Study Of Layered Structures Research Articles

Multicomponent Diffusion of Dusty Plasma in PMSE Including the Growth of Dust Particles

AbstractDusty plasma diffusion was applied to model the plasma response to perturbations in dust density, which yields small‐scale irregularities in electron density that are responsible for Polar Mesosphere Summer Echos. Previous diffusion models treated aerosols either as fixed‐charge dust or as multiple‐charge‐state dust using chemical rate equations. The growth of aerosol particles was previously considered in the study of layered structures in mesospheric clouds, but it has not been incorporated into dust diffusion. In this paper, a multicomponent diffusion of a dusty plasma, consisting of electrons, ions, and charged aerosols, is developed, accounting for the growth of the aerosols. It is shown that, for typical parameters in polar mesopause region, the evolution of the density structures of the dusty plasma undergoes an initial charging process (approximately 100 s), then an ambipolar diffusion process on ion time scale (approximately hundreds of seconds), and the aerosol diffusion on dust time scale (>104 s). Furthermore, the growth of the aerosols retards the dust diffusion and causes the transition from anticorrelation to correlation between the electron and ion density perturbations (contrary to only anticorrelation or correlation as in the case without considering the growth). The growth also bends the density profiles from upward shifting to downward sedimentation. In addition, larger initial grain radius and the width of the initial perturbation result in slower diffusion. The diffusion is much faster at 88 km than at 82 km.

Thermal stress analysis of laminated structures by a variable kinematic MITC9 shell element

ABSTRACTA linear static thermal stress analysis of composite shell structures is carried out by means of a shell finite element with variable through-the-thickness kinematic. The refined models used are both Equivalent Single Layer (ESL) and Layer Wise (LW) and they are grouped in the Unified Formulation by Carrera (CUF). These models permit the distribution of displacements, stresses and temperature along the thickness of the multilayered shell to be accurately described. The Principle of Virtual Displacement (PVD) is employed to derive the governing equations. The Mixed Interpolation of Tensorial Components (MITC) method is used to contrast the membrane and shear locking phenomenon for a nine-node shell element. Cross-ply plate, cylindrical and spherical shells with simply supported edges and subjected to bi-sinusoidal thermal load are analyzed and various thickness ratios are considered. The results, obtained with different theories contained in the CUF, are compared with both the elasticity solutions given in the literature and the analytical solutions obtained using higher-order models and Navier's method. From the analysis, one can conclude that the shell element based on the CUF is very efficient, and its use leads to reach higher accuracy than classical models in the study of layered structures.

Study of layered structures using modified acoustic resonator spectroscopy

A software package that makes it possible to record scans of the microwave spectrum of the high-overtone bulk acoustic resonator (HBAR) with an arbitrary frequency step in the entire range of the network analyzer is developed. Parameters (frequency and width) of several thousand resonant peaks can be obtained using the computerized processing of the scans. The proposed procedure allows an increase in the accuracy of the existing method for the measurement of the velocity of acoustic wave in material. For the layers with a thickness of several wavelengths, the method makes it possible to obtain the velocities of waves in the material under study using a single spectrum and does not require the comparison of the HBAR spectra measured prior to and after the deposition of the layer under study.

Study of Layered Structure on Contact Boundary Area of Formation Panasogan-Waturanda by Applying Ground Penetrating Radar Method

Study on Ground-penetrating radar (GPR) data from a common-offset profiling measurement carried out in the contact area between Panosogan and Waturanda Formations in Karangsambung, Kebumen – Central of Java is done. GPR RAMAC system is utilized. The aim of the study is to recognize and eliminate surface-scattering noise and ring-down effects, to image subsurface layered structure and to identify a contact area between Panosogan and Waturanda Formations. The processed data were analyzed with the help of instantaneous attributes and the so-called joint time frequency (JTFA) analysis. Study results show that some diffraction patterns appeared in radargram are resulting from scattering of surface-objects. These can be eliminated with f-k filtering and migration. Ring-down effect resulted from impedance mismatch between subsurface electrical properties and those of antenna is difficult to eliminate. However, it can be well recognized and analyzed in the JTF representation. Instantaneous attributes and JTF analysis are proved to be useful tools in imaging the contact area and subsurface layered structures.

Measurement of positively and negatively charged particles inside PMSE during MIDAS SOLSTICE 2001

A magnetically shielded, charge collecting rocket probe was used on two flights in the MIddle Atmosphere Dynamics and Structure (MIDAS) Studies of Layered STructures and ICE (SOLSTICE) 2001 rocket campaign over Andøya, Norway. The probe was a graphite collection surface with a permanent magnet underneath to deflect electrons. The first MIDAS was launched 17 June 2001 into a strong, multiply layered PMSE. The probe measured negative particles inside an electron biteout within the PMSE, having a peak charge number density of −1500 charges per cubic centimeter. The second MIDAS was launched 24 June 2001 into another strong, multiply layered PMSE. The probe saw a band of positive particles centered in the lowest radar echo maximum, and a negative particle layer accompanied by a positive ion excess. The charge number densities for the positive and negative PMSE particles were several thousand charges per cubic centimeter. Unexpectedly, 2 km beneath the PMSE, the probe also found a very pronounced negative layer, which was probably an NLC. Computer simulations of incoming, negatively charged ice grains were performed using a rarefied flow field representative of the MIDAS payload at zero angle of attack. Ice grains ≤1 nm in radius were diverted by the leading shock front, indicating the smallest detectable ice particle by this probe.

Development and Application of Instrumental Methods for Strain Analysisof Semiconductor Layers and Devices

Strain effects on semiconductor layers were studied by means of optical spectroscopic techniques with a device developed especially for the study of layered structures and microstructures. Raman, modulated photoreflectance and reflectance anisotropy spectroscopy (RAS) were applied. Measurements were performed on elemental semiconductors (Si), semiconductor alloys (Si–Ge) and III–V semiconductor compounds (GaAs). By application of RAS, strains lower than 10−4 could be resolved, which is at least one order of magnitude lower than those observable with Raman and modulated reflectance techniques. The RAS spectra of layers strained along either the [010] or [011] direction showed a derivative-like structure at E1-gap energies, which increased linearly and very quickly with increasing strain. The dependence of this spectral feature on applied strain was used to evaluate strain-dependent effects. This behaviour strongly suggests that RAS can be applied for the optical characterisation of strain in semiconductor microstructures and devices, with a higher efficiency and accuracy than that achieved by previously established optical methods such as Raman and modulation spectroscopy. In addition, the compactness and ease of operation of the instrumentation of RAS provides considerable potential for in situ monitoring/control of semiconductor fabrication conditions.

Application of resonance-enhanced X-ray standing waves to the study of layered structures by grazing-incidence X-ray reflectometry and secondary radiation

Abstract In this work we present a review of results on reflectivity, fluorescence and photoelectron spectra investigated in layered samples, in which resonance-enhanced X-ray standing waves (RE–XSW) are formed. The new experimental results of photoelectron energy distribution excited in a thin carbon film deposited on a Ni mirror, as well as results obtained earlier, are compared and discussed. The new photoelectron measurements were performed using a conventional X-ray tube as radiation source for the energy Cu Kα (8047 eV), and recorded with a flow proportional electron counter of about 15% energy resolution. Also, new results of grazing-angle reflectivity from a X-ray waveguide sample recorded with a 13-keV synchrotron radiation is reported. Comparison of the results with theoretical models based on the Fresnel formula and Parratt recursive algorithm is done. The reflectivity and in-depth electric field distribution dependencies on wavelength, roughness, as well as composition of structures are calculated and compared to experimental spectra. The possible fields of application of the resonance-enhanced XSW to the study of layered structures, showing also some limitations inherent to the method are discussed.

Real-Space Multiple Scattering Theory Method: Formalism and Applications

ABSTRACTDifferent forms of the real-space multiple scattering theory (RS-MST) formalism are compared in order to understand its convergence behavior with respect to truncation in the angular momentum expansions. In particular the so-called “folding method” or (1,n) mode is considered, in which the renormalized t-matrix T of the semi-infinite system has the dimension of n (n > 1) repeating units and the self-consistent equation for T is constructed by adding and contracting one such unit. It has been demonstrated in previous studies of layered structures that the folding method converges rapidly in both angular momentum (L) and site (n) indices and yields accurate results. The convergence behavior is an important factor to be considered in applying the various forms of the RS-MST method to layered structures as well as other systems with extended defects.

A REFLECTIVITY AND EXAFS STUDY OF LAYERED STRUCTURES

A REFLECTIVITY AND EXAFS STUDY OF LAYERED STRUCTURES

Backscattering and transmission electron microscopy studies of layered structures

Backscattering and transmission electron microscopy studies of layered structures