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At least 1,117 records · Page 62

Facile synthesis and temperature-dependent luminescence of single-phase dual-emitting CdTe@NaNO{sub 3} composite

Graphical abstract: Single-phase dual-emitting CdTe@NaNO{sub 3} composite was prepared by a facile and efficient aqueous ethanol phase assisted coprecipitation method. Its use in self-referencing luminescent thermometry was tested, by exploiting the temperature-dependence of fluorescence intensity ratio (green/red) in range of 273–473 K. - Highlights: • Single-phase green and red dual-emitting CdTe@NaNO{sub 3} composite was prepared. • CdTe QDs embedded in NaNO{sub 3} matrices exhibit photoluminescence quantum yields of 35%. • Temperature-dependent luminescent properties of CdTe@NaNO{sub 3} composite were studied. • It could be a good candidate for ratiometric temperature sensing with a high relative sensitivity. - Abstract: Single-phase dual-emitting CdTe@NaNO{sub 3} composite was prepared by a facile and efficient aqueous ethanol phase assisted coprecipitation method, providing a new type of solid-state luminescent material with processability, robustness and high luminescence. Cubic-shape Green + Red (G + R) CdTe@NaNO{sub 3} composite particles display single-excitation, dual-emission with two well-resolved, intensity-comparable fluorescence peaks. Its application potential in ratiometric luminescent thermometry was tested, by exploiting the temperature-dependence of fluorescence intensity ratio (green/red) in range of 273–473 K, and the maximum sensitivity is found to be 0.6183% K{sup −1} at 473 K. The results indicate that dual-emitting G + R CdTe@NaNO{sub 3} composite could be considered as potential candidates for ratiometric temperature sensing.

36 MATERIALS SCIENCE↗

Microstructural evolution of Q12{sup TM} alloy irradiated in PWRs and comparison with other Zr base alloys - 2016-0061

Based on the M5{sup R}* alloy metallurgy, the Q12{sup TM} alloy (Zr-1Nb-0.5Sn-0.1Fe) was developed by AREVA NP for structural components, with ultra-low tin addition and slightly increased iron content. The behavior of this alloy was tested under irradiation in a pressurized water reactor (PWR) and has shown improvement in irradiation creep strength and similar free growth compared with M5. This paper provides results on dimensional stability and details the microstructural evolution of the Q12 alloy under neutron irradiation in PWRs. The Q12 microstructural evolution under irradiation was studied for fast neutron fluences up to 13 X 10{sup 25} n/m{sup 2} (E>1 MeV) with analytical transmission electron microscopy observations. We focused on radiation-enhanced needle-like particles, Laves phases, and the linear density of -component loops. These results are compared with other quaternary zirconium-niobium-tin-iron alloys and with M5. All these results allow a general discussion about microstructural evolution and behavior under irradiation of quaternary-type alloys compared to M5 alloy. This study, in agreement with previous works on Zr-1Nb and quaternary alloys, seems to show that increasing the iron content with the presence of niobium and tin will decrease the -component loop linear density and delay the growth breakaway. (authors)

36 MATERIALS SCIENCE↗

Properties of Noise Cross-Correlation Functions Obtained from a Distributed Acoustic Sensing Array at Garner Valley, California

A field test that was conducted at Garner Valley, California, on 11 and 12 September 2013 using distributed acoustic sensing (DAS) to sense ground vibrations provided a continuous overnight record of ambient noise. Furthermore, the energy of ambient noise was concentrated between 5 and 25 Hz, which falls into the typical traffic noise frequency band. A standard procedure (Bensen et al., 2007) was adopted to calculate noise cross-correlation functions (NCFs) for 1-min intervals. The 1-min-long NCFs were stacked using the time–frequency domain phase-weighted-stacking method, which significantly improves signal quality. The obtained NCFs were asymmetrical, which was a result of the nonuniform distributed noise sources. A precursor appeared on NCFs along one segment, which was traced to a strong localized noise source or a scatterer at a nearby road intersection. NCF for the radial component of two surface accelerometers along a DAS profile gave similar results to those from DAS channels. Here, we calculated the phase velocity dispersion from DAS NCFs using the multichannel analysis of surface waves technique, and the result agrees with active-source results. We then conclude that ambient noise sources and the high spatial sampling of DAS can provide the same subsurface information as traditional active-source methods.

58 GEOSCIENCES↗

An Improved Refractive Focusing Optic

A diamond optic that can both dissipate the heat load while reducing phase profile errors of the beam will allow a more full realization of the benefits of the previous investments in light sources by allowing experiments that depend on high resolution imaging or spacial resolution. Reducing the x-ray spot size on samples will improve the quality of this information leading to better understanding of materials properties. During Phase I, we explored techniques for characterizing and improving the accuracy of the shape of diamond lenses, particularly in the apex of the parabolic curve, in order to make an optic whose optical performance exceeds what is currently available. We made efforts to reduce the lens surface roughness through a variety of dry etching methods. Additional work sought to make compound lenses with shorter focal lengths and to mount the lenses on copper supports by a variety of methods. Lastly, lenses were made and tested on the 1-BM beamline at APS.

42 ENGINEERING↗

Helical kink instability in a confined solar eruption

A model for strongly writhing confined solar eruptions suggests an origin in the helical kink instability of a coronal flux rope that remains stable against the torus instability. This model is tested against the well observed filament eruption on 2002 May 27 in a parametric MHD simulation study that comprises all phases of the event. Good agreement with the essential observed properties is obtained. These include the confinement, terminal height, writhing, distortion, and dissolution of the filament, and the flare loops. The agreement is robust against variations in a representative range of parameter space. Careful comparisons with the observation data constrain the ratio of the external toroidal and poloidal field components to B{sub et}/B{sub ep}≈1 and the initial flux rope twist to Φ≈4π. Different from ejective eruptions, two distinct phases of strong magnetic reconnection can occur. First, the erupting flux is cut by reconnection with overlying flux in the helical current sheet formed by the instability. If the resulting flux bundles are linked as a consequence of the erupting rope’s strong writhing, they subsequently reconnect in the vertical current sheet between them. This reforms the overlying flux and a far less twisted flux rope, offering a pathway to homologous eruptions.

79 ASTRONOMY AND ASTROPHYSICS↗

Muon Campus at Fermilab

The Muon Campus at Fermilab provides world class accelerator infrastructure supporting the next generation intensity frontier experiments. The anti-proton source from the Tevatron era was converted to the present day Muon Campus at the end of the collider program in 2011. Currently, the Muon Campus delivers highly polarized muon beams to the Muon g-2 experiment and in a few years, it will provide muon beams to the Mu2e experiment. The Muon g-2 experiment is a high precision test of the standard model; it is precise enough to measure QED, Weak, and QCD Standard Model contributions.The Muon g-2 experiment looks for a significant deviation from the Standard Model whereas the Mu2e experiment looks for rare processes using high intensity muon beams. The Muon g-2 experiment has measured the anomalous magnetic moment of muons to an unprecedented 460 ppb precision with Run 1 data. The experiment has completed 5 runs, accumulating 19$\times$ Brookhaven E821 data set. The Mu2e experiment has completed the construction phase and first beam to the Diagnostic Absorber was run on April 14, 2022. Installation and commissioning of the Mu2e experiment will begin in 2023 and beam commissioning and physics run is currently planned for 2026.

43 PARTICLE ACCELERATORS↗

GM Light Duty Fuel Cell Electric Vehicle Validation Data

General Motors LLC (GM) completed a multi-phase project with the Department of Energy to validate light-duty fuel cell electric vehicle (FCEV) performance and durability using dynamometer fuel cell system and real-world vehicle performance data. This project began with GM’s Gen 0 Fuel Cell Fleet vehicles with Technology Insertion operating strategies and materials, and extended to GM’s Gen 1 and early Gen 2 commercial-design intent Fuel Cell stacks and Fuel Cell Systems. The intent of this project was to understand how fuel cell materials, system architectures, and operating strategies impact fuel cell stack durability under fully dynamic operating conditions such as those seen in a light duty vehicle application. More than 87,000 hours of system run time were accumulated under this project simulating several vehicle lifetimes under aggressive driver usage conditions. Lessons learned from this demonstration project have helped expedite the development of a commercially viable, zero-petroleum, zero-emission, Fuel Cell propulsion system. Durability test results have enabled a substantial reduction in the precious metal content in the Fuel Cell Stack with each successive generation of stack design. Stack lifetimes between the first and current design iterations have increased nearly tenfold, while the overall precious metal content has been reduced by approximately 85%. The Gen 2 system power density (kW/gPt) is over five times that of the Gen 0 system. In addition, run time voltage degradation as a function of total platinum was reduced by more than an order of magnitude between the first and last phase of this project. GM is proceeding with a low volume production program aided by the results of the durability testing performed under this cooperative agreement.

08 HYDROGEN↗

Synthesis of TiO{sub 2} thin films using single molecular precursors by MOCVD method for dye-sensitized solar cells application and study on film growth mechanism

For dye-sensitized solar cells application, in this study, we have synthesized TiO{sub 2} thin films at deposition temperature in the range of 300–750 °C by metalorganic chemical vapor deposition (MOCVD) method. Titanium(IV) isopropoxide, (TIP, Ti(O{sup i}Pr){sub 4}) and Bis(dimethylamido)titanium diisopropoxide, (BTDIP, (Me{sub 2}N){sub 2}Ti(O{sup i}Pr){sub 2}) were used as single source precursors that contain Ti and O atoms in the same molecule, respectively. Crack-free, highly oriented TiO{sub 2} polycrystalline thin films with anatase phase were deposited on Si(1 0 0) with TIP at temperature as low as 450 °C. XRD and TED data showed that below 500 °C, the TiO{sub 2} thin films were dominantly grown in the [2 1 1] direction on Si(1 0 0), whereas with increasing the deposition temperature to 700 °C, the main film growth direction was changed to [2 0 0]. Above 700 °C, however, rutile phase TiO{sub 2} thin films have only been obtained. In the case of BTDIP, on the other hand, only amorphous film was grown on Si(1 0 0) below 450 °C while a highly oriented anatase TiO{sub 2} film in the [2 0 0] direction was obtained at 500 °C. With further increasing deposition temperatures over 600 °C, the main film growth direction shows a sequential change from rutile [1 0 1] to rutile [4 0 0], indicating a possibility of getting single crystalline TiO{sub 2} film with rutile phase. This means that the precursor together with deposition temperature can be one of important parameters to influence film growth direction, crystallinity as well as crystal structure. To investigate the CVD mechanism of both precursors in detail, temperature dependence of growth rate was also carried out, and we then obtained different activation energy of deposition to be 77.9 and 55.4 kJ/mol for TIP and BTDIP, respectively. Also, we are tested some TiO{sub 2} film synthesized with BTDIP precursor to apply dye-sensitized solar cell.

36 MATERIALS SCIENCE↗

Exploring the influence of iron substitution in lithium rich layered oxides Li 2 Ru 1– x Fe x O 3 : triggering the anionic redox reaction

Lithium rich layered materials are an interesting class of materials which exploit both anionic and cationic redox reactions to store energy upwards of 250 mA h g –1 . This paper aims to understand the nature of the redox reactions taking place in these compounds. Li 2 RuO 3 was used as the base compound, which is then compared with compounds generated by partially substituting Ru with Ti and Fe respectively. Electrochemical tests indicate that Fe substitution in the sample leads to an improvement in capacity, cycle life and reduction of potential decay. To elucidate the reason for this improvement in operando diffraction experiments were carried out, highlighting the formation of a secondary de-lithiated phase. The distortion of the pristine structure eventually induces frontier orbital reorganization leading to the oxygen redox reaction resulting in extra capacity. Local changes at Fe and Ru ions are recorded using in operando X-ray absorption spectroscopy (XAS). It was noted that while Ru undergoes a reversible redox reaction, Fe undergoes a significant irreversible change in its coordination environment during cycling. In conclusion, the changes in the coordination environment of oxygen and formation of O 2 n– type species were probed in situ using soft X-rays.

36 MATERIALS SCIENCE↗

High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MST

Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1–2 cm{sup −1} for beam width w = 1.5 cm and 15 cm{sup −1} for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Non-Condon nonequilibrium Fermi’s golden rule rates from the linearized semiclassical method

The nonequilibrium Fermi’s golden rule describes the transition between a photoexcited bright donor electronic state and a dark acceptor electronic state, when the nuclear degrees of freedom start out in a nonequilibrium state. In a previous paper [X. Sun and E. Geva, J. Chem. Theory Comput. 12, 2926 (2016)], we proposed a new expression for the nonequilibrium Fermi’s golden rule within the framework of the linearized semiclassical approximation and based on the Condon approximation, according to which the electronic coupling between donor and acceptor is assumed constant. In this paper we propose a more general expression, which is applicable to the case of non-Condon electronic coupling. We test the accuracy of the new non-Condon nonequilibrium Fermi’s golden rule linearized semiclassical expression on a model where the donor and acceptor potential energy surfaces are parabolic and identical except for shifts in the equilibrium energy and geometry, and the coupling between them is linear in the nuclear coordinates. Since non-Condon effects may or may not give rise to conical intersections, both possibilities are examined by considering the following: (1) A modified Garg-Onuchic-Ambegaokar model for charge transfer in the condensed phase, where the donor-acceptor coupling is linear in the primary-mode coordinate, and for which non-Condon effects do not give rise to a conical intersection; (2) the linear vibronic coupling model for electronic transitions in gas phase molecules, where non-Condon effects give rise to conical intersections. We also present a comprehensive comparison between the linearized semiclassical expression and a progression of more approximate expressions, in both normal and inverted regions, and over a wide range of initial nonequilibrium states, temperatures, and frictions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

THE SCHMIDT-KENNICUTT LAW OF MATCHED-AGE STAR-FORMING REGIONS; Pa{alpha} OBSERVATIONS OF THE EARLY-PHASE INTERACTING GALAXY TAFFY I

In order to test a recent hypothesis that the dispersion in the Schmidt-Kennicutt law arises from variations in the evolutionary stage of star-forming molecular clouds, we compared molecular gas and recent star formation in an early-phase merger galaxy pair, Taffy I (UGC 12915/UGC 12914, VV 254) which went through a direct collision 20 Myr ago and whose star-forming regions are expected to have similar ages. Narrowband Pa{alpha} image is obtained using the ANIR near-infrared camera on the mini-TAO 1 m telescope. The image enables us to derive accurate star formation rates within the galaxy directly. The total star formation rate, 22.2 M{sub Sun} yr{sup -1}, was found to be much higher than previous estimates. Ages of individual star-forming blobs estimated from equivalent widths indicate that most star-forming regions are {approx}7 Myr old, except for a giant H II region at the bridge which is much younger. Comparison between star formation rates and molecular gas masses for the regions with the same age exhibits a surprisingly tight correlation, a slope of unity, and star formation efficiencies comparable to those of starburst galaxies. These results suggest that Taffy I has just evolved into a starburst system after the collision, and the star-forming sites are at a similar stage in their evolution from natal molecular clouds except for the bridge region. The tight Schmidt-Kennicutt law supports the scenario that dispersion in the star formation law is in large part due to differences in evolutionary stage of star-forming regions.

79 ASTRONOMY AND ASTROPHYSICS↗

Metal-poor, strongly star-forming galaxies in the DEEP2 Survey: The relationship between stellar mass, temperature-based metallicity, and star formation rate

We report on the discovery of 28 z≈0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O iii] λ4363 emission line, which provides a “direct” measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFR with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 ± 0.61 dex above the z∼1 stellar mass–SFR relation and 0.23 ± 0.23 dex below the local mass–metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 dex, but significant dispersion remains (0.29 dex with 0.16 dex due to measurement uncertainties). This dispersion suggests that gas accretion, star formation, and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of ≈100{sub −75}{sup +310} Myr, which suggests stochastic star formation. Combining our sample with other z∼1 metal-poor galaxies, we find a weak positive SFR–metallicity dependence (at fixed stellar mass) that is significant at 94.4% confidence. We interpret this positive correlation as recent star formation that has enriched the gas but has not had time to drive the metal-enriched gas out with feedback mechanisms.

79 ASTRONOMY AND ASTROPHYSICS↗

Millicharged scalar fields, massive photons and the breaking of S U ( 3 ) C × U ( 1 ) EM

Under the assumption that the current epoch of the Universe is not special, i.e., is not the final state of a long history of processes in particle physics, the cosmological fate of SU (3) C × U (1) EM is investigated. Spontaneous symmetry breaking of U (1) EM at the temperature of the Universe today is carried out. The charged scalar field Φ EM which breaks the symmetry is found to be ruled out for the charge of the electron, q = e . Scalar fields with millicharges are viable and limits on their masses and charges are found to be q ≲ 10 –3 e and m ΦEM ≲ 10 –5 eV. Furthermore, it is possible that U (1) EM has already been broken at temperatures higher than T = 2.7 K given the nonzero limits on the mass of the photon. A photon mass of m γ = 10 –18 eV, the current upper limit, is found to require a spontaneous symmetry breaking scalar mass of m ΦEM ~ 10 –13 eV with charge q = 10 –6 e, well within the allowed parameter space of the model. Finally, the cosmological fate of the strong interaction is studied. SU (3) C is tested for complementarity in which the confinement phase of QCD + colored scalars is equivalent to a spontaneously broken SU (3) gauge theory. If complementarity is not applicable, SU (3) C has multiple symmetry breaking paths with various final symmetry structures. The stability of the colored vacuum at finite temperature in this scenario is nonperturbative and a definitive statement on the fate of SU (3) C is left open. Cosmological implications for the metastability of the vacua—electromagnetic, color, and electroweak—are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Methods for Quantitative Thermal Analysis of Lithium Solid-State and Beyond Battery Safety

The use of differential scanning calorimetry (DSC) to measure the thermal behavior of individual components and electrolyte/electrode combinations is common. However, here we focus on DSC tests on an anode, cathode, and electrolyte (ACE) component combination over a temperature range that includes many of the phase transitions and key reactions (i.e., to 500 °C) that contribute to thermal runaway. This method can help quantify the complex reaction network in a full cell, thereby informing potential safety issues. Here, we used DSC heat flow data from a solid-state Li 0.43 CoO 2 +C+PVDF | LLZO | Li metal ACE sample and its components to quantify key factors affecting results. We focused on three areas: (1) ACE sample preparation and assembly in DSC pans, (2) DSC measurement parameters, and (3) heat flow analysis. Key points include the choice of component ratios (e.g., commercially relevant N:P capacity ratio), the importance of conductive carbon and binder, type of pan used, DSC ramp rate, and integration method used when dealing with broad and overlapping exothermic peaks. This work deepens the scientific basis and best practices for obtaining heat flow data from ACE samples for early-stage evaluation of solid-state and beyond battery safety.

25 ENERGY STORAGE↗

Battery Electric Vehicle Eco-Cooperative Adaptive Cruise Control in the Vicinity of Signalized Intersections

This study develops a connected eco-driving controller for battery electric vehicles (BEVs), the BEV Eco-Cooperative Adaptive Cruise Control at Intersections (Eco-CACC-I). The developed controller can assist BEVs while traversing signalized intersections with minimal energy consumption. The calculation of the optimal vehicle trajectory is formulated as an optimization problem under the constraints of (1) vehicle acceleration/deceleration behavior, defined by a vehicle dynamics model; (2) vehicle energy consumption behavior, defined by a BEV energy consumption model; and (3) the relationship between vehicle speed, location, and signal timing, defined by vehicle characteristics and signal phase and timing (SPaT) data shared under a connected vehicle environment. The optimal speed trajectory is computed in real-time by the proposed BEV eco-CACC-I controller, so that a BEV can follow the optimal speed while negotiating a signalized intersection. The proposed BEV controller was tested in a case study to investigate its performance under various speed limits, roadway grades, and signal timings. In addition, a comparison of the optimal speed trajectories for BEVs and internal combustion engine vehicles (ICEVs) was conducted to investigate the impact of vehicle engine types on eco-driving solutions. Lastly, the proposed controller was implemented in microscopic traffic simulation software to test its networkwide performance. The test results from an arterial corridor with three signalized intersections demonstrate that the proposed controller can effectively reduce stop-and-go traffic in the vicinity of signalized intersections and that the BEV Eco-CACC-I controller produces average savings of 9.3% in energy consumption and 3.9% in vehicle delays.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

CLUMPY DISKS AS A TESTBED FOR FEEDBACK-REGULATED GALAXY FORMATION

We study the dependence of fragmentation in massive gas-rich galaxy disks at z >1 on stellar feedback schemes and hydrodynamical solvers, employing the GASOLINE2 SPH code and the lagrangian mesh-less code GIZMO in finite mass mode. Non-cosmological galaxy disk runs with the standard delayed-cooling blastwave feedback are compared with runs adopting a new superbubble feedback, which produces winds by modeling the detailed physics of supernova-driven bubbles and leads to efficient self-regulation of star formation. We find that, with blastwave feedback, massive star-forming clumps form in comparable number and with very similar masses in GASOLINE2 and GIZMO. Typical clump masses are in the range 10{sup 7}–10{sup 8} M {sub ⊙}, lower than in most previous works, while giant clumps with masses above 10{sup 9} M {sub ⊙} are exceedingly rare. By contrast, superbubble feedback does not produce massive star-forming bound clumps as galaxies never undergo a phase of violent disk instability. In this scheme, only sporadic, unbound star-forming overdensities lasting a few tens of Myr can arise, triggered by non-linear perturbations from massive satellite companions. We conclude that there is severe tension between explaining massive star-forming clumps observed at z >1 primarily as the result of disk fragmentation driven by gravitational instability and the prevailing view of feedback-regulated galaxy formation. The link between disk stability and star formation efficiency should thus be regarded as a key testing ground for galaxy formation theory.

79 ASTRONOMY AND ASTROPHYSICS↗

CTF_

CTF is a thermal-hydraulic simulation tool designed for modeling the reactor vessel region of light water reactors. The code is capable of modeling both coolant and solid regions and includes a nuclear fuel rod model. Coolant is represented with a 9-equation (two phases plus droplets and non-condensable gas) model with closure relationships being provided for normal and accident conditions. Meshing is done using the subchannel approach, which models the coolant region as a collection of parallel 1-D flow paths that communicate laterally through "gaps". CTF also includes a collection of supporting software tools that include: Xml2ctf - A utility for creating native CTF input decks from a simplified input file; pyCTF - A collection of Python utilities used for post-processing CTF results, manipulating CTF input models, and testing differences between output files; CTFFuel - A separate front-end to the CTF fuel rod solver package; Multistate - A separate driver for CTF that communicates through the code coupling interface; and veraAPI - A c++ interface to the code.

Salko, Robert K↗