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151.
Initial versus tangent stiffness‐based Rayleigh damping in inelastic time history seismic analyses
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In the inelastic time history analyses of structures in seismic motion, part of the seismic energy that is imparted to the structure is absorbed by the inelastic structural model, and Rayleigh damping is commonly used in practice as an additional energy dissipation source. It has been acknowledged that Rayleigh damping models lack physical consistency and that, in turn, it must be carefully used to avoid encountering unintended consequences as the appearance of artificial damping. There are concerns raised by the mass proportional part of Rayleigh damping, but they are not considered in this paper. As far as the stiffness proportional part of Rayleigh damping is concerned, either the initial structural stiffness or the updated tangent stiffness can be used. The objective of this paper is to provide a comprehensive comparison of these two types of Rayleigh damping models so that a practitioner (i) can objectively choose the type of Rayleigh damping model that best fits her/his needs and (ii) is provided with useful analytical tools to design Rayleigh damping model with good control on the damping ratios throughout inelastic analysis. To that end, a review of the literature dedicated to Rayleigh damping within these last two decades is first presented; then, practical tools to control the modal damping ratios throughout the time history analysis are developed; a simple example is finally used to illustrate the differences resulting from the use of either initial or tangent stiffness‐based Rayleigh damping model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
152.
Firat Aydin Abdurrahman Saydut Beniz Gunduz Isil Aydin Candan Hamamci 《洁净——土壤、空气、水》2012,40(4):444-448
Chemical speciation of vanadium is important to understand the true nature of this element in the environment as well as its biochemical pathways. Sample pretreatment, preparation, and chemical speciation methods were applied for vanadium in coal bottom ash here. Two‐stage microwave acid digestion was used to preparation of samples. Determination of vanadium was performed using inductively coupled plasma‐optical emission spectrometry (ICP‐OES). Speciation of vanadium was carried out using a seven‐step sequential extraction procedure of the coal bottom ash each releasing species of vanadium: Water soluble, exchangeable, carbonate, reducible, oxidizable, sulfide, and residual fractions. Total vanadium concentration in the coal bottom ash is 701 mg kg?1 d.w. The most abundant form of vanadium in coal bottom ash is residual fraction of vanadium (196 mg kg?1 d.w.). Relative abundances of the remaining vanadium fractions in coal bottom ash are as follows: Reducible (176 mg kg?1 d.w.) > sulfide (176 mg kg?1 d.w.) > carbonate (85 mg kg?1 d.w.) > oxidizable (50 mg kg?1 d.w.) > water soluble (10.6 mg kg?1 d.w.) > exchangeable (9.0 mg kg?1 d.w.). 相似文献
153.
A precise gravimetric geoid model in a mountainous area with scarce gravity data: a case study in central Turkey 总被引:1,自引:0,他引:1
Ramazan A. Abbak Lars E. Sj?berg Artu Ellmann Aydin Ustun 《Studia Geophysica et Geodaetica》2012,56(4):909-927
In mountainous regions with scarce gravity data, gravimetric geoid determination is a difficult task that needs special attention to obtain reliable results satisfying the demands, e.g., of engineering applications. The present study investigates a procedure for combining a suitable global geopotential model and available terrestrial data in order to obtain a precise regional geoid model for Konya Closed Basin (KCB). The KCB is located in the central part of Turkey, where a very limited amount of terrestrial gravity data is available. Various data sources, such as the Turkish digital elevation model with 3 ?? × 3?? resolution, a recently published satellite-only global geopotential model from the Gravity Recovery and Climate Experiment satellite (GRACE) and the ground gravity observations, are combined in the least-squares sense by the modified Stokes?? formula. The new gravimetric geoid model is compared with Global Positioning System (GPS)/levelling at the control points, resulting in the Root Mean Square Error (RMS) differences of ±6.4 cm and 1.7 ppm in the absolute and relative senses, respectively. This regional geoid model appears to be more accurate than the Earth Gravitational Model 2008, which is the best global model over the target area, with the RMS differences of ±8.6 cm and 1.8 ppm in the absolute and relative senses, respectively. These results show that the accuracy of a regional gravimetric model can be augmented by the combination of a global geopotential model and local terrestrial data in mountainous areas even though the quality and resolution of the primary terrestrial data are not satisfactory to the geoid modelling procedure. 相似文献
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Ground vibrations induced by blasting are one of the fundamental problems in the mining industry and may cause severe damage to structures and plants nearby. Therefore, a vibration control study plays an important role in the minimization of environmental effects of blasting in mines. This paper presents the results of ground vibration measurement induced by bench blasting at Magnesite Incorporated Company (MAS) open pit mine in Turkey. The scope of this study is to predict peak particle velocity and to determine the slope of the attenuation curve for this site. For this purpose, the blasting parameters of 43 shots were carefully recorded and the ground vibration components were measured for each event. After carrying out statistical analysis, the site specific parameters were determined to predict the peak particle velocity. In the light of this analysis, the prediction graphics of maximum charge weight per delay versus distance for different damage criteria was proposed to be able to perform controlled blasting in order not to damage to the nearby structures, especially to the plant where rotary and shaft kilns have been established. 相似文献
157.
Glibert PM Azanza R Burford M Furuya K Abal E Al-Azri A Al-Yamani F Andersen P Anderson DM Beardall J Berg GM Brand L Bronk D Brookes J Burkholder JM Cembella A Cochlan WP Collier JL Collos Y Diaz R Doblin M Drennen T Dyhrman S Fukuyo Y Furnas M Galloway J Granéli E Ha DV Hallegraeff G Harrison J Harrison PJ Heil CA Heimann K Howarth R Jauzein C Kana AA Kana TM Kim H Kudela R Legrand C Mallin M Mulholland M Murray S O'Neil J Pitcher G Qi Y Rabalais N Raine R Seitzinger S Salomon PS Solomon C 《Marine pollution bulletin》2008,56(6):1049-1056
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. 相似文献
158.
Marlon E. Pierce Geoffrey C. Fox Mehmet S. Aktas Galip Aydin Harshawardhan Gadgil Zhigang Qi Ahmet Sayar 《Pure and Applied Geophysics》2008,165(3-4):635-651
We describe our distributed systems research efforts to build the “cyberinfrastructure” components that constitute a geophysical Grid, or more accurately, a Grid of Grids. Service-oriented computing principles are used to build a distributed infrastructure of Web accessible components for accessing data and scientific applications. Our data services fall into two major categories: Archival, database-backed services based around Geographical Information System (GIS) standards from the Open Geospatial Consortium, and streaming services that can be used to filter and route real-time data sources such as Global Positioning System data streams. Execution support services include application execution management services and services for transferring remote files. These data and execution service families are bound together through metadata information and workflow services for service orchestration. Users may access the system through the QuakeSim scientific Web portal, which is built using a portlet component approach. 相似文献
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160.
Investigation of radio astronomical windows between 1 MHz and 2060 MHz in Universiti Malaya,Malaysia
Zamri Zainal Abidin Zainol Abidin Ibrahim Syed Bahari Ramadzan Syed Adnan Norwati Khairul Anuar 《New Astronomy》2009,14(6):579-583
An indoor and an outdoor radio frequency survey was conducted in Universiti Malaya, Malaysia, as a test site, for the purpose of developing radio astronomy research in Malaysia. This is the first radio astronomical survey of any such done in Malaysia. Observation and analysis were done in the radio frequency spectrum between 1 MHz and 2060 MHz. In this paper, the experimental setup and procedure of surveying are outlined and the measured data are interpreted. The eight radio astronomical windows were investigated from a 24 h observation, with the emphasis on two of the most important radio astronomical windows which are protected by the Malaysian Communications and Multimedia Commission (MCMC). Some intermittent observations were also done for referencing purposes. The radio frequency interferences (RFIs) are found to be relatively low. The overall relative Interference-to-Noise ratio (INR) at this test site ranges between 5.72% and 11.74%. The average strength of RFI in the eight focused radio astronomical windows at this site ranges between ?100 dBm and ?90 dBm (equivalently between 9.23 × 104 Jy and 93.29 × 104 Jy at resolution bandwidth of 125 kHz). 相似文献