一种Blinn-Phong BRDF红外反射模型的研究

针对红外场景仿真中辐射反射分量运算复杂、真实感欠缺等问题,提出一种Blinn-Phong BRDF红外反射模型,并基于Unity平台将其应用于三维红外仿真场景。该方法在对实测红外图像进行阈值分割的基础上,利用简化辐亮度运算和红外成像过程的仿真链路反演模型,求解目标表面温度值,根据红外辐射原理与可见光光照模型的理论相似性,将改进的Blinn-Phong光照模型移植到红外波段,并引入双向反射分布函数提高仿真精度,提出Blinn-Phong BRDF红外反射模型;最后基于该辐射反射模型构建零视距仿真场景,同时将仿真图像与实测图像进行比对,验证了反射模型的可信度和有效性。实验结果表明,提出的红外反射模型既有较高的仿真效率,又能够较好地模拟红外反射的高光现象,满足红外视景仿真对辐射反射的要求。     

Microwave Emission Model of Layered Snowpacks

A thermal microwave emission model of layered snowpacks (MEMLS) was developed for the frequency range 5–100 GHz. It is based on radiative transfer, using six-flux theory to describe multiple volume scattering and absorption, including radiation trapping due to total reflection and a combination of coherent and incoherent superpositions of reflections between layer interfaces. The scattering coefficient is determined empirically from measured snow samples, whereas the absorption coefficient, the effective permittivity, refraction, and reflection at layer interfaces are based on physical models and on measured ice dielectric properties. The number of layers is only limited by computer time and memory. A limitation of the empirical fits and thus of MEMLS is in the range of observed frequencies and correlation lengths (a measure of grain size). First model validation for dry winter snow was successful. An extension to larger grains is given in a companion article (Mätzler and Wiesmann, 1999). The objective of the present article is to describe and illustrate the model and to pave the way for further improvements. MEMLS has been coded in MATLAB. It forms part of a combined land-surface-atmosphere microwave emission model for radiometry from satellites(Pulliainen et al., 1998).     

Numerical investigation of the interactions between solitary waves and pile breakwaters using BGK-based methods

The interactions between a solitary wave, which can be used to model a leading tsunami wave, and a pile breakwater made of circular cylinders are numerically investigated. We use the depth-averaged shallow water equations, which are solved by the finite volume method based on the Bhatnagar–Gross–Krook (BGK) model. The numerical results are compared with the experimental data, which yields very good agreement between them when the ratio of wave height to water depth is small (<0.25). As this ratio exceeds the value of 0.25, the larger the ratio is, the bigger deviation of numerical results from experimental data is observed, the possible reasons for this observation are discussed. Both numerical and experimental results indicate that the transmission of the solitary wave decreases and the reflection of the wave increases with reducing gaps between the adjacent cylinders, and that both transmission and reflection coefficients are not very sensitive to the variation in wave height.     

一个可构造的反演状态模式

为了构造可扩充、可配置、可控制的状态模型,提出了一个可构造的反演状态模式.基于体系结构的反演模式和角色对象模式,讨论了状态设计模式中结构和行为的反演方法及其手段;给出了其反演模式体系结构的元级和基本级对象结构;使用MOP(metaobjeotprotoco1)规程给出了元级和基本级的关系,讨论了反演状态模式的元对象反演到基本级对象群的"截取和求精(interception和reification)”机制.此外,还给出了一个应用可构造的反演状态模式的[记账凭证处理型]应用事例.     

Retinex theory based active contour model for segmentation of inhomogeneous images

Intensity inhomogeneity in images makes automated segmentation of these images difficult. As intensity inhomogeneity is often caused by inhomogeneous light reflection, the Retinex theory can be used to reduce inhomogeneity. We introduce the Retinex theory into the active contour model, which is commonly used for image segmentation. The segmentation procedure is then guided by the image intensity and light reflection. In order to solve the proposed model efficiently, we develop a new fast Split Bregman algorithm. Experimental results on a variety of real images with inhomogeneity validate the performance of the proposed methods.     

悬臂梁式光纤振动传感的一种光调制方法的特性研究

从悬臂梁式光纤振动传感的基本原理出发，应用较为成熟的光纤连接耦合理论，导出了悬臂梁（反射体和敏感体）相对于稳定的光纤运动的一种光调制方法数学模型，通过计算机运算求得其特性曲线，为传感器的设计提供可靠的理论依据。     

The dynamic role of social media during Hurricane #Sandy: An introduction of the STREMII model to weather the storm of the crisis lifecycle

Social media has introduced a key ingredient, and a potentially unfamiliar variable, into the practice of crisis communication. In this paper, the authors critically assess the social media milestones related to Hurricane Sandy according to situational crisis communication theory (SCCT) (Coombs, 2007). Further, we discuss the crisis lifecycle of Hurricane Sandy with regard to the potential implementation of the STREMII model of social media crisis management, a proposed model originated through this research application. This original model develops from lessons and best practices discovered in historical and contemporary cases of social media crises and crisis management. The researchers acknowledge potential limitations and describe steps for further development of the model through research, all the while recognizing the powerful and paradoxical role of social media in the crisis management process. In reflection of Hurricane Sandy, further qualitative and quantitative examinations of crisis events are encouraged to evaluate the STREMII model continually in the dynamic social media climate and across the vast facets of crisis communication.     

基于大气反射-散射模型的复原图像中交通视频车灯检测

针对夜间复杂照明环境导致车灯检测率低的问题, 提出了一种基于大气反射-散射模型的复原图像中夜间交通视频车灯检测算法. 首先根据漫反射原理抑制路面漫反射光, 在对大气散射模型做了改进之后, 估计了大气散射模型中的大气光, 再根据暗原色先验理论估计环境光, 重新定义透射率, 从而得到了只含有车灯及反射区域的复原图像.为了进一步抑制该复原图像中的强光光晕, 再次利用暗原色先验理论重新估计环境光, 得到最终的复原图像. 最后对复原图像中的所有亮斑根据四类几何特征逐步筛选, 排除视野中的非车灯. 实验结果表明, 该方法在复杂雨雪天气、高密度及高速等不同情况下, 与同类先进算法相比具有较高的检测率, 较低的漏检率和误检率.     

A geometrical optics model based on the non-Gaussian probability density distribution of sea surface slopes for wind speed retrieval at low incidence angles

In this study, a large amount of data from precipitation radar (PR) and National Data Buoy Center (NDBC) buoys are collocated for the development and validation of a Geometrical Optics Model, in order to retrieve wind speed at small incidence angles. The omni-directional model is developed based on the combination of the quasi-specular scattering theory and non-Gaussian probability density distribution of ocean surface slope, and can be applied at incidence angles as high as 15°. There are four parameters included in the proposed model: the effective Fresnel reflection coefficient, the mean square slope, and the two coefficients associated with the kurtosis of the sea surface slope distribution. Using one half of the collocated data, the dependence of the four parameters on the in situ wind speed is acquired. The results show that the effective Fresnel reflection coefficient has a decrease relative to that obtained in previous studies. We combine the proposed model with the maximum-likelihood estimation (MLE) technique to retrieve the ocean surface wind speed at the 10 m height. The retrieved wind speeds are then validated against those measured by the NDBC buoys. The comparison shows that the root mean square error (RMSE) and bias between the model retrievals and buoy observations are 1.54 m s^–1 and 0.1 m s^–1, respectively, revealing high agreements in the wind speed estimations. The results of this study indicate that the proposed model and the PR measurements at low incidence angles can provide reasonably accurate estimates of the surface wind speeds within the range of 0–20 m s^–1.     

复杂阵地的合成导向矢量最大似然测高

雷达在目标低仰角测高时存在严重的多径效应,复杂阵地使多径回波产生无规律反射,造成幅度与相位发生不同程度的畸变.本文引入扰动多径模型,解决经典多径模型与复杂阵地的多径回波反射不匹配问题,研究基于扰动模型的合成导向矢量最大似然(synthesized vector maximum likelihood, SVML)测高方法.该方法引入扰动参数表征复杂阵地的多径回波现象,利用基于稀疏贝叶斯学习的扰动多径(perturbational multipath sparse Bayesian learning,PSBL)算法得到扰动参数,应用于SVML算法,提高了米波雷达在复杂阵地下的测高性能.     

Surface reflectance and normal estimation from photometric stereo

In this paper, we propose a new photometric stereo method for estimating diffuse reflection and surface normal from color images. Using dichromatic reflection model, we introduce surface chromaticity as a matching invariant for photometric stereo, which serves as the foundation of the theory of this paper. An extremely simple and robust reflection components separation method is proposed based on the invariant. Our separation method differs from most previous methods which either assume dependencies among pixels or require segmentation. We also show that a linear relationship between the image color and the surface normal can be obtained based on this invariant. The linear relationship turns the surface normal estimation problem into a linear system that can be solved exactly or via least-squares optimization. We present experiments on both synthetic and real images, which demonstrate the effectiveness of our method.     

Analysis and modeling of microstrip‐to‐coplanar flip chip package interconnects

In this paper, the discontinuity of a flip chip transition between a microstrip line and a coplanar waveguide is investigated and modeled using the finite‐difference time‐domain method (FDTD) to predict the overall S‐parameters of the package. Effects of the bump and via interconnects on the package performance are investigated and discussed. This includes the effects of different staggered transitions and ground connects on the package performance. A reduction of about 10 dB in the bump and via reflections can be achieved by staggering the signal (bump) and the ground connects (bump/via). A staggering distance of about twice the slot width gave minimum reflection over a wide band of frequencies. Moreover, the larger the relative distance between the ground and the center connects the less the reflection due to the discontinuity. Finally, the computed S‐parameters of the flip chip package using the FDTD solution are used to develop an equivalent circuit model for the transition discontinuity over a wide frequency band. The equivalent circuit model of the microstrip to coplanar waveguide discontinuity includes more elements and is more complex than other types of transitions. A TEE or PI circuit model has been used to approximate the general circuit model of the discontinuity. Good agreement has been obtained between the S‐parameters of the FDTD model and the equivalent circuit models over a wide frequency band. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 202–211, 2001.     

彩色图像人脸高光区域的自动检测与校正方法

人脸检测和识别受不同环境照明的影响很大,彩色图像中人脸高光区域的自动检测和辐射校正有助于对人脸的正确分析和识别.提出了一种在TSL(tint-saturation-luminance)彩色空间基于双色反射模型进行高光检测和辐射校正的新方法.通过考察肤色在各种不同彩色空间中的分布形态,以及对皮肤光谱反射特性的分析,采用关键的2维平面代替3维彩色空间进行高光分析.一方面降低了算法复杂度,另一方面又可以在序贯主分量分析中提出特征值比值,迅速而准确地自动检测是否有皮肤高光区域的存在,同时还可以鲁棒地确定皮肤双色反射矢量,应用双色反射模型进行肤色高光区域的辐射校正.     

基于组件的密码学虚拟实验室的设计与实现

基于组件技术的密码学虚拟实验室(CVL)以Java Applet实现客户端,以JavaBean的形式开发密码算法组件,利用Java反射技术实现了系统组件的动态分析,采用XML技术实现了实验组件信息的保存,结合计算机图论中的有向无环图的概念和Java线程机制,提出了一种基于有向无环图的管理线程控制机制,较好地反映了组件之间的数据依赖关系和运行管理过程.CVL实现了可视化实验流程的定制,实验流程的保存与读取以及密码算法的验证和性能分析性等功能.为科研、教学提供了一个很好的密码学实验平台,并给从事仿真系统开发的研究者提供了有力的参考模型.     

Principles of canonical action research

Abstract.  Despite the growing prominence of canonical action research (CAR) in the information systems discipline, a paucity of methodological guidance continues to hamper those conducting and evaluating such studies. This article elicits a set of five principles and associated criteria to help assure both the rigor and the relevance of CAR in information systems. The first principle relates to the development of an agreement that facilitates collaboration between the action researcher and the client. The second principle is based upon a cyclical process model for action research that consists of five stages: diagnosis, planning, intervention, evaluation and reflection. Additional principles highlight the critical roles of theory, change through action, and the specification of learning in terms of implications for both research and practice. The five principles are illustrated through the analysis of one recently published CAR study.     

Images of reflection: on the meanings of the word reflection in different learning contexts

Reflection is today a watchword in many learning contexts. Experience is said to be transformed to knowledge when we reflect on it, university students are expected to acquire the ability to reflect critically, and we want practitioners to be reflective practitioners in order to improve their professional practice. If we consider what people mean when they talk about reflection in practice, we will discover that they often mean different things. Moreover, their conceptions of reflection are guided by images rather than by definitions. This paper explores six distinct images of reflection and discusses the consequences of adopting one or more of these images in learning situations: (1) dedoublement, (2) analogical thinking, (3) mirror, (4) experiment, (5) puzzle solving, (6) criss-crossing a landscape. Reflective thinking can be improved if we are sensible of what we are reflecting about and according to which image of reflection we are doing it, since the step between using an image and seeing this image as a model is short. Using models, in turn, implies knowing their limits.     

超声波液体密度测量的一种声反射系数测定方法

用超声波测液体密度时,测量声反射系数是重点.提出一种将半波层反射模型简化后,利用相对稳态幅度测量声压反射系数的方法.将一个较薄固体作为半波层置于被测液体中,两侧对称地放置超声波换能器,换能器一个工作在脉冲回波模式,另一个工作在接收模式.调整信号频率使半波层和被测液体交界面的多重反射波达到最大程度干涉,此时被测液体与半波层之间的声反射系数只与两个换能器在稳态下的回波信号幅度比值有关.因此测得换能器的稳态回波信号幅度比,即可得到声反射系数.此方法简化了原来的半波层反射模型,采取对称布局,利用相对稳态幅度法,简化了理论推导过程,降低了测量上的精度要求.最后文章通过实验验证了方法的正确性.     

基于超声波传感器的未知狭窄环境导航算法

针对移动机器人在未知狭窄环境中的导航问题,利用证据理论中的矛盾因子,给出了一个自适应超声波传感器模型。利用该模型,结合D S证据理论融合算法以及证据格方法,实现了移动机器人在未知狭窄环境中的导航,并有效地减少了由于超声波传感器镜面反射所引起的不确定性。实验结果表明了该方法的有效性。     

基于表面等离子体效应的MEMS红外辐射源特性研究

研究了一种新型的基于二维光子晶体结构的表面等离子体共振SPR(Surface plasmon resonance)效应的红外辐射源,该辐射源基本结构为Si-SiO2(650nm)-Cr(100nm)-Au(800nm),并在Au表面刻蚀5μm的周期性排列的圆孔。设计加工了几种不同的结构,包括三种不同的圆孔间距即晶格常数:6μm,7μm,和8μm;四种占空比(圆孔直径与晶格常数之比):3/8,4/8,9/16和11/16;以及三种圆孔排列方式:正方形排列,六边型排列,和带规则缺陷六边型排列。本文采用红外傅立叶测量设备对辐射源进行测试分析,通过该辐射源的红外反射谱表征其辐射性能,并利用FDTD软件进行模拟,和实验数据作了比较。研究结果得出了红外辐射源反射谱波谷位置即SPR共振峰位置,波谷强度即SPR共振峰强度与不同结构参数之间的关系。研究发现该辐射源SPR共振峰位置基本与圆孔间距即晶格常数成正比,正方型排列基本接近于1:1,而六边型排列基本接近于3/2;常规六边型排列比带缺陷六边型排列和正方型排列具有更窄的半波宽和更大的SPR共振强度;随着占空比变大,该辐射源的SPR共振峰强度变大。