A very high frequency radio interferometer for investigating ionospheric disturbances using geostationary satellites. Determination of changes in exospheric electron content by a comparison of group delay and Faraday rotation

The theory and development of a VHF correlation radio interferometer for investigating ionospheric disturbances are discussed. The system was developed to receive signals from the geostationary Applications Technology Satellites. Amplitude and phase variations of the signal passing through the ionosphere can be detected by this instrument. The system consists of two superheterodyne receivers separated by a distance known as the baseline of the system. Since the system is a phase sensitive instrument, the local oscillators of the two receivers must be phase coherent. This is accomplished by using phase-locked loops for generating the local oscillators. The two signals from the separate receivers are cross-correlated by multiplying the two signals together and then time averaging the result. The sensitivity of the instrument is increased by off-setting one of the local oscillators by a small amount

Backscatter Inversion in Spherically Asymmetric Ionosphere

It is Well Known that Various Diurnal and Morphological Features of the Ionosphere Reveal Substantial Departures from the Normally Simplified Assumption of Spherical Symmetry at Certain Times of the Day or at Certain Geographic Locations. a Radio Ray Passing through Such an Ionosphere Must Bear Information About its Horizontal Gradients. the Leading Edge of a Backscatter Ionogram is Formed by Obliquely Propagated Radio Rays of Minimum Time Delay and Hence is Useful in Deducing Information About the Ionospheric Horizontal Gradients. in This Regard, the Ionospheric Electron Density Distribution is Modeled by a Locally Quasi‐parabolic Layer with Six Parameters. This Six‐parameter Space is Known as the \u27ion state.\u27 Our Object is to Seek the \u27best\u27 Ion state in the Sense that the Corresponding Mean Square Error in Group Delay is a Minimum. a Computer Program Has Been Written to Carry Out the Specified Procedure. a Number of Sample Calculations Are Presented and Discussed. Copyright 1979 by the American Geophysical Union

Modeling of Dielectric Mixtures Containing Conducting Inclusions with Statistically Distributed Aspect Ratio

An analytical model of composites made of a dielectric base and randomly oriented metal inclusions in the form of nanorods is presented. This model is based on the generalized Maxwell Garnett (MG) mixing rule. In this model, the nanorod particles are modeled as prolate spheroids with a statistically normal distribution of their aspect ratios. It is shown that parameters of the distribution laws affect the frequency characteristics of the composites both at microwave and optical frequencies. The results of computations are represented

Expert System Algorithms for Identifying Radiated Emission Problems in Printed Circuit Boards

Radiated emission algorithms for a printed circuit board EMC expert system are described. The expert system mimics the thinking processes that human EMC engineers would use to analyze circuit boards and make design recommendations. Working with limited information about the enclosure, cables or the exact nature of the signals, the expert system evaluates different structures on the printed circuit board looking for potentially strong radiated emission sources. Results obtained from the analysis of a sample printed circuit board are provided to demonstrate how the expert system quickly identifies problems that would otherwise be difficult to locate

A Circuit Approach to Model Narrow Slot Structures in a Power Bus

A coupled transmission line model for narrow slot structures in DC power planes is proposed. This approach, combined with SPICE-based cavity models and a segmentation method, provides an easy and fast way to model relatively complex structures of power planes with narrow slots often used for isolation purposes. This approach is used to achieve isolation using gapping. The cavity model formulations for rectangular and isosceles right triangular segments are reviewed. The rationale of modeling the narrow slot as a three-conductor transmission line is described. The modeling results are shown and compared with the output of a full wave simulation tool, HFSS, and with experimental measurements

Validation of Equivalent Circuits Extracted from S-Parameter Data for Eye-pattern Evaluation

S-parameter circuit model extraction is usually characterized by a trade off between accuracy and complexity. Trading one feature for another may or may not affect the goodness of the reconstructed S-parameter data, which are obtained from frequency domain simulations of the models extracted. However, the ultimate test for the validity of these equivalent circuit representations should be left to eye-diagram simulations, which provide useful insights, from an SI point of view, about the degradation of the signal, as it travels through the system. Physics based simplication procedures can be used to tune the models and achieve less complexity, whereas the comparisons of the eye-diagrams may help to quantify the goodness of an these circuits extracted. In fact, the most accurate model is not necessary the best to be used

Axonal Dynamics of Excitatory and Inhibitory Neurons in Somatosensory Cortex

Electrophysiology-delivery of fluorescent viral vectors-and two-photon microscopy were used to demonstrate the rapidity of axonal restructuring of both excitatory and inhibitory neurons in rodent cortical layer II/III following alterations in sensory experience

Molecular imaging of pulmonary inflammation in electronic and combustible cigarette users: a pilot study.

Electronic cigarette (EC) use has increased dramatically, particularly among adolescents and young adults, which, like cigarette use, can cause pulmonary inflammation and increase the risk of lung disease. This preliminary study used positron emission tomography with F-6-(1/2)(2-fluoro-propyl)-4-methylpyridin-2-amine (F-NOS) to quantify inducible nitric oxide synthase (iNOS) expression to characterize oxidative stress and inflammation in the lungs in vivo in three age- and sex-matched groups: (1) 5 EC users, (2) 5 cigarette smokers, and (3) 5 never smoke/vape controls. EC users showed greater F-NOS non-displaceable binding potential (BPND) than cigarette smokers ( = 0.03) and never smoke/vape controls ( = 0.01); whereas BPND in cigarette smokers did not differ from controls (p> 0.1). F-NOS lung tissue delivery and iNOS distribution volume did not significantly differ between groups. Although there were no group differences in peripheral inflammatory biomarker concentrations, F-NOS BPND correlated with the pro-inflammatory cytokine tumor necrosis factor-α concentrations (rs= 0.87, = 0.05) in EC users. Additionally, when EC users and cigarette smokers were pooled together, vaping episodes/cigarettes per day correlated with interleukin-6 levels (rs= 0.86, = 0.006). This is the first PET imaging study to compare lung inflammation between EC and cigarette users in vivo. We found preliminary evidence EC users had greater pulmonary inflammation than cigarette smokers and never smoke/vape controls, with a positive association between pulmonary and peripheral measures of inflammation

New Sensors and Sensor Fusion for a Ground-based Land Mine Detection System

The complexity of the detection and discrimination problem for land mines requires that multiple sensors and algorithms be employed. We have been attempting to develop a range of new sensors and sensor combinations that will contribute to the solution to this problem. The sensors discussed in this paper include heated waterjets combined with infrared images, non- contact acoustic focusing, and the detection of electromagnetic emissions from smart land mines