低压静电场辅助冷冻对竹笋品质的影响

为研究低压静电场辅助冷冻对竹笋冻结特性的影响，以冻结曲线、硬度、水分损失率、水分迁移、冰晶形态和组织微观结构为指标，探究低压静电场辅助冷冻（－35 ℃）和普通冷冻（－35 ℃）条件下竹笋品质的变化规律。结果表明：低压静电场辅助冷冻提高了冻结效率，改变了冰晶形态及分布，减轻了组织微观结构破损程度，改善了解冻汁液流失情况。与静电板间距10、20、30、40 cm处的冷冻竹笋解冻后水分损失率分别为14.16%、12.58%、9.73%、10.44%，显著低于对照组（21.01%）（P＜0.05），硬度分别为461.19、507.48、496.65 g和455.31 g，显著高于对照组（350.70 g）（P＜0.05）。低场核磁共振分析结果表明，在低压静电场辅助冷冻下竹笋解冻后汁液流失减少，扫描电子显微镜观察结果显示，竹笋纤维排列整齐，组织微观结构保持较好。低压静电场辅助冷冻可有效改善竹笋品质，可为利用低压静电场进行果蔬的冷冻贮藏和冷链运输提供参考。     

Morphology-controlled fabrication of nanostructured WO3 thin films by magnetron sputtering with glancing angle deposition for enhanced efficiency photo-electrochemical water splitting

Herein, the tungsten trioxide (WO₃) nanostructure thin films with different morphologies are firstly fabricated by magnetron sputtering with glancing angle deposition technique (MS-GLAD), followed by the post annealed treatment process in air ambient for 2 h. It is demonstrated that the geometry of MS-GLAD setup, mainly substrate position, played a crucial role in determining the morphology, crystallinity, optical transmittance, and photo-electrochemical (PEC) performance of the WO₃ nanostructured thin film. With the different substrate positions in the MS-GLAD system, the WO₃ nanorod film layer could be precisely changed to combine an underlying dense layer with a nanorod layer and then nanocolumnar film. Moreover, the prepared samples' chemical composition and work function are studied by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), respectively. The combining WO₃ nanostructure produced high PEC efficiency compared to the single layer of the WO₃ nanorods sample and the dense WO₃ thin film sample. Thus, morphology-controlled nanostructure film based on the MS-GLAD technique in our study provides a simple approach to enhance the photo-anode for PEC water splitting application.     

Finite element optimization of sample geometry for measuring the torsional shear strength of glass/metal joints

Assessment of mechanical properties of glass/metal joints is a challenging process, especially when the application relevant conditions of the joints have to be considered in the test design. In this study, a finite element method (FEM) is implemented to analyze a torsional shear strength test designed for glass-ceramic/steel joints aiming towards solid oxide fuel/electrolysis cells application. Deviations from axial symmetry of the square flanges (ends) of respective hourglass-shaped specimens and also supporting and loading sockets of the test set-up are included in the model to simulate conditions close to reality. Undesirable tensile stress and also shear stress concentration appear at the outer edge of glass-ceramic layers, which are less for the hollow-full specimen. The simulation results show that for a specimen with either 9 mm thick square- or 6 mm thick triangular-flanges, locally enhanced tensile stresses almost disappear, resulting in a symmetric shear stress distribution. The difference between the analytically derived nominal shear strength and the real critical shear stress derived via simulation reduces with decreasing the fracture torque.     

Remarkably enhanced energy storage properties of lead-free Ba0.53Sr0.47TiO3 thin films capacitors by optimizing bottom electrode thickness

The lead-free Ba_0.53Sr_0.47TiO₃ (BST) thin films buffered with La_0.67Sr_0.33MnO₃ (LSMO) bottom electrode of different thicknesses were fabricated by pulsed laser deposition method on a (001) SrTiO₃ substrate. It was found that the roughness of electrode decreases and substrate stress relaxes gradually with the increase of LSMO thickness, which is beneficial for weakening local high electric field and achieving higher E_b. Therefore, the recoverable energy density (W_rec) of BST films can be greatly improved up to 67.3 %, that is, from 30.6 J/cm³ for the LSMO thickness of 30 nm up to 51.2 J/cm³ for the LSMO thickness of 140 nm after optimizing the LSMO thickness. Furthermore, the thin film capacitor with a 140 nm LSMO bottom electrode shows an outstanding thermal stability from 20 °C to 160 °C and superior fatigue resistance after 10⁸ electrical cycles with only a slightly decrease of W_rec below 1.6 % and 3.7 %, respectively. Our work demonstrates that optimizing bottom electrodes thickness is a promising way for enhancing energy storage properties of thin-film capacitors.     

空压机润滑油系统可靠性试验研究

对空压机润滑系统进行分析,提出了一种润滑油压力调节机构,保证了空压机在高油温时油压正常,为空压机运动件提供充分润滑,从而提高空压机运行的可靠性。实验证明了该机构是可靠的,为空压机润滑系统设计提供了参考依据。     

Bond characteristics,vibrational spectrum and optimized microwave dielectric properties of chemically substituted NdNbO4

Coordination chemistry, bond state and vibrational spectrum of co-substituted microwave dielectric NdNb_1-x(Zr_0.5W_0.5)_xO₄ ceramics (x = 0.01∼0.05) were investigated. Raman spectra and XRD refinement showed a solid solution was formed. The compressed and elongated chemical bonds are responsible for the variations of crystal parameters and cell volume. Calculated chemical bond parameters indicated bond covalency, lattice energy and Nb-site bond energy act on the fluctuations of the permittivity, quality factor and temperature coefficient, respectively. Meanwhile, the infrared vibrational spectrum is fitted to quantify the contributions of observed IR mode to the intrinsic loss. Compact ceramic possesses excellent properties: ε_r ∼ 19.2, Q × f ∼ 55282 GHz and τ_f ∼ -11.36 ppm/°C with x = 0.04, at 1250°C.     

Efficient tri-wavelength actively Q-switched Yb:GAGG laser

An efficient acousto-optic Q-switched Yb-doped Gd₃Al_xGa_5−xO₁₂ (GAGG) (x = 0.5) laser is demonstrated. Under the absorbed pump power of 7.4 W, the maximum average output power of 1.4 W is obtained at the pulse repletion rate of 1 kHz , with the slope efficiency as high as 32%. The pulse width of 40 ns is achieved with the pulse energy and peak power of 1.4 mJ and 35 kW, respectively. What’ more, the output spectrum shows itself tri-wavelength in either CW or Q-switching mode. To our knowledge, this is the first time for realizing simultaneous tri-wavelength Yb:GAGG laser actively Q-switched operation.     

Fabrication and frequency response of a complex ultrasonic transducer for multilayer evaluation

To characterize the thickness of a corrosive fluid system's coated facilities, such as pipes, tubes, tanks, and structural members, a complex ultrasonic transducer capable of measuring multilayered parts was fabricated and the time and frequency responses were evaluated. The target transducer was constructed with two active dual elements made from tape-cast PbNb₂O₆ sheets and an additional thin-film active element made from sol–gel spin-coated Pb(Zr_0.52Ti_0.48)O₃ films. After adjusting the properties of each active element, a complex transducer was assembled after matching the impedance of each element and considering the minimal interference between the active layers. The impulse response of the assembled complex transducer shows excellent characteristics. Moreover, the assembled transducer's capability of accurately measuring the thickness assures that it can be directly applied to related industries.     

闪光灯泵浦Nd3+:GGG激光特性研究

用闪光灯泵浦掺钕钆镓石榴石(Nd^3 ：GGG)激光晶体，研究了脉冲宽度0．5ms、1ms、1．5ms和2ms的放电泵浦下激光输出，实验获得了1．92J的最大激光能量．