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The is a poster on the fabrication and characterization of NiZn and MnZn ferrites for ultra-high frequency (UHF) RF absorbers. This will be presented at the American Ceramic Society EMA 2025 conference.
Biofouling is a well-documented problem in naval engineering, but little is known about its effect on wave energy converter (WEC) performance. In this study, the software WEC-Sim is used to simulate the performance of a point absorber WEC that has been biofouled by “hard” species (e.g., mussels, barnacles) to varying degrees. Specifically, biofouling is assumed to change the nonlinear drag forces acting on the WEC, which have quantifiable effects on key performance characteristics such as optimal damping conditions, power, peak displacement, and peak velocity. The results of this analysis are then used to discuss strategies for WEC control as it relates to biofouling. Furthermore, the results show that average power production can decrease by as much as 15% with heavy biofouling and require an adjustment of the optimal control law by up to 20%.
This dataset contains gridded monthly Leaf Area Index (LAI) derived from the daily NOAA Climate Data Record (CDR) of AVHRR Leaf Area Index (LAI) and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), Version 5. This data record spans from 1981 to 2018 using data from eight NOAA polar orbiting satellites: NOAA-7, -9, -11, -14, -16, -17, -18 and -19. The data are projected on a 0.05 degree x 0.05 degree global grid, as in the original CDR. The original CDR is one of the Land Surface CDR Version 5 products produced by the NASA Goddard Space Flight Center (GSFC) and the University of Maryland (UMD), which is accompanied by algorithm documentation, data flow diagram and source code for the NOAA CDR Program. This dataset is in the netCDF-4 file format following ACDD and CF Conventions. This dataset has applied quality assurance information to only include "OK" data from the original CDR in the monthly aggregation.
This dataset contains gridded monthly Leaf Area Index (LAI) derived from the daily NOAA Climate Data Record (CDR) of AVHRR (Version 5) and VIIRS (Version 1) Leaf Area Index (LAI) and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR). This data record spans from 1981 to 2024 using data from NOAA polar orbiting satellites: NOAA-7, -9, -11, -14, -16, -17, -18, -19 and S-NPP. The data are projected on a 0.05 degree x 0.05 degree global grid, as in the original CDR. The original CDR is one of the Land Surface CDR products produced by the NASA Goddard Space Flight Center (GSFC) and the University of Maryland (UMD), which is accompanied by algorithm documentation, data flow diagram and source code for the NOAA CDR Program. This dataset is in the netCDF-4 file format following ACDD and CF Conventions. This dataset has applied quality assurance information to only include "OK" data from the original CDR in the monthly aggregation.
Solar flat plate collector (SFPC) is regarded as one of the best renewable energy devices to acquire hot water for domestic usage. Though its theoretical efficiency is projected at higher scale, its conversion efficiency is observed to be low due to various collector losses. Hence, to achieve improved performance of collector different techniques for heat transfer augmentation in circular pipes can be adopted. Among passive and active techniques available, passive is preferred over active due to economics and saving in exergy. Hence, in the present study absorber tube configuration is modified with internal grooves in the collector setup to enhance the rate of heat transfer. Also, fluids dispersed with metal oxide particles provide an increase in thermal conductivity such that ZnO-based aqueous EG mixture nanofluid is used as working medium to analyze the performance of collector setup. Also, the change in heat transfer rate and temperature profile of grooved tubes under forced laminar conditions for different working fluids are compared and reported.
The results of investigations to determine the convective heat-exchange coefficient in the inner heat-exchange channels (HECs) of the light-absorbing heat-exchange panels (LAHPs) of flat-plate solar water-heating collectors (FPSWHCs) are given based on the results of their short-term heat testing in fullscale quasi-stationary conditions. The research method is based on determining the value of the required parameter from the heat-balance equation formed for the inner surfaces of the LAHP HEC walls. The structures of the flow LAHPs with a sheet-piped and thin parallelepiped form are selected as the test objects. The thermal tests of the FPSWHC are carried out during the near-midday hours of the light day to ensure the quasi-stationary mode condition. The reliability of the proposed method and results of the investigations is proved by comparing the values of the thermal-efficiency coefficients of the FPSWHC LAHPs obtained using two independent approaches.
It has been proposed to introduce a new parameter into the practice of the heat calculation and testing of the flat-plate solar water-heating collectors (FSWHCs)—the coefficient of heat transfer from the light-absorbing panel (LAP) to the heat transfer fluid in its internal heat-exchange channels (HECs) reduced to the unit area of the frontal surface of their cases. The mechanism of the formation of this parameter is studied, the design expression is derived, and a practical example of the calculation to define its value is performed. The structures of the flowing LAPs of a sheet-piped thin parallelepiped form are selected as the objects of the investigation. The reliability of the results of the investigations is proved by comparing the values of the specific (relative to the area unit of the frontal surface of the case) heating efficiency of the collector obtained based on the various formulas.
With significant improvement in High Temperature Superconductors (HTS), several projects are adopting HTS technology for fusion power systems. Compact HTS tokamaks offer potential advantages including lower plant costs, enhanced plasma control, and ultimately lower cost of electricity. However, as compact reactors have a reduced radial build to accommodate shielding, HTS degradation due to radiation damage or heating is a significant and potentially design limiting issue. Shielding must mitigate threats to the superconducting coils: neutron cascade damage, heat deposition and potentially organic insulator damage due x-rays. Unfortunately, there are currently no hi-performance shielding materials to enable the potential performance enhancement offered by HTS. In this work, we present a manufacturing method to fabricate a new class of composite shields that are high performance, high operating temperature, and simultaneously neutron absorbing and neutron moderating. The composite design consists of an entrained metal-hydride phase within a radiation stable MgO ceramic host matrix. We discuss the fabrication, characterization, and thermophysical performance data for a series of down-selected composite materials inspired by future fusion core designs and their operational performance metrics. To our knowledge these materials represent the first ceramic composite shield materials containing significant metal hydrides.
The power harnessed by wave energy converters (WECs) in oceans is highly variable and, therefore, has a high peak-to-average power (PTAP) ratio. To minimize the cost of a WEC power take off (PTO) system, it is desirable to reduce the PTAP ratio while maximizing the mean power extracted by WECs. The important issue of how PTAP ratio reduction measures (such as adding an inertia element) can affect the mean power extracted in a reference model has not been thoroughly addressed in the literature. To investigate this correlation, this study focuses on the integration of the U.S. Department of Energy’s Reference Model 3, a two-body point absorber, with a slider-crank WEC for linear-to-rotational conversion. In the first phase of this study, a full-scale numerical model was developed that predicts how PTO system parameters, along with an advanced control algorithm, can potentially affect the proposed WEC’s PTAP ratio as well as the mean power extracted. In the second phase, an appropriate scaled-down model was developed, and extracted power results were successfully validated against the full-scale model. Finally, numerical and hardware-in-the-loop (HIL) simulations based on the scaled-down model were designed and conducted to optimize or make trade-offs between the operational performance and PTAP ratio. The initial results with numerical and HIL simulations reveal that gear ratio, crank radius, and generator parameters substantially impact the PTAP ratio and mean power extracted.
The syntheses of two triads are reported. Each triad is composed of two perylene-monoimides linked to a porphyrin via an ethyne unit, which bridges the perylene 9-position and a porphyrin 5- or 15-position. Each triad also contains a single tether composed of an alkynoic acid or an isophthalate unit. Each triad provides panchromatic absorption (350–700 nm) with fluorescence emission in the near-infrared region (733 or 743 nm; fluorescence quantum yield ~0.2). The syntheses rely on the preparation of trans-AB-porphyrins bearing one site for tether attachment (A), an aryl group (B), and two open meso-positions. The AB-porphyrins were prepared by the condensation of a 1,9-diformyldipyrromethane and a dipyrromethane. The installation of the two perylene-monoimide groups was achieved upon the 5,15-dibromination of the porphyrin and the subsequent copper-free Sonogashira coupling, which was accomplished before or after the attachment of the tether. The syntheses provide relatively straightforward access to a panchromatic absorber for use in bioconjugation or surface-attachment processes.
Synthetic ammonia produced from fossil fuels is essential for agriculture. However, the emissions-intensive nature of the Haber–Bosch process, as well as a depleting supply of these fossil fuels have motivated the production of ammonia using renewable sources of energy. Small-scale, distributed processes may better enable the use of renewables, but also result in a loss of economies of scale, so the high capital cost of the Haber–Bosch process may inhibit this paradigm shift. A process that operates at lower pressure and uses absorption rather than condensation to remove ammonia from unreacted nitrogen and hydrogen has been proposed as an alternative. In this work, a dynamic model of this absorbent-enhanced process is proposed and implemented in gPROMS ModelBuilder. This dynamic model is used to determine optimal designs of this process that minimize the 20-year net present cost at small scales of 100 kg/h to 10,000 kg/h when powered by wind energy. The capital cost of this process scales with a 0.77 capacity exponent, and at production scales below 6075 kg/h, it is less expensive than the conventional Haber–Bosch process.
Species in the mushroom genus Lepiota can cause fatal mushroom poisonings due to their content of amatoxins such as α-amanitin. Previous studies of the toxin composition of poisonous Lepiota species relied on analytical methods of low sensitivity or resolution. Using liquid chromatography coupled to UV absorbance and mass spectrometry, we analyzed the spectrum of peptide toxins present in six Italian species of Lepiota, including multiple samples of three of them collected in different locations. Field taxonomic identifications were confirmed by sequencing of the internal transcribed spacer (ITS) regions. For comparison, we also analyzed specimens of Amanita phalloides from Italy and California, a specimen of A. virosa from Italy, and a laboratory-grown sample of Galerina marginata. α-Amanitin, β-amanitin, amanin, and amaninamide were detected in all samples of L. brunneoincarnata, and α-amanitin and γ-amanitin were detected in all samples of L. josserandii. Phallotoxins were not detected in either species. No amatoxins or phallotoxins were detected in L. clypeolaria, L. cristata, L. echinacea, or L. magnispora. The Italian and California isolates of A. phalloides had similar profiles of amatoxins and phallotoxins, although the California isolate contained more β-amanitin relative to α-amanitin. Amaninamide was detected only in A. virosa.
Using galaxies as background light sources to map the Lyα absorption lines is a novel approach to study Damped Lyα Absorbers (DLAs). We report the discovery of an intervening z = 3.335 ± 0.007 DLA along a galaxy sight-line identified among 80 Lyman Break Galaxy (LBG) spectra obtained with our Very Large Telescope/Visible Multi-Object Spectrograph survey in the SSA22 field. The measured DLA neutral hydrogen (H i) column density is log(N{sub H} {sub i}/cm{sup −2}) = 21.68 ± 0.17. The DLA covering fraction over the extended background LBG is >70% (2σ), yielding a conservative constraint on the DLA area of ≳1 kpc{sup 2}. Our search for a counterpart galaxy hosting this DLA concludes that there is no counterpart galaxy with star formation rate larger than a few M{sub ⊙} yr{sup −1}, ruling out an unobscured violent star formation in the DLA gas cloud. We also rule out the possibility that the host galaxy of the DLA is a passive galaxy with M{sub *} ≳ 5 × 10{sup 10}M{sub ⊙} or a heavily dust-obscured galaxy with E(B − V) ≳ 2. The DLA may coincide with a large-scale overdensity of the spectroscopic LBGs. The occurrence rate of the DLA is compatible with that of DLAs found in QSO sight-lines.
Using Hubble Space Telescope Cosmic Origins Spectrograph observations of 89 QSO sightlines through the Sloan Digital Sky Survey footprint, we study the relationships between C iv absorption systems and the properties of nearby galaxies, as well as the large-scale environment. To maintain sensitivity to very faint galaxies, we restrict our sample to 0.0015 10{sup 9.5} M{sub ⊙}; lower-mass galaxies rarely exhibit significant C iv absorption (covering fraction f{sub C}=9{sub −6}{sup +12}% for 11 galaxies with M{sub ∗}<10{sup 9.5} M{sub ⊙}). Second, C iv detection within the M{sub ∗}>10{sup 9.5} M{sub ⊙} population depends on environment. Using a fixed-aperture environmental density metric for galaxies with ρ < 160 kpc at z<0.055, we find that 57{sub −13}{sup +12}% (8/14) of galaxies in low-density regions (regions with fewer than seven L>0.15 L∗ galaxies within 1.5 Mpc) have affiliated C iv absorption; however, none (0/7) of the galaxies in denser regions show C iv. Similarly, the C iv detection rate is lower for galaxies residing in groups with dark matter halo masses of M{sub halo}>10{sup 12.5} M{sub ⊙}. In contrast to C iv, H i is pervasive in the circumgalactic medium without regard to mass or environment. These results indicate that C iv absorbers with log N(C IV)≳13.5 cm{sup −2} trace the halos of M{sub ∗}>10{sup 9.5} M{sub ⊙} galaxies but also reflect larger-scale environmental conditions.
Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray emission. The Suzaku observatory detected six rapid X-ray spectral hardening events called “softness dips” in a ∼100 ks observation in 2011. All the softness dip events show symmetric softness-ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either ∼40% or ∼70% partial covering absorption to kT ∼ 12 keV plasma emission by matter with a neutral hydrogen column density of ∼(2−8) × 10{sup 21} cm{sup −2}, while the spectrum outside these dips is almost free of absorption. This result suggests the presence of two distinct X-ray-emitting spots in the γ Cas system, perhaps on a white dwarf (WD) companion with dipole mass accretion. The partial covering absorbers may be blobs in the Be stellar wind, the Be disk, or rotating around the WD companion. Weak correlations of the softness ratios to the hard X-ray flux suggest the presence of stable plasmas at kT ∼ 0.9 and 5 keV, which may originate from the Be or WD winds. The formation of a Be star and WD binary system requires mass transfer between two stars; γ Cas may have experienced such activity in the past.
Protogalactic environments are typically identified using quasar absorption lines and can manifest as Damped Lyman-alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). We use radio observations of Faraday effects to test whether these galactic building blocks host a magnetized medium, by combining DLA and LLS detections with 1.4 GHz polarization data from the NRAO VLA Sky Survey (NVSS). We obtain a control, a DLA, and an LLS sample consisting of 114, 19, and 27 lines of sight, respectively. Using a Bayesian framework and weakly informative priors, we are unable to detect either coherent or random magnetic fields in DLAs: the regular coherent fields must be ⩽2.8 μG, and the lack of depolarization suggests the weakly magnetized gas in DLAs is non-turbulent and quiescent. However, we find a mild suggestive indication that LLSs have coherent magnetic fields, with a 71.5% probability that LLSs have higher |RM| than a control, although this is sensitive to the redshift distribution. We also find a strong indication that LLSs host random magnetic fields, with a 95.5% probability that LLS lines of sight have lower polarized fractions than a control. The regular coherent fields within the LLSs must be ⩽2.4 μG, and the magnetized gas must be highly turbulent with a typical turbulent length scale on the order of ≈5–20 pc. Our results are consistent with the standard dynamo paradigm, whereby magnetism in protogalaxies increases in coherence over cosmic time, and with a hierarchical galaxy formation scenario, with the DLAs and LLSs exploring different stages of magnetic field evolution in galaxies.
We propose a new method for determining the thermal state of the intergalactic medium based on Voigt profile decomposition of the Lyα forest. The distribution of Doppler parameter and column density (b–N H i distribution) is sensitive to the temperature–density relation T = T 0 (ρ/ρ 0 ) γ-1 , and previous work has inferred T 0 and γ by fitting its low-b cutoff. This approach discards the majority of available data and is susceptible to systematics related to cutoff determination. We introduce an approach that exploits all information encoded in the b – N H i distribution by modeling its entire shape. We apply kernel density estimation to discrete absorption lines to generate model probability density functions, and then we use principal component decomposition to create an emulator that can be evaluated anywhere in thermal parameter space. We introduce a Bayesian likelihood based on these models enabling parameter inference via Markov Chain Monte Carlo. The method's robustness is tested by applying it to a large grid of thermal history simulations. By conducting 160 mock measurements, we establish that our approach delivers unbiased estimates and valid uncertainties for a 2D ( T 0 , γ) measurement. Furthermore, we conduct a pilot study applying this methodology to real observational data at z = 2. Using 200 absorbers, equivalent in path length to a single Lya forest spectrum, we measure $\mathrm{log}{T}_{0}={4.092}_{-0.055}^{+0.050}$ and $\gamma ={1.49}_{-0.074}^{+0.073}$ in excellent agreement with cutoff fitting determinations using the same data. Our method is far more sensitive than cutoff fitting, enabling measurements of log T 0 and γ with precision on $\mathrm{log}{T}_{0}$ (γ) nearly two (three) times higher for current data set sizes.
Light-absorbing particles (LAPs), mainly dust and black carbon, can significantly impact snowmelt and regional water availability over high-mountain Asia (HMA). In this study, for the first time, online aerosol–snow interactions are enabled and a fully coupled chemistry Weather Research and Forecasting (WRF-Chem) regional model is used to simulate LAP-induced radiative forcing on snow surfaces in HMA at relatively high spatial resolution (12 km, WRF-HR) compared with previous studies. Simulated macro- and microphysical properties of the snowpack and LAP-induced snow darkening are evaluated against new spatially and temporally complete datasets of snow-covered area, grain size, and impurity-induced albedo reduction over HMA. A WRF-Chem quasi-global simulation with the same configuration as WRF-HR buta coarser spatial resolution (1°, WRF-CR) is also used to illustrate the impact of spatial resolution on simulations of snow properties and aerosol distribution over HMA. Due to a more realistic representation of terrain slopes over HMA, the higher-resolution model (WRF-HR) shows significantly better performance in simulating snow area cover, duration of snow cover, snow albedo and snow grain size over HMA, as well as an evidently better atmospheric aerosol loading and mean LAP concentration in snow. However, the differences in albedo reduction from model and satellite retrievals is large during winter due to associated overestimation in simulated snow fraction. It is noteworthy that Himalayan snow cover has high magnitudes of LAP-induced snow albedo reduction (4% - 8%) in pre-monsoon seasons (both from WRF-HR and satellite estimates), which induces a snow-mediated radiative forcing of ~30-50 W m -2 . As a result, the Himalayas (specifically the western Himalayas) hold the most vulnerable glaciers and mountain snowpack to the LAP-induced snow darkening effect within HMA. In summary, coarse spatial resolution and absence of snow–aerosol interactions over the Himalayan cryosphere will result insignificant underestimation of aerosol effects on snow melting and regional hydroclimate.