PDT光敏剂HA在不同液相体系下的光谱特性研究

为了对候选光敏剂竹红菌甲素(HA)进行改性并保持其优异的敏化特性,对HA的光谱特性和激发态性质作了进一步的指认。系统研究了HA在不同液相体系下的吸收和荧光光谱,对指认HA的光谱和电子跃迁的机制提出了新的依据,结果表明,吸收带I产生于π-π*跃迁,吸收带Ⅱ和Ⅲ产生于P-π共轭所导致的L→aπ跃迁的电子振动结构;荧光发射带I和Ⅱ是产生于同一跃迁机制S1(L,aπ)→S0的正常荧光的振动结构。     

厚胶光刻非线性畸变的校正

利用厚胶光刻技术制作大深度微结构元件是一种有效的途径,但厚胶光刻过程中的非线性畸变对光刻面形质量的严重影响限制了该技术的应用,基于此,提出了一种对掩模透射率函数进行校正的方法。分析空间像形成及其在光刻胶内传递、曝光、显影等过程中非线性因素的影响,利用模拟退火算法对掩模透射率函数进行校正,以提高光刻面形质量,并以凹面柱透镜为例,给出了校正前后的显影轮廓模拟结果,其校正后浮雕面形的体积偏差仅为2.63%。该方法在有效改善面形质量的同时,并没有引起掩模的设计、制作难度及费用增加,这对于设计、制作高质量的微结构元件有重要意义。     

双缺陷模一维光子晶体的双光子吸收增强研究

采用真空镀膜工艺制备了具有762 nm和800 nm双缺陷模的含两个CdS缺陷层的TiO2/SiO2一维光子晶体,运用抽运探测技术测量了其双光子吸收。对于两个缺陷模,双光子吸收均得到很大的增强,其中缺陷模为800nm时的双光子吸收系数307 cm/GW要大于缺陷模为762 nm时的116 cm/GW,分别为单层CdS薄膜的48倍和18倍。这种双光子吸收的增强是由于光局域化导致一维光子晶体缺陷层内的电场强度增大而形成的。通过传输矩阵法计算了一维光子晶体的内部场强,发现800 nm波长光入射时缺陷层内的电场强度要大于762 nm波长光入射时的电场强度值。     

贵金属纳米材料的液相合成及其表面等离子体共振性质应用

金属中的表面等离子体共振是描述其导带电子在电磁场作用下集体振荡的一个物理概念。金属纳米颗粒由于其表面等离子体共振性质表现出独特的光学应用。本文在相关研究的基础上,综述了具备表面等离子体共振性质的不同形貌及多种复合结构的贵金属纳米材料的制备和应用,并对其发展及应用前景进行了展望。     

DNA体外缩合的研究进展

DNA缩合不仅是自然界常见的生理现象,也是非病毒载体介导基因转染的关键步骤。了解DNA体外缩合的性质与特征,将有助于设计出高效的非病毒转基因载体。本文综述了近十几年来以多价阳离子为缩合剂诱发的DNA体外缩合的研究进展,着重介绍了缩合的机理、过程、影响缩合的因素以及应用于转基因的最新成果。     

Visual Recognition of Traffic Signs in Natural Scenes Based on Improved RetinaNet

Aiming at recognizing small proportion, blurred and complex traffic sign in natural scenes, a traffic sign detection method based on RetinaNet-NeXt is proposed. First, to ensure the quality of dataset, the data were cleaned and enhanced to denoise. Secondly, a novel backbone network ResNeXt was employed to improve the detection accuracy and effection of RetinaNet. Finally, transfer learning and group normalization were adopted to accelerate our network training. Experimental results show that the precision, recall and mAP of our method, compared with the original RetinaNet, are improved by 9.08%, 9.09% and 7.32%, respectively. Our method can be effectively applied to traffic sign detection.     

Double Feature Extraction Method of Ship-Radiated Noise Signal Based on Slope Entropy and Permutation Entropy

In order to accurately identify various types of ships and develop coastal defenses, a single feature extraction method based on slope entropy (SlEn) and a double feature extraction method based on SlEn combined with permutation entropy (SlEn&PE) are proposed. Firstly, SlEn is used for the feature extraction of ship-radiated noise signal (SNS) compared with permutation entropy (PE), dispersion entropy (DE), fluctuation dispersion entropy (FDE), and reverse dispersion entropy (RDE), so that the effectiveness of SlEn is verified, and SlEn has the highest recognition rate calculated by the k-Nearest Neighbor (KNN) algorithm. Secondly, SlEn is combined with PE, DE, FDE, and RDE, respectively, to extract the feature of SNS for a higher recognition rate, and SlEn&PE has the highest recognition rate after the calculation of the KNN algorithm. Lastly, the recognition rates of SlEn and SlEn&PE are compared, and the recognition rates of SlEn&PE are higher than SlEn by 4.22%. Therefore, the double feature extraction method proposed in this paper is more effective in the application of ship type recognition.     

Optimizing the quasi-equilibrium state of hot carriers in all-inorganic lead halide perovskite nanocrystals through Mn doping: fundamental dynamics and device perspectives

Hot carrier (HC) cooling accounts for the significant energy loss in lead halide perovskite (LHP) solar cells. Here, we study HC relaxation dynamics in Mn-doped LHP CsPbI₃ nanocrystals (NCs), combining transient absorption spectroscopy and density functional theory (DFT) calculations. We demonstrate that Mn²⁺ doping (1) enlarges the longitudinal optical (LO)–acoustic phonon bandgap, (2) enhances the electron–LO phonon coupling strength, and (3) adds HC relaxation pathways via Mn orbitals within the bands. The spectroscopic study shows that the HC cooling process is decelerated after doping under band-edge excitation due to the dominant phonon bandgap enlargement. When the excitation photon energy is larger than the optical bandgap and the Mn²⁺ transition gap, the doping accelerates the cooling rate owing to the dominant effect of enhanced carrier–phonon coupling and relaxation pathways. We demonstrate that such a phenomenon is optimal for the application of hot carrier solar cells. The enhanced electron–LO phonon coupling and accelerated cooling of high-temperature hot carriers efficiently establish a high-temperature thermal quasi-equilibrium where the excessive energy of the hot carriers is transferred to heat the cold carriers. On the other hand, the enlarged phononic band-gap prevents further cooling of such a quasi-equilibrium, which facilitates the energy conversion process. Our results manifest a straightforward methodology to optimize the HC dynamics for hot carrier solar cells by element doping.

Mn doping modulates the hot carrier dynamics in all-inorganic lead halide perovskite nanocrystals according to the excitation energy.     

吸管法和比重计法测定土壤机械组成的比对研究

土壤机械组成是土壤的基本属性,也是第三次全国土壤普查(“三普”)的重要指标。参照“三普”规定的测定土壤机械组成的吸管法和比重计法的分析规范对来自河南封丘、江西鹰潭和新疆乌鲁木齐等地区的3种土壤试样进行分析,讨论平行测定的精密度和测定过程中的关键点,进而对两种测定方法进行评价。结果表明,吸管法和比重计法的分析过程中存在一些影响分析结果的重点步骤,这些关键细节对提升“三普”土壤机械组成结果准确性和分析效率至关重要。吸管法和比重计法测定获得的土壤质地类型结果基本一致。通过平行试样测定结果允许的绝对相差分析发现吸管法的精密度较比重计法稍差,但两者都能达到土壤普查的要求。通过两种土壤机械组成测定方法的比对研究,为基层实验室顺利开展本项目的测定提供借鉴,为第三次全国土壤普查工作提供技术支撑。     

Preparation and Electrochemical Performance of Three-Dimensional Vertically Aligned Graphene by Unidirectional Freezing Method

Three-dimensional vertically aligned graphene (3DVAG) was prepared by a unidirectional freezing method, and its electrochemical performances were evaluated as electrode materials for zinc−ion hybrid supercapacitors (ZHSCs). The prepared 3DVAG has a vertically ordered channel structure with a diameter of about 20−30 μm and a length stretching about hundreds of microns. Compared with the random structure of reduced graphene oxide (3DrGO), the vertical structure of 3DVAG in a three−electrode system showed higher specific capacitance, faster ion diffusion, and better rate performance. The specific capacitance of 3DVAG reached 66.6 F·g⁻¹ and the rate performance reached 92.2%. The constructed 3DVAG zinc−ion hybrid supercapacitor also showed excellent electrochemical performance. It showed good capacitance retention up to 94.6% after 3000 cycles at the current density of 2 A·g⁻¹.