HL—1装置边缘扰动谱的初步分析

一、引言目前许多实验都已证实托卡马克边缘扰动对等离子体的反常输运有重要的影响,由于扰动而产生的反常粒子输运流大约在玻(王母)扩散量级,而且,边缘扰动的大小、湍流频谱和波数谱的宽度对约束时间的影响很大。用探针对边缘等离子体进行湍流扰动分析已在许多托卡马克实验中进行过,用静电探针得到的电子密度扰动n和悬浮电位扰动,可以估计出扰动产生的粒子输运通量。本文主要给出了一套静电探针系统及其数据获取和频谱分析方法,     

JMCT反应性微扰计算功能的实现

蒙特卡罗中子输运程序用于反应堆设计与安全分析计算及校验时,微小的反应性扰动容易被统计涨落所掩盖,因此一般通过微扰计算处理此类问题。基于微分算子方法在JMCT程序中实现了反应性微扰计算功能。为保证计算的精度,JMCT考虑了非源扰动的高阶效应以及一阶裂变源扰动效应。选取了具有全局扰动、局部扰动的快中子与热中子裂变系统对JMCT反应性微扰计算功能进行了测试。测试系统覆盖了正负反应性变化。     

薄板声谐振子扰动的声学特征检测研究

为进行快速ＮＤＴ，研究了薄板声谐振子扰动和声学特征变化的关系，用有限元方法分析在睡无缺陷薄板的振动频率和振型。利用数字信号处理技术，实验研究了样品中缺陷对声学特征的影响。实现和理论分析结果一致性很好。研究结果有助于正确利用样品声学特征进行无损检测。     

自适应光学系统控制效果分析的功率谱方法

 用H-S 波前探测器得到校正前后波前相位时间功率谱, 分析了自适应光学控制系统对大气湍流扰动波前的时域校正效果。用这种方法比较了61单元自适应光学系统分别采用P-I 控制算法和Smith 纯滞后补偿控制算法对实际大气湍流扰动波前进行补偿实验时的校正效果。     

弱的参数周期扰动对一非线性系统安全域的影响与分形侵蚀安全域的控制

讨论了弱参数周期扰动对于非线性系统安全域的影响,在一定频率下的参数周期扰动将加速安全域的分形侵蚀,而在另一些频率的扰动下,将抑制安全域的分形侵蚀,并且存在着增进安全域的最优频率.提出了用弱参数周期扰动控制受到分形侵蚀的安全域的方法,并用Melnikov方法进行了分析.最后讨论了这种控制安全域的方法在实际环境中当具有外加噪声时的鲁棒性. 关键词： 分形吸引域边界 参数的周期扰动 控制     

嵌套双自适应光学系统的控制特性分析

望远镜等光学系统常常受到大气湍流以及内部像差扰动的影响,常规自适应光学系统被证明是消除外部大气湍流引起的像差的有效手段,然而当存在大幅度的内部像差扰动时,问题变得复杂。提出了一种嵌套双自适应光学系统结构,用内部独立嵌套自适应光学系统校正内部像差扰动,用常规自适应光学系统主要校正外部大气湍流扰动。进一步分析对比了它与常规自适应光学系统的校正能力,数值仿真了当同时存在上述两种像差时二者的校正效果。结果表明,合理设计嵌套双自适应光学系统的工作条件可使得在大多数情形下其校正效果优于常规单自适应光学系统,尤其在内部像差扰动相对较大时更加显著。     

相关分析法确定HL-1M装置磁流体的扰动模式

采用相关分析法模拟分析了HL-1M装置的磁扰动模式,模拟的结果同预期的结果一致。在具有磁流体不稳定性的典型放电中,探测到独立模m=2、3、4,耦合模m=2、3,以及同时出现的耦合模m=4、5和独立模m=5,给出了用扰动幅度的极向截面图分析磁扰动模式的结果,讨论了相关分析法在实验分析中的优点和局限性。     

空间傅里叶分析法识别MHD扰动模式

讨论了用空间傅里叶分析法确定托卡马克等离子体MHD磁扰动模式的方法。根据托卡马克实验的状况,对不同情况下的MHD磁扰动进行了详细的数值模拟,重点分析了该方法的系统误差,模拟结果与HL-1M装置上的实验结果进行了对比。比较结果表明,用空间傅里叶分析法识别托卡马克中的MHD扰动模式是一种可以行之有效的方法。     

电子束丝化扰动的孤立波解

本文用约化扰动方法讨论了与电子束丝化扰动相关的孤立波,导出了束电子密度扰动所满足的K-dV方程。 关键词：     

环境扰动约束下的稀疏贝叶斯定位方法

针对匹配场被动定位技术对海洋环境扰动敏感的问题,提出了一种基于稀疏贝叶斯学习的稳健匹配场处理方法。该方法通过分析环境扰动情况下的声场构成,建立了海洋环境扰动模型,同时结合水下定位问题的稀疏性,将匹配场被动定位问题表述为稀疏信号重构问题。然后,使用稀疏贝叶斯学习方法迭代更新目标位置及模型失配权向量,收敛至最优稀疏解作为目标定位结果。最后使用仿真数据和北厄尔巴岛的海试数据对算法进行了验证,仿真和实验结果表明:该算法在海洋环境模型失配情况下也能够准确定位,且能分辨水平间距为100 m的两个目标。因此,基于稀疏贝叶斯学习的稳健匹配场处理方法能够有效利用海洋环境扰动声场结构和水下定位稀疏特性,以增强匹配场处理的稳健性和定位精度,并且具有应对多源定位问题的能力。      

测量半导体材料电阻率的四探针公式的普遍形式

测量电阻率的四探针法公式中,要求是点接触而且探针的排列有一定的形状。实际上,接触总有一定的大小。本文考虑到接触面积大小的影响,并让四根探针排列成任意形状,导出了测量电阻率和薄层电阻的关系式。而直线四探针、方形四探针只不过是本公式的两个特例。 关键词：     

Measurement of charge transfer in electrostatic discharges

Experimental studies are reported that show the errors that arise in using unshielded probes for measuring charge transfer in electrostatic discharges. Comparable errors will apply where unshielded probes are used for current flow measurements. Errors are avoided by using shielded probes with an appropriate charge measurement circuit. These results are relevant to the design of probes to be included in IEC Standards.     

Enhanced Enantioselective Recognition with Diastereoisomeric BINOL Based Chiral Fluorescent Boronic Acid Sensors

We prepared the diastereoisomers of BINOL based bisboronic acid chiral probes (the probes are with dual chirogenic centers) for enantioselective recognition of chiral analytes, such as tartaric acids, D-sorbitol, etc. We found the diastereoisomeric probes give different emission intensity-pH profiles, a phenomenon was reported, probably, for the first time. We found that with the second chirogenic center, the selectivity of the probes toward chiral analytes can be improved. For example, the diastereoisomeric probes give drastically different response to D-sorbitol, the same selectivity was not found for the BINOL bisboronic acid probes with single chirogenic center. Our result with the diastereoisomeric probes is helpful for design of new chiral molecular probes to enhance the selectivity of the boronic acid sensors toward chiral analytes.     

Comparison of FÖrster-Resonance-Energy-Transfer Acceptors for Tryptophan and Tyrosine Residues in Native Proteins as Donors

Homogenous bioaffinity analysis with tryptophan/tyrosine residues in native proteins as FÖrster-resonance-energy-transfer (FRET) donors is feasible when suitable fluorophors can act as FRET acceptors in ligands (FRET probes) and FRET efficiency in complexes of proteins and FRET probes is high enough. In complexes of proteins and FRET probes, suitable acceptors should have excitation peaks around 335 nm and high rotation freedom, are preferred to have sufficient quantum yields and excitation valleys around 280 nm. In protein binding sites mimicked with mixtures of neutral phosphate buffer and organic solvents, quantum yields of candidate acceptors are altered inconsistently but their excitation peaks show tiny changes. Fluorophores as acceptors in such FRET probes are buried inside glutathione-S-transferase and have low rotation freedom, but are localized on streptavidin surface and display high rotation freedom; FRET efficiency in complexes of streptavidin and its FRET probes is much stronger than that in complexes of glutathione-S-transferase and its FRET probes. Specially, the quantum yield is about 0.70 for free 1-naphthylamine probe in neutral phosphate buffer, about 0.50 for 1-naphthylamine probe bound by streptavidin, and about 0.15 for that bound by glutathione-S-transferase. The quantum yield is about 0.06 for free dansylamide probe, about 0.11 for dansylamide probe bound by streptavidin and about 0.27 for that bound by glutathione-S-transferase. Therefore, 1-naphthylamine and dansylamide are effective acceptors when they localize on surfaces of complexes of proteins and FRET probes.     

Fiber optic probes for linear and nonlinear Raman applications – Current trends and future development

This review focuses on fiber optic probes for linear and nonlinear Raman spectroscopy, especially for medical applications. It aims at providing an overview over contemporary technology, recent first clinical trials, and helps identifying future developments necessary to bring the emerging technology to clinical end users. After a short introduction to linear and nonlinear Raman spectroscopic modalities, general design considerations will be discussed and compared to common fiber probe setups. Subsequently, examples for medical applications of fiber optic Raman probes will be given concentrating on probes for linear Raman spectroscopy as these devices are technologically more mature compared to their counterparts based on nonlinear Raman spectroscopy. The review also includes a brief summary of first multimodal fiber optic probes and highlights their benefits for clinical applications. Finally, probes are introduced which employ either nonlinear Raman spectroscopy or surface enhanced spectroscopy.     

pH-Sensitive Cyanine Dyes for Biological Applications

A series of functionalized, water-soluble, pH-sensitive pentamethine cyanine (Cy^TM5) dyes has been designed and synthesized. These probes are fluorescent in acidic media but are non-fluorescent in an alkaline environment. Subtle changes to the structure of these probes can lead to pronounced changes in the pKa of these probes. These probes have been utilized in a cellular environment to detect localized changes in pH using the IN Cell Analyzer, a confocal imager formatted for imaging of cell-based assays.     

Application of the van der Pauw method to conductivity measurements on mixed ionic-electronic solid conductors

The analysis of four point dc conductivity measurements by the van der Pauw method is generalized to mixed ionic-electronic solid conductors (MSC) with gas electrodes, e.g. doped and reduced CeO₂ in a controlled oxygen atmosphere. If such measurements are done with non-blocking voltage probes, the electronic and ionic currents at the probes do not vanish. The measurement then yields the total conductivity even if the current carrying electrodes are blocking for ions or electrons. By imposing a difference in the gas pressure at the two reversible voltage probes the ionic conductivity can be determined. The currents through the probes are calculated. If the probes are not reversible, then there exist voltage drops on the probes and the four point measurement cannot be used in the above manner to yield the conductivity. To overcome the difficulty that arises with non-reversible probes a four-point measurement with three blocking electrodes (two of which are the voltage probes) is suggested and analyzed. When the electrodes block ions then the electronic conductivity σ_e is measured and when they block electrons, the ionic conductivity σ_X⁺ is determined.     

Development of fluorescent probes for bioimaging applications

Fluorescent probes, which allow visualization of cations such as Ca(2+), Zn(2+) etc., small biomolecules such as nitric oxide (NO) or enzyme activities in living cells by means of fluorescence microscopy, have become indispensable tools for clarifying functions in biological systems. This review deals with the general principles for the design of bioimaging fluorescent probes by modulating the fluorescence properties of fluorophores, employing mechanisms such as acceptor-excited Photoinduced electron Transfer (a-PeT), donor-excited Photoinduced electron Transfer (d-PeT), and spirocyclization, which have been established by our group. The a-PeT and d-PeT mechanisms are widely applicable for the design of bioimaging probes based on many fluorophores and the spirocyclization process is also expected to be useful as a fluorescence off/on switching mechanism. Fluorescence modulation mechanisms are essential for the rational design of novel fluorescence probes for target molecules. Based on these mechanisms, we have developed more than fifty bioimaging probes, of which fourteen are commercially available. The review also describes some applications of the probes developed by our group to in vitro and in vivo systems.     

Responsive mechanism of three novel hypochlorous acid fluorescent probes and solvent effect on their sensing performance

Optical properties and responsive mechanisms of three newly synthesized fluorescent probes for hypochlorous acid(HOCl) are investigated by employing time-dependent density functional theory. The computational results show that the absorption and emission properties of these probes change obviously when they react with hypochlorous acid. It is found that the probe FHZ has the best performance according to the probing behavior. Moreover, the responsive mechanisms of the probes are studied by analyzing the distributions of molecular orbitals and charge transfer, which are shown as the photoninduced electron transfer(PET) for FHZ and the intramolecular charge transfer(ICT) for the other two probes. Specially,solvent effect on optical properties of the probe FHZ before and after reaction is studied within the polarizable continuum model(PCM). It is shown that performance of the probe depends crucially on the solvent polarity. Our computational results agree well with the experimental measurement, and provide information for design of efficient two-photon fluorescent probes.     

Positively Biased Probes in Magnetized Plasmas

Positively biased probes in magnetized plasmas can create several phenomena which are not described by standard probe theories. These include transient currents for pulsed electrodes in the regime of Electron MHD, relaxation oscillations induced by large probes and high frequency instabilities at the sheath‐plasma frequency. Although they may limit the use of probes for diagnostic purposes they also offer new applications and belong to the general knowledge of probes in plasmas (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)