10kHz腔倒空锁模皮秒激光器研究

将半导体可饱和吸收体(SESAM)锁模技术与腔倒空技术结合,采用半导体端面抽运方式实现了具有高重复频率、大单脉冲能量的皮秒激光器的运转.从理论上分析了腔倒空锁模输出的机理,建立起腔倒空锁模激光器运行的物理图像,并对影响激光器倒空率的一些因素进行了研究.实验上,实现端面抽运Nd:YVO4晶体的SESAM连续锁模后,在锁模...     

Paper engineered with cellulosic additives: effect of length scale

Composites of cellulose fibers were made with paper-making technology. Two types of microfibrillated cellulose (MFC), obtained by with either homogenization or ball milling, were blended with hardwood fibers to give composites having high strength and low air permeability. The strengthening effects of the MFCs were compared with strengthening by cellulose microparticles (CMPs) made by cryogenic milling, with and without polyamideamine-epichlorohydrin addition. The MFC from homogenization was fully retained on the fiber web due to a broad size distribution; in contrast, the retention ratio for MFC produced by ball milling was lower than 50 % because of its smaller particle size. The small size caused the resulting paper to display a more compact and denser structure. The main distinction between the papers made with the two types of MFC was the elongation at break under wet conditions, suggesting that they reinforce the paper in different ways. On the other hand, CMPs act as mechanical debonders and could find application in tissue paper, increasing paper bulk and decreasing the density and thus improve tissue softness.     

A comparison of H+-restacked nanosheets and nano-scrolls derived from K4Nb6O17for visible-light degra-dation of dyes

H＋-restacked nanosheets and nanoscrolls peeled from K4Nb6O17 display different structures and surface characters. The two restacked samples with increased surface areas have an amazing visible-light response for the photodegradation of dyes, which is superior to commercial TiO2 （P25） and Nb205. By comparison, H＋/nanosheets have a relatively faster photodegradation rate originated from large and smooth basal plane. The work reveals that dye adsorbed on the unfolded nanosheets can effectively harvest sunlight. Due to facile preparation, low-cost and high photocatalytic efficiency, H＋/nanosheets and H＋/nanoscrolls might be used for the visible light-driven degradation of organic dyes as a substitute for TiO2 in industry.     

Uncertainty Quantification for Modern High-Dimensional Regression via Scalable Bayesian Methods

Tremendous progress has been made in the last two decades in the area of high-dimensional regression, especially in the “large p, small n” setting. Such sample starved settings inevitably lead to models which are potentially very unstable and hence quite unreliable. To this end, Bayesian shrinkage methods have generated a lot of recent interest in the modern high-dimensional regression and model selection context. Such methods span the wide spectrum of modern regression approaches and include among others, spike-and-slab priors, the Bayesian lasso, ridge regression, and global-local shrinkage priors such as the Horseshoe prior and the Dirichlet–Laplace prior. These methods naturally facilitate tractable uncertainty quantification and have thus been used extensively across diverse applications. A common unifying feature of these models is that the corresponding priors on the regression coefficients can be expressed as a scale mixture of normals. This property has been leveraged extensively to develop various three-step Gibbs samplers to explore the corresponding intractable posteriors. The convergence of such samplers however is very slow in high dimensions settings, making them disconnected to the very setting that they are intended to work in. To address this challenge, we propose a comprehensive and unifying framework to draw from the same family of posteriors via a class of tractable and scalable two-step blocked Gibbs samplers. We demonstrate that our proposed class of two-step blocked samplers exhibits vastly superior convergence behavior compared to the original three-step sampler in high-dimensional regimes on simulated data as well as data from a variety of applications including gene expression data, infrared spectroscopy data, and socio-economic/law enforcement data. We also provide a detailed theoretical underpinning to the new method by deriving explicit upper bounds for the (geometric) rate of convergence, and by proving that the proposed two-step sampler has superior spectral properties. Supplementary material for this article is available online.     

Integrating intensity and texture differences for robust changedetection

We propose a novel technique for robust change detection based upon the integration of intensity and texture differences between two frames. A new accurate texture difference measure based on the relations between gradient vectors is proposed. The mathematical analysis shows that the measure is robust with respect to noise and illumination changes. Two ways to integrate the intensity and texture differences have been developed. The first combines the two measures adaptively according to the weightage of texture evidence, while the second does it optimally with additional constraint of smoothness. The parameters of the algorithm are selected automatically based on a statistic analysis. An algorithm is developed for fast implementation. The computational complexity analysis indicates that the proposed technique can run in real-time. The experiment results are evaluated both visually and quantitatively. They show that by exploiting both intensity and texture differences for change detection, one can obtain much better segmentation results than using the intensity or structure difference alone.     

Electron transfer properties and electrocatalytic behavior of tyrosinase on ZnO nanorod

In this work, the adsorption of tyrosinase on ZnO nanorods and its electrocatalytic behaviors were investigated. The mushroom tyrosinase with low isoelectric point was expected to adhere on the positively charged surface of ZnO nanorods by electrostatic attraction in a neutral solution. Scanning electron microscope images and spectroscopic analysis demonstrated the adsorption of tyrosinase on ZnO nanorods and the adsorbed tyrosinase remain its bioactivity to a large extent. In the presence of tyrosinase, a roughly and cyathiform of nanosized ZnO films was obtained. This open, three-dimensioned ramiform structure made the move through and exchange the electron with GCE more easily, and thus accelerating the electron transfer between electroactive and GCE. The adsorbed tyrosinase could catalyze the oxidation of phenol and catechol. The linear concentration ranges were from 0.02 to 0.1 mM and 0.01 to 0.4 mM, for phenol and catechol, respectively. The apparent Michaelis-menten constant , a reflection of the enzymatic affinity, was 0.24 mM for phenol and 1.75 mM for catechol, which suggests a large affinity to phenolic compound. The proposed methods presented a way for further studies of the immobilization and electrochemistry of proteins on nanostructured materials.     

Biodegradable Photothermal and pH Responsive Calcium Carbonate@Phospholipid@Acetalated Dextran Hybrid Platform for Advancing Biomedical Applications

A biodegradable multifunctional carrier for combination therapy with high efficiency and low side effect is essential for effective cancer treatment and for advancing biomedical applications. Therapeutics combination could reduce multidrug resistance and minimize doses through synergism. This study develops biodegradable gold nanorods@calcium carbonate particles coated with pH‐responsive acetalated dextran and phospholipid as an advanced platform for the incorporation of versatile molecular targeted therapeutics, including hydrophilic and hydrophobic drugs, as well as the model enzyme, green fluorescent protein, or antibody. The developed calcium carbonate based hybrid particles show good biocompatibility, stability with photothermal, and pH responsiveness, which protect the payloads from premature release, and maintain the enzyme activity. The therapeutics co‐loaded CaCO₃ based hybrid particles efficiently induce cancer cell death and reduce the multidrug resistance and HER2 expression with synergism. The photothermal effects promote ultrafast therapeutics release and induce significant cytotoxicity. Importantly, Anti‐HER2 antibody or HER2 targeted therapeutic is more effective in reducing HER2 expression when combined with drug or drugs via synergism. Overall, the cheap and simply manufactured biodegradable hybrid platform has great potential for advancing biomedical applications, including targeted photothermal combination therapy by co‐delivery of different types of therapeutics, including molecular targeted drugs, antibodies, and enzymes.     

α－β滤波器的基本问题分析与仿真研究

针对α-β滤波器滤波增益随采样时刻的增加而减小的问题,提出了一种根据位置滤波平均误差、速率滤波平均误差以及速度滤波效果确定滤波增益下降截止时刻的方法,并分析了可能影响滤波增益下降截止时刻的因素。仿真结果表明：通过该方法确定的滤波增益下降截止时刻可以使α-β滤波器的滤波效果达到最佳;滤波增益下降截止时刻与目标采样间隔的相关性最强,与过程噪声的相关性次之,与量测噪声的相关性最弱。     

基于人工鱼群粒子滤波的信号源定位

针对传统粒子滤波算法精度不高、难以满足移动监测车对无线电信号源定位需求的问题,提出了一种基于人工鱼群粒子滤波的信号源定位方法。将人工鱼群算法的优化思想引入到粒子滤波中,通过觅食行为和聚群行为驱动粒子向最优位置移动,改善粒子的分布。结合移动监测车对信号源定位的需要,建立了信号源波达角定位( AOA)的数学模型,在Matlab环境下对人工鱼群粒子滤波算法的信号源定位进行了仿真。实验结果表明,在保证实时性的前提下,该方法定位结果的最大误差为0.101%,定位精度远大于粒子滤波定位方法的估计精度,是一种有效、可行的定位方法。