Pitch Control of a Micro Air Vehicle with Micropressure Sensors

Maintaining stable flight of micro aerial vehicles is challenging, especially in complex, low-Reynolds-number flight environments while considering wind gust disturbance, flow separation, and flow reattachment. To date, most micro aerial vehicles use vision, inertial measurement units, and/or global positioning systems as their primary sensing and navigation devices; however, actual flow conditions over the aircraft wing surfaces cannot be captured directly. In this paper, a biologically inspired micro aerial vehicle pitch control system is designed using distributed pressure information. The pressure information on the wing surfaces of a micro aerial vehicle is directly measured by a array of digital barometric micropressure sensors and is then used to calculate the aerodynamic forces, center of pressure, pitching moment, etc. A new pitch motion model that can capture the pressure information is derived from the control perspective. A nonlinear controller is also designed to achieve accurate pitch control, which is robust with respect to bounded uncertainties and unmodeled dynamics. It is anticipated that this new micro aerial vehicle design, which uses real-time sensed pressure information, can significantly enhance the stability and agility of micro aerial vehicles. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc

Visible Reverse K-Nearest Neighbor Queries

Abstract — Reverse nearest neighbor (RNN) queries have a broad application base such as decision support, profile-based marketing, resource allocation, data mining, etc. Previous work on RNN search does not take obstacles into consideration. In the real world, however, there are many physical obstacles (e.g., buildings, blindages, etc.), and their presence may affect the visibility/distance between two objects. In this paper, we introduce a novel variant of RNN queries, namely visible reverse nearest neighbor (VRNN) search, which considers the obstacle influence on the visibility of objects. Given a data set P, an obstacle set O, and a query point q, a VRNN query retrieves the points in P that have q as their nearest neighbor and are visible to q. We propose an efficient algorithm for VRNN query processing, assuming that both P and O are indexed by R-trees. Our methods do not require any pre-processing, and employ half-plane property and visibility check to prune the search space. In addition, we extend our solution to tackle the visible reverse k-nearest neighbor (VRkNN) search, which finds the points in P that have q as one of their k nearest neighbors and are visible to q. Extensive experiments on synthetic and real datasets have been conducted which demonstrate the efficiency and effectiveness of our proposed algorithms. I

The putative signal peptide of glucagon-like peptide-1 receptor is not required for receptor synthesis but promotes receptor expression

Synopsis GLP-1R (glucagon-like peptide-1 receptor) mediates the 'incretin effect' and many other anti-diabetic actions of its cognate ligand, GLP-1 (glucagon-like peptide-1). It belongs to the class B family of GPCRs (G protein-coupled receptors) and possesses an N-terminal putative SP (signal peptide). It has been reported that this sequence is required for the synthesis of GLP-1R and is cleaved after receptor synthesis. In the present study, we conducted an in-depth exploration towards the role of the putative SP in GLP-1R synthesis. A mutant GLP-1R without this sequence was expressed in HEK293 cells (human embryonic kidney 293 cells) and displayed normal functionality with respect to ligand binding and activation of adenylate cyclase. Thus the putative SP does not seem to be required for receptor synthesis. Immunoblotting analysis shows that the amount of GLP-1R synthesized in HEK293 cells is low when the putative SP is absent. This indicates that the role of the sequence is to promote the expression of GLP-1R. Furthermore, epitopes tagged at the N-terminal of GLP-1R are detectable by immunofluorescence and immunoblotting in our experiments. In conclusion, the present study points to different roles of SP in GLP-1R expression which broadens our understanding of the functionality of this putative SP of GLP-1R and possibly other Class B GPCRs