虚拟数控车削系统中碰撞检测问题的研究

碰撞检测问题是虚拟数控车削系统的不可或缺的部分,有效、精确的碰撞检测对提高数控环境的真实性、增强虚拟环境的沉浸感有着非常重要的意义．碰撞检测问题就是测试物体之间是否存在相交的问题．采用合理的空间分割系统和层次包围盒是减少所需测试的多边形数目、提高碰撞检测的速度的有效方法．实验证明,采用基于空间分割方法的八叉树算法有效地提高了检测的速度,保证了虚拟动态加工环境中碰撞检测的实时性．     

关节型机器人虚拟安全空间研究

为提高工业机器人安全性,分析和研究了六轴关节式机器人Denavit-Hartenberg(D-H)模型,针对关节式机器人的安全问题提出了相应的保护策略.着重介绍了笛卡尔坐标系下虚拟安全空间的设置和表示方法,并提出了改进的碰撞测试算法.该方法以AABB包围盒方法为基础分离不可能碰撞物体,利用虚拟安全空间特点提出了在AABB方法不能判别区域进行狭义测试的方法,能够满足机器人安全空间检测的精度和快速性要求.最后介绍了应用该方法的安全控制器的设计与实现.     

交互虚拟装配仿真过程中物体间间隙动态计算方法

提出一种支持实时交互虚拟装配操作中物体间最小间隙的快速计算方法,该方法使用基于层次包围盒模型的最小距离计算快速定位场景中模型间距离最小的一个或一组包围盒,进而确定模型距离最近的目标多边形组群,最终计算最小间隙数值和位置.该方法优点为能够借助虚拟装配系统中动态碰撞检测功能以及并行计算体系完成最小间隙计算.随后将该计算方法集成到DPVAE（Distributed Parallel Virtual Assembly Environment）虚拟装配软件系统,并以某型轿车的底盘装配中间隙动态计算和显示为例进行应用验证.结果表明,该方法能够支持交互虚拟装配仿真中的间隙动态测量与显示.     

一种适用于地理信息系统的封闭图形拾取算法

为了解决传统图形拾取算法在应用于地理信息系统时出现的一些问题，本文以射线定理为指导思想，提出了一种用于封闭图形拾取的改进算法，并结合具体环境对该算法进行了简化。     

虚拟设计中碰撞检测技术的研究

针对目前虚拟设计中碰撞检测系统复杂、速率和精度达不到理想要求的现状,提出一种两阶段碰撞检测算法。该方法粗测阶段采用AABB包围盒进行相交测试,剔除完全不相交的目标物体;精测阶段采用空间投影技术结合z缓存算法对上一步结果的潜在性相交目标进一步测试,获得物体碰撞数据信息,最终完成目标物体的碰撞检测。实验结果表明,该算法检测效率优于传统包围体碰撞检测算法。该技术改进后可实现更精确的碰撞检测。     

基于面片模型的人机交互装配关键技术研究

针对现有的虚拟装配系统大部分是基于实体模型,其计算量大、渲染慢、装配速度慢并且难以处理来自不同CAD系统模型的问题,提出了基于面片模型的人机交互快速装配方法.利用面片所包含的几何信息通过边界表示法重构零部件装配所需的几何信息和空间位姿信息,给出了基于面片模型的装配约束定义.通过人机交互技术将复杂的约束组分解为多个单约束进行求解,实现了约束的快速、准确的求解;按照旋转矩阵和平移矩阵对零部件的空间位姿进行变化,实现装配;最后基于HOOPS三维图形数据平台开发了虚拟装配系统.实践证明,该方法可以有效地减少计算量、提高装配速度、实现协同装配.     

虚拟装配技术在液力变矩器设计开发中的应用

分析了虚拟装配技术的基本思想和设计流程,提出了在轿车液力变矩器设计开发中实施虚拟装配的基础环境以及具体的实施方法和途径,完成对液力变矩器总体设计进程的控制并进行液力变矩器模型的定义与分析．     

钢桥塔的点云虚拟装配及其整体线形控制方法

针对钢桥塔的装配施工中，传统的人工预装配过程耗时耗力、效率低下且难以对实际装配过程中的整体线形进行调控分析等问题，建立了基于点云的高精度曲线钢桥塔整体虚拟装配系统方法，降低钢桥塔节段制作误差、自重和温度等受力变形偏差和实际装配过程误差对桥塔整体线形的影响．首先，开展基于节段点云模型的曲线钢桥塔整体虚拟装配，以降低节段制作误差的影响．通过三维激光扫描仪优化扫描方案对各钢节段进行扫描，获取钢节段点云数据并进行点云预处理、参数化建模．基于各节段参数化点云模型，提出了利用RBF神经网络进行轴线预测的曲线钢桥塔节段三点空间定位方法，对钢桥塔节段进行虚拟装配．然后，结合某桥上塔柱的实际工程案例，通过逆向叠加桥塔自重和温度的施工变形，消除施工受力变形．针对实际施工过程中已产生的节段装配误差，利用“施工控制”的思想，通过对其后续节段装配控制点坐标的调整，逐步降低前期节段装配误差对整体线形的影响，进一步提高了曲线钢桥塔的整体装配精度．最后，对建成的花篮形上塔柱进行整体扫描并与设计模型进行了对比，验证了上述系统方法对提高曲线钢桥塔实际装配施工精度的积极作用，为类似复杂钢结构的装配施工提供了技术参考．     

基于蚁群算法的集装箱装载问题

探讨了蚁群算法在复杂集装箱装载问题中的应用．利用蚁群算法对解空间的搜索能力，结合二维链表结构的方法，对布局空间依次分割完成不同大小的三维矩形物体的装载，并给出了有效的编码形式和解码算法．通过对文献中提供的数据进行测试和比较说明本算法是有效的．     

智能化虚拟人感知模型的一种探索性研究

在智能化虚拟人自主行为模型的研究过程中，感知功能是建立虚拟人行为模型的基础．如何能够构建出准确模拟人类感知功能的感知模型是其研究的难点．本文在介绍三维虚拟场詈的建立和虚拟人模型的创建的基础上，着重讨论了虚拟人感知模型的一种实现方法．该方法通过建立空间查询表，对创建的虚拟场景信息进行有效地管理与查询，虚拟人实时对空间查询表进行查询，并引入基于AABB包围盒的碰撞检测算法对是否存在障碍物进行判断，引导自身进行下一步的动作，初步实现了对环境信息的感知．     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.