最新刊期
卷 54 ， 期 2 ， 2022
- 摘要：In view of the large terrain elevation difference along the Sichuan—Tibet railway, the steep topography of the long and large buried depth tunnel project, extremely poor traffic conditions, and the inability to implement vertical deep hole exploration, the existing directional exploration drilling rig has some shortcomings in the poor adaptability of railway survey in high mountain and canyon areas, and the directional exploration technology cannot meet the technical requirements of full-hole geological core coring in railway tunnel surveys. It is proposed to carry out research and development of ultra-long rope coring directional drilling tools and equipment, drilling technology and process, exploration model and railway super-long directional exploration application and demonstration project. Based on the summaries of the application status of ultra-deep directional drilling technology in the Sichuan—Tibet railway tunnel engineering survey, its development suggestions were put forward. The conclusions show that: 1) Through the research and development of ultra-deep horizontal directional exploration technology and equipment, the problem of horizontal deep-hole drilling equipment on the Sichuan—Tibet railway has been solved, and a set of horizontal rope directional drilling equipment and technology has been innovated, achieving zero domestic breakthroughs, and forming a set of ultra-long rope coring directional exploration method. 2) The self-developed GXD–5S kilometer-level full-hydraulic power-head directional drilling rig and super-long rope core directional drilling technology have been successfully applied to the Kazila Mountain No. 1 Tunnel of the Sichuan—Tibet railway and created a domestic horizontal rope as a demonstration project the two latest records of drill pipe PQ (diameter 122 mm) with depth 588 m and HQ (diameter 96 mm) with depth 974 m. 3) Through three survey modes of horizontal drilling, oblique drilling, and upside directional drilling, special geological factors for tunnel survey design in high mountains and valleys were constructed to obtain new geological models. 4) A total of 27 ultra-deep rope coring directional exploration drilling holes were completed in the Ya’an—Changdu section of the Sichuan—Tibet railway, of which the deepest horizontal directional drilling depth was 1888.88 m. Deep directional drilling technology provides a better support for the railway survey design and popularization and application.关键词：ultra-deep directional drilling technology;tunnel survey;horizontal directional drilling rig;ultra-long rope core;Sichuan—Tibet railway170|861|3更新时间：2024-11-27
- 摘要：Sichuan—Tibet railway is in the topographic crossing zone from the Sichuan basin to Qinghai Tibet Plateau. Regional characteristic geological factors such as active structure, valley unloading and freeze-thaw weathering along the line have strong control over the development and stability of unstable rocks. It is of great significance for railway route selection in the early stage to carry out the investigation of unstable rocks and the research on the rapid evaluation method of stability. Based on the interpretation of remote sensing and unmanned aerial vehicle images with verification of field investigation, the development characteristics of unstable rock at the entrance and exit of tunnels along the Sichuan—Tibet railway from Ya’an to Changdu were summarized, and the failure mode and rapid evaluation method of stability at high altitude were put forward considering the regional geological characteristics. The results show that: 1) There were 141 unstable rocks developed in the small and medium size (<1 000 m3). The deep canyon areas such as Dadu River, Yalong River and Jinsha River were the most densely developed. 2) The unstable rock was mainly developed in the freeze-thaw weathered Triassic sand-slate interbedded phyllite section above 3 000 m, accompanying with low stability; 3) The distribution of unstable rock was also related to the high seismic intensity area and active fault. The failure mode of unstable rock in this region showed that multiple indexes were coupled with each other, including the unloading behavior of ground stress, persist damage of freeze-thaw, and intermittent seismicity. Eight indexes were extracted, including special geological indexes of the Sichuan—Tibet area, the freeze-thaw, unloading behavior and seismic intensity, and five basic indexes of stability evaluation of unstable rock, terrain gradient, weathering intensity of rock mass, cavity, main control structural plane and lithology. The stability evaluation model of unstable rock in the cold region was established based on extension theory through comprehensively estimating the weight and relevancy of each index for the four stability levels. Analysis results of seven cases suggested that the stability estimation and controlling indexes were in accord with the field situation by using this method, which could quickly identify the stability of unstable rock in the alpine mountainous area of the Sichuan—Tibet railway.关键词：Sichuan—Tibet railway;development characteristics of unstable rock;tunnel portal;disaster mode;rapid evaluation method;extenics theory179|1257|2更新时间：2024-11-27
- 摘要：Recently the frequency of disaster chain of landslide, surge wave and glacier lake outburst increases, which poses a serious threat to the safety of downstream residents and engineering facilities. In order to describe quantitatively the hazards of this disaster chain, its evolution process and corresponding characteristics are analyzed and further divided into four stages including landslide motion, surge wave propagation, glacier lake outburst and flood propagation. The physical mechanisms and key factors of these stages are investigated and based on this the corresponding model and numerical scheme are also established. For example, the Savage–Hutter model and shallow water model are applied to describe landslide motion and surge/flood propagation, respectively. By determining the factors that connect each stage, the coupling and data transmission of these stages are achieved and therefore a comprehensive model of this disaster chain is presented for process simulation and hazard analysis. In order to verify the feasibility of the presented model and numeric scheme, a potential disaster chain in Mugecuo glacier lake near Yala village, Ganzi state of Sichuan province is studied. Based on the data of field investigation and satellite imagery, the process of disaster chain under several scenarios such as heavy rainfall and cascade dam break are performed and the simulated results are compared with that of empirical formula. These results show that the presented method is quite effective to simulate the disaster chain of landslide, surge wave and glacier lake outburst and the calculated data agree with that of empirical formula. It also indicates that the flood discharge can be increased significantly due to the effects of heavy rainfall or cascade dam break. This research provides a new idea for studying the disaster chain of landslide, surge and glacier lake outburst and has some consultative value to prevent and mitigate this type of disaster chain.关键词：disaster chain;landslide-induced surge;glacier lake outburst;physical model;numerical simulation;process analysis1410|1143|5更新时间：2024-01-10
SICHUAN—TIBET RAILWAY ENGINEERING AND ENVIRONMENT
- 摘要：In order to solve the problems of low detection accuracy and high false positive rate of traditional smart contract vulnerability detection methods and less consideration of bytecode level smart contract features in neural networks, a smart contract bytecode vulnerability detection method based on semantic perception graph neural network was proposed. First, in order to generate the control flow graph, the basic blocks divided by the smart contract bytecode were used as the nodes, and the call relationship between the basic blocks was extracted from the bytecode as the edges. Then, control flow graph is transmitted into the graph convolutional network for training to obtain the feature representation of the graph nodes; Afterwards, the contract bytecode instruction sequence is segmented, transformed into a word vector, embedded into a low-dimensional space and transmitted to a long short-term memory network for training. Then, the vector representation of bytecode semantic information was obtained. Finally, the generated node features and semantic features were spliced and transmitted to the full connection layer for dimensionality reduction. Combined with semantic information and node features, the vulnerability detection was carried out for smart contracts. The real smart contracts in public dataset were used for training and testing, and verified in two types of vulnerability classification datasets through traditional methods and artificial tags. The method proposed in this paper was compared with three traditional smart contract vulnerability detection tools and one smart contract vulnerability detection method based on neural network. The experimental results showed that the proposed network greatly improves the performance of network in terms of various indicators, and detects the contracts with vulnerabilities which are not detected by the other four methods. It shows that adding the bytecode semantic information to graph neural network can effectively improve the detection accuracy and reduce the false alarm rate.关键词：smart contract bytecode;GCN;semantic-aware;vulnerability detection1486|849|5更新时间：2024-01-10
- 摘要：Given the bottlenecks of existing adversarial example defense schemes, such as insufficient defense capability and high time consumption, an ensemble adversarial example defense scheme based on the generative adversarial network was proposed in this paper, by taking the advantages of the generative adversarial network and the ensemble learning in adversarial example research. In the scheme, a generative adversarial network was used to train multiple generators that can eliminate adversarial perturbations on the surfaces of adversarial examples, and the ensemble learning was used to integrate multiple generators as the final defense. The generative adversarial network was composed of generator and discriminator. While the generator takes adversarial examples as inputs and its purpose is to eliminate adversarial perturbations on the surface of adversarial examples, the discriminator takes benign examples and examples after eliminating the adversarial perturbations as inputs and its purpose is to distinguish them. The generator and discriminator were trained alternately, and the generator reaches to its best when the discriminator cannot distinguish them. The averaging method was adopted by the integration defense adopts as the integration strategy to learn from each other. Furthermore, the ability of a single defense is improved by averaging the defense results of multiple generators. The time consumption of defense was reduced by pre-training generators and the defense ability was improved by integrating multiple generators. Finally, the time consumption and defense ability of the proposed scheme was verified on the MNIST and CIFAR10 dataset. With the classification accuracy as the evaluation index, the defense ability of the proposed scheme on six kinds of adversarial examples was verified, and compared with seven existing defense schemes. Results showed that the proposed scheme can defend against multiple adversarial examples with very low time consumption, and its defense ability is better than the existing defense schemes.关键词：adversarial example;adversarial example defense;inference model;generative adversarial network1237|1120|0更新时间：2024-01-10
- 摘要：P2P botnet has become a new network attack platform because of its high concealment and robustness, which poses an increasing threat to cyberspace security. However, the existing detection methods based on rule analysis or traffic analysis can’t detect it effectively. In order to solve the problems of strong concealment and difficult identification of P2P botnets, a P2P botnet detection method based on graph neural network (GNN) was proposed. The method was based on the information of P2P botnet node interaction and network topology to realize detection and did not rely on the characteristics of traffic protocol. Firstly, the source IP, the destination IP, the outdegree, the indegree and the node betweenness centrality in P2P botnet traffic were extracted to construct a topology graph, an out-degree and in-degree graph and a betweenness centrality graph; Then, the weighted sum of adjacency matrices of the three feature graphs was fused by element-wise product to input into the detection model; Then, a graph convolution neural network based on attention mechanism was used to extract the features between nodes, and the neural collaborative filtering algorithm was used to realize the attention probability distribution of the central node and complete the node state update; Using the close connectivity between multi-layer graph convolution layers, the dimension reduction extraction of interactive features and the mining of high-order structure information were realized. The internal characteristics of botnet were automatically learned, and the botnet detection was completed through the node classification module. The proposed method was validated on the ISCX–2014 botnet dataset. The experimental results showed that the proposed deep graph neural network method outperforms the other two comparative methods in terms of detection accuracy and model stability when the training sample contains botnet nodes of large size. The model can effectively improve the detection ability and generalization ability of P2P botnets, as well as reduce the false positive rate.关键词：P2P botnet;deep learning;graph convolution neural networks;graph fusion;attention mechanism1421|1109|5更新时间：2024-01-10
ARTIFICIAL INTELLIGENCE SECURITY
- 摘要：Currently, the most common treatment method of waste glass is landfill disposal, which both causes pollution to the environment and wastes resources. As a result, realizing the re-utilization of solid waste and recycling economy becomes the important parts of sustainable development strategy. To improve the utilization rate of waste glass, waste glass powder was taken to replace part of the cement in concrete as supplementary cementitious material, while waste glass was applied to replace part of the stone and river sand as coarse and fine aggregate. In this way, the effect of its compounding method on the compressive strength of recycled concrete could be studied, thus determining optimal blending method. After that, the mechanical properties of recycled concrete with waste glass were further studied by conducting different experiments, such as splitting tensile, anti-flexural and axial compressive tests. Simultaneously, the effect of waste glass on the high temperature resistance of concrete was also discussed in detail. According to the results, the compressive strength of recycled concrete reached the maximum value of 53.43 MPa with 0, 25% and 25% (mass ratio) of waste glass powder, waste glass coarse aggregate and waste glass fine aggregate respectively, and the splitting tensile strength was 8.52% higher than that of ordinary concrete, the flexural strength was 1.47% higher than that of ordinary concrete, and the axial compressive strength was 19.17% lower than that of ordinary concrete; the strength of recycled concrete retention rate decreased with the growing of heated temperature, and the incorporation of waste glass had a significant improvement on the strength preservation of concrete after high temperature from 500 ℃ to 900 ℃.关键词：waste glass;compound;recycled concrete;mechanical properties;high temperature properties989|1080|1更新时间：2024-01-10
- 摘要：Expansive polystyrene granule cement (EPSC) non-demoulding latticed concrete wall is a composite wall integrating insulation and structure. The setting of diagonal bracing is a new mode of the wall. To study the seismic performance of the latticed concrete walls with diagonal bracing, laterally reversed low-cyclic loading tests on three prototype test specimens, including two new latticed walls with diagonal bracing and one traditional type were performed to investigate the mechanical properties such as bearing capacity, hysteresis curve, skeleton curve, ductility, stiffness degradation as well as the failure mode. The seismic performance difference of the new with diagonal bracing and the traditional latticed walls were compared and analyzed, the effect of EPSC on the seismic performance of composite walls were discussed. The test phenomena and analytical results showed that the new EPSC non-demoulding latticed wall with diagonal bracing had the higher bearing capacity, elastoplastic deformation capacity and energy dissipation capacity than the traditional one; the EPSC and the reinforced concrete skeleton works together to improve the energy dissipation capacity significantly, and to a certain extent improve the bearing capacity, stiffness and other mechanical properties of the wall. The study revealed the seismic performance characteristics of this new lattice composite wall, providing technical support for the engineering application.关键词：diagonal bracing;latticed concrete wall;expansive polystyrene granule cement (EPSC);quasi-static test;seismic performance889|683|0更新时间：2024-01-10
- 摘要：To explore the acoustic emission (AE) characteristics and corresponding fractal characteristics of sandstone under triaxial cyclic loading and unloading conditions, a series of conventional triaxial tests, as well as triaxial cyclic loading and unloading AE tests, were conducted on sandstone under different confining pressures. By analyzing the AE characteristics and fractal characteristics before and after the peak stress under the conditions of triaxial cyclic loading and unloading, the crack development and damage evolution during the progressive failure process of rocks were explored. Using the MTS815 Flex Test GT rock mechanics testing system and the PCI–Ⅱ type AE three-dimensional positioning real-time monitoring system, the three-axis cyclic loading and unloading acoustic emission tests under three groups of confining pressures 10, 20, and 30 MPa were carried out, and the damage evolution at the residual stage was also studied. Through conventional triaxial and cyclic loading and unloading tests, the stress-strain curves, AE ringing count, and hit number of the sandstone during the whole process of deformation and failure were obtained. The relationship between strength and deformation, as well as the relationship between AE and stress, was investigated, and the AE hit rate time series was used to calculate the correlation dimension. The influence of the phase space dimension on the correlation dimension at different cycle stages was analyzed. The test results showed that: 1) The confining pressure had an inhibitory effect on rock failure, and confining pressure increase could increase the strength of the rock. The cyclic loading and unloading process had a strengthening effect on the sandstone, and the peak strength in the triaxial cyclic loading and unloading process was higher than that in the conventional triaxial test. The change of the unloading modulus could better characterize the evolution of the internal structure of the rock. The compaction of inner pores could cause the unloading modulus to increase, and the internal damage expansion would cause the unloading modulus to decrease. 2) The acoustic emission ringing count rate and the hit rate under different confining pressures during the cyclic loading and unloading stages had the same changing law. The AE at the pre-peak stage was basically synchronous with stress loading, and almost no acoustic emission phenomenon occured in the unloading process; the rock bearing capacity at the residual stage after the peak decreased, and AE ringing count rate and hit rate were still increasing after the peak, showing a “lag” comparing with stress loading. The AE ringing count rate and hit rate decreased sharply at the beginning of unloading, but the generation of secondary fractures at the end of unloading would also cause a certain AE phenomenon. 3) The hit rate of AE had fractal characteristics. The correlation dimension decreased in the pre-peak cycle loading and unloading process; under the influence of phase space dimension on correlation dimension, the AE hit rate time series at different cycle stages gradually changed from random sequence to ordered sequence with the increase of cycle times, indicating that macro fractures gradually formed and cracks inside the rock tended to be orderly; in the post-peak residual stage, due to the development of secondary cracks and the acoustic emission phenomenon at the end of unloading, the correlation dimension increased.关键词：sandstone;damage;triaxial cyclic loading and unloading;acoustic emission;fractal;correlation dimension1132|828|7更新时间：2024-01-10
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Numerical Analysis of Uplift Bearing Mechanism for Shallow Circular or Helical Anchor Plate in Sand AI导读
摘要：A numerical study combining coupled Eulerian–Lagrangian method to large deformation analysis and modified Mohr–Coulomb elastic-plastic constitutive model that can describe the soil behavior of strain softening has been performed to investigate the pullout mechanism of circular or helical anchor plates in sand. The validity of the numerical model has been established through the comparison against the centrifugal tests of single-helix anchors. The uplift failure mechanism of circular anchors in sand with different compactnesses was then investigated. The failure modes, distributions of normal stress and changes of soil strength along failure surfaces in loose, medium and dense sands have been analyzed. It was demonstrated that the coefficients of lateral earth pressures and the friction angles along the failure surface were not constant. The coefficient of lateral earth pressure rose linearly from the edge of the plate, up to the peak value at approximately 0.2D (plate diameter), and then decreased exponentially to a stable value. The equivalent friction angle along the failure surfaces in loose and medium sand could be determined by the reduction formula proposed by Davis, and it would be overestimated approximately 3° in the dense sand. Furthermore, a theoretical calculation method for the uplift capacity of shallow circular or helical anchor plates was proposed based on the above analyses. Meanwhile, the comparison among several existing theoretical formulas has been made, and the applicability for each formula has been proposed, which can provide references for the engineering design.关键词：circular/helical anchor plate;uplift capacity;strain softening;failure mechanism958|759|2更新时间：2024-01-10 -
Rainfall Networks Optimization in Small Catchment of Loess Plateau Based on Information Entropy AI导读
摘要：Precipitation information is mainly collected by ground monitoring networks. Rainfall stations contain the fundamental input for planning, design, operation, and management of water resources systems. Reasonable rainfall gauges, which are effective and efficient in gathering precipitation information have received considerable attention. In order to analyze the relationship between rainfall information of 11 ground rainfall stations in Chabagou small catchment of the Loess Plateau, precipitation series from 2001 to 2010 were organized into appropriate sampling intervals (1-day, weekly, 15-days). Based on the information entropy theory and Maximum Information Minimum Redundancy criterion (MIMR), with the use of the spatial and temporal distribution characteristics of multi-year average precipitation, the existing rainfall station network in Chabagou catchment were evaluated and optimized. The results show that the rainfall in Chabagou catchment did not change significantly during the study period, and the rainfall showed a decreasing trend from southwest to northeast from 2001 to 2010. The changes of the joint entropy, the mutual joint information and the redundant information of rainfall series at different time scales were generally the same, and the joint information tended to be stable with the increase of stations. While the information transmitted between stations was less and less, the redundant information was more and more. With the increase of time scales, the joint entropy became more stable quickly and the redundant information became more. According to the variation of information entropy among rainfall stations in the Chabagou catchment, the rainfall station network was optimized, and the optimal density and distribution of rainfall stations in catchment at different time scales were determined. The optimized rainfall station network can reflect the rainfall information in the basin. The research results can provide a theoretical basis for the optimal layout of rainfall station network in the future.关键词：information entropy;optimization of rainfall networks;maximum information minimum redundancy criterion;Chabagou catchment938|777|2更新时间：2024-01-10 - 摘要：Measurement of instantaneous bed shear stress in open channel flows is challenging but extremely important. In order to accurately measure the instantaneous bed shear stress with particle image techniques, synthesized particle images with different image and flow parameters were applied to evaluate the measurement precision of particle image velocimetry (PIV), particle tracking velocimetry (PTV), and line correlation PIV (LCPIV). The measurement precision of all techniques in the near bed region were found to be degraded towards the bed. The wall-normal height of the bed influence equals the particle image radius for PTV and LCPIV, and is not shorter than the height of the interrogation window for PIV. Outside of the bed influenced region, the measurement of PTV is unbiased and is with the highest precision when the particle image density is relatively small and the particle image diameter is medium. Therefore, PTV is more suitable for the measurement of instantaneous bed shear stress. The ability of PTV for unbiased and high precision measurement of instantaneous bed shear stress was further validated with experiments in two open channel flows with a Reynolds number of 8007 and 11462, respectively. The experiment results also indicated that the distribution of instantaneous bed shear stress in the turbulent open channel flows, with a coefficient of variation of about 0.4, is non-Gaussian. Meanwhile, both the skewness and kurtosis increase with the Reynolds number of the flow. The results provide theoretical foundation and practical reference for measuring instantaneous bed shear stress in open channel flows.关键词：instantaneous bed shear stress;particle image measurement technique;statistical characteristics;open channel flow848|651|0更新时间：2024-01-10
- 摘要：Aiming at the outstanding problem that the composite bridge is affected by the gradient temperature in the life cycle of the northwest alpine and large temperature difference area. Based on the new-model corrugated steel web (CSW) simply supported composite box girder on a highway in Gansu Province, an analytical calculation method of temperature effect of the composite box girder bridge was established by considering the effective stiffness of the composite bridge panel, the internal force balance of the micro-section of the sub-beam, the deformation coordination between the sub-beam and the shear deformation effect of the web.The reliability of the method was verified by fine finite element numerical simulation. The results showed that under the vertical temperature gradient, the bending moment, stress and interfacial shear of the composite box girder were hyperbolic cosine distribution along the beam axis, while the relative slip between layers was hyperbolic sine distribution. Whether the web shear deformation was considered or not had a great influence on the temperature response of the composite box girder, and the influence range along the beam axis was mainly related to the interlaminar slip stiffness. Ignoring the shear deformation effect of corrugated steel web could easily lead to the small calculation results of interlayer slip in the middle of the beam, but the problems of excessive interlayer shear force and relative slip value near the end of the beam should be paid more attention in the structural design. The influence of temperature difference between composite bridge slab and web interface and concrete line expansion coefficient on the temperature response of the structure cannot be ignored. In the design, the adverse effects of the above factors on the structure can be weakened or eliminated by optimizing the layout of shear connectors.关键词：corrugated steel web;composite bridge panel;profiled steel plate;composite box girder;temperature effect;shear deformation1224|662|0更新时间：2024-01-10
- 摘要：Drainage holes are usually arranged to reduce the seepage pressure inside rock mass. The partial blockage of the drainage hole will limit the drainage capacity and threaten the safety of an engineering project. At present, the analysis of the filled drainage hole only considers the fluid movement in the unfilled area, and there are few theoretical studies that consider the flow in both the filled and unfilled regions. In view of this, a clear-seepage flow coupled theoretical model was presented to study the velocity distribution of the drainage hole with axisymmetric filled medium in the rock mass. In the model, the Navier–Stokes equation was adopted to describe the motion of the clear water in the hole, and the Darcy–Brinkman equation was employed to describe the movement of the seepage water in the filled medium. The analytical solutions of velocity distribution and discharge were derived under the shear stress jumping interface boundary condition, and the results of analytical solution for velocity shown good agreement with that of the numerical solution obtained by the fourth order Runge–Kutta method. Parameter sensitivity analyses shown that the flow velocity had a positive relation with the Darcy number (Da) and the relative thickness of the open region, and a negative relation with the ratio of viscosity and the stress jump coefficient. The flow velocity was more sensitive to the variation of the typical parameters and the influence of viscosity ratio on the velocity distribution could not be neglected when the stress jump coefficient is less than 0. Furthermore, with the increase of the relative thickness of the open region, the interface velocity gradually decreases when Da=1, while it firstly increases and then decreases when Da=0.1, and it gradually increases when Da<0.1. The research results of this paper can provide a theoretical basis for the calculation of the drainage capacity of the partially filled drainage hole. It is of great significance for developing the clear-seepage flow coupled theory of drainage holes and can provide a reference for the follow-up drainage hole dredging.关键词：axisymmetric filled drainage hole;clear-seepage coupled model;flow field analytical solution;stress jump coefficient913|668|0更新时间：2024-01-10
- 摘要：The mechanical properties of dangerous rock mass in the cold region are often deteriorated by freeze-thaw cycles due to temperature fluctuation. The establishment of stability analysis method of dangerous rock mass considering fracture toughness deterioration can provide a theoretical basis for long-term stability evaluation of dangerous rock mass engineering in the cold region. The essence of unstable failure of dangerous rock mass is the crack initiation and expansion of the main structural plane. Firstly, according to the theory of fracture mechanics and freezing separation pressure, considering the deterioration of rock of mode Ⅰ fracture toughness caused by freeze-thaw cycle and the frost heaving force of structural plane, the stability evaluation model of dangerous rock mass under freeze-thaw cycle was established. Secondly, based on circular cavity expansion theory, the meso degradation mechanism of ice frost heaving force on micropores in rock was analyzed, and the meso evaluation model of tensile strength under freeze-thaw cycle was established. Thirdly, the evolution equation of mode Ⅰ fracture toughness under freeze-thaw cycles was obtained by theoretical analysis of the relationship between mode Ⅰ fracture toughness and tensile strength, fracture process zone expansion radius. Finally, the deterioration law of the stability of dangerous rock mass under freeze-thaw cycles was analyzed based on an engineering example, and the influence of sensible parameters on the stability coefficient and frost heaving force of dangerous rock mass was discussed. The results showed that the stability of dangerous rock mass in the freeze-thaw environment was related to the tensile strength, elastic modulus, porosity, debris loss ratio and other factors of rock. Under the action of the freeze-thaw cycle, the hole with a smaller radius produced more frost heaving force and had a more significant deterioration effect on the stability of dangerous rock mass. There was a positive correlation between the elastic modulus of rock and the frost heave force, and the smaller the tensile strength of rock, the more likely the frost heave failure as to occur. When the debris loss ratio was greater than 0.8, the effect of the freeze-thaw cycle on the long-term deterioration of dangerous rock mass was stronger. Therefore, it is important to control the debris loss caused by frost heave failure for the long-term stability of dangerous rock mass in the cold region.关键词：dangerous rock mass;freeze-thaw cycle;fracture toughness;frost heaving force829|956|4更新时间：2024-01-10
- 摘要：To study the ultimate bearing capacity of carbon fiber reinforced polymer (CFRP) confined high-strength concrete filled steel tube stub columns under axial compression,the failure process and working mechanism of CFRP confined high-strength concrete filled steel tube (CFRP confined steel tube-HSC) stub columns under axial compression was discussed. The main differences and relationship between CFRP confined steel tube- HSC and CFRP confined concrete filled steel tube (CFRP confined steel tube-C) stub columns members were analyzed, which laid the foundation for the ultimate analysis of the bearing capacity of CFRP confined steel tube- HSC stub columns. Based on the limit equilibrium method, the stress analyses of HSC, steel tube and CFRP were carried out. The theoretical calculation formula of CFRP confined steel tube-HSC stub column was derived. The theoretical formula was verified by comparing the calculated results with the measured ones. Finally, the variations of the theoretical calculation results with the number of CFRP layers and the thickness of steel tube wall were analyzed. The results showed that compared with CFRP confined steel tube-C, CFRP confined steel tube-HSC had a poor constraint effect. For the bearing capacity improvement of CFRP confined steel tube-HSC stub column, the thick wall steel tube had a great advantage.关键词：CFRP confined steel tube-HSC;ultimate equilibrium method;ultimate bearing capacity;lateral pressure effect coefficient879|783|2更新时间：2024-01-10
- 摘要：In actual foundation treatment, electro-osmosis is often used in combination with preloading. In order to solve the deficiency in the theory about electro-osmotic consolidation solution considering both load action and layered configuration of soil, a one-dimensional consolidation equation of double-layered soil considering the combined action of load and electro-osmosis is established, by assuming that the flow velocity in soil can be superimposed by the flow velocity caused by hydraulic gradient and the flow velocity caused by potential difference. The analytical solutions for one-dimensional electro-osmotic consolidation of double-layered soil under constant and linear loading are obtained by using the feature function method. The effectiveness of the present solution is assessed by comparing against other existing analytical solutions and electro-osmotic consolidation test results. Based on the solution, the influences of soil parameters and load parameters on the consolidation characteristics of double-layered soil are discussed in detail. The results show that when the permeability of the subsoil is greater than that of the upper soil, in the early stage of consolidation, the amount of water flowing into the soil near the middle of the foundation is greater than the amount flowing out due to electro-osmosis, resulting in the phenomenon that the excess pore water pressure increases and the effective stress decreases in the early stage of consolidation. Reducing the compressibility of subsoil can improve the settlement rate and the excess pore water pressure dissipation rate of double-layered soil. Compared with the single electro-osmosis consolidation, the combined action of the load and electro-osmosis can not only improve the settlement rate of the double-layered soil, but also improve the strength of foundation after consolidation, which is more conducive to reducing the settlement after construction and speeding up the foundation treatment rate.关键词：double-layered soil;one-dimensional consolidation;electro-osmosis;load;analytical solution982|767|1更新时间：2024-01-10
HYDRAULIC & CIVIL ENGINEERING
- 摘要：The reverberant speech signal includes different frequency components induced by the effect of path delay. The frequency components are correlatedly modulated in frequency domain. In order to reduce the high correlation of reverberant speech in the spectrum, an improved generative adversarial network (GAN) algorithm based on additive frequency domain decomposition was proposed. Firstly, the short-time amplitude spectrums of the reverberant speech were processed with the logarithmic operation, by which the modulated amplitude spectrums of reverberant speech were converted into the linear ones, and then the convolved speech components were decomposed. After normalized by the sigmoid nonlinear function to balance the data distribution, the demodulated amplitude spectrums were applied to a deep fully convolutional network to train a GAN model. Finally, based on the adversarial learning mechanism of the generative model and the discriminative model, the distribution diversity of the reverberant speech and the source speech were effectively learned, and the enhanced speech signal was accurately reconstructed with the generative model. In experiments, the Chinese speech data set of Aishell was used to test the performance of the proposed algorithm. The dereverberation performances of GAN, FCN, and DNN with (or without) additive frequency domain decomposition were respectively compared and demonstrated by the difference of spectrograms. Experimental results showed that under four different reverberation time parameters, the PESQ, STOI, and LSD’s evaluation scores of GAN, FCN, and DNN with additive frequency domain decomposition are about 10% higher than the ones without additive frequency domain decomposition. In conclusion, the additive frequency domain decomposition can effectively improve the performance of GAN in speech dereverberation application. Generally, the algorithm can be also applied to the non-homologous speech dereverberation.关键词：speech dereverberation;logarithmic operation;additive frequency domain decomposition;generative adversarial network1119|822|0更新时间：2024-01-10
- 摘要：In order to solve the high expenditure of special license authorization for commercial central processing unit (CPU) and the improving performance of convolutional neural networks (CNNs), a configurable CNN accelerator was proposed based on multi-view parallelism. And it constructed the system on chip (SoC) with RISC−V (Reduced instruction set computing). Firstly, a set of interfaces incorporated control access bus and data access bus were expanded for high-speed accelerators. Secondly, each operation unit for CNNs was implemented by both multi-view parallelism and structure multiplexing. The hardware circuit structure for convolution unit would be affected by the different combination of view parallelism, thus multi-view parallelism was accomplished by reusing the basic arithmetic structure. The pooling unit was composed of row pooling and column pooling submodules, and which shared the structure of row pooling operation. For the fully connected, a method that parameters could be processed was employed to adapt to the hardware structure of convolution unit, thereby completing reuse between models. Then, different registers were designed for the hardware structure of different computing units, and combined with the open source RISC−V processor to realize multiple CNN models. Finally, different operation units, such as convolution, pooling and fully connected models, were respectively deployed on different platforms to calculate the latency, throughput and speedup ratio. The experimental results demonstrated that the speedup ratio of the same convolution structure on the designed accelerator and CPU platform was 189. The convolution operation of Visual Geometry Group was deployed in the designed accelerator, and the throughput could reach 178.6 GOPS. To sum up, an acceleration effect could be realized by multi-view parallelism, and different CNN models was able to be implemented by configuring registers.关键词：convolutional neural network;multi-view parallelism;configurable;system on chip;reuse;RISC−V843|973|0更新时间：2024-01-10
INFORMATION ENGINEERING
- 摘要：Autonomous tracking of weld seams is a key technology to robot welding intelligence, and its accuracy is an important indicator for evaluating welding quality. Changes in welding objects or conditions have the most direct impact on accuracy, especially when there are defects on the surfaces of the weldment, which will cause a large tracking error. This paper proposes a four-step method for welding seam tracking, which uses laser sensor to obtain contour data; the combined filtering algorithm which contains the limit filter and Gaussian filter is used to smooth the noise; the derivative method is used to initially locate the feature points, and by finding extreme points of the first derivative to locate the first type of feature points, and the second type feature points are located by finding the maximum points of the second derivative; the feature points obtained from the preliminary positioning is used as the dividing points, the groove contour data is fitted segmentally, the intersection points of the fitted lines accurately locates the feature points; through sensor calibration, the position of the sensor relative to the end coordinate system is obtained, and the feature points obtained by the sensor are transformed into the base frame with the help of the transformation matrix, then the positioning points of the robot are obtained; use the cubic spline interpolation method to generate the trajectory of the end of the welding torch, and drive the robot to run according to the predetermined trajectory to realize the tracking of the welding seam. Experiments have been conducted to verify the tracking effect of straight and curved welds. The results show that the tracking errors are approximately 0.628 mm and 0.736 mm during the initial positioning. After precise positioning, the errors are reduced to 0.387 mm and 0.429 mm, and the increase rate exceeds 38.4% and 41.7% respectively. In addition, the jitter phenomenon of the welding gun is reduced, and the accuracy requirement of automatic welding error ≤0.5 mm is reached, which shows an effectiveness of the tracking method proposed in the article and can provide reference for the research of high-precision tracking and automatic welding.关键词：welding robot;laser gauge;feature point extraction;seam tracking1853|1769|4更新时间：2024-01-10
- 摘要：A bistable speed bump vibration energy harvester is proposed by introducing the buckling beam and the one-way clutch. The occurring condition of bistable vibration of the buckling beam is obtained. The relationships between the equilibrium points and the depth of potential well and the structural parameters of buckling beam are derived from the nonlinear restoring force and potential energy equation.The mechanical model and dynamic equations of the vehicle-speed bump vibration energy harvester are established. Comparing the energy harvester proposed in this paper with linear monostable speed bump vibration energy harvester with/without one-way clutch, it is concluded that the introduction of the buckling beam greatly improves the energy harvesting efficiency of speed bump vibration energy harvester, and the power generation is increased nearly 42%. The introduction of the one-way clutch not only realizes the vibration energy harvesting of the up and down directions vibration energy of the speed bump, but also ensures the one-way rotation of the generator shaft. The power generation is increased by nearly 30%. Four types of common vehicle models and five types of speed bumps are selected for the power generation analysis, and the results show that the bigger the vehicle mass is, the larger the speed bump vibration amplitude and the input excitation are. The increasing in height of speed bump can lead to the increasing of power generation. On the contrary, the increasing in width of speed bump leads to the decrease of the power generation. Comparing the output voltage of speed bump vibration energy harvester with two kinds of flywheels with different moment of inertia, the output voltage of speed bump harvester with small moment of inertia is bigger than that with large moment of inertia.The trend of output voltage changing with load resistance is obtained. The speed bump harvester can output the maximum power with 1 Ω resistance. Finally, the output power of speed bump harvester increases rapidly with the increase of speed increasing ratio in the range of 1 to 40, and increases slowly in the range of 40 to 50.关键词：speed bump;bistable;one-way clutch;vehicle;power generation performance766|740|2更新时间：2024-01-10
MECHANICAL ENGINEERING
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