最新刊期
卷 47 ， 期 2 ， 2015
- 摘要：Abstract:The overtopping of the landslide dams was studied by means of theoretical analysis and flume tests. The factors that impact the dam breach were discussed and the fundamental procedure of the dam breach development by overtopping was stated. A new concept “flow depth” d as well as the criterion d0/D90 was carried out to establish the scales for the flume model.Based on the similarity criterion derived,a series of flume experiments were conducted.The experimental result showed a general agreement with the prototype data which on some degree identifies the rationality of definition of the criterion in the present study.The results could be applied as reference for the subsequent relevant researches.关键词：landslide dams;overtopping;flume experiment;flow depth;similarity criterion
- 2063
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- 11
发布时间：2023-11-14 - 摘要：Abstract:Goose-head-shaped anabranching (GHA) river takes on extremely winding planform and periodical alternation of river regime.But the planform and fluvial features vary with individuals.To investigate the formation and evolution of GHA river,providing theoretical support to river regulation,the individual differences among GHA sub-reaches in the middle and lower Yangtze River and its causes were studied.Fluvial features of GHA sub-reaches as degree of bending,length of the evolutional cycles and extent of riverbed deformation were summarized.Major causes of the differences were revealed that alignment of the inlet nodes and intensity of water flow deflection bring about individual difference of the GHA channels.The larger the traverse angle of inlet-outlet nodes is,the wider the goose-head-shaped branch develops.The more intensely water flow deflects,the shorter the evolutional cycle is.关键词：goose-head-shaped anabranching river;river-valley geomorphology;individual difference
- 2942
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发布时间：2023-11-14 - 摘要：Abstract:To study the characteristics of rip current by intersecting wave on mild slope barred beach with rip channel,the experiment of rip currents by intersecting random wave on the mild-slope barred beach with rip channel was done.Rip currents resulted from the two intersecting wave trains produced by the reflection of obliquely incident waves on a vertical wall which stands perpendicular to the coastal line.The two intersecting waves were with the same amplitude and frequency,but the opposite angle. The results of the distribution of wave heights,setup and velocity measuring by ADVs near the rip channel were shown to analyze the characteristics of rip currents on barred beaches with rip channel of mild slope.Shoreward of the bars,the alongshore pressure gradients between the bars and channels owing to the stronger breaking on the bars drive feeder currents that converge at the channels and turn offshore as rip currents.关键词：rip currents;intersecting wave;sand bar;rip channel;pollutant emission
- 2155
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- 1
发布时间：2023-11-14 - 摘要：Abstract:The dam abutment rock samples of weak rocks and structural planes of Jinping I High Arch Dam were collected,the similar specimens were prepared,and the test conditions were determined through the analysis of characteristics of arch dam running environment.Then the triaxial compression tests and the water-rock coupling triaxial compression tests were conducted in the test system of rock mechanics MTS. Results indicated that the strength parameters f and c of Jinping arch dam abutment faults material and weak rock mass have significant hydraulic pressure weakening effect. In the strength parameters, the friction coefficient f changes a little while the cohesion c significantly decreases when the water pressure increases. Considering the combined effect of both strength parameters, under engineering condition of 10MPa normal stress and 3MPa water pressure, the average weakening rate of the anti-shear strength τ of the main faults f2、f5、f13、f14、f18 is at around 25%,and the average weakening rate of the anti-shear strength τ of the lamprophyre dike X and other weak rock mass is about 40%. This quantitative test results of weakening effect can provide an important scientific basis for the methods of geo-mechanical model test and numerical calculation to analysis and evaluate the stability of high arch dam.关键词：high arch dam project;weak rock and structural plane of dam abutment;stress field;seepage field;coupling interaction;weakening effect
- 2040
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- 2
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- 4
发布时间：2023-11-14 - 摘要：Abstract:In order to predict the initiation angles of cracks,a new yield criterion was established for geotechnical materials with small plastic deformation.According to this yield criterion,the radii of the plastic region around crack tips for mode Ⅰ crack,mode Ⅱ crack and Ⅰ-Ⅱ mixed mode crack were obtained,and the plastic regions under uniaxial tension and pure shear were analyzed.The results showed that loading conditions,crack inclination angles and material internal friction angles affect the plastic core regions significantly.Based on the assumption that cracks propagate along the shortest radius of the plastic core region boundary,a fracture criterion which can predict crack initiation angles was obtained.The pre-existing test results agrees well with this fracture criterion,and its prediction result is more precise than those by other criteria.关键词：yield condition;radius of core region;crack initiation angles;fracture criterion
- 2400
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- 2
发布时间：2023-11-14 - 摘要：Abstract:The equipment of large vibration compaction was designed to do large laboratory vibration compaction test under the condition of different water content and different soil-stone proportions with sandy soil,silt soil and low liquid-limit clay.The soil pressure was collected to calculate the dynamic Poisson’s ratio,and then the deformation capability in each direction of foundation mixture in different compactness was studied.The change rule of dynamic Poisson’s ratio in soil-stone mixture was revealed.The correlation analysis model of Poisson’s ratio in soil-stone mixture was built.Sensitivity analysis on change of shear wave velocity in soil-stone mixture caused by change of dynamic Poisson’s ratio was conducted.The results showed that the dynamic Poisson’s ratio had little influence on shear wave velocity in soil-stone mixture,while the field shear wave velocity test of soil-stone foundation was done.The correlation parameters of soil-stone mixture could be calibrated and determined by Poisson’s ratio in most compact condition under fixed water content and fixed soil-stone proportion.Then the model of correlating surface wave and shear wave was built and field-verified, and a favorable effect was obtained.关键词：soil-stone mixture;dynamic Poisson’s ratio;shear wave velocity;vibration compaction
- 1900
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- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to research the dynamic response of vertically irregular RC frame structure in progressive collapse,a series of vertical irregular RC frames were built up as analysis models,and each model with the remove of bottom interior column was analyzed by using nonlinear static method and nonlinear dynamic method based on alternate path method,respectively.Two new analysis indexes were proposed for the vertical irregular RC frames.The result showed that the dynamic increase factor 2.0 suggested in GSA2003 is conservative.The ability of structures subjected to dynamic loads can be strengthened by reducing the value of B∶A or reducing the irregularity of structure,and the ability of the structure to resist progressive collapse can also be improved by increasing the number of tower bays properly.关键词：reinforced concrete frame structure;vertically irregular;alternate path method;nonlinear;progressive collapse;dynamic response
- 2254
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- 4
发布时间：2023-11-14 - 摘要：Abstract:Aimed to investigate the seismic and isolated performance of one pure continuous girder bridge across ocean,the seismic and isolated experimental model with the scale of 1∶10 was designed and made by simplifying continuous girder bridge as single pier model,and the shaking table test of seismic single pier model and isolated single pier model with lead rubber bearing (LRB) were carried out.Then the acceleration response,shear force of LRB,shear force at the top of pier and hysteretic performance of LRB were studied under inputting earthquake of 120,600,1 200 and 2 400 years return period respectively, and the state of seismic and isolated pier under different earthquake could be judged according to the experimental result of low-period recycle test. Experimental results showed that the acceleration response of superstructure of isolated bridge is reduced to 54% and 55% of seismic bridge under earthquake of 120 and 600 years return period respectively.With the increase of structural response,the displacement of isolated layer will become larger and the ability of energy dissipation of LRB will become stronger.The whole pier of isolated bridge is in the elastic state and the seismic response of pier is less the cracking load under earthquake of 2 400 years return period. However, the pier of seismic bridge had been reaches to cracking load of pier under earthquake of 600 years return period.关键词：seismic bridge;isolated bridge;seismic response;lead rubber bearing;vibration-reduced effect
- 1988
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- 4
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- 2
发布时间：2023-11-14 - 摘要：Abstract:In order to research the influence of infilled wall to the steel frame performance of anti-ground deformation,the column-top-swing and beam-column-strain were analyzed via the physical experiment for three types of frame (open-frame,close-frame and wallboard-infilled-frame) under differential settling.The effection of frame performance by sill beam and infilled wallboard,furthermore,the cooperation of infilled wallboard-sill beam-steel frame were analyzed.The results showed that the member distortion of open-frame was maximum,close-frame took second place, and the member distortion of wallboard-infilled-frame was minimal,by contrast,the measure sequence of integral-incline of the frames was just reverse.The measure sequence caused the column-top-swing by different position of beam-column members was column base> column top> girder side-column-end> girder middle-column-end> girder midspan. The sill beam added to the bottom of frame-column could decrease amount of deformation of framing members,but the integral-incline of the frames increased at the same time,therefor the sill beam could not reduce the gathering speed of frame-column-top-swing.The infilled wallboard could modify the distribution of internal force on frame girder and column obviously and reduce the gathering speed of frame-column-top-wing effectively.关键词：steel structure;frames;infilled wallboard;differential settling;experiments;cooperation
- 1905
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- 2
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- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to investigate the stability performance of dual-angle combined section speciments,axial compression and eccentric compression tests were conducted.The influence of prameter of speciments on ultimate bearing capacity were researched.A formula for axial compression and eccentric compression component was given and compared with results of normal coded.The rusults showed that all of the speciments are flexural buckling,eccentric compression has great influence on ultimate bearing capacity,lateral suppot can reduce the slenderness ratio of speciments and the bearing capacity of such component can improved by appropriately increasing the angle specification and the number of filler plate.Eccentric compression has a negative effect on bearing capacity,especially for weak axis.On the premise of structural requirements,the rigidity and connection way of lateral support have little impact on bearing capacity of such component.关键词：dual-angle steel;combined section;double internodes;eccentric compression;bearing capacity
- 1937
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- 0
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- 1
发布时间：2023-11-14 - 摘要：Abstract:To optimize noise management in fully homomorphic encryption scheme,a fully homomorphic encryption scheme with better parameters size was proposed.The security parameters of the scheme were estimated.Given security level,the maximal value of modulus q was got.Then the concert security parameters of the scheme were obtained by the condition of correct decryption among noise growth,circuit depth L and modulus q.The security parameters of Bra12 scheme also was obtained by the same way.The data showed that this scheme has better parameters size.The ciphertext from homomorphic multiplication is smaller by a factor about lb2 q than in Bra12 scheme and the corresponding tensored key is smaller by a factor about lb3 q than in Bra12 scheme.The matrix of key switching is smaller by a factor about lb2 q than in Bra12 scheme.The optimization for noise management is general,which can be used in the fully homomorphic encryption schemes based on LWE in which the noise growth depends on the secret key.关键词：fully homomorphic encryption;Binary-LWE;noise management;security parameters
- 2593
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- 4
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- 6
发布时间：2023-11-14 - 摘要：Abstract:A novel method for segmenting cardiac magnetic resonance images based on Snake model was proposed.An external force called extended neighborhood Sigmoid gradient vector flow ENSGVF was presented as the improvement of gradient vector flow (GVF) for Snake which has a good performance on deep and narrow concavity convergence,capture range and weak edge preserving.In terms of the segmentation of endocardium,and considering that the left ventricle is roughly a circle,a circle shape constraint was adopted on the basis of ENSGVF Snake models,which can eliminate the unexpected local minimum caused by image inhomogeneity and papillary muscle.For the segmentation of epicardium,making full use of the segmentation result of endocardium,a new external force field and a new shape constraint were constructed to achieve automatic precise segmentation.The experimental results showed that the proposed method can address the challenges of lake of edge inhomogeneity,image inhomogeneity,effect of papillary muscle,and improves the rate of accuracy.关键词：cardiac magnetic resonance images;Snake model;extended neighborhood Sigmoid gradient vector flow;shape constraint;image segmentation
- 2356
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- 2
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- 1
发布时间：2023-11-14 - 摘要：Abstract:The primary work to recognize butt weld defects automatically with X-ray radiographs is to achieve effective assessment area accurately. A specific image processing design was proposed to overcome extracting difficulties by combining X-ray imaging mechanism and weld gray features. Firstly, it conducts gray-scale transformation of the butt weld image based on X-ray imaging fundaments. Secondly, it corrects the offset of weld bead based on the regional gray variance. Thirdly, it adopts Least-squares method to fit the weld seam and determine its center. Lastly, it converts weld seam from annular to rectangular using the distance map. The results of 3 000 samples showed that the design can detect the center of weld seam and fit it with 100% success rate. The fitting ellipses showed that the weld seam deflection angle error is -0.216°±0.826°. Therefore, it is feasible to extract the effective weld seam area from low contrast digital X-ray image for future assessment.关键词：butt weld;X-ray radiographs;gray features;image processing
- 2358
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- 2
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- 2
发布时间：2023-11-14 - 摘要：Abstract:Against the complex architecture of weighted average multiresolution image fusion algorithm that based on the Piella framework, and fusion rules do not adequately take into account the human visual characteristics, an extended multiresolution image fusion model was presented to control the combination map only with the activity measure. On the basis of the extended model, a multiresolution image fusion method that combined fused image quality evaluation criteria and previous decomposition layer information was proposed. The method took into account the fact that fused image is more to the human eye as a sink, so the image quality evaluation criteria was introduced to the high-frequency sub-band fusion rules. On the other hand, taking into account the presence of multi-scale analysis, which made the current decomposition layer’s information holdings significantly less than the previous decomposition layer, the previous decomposition layer information was introduced to the low-frequency sub-band fusion rules. Experiments revealed that the new algorithm is effective and robust.关键词：image fusion;Piella frame;multi-resolution analysis;sonar images;fusion rules
- 1779
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发布时间：2023-11-14 - 摘要：Abstract:Lattice attribute-based cryptography has several attractive and distinguishing features. However,a lattice attribute-based signature scheme has not yet been presented till now.Consequently,an attribute-based signature scheme from lattices was constructed firstly. In the proposed scheme,the user’s secret key was issued according to the lattice basis delegation algorithm of SampleBasisLeft, and the signature on a message was outputted by using the preimage sampling algorithm of SampleLeft.Furthermore,the proposed scheme was strictly proved to be secure under the intractability of the small integer solution (SIS) problem in the standard model,namely,it was existential unforgeable against selective access structure and message attacks. The proposed scheme achieved the constant signature length. And the access structure used in the proposed scheme was constructed by AND-gates on multi-valued attributes.关键词：attribute-based signature;access structure;SIS problem;lattices
- 2193
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- 2
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发布时间：2023-11-14 - 摘要：Abstract:Aiming at the lack of sparseness of factorization matrix in the nonnegative matrix factorization (NMF) algorithm,a new constrained NMF algorithm was proposed.A sparseness constraint was added to the original nonnegative matrix factorization (NMF) algorithm,and the minimum correlation constraint was imposed on the coefficient matrices and the 2-norm constraint was imposed on the basis matrix at the same time,which can ensure the non-negative constraint and accurate decomposition,and can also make the decomposed matrix sparse as far as possible,saving more storage space.Comparison with the experiments showed that the propose algorithm has the better sparseness and smaller error than both the original NMF algorithm and the SNMF algorithm.关键词：non-negative matrix factorization (NMF);sparseness;the least correlated component constraints;2-norm
- 2416
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- 1
发布时间：2023-11-14 - 摘要：Abstract:The existing solutions in present cloud environment focused more on the functionality and performance of the system,and less on energy-consuming.An elastic resource management approach based on perception of energy consumption in cloud computing environment was designed.This approach accessed to information of resources cost and request changes firstly,then learned a wavelet-transform-based model to predict request rate,and mapped tasks to application execution units,where resources costs are relatively fixed,in order to achieve flexible management of system energy consumption according to request rate and cost information.The results showed that this approach achieves higher performance than different ones,which can more effectively reduce energy consumption on the premise of guaranteeing the quality of service.关键词：cloud computing;energy-consuming model;elasticity;predictive control
- 2193
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- 0
发布时间：2023-11-14 - 摘要：Abstract:Aiming to the resources allocation problem of embedding virtual networks onto the substrate network,a metric model of the network nodes’ resources was proposed.The breadth-first search method of traversing graphs,and the synchronization strategy of traversing virtual and substrate nodes were used,then adjacent nodes in the virtual network were embedded onto the neighbor nodes in the substrate network in their turn.Moreover,virtual nodes and virtual links were embedded in a coordinated way,and the embedding paths’ length of the virtual links were decreased evidently.Simulation results showed that the BFS-VNM algorithm reduces the scaling factor of virtual links effectively,and increases the network revenue-to-cost ratio and the acceptance ratio of virtual network requests.关键词：network virtualization;virtual network embedding;breadth-first search
- 2614
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- 9
发布时间：2023-11-14 - 摘要：Abstract:Efficient parallel algorithm on distributed-memory multi-computers was presented for solving Euler equations on unstructured grids.Domain decomposition method was employed to handle meshes properly and make each processor maintain load balancing.The GMRES implicit scheme and local time stepping techniques were used to accelerate the convergence of the solution of unsteady Euler equations to steady state.Numerical experiment performed for inviscid transonic flows around NACA0012 airfoil,ONERA M6 wing and DLR-F6 geometry(wing-body-pylon-nacelle) indicated that the proposed parallel algorithm have the advantages of high acceleration and efficiency,which is suitable for large-grained science computing on MIMD model.关键词：parallel algorithm;unstructured grids;Euler equations;Speed-up;parallel efficiency
- 1826
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- 1
发布时间：2023-11-14 - 摘要：Abstract:In order to solve the trust management problem of vehicles,a trusted model of secure routing of VANET for quantitative trust management based on Bayesian theory was proposed.In the proposed model,classified and dynamic management method of node trust was used.Meanwhile,the Beta distribution was used to describe the trust situation of the nodes based on the routing protocol framework of GeoDTN+Nav.The proposed model not only improved the security of routing,but also had the lower time complexity and good extensibility.The experimental results showed that,the trust model is effective and has good performance in the malicious nodes removal rate,the packet average arrival rate and the end-to-end average delay.关键词：vehicular ad-hoc network;Bayesian;trust;secure routing
- 2388
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- 2
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- 7
发布时间：2023-11-14 - 摘要：Abstract:In order to treat the problems of the blindness of cluster head selection and the imbalance of energy consumption in the cluster in LEACH，an improved algorithm LEACH-ED based on nodes,residual energy and distance factor of inter-cluster communication was proposed．The cluster head election mechanism based on the estimate of the node residual energy was optimized．Both the energy of the nodes and the distance between the cluster member nodes and the sink node were considered.The cluster member nodes communicated with sink node directly rather than culster head nodes，which were closer to the sink node than culster head．Compared with LEACH protocol,the results of simulation showed that the improved algorithm prolongs the network’s lifetime nearly 50 percent and the ability of data transmission of nodes is improved greatly.关键词：routing protocol;LEACH protocol;cluster heads selected;network’s lifetime
- 2252
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- 12
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- 6
发布时间：2023-11-14 - 摘要：Abstract:In order to reduce higher harmonic of magnetic field in magnetically levitated permanent-magnet planar motors with moving-coils,a novel principle of magnet parameter design was proposed,which was based on the average relative mean-square deviation between the real magnetic density and expected air-gap magnetic density.According to harmonic model of magnetic field,the three-dimensional magnetic density of this magnet arrangement was analyzed and then the average fundamental amplitude in different height levels was calculated.The expected fundamental model of this magnet arrangement was then presented,which together with the obtained harmonic model giving the average relative mean-square deviation between the real magnetic density and expected air-gap magnetic density.The principle of magnet parameter design was presented,which could be described as “to achieve the maximum average fundamental amplitude and minimum average relative mean-square deviation as far as possible”.Finally, the finite element simulation and measured results of the experimental prototype illustrated that the presented design method has a good inhibitory effect on the higher harmonics,especially on the second harmonic.关键词：planar motor;Halbach permanent-magnet array;harmonic model;second harmonic
- 2707
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- 2
发布时间：2023-11-14 - 摘要：Abstract:In order to estimate the static voltage stability for AC/DC hybrid transmission system,a probabilistic method taking account of the stochastic influence of the changes of load and the faults of generating and transmission equipment was proposed.The non-sequential Monte Carlo method was carried out with the samples of load state and generating and transmission equipment’s state.And the load state was obtained by the methods of load clustering and multivariate normal sampling.Furthermore,the L-index calculated with quasi steady state model of DC was used to assess the system voltage stability and the local voltage stability with an amount of random samples.Finally,the system IEEE-RTS was applied to demonstrate the validity.By the analysis of the frequency,probability distribution and sensitivity of the static voltage among the operation modes of DC bipolar,monopole and the original AC system,the results showed that the DC transmission ratio plays great role in static voltage stability which would be decreased when the ratio increases.关键词：AC/DC hybrid transmission system;static voltage stability;probabilistic evaluation;non-sequential Monte-Carlo method
- 1960
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- 2
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- 2
发布时间：2023-11-14 - 摘要：Abstract:In order to ensure system security when a number of transmission lines were on DC de-icing meanwhile and avoid heavy ice-coating on lines,a decision-making method of power system DC de-icing plan based on equal-risk was proposed.In this method,the equal expected load-shedding was the objective function,under the constraints and on the basis of the existing dc de-icing plan,lines’ de-icing time slots were determined by sequence.After DC de-icing time slot of a line was determined,the constraints of the rest lines need be updated and then DC de-icing decision-making of the next line was started.During each decision-making,the strongly restricted lines were arranged with first priority,then the selected line was arrange into the time slot with lowest expected load-shedding which was calculated according to Monte Carlo method. In addition,the urgency of DC de-icing was the constraint for the safety of the line.Finally,the example of Guizhou power grid verified the feasibility and effectiveness of the method.关键词：DC de-icing plan;system security;urgency of DC de-icing;expected load shedding;equal-risk method
- 2465
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- 2
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- 2
发布时间：2023-11-14 - 摘要：Abstract:Rolling 304 stainless steel tube by Pilger pipe mill-LG60 was taken as example to establish and verify cold rolled stainless steel tube spring back prediction model.Firstly,on the basis of uniaxial tensile test,the piecewise nonlinear constitutive equation was gained by dealing the data.Secondly,according to the plastic deformation law of the steel tube rolling and incremental theory,the numerical method of every strain component during the deformation was gained and the stress state was changed from triaxial stress state to uniaxial stress state.Besides,the springback prediction model was established according to the law of material’s unloading.Finally,by using the finite element software of DEFORM-3D,the complete simulation of rolling process was conducted,and the reliability and correctness of the springback prediction model were verified through the actual rolling test by Pilger pipe mill.The results showed higher accuracy of the model.关键词：piecewise nonlinear constitutive equation;incremental theory;nonlinear fitting;law of unloading
- 2127
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- 2
发布时间：2023-11-14 - 摘要：Abstract:Combustion diagnosis results show that when using methanol or ethanol fuel,the miniature internal combustion engine with glow-ignition has higher level of cyclic variations, lower rate of heat release and longer combustion duration.So,adding additives of nitromethane and hydrogen peroxide were investigated.With the additive of nitromethane,the start of combustion (SOC) is advanced,the combustion velocity is improved and the coefficient of variation is reduced.However,the combustion characteristics become poor when the hydrogen peroxide is added to the fuel.In order to analyze the effects of nitromethane on the combustion,experiments of adding different proportions of nitromethane to methanol fuel and ethanol fuel were investigated.Under the glow-ignition condition with alcohol fuels,the nitromethane affects its indicated mean effective pressure and characteristic of cyclic variation by the adjustment of SOC.Adding nitromethane makes the SOC advance and let the combustion duration shorten that lead to the decrease of cycle-by-cycle variation. While with high proportion of nitromethane,the SOC tends to become more dispersed and the cycle-by-cycle variations become more severe,which result in performance degradation.关键词：micro engine;methanol;ethanol;nitromethane;combustion diagnosis;cyclic variation
- 1913
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- 0
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- 0
发布时间：2023-11-14 - 摘要：Abstract:A modeling and simulation method of free-surface flow fields in unbaffled stirred tanks was established based on the volume of fluid (VOF) multiphase model.The validity of this method was tested by studying the turbulent flow fields in the eccentric and unbaffled concentric stirred tank agitated by a Rushton impeller.The detached eddy simulation (DES) and the standard k-ε turbulence model were employed to simulate the mean fluid velocities,respectively.Good agreements were found between the numerical and experimental results,only with somewhat under-predictions.The difference between the DES and experimental data is less than 12%,while it is worse for the k-ε model.Results showed that the combination of the DES and VOF model,as well as the simulation method proposed here,can predict the free-surface hydrodynamics in stirred tanks with satisfactory accuracy.关键词：unbaffled stirred tank;free surface;turbulence;detached eddy simulation (DES);volume of fluid (VOF)
- 2341
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- 1
发布时间：2023-11-14 - 摘要：Abstract:Automobile steering gear ratio is one of the key factors which effect vehicle steering portability and sensitiveness.In order to obtain good portability and sensitiveness at the same time, it requires the use of variable ratio steering gear. Based on envelope principle, a new digital design method of variable ratio gear was proposed by analyzing the major part characteristics of the mechanical variable ratio steering. This method considers the helical gear of the gear pair with alternating axis as a set of the intersecting planes which are obtained by using a set of some infinite close planes which are perpendicular to its axis to intersect the gear, and each section is called a “gear element ”. The meshing transmission process of the gear pair can be seen as a meshing process of a collection of gear element and variable ratio gear. The height value of every tooth profile point on the variable ratio gear is the minimum value of all intersections of the traverse gear element set during the meshing process and the line which passes through this point and perpendicular to the rack movement direction and the axis of the helical gear with this point meshing transmission. Based on this method, a mathematical model for calculating the variable ratio gear tooth profile point height value of the variable ratio gear pair with alternating axis was established,the solving algorithm was developed and the 3D model of the variable ratio gear was obtained. This method was successfully applied to the development of a certain variable ratio steering gear.Besides that,the feasibility of this method was verified by trial-producing a gear pair sample with alternating axis and testing it.关键词：variable ratio gear;gear pair with alternating axis;gear element;numerical calculation;automobile steering
- 2682
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- 5
发布时间：2023-11-14 - 摘要：Abstract:The degradation of Ciprofloxacin by thermally activated persulfate was investigated.The impact factors of temperature,the concentration of persulfate, pH value and typical ions were studied.The results showed that based on the pseudo-first-order oxidative reaction model,the second-order model displayed a satisfactory correlation.The degradation rate of Ciprofloxacin got ascend with the increase of temperature or the initial concentration of persulfate and the pH value showed the converse effect.The reaction activation energy was (105.25±14.43) kJ/mol.Lower concentration of chloride made the inhibition for the degradation while promotion was observed for the higher dosage. Both nitrate and sulfate could restrain the reaction in the higher concentration solutions differing from carbonate which played a greater inhibition at merely dosage of 0.01 mol/L on the degradation of Ciprofloxacin.关键词：persulfate;sulfate radical;Fluoroquinolones;ciprofloxacin;kinetics;impact factors
- 1779
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- 7
发布时间：2023-11-14 - 摘要：Abstract:The expansion of circulating fluidized bed fly ash (CFA) and the effect of CFA content,fineness of CFA and curing regimes on the expansion properties of cement paste were investigated.Moreover,the mechanism of expansion of CFA was discussed by XRD and SEM,as well as the control measure.The results indicated that the formation of ettringite in 7 days after the hydration of CFA results in expansion and relative humidity has significant effect on the expansion of CFA.Mechanical grinding can improve activities of CFA and release the expansion in early stage,adding aggregate and improving early strength are effective ways to control expansion.关键词：CFA;Expansion;ettringite;expansion control
- 1693
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the recycling value of waste hard alloy，Cobalt nanowires were synthesized by a magnetic-field-assisted method from acid leaching solution of waste hard alloy. The morphology and thermal stability of cobalt nanowires were tested. The experiments showed that the external magnetic field is the key factor to the morphology of products. With external magnetic field，the cobalt nanowires with an average length of 40 μm and diameter of 500 nm were synthesized.Meanwhile under the same preparation conditions but without external magnetic field，the spherical cobalt particles with no significant arrangement were prepared. When the temperature was less than 225.0 ℃，the cobalt nanowires prepared by this method had good air thermal stability. The study would not only improve the recycling value of waste hard alloy and stimulate the development of recycling economy of cobalt resource，but also have important theoretical basis and practical significance for guiding the preparation and applications of one-dimensional magnetic metal nanowires，especially cobalt nanowires.关键词：magnetic-field-assisted method;cobalt nanowires;thermal stability
- 1534
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发布时间：2023-11-14 - 摘要：Abstract:Cobalt powder was prepared by hydrazine hydrate reducing cobalt salt method at room temperature by using ethanol,ethylene glycol and glycerin as the solvent of cobalt ion,respectively.The influence of cobalt ion solvent on the particle morphology of cobalt powder and its mechanism were investigated.The results showed that,the prepared cobalt powder consists of FCC and HCP crystalline phase.Using ethanol as cobalt ion solvent,the dendritic primary particles can be gained when the concentration of Co2+ ion is too low (0.045 mol/L),and the near-spherical primary particles of cobalt powder can be gained when the rest of concentration of Co2+ ion is used.When ethylene glycol or glycerin is used as cobalt ion solvent,smooth spherical primary particles can be obtained because of the effect of micro reactor formed by polyhydric alcohols.The way of the ethanol content influencing the morphology is by means of affecting the nucleation,growth and diffusion of the formed crystal nucleus.However,the way of the polyhydric alcohol content influencing the morphology is by means of affecting the viscosity of solution,as well as the integrity and the quantity of micro reactors.In the investigation,when the addition of ethylene glycol is 80 mL,the uniform and smooth spherical cobalt powders can be obtained.关键词：spherical cobalt powder;hydrazine hydrate reduction;ethanol;ethylene glycol;glycerin;mechanism
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发布时间：2023-11-14 - 摘要：Abstract:The oxide film on the surface of titanium alloy is important to osseointegration.A new method was proposed to obtain required titanium oxide film during machining or forming process.Experiments were conducted which include turning in natural atmosphere,turning in oxygen-enriched atmosphere and rolling in oxygen-enriched atmosphere.The thicknesses of titanium oxide film were tested and surface topographies were observed respectively.Results showed that the thicknesses of titanium oxide film are 49 nm,456 nm and 1 558 nm in these three conditions.It proved that rolling after turning in oxygen-enriched atmosphere can obtain the required film thickness,also the micro/nano topography of is helpful to cell adherence.关键词：biomaterials;titanium alloy;oxide film
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发布时间：2023-11-14
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