Improvement of accuracy of interferometric measurement of wedge angle of plates

A method is proposed for improving the accuracy of measuring the wedge angle of transparent plates using a lateral-shear holographic interferometer. Consecutive processing of a pair of interferograms with doubled number of interference fringes leads to reduction of the observational error by a factor of two compared to traditional interferometric methods. Data on the experimental validation of the method are presented.     

Simulation of the superlinearity of dose characteristics of thermoluminescence of anion-defective aluminum oxide

The specific features revealed in the superlinearity of dose dependences of thermoluminescence of anion-defective aluminum oxide single crystals have been considered theoretically in terms of the model of an interactive trap system. The model explains the decrease in the degree of superlinearity at a low heating rate, as well as with an increase in the dose increment, the occupancy of deep traps, and the sensitivity of the crystals to radiation due to the increase in the concentration of luminescence centers. The obtained results indicate a widening of the possibilities of the model for interpreting experimental data in the investigation of the dose characteristics of thermoluminescence of the studied crystals.     

Measurement of degree of polarization of fluorescence of pure anthracene crystalline film

The polarization ratio (I _b/I_a) of fluorescence of a monocrystalline film of pure anthracene is measured correcting for all probable errors. Comparison with decay-time data brings out that deviation from the value obtained from absorption measurements is due to a loss of intensity in the a-polarized fluorescence as compared to what is expected from absorption data. This is interpreted as an evidence that anthracene crystal fluorescence is emitted from regions of local lattice imperfections. It is confirmed that the first electronic transition takes place along the short axis of the anthracene molecule.     

Formation of One-Dimensional Distributions of Values of Correlators of Network Traffic Aggregates

Russian Physics Journal - A mathematical model of the flow of aggregated load characteristics of network traffic data packets in the form of a set of analytical signals is proposed. The real parts...     

Rectangularity of hysteresis loop of ferrites as a function of volume of reverse domains in state of remanence

A study is made of the dependence of the coefficient of rectangularity of the hysteresis loop of ferrites of the Li-Mn-Mg and Mg-Mn-Zn system on the volume concentration of residual reverse domains. The latter is calculated from the results of measurements of the relative remanence on the basis of a model developed. It is shown that a high degree of loop rectangularity can be attained not only in the absence of reverse domains but also in the presence of a considerable volume concentration of such domains.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 109–114, June, 1978.     

Analysis of spectral characteristics of scattering of evanescent waves

The spectral scattering characteristics of nanoscale particles exhibited in the field of evanescent waves are analyzed using the method of discrete sources. The effect of various parameters on the behavior of the scattering characteristics is studied. The material of the particles is shown to have the most substantial effect on the scattering cross section.     

Generation of superpositions of coherent states of the motion of a trapped ion

We propose a method for preparing superpositions of coherent states of the motion of an ion in an anisotropic two-dimensional trap, in which the ion is tightly bound in the y direction. In the scheme the ion is excited by two resonant laser beams with equal amplitude, propagating along the x and y directions, respectively. In the Dicke-Lamb limit, an initial coherent state of the ion motion can be converted into a superposition of several coherent states on a circle through the laser-ion interactions and state-selective measurements on the ion. Received: 30 May 1997 / Revised: 29 July 1997 / Accepted: 22 October 1997     

Distribution of zeros of the partition function of the lattice gases of fisher and of temperley

The distributions of zeros of the partition function of lattice gas models of Fisher (at some temperature) and of Temperley are obtained. The former is a closed loop crossing the real axis and the latter is a part of the negative real axis.     

Effect on zero drift of accuracy of reciprocal tuning of elements of fiber-optic interferometer

The effect of the accuracy of reciprocal tuning of the elements of a fiber-optic interferometer (FOI) — laser, polarizer, and eigenaxes of single-mode-fiber (SMF) birefringence — is examined. It is shown that zero drift in the FOI consists of two parts — a constant part and a temperature-related variable part. Both of these parts are functions of the polarization state of the radiation at the entrance to the polarizer, the extinction coefficient of the polarized, and the orientation of the SMF eigenaxes with respect to the polarizer. The variable part of the zero drift is also a function of the birefringence and h-parameter of the SMF and the width of the radiation-source spectrum. Numerical estimates of FOI zero drift are made.Institute of Applied Physics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 7, pp. 817–824, July, 1991.     

Calculation of energy characteristics of adsorption of metals

Within the framework of the electron density functional, a technique is developed for calculation of the adsorption energy and variation in the electron work function for metal substrates due to metal atom adsorption. The corrections to the local density approximation, which are associated with non-uniformity of the electron density in the subsurface region and discontinuous ion charge distribution over the crystal lattice sites, are included into consideration. It is shown that adsorption of alkali metal atoms results in lower electron work function, while that of transition metals (cobalt, iron, and chromium) might both decrease and increase the electron work function. Formation of a variety of adsorption structures from metal atoms depending on the temperature is discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 14–19, July, 2007.     

Mechanisms of sublimation of silicon

An atomic modelling of the processes of desorption permits the determination of the energetically more favourable mechanisms of sublimation from a Si(111) surface. These include the creation of multi-vacancies, the presence of steps and the migration of atoms near the surface.     

Amenability of discrete subgroups of the group of diffeomorphisms of the circle

The amenability of several discrete subgroups of the group of diffeomorphisms of the circle is proved.     

Role of interactions of triplets of atoms in the formation of elastic properties of cubic crystals

It is widely known that the interaction of triplets of particles (which are not reducible to the sum of pair interactions) play an important role in formation the nonlinear and anisotropic properties of crystals. The aim of this work is to establish a general form of the dependence of these properties on interactions of triplets of atoms that is dependent only on the structure of the crystals. To separate the interactions of triplets of atoms from those of quadruples, we assume that the energy of triplets of interacting atoms depends only on the characteristics of a triangle whose vertices are the centers of gravity of interacting atoms. In this model, the internal energy must therefore be invariant upon rearrangement of the numbers of interacting atoms and any rotation of the triangle in isotropic space, P(3) × O(3). To specify the form of energy dependence on characteristics of selected triangles, we constructed an integral rational basis of invariants in dependence on the components of the vectors connecting the vertices of each triangle. Using the example of a simple dependence of the energy on basic invariants, we show how to move from the assumed energy dependence on invariants to the dependence of energy on lattice sums.     

Influence of rate of change of frequency on the overall pitch of frequency-modulated tones

The mechanism(s) determining pitch may assign less weight to portions of a sound where the frequency is changing rapidly. The present experiments explored the possible effect of this on the overall pitch of frequency-modulated sounds. Pitch matches were obtained between an adjustable unmodulated sinusoid and a sinusoidal carrier that was frequency modulated using a highly asymmetric function with the form of a repeating U or inverted U shaped function. The amplitude was constant during the 400-ms presentation time of each stimulus, except for 10-ms raised-cosine onset and offset ramps. In experiment 1, the carrier level was 50 dB SPL and the geometric mean of the instantaneous frequency of the modulated carrier, fc, was either 0.5, 1, 2, or 8 kHz. The modulation rate (fm) was 5, 10, or 20 Hz. The overall depth (maximum to minimum) of the FM was 8% of fc. For all carrier frequencies, the matched frequency was shifted away from the mean carrier frequency, downwards for the U shaped function stimuli and upwards for the repeated inverted U shaped function stimuli. The shift was typically slightly greater than 1% of fc, and did not vary markedly with fc. The effect of fm was small, but there was a trend for the shifts to decrease with increasing fm for fc = 0.5 kHz and to increase with increasing fm for fc = 2 kHz. In experiment 2, the carrier level was reduced to 20 dB SL and matches were obtained only for fc = 2 kHz. Shifts in matched frequency of about 1% were still observed, but the trend for the shifts to increase with increasing fm no longer occurred. In experiment 3, matches were obtained for a 4-kHz carrier at 50 dB SPL. Shifts of about 1% again occurred, which did not vary markedly with fm. The shifts in matched frequency observed in all three experiments are not predicted by models based on the amplitude- or intensity-weighted average of instantaneous frequency (EWAIF or IWAIF). The shifts (and the pitch shifts observed earlier for two-tone complexes and for stimuli with simultaneous AM and FM) are consistent with a model based on the assumption that the overall pitch of a frequency-modulated sound is determined from a weighted average of period estimates, with the weight attached to a given estimate being inversely related to the short-term rate of change of period and directly related to a compressive function of the amplitude.     

利用神经网络提高编码器精度的方法

介绍了编码器误差的构成及特点，针对系统误差的分布规律与特点提出了基于神经网络的误差修正方法。采用非线性逼近精度较高的径向基函数神经网络，以采样点的角度值作为网络的输人样本，以高精度检测编码器的检测值作为学习目标建立了误差修正模型。实验结果表明，采用此种方法可将编码器的精度提高至原来的3倍以上，可有效地改善编码器的系统精度。     

The effect of hydration of ions of inorganic salts on the shape of the Raman stretching band of water

The shape of the Raman stretching band of water molecules in aqueous solutions of electrolytes KBr, KCl, KI, NaCl, and NaI is studied. It is confirmed that the characteristics of the stretching band strongly depend on the concentration and type of salt. The behavior of different parameters of the band is explained in terms of the theory of hydration of salts.     

Mechanism of film growth of pulsed electrodeposition of nanocrystalline copper in presence of thiourea

This article reports the effect of addition of small amount of thiourea on mechanism of film growth, levelling and grain refinement of pulsed electrodeposition of nanocrystalline copper on stainless steel substrate using simple aqueous acidic copper sulphate solution prepared from 0.25 M CuSO₄·5H₂O and 0.5 M H₂SO₄. The amount of thiourea used in the electrolyte is 0 and 36 mg/l. The results indicate the change in morphology of the deposits with addition of thiourea leading to dendrite free copper deposits. The growth mechanism of the copper deposition is found to change from Volmer–Weber type to Frank-Vander Merwe type making the deposits smoother when deposited with thiourea addition. A small amount (36 mg/l) of thiourea addition leads to decrease in the average grain size of copper from 1160 nm to 14 nm. The results clearly reveal the formation of nanocrystalline copper by addition of thiourea with three orders of magnitude reduction in grain size as compared to the sample deposited without thiourea. Preferential segregation of sulphur (present in thiourea) along the grain boundaries of nanocrystalline copper is shown by energy filter imaging using ultra high resolution transmission electron microscope (TEM), thereby restricting the growth of copper grains during pulsed electrodeposition.     

Kinetics of Macrolocalization Patterns of Plastic Flow of Metals

The features of the macroscopic inhomogeneity of plastic deformation in the form of autowaves with a pulsating amplitude are analyzed, and data on the localization of sources of acoustic emission at different stages of plastic flow in the stretching of fcc mono- and polycrystals are presented. The relationship between the local components of the plastic distortion tensor in the strain localization zone is traced. The role of acoustic phenomena accompanying the localization of plastic strain in the development of the process of plastic deformation is considered.     

Improvement of the sensitivity of measurements in the formation of holographic interferograms of wedge plates

We consider the method for improving the sensitivity of measurements in the formation of aberration-free interference images of wedge plates, which do not require a priori knowledge of the position of the wedge edge. It is shown that the sensitivity in the measurement of the wedge angle in real time interferometry is doubled in the case of recording on the reference hologram of the wedge plate followed by its reconstruction by the object light wave that has passed through the wedge plate rotated through 180° relative to the normal. It turns out that recording of a pair of holograms of the wedge plate, one of which is the image of the wedge plate turned through 180° relative to the normal to the plate, makes it possible to increase the sensitivity of measurements by more than an order of magnitude by eliminating the systematic components of measuring errors due to complete compensation of aberrations. The results of experimental testing of the method are considered.     

Symmetry of Lagrangians of nonholonomic systems of non-Chetaev’s type

This paper studies the symmetry of Lagrangians of nonholonomic systems of non-Chetaev's type. First, the definition and the criterion of the symmetry of the system are given. Secondly, it obtains the condition under which there exists a conserved quantity and the form of the conserved quantity. Finally, an example is shown to illustrate the application of the result.