Integrating profiling LIDAR with Landsat data for regional boreal forest canopy attribute estimation and change characterization

Forest dynamics are characterized by both continuous (i.e., growth) and discontinuous (i.e., disturbance) changes. Change detection techniques that use optical remotely sensed data to capture disturbance related changes are established and commonly applied; however, approaches for the capture of continuous forest changes are less mature. Optical remotely sensed imagery is well suited for capturing horizontally distributed conditions, structures, and changes, while Light Detection And Ranging (LIDAR) data are more appropriate for capturing vertically distributed elements of forest structure and change. The integration of optical remotely sensed imagery and LIDAR data provides improved opportunities to fully characterize forest canopy attributes and dynamics.The study described in this paper captures forest conditions along a corridor approximately 600 km long through the boreal forest of Canada. Two coincident LIDAR transects, representing 1997 and 2002 forest conditions respectively, are compared using image segments generated from Landsat ETM+ imagery. The image segments are used to provide a spatial framework within which the attributes and temporal dynamics of the forest canopy are estimated and compared. Segmented and classified Landsat imagery provides a context for the comparison of sufficiently spatially related LIDAR profiles and for the provision of categories to aid in the application of empirical models requiring knowledge of land cover.Global and local approaches were employed for characterizing changes in forest attributes over time. The global approach, emphasized the overall trend in forest change along the length of the entire transect, and indicated that key canopy attributes were stable, and transect characteristics, including forest canopy height, did not change significantly over the five-year period of this study (two sample t-test, p = 0.08). The local approach analyzed segment-based changes in canopy attributes, providing spatially explicit indications of forest growth and depletion. The local approach identified that 84% of the Landsat segments intercepted by both LIDAR transects either have no change, or have a small average increase in canopy height (0.7 m), while the other 16% of segments have an average decrease in canopy height of 1.6 m. As expected, the difference in the magnitude of the changes was markedly greater for depletions than it was for growth, but was less spatially extensive. Growth tends to occur incrementally over broad areas; whereas, depletions are dramatic and spatially constrained. The approach presented holds potential for investigating the impacts of climate change across a latitudinal gradient of boreal forest.     

Monitoring tea fermentation/manufacturing by direct analysis in real time (DART) mass spectrometry

Factors such as fermentation methods, geographical origin and season can affect the biochemical composition of tea leaves (Camellia sinensis L.). In this study, the biochemical composition of oolong tea during the manufacturing and fermentation process was studied using a non-targeted method utilising ambient ionisation with a direct analysis in real time (DART) ion source and mass spectrometry (MS). Caffeine dominated the positive ionisation spectra throughout the manufacturing process, while the negative ion spectra collected during manufacturing were rich in ions likely to be surface lipids. Correlation analyses on the spectra revealed two volatile compounds tentatively identified as indole and geranic acid, along with ammonium and caffeine clusters/adducts with geranic acid that increased in concentration during the fermentation stages of the process. The tentative identifications were assigned using a combination of DART-ion-trap MSⁿ and DART-accurate mass MS¹ and MS² on tea samples and standard compounds. This study highlights the potential of DART-MS to rapidly monitor the progress of complex manufacturing processes such as tea fermentation.     

Cache Profiling技术

如何减少和隐藏cache失效的延迟,是人们关注的热点。编译器为了得到cache访问命中的情况,往往使用模拟器去跑一遍来得到结果,这样的速度很慢。为了克服以上缺点,提出了在编译器中作cache profiling来获取cache访问的信息。类似于value profiling和stride profiling,cache profiling对访存指令作插装,可以有效地提高速度,并且只需要编译器的支持即可。Cache profiling获得的信息可以用来改进指令调度、软件预取、生成cache hint和辅助线程等。     

AN INVESTIGATION ON COMPUTER-CONTROLLED TURNING AND CONTOUR DESIGNING OF SHAPED CONNECTION

0INTRODUCTIONConnection elements that transmitting torque are the basic elements in the mechanical equipments, they are discussed rather fully in Ref.［1］. Considering fundamentally, for transmitting torque, the crosssectional contour curve of connection elements should be a quasicircle smoothly joined, having no sharp corner in order to reduce the stress concentration. For transmitting the same torque, the shaped connection has relatively smaller structural size as compared with the…     

基于部分调用图的线程敏感Profiling技术

Profiling技术能提供程序实际执行时的相关信息。在动态编译环境中,Profiling的运行时开销导致难以收集较为复杂的运行时信息。该文提出一种基于部分调用图的Profiling技术,在收集多线程程序中线程相关的各种执行信息时,能有效减少运行时开销。在开放源码的虚拟机上实现了该Profiling技术。实验表明,其运行时开销只有原来的2%~4%。     

基于字符级截断式循环神经网络的人名国籍识别

人名是反映用户国籍的关键信息,不同国籍的人名在结构和组成成分方面存在差异性和关联性.目前,基于人名的国籍识别研究工作大部分将人名切分成多个独立的字符单元,忽略字符间微妙的搭配和序列关系.针对上述问题,文中提出基于字符级截断式循环神经网络的人名国籍识别模型,将人名通过滑动窗口的方式截断成多个子序列,利用长短期记忆单元模型学习不同子序列内部的字符组合关系,通过平均池化操作聚合所有子序列信息,获取最终的人名向量表示.最后根据该人名向量实现用户的国籍识别.截断式的子序列有利于模型更关注人名内部的细微差异.在Olympic运动员和Aminer学者数据集上的实验表明,文中模型性能较优.     

Reducing energy availability losses with open parallel microchannels embedded in a micropatterned surface

This article develops a new technique of reducing exergy losses of external viscous flow over surfaces, based on optimized microchannels embedded within the surface. The rate of entropy production and loss of available optimized energy are formulated by an integral solution and modified Blasius profiles of boundary layer flow. The optimized number of microchannels, width and height of each microchannel and spacing between microchannels involve a selective compromise between added heat exchange due to surface area, together with reduced friction through slip conditions within each microchannel. Mixed Knudsen numbers across each microchannel require simultaneous modelling of both slip‐flow and no‐slip conditions at the wall. Results involving the minimal entropy production and optimized microchannel profiles are presented and compared to other benchmark results involving classical macro‐scale configurations. Copyright © 2005 John Wiley & Sons, Ltd.     

异形凸曲前刀面硬质合金插齿刀构形误差分析与仿真

在提出一种硬质合金插齿刀的新构形方法（异形凸曲前刀面插齿刀）的基础上，建立了切削刃的数学模型。并且对新构形异形凸曲前刀面硬质合金插齿刀侧刃构形误差进行了分析，建立了插齿刀侧刃构形误差数学模型。利用MATLAB软件对侧刃空间曲线及其构形误差进行了仿真。     

一种特殊结构高频高速材料PCB加工问题探讨

随着电子、通讯产业的飞速发展,高频、RF设计越来越广泛,PCB上越来越多的运用到高频材料来满足信号传输的要求。为了满足客户对信号完整性以及信号接收与屏蔽匹配性等的要求,在PCB设计上经常采用混压及设计盲槽等方式,来满足其信号传输速度和灵敏度,但给PCB制造带来了一些其它工艺问题。通过对PTFE材料+热塑性PP金属盲槽流胶、成型板边毛边等关键工艺问题进行探讨,提供一种简单可行的解决方案与同行共勉。