介绍了交通需求组合模型(CTDM),建立了目的地-方式选择组合模型,采用逐层估计的极大似然估计法对其进行参数标定.按照意向偏好SP (stated preference)和行为偏好RP(revealed preference)数据结合使用的要求对SP调查方法加以改进,开发了“基于互联网的个体行为调查设计及数据采集平台”进行数据采集.利用调查数据进行需求组合模型参数标定.以上海市嘉定校区学生观影行为为例,对所提出的方法进行验证.结果表明,通过改进的SP数据标定的参数具有较高的精确度.

With the fact that traditional aggregate traffic demand model is unable to meet the requirements of transportation planning, researchers have introduced the disaggregate model into the application on transportation choice behavior modeling. The most two frequently used survey methods providing data for model estimation are RP and SP survey, and each has its advantages as well as disadvantages. A complementation between them used by a joint survey method called SP-off-RP method has been proposed afterwards. An effort is made to improve the survey method of SP-off-RP method. The improved SP-off-RP method is applied to the data collection work supporting a transit mode choice model by conducting an interactive survey on a website. The data is then analyzed in the parameter estimation for the discrete choice model. The results show that this method requires fewer subjects in survey while acquiring more data to obtain a more accurate result.

In recently years,the students of the suburban college town have to face many difficulties on travel due to the lack of supporting infrastructure and the backwardness of transportation condition.With the extension of urban rail network and the improvement of urban public transport, there will be more possibilities for solving transport problems.In this paper,by taking the Jiading Campus of Tongji university as an example,the data of students choice in virtual environment on travel are obtained by stated preference(SP)technique,and the discrete choice model which is built by these SP data could predict the contribution rate of travel modes in future on a given direction. Meanwhile,by using the discrete choice model,the possibility of optimization could be analyzed when the existed transport modes face the challenge of urban railway network. This research could be a theoratical support for the evalua- tion of optimum measurement of public transit on the condition that the urban railway is in operation.

The accessibility-oriented transport planning method is critical for many high population density cities in China. Most definitions of accessibility only consider spatial separation and ignore the influence of traveler choice on accessibility. In this paper, the combined travel demand model is employed in transport planning. The travelers’ choice behavior of the model is based on the random utility theory. The model overcomes inconsistence problem of the sequential four-step model on travel behavior and congestion effects. Based on the same random utility theory, an accessibility measure is proposed, which can be integrated into the combined travel demand model. The accessibility measure can reflect the traveler’s choices at different stages (travel choice, destination choice, mode choice and route choice). The properties of the accessibility measure are discussed through a numerical example.

对于中国许多高人口密度的城市,以可达性为导向的交通规划方法尤为重要.然而,已有的可达性指标只考虑了空间阻隔的影响,忽略了交通运行中出行者的选择行为对可达性的作用.此外,在交通规划中使用交通需求组合模型,其选择行为是基于随机效用理论,从而克服了四步模型存在的选择行为和结果不一致的问题.基于同样的随机效用理论,提出了可达性指标.该指标与交通需求组合模型能有效结合,并反映出行者在不同选择层次上的行为（出行选择、目的地选择、方式选择和路径选择）.通过简单的算例,分析了所提出的可达性指标的性质.

The present study investigates the effect of different mixing methods on the setting properties of bone cement. It was found that vacuum mixing decreased the setting time of the bone cement by nearly 2min (10%), compared to mixing in air. Two additional experiments, in which the bone cement powders were purged with argon or oxygen, and mixed with the methyl methacrylate monomer, revealed that oxygen concentrations in the bone cement had a great effect on the setting time. The setting time increases significantly as the oxygen concentration increases, which suggests that the decrease in the setting time by vacuum mixing may be attributed to the lower oxygen levels present in the mixer. No significant effect was observed on dough time or maximum exothermic temperature by varying oxygen concentrations in the bone cement mixer.

In this study we investigated the effect of the brand of surgical gloves on the dough time determination for acrylic bone cements. Four different brands of powder-free latex surgical gloves were tested. Two commercial bone cements, Surgical Simplex P and Palacos R, were used for dough time measurement following standard test methods for acrylic bone cements (ASTM F-451 and ISO 5833). The results show that the measured dough time depended largely on the brand of gloves used, and could vary by nearly 250%. The surface morphological structures of gloves, determined by SEM, probably contribute to the differences in the measured dough time. This study provides experimental evidence that supports the need to describe the type of gloves used, in detail, when dough time is reported. It also illustrates the importance of the glove brand, when bone cement is to be handled as a dough in the clinical setting.

New biodegradable poly(propylene fumarate)-based polymer networks have been prepared by radical polymerization using poly(propylene fumarate) (PPF) and poly(propylene fumarate)–diacrylate (PPF–DA) macromers. Two PPF–DAs were synthesized incorporating one (m=1) and two (m=2) fumarate units, and were employed in the synthesis of the polymer networks. The PPF/PPF–DA double bond ratio and the molecular weight of PPF–DA were varied to assess their effects on the mechanical properties of the resulting polymer networks as well as on their equilibrium water content. The compressive strength at fracture of PPF/PPF–DA (m=1) polymer networks increased from 11.2±1.8 to 66.2±5.5MPa as the double bond ratio of PPF/PPF–DA (m=1) decreased from 4 to 0.5. An increase in compressive modulus was also observed from 19.4±1.8 to 340.2±30.7MPa for the same range of the double bond ratio of PPF/PPF–DA. Increasing the molecular weight of PPF–DA (m=2) caused both the compressive strength at fracture and modulus of the corresponding polymer networks to increase to the ranges of 14.4±4.2 to 88.2±6.1MPa and 28.0±2.4 to 480.4±35.9MPa, respectively. Similarly, both were increased as the PPF/PPF–DA (m=2) double bond ratio decreased from 4 to 0.5. The PPF/PPF–DA crosslinked polymer networks showed negligible equilibrium water content for all 10 formulations tested in this study. The degradation reaction of the PPF/PPF–DA polymer networks under basic conditions was investigated. The degradation products were isolated and characterized by NMR and GC/MS as fumaric acid, propylene glycol, and poly(acrylic acid-co-fumaric acid) of weight average molecular weight of 5080. These data demonstrate that biodegradable PPF/PPF–DA polymer networks should have great potential as polymer scaffolds for orthopedic applications in tissue engineering.

4-Phenoxybut-1-ene undergoes both ortho and meta intramolecular photocycloaddition on 254 nm irradiation: in the latter process the addition is directed by the alkoxy tether to the arene 2,6-positions. Methyl substitution on the ethene and arene units does not affect the regiochemistry of the reaction but the presence of a 2′-methoxy group inhibits the meta process and only the ortho addition occurs.

A study to understand the delamination of laminated composite beams with a viscoelastic damping layer due to residual stresses resulting from cocuring is presented in this paper. The effects of residual stress concentration near the free edges of the laminate on the delamination is discussed. Numerical study is conducted to show the effects of laminate and viscoelastic material properties and various structural parameters such as the width of the composite beam, the thickness of the 0° ply angle layers, and the thickness of the compliance layers, on the failure of the composite beam.

This paper describes the formulation of a theory for the prediction of damping and natural frequencies of laminated composite beams with multiple viscoelastic damping layers. The damping layers are constrained (or sandwiched) by anisotropic laminates. The in-plane shear strains of the damping layers and the constraining layers are included in the model. Closed-form solutions for the resonance frequencies and modal loss factors of the composite beam system under simple supports are derived using the energy and Ritz method. A parametric study has been conducted to study the variation of dynamic stiffness and modal loss factor of the system with structural parameters (e.g., the ply orientations, of laminas, thickness of the damping layers and the laminates), operating temperature, and damping material properties. The design of composite beams for maximizing the damping capacity is also presented in this paper which includes the determination of operating temperature range corresponding to given structural parameters and finding optimal structural parameters corresponding to given temperature range. Finally, some experimental results are compared with theory for the cases of single and double damping layer beam systems that show good agreement between predicted and measured natural frequencies.

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This paper presents a dynamic model for the transverse vibration analysis of an adhesively bonded composite double-strap joint. The differential equations of motion of the joint system are derived using the energy method and Hamilton’s principle. It is assumed that the energy dissipated by the joint system is contributed by both the shear and longitudinal deformation of the adhesive layers. The combination of natural boundary conditions, forced boundary conditions, and continuity conditions yields the frequency equations to predict the system resonance frequencies and modal loss factors. The effects of structural parameters and material properties of the adhesive layer on the system modal loss factors and resonance frequencies are also studied.

Analysis of 1H and 13C NMR data by 2D NMR techniques was used for the structural identification of triquinanes and bulleranes considered as precursors of complex natural products such as (+)‐cerapicol. The polycyclic molecules are derived from a tandem Norrish Type I photoreaction and intramolecular arene–alkene meta photocycloaddition of aryl‐substituted norbornan‐2‐ones.