最新刊期
卷 55 ， 期 6 ， 2023
- 摘要：Along the upstream of the Jinsha River, a series of ancient tower relics were discovered during the recent investigation of paleo-landslide damming events in the three-parallel-rivers region of the Hengduan Mountains, among which the relics are most densely distributed in Zhuoying village, with the total number of 17 and were not reported in public before. The relics were left by a historical tribe or village and constituted part of the historical heritage in the Zang—Yi corridor. Forasmuch as the research of Zang—Yi corridor is mainly limited to social sciences, this paper is trying to investigate the place by means of natural science. Based on field survey and geological dating combined with literature review, the construction history of the relics were uncovered, and the effects of landslide damming events on the evolution of river geomorphology and river valley civilization were analyzed. The results shows that: 1) the construction time of the tower relics in Zhuoying village is between 1 780～1 490 a BP, corresponding to the late Donghan dynasty to Nanchao period, and the relics is most likely belong to the ancient Bailang nation according to its location. 2) the relics time coincided well with the period of changing water level at lacustrine beach due to landslidedamming of the river and the dam breaching of the Cuola paleo-dammed lake respectively; the lake-silting, hot-dry climate in the river valley and easy water intaking condition laid a solid foundation for the rise of Zhuoying village. 3) At around 1 510 a BP a big flood event led to the complete breaching of the Cuola dam, consequently worsening the living conditions such as the arable land loss by subsequent bank erosion, the inconvenient water intaking condition, and etc., which were the main factors leading to the abandonment of the village. 4) the river channel silting induced by paleo-landslide damming events along the rivers in Hengduan Mountains provided convenient route for the migration of historical nationalities, and abundant historic relics were thus kept, so a thorough investigation of the relics as those in Zhuoying village will deepen and expand our understanding of the ancient Bailang nation and Zang—Yi corridor.关键词：Jinsha River;tower relics;Zang–Yi corridor;ancient Bailang nation;paleo-landslide damming;silting;dam breaching1424|954|0更新时间：2023-11-29
SCIENTIFIC FRONTIERS
- 摘要：Faculty Development is a critical initiative launched by the Ministry of Education since the 12th Five-Year Plan to promote high-level construction of the teaching workforce. This article explores the connotation of academic excellence, revealing that said ‘excellence’ should include both subject-specific and pedagogical excellence. Through literature analysis, it confirms the prevalence and severity of valuing subject-specific scholarship over pedagogical scholarship. Therefore, the article proposes that leading research universities should set off from a core mission to cultivate talent and deepen their understanding that academic excellence involves the organic fusion and mutual reinforcement of first-class subject-specific and pedagogical scholarship. This concept should be effectively implemented and reflected in faculty development strategies, system construction, and model building. Finally, this institution’s faculty development is provided as an example to demonstrate the research and practical outcomes. Sichuan University, one of the first 30 universities to create a National Demonstrative Center for Faculty Development, in its 10 years of research and exploration, reveals with profound analysis the key notion that academic excellence entails the mutually reinforcing combination of subject-specific and pedagogical scholarship. It establishes a new concept of academic-excellence-led faculty development at research universities. By synergizing various methods across ‘teaching, research, and learning’, this center of Sichuan University pioneered a new path that integrates subject-specific scholarship with teaching scholarship to advance faculty development. Furthermore, constructed a multi-dimensional faculty development support system spanning across ‘university, schools or department, foundational faculty organizations’ levels, fostering a new mechanism that continuously motivates faculty to strive for excellence, and invigorate the faculty community. This novel model of faculty development spearheaded by academic excellence, has effectively driven innovations and reforms in teaching and learning, serving as a remarkable exemplar and inspiration, winning the 2022 National-level Teaching Achievement Award.关键词：academic excellence;faculty development;pedagogical scholarship;subject-specific scholarship;research universities434|643|0更新时间：2023-11-29
PROJECT OF THE NATIONAL TEACHING ACHIEVEMENT AWARD FOR HIGHER EDUCATION
- 摘要：The development of digital twin (DT) technology brings many conveniences to the intelligent management of power systems.However, as a key technology to promote the digitalization and intelligence of the energy and power industry, related research and applications are still in the initial stage. Systematic research is urgently needed to break through the adaptation key technologies of digital twin engineering application for the particularity of the energy and power industry. For this reason, the substation was took as an application scenario in this paper, the current situation of the operation and maintenance management of the substation were firstly analyzed, and the defects of the substation inspection mode, the insufficient model accuracy, the single perception parameter as well as the lack of in-depth data mining were pointed out. Then, a digital twin substation model framework was designed, which includes spatial information and equipment modeling, main equipment mechanism modeling, intelligent feedback control, equipment sensing network, model simulation and 3D visualization rendering and applications. The problems and challenges of substation digital twin technology are discussed, including professional intelligent development, mass data storage computing resource allocation, model research, data security, 3D virtual entity construction and dynamic update. In view of the problems and challenges raised, the research on key technologies to solve the problems was discussed, including the development of new sensors, distributed storage, cloud-edge collaborative computing, fusion modeling, trusted federation learning and other advanced technologies, as well as the 3D reconstruction of real scene and the dynamic visualization of point cloud. Combined with the design of digital twin model and the discussion of key technical issues, a set of application-oriented digital twin substation system design schemes were given, focusing on the real-time monitoring of equipment in the station, equipment fault diagnosis and fault prediction, operation and maintenance decision optimization and intelligent feedback Typical application scenarios including control.关键词：substation;digital twin;frame design;intelligent inspection;Compressed sensing;fusion modeling;trusted federated learning;three dimensional visualization766|5545|3更新时间：2023-11-29
- 摘要：Traditional rendering methods are not competent for rendering a large number of static and dynamic large-scale scene objects of digital twin cities such as streetlights and moving vehicles. The reason lies in that generating multiple independent scene objects on each spline causes objects of the entire scene use different meshes, resulting in a higher number of draw calls (DCs) and performance degradation. In this paper, a method based on global instance management for rendering all large-scale scene objects was proposed, which reduces the number of DCs (
$ {n_{{\rm{DC}}}} $ $ {n_{DC}} $ $ {n_{{\rm{DC}}}} $ $ {n_{{\rm{DC}}}} $ 关键词：global instance;digital twin city;large-scale scene;spline;draw calls319|581|0更新时间：2023-11-29 - 摘要：The 3D terrain rendering is widely used in many industries, such as the military, agriculture, transportation, and smart cities. The processing method for image data mainly adopts spatial meshing and establishes tile data at different levels. In order to improve the resolution of the 3D terrain, the number of sliced tiles is increasing exponentially, and the accessing, indexing, and rendering of massive tile data are technical problems that need to be overcome. In this paper, a real-time rendering method for layered image data based on TMS (tile map senice) was proposed to solve above problems and to address the severe chromatic aberration at the junction of different levels of images. In this method, service objects with different image layers were constructed, and the flexible control and management of the hierarchy, order, and position of digital twin city hierarchical images were realized. Meanwhile, three queues were stored for high, medium, and low relative priority of the loaded tiles in the viewport to speed up the scheduling and rendering of tile data. To accelerate the acquisition of image tile index, the screen pixel size was calculated according to the tile matrix range in the viewport. The final level of the image was determined by comparing it with the level of the current file resource after obtaining the preliminary level of the image tile. Then, the index of the image tile in the viewport was calculated, and the row and column number were calculated according to the latitude, longitude, and level to form the request path of the image resource. Finally, the two layers were blended sequentially from the lowest layer to obtain the correct blending result according to the size of the image hierarchy. In the paper, a set of 3D terrain rendering experiments were carried out on near, medium, far, and coastal multi-layer image data in practical applications. The results showed that the NVIDIA 2070 graphics card can achieve high real-time performance of 300 FPS and high-quality rendering. Therefore, the proposed method can flexibly render large-scale and multi-level image data to construct a 3D terrain of the digital twin cities.关键词：digital twin city;layered image data;3D terrain rendering;tile data;real-time rendering370|449|1更新时间：2023-11-29
DIGITAL TWINS AND THE METAVERSE
- 摘要：Aiming at the problem of stable and efficient detection of human blood glucose, an optical fiber sensor based on surface plasmon resonance (SPR) technology was proposed and successfully applied to the detection of glucose concentration in this paper. The structure of MMF (multimode fiber)–PCF (photonic crystal fiber)–PCF–MMF (MPPM) was spliced using the fiber fusion machine, then the gold film was deposited on its surface by magnetron sputtering. The gold film in the sensing region was modified with mercaptoethylamine, and glucose oxidase (GOD) was immobilized by glutaraldehyde to make the sensor with glucose specific recognition and low concentration glucose sensing was realized. For the refractive index sensitivity of the SPR sensor, the comparison experiments of two groups of sensors were designed. One was the comparison of sensors with the same structure and different sensing area lengths, and the other was the comparison of sensors with the same length and different structures. The research results showed that the length of the sensing region has a few effect on the refractive index sensitivity of the sensor; and the refractive index sensitivity of the MPPM structure is better than that of the MPM structure (improved about 101.84 nm/RIU), and the sensor of the MPPM structure has a deeper SPR resonance peak, which means higher detection accuracy. For the glucose sensor, a set of detection schemes for glucose concentration, specific recognition and stability were designed. It showed good linearity in the glucose concentration range of 0～0.8 mg/mL, with the glucose sensitivity of 29.61 nm/(mg/ml) and the fitting coefficient of 0.954. Compared with the traditional glucose sensor, the glucose sensor proposed in the paper has a compact structure, superior biocompatibility and high sensitivity.关键词：surface plasmon resonance;photonic crystal fiber;fiber-optic sensors;glucose concentration sensor412|490|0更新时间：2023-11-29
- 摘要：In order to solve the Mura defects caused by substrate blemishes and uneven coating during the inkjet printing of OLED emissive layer, a 3D numerical simulation model based on Bhatnagar-Gross-Krook-lattice Boltzmann method (BGK-LBM) was established to simulate and analyze the scattered deposition defects caused by the deviation of inkjet drop points near the pixel pits. Firstly, the maximum spreading radius of the inkjet droplets after impacting with different size, contact angles and different impact speeds was studied. Then, the spreading and rebounding of the inkjet droplet outside the pixel pits under different wettability gradients were studied using the maximum spreading radius as a reference. Finally, the phase diagrams of effective droplet deviations of different contact angles were obtained. The results showed that for the micron OLED inkjet droplets, the maximum spreading radius is proportional to the size and the impact velocity of the inkjet droplets, and inversely proportional to contact angle inside the pixel pits. For scattered inkjet droplet with deviation, when the maximum spreading radius is greater than or equal to the deviation of the inkjet droplet, it is re-entered the pixel slot under the traction of wettability gradient caused by the difference between the inner and outer contact angles of the pixel substrate. Also, the retraction of spreading droplet is proportional to the impact velocity. Therefore, the droplet is pulled to the more hydrophilic side with the influence of wettability gradient. And the inkjet droplet is pulled back into the pixel pits only if the edge of the droplets after impacting and spreading is entered into the pixel pit with wettability gradient. Finally, the defects of scatter deposition is inhibited. The proposed maximum spreading radius widens the effective range of the inkjet droplet outside the pixel pits, which can be used as a reference for production of OLED emissive layer.关键词：printed OLED;LBM;scattered droplet defect301|461|0更新时间：2023-11-29
MICRO/NANO OPTOELECTRONIC BIO-SENSOR
- 摘要：Based on the Haiwen Bridge, a 1g shaking table model test was adopted to further explore the dynamic time history response law of near-fault bridge pile foundations in strong earthquake areas. Under the action of 0.35g different types of seismic waves, the pile foundation acceleration, pile top relative displacement, pile bending moment dynamic time history response and its difference, and pile foundation damage analysis of non-fault and near-fault bridge were carried out. The results show that due to the influence of seismogenic fault and bulk material characteristics of fault fracture zone, the properties of the semi-infinite body of foundation soil are changed. Because the structure of the fault fracture zone is worse and its strength is weaker than that of the foundation soil, the amplification effect of fault fracture zone-foundation soil interaction on seismic waves is more obvious. As a result, the dynamic response characteristics of near-fault bridge pile foundations are more obvious than those of non-fault pile foundations, and the peak acceleration of the pile foundation, the relative displacement of the pile top, and the bending moment of the pile body are larger. And the peak acceleration appears earlier than that of non-fault pile foundation, with an average advance of 0.44 to 3.18 s. The time history response of pile top acceleration and relative displacement of near-fault pile foundation is larger at about 10 s. The displacement response begins to attenuate in the 30 s. During this period, the dynamic response characteristics of pile foundations are the most obvious. The maximum bending moment of near-fault pile foundation does not exceed its ultimate bending bearing capacity, and there is a surplus of 20.36%~28.41% bending bearing capacity. The fundamental frequency of the near-fault pile foundation does not change, which indicates that the pile foundation of Haiwen Bridge meets the requirement of seismic fortification intensity Ⅷ. To sum up, the influence of the difference in seismic wave spectrum characteristics on pile foundations should be considered in the seismic design of near-fault bridge pile foundations. The seismic analysis and checking calculation of near-fault bridge pile foundations should be carried out according to various types of seismic waves, and further enhance the anti-seismic capacity of near-fault pile foundations.关键词：bridge engineering;pile foundation;strong earthquake area;near fault;shaking table test;time-history response283|493|2更新时间：2023-11-29
- 摘要：Granular materials are composed of a large number of discrete particles with different particle shapes, and their mechanical properties are closely related to the particle shape of the particle system. At present, the macro and micro properties of non-spherical granular materials under complex stress paths are not fully understood. A series of constant-σ3 constant-b true triaxial tests on ellipsoid particle systems with a certain gradation was carried out utilizing the discrete element method (DEM), and the aspect ratio of ellipsoid particles AR was changed to reflect the effects of particle shape on the macro-mechanical properties, and the applicability of the commonly used three-dimensional strength criteria to the ellipsoid particle system was verified. The results showed that under the three-dimensional loading path, different from the consistency of the macro and micro evolution laws of the spherical particle system, the evolution laws of the macro stress surface and the micro fabric surface of the ellipsoidal particle system were inconsistent, and the linear relationship between the macro stress ratio and the partial value vs mean value ratio of the strong contact network fabric was not 1, which was attributed to the contribution of the weak contact network of the ellipsoidal particle system to the macro stress. The macroscopic strain and microscopic characteristics of the ellipsoid particle system were independent of the loading paths, such as normal contact force distribution, contact number, and coordination number distribution. In addition, the four of the three-dimensional strength criteria had better prediction capability when AR was larger, especially for Lade-Duncan criteria. The research provides a theoretical basis for improving understanding of the macro and micro properties of ellipsoidal granular materials under real stress states.关键词：DEM;particle shape;true triaxial numerical test;three-dimensional strength criterion;macro and meso behavior302|498|2更新时间：2023-11-29
- 摘要：Cyclic creep mechanical properties of brittle rock under the combined influence of high seepage pressure, confining pressure, and cyclic axial loading and unloading are of great significance to the stability evaluation of surrounding rock in deep underground engineering. The mechanism of the reverse sliding of the crack and the recovery of the extended crack is rarely studied. An expression of stress intensity factor for forward, reverse, or static sliding of the initial crack surface under the combined action of axial loading and unloading, confining, and seepage pressures was established, which was based on the wing crack extension model by forward sliding of the initial crack surface in the rock under the combined action of axial loading, confining pressure, and seepage pressure. The expression introduces the reverse and static sliding mechanical properties of the initial crack surface under the combined action of axial unloading, confining pressure, and seepage pressure to explain the recovery mechanism of the extended wing crack. A micro-macro mechanical model of cyclic creep was established under the action of wing crackgrowth and recovery driven by high internal seepage pressure, external confining pressure, and axial cyclic loading and unloading, which combined with the subcritical crack law, crack-strain model, and Hooke–Kelvin model. The complete elastic, viscoelastic, and plastic deformation of rock was described. The influence of high seepage pressure on elastic–visco–plastic stress–strain curves induced by forward sliding of initial crack surface and wing crack growth of brittle rocks was studied, which provided a basis for the selection of model parameters of applied stress and elastic modulus in cyclic creep. The effects of seepage pressure on forward, reverse, and static sliding of the initial crack surface, and visco-elastic strain ε1ve, plastic strain ε1p, and total strain ε1 induced by wing crack growth and recovery in cyclic creep were analyzed. The effects of seepage pressure on the elastic rebound, plastic rebound caused by crack recovery, failure time, and stress of cyclic creep were discussed. The effects of confining pressure on the elastic–visco–plastic cyclic creep strain were also studied. The study results are meaningful for the evaluation and prediction of fatigue life of underground engineering rock bodies under high seepage pressure.关键词：brittle rocks;high seepage pressure;cyclic creep failure;the extended crack recovery;reverse sliding of crack409|398|0更新时间：2023-11-29
- 摘要：In order to analyze the influences of train load on the proximity-sensitive structures during the operation period of the newly built subway viaduct, this study uses the example of the viaduct on the north extension line of Changsha Metro Line 1 spanning the existing expressway and main railway, and adjacent to the existing abutment pile foundation and frame bridge on both sides. The dynamic coupling numerical model of viaduct-strata-existing structure under train vibration load is employed to analyze the variation law of the dynamic response of the stratum and the existing structure at different depths, as well as the train running speed, axle load, approach distance, the modulus of the reinforced stratum, and damping ratio. The influence law is developed for horizontal displacement, velocity and acceleration of abutment pile foundation and frame bridge, respectively. The results show that: under the action of train vibration, the surface settlement value is about 40% of the horizontal displacement, and the ground deformation is dominated by the horizontal displacement. The deformation, velocity and acceleration trends of the framebridge are similar to those of the pile foundation, but their absolute values are relatively small. The characteristics of the dynamic response at different depths are obviously different, and the top of the pile and the top plate of the frame bridge are more affected. The dynamic response of the existing structure decreases and then increases with the increase of the train speed, and the change amplitude is small in the low-speed zone, while 80 km/h is the optimal running speed of the train. The dynamic response increases linearly with the increase of the axle weight of the train, and the axle weight has a significant effect on the dynamic response relative to the speed. The smaller the proximity distance is, the larger the dynamic response of the frame bridge is. When the horizontal distance between the new pile foundation and the frame bridge is less than 4 times of the pile diameter, the reinforcement measures are required. The dynamic response decreases with the increase of the stiffness of the reinforcement area, and after the ground modulus reaches 300 MPa, the effect of continuing to improve the reinforcement strength on the reduction of response is not obvious. The research results can provide useful reference for the construction and operation of similar projects.关键词：subway elevated bridge;adjacent structures;train dynamic load;dynamic response;numerical simulation;influence law475|491|0更新时间：2023-11-29
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Collapse-resistant Performance of Composite Beam-column Substructure with Cellularity Circular Hole AI导读
摘要：To investigate the influence of cellular beams on the collapse-resistant performance of composite beam-column structure, a 1/3 scale solid-webs (WUF) and composite beam-column substructure with cellularity Circular Hole (WUFC) specimens were fabricated, respectively. Two specimens were subjected to static loading collapse tests under the failure condition of the middle column. The test results showed that the damage mode of WUFC was that the first fracture occurred on the lower flange of the steel beam on the right side of the middle column node, followed by the fracture of the beam flange at the left and right side column nodes, while the damage mode of WUF only showed that the lower flange of the steel beam at the right side of the center column node fractures first, and then the crack developed vertically along the bolt hole and was finally sheared through. The deflection development of beams and internal force development trend of the two specimens were similar, but the better one of the deformation abilities was the WUFC specimen. The resistance mechanisms of the two specimens could be divided into compressive arching stage, flexural mechanism stage, and catenary mechanism stage. The initial stiffness of WUFC decreased by 8.5% compared to WUF during the compressive arching stage, as the openings weakened the flexural stiffness of the combined beam. In the catenary mechanism stage, the WUFC was fully developed, and the maximum load-carrying capacity and failure displacement of the WUFC increased by 42.7% and 31.9%, respectively, compared to the WUF. The appropriate openings on the beam web were conducive to the development of nodal rotation and axial forces at the beam end of the combined beam. Two specimens were modeled with ABAQUS. The finite element modeling method was verified by comparing the simulation results with the tests results. The influences of key parameters such as diameter to height ratio, hole spacing, and edge distance on the collapse-resistant performance of substructures were analyzed by the full-scale model. The numerical analysis results demonstrated that to ensure the great collapse-resistant performance of substructures, the diameter-to-height ratio should be 50%~70%, the hole spacing should be 1.0～1.4 times of the beam height, and the edge distance should be equal to the beam height.关键词：composite beam-column substructure;progressive collapse;parameter analysis;failure mode;load-resisting mechanism316|633|0更新时间：2023-11-29 - 摘要：Beam-column connections are an important part of frame structures. The premise of the analysis of the anti-collapse performance of structures is to clarify the mechanical properties of the connections. Based on the alternative load path method and considering the combined effect of the floor slab, the failure mode, mechanical property, and resistance mechanism of the composite beam-column substructure with rigid splicing connections in the minor axis were compared and investigated under the failure of the middle column. The composite beam-column substructure named RWUF and RWUT in the minor axis were selected to conduct a monotonic static loading test. The results indicate that the two specimens have gone through the elastic stage, compressive arching stage, and the mixed mechanism stage (flexure-catenary mixed stage). The first fracture of the specimens occurred in the mixed mechanism stage, and the catenary effect played a favorable role in the increase of the load after fracture. The fractures of the specimens occurred at the splicing point. The cracks at the tension flange of the steel beam of the specimen RWUF in the positive bending moment area continued expanding to the web until it was destroyed. Damage of specimen RWUT was only the fracture of the tension cover plate in the positive bending moment area. After the limited slipping of bolts, the axial deformation was continuously accumulated because of the extrusion of bolt holes. It is conducive to the rotation of the plastic hinge and provides a path for the transmission of the axial force. The catenary effect was significant in the later stage, and the overall resistance was improved. The dynamic evaluation of the substructure based on the principle of energy balance showed that the connection's nonlinear rotation ability directly affected the structure's collapse resistance. In the minor axis, the structure with a connection that the web and flange were united by bolts had a higher dynamic collapse resistance.关键词：composite beam-column substructure;minor axis;rigid connection;static loading test;anti- collapse performance314|488|0更新时间：2023-11-29
- 摘要：Discrete element method (DEM) is an important method to study the mechanical properties of unsaturated soils. The reliability of numerical simulation depends on the accurate calibration of the mesoscopic parameters of the unsaturated contact model. At present, there is a lack of systematic study on the calibration method of mesoscopic parameters of unsaturated contact model. In this paper, a method of calibrating the mesoscopic parameters of unsaturated contact model in DEM based on flexible boundary was proposed. The mesoscopic parameters of the unsaturated contact model were systematically calibrated, and the correlation between the mesoscopic parameters and the macro response of the unsaturated contact model was revealed through parameter sensitivity analysis. First, the range of mesoscopic parameters was optimized through orthogonal test design, and its sensitivity to macro response was analyzed. The sensitivity analysis results showed that the secant modulus (E50) of unsaturated soil was mainly affected by the friction coefficient (µ), suction (ψ), and Young's modulus (E), and the degree of influence was µ>ψ>E; The peak strength (Sp) of unsaturated soil was mainly affected by ψ and µ, and the degree of influence was ψ>µ>E. Secondly, according to the results of sensitivity analysis, the significant influence parameters of the relevant macroscopic response were determined, and the regression equation between the macroscopic parameters and the significant mesoscopic parameters of the unsaturated contact model was established by using the response surface analysis method based on the central composite test design (CCD). Thirdly, the most optimized model of mesoscopic parameters of unsaturated soil was established according to the regression equation, and the FMINCON function in MATLAB was used to solve it to obtain the optimal solution of mesoscopic parameters. Finally, the triaxial tests of unsaturated soil under different confining pressures were simulated by using the obtained parameters, which were compared with the laboratory tests to verify the validity of the calibrated parameters. This method provided a basis for further analysis of the mesoscopic mechanical properties of unsaturated soils.关键词：unsaturated soil;flexible boundary;mesoscopic parameter calibration;triaxial test;DEM261|457|3更新时间：2023-11-29
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Geomembrane–Geotextile Composite Rules for Bulging Deformation of Separated Composite Geomembrane AI导读
摘要：The separated composite geomembranes are widely used in the horizontal anti-seepage engineering of plain reservoir bases. To study the action principles of geomembrane and geotextile in bulging deformation and failure, based on the ring-constrained spherical bulging deformation model, laboratory bulging deformation test and theoretical analysis method of layered composite materials were adopted to analyze the bulging deformation and failure characteristics of the separated composite geomembrane (two geotextiles and one geomembrane 250 g·m–2/HDPE0.4 mm/250 g·m–2) and geomembrane-geotextile composite rules of bulging pressure and stress. The preliminary application of the rules was also discussed. The results showed that: When the separated composite geomembrane bulges, due to water/air permeability, the lowest geotextile in contact with the pressure medium was defined as ineffective bulging layers, while the upper geomembrane and geotextile layers were considered as effective bulging layers. The uppermost geotextile in the effective layer was the first to undergo fissure-type damage, and the geomembrane also failed instantly after the geotextile broke. The bulging pressure (including bursting pressure) was the total pressure of each effective layer, while the bulging stress (including bursting stress) was the sum of the product of each effective layer’s thickness percentage and stress. The bursting height and bursting strain of the separated composite geomembrane were approximately equal to that of the geotextile. The higher the stress in the effective layer of geomembrane/geotextile material itself, the higher the stress in the resulting composite materials. The greater the percentage of thickness of a material, the closer the stress of the composite materials was to the stress value of that material, and the degree of rapidity of approach was proportional to the magnitude of the stress difference between the effective layers. For different kinds of separated composite geomembranes combined with different sizes and types of base materials, the research results are helpful for determining the mechanical properties of bulge deformation and can provide a reference for material selections in practical applications.关键词：composite geomembrane;bulging deformation;mechanical characteristics;composite rules336|780|0更新时间：2023-11-29 - 摘要：As a by-product in the process of manufactured sand production, stone powder is one of the main characteristics that is different from natural sand. Based on the existing specifications, a design method of mixing ratio of stone powder in manufactured sand into the cementation system was proposed. The physical and mechanical properties of concrete with two lithology (limestone, granite) powders and their different contents were systematically tested. The microscopic action mechanism of stone powder on concrete was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FTIR), and thermogravimetric analyzer (TGA). The results showed that the compressive strength and splitting strength of concrete increased first and then decreased with the increase of the stone powder content when the stone powder was used to replace manufactured sand in accordance with the mix ratio of concrete in this test. Microscopic mechanism analysis showed that most of the stone powder in the manufactured sand was inert, and only a small amount of limestone stone powder which had limited chemical activity could promote the early hydration of cement and accelerate the development of the early strength of concrete. Stone powder in manufactured sand mainly played a physical filling role in concrete. When stone powder’s content was kept at 16%～19%, it could play a good micro-aggregate filling effect to improve the mechanical properties of concrete. When the content exceeded this range, the dilution effect would reduce the mechanical properties of concrete. In the case of the same content of stone powder, the overall microstructure of concrete samples in the granite stone powder group was denser than that in the limestone stone powder group, resulting in the macroscopic mechanical properties of concrete in the granite stone powder group was stronger than that in limestone stone powder group. Compared with similar studies, the optimal stone powder content obtained in this study was in a higher range. This study can provide a scientific basis for the mix ratio design of manufactured sand concrete with high stone powder content and the control of stone powder content in the process of making manufactured sand aggregate.关键词：manufactured sand;concrete;stone powder;macroscopic mechanical properties;microscopic mechanism401|542|1更新时间：2023-11-29
- 摘要：Perilous rock mass is highly susceptible to collapse disasters under seismic actions. To calculate the stability of toppling perilous rock mass under bidirectional ground motion and explore the influence of ground motion randomness on the dynamic fuzzy reliability of toppling perilous rock mass, the dynamic response of toppling perilous rock mass was analyzed by using structural dynamics and stochastic process theory. Firstly, based on the theory of structural dynamics, the mechanical model of the seismic dynamic response of toppling perilous rock mass and its motion equations on two main control surfaces were established. The Wilson-θ method and the pseudo-excitation method were respectively employed to solve the motion equations, and the calculation methods for the dynamic response of toppling perilous rock mass under deterministic seismic waves and stochastic seismic excitations were established. Then, based on the limit equilibrium theory, the calculation formula of the dynamic stability coefficient for toppling perilous rock mass under deterministic seismic was derived. The stochastic ground motion was considered as a stationary stochastic process, and the mean and variance of seismic force peak response of toppling perilous rock mass under stochastic seismic excitations were solved based on the first-passage failure criterion. As a result, a method for calculating the random dynamic stability of perilous rock mass has been established. Finally, the instability event of toppling perilous rock mass was regarded as a fuzzy event. The fuzzy failure criterion was introduced, and the improved Monte Carlo method was used to calculate the fuzzy reliability of perilous rock mass. A rapid calculation method for the dynamic fuzzy reliability was established, and the influence of seismic randomness on the fuzzy reliability was analyzed. The application of our method to an engineering example shows that the dynamic stability coefficient and fuzzy reliability of toppling perilous rock mass respectively increase by 6.34% and 22.83% after considering the randomness of ground motion, which reduces the failure probability of perilous rock mass. Moreover, the fuzzy reliability calculated using fuzzy failure criteria is more biased toward engineering safety. Considering the bi-directionality and randomness of seismic excitation, the dynamic stability of toppling perilous rock mass is effectively evaluated, which provides a reference for the evaluation of the random seismic dynamic stability of perilous rock mass.关键词：toppling perilous rock mass;bidirectional random seismic;Wilson-θ method;pseudo excitation method;fuzzy reliability246|470|0更新时间：2023-11-29
- 摘要：To grasp the effect of electrochemical repair on the seismic performance of concrete structures, numerical analysis and experimental verification of the seismic performance of concrete columns under conventional electric field strength are investigated. First, low-cycle fatigue experiments of steel bars were performed after electrochemical hydrogen charging, and the constitutive parameters Cf, Cd, and α of the reinforcing steel material were corrected in the OpenSees platform based on the test data. Second, low cyclic loading experiments of concrete columns were performed after electrochemical repair, and the effects of electrochemical repair on the seismic performance index of concrete columns were obtained. Finally, a finite element fiber model of the concrete column after electrochemical repair was established, and the numerical simulation results and experimental data were compared and analyzed. The results showed that the fatigue life of the electrochemically repaired steel specimens was reduced by about 5%, 30%, and 54% compared with that of the unrepaired steel specimens at loading amplitudes of ±1.0%, ±1.6%, and ±2.0% for the low circumference fatigue test of steel bars, respectively, indicating that the negative effect of hydrogen generated during electrochemical repair on the low circumference fatigue life of steel bars increased with the increase in amplitude; the shape of hysteresis curves of concrete columns before and after electrochemical repair was basically the same, and the peak load and energy dissipation capacity were also basically the same, indicating that electrochemical repair at common currents had a small effect on the seismic performance of concrete columns; the numerical simulation results of concrete columns were close to those of low cyclic loading experiments, indicating that the finite element fiber model proposed in this paper could be used to evaluate the effect of electrochemical repair on the seismic performance of concrete members.关键词：concrete structures;electrochemical repair;low cycle fatigue;seismic performance242|465|0更新时间：2023-11-29
- 摘要：The loess plateau in northwestern China is a landslide-prone area, and the loess with metastable structure, high porosity, and water sensitivity will show instability under external disturbance. In addition to the shearing behavior of soils, creep character is also considered crucial in determining the long-term shear strength. Reasonably evaluating the creep characteristic and long-term shear strength of reinforced loess is important to promote the engineering application. The creep test of reinforced loess was carried out by using large-scale direct shear equipment. The horizontal shear displacement-time curve was obtained, and the creep characteristics of reinforced loess under the condition of large displacement strength were studied. In addition, to overcome the shortcomings of the traditional creep model, this paper proposed the Modified Burgers model with nonlinear parameter β. Compared with the Burgers model, the Modified Burgers model could flexibly fit the loess creep test curve and more accurately describe the curve of non-attenuating creep in the accelerated creep stage. Three creep characteristics of straw-reinforced loess, i.e., attenuating creep, non-attenuating creep, and viscous flow, were identified. The results showed that the relationship between horizontal shear displacement and creep time indicated that the unreinforced and reinforced specimens behaved differently when subjected to the same shear stress ratio. The reinforced specimen performed superior in limiting the particle relative movement within the shear plane than the unreinforced specimen. The relationship between the creep rate and the shear stress ratio confirmed that the shear stress will lead to the relative displacement between the soil particles in the shear zone during the creep process, resulting in the failure of the specimen along the shear surface. The chain reaction of interparticle contact loss, accompanied by excessive viscous displacement, rapid weakening of creep resistance, and eventually accelerated creep displacement, provided a testimony revealing the formation mechanism of a slow-moving landslide.关键词：reinforced loess;large-displacement shear strength;creep;long-term shear strength;modified Burgers model341|523|1更新时间：2023-11-29
CIVIL ENGINEERING
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Study of Controlled Magnetic Circuit Permanent Magnetic Levitation Belt Conveyor Support System AI导读
摘要：To address the problem of rotational resistance generated by the traditional belt conveyor roller bearings, a new controlled permanent magnet support system is proposed, which consist of servo motor, double radial permanent magnet, magnetic guide, permanent magnet patch and roller shaft. First, we develop a model for the single-point controlled permanent magnet support system by the finite element method (FEM), and optimize the key structural parameters affecting the magnetic field distribution of the system by a simulation software of Maxwell electromagnetic. We analyze the influence of different spinning directions of the double radial permanent magnets on the suspension force of the system. Second, the magnetic path method is used to divide the magnetic flux paths of the magnetic conductors in the single-point controllable permanent magnet support system, followed by establishing the magnetic flux path model at each place to derive the analytic formula for the magnetic flux of the magnetic conductor legs. We employ the equivalent magnetic charge method to determine the magnetic induction intensity of the permanent magnet patch surface, and establish the levitation force model of the single-point controllable permanent magnet support system by considering the relationship of acting forces between the permanent magnets. Third, Maxwell electromagnetic simulation software is used to determine the suspension force correction coefficient λ1 and the air gap correction coefficient ε in the theoretical calculation model. A experimental platform of single-point controllable permanent magnet support system is built to obtain the relationship of suspension force characteristics and verify the theoretical calculation model. Finally, a dynamics model is established for the single-point controllable permanent magnet support system to analyze the feasibility of its stable suspension. The PID algorithm is investigated by integrating the control systems of a two-phase hybrid motor. Both simulation and experimental results show that the system air gap response can be stabilized at the set value to achieve a stable suspension quickly, which meets the controllability requirement. This work provides a certain theoretical basis for the research of low-drag belt conveyors.关键词：radial magnetized;finite element method;structure parameters;levitation force;proportional integral derivative405|654|0更新时间：2023-11-29 - 摘要：In order to study the effects of POB(polyphenyl ester) filler on the transfer film evolution and the friction properties of Nano-SiO2/PTFE composites, cold pressing and hot sintering processes were used to fabricate two kinds of composites, i.e., Nano-SiO2/POB-PTFE and Nano-SiO2/PTFE. On this basis, dry friction tests were carried out by intermittent weighing and in-situ observation techniques on an LSR-2M tester. The microscopic friction transfer mechanism of the transfer film was analyzed by characterizing its surface morphology, microstructure and three-dimensional morphology using optical microscope, thermal field emission scanning electron microscope (FESEM), and non-contact 3D surface profiler, respectively. The results showed that the morphology of Nano-SiO2/PTFE composites’ transfer film changes rapidly on the contact surface during repeated formation and shedding process, accompanied by serious wear and thus unsuccessful formation of complete transfer film. In addition, the transfer film generated by Nano-SiO2/PTFE composite was obviously stratified with significant traces of shedding, and a large number of rice-grained wear debris attached to the contact surface resulted in poor reflectivity. By contrast, the POB filled Nano-SiO2/PTFE composites not only enhanced the adhesion of wear debris on the contact surface, but also promoted the formation of uniform and continuous transfer film, leading to a good surface reflective property. In particular, the wear rate of Nano-SiO2/POB-PTFE composites was decreased by two orders of magnitude compared with that of Nano-SiO2/PTFE composites. POB and Nano-SiO2 can form a synergistic wear reduction effect in the friction transfer of PTFE composites due to the strong adhesion of POB and the mechanical interlock between the Nano-SiO2 and its frictional counterpart. This can effectively promote the uniform formation and stable adhesion of the transfer film and greatly reduce the wear rate. The above research provides important guidelines for the development of dry friction sealing materials for the piston rings in Stirling engine, and is conducive to the research and development of high-performance seals for solar dish Stirling system.关键词：POB;Nano–SiO2;PTFE;friction transfer;transfer film301|563|0更新时间：2023-11-29
- 摘要：Fatigue cracking is the main cause of pressure vessel safety failure; however, the traditional pressure vessel safety assessment method fails to take the time-varying nature of the safety decay process of crack defects into account, which leads to flawed safety margin characterization of crack defects. This paper investigates the depth and length expansion law of crack defects on the surface of pressure vessel during fatigue fracture by combining mechanical formula derivation, crack fatigue simulation and experiments, and explores the safety decay process of crack defects under fatigue load. The fatigue failure rate of the crack defects is defined by the safety decay path theory and the variation trend in crack defects along the time-varying path of safety decay during failure process. In addition, a new model for characterizing the safety decay rate of crack defects is developed by establishing the transient mathematical relationship between the safety decay time-varying path and the safety decay rate followed by developing calculation models of crack defect's remaining life in an integral form and safety margin. The experimental results show that the predicted remaining life of crack defects is close to the actual one. The predicted safety margin decreases slowly when the remaining life of the crack defects is more than 50% of the total life; while the predicted safety margin increases rapidly when the remaining life of the crack defects is less than 50% of the total life. This safety margin characterization agrees with both fatigue expansion law and safety decay process of crack defects, which is helpful for safety inspectors to identify and detect the crack defects close to failure.关键词：pressure vessel;safe decay rate;remaining life prediction;safety margin335|568|0更新时间：2023-11-29
- 摘要：Automated assembly puts forward high requirements for the absolute positioning accuracy of the robot. There is always a certain error between the theoretical and actual poses of the robot, and too low absolute positioning accuracy will be likely to cause collisions between parts in the assembly process. This seriously affects the application and promotion of the assembly robot. Therefore, a robot error modeling and parameter identification method based on the point sphere constraint is proposed: 1) the robot is controlled to coincide the calibration cone with the sphere of the target sphere in various postures by feeding back the end force condition through the six-dimensional force sensor installed at the end of the robot, and the position data of each joint at the time of contact is recorded; 2) the radius of the target sphere is used as the adaptation function, and the error parameters are identified by genetic algorithm, so as to establish a complete error compensation model. The seven-degree-of-freedom assembly robot is used as the research object. The positive kinematic equations of a seven-degree-of-freedom assembly robot are established by forward recursion based on its structural characteristics. The inverse kinematic equations of the robot are obtained by applying the fixed joint method and the inverse transformation method. The joint variable values are substituted into the positive kinematic equations for verification. The genetic algorithm is used to identify the error parameters, and the identification results are substituted into the kinematic model for verification. The experimental data of robot joint are collected by the point-sphere calibration method to identify error parameters through the genetic algorithm. The identified error parameters are substituted into the error model and the calculation results show that the absolute positioning accuracy is increased by 76.74%. This work provides useful references for the positioning calibration of multi-degree of freedom robot.关键词：7-DOF robot;kinematics;error model;parameter identification453|536|1更新时间：2023-11-29
- 摘要：The automated guided vehicle (AGV) is developed towards large scale and heavy duty with the rapid development of intelligent manufacturing. The optimization design of key load-bearing components can significantly reduce the weight of heavy-duty AGVs and their energy consumption during operation, leading to decreasing manufacturing and usage costs. Carbon fiber reinforced polymer (CFRP) was used as a lightweight replacement material, and the assembly was designed from material to structure to optimize the key load-bearing components of an 80t class AGV. The bi-directional evolutionary structural optimization (BESO) method was used to optimize the frame and rudder wheel mounting plate separately, while the cell sensitivity filtering technique was used to eliminate the fine bifurcation structure, resulting in an optimized structure suitable for actual manufacturing. Secondly, CFRP specimens with different layers and weave directions were prepared, and tensile and in-plane shear experiments were conducted to obtain the mechanical property of CFRP. Subsequently, the lay-up angles of the composite laminates were optimized, and the simulation results show that the optimal lay-up angles [–12/33/55/–68] of composite material can reduce the maximum Mises stress and displacement by 25.79% and 9.95%, respectively. Finally, a finite element analysis was performed, and the results show that the optimization design can reduce the weight of heavy-duty AGV significantly. The total mass of the optimized structure is reduced by 21.79% without significantly increasing the maximum stress and displacement, in which the mass of rudder wheel mounting plate is reduced to 8.83% after adopting the angle-optimized CFRP paving set. The modal analysis shows that the first sixth-order eigenfrequency of the new structure decreases slowly with increasing load in the approved working conditions, and varies smoothly between 61.95 and 109.75 Hz under full load. This work provides some guidelines for low energy consumption and low-cost manufacturing of heavy-duty AGVs.关键词：automatic guided vehicles;BESO;topology optimization;CFRP380|512|1更新时间：2023-11-29
MECHANICAL ENGINEERING
- 摘要：RGB depth map salient object detection (RGB–D SOD) is one of the research tasks in the field of computer vision. Existing models have achieved desired detection performance in simple scenes, but they cannot effectively handle complex scenes with multiple objects, low-quality depth maps, and background-similar object colors . In order to solve the above problems, a RGB–D salient object detection model is proposed based on three-branch multi-level Transformer feature interaction in this paper. Firstly, a cross-modal coordinate attention module is proposed to suppress the noise information of RGB and depth maps by employing coordinate attention, benefiting to extract more significant feature information for subsequent decoding stage. Secondly, through the feature fusion module, the highest three-layer feature maps are resampled to the same resolution and fed into the Transformer layer, which can effectively obtain the correlations between distant objects and the global information of the entire image. Then, a multi-level feature interaction module is proposed to effectively aggregate multi-level information for feature interaction, thus enabling more accurate location of salient objects as well as refinement of the boundary of salient objects. Finally, we design a Dense Dilated Feature Refinement Module to obtain rich multi-scale features by using dense dilation convolution to effectively address the number and size variations of objects. Experimental results on five public benchmark datasets with 19 models show that the proposed method achieves significant performance improvement over baselines on multiple evaluation metrics, which effectively improves the detection accuracy of salient objects in complex scenes. In addition, based on the P–R (precision-recall) curve and the F-measure curve, we can also intuitively observe that the proposed method achieves better detection results, with more complete and clearer saliency maps.关键词：salient object detection;coordinate attention;Transformer;feature interaction;dilated convolution;saliency map551|543|0更新时间：2023-11-29
- 摘要：In recent years, the development of ancient landslides on both sides of the Bailong River in Zhouqu County, Gansu Province has shown an active trend of resurrection, which has potential risks on the developed civil facilities of the downstream. It is believed that the early identification has become a topic of general concern for geological disaster prevention. In this paper, we use Sentinel–1A descending track SLC data and SBAS–InSAR techniques to perform the early identification of landslide hazard potential in Zhouqu County, especially along the Bailong River, aiming to identify the potential landslide hazard sites in Zhouqu County for their risk level classification. This work primarily focuses on analyzing four typical landslide temporal deformation processes with large creeping slide volume, and summarizes the relationship between landslide development and precipitation in Zhouqu County. The results shows that all the old landslides along the main stream of Bailong River and the tributary valley area of Zhouqu County in the northwest-southeast suffered from slid to some extent, and a total of 8 high-risk grade slopes have been identified, including, Siergou, Lijiebeishan, Hangga Village, Suoertou, Saneyanyu, Nanyu, Dachuan to Lianghekou and Qugaona Township landslides, which seriously threaten the life and property safety of residents in 15 villages and towns. In addition, the study on the most serious deformation of the Suoertou, Sanyanyu and Nanyu landslide demonstrate that the average deformation rate during the monitoring period is –80.14~21.48 mm/a, and the deformation variable is –482.01~493.31 mm, which has a higher possibility of recurrence in the future. Meanwhile, we also find that the gradual increase of precipitation in recent years may contribute more to its early recurrence. Analysis of typical landslides in Zhouqu County reveals that there is a correlation between landslide trailing edge deformation and precipitation, and the occurrence of landslides is greatly influenced by precipitation. Similarly, geological structure, topography and geomorphology, earthquakes and stratigraphic lithology also have some influence on the occurrence of landslides.关键词：SBAS–InSAR;early identification of landslide hazards;precipitation;Zhouqu;deformation characteristics605|587|6更新时间：2023-11-29
INFORMATION ENGINEERING
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