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971.
无干涉刀具轨迹的生成是复杂曲面数控加工编程中十分重要的问题.本文 提出了一种基于三角化曲面的刀具轨迹干涉消除的算法.该算法已成功应用于作者 开发的CAM系统中,实践表明该算法稳定可靠,效率较高.,It is very important to generate interference free tool path of sculptured surface. An algorithm of tool path interference elimination of sculptured surface based on surface triangulation is proposed in the paper. This algorithm has been used in CAM system which is developed by the authors. The practical re sult shows it is stable and efficient. 相似文献
972.
称一个简单图G是导出匹配可扩的,缩写为IM-可扩的,如果G的每一个导出匹配都包含在一个完善匹配中,研究导出匹配可扩图的度和条件,主要结果如下:(1)若图G有2n个顶点,且对于G中每一对不相邻的顶点u和v,d(u)+d(v)≥2「4n/3」-1,则G是出匹配可扩的;(2)若G是一有个有2n个顶点的无爪图,且对于G中每一对不相邻的顶点u和v,d(u)+d(v)≥2n+3,则G是导出匹配可扩的。同时,说 相似文献
973.
随着嵌入式系统的发展,在Linux下使用Qt开发嵌入式应用程序是嵌入式图形用户界面(GUI)系统应用研究的重点.通过一个通讯簿程序的设计,给出了基于Qt的嵌入式Linux程序开发的关键技术,包括QtDesigner、信号与槽机制的使用、程序主要功能代码的实现以及程序开发的整体过程. 相似文献
974.
Whiskers mimicking those of seals or rats might be useful for underwater tracking or tactile exploration. Several species of terrestrial and marine mammals with whiskers (vibrissae) use them to sense and navigate in their environment--for example, rats use their whiskers to discern the features of objects, and seals rely on theirs to track the hydrodynamic trails of their prey. Here we show that the bending moment--sometimes referred to as torque--at the whisker base can be used to generate three-dimensional spatial representations of the environment, and we use this principle to construct robotic whisker arrays that extract precise information about object shape and fluid flow. Our results will contribute to the development of versatile tactile-sensing systems for robotic applications, and demonstrate the value of hardware models in understanding how sensing mechanisms and movement control strategies are interlocked. 相似文献
975.
Clark IE Dodson MW Jiang C Cao JH Huh JR Seol JH Yoo SJ Hay BA Guo M 《Nature》2006,441(7097):1162-1166
Parkinson's disease is the second most common neurodegenerative disorder and is characterized by the degeneration of dopaminergic neurons in the substantia nigra. Mitochondrial dysfunction has been implicated as an important trigger for Parkinson's disease-like pathogenesis because exposure to environmental mitochondrial toxins leads to Parkinson's disease-like pathology. Recently, multiple genes mediating familial forms of Parkinson's disease have been identified, including PTEN-induced kinase 1 (PINK1; PARK6) and parkin (PARK2), which are also associated with sporadic forms of Parkinson's disease. PINK1 encodes a putative serine/threonine kinase with a mitochondrial targeting sequence. So far, no in vivo studies have been reported for pink1 in any model system. Here we show that removal of Drosophila PINK1 homologue (CG4523; hereafter called pink1) function results in male sterility, apoptotic muscle degeneration, defects in mitochondrial morphology and increased sensitivity to multiple stresses including oxidative stress. Pink1 localizes to mitochondria, and mitochondrial cristae are fragmented in pink1 mutants. Expression of human PINK1 in the Drosophila testes restores male fertility and normal mitochondrial morphology in a portion of pink1 mutants, demonstrating functional conservation between human and Drosophila Pink1. Loss of Drosophila parkin shows phenotypes similar to loss of pink1 function. Notably, overexpression of parkin rescues the male sterility and mitochondrial morphology defects of pink1 mutants, whereas double mutants removing both pink1 and parkin function show muscle phenotypes identical to those observed in either mutant alone. These observations suggest that pink1 and parkin function, at least in part, in the same pathway, with pink1 functioning upstream of parkin. The role of the pink1-parkin pathway in regulating mitochondrial function underscores the importance of mitochondrial dysfunction as a central mechanism of Parkinson's disease pathogenesis. 相似文献
976.
为了在《京都议定书》未来承诺期内将伐木制品(HWP)碳储存和排放相关的内容纳入缔约国强制性报告范围提供决策依据,根据可行性、准确性、满足《联合国气候变化框架公约》和《京都议定书》报告要求和国家政策相关性4项标准,对IPCC缺省法、储量变化法、生产法和大气流动法4种HWP碳储量计量方法及其不同层级的做法进行了评估。比较分析可得,在国家层面,不同方法得出的计量结果存在显著差异,将对缔约方在减排履约、经济社会和环境方面产生不同影响。因此,必须确定统一的HWP碳储量计量方法,避免遗漏和重复计算。然而,计量方法/做法对于实现国家政策目标各有利弊,不尽完善。 相似文献
977.
Water plays a first-order role in basal sliding of glaciers and ice sheets and is often a key constituent of accelerated glacier motion. Subglacial water is known to occupy systems of cavities and conduits at the interface between ice and the underlying bed surface, depending upon the history of water input and the characteristics of the substrate. Full understanding of the extent and configuration of basal water is lacking, however, because direct observation is difficult. This limits our ability to simulate ice dynamics and the subsequent impacts on sea-level rise realistically. Here we show that the subglacial hydrological system can have a large volume of water occupying basal crevasses that extend upward from the bed into the overlying ice. Radar and seismic imaging combined with in situ borehole measurements collected on Bench Glacier, Alaska, reveal numerous water-filled basal crevasses with highly transmissive connections to the bed. Some crevasses extend many tens of metres above the bed and together they hold a volume of water equivalent to at least a decimetre layer covering the bed. Our results demonstrate that the basal hydrologic system can extend high into the overlying ice mass, where basal crevasses increase water-storage capacity and could potentially modulate basal water pressure. Because basal crevasses can form under commonly observed glaciological conditions, our findings have implications for interpreting and modelling subglacial hydrologic processes and related sliding accelerations of glaciers and ice sheets. 相似文献
978.
979.
980.
尝试运用地域性技术与理论层面的研究来总结地域性对传统建筑文化、历史、环境、构造、空间的影响,并以南宁青秀山风景名胜旅游区西南入口大门建筑设计为案例,通过对其形式、功能、环境因子进行了分析,探寻了在当代景区大门设计过程中地域性表达的正确思路及方法. 相似文献