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Now showing items 145 - 160 of 295

  • Effect of internal pressure on corner radius and thickness distribution of shear hydro-bending of 5A02 aluminum alloy tube

    Wang Yong   Han Cong   Yuan Shi-jian  

    The effects of internal pressure on forming defects, corner radius and thickness distribution of 5A02 aluminum alloy shear hydro-bending tubes were studied by experiment. Numerical simulation was conducted to analyze the effect of internal pressure on axial strain and invariable lines of thickness strain. The ultra-small bending tubes were successfully manufactured when the relative internal pressure, ratio of internal pressure and yield stress of the material, is higher than 0.2. The relative bending radius of the first outer corner decreases from 0.3 to 0.025 when the relative internal pressure increases from 0.2 to 1.2. The axial thickness distribution is different in intrados and extrados. The changing rate of thickness is larger with a higher internal pressure. The minimum thickness decreases from 1.45 mm to 0.87 mm when the relative internal pressure changes from 0.2 to 1.2. The tube is divided into feeding zone, the first corner, shearing zone, the second corner and holding zone. The strain of feeding zone and the first corner is compressive caused by the feeding. The strain of the second corner and holding zone is tensile for far away from feeding punches. The strain of shearing zone changes from compressive to tensile with rising of internal pressure. On one hand, the smaller corner radius formed by higher internal pressure blocks the feeding. On the other hand, the corner filling strengthens the extensive strain of shearing zone. In the feeding zone and holding zone, thickness strain is positive, and the tube thickens. In the corner and shear zones, thickness strain is negative, and the tube thins.
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  • A research of turbocharged gasoline transient response

    Xu Xinsheng   Liu Jingping   Wang Yong   Zhao Zhichao   Xia Xiaolang   Fu Jianqin  

    To improve transient response of turbocharged gasoline; various kinds of optimization methods were studied by using engine performance simulation software GT-POWER. The results showed that: increasing valve overlap; using the series composite supercharge and replacing the original turbocharger with a VNT turbocharger can improve transient response characteristics of the original supercharge engine; when using the series composite supercharge; transient response of turbocharged gasoline hardly has any "hysteresis" phenomenon.
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  • A New Symbol Timing Synchronization Method for Wireless OFDM Systems

    Ai Bo   Ge Jian-hua   Wang Yong  

    This paper proposes a new method for the coarse symbol timing synchronization and frequency offset estimation in wireless OFDM systems. Different from the conventional method based on the correlation between cyclic prefix and its duplicated part in the single sample point; the proposed method employs the separated block of the correlation. Simulation results and the corresponding analysis demonstrate its better accuracy and steadiness. Besides these; the presented method can also be utilized to evaluate the multi-path profile of channels
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  • Discussion of “Carbon benefits of wolfberry plantation on secondary saline land in Jingtai oasis, Gansu – A case study on application of the CBP model” by Yaolin Wang, Chuanyan Zhao, Quanlin Ma, Yingke Li, Hujia Jing, Tao Sun, Eleanor Milne, Mark Easter, Keith Paustian, Hoi Wen Au Yong, John McDonagh (2015) [Journal of Environmental Management 157, 303–310]

    Azarnivand   Ali  

    Abstract Wang et al. (2015) employed driving force-pressure-state-impact-response (DPSIR) framework to provide a robust decision-making structure for carbon emission reduction by use of wolfberry plantation in the Jingtai oasis, China. DPSIR appropriately identified the causes of problem along with adopting the responses to the barriers associated with wolfberry plantation. However, the discusser argues that, the paper could have prepared more viable outcomes, if the authors had used causal network rather than causal chains through the DPSIR framework. Furthermore, they could have quantified the mutual relationship among the relevant factors to provide a detailed economic assessment. With this knowledge in hand, the current discussion letter suggests eDPSIR and meDPSIR to address drawbacks regarding conventional DPSIR framework. Due to proper performance of eDPSIR and meDPSIR, they are recommended as practical tools in the future environmental studies.
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  • A new method for linear model following adaptive control

    Wang Yong  

    The paper comes up with a new method for model following adaptive control. The key idea is to use linear controller, so as to avoid the problem of nonlinear infinite augmenting arithmetic operator in adaptive loops. Meanwhile, it has such virtues as simple calculation, short adaptive recycling, small following errors, etc. Using this method, we designed the sidelong control system of a fighter plane. The simulation on computer proves to be satisfactory.
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  • Improved breakdown voltage of AlGaN/GaN HEMTs grown on Si substrates using partially Mg-doped GaN buffer layer by MOCVD

    Wang Yong   Yu NaiSen   Deng DongMei   Li Ming   Sun Fei   Lau KeiMay  

    AlGaN/GaN high electron mobility transistors (HEMTs) were grown on Si substrates by MOCVD. In the HEMT structure, a 1 mu m GaN buffer layer was partially doped with Mg in an attempt to increase the resistivity and minimize the buffer leakage. The AlGaN/GaN HEMTs grown on undoped and partially Mg-doped GaN buffer layers were processed and the DC characteristics of the devices were characterized for comparing the effect of Mg doping. For the device with the partially Mg-doped GaN buffer layer, a lower drain leakage current density of 55.8 nA/mm, a lower gate leakage current density of 2.73 mu A/mm, and a higher off-state breakdown voltage of 104 V were achieved with device dimensions L (g)/W (g)/L (gs)/L (gd)=1/10/1/1 mu m, better than the device with the undoped GaN buffer layer, which has a higher drain leakage current density of 9.2 mu A/mm, a higher gate leakage current density of 91.8 mu A/mm, and a lower off-state breakdown voltage of 87 V with the same device dimensions.
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  • Design of Resistance Measurement Equipment for Motor Commutator Segment Based on LabWindows/CVI

    Wang Yong   Wang Xiaohong   Zhang Liwen   Zhang Jincan   Tian Wei  

    Traditional resistance measurement for DC motor commutator segment is manual. The process is complicated; the efficiency is low; and the cost is high. In order to enhance efficiency and precision of the resistance measurement; we design an automatic measurement equipment using virtual instrument technique. The equipment consists on industrial compute; stepping motor drive transmission system; low resistance measuring meter; host compute software. Making the equipment universal and automated is the core of design. We discuss working principle of the equipment; hardware design; software design; measurement experiment process and results analysis. Hardware design includes accurate position control of stepping motor; 4-wire method for resistance measurement; special fixture design for probe. Software design based on LabWindows/CVI platform includes serial communication; asynchronous timers; multi-thread; ActiveX control. The measurement experiment results indicate that the euipment can measure almost all kind of DC motor rotors accurately; also can record and save measurement results automatically.
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  • Research on Lean Analysis Algorithm for Equipment Centralized Monitoring in Big Data Era

    The equipment monitoring brought by the smart grid big data is difficult to effectively supervise the operation status of the whole network substation, and the typical defects(familial defects) are difficult to classify and locate. This paper proposes the substation operation state evaluation algorithm and typical defect classification algorithm. The operating state evaluation algorithm of the substation is based on different operation data generated by the substation. By normalizing the data of different dimensions, the substation is divided into different operating state levels. The typical defect classification algorithm establishes and maintains the historical experience database, and calculates the conditional probability of each information item to realize the correlation between the signal and the defect, and finally judge whether the signal is from a typical defect. These two algorithms are effective means for equipment monitoring professionals to realize intelligent supervision of substations and equipment in the era of big data.
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  • Dynamics of Zn between soil and plant in Northeast Leymus chinensis grassland

    Guo Ji-xun   Wang Yong   Zhou Tian  

    A study was conducted to determine the dynamic of Zn content between soil and plant in the natural protection zone of Leymus chinensis grassland in Changling County (44 degrees 30'-44 degrees 45'N; 123 degrees 31'-124 degrees 10'E), Jilin Province, China. Results showed that the total Zn content was lower, available Zn content had a moderate level in the soil, and the plants was not lack of Zn. During the growing season, content of total Zn and available Zn in soil showed a down-trend distribution along the soil profile. Content of total Zn had a significantly positive correlation with that of the organic matter, but it was negatively correlated to soil pH. Monthly dynamic of the average content of total Zn showed a "V" type curve in the growing season from May to August, and July was the nadir. The trend of the average content of available Zn was similar to the content of total Zn, but was down after August; Zn content variation in the organs and litter of L. chinensis was great, with the order of root > rhizome > leaf > stem > litter. The ratio of available Zn content in A layer versus B layer was more than 2 times that of the total Zn, which indicated that the soil of A layer had higher enrichment capacity of available Zn. The enrichment of Zn in the root of L. chinensis was 44.17 times as that in the. soil. The absorbing intensity of root had a significantly negative correlation with the activity of Zn in the son (r=-0.8800, p < 0.01).
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  • Corrosion behavior of Mg and Mg-Zn alloys in simulated body fluid

    Gao Jia-cheng   Wu Sha   Qiao Li-ying   Wang Yong  

    The corrosion behavior of Mg and Mg-Zn in simulated body fluid was studied. The mass loss of pure Mg, Mg-Zn-Zr and Mg-Zn-Zr-Y in simulated body fluid was measured using photovoltaic scale meter. Corrosion rate was determined through electrochemical tests. Finally, the corrosion mechanism was thermodynamically studied. The results show that the corrosion rate decreases with the lapse of time for both pure Mg and Mg alloys. The purer the alloy, the better the corrosion resistance exhibits. The corrosion behavior of Mg alloy is improved by the addition of trace Y.
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  • AC-space-charge effects on gap coupling coefficient of a klystron cavity

    Chuan-Lu Huang   Yao-Gen Ding   Wang Yong   Dong-Ping Gao  

    A novel model was developed to evaluate gap coupling coefficient considering ac-space-charge effects due to the bunching in the interaction gap. The formulation was derived based on Webster's debunching theory and the electron-stream oscillation equation with arbitrary gap field distribution on the gridless gap. The coupling coefficient with ac-space-charge effects was investigated through both analysis and particle-in-cell simulation. The calculation results are in reasonable agreement with the simulation results. With the ac-space-charge effects, the coupling coefficient is lower than that calculated by ballistic theory. It is found that the plasma gap transit angle is a key factor in the effects of ac space charge on the coupling coefficient. Large beam current or gap length and, hence, mean large plasma transit angle indicate strong ac-space-charge effects on the coupling coefficient.
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  • Particle-in-Cell Simulation and Optimization of Multigap Extended Output Cavity for a W-Band Sheet-Beam EIK

    Shuyuan Chen   Cunjun Ruan   Wang Yong   Changqing Zhang   Ding Zhao   Xiudong Yang   Shuzhong Wang  

    In this paper, a multigap extended output cavity was designed by 3-D simulations, which served as the output cavity for a W-band sheet-beam extended interaction klystron (SBEIK). In our numerical design, the circuit dimensions were systematically optimized by parametric finite-difference time-domain simulations, and the equivalent circuit for the output cavity was also analyzed. The proper external loading was selected by using a region of loss in 3-D, and the output power was optimized. The results were verified by using the coupler and the waveguide. The 2pi mode of the optimized five-gap extended output cavities had an ohmic Q (Q 0) of 1343.5, an external Q (Q e) of 501.6, and a loaded Q (Q L) of 365.2 at 94.5 GHz. The 3-D particle-in-cell simulations predict that the output cavity of the SBEIK (75 kV and 4 A) can stably produce more than 50 kW of output power using a prebunched beam.
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  • Photoelectrochemical characteristics of TiO2 nanorod arrays grown on fluorine doped tin oxide substrates by the facile seeding layer assisted hydrothermal method

    Sui Mei-rong   Han Cui-ping   Gu Xiu-quan   Wang Yong   Tang Lu   Tang Hui  

    TiO2 nanorod arrays (NRAs) were prepared on fluorine doped tin oxide (FTO) substrates by a facile two-step hydrothermal method. The nanorods were selectively grown on the FTO regions which were covered with TiO2 seeding layer. It took 5 h to obtain the compact arrays with the nanorod length of similar to 2 mu m and diameter of similar to 50 nm. The photoelectrochemical (PEC) properties of TiO2 NRAs are also investigated. It is demonstrated that the TiO2 NRAs indicate the good photoelectric conversion ability with an efficiency of 0.22% at a full-wavelength irradiation. A photocurrent density of 0.21 mA/cm(2) is observed at 0.7 V versus the saturated calomel electrode (SCE). More evidences suggest that the charge transferring resistance is lowered at an irradiation, while the flat-band potential (Vfb) is shifted towards the positive side.
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  • Estimation of the Maximum Output Power of Double-Clad Photonic Crystal Fiber Laser

    Chen Yue-E   Wang Yong   Qu Xi-Long  

    Compared with traditional optical fiber lasers, double-clad photonic crystal fiber (PCF) lasers have larger surface-area-to-volume ratios. With an increase of output power, thermal effects may severely restrict output power and deteriorate beam quality of fiber lasers. We utilize the heat-conduction equations to estimate the maximum output power of a double-clad PCF laser under natural-convection, air-cooling, and water-cooling conditions in terms of a certain surface-volume heat ratio of the PCF. The thermal effects hence define an upper power limit of double-clad PCF lasers when scaling output power.
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  • Growth mechanism of primary silicon in cast hypoeutectic Al-Si alloys

    Wang Shou-ren   Ma Ru   Wang Ying-zi   Wang Yong   Yang Li-ying  

    The microstructural features of hypoeutectic Al-10% Si alloy were observed using optical microscopy and electron backscatter diffraction. The results show that primary silicon particles are frequently found in hypoeutectic alloys. Hence, the nucleation and growth mechanisms of the precipitation of primary silicon of hypoeutectic Al-10% Si alloy melts were investigated. It was discovered that Si atoms are easy to segregate and form Si-Si clusters, which results in the formation of primary silicon even in eutectic or hypoeutectic Al-Si alloys. In addition, solute redistribution caused by chemical driving force and large pile-ups or micro-segregation of the solute play an important role in the formation of the primary silicon, and the solute redistribution equations were derived from Jackson-Chalmers equations. Once Si solute concentration exceeds eutectic composition, primary silicon precipitates are formed at the front of solid/liquid interface.
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  • Using Ant Swarm Intelligence for Data Clustering Analysis

    Wang Yong   Chen Jun  

    In this paper we present a new algorithm that uses the new swarm intelligence based techniques to investigate clustering. The algorithm, called CASI, combines a smart exploratory strategy based on ant colonies that locate the objects in a cluster with the probability, which is updated by the pheromone, while the rule of updating pheromone is according to total within cluster variance. We have applied this algorithm on two synthetic data and we have measured, through computer simulation, the proposed algorithm outperforms several existing approaches such as GCA, SOM.
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