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Search Results: 1 - 10 of 92601 matches for " SUN Daqian ZHOU Zhenfeng ZHAO Zongju Welding Division "
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Development of a New Electrode for Arc Wclding of Austempercd Ductile Iron(ADI)
SUN Daqian ZHOU Zhenfeng ZHAO Zongju Welding Division,Jilin University of Technology,Changchun,China To whom correspondence should be addressed,

材料科学技术学报 , 1992,
Abstract: The effect of Ca,Ba,Bi and Al on the amount of carbide in ductile iron weld metal,the microstructural characteristics of ADI weld metal and the effect of heat treatment process on the microstructure and mechanical properties of ADI weld metal have been studied.On this basis the optimum composition of weld and the optimum heat treatment process of ADI weld metal were de- termined and a new electrode for arc cold-welding (i.e.,without preheat) of ADI was developed.The ductile iron welded joint free from eutectic carbide can be produced by using this electrode before austempering and the weld metal obtained after austempering has a microstructure and mechanical properties similar to those of ADI.The mechanical properties of welded joints can match the require- ment of ADI.
Development of a New Welding Material for Arc Welding of As-cast Ferritic Ductile Iron
Daqian SUN,Zhenfeng ZHOU,Jingfei LUAN,

材料科学技术学报 , 1998,
Abstract: Using the nickel welding wire, the effect of alloying elements on the chilling tendency of partial fusion zone (PFZ) of arc-welded ferritic ductile iron and the mechanical properties of weld metal have been systematically studied. On this basis a new nickel electrode for arc welding of ferritic ductile iron (QT400-17) is developed for the first time. The mechanical properties of its weld metal can match those of ferritic ductile iron. The width of carbide layer (WCL) in PFZ is significantly decreased, the welded joint has excellent machinability and the weid metal has high hot cracking resistance
Effect of Si, Al and Bi on Structure and Properties of As-welded and Austempered Ductile Iron Weld Metals during Gas Welding
Daqian SUN,Zhenfeng ZHOU,Haicheng CAO,

材料科学技术学报 , 1996,
Abstract: Effect of Si, Al and Bi on the microstructure and mechanical properties of as-welded and austempered ductile iron weld metals has been studied with SEM, TEM, X-ray diffraction, image analysing system, tension and other test methods. Results show that increasing weld Si, Al and Bi content favours improving the chilling tendency of as-welded ductile iron weld and mechanical properties of austempered ductile iron weld and the mechanism is also discussed. On this basis the optimum chemical composition of weld is determined. The mechanical properties of weld and welded joint after austempering can match those of austempered ductile iron
Revision of a CCT Diagram of the Simulated ADI Weld Metal and Its Application in Actual Welding
Deyuan LI,Zhenfeng ZHOU,Daqian SUN Chengji SHAO,

材料科学技术学报 , 1998,
Abstract: A continuous cooling transformation (CCT) diagram of the simulated ADI weld metal has been developed by means of the Formastor-F diagram measurement apparatus, and revised by comparing with the actual welding. Finally the revised diagram was used to determine the welding technology
Effect of Si, Mn and Al on the Microstructure and Mechanical Properties of ADI Weld Metal
Effect of Si,Mn and Al on the Microstructure and Mechanical Properties of ADI Weld Metal

Daqian SUN,Zhenfeng ZHOU,Wenquan WANG,Lian LIU,

材料科学技术学报 , 2002,
Abstract: The effects of Si, Mn and Al on the microstructure and mechanical properties of ADI weld have been studied. The microstructure of ADI weld metal mainly consists of bainitic ferrite and retained austenite. Mechanical properties of ADI weld increase with increasing Si content, but an excess of Si(3.79%) results in decreasing the austemperability owing to decreasing the carbon content of the matrix austenite. Mn increases the retained austenite volume fraction, but the ductility and impact toughness of weld obviously decrease with increasing Mn content because of increased amount of martenite and twin martenite. In the range of 0.13%-0.64%AI, increasing Al content favours improving the mechanical properties of ADI weld. Therefore, it is very important to select suitable Si, Mn and Al contents to improve mechanical properties of ADI weld.
Microstructural Features of Friction-Welded Ti-6Al-4V Joint
Daqian SUN,Zhenan REN,Zhenfeng ZHOU,TNorth,YANG Zhai,SSathian,

材料科学技术学报 , 2000,
Abstract: Microstructural features of friction-welded Ti-6Al-4V joint have been investigated by both optical microscope and transmission electron microscope (TEM). The microstructure of the welded joint is not uniform. It can be classified into the phase transformed region(P), the deformed region(D) and the region of unchanged base metal(B). In the phase transformed region, the microstructure consists of platelike, acicular and equiaxed alpha phase plus beta phase between them and the dislocations can be observed in some or phase particles. The equiaxed alpha phase mainly distributes in the near center of rod specimen. The quantity of platelike and acicular alpha phase and the size of the grains increase progressively along the radial direction of the rod type welded joint. In the deformed region, the grains are reoriented and the microstructure consists of the elongated alpha phase containing a lot of dislocations and intergranular beta phase.
Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe-C-Cr Weld Surfacing Layer
Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe—C—Cr Weld Surfacing Layer

Daqian SUN,Wenquan WANG,Zhaozhi XUAN,Yue XU,Zhenfeng ZHOU,

材料科学技术学报 , 2003,
Abstract: Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).
Subtyping of type A influenza by sequencing the variable regions of HA gene specifically amplified with RT-PCR
An Yan,GuoHui Ding,ZhenFeng Zhou,Hui Dong,YaKun Zhang,Lei Zhu,YunGang He,GuoQing Zhang,YiXue Li,Bing Sun,Zhong Huang,Ke Lan,Li Jin,HongYan Wang,XiaoNing Wang,Zhong Yang,Yang Zhong,JianXin Dai,YaJun Guo,Hao Wang,XiaoYan Che,Fan Wu,ZhenGan Yuan,Xi Zhang,ZhiWei Cao,XiaoNong Zhou,JiaHai Zhou,ZhiYong Ma,GuangZhi Tong,GuoPing Zhao,WeiRong Jin,Hui Xiong
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0433-7
Abstract: The outbreak of a novel influenza A (H1N1) virus across the globe poses a threat to human health. It is of paramount importance to develop a rapid, reliable and inexpensive diagnostic procedure. Based on the bioinformatic information from public database, primers specific for influenza A virus surface protein haemagglutinin (HA) of several subtypes (including H1, H2, H3, H5, H7 and H9) were designed. Primer-specific PCR products were subjected to sequencing for accurately distinguishing H1 and H3 subtypes from others. This sequencing-based detection method will not only be applied to rapid detection and simultaneous subtype identification of new influenza A virus H1N1, but also provide the strategies to monitor other new types of influenza virus with explosive potential.
An Optical Biosensor for Monitoring Antigen Recognition Based on Surface Plasmon Resonance Using Avidin-Biotin System
Ying Mu,Hanqi Zhang,Xiaojun Zhao,Daqian Song,Zhen Wang,Jing Sun,Minjing Li,Qinhan Jin
Sensors , 2001, DOI: 10.3390/s10300091
Abstract: A novel optical biosensor based on simultaneous multiwave length detection surface plasmon resonance (SPR) has been developed for immunosensing. The sensor is designed on the basis of fixing angle of incidence and measuring the reflected intensities of light in the wavelength range of 400–800 nm. The SPR spectra are shown in terms of reflected light intensity verus wavelength of incident light. The intensity of the reflected light is the minimum at the resonant wavelength. The biorecognition surface, formed on a chemically modified gold layer, consists of avidin that is specifically bound with biotin. These sensing membranes were self-assembled on gold layer. The processes of sensing monolayer formation were studied in real time through observing the change of resonant wavelength. The modified surface was used as a model immunosensor and to detect successfully the human factor B (Bf). The Bf was determined in the concentration range of 0.5~100 μg/mL. Under optimum experimental conditions, the sensor has a good repeatability, reversibility and selectivity.
Relay Selection and Power Allocation in Amplify-and-Forward Cognitive Radio Systems Based on Spectrum Sharing  [PDF]
Daqian Zhao, Zhizhong Zhang, Fang Cheng
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2069
Abstract: In this paper, we consider a spectrum sharing scheme that is a joint optimization of relay selection and power allocation at the secondary transmitter, which aims to achieve the maximum possible throughput for the secondary user. This paper considers the scenario where the primary user is incapable of supporting its target signal-to-noise ratio (SNR). More especially, the secondary transmitter tries to assist the primary user with achieving its target SNR by cooperative amplify-and-forward (AF) relaying with two-phase. By exhaustive search for all candidate secondary transmitters, an optimal secondary transmitter can be selected, which not only can satisfy the primary user’s target SNR, but also maximize the secondary user’s throughput. The optimal secondary transmitter acts as a relay for the primary user by allocating a part of its power to amplify-and-forward the primary signal over the primary user’s licensed spectrum bands. At the same time, as a reward, the optimal secondary transmitter uses the remaining power to transmit its own signal over the remaining licensed spectrum bands. Thus, the secondary user obtains the spectrum access opportunities. Besides, there is no interference between the primary user and the secondary user. We study the joint optimization of relay selection and power allocation such that the secondary user’s throughput is maximized on the condition that it satisfies the primary user’s target SNR. From the simulation, it is shown that the joint optimization of relay selection and power allocation provides a significant throughput gain compared with random relay selection with optimal power allocation (OPA) and random relay selection with water-filling power allocation (WPA). Moreover, the simulation results also shown that our spectrum sharing scheme obtains the win-win solution for the primary system and the secondary system.
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