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Rare Metals 2013年第5期32卷 448-452页

作者： Wen Ma Bin Chen fu-shun Liu Qing Xu Division of Science and Technology Information General Research Institute for Nonferrous Metals School of Material Science and Engineering Beijing University of Aeronautics and Astronautics Metrology and Phsico-Chemical Institute Capital Aerospace Machinery Company

In this work, transformation behaviors and mechanical properties of cold-rolled shape memory alloy TisoNia9Fel by severe plastic deformation （SPD） were intensively investigated. The phase transformation behaviors, phase analysis, and microstructures were characterized by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）, respectively. Tensile testing was performed to analyze the effect of SPD on the mechanical properties and shape memory of TisoNi49Fel alloy. When the thickness reduction is beyond 30 %, the martensitic transformation is suppressed. After cold-rolling, the alloy is mainly com- posed of B2 parent phases with some stress-induced martensitic B 19t phases, and high density of dislocations are generated and the grains are obviously refined. The yield stress ab significantly raises from 618 MPa of 0 % cold rolling to 1,338 MPa of 50 % SPD. Shape-memory effect increases from 6.5 % without cold rolling to 8.5 % after 30 % SPD, ascribed to the induced defects in cold rolling. Those results indicate that TisoNi49Fel alloy has improved mechanical properties and potential commercial applications after SPD.

关键词： TiNiFe alloy Cold-rolling Severe plasticdeformation (SPD) Shape memory effect

Non-saturated throughput analysis of IEEE 802.11-based cognitive radio networks

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The Journal of China Universities of Posts and Telecommunications 2012年第6期19卷 6-13页

作者： ZHAO Yuan JIN shun-fu TIAN Nai-shuo College of Information Science and Engineering Yanshan University College of Science Yanshan University

Technology of cognitive radio networks has emerged as an effective method to enhance the utilization of the radio spectrum where the primary users have priority to use the spectrum, and the secondary users try to exploit the spectrum unoccupied by the primary users. In this paper, considering the non-saturated condition, the performance analysis for the IEEE 802.11-based cognitive radio networks is presented with single-channel and multi-channel, respectively. For the single-channel case, an absorbing Markov chain model describing the system transitions is constructed, and one-step transition probability matrix of the Markov chain is given. By using the method of probability generating function, the non-saturated throughput of the secondary users is obtained. For the multi-channel case, taking into account the negotiation-based sensing policy, the mean number of unused channels perceived by the second users is given, and then the non-saturated aggregate throughput of the secondary users is derived. Finally, numerical examples are provided to show the influences of the non-saturated degree, the number of the secondary users and the channel utilization of the primary users on the performance measures for the non-saturated throughput with single-channel and the non-saturated aggregate throughput with multi-channel.

关键词： cognitive radio networks IEEE 802.11 non-saturated throughput absorbing Markov chain probability generating function

Effect of Double Oxide Film Defects on Mechanical Properties of As-Cast C95800 Alloy

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Acta Metallurgica Sinica(English Letters) 2017年第6期30卷 541-549页

作者： Xin-Yi Zhao Zhi-liang Ning fu-Yang Cao Shan-Guang Liu Yong-Jiang Huang Jing-shun Liu Jian-Fei Sun School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China School of Materials Science and Engineering Inner Mongolia University of TechnologyHohhot 010051China

The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al （C95800） alloy were investigated in this study. Plane castings were produced with two types of pouting systems, and their tensile properties were measured and then analyzed by means of Weibull statistics method. The fracture surfaces of the tensile specimens were examined using scanning electron microscopy equipped with energy-dispersive spectroscopy. A large amount of double oxide film defects were observed on the tensile fractured specimens of the topfilled plane castings, and their chemical composition is identified to be Al2O3. Weibull statistics analyses showed that the double oxide film defects significantly reduce mechanical properties of the castings investigated. furthermore, the ultimate tensile strength is more obviously deteriorated by double oxide film defects than elongation.

关键词： Double oxide film defects C95800 alloy Running system Weibull statistics analysis

Microstructures,micro-segregation and solidification path of directionally solidified Ti-45Al-5Nb alloy

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China Foundry 2016年第2期13卷 107-113页

作者： liang-shun Luo Tong Liu Kun Li Yan-qing Su Jing-jie Guo Heng-zhi fu National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnoloryHarbin 150001China China FA W Casting Company Limited Changchun 130011China State Key Laboratory of Advanced Welding and JoiningHarbin Institute of Technolory.Harbin 150001.China

To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb(at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were *** results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm·s^(-1) under the temperature gradients of 15-20 K·mm^(-1), and the primary phase is transformed into an α phase at relatively higher growth rates(V >20 μm·s^(-1)). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm·s^(-1) under a temperature gradient of 15 K·mm^(-1). The increase of temperature gradient to 20 K·mm^(-1) can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as L L→β L+β L+β→αα+β_R β→ααα→γα+γα→α_2+γγ_R+(α_2+γ), in which β_R and γ_R mean the residual β and

关键词： TiAl-Nb alloy directional solidification microstructure micro-segregation solidification path

An Improvement to Multiple Criteria ABC Inventory Classification Using Shannon Entropy

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Journal of Systems Science & Complexity 2017年第4期30卷 857-865页

作者： ZHENG Shanshan fu Yelin LAI Kin Keung liang liang School of Public Affairs University of Science and Technology of China Department of Industrial and Manufacturing Systems Engineering University of Hong Kong School of Finance Jiangxi University of Finance and Economics International Business School Shaanxi Normal University School of Management Hefei University of Technology

This paper extends the Ng-model [Ng, 2007] for multiple criteria ABC inventory classification based upon Shannon entropy. The proposed approach determines the common weights associated with all criteria importance rankings, and provides a comprehensive scoring scheme by aggregating all rankings of the criteria importance. A numerical illustration is presented to compare the model with previous studies.

关键词： Inventory multiple criteria analysis Shannon entropy.

Experimental study and correlation development for the two-phase frictional pressure drop of flow boiling in copper foam fin microchannels

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Science China(Technological Sciences) 2024年第9期67卷 2758-2776页

作者： fu Kai XU XiangHua liang XinGang School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

Flow boiling in microchannels with porous walls has received extensive attention in recent years. Compared with the emphasis on heat transfer, there is a lack of research on the effect of the porous wall structures on the pressure drop characteristics. In this study, systematic experiments are performed to measure the pressure drop of water-vapor two-phase flow in five microchannels with copper foam fins, which consist of nine or six channels and fins of copper foam. The porosities of the foam fins range from0.78 to 0.82 and ratios of fin width to channel width range from 0.5 to 2. The channels are approximately 0.5 or 1 mm in width and 1 mm in height. Both adiabatic and flow boiling experiments are conducted with water at mass fluxes ranging from 66 to 407 kg/(m^(2)s). In the adiabatic experiments, the average quality in channels is between 0.017 and 0.846. In the flow boiling experiments, the outlet quality of channels is between 0.040 and 0.863. Slug flow, churn flow, annular flow, and wispy-annular flow are observed in adiabatic experiments. A two-phase frictional pressure drop correlation based on the Lockhart-Martinelli model is developed for copper foam fin microchannels by introducing the effects of the mass flux, porosity, ratio of fin width to channel width, and heating condition step by step. The mean absolute percentage errors of the new correlation are 7.53% for 325data points under adiabatic conditions and 5.51% for 268 data points under flow boiling conditions, respectively. This work provides insight into the correlations of frictional pressure drop in microchannels with porous walls.

关键词： two-phase flow boiling pressure drop correlation microchannel copper foam porous wall

Dynamic soil-tunnel interaction in layered half-space for incident plane SH waves

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 715-727页

作者： fu Jia liang Jianwen Qin Lin State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University Department of Civil Engineering Tianjin University

The dynamic soil-tunnel interaction is studied by indirect boundary element method （IBEM）, using the model of a rigid tunnel in layered half-space, which is simplified to a single soil layer on elastic bedrock, subjected to incident plane SH waves. The accuracy of the results is verified through comparison with the analytical solution. It is shown that soil-tunnel interaction in layered half-space is larger than that in homogeneous half-space and this interaction mechanism is essentially different from that of soil-foundation-superstructure interaction.

关键词： underground tunnel layered half-space plane SH wave indirect boundary element method soil-tunnel interaction site dynamic characteristics

Microstructural evolution of Al-Cu-Li alloys with different Li contents by coupling of near-rapid solidification and two-stage homogenization treatment

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China Foundry 2020年第3期17卷 190-197页

作者： Lei Luo liang-shun Luo Zhi-ping Li Hong-ying Xia Yan-qing Su liang Wang Jing-jie Guo Heng-zhi fu School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Microstructural improvement of Al-Cu-Li alloys with high Li content plays a critical role for the acquisition of excellent mechanical properties and ultra-low *** this regard,the Al-Cu-Li alloy castings with high Li content from 1.5 wt.%to 4.5 wt.%were prepared by near-rapid solidification,followed by two-stage homogenization treatment(490℃/16 h and 530℃/16 h).The microstructural evolution and solidification behavior of the as-cast and homogenized alloys with different Li contents were systematically studied by combining experiments with calculations by Pandat *** results indicate that with the increase of Li content,the grain sizes decrease,the solution ability of Cu in the matrixα-Al phase increases,while the content of secondary dendrites increases and the precipitated phases change from low melting point phases to high melting point phases under the near-rapid ***,by the coupling of near-rapid solidification and two-stage homogenization,the metastable precipitated phases(Al7Cu4Li and AlCu3)can be dissolved effectively in the alloys with Li content of 1.5 wt.%-2.5 wt.%;moreover,the stable precipitated phases(Al6CuLi3 and Al2CuLi)uniformly distribute at the grain boundaries in the alloys with Li content of 3.5 wt.%-4.5 wt.%.As a result,the refined and homogenized microstructure can be obtained.

关键词： Al-Cu-Li alloys ultra-low density near-rapid solidification two-stage homogenization treatment microstructural evolution

Detached-eddy simulation of supersonic flow past a spike-tipped blunt nose

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Chinese Journal of Aeronautics 2018年第9期31卷 1815-1821页

作者： Yuan XUE liang WANG Song fu School of Aerospace Engineering Tsinghua University

Space vehicle in atmosphere travels mostly at supersonic speed and generates a very strong bow shockwave around its blunt nose. Oblique shock and conical separated flow zone generated by a forward disk-tip spike significantly reduce the drag by reducing the high pressure area on the blunt nose. This study employs improved delayed detached eddy simulation to investigate the characteristic flow structures around a spike-tipped blunt nose at Mach number of 3 and Reynolds number（based on the blunt-body diameter） of 2.72x10;. The calculated time-averaged quantities agree well with experimental data. Characteristic frequencies in different flow regions are extracted using fast Fourier transform. It is found that two distinct instability modes exist: oscillation mode and pulsation mode. The former is related to the foreshock/turbulence interaction with nondimensional frequency at around 0.004. The latter corresponds to the interaction between turbulence and shock structures around the blunt nose, with a typical coherent structure shedding frequency at 0.092.

关键词： Detached-eddy simulation Drag reduction Oscillation mode Pulsation mode Spike-tipped blunt vehicle Supersonic flow

Effects of Metallic Ions on the Flotation of Spodumene and Beryl

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Journal of China University of Mining and Technology 2007年第1期17卷 35-39页

作者： WANG Yu-hua YU fu-shun School of Resources Processing and Bioengineering Central South University Changsha Hunan 410083 China

Effects of multivalent metallic cations, such as Ca2+ and Fe3+, on the flotation of spodumene and beryl were studied. The results show that Fe3+ and Ca2+ exhibit efficient activation on the flotation of spodumene and beryl. The ac- tivation of Fe3+ happens quite well within a pH range of 6-9 while the concentration of Fe3+ is 35 mg/L. Efficient acti- vation of Ca2+ takes place over at a pH over 11.6 at a concentration of 140 mg/L. The zeta potential of beryl and spo- dumene shifts slightly to positive values when activated by Ca2+, but markedly by Fe3+. New stretching frequencies of 1594.24 cm-1 and 1587.13 cm-1 have been found in the FTIR spectra of the two minerals after their interaction with Fe3+ and the collector. These new stretching frequencies are the asymmetric stretching frequencies of COO-(carboxyl anion), so thecollector may be chemically absorbed on the surface of Fe3+-activated beryl and spodumene.

关键词： spodumene beryl metallic ions activation flotation