Liang X.,Changzhou University
Physical Review B | Year: 2017
Grain boundaries are natural interfaces present in polycrystalline materials and have an important role in transport properties. In this work, the impact of grain boundary crystallographic mismatch, local impurity modulation, and spacing on lattice thermal conductivity is examined from the kinetic theory approach, with ZnO as a case study. We employ a dislocation-based model to describe the grain boundary scatterings of phonons, in which structural characteristics of grain boundaries are explicitly built-in and grain boundary scattering time depends on phonon frequency. This is in contrast to the gray model or the commonly used Casimir limit, which is blind to both grain boundary features and phonon frequency. We show that the lattice thermal conductivity generally decreases with grain boundary misorientation angle, and this dependence is significant for small grain boundary spacing while it tends to diminish for a large one. Intriguingly, our results show that local grain boundary chemistry can affect even more substantially than the crystallographic misfit on phonon relaxation time and interfacial thermal (Kapitza) resistance. Our results suggest new opportunities in tuning lattice thermal conductivity besides the nanostructure engineering approach, and demonstrates the synergetic effects of grain boundary characteristics on phonon conduction in polycrystals. © 2017 American Physical Society.
Wang Z.,Changzhou University |
Xu X.,Changzhou University |
Kwon O.,University of California at Los Angeles
Chemical Society Reviews | Year: 2014
Nucleophilic phosphine catalysis of allenes with electrophiles is one of the most powerful and straightforward synthetic strategies for the generation of highly functionalized carbocycle or heterocycle structural motifs, which are present in a wide range of bioactive natural products and medicinally important substances. The reaction topologies can be controlled through a judicious choice of the phosphine catalyst and the structural variations of starting materials. This Tutorial Review presents selected examples of nucleophilic phosphine catalysis using allenes and electrophiles. This journal is © the Partner Organisations 2014.
Zhang Y.,Changzhou University
Theoretical and Computational Fluid Dynamics | Year: 2012
A line contact inlet zone analysis is carried out for the hydrodynamic lubrication in a fully plastic asperity contact. A governing equation of the central film thickness i.e. the film thickness in the fully plastic contact area is derived. An equation predicting this film thickness is also derived. It is found that for the fully plastic contact, under relatively light loads the prediction accuracy for the central film thickness is good, while at the load heavy enough the prediction equation greatly overestimates the central film thickness and the central film thickness solved from the analytical governing equation is significantly low showing the asperity in boundary layer lubrication. For the fully plastic contact, the central film thickness is nearly half of that obtained based on the elastic contact assumption for relatively light loads or even lower for heavier loads. The hydrodynamic lubrication is found difficult to form in the fully plastic asperity contact for the carried load heavy enough or the significantly low sliding speed between the asperities. To achieve a high hydrodynamic lubrication film thickness in the fully plastic asperity contact it is recommended to employ a high sliding speed or a high fluid viscosity. However, in the fully plastic asperity contact, the potential hydrodynamic load-carrying capacity is limited and much smaller than that based on the elastic contact assumption or predicted by conventional line contact elasto-hydrodynamic lubrication theory. © Springer-Verlag 2011.
Zhang Y.,Changzhou University
Meccanica | Year: 2013
The present paper proposes a new type of hydrodynamic lubricated tilted pad thrust slider bearing which is augmented with the boundary slippage at the stationary contact surface in the inlet zone. This design is of purpose to reduce the friction coefficient but increase the load-carrying capacity of the bearing. A theoretical analysis is presented for this bearing. Computational results and design guides for this bearing are given. It is found that the most increase of the carried load of the bearing by the boundary slippage is around 30 %, while the most reduction of the friction coefficient of the bearing by the boundary slippage is more than 40 %. This advantage is reached when the boundary slippage zone occupies 80 % of the bearing lubricated area and the fluid-contact interfacial shear strength at the boundary slippage interface is very low. © 2012 Springer Science+Business Media Dordrecht.
Gao X.-H.,Changzhou University
Research in Astronomy and Astrophysics | Year: 2014
High-precision proper motions and radial velocities of 1046 stars are used to determine member stars using three-dimensional (3D) kinematics for open cluster NGC 188 based on the density-based spatial clustering of applications with noise (DBSCAN) clustering algorithm. By implementing this algorithm, 472 member stars in the cluster are obtained with 3D kinematics. The color-magnitude diagram (CMD) of the 472 member stars using 3D kinematics shows a well-defined main sequence and a red giant branch, which indicate that the DBSCAN clustering algorithm is very effective for membership determination. The DBSCAN clustering algorithm can effectively select probable member stars in 3D kinematic space without any assumption about the distribution of the cluster or field stars. Analysis results show that the CMD of member stars is significantly clearer than the one based on 2D kinematics, which allows us to better constrain the cluster members and estimate their physical parameters. Using the 472 member stars, the average absolute proper motion and radial velocity are determined to be (PMα, PMδ) = (-2.58 ± 0.22, +0.17 ± 0.18) mas yr-1 and Vr = -42.35 ± 0.05 km s-1, respectively. Our values are in good agreement with values derived by other authors. © 2014 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.
Zhang Y.,Changzhou University
International Journal of Heat and Mass Transfer | Year: 2016
The flow equation for a fluid confined in a nano channel proposed previously was re-examined by comparison with the molecular dynamics simulation (MDS) results. In themselves, this equation as well as the flow factor for the confined nano fluid flow were finely proven. The comparisons showed good agreements between the calculation results from this equation and the MDS results for both the Couette and Poiseuille flows. © 2015 Elsevier Ltd. All rights reserved.
He Y.,Changzhou University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015
We theoretically investigate a two-cavity optomechanical system in which a cavity (cavity a) couples to a mechanical resonator via radiation pressure and to another cavity (cavity c) via a common waveguide. In the excitation of a strong pump filed to cavity a, the steady-state entanglement between cavity a and c, as a quantum channel, can be generated, which provides an indirect optical pathway to excite cavity c by means of the pump filed. Quantum interference between the direct and indirect optical pathways gives rise to an optomechanically induced transparency appearing in the probe transmission of cavity c. Unlike in a typical optomechanically induced transparency effect, the electromagnetical control of the transmission is implemented by resorting to the quantum channel. Furthermore, the coupling strength of the two cavities is an important factor of the quantum channel, which can influence the width of the transparency window and the bistable behavior of the mean photon number in cavity a. We also illustrate that the electromagnetical control via quantum channel can be exploited to implement the optical switch and the slow light. © 2015 American Physical Society.
Zhang Y.,Changzhou University
International Communications in Heat and Mass Transfer | Year: 2016
The paper provides a calculation of the absolute value of the maximum flowing velocity of the Poiseuille flow across the wall separation in a nanoslit pore from the flow factor approach model, based on the input data known from the molecular dynamics simulation (MDS) results. It was found that this calculation matches well with the MDS result. © 2016 Elsevier Ltd.
Jiang G.-G.,Changzhou University
Energy Procedia | Year: 2011
At present there is the different level in China's circular economy development. To better measure the level of regional circular economy development, this paper builds the evaluation system of regional circular economy development, reflected the characteristic of resources recycling specially, and put forward the Fuzzy Comprehensive Evaluation Method to analysis circular economy development level in single region and Comparison Evaluation Method to analysis circular economy development level in different regions, so that enhance the evaluate ability in evaluation model and evaluation method of circular economy developing level. On this basis, this paper makes the empirical study on regional differences evaluation in circular economy development level through three typical provinces, Jiangsu, Heilongjiang, Qinghai Province. © 2011 Published by Elsevier Ltd.
Changzhou University | Date: 2012-08-14
A process for preparing a branched polymer, belonging to the fields of polymer synthesis and preparation of functional polymers. A vinyl monomer, such as styrene, toluene (benzene, xylene) as a solvent, is subjected to a self-initiated free radical polymerization at 60100 C. with a new type of compound (methyl (meth)acrylate peroxide) as the initiator and the branched monomer containing both polymerisable double bond and peroxide bond, which can be used to synthesize the branched polymers. The degree of branching of the polymer can be adjusted by adjusting the molar ratio of the new type of compound to polymerisable monomer. The process for preparing a branched polymer is carried out under the conditions of conventional free radical polymerization without the addition of the branched monomer and other assist initiators. The polymerization is simple and feasible, has a high monomer conversion, a controllable degree of branching for the polymer, and is highly suitable for synthesizing branched polymers from various monomers. Another advantage of this process is its low production cost.