Application of advanced core process monitoring procedures in German power reactors

The nuclear reactor core design and the nuclear fuel management have been changed remarkable during the last few years. This development was initiated by increasing costs for the fuel recycling and nuclear waste storage. The fuel material, the fuel pellet fabrication, the fuel assembly structure and the core composition have been varied to get an effective fuel exploitation. Based on advanced core process conditions the reactor power and the fuel burn-up have been increased at German plants in recent years. Improved dynamic process monitoring procedures are required to get more information about the varied core process behaviour during the reactor operation. Since several years ISTec has been performed investigations to the process monitoring based on process signal measurements in German nuclear power plants. Using the standard instrumentation of the plants process signals have been measured and analysed by means of the digital data acquisition system SIGMA. The measured time signals are influenced by core process transients, global and local process fluctuations and by signal line transfer functions. Advanced time series analysis methods have been applied to separate different process effects in the multiple signal matrix. The separation of different process influences can improve significantly the information about the process condition in the reactor core.     

Stochastic stabilization of differential systems with general decay rate

Some sufficient conditions concerning stability of solutions of stochastic differential evolution equations with general decay rate are first proved. Then, these results are interpreted as suitable stabilization ones for deterministic and stochastic systems. Also, they permit us to construct appropriate linear stabilizers in some particular situations.     

移动床过滤除尘的直接数值模拟研究及实验对比

利用格子气和软球模型建立气固两相流数值模拟计算模型，模拟计算了在同一风速下碰撞次数与粉尘粒径之间的关系，初步研究移动过滤层颗粒对粉尘尺寸的过滤选择性。计算统计的结果与实验结果对比发现，二者存在定性上的一致。计算结果表示在移动床过滤中过滤效率对尘粒粒径具有明显的选择性，而且研究结果还表明格子气自动机模型可用于模拟流体在复杂边界条件下多孔介质细微通道内部的流动。     

二维小波变换理论在地震信号去噪中的应用

针对地震信号随机干扰和规则干扰的特点，运用二维小波变换的理论，设计了相应的变换域去噪滤波器。理论记录和实际野外记录试算表明，二维小波变换具有较强的信噪分离作用。只要运用得当就能取得满意的效果。     

信息安全系统中一种高速随机序列发生器的设计与实现

对原来的真随机序列发生器进行研究和分析，指出存在的主要问题是：序列的输出速度较慢，把小波分析理论用于真随机序列发生器，改变原来的输出方式，设计一种新的高速随机序列发生器，以满足快速发展的信息安全系统的要求．     

3D Monte Carlo Analysis of Discrete Dopant Effects on Electron noise in Si Devices

A preliminary study of velocity fluctuations in simple devices using an atomistic model for the ionized impurity scattering is presented. The velocity fluctuations are responsible for thermal noise in semiconductor devices. In this paper the influence on the spectral density of velocity fluctuations of the boundary conditions, the doping level, the length of the resistors and the excess/default of impurities has been addressed.     

TES microcalorimeter readout via transformer

Readout configuration for Transition Edge Sensor (TES) electrically coupled to a low noise warm front-end via transformer is studied. The study was aimed at the implementation of the readout involved in imaging with microcalorimeter detector arrays using frequency multiplexing technique (Appl. Phys. Lett. 81(1) (2002) 159). A model describing both TES electrothermal reaction and the readout response is investigated. Contribution of electronic noise to TES energy resolution is calculated. Prospective readout architecture with TES electrical biasing from the warm readout side is introduced. The architecture allows building of large imaging detector arrays with TES. It is shown that an unprecedented combination of imaging and spectrometry features can be achieved with TES readout via transformer.     

阀门流场的数值模拟及流噪声的实验研究

采用非结构、非交错网格的有限体积法求解用二方程模型封闭的雷诺平均N S方程组 ,对水管路系统中 3种常见阀门的三维分离流动进行数值模拟。模拟结果表明 ,随着蝶阀、闸阀和球阀开度的减小 ,流体在蝶阀背面、球阀阀门内外分别形成两个方向相反的漩涡 ,闸阀的漩涡出现在挡板与管道的壁角处 ,并且漩涡在阀门下游逐渐消失。同时实验表明 ,阀门下游的流噪声大于阀门上游的流噪声 ,涡声是阀门噪声的主要来源     

Atmospheric effects of friction,friction noise and wear with silicon and diamond. Part II. SEM tribometry of silicon in vacuum and hydrogen

Scanning electron microscope (SEM) tribometric data on polycrystalline silicon (poly-Si) vs. poly-Si, Si(100) vs. Si(100) and Si(111) vs. Si(111) interfaces, obtained in Torr and in 0.2 Torr partial pressure of hydrogen gas ( ) from room temperature to 850^°C, were performed under standard and much slower thermal ramping rates. The friction data were analyzed per the methodology described in part I of this paper series. The results indicate a highly beneficial friction- and wear-reducing regime within a relatively narrow thermal region. This desirable region coincides with some chemisorption of excited species of molecular hydrogen just before the mass thermal desorption of surface hydrides. These data represent the tribochemical equivalent of a method routinely used in electronics, whereby deep electron traps (dangling Si bonds) are passivated by baking in molecular hydrogen. The also exerts a moderating influence on the size of the friction noise at all test temperatures. However, the general level of friction beyond the beneficial thermal region is high. In parallel, the general wear rate of Si representative of the entire range of standard thermal ramping in both atmospheric environments is in the extremely high 10^-12m³/(N m) range. Operating strictly in the beneficial, low-friction thermal regime resulted in a several orders-of-magnitude reduction in the wear rate over those measured under standard thermal ramping conditions. Although the results confirm previous findings that Si is not a good material of construction for miniaturized moving mechanical assemblies (e.g., microbearings and gears), there seems to be some limited possibility of gas-phase lubrication of Si micromechanisms with rarefied hydrogen at surface temperatures between 100 and 300^°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

具有未知系统偏差的自适应Kalman平滑器

提出一种有效的具有未知系统伯差的自适应Ｋａｌｍａｎ平滑器．应用状态空间方法和ＡＲＭＡ新息模型，基于白噪声估值器和输出预报器，给出线性离散定常系统自适应最优状态和偏差联合Ｋａｌｍａｕ平滑器，最后给出仿真实例．