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Low-Energy Calibration of the Hyper-Kamiokande Detector Utilizing a Deuterium Tritium Neutron Generator
No full textHyper-Kamiokande (HK) is a next-generation international neutrino experiment currently under construction in Japan. HK will explore proton decay and have the capability to detect Earth-crossing, atmospheric, solar, cosmic, and accelerator neutrinos. Expected to start data collection in 2027, HK will require periodic calibration for optimal performance. The calibration at lower energies will involve utilizing a Deuterium Tritium neutron Generator (DTG), entailing the generation of a radioactive N16 cloud strategically positioned in various locations within the water tank. A simulation of N16 cloud generation and decay was conducted in preparation for propagating the decay products through the detector volume using dedicated HK simulation software. The DTG will be deployed using a computer-controlled crane to achieve accurate positioning while prioritizing the cleanliness and safety of the detector
The Mid-infrared-emitting Jet in the Black Hole V404 Cygni in Quiescence
Get PDFObservations of some quiescent black hole X-ray binaries have revealed an excess of mid-infrared (MIR) emission above that expected from their donor stars. In one system, V404 Cygni, this excess has been variously suggested to arise from the accretion disk, circumbinary material, or a compact relativistic jet. Here we present simultaneous James Webb Space Telescope (JWST), Atacama Large Millimeter/submillimeter Array, and complementary multiwavelength observations undertaken to resolve this uncertainty. We observed large-amplitude 21 μm variability on short timescales with JWST, particularly a dramatic flare, which swiftly rose to ≈2.4 mJy, over 10 times the lowest observed MIR flux density. Similar variability was simultaneously observed from radio to X-ray wavelengths with other facilities throughout the campaign. This variability and the flat radio/millimeter/MIR spectral index (α = 0.04 ± 0.01) suggest that the MIR excess at and longward of 21 μm in V404 Cyg does not arise from the accretion disk or circumbinary material. Instead, the emission at 21 μm is dominated by synchrotron radiation from a jet, which persists into quiescence. This result reinforces the ubiquity of the disk-jet connection in accreting black holes across a range of masses and accretion rates
Improved Performance of Catalysts Containing Pt, Pt-Sn, and V in the Dehydrogenation of n-Butane by Radio-Frequency Induction Heating
Get PDFDue to an abundance of shale gas, manufacturers are interested in meeting increased demands for alkenes, especially n-alkenes, by the dehydrogenation of light alkanes. While the catalysts for these reactions have been studied for many years, alkene selectivity and deactivation remain challenging problems. This work addresses these problems by the substitution of a localized indirect heating method (radio-frequency induction heating, RF-IH) for more traditional process heating employing steam or burners (e.g., natural gas combustion). RF-IH has been applied to the dehydrogenation of n-butane to C4 alkenes by utilizing magnetically susceptible catalysts based on Fe/Fe3O4 susceptors. Magnetic core-shell catalysts with either Pt or V as active metals were synthesized to mimic typical n-butane dehydrogenation catalysts. For these catalysts, RF-IH operation resulted in significantly improved selectivity to alkenes and less deactivation when compared to conventional thermal heating, although the initial activities were not always as high as their thermally operated counterparts. These results provide motivation to continue investigating the effects of RF-IH and its benefits to certain heterogeneous catalytic processes
Adaptive Velocity and Acceleration Control of Autonomous Vehicle Systems
No full textThis article proposes a combined adaptive velocity and acceleration control (CAVAC) law for autonomous vehicles in the presence of uncertainties and nonlinearities. In particular, the global asymptotic stability of the nonlinear vehicle system under the proposed adaptive velocity control is shown to hold without real-time estimation of the vehicle parameters. Moreover, the CAVAC law is shown to achieve the string stability against energy bounded disturbances, and ensures the required intervehicle spacing, crucial to avoiding collisions in vehicle platoons. The simulation studies illustrate the advantages of the CAVAC law for the autonomous vehicle platoon in dealing with the speed limit changes, in mitigating issues induced by merging-exiting, in suppressing energy bounded disturbances, and in improving collision avoidance. The experiments on an electric vehicle (EV) validate the effectiveness of the proposed control laws
Novel Indoor Sensor/Access-Point Placement for Full Line-of-Sight (LoS) Coverage
No full textA cost-effective placement strategy of sensor(s)/access-point(s) for full coverage of the region of interest is always desirable in practice. In this work, we propose a novel systematic approach using the visibility graph of a given arbitrary indoor (simply- or multiply-connected) polygonal environment for full line-of-sight (LoS) coverage where a small (minimum) number of sensors/access-points are required. Two difficult but practical challenges, namely internal obstacles and link-distance restriction, for indoor sensor/access-point placement are also combated by our new approach. Our proposed new approach transforms the sensor/access-point placement problem into a graph partition problem. First, the location(s) of sensor(s)/access-point(s) are initialized by finding all maximal cliques of the aforementioned visibility graph. Then, we propose a new algorithm to eliminate the redundant sensor(s)/access-point(s) to further reduce the number of sensors/access-points but still retain the full LoS coverage, which significantly reduces the cost without compromising the coverage capacity. According to the simulation results from a number of arbitrary polygons, the numbers of sensors/access-points required by our approach are always less than the theoretical upper-bounds derived by the current study of the art gallery problem (AGP)
Reducing Alienation in Foreign Language Acquisition: A Contrastive Analysis of Diacritical Marks in French and Nigerian Indigenous Languages (Yorùbá as a Case Study)—Pedagogical Insights
No full textIn Nigeria, like in any other Anglophone African country, French remains a foreign language, unlike a mother tongue like the Yorùbá language that is acquired from home. Nigerian learners of French language get in contact with the language in schools. In their attempt to learn the language, they are confronted with numerous linguistic challenges, and one of these problems lies in the mastery of French diacritical marks (accent marks), which are absent in the language of instruction, English. Despite the existence of diacritical marks in Nigerian indigenous languages, learners often struggle to acquire and use French accents correctly.
In order to reduce the alienation students encounter while acquiring French accents, this paper conducts a contrastive analysis of accent marks in Yorùbá and French by examining the use of accents in both languages. The results reveal that while diacritical marks primarily indicate tone and meaning in Yorùbá, they serve phonetic and semantic purposes in French. Despite the differences, we believe the existence of accent marks in both languages can facilitate the acquisition of French accents in Yorùbá French learners. Leveraging the students’ familiarity with Yoruba diacritical marks, this paper proposes strategic pedagogical approaches to reduce alienation, enhance linguistic competence, preserve linguistic and cultural identity, and promote the appreciation of the two languages
Role of pH on Environmentally Persistent Free Radicals (EPFRs) Activation, and its Sensor Development
No full textThis research investigates the role of pH in activating Environmentally Persistent Free Radicals (EPFRs) and developing sensors to quantify airborne active EPFRs. Model EPFR was synthesized by utilizing copper (Cu) or iron (Fe) as transition metals and monochlorophenol (MCP) as the organic component deposited on the Cab-O-Sil surface. The generation of hydroxyl radicals per EPFR was measured in a buffered solution (pH 5.5–9.0) at 15, 30, 60, 120, 180, and 300 minutes using DMPO spin adducts. The mixed model two-way ANOVA was used for spin-trapping data analysis. A simple linear regression model was fitted in the sensor study. Results indicated that hydroxyl radical formation per EPFR varied significantly with time (p2.5) exhibited trends like synthetic EPFRs, where OH•/EPFR yield increased with time and pH. The lowest radical concentration was observed at pH 5.0 compared to pH 6.0 and 8.0. The reaction order and apparent rate constant were –0.31 and 0.001 rad·EPFR⁻¹·s⁻¹, respectively. EPFR activation to its anionic form was found to be the rate-limiting step dependent on deprotonation in the aqueous medium. Various dyes were evaluated for their response to EPFRs at pH 8.0. Reactive blue showed the highest response, followed by coccine red, congo red, and reactive green, while reactive yellow and indanthrone exhibited no significant response to EPFRs. The results on PM2.5 response on red coccine dye indicated that the ratio of EPFRs measured by the sensor to those measured by Electron Paramagnetic Resonance (EPR) ranged from 0.35 to 2.22. A ratio below 1 implies fewer active radicals or radicals do not present on the PM2.5 surface, whereas a higher ratio suggests surface active radicals. In summary, this study elucidates the influence of pH on EPFR activation in both synthetic and ambient particulates and lays the foundation for developing sensors to monitor and quantify active EPFRs in PM2.5