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101.
In-Hugh Choi Min-Yang Yang Won-Pyo Hong Tae-Sung Jung 《The International Journal of Advanced Manufacturing Technology》2005,25(3-4):325-333
Finish machining of a curved surface is often carried out by an NC system with curve interpolation in the field. This function, called a NURBS interpolation, adopts a feedrate optimizing strategy based on both the geometrical information of the curved path and dynamic properties such as the curvature of the curve, the allowable acceleration and the time constant. However, in the case of a finish cut using a ball-end mill, the curve interpolator needs to take the machining process into account for improved surface roughness, while reducing the polishing time. This surface roughness on high-speed machining is theoretically defined by the feed per tooth and the pickfeed at the given radius of the tool. In this study, the effect of low machinability at the bottom of a tool on surface roughness is also considered. A curve interpolation algorithm is proposed for generating particular feedrate commands that are able to control the roughness of a curved surface. The simulation of the machined surface by the proposed algorithm was carried out, and experimental results are presented. A feedrate scheme that depends on the inclination angle has important potential application in part finishes consistent with prescribed surface roughness. The results show that the proposed algorithm is potentially useful for roughness-controlled machining of curved surface products. 相似文献
102.
103.
Current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance, and over-estimate the erodible area by assuming it is not covered by roughness elements. We address these shortfalls with a new model which estimates aerodynamic roughness length (z0) using angular reflectance of a rough surface. The new model is proportional to the frontal area index, directional, and represents the geometric anisotropy of z0. The model explained most of the variation in two sets of wind tunnel measurements of aerodynamic roughness lengths (z0). Field estimates of z0 for varying wind directions were similar to predictions made by the new model. The model was used to estimate the erodible area exposed to abrasion by saltating particles. Vertically integrated horizontal flux (Fh) was calculated using the area not covered by non-erodible hemispheres; the approach embodied in dust emission models. Under the same model conditions, Fh estimated using the new model was up to 85% smaller than that using the conventional area not covered. These Fh simulations imply that wind erosion and dust emission models without geometric anisotropic sheltering of the surface, may considerably over-estimate Fh and hence the amount of dust emission. The new model provides a straightforward method to estimate aerodynamic resistance with the potential to improve the accuracy of wind erosion and dust emission models, a measure that can be retrieved using bi-directional reflectance models from angular satellite sensors, and an alternative to notoriously unreliable field estimates of z0 and their extrapolations across landform scales. 相似文献
104.
研究了通过磁控溅射方法制备高纯金属铀膜的可行性。采用X射线衍射(XRD)、俄歇电子能谱(AES)、扫描电镜(SEM)、表面轮廓仪分析了沉积在单晶硅或金基材上铀薄膜的微观结构、成分、界面结构及厚度、表面形貌和表面粗糙度。分析结果表明:磁控溅射制备的铀薄膜为纯金属态,氧含量和其它杂质含量均低于俄歇电子能谱仪的探测下限;溅射沉积的铀镀层与铝镀层之间存在界面作用,两者相互扩散并形成合金相,扩散层厚度约为10nm。铀薄膜厚度可达微米级,表面光洁,均方根(RMS)粗糙度优于15nm。 相似文献
105.
本文通过分析现有工程图纸扫描图象的识别与理解系统,提出了表面粗造度的自动识别算法,从而弥补了以往系统的不足,基于图形约束的表面粗造度整体识别算法符合技术人员的读图规律,处理速度快,可靠性高,该算法已在微机上调试成功。 相似文献
106.
针对激光设备非计划停机次数较多的问题,提出了一种基于遗传算法(Genetic Algorithm,GA)优化BP神经网络,建立激光设备故障预测模型的方法。利用激光设备的历史数据训练和调整预测算法,对激光设备采集的实时数据进行分析,按照算法模型预测故障发生概率,提前维护激光设备,减少非计划停机次数,提高激光设备的有效运行时间。通过测量各种情况下激光设备在切割零件时的数据变化,利用GA优化BP神经网络算法,建立激光设备故障预测模型。选取各种情形的切割零件的数据进行仿真预测和验证,以切割过程中各种情况的气体压力、激光功率、切割速度、加速度、各轴的温度和计算之后各轴的跟随误差作为模型输入,以粗糙度作为模型输出。结果表明,经过GA优化的模型在预测效果和预测精度上优于未经GA优化的模型,且模型经GA优化后,其粗糙度的预测精度和收敛速度得到了提升。 相似文献
107.
针对全球导航卫星系统反射信号的特性和我国北斗导航卫星系统反射信号在海面测高应用上的特点,证明了利用北斗倾斜地球同步轨道(IGSO)卫星反射信号对湖面和海平面进行岸基载波相位测高的可行性。实验分湖面和海面2组进行研究,用相位测高结果与实际测量结果对比的均方根误差(RMSE)描述测高结果的精度。在湖面岸基实验中,接收天线到湖面的相对高度为5.2m,IGSO7和IGSO10卫星相位测高结果的RMSE值达到厘米级,分别为3.23cm和4.98cm。在海面岸基实验中,海面的潮位高度差约2m,利用相位测高结果可以反演海面潮位。IGSO8卫星相位测高结果的RMSE为17.96cm,IGSO9卫星相位测高结果的RMSE为15.27cm,IGSO10卫星相位测高结果的RMSE为16.38cm。通过分析IGSO卫星仰角的变化,发现较大的卫星仰角变化率可以提高相位测高的结果的精度。 相似文献
108.
109.
Simone Dinarelli Giovanni Longo Antonio Francioso Luciana Mosca Marco Girasole 《International journal of molecular sciences》2022,23(17)
Erythrocytes’ aging and mechano-transduction are fundamental cellular pathways that determine the red blood cells’ (RBCs) behavior and function. The aging pattern can be influenced, in morphological, biochemical, and metabolic terms by the environmental conditions. In this paper, we studied the effect of a moderate mechanical stimulation applied through external shaking during the RBCs aging and revealed a strong acceleration of the aging pattern induced by such stimulation. Moreover, we evaluated the behavior of the main cellular effectors and resources in the presence of drugs (diamide) or of specific inhibitors of the mechano-transduction (probenecid, carbenoxolone, and glibenclamide). This approach provided the first evidence of a direct cross-correlation between aging and mechano-transduction and permitted an evaluation of the overall metabolic regulation and of the insurgence of specific morphological features, such as micro-vesicles and roughness alterations. Overall, for the first time the present data provided a schematic to understand the integration of distinct complex patterns in a comprehensive view of the cell and of its interactions with the environment. Mechano-transduction produces structural effects that are correlated with the stimulation and the strength of the environmental stimulation is paramount to effectively activate and trigger the biological cascades initiated by the mechano-sensing. 相似文献
110.