Yuan H.,Southwest Jiaotong University
Waste Management | Year: 2012
It has been determined by existing literature that a lot of research efforts have been made to the economic performance of construction waste management (CWM), but less attention is paid to investigation of the social performance of CWM. This study therefore attempts to develop a model for quantitatively evaluating the social performance of CWM by using a system dynamics (SD) approach. Firstly, major variables affecting the social performance of CWM are identified and a holistic system for assessing the social performance of CWM is formulated in line with feedback relationships underlying these variables. The developed system is then converted into a SD model through the software iThink. An empirical case study is finally conducted to demonstrate application of the model. Results of model validation indicate that the model is robust and reasonable to reflect the situation of the real system under study. Findings of the case study offer helpful insights into effectively promoting the social performance of CWM of the project investigated. Furthermore, the model exhibits great potential to function as an experimental platform for dynamically evaluating effects of management measures on improving the social performance of CWM of construction projects. © 2012 Elsevier Ltd.
Zhang H.,Southwest Jiaotong University |
Lewis F.L.,University of Texas at Arlington
Automatica | Year: 2012
A practical design method is developed for cooperative tracking control of higher-order nonlinear systems with a dynamic leader. The communication network is a weighted directed graph with a fixed topology. Each follower node is modeled by a higher-order integrator incorporating with unknown nonlinear dynamics and an unknown disturbance. The leader node is modeled as a higher-order nonautonomous nonlinear system. It acts as a command generator giving commands only to a small portion of the networked group. A robust adaptive neural network controller is designed for each follower node such that all follower nodes ultimately synchronize to the leader node with bounded residual errors. Moreover, these controllers are distributed in the sense that the controller design for each follower node only requires relative state information between itself and its neighbors. A simulation example demonstrates the effectiveness of the algorithm. © 2012 Elsevier Ltd. All rights reserved.
Li J.,Southwest Jiaotong University
Colloids and surfaces. B, Biointerfaces | Year: 2013
Both coverage and morphology of endothelial cells (ECs) on blood contact biomaterials were involved in the antithrombotic and anti-proliferative process. However, most researches have been focused on the ECs amount on the materials surface, but not the morphology. As of now, little is known about the relationship between the ECs morphology and the cytokine secretion, especially those anticoagulant factors on cardiovascular implants. In this study, three sizes of parallel micro-stripes of high molecular weight hyaluronic acid (HMW-HA) were fabricated on the NaOH-treated titanium (TiOH) surface. These micro-patterns of ridges/grooves were used to regulate the distribution, morphology and cytokine secretion of the ECs. The roughness of bare Ti and TiOH was detected by AFM, and the micro-pattern sizes were imaged by SEM. The chemical bonding of HMW-HA to the TiOH surface was demonstrated by FTIR, and the element distribution was examined by EDX. The morphology index of the ECs was analyzed to evaluate the orientation, elongation and spreading of the ECs on the micro-patterned surfaces and the control, while the cell number and cytokine secretion of the ECs were measured by related kits. The characterization of the ECs demonstrated that the bigger L/B index improved NO, PGI2, Fn release and TM, TFPI, E-Selectin expression as well as reducing vWF secretion. The platelet adhesion test and the whole blood clotting time test proved the increasing anticoagulation property of ECs with their elongation increasing. These results suggest that ECs morphology-related function can be regulated by different sizes of micro-patterns. Copyright © 2013. Published by Elsevier B.V.
Li X.-Y.,Southwest Jiaotong University
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2013
This paper presents fundamental solutions for an infinite space of one-dimensional hexagonal quasicrystal medium, which contains a penny-shaped or half-infinite plane crack subjected to two identical thermal loadings on the upper and lower crack lips. In view of the symmetry of the problem with respect to the crack plane, the original problem is transformed to a mixed boundary problem for a half-space, which is solved by means of a generalized method of potential theory conjugated with the newly proposed general solutions. When the cracks are under the action of a pair of point temperature loadings, fundamental solutions in terms of elementary functions are derived in an exact and complete way. Important parameters in crack analyses such as stress intensity factors and crack surface displacements are presented as well. The underlying relations between the fundamental solutions for the two cracks involved in this paper are discovered. The temperature fields associated with these two cracks are retrieved in alternative manners. The obtained solutions are of significance to boundary element analysis, and have an important role in clarifying simplified studies and serving as benchmarks for computational fracture mechanics can be expected to play. Copyright © The Royal Society 2013.
Li X.-Y.,Southwest Jiaotong University
International Journal of Solids and Structures | Year: 2014
This present work is concerned with planar cracks embedded in an infinite space of one-dimensional hexagonal quasicrystals. The potential theory method together with the general solutions is used to develop the framework of solving the crack problems in question. The mode I problems of three common planar cracks (a penny-shaped crack, an external circular crack and a half-infinite crack) are solved in a systematic manner. The phonon and phason elastic fundamental fields along with some important parameters in crack analysis are explicitly presented in terms of elementary functions. Several examples are given to show the applications of the present fundamental solutions. The validity of the present solutions is discussed both analytically and numerically. The derived analytical solutions of crack will not only play an important role in understanding the phonon-phason coupling behavior in quasicrystals, but also serve as benchmarks for future numerical studies and simplified analyses. © 2013 Elsevier Ltd. All rights reserved.