Ground-roll attenuation using modified common-offset–common-reflection-surface stacking     

Seyyed Ali Fa’al Rastegar  Abdolrahim Javaherian  Naser Keshavarz Farajkhah  Mehrdad Soleimani Monfared  Abbas Zarei 《应用地球物理》2016,13(2):353-363

We modified the common-offset–common-reflection-surface (COCRS) method to attenuate ground roll, the coherent noise typically generated by a low-velocity, low-frequency, and high-amplitude Rayleigh wave. The COCRS operator is based on hyperbolas, thus it fits events with hyperbolic traveltimes such as reflection events in prestack data. Conversely, ground roll is linear in the common-midpoint (CMP) and common-shot gathers and can be distinguished and attenuated by the COCRS operator. Thus, we search for the dip and curvature of the reflections in the common-shot gathers prior to the common-offset section. Because it is desirable to minimize the damage to the reflection amplitudes, we only stack the multicoverage data in the ground-roll areas. Searching the CS gathers before the CO section is another modification of the conventional COCRS stacking. We tested the proposed method using synthetic and real data sets from western Iran. The results of the ground-roll attenuation with the proposed method were compared with results of the f–k filtering and conventional COCRS stacking after f–k filtering. The results show that the proposed method attenuates the aliased and nonaliased ground roll better than the f–k filtering and conventional CRS stacking. However, the computation time was higher than other common methods such as f–k filtering.  相似文献   

New biorthogonal potential–density basis functions     

Alireza Rahmati  Mir Abbas Jalali 《Monthly notices of the Royal Astronomical Society》2009,393(4):1459-1466

We use the weighted integral form of spherical Bessel functions and introduce a new analytical set of complete and biorthogonal potential–density basis functions. The potential and density functions of the new set have finite central values and they fall off, respectively, similar to   r ^{−(1+ l )}  and   r ^{−(4+ l )}  at large radii, where l is the latitudinal quantum number of spherical harmonics. The lowest order term associated with   l = 0  is the perfect sphere of de Zeeuw. Our basis functions are intrinsically suitable for the modelling of three-dimensional, soft-centred stellar systems and they complement the basis sets of Clutton-Brock, Hernquist & Ostriker and Zhao. We test the performance of our functions by expanding the density and potential profiles of some spherical and oblate galaxy models.  相似文献   

Erratum to: Spring rainfall prediction based on remote linkage controlling using adaptive neuro-fuzzy inference system (ANFIS)     

Gholam Abbas Fallah-Ghalhary  Majid Habibi-Nokhandan  Mohammad Mousavi-Baygi  Javad Khoshhal  Akbar Shaemi Barzoki 《Theoretical and Applied Climatology》2010,101(1-2):235-235

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Assessment of Relationship Between Grouted Values and Calculated Values in the Bazoft Dam Site     

Ahmad Rastegarnia  Abdollah Sohrabibidar  Vahid Bagheri  Mehdi Razifard  Abbas Zolfaghari 《Geotechnical and Geological Engineering》2017,35(4):1299-1310

Seepage through foundation and abutments of a dam can potentially result in a waste of the water stored in dam reservoir, erosion of foundation materials, and development of uplift pressure in dam foundation which, consequently, threatens the long-term stability of the dam. In this study, the grout volume is estimated based on parameters such as joint aperture, the maximum penetration length of the grout, and calculated grout take in Bazoft dam site. Bazoft Dam is a hydroelectric supply and double-curvature arch dam with a height of 211 m located in Chaharmahal and Bakhtiari Province of Iran. The bedrock of Bazoft dam site consists of Asemari Formation (limy marl and marly lime), in the middle and upper parts of left abutment, and Jahrom Formation (limestone and dolomite) in the right abutment, river bed, and lower part of left abutment. The joint apertures were calculated based on the permeability and the joint spacing. Next, the maximum penetration length of the grout and grout volume were calculated. Using a statistical analysis, the relationship of the joint aperture, maximum penetration length, and the calculated grout volume with real grout take was also investigated. The results show that the grout take can be predicted with appropriate accuracy based on the calculated grout volume.  相似文献   

A two-dimensional experimental-numerical approach to investigate wave transformation over muddy beds     

Mohsen Soltanpour  S. Abbas Haghshenas  Tomoya Shibayama 《Ocean Dynamics》2015,65(2):295-310

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Robust Automatic Reduction of Multibeam Bathymetric Data Based on M-estimators     

Mohammad-Hadi Rezvani  Abbas Sabbagh  Alireza A. Ardalan 《Marine Geodesy》2013,36(4):327-344

Multibeam echosounders have commonly been employed for a wide range of applications including offshore survey, navigation, hydrogeology, and oceanography. Because the tremendous volume of the bathymetric data is demanding for some purposes and requires significant storage space, the data reduction plays a prominent role in practice. Additionally, the multibeam soundings are inevitably contaminated with sporadic outliers, and as such, the data cleaning can be challenging especially in shallow waters. We present a speedily robust method for reliably reducing the volume of the bathymetric data within grid cells. In this respect, robust M-estimators are recursively applied to the data in a patch-wise manner to alleviate the undesirable effects of the outlying observations. Accordingly, the reduced bathymetry is automatically made unaffected by the possible outliers once their equivalent weights have been downweighted. The performance of the presented method has been demonstrated by synthetic datasets and an experimental dataset collected by an ATLAS FS 20/100 kHz shallow-water multibeam echosounder in the offshore waters of Kish wharf. The reliability, efficiency, and capability of the proposed method have been verified, which makes it quite possible to meet the IHO requirements for special-order seafloor mapping.  相似文献   

Diatoms as a source for 4-desmethyl-23,24-dimethyl steroids in sediments and petroleum     

Sebastiaan W. Rampen  Stefan Schouten  Ben Abbas  Anna A.M. Noordeloos  Jan A.J. Geenevasen 《Geochimica et cosmochimica acta》2009,73(2):377-492

Analysis of the sterol composition of more than 100 diatom cultures, representing all major marine diatom orders, indicates that this group of algae may be an important source for 4-desmethyl-23,24-dimethyl steroids in sediments and petroleum, as their precursors, i.e. 4-desmethyl-23,24-dimethyl sterols, were present in 22 of the cultures. The phylogenetic positions of diatom species that produce 4-desmethyl-23,24-dimethyl sterols show that, within the centric diatoms, only a specific group of diatoms is able to produce these sterols, while within the pennate diatoms, a phylogenetic relationship between 4-desmethyl-23,24-dimethyl sterol-producing diatoms is less apparent. Based on the phylogenetic relationship, it is suggested that diatoms inherited the ability of producing these sterols from a single common ancestor, which originated between 150 and 100 Ma ago. Co-injection of an authentic 23R,24R-dimethyl-5α-cholestane standard with extracts confirmed its presence in sediments. We also tentatively identified three other 4-desmethyl-23,24-dimethyl sterane isomers having different side-chain stereo-configurations and observed that some of the isomers co-elute with other steranes including 24-ethyl-5α-cholestane.  相似文献   

Deriving preference order of post-mining land-uses through MLSA framework: application of an outranking technique   总被引：1，自引：0，他引：1  

Hossein Soltanmohammadi  Morteza Osanloo  Abbas Aghajani Bazzazi 《Environmental Geology》2009,58(4):877-888

This study intends to take advantage of a previously developed framework for mined land suitability analysis (MLSA) consisted of economical, social, technical and mine site factors to achieve a partial and also a complete pre-order of feasible post-mining land-uses. Analysis by an outranking multi-attribute decision-making (MADM) technique, called PROMETHEE (preference ranking organization method for enrichment evaluation), was taken into consideration because of its clear advantages on the field of MLSA as compared with MADM ranking techniques. Application of the proposed approach on a mined land can be completed through some successive steps. First, performance of the MLSA attributes is scored locally by each individual decision maker (DM). Then the assigned performance scores are normalized and the deviation amplitudes of non-dominated alternatives are calculated. Weights of the attributes are calculated by another MADM technique namely, analytical hierarchy process (AHP) in a separate procedure. Using the Gaussian preference function beside the weights, the preference indexes of the land-use alternatives are obtained. Calculation of the outgoing and entering flows of the alternatives and one by one comparison of these values will lead to partial pre-order of them and calculation of the net flows, will lead to a ranked preference for each land-use. At the final step, utilizing the PROMETHEE group decision support system which incorporates judgments of all the DMs, a consensual ranking can be derived. In this paper, preference order of post-mining land-uses for a hypothetical mined land has been derived according to judgments of one DM to reveal applicability of the proposed approach.  相似文献   

Geomagnetic coast and other effects deduced from the new observatory at Visakhapatnam, India     

B. J. Srivastava  Habiba Abbas  †  T. RamaGopal  D. R. K. Rao  B. M. Pathan 《Geophysical Journal International》2001,146(3):827-832

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Polycyclic aromatic hydrocarbons in Niger Delta soil: contamination sources and profiles     

A. Olajire Abbas  W. Brack 《International Journal of Environmental Science and Technology》2006,2(4):343-352

The distribution and sources of PAHs in soil as well as PAHs profiles have been investigated in areas with anthropogenic pollution in the Niger Delta (Nigeria) such as Warri and Ughelli. PAHs were identified in 21 soil samples (0–10cm upper layer) collected in May, 2003. The typical total PAHs level in Niger Delta soil ranged from 182 ± 112 - to - 433 ±256 íg/kg dw. PAH concentrations in soil samples from Warri Refinery, Tanker Loading point and Ugboko via Rapele oil field were quite high ( the mean ÓPAH concentrations were 433, 402 and 384 íg/kg dry weight respectively). The dominant PAHs in soil samples were pyrene, naphthalene and benzo[k]fluoranthene. The soil total PAHs (PAH_tot.) concentration, normalized to organic carbon content (OC), ranged from 11.4 to 47.2 mg PAH_tot. /kg OC; and showed that organic matter of the soil samples from Quality Control Centre, Ugelli West is highly contaminated with PAHs and had a value of 47.2 ± 31.2 mg PAH_tot./kg OC. Two and three ring aromatic hydrocarbons predominated in soil samples from Ughelli West, Tanker Loading point and Delta Steel Company, which is indicative of petrogenic origin.  相似文献