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11.
A novel procedure for the health assessment of large three-dimensional (3D) structures with several significant attractive features and improved implementation potential is proposed. Structures are represented by 3D finite elements and a substructure concept is used so that acceleration time histories can be measured only at small part(s) of the structure. Just by measuring relatively few noise-contaminated responses in the substructure, the health of the whole structure can be assessed by the system identification (SI) concept by tracking the stiffness parameter of all the elements using a significantly improved unscented Kalman filter (UKF) algorithm. Since measuring excitation time histories can be very problematic and expensive, the UKF algorithm is integrated with 3D iterative least-squares with unknown input algorithm. UKF fails to identify large structures due to convergence-related issues. The authors used short duration responses and multiple global iterations with weight factor and objective function instead of one long duration response generally used in UKF. For the preselected excitation, short duration eliminates multiple sources of excitation beyond the control of inspector. The weight factor helps accurately locate the defect spot. With informative examples, it is documented that the proposed method is superior to various other forms of Kalman filter-based algorithms. 相似文献
12.
Ching-Kuo Hsiung
Mohamed E. M. El-Sayed
《Advances in Engineering Software》1993,17(3):135-139The real benefit of structural optimization techniques is in the application of these techniques to large structures such as full vehicles or full aircraft. For these structures, however, the sequential computer's time and memory requirements prohibit solution. With the recent existence and rapid development of multi-processor computers, parallel processing of large-scale structural optimization problems is achievable. In this paper we discuss the parallel processing of structural optimization problems with parallel structural analysis on the Cray X-MP. Two different types of interface between the optimization and analysis routines are developed and tested. 相似文献
13.
动力子结构法中Ritz基的一种选择 总被引:1,自引:0,他引:1
基于弹性动力学变分原理,本文导出了混合型动力子结构方法的一种Ritz基矢量,即采用正交化的块Lanczos基代替主模态,结出了相应的子结构模态变换的格式和综合后的系统方程式.文未给出了算例. 相似文献
14.
Bridges are vital structures for worldwide physical infrastructure networks, and efficient inspection methods are needed to reveal and evaluate the health conditions of damaged critical bridges. In contrast to the superstructure inspection, underwater inspection methods are still time-consuming and labor-intensive tasks. As the underwater environment is invisible and hard to access, scouring and damage are easily neglected in traditional human diving. To address this problem, this paper presents a rapid underwater inspection framework using a sonar device and a deep convolutional network to provide quantitative measuring results for scour depth and apparent damage. The side-scan sonar and fixing platform were used to collect underwater images, and a modified semantic segmentation was designed based on the U-Net architecture. The pretrained residual building blocks and a designed feature fusion connection called Respath were utilized to replace the original encoder and skip connection. Comparative experiments showed that this modified architecture achieved the best performance in multiple-class segmentation for sonar images in which the mean intersection over union (mIoU) and IoU for specific apparent damage can reach up to 0.918 and 0.63, respectively. An on-site test was also conducted to validate the applicability of the proposed method, and the scour depth and two points of damage were identified based on the pixelwise segmentation images. Therefore, further structural evaluation can proceed based on these accurate measuring results. 相似文献
15.
《Geotextiles and Geomembranes》2021,49(5):1324-1338
The instability of railway tracks including mud pumping, ballast degradation, and differential settlement on weak subgrade soils occurs due to cyclic stress from heavy haul trains. Although geotextiles are currently being used as a separator in railway and highway embankments, their ability to prevent the migration of fine particles and reduce cyclic pore pressure has to be investigated under adverse hydraulic conditions to prevent substructure failures. This study primarily focuses on using geosynthetics to mitigate the migration of fine particles and the accumulation of excess pore pressure (EPP) due to mud pumping (subgrade fluidisation) using dynamic filtration apparatus. The role that geosynthetics play in controlling and preventing mud pumping is analysed by assessing the development of EPP, the change in particle size distribution and the water content of subgrade soil. Using 3 types of geotextiles, the potential for fluidisation is assessed by analysing the time-dependent excess pore pressure gradient (EPPG) inside the subgrade. The experimental results are then used to evaluate the performance of selected geotextiles under heavy haul loading. 相似文献
16.
一种新型的结构抗震试验方法 总被引:6,自引:1,他引:5
在分析原有几种抗震试验方法的基础上,提出了一种新的“混合试验方法”的设想。这种方法将振动台试验与拟动力试验结合起来,以期解决原有试验方法在大型、异型结构抗震研究中遇到的困难。对于这种方法存在的主要问题,本文进行了初步讨论,希望借鉴动态子结构法中的综合模态技术,进行深入的研究并达到实际应用。 相似文献
17.
18.
A. David Rae 《Crystallography Reviews》2013,19(4):155-229
Some common misconceptions in least-squares crystal structure refinement can be resolved by recasting the usual equations in terms of partial observations, partial models and partial residuals. An observation has components that are determined by an initial calculated model and each component, including the background, is considered to be a partial observation of the total observation. The use of partial observations, partial models and partial residuals allows various misconceptions to be identified and suggests ways to improve the least-squares methodology. A fixed component of a model of peak-plus-background does not fix its contribution to the observation for each refinement step. A covariance matrix obtained from the least-squares equations enables a standard uncertainty to be estimated for any function of the structural parameters. An oversight in current refinement methods is the failure to estimate the variances of components of the calculated model of an observation and the fraction of each residual associated with the various features of a refinement. A distinction should be made between least-squares equations for model development and least-squares equations for the estimation of a variance–covariance matrix. Methods for detecting systematic errors are discussed. A proposed look-ahead option for model development includes the assessment of the ability to refine parameters. For pseudo-symmetric structures, the use of symmetrized combinations of pseudo-equivalent intensities allows the reliability of minor components of the intensities to be better evaluated. It is also shown how homometric structure solutions can result from the use of powder diffraction data or equally twinned crystals. 相似文献
19.
20.
子结构物理参数识别与输入地震动的复合反演研究 总被引:14,自引:4,他引:10
利用结构的动力响应同时识别结构物理参数并反演输入过程的工作称为复合反演.本文研究一类基于子结构分析的地震动复合反演问题.通过结构动力矩阵的分解并结合作者提出的一种在输入信息未知的条件下识别结构物理参数的方法,提出了一类复合反演算法.算例分析表明了算法的实用性. 相似文献