最新刊期
卷 54 ， 期 6 ， 2022
- 摘要：Mass manufacturing industry is a platform and carrier that most comprehensively involves various new technologies such as digitalization, networking and intelligence in the new round of industrial transformation. Due to its characteristics of high industrial chain correlation, strong competitiveness and remarkable cluster development, mass manufacturing industry is a representative industry of advanced manufacturing technology and information technology. The industrial chain, supply chain, sales chain, and energy chain involved in mass manufacturing industry are constantly cross integrated, gradually forming a complex digital ecosystem composed of network structure and multiple value chains. Enterprises in mass manufacturing industry have an important ecological relationship of mutual growth, symbiosis, cooperation and competition. Ensuring the good evolution of digital ecosystem is an important way to promote the healthy and sustainable development of mass manufacturing industry, but it is extremely challenging due to data interaction barriers, information asymmetry, value chain islands, vicious competition and value fiction. Therefore, aiming at the bottlenecks of network structured value chain synergy in mass manufacturing industry, this paper focused on the network topology structure of multiple value chains to solve intra-chain or cross-chain enterprise trust and collaboration, multi-source information integration, business process optimization, resource scheduling integration and other problems. Two engines were developed in this paper: digital fusion engine with the functions of generation, aggregation, storage, management, analysis, and usage; and collaborative processing engine with the functions of requirement analysis, business modeling, process optimization, and execution management. Integrating digital flows such as supply and demand flow, business flow, technology flow, relationship flow and work flow, the evolutionary mechanism of digital ecological value chain in value flow, population status, system evolution and so on was investigated. The digital ecological theory of network structured value chain was studied and the digital ecological model based on ecological value chain was established to overcome the key challenges such as the difficulty of trustworthiness assurance, value management and control, and cross-chain traceability in cross-chain interaction under the mesh structure, thus, the robustness and resilience of the value chain are ensured. On this basis, for the application scenario of data-oriented intelligent service and network structured ecological value chain, the value chain operation technology based on block chain, the value chain optimization technology based on data driven techniques, and the new service technology based on artificial intelligence were studied. The service platforms with big data processing, analysis and mining of digital ecological multi-value chain were developed to achieve resource optimization, supply and demand optimization, collaborative optimization, value optimization and ecological optimization. Furthermore, the credible operation, data optimization, horizontal and horizontal collaboration, intelligent service and other needs of the network structured ecological value chain were realized, so as to effectively improve the output efficiency, service level and capability of the ecological value chain eventually. Aiming at providing reliable theoretical and technical support for the healthy and sustainable development of mass manufacturing industry in China, this work focused on the major national scientific and technological needs of mass manufacturing industry, such as digital ecological model construction and network structured value chain collaboration, and carry out relevant R & D and engineering demonstration. Finally, future research directions of network structured value chain digital ecology theory were prospected.关键词：mass manufacturing industry;network structured value chain;digital ecosystem;artificial intelligence;block chain
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发布时间：2024-04-07
FOCUS ON STATE KEY RESEARCH DEVELOPMENT PROGRAM OF CHINA
- 摘要：Landslides are the source and dynamic basis of the coupled movement of flash flood and sediment disaster in mountainous, the identification of landslide susceptibility areas is an important prerequisite for flash flood and sediment disasters prediction-prewarning and risk assessment. In the past, research about flash floods and sediment disaster prevention and control paid attention to the flood’s role while ignoring the effect of mass sources. To improve the prevention and control system of flash flood and sediment disasters in the medium and small mountainous catchments, a landslide susceptibility area early identification method based on ensemble learning was proposed, and an optimization experiment for data sample construction and influence factor selection process was conducted. The frequency ratio of factors on the underlying surface of landslide units was used as unsupervised learning algorithm data samples for clustering analysis, and non-landslide units are selected based on clustering algorithm susceptibility partitioning, which constituted ensemble learning algorithm data samples for landslide susceptibility partitioning with landslide units. Accuracy and coverage of the results of landslide susceptibility partitioning for medium and small mountainous catchment was compared between the simplex algorithms and fusion algorithms. The accuracy and coverage of landslide susceptibility identification were compared before and after the introduction of the mass-source as the underlying surface factor. Direct interpretation signs of loose deposits in the study area was established through high-resolution satellite remote sensing images, loose deposits area in the study area was identified through visual interpretation, area-volume power law relationship of loose deposits was established through regressive analysis and the distribution of the loose deposits in the study area was obtained. The mass source was regarded as the underlying surface factor, and the accuracy and coverage of landslide susceptibility areas results before and after the introduction of the source factor were compared. Results showed that the coverage rate of the K-means–RF and K-Means–AdaBoost fusion algorithm was 9.3%, 12.1% higher than the K-Means simplex algorithm, the accuracy and generalization ability of the two types of fusion algorithms were relatively similar, and the K-Means-AdaBoost fusion algorithm had a better prediction effect for landslides. The coverage of high susceptibility areas in the susceptibility partitioning of the K-Means–RF and K-Means–AdaBoost fusion algorithms after considering the object source factor was improved by 14.2% and 17.7%, respectively, and the recall rate was both improved by 12.1%.关键词：landslides;susceptibility;influence factor;ensemble learning
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发布时间：2024-04-07 - 摘要：In order to evaluate the forecast of the sub-seasonal to seasonal (S2S) forecasting system of the Beijing Climate Center (BCC) ,called BCC_S2S model for short, for daily precipitation and summer extreme precipitation events in the upper and middle reaches of the Yangtze River (UMRYR), based on the products of the BCC_S2S model, which reforecasts 60-day precipitation twice a week from 2005 to 2020, bilinear interpolation is implemented to downscale grid point data to station data. Then, various comparison is applied to evaluate the model performance. Three indexes are used to evaluate the daily precipitation forecasting, as correlation coefficient (CC), root mean square error (RMSE) and mean error (ME). For extreme precipitation events defined by percentile method, HSS index is used to evaluate individual station precipitation extremes. Hierarchical clustering method is used to classify regional precipitation extremes, and different precipitation extreme pattern is evaluated by comparing to the observations. The results show that, for the daily precipitation, the BCC_S2S model performance decreases with the increase of the leading period in each season, and the forecast skill stays low when the leading period is longer than 5～10 days. Forecast skill is evaluated detailly in six sub-regions. The CC indexes show similar trend as decreasing with the leading period increasing. And the ME indexes indicate that the model may over estimate precipitation in the middle-east parts of UMRYR, while under estimate that in Jinsha River Basin. The RMSE indexes are high in the middle-east parts of UMRYR. The box plots show that in most parts of UMRYR, the BCC_S2S model performs more stable in June due to the small range of errors. For the precipitation extremes, the HSS decreases with the leading period increasing in forecasting station precipitation extremes. In most parts of the UMRYR, the model performs better in high total-precipitation months. In the perspective of spatial distribution, the model can well represent the strong rainfall pattern for the four regional precipitation extremes in short leading period (0～10 d), but not in long leading period over 10 days. Generally, the BCC_S2S model performance for the daily precipitation and precipitation extremes in the UMRYR shows decreasing trend with the leading period increasing. And it performs better in June, which may be related with the better model performance in representing large scale synoptical systems such as the water vapor transportation or the front.关键词：the upper and middle reaches of the Yangtze River;sub-seasonal to seasonal (S2S);precipitation extremes;leading period;forecast accuracy
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发布时间：2024-01-10 - 摘要：Landslide deposits are one of the main sources of flash flood and sediment disaster, and their spatio-temporal distribution and evolution characteristics play an important role in the early identification of flash flood and sediment disaster areas and the study of risk areas. In order to explore the spatio-temporal evolution characteristics of landslide deposits in the Wenchuan earthquake zone, this paper selected Shouxi River Basin, a typical basin in Wenchuan, as the research area, and respectively interpreted the landslide deposits based on the five stage high-resolution remote sensing images in 2007, 2009, 2012, 2015 and 2018, and established a long time series data set of “pre-earthquake and post-earthquake” landslide deposits in the research area, and combined with the key control factors such as elevation, slope, aspect, distance from channel , distance from fault and average annual precipitation, quantitatively analyzed the relationship between evolution characteristics of landslide deposits and each factor based on certainty factor model (CF), finally calculated the vegetation fraction coverage (VFC) and the vegetation coverage recovery rate (VCRR) to explore the effect of vegetation restoration on landslide deposits activities. The research results showed that the areas of landslide deposits of five stage images were 15.68×104 m2, 442.45×104 m2, 252.86×104 m2, 146.07×104 m2, 98.97×104 m2, and were attenuated by exponential function mode. In addition, the predicted time for the area of landslide deposits to recover to the pre-earthquake level is about 21 a. The area with the strongest activity of post-earthquake landslide deposits in the study area is 1200～2400 m in elevation, 60° in slope, SE in slope direction, less than 800 m in distance from channel , less than 1500 m in distance from fault and 830～850 mm in the average annual precipitation . The evolution trend is that the activity of the landslide deposits increases in the area with an elevation of more than 2000 m, a slope of less than 40°, a distance of more than 200 m from the channel ,a distance of more than 1500 m from the fault, the average annual precipitation is more than 840 and decrease in the aspect of E, SE and S sides. VFC increases linearly with time after the earthquake, and it is predicted that the vegetation coverage will return to the pre-earthquake level at least 14 years after the earthquake. In 2012, 2015 and 2018, the areas with moderate or above VCRR account for 37.32%, 64.24% and 70.69%, respectively. In places with high VCRR, the activity of landslide deposits is low and decreases with time, and vegetation restoration can effectively reduce the activity of landslide deposits. The above research is of great significance to enrich the theory of landslide deposits evolution and flash flood and sediment disaster risk prediction.关键词：landslide deposits;spatio-temporal evolution;vegetation recovery;flash flood and sediment disaster;Shouxi River Basin
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发布时间：2024-01-10 - 摘要：The change in water transport capacity directly affects flooding risks. Apart from the effects of sediment-induced roughness and obstacle-induced drag on water capacity, the behavior of flow characteristics in diverging-converging channels under the influence of different narrow-width ratios and downstream waterlevels was particularly investigated and analyzed with numerical experiments. We find that the diverging-converging channels are characterized by the hydraulic rise in the wide section and hydraulic fall in the narrow section. When the Froude number in the diverging section exceeds 1, a submerged water jump can form due to the supercritical flow longitudinally shifting to the subcritical flow. Under low water level at the outlet, with the decrease of narrow-to-wide-section ratio, the effect of the hydraulic fall-rise-jump is more significant and the head loss in the diverging section increases greatly, reducing the water and sediment transport capacity of the wide and narrow channel. With the rise of outlet water level, the hydraulic–rise effect weakens, the hydraulic jump disappears, and the head loss in the diverging section decreases greatly, leading to the decrease of the river width variation effect and the improvement of the water convergence efficiency. The peak head loss ratio of diverging-to-converging increased with the decrease of channel narrow-width ratio with its maximum up to 6. In the case of the narrow-width ratio, the change in outlet water level has a great influence on the broadening/narrowing head loss ratio, which increases first and then decreases, and the water level with the peak loss ratio decreases with the increase of the narrow-width ratio. The results clearly demonstrated the distribution of water level and velocity along the converging-diverging channel and the associated characteristics of head loss, providing supportive knowledge for the prevention and mitigation of sediment-related water disasters in mountainous rivers.关键词：diverging-converging channels;narrow-to-wide-section ratio;outlet water level;water transport capacity;numerical modeling
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发布时间：2024-04-07
FORECAST AND EARLY WARNING OF FLASH FLOOD AND SEDIMENT DISASTERS IN MOUNTAINOUS REGIONS
- 摘要：In wireless sensor networks, nodes are susceptible to noise interference, which makes the transmission link quality worse, leading to packet loss and retransmission, thus speeding up the energy consumption of nodes and reducing the network life. Link quality prediction can provide a basis for upper layer routing protocols to select high-quality wireless links for communication, which can improve data transmission efficiency and reduce the number of retransmissions. A link quality prediction method based on gate current unit (GRU) was proposed in this paper. Specifically, the K-means++ algorithm optimized by the gap statistic algorithm was used to adaptively divide link quality levels according to the packet reception rate. In this way, the labels of link quality samples were obtained. Then, the received signal strength indicator mean, the link quality indicator mean and the signal to noise ratio mean were selected as the input. A link quality estimation model was constructed based on CatBoost because of its strength in classification, and the grid search optimization algorithm was employed to optimize the parameters of estimation model. Finally, the link quality level time series sample was constructed by sliding windows according to the results of the estimation model. GRU was used to extract link quality time series information. In order to improve the accuracy of prediction, the timing information was input to support vector regression to predict the link quality level at the next moment. Data collected from the real world were used in this paper. According to the different common interference types, three scenes of lab, corridor and parking lot were taken as experiments scenarios. The Mean square error was used to evaluate the performance of link quality prediction models, and the experimental results showed that compared with wavelet neural network, recurrent neural network, and random vector functional link and so on, the proposed method can predict the link quality level accurately.关键词：wireless sensor network;link quality prediction;gated recurrent unit;Gap Statistic algorithm;link quality level
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发布时间：2024-04-07 - 摘要：With the advent of the Internet of Everything era, the number of IoT devices with object detection capability has exploded. Accordingly, massive amounts of real-time data are generated at the edges of the network. Thus, edge computing has become an emerging computing paradigm that has the characteristics of low latency, low bandwidth and high security. While the traditional deep learning approaches usually assume that all data have been obtained before model training, a large number of new data and new categories are often gradually generated and obtained over time in real edge computing environment. In order to execute the object detection task efficiently on resource-constrained edge devices when the input data samples are accumulated and updated in batches, an incremental learning method based on knowledge distillation of multiple intermediate layers (ILMIL) was proposed in this paper. First, to preserve the obtained knowledge from existing data, a new metric called MFRRK was proposed for covering knowledge from multiple intermediate network layers. The discrepancy between the intermediate layers’ features of teacher model and student model were added in ILMIL to model training. Compared to the recent incremental learning methods based on knowledge distillation, the student model adapted ILMIL was able to alleviate forgetting by learning more knowledge of the old classes from the intermediate layers of the teacher model. Then, the incremental training for current model was conducted to avoid resource costs of using multiple independent models for training. To further reduce the model complexity, the model pruning technique can be used before knowledge distillation to compress the current model. Extensive experiments under different scenarios and conditions demonstrated that the proposed ILMIL method can effectively reduce the model calculation and storage costs, alleviate the catastrophic forgetting of existing knowledge, and maintain acceptable inference accuracy.关键词：object detection;edge computing;incremental learning;knowledge distillation;model compression
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发布时间：2024-01-10 - 摘要：As one of the important functions to realize industrial intelligence in Industrial Internet of Things (IIoT), remaining useful lifetime (RUL) prediction can predict the future degradation states of industrial equipment based on monitoring data and then reckon its remaining service time. Furthermore, the corresponding predictive maintenance strategies can be formulated in advance, and the reliability, availability, and safety of the equipment can be enhanced. In this paper, an attention-based remaining useful lifetime prediction method (ARULP) for IIoT was proposed. Firstly, in the model training stage, a local attention computation algorithm was designed by constructing a data-driven local attention computation model and utilizing the training data to compute the local attention measurements. Thus, the prediction model can pay more attention to the key information within a large amount of data. Then, a relevance vector machine based on local attention was designed by introducing the local attention mechanism into the learning process of implicit variables in the prediction model. The attention weights were updated to adjust the state prediction model adaptively and improve the prediction accuracy of the RUL for IIoT device. Finally, the ARULP method was applied in the model prediction stage to predict the degradation status and reckon the RUL for IIoT device. Extensive experiments based on the dataset of life test for accelerated rolling element bearings released by Xi’an Jiaotong University were carried out to predict the RUL for bearings with outer ring failure, inner ring failure, and holder failure under different working conditions. The experiment results showed that the prediction data of the ARULP method are the closest to the actual bearing degradation data and more accurate RUL prediction results can be obtained compared with RVM, AR, ARIMA, and LSTM benchmarks.关键词：Industrial Internet of Things;remaining useful lifetime;relevance vector machine;attention
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发布时间：2024-01-10
INTERNET OF THINGS
- 摘要：Investigations of historical landslide dams are of great significance for both in-depth understanding of regional tectonics and river evolution, and the safety of mountain river engineering. A section of the upper Jinsha River runs among the Jinsha River suture belt from the estuary of Baqu stream to the estuary of Maiqu stream. Due to the alpine and gorge geomorphy and active tectonics in the section, historical landslide dams are highly developed, among which Wangdalong paleo-landslide is characterized by the highest dam height, the largest volume of dammed lake and the longer silt history. Based on detailed field survey and data analysis of Wangdalong paleo-landslide in the upper reaches of Jinsha River, its formation and evolution are analyzed and the major conclusions are summarized as follows: 1) Wangdalong landslide is located in the suture area of Jinsha River and its main rocks comprise slate in the lower Zhongxinrong Formation (T1–2zh1) and quartz sandstone in the lower Gajin formation (Pgj1). Its source zone is a rock wedge confined by two discontinuities, i.e., the slate foliation of T1–2zh1 and fracture surface of the Wang-dalong Fault, which form an intersection line plunging towards the west. Xiongsong—Suwalong active fault cuts through the toe of the wedge and the wedge volume is estimated to be about 4.0×108 m3. 2) The landslide was probably triggered endogenically by an earthquake and exenogenically by lateral erosion due to its location on the concave-bank of the river, and the slide should occur in the Dali glaciations of the Late Pleistocene. 3) The dimensions of the landslide dam are approximately 1 700 m in length, 3 000 m in width and 450 m in height. The left side of the dam is lower than the right side, the elevation of the left side is about 2 735 m, while the right side can reach as high as about 2 770 m. 4) The dammed lake has a volume of about 26.6×109 m3, which extends upstream for about 176 km and to the estuary of Jiangqu creek, i.e. the damsite of Yebatan hydropower station. 5) The dam experienced three breaching events and the corresponding elevation of sluice bed are approximately 2 460 m, 2 400 m and 2 358 m (the present river level), respectively. 6) The first dam-break should most likely be induced by the dislocation of Xiongsong—Suwalong fault, earlier than 1900 a BP, and its empirically estimated flood is 21.0×104 to 39.8×104 m3/s, much larger than any historical records available in the reaches of Yangtze River.关键词：the upper reaches of the Jinsha River;landslide dam;paleo-dammed lake;geological dating;dam-breaching flood
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发布时间：2024-04-07 - 摘要：Tunnel vault collapse is the main type of tunnel accident that has brought huge injuries and deaths, and the causes and prevention of tunnel vault collapse have aroused great concern. To solve the safety problems of tunnel vault collapse, the occurrence mechanism and evolution law are investigated. Using the upper limit variational method, the collapse prediction model of tunnel vault in deep overburden ground is developed, and the prediction curve of tunnel vault collapse range is derived. Considering the progressive collapse characteristics of deep buried tunnel vault in weak and broken surrounding rock, the whole process curve of the progressive collapse range is derived and compared to the model test results. Furthermore, the control principle and bearing mechanism of tunnel collapse with pre-control and process control measures are respectively clarified. The method to determine the surrounding rock load of support measures is proposed. The following results are found. The width of tunnel collapse increases with initial cohesion and uniaxial tensile strength, however, it decreases with weight and the nonlinear coefficient. The height of Tunnel collapse increases with tensile strength and nonlinear coefficient, and it decrease with initial cohesion and weight. Considering the multiple attenuation of cohesion and tensile strength of surrounding rock, the prediction curve of progressive collapse of tunnel vault is in good agreement with the characteristics of model test. The control measures of vault collapse can be divided into pre-control and process control considering control mechanism and objectives. The ratio of deformation load to collapse load increases with initial stiffness coefficient and original rock stress, decreases with collapse height and elastic modulus, and is little affected by tunnel radius and Poisson’s ratio. Both deformation load and total load of surrounding rock increase with the increase of collapse load.关键词：collapse of tunnel vault;upper limit variational method;collapse range;progressive collapse;safety control;surrounding rock load
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发布时间：2024-01-10 - 摘要：Penstock is a common type of lining in water conservancy and hydropower projects, and its stability under external pressure is very important. In order to establish an accurate finite element method for calculating the critical external pressure of stiffened penstock, a reliable numerical model with multiple rings was proposed in the paper, and the results were compared with those calculated by the von Mises theoretical formula and the simplified formula used by design specification for steel penstocks. Considering the complex external environment, the influence of different constraint schemes of stiffening ring under the external pressure of penstock was comprehensively investigated. Based on the proposed numerical solution under particular constraint scheme, the effect of stiffening ring on the critical external pressure of penstock and its effective constraint length were studied. A new fast method for calculating the critical external pressure of stiffened penstock was developed based on the buckling critical external pressure formula of plain penstock. The results show that the eigenvalue buckling analysis in ABAQUS has high accuracy and is in good agreement with the results of the von Mises formula. However, the results of the simplified formula used in the specification differ from the von Mises formula to some extent with the change of the bending wave. For stiffened penstocks with different diameter-thickness ratios, the critical external pressure of the stiffened penstock increases with the increase of the constraints, and it decreases with the increase of the spacing and the ratio of the penstock. When the distance between the stiffening rings is greater than 20 m, no obvious fluctuation occurs. The fast calculation method for the critical external pressure of penstock presented in this paper can be applied to both plain penstock and stiffened penstock, which is accurate, simple and convenient, and can serve as an alternative method for the critical external pressure calculation in practical engineering.关键词：finite element;eigenvalue buckling;critical external pressure;Mises theory
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发布时间：2024-04-07 -
Optimization of Wing-shaped Measuring Flume Based on Bayesian Network Theory and Bionic Technology AI导读
摘要：Based on the working principle of a wing-shaped measuring flume, it will inevitably lead to head loss, and the channel gradient to ensure the free flow of measuring flume will increase with the increase of head loss. This paper proposes to reduce the working head loss of wing-shaped measuring flume by bionic optimization and expand its application scope in plain irrigation channels. In this paper, three kinds of bird wings are selected as bionic prototypes by exploring the drag reduction characteristics of bird wings. While 10 bionic wing curves are selected, 78 bionic wing-shaped measuring flume contour lines are obtained according to 10 angles of attack. Three shrinkage ratios are selected to carry out simulation tests under three flow conditions. The range analysis method is used to evaluate the significance level and superior level of the two factors of bionic wing-shaped measuring flume contour lines. The Bayesian network diagram model reasoning analysis method is used to solve the uncertainty problem of the optimal combination of bionic wing-shaped curves and angles of attack, and the application feasibility is verified by model test. The results show that the wing-shaped curve is the main factor affecting the optimization, and the cross-section curve between the pigeon body and the pigeon wing is the optimal curve, and the optimal angle of attack is –10°; The combination of the angle of attack of –5° and the optimal curve has the best effect. The cross-section curve of the simulated racing pigeon wing treated by the optimal curve according to the angle of attack of –5° is used as the optimal contour line of the bionic wing-shaped measuring flume. The critical submerged outflow states of the new curved measuring flume with simulated racing pigeon wing section under various working conditions are as follows: the measuring accuracy is very high (the average error of measuring flow is about 1.28%); the backwater height is reduced by 7.46% on average; the head loss is reduced by 5.81% on average; the maximum critical submerged degree can reach 0.933; the Froude number of the upstream is less than 0.4 (which can form a steady slow flow); and the minimum working ratio can reach 1:4 960. To sum up, it is feasible to optimize the wing-shaped measuring flume by bionic technology, and the new curved measuring flume with simulated racing pigeon wing section has good comprehensive water measuring performance, which can be used for accurate water measurement in small gradient canals in irrigation areas.关键词：numerical simulation;bionics;Bayesian network;range analysis;wing-shaped flume- 585
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发布时间：2024-01-10 - 摘要：Excessive sediment content during water diversion will lead to a series of engineering problems. In order to solve the problem of water and sediment separation during water diversion of sediment-laden rivers, sediment discharge facilities are often set at the channel head. As a new channel sediment discharge technology, the comprehensive performance and sediment discharge effect of the desilting channel with swirling flow are the key to its popularization and application. In this paper, the experimental study and numerical simulation are used to analyze the hydraulic characteristics and sediment discharge characteristics of the flow in the desilting channel with swirling flow. Firstly, according to the physical model, the experiment was carried out to obtain the corresponding hydraulic parameters and sand interception rate. Secondly, the accuracy of the numerical simulation is verified by the parameters obtained from the experiment. The numerical simulation results of the parameters such as flow velocity and water surface profile are consistent with the experimental values, and the numerical simulation can reflect the movement state of the flow in the desilting channel with swirling flow. Finally, combined with the model test and numerical simulation, the hydraulic characteristics and sediment discharge characteristics of the desilting channel with swirling flow are comprehensively analyzed. The results show that the flow pattern in the swirling flow generator is in the evolution sequence of free flow, critical flow and submerged flow with the increase of channel inflow. Under the submerged flow pattern, the rotating flow can be formed in the sediment discharge tunnel, which is beneficial to the suspension and uplifting of sediment and has little influence on the flow pattern in the diversion channel. With the increase of the water depth in the upstream channel, the diversion ratio of the sediment transport pipe decreases nonlinearly. When the relative water depth is 0.97, the diversion ratio of the sediment discharge tunnel is only 6.07%. When the relative water depth is 0.21, the maximum velocity in the desilting tunnel is increased by 175% compared with the average velocity in the channel, and the sediment interception rate for the sediment of the particle size of 0.075 mm～3.000 mm reaches 93.7%. In summary, the desilting channel with swirling flow is a channel sediment discharge technology with high sediment discharge rate and low water consumption. The results enrich the study of water and sediment separation technology in water diversion projects, and provide a new idea for solving the problem of channel sediment deposition.关键词：desilting channel with swirling flow;flow pattern;split ratio;sediment trapping efficiency
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发布时间：2024-01-10 - 摘要：To study the lateral bearing characteristics of inclined pile foundations under the combined action of vertical and lateral loads, indoor model tests and numerical simulations were carried out in conjunction with the pile foundation selection project of Hengqin Bridge in Zhuhai city. On this basis, the stress and deformation characteristics of inclined pile foundations under combined loads were analyzed under different pile inclinations, different pile top spacing different vertical loads, and different layer thickness ratio conditions. The results showed that increasing the pile inclination angle, the spacing between pile tops, the vertical load on the top of the pile cap, and the layer thickness ratio were beneficial to increase the lateral bearing capacity of the inclined pile foundation. The spacing between pile tops had the greatest influence on the lateral bearing capacity of the pile foundation, followed by the pile inclination angle, the vertical load on the top of the pile cap, and the layer thickness ratio. In the inclined pile foundation, the bending moment at the top of corner pile 2# was the largest, followed by corner pile 1# and middle pile 3#. The bending moment at the top of each foundation pile decreased with the increase of pile inclination and pile top spacing, and first decreased and then increased with the increase of vertical load; The transverse load sharing on the top of each foundation pile tended to be uniform with the increase of pile inclination, pile top spacing and vertical load on the top of the bearing platform. The lateral deformation of foundation soil on the right side of inclined pile foundation increased with the increase of lateral load, and the lateral deformation of foundation soil on the left side of pile foundation was almost unchanged with the increase of lateral load, but the degree of pile-soil separation increased gradually; Increasing the inclination angle of the pile could reduce the degree of pile-soil separation; The displacement isoline of foundation soil near the bottom of pile cap was wavy, and the displacement isoline of foundation soil far from the bottom of pile cap was elliptical. The results can serve for the design and construction of similar engineering.关键词：inclined pile foundation;combined load;lateral bearing;numerical simulation;model test
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发布时间：2024-01-10 - 摘要：Vision-based structural displacement monitoring methods have the disadvantages of strong dependence on target and light conditions. A new method to analyze the bridge vibration by projecting a laser strip on the surface of the bridge and tracking the center of the light band was proposed to overcome the problems. Specifically, the laser line was projected to the bottom or top surface of the beam through the high-power line laser and the continuous images of the laser line were taken by the tilted camera. Through subpixel tracking of the change of the laser stripe center line position in the image, the bridge displacement time histories can be obtained by geometric conversion, and then the dynamic parameters can be obtained. Under indoor experimental conditions, the hammer impact vibration test of a simply supported beam model bridge was carried out. The Sony 4K camera was used as the image acquisition equipment, and the linear variable differential transformer (LVDT) displacement sensors and seven accelerometers were used as the traditional data acquisition equipment. The results demonstrate that the intensity of the laser stripe cross section approximately obeys the Gaussian distribution, and the sub-pixel coordinates of its center can be obtained by the improved gray center method. The time histories of the center can be acquired by tracking the change of its coordinates. Compared with the LVDT data, the relative error extreme value of dynamic displacement measurement results obtained by the Sony camera was 3.17%. The relative error extreme value of the first two frequency identification by the Sony camera was 1.81%. Both the dynamic displacement measurement and the low-order modal parameter identification had achieved ideal results. Different from the fact that the spatial accuracy of modal shapes obtained by accelerometers was limited by the number of sensors, the spatial accuracy of modal shapes obtained by this method could reach pixel level, and there was almost no disturbance caused by the interference of ambient light. The proposed method offered a high-efficiency and cost-effective way for non-contact displacement measurement and modal identification of bridges.关键词：structural health monitoring;non-contact measurement;laser stripe;dynamic response;gray gravity method
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发布时间：2024-01-10 - 摘要：To study the flexural behavior of prestressed concrete (PC) composite girder bridge with truss webs, the model test of PC composite girder bridge with truss webs for the flexural behavior was conducted. To acquire the failure mode of PC composite girder bridge with truss webs, the changed rule of the strain in the bottom and top slab, and the deflection of the girder of PC composite girder bridge with truss webs with the variation of the load were studied. Meanwhile, the distribution rule of bending strain along the height of the section was revealed. The influence of height-span ratio, and unbalance loaded on the flexural behavior of PC composite girder bridge with truss webs was analyzed, and the calculation method for the cracking bent moment, the bent moment in the stage of the rebar yield, and ultimate bent moment of PC composite girder bridge with truss webs were put forward. The research result shows that the failure process of PC composite girder bridge with truss webs includes the elastic stage, cracking elastic stage, elastic-plastic stage, and failure stage. In the elastic stage and cracking elastic stage, the deflection of the bottom and top slab of PC composite girder bridge with truss webs met the plane-section assumption. During the loading process, there is no joint failure and local buckling failure of the truss web in the PC composite girder bridge with truss webs, Finally, the composite beam fails due to excessive deformation, and the overall mechanical performance is good. When the height-to-span ratio is between 1/16.25 and 1/9.00, the deflection and stress in the mid-span section of PC composite girder bridge with truss webs decrease with the increase of height-span ratio. When the ratio of height to span is greater than 1/11.50, the decreasing trend of deformation and stress in the mid-span section becomes slow. Since the PC composite girder bridge with truss webs had a lesser dead load, the unbalance loaded had a significant influence on the deflection and stress of the composite girder, and the magnification factors of the deflection and stress increased with the increase of height-span ratio. When considering the dead load effect of the main beam, the deformation and stress increase coefficients are 1.083～1.231 and 1.074～1.178, respectively. Compared with the results of finite element analysis and test, the calculation methods of the cracking moment, reinforcement yield moment and ultimate moment of PC composite beams with steel truss web presented in this paper have high accuracy.关键词：composite girder bridge;truss webs;bending performance;model test;finite element analysis
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发布时间：2024-01-10 - 摘要：In recent years, with the large-scale construction of urban rail transit in China, the number of new subway tunnel construction projects that use the artificial ground freezing method to underpass ground buildings has increased year by year. The freezing process of artificially frozen soil can easily cause uneven deformation of the upper-structure surface and adjacent buildings. To ensure the safety of overlying structure in the frozen double-track tunnel, it is necessary to get the frost heave law caused by different conditions in advance to select the optimal construction scheme. Taking the double-track tunnel of Shanghai metro line No. 18 passing down the running station of the No. 10 line as the research object, a similar simulation experiment was carried out. The law of frost heave uplift of the overlying station floor in two modes segmental freezing and the simultaneous freezing mode was studied. The deformation law of the upper station base slab during the construction process was obtained. The results showed that the upper structure’s maximum lift value generated by the segmental freezing occurred during the freezing period of the downline tunnel, and the lift value was 20.5 mm, which was less than the value of the simultaneous freezing mode. The base slab of the station was lifted as a whole mode of the segmental freezing mode, and the lifting speed of the second frozen tunnel during active freezing was 0.12 mm/d, which was greater than that of the upline tunnel when it was frozen by 0.08 mm/d. When the tunnel was in the construction of segmental freezing and segmental excavating, frost heave uplift and excavation settlement occurred alternately, and the displacement curve of the station floor was zigzag. In the actual project, methods such as coring were used to reduce frost heave, and it was concluded that the maximum lift value of the base slab was 25.41 mm. The base slab lift law obtained from the similar simulation experiment was in good agreement with the construction project data, which guided the construction of the project effectively.关键词：artificial freezing method;passing down the station;soft soil stratum;frost heave;base slab lift;excavation
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发布时间：2024-01-10 - 摘要：The cable-net supported glass roof is commonly located between adjacent structures, however, the relative displacement vibration of the main structure will be considered as the support excitation leading to over-tensioning or relaxation of the small-sagged cables. In order to investigate dynamic responses of small-sagged cables under support harmonic and stochastic excitations. Dynamic responses of three sets of specimens under the support harmonic excitation are tested with the dimensionless deformation parameter
$ \alpha {b^2} $ $ \alpha {b^2} $ $ \alpha {b^2} $ $ \alpha {b^2} $ $ \alpha {b^2} $ 关键词：small-sagged cables;support;harmonic excitations;stochastic excitations;dynamic responses;numerical simulation- 474
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发布时间：2024-01-10 - 摘要：Precast segmental prestressed bridge columns have been widely applied in the region of medium and low seismicity in the United States, however, there are few applications in China. Due to the lack of seismic damage data and insufficient knowledge of their seismic performance, their application in high seismicity is limited. According to the existing quasi-static test of precast segmental prestressed bridge columns, the numerical model of the precast column under bending load was developed by software ABAQUS and the nonlinear behavior was verified by experimental results. Based on the verified numerical model, influences of three parameters, namely reinforcement ratio of energy dissipation (ED) bars, area of prestressed tendons and initial prestressing level on seismic performance of precast segmental columns were investigated. The results show that the results of the model are in good agreement with the experimental results. With the increase in the reinforcement ratio of ED bars, the energy dissipation capacity bearing capacity, and residual displacement increase severely. As the area of the prestressed tendon increases, the bearing capacity and post-yield stiffness increase significantly, whereas the energy dissipation capacity decreases. With the increase of the initial prestressing level, the bearing capacity of the column increases, but the damage at the bottom of the precast columns is more severe. Therefore, when the target displacement drift is less than 4%, the initial prestressing level should be less than 50% of the ultimate tensile strength of prestressed tendons to avoid serious concrete damage, and the reinforcement ratio of ED bars should be less than 1% to achieve quick repair of columns after an earthquake. The research results could provide technical support for the seismic design of precast segmental prestressed bridge columns and their application in strong earthquake areas.关键词：precast segmental prestressed bridge column;seismic performance;reinforcement ratio of energy dissipation bars;area of prestressed tendons;initial prestressing level of prestressed tendons
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发布时间：2024-01-10 - 摘要：Every earthquake will pose a great threat to the collections housed in museums. To avoid the immeasurable damage caused by earthquakes, a sliding seismic isolation bearing for museum collections was developed to meet the urgent need for seismic safety for the objects housed in the museum. The isolation performance test of the sliding isolation bearing excited by multiple seismic motions was carried out on a shaking table to verify its seismic isolation effect. Then the finite element model of the sliding isolation bearing-showcase system was established and compared with the test results to verify the validity of the finite element model. Furthermore, the influence of the friction coefficient of the sliding rail of the bearing and the quality of the showcase on its seismic performance was investigated. Finally, a design method of the sliding isolation bearing for museum collections was proposed, and the effectiveness of the proposed design method was verified by taking a practical showcase as an example. The results showed that the sliding isolation bearing had good isolation performance, and its isolation rate increased with the increase of the peak acceleration of the input motions. Under the input motion action with the same peak acceleration, the isolation rate increased with the increase of the dominant frequency of the input motion. Changing the friction coefficient of the sliding rail or the quality of the showcase did not affect the optimal period design of the sliding isolation bearing, but the lower friction coefficient was more conducive to the realization of the isolation performance of the system. The mass change of the showcase had little influence on the acceleration response of the bearing surface and the displacement response of the sliding isolation bearing. The sliding isolation bearings could effectively reduce the seismic response of museum collections and protect the safety of the artifacts exhibited in the museum. The design method proposed in this study can provide guidance for the actual requirements of seismic protection of museum collections.关键词：sliding isolation bearing;horizontal isolation;museum showcase;shaking table test;finite element analysis
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发布时间：2024-01-10 - 摘要：In the cold regions of western China, initial damages, such as fissures, are ubiquitous in the rock mass, while the combined effects of load and freeze-thaw will greatly weaken the strength of rock mass and cause engineering disasters. To quantify and evaluate the influences of cyclic load and freeze-thaw cycles on the pore parameters and mechanical properties of different damaged rock masses in cold regions, nuclear magnetic resonance technology was used to test the microscopic pore parameters (such as the porosity and T2 spectrum distribution) of red sandstone at the initial damage stage, cyclic load stage and freeze-thaw cycle stage. Subsequently, the damaged samples were subjected to uniaxial loading with acoustic emission monitoring. The test results show that the pore structure and mechanical properties of red sandstones with different initial damage demonstrate consistent behaviors under the sequential action of cyclic load and freeze-thaw cycles. The porosity increases for the samples subjected to cyclic mechanical loading, due to the expansion of original pores. The porosity continues to increase for red sandstone subjected to freeze-thaw cycles, resulting from the newly generated small pores and expansion of original pores. In general, both cyclic load and freeze-thaw cycles can deteriorate the strength and elastic modulus of the samples. The strength reduction of the red sandstone was 5%～10% when subjected to freeze-thaw cycles, and was 20%～30%, under the combined load and freeze-thaw cycles. The lower the initial strength of red sandstone with different fracture damage, the greater the damage of the sample relative to the initial strength after being subjected to load and freeze-thaw. The sandstone samples were found to experience greater damage with the lower initial strength when subjected to load and freeze-thaw. In addition, the porosity increment of the samples subjected to the combined load and freeze-thaw cycles is found positively correlated with the decrease in the sample strength. The above research results can provide an important basis to achieve stable design and safe construction of engineering in cold regions of China.关键词：freeze-thaw cycles;cyclic load;single-fractured sample;porosity;peak strength
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发布时间：2024-01-10 - 摘要：In view of the flexural-shear failure of the plastic hinge zone of hydraulic reinforced concrete (RC) columns during earthquake, the shear capacity of the plastic hinge zone of hydraulic RC columns was studied. And, the quasi-static test data of 19 rectangular sections and 19 circular sections of RC columns failed in flexural-shear were collected from PEER-Structural Performance Database in the United States. Through statistical analysis, the reliability of the shear capacity formula in China's water conservancy industry “Design code for hydraulic concrete structures” (SL 191—2008) and the power industry “Design specification for hydraulic concrete structures” (DL/T 5057—2009) was evaluated. Then, because the shear capacity of the plastic hinge zone of RC columns decreases with the increase of deformation capacity after longitudinal reinforcement yielding, the correction coefficient with the ultimate drift ratio of column top as the parameter was introduced to modify the formula of shear capacity, and the reliability of the modified formula was verified. The results show that the hydraulic RC columns satisfied with shear capacity of current hydraulic concrete structures design code in china may suffer flexural-shear failure in plastic hinge zone which should pay more attention in the design. For RC columns failing in flexural-shear, the assurance rates of the shear capacity formulas for RC columns in “SL 191—2008 code” and “DL/T 5057—2009 code” are all less than 60%; compared with “SL 191—2008 code”, the deviation of the shear capacity formula for RC columns in “DL/T 5057—2009 code” is small, but its dispersion of the deviation is large; compared with rectangular section, the shear capacity formulas of RC column in the two hydraulic codes have less deviation for circular section RC column. Considering the effect that the shear capacity decreases with the increase of column top drift ratio, the modified formulas of the shear capacity have 85% assurance rate for the RC columns failing in flexural-shear, which provide reference for the shear capacity calculation of plastic hinge zone of hydraulic RC columns.关键词：hydraulic RC column;flexural-shear failure;shear capacity;ultimate drift ratio;design specification
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发布时间：2024-01-10 - 摘要：To study the seismic behavior of concrete frame structures reinforced with different high strength steel bars, spatial concrete frames (Group 1) reinforced with three types of rebars but keeping the same moment-strength at every critical section were designed in three seismic intensity zones according to current design codes. Inelastic seismic response analyses of the frames were performed under bi-directional horizontal ground motion inputs with OpenSEES software. Meanwhile, based on the frames reinforced with HRB400 rebars, the longitudinal bars in columns of frames in Zone 8 and Zone 9 (Group 2) were replaced by HRB500 and HRB600 rebars with the same area-ratio, and corresponding seismic response analyses were conducted to investigate the control effects on the structural yielding mechanism. The result of Group 1 showed that in the same seismic fortification zone, with the growth of the rebar strength, the whole displacements and local displacements of the frames increased slightly, but hinge ratios and rotation ductility demands decreased, which indicated better seismic performance in frames. The frames in Zone 8 and Zone 9 reinforced with HRB400 and HRB500 rebars demonstrated a column-hinge-dominated energy dissipation mechanism or one with more column hinges than beam hinges under rare-earthquake inputs, which implying an unfavorable seismic response. The counterpart frames reinforced with HRB600 rebar exhibited a notable improvement in seismic performance with significantly reduced column hinges, but maximum rotation and ductility demands of columns were larger than those of beams, which indicating failure in making full use of good energy dissipation of beams. The result of Group 2 showed that when the longitudinal bars of HRB400 in columns were replaced by higher-strength rebars with the same area ratio, the moment capacities of columns were enhanced substantially. Column hinges significantly reduced meanwhile beam hinges significantly increased, and the frames formed a beam-hinge-dominated energy dissipation mechanism, which indicating a noticeable improvement in the overall seismic performance of the structures.关键词：high-strength steel bars;reinforced concrete frame structures;bi-directional ground motion inputs;inelastic seismic response analyses;seismic performance.
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发布时间：2024-01-10 - 摘要：Floating structure is a new type of ecological structure suitable for the coastal and inland water conservancy projects. The application of floating structure in plain water conservancy and flood control projects will lead to the diversion of water flow and cause head loss, which will affect the flow capacity. Therefore, it is of practical significance to study and obtain the changing law of the resistance coefficient of the floating structure and the influence mechanisms. The physical model test and dimensional analysis were used to obtain the influencing factors affecting the resistance coefficient of the floating structure, i.e., the coefficient of water level change, the ratio of the length of the floating structure to the position of the floating structure, the relative water blocking area and the Reynolds number. The sensitivity analysis on influencing factors and resistance coefficient was conducted, and the results show that: 1) The increase in the coefficient of water level change results in a recirculation zone at the back surface of the structure, and both the turbulence intensity of the water flow particles and the resistance coefficient increase; 2) The change of the floating structures’ length and position will not cause the loss of water flow energy and has little effect on the resistance coefficient; 3) The increase in the relative water blocking area coefficient leads to the decrease of the water passing area, and the friction and collision of water particles consume water flow energy, causing the resistance coefficient to increase. 4) Within the range of the tested Reynolds number (3.5<lg Re<5.0), when the Reynolds number increases, the turbulent and irregular flow field was formed, and the influence of inertial force on the flow field is greater than that of the viscous force, with the resistance coefficient being decreased. 5) The sensitivity of each factor to the resistance coefficient is arranged in the descending order as follows: the coefficient of water level change>the relative water blocking area>Reynolds number>the ratio of length to position. Through the multivariate linear fitting based on the least square method, the calculation formula describing the resistance coefficient of the floating structure was obtained, and the formula was tested and analyzed by mathematical statistics. The formula can meet the engineering needs in terms of reliability and accuracy, and the form is simple and versatile, which can provide a theoretical basis for related projects.关键词：floating structure;resistance coefficient;Reynolds number;sensitivity;mathematical statistics
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发布时间：2024-01-10 - 摘要：To study the influence of various fibers on the fracture behavior of fly ash based geopolymer concrete (GPC), the three-point bending test of the notched concrete beam was carried out. The effects of the volume fraction of basalt fiber (BF), polyethylene-based polypropylene fiber (SPPF), and end steel fiber (SF) on the fracture properties of GPC were investigated, respectively. The results showed that: 1) The compressive strength and splitting tensile strength of BFGPC, SPPFGPC, and SFGPC were significantly improved compared with GPC. The maximum compressive strength was obtained at the volume rate of 0.2%BF, 0.8%SPPF, and 1.0%SF, respectively. The optimal volume rate corresponding to the splitting tensile strength was 0.2%BF, 0.4%SPPF, and 1.0%SF, respectively. 2) The fracture parameters of BFGPC first increased and then decreased with the increase of BF volume ratio, and the optimum dosage was 0.2%. Nonetheless, BFGPC exhibited brittle fracture characterized by BF tensile fracture. 3) In the low dosage range, the fracture parameters of SPPFGPC increased with the increase of fiber volume rate; In the high dosage range, the fracture parameters of SPPFGPC first increased and then decreased, and the optimal dosage was 1.5%; SPPFGPC failed with debonding and pull-out of SPPF. 4) As the volume ratio of SF increases, the fracture mechanical parameters and fracture energy of SFGPC gradually increased. SFGPC had significant ductile failure characteristics, and the recommended volume ratio of SFGPC was 0.5%～1.5%. 5) In the GPC system, SF enhancement and toughening effect are the best, BF enhancement is better than that of SPPF, but SPPF toughening is better than that of BF.关键词：fiber;geopolymer concrete;mechanical property;fracture toughness
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发布时间：2024-01-10
HYDRAULIC & CIVIL ENGINEERING
- 摘要：Aiming at the problem of feature redundancy in industrial control system traffic data and the poor detection ability of deep learning models for small-scale data sets, an industrial control system intrusion detection model based on feature selection and temporal convolutional networks was proposed. First, the abnormal features and sample imbalance data of the source domain dataset were processed to improve the quality of the source domain dataset. Secondly, in view of the feature redundancy of traffic data, a IGR–PCA feature selection algorithm was constructed by using the information gain rate and principal component analysis method, and the optimal feature subset was selected to achieve data dimensionality reduction. Then, according to the time series characteristics of industrial control system traffic data, the excellent processing ability of temporal convolution network (TCN) for time series data was used to construct a source domain temporal convolution network pretrained model on a large-scale source domain data set. Finally, combined with the transfer learning (TL) fine-tuning strategy, the traffic characteristics of the source domain sample data were obtained on a small-scale target domain dataset, and the target domain TCN–TL model was constructed. The experimental test was carried out using the public industrial control system data set. The experimental results showed that compared with other methods, the proposed method can reduce the data dimension and reduce the calculation amount while still having a superior detection effect. The model proposed in this paper has achieved good detection results on both large-scale source domain data sets and small-scale target domain data sets. In the target domain, the transfer learning fine-tuning strategy can be used to learn the knowledge in the source domain, and the detection accuracy rate is 99.06%. In the training time comparison, the proposed model consumes less training time. Meanwhile, it also has better generalization ability and can better protect the security of industrial control systems.关键词：industrial control system;intrusion detection;feature selection;temporal convolutional network;transfer learning
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发布时间：2024-01-10
INFORMATION ENGINEERING
- 摘要：In this paper, a differential flat control method based on the exact linearization of state feedback was proposed to improve the poor transient performance of the conventional PI controlled Buck converter. Firstly, based on the state space averaging method, an affine nonlinear model of the Buck converter with inductive current continuous conduction mode was established. Based on this model, the state feedback control rate was derived by using the state feedback exact linearization method, and the controllable linearization of the system was realized. Secondly, a feedforward controller was designed for the exact linearized model of the state feedback; and then, a disturbance observer was embedded in the feedforward controller to compensate the output current. Meanwhile, an error feedback compensator was designed to eliminate the deviation between the actual output and the desired output of the system caused by the unmodeled part and external disturbance of the actual system. Combining the feedforward controller and the feedback compensator, a differential flat control method based on the exact linearization of state feedback was proposed. The rapidly and accuracy of the Buck converter system can be respectively guaranteed by the differential term in the feedforward controller and the error term in the feedback compensator. Besides, based on the Jacobian matrix of the closed-loop system, the eigenvalue sensitivity theory was used to study the influence of converter circuit parameter changes on system eigenvalue. The study results show that reducing the inductance and increasing the capacitance is beneficial to improve the stability of the system. Finally, the experimental prototype of the Buck converter was built. The experimental results show that, compared with the traditional PI control method, the proposed differential flat control method based on accurate linearization of state feedback can better suppress the disturbances of input voltage and output current, has less regulation time and overshoot voltage, and shows better transient performance. Consequently, the proposed control strategy has certain engineering application value.关键词：Buck converter;state feedback exact linearization;disturbance observer;differential flat control;sensitivity
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发布时间：2024-01-10
ELECTRICAL ENGINEERING
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