Nuclear Data Sheets for A = 116

The 1960 version of the Nuclear Data Sheets for A = 116 has been revised on the basis of experimental data received before August 1973, with some later modifications received via private communications. Experimental data concerning the nuclear structure of ten isotopes were compiled and used in the construction of the level schemes and J^π-assignments.     

Synthesis and characterization of poly(keto-amines). 1. Self polycondensation of 4-aminophenacyl chloride

Novel poly(keto-amines), designated as poly(4-iminophenacyls) are prepared by self polycondensation of 4-aminophenacyl chloride under different experimental conditions. These polymers are insoluble in common solvents. The number average molecular weights of the polymer samples have been estimated by conductometric titration of a suspension of the polymer sample in formic acid against a standard perchloric acid. The polymer samples have been characterized by a comparative study of their IR spectra with those of the probable model compounds and by differential thermogravimetric analysis.     

Statistical models for renal micropuncture studies

Statistical issues relating to data analysis of re-collection micropuncture experiments are presented. In the presence of significant animal-treatment interaction, namely, differential response of each animal at different levels of the treatment, the conventional paired or unpaired t testing would not be entirely appropriate. Accordingly, two analysis of variance (ANOVA) models have been derived for the appropriate paired and unpaired designs of micropuncture experiments. Interactive computer programs have been written for both these analyses, and the results are illustrated with experimental data. An example is presented in which the results are statistically significant with paired t testing and by analysis of variance for unequal number of tubules but not when the animal-treatment interaction is included in the analysis of variance model. To investigate linkage in renal transport mechanisms, we propose the use of partial correlation analysis. Experimental results from our laboratory are used to illustrate these techniques.     

Optimization of multi-cell wings for strength and natural frequency requirements

The present work determines the optimal number of cells for minimum weight design of an aircraft wing under strength and natural frequency constraints for the two cases (i) uniform loading and (ii) a tip moment. Two SUMT optimization algorithms with and without parameters have been used and suggestions for faster convergence for one have been given. The importance of different starting design points and convergence criteria in getting the constrained minimum has been shown. The variables considered are length, chord, skin thickness and various spar thicknesses. The natural frequency has been obtained by the use of exact continuum theory of cylindrical tubes, and comparison with elementary theory has been made. The optimization results indicate that increasing the number of cells beyond two does not lead to any substantial reduction or increase in weight. Also, stringent convergence criterion and more than one starting point are necessarry for better results.     

Single- and dual-polarized millimeter-wave slot-ring antennas

Single- and dual-polarized dielectric lens-supported slot-ring antennas have been developed for operation at millimeter-wave frequencies. The antennas are fed with a coplanar waveguide (CPW) to be compatible with uniplanar mixers and low-noise amplifiers, and the feedline is shown to have a minimal effect on the antenna performance. The measured antenna patterns agree well with theoretical results and have symmetric main beams, low sidelobe levels (<-15 dB), low cross polarization (<-20 dB), and 27 dB directivity. A 2×2 array of single-polarized slot-ring antennas for monopulse applications demonstrates excellent patterns at 94 GHz with -3 dB crossover power levels in both elevation and azimuth scans. The dual-polarized slot ring antenna patterns are nearly identical to those of the single-polarized antenna, and two-port isolation is as low as -25 dB. The dielectric lens-supported slot-ring antenna is an excellent candidate for compact, low-cost millimeter-wave systems with fixed or variable polarization capabilities     

Cognitive Radio and Networking Research at Virginia Tech

More than a dozen Wireless @ Virginia Tech faculty are working to address the broad research agenda of cognitive radio and cognitive networks. Our core research team spans the protocol stack from radio and reconfigurable hardware to communications theory to the networking layer. Our work includes new analysis methods and the development of new software architectures and applications, in addition to work on the core concepts and architectures underlying cognitive radios and cognitive networks. This paper describes these contributions and points towards critical future work that remains to fulfill the promise of cognitive radio. We briefly describe the history of work on cognitive radios and networks at Virginia Tech and then discuss our contributions to the core cognitive processing underlying these systems, focusing on our cognitive engine. We also describe developments that support the cognitive engine and advances in radio technology that provide the flexibility desired in a cognitive radio node. We consider securing and verifying cognitive systems and examine the challenges of expanding the cognitive paradigm up the protocol stack to optimize end-to-end network performance. Lastly, we consider the analysis of cognitive systems using game theory and the application of cognitive techniques to problems in dynamic spectrum sharing and control of multiple-input multiple-output radios.     

Computer‐aided design methodology for linearity enhancement of multiwatt GaN HEMT amplifiers using multiple parallel devices

This article presents a design methodology for linearizing GaN HEMT amplifiers based on splitting a large FET into multiple parallel FETs with same total gate periphery and by biasing them individually. By varying the biases, the magnitude and the phase of the IMD3 components at the output of FET changes. A detailed simulation methodology using commercial microwave CAD software is presented. Simulation results show that by biasing one device in Class AB and other(s) in deep Class AB mode, IMD3 components of parallel FETs can be made out of phase to each other leading to cancellation and improvement in linearity. Three prototype circuits were simulated using (a) a single 5 mm FET (1 × 5 mm), (b) two parallel 2.5 mm FETs (2 × 2.5 mm), and (c) four parallel 1.25 mm FETs (4 × 1.25 mm), for a total gate periphery of 5 mm, over the frequency range of 0.8 to 1.0 GHz. IMD3 improvement up to 20 dBc was achieved with the 4 × 1.25 mm circuit when the FET biases were optimized. Measurement results show improvement in linearity up to 20 dBc for 4 × 1.25 mm circuit. The proposed method improves linearity without a substantial penalty on the power consumption and is straightforward to implement.     

Spectroscopic and Simulation Analysis of Facile PEDOT:PSS Layer Deposition-Silicon for Perovskite Solar Cell

In this research work, we have characterized and simulated a well-known hole transport material (HTM) for perovskite solar cell (PSC) and conductive polyme     

Intrinsically conducting polymers in flexible and stretchable resistive strain sensors: a review

Journal of Materials Science - Flexible and stretchable strain sensors are in great demand in advanced health care, human–machine interface, stretchable electronics, electronic skin, etc. Of...