Further investigation on the thermal decomposition of aluminium dialkylamides

Both dimethylamino- (I) and diethylamino-alane dimers (II), [(R₂N)₂AlH]₂ (I, R=Me; II, R=Et) decompose above 800° C under a few hundred Pa of hydrogen to dark greyish, hard (Vickers hardness larger than 2000), oxidation-resistive and oxidation-protective deposits which are tentatively identified as Al₅C₃N. The deposits are stable to moisture and diluted hydrochloric acid in contrast to those obtained below 800° C, but they easily dissolve in sodium hydroxide solution at room temperature evolving a gas. The deposits on a stainless steel substrate adhere strongly to the substrate and remain so on rapid heating and cooling. The electrical resistivity of the deposits is in the range 10² to 10⁴ cm.     

Identification of chemical oviposition stimulants from rice grain forSitophilus zeamais motschulsky (Coleoptera,Curculionidae)

Chemical components stimulating oviposition bySitophilus zeamais in rice grain were isolated from rice bran and were found to be a mixture of ferulates, diglycerides, and free sterols. Oviposition preference of the species can be induced by synergistic action of these compounds.     

Superconductivity of Zr-Nb-Si amorphous alloys

Superconducting amorphous alloys with high strength and good ductility have been found in rapidly quenched alloys of the Zr-Nb-Si system. These alloys were produced in a continuous ribbon form of 1 to 2 mm width and 0.02 to 0.03 mm thickness using a modified single roller quenching apparatus. The amorphous alloys were formed over the whole composition range between zirconium and niobium, but the silicon content was limited to the relatively narrow range between about 12 and 24 at%. All the amorphous alloys showed a superconducting transition whose temperature, T _c, increased from 2.31 to 4.20 K with increasing niobium content or with decreasing silicon content. The upper critical magnetic field, H _c2, and the critical current density, J _c, for Zr₁₅Nb₇₀Si₁₅ alloy were of the order of 4.5 Tesla(T) and 5.5×10⁶ A m^–2 at 1.5 K in the absence of applied field. The upper critical field gradient at T _c, , and the electrical resistivity at 4.2 K, _n, decreased from 2.89 to 2.10 T K^–1 and from 2.70 to 1.80m, respectively, with the amount of niobium. The Debye temperature, _D, the electron-phonon coupling constant, , and the bare density of electronic states at the Fermi level, N(E _f ) were calculated from the experimentally measured values of _n, , Young's modulus and density by using the strong-coupling theories. From the comparison of T _c with their calculated parameters, it was found that is the most dominant parameter for T _c. The GL parameter, , and the GL coherence length, _GL(0), were estimated to be 70 to 100 and about 7.6 nm, respectively, from the experimental values of and _n by using the GLAG theory and hence it is concluded that the present amorphous alloys are an extremely dirty type-II superconductor having a very weak flux pinning force.     

Efficient blind dereverberation and echo cancellation based on independent component analysis for actual acoustic signals

This letter presents a new algorithm for blind dereverberation and echo cancellation based on independent component analysis (ICA) for actual acoustic signals. We focus on frequency domain ICA (FD-ICA) because its computational cost and speed of learning convergence are sufficiently reasonable for practical applications such as hands-free speech recognition. In applying conventional FD-ICA as a preprocessing of automatic speech recognition in noisy environments, one of the most critical problems is how to cope with reverberations. To extract a clean signal from the reverberant observation, we model the separation process in the short-time Fourier transform domain and apply the multiple input/output inverse-filtering theorem (MINT) to the FD-ICA separation model. A naive implementation of this method is computationally expensive, because its time complexity is the second order of reverberation time. Therefore, the main issue in dereverberation is to reduce the high computational cost of ICA. In this letter, we reduce the computational complexity to the linear order of the reverberation time by using two techniques: (1) a separation model based on the independence of delayed observed signals with MINT and (2) spatial sphering for preprocessing. Experiments show that the computational cost grows in proportion to the linear order of the reverberation time and that our method improves the word correctness of automatic speech recognition by 10 to 20 points in a RT??= 670 ms reverberant environment.     

Analysis of neutron yield produced by high-energy proton

Comparisons have been made between computational results obtained with the BNL code system and experimental data measured by Vasfl'kov et al. for 56 x 56 x 64 cm natural and depleted uranium blocks surrounded by lead walls and primary proton energies of 400 and 660 MeV. The energetic protons from a linear accelerator are used to produce an intensive neutron source inthe uraniumblocko The computercode system prepared at BNL to perform nuclear design analyses of linear accelerator reactors consists of six main programs: NMTC for spallation-evaporation processes above 15 MeV, HIST3D for the analysis of collision event records obtained by NMTC to get P₃ neutron source distribution, DLC-2 to compile 100 energy group cross sections, TAPEMAKER for format conversion, ANISN to collapse 100 group cross sections to fewer group P₃ cross section sets, and the principal code TWOTRAN-II which performs neutron reaction and transport calculations in the energy range below 15 MeV. Our computational method gives conservative total neutron yields, i.e., underestimates of about 16.8–29.8% in comparison with measured values depending on proton energy. Radiative capture²³⁸U(n,) density distributions have been compared between the calculation and experiment. The calculated distribution has the higher peak in the central part of the target system and the steeper gradient both in the r and z directions.Brookhaven National Laboratory, Upton, New York 11973. Published in Atomnaya Énergiya, Vol. 47, No. 2, pp. 83–91, August, 1979.     

Formation of Zirconia Solid Solutions Containing Alumina Prepared by New Preparation Method

In the system ZrO₂–Al₂O₃, a new method for preparing ZrO₂ solid solutions from ZrCl₄ and AlCl₃ using hydrazine monohydrate is investigated. c -ZrO₂ solid solutions containing up to ∼40 mol% Al₂O₃ crystallize at low temperatures from amorphous materials. The formation mechanism is discussed from IR spectral data. The values of the lattice parameter α increase linearly from 0.5072 to 0.5105 nm with increasing Al₂O₃ content. At higher temperatures, transformation of the solid solutions proceeds as follows: c ( SS ) → t ( ss ) → t ( ss ) +α-Al₂O₃→ m +α-Al₂O₃. m -ZrO₂–α-Al₂O₃ composite ceramics are fabricated by hot isostatic pressing for 2 h at 1250°C and 196 MPa. Microstructures and mechanical properties are examined, in connection with increasing Al₂O₃ content.     

CO2 reduction using hydrothermal method for the selective formation of organic compounds

The reduction of CO₂ under hydrothermal conditions has been investigated. In typical experiment, Fe-powder, Ni-powder, solvent, and CO₂ have been reacted in a batch-type micro autoclave under hydrothermal conditions for several hours. Methane, formic acid, and hydrogen were generated after treatment in water. With the rise of Ni amount, the methane yield increased while hydrogen and formic acid decreased. It is supposed that Ni has acted as a hydrogenation catalyst. In basic solution, CO₂ was converted to formic acid selectively at 300°C involved with trace of methane. Considering the reduction characteristics of formic acid, the reaction pathway has been discussed. In experiments with the mixture of Fe and Fe₃O₄, trace of methanol was detected at the experiments with less amount of metallic Fe. It is inferred that the control on the effect of reductant is indispensable for oxygenated organic compound formation. Experiment on the effect of water has been conducted using hydrogen. Ethane yield increased with the amount of water, while there was no drastic change in the yield of methane. From these results, it is supposed that the steam reforming reaction of methane was involved in the reduction of CO₂, and effected on the C–C bond formation.     

Viscosity of Gaseous Mixtures of HFC-125 + Propane from 298.15 to 423.15 K at Pressures to 6.7 MPa

This paper reports experimental results for the viscosity of gaseous mixtures of HFC-125 (pentafluoroethane) + propane. The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K. The viscosity was measured for two mixtures containing 50.11 and 75.03 mol% HFC-125 in propane. The viscosity at normal pressure was analyzed with the extended law of corresponding states developed by Kestin et al., and the scaling parameters were obtained for unlike-pair interactions between HFC-125 and propane. The modified Enskog theory developed by Vesovic and Wakeham was applied to predict the viscosity for the binary gaseous mixtures under pressure. From comparisons between experimental results and calculated values of the HFC-125 + propane system, it should be concluded that the Vesovic-Wakeham method gives reliable predictions for the viscosity of a gaseous mixture containing both polar and nonpolar compounds.     

Magnetic Correlation in BETS2(Cl2TCNQ)

We carried out⁷⁷Se NMR measurements on BETS₂(Cl₂TCNQ) under pressure in order to investigate the magnetic properties of the insulating state which appears above 0.6 GPa. The relaxation rate 1/T₁ at 0.7 GPa shows small peak-like anomaly at 20 K, indicating a spin density wave transition as observed in BETS₂(Br₂TCNQ).