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121.
This research is part of a larger effort to better understand and quantify the epistemic model uncertainty in dynamic response-history simulations. This paper focuses on how calibration methods influence model uncertainty. Structural models in earthquake engineering are typically built up from independently calibrated component models. During component calibration, engineers often use experimental component response under quasi-static loading to find parameters that minimize the error in structural response under dynamic loading. Since the calibration and the simulation environments are different, if a calibration method wants to provide optimal parameters for simulation, it has to focus on features of the component response that are important from the perspective of global structural behavior. Relevance describes how efficiently a calibration method can focus on such important features. A framework of virtual experiments and a methodology is proposed to evaluate the influence of calibration relevance on model error in simulations. The evaluation is demonstrated through a case study with buckling-restrained braced frames (BRBF). Two calibration methods are compared in the case study. The first, highly relevant calibration method is based on stiffness and hardening characteristics of braces; the second, less relevant calibration method is based on the axial force response of braces. The highly relevant calibration method consistently identified the preferable parameter sets. In contrast, the less relevant calibration method showed poor to mediocre performance. The framework and methodology presented here are not limited to BRBF. They have the potential to facilitate and systematize the improvement of component-model calibration methods for any structural system. 相似文献
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A brief summary of Dr. G. V. Rao's research interests is presented. Many of his earlier studies were in conjunction with the
summer Monsoon Experiment of 1979 (MONEX-79). These included: 1) the structure of the Somali jet based on aerial observations;
2) sea-level air trajectories over the equatorial Indian Ocean; 3) structural features of the east African low-level flow;
4) effects of Indian Ocean surface temperature anomaly patterns on the summer monsoon circulations; 5) structures of the monsoon
low-level flow over the Arabian Sea; 6) characteristics and momentum-flux budgets of the Arabian Sea convective bands; and
7) evaporation and precipitation over the Arabian Sea during the monsoon seasons. Dr. Rao's research efforts in recent years
had focused on case studies of mesocyclones spawned by tropical cyclones (TCs) in Florida using Doppler radar data and a mesoscale
numerical model. These included: 1) research on tornadic mesocyclones spawned by TC Earl in 1998; 2) documentation of subtle
differences between tornadic and non-tornadic mesocyclones in TC Floyd in 1999; and 3) numerical simulation of the tornadic
environment observed in peninsular Florida during TC Earl in 1998. Preliminary findings show that the supercells' cold pools
interacted with an existing boundary resulting in increased baroclinicity and horizontal vorticity, and a maximization of
the tornado production potential by the updrafts. The model successfully simulated the mesoscale features of the mesocyclones
and the tornadic environment observed during TC Earl. A 24 h simulation of accumulated rainfall within the inner domain agreed
well with the observed precipitation pattern over the region. 相似文献
126.
David Tai-Wai Hui Karen Kit-Ying Shum Ji Chen Shyh-Chin Chen Jack Ritchie John O. Roads 《Natural Hazards》2007,42(1):193-207
Seasonal climate forecasts are one of the most promising tools for providing early warnings for natural hazards such as floods
and droughts. Using two case studies, this paper documents the skill of a regional climate model in the seasonal forecasting
of below normal rainfall in southern China during the rainy seasons of July–August–September 2003 and April–May–June 2004.
The regional model is based on the Regional Spectral Model of the National Centers for Environmental Prediction of the United
States. It is the first time that the model has been applied to a region dominated by the East Asian Monsoon.
The article shows that the regional climate model, when being forced by reasonably good forecasts from a global model, can
generate useful seasonal rainfall forecasts for the region, where it is dominated by the East Asia monsoon. The spatial details
of the dry conditions obtained from the regional climate model forecast are also found to be comparable with the observed
distribution. 相似文献
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This paper considers the ground trace of an artificial earth satellite. It determines the effects of the trace caused by perturbations due to atmospheric drag, the oblateness of the earth, and the moon and the sun as a third body.The necessary mathematical relations giving these perturbations which are available in literature are utilized (Betz, 1967; Brouwer and Clemence, 1961; Brouwer and Hori, 1961; Danby, 1962; Escobal, 1965; Kentet al., 1963; Kozai, 1962). Those relations unavailable elsewhere are derived.The computation was done by programming in FORTRAN language and utilizing an IBM 360/65.Captain, USAF 相似文献
129.
As a birefringent filter is tuned from the center of H to the continuum the H bright mottles appear to break up into a network of grains. The name filigree is suggested for this bright network. Its size, shape, contrast and time evolution is described as well as its relation to the abnormal granulation, magnetic field and spicules.On leave from The University of Hawaii. 相似文献
130.
Nodularia spumigena periodically proliferates to cause toxic algal blooms with some aquatic animals enduring and consuming high densities of the blue green algae or toxic lysis. N. spumigena contains toxic compounds such as nodularin and lipopolysaccharides. This current work investigates physiological effects of exposure from bloom conditions of N. spumigena cells and a post-bloom lysis. Biochemical and antioxidative biomarkers were comparatively studied over an acute 3-day exposure. In general, a post-bloom N. spumigena lysis caused opposite physiological responses to bloom densities of N. spumigena. Specifically, increases in glutathione (GSH) and glutathione peroxidase (GPx) and decreases in glutathione S-transferase (GST) were observed from the N. spumigena lysis. In contrast, N. spumigena cell densities decreased GSH and increased GST and lipid peroxidation (LPO) in mussels. Findings also suggest that at different stages of a toxic bloom, exposure may result in toxic stress to specific organs in the mussel. 相似文献