论偏置摆动从动件凸轮压力角的计算方法

在设计各种凸轮机构时,既要满足工艺要求,又要尽量改善受力状况,使机构的运动平稳可靠,这就要验算凸轮的最大压力角α_(max)。对于凸轮最大压力角α_(max)的求得,一般有三种方法:(1)作图法;(2)计算法;(3)查图表法.本文就织机上广泛使用的偏置摆动从动件的盘形开口凸轮为例,探索压力角的计算方法,并以常用的三种运动规律(简谐运动、椭圆比及正弦加速),求得凸轮行程中点处的压力角α,它同样适用于类似的引纬和打纬凸轮机构.以便在设计各种凸轮机构时,正确反映凸轮压力角的数值,供对比分析之用。     

按许用压力角确定摆杆盘形凸轮基本尺寸

基于平面凸轮机构与平面四杆机构运动和动力特性相似原理,导出摆动从动件盘形凸轮机构最大压力角作用位置与从动件运动规律的关系式。由关系式可知,最大压力角的位置仅与运动规律有关,与基本尺寸无关;最大压力角大小不仅与运动规律有关,而且与基本尺寸有关,在给定许用压力角的条件下,可确定凸轮基本尺寸,比其它方法简捷方便。     

打纬共轭凸轮机构的设计

提出一种适合打纬共轭凸轮机构的新型运动规律,建立的纬共轭凸轮廓线的坐标方程。利用三角函数运动规律的组合和主、回凸轮廓线的共轭特性,探讨打纬共轭凸轮机构的设计。推导出适合打纬共轭凸轮机构的双简谐运动规律的共轭凸轮廓线的坐标方程。研究表明,双简诸运动规律可用于设计打纬共轭凸轮机构,为设计高速织机凸轮机构奠定了理论基础。     

摆动从动件凸轮机构压力角规律的研究

论述了摆动从动件的四种常用运动规律对盘形凸轮压力角的影响,作出了压力角随凸轮转角变化规律的曲线;指出了在不同运动规律下,如何合理地确定凸轮与摆杆的相对转向,以使机构具有较高的传动效率;阐述了在基本尺寸不变的前提下有效降低压力角的根本原因;提出了等速运动规律下凸轮推程廓线上各点压力角的求法。对研究摆动从动件凸轮机构压力角和设计凸轮机构具有指导意义。     

单圆弧盘型凸轮机构特性的比较研究

提出了用高副低代的化归方法研究单圆弧对心直动滚子从动件盘型凸轮机构的特性．论证了化归后的机构瞬时速度、加速度和压力角与原机构等价，在此基础上讨论了原机构的运动特性．并以最大无量纲速度和加速度为标准，将凸轮机构从动件常用运动规律特性与该圆弧凸轮的从动件运动规律特性加以比较，指出其适用场合为中、高速轻载。     

平面三向织机打纬机构的运动规律和共轭凸轮设计

平面三向织物是由三组互成60°角的纱线交织而成。在织造过程中,经纱需作横向间歇运动,因此制织这种织物的织机应装有特殊的打纬机构。本文根据三向织机打纬机构的特殊要求,介绍了打纬机构的运动规律和共轭凸轮设计方法。制成的共轭凸轮经过实际使用,证明是可行和合理的。     

凸轮机构CAD与运动模拟

从工程实际出发，建立了以许用压力角为条件，通过求解凸轮基圆半径、偏距范围和滚子半径以及最大压力角及其出现位置，实现了16种从动件运动规律的凸轮机构计算机辅助设计，以及各种运动规律凸轮机构的运动模拟与仿真，即可作为工程设计所实用，也可作为教学辅助软件。     

平面凸轮廓线分析的一种数值计算方法

本文将拉格朗日五点数值微分公式应用于平面凸轮廓线分析,根据凸轮机构运动简图及凸轮廓线的极坐标值可直接计算从动件的位移、速度、加速度及压力角值.这样就解决了历来沿用的图解微分法存在的误差大的问题.这种方法适用于研究缺乏原始设计资料的凸轮机构(如国外进口机器中的凸轮机构),以及分析凸轮廓线尺寸误差对凸轮机构运动和压力角的影响.文中以滚子摆动从动件平面凸轮为例,其解题方法也适用于其它类型平面凸轮机构.文末附有数值计算实例.     

滚子从动件板形凸轮的设计

在精确制造或设计凸轮时,都要求用分析法。例如加工时需要知道凸轮轮廓坐标或刀具的中心坐标;强度计算或磨损计算时需要知道凸轮轮廓的曲率半径等。解决这个问题有些文献已经提出一些不同的方法。这里所提出的就是以凸轮压力角α和升角β为参数,推导系统设计公式的方法。为了计算方便还讨论了几根计算图线的设计问题。凸轮的设计步骤如下:(a)选定从动件的运动规律。(b)按最大压力角和图线(4)或(5)决定凸轮最小尺寸。(c)用公式(1)(2)(3)或(8)(9)计算凸轮理论轮廓坐标。如果滚子尺寸和刀具尺寸不同,还需用公式(6′)和(7′)继续计算。(d)如果需要考虑强度磨损或滚子半径用公式(13)计算凸轮轮廓的曲率半径。因为摆动从动件和移动从动件的凸轮在公式推导的方法上是一样的,所以仅对摆动从动件的凸轮公式推导作了详细的叙述。     

基于最优化方法的盘形凸轮最大压力角计算器的设计

凸轮压力角是凸轮机构位置的函数,影响其传力性能,过大会发生自锁。压力角传统求法复杂,利用凸轮最大压力角计算器,求解凸轮最大压力角简单易行,使凸轮机构在结构设计时,提前介入几何参数的选择变得简单、可行。     

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.     

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…     

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.     

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。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

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

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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     

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