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121.
Harford AJ Hogan AC Tsang JJ Parry DL Negri AP Adams MS Stauber JL van Dam RA 《Marine pollution bulletin》2011,62(3):466-473
Ecotoxicological studies, using the tropical marine diatom, Nitzschia closterium (72-h growth rate), were undertaken to assess potential issues relating to the discharge from an alumina refinery in northern Australia. The studies assessed: (i) the species’ upper thermal tolerance; (ii) the effects of three signature metals, aluminium (Al), vanadium (V) and gallium (Ga) (at 32 °C); and (iii) the effects of wastewater (at 27 and 32 °C). The critical thermal maximum and median inhibition temperature for N. closterium were 32.7 °C and 33.1 °C, respectively. Single metal toxicity tests found that N. closterium was more sensitive to Al compared to Ga and V, with IC50s (95% confidence limits) of 190 (140-280), 19,640 (11,600-25,200) and 42,000 (32,770-56,000) μg L−1, respectively. The undiluted wastewater samples were of low toxicity to N. closterium (IC50s > 100% wastewater). Environmental chemistry data suggested that the key metals and discharge are a very low risk to this species. 相似文献
122.
Maria Teresa Giugliano Alessandra Longo Rosario Montuori Vincenzo Piluso 《地震工程与结构动力学》2011,40(13):1455-1474
Structural engineering problems are always affected by many sources of uncertainty, such as aleatory of material properties, applied loads and earthquake intensity, therefore, seismic assessment of structures should be based on probabilistic methods. Since PBSD (Performance‐based Seismic Design) philosophy was formulated, many researches have been conducted in this field in order to develop simple and accurate procedures for evaluating structural reliability. An important contribution has been provided by Jalayer and Cornell, who have developed a closed‐form expression to evaluate the mean annual frequency of exceeding a defined limit state. In this paper, by assuming the record‐to‐record variability as the only source of uncertainty, the seismic reliability of concentrically braced frames designed according to traditional and innovative methodologies is investigated, and a comparison between their performances is presented. In particular, two design methodologies have been applied: Eurocode 8 provisions and a new design methodology based on a rigorous application of ‘capacity design’ criteria. The innovative reduced section solution strategy, based on the reduction of cross sections at bracing member ends, has also been analysed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
123.
Paolo Boccotti Felice Arena Vincenzo Fiamma Alessandra Romolo Giuseppe Barbaro 《Ocean Engineering》2011,38(2-3):509-518
A method for obtaining the directional spectrum, on assuming that the frequencies of the elementary waves are all different from one another, is re-proposed in a form suitable for applications to sea states near a coast. The method is applied to an interval of 10 h during which the sea state remained basically steady state off the beach at Reggio Calabria (east coast of the Straits of Messina). It is shown that the directional spectrum converges as the length of the time series data grows. A numerical simulation of a 10 h sea state confirms that the directional spectrum converges as the length of the time series grows, and the convergence is onto the known directional spectrum used to make the numerical simulation. Through the numerical simulation, it is proved that the method, generally, is suitable for applications even with short time series of wind waves (duration of about 100Tp). Finally, it is shown that the method is not necessarily inadequate even with short records of multimodal sea states with different modal directions, modal amplitude ratios and intermodal distances. 相似文献
124.
We studied the stability of the restricted circular three-body problem. We introduced a model Hamiltonian in action-angle Delaunay variables. which is nearly-integrable with the perturbing parameter representing the mass ratio of the primaries. We performed a normal form reduction to remove the perturbation in the initial Hamiltonian to higher orders in the perturbing parameter. Next we applied a result on the Nekhoroshev theorem proved by Pöschel [13] to obtain the confinement in phase space of the action variables (related to the elliptic elements of the minor body) for an exponentially long time. As a concrete application. we selected the Sun-Ceres-Jupiter case, obtaining (after the proper normal form reduction) a stability result for a time comparable to the age of the solar system (i.e., 4.9 · 109 years) and for a mass ratio of the primaries less or equal than 10–6. 相似文献
125.
Hron Karel Menafoglio Alessandra Palarea-Albaladejo Javier Filzmoser Peter Talská Renáta Egozcue Juan José 《Mathematical Geosciences》2022,54(1):71-93
Mathematical Geosciences - It often occurs in practice that it is sensible to give different weights to the variables involved in a multivariate data analysis—and the same holds for... 相似文献
126.
Arianna?Secchiari Alessandra?MontaniniEmail author Delphine?Bosch Patrizia?Macera Dominique?Cluzel 《Contributions to Mineralogy and Petrology》2018,173(8):66
The New Caledonia ophiolite hosts one of the rare examples of crust-mantle sections built in a nascent arc environment, providing the unique opportunity to investigate the first stages of arc magmatism in a subduction setting. The sequence consists of refractory harzburgites, overlain by ultramafic (dunites and wehrlites) and mafic lithologies (gabbronorites). The gabbronorites occur in the upper part of the sequence as decimetre to metre-size sills. They are mainly formed (??55 to 70 vol%) of Ca-rich plagioclase (An up to 96 mol%) and high Mg# (88–92), Al2O3-poor (1.5–2.4 wt%) clinopyroxene (8–20 vol%), often rimmed by interstitial or poikilitic orthopyroxene (6–27 vol%). Mg-rich olivine (3–15 vol%, Fo?=?87–89 mol%) occurs as anhedral, resorbed crystals. Whole rock (WR) compositions exhibit high Mg# (86–92) and strikingly low trace element contents. They own LREE-depleted patterns, with nearly flat (0.82?≤?DyN/YbN?≤?1.00) and low HREE (YbN?=?0.2–0.9) and positive Eu anomalies. Clinopyroxene trace element chemistry mirrors the extreme depletion of the WR. By contrast, FME enrichments are observed for WR and clinopyroxene. Geochemical models show that the gabbronorites crystallized from primitive, ultra-depleted melts bearing evidence of fluid contamination processes, but with significantly different geochemical signatures compared to boninitic rocks worldwide, i.e. lower LREE-MREE, and absence of Nb depletion and Zr–Hf enrichments. Nd isotopes (+?8.2?≤?εNdi?≤?+?13.1), together with radiogenic Pb isotopic ratios, support an origin from a DMM source variably modified by slab fluids. We propose that the geochemical signature of the New Caledonia gabbronorites reflect emplacement of primitive, non-aggregated, magma batches in the lower fore-arc crust, during the first phases of arc formation. 相似文献
127.
Juan Pablo de Rosas Alexander Dario Esquivel Diego Martinez Heimann Agustin E. Negri Flavia Lohaiza Diego Leonardo Valladares Alejandro I. Zavala Hugo Huck Jimena Juri Ayub 《Environmental Earth Sciences》2018,77(16):587
This work presents the results of a soil erosion study using the 7Be technique. This technique estimates the water erosion/deposition from the comparison between 7Be soil content of a reference site and an eroded or sedimented site. The soil samples were collected from an agricultural area of the semiarid region of Argentina near San Luis City, which has a marked rainfall season. The area has been used for crop cultivation, being subjected to plowing practices. The 7Be in the Reference Site was in the first centimeter of soil, showing the typical exponential decreasing of 7Be soil content with depth, with the 7Be inventories value being 340?±?50 Bq m?2 for the dry season and 571?±?48 Bq m?2 for the rainy season. The 7Be technique was applied to a potential eroded site subjected to traditional tillage practices (plowing). A net soil erosion value of 13.5 t ha?1 (1.35 kg m?2) was obtained. From the assumptions of the applied technique, we can draw the inference that this erosion was caused by rains produced in the month prior to the date of soil sampling. 相似文献
128.
Alessandra Celletti Gabriella Pinzari 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):327-344
In the framework of the orbital determination methods, we study some properties related to the algorithms developed by Gauss, Laplace and Mossotti. In particular, we investigate the dependence of such methods upon the size of the intervals between successive observations, encompassing also the case of two nearby observations performed within the same night. Moreover we study the convergence of Gauss algorithm by computing the maximal eigenvalue of the jacobian matrix associated to the Gauss map. Applications to asteroids and Kuiper belt objects are considered. 相似文献
129.
130.
M. Ciccotti N. Negri L. Sassi G. Gonzato F. Mulargia 《Journal of Volcanology and Geothermal Research》2000,98(1-4)
The results of a series of experiments aimed at characterizing the elastic and failure parameters of lava specimens from Mount Etna, Vulcano and Stromboli volcanos is presented. The double torsion—constant configuration—load relaxation method has been employed to obtain the behavior of the stress intensity factor versus mode I subcritical crack velocity. The experimental technique has been optimized in several respects. First, a very stiff machine, expressly designed and built, has been used. Second, all samples have been carefully machined to low tolerance. Third, the experimental conditions have been carefully controlled, with temperature variations within 1°C and humidity within 10%. Fourth, high resolution electronic measuring systems have been used together with a pulse stacking procedure. Fifth, the length of the prefracture has been optically checked. This optimization allowed us to measure the slope of the subcritical fracture propagation curve in the III region, which extends from velocities of 10−7 m/s to catastrophic, with a standard deviation around 20%, suggesting that the results can be effectively used for modeling purposes. As a by-product, we could measure the elastic parameters with an accuracy of a few percent. 相似文献