Preparation of Silica Aerogel/Resin Composites and Their Application in Dental Restorative Materials

As the most advanced aerogel material, silica aerogel has had transformative industrial impacts. However, the use of silica aerogel is currently limited to the field of thermal insulation materials, so it is urgent to expand its application into other fields. In this work, silica aerogel/resin composites were successfully prepared by combining silica aerogel with a resin matrix for dental restoration. The applications of this material in the field of dental restoration, as well as its performance, are discussed in depth. It was demonstrated that, when the ratio of the resin matrix Bis-GMA to TEGDMA was 1:1, and the content of silica aerogel with 50 μm particle size was 12.5%, the composite achieved excellent mechanical properties. The flexural strength of the silica aerogel/resin composite reached 62.9546 MPa, which was more than five times that of the pure resin. Due to the presence of the silica aerogel, the composite also demonstrated outstanding antibacterial capabilities, meeting the demand for antimicrobial properties in dental materials. This work successfully investigated the prospect of using commercially available silica aerogels in dental restorative materials; we provide an easy method for using silica aerogels as dental restorative materials, as well as a reference for their application in the field of biomedical materials.     

几种建筑材料的氡射气系数研究

通过天然γ能谱测量方法测定建材样品中的镭含量,计算理论上衰变产生的氡密度,以及用硫化锌闪烁法测定由样品释放到空气中的氡密度的方法来计算氡的射气系数。通过改变样品的颗粒度大小,以及改变样品的灼烧温度等条件,来研究氡射气系数的变化规律。结果表明,土坯砖射气系数在8.5%~29.4%,红砖射气系数在0.031%~3.5%之间,瓷砖射气系数在0.74%~4.5%之间;建筑材料的氡射气系数随着其自身颗粒度的增大而减小,随加工(灼烧)温度升高而减小。     

电子束蒸发制备ZnO薄膜及其晶体结构和电学性质

采用电子束蒸发法制备了ZnO薄膜。研究了退火温度及衬底对薄膜的结晶状况以及电学性质的影响．X射线衍射测试结果表明。相同蒸发条件下制备的ZnO薄膜，硅(100)衬底上薄膜晶粒尺寸为73nm。结晶情况明显好于陶瓷和玻璃衬底上的薄膜．退火之后，各种衬底上薄膜的结晶情况相对未退火时都有明显好转；400℃退火时。薄膜逐渐结晶；600℃退火时，ZnO薄膜体现良好的择优生长的趋势，晶粒长大，晶化程度提高，大部分晶粒发生了织构．在400℃退火后。掺入Al2O3的薄膜和未掺杂的ZnO薄膜的电阻率下降了一个多数量级，但掺入MgO的薄膜电阻率变大。这是由于MgO掺杂起到了补偿作用，掺入MgO有可能实现ZnO薄膜的P型掺杂．     

高性能计算机用热管复合制冷系统设计研究

根据高性能计算机全天候温控的需要,提出了综合应用蒸气压缩和动力型分离式热管制冷技术的复合冷源方案。在冬季及春、秋过渡的低温季节,运行热管循环不仅大幅降低环控装置的能耗,而且可以避免在低温环境运行压缩式制冷易发生的冷启动、回油润滑等问题。提出了蒸气压缩制冷、蒸气压缩/热管复合制冷和热管制冷的分区工作模式,引入复合制冷模式有效拓宽了热管运行温区,大幅提高了制冷系统的综合COP。模拟分析了在北京地区应用热管复合制冷技术的节能性能,相比常规的压缩制冷节能率高达40%。研究表明:热管复合制冷系统具有显著的节能减排优势,特别适用于全天候工作的机房、基站等高热密度电子集成系统的温控。     

矿物中药钟乳石的X射线衍射Fourier指纹图谱

研究矿物中药钟乳石X射线衍射Fourier指纹图谱.对10批主产地的钟乳石药材X射线衍射Fourier图谱进行分析,建立钟乳石X射线衍射Fourier指纹图谱,并通过相似度计算,区分钟乳石、其他含钙矿物中药、同种化学试剂CaCO3.主成分相同的矿物中药利用X射线衍射Fourier指纹图谱无法完全区分,但钟乳石与同种化学试剂CaCO3的X射线衍射Fourier图谱区别显著.利用X射线衍射Fourier指纹图谱可以很好的区分含有不同化学成分的矿物药,而对于主成分相同的矿物中药,就不能简单地利用它们的X射线衍射Fourier指纹图谱加以区分,即X射线衍射Fourier指纹图谱仅具有相对的专属性.     

In situ observation of NaBi(WO4)2 dendrite growth and the study on microstructure of solidification

The dendrite growth process of transparent NaBi(WO4)2 with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased in the diffusive-convective region. The growth rate of branch had the same change trends as the arm's. Based on the EPMA-EDS data of solidification structure of quenched NaBi(WO4)2 melt, it was found that there were component differences from stoichiometric concentration in the melt near the interface during the growth process.     

高效液相色谱法测定巴豆油中佛波醇

建立巴豆油中佛波醇（Phorbol）的含量测定方法。用HPLC测定水解后佛波醇的含量,并通过正交法优化巴豆油水解条件。采用Kromasil C₈（4.6mm×250mm,5μm）色谱柱,流动相为甲醇:水=20:80.流速为1.0mL/min.柱温为25℃,检测波长为234nm。在46.8—468μg/mL范围内佛波醇浓度与峰面积线性关系良好.回归方程为y=9820.8x+50238,r=0.9999;回收率为93.16%,RSD为2.73%。巴豆油的优化水解条件:温度20℃,料液比1:8（mL/mL）,水解3h,此条件下佛波醇的产率最高,平均产率为2.41%。所建方法易于操作、结果稳定、重现性好,可用于巴豆油中佛波醇的含量测定。     

基于高光谱成像技术的油菜叶片SPAD值检测

以油菜叶片为研究对象,利用高光谱成像技术,成功建立了叶绿素相对值SPAD值的预测模型。共采集了160个油菜叶片样本在380～1030 nm范围内的高光谱图像。选择500～900 nm之间的平均光谱作为油菜叶片样本的光谱。利用蒙特卡罗最小二乘法(monte carlo partial least squares, MC-PLS)剔除了13个异常样本,基于剩余的147个样本光谱数据与SPAD测量值进行分析,采用了不同的方法建立了多种预测模型,包括：全光谱的偏最小二乘法(partial least squares, PLS)模型,连续投影算法(successive projections algorithm, SPA)选择特征波长的PLS预测模型,“红边”位置(λ_red)的简单经验估测模型,三种植被指数R₇₁₀/R₇₆₀,(R₇₅₀-R₇₀₅)/(R₇₅₀-R₇₀₅)和R₈₆₀/(R₅₅₀*R₇₀₈)分别建立的简单经验估测模型,以及基于这三种植被指数的PLS预测模型。建模结果显示,全光谱的PLS模型预测效果最为精确,其预测相关系数r_p为0.833 9,预测均方根误差RMSEP为1.52。而使用SPA算法选出的8个特征波长所建立的PLS模型其预测结果可达到与全光谱的PLS模型非常接近的水平,而且在保证一定精度的条件下减少了大量运算,节省了运算时间,大幅提高了建模的速度。而基于红边位置和选择的三种植被指数而建立的简单经验估计模型其预测结果虽与基于全光谱的PLS预测模型有一定差距,但模型简单、运算量小,适合用于对精度要求不高的场合,对后续的便携仪器设备开发有一定的指导作用。     

Collisional dynamics of symmetric two-dimensional quantum droplets

The collisional dynamics of two symmetric droplets with equal intraspecies scattering lengths and particle number density for each component is studied by solving the corresponding extended Gross−Pitaevskii equation in two dimensions by including a logarithmic correction term in the usual contact interaction. We find the merging droplet after collision experiences a quadrupole oscillation in its shape and the oscillation period is found to be independent of the incidental momentum for small droplets. With increasing collision momentum the colliding droplets may separate into two, or even more, and finally into small pieces of droplets. For these dynamical phases we manage to present boundaries determined by the remnant particle number in the central area and the damped oscillation of the quadrupole mode. A stability peak for the existence of droplets emerges at the critical particle numberN_c ≃ 48 for the quasi-Gaussian and flat-top shapes of the droplets.     

Effect of Reactor Pressure on Qualities of GaN Layers Grown by Hydride Vapour Phase Epitaxy

The influence of reactor pressure on GaN layers grown by hydride vapour phase epitaxy （HVPE） is investigated. By decreasing the reactor pressure from0. 7 to 0.5 mm, the GaN layer growth mode changes from the island-like one to the step flow. The improvements in structural and optical properties and surface morphology of GaN layers are observed in the step flow growth mode. The results clearly indicate that the reactor pressure, similarly to the growth temperature, is One of the important parameters to influence the qualities of GaN epilayers grown by HVPE, due to the change of growth mode.