基于残差加权经验过程方法的自回归模型分布变点监测

Change monitoring of distribution in time series models is an important issue.This paper proposes a procedure for monitoring changes in the error distribution of autoregressive time series,which is based on a weighed empirical process of residuals with weights equal to the regressors.The asymptotic properties of our monitoring statistic are derived under the null hypothesis of no change in distribution.The finite sample properties are investigated by a simulation.As it turns out,the procedure is not only able to detect distributional changes but also changes in the regression coefficient and mean.Finally,we apply the statistic to a groups of financial data.     

Infrared image enhancement through saliency feature analysis based on multi-scale decomposition

To improve contrast between dim target region and background in infrared (IR) long-range surveillance, this paper proposes a fast image enhancement approach using saliency feature extraction based on multi-scale decomposition. Firstly, a smooth based multi-scale decomposition is designed and applied to original infrared image, generating sub-images with various frequency components at different decomposition levels. The dim target regions of sub-images are extracted by a local frequency-tuned based saliency feature detection method, secondly. With saliency maps created by saliency extraction using multi-scale local windows with different sizes, the sub-images are enhanced at different decomposition scales. Finally, the enhanced result is reconstructed by synthesizing the all sub-images with adjustable synthetic weights. Since salient areas are analyzed based on fast multi-scale image decomposition, IR image can be s enhanced with good contrast successfully and rapidly. Compared with other algorithms, the experimental results prove that the proposed method is robust and efficient for IR image enhancement.     

基于双阈值视觉注意模型的图像关注焦点检测

 图像关注焦点（FOA）检测是基于人眼视觉关注模型的图像感兴趣区提取的关键技术。为了更加精确、合理地搜索图像关注焦点,提出一种基于双阈值视觉关注模型的FOA检测算法。算法首先提取图像的亮度、颜色、方向和离散矩变换（DMT）特征,生成各个特征对应的特征图;然后将各特征图合并为一张包含多种特征的显著图;最后根据显著图的灰度直方图建立静态阈值与动态阈值,确定图像关注焦点的位置与数量。实验结果表明：新算法在图像关注焦点检测的准确性上较Itti模型有更为优秀的表现,更符合人眼视觉的关注习惯。     

ZIF-67 derived hollow Ni-Co-Se nano-polyhedrons for flexible hybrid supercapacitors with remarkable electrochemical performances

Nano-polyhedral NiSe₂/CoSe₂ (Ni-Co-Se) with hollow architectures are synthesized by selenizing the precursors of Ni-Co bimetallic hydroxides that are directly derived from ZIF-67. The as-fabricated Ni-Co-Se electrodes exhibit high specific capacitance of 1668 F/g at 1 A/g accompanying with outstanding rate capability (about 82.8% retention of the initial capacity at 20 A/g). The corresponding Ni-Co-Se//AC all-solid-state hybrid supercapacitors are assembled by directly using the Ni-Co-Se on carbon fabric as the positive electrode, which deliver high energy density and power density (38.5 Wh/kg at 802.1 W/kg, 32.0 Wh/kg at 8008.8 W/kg), excellent cyclic stability (82.3% retention after 5000 cycle) and robust mechanical flexibility (no obvious attenuation at bending to different angles). This work will provide a new and smart route for constructing transition metal selenides for supercapacitor devices.     

地基CE312热红外辐射计定标方法分析与评价

地基CE312热红外辐射计用于星载传感器的定标,其定标精度直接影响热红外传感器的场地定标精度。文章论述CE312-1b带宽辐亮度定标法和分谱辐亮度定标法的定标原理,利用实验室黑体对CE312-1b热红外辐射计进行定标,最后利用2010年8月青海湖的野外实测数据结合MODIS观测值,分析对比两种定标方法所得定标结果的准确性及误差来源。结果表明,带宽辐亮度定标法得到的CE312热红外辐射计定标系数相对分谱辐亮度定标法所得结果在准确性、适用性方面表现更好。     

非球形气溶胶粒子短波红外散射特性研究

利用T矩阵方法,以及基于扩散限制凝聚理论的广义多粒子米散射方法,研究了多种气溶胶粒子在1.6和2.0μm波段处,非球形单粒子和团簇粒子的光散射辐射特性,并分析了粒子有效半径、复折射指数、粒子形状、相对湿度等因素对非球形粒子散射特性的影响.分析表明,除了粒子有效半径和形状会在不同程度上引起粒子散射特性变化,相对湿度对其影响也比较大,球形粒子与非球形粒子在不同相对湿度下后向散射相对差异均在18%以上;当粒子体积较小时,水溶性气溶胶的后向散射强度随相对湿度的增加而增强,而当粒子体积较大时,则随相对湿度的增加而减弱;在体积相同的条件下,体积较小的团簇粒子的不对称因子比非球形单粒子平均偏大0.023,而体积较大的团簇粒子,却比非球形单粒子不对称因子平均偏小0.055;单粒子或等体积的团簇粒子,其不同波段之间单次散射反照率差异较大,最大可达0.226.该工作对研究气溶胶多次散射对CO₂浓度卫星反演精度影响具有重要的科学意义.     

Symbolic computation on the Darboux transformation for a generalized variable-coefficient higher-order nonlinear Schrödinger equation from fiber optics

Considering the propagation of ultrashort pulse in the realistic fiber optics, a generalized variable-coefficient higher-order nonlinear Schrödinger equation is investigated in this paper. Under certain constraints, a new 3×3 Lax pair for this equation is obtained through the Ablowitz-Kaup-Newell-Segur procedure. Furthermore, with symbolic computation, the Darboux transformation and nth-iterated potential transformation formula for such a model are explicitly derived. The corresponding features of ultrashort pulse in inhomogeneous optical fibers are graphically discussed by the one- and two-soliton-like solutions.     

Optical and electrical characteristics of InGaP/AlGaAs/GaAs composite emitter heterojunction bipolar/phototransistors (CEHBTs/CEHPTs)

We report on new InGaP/AlGaAs/GaAs composite emitter heterojunction bipolar and phototransistors (CEHBTs/CEHPTs) with a low turn-on voltage. The composite emitter comprised of the digital graded superlattice emitter and the InGaP sub-emitter is used to smooth out potential spike associated with the emitter–base heterojunction and to obtain a low emitter–base turn-on voltage. A fabricated CEHBT exhibits a small offset voltage of 55 mV and a low turn-on voltage of 0.83 V with a dc current gain as high as 150. In case of a CEHPT’s collector–emitter characteristics with base floating, optical gains increase with increasing input optical power. Furthermore, the collector current saturation voltage is small due to a low turn-on voltage. We obtain an optical gain larger than 6.83 with a collector current saturation voltage smaller than 0.5 V. On the other hand, performance results of a CEHPT with two- and three-terminal configuration were investigated and compared.     

Modeling an inhomogeneous optically thick laser induced plasma: a simplified theoretical approach

A simplified theoretical approach is developed for an optically thick inhomogeneous laser induced plasma. The model describes the time evolution of the plasma continuum and specific atomic emission after the laser pulse has terminated and interaction with a target material has ended. Local thermodynamic equilibrium is assumed allowing the application of the collision-dominated plasma model and standard statistical distributions. Calculations are performed for a two-component Si/N system. The model input parameters are the number of plasma species (or plasma pressure) and the ratio of atomic constituents. Functions are introduced which describe the evolution of temperature and size of the plasma. All model inputs are experimentally measurable. The model outputs are spatial and temporal distributions of atom, ion and electron number densities, evolution of an atomic line profile and optical thickness and the resulting absolute intensity of plasma emission in the vicinity of a strong non-resonance atomic transition. Practical applications of the model include prediction of temperature, electron density and the dominating broadening mechanism. The model can also be used to choose the optimal line for quantitative analysis.     

A note on the gambling team method

Gerber and Li (1981) formulated, using a Markov chain embedding, a system of equations that describes relations between generating functions of waiting time distributions for occurrences of patterns in a sequence of independent repeated experiments when the initial outcomes of the process are known. We show how this system of equations can be obtained by using the classical gambling team technique. We also present a form of solution of the system and give an example showing how first results of trials influence the probabilities that a chosen pattern precedes the remaining ones in a realization of the process.