基于块结构稀疏度的自适应图像修复算法

现有基于稀疏性的图像修复算法采用固定大小的待填充块和邻域一致性约束,且在全局搜索待填充块的最优匹配块,既降低了待修复区域的结构连贯性和纹理清晰性,又增加了算法的时间复杂度.针对上述问题,根据破损区域特性和块结构稀疏度间的关系,提出基于块结构稀疏度的自适应图像修复算法.根据最大优先权值点的块结构稀疏度值,设定不同参数以自适应选取待填充块大小、邻域一致性约束权重系数和局部搜索区域大小,并通过仿真实验分析讨论了各参数选取.实验结果表明本文算法较文献算法在峰值信噪比上提高0.3dB ～ 1.2dB,并且提高算法速度3～7倍.     

一种稀疏表示的二维DOA降维估计新算法

提出了一种基于空间锥角降维的二维DOA稀疏分解估计新方法,解决了利用稀疏表示方法进行二维DOA估计时计算复杂度大的问题.根据L阵列的结构特性,引入空间锥角表示信号的二维DOA信息,构造空间锥角冗余字典,通过稀疏正则化求解实现空间锥角的估计,然后利用求解得到功率实现L阵列中两个子阵之间的空间锥角配对,从而达到对多来波的二维DOA估计的目的,其避免了方位角和俯仰角组合而造成冗余字典庞大的问题,极大地减少了稀疏分解的计算量.仿真和实测数据结果均验证了该方法的有效性和优越性,为进一步的工程应用奠定了基础.     

基于梯度变化分析的弱目标检测

分析了噪声背景下弱目标区域的梯度分布特性,提出了一种利用弱目标边缘区域内梯 度分布特点来分割出弱目标的方法。为了提高分割的准确性,利用了帧间信息,根据目标的运动特征提取出真目标,并根据现场采集到的数据进行仿真,证明了该方法的有效性。     

梯度折射率对半透明介质温度场的影响

对梯度折射率半透明介质内辐射热平衡温度场进行了计算,考察了黑壁面及镜反射半透明界面时,线性和正弦两种不同折射率分布对温度分布的影响．当介质层边界为黑壁面,辐射能从光密介质向光疏介质传递时发生全反射导致某个热源在换热中的作用增大．当介质层具有镜反射半透明边界,除上述作用外,界面处的辐射换热也对介质内温度场产生影响．     

Fracture gradient prediction: an overview and an improved method

Abstract The fracture gradient is a critical parameter for drilling mud weight design in the energy industry. A new method in fracture gradient prediction is proposed based on analyzing worldwide leak-off test (LOT) data in offshore drilling. Current fracture gradient prediction methods are also reviewed and compared to the proposed method. We analyze more than 200 LOT data in several offshore petroleum basins and find that the fracture gradient depends not only on the overburden stress and pore pressure, but also on the depth. The data indicate that the effective stress coefficient is higher at a shallower depth than that at a deeper depth in the shale formations. Based on this finding, a depth-dependent effective stress coefficient is proposed and applied for fracture gradient prediction. In some petroleum basins, many wells need to be drilled through long sections of salt formations to reach hydrocarbon reservoirs. The fracture gradient in salt formations is very different from that in other sedimentary rocks. Leak-off test data in the salt formations are investigated, and a fracture gradient prediction method is proposed. Case applications are examined to compare different fracture gradient methods and validate the proposed methods. The reasons why the LOT value is higher than its overburden gradient are also explained.     

冀中坳陷霸县地区现今温压场及其与地热资源的关系

渤海湾盆地冀中坳陷霸县地区是地热资源富集区,其以"雄县模式"为示范引领,成功打造了中国第一个"无烟城"。为指导下一步地热能的勘探开发,基于大量油田钻井实测温度和压力数据,对该区现今地温梯度及温度、压力平面分布特征进行了系统研究,探讨了温压场与地热资源的关系。结果表明:(1)该区现今地温梯度介于21.8~73.5℃/km,平均值为33.5℃/km;(2)霸县地区地层温度随着深度的增加而逐渐升高,其平面变化特征与地温梯度展布特征相似,两者都与基底起伏形态具有很好的对应关系——对于同一深度,牛驼镇凸起温度最高,而廊固凹陷和霸县凹陷则较低,牛驼镇凸起北部、霸县凹陷中部及廊固凹陷中东部普遍存在高异常温度区,是潜在的地热资源有利开发区;(3)霸县地区现今地层压力以常压、弱超压为主,其平面分布规律随深度变化而存在着一定的差异,廊固凹陷南部和霸县凹陷南部在深度4 000 m处普遍发育中—强超压带,在开展下一步的地热能开发时需要格外注意。     

倾斜功能材料的开发动向

介绍了倾斜功能材料的概念；倾斜功能材料的合成工艺；倾斜功能材料的应用例及展望。     

Image segmentation towards new image representation methods

Very low bit-rate video coding has recently become one of the most important areas of image communication and a large variety of applications have already been identified. Since conventional approaches are reaching a saturation point, in terms of coding efficiency, a new generation of video coding techniques, aiming at a deeper “understanding” of the image, is being studied. In this context, image analysis, particularly the identification of objects or regions in images (segmentation), is a very important step. This paper describes a segmentation algorithm based on split and merge. Images are first simplified using mathematical morphology operators, which eliminate perceptually less relevant details. The simplified image is then split according to a quad tree structure and the resulting regions are finally merged in three steps: merge, elimination of small regions and control of the number of regions.     

广义时频表示的一种实时实现方法

本文研究了时频表示的实时实现算法及其算法优化问题，从广义局域自相关函数的物理意义出发，论证了广义时频表示的实时计算采用短时处理技术的可行性，并从两处着眼优化了算法，一得利用核函数共轭对称性，使时频表示的计算复杂度降低一半多；二是在计算解析信号过程中，给出了以任意帧移间隔的时域递推算法，进一步减少了实时算法的计算量。     

连续Gabor展开离散化后的混叠问题

为能进行数值计算，需对连续Ｇａｂｏｒ展开离散化有限化。本文就时域与频域两种情况，给出了在过采样率的一般情况下，有限离散化后的Ｇａｂｏｒ展开系数与原连续Ｇａｂｏｒ展开系数之间的关系，并由此推出了离散Ｇａｂｏｒ展开系数不产生混叠的条件——连续Ｇａｂｏｒ展开离散化的采样定理。最后给出了一个计算实例