The electron capture of H<Superscript>+</Superscript> ions in solid foils

The negative ion yields φ (H^?) and the neutral atom yields φ (H) of 0.6, 0.9, 1.2, 1.6 and 1.8 MeV H⁺ projectiles traversing various carbon foils have been measured. The experimental results showed that neither φ(H^?) nor φ(H) varies with the dwell time ^ at the same energy. φ(H)is larger than φ(H^?) by about 3–4 orders of magnitude. The charge exchanging between H⁺ ions and carbon foils was analyzed. It can be seen that the charge exchange is the most basic process. The experience formula of σ_c/σ_l has been gotten.     

Study of ion implanted Al0.25Ga0.75As/GaAs by Raman spectroscopy

This paper reported the effect of the weak damage in the Al_0.25Ga_0.75As/GaAs epitaxial layer induced by 0.8 MeV Si ions implantation with ion dose from 1 × 10¹⁴ to 5 × 10¹⁵ cm^-2. The Raman spectra measured on these samples showed that there were two kinds of phonon modes existing in the epitaxial Al_0.25Ga_0.75As films. The strains induced in the implanted layer and the corresponding lattice parameters were also evaluated as a function of the implanted dose. In addition, the Rutherford backscattering spectrometry/channeling (RBS/C) was also measured on these samples. These two measurement techniques all confirmed that the implantation only induced weak damage in the material.     

Study of ion implanted Al0.25Ga0.75As/GaAs by Raman spectroscopy

This paper reported the effect of the weak damage in the Al_0.25Ga_0.75As/GaAs epitaxial layer induced by 0.8 MeV Si ions implantation with ion dose from 1 × 10¹⁴ to 5 × 10¹⁵ cm^-2. The Raman spectra measured on these samples showed that there were two kinds of phonon modes existing in the epitaxial Al_0.25Ga_0.75As films. The strains induced in the implanted layer and the corresponding lattice parameters were also evaluated as a function of the implanted dose. In addition, the Rutherford backscattering spectrometry/channeling (RBS/C) was also measured on these samples. These two measurement techniques all confirmed that the implantation only induced weak damage in the material.     

Dinuclear copper (II) and nickel (II) systems with planar M2N2O2 bridge

The tridentate ligand systemb (abbreviated as inkR₂) readily yield copper (II) and nickel (II) species of the formula M₂ (inkR₂)₂(CLO₄)₂. 2xH₂O (x=0–1). Dinuclear formulation is based on variable temperature magnetic susceptibility and conductivity data and on the known structure of some related systems. The Cu₂ (inkR₂) ₂ ²⁺ species are strongly antiferromagnetic (?2J=600–800 cm^?1) while the Ni₂(inkR₂) ₂ ²⁺ species are diamagnetic. The major coordination sphere is planar around each metal (II). The metal ions in a dimer are linked by planar M₂N₂O₂ bridge. The copper (II) and nickel (II) species freely form solid solutions. In these statistical scrambling of copper and nickel occur among the metal ion sites of the dimeric structure. Powder epr spectra of such mixed crystals are indicative of axial geometry around copper (II) ion.     

Flip-chip-type high-T c gradiometer for biomagnetic measurements in unshielded environment

A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO₃ bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO₂/YSZ multilayer on ?50.8 mm Si wafer. The coupling coefficient between the flux transformer and the planar gradiometer is 0.18. The transformer increases effectively the resolution of the gradiometer. A magnetic field gradient resolution of 73 fT.cm^?1Hz^?1/2 in the white region and 596 fT.cm^?1Hz^?1/2 at 1 Hz has been obtained. High quality magnetocardiogram signals have been successfully measured by using this flip-chip-type gradiometer in an unshielded environment.     

Flip-chip-type high-Tc gradiometer for biomagnetic measurements in unshielded environment

A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO₃ bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO₂/YSZ multilayer on ϕ50.8 mm Si wafer. The coupling coefficient between the flux transformer and the planar gradiometer is 0.18. The transformer increases effectively the resolution of the gradiometer. A magnetic field gradient resolution of 73 fT.cm⁻¹Hz^−1/2 in the white region and 596 fT.cm⁻¹Hz^−1/2 at 1 Hz has been obtained. High quality magnetocardiogram signals have been successfully measured by using this flip-chip-type gradiometer in an unshielded environment.     

Research of processing techniques used in fabrication of solid oxide fuel cells and study of their selected properties

The processing techniques used in the fabrication of solid oxide fuel cells (SOFC) were studied. A fast, simple and convenient method of studying and fabricating SOFC was found. The properties of the single cell and the series stack of the SOFC were measured and studied. The maximum open voltage and short current density of the single cell are 1.18V and 360 mA/cm², respectively. And the maximum open voltage and short current density of the series stack of 7 cells are 7.30 and 400 mA/cm² respectively and the output power is about 2.0 w. Some simple applications were tried by using the SOFC series stack. Project supported by the National Plan Committee, Jilin Province Plan Committee, the National Natural Science Youth Fund Committee, Jilin Province Youth Science Fund Committee and the General Company of Transport and Energy of Jilin Province.     

Low temperature measurements of electrical activity and Hall mobility of boron implanted silicon

This work investigates the electrical behaviour of boron implanted silicon at temperatures from 300k to 4.2k by means of Hall effect and sheet resistivity measurements. The ion energy is 100 Kev and the doses are 1×10¹², 2×10¹², 5×10¹², 1×10¹³, 2×10¹³, 5×10¹³, 1×10¹⁴, 2.5×10¹⁴, 5×10¹⁴, and 1×10¹⁵ ions/cm².The most accurate information about the electrical activity can be only found from measurements at low temperatures. Furthermore, a reverse annealing takes place in the annealing temperature range from 500 to 600 °C, and this range is found to be independent of the ion dose. It is also clear that the electrical activity depends strongly on the annealing temperatures, especially for annealing temperatures greater than 600 °C. For ion dose 1×10¹⁵ ions/cm² complete activity can be obtained by annealing up to 900 °C.

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Zusammenfassung Die vorliegende Arbeit beschreibt Untersuchungen über das elektrische Verhalten des Borimplantierten Siliziums mittels Hall Effekt- und Schicht-Widerstand-Messungen im Temperaturbereich von 300k bis 4.2k. Die Ionenenergie betrug dabei 100 Kev, und die Ionendosen waren 1×10¹², 2×10¹², 5×10¹², 1×10¹³, 2×10¹³, 5×10¹³, 1×10¹⁴, 2.5×10¹⁴, 5×10¹⁴, und 1×10¹⁵ Ionen/cm².Es wurde festgestellt, daß genauere Informationen über die Aktivierung der implantierten Dopanden nur aus Tieftemperatur-Messungen erhalten werden können. Weiterhin findet man ein negatives Ausheilen im Bereich von 500 bis 600 °C. Die Grenzen dieses negativen Ausheilbereiches sind von den Ionendosen unabhängig. Es ist eindeutig, daß die Aktivierung der Dopanden sehr stark von der Ausheiltemperatur abhängig ist, insbesondere für Ausheiltemperaturen größer als 600 °C. Für die Ionendosis 1×10¹⁵ Ionen/cm² kann bei einer Ausheiltemperatur von 900 °C eine vollständige Aktivierung erreicht werden.

     

Angle- and time-resolved mass spectrometric study on pulsed laser ablation of an La-Ca-Mn-O target

Pulsed laser ablation (PLA) of an La₂O₃-CaO-MnO₂ target at 532 nm has been investigated by angle- and time-resolved quadrupole mass spectrometry. The results show that different kinds of metal oxides as well as metal ions and atoms are produced during the ablation at high laser fluence. The measured TOF spectra are fitted by multicomponent Maxwell-Boltzmann distribution with a stream velocity, which gives the translational energy of 6.34 and 0.43 eV for Mn⁺ ions and Mn atoms, respectively. It implies that ablated ions are mainly formed via a nonthermal process, while the neutral atoms mainly via a thermal one. The angular distributions of Mn + ions and Mn atoms can be described by a cos ⁿ θ and a bicosine function a cosθ+ (1-a)cos ⁿ θ, respectively. Possible mechanisms of laser ablation of La-Ca-Mn-0 are discussed. Project supported by the National Natural Science Foundation of China (Grant No. 29683001).     

Study of levels in51Cr through51V (p,nγ) reaction

The low lying levels in⁵¹Cr have been populated by⁵¹V (p, ny)⁵¹Cr reaction. The angular distribution of the ground state electromagnetic transitions from 1165, 1353, 1479 and 1557 keV states have been measured. The results are compared with the Hauser-Feshbach model of the statistical theory of nuclear reactions. The spins for the levels at 1165, 1479 and 1557 keV are shown to be 9/2^?, 11/2^? and 5/2^? respectively.     

Effect of the molecular weight of polystyrene on the viscosity of concentrated solutions

The viscosity of solutions of polystyrene of various molecular weights (from 1.04 · 10² to 3.8 · 10⁵) in a poor solvent (decalin) and a good solvent (ethylbenzene) has been measured at temperatures from 15 to 70°C over a broad range of shear stresses from 10² to 10⁶ dyne/cm². The nature of the solvent has a considerable influence on the critical molecular weight and the absolute value of the viscosities of the solutions over the entire range of molecular weights and on the form of the flow curves of decalin solutions of polystyrene as a function of temperature. The heat of activation of viscous flow increases with increase in molecular weight and shear stress on the interval 20–80°C. The results obtained are explained in terms of the effect of the molecular weight of the polymer, the nature of the solvent, stress and temperature on structure formation in the solution and on the orientation of the macromolecules and structures in the flow process.Ural Gor'kii State University, Sverdlovsk. Translated from Mekhanika Polimerov, No. 5, pp. 920–926, September–October, 1970.     

Raman and infrared spectra of ammonium selenate and lithium ammonium selenate

The Raman and infrared absorption spectra of (NH₄)₂ SeO₄, (ND₄)₂ SeO₄ and Li (NH₄) SeO₄ have been recorded at 300° K; while the spectra of the non-deuterated compounds have been recorded at 110° K also. (NH₄)₂ Se0₄ crystal exhibits 33 Raman lines, while LiNH₄SaO₄ shows 30 Raman lines at 300° K. Proper assignments have been given to the observed vibration frequencies. The SeO₄ ^?? ions and the (NH₄)⁺ ions are found to be highly distorted in these selenates. There is lowering of the N-H vibration frequencies due to hydrogen bonding. The present spectroscopic investigations do not reveal the existence of any phase transition in these selenates in the temperature region investigated.     

The D2Σ+ − X2Σ+ system of A10

Eleven bands of A10 belonging to the system (D² Σ ⁺-X² Σ ⁺) in the ultra-violet region have been analysed for their rotational structure. These are the 0-2, 1-3, 2-4, 0-3, 1-4, 3-0, 4-1, 3-1, 4-0, 5-1 and 6-1 bands lying at 2611.8Å, 2620.7Å, 2629.4Å, 2677.4Å, 2685.7Å, 2347.7Å, 2358.3Å, 2402.2Å, 2305.8Å, 2316.7Å and 2277.3Å respectively. The spin-splitting for the D² Σ ⁺ state has been determined from the doubling of the rotational lines observed for the bands 0-2, 1-3, 2-4 and 1-4. The rotational and vibrational constants (in cm^?1) evaluated for the D² Σ ⁺ state are: $$\begin{gathered} T_a = 40267 \cdot 6 \hfill \\ G(V) = 817 \cdot 47 (v + 1/2) - 4 \cdot 795 (v + 1/2)^2 - 0 \cdot 1107 (v + 1/2)^3 \hfill \\ B_v = 0 \cdot 56522 - 0 \cdot 0046 (v + 1/2) - 0 \cdot 00005 (v + 1/2)^2 \hfill \\ \gamma = 0 \cdot 004 \pm 0 \cdot 002 \hfill \\ \sigma = - 0 \cdot 4 \pm 0 \cdot 1 \times 10^{ - 6} \hfill \\ \end{gathered} $$      

Low energy gamma-ray measurements over Hyderabad,India

The results of the first low energy gamma-ray (0.2 to 1 MeV) measurements at equatorial latitudes conducted by two-balloon flights over Hyderabad, India (7.6° N GM), are presented. The energy resolution of the detectors was sufficient to detect the γ-ray peak at 0.5 MeV due to the electron-positron annihilation. The flux of the 0.5 MeV photons was found to be 0.090 ± 0.012 photons/cm² sec at an atmospheric depth of 10 gm cm² and 0.048 ± 0.011 photons/cm² sec at the top of the atmosphere. Comparison of our results with those obtained at higher latitudes, show the existence of a considerable latitude variation of the 0.5 MeV flux, about a factor of 4 between 55° and 7° latitudes at an altitude of 10 gm/cm².     

Paramagnetic resonance studies of Cu2+ doped in NH4Br

Electron Paramagnetic Resonance studies of Cu²⁺ doped in NH₄Br single crystals have been carried out for the first time. The room temperature data reveal that Cu²⁺ ions go predominantly to interstitial sites having square planar co-ordination of four Br^? ions. For this type of complexes the bromine: superhyperfine structure: is observed on the normal hyperfine structure lines of copper. Existence of other weak spectra indicates that a relatively few Cu⁺⁺ ions go substitutionally to (NH₄)⁺ ions, and are probably associated with a first or a second nearest neighbour cation vacancy, among the two, the latter being more predominant. However, the low temperature studies corresponding to the tetragonal phase of NH₄Br indicate that a number of Cu²⁺ ions at interstitial sites get readjusted to the lattice sites after phase transformation. The spectra in both the phases are analysed by the usual spin Hamiltonian method.     

Parameterizing above Guaranteed Values: MaxSat and MaxCut

In this paper we investigate the parameterized complexity of the problems MaxSat and MaxCut using the framework developed by Downey and Fellows. LetGbe an arbitrary graph havingnvertices andmedges, and letfbe an arbitrary CNF formula withmclauses onnvariables. We improve Cai and Chen'sO(2^2ckcm) time algorithm for determining if at leastkclauses of ac-CNF formulafcan be satisfied; our algorithm runs inO(|f| + k²φ^k) time for arbitrary formulae and inO(cm + ckφ^k) time forc-CNF formulae, where φ is the golden ratio . We also give an algorithm for finding a cut of size at leastk; our algorithm runs inO(m + n + k4^k) time. We then argue that the standard parameterization of these problems is unsuitable, because nontrivial situations arise only for large parameter values (k ≥ m/2), in which range the fixed-parameter tractable algorithms are infeasible. A more meaningful question in the parameterized setting is to ask whether m/2 + kclauses can be satisfied, or m/2 + kedges can be placed in a cut. We show that these problems remain fixed-parameter tractable even under this parameterization. Furthermore, for up to logarithmic values of the parameter, our algorithms for these versions also run in polynomial time.     

Multiple muon events observed underground

Observations are reported on events involving multiple penetrating particles recorded in a scintillator-neon flash tube telescope, at a depth of 1500 hg/cm² in the Kolar Gold Mines. From these, it is shown that: (1) the cross-section for nuclear interaction of muons of average energy ～200 GeV is ～ 6 × 10^?30 cm²/nucleon; (2) the decoherence curve for events involving two parallel muons is uniform over the range of distances from 0 to 2 metres; and (3) the angular distribution of double-parallel muons closely resembles that of single muons, implying that these two types of events are probably produced in the atmosphere in a similar manner.     

Superconvergence analysis of approximate boundary-flux calculations

Summary Certain projection post-processing techniques have been proposed for computing the boundary flux for two-dimensional problems (e.g., see Carey, et al. [5]). In a series of numerical experiments on elliptic problems they observed that these post-processing formulas for approximate fluxes were almost (O(h ²)-accurate for linear triangular elements. In this paper we prove that the computed boundary flux isO(h ² ln 1/h)-accurate in the maximum norm for the partial method of [5]. If the solutionuH ³() then the boundary flux error isO(h ^3/2) in theL ²-norm.     

Rate of Decay of Concentration Functions on Discrete Groups

Given an irreducible probability measure on a non-compact locally compact group G, it is known that the concentration functions associated with converge to zero. In this note the rate of this convergence is presented in the case where G is a non-locally finite discrete group. In particular it is shown that if the volume growth V(m) of G satisfies V(m) cm ^D then for any compact set K we have sup _gG ⁽ⁿ⁾(Kg) Cn ^–D/2.     

Study of the role of intermolecular interactions (hydrogen bonds) in the initial stage of orientation of polyvinyl alcohol and vinyl alcohol copolymers

The effect of hydrogen bond rupture on the process of destruction of the starting crystallite structure of polyvinyl alcohol and copolymers of vinyl alcohol and N-vinylpyrrolidone and -vinylcaprolactam has been investigated. The differential spectrum method is used to establish the frequency (3200 cm^–1) of the band corresponding to the vibrations of the bound hydroxyl groups; the temperature dependence of the optical density of the 3200 cm^–1 band has been recorded. The strength of the starting structure is calculated from the stress-strain diagram and its temperature dependence is plotted. It is concluded that the strength of the starting structure is chiefly determined by the presence of hydrogen bonds between the polymer macromolecules.Leningrad Kirov Institute of Textile and Light Industry. Translated from Mekhanika Polimerov, No. 2, pp. 327–329, March–April, 1971.