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Lu W.,Tsinghua National Laboratory for Information Sciences and Technology
Geophysics | Year: 2013

I have developed an accelerated sparse time-invariant Radon transform (RT) in the mixed frequency-time domain based on iterative 2D model shrinkage in the time domain. I denote it as SRTIS. In the traditional sparse time-invariant RT in the mixed frequency-time domain, the sparse RT is modeled as a sparse inverse problem that is solved by the iteratively reweighted least-squares (IRLS) algorithm in the time domain, and the forward and inverse RTs are implemented in the frequency domain. In this method, IRLS is replaced by iterative 2D model shrinkage, i.e., the sparsity of the Radon model is promoted by some simple 2D model shrinkage operations in the time domain. Synthetic and real data demultiple examples using the parabolic RTs are given to demonstrate the better performance of the SRTIS when compared with the least-squares-based RT, the frequency domain sparse RT, and the traditional time-domain sparse RT in the mixed frequency-time domain. © 2013 Society of Exploration Geophysicists. Source

Zhou L.,Tsinghua National Laboratory for Information Sciences and Technology
IEEE Sensors Journal | Year: 2014

In this paper, we present a new minimal solution for the extrinsic calibration of a 2D light detection and ranging (LIDAR) sensor and a perspective camera. This problem is formulated as registering three planes and the corresponding coplanar lines. All existing algorithms solve this problem by its geometric structure in the original or the dual 3D space. In contrast, our algorithm directly exploits the algebraic structure of the polynomial system to resolve this problem. This new algorithm is more abstract, however, and provides a more broadly applicable method to other problems that need to handle the similar polynomial system. The rotation matrix is estimated first. Then, the translation vector can be calculated by solving a system of three linear equations. Although the new approach is conceptually simple, it has 720 different versions caused by different permutations of variables. This results in different computational orders and affects the numerical behavior of the algorithm. A simple heuristic scheme is proposed to select the permutation of variables that yields numerically stable computational order with respect to the given input. Simulation and experimental results show that the proposed algorithm outperforms the existing state-of-the-art algorithms in terms of accuracy and numerical stability. © 2013 IEEE. Source

Chen W.,Tsinghua National Laboratory for Information Sciences and Technology
IEEE Transactions on Wireless Communications | Year: 2014

Cooperative communication suffers from multiplexing loss and low spectral efficiency due to the half duplex constraint of relays. To improve the multiplexing gain, successive relaying, which allows concurrent transmission of the source and relays, has been proposed. However, the severe inter-relay interference becomes a key challenge. In this paper, we propose a channel aware successive relaying protocol, also referred to as CAO-SIR, which is capable of thoroughly mitigating inter-relay interference by carefully adapting relays' transmission order and rate. In particular, a relay having a poorer link to the source is scheduled first to forward a message, the data rate of which is adapted to the link quality of the source-relay and relay-destination channels. By this means, each relay may decode the messages intended for the preceding relays, and then cancel these relays' interference in a low complexity which is equal to that of Decision Feedback Equalizer (DFE). To further optimize and analyze CAO-SIR, we present its equivalent parallel relay channel model, based upon which the adaptive relay selection and power allocation schemes are proposed. By employing M half duplex relays, CAO-SIR is capable of achieving an diversity-multiplexing tradeoff (DMT) given by d(r) = max { (M + 1) (1 - M+2/M+1 r), (1 - r) }, where d(r) and r denote the diversity and multiplexing gains, respectively. Its DMT asymptotically approaches the DMT upper bound achieved by (M + 1) x 1 MISO systems or M full duplex relays, when M is large. © 2014 IEEE. Source

Liu Y.-J.,Tsinghua National Laboratory for Information Sciences and Technology
CAD Computer Aided Design | Year: 2013

A natural metric in 2-manifold surfaces is to use geodesic distance. If a 2-manifold surface is represented by a triangle mesh T, the geodesic metric on T can be computed exactly using computational geometry methods. Previous work for establishing the geodesic metric on T only supports using half-edge data structures; i.e., each edge e in T is split into two halves (h e1,he2) and each half-edge corresponds to one of two faces incident to e. In this paper, we prove that the exact-geodesic structures on two half-edges of e can be merged into one structure associated with e. Four merits are achieved based on the properties which are studied in this paper: (1) Existing CAD systems that use edge-based data structures can directly add the geodesic distance function without changing the kernel to a half-edge data structure; (2) To find the geodesic path from inquiry points to the source, the MMP algorithm can be run in an on-the-fly fashion such that the inquiry points are covered by correct wedges; (3) The MMP algorithm is sped up by pruning unnecessary wedges during the wedge propagation process; (4) The storage of the MMP algorithm is reduced since fewer wedges need to be stored in an edge-based data structure. Experimental results show that when compared to the classic half-edge data structure, the edge-based implementation of the MMP algorithm reduces running time by 44% and storage by 29% on average. © 2012 Elsevier Ltd. All rights reserved. Source

Wang L.,Tsinghua National Laboratory for Information Sciences and Technology | Li L.-P.,Tsinghua National Laboratory for Information Sciences and Technology
International Journal of Electrical Power and Energy Systems | Year: 2013

Solving the non-convex economic load dispatch (ELD) problem with evolutionary algorithms has gained increasing research in recent years. In this paper, a differential harmony search (DHS) algorithm is proposed by combining the mechanisms of both differential evolution and harmony search. In the DHS, the pitch adjustment operation is cooperated with the different mutation operation to enhance the exploitation ability of harmony search, and both the memory consideration and the pitch adjustment are used to enhance the exploration ability of evolution search. In addition, a repair procedure and three simple selection rules are proposed for constraint handling. Numerical simulations are carried out based on different kinds of testing problems with various constraints including valve point effects, multi-fuels, ramp rate limit and prohibited operation zones. Simulation results and comparisons with the some existing algorithms demonstrate the effectiveness, efficiency and robustness of the proposed DHS algorithm. Finally, the effect of parameter setting on the DHS is investigated as well. © 2012 Elsevier Ltd. All rights reserved. Source

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