Geometric Spanner of Segments (Algorithms and Computation)

Algorithms and computation : 18th International Symposium, ISAAC 2007, Sendai, Japan, December 17-19, 2007 : proceedings ; ISAAC 2007 : (Lecture notes in computer science ; 4835)Proc. of ISACCGeometric spanner is a fundamental structure in computational geometry and plays an important role in many geometric networks design applications. In this paper, we consider a generalization of the classical geometric spanner problem (called segment spanner): Given a set S of disjoint 2-D segments, find a spanning network G with minimum size so that for any pair of points in S, there exists a path in G with length no more than t times their Euclidean distance. Based on a number of interesting techniques (such as weakly dominating set, strongly dominating set, and interval cover), we present an efficient algorithm to construct the segment spanner. Our approach first identifies a set of Steiner points in S, then construct a point spanner for them. Our algorithm runs in O(|Q| + n 2 logn) time, where Q is the set of Steiner points. We show that Q is an O(1)-approximation in terms of its size when S is relatively “well” separated by a constant. For arbitrary rectilinear segments under L 1 distance, the approximation ratio improves to 2

A Modest Proposal for the G20

A group of international scholars and policy-makers met in Beijing on 18th of March 2011, to discuss reforms in the international monetary system. There is a general consensus that there is a need for fundamental reforms in that system, which, even if it has not caused recent imbalances and instability in the global economy, has certainly proved ineffective in addressing them. While such reforms will require extensive discussion and deliberation, the consensus of the Beijing Group was that there was a modest proposal which could be adopted this year by the G20: a limited expansion of the current SDR system. This modest proposal, while limited in scope, could be play an important role in initiating discussions of deeper reforms and which would, at the same time, make a modest contribution to restoring the world's fragile economy to health, helping to achieve the aim expressed in the G20 Pittsburgh declaration for a "strong, sustainable and balanced growth"

Geometric Spanner of Objects under L1 Distance (Computing and Combinatorics)

Computing and combinatorics : 14th annual international conference, COCOON 2008, Dalian, China, June 27-29, 2008 : proceedings : (Lecture notes in computer science ; 5092)The 14th Annual International Computing and Combinatorics Conference (COCOON 2008)Geometric spanner is a fundamental structure in computational geometry and plays an important role in many geometric networks design applications. In this paper, we consider the following generalized geometric spanner problem under L 1 distance: Given a set of disjoint objects S, find a spanning network G with minimum size so that for any pair of points in different objects of S, there exists a path in G with length no more than t times their L 1 distance, where t is the stretch factor. Specifically, we focus on three types of objects: rectilinear segments, axis aligned rectangles, and rectilinear monotone polygons. By combining ideas of t-weekly dominating set, walls, aligned pairs and interval cover, we develop a 4-approximation algorithm (measured by the number of Steiner points) for each type of objects. Our algorithms run in near quadratic time, and can be easily implemented for practical applications

Mitochondrial C4375T mutation might be a molecular risk factor in a maternal Chinese hypertensive family under haplotype C

Here, we reported a Han Chinese essential hypertensive pedigree based on clinical hereditary and molecular data. To know the molecular basis on this family, mitochondrial genome of one proband from the family was identified through direct sequencing analysis. The age of onset year and affected degree of patients are different in this family. And matrilineal family members carrying C4375T mutation and belong to Eastern Asian halopgroup C. Phylogenetic analysis shows 4375C is highly conservative in 17 species. It is suggested that these mutations might participate in the development of hypertension in this family. And halopgroup C might play a modifying role on the phenotype in this Chinese hypertensive family

MPC-based 3-D trajectory tracking for an autonomous underwater vehicle with constraints in complex ocean environments

© 2019 Elsevier Ltd This paper presents a novel three-dimension (3-D) underwater trajectory tracking method for an autonomous underwater vehicle (AUV) using model predictive control (MPC). First, the 6-degrees of freedom (DoF) model of a fully-actuated AUV is represented by both kinematics and dynamics. After that, the trajectory tracking control is proposed as an optimization problem and then transformed into a standard convex quadratic programming (QP) problem which can be readily computed online. The practical constraints of the system inputs and states are considered effectively in the design phase of the proposed control strategy. To make the AUV move steadily, the control increments are considered as the system input and optimized. The receding horizon implementation makes the optimal control inputs be recalculated at each sampling instant, which can improve the robustness of the tracking control under the model uncertainties and time-varying disturbances. Simulations are carried out under two different 3-D trajectories to verify the performance of trajectory tracking under random disturbances, ocean current disturbances, and ocean wave disturbances. The simulation results are given to show the feasibility and robustness of the MPC-based underwater trajectory tracking algorithm