卤代效应对乙酸胍非线性光学性质的影响

针对具有应用价值的卤代乙酸胍（GXA）非线性光学（NLO）晶体研究不系统的问题，设计了系列三卤代和系列氯代的乙酸胍（GAc）体系，通过量子化学计算研究了系列GXA的结构、NLO性质和构效关系，探讨了卤代效应可能的影响机理。结果表明，卤代原子显著地改变了GXA分子构象，并通过不同方式参与强氢键作用来影响超分子堆积。卤代主要通过影响GXA分子的LUMO来改变其能隙（E_gap）。GXA的平均偶极矩（μ_total）和平均极化率<α>随卤原子数量以及半径的增大而增大。超极化率总体上相对于GAc降低，但影响复杂，其中，平均第1超极化率（β_total）随卤原子数量的增多而降低，平均第2超极化率（<γ>）则随卤原子的变大而显著增强。此外，并未发现E_gap与μ_total及<γ>之间存在明显的相关性。     

分层反压注射成型厚壁光学透镜的工艺分析

为了研究反压压力对成型厚壁光学透镜的影响，利用自行开发的分层反压注射成型厚壁光学透镜的实验方案，通过正交实验优化设计开展了工艺参数优化实验，研究了在不同分层方式下内外层反压压力对对厚壁光学透镜光学性能的影响，从而根据正交优化参数组合成型具有优异光学性能的理想厚壁光学透镜。 正交实验研究结果表明，使用聚甲基丙烯酸甲酯（PMMA）为厚壁光学透镜的原材料进行分层反压注射成型，能够有效减少厚壁光学透镜收缩率，同时随着内外层反压压力的提高，厚壁光学透镜的透光率和折射率均不同程度的得到提高，透镜光学性能优异。     

三维光学扫描技术在3D打印中的应用

采用先进的三维光学扫描技术,借助计算机软件对SLS打印的缸盖上水夹层砂芯进行三维数字化全尺寸扫描,检测分析了SLS打印砂芯尺寸精度及尺寸变化规律。检测结果显示:上水夹层砂芯不满足打印设备精度要求,需要改进打印工艺。根据三维光学扫描检测分析结果明确了3D打印工艺调整方向,改进了工艺打印的缸盖上水夹层砂芯,经过三维光学扫描检测,砂芯尺寸精度得到了有效地提高。通过对三维光学扫描技术在3D打印中的应用研究,对SLS打印砂芯精度检测提供了一种更为准确直观的测量方法,三维光学扫描检测结果作为SLS打印工艺参数调整依据,为SLS打印出合格的砂芯奠定基础。     

Intrinsic second-order nonlinearity in chalcogenide glasses containing HgI2

Frequency conversion using nonlinear optical (NLO) crystals is widely used in advanced photonic technologies to produce coherent light in the spectral regions where the available laser sources are missing. Isotropic glasses usually do not show second order nonlinear processes like second harmonic or difference frequency generation (SHG, DFG) except for temporarily induced anisotropy under external stimuli. Here, we show that a HgI₂–Ga₂S₃–GeS₂ homogeneous glass exhibits a strong intrinsic SHG response comparable with that of the well-known NLO single crystal LiNbO₃. The origin of this extremely rare phenomenon seems to be noncentrosymmetric bent HgI₂ molecules embedded in a sulfide glassy host. Taking into account the unique properties of chalcogenide glasses (wide IR transmission, low phonon density, unlimited ability to be modified changing the appropriate glass properties, fiber drawing and thin layer design), the observed phenomenon opens up the possibility of creating fundamentally new devices for mid-IR photonics.     

Preparation of organic–inorganic hybridized dual-functional antifog/antireflection coatings on plastic substrates

Dual-functional antifog/antireflection coatings with a special bi-layer structure for plastic substrates were prepared. The superhydrophilic top layer was a crosslinked network of dipentaerythritol hexaacrylate (DPHA), hydrophilic agent (synthesized from Tween 20, isophorone diisocyanate, 2-hydroxyethyl methacrylate), and organically modified silica. The high-refractive-index bottom layer was composed of TiO₂ nanoparticles and DPHA. The two layers were chemically bonded through a UV-curing process. By tuning the thicknesses of the two layers, a series of coatings were prepared. These coatings were highly transparent and able to reduce reflectance. In addition, they adhered well to the substrate, and demonstrated superb antifogging capability on steam tests. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48822.     

Effect of fatigue loading-confining stress unloading rate on marble mechanical behaviors: An insight into fracture evolution analyses

Rocks in underground works usually experience rather complex stress disturbance. For this, their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions. The effects of stress disturbances on rock geomechanical behaviors under fatigue loading conditions and triaxial unloading conditions have been reported in previous studies. However, little is known about the dependence of the unloading rate on fatigue loading and confining stress unloading (FL-CSU) conditions that influence rock failure. In this paper, we aimed at investigating the fracture behaviors of marble under FL-CSU conditions using the post-test X-ray computed tomography (CT) scanning technique and the GCTS RTR 2000 rock mechanics system. Results show that damage accumulation at the fatigue stage can influence the final fracture behaviors of marble. The stored elastic energy for rock samples under FL-CSU tests is relatively larger compared to those under conventional triaxial tests, and the dissipated energy used to drive damage evolution and crack propagation is larger for FL-CSU tests. In FL-CSU tests, as the unloading rate increases, the dissipated energy grows and elastic energy reduces. CT scanning after the test reveals the impacts of the unloading rate on the crack pattern and a fracture degree index is therein defined in this context to represent the crack dimension. It shows that the crack pattern after FL-CSU tests depends on the unloading rate, and the fracture degree is in agreement with the analysis of both the energy dissipation and the amount of energy released. The effect of unloading rate on fracture evolution characteristics of marble is revealed by a series of FL-CSU tests.     

Unraveling the film-formation kinetics of interfacial polymerization via low coherence interferometry

Interfacial polymerization (IP) is one of the most important methods for fabricating thin film composite (TFC) membranes. Understanding the film-formation mechanisms is of great value for developing membranes with enhanced performance. This work proposed a novel method to in situ characterize the film-formation kinetics via low coherence interferometry (LCI). The polyamide film formed at the liquid–substrate interface was scanned in real time; the polymerization induced significant variations in the optical properties around the reaction zone. After mitigating the effects of the perturbed interface, the surface-averaged intensity profiles provide a solid basis for analyzing the film-formation kinetics at various depths. In particular, the effects of the monomer concentrations were investigated to reveal the asymmetric growth and development of irregular substructures. All the characterization results confirm that the LCI-based characterization is a powerful tool for studying the structural evolution of the IP layer and thereby providing deeper insights for optimizing TFC membranes.     

光学材料的磨削损伤控制试验研究

基于K9玻璃不同的磨削工艺参数确定其磨削损伤层深度随工艺参数变化的规律，并通过工件磨削损伤层深度的动态检测研究其裂纹扩展规律。结果表明:工件磨削过程中的裂纹损伤是动态扩展过程。固定工艺参数下，裂纹稳态扩展，损伤层深度不变；采用损伤更小的工艺参数磨削，裂纹的扩展速度小于材料的去除速度，其损伤层深度逐渐减小，损伤的去除速度逐渐减慢直至二者间达到稳态平衡。同时，为了去除前道工序的损伤层，后道工序的材料去除量需达到前道工序损伤层深度的2～3倍。      

Investigation of fluidized bed behaviour using electrical capacitance tomography

The temporal and cross-sectional distributions of particles in a 127 mm diameter fluidized bed have been obtained using a new generation, high-speed electrical capacitance tomography. Two planes of eight electrodes were used and mounted at 160 and 660 mm from the gas distributor which was a 3 mm thick porous plastic plate (maximum pore size of 50-70 μ m). 3 mm diameter, nearly-spherical polyethylene granules made up the bed. Experiments at sampling frequencies of 200-2000 cross-sections per second and gas superficial velocities from just below the minimum fluidization to 83% above minimum fluidization velocities were used. The time series of the cross-sectional average void fractions have been examined both directly and in amplitude and frequency space. The last two used probability density functions and power spectral densities. The information gathered shows that the fluidized bed was operating in the slugging mode, which is not surprising given the size of the particles. It has been found that an increase in the excess gas velocity above the minimum fluidization velocity resulted in an increase in the mean void fraction, an increase in the length and velocity of the slug bubbles as well as the bed height, and a slight decrease in the slug frequency. The results are presented in a level of detail suitable for comparison with later numerical simulation.     

Applicability of electrical resistance tomography to the analysis of fluid distribution in haemodialysis modules

This work aims to explore the applicability of electrical resistance tomography (ERT) in the analysis of fluid distribution in haemodialysis modules, which is not straightforward due to the complex geometry of the hollow fibre bundles and the small sizes of the modules. On the other hand, ERT is potentially a suitable and convenient technique for investigation in this field due to its cost-effectiveness and capacity to perform measurements in opaque systems. After a preliminary estimation of the fibre bundle local distribution, the assessment of the technique is performed by observing the time evolution of the measured conductivity maps during the module filling and emptying operations with water and air, which are alternatively fed inside or outside the fibre bundle. Reliable conductivity maps are obtained by placing the module vertically or horizontally. Additional experimental data collected by feeding liquid mixtures of different sodium chloride concentrations show that the technique is suitable for detecting concentration variations, due to the mass transfer through the fibres, and flow maldistribution, due to the specific geometry of the module. From the preliminary results collected in this work, the technique appears to be adequate for the collection of data that can support the optimization of the module geometry and computational model validation.