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1.
《Progress in Surface Science》2022,97(3):100663
High-reflective multilayer laser coatings are widely used in advanced optical systems from high power laser facilities to high precision metrology systems. However, the real interface quality and defects will significantly affect absorption/scattering losses and laser induced damage thresholds of multilayer coatings. With the recent advances in the control of coating design and deposition processes, these coating properties can be significantly improved when properly engineered the interface and defects. This paper reviews the recent progress in the physics of laser damage, optical losses and environmental stability involved in multilayer reflective coatings for high power nanosecond near-infrared lasers. We first provide an overview of the layer growth mechanisms, ways to control the microstructures and reduce layer roughness, as well as the nature of defects which are critical to the optical loss and laser induced damage. Then an overview of interface engineering based on the design of coating structure and the regulation of deposition materials reveals their ability to improve the laser induced damage threshold, reduce the backscattering, and realize the desirable properties of environmental stability and exceptional multifunctionality. Moreover, we describe the recent progress in the laser damage and scattering mechanism of nodule defects and give the approaches to suppress the defect-induced damage and scattering of the multilayer laser coatings. Finally, the present challenges and limitations of high-performance multilayer laser coatings are highlighted, along with the comments on likely trends in future. 相似文献
2.
In the pursuit to enlarge the library of polyimide materials for energy applications, new polyimide/MWCNTs composite films have been developed by MWCNTs-assisted polycondensation reaction of a hydroxyl and triphenylmethane-containing diamine with benzophenone tetracarboxylic dianhydride targeting to highlight their electrical storage capability as flexible electrodes in micro-supercapacitors (mSCs). The Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, fluorescence, and Raman spectroscopies were used to demonstrate the evolution of interfacial interactions between MWCNTs and the precursors (diamine monomer and intermediate polyamidic acid) and polyimide matrix that proved to be the origin of MWCNTs homogeneous dispersion. Thus, composite films incorporating 1, 3, 5, and 10 w.t.% MWCNTs were obtained and thoroughly investigated with regard to their morphology, mechanical behavior, thermal stability, and electrical conductivity. The electrochemical performance of these composites was first analyzed in a classical three-electrode cell by cyclic voltammetry and galvanostatic charge-discharge in both aqueous and organic electrolyte systems. By far, the best electrical storage capacity was obtained with the composite polyimide film containing 10% MWCNTs that was further used as both active material and current collector in a flexible symmetric mSC realized by a straightforward and low-cost procedure. In the attempt to better exploit the advantages of this composite film, it was layered with a graphite-containing paint and tested as an electrode in a flexible mSC, which provided satisfactory results. To our knowledge, this is the first report on the electrical charge storage capability of a polyimide/MWCNTs free-standing film as a flexible electrode in mSCs, which do not require time- and resource-consuming processing steps. 相似文献
3.
Giorgia Scetta Jianzhu Ju Nathan Selles Patrick Heuillet Matteo Ciccotti Costantino Creton 《Journal of polymer science. Part A, Polymer chemistry》2021,59(8):685-696
We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial thermoplastic polyurethane elastomers (TPU) often considered as a sustainable replacement for common filled elastomers. All TPU have similar hard segment contents and linear moduli but sensibly different large strain properties as shown by X-ray analysis. Despite these differences, we found a stiffening effect after conditioning in step cyclic loading which greatly differs from the common softening (also referred as Mullins effect) observed in chemically crosslinked filled rubbers. We propose that this self-reinforcement is related to the fragmentation of hard domains, naturally present in TPU, in smaller but more numerous sub-units that may act as new physical crosslinking points. The proposed stiffening mechanism is not dissimilar to the strain-induced crystallization observed in stretched natural rubber, but it presents a persistent nature. In particular, it may cause a local reinforcement where an inhomogeneous strain field is present, as is the case of a crack propagating in cyclic fatigue, providing a potential explanation for the well-known toughness and wear resistance of TPU. 相似文献
4.
The present study was conducted to evaluate the effect of ultrasonic (US) treatment on chemical characteristics and antioxidant potential of pulps obtained from eight mango varieties indigenous to Pakistan. There was a significant (p < 0.05) effect of varieties and US treatment on chemical characteristics i.e. pH, acidity, TSS, vitamin C contents, total sugars (%), reducing sugars (%) and non-reducing sugars (%). Microstructure evaluation of pulp from all mango varieties showed deshaped middle lamella and cell wall of cells after 8 min of US treatment. At 4 min of US treatment as per shaped cell wall and middle lamella, the chemical characteristics and antioxidant potential were higher. The total phenolics (TP), flavonoids (TF) and total antioxidant activity (TAA) of pulp from most varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after each treatment i.e. 8 and 12 min. The maximum value (314.17 μg AAE/mL pulp) of DPPH was shown by pulp from Dosehri and the minimum (158.67 μg AAE/mL pulp) was found in pulp from Langra before US treatment. The DPPH values of pulp from most of the varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after each treatment but pulp from Langra showed increasing trend after 8 min of US treatment which decreased after 12 min of treatment. The total anthocyanin (TA) values of pulp from Chaunsa, Dosehri, Sindhri, Gulab Khas and Langra increased abruptly after US treatment for 4 min but decreased successively after subsequent treatment. The pulp from Desi, Anwar Ratol, Gulab Khas and Langra showed an abrupt decrease in TA after 8 min of US treatment. An increasing trend of values of total carotenoids (TC) was shown by pulp from all mango varieties after 4 min of US treatment but decreasing trend was observed with subsequent increase in time of US treatment. 相似文献
5.
近年来,机器学习等人工智能技术被应用于蛋白质工程,其在蛋白质结构、功能预测、催化活性等研究中具有独特优势。在未知蛋白质结构的情况下,将蛋白质序列和功能特性与机器学习相结合,基于序列-活性关系(innovative sequence-activity relationship,ISAR)算法,将蛋白质氨基酸序列数字化,用快速傅里叶变换(fast four transform,FFT)进行预处理,再进行偏最小二乘回归建模,可在数据集较少情况下拟合得到最佳模型。通过机器学习对紫色球杆菌视紫红质(gloeobacter violaceus rhodopsin,GR)的突变体蛋白质氨基酸序列与光谱最大吸收波长进行建模,获得了最佳模型。用最佳索引LEVM760106建模得到的确定系数R2 为0.944,均方误差E为11.64。用小波变换进行的预处理,其R2 虽也约为0.944,但E大于11.64,不及FFT进行的预处理。方法较好地解决了蛋白质序列与功能特性之间的数学建模问题,在蛋白质工程中可为预测更优的突变体提供支持。 相似文献
6.
7.
以典型的双稳态系统——屈曲梁结构为例,基于等效模型,结合解析、数值和实验手段,研究了双稳态结构中的1/2次谐波共振特性、演化过程、参数调节规律及其对隔振特性的影响.研究发现,当非线性刚度系数或激励幅值增加到一定程度时,系统会在一定带宽下产生显著的1/2次谐波共振;随着激励幅值增加,阻尼系统的1/2次谐波遵循“产生-增强-衰退-消失”的过程,该过程对峰值频率和峰值传递率有重要影响;适当提高非线性强度能有效改善双稳态结构隔振特性.针对双稳态屈曲梁结构开展的实验验证了1/2次谐波特性和隔振特性变化规律. 相似文献
8.
9.
We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing
it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate
εF
2(x,Q)2/ε In Q
2 using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data. 相似文献
10.
单甲基原位改性SiO2疏水减反膜的制备与性能研究 总被引:1,自引:0,他引:1
在碱性条件下通过TEOS和MTES的共水解缩聚反应制备了单甲基原位改性的SiO2溶胶,并使用提拉法在K9玻璃基片上镀制了疏水减反膜。通过透射电镜(TEM)考察了镀膜溶胶的微结构,分别使用红外光谱(FTIR)分析了薄膜的组分,用原子力显微镜(AFM)观察了薄膜的表面形貌和起伏状况,用紫外可见光谱(UV-vis)考察了薄膜的减反射性能,用接触角仪测量了薄膜对水的接触角。并使用“R-on-1”的方式测量了薄膜在Nd:YAG激光(1 064 nm,1 ns)作用下的损伤阈值。结果表明,通过共水解缩聚反应可以把甲基引入镀膜溶胶簇团中,改善了溶胶簇团的网络结构,使薄膜得到相当好的疏水性能和更好的抗激光损伤性能,同时薄膜能保持较好的减反射性能。 相似文献