光纤通信中自相位调制与四波混频影响因素仿真

为了解决在高速率传输过程中,光纤介质的非线性效应及其在波分复用(WDM)系统中光信号造成的严重衰减问题,围绕自相位调制和四波混频两种非线性效应进行分析,采用Opti System模拟软件分析了造成SPM和FWM效应的主要变量因素.结果表明,输入功率、信道间隔以及色散是造成自相位调制和四波混频性能变化的主要原因,通过调整这些参数可以提高光纤传输性能,为进一步优化奠定了基础.     

基于BCJR的GMSK混合信号分离算法研究

针对GMSK混合信号单通道盲分离问题,提出将BCJR算法用于GMSK混合信号分离。根据GMSK信号连续相位的特点,通过建立混合信号模型的有限状态马尔科夫性,推导了利用BCJR算法实现GMSK混合信号分离过程。在不增加算法复杂度的情况下,选择每个时刻后验概率的多个极大值对分离算法进行了改进。仿真实验表明,在调制参数比较相近的条件下,即使相对幅度、相对相位、相对时延估计不够准确,改进算法仍能取得较好的分离效果。     

TRD工法水泥土墙现场取芯的三轴渗透试验

为提高TRD工法在国内的应用水平,通过对天津市某基坑项目TRD水泥土墙进行现场取芯,在实验室内进行三轴渗透试验,得出水泥土墙在不同水泥掺入比条件下的芯样渗透系数曲线、不同养护龄期条件下芯样的渗透特性关系和不同土层条件下的芯样渗透系数对比,并分析产生上述曲线关系的原因,得出满足基坑止水要求的水泥经济掺入比和合理的养护龄期,给出了不同龄期下TRD水泥土墙渗透系数与水泥掺入比的经验公式.结果表明,TRD工法优于传统的SM W工法.     

细胞自动机：简单的规则，复杂的行为

细胞自动机是一种时间、空间与状态都离散的数学模型。回顾了初等细胞自动机模型的应用及其符号动力学刻画的相关文献,在大量统计性质和计算机模拟基础上,着重分析具有鲁棒Bernoulli移位特征的细胞自动机规则的一些符号动力学性质,揭示了细胞自动机的简单规则中蕴含着复杂、混沌的非线性动力学特性。这些结果丰富了细胞自动机的理论基础,也将促进符号动力系统的理论和应用的研究。     

潜水搅拌器安装角度对搅拌效果的影响

研究潜水搅拌器水平安装角度对搅拌池内流场的影响,建立不同的水平安装角度,通过Fluent对潜水搅拌机的搅拌槽内流场进行三维数值模拟,得出不同方案的速度分布情况.利用UDF模块,分别计算流场中流速达到搅拌效果的有效搅拌流体体积及其占整个流场体积的百分比,通过比较,选出最优的潜水搅拌器安装方案,提出了评价潜水搅拌器效能及其安装布置优劣的新方法——有效搅拌域法,利用此方法,使潜水搅拌器的搅拌效果分析更加准确.     

基于动态竞争的实时多媒体会议混音算法

为了解决大规模会议中的混音噪声问题,提出语音短时累积能量的概念,并据此设计基于动态竞争模式的实时多媒体会议混音算法。该算法依据会议所有成员的语音短时累积能量,通过动态竞争、自我淘汰、强制淘汰三个过程,实时从会议所有成员中选择当前的发言者,并进行混音。仿真结果显示,该算法可解决大规模会议中混音质量与会议人数成反比的问题。     

深层搅拌水泥桩加固软土地基的试桩工艺研究

工艺试桩是桩基施工的一项重要工作,文章结合具体工程实例,通过选取几组有代表性的基桩的施工和检测资料,分析并拟定出试桩的施工工艺参数,总结出施工经验.     

Turbulence damping above the cloud height in suspensions of concentrated slurries in stirred tanks

Poor mixing in the clear liquid layer above the cloud height has been reported by several authors. This study uses LDV measurements to quantify turbulence above the cloud using a liquid level of 1.5 T to remove the barrier of a free surface at H = T. A D = T/3, down-pumping PBT was used at an off-bottom clearance of C = T/3. Three slurries were tested at impeller speeds 0.8, 1, and 1.2N_js. The change in turbulence was quantified using the normalized root mean square (RMS) of the fluctuating velocity summed and averaged over each radial traverse. A significant difference between the fluctuating values of the cloud height—minimum, average, and maximum—was observed. The turbulence decays until the maximum cloud height. Beyond that, it remains constant and near zero. The effects of both particle size and solids concentration prove to be important.     

Mechanisms and conditions that affect phase inversion processes: A review

The phenomenon of phase inversion occurs in liquid‐liquid dispersions found in a variety of chemical engineering fields. From simple oil‐water mixtures to complex polymeric systems, the operating variables that affect this physical phenomenon are discussed in this work. The contribution on this matter by a large number of researchers is critically assessed, outlining both coherent and conflicting results. A detailed review of the mechanisms by which phase inversion takes place is also provided. While this subject has been studied for the past 50 years, this multivariate nonlinear process is not yet comprehensively understood, and this review article aims to describe the conclusions so far reached to provide insight for future research.     

Herleitung und Validierung eines einfachen Modells zur Beschreibung des Misch- und Entmischungsprozesses beim Feststoffmischen

Discontinuous solids mixing processes are largely carried out over the mixing time. The required mixing time is often determined separately in mixing tests. It remains to be seen whether this corresponds to the optimum. There is a lack of models to describe the mixing quality curve over time. The present article adds a simple, two-parameter model that considers not only the homogenization but also the segregation process. In this way, possible mixing quality optima can be approximated with the help of fewer mixing tests that have been carried out.