最新刊期
卷 52 ， 期 4 ， 2020
- 摘要：The large-scale access and application of renewable energy is one of the basic features of the Electrical Internet of Things (EIoT). Its inherent uncertainty will affect the safe and stable operation of the power grid on the one hand, and on the other hand, it cannot directly participate in the electricity market. As a multi-energy aggregation model, virtual power plant (VPP) can coordinate and control distributed energy resource (DER) and participate in the electricity market in the form of an aggregation, which is of great significance for improving the safe and economic operation level of power grid and promoting clean energy consumption in the construction content of EIoT. The research on VPP has a long history both at home and abroad. In the European FENIX project, VPPs are aimed at achieving the goal of reliable grid connection and electricity market operation of DERs, and VPPs in North America are mainly based on demand response and aggregate a large number of controllable loads. In China, State Grid Jibei Electric Power Company’s VPP demonstration project takes into account the interaction of “source–grid–load–storage”, and aggregates ubiquitous adjustable resources into an Internet power plant that can interact flexibly with the power grid. On this basis, the research status of VPP in three aspects of coordination control, optimal dispatch and participation in electricity market transactions was first analyzed. The coordination control objects of VPP mainly include various DERs, energy storage system, controllable loads as well as electric vehicles. The coordination control methods are mainly divided into centralized control and decentralized control. Under centralized control, all decisions of VPP are made by the central control unit. In decentralized control, the decision of VPP is replaced by each agent system. The optimal dispatch of VPP refers to the optimization of the capacity configuration or output of multiple internal DERs or participation in power grid scheduling as a whole under the premise of meeting the output constraints of each unit and network constraints, with the goal of maximizing profits, minimizing operating costs and minimizing carbon emissions. In addition, VPPs can quickly respond to changes in market prices and load demands when participating in electricity market transactions by using their advanced communication technology, which plays an important role in promoting electricity market liberalization, increasing market flexibility, and guiding users in peak load and frequency modulation. Secondly, the key technologies of VPP in EIoT were discussed in detail, including edge–cloud computing architecture, blockchain technology and big data technology. The edge–cloud computing architecture, on the one hand, selects the load of involved in the demand response of VPP through the cloud master station, and on the other hand, perceives the user’s power consumption behaviors through edge computing, making it more accurate in VPP’s bidding strategies. The characteristics of decentralization and transparency of blockchain are similar to the geographical dispersion of VPP and the coordination control in the scheduling process. Meanwhile, the blockchain technology can also ensure the fairness and information security of VPP when participating in electricity market transactions. The big data technology, on the one hand, can be used to predict the output of each DER more accurately, and on the other hand, it can also be used to process various information inside VPP, which can improve the speed and accuracy of data exchange and processing of each unit. Finally, the research of VPP in EIoT was prospected. The model and optimal dispatching method of VPP with locational marginal price as well as the cyber-physical security of VPP and countermeasures were considered.关键词：Electrical Internet of Things;virtual power plant;electricity market;coordination control
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发布时间：2024-01-08 - 摘要：Currently, plenty topics in terms of the physical support technologies and the market operating technologies of integrated energy services (IESs) have been researched. It is obvious that a number of remarkable contributions related to the physical support technologies of IESs can be identified. However, few valuable conclusions of the market operating technologies can be summarized, which significantly prevents the IESs in China from being developed with marketization and scalability. Therefore, this paper focused on the synergetic development of the energy internet (EI) and the IESs, which analyzes the promotional effects of the EI for serving the scalability of IESs from three aspects including the organizational form of market, the business model of service providers, and the digital strategy of business process. Moreover, this paper further researched and discussed the market operating models of IESs and matching technologies. Three detailed works done by this paper were presented as, the first one was based on the trends of the market maturity level and the transparency of relevant information, the development of IESs market in China was divided into three phases including the unorganized phase of decentralized competitive market, the locally plat-formalized phase of information aggregation, and the global ecological phase of industrial eco-management. In each phase, the organizational form of market considering the participations of the energy service providers, the information operators, and the platform of IESs were established. The second one was based on the individual-valued property and the operating procedure of the aforementioned three market participants, a business model was constructed in terms of satisfying the energy users’ diversified demands, linking the supply and requisitioning parties to close the deal, and guiding the behaviors of the variousmarket participants. The third one was the model theories and the technology frameworks of four key technologies of the market operating models of IESs were designed, including: 1) the energy users’ multi-level portrait model with considering the energy-consumption-behavior characteristics, the energy-demand characteristics, and the service potentialities of which were achieved based on the big data analytic, cloud computing, and the Internet of things (IOT) was presented; 2) the energy service providers’ comprehensive portrait technology through the establishment of an evaluation index system covering the three aspects of enterprise strength, service capabilities and service products of which were achieved based on the Fuzzy comprehensive evaluation, the data envelope analysis, and the integrated weigh was presented; 3) the accurate market portrait technology which analyze and predict the supply and demand trends in the future, influencing factors and changing laws of various service products and service markets was presented. Besides, according to the functional characteristics of market subjects, the idea of short term market potential assessment method which suitable for energy service providers and information operators, and the idea to analyze the trend of mid long term market trend which suitable for the platform of IESs were illustrated respectively; 4) the proactive push strategy for IESs based on the multi-criteria decision-making, as well as the service recommendation strategy forthe stage of information aggregation and industrial ecological which based on the theoretical method were presented. At last, a number of suggestions of serving future researches, practices and policy decisions were put forward from the aspects of the promotions of the concentration and the openness of the market, the guidance and the cultivation of the energy consumption behavior of users in the demand side, and the improvements of the ability to obtain energy data and the data processing capacities. Summarizing, the development of the EI will innovate the traditional energy service supply and demand model, and reshape the format of IESs. It is necessary to carry out more extensive research and practical work in terms of market operation models and technologies in the future which will contribute to realize large-scale development of IESs.关键词：energy Internet;integrated energy services;market operation;development stage;business model;key technologies
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发布时间：2024-01-08
INVITED CONTRBUTION OF ELECTRICAL INTERNET OF THINGS
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Spatial–Temporal Multi-granular Attribute Analysis and Knowledge Discovery Method for Voltage Sag AI导读
摘要：In order to mitigate voltage sag related problems based on power quality monitoring data, it is meaningful to improve the efficiency of power quality data analysis. Due to depending on accurate models of voltage sag, the traditional methods are inadequate for complex problems with multiple uncertainty factors. Therefore, the spatial–temporal multi-granular attribute analysis of voltage sag data and a related knowledge discovery method were proposed in this paper. Inspired by the cognitive hierarchy of complex problems, a framework consisted of “data—characteristic—index—information—knowledge” was proposed as a general technical route for voltage sag related problems. Based on the framework, to solve the problem of information loss caused by single granular, sag information in different granular was extended by voltage sag spatial–temporal multi-granular analysis. The relationship between power system structure attribute and voltage sag was discovered by granular reduction. Then, knowledge about voltage sag severity and propagation was derived. The synthetic and measured data were used to validate the effectiveness of the proposed method. Results showed that the proposed method can describe and resolve complex problems with many uncertainty factors.关键词：power disturbance;voltage sag;spatial–temporal multi-granularity;knowledge discovery;propagation law- 2700
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发布时间：2024-01-08 - 摘要：In order to address the issue that the charging service is difficult to make quantitative price, apricing model of electric vehicle charging service based on system dynamics was proposed. The location of charging service network in the Electrical Internet of Things and the relationship between multiple subjects were first analyzed. Then, some other multi-dimension factors were took into account, such as social development, population growth, the scale of the electric vehicle, scientific level, the quantity of charging piles, construction costs, and afterwards the causality between multi-dimensional factors based on historical data was quantified. Finally, a system dynamics simulation model of charging service price was established, then the charging service price was obtained from the model and the impact of various factors on charging service price was analyzed. According to the initial value of the set parameters and different scenarios, the price of charging service and the trend of change was simulated. The simulation results showed that the change curve of electric vehicle charging service price appears to be V-shaped under the setting conditions in the example scenario. In the early stage, the price of charging service decreases gradually, which is mainly affected by the government subsidy policy. In the middle stage, the price increases slightly. The reason is that the government subsidy policy has been continuously weakened, and the charging service network has been further improved, and the newly-built charging facilities have led to an increase in the construction cost. In the later period, the charging service price gradually stabilizes and fluctuates at the peak. At this time, the charging service price is mainly affected by construction cost. The paper provides an operational macro dynamic quantitative analysis model for charging service price, which provides a reference for the operation and planning of charging service network in the future.关键词：Electrical Internet of Things;charging service network;electric vehicle;charging service price;system dynamics;pricing model
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发布时间：2024-01-08 - 摘要：The traditional methods of non-intrusive load monitoring have the disadvantages of complicated implementation, difficulty of real-time computing, and repeated training requirement of the dataset threshold. In view of this, a fast event detection algorithm based on hypothesis testing, named compound hypothesis testing algorithm, was proposed in this paper. In the algorithm, the total power signal collected by intelligent electric meter was detected through Chi-square goodness-of-fit test to find out the time point at which events may occur. Then the Z test was used for the two time windows respectively, with the event inspection being conducted for suspects only. Based on the test results, the occurrence of events can be determined accordingly. The calculation was simple and fast. On the BLUED data set, the event detection performance of compound hypothesis testing algorithm and the standard Chi-square goodness-of-fit test method were simulated and compared. The experimental results showed that, the stability and the robustness of the compound hypothesis test algorithm for different base loads were verified. It is concluded that the method proposed in the paper can not only accurately identify the switch events, but also ensure the characteristics of fast and concise operation speed, thereby improving the recognition accuracy of event detection. Therefore, the proposed method has certain application value and reference significance.关键词：non-intrusive event detection;Chi-square goodness of fit;Z-test;robustness
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发布时间：2024-01-08 - 摘要：With the development of Electrical Internet of Things (EIoT), traditional communication technologies and computing platforms have been unable to adapt to the huge scale of data transmission and computing. 5G communication technology and the edge computing will become the backbone force supporting the construction of the Electrical Internet of Things. The “multi-station integration” mode provides a new direction for the operation of edge data center, and the operation method of multi-station integration needs to be further studied. In order to study the data migration method of edge data center and the collaborative optimization problem of each function station under the mode of “multi-station integration”, a fusion station operation architecture covering data center and energy storage power station was designed in this paper. Then, a load model of data center and a mathematical model of energy storage station were constructed. Based on the mixed integer nonlinear programming method, a collaborative optimization and data migration scheduling model of integrate station with the goal of minimizing the total annual cost was established. Through solving the optimization model, the optimal data migration scheduling strategy and the optimal operation scheme of energy storage power station were determined. The simulation analysis of data migration strategy and the role of energy storage power station were carried out by case study. The calculation results showed that, the typical daily operation cost is reduced by 2.38% and the annual total cost is reduced by 1.36% after the implementation of the data migration strategy. After the energy storage power station is used to cut peak and fill valley, the typical daily operation cost is further reduced by 8.34% and the annual total cost is further reduced by 4.67%. The analysis results showed that the operation cost could be reduced when the data load is allocated according to a certain strategy under the condition of meeting the delay constraint. Combined with the time-of-use electric rate structure, the energy storage power station participating in the power dispatching could further transfer the peak load to the valley load, thus significantly reducing the operation cost.关键词：multi-station integration;data center;data migration;energy storage power station;mixed integer nonlinear programming
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发布时间：2024-01-08 -
Research on Non-intrusive Load Decomposition Based on Improved AP Clustering and Optimized GRNN AI导读
摘要：The proposal of Electrical Internet of Things (EloT) has promoted the rapid development of smart electricity and load monitoring. In order to solve the problems that traditional non-intrusive load monitoring and decomposition (NILMD) is very time-consuming and has low identification accuracy, the semi-supervised learning (SSL) was used to cluster data and then establish characteristic data set, combined with load decomposition of fruit fly optimization algorithm with generalized regression neural network (FOA–GRNN). First, with the input of active power and current data, the similarity matrix was optimized with the method of semi-supervised learning. The operating state and power information of the electrical equipment were mined based on affinity propagation clustering. Then the operating state was represented as classification label with digital coding. Second, the time series data of the total active power, reactive power and current as well as the classification label matrix of the corresponding series were all input. To complete the model optimization and training, the optimal Spread value of the generalized regression neural network (GRNN) was obtained by using the optimization ability of the fruit fly optimization algorithm (FOA). Subsequently, the test time series data was input to obtain the classification matrix, that is, the operating status of each device, whose corresponding power information was utilized to reconstruct and fit the total active power in a way to complete the load decomposition. Through simulation comparison, the identification accuracy of the operating status of all electrical equipment is about 86% and that of single electrical equipment is about 96%. The proposed method is not time-consuming and significantly improves the mining ability and decomposition identification ability of load characteristics information.关键词：non-intrusive load decomposition and monitoring;semi-supervised affinity propagation clustering;fruit fly optimization algorithm;generalized regression neural network- 2804
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发布时间：2024-01-08
ELECTRICAL INTERNET OF THINGS
- 摘要：In order to study the influence of axial compression ratio on corrugated steel plate-concrete composite shear walls(SPCSW), ABAQUS finite element software with different axial compression ratio was used for the nonlinear analysis of vertical corrugated steel plate-concrete composite shear wall (SPCSW–2) and horizontal corrugated steel plate-concrete composite shear wall (SPCSW–3) and the analysis results were verified by experiments. The results of finite element analysis show that when the axial compression ratio is in the range of 0.15 to 0.45 and increases gradually, the bearing capacity and energy dissipation capacity of SPCSW–2 were increased, and its ductility and deformation capacity were weakened. When the axial compression ratio exceeds 0.6, The seismic performance of shear wall is poor. When the axial compression ratio was in the range of 0.15 to 0.30 and increases gradually, the bearing capacity of SPCSW–3 increases, and its ductile and deformation capacity weakens, but it has no significant effect on the energy dissipation capacity. When the axial compression ratio exceeds 0.45, the seismic performance of shear wall is poor. When the axial compression ratio is more than 0.6, the displacement angle in the limit state is lower than the limit requirement of displacement angle. When the axial compression ratio is in the range of 0.15 to 0.30 and the axial compression ratio of SPCSW–2 and SPCSW–3 is the same, the former shows better seismic performance. In order to ensure the reliability of the finite element analysis, a quasi-static test was carried out on the two shear walls. The experimental results showed that the finite element analysis results were in good agreement with the experimental results, so the results of finite element analysis can provide a reference for the follow-up practical engineering.关键词：corrugated steel plate-concrete composite shear wall;axial compression ratio;finite element analysis;seismic performance
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发布时间：2024-01-08 - 摘要：In order to propose a design method and understand if it is possible to reduce the amount of lateral hoops and then construction cost of reinforced concrete filled steel tubular column (R–CFST) subjected to axial force, investigations were performed respectively on the ultimate strength evaluation-equation and the influence of lateral hoops on the mechanical performance of R–CFST, by means of both compression test and numerical simulation. The test variables included the patterns and spacing of lateral hoops. Two patterns with flat and spiral hoops and three different spacing of flat hoops were used. 8 R–CFSTs in 4 groups and 3 concrete filled steel tube (CFST) specimens were prepared. Analyses results on load-transfer performance, ductility, confinement and composite effect, and failure mode indicated that: before-ultimate loading performance and ultimate load-bearing capacity of the member were not relevant to the patterns of lateral hoops; differences in spacing of flat hoops would not cause significant changes in mechanical performance of member, and thus larger spacing was recommended to obtain a time and work saving construction process; spiral hoops would bring improvement to ductility and post-ultimate loading performance of the member, and thus spiral hoops were recommended when the ductility or seismic performance was the main concern. Based the experimental results, the numerical simulation method for R–CFST was investigated and a constitutive equation for its concrete core was proposed. Simulation results showed a good agreement with test results, which further confirmed the reliability of the test. At the end, investigations on prediction methods of ultimate load-bearing capacity of R–CFST were conducted. As results, the equation from US code was found to be conservative, and equations which were modified based on the Chinese code were proposed. Verification results against known experimental data indicated that the equations proposed were applicable in engineering design of R–CFST member subjected axial load.关键词：concrete filled steel tubular column;lateral hoops;compression test;number simulation;load-bearing capacity
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发布时间：2024-01-08 -
Experimental Study on Solute Transport Characteristics of Filling Fracture Based on Self-potential AI导读
摘要：In order to describe the solute transport process and characteristics in the filling fracture, the solute transport test model of filling fracture was designed and manufactured. The solute transport tests under different flow velocity conditions were carried out. The solute transport characteristics in the filling fracture were studied and the internal solute transport process was described in detail combining with the real-time dynamic monitoring data of self-potential (SP) at different measuring points. The results showed that: 1）In the range of 0.0733～0.9630 mm/s, the permeability coefficient of the filling fracture was 1.85 mm/s, which was close to the permeability coefficient of the filled porous medium 1.79 mm/s, and the water flow complies with Darcy’s law; 2） When the actual average flow velocity was 0.247 mm/s, 0.431 mm/s, 0.661 mm/s, the peak solute concentration at the sampling point was 5.14 g/L, 5.50 g/L, 5.78 g/L, and the initial and peak solute arrival times were all reduced, with the initial arrival times of 4640 s, 2640 s, and 1560 s, and the peak arrival times of 5480 s, 3360 s and 2040 s, respectively. 3） Under the conditions of the actual flow velocity of the three kinds of water currents, the SP response showed similar characteristics during the solute transport. The absolute value of the SP peak at the measuring electrode was gradually reduced from 1# to 6# along the flow direction, and the steepness gradually decreased when the peaks came out in sequence. In addition, both the solute dispersion front and the solute dispersion peak concentration point were moving at a uniform speed with the flow of water, and the corresponding average initial flow velocity of the solute dispersion front were 0.214 mm/s, 0.396 mm/s, 0.685 mm/s, and the average flow velocity peaks corresponding to the solute dispersion peaks were 0.189 mm/s, 0.347 mm/s and 0.571 mm/s. 4） The actual average flow velocity based on the peak SP calculation was basically the same as the calculation result using the peak solute concentration, but the peak SP calculation result was closer to the actual average flow velocity (flow calculation result), and the accuracy was increased by 1.5%; as the flow rate continued to increase, the macro-average flow velocity error calculated from the peak SP was reduced by 9.9%. 5） The test showed that compared with the peak SP value, the macroscopic average velocity of the filling fractured flow calculated using the initial SP value was closer to the macroscopic average velocity of the flow calculated from the flow data.关键词：filling fracture;solute transport;self-potential;average velocity;tracer test- 2105
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发布时间：2024-01-08 - 摘要：In recent years, inclined pile groups have been widely used in the construction of wharf and bridge foundation to resist lateral load, while its vertical bearing characteristics also attract the attention of researchers. How to evaluate the vertical bearing characteristics and pile effect of inclined pile groups is important in engineering. In this paper, combined with the pile foundation selection project of Hanjiang Bridge on Xiamen—Shenzhen passenger dedicated railway line, five kinds of pile spacing analysis models are established for the pile group foundation with inclination angle of 0 °～12 °, and the bearing characteristics and pile group effect are simulated and analyzed by finite element method. The results show that in terms of vertical bearing characteristics of pile foundation with different distance from group, the most reasonable inclination angle is about 8°. The load-settlement curve of vertical pile foundation is slow variant and the inclined pile foundation is steep variant. The settlement decreases suddenly when the pile spacing reaches 4 times of the diameter of the pile, and the sudden decrease value of vertical pile foundation is larger than that of inclined pile foundation. The influence range of soil deformation field of inclined pile base is larger than that of vertical pile foundation. With the increase of load and pile spacing, the vertical deformation of soil between piles decreases significantly, the clamping effect of soil between piles weakens, and the friction resistance of upper part of pile side increases gradually under the action of stress. The axial force of vertical pile group has the property of angular pile > side pile > middle pile, and the axial force of inclined pile group has medium pile > angle pile > side pile, whereas the change rate of axial force increases with the increase of pile spacing. The load sharing at the top of the pile tends to be uniform with the increase of the inclination angle and pile spacing of the pile group, and the effect coefficient of the vertical pile group increases rapidly before the pile spacing is 4 times of the pile diameter, and slows down after 4 times of the pile diameter. When the vertical pile spacing is 5 times of the pile diameter, the pile group effect coefficient is stable, and the inclined pile foundation is stable when the pile diameter is 6 times, and the pile group effect coefficient of 8° inclined pile foundation is the largest under different pile spacing.关键词：inclined pile foundation;vertical bearing;pile group effect;numerical simulation;model test
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发布时间：2024-01-08 - 摘要：Taking a complex practical project that the sea embankment undercrossing an existed expressway bridge in deep soft soil region as research case, utilizing the 3D finite difference numerical simulation as research method, and considering the special reinforcement design, a detail engineering influence analysis for the existed end-bearing pile foundation induced by filling was conducted. The results showed that: 1) Based on the dynamic design optimization by CAD&CAE, the optimized reinforcement scheme, i.e., bored pile + frame connection beam + high pressure jet grouting, was determined, the frame structure showed good integrity and synergistic force characteristics, and the high-pressure jet grouting would effectively improve the engineering properties of soft soil, the “hard crust layer” effectively reduced the consolidation deformation of overlying soft soil; 2) Under the action of additional loading, pressure arch was formed in the frame structure, extrusion induced from transverse direction could be reduced effectively, the additional horizontal displacement of piles under both ramps would be effectively controlled, and in the direction along bridge axis, large area additional loading was transferred to additional bending moment of bored piles and axial force of connecting beams, so the additional bending moment increment of piles could be effectively controlled, after filling, the maximum horizontal displacement on pile top was 4.38 mm, and the maximum increase of compressive stress was less than 0.9 MPa, which met the control requirements well; 3) The whole supporting structure could be regarded as the sleeve around bridge piles, accompanying with symmetrical thin-layer filling of embankment, it would effectively reduce the relative deformation between bridge piles and surrounding soil, and played a significant role in controlling the axial force increment of piles. To sum up, finely numerical simulation effectively overcame the limitations of technical specifications method in complex engineering applications, and provided a necessary technical support in evaluation applicability of project scheme and effect.关键词：large-area loading;undercrosss existed bridge;pile foundation;deep soft soil;reinforcement scheme;3D finite difference element
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发布时间：2024-01-08 - 摘要：With the gradual optimization of China secondary energy structure, a large number of high concrete dam projects have emerged in the southwestern region, and their seismic safety issues have become increasingly prominent. A concrete damage model considering hysteresis effect under cyclic loading was developed to solve the complicated material non-linear problem during high concrete dam earthquake. The tension and compression skeleton curves that conform to the actual deformation characteristics of concrete were used in the proposed model for adapting to the anisotropy of material tension and compression. The skeleton curves contained the softening section coefficient to adapt to the dispersion of test results. The expression of characteristic points of loading and unloading hysteresis effect that did not depend on the shape of the skeleton curve was used to establish an unloading path and a reloading path that reflected the hysteresis effect of softening section under the cyclic loading of concrete. A critical value of residual strain was suggested to solve the continuous divergence problem, that the ratio of residual plastic strain to unloading strain increased with the unloading strain. The model transmitted the complex multi-axis problem to a uniaxial equivalent strain space for problem solving, with fewer calculation parameters and simple mathematical expressions. The reliability and efficiency of the proposed model were investigated for nonlinear problems solving by comparing the concrete cyclic tensile load test with the earthquake damage simulation of Koyna gravity dam. This study can provide effective theoretical support for seismic analysis and safety evaluation of high concrete dams.关键词：damage model;circle loading;hysteresis effect;anti-seismic analysis
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发布时间：2024-01-08 - 摘要：Hybrid simulation has been regarded as an innovative and feasible solution of conducting anti-seismic test of structures. In hybrid simulations, the test duration mainly depends on numerical calculation duration, data communication duration, and loading duration. The differences in integration methods selection and numerical modelling may lead to a large variation of test durations, which may even affect the accuracy of the test results. OpenFresco is an environmental independent software framework for implementing hybrid tests. However, the research on the test duration of hybrid simulation based on OpenFresco has not been sufficiently studied. A single-storey and single-span frame was analysed in this paper. Specifically, the steel column was selected as the experimental substructure whilst the rest of the model was taken as the numerical substructure. The test results helped to reveal the factors which might influence the duration of hybrid simulation. It could be concluded that integration method, model complexity, and ramp time were the main factors affecting the durations of hybrid simulations. Moreover, the relation between the test duration and test accuracy was also discussed. The results showed that the explicit integration method and the Newmark integration method with fixed steps were recommended in the hybrid simulation based on OpenFresco. Besides, the numerical model should be simplified to improve the test accuracy.关键词：hybrid simulation;test duration;OpenFresco;integration;test accuracy
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发布时间：2024-01-08 -
Local Stress Analysis in Welding Area of U-rib of Steel Deck Considering Welding Residual Stress AI导读
摘要：In order to study the local stress characteristics at weld joints between the top plate and U-rib of orthotropic steel deck considering the combination of external loads and welding residual stresses, taking a wide body steel box girder as the project example, the numerical simulation of welding process of the welding seams was carried out based on thermal elastoplastic finite element theory. The changes of temperature field and stress field in welding process were analyzed. The combination of welding residual stress and external loads was realized by the method of initial stress. The results showed that the peak value of the residual tensile stress perpendicular to the direction of the weld at the bottom of the steel deck was close to the yield strength of the material, and the stress in the area far away from the weld seam decreased sharply. The transverse residual stress at the weld toe was obviously greater than that at the weld root. From top surface to bottom surface of the steel deck, the longitudinal residual stress changed from compressive stress to tensile stress, and the change trend of the transverse residual stress was “tensile stress to compressive stress to tensile stress”. Considering the residual stress in the way of initial stress, the relative error of stable stress field can be controlled within 5.0%. The influence of self-weight and secondary dead load on the distribution characteristics of local stress field and the extreme value of stress at weld root and weld toe was not significant (within 1.7%). When the local symmetrical wheel loads was considered in the external load but the dissipation of residual stress under the external loads was not considered, the maximum values of transverse stress perpendicular to the weld at the weld root and weld toe increased by 10.7% and 17.6%, respectively. Under welding residual stress and the combination of external loads and welding residual stresses, the distribution of the stress along the thickness of the top plate at the weld toe and weld root were in accordance with the rule of “straight line and parabola”.关键词：orthotropic steel deck;welding residual stress;fatigue;thermal elastoplastic;initial stress- 2306
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发布时间：2024-01-08 - 摘要：Compared with the traditional pipe curtain method, the pipe-roof pre-construction method has the characteristics of small jacking pipe spacing and large jacking pipe diameter. At present, there are few applications for close-packed large-diameter pipe jacking. The theoretical studies on the construction sequence of close-packed pipe jacking and the surface settlement law of pipe jacking construction are insufficient. The deformation trend of soil in close-packed pipe jacking construction is quite different from that of single pipe jacking. The traditional Peck formula used to predict the surface settlement is difficult to apply. In order to figure out the construction sequence and deformation law of close-packed pipe jacking construction, a large-scale model test was conducted to study the three typical pipe jacking construction schemes. The interactions between close-packed large-diameter jacking pipes and the characteristics of ground deformation during pipe jacking construction were studied. Based on the test results, in the test scheme considering the pipe soil arching effect, the maximum surface settlement at the central axis of the pipe-roof was only 6.09 mm, which was smaller than the other two sets of schemes. There was not only mutual supports between the densely packed pipes, but also the pipe soil arching effects formed by the pipe joint and the surrounding soil providing a protection for the construction of the lower pipe. The best order of construction was first to construct the upper pipe and then to construct the pipe-roof on both sides and the lower row pipes. The ground surface settlement caused by close-packed pipe jacking construction was predicted by the improved Peck formula, which considered the supporting effect of soil arching between the adjacent pipes, and modified the specific methods of parameter selections. The prediction results of the improved Peck formula were in good agreements with the lateral surface settlement curves obtained by the model tests.关键词：pipe-roof pre-construction method;dense pipe jacking;Peck formula;pipe soil arching effect;surface settlement
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发布时间：2024-01-08 - 摘要：With the large-scale construction of high-rise buildings in recent years, the depth of the excavations has gradually increased. Since deep excavations are usually located in the prosperous areas of the city, and close to various buildings, how to deal with the impact of the construction process such as soil excavation and retaining structure installation on the surrounding environment has become the key issue to the research of deep excavation. The deep excavation of tieback anchored pile retaining structure near the shallow foundation building is studied in this paper. Based on the field observations, the variations of pile deformation, pile head displacement and building settlement were analyzed in detail. Numerical models were established using FEM (finite element method) program Plaxis. A reasonable soil constitutive model was selected by comparing the calculated results with the field monitoring results. Two key parameters, including the position of the adjacent building foundation and the additional stress of the foundation, were discussed, in order to obtain the disturbance behaviors between the anchored pile wall excavation and adjacent building. The research results showed that the concrete supports and the crown beam would increase the influence region of the excavation corner effect while restraining the deformation of the retaining pile head. For excavation unloading issues, the calculated results obtained from Hardening−Soil（HS） model are more accurate than those from the Mohr−Coulomb（MC） model. The primary influence zone locates at the region within 2.5He (excavation depth) behind the retaining structures. The maximums of average building settlements and building inclinations are 0.6He and 1.1He. The positions of the maximum of average building settlement and the ground surface maximum settlement are identical. The position of the maximum of inclination is located at the inflection point of the ground settlement curve. For this project, when the buried depth of the building foundation is 2.5 m and the distance between the retaining pile of the deep excavation and the center of the building changes within the range of 7.5～52.5 m, the maximums of the average settlement and inclination of the building are about 8.3 mm and 0.00025, respectively. Furthermore, for each additional floor, the settlement and inclination of buildings increase about 0.9 mm and 0.7×10–4, respectively, and the maximum lateral displacement of the retaining structure of the deep excavation increases by 1.4～2.0 mm, of which the increment increases with the number of floors.关键词：tieback anchored pile retaining structure;deformation behavior;building;numerical model;deep excavation
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发布时间：2024-01-08 -
Comparative Study on Methods of Early Warning Index of Flash Flood Disaster Induced by Rainstorm AI导读
摘要：Affected by steep geomorphology and intensive rainfall, mountain rivers are characterized by steep rise and fall hydrograph, greatly shortening the response time of residents along the river and posing great challenges to the high-precision early warning and forecasting of flash floods. Flash flood early warning is an important part of non-structural measures for disaster prevention and damage reduction and is commonly divided into water level early warning and precipitation early warning. Since the flood period is extremely short in small-sized basins where automatic monitoring stations cannot cover all the areas, the water level early warning is unpopularly used in China. The early warning based on rainfall threshold calculated by the water level/flow inversion method often misses the event due to the same frequency assumption of the rainstorm and flood, which cannot meet the actual need of mountainous flash flood prevention. To improve the early warning accuracy and increase the warning advance time of flash floods, two new methods of calculating the early warning indicators are proposed, based on methods of the rising rate in flood level and real-time accumulated precipitation. Taking the "8·16" flash flood disasters in Zhongdu River Basin (a tributary of Jinsha River in Sichuan Province) as an example, the early warning indicators are calculated by the above-mentioned methods, and the calculated results are compared to each other regarding the early warning accuracy and advance time. The results show that the early warning accuracy of inversion on water level/flow is limited in achieving the expected early-warning effect. The early warning accuracy based on the method of flood rising rate is higher. However, the early warning period from the stage rise to the peak is found to be affected by the flash flood characteristics and is relatively short. The method based on the real-time accumulated precipitation issues every alarm and prolongs the warning advance time of flash flood effectively. In addition, if the minimum 30 minutes flood warning advance time is required, the two new methods can extend the warning time by at least 30%. In conclusion, setting the threshold of accumulated rainfall combined with the rising rate of flood for disaster early warning is suggested to improve the early warning accuracy of flash flood disaster.关键词：flash flood disaster;water level occurred disaster;rising rate of flood level;the real-time accumulated precipitation;flash flood early warning- 2756
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发布时间：2024-01-08 - 摘要：The soil-rock mixture slope has the characteristics of complex physical and mechanical properties and strong nonlinearity, which is greatly affected by geometric factors such as the rock distribution and rock particle size. In order to investigate the effect of geometric parameters on the stability of soil-rock mixture slopes, the ABAQUS software nonlinear analysis method was utilized based on the random generation method of block-shape database proposed by the team. Considering a variety of geometric influencing factors such as the rock content, maximum rock particle size and rock distribution, a large number of finite element models for calculation and analysis were established. The results showed that the safety factor of slope increased with the increase of rock content and the increasing rate was largest when the rock content was in the range of 50%～60%. With the increase of rock content, the standard deviation of the safety factor of the slope in the same particle size group and the difference of model safety factor increased. With the increase of the maximum particle size, the impact of the rock distribution on the safety factor of the model and the standard deviation of the safety factor of the slope in the same particle size group increased, the stability of the slope first decreased and then increased. With the increase of rock content and maximum particle size, the influence of rock distribution on slope stability increased. The influence of the rock distribution on the stability of the soil-rock mixture slope varied with the rock particle size. The existence of large size rock made the sliding face the move away from free face of slope, while the dense small size rocks mostly made the sliding face hackly, both of which increased the stability of the slope. When the rock long axis and slope angle was 90° or 135°, the plastic zone of slope was divergent, the sliding surface was more internal, and the slope stability increased. When the angle between the long axis of the block stone and the slope was 0° or 45°, it was contrary to the above situation. Under normal sedimentary conditions, slope stability decreased with the increase of the ratio of axial length to axial length. The sliding face became smoother and the plastic zone became more concentrated. It can be concluded that the rock content, rock particle size and rock distribution had great influences on the slope stability. With different geometric parameters, slope stability varied greatly and had a certain regularity, which was of certain reference value to the practical projects.关键词：soil-rock mixture slope;random distribution;rock content;rock particle size;rock distribution
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发布时间：2024-01-08 - 摘要：Based on the shape of the braided river in the middle reaches of the Yalu Tsangpo River, the study established a mathematical model for the simulation of sediment transport in braided rivers. The numerical calculation used a two-dimensional hydrodynamic and non-viscous sediment coupling model to simulate the sediment transport in the braided river. The model is based on the incompressible Reynolds average N–S equation, which included continuous equations, momentum equations, riverbed deformation equations, and total sand transport equations. The mathematical model calculated the suspended sediment and the sediment transport rate through the theory of total sediment transport. When simulating flood peak flow, the peak of the sediment concentration process and the suspended sediment transport rate of the braided river lags was behind the inflow process, causing a phase difference. The smaller the sediment particle, the smaller the phase difference. The phase difference of sands, whose particle sizes were 0.01 mm and 0.02 mm, was about 0, and the phase difference caused by the rate of exit suspension sediment transport was less than that caused by sediment concentration. The sedimentation of 0.30 mm, 0.20 mm and 0.10 mm particle size in the braided river exceeded 50%. In the calculation of sediment transport, the topographic renewal caused by sediment start-up and sedimentation was considered, and the influence of the sediment flow on the topographic changes during the movement of the braided river was analyzed, which established a numerical simulation example for the research prediction of the natural braided river.关键词：braided river;sediment transport;Yalu Tsangpo River;numerical simulation
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发布时间：2024-01-08 - 摘要：The interaction between cracks is an important research content of fracture mechanics. However, there are few studies on the internal cracks interactions. Based on 3D-ILC, parallel internal cracks in the brittle solids have been generated. Experimental research were performed on the Brazilian discs with the cracks. The process of crack propagation was recorded, the law of the stress birefringence, the failure load and the fracture characteristics were analyzed. Based on the M integral and strain energy density factor theory, the distribution of KⅠ, KⅡ, KⅢ was revealed and the crack propagation were simulated as well. The results showed that: 1) The applicability of the technique 3D-ILC was proved in the research of multi-internal crack interactions. 2) The failure morphology included symmetric sphincter crack, upper wing crack, lower wing crack, secondary crack, vertical crack and penetrating crack. The smooth region of the wing crack fracture was type Ⅰ–Ⅱ crack, the side was type Ⅰ–Ⅱ–Ⅲ crack with lances-like surface; 3) The failure load of the sample with internal cracks was 17.73% of that of intact sample. The relationship between internal crack growth rate and loading force followed a nonlinear rule. 4) There was shieling interaction between the two internal cracks. 5) Based on the M-integral and strain energy density factor theory, the numerical simulation results were in accordance with that of the experiment. The results provide a physical test and numerical simulation reference for the study of three-dimensional internal crack Ⅰ–Ⅱ–Ⅲ composite fracture and multi-crack interaction.关键词：rock-like material;brittle fracture mechanics;crack propagation;double embedded cracks;crack interaction
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发布时间：2024-01-08 - 摘要：Pile-soil composite subgrade is a common treatment method for soft foundation section of expressway. However, at present, composite subgrade often meets the requirements of quality inspection but still has a large settlement after construction, which seriously affects the safety and comfort of driving. In order to forecast and evaluate the post-construction settlement of pile-soil composite subgrade early, post-construction settlement under 157 sections of the composite subgrade condition were analyzed. Utilizing the theoretical analysis and field test methods, and introducing elastic cushion and delayed loading to the current static load tests, the evaluation parameters of residual subsidence Sr and sedimentation rate Vt were obtained. Then the evaluation index was obtained from the measured data of composite subgrade after construction by the method of probability statistical analysis. Finally a new method for the early detection and evaluation of post-construction settlement was presented. The results showed that more than 90% of the composite subgrade completed the pile-soil stress ratio adjustment of cushion, and could achieve the stability of the pile soil stress ratio under actual load with a time delay of 48 hours, when conducting the delay load test under the condition of double designed value of bearing capacity. The maximum residual settlement of the delayed load holding tests followed logarithmic normal distribution when it is less than 7.0 mm or greater than 12.0 mm, while it followed the inverse Γ–distribution when it is greater than 7.0 mm and less than 12.0 mm. When the required values of post-construction settlement after 15 years were 100 mm, 200 mm and 300 mm, the corresponding maximum residual settlement Sr max of the delayed load holding test were 4.50 mm, 13.30 mm and 35.41 mm, respectively. The corresponding Vt=48 h were 0.021 mm/h, 0.046 mm/h and 0.055 mm/h, respectively. The probability of satisfaction were 47.61%, 87.49% and 96.93%, respectively. The field example showed that the proposed evaluation index was in good agreement with the value of the actual situation. The evaluation method was beneficial to the early evaluation of construction quality and the timely formulation of remedial measures. This method can not only enrich the post-construction settlement prediction method, but also help to expand the existing composite roadbed quality detection index system from single strength detection to strength and settlement detections.关键词：composite subgrade;time-delay holding test;post-contruction settlement;early detection and evaluation method;probability statistical analysis;control standards
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发布时间：2024-01-08 - 摘要：For open-ended jacked pipe pile, the pile body is subjected to complex forces during pile jacking, especially the soil plug resistance caused by soil plug effect inside the pile body, which has a significant influence on the pile side resistance. Therefore, it is of great significance to carry out a comprehensive experimental study on the mechanical mechanism of jacked pile and the side resistance separation of open-ended pipe pile for the construction and bearing capacity determination of jacked pile. The influence of the pile end form on the pile penetration mechanism in the homogeneous cohesive soil layer was discussed by means of laboratory model tests. Based on the development of the double-wall open-ended model pipe pile, and combining utilization of sensitized fiber Bragg grating strain sensor and double-diaphragm temperature-self-compensating fiber Bragg grating earth pressure sensor, the “soil plug resistance” implied in the pile jacking resistance was separated, and the variation rules of axial force and pile jacking resistance of the pile during the penetration of open-ended pipe pile were obtained. The test results showed that the different pile end forms not only affected the development of pile end resistance, but also had a significant influence on pile side resistance. With the increase of depth, the axial force of the close-ended pile decreased continuously, and the decline rate of axial force acting on the open-ended pile far from the pile end increased gradually, and the axial force near the pile top was basically 0. The unit pile side resistance continued to increase with depth, and the degree of unit pile side resistance of the open-ended pile external pipe pile body was less than that of the close-ended pile. At the same depth, with the increase of penetration depth, the unit pile side resistance decreased continuously, i.e., the phenomenon of "side resistance degradation". Moreover, with the increase of penetration depth, the unit pile side resistance at this position decreased more, which was consistent with the existing research conclusions on the mechanical properties of jacked pile penetration. The research results can provide references for the construction design of jacked pile in cohesive soil.关键词：jacked pile;axial force;unit skin friction;mechanical mechanism;clayey soil;experimental test
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发布时间：2024-01-08
HYDRAULIC & CIVIL ENGINEERING
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In-situ Calibration Method for Dual-sensor Weighing System Based on Sensitivity Change Mechanism AI导读
摘要：The sensitivity coefficient is no longer the same before and after the installation of weighing system sensor due to the unbalance loading resulting from the shape error of the sensor mounting surface. Thus, it need to be re-calibrated before use. For dual-sensor systems, due to the different installation conditions of each sensor, the sensitivity coefficient is not only different before and after installation, but also not the same as each other, on the other hand, due to the randomness of load center when calibrating, there is no guarantee that the two sensor bear the same force, so the load weight is unknown. The stochastic interaction between unbalance loading and randomness of loading position makes it difficult to calibrate the sensitivity coefficient of the dual-sensor system. At present, the common calibration method is to attach potentiometer and other components to the processing circuit to changing the magnification of the original signal to make the sensitivity of each path be the same, and then load standard weight to complete the calibration. This method needs to change the original circuit, which may bring unknown influence, and it’s difficult to realize for integrated processing circuit. Aiming at the these problems the sensor force model was established, the influence mechanism of unbalance loading and gravity position on sensitivity coefficient was defined by force analysis,and the sensitivity calibration algorithm was deduced. The sensitivity coefficient of dual sensor system was decomposed into two parts, coupling coefficient and conversion coefficient, and calibration could be completed after loading two times in different positions with the same standard weight. This new calibration method could ensure the measurement accuracy of the system under unbalance loading. The experimental results showed that the new method did not change the original measuring circuit and mechanical structure, and the system error was less than 0.03%.关键词：weighing system;dual-sensor;force analysis;calibration;coupling coefficient- 2366
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发布时间：2024-01-08 - 摘要：Vibration isolation is almost not taken into consideration in micro-cultivator design at present. When the machine is running, it will generate excessive vibration and make the operator unbearable. Aiming at solving the problem, the mathematical model of magnetorheological (MR) elastomer with variable stiffness and damping was established based on the model of MR fluid and the equivalent stiffness and damping were calculated by the model. Meanwhile, a new structure MR elastomer vibration isolator was designed and mathematical model of vibration isolation system was built. The influence of stiffness and damping to the system stability was studied then. Subsequently, variable stiffness and damping control strategies were constructed according to the characteristics of MR elastomer. Based on these data, the Simulink simulation model was constructed to carry out simulation analysis to verify the control effect from the simulation results by adopting PID control, ON/OFF control and no control strategies. The results showed that: in step input, the displacement and velocity responses of PID control system would tend to stability much more rapidly than those of ON/OFF control. The maximum displacement and velocity amplitudes of ON/OFF control were about two times and eight times than those of PID control, respectively; it would take a very long time for displacement and velocity responses of no control tending to stability and the amplitudes were the largest. In multi-frequency sine input, the displacement amplitude of no control was five times more than that of ON/ OFF control and about ten times than that of PID control. The velocity amplitude of no control was seven times than that of ON/OFF control. However, the velocity amplitude of ON/OFF control was slightly larger than that of PID control. In random input, the displacement amplitude of ON/OFF control was smaller than that of no control, but it was larger than that of PID control overall. Furthermore, the displacement curve of PID control was the smoothest. The velocity curve fluctuation of PID control was the smallest, the ON/OFF control was the second, and the fluctuation without control was the largest. In hybrid input, the displacement and velocity amplitudes of no control were about four times and seven times than those of ON/OFF control, respectively and the displacement and velocity amplitudes of ON/OFF control were both two times than those of PID control, respectively. The displacement and velocity curves fluctuation of PID control were the smallest. In conclusion, PID control strategy is simple and PID control effect is the best. It will lay a theoretical foundation for future controller development and experiment verification.关键词：micro-cultivator;MR elastomer;vibration isolation system;control strategy
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发布时间：2024-01-08 - 摘要：Multi–robot cooperation is widely used in cooperative handling, stamping, welding and other fields, with higher precision and more flexibility. The interpolation algorithm and the force/position control performance determine the smoothness of the trajectories and the stability of the cooperative operation, and also directly affect the bearing capacity and the operation quality. In this paper, the force/position control technology in the process of two robots cooperative handling was studied. First, the clamping characteristics and stress state of two robots cooperative handling were analyzed, and the ideal mathematical model of cooperative handling system was established. Next, according to the mathematical model of the second–order damping system of the master–slave robot, the master–slave cooperative control mode was adopted to design the force/position control strategies respectively. The optimized fuzzy self–tuning position control based on the ideal position was presented for the master robot, and the damping control with the optimized bacterial foraging algorithm based on the force optimization of position deviation of the master robot was presented for the slave robot, and the design of the controller was carried out. Then, the main body of the algorithm and its cost function were programed in MATLAB, and the control system was established in Simulink. Finally, the whole controller was simulated. The simulation results were as follows. The maximum position error of the master was 1.53 mm, and the maximum force error of the slave was 0.038 N. The position error of tracking down between the slave and the master was within 0.18 mm, and the slave could quickly correct the master–slave speed deviation within 0.2 s. The simulation results showed that compared with the conventional PD control method, the proposed controller could reduce the maximum tracking error by 40% and effectively eliminate the zero–crossing oscillations of the force tracking. This method could significantly improve the dynamic performance of the system.关键词：dual robots;cooperative handling;position control;damping control;fuzzy adaptive;bacterial foraging algorithm(BFA)
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发布时间：2024-01-08 - 摘要：In the initial design stage of machine tools, only the information of tolerance of machine tools’ key components is known. Since geometric errors of machine tools can play the role of guidance for the accuracy design of machine tools, geometric errors were obtained only by making use of design experiences. Hence, it is important to predict the geometric errors accurately in the design process of new machine tools. A new approach to predict geometric error based on tolerance of machine tools’ guideways was proposed. Firstly, the mapping relationship between tolerance and profile errors of machine tools’ guideways was established by utilizing the truncated Fourier series function to fit curve of guideways surface profile. Meanwhile, the mapping relationship between profile errors and geometric errors of guideways was established. Since profile errors are regarded as a bridge between tolerance and geometric errors of machine tools’ guideways, geometric errors prediction model based on tolerance of guideways was proposed. Then, simulation verification was carried out. Simulation results showed that the range of the predicted kinematic error (positioning error, y direction and z direction straightness error, roll error, pitch error, and yaw error) is 17.12 μm, 56.57 μm, 70.71 μm, 28.28 μrad, 141.42 μrad, and 113.14 μrad, respectively. Finally, a measuring experiment was carried out by using a dual-frequency laser interferometer. The measured and identified results could be fitted precisely by Fourier curve fitting method. The fitting results showed that the range of the measured kinematic errors was 16.96 μm, 59.43 μm, 68.63 μm, 28.65 μrad, 135.40 μrad, and 111.58 μrad, respectively. By means of contrasting the measured results and predicted results, residual errors were no more than 10% of the measured results. Therefore, in the design stage of machine tools, this method is effective enough for predicting geometric errors and can be used to replace the measurement of geometric errors, and lays a foundation for designers. And its basic idea can be applied to other type of guideways.关键词：machine tools’ guideways;truncated fourier series function;geometric error;tolerance;profile error
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发布时间：2024-01-08
MECHANICAL ENGINEERING
- 摘要：In order to improve the feature utilization rate of the image to be detected, a Deepfake video detection model based on consistency of spatial-temporal features was proposed, inspired by the observation that there are slight inconsistency and discontinuity in the facial expression changes of the characters in Deepfake videos. In the model, the convolutional neural network (CNN) was used to extract the spatial features from the video to be detected, and an optical flow method was used to perform temporal features between consecutive frames of the video. Then another CNN was used to extract the abstract and in-depth features from the optical flow map. After the temporal features and spatial features were transformed from original representation space to a new feature space by neural networks, a fully connected neural network was used to classify the combined spatial and temporal features space to achieve the detection target. The model proposed in the paper was trained on the Faceforensics++, an open source Deepfake dataset. The experimental results indicated that the detection accuracy of the proposed model reaches 98.1%, and the AUC value reaches 0.998 1. By comparing with the existing Deepfake detection models, the proposed model is superior to the existing models in terms of detection accuracy and AUC value, which verifies the effectiveness of the proposed model.关键词：fake images;Deepfake detection;temporal features;spatial features
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发布时间：2024-01-08
CYBERSPACE SECURITY
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