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  • 1
    Electronic Resource
    Electronic Resource
    On a homogeneous algorithm for the monotone complementarity problem (1999)
    Springer
    Mathematical programming 84 (1999), S. 375-399 
    Details
    ISSN: 1436-4646
    Keywords: Key words: monotone complementarity problem – homogeneous and self-dual – infeasible-starting algorithm ; Mathematics Subject Classification (1991): 90C25, 90C33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101070050027
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  • 2
    Electronic Resource
    Electronic Resource
    Presolving in linear programming (1995)
    Springer
    Mathematical programming 71 (1995), S. 221-245 
    Details
    ISSN: 1436-4646
    Keywords: Linear programming ; Presolving ; Interior-point methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Most modern linear programming solvers analyze the LP problem before submitting it to optimization. Some examples are the solvers WHIZARD (Tomlin and Welch, 1983), OB1 (Lustig et al., 1994), OSL (Forrest and Tomlin, 1992), Sciconic (1990) and CPLEX (Bixby, 1994). The purpose of the presolve phase is to reduce the problem size and to discover whether the problem is unbounded or infeasible. In this paper we present a comprehensive survey of presolve methods. Moreover, we discuss the restoration procedure in detail, i.e., the procedure that undoes the presolve. Computational results on the NETLIB problems (Gay, 1985) are reported to illustrate the efficiency of the presolve methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01586000
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  • 3
    Electronic Resource
    Electronic Resource
    Agri-environmental schemes and the European agricultural landscapes: the role of indicators as valuing tools for evaluation (2000)
    Springer
    Landscape ecology 15 (2000), S. 271-280 
    Details
    ISSN: 1572-9761
    Keywords: agricultural landscapes ; agri-environmental policy ; Europe ; indicators on policy effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Europe most conservation values, from biodiversity to scenic sites, are integral parts of agricultural landscapes. When these landscapes change as a result of agricultural policies, natural values – species, habitats, landscapes – are usually affected. Until recently however, these values have not been part of agricultural policies. The impacts of such new policies are difficult to evaluate because landscapes are complex and diverse, and the effects of policy are rarely immediate or causal. This paper evaluates the potential effects of Agri-environmental Regulation EC 2078/92 on European agricultural landscapes through the use of agri-environmental indicators (AEIs) on policy effects. After discussing the general framework of the evaluation methodology through the use of AEIs, we distinguish two types of agri-environmental policy (AEP) effects: policy performances and policy outcomes. The impediments to direct measurement of policy outcomes are stated. The potential for measuring policy performances are checked in two case study areas, one in Spain and one in Denmark, characterized by extensive agricultural land-uses and by the dual process of intensification/abandonment that is threatening their natural values. Both study areas are currently targeted by agri-environmental schemes under Reg. 2078/92. The realisability or availability of suitable statistical data to construct and report each AEI is stated for both types of effects. A problem of scale and content is found in most of the available statistics for assessing policy outcomes and the need for data at farm level is concluded to be indispensable if policy performances are to be measured. Effects of policy performance are measured for key selected AEIs in each study area on the basis of the results of a field survey based on questionnaires of participating and non-participating farmers in the AEP schemes. The main effects may be catalogued as improvement effects or protection effects since they represent a change in participant over non-participant farmers' decisions. Finally, the importance of this type of policy evaluation approach is discussed in the light of the likely future development of AEP in the European Union.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008155229725
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  • 4
    Electronic Resource
    Electronic Resource
    A Computational Study of the Homogeneous Algorithm for Large-scale Convex Optimization (1998)
    Springer
    Computational optimization and applications 10 (1998), S. 243-269 
    Details
    ISSN: 1573-2894
    Keywords: monotone complementarity problem ; homogeneous and self-dual model ; interior-point algorithms ; large-scale convex optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Recently the authors have proposed a homogeneous and self-dual algorithm for solving the monotone complementarity problem (MCP) [5]. The algorithm is a single phase interior-point type method; nevertheless, it yields either an approximate optimal solution or detects a possible infeasibility of the problem. In this paper we specialize the algorithm to the solution of general smooth convex optimization problems, which also possess nonlinear inequality constraints and free variables. We discuss an implementation of the algorithm for large-scale sparse convex optimization. Moreover, we present computational results for solving quadratically constrained quadratic programming and geometric programming problems, where some of the problems contain more than 100,000 constraints and variables. The results indicate that the proposed algorithm is also practically efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018369223322
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  • 5
    Electronic Resource
    Electronic Resource
    A goodness of fit test for the rasch model (1973)
    Springer
    Psychometrika 38 (1973), S. 123-140 
    Details
    ISSN: 1860-0980
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract The Rasch model is an item analysis model with logistic item characteristic curves of equal slope,i.e. with constant item discriminating powers. The proposed goodness of fit test is based on a comparison between difficulties estimated from different scoregroups and over-all estimates. Based on the within scoregroup estimates and the over-all estimates of item difficulties a conditional likelihood ratio is formed. It is shown that—2 times the logarithm of this ratio isx 2-distributed when the Rasch model is true. The power of the proposed goodness of fit test is discussed for alternative models with logistic item characteristic curves, but unequal discriminating items from a scholastic aptitude test.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291180
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  • 6
    Electronic Resource
    Electronic Resource
    Paired comparisons with individual differences (1976)
    Springer
    Psychometrika 41 (1976), S. 141-157 
    Details
    ISSN: 1860-0980
    Keywords: Bradley-Terry model ; sufficiency ; individual parameters ; goodness of fit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract A model of Bradley-Terry type for paired comparisons is considered. In addition to the usual parameters, the model allows for individual parameters and corresponding parameters for the choice-alternatives. The model is applied to a set of data from a Danish investigation of the attitude of blue collar workers towards alternative social gains. The proposed model is finally compared to a model recently suggested by Schönemann and Wang.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291835
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  • 7
    Electronic Resource
    Electronic Resource
    Sufficient statistics and latent trait models (1977)
    Springer
    Psychometrika 42 (1977), S. 69-81 
    Details
    ISSN: 1860-0980
    Keywords: logistic latent trait ; minimal sufficient statistic ; Rasch model ; equidistant scoring ; sufficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract For questionnaires with two answer categories, it has been proven in complete generality that if a minimal sufficient statistic exists for the individual parameter and if it is the same statistic for all values of the item parameters, then the raw score (or the number of correct answers) is the minimal sufficient statistic. It follows that the model must by of the Rasch type with logistic item characteristic curves and equal item-discriminating powers. This paper extends these results to multiple choice questionnaires. It is shown that the minimal sufficient statistic for the individual parameter is a function of the so-called score vector. It is also shown that the so-called equidistant scoring is the only scoring of a questionnaire that allows for a real valued sufficient statistic that is independent of the item parameters, if a certain ordering property for the sufficient statistic holds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02293746
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  • 8
    Electronic Resource
    Electronic Resource
    Goodness of fit tests for paired comparison models. A reply (1978)
    Springer
    Psychometrika 43 (1978), S. 131-131 
    Details
    ISSN: 1860-0980
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02294101
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  • 9
    Electronic Resource
    Electronic Resource
    Georg Rasch (1901–1980) (1982)
    Springer
    Psychometrika 47 (1982), S. 375-376 
    Details
    ISSN: 1860-0980
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02293703
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  • 10
    Electronic Resource
    Electronic Resource
    Residualanalysis in the polytomous rasch model (1995)
    Springer
    Psychometrika 60 (1995), S. 375-393 
    Details
    ISSN: 1860-0980
    Keywords: polytomous Rasch model ; residuals ; latent structure model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract Residuals for check of model fit in the polytomous Rasch model are examined. Comparisons are made between using counts for all response pattern and using item totals for score groups for the construction of the residuals. Comparisons are also, for the residuals based on score group totals, made between using as basis the item totals, or using the estimated item parameters. The developed methods are illustrated by two examples, one from a psychiatric rating scale, one from a Danish Welfare Study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02294382
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