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.     

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.     

A mathematical programming approach to a problem in variance penalised Markov decision processes

In this paper we present three algorithms for solving a problem in which it is required to get an optimal compromise between the average expected reward per unit time and the variance of the reward per unit time. The algorithms lead to an-optimal solution, where>0 is arbitrary.     

Thermophysical Properties of the Zr–0.01Nb Alloy at Various Heating Rates and Repeated Cycles of Heating–Cooling

The results of an experimental study of the heat capacity, enthalpy, electrical resistivity, and spectral emissivity (for the wavelength of 0.65 m) of the Zr–0.01Nb alloy in the temperature range from 900 to 2000 K are presented. The study was carried out using subsecond pulse heating of the samples by passing electrical current through them. Experiments were conducted at different heating rates (10³ to 10⁴K·s^–1), and a series of experiments consisted of several cycles of pulse heating and subsequent cooling. The effect of these parameters on the temperature dependence of thermophysical properties in the region of the –transition was studied. With an increase in the heating rate, the temperature of the – transition, and the maximum in the heat capacity shifted to higher temperatures. There are significant differences in properties over the temperature range of the – transition for the various heating cycles.     

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.     

Solid-liquid phase equilibria of (α-methylnaphthalene + β-methylnaphthalene) and (chlorobenzene + bromobenzene) systems under high Pressures

Solid-liquid phase equilibria of the (-methylnaphthalene + -methylnaphthalene) and the (chlorobenzene + bromobenzene) systems have been investigated at temperatures from 278 to 343 K and pressures up to 500 MPa using a high-pressure optical vessel. The uncertainties of the measurements of temperature, pressure, and composition were within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. In both systems, the freezing and melting pressures at a constant composition increase almost linearly with increasing temperatures. In the former system, where the two components can form a solid solution with one another to a limit extent, the eutectic point shifts to a higher temperature and to a -methylnaphthalene-rich composition with increasing pressures. In the latter system, where the two components are completely soluble in each other in the solid phase, the freezing points of all mixtures lie between those of the pure components at each pressure. It is found that the coexistence curves obtained can be expressed by a quadratic equation in pressure.     

Effective Łojasiewicz inequalities in semialgebraic geometry

The main result of this paper can be stated as follows: letV ⁿ be a compact semialgebraic set given by a boolean combination of inequalities involving only polynomials whose number and degrees are bounded by someD > 1. LetF, G[X₁,, X_n] be polynomials with degF, degG D inducing onV continuous semialgebraic functionsf, g:VR. Assume that the zeros off are contained in the zeros ofg. Then the following effective ojasiewicz inequality is true: there exists an universal constantc ₁ and a positive constantc ₂ (depending onV, f,g) such that for allxV. This result is generalized to arbitrary given compact semialgebraic setsV and arbitrary continuous functionsf,g:V . An effective global ojasiewicz inequality on the minimal distance of solutions of polynomial inequalities systems and an effective Finiteness Theorem (with admissible complexity bounds) for open and closed semialgebraic sets are derived.     

Novel methodology to investigate superconducting dielectric resonators

An analytical method is presented for investigating the resonant behavior of a c-axis oriented YBa₂Cu₂O_7–(0) thin film on a resonator composed of LaAlO₃ (001). The concept of the negative dielectric medium for a superconductor is introduced within the framework of the two-fluid model, which permits us to treat a superconductor as any other penetrable materials so that only its electromagnetics are concerned. A conformai transformation is further suggested to map the original open boundary-value problem to a closed one. This not only makes the original problem readily solvable by using the variational technique, but is also a powerful tool for analyzing some kinds of problems such as the propagation characteristics of the superconducting microstripe and coplanar waveguide structures.     

(Pre)kernel catchers for cooperative games

The paper provides a new (pre)kernel catcher in that the relevant set always contains the (pre)kernel. This new (pre)kernel catcher gives rise to a better lower bound _*** such that the kernel is included in strong -cores for all real numbers not smaller than the relevant bound _***.The research for this paper was done under the sponsorship of both the Dutch Organization for the Advancement of Scientific Research (NWO) and the National Science Council (NSC) of Taiwan during a stay of Dr. Chih Chang at the University of Twente, Enschede, The Netherlands.     

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.     

Finite element recovery techniques for local quantities of linear problems using fundamental solutions

We show that local quantities of interest such as displacements or stresses of a FE–solution can be calculated with improved accuracy if fundamental solutions are employed. The approach is based on Bettis theorem and an integral representation of the local quantities via Greens function. The unknown Greens function is split into a regular part and a fundamental solution so that only the regular part must be approximated on the finite element ansatz space. Some numerical studies for linear elasticity will illustrate our approach.     

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.     

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.     

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.     

Current Noise in HgBa2CuO4+δ High Tc Superconductor

Experimental results of current noise in magnetic fields up to 1 kG after zero field cooling and field cooling are reported in bulk HgBa₂CuO₄₊ prepared with vapor–solid reaction in a two-temperature zone reactor. Noise measurements performed in Hg-based superconductor materials are compared with previously studied superconductors, in particular, YBa₂Cu₃O_7–. A maximum in the noise is observed at the same resistance, approximately one order of magnitude lower than the normal state value and independently of the applied field. This result is consistent with experiments in bulk YBa₂Cu₃O_7– samples and with percolative model simulations of lattice junctions in which the maximum is obtained at the same value of the concentration of superconducting junctions and, thus, at the same macroscopic resistance. Maximum intensity is shown to increase with magnetic field up to 1 kG, with noise values slightly higher in the field cooling procedure. Our results attest that weak-link effects, as in YBa₂Cu₃O_7–, dominate superconducting properties of bulk HgBa₂CuO₄₊. With respect to YBa₂Cu₃O_7–, no saturation at high magnetic field in both noise and magnetoresistance measurements is observed.     

Sintering Behavior of Hot-Pressed Ca–αSialon Ceramics

On the basis of phase relationships in the Ca–Si–Al–O–N system, a Ca––sialon ceramic was synthesized using the hot-pressing technique. The reaction sequences and densifications of the Ca––sialon vs. firing temperatures have been characterized in detail. The present experiments reveal a reaction sequence as follows: at 1250°C the reactant mixture started to soften, at 1300°C a gehlenite phase was produced, at 1500°C the gehlenite phase was resolved into a liquid phase and a Ca––sialon started to form, and at 1600°C the formation of Ca––sialon was complete. The product was stable and almost entirely single phase Ca––sialon. Accompanying to the above sequences, densification also proceeded via a liquid-phase sintering, particle rearrangement, solution–reprecipitation, and grain growth process. In the final microstructure elongated grains of Ca––sialon were obtained, improving the fracture toughness of this Ca––sialon ceramic.     

Magnetic order in thet-J andt-t′-J models

The magnetic structure of thet-J andt-t-J models are investigated. Assuming that the ground state has magnetic long-range order, we calculated the energy of some magnetically ordered states using a simple transformation of the models and theS approximation. The result shows that the Néel state is destroyed by doped holes unless the next-nearest neighbor hoppingt is finite, and that the ferromagnetic phase appears at moderate doping. Mean field analysis shows that the intermediate phase between the Néel and ferromagnetic phase has spiral spin order, although the spiral phase is shown to be unstable against density fluctuations.On leave from the Department of Materials Science, Faculty of Science, Hiroshima University, Higashi-Hiroshima 724, Japan.     

Computing presentations for subgroups of polycyclic groups and of context-free groups

Algorithms for solving uniform decision problems for algebraic structures crucially depend on the chosen finite presentations for the structures under consideration. Rewriting techniques have been used very successfully to solve uniform decision problems, when the presentations considered involve finite, noetherian, and ()-confluent rewriting systems. Whenever the class of algebraic structures considered is closed under the operation of taking finitely generated substructures, then the algorithms for solving the uniform decision problems can be applied to the substructures as well. However, since these algorithms depend on the form of the presentations, this involves the task of constructing a presentation of a certain form for a substructure given a presentation of this form for the structure itself and a finite set of generating elements for the substructure.This problem, which has received a lot of attention in algebra, is here investigated from an algorithmic point of view. The structures considered are the following two classes of groups, which have been studied extensively before: the polycyclic groups and the context-free groups.Finitely generated context-free groups can be presented by finite, monadic, and -confluent string-rewriting systems. Due to their nice algorithmic properties these systems provide a way to effectively solve many decision problems for context-free groups. Since finitely generated subgroups of context-free groups are again contextfree, they can be presented in the same way. Here we describe a process that, from a finite, monadic, and -confluent string-rewriting system presenting a context-free groupG and a finite subsetU ofG, determines a presentation of this form for the subgroup U ofG that is generated byU. For finitely presented polycyclic groups we obtain an analogous result, when we use finite confluent PCP2-presentations to describe these groups.This work was performed while this author was visiting at the Fachbereich Informatik, Universität Kaiserslautern, during his sabbatical 1991/92     

Experience in polyharmonic analysis of the parameters of the earth’s rotation

A method for approximating time series by an nth degree trigonometric polynomial for a series of parameters of the Earths rotation, calculated from GPS and GLONASS measurements, is tested. Satisfactory agreement is obtained between the model and experimental data. The results can be used for complex modeling and forecasting of the parameters of the Earths rotation.Translated from Izmeritelnaya Tekhnika, No. 12, pp. 40–42, December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

The dependence of stress intensity factors and weight functions on elastic constants

We investigate the dependence of stress intensity factors (SIFs) on elastic constants in two-dimensional elastic isotropic bodies. Bueckners weight function theory is used for the derivation of the dependence of SIFs on elastic constants. The dependence of SIFs on Poissons ratio shows up when the resultant tractions on each of the contours L _k separately is not zero in multiply connected bodies. As an example we calculate K ₁ for Griffith crack under concentrated loading applied on the upper crack face.