New high-pressure Sr-Ca-Cu-O compounds and their superconducting properties

It is shown for (Sr, Ca)_1–y CuO_2.00+z (nominal composition) superconductors fabricated under a high pressure of 5 GPa and at 930°C that, as z increases, the Meissner fraction increases from a few percent to 20% and then starts to decrease. In the X-ray powder diffraction pattern for the sample with the maximum Meissner fraction, it is obvious that the infinite-layer structure has been decomposed and a new structure becomes the major phase. It appears that the new structure is the 0223 structure which consists of rock-salt and the infinite-layer type blocks. This material is likely to be a new superconducting cuprate.     

Heat Inputs to Sub-mK Temperature Cryostats and Experiments from γ-Radiation and Cosmic Ray Muons

We measured the spectrum of energies deposited by -radiation, emanating from radioactive materials in the laboratory that houses our mK cryostat, and by cosmic ray muons. This allows us to quantify the heat input that adversely affects the lowest temperature accessible in sub-mK experiments. We use our nuclear stage, stage plate and experimental cell as a prototype model system, and calculate the power deposited due to low energy (below 2.65 MeV) background radiation quanta (~20 pW). This is significantly less than the power (~120 pW) deposited in the nuclear and experimental stages by muons. Installation of a 5 cm thick lead wall around the cryostat reduced the energy due to the flux of quanta by a factor of ~10 to ~2 pW, and the number of quanta by a factor of ~20. The lower energy, soft cosmic ray component was also affected by introducing the same thickness of lead, reducing the overall count of cosmic ray derived particles by ~15% and the heat leak to ~100 pW.     

Microstructure Development and Property Improvement in Mill Products Produced from Ingot Metallurgy and Powder Metallurgy Ni-Based Superalloys of the Same Chemical Composition

Despite projected inroads from competing materials Ni-based superalloys remain the material of choice in the hot sections of advanced gas turbine engines. In this paper microstructural development and improvement of mechanical properties in mill products produced by ingot metallurgy (IM) and powder metallurgy (PM) techniques are discussed. Particular attention is given to approaches to improvement in ingot ductility. Thermomechanical treatment schemes used during forging of a complex-alloyed Ni-based superalloy are recommended. It is demonstrated that the PM technique used for production of this complex-alloyed superalloy is a promising approach. On the basis of the studies carried out the salient features of the structure of material produced both by both IM and PM techniques have been defined. The mechanical properties of two versions of an advanced Ni-base superalloy produced by IM and PM techniques are discussed. The best combination of mechanical properties are exhibited by a PM material with a necklace structure; and this latter structure is superior to a fine grained structure for IM product also.     

Chemical Durability of Waste Fluorescent Glass and Shell–Derived Glass-Ceramics

In order to obtain glass-ceramics reinforced by -wollastonite, pressed specimens prepared by powdered waste fluorescent glass and refuse shell dumped in the seashore were heat-treated at 800°C, 900°C, and 1000°C. Chemical stability of the heat-treated specimens was analyzed by weight changes and by observation of surface morphology and composition, by field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Chemical durability of the samples, especially at the glass-matrix area, was decreased with an increase in the heat-treatment temperature from 800°C to 1000°C.     

Maximizing pseudoconvex transportation problem: a special type

The paper discusses a non-concave fractional programming problem aiming at maximization of a pseudoconvex function under standard transportation conditions. The pseudoconvex function considered here is the product of two linear functions contrasted with a positive valued linear function. It has been established that optimal solution of the problem is attainable at an extreme point of the convex feasible region. The problem is shown to be related to indefinite quadratic programming which deals with maximization of a convex function over the given feasible region. It has been further established that the local maximum point of this quadratic programming problem is the global maximum point under certain conditions, and its optimal solution provides an upper bound on the optimal value of the main problem. The extreme point solutions of the indefinite quadratic program are ranked to tighten the bounds on the optimal value of the main problem and a convergent algorithm is developed to obtain the optimal solution.     

The “Paramagnetic” Meissner Effect in Superconductors

There are a number of publications concerning the observation of a paramagnetic signal in HTSC ceramic samples during field-cooling procedures. Some authors assume that this signal is connected with spontaneous currents and discuss the possibility of the existence of -junctions in Josephson media. In this work, it is shown that the paramagnetic signal could appear in the case of capture and compression of the magnetic flux in a sample during field-cooling procedures. The results of numerical calculation of the magnetic moment for different configurations of the sample and flux compression are presented. The unusual behavior of longtime relaxation of the magnetic moment in experiments on capture of magnetic flux is discussed.     

Vibration Diagnostics of a Damaged Inclined Cylindrical Shell

Free vibrations of an inclined cylindrical shell with a breathing crack are analyzed by the authors in view of the results of spectral diagnostics of transverse vibrations of a beam with a closing crack, which were obtained by A. A. Matveev and A. P. Bovsunovskii at the Institute of Problems of Strength of the National Academy of Sciences of Ukraine. Elastic characteristics of the shell are interpreted as a certain bilinear system. Data on the stiffness degradation due to the crack opening can be used for the selection of vibration damage indicators. We have obtained relationships between the relative stiffness degradation, crack depth, and crack location. It is demonstrated that the potential energy of tension of the shell median surface must be taken into account. We have found that the efficiency of detecting damages using vibration diagnostic methods improves with increasing shell thickness.     

Evolution of the Electronic Structure of Y-Bi-2212 from the Antiferromagnetic to the Superconducting Regime

The phase diagram of the cuprate superconductors at low doping and low temperatures in the non-superconducting state is dominated by magnetic correlations. When increasing the hole concentration in the CuO₂-planes from zero an antiferromagnetic (AF) insulating phase is followed for hole concentrations greater than approximately 0.08 by the superconducting phase. For the range of doping in between the situation is less clear and several models exist. For Bi₂Sr₂Y _x Ca_1–xCu₂O₈ in the range of Y-concentrations 0.9 < x < 0.0 the evolution of the electronic structure starting from the AF phase at x = 0.9, which in this respect can be regarded as the parent compound of the superconducting phase, and its gradual development into the superconducting range can be studied on one system. In this series the CuO₂-planes are kept embedded in a nearly identical environment for each hole concentration. Especially the results from the AF phase deviate from former reports attained mainly from oxychlorides.     

Detecting Explosions with Ionizing-Radiation Measurement of Scattered 137Cs γ-Rays

Measurements have been made on the spectra of the rays scattered by trotyl and by substances similar to it in density and composition placed behind various shielding materials. The experiments check the scope for implementing -tomography for observing and identifying explosives.     

A “gel” model for coal

Coal is a sedimentary, organic rock which is almost never in a state of thermal equilibrium. Because of its importance, the thermal properties of this ill-characterized substance are of great interest. Recent work has shown that coal has many of the characteristics of a gel-type structure. We have made this observation the basis for a model study of the thermal properties of a gel system, using the equation-of-motion method to determine the density of states for the system and, thereby, its heat capacity. This model has one of the essential features of a model of coal, namely, a porous structure. With a hexagonal close-packed lattice as the basis for our gel, we have calculated the frequency spectrum for several particle densities. The disorder in the system has a marked effect on the frequency spectrum, shifting a larger number of modes from high to low frequencies. Also, for a gel with 3% vacancies, and in-plane, out-of-plane bond strengths at the ratio 2 1, there is a further shift to lower frequencies and the two-peaked spectrum expected for such an anisotropic structure develops. The heat capacity is affected only at low temperatures. We conclude that the gel model provides a satisfactory basis for development as a model of coal.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Effects of measurement errors on sample monitoring reliability

Results are presented on the effects of measurement errors on items in routine production as regards the reliability of results on sampling inspection obtained by Monte Carlo simulation. The customers and the makers risks are examined in relation to the distributions of the measurement errors and the values of them.Translated from Izmeritelnaya Tekhnika, No. 12, pp. 8–11, December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

“Pseudogap” in High-Temperature Superconductors

It is shown that an existence of a pseudogap and peculiarities of its behavior under temperature and doping variation, both at doping above and below the optimal one, naturally follow from the impurity mechanism of high-temperature superconductivity, which is an additional argument in favor of it. Main attention is paid to the tunneling spectroscopy experimental data.     

Investition bei Unsicherheit als Erklärung für hohe implizite Diskontraten bei Energiesparinvestitionen

Zusammenfassung Die Tatsache, daß Konsumenten (und auch Unternehmen) hohe implizite Diskontraten bei der Entscheidung über Energiesparinvestitionen verwenden, wird häufig beobachtet. Dies wird fast einhellig als Marktversagen angesehen und hat viele Analytiker dazu veranlaßt, entweder für öffentliche oder bezuschußte Energiesparinvestitionen zu plädieren. In dieser Arbeit wird die Theorie der Realoptionen auf ein bekanntes Beispiel angewandt: der Wahl zwischen konventioneller Glühbirne und Sparlampe bei unterstellter Risikoneutralität des Entscheidungsträgers. Es zeigt sich, daß die dem Wert der Option des Abwartens und Aufschiebens der Investition Rechnung tragenden impliziten Diskontraten nahe den beobachteten Werten liegen. Deshalb bedarf die Schlußfolgerung eines Marktversagens aus hohen impliziten Diskontraten einer sorgfältigeren und feineren Analyse. Dies trifft a fortiori auf due Empfehlung von Energiesparprogrammen zu.Die Autoren sind zwei anonymen Gutachtern zu Dank für ihre konstruktiven Vorschläge verpflichtet     

The influence of the polarization of the radiation on the accuracy of the transmission of the dimensions of the unit of temperature in radiation thermometry

The results of an investigation of different types of tungsten lamps in order to estimate the components of the error budget of spectrum-pyrometer apparatus are presented. Quantitative relations are considered and the results of experimental research, which enable systematic methods to be developed for eliminating the influence of polarization of the radiation of the lamps in standard radiation thermometry, are analyzed.Translated from Izmeritelnaya Tekhnika, No. 9, pp. 42–45, September, 2004.     

Observation ofd-wave interference pattern:Short junction is crucial

The properties of a one-dimensional 0--Josephson junction, consiting of ans-d junction or selected boundaries between three suitably orientedd-wave superconductors, are studied. It is shown that ad-wave type interference pattern can only be observed in the field-modulated critical current if the junction is short compared to the Josephson penetration depth. However, the behavior of a 0- junction is found to be indistinguishable from that of a 0-junction betweens-wave superconductors in the long junction limit, due to the formation of a -vortex.     

Phonon Raman scattering of R2CuO4 (R = Pr, Nd, Sm, and Gd)

For Gd₂CuO₄, a new symmetry-forbidden phonon for the tetragonal T structure is observed. This implies that oxygen in the CuO₂ plane is locally distorted along the CuO₂ plane. Such distortion has never been observed for other T-type superconductors, which show superconductivity by Ce doping. The disappearance of superconductivity for Gd can be correlated with the appearance of the distortion due to oxygen in the CuO₂ plane.     

Development of methods and instruments of the Russian service for determination of the Earth’s orbital parameters

The state and future outlook of research to determine the Earths orbital parameters, i.e., Universal Time and the coordinates of the pole, carried out by the State Time and Frequency Service and in calculations of the Earths orbital parameters are described.Translated from Izmeritelnaya Tekhnika, No. 1, pp. 24–27, January, 2005.