基于最小全变差的SAR图像自聚焦算法

该文分析了方位一维图像的全变差范数随二次相位误差的变化情况,得到全变差范数是二次相位误差的单峰函数的结论,且在二次相位误差等于零时全变差范数最小。从而利用全变差范数作为性能函数,采用黄金分割最优化算法,通过循环迭代得到自聚焦的SAR图像。实验结果表明此算法在处理二次相位误差时优于相位梯度自聚焦算法。通过算法复杂度的分析表明该算法的计算量约为相位梯度自聚焦的二分之一。     

基于结构组全变分模型的图像压缩感知重建

针对基于传统全变分(TV)模型的图像压缩感知(CS)重建算法不能有效地恢复图像的细节和纹理,从而导致图像过平滑的问题,该文提出一种基于结构组全变分(SGTV)模型的图像压缩感知重建算法。该算法利用图像的非局部自相似性和结构稀疏特性,将图像的重建问题转化为由非局部自相似图像块构建的结构组全变分最小化问题。算法以结构组全变分模型为正则化约束项构建优化模型,利用分裂Bregman迭代将算法分离成多个子问题,并对每个子问题高效地求解。所提算法很好地利用了图像自身的信息和结构稀疏特性,保护了图像细节和纹理。实验结果表明,该文所提出的算法优于现有基于全变分模型的压缩感知重建算法,在PSNR和视觉效果方面取得了显著提升。     

风云三号(D)气象卫星微波湿温度计系统建模和仿真

针对风云三号卫星微波湿温度计,该文建立了全功率式微波辐射计系统的仿真模型,重点对热辐射噪声源、混频器、低噪放、滤波器与检波器等关键性器件进行了参数化建模。从信号处理的角度对全功率式微波辐射计的工作过程进行了模拟,并对仿真系统的输出功率、灵敏度和线性度进行评估与分析。通过与实际仪器的测试结果对比,验证了所提仿真模型的正确性。

     

酶解柚皮生产还原糖的工艺优化

本文以琯溪蜜柚皮为原料,用果胶酶水解柚皮产生还原糖,通过响应面法优化酶解条件。以果胶酶添加量、酶解时间、酶解温度和料液比为单因素,在单因素试验的基础上选取合适的水平,根据Box-Behnken方法设计试验并建立模型,对柚皮酶解条件进行优化。结果表明,柚皮酶解的最佳工艺参数为:料液比为1:5 g/mL,果胶酶添加量150 U/g,酶解温度40 ℃,酶解时间3 h。在此条件下,酶解后还原糖含量为21.76 mg/g,比酶解前增长了2.54倍,与预测值2.62倍接近,说明用响应面法优化的柚皮酶解工艺可行。     

普洱茶茶褐素对高糖饮食大鼠糖脂代谢关键酶及组织切片的影响

目的:以普洱茶茶褐素为研究对象,研究普洱茶茶褐素对高糖饮食大鼠糖脂代谢关键指标以及肝脏、胰腺组织病理切片的影响。方法:雄性SD大鼠60只,按体重、血清总胆固醇、血清甘油三酯、高密度脂蛋白、低密度脂蛋白、空腹血糖无显著性差异分为6组(n=10):正常对照组、高糖模型组、阳性(罗格列酮)对照组、茶褐素低、中、高剂量组(即给药量分别为0.281、0.562、1.124 g/kg·bw)。实验动物每天定时给药,自由摄食和饮水,正常对照组喂以基础饲料和饮用蒸馏水,其他各组都以高糖饲料喂养和饮用15%果糖水,共喂养9周。测定大鼠血清糖脂代谢指标,通过电子显微镜观察大鼠肝脏、胰腺病理变化的影响。结果:干预期结束后,与高糖模型组相比,茶褐素能抑制高糖饮食大鼠血清中FINS、HOMA-IR、LPL、SCD-1、FAS、TNF-α、IL-1β、IL-6(p<0.05)水平的升高,降低HOMA-β、HSL、FFA、LEP水平;能有效增加高糖饮食大鼠GK、HMG-COA、HOMA-IS(p<0.05)水平,增加PK、FACL水平;大鼠肝脏和胰腺HE染色后,在显微镜下观察高糖模型组都有一定程度的病变,灌胃茶褐素后得到改善,说明普洱茶茶褐素可以降低高糖饮食大鼠肝脏脂质沉积和胰岛损害的程度,预防高血糖症的发生。结论:茶褐素能够调节高糖饮食大鼠糖脂代谢关键酶活性,加速高糖饮食大鼠脂质代谢,降低高糖饮食大鼠胰岛损害的程度。     

基于非局部低秩和加权全变分的图像压缩感知重构算法

为准确有效地实现自然图像的压缩感知(CS)重构,该文提出一种基于图像非局部低秩(NLR)和加权全变分(WTV)的CS重构算法。该算法考虑图像的非局部自相似性(NSS)和局部光滑特性,对传统的全变分(TV)模型进行改进,只对图像的高频分量设置权重,并用一种差分曲率的边缘检测算子来构造权重系数。此外,算法以改进的TV模型与NLR模型为约束构建优化模型,并分别采用光滑非凸函数和软阈值函数来求解低秩和全变分优化问题,很好地利用了图像的自身性质,保护了图像的细节信息,并提高了算法的抗噪性和适应性。仿真结果表明,与基于NLR的CS算法相比,相同采样率下,该文所提算法的峰值信噪比最高可提高2.49 dB,且抗噪性更强,验证了算法的有效性。     

基于DEA-Malmquist方法的新疆与全国小麦主产区生产效率动态比较研究

基于2004—2021年我国十大小麦主产区和新疆小麦的成本收益数据,运用数据包络分析模型（DEA）和全要素生产率指数（Malmquist）、从地域横向和时间纵向上分析了新疆小麦全要素生产率的现状及存在的问题。研究结果发现：（1）规模效率、综合技术效率和纯技术效率在两个阶段上显著,新疆小麦生产效率主要受技术水平制约。（2）新疆小麦全要素生产率在整体上处于增长趋势,技术进步是影响全要素生产率的主要因素。（3）新疆小麦生产在纯技术效率和技术进步方面均优于主产区平均水平,规模效率则还有较大进步空间。由此进一步优化生产规模并促进技术水平的提升对于新疆小麦生产效率的增长具有重要作用。     

模糊数学感官评价法优化猕猴桃果糕制作配方

以猕猴桃为原料,利用模糊数学感官评价法优化其果糕的制作配方。在单因素实验基础上,选取白砂糖、异麦芽酮糖醇、魔芋胶、卡拉胶和柠檬酸添加量为影响因素,以色泽、组织状态、口感和风味为评价指标,应用正交试验进行分析,并对优化后果糕的质构特性进行测定。结果表明,最佳制作配方为:白砂糖添加量40%,异麦芽酮糖醇添加量10%,魔芋胶添加量1.25%,卡拉胶添加量0.75%,柠檬酸添加量0.5%(以果肉匀浆重量100%为标准)。在此配方条件下制作的果糕模糊数学感官评分最高(91.15±0.82)分,产品呈均匀的黄绿色,猕猴桃香味浓郁,酸甜适宜,软硬适中,富有嚼劲。利用质构仪确定了优化后果糕的质构特性:硬度587.42±19.32 g,黏性(-76.81±8.12)g/s,弹性0.88±0.02,凝聚性0.66±0.00,胶黏性391.24±13.40,咀嚼性343.22±11.53,回复性0.22±0.00,测定结果均在消费者喜爱的质构特性区间内。本研究可为猕猴桃的精深加工及其系列\     

Microanalysis of supersaturated gas release based on wall-attached bubbles

Supersaturation of dissolved gases in natural water, due to spillage from high dams and other factors, may cause fish mortality. In previous experiments, the dissipation coefficient has been used to denote the degassing process of total dissolved gas(TDG) saturation. These experiments mainly analyzed supersaturated TDG dissipation from a macroscopic view. To precisely clarify the mechanism of supersaturated TDG release, this study investigated bubble adsorption at a wall surface from a microscopic view. The experiment was conducted in a Plexiglas-wall container filled with supersaturated TDG water. A model that calculates the adsorption flux of supersaturated TDG by a solid wall, and helps describe construction for a contact angle at a three-phase intersection, was developed according to Young's equation. This model was used to investigate the formation process of bubbles adsorbed on a solid polymethyl methacrylate(PMMA) surface in supersaturated TDG water. The adsorption effect of a solid wall on TDG release was analyzed based on the experimental data. The modeling results were compared with observations under different wall area conditions, and it was found that TDG release tended to increase with wall area. This study helps improve our understanding of the mechanisms of supersaturated TDG release and provides an important theoretical method for accurate calculation of the release process. The adsorption flux model of the solid wall provides mitigation measures to combat the adverse effects of TDG supersaturation,which will be beneficial to the protection of aquatic organisms in hydropower-regulated rivers.     

The Intermolecular Pauson-Khand Reaction: Applications,Challenges, and Opportunities

The rapid assembly of complex organic molecules from simple and structurally diverse building blocks is a prevalent challenge in organic synthesis. The Pauson-Khand reaction (PKR) is a method of choice for the construction of five membered rings that has historically been popularized as a late-stage intramolecular cyclization method. The intermolecular version of the PKR, on the other hand, constitutes a powerful approach for the rapid assembly of densely functionalized cyclopentanic cores at early stages of a synthetic sequence. Despite its potential, the intermolecular PKR is much less prevalent in the organic synthesis literature due to several historical limitations, most importantly a reduced scope with respect to the alkene component of the reaction. The last decade has witnessed important developments in the area including a) experimental and theoretical studies that provide a good mechanistic understanding of the reaction and its selectivity, b) methodological developments that have broadened the scope of potential alkene partners, and c) the development of catalytic enantioselective versions that provide useful levels of enantioselectivity. In parallel, remarkable synthetic applications of the intermolecular PKR have emerged, including (enantioselective) total syntheses of complex natural products (polycyclic terpenes, alkaloids, prostanes) as well as examples of industrial relevance. A fundamental limitation of the PKR that needs to be addressed in the future is the current lack of a ligand-accelerated version of the reaction, which would be a promising advance towards developing more efficient and general catalytic (enantioselective) reactions.