随机区块法在空间点格局分析中的应用

利用一种以随机模拟技术为基础的空间点格局分析方法——随机区块法对长白山阔叶红松林中5个主要树种的空间格局及空间关系进行了分析。随机区块法利用ICS(t)=s2(t)/(t)-1来衡量不同尺度t上空间点的分布格局,并通过随机模拟技术构建零假设的95%或99%置信区间,以确定空间点格局偏离零假设的显著性程度。结果表明,除蒙古栎、山荆子、怀槐为随机分布外,其它树种均在局部空间尺度上呈聚集分布;并且绝大多数种对或种组在局部空间尺度上呈正相关关系。随机区块法克服了小样方统计法研究尺度单一的问题,也避免了以空间点距离为基础的点格局分析过程中边缘效应带来的影响和误差,尤其是在多变量点格局分析中具有明显的优势。

区块法在地籍测绘中的应用与分析

将区块法应用到地籍测绘中,通过实例分析发现这种计算方法可以避免解算大量的方程式,但必须承担极多数量的单个变换运算。除了块的连接和全区平差程序可以公用外,主要是用计算时间来解决容量的预算。区块法地籍测量方案与常规地籍测量方法相比,测量时间有所缩短,解决了因地籍测量起始点的不同而造成得权属纠纷问题。

浅谈区块法地籍测量

地箱测量工作涉及面广，权属调查制约因素多，种快速、经济的地籍测量模式对开展地籍测量工作具有实际意义。根据实际调研工作经验，提出取区块法地籍测量的试验方法，并通过实例论证区块法地籍测量的可行性。理论扣实践证明，当独立块有足够的相对精度时，只要区域周围有一定数量的堀建控制点，区域内部无控制点条件下，这种方法平均精度仍然保持在独立块误差量级，并且几乎不受区域大小的限制。

基于混频已实现GARCH模型的波动预测与VaR度量

本文将Hansen等(2012)的Realized GARCH模型扩展为包含日内收益率、日收益率以及已实现波动率的混频已实现GARCH模型(M-Realized GARCH模型)。该模型将日内交易分为前后两段,引入了混频均值方程,并对混频均值方程的残差分别建立条件波动率方程和已实现日波动率方程。本文采用2013—2016年沪深300指数混频数据,分别在扰动项服从正态分布、t分布和广义误差分布的假设下,采用损失函数、SPA检验、kupiec检验和动态分位数检验法,对GARCH、Realized GARCH和MRealized GARCH模型的波动率预测和VaR度量效果进行对比研究,得出M-Realized GARCH模型能提高预测精度,且VaR实际失败率与理论失败率一致,失败发生之间不相关。最后,本文利用Block bootstrap方法抽样得到混频数据,模拟证明了M-Realized GARCH模型比Realized GARCH模型具有更高的预测精度。

A framework to create video-transition effects

The paper presents a framework for developing a variety of video transition effects. The framework is designed to deal with the problem of inefficiency for programmers to generate more and more diversified video transition, which is caused by excessive coupling between the sub-modules of the system. So the framework is designed to be modular, flexible and extensible. Based on the analysis of common features of different effects, the implementation of video transition effect is divided into 4 sub-odules, each of which can be designed and developed independently. Furthermore, these sub-modules can be easily sub- stituted, modified and reused. We present a formal description of our framework, and give typical study cases to show the extensive utility of the framework.

A Practical Online Approach to Protecting Kernel Heap Buffers in Kernel Modules

Heap overflow attack is one of the major memory corruption attacks that have become prevalent for decades. To defeat this attack,many protection methods are proposed in recent years. However,most of these existing methods focus on user-level heap overflow detection. Only a few methods are proposed for kernel heap protection. Moreover,all these kernel protection methods need modifying the existing OS kernel so that they may not be adopted in practice. To address this problem,we propose a lightweight virtualization-based solution that can protect the kernel heap buffers allocated for the target kernel modules. The key idea of our approach is to combine the static binary analysis and virtualization technology to trap a memory allocation operation of the target kernel module,and then add one secure canary word to the end of the allocated buffer. After that,a monitor process is launched to check the integrity of the canaries. The evaluations show that our system can detect kernel heap overflow attacks effectively with minimal performance cost.

REMARKS ON NETWORK COMMUNITY PROPERTIES

This paper discusses a popular community definition in complex network research in terms of the conditions under which a community is minimal, that is, the community cannot be split into several smaller communities or split and reorganized with other network elements into new communities. The result provides a base on which further optimization computation of the quantitative measure for community identification can be realized.

ANALYSIS OF MINIMUM NUMBERS OF LINEARLY ACTIVE S-BOXES OF A CLASS OF GENERALIZED FEISTEL BLOCK CIPHERS

For a class of generalized Feistel block ciphers, an explicit formula for the minimum numbers of linearly active S-boxes of any round r is presented.