bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gain, Band Width, and Noise Characteristics of the Variable-Parameter Amplifier
Authors: Heffner H. , Wade G. 
Published: April 2005

The variable parameter (or parametric) principle of amplification is characterized by a typical arrangement in which a variable energy storage element, such as an inductor or a capacitor, is suitably coupled to two resonant circuits. If the value of the energy storage element is made to vary in the proper way, energy is fed from the source which drives the element (that is, the pump) to the fields of both the resonant circuits. This paper describes the behavior relative to gain, band width, and noise of this type of amplifier.
Specifically, it is shown that to increase gain, the Q of one of the resonant circuits, the one commonly called the idling circuit, must be increased or the variation in the variable reactance must be increased. The band width is inversely proportional to this Q and to the voltage gain. Hence, for high gain, the amplifier is normally a narrow band device. One of the most important sources of noise is the thermal noise originating in the idling circuit. However, in principle this source can be reduced indefinitely by making the idling frequency approach the pumping frequency or by artificially cooling the idling circuit. In this fashion very low noise figures should be possible.
The parametric principle can also be applied to producing frequency conversion with large conversion gain. The appendix presents the expressions for gain, band width, and noise figure for this application. The behavior of the converter relative to gain, band width, and noise is quite similar to that of the amplifier.
General Solution of the Luneberg Lens Problem
Authors: Morgan Samuel P. 
Published: April 2005

The general solution is obtained for the index of refraction of a variable-index, spherical lens which will form perfect geometrical images of the points of two given concentric spheres on each other. One conjugate sphere is assumed to be outside the lens or at its surface, while the other may be either inside, outside, or at the surface. If one of the spheres is of infinite radius, the lens will focus a parallel beam perfectly at a point on the other sphere.
It is shown that the index of refraction may be specified arbitrarily, subject to two simple conditions, in an outer shell of any desired thickness less than the radius of the lens. The index of the central portion is then expressed in terms of a function which is tabulated, and of an integral involving the index of the outer shell. Some properties of the general solution are discussed, and various special solutions are derived.
Characteristics of the Annealing Kinetics of Tin Films Deposited at 88°K
Authors: Priest J. , Chiou C. , Caswell H. L. 
Published: April 2005

The electrical resistance of evaporated, high purity tin films deposited at 88°K decreases rapidly in two temperature regions as determined by isothermal annealing studies. One pronounced annealing peak occurs at 110°K and has an activation energy of 0.34±0.06 ev. The second much less pronounced peak at 180°K has an activation energy of 0.74±0.10 ev.
The annealing characteristics of five pure films varying in thickness from 960 A to 4100 A and a film deposited in a high partial pressure of N2 are quite reproducible. The presence of O2 during evaporation, however, drastically altered the annealing kinetics and increased the activation energy at any given temperature. The defect resistivity at the time of evaporation was the same for all five pure films and a film deposited in a high partial pressure of N2, but is about 75% higher for the film deposited in the presence of O2.
Specific Friction Force in a Graphite Brush Contact as a Function of the Temperature in the Contact Spots
Authors: Holm Else 
Published: April 2005

Measurements by different workers have indicated that the friction coefficient μ of a graphite brush contact decreases with rising contact temperature T. If P = mechanical load, Ab = load bearing area and F = friction force, the average pressure is p̄ = P/Ab and the specific friction force ψ = F/Ab. Hence μ = F/P = ψ/p̄. It will be shown in this paper that the measured μ(T) effect during smooth sliding is caused by the decrease of ψ with rising T.
The specific friction force is a function of the character of the sliding surface alone, and μ is, in addition, a function of the actual pressure in Ab. It is shown that sliding, after a relatively short time, leads to a stage during which Ab, thus also p̄, remains practically constant for more than 10 hr. The (μ,T) test begins when such an ``initial stage,'' defined by μ=μ0, T = T0 and constant contact voltage U, has been reached. It involves T increasing above T0 and then decreasing to T0 again, whereby the time of the test is short enough for constancy of p̄. During a perfect (μ,T) test, the forward and reversed curves agree with each other indicating that Ab has remained constant.
For all sliding stages with constant p̄, the relationship mentioned above can be written: μ(T) = constψ(T), which makes it possible to study ψ as a function of T by studying μ as a function of T. The decrease of ψ with rising T is explained by assuming that adherence bonds in Ab are broken or loosened by T according to a probability exp(−φ/kT) = exp(−11600 φ/T) with φ in ev. The measured, strong dependence on T results from the activation energy φ=0.07 to 0.1 ev between the graphite ``platelets'' being of the order of kT. Hence it is expected that μ and ψ are inversely proportional to the probability factor. It was found that at constant Ab up to about 500°K (the upper limit measured): ψ(T)ψ(T0)=μ(T)μ(T0)=exp[11600[open pi](1T−1T0)]gives a very good agreement in the case of graphite members when the binding energy is assumed to be φ=0.09 ev. For these contacts, ψ decreases from 0.12 to about 0.065 ton/cm2; simultaneously μ decreases from 0.13 at 115°C to 0.07 at about 200°C. This has been found at atmospheric air pressure with dew point about 279°K and also in vacuum of 10−4 mm Hg with dew point about 75°K. With a copper and gold ring at atmospheric air pressure, the (μ,T) curves have a somewhat steeper slope and agreement with theory requires ψ=0.12 or 0.10 ev, respectively.
At temperatures of about 500°K, μ and ψ decrease very slowly and may reach a lower limit at temperatures when the chemisorbed gases on the graphite platelets begin to evaporate.
Kinking and the Fracture of Ionic Solids
Authors: Stokes R. J. , Johnston T. L. , Li C. H. 
Published: April 2005

A single crystal undergoing plastic bending develops constraints due to the gradient in lateral contraction across the beam. These constraints result in lateral stresses which may be relieved by the process of anticlastic kinking. Anticlastic kink boundaries in rocksalt structure solids consist of arrays of {121}〈110〉 edge dislocations formed by the interaction of two systems of {110}〈110〉 glide dislocations, one system being responsible for slip in the main part of the crystal beam, the other confined to its corner.
Temperature affects the structure of kink boundaries and their subsequent role in initiating fracture.
I. At high temperatures (∼0.3 Tm). The resultant edge dislocations in the boundary can move over their {121} slip planes and the kinks become sharp. The resultant dislocations are ineffective barriers to slip and the crystals are ductile.
II. At low temperatures (∼0.1–0.2 Tm). The resultant edge dislocations are immobile and the kinks consist of a diffuse array. The resultant dislocations provide strong barriers to slip and cracks nucleate at the kink boundary.
III. At very low temperatures (∼0.1 Tm). Fracture occurs before the second set of {110}〈110〉 glide dislocations have been activated to generate anticlastic kinks. Relaxation of the lateral stress results in a complex fracture.
Electric Characteristics of Gamma-Ray Irradiated Shielding Window Glass
Authors: Yamamoto Kakuji , Tsuchiya Masao 
Published: April 2005

Induced color of shielding window glass of various kinds by γ-ray irradiation is studied. With Co60−1 kc as radiation source, 23°±3°C as irradiation temperature, 105 R/h as exposure dose rate and 105−107 R as total exposure dose, the coloration increases gradually.
Volume resistivity of glass and its change by gamma-ray irradiation are measured. 100 V dc is applied to a sheet of glass sandwiched between two electrodes to measure the change of its electric resistance with time. The quantity of induced space charge by radiation is calculated by time integration of the current which is obtained from reciprocal of the resistance. Resistance of high density glass is found to become minimum—hence the current becomes maximum—at the exposure dose of 106 R and increases as the dose increases, but resistance of medium density glass decreases gradually. Change of the resistance is exponential and the charge is always positive at any dose. This testifies that glass is electrized by radiation. On the other hand, linearity is established between the quantity of space charge and the dose in a range of 105 to 4×106 R. This suggests the possibility of the electrization to be utilized for dosimetry.
The above not only demonstrates the physical properties of shielding window glass and the effect of radiation on it but seems to help to find the means of preventing the breakdown by radiation of glass.
Anisotropy in the Superconductivity of Deformed Re Single Crystals
Authors: Hauser J. J. 
Published: April 2005

Single crystals of rhenium with a resistivity ratio (ρ300°K/ρ4.2°K) of approximately 1500 were grown by the floating-zone technique. The crystals were then deformed by tension. Samples were selected where the deformation took place primarily on one slip system, i.e., on the (101̄0) slip plane along the &lt;1̄21̄0&gt; slip direction.
Measurements of the resistance were made to determine the variation of the critical current with applied magnetic field. The deformed samples revealed an anisotropy in the transition field (the transition field being the field at which the smallest measureable amount of normality is observed) increasing with decreasing current as one approaches the range where filamentary conduction is important. The transition field was a minimum when the field was perpendicular to the active slip plane. The anisotropy at low current disappeared upon annealing the samples at 2700°C for 1.5 h and only the demagnetization effects remained. These results can be interpreted in terms of the anisotropic dislocation density introduced by this particular deformation.
Constriction of Hard Direction Hysteresis Loops in Thin Permalloy Films
Authors: Middelhoek S. 
Published: April 2005

According to single domain theory, thin Permalloy films with uniaxial anisotropy should have straight hard direction M-H loops without hysteresis. Practically, however, the M-H loops of almost all films are open, when the ac field is applied exactly in the hard direction and the earth's magnetic field is carefully compensated. Moreover, films thicker than about 800 A often show hard direction hysteresis loops which are constricted at the origin.
As is well known, magnetization reversal in the hard direction is associated with the splitting up of the film into a great number of long domains parallel to the easy axis. Whether the walls separating these domains are of the Bloch or Néel type depends upon the strength of the applied field. It will be shown that the constricted loops can theoretically be constructed when, in addition to the anisotropy energy and the energy of the magnetization in the applied field, the energy of these walls is considered. Bitter observations of the reversal process confirm the theory, showing that the constriction is actually a result of Neél-Bloch-Néel wall transitions.
Lattice Theory of Spin Configuration
Authors: Bertaut E. F. 
Published: April 2005

In the frame of a given crystallographic symmetry a matrix ζ(k) is constructed, the eigenvectors and eigenvalues of which are directly related to the spin configuration and magnetic exchange energy, respectively. For Bravais lattices the matrix equation reduces to Villain's equation.
When chemical and magnetic unit cells coincide, the eigenvectors of ζ(0) are shown to be identical to the ``basis of irreducible representations'' used by Turov and Dzialoshinski in the construction of an invariant Hamiltonian.
The usefulness of both methods is discussed. The matrix theory is more general in the sense that it remains valid for magnetic cells different from the chemical one. Although the theory presented here starts from conventional crystallographic symmetry, it contains all the configurations possible in the so-called magnetic groups and even those not contained there (helical configurations).
The theory includes isotropic as well as anisotropic (crystalline field, dipolar, pseudodipolar, antisymmetric) coupling in the order 2 approximation.
Various examples of magnetic structures in the fields of perovskites, ilmenites, spinels, garnets, etc., are presented.
Ferromagnetic Resonance in Single-Crystal Nickel Films
Authors: Pomerantz M. , Freedman J. F. , Suits J. C. 
Published: April 2005

Ferromagnetic resonance measurements have been carried out on single-crystal nickel films obtained by epitaxial evaporation on NaCl under various evaporation conditions. Resonance measurements on thin films by previous investigators have yielded anomalous values of 4πM which have tentatively been attributed to stress in the films. In this paper it is shown that there is a second factor which must be taken in consideration to explain the shift in resonance peak.
Films that were grown at high temperatures (400°C) and in good vacuum (10−10 mm Hg) exhibited an apparent saturation magnetization only 60–70% of the bulk value. This is in accord with the results of ferromagnetic resonance experiments of Kuriyama et al., who attempted to explain their results by the presence of large tensile stresses in the films. However, electron microscope studies of films grown under the above conditions indicated that the films formed discrete, well-separated islands of nickel. The observed particle sizes are such that the demagnetizing factor perpendicular to the film is 60–70% of the value for a continuous planar film. This implies that the shift in the resonance peak was caused not by stresses but by a lowering of the demagnetizing field resulting from the discrete particle growth.
To further substantiate this, continuous films grown at lower temperatures (300°C) and in technical vacuum (10−5 mm Hg) exhibited a magnetization approximately 60% higher than the bulk material values. X-ray diffraction indicated the presence of large compressive stresses in these films. That the increased magnetization was induced by these compressive stresses was convincingly shown by the decrease of the saturation magnetization to bulk value when the stress was relieved by the introduction of water vapor into the cavity. No such change in the external field at resonance was observed for the discontinuous films under a similar exposure to water vapor.
Magnetization of Localized States in Metals
Authors: Wolff P. A. , Anderson P. W. , Clogston A. M. , Matthias B. T. , Peter M. , Williams H. J. 
Published: April 2005

A study has been made of the magnetic properties of dilute solutions of iron in various nonmagnetic 4d series elements and alloys. In some cases the iron atoms possess a localized magnetic moment which manifests itself as an inverse temperature dependence in the susceptibility of the solution. The occurrence of the moment is determined by the valence electron concentration in the solute element (or alloy). As a function of this quantity one finds portions of the 4d series in which localized moments are strictly absent, interspersed by regions—one centered near Mo, the other in the vicinity of Rh and Pd—in which magnetization occurs and at whose edges the moments appear almost discontinuously.
This behavior may be understood in terms of a theoretical model in which the magnetization is ascribed to a virtual level, of the type proposed by Friedel, of the iron atom. Polarization occurs when the virtual level lies near the Fermi level and is sufficiently sharp in energy. A self-consistent Hartree-Fock calculation indicates that under these circumstances the impurity atom develops an exchange potential which splits the level—causing it to have different energies for spin-up and spin-down electrons and thus giving rise to magnetization. The model gives a qualitative description of the experiments and, in particular, is able to account for the fact that the impurity atoms sometimes carry a moment that is a fraction of a Bohr magneton.
Substitutions of Divalent Transition Metal Ions in Yttrium Iron Garnet
Authors: Geller S. , Williams H. J. , Sherwood R. C. , Espinosa G. P. 
Published: April 2005

Various amounts of the divalent ions of manganese, iron, cobalt, and nickel have been substituted for trivalent iron in yttrium iron garnet. The effect of substitution of Fe2+ or Mn2+ ions in dodecahedral sites has also been studied. Electrical balance was accomplished by the simultaneous substitution of tetravalent silicon or germanium. Under these conditions, it is concluded that the divalent ions prefer octahedral sites.
The great affinity of silicon for the tetrahedral sites in the garnets results in the reduction of trivalent to divalent iron at high temperatures even in air atmosphere when appropriate amounts of finely divided silica are present. In Y3Fex2+Fe5−2x3+SixO12, the maximum attainable value of x (under the conditions of our experiments) appears to be 0.45. In attempting to put Fe2+ ions into dodecahedral sites, greatest success was attained when there was also some in the octahedral sites as in {Y2.9Fe0.12+}[Fe0.32+Fe1.73+](Fe2.63+Si0.4)O12. The 0.1 was the maximum amount that could be put into the dodecahedral sites.
Although, it appears that the Co2+ ion is the easiest to substitute into yttrium iron garnet, it is perhaps the most difficult to understand, and only a few of the results on experiments with this ion are included.
In all substitutions of divalent magnetic ions not involving the dodecahedral sites, the 0°K moments are smaller than those calculated on the basis of the simplest interaction model. Several possible explanations are explored; a plausible one is the random canting of some tetrahedral ion moments resulting from weaker interaction with the octahedral divalent ions. The possibility that some of the divalent ions enter tetrahedral sites is not entirely excluded especially in the case of the Co2+ ion.
The divalent magnetic ions do not behave like the trivalent magnetic lanthanide ions when substituted in the dodecahedral sites. They appear not to contribute to the net spontaneous moment appreciably.
Recent Developments in Soft Magnetic Alloys
Authors: Adams Edmond 
Published: April 2005

The present status of soft magnetic alloys used in power generation, communication, and special devices applications will be reviewed with emphasis on future prospects for their improvement. Although the study of microscopic structure of magnetic materials has led to important advances, present and future improvements require an understanding of the fundamental processes of magnetization and a study of submicroscopic and atomic influences.
The bulk of present day magnetic materials is based on alloys of iron with silicon, aluminum, nickel, and cobalt in varying proportions. Their quality has been constantly upgraded by better control of purity and composition through improvements in melting, processing, and annealing practices. Some examples of how each of these factors affects the ultimate magnetic properties of soft magnetic alloys will be given. Brief summaries will also be presented on the magnetic properties of current soft magnetic materials and how they relate to modern devices. Some interesting properties of magnetic alloys based on iron, silicon and/or aluminum will be reported. The development of a hardenable, corrosion and abrasion resistant nonmagnetic alloy based on a ductile intermetallic compound TiNi will also be disclosed.
Magnetic Properties of Tape-Wound Cores of High-Purity 3% Silicon-Iron with the (110)[001] Texture
Authors: Walter J. L. 
Published: April 2005

Tapes, 1 mil thick, with sharp (110)[001] textures have been prepared from high-purity 3% silicon-iron. Surface energy driving forces were utilized to obtain the texture in the impurity-free silicon-iron.
Magnetic properties of wound cores were measured at 60, 400, and 1000 cps. Exceptionally high values of peak induction, residual induction, and squareness, compared to ordinary silicon-iron, were obtained. Losses and excitation were comparable to 1-mil Deltamax properties.
In a half-wave magnetic amplifier, the silicon-iron cores produced as much as 22% higher current output and 40% higher gain than did equivalent Deltamax cores.
Study of Particle Arrangements and Magnetic Domains on the Surface of Permanent Magnets
Authors: Kronenberg K. J. 
Published: April 2005

Some types of permanent magnets are compacts of very small particles. Their properties depend largely on mutual magnetic influence between particles or groups of them. To determine these, more should be known about packing arrangements, orientation, separating layers, and the homogeneity of the compact. A method is described which makes surface details visible and simultaneously reveals magnetic phenomena of such compacts. The size of the compacted particles mostly requires the resolving power of an electron microscope. Special replicating techniques combine shadow-graphing and colloid application even on rough and porous surfaces.
Examples are presented of such surface studies on barium ferrite and iron-cobalt particle magnets. Surfaces of barium ferrite magnets with crystal sizes of 0.2–1 μ show indications of magnetic domains smaller than observed before, sometimes with less than 0.1 μ-width. On compacts of small elongated iron-cobalt particles, structures have become visible which indicate particle groupings varying with the methods of compacting. Colloid outlines surface pole arrangements in correlation to particle groups.
Magnetic Susceptibility and Internal Friction of Tetragonal Manganese-Copper Alloys Containing 70 Percent Manganese
Authors: Schwaneke A. E. , Jensen J. W. 
Published: April 2005

Relation of structure to magnetic susceptibility and internal friction is described for a 70% manganese-30% copper alloy. The aged alloy exhibits a reversible fct to fcc transition at temperatures from 20° to 140°C, depending on the amount of aging. Magnetic susceptibility apparently obeys the Curie-Weiss law but a change is observed in the temperature-susceptibility curve at the structure transition temperature. The low-stress internal friction of this alloy shows a resonance peak at the temperature of the structure change.
Aging experiments with the 70 and 80% manganese alloys give evidence that quenching of alloys containing more than 80% manganese from solid-solution temperatures does not prevent changes typical of alloys aged to initiate precipitation of alpha manganese. Thus the fct⇄fcc transformation that others have associated with the disappearance of antiferromagnetic ordering also is associated with an early stage of the alpha-manganese precipitation.