基于Workbench平台的簧片哨发声机理及特征

基于Workbench平台对簧片哨物理模型进行双向流固耦合计算,对其发声机理及特征进行分析。结果表明:簧片发声的主因是射流对簧片的升力作用;当升力的某一频率与簧片的固有频率相近或者相同时,簧片的固有频率将被激发。随着射流压强增大,簧片的谐振频率逐渐增多,且谐振频率与基频近似呈奇数倍关系。在喷距不大于5mm的工作状态下,基频保持稳定;在喷距大于6mm的工作状态下,基频开始发生跃迁;随着喷距的增大,谐频逐渐消失,但是射流压强增大又导致谐频的出现。     

脉动流对壁面边界层流动的数值研究

为了研究非稳态尾迹对平板表面流动和换热的影响,本文将非稳态尾迹引起的主流速度脉动简化为正弦变化,通过数值的方法研究了脉动频率和振幅对平板壁面边界层流动和换热的影响,研究结果表明:边界层内的速度、壁面温度、壁面摩擦系数和平均换热系数随着时间的变化做周期性脉动;边界层内流动与主流之间存在着相位差,壁面距离越小,相位差越大;边界层内的速度和壁面摩擦系数脉动幅度的大小与主流脉动频率和振幅成正比;壁面温度和壁面平均换热系数的波动大小与主流脉动频率成反比,与脉动振幅成正比,当主流脉动频率和脉动振幅增加到一定值后,靠近壁面的地方出现回流,回流强度与脉动频率和振幅成正比。     

管内振动壁面射流流场的数值模拟

采用动网格技术和k-ε两方程湍流模型,通过求解二维非定常不可压雷诺时均NavierStokes方程,对局部壁面振动的管内射流流场进行数值模拟,分析局部振动壁面的振幅和频率对流动的影响.结果表明,射流孔下游壁面静压随振幅、频率的增加而增加;射流孔附近静压在126°相位角降到最低.射流孔的平均流量随振幅的增加而减小,随频率的增加而增加;流量波动随振幅、频率的增加而增大,高频率对主流的影响更加明显.     

音波振荡器数值模拟

音波振荡器的振荡特性和总压损失是影响静止式气波制冷机制冷效率的重要因素,通过数值模拟研究发现二者受元件几何尺寸的影响.计算了不同几何结构尺寸下音波振荡器内的流动,总结了几何因素对射流振荡和总压损失的影响规律,并分析了其内在原因,发现:射流振荡周期只随控制管长成正比例规律变化,不受其他几何因素的影响;分流劈距在一定区间范围内,射流才能稳定振荡,且振荡区间的上限和下限均随位差的变化而变;音波振荡器的喷嘴喉部长度、分流劈距、位差及分流劈形状对总压损失有显著影响,控制口宽度、分流劈张角、分流劈尖半径对总压损失也有一定程度的影响.     

射流偏转板劈尖形变对其零位特性的影响

采用RNGk-ε湍流模型和气穴模型对射流偏转板伺服阀的前置级三维流场进行了仿真,分析了劈尖微小形变对伺服阀前置级射流气穴强弱、零位压力增益、零位流量增益和泄漏流量的影响.结果表明:劈尖为平顶时气相体积分数最高;随着偏转板位移的增大,前置级气相体积分数呈增大趋势;劈尖为平顶时前置级压差较大、零位压力增益比其他结构分别大21.5%和26.0%;劈尖为尖顶时前置级流量较大,零位流量增益比其他两种结构大19.1%和18.6%;劈尖为尖顶时前置级泄漏流量为7.51mL/s,泄漏流量最小;随着偏转板位移的增大,泄漏流量基本不变.     

微机械振动陀螺闭环自激驱动理论分析及验证

根据微机械振动陀螺驱动控制的要求,对基于自动增益控制的自激驱动陀螺系统进行了理论分析,在系统存在相位不平衡时,利用近似平均法得到了结构的起振条件及稳态幅度表达式。理论分析和实验测试表明：参考电压须大于某一临界值结构才能起振,较大的参考电压能达到大的稳态振幅,提高信噪比;系统相位偏差将导致系统谐振频率偏离固有谐振点,同时引起稳态振幅变小;改变滤波器时间常数能改变起振时间。陀螺闭环自激系统测试得到谐振频率10 min内稳定度达到±8 ppm,振动幅度1 h内最大漂移0.1%。     

振动力场作用下PP/CaCO3共混物的力学性能

为研究新型动态三螺杆挤出成型技术对制品力学性能的影响,以PP/CaCO3共混物作为研究对象,在振动频率0～60Hz、振幅0～250μm的范围内对三螺杆挤出机施加振动,制成试样后进行拉伸强度、冲击强度测试和扫描电镜观察,研究不同振动参数对共混物力学性能及断面形态结构的影响.结果表明:制品的力学性能对振动参数的响应存在一个最佳值;与没有引入振动(稳态)的挤出相比,振动频率为20Hz、振幅为225μm时,共混物的冲击强度提高了21.7%;振动频率为20Hz、振幅为145μm时,共混物的拉伸强度提高了10.4%.     

裂面形貌扰动对晶内微裂纹演变影响的有限元分析

根据表面扩散控制下物质迁移规律,建立有限单元法,对裂面形貌扰动下二维徼裂纹演变过程进行数值模拟.结果表明:裂尖的几何形状对微裂纹圆柱化时间起决定性作用;在裂面形貌扰动振幅不变的情况下,扰动频率越高,其对裂腔分节临界形态比的影响越小,且波数为奇数的微裂纹更容易分节;振幅对裂腔分节起阻碍作用;裂面形貌扰动频率越小,振幅对裂腔分节临界形态比的影响越显著.     

SI-FLAT板形仪检测原理的流固耦合振动分析

为从力学本质上揭示SI-FLAT非接触式板形仪的检测原理,基于薄板流固耦合振动理论,建立了薄板振幅与残余应力关系的数学模型.在非协调F?ppl-von Kármán方程组的平衡方程中引入惯性项与流体压强项,利用气动载荷在时间上的周期性将流体速度函数、流体压强函数、薄板挠度函数和薄板应力势函数的时间变量分离出来,得到描述SI-FLAT板形仪稳定工作状态的偏微分方程组.进一步利用分离变量法求解该方程组,最终建立起薄板振幅与残余应力的数学关系.同时结合实测残余应力数据,利用Siemens提出的振幅-残余应力模型反算得到实际薄板振幅分布,并将其与流固耦合振动模型计算的振幅进行对比,验证了提出的数学模型的可靠性.进一步利用流固耦合振动模型分析了气泵进风口流体速度、检测距离和激振频率对振幅的影响,为SI-FLAT板形仪科学合理的利用提供了理论依据.     

振动力场对聚合物动态加工功耗的影响

为探讨动态成型工艺参数对聚合物动态加工功耗的影响规律,文中采用熔体输运模型研究自行研制的同轴圆筒动态流变装置电机功耗对振动力场的响应,建立了振动力场下电机动态输出功率与稳态输出功率差的理论模型.对同轴圆筒动态流变装置电机功耗进行了测量,并与理论计算功耗进行比较,发现理论模型能较好地预测电机功耗随振动参数的变化,实验数据和理论模型均表明动态加工电机功耗随振动频率和振幅的增大而减小.文中还通过实际加工中脉动注塑机能耗随振动频率和振幅的变化证实了理论模型的可行性.     

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.