Large Cross‐Free Sets in Steiner Triple Systems

A cross‐free set of size m in a Steiner triple system is three pairwise disjoint m‐element subsets such that no intersects all the three ‐s. We conjecture that for every admissible n there is an STS(n) with a cross‐free set of size which if true, is best possible. We prove this conjecture for the case , constructing an STS containing a cross‐free set of size 6k. We note that some of the 3‐bichromatic STSs, constructed by Colbourn, Dinitz, and Rosa, have cross‐free sets of size close to 6k (but cannot have size exactly 6k). The constructed STS shows that equality is possible for in the following result: in every 3‐coloring of the blocks of any Steiner triple system STS(n) there is a monochromatic connected component of size at least (we conjecture that equality holds for every admissible n). The analog problem can be asked for r‐colorings as well, if and is a prime power, we show that the answer is the same as in case of complete graphs: in every r‐coloring of the blocks of any STS(n), there is a monochromatic connected component with at least points, and this is sharp for infinitely many n.     

Low-Energy Dislocation Structure (LEDS) character of dislocation boundaries aligned with slip planes in rolled aluminium

For the specific slip geometry of two sets of coplanar systems (a total of four systems) in fcc metals, the range of dislocation networks in boundaries aligned with one of the two active slip planes is predicted from the Frank equation for boundaries free of long-range elastic stresses. Detailed comparison with experimental data for eight dislocation boundaries in cold-rolled aluminium grains of the 45° ND rotated Cube orientation is conducted. It is concluded that the boundaries are Low-Energy Dislocation Structures, which are in good agreement with the Frank equation while also lowering the energy by dislocation reactions. Cross slip plays a role in the boundary formation process.     

Effect of pH value on the growth morphology of KH2PO4 crystal grown in defined crystallographic direction

KH₂PO₄ single crystals were grown in aqueous solution at different pH values by using “point seeds” with a defined crystallographic direction at 59 degree to the Z axis. Atomic Force Microscope (AFM) was applied to observe the surface morphology of (100) face. It was found that at the same supersaturation, the larger steps appeared at the lower pH value before appearance of 2D nucleus. We found that 2D nucleus was occurred at σ ≤ 0.04 when pH value is <2.8. The occurrence of 2D nucleus was caused by the decreasing step‐edge free energy with the decreasing of pH value in the growth solution. In this paper, we observed the morphologies of (100) faces of KDP crystals which grew in solutions with different pH values. 2D nucleuses appeared on the terrace of growth steps when pH value down to 2.8 and 3.2 at supersaturation of 0.04, while pH value down to 2.4, only 2D nucleation control the growth. Therefore, the pH value can change the growth mechanism of KDP crystals.     

An Edge Server Placement Method Based on Reinforcement Learning

In mobile edge computing systems, the edge server placement problem is mainly tackled as a multi-objective optimization problem and solved with mixed integer programming, heuristic or meta-heuristic algorithms, etc. These methods, however, have profound defect implications such as poor scalability, local optimal solutions, and parameter tuning difficulties. To overcome these defects, we propose a novel edge server placement algorithm based on deep q-network and reinforcement learning, dubbed DQN-ESPA, which can achieve optimal placements without relying on previous placement experience. In DQN-ESPA, the edge server placement problem is modeled as a Markov decision process, which is formalized with the state space, action space and reward function, and it is subsequently solved using a reinforcement learning algorithm. Experimental results using real datasets from Shanghai Telecom show that DQN-ESPA outperforms state-of-the-art algorithms such as simulated annealing placement algorithm (SAPA), Top-K placement algorithm (TKPA), K-Means placement algorithm (KMPA), and random placement algorithm (RPA). In particular, with a comprehensive consideration of access delay and workload balance, DQN-ESPA achieves up to 13.40% and 15.54% better placement performance for 100 and 300 edge servers respectively.     

油菜叶片的光谱特征与叶绿素含量之间的关系研究

叶绿素是作物生长中的重要因素,是植物营养胁迫、光合作用能力和生长状况的良好指示剂。实时、可靠的作物营养诊断是进行科学施肥管理的基础,也是实践精细农业的关键技术之一。采用便携式可见-近红外光谱仪,在室外自然光照条件下对不同氮肥水平下油菜叶片的光谱特性进行了研究,并根据作物特有的光谱特征,采用逐步回归分析方法建立了油菜叶片的叶绿素含量与红边位置和绿峰位置之间的定量分析模型。结果表明,将红边位置、绿峰位置二者作为自变量时,建立的模型效果优于采用单一的红边位置为自变量时建立的模型效果。其相关系数分别为0.863和0.848;校正标准偏差SEC分别为5.273和5.459, 说明采用红边位置和绿峰位置这两个参数更能很好地预测叶片的叶绿素含量。     

基于曲线拟合的亚像素边缘定位方法的研究

图像的边缘定位是图像测量的关键之一,随着测量精度要求的提高,已由早期的像素级边缘定位发展到了现在的亚像素级边缘定位。根据地球在地球敏感器CCD阵面中的成像特性,提出了一种基于曲线拟合的亚像素边缘定位方法以获取地球“灼热圆盘”的边缘。该方法利用曲线拟合获得的拟合斜率以及灰度值来提取图像的边缘。仿真结果表明,采用曲线拟合亚像素边缘定位法可使图像的边缘定位精度达到百分之几个像素,具有较高的精度。     

自然地面背景下红外目标检测算法

为了快速准确地检测出以地面物体为背景的红外序列图像中的目标,结合小波变换的特点及其应用于图像边缘检测的优点,提出了一种基于小波技术的图像预处理算法。该方法利用图像边缘在目标识别中的重要作用,讨论了基于小波变换的图像边缘检测方法,并结合地面背景红外图像自身的特点,大大地提高了单帧的检测概率。     

Canny算法的改进及其硬件的实现

传统的Canny边缘检测算法是先对图像进行平滑,然后利用二维滤波器计算图像的梯度值,从而得到梯度直方图。通过基于梯度直方图来选取双阈值,最后进行基于双阈值的非极大值抑制,得到边缘检测的图像。为了能很方便地在硬件中实现这种算法,对传统的Canny算法进行了适当的改进,利用模板来代替原算法中的卷积,从而使得该算法在FPGA(Field Programmable Gate Array)中可以完全利用原理图来实现。     

微分Haar-Gaussian小波变换在大景深物体边缘测量中的应用

提出了微分Haar_Gaussian小波变换算法并将其应用于边缘检测,在空域和频域中进行变换,并应用带宽匹配方法和远心测量光学系统,提高了运算速度,通过对实际大景深物体离焦像的边缘测量,得到了准确的结果。