空心板抗弯强度计算的直接电算法和试算法

传统的空心板抗弯强度计算存在误差。为避免这一误差,本文讨论了直接电算求解法和试算法,并给出了相应的程序语句和计算实例。

预应力混凝土空心板竹劈子内模

竹劈子内模的投资少,强度高、适应变形、拆装方便。

Facile template-induced synthesis of Ag-modified TiO_2 hollow octahedra with high photocatalytic activity

Noble metal/titania hollow nanomaterials usually exhibit excellent photocatalytic activity because of their high specific surface area,low density,good surface permeability,strong light-harvesting capacity,and rapid interfacial charge transfer. However,the present preparation methods usually include complicated and multistep procedures,which can cause damage to the hollow nanostructures. In this paper,a facile template-induced synthesis,based on a template-directed deposition and in situ template-sacrificial dissolution,was employed to prepare Ag-modified TiO 2（Ag/TiO 2） hollow octahedra using Ag2 O octahedra as templates and TiF 4 as the precursor. In the synthetic strategy,the shells of TiO 2 hollow octahedra were formed by coating TiO 2 nanoparticles on the surface of Ag2 O templates based on the template-directed deposition. Simultaneously,the Ag2 O templates can be in situ removed by dissolving the Ag2 O octahedral template in HF solution produced via the hydrolysis reaction of TiF 4 in the reaction system. In addition,Ag nanoparticles were deposited on the inside and outside surfaces of TiO 2 shells by effectively using the photosensitive properties of Ag2 O and Ag＋ ions under light irradiation,along with the formation of TiO 2 hollow octahedra. The Ag/TiO 2 hollow octahedra exhibited high photocatalytic activity because of their（1） short diffusion distances between photogenerated electrons and holes because of the thin shells of Ag/TiO 2 hollow octahedral,（2） deposition of Ag nanoparticles on the inside and outside surfaces of TiO 2 shells,and（3） rapid interfacial charge transfer between TiO 2 shells and Ag nanoparticles. This work may also provide new insights into preparing other Ag-modified and hollow nanostructured photocatalysts.

Preparation of Manganese Oxide Hollow Spheres Using pH-responsive Microgels as Templates

Manganese oxide hollow spheres were prepared by a novel and facile approach using pH- responsive microgels as templates. The final products were thoroughly characterized with X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared, and transmission electron microscopy. The results reveal that the shell thickness of manganese oxide hollow spheres increased with the dosage of KMnO4, which implies that a controllable and feasible strategy for manganese oxide hollow spheres prepa- ration has been established. Further studies on the microgels template showed some of them had an irreversible swelling/deswelling transition due to the uneven cross-link extent. Based on the results, a probable formation mechanism for the hollow spheres was proposed.

Fabrication of TiO_2 hollow microspheres using K_3PW_(12)O_(40) as template

Fabrication of TiO 2 hollow microspheres（TiO 2-HMSs） has attracted considerable attention owing to their low density,high photoreactivity,and easy to separate and reuse. A fluoride-free method for the fabrication of TiO 2-HMSs is reported by refluxing a mixed solution of H3PW12O40（0.4 mmol）,KCl（2.5 mmol） and Ti（SO4）2（2–25 mmol） at 125 °C for 8 h,followed by decomposition of the K3PW12O40（KPW） template in basic solution. The prepared TiO 2-HMSs are characterized by X-ray diffraction,transmission electron microscopy,scanning electron microscopy,Fourier transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The activities of the photocatalysts are evaluated by photocatalytic degradation of Brilliant Red X-3B,an anionic dye,under UV irradiation. It is observed that the TiO 2-HMSs exhibit diameters of approximately 0.5–1 μm,and the photocatalytic activity of TiO 2-HMSs initially increases and then decreases with an increasing amount of Ti（SO4）2. The TiO 2-HMSs prepared in the presence of 4 mmol Ti（SO4）2 exhibit the highest photocatalytic activity,which is 2.1 times higher than TiO 2 nanoparticles（prepared in the absence of the KPW template）. The enhanced photocatalytic activity of the prepared TiO 2-HMSs is ascribed to the improved crystallization,coupling effect between TiO 2and the residual KPW template,and the unique hollow structures of TiO 2-HMSs.

Numerical simulation and experimental study on constant amplitude fatigue behavior of welded cross plate-hollow sphere joints

In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula,the WCPHSJs were fatigue tested.A total of 19 specimens were tested under constant amplitude fatigue loads using a specially designed test rig.The joint was analyzed statically by t e finite element analysis(F3A),and metallographic analysis of fatigue fracture was done by the electron scanning microscope.Numerical simulation and experimental results show that the hot-spot of WCPHSJ lies at the weld toe location where severe stress is concentrated.Fatigue cracks initiate at the weld toe and then propagate circumferentially around the sphere with a diameter equivalent to the width of the cross plate up to the fatigue facture.The initial welding defects and constructional detail constitute the main factor of fatigue failure.The S-N curves for the joints were developed through a linear regession analysis of fatigue data.A formula for calculating constant amplitude fatigue,base on the concept of the hot spot stress amplitude,is proposed.

Full-scale model tests and nonlinear analysis of prestressed concrete simply supported box girders

Full-scale model tests were carried out on a 30 m span prestressed concrete box girder and a 20 m span prestressed concrete hollow slab. Failure models were prestressed reinforcement tensile failure and crashing of roof concrete, respectively. The ductility indexes of the box girder and hollow slab were 1.99 and 1.23, respectively, according to the energy viewpoint. Based on the horizontal section hypothesis, the nonlinear computation procedure was established using the limited banding law, and it could carry out the entire performance analysis including the unloading, mainly focusing on the ways to achieve the unloading curves computation through stress-strain, moment-curvature and load-displacement curves. Through the procedure, parameters that influence on the bearing capacity, deformation performance and ductility of the structures were analyzed. Those parameters were quantity of prestressed reinforcement and tension coefficients of prestressed reinforcement. From the analysis, some useful conclusions can be obtained.

各种桥梁、涵洞工程

U448.121 9908256芜湖长江大桥设计与关键技术研究〔刊〕/林国雄,方秦汉,秦顺全…∥桥梁建设.—1998,(4).—1～8

SnO_2 hollow spheres:Polymer bead-templated hydrothermal synthesis and their electrochemical properties for lithium storage

SnO2 hollow spheres have been synthesized via a facile hydrothermal method using sulfonated polystyrene beads as a template followed by a calcination process in air.X-ray diffraction,scanning electron microscopy,and transmission electron microscopy show that the as-obtained SnO2 hollow spheres have a wall thickness of about 50 nm,and consist of nanosized SnO2 particles with a mean diameter of about 15 nm.Electrochemical measurements indicate that the SnO2 hollow spheres exhibit improved electrochemical performance in terms of specific capacity and rate capability in comparison with commercial SnO2 when used as anode materials for lithium-ion batteries.The enhanced performance may be attributed to the spherical and hollow structure,as well as the building blocks of SnO2 nanoparticles.

Propagation properties of controllable dark-hollow beams through fractional Fourier transform systems

Based on the definition of fractional Fourier transform(FrFT) in the cylindrical coordinate system,the propagation properties of a controllable dark-hollow beam(CDHB) are investigated in detail.An analytical formula is derived for the FrFT of a CDHB.By using the derived formula,the properties of a CDHB in the FrFT plane are illustrated numerically.The results show that the properties of the intensity of the beam in the FrFT are closely related to not only the fractional order but also initial beam parameter,beam order and the lens focal length of the optical system for performing FrFT.The derived formula provides an effective and convenient way for analyzing and calculating the FrFT of a CDHB.