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91.
Today’s vehicles are designed with lighter weight to increase performance and to lower fuel consumption, while at the same
time meeting the demands of safety requirements. Reducing the cross-section of structural elements to achieve weight reduction
can lead to adverse effects on passive safety of the vehicle. In such cases, necessary design modifications must be created
to overcome the adverse effects. For this purpose, front rail columns with crush initiators are used in the front zone of
cars. These shock-absorbing elements act as energy consuming devices that convert impact energy (kinetic energy) into plastic
deformation energy. Simulation of this energy conversion phenomenon is the subject of this paper. The primary objective of
this study is to computationally determine how various crush initiators can reduce the maximum crushing force and how different
types of structural modifications affect the observed folding form. The ribs near the crash area are placed in two rows and
four different configurations on all facing sides of the column in order to decrease reaction forces and absorb more kinetic
energy. These structures are analyzed under axially loaded crushing forces using the explicit nonlinear finite element analysis
solver ANSYS/LS-DYNA. 相似文献
92.
The aim of this paper is to study visual autonomous navigation of unmanned aerial vehicle (UAV) in indoor global positioning system (GPS) denied environment. The UAV platform of the autonomous navigation flight control system is designed and built. The principle of visual localization and mapping algorithm is studied. According to the characteristics of UAV platform, the visual localization is designed and improved. Experimental results demonstrate that the UAV platform can realize the tasks of autonomous localization, navigation and mapping based on visual in unknown environments. 相似文献
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A novel method is presented to improve the recognition rate of warhead in this paper. Firstly, a tool for electromagnetic calculation, like CST Microwave Studio, is used to simulate the frequency response of the electromagnetic scattering. Secondly, the echo and further the range profile are acquired from the frequency response by further processing. Thirdly, a set of discriminative features is extracted from the range profiles of the target. Fourthly, these features are used to construct a dictionary for the sparse representation classifier. Finally, the sample of the target can be classified by solving the sparsest coefficients. Since the reconstruction result is determined by a linear combination of the training samples, this method has a good robustness for the variable features. By formulating the problem within a feature-based sparse representation framework, the presented method combines the discriminative features of each sample during the sparse recovery process rather than in a postprocessing manner. Moreover, based on the feature representation space rather than a single feature or image pixel, the constructed dictionary exhibits both strong expressive and discriminative powers that can enhance the classification performance of the test sample. A series of test results based on the simulated data demonstrates the effectiveness of our method. 相似文献
95.
分析了高校计算机网络实验教学的现状,结合我校实际情况,构建了基于虚拟仿真技术的计算机网络实验室。详细探讨了实验室软硬件条件和教学内容的建设,进一步完善了实验教学体系。 相似文献
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Growing customer demands and more stringent regulations to reduce harmful air emissions from ships have resulted in an increased interest for the installation of shipboard abatement technologies. Specifically, the selective catalytic reduction (SCR) technology to reduce emissions of nitrogen oxides (NOx) was early adopted by several Swedish shipping companies. The potential NOx reduction efficiency of the SCR is well established, but the practical experiences of shipboard installations have been less documented. This paper reviews from a systems perspective the practical experiences of marine SCR installations in Swedish shipping. The aim is to identify important not only technical but also human and organizational conditions necessary for safe, efficient, and sustainable SCR operations at sea. Further, to investigate to what extent the capabilities and limitations of human operators and maintainers are taken into account in the design and installation phase of the systems. Two focus group interviews (n?=?10) and five individual interviews were held with relevant stakeholders in the industry, following a semi-structured schedule on the themes installation, operation, maintenance, and training. The results show that deficiencies in the overall system design—with a combination of technical issues, maintenance access problems, and untrained operators with inadequate understanding of the SCR process—have led to inefficient, costly, and unsafe operations. It is concluded that installations and operations of marine SCR systems, and possibly other forthcoming abatement technologies, would benefit from the use of traditional ergonomic principles and methods. This would in turn contribute towards increased sustainability and a reduced environmental impact from shipping. 相似文献