The developmental situation of space welding technology at home and abroad is introduced. Then it is put forward that the designing scheme and the computer aided design （CAD） method of main single lens of the domest...
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The developmental situation of space welding technology at home and abroad is introduced. Then it is put forward that the designing scheme and the computer aided design （CAD） method of main single lens of the domestic space electron beam gun with equal-diameter three-cylinder simple lens, and the flowing-pipe way of calculating the space charge density of the main lens area ,in the electron gun is analyzed. The parameters calculation of the focusing system is completed through Language C utilizing computer programming and a satisfying result is gotten. The result shows that the calculation and design method are correct ： the dispersed focusing current of electron beam is less, the beam section is less in the deflected magnetic field, the minimal radius of beam spot on the workpiece is about 0.65615mm, and all these can meet the requirements of the space welding and cutting.
In this paper, we propose a novel active queue management (AQM) scheme based on the Random Early Detection (RED) of the loss ratio and the total sending rate control, called LRC-RED, to regulate the queue length with ...
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ISBN:
(纸本)0769524052
In this paper, we propose a novel active queue management (AQM) scheme based on the Random Early Detection (RED) of the loss ratio and the total sending rate control, called LRC-RED, to regulate the queue length with small variation and to achieve high utilization with small packet loss. This scheme measures the latest packet loss ratio, and uses it and the total sending rate as complements to queue length in order to dynamically adjust packet drop probability. Further, we also provide the design rules for this scheme based on the well-known TCP control model. On the basis of the design rules, we develop a simple, scalable and systematic rule for tuning the control parameters which can be adaptive to dynamic network conditions. Through ns 2 simulations, we show the faster response time and better robustness of the proposed LRC-RED as compared with the Loss Ratio based RED (LRED) [5] algorithm.
The influences of sintering temperature, soaking time and annealing time on the quality factor of Ba(Mg/13Nb2/3)O3 microwave dielectric ceramic were investigated. The result showed that Qf value increased as the sinte...
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The influences of sintering temperature, soaking time and annealing time on the quality factor of Ba(Mg/13Nb2/3)O3 microwave dielectric ceramic were investigated. The result showed that Qf value increased as the sintering temperature increasing. It was ascribed to the increasing of the relative density and ordering parameter S. The maximum value of Qf, 49500 GHz, was gained at 1550°C. With soaking time increasing, Qf value increased. The increasing of B-site 1:2 ordering degree and grain size should be responsible for the improvement of Qf value. When soaking time was 16 h, Qf value reached 58000 GHz. Annealing time had great effect on Qf value. With annealing time increasing, Qf value increased quickly. This was because of the improvement of B-site 1:2 ordering caused by annealing. A high Qf value, 71500 GHz, was acquired when annealing time was 48 h.
A 3-phase to 3-phase matrix converter is developed based on 600 V/100 A RB-IGBT (Reverse Blocking IGBT). This RB-IGBT is newly developed based on ultra-thin wafer technology and one important feature of it is reverse ...
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A 3-phase to 3-phase matrix converter is developed based on 600 V/100 A RB-IGBT (Reverse Blocking IGBT). This RB-IGBT is newly developed based on ultra-thin wafer technology and one important feature of it is reverse leakage current is mostly affected by Vge. Under the same temperature condition, when Vce is negative, a positively biased Vge leads to the great reduction of the reverse leakage current therefore, a novel commutation method is proposed for reducing the losses caused by this reverse leakage current. The realization of this method is based on output current direction and certain voltage polarities of bi-directional switches and it is featured as a 2-step commutation. A simple circuit in the designed RB-IGBT drive circuit is used to obtain the required signals by sensing Vce of RB-IGBT. Then the constant Volts/Hz method is employed for controlling the matrix converter induction motor drive. Finally, detail experimental results and analysis are presented.
A fast simulation scheme for 3D curved binder flanging and blank shape prediction of sheet metal based on one‐step inverse finite element method is proposed, in which the total plasticity theory and proportional load...
A fast simulation scheme for 3D curved binder flanging and blank shape prediction of sheet metal based on one‐step inverse finite element method is proposed, in which the total plasticity theory and proportional loading assumption are used. The scheme can be actually used to simulate 3D flanging with complex curve binder shape, and suitable for simulating any type of flanging model by numerically determining the flanging height and flanging lines. Compared with other methods such as analytic algorithm and blank sheet‐cut return method, the prominent advantage of the present scheme is that it can directly predict the location of the 3D flanging lines when simulating the flanging process. Therefore, the prediction time of flanging lines will be obviously decreased. Two typical 3D curve binder flanging including stretch and shrink characters are simulated in the same time by using the present scheme and incremental FE non‐inverse algorithm based on incremental plasticity theory, which show the validity and high efficiency of the present scheme.
The title complex [Cu(C12H8N2) · (H2O)2]SO4 was synthesized by hydrothermal method and characterized by elemental analysis, IR and X-ray single crystal structural analysis. The crystal structure indicates that th...
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The title complex [Cu(C12H8N2) · (H2O)2]SO4 was synthesized by hydrothermal method and characterized by elemental analysis, IR and X-ray single crystal structural analysis. The crystal structure indicates that the compound forms a stratiform, built from the SO42- and [Cu(C12H8N2) · (H2O)2]2+ through hydrogen bonds. The chemical formula weight of complex is 375.84. The crystal structure is monoclinic, pace group C2/c with a = 1.485 3(3) nm, b = 1.381 1(3) nm, c = 0.701 0(14) nm, β = 108.650°, V= 1.362 5(15) nm3, Dc = 1.832 g/cm3 ,F(000) = 764, Z = 4,R1 = 0.0290, wR2 = 0.0862. The result of the single crystal X-ray diffraction analysis is in agreement with that of IR measurement, both of them show that the Cu2+ is coordinated by two nitrogen and two oxygen. In addition, the thermostability and IR spectral of the compound were discussed.
The transient temperature field analysis aims at the thermal response of LPG vessel under pool fire surrounding environment. The finite element analysis method is used to calculate the temperature field. The thermal b...
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The transient temperature field analysis aims at the thermal response of LPG vessel under pool fire surrounding environment. The finite element analysis method is used to calculate the temperature field. The thermal boundary conditions of LPG vessel are determined according to heat transfer theory and calculated by the software PLGS99. The results show that the maximum temperature gradient of vessel appears near the highest surface where the liquid can reach, and fluctuation of liquid surface is the main reason of high temperature gradient.
Plasma Immersion Ion Implantation (PIII) has been proved to be a useful technique for surface modification of components with sophisticated shape. Based on the results of conventional three-ball-on-rod testing, the ro...
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Plasma Immersion Ion Implantation (PIII) has been proved to be a useful technique for surface modification of components with sophisticated shape. Based on the results of conventional three-ball-on-rod testing, the rolling contact fatigue (RCF) life of GCr15 steel treated by PIII technique was studied. During the study, nitrogen plasma was generated and the implantation voltage was varied from 20 to 40 kV. The fatigue test results reveal that implantation voltage has a great influence on RCF life. Compared with the untreated sample, N10and N50 (failure probability is 10% and 50% , respectively) life of the sample with the implantation voltage of 30 kv was increased by 58.8% and 223.5% , respectively.
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