Atmospheric optical turbulence over land in middle east coastal environments: prediction modeling and measurements

Beam intensity scintillations, characterized by a refractive-index structure parameter and caused by variations of macrometeorological features of the coastal atmosphere such as air temperature, wind speed and direction, and relative humidity, are examined theoretically and experimentally. In our theoretical analysis we present two well-known models considered separately for over-water and over-land atmospheric optical communication or imaging channels. By means of comparison with our experiments carried out in midland coastal environments in southern and northern Israel, we show the limitations of the models to predict the refractive-index structure Cn2 parameter for both daytime and nighttime turbulent atmospheres in different coastal zone meteorological conditions. We also present an extension of an existing model with two different practical applications that, as is shown experimentally, can be a good predictor of Cn2 for optical atmospheric paths over midland coastal zones.     

Wide-aperture,line-focused ultrasonic material characterization system based on lateral scanning

We present a new wide-aperture, line-focused ultrasonic material characterization system. The foci of the transmitting and receiving transducers are located in the specimen-immersion liquid interface; and the output voltage V(x, t) of the system is recorded as a function of the lateral position of the receiving transducer. The two-dimensional spectrum of V(x, t) can be expressed as a product of the transfer function of the system and the reflectance function of the interface. In comparison with a system based on scanning in the z direction, the angular resolution of the proposed technique increases with decreasing angle of incidence. There are no geometrical restrictions on the length of the recorded spatial data and the angle of incidence in the case of lateral scanning. The temperature coefficient of the measurement error is low because of the constancy of the propagation distance of ultrasound in the immersion fluid during data acquisition.     

Earthquake science research with a microsatellite

Reliable, repeatable earthquake forecast is a subject surrounded by controversy and scepticism. What is clear is that reliable forecast would be a critical tool for effective earthquake disaster management. It is proposed that satellites and ground-based facilities may detect earthquake precursors in the ionosphere a few hours or days before the main shock. A low-cost 100 kg class satellite carrying a topside sounder is proposed, to make systematic measurements over seismically active zones. The mission aims to confirm or refute the hypothesis of ionospheric earthquake precursors, define the reliability and reproducibility, and enable further scientific understanding of their mechanisms.     

Correlation Between <Emphasis Type="Italic">T</Emphasis><Subscript>c</Subscript> and Hyperfine Parameters of Fe in Layered Chalcogenide Superconductors

Although pairing mechanism in unconventional superconductors is still an open question, the density of states at the Fermi level is considered to be one of the factors affecting the superconducting transition temperature. Herein, we report on ⁵⁷Fe-Mössbauer studies of β-FeSe, FeSe _0.5Te _0.5, and Rb _0.8Fe _1.6Se ₂ superconductors as well as two intercalate products consisting of FeSe layers and a lithium-containing molecular spacer in between. In these materials, the hyperfine parameters of ⁵⁷Fe are directly related to the 3d-electron density on Fe atoms and show strong correlation with superconducting properties.     

Investigating factors associated with the spillover effect of investments in telecoms: Do some transition economies pay too much for too little?

One of the routes by which investments in information and communication technologies (ICT) could impact a macroeconomic bottom line of economies is by contributing to total factor productivity (TFP), an important component of economic growth. While the more traditional “investments to revenues” resource-intensive path has been well researched, the nature of the indirect “investments to TFP” link remains much less clear. Specifically, it is not well understood what conditions must be present for economies to exhibit the relationship between investments and TFP. In the current study, conducted in the context of 18 transition economies in Europe and the former Soviet Union, we aim to identify some of the factors associated with the presence of the relationship between the subset of investments in ICT, investments in telecoms, and two components of TFP – change in efficiency and change in technology. The results of the analysis of the data set spanning from 1993 to 2002 suggest that while the presence of the link between investments and change in technology was associated with the level of investments, the presence of the relationship between investments and change in efficiency was associated with the quality of a full-time telecom workforce. The consequent analysis of the data set spanning from 2003 to 2008 supports this finding and also provides evidence of the importance of the macroeconomic strategies that balance an increase in the levels of investments with the increase in the levels of efficiency of utilization of investments and the generation of revenues.     

Control of dynamic microsystems

This paper formulates and solves control problems for nonlinear microsystems which comprise micro-electromechanical devices, micromachined transducers and microelectronics. We perform a consistent dynamic analysis and coherent designs with a minimum level of simplifications using high-fidelity mathematical models. The proposed methodology enables practical implementation for multi-input/multi-output systems due to overall conceptual consistency, design coherence, computational efficiency, algorithmic effectiveness and hardware simplicity. Various issues in nonlinear analysis and control are examined and experimentally verified substantiating design concepts for high-performance microsystems. The reported findings are demonstrated for a proof-of-concept closed-loop electrostatic microactuator.     

Application of the wavelet transform for feature extraction in the analysis of hyperspectral laser-induced fluorescence data

Remote-sensing approaches for environmental protection and exploration have evolved rapidly in the last decade. Among the new operational tools, hyperspectral Fluorescent LiDAR System (FLS®) lidar has demonstrated a high sensitivity and the ability to function in complex environments for real-time, robust oil-spill monitoring on airborne or ship-borne analytical platforms. The capabilities of such analytical platforms include real-time analysis of laser-induced fluorescence (LIF) data. Although numerous examples of the application of signal theory to the analysis of hyperspectral data appear in the remote-sensing literature, the conventional data analysis strategies are not well adapted to the practical issues of the LIF applications. The aim of this article is to provide a new approach for LIF lidar analytical platforms, which is focused on the specifics of hyperspectral LIF data. The approach is based on structural data analysis and interpretation, through which more detailed spectral matching is performed. This article is based on a simulated experiment in which the spectra of actual seawater and well-known types of petroleum products were combined to demonstrate the wavelet-transform-based analysis of LIF data. The final part of the article demonstrates the application of the wavelet transform to the structural analysis of LIF data from field experiments for the detection and identification of oil products in difficult environmental conditions.     

Microwave Dielectrics in the (La1/2Na1/2)TiO3–Ca(Fe1/2Nb1/2)O3 System

Dielectric properties of the system (1 − x)(La_1/2Na_1/2)TiO₃– _x Ca(Fe_1/2Nb_1/2)O₃, where 0.4 # x # 0.6, have been investigated at microwave frequencies. The temperature coefficient of resonant frequency (τ_f), nearly 0 ppm/°C, was realized at x = 0.58. These ceramics had perovskite structure and showed relatively low dielectric losses. A new dielectric material applicable to microwave devices having Q · f of 12000–14000 GHz and a dielectric constant (ε_r) of 59–60 has been obtained at 1300–1350°C for 5–15 h sintering.