Radio pulsar B0950++08: Radiation in Magnetosphere and Sparks above Surface

The nearby radio pulsar B0950$+$08 with full duty cycle is targeted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST, 110 minutes allocated), via adopting polarization calibration on two ways of baseline determination, in order to understand its magnetospheric radiation geometry as well as the polar cap sparking. % The radiation of the main pulse could not be informative of magnetic field line planes due to its low linear polarization ($<10 \%$) and the position angle jumps, and the polarization position angle in the pulse longitudes whose linear fractions are larger than $\sim 30 \%$ is thus fitted in the classical rotating vector model (RVM). % The best RVM fit indicates that the inclination angle, $\alpha$, and the impact angle, $\beta$, of this pulsar are $100.5^{\circ}$ and $-33.2^{\circ}$, respectively, suggesting that the radio emission comes from two poles. % Polar cap sparking in the vacuum gap model, either the annular gap or the core gap, is therefore investigated in this RVM geometry, resulting in a high-altitude magnetospheric emission at heights from $\sim 0.25R_{\rm LC}$ to $\sim 0.56R_{\rm LC}$, with $R_{\rm LC}$ the light cylinder radius. % It is evident that both sparking points of the main and inter pulses are located mainly away from the magnetic pole, that is meaningful in the physics of pulsar surface and is even relevant to pulsar's inner structure.Comment: 13 pages, 9 figures, submitte

Increasing Area and Decreasing Depth: Climate Change Influence on Snow Variations in the Qilian Mountains

The Qilian Mountains serve as a critical water source for the Yellow River and various inland rivers, playing a pivotal role in regulating the regional climate. Given their significance as one of the foremost water resources in the area, the spatial and temporal dynamics of the snow are crucial for understanding potential impacts on regional hydrology and ecology. This study examines the characteristics of spatial and temporal variations in snow-covered extent (SCE), snow depth (SD), snow-covered days (SCD), snow onset date (SOD), and snow end date (SED) within the Qilian Mountains region. We investigate the hydrological and ecological implications utilizing snow area and phenology data, alongside SD data. The findings indicate that: (1) the distribution of snow across the Qilian Mountains mainly splits between the central and western areas, with the central region showing deeper snow than both the eastern and western parts; (2) the area covered by snow in the Qilian Mountains is growing, but the depth of the snow is on a decline, especially in the central area; (3) in terms of snow phenology, most of the region is witnessing an earlier start of SOD, a longer SCD, and an earlier SED. An overall increase in precipitation is identified as the key factor behind the expanded SCE in the Qilian Mountains, while rising temperatures are pinpointed as the primary cause for the reduction in SD. As global climate change intensifies, the observed alterations in the snow of the Qilian Mountains present emerging challenges for regional water security and ecological equilibrium

Dielectric and elastic properties of 0.70Pb(Mg 1/3 Nb 2/3 ) O 3 -0.30PbTiO 3 single crystal and their electric-field dependence

Abstract The dielectric and elastic properties of [001] coriented 0.7Pb(Mg 1/3 Nb 2/3 )O 3 -0.3PbTiO 3 (PMN-0.3PT) crystal were investigated as a function of poling field at 300 and 360 K, respectively. At 300 K, the dielectric constant and elastic compliance of rhombohedral PMN-0.3PT crystal change drastically at a critical field corresponding to an electric-induced ferroelectric phase transition. At 360 K, the PMN-0.3PT crystal is tetragonal, its dielectric constant and elastic compliance change drastically at two critical fields, which indicates an intermediate phase. Furthermore, much small dielectric loss factors and mechanical loss factors are observed in mono-domain state, which indicates that losses mainly come from domain wall contributions

Dielectric and elastic properties of 0.70Pb(Mg 1/3 Nb 2/3 ) O 3 -0.30PbTiO 3 single crystal and their electric-field dependence

Abstract The dielectric and elastic properties of [001] coriented 0.7Pb(Mg 1/3 Nb 2/3 )O 3 -0.3PbTiO 3 (PMN-0.3PT) crystal were investigated as a function of poling field at 300 and 360 K, respectively. At 300 K, the dielectric constant and elastic compliance of rhombohedral PMN-0.3PT crystal change drastically at a critical field corresponding to an electric-induced ferroelectric phase transition. At 360 K, the PMN-0.3PT crystal is tetragonal, its dielectric constant and elastic compliance change drastically at two critical fields, which indicates an intermediate phase. Furthermore, much small dielectric loss factors and mechanical loss factors are observed in mono-domain state, which indicates that losses mainly come from domain wall contributions

Enhancement of Ultrasonic Transducer Bandwidth by Acoustic Impedance Gradient Matching Layer

High-performance broadband ultrasound transducers provide superior imaging quality in biomedical ultrasound imaging. However, a matching design that perfectly transmits the acoustic energy between the active piezoelectric element and the target medium over the operating spectrum is still lacking. In this work, an anisotropic gradient acoustic impedance composite material as the matching layer of an ultrasonic transducer was designed and fabricated; it is a non-uniform material with the continuous decline of acoustic impedance along the direction of ultrasonic propagation in a sub-wavelength range. This material provides a broadband window for ultrasonic propagation in a wide frequency range and achieves almost perfect sound energy transfer efficiency from the piezoelectric material to the target medium. Nano tungsten particles and epoxy resin were selected as filling and basic materials, respectively. Along the direction of ultrasonic propagation, the proportion of tungsten powder was carefully controlled to decrease gradually, following the natural exponential form in a very narrow thickness range. Using this new material as a matching layer with high-performance single crystals, the &minus;6 dB bandwidth of the PMN-PT ultrasonic transducer could reach over 170%, and the insertion loss was only &minus;20.3 dB. The transducer achieved a temporal signal close to a single wavelength, thus there is the potential to dramatically improve the resolution and imaging quality of the biomedical ultrasound imaging system