最新刊期
卷 43 ， 期 3 ， 2011
- 摘要：Abstract:A new plug arrangement,which was a combination of vertical gradually contracted plug and venturi plug as well as horizontal gradually contracted plug,was proposed for meeting the requirement of energy dissipation of plug discharge tunnel.The plug discharge tunnel with high head,large flow rate and low tailwater lever was reconstructed from a diversion tunnel.Then the RNG k-εtwo-equation model for turbulent flow and the VOF method were applied to simulate the turbulent flow in the plug discharge tunnel. The distribution of some important hydraulic characteristics was obtained, such as pressure, velocity, and energy dissipation rate. Moreover, parts of the calculations were compared with the experiments．It was concluded that the strong turbulence, strong shear jet and large-scale vortex flow in the pressure plug discharge tunnel could be simulated. And the new plug arrangement remarkably enhanced the efficiency of energy dissipation due to the strong turbulence taking place in the plug discharge tunnel.关键词：plug discharge tunnel;Energy dissipation;numerical simulation;hydraulic characteristics
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发布时间：2023-11-14 - 摘要：Abstract:In order to study the dam break flow in mountain river, SPH method was used to solve the dam break flow model based on the two dimensional shallow water equations. Since the Lagrangian SPH method has good stability and accuracy in dealing with convection dominated problems and is meshfree method, there is no need to divide the grid and to determine the wet-dry grid, therefore it well resolves the issues that mountain river dam break flow velocity is acute, water level range is large, moving boundary changes frequently, and the calculation region is difficult to determine. The model was used to simulate the mountain river dam break flow and preliminarily represents the dam break flow process. The analysis showed that the simulation results are reasonable and the SPH method is feasible to simulate the dam break flow.关键词：mountain river;shallow water;SPH;dam break
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发布时间：2023-11-14 - 摘要：Abstract:In order to propose a scientific and reasonable, simple and intuitive， and universal common model for the assessment of ground water quality, an exponential universal formula of power function in logarithm form suitable for multi-indexes was presented by setting up normalized transform for ground water indices. Particle Swarm Optimization (PSO) was used to optimize the parameters in the presented formula. The presented formula was used and compared with some methods in several evaluating cases. The results showed that the formula is free from the restrictions of the kinds and numbers of indices, which has generality and practicality, and provides a new universal and simplified approach to the water quality assessment.关键词：surface water;water evaluation;power function in logarithm form;exponential formula;universal formula;particle swarm optimization;parameter optimization
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发布时间：2023-11-14 - 摘要：Abstract:In order to obtain the dynamic response of defective large-diameter pipe pile in low strain integrity testing when subjected to transient concentrated load, a computational model and wave equation of large diameter pipe pile with variable wave impedance were established based on radial invariability assumption. The analytical solution of wave equation in frequency domain was obtained by Laplace transformation method. The dynamic responses in time domain were obtained by Fourier inverse transformation. The results of analytical solution were compared with that of 3D finite element method and 1D wave theory. The results indicated that the results of analytical solution well matched the 3D-FEM results. The velocity responses at 90°point calculated by 3D-FEM, analytical solution and 1D wave theory had little difference. The dynamic responses at different points on top of the pile showed that the arrival time of incident wave crests varied with radius angle. The smaller the radius angle, the earlier the arrival time. The arrival time of defect reflected wave crests was different among different points when depth of defect was not very deep. However, the difference was decreased when the defect was deeper. The high-frequency interference was the least at 90°point. The results of the analytical solution could well meet the measured results.关键词：large-diameter pipe pile;low strain integrity test;dynamic response;three dimensional effects;analytical solution
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发布时间：2023-11-14 - 摘要：Abstract:Due to the lack of hydrological information, the river roughness calibration algorithm usually is unstable, and the calibrated roughness may deviate from the true value seriously. In order to treat this problem, a model, which utilized the prior information to regularize the under-determinate inverse problem, was proposed. The method could improve the stability and reliability of inverse solution. In this inverse model ,both the error minimization and the empirical information were took account of. A river network case was used to test the effectiveness of the model. Its numerical stability, uniqueness of solution and reliability of results were discussed. At last, this model was applied in the real case of creek Kootenai. The result of these cases showed that the present model can calibrate river roughness effectively with high numerical stability and reliable results.关键词：river roughness;prior information;inverse model
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发布时间：2023-11-14 - 摘要：Abstract:Creep deformation is an important feature of high rockfill dams. Excessive settlement may endanger the stability of the dam or impair its normal operation. 3D FEM analysis based on power function creep constitutive model was used to predict the long term deformation of a 300 m high rockfill dam named Shuangjiangkou. Furthermore, a preliminary attempt was made to study the impact of scale effect on the long-term deformation of high rockfill dam. It was demonstrated that the deformation of Shuangjiangkou core rockfill dam becomes stable 3 years after full-filling, and under control. The scale effect research indicated that the specimens for laboratory testing have smaller long-term deformation than the real rockfill, which will influence the precision of numerical simulation.
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发布时间：2023-11-14 - 摘要：Abstract:Based on five-order Hermite interpolation and Galerkin weighted residual method, a new universal time finite element method was proposed to obtain structural dynamic response. This method was characterized as a highly stable, accurate, reliable and no need of complicated middle computational procedure. Besides, the method was a real time finite element method, which acquired structural dynamic response in all time domains according to the basic rules of finite element method. The satisfactory results of two typical examples validated the accuracy and reliability of the method.关键词：dynamic response;universal time finite element method;five-order Hermite interpolation
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发布时间：2023-11-14 - 摘要：Abstract:The physical properties, swelling-shrinkage characteristics and shear strength of an expansive soil modified with waste tire rubber particles were studied.The expansive soil used was obtained from Jingzhou, Hubei Province, China. The test results showed that when the mass fractions of rubber particles was under 23%, the liquid limit and plastic index of the modified expansive soil increased with the increment of mass fractions of rubber particles，while the plastic limit had little change. Compared with the unmodified expansive soil, the maximum dry density of the modified expansive soil decreased and the optimum water content was almost unchanged, the cohesion and the shear strength of the modified expansive soil decreased clearly, but the shear strength and the internal friction angle of the modified expansive soil had little change with the increment of mass fractions of rubber particle. The swelling-shrinkage characteristics of the modified soil were significantly weakened. Moreover, the best modified effect was obtained under a mass fraction of waste tire rubber particles of 23%.关键词：waste tire rubber particles;expansive soil;modifying;swelling-shrinkage characteristics;shear strength
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发布时间：2023-11-14 - 摘要：Abstract:Compressive properties of concrete containing Ground Granulated Blast Furnace Slag(GGBFS) reinforced by polypropylene fibers were investigated on Φ101.6 mm×203.2 mm cylindrical specimens. Parameters under investigation were axial compressive strength, static elastic modulus, and poisson’s ratio. The instrumentation used comprised a compression testing machine, a compressometer, bearing plates, a LVDT setup connected with a computer data acquisition system, and data transfer devices. Results showed that polypropylene fibers decrease the compressive strength and static elastic modulus but increase poission’s ratio, while slag improves the compressive strength and static elastic modulus. The compatibility of acid polycarboxylate superplasticizer with cement is good. The Composition effects of polypropylene fibers, slag and acid polycarboxylate superplasticizer are significant. A new constitutive formulation was proposed based on experimental data, which is more suitable for polypropylene fiber reinforced concrete containing slag to describe the relationship between static elastic modulus and compressive strength. Scanning Electron Microscope(SEM) micrographs revealed that the resulted hydrated products have different morphologies, which influences the compression properties.关键词：composites;concrete;compressive strength;static modulus of elasticity
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发布时间：2023-11-14 - 摘要：Abstract:Based on the genetic algorithm of inverse problem and the 3-D FEM, non-adiabatic temperature rise test of rectangle with cooling pipe based on actual project was done to identify adiabatic temperature rise, heat exchange coefficient and so on. The comparison results showed that different temperature control parameters can indicate the real thermal properties of concrete in site. The method of the combination of test and reverse analysis is simple and economical, and many temperature control parameters can be obtained simultaneously, so it has high engineering values in the future.关键词：reverse analysis;concrete test;water pipe cooling;temperature control parameters;adiabatic temperature rise
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发布时间：2023-11-14 - 摘要：Abstract:A reasonable and feasible nonlinear way was used to analyze whether surrounding rock steady based on monitoring result. Not only was determined potential fracturing section and influenced section, but also displacement of surrounding rock where all measurement points of three apparatuses located in 20 days was forecasted by qualitative analysis of R/S method and quantitative prediction of BP networks. Some problems, including whether potential dangerous section cracks, exact time of fracturing and crack depth, were investigated. Time space criterion on surrounding-rock fracturing was presented. It was shown that the section where displacement-time series satisfy Δ<0 is possible fracturing one.The occurrence of Δ positive maximum of continuous displacement-time series in fracturing section indicates the alarm of forthcoming fracturing of surrounding rock, and the appearance of minus maximum is the possible fracturing time.关键词：displacement of surrounding rock;displacement-time series;catastrope theory;R/S method;BP networks
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发布时间：2023-11-14 - 摘要：Abstract:Based on the silicate content in geothermal water，adjusting the addition amount of scale inhibitors can prevent the formation of silicate scale on the surface of returning pipes in the deep underground. Consequently, an automatic system for determining the high-concentration silicate was proposed. This analytical process was as follows. First, NaOH solution mixed with a sample of geothermal water in premixing coil to make polymeric silicon translate into active silicon like H4SiO4 and SiO32-.And then volumes of the sample and a chromogenic agent were measured simultaneously and automatically, injected into two carriers, merged and reacted in a reaction coil in manner of the reagent enwrapping the sample. Formed product entered into a masking coil of eliminating interferences and a flow detector in turn, and was determined under the wavelength of 405 nm. Optimized conditions were as follows: Concentrations of ammonium molybdate, NaOH and oxalic acid were 2% (w/v), 0.1 mol·L-1,and 1% (w/v), respectively,lengths of premixing, reacting and masking coils were 350, 510, and 300 cm, respectively; the total flow rate was 5.0 ml· min-1.This method only consume 25 μl of the sample and 115 μl of the chromogenic reagent per time, its determination range was 25~800 mg·L-1(SiO2),relative standard deviation was less than 0.81%, recovery ranges were 96.2%~117.0%, about 180 samples can be analyzed per hour. Merits of the system were good reproducibility, high analysis speed, less test cost, and not needing to predilution for determination of high concentrations silicate. The most important was that it realized continually monitoring of the high concentration of silicate in the geothermal water.关键词：flow injection analysis;spectrophotometry;high concentrations silicate;geothermal water
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that MnS2O6 formed in the process of flue gas desulfurization and denitration with pyrolusite slurry will lower the purity of byproduct, the decomposition characteristics of MnS2O6 in liquid phase were studied. The decomposition rate of MnS2O6 was measured instead of the formation rate of SO2 based on the decomposition products of MnS2O6 and iodometry principle for SO2 determination. Factors affecting decomposition rate were investigated, which included manganese dithionate concentration, sulfuric acid concentration, manganese sulfate concentration, manganese nitrate concentration and reaction temperature. Experiment results indicated that the MnS2O6 decomposition rate increases with the increasing of manganese dithionate concentration, sulfuric acid concentration and reaction temperature, but decreases with manganese sulfate concentration increasing, and is independent of manganese nitrate concentration. The reaction is 0.8 order for manganese dithionate and 1.2 order for sulfuric acid, the activation energy is 96.9 kJ·mol-1 and the pre-exponential factor is 1.61×10^10 s-1.The study provided theoretical basis for the removal of MnS2O6 in the absorption solution of flue gas desulfurization and denitrificaiton with pyrolusite slurry.关键词：pyrolusite slurry;desulfurization and denitration;manganese dithionate;decomposition rate;reaction kinetics
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发布时间：2023-11-14 - 摘要：Abstract:The super-fine down powder was modified by 3-mercaptopropyl trimethoxysilane(KH590), phenyl isocyanate(PI) and octadecyl isocyanate(ODI), respectively. The modified super-fine down powder was characterized by Fourier transform infrared (FTIR) spectrum, Thermogravimetry (TG), water contact angle, moisture absorption. The results showed that PI and ODI are chemically bonded to the surface of down powder. The down powder modified by PI and ODI has good hydrophobic property and excellent moisture absorption capacity. The initial temperature of thermal degradation for the modified down powder increases by about 4~7 ℃. However, the modification of KH590 has no evident influence on the down powder. The modification of PI and ODI could improve the surface property of down powder and the non-polar matrix (e.g. polypropylene, et al) and increase the moisture absorption of non-polar fiber. This modification could also favor the thermal process of the relevant composites.关键词：down powder;surface modification;hydrophobic property
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发布时间：2023-11-14 - 摘要：Abstract:Using WO3/ZrO2 solid superacid as catalyst, the performance of H2O2/WO3/ZrO2 system on the catalytic oxidative deep desulfurization of diesel were studied. The technical parameters,such as the amount of oxidant,the dosage of catalyst,the reaction temperature and the reaction time were investigated.Furthermore,the power ultrasound was introduced to enhance the process.The effects of ultrasonic frequency,intensity and time on the desulfurization were investigated.The experiment results revealed that under the optimum oxidative desulfurization conditions of oxidation temperature 60 ℃，reaction time 90 min，the oxidant dosage V(H2O2)∶V(diesel)= 1∶10 and the catalyst dosage 15 g/L diesel，after extraction of oxidized diesel the removal efficiency of sulfur compounds was up to 91.0%.The oxidation time with ultrasound were shortened to 40 min and the removal efficiency of sulfur compounds was increased to 95.6%.关键词：diesel;oxidative desulfurization;solid superacid;extraction;ultrasound
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发布时间：2023-11-14 - 摘要：Abstract:The treatment of mature leachate from municipal landfill was investigated by using a system of a two-stage up-flow anaerobic sludge blanket (UASB)，anoxic-oxic (A/O) reactor and a sequencing batch reactor (SBR).During operation,denitrification took place in the first stage UASB (UASB1).The effluent nitrite and nitrate of UASB1 was further removed in the second stage UASB (UASB2) by using the residual chemical oxygen demand (COD).And then the denitrification was accomplished by using the residual COD in the anoxic zone of A/O reactor.And the ammonium nitrogen was removed via nitrite in the oxic zone of A/O reactor.At last,the nitrite and nitrate which was produced by the nitrification was removed in SBR.The experiment experienced three stages during 140 d.Raw leachate was pumped in the system at the first stage（20 d).The raw leachate mixed with domestic wastewater in the ratio of 1 was pumped in the system at the second stage（60 d) to achieve the partial nitrification and denitrification stably.The raw leachate mixed with the effluent of A/O reactor in the ratio of 1 was pumped in the system at the last stage（60 d),and partial nitrification and denitrification was achieved stably.The operational results of 140 d were that the total nitrogen（TN）and ammonium nitrogen concentrations of influent were about 2 300 mg·L-1 and 2 000 mg·L-1,respectively.The partial nitrification was achieved stably in the A/O reactor at the second stage and the third stage.The nitrite accumulation ratio was 70%～88%.The nitrite and nitrate which were produced by the nitrification in the A/O reactor could be taken out relative completely in SBR.The ammonium nitrogen concentration of final effluent was less than 2 mg·L-1.The TN concentration of final effluent was 18～20 mg·L-1.The ammonium nitrogen and TN removal efficiency were 99.7% and 98%,respectively.关键词：mature landfill leachate;partial nitrification;UASB
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发布时间：2023-11-14 - 摘要：Abstract:ABS/PET/APP mixtures with different synergic agents (SA) were prepared for investigating the effect of SA (2, 2’-bis (2-oxazoline) (BOZ), thermoplastic phenolic resins (TPPF), manganese dioxide, montmorillonite (MMT), zinc borate, 4A Zeolite, zinc oxide (ZnO), and attapulgite) on the flame retardancy of mixtures, and the thermal degradation and charring of ABS/PET/APP was analyzed. It was concluded that a novel intumescent flame retardant containing APP (acid source and a blowing agent) and PET (carbon source) was obtained because APP mainly catalyzed PET to degrade into charring in ABS/PET/APP mixture on heating. The flammability of ABS/PET/APP mixtures with different SA was measured by the limited oxygen index (LOI) and UL-94 tests. Except for ABS/PET/APP/attapulgite mixture, ABS/PET/APP mixtures with other SA all passed the V-0 rating in UL-94 tests, the LOI of which was improved compare with ABS/PET/APP mixture. Thermo-oxidative degradation behaviors of mixtures were analyzed by thermal gravimetric analyzer (TGA), which showed an increasing char yield of ABS/PET/APP mixtures due to the addition of SA. And scanning electron microcopy (SEM) showed the denser carbon layer formation on the surface of ABS/PET/APP mixtures with SA (except for attapulgite) after burning.关键词：ABS/PET;APP;synergic agents;intumescent flame retardant
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发布时间：2023-11-14 - 摘要：Abstract:AgGa0.6In0.4Se2 polycrystalline materials were synthesized by mechanical and temperature oscillation method in a two-layer quartz ampoule using high-purity elements according to the stoichiometry with an excess of 1% Se. The melting and freezing points of the materials were determined to be 804.3 ℃ and 775.6 ℃, respectively, through thermal analysis. A crack-free AgGa0.6In0.4Se2 crystal of Φ20 mm×60 mm was grown by modified vertical Bridgman method in a two-layer carbon coated quartz ampoule with specially designed seed pocket. The crystal was with chalcopyrite structure. The lattice constants of aand cwere 0.602 32 nm and 1.118 33 nm, respectively. The reflection faces and cleavage face were (112) faces. A wafer with 2 mm thickness was cut from the as-grown crystal. Its transmittance was up to or more than 60% in a range of 0.836~19.65 μm. Its calculated band gap was about 1.48 eV. The results proved that the grown crystal was of integral structure and high quality, and it can be used for fabrication of mid-far infrared nonlinear optical devices.关键词：AgGa1-xInxSe2;single crystals;characterization;optical materials
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发布时间：2023-11-14 - 摘要：Abstract:Effective thermal conductivity of porous media was investigated by experimental and numerical approaches. Fractal pore network model, which was the combination of fractal theory and pore network model, was used to research the effective thermal conductivity of porous media. The numerical results agreed well with experimental ones, which indicated that the fractal pore network model is suitable for researching effective thermal conductivity of porous media. The effects of pore-throat ratio, coordination number, vertical throat proportion, throat length, porosity, thermal conductivity of matrix and fluid on the effective thermal conductivity of porous media were studied. It was revealed that vertical throat proportion can enlarge the thermo-resistance of porous media and decrease its effective thermal conductivity. If thermal conductivity of matrix is larger than that of fluid, the effective thermal conductivity of porous media increases with the increase of pore-throat ratio and decrease of throat length. When the number of parallel throat is fixed, the effective thermal conductivity of porous media increases with the decrease of coordination number. On the contrary, when the number of vertical throat is fixed, the effective thermal conductivity of porous media increases with the increase of coordination number.关键词：porous media;effective thermal conductivity;fractal pore network model
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发布时间：2023-11-14 - 摘要：Abstract:The effect of TiO2 content on crystalline structure and constituent phases, micro-harness, friction-wear performance and wear mechanisms of air plasma sprayed Al2O3 based coatings was studied. Three variations of 0, 13% and 40% for TiO2 content in weight ratio percentage were selected, namely, pure Al2O3, Al2O3-13%(wt)TiO2 and Al2O3-40%(wt)TiO2 ceramic coatings. XRD was used to analyze crystalline structure and constituent phases of coatings and Vickers micro-hardness tester to measure micro-hardness of coatings. An SRV wear tester was employed to evaluate friction-wear performance of the coatings under dry condition using two types of wear counterparts with extremely discrepant material nature, i.e. AISI52100 steel ball and Al2O3 ceramic ball. Wear mechanisms were examined with SEM. The results showed that the hardness of coatings decreased with the increase of TiO2 content. The Al2O3 based ceramic coatings showed the same trend irrespective of material nature of wear parts, indicating that the wear resistance decreased with increasing TiO2 content. No strengthening in wear performance was obtained with Al2O3 based coatings with TiO2.关键词：ceramic coatings;aluminum oxide;titanium oxide;friction-wear performance;micro-hardness
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发布时间：2023-11-14 - 摘要：Abstract:On a new torsional wear tester, the torsional wear tests of bovine hip joint articular cartilage flat against Al3O2 femoral heads(with diameter of 28 mm) were carried out with various angular displacement amplitudes ranging from 0.5°to 5°and imposed loads ranging from 5 to 50 N. Based on the analysis of the frictional kinetics of torsional fretting, the wear were observed by electron microscope(SEM) and Hematoxylin-Eosin(HE) stain, and the damage characteristics of joint articular cartilage also were discussed. The results indicated that two kinds of T-θ curves(i.e. parallelogram and elliptical curves) were observed during the process of torsional wear. Parallelogram mainly occurred at slip status(SS) and elliptical loops appeared at partial slip status(PSS). The damage of bovine hip joint articular cartilage under torsional fretting PSS was very slight and the folding was the main damage. Under SS, along the radial direction, the wear scar could be divided to three zones, i.e. the adhesive zone, folding and micro-crack zone, and delamination zone, respectively. The wear mechanism performed as delamination and micro-cracking.关键词：friction and wear;torsional wear;articular cartilage;wear mechanism
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发布时间：2023-11-14 - 摘要：Abstract:To effectively predict the protein-protein interactions, an ensemble learning with artificial neural network and supporting vector machine as the individuals was used, and the feature selection of protein sequence was indicated by auto covariance and dipeptide composition.The prediction accuracy and AUC reached 92.16%, 94.38% and 0.972 5,0.981 5, respectively. A comparison among artificial neural network, supporting vector machine and ensemble learning showed that the ensemble learning revealed more superior performance than the others and can improve the prediction accuracy while avoiding the instability of prediction caused by sampling learning.关键词：ensemble learning;artificial neural network;support vector machine;protein-protein interactions
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发布时间：2023-11-14 - 摘要：Abstract:The solution of the following programs:while(x∈Ω) do {x:〖KG-*3〗=f(x)} end, which was called as Non linear Programs over intervals,was presented,where x was a program variable,Ω(Ω=(a1,b1‖∪‖a2,b2‖∪…∪‖an,bn)，while ‖∈{(,),［,］}，n∈N*) was a set of intervals,and f was a polynomial function.It was proved that, when φ(b1)φ(a2)>0,…,φ(bn－1)φ(an)>0（φ(x)=f(x)－x）,the necessary condition for non-termination of the above program was that there existed fixed point within Ω or on the boundaries of Ω.Furthermore,if there were fixed points within Ω,the above condition was not only necessary but also sufficient.When all fixed points were on the boundaries of Ω,the corresponding necessary and sufficient condition of nontermination was established by introducing more constraints,and a decision algorithm for continuous polynomial function was presented.关键词：program verification;computer algebra;nonlinear program;fixed point
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发布时间：2023-11-14 - 摘要：Abstract:To avoid the drawback of histogram shifting algorithm, which has lower embedding capacity and is not suitable for color images, a reversible information hiding algorithm for color images based on prediction error difference histogram shifting was proposed. In addition to the difference between random two components, the algorithm also added the third component to calculate difference value, according to the relationship between prediction errors, the difference was divided into five kinds, so as to effectively reduce the difference value to improve the embedding capacity and stego-image quality. The embedding scheme expanded pixels value to embed information, and utilized the expandability of pixels value to locate pixels which can not be expanded, and embed a few flag information instead of overflow location map, with two steps embedding method, avoid using worst test method to determine expandability of pixels value, therefore the quantity of auxiliary information was decreased. Experimental results showed the embedding capacity and the quality of stego-image are significantly improved, when compared with other new or classical reversible embedding algorithms.关键词：reversible data hiding;difference histogram shifting;prediction error difference;histogram shifting;expandability of pixels value
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of losing texture information in the existing image denoising algorithms, fractional calculus based on the definition of Riemann-Liouville was applied to image denoising. The structures and numerical calculation methods of the fractional integral masks on eight directions were given. Then, the corresponding circuit model was proposed. The qualitative and quantitative analysis of the simulation experiments proved that this method could be applied to both grayscale images and color images. And through this method, the fractional integral operation could be completed one off, the noises could be removed in high precision and the texture information of the images could be held on. The method could be used to image denoising in real time.关键词：fractional integral;fractional mask;image denoise;texture preservation;fractional interpolation
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the SNR of low-dose CT image, a novel adaptive noise reduction algorithm for low-dose CT sinogram was proposed based on the MCMC method. The algorithm adaptively estimated the smoothness parameter of the priori model and the noise variance, and then utilized the conditional expectation of the noisy sinogram as the restored sinogram. The parameters were estimated by an EM algorithm and in this procedure a Gibbs sampler was used to draw samples from the local posterior distribution to handle the complicated computation problem, and then the Gibbs sampler was used once again to compute the conditional expectation of the noisy sinogram. The effectiveness of the proposed algorithm was validated by both computer simulations and experimental studies. The gain of the proposed approach over other methods was quantified by noise-resolution tradeoff curves.关键词：low-dose X-ray CT;noise reduction;parameter estimation;MCMC algorithm;EM algorithm
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发布时间：2023-11-14 - 摘要：Abstract:In order to increase image registration accuracy in change detection, from the view of multi-scale fusion,a method was proposed for region variation detection,which applied the multi-scale analysis to remote sensing image.First of all, Wavelet transform was adopted to decompose original images, then Mahalanobis distance decision function was used to detect the changes of different scale images, and finally Markov random field was applied to fuse different scale change detection results. Since Markov random field fusion method took full account of the correlation between the adjacent pixels and the links of different scale change detection results, the fusion results were more accurate and practical. The testing results showed that this method is effective and robust.关键词：change detection;multi-scale;Mahalanobis distance;Markov random field;image fusion
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发布时间：2023-11-14 - 摘要：Abstract:Based on immune danger theory, a danger zone generating mechanism, a danger zone radius calculation method and the calculating formula of the danger signals signal_0 by antigen necrosis and the antigen detected danger signals signal_1 were given according to the intrusion detection application.In addition, a detection algorithm in the danger zone was presented according to the signal_0 and signal_1.The experiments showed that the proper selection of the dangerous area radius is helpful for the improvement of the efficiency of intrusion detection system, and make both the false negative rate and false detection rates remained at a lower level.关键词：danger theory;danger zone;consanguinity;network intrusion detection
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发布时间：2023-11-14 - 摘要：Abstract:Aiming at feature extraction for QAR data, a method of maximum margin discriminant analysis for one-class classification was given, and by adding orthogonality restriction on it, a maximum margin feature extraction method was put forward.For the large sample learning problem of QAR data, a modified representation for maximum margin discriminant analysis for one-class classification with orthogonality restriction was presented, by transforming the modified representation to minimum enclosing ball problem. Finally a maximum margin method of feature extraction based on minimum enclosing ball problem with orthogonality constraints was proposed, which had good performance in the real dataset from a type of aircraft, so it effectively solved the large sample feature extraction problem for QAR data.关键词：air traffic;feature extraction;minimum enclosing ball;quick access recorder
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发布时间：2023-11-14 - 摘要：Abstract:GPS communication stoppages could disable navigation systems. In order to obtain navigation fault-tolerance and to optimize systems, a high available distributed navigation algorithm was proposed with access vestige data fusion. Its main idea, processing models, data structures and working flows were presented, and Monte Carlo method was utilized to evaluate these passable accesses. Further, a two-dimension overlay space was constructed to deal with matching access information and navigation requires. At last, the algorithm performance was analyzed in a series of simulation. Simulation results showed that this algorithm has better fault-tolerance, higher suitability and faster response delays than the traditional ones.关键词：navigation;vestiges;information fusion;fault-tolerance
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发布时间：2023-11-14 - 摘要：Abstract:Since clonal selection algorithm lacks of adaptive capacity when solving multimodal problems, a novel adaptive immune algorithm，which was based on immune danger theory, immune network and clonal selection theory, was proposed to emulate the entire immune mechanisms and to enhance the performance for complex multimodal problems. The environment of antibody population and the corresponding danger signal of each antibody were incorporated into the process of immune response, which preserved the diversity of antibody population and then alleviated the premature of the algorithm to some extent. The algorithm was proved theoretically to be convergent with Markov chain model. Simulation results on the classical benchmark functions showed that, compared to clonal selection algorithm, this algorithm has good performance of global convergence and multimodal searching ability, and has a fast convergence speed with good quality of solution.关键词：danger theory;immune network;artificial immune systems;evolutionary algorithms
- 2806
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- 4
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- 3
发布时间：2023-11-14 - 摘要：Abstract:Feature extraction was studied. First, a new feature, compactness of power spectral, was brought forward. This feature extracted from frequency field was robust and not sensitive to noise. It needed no prior information. Then some difference processes of signal phase character were done and an improved parameter unwrapped difference phase normalized variance was given. This parameter did not rely on frequency and was more practical. The detection method of single frequency component was also re-defined, and the new extraction method after this re-definition was more robust and discriminable. At last signal classification system was designed, and the classification of AM, SSB, 2FSK, 4FSK, 8FSK, BPSK, QPSK and 8PSK was completed. The experiment simulation result showed that whenSNR of signal was more than 10 dB, the recognition accuracy is more than 92%.关键词：modulation classification;feature extraction;unwrapped difference phase normalized variance;single frequency component
- 2063
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- 14
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- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to get uniform ultrasound images with clear structure, a novel and adaptive ultrasound attenuation compensation method based on image texture analysis was investigated. The attenuation process of acoustic signals transmitted in soft tissue was modeled, with the introduction of tissue attenuation coefficient and depth dependent attenuation compensation. After giving the 2-D co-occurrence matrices and 1-D sum and difference histograms based image texture parameters, the basic idea to precisely estimate tissue attenuation coefficient and properly compensate the attenuated ultrasound power was proposed. Algorithms were verified both in tissue-mimicking phantom with known attenuation coefficient and in vivo ultrasound images acquired from a clinical ultrasound system. Testing results presented accurate tissue attenuation coefficients and also uniform attenuation compensated ultrasound images.关键词：ultrasonic imaging;attenuation;gain control;image analysis;Texture
- 3000
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- 26
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- 1
发布时间：2023-11-14 - 摘要：Abstract:To obtain grid-scroll chaotic attractor under the frame of the three-order Colpitts oscillator model, based on the formation mechanism of chaotic attractor, an approach for generating a grid scroll chaotic system was presented by introducing two unit sawtooth wave functions to modify the model equations from which the index-2 equilibrium points with grid distribution can be formed by the modified three-dimensional system and a (2M+1)×(2N+1)-grid scroll chaotic attractor was evolved. By using conventional dynamical analysis methods, the dynamical behaviors of the proposed system were analyzed. With the help of discretization, digital circuit implementation and corresponding experimental verification were performed based on a microcontroller. The experimental outputs were similar to those of numerical simulations, from which the feasibility and realizability of the generating grid scroll chaotic attractor under the frame of Colpitts oscillator model were illustrated.关键词：chaotic system;sawtooth wave function;Colpitts oscillator;microcontroller
- 2819
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- 8
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- 2
发布时间：2023-11-14 - 摘要：Abstract:To solve the problem that the generators can improve their market power in PAB auction repeatedly by auction learning, based on the PAB auction mechanism in the electricity market, the random matching mechanism of optimal probability was proposed, an optimal probability distribution method was developed to minimize the average transaction price，and the information disturbance of probability was used to affect the learning ability of generators and weaken theirs market power behavior. Simulations showed that compared with the price level matching mechanism and completely random matching mechanism, random matching mechanism of optimal probability can affect the learning ability of generators more effectively.关键词：information disturbance;random matching of probability;signal transmission;Pay As Bid(PAB);electricity market
- 3017
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- 0
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- 2
发布时间：2023-11-14 - 摘要：Abstract:For large scale AC/DC transmission schemes with multiple series capacitors compensations, how to assess the risk of subsynchronous resonance (SSR) rapidly and efficiently is of great practical significance to ensure that the grid operates safely and stably. Taking the meeting summer peaks in 2009 of China Southern Power Grid as the practical project, by combining a static equivalence method, modified two point loadflow calculation which takes resistance into account, with frequency scanning method, the rapid risk assessment of SSR caused by mutiple series capacitors compensations in large scale power grid was realized. Then by using PSCAD/EMTDC, the detailed electromagnetic transient model (of course including the shaft model) was established to do the fault simulation certification aiming at generating units which have the risk of SSR. The analysis results showed that this rapid assessment approach works well and has strong practicability.关键词：Subsynchronous Resonance(SSR);series capacitor compensation;rapid risk assessment of SSR
- 3118
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- 0
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- 1
发布时间：2023-11-14 - 摘要：Abstract:A new hydraulic system was built in order to recycle the potential energy of forklift.The work process of the new system was analyzed after expounding the work principle. Compared with current hydraulic system, throttle loss decreased because of the use of a new secondary regulation component Hydraulic Transformer (HT). The mathematical models of hydraulic transformer and hydraulic accumulator were established and the characteristic relations among accumulator valid volume, accumulator efficiency and HT port plate control angle were analyzed. The difference of potential energy recovery style between new hydraulic system and current hydraulic system was concluded. The potential energyre recycled was educed in the condition of no-load, half-load and full-load. The result indicated that the ability of recycling potential energy is improved by new hydraulic system and recovery effect is significant with the increase of pressure ratio.关键词：forklift;hydraulic system;recovery of potential energy;hydraulic transformer;hydraulic accumulator
- 2966
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- 2
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- 0
发布时间：2023-11-14 - 摘要：Abstract:Feed rate’s effect on the stability of milling was absent in traditional two dimensional stability limit prediction diagrams. To address this issue, a new model of cutting force coefficients was proposed. This model was expressed by a quadratic polynomial equation using feed per tooth as its variable. For this purpose, central composite experiment with a set of feed rates generated by quadratic regression was designed and conducted. Milling force coefficients under certain cutting conditions were derived based on the measured milling force. The regression parameters were then estimated using least square method. The model reliability was verified by significance test. The model prediction performance was validated by comparing the prediction force with the measurement. Based on the proposed model of cutting force coefficients, the feed rate factor was introduced into the stability prediction, which converted the two-dimensional stability diagram into a three-dimensional one and revealed the nonlinear relationship among the rotational speed, feed rate and axial cut depth in the critical stability.关键词：milling force coefficients;feedrate;quadratic regress combination design;three-dimensional stability diagram
- 2354
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- 6
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- 2
发布时间：2023-11-14 - 摘要：Abstract:Based on the theory of thermal expansion deformation of metallic materials, extensional beam theory, non-uniform temperature distribution of the Euler-Bernoulli beam and Kirchhoff theory of plane-section assumption, a novel model was proposed to calculate the bending thermal deformation of lathe bed and upright column of double-column vertical NC gear hobbing machine.The research on the axial deformation and bending deformation of the upright column were also carried out by utilizing the deformation theory of the deformation element and equilibrium element Method. Compared the calculation results with the practical experimental values of the thermal deformation of the machine tool, it was shown that the relative error of the results was lower than 5%. The above analysis indicated the effectiveness and validity of the research method, which has great reference value and instructive significance for optimum structural design, cutting point position error prediction and compensation on double-column vertical NC gear hobbing machine.关键词：double upright column;NC gear hobbing machine;thermal deformation;temperature gradient;cutting point;tooth trace deviation
- 2485
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- 12
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- 3
发布时间：2023-11-14 - 摘要：Abstract:Since the psychological feelings of products are decided by the three dimensional form feature lines,a product form design method based on quantizing form feature lines was put forward.Based on the Kansei engineering technology,the form perceptual cognitive factors were quantified.Semantic differential, factor analysis and multiple linear regression methods were used synthetically to deal with product images data,then the relations between images and feature lines were determined.Operating product form feature lines helps to develop the product which meets user's perceptual image.The cell phone form was taken as an example to test the validity.关键词：Kansei engineering;form feature lines;images;form design
- 2474
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- 18
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- 2
发布时间：2023-11-14 - 摘要：Abstract:The hydraulic system of hydraulic rolling-shearer was designed according to rolling-shear principle. Based on rolling-shear equation,the position of cylinders was controlled by proportion servo valves and transducers to realize rolling-cut.Transfer function of whole hydraulic system was given by establishing three equations for it.The simulation for the positioning control effect of hydraulic cylinder was set up by Simulink,from which the scope of controlling parameters can be achieved,but overshoot vibration generated in the process of changing control parameters can not be detected directly from simulation,without proper adjustment in actual debugging process.The controlling of hydraulic system should have superior robustness and self adjustment ability to ensure relatively stable compensation accuracy under different circumstances.The position precision of cylinders and high-quality steel cross section of production prototype proved the designing validity of the hydraulic system.关键词：hydraulic rolling-shear;hydraulic system model;position control;simulation research
- 2881
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- 18
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- 5
发布时间：2023-11-14 - 摘要：Abstract:In order to meet the motion control requirements of high speed and high precision, a fast fouth-order trajectory planning and feedforward control algorithm was investigated. Due to the drawbacks of computation complexity and low efficiency residing in the existing algorithm, the whole computation process was revised. By pre-computing in classifying the trajectory, a large amount of useless computation, comparison and decision-making were avoided. The velocity and efficiency of the revised algorithm were greatly improved so that it is suitable for real time computation. The implementation aspects were also discussed, and the discretization error was analyzed and compensated. Finally the feedforward control structure based on the fouth order trajectory was set up. The simulation result showed the effectiveness and reliability of the algorithm proposed.关键词：fouth-order trajectory planning;point-to-point motion;feedforward control;error compensation
- 3287
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- 18
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- 1
发布时间：2023-11-14
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