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<jats:title>Abstract</jats:title> <jats:p>We study the spontaneous emission (SE) of an excited two-level nonrelativistic system (TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS's transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initial being at rest are obtained, it is found in the first order of the mass $M$ that the frequency of the emitted photon is smaller than the transition frequency of the TLS and the SE rate is smaller than the SE rate $\Gamma_{f}$ of the TLS fixed in the same waveguide. The SE rate for the TLS initial being moving is obtained in the second order of the mass $M$. The SE rate is smaller than $\Gamma_{f}$ but it is dependent not only of the atomic mass but also of the initial momentum. The carried frequency of the emitted photon is decreased when it travels along the direction of the initial momentum but is increased when it travels in the opposite direction of the initial momentum.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To study the influence of thickness on the magnetic properties of REBCO (RE = Y, Gd, Sm, Nd, etc.) bulk superconductors, a single domain gadolinium barium copper oxide (GdBCO) bulk superconductor fabricated by the RE + 011 top seeded infiltration growth (RE + 011 TSIG) method was continuously sliced along the bottom to obtain samples of different thickness. The levitation force and attractive force of these samples were tested at 77 K in the zero-field-cooled (ZFC) state. It was found that as the sample thickness decreases, the levitation force decreases gradually whereas the attractive force increases. This is related to the varied ability to resist the penetration of magnetic field occasioned by varying sample thickness, which were deeply revealed combined with the characteristics of the non-ideal type-II superconductor. Further, the levitation force exhibits a trend of slow initial change followed by rapid change, which may be attributed to the growth of the sample. Measurement of the trapped field shows that a similar distribution of trapped field at the top and bottom surfaces can be achieved by removing some materials from the bottom of the bulk. These results provide a reference for meeting the actual requirements of REBCO bulks of different thicknesses and greatly contribute to practical design and application. Keywords: single domain GdBCO bulk superconductor; thickness; levitation force; attractive force</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Diffusion on a spherical surface with trapping is a common phenomenon in cell biology and porous systems. In this paper, we have studied the diffusion dynamics in a branched spherical structure and explored the impact of the geometry of the structure on the diffusion process. The process is a spherical movement that occurs only for a fixed radius and is interspersed with a radial motion inward and outward of the sphere. Two scenarios govern the transport process in the spherical cavity: free diffusion and diffusion under external velocity. The diffusion dynamics have been described using the concepts of probability density function (PDF) and mean square displacement (MSD) by Fokker-Planck equation in spherical coordinate system. The effects of dead ends, sphere curvature, and velocity on PDF and MSD have been analyzed numerically in detail. We found a transient non-Gaussian distribution and sub-diffusion regime governing the angular dynamics. The results show that there is an enhancement in the diffusion dynamics as the curvature of the spherical surface increases and an external force is applied in the same direction of the motion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, AlGaN/GaN heterojunction field-effect transistors (HFETs) with p-GaN cap layer are developed for normally-off operation, in which an in-situ grown AlN layer is utilized as gate insulator. Compared with the SiN<jats:sub>x</jats:sub> gate insulator, the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region, which helps to positively shift the threshold voltage. In addition, the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage. Owing to the introduction of AlN layer, normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized. Furthermore, the field-effect mobility is approximately 1500 cm<jats:sup>2</jats:sup>V<jats:sup>-1</jats:sup>s<jats:sup>-1</jats:sup> in 2DEG channel, implying the good device performance.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Mimicking tactile perception is critical to the development of advanced interactive neuromorphic platforms. Inspired by cutaneous perceptual functions, a bionic tactile perceptual platform is proposed. PDMS based tactile sensors act as bionic skin touch receptors. Flexible indium tin oxide neuromorphic transistors fabricated with a single-step mask processing act as artificial synapses. Thus, the tactile perceptual platform possesses the ability of information processing. Interestingly, the flexible tactile perception platform can find applications in information encryption and decryption. With adoption of cipher, signal transmitted by the perception platform is encrypted. Thus, the security of information transmission is effectively improved. The flexible tactile perceptual platform would have potentials in cognitive wearable devices, advanced human-machine interaction system and intelligent bionic robots.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> <jats:bold>Background:</jats:bold> The ultrasonic backscatter (UB) has the advantage of non-invasively obtaining bone density and structure, and it is expected to be an assessment tool for osteoporosis early diagnosis. The previous UB measurements were all based on exciting a short single-pulse and analyzed the ultrasonic signals backscattered in bone. Purpose: This study aims to investigate an amplitude modulation (AM) ultrasonic excitation with UB measurements for estimating bone characteristics. <jats:bold>Methods:</jats:bold> The AM multiple lengths excitation and backscatter measurement (AM-UB) functions were integrated into a portable ultrasonic instrument for bone characterization. The apparent integrated backscatter coefficient in the AM excitation (AIB<jats:sub>AM</jats:sub>) was calculated on the AM-UB instrumentation. The correlation coefficients of the AIB<jats:sub>AM</jats:sub> estimating volume fraction (BV/TV), structure model index (SMI), and bone mineral density (BMD) were analyzed. <jats:bold>Results:</jats:bold> Significant correlations (|R| = 0.82 – 0.93, p &amp;#60; 0.05) were found between the AIB<jats:sub>AM</jats:sub>, BV/TV, SMI, and BMD. When increasing the AM excitation length, the AIB<jats:sub>AM</jats:sub> values show more stabilized both in 1.0 MHz and 3.5 MHz measurements. The recommendations in AM-UB measurement were that the avoided length (T1) should be less than AM excitation length, and the analysis length (T2) should be appropriately long but not more than AM excitation length. <jats:bold>Conclusions:</jats:bold> This study conducts an AM-UB measurement for cancellous bone characterization. Increasing AM excitation length can significantly improve AIB<jats:sub>AM</jats:sub> values stability with varied analyzed signals. The study suggests the portable AM-UB instrument with the integration of real-time analytics software that might provide a potential tool for osteoporosis early screening.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Theoretical calculations of the energy levels and magnetic dipole transition parameters for the 1s<jats:sup>2</jats:sup>2s<jats:sup>2</jats:sup>2p<jats:sup>3</jats:sup> and 1s<jats:sup>2</jats:sup>2p<jats:sup>5</jats:sup> configurations of nitrogen isoelectronic sequence with Z=21~30 are performed using multi-congfiguration Dirac-Fock(MCDF) method. Based on the relativistic computational code GRASP2k compiled within the framework of MCDF method, the electron correlations, Breit interaction and QED effects are well treated in detail. The energy levels, line strengths and transition rates of magnetic dipole transition are obtained and compared with the experimental data available. For most cases, good agreements are achieved and the relative differences of them are less than 0.114%, 8.43% and 9.80%, respectively. The scaling laws of the fine structure splitting and transition rate are obtained on the isoelectronic sequence and the corresponding physical mechanisms are discussed. The data sets for tables are openly available at https://www.scidb.cn/s/7nYvem.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Low-voltage trigger silicon-controlled rectifier (LVTSCR) has attracted widespread attention due to its trigger capability at a low voltage range. However, the relatively low holding voltage of traditional LVTSCR potentially increases the risk of latch-up. In this paper, a novel structure of LVTSCR with low trigger voltage and high holding voltage has been proposed for electrostatic discharge (ESD) protection. The proposed ESD protection device possesses an ESD implant and a floating n-well which enhances the current discharge capability of the Gate-grounded NMOS and weakens the current gain of the silicon-controlled rectifier current path. Based on the simulation results, the proposed device retains a low trigger voltage characteristic of LVTSCR and simultaneously increases the holding voltage to 5.53 V, providing an effective way to meet the ESD protection requirement of the 5 V CMOS process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>UiO-66 is a potential material for adsorption heat transformation (AHT) with high specific surface area, and excellent thermal and chemical stability. However, the low water adsorption capacity of UiO-66 in the low relative pressure range (0&amp;#60;P/P<jats:sub>0</jats:sub>&amp;#60;0.3) limits its application in AHT. We prepared the UiO-66 modified by MgCl<jats:sub>2</jats:sub> with the methods of solvothermal and impregnation, and studied their water vapor adsorption performance and heat storage capacity. Attributed to the extremely high saturated water uptake and excellent hydrophilicity of MgCl<jats:sub>2</jats:sub>, the water adsorption performance of UiO-66 was improved, although the introduction of MgCl<jats:sub>2</jats:sub> reduced its specific surface area and pore volume. The water adsorption capacity at (P/P<jats:sub>0</jats:sub>=0.3) and the saturated water adsorption capacity of the UiO-66 (with MgCl<jats:sub>2</jats:sub> content of 0.57 wt.%) modified by the solvothermal method was 0.27 g/g and 0.57 g/g at 298 K, respectively, which is 68.8 % and 32.6 % higher than that of pure UiO-66. Compared with pure UiO-66, the water adsorption capacity of the UiO-66 (with MgCl<jats:sub>2</jats:sub> content of 1.02 wt.%) modified by the impregnation method is increased by 56.3 % and 14.0 % at the same pressure, respectively. During 20 water adsorption/desorption cycles, the above two materials showed high heat storage densities (~1293 J/g and 1378 J/g). Therein, the UiO-66 modified by the solvothermal method exhibits excellent cyclic stability. These results suggest that the introduction of an appropriate amount of MgCl<jats:sub>2</jats:sub> makes UiO-66 more suitable for AHT applications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ferroelectric (FE) HfZrO/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> gate stack AlGaN/GaN metal-FE-semiconductor heterostructure field-effect transistors (MFSHEMTs) with varying Al<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Ga<jats:sub>1-<jats:italic>x</jats:italic> </jats:sub>N barrier thickness and Al composition are investigated and compared by TCAD simulation with non-FE HfO<jats:sub>2</jats:sub>/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> gate stack metal-insulator-semiconductor heterostructure field-effect transistors (MISHFETs). Results show that the decrease of the two-dimensional electron gas density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHFETs due to the enhanced FE polarization switching efficiency. The electrical characteristics of MFSHEMTs, including transconductance, subthreshold swing, and on-state current, effectively improve with decreasing AlGaN thickness in MFSHEMTs. High Al composition in AlGaN barrier layers that are under 3 nm thickness plays a great role in enhancing the two-dimensional electron gas density and FE polarization in MFSHEMTs, improving the transconductance and the on-state current. The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs, affording favorable conditions for further enhancing the device.</jats:p>