On mesh refinement and accuracy of numerical solutions

This paper investigates mesh refinement and its relation with the accuracy of the boundary element method (BEM) and the finite element method (FEM). TO this end an isotropic homogeneous spherical volume conductor, for which the analytical solution is available, wag used. The numerical results obtained with the BEM and FEM were compared with the results of the andytical solution. The results show that the accuracy of the numerical solutions is improved by enriching a mesh only if the enriched mesh not only incorporates a greater number of nodes but also follows more closely the actual geometry of the volume conductor involved

Constrained tGAP for generalisation between scales: the case of Dutch topographic data

This article presents the results of integrating large- and medium-scale data into a unified data structure. This structure can be used as a single non-redundant representation for the input data, which can be queried at any arbitrary scale between the source scales. The solution is based on the constrained topological Generalized Area Partition (tGAP), which stores the results of a generalization process applied to the large-scale dataset, and is controlled by the objects of the medium-scale dataset, which act as constraints on the large-scale objects. The result contains the accurate geometry of the large-scale objects enriched with the generalization knowledge of the medium-scale data, stored as references in the constraint tGAP structure. The advantage of this constrained approach over the original tGAP is the higher quality of the aggregated maps. The idea was implemented with real topographic datasets from The Netherlands for the large- (1:1000) and medium-scale (1:10,000) data. The approach is expected to be equally valid for any categorical map and for other scales as well

Constrained set-up of the tGAP structure for progressive vector data transfer

A promising approach to submit a vector map from a server to a mobile client is to send a coarse representation first, which then is incrementally refined. We consider the problem of defining a sequence of such increments for areas of different land-cover classes in a planar partition. In order to submit well-generalised datasets, we propose a method of two stages: First, we create a generalised representation from a detailed dataset, using an optimisation approach that satisfies certain cartographic constraints. Second, we define a sequence of basic merge and simplification operations that transforms the most detailed dataset gradually into the generalised dataset. The obtained sequence of gradual transformations is stored without geometrical redundancy in a structure that builds up on the previously developed tGAP (topological Generalised Area Partitioning) structure. This structure and the algorithm for intermediate levels of detail (LoD) have been implemented in an object-relational database and tested for land-cover data from the official German topographic dataset ATKIS at scale 1:50 000 to the target scale 1:250 000. Results of these tests allow us to conclude that the data at lowest LoD and at intermediate LoDs is well generalised. Applying specialised heuristics the applied optimisation method copes with large datasets; the tGAP structure allows users to efficiently query and retrieve a dataset at a specified LoD. Data are sent progressively from the server to the client: First a coarse representation is sent, which is refined until the requested LoD is reached

Facts of fractures of the hand

In order to assess and possibly improve our practice of hand fracture treatment, studies were performed that led to this thesis, introduced in chapter 1. An evidence-based protocol and manual of operative treatment of fractures of phalanges was compiled, chapter 2. The results of operative treatment of phalangeal fractures at the department of Plastic, Reconstructive, and Hand Surgery of the Erasmus University Medical Center, Rotterdam, the Netherlands were assessed and risk factors for nonunion and malunion identified, chapter 3. The digital functional loss in severely injured hands was quantified (chapter 4). Associated soft tissue injury, level of injury, and arthrodesis were risk factors for diminished function. A quantification of digital functional loss for combinations of these risk factors was made. In chapter 5, correlation between impairment and disability was assessed following treatment for severe hand injuries. No statistically significant correlation existed between AMA impairment ratings for the hand and DASH (disability) module scores. A prospective study audit was performed on quality of treatment of phalangeal and metacarpal fractures, chapter 6. Eighty-three percent of diagnoses were correct and 89% of treatment plans were according to protocol, 80% healed properly, and osteosynthesis was deemed adequate in 81% of cases. In chapter 7, financial and logistic impact of phalangeal and metacarpal fractures was prospectively assessed. Hospital costs, hospital visits, days in the hospital, number of operations, and period off work were recorded. Variables that influenced outcome data were statistically tested. In chapter 8 results of the aforementioned studies are discussed, and recommendations for improvement of operative treatment of phalangeal and metacarpal fractures are provided