A Modeling approach for analysis and improvement of spindle-holder-tool assembly dynamics

The most important information required for chatter stability analysis is the dynamics of the involved structures, i.e. the frequency response functions (FRFs) which are usually determined experimentally. In this study, the tool point FRF of a spindle-holder-tool assembly is analytically determined by using the receptance coupling and structural modification techniques. Timoshenko’s beam model is used for increased accuracy. The spindle is also modeled analytically with elastic supports representing the bearings. The mathematical model is used to determine the effects of different parameters on the tool point FRF and to identify contact dynamics from experimental measurements. The applications of the model are demonstrated and the predictions are verified experimentally

Supply Chain Analysis of Fresh Fruit and Vegetables in Germany

With a population of 82.5 million, the German market is the largest in the EU and therefore of special interest for the trade partners. Despite an unsatisfying economic development in the last years (lowest GDP growth in the EU and rising unemployment, see Table 9 in the annex) Germany is still a very attractive market with well funded consumers. Although agriculture has a small and declining contribution to the country?s gross domestic product, in the wider definition of the agribusiness, it is still one of the most important sectors with regard to turnover and employment. Taking consumers? expenditure for food as a proxy for the total turnover of the agribusiness yields a figure of 240 billion – in 2003, nearly as much as the turnover of the car industry in Germany. In total, 4.5 million people are employed in the agribusiness, which is 11.6% of Germany?s total labour force. Among agricultural markets, the market of fruit and vegetables is of special interest for the trade with Mediterranean countries and also of special importance for the food industry and the food consumption. In 2003 consumers? expenditure for fresh fruit and vegetables were more than 10 billion ?. The processing industry of fruit and vegetables generated another 6.5 billion – turnover, demonstrating the importance of fruit and vegetables in Germany. Bearing in mind that the self sufficiency ratios for fruit and vegetables in Germany are low (13% respectively 50%), the extent of market opportunities for the Mediterranean countries become obvious. Against this background it is the objective of this report to analyse the supply chain of fresh fruit and vegetables in Germany. In the second chapter the current market situation is briefly presented with regard to production, consumption and trade in Germany. Other aspects covered in this chapter are the demographic structure in Germany, important consumer trends and food quality issues. The third chapter is devoted in depth to the analysis of the supply chains for both fruit and vegetables. In this chapter the different actors and market channels are described with regard to their task and importance in the supply chain. In the fourth chapter the overall institutional structure is analysed. After the conclusions in the fifth chapter extensive tables and figures can be found in the annex. --

Bewertung von Landschaftsfunktionen mit Choice Experiments

The first application of choice experiments as an environmental valuation method in Germany clearly demonstrates the potential of this method for the valuation of agriculture's multifunctionality. Choice experiments are a reasonable enhancement of the conjoint analysis as they are capable of calculating the theoretically correct welfare measures in the form of implicit prices. In combination with business and ecological models this allows for the comprehensive valuation of agriculture's multifunctionality in the sense, that in addition to the supply or cost side of land use scenarios the demand or benefit side is accounted for. In this study the integrated ecological and economical valuation of land use scenarios was demonstrated for two different scenarios. The welfare changes for the regional population due to changes in the quality or quantity of several landscape functions like drinking water quality, biodiversity, food production and landscape aesthetics were calculated. The inclusion of both supply and demand in this cost-benefit study is an important step forward for the development of sustainable land use concepts.choice experiments, environmental valuation, multifunctional agriculture, Environmental Economics and Policy,

The self-excitation damping ratio: A chatter criterion for time-domain milling simulations

Regenerative chatter is known to be a key factor that limits the productivity of high speed machining. Consequently, a great deal of research has focused on developing predictive models of milling dynamics, to aid engineers involved in both research and manufacturing practice. Time-domain models suffer from being computationally intensive, particularly when they are used to predict the boundary of chatter stability, when a large number of simulation runs are required under different milling conditions. Furthermore, to identify the boundary of stability each simulation must run for sufficient time for the chatter effect to manifest itself in the numerical data, and this is a major contributor to the inefficiency of the chatter prediction process. In the present article, a new chatter criterion is proposed for time-domain milling simulations, that aims to overcome this draw-back by considering the transient response of the modeled behavior, rather than the steady-state response. Using a series of numerical investigations, it is shown that in many cases the new criterion can enable the numerical prediction to be computed more than five times faster than was previously possible. In addition, the analysis yields greater detail concerning the nature of the chatter vibrations, and the degree of stability that is observed

Transprofessionalität

Transprofessionalität ist eine Form der Teamarbeit, bei der mehrere Individuen aus unterschiedlichen Berufspraxis-Feldern (insbesondere solchen mit Dienstleistungsbezug) miteinander interagieren und dabei ihre jeweiligen spezialisierten Wissensbestände, Kenntnisse oder Erfahrungen einbringen. Sie hat das Ziel, auf partnerschaftlichem Wege übergreifende Lösungen für praktische Problemstellungen zu finden, die unterschiedliche Fachrichtungen oder Professionen integrieren. Transprofessionelle Didaktik zielt auf gemeinsames, problemorientiertes Lernen, das etablierte berufliche und fachliche Grenzsetzungen überwindet. Sie knüpft an die didaktischen Potenziale von Multi- und Interprofessionalität an und lässt sich in einem emphatischen Sinn als das professionstheoretische Pendant einer transdisziplinären Beschäftigung mit Hochschulbildung beschreiben. (Herausgeber)Transprofessionality is a form of teamwork in which several individuals from different professional practice fields (especially those related to services) interact with each other, contributing their respective specialized knowledge bases, expertise or experience. It aims to find cross-cutting solutions to practical problems that integrate different disciplines or professions in a collaborative way. Transprofessional didactics aims at joint, problem-oriented learning that overcomes established professional and technical boundaries. It ties in with the didactic potentials of multi- and interprofessionality and can be described in an emphatic sense as the profession-theoretical counterpart of a transdisciplinary engagement with higher education. (Editor

Analogue of cosmological particle creation in an ion trap

We study phonons in a dynamical chain of ions confined by a trap with a time-dependent (axial) potential strength and demonstrate that they behave in the same way as quantum fields in an expanding/contracting universe. Based on this analogy, we present a scheme for the detection of the analogue of cosmological particle creation which should be feasible with present-day technology. In order to test the quantum nature of the particle creation mechanism and to distinguish it from classical effects such as heating, we propose to measure the two-phonon amplitude via the $2^{\rm nd}$ red side-band and to compare it with the one-phonon amplitude ($1^{\rm st}$ red side-band). PACS: 04.62.+v, 98.80.-k, 42.50.Vk, 32.80.Pj.Comment: 4 pages, 2 figure

PTArcade

This is a lightweight manual for PTArcade, a wrapper of ENTERPRISE and ceffyl that allows for easy implementation of new-physics searches in PTA data. In this manual, we describe how to get PTArcade installed (either on your local machine or an HPC cluster). We discuss how to define a stochastic or deterministic signal and how PTArcade implements these signals in PTA-analysis pipelines. Finally, we show how to handle and analyze the PTArcade output using a series of utility functions that come together with PTArcade.Comment: 26 pages, 2 figures, 2 table