Modeling Measured 3D Tire Contact Stresses in a Viscoelastic FE Pavement Model

Three‐dimensional (3D) contact stresses occurring between the road surface and the tire that were measured with the South African Vehicle Road Surface Pressure Transducer Array (VRSPTA) device under a moving wheel are transformed to a corresponding force/stress pattern representing the actual contact stress state under the tire by means of a software program. In combination with a dynamic load function such force patterns derived from these Stress‐in‐Motion (SIM) measurements with the VRSPTA device are used to introduce a more advanced load representation of the tire‐pavement interface into a three‐dimensional (3D) finite element (FE) model. Further, a method is presented to derive viscoelastic material properties of asphalt concrete (AC) mixes from dynamic frequency sweep shear (FS‐S) tests of lab specimens or field cores that can be used to define material behavior of the AC layers in the 3D FE pavement model. Linear elastic layered theory is utilized to validate the results of the FE computations in order to demonstrate that the FE method can successfully be used to include SIM measurements for more advanced analysis and design of pavements. First results of the 3D FE simulation of a load circle of the Heavy Vehicle Simulator (HVS) during accelerated pavement testing of a pavement test section are presented. These results encourage employment of the FE pavement model for further simulation work to assess the rutting potential of AC mixes in combination with different tire types and loading situations.     

Spectral Analysis and Parametric Study of Stochastic Pavement Loads

This paper investigates the effects of vehicle parameters, speed, and surface roughness on the power spectral density (PSD) of stochastic pavement loads. Pavement surface roughness is modeled as a zero-mean stationary random field. A quarter-vehicle model is established to simulate the vibrations of heavy and passenger vehicles with typical parameters. Tire damping is also included in the consideration of stochastic pavement loads; this was assumed to be zero in many previous investigations. The PSD roughness proposed by the ISO is adopted in the simulation of the loads. An important indicator of the stochastic loads, the so-called energy cumulative distribution function, is introduced to describe the frequency distribution of load energy. The results show that passenger vehicles produce more high-frequency loads than heavy vehicles, while more of the loads generated by heavy vehicle are primarily distributed in the low-frequency region. It is also found that the effect of tire damping on stochastic pavement loads is not negligible especially if the loads of interest are concentrated in the high-frequency region. The results of the study may be useful in optimum design of vehicle suspensions and prediction of dynamic pavement response.     

Laboratory and Field Performance of Cellular Fiber-Reinforced Polymer Composite Bridge Deck Systems

This paper addresses the laboratory and field performance of multicellular fiber-reinforced polymer (FRP) composite bridge deck systems produced from adhesively bonded pultrusions. Two methods of deck contact loading were examined: a steel patch dimensioned according to the AASHTO Bridge Design Specifications, and a simulated tire patch constructed from an actual truck tire reinforced with silicon rubber. Under these conditions, deck stiffness, strength, and failure characteristics of the cellular FRP decks were examined. The simulated tire loading was shown to develop greater global deflections given the same static load. The failure mode is localized and dominated by transverse bending failure of the composites under the simulated tire loading as opposed to punching shear for the AASHTO recommended patch load. A field testing facility was designed and constructed in which FRP decks were installed, tested, and monitored to study the decks’ in-service field performance. No significant loss of deck capacity was observed after more than one year of field service. However, it was shown that unsupported edges (or free edges) are undesirable due to transitional stiffness from approach to the unsupported deck edge.     

Effectiveness of Scrap Tire Chips as Sorptive Drainage Material

Scrap tire disposal is a problem of growing concern. One solution to this problem is innovative methods for the reuse and recycling of scrap tires. Based on batch isotherm tests, scrap tire chips have been identified to be good sorbents of volatile organic compounds (VOCs) and could be used as leachate drainage layer material in solid waste landfills and in other similar applications. To demonstrate the effects of tire chips on the leachate they come in contact with in a drainage layer over a liner, large-scale tank tests simulating the drainage layer and the clay liner and also field tests were performed. Two cells were constructed in a landfill: one with scrap tire chips and the other with gravel leachate collection layer. According to the results of the large-scale tank tests and field tests, shredded tire chips have a significantly positive impact on the quality of the leachate with which they come in contact. The use of scrap tires in landfills would reduce the magnitude of the current tire disposal problem (a 1 ha landfill requires approximately 300,000 tires to fill 0.3 m of a leachate collection layer) and convert one waste into a beneficial construction material and simultaneously mitigate the problem of VOC transport from through landfill liners.     

Undrained Bearing Capacity of Two-Strip Footings on Spatially Random Soil

A probabilistic study on the interference of two parallel rough rigid strip footings on a weightless soil with a randomly distributed undrained shear strength performed. The problem is studied using the random finite element method, where nonlinear finite element analysis is merged with random field theory within a Monte Carlo framework. The variability of undrained shear strength is characterized by a lognormal distribution and an exponentially decaying spatial correlation length. The estimated bearing capacity statistics of isolated and two footings cases are compared and the effect of footing interference discussed. Although interference between footings on frictionless materials is not very great, the effect is shown to be increased by soil variability and spatial correlation length.     

软接触结晶器连铸实验与电磁场分析

软接触结晶器连铸准三维电磁场数值模拟,结合锡等低熔点金属的软接触连铸实验,分析了软接触结晶器连铸中电磁场频率及感应圈电流等与铸坯表面磁感应强度、电磁力及电磁压力的关系。     

熔融Sn-3.0Ag-0.5Cu在倾斜铜基板上表面形貌的模拟

通过润湿性实验,借助有限元软件Surface Evolver模拟研究了在490 K温度下熔融态的无铅焊料Sn-3.0Ag-0.5Cu在倾斜铜基板上的铺展行为及界面特性.根据经验方程拟合熔滴侧面轮廓曲线并获得三相点处的接触角大小.经计算发现,在基板的倾斜角度较小时,三相接触线几乎不发生移动,三相接触线的后三相点沿基板向前移动,前三相点保持不动,相应地,前进角逐渐增大并达到最大值.随着基板倾斜角度的继续增大,前三相点开始向前移动,导致前进角逐渐减小,最终熔滴从基板上滑落.通过模拟铺展过程表征了接触角的滞后现象;通过SEM及EDS手段分析界面微观结构,说明了在润湿过程中发生了界面化学反应,确定了金属间化合物Cu6Sn5生成并呈扇贝形分布.     

Conformable Tire Patch Loading for FRP Composite Bridge Deck

Fiber-reinforced polymer (FRP) composites are increasingly being used in bridge deck applications. However, there are currently only fledgling standards to design and characterize FRP deck systems. One area that should be addressed is the loading method for the FRP deck. It has been observed that the type of loading patch greatly influences the failure mode of a cellular FRP deck. The contact pressure distribution of a real truck loading is nonuniform with more concentration near the center of the contact area as a result of the conformable contact mechanics. Conversely, the conventional rectangular steel patch on a FRP deck act like a rigid flat punch and produces stress concentration near the edges. A proposed simulated tire patch has been examined for loading a cellular FRP deck with the load distribution characterized by a pressure sensitive film sensor and three-dimensional contact analysis using ANSYS. A loading profile is proposed as a design tool for analyzing FRP deck systems for strength and durability. Local top surface strains and displacements of the cellular FRP deck are found to be higher with proposed loading profile compared to those for the conventional uniformly distributed loading. Parametric studies on the deck geometry show that the global displacement criterion used for characterizing bridge deck is inadequate for a cellular FRP deck and that the local effects must be considered.     

用流函数分析平面轧制问题

给出了一种用流函数求解理想刚塑性材料的平面应变轧制的方法。速度场被分解为基础速度场和附加速度场。基础速度场满足边界上给定的速度条件,附加速度场满足齐次边界条件。与这两部分速度场相对应,有基础流函数和附加流函数。基础流函数可以确定地写出,附加流函数则借助于Weierstrass定理写成完备空间的向量族,即多项式。通过使全功率极小化,可以将多项式系数确定。用这一方法求得了速度场、应力场、塑性区前后边界,接触弧上中性点的位置和轧制单位压力,并与工程方法的计算结果作了比较。     

Simultaneous determination of thiabendazole and its major metabolite, 5-hydroxythiabendazole, in bovine tissues using gradient liquid chromatography with thermospray and atmospheric pressure chemical ionisation mass spectrometry

Modification of an existing neural structure to support a second function will produce a trade-off between the two functions if they are in some way incompatible. The trade-off between two such sensory functions is modeled here in pyramidal neurons of the gymnotiform electric fish's medullar electrosensory lateral line lobe (ELL). These neurons detect two electric stimulus features produced when a nearby object interferes with the fish's autogenous electric field: (1) amplitude modulation across a cell's entire receptive field and (2) amplitude variation within a cell's receptive field produced by an object's edge. A model of sensory integration shows that detection of amplitude modulation and enhancement of spatial contrast involve an inherent mechanistic trade-off and that the severity of the trade-off depends on the particular algorithm of sensory integration. Electrophysiology data indicate that of the two algorithms for sensory integration modeled here for the gymnotiform fish Brachyhypopomus pinnicaudatus, the algorithm with the better trade-off function is used. Further, the intrinsic trade-off within single cells has been surmounted by the replication of ELL into multiple electrosensory map segments, each specialized to emphasize different sensory features.     

Bearing Capacity of Rough Rigid Strip Footing on Cohesive Soil: Probabilistic Study

A probabilistic study on the bearing capacity of a rough rigid strip footing on a weightless cohesive soil is carried out to assess the influence of randomly distributed undrained shear strength. Nonlinear finite element analysis is merged with random field theory in conjunction with a Monte Carlo method. In a parametric study, the mean shear strength is held constant while the coefficient of variation and spatial correlation length of cohesion are varied systematically. The influence of the spatial variation of cohesion on the mean bearing capacity is discussed. The results are also presented in a probabilistic context to determine the probability of failure. A comparison between rough and smooth footing conditions is also made.     

Muscarinic elicitation of EEG asymmetry in freely moving rats

A method for determining whether structures distributed along a cell's membrane represent a random spatial distribution is presented in this paper. Two three-dimensional (3-D) images are acquired from one cell by wide-field digital imaging of cells which have been labeled with two different fluorescent antibodies. Prior to spatial analysis, a constrained regularized least squares restoration of the images is performed. This is followed by registration via fiducial markers (dual-labeled beads). A deformable model is then used to map data near the surface to the surface. Finally, each resulting data set is analyzed to determine whether it is spatially random. To do this, we generalize the test for complete spatial randomness of points in a plane, to test voxels distributed along a voxelized membrane in three dimensions. We also test whether the distribution of one protein is independent of the distribution of a second protein. The method is applied to compare the distribution of the protein kinase C to that of vinculin. Vinculin is a protein which anchors intracellular filaments to the cell's plasma membrane. It is also used as a (sparse) membrane marker for the deformable model. Protein kinase C facilitates molecular motors inside the cell. These may be associated with actin and myosin filaments.     

Allelic diversity at the merozoite surface protein-1 locus of Plasmodium falciparum in clinical isolates from the southwestern Brazilian Amazon

A rapid dynamic imaging technique based on polar k-space sampling is presented. A gain in temporal resolution is achieved by angular undersampling. A detailed analysis of the point spread function of angular undersampled polar imaging reveals a reduced diameter of the corresponding circular field of view. Under the assumption that dynamic changes are restricted to a local circular field of view, angular undersampled dynamic imaging allows the recording of rapid changes at high temporal and spatial resolution. The theoretical and experimental details of the technique are presented.     

Transient thermal model of the continuous single-wheel thin-strip casting process

A transient heat-transfer model (STRIP1D) has been developed to simulate the single-roll continuous strip-casting process. The model predicts temperature in the solidifying strip coupled with heat transfer in the rotating wheel, using an explicit finite difference procedure. The model has been calibrated using strip thickness data from a test caster at ARMCO Inc. (Middletown, OH) and verified with a range of other available measurements. The strip/wheel interface contact resistance and heat transfer were investigated in particular, and an empirical formula to calculate this heat-transfer coefficient as a function of contact time was obtained. Wheel temperature and final strip thickness are investigated as a function of casting speed, liquid steel pool depth, superheat, coatings on the wheel hot surface, strip detachment point, wheel wall thickness, and wheel material.     

Influence of Optimized Tire Shreds on Shear Strength Parameters of Sand

This paper presents the usefulness of optimizing the size of waste tire shreds on shear strength parameters of sand reinforced with shredded waste tires. A relatively, uniform sand has been mixed with randomly distributed waste tire shreds with rectangular shape and compacted at 2° of compaction. Waste tire shreds were prepared with a special cutter in three widths of 2, 3, and 4?cm and various lengths for each shred width. Three shred contents of 15, 30, and 50% by volume were chosen and mixed with the sand to obtain a uniformly distributed mixture. In order to compare the shear strength of different sand–tire shred samples, two compaction efforts in terms of sand matrix unit weights of 15.5 and 16.8?kN/m3 were considered. The results show that the influencing parameters on shear strength characteristics of sand–shred mixtures are normal stress, sand matrix unit weight, shred content, shred width, and aspect ratio of tire shreds. With the selected widths of shreds, compaction efforts, shred contents, and the variations of aspect ratios, it is possible to increase the initial friction angle ?1 up to 113.5%, that is ?1 = 67°. The average value for the influence of aspect ratio variations on increase in friction angle of the mixtures for all tests has been found to be about 25%. These average values for lower and higher compacted samples containing different widths and aspect rations were 37.6 and 17.2%, respectively. It has been investigated that for a given width of tire rectangular shreds, there is solely a certain length, which gives the greatest initial friction angle for sand–tire shred mixtures. This is the main contribution of this paper.     

Field Evaluation of a Leachate Collection System Constructed with Scrap Tires

Landfilling costs and the potential uses of scrap tires have prompted researchers to investigate beneficial reuses. One important application is the use of tire chips as a leachate collection material in municipal solid waste landfills. Laboratory and field studies were conducted to investigate the performance of tire chips as a drainage medium in landfills. The laboratory portion of the program included a series of hydraulic conductivity and compressibility tests. Two field test cells, one with tire chips and another with gravel as the control, were constructed. The tire-chip cell was instrumented with flowmeters, thermistors, and gas collection devices to evaluate the hydraulic performance as well as the potential for spontaneous combustion. Leachate collected from the two cells was analyzed to determine if tire chips would potentially contaminate the groundwater. The results indicated that adequate drainage conditions were present within the tire-chip layer. The presence of insignificant quantities of carbon monoxide, and the lack of oxygen, and recorded low temperatures suggested that a combustion hazard was not present. The field leachate data indicated that tire chips can be safely used as part of a landfill leachate collection layer, even though it may not be suitable to place them near drinking water sources.     

Probabilistic Analysis of Coupled Soil Consolidation

Coupled Biot consolidation theory was combined with the random finite-element method to investigate the consolidation behavior of soil deposits with spatially variable properties in one-dimensional (1D) and two-dimensional (2D) spaces. The coefficient of volume compressibility (mv) and the soil permeability (k) are assumed to be lognormally distributed random variables. The random fields of mv and k are generated by the local average subdivision method which fully takes account of spatial correlation, local averaging, and cross correlations. The generated random variables are mapped onto a finite-element mesh and Monte Carlo finite-element simulations follow. The results of parametric studies are presented, which describe the effect of the standard deviation, spatial correlation length, and cross correlation coefficient on output statistics relating to the overall “equivalent” coefficient of consolidation. It is shown that the average degree of consolidation defined by excess pore pressure and settlement are different in heterogeneous soils. The dimensional effect on the soil consolidation behaviors is also investigated by comparing the 1D and 2D results.     

帘线钢凝固过程夹杂物生成热力学及工业实践

 非金属夹杂物是影响帘线钢拉拔性能的重要因素之一,为了研究帘线钢中夹杂物的生成及转变机理,使用ASPEX自动扫描电镜观察分析了帘线钢工业生产过程中不同碱度条件下从钢液到铸坯中非金属夹杂物的转变现象,并使用FactSage7.0热力学计算软件对非金属夹杂物的转变机理进行了讨论。在高碱度条件下,钢液中非金属夹杂物主要类型为低熔点的CaO-SiO₂-Al₂O₃-MnO,铸坯中非金属夹杂物的CaO和MnO含量有所降低,同时SiO₂含量有所增加。在低碱度炉次中,钢液中非金属夹杂物主要为较高熔点的SiO₂-MnO-CaO类型,Al₂O₃含量较低。连铸坯中非金属夹杂物的SiO₂含量与钢液相比有所增加,同时MnO含量降低。热力学计算结果表明,帘线钢凝固和冷却过程中的非金属夹杂物转变由夹杂物自身的相转变和析出、非金属夹杂物和钢液间的化学反应以及溶解氧和钢基体化学成分的反应3方面原因造成。热力学计算结果较好地解释了帘线钢工业生产中钢液和铸坯中非金属夹杂物成分和形貌的转变,为帘线钢中非金属夹杂物的控制提供参考。     

Motion integration with dot patterns: effects of motion noise and structural information

To better understand how local motion detectors merge their responses so as to permit the global determination of objects' movements in the visual field, direction discrimination of performance was measured using a flexible class of moving dots--two sets of dots translating sinusoidally 90 deg out of phase along orthogonal axes. When dots' velocities are combined, a global motion along a circular trajectory emerges, clockwise or counter-clockwise depending on the sign of the phase lag. However, the results of the present experiments indicate that dot patterns are segregated into distinct, but interacting, streams when each dot motion can be accurately determined. In contrast, perceptual coherence of the global motion occurs when each local motion signal is "blurred" by a "motion noise". Direction discrimination performance then increases regularly with both noise amplitude and noise frequency, i.e., noise speed. Performance also increases when relative motion between dots is added. Testing different dot configurations indicates that performance is better for spatial arrangements that display structural properties (a square shape), as compared to overlapping random distributions. Interestingly, when the delay between stimulus onset and motion onset increases up to 300 msec, performance improves when dot patterns convey come form of structural organization but not when the dots are distributed at random. Relations of these results to existing models of motion integration are considered.     

The effect of thermal contact resistance on the solidification process of a pure metal

The role of thermal contact resistance between a casting and a metal mold, as well as the effect of natural convection in the melt during solidification of a pure metal, is numerically studied. Numerical simulation is performed for a two-dimensional rectangular cavity using the coordinate transformation by boundary-fitted coordinate, and pure aluminum is used as the phase-change material. The influ-ences of thermal contact resistance on the interface shape and position, solidified volume fraction, streamlines, temperature field, and the local heat transfer are investigated.