Deposition of Ruthenium-106 on a Concave Metal Surface of a Substrate of an Ophthalmic Applicator—a Closed Source of Beta Radiation

Radiochemistry - A method of 106Ru deposition on a concave metal surface of an ophthalmic applicator substrate is reported, which consists in preparing the substrate surface by coating it with a...     

Shannon's entropy as a measure of the “life” of the literature of a discipline

The paper is divided in two parts. Part I deals with the novel use of the concept ofentropy H (measured in nepers) of the ageT of references cited in the literature of a specialty, and the derived parameterS=exp(H) (measured in years). We have proposed to useS (orH) as a measure of the obsolescence of the literature. The concept of entropy comes from the Theory of Information (Shannon) where its mathematical properties have been widely studied and are thus available.H andS have been calculated for the log-normal probability density functions (which model the empirical distributions ofT) of some IEEE journals and for the 58-year collection of an electronics journal, and then they have been compared to the total utility function, this latter defined in the literature. Part II recalls and discusses the mean residual life,M(T), and the expected lifeE(T), of a reference of ageT (concepts borrowed from lifetime data analysis). Besides their intrinsic applications, another possible application of these concepts may be in defining quantitatively the age of historical papers. Examples taken from the literatures of the XX and XIX centuries have been reported.Paper presented at the Fourth International Conference on Bibliometrics, Informetrics and Scientometrics in Berlin (Germany), September 11–15, 1993.     

Cooling of a coarse lump in a bed of “fine” particles

The cooling of a coarse lump having the form of a rectangular prism in a blow-through bed of fine particles is discussed. A solution is obtained for large and small values of Fo by using Laplace transforms.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 3, pp. 434–440, March, 1976.     

Diagnosis of the Thermal Bow of a Shaft in a Three Stage Centrifugal Compressor

In practice many turbo-machines driven by motors are started up to perational speed within a very short time,i.e.in less than 20 seconds .For this type of machines the compatibility of thermal deformaiton of the rotor stucture must be taken into account in the machine desing ,or the thermal defromation will be constrained and a huge resultant force can cause the shaft bending and consequently resulting in violent vibrations.In this paper,detection of thermal bow of a shaft in a three stage centrifugal compressor in a petrochemical plant is presented .The diagnostic results show that the thermal bow was induced by the incompatibility of axial thermal deformation of the rotor stucure.A remedial action allowing free axial thermal expansion of the outer parts of the rotor is suggested.     

Equalization of the Concentration of a Scalar Impurity in a Flow‐Type Chamber

Experimental and theoretical investigations of the time of equalization of the concentration of an impurity in a rectangular flowtype chamber have been carried out. It has been shown that the process of equalization of the concentration with time is exponential in character. The characteristic equalization time has been computed using the theory of turbulent diffusion. Theoretical results describe experimental regularities with an accuracy of about 10%. The value of the coefficient of turbulent diffusion for different configurations of flows in the chamber has been obtained from a comparison of experimental and calculated results.     

Thermal Mathematical Model of the H‐Shaped Block of a Nonhermetic Instrumental Compartment of a Geostationary Spacecraft

A dynamic thermal mathematical model in distributedlumped parameters, a computational algorithm, and a software of numerical calculations have been developed. The results of these calculations for multidimensional nonstationary temperature fields in operation of the onboard devices and a network of uncontrolled heat pipes in a nontraditional Hshaped block of the servicesystem module of a nonhermetic instrumental compartment of promising durable geostationary spacecraft under the conditions of orbital operation have been obtained.     

The Variation of “Surface” Pressure in a Nanocrystal as a Function of Temperature

The Mie-Lennard-Jones potential of interatomic interaction is used to derive an expression for “surface” pressure in a nanocrystal with free surface. The nanocrystal has the form of a parallelepiped with a square base. The number of atoms N may vary from eight to ∞. It is found that a certain “inversion temperature” T _i exists for any substance, where the temperature dependences of surface pressure for different sizes of nanocrystal intersect. When the crystal disperses in the T < T _i region, the “surface” pressure increases, and in the T > T _i region decreases, with decreasing size of nanocrystal: P _sf(N) ～ N ^?1/3. The greater the deviation of the nanocrystal shape from cubic, the stronger the dependence P _sf(N). It is demonstrated that, at some temperatures (T < T ₀), the “surface” pressure compresses the nanocrystal, and at other temperatures-stretches this nanocrystal, as its size decreases. The more clearly the quantum effects are defined in the crystal, the lower the value of the “temperature of zero surface pressure” T ₀, which depends on the nanocrystal size and shape.     

An Application of a Multivariable Self-Tuning Regulatorto the Control System of a Equipment Spare Parts

1IntriductionSelf-tUningconealisoneofthemostfundamentaltypesinadaptivecontrol,whichhasbeensuccessfullyappliedinmanykindsofindustrialfields.HoweVer,itisdifficulttOfindthatadaptivecontrolisaPPliedinthedOInainofmanagement.SPeakinggenelally,theadaptabili...     

Role of Capillary Forces in Filtration of a Gas–Condensate Mixture near a Well

The problem of steadystate flow of a gas–condensate mixture near an operating well is considered. The effect of capillary forces on condensate distribution in a porous medium is studied both analytically and numerically. It is shown that capillary forces can serve to decrease the amount of condensate, with the effect occurring in both cases — wetting and nonwetting liquid phases.     

Features of the Motion of a Circulating Bed in a Large‐Volume Spherical Packing

An experimental study has been made of the motion of a circulating fluidized bed in a column filled with a largevolume spherical packing. It has been established that, once the feed of the loose material ceases, the motion of the bed continues up to the total removal of the disperse medium from the column with a velocity acquired in constant circulation. A procedure based on the processing of experimental results has been proposed for calculation of the operating conditions of apparatuses in which the indicated motion can be employed.     

Excitation of Narrow‐Band Pulsations in a Short Portion of Transition from the Smaller Diameter of a Pipe to a Larger Diameter and Possibilities of Preventing Them

By using models of the portions of the circuit of main gascompressor stations, data on the frequencies of narrowband pressure pulsations have been obtained; these data demonstrate the jet character of flow in divergent channels with angles of opening on one side of 12°47 and 23°50. It has been shown that narrowband acoustic disturbances are generated in the internal flow with largescale hydrodynamic structures. Intense narrowband pulsations are prevented by a grid of internal divergent channels in the transition portion with small angles of opening in canals and in excitation of certain disturbances upstream of a short divergent channel.     

Modeling of the Thermal Field of a Workpiece in Milling of Austenitic Steel by a Finger‐Type Cutter

The authors report results of modeling thermal fields by the method of finite elements under conditions of milling of 00H17N14M2A austenitic steel by a fingertype cutter. A solution of the problem of unsteady nonlinear heat conduction has made it possible to find the temperature distribution in the surface layers of a workpiece as a function of the cutting rate and the position of the tip of the cutter edge.     

Choice of a γ-emission source for phase analysis of a material by nuclear γ-resonance

Consideration is given to the influence of nonresonance attenuation of resonance -quanta by the lattice of a -emission source, on the shape of a monoline in the Mössbauer spectrum. It is shown that this effect leads to increased error in the phase analysis of a material in nuclear -resonance spectroscopy. Criteria are determined for the suitability of a -emission source for use in the phase analysis of materials by this method. The actuality of the problem is shown for the most widely used Mossbauer isotopes.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 55–57, June, 1994.     

Vapor-phase synthesis of a solid precursor for α-alumina through a catalytic decomposition of aluminum triisopropoxide

A new solid precursor, hydrous aluminum oxide, for α-alumina nanoparticles was prepared by thermal decomposition of aluminum triisopropoxide (ATI) vapor in a 500 mL batch reactor at 170-250 °C with HCl as catalyst. The conversion of ATI increased with increasing temperature and catalyst content; it was nearly complete at 250 °C with the catalyst at 10 mol% of the ATI. The obtained precursor particles were amorphous, spherical and loosely agglomerated. The primary particle size is in the range 50-150 nm. The ignition loss of the precursor was 24%, considerably lower than 35% of Al(OH)₃, the popular precursor for alumina particles. Upon calcination of the precursor at 1200 °C in the air with a heating rate of 10 °C/min and a holding time of 2 h, the phase was completely transformed into α. The spherical particles composing the precursor turned worm-like by the calcination probably due to sintering between neighboring particles. The surface area equivalent diameter of the resulting α-alumina was 75 nm.     

Distribution of crack extension force,the Ĵ-integral,along a through-crack-front of a plate

The -integral is an extension of the J-integral proposed by Rice. It represents the crack-extension force; i.e., the energy release rate per unit of a crack-tip translation in three-dimensional elastic-plastic materials. The distribution of the -integral along the crack-front in a plate subjected to a monotonic loading is determined by a three-dimensional elastic-plastic finite element method.The three-dimensional calculation elucidates that the -integral takes its maximum value at the mid-thickness of the plate and takes a smaller value near the plate surfaces. It is shown that the -integral at the mid-thickness takes an intermediate value between those obtained by two-dimensional plane-strain and plane-stress computations; and that for a compact specimen it agrees with the J-integral value determined from the computed load versus the load-line-displacement curve using the Merkle-Corten formula.

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Résumé L'intégrale J est une extension de l'intégrale J proposée par Rice. Elle représente une force d'extension d'une fissure, à savoir le taux de relaxation de l'énergie par unité de translation de l'extrémité de la fissure dans des matériaux tridimensionnels élasto-plastiques. On détermine la distribution de l'intégrale J le long du front de fissuration dans une tôle soumise à charge croissante, à l'aide d'une méthode élastoplastique par éléments finis sur trois dimensions.Le calcul tridimensionnel permet d'établir que l'intégrale J revêt sa valeur maximale à mi-épaisseur de la tôle, et une valeur plus faible au voisinage des surfaces de la tôle.On montre que l'intégrale J à mi-épaisseur prend une valeur intermédiaire entre les valeurs ci-dessus, lorsqu'elle est déterminée par calculs à deux dimensions en état plan de déformation on en état plan de tension. On montre aussi que, dans le cas d'une éprouvette compacte, cette valeur est en accord avec la valeur de l'intégrale J établie à partir de la courbe calculée en fonction du déplacement sur la ligne de charge, à l'aide de la formule de Merkle-Corten.

     

Study of Thermal Fatigue Resistance of a Composite Coating Made by a Vacuum Fusion Sintering Method

Thermal fatigue behavior of a Ni-base alloy chromium carbide composite coating made by a vacuum fusion sintering method are dicussed,Results show that thermal fatigue behavior is associated with cyclic upper temperature and coating thickness,As the thickness of the coating decreases ,the ther-mal fatigue resistance increases,The thermal fatigue resistance cuts down with the thermal cyclic upper temperature rising,The crack growth rate decreases with the increase in cyclic number until crack arrests.Thermal fatigue failure was not found along the interface of the coating/matrix.The tract of thermal fatigue crack cracks along the interfaces of phases.     

Sol-gel transition of a mixture of gelatin and κ-carrageenan

Abstract

The characteristics of sol-gel transition of a mixture made by mixing two kinds of gelling agents of different nature, i.e. gelatin and carrageenan were examined. The sample solutions consisted of 3.00 wt % gelatin solution, 1.00 wt % κ-carrageenan solution and 4.00 wt% mixed solution which was prepared by mixing the said gelatin and carrageenan solutions in the ratio 3:1. In the experiment, the optical rotation and the dynamic viscoelasticity were measured under the same temperature change program. As the sample solutions were cooled, the carrageenan solution started to show a change in the specific rotation in the first place, followed by the mixed solution and finally the gelatin solution. The gelatin and the mixed solutions had the same increasing tendency in the specific rotation, whereas the carrageenan solution changed a little. When the mixed solution was chilled to set, it turned into a highly elastic gel. In the mixed solution, the gelation of carrageenan was found to precede that of gelatin.     

Grey Problems of a Mechanical Transmission System in a Reliability Study

1 IntroductionReiability acted as an imPortant index that was aPPied to weigh the quality of a mechanicalProdct, and it has brOadiy been thought. Currently, an imPortant taSk of machine scope is to aimat the market's needs inside and outside the country and adust the strUcture of ProductS tooccuPy the Inarket in Products of high qualiy It is a key aspeCt of all tO sahsfy reiability needsof users in the new Products explored. The machine transAnssion system is an imPortantcomPosition of…     

Vibration-Induced Attraction of a Particle Towards a Wall in Microgravity—The Mechanism of Attraction Force

The effects of small vibrations on a particle oscillating near a solid wall in a fluid cell, relevant to material processing such as crystal growth in space, have been investigated by three dimensional direct numerical simulations. Simulations have been conducted for a solid spherical particle suspended in a fluid cell filled with a fluid of 1 cSt viscosity, vibrating sinusoidally in a horizontal direction. The simulations revealed the existence of a vibration-induced force attracting the particle towards the nearest cell wall which varied with the cell vibration frequency. The mechanism for this attraction force as well as an example showing the effects of this force on the particle are presented in this paper. The predicted flow patterns around the particle unveiled an accelerated flow in the gap between the particle and the nearest wall as well as a pressure decrease in accordance with Bernoulli’s principle, which would result in the attraction force.