Total factor productivity (TFP) is of critical importance to the sustainable development of construction industry. This paper presents an analysis on the impact of migrant workers on TFP in Chinese construction sector. Interestingly, Solow Residual Approach is applied to conduct the analysis through comparing two scenarios, namely the scenario without considering migrant workers (Scenario A) and the scenario with including migrant workers (Scenario B). The data are collected from the China Statistical Yearbook on Construction and Chinese Annual Report on Migrant Workers for the period of 2008–2015. The results indicate that migrant workers have a significant impact on TFP, during the surveyed period they improved TFP by 10.42% in total and promoted the annual average TFP growth by 0.96%. Hence, it can be seen that the impact of migrant workers on TFP is very significant, whilst the main reason for such impact is believed to be the improvement of migrant workers’ quality obtained mainly throughout learning by doing.

Previous literature has recognized that workers' unsafe behavior is the combined result of both isolated individual cognitive processes and their interaction with others. Based on the consideration of both individual cognitive factors and social organizational factors, this paper aims to develop an Agent-Based Modeling (ABM) approach to explore construction workers' sociocognitive processes under the interaction with managers, coworkers, and foremen. The developed model is applied to explore the causes of cognitive failure of construction workers and the influence of social groups and social organizational factors on the workers' unsafe behavior. The results indicate that (1) workers' unsafe behaviors are gradually reduced with the interaction with managers, foremen, and workers; (2) the foreman is most influential in reducing workers' unsafe behaviors, and their demonstration role can hardly be ignored; (3) the failure of sociocognitive process of construction workers is affected by many factors, and cognitive process errors could be corrected under social norms; and (4) among various social organizational factors, social identity has the most obvious effect on reducing workers' unsafe behaviors, and preventive measures are more effective than reactive measures in reducing workers' unsafe behaviors.

The current construction industry, which has a high accident rate and declining labor productivity, urgently requires efficient and practical management policies. Research has shown that social norms within informal groups have considerable influence on construction workers, while studies on informal groups of construction workers (IGCWs) have been scarce. Current theories of informal groups have not been analyzed in combination with construction industry characteristics. The purpose of this paper is to develop a theoretical framework of IGCWs, including definitions, types, characteristics, causes, and functions. First, on the basis of existing theoretical research of informal groups, two semistructured interviews were designed to collect data from managers and workers. Then, a qualitative approach using grounded theory with NVivo software was employed to code the interview information, and 25 subcategories were obtained: 5 types, 10 characteristics, 4 causes, and 6 functions of IGCWs. Eventually, a conceptual model was established to explain the definition of IGCWs according to the interview data and subcategories identified. This study not only contributes to improving behavioral science theory, especially group behavior theory and human relations theory, but also contributes to constructing an informal group theory of the construction industry. In practical terms, the targeted identification of IGCWs is useful for managers in taking measures to more effectively manage construction workers.

In this work, titanium dioxide (TiO2)-incorporated rice straw fiber (RS)/poly(butylene succinate) (PBS) biocomposites were prepared by injection molding with different TiO2 powder loadings. The RS/PBS with 1 wt% TiO2 demonstrated the best mechanical properties, where the flexural strength and modulus increased by 30.34% and 28.39%, respectively, compared with RS/PBS. The non-isothermal crystallization of neat PBS, RS/PBS composites, and titanium-dioxide-incorporated RS/PBS composites was investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The non-isothermal crystallization data were analyzed using several theoretical models. The Avrami and Mo kinetic models described the non-isothermal crystallization behavior of neat PBS and the composites; however, the Ozawa model was inapplicable. The crystallization temperature (Tc), half-time of crystallization (t1/2), and kinetic parameters (FT) showed that the crystallizability followed the order: TiO2-incorporated RS/PBS composites > RS/PBS > PBS. The RS/PBS with 1 wt% TiO2 showed the best crystallization properties. The Friedman model was used to evaluate the effective activation energy of the non-isothermal crystallization of PBS and its composites. Rice straw fiber and TiO2 acted as nucleating agents for PBS. The XRD results showed that the addition of rice straw fiber and TiO2 did not substantially affect the crystal parameters of the PBS matrix. Overall, this study shows that RS and TiO2 can significantly improve the crystallization and mechanical properties of PBS composites.

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The vibration isolation system is now indispensable to high-precision instruments and equipment, which can provide a low vibration environment to ensure performance. However, the disturbance with variable frequency poses a challenge to the vibration isolation system, resulting in precision reduction of dynamic modeling. This paper presents a velocity self-sensing method and experimental verification of a vibration isolation system. A self-sensing actuator is designed to isolate the vibration with varying frequencies according to the dynamic vibration absorber structure. The mechanical structure of the actuator is illustrated, and the dynamic model is derived. Then a self-sensing method is proposed to adjust the anti-resonance frequency of the system without velocity sensors, which can also reduce the complexity of the system and prevent the disturbance transmitting along the cables. The self-sensing controller is constructed to track the variable frequency of the disturbance. A prototype of the isolation system equipped with velocity sensors is developed for the experiment. The experiment results show that the closed-loop transmissibility is less than −5 dB in the whole frequency rand and is less than −40 dB around, adding anti-resonance frequency which can be adjusted from 0 Hz to initial anti-resonance frequency. The disturbance amplitude of the payload can be suppressed to 10%.

The dynamic model of multi-rigid-body system and rigid-flexible coupling system of 2K-V cycloid pin gear reducer are constructed with ADAMS, the output-angle error curves are obtained by multi-body system dynamic simulation, and the influence of elastic deformation come from planet gear, cycloid gear and pin gears on the transmission accuracy are analyzed. The work this paper introduced provides a useful approach for further study on the dynamic transmission accuracy of precision gear drive system, exploration of active control technology for the transmission accuracy and improvement of structural design for the gearing.

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