On finding approximate solutions of qualitative constraint networks

Qualitative Spatial and Temporal Reasoning (QSTR) represents spatial and temporal information in terms of human comprehensible qualitative predicates and reasons about qualitative information by solving qualitative constraint networks (QCNs). Despite significant progress in the past three decades, more and more evidence has shown that it is inherently hard to find exact solutions for expressive qualitative constraints. In many applications, however, we are often required to make decisions in a very limited time. In these cases, finding a good approximate solution in seconds is much more desirable than waiting days for an exact solution. In this paper, we will exploit the algebraic structure of qualitative calculi (e.g. Interval Algebra and RCC8) as well as their conceptual neighbourhood graphs to develop approximate methods for consistency checking in QSTR. Moreover, we propose and empirically compare four independent methods to serve as tools for finding good approximate solutions for the given qualitative calculi. © 2013 IEEE

Analytical studies of groundwater-head fluctuation in a coastal confined aquifer overlain by a semi-permeable layer with storage

Analytical studies are carried out to investigate groundwater-head changes in a coastal aquifer system in response to tidal fluctuations. The system consists of an unconfined aquifer, a semi-confined aquifer and a semi-permeable confining unit between them. An exact analytical solution is derived to investigate the influences of both leakage and storage of the semi-permeable layer on the tide-induced groundwater-head fluctuation in the semi-confined aquifer. This solution is a generalization of the solution obtained by Jiao and Tang (Water Resource Research 35 (1999) 747-751) which ignored the storage of the semi-confining unit. The analytical solution indicates that both storage and leakage of the semi-permeable layer play an important role in the groundwater-head fluctuation in the confined aquifer. While leakage is generally more important than storage, the impact of storage on groundwater-head fluctuations changes with leakage. With the increase of leakage the fluctuation of groundwater-head in the confined aquifer will be controlled mainly by leakage. The study also demonstrates that the influence of storativity of the semi-permeable layer on groundwater-head fluctuation is negligible only when the storativity of the semi-permeable layer is comparable to or smaller than that of the confined aquifer. However, for aquifer systems with semi-permeable layer composed of thick, soft sedimentary materials, the storativity of the semi-permeable layer is usually much greater than that of the aquifer and its influence should be considered. © 2001 Elsevier Science Ltd. All rights reserved.postprin

On generalized expectation-based estimation of a population spectral distribution from high-dimensional data

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A social spider algorithm for global optimization

The growing complexity of real-world problems has motivated computer scientists to search for efficient problem-solving methods. Metaheuristics based on evolutionary computation and swarm intelligence are outstanding examples of nature-inspired solution techniques. Inspired by the social spiders, we propose a novel social spider algorithm to solve global optimization problems. This algorithm is mainly based on the foraging strategy of social spiders, utilizing the vibrations on the spider web to determine the positions of preys. Different from the previously proposed swarm intelligence algorithms, we introduce a new social animal foraging strategy model to solve optimization problems. In addition, we perform preliminary parameter sensitivity analysis for our proposed algorithm, developing guidelines for choosing the parameter values. The social spider algorithm is evaluated by a series of widely used benchmark functions, and our proposed algorithm has superior performance compared with other state-of-the-art metaheuristics.postprin

How foreign firms achieve competitive advantage in the Chinese emerging economy: Managerial ties and market orientation

As China experience unprecedented changes in its social, legal, and economic institutions, on what should foreign firms focus more to overcome this challenge, managerial ties or market orientation? This study investigates how managerial ties and market orientation affect competitive advantage and, consequently, firm performance in China. On the basis of a survey of 179 foreign firms in China, we find that both managerial ties and market orientation can lead to firm success-but in different ways. Market orientation enhances firm performance by providing differentiation and cost advantages, whereas managerial ties improve performance through an institutional advantage (i.e., superiority in securing scarce resources and institutional support). Institutional advantage, in turn, leads to differentiation and cost advantages and consequently superior performance. © 2009 Elsevier Inc.postprin

A local moments estimation of the spectrum of a large dimensional covariance matrix

This paper considers the problem of estimating the population spectral distribution from a sample covariance matrix when its dimension is large. We generalize the contour-integral based method in Mestre (2008) and present a local moment estimation procedure. Compared with the original, the new procedure can be applied successfully to models where the asymptotic clusters of sample eigenvalues generated by different population eigenvalues are not all separate. The proposed estimates are proved to be consistent. Numerical results illustrate the implementation of the estimation procedure and demonstrate its efficiency in various cases.postprin

Factor V Leiden and thrombosis in patients with systemic lupus erythematosus: a meta-analysis.

The aim of this study was to perform a meta-analysis of the association between the factor V Leiden polymorphism (FVL) and thrombosis among patients with systemic lupus erythematosus (SLE) and/or antiphospholipid antibody (aPL) positivity. Included studies recruited patients based on SLE or aPL-positive status, confirmed subjects' SLE diagnosis as defined by the American College of Rheumatology, and documented thrombotic events. Excluded studies were non-English or considered only arterial thrombosis. Individual patient data, available from 5 studies, together with unpublished data from 1210 European-American SLE patients from the UCSF Lupus Genetics Collection genotyped for FVL, were further analyzed. Seventeen studies (n=2090 subjects) were included in the initial meta-analysis. Unadjusted odds ratios (OR) were calculated to assess association of FVL with thrombosis. The OR for association of thrombosis with FVL was 2.88 (95% confidence interval (CI) 1.98-4.20). In the secondary analysis with our individual patient dataset (n=1447 European-derived individuals), SLE subjects with the FVL polymorphism still had more than two times the odds of thrombosis compared to subjects without this polymorphism, even when adjusting for covariates such as gender, age and aPL status. SLE and/or aPL-positive patients with the FVL variant have more than two times the odds of thrombosis compared to those without this polymorphism

Formation of artificial granules for proving gelation as the main mechanism of aerobic granulation in biological wastewater treatment

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In vitro propagation and homing of liver-derived dendritic cell progenitors to lymphoid tissues of allogeneic recipients: Implications for the establishment and maintenance of donor cell chimerism following liver transplantation

Dendritic cell (DC) progenitors were propagated in liquid culture from nonparenchymal cells resident in normal mouse (B10.BR; H-2k, I-E+) liver in response to granulocyte-macrophage colony stimulating factor (GM-CSF). The liver-derived DC progenitors were MHC class II-/dim and did not express counter receptors for CTLA-4, a structural homologue of the Т cell activation molecule CD28. Following subcutaneous or intravenous injection, these liver-derived cells migrated to Т cell-dependent areas of lymph nodes and spleen of unmodified, allogeneic (BIO; H-2b; I-E_) recipients, where they were identified 1-5 days, and 1 and 2 months after injection by their strong surface expression of donor MHC class II (I-Ek) and their dendritic morphology. Maximal numbers of liver-derived DC in the spleen were recorded 5 days after injection. Both clusters of strongly donor MHC class II+ cells— and (more rarely) dividing cells—could also be identified, suggesting cell replication in situ. Using the same techniques employed to generate DC progenitors from normal liver, GM-CSF-stimulated cells were propagated for 10 days from the bone marrow and spleen of nonimmunosuppressed mice sacrificed 14 days after orthotopic liver transplantation (B10;H-2b → C3H;H-2k). Immunocytochemical staining for recipient and donor MHC class II phenotype revealed the growth both of host cells with DC characteristics, and of cells expressing donor alloantigens (I-Ab). These results are consistent with the growth, in response to GM-CSF, of donor-derived DC from progenitors seeded from the liver allograft to recipient lymphoid tissue. The functional activity of the progenitors of chimeric DC and the possible role of these cells in the establishment and maintenance of donor-specific tolerance following liver transplantation remain to be determined. © 1995 by Williams and Wilkins