68 research outputs found
Revisiting the detection rate for axion haloscopes
The cavity haloscope has been employed to detect microwave photons resonantly
converted from invisible cosmic axions under a strong magnetic field. In this
scheme, the axion-photon conversion power has been formulated to be valid for
certain conditions, either or . This remedy, however, fails when these two quantities are
comparable to each other. Furthermore, the noise power flow has been treated
independently of the impedance mismatch of the system, which could give rise to
misleading estimates of the experimental sensitivity. We revisit the analytical
approaches to derive a general description of the signal and noise power. We
also optimize the coupling strength of a receiver to yield the maximal
sensitivity for axion search experiments.Comment: 15 pages, 7 figure
Fabrication of polyimide nanotubes and carbon nanotubes containing magnetic iron oxide in confinement
Polyimide nanotubes with tunable wall thickness were fabricated
by a precursor impregnation method using an AAO
template, and carbon nanotubes containing magnetic iron
oxide were obtained using ferric chloride-embedded polyimide
precursor by a carbonization process.This work was supported by Korea Science and Engineering
Foundation through the Hyperstructured Organic Materials
Research Center
Search for the Sagittarius Tidal Stream of Axion Dark Matter around 4.55 eV
We report the first search for the Sagittarius tidal stream of axion dark
matter around 4.55 eV using CAPP-12TB haloscope data acquired in March of
2022. Our result excluded the Sagittarius tidal stream of
Dine-Fischler-Srednicki-Zhitnitskii and Kim-Shifman-Vainshtein-Zakharov axion
dark matter densities of and GeV/cm,
respectively, over a mass range from 4.51 to 4.59 eV at a 90% confidence
level.Comment: 6 pages, 7 Figures, PRD Letter accepte
Carotid Intima-Media Thickness, Not Carotid Plaque, is Associated With Large Territory Cerebral Infarction in Patients With Ischemic Stroke
gas handling system and RF discharge for optical pumping
Axions are hypothetical pseudo scalar particles that appear in the solution of the strong CP problem. Axions can also be a dark-matter candidate if their mass is in light regime. Many of these haloscope experiments to detect axions are based on this assumption. In addition, Moody and Wilczek postulated an interaction between monopole and dipole masses that can be mediated by axions at macroscopic scale \cite{Moody}. We propose new experiment that can detect axions by measuring by pseudo-magnetic field induced between monopole and dipole. For this experiment, we have developed He polarization system using metastable exchange optical pumping (MEOP) technique
Quintessential Axions from a New Confining Force
Almost massless mesons created at the condensation scale of extra nonabelian
gauge group can be candidates of dark energy source. This can be another
motivation for introducing an additional confining force.Comment: 7 pages, 3 figure
Implementation of Formic Acid as a Liquid Organic Hydrogen Carrier (LOHC): Techno-Economic Analysis and Life Cycle Assessment of Formic Acid Produced via CO<sub>2</sub> Utilization
To meet the global climate goals agreed upon regarding the Paris Agreement, governments and institutions around the world are investigating various technologies to reduce carbon emissions and achieve a net-negative energy system. To this end, integrated solutions that incorporate carbon utilization processes, as well as promote the transition of the fossil fuel-based energy system to carbon-free systems, such as the hydrogen economy, are required. One of the possible pathways is to utilize CO2 as the base chemical for producing a liquid organic hydrogen carrier (LOHC), using CO2 as a mediating chemical for delivering H2 to the site of usage since gaseous and liquid H2 retain transportation and storage problems. Formic acid is a probable candidate considering its high volumetric H2 capacity and low toxicity. While previous studies have shown that formic acid is less competitive as an LOHC candidate compared to other chemicals, such as methanol or toluene, the results were based on out-of-date process schemes. Recently, advances have been made in the formic acid production and dehydrogenation processes, and an analysis regarding the recent process configurations could deem formic acid as a feasible option for LOHC. In this study, the potential for using formic acid as an LOHC is evaluated, with respect to the state-of-the-art formic acid production schemes, including the use of heterogeneous catalysts during thermocatalytic and electrochemical formic acid production from CO2. Assuming a hydrogen distribution system using formic acid as the LOHC, each of the production, transportation, dehydrogenation, and CO2 recycle sections are separately modeled and evaluated by means of techno-economic analysis (TEA) and life cycle assessment (LCA). Realistic scenarios for hydrogen distribution are established considering the different transportation and CO2 recovery options; then, the separate scenarios are compared to the results of a liquefied hydrogen distribution scenario. TEA results showed that, while the LOHC system incorporating the thermocatalytic CO2 hydrogenation to formic acid is more expensive than liquefied H2 distribution, the electrochemical CO2 reduction to formic acid system reduces the H2 distribution cost by 12%. Breakdown of the cost compositions revealed that reduction of steam usage for thermocatalytic processes in the future can make the LOHC system based on thermocatalytic CO2 hydrogenation to formic acid to be competitive with liquefied H2 distribution if the production cost could be reduced by 23% and 32%, according to the dehydrogenation mode selected. Using formic acid as a LOHC was shown to be less competitive compared to liquefied H2 delivery in terms of LCA, but producing formic acid via electrochemical CO2 reduction was shown to retain the lowest global warming potential among the considered options
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