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Search Results: 1 - 10 of 34396 matches for " Daniel Volker "
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A Learner-Centered Design, Implementation, and Evaluation Approach of Learning Environments to Foster Acceptance
Daniel Mueller,Volker Zimmermann
International Journal of Advanced Corporate Learning (iJAC) , 2009, DOI: 10.3991/ijac.v2i3.940
Abstract: Most organizations don’t focus on what learners really do with their learning environments. Changing the perspective to the learner shows that they enlarge the organizational ones with their own technology-enhanced learning world, using a broad spectrum of technologies: company- and/or higher education-owned Learning Management Systems, social network platforms such as Facebook, mySpace, or Ning, search engines, open web services in the internet like blogs or wikis, and a lot more other applications. In this context, one of the challenges for today’s organizations is how to create well-accepted and used learning environments that drive learners’ success. As errors in requirements specifications have been identified as a major contributor to costly software project failures. Hence it may be highly beneficial if the designers and/or developers of learning environments could verify requirements by predicting learners’ acceptance and usage based on evaluations during the earliest stages of the learning environment development phase. Previous findings of such an approach in the field of CRM software implementation showed that pre-prototype user acceptance tests did have almost equal informational value than their prototype counterparts that ensure hands-on experience with the system. More concrete, we focus on interventions of specific design features during the pre-implementation phase of learning environments. They may help minimizing learners’ initial resistance by providing a realistic preview of the system to enable potential learners to develop accurate perceptions and find out how the system may help them to improve their learning process. The paper proposes a solution by examining the influence of specific design features of learning environments on user acceptance, particularly on the antecedents of perceived usefulness and perceived ease of use. We want to extrapolate the influence of specific design features on specific aspects of perceived usefulness and perceived ease of use in order to enhance designers’ and/or developers ability to identify and improve design features during learning environment implementation to enhance critical determinants. The goal of the current work is the improvement of design science in the topic of technology-enhanced learning. To ensure cross-organizational applicability, the approach suggests an application within higher education institutions as well as corporate organizations.
Spatial random permutations and infinite cycles
Volker Betz,Daniel Ueltschi
Physics , 2007, DOI: 10.1007/s00220-008-0584-4
Abstract: We consider systems of spatial random permutations, where permutations are weighed according to the point locations. Infinite cycles are present at high densities. The critical density is given by an exact expression. We discuss the relation between the model of spatial permutations and the ideal and interacting quantum Bose gas.
Critical Temperature of Dilute Bose Gases
Volker Betz,Daniel Ueltschi
Physics , 2009, DOI: 10.1103/PhysRevA.81.023611
Abstract: We compute the critical temperature of Bose-Einstein condensation in dilute three-dimensional homogeneous Bose gases. Our method involves the models of spatial permutations and it should be exact to lowest order in the scattering length of the particle interactions. We find that the change in the critical temperature is proportional to a rho^{1/3} with constant c = -2.33; this contradicts the current consensus among physicists.
Spatial random permutations with small cycle weights
Volker Betz,Daniel Ueltschi
Mathematics , 2008, DOI: 10.1007/s00440-009-0248-0
Abstract: We consider the distribution of cycles in two models of random permutations, that are related to one another. In the first model, cycles receive a weight that depends on their length. The second model deals with permutations of points in the space and there is an additional weight that involves the length of permutation jumps. We prove the occurrence of infinite macroscopic cycles above a certain critical density.
Spatial random permutations and Poisson-Dirichlet law of cycle lengths
Volker Betz,Daniel Ueltschi
Mathematics , 2010, DOI: 10.1214/EJP.v16-901
Abstract: We study spatial permutations with cycle weights that are bounded or slowly diverging. We show that a phase transition occurs at an explicit critical density. The long cycles are macroscopic and their cycle lengths satisfy a Poisson-Dirichlet law.
ParsEval: parallel comparison and analysis of gene structure annotations
Standage Daniel S,Brendel Volker P
BMC Bioinformatics , 2012, DOI: 10.1186/1471-2105-13-187
Abstract: Background Accurate gene structure annotation is a fundamental but somewhat elusive goal of genome projects, as witnessed by the fact that (model) genomes typically undergo several cycles of re-annotation. In many cases, it is not only different versions of annotations that need to be compared but also different sources of annotation of the same genome, derived from distinct gene prediction workflows. Such comparisons are of interest to annotation providers, prediction software developers, and end-users, who all need to assess what is common and what is different among distinct annotation sources. We developed ParsEval, a software application for pairwise comparison of sets of gene structure annotations. ParsEval calculates several statistics that highlight the similarities and differences between the two sets of annotations provided. These statistics are presented in an aggregate summary report, with additional details provided as individual reports specific to non-overlapping, gene-model-centric genomic loci. Genome browser styled graphics embedded in these reports help visualize the genomic context of the annotations. Output from ParsEval is both easily read and parsed, enabling systematic identification of problematic gene models for subsequent focused analysis. Results ParsEval is capable of analyzing annotations for large eukaryotic genomes on typical desktop or laptop hardware. In comparison to existing methods, ParsEval exhibits a considerable performance improvement, both in terms of runtime and memory consumption. Reports from ParsEval can provide relevant biological insights into the gene structure annotations being compared. Conclusions Implemented in C, ParsEval provides the quickest and most feature-rich solution for genome annotation comparison to date. The source code is freely available (under an ISC license) at http://parseval.sourceforge.net/.
On linear combinations of units with bounded coefficients and double-base digit expansions
Daniel Krenn,J?rg Thuswaldner,Volker Ziegler
Mathematics , 2012, DOI: 10.1112/S0025579311001884
Abstract: Let $\ord$ be the maximal order of a number field. Belcher showed in the 1970s that every algebraic integer in $\ord$ is the sum of pairwise distinct units, if the unit equation $u+v=2$ has a non-trivial solution $u,v\in\ord^*$. We generalize this result and give applications to signed double-base digit expansions.
Random permutations with cycle weights
Volker Betz,Daniel Ueltschi,Yvan Velenik
Mathematics , 2009, DOI: 10.1214/10-AAP697
Abstract: We study the distribution of cycle lengths in models of nonuniform random permutations with cycle weights. We identify several regimes. Depending on the weights, the length of typical cycles grows like the total number $n$ of elements, or a fraction of $n$ or a logarithmic power of $n$.
On distinct unit generated fields that are totally complex
Daniel Dombek,Zuzana Masáková,Volker Ziegler
Mathematics , 2014,
Abstract: We consider the problem of characterizing all number fields $K$ such that all algebraic integers $\alpha\in K$ can be written as the sum of distinct units of $K$. We extend a method due to Thuswaldner and Ziegler that previously did not work for totally complex fields and apply our results to the case of totally complex quartic number fields.
New technical approach for the repair of an abdominal wall defect after a transverse rectus abdominis myocutaneous flap: a case report
Daniel A Kaemmer, Joachim Conze, Jens Otto, Volker Schumpelick
Journal of Medical Case Reports , 2008, DOI: 10.1186/1752-1947-2-108
Abstract: We report the case of a woman who had bilateral transverse rectus abdominis myocutaneous flap (TRAM-flap) breast reconstruction. The surgery led to the patient developing an enormous abdominal bulge that caused her disability in terms of abdominal wall and bowel function, pain and contour. In the absence of rectus muscle, the large defect was repaired using a combination of the abdominal wall component separation technique of Ramirez et al and additional mesh augmentation with a lightweight, large-pore polypropylene mesh (Ultrapro?).The procedure of Ramirez et al is helpful in achieving a tension-free closure of large defects in the anterior abdominal wall. The additional mesh augmentation allows reinforcement of the thinned lateral abdominal wall.Abnormalities of the abdominal wall contour after breast reconstruction with autologous tissue transfer have previously been reported as problematic, with a lower abdominal bulge being the most frequently reported abnormality [1]. Although the cosmetic results and patient satisfaction seem to be good in most cases with regards to shape, symmetry and muscular function, differences become obvious in the morbidity of the donor site [2-5]. Modifications and new techniques have been developed to reduce complications, but none of these modifications is able to prevent contour abnormalities of the donor site completely [6], and new techniques, which preserve the anterior rectus sheath are limited in their use by anatomic variations [2].In addition to the aesthetic disturbance, these defects can also lead to adverse interference of the abdominal wall functions, as a thrust bearing for the intraabdominal pressure and as an antagonist of the back muscles and part of the respiratory system. To date, these side effects have not attracted attention in the literature and no therapeutic approaches have been reported.Here we present the case of a woman with an extreme bulge of the lower abdominal wall following bilateral transverse rectus
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