Contribution to the investigation of small intermediate-depth earthquakes in the Vrancea region     

Cornelius Radu  Vladimír Tobyáš 《Studia Geophysica et Geodaetica》1968,12(4):402-406

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Comparative study of statistical methods to identify a predictor for discharge at Orsova in the Lower Danube Basin     

Ileana Mares  Constantin Mares  Venera Dobrica  Crisan Demetrescu 《水文科学杂志》2020,65(3):371-386

ABSTRACT

The aims of this study are to investigate the influence of large-scale atmospheric circulation quantified by indices such as the North Atlantic Oscillation index (NAOI), the Greenland-Balkan Oscillation index (GBOI) and blocking-type indices on the Lower Danube discharge. We separately analysed each season for the 1948–2000 period. In addition to the statistical linear procedure, we applied methods to quantify nonlinear connections between variables, as mutual information between predictors and predictand, using Shannon’s information entropy theory. The nonlinear correlation information between climate indices and discharge is higher than that obtained from the linear measure, providing more insight into real connections. Also, the non-stationarity of the link between variables is highlighted by spectral coherence based on wavelet analysis. For the physical interpretation, we analyse composite maps over the Atlantic-European region. The most significant influence on the discharge of the Lower Danube Basin is given by the GBOI and blocking-type atmospheric circulation over Europe.  相似文献   

Use of carbon rather than dry weight to assess the DNA content and nutritional condition index of sole larvae   总被引：1，自引：1，他引：1  

Bergeron  Jean-Pierre; Ruyet  Jeannine Person-Le; Koutsikopoulos  Constantin 《ICES Journal of Marine Science》1997,54(1):148-151

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Analysis of liquefaction susceptibility of nearly saturated sands     

Ahmad Jafari‐Mehrabadi  Majid Abedinzadegan Abdi  Radu Popescu 《国际地质力学数值与分析法杂志》2007,31(5):691-714

A new constitutive formulation for simulating the behaviour of nearly saturated sands under seismic loads is presented. The formulation is based on combining the Henry's law for dissolution of gas in water, the ideal or perfect gas law and the law of conservation of mass. The effects of transient air dissolution in water on the compressibility of partially saturated soils are also taken into account. The model was calibrated based on numerical simulations of isotropically consolidated cyclic triaxial tests conducted on partially saturated samples of Toyoura sand. A multi‐yield plasticity soil constitutive model implemented in the finite element code DYNAFLOW was used for these numerical simulations. It is shown that the formulation proposed here is able to reasonably predict the soil cyclic undrained behaviour at various degrees of saturation (95% and higher). Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Trace Element Data for Gold, Iridium and Silver in Seventy Geochemical Reference Materials     

Marc Constantin 《Geostandards and Geoanalytical Research》2009,33(1):115-132

New concentrations for Au, Ir and Ag obtained by instrumental neutron activation analysis are presented for seventy geochemical reference materials. Results in agreement with literature values for Au and Ir down to concentrations of a few ng g⁻¹ were obtained. For Au and Ir concentrations above 10 ng g⁻¹, the repeatability of replicate analyses of reference materials was mostly better than 10%. For concentrations between 1 and 10 ng g⁻¹ the RSD for Ir was 10–30%, whereas for Au it was higher and more variable (20–50%). In addition, concentrations for Cd and Hg are presented for some of the same reference materials. The high RSD at relatively high concentrations seen in gold for some RMs (e.g., WMG-1, WMS-1) did not exist for Ir and suggests homogeneity for this platinum-group element at the sub-sample size used in this study. For the following eight RMs, mostly ultramafic rocks (CHR-Pt+, OREAS-13P, OREAS-14P, PCC-1, UMT-1, WMG-1, WMS-1, WPR-1), Ir measurements agreed within ± 10% of mostly certified or recommended concentrations, which ranged from 2 ng g⁻¹ to 6 μg g⁻¹. For the reference material UB-N, iridium concentration compared favourably to published results obtained by isotope dilution ICP-MS methods and a previously unrecognised heterogeneity is inferred for Au, Hg and Sb, but not for the other measured elements.  相似文献   

Reinforced concrete beam–column joints with crossed inclined bars under cyclic deformations     

Constantin E. Chalioris  Maria J. Favvata  Chris G. Karayannis 《地震工程与结构动力学》2008,37(6):881-897

This experimental study investigates the effectiveness of crossed inclined bars (X‐bars) as joint shear reinforcement in exterior reinforced concrete beam–column connections under cyclic deformations. Test results of 20 joint subassemblages with various reinforcement ratios and arrangements including X‐bars in the joint area are presented. The X‐type, non‐conventional reinforcement is examined as the only joint reinforcement and in combination with common stirrups or vertical bars. The experimental results reported herein include full loading cycle curves, energy dissipation values and a categorization of the observed damage modes. Based on the comparisons between the overall hysteretic responses of the tested specimens, it is deduced that joints with X‐bars exhibited enhanced cyclic performance and improved damage mode since a distinct flexural hinge was developed in the beam–joint interface. Further, the combination of crossed inclined bars and stirrups in joint area resulted in enhanced hysteretic response and excellent performance capabilities of the specimens. However, in some specimens with X‐bars as the only joint shear reinforcement, the deformations of the bent anchorage of the beam's bars caused considerable damages at the back of the joint area. Discussion for a potential replacement of the joint stirrups with X‐type reinforcement in some cases of exterior joints is also included. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Seismic design procedure and seismic response of post‐tensioned self‐centering steel frames     

Hyung‐Joon Kim  Constantin Christopoulos 《地震工程与结构动力学》2009,38(3):355-376

Post‐tensioned (PT) self‐centering moment‐resisting frames (MRFs) have recently been developed as an alternative to welded moment frames. The first generation of these systems incorporated yielding energy dissipation mechanisms, whereas more recently, PT self‐centering friction damped (SCFR) moment‐resistant connections have been proposed and experimentally validated. Although all of these systems exhibited good stiffness, strength and ductility properties and stable dissipation of energy under cyclic loading, questions concerning their ultimate response still remained and a complete design methodology to allow engineers to conceive structures using these systems was also needed. In this paper, the mechanics of SCFR frames are first described and a comprehensive design procedure that accounts for the frame behavior and the nonlinear dynamics of self‐centering frames is then elaborated. A strategy for the response of these systems at ultimate deformation stages is then proposed and detailing requirements on the beams in order to achieve this response are outlined. The proposed procedure aims to achieve designs where the interstory drifts for SCFR frames are similar to those of special steel welded moment‐resisting frames (WMRFs). Furthermore, this procedure is adapted from current seismic design practices and can be extended to any other PT self‐centering steel frame system. A six‐story building incorporating WMRFs was designed and a similar building incorporating SCFR frames were re‐designed by the proposed seismic design procedure. Time‐history analyses showed that the maximum interstory drifts and maximum floor accelerations of the SCFR frame were similar to those of the WMRF but that almost zero residual drifts were observed for the SCFR frame. The results obtained from the analyses confirmed the validity of the proposed seismic design procedure, since the peak drift values were similar to those prescribed by the seismic design codes and the SCFR frames achieved the intended performance level under both design and maximum considerable levels of seismic loading. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Seismic response of a case study soft story frame retrofitted using a GIB system          下载免费PDF全文

Hossein Agha Beigi  Constantin Christopoulos  Timothy Sullivan  Michele Calvi 《地震工程与结构动力学》2015,44(7):997-1014

This paper presents results from a numerical investigation into the seismic retrofit of a soft story frame using a novel gapped‐inclined brace (GIB) system. The GIB system consists of a pinned brace and a gap element that is added to the first story columns of the frame. The inclusion of GIB elements in addition to increasing the lateral capacity of columns at the first story increases the post‐yield stiffness ratio of the system and reduces the P‐delta effects on the columns, while not increasing the first story lateral resistance or stiffness. This allows for the isolating benefits of the soft story to protect the upper floors of the structure from damage while avoiding excessive deformations and reducing the propensity for collapse. A six‐story RC frame with masonry infills on all floors except for the first floor is studied. The dynamic response of the retrofitted building using the GIB system is investigated numerically and is compared with the response of the original un‐retrofitted building and the same building in which masonry infills are added to the first story to mitigate the soft story response. Results from the nonlinear time‐history analyses indicate that the GIB system could provide a reliable seismic retrofit mechanism for soft story buildings, which greatly reduces the likelihood of collapse by increasing the displacement capacity of the soft storey and by reducing P‐delta effects, while minimizing the overall damage and losses in the building by taking advantages of the isolation that is provided by the soft story to the rest of the structure located above. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Physicochemical Characterization and Use of Heat Pretreated Commercial Instant Dry Baker's Yeast as a Potential Biosorbent for Cu(II) Removal          下载免费PDF全文

Ana‐Maria Stanescu  Ligia Stoica  Carolina Constantin  Ioana Lacatusu  Ovidiu Oprea  Florin Miculescu 《洁净——土壤、空气、水》2014,42(11):1632-1641

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Measurement of radon potential from soil using a special method of sampling     

Constantin Cosma  Botond Papp  Mircea Moldovan  Victor Cosma  Ciprian Cindea  Liviu Suciu  Adelina Apostu 《Acta Geophysica》2010,58(5):947-956

Soil radon gas and/or its exhalation rate are used as indicators for some applications, such as uranium exploration, indoor radon concentration, seismic activity, location of subsurface faults, etc., and also in the studies where the main interest is the field verification of radon transport models. This work proposes a versatile method for the soil radon sampling using a special manner of pumping. The soil gas is passed through a column of charcoal by using passive pumping. A plastic bottle filled with water is coupled to an activated charcoal column and the flow of water through an adjustable hole made at the bottom of bottle assures a controlled gas flow from the soil. The results obtained for the activity of activated charcoal are in the range of 20–40 kBq/m³, for a depth of approximately 0.8 m. The results obtained by this method were confirmed by simultaneous measurements using LUK 3C device for soil radon measurements. Possible applications for the estimation of radon soil potential are discussed.  相似文献