algorithm
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发布时间：2023-11-14 - 摘要：Abstract:The disadvantage of conventional fiber model is its neglect of the nonlinear shear effect, and it is difficult to simulate the nonlinear response of the shear wall and other similar components with fiber model. The method of directly defining the nonlinear shear restoring force relationship at the section level was suggested. Within this method, the flexural and axial stiffness could be calculated by the traditional fiber model formulas, while the shear stiffness was calculated according to the predefined sectional shear restoring force relationships. The combined integrated sectional stiffness matrix could be obtained by combining the shear stiffness, flexural stiffness and axial stiffness. Based on the OpenSees framework and its functional command of Section Aggregator, it was convenient to simulate the nonlinear shear effect at the section level. Taking the experimental results of 15 shear walls of China as the benchmark, the formulas of Hirosawa, which was used to define the characteristic parameters of the shear restoring force skeleton curve, were calibrated and modified. The low cyclic reserved loading tests of two typical shear walls were simulated by the above-mentioned method. Results showed that the modeling method of considering the shear effect could simulate the maximum shear force, stiffness degradation and pinch shrinkage of the shear wall more effectively, while the actual mechanical behavior of shear wall could not be obtained by the modeling method that ignore the shear effect.关键词：reinforced concrete;shear walls;shear deformation;nonlinear analysis;fiber model
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发布时间：2023-11-14 - 摘要：Abstract:To research the regional characteristic and the water-sensitive shear strength of red clay, a series experiments which based on the sample of the red clay located in the Guangdong Yunfu region were done in this article, and the rule of the water-sensitive shear strength was discovered by considering the change of the moisture content directly without measuring the matric suction. The results showed that: The red clay has high moisture content, high liquid limit, high plasticity, contraction dilation, fracture property, high porosity ratio, low compression, and \"pseudo-powder\", etc; Red clay stress-strain curve is the enhanced curve, and there is a large difference between high and low moisture content at shear strength, the shear strength increase with the moisture content decrease. Cohesion with the increase in moisture content, showing a first-order exponential decay, while internal friction angle showing the characteristics of sub-functions; It comes the concept of \"shear strength surface on critical moisture content\" through the water sensitivity test results, and it can be determined that whether the soil reaches the shear strength through a recognition process based on known overlying pressure and wet-dry state of the clay, and this can provide a reference for practical engineering.关键词：Red clay;Engineering properties;shear strength;Water sensitivity
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发布时间：2023-11-14 - 摘要：Abstract:The determination of the position and attitude of the strength cracking of the arch dam has been an advanced research in dam engineering. As a complicated statically indeterminate system, the computation effort on the dam and its foundation is huge. How to decrease the computation scale and improve the computation efficiency was an important problem in numerical analysis of arch dam. With currently computer facilities, the most possible area of the cracking was first located and its elements were used as the locating elements. The locating elements were further divided into smaller elements, from which the accurate position of the cracks were determined. New nodes appeared after the division of the locating elements and these new nodes were attached to the nodes of initial elements by nodes stiffness attaching method. In that case, the element stiffness matrix was replaced with the stiffness matrix of attached elements; the stiffness matrix and the numerical methods of the main program could be kept the same. Since the method of location attaching was just a unit of the main program, the computation scale was decreased and efficiency was improved. The method was used in an example engineering problem and proved to be able to determine the position and attitude of the strength cracking. The method is found to be very useful since the cracking can be rationally estimated in practice..关键词：hydraulic structure;arch dam;attitude of strength cracking;orientation & agglomerating element
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发布时间：2023-11-14 - 摘要：Abstract: In order to analyze the feasibility of a single specimen used for step-loaded relaxation tests and study the time dependent stress relaxation properties of rockfill，two types of the drained triaxial compression tests were carried out with large-scale triaxial apparatus for rockfill. One is the constant-strain-rate triaxial compression tests, and the other is the step-loaded drained triaxial relaxation tests under different confined pressures and strain levels. A hyperbolic function was presented to simulate the laws of stress relaxation. The results show that the relaxation phases have little effect on stress-strain behavior at subsequent constant-strain-rate triaxial compression tests. This means a single specimen can be used reliably for step-loaded relaxation tests. The volumetric strain increase is 0.13％～0.71％ and the magnitude of stress decrease is 16％～28％ during relaxation phases. The rockfill can sustain a constant, nonzero value of deviator stress in the end. The laws of stress relaxation of rockfill can be simulated by the hyperbolic functions reasonably. Parameters analyses show that the decay of the deviator stress rate at the initial time is a constant value, independent of the confined pressure and the strain level.关键词：stress relaxation;rockfill;compressing testing;hyperbolic functions;stress-strain curves
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发布时间：2023-11-14 - 摘要：Abstract:Abstract:Flood waves resulting from flash floods have been responsible for numerous damage and losses of life. In the present study, an experiment was conducted to investigate surging waters down a stepped channel, which is 2.4m long, 0.5m wide and with a slope of 0.133, both in the circumstances of being roughed and non-roughed. Wave front propagation data from the non-roughed series compared with Chanson’s [2004] showed, that for some smaller flow rate, since the relative step height h*, defined as the ratio of step height to the characteristic length of flow rate raised, the dimensionless wave front celerity would no longer remain constant as C*=1.5 given by Chanson, but reduce as the flow rate lessened. Another analysis of the data from the roughed series showed, that the large roughness has a significant negative effect on the flash flood propagation, as well as on the energy carried by the rushing water. And this may provide some advice on the flash flood defense during the reconstruction in the earthquake-hit area.
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发布时间：2023-11-14 - 摘要：Abstract:In order to investigate the responses of laterally loaded single piles and the principle of the pile-soil interaction, the deflection curve differential equation based on the three-parameter method was introduced. Based on the pre-existing analytical solutions for laterally loaded piles in which the coefficient of subgrade reaction was assumed to be a constant and the continuity principle of pile responses, the semi-analytical solutions were submitted. The relevant computer program was developed by Fortran programming, and the obtained solutions were verified by comparing them with the pre-existing solutions corresponding to a special case.The calculation results indicated that the boundary condition at the pile tip plays a marginal role in pile responses when the pile length is comparatively great,the influences of two parameters from the coefficient of subgrade reaction, including the index and the parameter which represents the ability of soil at the ground surface to resist the lateral deflection on pile responses are too great to be ignored, and the obtained solutions are effective and can be applied widely.关键词：soil structure interaction;pile;semi-analytical solution;subgrade reaction method;deformation
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发布时间：2023-11-14 - 摘要：Abstract:The numerical simulations for the benchmark test of a 12-story reinforced concrete frame model carried out in Tongji University in 2003 were conducted in consideration of cumulative effect caused by series of earthquake events in platform of OpenSees. Meanwhile the damage status of the model was evaluated by using the System Identification toolbox of OpenSees formed by the principle of the improved direct stiffness method. Through comparison with the damaging description in several cases during the test, it is demonstrated that the preliminary assessment by using the System Identification Toolbox to conduct damage detection of 3-D frame structures in different direction are feasible and effective.关键词：OpenSees, Benchmark Test of a 12-story Reinforced Concrete Frame Model, Seismic Cumulative Effect, OpenSees System Identification Toolbox, Preliminary Assessment
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发布时间：2023-11-14 - 摘要：Abstract:Based on the construction feature and “block-frame-outer frame” failure characteristics of the multi-ribbed composite wall, the strengthen method for damaged multi-ribbed composite wall with aerated concrete blocks to recovery and enhance the seismic performance of the structure was proposed firstly. Through cyclic loading tests on strengthen composite wall, the failure process and steel bars strain were analysis, and the hysteretic curve character and seismic performance such as bearing capacity, stiffness, ductility and so on were researched mainly. Test results showed that the failure and cracks distribution characters of the strengthen composite wall was similar to the standard wall, and the main seismic performance index was close to or equated to the standard wall; it was effective that using aerated concrete blocks (or other blocks with a certain strength) to strength the damaged composite wall. The strengthen method was effective, convenient and cost cheap, and provided reference to strength the multi-ribbed composite wall structure in earthquake area.
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发布时间：2023-11-14 - 摘要：Abstract:According to hydrologic and sediment observation data, the flow and sediment features flowing into and out of Three Gorges reservoir are analyzed systematically. Selecting the representative hydrolagical stations located in the upper reaches of the Yangtze River, including mainstream and its tributaries, a comparative analysis on the changes of the annual runoff, the annual sediment yield, the annual average sediment concentration, et al of each station before and after the years of the Three Gorges Project starting water storage is conducted in this paper. In addition, based on the multi-resolution function of wavelet analysis, from the multi-time scale point, this paper analyzes the time series of annual runoff data from 1950 to 2008 of Zhutuo, Cuntan and Yichang station. The results indicate that, the ratio of reservoir inflow volume to the multi-year average discharge changes little after the Three Gorges Project storing water, but the sediment concentration is significantly less than normal. In the past 50 years, the annual runoff time series of the upper reaches of the Yangtze River periodically varies, presented as a cycle of abundance-low- abundance, and the dominant period is 12-year. At present, the incoming runoff of the upper reaches of the Yangtze River lies at a relative low status.
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发布时间：2023-11-14 - 摘要：Abstract:Abstract: The characteristics of water temperature distribution in Xiangxi Bay were studied by numerical simulation method after the Three Gorges Reservoir had been put into operation, the result is that, the Xiangxi Bay is the water body of seasonal temperature stratification, and the thermocline can be observed in the period of stratification, Furthermore, the impact of the water temperature distribution on the vertical transport of suspended solids was discussed. Through derivating the relation of water temperature and settling velocity, it is shown that the settling velocity is significantly affected by temperature, and under the conditions of weak hydrodynamic, the water temperature stratification makes the settling velocity of suspended solids is gradient distribution, then the suspended solids are enriched at the epilimnion, finally the concentration of materials will be stratified in vertical.关键词：tributary bay;numerical simulation;water temperature stratification;suspended solids;settling velocity
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发布时间：2023-11-14 - 摘要：Abstract:The hydropower plants in China are mostly located in southwest region where the seismic intensity is high. Aiming at the issue of seismic damage mechanism of underground powerhouse, Yingxiuwan and Yuzixi hydropower plants which were nearest to the epicenter of Wenchuan M8.0 earthquake were taken as the objects of analysis. Firstly, the post-earthquake in-situ investigation was conducted on the structures of the two hydropower plants. Then, the finite element mesh, which simulated both surrounding rock and powerhouse structures of Yingxiuwan plant, was established. The wave field method was employed to perform numerical calculation on the structural stability of underground caverns under seismic effect. Finally, based on the numerical results and in-situ investigation conclusions, the seismic damage mechanism of underground powerhouse structures was expounded. The in-situ investigation results showed that the seismic damages of underground structures were mostly surface shedding and closed cracks. The damage degree of underground structures was much smaller than that of ground structures. The seismic damage laws revealed by numerical calculation basically agreed with the investigation findings. This indicated that the seismic damage mechanism could be analyzed by using numerical results. It was therefore concluded that the incident angle of seismic wave was the external cause of seismic damage; the nonuniformity of spatial distribution of powerhouse concrete was the internal cause; the existence of rock mass surrounding the underground powerhouse accounted for the fundamental difference between underground and ground seismic damages.
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发布时间：2023-11-14 - 摘要：Abstract:The spring discharge is difficult to simulate in Karst areas under human activity. An integrated model (MODFLOW-ANN) was developed by combining the merits of the numerical groundwater flow model - MODFLOW and the artificial neural network model (ANN). Based on the application in the Xiaonanhai spring catchment of a karst region, Henan Province, the principles and algorithms of the integrated model were discussed, and the results were compared between MODFLOW and MODFLOW-ANN. The coefficient of determination, relative error and correlation were 0.79、4.98% and 0.84 for MODFLOW, respectively, and 0.88、1.22% and 0.89 for MODFLOW-ANN, respectively. The results show that this integrated approach could take advantage of the groundwater numerical analyzing capacity of MODFLOW and the nonlinear approximation ability of ANN, thus precisely predicting the peaks and troughs of spring discharge. This model improved the predicting accuracy and was successfully applied to model the spring discharge dynamic. This study could provide reference and guidance for further exploitation of groundwater in the spring catchment of Karst areas.关键词：spring discharge;Karst;artificial neural networks;numerical model;groundwater
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发布时间：2023-11-14 - 摘要：Abstract:The amidoximed polyacrylonitrile fiber (denoted as AO-PAN) was used to coordinate with five metal ions including Fe3+ , Cu2+ , Co2+ , Ce3+ and La3+, respectively, to produce the amidoximed PAN fiber-metal complexes. Coordinating kinetics and isotherm of AO-PAN with metal ions were mainly studied and effect of initial concentration and temperature on coordinating capacities of AO-PAN to metal ions was also examined. The results indicated that the coordination processes for five metal ions was found to fellow the pseudo-first-order equation, and coordinating isotherm of the metal ions with AO-PAN is consistent with Langmuir and Freundlich isotherm equations. Increasing the initial concentration of metal ions and higher temperature leads to an enhanced metal ion coordinating capacities. Moreover, reaction rate constants of five metal ions with AO-PAN increase with the elevation of temperature, and are ranked in this order: Fe3+ > Cu2+ > Co2+ > Ce3+ > La3+ at the same condition, but their activation energy shows a reverse trend. The value of △H0>0, △S0 >0, △G0<0, which shows that the coordination of AO-PAN with metal ions is a spontaneous and endothermic process.关键词：modified polyacrylonitrile fiber;metal ions;coordination;kinetics
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发布时间：2023-11-14 - 摘要：Abstract:Novel acrylic hybrids emulsion(PAH) with 98.8 mgKOH/g hydroxyl value and 45.0%(wt) solids content were designed and synthesized by semi-batch seeded emulsion polymerization with β-hydroxyethyl methacrylate (HEMA) as a hydroxy monomer, which polar monomers were multi-stages added and carboxyl groups were neutralized during the polymerization process. TEM photos show that PAHs were composed of two kinds of emulsion particles including one covered with carboxy groups(P1) and the other carrying hydroxy groups(P2). Nano-granularity analysis show that average diameters of the PAHs were smaller and its particle distributions were much broader than those of the common hydroxy polyacrylate emulsions (HPAE). Two component waterborne polyurethane coatings (2K-WPU) were prepared with PAH, and the properties of 2K-WPU films indicated that the optimal mass ratio of carboxy / hydroxy groups in P1 and P2 were 1：0 and 1：3, respectively. The FT-IR spectra show that the reactions between NCO and OH in 2K-WPU films were completely finished in 3 days. AFM pictures indicated that the surface of 2K-WPU cured films were excellent.关键词：two-component waterborne polyurethane;polyacrylate emulsion;hybrid
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发布时间：2023-11-14 - 摘要：Abstract:The π-A isotherms for monolayers of three amphiphilic rutin esters, rutin-4”’-O-stearate (RS), rutin-4”’-O-laurate (RL) and rutin-4”’-O-caproate (RC), were measured at the air-water interface and an air-aqueous aluminum sulfate solution interface. The properties of the monolayers of three rutin esters were related to the carbon number of alkyl, the compression rate and the property of substrate. Although RS and RL showed scant water solubility, they formed monolayers with the liquid-expanded phase when spread on water. While RC could not form insoluble monolayer at the air-water interface, which may be due to the larger water solubility of RC. Appropriately low compression rate was critical to form relatively stable monolayers. When spread on an aqueous aluminum sulfate solution, the formation of a complex between the aluminum ions and the rutin ester resulted in higher values of acoll for RS and RL monolayers compared with their values on water, and RC could spread as liquid-expanded phase monolayer. The results described in this paper provide valuable information for investigating the interaction of flavonoids and biomembranes and the anti-oxidant mechanism of flavonoids.关键词：Rutin ester;Monolayer;Air-water interface;Air-Aqueous aluminum sulfate solution interface
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发布时间：2023-11-14 - 摘要：Abstract:Polymeric drug delivery systems are used to improve aqueous solubility and photostability. Camptothecin (CPT) is a plant alkaloid that is practically insoluble in water and photosensitive. In this study, PAMAM-Poloxamer dendrimers were synthesized and characterized by FT-IR and 1HNMR. Their cytotoxicity was investigated by MTT assay . The potential of PAMAM-poloxamer dendrimers as drug carriers of CPT by improving aqueous solubility and photostability was researched. The results showed that PAMAM-Poloxamer dendrimers exhibited lower toxicity in comparison with PAMAM., and could increase the solubility and photostability of CPT. These studies indicated that PAMAM-poloxamer dendrimers might be considered as a new drug carrier.关键词：PAMAM-poloxamer dendrimers;synthesis;MTT;drug carrier
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发布时间：2023-11-14 - 摘要：Abstract:Sodium dodecyl sulfate(SDS) was used to modify CuO/TiO2 to have organic groups on its surface. The crystal, structure, chemical composition, surface groups and photoluminescence properties of catalysts were characterized by XRD, N2 adsorption-desorption, BET、XRF、FTIR 、UV-Vis DRS and three-dimensional fluorescence. The results show that UV-Vis absorption edges have nothing to do with the concentrations of SDS, and the UV-Vis absorption edges reach 830nm. But the N2 adsorption isothermal curves change from Ⅳ type toⅤ after SDS is added. Although the BET surface and total pore volume become the smallest when the concentration of SDS is critical micelle concentration(CMC), the particle size and average pore diameter reach the biggest. The oxygen vacancy concentration and groups of C—C and —CH— also reach the most at CMC. Photocatalysts prepared under this concentration has best catalytic performance.关键词：sodium dodecyl sulfate;photocatalysis;characterize;surface groups
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发布时间：2023-11-14 - 摘要：Abstract:Abstract：A novel acclimation of “independent”and “on-line” was developed to study the power generation performance of this acclimate mode with three anodic materials including carbon felt, carbon cloth and carbon paper. The experimental results showed that the anodic characters such as the surface area, aperture distribution, surface roughness and surface electric potential had directly affected the biomass on anode in the period of “independent acclimation”. It was clear that the anodic materials were in turn carbon felt, carbon cloth and carbon paper for abundant biomass on it by SEM. After about 10h in “on-line acclimation”, the electrocatalytic activity of bacteria catalyzer was increased significantly. In the second cycle, the output voltages for MFCs reached the peak (carbon felt/0.803V; carbon cloth/0.604V; carbon paper/0.574V). In the third cycle, MFCs maintained a high stable running for long period, especially the carbon felt-biofilm，the maximal output voltage (0.78V) of it could keep more than 180h. Comparing with power density of MFCs, the priority was in turn the carbon felt (1339.6 mW/m3), carbon paper (96.8mW/m3) and carbon cloth (80mW/m3). The efficiencies of COD removal were in turn carbon felt (89.5%), carbon paper (79%) and carbon cloth (74.7%). The main merits of the acclimation were convenient operations and high electrical functions.关键词：Microbial fuel cell (MFC);Acclimation;Biofilm;Electro-microorganism
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发布时间：2023-11-14 - 摘要：Abstract: The presence of phosphorus pesticides in the aquatic environment has raised concerns due to the poor degradation in conventional water treatment plants.In this study,sonolytic degradation of dimethoate in aqueous solution was investigated.The effects on its degradation rate by ultrasonic frequency and power, dimethoate’s initial concentration and initial pH value, and the concentration of humic acid and different ions are studied.The results indicate that at the conditions in question,600 kHz is the optimal frequency for dimethoate degradation and the degradation rate of dimethoate increased with enhancement of input power and decreasing initial concentration.The added inorganic ions can contribute diverse effects on the degradation.Carbonate and bicarbonate ions have negative effecst while bromonium and ferrous ions have positive effects.During the initial period,lower pH value is favorable,however,the constant of degradation rate decreases as the concentration of pre-existing humic acid increases.It is proved that sonolytic process has shown great potential for the removal of dimethoate.Besides,the mechanism of the degradation is also proposed.关键词：sonolytic degradation;dimethoate;kinetics;impact factors
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发布时间：2023-11-14 - 摘要：Abstract:Dyx（Co40Ag60）100-x (x=0, 0.7, 1.4, 2.1, 2.8, 3.5) granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Dyx（Co40Ag60）100-x films favors the (111) plane preferential orientation. The high annealing temperature t can promote the (111) plane of Ag preferential orientation and Co dissolving in Ag to separate from Ag and accelerate grain growing. Dy element plays the role of a grain refiner and retards the (111) plane preferential orientation result in increasing grains boundary and resistance of films. Magnetic measurements indicated that the value of GMR decreases of all films when annealing temperature is higher 250℃ because of increasing of resistance of films, but it can enhance sensitivityof films doped small Dy element. For small amount of addition Dy to CoAg granular films and proper heat treatment, Dy element can keep the value of GMR a constant and enhance sensitivity. Both maximum values of GMR and sensitivity are -18% and 1.5×10-4 (A/m)-1, respectively.关键词：Giant magnetoresistance;Granular films;Magnetic particle
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发布时间：2023-11-14 - 摘要：Abstract:Strontium-doped calcium polyphosphate (SCPP) which were a series of calcium polyphosphate (CPP) respectively containing 0,1,2,5,8,10 mol% of Ca2+ replaced by Sr2+ used as a novel bone material were prepared. The influence of SCPP on cellular behavior and angiogenic factors which were vascular endothelial growth factor (VEGF) and basic fibroblastic growth factor (bFGF) of osteoblasts was investigated, which provides experimental basis for elucidating mechanism of SCPP promoting vascularization. Osteoblasts were cultured with SCPP scaffolds, XRD, MTT assay, quantitative detection of ALP activity, scanning electron microscopy (SEM) observation, Reverse Transcription-Polymerase Chain Raction (RT-PCR) analysis and Enzyme-linked Immunosorbent Assay (ELISA) were used to investigate. The results showed that, compared with the control, the cellular proliferation, ALP activity as well as the mRNA and protein expression of the angiogenic factors (VEGF and bFGF) of the SCPP group were significantly promoted (p<0.05), and 8% SCPP showed the highest expression. SCPP is a potential material with “promoting vascularization”, and may serve as a promising scaffold for bone tissue engineering and bone implant materials.关键词：Strontium-doped calcium polyphosphate;vascularization;vascular endothelial growth factor;basic fibroblastic growth factor
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发布时间：2023-11-14 - 摘要：Abstract:Metallic foams in liquid state, which is consisted of random packing of gas bubbles in a small amount of metal in liquid state with lots of gas/ liquid interfaces, are typical forms of soft materials. That is in non-equilibrium essentially. Drainage means that liquid flows inside a micro-channel of foams, which is one of primary factors to liquid foams’ stability. In this paper, we present a structural model of a single node with different liquid holdup by Surface Evolver（2.30）firstly. Then CFD (FLUENT) is used in computing the velocity field in a single node. The compute results suggest that average velocity and mass flow rate is satisfied with the correction of and the linear relationship between mass flow rate and pressure difference is satisfied with the correction of approximately. The research on Nodes’ function in foam drainage will give us more deep insight on foams’ stability and drainage.
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发布时间：2023-11-14 - 摘要：Abstract:The characters of friction contact in particle material were quite complexness. Non-elasticity contact in normal regard as damage through contact, according to continuous damage theory, based on the reasonable assumption, we defined the damage variable of particle material and created the corresponding damage evaluation equation. Combined with Lemaitre equivalent strain assumption, we researched on the effecting of particle material damage through contact on characters of friction contact. The results indicated that the damage through contact model of particle material can predict the character of normal pressure-contact deformation. Normal stress on contact area is easy curve and contact area exaggeration when damage through contact has been considered. The characters of tangential micro-displacement can be predicted by considered damage through contact.
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发布时间：2023-11-14 - 摘要：Abstract:In real life, many attributes of a user are monitored by a single authority, which will inevitably increase its workload and reduce its efficiency. In this paper, the proposed multi-authority Attribute-based Signature scheme is that many attributes are monitored by many different authorities respectively, and in addition, a credible central authority is required to manage and constraint these authorities ,then a new signature scheme is constructed and by using the methodology of reductionist security argument its security is proved equal to discrete logarithm problem and computational Diffie-Hellman problem . This scheme has some advantages, such as protecting the private information of a user, and a higher efficiency in signature.关键词：multi-authority;Attribute-based;CDH problem;collusion attack
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发布时间：2023-11-14 - 摘要：Abstract:Security analyses of an ID-based aggregate signature scheme presented by Song, Kim, Lee and Yoon were given in this paper. It is found that the scheme is universally forgeable. We presented a new identity-based aggregate signature scheme from bilinear pairings. Its security proof was given in the random oracle model and it could be tightly reduced to computational Diffie-Hellman problem. Compared with the existing ID-based aggregate signature schemes, our scheme greatly improves the efficiency of signature communication and verification since the verification algorithm only requires 3 pairing evaluations and the size of the signature generated by our scheme is only about 320 bits.关键词：identity-based cryptography;aggregate signature;bilinear pairings
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发布时间：2023-11-14 - 摘要：Abstract:Analysis of one strong designated verifier signature scheme is given in this paper. The result shows that the scheme can not satisfy the strongness property required by strong designated verifier signature schemes. Exploiting the flaw existing in Li et al.’s scheme, a forgery attack on the scheme is also given in the same paper. Using this forgery attack, any third party, who even has neither the private key of the signer nor that of the designated verifier, can also generate a valid signature. Based on Cha et al.’ ID-based signature scheme, a novel ID-based strong designated verifier signature scheme is put forward at last, which is much more efficient than existing ID-based strong designated verifier signature schemes and satisfies all the properties required by the strong designated verifier signature schemes. In this paper, it is also proved secure in the random oracle model under the hardness assumption of bilinear Diffie-Hellman problem.关键词：Identity-based cryptosystem;Strong designated verifier signature;ID-based strong designated verifier signature scheme;Bilinear Diffie-Hellman problem;ROM
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发布时间：2023-11-14 - 摘要：Abstract:As a more and more important cradle of public opinion via Internet, BBS (Bulletin Board Service) has become an important study in recent years. However, how to build its model has troubled researchers for a long time. In this paper, the swarm intelligence inspires a new thought into us to build a collective opinion formation model for a certain topic in BBS. For the model, we give some definitions firstly. And the rules through an example are given, too. At last, a simulation is made for the model. Some important conclusions are attained form the experimental results. From the model, it give us a possible method to study the collective behavior and opinion formation in BBS.关键词：Swarm intelligence;Collective behavior;Opinion formation;Topic;BBS
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发布时间：2023-11-14 - 摘要：Abstract:This paper studied the mechanism of guiding the Internet public opinion based on point centrality in SNA. The arithmetic of guiding public opinion was designed, and the effect of the common methods of guiding public opinion in the Internet through the maximal point centrality in SNA was quantitatively analyzed. Compared the result of the common methods using the data of an event occurred in Tianya forum, the methods were simulated. The advice was proposed to guide the Internet public opinion in all stages of its evolvement. The study is theoretically directive and practically useful.关键词：public opinion;guiding;effect;SNA
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发布时间：2023-11-14 - 摘要：Abstract:For the low efficiency of skyline computation on enormous and high-dimensional datasets, a new multi-core parallel skyline algorithm, named MPSSI (Multi-core Parallel Skyline computation based on Sorting and Incomparability), is proposed. The given dataset is first pre-ordered to simplify the whole algorithm. Then the dataset space is divided into several disjoint regions via a carefully selected pivot point, and by the dominance relations among regions, the number of dominance testing is reduced. Finally, all functions in MPSSI have been paralleled on multi-core platform to improve efficiency. MPSSI is characterized by simple process, good progressiveness and nice scalability. The experiment results show that, on enormous and high-dimensional datasets, MPSSI can significantly improve efficiency and almost reach linear relative speedup.关键词：skyline computing;multi-core;parallel algorithms;sorting;information retrieval
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发布时间：2023-11-14 - 摘要：Abstract:Presently, most schemes use syntactic approaches to represent and match the security policy for web service, where pairs of policies are compared for structural and syntactic similarity to determine compatibility, which is prone to result in false negative because of lacking semantics. In this paper, we proposed a novel approach to express and match the security supply-and-demand policy of web service based on semantics. Through constructing a general security ontology, we presented the definition method and matching algorithm of semantic security supply-and-demand policy for web service, and translated the matching problem of security policy into the semantic based subsumption reasoning problem. Both the theory analysis and experiment evaluation show that, the proposed approach can present the necessary semantic information in the representation of policy and effectively improve the accuracy of matching result, thus overcome the deficiency of the syntactic approaches, and can also simplify the definition and administration of the policy at the same time, which thereby provides a more effective solution for the expression and matching problem of security policy in web service environment.关键词：Web service;security policy;semantic;subsumption
- 2519
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- 20
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- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to simulate the nerve impulse waveform characteristic of the creature,a Riemann-Liouville fractional-order neural pulse oscillator was put forward in this paper,and it was used to simulate biologic neural signal.The computer simulation showed that it was a fractal dimension oscillator and it’s parameters can be adjusted according to the actual biologic neural signal, it’s output was not square wave or not rectangular wave,it can simulated shape characteristic of the actual biology neural signal such as neural pulse signal of the posterior cricoarytenoid muscle, action potential and so on by and large,it can provide technical support for neuronal function restoration in the future. These simulations indicated that the essence of the biology neural pulse was fractal dimension , not integral dimension.关键词：Fractional derivatives,Neural pulse,Oscillator,Fractal dimension
- 3397
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- 10
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- 1
发布时间：2023-11-14 - 摘要：Abstract:In order to improve the effect of image enhancement, A new method of image enhancement was presented in this paper. Firstly, this method in this paper inherited the fine characteristics of the traditional fractional order differential, and broke the idea to take an unit step in G-L definition to use non-integer step, which increased the accuracy of the fractional order differential numerical calculation. What’s more, the method utilized the linear weighting method based on Lagrange polynomial section interpolation to determine the gray values of the non-integer step pixel. To a certain extent, it could play a role in noise reduction. Therefore, the method proposed in this paper had made a better balance between enhancing the image details and denoising. The experimental results shew that in the noise-free case, the method proposed in this paper compared with the traditional fractional differential operator in the image enhancement was better; in a noise case, the method had a certain amount of noise immunity.关键词：image enhancement;non-integer step;fractional order differential;Lagrange polynomial
- 3029
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- 12
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- 11
发布时间：2023-11-14 - 摘要：Abstract:Aiming at how to establish the ideal standard for the edge detection, a new image edge detection method was proposed based on a combination of least squares support vector machine (LSSVM) and cellular automata. Polynomial and Gaussian kernel function was deployed to construct a new kind of kernel function. LSSVM selected the new kernel function and fitted the image intensity surface for the neighborhood of every pixel. The gradient operators which were deduced from the above LSSVM convoluted with the image gray values to get the image gradient values. Gradient values were evolved out by cellular automata with the designed local rules in order to achieve the best edge detection performance. Simulation results showed that edges were a pixel width and edge positioning was accurate. As illustrated that the proposed algorithm was feasible. Furthermore, the proposed algorithm was higher than the Sobel and the Canny algorithm in detection performance.关键词：least squares support vector machine;cellular automata;edge detection;fitting;evolution rules
- 3646
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- 16
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- 5
发布时间：2023-11-14 - 摘要：Abstract:The signal-to-noise ratio of Charge Coupled Devices(CCD) output can be improved by the optimization of control parameters of Correlated Double Sampling (CDS). However, the control parameters of CDS of high-speed CCDare difficult to determine from experiments. An adaptive algorithm was proposed to get a better signal to noise ratio of CCD output. With fixed target and exposure parameters, the CDS control parameters such as the width of reset pulse, the timing of noise sampling and data sampling were tuned. The images on all combination of the CDS control parameters were acquired. The square sum of the Tenengrad function of all pixels on each image was used to evaluate the quality of the image. The combination of three CDS parameters corresponding to the maximum sum was chosen as CDS control parameters, resulting the best signal-to-noise ratio of the CCD out. Finally, the algorithm was implemented in Field Programmable Gate Array (FPGA) and the experiments results showed that compared with the best image acquired without adaptive algorithm, the parameters of Edge Profile are improved from 507.4 pixels per PH to 763.8 pixels per PH, the parameters of MTF50 improved from 526.5 LW/PH to 937.8 LW/PH.It showed that adaptive algorithm can effectively improve the signal to noise ratio of CCD output.关键词：Charge Coupled Devices(CCD);Correlated Double Sampling(CDS);adaptive algorithms
- 3339
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- 16
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- 1
发布时间：2023-11-14 - 摘要：Abstract:Aiming at the gain, offset and time delay channel mismatches estimation problem of time interleaved ADC system, a high accuracy comprehensive approach based on least square was presented, which required no extra circuits and eliminated the limitation of channel number. Then Monte Carlo simulations were done to compare this approach with Cramer-Rao Lower Bound(CRLB). Finally, the estimation method was used to measure the channel mismatches of a real time interleaved 400 MSps/12 bit digitizer. Simulation and experiment demonstrated that the accuracy of the calculation method is high, and quantization error, spurious and harmonic distortion have little influence on it. This method can effectively obtain the channel mismatches of actual time interleaved ADC system.关键词：time-interleaved ADC system;channel mismatch;least square estimation;Cramer-Rao Lower bound
- 2980
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- 5274
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- 1
发布时间：2023-11-14 - 摘要：Abstract:A Fractional Fourier Transform domain receiver for Ultra-wideband system was proposed to avoid the restriction of the multi-path separation in the existing receivers. Chirp signals with concentration in Fractional Fourier Transform domain were used as pulse waveforms in the system designed, and the energy aggregation characteristic of Chirp signals was used to obtain the multi-path component by filtering in fractional domain. According to the time-shiftng property of Fractional Fourier Transform, the phase correction at the multi path positions of template signal was made by the phase correction factor in fractional domain, which was got from the estimated delay and the phase of the multi-paths in time domain. At last the demodulation was made, combining the received signal with the phase correction factor. The simulation results indicated that the proposed receiver could get the better BER performance than conventional receivers. Moreover, because the influence of inter-symbol interference was not serious, high data rate transmission could be achieved.关键词：Ultra-wideband (UWB);Fractional Fourier Transform (FrFT);receivers;phase information
- 2472
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- 16
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- 0
发布时间：2023-11-14 - 摘要：Abstract:The relative translational and rotational dynamic models were established to meet the requirement of spacecraft high-precision formation flight. Relative attitudes of master-slave spacecraft were expressed by multiplication cross and the error dynamic equations were set up, on which nonlinear dynamic model of 6 DOF (Degree of Freedom) was proposed. Based on this model, a sliding mode controller was developed to make the translational and rotation of spacecraft correctly track the desired state trajectory and the system was showed as uniform asymptotic stability by Lyapunov theory. Simulation results indicated that the designed controller can guarantee the closed loop system to be uniform asymptotic convergence (UAC). The proposed model and the controller provide a useful theoretical reference for spacecraft formation applications of on orbit service etc.关键词：spacecraft;DOF;sliding mode control;quaternion
- 3145
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- 12
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- 0
发布时间：2023-11-14 - 摘要：Abstract:The decentralized state feedback control was studied for a kind of nonlinear interconnected systems with time-varying delay in both states and inputs. The delay-dependent stabilization sufficient conditions were derived for the whole close-loop fuzzy interconnected systems, by introducing a new Lyapunov functional. The corresponding decentralized fuzzy controller was gotten by using the parallel distribute compensation scheme and solving a set of linear matrix inequalities (LMIs). Both the theory analysis and simulation example showed that the interconnected systems are getting stable under the action of the designed controller.关键词：delay systems;fuzzy control systems;fuzzy bilinear model;nonlinear interconnected systems;decentralized control
- 2298
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- 4
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- 0
发布时间：2023-11-14 - 摘要：Abstract:The static and couple separation swing frame is a crucial technology of double-plane vertical dynamic balancing machine. In order to effectively separate the static and couple vibration in structure, a new swing frame is introduced which is based on the analysis static and couple separation property of traditional vertical dynamic balancing swing frame, it can eliminate the impact of couple on the horizontal movement of spring board by adopting cross spring pole, through the establishment of vibration equation, the vibration property of statics and couples movement is discussed, the influence factors of static and couple separation is analyzed. The experimental results show that the impact of couple on horizontal movement of the swing frame is litter, it can achieve effectively separation of static and couple movement, and eliminate the impact of couple unbalance on static unbalance, so it is far better than traditional swing frame structure.关键词：vertical dynamic balancing;static and couple separation;swing frame
- 2170
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- 6
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- 4
发布时间：2023-11-14 - 摘要：Abstract:Abstract: According to the perturbation problem of system parameter and controller in active suspension, H2/generalized H2 optimal control method based on static output feedback was discussed. The existence condition and design approach of non-fragile controller were presented via a set of bilinear matrix inequalities. Taking half-car model as example, non-fragile active suspension was designed using suspension deflection, which demonstrated its robustness and non-fragility by analyzing it from frequency domain and time domain. Finally, real-time simulation experiment based on dSPACE was made to validate the proposed method.关键词：Active suspension;Non-fragile;H2/generalized H2;dSPACE
- 3053
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- 12
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- 1
发布时间：2023-11-14 - 摘要：Abstract:abstract: rolling-cut bilateral shear is a kind of shearing structure, which works on both sides of steel plates continuously advancing with rated width. In order to realize pure rolling-cut shearing, through analysis of shearing-cut mechanism in space of a new model of rolling-cut bilateral shear and kinematics, by simplifying rolling-cut bilateral shear which comes out the simplified model based on linkage structure and applying plurality & matrix to the establishment of kinemics model of linkage structure, programming relevant functional simulation module, adopting SIMLINK for simulating the kinematics, all these are provided as a foundation of the design, analysis of control principal, and using in practice of shearing-cut mechanism.关键词：rolling-cut bilateral shear linkage structure kinematics simulate
- 2584
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- 8
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- 8
发布时间：2023-11-14
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