A Sharp upper bound for the spectral radius of a nonnegative matrix and applications

In this paper, we obtain a sharp upper bound for the spectral radius of a nonnegative matrix. This result is used to present upper bounds for the adjacency spectral radius, the Laplacian spectral radius, the signless Laplacian spectral radius, the distance spectral radius, the distance Laplacian spectral radius, the distance signless Laplacian spectral radius of a graph or a digraph. These results are new or generalize some known results.Comment: 16 pages in Czechoslovak Math. J., 2016. arXiv admin note: text overlap with arXiv:1507.0705

Design and Implementation of a Z-Axis MEMS Gyroscope with a Symmetric Multiple-Mass Mechanical Structure

This thesis presents a z-axis MEMS gyroscope with a symmetric mechanical structure. The multiple-mass design prioritizes the sense-mode Quality Factor (Q) and thus improves its scale factor. The proposed mechanically coupled, dynamically balanced anti-phase sense-mode design minimizes energy dissipation through the substrate in order to maximize the Q. Numerical simulation is implemented in a finite element analysis software, COMSOL, to identify the two operation modes of the gyroscope: drive-mode and sense-mode. The multiple-mass gyroscope design is further fabricated using a one-mask process. Experimental characterization of frequency response in both drive-mode and sense-mode of the device are conducted, proving the design concept for improving the Q in the sense-mode

STUDY ON CORROSION ACTIVITY OF CARBON STEEL IN CONCRETE SIMULATED PORE SOLUTION UNDER STATIC TENSILE AND COMPRESSIVE STRESSES

Reinforced concrete is a structure material made up of concrete with relatively lower tensile strength containing reinforcements with higher tensile strength and better ductility, which are embedded into fresh concrete to resist tensile stress in certain regions of concrete. Steel reinforced concrete is most widely used around the world in civil engineering structures, water conservancy and highway construction due to its durability strength and reasonable cost. However, reinforced concrete structures such as bridges and parking lots slabs inevitably experience variable loads and constant degradation from the aggressive environments, such as marine and deicing salts. Therefore, it is imperative to study the synergic impact of different types of loadings and exposure to chloride ions on the corrosion of steel rebars. Clear understanding of such processes assists improving the resiliency of the structures and helps extending the service life of the constructions by modifying the design codes of structural steel, which will thus improve the durability and safety of next generation of sustainable infrastructures. In addition, it is necessary to understand the fundamental mechanism of steel passivation and depassivation processes in concrete under stresses, then more reliable and robust service life modeling tools can be made to help engineers predict the state and performance of rebar in concrete structures. Hence, in order to obtain detailed understanding of the effect of both tensile and compressive stresses on passive film and the depassivation process, experiments were performed on steel immersed in concrete simulated pore solution under different types and degrees of loadings. Simulated concrete pore solution was chosen in order to obtain the results in a reasonable time frame required for this project. Several electrochemical measurement techniques were used. Besides, Mott-Schottky technique was utilized to investigate the semi-conductive behavior of the passive film, which is formed on the surface of the steel rebars. Results indicate that steel specimens in chloride free pore solution under tensile loadings passivate more rapidly compared to those under compressive loadings. However, the situation in chloride contaminated solution is different and steel under tensile stress exhibit more corrosion than that under compressive stress and no load

Tailoring Accelerating Beams in Phase Space

An appropriate design of wavefront will enable light fields propagating along arbitrary trajectories thus forming accelerating beams in free space. Previous ways of designing such accelerating beams mainly rely on caustic methods, which start from diffraction integrals and only deal with two-dimensional fields. Here we introduce a new perspective to construct accelerating beams in phase space by designing the corresponding Wigner distribution function (WDF). We find such a WDF-based method is capable of providing both the initial field distribution and the angular spectrum in need by projecting the WDF into the real space and the Fourier space respectively. Moreover, this approach applies to the construction of both two- and three-dimensional fields, greatly generalizing previous caustic methods. It may therefore open up a new route to construct highly-tailored accelerating beams and facilitate applications ranging from particle manipulation and trapping to optical routing as well as material processing.Comment: 8 pages, 6 figure