融合饱和梯度和Laplace谱的概率松弛匹配算法

文章将彩色图像的色彩信息和邻域信息引入谱匹配算法中,运用更能反映图的结构信息的Laplace谱,提出了一种融合彩色图像特征点的饱和梯度和Laplace谱的概率松弛匹配算法。先根据特征点点集的Laplace谱的相关性作为初始匹配,再利用概率松弛迭代寻找点之间匹配关系。实验结果表明该算法可获取较高的匹配精度。

梯度饱和土层的一维固结度的计算

研究了梯度饱和土层在外荷载下的固结作用,利用Biot理论给出了固结的基本微分方程,一些材料常数假设为指数模型,当梯度系数为零时,退化为一维均匀饱和土层的固结,利用分离变量等方法,得到透水和不透水边界条件下孔隙压力,给出了固结度曲线。当梯度系数不为零时,给出了梯度饱和土在外荷载下的孔隙压力,利用固结度的定义,数值算例出了梯度饱和土层的固结度变化曲线,分析和讨论了梯度系数等对固结度的影响。这些结果对地基下沉量计算和预测有一定的理论价值和意义。

基于自适应梯度优化的二值神经网络

二值神经网络由于在储存空间和计算上的高效性,在视觉任务中被广泛运用.为了训练不可导的二值网络,直通近似(Straight-Through Estimator)和S型近似(Sigmoid)等多种松弛优化方法被用来拟合量化函数.但是,这些方法存在两个问题:(1)由于松弛函数和量化算子的差异导致的梯度失配;(2)由于激活值饱和引起的梯度消失.量化函数自身的特性使二值网络梯度的准确性和有效性无法同时保证.本文提出了基于自适应梯度优化的二值神经网络(Adaptive Gradient based Binary Neural Networks,AdaBNN),其通过自适应地寻找梯度准确性和有效性之间的最佳平衡来解决梯度失配和梯度消失的问题.具体而言,本文从理论上证明了梯度准确性和有效性之间的矛盾,并通过比较松弛梯度的范数和松弛梯度与真实梯度之间的差距,构建了这一平衡的度量标准.因此,二值神经网络能根据所提出的度量调整松弛函数,从而得到有效训练.在ImageNet数据集上的实验表明,本文的方法相较于被广泛使用的BNN网络将top-1准确率提升了17.1%.

基于饱和度梯度的彩色序列图像光流场计算

传统的基于亮度守恒的光流法仅利用图像灰度信息进行光流求解,忽略了对包含丰富信息的色彩信息的利用。而彩色光流法虽然利用了彩色图像各通道信息,却忽略了对邻域信息的利用,造成存在各通道线性相关而无法求解的问题。同时,上述方法在光照变化时均不能得到正确的光流场估计。将基于饱和度的梯度计算方法引入灰度光流的计算方法中,提出了基于饱和度梯度的彩色光流计算方法,该方法有效地利用了彩色图像的色彩信息和邻域信息。试验结果证明：该方法提高了算法对光照变化的适应性,得到了更加精确的光流场估计,且避免了各通道线性相关的问题,为运动目标检测奠定了基础。

Face mask detection algorithm based on HSV+HOG features and SVM

To automatically detecting whether a person is wearing mask properly,we propose a face mask detection algorithm based on hue-saturation-value(HSV)+histogram of oriented gradient(HOG)features and support vector machines(SVM).Firstly,human face and five feature points are detected with RetinaFace face detection algorithm.The feature points are used to locate to mouth and nose region,and HSV+HOG features of this region are extracted and input to SVM for training to realize detection of wearing masks or not.Secondly,RetinaFace is used to locate to nasal tip area of face,and YCrCb elliptical skin tone model is used to detect the exposure of skin in the nasal tip area,and the optimal classification threshold can be found to determine whether the wear is properly according to experimental results.Experiments show that the accuracy of detecting whether mask is worn can reach 97.9%,and the accuracy of detecting whether mask is worn correctly can reach 87.55%,which verifies the feasibility of the algorithm.

The influence of elevation on soil properties and forest litter in the Siliceous Moncayo Massif,SW Europe

Understanding the effects of elevation and related factors(climate,vegetation) on the physical and chemical soil properties can help to predict changes in response to future climate or afforestation forcings.This work aims to contribute to the knowledge of soil evolution and the classification of forest soils in relation to elevation in the montane stage,with special attention to podzolization and humus forms.The northern flank of the Moncayo Massif(Iberian Range,SW Europe) provides a unique opportunity to study a forest soils catena within a consistent quartzitic parent material over a relatively steep elevation gradient.With increasing elevation,pH,base saturation,exchangeable potassium,and fine silt-sized particles decrease significantly,while organic matter,the C/N ratio,soil aggregate stability,water repellency and coarse sand-sized particles increase significantly.The soil profiles shared a set of properties in all horizons:loamy-skeletal particle-size,extreme acidity(pH-H_2O<5.6) and low base saturation(<50%).The most prevalent soil forming processes in the catena include topsoil organic matter accumulation and even podzolization,which increases with elevation.From the upper to lower landscape positions of wooded montane stage of the Moncayo Massif,mull-moder-mor humus and an UmbrisolCambisol-Podzol soil unit sequences were found.

Initiation and Development of Water Film by Seepage

When water seeps upwards through a saturated soil layer,the soil layer may become instability and water films occur and develop.Water film serves as a natural sliding surface because of its very small friction.Accordingly,debris flow may happen.To investigate this phenomenon,a pseudothree-phase media is presented first.Then discontinuity method is used to analyze the expansion velocity of water film.Finally,perturbation method is used to analyze the case that a water flow is forced to seep upwards through the soil layer while the movement of the skeleton may be neglected relative to that of water.The theoretical evolutions of pore pressure gradient,effective stress,water velocity,the porosity and the eroded fine grains are obtained.It can be seen clearly that with the erosion and redeposited of fine grains,permeability at some positions in the soil layer becomes smaller and smaller and,the pore pressure gradient becomes bigger and bigger,while the effective stress becomes smaller and smaller.When the effective stress equals zero,e.f.liquefaction,the water film occurs.It is shown also that once a water film occurs,it will be expanded in a speed of U(t)(1-ε).

The establishment of a new deliverability equation considering threshold pressure gradient

The flowing mechanism of a low permeability gas reservoir is different from a conventional gas reservoir,especially for that with higher irreducible water saturation the threshold pressure gradient exists. At present,in all the deliverability equation,the additional pressure drop caused by the threshold pressure gradient is viewed as constant,but this method has big error in the practical application. Based on the non-Darcy steady flow equation,the limited integral of the additional pressure drop is solved in this paper and it is realized that the additional pressure drop is not a constant but has something to do with production data,and a new deliverability equation is derived,with the relevant processing method for modified isochronal test data. The new deliverability equation turns out to be practical through onsite application.

Isothermal diffusion of water vapor in unsaturated soils based on Fick’s second law

In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.

基于Dopout与ADAM优化器的改进CNN算法

在分析当前卷积神经网络模型特征提取过程中存在问题的基础上,提出了基于Dropout与ADAM优化器的改进卷积神经网络算法（MCNN-DA）.设计了二次卷积神经网络结构,通过引入基于Re LU的激活函数以避免梯度消失问题,提高收敛速度;通过在全连接层和输出层之间加入Dropout层解决过拟合问题,并设计了ADAM优化器的最小化交叉熵.以MNIST和HCL2000数据集为测试数据,测试分析了ADAM优化器的不同学习率对算法性能的影响,得出当学习率处于0.04~0.08时,算法具有较好的识别性能.与三种算法的实验比较结果表明：本文算法的平均识别率最高可达99.21%;对于HCL2000测试集,本文算法的平均识别率比基于支持向量机优化的极速学习机算法提高了3.98%.

Propagation of plane wave in non-homogeneously saturated soils

Based on Biot's model for fluid-saturated media,which takes the inertial,fluid viscous,mechanical couplings,compressibility of grains and fluid into account,the dispersion equations of plane waves in non-homogeneously saturated soil are established by using reverberation ray matrix method(RRMM) with the aid of Helmholtz theorem.The non-homogeneity considered is a gradient variation in material properties with depth.The propagation characteristic of elastic waves in non-homogeneously saturated soil is analyzed by numerical example in this paper.The results show that the wave number and dissipation change little for two kinds of compression along the variation direction of the material properties,however,the non-homogeneity has significant effect on the wave number and dissipation of shear wave.

Investigation of the correlation between internal gradients and dephasing effect in inhomogeneous field

Internal magnetic gradient plays a significant role in Nuclear Magnetic Resonance(NMR)measurements of fluid saturated porous media.The quantitative characterization and application of this physical phenomenon could effectively improve the accuracy of NMR measurements and interpretations.In this paper,by using the equivalent magnetic dipole method,the three-dimensional distribution of internal induced magnetic field and its gradients in the randomly packed water saturated glass beads are quantitatively characterized.By simulating the diffusive motion of water molecules in porous media with random walk method,the computational dephasing effects equation related to internal gradients is deduced.Thereafter,the echo amplitudes are obtained and the corresponding T2-G spectrum is also inverted.For the sake of verifying the simulation results,an experiment is carried out using the Halbach core analyzing system(B0=0.18 T,G=2.3 T/m)to detect the induced internal field and gradients.The simulation results indicate the equivalent internal gradient is a distribution of 0.1-0.3 T/m,which matched well with the experimental results.