关于PSD迭代法收敛的充分必要性定理

本文在线性方程组系数矩阵A为相容次序矩阵及A的Jacobi迭代矩阵的特征值μ_j均为实数且μ_j~2<1的条件下,得出了PSD迭代法收敛的充分必要性定理,并由此而得到了一个易于判别的PSD法收敛性定理。     

考虑参数不确定性的非线性梁随机振动分析

非线性系统的随机振动分析一直是结构动力学领域中的难点,已有一些研究表明基于矩等效的线性化方法在功率谱预测上会得到不恰当的分析结果;另一方面,由于不确定性在实际工程中普遍存在,如果同时考虑非线性和不确定性,更是显著增加了问题难度。本文以具有非线性非理想边界梁为研究对象,基于梁模型的动力学微分方程推导了对应的广义频响函数,并应用Volterra级数理论建立了非线性系统随机振动的谱分析方法,最后,结合蒙特卡洛抽样方法计算了具有参数不确定性非线性梁响应功率谱的均值和方差,讨论了不确定性对结构随机振动响应统计特征的影响。     

MALDI-TOF Mass Spectrometry Study of the Phosphorylated Tau Peptides

Fragmentation of phosphorylated Tau peptides in matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) has been investigated.According to the post-source decay (PSD) in MALDI-TOF-MS, there are two different patterns of cleavage in phosphopeptides, which can be used to determine the phosphorylated site in peptides.In the synthetic tau peptides, the fragmentation at proline residue occurs strongly and this is useful to determine the structure of tau peptides.     

Glass capillary gas chromatography of highly polar solutes like diols,acids and amines deactivation of fused silica and pretreated alkali glass support surfaces

Summary The method of support surface deactivation by PSD (alkylpolysiloxane degradation) at temperature between 300 and 450°C previously described was used to deactivate both fused silica and alkali glass surfaces of capillary columns. The latter surfaces had to be pretreated before deactivation with aqueous HCl leaching or by the dealkalisation method using flowing HCl gas at 450°C and subsequent rinsing with water for alkali removal. Excellent alkylpolysiloxane columns with regard to tailing and irreversible adsorption of highly polar solutes have been obtained on both fused silica and the pretreated alkali glass. Fused silica does not require pretreatment before deactivation by the PSD-method, however. Good polyethyleneglycol (Carbowax 20 M) columns can also be obtained by coating the two types of surfaces when no deactivation is necessary. Deactivation by the PSD method cannot be applied in this case because polar stationary liquids do not adhere to alkylpolysiloxane deactivated surfaces. Sample capacity problems arising when separating highly polar solutes with non-polar stationary phases have also been investigated.     

Study of the filter method for neutron pulse-height distributions measured with organic scintillators

Identification of neutron sources is of interest in several fields, such as homeland security or basic nuclear physics. Organic scintillators offer the possibility to unfold fast-neutron energy spectra. Since organic scintillators are sensitive to neutrons and gamma-rays, a method to discriminate these two types of particles is required. This paper is focused on investigation of the discrimination properties of the filter method by using a new procedure. We compare the results of an experimental filter method to a digital pulse-shape discrimination (PSD) method based on charge integration. In addition, these methods are compared to the simulation results obtained with the MCNPX-PoliMi code. The experimental and numerical investigations were performed with a ²⁵²Cf spontaneous-fission neutron source. The integration of the number of counts gave the relative differences between the experimental filter and digital PSD neutron pulse-height distributions (PHDs) and simulated PHDs less than approximately 5% in the range between 60 keVee and 1.715 MeVee of light output. Above 1.715 MeVee, the PSD method has advantages over the filter method, due to the filter method having significantly worse counting statistics. The results show that the filter method has potential for robust neutron measurements when the PSD method cannot be applied, such as for ‘old’ organic plastic scintillators without PSD capability.     

利用功率谱密度评价离子束抛光光学元件表面粗糙度

利用功率谱密度(PSD)评价光学表面粗糙度具有传统评价手段(Ra)所不具备的优势。给出了功率谱密度的计算方法,以及抽样方向与一维PSD曲线的关系。在离子束抛光K9玻璃实验中引入PSD曲线,以评价抛光光学零件的光学表面粗糙度,结合PSD曲线与Ra值能够更全面的指导光学加工。     

Adsorption behavior of partially collapsed polyacrylate coils on mica surfaces: A reciprocal space approach

In this article, we investigate tapping mode atomic force microscopy images of intermediate states along the coil to globule transition of sodium polyacrylate coils containing Ca²⁺ as specifically binding ions. The structural correlations within single adsorbed molecules are established using power spectral density (PSD) curves. The PSD curves of several single molecules are averaged to give the so called 2D form factor so as to obtain information of higher statistical merit. A proper interpretation of the 2D form factor and comparison with form factor analysis of the very same sample solution available through small angle neutron scattering provides an alternative quantification of changes in conformation which a single polyacrylate molecule undergoes as it moves from 3D solution to 2D surface and is inevitably distorted in shape because of sample history. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1553–1561, 2010     

直升机旋翼桨叶气动力学参数飞行测试系统

根据某型号直升机定型试飞的需要,研制出了动态测量旋翼桨叶气动力学参数的光电测试系统。其中运动参数(挥舞角、摆振角和变距角)由二维位置敏感传感器响应桨叶表贴发光点的位置变化测得,挥舞应变由光纤光栅传感器测得。利用自主搭建的桨叶运动姿态仿真平台开展了相关测试实验。结果表明:各角度值与对应输出电压间有很好的线性关系,测量范围内的角度测量误差小于1%;光纤光栅与电阻应变片对比测试的一致性较好,线性相关系数达到了0.999;光纤光栅应变测量的复现性很好,两次应变测量的相对偏差仅为1.22%。系统具有较高的测试精度。     

I-提升模的有限直和

I-提升模的直和不一定是I-提升模.本文给出了使I-提升模的直和仍是I-提升模成立的条件,即证明了当M=M1⊕M2,其中M1和M2是I-提升的.如果Mi是Mj-投射的（i,j=1,2）或M是duo模,则M是I-提升的.     

The tamed Milstein method for commutative stochastic differential equations with non-globally Lipschitz continuous coefficients

For stochastic differential equations (SDEs) with a superlinearly growing and globally one-sided Lipschitz continuous drift coefficient, the classical explicit Euler scheme fails to converge strongly to the exact solution. Recently, an explicit strongly convergent numerical scheme, called the tamed Euler method, has been proposed in [8] for such SDEs. Motivated by their work, we here introduce a tamed version of the Milstein scheme for SDEs with commutative noise. The proposed method is also explicit and easily implementable, but achieves higher strong convergence order than the tamed Euler method does. In recovering the strong convergence order one of the new method, new difficulties arise and kind of a bootstrap argument is developed to overcome them. Finally, an illustrative example confirms the computational efficiency of the tamed Milstein method compared to the tamed Euler method.