Dynamic characteristics of a base isolated building from ambient vibration measurements and low level earthquake shaking   总被引：3，自引：0，他引：3  

C. E. Ventura  W. D. Liam Finn  J. -F. Lord  N. Fujita 《Soil Dynamics and Earthquake Engineering》2003,23(4):313-322

Ambient vibration tests were conducted on a base-isolated apartment building in Takamatsu, Japan, to determine the mode shapes and the associated natural frequencies and damping ratios at very low levels of excitation. The latest developments in signal analysis for modal decomposition are used to analyze the ambient response data. A finite element model of the building and isolators was calibrated and refined using the experimental results from the ambient vibration tests. This model was then used to simulate the recorded response of the building under excitation from a small earthquake. The finite element model, calibrated by ambient vibration data and the low level of earthquake shaking, provides the starting point for modelling the non-linear response of the building when subjected to strong shaking.  相似文献   

Access and Equity in Greenspace Provision: A Comparison of Methods to Assess the Impacts of Greening Vacant Land     

Megan Heckert 《Transactions in GIS》2013,17(6):808-827

This research explores three methods of measuring access to greenspace in Philadelphia and their implications for assessing equity in access based on race and socioeconomic status. These three methods are then used to assess the impacts of a vacant land greening program which turns vacant lots into temporary greenspaces. This research explores the differences between findings when access to greenspace is measured based on distance to any greenspace, total amount of greenspace to which residents have access, or a hybrid measure in which access is determined based on proximity to a threshold amount of greenspace. Not only do assessments of equity differ between the three approaches, but so do determinations of the impact of greening vacant land. Blacks, Hispanics and renters are more likely to live close to a public greenspace than whites or homeowners, but live in proximity to smaller overall amounts of greenspace. Greening vacant land increases the proportion of all residents who live within walking distance of a greenspace and lessens but does not eliminate differences in total greenspace access. The greatest effects of greening vacant land are seen in addressing differences in relative likelihood of having access to a threshold amount of greenspace.  相似文献   

The Use of Environmental Features on Tactile Maps by Navigators Who Are Blind     

Amy Lobben  Megan Lawrence 《The Professional geographer》2013,65(1):95-108

Maps designed for and used by sighted audiences benefit from map symbol standardization and convention but, with very limited exception (most notably two European projects), neither standardization nor convention guides the design and use of symbols for tactile maps. In this project, we developed and field tested symbolization for and use of tactile street maps. The development process included consultation with the literature as well as with field experts (orientation and mobility teachers, Braillists, and teachers working with students who are blind or have low vision). Following development, we undertook a three-year field testing and validation phase, in which we conducted pilot testing and formal testing with travelers who are blind or have low vision. Research results reveal not only a discriminable and useful tactile symbol set but also environmental feature use by travelers who are blind or have low vision.  相似文献   

Quaternary coastline evolution of Lake Ohrid (Macedonia/Albania)     

Nadine Hoffmann  Klaus Reicherter  Christoph Grützner  Jochen Hürtgen  Andreas Rudersdorf  Finn A. Viehberg  Martin Wessels 《Central European Journal of Geosciences》2012,4(1):94-110

Lake Ohrid (between FYR of Macedonia and Albania), situated in an active tectonic region of the Balkanides, is characterized by N ?? S trending active faults. To reconstruct the Holocene shoreline evolution we investigated the coastline using sediment cores and geophysical methods to image sedimentary and tectonic structures. We revealed areas of differing sedimentation regimes. The plains north and south of the lake are dominated by clastic input related to climate variations and uplift/erosion, whereas the steep western and eastern margins are controlled by recent tectonics. Furthermore, no evidence for a much higher lake-level during the Holocene was found in the plains north and south of the lake, except rare temporary floodings. This is supported by mappings of the limestone cliffs around Lake Ohrid, which yielded no evidence for abrasional platforms or notches as indicators for past highstands.  相似文献   

Shock Wave Interactions in Rock Blasting: the Use of Short Delays to Improve Fragmentation in Model-Scale     

Daniel Johansson  Finn Ouchterlony 《Rock Mechanics and Rock Engineering》2013,46(1):1-18

A series of detailed small-scale tests have been made to investigate the use of short delays to promote better fragmentation caused by shock wave interactions. The block design had a size of 650/660 × 205 × 300 mm (L × W × H) and two rows with five Ø 10-mm blastholes in each row. The spacing (S) and burden (B) were 110 and 70 mm, respectively, giving an S/B ratio of 1.6. The results showed no distinct differences or high improvements of the fragmentation when the delays were in the time range of interactions compared with no shock wave interactions. The decrease of x ₅₀ (mean size) was around 20 % at a delay time ~1.1 ms/m burden compared with longer delays like 2 ms/m. A statistical analysis of the results has been made to evaluate the minimum at short delays and it is not significant.  相似文献   

Tsunami impact assessment: development of vulnerability matrix for critical infrastructure and application to Christchurch,New Zealand     

Williams  James H.  Wilson  Thomas M.  Horspool  Nick  Lane  Emily M.  Hughes  Matthew W.  Davies  Tim  Le  Lina  Scheele  Finn 《Natural Hazards》2019,96(3):1167-1211

Natural Hazards - Tsunamis can have severe impacts on society. In addition to casualties and damage to buildings, they can also damage and disrupt critical infrastructure. To support effective risk...  相似文献   

Defining Optimal Freshwater Flow for Oyster Production: Effects of Freshet Rate and Magnitude of Change and Duration on Eastern Oysters and <Emphasis Type="Italic">Perkinsus marinus</Emphasis> Infection     

Megan K. La Peyre  Bryan Gossman  Jerome F. La Peyre 《Estuaries and Coasts》2009,32(3):522-534

In coastal Louisiana, the development of large-scale freshwater diversion projects has led to controversy over their effects on oyster resources. Using controlled laboratory experiments in combination with a field study, we examined the effects of pulsed freshwater events (freshet) of different magnitude, duration, and rate of change on oyster resources. Laboratory and field evidence indicate that low salinity events (<5 psu) decreased Perkinsus marinus infection intensities. Furthermore, when salinity was low (<5 psu), parasite infection intensities continued to decrease even as temperatures exceeded 20°C. At the same time, oyster growth was positively correlated with salinity. To maximize oyster production, data indicate that both low and high salinity events will be necessary.  相似文献   

Relaxational effects in radiating stellar collapse     

Megan Govender  Roy Maartens  Sunil D. Maharaj 《Monthly notices of the Royal Astronomical Society》1999,310(2):557-564

Relaxational effects in stellar heat transport can in many cases be significant. Relativistic Fourier–Eckart theory is inherently quasi-stationary, and cannot incorporate these effects. The effects are naturally accounted for in causal relativistic thermodynamics, which provides an improved approximation to kinetic theory. Recent results, based on perturbations of a static star, show that relaxation effects can produce a significant increase in the central temperature and temperature gradient for a given luminosity. We use a simple stellar model that allows for non-perturbative deviations from staticity, and confirms qualitatively the predictions of the perturbative models.  相似文献   

Evaluation of WaPOR V2 evapotranspiration products across Africa     

Megan L. Blatchford  Chris M. Mannaerts  Sammy M. Njuki  Hamideh Nouri  Yijian Zeng  Henk Pelgrum  Steven Wonink  Poolad Karimi 《水文研究》2020,34(15):3200-3221

The Food and Agricultural Organization of the United Nations (FAO) portal to monitor water productivity through open-access of remotely sensed derived data (WaPOR) offers continuous actual evapotranspiration and interception (ETIa-WPR) data at a 10-day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250 m) covers Africa and the Middle East (L1). The national level (100 m) covers 21 countries and 4 river basins (L2). The third level (30 m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa-WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long-term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa-WPR against in situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa-WPR is performing well, but with some noticeable overestimation. The ETIa-WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa-WPR shows mixed results at point scale as compared to EC flux towers with an overall correlation of 0.71, and a root mean square error of 1.2 mm/day. The level consistency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa-WPR is overestimating at low ETIa-WPR and underestimating when ETIa is high. In irrigated areas, ETIa-WPR values appear to be consistently overestimating ETa. The relative soil moisture content (SMC), the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa-WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa-WPR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.  相似文献   

The polarization of continuum radiation in sunspots     

G. D. Finn  J. T. Jefferies 《Solar physics》1974,39(1):91-106

Expressions are derived for the Stokes parameters of light scattered by a layer of free electrons and hydrogen atoms in a sunspot. A physically reasonable sunspot model was found so that the direction of the calculated linear polarization agrees reasonably with observations. The magnitude of the calculated values of the linear polarization agrees generally with values observed in the continuum at 5830 Å. Circular polarization in the continuum also accompanies electron scattering in spot regions; however for commonly accepted values of the longitudinal magnetic field, the predicted circular polarization is much smaller than observed.  相似文献