Large scale wireless sensor networks raise many challenges in the design of efficient and effective routing algorithm due to their complexity and hardware constraints. However, the scalability challenge may be mitigated from a macroscopic perspective. One example is the distributed De la Garza iteration (DDLGI) algorithm for global routing load-balancing, based on a set of partial differential equations iteratively solved by the De la Garza method. We theoretically analyze the parallelism of DDLGI and illustrate that the region of interest may impact the degree of parallelism and error. Furthermore, though DDLGI always converges, the slow convergence and long-range information exchange problems may lead to excess energy consumption in communication. Thus, we propose various enhanced De la Garza routing (E-DLGR) algorithms to alleviate the energy consumption problem by which nodes may exchange less information and only need to exchange information with closer nodes to complete each iteration. Our theoretical analysis and simulation results show that the proposed E-DLGR algorithms may have less transmission overhead, thus further reducing energy consumption, and converge faster while still maintaining adequate accuracy.
Mapping road surface features, such as manholes, traffic markings, and cracks, is an essential task for transportation facility management. Although, these features can be rapidly surveyed using the latest mobile mapping techniques, a sophisticated sensor system with a complicated post-processing procedure is usually required. In this study, an efficient framework for modeling road surface features is proposed using a single camera system installed on a moving platform. First, the road surface images along a route of interest are acquired and potential objects are identified based on their shapes and recorded spectra in the images. Then, the contour pixels of the identified objects are extracted by the Canny edge detection technique. Finally, the 3D coordinates of the detected features in object space are obtained by integrating the profile-image technique and the instantaneous exterior orientation parameters of the platform. Based on the numerical results from a case study, it has been demonstrated that a fully automatic and reliable extraction of road surface features can be easily achieved by implementing the proposed approach. Consequently, the modeling of road surface features, which essentially contributes to the management of transportation facilities, can be executed in a cost-efficient manner. 相似文献
Ultrafine cellular microstructures around alumina particles in a low-carbon steel were observed, which survived even after cyclic austenitization. This indicates that their formation is closely related to internal stress because of a structural heterogeneity during phase transformation rather than to externally applied forces or deformation. Thermo-elasto-plastic finite element analysis confirmed the evolution of a large hydrostatic pressure around an alumina particle due to thermal mismatch during cooling. Therefore, the fine cellular microstructure might be generated as a result of the hydrostatic pressure, which retards the phase transformation around the particle during cooling. In addition, we observed microstructural similarity with the same steel processed under an ultra-high pressure, which was the evidence for the role of the delay in the transformation caused by the hydrostatic pressure. 相似文献
The dissolution process of a galvannealed coating layer on dual-phase steel was examined by correlating a stripping test, metallographic observations and a polarisation test in an acidified chloride solution. The galvannealed coating layer was composed of several Fe–Zn intermetallic phases, namely the gamma, delta, and zeta phases, from the substrate. The dissolution began from the outermost zeta phase and proceeded to the gamma and then the delta phase. The dissolution rates for each intermetallic phase and galvanic couples were measured and estimated through a polarisation test, and the gamma phase in the gamma-substrate galvanic couple exhibited the highest corrosion rate. 相似文献
An imperceptible digital watermarking algorithm based on 4-level discrete wavelet transform, discrete cosine transform and singular value decomposition is designed. In this method, the 4-level diagonal sub-band image is obtained by performing the 4-level two-dimensional wavelet transform on the original image, and then a coefficient matrix is produced by applying the discrete cosine transform on the 4-level diagonal sub-band image. A diagonal matrix is constructed by performing the singular value decomposition on the coefficient matrix. The watermark is scrambled by Arnold transform and Logistic map, then the scrambled watermark is processed by the singular value decomposition. Later, the encryption process is completed by embedding the scrambled watermark singular value into the singular value of the coefficient matrix. Simulation results demonstrate that the proposed digital watermarking algorithm could resist JPEG compression attack, Salt and Pepper noise attack, Gaussian noise attack, filter attack, brightness change attack, geometric attack, cut attack, etc.
