Optimizing the Post Sandvik Nanoflex material model using inverse optimization and the finite element method

This article describes an inverse optimization method for the Sandvik Nanoflex steel in cold forming\ud processes. The optimization revolves around measured samples and calculations using the Finite Element\ud Method. Sandvik Nanoflex is part of the group of meta-stable stainless steels. These materials are characterized\ud by a good corrosion resistance, high strength, good formability and crack resistance. In addition, Sandvik\ud Nanoflex has a strain-induced transformation and, depending on austenising conditions and chemical composition,\ud a stress-assisted transformation can occur. The martensite phase of this material shows a substantial aging\ud response. The inverse optimization is a sub-category of the optimization techniques. The inverse optimization\ud method uses a top down approach, as the name implies. The starting point is a prototype state where the current\ud state is to converge on. In our experiment the test specimen is used as prototype and a calculation result as\ud current state. The calculation is then adapted so that the result converges towards the test example. An iterative\ud numerical optimization algorithm controls the adaptation. For the inverse optimization method two parameters\ud are defined: shape of the product and martensite profile. These parameters are extracted from both calculation\ud and test specimen, using Fourier analysis and integrals. An optimization parameter is then formulated from\ud the extracted parameters. The method uses this optimization parameter to increase the accuracy of ”The Post”\ud material model for Sandvik Nanoflex. [1] The article will describe a method to optimize material models, using\ud a combination practical experiments, Finite Element Method and parameter extraction

Gidsen in de stadse jungle, biologentweeling wekt verwondering voor stadsecologie

Conservation Biolog

Volatilization of parathion and chlorothalonil after spraying onto a potato crop

At fourteen times after application of parathion and chlorothalonil to a potato crop their rates of volatilization were determined by the aerodynamic and Bowen ratio methods. The highest volatilization rate of parathion occurred shortly after application. In the first hours after application its volatilization rate decreased sharply; thereafter it decreased more gradually. The volatilization rate of chlorothalonil at one week after application did not differ much from that shortly after application. Weather conditions in the first twenty-four hours after application of both pesticides were simulated in a chamber. The volatilization of parathion in the chamber had the same order of magnitude as that determined in the field

Prognostic factors and patterns of recurrence in esophageal cancer assert arguments for extended two-field transthoracic esophagectomy

BACKGROUND: High recurrence rates determine the dismal outcome in esophageal cancer. We reviewed our experiences and defined prognostic factors and patterns of recurrences after curatively, intended transthoracic esophagectomy. METHODS: Between January 1991 and December 2005, 212 consecutive patients underwent a radical transthoracic esophagectomy with extended 2-field lymphadenectomy. Recurrence rates, survival, and prognostic factors were analyzed (minimal follow-up period, 2 y). RESULTS: Radicality was obtained in 85.6%. The median follow-up period was 26.6 months. The overall recurrence rate at I, 3, and 5 years was 28%, 44%, and 64%, respectively, and locoregional recurrence rate was 17%, 27%, and 43%, respectively. Overall survival rates, including postoperative deaths, were 45% and 34% at 3 and 5 years, respectively. pT stage and lymph node (LN) ratio greater than .20 were independent prognostic factors for survival and recurrences. Radicality was most prognostic for survival, and for N+ greater than 4 positive LN for recurrences. CONCLUSIONS: Radicality and LN ratio are strong prognostic factors. High radicality and adequate nodal assessment are guaranteed by an extended transthoracic approach. (C) 2010 Elsevier Inc. All rights reserved

Degregatie van broedvogelgegevens van atlasblok naar kilometercel

VakpublicatieInstitute of Environmental Science

Van nat naar droog : een aktualisering van het voorkomen van natte ecosystemen in Nederland

VakpublicatieInstitute of Environmental Science

De milieukwaliteit van de ecodistricten het laagveengebied en de kalkrijke duinen

VakpublicatieInstitute of Environmental Science

Non-Covalently Stabilized Alginate Hydrogels as Functional Cell Scaffold Material

Biopolymers are an attractive class of compounds for being used in biomedical applications as they are widely available from biomass. Their drawback is the lack of mechanical stability and the ability to tune this properly. Covalent chemical cross-linking is an often used approach but it limits usability due to legislation as well as the need of advanced and specialized knowledge by end users such as clinicians. Here, increased and tunable mechanical properties are achieved of alginate-based hydrogels with non-covalent approaches using linear polyethyleneimine (LPEI) as a polyelectrolyte rather than only multivalent metal ions (Ca2+). Gel stiffness increases with increasing LPEI content. Gel morphology changes from a thin fibrous mesh for alginate-Ca2+ to thicker fibrous networks when LPEI is introduced. The gels are able to efficiently release encapsulated small molecular dyes and the gels are able to host cells. For the cell encapsulation human skin fibroblasts (HSkF) and human bone marrow-derived mesenchymal stem cells (hBM-MSC) are used. HSkF can be successfully incorporated without diminished viability while the matrix components and gel preparation method are not compatible with hBM-MSC. The newly developed alginate-based system is regarded as a potential candidate for wound dressing materials