1/2波片对机载激光雷达偏振探测影响的研究

利用平面平行板模型和晶体膜层理论定量分析了1/2波片对机载激光雷达回波信号偏振探测的影响。计算结果表明:当入射光波长为532nm时,1/2石英波片对机载激光雷达回波信号平行分量与垂直分量透过率比值的影响幅度为0.82～1.196,1/2方解石波片对机载激光雷达回波信号的平行分量与垂直分量透过率比值的影响幅度为0.86～1.27;若用1/2石英波片测得的k=1.2,当考虑石英波片对五的影响时,则偏振探测两通道k的真实值应在1.003～1.463之间;若用1/2方解石波片测得的k=1.2,当考虑方解石波片对k的影响时,偏振探测两通道k的真实值应在0.945～1.395之间。由于1/2波片对k的影响,使机载激光雷达反演得到卷云等探测目标的退偏振比有较大的系统误差。     

构建先进实验平台,适应系列课程实践教学需求

传统的微机系列课程实验教学模式已不适应研究型大学理工科学生"创新型人才培养"的要求。从"模块化微机类课程实验平台"的构建、实验教学方法的探索、多层次实验教学内容的革新和针对"创新型人才培养"的系列实验教程的编著等几方面,探讨了微机系列课程实践教学的改革,并逐步付诸实施,在实际教学过程中成效显著。     

Electro-Optical and Thermophysical Characterization of Poly (Tripropylene Glycol Di-Acrylate)/Liquid Crystal Composite Materials Prepared by Polymerization Induced Phase Separation

Abstract

This work examines the development and characterization of tripropylene glycol di-acrylate/liquid crystal E7 (TPGDA/LC E7) PDLCs composite materials (polymer-dispersed-liquid-crystals). These systems were produced by UV irradiation photopolymerization (PIPS) of a mixture of the monomer tripropylene glycol di-acrylate (TPGDA) and the liquid crystal E7 (LC E7, a mixture of three cyano-biphenyl and one cyano-terphenyl LCs), in the presence of 2?wt% (of the acrylate/E7 mixture) of a photoinitiator. Electro-optical, thermal and optical characterization was used to understand the effect of the LC concentration on the electro-optical and thermo-physical properties of these materials. Polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) studies were performed to observe the system morphology and to determine the transition temperatures of these materials, both as a function of their composition. The findings showed a slight variation of the nematic-isotropic transition temperature, T_NI, of the LC E7 and of the glass transition temperature, T_g, of the TPGDA polymeric matrix as a function of the mass percentage of the LC E7. A very good electro-optical response for the composition 30/70?wt % TPGDA/LC E7 was obtained.     

某型机进近段高精度相对姿态实时测量技术

某型机在飞行训练过程中，进近段的二维相对姿态数据对于该型机安全着陆有着至关重要的作用。基于无线网络电台的双向数据传输系统能够实时获取进近段飞机相对理想着陆点的水平、垂直相对位置数据。通过上行链路上传着陆点的姿态数据，下行链路实时下传动动差分后的差分数据,最后在中心控制站进行二次数据处理。该技术获得的进近段二维相对姿态精度达到厘米级，满足飞行训练的需求。同时结合飞机显控数据以及视景图，以多角化动态关联的方式将实时获取的姿态数据等呈现给指挥员，更好地辅助指挥员进行着陆指挥工作。     

Renewability is not Enough: Recent Advances in the Sustainable Synthesis of Biomass‐Derived Monomers and Polymers

Taking advantage of the structural diversity of different biomass resources, recent efforts were directed towards the synthesis of renewable monomers and polymers, either for the substitution of petroleum‐based resources or for the design of novel polymers. Not only the use of biomass, but also the development of sustainable chemical approaches is a crucial aspect for the production of sustainable materials. This review discusses the recent examples of chemical modifications and polymerizations of abundant biomass resources with a clear focus on the sustainability of the described processes. Topics such as synthetic methodology, catalysis, and development of new solvent systems or greener alternative reagents are addressed. The chemistry of vegetable oil derivatives, terpenes, lignin, carbohydrates, and sugar‐based platform chemicals was selected to highlight the trends in the active field of a sustainable use of renewable resources.     

船舶与海洋平台结构冰载荷的高性能扩展多面体离散元方法

船舶与海洋平台结构的冰载荷是寒区海洋工程结构物设计中的关键参数,而离散元方法是有效计算结构冰载荷的重要手段. 本文采用基于闵可夫斯基和原理的扩展多面体离散元方法模拟船舶与海洋平台结构的相互作用过程. 其中,构造扩展多面体的近似包络函数并建立了基于优化模型的快速接触搜索算法;考虑单元间粘结作用的刚度软化过程建标识码元间的粘结-破碎模型. 同时,发展了 CPU-GPU 协同异构环境下的高性能并行算法. 为分析海冰与海洋结构作用中的冰载荷,采用ISO标准验证了扩展多面体离散元分析结构冰载荷的准确性. 采用离散元方法计算了船舶结构的冰载荷,研究了船舶结构表明的线载荷分布特点,并采用船舶结构冰阻力经验公式验证了计算结果的合理性. 采用离散元方法计算了平整冰区与多桩腿平台结构的相互作用,分析各桩腿上的冰载荷特点. 针对碎冰区的海冰管理过程,采用离散元方法分析了船舶结构绕行过程中的船舶和海洋平台结构冰载荷. 本文方法可有效应用于海洋结构冰载荷分析,能为极地船舶与海洋平台结构的设计和安全运行提供科学的分析手段.      

The physical properties of alkene-terminated liquid crystal molecules/E8 mixture and the electro-optical properties as they doped in polymer-dispersed liquid crystal systems

Effects of the content of fluorinated alkene-terminated liquid crystal (LC) molecules on the physical properties of the fluorinated alkene-terminated LC/E8 mixture were studied. The morphology and electro-optical properties as they doped in polymer-dispersed liquid crystal (PDLC) films were investigated. The detailed discussion of the obtained results is given. As a result, comparing with the physical properties of the series of LC mixtures with the same content of the analogous fully saturated compounds doped with E8, we find that the birefringence is significantly larger for the LC mixture with the alkene-terminated materials. Both fluorinated alkene-terminated LC molecules and the analogous fully saturated compounds doped with E8 reduce the driving voltage of PDLC films. Moreover, PDLC films with the fluorinated alkene-terminated LC molecules possessed higher contrast ratio and faster response time than that of the PDLC films prepared by adding the same mass fraction of the analogous fully saturated compounds. Thus, the ability to manipulate physical properties of LC mixture and electro-optical properties of PDLC films by changing the LC molecular structures may have future relevance for new LC structures design and applications of PDLC films.     

Single layer graphene: an alternative electrode material for ferroelectric liquid crystal based displays

We made comparative investigations on indium tin oxide (ITO) and single-layer graphene (SLG)-coated glass substrate as electrodes, specially for ferroelectric liquid crystal (FLC)-based system. We experimentally examined the comparative behaviour of important electro-optical FLC parameters for ITO- and SLG-based sample cells. The parameters are observed to be almost similar for both the cells. Interestingly, the value of threshold voltage is observed lower in SLG-based cell in comparison to that of conventional ITO/ITO cell. The presented results will definitely add a step to prove the suitability of graphene to be used as transparent electrodes in FLC-based display devices.     

Stimuli-Triggered Strand Displacement-Based Multifunctional Gene Detection Platform Controlled By A Multi-Input DNA Logic Gate

Highly sensitive detection of various cancer related genes is of great significance in a number of biomedical applications. Here we describe a logic-controlled multifunctional platform that is capable of detecting two kinds of gene sequences with a 2-aminopurine (2-AP) as a quencher-free fluorescent probe, the fluorescence of which dramatically increases when it loops out the DNA helices. This detection platform is assembled from the split ATP aptamer, G-quadruplex, and the antisense strands of the P53 and K-ras genes, together with their complementary components. It is selectively activated by ATP and K⁺ via the target-induced DNA strand displacement, enabling the exposure of two long toehold regions that allow the P53 and K-ras genes to trigger the next DNA strand displacements. A hairpin DNA containing a looped-out 2-AP in the stem is finally released, accompanying with a significant increase of fluorescence intensity. The whole process behaves as a four-input AND logic gate. Such a logic-controlled gene detection platform is able to convert the external stimulation of ions and biomolecules into a detectable fluorescence output and functions well in gene detection.     

Designing and fabrication of a novel gold nanocomposite structure: application in electrochemical sensing of bisphenol A

In this article, a highly sensitive electrochemical sensor is introduced for direct electro-oxidation of bisphenol A (BPA). The novel nanocomposite was prepared based on multi-walled carbon nanotube/thiol functionalised magnetic nanoparticles (Fe₃O₄-SH) as an immobilisation platform and gold nanoparticles (AuNPs) as an amplifying electrochemical signal. The chemisorbed AuNPs exhibited excellent electrochemical activity for the detection of BPA. Some analysing techniques such as Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and energy-dispersive x-ray diffraction exposed the formation of nanocomposite. Under optimum conditions (pH 9), the sensor showed a linear range between 0.002–240 μM, with high sensitivity (0.25 μA μM^?1) along with low detection limit (6.73 × 10^?10 M). Moreover, nanocomposites could efficiently decrease the effect of interfering agents and remarkably enhance the utility of sensor at detection of BPA in some real samples.