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11.
V. Badescu 《Meteorology and Atmospheric Physics》2001,78(3-4):195-204
Summary
Stationarity of daily averaged surface pressure time series on Mars can be obtained (by differencing) for short time intervals
only. Large pressure variance intervals are usually associated with the dust storm season. Medium and small pressure variance
intervals can be found usually during clear sky periods. General auto-regressive integrated moving average (ARIMA) models
were developed for daily average pressure forecasting at Viking Lander sites. A procedure to find the “appropriate” model
for a given time series was developed. It is based on various degrees of differencing the original time series and a t-statistics-assisted
estimation of the significance of the fitted coefficients. A method employing the cumulative spectrum of the residuals was
used to check the models. ARIMA (3,2,3) seems to be the most “appropriate” model to forecasting the daily average surface
pressure on Mars.
Received December 16, 1999/Revised October 17, 2000 相似文献
12.
Viorel Badescu 《Icarus》2011,216(2):485-491
Bodies with water, ammonia or ethane oceans are possible in interstellar space. This may happen for optically thick atmospheres of methane, ethane and carbon dioxide. 相似文献
13.
Hysteretic behaviour of reinforced concrete members is strongly dependent on local conditions such as quality of materials, workmanship, construction and design practice. Low strength concrete was found in most of the damaged concrete structures after the earthquakes that have hit Eastern Europe in the past 50 years. Quality of concrete had a great impact, especially on shear controlled reinforced concrete short columns. Existing models of the effective strength, stiffness and deformation capacity of structural members need to be confirmed locally by experimental research as the large data sets used to calibrate the analytical models comprise results obtained on specimens with various characteristics. In this study, effective stiffness and deformation models available in literature are compared with the results of an experimental testing program conducted by the authors to investigate the hysteretic response of reinforced concrete short columns with low concrete strength, designed and detailed according to the local practice in the past. The hysteretic behaviour of the specimens is presented together with a comparison of the experimental data with predicted values and conclusions on the suitability of the applied models are drawn. 相似文献
14.
Gary R. O'Brien Darrell S. Kaufman Warren D. Sharp Viorel Atudorei Roderic A. Parnell Laura J. Crossey 《Quaternary Research》2006,65(3):366-379
Holocene and modern travertine formed in spring-fed Havasu Creek of the Grand Canyon, Arizona, was studied to determine the factors governing its oxygen-isotope composition. Analysis of substrate-grown travertine indicates that calculated calcite-formation temperatures compare favorably with measured water temperatures, and include silt-rich laminae deposited by monsoon-driven floods. Ancient spring-pool travertine is dated by U-series at 7380 ± 110 yr and consists of 14 travertine-silt couplets of probable annual deposition. One hundred eighty high-resolution δ18O analyses of this mid-Holocene sample average −11.0‰ PDB. The average value for modern travertine is 0.5‰ lower, perhaps because mid-Holocene temperature was higher or there was proportionally greater summer recharge. δ18O cyclicity in the mid-Holocene travertine has average amplitude of 1.9 ± 0.5‰ PDB, slightly less than the inferred modern-day annual temperature range of Havasu Creek. The annual temperature range might have been reduced during the 14-yr interval compared to present, although other non-temperature factors could account for the muted annual variation. Silt-rich laminae within isotopically lower calcite in the modern and mid-Holocene travertine verifies the seasonal resolution of both samples, and suggests that similar temperature-precipitation conditions, as well as monsoon-generated summer floods, prevailed in the mid-Holocene as they do throughout the Grand Canyon region today. 相似文献
15.
Viorel Badescu Christian A. Gueymard Sorin Cheval Cristian Oprea Madalina Baciu Alexandru Dumitrescu Flavius Iacobescu Ioan Milos Costel Rada 《Theoretical and Applied Climatology》2013,111(3-4):379-399
Fifty-four broadband models for computation of solar diffuse irradiation on horizontal surface were tested in Romania (South-Eastern Europe). The input data consist of surface meteorological data, column integrated data, and data derived from satellite measurements. The testing procedure is performed in 21 stages intended to provide information about the sensitivity of the models to various sets of input data. There is no model to be ranked “the best” for all sets of input data. However, some of the models performed better than others, in the sense that they were ranked among the best for most of the testing stages. The best models for solar diffuse radiation computation are, on equal footing, ASHRAE 2005 model (ASHRAE 2005) and King model (King and Buckius, Solar Energy 22:297–301, 1979). The second best model is MAC model (Davies, Bound Layer Meteor 9:33–52, 1975). Details about the performance of each model in the 21 testing stages are found in the Electronic Supplementary Material. 相似文献
16.
Different models are used to evaluate the seashore effects of the tsunami generated by an asteroid impacting the shallow-water
plateau in the northwest basin of the Black Sea. The shortest distance between the impact location and the coast is about
185 km. The tsunami’s effects on the coastal regions depend on many factors among which the most important is asteroid size.
The tsunami generated by a 250-m asteroid reaches the nearest dry land location in 35 min and needs about 2 h to arrive all
over the Black Sea coast. The run-up value is about 2 m high on Turkish and Crimean coasts. In the western Black Sea regions,
the wave height is about 3 m. The run-up values strongly depend on bathymetry and topography peculiarities. The run-up values
in case of the tsunami generated by a 1,000-m-sized asteroid are up to five to six times larger than in case of the 250-m
impactor, depending on location. Differences between the tsunami’s dynamics on coastal regions situated in the proximity of
deep water and shallow water, respectively, are outlined. Aspects concerning accidental or deliberate nuclear explosions are
briefly referred. Possible social consequences and prevention are shortly discussed. 相似文献
17.
O. Vaduvescu M. Popescu I. Comsa A. Paraschiv D. Lacatus A. Sonka A. Tudorica M. Birlan O. Suciu F. Char M. Constantinescu T. Badescu M. Badea D. Vidican C. Opriseanu 《Astronomische Nachrichten》2013,334(7):718-728
The ESO/MPG WFI and the INT WFC wide field archives comprising 330 000 images were mined to search for serendip‐itous encounters of known Near Earth Asteroids (NEAs) and Potentially Hazardous Asteroids (PHAs). A total of 152 as‐teroids (44 PHAs and 108 other NEAs) were identified using the PRECOVERY software, their astrometry being measured on 761 images and sent to the Minor Planet Centre. Both recoveries and precoveries were reported, including prolonged orbital arcs for 18 precovered objects and 10 recoveries. We analyze all new opposition data by comparing the orbits fitted before and after including our contributions. We conclude the paper presenting “Mega‐Precovery”, a new online service focused on data mining of many instrument archives simultaneously for one or a few given asteroids. A total of 28 instrument archives have been made available for mining using this tool, adding together about 2.5 million images forming the “Mega‐Archive” 相似文献
18.
The hydrogen sulfide rich waters of the Black Sea pose a potential danger for the surrounding land regions. The impact of
an asteroid exceeding tens of meters in size may cause both a tsunami wave and a catastrophic poisonous gas release in the
atmosphere. Some effects of this last phenomenon on the Southern Black Sea coastal regions are evaluated in this paper. The
initial surface area of the poisonous cloud depends on asteroid size. The initial thickness of the cloud depends, in addition,
on sea depth at impact location. The wind speed plays an important role in H2S cloud dynamics. At 10 m/s wind speed, the cloud margins reach 185 km from the impact location in about 3 h. The maximum
distance traveled by the hydrogen sulfide cloud increases by increasing the asteroid size and wind speed. The influence of
the impact position on the distance traveled by hydrogen sulfide clouds is rather weak, as long as the seawater depth does
not change significantly. The land surface area covered by the H2S cloud generated by a 1,000 m size asteroid ranges between about 6,400 and 12,000 km2. This may affect up to 3,000,000 people. When a 250 m size asteroid is considered, the covered land surface area ranges between
about 1,400 and 2,100 km2 and up to 120,000 people may be affected. In case of a 70 m size asteroid, the cloud covers up to 280 km2 of land. This may affect up to about 70,000 people. These evaluations do not include the population of the towns on or near
the seashore. A simple methodology to estimate the environmental risks of the potential asteroid impact was proposed. Sites
less than 160 km from the impact place are at risk. 相似文献
19.
AbstractThe Northern part of Great-India underwent an early rifting phase in the late Paleozoic, just at the end of the large scale Gondwanian glaciation. The beginning of the rifting processes is marked by large hiatus and discontinuities (para- conformities) between the early or middle Paleozoic sedimentary succession and the discontinuous middle-late Permian Traps and transgressive sediments. The Northern Indian passive margin consists of the present High and Lower Himalaya and a small part of the Indian craton and their sedimentary cover. The Permian rift shoulder is located in the Higher Himalaya, with part being in the underthrusted Lower Himalaya. The rim basin (landward of the shoulder) is well developed in the Pottawar- Salt Range area. From the rifting to the beginning of the drifting stages (early late Permian to late early Triassic time), the sedimentary evolution is characterised by three transgressive- regressive (T-R) second order cycles, two in the late Permian and one in the early Triassic. The break-up of the rift occurred during the second cycle (late Dzhulfian).In the Salt Range area, these three T-R cycles have been subdivided in eight third order sequences, five sequences for the upper Permian and three for the lower Triassic.At the end of Permian, hiatuses, gaps and local erosion of part of the margin are direct consequences of a first order relative sea-level fall; this is also the time of the largest extinction event of the Phanerozoic that deeply affected the carbonate productivity and the stratal patterns. With the following worldwide sea-level rise, a rapid and large scale transgression occurred in the early Triassic, well dated and recorded on the whole margin. High rate thermal subsidence gave way to generalized pelagic deposits about 2 My after the transgression.Profiles of whole rock inorganic carbon and oxygen isotopes from Guryul Ravine and Palgham sections in Kashmir, Nammal Gorge and Landu sections in Trans Indus Ranges (Pakistan), Thini Chu section in Kali Gandaki Valley, Central Nepal are presented in connection with the sequence stratigraphic analysis. The upper Permian record of high positive δ13C values are closely correlated with the second order T-R cycles and the third order sequences. The results presented in this study confirm the drastic drop of δ13C from the high positive values that characterised the upper Permian to lower values in the lower Triassic time. Stratigraphic correlation problems in the lower Triassic using carbon isotope geochemistry are briefly discussed. A positive δ13C excursion of 4–5% near the Smithian - Spathian substages boundary is observed for the first time. The δ18O values of samples from all the sections display major variations suggesting that the oxygen isotope record has been significantly affected by meteoric diagenesis, deep burial diagenesis or/and monsoon signature. 相似文献
20.
Coastal changes at the Sulina mouth of the Danube River as a result of human activities 总被引：2，自引：0，他引：2
Sulina, the middle distributary of the Danube Delta, has been significantly changed by human activities over the past 150 yr. These include engineering works in the second half of the 19th century, when the channel was transformed for navigation and the construction of jetties which nowadays extend 8 km seawards. These interventions have strongly affected the natural processes of the Black Sea coast near the Sulina mouth. To the south of the Sulina mouth, the natural mild erosion has been reversed in the area close to the jetties where accretion is occurring, while southwards the greatest erosion rate along the entire Romanian coast, of more than 20 m/yr, has been recorded. Sediment accumulation in the northern part of the mouth is also huge and has brought to the creation and swift elongation of a sediment spit in several decades. Thus, the bay located here suffers from a rapid transformation into a lagoon. 相似文献