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The competitive bidding system has been to blame for abnormally low bids, which are considered as one of the main causes of poor project quality. Previous studies have regarded the pricing of bidders as an optimum decision based on contractor's cost and market competition level. However, the sell to produce characteristic of construction projects may induce contractors to offer a low bid and then make up the amount initially sacrificed from beyond-contractual reward (BCR) gained through cutting corners and claims. System dynamics was adopted in this study to develop a contractor's pricing model with consideration of the dimensions of cost, market competition, and BCR. The model was then examined by statistical analysis of data collected from 44 highway projects in Taiwan. It was found that the equilibrium market price is significantly associated with BCR, which is assumed to be determined by the strictness of the owner's construction management, including both soundness of contract and tightness in construction supervision. Research results suggest that contractors divide the market into different segments according to the owner's strictness of construction management and the equilibrium price level of each market segment varies. The price level for projects with a strict owner is remarkably higher than for those with relatively less strict owners. Improvement in the construction management system of projects is crucial to lower the possibility that contractors gain BCR and do opportunistic bidding, and to further enhance project quality. DOI: 10.1061/(ASCE)0733-9364(2007) 133:6(409) CE Database subject headings: Construction industry; Bids; Pricing; Simulation models.

Design, simulation and experimental implementation of a wavelet basis function network learning controller for linear brushless dc motors (LBDCM) are considered. Stability robustness with position tracking is the primary concern. The proposed controller deals mainly with external disturbances, e.g. nonlinear friction force and payload variation in motion control of linear motors. It consists of two parts, one is a state feedback component, and the other one is a learning feedback component. The state feedback controller is designed on the basis of a simple linear model, and the learning feedback component is a wavelet neural controller. The attenuation effect of wavelet neural networks on friction force is first verified by the numerical method. The learning effect of wavelet neural networks on friction force is also shown in the numerical results. Then, a wavelet neural network is applied on a real LBDCM to on-line suppress the friction force, which may be variable due to the different lubrication. The effectiveness of the proposed control schemes is demonstrated by simulated and experimental results.

A new study uses piezoreflectance and photoreflectance to investigate low temperature AlGaAs/GaAs multiple quantum wells interdiffusion at room temperature.

Research has been conducted on the two-dimensional transition-metal coordinated polymers. The synthesis of these polymers in superheated water solutions has been carried out.

The properties of the flow structure and shear-layer vortex shedding of double concentric jets separated by a disk are experimentally investigated. Average flow patterns in the prepenetration, transition and penetration regimes are measured. The turbulence characteristics in the shear layer and at the stagnation point are closely related to the characteristic modes of vortex shedding. With the increase of annulus Reynolds number, the Reynolds stresses are small in the subcritical mode, increase considerably in the transitional mode, increase a little in the supercritical mode and are almost constants in the fully turbulent mode.