浅议超高层办公建筑的功能与设施

城市办公综合体因强大的综合功能和创造财富的能力为各国所青睐,其设计是极其复杂且具挑战性的项目,但也有一定的普遍规律。本文针对摩天楼的背景、超高层办公综合体的功能分布、办公层的标准模式及超高层办公综合体的若干配套设施等问题,进行较详细的分析和论述。     

PVC基磁流变弹性体的制备及性能表征

制备了以聚氯乙烯(PVC)糊树脂为基体的磁流变弹性体(MRE);研究了其静态力学性能、动态力学性能、SEM形貌和热降解性能.实验结果表明:PVC基磁流变弹性体的断裂强度随铁粉含量呈现出先上升后下降的趋势,磁致模量、相对磁流变效应和损耗因子均随铁粉含量的增加而增大,损耗因子几乎不依赖于磁场强度.当铁粉质量分数为80％时,最大磁致模量为1.06 MPa,损耗因子最大为0.35.TGA结果说明:随着铁粉含量的增加,PVC基MRE的热降解趋势增强.     

基于Birgé-Massart阈值的烟气发电机组状态特征弱信息提取方法

烟气发电机组是石油化工行业中的一种高速旋转大型机械,用于将催化裂化再生烟气中具有的能量转变成机械能。为保证机组安全、稳定运行而进行的运行状态监测,需解决机组在大量背景噪声下状态特征弱信息提取的问题。为此研究基于Birgé-Massart惩罚函数策略获取阈值的信号小波变换模极大值抑制噪声算法。由Birgé-Massart惩罚函数策略获取阈值,在小波变换不同分解尺度上构建不同的模极大值点邻域来影响模极大值点搜索过程,获得小波分解各尺度上合适的模极大值点序列,凸显状态特征信息,利用Mallat的交错投影法重构信号。为验证该算法的有效性,将该算法与Rigrsure、Sqtwolog、Heursure、Minimaxi四种阈值抑噪方法进行比较,结果表明该算法具有更好的信噪比和方均根误差。应用该算法对现场采集的振动信号进行状态特征弱信息提取处理,结果表明处理后的信号在保留突变点的同时,具有良好的光滑性,可以用来进行烟气发电机组状态特征信息的提取。     

刚玉骨料种类与粒度对刚玉-莫来石材料抗热震性的影响

以莫来石和电熔白刚玉或板状刚玉为骨料,氧化铝粉、氧化硅粉、红柱石粉为基质料,纸浆为结合剂,同时以≤0.15 mm(100目)的刚玉细骨料取代较粗(1～0.15 mm或0.5～0.15 mm)的刚玉骨料,制备了2个系列、不同粒度级配的刚玉-莫来石试样,并分别以抗折强度保持率和弹性模量保持率为评价指标,研究了刚玉骨料种类和粒度对刚玉-莫来石材料性能的影响。结果表明:1)分别以白刚玉和板状刚玉为骨料时,刚玉-莫来石材料热震后的弹性模量保持率与抗折强度保持率并不完全一致;2)以≤0.15 mm骨料代替较粗骨料,虽能提高材料强度,但可能会降低其抗热震性能。分析认为:刚玉-莫来石材料抗临界危险裂纹扩展能力与材料热震强度保持率一致,相对于弹性模量保持率,以强度保持率作为此类材料抗热震性的评价标准更为合适;由于板状刚玉骨料周围残余应力的存在,热震实验后以板状刚玉为骨料的刚玉-莫来石材料具有更高的抗折强度保持率。     

Railroad track modulus estimation using ground penetrating radar measurements

Track defects and failures resulting from weak strength and buckling cause many of the railroad accidents. One parameter that greatly affects track performance and safety is the track vertical modulus, which is a measure of the vertical stiffness of the rail foundation. Current techniques for track modulus measurement, while accurate, are time-consuming, labor-intensive, require track closure, and provide only single-point information. Ground penetrating radar (GPR) is a non-destructive and non-invasive technology that has shows great potential for imaging subsurface features and assessing the integrity of track substructure. The technique is based on the principles of electromagnetic wave reflection from and transmission through distinct layers of varying dielectric properties. A single electromagnetic pulse of energy at an appropriate frequency is launched into the ground, and reflections from various subsurface layers are recorded in the form of an image. Since studies have shown that the electrical properties of base course aggregates can be used to infer their strength properties, we hypothesize that the information on the track substructure layering characteristics can be used to indirectly infer track modulus. Using a comprehensive set of coincident GPR and track modulus measurements acquired over various types of railroad track geometries, a multivariate linear regression model has been developed. Our analysis reveals a consistent relationship between the weighted average of subsurface 400 MHz GPR reflectivities at specific depths to the measured track modulus with an accuracy of better than approximately 3.4 MPa (500 lb/in./in.). The model is thus able to predict track modulus from GPR measurements, and would considerably reduce the time and expense of operational track maintenance strategies.     

Tensile strength and microstructure of Al2O3-ZrO2 hypo-eutectic fibers

Al₂O₃-ZrO₂(Y₂O₃) eutectic materials possess good fracture strengths and creep resistance. Increased Al₂O₃ content is one means to further improve creep resistance. The objective of this study is to examine fracture strength of Al₂O₃-rich (hypoeutectic) compositions at varying Y₂O₃ contents. Fibers 160-220 μm in diameter with 68 m/o Al₂O₃ and 1.1-7.6 m/o Y₂O₃ (30.5 to 16 m/o ZrO₂) were directionally solidified at 0.11 mm/s using the laser-heated float-zone process. Defect populations increased in size and severity with higher Y₂O₃ contents. However, fibers maintained 1 GPa fracture strength in the presence of numerous pores and shrinkage cavities, which extend with crack-like morphology along the fiber axis.     

Non-linear viscoelastic behaviour and modulus recovery in silica filled polymers

The viscoelastic properties of different silica filled polymers were investigated. A variety of rheological observations was studied in the molten state, such as Payne effect and modulus recovery kinetics, in ethylene vinyl acetate, polystyrene and polypropylene filled with non-porous silica. The concept of the filler network breakdown seems to be adequate in describing the strain-dependence of dynamic mechanical properties of composites. Recovery tests of the complex shear modulus performed by subsequent strain sweep or time sweep experiments show evidence that the initial equilibrium network structure cannot completely restore within several hours. Furthermore, new strain sweep experiment after in situ crystallisation (or glass transition in polystyrene composites) of the sample leads to a total recovery of the linear modulus suggesting that the silica network structure in molten state have the memory of the silica structure in solid state. On the other hand, the complex shear modulus measured at lower strain for cross-linked EVA composites are perfectly recoverable in few seconds as proven by subsequent strain sweeps.     

提高日用陶瓷制品机械强度的探讨

根据日用陶瓷制品破坏的原因,采取合理的工艺控制措施,提高其弹性模量和断裂表面能,减小内部裂纹尺寸,可以提高其机械强度,适应机械洗刷的要求。     

陶瓷砖断裂模数测量结果的不确定度评定

对陶瓷砖断裂模数测量不确定度的来源进行了分析,并对各不确定度分量进行了分析和量化,求得合成标准不确定度和扩展不确定度分别为10.04%和20.08%。     

Load-settlement behaviour of a strip footing resting on iron ore tailings as a structural fill

This study presents a laboratory investigation of load-settlement behaviour of a strip footing resting on iron ore tailings used as a structural fill.The footing was placed at various depths in the tailings bed.The relative density of the tailings was varied as D_r = 50%,70%and 90%.An incremental load was applied on the footing while observing the settlement until the failure took place.The results obtained for tailings were compared with those for the sandy soil.It is observed that the load-bearing capacity and stiffness increase with an increase in footing embedment depth and relative density.Compared to load-settlement behaviour of Perth sandy soil,the tailings fill could have as high as 22 times and 13.5 times the load-bearing capacity and stiffness,respectively.Therefore,the replacement of sandy soil with iron ore tailings for structural fills is cost-effective,and moreover,this application contributes to environmental sustainability in construction.