On the absence of shear cracking and grain boundary cavitation in secondary tensile regions of Ti–6Al–4V–0.1B alloy during hot (α + β)-compression

Deformation instabilities, such as shear cracking and grain boundary cavitation, which are observed in the secondary tensile region of Ti–6Al–4V alloy during compressive deformation in the (α?+?β)-phase field, do not form in Ti–6Al–4V–0.1B alloy when processed under the same conditions. This has been attributed to the microstructural modifications, e.g. the absence of grain boundary α and adjacent grain boundary retained β layers and a lower proportion of 90^o-misoriented α-colonies that occur with boron addition.     

Formation of Composites in the System of Organic Europium Complexes–Silica

Lanthanide doped sol–gel glasses are an attractive type of luminescent material which can be processed at ambient temperatures. However, it is very difficult to obtain a uniform distribution of the complexes in glass materials because of their strong tendency to cluster formation. This problem can be solved by covalently linking of lanthanide complexes to silica matrix. In our work such materials were obtained by the sol–gel method of hydrolysis and polycondensation of tetramethoxysilane with europium complexes containing trimethoxysilyl groups. For this purpose we synthesized a novel ligand — (N-3-trimethoxysilylpropyl)-N′-1,10-phenanthroline-5-yl-thiocarbamide — and corresponding complexes [Eu(tta)₃phen′]Cl₃ and [Eu(pta)₃phen′]Cl₃. Our approach enabled us to simplify the synthetic procedure. A number of uniform samples showing intense luminescence have been obtained and the concentration dependence of their luminescence has been studied.     

Sliding Wear Studies on Aluminium–Copper Composites

Metal–metal composites are prepared by dispersing copper particulates in an aluminium matrix using stir-cast technique. Behaviour of the same is compared with the alloy having similar composition. Wear behaviour of the alloy in the cast condition is superior to the homogenized condition, though cast structure exhibit low hardness compared to the other. This is attributed to the easy crack propagation along the CuAl₂ precipitates in the homogenized condition, compared to the grain boundary in the as-cast structure. Wear properties of the resultant composite are superior to the alloy. Effect of particulate composition is studied by varying the copper concentration between 5 and 15 wt%. Composites with high copper content exhibit better wear resistance than the dilute ones, which is attributed to the increased hardness due to large population of intermetallics.     

ХроматограФкчеекое разделеиие изотоиов җелеза

Es werden Aufbau, Arbeitsweise und Eigenschaften einer Apparatur beschrieben, mit der natiürliche Tritium-Aktivitäten in Oberflächen- und Grundwässern gemessen werden können. Diese Messungen erfolgen in 4 Arbitsschritten: elektrolytische Anreicherung der natiärlichen Tritium-Konzentrationen, Messung des Anreicherungsfaktors mit einem Flüssigkeitsszintillationszähler, Synthese von Äthan aus dem angereicherten Probenwasser und tritiumfreiem Acetylen, Messung des Probentritiums in Äthan mit einem Proportionalzähler. Die untcre Nachweisgrenze (Meβzeit 48 Studnden, statistischer Fehler 50%) beträgt 1 T.E.     

Specifications of dust-ion-acoustic shock waves affected by dust charge variation in four-component dissipative quantum plasma

ABSTRACT

Nonlinear propagation of dust-ion-acoustic shock waves in an unmagnetized, collisionless four-component quantum plasma containing electrons, positrons, ions and negatively charged dust grains affected by dust charge variations and viscosity of ions is studied using quantum hydrodynamic model. Considering dust charge variation give rise to calculating of charging currents of the plasma particles. These currents have been calculated with orbit limited motion theory and using Fermi-distribution functions or Boltzmann–Maxwell distribution depending on quantum or classical particles, respectively. The basic characteristics of quantum dust-ion-acoustic shock waves are investigated by deriving Korteweg–de Vries–Burgers equation under the reductive perturbation method. Depending on the relative values of the dispersive and dissipative coefficients, oscillatory and monotonic shock waves can propagate in the plasma model. The effect of chemical potential and density of dust particles on the shock wave’s height and thickness is investigated. In addition, the critical value of H (H_c) is calculated and it is shown that for R?>?0 compressive shock waves and for R?<?0 rarefactive ones can exist. The present study is applicable to researchers on quantum nonlinear structures in dense astrophysical objects and ultra-small micro- and nano-electronic devices.     

EPR of Cu2+-doped Cs2CO3 and CsHCO3: evidence of the Jahn–Teller effect

Cu²⁺-doped Cs₂CO₃ and CsHCO₃ single crystals were investigated by electron paramagnetic resonance between 113–273 and 173–313 K, respectively. For both single crystals, two sites were observed for the Cu²⁺ at ambient temperature for arbitrary orientations of the single crystals in the magnetic field. However, when the temperature is varied, the spectra indicate the equivalence of the two sites at 225 and 240 K for the single crystals, respectively, to the above order. Below and above these temperatures two sites for Cu²⁺ appear, and below 133 and 173 K the signals do not vary and two sites were always observed. This is attributed to the transition of the dynamic Jahn–Teller effect to a static situation at lower temperatures. Cu²⁺ seems to replace Cs⁺ and the charge compensation is fulfilled by another Cs⁺. Spin-Hamiltonian parameters for both single crystals at ambient temperature are reported and discussed.     

Detection on micro-Doppler effect based on 1550 nm laser coherent radar

A laser coherent detection system of 1550 nm wavelength was presented, and experimental research on detecting micro-Doppler effect in a dynamic target was developed. In this paper, the return signal in the time domain is decomposed into a set of components in different wavelet-scales by multi-resolution analysis, and the components are associated with the vibrational motions in a target. The micro-Doppler signatures are extracted by applying the reconstruction (inverse wavelet transform). During the course of the final data processing frequency analysis and time–frequency analysis are applied to analyze the vibrational signals and estimate the motion parameters successfully. The experimental results indicate that the micro-Doppler information in a moving can be effectively detected, and tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analysis and time–frequency analysis.     

Modeling emissivity of low-emissivity coating containing horizontally oriented metallic flake particles

The scattering and absorption cross sections of horizontally oriented metallic flake particles are estimated by extended geometric optics that includes diffraction and edge effects. Emissivity of the coating containing those particles is calculated using Kubelka–Munk theory. The dependence of emissivity of the coating on the radius, thickness, content of metallic flake particles and coating thickness is discussed. Finally, theoretical results are compared with the experimental measurements with Al/acrylic resin coating system and the results show that simulation values are in good agreement with experimental ones.