Tire stiffness and damping determined from static and free-vibration tests

Stiffness and damping of a nonrolling tire were determined experimentally from both static force-displacement relations and the free-vibration behavior of a cable-suspended platen pressed against the tire periphery. Lateral and force-and-aft spring constants and damping factors of a 49 x 17 size aircraft tire for different tire pressure and vertical loads were measured assuming a rate-independent damping form. In addition, a technique was applied for estimating the magnitude of the tire mass which participates in the vibratory motion of the dynamic tests. Results show that both the lateral and force-and-aft spring constants generally increase with tire pressure but only the latter increased significantly with vertical tire loading. The fore-and-aft spring constants were greater than those in the lateral direction. The static-spring-constant variations were similar to the dynamic variations but exhibited lower magnitudes. Damping was small and insensitive to tire loading. Furthermore, static damping accounted for a significant portion of that found dynamically. Effective tire masses were also small

Accelerometer-controlled automatic braking system

Braking system, which employs angular accelerometer to control wheel braking and results in low level of tire slip, has been developed and tested. Tests indicate that system is feasible for operations on surfaces of different slipperinesses. System restricts tire slip and is capable of adapting to rapidly-changing surface conditions

Experimental investigation of an accelerometer controlled automatic braking system

An investigation was made to determine the feasibility of an automatic braking system for arresting the motion of an airplane by sensing and controlling braked wheel decelerations. The system was tested on a rotating drum dynamometer by using an automotive tire, wheel, and disk-brake assembly under conditions which included two tire loadings, wet and dry surfaces, and a range of ground speeds up to 70 knots. The controlling parameters were the rates at which brake pressure was applied and released and the Command Deceleration Level which governed the wheel deceleration by controlling the brake operation. Limited tests were also made with the automatic braking system installed on a ground vehicle in an effort to provide a more realistic proof of its feasibility. The results of this investigation indicate that a braking system which utilizes wheel decelerations as the control variable to restrict tire slip is feasible and capable of adapting to rapidly changing surface conditions

Molecular dynamics study of the thermopower of Ag, Au, and Pt nanocontacts

Using molecular dynamics simulations of many junction stretching processes we analyze the thermopower of silver (Ag), gold (Au), and platinum (Pt) atomic contacts. In all cases we observe that the thermopower vanishes on average within the standard deviation and that its fluctuations increase for decreasing minimum cross-section of the junctions. However, we find a suppression of the fluctuations of the thermopower for the s-valent metals Ag and Au, when the conductance originates from a single, perfectly transmitting channel. Essential features of the experimental results for Au, Ag, and copper (Cu) of Ludoph and van Ruitenbeek [Phys. Rev. B 59, 12290 (1999)], as yet unaddressed by atomistic studies, can hence be explained by considering the atomic and electronic structure at the disordered narrowest constriction of the contacts. For the multivalent metal Pt our calculations predict the fluctuations of the thermopower to be larger by one order of magnitude as compared to Ag and Au, and suppressions of the fluctuations as a function of the conductance are absent.Comment: 13 pages, 10 figure

Wind loads on a house roof

CER72-73KJD-JEC22.March 1973.Includes bibliographical references (pages 40-42).Prepared under National Bureau of Standards Contract No. NBS 273-70.Circulating copy deaccessioned 2020.The wind loads on the roof of a house were experimentally investigated by placing a 1:50 scale model house in a wind tunnel capable of generating thick, turbulent shear flows. The effects of roof geometry and wind direction were isolated by making the wind-tunnel flow representative of natural winds over very flat, open terrain. This flow simulation was accomplished by placing vortex generators at the entrance to the wind-tunnel test section. Mean pressures, root-mean-square values of the fluctuating pressures, and instantaneous peak pressures were measured at 11 preselected locations on the model's roof for 24 wind directions. A secondary purpose of the study was to determine the effects of an upwind fence on the roof pressures

On new emerging concepts of modeling petroleum digital ecosystems by multidimensional data warehousing and mining approaches

Petroleum system and its ingredients are narrated for each and every oil and gas field in each and everypetroleum-bearing sedimentary basin. A new concept of ecosystem and its digitization are emerging within the generic petroleum system. Significance of this concept is to make connectivity among petroleum systems through attributes of ingredients and their contextualization and specification. Most popularly known ingredients are geological structure, reservoir, source and seal rocks. Other ingredients involved are in the form of process of these ingredients such as maturation (of source rocks) and migration and timing (of formation of structure, reservoir and seal rocks). One can notice the connectivity among primary petroleum system ingredients, through different processes, such as maturation of source rocks and charging capability and migration of hydrocarbons into suitablestructural (structure) entrapment areas of reservoir. Unless the phenomenon of interconnectivity is understood; integration between ingredients and processes in the context of digital representation and visualization, petroleum system existence and its survival cannot be well explained. Its value cannot beadded in terms of petroleum accumulations and volumes, unless these phenomena are explicit. Authors propose ontology based data warehousing and data mining technologies, in which, conceptualization and contextualization of multiple data dimensions (petroleum system?s ingredients and processes), integration (within data warehouse environment) and data mining of interpretable emerging petroleum digital ecosystems are accomplished. Multidimensional data warehousingand mining facilitate an effective interpretation of petroleum systems, minimizing the ambiguities involved during structure and reservoir qualifications and quantifications

Vom "Impuls" zur Sozialität: Reflexionen über die "Natur" des musikalischen Improvisierens

"Das Phänomen der musikalischen Improvisation stellt für die Sozialwissenschaften eine Herausforderung dar, nicht zuletzt deshalb, weil das 'Spielen aus dem Stegreif' - anders als das Interpretieren und Spielen komponierter Musikstücke - die zentrale Frage der Beziehung zwischen a) Natur, b) dem Ausdruck der Individualität und c) Sozialität unter einen neuen Blickwinkel stellt. Der Musiker ist beim Improvisieren in der Lage - anders als beim Interpretieren komponierter Musik -, seine musikalischen, 'impulshaften' und individuellen Gedanken in 'Echtzeit' zu offenbaren. Darüber hinaus ist das Problem der Koordination - und somit der Sozialität - zwischen den Musikern beim Improvisieren vor allem relevant, weil die Unvorhersehbarkeit dessen, was er/ sie selbst und die Mitmusiker spielen werden, die Komplexität eines möglichen gelungenen gemeinsamen Musizierens erhöht. Wie sind die erhöhte Ausdrucksmöglichkeit der Individualität mit der gesteigerten Komplexität der Sozialität beim Improvisieren zu vereinbaren? Im Rahmen des empirischen Forschungsprojektes 'Improvisation als 'neuer' Handlungstypus. Eine handlungstheoretische Exploration der musikalischen Improvisation' stellte sich heraus, dass die Kategorie des 'Impulses' (Kategorie erster Ordnung) eine zentrale Stellung in der Erklärung dieser Fragen einnimmt. So ist der Impuls für die untersuchten Free Jazz Musiker einerseits ein ummittelbarer, spontaner Ausdruck ihrer Individualität aber auch ein Mittel der Erzeugung des Gruppenausdrucks auf der Basis des 'gemeinsamen Atmens' und des 'Gruppen-Pulses'. Der körperliche, 'natürliche' 'Impuls', einen Klang zu erzeugen, vereinigt somit Natur, Individualität und Sozialität. In der Präsentation wird die Verfasserin sich mit dieser Kategorie auseinandersetzen und erklären, wie die prozesshafte Entwicklung vom musikalischem 'Impuls' bis zur Sozialität des gemeinsamen Musizierens die 'Natur' der Improvisation beleuchten kann." (Autorenreferat