Model independent assertions for integration of heterogeneous schemas

Due to the proliferation of database applications, the integration of existing databases into a distributed or federated system is one of the major challenges in responding to enterprises' information requirements. Some proposed integration techniques aim at providing database administrators (DBAs) with a view definition language they can use to build the desired integrated schema. These techniques leave to the DBA the responsibility of appropriately restructuring schema elements from existing local schemas and of solving inter-schema conflicts. This paper investigates theassertion-based approach, in which the DBA's action is limited to pointing out corresponding elements in the schemas and to defining the nature of the correspondence in between. This methodology is capable of: ensuring better integration by taking into account additional semantic information (assertions about links); automatically solving structural conflicts; building the integrated schema without requiring conforming of initial schemas; applying integration rules to a variety of data models; and performing view as well as database integration. This paper presents the basic ideas underlying our approach and focuses on resolution of structural conflicts.     

W-Ni-Cu合金中粘结相对膨胀系数等性能的影响

膨胀系数小是钨基合金的主要特性之一。本文研究W-Ni-Cu合金膨胀系数与粘结相的量之间的关系,从理论和实验上探讨了提高合金膨胀系数,同时保持合金良好综合性能的途径。     

Property of eigenvalues and eigenfunctions for an interface V-notch in antiplane elasticity

The so-called pseudo-orthogonal property of the eigenfunction expansion form is proved to be valid for the case of an antiplane interface V-notch and the corresponding path-independent integral is derived. The relation between the path-independent integral and the stress intensity factor of the notch is found. The influence of loads on the related integral is also presented.     

Remote Sensing Monitoring and Spatiotemporal Pattern of Land Use/Cover Change in Built-up Area of Tianjin in the Past 70 Years

Urban land use/cover changes have an important impact on urban ecosystem services functions and the environmental quality of human settlements. This study mapped urban expansion process using the historical data, remote sensing images and urban planning maps, and acquired the urban impervious surface and green space fraction based on big data platform. We analyzed the process of Tianjin urban expansion rate, intensity and urban land cover change since 1949, and revealed the driving factors in the process of urban expansion with social economic and policy factors. The results showed that the built-up area increased from 49.15 km² in 1949 to 663.39 km² in 2015. The expansion has undergone four stages of "acceleration – deceleration – acceleration - deceleration"; the urban expansion mode presents the filled with built-up area and along with the neighboring transportation trunk lines. The proportion of green space in the built-up area is increasing, indicating that the urban ecological greening in the main urban area of Tianjin has been improved.     

膨胀防砂筛管技术及应用

膨胀套管技术是20世纪90年代才兴起的一门节约井眼直径的钻井技术,起源于美国,现已投入实践,收到了很好的效果,而在我国还处于理论探索阶段。它是一种适用于井下防砂的膨胀筛管技术,膨胀防砂筛管实质上是具有一系列串联的、互相交错的轴向割缝的管子,割缝的布置使管柱更易于膨胀。在钻井工业中,对防砂起到了很好的作用,并且可以提高油井的产量。介绍了膨胀防砂筛管的组成及膨胀机理、现场应用情况和所需研究的内容,最后对我国膨胀管技术的发展提出了一些建议。     

影响预交联凝胶颗粒性能的因素分析

从凝胶颗粒的基本特征、外观形态、粒径分布分析入手,研究了膨胀倍数及粘弹性等特征参数,评价了颗粒的物理化学性能。实验结果表明,预交联凝胶颗粒适宜于高矿化度的地层,对pH值无具体要求,长期热稳定性好。在95℃条件下考察两年和120℃条件下考察一年均未发现脱水现象。膨胀倍数在30-200倍,也可根据实际选择合适的膨胀倍数。     

梨树煤矿九井北翼3~#探煤巷锚网护帮工程实践

梨树煤矿912掘进队施工北翼3#探煤巷做为补充勘探。施工中,半煤巷帮采用锚网支护、控制两帮位移,避免了由于片帮、巷道跨度大引起的冒顶现象。     

贺西煤矿三采区运输巷扩刷变形分析与控制

基于扩刷施工后大断面巷道围岩控制难题,以贺西煤矿4#煤层三采区运输巷扩刷施工为研究背景,理论分析了扩刷后大断面巷道围岩控制难点,采用FLAC3D软件模拟了运输巷扩刷前后围岩铅直应力与塑性区的分布与演化特征。结果显示:扩刷后巷道围岩铅直应力集中区及塑性区分布范围明显增大,巷道浅部围岩存在3.5m厚连续均匀分布的"塑性环"。据此,提出锚杆索+注浆+U型钢棚等联合支护技术,锚杆支护后在巷道浅部围岩形成厚度为1.6m的预应力拱形承载结构。试验表明:巷道顶底板与两帮最大移近量分别为218mm和165mm,扩刷后巷道围岩变形得到了有效控制。     

声振信号联合1D-CNN的大型电机故障诊断方法

针对复杂运行环境下大功率电动机故障诊断准确率不高、算法泛化能力差的问题,提出一种声振信号联合一维卷积神经网络（1D-CNN）故障诊断方法. 首先对采集到的声信号采用背景噪声库联合稀疏表示去除噪声,然后将声音信号进行带通滤波（7~20 kHz）,叠加低频振动信号（7 kHz内）形成频带更完整的电动机状态表征信息. 再对经过滤波提纯处理后的信息进行重叠式数据扩容,获取1D-CNN训练所需大量数据. 最后将数据样本输入1D-CNN进行学习训练,采用局部均值归一化（local response normalization,LRN）和核函数去相关性改进1D-CNN模型结构,降低抽油机正负半周工况波动对电动机诊断准确性的影响. 诊断结果表明:声振信号联合分析的卷积神经网络故障诊断总体诊断准确率达到了97.75%,泛化能力好,与传统的电动机故障诊断方法相比优势明显.     

高速射弹并联入水过程空泡演化特性试验

为研究多射弹并联入水时多空泡演化特征,首先设计了可用于双射弹水平高速入水的发射装置,通过试验验证了该系统的可行性;然后基于该系统进行了不同空化器直径、径向间距的双射弹并联入水试验,利用高速摄影技术采集到双射弹在并联入水运动过程;最后对采集到的运动序列图片进行数据分析,得到双射弹在并联入水过程中的双空泡演化规律,揭示了射弹并联入水过程中空泡之间的耦合演化机理. 试验结果表明: 高速射弹并联入水过程中,其空泡演化过程存在穿越、吸引及截断3种典型现象;空化器直径与射弹径向间距均是影响双空泡耦合特性的重要因素.相同射弹径向间距时,随着射弹空化器直径减小,双空泡之间的耦合程度减弱,完全穿越转变成部分穿越现象;相同的空化器直径时,随着双射弹的径间距增大,射弹的脱落空泡之间的吸引现象逐渐减弱,但是脱落空泡的偏移幅值随着径向间距的增大呈现先增大后减小的变化趋势;当双射弹存在前后距离时,先发射弹易出现空泡的截断现象.随着轴向间距增大,截断现象将减弱.根据独立膨胀原理可知,相同条件下射弹前后间距减小时截断现象亦将减弱.