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In situ synthesis and hardness of TiC/Ti_5Si_3 composites on Ti-5Al-2.5Sn substrates by gas tungsten arc welding

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International Journal of Minerals,Metallurgy and Materials 2013年第3期20卷 284-289页

作者： wen-qing Yan Le Dai Chi-bin Gui School of Mechanical and Automotive Engineering South China University of Technology School of Materials and Metallurgy Wuhan University of Science and Technology Military Representative Office of Navy 407 Factory College of Materials Science and Engineering Huazhong University of Science and Technology

TiC/TisSi3 composites were fabricated on Ti-5A1-2.5Sn substrates by gas tungsten arc welding （GTAW）. Identification of the phases was performed using X-ray diffraction （XRD）. The microstructures were analyzed using scanning electron microscopy （SEM） combined with energy-dispersive X-ray spectrometry （EDS） and optical microscopy （OM）. The Vickers hardness was measured with a micro-hardness tester. The TiC/TisSi3 composites were obtained in a double-layer track, and the Vickers hardness of the track increased by two to three times compared with the Ti-5A1-2.5Sn substrate.

关键词： titanium alloys surface modification gas tungsten arc welding (GTAW) microstructure hardness

Lanthanum incorporated in MCM-41 and its application as a support for a stable Ni-based methanation catalyst

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Journal of Rare Earths 2018年第4期36卷 367-373页

作者： Yang Han Bo wen Mingyuan Zhu bin Dai School of Chemistry and Chemical Engineering of Shihezi University Shihezi 832000China Key Laboratory for Green Processing of Chemical Engineering of Xinjiang bingtuan Shihezi 832000Chino

Herein, lanthanum was incorporated via hydrothermal synthesis into a MCM-41 framework structure with La/Si molar ratios from 0.01 to 0.1. Samples of NiO supported on LaMCM-41 were prepared using the impregnation method. The catalyst performance was evaluated using a fixed bed CO methanation reactor. A Ni/LaMCM-41 catalyst with La/Si = 0.1 shows the best catalytic performance with a CO conversion of almost 100% and a CH4 selectivity of 89.5% at 250 ℃ under a pressure of 1.5 MPa and at an airspeed of 36,000 mL/（g·h）. Compared with Ni-La/MCM-41（La/Si = 0.1） and Ni/MCM-41 prepared via the impregnation method, Ni/LaMCM-41（La/Si = 0.1） shows a higher CO conversion and CH4 *** a 100 h stability test, the Ni/LaMCM-41（La/Si = 0.1） catalyst shows excellent stability; furthermore, the CO conversion is always greater than 98.0%, which is significantly better than the results for Ni/*** experimentally demonstrate that elemental La enters the framework of MCM-41. The Ni/LaMCM-41 catalyst performs well because the La reduces the average particle size of the NiO particles and enhances the interaction between NiO and MCM-41; moreover, the introduction of La significantly inhibits the sintering of the catalyst and the formation of carbon deposits.

关键词： Syngas methanation LaMCM-41 Anti-carbon deposition Catalytic stability Rare earths

Rate of the phase transition for a charged anti-de Sitter black hole

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Science China(Physics,Mechanics & Astronomy) 2023年第4期66卷 61-66页

作者： Zhen-Ming Xu bin Wu wen-Li Yang School of Physics Northwest UniversityXi'an 710127China Institute of Modern Physics Northwest UniversityXi'an 710127China Shaanxi Key Laboratory for Theoretical Physics Frontiers Xi'an 710127China Peng Huanwu Center for Fundamental Theory Xi'an 710127China

Phase transition is a core content of black hole thermodynamics. This study adopted Kramer’s escape rate method for describing the Brownian motion of particles in an external field to investigate the intensity of the phase transition between small and large black hole states. Some existing studies mostly focused on the formal analysis of the thermodynamic phase transition of black holes, but they neglected the detailed description of the phase transition process. Our results show that the phase transition between small and large black holes for charged anti-de Sitter(AdS) black holes presents serious asymmetric features, and the overall process is dominated by the transition from a small black hole to a large black hole. This study filled a research gap of a stochastic process analysis on the issue of the first-order phase transition rate in the Ad S black hole.

关键词： black hole thermodynamics phase transition thermal potential Kramer’s escape rate

Dynamic Characteristics of Hydrocarbon Fuel within the Channel at Supercrit- ical and Pyrolysis Condition

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Journal of Thermal Science 2017年第6期26卷 560-569页

作者： YU bin ZHOU Weixing QIN Jiang BAO wen Harbin Institute of Technology 150001 Heilongjiang China

Regenerative cooling with fuel as the coolant is used in the scramjet engine. In order to grasp the dynamic cha- racteristics of engine fuel supply processes, this article studies the dynamic characteristics of hydrocarbon fuel within the channel. A one-dimensional dynamic model was proved, the thermal energy storage effect, fuel volume effect and chemical dynamic effect have been considered in the model, the ordinary differential equations were solved using a 4th order Rungc-Kutta method. The precision of the model was validated by three groups of expe- rimental data. The effects of input signal, working condition, tube size on the dynamic characteristics of pressure, flow rate, temperature have been simulated. It is found that cracking reaction increased the compressibility of the fuel pyrolysis mixture and lead to longer responding time of outlet flow. The responding time of outlet flow can reach 3s when tube is 5m long which will greatly influence the control performance of the engine thrust system. Meanwhile, when the inlet flow rate appears the step change, the inlet pressure leads to overshoot, the overshoot can reach as much as 100%, such highly transient impulse will result in detrimental effect on fucl pump.

关键词： dynamic characteristics n-Decane supercritical pyrolysis

Reducing the biases in shortwave cloud radiative forcing in tropical and subtropical regions from the perspective of boundary layer processes

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Science China Earth Sciences 2016年第7期59卷 1427-1439页

作者： SUN wen Qi LI Li Juan WANG bin State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences Ministry of Education Key Laboratory for Earth System Modeling Center of Earth System Science Tsinghua University

Biases in shortwave cloud radiative forcing(SWCF), which cause overestimates in tropical regions and underestimates in subtropical marine stratocumulus regions, are common in many climate models. Here, two boundary layer processes are investigated in the atmospheric model GAMIL2, entrainment at the top of the boundary layer and longwave radiative cooling at the top of stratocumulus clouds, in order to reduce biases and reveal the mechanisms underlying these processes. Our results show that including the entrainment process in the model can reduce negative SWCF biases in most tropical regions but increases positive SWCF biases in subtropical marine stratocumulus regions. This occurs because entrainment reduces the low-level cloud fraction and its cloud liquid water content by suppressing the vertical turbulent diffusion in the boundary layer and decreasing the relative humidity when warm and dry free atmosphere is entrained in the boundary layer. Longwave radiative cooling at the top of stratocumulus clouds can enhance turbulent diffusion within the stratocumulus-topped boundary layer. When combined with the entrainment process, longwave radiative cooling reduces the positive SWCF biases in subtropical marine stratocumulus regions that are observed using the entrainment process alone. The incorporation of these two boundary layer processes improves the simulated SWCF in tropical and subtropical regions in GAMIL2.

关键词： SWCF GAMIL2 Boundary layer Entrainment Stratocumulus

Promoting the mechanical properties of Ti42Al9V0.3Y alloy by hot extrusion in the α+β phase region

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第10期11卷 738-743页

作者： wen-chen XU Hao ZHANG De-bin SHAN Department of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

Hot extrusion was conducted in the α+β phase region for promoting mechanical properties of Ti42Al9V0.3Y. The microstructures and tensile properties before and after hot extrusion were studied. The results show that the microstructure of the as-cast alloy mainly consists of massive γ phase in β matrix and the as-extruded alloy mainly consists of lamellar α2/γ, lamellar β/γ, and strip γ propagating from elongated β phase. In the as-cast alloy, the predominantly observed fracture mode is transgranular cleavage failure at room temperature and intergranular fracture at 650-750 °C. After hot extrusion, it transforms into transgranular cleavage-like failure, including translamellar cleavage and delamination. The excellent tensile properties of the as-extruded material are attributed to the obvious refined microstructure with broken YAl2 particles and the micro-crack shielding action of the TiAl lamellasome.

关键词： TiAl alloy Microstructure Mechanical property Hot extrusion

QKD-based quantum private query without a failure probability

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Science China(Physics,Mechanics & Astronomy) 2015年第10期58卷 12-17页

作者： LIU bin GAO Fei HUANG Wei wen QiaoYan State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications College of Computer Science Chongqing University

In this paper, we present a quantum-key-distribution(QKD)-based quantum private query(QPQ) protocol utilizing single-photon signal of multiple optical pulses. It maintains the advantages of the QKD-based QPQ, i.e., easy to implement and loss tolerant. In addition, different from the situations in the previous QKD-based QPQ protocols, in our protocol, the number of the items an honest user will obtain is always one and the failure probability is always zero. This characteristic not only improves the stability(in the sense that, ignoring the noise and the attack, the protocol would always succeed), but also benefits the privacy of the database(since the database will no more reveal additional secrets to the honest users). Furthermore, for the user's privacy, the proposed protocol is cheat sensitive, and for security of the database, we obtain an upper bound for the leaked information of the database in theory.

关键词： quantum private query quantum key distribution single-photon signal

Observations of the Singlets of Higher-Degree Modes Based on the OSE

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Journal of Earth Science 2018年第6期29卷 1398-1408页

作者： Shi-Yu Zeng wen-bin Shen School of Geodesy and Geomatics/Key Laboratory of the Geospace Environment and Geodesy Wuhan University State Key Laboratory for Information Engineering in Surveying Mapping and Remote SensingWuhan University

In this study,we selected 18 SG（superconducting gravimeter）records from 15 GGP stations with 99 vertical and 69 horizontal components of IRIS broad-band seismograms during 2004 Sumatra Earthquake to detect the splitting of higher-degree Earth’s free oscillations modes（0S4,0S7〈sub〉0S10,2S4,1S5,2S5,1S6）and 12 inner-core sensitive modes（25S2,27S2,6S3,9S3,13S3,15S3,11S4,18S4,8S5,11S5,23S5,16S6）by using OSE（optimal sequence estimation）method which only considers *** indicate that OSE can completely isolate singlets of high-degree modes in time-domain,effectively resolve the coupled multiplets independently,and reduce the possibility of mode mixing and end effect,showing that OSE could improve some signals’signal-to-noise *** the results of SG records with seismic data sets suggests that the number of SG records is inadequate to detect all singlets of higher *** we mainly selected plentiful seismograms of IRIS to observe the multiplets of higher *** estimate frequencies of the singlets using AR method and evaluate the measurement error using bootstrap ***,we compared the observations with the predictions of PREM-tidal *** study demonstrates that OSE is effective in isolating singlets of Earth’s free oscillations with higher *** experimental results may provide constraints to the construction of 3D Earth model.

关键词： free oscillation mode splitting detection high-degree modes OSE

Probabilistic greedy pursuit for streaming compressed spectrum sensing

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The Journal of China Universities of Posts and Telecommunications 2011年第5期18卷 15-21页

作者： LU Yang GUO wen-bin WANG Xing WANG wen-bo Key Laboratory of Universal Wireless Communication Ministry of EducationBeijing University of Posts and TelecommunicationsBeijing 100876China

This paper presents a probabilistic greedy pursuit （PGP） algorithm for compressed wide-band spectrum sensing under cognitive radio （CR） scenario. PGP relies on streaming compressed sensing （CS） framework, which differs from traditional CS processing way that only focuses on fixed-length signal＇s compressive sampling and reconstruction. It utilizes analog-to-information converter （AIC） to perform sub-Nyquist rate signal acquisition at the radio front-end （RF） of CR, the measurement process of which is carefully designed for streaming framework. Since the sparsity of wide-band spectrum is unavailable in practical situation, PGP introduces the probabilistic scheme by dynamically updating support confidence coefficient and utilizes greedy pursuit to perform streaming spectrum estimation, which gains sensing performance promotion progressively. The proposed algorithm enables robust spectrum estimation without the priori sparsity knowledge, and keeps low computational complexity simultaneously, which is more suitable for practical on-line applications. Various simulations and comparisons validate the effectiveness of our approach.

关键词： cognitive radio wide-band spectrum sensing streaming compressed sensing probabilistic greedy pursuit support confidence coefficient