活性粉末混凝土（RPC）研究应用现状

经特殊的配制方法获得的活性粉末混凝土RPC自问世以来凭借其优越性能,如超高抗压强度及耐久性等,具有广阔的研究前景与应用市场,深受工程材料界人士的青睐。本文重点介绍了近年来RPC的配置理论、相关性能的研究应用进展,分析了RPC目前所存在的突出问题,并对RPC未来的发展提出了相应建议。     

氟橡胶的红外光谱研究

采用红外(IR)光谱,包括一维红外光谱、二阶导数红外光谱、四阶导数红外光谱和去卷积红外光谱对氟橡胶(FKM)的分子结构进行了研究。试验发现:氟橡胶的红外吸收模式主要包括CH2不对称伸缩振动模式(νasCH2-FKM)、CH2对称伸缩振动模式(νsCH2-FKM)、CH2弯曲伸缩振动模式(δCH2-FKM)、CF2不对称伸缩振动模式(νasCF2-FKM)、CF2对称伸缩振动模式(νsCF2-FKM)和CFCl伸缩振动模式(νCFCl-FKM)等。研究发现:氟橡胶的去卷积IR光谱的谱图分辨能力要优于相应的一维IR光谱、二阶导数IR光谱和四阶导数IR光谱。此研究拓展了IR光谱在氟橡胶结构及应用研究的范围。     

封闭多官能异氰酸酯交联发泡剂的研制及PA6发泡成型初探

以甲苯二异氰酸酯(TDI)、六亚甲基二异氰酸酯(HDI)、聚醚多元醇为主要原料合成了多官能异氰酸酯预聚体并用无水甲醇封闭,得到封闭多官能异氰酸酯预聚体(BI),并将其作为交联剂和发泡剂用于聚酰胺6(PA6)的挤出发泡成型,通过傅里叶红外光谱仪、扫描电子显微镜、熔体流动速率仪等分析研究了封闭前后多官能异氰酸酯预聚体的结构变化及不同BI含量对PA6熔体强度和泡孔结构的影响。结果表明,随着BI含量的增大,PA6的熔体强度显著提高,泡孔变得更细密、均匀。     

基于统计特性随机森林算法的特征选择

针对由静息态功能磁共振成像(R-fMRI)得到的脑功能连接矩阵数据运用传统特征选择方法处理的结果,存在特征冗余,无法确定最终特征维数等问题,提出一种全新的特征选择算法.该算法在随机森林(RF)算法中结合统计特性,根据袋外数据的分类效果得到保留的特征,并将其运用在对精神分裂患者与正常被试者的识别实验中.实验结果表明,与传统的主成分分析(PCA)方法相比,该算法可以有效保留重要特征,提高识别精度,且保留的特征具有很好的医学解释性.     

High precision synchronization of shaped nanosecond pulse with compressible chirped short pulse used in front-end of ICF

A method for electrical waveform generation based on chirped pulse stacker in intensity modulation pulse shaping is provided as a means for high precision synchronization between nanosecond shaped pulse and compressible chirped short pulse in inertial confinement fusion (ICF) research. The arbitrary shaped optical pulse could be obtained, and the measured synchronization precision between ultra-short pulse and shaped optical pulse with the same or different wavelengths is better than 2.75 ps root mean square error.     

Transient thermal effects in end-pumped cryogenic Yb:YAG regenerative amplifier

The three-dimensional heat deposition of the cryogenic Yb:YAG regenerative amplifier, which is yielded by pulsed pumped laser, is derived in details based on the theory of quasi-three-level rate equations. Furthermore, the transient temperature field, stress, and strain induced by the thermal gradients in the laser crystal are analyzed by use of the finite element method. Then the thermally induced lens and depolarization in the cryogenic regenerative amplifier are theoretically studied. We find that for the pump and cooling structure which has been designed, the focal length of the thermally induced lens is about 15?m and the depolarization rate could be ignored. The maximum output energy 10.2?mJ at a repetition rate of 10?Hz with nearly TEM₀₀ mode profile is obtained using the designed pump and cooling structure.     

Synthesis and luminescence properties of a novel phosphor Ca2–x/2Si1–xPxO4:Eu2+for near UV-excited white-light-emitting diodes

A novel green-emitting phosphor,Eu2+-doped Ca2-x/2 Si1-x Px O4(0.25≤x≤0.30),was prepared through a conventional solidstate reaction.X-ray diffraction(XRD),photoluminescence(PL) and decay studies were employed to characterize the sample,which was assigned to P63mc space group in the hexagonal system.The effect of P-doping on the α-Ca2 SiO4 was studied and P2 O5 broken down by the raw material of(NH4)2 HPO4 played an important role in stabilizing α-Ca2 SiO4 which can only be stable at high temperature.The XRD patterns of the Ca2-x/2 Si1-x Px O4 host were found pure and optimized when the mole fraction of P2 O5 was 14.5%.The diffuse reflectance spectra of the Ca1.855 Si0.71 P0.29 O4 and Ca1.845 Si0.71 P0.29 O4 :0.01Eu2+covered the spectral region of 230-400 nm,implying that the phosphor was suitable for UV or near-UV LED excitation.The phosphor could be effectively excited in the near UV region with the maximum at 372 nm.The emission spectrum of the Ca1.845 Si0.71 P0.29 O4 :0.01Eu2+phosphor showed an asymmetrical single intensive band centered at 513 nm,which corresponded to the 4f65d1→4f7transition of Eu2+.Eu2+ions might occupy two types of Ca2+sites in the Ca1.855 Si0.71 P0.29 O4 lattice and form two corresponding emission centers,which led to the asymmetrical emission of Eu2+in Ca1.855 Si0.71 P0.29 O4.The effects of Eu2+-doped concentration in Ca1.855-x Si0.71 P0.29 O4 :xEu2+on the PL were also discussed,the optimum doping concentration of Eu2+was 1 mol.% and the critical distance of the energy transfer was also calculated by the concentration-quenching method.The non-radiative energy transfer between Eu2+seemed to be caused by the multipole-multipole interaction.The fluorescence lifetime of Eu2+was found to be 0.55711 μs.The results suggested that these phosphors might be promising candidates used for near UV light excited white LEDs.     

POMS/陶瓷复合膜的制备及其油气回收应用研究

采用两步合成法制备3种不同黏度的聚甲基辛基硅氧烷(POMS)高聚物,通过Mark-Houwink-Sakurada公式计算出共聚物的粘均分子量.采用红外光谱(FT-IR)对其结构进行表征.以孔径0.2μm的ZrO2管式膜为支撑体,采用浸渍提拉法成功制备了3种POMS/陶瓷复合膜,将其用于正庚烷/氮气(n-C7 H16/N2)混合体系的分离.3种POMS/ZrO2复合膜的渗透速率和分离因子均随进料浓度及操作压力的增加而增大,随操作温度升高而减小.     

双线梯形螺纹车削精度控制方法探究

针对双头梯形螺纹车削中易出现的分线不均、螺距不等、大小牙等精度问题,分析比较常用的几种加工方法,并加以适当的改进。采用固定斜率式斜进法粗车较大螺距螺纹,宽刃刀切槽轴向分线,精车二次分线等方法。保证了螺纹的精度,又能大大提高车削效率。     

Synthesis and characterization of a high refractive diglycidyl ether of thiodibenzenethiol epoxy resin

High refractive index of epoxy resins used as encapsulant in light-emitting diode (LED) is essential in improving the light extraction efficiency, reducing heat and prolonging the service life of LED packages. In this study, diglycidyl ether of thiodibenzenethiol (DGETDBT), an epoxy resin with high refractive index, was synthesized via a novel method and its chemical structure was characterized with Fourier-transform infrared (FTIR) spectrometer and ¹H NMR spectrometer. Using m-xylylenediamine (MXDA) as curing agent, the curing behavior of DGETDBT was studied by differential scanning calorimetry (DSC) and was compared with that of diglycidyl ether of bisphenol A (DGEBA), a generally used encapsulant in LED. The thermal behavior and optical performance of these two resins were investigated with thermogravimetric analyses, UV?CVis scanning spectrophotometer, and Abbe refractometer, respectively. The results showed that DGETDBT/MXDA resin demonstrated similar curing and thermal behavior to DGEBA/MXDA resin. But its refractive index reaches 1.698, which is significantly higher than that of DGEBA/MXDA resin (1.604). Comparatively, DGETDBT resin can be expected to be a more effective encapsulant of LED.