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1. Optimizing pink‐beam fast X‐ray microtomography for multiphase flow in 3D porous media

   https://doi.org/10.1111/jmi.12872  

   MEISENHEIMER, D. E. ; RIVERS, M. L. ; WILDENSCHILD, D. ( February 2020 , Journal of Microscopy)

   A fast pink‐beam X‐ray microtomography methodology was developed at the GSECARS 13‐BMD beamline at the Advanced Photon Source to study multiphase flow in porous media. The white beam X‐ray distribution of the Advanced Photon Source is modified using a 1‐mm copper filter and the beam is reflected off a platinum mirror angled at 1.5 mrad, resulting in a pink beam with X‐ray intensities predominately in the range of 40–60 keV. Bubble formation in the wetting phase and wettability alteration of the solid phase from x‐ray exposure can be a problem with high flux and high energy beams, but the suggested pink‐beam configuration mitigates these effects. With a 14‐second acquisition time for capturing a complete dataset, the evolving fluid‐fronts of nonequilibrium three‐dimensional multiphase flow can be studied in real‐time and the images contain adequate image contrast and quality to measure important multiphase quantities such as contact angles and interfacial areas.

   Understanding how fluids are transported through porous materials is pertinent to many important societal processes in the environment (e.g. groundwater flow for drinking water) and industry (e.g. drying of industrial materials such as pulp and paper). To develop accurate models and theories of this fluid transportation, experiments need to track fluids in 3‐dimensions quickly. This is difficult to do as most materials are opaque and therefore cameras cannot capture fluid movement directly. But, with the help of x‐rays, scientists can track fluids in 3D using an imaging technique called x‐ray microtomography (μCT). Standard μCT takes about 15 minutes for one image which can produce blurry images if fluids are flowing quickly through the material. We present a technique, fast μCT, which uses a larger spectrum of x‐rays than the standard technique and acquires a 3D image in 14 seconds. With the large amount of x‐rays utilized in this technique, bubbles can start to form in the fluids from x‐ray exposure. We optimized the utilized x‐ray spectrum to limit bubble formation while still achieving a rapid 3D image acquisition that has adequate image quality and contrast. With this technique, scientists can study fluid transport in 3D porous materials in near real‐time for the improvement of models used to ensure public and environmental health.

    

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2. UAV Air-to-Ground Channel Characterization for mmWave Systems

   Khawaja, Wahab ; Ozdemir, Ozgur ; Guvenc, Ismail ( September 2017 , IEEE Vehicular Technology Conference (VTC) workshop on 5G Millimeter-Wave Channel Measurement, Models, and Systems)

   Communication at mmWave bands carries critical importance for 5G wireless networks. In this paper, we study the characterization of mmWave air-to-ground (AG) channels for unmanned aerial vehicle (UAV) communications. In particular, we use ray tracing simulations using Remcom Wireless InSite software to study the behavior of AG mmWave bands at two different frequencies: 28 GHz and 60 GHz. Received signal strength (RSS) and root mean square delay spread (RMS-DS) of multipath components (MPCs) are analyzed for different UAV heights considering four different environments: urban, suburban, rural, and over sea. It is observed that the RSS mostly follows the two ray propagation model along the UAV flight path for higher altitudes. This two ray propagation model is affected by the presence of high rise scatterers in urban scenario. Moreover, we present details of a universal serial radio peripheral (USRP) based channel sounder that can be used for AG channel measurements for mmWave (60 GHz) UAV communications. 

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3. Sub-GHz In-Body to Out-of-Body Communication Channel Modeling for Ruminant Animals for Smart Animal Agriculture

   https://doi.org/10.1109/TBME.2022.3213262  

   Datta, Arunashish ; Kaur, Upinder ; Malacco, Victor ; Nath, Mayukh ; Chatterjee, Baibhab ; Donkin, Shawn S. ; Voyles, Richard M. ; Sen, Shreyas ( October 2022 , IEEE Transactions on Biomedical Engineering)

   Sensors in and around the environment becoming ubiquitous has ushered in the concept of smart animal agriculture which has the potential to greatly improve animal health and productivity using the concepts of remote health monitoring which is a necessity in times when there is a great demand for animal products. The data from in and around animals gathered from sensors dwelling in animal agriculture settings have made farms a part of the Internet of Things space. This has led to active research in developing efficient communication methodologies for farm networks. This study focuses on the first hop of any such farm network where the data from inside the body of the animals is to be communicated to a node dwelling outside the body of the animal. In this paper, we use novel experimental methods to calculate the channel loss of signal at sub-GHz frequencies of 100 - 900 MHz to characterize the in-body to out-of-body communication channel in large animals. A first-of-its-kind 3D bovine modeling is done with computer vision techniques for detailed morphological features of the animal body is used to perform Finite Element Method based Electromagnetic simulations. The results of the simulations are experimentally validated to come up with a complete channel modeling methodology for in-body to out-of-body animal body communication. The experimentally validated 3D bovine model is made available publicly on https://github.com/SparcLab/Bovine-FEM-Model.git GitHub. The results illustrate that an in-body to out-of-body communication channel is realizable from the rumen to the collar of ruminants with $\leq {90}~{\rm dB}$ path loss at sub-GHz frequencies ( $100-900~MHz$ ) making communication feasible. The developed methodology has been illustrated for ruminants but can also be used for other related in-body to out-of-body studies. Using the developed channel modeling technique, an efficient communication architecture can be formed for in-body to out-of-body communication in animals which paves the way for the design and development of future smart animal agriculture systems. 

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4. A Comparison of Hybrid Beamforming and Digital Beamforming with Low-Resolution ADCs for Multiple Users and Imperfect CSI

   https://doi.org/10.1109/JSTSP.2018.2813973  

   Roth, Kilian ; Pirzadeh, Hessam ; Swindlehurst, A. Lee ; Nossek, Josef A. ( March 2018 , IEEE Journal of Selected Topics in Signal Processing)

   For 5G it will be important to leverage the available millimeter wave spectrum. To achieve an approximately omni- directional coverage with a similar effective antenna aperture compared to state-of-the-art cellular systems, an antenna array is required at both the mobile and basestation. Due to the large bandwidth and inefficient amplifiers available in CMOS for mmWave, the analog front-end of the receiver with a large number of antennas becomes especially power hungry. Two main solutions exist to reduce the power consumption: hybrid beam forming and digital beam forming with low resolution Analog to Digital Converters (ADCs). In this work we compare the spectral and energy efficiency of both systems under practical system constraints. We consider the effects of channel estimation, transmitter impairments and multiple simultaneous users for a wideband multipath model. Our power consumption model considers components reported in literature at 60 GHz. In contrast to many other works we also consider the correlation of the quantization error, and generalize the modeling of it to non- uniform quantizers and different quantizers at each antenna. The result shows that as the Signal to Noise Ratio (SNR) gets larger the ADC resolution achieving the optimal energy efficiency gets also larger. The energy efficiency peaks for 5 bit resolution at high SNR, since due to other limiting factors the achievable rate almost saturates at this resolution. We also show that in the multi- user scenario digital beamforming is in any case more energy efficient than hybrid beamforming. In addition we show that if mixed ADC resolutions are used we can achieve any desired trade-off between power consumption and rate close to those achieved with only one ADC resolution. 

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5. The Abell 3391/95 galaxy cluster system: A 15 Mpc intergalactic medium emission filament, a warm gas bridge, infalling matter clumps, and (re-) accelerated plasma discovered by combining SRG/eROSITA data with ASKAP/EMU and DECam data

   https://doi.org/10.1051/0004-6361/202039590  

   Reiprich, T. H. ; Veronica, A. ; Pacaud, F. ; Ramos-Ceja, M. E. ; Ota, N. ; Sanders, J. ; Kara, M. ; Erben, T. ; Klein, M. ; Erler, J. ; et al ( March 2021 , Astronomy & Astrophysics)

   null (Ed.)

   Context. Inferences about dark matter, dark energy, and the missing baryons all depend on the accuracy of our model of large-scale structure evolution. In particular, with cosmological simulations in our model of the Universe, we trace the growth of structure, and visualize the build-up of bigger structures from smaller ones and of gaseous filaments connecting galaxy clusters. Aims. Here we aim to reveal the complexity of the large-scale structure assembly process in great detail and on scales from tens of kiloparsecs up to more than 10 Mpc with new sensitive large-scale observations from the latest generation of instruments. We also aim to compare our findings with expectations from our cosmological model. Methods. We used dedicated SRG/eROSITA performance verification (PV) X-ray, ASKAP/EMU Early Science radio, and DECam optical observations of a ~15 deg 2 region around the nearby interacting galaxy cluster system A3391/95 to study the warm-hot gas in cluster outskirts and filaments, the surrounding large-scale structure and its formation process, the morphological complexity in the inner parts of the clusters, and the (re-)acceleration of plasma. We also used complementary Sunyaev-Zeldovich (SZ) effect data from the Planck survey and custom-made Galactic total (neutral plus molecular) hydrogen column density maps based on the HI4PI and IRAS surveys. We relate the observations to expectations from cosmological hydrodynamic simulations from the Magneticum suite. Results. We trace the irregular morphology of warm and hot gas of the main clusters from their centers out to well beyond their characteristic radii, r 200 . Between the two main cluster systems, we observe an emission bridge on large scale and with good spatial resolution. This bridge includes a known galaxy group but this can only partially explain the emission. Most gas in the bridge appears hot, but thanks to eROSITA’s unique soft response and large field of view, we discover some tantalizing hints for warm, truly primordial filamentary gas connecting the clusters. Several matter clumps physically surrounding the system are detected. For the “Northern Clump,” we provide evidence that it is falling towards A3391 from the X-ray hot gas morphology and radio lobe structure of its central AGN. Moreover, the shapes of these X-ray and radio structures appear to be formed by gas well beyond the virial radius, r 100 , of A3391, thereby providing an indirect way of probing the gas in this elusive environment. Many of the extended sources in the field detected by eROSITA are also known clusters or new clusters in the background, including a known SZ cluster at redshift z = 1. We find roughly an order of magnitude more cluster candidates than the SPT and ACT surveys together in the same area. We discover an emission filament north of the virial radius of A3391 connecting to the Northern Clump. Furthermore, the absorption-corrected eROSITA surface brightness map shows that this emission filament extends south of A3395 and beyond an extended X-ray-emitting object (the “Little Southern Clump”) towards another galaxy cluster, all at the same redshift. The total projected length of this continuous warm-hot emission filament is 15 Mpc, running almost 4 degrees across the entire eROSITA PV observation field. The Northern and Southern Filament are each detected at >4 σ . The Planck SZ map additionally appears to support the presence of both new filaments. Furthermore, the DECam galaxy density map shows galaxy overdensities in the same regions. Overall, the new datasets provide impressive confirmation of the theoretically expected structure formation processes on the individual system level, including the surrounding warm-hot intergalactic medium distribution; the similarities of features found in a similar system in the Magneticum simulation are striking. Our spatially resolved findings show that baryons indeed reside in large-scale warm-hot gas filaments with a clumpy structure. 

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