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Driving Mechanism (driving + mechanism)
Selected AbstractsDevelopment of a high-speed electromagnetic repulsion mechanism for high-voltage vacuum circuit breakersELECTRICAL ENGINEERING IN JAPAN, Issue 1 2008Mitsuru Tsukima Abstract This paper presents a design and testing of a new high-speed electromagnetic driving mechanism for a high-voltage vacuum circuit breaker (VCB). This mechanism is based on a high-speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3D nonlinear finite-elements magnetic field analysis and investigated its internal friction and eddy-current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics,contact velocity, response time, and so on, required for the high-speed VCB. A prototype VCB, which was built based on the above analysis, shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 34,40, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20398 [source] Episodic stream water pH decline during autumn storms following a summer drought in northern SwedenHYDROLOGICAL PROCESSES, Issue 9 2002Hjalmar Laudon Abstract The sources of episodic pH decline in four streams from northern Sweden during the autumn of 1996 were quantified. The events, in which pH dropped by between 1·0 and 2·4 units, were preceded by an extensive summer drought. Total organic carbon, which increased 100% to 160% during peak flow, was the most important driving mechanism of the episodic pH decline. Sulphate, however, was relatively more important during these autumn events than during spring flood. In the sites where past and present anthropogenic deposition were believed to be the main source of sulphate in stream water, sulphate contributed less than 0·3 pH units to the pH decline. In catchments where natural sources of sulphate are known to be important, sulphate contributed up to 0·6 units of pH decline. The export of sulphate during the episodes was two to nine times higher than what was expected from deposition only. The drought preceding the study episodes resulted in some of the lowest ground water levels during the 1990s in that region. The large export of sulphate was probably due to oxidation of natural sulphate bearing minerals in the soil and/or previously deposited sulphate driven by the low ground water level preceding the episodes. Copyright © 2002 John Wiley & Sons, Ltd. [source] A new family of hybrid 4-DOF parallel mechanisms with two platforms and its application to a footpad deviceJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2005Jungwon Yoon This paper proposes a new family of 4-degrees-of-freedom (DOF) parallel mechanisms with two platforms and its application to a footpad device that can simulate the spatial motions of the human foot. The new mechanism consists of front and rear platforms, and three limbs. Two limbs with 6-DOF serial joints (P -S-P-P) are attached to each platform and are perpendicular to the base plate, while the middle limb is attached to the revolute joint that connects the front and rear platforms. The middle limb is driven by the 2-DOF driving mechanism that is equivalent to active serial prismatic and revolute joints (Pe - Re), or prismatic and prismatic joints (Pe - Pe) with two base-fixed prismatic actuators. Since the middle limb perpendicular to the base plate has 3-DOF serial joints (Pe - Re -R or Pe - Pe -R), two new 4-DOF parallel mechanisms with two platforms can generate pitch motion of each platform, and roll and heave motions (1T-3R) or pitch motion of each platform and two translational motions (2T-2R) at both platforms, according to the type of the 2-DOF driving mechanism. Kinematic analyses of the 1T-3R mechanism were performed, including inverse and forward kinematics and velocity analysis. Based on the 1T-3R mechanism, a footpad device was designed to generate foot trajectories for natural walking. © 2005 Wiley Periodicals, Inc. [source] Kinetic and strain-driven growth phenomena on Si(001)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2004C. Schelling Abstract Self-organization phenomena in semiconductors are usually based on strain-driven island growth during hetero epitaxial layer deposition. However, kinetic phenomena can become important and even dominating at the low growth temperatures usually employed during molecular beam epitaxy. We report on kinetic step bunching on Si(001), and identify the driving mechanism on the atomic scale via kinetic Monte Carlo simulations. Another phenomena discussed is facet formation during annealing of SiO2 -covered Si(001) nanostructures at the relatively low temperatures usually employed for oxide desorption. Both phenomena are combined to facilitate perfect ordering of self-assembled Ge dots on facetted Si(001) nanostructure templates. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Introductory perspective on the COREF ProjectISLAND ARC, Issue 4 2006Yasufumi Iryu Abstract Coral reefs are tropic to subtropic, coastal ecosystems comprising very diverse organisms. Late Quaternary reef deposits are fossil archives of environmental, tectonic and eustatic variations that can be used to reconstruct the paleoclimatic and paleoceanographic history of the tropic surface oceans. Reefs located at the latitudinal limits of coral-reef ecosystems (i.e. those at coral-reef fronts) are particularly sensitive to environmental changes , especially those associated with glacial,interglacial changes in climate and sealevel. We propose a land and ocean scientific drilling campaign in the Ryukyu Islands (the Ryukyus) in the northwestern Pacific Ocean to investigate the dynamic response of the corals and coral-reef ecosystems in this region to Late Quaternary climate and sealevel change. Such a drilling campaign, which we call the COREF (coral-reef front) Project, will allow the following three major questions to be evaluated: (i) What are the nature, magnitude and driving mechanisms of coral-reef front migration in the Ryukyus? (ii) What is the ecosystem response of coral reefs in the Ryukyus to Quaternary climate changes? (iii) What is the role of coral reefs in the global carbon cycle? Subsidiary objectives include (i) the timing of coral-reef initiation in the Ryukyus and its causes; (ii) the position of the Kuroshio current during glacial periods and its effects on coral-reef formation; and (iii) early carbonate diagenetic responses as a function of compounded variations in climate, eustacy and depositional mineralogies (subtropic aragonitic to warm-temperate calcitic). The geographic, climatic and oceanographic settings of the Ryukyu Islands provide an ideal natural laboratory to address each of these research questions. [source] Plant species and growth form richness along altitudinal gradients in the southwest Ethiopian highlandsJOURNAL OF VEGETATION SCIENCE, Issue 4 2010Wana Desalegn Abstract Questions: Do growth forms and vascular plant richness follow similar patterns along an altitudinal gradient? What are the driving mechanisms that structure richness patterns at the landscape scale? Location: Southwest Ethiopian highlands. Methods: Floristic and environmental data were collected from 74 plots, each covering 400 m2. The plots were distributed along altitudinal gradients. Boosted regression trees were used to derive the patterns of richness distribution along altitudinal gradients. Results: Total vascular plant richness did not show any strong response to altitude. Contrasting patterns of richness were observed for several growth forms. Woody, graminoid and climber species richness showed a unimodal structure. However, each of these morphological groups had a peak of richness at different altitudes: graminoid species attained maximum importance at a lower elevations, followed by climbers and finally woody species at higher elevations. Fern species richness increased monotonically towards higher altitudes, but herbaceous richness had a dented structure at mid-altitudes. Soil sand fraction, silt, slope and organic matter were found to contribute a considerable amount of the predicted variance of richness for total vascular plants and growth forms. Main Conclusions: Hump-shaped species richness patterns were observed for several growth forms. A mid-altitudinal richness peak was the result of a combination of climate-related water,energy dynamics, species,area relationships and local environmental factors, which have direct effects on plant physiological performance. However, altitude represents the composite gradient of several environmental variables that were interrelated. Thus, considering multiple gradients would provide a better picture of richness and the potential mechanisms responsible for the distribution of biodiversity in high-mountain regions of the tropics. [source] | |||||||||||||