A Solution Set-Based Entropy Principle for Constitutive Modeling in Mechanics

Entropy principles based on thermodynamic consistency requirements are widely used for constitutive modeling in continuum mechanics, providing physical constraints on a priori unknown constitutive functions. The well-known M\"uller-Liu procedure is based on Liu's lemma for linear systems. While the M\"uller-Liu algorithm works well for basic models with simple constitutive dependencies, it cannot take into account nonlinear relationships that exist between higher derivatives of the fields in the cases of more complex constitutive dependencies. The current contribution presents a general solution set-based procedure, which, for a model system of differential equations, respects the geometry of the solution manifold, and yields a set of constraint equations on the unknown constitutive functions, which are necessary and sufficient conditions for the entropy production to stay nonnegative for any solution. Similarly to the M\"uller-Liu procedure, the solution set approach is algorithmic, its output being a set of constraint equations and a residual entropy inequality. The solution set method is applicable to virtually any physical model, allows for arbitrary initially postulated forms of the constitutive dependencies, and does not use artificial constructs like Lagrange multipliers. A Maple implementation makes the solution set method computationally straightforward and useful for the constitutive modeling of complex systems. Several computational examples are considered, in particular, models of gas, anisotropic fluid, and granular flow dynamics. The resulting constitutive function forms are analyzed, and comparisons are provided. It is shown how the solution set entropy principle can yield classification problems, leading to several complementary sets of admissible constitutive functions; such problems have not previously appeared in the constitutive modeling literature

Ökologischer Kreislauf Moorbad Harbach: Life Cycle Assessment (LCA) for Agricultural Plant Production and Transportation

In 1992 the community of Moorbad Harbach (Austria), located near the border of the Czech Republic and dominated by extensive agricultural practice on small scale farms, decided to initiate activities for regional devolopment. About 40 farms (27 %) converted to organic farming, a local marketing service as well as regional food processing businesses (slaughterhouse, dairy), operating as linkages between regional agriculture and the local spa hotel were founded. The basic idea for the work presented here was to evaluate the – especially ecological – consequences of such a regional conversion. One part of this attempt of evaluation was carried out as a LCA for the agricultural production in Moorbad Harbach. The emphasis of the study was to compare plant production before and after the regional conversion to organic farming. In another step changes in transportation distances and quantities with special regard to transport of raw milk and milk products were quantified

Organic Farming in Austria

During the present decade, Austria has experienced a dramatic increase in organic farming among those countries that comprise the European Union (EU). For example, in 1992, approximately 2,000 farms were practicing organic, ecological, or biodynamic farming methodes. By 1997 the number of certified organic farms plus those in transition from conventional farming had increased 10-fold to some 20,000 farms. This represents almost 9% of the total farms in Austria and an area of 345,375 ha, or 10% of the total cultivated farmland. The largest concentration of organic farms is in regions with a high proportion of alpine grassland or pastures. Approximately 50% of the organic farms range in size from 5 to 15 ha. The strong organic movement in Austria can be attributed to a) government subsidies which provide incentives to organic farmers and b) widepread acceptance of organic products and their brand names by large food chains and supermarkets. More than 60% of organic farmers are affiliated with associations and organizations that provide advisory and support services in marketing activities. Certification of organic farms and food processors is conducted by seven monitoring bodies according to EU regulations No. 2092/91, which guarantees legally-binding standards of food saftey and quality to EU consumers, and according to the Austian Alimentari Codex. Since January 1998, all monitoring/certifying bodies in Austria must verify accreditation according to rgulation European Norm 45011. The major supermarket chain offers a variety of organic dairy and meat products, as well as organic ice cream, pizza, vegetables, fruits, baby foods, and bread. The current domestic wholesale value of organic products arketed from Austria farms is approximately 170 million US$ annually. Unfortunately, funding for support of scientific research and extension to enhance organic farming and marketing has not kept pace with the increasing number of organic farms and farmers. Additional funding is essential to ensure the sustainable development of the organic movement and the organic market

Versuch der monetären Bewertung ökologischer Leistungen des Biologischen Landbaus im Bereich Grund- und Trinkwasser am Beispiel des Einzugsgebietes der Fernwasserversorgung Mühlviertel/OÖ

Die tatsächlichen oder potentiellen volkswirtschaftlichen (externen) Kosten durch Umweltbelastung der intensiven Landbewirtschaftung werden der Allgemeinheit aufgebürdet, anstatt als Preis- bzw. Kostenfaktor in das betriebliche Rechnungswesen einzugehen. U.a. in Hinblick auf eine Verringerung externer Kosten der Landwirtschaft infolge Grund- und Trinkwasserbelastung wird der Ökologische Landbau als wirksame Alternative diskutiert. Eine Vielzahl wissenschaftlicher Untersuchungen belegt denn auch das hohe Maß an Grundwasserverträglichkeit des Biologischen Landbaus: So wiesen u. a. VEREIJKEN und WIJNANDS (1990),BRANDHUBER und HEGE (1992), MATTHEY (1992), SCHULTE (1996), BERG et al. (1997) sowie SCHLÜTER et al. (1997) deutlich niedrigere Nitratgehalte des Sickerwassers unter biologisch bewirtschafteten Flächen als unter konventionell oder integriert bewirtschafteten Vergleichsflächen nach. Aufgrund der Verringerung der Nitrat- und Vermeidung der Pestizidbelastung von Grund- und Trinkwasser durch Biologischen Landbau ist daher zu prüfen, in welchem Ausmaß durch diese Bewirtschaftungsform externe Kosten eingespart werden können

GemüseSelbstErnte: Weiterentwicklung und Transfer sowie Ermittlung des Beitrags zur Gesundheitsförderung

Ziel des Projekts „GemüseSelbstErnte – Weiterentwicklung und Transfer sowie Ermittlung des Beitrags zur Gesundheitsförderung“ war es das Konzept der GemüseSelbstErnte bekannt zu machen und weiter zu entwickeln (Transfer). Zusätzlich wurden die Verbundeffekte für die Direktvermarktung quantifiziert und die Auswirkungen auf das Ernährungsverhalten der Nutzer überprüft (Forschung). Transfer Der Kenntnisstand von Erzeugern, Beratern und Verbrauchern über die GemüseSelbstErnte konnte mit einer intensiven Öffentlichkeitsarbeit, die zwei Messeauftritte (u.a. auf der IGW 2004), acht Vorträge, elf Fachartikel und drei Workshopangebote mit insgesamt 36 Teilnehmern umfasste, deutlich verbessert werden. 170 Personen forderten Informationsmaterial an. Außerdem wurden verschiedene Materialien erstellt: - ein Leitfaden für Erzeugerbetriebe, - ein zehnminütiger Schulungsfilm und drei Internetclips, - eine Beschreibung des Konzepts im Internetportal oekolandbau.de und - ein Handbuch für Nutzer mit Informationen zu jeder Gemüsekultur Angestoßen durch das Projekt starteten zwei neue Betriebe eine GemüseSelbstErnte in 2003, denen sich weitere sechs Betriebe in 2004 anschließen wollen. Forschung Mit der Einschränkung, dass es sich um ein einjähriges Vorhaben handelte, lassen sich folgende Ergebnisse festhalten: Der zusätzliche Umsatz in der Direktvermarktung während der GemüseSelbstErnte-Saison betrug auf zwei untersuchten Betrieben durchschnittlich 3.900 €. Dabei bestehen Potenziale zur Ausweitung dieser Umsätze. Bei den Untersuchungen zum Ernährungsverhalten der Nutzer wurde deutlich, dass diese sich oftmals bereits vor dem Einstieg in die GemüseSelbstErnte mit einem überdurchschnittlich hohen Gemüseanteil ernährten. Durch die Teilnahme steigt jedoch die Vielfalt der verzehrten Gemüsearten. Ausschlaggebende Motive für eine Teilnahme an der GemüseSelbstErnte sind die Versorgung mit frischem Gemüse in guter Qualität und die Kontrolle der Erzeugung

Ermittlung der Vorfruchtwirkung unterschiedlicher Wintererbsengenotypen in Rein- und Gemengesaat

In organic farming the cultivation of leguminous crops is one of the most important sources of nitrogen (N). However, in the case of winter field peas, the amount of N fixed, N supply to the subsequent crop and N balance there are hardly any published data. Therefore, the pre-crop effect of six genotypes of winter pea (five regular leaf type, one semi-leafless cultivar) and one semi-leafless spring pea cultivar in single and mixed cropping (with rye spring barley respectively) was examined in three suc-cesive growing seasons (2003/04-2005/06). Immediately after harvest, a catch crop was sown and sampled during the first half of October to determine biomass dry matter and N uptake. In single cropping, N uptake by the catch crop was usually significantly higher after regular leaf type peas in two years, whereas in mixed cropping it was only in one (p<0.05). It is suggested that response of N uptake was - among other possible factors (like e.g. soil tillage after harvest) – due to the mineralized N content in soil at harvest as both correlated significantly (R² between 0.53* and 0.79***, with exception of semi-leafless winter pea (R²=0,19)). It is very important to protect the large N quantities after conventional leafed winter pea cultivars as a sole crop against leaching. Results for the third experimental season will be presented at the conference

Ecomat und Dammkultur – Alternative Bodenbearbeitungssysteme im Ökologischen Landbau – Erste Ergebnisse aus einem Exaktversuch

In the interdisciplinary research project a field experiment of alternative tillage systems in organic farming was installed. Ridge till system from Turiel-Major and Ecomat-system from Kverneland will be compared with conventional ploughing system. Within the project, located on the experimental farm of the University of Kassel, regular yearly workshops are led. Due to the regular contact with farmers, advisers, developers and scientists knowledge of practice will be carried into scientific research, the transfer of knowledge will be carried on. The change to the Ecomat-system is simple. Take notice that after very shallow till-age, like stubble cultivation (short stubble) or turning grass-clover, the following tillage has to be done a few cm deeper. In the year of implementing the Ecomat-system there were no decreases in yields. The mineralization of Nitrogen was the same as in the ploughing system. When changing to the ridge till system the width of the dams (90 cm) must fit to the track width, planting and harvesting equipment. After stubble cultivation in the ridge till system mineralization of N increased. This N was taken up by the catch crop. Leaching of N is not expected. Even in the first year after changing the tillage systems the alternative systems Eco-mat and ridge till showed higher saturated hydraulic conductivity than the conventional ploughing system. This leads to much lower susceptibility of soil erosion when using these soil layer conservation systems