A simple method for evaluating the maximum slip of anchorages

The analytical solutions to the bond problem for monotonically increasing loads are developed for a monomial exponential local bond stress-slip relationship (law) – “exact solution” –, a linear local law – “proposed solution” – and a constant bond stress distribution, such as that recommended by the Eurocode. The three solutions are thoroughly developed for the pull-out of a bar embedded in a cylindrical element, with longitudinal concrete in tension. For short anchorages, which undergo a rigid motion and whose “exact solution” requires a complex iterative procedure, the “proposed solution” explicitly provides very accurate bond stress distributions. On the basis of this accuracy, an approximate expression for the slip distribution is derived. The proposed approximate solution is the first one providing a direct slip expression for short anchorages. Approximate explicit expressions for the maximum bond stress and the maximum slip are also given. The comparison between the maximum slip values measured during experimental tests and the corresponding values obtained from the proposed approximate expression demonstrates the accuracy of the latter.     

Equipment for the Spectral Characterization of High-Temperature Particles

The spectral radiant characteristics of plume particles of a solid rocket engine are important in the design of the engine specific impulse, ablative material, and plume flame hiding. These parameters are measured from tests of the engine. Some equipment has been established to realize particle heating, uniform particle distribution, and measurements based on an FTIR spectral instrument. The equipment is based on SiC heating and is divided into a warm-up chamber and a measurement chamber to improve the particle temperature stability. A special design of uniform particle distribution combined with an acoustic levitation device is used to determine the particle falling speed. The spectral characteristics and the transmission rate of the particles have been measured by using the system including a standard blackbody, an assembled optical system, and an FTIR spectrometer. The measurements of particle concentration and temperature are given in detail. The instrument specifications are as follows: temperature range – 60–1500 °C; spectral range – 0.60–25 μm; and particle dimension range – 10–500 μm. Paper presented at the Seventh International Workshop on Subsecond Thermophysics, October 6–8, 2004, Orléans, France.     

The share of items of highly productive sources as a function of the size of the system

Summary The research in this paper is based on the paper of D.W. Aksnes & G. Sivertsen: The effect of highly cited papers on national citation indicators, Scientometrics 59 (2) (2004), 213-224, where one states that “the few highly cited papers account for the highest share of the citations in the smallest fields”. This, at first sight, evident property is examined in the theoretical models that exist in the literature. We first define exactly what we mean by “size of a field” (i.e. when is a field “smaller” or “larger” than another one). We show that there are two, non-equivalent possible definitions. Next we define exactly the possible property under study. This leads us again to two possible, non-equivalent formulations. Hence, in total, there are four different formulations to consider. We show, by giving counterexamples, that none of these four formulations are true in general. We also express conditions (in Lotkaian and Zipfian informetrics), under which the property of Aksnes and Sivertsen is true. All these results are not only valid in the papers-citations relationships but in any informetric source-item relationship. In this connection we present formulae describing the share of items of highly productive sources as a function of the parameters of the system (e.g. the size of the system).     

Modernization of the MAS-1 microscope for use in measurements of the spectra of internal conversion electrons

Efforts to increase the speed with which microscopic objects are measured are described. These efforts include the modernization of the MAS-1 automatic scanning microscope and the development of programs to reach an initial point and for carrying out automatic point-to-point linear transitions with a specified step. The error in realizing a transition to a given point with specified coordinates is shown to amount to 1 μm. Translated from Izmeritel’naya Tekhnika, No. 1, pp. 22–24, January, 2009.     

The effect of the shape of the strain-softening diagram on the bearing capacity of concrete beams

The effect of the shape of the strain-softening diagram on the bearing capacity of three-point loaded beams, as calculated by the “fictitious crack model”, is analysed. It is shown that if, at peak load, the openings at the nodes along the fracture zone are smaller than the displacement corresponding to the break-point of the bilinear softening approximation, the maximum load only depends on the slope of its initial linear portion. A “limit break-point” (L) is defined such that bilinear strain-softening diagrams with the same initial slope, and whose break-points are located beyond Point L, will lead to the same maximum load of bent beams. The location of that “limit break-point” as a function of initial slope, beam size and notch depth is also studied; the effect of these variables is explained in terms of notch sensitivity.     

On the application of the “Russian Roulette and Splitting” simulation technique for the reliability assessment of mechanical systems

A selective Monte Carlo simulation (MCS) technique, namely, the “Russian Roulette and Splitting” technique, is applied for the assessment of the reliability of structures under stochastic excitations. The basic features of the algorithm are described and discussed. As a numerical example the technique is used for the numerical solution of the first passage problem. The results are compared with available solutions obtained by another variance reduction technique—the “Double & Clump” procedure. Translated from Problemy Prochnosti, No. 3, pp. 131–138, May–June, 1997.     

Relation of the title length of a journal article to the length of the article

The great importance of titles being highly informative is almost unanimously accepted in literature, assuming that the more informative titles are, the more effectively they serve their functions. The most common measure of title “informativeness” has been the number of “significant” (i.e., non-trivial) words included in it, and one of the factors which might be associated with it is the length of the paper, measured by its number of pages. The present study attempted to test, in a large group of journals from different areas and over six decades, the hypothesis that a paper with more pages will have more “significant” words in its title. Large samples of original research papers were drawn from each decade year of twenty-four leading journals selected from the sciences, the social sciences and the humanities. For each paper, the number of “significant” words in the title was correlated with the number of pages. Findings indicate a difference between the scientific journals on the one hand, and the social sciences and humanities journals on the other. A moderate positive correlation was found in most scientific journals for many periods. In the social sciences journals, and to a greater extent, in the humanities journals, a significant positive correlation was limited to only a few periods, while the rest showed a very low correlation, or even a negative one. The different findings for the sciences are perhaps attributable to their unique inherent features. This revised version was published online in August 2006 with corrections to the Cover Date.     

Monitoring of the characteristics of Josephson microcircuits used in standards of the volt

The results of investigations of microcircuits based on Nb−AlO_x−Nb Josephson tunnel junctions, used in modern standards of the volt, are presented. The measured static characteristics of the microcircuits, their temperature dependences in the 4.2–1.7 K temperature range, the frequency response in the 54–80 GHz frequency band, and the attenuation in a microstrip line are used to optimize the construction of microcircuits and their manufacturing technology at PTB (Physikalisch-Technische Bundesanstalt, Germany). It is shown that microcircuits of a new construction, made using a modified PTB technology, have better characteristics and can be used as the unit of voltage at the level of both 1 V and 10 V. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 43–48, November, 1997.     

Comparison of the dimensions of electrical resistance units, supported on the basis of the hall quantum effect, in the All-Russia Research Institute of Metrological Service and the Czech Metrological Institute

VNIIMS (Russia) and CMI (Czech Republic) quantum Hall resistance standards are compared using a VNIIMS portable resistance standard of 1 and 10 kΩ. Conformity is established for the dimensions of units within the limits of relative expanded (k = 2) uncertainty of 10⁻⁷. Translated from Izmeritel’naya Tekhnika, No. 12. pp. 58–61, December, 2008.     

Radiation characteristics of heat protective materials of the buran orbital spacecraft

Some features of investigations of the temperature dependence of the integrated and spectral emissivity of erosion-resistant coatings on a low-thermal conductivity fibrous heat insulation are discussed. Results are provided for the standard ‘black’ and ‘white’ coatings. A study is made of the influence of repeated attacks of the high-temperature dissociated air on the integrated emissivity of the ‘black’ coating. Data are obtained on the radiation characteristics of this coating after full-scale tests during the Buran orbital spacecraft flight. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 26–30, January–February, 2000.     

Mathematical simulation of gravitational waves in the ocean in the approximation of “shallow water”

Problems of the behavior of gravitational waves in the approximation of “shallow water” — motion of a solitary wave over the water surface, exit of a wave to the shore, passage of a solitary wave over a submerged rock — are solved. The solution of the first problem showed that in modeling the motion of a solitary (soliton-type) wave the “shallow water” approximation breaks down at a ratio of water depth to wavelength equal to 0.3. An analysis of the results of solution of the second problem indicates that the “shallow water” approximation cannot be used for calculation of the height of a wave in its exit to the shore but it can be used for estimation of the distance from the shore where the wave is turned over. It follows from the solution of the third problem that the “shallow water” approximation is suited only for obtaining a qualitative picture of the distortion of the profile of a wave in its motion over a rock.     

Temperature measurements in the pulsed laser heating of metals

The results of an investigation of the temperature dynamics of certain metals, measured by a photoemission method with a time resolution of 1 μsec, when they are heated in air and in an argon medium by millisecond laser radiation (λ = 1.06 μm) with energy densities of 75–140 J/cm² are presented.     

Formation of dendritic precipitates in the beta phase of Cu-based alloys

The isothermal treatment of the β phase in some Cu-based alloys produces its decomposition by an earlier precipitation of γ phase. During their growth, by means of a diffusion-controlled process, the precipitates show evidences of morphological changes. In the first stages and for a Cu–Zn–Al alloy, the morphology is spherical and cuboidal, but develops more complex shapes such as dendrites, owing to composition fields, interphase overlapping, crystallography characteristics, and relative orientation. In this work, a dendritic γ precipitate characterization is done and morphological theoretical predictions are applied, for Cu–Zn–Al and Cu–Al–Be alloys.     

Algorithms providing guaranteed estimates of the confidence factors for monitoring the serviceability of radioelectronic measuring instruments

Algorithms are given which enable one to estimate the conditional probabilities that errors of the “spurious” or “undetected” fault type will appear when monitoring the serviceability of ground-based control and measuring devices. The algorithms are based on a modeling of random processes with a truncated distribution. By way of an example it is shown that the use of these algorithms can considerably extend the range of time sections for obtaining estimates. Translated from Izmertel'naya Tekhnika, No. 4, pp. 20–24, April, 1997.     

Frequency dependence of the complex impedances and dielectric behaviour of some Mg-Zn ferrites

Complex impedances of some magnesium-zinc ferrites, MgxZn1-xFe2O4 (x=0.4, 0.5, 0.6 and 0.7), in the frequency range of 1 mHz-10 MHz were measured at 300 K. The complex-plane impedance spectrum from each sample indicates that the capacitive and the resistive properties of the materials are mainly attributed to the processes that associated with the bulk (grain) and the grain boundary. A low-frequency dispersion (LFD) and a negative capacitance regions are also observed at low frequencies. A small series resistance of about the same value for all samples is also observed. The bulk and the grain boundary components are analysed by assuming a two-layer leaky capacitor. The simulated complex impedances using the Cole-Cole expression are in agreement with the measured values. The dielectric properties of the materials are attributed to the interfacial polarization and LFD at low frequencies and the orientational polarization at high frequencies. These properties result in the dielectric loss which composed of a Debye-like loss peak at high frequency end and a strong LFD below 1 Hz. Both regions exhibit universality with regard to the power-law relation between the dielectric loss (ε″r or χ″) and frequency as given by ε″r∝ωn-1, where n=0.14 and n=0.02, respectively. The exponent is marginally negative, n=−0.03, in the region of negative capacitance below 3–4 mHz. The variations of the above properties and the characteristic parameters for different compositions of the Mg-Zn ferrites are discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Thermal model “melt-nucleus” and study of the characteristics of the transition zone under the effect of the electronic structure of the 3d-elements in aluminum

On the basis of the model thermal parameters of the transition zone “aluminum melt—3d-nucleus” it is shown that a change in the degree of filling has two extrema that are related to d⁵ and d¹⁰ states.     

Exposing the nonlinear viscoelastic behavior of asphalt-aggregate mixes

In this study asphalt-aggregate mixes are treated as both viscoelastic and viscoplastic. Following a damage mechanics approach, a nonlinear viscoelastic constitutive formulation is generated from a linear formulation by replacing ‘applied stresses’ with ‘effective viscoelastic stresses’. A non-dimensional scalar entity called ‘relative viscoelastic stiffness’ is introduced; it is defined as the ratio of applied to effective viscoelastic stress and encapsulates different types of nonlinearities. The paper proposes a computational scheme for exposing these nonlinearities by uncovering, through direct analysis of any test data, changes experienced by the ‘relative viscoelastic stiffness’. In general terms, the method is based on simultaneous application of creep and relaxation formulations while preserving the interrelationship between the corresponding time functions. The proposed scheme is demonstrated by analyzing a uniaxial tension test and a uniaxial compression test (separately). Results are presented and discussed, unveiling and contrasting the character of viscoelastic nonlinearities in both cases. A conceptual viewpoint is offered to explain the observations, illustrating the requirements from any candidate constitutive theory.     

Influence of the mechanism and parameters of hardening of modified novolac phenol-formaldehyde resins on the physicomechanical properties of the composite

We study the influence of concentrations of the components of reactive compositions and the conditions of production and hardening of phenol-formaldehyde resins with the help of epoxy resins in the presence of polyvinylpyrrolidone on the physicomechanical, thermal, adhesion, insulation, and anticorrosion properties of the composites. The positive effect of modifications with polyvinylpyrrolidone and epoxy resin manifests itself within the following ranges of concentrations: 0.5–1 wt.% of polyvinylpyrrolidone and 25–30 wt.% of ED-20 in the presence of 1 wt.% of N, N-dimethylaniline. Thus, the adhesion strength of a glue based on the developed composition becomes four times higher and constitutes 5–6 MPa; the impact strength, static strength in bending, surface hardness, and the specific bulk electric resistance of the specimens hardened at 150–160°C for 25–30 min become 1.5–2.5 times higher and are equal to 5–6J/m², 15–17 MPa, 350–420 MPa, and (5.5–6.5)⋅10¹⁰ Ω⋅m, respectively. The behavior of these characteristics strongly depends on the conditions of hardening. We optimized the composition of modified phenol-formaldehyde resins, which made it possible to produce materials with predicted properties.     

A Determination of the Ratio of the Zinc Freezing Point to the Tin Freezing Point by Noise Thermometry

A Johnson-noise thermometer (JNT) has been used with a quantized voltage noise source (QVNS), as a calculable reference to determine the ratio of temperatures near the Zn freezing point to those near the Sn freezing point. The temperatures are derived in a series of separate measurements comparing the synthesized noise power from the QVNS with that of Johnson noise from a known resistance. The synthesized noise power is digitally programed to match the thermal noise powers at both temperatures and provides the principle means of scaling the temperatures. This produces a relatively flat spectrum for the ratio of spectral noise densities, which is close to unity in the low-frequency limit. The data are analyzed as relative spectral ratios over the 4.8 to 450 kHz range averaged over a 3.2 kHz bandwidth. A three-parameter model is used to account for differences in time constants that are inherently temperature dependent. A drift effect of approximately −6 μK·K⁻¹ per day is observed in the results, and an empirical correction is applied to yield a relative difference in temperature ratios of −11.5 ± 43 μK·K⁻¹ with respect to the ratio of temperatures assigned on the International Temperature Scale of 1990 (ITS-90). When these noise thermometry results are combined with results from acoustic gas thermometry at temperatures near the Sn freezing point, a value of T − T ₉₀ = 7 ± 30 mK for the Zn freezing point is derived.     

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)