用端铣刀数控加工自由曲面的刀具干涉检测

针对用端铣刀在自由曲面上进行3轴数控加工，提出了一种系统的刀具干涉检测方法．加工自由曲面时，刀具干涉可能出现在包括刀具驱动面在内的刀具周围任何区域．提出用检测线代替检测面来寻找加工自由曲面时可能出现刀具干涉的方法，可极大地加快检测过程，改善加工精度和可靠性，而且有利于产品的几何设计和指导影响加工效率的刀具选择．研究表明，所提的方法和算法合理有效．     

组合曲面加工无干涉刀具路径的产生

根据过渡曲面的特性及目前加工方法的缺陷提出了采用成形刀沿纵向加工等半径圆弧过渡曲面的新方法，并给出了刀具轨迹及干涉检查的算法．此方法大大提高了加工精度和效率．     

基于UG平台的结晶器搅拌桨CAD/CAM的集成

结晶器搅拌桨采用船用螺旋桨结构，桨叶为复杂曲面．应用Delphi7开发了搅拌桨叶面型值点计算模块，并以CAD／CAM集成系统UG软件为平台，应用其二次开发工具OPEN GRIP建立了搅拌桨的三维实体模型；在分析搅拌桨数控加工特点的基础上，研究了搅拌桨多轴数控铣削加工工艺．利用UG的CAM模块完成搅拌桨的数控编程，实现了搅拌桨CAD／CAM集成．将研究结果应用于搅拌桨生产，搅拌桨的设计一制造周期缩短了70％～80％；几何精度检验结果表明，搅拌桨加工精度显著提高，搅拌桨导边与随边几何误差小于0．05mm；经静平衡检验，不平衡量小于搅拌桨质量的0．05％．     

空间等半径过渡曲面成形刀纵向加工的算法

根据过渡曲面的特性及目前加工方法的缺陷提出了采用成形刀沿纵向加工等半径圆弧过渡曲面的新方法，并给出了刀具轨迹及干涉检查的算法，此方法大大提高了加工精度和效率。     

三阶切触法加工自由曲面无干涉刀位规划

基于三阶切触法刀具包络曲面的局部重建原理,提出了刀具可行空间约束下平底刀加工自由曲面的无干涉刀位规划方法. 通过工件表面到刀具轴线的距离来分析刀具与工件的局部和整体干涉,并解析求解二阶切触刀具姿态,进而建立二阶切触无干涉刀具可行空间. 在此基础上,通过计算设计曲面与包络曲面沿进给垂直方向的诱导法曲率导数,在可行空间内优化搜索最接近三阶切触的刀位. 拉伸曲面和螺旋曲面的刀位规划和切削带宽的计算结果表明,该方法可以有效地避免刀具干涉,并显著提高加工效率.     

多轴机床加工自由曲面的干涉避免与刀轴优化

针对平底刀加工复杂自由曲面，从刀具与曲面的干涉特征分析入手，提出了“无刀底干涉→无曲率、刀杆干涉”的刀具干涉避免策略，并阐述了相应的刀轴矢量调整方法．实例分析表明，算法的应用不仅能快速、有效地解决平底刀加工自由曲面的干涉问题，而且也能促进自由曲面加工效率的进一步提高．     

用密切曲率法加工自由曲面及其刀位轨迹的排列

采用中凹的盘形铣刀取代传统的球头铣刀，在每一行程中让刀具运动形成的包络面与被加工表面之间在垂直于进给方向的法截面中达到三阶密切，从而大幅度减少了走刀次数，增加了切削宽度，提高了加工效率．文中给出了边界不受限制的单张曲面的刀位及刀具轨迹的计算方法．     

双圆弧谐波刚轮刮齿加工原理及刀具设计

为提高谐波齿轮的加工精度和效率,提出一种适应双圆弧谐波刚轮的刮齿加工原理和刀具设计方法 .根据包络理论求解谐波刚轮共轭齿廓,并采用最小二乘法拟合;通过构建刮齿加工坐标系和前刀面坐标系求解刮齿刀具共轭面和前刀面模型,并用NURBS曲面拟合;根据牛顿迭代法求解前刀面与共轭面交点获取切削刃数据,导入CAD软件建立刮齿刀具数学...     

基于分层递阶模型的多轴加工过程分析与运动度量规划

针对复杂曲面多轴数控加工过程的复杂性,提出了一种面向多轴加工的分层递阶构造模型,即利用铣削过程的几何、运动学与力学模型综合分析多轴加工规律.切削工件几何模型采用深度元素法,通过分析刀具与工件接触区域,得到刀具在不同瞬时的轴向范围及沿轴向各微元的切入角和切出角,转换为铣削力模型所需的几何信息,同时运动学模型又为几何与力学模型提供计算依据.采用序列二次规划法优化进给速度,使机床工作在多个约束条件的最大范围值内.五轴螺旋桨加工实验表明,在满足加工精度条件下,优化的进给速度使零件加工效率提高约20%.     

浅谈组合刀具及其应用

目前我国部分大型机械设备在采用传统工艺加工过程中存在加工精度低、加工效率低、装夹困难等缺陷,采用组合刀具可有效弥补上述缺陷。     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.