最新刊期
卷 55 ， 期 2 ， 2023
- 摘要：At present, network threats have entered the era of unknown threats. However, traditional network security is based on “Maginot” static passive defense, which lacks autonomy and endogenous security ability of self evolution. The unknown threats can only be remedied afterwards by “patching”. Yet, this method is often accompanied by huge losses, and new ideas should be sought. The network security protection system has striking similarities with the human immune system. The immune system does not require prior knowledge of viruses, has strong learning and deduction ability, and is born with the ability to inactivate unknown viruses. Inspired by immune system, with “unknown threat” as the core and “artificial immunity” as the innovative means, this research focused on four key scientific issues, including the evolution mechanism of network security system, network adaptive trusted transmission conditions, the rapid discovery mechanism of unknown threat, and the rapid response strategy of unknown threat. Meanwhile, a basic theory, three key technologies, and a prototype system were studied in this paper. Through the research on new network architecture and basic theory based on immunity for endogenous security, the mRNA immune-based trusted network addressing and routing control technology, the large-scale dynamic trusted behavior analysis and unknown network threat discovery technology, and the immune-based network dynamic risk assessment and control technology, the traditional “patch” passive defense network security technology bottleneck will be broken, thereby laying the basic theory and method of the new network system supported by endogenous security. Finally, by constructing a new immune-based network prototype system for endogenous security, the research results were technically verified, and the proposed theories and methods can be further improved according to the verification results. Through the above research, the following five innovations have been achieved: 1) the cyberspace security immune architecture for endogenous security, 2) the mRNA immune-based trusted network addressing and routing control method, 3) the adaptive discovery method of unknown network threats based on gene evolution, 4) the real-time quantitative calculation method of network dynamic risk based on human body temperature warning mechanism, 5) the rapid dynamic feedback iterative network risk control method based on specific immunity. The research results have important theoretical significance and practical application value for scientific research, technology research, and industrial development of cyberspace security protection.关键词：endogenous security;network intrusion detection;risk assessment;risk control;artificial immune system
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发布时间：2024-01-10
FOCUS ON STATE KEY RESEARCH DEVELOPMENT PROGRAM OF CHINA
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Development and Application of Dual-structure TBM for Complex and Changeable Geological Tunnels AI导读
摘要：Southwest arduous mountain tunnel construction faces severe challenges in terms of plateau alpine, large terrain height difference, complex geological conditions, etc. The application of a full-section tunnel boring machine (TBM) is one of the effective ways to efficiently complete the Sichuan-Tibet Railway tunnel, but the conventional TBM can no longer meet the complex geological and variable tunnel construction requirements. To ensure the safe and efficient construction of TBMs, a new dual-structure TBM was proposed to adapt to the extremely complex geological environment. Through the research and practice of TBM engineering under complex geological conditions, firstly, the adaptability of different models of TBMs under adverse geological conditions was discussed, and the tunnel deformation mechanism of open type TBMs under high ground stress rock explosion stratum, dense zone of joints and altered rock stratum was analyzed in depth; furthermore, based on the conventional open TBM structure, a series of innovative designs have been developed, such as advance geological forecasting interface, mainframe structure enhancement, reinforced support capability and slag removal capability, advance ground stress release, safety protection measures, anti-seize, and extrication, etc. In view of the limitations of single-structure TBM in facing complex geology, a conventional geological "net-spray-anchor" design has been established. Finally, based on the Sejila Mountain project, we evaluated the adaptability of dual-structure TBMs in poor geological conditions by combining the application of dual-structure TBMs in the field. Finally, based on the Sejila Mountain project, we evaluated the adaptability of dual-structure TBMs in adverse geological conditions, and the overall tunneling rate results in the field showed that the dual-structure TBM was effective in the construction of geologically variable tunnels.关键词：treacherous mountain tunnels;adaptability;dual-structure TBM;complex and changeable geology- 405
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发布时间：2024-01-10 - 摘要：The areas where tunnels run through faults are the key areas for seismic design and easily to be seriously damaged in earthquakes. Since the current design methods seldom considered tunnels passing through faults, the tunnel was simplified to three shear beams on a viscoelastic foundation under different strata along the longitudinal direction, and the analytical solution of the longitudinal seismic steady-state responses of tunnels passing through the faults was derived. A simplified analysis method was proposed for the longitudinal seismic responses of tunnels passing through faults. First, a shear beam on Kelvin’s viscoelastic foundation was utilized to simulate the lining segment. The longitudinal responses of a lining segment under external loads were derived by using Green’s function method, Laplace transform, Laplace inverse transform, and residue theorem. Then, the analytical solution of longitudinal responses of the tunnel crossing the fault was obtained by combining with the continuity condition of the lining segment. Next, the validity and feasibility of the proposed method were verified by comparing with the numerical analysis. Finally, the sensitivity analysis of parameters was conducted using the proposed method to reveal the influences of parameters on seismic responses of tunnels through faults. The results showed that increasing the bending stiffness of the lining could reduce the displacement responses of the lining, but at the same time significantly increased the internal forces of the lining. Reinforcing the fault surrounding rock could reduce the displacement responses of the lining, as well as the internal force responses of the lining, and reduce the influence range of the fault on the seismic responses of the tunnel along the tunnel axis under the action of ground motion. The damping made the vibration of the tunnel lining appear asynchronous along the longitudinal direction. The higher the frequency of the wave was, the more obvious the vibration asynchrony of tunnel lining was. The proposed method could make a quick calculation of the seismic responses of fault-crossing tunnels, which provided a reference for the seismic design of related tunneling projects.关键词：tunnel engineering;analytic method;fault;longitudinal seismic response;viscoelastic foundation beam
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发布时间：2024-01-10 - 摘要：Cracked bedding rock slopes (CBRSs) are numerous in the southwest mountainous area. The action of earthquakes often causes disasters, such as collapses and landslides. The distribution law of the structural plane is herein detailed via field research and references to engineering geological data based on a CBRS project in the southwest mountain area. Moreover, the overall stability of the slope is examined through stereographic projection. On this basis, multiple groups of CBRS models were established through discrete-element UDEC, and their dynamic characteristics and failure modes were analyzed by loading EL–Centro and Kobe waves. Further, the sensitivity of joint parameters to displacement and acceleration responses was studied. The research results demonstrate that the displacement response of the slope first increases and then decreases, and the maximum displacement response of the slope occurs at M4. The PGA amplification coefficient of the slope model clearly demonstrates the elevation amplification effect, and the type of seismic wave affects the PGA response law. The local FFT amplitude drops as the seismic wave crosses the structural plane at the intersection of strong and weak weathering. The CBRS fails under the fracture propagation–sliding failure mode of the strongly weathered rock mass. According to the sensitivity analysis of joint parameters, the spacing of strong weathered joints has the greatest influence on acceleration amplification, whereas the bedding spacing in weakly weathered rock regions has the most pronounced effect on displacement. The numerical simulation analysis reveals the dynamic response law and failure mode of a CBRS under earthquake, which provides a useful reference for further studying the disaster mechanism and preventing such slope occurrences.关键词：bedding rock slope;degree of weathering;dynamic response;evolution process of instability;parameters sensitivity
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发布时间：2024-01-10 - 摘要：In order to evaluate the stability of roadbed in frozen soil area, the dynamic shear modulus and damping ratio of fill along Qinghai—Tibet railway are analyzed by means of laboratory test and theoretical analysis. Firstly, the long-term consolidation undrained cyclic triaxial tests were carried out to analyze the effects of different negative temperature and cyclic stress ratio on dynamic shear modulus and damping ratio of subgrade silty clay and foundation sand. The results show that for subgrade silty clay, the dynamic shear modulus is negatively correlated with temperature, and increases with the increase of cyclic stress ratio, and the damping ratio decreases with the increase of dynamic shear modulus. For foundation sand, the dynamic shear modulus and damping ratio show the same trend under the influence of temperature as that of silty clay, but the value of dynamic shear modulus is about 110 MPa higher than that of damping ratio under the condition of –10 ℃ temperature and cyclic stress ratio of 0.2, which is 1.22 times, and the damping ratio is 0.66 times. It is worth noting that the dynamic shear modulus of sand responds to the peak value when the cyclic stress ratio is about 1, which means that when the dynamic stress amplitude reaches the confining pressure, the dynamic shear modulus tends to decrease while the damping ratio tends to increase with the increase of the cyclic stress ratio. Then, based on the high cycle model proposed by Wichtmann, the prediction model of dynamic shear modulus was established, which can well reflect the response law of dynamic shear modulus with vibration number under the influence of temperature and cyclic stress ratio. The fitting parameter w0 reflects the law of dynamic shear modulus increasing first and then decreasing with cyclic stress ratio. The fitted mathematical relationship shows that the dynamic response law of soil changes significantly when the number of long-term vibrations is about 13000 or the vibration duration is more than 8 minutes. Finally, based on Hardin-Drnevich hyperbolic model, the experimental results of dynamic shear modulus and damping ratio were fitted, and the functional relationship between dynamic shear modulus and damping ratio was obtained, so as to roughly predict the trend and range of damping ratio with the change of dynamic shear modulus. With the increase of normalized shear modulus, the damping ratio tended to decrease.关键词：Qinghai—Tibet railway;dynamic triaxial test;dynamic mechanical parameters;cyclic stress ratio;multiple-cycle forecasting empirical model
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发布时间：2024-01-10 -
Numerical Optimization Analyses of Dangerous Rock Mass Sliding Failure Under Freeze-thaw Cycles AI导读
摘要：The action of freeze-thaw (F–T) cycles is the main inducement for the collapse and instability of dangerous rock mass in cold regions, and it is particularly important to carry out numerical optimization analysis on the disaster pregnant factors of sliding failure of dangerous rock mass in cold regions. Firstly, based on the limit equilibrium theory, the stability analysis model of sliding dangerous rock mass under the action of F–T cycles was established by considering the frost heave force of through section structural plane, the deterioration of the cohesive force of the locked section, and the evolution of the freezing depth. Secondly, based on the theory of rock frost heave and considering the water migration during the freezing process, the calculation method of the frost heave force of the through structural plane section was derived. Thirdly, the mesoscopic defects of rock were simplified to numerous circular pores. According to the expansion theory of circular pores and the Mohr–Coulomb yield criterion, the process of pore frost heave failure was analyzed, and the meso degradation model of rock cohesion in the non-penetrated section under the action of the freeze-thaw cycle was constructed. Finally, the calculation method of the evolution of the rock freezing depth of the locked section with the number of F–T cycles was obtained by improving Stephan’s empirical formula. Combined with the engineering calculation example to analyze the influence of each sensitive parameter on the stability of the dangerous rock body, it was found that the stability of sliding dangerous rock mass showed a fast and then slowly declined with the increase of the number of F–T cycles. The stability coefficient of sliding dangerous rock mass was positively correlated with the freezing temperature. At the same freezing temperature, the stability coefficient decreased with the increase of the number of F–T cycles with a significant marginal decreasing effect. The stability of dangerous rock mass was negatively correlated with the rock debris loss ratio, and the rock debris loss ratio changed both the trend of stability deterioration and the degree of deterioration. Controlling the rock debris loss ratio was conducive to the long-term stability of the dangerous rock mass in cold regions.关键词：freeze-thaw cycles;limit equilibrium;frost heave force;mesoscopic deterioration;freezing depth;rock debris loss- 398
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发布时间：2024-01-10
ENGINEERING AND ENVIRONMENT IN CHALLENGING MOUNTAINOUS REGIONS
- 摘要：When faults occur in the receiving-end power grid, the sending-end power supply is required to have black-start capability. At present, the existing black-start power sources in China are mainly thermal power plants and hydropower plants. With a high proportion of wind power enormously connected to the main grid, wind turbines are required to have a certain black-start capability. However, due to the uncertainty and volatility of wind energy, it is difficult for wind turbines to participate in black start alone. In order to make wind turbines have better black start ability to participate in power grid restoration, this paper proposed a three-stage coordinated recovery strategy for the receiving-end power grid based on the combined wind-storage system for doubly-fed wind farms. In the initial stage, the AC frequency and voltage were established through the energy storage device so that the wind turbine can smoothly connected to the main grid. Then, in the middle stage, the control mode of the energy storage device was switched and a virtual synchronous control was designed on the rotor side of the wind turbine to provide support of frequency and voltage for the system, and some generator sets and loads can recover. After that, in the later stage, an additional robust controller based on H2/H∞ was designed on the energy storage side, which can suppress the low-frequency oscillation when multiple units connected to the grid, so as to realize the stable recovery of the receiving-end power grid. Finally, a wind-storage combined system model was built based on PSCAD/EMTDC and the black start and restoration of power grid restoration was simulated. The simulation results show that the proposed joint startup of both wind turbine and energy storage can realize the smooth grid connection of wind turbine; In the grid connection process of plant load and generator, switching energy storage control mode of wind turbine can maintain the voltage and frequency of in the stable range; Moreover, in the stage of recovery and later operation of receiving power grid, the designed robust controller designed has a good effect on suppressing low-frequency oscillation; Compared with the conventional control modals, the virtual synchronization control adopted in the process of system startup and recovery has a stronger ability to support the system; Thus, the effectiveness and feasibility of the proposed coordinated restoration strategy of wind and energy storage system participating in the black start of the receiving power grid are fully verified.关键词：wind-storage combined system;black start;doubly fed induction generator;virtual synchronization control;robust control
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发布时间：2024-01-10 - 摘要：With the large number of nonlinear loads connected into the power grid and the gradual increase of the power electronic rate, the harmonic problem is becoming more and more serious. It is an effective solution to carry out the regional management of harmonic pollution in the power system. The significance of the harmonic pollution zoning is that the harmonic distortion in the same zone is mainly caused by the harmonic source in this zone, and is less affected by the harmonic sources in other zones. On this basis, an anti-time-shift clustering algorithm, i.e. kDBA++ was proposed. First, considering the characteristics of power quality monitoring data such as high dimensions and noise, the Picesise Aggregate Approximation (PAA) algorithm was used to compress and denoise the data to reduce the subsequent computational complexity. Secondly, the kmeans++ algorithm was used as the logical framework. Considering the time shift phenomenon between data under asynchronous measurement, it is difficult to directly use kmeans++ to carry out clustering. To solve this issue, the dynamic time warping (DTW) distance was introduced to optimize the kmeans++ algorithm. Furthermore, to overcome the limitations that the clustering centroids are difficult to obtain under the DTW distance, the DTW Barycenter Averaging algorithm (DBA) was integrated into kmeans++, and finally the proposed kDBA++ algorithm was obtained. The IEEE123 node simulation system and actual engineering cases were used to carry out algorithm comparison research. The analysis results show that the proposed kDBA++ algorithm has better clustering accuracy than the existing algorithms, and can accurately carry out harmonic pollution zoning. In addition, the transfer impedance matrix of the harmonic pollution zoning and the harmonic contribution degree were used to verify the correctness of the obtained zones. The analysis results indicate that each harmonic source has a great influence on the harmonic distortion of the nodes in the zone where it is located, while it has little influence on the nodes in different zones. Thus, the practicability and effectiveness of the proposed method are verified.关键词：harmonic pollution;time-shift characteristics of monitoring data;harmonic pollution zoning;kDBA++ clustering algorithm
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发布时间：2024-01-10 - 摘要：Driven by the goal of “double carbon”, the distributed energy sources represented by the photovoltaic (PV), is being integrated into the distribution power system and the distribution gas system on a large scale. The coupling between the two systems also has become closer, which brings new opportunities for the construction of low-carbon sustainable energy systems. However, the stochastic nature of distributed energy sources inevitably creates potential operational risks between the two systems. Based on this, this paper proposed a multi-timescale optimal scheduling model for regional integrated energy systems with high proportional PV penetration. Firstly, a day-ahead scheduling model of the electricity-gas integrated regional energy system considering energy storage devices was established under the premise of high PV penetration. The model was linearized by using the second-order-cone relaxation. Secondly, based on the theoretical basis of the CVaR risk assessment model, the loss function was established and simplified. Thirdly, the CVaR risk assessment model was considered in the real-time scheduling process. The real-time scheduling model of the regional integrated energy system considering the CVaR risk assessment was established to balance the risk cost caused by the renewable energy uncertainty under different risk attitudes. Finally, the two aforementioned models were combined. Thus the regional integrated energy system day-ahead-real-time multi-timescale scheduling model was established to analyze the interaction and energy flow between the regional power system and the regional gas system. The model was validated by different load intensity scenarios in the case analysis. The changes of system power purchase and different parameters of equipment operations under different scenarios were also analyzed. The results show that the proposed model can effectively mitigate the operational risks caused by the random fluctuations of new energy sources. At the same time, the operational regulation of the coupled equipment can promote the coupled operation of the regional integrated energy system and achieve good economic benefits.关键词：distributed energy sources;energy storage;high proportion photovoltaic;multi-timescale;conditional value at risk (CVaR)
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发布时间：2024-01-10 - 摘要：Large-scale PV adopts DC overhead lines for flexible DC grid connection is one of the trends of new energy grid-connected in the future. However, the high probability of DC short-circuit fault of overhead line can easily lead to the disconnection of photovoltaic power stations or the damage of power electronic devices in converter stations. To solve this problem, firstly, according to the characteristics of flexible direct current transmission system and photovoltaic power station, the corresponding mathematical and simulation system model were established. Secondly, in view of the single-pole short-circuit grounding fault condition of DC overhead line in the high-voltage DC power transmission system with large-capacity PV through bipolar modular multilevel converter, the fault characteristics were analyzed. Finally, considering the control mode of DC circuit breaker and converter station, as well as the power output of photovoltaic power station comprehensively, the coordinated control strategy of DC fault traversal were proposed. That is, when a fault occurs, the power transmission is continued by using the non-fault pole converter station, and the unbalanced power is calculated according to the rated power of the converter station and the output power of the photovoltaic power station. By making full use of the power output characteristics of the photovoltaic array, the DC line voltage in the photovoltaic power station is optimized, and the output power of the photovoltaic power station is reduced. To solve the problem of DC overhead line fault traversal under instantaneous failure, the load reduction of photovoltaic power station and power feed-forward incremental control of converter station were proposed, so as to maintain the power balance of the system and improve the grid connection stability of the system. Based on the simulations on PSCAD/EMTDC, the comparison of system parameters before and after fault traversal measures shows that the proposed method can effectively maintain the operating characteristics of photovoltaic power station and flexible DC system, and smoothly achieve fault traversal.关键词：photovoltaic power station;fault ride through;high voltage direct current
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发布时间：2024-01-10 - 摘要：In the hydro-rich areas with high proportion of hydropower in the transmission network, the capacity utilization of transmission lines varies seasonally due to the impact of hydropower abundance and depletion characteristics. Therefore, it is important to investigate the expansion planning method of coordinating the capacity utilization of transmission lines with the system economy. On this basis, an expansion planning method of transmission network with high proportion of hydropower was proposed in this paper by taking into account the capacity utilization of transmission lines. The capacity utilization of transmission lines was used to guide the transmission network expansion planning decision considering the impact of hydropower abundance and depletion characteristics. First of all, the capacity utilization of transmission lines index was proposed by considering the safety margin and development margin. Second, the optimal dispatching model of transmission network with high proportion of hydropower was constructed with the objective of minimizing the generation cost, the penalty cost of load shedding and the penalty cost of hydropower spillage. After that, calculation method of the congestion capacity utilization of transmission lines and the congestion rate of transmission network were proposed. The severe congestion scenarios were identified by calculating the capacity utilization of transmission lines and congestion rate of transmission network under four different operation scenarios: High load during abundant water period, low load during abundant water period, high load during dry water period and low load during dry water period, respectively. Finally, with the objective of minimizing the cost of investing in transmission lines, the operation cost of transmission network, the penalty cost of load shedding and the penalty cost of hydropower spillage, the transmission network expansion planning model with high proportion of hydropower were constructed. Specially, the severe congestion scenarios were incorporated into the transmission network expansion planning model to derive the investment decision of transmission lines. The proposed transmission network expansion planning model was simulated with four cases: Without expansion planning, expansion planning without considering capacity utilization of transmission lines, expansion planning considering capacity utilization of transmission lines, and expansion planning considering higher congestion rate threshold. The simulation results show that the considering of capacity utilization of transmission lines in the transmission network expansion planning with high proportion of hydropower can help reduce blockage and security risk of the system. The effectiveness of the transmission network expansion planning method with high proportion of hydropower considering the capacity utilization of transmission lines is verified.关键词：expansion planning;hydropower consumption;capacity utilization of transmission lines;congestion scenario
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发布时间：2024-01-10 - 摘要：Due to its unique advantages, the multiple renewable energy complementary combined power generation technology is becoming one of the preferred power supply scheme under the “carbon peaking and carbon neutrality” context. The optimal dispatching of this complementary coordinated generation system considering its complex uncertain coupling characteristics has attracted more and more attention. For uncertain optimal dispatching problems, this paper introduced the data-driven distributionally robust optimization (DRO) theory, which can better balance the uncertainty and the robustness of the problem. A new coordinated optimal dispatching method for the cascaded hydro-PV-pumped storage combined system was further proposed based on the data-driven DRO theory. This method established a two-stage DRO dispatch model to formulate the daily dispatch schedule considering the complementary economic dispatch cost of the system firstly. The comprehensive norm constraint was introduced to limit the probability confidence interval. Considering the adjustment cost of the real-time operation under the worst distribution, the optimal dispatch schedule was formed by the optimized adjustment scheme for the day-ahead dispatch schedule, the daily dispatch schedule and the adjustive dispatch scheme. The two-stage dispatch model was solved by the CCG algorithm according to the MP-SP framework finally. In order to verify the performance of the proposed method, the actual operation data of the demonstration area in Sichuan was taken to carry out the validity verification, the performance comparative analysis and the simulation verification of computational efficiency. The results show that, the validity of the proposed scheduling method is verified in the data scale and the confidence level dimensions. For the robustness and economy comparison of the SO, the RO and the proposed method, the method proposed in this paper can achieve higher robustness than SO and higher economy than RO. Comparing the calculation time of this scheduling method with the probabilistic sequential production simulation method, this method achieves a higher computational efficiency with the same computational accuracy. Based on the two-stage dispatching model and the iterative calculation, the data-driven DRO coordinated dispatching method for the cascaded hydro-PV-pumped storage combined system can achieve the balance between the economy and robustness of the dispatching results. Its efficient performance has been verified and a new way is obtained for the complementary coordinated dispatching of multi renewables.关键词：cascaded hydro-PV-PSH system;coordinated dispatch;hydro-PV complementation;data-driven distributionally robust optimization (DRO);CCG algorithm
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发布时间：2024-01-10 -
Design and Realization of the Distributed Data Center of Full-view Synchronized Measurement System AI导读
摘要：The full-view synchronized measurement system (SYMS) has realized the all-directional real-time detection of power systems with high proportion of power electronics. As a platform for receiving and analyzing measurement data, the data processing ability of the SYMS master station is of great significance to ensure the stable operation and application effect of the SYMS. However, due to the reasons as the large number of data types, the surge in the number of devices, and the complexity of the data analysis process, it is difficult for SYMS master station with a centralized architecture to guarantee the real-time performance and reliability of the data processing. Therefore, a distributed master station design method for the SYMS system was proposed and implemented in this paper. Firstly, the proposed method analyzed the communication modes of different measurement devices of SYMS, established a multi-source heterogeneous data adapter based on the open source phasor data concentrator. This paper also designed and implemented a load balancing cluster of the main station front-end server based on the HAProxy. Secondly, aiming at the problem of high delay of the data online analysis of master stations, the Storm based on the stream processing framework was designed and developed to adapt the distributed computing method with multi-language and multi-time window algorithm. The SYMS distributed master station including the pre-data processing platform and the online application platform was further built. The actual system test results show that, compared with the centralized architecture, the proposed architecture can effectively balance the load in actual operation and improve the computing speed through the distributed method. The proposed architecture also have stronger concurrent processing capabilities and shorter delay for multi-type real-time measurement data. Furthermore, it can effectively monitor the abnormal state of the system. Therefore, it can provide the data foundation and application platform for characteristic analysis, modeling, closed-loop control and other applications of the new power system.关键词：full-view synchronized measurement system;distributed architecture;data center;OpenPDC;Storm- 459
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发布时间：2024-01-10 - 摘要：In recent years, under the background of “double carbon”, the distributed new energy generation with nearly zero marginal generation cost has developed rapidly. However, how to study the energy trading mechanism among the “prosumers” of distributed new energy generations and its impact on the power system planning face important challenges. Focusing on the impact of such transaction behavior on the planning level for photovoltaic-storage aggregated energy systems, an optimal configuration method for the capacity of photovoltaic and energy storage systems based on the virtual electricity transaction mechanism was proposed. Firstly, aiming to generate electrical pricing and simulate the optimal operation state under a certain capacity configuration, a negotiation and matching mechanism for the electricity transaction between aggregators were established based on the benefit function of photovoltaic-storage aggregated energy system. Secondly, considering the impact of decentralized transaction behavior of aggregators on the capacity configuration, an optimal capacity configuration model of photovoltaic-storage aggregated energy systems considering the virtual energy transaction was proposed. The transaction cost was added in the operation level to integrate the impact of transaction behavior into the model. The minimum cost of the capacity configuration was taken as the objective function. The transaction and configuration constraints were accounted for the security of the systems. Finally, the simulation was carried out in the MATLAB. Simulation results of the transaction algorithm parameter, the transaction process and the final capacity configuration show that, the transaction and pricing behavior between aggregators can be guided and the decentralized transaction of aggregators can be simulated by the benefit function proposed in this paper. The electricity price and load level are affected by the capacity configuration of photovoltaic and energy storage systems. Compared with other random schemes, the optimal capacity configuration scheme proposed in this paper meets the normal consumption of load and avoids the waste investment of the energy storage planning. This paper also provides the electricity pricing strategies for aggregators with the tradable clean energy at the transaction level, and provides an effective reference for the optimal capacity configuration method of the photovoltaic-storage aggregated energy system considering the impact of the distributed new energy transaction behavior.关键词：operation and simulation;optimal configuration;photovoltaic-storage aggregated power systems;virtual energy transaction
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发布时间：2024-01-10 - 摘要：With the continuous advancement of the construction of the power system with renewable energy as the main body and the distributed smart grid, the problem of the large-scale integration and consumption of renewable energy generations with random characteristics has become increasingly prominent under the strategic goals of “double carbon”. A day-ahead economic dispatch model for the building integrated energy system (BIES) was proposed in this paper. With its characteristics of multiple load requirements and flexible regulation, this model aimed to maximize the local consumption of the renewable energy on the basis of meeting the energy demand and grid interaction. First of all, according to the characteristics of the building energy consumption, the “determining power generation by heat” operation mode of the combined heat and power (CHP) system was decoupled by configuring the ground source heat pump and other electrical heating equipment with high energy efficiency ratio. The hybrid energy storage system with battery and heat storage tank was also introduced to further enhance the system adjustment ability. Then, considering the constraints such as the supply and demand balance, the equipment output, the energy storage operation, and the tie-line power exchange, the minimum total operating cost was taken as the objective function including the unit start-up, the unit shutdown, the loss of wind and photovoltaic power generations. The day-ahead economic dispatch optimization model of the system was further established, and CPLEX was used to solve this mixed integer linear programming problem. Finally, the system operation cost, the energy utilization rate and the renewable energy consumption capacity were taken as the evaluation indicators for simulations under different scenarios. The simulation results show that, compared with the traditional “heat and power distribution” mode, the BIES with the ground source heat pump and the hybrid energy storage system can reduce the operation cost by about 50%, and improve the energy utilization rate by about 50%. It can also completely consume the renewable energy generations. With the increase of the energy efficiency ratio of the energy conversion equipment, its operation cost can be further reduced, which has good operability and socio-economic benefits.关键词：building integrated energy systems (BIES);renewable energy consumption;ground source heat pump;hybrid energy storage
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发布时间：2024-01-10
NEW TYPE POWER SYSTEM
- 摘要：The analysis of rock slice images often relies on professionals to observe under a microscope and provide identification results, which is not only time-consuming and labor-intensive but also greatly affected by the equipment limitations. In recent years, automatic recognition methods for thin slice images have been proposed. However, most of these methods use a supervised strategy, which is limited by a large number of manual labeling and brings great difficulties to the generalization and application. In addition, when a model is applied to different reservoirs, lithology, and other targets, its generalization is greatly limited. Aiming at this problem, a method combining a superpixel algorithm with deep learning and semi-supervised self-training was proposed to achieve the automatic segmentation and component identification of thin-section images only by relying on 6% of manual labels, which greatly enhances the practical application of this method. First, the superpixel algorithm SLIC was used to pre-segment the rock image, and then the rough merging based on the color features of the segmented slices and cut according to the minimum circumscribed rectangle were performed, and. The cut rock component segmentation image was used as the basic data set for subsequent processing, and only 6% of the rock component data need to be manually labeled; then these data were passed through an improved self-training method, using the improved VGG16 model as the main model and the ResNet18 model as the judgment model, and constantly generate high-confidence pseudo-labels using iteratively optimizing the tuning and extending it to the entire dataset, and finally obtain a component identification model with high stability, accuracy, and consistency. Through the testing and analysis of actual data, the method combining SLIC and semi-supervised self-training proposed in this paper can recognize 6 types of rock components with an accuracy of 96%. It can help users basically achieve automatic component identification under the condition of little data difference. When there is a large difference in the datasets, only a small number of samples can be labeled to achieve automatic component identification. Through theoretical verification and actual data testing, the proposed method has high generalization and reliability and can provide sufficient accuracy and convenience in practical applications.关键词：SLIC;VGG16;ResNet18;rock image;image segmentation;semi-supervised learning;self-training;super-pixel
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发布时间：2024-01-10 - 摘要：Steel scrap is an important source of ferrite for the modern steel industry and an important raw material for steel companies to achieve carbon neutrality. The price of different grades of scrap varies greatly and its quality directly affects the production cost and product quality of steel enterprises. Therefore, the classification and grading of scrap before feeding into the furnace has received widespread attention and great concern from steel enterprises. To address the problems of low efficiency, poor safety, and fairness in the classification and rating of scrap by traditional manual methods, a scrap classification and rating model (CCBFNet) based on the spatial and channel attention mechanism and weighted bidirectional feature fusion network was proposed in the paper. Firstly, a physical model of scrap quality checking was built to simulate the production operation scene of unloading scrap by trucks, and high-resolution vision sensors were used to collect the images of different types of scrap. Secondly, a deep learning model combining attention and feature fusion was designed for scrap quality inspection in the model training stage, and the spatial and channel attention module (CBAM) was added to the backbone network to extract features from the collected scrap image dataset, focusing and retaining the important features of the images; then, a weighted Bidirectional Feature Pyramid Network (BFPN) was used. Secondly, the multi-scale feature fusion was performed by balancing the multi-scale feature information using the Bidirectional Feature Pyramid Network (BiFPN). Finally, in the model prediction stage, the constructed scrap quality verification model CCBFNet was used for scrap category and quality grading to verify the accuracy and detection efficiency of the model. Based on the homemade scrap validation dataset, the performance of CCBFNet was compared with the mainstream target detection Faster R–CNN, YOLOv4, YOLOv5 series, and YOLOv7. The experimental results showed that the Acc of CCBFNet reaches 86.8% and the mAP is 89.2%, which are higher than the compared target detection models. The proposed CCBFNet can fully meet the actual production applications in terms of accuracy, real-time and recognition rating efficiency, solve many difficulties in the process of scrap classification and rating, and realize the intelligent quality inspection and fair determination of scrap.关键词：recycling iron–steel materials;scrap intelligent rating;deep learning;attention mechanism
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发布时间：2024-01-10 - 摘要：Early passive rehabilitation training after stroke can promote brain nerve remodeling and even regain motor ability. Most upper limb rehabilitation robots use parameterized regular curves as passive training trajectories, which fail to integrate the experience of rehabilitation doctors and the individual characteristics of patients, or lack smooth optimization of three-dimensional customized trajectories and safe interaction during training. Therefore, this research studied the trajectory customization, optimization and tracking control strategy based on the novel end-effector 3 degrees of freedom (DOFs) upper limb rehabilitation robot. Firstly, the admittance algorithm and force compensation strategy were applied in Cartesian space to realize the customization of the trajectory by the physiotherapist. Then, the original trajectory data were compressed by Douglas-Peucher method to obtain a few via points. The non-uniform rational B-spline curve (NURBS) was used for interpolation, and an improved butterfly optimization algorithm (BOA) based on dynamic switching probability and t mutation was used to minimize the trajectory curvature. Finally, the sliding mode adaptive control based on the radial basis function (RBF) network and the speed feedforward plus PID control strategy were designed to control the trajectory tracking. In addition, the admittance-impedance control was added, forming a multi-mode tracking controller, to make the training safe with the large human-robot interaction force. The results showed that the dragging force of trajectory customization is within 5N. The improved BOA algorithm has higher convergence speed and accuracy, and the curvature of the optimized trajectory is smaller. The control strategy can resist the interference within the threshold and keep the tracking error within 6mm. The mode can switch in 0.3s, to compliant to large interaction force and improve the safety of training .关键词：rehabilitation of upper limbs;butterfly optimization algorithm;trajectory customization;trajectory optimization;trajectory tracking control
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发布时间：2024-01-10 - 摘要：At present, using electroencephalogram signals combined with deep learning methods for depression auxiliary detection still suffers from some problems such as insufficient feature extraction and low accuracy of detection. In order to extract more representative features and improve the accuracy of depression auxiliary detection, this study modifies the model from two aspects: feature extraction and network framework. A depression auxiliary detection model was proposed by combining the modified VGG–16 network and the channel attention mechanism based on the Squeeze-and-excitation Networks(SEMod–VGG). Firstly, the differential entropy of frequency bands named α(Alpha), θ(Theta) and β (Beta) in electroencephalogram were fused with the power spectral density for the corresponding channels to form a four-dimensional fusion feature which takes on time-frequency and energy attributes; Then, for the four-dimensional feature, the existing VGG–16 model was modified and two different scales convolution kernels , 5×5 and 7×7 were simultaneously used to improve the generalized characterization of the feature while extracting the time-frequency and power information of the electroencephalogram signals. Subsequently, the channel attention mechanism based on Squeeze-and-excitation Networks was combined with the modified detection model to calibrate the weights of the electrode channels. Finally, the ten-fold cross validation was utilized to optimize the least squares support vector machine, which improves the limitations of traditional support vector machine. Experimental evaluation in three aspects, namely, auxiliary detection accuracy, recall and network performance were conducted in the paper. The results on the MODMA dataset showed that SEMod–VGG yields the best accuracy for detection when four-dimensional fusion features are used as input: 92.21% for 3 channels, 93.47% for 16 channels and 95.76% for 128 channels. Besides, the detection recall of the model also reaches a higher level: 91.57% for 3 channels, 92.46% for 16 channels and 96.80% for 128 channels. Compared with the existing models of depression auxiliary detection, the proposed fusion features are more characterizing for depression, and the model achieves significant improvements in detection accuracy, recall and model efficiency.关键词：electroencephalogram;depression auxiliary detection;feature fusion;channel attention;least squares support vector machines
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发布时间：2024-01-10
INTELLIGENCE INTERDISCIPLINARY SCIENCE AND ENGINEERING
- 摘要：Hoek–Brown strength criterion has been widely used in rock and rock mechanics analysis, rock slope stability analysis, rock tunnel design, and other fields, but the conventional Hoek–Brown strength criterion does not consider the influence of intermediate principal stress on rock strength, and its application cannot reflect the true triaxial mechanical properties of rock. Therefore, it is necessary to improve the Hoek–Brown strength criterion. By analyzing the true triaxial test results of rock, the influence law of rock intermediate principal stress on rock strength was clarified. There are two characteristics of strengthening and restraining its influence: when it is greater than the critical value
$\sigma_2^* $ $\sigma_2^* $ 关键词：strength criterion;Hoek–Brown strength criterion;intermediate principal stress;true triaxia- 360
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发布时间：2024-01-10 - 摘要：Design flood determines reservoir safety in the context of reservoir flood control operation. However, many uncertainties come with design flood calculation process. This paper proposes a reservoir risk operation model for flood control under design flood uncertainty and explores reservoir flood control operations. Specifically, the Copula function is employed to establish the joint distribution model of flood peak and the maximum three-day flood volume. The Monte Carlo method is used to resample the bivariate design flood under specific return period. Moreover, in order to lower the impact from selection singleness in the traditional design flood hydrograph, we classify the measured flood processes into different types and perform random simulations to generate large amount of design flood processes. Finally, the economic index conditional value at risk (CVaR) is introduced to measure the risk of the maximum reservoir level exceeding the flood control water level in the process of reservoir flood control. A reservoir risk operation model for flood control employing CVaR is established. Different reservoir flood control operations can be obtained under different risk coefficient values. The Ankang reservoir is selected as the case study. It can be seen that design flood uncertainty is considerably large with secondary type return period of one hundred years. The K-means clustering method divides the measured flood processes into three categories. Then, the Monte Carlo method is used to simulate different types of flood processes and obtain a large amount of design flood processes. Facing the uncertain design flood processes, we derive reservoir flood control operations under different risk coefficients. This paper establishes the reservoir risk operation model for flood control which can effectively copes with the uncertain design flood. The results can provide support for making reservoir flood control operations under design flood uncertainty.关键词：Copula function;Monte Carlo;random simulation;CVaR;flood control operation
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发布时间：2024-01-10 - 摘要：Aiming at the prediction of the uplift capacity of shallow-buried inclined strip anchor plates, the nonlinear Mohr-Coulomb failure criterion was employed in the analyses, and an asymmetric curve failure mechanism of the soil mass above the anchor plate in a limit state was proposed. Then based on the upper bound method and the principle of virtual power, the analytical solutions for the ultimate pullout force of the anchor plate and the soil failure curve were deduced. On this basis, the influence laws of buried depth ratio, inclination angle, nonlinear coefficient, initial cohesion, unit weight, and ground overload on the ultimate pullout force and soil failure range were obtained. The results show that the ultimate pullout force of the anchor plate increases with the increase of inclination angle, buried depth ratio, initial cohesion, unit weight, and ground overload, but decreases with the increase of nonlinear coefficient. The failure range of the soil mass decreases with the increase of nonlinear coefficient and unit weight but increases with the increase of initial cohesion and ground overload. The inclination angle, buried depth ratio of the anchor plate and the initial cohesion, and nonlinear coefficient of the soil mass have a significant influence on the uplift capacity and failure range, and more attention should be paid to engineering design and construction. Finally, a comparison analysis with existing research works was conducted. The ultimate pullout force and the failure range of the anchor plate obtained by this method are in good agreement with the results of existing research methods, which further verifies the effectiveness of the proposed method. The research work can provide some theoretical references for the design and construction of strip anchor plates.关键词：nonlinear Mohr–Coulomb failure criterion;inclined anchor plate;uplift capacity;upper bound theorem
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发布时间：2024-01-10 - 摘要：With the popularization and application of tunnel boring machine (TBM) in the rock roadway excavation of deep coal mines, the bad formation had become the main factors that influence the safety and working efficiency of TBM excavated deep-buried coal mine roadways. To solve the problems of supporting TBM excavated coal mine roadways in undesirable grounds, the fabricated support structure for TBM excavated coal mine roadways was proposed and the full-scale models of fabricated support structure were manufactured. The Full-scale loading tests of the supporting structure under different lateral pressure coefficients were carried out to study the deformation and failure form, bearing capacity, and strain distribution characteristics of the prefabricated roadway support structure, the influencing factors of the supporting structure bearing capacity were determined and the failure mechanism of the support structure was revealed. Moreover, numerical tests of support structures were conducted to obtain parameters such as axial force and bending moment that were difficult to be monitored in experimental tests. The partial failure first appeared at the segment joints and the middle portion of the segments, which in turn led to the overall instability of the structure. When the lateral pressure coefficientλ=1.0 and 1.5, the ultimate bearing load of the support structure was 3972.2 and 2763.2 kN, respectively. With the increase of the lateral pressure coefficient, the bearing capacity of the support structure decreased exponentially, and the deformation and failure of the structure became more obvious. The ultimate bearing capacities of the supporting structures in the mechanical test were slightly smaller than that of the numerical tests, and the results of the mechanical test and the numerical test were in good agreement. In the uniform load test, the axial force at the joints of the supporting structure was relatively large, the bending moments at the mid-span of the joints and segments were large, and the bending moments were positive. In the non-uniform load test, the axial force of the supporting structure was slightly reduced. The bending moment values were both positive and negative, and the bending moment was higher than that of the uniform load test.关键词：tunnel boring machine;coal mine roadways;support structure;full-scale test;numerical analysis
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发布时间：2024-01-10 -
Design and Experimental Study of Pressure-retaining Sampling Device for Sediments in Hadal Trenches AI导读
摘要：To realize pressure-retaining sampling of deep-sea sediments, a self-sealing all-depth oceanic sediment pressure retaining sampling system based on the lander is proposed. The sampling system comprises a deep-sea oil-filled motor, transmission machinery, sampling machinery, pressure holding cylinder, accumulator, pressure sensor, multiple high-pressure needle valves, and stainless steel capillary. In addition, an underwater battery dedicated to ultra-high deep-sea pressure is also designed to power the sampler for autonomous sampling on the seabed. The total weight of the equipment is 60 kg, and the underwater weight is 45 kg. The structure of the device is simplified, and the weight is reduced by designing a new sampling machinery with petal compression ring-shaped sampling, self-sealing at the lower end, and self-balancing at both ends. Through the analysis and calculation of the penetration process of the sampler, the value of the maximum penetration force is 786.5 N. A penetration test platform was built to simulate the sediment sampling process, and the sampling ability and penetration force of the sampler was tested in clays with different properties. The test results were consistent with the calculated results. For the three clays of complex plasticity, plasticity, and fluid plasticity, the sampling volume of the sampler is 410 mL, 120 mL, and 20 mL, respectively, and the maximum penetration force is 720 N, 210 N, and 20 N, respectively. To verify the sealing performance and strength of the pressure-retaining cylinder of the sampler, an internal pressure test of 110 MPa was carried out. The pressure was maintained for 120 minutes without pressure drop. To verify the working stability and pressure retaining performance of the sampler under high pressure, several tests were carried out in 60 MPa and 100 MPa high-pressure chambers. The test results showed that the pressure holding rate was over 90% at 60 MPa and over 88% at 100 MPa. Finally, in the TS21 voyage of China’s 2021 oceanic scientific expedition, the sampler carried by the “Striver”, a manned submersible, for three in-situ tests in the West Philippine Basin and the Mariana Trench, and the proposed samplers all completed the preservation sampling task. The pressure-retaining rate exceeded 80%, and a total of more than 700 mL of pressure-retaining sediment samples were obtained.关键词：hadal;pressure-holding sampling;penetration force;sediment;hyperbaric chamber test;sea trial- 459
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发布时间：2024-01-10 - 摘要：The accurate measurement of the at-rest earth pressure coefficient K0 for coarse-grained soil is important in the analysis and design of geotechnical engineering such as the earth rockfill dam. The laboratory K0 test results of the coarse-grained soil usually cannot accurately reflect its K0 value due to scale effects. To investigate the scale effect of K0 for coarse-grained soil, and propose a method to eliminate its influence, several K0 tests for the sandy gravel and the rockfill were performed by using a special large-size K0 testing apparatus. By changing the maximum grain size dM, scale method, and relative densityDr0, 24 groups of specimens were designed. K0 tests for all specimens were conducted by a large-size K0 apparatus, to quantitatively study the multiple influences of dM, scale method and Dr0 on the K0 of coarse-grained soils, and investigate the method that can predict the K0 behavior of sandy gravel in situ based on the laboratory test results and eliminate the influence of scale effects on K0. The test data show that: when the scale method andDr0 are the same, K0 for coarse-grained soil trend to decrease observably with increasing dM, therefore scale effect results in the obvious increasing value of K0 for coarse-grained soil, and the smallerdM for reducing scale soil, the stronger influence of scale effect on itsK0; Scale method have some influence onK0 for coarse-grained soil with the samedM andDr0, and the increasing value of K0 for test specimens prepared by replacement technique is the least, therefore adopting the replacement technique to prepare test specimen can reduce the influence of scale effect on K0 for coarse-grained soil; Compared withdM, Dr0 have a stronger influence onK0 for coarse-grained soil, and the largerDr0, the stronger influence of dM onK0 for coarse-grained soil. Based on theK0 test data of sandy gravel and previous research results, an empire equation, which could predict the K0 behavior of sandy gravel in situ based on the laboratory test results, was proposed to eliminate the influence of scale size on K0 for coarse-grained soil. Furthermore, the accuracy and applicability of the empire equation were verified by the K0 test data of the rockfill.关键词：coarse-grained soil;at-rest earth pressure coefficient;scale effect;maximum grain size;scale method;relative density
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发布时间：2024-01-10 - 摘要：Composite geomembrane has been widely used in reservoir seepage prevention. Usually, composite geomembrane is composed of geomembrane and geotextile, which plays a protective and strengthening role and has an important influence on the swelling deformation of composite materials. The phenomenon of geotextile inflation was simplified as a hoop-constrained spherical bulging deformation model. With the help of the impermeable film laid under the geotextile, the bulging deformation test was carried out through bulging deformation test equipment, and the deformation characteristics and mechanical characteristics of geotextile bulging were studied. With the help of a microscope, the fiber structure change process and bursting mechanism during the deformation of geotextile are emphatically analyzed. The results showed that the bursting pressure of the geomembrane was about 50%～60% of the bursting pressure of the geomembrane. It could be seen that in addition to protecting the geomembrane, it would also restrain the deformation of the geomembrane and increase its resistance to deformation. In the bulging deformation of geotextile, the tensile stress–strain curve approximately showed the characteristics of plastic deformation, which could be divided into four stages: linear elasticity, yield, strengthening, and bursting and breaking. The swelling deformation shape of the geotextile was hemispherical, and the tear point generally appears at the crown top and further expanded to the spindle-shaped tear failure. The microstructure analysis showed that the twining point formed by the needled short fiber had a certain entanglement force, and the fiber between the twining points had a certain tensile strength. The gradual failure of the twining force of the twining point and the fiber fracture were the main reasons for the swelling deformation failure of the geotextile. The greater the mass of geotextile per unit area, the denser the fiber and the entanglement, the greater the swelling pressure that can withstand, and the stronger the ability to resist deformation. The research results had a practical significance for analyzing the contribution of geotextiles on the membrane to the strength of geomembrane bulging deformation.关键词：geotextile;bulging deformation;bursting analysis;mechanical properties;fiber;bound node
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发布时间：2024-01-10
HYDRAULIC & CIVIL ENGINEERING
- 摘要：Aiming at the harm of UAVs in the aspects of out-of-control accident and air traffic control interference, a GNSS navigation spoofing method based on point-by-point offset was proposed in this paper, which decoys target UAV to fly away from sensitive areas and protect ground security by reconstructing the wrong navigation coordinate system. It regards the entire UAV spoofing course as time-iterative process of one-step position spoofing bias. Firstly, the actual positions and actual control inputs were estimated according to the kinematica model of UAV and external measurement information; then, the pre-set fraudulent control effects were cancelled out from the actual control inputs, and the deceptive GNSS signals were designed and constructed so that the filter position estimates in GNSS/INS integrated navigation mode were still close to the original expected point, but had the offset; finally, the real state point of UAV was moved to the spoofed target point caused by the trajectory tracking control inputs generated by the offset , thereby achieving a one-step covert spoofing effect. Finally, the point-by-point position offset spoofing of UAV was completed by the iterative application of the one-step spoofing process over time. Simulation results verified the effectiveness of the proposed GNSS navigation spoofing method of UAV. The simulation results showed that the target UAV can slowly deviate from the original trajectory and track the deceptive trajectory by using the GNSS navigation spoofing method based on point-by-point offset, and the trajectory estimated by the integrated navigation filter still tracks the original reference trajectory, thus achieving the purpose of satellite navigation deception. The proposed spoof jamming technique based on point-by-point pull-biased satellite navigation can be used to protect key areas/personnel at low altitude.关键词：UAV;one-step position spoofing;point-by-point offset;GNSS navigation spoofing;GNSS/INS integrated navigation
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发布时间：2024-01-10 - 摘要：Due to the complexity of multi-hop KBQA, most existing works capture a wider range of higher-order neighbour information via multi-layer GNNs. This approach combines multi-order information that sacrifices node discriminativeness to obtain more global information. Furthermore, it suffers from the over-smoothing problem, since fusing the multi-order information ignores the confidence of the neighbours, as neighbours closer to the node have the higher confidence. Another problem with multi-hop KBQA is that many datasets commonly do not provide the supervision information of intermediate paths. Thus, the weak-supervision problem usually makes the model lack effectual guidance information when conducting path reasonings, which results in reduced model reasoning ability. Aiming to solve the above problems, an approach of Multi-view Semantic Reasoning Networks (Multi-view SRNs) which utilizes information from both global and local views to jointly perform the reasoning was proposed in this paper. Namely, the global view information refers to the multi-order neighbour information of the node, which provides more numbers of crucial evidence for the reasoning, while the local view barely focuses on the first-order neighbour information of the node, which makes the node representation more discriminative, thereby alleviating the over-smoothing problem of the global information. Moreover, the original question was decomposed into multiple sub-questions as the guiding information for intermediate path reasoning. Then, an innovative loss function based on the uniformity and consistency of the semantic composition of the question was designed to improve the question decomposition quality, which promotes the ability of the model for intermediate path reasoning. The extensive experimental results on three benchmark datasets convincingly demonstrate that multi-view semantic information can provide a more comprehensive evidence for the reasoning, and the proposed method of decomposing the question into sub-questions is able to increase the intermediate path reasoning accuracy.关键词：multi-hop knowledge base question answering;graph neural networks;multi-view;semantic reasoning;weak supervision
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发布时间：2024-01-10
INFORMATION ENGINEERING
- 摘要：For micro-small high-speed on-off valves, large flow and high-frequency response increase the flow force of the spool and affect its motion state. Therefore, analysis and compensation of the flow force are the key factors to improve the performance of the valve. To solve the problem that the traditional steady-state flow force theory calculation formula is not applicable due to the complex flow field structure of the ball valve high-speed on-off valve in high-frequency opening and closing state, the CFD method was used to study the flow force. Firstly, COMSOL software was utilized to establish the geometric model of the fluid field. Then, the pressure and streamline distribution diagram, flow curves, and steady-state flow force curves of the valve ball and spool under different valve openings were obtained by using the weakly compressible fluid and standard k–ε turbulence model and dynamic grid technology. Finally, to compensate for the reduced steady-state flow force, the valve port structure was optimized and the optimal parameters were determined according to the relationship between different valve port structure parameters and the force of the valve core, and the opening and closing time of the valve port. The results showed that the steady-state flow force of the valve ball in the oil inlet hole would decrease first and then increase with the opening of the valve port, but the steady-state flow force of the valve ball in the oil inlet hole was smaller than that of the valve ball in the oil return hole, so the steady-state flow force change on the spool was similar to that on the valve ball in the oil return hole. Reducing the diameter of the push rod and changing the flow channel into a gradually expanding flow channel could effectively compensate for the reduced steady-state flow force. Compared with the original structure, the opening and closing time of the improved optimal structure decreased from 1.047 ms to 0.714 ms, and the steady-state flow force compensation effect was obvious.关键词：high-speed on–off valve;ball valve;flow force;CFD;compensation
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发布时间：2024-01-10 - 摘要：In the mesoscale, the proportion of the physical short crack stage in the whole fatigue life is usually high. And the expansion rate of the physical short crack is faster than that of the long crack. This phenomenon has caused potential damage to the material. The early hidden damage such as physical short cracks cannot be effectively detected by traditional nondestructive testing technology. Therefore, metal magnetic memory technology, which can detect early hidden damage and abnormal stress concentration, is introduced to explore physical short crack propagation. Aiming at the difficult parameter characterization problem caused by the specificity of physical short crack growth at the mesoscale, the characterization laws and model of physical short crack growth based on magnetic property parameters (MPPs) were conceived based on micro-experiment. The experiment material is Q235 steel. LWD–1000 long-distance microscope and TSC–5M–32 Tester of Stress Concentration were carried out to observe in-situ the evolution process of crack growth and MPPs, respectively. The characterization laws of MPPs were obtained for physical short crack growth at the mesoscale. The experimental results show that when the length is 0～100 μm, the growth rate increases continuously and peaks occur. The normal component Hp(y) changed from –26.875 A/m to 7.25 A/m with a polar jump. The tangential component Hp(x) changed from –17.24 A/m to –68.78 A/m with a significant increase in absolute value. When the length is 100 μm, the short cracks converge to form the main crack, the crack growth rate slows down, Hp(x) and Hp(y) jump sharply and ΔHp peak appears. When the length is 100～1 000 μm, the growth rate of the main crack increases again and increases continuously. The polarity of Hp(y) changes, the absolute value of Hp(x) increases greatly again, and the ΔHp shows an increasing trend. Furthermore, based on the MPPs, the characterization models of short crack growth rate and remaining life at the mesoscale were established, respectively. The verification results show that the maximum relative errors in the model are 6% and 4%, respectively, which provides a new idea for the characterization and evaluation of early hidden damage in engineering practice.关键词：meso-scale;physical short crack;magnetic property parameters;crack propagation;characterization laws
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发布时间：2024-01-10
MECHANICAL ENGINEERING
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