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<jats:p>Acoustic characteristics of pulse detonation engine (PDE) sound propagating in enclosed space are numerically and experimentally investigated. The finite element software LS-DYNA is utilized to numerically simulate the PDE sound propagating in enclosed space. Acoustic measurement systems are established for testing the PDE sound in enclosed space, and the time-frequency characteristics of PDE sound in enclosed space are reported in detail. The experimental results show that the sound waveform of PDE sound in enclosed space are quite different from those in open space, and the reflection and superposition of PDE sound on the walls of enclosed space results in the sound pressure oscillating obviously. It is found that the peak sound pressure level (PSPL) and overall sound pressure level (OASPL) of PDE sound in enclosed space are higher than those in open space and their difference increases with the rise of propagation distance. The results of the duration of PDE sound indicate that the A duration of PDE sound in enclosed space is higher than that in open space except at measuring points located at 2-m and 5-m while the B duration is higher at each of all measuring points. Results show that the enclosed space has a great influence on the acoustic characteristic of PDE sound. This research is helpful in performing PDE experiments in enclosed laboratories to prevent the PDE sound from affecting the safety of laboratory environment, equipment, and staffs.</jats:p>

<jats:p>To promote high-speed boundary layer transition, this paper proposes an active self-sustaining dual jets (SDJ) actuator utilizing the energy of supersonic mainflow. Employing the nanoparticle-based planar laser scattering (NPLS), supersonic flat-plate boundary layer transition induced by SDJ is experimentally investigated in an <jats:italic>Ma</jats:italic>-2.95 low-turbulence wind tunnel. Streamwise and spanwise NPLS images are obtained to analyze fine flow structures of the whole transition process. The results reveal the transition control mechanisms that on the one hand, the jet-induced shear layer produces unstable Kelvin–Helmholtz instabilities in the wake flow, on the other hand, the jets also generates an adverse pressure gradient in the boundary layer and induce unstable streak structures, which gradually break down into turbulence downstream. The paper provides a new method for transition control of high-speed boundary layer, and have prospect both in theory and engineering application.</jats:p>

<jats:p>A new photon-in/photon-out endstation at beamline 02B02 of the Shanghai Synchrotron Radiation Facility for studying the electronic structure of energy materials has been constructed and fully opened to users. The endstation has the capability to perform soft x-ray absorption spectroscopy in total electron yield and total fluorescence yield modes simultaneously. The photon energy ranges from 40 eV to 2000 eV covering the <jats:italic>K</jats:italic>-edge of most low <jats:italic>Z</jats:italic>-elements and the <jats:italic>L</jats:italic>-edge of 3d transition-metals. The new self-designed channeltron detector allows us to achieve good fluorescence signals at the low photon flux. In addition, we synchronously collect the signals of a standard reference sample and a gold mesh on the upstream to calibrate the photon energy and monitor the beam fluctuation, respectively. In order to cross the pressure gap, <jats:italic>in situ</jats:italic> gas and liquid cells for soft x-ray absorption spectroscopy are developed to study the samples under realistic working conditions.</jats:p>

<jats:p>Beryllium carbide is used in inertial confinement fusion (ICF) capsule ablation material due to its low atomic number, low opacity, and high melting point properties. We used the method of climbing image nudged elastic band (CINEB) to calculate the diffusion barrier of copper atom in the crystal of beryllium and beryllium carbide. The diffusion barrier of copper atom in crystal beryllium is only 0.79 eV, and the barrier in beryllium carbide is larger than 2.85 eV. The three structures of beryllium carbide: anti-fluorite Be<jats:sub>2</jats:sub>C, Be<jats:sub>2</jats:sub>C-I, and Be<jats:sub>2</jats:sub>C-III have a good blocking effect to the diffusion of copper atom. Among them, the Be<jats:sub>2</jats:sub>C-III structure has the highest diffusion barrier of 6.09 eV. Our research can provide useful help for studying Cu diffusion barrier materials.</jats:p>

<jats:p>Using first-principles calculations based on density functional theory (DFT), we investigate the potential hydrogen storage capacity of the Na-decorated net-Y single layer nanosheet. For double-side Na decoration, the average binding energy is 1.54 eV, which is much larger than the cohesive energy of 1.13 eV for bulk Na. A maximum of four H<jats:sub>2</jats:sub> molecules can be adsorbed around each Na with average adsorption energies of 0.25–0.32 eV/H<jats:sub>2</jats:sub>. Also, H<jats:sub>2</jats:sub> storage gravimetric of 8.85 wt% is obtained, and this meets the U.S. Department of Energy (DOE) ultimate target. These results are instrumental in seeking a promising hydrogen energy carrier.</jats:p>

<jats:p>Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub> <jats:italic>T<jats:sub>x</jats:sub> </jats:italic> nanosheet, the first synthesized MXene with high capacity performance and charge/discharge rate, has attracted increasingly attention in renewable energy storage applications. By performing systematic density functional theory calculations, the theoretical capacity of the intrinsic structure of single- and multi-layered Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub> <jats:italic>T</jats:italic> <jats:sub>2</jats:sub> (<jats:italic>T</jats:italic> = F or O) corresponding to <jats:italic>M</jats:italic> (<jats:italic>M</jats:italic> = Li and Na) atoms are investigated. Theoretical volumetric capacity and gravimetric capacity are obtained, which are related to the stacking degree. The optimal ratios of capacity to structure are determined under different stacking degrees for understanding the influence of surface functional groups on energy storage performance. Its performance can be tuned by performing surface modification and increasing the interlayer distance. In addition, the reason for theoretical capacity differences of <jats:italic>M</jats:italic> atoms is analyzed, which is attributed to difference in interaction between the <jats:italic>M</jats:italic>-ions and substrate and the difference in electrostatic exclusion between adsorbed <jats:italic>M</jats:italic>-ions. These results provide an insight into the understanding of the method of efficiently increasing the energy storage performance, which will be useful for designing and using high performance electrode materials.</jats:p>

<jats:p>We present the experiment observation of a giant topological Hall effect (THE) in a frustrated kagome bilayer magnet Fe<jats:sub>3</jats:sub>Sn<jats:sub>2</jats:sub>. The negative topologically Hall resistivity appears when the field is below 1.3 T and it increases with increasing temperature up to 300 K. Its maximum absolute value reaches <jats:italic>∼</jats:italic> 2.01 µΩ<jats:italic>·</jats:italic>cm at 300 K and 0.76 T. The origins of the observed giant THE can be attributed to the coexistence of the field-induced skyrmion state and the non-collinear spin configuration, possibly related to the magnetic frustration interaction in Fe<jats:sub>3</jats:sub>Sn<jats:sub>2</jats:sub>.</jats:p>

<jats:p>The design of the active region structures, including the modifications of structures of the quantum barrier (QB) and electron blocking layer (EBL), in the deep ultraviolet (DUV) AlGaN laser diode (LD) is investigated numerically with the Crosslight software. The analyses focus on electron and hole injection efficiency, electron leakage, hole diffusion, and radiative recombination rate. Compared with the reference QB structure, the step-like QB structure provides high radiative recombination and maximum output power. Subsequently, a comparative study is conducted on the performance characteristics with four different EBLs. For the EBL with different Al mole fraction layers, the higher Al-content AlGaN EBL layer is located closely to the active region, leading the electron current leakage to lower, the carrier injection efficiency to increase, and the radiative recombination rate to improve.</jats:p>

<jats:p>Two soluble tetraalkyl-substituted zinc phthalocyanines (ZnPcs) for use as anode buffer layer materials in tris(8-hydroxyquinoline)aluminum (Alq<jats:sub>3</jats:sub>)-based organic light-emitting diodes (OLEDs) are presented in this work. The hole-blocking properties of these ZnPc layers slowed the hole injection process into the Alq<jats:sub>3</jats:sub> emissive layer greatly and thus reduced the production of unstable cationic Alq<jats:sub>3</jats:sub> (<jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{Alq}}}_{3}^{+}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">Alq</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_1_017302_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) species. This led to the enhanced brightness and efficiency when compared with the corresponding properties of OLEDs based on the popular poly-(3, 4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) buffer layer. Furthermore, because of the high thermal and chemical stabilities of these ZnPcs, a nonaqueous film fabrication process was realized together with improved charge balance in the OLEDs and enhanced OLED lifetimes.</jats:p>

<jats:p>Spin-dependent transport in ferromagnet/organic-ferromagnet/metal junctions is investigated theoretically. The results reveal a large tunneling magnetoresistance up to 3230% by controlling the relative magnetization orientation between the ferromagnet and the central organic ferromagnet. The mechanism is explained by distinct efficient spin-resolved tunneling states in the ferromagnet between the parallel and antiparallel spin configurations. The key role of the organic ferromagnet in generating the large magnetoresistance is explored, where the spin selection effect is found to enlarge the difference of the tunneling states between the parallel and antiparallel configurations by comparing with the conventional organic spin valves. The effects of intrinsic interactions in the organic ferromagnet including electron–lattice interaction and spin coupling with radicals on the magnetoresistance are discussed. This work demonstrates a promising potential of organic ferromagnets in the design of high-performance organic spin valves.</jats:p>