103,651 research outputs found
Hohmann spiral transfer with inclination change performed by low-thrust system
No full textThis paper investigates the Hohmann Spiral Transfer (HST), an orbit transfer method previously developed by the authors incorporating both high and low-thrust propulsion systems, using the low-thrust system to perform an inclination change as well as orbit transfer. The HST is similar to the bi-elliptic transfer as the high-thrust system is first used to propel the spacecraft beyond the target where it is used again to circularize at an intermediate orbit. The low-thrust system is then activated and, while maintaining this orbit altitude, used to change the orbit inclination to suit the mission specification. The low-thrust system is then used again to reduce the spacecraft altitude by spiraling in-toward the target orbit. An analytical analysis of the HST utilizing the low-thrust system for the inclination change is performed which allows a critical specific impulse ratio to be derived determining the point at which the HST consumes the same amount of fuel as the Hohmann transfer. A critical ratio is found for both a circular and elliptical initial orbit. These equations are validated by a numerical approach before being compared to the HST utilizing the high-thrust system to perform the inclination change. An additional critical ratio comparing the HST utilizing the low-thrust system for the inclination change with its high-thrust counterpart is derived and by using these three critical ratios together, it can be determined when each transfer offers the lowest fuel mass consumption. Initial analyses have shown the HST utilizing low-thrust inclination change to offer the greatest benefit at low R2 (R2 - R1) and large AI (AI > 30º). A novel numerical optimization process which could be used to optimize the trajectory is also introduced
Solar Sail Augmented Hohmann Transfer
No full textThe aim of this correspondence is to analyze the performance of a solar sail-based spacecraft in a two-impulse orbit transfer between circular and coplanar heliocentric orbits of assigned radii. In particular, assuming a transfer trajectory with a sweep angle and a flight time equal to those of a classical Hohmann orbit, the sail propulsive acceleration is used to minimize the total velocity variation required by the two tangential impulses. In this sense, the article quantifies the optimal performance of a solar sail augmented Hohmann transfer as a function of the sail characteristics
Lehrplan Schwimmsport 02: Vermittlung und Training im Schwimmen
No full textVolck G, Freitag W, Hohmann A, Ungerechts B. Lehrplan Schwimmsport 02: Vermittlung und Training im Schwimmen. 1. Auflage. Schorndorf: Hofmann; 2012
Boesch, C., Hohmann, G. & Marchant, L. F. (eds). — Behavioural diversity in chimpanzees and bonobos. Cambridge University Press, Cambridge, New York, Melbourne, Madrid & Cape Town. 2002
No full textErard Christian. Boesch, C., Hohmann, G. & Marchant, L. F. (eds). — Behavioural diversity in chimpanzees and bonobos. Cambridge University Press, Cambridge, New York, Melbourne, Madrid & Cape Town. 2002. In: Revue d'Écologie (La Terre et La Vie), tome 59, n°4, 2004. pp. 607-609
Vertrauensbildung geht anders
No full textFehrenbach HG, Hohmann S, Lasser J. Vertrauensbildung geht anders. Wiarda-Blog. 20.04.2023
Chimpanzee hunting behavior
No full textThe pursuit, capture and consumption of small-and medium-sized vertebrates, appears to be typical of all chimpanzee (Pan troglodytes) populations, although large variation exists. Red colobus monkeys (Piliocolobus sp.) appear to be the preferred prey but intensity and frequency of hunting varies from month to month and between populations. Hunting is a predominately male activity and is typically opportunistic, although there is some evidence of searching for prey. The degree of cooperation during hunting, as well as prey selection, varies between East and West African populations and may be related to the way the kill is divided: in West Africa, hunters often collaborate, with kills tending to be shared according to participation, whereas in East Africa, the kill is typically divided tactically by the male in possession of the carcass, trading meat with females in return for sex or with other males to strengthen alliances, and cooperation in hunting is more limited. The adaptive function of chimpanzee hunting is not well understood, although it appears that it may be both a means to acquire a nutritionally valuable commodity that can then be traded and as a means for males to display their prowess and reliability to one another
The Hunting Behavior and Carnivory of Wild Chimpanzees
No full textThe pursuit, capture and consumption of small- and medium-sized vertebrates appear to be typical of all chimpanzee (Pan troglodytes) populations, although large variation exists. Red colobus monkeys (Piliocolobus sp.) appear to be the preferred prey, but intensity and frequency of hunting varies from month to month and among populations. Hunting is a predominately male activity and is typically opportunistic, although there is some evidence of searching for prey. The degree of cooperation during hunting, as well as prey selection, varies between East and West African populations and may be related to the way the kill is divided: in West Africa, hunters often collaborate, with kills tending to be shared according to participation, whereas in East Africa, cooperation in hunting is more limited and the kill is typically consumed selfishly, or divided in response to harassment (begging) by others. In some cases it may be shared tactically, trading meat with other males to strengthen alliances. The adaptive function of chimpanzee hunting is not well understood and a variety of hypotheses have been proposed. Ideas that chimpanzees hunt to make up for nutritional shortfalls, or to acquire meat to trade for sex, have failed to find empirical support, while recent work favors nutritional benefits of some kind. Nevertheless, cross-population studies evaluating multiple hypotheses are in their infancy, and there is much to be learned. In particular, very little is known about hunting of non-primates, particularly ungulates, or the impact that variation in levels of hunting, and of carcasses to share and consume, has on patterns of chimpanzee behavior. If one goal of studying this topic is to shed light on the behavioral ecology of hominins, then efforts to understand the diversity of hunting and carnivory in wild chimpanzees are needed
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
