The unsafe behaviors of construction workers are often the immediate causes of construction accidents, but the underlying causation of such behaviors are not well understood. This research regards the management of construction safety as a system, and seeks to use system dynamics to demonstrate how the system influences construction workers in terms of unsafe behaviors. First, individual and environmental conditions that can lead to an unsafe behavior are identified through a holistic cognitive analysis and management conditions that affect such conditions are identified. Second, a system dynamics model for the causation of unsafe behaviors (SD-CUB) is developed to characterize the causal structure of the system. The SD-CUB model involves relationships among management, individuals, and environmental conditions that can eventually lead to workers' unsafe behaviors. Third, a variety of model tests are conducted to build the confidence of the SD-CUB model. A five-week survey and observation on a building construction project is conducted to demonstrate that the SD-CUB model generates correct patterns of behavior. The model tests also imply that safety and production can actually support each other, management conditions on supervisory level are effective on the improvement of workers' safety awareness, and preventive actions are more effective than reactive actions on the enhancement of safety performance. The SD-CUB model can also be used as a basis for simulation of various site scenarios to explore the best solution to prevent and correct unsafe behaviors, and by redesigning the causal structure, the leverage points and critical management strategies can be determined.

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In this study, it was found that sodium dodecylbenzene sulfonate (SDBS)-modified LDHs can significantly enhance the chemiluminescence (CL) from the periodate-hydrogen peroxide (IO4 –-H2O2) CL reaction. Using CL spectrum, powder X-ray diffraction measurements, scanning electron microscope images, transmission electron microscopy images, Fourier transform infrared spectroscopy, the quenchers for reactive oxygen species, and elemental analysis techniques, the enhancement mechanism of SDBS-modified LDHs on the IO4 –-H2O2 CL was discussed in detail. The results showed that the adsorbed SDBS on the external surface of SDBS-modified LDHs made the disappearance of electrostatic repulsion between anionic surfactants and anionic CL reactants, resulting in the concentrating of anionic CL reactants on the adsorbed surfactant layers of SDBS-modified LDHs and the higher CL efficiency in LDH microenvironment. The success of this work expands currently limited applications of anionic surfactants in CL field.

This paper is devoted to improving the synchronization and robustness performance of a parallel robot used for automobile electro-coating conveying via a novel synchronous robust sliding mode control (SMC). A sliding surface is designed based on a composite error, which is composed of the tracking error of each joint and the synchronization errors among the joints. By incorporating a nonlinear disturbance observer into the finite-time SMC based on the composite error, the synchronous robust SMC of the parallel robot is realized. The finite-time Lyapunov stability of the sliding variable and the asymptotic convergence of the tracking error and synchronization error have been proved theoretically. The lumped disturbance in the system is estimated by the proposed scheme, and restriction on the change rate of the lumped disturbance has been relaxed. Due to the feedforward compensation with the disturbance estimation value, the switching gain of SMC required is merely larger than the upper bound of the disturbance estimation error, rather than the upper bound of the disturbance, resulting in chattering attenuation. Finally, the numerical simulation and experiment on the prototype system of the parallel robot are implemented to validate the effectiveness of the synchronous robust SMC.