Optimization of Laser Beam Transformation Hardening by One Single Parameter

The process of laser beam transformation hardening is principally controlled by two independent parameters, the absorbed laser power on a given area and the interaction time. These parameters can be transformed into two functional parameters: the maximum surface temperature and the hardening depth.\ud \ud It has been proved that with a constant hardening depth the results hardness. residual stress. etc.) can be optimized easily with respect to only one independent parameter, the maximum surface temperature. which is applied directly in adaptive control strategies

Reduction of heat losses from greenhouses by means of internal blinds with low thermal emissivity

Heat losses in greenhouses may be substantially reduced by the use of heat reflecting blinds. Quantitative results are obtained solving a mathematical heat flow model by numerical methods. Special attention has been given to the emissivity and transmittance of the screen and the ventilation through screen and glass. The heat losses by condensation are obtained from a simultaneously solved moisture balance. In most cases condensation on the lower side of the screen influences the emissivity. An unexpectedly large part of the heat is transmitted by ventilation. The emissivity of the coated surface has been measured for a number of screen materials. The durability of the coatings is also taken into consideration. For greenhouse application it is always necessary to protect against corrosion

Organic greenhouse horticulture in the Netherlands

The total area occupied in the Netherlands by organic horticulture under glass is growing steadily. Several growers convert to this form of horticulture every year and some existing organic growers are expanding their businesses. However, increasing imports from Spain and other south European countries, together with rising costs, means less room for economic development within this sector. The report contains sector information, sector aspirations and current research projects

Metal surface temperature induced by moving laser beams \ud

Whenever a metal is irradiated with a laser beam, electromagnetic energy is transformed into heat in a thin surface layer. The maximum surface temperature is the most important quantity which determines the processing result. Expressions for this maximum temperature are provided by the literature for stationary cases. In practice, however, moving beams are of more importance.\ud Based on a fast numerical algorithm which allows calculation of the induced temperature profile, the maximum surface temperature for stationary and moving laser beams is calculated. Next, two types of approximating functions are presented relating the scanning speed to the maximum surface temperature. Using dimensionless numbers, the results can be applied to different material

Accuracy of Surface Plate Measurements - General Purpose Software for Flatness Measurement

Flatness departures of surface plates are generally obtained from straightness measurements of lines on the surface. A computer program has been developed for on-line measurement and evaluation, based on the simultaneous coupling of measurements in all grid points. Statistical methods are used to determine the accuracy of the measurements. The program runs on standard personal computers and supports different types of measuring instruments like electronic levels, autocollimators, laser interferometers or straight edge based instruments. Apart from the given height map, some meaningful characteristic parameters: sphericity, torsion and waviness are obtained. They have been proven very valuable to record long term effects of surface plates. Reliable measurements with an accuracy of 0.1 μm/m demonstrate the capabilities of the method

Some Aspects of the Relationship between the Freiburg School and the Austrian School

This paper is about some aspects of the interre-lationship of the Freiburg School and the Austrian School. The relationships between these schools will be discussed in the field of econo-mic theory and economic policy. No attention will be paid to the similarities and differen-ces in the field of social phi-loso-phy and methodo-lo-gy. For the Frei-burg School we will concentrate on W. Eucken, F.A. Hayek and W. Röpke. For the Austrian School the following writers will be contem-plated: L. Mises and F.A. Hayek. Also the connection to Schumpeter will be discussed. In the case of Hayek there is a perso-nal union. The paper consists of the following sections:+ Eucken and the Austrian School. + Röpke and the Austrian School.+ Some closing remarks. The five authors who have got our special attention in trying to say something on the relationships between the Freiburg and the Austri-an School took different positions in economic theory and economic policy. Schumpeter and Mises belong to the same generation of the Austrian School. Schumpeter studied the relations between socialism, capitalism and democracry but obstained from formu-lating ideas on a policy to influence the developments he prophetized. Mises staunchly defended libera-lism and attacked the cen-trally administered economy and interventionism. He questi-oned whether the renewal of libera-lism (by e.g. Eucken, Hayek and Röpke), for which the founda-ti-ons were laid by Cannan, Knight and himself would avoid interventi-onism (i.e. interfe-rences in the economic process by direct controls). Eucken, Hayek and Röpke were looking for possibilities to influence developments. In principle the disagreement between the fundamental position of Mises and this triumvira-te may bedescribed as follows. In contrast to Mises they thought that their diagnosis of the crisis of society had to be followed by showing a way out of that crisis by the programmes of active policy they formulated. The crisis accor-ding to them was so deep and severe that they felt themsel-ves obliged to do their utmost to turn the tide. For that reason they thought active policies were neces-sary, with avoidance of centrallyadmi-nis-tered econo-mies and the kind of interventionism which Mises in their opinion with convincing arguments warnedagai-nst.J.E.L.code: B29, B31, P10, P51Economics ;

Monadic parser combinators

In functional programming, a popular approach to building recursive descent parsers is to model parsers as functions, and to define higher-order functions (or combinators) that implement grammar constructions such as sequencing, choice, and repetition. Such parsers form an instance of a monad, an algebraic structure from mathematics that has proved useful for addressing a number of computational problems. The purpose of this report is to provide a step-by-step tutorial on the monadic approach to building functional parsers, and to explain some of the benefits that result from exploiting monads. No prior knowledge of parser combinators or of monads is assumed. Indeed, this report can also be viewed as a first introduction to the use of monads in programming

Characteristic numbers to describe the detail transfer quality of electro-chemical machining

For reproducing processes such as electrochemical machining (ecm) the accuracy of the reproduction is an important process parameter. Characteristic numbers which are a measure of this accuracy are proposed in this paper. Due to the non-linearity of the process a detail transfer function, which is helpful in linear cases, cannot be used, as will be shown from experimental work. Based on the same experiments, a characteristic radius and the standard deviation of a normal profile are proposed to describe the quality of the detail transfer. These numbers, which are easily interpreted criteria for quality and accuracy, have been proved to be almost independent of the geometry. Although developed for optimizing the ecm process, these values are also valid for edm and other reproducing processes. The usefulness of the characteristic numbers is illustrated by a comparison of continuous and pulsed ecm processes

The melting performance of single screw extruders

A number of recent screw designs is analyzed for melting performance, using a simple analytical approach based on Tadmor's original work. The melting length for a screw with constant depth channel is used as reference. An ideal compression screw will have a melting length of one-half the melting length of the reference screw. The Maillefer melt separation principle is discussed. The Maillefer screw melts in 2/3 of the length of the reference screw. Screws by Barr, by Dray and Lawrence and by Kim are shown to approach the ideal compression screw. A new design screw, using ideal compression and multiple channels and having a very large screw pitch, is shown to be a considerably more efficient melting device than any of the other, screws discussed