基于H.264的改进阈值的可变自适应十字搜索算法

H.264视频编解码标准的算法复杂度高,不能满足视频监控和无线传输中要求的高压缩比、低码率和实时性的要求,通过分析可知运算量最大的是运动估计模块,本文对该模块的算法进行优化。在ARPS算法的基础上结合预测的初始点和自适应调节臂长的搜索策略的优点,采用可变阈值的早期终止策略和简单的搜索模板的算法。实验表明该算法在有效减少搜索点数的情况下并不会对图像质量产生较大的影响,提高了运动估计算法的搜索速率和鲁棒性。     

Predicting external sulphur requirement of alfalfa from sulphate sorption isotherm of Tanzanian soils

For Tanzanian soils dominant in hydrous oxides of iron and amorphous ferri-alumino silicate, a 48-hour (hr) mixing period with the sulphate (SO₄) solution was adequate for a near-equilibrium condition. Although differing in their SO₄ sorption capacity, all the soils sorbed SO₄ at or beyond 1µg ml^–1 sulphur (S) concentration in the supernatant. Hydroxyl (OH) ions were displaced during SO₄ sorption as indicated by a significant positive correlation between the amount of sorbed SO₄ and the difference in pH values determined in 0.1N K₂ SO₄ and 0.1N KCl, i.e. the dpH values.In a greenhouse experiment, alfalfa was grown on eight soils at six adjusted S concentrations. Sulphur deficiency symptoms appeared in the control pots of those soils which were low in native sorbed SO₄, SO₄ sorption capacity and initial soil solution S concentration. Sulphur fertilization increased dry matter (DM) yield as well as response to applied S. The external S concentration, i.e. adjusted S concentration required for 95% of the maximum DM yield, ranged from 0.8 to 8.2µg S ml^–1 with values less than 2.0 on most of the soils. The external S concentration decreased hyperbolically as the SO₄ sorption capacity of the soils increased. The total amount of fertilizer S required to obtain the external S concentration in solution, and at the same time satisfy the SO₄ sorption capacity of the soil at the external S concentration (determined from the sorption isotherm) was defined as the external S requirement for the specified yield level of alfalfa. The external S requirement for 95% of the maximum yield of alfalfa varied from soil to soil due to differences in their capacity and intensity for S nutrition.Part of a thesis by the senior author for the MSc (Agric) degree of the University of Dar es Salaam     

Markov随机场与Gaussian曲线在MR图像分割中的应用

针对扫描的人脑组织MR图像边缘分辨率低、模糊性大的特点,本文提出了一种基于模糊Markov随机场和Gaussian曲线相结合的MR图像最佳阈值分割方法。该方法通过对图像的像素邻域属性的统计将模糊论引入其中,建立模糊Markov随机场,并利用Gaussian曲线对二维直方图最佳一维投影进行拟合,确定出图像中各脑组织的二维阈值点,在二维直方图上实现对脑组织的分割。通过实验表明,本算法能够有效提高脑组织的分辨率,对噪声的鲁棒性、结果区域的连通性相对于一维Otsu和二维Otsu算法都有了很大的提高。     

基于重加权快速交替方向法的频谱感知

在认知无线电网络中,由于深衰落和低信噪比的影响,单个认知用户的宽带频谱检测性能较差,且算法复杂度较高。针对该问题,提出一种基于重加权快速交替方向法的频谱感知算法。利用目标函数的凸性,通过求导简化辅助变量的更新过程。对目标函数进行线性化处理,增加一个二次项,使待估变量更新时部分项线性化的增广拉格朗日函数成为严格凸函数,并使用迭代软阈值算法进行求解。在目标项中增加大权值抑制信号中的非零元素,获得接近于最小?0范数的解。实验结果表明,该算法能有效提高低信噪比环境下的检测概率和检测速度。     

基于SVM模型的妫水河叶绿素a浓度的遥感反演

以北京市妫水河为研究区,基于2011年9月25日和2012年9月30日的两期叶绿素a浓度实测数据和准同步的环境一号卫星(HJ-1A)多光谱数据,分别构建一元线性和多元支持向量机模型(SVMM),通过决定系数R²和平均相对误差对模型的精度进行检验,用模型进行水体叶绿素a浓度的反演,并分析其时空分布特征。研究表明:在样本数较少的情况下,SVM具有很强的非线性映射能力,能够取得较好的预测结果,更适用于反演叶绿素a浓度。时间分布上,研究区叶绿素a浓度呈增加趋势,均值上升了6.86 μg/L;空间分布上,深水区叶绿素a浓度值低于浅水区,上游高于下游。国产HJ-1A CCD2多光谱数据以其4 d的时间分辨率,在水质动态变化监测方面具有优势。     

IGA-DFNN在瓦斯浓度预测中的应用

为了准确预测采煤工作面的瓦斯浓度,提出免疫遗传算法优化的动态模糊神经网络瓦斯浓度动态预测方法。用无线传感网络系统采集工作面瓦斯浓度数据作为样本,通过小波分析对样本数据进行降噪滤波预处理。采用IGA算法对DFNN网络参数进行优化,建立了瓦斯浓度的预测模型。通过MATLAB仿真研究表明,所建模型对采煤工作面的瓦斯浓度演变趋势预测合理,并且经过IGA算法优化DFNN网络比单纯的DFNN网络具有更快、更准确的预测功能,可以为防治煤矿瓦斯积聚提供更好的理论支持。     

十二烷基苯磺酸钠水溶液聚集性质的研究

用滴体积法测出十二烷基苯磺酸钠（ＳＤＢＳ）稀水溶液的表面张力；然后求出其临界胶束浓度（ＣＭＣ）。同时通过溶液的电导率、吸收光谱以及荧光光谱测定求出其ＣＭＣ。这样测出的ＣＭＣ值为１．２～１．６×１０－３ｍｏｌ／Ｌ，与文献值相符。也研究了部分水解的聚丙烯酰胺（ＰＨＰＡＭ）对ＳＤＢＳ聚集性质的影响；发现ＳＤＢＳ的ＣＭＣ值随ＰＨＰＡＭ的加人而减少并且ＰＨＰＡＭ水溶液的粘度随ＳＤＢＳ的存在而急剧降低（类似盐效应）。这些方法与性质对强化采油（ＥＯＲ）是重要的。     

Trail-following responses of the Argentine ant,Iridomyrmex humilis (Mayr), to a synthetic trail pheromone component and analogs

Behavioral evidence indicates that (Z)-9-hexadecenal (Z9-16ALD) is a trail pheromone component ofIridomyrmex humilis, and that the true trail pheromone may be multicomponent. Trail-following responses ofI. humilis workers to several concentrations of syntheticZ9-16ALD, a constituent of the Pavan's gland, were found to be comparable to responses to gaster extract trails containing ca. 100 times lessZ9-16ALD. Of the five aldehyde analogs tested, only (Z)-7-hexadecenal (Z7-16ALD) elicited significant trail-following. However, following responses to severalZ9-16ALD-Z7-16ALD combinations were lower than responses toZ9-16ALD alone. Trails on filter paper of biologically relevant concentrations ofZ9-16ALD lose activity within 2 hr in the laboratory. The release rate ofZ9-16ALD measured from filter paper trails was 0.25 ± 0.10 pg/cm-sec. This was used to estimate the trail-following threshold for this compound of Argentine ant workers.     

开封引黄灌区灌溉条件下稻田土壤盐分阈值研究

结合各生育期水稻耐盐度、各处理实际种前初始土壤含盐量和对应生育期最高的土壤含盐量,分析了各灌溉处理条件下的稻田土壤含盐量在水稻各生育期的动态变化规律和允许初始土壤含盐量阈值.结果表明:控制灌溉及控制灌溉加淋洗条件下,各水稻生育期土壤含盐量均有不同程度降低,随着淋洗水量的增加土壤含盐量逐渐降低,并获得了不同灌溉方式下的允许稻田初始土壤含盐量阈值.此结论对实际应用有指导意义.