颗粒粒度分布分辨率的研究

粒度分布分辨率对于颗粒的测量是至关重要的,也是评估仪器分辨率的重要条件。但是当前诸多对于粒度分布分辨率的描述都没有给出明确的分辨临界点,也就无法评估仪器的分辨率。作者通过正态分布、RRB分布以及对数正态分布三种颗粒分布模型模拟确立了分辨临界并进行了验证,结果表明所确立的分辨临界是准确而合理的。影响仪器分辨率的评估准确性的另一方面是标准颗粒的选取,其中颗粒的分布参数是选择标准颗粒的关键。在应用分辨临界评估仪器分辨率时,发现分布参数的值越大,评估结果的准确性就会越高。

基于软阈值的小波图像增强方法

针对传统图像增强中存在的一些问题,如增强噪声、丢失细节等,提出了一种基于软阈值的小波图像增强方法。图像经过小波分解后可以得到一系列不同尺度上的子带图像,在不同尺度的子带图像上进行基于软阈值滤波的细节系数增强,再进行小波重构,即可得到增强后的图像。该方法可以有效地增强图像的细节信息,保持图像的边缘特征,改善图像的视觉效果。

一种基于D-MR-DCT的彩色图像水印算法

提出一种基于D-MR-DCT域的彩色图像水印算法。算法首先选择彩色图像的绿色分量进行分块D-MR-DCT变换,提取每块四个子带的第一个系数组成新矩阵并对其进行D-MR-DCT变换,将经过置乱和分割的灰度水印的奇异值分别嵌入到D-MR-DCT变换得到的四个子带分解的奇异值中,经过相应的逆变换得到含水印图像。实验结果表明,算法提高了水印抗JPEG压缩的鲁棒性,并对添加噪声、几何剪切、图像缩放等具有良好的鲁棒性。

LC698S片上指纹算法的优化与应用

主要介绍在无MMU支持的硬件环境中,为了解决程序运行的内存碎片的问题,利用自定义的内存池(Memory Pool)为指纹程序分配内存空间,通过片内RAM实现指纹识别功能的方案。本文对经典的预处理算法以及以特征点的拓扑结构作为特征值的识别算法作了进一步的优化。除此之外,本文提出分辨率动态分布算法,这种算法降低了原图像分辨率,改变了图像大小,节省了片内RAM空间,加快了图像处理速度,使得FAR与FRR达到识别要求,同时缩短指纹识别时间。

双反射面互补结构的折反射全向成像系统设计

为解决折反射全向成像空间分辨率低、分辨率分布不均匀的问题,提出一种双反射面互补结构的折反射全向成像系统。通过使空间点在全向图的内外环互补二次成像,有效改善全向成像的分辨率分布不均匀问题,并通过限制成像系统的垂直视域以得到较高的空间采样分辨率。详细阐述了两个反射镜面的面型参数和系统尺寸的计算方法,并通过光线追踪推导出全向图与柱面全景图之间的坐标映射关系。实验结果表明,该全向成像系统的分辨率分布明显更为均匀,全向图内外环之间存在很强的互补性。此外,互补二次成像的亚像素采样偏移为下一步的超分辨率柱面全景空间重建奠定了重要基础。

Structural Health Monitoring by Using Fiber-Optic Distributed Strain Sensors With High Spatial Resolution

In this paper, we review our researches on the topics of the structural health monitoring （SHM） with the fiber-optic distributed strain sensor. Highly-dense information on strains in a structure can be useful to identify some kind of existing damages or applied loads in implementation of SHM. The fiber-optic distributed sensors developed by the authors have been applied to the damage detection of a single-lap joint and load identification of a beam simply supported. We confirmed that the applicability of the distributed sensor to SHM could be improved as making the spatial resolution higher. In addition, we showed that the simulation technique considering both structural and optical effects seamlessly in strain measurement could be powerful tools to evaluate the performance of a sensing system and design it for SHM. Finally, the technique for simultaneous distributed strain and temperature measurement using the PANDA-fiber Bragg grating （FBG） is shown in this paper, because problems caused by the cross-sensitivity toward strain and temperature would be always inevitable in strain measurement for SHM.

Altered relationship between thickness and intrinsic activity amplitude in generalized tonic–clonic seizures

A thinner cortex has higher potential for binding GABA receptor A which is associated with larger amplitudes of intrinsic brain activity(i BA). However, the relationship between cortical thickness and i BA is unknown in intact and epileptic brains. To this end, we investigated the relationship between cortical thickness measured by highresolution MRI and surface-based i BA derived from resting-state functional MRI in normal controls(n = 82) andpatients with generalized tonic–clonic seizures(GTCS)only(n = 82). We demonstrated that the spatial distribution of cortical thickness negatively correlated with surface-based i BA amplitude at both whole-brain and within independent brain functional networks. In GTCS patients,spatial coupling between thickness and i BA amplitude decreased in the default mode, dorsal attention, and somatomotor networks. In addition, the vertex-wise acrosssubject thickness–i BA amplitude correspondence altered in the frontal and temporal lobes as well as in the precuneus in GTCS patients. The relationship between these two modalities can serve as a brain-based marker for detecting epileptogenic changes.

Three-Dimensional Sub-100 nm Super-Resolution Imaging of Biological Samples Using a Phase Ramp in the Objective Pupil

Localisation microscopy overcomes the diffraction limit by measuring the position of individual molecules to obtain optical images with a lateral resolution better than 30 nm. Single molecule localisation microscopy was originally demonstrated only in two dimensions but has recently been extended to three dimensions. Here we develop a new approach to three-dimensional （3D） localisation microscopy by engineering of the point-spread function （PSF） of a fluorescence microscope. By introducing a linear phase gradient between the two halves of the objective pupil plane the PSF is split into two lateral lobes whose relative position depends on defocus. Calculations suggested that the phase gradient resulting from the very small tolerances in parallelism of conventional slides made from float glass would be sufficient to generate a two-lobed PSF. We demonstrate that insertion of a suitably chosen microscope slide that occupies half the objective aperture combined with a novel fast fitting algorithm for 3D localisation estimation allows nanoscopic imaging with detail resolution well below 100 nm in all three dimensions （standard deviations of 20, 16, and 42 nm in x, y, and z directions, respectively）. The utility of the approach is shown by imaging the complex 3D distribution of microtubules in cardiac muscle cells that were stained with conventional near infrared fluorochromes. The straightforward optical setup, minimal hardware requirements and large axial localisation range make this approach suitable for many nanoscopic imaging applications.

Projected impacts of climate change on protected birds and nature reserves in China

Knowledge about climate change impacts on species distribution at national scale is critical to biodi- versity conservation and design of management programs. Although China is a biodiversity hot spot in the world, potential influence of climate change on Chinese protected birds is rarely studied. Here, we assess the impact of climate change on 108 protected bird species and nature reserves using species distribution modeling at a relatively fine spatial resolution （1 km） for the first time. We found that a large proportion of protected species would have potential suitable habitat shrink and northward range shift by 77-90 km in response to projected future climate change in 2080. Southeastern China would suffer from losing climate suitability, whereas the climate conditions in Qinghai-Tibet Plateau and northeastern China were projected to become suitable for more protected species. On average, each protected area in decline of suitable climate for China would experience a 3-4 species by 2080. Cli- mate change will modify which species each protected area will be suitable for. Our results showed that the risk of extinction for Chinese protected birds would be high, even in the moderate climate change scenario. These findings indicate that the management and design of nature reserves in China must take climate change into consideration.

High resolution full-spectrum water Raman lidar

Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study. For this purpose, we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice, water droplets and water vapor simultaneously. A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of-0.19 nm in the full Raman spectrum range of water, Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.

A maximum a posteriori super resolution algorithm based on multidimensional Lorentzian distribution

This paper presents a threshold-free maximum a posteriori (MAP) super resolution (SR) algorithm to reconstruct high resolution (HR) images with sharp edges. The joint distribution of directional edge images is modeled as a multidimensional Lorentzian (MDL) function and regarded as a new image prior. This model makes full use of gradient information to restrict the solution space and yields an edge-preserving SR algorithm. The Lorentzian parameters in the cost function are replaced with a tunable variable, and graduated nonconvexity (GNC) optimization is used to guarantee that the proposed multidimensional Lorentzian SR (MDLSR) algorithm converges to the global minimum. Simulation results show the effectiveness of the MDLSR algorithm as well as its superiority over conventional SR methods.

The lower and upper bounds of the degree distribution of a graded algebra

For a graded algebra,the minimal projective resolution often reveals amounts of information.All generated degrees of modules in the minimal resolution of the trivial module form a sequence,which can be called the degree distribution of the algebra.We try to find lower and upper bounds of the degree distribution,introduce the notion of(s,t)-(homogeneous) determined algebras and construct such algebras with the aid of algebras with pure resolutions.In some cases,the Ext-algebra of an(s,t)-(homogeneous) determined algebra is finitely generated.

Constraining fast radio burst progenitors with gravitational lensing

Fast Radio Bursts(FRBs)are new transient radio sources discovered recently.Because of the angular resolution restriction in radio surveys,no optical counter part has been identified yet so it is hard to determine the progenitor of FRBs.In this paper we propose to use radio lensing survey to constrain FRB progenitors.We show that,different types of progenitors lead to different probabilities for a FRB to be gravitationally lensed by dark matter halos in foreground galaxies,since different type progenitors result in different redshift distributions of FRBs.For example,the redshift distribution of FRBs arising from double stars shifts toward lower redshift than of the FRBs arising from single stars,because double stars and single stars have different evolution timescales.With detailed calculations,we predict that the FRB sample size for producing one lensing event varies significantly for different FRB progenitor models.We argue that this fact can be used to distinguish different FRB models and also discuss the practical possibility of using lensing observation in radio surveys to constrain FRB progenitors.

A Comparative Study of the Local Heat Transfer Distributions Around Various Surface Mounted Obstacles

In many engineering applications,heat transfer enhancement techniques are of vital importance in order to ensure reliable thermal designs of convective heat transfer applications.This study examines experimentally the heat transfer characteristics on the base plate around various surface mounted obstacles.Local convection coefficients are evaluated in the vicinity of each individual protruding body with great spatial resolution using the transient liquid crystal technique.Five different obstacles of constant height-to-hydraulic diameter ratio(~1.3) are considered.These include:a cylinder,a square,a triangle,a diamond and a vortex generator of delta wing shape design.The experiments were carried out over a range of freestream Reynolds numbers,based on the hydraulic diameter of each obstacle,varying from 4,000 to 13,000.The results indicate a negligible effect of the flow speed on the heat transfer topological structure and a considerable effect of the obstacle geometry on the level and distribution of heat transfer enhancement.