沥青混合料铺装层现场模量探究-以钢桥面铺装为例

沥青混合料铺装层在荷载作用下的力学响应为铺装体系的设计提供必要的指导,在铺装层力学响应的计算中,各层模量是一个重要的输入参数。过往研究中,研究人员主要通过室内试验的方法确定铺装层混合料的模量值,但忽略了混合料的室内试验模量值与其现场模量值可能存在的偏差。针对以上问题,文章以一处钢桥面铺装工程为例,介绍一种确定沥青混合料铺装层现场模量主曲线的方法:基于不同加载工况下铺装层底部的应变实测数据,利用有限元模型对铺装层混合料的现场模量进行反算,拟合得到相应的混合料现场模量主曲线并验证其适用性。此外,将反算得到的混合料现场模量与其室内试验模量进行对比,分析两类模量之间的差异性。研究结果表明,反算得到的铺装层混合料的现场模量在不同加载工况下变化显著,其数值随加载温度的增加而减小,随加载频率的增加而增大,表现出黏弹性的特征;利用不同加载工况下的混合料现场模量值可以较好地拟合得到混合料的现场模量主曲线,且该模量主曲线经过验证后证明有效。对比铺装层混合料的单轴压缩试验模量与现场模量发现:混合料的室内模量值与现场模量值在不同加载工况下并不完全匹配,其现场模量值普遍要小于对应的室内压缩模量值;两类模量对应的模量主曲线之间也有较大偏差,在加载频率较高或较低时,主曲线间的偏差更为显著;可采用幂函数对两类混合料的室内模量进行修正,使修正后的室内模量能够反映铺装层混合料的现场模量特征。

光纤涂层老化性能研究

对四种常用的光纤涂层性能试验方法,逐一加以评价介绍,并根据试验结果,比较了几种涂层的性能特点.

Analysis and numerical simulation of indoor thermal environments in some university classrooms

In order to study the indoor thermal environments in university classrooms in Tianjin,a field study and a questionnaire survey for a main teaching building are carried out.First,the thermal sensations of participants in the typical classrooms are studied by 180 questionnaires.Then,based on the measured data,the temperature changes in the classrooms during a year are simulated by the DeST software.The results show that the indoor thermal environments in the northern classrooms on the first floor are better than those in other classrooms.And the measurement results accord with the simulation results.These results can be used as a reference for the study of the indoor thermal environments in other seasons.

Experimental and simulation investigation into the cause and treatment of rail corrugation for metro

The cause and treatment of rail corrugation for the metro have always been a popular and challenging issue. In this work, the field measurements were carried out on rail corrugation, track stiffness, and the track dynamic response. A three-dimensional finite element model was developed to investigate the cause of rail corrugation. The constraints on rail vibration from two wheelsets and adjacent wheel-rail interactions were taken into account in the model. According to experimental and simulation results, the suppression measure for rail corrugation was proposed and the suppression mechanism was discussed. It was found that the cause of rail corrugation is related to vertical and lateral vibration of the rails outside the two wheelsets at around 380 Hz. The increased stiffness of the fasteners reduces the vibration energy of the rail and the wheel-rail force. However, simply increasing the stiffness of the fasteners may not be effective in the suppression of rail corrugation. If necessary, the rails need to be grinded to reduce the roughness to a certain level, so that increasing the fastener stiffness can effectively suppress the rail corrugation.

Preliminary validation of SMOS sea surface salinity measurements in the South China Sea

The SMOS(soil moisture and ocean salinity) mission undertaken by the European Space Agency(ESA) has provided sea surface salinity(SSS) measurements at global scale since 2009.Validation of SSS values retrieved from SMOS data has been done globally and regionally.However,the accuracy of SSS measurements by SMOS in the China seas has not been examined in detail.In this study,we compared retrieved SSS values from SMOS data with in situ measurements from a South China Sea(SCS) expedition during autumn 2011.The comparison shows that the retrieved SSS values using ascending pass data have much better agreement with in situ measurements than the result derived from descending pass data.Accuracy in terms of bias and root mean square error(RMS) of the SSS retrieved using three different sea surface roughness models is very consistent,regardless of ascending or descending orbits.When ascending and descending measurements are combined for comparison,the retrieved SSS using a semi-empirical model shows the best agreement with in situ measurements,with bias-0.33 practical salinity units and RMS 0.74.We also investigated the impact of environmental conditions of sea surface wind and sea surface temperature on accuracy of the retrieved SSS.The SCS is a semi-closed basin where radio frequencies transmitted from the mainland strongly interfere with SMOS measurements.Therefore,accuracy of retrieved SSS shows a relationship with distance between the validation sites and land.

Investigation of Key Parameters for 3-D Dredging Plume Model Validation

Dredging plume dispersion studies, use dredging plume models to predict the fate of sediment plumes resulting from dredging activities and dredge spoil disposal. The model results are applied as input to environmental impact assessment of the proposed dredging, particularly those associated with suspended sediments and sedimentation. Model validation and performance are still not resolved because of the difficulty of site measurements and the understanding of the parameters used in the model. This paper presents a 3-D dredging plume model based on the MIKE3 software package to investigate parameters which affect the model performances. As a result of lack of site data for the public domain uses, the model scenarios are designed artificially for sensitive runs to identify the key parameters affecting plume behaviours. The factors include dredging spill rates using different dredging methods, equipment and sediment settling velocities. The influence of wave and wind effects combined with tidal forces on the sediment re-suspended rates and the advection/dispersion scales are also assessed.

Migration law of respirable dust on a super-long fully mechanized double-shearer working face

In order to understand the migration law of respirable dust and gain reasonable design parameters for dust control on a super-long double-shearer fully mechanized working face, this paper describes research carried out using a numerical simulation package(Fluent) based on gas-solid coupling dispersed multiphase flow model and field measurement to research different technology modes, dust distribution law at different intervals where shearers work in opposite directions on the lower 9303 face, No. 2 Jining Mine,Yankuang Coal Mining Co. Results show that the concentration of dust 3–6 m away from the shearers working in the same directions was large, while the impact area of respirable dust near the shearer increased significantly to 5–6 m with the distance between two shearers working in opposite directions.The concentration of dust on a double-shearer face was considerably higher than that of a face with one shear under the combined effect of wind speed on the face and disturbed wind around the shearer, while the dust concentration near the shearer on the return side was considerably higher than that on the inlet side. The concentration of dust on a double-shearer face along the airflow declined slowly so that dust was hard to control. Simulation results confirmed the results of field measurement, which could provide reference for dust prevention design.

Macroeconomic Impacts of Contemporary Electricity Reform： 19 OECD and Seven Australian States

This paper examines the impacts of market-oriented electricity reform on macroeconomic variables. It develops an ad hoc econometric model for this purpose, using a panel data of 19 developed countries plus seven Australian States for the period of 1970-2008. Significance of the impacts is firstly tested against three distinct institutional features of electricity reform, namely： （1） organizational restructuring （i.e., functional unbundling of traditionally vertically integrated industry）; （2） market restructuring （introduction of mandatory bid-based spot market）; and （3） privatization. The extents of the impacts are, then, quantified in terms of relative contribution of such institutional changes to aggregate output growth in short-run, medium-run and long-run. The results reveal that only functional unbundling has made significant contribution to output growth. The results, further, specify that functional unbundling has made, on average, an additional 0.06% and 2.7% contribution to output growth rate in medium-run and long-run respectively.