Prototyping Large-Sized Objects Using Freeform Thick Layers of Plastic Foam

Current Rapid Prototyping systems are primarily aimed at small-sized objects containing many shape details. In this paper a Rapid Prototyping technology is presented that is aimed at largesized objects having a complex, freeform outer shape. This new technology builds the model out ofthick layers, each having freeform outside faces. The paper will present: an overview of current methods to produce large prototypes, the basics of the new method, the technology used to produce the layers, the toolpath planning and finally the overall system design.Mechanical Engineerin

Vleselijke lusten belasten de natuur

De auteurs betogen in dit hoofdstuk dat (1) verduurzaming van de landbouw veel meer omvat dan het vergroten van economische en milieutechnische efficiënties, (2) intensivering en schaalvergroting behalve voordelen ook nadelen kennen, waaraan in de praktijk veel te gemakkelijk voorbij wordt gegaan, (3) frequent als 'oplossingen' aangedragen voorstellen geen echte oplossingen blijken te zijn en (4) Wageningen UR met een opener vizier zou moeten opereren

Linking catchability and fisher behaviour under effort management

Catchability is crucial for the economic performance of fisheries and their management. However, in many bio-economic simulation models it is assumed to be either constant or it is largely ignored, despite the fact that it is known to vary due to technical, environmental and behavioral factors. Such variation can cause the relationship between effort and fishing mortality to be nonlinear. This paper provides evidence for the possibility of nonlinear optimizing behavior from the Dutch beam trawl fishery, provides a methodology for estimating the curvature of the resulting relation, and a simple way of implementing these processes within a bio-economic model. Moreover, it shows the influence of a nonlinear relationship between effort and fishing mortality in a model of effort management (EU long-term flatfish management plan)

A methodology to support the decision to invest in spatially variable nitrogen fertilisation

AbstractThis paper reports a methodology to define and select basic activities for spatially variable N-management, referred to as management tracks. Their main purpose is to support decision making whether or not to apply variable nitrogen fertilisation. The methodology is based on biophysical simulation of crop growth and nitrogen leaching (WAVE) in combination with economic optimisation (linear programming) and enables a normative environmental-economic evaluation of site specific N-management to be made. The partial results of a case study with an input-intensive and an input-extensive crop (ware potato and winter wheat, respectively) showed that site specific nitrogen management led to positive returns over variable costs compared to uniform N-application, conditional on the validity of the WAVE model used in simulating yield effects. The investments that could be allowed for at maximum were 6,300 Dfl and 13,500 Dfl for winter wheat and ware potato, respectively, assuming application to an area of 100 ha. A pollution tax or a tax on nitrogen designed to internalise pollution costs in agricultural production raises these maximum amounts to 7,600 and 33,700 Dfl, respectively. Practical feasibility requires site-specific nitrogen management to be integrated with time specific management since optimal N-tracks were found to be highly weather dependent. Besides, spatially variable management cannot be achieved unless good farming practices (soil testing and crop scouting) are already in place

Comparison of the Breakdown Strength of N2, CO2 and SF6 using the Extended Up-and-Down Method

Electrical Engineering, Mathematics and Computer Scienc

Nutrient balances in Field vegetable production systems

In this review paper an overview of the nitrogen (N) and phosphorus (P) cycles in agricultural systems is presented. The information summarized provides general information on the important processes involved as they relate to losses from agricultural systems. Such background information is a prerequisite for designing management strategies to achieve a sustainable balance between reducing the environmental impact of N losses and protecting farmers' profitability. In field vegetable production most N is lost via nitrate leaching because often large amounts of nitrogen remain in the soil after harvest of the crop. This N includes residual soil mineral N and N present in crop residues. Quantitative data are presented on residual soil mineral N, N present in crop residues and nitrate leaching in field vegetable production systems. To combat too high nitrate leaching from agricultural soils the European Commission has issued the Nitrate Directive. Information on this Directive and on how the Dutch government imposed legislation to meet the demands of the Nitrate Directive is given. The project "Farming with a future" is also presented. This new project has been set up in The Netherlands to develop and test environmentally and economically sustainable field crop production systems. As an example of the first results of the project, N balances of two systems of leek production are shown