最新刊期
卷 48 ， 期 4 ， 2016
- 摘要：Abstract:A leading reservoir followed by diversion cascades which can make full use of the waterhead is very common in the small mountain rivers, due to it’s large gradient ratio. To understand the water temperature cumulative effects of a leading reservoir followed by diversion cascades, a field observation in a small mountain river of southwest China was performed to collect the water temperature data, both inflow and outflow, of each cascade reservoir. The results indicated that the leading reservoir had a large capacity of heat regulation. Since there was significant water temperature stratification, the gradient of water temperature was 0.15℃/m, in spring. The water intake in front of the dam can suck water from upper layer of the reservoir and the suction height was about 8m. The difference between the outflow water temperature and the water temperature in the middle of water intake was 1.3℃. When compared the outflow water temperature process with the natural temperature process, one month of delay was observed, presenting as colder water in March to April and warmmer water in September to December, with the biggest difference reaching up to -1.7℃ and 2.8℃, respectively. In addition, the data showed no difference between the inflow and outflow water temperature in the diversion cascade. Connected diversion cascades leaved no space for the low temperature water discharged from the leading reservoir to recover, and the low temperature water phenomenon was more severe in the downstream in spring, but the high temperature water phenomenon was weakened in the downstream in autumn.关键词：water temperature;cumulative effect;small watershed;diversion cascade;leading reservoir
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发布时间：2023-11-14 - 摘要：Abstract:The monthly meteorological data from 1960 to 2012 in 8 stations in Sichuan agricultural regions was used to calculate the precipitation satisfied degree, and the grain production and reduction due to drought in Sichuan from 1988 to 2007 was used to calculate the grain reduction rate in “wheat-rice” and “wheat-corn-sweet potato” cropping systems respectively. The drought risk probability of the precipitation satisfied degree was calculated by normal distribution function, and of the grain reduction rate due to drought was studied by information diffuse theory. The results showed that under the two cropping systems precipitation can’t satisfy the crop water requirement in one year every five years in most agricultural regions of Sichuan province, so the irrigation is needed. In “wheat-rice” and “wheat-corn-sweet potato”, the probability of medium drought, heavy drought and severe drought is 39.7%、10.9%、4.9% and 32.7%、6.1%、3.2%, respectively. The precipitation satisfied degree is well related with the grain reduction rate. When the grain reduction rate indicated medium or heavy drought, the precipitation satisfied degree anomaly must indicate the occurrence of drought. However, when the precipitation satisfied degree anomaly indicated the occurrence of drought, the grain reduction rate did not necessarily judge the medium or heavy drought.
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发布时间：2023-11-14 - 摘要：Abstract:An ArcGIS based unsaturated-saturated nitrogen transformation and transport software ArcNLET has been established. This software considered the nitrogen transformation and transport processes from point contamination sources infiltrating into soil, then arriving at the water table and continuing to transport along the groundwater flow. One-dimensional vertical water flow and nitrogen transport equations were solved to obtain the nitrogen concentrations at the water table. The groundwater flow was assumed as the two-dimensional horizontal flow. The reactive nitrogen transport equations of ammonium and nitrate were solved by the analytical solution. Then the nitrogen loads to water bodies were calculated. It was applied to estimate the nitrogen load to surface water bodies in Julington Creek watershed in Florida State U.S. The results showed the strong spatial variability of nitrogen concentration at the water table below each point source, which demonstrated the necessity of estimating the soil nitrogen transport due to the complex topography and soil characteristics. Ammonium contributed 26% of total nitrogen loads to surface water bodies. It indicated that the nitrogen contamination risk would be under-estimated if ignoring the ammonium in the aquifer. This software can provide the quantitative estimation of the nitrogen loading to surface water bodies, which is hard to be measured. The modules can be chosen independently according to the requirements of users. ArcGIS provides the pre- and post- processing results visually and easily. The model owns great potential value to be used in the regional nitrogen loading calculation with point contamination sources.关键词：modified ArcNLET, unsaturated-saturated nitrogen transport, nitrogen loads, ammonium, nitrate, ArcGIS
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发布时间：2023-11-14 - 摘要：Abstract:The water temperature structure of reservoir is influenced by meteorological elements and inflow temperature, and presents regular change over a year. But the law of its daily variation is relatively lack. Based on Longtan reservoir, a prototype observation in front of the dam, which was divided into six stages, was performed from November 2011 to September 2012. The data analysis results showed that water temperature stratification is relatively stable during the observation period except January, and double thermocline was observed in July and September; The surface temperature had a big variation, while the bottom temperature was relatively stable throughout the year; The influence scope of meteorological elements on the water temperature in front of the dam was related to the season. In summer the reservoir water impacted by the meteorological elements was deeper than the others. The higher the temperature was, the earlier the maximum temperature appeared. Air temperature and solar radiation were the main factors affecting the diurnal variations of the structure of water temperature. In addition, the daily significantly change area of water temperature structure was only within 20m of the surface, which indicted that the diurnal change of surface water temperature hardly affected the temperature of discharge water.关键词：in front of the dam;water temperature structure;daily variation;meteorological elements;discharge water
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发布时间：2023-11-14 - 摘要：Abstract:Multi-objective beneficial dispatch is a significant mean of getting more benefit for cascade reservoir in the Jinsha River. The key step of this problem is to control water allocation between different reservoirs and different operation tasks. Therefore, we analyzed competition or collision relationship among power generation, firmed output and navigation discharge of cascaded hydro plant. Based on engineering requirement of hydropower station in Jinsha River, a model of multi-objective beneficial dispatch for cascade reservoirs is developed. The purpose of this model is to maximize generating energy, firmed output and navigation discharge simultaneously. By a proposed mnulti-objective evolutionary algorithm, the Pareto optimal solution set is obtained, which provides scientific decision references for joint operation of cascade reservoirs in Jinsha River.关键词：Jinsha River;reservoir operation;multi-objective optimization;power generation;navigation dispatch
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发布时间：2023-11-14 - 摘要：Abstract:in order to obtain the progress of longitudinal erosion and effects of different factors, we conducted 6 flume tests. The results indicate that: the longitudinal erosion process includes 3 stages. At stageⅠ,the outflow is slow, and the suspended load wastransported to downstream mainly during the process.At stageⅡ, the depth of the breach changed rapidly.The bed load wastransported fiercely due to backward erosion. Atstage Ⅲ, the velocity and rateof outflow decreased, armor layer was formed which protected the sediment under the armor layer from eroding. At last, dynamic equilibrium was achievedbetween the water phase and sediment phase. With inflow rate increasing, the breach time decreases and outflow discharge increases, this leads to greaterstream power and highererosion rate. And the bottom of the breach become smoothly due to large inflow rate. The slope of the erosive characteristics curve becomes larger with the outflow discharge increasing. The shape of erosive curve changes from multi-peak curve to mono-peak curve with downstream slope increasing. The steepslope of downstream also increases the outflow discharge and erosion rate, and decreases the residual height of the dam. The factor J3 which is equal tothe third power of tangent values of the bed slope and downstream slope’s summation, can reflect the stability of soil particles in differentdownstream slopes. The shortcoming of current study is that the effects of material diversity on the dam breaching process was not considered and shall be investigated in the future work.关键词：natural dam breach;longitudinal erosion;retrogressive erosion;discharge
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve integral stability analysis of foundation pits under seepage, the integral stability analysis method of foundation pits close to river, considering water level fluctuation, the transient seepage and the diaphragm wall, was proposed based on the improved critical slip field of slope. Taking the foundation pit of Dadongmen station in metro line 1 of Hefei city for example, the seepage analysis of the foundation pit with corresponding parameters were carried out and then the obtained pore-water pressure fields were imported into the program of the method to evaluate changes in the factor of safety with changing river water level and excavation depth. In addition, emphases were given to research the influence of seepage on the integral stability of the foundation pit. The results showed that the method can search for the most dangerous slip surface of any shape and the safety factor is more reasonable than the traditional method in calculation of the integral pit stability. Moreover, the seepage have more influence on the integral stability of the foundation pit and the change of pore water pressure field can lead to change the position of slip surface.关键词：foundation pit excavation;diaphragm wall;critical slip field of slope;close to river;seepage
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发布时间：2023-11-14 - 摘要：Abstract:According to the possible durability problem of high liguid limit clay as roadbed filling in rainy climate, a series of tests on water stability characteristics of pure high liquid limit soil and lime or cement improved soil were carried out.The pure soils was red clay which picked from under-construction Longquan-Pucheng Highway section. The tests focused on the unconfined compression strength and CBR under ordinary water immersion and drying-wetting cycle condition. Exprimetal results indicated that compacted high liquid limit clay with higher initial saturation had lower humidification speed , destructed slowlier, and had higher water stability. The unconfined compression strength and CBR of most pure high liquid limit clay and improved soils decreased with the increase of soaking duration. But CBR value of 4% lime-improved soils with water immersion increased within a porid. During drying-wetting cycles, the CBR value of the high liquid limit clay increased first and then decreased. The unconfined compression strength of improved high liquid limit soils improved with high dosage of lime or cement kept unchanged or decreased slightly and the soil still kept a high strength after multiple cycles.关键词：high liquid limit clay;improved soil;water stability;drying-wetting cycle;unconfined compressive strength;CBR
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发布时间：2023-11-14 - 摘要：Abstract:Flood and debris flow are the main contributor of mountain hazards in China. Along these years, due to the space limitation, buildings, which are the main element at risk, are mostly located at debris flow alluvial fan. This have led to buildings extreme vulnerable when mountain hazards occur. Based on the characteristic of debris flow impact and structural behavior of masonry structure, failure mechanism of the masonry brick wall is identified. The bending stress failure criteria of brick wall is calculated based on the debris flow velocity and depth. Failure curve of brick walls are constructed to assess wall failure subject to different flow velocity and depth. Base on the result, two structure optimization plan are proposed. The brick wall failure model and optimization plan is verified by a masonry building at Qi Pan Valley after a devastating debris flow event on 2013. The advantages and limitations of two structure optimization plan were discuss.
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发布时间：2023-11-14 - 摘要：Abstract:In order to study the seismic performance of the extended-end-plate connecting joint in between T-shaped concrete-filled rectangular composite tubular column and reinforced concrete beam, nine specimens have been designed and manufactured in the proportion of 1:2 and tested under low-cycle repetitive loadings. Based on tests process and results, the deformation process of specimens under load was observed, hysteresis curve and skeleton curve were described, and the load characteristics, ductility, energy dissipation and stiffness degradation of the joints were analyzed. Results also show that this type of joints have plumper hysteretic curve with ductility coefficient greater than 3.48 and viscous damping coefficient greater than 1.5, which indicate excellent seismic performance. With extended length of corbels, initial stiffness and ultimate load of the joints can be improved; with thickened end-plate and stiffeners, ultimate load and energy dissipation of the joints can be increased, where adding stiffeners can improve thin end-plate joints more significantly than thick end-plate joints; with increased diameter of the bolt, initial stiffness of the joints can be improved, but it only affects its loading capacity within limits.关键词：T-shaped concrete-filled rectangular composite tubular column;extended-end-plate connecting joint;quasi-static test;seismic performance
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发布时间：2023-11-14 - 摘要：Abstract:Previous fatigue tests on the anchorage zones, the orthotropic steel decks and the suspenders of suspension bridges are only the experiments of single component. But the stresses of these components are very complex and in a complicated spatial stress states, and the boundary conditions on the model have the great impact on fatigue test results. To evaluating the fatigue performance on the key structural details of Qingcaobei Yangtze River bridge, and verifying the rationality of the design, safety and durability of the bridge, a 1:4 scaled integration model fatigue test including main cables, anchorage zones, hangers and box girders is carried out. Experiment results show that, the stresses redistribution in the integrated model after fatigue loading is not obvious; the principal stresses of static loads test during the fatigue experiment are small different; the relationship between displacement and load is approximately linear. Displacement and each static load test values in the process of loading and unloading has good symmetry and recoverability, which shows that the whole structure is in the elastic stage. Fatigue cracks are not found in the key structure details the structure under the design of fatigue loading, so the structural fatigue performance meet the design requirements. Through the study of the fatigue experiment of integrated model structure, the fatigue performance of the integrated model can reflect the actual fatigue performance of the cable-anchorage -hanger-girder structure, and the integrated fatigue experiment can provide some certain reference significance.关键词：Cable-hanger-girder;Integrated model structure;fatigue performance;suspension bridge;Fatigue crack.
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发布时间：2023-11-14 - 摘要：Abstract:To further explore the axial compression performance of concrete columns strengthened with TRC, the effects of textile layers, the lap length of textile and short fibers used to modify fine grain concrete as the TRC matrix on axial compression performance of reinforced columns was studied in this paper. The results indicated that the failure pattern and ductility of TRC-strengthened plain concrete column was improved, and the bearing capacity was increased by 17.32%. For the RC columns strengthened with TRC, the lap length of textile and short fibers modifying fine grain concrete did not have obvious influence on the constraint effect of TRC, but TRC constraint effect was increased obviously and the ductility of columns was improved with the increase of textile layers, and the bearing capacity was increased up to 14.74%. At the end of this paper, calculation formulas of the ultimate bearing capacity of RC columns strengthened with TRC were deduced and the calculation model was given. The research results provided the reference for the engineering application of TRC-strengthened concrete column.关键词：textile reinforced concrete;axial compression;textile layers;lap length of textile;high-quality concrete modified by short fibers;computational model
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发布时间：2023-11-14 - 摘要：Abstract:To evaluate the safety against seismic collapse of EBSFs (Eccentrically Braced Steel Frames), 24 representative EBSFs in areas of seismic fortification intensity VIII and IX were designed. Then their capacity against seismic collapse was researched by the CMR (Collapse Margin Ratio) index from IDA (Incremental Dynamic Analysis) based on the automatic control program according to seismic collapse evaluation system of FEMA P695. The results show that EBSF system possesses necessary safety against seismic collapse, the CMRs of EBSFs decrease with the increase of stories (height), i.e., higher structures have weaker capacity against seismic collapse, greater collapse probability; the structures in areas of seismic fortification intensity VIII possess larger CMRs and lower collapse risk than those in areas of seismic fortification intensity IX, when subjected to corresponding scarce earthquakes respectively; and the EBSFs with V-shape braces have larger CMRs, thus greater capacity against seismic collapse than those with K-shape braces.关键词：EBSF;seismic collapse;collapse margin ratio;safety;IDA
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发布时间：2023-11-14 - 摘要：Abstract:Due to the weakness of match information and influence of noise, the calculation precision of depth cannot be guaranteed. Therefore fusion of multiple depth maps is a typical technique for multi-view stereo (MVS) reconstruction. This paper introduced an antinoise fusion method that took advantage of the confidence of 3D points. This method first performed a refinement process on every depth map to enforce consistency over its neighbors, which could remove most errors and fill many holes simultaneously. After refinement, it deleted redundancies of every point by retaining the point that its confidence was maximal in its neighbors. Finally, it obtained a point cloud by merging all depth maps and used an iterative least square algorithm to further eliminate the noise points. The quality performance of the proposed method was evaluated on several data sets and the comparison with other algorithm was also given in the paper.关键词：multiple view stereo;3D reconstruction;fusion of depth maps;confidence;iterative least square algorithm
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of flotation bubbles that the information is weak in bubble edges, which causes image segmentation hard, the new algorithm combining the Fractional Differential, improved level set and Watershed was proposed. The algorithm includes three steps: Image enhancement: the Fractional differential order is automatically determined on image texture information by using fractal analysis, and the improved adaptive fractional differential algorithm is used to enhance bubble edges; Bubble white spot extraction: the traditional Level set algorithm is improved, and it is applied for extracting white spots of bubbles; Image segmentation: the internal and external markers of bubbles are utilized to correct the gradient images, and finally the marked Watershed segmentation algorithm is used to delineate bubbles. For a number of Lead Zink ore froth images with different bubble sizes, we compared several traditional image segmentation algorithms with the new algorithm, the experimental result shows the proposed algorithm can improve the image segmentation accuracy and is effective in reducing the over-segmentation problem. The proposed algorithm is effective in segmenting flotation bubbles.关键词：Flotation;fractional differential;Fractal analysis;Level set;Watershed
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发布时间：2023-11-14 - 摘要：Abstract:In order to extend range of fractional differential order and to improve brightness when fractional differential methods are applied to image enhancement, a local fractional differential algorithm for image enhancement is proposed. First, according to theory of local fractional differential, a local fractional differential algorithm for image enhancement is deduced. Then, on basis of a new constructed fractional differential template for image enhancement, a new template joined a set of brightness control functions for texture, edge and brightness enhancement is gotten. Experiments and results show that the proposed method can extend the range of fractional differential order, and it not only can enhance edges, textures and other details of the image, but also can significantly improve the contrast and lightness of the image; experiments also show that the visual effect of enhanced images is better than that of traditional fractional differential-based methods.关键词：image enhancement;fractional differential;local fractional derivative;fractional differential mask;contrast enhancement
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发布时间：2023-11-14 - 摘要：Abstract:In order to overcome the shortcomings of MIDDs approach proposed by Canh Ngo et al, some improvements are proposed. New graph structures which edge is a tuple of node-variable reduced interval partition and the state value marking critical attribute were designed for the improved MIDDs and X-MIDDs, named iMIDDs and iX-MIDDs respectively. In addition, the combining-algorithm identifier is also added to iX-MIDDs decision-leaf nodes. Operations and processing of policy elements match, policy evaluation, and iMIDD to iX-MIDD transformation are introduced. Complexities analysis and simulation show both space and evaluation time complexities of proposed approach are equivalent to the MIDDs’. New approach could be applied in various policy management problems.关键词：access control;decision diagrams;security policy;policy management;XACML
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发布时间：2023-11-14 - 摘要：Abstract:The construction of the Data Center(DC) using Software Defined Network(SDN) technology is a hot research topic at present. The SDN can well meet the requirements of centralized control, virtual machine deployment and migration in DC. However, the biggest difficulties are the flow optimization problem along with the scalability restrictions and the energy consumption brought by TCAM. Meanwhile, there are a mass of mice flows which have brought more cost and delay. Therefore, a new type of data plane model named the VADC is proposed herein. It applies a kind of source routing address named the vector address (VA) as the switching label. The VA defines the communication path independently. Thus, the switches can accomplish the data forwarding process solely. The VADC model has three advantages: (1) Switches don’t use the TCAM to store flow table cause that there is no need for table look-up. Thus can solve the problem of scalability in the DC significantly while reduce the cost and complexity of switches. (2) The VADC simplifies the establishment of the new flows. There is no need to download the flow table to VADC switches. Thus, the amount of control signaling consumed can reduce by about 73%. (3) We implement the VADC switch on the NetFPGA platform. The results show the hardware resources consumption of the VADC switch is only 28% of the OpenFlow switch.关键词：SDN;DC;Virtual machine;TCAM;Flow;NetFPGA
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发布时间：2023-11-14 - 摘要：Abstract:The existing frequent closed graph(FCG) mining methods under standalone mode can not process massive Internet datasets, by improving the Apriori algorithm, an iterative algorithm AMR(Apriori based on MapReduce) was proposed to mine FCGs of large scale dynamic networks based on Hadoop. First of all, the edge sets of dynamic networks were stored in the key-value table, and a serialized subgraph coding mechanism was designed to ensure the uniqueness of frequent subgraphs(FSG). Secondly, a communication mechanism was proposed to pass subgraph codes, and to ensure the accuracy of FCG, local supports in each partition were aggregated to a global one. Finally, FCGs were achieved by pruning the FSGs. AMR was used in the dynamic networks of both country and AS level Internet, and experimental results showed that FCG can accurately characterize the topology of backbone Internet, thus verifying the efficiency and effectiveness of AMR in mining FCG of large scale dynamic networks.关键词：Hadoop;dynamic networks;large scale Internet;frequent closed graph
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发布时间：2023-11-14 - 摘要：Abstract:In order to overcome the drawbacks of most existing data aggregating schemes for wireless sensor networks (WSN) and provide capabilities of data privacy, unforgeability, defending external and internal attacks, tracing and fixing data mistakes, as well as better security and efficiency, a verifiable data aggregation scheme using Homomorphic Encryption (HE) techniques was proposed, in which sensors’ identities were included in digital signatures to achieve data distinguishability, so as to provide the proposed scheme with functions of data verification, tracing and modification. The ElGamal cryptosystem was adopted as a basic scheme to encrypt confidential data. Blinding factors were introduced to provide the scheme with defence capability against internal attacks. Using a kind of multiplicativelly homomorphic secure summation algorithm, a blinding factor generating method which avoids the need for a trusted third party (TTP) was proposed to avoid possible risks introduced by using of TTP. Security and efficiency analysis was given hereafter, as well as comparisons with some classical schemes. It shows that the proposed scheme is secure and the overall performance is better than the existing schemes.关键词：data aggregation;Homomorphic Encryption (HE);digital signature;trusted third party (TTP)
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that the existing link prediction models based on local information between nodes considered the dependent relationships between common neighbor nodes insufficiently and failed to fully make use of the network topology information, meanwhile improve the accuracy of links prediction, this paper put forward the link prediction method based on hidden naive Bayes model. The algorithm fully considered the interdependence between common neighbor nodes and difference between interdependence. Then the similarity of nodes were computed through hidden naive Bayes classification model and the dependence between nodes were measured by utilizing the conditional mutual information. Through the above methods, the link prediction accuracy was finally improved. In the simulation, DBLP and Email data sets were used as the experimental data and the method of AUC and Precision were used to evaluate the forecasting models. Results show that the predictive effect of proposed algorithm is better than that of the mainstream method which effectively verified the accuracy of the method.关键词：hidden naive bayes;link prediction;similarity;conditional mutual information
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发布时间：2023-11-14 - 摘要：Abstract:In order to achieve the parameter identification and reduce the diagnosis cost of analog circuit, Unlike the methods based on digital signal processing (DSP) or artificial intelligence, a new method based on matrix perturbation theory for analog circuit fault diagnosis is proposed. in the view of algebraic theories, And by analyzing the problems of fault modeling, fault feature extraction and the tolerance handling in fault diagnosis for analog circuit, this paper attempts to construct a theoretical framework that integrates fault detection, fault location and parameter identification based on the relationship between the device parameters and response matrix eigenvalues. By comparing the proposed model with its counterparts, the experimental results show that the proposed model outperforms its counterparts in the respect of computational cost and fault parameter identification. In two experiments, the identification errors are less than 2.35%.关键词：analog circuit;parameter identification;fault diagnosis;fault model;eigenvalues
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发布时间：2023-11-14 - 摘要：Abstract:Considering the low communication performance such as long time delay and imbalance problem of industrial switched Ethernet network, a multi-objective optimization method based on 0-1 mapping matrix and Non-dominated Sorting Genetic Algorithm-Ⅱwas proposed. In this method, a multi-objective optimization model was constructed by means of the special characteristics of 0-1 mapping matrix, multi-point asexual crossover and double mutation strategies were utilized to achieve population evolution, and then the corresponding discrete Pareto front of the switched Ethernet topology structure mapping matrix was obtained. Benchmark test and simulation results showed the communication load between sub networks was dramatically reduced, and the possibility of information congestion or idle power in local networks was decreased after the network structure optimization.关键词：Ethernet;network topology;multi-objective optimization;NSGA-Ⅱ;Mapping Matrix;Pareto Front
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发布时间：2023-11-14 - 摘要：Abstract:In order to deal with the problems that dense fog influenced the image quality, a dense fog image defogging algorithm was put forward. In this paper, the physical model of imaging in fog was simplified，and the concept of fog concentration factor was put forward. The relationship between visibility and fog concentration factor was established when this paper analyzed the factors affecting the concentration of fog. By seeking the value of the fog concentration factor and Estimating the value of atmospheric light using guided filtering, the dense fog image could be recovered. Experimental results showed that after the algorithm the image brightness is higher, the image contrast and resolution is higher, and the overall visual perception of the image is better.
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发布时间：2023-11-14 - 摘要：Abstract:In order to assess the effect of sensitive equipment by voltage sag accurately, a voltage sag characteristic identification method is proposed, which based on the consequences of state and process parameter immunity time (PIT). The characteristics of voltage sag is classified to a basic set and an additional set and the concepts of voltage sag characteristic set, virtual voltage sag and influenced event of sensitive equipment caused by voltage sag are introduced in this study. Using PIT to measure the consequences of state of equipment to voltage sag. Using the duration, that from the sag occurs to the process parameter reach to the acceptable limit value, as PIT. The mapping relation between virtual voltage sag characteristic and PIT is studied in this paper, using limit value of acceptable process parameter to identify the sensitive characteristics. Using the tests on PV inverter and personal computer (PC) to verify the proposed method. The result shows that the sensitive sag characteristics of PV inverter includes magnitude, duration and phase-angle jump, the sensitive sag characteristics of PC are magnitude and duration. The identification results proposed by the method are consistent with the test result, proving the correctness and rationality of the proposed method.
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发布时间：2023-11-14 - 摘要：Abstract:Solving Process problem needs the support of method and knowledge. To organize relative resources in accordance with requirement, an innovative process design service model based on Service-Oriented Architecture was proposed. Strategy service and knowledge service were built from the dimensions of knowledge, method and computer aided tool. The ontology of services was built, and the system architecture was described from service level perspective. Design methods and knowledge resources were encapsulated as services by semantic description and unified expression. These services constituted coarse-grained service components according to logical relation. To assist designers creatively solve process problems, these services were organized according to the procedure of problem-solving and the solving strategy based on process problem classification. An optimization design of turbine shaft process was taken as an example to verify the effectiveness of the proposed service model.关键词：process innovation;problem-solving;SOA
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发布时间：2023-11-14 - 摘要：Abstract:The effect of bearing raceway lubrication status and contact force on the service life of bearing is significant. In order to improve the service life of cylindrical roller bearing, one method is proposed that bearing outer is slotted and filled with elastomer. The effects of different pore size and four fillering materials with nitrile rubber, nylon-1010, hard aluminum alloys and red copper on the contact force between the inner ring raceway and rollers of bearing have been calculated with finite element method (FEM). A mixed lubrication model is established by considering the real surface roughness of cylindrical roller bearing, and the influence of different fillering materials on lubrication performance of bearing under different rotation speeds conditions has been obtained as well. The results show that the effect of bearing outer filled with elastomer on lubrication performance and contact force is significant. The contact force of the maximum force roller and inner ring raceway decreases with the decreasing of the elastic modulus of filler materials. And it is found that nitrile rubber and nylon-1010 can obviously increase the contacts number and effectively reduce the contact force. The increase in speed increased film thickness but reduced coefficient of friction, contact load ratio, contact area ratio and max. von mises stress. And the lubrication performance of nitrile rubber fillering materials bearing is best.关键词：cylindrical roller bearing;fillers;contact force;lubrication performance;finite element analysis
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发布时间：2023-11-14 - 摘要：Abstract:The majority of mechanical parts worked under mixed lubrication conditions, especially for components worked under extreme conditions such as high speeds, heavy loads and surfaces with significant roughness. However, it’s difficult to deal with the problem of contact and lubrication at same time. Howeve the previous studies were under full-film condition and mostly with smooth surfaces. So the mixed lubrication is the weak point for the study of interface mechanics. The accurate system numerical method be used to solve the the unified model for mixed thermal elastic hydrodynamic lubrication(TEHL) . The result shows that the model was accuracy which can simulate the transition from Mixed to Full-Film Lubrication.关键词：mixed lubrication;thermal elastic hydrodynamic lubrication;rough caculation
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发布时间：2023-11-14 - 摘要：Abstract:In order to study the influence of residual stress on rolling contact, a simplified 2-D finite element model of cylindrical roller bearing was established. Then different residual stresses were applied to the model, followed by elastoplastic analysis. The effects of the characterization parameters of residual stress i.e. gradient, magnitude and depth on rolling contact were analyzed. The results showed that residual compressive stress can reduce the elastic contact stress and the plastic strain, while the residual tensile stress with the same magnitude of residual compressive stress can increase them more significantly. The parametric study showed that: residual compressive stress with a smaller gradient and residual tensile stress with a zero gradient lead to smaller plastic strains; plastic strain rises with the increasing of residual compressive stress and the decreasing of residual tensile stress; deepening residual compressive stress a proper depth can reduce plastic strain thus increasing rolling contact fatigue life while the deepening of residual tensile stress will result in larger plastic strain and fatigue damage.关键词：residual stress;rolling contact;elastoplastic analysis;characterization parameters
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发布时间：2023-11-14 - 摘要：Abstract:Abstract:To solve the problem of trajectory combination and connection of spraying robot for large curvature combination surfaces, combined with surface fitting theory and modeling method of spray gun, the trajectory optimization model of spray gun was established , and the algorithmic program was put forward to satisfy the spray gun trajectory from beginning to end. First, the large curvature of composite surface was transformed to natural quadric combination curved surface patches with the theory of surface fitting. Based on the coating growth model built, the trajectory was optimized for the natural quadric juncture of different types. Secondly, based on the model and the idea of exchange and the exchange of the sequence, the new algorithm was designed to solve the problem of trajectory combination. The corresponding algorithm program was written to realize the global optimization of spray trajectory. Finally, the validity of the model and the feasibility of the algorithm were verified by the spraying experiment of a certain kind of car shell. The continuous spraying large curvature composite surface was realized.关键词：Large curvature surfaces;trajectory optimization;Trajectory connection;Spraying robot
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发布时间：2023-11-14
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