AUTOMATIC DISPLACEMENT ANALYSIS OF PLANAR MECHANISMS WITH MATCHING BASIC KINEMATIC CHAINS METHOD

A simple, efficient, automatic and universal method to fulfill displacementanalysis of a great deal of mechanisms regenerated by Yan's mechanism creative theory has beendeveloped. For a regenerated mechanism, at first, the method identifies its type and structure andchanges it into a rigid structure by fixing the ground link and the input link. And then this rigidstructure is decomposed into a set of basic kinematic chains (BKCs). By matching the type of BKC,the displacement analysis equations can be set up, and all possible configurations, in whichpositions of all movable links are considered, can be given out.

Failure mechanism and influencing factors of cement sheath integrity under alternating pressure

The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-formation(CSF)system under alternating pressure is established based on the Mohr-Coulomb criterion and thick-walled cylinder theory,and it has been solved by MATLAB programming combining global optimization algorithm with Global Search.The failure mechanism of cement sheath integrity is investigated,by which it can be seen that the formation of interface debonding is mainly related to the plastic strain accumulation,and there is a risk of interface debonding under alternating pressure,once the cement sheath enters plasticity whether in shallow or deep well sections.The matching relationship between the mechanical parameters(elastic modulus and Poisson's ratio)of cement sheath and its integrity failure under alternating pressure in whole well sections is studied,by which it has been found there is a“critical range”in the Poisson's ratio of cement sheath.When the Poisson's ratio is below the“critical range”,there is a positive correlation between the yield internal pressure of cement sheath(SYP)and its elastic modulus.However,when the Poisson's ratio is above the“critical range”,there is a negative correlation.The elastic modulus of cement sheath is closely related to its Poisson's ratio,and restricts each other.Scientific and reasonable matching between mechanical parameters of cement sheath and CSF system under different working conditions can not only reduce the cost,but also protect the cement sheath integrity.

Farmer's Perception on Supply-Demand Matching of New Variety and Its Influence Factors

Using disordered multinomial logistic regression and multiple linear regression method,385 copies of questionnaires on farmer are analyzed to explore the relationship between peasant's psychological traits,peasant's cognition on seed technology and perception on supplydemand matching of new variety.Research results show that the vast majority of farmers think that current new variety is at high-level supplydemand balance and the oversupply status,and updating speed of new variety on the market is faster;the farmers preferring risk,seeking innovation and having strong learning and cognition ability may select high-level supply-demand matching state,and the farmers understanding the importance and difference of seed technology tend to choose high-level supply-demand matching situation;the farmers with strong learning and cognition ability can acknowledge the importance and difference of seed technology,while the farmers preferring risk can perceive the difference of seed technology;psychology seeking the innovation and learning and cognition ability affect the farmer's perception on supplydemand matching status of new variety via affecting the farmer's cognition on technical difference.

Reliability analysis of the velocity matching of coal cutting and caving in fully mechanized top-coal caving face

The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.

Mechanisms and experimental research of ion-matched waterflooding to enhance oil recovery in carbonate reservoirs: A case of Cretaceous limestone reservoirs in Halfaya Oilfield, Middle East

Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.

Crystallography of Zr poisoning of Al-Ti-B grain refinement using edge-to-edge matching model

The mechanism of zirconium poisoning on the grain-refining efficiency of an Al-Ti-B based grain refiner was studied. The experiment was conducted by melting Al-5Ti-1B and Al-3Zr master alloys together. The edge-to-edge matching model was used to investigate and compare the orientation relationships between the binary intermetallic compounds present in the Al-Ti-B-Zr system. The results show that the poisoning effect probably results from the combination of Al3 Zr with Al3 Ti and the decreased amount of Ti solute, for Al3 Ti particles have good crystallographic relationships with Al3 Zr. Totally six orientation relationships may present between them, while they play vital roles in grain refinement. TiB2 particles appear to remain unchanged because of a bit large misfit. Only one orientation relationship may present between them to prevent Al3 Zr phase from forming on the surface of TiB2, though TiB2 is agglomerated. The theoretical calculation agrees well with the experimental results. The edge-to-edge matching model is proved to be a useful tool for discovering the orientation relationships between phases.

On Model of Translation Beginners' Mechanism of Mental Translation

Translation process is a process of information processing, and also a process of translators' thinking activity. During the process of translation or bilingual communication, translators or bilingual users employ mental translation. To expound how beginners communicate or translate in the bilingual environment, the model of mechanism of mental translation, i.e. match-making mechanism of mental translation, is theoretically constructed.

Numerical investigations on performance improvement mechanism of a high-power vertical centrifugal pump with special emphasis on hydraulic component matching

The purpose of this paper is to investigate the performance improvement mechanism of a high power vertical centrifugal pump by using numerical calculations.Therefore,a comparative study of energy losses and internal flow characteristics in the original and optimized models was carried out with special attention to the hydraulic component matching.The optimized model(model B)was obtained by optimizing the vaned diffuser and volute based on the original model(model A),mainly the diffuser inlet diameter,diffuser inlet vane angle,volute channel inlet width and volute throat area were changed.Firstly,the comparative results on performance and energy losses of two models showed that the efficiency and head of model B was significantly increased under design and part-load conditions.It is mainly due to the dramatic reduction of energy loss PL in the diffuser and volute.Then,the comparisons of PL and flow patterns in the vaned diffuser showed that the matching optimization between the model B impeller outlet flow angle and diffuser inlet vane angle resulted in a better flow pattern in both the circumferential and axial directions of the diffuser,which leads to the PL3 reduction.The meridian velocity Vm of model B was significantly increased at diffuser inlet regions and resulted in improvements of flow patterns at diffuser middle and outlet regions as well as pressure expansion capacity.Finally,the comparisons of PL and flow characteristics in the volute showed that the turbulence loss reduction in the model B volute was due to the flow pattern improvement at diffuser outlet regions which provided better flow conditions at volute inlet regions.The matching optimization between the diffuser and volute significantly reduced the turbulence loss in volute sections 1–4 and enhanced the pressure expansion capacity in sections 8–10.

基于注意力与密集重参数化的目标检测算法

针对目标检测任务中背景复杂、目标尺寸差异大等因素导致目标检测结果较差的问题,本文提出基于注意力和密集重参数化的目标检测算法。首先,基于CSP-DarkNet提出高效的特征提取网络,主要包括密集重参数化模块和CASA模块2个设计。前者利用密集连接保留浅层特征,又通过重参数化结构降低网络复杂度;后者CASA模块用于获取需要的目标信息。其次,特征融合在特征金字塔(FPN)和路径聚合网络(PAN)的基础上,引入内容感知特征重组(CARAFE)进行上采样,有效解决了邻近插值法等未能捕捉丰富语义信息的问题;提出更高效的C3-G模块,获取丰富的梯度信息,增强模型表达能力和感知能力;同时,引入深度可分离卷积提升运算效率。最后,检测输出采用在更大范围上跨领域正负样本匹配策略扩充正样本数量,提升检测效果。该算法在MS COCO和PASCAL VOC数据集上的mAP@0.5分别达到了57.5%和83.0%,充分说明了本文算法的先进性。

融合梯度先验与全局聚合的立体匹配算法

现有基于学习的立体匹配算法具有一定局限性,通常特征提取部分使用的常规卷积倾向于捕捉外观信息,忽略了结构信息的提取,并且由于卷积感受野的限制,这些算法在弱纹理、重复纹理等病态区域性能较差.为此本文提出了一种融合梯度信息及全局代价聚合的立体匹配网络模型(GFGANet).首先,设计了差分卷积残差组(CDC-ResBlock-Groups),显式编码结构信息提高特征表达,然后设计全局代价聚合模块(Trans-Hourglass),有效聚合代价体并捕获全局上下文,最后采用加窗视差回归降低了视差标签不平衡的影响,此外使用StereoDRNet的后处理进行视差细化.实验表明,所提方法在重复纹理,弱纹理区域表现优异,在SceneFlow中的端点误差(EPE)仅为0.645px,KITTI 2015上的误匹配率为2.04%,与基础模型PSMNet相比,性能显著提升.

数智时代科技成果供需对接机制

为探究我国数智时代科技成果供需对接影响因素和机制作用,梳理我国科技成果供需对接模式及演变历程,构建科技成果供需对接影响因素概念模型,运用扎根理论和文献分析方法归纳出供方、需方、平台、政策、资金和技术因素等影响因素,运用DEMATEL方法分析影响因素之间的影响度。基于分析结果,提出我国科技成果供需对接机制为从应需引供模式转变为掘需育供模式,从上下游关系转变为共同体关系,从局域平台转变为广域平台,从信息化转变为智慧化,从单点服务转变为全链条服务,从技术发展转变为多要素融合发展。

利用BERT和覆盖率机制改进的HiNT文本检索模型

为有效提升文本语义检索的准确度,本文针对当前文本检索模型衡量查询和文档的相关性时不能很好地解决文本歧义和一词多义等问题,提出一种基于改进的分层神经匹配模型(hierarchical neural matching model,HiNT)。该模型先对文档的各个段提取关键主题词,然后用基于变换器的双向编码器(bidirectional encoder representations from transformers,BERT)模型将其编码为多个稠密的语义向量,再利用引入覆盖率机制的局部匹配层进行处理,使模型可以根据文档的局部段级别粒度和全局文档级别粒度进行相关性计算,提高检索的准确率。本文提出的模型在MS MARCO和webtext2019zh数据集上与多个检索模型进行对比,取得了最优结果,验证了本文提出模型的有效性。

基于特征增强和语义相关性匹配的图像文本检索方法

为实现图像文本检索中图像与文本的精确语义连接,提出一种基于特征增强和语义相关性匹配(FESCM)的图像文本检索方法。首先,通过特征增强表示模块,引入多头自注意力机制增强图像区域特征和文本单词特征,以减少冗余信息对图像区域和文本单词对齐的干扰;其次,通过语义相关性匹配模块,不仅利用局部匹配捕获局部显著对象之间的对应相关性,还把图像背景信息融入图像全局特征,利用全局匹配实现精确的全局语义相关性;最后,通过局部匹配分数和全局匹配分数获取图像和文本的最终匹配分数。实验结果表明,基于FESCM的图像文本检索方法在Flickr8k和Flickr30k基准数据集上的召回率总值比扩展的视觉语义嵌入方法分别提升了5.7和7.5个百分点,在MS-COCO数据集比双流层次相似度推理方法提升了3.7个百分点。因此该方法可以有效提高图像文本检索的准确度,实现图像与文本的语义连接。

基于轨迹扰动和路网匹配的位置隐私保护算法

针对现有扰动机制未考虑位置点语义关系导致数据可用性较低的问题,提出一种基于差分隐私(DP)的轨迹位置隐私保护机制(DP-TLPM)。首先,DP-TLPM利用滑动窗口提取轨迹停留点生成模糊区域,再利用指数机制和拉普拉斯机制对该区域进行采样;其次,为了消除采样点中可能存在的无语义位置点,提出一种路网匹配算法,对轨迹分段并利用误差椭圆匹配(EEM)进行迭代匹配;最后,根据匹配后的位置点形成扰动轨迹,由用户端将扰动轨迹发送至服务器。实验以混淆质量和均方根误差(RMSE)为评价标准对该机制进行综合评测。与GeoInd算法相比,DP-TLPM的数据质量损失降低了24%,轨迹的混淆质量提高了52%,从隐私保护强度和数据质量两方面验证了该算法的有效性。

基于仿斑马鱼和仿鹰眼视觉的复杂背景下目标识别

针对反制无人机识别系统在公共场所内部复杂背景下的无人机识别问题,该文研究了一种基于仿斑马鱼模板匹配视觉识别和仿鹰眼视觉注意的目标识别方法,通过建立不同姿态的无人机模板数据库,采用仿鹰眼视觉搜索机制,结合尺度不变特征变换,将姿态模板图像与目标进行匹配,获得粗略的目标区域。然后计算模板姿态与目标姿态的Hausdorff距离,比较目标姿态相似性,获得最相似姿态。采用仿鹰眼视觉注意机制对遮挡图像进行处理,提高目标识别的显著性。实验结果表明,该方法能够在不同复杂背景下实现无人机的准确识别,与光谱残差的显著性目标识别方法相比,平均运行时间提高23.5%,与差异哈希算法相比,具有更高的结构相似性指数。

引入轻量级Transformer的自适应窗口立体匹配算法

现有端到端的立体匹配算法为了减轻显存消耗和计算量而预设固定视差范围,在匹配精度和运行效率上难以平衡。提出一种基于轻量化Transformer的自适应窗口立体匹配算法。利用具有线性复杂度的坐标注意力层对低分辨率特征图进行位置编码,减轻计算量并增强相似特征的辨别力;设计轻量化Transformer特征描述模块,转换上下文相关的特征,并引入可分离多头自注意力层对Transformer进行轻量化改进,降低Transformer的延迟性;用可微匹配层对特征进行匹配,设计自适应窗口匹配细化模块进行亚像素级的匹配细化,在提高匹配精度的同时减少显存消耗;经视差回归后生成无视差范围的视差图。在KITTI2015、KITTI2012和SceneFlow数据集上的对比实验表明,该算法比基于标准Transformer的STTR在匹配效率上快了近4.7倍,具有更快的运行速度和更友好的存储性能;比基于3D卷积的PSMNet误匹配率降低了18%,运行时间快了5倍,实现了更好的速度和精度的平衡。

基于可调叶高扩压器的离心压气机构型流动机理研究

离心叶轮/扩压器匹配关系恶化直接限制了离心压气机的稳定工作范围.以Radiver离心压气机为研究对象,借助经过校核的数值模拟方法开展了基于可调叶高扩压器的离心压气机叶轮/扩压器匹配关系及流动机理研究.结果表明:通过建立能够指导扩压器叶高调节方向和量值的“压气机工作流量-扩压器最佳叶高”正相关对应关系,即可在压气机近失稳点等小流量点主动降低扩压器叶高以改善压气机稳定工作裕度.在设计转速下,引入可调叶高扩压器能够使离心压气机的稳定裕度提升18.8%、流量范围拓宽385%且峰值效率提高0.45%;随着压气机工作点向小流量工况偏移,降低扩压器叶高可以抑制扩压器来流正攻角,优化重构其通道内部涡系结构,减小扩压器吸力面和压力面/轮毂角区的低速区,进而改善叶轮/扩压器匹配关系,抑制扩压器内部流动失稳发生,提升离心压气机稳定裕度和效率指标.

高海拔铁路隧道斜井机械化配套与快速施工

为解决高海拔高寒地区斜井施工存在气压低、含氧量低、温差大、严寒干燥等问题,以某高海拔铁路隧道斜井工程为背景,结合围岩等级、断面大小、海拔高度,根据斜井施工机械化配套原则,提出高海拔陡坡长斜井机械化安全快速进洞施工工法,并选配超前支护、钻爆、装运、喷锚支护、衬砌等机械化作业线的成套设备。基于高度机械化的设备配套,提出“快挖、快运、快支”的高效施工技术以及各工序快速衔接工艺。以控制围岩变形为核心,构建一套积极干预加固围岩、注重早期支护并快速闭合的主动支护体系。结果表明:与普通钻爆法施工相比,采用三臂凿岩台车高度机械化配套施工效率高,月最快进尺为180 m,较人工钻爆法施工月进尺为130 m相比提高了近30%,施工质量稳定,作业人员投入少,且拱顶沉降和周边收敛均小于规范要求值,衬砌强度可靠,可实现高海拔小断面隧道“快挖、快支、主动支、快封闭”。

融合角色心理画像的心理健康文本匹配模型

全球心理健康问题形势严峻,由于心理健康服务的从业人员不足,遭受心理健康困扰的人并不总是能获得专业的心理健康服务.检索式心理健康社区自动问答可以快速地为需要心理健康服务的人提供相应的信息自助服务.与传统检索式社区问答中的文本匹配不同,在匹配支持帖和求助帖时,需要考虑2种不同层面的匹配准则:语义层面和心理层面.为了解决该问题,提出融合角色心理画像的2阶段文本匹配模型(two-stage text matching model integrating characters’mental portrait,T2CMP),该模型引入心理特征用于构建角色心理画像,从而辅助模型理解文本心理层面的内容和匹配关系.同时为了提升检索效率以及减少大量负样例带来的噪声问题,将文本匹配任务拆分为2阶段的序列型子任务.首先针对每条求助帖,使用基于语义的筛选模型甄别出候选支持帖;然后依据用户的角色心理画像,使用多层注意力机制将其与语义信息有效融合,提高模型的总体效果.在MHCQA数据集上的实验结果显示,T2CMP比现有优秀算法拥有更高的F1值.

双向注意力文本关键词匹配法条推荐

提出一种双向注意力文本关键词匹配的法条推荐模型(BiAKLaw)。该模型以预训练语言模型BERT作为基础匹配模型,利用双向注意力机制提取字符级对齐特征和关键词差异特征,融合对齐特征、差异特征和关键词语义表征来提升匹配效果。在裁判文书交通肇事和故意伤害数据集上的实验结果表明,与BERT模型相比,BiAKLaw在评价指标F1上分别提升3.74%和3.43%。