Design optimization of high-precision aerostatic equipment based on orifice restriction

2019 ◽  
Vol 233 (10) ◽  
pp. 3459-3474
Author(s):  
Tao Lai ◽  
Xiaoqiang Peng ◽  
Junfeng Liu ◽  
Chaoliang Guan ◽  
Xiaogang Chen ◽  
...  
Keyword(s):  
Finite Difference Method ◽  
High Precision ◽  
Structural Parameter ◽  
Error Feedback ◽  
Aerostatic Bearing ◽  
Proposed Model ◽  
Gas Gap ◽  
Processing Difficulty ◽  
Optimum Working ◽  
Good Agreement

The aerostatic lubrication model with orifice restriction is built based on finite difference method. The model is solved by combination of flux-error feedback and optimization of grids parameter. The stiffness of aerostatic bearing can be improved by reducing the diameter of the orifice, but the optimum working gas gap is reduced and the processing difficulty of surface throttle is improved. The experiments of load and stiffness are carried out on the slider (50 × 50 mm) with the diameter of orifice at 50 µm. The experimental results and theoretical calculation are in good agreement; thus, the model is verified. The structural parameter of two, three, and four orifice gas-bearings is optimized, respectively, based on the proposed model, and the optimum positions of the orifices are obtained. According to the results, the aerostatic bearing guideways, made up of optical material (K9), are manufactured by some optical ways, and the lubrication of the small gas gap is guaranteed; meanwhile, the straightness accuracy of the aerostatic bearing guideways is 0.1 µm/200 mm. The analysis result verifies that the calculation method and the aerostatic lubrication model are significant to the design of high-precision aerostatic equipment.

scholarly journals Optimal design of high-performance aerostatic equipment based on finite difference method with flux error feedback

2020 ◽  
pp. 002029401882412
Author(s):  
Tao Lai ◽  
Xiaoqiang Peng ◽  
Junfeng Liu
Keyword(s):  
Optimal Design ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
High Performance ◽  
Performance Test ◽  
Error Feedback ◽  
Analysis And Design ◽  
Proposed Model ◽  
Ultra Precision

This paper proposes an aerostatic lubrication model with the use of finite difference method, and the solution of the model is designed with the combination of flux error feedback and grid parameter optimization. The model and solution are validated by the performance test on the slider with the diameter of orifice at 50 and 200 μm. Finally, the proposed model is applied to the optimal design of the aerostatic turntable, and the type, parameter and configuration of the restriction are determined by the optimal results. To guarantee the accuracy of key parts, the ultra-precision turning technology is applied to manufacture of turntable, and the runout of the end face meets the design requirements through the verification. The proposed model and solution are significant to the analysis and design of high-performance aerostatic equipments.

scholarly journals Separate Universe calibration of the dependence of halo bias on cosmic web anisotropy

2020 ◽  
Vol 499 (3) ◽  
pp. 4418-4431 ◽  
Author(s):  
Sujatha Ramakrishnan ◽  
Aseem Paranjape
Keyword(s):  
Dark Matter ◽  
High Precision ◽  
Gaussian Distribution ◽  
Initial Perturbation ◽  
Analytical Framework ◽  
Web Environment ◽  
Wide Range ◽  
Galaxy Assembly ◽  
Very High ◽  
Good Agreement

ABSTRACT We use the Separate Universe technique to calibrate the dependence of linear and quadratic halo bias b1 and b2 on the local cosmic web environment of dark matter haloes. We do this by measuring the response of halo abundances at fixed mass and cosmic web tidal anisotropy α to an infinite wavelength initial perturbation. We augment our measurements with an analytical framework developed in earlier work that exploits the near-lognormal shape of the distribution of α and results in very high precision calibrations. We present convenient fitting functions for the dependence of b1 and b2 on α over a wide range of halo mass for redshifts 0 ≤ z ≤ 1. Our calibration of b2(α) is the first demonstration to date of the dependence of non-linear bias on the local web environment. Motivated by previous results that showed that α is the primary indicator of halo assembly bias for a number of halo properties beyond halo mass, we then extend our analytical framework to accommodate the dependence of b1 and b2 on any such secondary property that has, or can be monotonically transformed to have, a Gaussian distribution. We demonstrate this technique for the specific case of halo concentration, finding good agreement with previous results. Our calibrations will be useful for a variety of halo model analyses focusing on galaxy assembly bias, as well as analytical forecasts of the potential for using α as a segregating variable in multitracer analyses.

scholarly journals Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1286
Author(s):  
Krzysztof Górecki ◽  
Przemysław Ptak
Keyword(s):  
Integrated Circuits ◽  
Optical Model ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Junction Temperature ◽  
Optical Parameters ◽  
Spice Simulation ◽  
Light Emitting ◽  
Proposed Model ◽  
Good Agreement

This paper concerns the problem of modelling electrical, thermal and optical properties of multi-colour power light-emitting diodes (LEDs) situated on a common PCB (Printed Circuit Board). A new form of electro-thermo-optical model of such power LEDs is proposed in the form of a subcircuit for SPICE (Simulation Program with Integrated Circuits Emphasis). With the use of this model, the currents and voltages of the considered devices, their junction temperature and selected radiometric parameters can be calculated, taking into account self-heating phenomena in each LED and mutual thermal couplings between each pair of the considered devices. The form of the formulated model is described, and a manner of parameter estimation is also proposed. The correctness and usefulness of the proposed model are verified experimentally for six power LEDs emitting light of different colours and mounted on an experimental PCB prepared by the producer of the investigated devices. Verification was performed for the investigated diodes operating alone and together. Good agreement between the results of measurements and computations was obtained. It was also proved that the main thermal and optical parameters of the investigated LEDs depend on a dominant wavelength of the emitted light.

Static and Dynamic Structure of Molecular Monomers and Dimers of the Rare-earth Fluorides

2001 ◽  
Vol 56 (5) ◽  
pp. 381-385
Author(s):  
Z. Akdeniz ◽  
M . Gaune-Escard ◽  
M. P. Tosi
Keyword(s):  
Rare Earth ◽  
Bond Length ◽  
Geometrical Structure ◽  
Vibrational Mode ◽  
Dynamic Structure ◽  
Molecular Shape ◽  
Proposed Model ◽  
Infrared Studies ◽  
Charged Clusters ◽  
Good Agreement

Abstract We determine a model of the ionic interactions in RF3 compounds, where R is a rare-earth element in the series from La to Lu, by an analysis of data on the bond length and the vibrational mode frequencies of the PrF3, GdF3 and HoF3 molecular monomers. All RF3 monomers are predicted to have a pyramidal shape, displaying a progressive flattening of the molecular shape in parallel with the lanthanide contraction of the bond length. The vibrational frequencies of all monomers are calculated, the results being in good agreement with the data from infrared studies of matrix-isolated molecules. We also evaluate the geometrical structure and the vibrational spectrum of the La2F6 and Ce2F6 dimers, as a further test of the proposed model. -PACS 36.40.Wa (Charged clusters)

Reloading Stress Relaxation Behavior Analysis Based on a Creep Model for High Temperature Bolting Steel

2013 ◽  
Vol 328 ◽  
pp. 950-954
Author(s):  
Wei Wei Zhang ◽  
Hong Xu ◽  
Hong Yuan Li
Keyword(s):  
High Temperature ◽  
Stress Relaxation ◽  
Steady State Creep ◽  
Relaxation Behavior ◽  
Creep Model ◽  
National Research Institute ◽  
Time Intervals ◽  
Stress Relaxation Behavior ◽  
Proposed Model ◽  
Good Agreement

An analytical method based on a creep model is being developed to investigate the effect of retightening on stress relaxation behavior for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial reloading stress relaxation testing, which were performed by the National Research Institute for Metals of Japan (NRIM) for 12Cr-1Mo-1W-1/4V stainless steel bolting material at 550°C. It was shown that the proposed model based on Altenbach-Gorash-Naumenko creep model for the primary and steady state creep could be applied for the present data. The calculated residual stresses versus time curves were in good agreement with the measured for initial stress level of 273.6MPa at 550°C and for specific reloading time intervals of 24, 72, 240, and 720 hours.

scholarly journals Compact Model for Bipolar and Multilevel Resistive Switching in Metal-Oxide Memristors

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 98
Author(s):  
Eugeny Ryndin ◽  
Natalia Andreeva ◽  
Victor Luchinin
Keyword(s):  
Metal Oxide ◽  
Equation System ◽  
Software Implementation ◽  
Compact Model ◽  
Metal Oxide Films ◽  
Bipolar Switching ◽  
Proposed Model ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Good Agreement

The article presents the results of the development and study of a combined circuitry (compact) model of thin metal oxide films based memristive elements, which makes it possible to simulate both bipolar switching processes and multilevel tuning of the memristor conductivity taking into account the statistical variability of parameters for both device-to-device and cycle-to-cycle switching. The equivalent circuit of the memristive element and the equation system of the proposed model are considered. The software implementation of the model in the MATLAB has been made. The results of modeling static current-voltage characteristics and transient processes during bipolar switching and multilevel turning of the conductivity of memristive elements are obtained. A good agreement between the simulation results and the measured current-voltage characteristics of memristors based on TiOx films (30 nm) and bilayer TiO2/Al2O3 structures (60 nm/5 nm) is demonstrated.

Modeling Hydroplaning and Effects of Pavement Microtexture

2005 ◽  
Vol 1905 (1) ◽  
pp. 166-176 ◽  
Author(s):  
G. P. Ong ◽  
T. F. Fwa ◽  
J. Guo
Keyword(s):  
Three Dimensional ◽  
Flow Simulation ◽  
Experimental Results ◽  
Tire Pressure ◽  
Finite Volume Model ◽  
Proposed Model ◽  
Loss Of Contact ◽  
The One ◽  
Theoretical Considerations ◽  
Good Agreement

Hydroplaning on wet pavement occurs when a vehicle reaches a critical speed and causes a loss of contact between its tires and the pavement surface. This paper presents the development of a three-dimensional finite volume model that simulates the hydroplaning phenomenon. The theoretical considerations of the flow simulation model are described. The simulation results are in good agreement with the experimental results in the literature and with those obtained by the well-known hydroplaning equation of the National Aeronautics and Space Administration (NASA). The tire pressure–hydroplaning speed relationship predicted by the model is found to match well the one obtained with the NASA hydroplaning equation. Analyses of the results of the present study indicate that pavement microtexture in the 0.2- to 0.5-mm range can delay hydroplaning (i.e., raise the speed at which hydroplaning occurs). The paper also shows that the NASA hydroplaning equation provides a conservative estimate of the hydroplaning speed. The analyses in the present study indicate that when the microtexture of the pavement is considered, the hydroplaning speed predicted by the proposed model deviates from the speed predicted by the smooth surface relationship represented by the NASA hydroplaning equation. The discrepancies in hydroplaning speed are about 1% for a 0.1-mm microtexture depth and 22% for a 0.5-mm microtexture depth. The validity of the proposed model was verified by a check of the computed friction coefficient against the experimental results reported in the literature for pavement surfaces with known microtexture depths.

scholarly journals The evidence for a spatially flat Universe

2020 ◽  
Vol 496 (1) ◽  
pp. L91-L95 ◽  
Author(s):  
George Efstathiou ◽  
Steven Gratton
Keyword(s):  
High Precision ◽  
Strong Support ◽  
Inflationary Cosmology ◽  
Density Parameter ◽  
Acoustic Oscillations ◽  
Astrophysical Data ◽  
Flat Universe ◽  
Polarization Spectra ◽  
The Universe ◽  
Good Agreement

ABSTRACT We use a new and statistically powerful Planck likelihood to show that the Planck temperature and polarization spectra are consistent with a spatially flat Universe, in contrast to recent claims in the literature. When combined with other astrophysical data, particularly geometrical measurements of baryon acoustic oscillations, our likelihood constrains the Universe to be spatially flat to extremely high precision. We deduce a curvature density parameter ΩK = 0.0004 ± 0.0018 in good agreement with the 2018 results of the Planck team. In the context of inflationary cosmology, the observations offer strong support for models of inflation with a large number of e-foldings and disfavour models of incomplete inflation.

scholarly journals Modelling the Characteristics of Ring-Shaped Magnetoelastic Force Sensor in Mohri’s Configuration

Sensors ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 266 ◽  
Author(s):  
Anna Ostaszewska-Liżewska ◽  
Roman Szewczyk ◽  
Peter Raback ◽  
Mika Malinen
Keyword(s):  
Experimental Data ◽  
High Sensitivity ◽  
Force Sensor ◽  
Inhomogeneous Distribution ◽  
The Finite Element Method ◽  
The Core ◽  
Magnetoelastic Effect ◽  
Proposed Model ◽  
Distribution Of Stresses ◽  
Good Agreement

Magnetoelastic force sensors exhibit high sensitivity and robustness. One commonly used configuration of force sensor with a ring-shaped core was presented by Mohri at al. In this configuration force is applied in the direction of a diameter of the core. However, due to inhomogeneous distribution of stresses, model of such sensor has not been presented yet. This paper is filling the gap presenting a new method of modelling the magnetoelastic effect, which is especially suitable for the finite element method. The presented implementation of proposed model is in good agreement with experimental data and creates new possibilities of modelling other devices utilizing magnetoelastic effect.

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