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Influence of cooling conditions on the hot ductility of Nb-Ti-bearing steels

METALLURGICAL RESEARCH & technology 2015年第6期112卷

作者： Yang, Xiaogang Zhang, Lifeng Li, Shusen Li, Ming Univ Sci & Technol Beijing Sch Met & Ecol Engn Beijing Key Lab Green Recycling & Extract Met GRE Beijing 100083 Peoples R China Qianan Steelmaking Co Ltd Shougang Grp Qianan City 064404 Peoples R China

The hot ductility of Nb-Ti-bearing low-carbon steels was studied. Four cooling methods were designed to investigate the influence of cooling conditions on the hot ductility at temperatures range from 650 degrees C to 1005 degrees C. Increasing the cooling rate generally deteriorates the ductility. However, the high cooling rate RA values were significantly increased when cooling was made in two steps: samples were slow cooled at high temperature zone before being cooled to the test temperatures by fast cooling. Slow cooling guaranteed relative beneficial coarse precipitates, while fast cooling was recommended for refining alpha/gamma transformation microstructures. Proeutectoid ferrite film has a significant influence on the hot ductility of the steel: thicker proeutectoid ferrite film resulted in a ductility deterioration when the thickness of the ferrite film was larger than 5 mu m. The precipitates found were mainly (TixNb1-x)N with high titanium content.

关键词： Continuous Casting cooling method precipitates ferrite films hot ductility

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Bipartite-Oriented Distributed Graph Partitioning for Big Learning

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Journal of Computer Science & technology 2015年第1期30卷 20-29页

作者：陈榕施佳鑫陈海波臧斌宇 Shanghai Key Laboratory of Scalable Computing and Systems Institute of Parallel and Distributed Systems Shanghai Jiao Tong University Shanghai 200240 China

Many machine learning and data mining （MLDM] problems like recommendation, topic modeling, and medical diagnosis can be modeled as computing on bipartite graphs. However, inost distributed graph-parallel systems are oblivious to the unique characteristics in such graphs and existing online graph partitioning algorithms usually cause excessive repli- cation of vertices as well as significant pressure on network communication. This article identifies the challenges and oppor- tunities of partitioning bipartite graphs for distributed MLDM processing and proposes BiGraph, a set of bipartite-oriented graph partitioning algorithms. BiGraph leverages observations such as the skewed distribution of vertices, discriminated computation load and imbalanced data sizes between the two subsets of vertices to derive a set of optimal graph partition- ing algorithms that result in minimal vertex replication and network communication. BiGraph has been implemented on PowerGraph and is shown to have a performance boost up to 17.75X （from 1.16X） for four typical MLDM algorithnls, due to reducing up to 80% vertex replication, and up to 96% network traffic.

关键词： bipartite graph graph partitioning graph-parallel system

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2-Methyl-2,4-pentanediol gas sensor properties of nano-SnO2 flat-type coplanar gas sensing arrays at low detection limit

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MATERIALS SCIENCE-POLAND 2014年第2期32卷 181-187页

作者： Zhu, Chao Huang, Kaijin Yuan, Fangli Xie, Changsheng Huazhong Univ Sci & Technol State Key Lab Mat Proc & Die & Mould Technol Wuhan 430074 Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing 100190 Peoples R China Wuhan Univ Technol State Key Lab Adv Technol Mat Synth & Proc Wuhan 430070 Peoples R China

Nano-SnO2 flat-type coplanar 2-Methyl-2,4-pentanediol (MPD) gas sensor arrays were fabricated by a screen-printing technique based on nano-SnO2 powders prepared by a hydrothermal method. The results show that the fabricated gas sensor arrays have good MPD gas sensing characteristics, such as good selectivity and response-recovery characteristics. Especially, they can be used for detecting the concentration of MPD gas as low as 1 ppm which is much lower than the legal concentration of 20 ppm or 25 ppm. The good sensing properties indicate that the SnO2 gas sensor arrays have great potential for on-line or portable monitoring of MPD gas in practical environments.

关键词： flat-type coplanar gas sensor arrays gas sensing properties low detection limit 2-methyl-2,4-pentanediol nano-SnO2 powders

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Gas-sensing properties and in situ diffuse reflectance infrared Fourier transform spectroscopy study of formaldehyde adsorption and reactions on SnO2 films

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JOURNAL OF MATERIALS RESEARCH 2014年第1期29卷 139-147页

作者： Zhang, Zhenxin Huang, Kaijin Yuan, Fangli Xie, Changsheng Huazhong Univ Sci & Technol State Key Lab Mat Proc & & Mould Technol Wuhan 430074 Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing 100190 Peoples R China Wuhan Univ Technol State Key Lab Adv Technol Mat Synth & Proc Wuhan 430070 Peoples R China

Formaldehyde (HCHO) is widely used in construction, wood processing, furniture, textile, and carpeting industries. However, it is highly toxic. It strongly irritates human eyes and nose, and is a carcinogen. In this paper, the effects of gas concentration and operating temperature on the sensing properties of the nano-SnO2 flat-type coplanar gas sensor arrays to formaldehyde were studied. The results revealed that the nano-SnO2 flat-type coplanar gas sensor arrays exhibited good sensitivity such as a fast response, short recovery time, and low detection limit. In addition, the adsorption and surface reactions of formaldehyde on SnO2 films were also studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at 200-300 degrees C. Molecularly adsorbed formaldehyde, formate, dioxymethylene, polyoxymethylene, H2O, and CO2 surface species were formed during formaldehyde adsorption at 200-300 degrees C. Moreover, a possible mechanism of the reaction process was given.

关键词： Formaldehyde

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Multi-band Microwave Metamaterial Perfect Absorber Based on Mie Resonance Theory

Multi-band Microwave Metamaterial Perfect Absorber Based on ...

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Progress in electromagnetics Research Symposium (PIERS)

作者： Chen, Jun-Feng Wang, Guo-Dong Chen, Zhao-Quan Liu, Ming-Hai Hu, Xi-Wei Huazhong Univ Sci & Technol Sch Elect & Elect Engn State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Peoples R China Univ ITMO St Petersburg 197101 Russia Anhui Univ Sci & Technol Coll Elect & Informat Engn Huainan 232001 Peoples R China

ISBN: (纸本)9781934142288

A multi-band metamaterial absorber (MA) with near-unity absorption based on Mie resonance theory is proposed in the microwave region. It is composed of an array of di-electric cubes with different geometric parameters and a metallic ground plane. The simulated results show that four absorption peaks at 7.31GHz, 7.58GHz, 7.90GHz and 8.19GHz with the corresponding absorption rates of 99.05%, 99.37%, 99.65% and 99.16%, respectively. In addition, the composite MA is polarization-insensitive at the normal incidence and maintains high absorption rates at wide angles of incidence for both TE and TM wave. The influences of the permittivity and the side length of the dielectric cubes on its absorption characteristics are also investigated. This MA would be a promising candidate as absorbing elements in scientific and technical applications, such as cloaks, perfect lens and filters.

关键词： Metamaterials

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Statistical-fluctuation analysis for quantum key distribution with consideration of after-pulse contributions

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Physical Review A 2015年第6期92卷 062344-062344页

作者： Hongxin Li Haodong Jiang Ming Gao Zhi Ma Chuangui Ma Wei Wang University of Foreign Languages Luoyang Henan China

The statistical fluctuation problem is a critical factor in all quantum key distribution (QKD) protocols under finite-key conditions. The current statistical fluctuation analysis is mainly based on independent random samples, however, the precondition cannot always be satisfied because of different choices of samples and actual parameters. As a result, proper statistical fluctuation methods are required to solve this problem. Taking the after-pulse contributions into consideration, this paper gives the expression for the secure key rate and the mathematical model for statistical fluctuations, focusing on a decoy-state QKD protocol [Z.-C. Wei et al., Sci. Rep. 3, 2453 (2013)] with a biased basis choice. On this basis, a classified analysis of statistical fluctuation is represented according to the mutual relationship between random samples. First, for independent identical relations, a deviation comparison is made between the law of large numbers and standard error analysis. Second, a sufficient condition is given that the Chernoff bound achieves a better result than Hoeffding's inequality based on only independent relations. Third, by constructing the proper martingale, a stringent way is proposed to deal issues based on dependent random samples through making use of Azuma's inequality. In numerical optimization, the impact on the secure key rate, the comparison of secure key rates, and the respective deviations under various kinds of statistical fluctuation analyses are depicted.

关键词： Quantum cryptography

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Bonding and interfacial reaction between Ni foil and n-type PbTe thermoelectric materials for thermoelectric module applications

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JOURNAL OF MATERIALS SCIENCE 2014年第4期49卷 1716-1723页

作者： Xia, Haiyang Drymiotis, Fivos Chen, Cheng-Lung Wu, Aiping Snyder, G. Jeffrey CALTECH Dept Mat Sci Pasadena CA 91125 USA Tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China Minist Educ Key Lab Adv Mat Proc Technol Beijing Peoples R China Acad Sinica Inst Phys Taipei 11529 Taiwan

Integration of next generation thermoelectric materials in thermoelectric modules requires a novel or alternative approach for mating the brittle semiconducting thermoelectric materials and the ductile metal interconnects. In this study, pure Ni foil was directly bonded to PbTe-based thermoelectric materials using a rapid hot-press. The materials were sintered at 600 and 650 degrees C, under a pressure of 40 MPa and for various holding times. The resulting interfacial microstructures of the Ni/PbTe joints were investigated. Additionally, the distributions of elements and the phases formed at the Ni/PbTe interface were analyzed. The beta(2) phase (Ni3 +/- xTe2, 38.8-41 at.% Te) was identified at the Ni/PbTe joints bonded at both 600 and 650 degrees C. A ternary phase with approximate composition Ni5Pb2Te3 was found at the Ni/PbTe joints bonded at 650 degrees C. Additionally, the PbTe(Ni) phase was observed along the Ni grain boundaries for both bonding temperatures. Thermodynamics calculation results indicate that only the beta(2) phase can be formed at the Ni/PbTe interface at 900 K among the binary nickel tellurides.

关键词： Grain boundaries

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A Broadband Terahertz Metamaterial Absorber Based on Square Ring Resonators

A Broadband Terahertz Metamaterial Absorber Based on Square ...

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Progress in electromagnetics Research Symposium (PIERS)

作者： Wang, Guo-Dong Chen, Jun-Feng Hu, Xi-Wei Liu, Ming-Hai Huazhong Univ Sci & Technol Sch Elect & Elect Engn State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Peoples R China

ISBN: (纸本)9781934142288

A simple design of broadband metamaterial absorber (MA) is numerically investigated at terahertz frequencies in this paper. The unit cell of this absorber consists of two square rings with different geometric dimensions, a dielectric substrate and continuous metal film. A wide frequency band ranging from 2.95 THz to 3.71 THz with absorption rate of over 90% is obtained. Distributions of surface current density on the front and back metallic layers are illustrated. Finally, the loss contributions of metallic structures and dielectric substrate are also discussed. The proposed absorber is an ideal candidate as absorbing elements in many applications, such as thermal detectors, terahertz imaging, and stealth technology.

关键词： Stealth technology

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Comparative Study of the Dynamic Response of Concrete Gravity Dams Subjected to Underwater and Air Explosions

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JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES 2015年第4期29卷

作者： Wang, Gaohui Zhang, Sherong Kong, Yuan Li, Hongbi Tianjin Univ State Key Lab Hydraul Engn Simulat & Safety Tianjin 300072 Peoples R China

The response of dam structures subjected to explosion shock loading is a key element in assessments for the dam antiknock safety and antiterrorism applications. The physical processes during an explosive detonated in underwater/air and the subsequent response of structures are extremely complex, involving many complex issues such as the explosion, shock wave propagation, shock wave-structure interaction, and structural response. In addition, there exists a significant contrast in wave propagation phenomena in the water and the air medium due to their different physical properties and interface phenomena. In this paper, a fully coupled numerical approach with combined Lagrangian and Eulerian methods is used to simulate the dynamic responses of a concrete gravity dam subjected to underwater and air explosions. The shock wave propagation characteristics from explosions in water and air are simulated and compared. The damage profiles of concrete gravity dams subjected to underwater and air explosions are discussed. The influence of the blast loading from explosions in water and air on the dynamic response and the damage of the dam is also investigated. The analysis results show that a submerged explosion causes significantly more damage to the dam in water than the same mass of explosive in air. (C) 2014 American Society of Civil Engineers.

关键词： Concrete gravity dam Underwater explosion Air explosion Explosion shock loading Shock wave propagation Coupled model

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Gas sensing properties and in situ diffuse reflectance infrared Fourier transform spectroscopy study of trichloroethylene adsorption and reactions on SnO2 films

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APPLIED SURFACE SCIENCE 2014年 300卷 98-103页

作者： Zhang, Zhenxin Huang, Kaijin Yuan, Fangli Xie, Changsheng Huazhong Univ Sci & Technol State Key Lab Mat Proc & Die & Mould Technol Wuhan 430074 Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing 100190 Peoples R China Wuhan Univ Technol State Key Lab Adv Technol Mat Synth & Proc Wuhan 430070 Peoples R China

The detection of trichloroethylene has attracted much attention because it has an important effect on human health. The sensitivity of the SnO2 flat-type coplanar gas sensor arrays to 100 ppm trichloroethylene in air was investigated. The adsorption and surface reactions of trichloroethylene were investigated at 100-200 degrees C by in-situ diffuse reflection Fourier transform infrared spectroscopy (DIRFTS) on SnO2 films. Molecularly adsorbed trichloroethylene, dichloroacetyl chloride (DCAC), phosgene, HCl, CO, H2O, CHCl3, Cl-2 and CO2 surface species are formed during trichloroethylene adsorption at 100-200 degrees C. A possible mechanism of the reaction process is discussed. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Trichloroethylene In situ DRIFTS Flat-type coplanar gas sensor arrays SnO2 films

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