数控雕刻装夹方法探讨

数控雕刻技术是传统雕刻技术和现代数控技术结合的产物,在数控雕刻加工中,对传统机械加工装夹方法和新方法进行比较和分析,提高了工件加工效率和加工质量。     

汉字雕刻数控加工教学的设计与实践

随着数控加工实践教学条件的改善,创新教育与先进加工技术相结合的实践教学受到了越来越多的重视。本文以培养学生工程实践能力与创新能力为着眼点,以汉字雕刻数控加工为教学案例,制定了详细的教学内容、教学方法及评价方法,取得了良好的教学效果。     

数控加工仿真系统在数控教学和鉴定中的应用研究

计算机技术不断发展,数控加工仿真系统越来越完善,在教学中起到了非常大的作用。数控加工仿真系统安全、经济实用。教师在繁重的教学活动中得到了释放,能够集中精力帮助学生分析、解决实际问题,保证了教学质量,使教学效果得到了显著增强,并提高了鉴定考试的通过率。     

关于数控加工实验教学方法的研究

本文通过分析数控加工实验教学存在的问题,并提出有效的数控加工实验教学方法,致力于培养优秀的数控加工人才,满足现代化数控加工的需求.     

数控加工中的对刀方法

本文分析了数控机床的对刀原理,讨论了几种常用的对刀方法,并用典型的实例加以说明。     

VR技术在中职学校数控加工教学中的应用

随着虚拟技术的广泛普及,目前VR技术已经广泛应用在医护、教学以及机械工程制造等领域。基于职业院校数控加工专业的教学需求,VR技术已经逐渐成为理实一体、项目教学趋势下的一种重要教学手段。在数控加工教学中引进VR技术,不但会解决数控加工实训教学过程中可能遇到的设备型号不一致、教学安全等问题,而且还可以在很大程度上起到节约教学材料和保护环境等作用,极大地推动了数控加工专业的发展。     

数控高速加工技术综述

高速切削技术是机械制造业发展的必然趋势,其应用将大幅度地提高加工效率和加工质量。高速切削技术不仅涉及到高速切削加工工艺及高速切削杌理,而且包括高速切削所用的刀具、机床等诸多因素。本文着重介绍了高速切削各相关技术的研究动态,并对高速切削技术的应用前景进行了展望。     

数控加工仿真系统在数控教学中的应用探析

该文从探索数控加工仿真系统在数控教学中应用的角度,阐述了数控加工仿真系统软件在教学中的应用方法,并针对在数控教学应用中存在的问题提出了应对措施,体现了数控教学中的一种新的现代教育理念、教学方法和教学模式。     

基于Master CAM软件的文字雕刻加工技术

本文以实例作为导引,阐述了应用Master CAM软件实现平面文字雕刻的方法,给出了具体的操作步骤,为目前雕刻加工提供了一个参考案例.     

数控加工参数优化的探讨

在各种先进制造技术的发展中,作为主流的数控(NC)技术在快速发展过程中,出现了传统切削参数的选择不能适应提高生产率、降低生产成本、提高设备利用率的问题。如何运用现代切削理论、进行数学建模和模型分析方法寻求切削参数的最优组合,是切削参数选择的一个重要方向,本文对数控加工参数优化方法进行了探讨,希望给人们一点启示。     

数控机床工件坐标系的设定

因为在加工过程中,工件坐标系与机床坐标不重合,从而进行工件坐标系的设定.本文阐述了数控车床和数控加工中心工件坐标系的各种设定方法.     

基于图像数据的鞋帮缝制数控代码生成

针对制鞋行业中鞋帮缝制自动化水平不高的问题,提出了一种实现由图像格式到图形格式转化,再由图形格式文件生成数控代码的方法。该方法利用摄像机拍摄鞋帮面图像,经图像处理且运用矢量化算法可实现图像到图形的转换,形成的图形文件经过轮廓偏置处理及后置处理之后生成NC代码,并给出了一个应用实例。     

基于非对称逆布局表示的图像周长计算方法

The non-symmetry anti-packing image representation （NAIR） uses a sequence of the instances of some predefined prototypes to represent an image. While significantly reducing the instances required to represent an image in contrary to the quadtree and the linear quadtree, however, NAIR has lost the explicit space relationship among these instances and hence made some geometric operations such as perimeter computation hard to be implemented. In this paper, longitude and latitude grid （L^2G）, a data structure which can restore lost space relationship from the NAIR is first presented, and then a novel algorithm to compute the perimeters of the images represented by the NAIR is presented. The experimental results show that the new algorithm has saved at least 90% of the running time comparing with that based on the quadtree.     

Deadline-aware network coding for video on demand service over P2P networks

INTRODUCTION With the widespread deployment of broadband access, Video-on-Demand (VoD) streaming on the Internet has received increasing attention recently. In VoD service, video streams are delivered to asyn- chronous users with low delay and VCR-like opera- tion support (e.g., pause, fast-forward, and rewind). However, streaming to a large population of clients is very challenging due to the limited server capacity and little deployment of IP multicast in today’s Internet (Quinn a…     

Bayesian networks modeling for thermal error of numerical control machine tools

The interaction between the heat source location, its intensity, thermal expansion coefficient, the machine system configuration and the running environment creates complex thermal behavior of a machine tool, and also makes thermal error prediction difficult. To address this issue, a novel prediction method for machine tool thermal error based on Bayesian networks （BNs） was presented. The method described causal relationships of factors inducing thermal deformation by graph theory and. estimated the thermal error by Bayesian statistical techniques. Due to the effective combination of domain knowledge and sampled data, the BN method could adapt to the change of running state of machine, and obtain satisfactory prediction accuracy. Experiments on spindle thermal deformation were conducted to evaluate the modeling performance. Experimental results indicate that the BN method performs far better than the least squares （LS） analysis in terms of modeling estimation accuracy.     

Graphic processing unit-accelerated mutual information-based 3D image rigid registration

Mutual information (MI)-based image registration is effective in registering medical images, but it is computationally expensive. This paper accelerates MI-based image registration by dividing computation of mutual information into spatial transformation and histogram-based calculation, and performing 3D spatial transformation and trilinear interpolation on graphic processing unit (GPU). The 3D floating image is downloaded to GPU as flat 3D texture, and then fetched and interpolated for each new voxel location in fragment shader. The transformed results are rendered to textures by using frame buffer object (FBO) extension, and then read to the main memory used for the remaining computation on CPU. Experimental results show that GPU-accelerated method can achieve speedup about an order of magnitude with better registration result compared with the software implementation on a single-core CPU.     

Expression of bone morphogenetic protein 2, 4, and related components of the BMP signaling pathway in the mouse uterus during the estrous cycle

The objective was to investigate the expression of bone morphogenetic protein (BMP) family members in the mouse uterus during the estrous cycle by real-time polymerase chain reaction (PCR) and immunohistochemistry. Uterine samples from Swiss ICR mice were collected and dissected free of surrounding tissue. One uterine horn was snap frozen in liquid nitrogen immediately after collection and stored at −80 °C for RNA extraction, and the other was fixed in 40 mg/ml paraformaldehyde at room temperature for immunolocalization of BMP2 protein. Real-time PCR analysis showed that the expression level of Bmp2 was significantly higher at proestrus than at estrus and metestrus (P<0.05). The relative abundance of Bmp4 exhibited significant fluctuations, but there were no statistically significant differences between the expression levels of Bmp2 and Bmp4 (P>0.05). The expression levels of Bmpr1a and Bmpr2 remained unchanged during estrous cycles. However, the level of Bmpr1b mRNA decreased significantly at estrus (P<0.05), increasing subsequently at metestrus. Furthermore, the level of Bmpr1b mRNA was significantly lower than those of Bmpr1a and Bmpr2 mRNA at the corresponding stages (P<0.05). All three receptor-regulated Smads (R-Smads) detected were differentially expressed in the mouse uterus and the expression levels of Smad1 and Smad5 were significantly higher than that of Smad8 (P<0.05). In addition, the expression level of Smad4 did not change substantially throughout the estrous cycle. Immunohistochemical experiments revealed that BMP2 protein was differentially expressed and localized mainly in the uterine luminal and glandular epithelial cells throughout the estrous cycle. In conclusion, our results provide information about the variation in the mRNA levels of Bmp2 and Bmp4 and related components of the BMP signaling pathway. The data provide quantitative and useful information about the roles of endometrial BMP proposed and demonstrated by others, such as the degradation and remodeling of the endometrium.     

意境余论

意境不仅是情景交融,而且要有言外之意、象外之象。而象外之象与言外之意有层次上的差异。言外之意体现意象之间的虚实关系,而象外之象是意象内部的虚实关系建立之后的结果,唐代诗歌的代表作是意境的完美体现。     

Low-leakage diode-triggered silicon controlled rectifier for electrostatic discharge protection in 0.18-μm CMOS process

A diode-triggered silicon controlled rectifier （DTSCR） is being developed as an electrostatic discharge （ESD） protection device for low voltage applications. However, DTSCR leaks high current during normal operation due to the Darlington effect of the triggering-assist diode string. In this study, two types of diode string triggered SCRs are designed for low leakage consideration; the modified diode string and composite polysilicon diode string triggered SCRs （MDTSCR ＆ PDTSCR）. Compared with the conventional DTSCR （CDTSCR）, the MDTSCR has a much lower substrate leakage current with a relatively large silicon cost, and the PDTSCR has a much lower substrate leakage current with similar area and shows good leakage performance at a high temperature. Other DTSCR ESD properties are also investigated, especially regarding their layout, triggering voltage and failure current.