Two-photon excitation of nitric oxide fluorescence as a temperature indicator in unsteady gas-dynamic processes

A laser induced fluorescence technique, suitable for measuring fluctuating temperatures in cold turbulent flows containing very low concentrations of nitric oxide is described. Temperatures below 300 K may be resolved with signal to noise ratios greater than 50 to 1 using high peak power, tunable dye lasers. The method relies on the two photon excitation of selected ro-vibronic transitions. The analysis includes the effects of fluorescence quenching and shows the technique to be effective at all densities below ambient. Signal to noise ratio estimates are based on a preliminary measurement of the two photon absorptivity for a selected rotational transition in the NO gamma (0,0) band

A method for the prediction of detection ranges for pulsed doppler radar

Modern radar systems must provide greater detection ranges both against high and low altitude targets because of the significant advances in weapon speed and range. Extended range indicates that the power transmitted by the radar must be increased. It follows, that ground return becomes a problem even at high altitudes. There are at present three basic types of radars which are (1) pulsed, (2) continuous wave, and (3) pulsed doppler radar. The conventional pulsed radar now closely approaches the theoretical optimum performance; however, it does not have the inherent ability to distinguish between ground return and moving targets. The continuous wave radar has the ability to distinguish between fixed and moving targets but does not retain the time form of the information and also the continuous wave radar has practical difficulties which limit the usefulness of this system in airborne applications. The pulsed doppler radar detects the doppler frequency shift of moving targets, as in the continuous wave radar, while retaining the time form of the returned information as in pulsed radar systems. It is important to be able to evaluate and predict the operation of a radar as well as the comparison of different radars. Range performance and detection range capabilities are methods by which radars are compared and their operation predicted. Statement of the problem. It is the purpose of this study to present a method for computing the range performance of an air-interceptor pulsed doppler radar in terms of detection ranges. The analysis of the detection range performance includes target scintillation --The Problem and Definitions of Terms Used, pages 1-2

Path Planning for Aircraft Under Threat of Detection from Ground-Based Radar with Uncertainty in Aircraft and Radar States

Mission planners for manned and unmanned aircraft operating within the detection range of ground-based radar systems are often concerned with the probability of detection. Several factors influence the probability of detection, including aircraft position and orientation, radar position, and radar performance parameters. Current path planning algorithms assume that these factors are known with certainty, but in practice, these factors are estimated and have some uncertainty. This dissertation explores methods to consider the uncertainty in the detection factors for an aircraft path planner. First, the detection model is extended to include uncertainty in the aircraft position and orientation, radar position, and radar parameters. Second, an efficient method to estimate the aircraft position and orientation uncertainty is presented that enables rapid path evaluation. Third, the extended radar model and efficient aircraft uncertainty calculation are incorporated into a path planner that evaluates the sources of uncertainty and provides actionable information to the mission planner

JPL basic research review

Current status, projected goals, and results of 49 research and advanced development programs at the Jet Propulsion Laboratory are reported in abstract form. Areas of investigation include: aerodynamics and fluid mechanics, applied mathematics and computer sciences, environment protection, materials science, propulsion, electric and solar power, guidance and navigation, communication and information sciences, general physics, and chemistry

Photoacoustic fluctuation imaging: theory and application to blood flow imaging

Photoacoustic fluctuation imaging, which exploits randomness in photoacoustic generation, provides enhanced images in terms of resolution and visibility, as compared to conventional photoacoustic images. While a few experimental demonstrations of photoacoustic fluctuation imaging have been reported, it has to date not been described theoretically. In the first part of this work, we propose a theory relevant to fluctuations induced either by random illumination patterns or by random distributions of absorbing particles. The theoretical predictions are validated by Monte Carlo finite-difference time-domain simulations of photoacoustic generation in random particle media. We provide a physical insight into why visibility artefacts are absent from second-order fluctuation images. In the second part, we demonstrate experimentally that harnessing randomness induced by the flow of red blood cells produce photoacoustic fluctuation images free of visibility artefacts. As a first proof of concept, we obtain two-dimensional images of blood vessel phantoms. Photoacoustic fluctuation imaging is finally applied in vivo to obtain 3D images of the vascularization in a chicken embryo

Seventy Years of Radar and Communications: The Road from Separation to Integration

Radar and communications (R&C) as key utilities of electromagnetic (EM) waves have fundamentally shaped human society and triggered the modern information age. Although R&C have been historically progressing separately, in recent decades they have been moving from separation to integration, forming integrated sensing and communication (ISAC) systems, which find extensive applications in next-generation wireless networks and future radar systems. To better understand the essence of ISAC systems, this paper provides a systematic overview on the historical development of R&C from a signal processing (SP) perspective. We first interpret the duality between R&C as signals and systems, followed by an introduction of their fundamental principles. We then elaborate on the two main trends in their technological evolution, namely, the increase of frequencies and bandwidths, and the expansion of antenna arrays. Moreover, we show how the intertwined narratives of R\&C evolved into ISAC, and discuss the resultant SP framework. Finally, we overview future research directions in this field

Roadmap on semiconductor-cell biointerfaces.

This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in interfacing, monitoring, and manipulating the activity of biological components, and discusses the possibility of using active semiconductor-cell interfaces for discovering new signaling processes in the biological world