Li Y.,Chongqing University of Posts and Telecommunications |
Li Y.,Nanjing Southeast University |
Zhang Z.,Patent Examination Cooperation Center |
Wang C.,InterDigital Communications |
And 2 more authors.
IEEE Transactions on Vehicular Technology | Year: 2013
Cooperative communications enhance the performance of wireless networks by allowing nodes to cooperate with each other to achieve spatial diversity gains. To obtain cooperation gains, appropriate relay node(s) should be selected according to network topology and channel state information (CSI). However, in ad hoc wireless networks, the CSI is random, and the network topology is dynamic. This complicates relay selection, and in turn, makes it difficult to implement cooperative communications in ad hoc wireless networks. To tackle the issue, this paper proposes blind cooperative communications (BCC) for multihop ad hoc wireless networks. In BCC, intermediate nodes and the destination node in a multihop path first listen and cache the data from two-hop-away upstream nodes, and then combine the cached data with the data forwarded by the upstream to obtain diversity gains. The performance of BCC is evaluated by analysis and simulations to show that BCC can significantly increase the packet delivery ratio (PDR) and the average end-to-end throughput (AET). Compared with existing cooperation methods, BCC requires neither CSI and topology information nor additional signaling overheads, making it extremely easy to implement in dynamic multihop ad hoc wireless networks. © 2013 IEEE.
Xu L.,Beihang University |
Zhou W.,Beihang University |
Li X.,Beihang University |
Tang S.,Patent Examination Cooperation Center
IEEE Transactions on Instrumentation and Measurement | Year: 2011
In this paper, a novel approach is presented to the measurement of wet gas flows by using a throat-extended Venturi meter (TEVM) and soft-computing approximation techniques. Results obtained by using an industrial-scale test rig suggest that the flow rate of wet gas flowing in the TEVM is related not only to the static features but also to the dynamic features of the differential pressures (DPs) across the converging and the extended throat sections of the Venturi meter, as well as the static pressure and temperature signals within the Venturi meter. The relation between the signal features and the gas/liquid flow rates of wet gas is established through the use of backpropagation (BP) artificial neural network (ANN) and support vector machine (SVM) approximation techniques. The experimental test carried out within static pressure range of 0.3-0.8 MPa, gas flow rate range of 0.0139-0.0444 m3s/, and liquid flow rate range of 3.0556 × 10-4-0.0015 m3/s suggested that it is a cost-effective and viable method to solve the problem of wet gas metering by combining a revised Venturi meter and soft-computing approximation techniques. © 2006 IEEE.
Chen M.-S.,Central South University |
Chen M.-S.,State Key Laboratory of High Performance Complex Manufacturing |
Lin Y.C.,Central South University |
Lin Y.C.,State Key Laboratory of High Performance Complex Manufacturing |
Ma X.-S.,Patent Examination Cooperation Center
Materials Science and Engineering A | Year: 2012
The dynamic recrystallization behavior in 42CrMo steel was investigated by hot compression tests. The effects of deformation temperature, strain rate, and initial austenite grain size on the dynamic recrystallization behavior were discussed. Based on the experimental results, the kinetic equations for the dynamic recrystallization behavior of 42CrMo steel were proposed. Results indicate that the effects of the deformation temperature, strain rate and initial austenitic grain size on the dynamic recrystallization behavior in 42CrMo are significant. The dynamic recrystallization in 42CrMo steel easily occurs at high deformation temperature, low strain rate and fine initial austenitic grain. A good agreement between the experimental and predicted results shows that the proposed kinetic equations can give an accurate estimate of the dynamic recrystallization behavior in hot deformed 42CrMo steel. © 2012 Elsevier B.V.
Li H.-L.,Patent Examination Cooperation Center |
Zhao J.-Z.,CAS Shenyang Institute of Metal Research
TMS Annual Meeting | Year: 2013
Strip casting experiments were carried out with Al-Pb alloys in a static magnetic field. Samples with well dispersed microstructures were obtained. A model was developed to describe the microstructure evolution in a hyper-monotectic alloy strip cast in a static magnetic field. The microstructure formation was calculated. The numerical results agree well with the experimental ones. They indicate that the magnetic field affects the microstructure formation mainly through the suppression of convections. It causes a more uniform distribution of the nucleation rate and the number density of the minority phase droplets along the radial direction of the sample. All these are favorable for the obtaining of a hyper-monotectic alloy with well dispersed microstructure.
Shao W.,Anhui University of Science and Technology |
Shao W.,CAS Beijing National Laboratory for Molecular |
Zhang Y.,Anhui University of Science and Technology |
Wang Z.,Anhui University of Science and Technology |
And 3 more authors.
Industrial and Engineering Chemistry Research | Year: 2012
The influence of the addition of low amounts of ultrahigh-molecular-weight polyethylene (UHMWPE) on the crystallization kinetics of isotactic polypropylene (iPP) in iPP/UHMWPE blends has been investigated by means of differential scanning calorimetry (DSC) and polarized optical microscopy. During the nonisothermal crystallization process, the primarily formed UHMWPE crystals serve as heterogeneous nucleating agents for iPP nucleation, whereas during the isothermal crystallization process, UHMWPE is in the molten state, iPP nucleation preferentially occurs at the UHMWPE and iPP phase interfaces, and the spherulitic growth rates are not obviously affected. It is particularly interesting to find a critical UHMWPE content (2.5 wt %) in the blends to induce the highest iPP nucleation rate; however, above the critical UHMWPE content, the iPP nucleation rate slows because of aggregation of the UHMWPE component. A delicately designed DSC measurement provides insight into the nucleation mechanism of iPP at the interfaces between the UHMWPE and iPP phase domains. It is proposed that the concentration fluctuations generated from the unstable inhomogeneous phase interfaces in the iPP/UHMWPE blends promote the formation of nuclei, which eventually enhances the nucleation and overall crystallization rates of the iPP component. © 2012 American Chemical Society.
Li M.,Nankai University |
Tian Y.,Nankai University |
Tian Y.,Patent Examination Cooperation Center |
Zhao Y.,Nankai University |
Bu W.,Nankai University
PLoS ONE | Year: 2012
Heteroptera, or true bugs, are the largest, morphologically diverse and economically important group of insects with incomplete metamorphosis. However, the phylogenetic relationships within Heteroptera are still in dispute and most of the previous studies were based on morphological characters or with single gene (partial or whole 18S rDNA). Besides, so far, divergence time estimates for Heteroptera totally rely on the fossil record, while no studies have been performed on molecular divergence rates. Here, for the first time, we used maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) with multiple genes (18S rDNA, 28S rDNA, 16S rDNA and COI) to estimate phylogenetic relationships among the infraorders, and meanwhile, the Penalized Likelihood (r8s) and Bayesian (BEAST) molecular dating methods were employed to estimate divergence time of higher taxa of this suborder. Major results of the present study included: Nepomorpha was placed as the most basal clade in all six trees (MP trees, ML trees and Bayesian trees of nuclear gene data and four-gene combined data, respectively) with full support values. The sister-group relationship of Cimicomorpha and Pentatomomorpha was also strongly supported. Nepomorpha originated in early Triassic and the other six infraorders originated in a very short period of time in middle Triassic. Cimicomorpha and Pentatomomorpha underwent a radiation at family level in Cretaceous, paralleling the proliferation of the flowering plants. Our results indicated that the higher-group radiations within hemimetabolous Heteroptera were simultaneously with those of holometabolous Coleoptera and Diptera which took place in the Triassic. While the aquatic habitat was colonized by Nepomorpha already in the Triassic, the Gerromorpha independently adapted to the semi-aquatic habitat in the Early Jurassic. © 2012 Li et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Wang L.,Control Iron and Steel Research Institute, China |
Du Z.,Control Iron and Steel Research Institute, China |
Fan C.,Patent Examination Cooperation Center |
Xu L.,Control Iron and Steel Research Institute, China |
And 2 more authors.
Journal of Alloys and Compounds | Year: 2011
Magnetostrictive and piezoelectric laminate composites of Fe-Ga and BaTiO3 have been studied. The magnetoelectric (ME) coefficients have been characterized for the transversely magnetized and transversely polarized transverse-transverse (TT) mode. At lower frequencies, the ME voltage coefficient of the laminate was 12.5 mV/Oe. Near the natural resonant frequency (∼95 kHz) of the laminate, the ME voltage coefficient was found to be dramatically increased to 28.5 mV/Oe. In addition, the induced ME voltages were near linear functions of AC magnetic field. © 2010 Elsevier B.V. All rights reserved.
Wang Z.,Taiyuan University of Technology |
Xiong X.,Taiyuan University of Technology |
Zhang H.,China Coal Research Institute |
Chen D.,Patent Examination Cooperation Center
Zhendong Ceshi Yu Zhenduan/Journal of Vibration, Measurement and Diagnosis | Year: 2010
The essence of cutting coal is a process of impacting and breaking the coal with picks. It is difficult to analyze the dynamic process based on the theory and experiment methods. This paper presents a 3-dimensional digital model using the simulation module of impact and cutting in ANSYS/LS-DYNA, and the dynamic process of cutting coal with conical picks is simulated visually. Time curves of speed, acceleration and energy related to researched parts were obtained. Effects of different pick installation angles on cutting efficiency were analyzed. The conclusion is that when the pick installation angle is 40° its cutting efficiency is higher than others.
Bai Y.,Beijing Institute of Technology |
Wu F.,Beijing Institute of Technology |
Yang H.-T.,Tianjin Lishen Battery Joint Stock Co. |
Zhong Y.,Patent Examination Cooperation Center |
Wu C.,Beijing Institute of Technology
Advanced Materials Research | Year: 2012
Spinel LiMn 2O 4 was modified with Y 2O 3 coating by a chemical process. The crystal structures of the as-prepared samples were investigated by X-ray diffraction (XRD). The charge/discharge characteristics of the modified samples were evaluated at different rates between 3.0 and 4.4V. The discharge capacities of 2.0 wt.% Y 2O 3-coated LiMn 2O 4 are 116 mAh·g -1, 99.7mAh·g -1, 93.3mAh·g -1 and 82.9mAh·g -1 at 0.1C, 0.5C, 1C and 2C rates (at 20°C). The cycle abilities improvement of the spinel LiMn 2O 4 coated with Y 2O 3 are demonstrated at elevated temperature (55°C) and high rates (2C). From the analysis of electrochemical impedance spectroscopy (EIS), the improvement of cycle ability may be attributed to the suppression on the formation of the passivating films and the reduction of Mn dissolution, which result from the surface modification with Y 2O 3.
Jiao Q.,Beijing Institute of Technology |
Fu M.,Beijing Institute of Technology |
You C.,Patent Examination Cooperation Center |
Zhao Y.,Beijing Institute of Technology |
Li H.,Beijing Institute of Technology
Inorganic Chemistry | Year: 2012
The hollow Co 3O 4 microspheres were prepared by a gas-liquid diffusion reaction in the presence of ionic liquid [Bmim][BF 4] in combination with calcination at 300 °C. Their structures and morphologies were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy. The growth mechanism of hollow Co 3O 4 microspheres was proposed. The ethanol sensing properties were measured using a WS-30A gas sensor measurement system. The influence of working temperatures, ethanol concentrations, and specific surface areas of Co 3O 4 microspheres on the ethanol sensing properties was investigated. The hollow Co 3O 4 microspheres showed excellent sensitivity to ethanol vapor at a lower operating temperature. © 2012 American Chemical Society.