Influence of linear elastic stresses on dynamic magnetostriction of cold-rolled transformer steel

The anisotropy of dynamic magnetostriction is investigated without external stresses, in extension, and in compression. Results are obtained expressing the (B) dependence for constant elastic stresses and also — () for certain induction values. Oscillograph traces are taken of the (H) and B(H) hysteresis loops with the specimens under investigation in extension and compression.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 110–115, May, 1977.     

Electronic conduction properties of silver particles in cesium oxide

The electronic conductivity of a particular metallic particles/semiconductor system, i.e. Ag particles in cesium-oxide thin film, has been studied. The experimental results show a transition from a polycrystalline semiconductor to metallic behavior as characterized by the conductivity-temperature curve (log bs 1/T), and a five order of magnitude increase in the room temperature value of the conductivity with surface Ag content increasing from an equivalent thickness of 2Å to 20Å. It was observed by TEM that the deposited Ag was mainly in the form of dispersed particles with the particle size varying from 20 to 200Å and their separations varying from hundreds to tens of angstroms over the Ag content range. These results can hardly be explained with the model of direct electron tunneling through the Schottky barrier at the Ag-particle/cesium-oxide interface. A microstructure model with two conduction layers is presented, and an analogy to the hopping conduction mechanism is proposed to explain the electronic conduction behavior. This model predicts that the attenuation length for electronic wavefunctions localized at Ag particles falls in the range 20–50Å.     

A model of Piron's preparation-question structures in Ludwig's selection structures

We give a model of the basic Jauch-Piron (JP) approach to quantum physics, i.e., of preparation-question structure (with four basic axioms and without axioms C, P, A), in terms of Ludwig's selection structure; in the latter structure the primitive notion of individual sample of a physical entity is formally described (without making reference to any probability concept). Once we interpret Piron's concept of question in Ludwig's context of a selection structure, we find that there is no difficulty in formalizing notions such as performable together questions; moreover, results such as = or ()= can be formally proved. We develop the theory along the lines of the JP approach; the set of JP propositions is derived and it turns out to be a complete lattice, as happens in Piron's theory, but with a different physical interpretation of the lattice operations. Finally, we study some connections between the standard Ludwig foundation and our approach.     

H2-induced changes in electrical conductance of β-Ga2O3 thin-film systems

H₂-induced changes of electrical conductivity in polycrystalline, undoped -Ga₂O₃ thin films in the temperature range of 400–650° C are described. The sheet conductance of these films depends reversibly, according to a power law p ^1/3, on the partial pressure of hydrogen in the ambient atmosphere of the Ga₂O₃ film. A bulk vacancy mechanism is excluded by experiments and it is shown that the interaction is based on a surface effect. Changes in conductance are discussed to result from the formation of an accumulation layer due to chemisorption on the grain surfaces. Typical coverages are determined to be approximately 10^–4 ML for pH₂=0.05 bar and T=600° C. A possible explanation of the p ^1/3 power law is provided.     

Rapid increase in the delay time for the breakdown of gas-filled gaps in high electric fields

An experimental study is reported of the delay-time statistics for electrical breakdown in air in intense electric fields E = 100–200 kV/cm. The dependence of the statistical delay time t_st for the breakdown on the gap width is obtained for various fields E. With E = 100 kV/cm and with an air pressure of p = 1 atm, the delay time is 20 nsec and depends weakly on in the range 5 = 3–10 mm. As the gap width is reduced from 3 to 2 mm, t_st increases sharply, reaching 3000 nsec. The gap width at which the sharp increase in t_st sets in decreases with increasing E. The gap-width dependence of t_st has the same nature at different pressures. The minimum delay time has been measured to be 8 nsec.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 2, pp. 36–39, February, 1969.     

Detecting torsion from massive electrodynamics

A new method of detecting torsion in the case of massive electrodynamics is proposed. The method is based on the study of spectral lines of hydrogen-like atoms placed in a torsion field, where the interaction energy between the torsion vector field Q and an electric dipole is given by P · Q. All the methods designed so far have been based on spinning test particles interacting with magnetic fields in which the energy splitting is given by S · B on a Stern-Gerlach type experiment. We arrive at an energy splitting of order of 10^–21erg 10^–9eV, which is within the frequency band of radio waves.     

Inelastic action of a gradient radio-frequency neutron spin flipper

The energy shift due to the inelastic interaction of the neutron with the time dependent magnetic fields of a gradient radio-frequency spin flipper was studied. A nondispersive perfect crystal spectrometer was used to measure extremly small energy changes of E0.2 eV. The gradient of the magnetic field causes a broadband action of the spin flipper which facilitates its use for new active neutron optical components.     

Study ofA+A→0 with probability of reaction and diffusion in one dimension and in fractal substrata

We present Monte Carlo simulations of annihilation reactionA+A0 in one dimensional lattice and in three different fractal substrata. In the model, the particles diffuse independently and when two of them attempt to occupy the same substratum site, they react with a probabilityp. For different kinds of initial distributions and in the short an intermediate time regimes, the results for 0<p1 show that the density ofA particles approximately behaves as (t)=(t=0)f(t/t ₀), with the scaling functionf(x)1 forx1,f(x)x ^–y forx1. The crossover timet ₀, behaves ast _{0 0eff} ^–1y where theeffective initial density _0eff depends on (t=0) and on the kind of initial distribution. For a given substratum of spreading dimensiond _s, the exponenty(d _s/2<y<1) depends only onp and its value increases asp decreases (y1 whenp0). In the very long time regime it is expected thatp(t)t ^–ds/2 independently ofp.     

Damage created by high-current-density implants of phosphorus into 〈100〉 and 〈111〉 silicon wafers

The damage left by high-current-density, 9 A/cm², implants of 120 keV phosphorus into 100 and 111 silicon oriented substrates was investigated as a function of the fluence in the range 4×10¹⁵–1.5×10¹⁶/cm². The samples were analyzed by 2 MeV He⁺ channeling and transmission electron microscopy. Initially a buried amorphous layer forms at low fluences until the wafer temperature saturates at 450 °C at a fluence of 4.5×10¹⁵/cm². As the fluence is further increased ion-assisted regrowth of this initial buried amorphous layer takes place and is 2 to 2.5 times faster (with respect to ion fluence) for 100 substrates than for 111 substrates. At higher fluences, most of the residual damage is located at a depth equal to the sum of the projected range and of the straggling. In the regrown layers twins are found in both orientations, and in some cases a hexagonal silicon phase is present at high fluences. The results are compared with the ion assisted regrowth of amorphous layers at well defined temperatures in the 250°–400 °C range.     

Generation of Electric Fields and Currents in the Earth's Ionosphere Within the Framework of the Planetary-Generator Model

We present a solution for the problem of generation of electric fields and currents in the lower ionosphere of the Earth due to the nonuniform rotation of the magnetized planet and its plasma envelope with inhomogeneous conductivity (the planetary generator model). The angular velocity _p(r,) and the conductivity profile (r) of the plasma envelope are specified taking into account the experimental data. It is shown that under these conditions, the current system of the planetary generator is a single current loop localized mainly in a narrow layer corresponding to the high-conductivity region at heights h₁100 km. The thickness of this layer is about the conductivity scale. Within the framework of this model, we estimate the total current circulating in the ionosphere and the current flowing in the planet and calculate the characteristic values of the electric fields generated. Comparison between the calculation results and the experimental data shows that the considered mechanism of current generation can be significant for analyzing current systems in the lower ionosphere of the Earth.     

Investigation of the (n, γf) process on a235U nucleus

The fluctuations of uranium X-rays yield in coincidence with fission of the²³⁵U nucleus were observed at several neutron resonances. The results show the dependence ofK ₁ yield on fission width _f. This dependence is explained by the (n, f) process which is the result of competition between fission and -decay during the deexcitation of the²³⁶U compound nucleus. The mean width _f was determined to be equal to (2·1 _–1·7 ^+1·5 ) meV. The mean energy of prefission-rays was found to be (750 _–130 ⁺⁴⁰⁰ ) keV. It seems that the -transitions taking place before fission of the²³⁶U compound nucleus are mostly of the magnetic dipole.It is a great pleasure to express our gratitude to Yu. I. Kolgin for considerable help in all the experimental work, to L. B. Pikelner and Yu. P. Popov for many useful discussions, I. M. Salamatin, A. Mateeva for the programme supply of the experiment, to A. A. Bogdzel and V. G. Tishin for taking part in different steps of the work.     

The critical point indices of ferroelectric and ferromagnetic phase transitions

Magnetic transitions are described by the critical indices0,1/3,4/3 while some ferroelectric transitions appear to give0,R~1/2,1. It is pointed out that these two sets of values for the critical indices are allowed by the scaling laws and stability conditions near the phase transitions.The authors thank Prof. R. S. Krishnan for his encouragement and Mr. B. Viswanathan for some discussions. The financial assistance from DAE and CSIR is also acknowledged.     

F2-laser patterning of GaPO4 resonators for humidity sensing

Piezoelectric gallium orthophosphate (GaPO₄) thickness – shear mode resonators were patterned by F₂-laser ablation and employed for gas sensing. The thickness of GaPO₄ crystals was reduced from 215 m to 115 m by laser ablation and the piezoelectric fundamental resonance frequency in the thinned region increased thereby from 6 MHz to 12 MHz. The Q values of laser-thinned and pristine resonators in air were Q7000 and Q95000, respectively. The GaPO₄ crystals were coated by thin polyimide layers that served as receptor for water vapour. The resonance frequency of coated crystals decreased linearly with increasing level of relative humidity (RH) and the sensitivity for laser-patterned 12 MHz GaPO₄ resonators, S_RH-98 Hz/%RH, was much larger than for the pristine 6 MHz GaPO₄ resonators. PACS 61.10.-i; 68.37.-d; 81.15.Fg     

Superstability estimates for anharmonic systems

We consider an anharmonic crystal described by variablesS _x ,x ^d ,S _x , with one-body interaction ¦S _x ¦ and nearest neighbor (n.n.) two body interaction ¦S _x –S _y ¦. We prove that, for ^d bounded, , where is the correlation function for the free boundary condition Gibbs state in ,>0 and are suitable constants independent of and . This generalizes previous results obtained in the case.Research partially supported by Consiglio Nazionale delle Ricerche.     

Attenuation of powerful ruby laser pulses in the atmosphere by resonant absorption of water vapor

The attenuation of a ruby laser pulse at the wavelength = 6943.8å is calculated under conditions of spectroscopic saturation for a parallel beam and a diverging beam with divergence angle = 10^–5 rad. It is shown that deviation from the Bouguer law may reach 45% at a path length = 2 km for an initial power level of I₀ = 0.5I_s for the parallel beam, and 20% for I₀ = 0.25I_s for the divergent beam (I_s, saturation power).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–12, February, 1978.     

Ultra-high piezoelectric response in 〈<Emphasis Type="Bold">110</Emphasis>〉- oriented polydomain Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>- PbTiO<Subscript>3</Subscript> single crystals

The piezoelectric constant and electromechanical coupling coefficients of 110-oriented polydomain0.71Pb(Mg_1/3Nb_2/3)O₃-0.29PbTiO₃ single crystals were determined experimentally by using resonance methods. It was confirmed that the single-crystal system has large electromechanical coupling coefficients k₃₃ (91%), k₃₃ (83%), and k₃₁ (81%), and piezoelectric constant d₃₃ (1400 pC/N), which are comparable to those of 001-oriented crystals, and we also found that the values of k₃₃ and k₃₁ are sensitive to the cuts of the crystals. X-ray-diffraction measurements on 110-oriented crystals have shown that the origin of the high piezoelectric response should be attributed to the orthorhombic distortion. Our results show that the 110-oriented crystals are also promising for a wide range of electromechanical transducer applications, since the 110-oriented crystals can be grown from 110-oriented seed crystals in the modified Bridgman technique. PACS 77.80.Bh; 77.84.Dy; 77.65.Bn     

Slowing down of retrieval in the hopfield model

The variation of the convergence time, as a function of the storage capacity is studied numerically for systems ranging in size fromN=1000 toN=16,000 neurons. is found to increase likeexp[–A(_c–)] as one nears the critical storage capacity _c =0.142=0.002.     

Luminescence of AgCl excited by u.v. laser light

The spectral distribution and decay of the blue-green luminescence of AgCl has been measured at very low temperatures, using u.v. laser excitation. A structure was observed in the emission band at 77°K. The decay consists of three processes: a) a very fast process which follows the laser pulse (10^–8 sec), b) a fast exponential process which is also observed with low intensity u.v. excitation,(10^–4–10^–5 sec) and, finally, c) a slow exponential process (seconds).     

Superradiating 4P-4S-3P cascade of sodium vapour arising on the leading edge of the exciting laser pulse

Investigations of the superradiating cascade of sodium vapour 4P-4S-3P ₁ = 2.21 µm and ₂=1.14 µm) arising on the leading edge of the exciting laser pulse were carried out. The dependences of the actual delay time _D of the ₁ pulse on the population rise time of the laser-excited 4P state were measured and compared with those calculated following the existing theoretical model. The dependence of the actual delay time _D on the inverse density of excited atoms 1/N* is also presented. Analysis of this dependence revealed the influence of the Doppler dephasing and of the second, ₂, transition on the formation of the ₁ superradiance.