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.     

On primitive and free roots in a finite field

In this paper them-dimensional extension of the finite field of orderq is investigated from an algebraic point of view. Looking upon the additive group as a cyclic module over the principal ideal domain , we introduce a new family of polynomials over which are the additive analogues of the cyclotomic polynomials. Two methods to calculate these polynomials are proposed. In combination with algorithms to compute cyclotomic polynomials, we obtain, at least theoretically, a method to determine all elements in of a given additive and multiplicative order; especially the generators of both cyclic structures, namely the generators of primitive normal bases in over , are characterized as the set of roots of a certain polynomial over .     

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.     

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.     

Hydrogen reduction of Cu-Mn-Fe-O spinel solid solutions

The crystal-chemical transformations accompanying the hydrogen reduction of Cu_xMn₁ - xFe₂O₄ (x = 0.2, 0.5, 0.8) solid solutions are investigated, and general equations describing these processes over the entire composition range (0 x 1) are derived. The results on the character of the processes involved differ radically from earlier findings. The equilibrium oxygen pressure is evaluated for the low-oxygen phase boundary of the spinel solid solutions throughout their stability region. For solid solutions, which are of practical interest, the data are well represented by the equation , which is of importance in controlled synthesis of single-phase materials in this system.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 332–338.Original Russian Text Copyright © 2005 by E. Zinovik, M. Zinovik.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

The effect of temperature on the electric conductivity property of Bi3Zn2Sb3O14 pyrochlore type phase

The electric conductivity characteristic of ceramics was investigated by impedance spectroscopy in the frequency range from 5 Hz to 13 MHz. Electric measurements were performed at temperatures in the range from 25 to 700 °C. The phase type pyrochlore was synthesized by the polimeric precursors method. Ceramic presenting a relative density of 98% of the theoretical density was prepared. The data were presented in Nyquist diagrams form, from which the electric resistivity was determined. The electric conductivity followed the Arrhenius law with an apparent activation energy of the conduction process equal to 1.37 eV. The electric conductivity at room temperature was determined by extrapolation being equal to . Between 400 and 700 °C, the conductivity values were and , respectively.     

Electrical and magnetic properties of BaTiO3−(Ni0.3Zn0.7)Fe2.1O4 composites

Ceramic composites consisting of ferroelectric and ferrite ( were synthesized by the mixed oxide route. The phase assemblage, electrical and magnetic properties of the samples were investigated. The results indicates that the phase is compatible with ( phase, and dense diphasic composite ceramics were obtained. Electrical resistivity of composites varies with increasing amounts of ( phase, and shows a percolation-like drop. Magnetic hysteresis loops were observed in the composites.     

Growth of aluminium nitride whiskers by sublimation-recrystallization method

Aluminium nitride (AlN) with various morphologies was fabricated through a sublimation-recrystallization method. The influences of type of reactor and temperature gradient were explored, as well as the orientations and growth mechanism of the obtained AlN whiskers. In the early stage of preparation, a vapour-liquid-solid (VLS) mechanism dominated, producing AlN pillars, whiskers and noncrystalline fibres. In the later stage, as the catalyst liquid was removed by volatilization, the pillars and noncrystalline fibres stopped growing, but the growth of AlN whiskers continued through a vapour-solid (VS) mechanism. By Laue method and rotating-crystal method of x-ray diffraction, together with electron diffraction, most of the AlN whiskers were discovered to grow on planes , or , where l=0, 1, 2, 3, along crystal axes , or , where w=0, 1, 2, 3. Oblique grown whiskers also appeared, with a growth direction at an angle of about 54° to the growth plane, .     

The Validity of Using the Microscopic Hyperbolic Heat Conduction Model Under a Harmonic Fluctuating Boundary Heating Source

The validity of using the microscopic hyperbolic heat conduction model under a harmonic fluctuating boundary heating source is investigated. It is found that using the microscopic hyperbolic heat conduction model is essential when . The phase shift between the electron-gas and solid-lattice temperatures is found to be . This phase shift reaches a fixed value of 1.5708 rad at very large values of . It is found that the use of the microscopic hyperbolic heat conduction model is essential when ¯>1×10⁹ rads^–1 for most metallic layers independent of their thickness.     

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.     

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.     

Eine Erweiterung der Analogie zwischen der Gasdynamik und Flachwasserströmungen auf rotierende Systeme mit konservativen Massenkräften

Zusammenfassung Die bekannte Analogie zwischen den Theorien reibungsfreier flacher Wasserströmung und der isentropen idealen Gasdynamik wird im zweidimensionalen instationären Fall durch Zulassung rotierender Bezugssysteme und konservativer Massenkraftfelder erweitert. Damit kann man in einem rotierenden Wasserbehälter mit geeignet gestaltetem Boden u. a. atmosphärische Probleme näherungsweise studieren.

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Summary The well known analogy of the theories of nonviscous shallow water flows and isentropic ideal gasdynamics is generalized in the two-dimensional nonstationary case to apply to rotating systems with conservative body forces. This enables one, in particular, to simulate atmospheric problems by use of a rotating water tank with suitable bottom shape.

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Liste der verwendeten Symbole spezifische Wärme des Gases bei konstantem Druck - Fr in (2) definierteFroude-Zahl - Gravitationsbeschleunigung - H ortsabhängige Ruhetiefe bei Drehung des Wassers als starrer Körper - Druck - atmosphärischer Druck auf der freien Wasseroberfläche - Bezugslänge - Zeit - absolute Temperatur - Geschwindigkeitskomponenten parallel zu den Achsen - kartesische Koordinaten - durch Abweichung von der Drehung des Wassers als starrer Körper verursachte orts-und zeitabhängige Änderung der Wassertiefe - Verhältnis der spezifischen Wärmen des Gases - zu gehörende Wellenlänge - Dichte - Winkelgeschwindigkeit Mit 1 Textabbildung1 Boden des Wasserbehälters 2 freie Wasseroberfläche II freie Wasseroberfläche bei einer Drehung des Wassers als starrer KörperEin oberer Querstrich gibt an, daß die betreffende Größe eine physikalische Dimension hat; Größen ohne einen solchen Querstrich sind dimensionsfrei.     

Anisotropic flow and fracture in beryl [Be3Al2(SiO3)6]

Flow and fracture resulting from Vickers indentation testing on {0 0 0 1} and {10 0 } planar orientations have been examined. Flow characterized by indent shape differentiation was analysed to belong to the slip system with planes of the types { 10 0} and {11 0}. The ensuing fracture paths were resolved to propagate along {1 0 0} and {1 1 } cleavage planes whileK _c values obtained for them were 0.196 and 0.248 MPam^1/2, respectively.     

Structural features of Σ = 19, [110] GaAs tilt grain boundaries

= 19, [110] tilt grain boundaries have been observed to facet parallel to particular planes; the facets lie along _A/ _B, ( )_A/ )_B and ( )_A/( )_B. The structural unit of the = 19 ( )_A/( )_B [110] boundaries consists of 5- and 7-member rings, which are similar to the core structure of a/2[110] edge dislocations. The polarities in each grain on either side of the boundaries has been confirmed by CBED methods; a lower number of anti-site type cross-boundary bonds occur along the boundaries compared to when the polarity of one grain is reversed. The presence of 7-member rings and anti-site cross-boundary bonds results in a more open atomic structure at the boundary, shortening the distance between the first and the second {331} atomic planes from the boundary plane by 40%.     

Cu3Ge Schottky contacts on n-GaN

The electrical properties and thermal stability of (hereafter referred to as ) Schottky contacts to n-GaN as a function of the Ge concentration and annealing temperature are studied. Upon rapid thermal annealing the /n-GaN Schottky diode is formed at 300 °C and is stable up to 650 °C. At 700 °C the agglomeration occurs in the films. For the Cu-25 at % Ge films the ideality factor, n, barrier height, , and flat band barrier height, , of the /n-GaN diodes are in the ranges of 1.22–1.36, 0.53–0.72 eV, and 0.65–0.97 eV, respectively, being decreased with the annealing temperature. Higher Ge concentration in the Cu-35 at % Ge films results in larger n, , and of /n-GaN Schottky diodes. The film is expected to be a suitable candidate for stable Schottky contacts to n-GaN at elevated temperatures.     

Transmission electron microscope study of a directionally solidified Cu-MgCu2 eutectic

The crystallography and the interface structure of a unidirectionally solidified Cu-MgCu₂ eutectic alloy have been examined by transmission electron microscopy. The microstructure of the eutectic was found to be lamellar and regularly interrupted by faults. The preference of the particular orientation relationship could not be explained by relative atomic densities of the planes comprising the interface. Based on the defect contrast observed and extinction distance calculations, it is suggested that the fine array of defects observed at the interface may be characterized as steps with step vectors parallel to or Dislocations were also observed at the interface but they were rarely regular.     

Microstructural development of Ti-24Al-14Nb-3V-0.5Mo alloy during hot tensile deformation

Microstructure of the Ti-24Al-14Nb-3V-0.5Mo (at.%) alloy deformed from room temperature to 700°C was studied by the H-800 transmission electron microscope (TEM) equipped with a side entry goniometer stage capable of ±45° tilt on the X or Y axis operating under two-beam condition. Especially dislocation types and slip systems of the ₂-phase (D0₁₉) were analyzed in accordance with invisibility criterion. The results indicated that with increasing the deformation temperature from room temperature to 700°C, the slip of -type dislocations on prismatic planes in the ₂-phase was enhanced whereas that on basal plane (0001) with hexagonal networks morphology was suppressed during tensile deformation. Being immobile, the dislocation networks were thought to be mainly responsible for the low ductility at low temperature. When the test temperature was increased to 700°C, the -type dislocation glide on pyramidal planes was also observed, but the hexagonal dislocation networks formed by the slip of -type dislocations on basal planes were hardly seen. During the high temperature deformation microstructural refinement was also observed due to dynamic recovery and recrystallization. This, together with the precipitation of secondary ₂ phase and O phase during deformation all contributed to ductility of the present alloy at high temperature.     

Decay of 175Hf and 181Hf

Nuclear-physical properties of ¹⁷⁵Hf and ¹⁸¹Hf produced by neutron irradiation of natural hafnium in the SM-3 nuclear reactor were studied. The X-ray and -ray spectra were measured with high-energy-resolution HPGe and Ge(Li) detectors. The half-lives T1/2 (days) were determined: ¹⁷⁵Hf 71.9±1.3 and ¹⁸¹Hf 42.12±0.25. The relative intensities (rel. units) of the -ray lines (keV) of ¹⁸¹Hf are as follows: 133.03, 54.0±1.6; (136.28 + 136.86), 8.9±0.3; 345.919, 20.4±0.6; and 482.193, 100. The ratios of the intensities in the X-ray spectrum were measured: , , , and .     

On the theory of plasticity with smooth surfaces of loading

The well-known theories of plastic yield with smooth surfaces of loading are developed and generalized on the basis of a model of a nonlinear anisotropically hardened medium based on the concept of slip. Unlike the commonly used procedure of application ofa priori known laws of hardening (variation of the surface of loading in the process of plastic deformation), we suggest a method for the experimental evaluation of a universal function of the material appearing in the constitutive equations for arbitrary complex loading processes including elastic unloading and plastic deformation in the direction opposite to the initial one. The constitutive equations are relatively simple and, hence, can easily be used for the statement and solution of boundary-value problems in the theory of plastic yield. Dnepropetrovsk State University, Dnepropetrovsk. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 6, pp. 63–70, November–December, 1997.     

Hole Density in Charge Stripes and Effect of Next-Nearest-Neighbor Transfer

By applying a variational Monte Carlo method to the two-dimensional t-J model, a couple of properties of striped states are studied. In the charge domain walls vertical (or horizontal) to the lattice (VDW), the hole density is favorable in energy similarly for 0.5 , whereas in the diagonal domain walls (DDW) the stable hole density is limited to = 1. Negative next-nearest-neighbor transfer (t/t < 0) further stabilizes VDW with = 0.5 and DDW with = 1 against the -wave superconducting state.