http://hdl.handle.net/2440/292 Wed, 19 Jun 2013 17:58:09 GMT 2013-06-19T17:58:09Z http://hdl.handle.net/2440/78415 Title: Mechanically tunable terahertz metamaterials Author: Li, Jining; Shah, Charan M.; Withayachumnankul, Withawat; Ung, Benjamin Seam Yu; Mitchell, A.; Sriram, Sharath; Bhaskaran, Madhu; Chang, Shengjang; Abbott, Derek Abstract: Electromagnetic device design and flexible electronics fabrication are combined to demonstrate mechanically tunable metamaterials operating at terahertz frequencies. Each metamaterial comprises a planar array of resonators on a highly elastic polydimethylsiloxane substrate. The resonance of the metamaterials is controllable through substrate deformation. Applying a stretching force to the substrate changes the inter-cell capacitance and hence the resonance frequency of the resonators. In the experiment, greater than 8% of the tuning range is achieved with good repeatability over several stretching-relaxing cycles. This study promises applications in remote strain sensing and other controllable metamaterial-based devices. Mon, 31 Dec 2012 13:30:00 GMT http://hdl.handle.net/2440/78415 2012-12-31T13:30:00Z http://hdl.handle.net/2440/78410 Title: Robust H∞ synchronization of a hyper-chaotic system with disturbance input Author: Wang, Bo; Shi, Peng; Karimi, Hamid Reza; Song, Yong-Duan; Wang, Jun Mon, 31 Dec 2012 13:30:00 GMT http://hdl.handle.net/2440/78410 2012-12-31T13:30:00Z http://hdl.handle.net/2440/78407 Title: Automated authorship attribution using advanced signal classification techniques Author: Ebrahimpour, Maryam; Putnins, Talis Janis; Berryman, Matthew John; Allison, Andrew Gordon; Ng, Brian Wai-Him; Abbott, Derek Abstract: In this paper, we develop two automated authorship attribution schemes, one based on Multiple Discriminant Analysis (MDA) and the other based on a Support Vector Machine (SVM). The classification features we exploit are based on word frequencies in the text. We adopt an approach of preprocessing each text by stripping it of all characters except a-z and space. This is in order to increase the portability of the software to different types of texts. We test the methodology on a corpus of undisputed English texts, and use leave-one-out cross validation to demonstrate classification accuracies in excess of 90%. We further test our methods on the Federalist Papers, which have a partly disputed authorship and a fair degree of scholarly consensus. And finally, we apply our methodology to the question of the authorship of the Letter to the Hebrews by comparing it against a number of original Greek texts of known authorship. These tests identify where some of the limitations lie, motivating a number of open questions for future work. An open source implementation of our methodology is freely available for use at https://github.com/matthewberryman/autho​r-detection. Mon, 31 Dec 2012 13:30:00 GMT http://hdl.handle.net/2440/78407 2012-12-31T13:30:00Z http://hdl.handle.net/2440/78402 Title: Gain-scheduled worst-case control on nonlinear stochastic systems subject to actuator saturation and unknown information Author: Shi, Peng; Yin, Yanyan; Liu, Fei Abstract: In this paper, we propose a method for designing continuous gain-scheduled worst-case controller for a class of stochastic nonlinear systems under actuator saturation and unknown information. The stochastic nonlinear system under study is governed by a finite-state Markov process, but with partially known jump rate from one mode to another. Initially, a gradient linearization procedure is applied to describe such nonlinear systems by several model-based linear systems. Next, by investigating a convex hull set, the actuator saturation is transferred into several linear controllers. Moreover, worst-case controllers are established for each linear model in terms of linear matrix inequalities. Finally, a continuous gain-scheduled approach is employed to design continuous nonlinear controllers for the whole nonlinear jump system. A numerical example is given to illustrate the effectiveness of the developed techniques. Mon, 31 Dec 2012 13:30:00 GMT http://hdl.handle.net/2440/78402 2012-12-31T13:30:00Z