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  • 1
    Publication Date: 2013-12-22
    Description: With the improvement of technology and manufacturing level of hydraulic turbine, there is a trend to increase the power concentration of the units. As a consequence, heads, fluid velocities and rotational speeds are higher which lead to larger hydraulic excitation forces on the structures. Accordingly, vibration and high stress levels will arise, which may cause fatigue damage. Therefore, how to predict the natural frequencies and mode shapes of the runner during the design stage is of paramount importance. In this paper, numerical simulation to analyze the influence of the surrounding water in a pump-turbine runner modal has been carried out by using finite element method. The modal behavior of the runner in air and in water has been calculated. In addition, the added mass effect by comparing the natural frequencies and mode shapes in both cases has been determined. The results show that, due to the added mass effect of the surrounding water, natural frequencies are considerabl...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 2
    Publication Date: 2015-12-19
    Description: Cornell University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. In pushing the limits, a high quality factor of the cavities (2•10 10 ) and high beam currents (100 mA accelerated plus 100 mA decelerated) were targeted. The design of the cryomodule and the results of components tested before assembly will be presented in this paper.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 3
    Publication Date: 2015-04-26
    Description: In processing non-oriented electrical steel sheets using conventional rolling schemes, the most common texture components obtained after final annealing are the magnetically unfavourable //ND (?) and //RD (?) fibres. A lot of researches have been carried out trying to optimize the processes to produce the favourable //ND (?) fibre. However, since the final texture is formed through a series of texture evolution steps during the solidification, hot rolling, cold rolling and annealing processes, it is quite challenging to tailor the texture of the final product. In this study, a new rolling scheme was examined, in which the cold rolling direction (CRD) was inclined to the hot rolling direction (HRD) at an angle from 0? to 90? (with a 15? increment). This was intended to alter the texture commonly produced by cold rolling along the HRD, and to optimize the final recrystallization texture. The cold rolling and recrystallization textures of two non-ori...
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    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
    Publication Date: 2015-07-17
    Description: Vulcanization was an important step in tire production process, directly determining the mechanical properties of the tire which was the most energy-intensive link. The traditional vulcanization process of a flat tire did not consider the post curing effect, which may result in a waste of energy. Early finite element simulation showed that the traditional process caused excessive vulcanization. In order to find ways to improve the curing process, in the paper effect of process parameters on the flat tire vulcanization had been studied. Curing parameters included heating temperature, curing time and preheating temperature. Corresponding to these three factors, the three-dimensional model was established by ABAQUS finite element software to carry out three groups of simulation. Result showed that heat source temperature on the maximum temperature was the largest, effect of preheating temperature was the lowest; heat source temperature on the curing degree was the largest, effect of...
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    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
    Publication Date: 2014-12-11
    Description: The causes of resonance of a certain model pump-turbine unit during startup process were investigated in this article. A three-dimensional full flow path analysis model which contains spiral case, stay vanes, guide vanes, runner, gaps outside the runner crown and band, and draft tube was constructed. The transient hydraulic excitation force of full flow path was analyzed under five conditions near the resonance region. Based on one-way fluid- structure interaction (FSI) analysis model, the dynamic stress characteristics of the pump-turbine runner was investigated. The results of pressure pulsation, vibration mode and dynamic stress obtained from simulation were consistent with the test results. The study indicated that the hydraulic excitation frequency ( Z g * f n ) Hz due to rotor-stator interference corresponding to the natural frequency of 2ND+4ND runner mode is the main cause of resonance. The relationship among pressure pulsation, vibration mo...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 6
    Publication Date: 2017-08-01
    Description: The surface of an annealed Cu plate was processed by a high pressure surface rolling (HPSR) process. It is found that the deformed surface layer in the Cu plate after HPSR can be as thick as 2 mm and is characterized by a gradient microstructure, with grain sizes varying from the nanoscale in the topmost surface to the microscale in the bulk. The hardness varies from 1.37 GPa at the topmost surface to about 0.6 GPa in the coarse-grained matrix. The results of the investigation demonstrate that the HPSR process shows good potential for the generation of thick gradient microstructures on the surface of bulk metallic materials.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
    Publication Date: 2018-05-17
    Description: The antimicrobial activities of silver based nanocomposites are usually studied in terms of Ag content and ion release rate. Under this condition, controllable silver ions release with high antibacterial activity is the basis for silver based nanocomposite. The goal is to investigate the influence of O 2 content and titanium oxide barrier thickness on the evolution in morphology. The SEM/TEM results showed that the size of Ag nanoparticles has a clear dependence on O 2 concentration in reactive sputtering process; increased oxygen implies larger Ag nanoparticles in the matrix. In addition, a clear suppressing effect and better size distribution is obtained after the thickness of coated titanium oxide barrier is verified.
    Print ISSN: 1757-8981
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
    Publication Date: 2017-12-30
    Description: Fermilab’s 1.3 GHz prototype cryomodule for the Linac Coherent Light Source Upgrade (LCLS-II) has been tested at Fermilab’s Cryomodule Test Facility (CMTF). Aspects of the cryomodule design have been studied and tested. The cooldown circuit was used to quickly cool the cavities through the transition temperature, and a heater on the circuit was used to heat incoming helium for warmup. Due to the 0.5% slope of the cryomodule, the liquid level is not constant along the length of the cryomodule. This slope as well as the pressure profile caused liquid level management to be a challenge. The microphonics levels in the cryomodule were studied and efforts were made to reduce them throughout testing. Some of the design approaches and studies performed on these aspects will be presented. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. This work was supported, in part, by the LCLS-II Project.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    Publication Date: 2017-12-23
    Description: The theory of phase control of coherence, entanglement and quantum steering is developed for an optomechanical system composed of a single mode cavity containing a partially transmitting dielectric membrane and driven by short laser pulses. The membrane divides the cavity into two mutually coupled optomechanical cavities resulting in an effective three-mode closed loop system, two field modes of the two cavities and a mechanical mode representing the oscillating membrane. The closed loop in the coupling creates interfering channels which depend on the relative phase of the coupling strengths of the field modes to the mechanical mode. Populations and correlations of the output modes are calculated analytically and show several interesting phase dependent effects such as reversible population transfer from one field mode to the other, creation of collective modes, and induced coherence without induced emission. We find that these effects result from perfect mutual coherence betwee...
    Electronic ISSN: 1367-2630
    Topics: Physics
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  • 10
    Publication Date: 2013-12-22
    Description: Unbalanced radial force is a serious adversity that restricts the working pressure and reduces service life of the single-action vane pump. For revealing and predicting the distribution of radial force on the rotor, a numerical simulation about its transient flow field was performed by using dynamic mesh method with RNG κ ε -turbulent model. The details of transient flow characteristic and pressure fluctuation were obtained, and the radial force and periodic variation can be calculated based on the details. The results show: the radial force has a close relationship with the pressure pulsation; the radial force can be reduced drastically by optimizing the angle of port plate and installing the V-shaped cavity; if the odd number vanes are chosen, it will help reduce the radial force of rotor and optimize the pressure fluctuation effectively.
    Print ISSN: 1757-8981
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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