最新刊期
卷 51 ， 期 3 ， 2019
- 摘要：River and lake shorelines and inland river bottomland are not only the important transition zone between terrestrial and aquatic systems in nature, but also the key area to maintain the ecological health of river and lake systems, as well as the important basis for the economic and social development along the coast. In the dynamic evolution, the contradiction between the protection and utilization of river and lake shorelines and bottomland is apparent, such as the use and disorder of shoreline, the use of deep water instead of shallow water, the encroachment of river channel and normal flood discharge, the natural evolution and river potential control, the connection between rigid bank protection and material, and in particular the cumulative effects of unreasonable development influence flood control, water supply, shipping and ecological environment seriously, and even harder to repair. With the coordinated promotion of ecological priority and green development concept, it is an urgent need and development trend to study the key technology of efficient utilization and protection of river and lake shorelines and inland river bottomland resources. The national key research and development project " research on key technology for efficient utilization and protection of river and lake shorelines and inland river bottomland” is to put forward the theoretical methods for the classification and functional impact assessment of river and lake shorelines in China, to coordinate the protection and utilization mode of river and lake shoreline in the dual demands of ecological environment protection and economic development, develop river water and shoreline dynamic monitoring and function assessment techniques, build a dynamic monitoring pattern and service platform on the river lake, and provide scientific and technological support for the construction of ecological shoreline and safe shoreline. The project will take a multi-disciplinary, multi-means, multi-method integrated technical route, from the basic theory, key technology and demonstration and application of three levels to carry out research. Through the project study, it is expected to propose three new methods of classification, determination and function evaluation theory of river and lake protection shorelines in China, develop and establish 4 sets of new technical systems, such as monitoring technology and functional assessment system for river and lake waters and shorelines, protection and utilization technology and evaluation index system for shorelines and shoals of rivers and lakes that coordinate ecological environmental protection and economic development, construct a river and lake shoreline dynamic supervision service platform meeting the management requirements of level 4 " river and lake length system”, and carry out demonstrations in five representative river and lake reservoirs, including urban river Banks, rural beaches, delta river networks, plateau urban lakes and important water sources. Results will also promote dynamics of rivers and lakes, riverbed evolution, water ecology, water conservancy planning such as academic progress, the depth of the water conservancy and internet integration for the coastline of lakes and river bottomland and direct-cleaning coastline of efficient utilization of resources, provide strong technical support for the scientific protection management, and has significant social and economic and ecological environment benefit.关键词：river and lake shoreline;efficient use;protection
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发布时间：2024-01-05 - 摘要：Cellulose, as the most abundant renewable resource on earth, is an ideal raw material for producing various functional materials, because of its biodegradability, biocompatibility, non-toxicity, low-cost, environmental friendliness and safety risks. Based on the utilization of cellulose resources, the review introduced the recent advances in cellulose-based functional materials, focusing on the function and application of four major morphological cellulose materials: including research progress in the field of adsorption separation and protein immobilization based on unique spherical spatial configuration and network structure of cellulose microspheres. Research progress in the fields of medical, intelligent, electrode and separation materials based on the superior biocompatibility of cellulose hydrogel and the three-dimensional porous structure of cellulose aerogel. Research progress in the field of high performance plastics, optoelectronics and smart materials based on high transparency and toughness of cellulose film. Research progress in the field of textiles and electronic materials based on the high toughness, woven, and low density of cellulose fibers. Finally, the perspectives for the future development of cellulose-based materials were put forward, and the key scientific problems that need to be solved in the application-oriented research process of the above four morphological cellulose-based functional materials were discussed. We hope that this work could provide valuable reference and guidance for future design and application on functional cellulose-based materials.关键词：resource development;cellulose beads;cellulose hydrogel;separation;diagnosis
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发布时间：2024-01-05 - 摘要：The stability of a rigid barrier is determined by the spatio-temporal distribution of the impact of debris flow when the debris flow runs up. However, current approaches used to estimate the debris flow impact have not considered the impact load produced by running up flow. In order to explore the spatio-temporal distribution of debris flow impact, a series of debris flow impact experiments are carried out and a contact surface pressure gauge sensor (called Tactilus®, is produced by Sensor Products LLC) was used to record the evolution of the impact force at the barrier. The experiments result showed that the history of maximum impact force in the space of low density debris flow fluctuated more drastically with a relative long time. In addition, the longitudinal attenuation of the impact force was the logarithmic function for the low density debris flow, while the high density debris flow with linear attenuation. These attenuation modes with different density were fundamentally governed by the grain-fluid interaction. On the other hand, the horizontal distribution of debris flow impact force can be regarded as the equivalent distribution. In order to simplify the engineering design, the longitudinal distribution of debris flow impact can be generalized to triangular distribution, from which a new impact model considering the effect of running up was proposed.关键词：debris flow;impact force;spatio-temporal distribution;rigid barrier
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发布时间：2024-01-05 -
Experimental Study of Shear Creep Characteristic of Moraine Soil in Dadu River Bridge in Luding AI导读
摘要：The sediment of the Kangding Bank of Luding Dadu River Bridge of Sichuan–Tibet Expressway mostly consists of very thick moraine soli. In order to study the shear creep characteristic of moraine soil and the long-term deformation of bridge gravity anchor, the in-situ shear creep test was carried out using automatic data acquisition system. Based on the test result, the shear creep characteristic, creep model and long-term deformation of gravity anchor of moraine soil were analyzed. The results showed that the duration of transient creep was less than 0.1 h. In addition, the transient creep was characterized by delayed deformation after loading, and the creep rate fluctuant decrease in the decelerating creep stage. In addition, the creep rate was characterized by stepped growth and multi-stage change in steady creep stage, and jump phenomenon could be found in the shear deformation-time curve, which indicated the deformation adjustment effect of soil skeleton particle. The experiment of shear creep test of moraine soil showed a small creep deformation and convergence creep characterized by creep rate gradual decreasing when the shear stress was less than the long-term strength. The creep deformation rapidly increased when the shear stress was close to or larger than the long-term strength. For the convergence creep characteristic of moraine soil, the non-linear modified Burgers model was used to describe the shear creep characteristic of moraine soil. According to the fitting model of the test result corresponding to the stress level of gravity anchor of Luding Dadu River Bridge, the long-term deformation of gravity anchor of Luding Dadu River Bridge is predicted to be millimeter magnitude, which is preliminarily validated by time series InSAR and deep displacement monitoring. The proposed method of analyzing long-term deformation and stability of structures based on shear creep test result, can be considered as a reference for design.关键词：moraine soil;shear creep;long-term shear strength;creep model;long term deformation prediction- 2515
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发布时间：2024-01-05 - 摘要：Similar simulation test is an effective way to study the height of mining overburden caving zone and fracture zone, and accurate monitoring of strata displacement is the key to study the height of the zones. In order to achieve accurate, continuous and real-time monitoring of displacement of cover rock, the test requirements and implementation principles of the internal displacement of the model were put out. A continuous displacement monitoring device consisting of micro multi-point displacement meter, grating ruler, data acquisition instrument and visualization software was developed. With the help of the device and simulation experiment, characteristics of cover rock of a mine was researched. The results showed that: 1) The continuous displacement monitoring device could continuously monitor the displacement of measuring points inside the model, and the test results were consistent with the results of the surface displacement of the model. 2) When the test model surface was not exposed, this method could effectively monitor the displacement in the test model. 3) The height of the caving zone was 8.0 m, which was about 6.3 times of the mining height. The height of the crack growth was 30.0 m in the mine,which was about 24 times of the mining height. 4) The vertical displacement of the caving zone has a " ladder like” rule, while the vertical displacement of the fracture zone was relatively gentle and the vertical displacement of the fracture zone changed relatively gently, and then the boundary between the fallen zone and the fracture zone can be judged accordingly.关键词：coal and gas co-production;crack;caving zone;simulation test;displacement acquisition
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发布时间：2024-01-05 - 摘要：As a typical concrete double-curvature arch dam, Yebatan arch dam has a height of 217 m. The faults and crushing fracture zones are densely intertwined at the dam site area, and deep unloading rock masses are distributed throughout the elevation range on both abutments. Especially at the elevation of 2 750 m, there are strong relaxation unloading rock masses on the left and right abutments. Because of its low strength and strong compressibility, it has an important effect on the stability and safety of the structure. In view of the above questions, the geo-mechanical model test is used to investigate the stability and deformation characteristics of the abutments with deep unloading rock masses in Yebatan arch dam. Firstly, a 2 750 m elevation plane model of Yebatan arch dam was established. Through the overloading test method, the displacement and strain of dam body, the distribution characteristic of displacement of abutment and resistance body, and the failure process and failure modes are obtained. According to the data analysis, the breakaway overload safety factor K1 is 1.6~1.8, the nonlinear deformation overload safety factor K2 is 2.4~2.6, and the ultimate overload safety factor K3 is 3.8~4.2. According to the results of the model test, the deformation characteristics of deep unloading rock masses and the influence on the working behavior of arch dams are obtained. It also indicates that at the 2 750 m elevation of Yebatan arch dam, the relaxation unloading rock masses with type Ⅳ s on the left bank is closer to the arch end, and has larger displacement than the right bank, which has more significant attenuation effect on transmission of the displacement and the load, which has a significant impact on the stability and safety of the structure.关键词：deep unloading rock mass;abutment stability;geo-mechanical model test;Yebatan arch dam
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发布时间：2024-01-05 - 摘要：Based on MATLAB image processing and computer vision module, this study developed a non-intrusive method to measure full-field water depth. First, the Camera Calibration toolbox was used to calibrate the camera to obtain the calibration code; Second, the experimental video which recorded water flow movement was saved frame by frame and the barrel distortion of each image caused by wide angle lens was eliminated by calibration code. Then the images were grayed and binarized, and the median filter was added to eliminate image noise; Finally, the number of black pixels in binary images was counted and converted to actual water depth to obtain its spatial and temporal distribution characteristics. This method was applied to experiment of intensively unsteady flow–dam-break flows, in which the upstream water depth was 500 mm and the depth ratio (ratio of initial downstream to upstream water depth) was from 0 to 0.9. The observation showed that dam-break flows could be roughly divided into three modes: simple wave (depth ratio was 0), discontinuity wave (depth ratio was from 0 to 0.4) and undulation wave (depth ratio was from 0.4 to 1.0). Three typical conditions (depth ratio was 0, 0.3, 0.6) were chosen to compare with the results of wave probe. The results showed that wave probe had larger values of water level when compared with image processing data in the gradually varying flow area with smooth water surface, the shock wave area with discontinuous water flowing between downstream and front of wave, and the rolling wave area with obvious fluctuations on water surface, except for the upstream and downstream areas where both results agreed well with each other. The more intensive the water flow was, the larger the differences were. There was no need to install intrusive measuring instruments in water channel by using this method, it could not only obtain full-field water depth and water evolution process completely, but also capture water details such as leap, tumbling, fluctuations and air entrainment. In addition, the stable lighting and dyeing concentration in the experiment could help reduce the image noise and improve the image quality, thus further improve the accuracy of measurement results.关键词：water depth measurement;non-intrusive;full-field;image process;dam-break flows
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发布时间：2024-01-05 - 摘要：The confluence of flow in open channel often forms complex flow structure, thereby affecting the water and sediment movement and river bed deformation at the confluence zone. The flow movement at the confluence zone of the Baisha River and the Minjiang River was analyzed based on the two-dimensional mathematical model which was verified by the measured data. The results show that: the variation of incoming water of mainstream and tributary will cause different backwater zone, mixing zone, extrusion zone and separation zone. With the increasing of discharge ratio R(the ratio of tributary to mainstream), within the backwater zone, the top support action of tributary becomes stronger, and the water level is high; within the mixing zone, the flow velocity decreases because of the enhanced interaction between tributary and mainstream; within the extrusion zone, the position of the highest velocity is closer to right bank and the high speed belt is narrower with the enhancing of the extrusion. Under the compression effect fromthe mainstream, the flow direction of tributary which flows into mainstream with right-angle will change observably. However, the curved bank of the Baisha River can make the tributary flow along the riverbank and adjust the flow direction simultaneously, which will restrain the formation of the separation zone effectively. In the two comparisoncases that the tributary stays the same while the mainstream flow changes, the greater the difference between the mainstream and the tributary, the stronger the mainstream's backwater effect is to the tributary, the longer the distance from the supporting point to the confluence zone, and the larger the backwater zone is. This study can provide theoretical basis for flood control and river regulation of the Dujiangyan reach by revealing the flow characteristics of mainstream and tributary when they impact, extrude and mix with each otherat the confluence zone.关键词：river confluence zone;Dujiangyan reach;numerical simulation;ratio of discharge
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发布时间：2024-01-05 - 摘要：In recent years, flashfloods have occurred frequently in the gully regions of small-scale watersheds. They have caused a great deal of damages to the local economy and properties. In order to prevent and control mountainous flashflood disasters, accurately forecasting and early warning of this kind of flashfloods is particularly important. However, it is very difficult to simulate the flashflood evolution in the gully regions because of the lack of controlling cross section information and observed flashflood data in the regions. To overcome these problems, firstly, the generalized orientation of a river or gully was obtained based on the DEM data of the study region. In order to determine the channel width and depth, an applicable selection criterion of two channel width formulas are proposed according to the theory of river network classification and the concept of stable river width. Secondly, a coupled model of one and two dimensional (1–2D) flashflood routing was developed based on the theory of diffusive wave to improve the simulation efficiency and to solve the easily overlanding problem due to irregular and small size of the gully. In order to verify the accuracy and efficiency of the coupled 1–2D model, a case study was conducted at the Manshui river-basin in Fangshan District of Beijing city, and the simulated results of the coupled 1–2D model were compared with those of the 2D shallow water model and the observed data. The results indicate that the coupled 1–2D model has a reasonably high accuracy which is almost the same as that of 2D shallow water model in the aspects of flashflood discharge, water level, total volume and peak arrival time. In addition, the simulating efficiency of the coupled 1–2D model is higher than that of 2D shallow water model, which implies the coupled 1–2D model is much more suitable for the numerical prediction and early warning of flashfloods than the 2D shallow water model in small scale watersheds.关键词：mountainous areas;1,2D coupled;flood routing;gully
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发布时间：2024-01-05 - 摘要：Pile-sheet retaining wall is widely used in the cutting slope, embankment engineering and landslide treatment. The slab located at the behind of stabilizing piles, for example, is one of the most popular structural form in the engineering design, leading to some conservatism in the design. In order to investigate the transfer behavior of earth pressure and the regularities of distribution considering different setting location of retaining wall slab in the Pile-sheet retaining wall, three typical laboratory model tests (slab located in front of piles, slab located behind of piles and without slab) were conducted. The overall deformation and the fracture surface of the filling soil were observed, and the earth pressure on the stabilizing pile and retaining slab were also monitored. The experimental results showed that under the action of horizontal thrust, the retaining wall slab backfill of the three typical working conditions all generated an overall crack across the loading surface. The distribution of earth pressure on piles and retaining slab were " spoon-shaped” and " trapezoidal shaped” respectively. Compared to the case of slab located behind of piles, the earth pressure undertook by the stabilizing piles was much larger for the case of slab located front of piles, and the earth pressure undertook by the retaining slab was smaller instead. Soil arching effects of the filling soil was weakened because of the existence of retaining slab, especially for the case of retaining slab located behind of the piles. However, soil arcing still had the formation conditions and development space for the case of retaining slab located in front of the piles. In comparison, the slab located in front of piles could effectively reduce the earth pressure acting on the retaining slab because of the development of soil arching effect, and reduce the earth pressure acting on the retaining slab. Therefore, it was recommended to use the structure of slab located front of piles or the flange of pile. The research results can provide reference for the reasonable design of pile-sheet retaining wall.关键词：pile-sheet retaining wall;model test;Earth pressure;setting location;soil arching
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发布时间：2024-01-05 - 摘要：Using the THMC rock test system and industrial CT, the gas permeability test of the whole process of loading of salt rock with different impurity content and the pre-load and post-failure mesoscopic scanning were carried out. The influence of confining pressure and impurity content on the permeability characteristics of contaminated rock salt during loading was discussed. The results showed that the permeability of contaminated salt rock at 5 MPa confining pressure showed an overall increasing-pacing variation. However, the high-impurity looming phase obviously lags behind the low-content salt rock. The permeability at 10 MPa confining pressure had a declining transition point and the overall performance was increasing—decreasing—rising to flattening characteristics. The confining pressure had a significant effect on the permeability during the loading destruction process. The permeability of contaminated salt rock under a confining pressure of 10 MPa was about 2～3 orders of magnitude lower than that under 5 MPa confining pressure. When the impurity content was less than 45%, the higher the impurity content, the lower the permeability during the destruction process. When the impurity content exceeded 45%, the permeability during the destruction process was high, and the amount was equivalent to pure salt rock. The porosity of the impurity salt rock before loading was about 1%, and increased about 10 times after the infiltration damage. The porosity of the high-impured salt rock and the pure salt rock was close to that after the loading and destruction, however the porosity of low salt rock was relatively low. The microscopic characteristics of crack distribution under different confining pressure and impurity content under different influences were obtained. The low-concentration impurity content of low-salt rock was characterized by a single shear surface failure, and pure salt rock and high impurity salt rock showed the destruction characteristics of the conjugate double shear surface, resulting in high permeability of the destruction process. The high confining pressure was characterized by large horizontal deformation, and the failure characteristics were dense micro-crack with the direction of the crack in the same direction as
$\sigma_1$ 关键词：impurity content;salt rock;permeability;volumetric strain;CT scan;porosity- 2269
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发布时间：2024-01-05 - 摘要：With the frequent occurrence of earthquake disasters in recent years, underground structures in strong earthquake areas have been repeatedly damaged. Long and large tunnel is an important fundamental project for the implementation of China’s western development strategy, and its seismic safety problem is particularly prominent. By introducing incremental dynamic analysis (IDA) and combining with seismic fragility analysis method, a seismic performance assessment method for tunnel structure based on damage coefficient index was proposed. In this method, the damage coefficient of the characteristic part of lining structure after earthquake was taken as the demand measure, and the peak ground acceleration of the earthquake was taken as the intensity measure. Then, the 5–level seismic damage classification standard and 4–level seismic performance level suitable for the seismic safety evaluation of tunnel structure were suggested. Taking a tunnel project as an example, the seismic fragility curves of the characteristic parts of lining structure under different seismic performance levels were obtained through a great deal of nonlinear dynamic time-history calculation. Furthermore, the failure probabilities of lining structure under different seismic fortification standards were analyzed. The results showed that the lining structure was nearly undamaged under 8–intensity frequent seismic load. The probabilities of haunch in nearly intact state and slight damage state were 87.6% and 10.72% under 8–intensity fortified seismic load, respectively. The probabilities of haunch in slight damage state and medium damage state were 68.7% and 20.8% under 8–intensity rare seismic load, respectively. The seismic performance of the haunch, spandrel, arch foot, top arch and bottom arch of lining structure increased in turn under horizontal and vertical seismic motion input. The haunch, spandrel and arch foot were the weak parts of seismic design of lining structure. The method can well consider the randomness of seismic motion, and provide an effective way for the seismic safety evaluation of tunnel structure. The research results can also provide references for seismic design of tunnel structure.关键词：tunnel structure;seismic performance assessment;incremental dynamic analysis;seismic fragility;failure probability
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发布时间：2024-01-05 - 摘要：RC beam strengthened with aluminum alloy plate is a good solution for the purpose of increasing bearing capacity of concrete beam. At the same time, the ductility and energy-dissipating capacity will also be better, especially satisfying the reinforcement engineering at erosion and cold environments. As the stress of aluminum alloy plate is transmitted to the RC beam through the bonding layer, the strengthening effect of the RC beam strengthened with aluminum alloy plate is determined by the bonding property between aluminum alloy plate and concrete. As the study foundation of RC beam strengthened with aluminum alloy plate, the experimental and theoretical studies on interfacial bond strength between aluminum alloy plate and concrete were given. In-plane shear tests of 105 specimens were carried out. Specimens which were not treated on the bonding interface were failured in the form of interfacial debonding. The other specimens were failured in the form of being stripped of concrete layer. The bonding property of the interfacial debonding was much worse than the stripping of the concrete layer, indicating the necessity of treating on the bonding interface. The ultimate bond loads between aluminum alloy plate and concrete were got. Shear stresses distribution curves and effective bond length were obtained according to the relationship between the change rate of normal stress of aluminum alloy plate and interfacial shear stress. Assuming that the shear stress is the same along the effective bond length, the bonding strength between aluminum alloy plate and concrete was obtained. The influencing factors on interfacial bond strength, such as interface treatment, concrete strength, width and thickness of aluminum alloy plate and bonding length, were discussed. Based on statistics regression analysis of experiment data, the modified Niedermeier model of interfacial bond strength between aluminum alloy plate and concrete was put forward. The theoretical calculation formula on effective bond length and bonding strength was obtained. The theoretical values of bonding strength are in good agreement with the testing values. The largest error is 8.98%, the average error is 0.004, the standard deviation is 0.041.关键词：aluminum alloy plate;concrete;interfacial bond strength;in-plane shear test;shear stress
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发布时间：2024-01-05 - 摘要：Elastic modulus of concrete plays an important role in civil engineering design, thus it is important to keep the accuracy of its computation. Based on the on-hand three-layered spherical-shell model, an equivalent inclusion that consists of the aggregate, the interfacial transition zone and cement mortar was made, and its elastic modulus was calculated by the three-layered spherical-shell model. Then, the concrete was seen as a two-phase composite, which consists of the equivalent inclusion and basic cement mortar. Under the fixed-grid background, the extended finite element method without augmented degree of freedom was used to calculate the effective modulus of two-dimensional two-phase concrete composed of equivalent inclusions and cement mortar. This kind of XFEM can avoid the problem of dimensional inconsistency after aggregate distribution being changed. And the aggregate degradation was obtained through giving different aggregate diameters. It was shown that the aggregate degradation has no influence on the effective modulus of concrete, and the analytical solutions for predicting the effective modulus of concrete are only reliable when aggregate content is low, and the effective modulus of concrete has a linear relationship with aggregate content.关键词：concrete;interfacial transition zone;extended finite element method;effective elastic modulus
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发布时间：2024-01-05 - 摘要：Flood forecasting is usually based on the simulation of rainfall-runoff models. In this study, based on the saturation excess runoff mechanism, a distributed three-source runoff model was developed for rainfall-runoff simulation in mountainous areas. Firstly, a watershed was delineated into several hillslope units and a digital terrain analysis was conducted to extract the topographic features from the DEM dataset, the discretization of the parameters was realized by the digitization of the watershed at the same time and providing the necessary support for the application of the model. Secondly, the runoff yield in the slope surface unit was calculated by using the flow continuity equation and Darcy formula. Taking the simplified kinematic wave equation of Saint–Venant equations being as the governing equation, the approximate partial differential equation of slope surface flow was derived, and the confluence of each slope surface unit was calculated with characteristic line method. Storm runoff can then be simulated from the unsaturated lateral flow to the saturated overland flow on the hillslope unit of the proposed distributed runoff model. Moreover, outflows from the hillslope units were confluent and routed by using an improved Muskingum–Cunge method in the main channel. To test the applicability of the model, the simulations by using the hydrological records of Goodwin Creek experimental watershed in USA were assessed by the deterministic coefficient, correlation coefficient. The results showed that the proposed distributed runoff model can afford precise rainfall-runoff simulations and the accuracy can meet the requirement of forecasting. In general, the developed model can extend the applicability for rainfall-runoff routing from small hillslopes to mid-size or larger watersheds.关键词：distributed;saturation-excess runoff mechanism;hillslope flow;Muskingum–Cunge method;Goodwin Creek Watershed;rainfall-runoff simulation
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发布时间：2024-01-05 - 摘要：Mountain torrents caused by extremely strong rainfall in mountain basins are frequently occurred, resulting in loss of life and great destruction of economic activities. It is very important to realize the goal of disaster monitoring and risk management to understand scientifically the occurrence and development process of disasters in such extreme weather. The simulation of mountain torrent process is an important scientific means to recognize the disaster, and the accuracy of model calculation is the key to the simulation of mountain torrents. In this paper, the model of infiltration-excess and saturation-excess were combined with the instantaneous unit line hydrological model of motion wave geomorphology (KW–GIUH model), the runoff model which was suitable for heavy rainfall in mountain basin was selected, and the simulation accuracy of mountain flood process was improved. Based on the study of the Pingtong River, the first tributary of Fujiang River in a typical mountain basin, two historical heavy rainfall processes were simulated. The results showed that the simulation accuracy of KW–GIUH model was more accurate than that of kw-giuh model. The mixed runoff production model with first infiltration-excess and then saturation-excess was more effective than the single one, and the model suitable for heavy rainfall in mountainous area was the mixed runoff production model which was first infiltration-excess and then saturation-excess.关键词：mountainous watershed;heavy rainfall;runoff pattern;KW–GIUH model
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发布时间：2024-01-05 - 摘要：The supersaturated total dissolved gas (TDG) generated by high dam discharge can cause downstream fish develop bubble disease or even suffer death. In order to alleviate the impact of TDG supersaturation on fish, it is necessary to study the tolerance characteristics of fish in river to TDG supersaturation. According to the characteristics of TDG supersaturation in river, the tolerance of fish under constant TDG supersaturation and gradually varied TDG supersaturation was studied in laboratory. Schizothorax prenanti, a rare and endemic species in the upper Yangtze River, was chosen as object in this study. Median lethal time (LT50) was used to evaluate the tolerance of Schizothorax prenanti to supersaturated TDG under different conditions, and survival analysis method was used to analyze the difference of experiments under different conditions. The results showed that the LT50 were 27.7 h under the condition of TDG supersaturation at 120%. The LT50 of the experimental fish under gradually varied TDG supersaturation (110%～130%) was 58.2% lower than that under constant TDG supersaturation, although they have same mean value of TDG. LT50 of the experimental fish with a history of 72 h pre-exposure (115% TDG) was 72.5% lower than that under constant TDG supersaturation, after they underwent a gradually varied TDG supersaturation (110%～130%) stress for 24 h. Low-level TDG supersaturation stress had certain damage to experimental fish. Compared to the healthy experimental fish directly subjected to gradually varied TDG supersaturation, LT50 of those with a history of TDG pre-exposure reduced by 25.4%. Bubble disease occurred in Schizothorax prenanti both under constant TDG supersaturation and gradually varied TDG supersaturation stress. The mainly symptoms of bubble disease in experimental fish were pectoral, dorsal and caudal bubbles. The study revealed the tolerance and bubble disease characteristics of Schizothorax prenanti under the gradually varied TDG supersaturation, which was helpful for the next study of reservoir ecological scheduling and bubble response of fish to TDG supersaturation stress.关键词：total dissolved gas supersaturation;variation;middle and upper reaches of the Yangtze River;Schizothorax prenanti;tolerance
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发布时间：2024-01-05 - 摘要：In natural rivers, the dispersion is mainly caused by the non-uniform distribution of longitudinal flow velocity in the cross-section. The inhomogeneity of the velocity distribution is more obvious when there is partial emergent vegetation in the river. In order to study the longitudinal dispersion in the flow with partially emergent vegetation, assuming that the variables are constant in the vertical direction, a two-dimensional domain consisting of flow direction and lateral direction was simulated, and the Random Displacement Model (RDM) based on Lagrangian method was introduced. This model directly uses discrete particles with independent motion to describe the transport of matter, and it is no longer necessary to solve the advection-diffusion equation. The RDM simulates the distribution of pollutants mainly based on the transverse distribution of the vertically average flow velocity and transverse turbulence diffusion coefficient. Among them, the lateral velocity distribution formula adopts a simplified empirical formula based on shear vortex. The advantage of this formula is that it does not require rating the secondary flow coefficient, and the physical meaning is clear; with the dimensional relationship and the genetic algorithm, the explicit empirical formula of the outer layer width of the shear vortex was proposed, which is mainly determined by the water depth and the bottom friction. The diameter and density of the vegetation have little effect on the outer structure of the vortex. Besides, the model of the lateral distribution of the turbulent diffusion coefficient was given based on previous measured data, revealing the dynamic characteristics that the lateral turbulence diffusion at the junction is much greater than that of the stable zone. In order to verify the accuracy of the random displacement model, an indoor experiment was conducted in a long and straight partial vegetated water tank. The measured values of the concentration process lines at different points in the flow field agree well with the simulated values, indicating that the RDM can effectively simulate longitudinal dispersion of flow with partial vegetation, and provide a new method for the assessment of the mixing and transport of pollutants in ecological rivers.关键词：partial emergent vegetation;random displacement model;lateral turbulent diffusion coefficient;velocity profile;longitudinal dispersion
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发布时间：2024-01-05 - 摘要：In order to solve the problems that the association rules are not fully exploited, the attack scenario chain breaks in the existing attack scene reconstruction methods, and false alarms of security device affect the accuracy of attack scene reconstruction, an attack scenario association rule mining method based on alarm attributes similarity clustering was proposed in this paper. The method can effectively mine attack scene association rules, reduce attack chain breaks, restore actual multi-step attacks, and help the security administrator to deeply understand the attacker’s intrusion behaviors and master the attack. First, the alarm data including the original alarms of security device in the real network and the data source was preprocessed and normalized. By constructing an alarm time series, the FFT and Pearson correlation coefficients were used to analyze the characteristics of the false alarm period to generate a false alarm filtering rule. Then, an alarm attributes clustering method based on dynamic time threshold was proposed. The similarity between alarms was characterized by the similarity of alarm attributes. The clustering time was updated according to the interval between alarms and the dynamic time threshold. Finally, the Apriori frequent item mining algorithm was used to generate the attack scene sequence pattern, and the attack sequences with repeated steps were merged to generate the associationrules. The experiments results showed that the proposed method can effectively alleviate the impact of attack chain breaks and false alarms. Compared with the comparison methods, the integrity of the generated attack scene association rules can be effectively improved.关键词：attack scenario reconstruction;alert correlation;attribute similarity;false alarms
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发布时间：2024-01-05 - 摘要：In order to improve efficiency and solve the security vulnerabilities of the secure set computation protocols in practical applications, two secure two-party protocols for set membership and set intersection were proposed based on discrete logarithm problem and the polynomial representation of sets with which the set operation problem could be transformed into a polynomial evaluation problem. Firstly, a latest efficient secure set membership protocol was analyzed, and a security vulnerability of leaking the privacy of the participants by obtaining the element of participants on the brute attack was found. To overcome the security vulnerability, a new method was introduced by representing sets by polynomials and randomizing the polynomials, which could ensure the security of the participants without any leakage of interactions. Based on the discrete logarithm problem and the new method, a new secure set membership protocol was presented. The protocol could judge set-element membership with high-efficiency, and did not leak any other information about the participants besides the size of the set. Further, a secure set intersection protocol was showed according to the same technique. The security proofs of both protocols were given under the semi-honest model by using the probability polynomial time simulator, which indicated that the simulator views were computationally indistinguishable from the original protocols’ execution views. Finally, the detailed analysis about the protocols’ performance was presented, showing that both protocols were more efficient than other protocols since their communication complexity and computational complexity were smaller.关键词：secure set intersection;secure set membership;discrete logarithm problem;secure two-party computation
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发布时间：2024-01-05 - 摘要：In order to solve the issue of key management and authentication for unmanned aerial vehicle (UAV) networks, two authentication schemes targeted for different UAV networking conditions were proposed in the paper, including a scheme for UAV network supported by ground station (ASUSG) and a scheme for UAV network without ground station (ASWGS). Based on the elliptic curve cryptography, ASUSG was designed by making full use of the scenario characteristics of stable communication link and sufficient computing resource vesting in the ground station. In ASUSG, the ground station was the key generation center, which could distribute public key to UAV instantly and assist UAVs in achieving identity authentication, establishing secure communication links and reducing the computing task of UAVs. ASWGS was designed based on identity-based encryption, in which the identity authentication and key agreement of nodes could be realized without the support of ground station using the threshold cryptography. When networking, the masking key was exploited by nodes to transmit the secret share used to generate the node’s private key in the open channel, realizing the distributed generation of the node’s private key. By presetting the share of the public key of the node in UAVs, the interference behaviors of malicious nodes were effectively prevented with less computational overhead. Security analysis demonstrated that the schemes proposed in the paper could resist many typical security threats effectively, such as identity spoofing attack, message replay attack, man-in-the-middle attack and so on. At the same time, a simulation experiment was designed on Linux platform based on the national secret algorithm. Experimental results showed that compared with the existing schemes, UAV nodes in ASUSG and ASWSG need less computational overhead in the process of key management. It can be concluded that these two schemes could achieve the authentication and secure communication of UAV networking under resource-limited scenarios.关键词：UAV network;authentication scheme;elliptic curve;identity-based encryption;threshold cryptography
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- 1704
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发布时间：2024-01-05 - 摘要：In order to deeply study the propagation process of malicious software programs in wireless sensor networks, discuss propagation models of malicious software in the presence of time lag and analyze their propagation behaviors, a delay-based malicious software propagation model for wireless sensor networks was established based on the existing research on the security issues of wireless sensor networks. Based on the theory of infectious diseases and the characteristics of sensor nodes such as limited energy and delay, the dissemination process and characteristics of sensor nodes were analyzed in detail. The correctness and completeness of the state transition relationship, the existence of equilibrium point, the local stability and global stability in the model system were analyzed and proved. Based on theoretical analysis, a simulation model was established, in which the corresponding propagating ratio was set up, the simulation experiments were carried out on the changes of the number of nodes in each state during the propagating process, and the stability analysis of the system was provided. The values and changes of the time delay in the propagating process were simulated, and the influence of the time delay and the determination of the threshold were analyzed. At the same time, the comparative analysis of different propagation models was provided between the typical stable delay network worm propagation models and the proposed model. Experiments verified the validity of the theoretical stability analysis, determined the parameter threshold which affects the stability of the propagation and its impact on the propagation. The proposed model was compared with other models, and the influence of time delay on the system was analyzed. The proposed model has provided the analysis and research ideas for the spread and control of malicious software and has the guiding significance for the establishment of a security strategy to curb the spread of malicious programs in mobile wireless sensor networks.关键词：wireless sensor network;epidemic model;time delay;Lyapunov stability;malware
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发布时间：2024-01-05 - 摘要：Owing to the structure of the swing frame, the vibration center of the traditional two-plane vertical balancing machine is fluctuated, which often leads to the large error on measurement and the poor effect for static-couple separation. Based on the theoretical derivation of the vibration model of the traditional two-plane vertical balancing machine, the position formula of the vibration center was established, the torsional stiffness of the springboard around the vibration center was calculated, and the source of error was obtained by the change trend chart of the vibration center and torsional stiffness in the end. In accordance with the source of error, a static-couple separation swing frame that can keep the vibration center unchanged was presented, the position formula of the vibration center was also derived based on the vibration model and the invariance of the vibration center was verified. The constant stiffness value was proved by the torsion stiffness formula of the static-couple separation system, and the measurement stability of the sensor was realized. By the modal analysis of the static-couple separation swing frame, it was found that the flexure hinge only passed the swing signal while the translational spring plate only transferred translational signal. The two functions were independent of each other, which fundamentally determined the static-couple separation of the swing frame. The influence of structural parameters on the swing frame was analyzed for optimizing the design of structure too. Ultimately, the dynamic balance measurement experiments showed that the static-couple separation swing frame effectively improved the capability of static-couple separation for low speed rotating loads and provided an important basis for the structure design of balancing machine swing frame.关键词：two-plane vertical balancing machine;vibration center;static-couple separation;torsional stiffness;modal analysis
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发布时间：2024-01-05 - 摘要：Chatter in machining process is the main factor limiting the machining quality and machining efficiency. The traditional machining stability prediction models are mostly based on the machine tool dynamics under stationary state, and use the constant cutting force coefficients to represent different cutting conditions. However, in real machining process, system dynamics and the cutting force coefficients will change caused by the factors such as the spindle speed, leading inaccurate chatter prediction. Thus, a method to modify the conventional machining stability lobe diagram (SLD) is proposed to ensure the prediction accuracy based on the relationships among cutting parameters, system dynamics and cutting force coefficients. In this method, the sample information of the spindle speed is initially set up, and then the speed-dependent bearing stiffness is applied into the whole machine tool finite element model (FEM). Then the tool tip frequency response functions (FRFs) are obtained and their related modal parameters are identified. Therefore, with these sample modal parameters, the tool tip FRFs at any speed can be reorganized based on the modal fitting technique and the interpolation algorithm.A response surface method is established for predicting the cutting force coefficients under different machining conditions, which are further combined with the speed-dependent tool tip FRFs to be the inputs of the machining stability mathematical model. This model is combined with the adaptive particle swarm optimization algorithm to achieve the limiting cutting depth at any spindle speed. Then a modified SLD in full spindle speed range is plotted. The proposed method is applied to a three-axis vertical machining center, and different sets of the predicted no chatter cutting parameters are adopted to carry out the chatter tests. And the frequency spectrums of the cutting force signals are analyzed to indicate that no chatter occurred, which verify the feasibility of the proposed method and show that it can lay a foundation for the cutting parameters selection.关键词：machining stability;stability lobe diagram;operational conditions;cutting parameters
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- 1261
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发布时间：2024-01-05 - 摘要：In order to solve the problem of vehicle environment perception in foggy environment, aiming at the situation that the algorithm of vehicle visual distance defogging can not automatically acquire visibility, restored image color oversaturation, and loss of details seriously, etc, an improved non-linear dichotomy root-finding algorithm , which utilizes the spatial quality of no-BRISQUE revises the visibility in real time, and finally realizes the automatic evaluation of visibility, is proposed to overcome the non-real-time and subjectivity of visibility acquisition by traditional instrument measurement and visual measurement methods. An improved non-linear dichotomy root-finding algorithm is proposed,. The relationship function between atmospheric visibility and vehicle visual distance is improved. The error between the transmittance value calculated from the improved vehicle visual distance and the actual transmittance is reduced, the Halo effect is reduced, and the image details are increased. Experiments show that the transmittance estimation based on visibility can adaptively process haze video under atmospheric light scattering model. The reconstructed video image has clear picture quality, bright color and no distortion, and can retain a large amount of image information. The processing video is smooth and no jamming. It also has good fog removal effect for vehicle video with changing traffic scenes in foggy environment.关键词：vehicle vision;dichotomy;visibility;video fogging
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发布时间：2024-01-05 - 摘要：To ensure cutting stability and obtain accurate stability lobes diagram (diagram of cutting speed–cutting depth), need to get the frequency response function (FRF) of the tool nose. The tool tip is in a rotating state during processing, and its frequency response function cannot be directly obtained through the adhesive sensor.Therefore the dynamic parameter identification of the shank structure is the premise for accurate prediction the tool nose's FRF. In order to solve this problem, based on the theory of modal analysis, the method of modal joint optimization simulation was used to identify the dynamic parameter of the joint part. Through the evenly distributed spring damping units to simulate contact characteristics, the modal frequency and amplitude of the modal experiment and finite element analysis were served as the optimized constraints and optimized goals, which were combined with least square method to construct multi-objective optimization function, The nonlinear programming function optimization algorithm was used under MATLAB–ANSYS integration environment to realize the junction parameters identification. By used the method of construct the sample points in order to reduce the number of calls the ANSYS finite element analysis.By used the method of design variable sampling interval normalization process in order to avoid the unreasonable sampling. Brought the optimize recognition results into Ansys model for forecasting tool point FRF. The result showed that the two curves fitting degree of frequency response function are high and the first two order natural frequency of harmonic response analysis error are 0 and 0.04%. The feasibility of this method is verified, which can provide support for further obtaining stable lobe pattern.关键词：joint simulation;optimization;tool shank;joint part;parameter identification
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发布时间：2024-01-05 - 摘要：The drum-worm transmission device was designed as a robot reducer applied to the robot joint, which benefits the domestic localization of robot reducer. Surfaces of the beveloid internal gear tooth were used as the tool surfaces. By analyzing the internal meshing motion of the drum-worm pair, 6 frames were established. Relationships between the worm-wheel’s rotation angle, the worm’s rotation angle and working angle were determined by the auxiliary frame and the working frame on the internal gear. According to meshing principles, equations of the drum-worm pair’s meshing, second limit curve and first limit curve were established and then drawn by MATLAB R2013b. According to parameters of the U10PLUS KV170 motor, design parameters of the drum-worm transmission device were determined. Spirals of the worm-tooth’s surfaces were drawn by MATLAB to output ibl files, and then 3D-models of the drum-worm transmission device were drawn by Creo 2.0. The assemble of the internal gear and the worm in the Creo simulation environment without interference-fit was realized by adjusting the relative axial position of the beveloid internal gear with symmetrical wedge teeth. Comparing with the 220 mm-center-distance toroidal worm pair with same design parameters, the center distance of the drum-worm pair was reduced to 100 mm, which indicated that the drum-worm pair was more compact. According to distributions of the drum-worm pair’s contact lines on both surfaces of a tooth, the internal gear’s width was reduced from the 110 mm design-width to the 75 mm working width. Analyzing relative positions between the worm pair’s first limit curve and tooth-root lines, the non-undercutting was determined by the first curve distributed inside the worm’s tooth-root. Combined with traditional design methods, the beveloid internal gear plane enveloping external-rotor drum-worm transmission device with an integrated structure of drive, transmission and support was designed. In terms of driving, the motor was installed inside the worm to realize the integration of the worm and the motor. In terms of transmission, the relative axial position of the internal gear was adjusted to realize the worm pair’s backlash adjustment and wear compensation. In terms of support, the support shaft was used for positioning and installation to simplify the device structure without cabinet installation. Symmetrical wedge teeth of the internal gear benefited installation and adjustment of the worm pair to realize the backlash adjustment and the wear compensation as well as the improvement of utilization ratio of the worm pair. Designing internal gear according to working width benefited the reduction of manufacture cost of the internal gear. Rationalities of the meshing transmission were verified by analyzing spacial positions of the worm pair’s contact lines, second limit curve and first limit curve as well as the worm’s tooth-root lines. The design scheme of an integrated structure of drive, transmission and support applied to the robot joint was proposed, and the design of the beveloid internal gear plane enveloping external-rotor drum-worm transmission device was realized.关键词：beveloid gear teeth;plane enveloping;external-rotor;robot reducer
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发布时间：2024-01-05 - 摘要：In order to prepare waterborne fluorinated polyurethanes (WFPUs) with excellent hydrophobic and mechanical properties, three kinds of hydroxyl-terminated poly(fluoroalkyl methacrylates) (P3FMA, P6FMA and P12FMA) with different length of fluorinated side chains were introduced into waterborne polyurethanes (WPUs) and three series of side chained waterborne fluorinated polyurethane (WFPUs) (WFPUs–P3FMA, WFPUs–P6FMA and WFPUs–P12FMA) were synthesized. The analysis of infrared spectroscopy FTIR confirmed the successful introduction of hydroxyl-terminated poly(fluoroalkyl methacrylates) into WPUs molecular. The deconvolution results of FTIR showed that the content of hydrogen bonded carbonyl increased with the increase of fluorinated side chains and the longer fluorinated side chains could strengthen the hydrogen bonding interaction and the interaction of hard segments. The measurements of static contact angle and surface free energy indicated that the static contact angle of the three kinds of WFPUs films firstly increased with the increase of fluorine content, and then kept a constant value, at the moment, the surface free energy of the three kinds of WFPUs films was 34.78, 32.41 and 15.94 mN/m respectively. Thus, the WFPUs films with the longest fluorinated side chains had the lowest surface free energy and the excellent hydrophobic properties. The studies of X-ray photoelectron spectroscopy (XPS) revealed that the surface fluorine content increased with the increase of the bulk fluorine content and confirmed that P12FMA with the longest fluorinated side chains had the best fluorine surface enrichment properties. The results of X-ray diffraction (XRD) revealed that the crystallinity of the hard segment of WFPUs was enhanced with the increase of fluorinated side chains length. The results of mechanical properties showed that the films of WFPU2–P12FMA with the highest strength and elongation at break when the bulk fluorine content of the three kinds of WFPUs films was the same. Therefore, WFPUs films with outstanding hydrophobic and mechanical properties could be obtained through P12FMA modifying WPUs.关键词：waterborne fluorinated polyurethane;the length of fluorinated side chains;surface free energy;hydrogen bonding
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发布时间：2024-01-05 - 摘要：Using Suizhong 36−1 naphthenic crude oil as raw material, rubber plasticizer Coastal N4006 and N4010 base oil, conforming to the standard of chemical industry standard (tentative), were developed through vacuum distillation process and high-pressure hydrogenation technology The heat and UV resistant mechanical performance of the Coastal N4006/N4010 oil extended SBS system were investigated, and its aging mechanism was studied by FTIR analysis. The SBS/oil blends showed favorable mechanical properties with an over 10 MPa tensile strength and an over 900% elongation at break, remained high tensile strength after thermo oxidative (over 90%) and UV aging for 24 h (over 60%). The FTIR absorption peaks appeared around 3 300、1 720 and 1 170 cm–1 after UV irradiation, indicating that the main newly increased groups after aging and degradation were carboxylic acid and aliphatic ester groups. The FTIR spectroscopy of samples after thermo-oxidative aging remained the same with the unaged ones, which again proved the excellent thermal stability.关键词：naphthenic oil;rubber plasticizer;UV stability;thermal stability
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发布时间：2024-01-05
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