Status Quo Analyse von Dauerversuchen zum Ökologischer Pflanzenbau

The research project focused on a status-quo analysis of long-term field experiments for organic farming in Germany, Austria and the German speaking part of Switzerland. The study comprised long-term field experiments with an expected minimum duration of five years. The status-quo analysis categorized the long-term field experiments into four main research fields: a) system comparison, b) production engineering, c) fertilisation and d) soil fertility and further key aspects. All in all, 47 long-term field experiments were identified. The four main research fields chosen were investigated in 20, 24, 27 and 46 long-term field experiments, respectively. The system comparison of the main research fields identified the major research into “conventional versus organic farming” and “organic farming: ‘stocking ratio’ versus stockless” with eight resp. twelve experiments. In production engineering research focused on “soil cultivation” with 14 experiments. Soil fertility and further key aspects, yield and humus formation/humus balance were investigated in 40 resp. 35 field experiments

Evaluation of spray deposits from low volume spray nozzles

This study was conducted as a part of Weed Control Machinery Project, a cooperative investigation by the Agricultural Engineering Department of the University of Missouri and the Crop Production Engineering Research Branch, Agricultural Engineering Research Division, Agricultural Research Service, U.S. Department of Agriculture--P. [3].Digitized 2007 AES.Includes bibliographical references (pages 28-29)

Investigation of power dissipation in a collimated energy beam

To satisfy the worldwide demand for large ultra-precision optical surfaces, a fast process chain - grinding, polishing and plasma figuring- has been established by the Precision Engineering Institute at Cranfield University. The focus of Cranfield Plasma Figuring team is the creation of next generation of highly collimated energy beam for plasma figuring. Currently, plasma figuring has the capability to shorten processing duration for the correction of metre-scale optical surfaces. High form accuracy can be achieved (e.g. 2.5 hours and 31 nm RMS for 400mm diameter surface). However, it is known that Mid Spatial Frequency (MSF) surface errors are induced when the plasma figuring process is carried out. The work discussed in this paper deals with the characterisation of highly collimated plasma jets delivered by the Inductively Coupled Plasma (ICP) torches. Also a computational fluid dynamics (CFD) model is introduced. This model is used to assess the behaviour of the plasma jet within the best known processing condition. Finally temperature measurement experiments were performed to determine the energy dissipated values that characterise best the ICP torch coil and its De-Laval nozzle

Short interval control for the cost estimate baseline of novel high value manufacturing products – a complexity based approach

Novel high value manufacturing products by default lack the minimum a priori data needed for forecasting cost variance over of time using regression based techniques. Forecasts which attempt to achieve this therefore suffer from significant variance which in turn places significant strain on budgetary assumptions and financial planning. The authors argue that for novel high value manufacturing products short interval control through continuous revision is necessary until the context of the baseline estimate stabilises sufficiently for extending the time intervals for revision. Case study data from the United States Department of Defence Scheduled Annual Summary Reports (1986-2013) is used to exemplify the approach. In this respect it must be remembered that the context of a baseline cost estimate is subject to a large number of assumptions regarding future plausible scenarios, the probability of such scenarios, and various requirements related to such. These assumptions change over time and the degree of their change is indicated by the extent that cost variance follows a forecast propagation curve that has been defined in advance. The presented approach determines the stability of this context by calculating the effort required to identify a propagation pattern for cost variance using the principles of Kolmogorov complexity. Only when that effort remains stable over a sufficient period of time can the revision periods for the cost estimate baseline be changed from continuous to discrete time intervals. The practical implication of the presented approach for novel high value manufacturing products is that attention is shifted from the bottom up or parametric estimation activity to the continuous management of the context for that cost estimate itself. This in turn enables a faster and more sustainable stabilisation of the estimating context which then creates the conditions for reducing cost estimate uncertainty in an actionable and timely manner

Effect of Clay Amounts on Morphology and Mechanical Performances in Multiscale PET Composites

This work presents an investigation of the properties of poly(ethylene terephthalate)/glass fibers/nanoclay multiscale composites. The aim is to demonstrate the effect of adding various clay amounts on the morphology and mechanical performances of multiscale PET composites. Multiscale composites were prepared by adding 0.5, 1.0, 3.0, and 5.0 wt% of Cloisite 15A montmorrillonite. Initially, a masterbatch of pure PET blended with 10 wt% of Cloisite 15A was obtained in a co-rotating twin screw extruder. The multiscale composites were then blended via mechanical mixing, and injection moulded by adding the masterbatch to the glass fibre reinforced matrix. The morphological and mechanical characterizations of all compounds are discussed. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the characteristic (001) peak of the nanocomposite obtained by extrusion (masterbatch) shifted to the lower angle region stating an intercalated structure. However, the subsequent injection moulding process changed the morphological structure of the multiscale nanocomposites reducing the basal distance mostly for small loadings of nanoclay. The addition of nanoclay to PET matrices increases the degree of crystallinity, the clay platelets possibly playing the role of nucleating agent, as revealed by DSC and FTIR. The time relaxation spectra broaden as seen by DMA, as the ratio of clay/polymer interfaces increases. The yield stress of composites with 0.5 and 1 wt% of C15A content are enhanced. For more than 3% of nanoclay, the yield stress decreases. The Young’s modulus is increased when adding nanoclay. Indeed, clay exfoliation was not attained, but the intercalated particle dispersion improved the stiffness properties of PET/glass fibers/nanoclay composites

Spontaneous emission control in high-extraction efficiency plasmonic crystals

We experimentally and theoretically investigate exciton-field coupling for the surface plasmon polariton (SPP) in waveguide-confined (WC) anti-symmetric modes of hexagonal plasmonic crystals in InP-TiO-Au-TiO-Si heterostructures. The radiative decay time of the InP-based transverse magnetic (TM)-strained multi-quantum well (MQW) coupled to the SPP modes is observed to be 2.9-3.7 times shorter than that of a bare MQW wafer. Theoretically we find that 80 % of the enhanced PL is emitted into SPP modes, and 17 % of the enhanced luminescence is redirected into WC-anti-symmetric modes. In addition to the direct coupling of the excitons to the plasmonic modes, this demonstration is also useful for the development of high-temperature SPP lasers, the development of highly integrated photo-electrical devices, or miniaturized biosensors.Comment: Spontaneous emission control in high-extraction efficiency plasmonic crystal

Analytical prediction of part dynamics for machining stability analysis

An analytical procedure is developed to predict workpiece dynamics in a complete machining cycle in order to obtain frequency response functions (FRF) which are needed in chatter stability analyses. For this purpose, a structural modification method which is an efficient tool for updating FRFs is used. The removed mass by machining is considered as a structural modification in order to determine the FRFs at different stages of the process. The method is implemented in a computer code and demonstrated on different geometries. The predictions are compared and verified by FEA. Predicted FRFs are used in chatter stability analyses, and the effect of part dynamics on stability is studied. Different cutting strategies are compared for increased chatter free material removal rates considering part dynamics

Reactive Atom Plasma (RAP) figuring machine for meter class optical surfaces

A new surface figuring machine called Helios 1200 is presented in this paper. It is designed for the figuring of meter sized optical surfaces with form accuracy correction capability better than 20 nm rms within a reduced number of iterations. Unlike other large figuring facilities using energy beams, Helios 1200 operates a plasma torch at atmospheric pressure, offers a high material removal rate, and a relatively low running cost. This facility is ideal to process large optical components, lightweight optics, silicon based and difficult to machine materials, aspheric, and free form surfaces. Also, the surfaces processed by the reactive atom plasma (RAP) are easy to fine polish through hand conventional sub-aperture polishing techniques. These unique combined features lead to a new capability for the fabrication of optical components opening up novel design possibilities for optical engineers. The key technical features of this large RAP machine are fast figuring capabilities, non-contact material removal tool, the use of a near Gaussian footprint energy beam, and a proven tool path strategy for the management of the heat transfer. Helios 1200 complies with the European machine safety standard and can be used with different types of reactive gases using either fluorine or chlorine compounds. In this paper, first the need for large optical component is discussed. Then, the RAP facility is described: radio frequency R.F generator, plasma torch, and 3 axis computer numerically controlled motion system. Both the machine design and the performance of the RAP tool is assessed under specific production conditions and in the context of meter class mirror and lens fabrication

Surface roughness variation of thin wall milling, related to modal interactions

High-speed milling operations of thin walls are often limited by the so-called regenerative effect that causes poor surface finish. The aim of this paper is to examine the link between chatter instability and surface roughness evolution for thin wall milling. Firstly, the linear stability lobes theory for the thin wall milling optimisation was used. Then, in order to consider the modal interactions, an explicit numerical model was developed. The resulting nonlinear system of delay differential equations is solved by numerical integration. The model takes into account the coupling mode, the modal shape, the fact that the tool may leave the cut and the ploughing effect. Dedicated experiments are carried out in order to confirm this modelling. This paper presents surface roughness and chatter frequency measurements. The stability lobes are validated by thin wall milling. Finally, the modal behaviour and the mode coupling give a new interpretation of the complex surface finish deterioration often observed during thin wall milling