A seminar was held on November 17th, 2015 by the Faculty of Information Technology, in which three presentations were given by Assistant Professor Pei Dang, Assistant Professor Feng Li, AssistantProfessor Xiaoping Lu respectively.
Speaker: Pei Dang
Title: Extra-strong uncertainty principle in signal analysis
Abstract: We propose stronger uncertainty principles in different settings, for example, the classical setting for Fourier transform and for Linear canonical transform, periodic signals and spherical signals settings. We also deduce the conditions that give rise to the equal relation of the uncertainty principle. The work strengthens the result established by L. Cohen on uncertainty principle involving phase derivative.
Speaker: Li Feng
Title: A Novel Approach for Performance Analysis of Polling Schemes in IEEE 802.11
Polling schemes, which can provide strict quality of service guarantees, are widely adopted in IEEE 802.11 standards, such as IEEE 802.11 PCF and HCCA. Existing performance analysis approaches are tedious, complicated, or lack scalability. In this talk, we introduce a novel framework to revisit the delay performance of an IEEE 802.11 PCF network and its power management extension. Our framework leverages a salient feature of 802.11 polling schemes: IEEE 802.11 networks dictate a fixed period over which each node is polled sequentially. With this framework, we respectively apply the classic M/G/1 vacation model and the classic pure limited queueing model to analyze the delay performance in a straightforward manner, thereby avoiding reconstructing a new analysis model as done in previous research. Compared with related work, our approach is simpler, more scalable, and more general. Simulations show that our analytical results are very accurate for both homogeneous and heterogeneous traffic. We believe that our approach is also applicable for analyzing the performance of the polling schemes in the emerging networks such as 802.11 ac/ad, Internet of Thing, and Smart Grid.
Speaker: Xiaoping Lu
Title: Shape Determination for asteroids
Based on an efficient numerical integration, called LEBEDEV quadrature, a fast ellipsoid shape model for asteroid is presented to simulate the variation of observed brightness, i.e. lightcurves. The fast method can simultaneously derive the shape model with other physical parameters, such as rotational period, orientation of spin axis in an efficient way. Furthermore, in order to simulate the asymmetric surface of asteroids, a more general shape model, called ‘CELLINOID’, is applied to simulate the asymmetric lightcurves with different extreme values. The shape model consists of eight octants of ellipsoids having different semi-axes, with the constraint that adjacent octants must have two equal semi-axes in common. Simply extended from ellipsoid shape model, CELLINOID model can derive the shape and other physical parameters more accurately than ellipsoid model. Additionally, a method to make the observation plan for collecting more lightcurves in various observing geometry is introduced, too. Employing these lightcurves, the shape model and physical parameters of asteroids can be refined.