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.     

Errors in measuring the directivity of a field by the method of a reference field in the range of 25–400 MHZ

Conclusions The cited data on error components in measuring the field-strength lead to the conclusions that the reference field (provided that the distances are measured with an error of ±2%) can be determined with an error of 6%, at frequencies up to 150 MHz, and of ±7% in the range from 150 to 400 MHz. The error in determining the resulting field-strength is smaller for small angles of elevation, since the beam reflected from the ground has a substantial effect on the value of the field.     

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.     

Is the proton radius a player in the redefinition of the International System of Units?

It is now recognized that the International System of Units (SI units) will be redefined in terms of fundamental constants, even if the date when this will occur is still under debate. Actually, the best estimate of fundamental constant values is given by a least-squares adjustment, carried out under the auspices of the Committee on Data for Science and Technology (CODATA) Task Group on Fundamental Constants. This adjustment provides a significant measure of the correctness and overall consistency of the basic theories and experimental methods of physics using the values of the constants obtained from widely differing experiments. The physical theories that underlie this adjustment are assumed to be valid, such as quantum electrodynamics (QED). Testing QED, one of the most precise theories is the aim of many accurate experiments. The calculations and the corresponding experiments can be carried out either on a boundless system, such as the electron magnetic moment anomaly, or on a bound system, such as atomic hydrogen. The value of fundamental constants can be deduced from the comparison of theory and experiment. For example, using QED calculations, the value of the fine structure constant given by the CODATA is mainly inferred from the measurement of the electron magnetic moment anomaly carried out by Gabrielse's group. (Hanneke et al. 2008 Phys. Rev. Lett. 100, 120801) The value of the Rydberg constant is known from two-photon spectroscopy of hydrogen combined with accurate theoretical quantities. The Rydberg constant, determined by the comparison of theory and experiment using atomic hydrogen, is known with a relative uncertainty of 6.6×10(-12). It is one of the most accurate fundamental constants to date. A careful analysis shows that knowledge of the electrical size of the proton is nowadays a limitation in this comparison. The aim of muonic hydrogen spectroscopy was to obtain an accurate value of the proton charge radius. However, the value deduced from this experiment contradicts other less accurate determinations. This problem is known as the proton radius puzzle. This new determination of the proton radius may affect the value of the Rydberg constant . This constant is related to many fundamental constants; in particular, links the two possible ways proposed for the redefinition of the kilogram, the Avogadro constant N(A) and the Planck constant h. However, the current relative uncertainty on the experimental determinations of N(A) or h is three orders of magnitude larger than the 'possible' shift of the Rydberg constant, which may be shown by the new value of the size of the proton radius determined from muonic hydrogen. The proton radius puzzle will not interfere in the redefinition of the kilogram. After a short introduction to the properties of the proton, we will describe the muonic hydrogen experiment. There is intense theoretical activity as a result of our observation. A brief summary of possible theoretical explanations at the date of writing of the paper will be given. The contribution of the proton radius puzzle to the redefinition of SI-based units will then be examined.     

Experimental Studies of the Influence of a High‐Frequency Electromagnetic Field on the Convection of Fluids in a Vertical Tube

Results of experimental studies of the influence of a highfrequency electromagnetic field on a change in the levels of fluids in a vertical tube are reported.     

Fuzzy Reliability Analysis of the Shaft of a Steam Turbine

Field surveying shows that the failure of the steam turbine‘s coupling is due to fatigue that is caused by compound stress. Fuzzy mathematics was applied to get the membership function of the fatigue strength rule. A formula of fuzzy reliability of the coupling was derived and a theory of coupling‘s fuzzy reliability is set up. The calculating method of the fuzzy reliability is explained by an illustrative example.     

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.     

Identification of the Parameters of a Nested Cylindrical Heat Source under Stationary Self‐Heating of a Raw Material Mass of the Same Form

This paper describes a computer method for determining the coordinate of the center, the heatrelease power, and the sizes of a homogeneous internal cylindrical heat source in a stationary axially symmetric temperature field arising under selfheating of a plant raw material.     

Radon atoms — a probe of the evolution of the hardened cement paste structure

A new method of investigating the evolution of the hardened cement paste structure is proposed, based on the application of radon atoms as radioactive indicators. The application of this method (called the radiometric emanation method, REM) enabled us to follow continuously changes in the surface area and gel porosity directly during the setting and hardening of the cement paste, under conditions of required temperature and humidity. The advantage of the REM application in studying cement paste samples prepared of portland cement and slag cement (water to cement ratio = 0.3) at various temperatures from 20 up to 85° C is shown in comparison with commonly used methods.     

Numerical Investigation of the Hydrodynamics of a Twisted Flow in a Vortex Chamber Based on the Two‐Parameter Model of Turbulence

An approach based on solution of complete averaged Navier–Stokes equations in vortex chambers using a lowReynolds k– model of turbulence is considered. The problem is solved in the variables vortex, stream function, and circular component of the velocity. The method of oriented pseudoconvection is used for problems of the dynamics of twisted flows. The method allows one to retain second order of accuracy of convective terms and provide stability of the solution for rather high Reynolds numbers. The problem of formulation of boundary conditions of second order of accuracy for vorticity on a solid wall at angular points is considered. An analysis of the results obtained shows that numerical calculations within the framework of the considered model of turbulence agree with experimental data rather well.     

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

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

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.     

Change of the Sign of the Effect with Increase in the Intensity of High‐Frequency Acoustic Excitation of a Turbulent Jet

Results of an experimental investigation of highfrequency acoustic excitation of turbulent jets for different intensities of the acoustic field are presented. It is shown that upon reaching a certain limiting level of excitation at high frequencies, the sign of the effect changes, i.e., at this level, highfrequency excitation leads to generation of turbulence in the jet rather than its suppression. Hence it follows that the highfrequency acoustic effect that suppresses turbulence is most efficient within an optimum range of frequencies and at an optimum level of excitation.     

Quantum dynamics of the phase of a Bose–Einstein condensate

Abstract

In this review we discuss the dynamics of the phase of trapped Bose–Einstein condensates. In particular we consider the phenomena of phase decoherence (termed also as phase collapse, or diffusion), and phase revival in systems of interacting atoms. We analyse the dependence of the collapse and revival times on the trap potential, dimensionality of the gas, atom number fluctuations, and on the coherent dynamics of the condensate. We show that in a class of experimentally relevant systems, the collapse time is relatively short, and in some cases vanishes in the limit of a large number of atoms, implying that the trapped Bose gas cannot sustain a well-defined quantum phase, and that the phase memory is lost on a relatively short time scale. Furthermore, we calculate the relative atom number fluctuations or a model of two interacting condensates, and show that the fluctuations are generically sub-Poissonian.     

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.     

Assessing the performance of a vertically disintegrated chain by the DEA approach–a case study of Taiwanese semiconductor firms

The competitiveness of an individual firm depends upon the competitiveness of the value chain to which it belongs. The core constraint of virtually every chain is that chains are structured, measured and managed in parts, i.e. vertically disintegrated, rather than as a whole. Assessing the performance of vertically disintegrated firms can provide an insight of how each firm acts in such a value chain. This paper aims to study the operating performance of the vertically disintegrated chain in the integrated circuits (IC) industry. A performance evaluation was completed for 48 leading vertically disintegrated semiconductor companies in Taiwan, including 17 in design, 10 in fabrication and 21 in packaging/testing, using the data envelopment analysis (DEA) approach which inherently recognises tradeoffs among various measures. The empirical results indicate that the IC design firms perform better than IC fabrication and IC packaging/testing firms. Overall, semiconductor firms in Taiwan still have room for performance improvement. In addition, the empirical results suggest that an IC company's scale of size does play an important role in influencing its operating efficiency. One can increase performance by consolidating with other smaller units to achieve an optimal size. In addition, an analysis of operating performance by DEA can provide a semiconductor firms’ operations with insights into resource allocation competitive advantages, and help with strategic decision-making, especially regarding operational styles under an intense competitive environment.     

Investigation of the Thermostability of Glass‐Ceramics of a Lithium Alumosilicate Composition

This paper presents the results of investigations of the thermostability of the glassceramics obtained by ceramic technology with the use of the method of casting blanks from highdensity aqueous suspensions of lithium alumosilicate glass with their subsequent sintering and crystallization under combined conditions of treatment. It is shown that the basic factors influencing the thermostability of materials are the values of the elastic modulus, CTLE, and porosity. Experiments and calculations indicate that the glassceramics exceeds the known radiotechnicalpurpose pyroceramics in thermostability and can be used in articles designed to operate under hard conditions.