Mass measurements of neutron-deficient Y, Zr, and Nb isotopes and their impact on rp and νp nucleosynthesis processes
Not Available
07 ISOTOPE AND RADIATION SOURCES↗
Engineering topics
Zhou, X.
Publications and source records attributed to Zhou, X..
Intergranular stress study of TC11 titanium alloy after laser shock peening by synchrotron-based high-energy X-ray diffraction
The distribution of residual lattice strain as a function of depth were carefully investigated by synchrotron-based high energy X-ray diffraction (HEXRD) in TC11 titanium alloy after laser shock peening (LSP). The results presented big compressive residual lattice strains at surface and subsurface, then tensile residual lattice strains in deeper region, and finally close to zero lattice strains in further deep interior with no plastic deformation thereafter. These evolutions in residual lattice strains were attributed to the balance of direct load effect from laser shock wave and the derivative restriction force effect from surrounding material. Significant intergranular stress was evidenced in the processed sample. The intergranular stress exhibited the largest value at surface, and rapidly decreased with depth increase. The magnitude of intergranular stress was proportional to the severity of the plastic deformation caused by LSP. Two shocks generated larger intergranular stress than one shock.
36 MATERIALS SCIENCE↗
Effect of Mn Doping on the Structural, Magnetic, and Magnetocaloric Effect of Fe{sub 17}Dy{sub 2} Compounds
Crystal structural and magnetic properties of polycrystalline (Fe{sub 1−x}Mn{sub x}){sub 17}Dy{sub 2} (x = 0.0, 0.1, 0.2, and 0.3) compounds were studied by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) measurements. The results show that (Fe{sub 1−x}Mn{sub x}){sub 17}Dy{sub 2} forms as a substitutional solid solution with the hexagonal Th{sub 2}Ni{sub 17} type. The unit cell volume increases with Mn content. The Curie temperature (T{sub C}) can be tuned from 364 K for x = 0.0 to 80 K for x = 0.3. The magnetic transition at T{sub C} is a typical second-order ferromagnetic-paramagnetic transition. For an applied field change from 0 to 5 T, the maximum magnetic entropy change (| − ΔS{sub M}|) for (Fe{sub 1−x}Mn{sub x}){sub 17}Dy{sub 2} (x = 0.0, 0.1, and 0.2) compounds are 3.9, 2.8, and 1.7 J kg{sup −1} k{sup −1}, respectively. The high ΔS{sub M}, appropriate T{sub C}, and a high performance-to-cost ratio make (Fe{sub 1−x}Mn{sub x}){sub 17}Dy{sub 2} compounds a candidate materials for room-temperature magnetic refrigeration applications.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
The in-depth residual strain heterogeneities due to an indentation and a laser shock peening for Ti-6Al-4V titanium alloy
In this paper, heterogeneity of the through-thickness residual strain due to the laser shock peening (LSP) in comparison with that due to the indentation was studied in Ti-6Al-4V alloy samples. The latter is almost a quasi-static process while the former features extremely high strain-rate deformation. The synchrotron based high-energy X-ray diffraction was employed to investigate the through-thickness residual strain distribution. The studied two samples after the two processing procedures share the following features: (i) the pressure affected depths are both ~2 mm and (ii) the largest magnitudes of the compressive residual strains parallel to the surface are ~4,000 με. However, the pit depth for the indentation sample is ~9 times larger than that for the LSP. The position featuring the largest magnitude of the compressive residual strain is in the sub-surface for the indentation while it is in the surface for the LSP. Results of the elastic-visco-plastic finite element simulation for the indentation indicate that the position featuring the maximum accumulative plastic shear as defined in this paper corresponds to the location with the largest magnitude of compressive residual strain. To validate this finding, full width at half maximum (FWHM) of the X-ray diffraction profile, which is proportional to the level of the plastic deformation, is also studied. Finally, it is found that positions with the largest FWHM indeed correspond to the largest magnitude of compressive residual strain for both tests.
36 MATERIALS SCIENCE↗
The Simulation of Precipitation Evolutions and Mechanical Properties in Friction Stir Welding with Post-Weld Heat Treatments
A finite element model of friction stir welding capable of re-meshing is used to simulate the temperature variations. Re-meshing of the finite element model is used to maintain a fine mesh resolving the gradients of the solution. The Kampmann–Wagner numerical model for precipitation is then used to study the relation between friction stir welds with post-weld heat treatment (PWHT) and the changes in mechanical properties. Results indicate that the PWHT holding time and PWHT holding temperature need to be optimally designed to obtain FSW with better mechanical properties. Higher precipitate number with lower precipitate sizes gives higher strength in the stirring zone after PWHT. The coarsening of precipitates in HAZ are the main reason to hinder the improvement of mechanical property when PWHT is used.
36 MATERIALS SCIENCE↗
Magnetic Resonance with Squeezed Microwaves
Not Available
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Towards Resolving the Atomization Process of an Idealized Fire Sprinkler with VOF Modeling
Fire suppression modeling depends on accurate characterization of the atomization processes of fire sprinklers.Numerical modeling, particularly the volume of fluid (VOF) method, has been applied to understanding the atomization behavior of an idealized sprinkler geometry consisting of a 9.5 mm inner-diameter cylindrical nozzle and a flat, 25.4 mm diameter disk with a liquid flow rate of 0.87 L/s. The simulations have been performed with an OpenFOAM based VOF solver, using the isoAdvector scheme for interfacial reconstruction. The sheet breakup distance and film thickness were calculated and compared with measurements from a previous study. A mesh refinement study identified the sensitivities in the predicted quantities to mesh resolution. This study enables furtherapplication of the model to simulation of the fully atomized spray.
Engineering↗
Airside HVAC BESTEST: HVAC Air-Distribution System Model Test Cases for ASHRAE Standard 140
This paper summarizes recent work to develop new airside HVAC equipment model analytical verification test cases for ANSI/ASHRAE Standard 140, Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs. The analytical verification test method allows comparison of simulation results from a wide variety of building energy simulation programs with quasi-analytical solutions, further described below. Standard 140 is widely cited for evaluating software for use with performance-path energy efficiency analysis, in conjunction with well-known energy-efficiency standards including ASHRAE Standard 90.1, the International Energy Conservation Code, and other international standards. Airside HVAC Equipment is a common area of modelling not previously explicitly tested by Standard 140. Integration of the completed test suite into Standard 140 is in progress.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
High-precision Q EC values of superallowed 0 + → 0 + β-emitters 46 Cr, 50 Fe and 54 Ni
Short-lived 46 Cr, 50 Fe and 54 Ni were studied by isochronous mass spectrometry at the HIRFL-CSR facility in Lanzhou. The measured precision mass excesses (ME) of 46 Cr, 50 Fe and 54 Ni are -29471(11) keV, -34477(6) keV and -39278(4) keV, respectively. The superallowed 0 + →0+β-decay Q values were derived to be Q EC ( 46 Cr) =7604(11) keV, Q EC ( 50 Fe) =8150(6) keV and Q EC ( 54 Ni) =8731(4) keV. The values for 50 Fe and 54 Ni are by one order of magnitude more precise than the adopted literature values. By combining the existing half-lives and branching ratios, we obtained the corrected ℱt values to be ℱt( 50 Fe) =3103(70) s and ℱt( 54 Ni) =3076(50) s. The main contribution to the ℱt uncertainties is now due to β-decay branching ratios, still, more high-precision measurements of the half-lives, the masses, and especially the branching ratios are needed in order to satisfy the requirements for a stringent CVC test.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
ELECTRON ACCELERATION BY CASCADING RECONNECTION IN THE SOLAR CORONA. II. RESISTIVE ELECTRIC FIELD EFFECTS
We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics. Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.
79 ASTRONOMY AND ASTROPHYSICS↗
LUT REVEALS AN ALGOL-TYPE ECLIPSING BINARY WITH THREE ADDITIONAL STELLAR COMPANIONS IN A MULTIPLE SYSTEM
A complete light curve of the neglected eclipsing binary Algol V548 Cygni in the UV band was obtained with the Lunar-based Ultraviolet Telescope in 2014 May. Photometric solutions are obtained using the Wilson–Devinney method. It is found that solutions with and without third light are quite different. The mass ratio without third light is determined to be q = 0.307, while that derived with third light is q = 0.606. It is shown that V548 Cygni is a semi-detached binary where the secondary component is filling the critical Roche lobe. An analysis of all available eclipse times suggests that there are three cyclic variations in the O–C diagram that are interpreted by the light travel-time effect via the presence of three additional stellar companions. This is in agreement with the presence of a large quantity of third light in the system. The masses of these companions are estimated as m sin i′ ∼ 1.09, 0.20, and 0.52 M{sub ⊙}. They are orbiting the central binary with orbital periods of about 5.5, 23.3, and 69.9 years, i.e., in 1:4:12 resonance orbit. Their orbital separations are about 4.5, 13.2, and 26.4 au, respectively. Our photometric solutions suggest that they contribute about 32.4% to the total light of the multiple system. No obvious long-term changes in the orbital period were found, indicating that the contributions of the mass transfer and the mass loss due to magnetic braking to the period variations are comparable. The detection of three possible additional stellar components orbiting a typical Algol in a multiple system make V548 Cygni a very interesting binary to study in the future.
79 ASTRONOMY AND ASTROPHYSICS↗
Airside HVAC BESTEST. Adaptation of ASHRAE RP 865 Airside HVAC Equipment Modeling Test Cases for ASHRAE Standard 140. Volume 1, Cases AE101-AE445
This report documents a set of diagnostic analytical verification cases for testing the ability of whole building simulation software to model the air distribution side of typical heating, ventilating and air conditioning (HVAC) equipment. These cases complement the unitary equipment cases included in American National Standards Institute (ANSI)/American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 140, Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs, which test the ability to model the heat-transfer fluid side of HVAC equipment.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Photometric and period investigation of the late F-type overcontact binary II UMa
II UMa is a late F-type (F5) contact binary with a close-in tertiary and a distant visual companion. According to the four-color (B V R{sub c}I{sub c}) light curves’ solutions of II UMa, it is a high fill-out (f = 86.6%) and low-mass ratio (q = 0.172) contact binary system, which indicates that it is at the late evolutionary stage of late-type tidal-locked binary stars. The masses of the primary star and secondary star are calculated to be M{sub 1}=1.99M{sub ⊙} and M{sub 2}=0.34M{sub ⊙}. The primary star has evolved from the zero-age main sequence, but it still appeared before the terminal-age main sequence, and the secondary star is even more evolved. Considering the mass ratio (M{sub 3}/M{sub 1}=0.67) obtained by spectroscopic observations, the mass of the close-in tertiary is estimated to be M{sub 3}=1.34M{sub ⊙}. The period variations of the binary system are investigated for the first time. According to the observed–calculated (O−C) curve analysis, a continuous period increase at a rate of dP/dt=4.88×10{sup −7} day yr{sup −1} is determined. The parabolic variation in the O−C curve may be part of a cyclic period of change, or the combined period of change of a parabolic variation and a cyclic one. More instances of minimum light are needed to confirm this. The presence of the tertiary component may play an important role in the formation and evolution of this binary system by drawing angular momentum from the central system during the pre-contact stage.
79 ASTRONOMY AND ASTROPHYSICS↗
Controlling spin relaxation with a cavity
Spontaneous emission of radiation is one of the fundamental mechanisms by which an excited quantum system returns to equilibrium. For spins, however, spontaneous emission is generally negligible compared to other non-radiative relaxation processes because of the weak coupling between the magnetic dipole and the electromagnetic field. In 1946, Purcell realized that the rate of spontaneous emission can be greatly enhanced by placing the quantum system in a resonant cavity. This effect has since been used extensively to control the lifetime of atoms and semiconducting heterostructures coupled to microwave or optical cavities, and is essential for the realization of high-efficiency single-photon sources. In this paper, we report the application of this idea to spins in solids. By coupling donor spins in silicon to a superconducting microwave cavity with a high quality factor and a small mode volume, we reach the regime in which spontaneous emission constitutes the dominant mechanism of spin relaxation. The relaxation rate is increased by three orders of magnitude as the spins are tuned to the cavity resonance, demonstrating that energy relaxation can be controlled on demand. Our results provide a general way to initialize spin systems into their ground state and therefore have applications in magnetic resonance and quantum information processing. Finally, they also demonstrate that the coupling between the magnetic dipole of a spin and the electromagnetic field can be enhanced up to the point at which quantum fluctuations have a marked effect on the spin dynamics; as such, they represent an important step towards the coherent magnetic coupling of individual spins to microwave photons.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
A solar-type stellar companion to a deep contact binary in a quadruple system
The four-color (B, V, R{sub c}, I{sub c}) light curves of V776 Cas are presented and analyzed using the Wilson–Devinney method. It is discovered that V776 Cas is an early F-type (F2V) overcontact binary with a very high contact degree (f = 64.6%) and an extremely low-mass ratio (q = 0.130), which indicate that it is at the final evolutionary stage of cool short-period binaries. The mass of the primary and secondary stars are calculated to be M{sub 1} = 1.55(±0.04) M{sub ⊙}, M{sub 2} = 0.20(±0.01) M{sub ⊙}. V776 Cas is supposed to be formed from an initially detached binary system via the loss of angular momentum due to the magnetic wind. The initial masses of the present primary and secondary components are calculated to be M{sub 1i} = 0.86(±0.10) M{sub ⊙} and M{sub 2i} = 2.13(±0.04) M{sub ⊙}. The observed–calculated curve exhibits a cyclic period variation, which is due to the light-travel time effect caused by the presence of a third component with a period of 23.7 years. The mass of the third component is estimated to be M{sub 3} = 1.04(±0.03) M{sub ⊙} and the orbital inclination of the third component is calculated to be i′ = 33.°1. The distance of the binary system to the mass center of the triple system is calculated to be a{sub 12}{sup ′} = 3.45 AU. The presence of the close-in tertiary component may play an important role in the formation and evolution of this binary system by drawing angular momentum from the central system.
79 ASTRONOMY AND ASTROPHYSICS↗
Ridge InGaAs/InP multi-quantum-well selective growth in nanoscale trenches on Si (001) substrate
Metal organic chemical vapor deposition of InGaAs/InP multi-quantum-well in nanoscale V-grooved trenches on Si (001) substrate was studied using the aspect ratio trapping method. A high quality GaAs/InP buffer layer with two convex (111) B facets was selectively grown to promote the highly uniform, single-crystal ridge InP/InGaAs multi-quantum-well structure growth. Material quality was confirmed by transmission electron microscopy and room temperature micro-photoluminescence measurements. This approach shows great promise for the fabrication of photonics devices and nanolasers on Si substrate.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Reaching the quantum limit of sensitivity in electron spin resonance
The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science, from in vivo imaging to distance measurements in spin-labelled proteins. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here in this work, using a Josephson parametric microwave amplifier combined with high-quality-factor superconducting microresonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. In conclusion, the detection volume of our resonator is ~0.02nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗