PERFORMANCE ANALYSIS AND KINEMATIC DESIGN OF PURE TRANSLATIONAL PARALLEL MECHANISM WITH VERTICAL GUIDE-WAYS

Performance analysis and kinematic design of the 3-PUU pure translational parallel mechanism with vertical guide-ways are investigated. Two novel performance indices, the critical slider stroke and the main section area of workspace, are defined; The expressions of two other indices, i.e. the global dexterity and global force transfer ratio are revised based on the main section of workspace. Using these indices, performance changes versus the varieties of dimensional parameters of mechanism are investigated in detail and the graphic descriptions of change tendencies of the performance indices are illustrated. By means of these obtained graphic descriptions, kinematic parameters for the 3-PUU pure translational parallel mechanism with better characteristics can be directly acquired.

Type Synthesis Method for the Translational Decoupled Parallel Mechanism Based on Screw Theory

Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control system of the parallel mechanism. And recently,the research on the decoupled parallel mechanism becomes one of the research hot points in the mechanism fields. In this paper,a type synthesis method for the translational decoupled parallel mechanism( TDPM) is proposed based on the screw theory. To achieve the decoupling characteristics of the translational parallel mechanism,the translational decoupled criterion for type synthesis of the branches are presented in this paper. According to this criterion and the realization conditions of rotational degree of freedom of the mechanism proposed former,a large number of branches for the TDPM are obtained. Taking the three degrees of freedom( DOFs) TDPM as an example,the process of type synthesis is discussed in detail. Using this proposed type synthesis method,a serial of translational decoupled parallel mechanisms, including but not limited to all the existing typical 3-DOF TDPMs, are obtained, which identifies the correctness and effective of the method. The contents of this paper provide a reference and possess significant theoretical meanings for the synthesis and development of the novel decoupled parallel mechanisms.

Workspace of Translation 3-UPU Parallel Manipulators

To determine workspace and relationship between the workspace and geometry of parallel manipulator is important for optimum design of parallel manipulators. In this paper, the workspace and the relationship between the workspace and the geometry of 3-UPU parallel manipulators with pure translation are investigated. Geometric and non-geometric constraints are defined and taken account of in determining the workspace of the translation 3-UPU manipulators. A direct average condition number is used as the global performance index of the workspace. This research shows that there exists an optimal value of the direct average condition number favorable for a good design of parallel mechanisms. The results presented in this paper are useful for the optimum design of 3-UPU parallel manipulators.

Topology Search of 3-DOF Translational Parallel Manipulators with Three Identical Limbs for Leg Mechanisms

Three-degree of freedom（3-DOF） translational parallel manipulators（TPMs） have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are created mainly on designers＇ intuition, empirical knowledge, or associative reasoning and the topology synthesis researches of 3-DOF TPMs are still limited. In order to find out the atlas of designs for 3-DOF TPMs, a topology search is presented for enumeration of 3-DOF TPMs whose limbs can be modeled as 5-DOF serial chains. The proposed topology search of 3-DOF TPMs is aimed to overcome the sensitivities of the design solution of a 3-DOF TPM for a LARM leg mechanism in a biped robot. The topology search, which is based on the concept of generation and specialization in graph theory, is reported as a step-by-step procedure with desired specifications, principle and rules of generalization, design requirements and constraints, and algorithm of number synthesis. In order to obtain new feasible designs for a chosen example and to limit the search domain under general considerations, one topological generalized kinematic chain is chosen to be specialized. An atlas of new feasible designs is obtained and analyzed for a specific solution as leg mechanisms. The proposed methodology provides a topology search for 3-DOF TPMs for leg mechanisms, but it can be also expanded for other applications and tasks.

Type Synthesis of Fully Decoupled Three Translational Parallel Mechanism with Closed-Loop Units and High Stifness

In order to solve the problem of weak stifness of the existing fully decoupled parallel mechanism, a new synthesis method of fully decoupled three translational (3T) parallel mechanisms (PMs) with closed-loop units and high stifness is proposed based on screw theory. Firstly, a new criterion for the full decoupled of PMs is presented that the reciprocal product of the transmission wrench screw matrix and the output twist screw matrix of PMs is a diagonal matrix, and all elements on the main diagonal are nonzero constants. The forms of the transmission wrench screws are determined by the criterion. Secondly, the forms of the actuated and unactuated screws can be obtained according to their relationships with the transmission wrench screws. The basic decoupled limbs are generated by combination of the above actuated and unactuated screws. Finally, a closed-loop units construction method is investigated to apply the decoupled mechanisms in a better way on the high stifness occasion. The closed-loop units are constructed in the basic decoupled limbs to generate a high-stifness fully decoupled 3T PM. Kinematic and stifness analyses show that the Jacobian matrix is a diagonal matrix, and the stifness is obviously higher than that of the coupling mechanisms, which verifes the correctness of the proposed synthesis method. The mechanism synthesized by this method has a good application prospect in vehicle durability test platform.

Improving Parallel Corpus Quality for Chinese-Vietnamese Statistical Machine Translation

The performance of a machine translation system heavily depends on the quantity and quality of the bilingual language resource. However,getting a parallel corpus,which has a large scale and is of high quality,is a very difficult task especially for low resource languages such as Chinese-Vietnamese. Fortunately,multilingual user generated contents（ UGC）,such as bilingual movie subtitles,provide us access to automatic construction of the parallel corpus. Although the amount of UGC parallel corpora can be considerable,the original corpus is not suitable for statistical machine translation（ SMT） systems. The corpus may contain translation errors,sentence mismatching,free translations,etc. To improve the quality of the bilingual corpus for SMT systems,three filtering methods are proposed： sentence length difference,the semantic of sentence pairs,and machine learning. Experiments are conducted on the Chinese to Vietnamese translation corpus.Experimental results demonstrate that all the three methods effectively improve the corpus quality,and the machine translation performance（ BLEU score） can be improved by 1. 32.

Optimization Parameter of Transformation of Parallel Translation for Ship Pitch Simulation

The transformation of parallel translation can improve the smoothness of discrete series sometimes. In this paper, for ship pitch, a method to modify the system error is proposed via the transformation of parallel translation, which can give the optimize parameters using the Method of Minimum Squares. The series in the method can fit white exponential law better, and then be applied in GM (1,1) very well. The numerical experiments imply that the method is practical, which make the ship pitch system model more accurate than GM ( 1,1 ).

Korean Morphological Analysis for Korean-Vietnamese Statistical Machine Translation

This paper describes the experiments with Korean-to-Vietnamese statistical machine translation(SMT). The fact that Korean is a morphologically complex language that does not have clear optimal word boundaries causes a major problem of translating into or from Korean. To solve this problem, we present a method to conduct a Korean morphological analysis by using a pre-analyzed partial word-phrase dictionary(PWD).Besides, we build a Korean-Vietnamese parallel corpus for training SMT models by collecting text from multilingual magazines. Then, we apply such a morphology analysis to Korean sentences that are included in the collected parallel corpus as a preprocessing step. The experiment results demonstrate a remarkable improvement of Korean-to-Vietnamese translation quality in term of bi-lingual evaluation understudy(BLEU).

A parallel two-level finite element method for the Navier-Stokes equations

Based on domain decomposition, a parallel two-level finite element method for the stationary Navier-Stokes equations is proposed and analyzed. The basic idea of the method is first to solve the Navier-Stokes equations on a coarse grid, then to solve the resulted residual equations in parallel on a fine grid. This method has low communication complexity. It can be implemented easily. By local a priori error estimate for finite element discretizations, error bounds of the approximate solution are derived. Numerical results are also given to illustrate the high efficiency of the method.

A Corpus-based Study of the Chinese Translation for the Conditional Clause Pattems in Intemational Legal Instruments

The Chinese translation for international legal instruments is an indispensable part in national political and economic fields. Apart from legal terminology, the syntactical features of international legal instruments also deserve study. They are easy to be seen in the use of some typical sentence patterns, such as long and complex sentence structures, passive voice and provisos or conditional clauses. Based on the parallel English-Chinese international conventions, this paper mainly evaluates the current Chinese translation and summarizes the use frequency and translation strategies for the conditional clause patterns. From the perspective of memetics, sentence patterns can be units of imitation, and the summary of and comments on them and their Chinese translation will promote the transmission across culture and help a legal translator improve his/her expertise, which will eventually be good for successful cooperation in international business.

单回路空间两平移并联机构拓扑设计与尺度优化

针对狭小空间内工作机器的需求,根据基于方位特征集的并联机构拓扑设计理论和方法,设计了12个移动副驱动的单回路空间两平移并联机构,并对其进行了自由度计算;对其中8个机构进行运动学建模,分别推导出其一元八次方程(封闭解)和符号式反解,并进行数值算例验证;运用差分进化算法以限定尺度约束下的可达工作空间最大为优化目标,分别对其中8个机构进行尺度优化,并求得其对应的可达工作空间,对比分析后优选出2个具有最大可达工作空间的两平移并联机构;为刚度分析、动力学分析及结构设计奠定了基础。

一种灵活高效的增量式Web平行语料抽取方法

从Web中抽取平行语料对于机器翻译和其他多语语言处理任务来说非常重要,由此提出了一种从Web中灵活高效地增量抽取平行语料的方法,通过持续地对Common Crawl的Web抓取存档进行下载、扫描和分析统计,增量更新域名下的语言文本长度统计数据。对于任意给定的感兴趣目标语言对,抽取方法基于域名下的语言文本长度统计数据确定抓取网站入口,并根据目标语言进行定向抓取,忽略多语域名和目标语言外的链接。此外还提出了一种在多语域名内基于语义相似性进行全局对齐的新的句子对齐方法。实验表明,增量抽取能够持续不断地获得新的平行语料,根据指定的语言对进行抽取,可以灵活地获得感兴趣的目标语言对平行语料;新的对齐方法在对齐效率上明显优于全局方法,且能完成局部方法无法完成的对齐;在6个语言方向中,抽取到的平行语料在4个中低资源语言方向的质量优于现有Web开源平行语料,在2个高资源语言方向的质量接近现有最好的Web开源平行语料。

基于情感语义增强编解码的神经机器翻译方法

针对目前神经机器翻译模型仅依赖平行语料训练而无法充分挖掘深层语言知识的问题,提出一种基于情感语义增强编解码的神经机器翻译方法,旨在通过引入额外的情感语义,提高模型对语言深层次信息的理解能力。首先,利用word2vec技术获取语料中所有单词的词嵌入,将其输入到一个融合模型中进行训练。该融合模型结合了基于GRU和文档嵌入的机制,以获取单词级别和文档级别的情感语义表征;其次,在情感融合阶段,采用加权公式将单词级别和文档级别的情感语义有机地融合,形成更为综合的情感语义表征;最后,将此表征与上下文语义表征按位相加,以全面引入情感信息,并将其作为输入传递到机器翻译模型的编码器和解码器中。在多个基准数据集上的实验显示,相较于传统的Transformer模型,该方法在IWSLT数据集上性能显著提升,BLEU值增加1.3至1.62。在WMT数据集上也取得良好性能,证实了融合情感语义在机器翻译中的有效性。

一种新型3-RRPU并联机构的运动学及鲁棒控制研究

针对现有的三平移并联机构大多正解不唯一、较难实现精确稳定运动控制的问题,提出了一种新的3-RRPU型三平移并联机构,同时研究了机构的运动学、动力学及轨迹跟踪控制方法。首先,运用螺旋理论分析了该机构三平移的原理,进行了驱动输入的选取与论证,对机构平台奇异性、驱动奇异性和支链奇异性进行了分析;其次,运用运动学理论建立了运动学模型,推导了位置正、逆解析解;再次,运用拉格朗日动力学理论建立了机构操作空间的刚体动力学模型;最后,提出了一种基于非线性反馈解耦的自适应滑模轨迹跟踪控制方法,以证明其控制稳定性,并基于动力学模型对空间轨迹跟踪精度和控制力矩进行了仿真分析。研究结果表明:3-RRPU并联机构的位置正解在一般位形下具有唯一性,机构的平台奇异位形和驱动奇异位形少且无支链奇异。该轨迹控制方法可使机构在载荷20 kg、速度0.18 m/s、加速度0.12 m/s 2下,实现0.002 m以内的高精度复杂轨迹跟踪;基于Sigmoid函数的轨迹控制方法还能有效削弱控制力矩的抖振,为实现工业领域高速、高精度、高性能的三平移运动提供了新方法。

双语平行思政语料库在翻译教学中的应用探索

翻译是一种跨文化的语言交际活动,翻译教学是一个跨语言跨文化的育人行为。如何在翻译课程中实现政治认同、国家意识、文化自信等思想政治教育与翻译知识和技能传授的有机融合,是近年来学界较为关注的话题。本文以《习近平谈治国理政》多语种数据库综合平台为例,探讨如何将双语平行思政语料库应用于翻译教学实践。从思政内容教学、词汇翻译教学、翻译技能教学三个方面分析如何在培养学生翻译技能的同时帮助他们提升民族文化自信,培养传播中华优秀传统文化的能力,寓价值观引导于知识传授和能力培养之中,使翻译教学与思政教学同向同行,为深化大学英语翻译教学改革提供借鉴。

一种具有弯曲平移特性的2T1R并联机构设计与位置分析

基于方位特征(Position and Orientation Characteristic,POC)集方程的并联机构设计理论,设计了一种具有符号式位置正解并且存在部分运动解耦特性的两平移一转动(2T1R)并联机构。对该机构进行了方位特征集、自由度以及耦合度等拓扑性能的分析;基于拓扑结构运动学建模原理,求解了该机构的解析式位置正解、解析式逆解,并通过位置逆解进行了验算,证明了该机构具有弯曲平移的运动特性。传统的只有平直运动的2T1R并联机构要实现曲线平移,需要将多个平直移动通过复杂算法进行曲线拟合,而该机构只需通过一维弯曲平移即可实现,极大降低了机构的复杂程度及控制算法的难度。

Error analysis and optimization of a 3-degree of freedom translational Parallel Kinematic Machine

In this paper, error modeling and analysis of a typical 3-degree of freedom translational Parallel Kine- matic Machine is presented. This mechanism provides translational motion along the Cartesian X-, Y- and Z- axes. It consists of three limbs each having an arm and forearm with prismatic-revolute-revolute-revolute joints. The moving or tool platform maintains same orientation in the entire workspace due to its joint arrangement. From inverse kinematics, the joint angles for a given position of tool platform necessary for the error modeling and analysis are obtained. Error modeling is done based on the differentiation of the inverse kinematic equations. Variation of pose errors along X, Y and Z directions for a set of dimensions of the parallel kinematic machine is presented. A non-dimensional performance index, namely, global error transformation index is used to study the influence of dimensions and its corresponding global maximum pose error is reported. An attempt is made to find the optimal dimensions of the Parallel Kinematic Machine using Genetic Algorithms in MATLAB. The methodology presented and the results obtained are useful for predicting the performance capability of the Parallel Kinematic Machine under study.

三平移4PPa-2Pa并联机构运动学分析与优化设计

设计一种三平移4PPa-2Pa并联机构,根据方位特征集分析机构自由度,建立运动学方程并推导得到逆解,通过数值算例对运动学正逆解进行验证,采用极坐标搜索法得到机构的工作空间,建立能够适应不同给定任务工作空间的包含约束的数学模型,分别以长方体和球体的任务工作空间为例,以工作空间体积V最小化作为优化目标函数,通过遗传算法优化得到满足给定任务工作空间下所对应的结构参数优化解。研究结果表明:优化后的工作空间恰好和给定的任务工作空间相切,工作空间利用率显著提升,通过算例验证了该模型的正确性,具有一定的应用价值。

功能对等理论视角下外宣文本排比修辞英译探究

该文基于功能对等理论,探讨外宣文本排比修辞的英译策略。首先,概述了功能对等理论,强调其追求多维度对等,而非单纯的形式对应;其次,对汉英排比修辞的定义、汉英排比修辞的分类及汉英排比修辞的差异进行了阐述,并分析外宣文本排比修辞的语言单位分类及其英译处理,包括直译与意译、增译与省译、重组与转换等翻译方法。总结指出,在翻译外宣文本排比修辞时,译者应依据语境,注重原文内容与意义的传达,灵活运用多种翻译技巧,以实现忠实性与可读性的统一。同时,遵循“内容优先”原则,促进中国文化的国际传播,进而提升国家形象与软实力。

基于语料库的纳西族英雄史诗《黑白之战》译本风格对比研究

本研究基于自建的《黑白之战》英汉平行语料库,借助Python的自然语言处理包,从语言特征(类符/形符比,平均词长,平均句长,词汇密度)对孙兴文译本和涂沙丽译本的翻译风格进行对比。研究发现,涂译本的类符/形符比,平均词长,词汇密度均高于孙译本,但平均句长小于孙译本,涂译异化程度更高,孙译则更加归化。