1,721,154 research outputs found
Outlier detection and least trimmed squares approximation using semi-definite programming
No full textRobust linear regression is one of the most popular problems in the robust statistics community. It is often conducted via least trimmed squares, which minimizes the sum of the k smallest squared residuals. Least trimmed squares has desirable properties and forms the basis on which several recent robust methods are built, but is very computationally expensive due to its combinatorial nature. It is proven that the least trimmed squares problem is equivalent to a concave minimization problem under a simple linear constraint set. The “maximum trimmed squares”, an “almost complementary” problem which maximizes the sum of the q smallest squared residuals, in direct pursuit of the set of outliers rather than the set of clean points, is introduced. Maximum trimmed squares (MTS) can be formulated as a semi-definite programming problem, which can be solved efficiently in polynomial time using interior point methods. In addition, under reasonable assumptions, the maximum trimmed squares problem is guaranteed to identify outliers, no mater how extreme they are.<br/
Coordinating multiple concurrent negotiations
No full textTo secure good deals, an agent may engage in multiple concurrent negotiations for a particular good or service. However for this to be effective, the agent needs to carefully coordinate its negotiations. At a basic level, such coordination should ensure the agent does not procure more of the good than is needed. But to really derive benefit from such an approach, the agent needs the concurrent encounters to mutually influence one another (e.g. a good price with one opponent should enable an agent to negotiate more strongly in the other interactions). To this end, this paper presents a novel heuristic model for coordinating multiple bilateral negotiations. The model is empirically evaluated and shown to be effective and robust in a range of negotiation scenarios
Reasoning about commitments in multiple concurrent negotiations
No full textAutomated negotiation by software agents is a key enabling technology for agent mediated e-commerce. To this end, this paper considers an important class of such negotiations - namely those in which an agent engages in multiple concurrent bilateral negotiations for a good or service. In particular, we consider the situation in which a buyer agent is looking for a single service provider from a number of available ones in its environment. By bargaining simultaneously with these providers and interleaving partial agreements that it makes with them, a buyer can reach good deals in an efficient manner. However, a key problem in such encounters is managing commitments since an agent may want to make intermediate deals (so that it has a definite agreement) with other agents before it gets to finalize a deal at the end of the encounter. To do this effectively, however, the agents need to have a flexible model of commitments that they can reason about in order to determine when to commit and to decommit. This paper provides and evaluates such a commitment manager and integrates it into the negotiation model
Through life asset management by integrated life cycle costing and concurrent engineering
No full textSerially Concatenated Luby Transform Coding and Bit-Interleaved Coded Modulation Using Iterative Decoding for the Wireless Internet
No full textIn Bit-Interleaved Coded Modulation (BICM) the coding and modulation schemes were jointly optimized for the sake of attaining the best possible performance when communicating over fading wireless communication channels. The iterative decoding scheme of BICM (BICM-ID) invoking an appropriate bit-to-symbol mapping strategy enhances its achievable performance in both AWGN and Rayleigh channels. BICM-ID may be conveniently combined with Luby Transform (LT) codes, which were designed for handling packetized wireless Internet data traffic in erasure channels without retransmitting the corrupted packets. By jointly designing a serially concatenated LT-BICM-ID code, an infinitesimally low Bit Error Rate (BER) is achieved for Signal to Noise Ratios (SNR) in excess of 7.5dB over wireless Internet type erasure channels contaminated by AWGN
Systematic Luby Transform Codes and their Soft Decoding
Full text linkLuby Transform codes (LT) were originally designed for the Binary Erasure Channel (BEC) encountered owing to randomly dropped packets in the statistical multiplexing aided classic wireline-based Internet, where transmitted packets are not affected by the fading or noise of the propagation environment of the wireless Internet. For the sake of transmitting data over the BEC routinely encountered in statistical multiplexing aided wireless Internet - style scenarios, we applied the belief propagation algorithm for decoding LT codes and designed a novel version of LT codes, which we refer to as systematic LT codes. When using soft decoding of the proposed systematic LT code, the decoding process becomes capable of preventing the potentially avalanche-like inter-packet error propagation. For example, the systematic LT(1000,3000) code achieved a BER below 10?5 at Eb/N0 = 3.5dB after six decoding iterations. An even lower Eb/N0 of 2.7dB was required, when using a longer systematic LT(10000,30000) code for transmission over the AWGN channel. In the combined BEC-AWGN channel the BER recorded at the output of the systematic LT(1000,3000) code was about 10?5 at Eb/N0 = 4.5dB, when encounter an erasure probability of Pe = 0.1
Discontinious Galerkin formulations for thin bending problems
No full textA structural thin bending problem is essentially associated with a fourth-order partial differential equation. Within the finite element framework, the numerical solution of thin bending problems demands the use of C^1 continuous shape functions. Elements using these functions are challenging and difficult to construct. A particular discontinuous Galerkin method has been used to deal with thin bending problems. It exploits standard Lagrange finite element basis functions with displacement degrees-of-freedom only. The method relies on a lifting operation to transform jumps in the normal derivative across element boundaries to a field defined on element interiors. By introducing special integrals over element boundaries, continuity requirements associated with thin bending problems are met weakly while consistency of the Galerkin problem is preserved and the stability of the formulation is controlled. The approach is formulated for a range of bending problems. Firstly, a finite element formulation for linear Kirchhoff plates is proposed. The formulation is analysed in terms of stability and convergence. A priori error estimates are supported by a range of numerical examples, including static plate bending, plate buckling and vibration. The method has also been developed for geometrically linear and nonlinear thin shell models. For geometrically nonlinear problems, an exact linearisation of the proposed formulation is presented. Using the approach, a non-smooth shell geometry can be dealt with. The performance of the approach is demonstrated via a range of numerical benchmark tests for both geometrically linear and nonlinear thin shells. Based on the obtained results, it can be concluded that the proposed formulation is robust, accurate and relatively simple. As a thin shell theory has been addressed directly, shear locking is completely avoided. Although membrane locking exists, it can be alleviated when high-order basis functions are used. Cubic elements perform particularly well in various challenging benchmark tests. The method is general in sense that it does not rely on a particular element type or shape.Civil Engineering and Geoscience
Amalgamated Generalized Low Density Parity Check and Luby Transform Codes for the Wireless Internet
Full text linkLuby Transform codes (LT) were originally designed for the Binary Erasure Channel (BEC) encountered owing to randomly dropped packets in the statistical multiplexing aided Internet, where transmitted packets are not affected by the fading or noise of the environment. For the sake of transmitting data over the BEC routinely encountered in statistical multiplexing aided wireless Internet-style scenarios, LT codes have to be combined with classic channel codes. In this paper we introduce a novel amalgamated LT coding and Generalized Low Density Parity Check (G-LDPC) coding scheme. Upon exploiting the packet erasure information provided by the GLDPC decoder for the LT decoder, the proposed scheme achieves a low Bit Error Ratio (BER) for Packet Error Ratio (PER) Eb/N0 values in excess of 3.2dB when transmitting data over the AWGN-BEC channel having a packet erasure probability of Pe=0.1. When communicating over the Rayleigh-BEC channel at Pe=0.1, an Eb/N0 value of 5.3 dB was required. In comparison to the serially concatenated LT-GLDPC scheme using no information exchange between the G-LDPC decoder and the LT decoder, the amalgamated LT-GLDPC arrangement achieved an Eb/N0 gain of up to 1.6-2.5 dB
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
