船用复合材料螺旋桨研究进展

复合材料具有比强度高,阻尼性能好及可调整纤维铺层以控制结构变形等优点.复合材料应用于螺旋桨将改善螺旋桨的推进性能和振动特性.通过对国内外复合材料螺旋桨研究成果的回顾、总结和归纳,得出了传统的算法已不满足复合材料螺旋桨的设计和预报要求,复合材料螺旋桨的设计和预报算法需考虑桨叶变形引起的空间流场变化的结论.分析了可借助纤维增强材料所具有的弯扭耦合特性,调整桨叶纤维材料铺层和桨叶结构形式来提高螺旋桨推进效率的规律性.总结了复合材料螺旋桨研究中的关键技术和复合材料螺旋桨设计流程,并指出了复合材料螺旋桨未来研究的趋势.      

原子分子在Pt(100)表面吸附的第一性原理研究

本文系统研究了H、N、O、C、S等原子,N_2、NH_3、NO、CO等分子和CH_3、CH、CH_2和OH等自由基在Pt(100)表面的吸附.从能量上来看,吸附能力从小到大的顺序是N_2NH_3COCH_3NOHOHNCH2OSCHC.原子类吸附物中H、N、O的最稳定吸附位均为桥位,而S、C则倾向于四重空位.所研究的分子吸附物(N_2、NH3、CO、NO),N_2和NH_3有且只有一种顶位吸附结构,CO和NO均优先吸附在空位.自由基吸附物(CH、CH_2、CH_3、OH)在Pt(100)表面上的吸附,CH_3优先吸附在顶位,CH_2、OH它们的最稳定吸附位均为桥位.原子、分子和自由基吸附后,会引起Pt(100)原子层间距的改变.     

Synthesis and Crystal Structure of a Novel Zinc Phosphonate Compound： [Zn（phen）（m-OOCC6H4PO3H）]

A novel zinc（H） metal phosphonate compound [Zn（phen）（m-OOCC6H4PO3H）] 1 （phen = phenanthroline） has been synthesized under hydrothermal conditions. Single-crystal X-ray structure analysis reveals that compound 1 belongs to the triclinic system, space group P1 with a = 9.3356（19）, b = 10.203（2）,c = 10.743（2）A,α = 76.3030（70）, β= 69.2317（51）, y = 84.3833（74）°,V = 929.4（3） ,A3, Z = 2, C2OH15N2O5PZn, Mr = 459.68, Dc = 1.643 g/cm^3,μ= 1.444, mm^-1, F（000） = 468, the final R = 0.0330 and wR = 0.0848. In the structure, the central ion Zn（H） is five-coordinated, linking three O atoms with one from carboxyl and the other two from phosphonyl group. The remained two coordinate sites were occupied by two N atoms from one phen molecule to form the asymmetric unit. Then every two adjacent asymmetric units are bridged by the O atoms from phosphonate group and carboxyl to give rise to a 1D chain along the b axis. These chains are constructed by weak π-π stacking interactions and C-H…π interactions to generate a 3D supramolecular framework.     

Improvement in a-plane GaN crystalline quality using wet etching method

Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 （high） phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 （high） peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 （high） peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples.     

基于EEMD-MRA方法的LIBS信号处理研究

LIBS技术优点众多,但由于光谱噪声干扰和基体效应等因素,影响了分析的准确度[1];EEMD方法能清晰的将LIBS信号中的不同特征成分自适应的分解开来。MRA方法能够补偿元素信号之间的互干扰,可进一步提高LIBS信号的准确性。通过自行搭建的测试系统获得了标准样品的原始信号,使用EEMD-MRA方法进行处理后,元素浓度曲线的决定系数R2得到了极大的提高,大大的提高数据的准确性,为LIBS信号的处理提供了一种全新的方式。     

兰州重离子回旋加速器主场电源改造

为满足分离扇回旋加速器（SSC）对于磁场精度的需求,需对其主场电源进行改造。提出开关电源与线性电源相结合的方式作为SSC主场电源的改造方案。电源总体分为两部分,采用模块化的开关电源作为前级电压源,三极管线性调整电路作为后级模块的主电路,充分利用两种电源的优势,实现高稳定度、低纹波的电流输出,同时大幅度提升电源的功率密度和可靠性。文章介绍了电源的工作原理及改造过程,详细阐述了三极管线性放大原理以及管压降控制电路、输出电流控制电路的设计与实现,通过仿真对电路进行功能验证,最终在电源样机上进行实验测试。测试结果表明:改造后主场电源输出电流稳定度达到了±3.99×10?6,电流纹波达到了2.7×10?9,各项性能均优于改造前。     

Magnetic polaron-related optical properties in Ni(Ⅱ)-doped Cd S nanobelts: Implication for spin nanophotonic devices

Emissions by magnetic polarons and spin-coupled d-d transitions in diluted magnetic semiconductors(DMSs)have become a popular research field due to their unusual optical behaviors.In this work,high-quality NiI₂(Ⅱ)-doped CdS nanobelts are synthesized via chemical vapor deposition(CVD),and then characterized by scanning electron microscopy(SEM),x-ray diffraction,x-ray photoelectron spectroscopy(XPS),and Raman scattering.At low temperatures,the photoluminescence(PL)spectra of the Ni-doped nanobelts demonstrate three peaks near the band edge:the free exciton(FX)peak,the exciton magnetic polaron(EMP)peak out of ferromagnetically coupled spins coupled with FXs,and a small higher-energy peak from the interaction of antiferromagnetic coupled Ni pairs and FXs,called antiferromagnetic magnetic polarons(AMPs).With a higher Ni doping concentration,in addition to the d-d transitions of single Ni ions at 620 nm and 760 nm,two other PL peaks appear at 530 nm and 685 nm,attributed to another EMP emission and the d-d transitions of the antiferromagnetic coupled Ni²⁺-Ni²⁺pair,respectively.Furthermore,single-mode lasing at the first EMP is excited by a femtosecond laser pulse,proving a coherent bosonic lasing of the EMP condensate out of complicated states.These results show that the coupled spins play an important role in forming magnetic polaron and implementing related optical responses.     

Quantum phase transitions in CePdAl probed by ultrasonic and thermoelectric measurements

CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressure- or field-tuned, extended quantum critical phase at zero temperature. Identifying characteristic signatures of the emerging quantum critical phase, which are expected to be distinct from those near a quantum critical point, remains challenging. In this work, by performing ultrasonic and thermoelectric measurements down to very low temperatures in a ³He-⁴He dilution refrigerator in the presence of magnetic field, we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase, including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.     

登机时间最优化解决方案

为了使航空公司获得更多的利润,应该尽量缩短乘客登机时间.以AirBus公司的A320飞机为例,利用已知统计数据、Matlab软件和R语言,建立登机顺序模型,并检验其合理性,同时设计出三种更好的模型供航空公司研究和实际操作.     

基于室温脉冲量子级联激光器的NO气体检测中的光谱处理方法研究

报导了采用基于室温脉冲量子级联激光器的脉内光谱检测技术,利用中心波长为1904 cm^-1的量子级联激光器,在实验室对NO气体样品进行检测的研究结果. 针对单线直接吸收光谱反演算法进行了研究,介绍了基线拟合的最小二乘算法以获取其吸光度,根据HITRAN数据库中相应吸收谱线的吸收线强,采用扫描积分实现了气体浓度的反演,避免了标气标定造成的误差及污染;通过拟合残差分析得到了系统的检测限,达到34×10^-6 m.