In order to assess temperature field in microwave heating for recycling asphalt pavements,a 2D mathematic heat transfer model was developed based on Fourier heat transfer theory The microwave internal heat?generation was researched by using surface field of pyramidal horn replacing approximate radiation field In addition，the boundary conditions were built and normalization processing was implemented The control volume based finite differential method (CV-BDM) was used to establish the implicit discrete scheme of the conservation
equations,and the numerical value simulation was employed By continuous or intermittent
radiation heating technique,a microwave heating experimental system at 2 145 GHz was carried out to investigate temperature variation characteristics of asphalt pavements along with heating time The result shows that (1) the increase of temperature of asphalt mixture during microwave heating is obviously nonlinear,the temperature rises slowly in the initial stage of the heating but increases rapidly in the late heating period; (2) the temperature distribution is non-uniform that the temperature in central area of the surface is higher while it is lower on edge; (3) the uniformity of temperature within asphalt mixtures can be improved by using intermittent heating technique,and the heating time must be reasonable The simulation results are in preferable agreement with the experiment
为了探讨贫混凝土基层沥青路面在不同路面结构和材料参数下的温度应力状况,利用三维有限元数值方法,分析了沥青面层厚度和模量、贫混凝土基层厚度和模量以及基层缩缝宽度对沥青路面温度应力的影响。结果表明:沥青面层厚度对路面温度应力有显著影响,但沥青面层模量对路面温度应力影响不明显|贫混凝土基层厚度和模量对温度应力影响不显著|基层缩缝宽度对路面温度应力有显著影响。适当增加沥青面层厚度对延缓反射裂缝十分有效,适当增加沥青面层模量对延缓反射裂缝只起到较小的作用|改变贫混凝土基层的厚度、模量对延缓反射裂缝作用不明显|适当宽度的基层缩缝对延缓反射裂缝效果显著。
To cope with the fatigue cracking occurred to the asphalt mixture on steel deck avement,it is put forward that the fatigue life of asphalt mixture can be improved by reducing the ailure energy of each hysteresis loop of asphalt mixture according to the cumulative dissipated energy and hysteresis loop theory in the principle of viscoelasticity for asphalt mixture Based on this principle,a kind of modified asphalt with high elasticity was developed,and its high and low temperature performances and fatigue performances were also tested The result shows that (1) low temperature deformability of the high?elastic modified asphalt mixture has remarkably improved and low temperature bending strain of girder at -10 ℃ is above 10 000 με; (2) the fatigue life of modified asphalt mixture with high elasticity has greatly improved by 4?point bending beam test compared with common modified asphalt mixture The fatigue life at 1 000 με deformability is about 19 million times which is about 20 times longer than that of ordinary asphalt mixture
量化研究了沥青混合料冻融劈裂试件微观结构的损伤特性。基于冻融劈裂前后试件的CT图像,以CT值和损伤变量为基础,根据试件内部损伤特征,借助损伤力学基本概念,通过适当的数学假设,建立了冻融劈裂前后沥青混合料试件内部结构CT值分布规律的数学模型。利用CT值和损伤变量实现了对冻融劈裂前后试件内部微观损伤的量化。以损伤力学概念为基础,给出了沥青混合料损伤密度的定义,推导了以CT值表示的混合料密度损伤变量表达式,从而将CT值和损伤变量联系起来。利用损伤变量可以对混合料试件冻融劈裂前后内部微观结构的变化进行对比分析,实现了试件内部微观损伤特性变化的定量对比。对冻融劈裂前后试件上中下3个层位损伤变量的计算结果表明,冻融劈裂后试件各层位相应的损伤变量均有不同程度的增加,与CT图像表明的试件内部损伤明显加剧相吻合。
分别利用级配检验和无核密度仪检测的方法,调查总结了AC-25和AC-13沥青混合料摊铺离析和压实离析的规律。依据该规律设计模拟级配离析和压实离析的混合料,进行了模拟动水压力试验以评价它们的抗水损坏能力。与设计级配AC-13C混合料相比较,模拟摊铺机端部离析和容许级配最粗离析的沥青混合料在动水冲刷3 h,即正负压交替作用1 350次后,25℃劈裂强度损失都超过了30%;当击实功不足时,容许级配最粗离析的沥青混合料在动水冲刷3h后25℃劈裂强度损失48.2%。即使不考虑压实不足,模拟级配粗离析和容许级配最粗离析的AC-13C混合料都显得抗水损坏能力不足。从保证沥青混合料抗水损坏能力的角度建议了沥青混合料生产和现场摊铺阶段的级配控制要求。
In the light of semi?rigid material as base course for perpetual asphalt pavement,the bearing capacity and fatigue life of asphalt pavement with semi-rigid base cause and different asphalt layer's thickness were computed with BISAR30 after chosen typical pavement The impact of thickened layer on the stress of the semi?rigid base,the dry shrinkage and temperature shrinkages of the material were analyzed,and its adaptability as base for perpetual pavement was studied The result shows that (1) under the same load,with thickening of the asphalt layer,the compressive stress on the top and the tensile stress at the bottom of the semi?rigid base decrease obviously and the fatigue life of
the base increases substantially; (2)the impact of temperature and humidity on the
semi-rigid base is remarkably weakened,which leads to the fractures,erosion and reflecting cracks of the semi?rigid base to be controlled effectively
Stresses of pavement with flexible base of LSAM-30，ATPB-30 and AC-30I at the most adverse point under the function of traffic load and temperature load as well as the coupling of them were calculated and compared by finite element method. The result indicates that flexible bases of LSAM?30 and ATPB?30 are more effective in the prevention of reflection crack Because of the great volume of coarse aggregate and large maximum nominal particle?size,the LSAM-30 thermal conductivity is greater,and the temperature shrinking coefficient is lower as well as the modulus of resilience,which could reduce the emperature gradient among the structure layers effectively and then minish the thermal stress At the
same time,the adequate flexibility performance of the LSAM may also absorb strain energy at the crack of the semi?rigid subbase sufficiently As a result,itpresented preferable reflection crack resistance A case study was conducted to do comparative analysis of anti?cracking performance of LSAM-30,ATPB-30 and AC-30I flexible bases A long?term follow?up observation of test roads with the three bases shows that the pavement with LSMA base is in good condition and no sign of crack found while pavements with ATPB?30 and AC?30I flexible bases have varying degrees of crack LSMA flexible base has an obvious performance of anti-crack
为修复水泥混凝土路面DBI施工对接缝部位混凝土产生的扰动破坏,在滑模摊铺机后部增设两块振动平板进行补振。根据振动传播理论,为保证混凝土中粗集料获得最佳振动,提出选用2 300~3 000次/min的振动频率。按有效振动液化原理提出了振动颗粒极限振幅的确定方法。从有效振动深度等边界条件提出振动电机偏心矩的确定方法。结合广东省粤赣高速公路某标段滑模摊铺施工,进行了振动板的实例设计,工程应用表明,振动板能有效消除接缝部位混凝土的缺陷,传力杆牢固可靠;路面平整度显著提高,平整度合格率达到91%以上,比没有加装振动板的标段高23%。
Impacts on asphalt mixture's high temperature performance with PR series additives added by means of rutting test and Repeated Shear Test (Constant Height) (RSCH) were investigated The analytic results of the two tests show that (1) rutting test is not suitable for the high temperature performance evaluation of asphalt mixture with PR series additives added for the reason of the conflict between dynamic stability and rut depth; (2) the results of RSCH,such as K1,K2,N and γ,show very well consistency which is suitable
for the high temperature performance evaluation of asphalt mixture with PR series additives
added The results of RSCH show that asphalt mixture with PR PLAST S (PRS)
added has the best performance,the PR FLEX MODULE (PRM) one is the next and t
he original one is the worst for the high temperature anti?shear performance
To analyze influencing factors and evaluation method of low-temperature performance of porous asphalt mixture,first,three kinds of modified binder were chosen as original,thin film aging and pressure aging samples for customary index test and bending beam rheometer (BBR) test at -12 ℃ to evaluate low-temperature performance of these modified binders Then,evaluation of the low-temperature anti?cracking performance of different kinds of porous asphalt mixture was made by thermal stress restrained sample test (TSRST) At the sam
e time,the result of abovementioned TSRST were compared with the TSRST result of
samples of the porous asphalt mixtures after long?term aging to evaluate the influence of
aging on low-temperature performance of porous asphalt mixtures The results show that (1) TSRST result of porous asphalt mixtures coincides with creep stiffnesses of BBR test of modified binders; (2) the fracture temperatures of the porous asphalt mixtures increase and their fracture stresses decrease after aging; (3) the fracture stresses of porous asphalt mixtures are just one-third of those of dense?gradation asphalt mixtures while the fracture temperatures almost the same,which indicates that their low?temperature performances are almost the same
为制定、补充、修改和完善我国公路行业现行的设计规范和标准;研究我国现行高速公路上行驶的交通荷载标准。从实际出发,根据我国现有高速公路交通荷载现状,在全国范围内实地调查高速公路正在运营的各种车辆荷载,共采集了近7万辆汽车的相关动态数据。根据车辆荷载的实态调查、统计和分析结果,采用数理统计和可靠度理论分析的方法,根据不同的研究目的,分别建立高速公路车辆荷载谱,为进行标准规范修编提供有力的数据支撑。研究结果表明:我国国土面积较大,各地车辆荷载形式众多,不能简单套用同一标准,应根据不同的研究目的,从不同研究理论的角度,根据实际计算、分析的结果,分类研究制定出适合各自研究目的的交通荷载标准。
Mori-Tanaka equivalent inclusion micromechanics theory was employed to investigate the viscoelasticity of asphalt mixture Asphalt mixture was regarded as composites which treated coarse aggregate as a rigid inclusion and the mixture of fine aggregate,filler and binder as viscoelastic matrix The constitutive relations of coarse aggregate inclusion and fine aggregate-filler-binder matrix were converted into elastic problems by Laplace transformation Then the Mori-Tanaka equivalent inclusion and average theory were used to deduce the
viscoelastic performance of asphalt mixture based on that of asphalt mortar in
Laplace space The result shows that (1) coarse aggregate inclusion can enhance
the viscoelastic performance of fine aggregate?filler?binder matrix and viscoelastic constitutive relation of asphalt mixtures can be expressed as the product of an enhancement coefficient of coarse aggregate and the viscoelastic constitutive relation of fine aggregate?filler?binder matrix; (2) the viscoelasticity of the complex asphalt mixture can be predicted from the viscoelasticity of the homogeneous fine aggregate?filler?binder matrix by using the nhancement coefficient; (3) the enhancement coefficient is higher than 10 and it rises with increasing of coarse aggregates' volumetric fraction or Poisson's ratio of fine aggregate-filler-binder matrix but the effect of the former is more important than that of the latter
he prestressed concrete skewed box girder with transversely segmental construction was brought out on the basis of the need in the engineering,both model experiments and FE analysis of the presented construction and the beam box with integral construction were carried out With the analysis of the obtained data by mathematical statistics,comparison of table and graph,and the corresponding FE analysis,the difference of mechanical performances of both constructions was analyzed under various experimental loading cases The results
show that (1) the deflection of the presented construction is about 53% larger than that of the beam box with integral construction,the longitudinal strain is 135% larger than that of the latter,and the longitudinal strain of the cast concrete is 59％ as large as that of the same area at the beam box with integral construction before concrete cracking; (2) there exists stress redistribution in the cross-section of presented construction,which can restrain the tensional distortion of the wet?joint,and the value of the stress cannot be computed by the current FE program
Four methods of erecting steel stiffening truss girder of suspension bridge,including the deck lifting gantry crane method,the cable-mounted crane method,the cantilever erection method with derrick crane and the incremental launching method,were studied Based on construction conditions of the bridge,according to the optimal combination of various factors such as construction safety,quality,period,environmental protection and economic performance,etc,the cantilever erection method with derrick crane was recommended for the bridge. On this basis,three categories of connection in cantilever erection methods,including the all hinged method,the successive fully splicing method and the successive splicing with temporary erection hinge method,were studied The successive splicing with temporary erection hinge method was recommended in the bridge with consideration of the requirements of construction safety,quality and time limit In addition,the traction method of hangers at the top end during cantilever erection was studied Finally,the erection method of three key
stages,including the first segment near the pylon,the standard segment,as well as the closure segment of steel stiffening truss girde,r was studied. The cantilever erection method with derrick crane provides a new way for design and construction of long-span suspension bridge with steel stiffening truss girder in the western area of China
针对整体式桥台曲线箱梁桥的结构特点,运用结构分析软件ANSYS的APDL语言实现多模态反应谱法的自动迭代,以简化该类桥梁的动力特性分析。对该类桥梁的计算模型及影响其动力特性的主要参数进行了分析,通过动态时程分析法比较了迭代多模态反应谱法的可行性和准确性。结果表明:该类桥梁不存在纯粹某一方向的振型;1阶横弯、1阶纵弯和3阶竖弯分别对横、纵和竖向的振型贡献最大;1阶横弯和1阶纵弯频率受台后土及桩侧土密实度的影响最大,其次是地震激励频率和桥宽;3阶竖弯频率基本不受各种参数的影响;迭代多模态反应谱法可以作为该类桥梁抗震计算的一种估算手段。
In order to study the fatigue behavior of RC beams strengthened with High Performance Ferrocement Laminates (HPFL) under overloading conditions,static and fatigue experiments were conducted on two control beams and nine strengthened beams The failure mode,fatigue life,deflection and material strain under overloading conditions were analyzed The result shows that (1) fatigue failure of the beams subjected to overload starts with steel rupture at the bottom and the fatigue life is only between 327 000 and 668 000 while fatigue
life of strengthened beams is greater than two million times in case of not overload
ing; (2) compared with the control specimen,the fatigue life of strengthened beams is obvio
usly extended and increased with the increase of steel mesh consumption; (3) after the same number of cycles,the deflections,the strains of concrete and steels of four strengthened beams are lower than those of the control specimen Debonding at the interface of HPFL and concrete is not observed because of shear pins planted at the end of the beams
为深入研究部分斜拉桥的极限承载能力,以国内第1座已建混凝土部分斜拉桥——漳州战备大桥为例,对其进行极限承载能力分析。运用ANSYS有限元分析软件,采用基于非线性连续介质力学理论的全过程分析方法,假定混凝土为理想的弹塑性材料,采用Drucker-prager屈服准则,钢筋为多线性等向强化材料,采用Mises屈服准则,建立了有限元U.L.列式的几何非线性与材料非线性耦合空间分析模型。分析结果表明:当活载系数λ<|3时,部分斜拉桥结构的非线性特征不明显。部分斜拉桥达到极限承载力时,其破坏模式属材料强度达极限状态这种类型,此时结构还未出现极值点失稳现象。决定其极限承载力的主要因素是混凝土材料非线性。中跨布载时结构极限承载力最小,活载系数λ=7.8,极限安全系数k=1.78。
The effect of damaged transverse connection of diaphragm beams on the bearing capacity of prefabricated concrete T?beam bridges was studied through model experiment and finite element analysis On the basis of standard drawing of 16 m T?beam bridge,a refabricated concrete T?beam bridge model on the scale of 1 to 4 was designed by using of welding steel plate The impacts of different condition on transverse load distribution were discussed The result shows that (1) flange connection has little impact on the transverse load distribution when the diaphragm beams are connected reliably; (2) the damage of transverse connections has much influence on the transverse load distribution of adjacent girders but it has little effect on the girders apart from them; (3) if a certain transverse connection is damaged entirely except for that of the end diaphragm beams,the load distribution would not degenerate to the conditions determined by the flange connection because of the advantageous effects of the other diaphragm beams; (4) only when the bilateral diaphragms of one beam are damaged at the same time,the lateral load distribution will degenerate to the conditions determined by the flange connection
以某座普通钢筋混凝土连续箱梁桥为研究背景,提出了在箱梁翼缘悬挑钢悬臂梁的新型拓宽方法。应用有限元软件ANSYS,建立了板实结合的空间有限元模型,分析这种特殊的加宽方式存在的接触非线性问题,并引入子模型技术提高分析效率。通过对两种主要工况下的钢悬臂梁参数分析,讨论了影响接触面正应力的主要因素。分析结果表明,钢悬臂梁的合理设计能使钢混凝土接触面始终处于受压状态,不会出现裂缝,接触面的各项应力水平能满足钢悬臂梁从架设到长期运营期间的要求,钢悬臂梁的拓宽方法可同时应用于不需要增加桥墩的桥梁双侧或单侧拓宽改造工程。
Confronted with accidents in a shallow?buried weak tunnel using the bench excavation method,such as great subsidence and cracks in the ground surface as well as those in the preliminary support,a double downside drifts construction method was presented The drifts were used to detect geological conditions and reinforce the lower parts of the tunnel Its construction procedures and load transiting mechanism were then described Its Construction behavior was also studied by numerical simulation using software MIDAS The results show that (1) double-side drifts can improve tunnel load,the key construction step is arch ring excavation and core soil is good to keep tunnel steady; (2) weak parts mainly l
ocate at wall foot of drifts,wall foot and crown foot of tunnel,and the connections; (3) reinforcement of soil under the drifts has no apparent effect on improving rock deformation and support load Advice on construction was proposed that main parts to be reinforced are drifts (its foot depth,connection parts with tunnel,and its corners) and core soil should be kept if rock is unsteady and needs reinforcing
在研究钢芯FRP包裹束的构造和力学性能的基础上,分别对以钢芯FRP包裹束、FRP束和钢束为预应力材料的预应力混凝土梁进行全过程受力分析。结果表明,钢芯FRP包裹筋可代替钢束作为预应力筋,对梁的受力性能的影响在桥梁工程应用的许可范围内,并且采用钢芯FRP包裹筋为预应力较FRP束更为实用|钢芯FRP包裹筋具有双线性特征,预应力钢芯FRP包裹筋混凝土梁的张拉控制应力应小于钢芯FRP包裹筋的名义屈服应力|钢芯FRP包裹束的预应力混凝土梁除具有与FRP束预应力混凝土梁同样的耐久性外,还能通过改变其微结构设计,适应不同的力学性能要求。
In order to improve shield tunneling performance and provide guides for shield construction,prediction models of shield tunneling rate in alternation of mud rock and sand rock stratum of Chongqing Yangtze River tunnel were discussedBased on the field shield excavation tests,shield tunneling data were acquired by data acquisition and storage system of shield machineMeanwhile rock point load index (PLI) tests were carried out to produce rock strength parametersSubsequently,the relationships of shield tunneling rate with PLI and
thrust force of cutter wheel were studiedUpon the above data and analysis,tunneling ra
te prediction models of mud rock and sand rock strata were built by means of mul
tiple regression analysis methodThe research and application show that (1) in the two strata,the higher the rock strength,the lower the tunneling rate,and the higher the thrust force of cutter wheel,the faster the tunneling rate;(2) the relationships of tunneling rate with thrust force and point load index are all subjected to exponential functionThe models can be used conveniently with simple form,few parameters,and high precisionSimultaneously the models can also be used to perform back analysis of rock PLI only with simple t
ransposition.
A new way of anti?rutting was put forward by improving modulus of asphalt concrete and the effect of high modulus asphalt concrete (HMAT) on rutting was studied in view of mechanicsStarting from the mechanism of rutting,the mechanical property of HMAT and the effect of modulus of middle layer on rutting were analyzedThe dynamic stability and modulus of HMAC were analyzed by test,and the mechanical property of pavement structure and the mechanical response of high modulus pavement structure were analyzed by numerical calculationThe result show that (1) increase of the dynamic stability and modulus of HMAC help to against rutting;(2) the maximum shear stress occurs in middle layer of pavement structure according to mechanical calculation,HMAC can raise elastic mo
dulus of middle layerHMAC can also improve stress state of pavement structure,reduce shear strain and asphalt pavement rutting
由于曲线梁桥独特的构造特点,其振型存在"弯扭耦合"现象。为了判定曲线梁桥各阶"弯扭耦合"振型的主方向是弯曲或纯扭转,把曲线梁桥的每阶振型分解为竖向弯曲、纯扭转、横向弯曲和纵向移动4个子方向,把每阶振型的能量亦分成竖向弯曲能量、扭转能量、横向弯曲能量和沿纵向平移能量4个方向上的能量,引入4个方向参数来分别表示各子方向能量所占各阶振型能量的比值。然后从结构动力学理论知识出发,根据无阻尼系统每阶振型动能和变形能之和为常数的基本原理,推导了4个方向参数的计算公式,推导结果显示,方向系数仅为结构质量、截面几何特性和振型向量的表达式。最后提出了一种根据方向参数值的大小判定曲线梁桥各阶振型以哪个子方向为主的方法,并通过实例介绍了该方法的应用。
Following the design principle of maximum green wave bandwidth and making use of the time?space diagram for arterial road coordinate control,many problems existed in classical algebraic method such as the determination of value range of ideal intersection distance,the calculation of green wave bandwidth,the selection of optimal intersection distance and the value of signal offsets were deeply analyzed through some practical examples On the basis of detailed analysis,the value range of ideal intersection distance was determined by
the allowable value range of common signal cycle,a new calculation method for green wave bandwidth was resented,and a new selection rule of optimal intersection dista
nce was established The examples effectively demonstrate that the improved classical algebraic method can make arterial road coordinate control system get green wave bandwidth as wide as possible and obtain optimal common signal cycle and green wave bandwidth more practically and accurately
The searching region of interesting was set to cut cost time of identifying bent lane edge The parabola mode was used to fit bent lane edge According to the fact that the location of lane edge cannot break,three representative points in identified parabola were selected,forecast model was established aimed at each point Kalman filtering method was used to forecast the position of the lane edge accurately and the searching region of interesting was set consequently Parabola parameters were searched in the region of interesting based on suitable goal function,so the searched area was limited accurately in
a narrow range It is confirmed by experiments that the proposed method can sho
rten the real time of identification greatly and enhance the reliability and robustness of identification
Travel time prediction of urban networks was studiedSince urban travel times are stochastic and uncertain,a model for addressing urban travel time prediction by using transport information granular computing theory based on rough set was proposedAn urban route of Delft,the Netherlands,was selected as the test bed to test the proposed modelThe results show that (1) feed with raw data,the model produces error of 35%;(2) with data pre?processing,the model improves performance significantly;(3) the classifications of condition and decision attributes significantly influence the accuracyWith the optimal
setting of the ranges,the proposed model is able to describe traffic phenomen
a with physical meaningOverall,the accuracy is acceptable
针对西南地区岩溶隧道的实际工程,开展了隐伏岩溶群对公路隧道顶板承载力影响的三维数值敏感性分析研究。经对岩溶顶板稳定性影响因素分析,选择溶洞顶板厚度、顶板岩体的工程地质特性(定量指标为岩体的力学参数)、溶洞的宽度、溶洞高度、上覆土层厚度为影响溶洞顶板稳定性的五个主要影响因素作为影响因子,进行正交敏感性数值试验。根据影响因素敏感度的正交三维有限元法分析结果得出,影响顶板承载力和顶板中心下沉位移大小顺序依次为:岩体力学参数、顶板岩层厚度、覆盖土层厚度、溶洞宽度、溶洞高度。
In order to standardize and conduct use of road traffic signs and retro-reflective material and enhance night visibility of traffic signs,grades,categories,structures,photometric characteristics,colorimetric characteristics and relative standards of traffic signs and retro?reflective materials were analyzed to find out the relation between retro?reflectivity and night visibility of traffic signs By analyzing the use status of domestic retro?reflective materials for traffic signs currently,it is considered that the relation between night visibility and retro?reflectivity is complex Grades,categories and structures of retro?reflective materials and their arrangement in pairs or groups should be researched deeply for amendment of relative standards and criteria of traffic signs
首先,提出了基于合同模式下交叉口的通行权分配问题,根据相邻局中人之间的流量特征和服务水平,建立合同模式的讨价还价模型,并用Nash均衡效用衡量双方谈判的效果。其次,根据有效性和防策略性,证明了局中人价格策略均衡和路网流均衡的条件是所有的旅行者都遵循基于合同模式的路径选择规则,通过路网中局中人之间最终的均衡策略价格,所有的旅行者都按照自己的真实偏好选择报价总和最小的路径,从而实现系统最优和用户最优之间的协调。最后设计了求解合同模式模型的算法,并用一个算例说明了模型和算法的有效性。
For improving traffic flow forecasting precision,a forecasting method that combines nonlinear regression Support Vector Machines (SVM) with Principal Component Analysis (PCA) was proposed PCA was used to extract features from forecasting variables and produce fewer principal components These principal components were input to nonlinear regress SVM for traffic flow forecasting The kernel parameters of the SVM were determined with Bayesian inference The efficiency of the method was illustrated through analyzing Jinan urban traffic flow data Analysis results show that the traffic flow forecasting method that combines nonlinear regression SVM with PCA can not only improve forecasting precision but reduce computation cost,which can improve the real?time performance of forecasting The forecasting precision of the proposed method is higher than that of commonly used traffic flow forecasting methods
从车头间距构成的理论分析入手,考虑了跟驰时间变量和车速随机分布的特性,建立了跟驰时间模型和车头间距随机项模型,进而建立了改进的车头间距模型,在此基础上建立了改进的通行能力模型,以《HCM2000》中的高速公路临界速度数据作为评定标准标定模型的参数,并计算确定理论通行能力值,该值与《HCM2000》中的通行能力值相差很小,证明该模型能够拟和实际的道路交通流情况,同时分析了最大跟驰时间和速度均方差对通行能力的影响,最后采用城市主干道的调查数据对模型进行了标定和验证,验证结果表明,该模型经过标定后可以拟和城市道路的交通流状况,进一步说明了模型的实用性。
Based on consulting a number of literatures,the classification of brake vibrations and noises,a review of mechanisms,research methods and influence factors on break groan which has not been researched in China was presented The brake groan results from the stick?slip moving between the brake disk and pads The research methods include test research and theoretical research,and the latter can be divided into the methods of linear and nonlinear system dynamics,multi?body system dynamics and finite element analysis System friction,mechanical system parameters and power transmission system parameters are the factors that influence brake groan Finally,it is pointed out that the future research should focus on the mechanism of brake groan as well as the influence parameters in vibration source and transmission path systematically to instruct the matching and optimization of system parameters
A half-vehicle model with 4?DOF was built up In response to a nonlinear,time delay and uncertain system of vehicle suspension,an improved fuzzy PID controller of the active suspension was designed Taken SANTANA2000's suspension parameter for simulation and taken a step function as the input of simulation road,time?domain simulation in Matlab was finished The simulation result indicates that the ride comfort (such as vertical occeleration,dynamic flexibility of suspension and dynamic load of wheel ) was improved obviously by using the active suspension with improved fuzzy PID controller The time of response reach to steady state was shortened notably The active suspension with improved fuzzy PID controller is superior to the passive suspension and the simple active suspension with fuzzy controller in improving the ride comfort and maneuverability All of these advantages are of considerable referential values in development of vehicle's active suspension controller
将遗传算法应用于以SVM为弱分类器的AdaBoost算法,产生了一种识别率高,泛化能力好的强分类器,本文称之为GA-AdaBoostSVM算法。该算法先训练多个支持向量机作为弱分类器,然后用AdaBoost算法将多个弱分类器组合成一个强分类器,在组合的同时采用遗传算法对各弱分类器的权值进行全局寻优。此算法特点在于:(1)传统的Ad-aBoost算法,对所有弱分类器的权值无法给出一个最优的组合,GA-AdaBoostSVM算法用遗传算法对弱分类器的权值进行全局寻优,得到的强分类器具有更高的识别准确率。(2)为提高强分类器的泛化能力,在训练弱分类器时,合理调整RBF核的参数,使各个弱分类器在准确率和差异性之间得到折中,从而提高整合后的强分类器的泛化能力。最后,通过试验与传统AdaBoostSVM进行对比,表明GA-AdaBoostSVM的优越性。
The influence on economic benefit under the condition of self-supporting logistics,outsourcing logistics or both concomitant patterns in manufacturing enterprise was analyzed by introducing the logistics outsourcing proportion λ Considering the cost and income of self?supporting logistics and outsourcing logistics in manufacturing enterprise,the corresponding mathematical model was set up The relationship between product sale price and logistics outsourcing proportion λ was discussed,and the influences of λ on selling price,sales volume of manufacturing enterprise,profit of manufacturing/logistics enterprise and total profit were analyzed under the condition of maximizing the manufacturing enterprise's profit It is concluded by using comparative static analysis that the increase of logistics outsourcing proportion has a positive effect on improving the benefit of the manufacturing enterprise and the logistics enterprise and reducing selling price
针对传统的车辆换道模型在换道过程中存在着侧向加速度过大或产生跃变、轨迹曲率不连续以及换道过程起始时刻侧向加速度不为零的问题,以四段式车道变换理论为基础,提出一种新的车辆自由换道轨迹函数,并引入B样条理论对换道轨迹进行再规划,进而建立一种新的高速公路车辆自由换道模型。该模型能够较好的解决传统车道变换模型存在的上述缺陷。给定车辆换道轨迹性能评价参数,利用Matlab仿真计算得到新模型产生的换道轨迹,并与另外两种换道模型产生的轨迹进行对比分析。分析结果验证了该模型的正确性及有效性。
In order to assess temperature field in microwave heating for recycling asphalt pavements,a 2D mathematic heat transfer model was developed based on Fourier heat transfer theory The microwave internal heat?generation was researched by using surface field of pyramidal horn replacing approximate radiation field In addition，the boundary conditions were built and normalization processing was implemented The control volume based finite differential method (CV?BDM) was used to establish the implicit discrete scheme of the conservation
equations,and the numerical value simulation was employed By continuous or intermittent
radiation heating technique,a microwave heating experimental system at 2 145 GHz was carried out to investigate temperature variation characteristics of asphalt pavements along with heating time The result shows that (1) the increase of temperature of asphalt mixture during microwave heating is obviously nonlinear,the temperature rises slowly in the initial stage of the heating but increases rapidly in the late heating period; (2) the temperature distribution is non-uniform that the temperature in central area of the surface is higher while it is lower on edge; (3) the uniformity of temperature within asphalt mixtures can be improved by using intermittent heating technique,and the heating time must be easonable The simulation results are in preferable agreement with the experiment
针对供应商采购量与存货水平临界点数量关系的两种情况,主要研究物品无形变质与存货影响销售率现象对库存补充策略和运输费用的影响,进一步探讨库存-运输整合优化问题。在物品发生无形变质并允许缺货的条件下,建立了供应商的库存-运输整合优化模型,讨论了存货影响销售率现象对库存更新周期、订货批量、平均库存与运输总成本的影响,得到了供应商的最优库存更新周期和最佳订货批量。最后,通过算例进行实证研究,为供应商在无形变质物品的库存-运输整合决策中提供了借鉴与参考。
为合理预测公路隧道内交通噪声传播状况,界定了公路隧道内的长空间声场特性,系统阐述了3种基于像源理论的交通噪声预测模型,通过在实体隧道中测定声源分别为低频和高频、接收者在不同位置时的噪声值,并将其与三种理论模型预测值进行对比,结果表明:相干模型在低、中、高频范围内比不相干模型和ASJ模型能更精确地预测隧道内噪声传播状况,其预测值与实测值误差在2dB左右;而不相干模型和ASJ模型仅可用于预测高频段时噪声的平均值。可见,相干模型是预测以中低频为主的公路隧道内交通噪声传播的合理模型,该预测模型可用于进行公路隧道内降噪优化设计。
为岩质边坡应用植物防护提供理论依据和应用经验,结合湖北荆宜高速公路红色粉砂岩路堑边坡采用厚层基材植物防护的科研实例,采用Mont-Carlo随机模拟、室内外试验等方法,在对红色粉砂岩岩性、稳定性进行分析的基础上,研究了红色粉砂岩边坡采用厚层基材植物护坡的可行性、厚层基材植物护坡的动态机制、护坡植物选择和基材层的设计。结果表明:正常工况下红色粉砂岩边坡较稳定,但在降雨条件下冲蚀严重,稳定性降低|研究区雨水充分,岩体内部微裂隙发育,导水性强,能够提供植物生长的养分和水分,为厚层基材植物护坡提供了良好的环境;护坡过程的第3阶段为植物护坡正常、理想的工作阶段,厚层基材植物护坡能达到功能、环境和视觉的统一效应,植物的选择及基材的设计是关键;实践证明,在红色粉砂岩边坡应用厚层基材植物防护是可行的,可以大规模推广。
