Three Dimensional Elasticity Analyses for Isotropic and Orthotropic Composite Cylinders

The demand for using shell theories comes from its efficiency in computational and analytical cost. On another side, new materials that are orthotropic and/or anisotropic in nature are discovered and broadly used in many fields. Many advanced shell theories are developed for these new materials, particularly in the recent decades. A study about the accuracy of these shell theories is very meaningful to build confidence in them for further applications. This study requires a precise benchmark against which shell theories can be tested. This is the main research subjective in this dissertation: to build a set of solutions using the three dimensional (3D) theory of elasticity against which shell theories can be tested for accuracy. The contents of this dissertation to support this research include a comprehensive literature review for the shell theories and recent usage and to find the gaps which need to be filled. These gaps include, among others, the lack of studies on the accuracy of the theories used and the absence of results using the 3D theory, particularly for orthotropic materials. Some of these studies are conducted here. The deficiency of some commercial finite element packages is discussed here. The reasons for the absence of accurate results are investigated. The 3D theory and analyses of isotropic and orthotropic materials of hollow cylinders is investigated here for reliable results

Ideal Tightly Couple (t,m,n) Secret Sharing

As a fundamental cryptographic tool, (t,n)-threshold secret sharing ((t,n)-SS) divides a secret among n shareholders and requires at least t, (t<=n), of them to reconstruct the secret. Ideal (t,n)-SSs are most desirable in security and efficiency among basic (t,n)-SSs. However, an adversary, even without any valid share, may mount Illegal Participant (IP) attack or t/2-Private Channel Cracking (t/2-PCC) attack to obtain the secret in most (t,n)-SSs.To secure ideal (t,n)-SSs against the 2 attacks, 1) the paper introduces the notion of Ideal Tightly cOupled (t,m,n) Secret Sharing (or (t,m,n)-ITOSS ) to thwart IP attack without Verifiable SS; (t,m,n)-ITOSS binds all m, (m>=t), participants into a tightly coupled group and requires all participants to be legal shareholders before recovering the secret. 2) As an example, the paper presents a polynomial-based (t,m,n)-ITOSS scheme, in which the proposed k-round Random Number Selection (RNS) guarantees that adversaries have to crack at least symmetrical private channels among participants before obtaining the secret. Therefore, k-round RNS enhances the robustness of (t,m,n)-ITOSS against t/2-PCC attack to the utmost. 3) The paper finally presents a generalized method of converting an ideal (t,n)-SS into a (t,m,n)-ITOSS, which helps an ideal (t,n)-SS substantially improve the robustness against the above 2 attacks

Exceptional Points in a Non-Hermitian Topological Pump

We investigate the effects of non-Hermiticity on topological pumping, and uncover a connection between a topological edge invariant based on topological pumping and the winding numbers of exceptional points. In Hermitian lattices, it is known that the topologically nontrivial regime of the topological pump only arises in the infinite-system limit. In finite non-Hermitian lattices, however, topologically nontrivial behavior can also appear. We show that this can be understood in terms of the effects of encircling a pair of exceptional points during a pumping cycle. This phenomenon is observed experimentally, in a non-Hermitian microwave network containing variable gain amplifiers.Comment: 7 pages, 7 figures. The first author did the experiment, and the second author did the theoretical stud

Microwave-assisted photocatalytic degradation of dimethyl phthalate using a microwave discharged electrodeless lamp

The microwave-assisted photocatalytic degradation (MW/PC) of dimethyl phthalate (DMP) was investigated, using a microwave discharged electrodeless lamp (MDEL) as the UV source. DMP could be rapidly and completely degraded by the MW/PC process. The effects of photocatalyst dosage, UV light intensity, initial pH and concentration of DMP, as well as irradiation time, were studied in detail. Synergistic effects were found to exist between microwave irradiation and TiO2 photocatalysis, and the greater efficiency of the MW/PC process might be ascribed to non-thermal effects of microwave irradiation. Detection results confirmed that microwave irradiation could give rise to the generation of hydroxyl radicals. The major intermediates of DMP in the MW/PC process were deduced to be phthalic acid monomethyl ester, phthalic acid, o-phenyl diethyl ketone and o-phthalic anhydride. Based on the results, two initial degradation pathways of DMP were proposed

A Novel Neutral-Point Potential Balance Strategy for Three-Level NPC Back-to-Back Converter Based on the Neutral-Point Current Injection Model

The neutral-point (NP) potential balance control in three-level neutral-point-clamped (NPC) back-to-back converter is a research nodus. Its current strategies are the same as the strategies of a single three-level NPC converter. But the strategies do not give full play to its advantages that the neutral-point current can only flow through the connected midlines in both sides of the converter but does not flow through the DC-bus capacitors. In this paper, firstly the NP potential model based on the NP current injected is proposed. It overcomes numerous variable constraints and mutual coupling in the conventional model based on the zero-sequence voltage injected. And then on this basis, three NP-potential balance control algorithms, unilateral control, bilateral independent control, and bilateral coordinated control, are proposed according to difference requirements. All of these algorithms use the midlines rather than the DC-bus capacitors to flow the NP current as much as possible. Their control abilities are further quantitatively analyzed and compared. Finally, simulation results verify the validity and effectiveness of these algorithms