Lanzhou Jiaotong University
Lianran, China
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Chang Q.,Lanzhou Jiaotong University
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2015

Although Smoluchowski theory, Camp-Stein theory and Micro vortex theory have been proposed successively up to now in the development of flocculation dynamics, there are still some disadvantages in this area, for example, the mechanism of flocculation in turbulent flow has not been totally revealed and its velocity equation which is more in line with the actual process have not been obtained. This current state has been affecting the design and scale up of flocculation basin seriously. The Particle Image Velocimetry (PIV) and the Computational Fluid Dynamics (CFD) developed in recent years make it possible to verify the reasons which cause the turbulent flocculation and to develop the turbulent flocculation dynamics further. © 2015, Science Press. All right reserved.

Xiang W.-L.,Lanzhou Jiaotong University | Xiang W.-L.,Tianjin University | An M.-Q.,Lanzhou Jiaotong University
Computers and Operations Research | Year: 2013

Artificial bee colony (ABC) algorithm has already shown more effective than other population-based algorithms. However, ABC is good at exploration but poor at exploitation, which results in an issue on convergence performance in some cases. To improve the convergence performance of ABC, an efficient and robust artificial bee colony (ERABC) algorithm is proposed. In ERABC, a combinatorial solution search equation is introduced to accelerate the search process. And in order to avoid being trapped in local minima, chaotic search technique is employed on scout bee phase. Meanwhile, to reach a kind of sustainable evolutionary ability, reverse selection based on roulette wheel is applied to keep the population diversity. In addition, to enhance the global convergence, chaotic initialization is used to produce initial population. Finally, experimental results tested on 23 benchmark functions show that ERABC has a very good performance when compared with two ABC-based algorithms. © 2012 Elsevier Ltd.

Su H.,Lanzhou Jiaotong University
Procedia Engineering | Year: 2011

To tackle with the premature matter of particles when seeking optimization in local small space in terms of quantum-behaved particle swarm optimization(QPSO), chaos optimization strategy was combined to QPSO algorithm, and defined as chaos quantum-behaved particle swarm optimization(CQPSO) algorithm. The algorithm firstly applied QPSO algorithm to implement evolution operation till QPSO algorithm was in premature state, then chaos seeking mechanism was started to induct the particles to quickly jump out the local optimization, and thus, the convergence speed of QPSO was quicken. In this paper, CQPSO was applied to optimal the weight values of BP neural network, and the optimized well neural network was applied to implement short-term load forecasting(STLF). Eventually, simulation results show that the algorithm possesses high forecasting accuracy, and is an ideal optimal algorithm. © 2011 Published by Elsevier Ltd.

Niu H.,Lanzhou Jiaotong University | Zhou X.,Arizona State University
Transportation Research Part C: Emerging Technologies | Year: 2013

This article focuses on optimizing a passenger train timetable in a heavily congested urban rail corridor. When peak-hour demand temporally exceeds the maximum loading capacity of a train, passengers may not be able to board the next arrival train, and they may be forced to wait in queues for the following trains. A binary integer programming model incorporated with passenger loading and departure events is constructed to provide a theoretic description for the problem under consideration. Based on time-dependent, origin-to-destination trip records from an automatic fare collection system, a nonlinear optimization model is developed to solve the problem on practically sized corridors, subject to the available train-unit fleet. The latest arrival time of boarded passengers is introduced to analytically calculate effective passenger loading time periods and the resulting time-dependent waiting times under dynamic demand conditions. A by-product of the model is the passenger assignment with strict capacity constraints under oversaturated conditions. Using cumulative input-output diagrams, we present a local improvement algorithm to find optimal timetables for individual station cases. A genetic algorithm is developed to solve the multi-station problem through a special binary coding method that indicates a train departure or cancellation at every possible time point. The effectiveness of the proposed model and algorithm are evaluated using a real-world data set. © 2013 Elsevier Ltd.

Zhang Y.-H.,Lanzhou Jiaotong University
Journal of Structural Engineering (United States) | Year: 2012

Shear lag effect in thin-walled box girders has been studied over several decades. However, the methods adopted in many papers have some deficiencies. In the present work, an improved displacement function for shear lag warping in a box girder with cantilever slabs is established. Based on the concept of generalized force corresponding to the generalized displacement for shear lag and the relevant geometrical properties, an improved finite-segment method is proposed to simplify the shear lag analysis of complex box girders. The homogeneous solution of the governing differential equation for shear lag is adopted as the element displacement function. The formulas of the element stiffness matrix and the equivalent nodal force vector are derived. A general formula expressed in terms of the generalized moment is presented to calculate the stress. A finite-element computer program is developed by using FORTRAN language and is used to analyze a cantilever box girder model and a continuous prestressed concrete box girder. The theoretical results are in good agreement with the test results, validating the proposed method and formulas. This paper also reveals for the first time the characteristics of the generalized moment for shear lag. © 2012 American Society of Civil Engineers.

Yan E.,Lanzhou Jiaotong University
Physica B: Condensed Matter | Year: 2012

Pseudopotentials and plane-wave basis set method is used to investigate the electronic structure and magnetic properties for state-of-the-art zinc-blende and rocksalt M N (M=K, Na) alloys. We find that these compounds exhibit half-metallic characters with an integer magnetic moment of 2.00 μB. The half-metallic properties result from a fully spin-polarization of s and p states. The origin of energy gap mainly comes from the hybridization both s and p states. Total energies calculations indicate the rocksalt phase is lower in energy than the zinc-blende one. The difference of total energy are about 0.035 Ry per formula unit for KN and NaN, respectively. For these compounds, SlaterPauling curve Mt=( Zt-4) (in μB unit) is obeyed between valence electrons and total magnetic moment. Meanwhile, we also find the preservation of half metallic characters when the lattice parameter is moderate compressed. © 2011 Elsevier B.V.All rights reserved.

Niu H.,Lanzhou Jiaotong University
International Journal of Computational Intelligence Systems | Year: 2011

This study focuses on how to determine the skip-stop scheduling for a congested urban transit line during the morning rush hours. A transit schedule with uneven headways and skip-stop operations is adopted to match the time-dependent demands and accelerate the circulative utilizations of vehicles. This schedule allows the buses to run on unequal vehicle-departure intervals and to skip some stations. A nonlinear programming model is formulated to minimize the overall waiting times and the in-vehicle crowded costs subjected to a limited number of vehicles. According to the layered characteristics of the skip-stop scheduling, a bilevel genetic algorithm is developed to solve the proposed model. The possible departure times of vehicles at the terminal are searched by the outer genetic algorithm and the skip-stop operations are solved by the inner genetic algorithm. Finally, the proposed model and algorithm are successfully tested with the help of a real-world case. © 2011 Copyright Taylor and Francis Group, LLC.

Chu K.,Lanzhou Jiaotong University | Jia C.,University of Science and Technology Beijing
Physica Status Solidi (A) Applications and Materials Science | Year: 2014

Graphene nanoplatelets (GNPs) exhibit ultra-high strength and elastic modulus. Therefore, they are potential ideal reinforcements in metal-matrix composites (MMCs). In this work, we report the use of GNPs to strengthen the bulk Cu-matrix composites. GNP reinforced Cu-matrix (GNP/Cu) composites were prepared by a combination of the ball milling and hot-pressing processing, and their mechanical properties were investigated. Microstructure studies indicated that the GNPs with 0-8 vol.% contents were well dispersed in the Cu matrix by ball milling. Compared to unreinforced Cu, the GNP/Cu composites showed a remarkable increase in yield strength and Young's modulus up to 114 and 37% at 8 vol.% GNP content, respectively. The extraordinary reinforcement is attributed to the homogeneous dispersion of GNPs and grain refinement. However, the mechanical improvement of GNP/Cu composites was still below the theoretical value. The possible reasons for this deviation were discussed and the methods for further mechanical improvement of GNP/Cu composites were proposed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The invention provides a novel production method of electro-depositing and refining metal chloride by a membrane process. The novel production method comprises the following steps: using a cation selective diaphragm and an anion selective diaphragm to divide an electrolytic cell into an anode chamber, a middle partition chamber and a cathode chamber in sequence, wherein an anode, a cathode, an anode liquor and a cathode liquor are respectively arranged in the anode chamber and the cathode chamber correspondingly; the anode liquor is a diluted sulfuric acid solution, the cathode liquor is a acid metal chloride solution, and a diluted hydrochloric acid solution is contained in the middle partition chamber; reducing the metal cation at the cathode, and separating out reduced metal cation in the form of a single simple substance while introducing direct-current power for electrolysis; and simultaneously carrying out water oxidation reaction at the anode to acquire oxygen gas, and 5%-10% of hydrochloric acid solution can be acquired in the middle partition chamber. With the adoption of the production method provided by the invention, the problem that chlorine gas is generated in a normal metal chloride electro-deposition process is solved thoroughly, high-concentration hydrochloric acid byproducts which can be recycled, and high in economic value can be obtained; and moreover, the acquired metal product has good quality, and the method is a novel method satisfying the green metallurgical environment-friendly development.

The invention provides a novel production method of electro-depositing and refining metal chloride by a membrane process. The invention further provides a method for preparing a cation selective membrane. The method comprises two major steps. Step I: Preparing a sulfonic-containing base membrane by mixture of manganese dioxide/polyvinylidene fluoride and polymerization of sulfonic-group containing monomers. Step II: Grafting of the base membrane with phenolic groups using plasma irradiation.

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