Monomer casting nylon-6-b-polyether amine copolymers: Synthesis and properties

MC nylon-6-b-polyether amine copolymers were prepared with macro-initiator based on amino-terminated polyether amine functionalized with isocyanate via in-situ polymerization. It was found that the introduction of polyether amine delayed the polymerization process of caprolactam by increasing apparent activation energy and pre-exponential factor, resulting in the decrease of molecular weight of nylon-6. The motion of molecular chain of the copolymers was easy because of the decreased hydrogen bonds and weakened inter-molecular forces. The physical entanglement of molecular chains of the copolymers was significant and strong which increased the entanglement density. Only the nylon-6 phase crystallized in the copolymers and the crystal grain size, spherulite size and crystallinity of the copolymers decreased. A small amount of γ crystal formed at high polyether amine content. The copolymers presented obvious strain hardening behavior in stress-strain curves and the loss factor dramatically increased while the glass transition temperature and storage module decreased. The fracture surface of the copolymers became rough and presented hairy structure, indicating that the toughening mechanism of the copolymers corresponded to the multi-layer crack extension mechanism.     

Effects of apparent image velocity and complexity on the dynamic visual field using a high-speed train driving simulator

Train driving is a highly visual task. The visual capabilities of the train driver affects driving safety and driving performance. Understanding the effects of train speed and background image complexity on the visual behavior of the high-speed train driver is essential for optimizing performance and safety. This study investigated the role of the apparent image velocity and complexity on the dynamic visual field of drivers. Participants in a repeated-measures experiment drove a train at nine different speeds in a state-of-the-art high-speed train simulator. Eye movement analysis indicated that the effect of image velocity on the dynamic visual field of high-speed train driver was significant while image complexity had no effect on it. The fixation range was increasingly concentrated on the middle of the track as the speed increased, meanwhile there was a logarithmic decline in fixation range for areas surrounding the track. The extent of the visual search field decreased gradually, both vertically and horizontally, as the speed of train increased, and the rate of decrease was more rapid in the vertical direction. A model is proposed that predicts the extent of this tunnel vision phenomenon as a function of the train speed.Relevance to industryThis finding can be used as a basis for the design of high-speed railway system and as a foundation for improving the operational procedures of high-speed train driver for safety.     

Hygrothermal deformation of orthotropic nanoplates based on the state-space concept

This paper deals with the investigation of the effect of hygrothermal conditions on the bending of nanoplates using Levy type solution model employing the state-space concept. The nanoplates are assumed to be subjected to a hygrothermal environment. The two-unknown function plate theory is used to derive the governing differential equations on the basis of Eringen's nonlocal elasticity theory. The governing equations contain the small scale effect as well as hygrothermal and mechanical effects. These equations are converted into a set of first-order linear ordinary differential equations with constant coefficients. Analytical solution of bending response for nanoplates under combinations of simply supported, clamped and free boundary conditions is obtained. Comparison of the results with those being in the open literature is made. The influences played by small scale parameter, temperature rise, the degree of moisture concentration, boundary conditions, plate aspect ratio and side-to-thickness ratio are studied.     

GPRS手机入网测试自动化

全球移动通信系统(GSM)广泛的应用于现代通信系统就在于其良好的兼容性,不同的移动设备之间在遵守一定协议规范的条件下可以相互通信;本设计测试的是GSM第11系列GSM11.10,他包括诸多测试项,只对接收机参考灵敏度电平在GSM900与DCS1800两个频段进行测量。给出了传统形式下的手动测试和自动测试平台的比较,并建立了收信机参考灵敏度指标的自动测试平台。     

Effect of corrugated plates in an in-phase arrangement on the heat transfer and flow developments

In the present study, the numerical results of the heat transfer and flow developments in the corrugated channel under constant heat flux conditions are presented. The test section is the channel with two opposite corrugated plates which all configuration peaks lie in an in-phase arrangement. The corrugated plates with three different corrugated tile angles of 20°, 40°, and 60° are tested with the height of the channel of 12.5 mm. The model was simulated for the Reynolds number and heat flux in the ranges of 400–1600 and 0.5–1.2 kW/m², respectively. The flow and heat transfer developments are simulated by using the k-ε standard turbulent model. A finite volume method with the structured uniform grid system is employed for solving the model. The predicted results are validated by comparing with the measured data. There is reasonable agreement from the comparison between the numerical data and experimental data. Effects of relevant parameters on the heat transfer and flow developments are discussed. Due to the breaking and destabilizing in the thermal boundary zone, the corrugated surface has significant effect on the enhancement of heat transfer and pressure drop.     

Applications of electronically facilitated bidding model to preventing construction disputes

When a lump-sum public construction project is implemented, disputes often arise concerning issues around the accuracy of contracted quantities, the acceptability of unit prices of cost items, and whether an “equal (or equivalent)” for a product (equipment or material) can be used. In Taiwan, contracted quantities and unit prices are primarily based on owner's estimations, and the trademarks of a product specified in a tendering documentation are only for reference. A contractor has to struggle for profit when the amount of work completed differs from the contracted amount, when change orders are priced according to the owner's estimates, and when inexpensive equals may be used. This work comprehensively elaborates the background of the current practice, and presents experience of applying an electronically facilitated bidding model to evaluating the bidder's submitted quantities, unit prices and equals in several practical projects in Taiwan. Results of this study indicate that the aforementioned construction disputes can be prevented or at least mitigated.     

DF_4内燃机车柴油机润滑油的热重分析

通过对DF_4内燃机车柴油机润滑油的热重曲线TG和微商热重曲线DTG的分析,探讨了这种润滑油的衰变规律。     

Experiments and simulations of the mechanical performance of repaired panels

Firstly, the compress experiment is undertaken to investigate the efficiency of repaired panels in this paper, and then modeling of the mechanical behavior of the repaired composite panel under compressive static load is conducted by using of the finite element method. The effect of geometric non-linearity on the stress–strain response is considered in the numeric analysis. Fatherly, the user material subroutine (UMAT) is integrated with the ABAQUS package with the geometric non-linearity effect for studying the damage initiation and its progression in the composite structure, and quadrilateral, linear, thick shell elements (S8R) are adopted. Finally, the predicted strain distribution, damage evolution and strength of the laminate are compared with the test results.