A study of sustainable practices in the sustainability leadership of international contractors

With an increasing global need for sustainable development, numerous world‐leading construction corporations have devoted significant efforts to implementing sustainable practices. However, few previous studies have shared these valuable experiences in a systematic and quantitative way. RobecoSAM has published The Sustainability Yearbook annually since 2004, which lists the sustainability leaders in various industries, including the construction industry. Learning from those sustainability leaders in the construction industry can provide useful references for construction‐related companies when developing their sustainable development strategies. Based on a comprehensive literature review, this paper identified 51 methods used for improving sustainability performance and 34 outcomes achieved via these methods. These methods and outcomes are used for coding the sustainable practices of sustainability leaders in the construction sector. Using the coding system, 133 annual sustainability reports issued by 22 sustainability leaders (The Sustainability Yearbook, RobecoSAM 2010–2016) in the construction sector were analyzed using content analysis. Social network analysis was then employed to identify the key adopted methods and achieved outcomes (KAMAO) of these leaders. The dynamic trend and regional analysis of KAMAO are also presented. These KAMAO findings provide valuable guidance for international contractors to develop a better understanding of the primary sustainable methods adopted by sustainability leaders in the construction sector and the top outcomes achieved by these leaders. The findings also provide a useful reference for international contractors to evaluate their current sustainability‐related strategies and make improvements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156206/2/sd2020.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156206/1/sd2020_am.pd

A novel robust fixed‐time fault‐tolerant tracking control of uncertain robot manipulators

Abstract This paper presents a novel robust fixed‐time fault‐tolerant control for global fixed‐time tracking of uncertain robot manipulators with actuator effectiveness faults. With the sufficient consideration of the effects on uncertain dynamics, external disturbances and actuator effectiveness faults to the trajectory tracking performance, a singularity‐free robust fault‐tolerant control with an auxiliary vector is constructed for the fixed‐time tracking control of uncertain robot manipulators. Lyapunov stability theory is employed to prove the global fixed‐time stability ensuring that both the position and velocity tracking errors converge globally to the origin within a fixed time. The appealing advantages of the proposed control are as follows: (i) it is easy to implement with the global robust fixed‐time fault‐tolerant tracking control for uncertain robot manipulators featuring with faster transient convergence rate and higher steady‐state tracking precision; (ii) the settling time is independent of the initial states of closed‐loop system and can be calculated in advance for robot manipulators with uncertain dynamics, external disturbances and actuator faults. Extensive simulations on a two‐DOFs robot are presented to demonstrate the effectiveness and improved performances of the proposed approach

Correlation Stability Problem in Selecting Temperature-Sensitive Points of CNC Machine Tools

In the thermal-error compensation of CNC machine tools, temperature-sensitive points (TSPs) are used for predicting thermal error and need to have a high correlation with the thermal error. The stability of the correlation between TSPs and the thermal error is the key to long-term prediction accuracy. In this paper, the uncertainty-calculation method of the correlation coefficient is proposed to measure the stability of the correlation, and the reasons that affect the stability of the correlation of TSPs are analyzed. Then, the uncertainty-correlation coefficient is proposed, which can comprehensively evaluate the correlation and the stability of the correlation between TSPs and the thermal error. Through long-term experimental verifications, compared with the current TSP selection algorithm, the uncertainty-correlation coefficient can help to select a more stable TSP and improve the long-term prediction accuracy of the thermal error

Correlation Stability Problem in Selecting Temperature-Sensitive Points of CNC Machine Tools

In the thermal-error compensation of CNC machine tools, temperature-sensitive points (TSPs) are used for predicting thermal error and need to have a high correlation with the thermal error. The stability of the correlation between TSPs and the thermal error is the key to long-term prediction accuracy. In this paper, the uncertainty-calculation method of the correlation coefficient is proposed to measure the stability of the correlation, and the reasons that affect the stability of the correlation of TSPs are analyzed. Then, the uncertainty-correlation coefficient is proposed, which can comprehensively evaluate the correlation and the stability of the correlation between TSPs and the thermal error. Through long-term experimental verifications, compared with the current TSP selection algorithm, the uncertainty-correlation coefficient can help to select a more stable TSP and improve the long-term prediction accuracy of the thermal error

Alkali-Etched NiCoAl-LDH with Improved Electrochemical Performance for Asymmetric Supercapacitors

Hydrotalcite, first found in natural ores, has important applications in supercapacitors. NiCoAl-LDH, as a hydrotalcite-like compound with good crystallinity, is commonly synthesized by a hydrothermal method. Al3+ plays an important role in the crystallization of hydrotalcite and can provide stable trivalent cations, which is conducive to the formation of hydrotalcite. However, aluminum and its hydroxides are unstable in a strong alkaline electrolyte; therefore, a secondary alkali treatment is proposed in this work to produce cation vacancies. The hydrophilicity of the NiCoAl-OH surface with cation vacancy has been greatly improved, which is conducive to the wetting and infiltration of electrolyte in water-based supercapacitors. At the same time, cation vacancies generate a large number of defects as active sites for energy storage. As a result, the specific capacity of the NiCoAl-OH electrode after 10,000 cycles can be maintained at 94.1%, which is much better than the NiCoAl-LDH material of 74%