同一波长曝光和再现的光互连导板的制备

全息干版薄膜在曝光后处理过程中产生收缩，致使曝光产生的光栅条纹倾斜度增大，从而使再现光经布喇格光栅衍射后，射入先导板的入射角增大，导致再现光在光导板中产生全反射。通过这种方法，在全息干版上制备出同一波长曝光和再现的光互连导板。     

单座容积超大型厅堂顶部材料吸声效率的研究

单座容积超过国家标准推荐上限值两倍及以上的厅堂定义为超大型厅堂,这类厅堂在观演建筑中越来越多。在超大型厅堂的音质设计中,为了控制厅堂内的混响时间,顶部往往需要布置吸声材料。借助厅堂音质计算机模拟分析软件,以三个超大型厅堂模型的混响时间为例,探讨了吸声材料布置在顶部时的吸声效率。研究结果表明,顶部材料的吸声效率与声源到顶面的距离和声源的频率均呈负相关,而材料自身的吸声系数对顶部吸声效率的影响较小。     

Fluid transport in high volume fly ash mixtures with and without internal curing

The transport of fluid and ions in concrete mixtures is central to many aspects of concrete deterioration. As a result, transport properties are frequently measured as an indication of the durability that a concrete mixture may be expected to have. This paper is the second in a series investigating the performance of high volume fly ash (HVFA) mixtures with low water-to-cementitious ratios (w/cm) that are internally cured. While the first paper focused on strength and shrinkage, this paper presents the evaluation of the transport properties of these mixtures. Specifically, the paper presents results from: rapid chloride migration (RCM), rapid chloride penetration test (RCPT), apparent chloride diffusion coefficient, surface electrical resistivity, and water absorption. The test matrix consisted of mortar samples with two levels of class C fly ash replacement (40% and 60% by volume) with and without internal curing provided with pre-wetted lightweight fine aggregates (LWA). These mixtures are compared to plain ordinary portland cement (OPC) mortars. The results indicate that HVFA mixtures with and without internal curing provide benefits in terms of reduced transport coefficients compared to the OPC mixtures.     

Effect of doping with Nd ions on the structural and ferroelectric properties of Ca0.28Ba0.72Nb2O6 single crystal

The crystal structure of Ca_0.28Ba_0.72Nb₂O₆ (CBN-28) crystal with Nd-doping has been determined from X-ray single crystal diffraction data, in the tetragonal system with space group P4bm and the following parameters: a = b = 12.458 Å, c = 3.954 Å, V = 613.688 Å³, and Z = 5. X-ray diffraction results on a Nd-doped CBN-28 single crystal also have demonstrated that Nd³⁺ and Ca²⁺ occupy the same site in the crystal structure. Dielectric and ferroelectric measurements have been performed. Transition from ferroelectric to paraelectric at around 223 °C has been observed. The Nd-doped crystal has a lower Curie temperature (T_m) than that of undoped CBN-28 crystal. The spontaneous polarization (P_s) and coercive electric field (E_c) also decrease compared with their values in the undoped CBN-28 crystal.