Lehmann R.,FH Dresden
Survey Review | Year: 2017
This contribution describes an automatic and robust method, which can be applied to all classical geodetic computation problems. Starting from given input quantities (e.g. coordinates of known points, observations), computation opportunities for all other relevant quantities are found. For redundant input quantities, there exist a multitude of different computation opportunities from different minimal subsets of input quantities, which are all found automatically, and their results are computed and compared. If the computation is non-unique, but only a finite number of solutions exist, then all solutions are found and computed. By comparison of the different computation results, we may detect outliers in the input quantities and produce a robust final result. The method does not work stochastically, such that no stochastic model of the observations is required. The description of the algorithm is illustrated for a practical case. It is implemented on a webserver and is available for free via internet. © 2017 Survey Review Ltd
Fowler J.W.,Arizona State University |
Dauzere-Peres S.,Ecole Nationale Superieure des Mines de Saint - Etienne CMP |
Mason S.J.,Clemson University |
Rose O.,FH Dresden
Journal of Scheduling | Year: 2011
In this paper, we discuss scheduling problems in semiconductor manufacturing. Starting from describing the manufacturing process, we identify typical scheduling problems found in semiconductor manufacturing systems. We describe batch scheduling problems, parallel machine scheduling problems, job shop scheduling problems, scheduling problems with auxiliary resources, multiple orders per job scheduling problems, and scheduling problems related to cluster tools. We also present important solution techniques that are used to solve these scheduling problems by means of specific examples, and report on known implementations. Finally, we summarize some of the challenges in scheduling semiconductor manufacturing operations. © Springer Science+Business Media, LLC 2010.
Lehmann R.,FH Dresden |
Neitzel F.,Sudan University of Science and Technology
Journal of Geodesy | Year: 2013
Geodetic adjustment models are often set up in a way that the model parameters need to fulfil certain constraints. The normalized Lagrange multipliers have been used as a measure of the strength of constraint in such a way that if one of them exceeds in magnitude a certain threshold then the corresponding constraint is likely to be incompatible with the observations and the rest of the constraints. We show that these and similar measures can be deduced as test statistics of a likelihood ratio test of the statistical hypothesis that some constraints are incompatible in the same sense. This has been done before only for special constraints (Teunissen in Optimization and Design of Geodetic Networks, pp. 526-547, 1985). We start from the simplest case, that the full set of constraints is to be tested, and arrive at the advanced case, that each constraint is to be tested individually. Every test is worked out both for a known as well as for an unknown prior variance factor. The corresponding distributions under null and alternative hypotheses are derived. The theory is illustrated by the example of a double levelled line. © 2013 Springer-Verlag Berlin Heidelberg.
Meffert P.J.,University of Greifswald |
Dziock F.,FH Dresden
Landscape Ecology | Year: 2013
We analysed the effect of the urban matrix, the urban space surrounding distinct habitat patches, on bird communities. In doing so we assessed the impact of urbanisation beyond the effect of habitat loss. We used a set of 54 wasteland sites of early successional stages that were scattered over the entire urban area of Berlin, Germany. Sites were similar to each other in habitat structure but differed in their surroundings, the urban matrix. Thus, our study design allows to investigate associations between birds and the urban matrix. Our measures for urbanisation are human population density and degree of sealing within 50 to 2,000 m buffer zones surrounding each wasteland site. Along the urbanisation gradients we calculated three measures of bird communities: alpha diversity, beta diversity, and trait profile of the entire bird community regarding food, life-history, and behavioural traits. Alpha diversity did not change significantly along the gradients of urbanisation. However, beta diversity increased along the urbanisation gradients with urbanisation at the local scale (50 m) but decreased at the landscape scale (200 and 2,000 m). Fourth-corner analysis of relationships between urbanisation and species traits showed trait shifts: adult survival rate increased with human population density and densities of birds that are more often reported to show innovative behaviour increased with both human population density and degree of sealing. We conclude that the influence of the urban matrix contributes to the homogenisation of the avifauna by filtering certain species traits and promoting others. © 2013 Springer Science+Business Media Dordrecht.
Meffert P.J.,TU Berlin |
Dziock F.,FH Dresden
Biological Conservation | Year: 2012
Bird species of cultivated landscapes have been declining dramatically for decades. The main cause for this decline is intensified agricultural practice. At the same time, worldwide urbanisation increases and has severe impacts on land use. Urban wastelands, i.e., unused land within urban agglomerations, are known to provide habitat for endangered animals, but to date systematic research on birds is rare. We aim at assessing environmental characteristics of urban wastelands that meet the requirements of rare and declining bird species. In the city of Berlin, Germany, we surveyed birds on 55 wasteland sites dominated by sparse vegetation. Our analysis includes quantitative measurements of residential human density and degree of sealing at different spatial scales, a detailed vegetation mapping, and data on human intrusion. Boosted regression trees were used to model the occurrence of eight bird Species of European Conservation concern (SPEC). Overall we found 12 SPEC species; for eight data were sufficient to built models. Our findings reveal that the occurrence of endangered bird species depends most strongly on area size and vegetation structure and to a lesser extent on the composition of the urban matrix. On-site features accounted for roughly two third of the explained variance and degree of urbanisation in the surroundings for the remaining one third. Intrusion of humans or dogs had no measurable negative effect on species occurrence. As a rule of thumb, plots above 5. ha harbour SPEC species, those above 7. ha are valuable for several sensitive open-land bird species. We show that wasteland habitats have potential for nature conservation that should be considered by urban planners and landscape architects. Knowledge about crucial habitat features (few trees and shrubs, sparse vegetation) enables us to create and maintain urban green spaces that enhance protection of rare and declining species. Urban wastelands may not have the potential to fully compensate for changes and population declines outside urban areas, but they may help to offset the loss of biodiversity in the countryside. © 2012 Elsevier Ltd.
Lehmann R.,FH Dresden
Journal of Geodesy | Year: 2014
Transformations between different geodetic reference frames are often performed such that first the transformation parameters are determined from control points. If in the first place we do not know which of the numerous transformation models is appropriate then we can set up a multiple hypotheses test. The paper extends the common method of testing transformation parameters for significance, to the case that also constraints for such parameters are tested. This provides more flexibility when setting up such a test. One can formulate a general model with a maximum number of transformation parameters and specialize it by adding constraints to those parameters, which need to be tested. The proper test statistic in a multiple test is shown to be either the extreme normalized or the extreme studentized Lagrange multiplier. They are shown to perform superior to the more intuitive test statistics derived from misclosures. It is shown how model selection by multiple hypotheses testing relates to the use of information criteria like AICc and Mallows’Cp, which are based on an information theoretic approach. Nevertheless, whenever comparable, the results of an exemplary computation almost coincide. © 2014, Springer-Verlag Berlin Heidelberg.
Lehmann R.,FH Dresden
Journal of Geodesy | Year: 2012
We investigate extreme studentized and normalized residuals as test statistics for outlier detection in the Gauss-Markov model possibly not of full rank. We show how critical values (quantile values) of such test statistics are derived from the probability distribution of a single studentized or normalized residual by dividing the level of error probability by the number of residuals. This derivation neglects dependencies between the residuals. We suggest improving this by a procedure based on the Monte Carlo method for the numerical computation of such critical values up to arbitrary precision. Results for free leveling networks reveal significant differences to the values used so far. We also show how to compute those critical values for non-normal error distributions. The results prove that the critical values are very sensitive to the type of error distribution. © 2012 Springer-Verlag.
Schmidt M.,FH Dresden |
Weber G.,FH Dresden
Pattern Recognition | Year: 2013
We propose a probabilistic classifier for multi-touch gestures specified by users themselves. The template-based gesture classifier allows selecting gesture types more freely without constraints regarding implementation issues and considers multi-finger or bi-manual operations. The statistical approaches to the classification scheme are presented. The basic concepts of separating input into tokens, retrieving local features and applying a new method of sensor fusion under uncertainty are adaptive to broader application ranges. Results from testing against a set of sophisticated samples show that this approach performs well and, while recognition benefits from more complex gestures, it also distinguishes subtly different gestures. © 2013 Elsevier Ltd. All rights reserved.
Steiner U.,FH Dresden
Journal of Alloys and Compounds | Year: 2014
Phase pure powder samples of hexagonal indium tungsten bronze In xWO3 (x = 0.25-0.35) were synthesized by solid state reaction at 1173 K. The phase relations of InxWO3 with neighboring binary and ternary phases were determined in the phase diagram In-W-O. Systematic chemical vapor transport experiments were carried out on source materials with compositions corresponding to miscellaneous two-phase and three-phase regions using NH4X (X = Cl, Br, I) as transport agent. Crystals of hexagonal indium tungsten bronze were deposited beside In 2W3O12 with composition corresponding to the indium poor phase boundary and dimensions up to a few mm in a temperature gradient 1173 K → 1073 K starting from ternary mixtures In xWO3/In2W3O12/In 0.02WO3. Sole deposition of InxWO3 single crystals with composition x ≈ 0.33 was observed from ternary mixtures InxWO3/W18O49/WO2 with a migration rate of about 0.5 mg/h (transport agent NH4Cl). © 2014 Elsevier B.V. All rights reserved.
Lehmann R.,FH Dresden
Journal of Geodesy | Year: 2013
The concept of outlier detection by statistical hypothesis testing in geodesy is briefly reviewed. The performance of such tests can only be measured or optimized with respect to a proper alternative hypothesis. Firstly, we discuss the important question whether gross errors should be treated as non-random quantities or as random variables. In the first case, the alternative hypothesis must be based on the common mean shift model, while in the second case, the variance inflation model is appropriate. Secondly, we review possible formulations of alternative hypotheses (inherent, deterministic, slippage, mixture) and discuss their implications. As measures of optimality of an outlier detection, we propose the premium and protection, which are briefly reviewed. Finally, we work out a practical example: the fit of a straight line. It demonstrates the impact of the choice of an alternative hypothesis for outlier detection. © 2012 Springer-Verlag Berlin Heidelberg.