In this paper, computer modelling and geometric construction of Burmester curve for synthesis of spherical mechanisms is presented. Rigid shell guidance in four specified positions on a sphere is performed by a 4R spherical linkage. The synthesis of such a linkage requires obtaining the associated Burmester curves on the reference sphere. Based on the Burmester theory and beside the computational and modelling abilities of the symbolic mathematical software namely Maple, an accurate as well as fast procedure for geometric construction of Burmester curve is developed. In the first part, the concepts of orientation and position on the sphere, pole of the motion and the related parameters are extended for modelling by the Maple. In the second part, the concepts of complementary axis quadrilateral and its imaginary motion, the center and circle axis cones and Burmester curve are derived. In the final part, using the prepared procedure and through a numerical example, a 4R spherical linkage for guiding an antenna to meet four specified postures in a three-dimensional working space is synthesized. 相似文献
In this paper, we investigate the uniform convergence of continuous linear set-valued functions on compact sets. We also consider conditions under which the family of continuous linear extensions of a differential iteration semigroup of continuous linear set-valued functions is a differentiable iteration semigroup. In particular, since the cones and normed spaces are not supposed to be complete our main results generalize some recent results on Hukuhara’s derivative of set-valued functions. 相似文献
In this study, a new sample vial has been designed for the extraction and determination of methyl tert-butyl ether (MTBE) in water samples by headspace solid-phase microextraction method. The special feature of this new vial is cooling the HS above the aqueous sample by cold water stream for maximum analyte absorption on SPME fiber coating. The analysis was by a gas chromatograph equipped with flame ionization detector and a capillary column (CP-sil 13 CB). Some significant variables affecting the extraction procedure were optimized. By use of divinylbenzene/carboxen/polydimethylsiloxane fiber, a sample volume of 10 mL, stirring rate of 1,000 rpm, salt concentration of 24%, extraction time of 15 min and extraction temperature of 83 °C, detection limit of 0.022 μg L−1 and a good linearity (R2 = 0.998) in a calibration range of 0.1–400 μg L−1 were achieved. The relative standard deviation for triplicate runs ranged between 6 and 8%. The method could be applied to the analysis of trace levels of MTBE in various water samples.
Sensor location selection for structures is demonstrated via identifiability analysis. The sensitivities of sensor outputs to structural stiffness coefficients are computed by a model and transformed via continuous wavelet transforms into the time-scale domain to characterize their shape attributes and accentuate their differences. Regions are then sought in the time-scale plane wherein the wavelet coefficient of an output sensitivity surpasses all the others’ as indication of the sensitivity's uniqueness. This yields a comprehensive account of identifiability by each output for individual stiffness coefficients as the basis for output selection. The proposed output selection strategy is demonstrated for an eight-storey building frame model. 相似文献
We construct a warm inflation model with inflaton field non-minimally coupled to induced gravity on a warped DGP brane. We
incorporate possible modification of the induced gravity on the brane in the spirit of f(R)-gravity. We study cosmological perturbations in this setup. In the case of two field inflation such as warm inflation, usually
entropy perturbations are generated. While it is expected that in the case of one field inflation these perturbations to be
removed, we show that even in the absence of the radiation field, entropy perturbations are generated in our setup due to
non-minimal coupling and modification of the induced gravity. We study the effect of dissipation on the inflation parameters
of this extended braneworld scenario. 相似文献
Wave packet broadening in usual quantum mechanics is a consequence of dispersion behavior of the medium which the wave propagates
in it. In this paper, we consider the problem of wave packet broadening in the framework of Generalized Uncertainty Principle(GUP)
of quantum gravity. New dispersion relations are derived in the context of GUP and it has been shown that there exists a gravitational
induced dispersion which leads to more broadening of the wave packets. As a result of these dispersion relations, a generalized
Klein-Gordon equation is obtained and its interpretation is given. 相似文献
The ability of absolute-pitch (AP) musicians to identify or produce virtual pitch from harmonic structures without feedback
or an external acoustic referent was examined in three experiments. Stimuli consisted of pure tones, missing-fundamental harmonic
complexes, or piano notes highpass filtered to remove their fundamental frequency and lower harmonics. Results of Experiment
I showed that relative to control (non-AP) musicians, AP subjects easily (>90%) identified pitch of harmonic complexes in
a 12-alternative forced-choice task. Increasing harmonic order (i.e., lowest harmonic number in the complex), however, resulted
in a monotonic decline in performance. Results suggest that AP musicians use two pitch cues from harmonic structures: 1) spectral
spacing between harmonic components, and 2) octave-related cues to note identification in individually resolved harmonics.
Results of Experiment II showed that highpass filtered piano notes are identified by AP subjects at better than 75% accuracy
even when the note’s energy is confined to the 4th and higher harmonics. Identification of highpass piano notes also appears
to be better than that expected from pure or complex tones, possibly due to contributions from familiar timbre cues to note
identity. Results of Experiment III showed that AP subjects can adjust the spectral spacing between harmonics of a missing-fundamental
complex to accurately match the expected spacing from a target musical note. Implications of these findings for mechanisms
of AP encoding are discussed.
The text was submitted by the authors in English. 相似文献
The reaction of various primary amines with acetylenic esters at ambient temperature in THF/H2O (50:50) produced related enaminones. Subsequently reaction of these in situ prepared enaminones with dibenzoylacetylene
leads to 3-alkylidene-2,3-dihydro-1H-pyrrol-2-ol derivatives in good yields. The reaction of these products with various alcohols in the presence of a catalytic
amount of HCl produced highly functionalized pyrroles in nearly quantitative yields. 相似文献