Electron and plasma stream reflection at a nonadiabatic mirror

Experimental investigations of the phenomena occurring when low density electron and plasma beams are injected into a nonadiabatic magnetic mirror are presented. Effects of nonadiabaticity and mirror ratio on the reflectivity of the magnetic mirror are measured. Transition of the mirror from adiabatic to strongly nonadiabatic results in setting up of a potential barrier which enhances the reflectivity.     

Formation of Mg2Ni nanofibres in a Mg-based metal matrix composite

A Mg–Mg₂Ni nano-eutectic and MgO-reinforced Mg-based metal matrix composite (Mg-MMC) was synthesized by in-situ reactions. When a Mg-rich sample containing 20?wt%?NiO is sintered at 420°C, MgO, Ni and Mg₂Ni are formed in the Mg matrix. When a sample molten at 550°C is furnace-cooled to room temperature, a lamellar two-phase Mg–Mg₂Ni eutectic is formed, with the Mg₂Ni lamella about 1.5?µm thick. Proeutectic Mg together with the MgO formed in situ act as heterogeneous nuclei for the growth of the Mg–Mg₂Ni eutectic. Quenching the molten sample to room temperature results in a lamellar two-phase eutectic containing Mg₂Ni nanofibres. In the eutectic grown at the Mg grain, the Mg₂Ni nanofibres with a diameter of about 25?nm are bent, whereas in the eutectic grown at the MgO grain, the Mg₂Ni nanofibres with a diameter of about 30?nm are long and straight, while the Mg phase of this eutectic is oxygen enriched. The differences in morphologies between the two Mg–Mg₂Ni eutectics are ascribed to the growth rates of Mg and Mg₂Ni, which differ in the eutectic grown at the Mg grain, but remain similar when growth takes place at the MgO grain.     

Preparation of ZnO nanopowders by thermal plasma and characterization of photo-catalytic property

Nano-sized zinc oxide (ZnO) powders were prepared via a thermal plasma process from micro-sized zinc powder while oxygen was employed as a reaction gas. Two different carrier gases, oxygen and argon, were evaluated and the flow rate of the reaction gas was controlled. The photo-catalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV and visible region. The prevailing goal of this study is to improve the photo-catalytic activity of nano-sized ZnO powders for the removal of environmental pollutants. The ZnO nanopowders were characterized by XRD, SEM, BET, and UV-vis spectrometry. Their mean crystallites sizes ranged from 26.5 nm to 48.6 nm. It was confirmed by a XRD analysis that the ZnO nanopowders had a high quality wurtzite structure. SEM and XRD results show that the size of the particles synthesized increased with an increase of the flow rate of the oxygen reaction gas. The powder obtained using the argon carrier gas with higher oxygen reaction gas flow rate was more rod-shape. The MB decomposition rates of the obtained ZnO nanopowders were studied under the UV and visible region. In the UV region, synthesized ZnO could decompose MB as well as commercial ZnO. However, in the visible region, the MB decomposition rate obtained using ZnO was much higher than that by commercial ZnO.     

Passage of radio waves through a stream of low-temperature turbulent plasma

Institute of Radio Engineering and Electronics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 7, pp. 804–812, July, 1990.     

Mg2Ni分子的结构和势能函数

采用密度泛函B3LYP方法在6-311+g(d,p)基组水平上对MgNi、Mg2和Mg2Ni分子的各种可能的结构进行优化,得到了它们的几何构型、平衡核间距、离解能和谐振频率.采用最小二乘法拟合MgNi和Mg2分子的Murrell-Sorbie势能函数,在此基础上导出光谱数据和力常数.通过多体项展式理论导出Mg2Ni分子的解析势能函数,并绘出了Mg2Ni分子的等值势能面,其等值势能面正确地反应了基态Mg2Ni分子的平衡构型特征.     

Quenching of the plasma oscillation in the counter stream type beam-plasma interaction

It is shown experimentally that uenching by an external wave of a natural oscillation in the electron beam-plasma interaction of counter stream type occurs at discrete frequencies resonantly, where the velocity distribution function of beam electrons does not change substantially.     

Description of the relativistic plasma stream corotating with the pulsar magnetosphere

The equation of the motion of the relativistic plasma stream which corotates with the pulsar magnetosphere written in the noninertial frame of a rotating magnetic field line and the same equation written in the rest inertial frame are compared with each other. The possibility of the freezing-in condition use in the rest inertial frame is discussed.     

等离子体微波辐射简介和研究进展

近年来,等离子体微波辐射作为新兴高功率微波源,因其具有频带宽、相干和可调谐等优点,因而受到国际上的广泛关注.本文着重介绍了几种典型的等离子体微波辐射理论和实验研究现状,包括电子束与等离子体互作用、等离子体局部扰动、三波互作用等.     

Theory of two-proton radioactivity with application to 19Mg and 48Ni

If the soft supersymmetry (SUSY) breaking masses and couplings are complex and cancellations do take place in the SUSY induced contributions to the fermionic electric dipole moments, then the CP-violating soft phases can drastically modify much of the known phenomenological pattern of the minimal supersymmetric standard model. In particular, the squark loop content of the dominant Higgs production mechanism at the Large Hadron Collider, the gluon-gluon fusion mode, could be responsible for large corrections to the known cross sections.     

Convective model of a microwave discharge in a gas at atmospheric pressure in the form of a spatially localized plasma

Experiments and a theoretical model consistent with them are presented which show that a stationary microwave discharge in a gas at atmospheric pressure under the action of free convection due to the action of the buoyant force on the heated air can be spatially localized, taking a spheroidal shape. Vortex motion inside the spheroid gives this localized plasma formation some of the properties of a material body which are manifested in a distinct material isolation from the surrounding space, in the formation of a narrow thermal boundary layer and flow separation, and in the formation of secondary vortices in the wake region. The characteristic radius of the stationary localized plasma is governed mainly by the wavelength of the microwave radiation a∼0.137λ. Energy balance is established to a significant degree by convective cooling of the microwave-heated structure. Zh. éksp. Teor. Fiz. 112, 877–893 (September 1997)     

Diffraction of electromagnetic waves by a half-plane which is permeable to a stream of cold plasma

Diffraction of plane electromagnetic waves by a conducting half-plane located in an orthogonal stream of cold plasma is studied. It is assumed that the half-plane has almost no mechanical effect on the particles of the medium. (For example, the half-plane can be a model of a metal grid with fairly small cells.) The general solution of the problem has been obtained by the Wiener-Hopf-Fock technique. The scattering field containing waves of two types is studied analytically and numerically. The behavior of these waves away from the half-plane edge is analyzed. It is shown that the electric field at the edge is finite, and the shadow area is absent under certain conditions. Radiophysical Research Institute of the State University of St. Petersburg., Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40. No. 4, pp. 399–419, April, 1997.     

Flame-fluorescence detection of Mg,Ni, and Pb with a frequency-doubled dye laser as excitation source

The determination of traces of Mg, Ni, and Pb by atomic fluorescence spectrometry using frequency doubled dye laser emission for excitation is reported. Low detection limits and long linear analytical working curves demonstrate the qualification of this method for quantitative analysis.     

Erosion of polyimide modified by amorphous silica sol in the stream of oxygen plasma

Polymeric coatings derived from Kapton H polyimide, thermoplastic polyimide (PI), and a composite with amorphous silica sol (PI-SS) were irradiated in a magnetoplasma dynamic accelerator of oxygen plasma simulating the action of atomic oxygen (AO). The volumetric erosion coefficients of polymers were calculated, and the comparative analysis of the stability of coatings was performed. The changes in morphology of polymer surfaces before and after irradiation were studied by means of scanning electron microscopy. It was shown that the PI-SS composite has increased resistance to atomic oxygen. The composition of the PI-SS composite was found at which the particles of silica sol are uniformly dispersed over the polymer volume that explains a better resistance of PI-SS polymeric-inorganic compositions to the action of atomic oxygen. The lowest stability was registered for the coating based on Kapton H polyimide. The surfaces of all coatings after irradiation were found to possess a carpetlike morphology. Each polymer featured a number of distinctive peculiarities of the surface structure caused by the differences in the chemical structure of the polymides under investigation.     

Probing the microstructural evolution of polyviologen-silica hybrid nanopowders during intermediate processing using X-ray microtomography

Polyviologen polymers are potential template agents for hydrolytic sol–gel processing of silica particles. The resultant polyviologen-silica hybrid nanopowders are amorphous aggregates of roughly spherical shape, which can be harvested from the sol–gel solution and processed to green body products under different environmental conditions. A bench-top X-ray microtomography system, with a spatial resolution of 5 μm is used to produce three-dimensional images of the dynamic processing of the nanopowders. Various processing routes are imaged using a custom built environmental chamber where the temperature, atmospheric pressure, and compaction force can be controlled. This allows processes such as vacuum sintering and microwave sintering to be studied. The three-dimensional images reveal the axial and radial distributions of the molten polyviologen polymer within a matrix of agglomerates of the silica nanoparticles. Such observations are crucial to the optimisation of the processes that are used to produce the green body products so as to preserve desirable nano-intensive properties. PACS 82.35.Np; 87.59.-e; 81.07.Pr; 87.59.Bh