基于层次隐马尔科夫模型和变长语义模式的入侵检测方法

分析了定长系统调用短序列在入侵检测系统应用中的不足,利用进程堆栈中的函数调用返回地址信息,提出了一种变长短序列的语义模式切分方法,并根据这种变长语义模式之间的层次关系和状态转移特性提出了基于层次隐马尔科夫模型的入侵检测方法。实验结果表明,与传统的隐马尔科夫模型相比,基于层次隐马尔科夫模型的入侵检测方法具有更好的检测效果。

基于变长系统调用序列模式的入侵检测方法研究

提出了一种变长序列模式的寻找算法,从训练序列中找出一组基本相对独立的变长序列模式,并在模式集的更新过程中自动定义了模式间的前后次序关系,以此构建了一个描述进程执行模式的DFA。针对已有基于变长序列模式的模式匹配算法需要向前预测若干个系统调用号的缺点,设计了一个更好的模式匹配算法。实验结果表明,算法在模式寻找过程中是稳定的,并在保持小规模模式集的情况下,取得了很低的误报率和漏报率。

一种进程系统调用重复子序列的压缩算法

以往入侵检测系统中采用的进程检测方法并未对进程系统调用序列中产生的重复子序列进行处理。本文提出了一种进程系统调用重复子序列的压缩算法,在系统调用序列收集过程中找出重复子序列,再将其作为一个整体参与模式的提取与检测。测试表明,对系统调用序列中的重复子序列进行压缩后能有效减少系统调用序列的长度,从而简化模式的学习和检测,提高进程检测的效率。

Super long-range diffusion of carbon during proeutectoid ferrite transformation

In order to explore the possible diffusion distance of carbon during proeutectoid ferrite transformation, a slow cooling test of low carbon steel was carried out under vacuum of the thermal simulator. The microstructure and thermal expansion curve were discussed and the carbon concentration inside the sample was measured. The ferrite layer of about 450 μm thickness was obtained without pearlite on the surface of the sample in the microstructure. The thermal expansion curve shows that the ferrite layer without pearlite is formed during the local phase transformation, which is followed by the global transformation. The carbon concentration in the core of the sample (0.061%) is significantly higher than that of the bulk material (0.054%). All results show that carbon has long-range diffusion from the outer layer to the inner layer of the sample. The transformation is predominantly interface-controlled mode during local transformation, and the interface migration rate is about 2.25 μm/s.

Environmental Capital,Negative Externality and Carbon Finance Innovation

In the context of global climate change,the internalization of negative externality,which is brought about by the traditional mode of economic growth,has become an inevitable choice.In order to achieve the internalization,it is necessary to make innovations on the market mechanism and system,find the value of environmental capital,establish a new mode of economic growth based on environmental capital,and then transform the environmental capital,an exogenous factor of economic growth,into an endogenous factor.Of this,the key of market mechanism and system innovation is the financial innovation that is based on environmental capital and negative externality;the government defines the initial property right of environmental resources and establishes environment energy trading market,so as to guide enterprises to trade environmental resources(represented by carbon emission permit trading) based on the Clean Development Mechanism,and to vigorously develop environmental finance and carbon finance.

Phase Effect on Mode Coupling in Kelvin—Helmholtz Instability for Two-Dimensional Incompressible Fluid

This paper studies the phase effect in mode coupling of Kelvin-Helmholtz instability in two-dimensionalincompressible fluid.It is found that there is an important growth phenomenon of every mode in the mode couplingprocess.The growth changes periodically with phase difference and in the condition of our simulation the period is about0.7π.The period characteristic is apparent in all stage of the mode coupling process,especially in the relatively laterstage.

Response of Pinus taiwanensis growth to climate changes at its southern limit of Daiyun Mountain, China's Mainland Fujian Province

The Pinus taiwanensis trees of a Chinese endemic species form pure forests at infertile sites in humid subtropical China, which can aid soil reservation and ecological resiliency at such sites. Herein, we used dendrochronological methods to investigate the growth patterns and their relationship with climate by analyzing 158 cores of 79 P. taiwanensis trees at 4 sites in their southernmost distribution in China's Mainland at Daiyun Mountain in Fujian Province. Tree growths at sites with favor- able conditions generally showed an age-related growth trend, which decreased from approximately 5 mm to 0.5 mm in about a century. Trees in moderately stressed environments established high growth in their juvenile periods but were highly suscep- tible to environmental stresses such as a sharp growth decline in the 1990s. The temperature in February and the moisture in July are the major limiting factors for most of the tree growths, except for a few extremely stressed P. taiwanensis trees. The growth of the dwarf P. taiwanensis trees, with all ring diameters of the first 20 years less than 4 ram, is mainly limited by the dry climate in May. Under the potential future warming trend, drought stress can be particularly threatening to these dwarf P. taiwanensis trees, which are likely to be the germplasm resources for this species in this region.

Reducing the climate shift in a new coupled model

Climate drift refers to spurious long-term changes that may be inherent in coupled models when external forcing factors are fixed. Understanding the sources of this drift and tuning the drift are crucial for obtaining reasonable simulations from coupled models. To prepare for the upcoming Coupled Model Intercomparison Project Phase 6, a new coupled model has been constructed based on the Community Earth System Model and the Grid-point Atmospheric Model of IAP LASG version 2. However, the surface temperature predicted by the new model is too underestimated, and this underestimation is caused by a type of climate drift, i.e., ‘‘initial shock.'' This study analyzes the source of the cold surface temperature from the perspective of energy balance and attempts to reduce the surface temperature drift by tuning the relative humidity threshold for low cloud.

Morphological evolution of the solid-liquid interface near grain boundaries during directional solidification

Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that the grain boundary provides the starting point of morphological instability of the solid-liquid interface. The initial perturbation near the grain boundary is significantly larger than other perturbations on the interface. The initial shape of the interface and the competition between the thermal direction and preferred crystalline orientations determine the subsequent growth pattern selections. The temporal variations of the curvature radius of cell/ridge tips near the grain boundary have also been studied when the instability occurs. This process is divided into three parts. As the pulling velocity increases, dendrites at the grain boundary grow in two different directions to form a bicrystal microstructure. Side branches on either side of the dendrite exhibit different growth patterns.