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.     

基于BIM技术的绿色建筑装饰设计评价研究

随着科技的进步,城市建筑从高能耗向绿色节能转变已经成为历史必然。根据中国绿色建筑标准相关设计规范和BIM设计模型特征,提出了绿色建筑装饰设计评价,包括评价要素,评价结构,评价工具和评价方法。以某县行政审批中心的建筑装饰设计为例进行了评价和分析,为绿色建筑设计评价的BIM平台建设提供了思路和参考。     

Adjustable insulation for enhancing the performance of phase change materials in buildings

The energy savings of a building roof integrated with a phase change material (PCM) and different insulation strategies are presented in this paper. The proposed roof structure includes a concrete slab with a PCM layer and an air cavity insulation, which can be adjusted according to certain strategies. The adjustable insulation is devised to enable a reduced total heat gain throughout 24 h in summer days, thereby improving the performance of the PCM. The heat gain/loss through the roof with the PCM layer and adjustable insulation is compared with that of the roof with the PCM layer and fixed insulation during a typical year in Hangzhou, China. The effects and optimization of the melting temperature of the PCM are also explored. The simulation results show that, overall, the adjustable insulation can reduce the daily heat flux through the roof by approximately 20% compared with the conventional fixed insulation.     

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。      

我国建筑石料用灰岩采矿权成交价变化分析

砂石资源采矿权出让收益是地方财政收入的重要来源。近年来,砂石资源供应紧张价格大幅上涨的背景下,本文以典型的砂石资源建筑石料用灰岩为例,分析了全国及部分典型省份建筑石料用灰岩采矿权成交价的变化特征,主要结论是2011～2018年我国建筑石料用灰岩采矿权平均成交单价与砂石市场供应价格均呈上升趋势但前者涨幅远高于后者,并且采矿权成交单价的区间分布结构年度变化差异也较大,不同区域平均成交单价年度变化规律分异明显,贵州、甘肃两省采矿权成交单价相对较低且变化幅度相对较小,山西、吉林、湖北、广西4省采矿权成交单价相对较高且变化幅度相对较大。最后,从平抑砂石价格过快上涨、加强矿业权市场建设、促进砂石资源区域供需平衡、维护良好砂石市场价格秩序的角度提出了有关政策建议。     

Simultaneous accommodation of Dy3+ at the lattice site of β-Ca3(PO4)2 and t-ZrO2 mixtures: Structural stability,mechanical, optical,and magnetic features

Structurally stable β-Ca₃(PO₄)₂/t-ZrO₂ composite mixtures with the aid of Dy³⁺ stabilizer were accomplished at 1500°C. The precursors comprising Ca²⁺, P⁵⁺, Zr⁴⁺, and Dy³⁺ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca₃(PO₄)₂ occurred only at 1300°C, whereas the evidence of t-ZrO₂ crystallization is obvious at 900°C. The dual occupancy of Dy³⁺ at β-Ca₃(PO₄)₂ and t-ZrO₂ structures was evident; however, Dy³⁺ initially prefers to occupy β-Ca₃(PO₄)₂ lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO₂. The typical absorption and emission behavior of Dy³⁺ were noticed in all the systems and, moreover, the surrounding symmetry of Dy³⁺ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy³⁺. A gradual increment in the phase content of t-ZrO₂ in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions.     

Synthesis of highly transparent and thermally stable copolyimide with fluorine-containing dianhydride and alicyclic dianhydride

The development of optical films is highly desirable for applications in flexible displayers. In this work, a copolyimide (co-PI) film with high thermal stability and high transparency was prepared by the copolymerization of 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl ether, cyclobutanetetracarboxylic dianhydride, and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). The effects of aliphatic dianhydride and fluorine dianhydride monomers on the optical, thermal, and mechanical properties of the co-PIs were discussed in detail based on the experimental results and theoretical simulations. We found that the preparation of polyimide (PI) based on the combination of two dianhydrides could obtain the PI film with excellent comprehensive performance due to nonconjugated structure and strong electron-withdrawing effect. Through the structure and composition optimization, a PI film of PI-6FDA-70 with T_g of 300 °C, T_d10% more than 500 °C, the average transparency of 90% and the elongation at the breakage more than 8% was prepared. Such molecular design provides a practical approach to develop high-performance colorless PI films. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48603.     

Assessing the impact of non-ideal optical factors on optimized solar dish collector system with mirror rearrangement

An optimized solar dish collector (OPSDC) system was proposed in our previous work, which can achieve excellent the optical efficiency and flux uniformity under ideal optics. On this basis, the impacts of the non-ideal optical factors on the optical performance of OPSDC system with a cylindrical and conical receiver are studied in detail and compared with the conventional solar dish collector (COSDC) system in this paper. Where the non-ideal optical factors considered are relatively comprehensive, including the mirror slope error, tracking error, installation error of the mirror and receiver, and receiver's absorptivity degeneration. An optical model with the non-ideal optical factors is built in detail by the ray tracing method, and the corresponding ray tracing codes are developed and verified by literatures and optical software OptisWorks 2012. The results show that the OPSDC system not only has a significantly smaller peak local concentration ratio (LCR) and non-uniformity factor than the COSDC system under the same non-ideal optical factor, but also has excellent optical performance. This means that OPSDC system can effectively avoid the heat absorber generating high-temperature hot spots, thus significantly improving its working reliability and service lifetime. In addition, the tracking error, installation error of the receiver and mirror all lead to the increase of the peak LCR and non-uniform factor, while the mirror slope error and absorber's absorptivity degeneration are conducive to reducing the peak LCR and non-uniform factor. This work can provide a reference for error control of COSDC system and OPSDC system in manufacturing, installation and operation.