Analysis of the effect of the shape of the radiation pattern on the accuracy of azimuth measurements by the monopulse method

The effect of the shape of the radiation pattern of the difference channel of a monopulse antenna on the accuracy of angular-coordinate measurements is estimated. The least root mean square deviation is obtained using a radiation pattern with a Chebyshev amplitude distribution. Of the practical amplitude distributions a “parabola on a pedestal” of 0.1–0.316 is preferable. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 53–54, April, 1998.     

Determination of the uniformity of the carrier lifetime in a material from the profile of the amplitude spectrum of an ion detector

An analysis is made of charge transport in the neutral base of a p ⁺-n structure as a result of its diffusion to the boundary of the p-n junction under conditions where nonequilibrium carriers are generated by single α-particles. It is assumed that nonuniformity of the carrier lifetime (τ), described by a Gaussian distribution, exists over the area of the structure. The profile of the transported charge spectrum is calculated for these conditions and its correlation with the measure of nonuniformity τ is obtained. Since the tracks of the diffusing α-particles occupy an extremely small volume, recording them is equivalent to local probing of the material for τ. It is suggested that the calculated function should be used as a calibration function to determine the spread of τ values in materials. The method is tested on Si for a surface-barrier structure by recording 8.78 MeV π-particles. Pis’ma Zh. Tekh. Fiz. 24, 44–50 (March 12, 1998)     

Study on the interaction between the shape and the temperature field of the melt in the electromagnetic shaping process

Based on analyses for the electromagnetic pressure on the melt and the heat induced in the melt, the ratio of heat to pressure Q₀/P_m is defined, to give the relationship between Q_o/P_m and the thickness a, the electromagnetic parameter (μγ) of the melt and the electric current frequency/under the electromagnetic confinement and shaping process. If Q_o/P_m is large, any adjustment to the melt shape will easily cause a variation of the temperature in the melt. In this situation, there appears to be a more sensitive interaction between the shape and the temperature field and a more narrow adjustment range for the process. Experiments on thin plate samples with a cross-section of 6 mm × 18 mm are done with two kinds of induction coils. The results show that when a coil with a trumpet inside wall is used and the positions of the melt top and the S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of the S/L interface is high. Under these conditions, a more stable and wider coupling between the shape and the temperature field is continuously maintained and samples with a smooth surface and unidirectional crystals are successfully obtained.     

On the change in the modulus of elasticity with a decrease in the size of a nanocrystal

A model of nanocrystal in the form of a rectangular parallelepiped with a variable surface shape is used to show that, at high temperatures, modulus of elasticity B decreases with a decrease in size of the nanocrystal N, which is due to the increase in the surface pressure. However, at low temperatures, dependence B(N) is less pronounced and can even rise with a decrease in the nanocrystal size. This is because, at low temperatures, the increase in the surface pressure (which is larger than at high temperatures) leads to an increase in the modulus of elasticity for the entire nanocrystal. The more the nanocrystal shape deviates from the most energetically stable shape, the more pronounced the change in the dependence B(N) is.     

The Design of the Input Stage for the Very Front-End of the CUORE Experiment

We describe the criteria for the selection of the input transistor of the very front-end for the detector, an array of 988 macro bolometers. Each of such macro bolometer is composed of a crystal of TeO₂, having a mass of 750 g, to which a thermistor is glued. Due to the very large mass of the crystals, the detector response time is very slow and limited to a few Hz. The quoted characteristic for the CUORE (Cryogenic Underground Observatory on Rare Events) detectors make it attractive a solution based on a complete room temperature operated front-end. The very important requirements of such a solution are a very small parallel and low frequency series noise. We worked to the selection of a Si JFET having a gate area and pinch-off voltage that fulfils the CUORE requirements. The selected JFET has an input gate current of less than 60 fA at 40°C (the expected operating temperature at regime). The noise at 1 Hz is about 3 nV/ at the operating point of I _DS of 0.5 mA and V _DS of 0.5 V, selected for having small power dissipation. Thanks to the quoted results the limit in the energy resolution given by the preamplifier is about 10 times better than that presently achievable by the crystals tested and candidate for CUORE. The wafer from which the semi-custom JFET has been cut was previously probed. All the production consisting of 1200 JFETs pairs is already available.      

Discussion of the feasibility of the Einstein refrigeration cycle

A careful modelling of the thermodynamic properties of the water–ammonia–butane system, the working fluid mixture used in the Einstein cycle, with the Patel–Teja cubic equation of state is performed. Numerical simulation is used to investigate the feasibility limits of this refrigeration cycle. Two modified configurations of the cycle are considered. A conflict between the evaporator and the condenser/absorber operating conditions is noted. The condenser/absorber operation needs a higher system pressure, which limits the refrigeration temperature in the case of air-cooling. On the other hand, the condensation of ammonia and the presence of a small quantity of water in the evaporator limit also the refrigeration temperature. In the case of a water-cooled machine, with a condenser/absorber temperature of 30 °C, the cycle COP reaches 0.19 which is still low.     

A microcontinuum analysis of the self propulsion of the spermatozoa in the cervical canal

The hydrodynamics of the self propulsion of a spermatozoa, swimming through the mucus filling the cervical channel, is investigated. The mucus is modeled as a micropolar fluid and the spermatozoa as a 2-dimensional sheet swimming at low Reynolds number between two rigid walls. The wavelengths of the propulsive waves passing down the sheet are assumed to be very large compared to the channel spacing, but the amplitude of the propulsive waves is arbitrary. Expressions for the propulsive velocity and the energy expended by the swimming sheet are obtained in terms of various parameters involved. The results are elaborated through graphs. It is found that both the propulsive velocity and the rate of working by the sheet increase as the value of the micropolar parameters $\text{N}$ increases and that of $\text{L}$ decreases.     

Study on the interaction between the shape and the temperature field of the melt in the electromagnetic shaping process

Based on analyses for the electromagnetic pressure on the melt and the heat induced in the melt, the ratio of heat to pressure Q₀/P_m is defined, to give the relationship between Q₀/P_m and the thickness a, the electromagnetic parameter (μγ) of the melt and the electric current frequency f under the electromagnetic confinement and shaping process. If Q₀/P_m is large, any adjustment to the melt shape will easily cause a variation of the temperature in the melt. In this situation, there appears to be a more sensitive interaction between the shape and the temperature field and a more narrow adjustment range for the process. Experiments on thin plate samples with a cross-section of 6 mm×18 mm are done with two kinds of induction coils. The results show that when a coil with a trumpet inside wall is used and the positions of the melt top and the S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of the S/L interface is high. Under these conditions, a more stable and wider coupling between the shape and the temperature field is continuously maintained and samples with a smooth surface and unidirectional crystals are successfully obtained.     

Development of the bubble technique for the measurement of the surface energy of solids

A method for the measurement of the surface energy of copper at 500† C is described. Argon or krypton gas is introduced into a thin surface layer of a specimen by an ion implantation process and subsequent annealing precipitates this gas. At equilibrium the gas pressure in the small bubbles formed is balanced by the surface tension forces andγ=1560±160 erg cm⁻² has been measured.     

Interpretation of the time axis from the standpoint of the theory of fuzzy sets

The time axis is interpreted from the standpoint of the theory of fuzzy sets. It is shown that a continuous, uniformly dense fragment of the time axis can be obtained from a sequence of fuzzy time intervals, each of which is constructed from two consecutive time marks.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 32–34, August, 1993.     

On the autonomy of the process region

Two methods are examined for accurately calculating stress intensity factors in two and three dimensions: the stiffness derivative technique and the J-integral method. In two dimensions the J-integral is expressed as an area integral, whereas in three dimensions it is a volume integral. With both techniques, a virtual crack extension is introduced. Although the expressions employed for each method are quite different, it is proven that when written analytically for finite element calculation, they reduce to identical expressions.Numerical calculations are carried out in both two and three dimensions. As a result of the equivalence of the two methods, close numerical agreement is expected. For two-dimensional geometries and a penny shaped crack in a finite height cylinder, there is at least five significant figure agreement between solutions determined by both methods. For an elliptical crack embedded in a plate, the agreement is generally to four significant figures.     

Analysis of the features of the measurement of the magnetization of hollow cylinders using an induction transducer

A formula for calculating the effect of the dimensions of a hollow cylinder of material with a high magnetic permeability on the fraction of the magnetic flux, closing through its inner cavity, is obtained. The influence of this effect on the results of a measurement of the magnetization of hollow cylinders of different length and wall thickness is analyzed. It is shown that it is necessary to take this into account in magnetic measurements. Translated from Izmeritel’naya Tekhnika, No. 4, pp. 47–50, April, 2009.     

Radar recording of the concluding stage of the turning of the rudder of a sea-going ship

By processing the results of natural measurements of the circulation of a ship, it is established that the presence of a maximum of the angular acceleration, the position of which corresponds to the stage of the completion of the turning of the rudder, is an identification indicator of the maneuvering period. It is shown that the accuracy of the radar measurement is acceptable for recording the time taken for the rudder turning stage of a sea-going ship to be completed. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 51–56, June, 2008.     

Study of the Influence of the Source Quality on the Determination of the Shape Factor of Beta Spectra

We are developing metallic magnetic calorimeters for beta spectrometry with the aim of determining the shape factors of beta spectra. The beta emitter is enclosed inside the detector absorber and the absorber size is chosen such that the detection efficiency is close to 100% for the entire spectrum. The nature of the deposit of the beta emitter is critical for precise measurement. A dependence of the shape of the spectrum on the quality of the source has been observed, supposedly due to interactions between the electrons and the deposit itself. We chose for this comparative study a nuclide with an allowed transition whose theoretical spectrum is relatively well-known, ⁶³Ni, a pure beta emitter with an endpoint energy of 66.98?keV. Results of measurements of ⁶³Ni deposited with different techniques are presented and compared to each other and to the theoretical spectrum.     

Computation of the Optical Constants of a Thin Dielectric Layer from the Envelopes of the Transmission Spectrum,at Inclined Incidence of the Radiation

Abstract

A mathematical expression for the transmission of a thin dielectric layer on a transmitting substrate is found. The finite dimensions of the substrate and its absorption are taken into account. The cases of inclined incidence of non-polarised, s- and p-polarised radiation to the layer are investigated. A way of determining the optical constants n(λ) and k(λ) of the layer from the envelopes of the transmission spectrum is offered. Computation of n(λ) and k(λ) of a model optical system at different angles of radiation incidence is performed as well as analysis of the results obtained.     

Gaussian quadrature formulas for the numerical integration of Bromwich's integral and the inversion of the laplace transform

Summary An approximate formula for the inversion of the Laplace transformF(p) is studied. The formula is exact wheneverF(p) is a linear combination ofp ^–s+k ,k=0, 1, 2, ..., 2N–1, withs an arbitrary positive real number. The formula is derived from a gaussian integration formula for Bromwich's inversion integral.A numerical example is given as illustration of the use of the approximate inversion formula.     

Study into the Pattern of Flashing of Liquid in the Vicinity of the Limit of Its Attainable Superheating

The pattern of flashing of liquid in the vicinity of the limit of its attainable superheating is investigated experimentally. The Skripov criterion is used, according to which, in the case of homogeneous boiling, the product of the mean expectation time for boiling by the magnitude of volume being superheated at preassigned temperature and pressure is a constant quantity. The experiments are performed with n-pentane. Thanks to thorough degassing of the liquid being investigated, the temperature of the previously attained superheating is exceeded by 1.0–1.5°C. The mean lifetime is measured in several glass capillaries of substantially different volumes. The data obtained point to the invalidity of the criterion of homogeneity of boiling of liquid in the vicinity of the limit of its attainable superheating. Also studied is the probability density of the expectation times for boiling with respect to magnitude. It is demonstrated experimentally that the probability density curve has a small empty portion at the beginning, an abrupt rise to a maximum, and a close-to-exponential decrease. This form of the probability density function is typical of unsteady-state random processes.     

Solution of the conjugate problem of the gas flow in the pulling of fluoride fiber light guides

A mathematical model is suggested for the congugate problem of the inert gas flow in a furnace channel during stretching of fluoride glass billets into optical fiber. Based on an analysis of preliminary results of a numerical investigation of gas supply from top to bottom and from bottom to top it is shown that the second variant is more effective for creating a protective atmosphere.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 3–4, pp. 319–323, September–October, 1994.     

Constancy of the Surface Energy during the Melting of a Nanocrystal

The relation for the surface free energy @sgr; as a function of size and shape of a nanocrystal is derived. The nanocrystal has the form of a parallelepiped with a square base. The ratio of the lateral edge length to the base edge length f defines the shape of a system. It is shown that the value of @sgr; decreases with degreasing number of atoms N in a nanocrystal. The higher the deviation of the form parameter f from unity, the stronger the dependence @sgr;(N). It is found that the surface free energy decreases with the temperature T; in so doing, the quantity (d/T) is the greater, the smaller the size of the nanocrystal or the greater the deviation of the nanocrystal shape from the most thermodynamically stable, cubic, shape. It is shown that the nanocrystal melts when its surface energy decreases to a certain value independent of size and shape. The conditions are discussed under which the crystal fragmentation and dendritic growth are realized.