74,069 research outputs found
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Modelling and simulation of the dynamic cutting process and surface topography generation in nano/micro cutting
In nano/micro cutting process, the surface quality is heavily dependent on all the dynamic factors in machining including those from the material, tooling, cutting parameters, servo accuracy, mechanical structure deformation, and non-linear factors as well. The machined surfaces are generated based on the tool profile and the real tool path combining with the various external and internal disturbances. To bridge the gap between the machining conditions and the surface quality, the integrated simulation system presented involves the dynamic cutting process, control/drive system and surface generation module. It takes account all the intricate aspects of the cutting process, such as material heterogeneity, regenerative chatter, built-up edge (BUE), spindle run-out, environmental vibration, and tool interference, etc. The frequency ratio method is used to interpret the surface topography and texture formation. The proposed systematic modelling approach is verified by the cutting experiment
Recommended from our members
Dynamic cutting process modelling and its impact on the generation of surface topography and texture in nano/micro cutting
In the nano/micro cutting process, the surface quality is heavily dependent on all the dynamic factors, including those from the material, tooling, process parameters, servo accuracy, mechanical structural stiffness, and non-linear factors as well. The machined surface is generated based on the tool profile and the real tool path combining with the various external and internal disturbances. To bridge the gap between the cutting process and the surface topography/texture generation, an integrated simulation-based approach is presented involving the dynamic cutting process, control/drive system, and the surface generation. The simulations take account of all the intricate aspects of the cutting process resulting in the surface topography and texture formation, such as material heterogeneity, regenerative chatter, built-up edge (BUE), tool wear, spindle runout, environmental vibration, tool interference, etc. Both the frequency ratio method and sampling theoremare used to interpret the surface topography and texture formation. The effects of non-linear factors on the surface generation are simulated and analysed through the power spectral density (PSD) and significance on surface texture. The relationships among cutting force, tool path, and surface profile are discussed in detail. Furthermore, the proposed systematic modelling approach is verified by cutting trials, which provide the coincident results of the surface topography and areal power spectral density (APSD)
The Radio and Gamma-Ray Luminosities of Blazars
Based on the -ray data of blazars in the third EGRET catalog and
radio data at 5 GHz, we studied the correlation between the radio and
-ray luminosities using two statistical methods. The first method was
the partial correlation analysis method, which indicates that there exist
correlations between the radio and -ray luminosities in both high and
low states as well as in the average case.
The second method involved a comparison of expected -ray luminosity
distribution with the observed data using the Kolmogorov--
Smirnov (KS) test. In the second method, we assumed that there is a
correlation between the radio and -ray luminosities and that the
-ray luminosity function is proportional to the radio luminosity
function. The KS test indicates that the expected gamma-ray luminosity
distributions are consistent with the observed data in a reasonable parameter
range. Finally, we used different -ray luminosity functions to estimate
the possible 'observed'
-ray luminosity distributions by GLAST.Comment: 8 pages, 4 figures, one table, PASJ, 53 (2001
Thermal elastohydrodynamic lubrication of spur gears
An analysis and computer program called TELSGE were developed to predict the variations of dynamic load, surface temperature, and lubricant film thickness along the contacting path during the engagement of a pair of involute spur gears. The analysis of dynamic load includes the effect of gear inertia, the effect of load sharing of adjacent teeth, and the effect of variable tooth stiffness which are obtained by a finite-element method. Results obtained from TELSGE for the dynamic load distributions along the contacting path for various speeds of a pair of test gears show patterns similar to that observed experimentally. Effects of damping ratio, contact ratio, tip relief, and tooth error on the dynamic load were examined. In addition, two dimensionless charts are included for predicting the maximum equilibrium surface temperature, which can be used to estimate directly the lubricant film thickness based on well established EHD analysis
Transient effect of lubricant on elastohydro-dynamic film thickness
The inlet solution of the elastohydrodynamic lubricated rolling contact problem was obtained by considering lubricants with transient viscosity. The effect of the viscoelastic retardation time of the lubricant on the center film thickness was investigated. The effect of transient viscosity in response to a sudden pressure was found to be insignificant in determining the film thickness in elastohydrodynamic contacts
Polarization and Variations of BL Lacertae Objects
BL Lacertae objects are an extreme subclass of AGNs showing rapid and
large-amplitude variability, high and variable polarization, and core-dominated
radio emissions. If a strong beaming effect is the cause of the extreme
observation properties, one would expect that these properties would be
correlated with each other. Based on the relativistic beaming model,
relationships between the polarization and the magnitude variation in
brightness, as well as the core- dominance parameter are derived and used
statistically to compare with the observational data of a BL Lacertae object
sample. The statistical results are consistent with these correlations, which
suggests that the polarization, the variation, and the core-dominance parameter
are possible indications of the beaming effect.Comment: 6 pages, two figures, one table, some revisions. PASJ, 53 (2001
Colouration in crab spiders: substrate choice and prey attraction
Published version: http://jeb.biologists.org/content/208/10/1785/F3.expansio
Basic properties of Gamma-ray loud blazars
In this paper, a method is proposed to determine the basic properties of
-ray loud blazars, among them the central black hole mass, M, the
Doppler factor, , the propagation angle of the -rays with
respect to the symmetric axis of a two-temperature accretion disk, , and
the distance (i.e. the height above the accretion disk), d at which the
-rays are created, for seven -ray loud blazars with available
GeV variability timescales and in which the absorption effect of a -ray
and the beaming effect have been taken into account. Our results indicate that,
if we take the intrinsic -ray luminosity to be times the
Eddington luminosity, , the masses of the
blazars are in the range of , the Doppler
factors () lie in the range of 0.57 to 5.33 the angle () is in
the range of to 43 and the distance (d) is in the range
of 26R_{g} to 411R_{g}. Our model results are independent of -ray
emission mechanisms but they do depend on the X-ray emission mechanism of the
accretion disk.Comment: 14 pages, 3 tables, A&A accepte
The role of UV in crab spider signals: effects on perception by prey and predators
Australian crab spiders Thomisus spectabilis sit on the petals of flowers and ambush prey such as honeybees. White-coloured T. spectabilis reflect in the UV (UV+ spiders) and previous research has shown that their presence, curiously, attracts honeybees to daisies. We applied an UV-absorber (Parsol®) to create UV-absorbing (UV–) spiders that did not reflect any light below 395 nm wavelength. These physical changes of visual signals generated by crab spiders caused honeybees to avoid flowers with UV– spiders on their petals. They also affected the perception of UV– spiders by honeybees and a potential avian predator (blue tits). Compared to UV+ spiders, UV– spiders produced less excitation of the UV-photoreceptors in honeybees and blue tits, which translated into a reduced UV-receptor contrast and a reduced overall colour contrast between UV– spiders and daisy petals. Our results reveal that a clean physical elimination of reflection in the UV range affects perception in predators and prey and ultimately changes the behaviour of prey.7 page(s
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