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Structural synthesis of ancient Chinese foot-operated
silk-reeling mechanism
Kuohung HSIAO, Yuhsun CHEN, Hongsen YAN,
Front. Mech. Eng.. 2010, 5 (3): 279-288.
https://doi.org/10.1007/s11465-010-0101-2
This work synthesizes the structures of the foot-operated silk-reeling mechanism, which was vaguely depicted in many literatures in ancient China. Based on the analysis of the mechanism, the structural characteristics and design constraints of the mechanism with indeterminate links and joints are concluded. Then, according to the concepts of generalization and specialization subject to the concluded design constraints, all feasible structures of the mechanism that met the technological standards of the subject’s time period are reconstructed. This reconstruction process provides a logical foundation to better understanding, clarification, and suggestions for the issue of ancient mechanical drawings with indeterminate links and joints.
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Machine of testing the ceramic’s bending
strength properties at high temperature and ultra-low speed
Jianhui ZHANG, Fang YE, Onuki AKIYOSHI,
Front. Mech. Eng.. 2010, 5 (3): 289-293.
https://doi.org/10.1007/s11465-010-0094-x
According to the established rules for testing ceramic’s bending strength, the falling velocity of the pressure head of the machine should be more than 0.5 mm/min. For the machine of testing the ceramic’s bending strength properties, most designs adopt the lowest falling velocity as 0.5 mm/min. In the fields such as aerospace and deep-ocean exploration, the utilization of ceramic materials that work at normal temperature, low temperature, or even high temperature and bend at an ultra-low velocity is increasing; thus, the intense requirements for the machine of testing the ceramic’s bending strength properties at high temperature and ultra-low speed (MTCBSP) and its experimental basis are put forward. This research developed an MTCBSP suitable for normal temperature and high temperature with the lowest falling velocity of 0.05 mm/min, and manufactured a drive reducer for ultra-low speed and high-temperature working condition. In the test, equipment includes a high-temperature furnace, bending die for four-point bending, and protection system of inert gas, which was placed in the high-temperature furnace to prevent the ceramic sample from being oxidized to diminish its effects. The results show that the lowest falling velocity of the pressure head of this new machine is 0.05 mm/min, and the mechanical properties of silica glasses are noticeably different at the same high temperature and the different falling velocities of 0.5 mm/min and 0.05 mm/min.
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Dynamical analysis of droplet impact spreading
on solid substrate
Zhaomiao LIU, Huamin LIU, Xin LIU,
Front. Mech. Eng.. 2010, 5 (3): 308-315.
https://doi.org/10.1007/s11465-010-0020-2
This paper investigates the impact spreading of a droplet on a solid substrate using numerical simulation on the basis of a volume-of-fluid (VOF) model. The process of droplet spreading is described, the analysis of low speed and high speed droplet spreading, and more than one droplet spreading simultaneously is performed. The pressure, velocity, and spreading factor during the droplet spreading are reported. According to the spreading factor’s evolvement, the process of droplet spreading can be classified into spreading phase and recoiling phase. The spreading factors are almost the same at the low speed droplet spreading; however, the pressures on the substrate are quite different and air entrainment may be found as the impact speeds in a certain range. The impact speed impacts on the spreading factors in high speed droplet spreading. The spreading factor obviously increases with increasing impact speed; however, splashing will appear in the status when the speed is high enough in the high speed droplet spreading. The distance between the neighbor droplets affects the film’s quality, and only the distance between the static diameter and the maximum diameter can ensure the film’s quality. The results could help in understanding the process of droplet spreading and provide advice on the operation of a spray coating process.
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Remote calibration system for frequency based
on in-place benchmark
Xiaobin HONG, Guixiong LIU, Zhuokui WU, Xipeng DU,
Front. Mech. Eng.. 2010, 5 (3): 316-321.
https://doi.org/10.1007/s11465-010-0021-1
According to the deficiencies of remote calibration mode based on material object reference, a new model of a remote calibration system for frequency based on in-place benchmark is introduced, which is made of a calibration subsystem on the spot and a remote management subsystem. The key technology of some key problems for the remote calibration system is particularly discussed, including the time and frequency benchmark receiving module based on global positioning system (GPS), frequency comparison based on a phase method, frequency division based on dual high-frequency phase locked loop (PLL), and remote calibration based on the web. The results show that the system possesses some characteristics, such as high precision, good versatility, and no limitation of time and place.
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WEIS wheel speed real-time measuring method for
VOSM
Mengyao PAN, Guixiong LIU, Xiaobin HONG, Tusheng LIN,
Front. Mech. Eng.. 2010, 5 (3): 322-327.
https://doi.org/10.1007/s11465-010-0022-0
Wheel speed is one of the key parameters of vehicle operating attitude. To solve the problems in traditional wheel speed measuring methods, such as low measurement precision and the lack of real-time monitoring of the vehicle’s operating attitude, a wheel embedded intelligent sensors (WEIS) wheel speed measuring method for vehicle operating safety states monitoring (VOSM) is innovatively proposed. Radial acceleration signal is obtained through a WEIS module embedded in the hub. Using wavelet packet to implement wavelet de-noising for the non-stationary acceleration signals, and adopting short-time Fourier transform (STFT) algorithm to extract the signal characteristics, the wheel speed measurement can be achieved. The experimental result shows that under experimental conditions the speed measurement error is −2.05%, and the speed measuring response time is 0.45 s.
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Reverse engineering in the construction of numerical
simulation oriented patient-specific model of stented aortic arch
aneurysm
Xianlong MENG, Wenyu FU, Yun ZHANG, Aike QIAO,
Front. Mech. Eng.. 2010, 5 (3): 328-335.
https://doi.org/10.1007/s11465-010-0026-9
Patient-specific models are widely used in hemodynamic simulations. The flow in the boundary layer changes so strongly that fine meshes in the boundary layer are required in numerical simulations, especially for the calculation of wall shear stress and its gradient. To precisely analyze hemodynamics, it is necessary to investigate the approaches to the reconstruction of a numerical simulation-oriented patient-specific model for aortic arch aneurysm that can perform particular meshing in the boundary layer. Based on a surface model of aortic arch aneurysm in STL format, reverse engineering concept was applied to reconstruct a solid model using CAD software Geomagic and Pro/E, and a simplified model of stent for the intervention of aortic arch aneurysm was also created. After these models were imported to ANSYS, a block modeling approach was employed to divide the whole model into several domain blocks to adopt different meshing strategies. Particular meshing was performed especially in the boundary layer and around the stents. The finite element model particularly suitable for numerical simulation of hemodynamics was obtained. Hemodynamic simulation was performed, using the constructed finite element model to verify its applicability. The results indicate that reverse engineering concept and the proposed block modeling approach can be used to divide the solid model of aortic arch aneurysm into multiple volumes, which can be meshed according to particular requirements in each volume; the finite element model of stented aortic arch aneurysm can be employed to simulate hemodynamics. The approaches of modeling were applicable not only for aortic arch aneurysm, but also for similar model reconstruction as a reference in hemodynamic simulation investigations.
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Dynamics analysis of bladder-urethra system based
on CFD
Qinghua JIN, Xiaojun ZHANG, Xiaoyang LI, Jianliu WANG,
Front. Mech. Eng.. 2010, 5 (3): 336-340.
https://doi.org/10.1007/s11465-010-0027-8
A mathematical model for a bladder-urethra system can provide basic analysis for the disabled urethra closure of stress urinary incontinence (SUI) patients in a clinic. Based on computational fluid dynamics (CFD), we developed a three-dimensional urodynamic bladder-urethra system, which includes bladder, bladder neck, prostate, and urethra. The realistic recirculation process of the urinary bladder during the physiologic voiding process in conjunction with a flow simulation through the female urinary bladder and urethra is presented. The computational results show that a dead-water zone and the zone of secondary flow occur, independent of the shape of the prostatic urethra. For the pathological prostata, the extreme constriction of the prostatic urethra results in an additional wide-stretched dead-water zone. The simulation results does not only improve urinary incontinence surgery for clinicians, but can also provide a basis for theoretical analysis.
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15 articles
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