μ+SR Study on Bi2Sr2Ca1−x Y x (Cu1−y Zn y )2O8+δ around the Hole Concentration of \frac{1} {8} per Cu

In order to study the effect in different high-T _c oxides from the La-system, muon spin relaxation measurements were applied to the Zn-substituted Bi-2212 system, Bi ₂ Sr ₂ Ca _1–x Y _x (Cu _1–y Zn _y ) ₂ O ₈₊ , around the hole concentration p= per Cu. It has been revealed that the magnetic correlation between Cu spins is anomalously enhanced in the Zn-substituted samples at per Cu, proving the existence of the effect" in the Bi-2212 system as well.     

Experimental Observation of 2 – Anion and its para → ortho Conversion in Solid para hydrogen Using High–Resolution ESR Spectroscopy

We present experimental observations and study of in solid parahydrogen. Since the parahydrogen molecule does not produce local magnetic fields, high–resolution ESR spectra of trapped radicals can be observed in the solid parahydrogen matrices. Using this high–resolution ESR spectroscopy, new quartet ESR signals were observed in –rays irradiated solid parahydrogen and assigned as In addition, para– was observed to convert into ortho– on the storage at 4.2 K. On the other hand, ortho–H ₂ molecule converts into para– at cryogenic temperatures. The difference in the conversion between the H ₂ molecule and the anion is explained by the parity conservation law of wavefunctions on exchanging the protons in homonuclear diatomic molecules such as the anion and H ₂ molecule.     

Electrical properties of Pd–Au/(In x –Sn1 – x ) Oxide/Si(p)/Al heterojunction diodes

Current–voltage (I–V ) and capacitance–voltage – characteristics of [Pd–Au/( – ) Oxide/Si(p)/Al] semiconductor oxide semiconductor (SOS) solar cells were measured in the temperature range between 300 and 500 K. The dark forward current–voltage curves were found to be independent of temperature. Consequently, the diode quality factor was temperature dependent. Analysis of the data indicated that the predominant carrier transport mechanism of the samples in the intermediate bias voltage region was thermionic field emission and recombination tunneling. From the experimental data it was found that, the open circuit voltage – , the short circuit current – and the fill factor 0.28–0.32, under illumination of 1124 lux.     

Parallel Line Search in Method of Feasible Directions

In this paper the line search procedure within the method of feasible directions is parallelized and used in the solution of constrained structural optimization problems. As the objective function is linear in the variables, the step size problem reduces to a zero finding problem. That is, the step size is the distance along the direction vector to the nearest constraint boundary. Zero finding is accomplished in two steps—a march along the direction vector to bracket the zero followed by an interval reduction scheme. Both these steps are parallelized using MPI for message passing. When implemented on a cluster of workstations, for a convergence parameter of 10^–6, the time for optimization of composite pressure vessel reduces from 3 hours to hour when 64 processors are utilized, with a speedup of 7.0.     

A Monte Carlo Study of Disorder in the High Pressure Mixed Crystal N2-Ar

In order to obtain a better notion of the experimental results in our laboratory, Monte Carlo calculations have been performed of the N ₂-Ar crystal on the N ₂-rich side, in the p-T region where the and phases exist in pure N ₂. Considering the enthalpy, the system prefers the Ar atoms to be located on the sphere positions. The * phase is present for mixtures down to but is most likely metastable. The *-* transition shifts to lower temperatures with decreasing . The 2 ^nd order transition within the phase continues to exist to even smaller . In contrast to the * -* transition, the transition temperature for the 2 ^nd order transition does not shift to lower temperatures. For a mixture of it is within 5 K from the pure 2 ^nd order transition at a pressure of 7.0 GPa.     

Counterflow-Driven Textural Phase Transitions in Superfluid 3He-A1

We have studied second sound propagation through superftuid ³ He-A ₁ filling a rectangular resonator equipped with 3 pairs of transducers. The -texture was manipulated using one transducer to drive an oscillatory counterflow while measuring the resonant response of an orthogonal transducer pair. We observed abrupt signal changes and hysteresis effects depending on drive frequencies and amplitudes. We analyzed our experiments by examining planar -textures strongly coupled to the linear second sound wave equation. Evidence of first-order phase transitions was obtained numerically. The results are qualitatively consistent with the experimental findings. Our physical intuition did not anticipate these striking discontinuous phenomena.     

Laminar thermal boundary layer on a continuous accelerated sheet extruded in an ambient fluid

Summary Exact boundary layer similarity solutions are developed for flow, friction and heat transfer on a continuously accelerated sheet extruded in an ambient fluid of a lower temperature.Melt-spinning, polymer and glass industries and the cooling of extruded metallic plates are practical applications of this problem.Results for skin-friction and heat-transfer coefficients are given. Larger acceleration is accompanied by larger skin-friction and heat-transfer coefficients. Rapid cooling of the sheet is accompanied by a larger Nusselt number.Nomenclature sheet width - c dimensionless constant - c _f local skin friction coefficient - F dimensionless transformed stream function - G dimensionless transformed temperature - local heat transfer coefficient - fluid thermal conductivity - length of deformation zone - m exponent of surface speed variation - q exponent of surface temperature variation - T dimensionless temperature - sheet surface temperature - solidification temperature - ambient temperature - sheet thickness - u velocity component along the sheet - u _s sheet surface velocity - wind up velocity - v velocity component normal to the sheet - x dimensionless coordinate along the sheet - y dimensionless coordinate normal to the sheet - Nu Nusselt number, - Pr Prandtl number, - Re Reynolds number, - =Re^–0.5 - dimensionless similarity coordinate - dynamic viscosity - kinematic viscosity - fluid mass density - sheet mass density - wall shear stress - dimensionless stream function With 3 Figures     

Textures in3He-A: Magnetic deformation in a narrow slab

A variational technique is used to analyze the deformed texture of superfluid³He-A in a narrow slab subject to a perpendicular magnetic field. Specific predictions are made for the anisotropy parameters and , averaged across the width.     

Collective-mode spectroscopy of textures in superfluid3He-B

A phenomenological theory for the propagation of the real squashing modes in superfluid³He-B is presented. This allows one to calculate the splitting of the real squashing (rsq) mode spectrum caused by the combined effects of magnetic field, dispersion, and texture in the experimentally important range of magnetic fields from 0 to 10³ Gauss. This serves to provide a tool for the rsq-mode spectroscopy of the -textures in³He-B. In particular, a new gyrosonic effect is suggested: the intensity of the rsq modes generated in textures depends on the sense of rotation—even when the axis of rotation coincides with the direction of the ultrasound propagation .     

The Dynamic Structure Factor of 4He beyond the Roton Minimum

The dynamic structure factor S( , ) of ⁴ He is studied at zero temperature in the momentum region at and above the roton minimum by field-theoretical methods. The model is derived from the Gavoret-Nozières (GN) two particle propagator by introducing the concept of quasiparticles. In this way a connection between the field theory of GN and the phenomenological models of Zawadowski-Ruvalds-Solana (ZRS) type is obtained. An improved expression for the dynamic structure factor within ZRS-like models is found. Numerical results for S( , ) are presented for momentum and energy independent effective interactions between quasiparticles.     

The Smallest Correction of an Inconsistent System of Linear Inequalities

The problem of calculating a point x that satisfies a given system of linear inequalities, A x #x2265; b, arises in many applications. Yet often the system to be solved turns out to be inconsistent due to measurement errors in the data vector, b. In such a case it is useful to find the smallest perturbation of b that recovers feasibility. This motivates our interest in the least correction problem and its properties.Let A x #x2265; b be an inconsistent system of linear inequalities. Then it is always possible to find a correction vector y such that the modified system A x #x2265; b #x2212; y is solvable. The smallest correction vector of this type is obtained by solving the least correction problem Let denote the convex cone which consists of all the points for which the system A x #x2265; u is solvable. Let denote the polar cone of . It is shown that the least correction problem has a simple geometric interpretation which is based on the polar decomposition of into and . A further insight into the least correction concept is gained by exploring the duality relations that characterize such problems.     

Natural damped frequencies and axial response of a rotating finite viscous liquid column

Summary For a finite solidly rotating cylindrical liquid column the damped natural axisymmetric frequencies have been determined. The liquid was considered incompressible and viscous. The cases of freely slipping edges and that of anchored edges have been treated. It was found that instability appears in a purely aperiodic root for the spinning liquid bridge. This is in contrast to the instability appearing in the damped oscillatory natural frequency of a nonspinning liquid column at . The spinning viscous liquid column exhibits the same instability as the frictionless liquid. It appears at for axisymmetric oscillations.List of symbols a radius of liquid column - I _m modified Bessel function of first kind and orderm - s complex frequency ( ) - r, ,z polar cylindrical coordinates - p pressure - t time - u, v, w radial-, azimuthal- and axial velocities of liquid, respectively - Weber number - h height of liquid column - dynamic viscosity of liquid - v kinematic viscosity of liquid (v=/) - density of liquid - surface tension of liquid - _r , _rz shear stress - (r, z, t) circulation - (r, z, t) streamfunction - ₀ angular velocity of liquid column about the axis of symmetry - (,t) free surface displacement     

Effect of the addition of Y2O3 on the structure, microstructure and piezoelectric properties of PZT(53/47)

In this work, an attempt is made to study system with x=0.0125, 0.025, 0.050, 0.075 and 0.1. It was shown that there is limited solid solubility (0.625 mol %) of or 1.25 mol % of in PZT(53/47). For higher levels of dopant, mainly two other extra second phases were detected. The first was a Zr-rich phase in which some and small amounts of was dissolved. The second one was a Pb solid solution composed of mainly PbO, and which was initially also seen in calcined samples. The formation of Zr-rich phase is thought possibly to originate due to the sublimation of Pb from source during the sintering process. For higher x values, a structural shift towards Ti-rich region of PZT's phase diagram is seen. All piezoelectric parameters of the doped samples such as , are seen to decline sharply compared to that of undoped samples. Increasing the level of dopant gave rise to the increase of conductivity and dielectric loss of sintered samples. The formation of non-ferroelectric extra phases, and the Zr/Ti change of the main formed phase is believed to be responsible for this behavior.     

Ordering and Phase Transitions in Deuterium Monolayers Physisorbed on Krypton Preplated Graphite

Deuterium physisorbed on exfoliated graphite preplated by a krypton monolayer has been investigated by heat–capacity measurements in the complete submonolayer coverage range up to the initial stages of bilayer film formation. A detailed phase diagram has been mapped out. The commensurate phase covering most part of the phase diagram in the submonolayer region exhibits two–dimensional (2D) Ising symmetry. At the commensurate–incommensurate transition a reentrant fluid phase extending down to 1.5 K has been found, which confirms theoretical predictions.     

Computer-aided design of small patch antenna using (Al, Mg)TaO2 ceramics

The microwave dielectric properties of (AMT) ceramics and the design of small coplanar waveguide fed antenna (CPWFA) have been investigated. ( and ( have orthorhombic and tetragonal structure, respectively. As ( concentration increased, AMT ceramics transformed into the tetragonal structure. Specimens having tetragonal single phase could be obtained above x=0.6. As ( concentration increased, the grain size, dielectric constant and quality factor (Q) significantly increased and the temperature coefficient of resonant frequency changed from negative to positive. The of was realized at x=0.65 and the Q · f _O value and for this composition were 112 470 GHz and 26.1, respectively. Newly developed dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using high dielectric constant AMT ceramics, insetting slits into the patch, and fabricating CPW feed line in the ground plane. The slits play a role in not only lowering a center frequency but also fine tuning for the proposed antenna together with the open stub of CPW feed line. The CPWFA with slits has a lower center frequency than the conventional CPWFA, which suggests that the antenna size can be reduced by as much as 16.3%. The structure simulations of the CPWFAs have been performed to obtain impedance matching and to investigate the effects of slits. Experimental results of the fabricated device were in good agreement with the simulation.     

Non-linear response of internal friction to tensile strain rate and frequency during plastic deformation of high-purity aluminium

The internal friction of high-purity aluminium during the process of plastic deformation was measured by a middle torsion pendulum on a modified tensile testing machine. The effects of tensile strain rate, , in the range of 0.73×10^–6 to 50×10^–6s^–1, and frequency of internal friction measurement, f, in the range of 0.38 to 2.6 Hz were studied. The results showed a non-linear dependence of internal friction, Q ^–1, on and f ^–1 or on (=2 f). The interrelationship between internal friction during the process of plastic deformation and dislocation motion, and the effect of non-linearity on the dynamic behaviour of dislocations are discussed.     

Effect of phosphorus additions on the spacing between primary silicon particles in a Bridgman solidified hypereutectic Al-Si alloy

The effect of 100 ppm addition of phosphorus on primary silicon particle number density per unit area N _A and corresponding interparticle spacing is reported for a Bridgman solidified Al-20 wt%Si base alloy. The phosphorus (added as Al-Fe-P base or Al-Cu-P alloys) results in a factor of 3 increase in N _A and a factor of 2 reduction in for the range of conditions studied. In its absence the results conform to = 256 ± 24 m (K/s)_1/3 where is cooling rate during solidification in good agreement with earlier data. When published data on the effect of 0.02 to 0.2 wt%P are included the combined results are well represented by = 250 – 215 (wt%P)^0.17 ( in m, in K/s).     

Phonon Thermal Conductivity of Stripe Ordering La2–x Sr x NiO4

We have studied the thermal conductivity of stripe ordering La _2–x Sr _x NiO ₄. In particular, long range stripe order is well established for x = 1/3. For this composition is enhanced in the charge ordering phase and exhibits a clear maximum at low T. Even small deviations from this stochiometry cause a strong change of : the low T-maximum is suppressed and no anomaly is observed at high T. Our data confirm that the stripe phase is most stable for x = . Moreover, we find clear differences in the thermal conductivity for x > and for x < , respectively, which indicates different properties of the stripe ordered phase in these two regions of the phase diagram.     

The Orientational Ordering of Molecular Hydrogen in 2D

The orientational ordering of ortho-hydrogen molecules on a triangular lattice is calculated as a function of ortho concentration using the method of restricted traces. The calculated temperatures for the transitions from the disordered phase to the long range pinwheel ordered phase show a strong concentration dependence with a critical concentration X _c=73% below which the long range ordering is not realized in this model. The results are consistent with recent NMR studies of ortho-para hydrogen mixtures adsorbed as a commensurate × structure on hexagonal boron nitride for which X _c=69±4%. The values of the observed transition temperatures can only be understood if there is a large renormalization of the effective quadrupolar interaction constant in 2D.     

Fermi surface and extended van Hove singularity in the non-cuprate layered perovskite superconductor Sr2RuO4

With high-resolution (22 meV) angle-resolved photoemission spectroscopy, the Fermi surface of the first copper free layered-perovskite superconductor, Sr₂RuO₄, was determined. We observed three bands to cross the Fermi energy in qualitative agreement with LDA band structure calculations; one electron-like surface encircling the point in the projected Brillouin zone, and two hole-like surfaces around the point. The most striking aspect of the measurements is the observation of an extended van Hove singularity. It is located 17 meV below the Fermi energy and extends around the point for about 0.2 Å^–1 along both the — — and the — — directions.These observations demonstrate that van Hove singularities near the Fermi surface are a more generic feature of layered oxides, and call for a clarification of their exact role in oxide superconductivity.We are grateful to D. Singh for making available his band structure calculations. D. H. Lu thanks the VW Foundation for financial support.