基于改进的参数活动轮廓模型的图像分割方法

参数活动轮廓模型（SNAKE模型）被广泛应用于医学图像分割中。传统的SNAKE模型对初始轮廓非常敏感,必须给定在图像边缘附近,否则容易陷入局部极小而无法收敛到真实轮廓处。提出一种基于距离变换的距离势能模型作为自适应外力,能很好地引导SNAKE逼近真实边界而不依赖于特定的初始轮廓的位置。实验结果表明：该算法快速有效,能在更大的范围内捕捉图像特征,是一种有效的图像分割的算法。     

Chaos and chaotic control in a relative rotation nonlinear dynamical system under parametric excitation

This paper studies the chaotic behaviours of a relative rotation nonlinear dynamical system under parametric excitation and its control. The dynamical equation of relative rotation nonlinear dynamical system under parametric excitation is deduced by using the dissipation Lagrange equation. The criterion of existence of chaos under parametric excitation is given by using the Melnikov theory. The chaotic behaviours are detected by numerical simulations including bifurcation diagrams, Poincaré map and maximal Lyapunov exponent. Furthermore, it implements chaotic control using non-feedback method. It obtains the parameter condition of chaotic control by the Melnikov theory. Numerical simulation results show the consistence with the theoretical analysis. The chaotic motions can be controlled to period-motions by adding an excitation term.     

基于光纤光参量放大的异步双波长全光再生技术研究

本文提出了一种新型的多波长全光再生方案,利用相位时钟光纤光参量放大,并采用相邻信道偏振正交的方法,实现对由异步信源产生的双波长信号全光再生.理论分析了参量放大中的增益饱和现象用于幅度噪声抑制,以及利用相位时钟及后续色散实现对信号定时的机理.在这个基础上,对两个独立信源产生的异步双波长10 Gbit/s信号进行再生实验,实验表明该方案有效的抑制了基于多波长3R再生系统中信道间的四波混频与交叉相位调制等非线性干扰.系统在单波长和双波长情况下分别将两路信号信噪比改善了至少6.5 dB与4.5 dB.误码率测试结     

参数化设计方法在地矿图件计算机辅助编绘中的应用

应用参数化设计方法对ＣＡＤ基础软件进行二次开发,可使地矿点源信息系统更能适应复杂地矿图件的编绘工作;以线型制作和图案填充为便说明,经设计的具体实现途径是用参数化表达图元内部特征和建立图元间关联关系的数据库;应用参数化设计方法进行图件编绘程序开发,关键在于建立正确的灵堂模型和灵活地应用数据库技术。     

基于湿度应力场理论的膨胀岩弹塑性本构关系

由于含水率的变化使膨胀岩的弹性模量、泊松比和屈服极限等力学性能都将发生变化,从而引起膨胀应力、塑性流动和随湿度场而变化的屈服准则等都相互耦合在一起,因此,提出了基于湿度应力场理论的膨胀岩的弹塑性本构模型,并运用参变量变分原理建立了处理这一类问题的数值变分原理及其相应的有限元形式。     

Instability Assessment of Deep-Sea Risers Under Parametric Excitation

This study deals with the nonlinear dynamic response of deep-sea risers subjected to parametric excitation at the top of a platform.As offshore oil and gas exploration is pushed into deep waters,difficulties encountered in deep-sea riser design may be attributed to the existence of parametric instability regarding platform heave motions.Parametric resonance in risers can cause serious damage which might bring disastrous accidents such as environment pollution,property losses and even fatalities.Therefore,th...     

5cm微带“参放”定量检测

简要地说明了７１３雷达微带“参放”的原理，提出一种“参放”调试方法，使机务人员对分布参数电路的原理分析调度及注意事项有进一步的了解。     

Evaluation of liquefaction potential of marine sandy soil with piles considering nonlinear seismic soil–pile interaction; A simple predictive model

Abstract

An elastoplastic, dynamic, finite-difference method was applied to study the effects of nonlinear seismic soil–pile interaction on the liquefaction potential of marine sand with piles. The developed model was well validated using the centrifuge test. The results showed that acceleration, bending moment, and excess pore water pressure complied well with centrifuge test results. The effect of different affecting parameters on liquefaction potential was investigated using parametric study. Using a sensitivity analysis, the pile embedment parameter was shown to be the most influential parameter. Finally, applying the evolutionary polynomial regression technique, a new model for predicting the liquefaction potential was presented.     

Geological control of shallow gas and pockmarks in the Norwegian Channel; high resolution shallow subbottom profiling of small scale features

High resolution bathymetric and fine-scale parametric subbottom profiling along a line to the SW of Stavanger, Norway near the NE flank of the Norwegian Channel, show pockmarks clustered over neotectonic shallow fold structures in Quaternary sediments. Detailed profiles of the pockmarks indicate that they are collapsed gas seeps, rather than being collapse structures that followed doming and breaching with a more dramatic gas burst. The gentle folding and weak structures along the margin of a Mesozoic through Cenozoic sedimentary basin are probably due to differential uplift generating light compressional strain.