Review of photoacoustic imaging plus X

Photoacoustic imaging (PAI) is a novel modality in biomedical imaging technology that combines the rich optical contrast with the deep penetration of ultrasound. To date, PAI technology has found applications in various biomedical fields. In this review, we present an overview of the emerging research frontiers on PAI plus other advanced technologies, named as PAI plus X, which includes but not limited to PAI plus treatment, PAI plus new circuits design, PAI plus accurate positioning system, PAI plus fast scanning systems, PAI plus novel ultrasound sensors, PAI plus advanced laser sources, PAI plus deep learning, and PAI plus other imaging modalities. We will discuss each technology's current state, technical advantages, and prospects for application, reported mostly in recent three years. Lastly, we discuss and summarize the challenges and potential future work in PAI plus X area

A Tutorial on Clique Problems in Communications and Signal Processing

Since its first use by Euler on the problem of the seven bridges of K\"onigsberg, graph theory has shown excellent abilities in solving and unveiling the properties of multiple discrete optimization problems. The study of the structure of some integer programs reveals equivalence with graph theory problems making a large body of the literature readily available for solving and characterizing the complexity of these problems. This tutorial presents a framework for utilizing a particular graph theory problem, known as the clique problem, for solving communications and signal processing problems. In particular, the paper aims to illustrate the structural properties of integer programs that can be formulated as clique problems through multiple examples in communications and signal processing. To that end, the first part of the tutorial provides various optimal and heuristic solutions for the maximum clique, maximum weight clique, and $k$-clique problems. The tutorial, further, illustrates the use of the clique formulation through numerous contemporary examples in communications and signal processing, mainly in maximum access for non-orthogonal multiple access networks, throughput maximization using index and instantly decodable network coding, collision-free radio frequency identification networks, and resource allocation in cloud-radio access networks. Finally, the tutorial sheds light on the recent advances of such applications, and provides technical insights on ways of dealing with mixed discrete-continuous optimization problems

NIAC Phase II Orbiting Rainbows: Future Space Imaging with Granular Systems

Inspired by the light scattering and focusing properties of distributed optical assemblies in Nature, such as rainbows and aerosols, and by recent laboratory successes in optical trapping and manipulation, we propose a unique combination of space optics and autonomous robotic system technology, to enable a new vision of space system architecture with applications to ultra-lightweight space optics and, ultimately, in-situ space system fabrication. Typically, the cost of an optical system is driven by the size and mass of the primary aperture. The ideal system is a cloud of spatially disordered dust-like objects that can be optically manipulated: it is highly reconfigurable, fault-tolerant, and allows very large aperture sizes at low cost. This new concept is based on recent understandings in the physics of optical manipulation of small particles in the laboratory and the engineering of distributed ensembles of spacecraft swarms to shape an orbiting cloud of micron-sized objects. In the same way that optical tweezers have revolutionized micro- and nano-manipulation of objects, our breakthrough concept will enable new large scale NASA mission applications and develop new technology in the areas of Astrophysical Imaging Systems and Remote Sensing because the cloud can operate as an adaptive optical imaging sensor. While achieving the feasibility of constructing one single aperture out of the cloud is the main topic of this work, it is clear that multiple orbiting aerosol lenses could also combine their power to synthesize a much larger aperture in space to enable challenging goals such as exo-planet detection. Furthermore, this effort could establish feasibility of key issues related to material properties, remote manipulation, and autonomy characteristics of cloud in orbit. There are several types of endeavors (science missions) that could be enabled by this type of approach, i.e. it can enable new astrophysical imaging systems, exo-planet search, large apertures allow for unprecedented high resolution to discern continents and important features of other planets, hyperspectral imaging, adaptive systems, spectroscopy imaging through limb, and stable optical systems from Lagrange-points. Furthermore, future micro-miniaturization might hold promise of a further extension of our dust aperture concept to other more exciting smart dust concepts with other associated capabilities. Our objective in Phase II was to experimentally and numerically investigate how to optically manipulate and maintain the shape of an orbiting cloud of dust-like matter so that it can function as an adaptable ultra-lightweight surface. Our solution is based on the aperture being an engineered granular medium, instead of a conventional monolithic aperture. This allows building of apertures at a reduced cost, enables extremely fault-tolerant apertures that cannot otherwise be made, and directly enables classes of missions for exoplanet detection based on Fourier spectroscopy with tight angular resolution and innovative radar systems for remote sensing. In this task, we have examined the advanced feasibility of a crosscutting concept that contributes new technological approaches for space imaging systems, autonomous systems, and space applications of optical manipulation. The proposed investigation has matured the concept that we started in Phase I to TRL 3, identifying technology gaps and candidate system architectures for the space-borne cloud as an aperture

The NASA SBIR product catalog

The purpose of this catalog is to assist small business firms in making the community aware of products emerging from their efforts in the Small Business Innovation Research (SBIR) program. It contains descriptions of some products that have advanced into Phase 3 and others that are identified as prospective products. Both lists of products in this catalog are based on information supplied by NASA SBIR contractors in responding to an invitation to be represented in this document. Generally, all products suggested by the small firms were included in order to meet the goals of information exchange for SBIR results. Of the 444 SBIR contractors NASA queried, 137 provided information on 219 products. The catalog presents the product information in the technology areas listed in the table of contents. Within each area, the products are listed in alphabetical order by product name and are given identifying numbers. Also included is an alphabetical listing of the companies that have products described. This listing cross-references the product list and provides information on the business activity of each firm. In addition, there are three indexes: one a list of firms by states, one that lists the products according to NASA Centers that managed the SBIR projects, and one that lists the products by the relevant Technical Topics utilized in NASA's annual program solicitation under which each SBIR project was selected

Landslide motion assessment including thermal interaction : an MPM approach

Risk associated with landslides of natural or man-made origin depends on the prediction of the post-failure behaviour of the mobilized mass. Numerical models capable of integrating the landslide geometry and its evolution, the coupled hydro mechanical interaction and the soil properties in the context of dynamic forces and large displacements are currently under development. This thesis is a contribution to this effort. In this sense, the material point method (MPM) is especially suited for analyzing landslides with large displacements. This numerical procedure must be accompanied by tests under controlled conditions in order to accurately check and calibrate the numerical response. In this thesis the capabilities of the MPM code developed are evaluated through the modelling of scaled laboratory slope tests with large displacements. In order to achieve an adequate comparison of the experimental and numerical results, the experiments are analysed by means of the interpretation of sequential digital images of the movement of the granular medium during the test (PIV technique). A novel procedure is developed to obtain the field of deformations over time and the tracking of particle path in a manner suitable for comparison with numerical results calculated in MPM. The main objective of the thesis was the development of a comprehensive calculation tool capable of simulating the behaviour of the slides from the initial triggering to the post-failure phase including thermal effects that determine the evolution of the movement. A formulation for non-isothermal problems coupled with hydraulic and mechanical behaviour in MPM was developed and implemented. The formulation includes the dissipation of frictional work as heat, which takes place, mainly, in shear bands. The described phenomena are strongly dependent on the thickness of the shear band and this result in a strong dependence of the numerical results in MPM with the discretization mesh. A novel procedure to solve this problem is presented in this thesis. Finally, very rapid Vajont landslide (Italy 1963) is modelled. A plain strain 2D model is presented without an “a priori” definition of the sliding surface. In fact, in a generalization of previous and recent work, the mobilized materials are not restricted to rigid solids interconnected along a predefined contact surface and the heat generation is not it is limited to a single predefined surface. Thus, thermal interaction processes are developed throughout the model as a function of the location and intensity of deformations.El riesgo asociado con deslizamientos de origen natural o artificial depende de la predicción del comportamiento posterior a la rotura de la masa movilizada. Actualmente se están desarrollando modelos numéricos capaces de integrar la geometría del deslizamiento y su evolución, la interacción hidromecánica acoplada y las propiedades del suelo en el contexto de fuerzas dinámicas y grandes desplazamientos. Esta tesis es una contribución a este esfuerzo. En este sentido, el método del punto material (MPM) es especialmente adecuado para analizar deslizamientos con grandes desplazamientos. Este procedimiento numérico debe ir acompañado de ensayos bajo condiciones controladas para poder comprobar y calibrar la respuesta numérica. En esta tesis se evalúan las capacidades del código MPM desarrollado, mediante la modelación de ensayos de laboratorio a escala con grandes desplazamientos. Para lograr una adecuada comparación de los resultados experimentales y numéricos, se analizan los experimentos mediante la interpretación de imágenes digitales secuenciales del movimiento del medio granular durante el ensayo (técnica PIV). Con este fin, se desarrolla un procedimiento novedoso para la obtención del campo de deformaciones en el tiempo y el seguimiento de la trayectoria de las partículas de forma idónea para la comparación con resultados numéricos calculados en MPM. El principal objetivo de la tesis fue el desarrollo de una herramienta potente de cálculo capaz de simular el comportamiento de los deslizamientos desde la rotura inicial hasta la fase de post-rotura incluyendo efectos térmicos que determinan la evolución del movimiento. Para esto, se desarrolla e implementa una formulación para problemas no isotérmicos acoplados con el comportamiento hidráulico y mecánico en MPM. Esta formulación incluye la disipación del trabajo friccional en forma de calor, lo cual ocurre principalmente en las bandas donde se localiza la deformación de corte. Este fenómeno descrito es fuertemente dependiente con el espesor de la banda de corte y esto se traduce en una fuerte dependencia de los resultados numéricos en MPM con la malla de discretización empleada. En esta tesis se presenta un novedoso procedimiento para solventar este problema. Por último se presenta la modelación del movimiento ocurrido en el deslizamiento rápido de Vajont (Italia 1963). Se introduce un modelo 2D en deformación plana sin una definición "a priori" de la superficie de deslizamiento. De hecho, generalizando los trabajos hechos anteriormente, los materiales movilizados no se restringen a solidos rígidos interconectados a lo largo de una superficie de contacto predefinida y la generación de calor no se limita a una única superficie predefinida. Así, los procesos de interacción térmica se desarrollan en todo el modelo en función de la localización e intensidad de las deformaciones.Postprint (published version

Research program of the Geodynamics Branch

This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members

Gravity and geodesy of the Jovian system bodies with the Juno and JUICE missions

The key to the understanding of our Solar System, how it originated and evolved, lies with the exploration of the miniature system of its largest planet, Jupiter. To this end, a number of space missions have been dedi- cated to probing the planet itself and its satellites, aiming at studying and comprehending the physical phenomena taking place within the system. In this context, a fundamental role is played by the determination of the gravity field of the bodies forming the system, by means of onboard radio science experiments. The main purpose of my research is to assess the accuracies attainable with the gravity measurements performed by NASA’s Juno and ESA’s JUICE missions, that will influence the comprehension of the interior structure and dynamics of the Jovian system bodies. In the frame of this dissertation I show how the precise reconstruction of the gravitational potential of Jupiter and its largest moons have the potential of improving our knowledge of the geodesy of the whole system

FR3D: Three-dimensional Flow Reconstruction and Force Estimation for Unsteady Flows Around Extruded Bluff Bodies via Conformal Mapping Aided Convolutional Autoencoders

In many practical fluid dynamics experiments, measuring variables such as velocity and pressure is possible only at a limited number of sensor locations, \textcolor{black}{for a few two-dimensional planes, or for a small 3D domain in the flow}. However, knowledge of the full fields is necessary to understand the dynamics of many flows. Deep learning reconstruction of full flow fields from sparse measurements has recently garnered significant research interest, as a way of overcoming this limitation. This task is referred to as the flow reconstruction (FR) task. In the present study, we propose a convolutional autoencoder based neural network model, dubbed FR3D, which enables FR to be carried out for three-dimensional flows around extruded 3D objects with different cross-sections. An innovative mapping approach, whereby multiple fluid domains are mapped to an annulus, enables FR3D to generalize its performance to objects not encountered during training. We conclusively demonstrate this generalization capability using a dataset composed of 80 training and 20 testing geometries, all randomly generated. We show that the FR3D model reconstructs pressure and velocity components with a few percentage points of error. Additionally, using these predictions, we accurately estimate the Q-criterion fields as well lift and drag forces on the geometries.Comment: 29 pages, 10 figures. Accepted at International Journal of Heat and Fluid Flo