Bayesian image reconstruction in astronomy     

Jorge Núñez  Jorge Llacer 《Astrophysics and Space Science》1990,171(1-2):341-349

This paper presents the development and testing of a new iterative reconstruction algorithm for astronomy. We propose a maximuma posteriori method of image reconstruction in the Bayesian statistical framework for the Poisson noise case. The method uses the entropy with an adjustable sharpness parameter to define the prior probability and the likelihood with data increment parameters to define the conditional probability. The method allows us to obtain reconstructions with neither the problem of the grey reconstructions associated with the pure Bayesian reconstructions nor the problem of image deterioration, typical of the maximum likelihood method. Our iterative algorithm is fast, stable, maintains positivity, and converges to feasible images.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

Geologic evolution of the Canarian Islands of Lanzarote,Fuerteventura, Gran Canaria and La Gomera and comparison of landslides at these islands with those at Tenerife,La Palma and El Hierro     

J. Acosta  E. Uchupi  A. Muñoz  P. Herranz  C. Palomo  M. Ballesteros  ZEE Working Group 《Marine Geophysical Researches》2005,26(1):77-82

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Did the East Pacific rise subduct beneath the North America plate (western Mexico)?     

F. Michaud  J. Dañobeitia  R. Bartolomé  R. Carbonell  L. Delgado Argote  D. Cordoba  T. Monfret 《Geo-Marine Letters》2001,20(3):168-173

New data collected between the northernmost tip of the East Pacific rise (18°05'N, 105°35'W) and the Middle America trench provide evidence that the seafloor, which lacks significant sedimentary cover, has a typical spreading-derived abyssal hill topography. The tectonic fabric of this seafloor is concave to the west, as it is today at the tip of the East Pacific rise. Farther to the east, at the outer wall of the trench, the seafloor topography exhibits a north-south trending fabric. We suggest that this fabric originated along the East Pacific rise, as it reached the trench and possibly subducted beneath the North America plate prior to the development of the complex connection of the East Pacific rise with the Rivera transform.  相似文献   

构造沉降对近代洞庭湖区演变的贡献——答李春初先生对《洞庭湖地质环境系统分析》的质疑   总被引：15，自引：0，他引：15  

梁杏  张人权  皮建高  张国梁 《海洋与湖沼》2001,32(6):690-696

为回应对《洞庭湖地质环境系统分析》系列研究成果提出的质疑,在理论分析、宏观时空分析以及大量举证的基础上,论证了构造沉降对近代洞庭湖演变起着主导作用。作者利用地形图比对求算的洞庭湖堤围区视构造沉降速率,不仅与重复水准测量成果一致,还得到有关中国大陆第四纪以来构造活动加剧的研究成果的定性支持。作者在研究中应用的“假设－演绎法”是一种富有创造性的科学方法。因此,《洞庭湖地质环境系统分析》的基本结论是成立的。  相似文献   

Mobility of heavy metals from coal fly ash   总被引：7，自引：0，他引：7  

J. L. Fernández-Turiel  W. de Carvalho  M. Cabañas  X. Querol  A. López-Soler 《Environmental Geology》1994,23(4):264-270

The mobility of Cd, Co, Cu, Ni, Pb, Sb, and Zn from six different coal-fired power plant fly ashes that show a wide compositional range was examined using a sequential extraction procedure in order to assess their mobility when these wastes are ponded or landfilled. The extraction sequence was as follows: (1) water extractable, (2) cation exchangeable (CH₃COONH₄ at pH 7), (3) surface oxide-bound cations (CH₃COONH₄ at pH 5), (4) Fe oxide-bound cations (HONH₃Cl), and (5) residual (HF, HCl, HNO₃, 211). The heavy metal contents in the extraction solutions were determined by anodic (Cd, Cu, Pb, Sb, and Zn) and cathodic (Ni and Co) stripping voltammetry. The results reveal differences in the total contents of the selected trace elements among the fly ash samples, which must be related to differences in coal composition and combustion technology. The extractable fraction under natural conditions ranges from 1.5 to 36.4 percent of the total element content. Cadmium, Co, Cu, and Zn show the highest extractable fraction (10.8–18.9 percent on average). Cadmium is the most easily water-extractable element, while Co, Cu, and Zn increase their mobility as the severity of the extraction increases. Cobalt, Ni, Pb, and Zn are mainly associated with the surface oxide-bound and Fe oxide-bound fractions. Nickel, Pb, and Sb have low mobility potentials (5.3–6.6 percent as extractable fraction), but Sb presents a relatively high water-extractable fraction.  相似文献   

10 and 20 Micron imaging with arrays     

B. Jones  R. K. Piña  R. C. Puetter 《Experimental Astronomy》1994,3(1-4):37-44

We discuss imaging with arrays in the thermal IR. Aspects of the design and performance of the Golden Gopher, an infrared array camera are presented. This instrument operates in a high-background environment, for ground-based astronomical imaging from 5 to 27 m. It is built around a 20×64 element Si:As Impurity Band Conduction (IBC) device manufactured by GenCorp Aerojet Electronic Systems Division, and has a noise-equivalent flux density (NEFD) of 23.5mJy min ^-1/2 arcsec^-2 at =10m, =1m, on the Mt. Lemmon 1.5m telescope. We present and discuss a sample of the data. In addition we discuss the design and expected performance of the Long Wavelength Spectrometer which is now under construction for the Keck telescope.  相似文献   

On the Thermochemical Instability of an Ionized Plasma Cooled by Oxygen Forbidden Lines     

M.C. Bessega  M.H. Ibáñez S 《Astrophysics and Space Science》1997,256(1-2):365-368

The thermal stability of an ionized hydrogen plasma in which the reaction OIII + (h) OIV + e^- proceeds is analyzed. The gas is assumed to be heated by a diluted stellar radiation of effective temperature T_*. The stability analysis is carried out taking into account the chemical relaxation time effects from which a fifth order dispersion relation is obtained instead the fourth order polynomial obtained when such effects are neglected. The effects of the thermal conduction are also considered.  相似文献   

Correlation Between the Population of Active Species in Low Pressure Plasmas and Their Reactions with Organic Compounds     

Pedro Patiño 《Astrophysics and Space Science》1997,256(1-2):523-527

The oxidation of four alkanes, two olefins and twelve aromatic compounds in the liquid phase with either high voltage or radio frequency glow discharges has been studied. The results of the liquid-plasma interactions of this work considerably differ from those in homogeneous gas phase. Neither fragmentation products in the traps nor polymers on the reactor walls have been detected. The selectivity of product formation is far superior to plasma oxidations in gas phase, making these techniques attractive for preparative chemistry. Total conversion, i.e., mass transformed against initial mass of substrate, has been studied as a function of the temperature of the liquid and the oxygen flow rate in the reactor. Optical emission spectroscopy has been utilized to detect and monitor the active species in the plasma. At the conditions for maximum oxidation no evidence of O₂(¹_g) has been observed. A correlation between the behavior of the O(³P) population in the discharge and the reactivity of the different compounds, as a function of the oxygen flow rate in the reactor, is presented.  相似文献   

Water lily (<Emphasis Type="Italic">Nymphaea</Emphasis> sp.): an alternative organic amendment for treatment of hydrocarbon-contaminated soil by chemical–biological stabilization     

V. I. Domínguez-Rodríguez  R. H. Adams-Schroeder  J. A. Goñi-Arévalo  I. López-Vidal 《International Journal of Environmental Science and Technology》2018,15(9):1851-1858

The chemical–biological stabilization technology has been employed in several successful studies using sugarcane cachasse as the organic amendment. However, in some petroleum-producing areas, there are no sugar mills nearby (which is the source of this material), and the cost of transport to the contaminated site is prohibitive. Therefore, water lily, which is considered a weedy plant in many tropical and subtropical areas, was evaluated as an alternative. In 3-month experiment, water lily was compared (with and without addition of molasses) with cachasse for the treatment of clayey sediment contaminated with > 6% extra-heavy crude oil. All treatments resulted in a reduction in the hydrocarbon concentration of 15–23%, without significant differences (P > 0.05). During this process, the pH was reduced to the 7–7.5 range and water repellency (molarity ethanol drop) to 3.5–3.6 M. Also, field capacity increased to 36.3–38.5% humidity, establishing adequate conditions for the development of vegetation at this site. Likewise, toxicity was reduced to practically null (Vibrio fischeri bioassay), and hydrocarbons in leachates were reduced to 3.4–4.3 mg/l, conditions adequate for the protection of groundwater and human health in rural areas. This study confirms that water lily is an adequate substitute for the application of this treatment method for hydrocarbon-contaminated sites that are far from sugar production areas.  相似文献   

Spatial and temporal variation of natural recharge in the semi-arid valley of Aguascalientes,Mexico     

Martín Hernández-Marín  Lilia Guerrero-Martínez  Alfredo Zermeño-Villalobos  Lorena Rodríguez-González  Thomas J. Burbey  Jesús Pacheco-Martínez  Sergio I. Martínez-Martínez  Norma González-Cervantes 《Hydrogeology Journal》2018,26(8):2811-2826

The investigation involves a temporal and spatial analysis to characterize recharge in the Aguascalientes valley in central Mexico. The results are based on a two-part methodological strategy using a geospatial and numerical analysis. Results from the geospatial analysis are based on the analytical hierarchical process (AHP) method, which involves developing a zoning map that qualifies the conditions for groundwater recharge in the valley. In addition, one-dimensional numerical modeling based on the van Genuchten equation was applied for various soil column configurations to estimate the transit time of recharge through the vadose zone. The analysis was performed over a 20-year period from 1995 to 2015. The results of the geospatial analysis indicate that the optimal area for groundwater recharge is the lower zone of the valley, particularly the portion influenced by surface discontinuities. The shortest estimated period of recharge for water to pass through the vadose zone is approximately 4.25 years.  相似文献