Phase transition in electrorheological plasmas

Applying an external electric AC field to a dusty plasma, the micro-particles arrange in strings or chains. In analogy to electrorheological fluids, such a system is called electrorheological plasma. Turning gradually the AC field into a DC field, the string formation is diminished until it vanishes completely in the DC case. In this way, a cross-over transition from a string-like to an isotropic micro-particle many-body system can be investigated. Experimental investigations of electrorheological plasmas are performed under microgravity conditions in parabolic flights. For analysing the image data, a supervised machine learning code was developed and a continuous cross over was found. A molecular dynamics simulation showed qualitatively similar results but also some deviations from the experimental results.     

Analysis of some elements in three Chrysolina (Coleoptera, Chrysomelidae) species by EDXRF spectrometry

In this investigation, the concentration levels of potassium, calcium, iron, nickel and cadmium for three Chrysolina species were measured in the region of Erzurum (Turkey) located at latitude 40°17′ north and longitude 41°17′ east. The concentrations measured by energy dispersive X-ray fluorescence (EDXRF) spectrometry were analysed. Photons of 59.5 keV and 5.9 keV emitted, respectively, by an annular ²⁴¹Am and ⁵⁵Fe radioactive source were used to excite the characteristic X-rays of various elements present in the insect samples. These results are presented and discussed in this paper.     

Point Source of Nonstationary Polarized Radiation in a Homogeneous Fluctuating Medium

Based on the method of irreducible representations of the rotation group, we obtain an analytical expression for the source function of the radiative transport equation with allowance for polarization of light. The scattering indicatrix is assumed Rayleigh. It is shown that not all polarization characteristics of light in a fluctuating medium are lost in time. Some of them always carry information about the emitter and the scattering medium.     

Measurements of K X-ray fluorescence cross sections of Fe,Co, and Ni in an external magnetic field

The effects of the external magnetic field has been investigated on the K XRF cross sections of Fe, Co, Ni, and some of their compounds by using an energy dispersive X-ray fluorescence spectrometer. The samples were irradiated by using the γ-rays of 59.537 keV emitted from an ²⁴¹Am radioisotope source of 100 mCi. The samples were prepared from pure foil of Fe, Co, Ni, and some of their compounds. The external magnetic fields have been applied two opposite directions and the magnitude of the external magnetic field has been fixed at 0.400 T and −0.400 T. The measured K XRF cross sections have been compared with the calculated theoretical data and interpolated values of Puri et al. Our experimental results show that the K XRF cross sections have been affected by the external magnetic field.     

The spatial polarization distribution over the dome of the sky for abnormal irradiance of the atmosphere

The paper deals with the polarized radiative transfer within a slab irradiated by a collimated infinitely wide beam of arbitrary polarized light. The efficiency of the proposed analytical solution lies in the assumption that the complete vectorial radiative transfer solution is the superposition of the most anisotropic and smooth parts, computed separately. The vectorial small-angle modification of the spherical harmonics method is used to evaluate the anisotropic part, and the vectorial discrete ordinates method is used to obtain the smooth one. The azimuthal expansion is used in order to describe the light field spatial distribution for the case of abnormal irradiance and to obtain some known neutral points in the sky especially useful for polarized remote sensing of the atmosphere.     

Analytical modeling of chatter stability using multi-dimensional approach

Machining is one of the most common manufacturing processes in industry due to its high flexibility and ability to produce parts which excellent quality. Chatter, a type of self excited vibrations arising in metal cutting operations, is a major limitation in machining resulting in poor quality and reduced productivity. Under certain conditions, the cutting process may become unstable yielding oscillations with high amplitudes and cutting forces. Stability analysis of the dynamic cutting process can be used to determine chatter-free machining conditions with high material removal rate. Usually, one dimensional models are used for stability analysis of machining. However, based on the geometry of the actual machining process, multi-directions would have to be used for accurate modeling of the process dynamics and the stability. In this presentation, multi directional models for turning and milling processes are presented. The effects of multi directional process mechanics on the stability are demonstrated by applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)