基于Python的网络协议分析工具的研究与应用

随着人们对网络安全重视程度的加深,网络协议朝着复杂化、多样化发展,而传统的协议解析工具存在着扩展性差、功能固定等局限.为了更好地符合实际需要,本文提出一种基于Python的支持自定义协议扩展和密态包解析的网络协议分析工具,主要对网络数据包解析技术进行了研究,采用脚本扩展的方式实现了对数据包的捕获、过滤并进行解析,同时加入了自定义密态包解析功能.实验结果表明,数据包密文部分的解析还原达到了预期效果.     

Bifurcation behaviors of an Euler discretized inertial delayed neuron model

This paper presents an Euler discretized inertial delayed neuron model, and its bifurcation dynamical behaviors are discussed. By using the associated characteristic model, center manifold theorem and the normal form method, it is shown that the model not only undergoes codimension one (flip, Neimark-Sacker) bifurcation, but also undergoes cusp and resonance bifurcation (1:1 and 1:2) of codimension two. Further, it is found that the parity of delay has some effect on bifurcation behaviors. Finally, some numerical simulations are given to support the analytic results and explore complex dynamics, such as periodic orbits near homoclinic orbits, quasiperiodic orbits, and chaotic orbits.     

Analytical investigation on thermal-induced warpage behavior of ultrathin chip-on-flex (UTCOF) assembly

The serious warpage issues of ultrathin chip-on-flex (UTCOF) assembly induced by mismatched thermal stresses have greatly affected the mechanical stability and reliability of emerging ultrathin chip packaging technology. Currently, a theoretical prediction as a convenient and straightforward approach is still lacked for describing effectively the thermal-mechanical behavior of UTCOF during the adhesive curing and cooling process. In consideration of the adhesive thickness approximating to ultrathin chip and flexible substrate thickness, we develop a layerwise-model of ultrathin chip-adhesive-flex structure under plain strain condition, where the behavior of thick adhesive bonding can be described precisely through increasing the subdivided mathematical plies. Further, the analytical results show that the concave and convex forms of ultrathin chip warpage yield at the end of the curing and cooling process respectively. Meanwhile, the effects of its structure dimensions and material properties are also revealed for discussing a way to relieve the extent of ultrathin chip warpage. Additionally, in order to verify the validity of the theoretical prediction, we also introduce the corresponding numerical technique and experimental method. These results suggest that a kind of rigid and ultrathin flexible substrate such as metal foil should be adopted for small warpage of ultrathin assembly.     

Experiments on and predictions about properties of sand bonded by microbe cement

Microbe cement as a new bonding material is presented. Sandstone (0.05 m diameter, 0.5 m height) and sandpile (0.125 m³) are joined by microbe cement to make a whole body. Evolutions in the related properties of treated sand samples are examined through compressive strength and calcite content. Results indicate that the structure of the cemented body is nonuniform, that the calcite content decreases with distance from the injection port, and that the compressive strength also decreases with distance from the injection port. In addition, evolutions in the measured calcite content and compressive strength are summarized by a numerical model that considers microbe concentration distribution. The numerical results of the calcite content at different positions for 0.5 m height sandstone are similar to the test results, and the experimental results for calcite content and compressive strength of 0.125 m³ cubic sandpile are similar to the numerical results. Prediction results indicate that the simulations should become a significant supplementary tool when microbe cement is applied in actual engineering projects.     

Kinetic theory for aquatic animal distribution simulation

Identifying the underlying mechanisms that influence the spatial patterns in populations improves the forecasts of the alternative management strategies on the spatial dynamics of the populations, which are critical for assessing and managing the fisheries and improving the water resource management. This paper described a new approach of the numerical model for the prediction of the aquatic animal distribution in the flows. The model was developed based on the kinetic theory of gases, the mechanism of the aquatic animal movement and the flow hydrodynamic patterns. The model was validated using the available experimental data and an acceptable agreement was obtained. A comprehensive parameter study was then conducted to help understand the impact and the sensitivity of each parameter to the aquatic animal distribution. The promising results of the model reveal the prospect of applying this model to the reliable prediction of the aquatic animal distribution within a relatively large water area.     

Boost变换器负调电压建模分析

摘要 以电容电压作为输出反馈的Boost变换器是一个非最小相位系统,非最小相位反应引起的负调严重的影响系统的暂态性能及稳态性能。研究引起负调与变换器参数之间的关系对Boost变换器优化设计是一个关键问题。本文根据Boost变换器小信号数学模型推导给出非最小相位系统的负调电压表达式,指出衡量负调电压的两个指标：负调电压大小和负调电压峰值时间。根据负调电压表达式分析了输入电压、储能电感、占空比、占空比变化量、负载、滤波电容等参数对负调电压的影响。研究结果表明：输入电压和占空比变化量仅影响负调电压大小;储能电感、占空比、负载、滤波电容不仅影响负调的大小,同时影响负调的峰值时间。研究所得结论为Boost变换器的参数优化设计以及减小负调电压提高系统暂态性能及稳态性能提供了理论依据。仿真和实验结果验证了理论分析的正确性。     

基于Pro/E的机柜参数化设计

基于Pro/E软件的三维建模及其参数化功能,结合厂家型材,采用参数化设计方法,建立了某种机柜的参数化模型。机柜参数化设计方法和传统设计方法在实际工作中的应用情况对比结果表明,机柜参数化设计方法可大幅缩短机柜设计的时间,提高设计效率。     

双频激电法在某地热勘查中的应用

主要介绍采用双频激电测深对江西某地区地热进行勘查.以视电阻率为主,对不同测深点所测得的数据进行处理、一维反演,结合地质资料,圈定低阻含水层,进一步作出规划,以便降低钻探的成本.     

自适应噪声谱估计抵消技术及其应用

为扩大虚拟暗室EMI(electromagnetic interference,电磁干扰)测试系统的应用范围,提高系统测量精度,改善其在复杂环境下的测试效果,借助自适应滤波及维纳滤波理论对基于传统自适应噪声抵消模型建立的测试系统进行分析,传统测试系统的参考通道存在的设备辐射分量制约了系统应用范围,从而不能实现任意信噪比环境下的高精度测量.同时,提出基于谱估计的自适应噪声抵消模型,该模型建立的虚拟暗室系统通过对测试系统主通道信号进行谱估计,得到设备辐射信号及噪声信号的功率谱密度,并根据该功率谱密度对参考通道信号进行针对性抑制,以滤除参考通道辐射信号分量,从而提高测试系统的适用性及精度.仿真实验表明:该方法在高、低信噪比环境下均能准确地提取设备辐射信号并准确复现受试设备的辐射信号,提高了虚拟暗室系统对环境噪声的抑制能力,增强了虚拟暗室系统的环境适应性.     

H桥级联STATCOM自适应死区补偿方法

为消除死区效应对H桥级联静止同步补偿器(STATCOM)输出电压及电流的影响,提出一种新的死区补偿方法.根据离散扰动观测器的工作原理,设计相应的观测器,对由于死区效应引起的STATCOM输出电压与参考电压的差值进行实时在线观测,并将观测到的差值作为补偿量,引入到无差拍控制系统中,实现对死区的自适应补偿.仿真与实验结果表明,该方法可以有效地提高死区补偿效果,消除零点电流箝位现象,降低STATCOM输出电流的谐波含量.