最新刊期
卷 49 ， 期 Z1 ， 2017
- 摘要：Abstract:Under the action of lateral scour by near bank flow,bank failure of concave bank of meandering river is the direct drive of bend lateral migration.Field surveys in 2011—2016 suggested that numerous meandering rivers,called peatland meandering river,had developed in the peatland swamp of the Zoige basin in the Yellow River source,where the upper layer of river bank was peat and the bottom layer is silt. Based on field investigation and lateral scour process,the process of lateral scour and critical torque balance of bank failure were analyzed to reveal the bank failure mechanism.Bank failure of peatland meandering river consisted of lateral scour in the silt layer and bank collapse in the peat layer.Three stages of lateral scour in the silt-layer were simplified as firstly flow scour of downstream bend apex in concave bank,lateral scour up to the maximum distance,and finally longitudinal scour along the bank.Furthermore,the relation between near bank velocity and lateral scour distance was obtained,i.e. near-bank reducing with increasing lateral distance.The formula of lateral scour rate was deduced that a simple method was proposed to estimate the lateral scour coefficient.The prediction value of critical width of peat slump blocks was in agreement with the measurements.关键词：meandering river;bank failure;lateral scour;peatland;Zoige basin
- 1905
- |
- 1300
- |
- 0
发布时间：2023-11-14 -
Experimental Study on Channel Response with Different Flow and Sediment Conditions in Mountain River
摘要：Abstract:The conditions of incoming water and sediment changes frequently as the result of earthquake,rainstorm,landslide,debris flow and other disasters.Riverbed clogging and overbank flood caused by these changes can lead to destructive flood disasters.In order to analyze the influences of variable conditions of incoming water and sediment on the channel deformation and flood water-level,the motions of flow-sediment of a typical channel in Longxi River of Min River’s tributary reach was investigated and physically simulated on the basis of the research of topography,the composition of bed material and the characteristics of water-sediment condition.Furthermore,the flood disaster mechanism induced by the dual fuction between flow-sediment and channel responses actions was pointed out.There were two schemes involving pure water and sediment laden flow,and seven test conditions were carried out.Sharmov formula was used to calculate the incipient velocity of sediment compared with mean velocity at across sections.The elevation diagrams of three across-sections was drawn as well as hydrographs along the river.The analysis indicatesd that the flood control safety of Longchi Town could not be affected by pure water.On the contrary,the mean velocity reduces dramatically and the flood inundats the bank when a great deal of sediment flow down with the flood，because the gradient decreased and the river width became wider in this reach.The results highlighted the important role of the sediment supply in mountain rivers and showed that the adjustment of the riverbed transport sediment dynamic of different regions controled the sediment transport distance with the increasing amount of sediment supply, causing local riverbed clogging, leading to an increase of flood level and even overbank flood and flood disaster.- 2285
- |
- 1076
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Flow structure will become more complex when there are large scale congeries in the river.Based on the flume experiment study,the three dimensional flow structure of river channel under the influence of congeries was studied,and the velocity was measured using the Acoustic Doppler Velocimeter(ADV).The analyses of the velocity around the congeries at different plane showed that congeries led to water block at theupstream of congeries,and then waterfall.The direction of the maximum longitudinal velocity from the congeries gradually turns to the right bank and the bottom of the riverbed in the vertical,and then rise and return to the natural state at the downstream of congeries.The main stream was in hydraulic jump state affected by the shrinkage of the river section around the congeries.Under the influence of the flow area of the river section cutted down and the inertia of the flow,the maximum velocity occured in the downstream position of the congeries.Transverse velocity appeared positive and negative values in a certain depth at the section of congeries.Water flows to the left bank in the upper layer of the depth,and to the right bank in the lower layer.It occured to reverse flow in the upper and lower layers.At the same time,this phenomena also appeared in the vertical velocity.It appeared spiral flow in the test section.Du to the influence of the congeries,the flow from the surface to the bed was in different width contraction.Besides,the spiral flow interactiving with the hydraulic jump made the flow in a complicated three dimensionalstate.关键词：congeries;the three-dimensional velocity;velocity profile;spiral flow;hydraulic jump
- 1922
- |
- 996
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:According to the problem of relatively low strength and relatively high cost of high-water material, choosing fly ash and silica fume as two additives,the properties of modificated high water material was studied,and the additive content were 5%,10%,15% and 20%,respectively.The internal microstructure and macroscopic properties of high water material mixed with additives were studied using SEM scanning electric microscopy and computer-controlled electronic universal testing machine.Experimental results showed that additives had a great impact on properties and microstructure.The addition of 20% fly ash or 10% silica fume both could improve the compressive strength to 0.36 MPa and the strength was increased by 20% compared with pure high-water material.Besides,the residual strengths were improved effectively.The morphology,diameter and space mesh structure of high-water material were changed due to fly ash and silica fume addition.The crystal morphology of high water material mixed with fly ash were dominated by needle bar,and the number of large diameter crystal was increased, the crystal structure’s pore was filled with ball-shaped calcium silicate hydrate and residues.The branches morphology of material mixed with silica fume increased the connection of crystals and the compactness of mesh structure.It was proved that the compressive strength was determined by crystal morphology,diameter,lap of the crystal structure and the dense state of lattice structure.关键词：high-water material;modification;fly ash;silica fume;the compressive strength;microstructure
- 1811
- |
- 1130
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to explore new measures to relieve the effects of thermal stratified reservoirs.By taking a built large reservoir as an example,a temperature control curtain was used to improve the effects.Laterally 2-D water temperature model was applied to compute water temperature of vertical stratified reservoir and selective water withdrawal.Six curtain plans were designed which included different height,submerged depth and location of curtain.Water temperature and flow field were also analyzed.The results showed that water temperature profiles and flow field were noticeably influenced by curtain.The bottom water was inhaled more in the 3 partial shield plan,these three plans could not improve temperature of withdrawal.However,bottom full shield plans improved the water temperature obviously,a large amount of surface water was taken,which made the temperature of reservoir reduced evidently.Submerged depth should be determined by the thickness of water intake layer.There would be a better effect when submerged depth was near the thickness of water intake layer.The effect of curtain position on the withdrawal water temperature was not obvious.Compared with no curtain,the water temperature raised 3.4, 2.1, 1.1, 0.4 ℃,respectively between May to August.关键词：reservoir water temperature;selective water withdrawal;curtain
- 1892
- |
- 1040
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Jets are widely used in various hydraulic applications.To observe the evolution of flow field and to investigate the mechanism of a submerged jet,Large eddy Simulations(LES) was utilized to simulate flow field with finite volume method (FVM) for discretization and PISO method for pressure calculation.From the analysis of the evolution of pressure field,the contours of pressure presented to be a cluster of concentric circles,and high pressure and low pressure circles appeared alternately along the jet axis.During the jet impinging, the concentric circles were moving along the jet with deformation,further splitting and merging.In the submerged jet zone and the front of jet impingement zone,the pressure in the center of concentric circles fluctuated and tended to be ascending; in wall jet zone,with a narrow range,the pressure in the center of concentric circles fluctuated at relatively low frequency.From the analysis of the evolution of velocity field,the jet was swinging and the mass of high velocity in the axis separated from main flow as time passed by.It was also found that the velocity had the negative correlation with pressure on a fixed point of jet.From the analysis of the evolution of vorticity field,two beams of vorticity in the field were distributed as the shape of lotus root and swung with time.Comparing vorticity field with pressure field,the results showed that it was vortex swinging that caused the jet swing and pressure distribution was also affected by vortices.The submerged jet field had the characteristic of randomness and was strongly turbulent.We reach the general conclusions from evolution of flow field and inherent relationship among velocity,pressure and vorticity,while there still remains many other aspects to be investigated,such as the quantitative analysis of jet swinging.关键词：submerged jet;LES;flow field structure;pressure evolution;vortex motion
- 2613
- |
- 1170
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:River reaches in the mountain area are often in the alternation between bedrock exposure and alluvial covered.The field survey found that at least several rivers in the transition zone between Qinghai-Tibet Plateau and Sichuan Basin have the abnormal phenomena that bed rock is exposure in gentle slope reaches and alluvial deposits are covered in the steep slope reaches.In order to study the abnormal phenomena,taking the Longxi River,which is the secondary tributary of Minjiang River as a case study,field observation and data collection were carried out many times.By extracting basin’s terrain data,the longitudinal profile of the truck stream were obtained and analyzed.Moreover,combined with the pervious flume experiment results,sediment transport and distribution characteristics in Longxi River was further illustrated,and the conclusions were obtained as the lithology of Longxi River basin is mainly sandstone,from the head waters,the slopes of truck stream have four distinguish reaches with different slopes and bed surface characteristics,namely,steep,gentle,steep and gentle successively,with average slope of 8.1%,0.2%,6.2% and 1.2% respectively, the two steep reaches are alluvial covered but the two gentle reaches are bed rock exposure,The steep slope reaches are supplied from colluvially derived sediment of the hillslopes,particles from sand to large boulders will gradually form relatively stable interlock structures with high resistance,and the bed roughness of narrow and deep channel enhances the erosion resistance of the bed surface, which will inhibit bedrock exposure.The interlocked structures also result in very low sediment transport rate to the downstream gentle slope reaches;moreover,the rare sandstone grains transported downstream are easily broken into smaller ones, which are more mobile,generating the bedrock exposure phenomenon to be prominent; steep slope reaches covered by alluvial deposits will suppress the erosion rate of narrow and deep bedrock and further affect the evolution of basin geomorphology,for e.g.,promote stream piracies.关键词：bedrock exposure;alluvial cover;longitudinal profile;interlock structures
- 1998
- |
- 1302
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The optimal dispatching for flood control of reservoir can reduce floods, achieve floodwater utilization and improve the operating efficiency of reservoirs.However,the previous studies on combined flood control dispatching of cascade reservoirs only give calculation of flood discharge capacity of reservoirs without the consideration of the specific opening of gates.The gate opening and closing conditions of hydropower stations are summarized and the digital forms of flood discharge gates are prepared in accordance with the operation requirements of gates.The digital forms of gates are used to solve the constraints of flood discharge of gates.The preparation of digital forms requires calculation of several sub-units,each of which is composed of gate combinations within a specific range of flow rate at a given water level.Each unit contains a number of different ways of combination,each of which includes a number of representative gate combinations.The application of digital forms can depends on the expected let-down flow rate of hydropower stations.Dichotomy can be used to seek for gate combination scheme,and the minimum sum of squares of deviations of gate opening and the minimum change of gate opening can be used as the objective functions.Correction can be made to the error between the let down flow rate of gate and the flow rate calculated with the multi-step progressive optimality algorithm so as to make real time allocation for the flood discharge capacity of hydropower stations and adjust the gate opening in a quicker and more accurate way.A sample calculation is conducted based on the optimal dispatching for flood control of cascade reservoirs at the downstream of a river basin.The opening times of gate of hydropower stations are reduced after considering the fact that the let-down flow rate of optimal dispatching for flood control of gates in operation is more uniform than that of the original hydropower station inactual operation and through comparison and optimization of the gate openings in two adjacent time intervals,thus obtaining the optimal dispatching of gates in operation superior to the actual dispatching.The results indicate that the method using digital forms of flood discharge gates is correct.关键词：flood control;cascade reservoirs;floodgates digital tables
- 2076
- |
- 850
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Power and energy balancing is an important measure for electric power dispatching department to balance benefits and allocate generation scheduling of power stations.Due to the mutual influences,cascade hydropower stations are often taken as a group in power and energy balancing.In order to realize rational load allocation of cascade hydropower stations after power and energy balancing,a short-term daily total load optimal allocation model was established, and a nested optimization algorithm was proposed for the purpose of obtaining the daily operation schedule during the load allocation process.The proposed nested optimization algorithm sets the maximal energy storage as the objective in the outer optimization,and nests an inner optimization unit,a short-term optimal dispatching unit in every outer optimal calculating process.The load allocation was realized in the outer optimization layer and the optimal operation schedule was obtained by the inner optimization unit.The Dagangshan and the downstream hydropower stations located in the lower reach of Dadu River were used in a case study,and a typical day was chosen to illustrate the model and the nested optimization algorithm.The results showed that the daily total load was allocated through the regulating function of the key reservoir while the rest of the reservoirs’water level at the beginning of the day was equal to that at the end.The water level fluctuations were reasonable,and the daily regulating capacity was fully used to avoid excessive abandoned water.Besides,the output process of each hydropower station was kept stable within a peak or trough period which satisfied the peak-valley ratio limits,and thus it could provide reference for power dispatching department to develop and issue the power generation schedule.In summary,the daily total load optimal allocation model and the nested optimization algorithm are efficient to allocate total load of cascade hydropower stations,to realize the coordination of water and load,and to achieve efficient use of hydropower resources.关键词：cascade hydropower stations;power and energy balance;load allocation;short term optimal dispatching;nested optimization
- 2005
- |
- 1032
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In the process of the roadbed construction of highway engineering in humid and rainy regions in the south of China,the high limit liquid soil is very widely used.The mechanical properties of high liquid limit soil directly affect the long-term stability of the roadbed.Because of the heavy rainfall,it is very difficult to fill the roadbed fill in the actual project, which affects the safety and stability of the roadbed.Therefore,in order to ensure the safety of the roadbed,it is significant to study physical properties of high liquid limit clay and engineering characteristics deeply,especially on the high liquid limit the safety and stability of roadbed.Moreover,there are few studies on the water stability, shear strength index and the change rule of the high liquid limit soil,so it is useful to study the influence factors of the strength of roadbed stability and slope stability In order to study the physical and mechanical properties of the high liquid limit soil of a highway roadbed, the change in mechanical properties of the high liquid limit soil with compaction degree and water content was analyzed by confined compression,rebound,triaxial shear strength tests of soils from two cross sections of the roadbed of a highway,The test results showed that the roadbed soil is moderate compressibility.For the same water content,cohesionc and internal friction angle φ,compression modulusEs,compression indexCcincrease with the increase of compaction degree,and rebound index Csincreases slightly with the increase of compaction degree.For the same compaction degree,the soil samples that their water content are greater than the optimum water content are tested.The compression modulus Es,compression indexCcand rebound index Csncrease with the increase of water content,cohesion c decrease with the increase of water content,the internal friction angle φhardly changes when the water content increases.关键词：high limit liquid;roadbed;compressibility;shear strength
- 2126
- |
- 1020
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:With the further development of hydropower engineering towards southwest area,the geological conditions of tunnel engineering are more and more complex.To solve the failures problem of surrounding rock masses (such as large deformation and collapse) with developed joint fissures,fault or other weak fractured zone during the tunnel excavation process,flood discharge tunnel at the Changheba Hydropower Station was selected as a case study example,and the supporting measures were studied to ensure the stability of surrounding rock and the construction safety.The reasons and solution for the failure of surrounding rock were concluded through comprehensive analyses of field investigation results,tunnel designed schemes,engineering geological conditions and finite element calculation.First,according to the failure of surrounding rock and actual geological conditions in the 0~30 m section of flood discharge tunnel engineering incombination with the investigation of specific construction measures of excavation and supporting,the influencing factors and modes of surrounding rock failure were studied.Then a typical finite element model of 30 m cross section for flood discharge tunnel was established.Considering the nonlinear deformation of surrounding rock,mohr-coulomb constitutive relation was used,and the stress and displacement of surrounding rock were calculated using finite element software.From the analysis of influencing factors and models of surrounding rock failure,influencing factors could be classified into three aspects:1) there were many joints in the surrounding rock of this section of flood discharge tunnel and the rock mass were cracked.This,the stability of surrounding rock was poor;2)There existed high crustal stress in the engineering area and there was some energy in the rock mass,and when the tunnel was excavated,the high crustal stress would be released so that the rock mass would be more cracked;3) the design of supporting measures was inappropriate.Ordinary bolting and shotcreting could not effectively restrain the deformation of surrounding rock and would lead to the rock failure.The physical and mechanical properties of surrounding rock were the leading factor of failures,which suggested that the failure mode of surrounding rock was rock mass structure-led failure mode.The finite element calculation results showed that,under the condition of original supporting,there was large deformation in the parts which were cut by the structural planes.Deformation of surrounding rock in fracture zone was effectively controlled after being timely supported.For the potential instability problems in the fracture zones of tunnel,advance supporting measures and spray anchoring,steel supporting,anchor wire bundle combined supporting measures were applied,which could restrain the deformation of surrounding rock and ensure the stability of surrounding rock.Moreover,the field monitoring data and application effects proved that the effectiveness of reinforcing supporting measures timely controlled the stability of surrounding rock mass.关键词：tunnelling engineering;fractured zone;failure modes;control of surrounding rock stability;numerical simulation
- 2198
- |
- 1532
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Plants are sophisticated and intelligent natural construction materials,which can be used for enhancing the stability of shallow soil slopes and minimizing surface erosion.It is evident that the use of plants can be low-cost,sustainable (almost maintenance free) and environmentally friendly.Vegetation used in shallow slope protection has a wide application prospect in southwest China,so it is important to understand the mechanism of vegetation in slope engineering stabilization.The stabilized mechanism is influenced by a lots of factors,in which the synergistic effect of root-soil mass is the focus of current research.Due to the different inclination of roots,the shear strength of root-soil system becomes complicated.Direct and triaxial shear test were performed on soil sample with different inclinations of artificial roots to investigate the reinforcement effect.Test results indicated that the peak shear strength and the residual shear strength of roots reinforced soil were obviously larger than soil without roots,and followed the laws of τp pure<τp90°<τp45°<τp135°.In the direct shear test,the largest shear strength was detected and strain hardening was observed when the inclination of roots was 135°,and strain softening tendency of soil samples with roots was controlled at different levels.When the inclination of roots was 135°,the root reinforcement effect was the most obvious and the residual strength was also the largest.It was indicated that proper inclination of roots may enhance the synergistic effect between roots and soil,then the strength of root-soil mass could be improved.The ductile deformation characteristics of root soil system could help improve the safety of the slope.This research results is valuable for vegetated slope engineering practice.关键词：shallow landslide;vegetated slope;root angle;shear strength;grass root;shrub root
- 1952
- |
- 1056
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:With the development of national economy,a large number of engineering projects were constructed in cold regions.Studying the mechanical properties of frozen soils is of great importance for engineering construction in cold regions.During the numerical analysis of coupled water,heat and stress in saturated freezing soil,it is necessary to construct a frost heave model reflecting moisture migration and the formation process of segregated ice lenses.Considering the influence on the driving force of water caused by suctions on the ice water interface and relations between the coefficient of transmissivity and void ratio in unfrozen soil zone,expressions of hydraulic head and hydraulic conductivity were modified on the basis of existing coupled model.Our results showed that the pore structures of the modified models appeared different degree of change,causing differences in the formation and distribution of ice lenses.After the expression of hydraulic head was modified,the frost heave curve of model behaved as an “S” type,the thickness of ice lenses increased and the time when ice lenses appeared advanced.Due to a decreasing permeability coefficient with the reduction of void ratio in unfrozen soils,the amount of moisture migration and frost heave was greatly reduced,and the time when ice lenses appeared was delayed.Based on the simulation results,the formation and stratification of ice lenses was theoretically analyzed.Ice lenses could be formed if there was sufficient water migrated to frozen soil zone before the formation of an aquiclude.The stratification of ice lenses depended on the capability of ice crystals separating soils and forming ice lenses.Combined with the Darcy’s law,the hydrating rate was used to reflect the influence of both hydraulic head and hydraulic conductivity on our results.The existing separation criterion could be used to explain the growth of final segregated ice lenses and it is suggested that the hydrating rate shoud be the criterion for the formation of early ice lenses.关键词：the coupling of water,heat and stress;hydraulic head;hydraulic conductivity;flux rate;ice lenses;formation and stratification
- 2361
- |
- 1606
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In the course of operation,the different parts of earth rock dam are usually at different stress levels,accordingly,it will produce different seismic additional stress in different parts in the case of earthquake.The stress state is an important factor for the dynamic properties of coarse aggregate.In order to study the influence of the stress state on the seismic behavior of the dam,experimental research on dynamic characteristics of coarse granular materials under different confining pressures,different consolidation stress ratio and different dynamic stress were carried out.The results showed that under different confining pressures,the values of the largest dynamic elastic modulus gradually increased with the increase of the confining pressure and consolidated stress ratio and decreased with the increase of the dynamic strain,and the decreased ratio gradually decreased with the increase of the confining pressure and consolidated stress ratio.Under different confining pressure,the damping ratio gradually increased with the increase of the dynamic strain.With the increase of the confining pressure,the damping ratio λ exhibited a gradual decease tendency.The maximum dynamic elastic modulus and damping ratio under different confining pressures were scattered,and could not be described by dynamic strain.Under the same confining pressure and consolidated stress ratio,with the increase of the dynamic stress,the dynamic permanent axial deformation and volume both had a certain increase.Under the same confining pressure and dynamic stress,the dynamic permanent axial deformation increased with the increase of the onsolidated stress cratio,and the dynamic permanent volume deformation slightly decreased with the increase of the consolidated stress ratio.Under the same consolidated stress ratio and dynamic stress,with the increase of the confining pressure,the dynamic permanent axial deformation and volume both had a certain increase.The amplitude of the axial dynamic strain was not uniform,which was generally larger at the first several cycles and gradually become small at later stage and usually tended to a fixed valued at about the tenth cycle.关键词：stress state;coarse aggregate;dynamic property;influence factor;experimental study
- 1819
- |
- 628
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:With the developing of hydroelectricity resource, more and more hydropower stations were built in alpine valleys which had complex geographic and geomorphic conditions,and many of them were built in underground with bedded rock.Therefore it has been a critical issue to quantitatively analyze the deformation and stability of underground powerhouse located in bedded rock.The deformation of bedded rock with different dense was analyzed in this case by means of field monitoring and numerical simulation.The results of deformation monitoring,acoustic wave testing and microseismic monitoring were employed to reveal the deformation law and damage zone of surrounding rock.Based on the characteristics of geologic framework and measured data,a calculation model was established to study the stress and deformation field,and plastic zone for the purpose of searching for the potential damage zone of the underground powerhouse during excavation unloading by using the plastic zone had a close connection with that of deformation.The difference of deformation was the result of discrete element analysis procedure UDEC.It was shown by the simulation and microseismic monitoring toghther that when the 6th floor which is between the elevation 815~809 m,the deformation value of elevation 812 m at the upstream side wall increases the fastest, and the amount of maicroseismic events around it increased rapidly.As a whole,the unloading of X axis was more acute than that of Y axis;the defomation value of the upstream side was greater than that of the downstream side.The maximum value of the deformation appears at the elevation of 812 m at the upstream side wall where the value of deepness of the plastic zone is largest.The distribution was more intensive bedding joint at the upstream side than that of the downstream side. The deformation of the surrounding rock has a close connection with the dense of the bedding joint,and the excavation will lead to the activity of bedding joint,leading to the damage of the surrounding rock and reducing the overall strength of the surrounding rock.The severer the excavation is,the faster the quantity of microseismic event increases.The research results will provide useful references for later construction and operation of the underground powerhouse.关键词：underground powerhouse;layered and jointed rock masses;UDEC;microseismic monitoring;deformation characteristic;surrounding rock damage
- 2251
- |
- 1280
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Rockfall is one of the main geological disasters in mountainous areas,and the range of its distribution is very wide.It always occurs suddenly and hard to be forecasted, which can damage structures,obstruct transportation,threaten human lives and cause other serious consequences.The design of protective structure is based on the analysis of rockfall trajectories.However,the researches about the rockfall are limited,resulting in poor prevention treatments of rockfall.Based on a variety researches of rockfall cases the three-dimensional discontinuous deformation analysis(3-D DDA)was used to study the rockfall prevention subject.Compared with the two-dimensional model,the three dimensional model can take 3-D terrain into consideration,and analyze divergence angle.Rockfall on a rock slope was analyzed using 3-D DDA for countermeasures.The movement characteristics were investigated by numerical analysis with consideration of collisions between rockfall blocks.The results showed that wether to consider the collisions between rockfall blocks would cause a huge difference,and the collisions among falling rocks would usually cause the total energy loss, but some blocks would obtain the kinetic energy through collisions and move a longer distance.The interactions among falling rocks couldn’t be ignored.Compared with the existing methods,3-D DDA could directly simulate the collisions among the rocks,which was correspond to multi-blocks rockfall events. Effect of protective measure was verified by the movement characteristics.This method can be used to predict the multi-blocks rockfall movement characteristics on rock slopes,and offer a reference for planning and designing rockfall countermeasures.关键词：rockfall;movement behaviors;3-D DDA;multi-blocks
- 2068
- |
- 946
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The creep of dam foundation and reservoir bank in hydraulic engineering,under the action of long-term high stress and high water pressure,will exert a significant impact on the engineering stability.Aiming at the creep of rock under the fluid-solid coupling in hydraulic engineering and choosing the Sinian-sandstone of some hydropower station’s draw water tunnel as the research subject,the physical and mechanical parameters and micro-structure of dry or saturated sandstone were tested using MTS testing machine and SEM method,respectively,and the main physical parameters and changes of micro-structure under different conditions were analyzed.On this basis,the creep experiment of sandstone under different water pressure was carried out using the exclusive rock mechanical creep testing system to analyze the impact that water pressure exerted on the creep deformation,the creep rate and long-term strength of the rock specimen.The results indicated that there was numerous micro-pores in the sandstone,which exhibited softening behavior in saturated condition,and both the compressive strength and elastic modulus of saturated sandstone were less than that of the dry sandstone.The acceleration of rock creep,the reduction of sandstone strength and the decrease of sandstone’s deformation-resisting ability were caused by the increase of water pressure.The higher water pressure was,the larger the initial strain rate of creep would be,the longer the time needed to reach the stable state of creep would be as well as the larger the creep deformation of stable stage was.The water could penetrate the rock internal through its pores on the surface,and during the development of fissures,the water pressure forced into the crack tip resulting in a kind of wedging action, which prompted the extension and transfixion of fissures and quickened the crack and deformation of rocks,therefore,the bearing capacity and long-term strength of rocks both decreased.关键词：rock mechanics;water confining pressure;sandstone;creep experiment;creep law
- 2165
- |
- 920
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:A series of Discrete Element Method (DEM) simulations of triaxial compression tests of rockfill materials (RFM) were presented to investigate the mechanical and deformation properties of rockfill,and the sensitivity of some related parameters were also studied.Two different DEM simulation approaches were employed,namely,the spherical-particle model and the sphere-clump model，and particular attention was given to the variation of RFMs strength due to the use of sphere-clumps.For the sphere-clumps model,the influence of microscopic properties of RFMs,such as Young’s modulus and friction angle,had also been examined.According to the deviator stress-axial strain and volumetric strain-axial strain curves,the peak/residual strength,strain,Young’s modulus,and the shear compression/dilation properties were analyzed.This study described how modeling parameters could influence the granular properties.According to the numerical results,as the confining pressure increased from 300 kPa to 1 000 kPa,the peak deviator stress of the spherical-particle model increased from 500 kPa to 1 700 kPa,while for the sphere-clump model,it increased from 1 400 kPa to 3 500 kPa.This trend showed apparent enhancement of shear strength when the sphere-clump model was used in the simulations.As the friction angle increased from 10° to 50°,the peak deviator stress of the sphere-clump model varied from less than 1 000 kPa to 3 250 kPa and the max volume strain increased from 6.5% to 20%.As the Young’s modulus increased from 107 Pa to 109 Pa, the shear strength increased from 1 350 kPa to 2 575 kPa,and the volumetric deformation of the granular sample transformed from shear contraction to dilation.关键词：RFM;DEM;granular clumps;shear strength;deformation;triaxial compression test
- 1973
- |
- 1768
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Focusing on the mixed mode fracture(Ⅰ-Ⅱ),the cracked straight through Brazilian disc(CSTBD) of gypsum was chosen for investigating the mechanical characteristics of mixed mode fracture.Adopting the displacement servo,the applied load and the displacement were monitored.Based on the peak loading and classical theory of mixed mode fracture,the mixed mode fracture toughness of rocks were calculated.The PFC3D code was chosen to simulate the evolution of cracks and adopt the point loading to replace the traditional loading manner.On the basis of the experimental results of cracked straight through Brazilian disk test under different angle β,by testing whether it was consistent for the outcomes of laboratory experiments and numerical simulations，microcosmic parameters were calibrated.By analyzing the mixed-mode Brazilian disk under microcosmic and macrocosmic perspectives,the microcosmic characteristics of simulations were coincident with the Brazilian disk destructive processes.The results showed that when the value of β was between 0 and 75°，there was a linear relation between KⅠ-KⅡ and β；according to the experimental results，a fitting equation between peak load values and β could be established to predict the peak load values with different β;according to three-dimensional simulations,the critical values of tensile and press transition angle on crack tips were greater in the three dimensional space than that in the two dimensional space，the error range was between 4% and 7%, in addition that the critical angle had significant spatial effect and gradually increases from surface to mid-span section.As β augments，the maximum tensile stress point moved from the crack tip towards the center of Brazilian disk and the rate monotonously increased with the increase of the loading angle.The three-dimensional analytical results denotes that the spatial effect of three fracture modes were different,the mode was minimal，and yet the Brazilian split was maximal.关键词：cracked straight through Brazilian disc（CSTBD）;mixed mode（Ⅰ-Ⅱ）;loading angle;spatial effect
- 2046
- |
- 852
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to improve the tracking ability of the surface maneuvering target,the surface target was modeled as an elliptical area,and an interacting multiple model (IMM) strong unscented particle filter based on fuzzed model probability was proposed.Firstly,a measurement equation of the elliptical area target was derived by using the extended area target measurements of modern radars.Then,the IMM-SUPF was obtained by introducing the strong unscented particle filter (SUPF) into IMM.Laterly,the strong tracking unscented Kalman filter (STUKF) was utilized to generate the proposal distribution in SUPF,and a fading factor was provided in STUKF for adjusting the proportion of state-model covariance and measurement-model covariance,making the proposal distribution more consistent with the posterior probability distribution of true state and the estimation precision of the sub-filters for IMM algorithm higher.At last,the model probabilities of particles were fuzzed by the proposed fuzzy membership function.In this way,the model probabilities of particles for filter with true target model was higher while the model probabilities of particles for the incompatible filters was lower.Accordingly,the fusion accuracy of the IMM algorithm was improved.Monte-Carlo simulation results demonstrated that the tracking precision of IMM algorithm for the area target was higher than that of IMM algorithm for the particle target,and the proposed IMM algorithm had faster convergence speed and slighter overshoot than the traditional one.Moreover,the developed IMM algorithm provided higher precision than the IMM-UPF for the area target.By modeling the surface target as an elliptical area and designing the fuzzed model probability based IMM-SUPF,the proposed IMM algorithm achieved better estimation performance than the traditional IMM algorithm for the particle target.关键词：interacting multiple model;maneuvering area target;strong unscented particle filter;model probability
- 1819
- |
- 1658
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:An improved fuzzy algorithm based on multi-label AdaBoost was proposed for classifing heart valve diseases.To reflect the severity of the disease,a membership function was used to map ultrasonic diagnosis to a fuzzy value in ［0, 1］,and the ultrasonic diagnosis was described by a fuzzy label matrix.Then,cosine similarity was adopted to capture the complex correlations among heart valve diseases.Besides,a supplementary label matrix was incorporated,which augments the fuzzy label matrix by exploiting the label correlations.The label space was divided into three parts:label set,relevant label set and irrelevant label set.In order to minimize ranking loss,the sample weight update speed was adjusted and weak learner was forced to reward relevant labels by setting different labels with different weight adjustment factors.The experimental results on clinical transthoracic echocardiography (TTE) data sets illustrated that the proposed algorithm in which the fuzzy label matrix was quantified on ultrasonic diagnosis results got the best classification performance.Specially,the severity of the disease such as “non” was mapped as 0,“slight” was mapped in ［0.8, 0.85］, “moderate” was mapped in ［0.85, 0.9］,“severe” was mapped in ［0.9, 1］ by the membership function.The label correlation matrix was calculated through cosine similarity on crisp label space,where value 1 denoting sick and value 0 denoting non-sick.The performance of the proposed algorithm on five multi-label evaluation criteria were better than AdaBoost.MLR algorithm,AdaBoost.MR algorithm,BPMLL algorithm,RankSVM algorithm and ML-KNN algorithm,and the predict results of the proposed algorithm were closer to real ultrasonic diagnosis results.关键词：heart disease;valve disease;multi-label classification;fuzzy classification;AdaBoost algorithm;label correlation;membership function
- 1967
- |
- 1182
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to improve speed and precision of binocular stereo matching,this paper deals with 3D reconstruction with binocular speckle images based on heterogeneous multi-core processor.On the basis of passive binocular stereo vision model and with the assistant of projecting white binary speckle pattern,the deformed speckle images were captured and then polar-rectified.Exploiting the improved traditional fast-ZNCC calculation method and zero-mean normalized cross correlation (ZNCC) as the correlation function,the shortcomings of low precision and low efficiency of the conventional stereo vision algorithm for weak texture regional reconstruction were effectively overcame.The developed algorithm was implemented on Myriad2 platforms characterized by heterogeneous multi-core architecture achieving accurate and efficient three dimension reconstruction.The experiments demonstrated that the efficiency and performance in 3D reconstruction were significantly improved without any loss of accuracy assisted by the heterogeneous computational architecture.关键词：speckle;3D reconstruction;Myriad2;ZNCC
- 1992
- |
- 1994
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Integral imaging is one of the most popular three-dimensional (3D) display technologies,since it has many advantages,such as naked-eye watching, no obvious visual fatigue and truly reconstruction of 3D image.During the assembly process of the integral imaging 3D display,the elemental image array is usually scaled since the size of elemental image array isn’t an integral multiple of the pixel size of display screen,and translated due to the assemblage error and the low manufacturing precision of the micro-lens array.In order to study the effects of the scaling and translation of elemental image array on the integral imaging 3D visualization,based on the theory of geometrical optics,the variation of the 3D image depth and 3D viewing angle under the two conditions were analyzed by using the integral imaging reconstruction technology and analytical method of viewing angle.The result of the simulated reconstruction experiments demonstrated that the 3D image depth decreased when elemental image array zoomed in,and the 3D image depth increased when elemental image array zoomed out.The result of the optical reconstruction experiments demonstrated that the 3D viewing angle increased when elemental image array zoomed in,and the 3D viewing angle decreased when elemental image array zoomed out.The optical reconstruction experiments also demonstrated that the translation of elemental image array caused the translation of 3D viewing angle,but had little impact on the width of the 3D viewing angle.From the results of the simulation experiments and optical reconstruction experiments,the conclusion was that the scaling of the elemental image array would cause the distortion of 3D image depth and the degradation of 3D viewing angle,while the translation of elemental image array had no obvious influence on integral imaging 3D display.The research results are useful in developing and optimizing of integral imaging 3D display.关键词：integral imaging;elemental image array;3D image depth;3D viewing angle
- 1807
- |
- 906
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Currently,software-based and hardware-based network flow export technologies are lack of scalability and data accuracy.In order to solve these problems,an accurate,general,scalable and high-speed network traffic processing framework called NTCI-Flow was presented.Firstly,the high-performance network packet capture was realized based on PF_RING DNA and the network packets were grouped and distributed according to the load balancing strategy based on network packet five-tuple.By using batch,lock-free queue and multi-thread technology,multiple network packets were encapsulated into a single large message sent in parallel,which improved and optimized the packet forwarding performance.Secondly,Kafka message system were used as a middleware to receive and cache network packets,in order to achieve the network packet distributed import.Thirdly,based on Storm,the real-time stream processing platform was built and the distributed streaming application was developed and deployed.Network packets were read from Kafka and the five tuples,packet size,timestamp were parsed and extracted.Then the network flow reorganization were completed.Finally,the Hive stream data import module was added and the exported network flows were stored in HDFS in Parquet format.Meanwhile,the Hive Metastore was used to store and manage the metadata.Time-based dynamic partitioning mechanism was adopted to reduce unnecessary disk IO when retrieved by time.The experimental results showed that the network traffic acquisition module could achieve accurate acquisition and forwarding of 10 gigabit traffic,even in the case of the smallest packet (60 byte),it could guarantee only 0.03% packet loss rate;the throughput of the traffic import module was related to the disk writing performance.When using 7 hard disks,the throughput was up to 775 MB/s;the distributed stream reorganization module had good versatility and expansibility,and the ability of processing 1.26×107 packets could be achieved by simple configuration.At present,NTCI-Flow is being used to collect and deal with an agency’s export traffic.The agency’s average traffic is about 3.5 Gbps and the peak bandwidth is 6 Gbps.The maximum number of packets per second can be up to one million.In this practical application,NTCI-Flow is running well,and the traffic data obtained is more accurate than that of NetStream.关键词：packet capture;big data;distributed;Storm;flow restructuring
- 2401
- |
- 1414
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:At present，the air-conditioning load participates in the demand side management of power grid,and the operation characteristics of the load are in accordance with the fixed frequency.Considering that under the same temperature interval,the number of status of the fixed frequency air-conditioning varies in different temperature ranges,in this paper the air-conditioning load was divided into two types,namely fixed frequency air-conditioning and variable frequency air-conditioning.And an optimal scheduling strategy for air conditioning load groups to participate in power grid regulation was proposed.To effectively solve load fluctuations caused by changes in the number of operating condition during the temperature regulation,a strategy combining the temperature control and direct on/off control was used for the fixed frequency air-conditioning.In response to the user-side demands,the steady-state and dynamic load models were established for the variable frequency air-conditioning based on their operating characteristics.Based on the load model of fixed frequency air-conditioning and variable frequency air-conditioning,discrete particle swarm optimization algorithm was used to simulate and optimize the scheduling model.Given the air-conditioning load that participated in the demand response was fixed,five kinds of control strategies were simulated in two cases of the different regulation durations under the same reduction amount,and the different reduction amounts under the same regulation duration.The results showed that under the same reduction amount or the same regulation duration,the increasingly elevated regulation duration or reduction amount would lead to the decreased flexibility of the temperature regulation mode in each aggregate group.However,the ratios of the standard deviation of the regulation to the reduction amount were less than 3% in general,and the maximum power saving of air conditioning load group can be calculated under the same reduction amount or duration.Therefore,within a certain regulation range,the air-conditioning load as the demand side resource can fit the control target effectively.In addition,the load aggregators can achieve the reasonable load reduction amounts and reduction durations based on the regulation of the air-conditioners so as to improve the peak valley characteristics of the grid load.关键词：air conditioning;load aggregator;demand side management;scheduling strategy
- 1988
- |
- 1252
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Nuclear-fuel-safety-rod-driving mechanism is an important part of the nuclear reactor and its seismic characteristic is a very critical parameter in safety evaluation.In the preliminary design stage,the simulation of the distribution of stress under seismic load is helpful to improve its seismic characteristic.To ensure that the nuclear fuel safety rod driving mechanism functions safely and reliably in the whole longevity,the seismic analysis was carried out at the level of preliminary design.First,the model of nuclear-fuel-safety-rod-driving mechanism was simplified based on the parameter settings.Second，the seismic response spectrum was ensured, referring to domestic and overseas seismic fortification criterion，and then the practical condition was analyzed and converted to boundary condition in finite element model.The stress distribution of the whole mechanism and the outer sleeve and the single internal structure were calculated and compared.And the influence of the outer sleeve on seismic characteristic was studied.The typical node paths were constructed based on the features of three models.The comparison of the extracted stress from the node paths showed the difference of stress distribution of three models.The results indicated that directly analyzing the stress distribution of the outer sleeve could evaluate the rationality of the whole mechanism.The outer sleeve can efficiently reduce the stress of internal structure under seismic load,the stress distribution of the outer sleeve is nearly the same with the whole internal structure,and the stress distribution of the single outer sleeve is nearly the same with the outer sleeve,which is a great reference to the engineering design.By this way,the efficiency of design would be enhanced and the risk would be reduced.关键词：safety rod;driving mechanism;seismic analysis;response spectrum method
- 1641
- |
- 1424
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Ti(C, N) cermet possesses the properties of excellent wear resistance and high corrosion resistance,which has been widely used in cutting tools,moulds,sliding bearings and other wear-resistant parts.However,it is badly worn or even destroyed when serving as dry self-mated wear pairs in sliding bearings.In order to enhance the properties of excellent wear resistance and high corrosion resistance further,Ti (C, N)-based cermets with different additions of AlN were prepared by powder metallurgy method.The mechanical properties of TRS,HRA,relative density,wear properties.etc were tested.Microstructure of the species with different additions of AlN were investigated by optical scope,SEM,EDS.The results showed that the typical core-rim structure of cermets could be found when AlN was added,and with the increase of AlN,the inner rim became blurry,outer rim became thinner,the average grain size decreased,the porosity increased.In the range of 0 and 1.0%,with the increase of AlN，the relative density of Ti (C,N)-based cermets decreased,HRA and TRS increased slightly.The self-mated dry friction properties increased first and then decreased,and the best properties were achieved when the addition of AlN was 0.5%.The addition of AlN caused the effect of grain refinement strengthening.The Al solid solved in binder phase strengthened the binder phase.However,the cermets tended to lose N because of the addition of AlN，and the porosity increased，the relative density decreased.When the addition content was 0.5%,the rim phase in the cermets showed the proper thickness,the tendency of losing N was not serious,the porosity was small,the effect of grain refinement strengthening and the Al solid solved in binder phase strengthening the binder phase were dominant.The cermets showed the best friction properties.关键词：Ti (C,N)-based cermets;AlN;self-mated wear pairs;dry friction
- 1745
- |
- 890
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:As an axially movable teeth transmission,oscillating-disc movable teeth transmission has the advantage of small radial dimension, but its application is limited by complicated structure and unbalanced load and force-coupling.In this paper,the theoretical calculation,modeling and simulation,mapping analysis and variable-controlling approach,and softwares such as Pro/E and MATLAB,were used to improve the structure of oscillating-disc movable teeth transmission and analyze its tooth profile.Based on existing research results,through theoretical calculations,the two-tooth-difference form of oscillating-disc movable teeth transmission and its motion equation and tooth profile equation were derived, and the new structure of two-phase surge wheel was designed.By 3D modeling,the curvature distribution of end gear was simulated,the variation along pitch cylinder and the distribution on the spatial tooth surface were analyzed respectively.According to the instantaneous circular motion model,the addendum on the spatial tooth surface was determined,the corresponding formulas of the coordinate vector and the radius of curvature were derived.Referred to the principle of the top cut in the planar movable teeth transmission,the boundary condition of the top cut in the two-tooth-difference oscillating-disc movable teeth transmission was calculated.The influences of parameters such as the radius of the pitch circle,the transmission ratio,the amplitude and the radius of the movable tooth on the tooth profile were analyzed by the variable-controlling approach,and the influence degree of each parameter was studied in the same coordinate system by using the relative deviation as the independent variable.Finally,the actual tooth vertex of end gear was located inside the pitch cylinder instead of on it’s surface.Varieties such as the decrease of pitch circle radius,the increases of transmission ratio,amplitude and movable tooth radius,were all found contributing to narrowing the tooth profile and leading to the top cut.The former two parameters actually changed the circumferential distribution of the tooth profile,while the latter two changed the distribution axially instead.关键词：two-tooth-difference;oscillating-disc movable teeth transmission;tooth profile;top cut
- 1694
- |
- 1332
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to prepare a varies of Fe-Ni bimetal oxides (Fe-NiOx) catalysts by sol-gel method,the precursor of different Fe,Ni mole ratio was calcined at 400,500,600 ℃.Catalytic ability of Fe-NiOx catalysts with different calcination temperature and metal element mole ratio was measured by the degradation rate of dimethyl phthalate (DMP) during the oxidation process.Influence of Fe-NiOx catalysts dosage as well as mole ratio between peroxomonosulfate (PMS) and DMP was also investigated so as to study the suitable experimental conditions.The results showed that catalysts calcined at 400 ℃ and 500 ℃ had have nearly the same DMP degradation rate which was is 16.54％,17.84％,respectively,while that of catalysts calcined at 600 ℃ increased sharply to 35.35％.Adding catalysts of c(Fe)∶c(Ni)=1∶4, 1∶2, 1∶1, 2∶1, 4∶1, DMP degradation rate was 22.61％,32.63％,35.35％,38.60％ and 39.14％, so it could be seen that catalytic ability of different catalysts was in proportion to the relative content of Fe during the synthesis process.Raising ratio of PMS and DMP from 5∶1 to 20∶1,DMP degradation rate increased to 45.79％,and the amount of DMP hardly decreased when the ratio reached 30∶1.Increasing the dosage of Fe-NiOx catalysts, DMP degradation rate had a similar trend to that of different reactant ratio.Therefore,the optimal conditions of the system was that the ratio of PMS and DMP was 20∶1 and dosage of Fe-NiOx catalysts was 200 mg/L.Adding tert butyl alcohol (TBA),ethyl alcohol (EA) which was radical scavenger of different radicals,the degradation of DMP decreased from 49.85% to 21.44% and 19.24%,respectively,indicating that the active substance was mainly hydroxyl radicals (·OH) and there was a little sulfate radicals (·SO-4 keywords: peroxomonosulfate dimethyl phthalate sulfate radical bimetal oxides 文章编号：201600969 中图分类号： 文献标志码： 基金项目:国家自然科学基金资助项目（51508353）；成都市科技惠民资助项目（2015-HM01-00279-SF) 作者单位张古承 四川大学 建筑与环境学院 张静 四川大学 建筑与环境学院 张永丽 四川大学 建筑与环境学院 卫陈默 四川大学 建筑与环境学院 Author NameAffiliationZhang Gucheng College of Architecture & Environment,Sichuan Univ. Zhang Jing College of Architecture & Environment,Sichuan Univ. Zhang Yongli College of Architecture & Environment,Sichuan Univ. Wei Chenmo College of Architecture & Environment,Sichuan Univ. 作者简介: 引用文本： 张古承,张静,张永丽,卫陈默.制备条件对Fe-NiOx催化过硫酸氢钾的影响[J].工程科学与技术,2017,49(Z1):202-206. Zhang Gucheng,Zhang Jing,Zhang Yongli,Wei Chenmo.Effect of Preparation Condition on Fe-Ni Bimetal Oxides in Catalytic Peroxomonosulfate Process[J].Advanced Engineering Sciences,2017,49(Z1):202-206.关键词：peroxomonosulfate;dimethyl phthalate;sulfate radical;bimetal oxides
- 1495
- |
- 772
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:With the development of powder metallurgy technology,metallic powder has been widely used in the preparation of metal-alumina-based ceramic composites.Metal plays an important role in enhancing sintering activity,strengthening and toughening.In order to study the effect of metallic elements on the mechanical properties of alumina ceramics from the atomic scale, the first-principles calculation method based on density functional theory (DFT) was adopted.A typically ductile metal,Cu,substituted Al3+ of Al2O3 mixed structure cell model and pure Al2O3cell model were established,respectively.And the tensile strength and fractural properties of these two models were investigated via the first principle calculations tensile test (FPCTT),which could be applied to simulate the ideal tensile deformation of crystal along uniaxial direction.The effect of Cu on the Al2O3 was elucidated based on the analysis of charge density distribution and its difference,and the Mulliken charge population,etc.,from the electronic structure and mechanical properties of the systems.The results showed that the ideal tensile strength of pure Al2O3 crystal was 55.51 GPa with a critical strain of 18%.Moreover,the mode of fracture was plastic deformation,with obvious yield-effect,due to the gradual movement of Al atoms approaching to neighboring O atoms layers during the stretching process.The tensile strength of the doped system was 40.33 GPa with the corresponding strain of 12%.And the doping structure exhibited brittle fracture with the relatively weaker strength of Cu—O bond compared to that of Al—O.Consequently,the alloying Cu forms a weaker Cu—O bond which broke preferentially during the uniaxial tensile deformation process,leading to the fracture of bulk structure.The effect of alloying Cu will weaken the binding strength of bulk materials and further decrease the tensile strength of Al2O3.
- 2306
- |
- 1382
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Magic-size nanocrystals (MSNCs) have recently attracted much attention because they are more stable compared to their similar-sized counterparts called regular nanocrystals (RNCs) due to their defined molecular structures.However,the synthesis of MSNCs in pure form has been acknowledged to be challenging since the coexistence of different types of MSNCs and RNCs is difficult to avoid.In the present study,CdTe MSNCs were prepared from cadmium-acetate/carboxylic acid and tri-n-octylphosphine telluride in non-coordinating solvent 1-octadecene.It was generally found that only with small amounts of carboxylic acid it was possible to obtain MSNCs of high purity.Furthermore,two different types of CdTe MSNCs were synthesized by simply varying the reaction temperature.TEM,HRTEM,XRD,EDX and XPS were used to examine the morphology,composition and crystal structure of the as-prepared CdTe MSNCs which exhibit a dot-like morphology,a wurtzite structure and a Cd-rich surface composition.Additional experiments were performed to study the growth mechanism of MSNCs using UV-vis absorption real-time monitoring.The results suggested that larger MSNCs growth at the expense of smaller ones partly dissolving into monomer which serve as growth material similar to Ostwald ripening commonly observed for RNCs.关键词：CdTe;magic-size nanocrystals;high-purity;growth mechanism;carboxylic acid
- 1583
- |
- 964
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:he photocatalytic degradation performance and the influence variation on membrane fouling for the TiO2 nanotube catalysts,prepared by hydrothermal method,were investigated by photodegrading Acid red B wastewater (12 mg/L) using a kind of three-phase fluidized bed equipment coupling photocatalysis oxidation and membrane separation (E-PS).The results indicated that the degradation efficiency of Acid red B wastewater firstly increased,and finally decreased with the increase of hydrothermal time and calcination temperature,while the opposite phenomenon on the membrane fouling was observed and the optimal time and temperature were determined as 12 h and 400 ℃,respectively.The membrane fouling decreased with increase of air rinsing time intervals,and the optimal intervals was regarded as 30 min.The membrane fouling in E-PS during intermittent operation was lower than that during continuous operation.Compared to the commercial TiO2,the TiO2 nanotube exhibited higher photocatalytic degradation performance and lower influence on the membrane fouling.关键词：TiO;2;nanotube;photocatalysis;membrane separation;membrane fouling
- 1504
- |
- 796
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Fatigue damage is the main cause of the deficiency of steel structures.Traditional steel structure strengthening methods,which include steel plate welding,rivet connecting,bolting and so on,tend to cause stress concentration.CFRP has high strength and rigidity,and CFRP strengthening has unique advantage of strengthening steel structure in contrast to the traditional retrofit methods.Through fatigue tests on three groups of open-hole steel plates with CFRP strengthening,fatigue failure mode were described and related fatigue life and deformation curves were analyzed.Similarities and differences were compared in fatigue life,crack growth,cooperative working condition between three groups of steel plates and CFRP.It was found that the yielding load of the repaired specimens increases obviously,the flaws on the surface of steel plate could be repaired and crack propagation speed could be slowed with the use of CFRP strengthening. The ductility and fatigue life could also be increased.With the increase of the number of CFRP layers,the fatigue life could be improved by 4.7% and 77.8% with one layer CFRP and three layer CFRP.The results showed that the carbon fiber sheets reduce the difference between the deformability of the steel plate under different stress effectively.The difference decreased when the CFRP increased.Observation showed that the more CFRP stickup layer the steel plate had,the bigger its limit deformation against broken was.The limit deformation to steel plate with three-layer carbon fiber sheet was above 0.9 mm.关键词：open hole steel plate;fatigue life curve;CFRP;fatigue deformation curve
- 1544
- |
- 828
- |
- 0
发布时间：2023-11-14
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0