大跨间双钢筋混凝土叠合楼板的开发与应用

随着我国经济的不断发展,建筑行业也正在不断改革,在叠合结构的应用中,双钢筋混凝土叠合楼板正在不断地在我国建筑中应用。本文主要先从大跨间双钢筋混凝土叠合楼板方面进行研究,然后根据实际工程需要,研发一套符合实际的相应技术。

Finite element model updating for large span spatial steel structure considering uncertainties

In order to establish the baseline finite element model for structural health monitoring,a new method of model updating was proposed after analyzing the uncertainties of measured data and the error of finite element model.In the new method,the finite element model was replaced by the multi-output support vector regression machine(MSVR).The interval variables of the measured frequency were sampled by Latin hypercube sampling method.The samples of frequency were regarded as the inputs of the trained MSVR.The outputs of MSVR were the target values of design parameters.The steel structure of National Aquatic Center for Beijing Olympic Games was introduced as a case for finite element model updating.The results show that the proposed method can avoid solving the problem of complicated calculation.Both the estimated values and associated uncertainties of the structure parameters can be obtained by the method.The static and dynamic characteristics of the updated finite element model are in good agreement with the measured data.

Applicability of small resistance fastener on long-span continuous bridges of high-speed railway

Ballastless tracks have been widely applied in high-speed railway (HSR). The adaptability research between continuous welded rails (CWR) and long-span bridges of HSR is of great practical engineering significance. Based on the HSR long-span continuous bridges, the integrative spatial finite element model of track-bridge-pier-foundation system was established with the nonlinear spring element simulating the longitudinal resistance between track and bridge. Comparative study on the various additional longitudinal forces of CWR using the common fasteners and small resistance fasteners was carried out. Analysis results indicate that the additional expansion forces and additional rail-breaking forces in long-span ballastless continuous girders can be reduced evidently by 40% 50% after adopting small resistance fasteners, but lead to greater rail broken gap. The small resistance fasteners have little influence on the additional force only caused by vertical load, but can reduce the additional force caused by vertical load combined with braking load by over 10%. Besides, transient analysis method is proved to be more accurate and safe in calculating additional longitudinal forces when the train running or braking on the bridge, compared with the traditional static method.

Developing a Coherent Stratigraphic Scheme of the Albertine Graben-East, Africa

The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene （ca 15 Ma） to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.

Cultivation Practice of Pleurotus Fossulatus on Rice Straw

Pleurotusfossulatus, a member of oyster mushrooms, was successfully cultivated on rice straw. At least two flushes of fruit body developed at 22 ℃. The first flush of fruit body initiation took place on the 21 st day and second one appeared on 38th day. The biological efficiencies （BE） were found to be 30.8% and 14.6% for first and second flush, respectively. The differentiation pattern of pileus and gills of this mushroom was found to be different from that of other reported species of oyster mushroom. The mushroom （P. fossulatus） took about 20 days for spore formation from primordia initiation and this time span was noted to be highest among all the published reports about any other Pleurotus spp. The BE were 25.9% and 12.5% in first and second flush, respectively when the mushroom was harvested on 18th day （after its initiation of primordia）, i.e., before gill formation. However, the BE was found to be 14-16% lesser in comparison to that harvested after sporulation.

Effect of the span of Australian GPS coordinate time series in establishing an optimal noise model

The span of coordinate time series affects the determination of an optimal noise model. We analyzed position data recorded for 10 continuous Global Positioning System （GPS） sites from 1998.0 to mid-2009 on the Australian Plate to estimate the best noise model and thereafter obtain the true uncertainties of the velocity, employing the maximum likelihood estimation （MLE） method. MLE was employed to analyze the data in four ways. In the first two analyses, the noise was assumed to be a combination of flicker noise and white noise for the raw time series and spatially filtered time series. In the final two analyses, the spectral indices and amplitudes were simultaneously estimated for a power law noise plus white noise model for the raw time series and spatially filtered time series. We conclude that the noise model of GPS time series in Australia can be best described as the combination of flicker noise and white noise. Velocity uncertainties fall below -0.2 mm/yr when the time span exceeds -9.5 years. A comparison of noise amplitudes and maximum likelihood estimation values between the raw and spatially filtered time series suggests that traditional spatial filtering to remove common-mode errors might not be applicable to the raw time series of this region.

A Case Study of an Iranian EFL Student Teacher＇s Professional Preparation and Development from the Perspective of Social Constructivist Approach

Language teacher professional development has recently shifted away from transmissionist approaches based on cascading or transfer of external knowledge toward social constructivist paradigm with a focus on the situationality of learning and teaching as social processes of sharing and （re）constructing personal meanings, understandings, and skills. The social constructivist view of teacher education values teachers＇ agency in constructing and shaping personalized knowledge as a socially constructed experiential process in context. So, the researcher as an EFL educator in an Iranian teacher education university investi- gates the professional development of an EFL teacher during a three-year-time span both as a student and then as a teacher. Teacher journals, observation, and interview as three appropriate data gathering tools were used to obtain triangulated data. Student teacher professional change during the time span, multidimensionality of professional development, and discursively shaped personal beliefs and knowledge and their influence on teaching actions and practices were the emerged themes of data analysis based on Strauss （Qualitative analysis for social scientists. Cambridge University Press, Cambridge, 1998） constant comparative method, including three steps of open coding, axial coding, and selective coding. The findings of this research challenge the transmission nature of teacher education which assumes student teachers as the conduits, requiring to be filled with skills, input, and knowledge lectured by educators as authority figures.