金属纳米颗粒-聚电解质多层膜的X射线反射率研究

用静电自组装技术制备了不同层数的Au纳米颗粒-聚电解质多层膜,用X射线反射及原子力显微镜对膜的微结构进行了表征.研究发现,当Au纳米颗粒下面的聚电解质层较薄时,膜中无清晰的界面结构;随着Au纳米颗粒下面的聚电解质层的增厚,金属-聚电解质多层膜的界面变得越来越清晰.     

极紫外多层膜残余应力初步研究

 针对极紫外多层膜在激光等离子体诊断、极紫外光刻等方面的应用,进行了Mo/Si多层膜残余应力的实验研究,讨论了多层膜残余应力的成因。实验结果表明：Mo单层膜表现为张应力, Si单层膜表现为压应力;通过传统方法制备的13.0 nm处高反射率的40对Mo/Si多层膜会产生-500 MPa左右的压应力,其压应力主要是由膜层之间的贯穿扩散引起的;通过改变膜层比率可以在一定程度上补偿因贯穿扩散产生的压应力,但是以牺牲多层膜反射率为代价。     

Learning finite binary sequences from half‐space data

The problem of inferring a finite binary sequence w *∈{−1, 1}ⁿ is considered. It is supposed that at epochs t=1, 2,…, the learner is provided with random half‐space data in the form of finite binary sequences u ^(t)∈{−1, 1}ⁿ which have positive inner‐product with w *. The goal of the learner is to determine the underlying sequence w * in an efficient, on‐line fashion from the data { u ^(t), t≥1}. In this context, it is shown that the randomized, on‐line directed drift algorithm produces a sequence of hypotheses {w^(t)∈{−1, 1}ⁿ, t≥1} which converges to w * in finite time with probability 1. It is shown that while the algorithm has a minimal space complexity of 2n bits of scratch memory, it has exponential time complexity with an expected mistake bound of order Ω(e^0.139n). Batch incarnations of the algorithm are introduced which allow for massive improvements in running time with a relatively small cost in space (batch size). In particular, using a batch of 𝒪(n log n) examples at each update epoch reduces the expected mistake bound of the (batch) algorithm to 𝒪(n) (in an asynchronous bit update mode) and 𝒪(1) (in a synchronous bit update mode). The problem considered here is related to binary integer programming and to learning in a mathematical model of a neuron. ©1999 John Wiley & Sons, Inc. Random Struct. Alg., 14, 345–381 (1999)     

The capacity of majority rule

Let 𝔹ⁿ={−1, 1}ⁿ denote the vertices of the n-dimensional cube. Let U(m) be a random m-element subset of 𝔹ⁿ and suppose w ∈𝔹ⁿ is a vertex closest to the centroid of U(m). Using a large deviation, multivariate local limit theorem due to Richter, we show that n/π log n is a threshold function for the property that the convex hull of U(m) is contained in the positive half-space determined by w . The decision problem considered here is an instance of binary integer programming, and the algorithm selecting w as the vertex closest to the centroid of U(m) has been previously dubbed majority rule in the context of learning binary weights for a perceptron. © 1998 John Wiley & Sons, Inc. Random Struct. Alg., 12, 83–109, 1998     

Mössbauer-effect studies of multilayers and interfaces

The usefulness of Mössbauer spectroscopy for the investigation of magnetic multilayer systems is described. By applying ⁵⁷Fe Mössbauer spectroscopy, the behavior of ultrathin magnetic layers, such as FCC-like Fe films on Cu(0 0 1), is studied. Position-specified (depth-selective) information is available by preparing samples in which monatomic ⁵⁷Fe probe layers are placed at specific vertical positions, e.g. at interfaces or at the surface. As demonstrated for epitaxial chemically ordered Fe₅₀Pt₅₀ alloy films and polycrystalline nanostructured Tb/Fe multilayers, the Fe-spin structure can be determined directly, and a site-selective Fe-specific magnetic hysteresis loop can be traced in very-high-coercivity materials. For the studies of non-magnetic layers, on the other hand, hyperfine field observations by ¹⁹⁷Au and ¹¹⁹Sn probes are worthwhile. Spin polarizations in Au layers penetrating from neighboring ferromagnetic 3D layers are estimated ¹⁹⁷Au from Mössbauer spectra and are also studied by inserted ¹¹⁹Sn probes in Au/3D multilayers. In the Sn spectra for Cr/Sn multilayers, it was found that remarkably large spin polarization is penetrating into Sn layers from a contacting Cr layer, which suggests that Cr atoms in the surface layer have a ferromagnetic alignment.     

叠层型串联ISE的电分析化学性能与Nernst倍增效应

设计了多元叠层型串联ISE,结构紧凑,组装简便,适用于微体积样液分析。对四元叠层型串联ISE的试验表明:与现行ISE比较,其线性响应斜率、测定精密度与灵敏度均增大4倍,但响应速度、选择性系数与检测下限不变。     

电化学方法制备铜钴纳米多层膜

采用旋转圆盘电极、双脉冲电位法从单一的含有铜离子和钴离子的镀液中电沉积Ｃｕ－Ｃｏ纳米多层膜、并用ＴＥＭ．ＡＥＳ和Ｘ－射线衍射研究镀层的形貌和组成。结果表明：多层膜结构为纯铜和含有少量铜的铜钴合金层交替组成,铜在钴层中的含量,随镀液中的铜含量的增大和转速的提高而提高。     

Manipulation of effective thermal conductivity of multilayer thin film by varying thickness ratio of layers using Monte Carlo simulation

Using the kinetic-type Monte Carlo method, we have simulated the effective thermal conductivity of multilayer thin film with spectral diffuse mismatch model for interface treatment. The results show a monotonously increasing relationship between the thermal conductivity and the material thickness closer to isothermal boundary with a varied size ratio whereas the fixed material amount in two four-layer thin films. This is explained by relatively more significant size effect of the layer closer to the isothermal boundary than that of the layer apart from the isothermal boundary. The finding in the present work guides a new way for optimization and design of interface structures at micro- and nano-scale.     

Detection of liner surface defects in solid rocket motors using multilayer perceptron neural networks

Debonding problems along the propellant/liner/insulation interface are a critical point to the integrity and one of the major causes of structural failures of solid rocket motors. Current solutions are typically restricted to methods for assessing the integrity of the rocket motors structure and visually inspecting their components. In this context, this paper presents an improved algorithm to detect liner surface defects that may compromise the bonding between the solid propellant and the insulation. The use of Local Binary Patterns (LBP) provides a structural and statistical approach to texture analysis of liner sample images. Along with color information extraction, these two methods allow the representation of image pixels by feature vectors that are further processed by a Multilayer Perceptron (MLP) neural network classifier. The MLP neural network analyzes liner sample images and classifies each pixel into one of three classes: non-defect, foreign object, and defect. Several tests were executed varying different parameters to find the optimal MLP configuration, and as a result, the best classification accuracy of 99.08%, 90.66%, and 99.48% was achieved for the corresponding classes. Moreover, the defect size estimate showed that the MLP classifier correctly identified defects less than 1 mm long, with a relatively small number of training examples. Positive results indicate that the algorithm can identify liner surface defects with a performance similar to human inspectors and has the potential to assist or even automate the liner inspection process of solid rocket motors.     

Development of soft X-ray multilayer laminar-type plane gratings and varied-line-spacing spherical grating for flat-field spectrograph in the 1–8 keV region

W/C and Co/SiO₂ multilayer laminar-type holographic plane gratings (groove density 1/σ = 1200 lines/mm) in the 1–8 keV region are developed. For the Co/SiO₂ grating the diffraction efficiencies of 0.41 and 0.47 at 4 and 6 keV, respectively, and for the W/C grating 0.38 at 8 keV are observed. Taking advantage of the outstanding high diffraction efficiencies into practical soft X-ray spectrographs a Mo/SiO₂ multilayer varied-line-spacing (VLS) laminar-type spherical grating (1/σ = 2400 lines/mm) is also developed for use with a flat field spectrograph in the region of 1.7 keV. For the Mo/SiO₂ multilayer grating the diffraction efficiencies of 0.05–0.20 at 0.9–1.8 keV are observed. The FWHMs of the measured line profiles of Hf-Mα₁(1644.6 eV), Si-Kα₁(1740.0 eV), and W-Mα₁ (1775.4 eV) are 13.7 eV, 8.0 eV, and 8.7 eV, respectively.