Active Contours and Mumford-Shah Segmentation Based on Level Sets

IntroductionThe basic idea in active contour models orsnakes is to evolve a curve,subject to constraintsfrom a given image,in order to detect objects inthat image.For instance,starting with a curvearound the object to be detected,the curve movestoward its interior normal and has to stop on theboundary of the object.LetΩ be a bounded open subset of R2 ,with Ω its boundary. Let u0 ∶Ω→ R be a given image,and C( s)∶ [0 ,1 ]→ R2 be a parameterized curve. Inthe classical snakes and active…     

BIFURCATIONS AND CHAOS CONTROL IN TCP-RED SYSTEM

Internet is heterogeneous in nature,and ex-tremely wide variations in parametric perturbationlead to a very rich world of dynamical behaviorsranging from s mooth,stable operation to rathercomplicated irregular patterns.In[1],the occur-rence of chaotic behavior in TCP has been reportedfor the first ti me.Since the seminal work of Mathisand Floyd[2-3],there have been increasing interestsin the dynamical characteristics of Internet.In theprevious work,TCP congestion control algorithmplus RED…     

等参局部平均随机场的随机有限元分析

本文提出了一种正交化等参局部平均的随机场模型,并给出了分析该随机场模型的随机有限元列式。算例表明,本文的方法具有较高的计算精度,且输入数据较少。     

��������������������������� �滮ģ�ͼ��ⷨ�о�

合理规划区域性物流配送中心，对于提高物流配送服务水平，降低物流配送成本具有重要意义.实际物流配送系统中，需求点的物流配送需求是随机变量.因此，传统的把配送需求假定为已知常数的规划模型，不能反映需求量的随机性对区域性物流配送中心规划的影响.本文研究当物流需求量为随机变量时，区域性配送中心的随机规划模型和解法.由于引入了随机变量，所建立的规划模型更加符合实际;在模型求解过程中,则利用了确定性等价及过滤条件把模型简化成了多个简单的线性规划子问题,简化了模型求解，从而使之更易于在区域性物流配送中心的规划中得到运用.     

基于层叠条件随机场的网络入侵识别

为了能够在网络环境中从大量底层入侵警报信息中正确有效地识别其背后隐藏的攻击意图和规划,提出了基于层叠条件随机场模型的网络入侵识别方法.该方法首先在低层条件随机场中解决对简单的入侵识别,并将结果传递到高层的条件随机场模型以进行对复杂的入侵识别,实现了自适应、智能化的入侵检测系统.实验结果表明,该方法有较低的误报率,综合看来比传统方法优越.     

公轨两用拱桥吊杆的疲劳分析

提出了一种公轨两用拱桥吊杆的疲劳分析方法。依据交通流量调查和相关规范中汽车及轻轨车荷载谱的规定,基于Monte-carlo原理,模拟产生了通过桥梁的双向多车道汽车车流及双向轻轨车车流。针对典型吊杆的影响线开展模拟车流加载,得到杆件应力历程,通过泄水法得到杆件应力谱,按照Palmgren-Miner线性累积损伤理论,计算得到各吊杆的等效应力幅并进行设计基准期内的损伤度评估。以某公轨两用拱桥进行实例分析,同时考虑6线行车道公路荷载和双线轻轨荷载,对吊杆开展了疲劳分析。计算结果表明:采用模拟车流法可方便开展公轨两用特大桥构件的疲劳分析和疲劳剩余寿命评估。     

Estimating the ride quality characteristics of vehicles with random decrement analysis of on-the-road vibration response data

This paper describes the application of a practical analytical technique based on the random decrement method to estimate the rigid sprung mass dynamic characteristics (frequency response function) of road vehicles using only vibration response data during constant-speed operation. A brief history and development of the random decrement technique is presented, along with a summary of work undertaken on optimal parameter selection to establish the random decrement signature. Two approaches to estimate the dynamic characteristics from the random decrement signature are described and evaluated. A custom, single-wheeled vehicle (physical quarter car) was commissioned to undertake a series of on-the-road experiments at various nominally constant operating speeds. The vehicle, also instrumented as an inertial profilometer, simultaneously measured the longitudinal pavement profile to establish the vehicle's actual dynamic characteristics during operation. The main outcome of the paper is that the random decrement technique can be used to provide accurate estimates of the sprung mass mode of the vehicle's dynamic characteristics for both linear and nonlinear suspension systems of an idealised vehicle.     

High-frequency random vibration analysis of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads using a hybrid SEM–SM method

A hybrid Spectral Element Method (SEM)–Symplectic Method(SM) method for high-efficiency computation of the high-frequency random vibrations of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads is presented. First, the Williams-Landel-Ferry (WLF) formula and Fractional Derivative Zener (FDZ) model were, respectively, applied for prediction and representation of the frequency-dependent dynamic properties of Vossloh 300 rail pads frequently used in China's high-speed railway. Then, the proposed hybrid SEM–SM method was used to investigate the influence of the frequency-dependent dynamic performance of Vossloh 300 rail pads on the high-frequency random vibrations of high-speed vehicle–track systems at various train speeds or different levels of rail surface roughness. The experimental results indicate that the storage stiffness and loss factors of Vossloh 300 rail pad increase with the decrease in dynamic loads or the increase in preloads within 0.1–10,000?Hz at 20°C, and basically linearly increase with frequency in a logarithmic coordinate system. The results computed by the hybrid SEM–SM method demonstrate that the frequency-dependent viscous damping of Vossloh 300 rail pads, compared with its constant viscous damping and frequency-dependent stiffness, has a much more conspicuous influence on the medium-frequency (i.e. 20–63?Hz) random vibrations of car bodies and rail fasteners, and on the mid- (i.e. 20–63?Hz) and high-frequency (i.e. 630–1250?Hz) random vibrations of bogies, wheels and rails, especially with the increase in train speeds or the deterioration of rail surface roughness. The two sensitive frequency bands can also be validated by frequency response function (FRF) analysis of the proposed infinite rail–fastener model. The mid and high frequencies influenced by the frequency-dependent viscous damping of rail pads are exactly the dominant frequencies of ground vibration acceleration and wheel rolling noise caused by high-speed railways, respectively. Even though the existing time-domain (or frequency-domain) finite track models associated with the time-domain (or frequency-domain) fractional derivative viscoelastic (FDV) models of rail pads can also be used to reach the same conclusions, the hybrid SEM–SM method in which only one element is required to compute the high-order vibration modes of infinite rail is more appropriate for high-efficiency analysis of the high-frequency random vibrations of high-speed vehicle–track systems.     

码头岸坡土体相关距离的求解

码头岸坡多为天然土层沉积而成,土体参数具有空间变异性,应用随机场理论可以实现土性参数的点变异性到空间变异性的转化。土性参数随机场是一个平稳随机场,相关距离是描述土性参数随机场的一个重要指标。基于随机场理论,利用静力触探曲线数据按相关函数法拟合求解了码头岸坡土体的相关距离,为今后开展码头岸坡的可靠度研究打下基础。