Medical image contrast enhancement based on improved sparrow search algorithm

The collection or transmission of medical images is often disturbed by various factors, such as insufficient brightness and noise pollution, which will result in the deterioration of image quality and significantly affect the clinical diagnosis. To improve the quality of medical images, a contrast enhancement method based on improved sparrow search algorithm is proposed in this paper. The method is divided into two steps to enhance the medical images. First, a new transform function is introduced to improve the brightness or contrast of medical images, and two parameters in the transform function are optimized by the improved sparrow search algorithm. Second, adaptive histogram equalization method with contrast limited is used to equalize the result image of the previous step to make the pixel distribution of the image more uniform. Finally, a large number of experiments and qualitative and quantitative analyses were conducted on the common data sets. The analysis results demonstrate that the presented approach outperforms some existing medical image processing approaches.     

Polarized Optoelectronics of CsPbX3 (X = Cl,Br, I) Perovskite Nanoplates with Tunable Size and Thickness

Low dimensional semiconductor nanomaterials have shown their tailorable properties for a variety of promising applications in decades. Here a general strategy to synthesize all‐inorganic CsPbX₃ (X = Cl, Br, I or their mixture) perovskite 2D nanoplates by introducing additional metal halides MX'₂ or MX'₃ (M = Cu, Zn, Al or Pb, etc.; X' = Cl, Br or I) is reported. These CsPbX₃ perovskite nanoplates have uniform thickness and tunable size, which can be feasibly controlled by the component and ratio of the metal halides, temperature, time, and ligands. The well‐defined morphology of the nanoplates makes them ideal building blocks for the self‐assembly in the face‐to‐face and column‐by‐column arrangement. Compared to the optically isotropic CsPbX₃ nanocubes, the 2D CsPbX₃ nanoplates exhibit remarkable polarized UV–vis absorption and photoluminescence not only in liquid solvent and solid resin matrix, but also in self‐assembled films. An optoelectronic photodetector sensitive for linear polarized light is fabricated to demonstrate the proof‐of‐concept.     

有机发光器件的一种失效机制

制备了结构为铟锡氧化物(ITO)/NPB/插入层/Alq/LiF/Al的有机电致发光(EL)器件,测量了器件发光随电压变化的光谱和电压-电流-亮度特性,观察到这种结构器件在电压升高的过程中总是在某电压附近有一个光谱、亮度和效率等性能突变的不可逆过程,这是由于在发光区域附近的纳米薄层材料将导致电荷在该区域的局部聚集,并引起该薄层材料局部破坏。这一失效的机制表明,尽管在器件制备过程中可能需要在器件中使用几纳米厚的有机层,但是应当考虑尽量避免,以使器件内载流子分布合理,避免此类失效过程发生。     

多基线数字近景摄影测量在街道立面测量中的应用探讨

阐述了采用多基线数字近景摄影测量进行街道立面测量的作业流程和作业方法以及成果数据的编辑和减少外业工作量的检查验收方式。同时,对无法进行多基线摄影的特殊情况,采用外业碎部测量进行辅助测量的作业方式、方法进行了介绍。利用多基线数字近景摄影测量进行街道立面测量,将大量外业工作移到室内,可有效减少外业工作量。     

寒区裂隙冻岩隧道岩-水-冰力原位测试及冻胀力模型

为了研究寒区裂隙冻岩隧道冻胀力并建立合理的计算模型,以川藏公路雀儿山隧道为工程依托,组合利用水压力计、土压力盒和多点铂电阻温度传感器进行冻胀力原位测试,考虑静水压力,提出了裂隙成环贯通原位冻胀时的隧道宏观冻胀力理论模型,并将计算结果与原位测试结果进行了比较分析。研究结果表明：现场原位测试方法考虑了岩-水-冰在冻结过程中随时间和温度的变化特征,避免了对裂隙岩石细观结构模型的讨论,方案合理且易于实施;裂隙岩石冻结前水压力随径向深度增加而线性减小,径向1.5～2m围岩内裂隙水挤出形成急剧增压区间,靠近结构处水压力降到最低;原位测试得到冻胀压力0.615～3.355MPa,空间分布以拱顶处最小,拱腰处最大,冻胀力模型计算得到的冻胀压力约0.46MPa,去除水压力,裂隙成环贯通宏观冻胀力理论模型计算结果接近于工程实际。     

基于双DSP的双PWM变频器控制平台设计

首先通过分析双PWM变频器拓扑结构和现有的系统控制策略,确定了控制平台的硬件需求。采用模块化的设计方法设计了一套基于双定点数字信号处理器TMS320F2812的控制平台。同时,对各硬件单元的设计方法和所实现的功能分别进行了详细描述。该平台既可以作为双PWM变频器专用控制平台,也可以作为通用开发板使用。最后以1台55 kW的三相两电平双PWM背靠背变频器和1台2.2 kW的三相变频调速系统为例,验证了所提出的控制平台设计的正确性和可行性。     

数字化胸部X射线摄影中铜滤过对受检者辐射剂量的影响

采用西门子公司生产的数字化X射线透视摄影系统,在不同的附加铜滤过(0、0.1、0.2、0.3 mm)下,对不同厚度的聚甲基丙烯酸甲酯(PMMA)模体进行胸部摄影。利用对比度噪声比评估不同附加铜滤过对图像质量的影响,同时使用辐射剂量仪记录不同铜滤过下的体表入射剂量,以探讨数字化胸部X射线摄影中,附加铜滤过对受检者体表入射...     

Perovskite Anion Exchange: A Microdynamics Model and a Polar Adsorption Strategy for Precise Control of Luminescence Color

Inorganic perovskite quantum dots (QDs) have natural advantages in the field of light-emitting diodes (LEDs) because of their high color purity and tunability in a wide range. However, when manufacturing efficiently mixed-anion perovskite QDs (CsPbBr_xI_3−x) to meet the requirements of the pure red color standard in the display field (≈630 nm), results are difficult to control accurately due to the lack of exploration of its microscopic mechanism. Here, a microdynamics model is constructed for anion exchange dominated by vacancies which revealed the key role of polar solvent in reducing the surface energy barrier of anions through first-principle calculations. Besides, a polar solvent construct in situ anion exchange channels method is proposed. Then, the precise control of anion exchange is demonstrated, and the precise regulation spectrum of the whole red-light range (600–680 nm) is achieved. Finally, various QD LEDs (QLEDs) based on these tunable QDs are fabricated and exhibit excellent photoelectric performance in the main red range (620–680 nm). Among them, the champion QLEDs, have peak external quantum efficiency (EQE) of 16.3% at 633 nm and peak EQE of 18.2% at 646 nm, showing potential in meeting the requirements of display standard.     

基于选择性神经网络集成的地基云状识别算法

针对传统地基云图云状识别模型精度较低的问题,提出一种基于K均值算法的选择性神经网络集成的方法。该方法以BP神经网络集成模型为基础,采用K均值聚类算法选择部分有差异性的个体神经网络进行集成,建立了云状分类模型。通过对云图样本进行仿真实验,结果表明所提出的算法相对于单个BP神经网络及传统的BP_AdaBoost集成算法用于云图的分类,能有效地提高云图识别分类的精度。