改进的固定点图像复原算法（英文）

研究了周期边界条件下,Tikhonov正则化的固定点算法,提出了变化正则化参数的方法。首先对正则化参数取较大值,抑制复原图像中的噪声,通过得出的收敛结果来修正初始梯度;然后对正则化参数取较小值,以增强复原图像中的细节。实验结果表明,与当前求解L1范数正则化函数和全变分正则化函数的流行算法比较,本文算法对于运动模糊与高斯模糊图像的复原效果更佳。     

A continuous stream flash evaporator for the calibration of an IR cavity ring-down spectrometer for the isotopic analysis of water

A new technique for high-resolution simultaneous isotopic analysis of δ¹⁸O and δD in liquid water is presented. A continuous stream flash evaporator has been designed that is able to vapourise a stream of liquid water in a continuous mode and deliver a stable and finely controlled water vapour sample to a commercially available infrared cavity ring-down spectrometer. Injection of sub-microlitre amounts of the liquid water is achieved by pumping liquid water sample through a fused silica capillary and instantaneously vapourising it with 100% efficiency in a home-made oven at a temperature of 170?°C. The system's simplicity, low power consumption and low dead volume together with the possibility for automated unattended operation provides a solution for the calibration of laser instruments performing isotopic analysis of water vapour. Our work is mainly driven by the possibility to perform high-resolution online water isotopic analysis on continuous-flow analysis (CFA) systems typically used to analyse the chemical composition of ice cores drilled in polar regions. In the following, we describe the system's precision and stability and sensitivity to varying levels of sample size and we assess the observed memory effects. A test run with standard waters of different isotopic compositions is presented, demonstrating the ability to calibrate the spectrometer's measurements on a VSMOW scale with a relatively simple and fast procedure.     

Density determination of slush nitrogen by the improved capacitance-type densimeter

Slush nitrogen is considered to be a better coolant than subcooled liquid nitrogen for the high-temperature superconducting cable cooling because of its greater density and cooling capacity. The capacitance-type densimeter is utilized to determine the density of slush nitrogen in this paper. In order to improve the densimeter performance, the bulk shielding method, based on the application of the double-shielded cables, is introduced, and the influence of the frequency of the applied voltage is investigated. The parasitic capacitance of the densimeter system is significantly reduced, and the fluctuation of the capacitance is depressed within ±2.0 × 10⁻⁴ pF at a frequency of 1.0 MHz, and the typical sensitivity of the differential type densimeter is 3.718 pF and the high accuracy of within ±0.25% for density measurement is obtained. In process of producing slush nitrogen by the freeze-thaw method, the discharge rate is 4 l/s and the time of the freeze and thaw cycles is 10 s and 5 s respectively to obtain slush nitrogen with fine solid particles, and slush density is measured by the densimeter system. According to the experimental results, the rotating speed, higher than 50 rpm in this study, is necessary to homogenize slush nitrogen for the high accuracy of the density measurement.     

DEFORMING METRICS WITH POSITIVE CURVATURE BY A FULLY NONLINEAR FLOW

By studying a fully nonlinear flow deforming conformal metrics on a compact and connected manifold, we prove the long time existence and the exponential convergence of the solutions of the flow for any initial metric g0 with the Schouten tensor Ag0 ∈Γk.     

Structural damage identification based on best achievable flexibility change

A new method based on best achievable flexibility change is presented in this paper to localize and quantify damage in structures. Central to the damage localization approach is the computation of the Euclidean distances between the measured flexibility change and the best achievable flexibility changes. The location of damage can be identified by searching for a value that is considerably smaller than others in these distances. With location determined, a simple extent algorithm is then developed. Three examples are used to demonstrate the efficiency of the method. Results indicate that the proposed procedure may be useful for structural damage identification.     

Ab initio molecular dynamics simulations on structural change of supercooled liquid Si at different temperatures from 1700 to 1100 K

Using ab initio molecular dynamics simulations, the local atomic structure and electronic properties of supercooled liquid Si (l-Si) at different temperatures from 1700 to 1100 K were studied. Our calculated coordination numbers present no obvious change in the temperature range investigated. Our results indicate that the structure of supercooled l-Si may be well described as a combined local atomic configuration of white-tin and diamond type structures. Upon cooling from 1700 to 1100 K, the tetrahedral white-tin type ordering collapses gradually toward the tetrahedral diamond-type structure. No drastic change behavior is observed in our work.     

Structural, electronic and thermodynamic properties of cubic Zn3N2 under high pressure from first-principles calculations

The structural, electronic and thermodynamic properties of cubic Zn₃N₂ under hydrostatic pressure up to 80 GPa are investigated using the local density approximation method with pseudopotentials of the ab initio norm-conserving full separable Troullier-Martin scheme in the frame of density functional theory. The structural parameters obtained at ambient pressure are in agreement with experimental data and other theoretical results. The change of bond lengths of two different types of Zn-N bond with pressure suggests that the tetrahedral Zn-N bond is slightly less compressible than the octahedral bond. By fitting the calculated band gap, the first and second order pressure coefficients for the direct band gap ofthe Zn₃N₂ were determined to be 1.18×10⁻² eV/GPa and −2.4×10⁻⁴ eV/(GPa)², respectively. Based on the Mulliken population analysis, Zn₃N₂ was found to have a higher covalent character with increasing pressure. As temperature increases, heat capacity, enthalpy, product of temperature and entropy increase, whereas the Debye temperature and free energy decrease. The present study leads to a better understanding of how Zn₃N₂ materials respond to compression.     

石蜡微胶囊的制备

针对太阳能利用以及一些蓄热场合,通过示差扫描量热法（DSC）选取了合适的石蜡,以脲醛树脂为囊壁,采用原位聚合法制备了石蜡一脲醛树脂微胶囊,拟将此微胶囊添加到上述应用场合的传热流体中,提高传热流体的热容。实验结果表明,乳化剂OP更适合于熔点60℃石蜡微胶囊的制备。     

Highly conformal growth of microstructured polypyrrole films by electrosynthesis on micromachined silicon substrates

A novel technology for fabricating microstructured polypyrrole (PPy) films is presented based on PPy electrosynthesis on micromachined silicon substrates. PPy light-activated electropolymerization is performed on n-type microstructured silicon featuring lattices of square-like pores with pitch of 8 μm, size (s) of 5 μm, and depth (d) from 5 μm up to 50 μm. Scanning electron microscopy (SEM) highlights as light-activation allows a highly conformal polymer growth yielding a three-dimensional PPy structure perfectly replicating the silicon microstructure to be achieved up to high aspect-ratio (HR = d/s). Arrays of highly ordered PPy hollow microtubes with depth up to 50 μm and thickness up to 1 μm are obtained. Chemical analysis of microstructured PPy films is performed by X-ray photoelectron spectroscopy (XPS) and their electrochemical activity is verified by cyclic voltammetry (CV).     

Statistical properties of signal entropy for use in detecting changes in time series data

Detecting changes in an underlying time series model for a system is an important task in many different fields, including econometrics, geophysics and process control. Specifically, in process control, detecting model changes is often the first step for fault detection, plant‐model mismatch assessment and data quality assessment for system identification. Signal entropy, which basically measures the amount of disorder in a given signal, can, not only segment a time series, but can also determine which regions have similar underlying models. Thus, the changes between the input and output signals can be used to determine when model is no longer an accurate representation of the system by comparing the current differential entropy against the historical differential entropy. This paper presents the statistical properties of signal entropy for discrete time systems. An example of the general results is provided by determining the entropy characteristics for first‐order systems driven by white noise. As well, a change detection index is proposed to assess changes in the time series model, which is tested on an experimental system. Copyright © 2013 John Wiley & Sons, Ltd.