Experimental verification of a wireless sensing and control system for structural control using MR dampers     

Chin‐Hsiung Loh  Jerome P. Lynch  Kung‐Chun Lu  Yang Wang  Chia‐Ming Chang  Pei‐Yang Lin  Ting‐Hei Yeh 《地震工程与结构动力学》2007,36(10):1303-1328

The performance aspects of a wireless ‘active’ sensor, including the reliability of the wireless communication channel for real‐time data delivery and its application to feedback structural control, are explored in this study. First, the control of magnetorheological (MR) dampers using wireless sensors is examined. Second, the application of the MR‐damper to actively control a half‐scale three‐storey steel building excited at its base by shaking table is studied using a wireless control system assembled from wireless active sensors. With an MR damper installed on each floor (three dampers total), structural responses during seismic excitation are measured by the system's wireless active sensors and wirelessly communicated to each other; upon receipt of response data, the wireless sensor interfaced to each MR damper calculates a desired control action using an LQG controller implemented in the wireless sensor's computational core. In this system, the wireless active sensor is responsible for the reception of response data, determination of optimal control forces, and the issuing of command signals to the MR damper. Various control solutions are formulated in this study and embedded in the wireless control system including centralized and decentralized control algorithms. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The remarkable occurrence of large rainfall-induced debris flows at two different locations on July 12, 2008, Southern Sierra Nevada, CA, USA     

Jerome V. DeGraff  David L. Wagner  Alan J. Gallegos  Margie DeRose  Casey Shannon  Todd Ellsworth 《Landslides》2011,8(3):343-353

On July 12, 2008, two convective cells about 155 km apart produced a brief period of intense rainfall triggering large debris flows in the southern Sierra Nevada. The northernmost cell was centered over Oak Creek Canyon, an east-flowing drainage, and its tributaries near Independence, CA, USA. About 5:00 p.m., debris flows passed down the South Fork and North Fork of Oak Creek to merge into a large single feature whose passage affected the historic Mt. Whitney Fish hatchery and blocked California State Highway 395. At about the same time, the southernmost cell was largely centered over Erskine Creek, a main tributary of the west-flowing Kern River. Debris flows issued from several branches to coalesce into a large debris flow that passed along Erskine Creek, through the town of Lake Isabella, CA, USA and into the Kern River. It was observed reaching Lake Isabella about 6:30 p.m. Both debris flows caused significant disruption and damage to local communities.  相似文献   

WHY CAN'T GEOGRAPHERS WRITE THEIR OWN STORY?     

Jerome E. Dobson 《Geographical review》2006,96(3):480-483

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The Monitor project: rotation of low-mass stars in the open cluster M34     

Jonathan Irwin  Suzanne Aigrain  Simon Hodgkin  Mike Irwin  Jerome Bouvier  Cathie Clarke  Leslie Hebb  Estelle Moraux 《Monthly notices of the Royal Astronomical Society》2006,370(2):954-974

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Gray swans: comparison of natural and financial hazard assessment and mitigation     

Jerome L. Stein  Seth Stein 《Natural Hazards》2014,72(3):1279-1297

Even advanced technological societies are vulnerable to natural disasters, such as the 2011 Tohoku earthquake and tsunami, and financial disasters, such as the 2008 collapse of the US housing and financial markets. Both resulted from unrecognized or underappreciated weaknesses in hazard assessment and mitigation policies. These policies relied on models that proved inadequate for reasons including inaccurate conceptualization of the problem, use of a too-short historic record, and neglect of interconnections. Japanese hazard models did not consider the possibility of multiple fault segments failing together, causing a much larger earthquake than anticipated, and neglected historical data for much larger tsunamis than planned for. Mitigation planning underestimated the vulnerability of nuclear power plants, due to a belief in nuclear safety. The US economic models did not consider the hazard that would result if many homeowners could not pay their mortgages, and assumed, based on a short history, that housing prices would keep rising faster than interest rates. They did not anticipate the vulnerability of the financial system to a drop in housing prices, due to belief that markets functioned best without government regulation. Preventing both types of disasters from recurring involves balancing the costs and benefits of mitigation policies. A crucial aspect of this balancing is that the benefits must be estimated using models with significant uncertainties to infer the probabilities of the future events, as we illustrate using a simple model for tsunami mitigation. Improving hazard models is important because overestimating or underestimating the hazard leads to too much or too little mitigation. Thus, although one type of disaster has natural causes and the other has economic causes, comparison provides insights for improving hazard assessment and mitigation policies. Instead of viewing such disasters as unpredictable and unavoidable “black swan” events, they are better viewed as “gray swans” that—although novel and outside recent experience—can be better foreseen and mitigated.  相似文献   

An empirical test of household identification risk in geomasked maps     

Dara E. Seidl  Piotr Jankowski  Atsushi Nara 《制图学和地理信息科学》2013,40(6):475-488

ABSTRACT

Geomasking techniques displace point data to new locations in order to protect privacy while maintaining overall spatial distributions. If the end users of geomasked data are unaware that the data are masked, there is a risk that they will incorrectly associate individuals at the new locations with the masked data attributes. The probability of correct and false household identification depends on human understanding of whether maps contain masked coordinates and the spatial relationships of the points to contextual geographic data. Using a map-based experiment, this study finds that confidence in performing a household identification is substantially lowered when masked points are situated equidistantly between residential parcels. Despite initial notifications that data are masked, map users often report confidence in assigning masked points to specific households. Only map users who receive frequent notifications that the points are masked have reduced confidence in associating them with particular households, thereby lowering identification risk.  相似文献   

Earthquake-induced pounding between equal height multi-storey buildings considering soil-structure interaction     

Sayed Mahmoud  Ayman Abd-Elhamed  Robert Jankowski 《Bulletin of Earthquake Engineering》2013,11(4):1021-1048

The present paper investigates the coupled effect of the supporting soil flexibility and pounding between neighbouring, insufficiently separated equal height buildings under earthquake excitation. Two adjacent three-storey structures, modelled as inelastic lumped mass systems with different structural characteristics, have been considered in the study. The models have been excited using a suit of ground motions with different peak ground accelerations and recorded at different soil types. A nonlinear viscoelastic pounding force model has been employed in order to effectively capture impact forces during collisions. Spring-dashpot elements have been incorporated to simulate the horizontal and rotational movements of the supporting soil. The results of the numerical simulations, in the form of the structural nonlinear responses as well as the time-histories of energy dissipated during pounding-involved vibrations, are presented in the paper. In addition, the variation in storeys peak responses and peak dissipated energies for different gap sizes are also shown and comparisons are made with the results obtained for colliding buildings with fixed-base supports. Observations regarding the incorporation of the soil-structure interaction and its effect on the responses obtained are discussed. The results of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of equal height buildings during earthquakes, especially the response of the lighter and more flexible structure. It has been found that the soil flexibility decreases storey peak displacements, peak impact forces and peak energies dissipated during vibrations, whereas it usually leads to the increases in the peak accelerations at each storey level.  相似文献   

A STREAM-GRADIENT INDEX APPLIED TO SUBHUMID MONTANE STREAMS     

Jerome V. DeGraff 《自然地理学》2013,34(2):174-183

Hack (1973) introduced the stream-gradient index as a measure to analyze longitudinal stream profiles. It is derived from the channel slope at a point and channel length as measured along the longest stream above that point. In the eastern United States, empirical evidence shows the stream-gradient index to be a rough approximation of stream power or competence. Validity of this relationship in other geomorphic and climatic regions was unproven. Eight canyon drainages in the Bear River Range, north-central Utah, provide a basis for testing the validity of stream-gradient index analysis in a subhumid montane area. These drainages are found to have a drainage area to discharge function, rate of increase in channel width downstream, and coverging stream network with an average length proportional to a power of the drainage similar to Hack's original study area. These similarities indicate that use of stream-gradient indices as approximations of stream power are valid in subhumid montane areas. Stream-gradient index analysis of canyon streams in the Bear River Range illustrates drainage adjustment to tectonic activity, bedrock lithology, and structural attitude.  相似文献   

U-Pb geochronology of basement rocks in central Tibet and paleogeographic implications   总被引：14，自引：0，他引：14  

Jerome Guynn  Paul KappGeorge E. Gehrels  Lin Ding 《Journal of Asian Earth Sciences》2012,43(1):23-50

The ages and paleogeographic affinities of basement rocks of Tibetan terranes are poorly known. New U-Pb zircon geochronologic data from orthogneisses of the Amdo basement better resolve Neoproterozoic and Cambro-Ordovician magmatism in central Tibet. The Amdo basement is exposed within the Bangong suture zone between the Lhasa and Qiangtang terranes and is composed of granitic orthogneisses with subordinate paragneisses and metasedimentary rocks. The intermediate-felsic orthogneisses show a bimodal distribution of Neoproterozoic (920-820 Ma) and Cambro-Ordovician (540-460 Ma) crystallization ages. These and other sparse basement ages from Tibetan terranes suggest the plateau is underlain by juvenile crust that is Neoproterozoic or younger; its young age and weaker rheology relative to cratonic blocks bounding the plateau margins likely facilitated the propagation of Indo-Asian deformation far into Asia. The Neoproterozoic ages post-date Rodinia assembly and magmatism of similar ages is documented in the Qaidaim-Kunlun terrane, South China block, the Aravalli-Delhi craton in NW India, the Eastern Ghats of India, and the Prince Charles mountains in Antarctica. The Amdo Neoproterozoic plutons cannot be unambiguously related to one of these regions, but we propose that the Yangtze block of the South China block is the most likely association, with the Amdo basement representing a terrane that possibly rifted from the active Yangtze margin in the middle Neoproterozoic. Cambro-Ordovician granitoids are ubiquitous throughout Gondwana as a product of active margin tectonics following Gondwana assembly and indicate that the Lhasa-Qiangtang terranes were involved in these tectono-magmatic events. U-Pb detrital zircon analysis of two quartzites from the Amdo basement suggest that the protoliths were Carboniferous-Permian continental margin strata widely deposited across the Lhasa and Qiangtang terranes. The detrital zircon age spectra of the upper Paleozoic Tibetan sandstones and other rocks deposited in East Gondwana during the late Neoproterozoic and Paleozoic are all quite similar, making it difficult to use the age spectra for paleogeographic determinations. There is a suggestion in the data that the Qiangtang terrane may have been located further west along Gondwana’s northern boundary than the Lhasa terrane, but more refined spatial and temporal data are needed to verify this configuration.  相似文献   

Aquifer heterogeneity: Hydrogeological and hydrochemical properties of the Botany Sands aquifer and their impact on contaminant transport   总被引：1，自引：0，他引：1  

J. Jankowski  P. Beck 《Australian Journal of Earth Sciences》2013,60(1):45-64

Detailed geological mapping and drilling has shown that the contact between the Cambrian volcano‐sedimentary sequence at Rosebery and the Mt Read Volcanics is formed by a major thrust fault dipping east at 40° and having a displacement of at least 1.5 km. The sedimentary sequence is part of the Dundas Group, a Middle to Late Cambrian forearc‐like sequence which unconformably overlaps the volcanics south of Rosebery. The Rosebery Thrust Fault marks the eastern boundary of a zone of folding, faulting and disruption which affects the Dundas Group and the tectonically interfingered and underlying basaltic greywacke‐mudstone sequence of the Crimson Creek Formation. At least some of this deformation occurred prior to deposition of the Ordovician Limestone, as evidenced by marked angular discordances. The complex area can be interpreted as a Cambrian accretionary prism‐forearc‐arc sequence developed above an east‐dipping subduction zone.

The Henty Fault System, which cuts obliquely through the Mt Read belt and encloses a misfit wedge of sediments, pillow lavas, gabbros and ultramafic rocks, is interpreted as a remnant of an inter‐arc basin. The fault system separates a dacitic‐andesitic arc segment to the northwest from a more rhyolitic segment to the southeast. The latter is overlain by a younger arc sequence, the Tyndall Group, which may have been the source for the Dundas Group volcanic detritus.  相似文献