梁结构振动支承约束反力控制

支承或连接构件对梁结构的动力学性能有至关重要影响,必须保证其在振动过程中不发生破坏或者失效。通过合理设计和布局附加弹性支承可以实现对这些重要连接构件所承受约束反力的控制。应用微分变换法推导含附加支承的梁结构支承约束反力及其对于附加支承位置和刚度的灵敏度表达式,并通过优化设计附加支承位置和刚度实现具有弹性约束端的简支梁结构各支承约束反力的平衡,可提高结构的动力学性能。     

Optical design of the Lyman alpha based beam emission spectroscopy(LAB)diagnostic on the HL-2A tokamak

In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel.     

Synthesis and luminescence properties of reddish-orange-emitting Ca2GdNbO6:Sm3+ phosphors with good thermal stability for high CRI white applications

Novel reddish-orange-emitting Ca₂GdNbO₆:Sm³⁺ phosphors based on the emission of ⁴G_5/2 → ⁶H_9/2 transition at 651 nm with the chromatic coordinate of (0.633, 0.366) were synthesized. The crystal structure and chemical purity were identified in detail. Under the 407 nm excitation, the optimum concentration of Sm³⁺ ion was found to be 5 mol% dominated by the dipole-dipole interaction in the Ca₂GdNbO₆ host material. The color purity of the sample with optimum doping was estimated to be about 78.38%. Besides, the thermal stability was also studied, and it was further found that the emission intensity remained 65.32% at 423 K. The packaged white LED device exhibited excellent CRI and CCT values of 92.43 and 4896 K. Finally, the polydimethylsiloxane film with a stable structure and flexible property was prepared. These above results reveal that novel reddish-orange-emitting Ca₂GdNbO₆:Sm³⁺ phosphors can be applied in high CRI white communication and flexible display applications.     

Zinc-Deficiency Induced g-C3N4 Nanosheets: Photocatalytic Nitrogen Fixation Study and Carrier Dynamics

Catalysis Letters - g-C3N4 has great application prospect in the field of photocatalytic nitrogen fixation owing to the advantages of abundant raw materials, low toxicity, low consumption, high...     

The influence of processing methods on the dielectric properties of BaTi1-xGdxO3-x/2 - Based materials

In this study, the intermediate rare-earth oxide Gd₂O₃ (Gd) was substituted in different amounts (x = 0.2–2 mol%) for the formulation of BaTi_1-xGd_xO_3-x/2 (BTG_x) dielectric materials. The effect of B-site substitution was confirmed by the additional Raman active A_1g octahedral peak at ~835cm^-1 strengthened at x ≥ 0.4 mol%. Additionally, properties of 0.9BTG_0.007-0.1BA dielectric ceramics were analysed based on the influence of various processing methods as a function of sintering temperature. The focal samples were labelled Method-A (direct-mix) and Method-B (indirect-mix). As the sintering temperature (1075–1200 °C) increased, the 1 kHz response of the ε–T curves of Method-A samples transformed from a single peak to broad-narrow double peaks of high dielectric loss tangent (tan δ). Nonetheless, samples of Method-B possessed a clearly defined transmission electron microscopy (TEM) core-shell structure, flattened double-peak ε-T curves, optimised dielectric properties (ε = ~1563–1851 and tan δ < 1.5% at room temperature), and a wide-ranging temperature behaviour that meets the X8R dielectric standards (ΔC/C_25°C < ±15%). The maximum dielectric breakdown strength of Method-B samples reached ~131 kVcm, while the energy storage density was ~0.726 J/cm³ at a maximum efficiency of ~80% at 1100 °C. Thus, exhibiting good potentials for balancing temperature stability with energy storage applications.     

小型无线场强探测传感器研究

近年来,微波加热因其高效性和清洁无污染等优点广泛应用于各个领域。然而,微波加热的不均匀性限制了微波作为高效加热能源的应用。通过测量和分析加热腔中的电场分布情况可以帮助设计人员改进微波加热腔体设计,提高微波加热的均匀性。现有的场强测量设备均为有线设备,应用场景极为有限。因此,本文提出了一种由探头、接收机和上位机三部分组成的无线场强探测传感器。介绍了无线场强探测传感器的结构和原理,采用横电磁波小室进行校准。通过一系列测量实验表明实测值与标准场强仪测量值一致性较好,可满足工程测量需求。     

Preparation of a ternary hybrid of P-g-C3N4@PGS-Ti and its enhancement of the flame retardancy of epoxy resins

A novel ternary hybrid flame retardant named P-g-C₃N₄@PGS-Ti was prepared through step-by-step method. First, titanium dioxide was loaded on PGS to make PGS-Ti (where PGS = palygorskite), and then, PGS-Ti was decorated by phosphor-doped g-C₃N₄ (abbreviated as P-g-C₃N₄) to prepare a ternary flame retardant of P-g-C₃N₄@PGS-Ti. It showed that P-g-C₃N₄@PGS-Ti could efficiently improve the flame retardancy of epoxy resins (EP). The structure and the morphology of P-C₃N₄@PGS-Ti were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scaanning electron microscopy and hermogravimetric analysis (TGA). The flame retardancy and the burning behavior of 5 wt% P-g-C₃N₄@PGS-Ti composited EP were well investigated through TGA, limiting oxygen index (LOI), cone calorimeter test (CCT) and vertical burning test (UL-94 standard). It was found that the peak heat releasing (pk-HRR) of the EP/P-g-C₃N₄@PGS-Ti composite reduced 36% (from 1459 to 852 kW/m²) with the addition of 5 wt% of P-g-C₃N₄@PGS-Ti flame retardant to the matrix of EP. The combustion residue analysis showed that the EP/P-g-C₃N₄@PGS-Ti composite gained the most continuous and firmest char yield due to the synergistic effect of PGS, TiO₂ and the introducing of P element. The mechanism proved that the combination of gas phase and condensed phase flame-retardant processes were well coordinated to improve the fire retardancy for EP. We tested and studied the mechanical properties of EP/P-g-C₃N₄@PGS-Ti composites. Only 2.4% decreasing of flexural strength and 23.5% decreasing of impact strength in EP/P-g-C₃N₄@PGS-Ti composites compared to pure EP, respectively. But according to the test results of EP/P-g-C₃N₄@PGS-Ti composite material and the control sample in the system, EP/P-g-C₃N₄@PGS-Ti composite material had the highest flexural modulus and impact strength.     

Investigating the effect of water-mixing nitrogen atmospheric pressure plasma jet on polyether-ether-ketone and time stability under different conditions

Possessing excellent properties including good biocompatibility, high strength, and stiffness, polyether-ether-ketone (PEEK) has significant application values in medical and industrial fields. However, the relatively poor wettability and low adhesion limit its further applications. Atmospheric pressure plasma jet (APPJ) has been utilized for adjusting PEEK properties, but better hydrophilization effect and time stability after treatment are still urgently needed. In this paper, we employ a water-mixing nitrogen (N₂ H₂O) APPJ to process PEEK, and surface wettability can be effectively improved (contact angle ~18° within 2 min, distance between sample and nozzle outlet: 10 mm) without inducing obvious microstructure damages. Additionally, after storing for 40 days, the sample treated by N₂ H₂O APPJ also possessed better wettability (~54°) compared with that treated by N₂ APPJ (~65°). On the basis of this low-damage and high-efficient modification method, we perform aging experiments under different conditions (different temperatures 25, −10°C; and low vacuum condition: 50 kPa) to determine a relatively optimum storing condition for this method. The experiment results indicate that low temperature and vacuum are conducive to retaining the plasma-induced wettability (~34°). The treatment method and storing conditions for PEEK presented here may facilitate the application of PEEK in various fields.