Walking Humanoids for Robotics Research

We present three humanoid robots aimed as platforms for research in robotics, and cognitive development in robotics systems. The 'priscilla' robot is a 180cm full scale humanoid, and the mid-size prototype is called 'elvis' and is about 70cm tall. The smallest size humanoid is the 'elvina' type, about 28 cm tall. Two instances of 'elvina' have been built to enable experiments with cooperating humanoids. The underlying ideas and conceptual principles, such as anthropomorphism, embodiment, and mechanisms for learning and adaptivity are introduced as well

The Soft Path for Water

There are two primary ways of meeting water-related needs, or more poetically, two paths. One path -- the "hard" path -- relies almost exclusively on centralized infrastructure and decision making: dams and reservoirs, pipelines and treatment plants, water departments and agencies. It delivers water, mostly of potable quality, and takes away wastewater. The second path -- the "soft" path -- may also rely on centralized infrastructure, but complements it with extensive investment in decentralized facilities, efficient technologies, and human capital.1 It strives to improve the overall productivity of water use rather than seek endless sources of new supply. It delivers diverse water services matched to the users' needs and works with water users at local and community scales. This chapter tells the tale of these paths up to the present. Decisions made today, and actions of future generations, will write the conclusion of the story

The Schr\"odinger Functional - a Renormalizable Probe for Non-Abelian Gauge Theories

Following Symanzik we argue that the Schr\"odinger functional in lattice gauge theories without matter fields has a well-defined continuum limit. Due to gauge invariance no extra counter terms are required. The Schr\"odinger functional is, moreover, accessible to numerical simulations. It may hence be used to study the scaling properties of the theory and in particular the evolution of the renormalized gauge coupling from low to high energies. A concrete proposition along this line is made and the necessary perturbative analysis of the Schr\"odinger functional is carried through to 1-loop order.Comment: 68 page

Anmerkungen zur Entwicklung des Journal of Agriculture and Rural Development in the Tropics and Subtropics

In der zweiten Jahreshälfte 2009 scheidet der langjährige geschäftsführende Schriftleiter des Journal of Agriculture and Rural Development in the Tropics and Subtropics, Dipl.-Ing. Hans Hemann, aus der Redaktion dieser Zeitschrift aus. In Würdigung der geleisteten Arbeit erfolgt in dem vorgelegten Artikel eine Dokumentation der Entwicklung der Zeitschrift von ihren Anfängen als Alumni-Zeitschrift bis zur heutigen international anerkannten Fachzeitschrift. Prof. Ernst Albert Fabarius, der Mitbegründer und erster Direktor der Deutschen Kolonialschule in Witzenhausen schuf die Zeitschrift zur Information und Kontaktpflege mit den Absolventen, den Freunden und Gönnern der Lehranstalt. Erst nach seinem Tod 1927 kam es zu vorsichtigen Versuchen der Zeitschrift einen mehr fachlichen Charakter zu verleihen, ohne dabei allerdings die Aufgabe des Kontaktes zu den Absolventen, Freunden und Gönnern aus dem Auge zu verlieren. Der Übergang von der Alumni-Zeitschrift zur Fachzeitschrift für die Landwirtschaft in den Tropen und Subtropen wurde 1966 vollzogen, nach dem die Lehranstalt ihren Betrieb wieder aufgenommen hatte. Aus dem Deutschen Kulturpionier wurde Der Tropenlandwirt. Im Jahre 1994 fusionierte die Zeitschrift mit Beiträge zur tropischen Landwirtschaft und Veterinärmedizin, der bis dahin von dem Institut für Tropische Landwirtschaft der Universität Leipzig herausgegebenen Fachzeitschrift. Als schließlich der Kreis der Leser und der Autoren zunehmend aus dem internationalen Umfeld kam, erfolgte die Umstellung auf eine überwiegend englischsprachige Fachzeitschrift. Der Name wurde entsprechend in Journal of Agriculture and Rural Development in the Tropics and Subtropics geändert. Hans Hemann hat neben der oft mühsamen Redaktionsarbeit diese Entwicklung von 1979 bis 2009 mitgetragen und vor allem die verschiedenen Änderungen umgesetzt

Quo vadis Süßwasser? Anmerkungen zum "Internationalen Jahr des Süßwassers 2003"

The United Nations General Assembly proclaimed in a resolution in 2002 the “Internnational Year of Freshwater 2003”. The aim of the year is to raise awareness of the importance of protecting and managing freshwater resources in a sustainable way. On occasion of the International Year of Freshwater the author highlights the competing demands and gives a short description of three scenarios of freshwater use. From these scenarios it can be concluded that only the establishment of a sustainable, integrated water management will avoid a water crisis and maintain food security

Comptonization and the Spectra of Accretion-Powered X-Ray Pulsars

Accretion-powered X-ray pulsars are among the most luminous X-ray sources in the Galaxy. However, despite decades of theoretical and observational work since their discovery, no satisfactory model for the formation of the observed X-ray spectra has emerged. In this paper, we report on a self-consistent calculation of the spectrum emerging from a pulsar accretion column that includes an explicit treatment of the bulk and thermal Comptonization occurring in the radiation-dominated shocks that form in the accretion flows. Using a rigorous eigenfunction expansion method, we obtain a closed-form expression for the Green's function describing the upscattering of monochromatic radiation injected into the column. The Green's function is convolved with bremsstrahlung, cyclotron, and blackbody source terms to calculate the emergent photon spectrum. We show that energization of photons in the shock naturally produces an X-ray spectrum with a relatively flat continuum and a high-energy exponential cutoff. Finally, we demonstrate that our model yields good agreement with the spectra of the bright pulsar Her X-1 and the low luminosity pulsar X Per.Comment: 6 Pages, 2 Figures, To appear in "The Multicoloured Landscape of Compact Objects and their Explosive Progenitors" (Cefalu, Sicily, June 2006). Eds. L. Burderi et al. (New York: AIP

Spectral Formation in X-Ray Pulsar Accretion Columns

We present the first self-consistent model for the dynamics and the radiative transfer occurring in bright X-ray pulsar accretion columns, with a special focus on the role of the shock in energizing the emerging X-rays. The pressure inside the accretion column of a luminous X-ray pulsar is dominated by the photons, and consequently the equations describing the coupled radiative-dynamical structure must be solved simultaneously. Spectral formation in these sources is therefore a complex, nonlinear phenomenon. We obtain the analytical solution for the Green's function describing the upscattering of monochromatic radiation injected into the column from the thermal mound located near the base of the flow. The Green's function is convolved with a Planck distribution to model the X-ray spectrum resulting from the reprocessing of blackbody photons produced in the thermal mound. These photons diffuse through the infalling gas and eventually escape out the walls of the column, forming the observed X-ray spectrum. We show that the resulting column-integrated, phase-averaged spectrum has a power-law shape at high energies and a blackbody shape at low energies, in agreement with the observational data for many X-ray pulsars.Comment: Accepted for publication in ApJ Letters. Several typos noticed during the proof review were correcte

Experimental investigation of a cascaded organic Rankine cycle plant for the utilization of waste heat at high and low temperature levels

A power plant with two cascaded organic Rankine cycles (CORC) to exploit waste heat from a 800 kWe combined heat and power plant, fueled by biogas, is designed and tested. Heat from the exhaust gas is utilized with a high temperature organic Rankine cycle (HT-ORC), where toluene is employed as a working fluid. The heat discharged from the HT-ORC as well as heat from the engine coolant and additional heat from the exhaust gas is supplied to a low temperature ORC (LT-ORC) with the working fluid Solkatherm SES36. The design of the CORC and the selection of working fluids is presented, aiming at a maximum plant efficiency, but also complying with environmental, safety and practical issues. Furthermore, plant components and construction details are described. After manufacturing, initial tests are carried out, obtaining thermodynamic conditions that are close to the design of the HT-ORC, where a maximum electrical turbo-generator output of 17.5 kW is measured. The cascading of the low temperature heat sources and the transfer to the LT-ORC is shown as well as the basic operation of the LT-ORC. However, several problems occurred, such as a turbo-generator damage in the HT-ORC, a too high condensation pressure and a low working fluid mass flow rate in the LT-ORC, which are discussed together with proposed optimization measures