Influences of petrographic and textural properties on the strength of very strong granitic rocks     

Hakan Ersoy  Serhat Acar 《Environmental Earth Sciences》2016,75(22):1461

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Silver eel migration behaviour in the Baltic     

Westerberg  Hakan; Lagenfelt  Ingvar; Svedang  Henrik 《ICES Journal of Marine Science》2007,64(7):1457-1462

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Sloshing in a three-dimensional rectangular tank: Numerical simulation and experimental validation   总被引：1，自引：0，他引：1  

Hakan Akyild&#x;z  N. Erdem Ünal 《Ocean Engineering》2006,33(16):2135-2149

Pressure variations and three-dimensional effects on liquid sloshing loads in a moving partially filled rectangular tank have been carried out numerically and experimentally. A numerical algorithm based on the volume of fluid (VOF) technique is used to study the non-linear behavior and damping characteristics of liquid sloshing. A moving coordinate system is used to include the non-linearity and avoid the complex boundary conditions of moving walls. The numerical model solves the complete Navier–Stokes equations in primitive variables by using of the finite difference approximations. In order to mitigate a series of discrete impacts, the signal computed is averaged over several time steps. In order to assess the accuracy of the method used, computations are compared with the experimental results. Several configurations of both baffled and unbaffled tanks are studied. Comparisons show good agreement for both impact and non- impact type slosh loads in the cases investigated.  相似文献   

Geochemistry,zircon UPb ages and Hf isotopes of granites and pegmatites from Gubrunde region in the Eastern Nigeria Terrane: Insight into magmatism and tectonic evolution of the late Pan-African orogeny     

Saleh Ibrahim Bute  Xiaoyong Yang  Xueming Yang  Musa Bala Girei  Amuda Abdulgafar Kayode  Yigan Lu 《Chemie der Erde / Geochemistry》2022,82(1):125809

This study reports a new dataset of whole-rock geochemistry, biotite chemistry, in situ zircon UPb geochronology and Hf isotope for a suite of granite and associated pegmatite samples from the Gubrunde region in the Eastern Nigeria Terrane (ENT), Nigeria. The Gubrunde granitic rocks are weakly ferroan, peraluminous and calc-alkalic to alkali-calcic in composition, and show I-type affinity. The zircon UPb geochronology gives an age of ~580 Ma for the rocks, although the presence of inherited zircons with early Pan-African ages of 696 ± 12, 647 ± 7 and 624–613 Ma are evident indicative of a complex history of their source rocks. The Gubrunde granite and the pegmatite yielded similar average Hf crustal model age T_DM2 of 1.9 ± 0.1 Ga and εHf(t) values ?6.2 ± 1.2, suggesting that they may have sourced from reworked old crustal rocks with minor contributions from the mantle. The granite and the pegmatite were likely to connect by fractional crystallization under low to moderate pressure (~2.2 to 3.0 kbar) and temperature (~717 °C), and low oxygen fugacity (<ΔNNO ?1.14). The ca. 580 Ma magmatism may have been triggered by delamination of the lithospheric mantle as a consequence of crustal thinning during waning stage of the Pan-African orogeny.  相似文献   

Source apportionment of trace metals in surface waters of a polluted stream using multivariate statistical analyses   总被引：16，自引：0，他引：16  

Pekey H  Karakaş D  Bakoğlu M 《Marine pollution bulletin》2004,49(9-10):809-818

Surface water samples were collected from ten previously selected sites of the polluted Dil Deresi stream, during two field surveys, December 2001 and April 2002. All samples were analyzed using ICP-AES, and the concentrations of trace metals (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Pb, Sn and Zn) were determined. The results were compared with national and international water quality guidelines, as well as literature values reported for similar rivers. Factor analysis (FA) and a factor analysis-multiple regression (FA-MR) model were used for source apportionment and estimation of contributions from identified sources to the concentration of each parameter. By a varimax rotated factor analysis, four source types were identified as the paint industry; sewage, crustal and road traffic runoff for trace metals, explaining about 83% of the total variance. FA-MR results showed that predicted concentrations were calculated with uncertainties lower than 15%.  相似文献   

Optimum parameter selection in offset-dependent predictive deconvolution: testing on multichannel marine seismic data     

Güney  Recep  Karslı  Hakan  Dondurur  Derman 《Marine Geophysical Researches》2019,40(4):601-617

Marine Geophysical Research - Predictive deconvolution is an effective way to suppress multiple reflections, especially short path multiples, in seismic data. However, the effectiveness of the...  相似文献   

Seasonal variations and distributions of dissolved free and total carbohydrates at the İzmir Bay, Aegean Sea     

ALYURUK Hakan  KONTAS Aynur 《海洋学报(英文版)》2018,37(8):6-14

Seasonal variations and distributions of dissolved carbohydrate concentrations at the İzmir Bay were investigated with salinity, chlorophyll a (Chl a), and dissolved organic carbon (DOC) levels to understand their relationships. Samples were collected from surface, subsurface and bottom depths at seven stations. DOC concentrations ranged from 32.2 to 244.2 μmol/L, and in general, DOC levels increased from winter to summer, then slightly decreased in autumn. Monosaccharide (MCHO), polysaccharide (PCHO) and total dissolved carbohydrate (TDCHO) levels were found between 0.7-8.3, 0.7-19.5, and 2.6-24.6 μmol/L. DOC, MCHO, PCHO and TDCHO levels were found higher in middle-inner bays, under the influence of anthropogenic inputs, compared to outer bay. Seasonal changes of MCHO/DOC, PCHO/DOC and TDCHO/DOC ratios were statistically significant (p<0.05) and the ratios showed decrease trends from winter to summer-autumn seasons. Distributions of TDCHO/DOC ratios at wide ranges (2.5%-42.3%) indicated the presence of newly forming and degrading fractions of DOM. According to results of factor analysis, Chl a, MCHO and TDCHO were explained in the same factor groups. In conclusion, the results showed that dissolved carbohydrate levels in the İzmir Bay might be influenced by biological processes and terrestrial/anthropogenic inputs.  相似文献   

Determination of optimum kernel bandwidth for northern Marmara region,Turkey     

Hakan Karaca 《Acta Geophysica》2018,66(4):633-642

As a relatively recent development, spatial smoothing methods have been introduced to identify seismic patterns. Among the methods developed to model the spatial variation, methods based on utilization of 3-D Gaussian isotropic kernels have a wide reception. The most important question remaining to be answered in the application of these methods is the determination of the optimum kernel bandwidth. At the present, researchers’ efforts to clarify the subject have still not yet finalized, this study aims to provide insightful knowledge for future efforts. In this study, for the region bounded by 27°–33° longitudes and 39°–41° latitudes, where the western section of the famous Northern Anatolian fault lies, smoothing techniques are implemented to determine the optimum smoothing kernel bandwidth for point sources. The influence of the modeling of seismicity through the computation of the optimum smoothing kernel bandwidth is examined. In addition, the sensitivity of each smoothing technique to the seismic patterns, whether densely clustered or scarcely populated, is investigated. In the end, the smoothing method based on optimum neighbor number is identified as highly sensitive to the density of seismicity and seismic clusters, and better in modeling high seismicity compared to the model based on single optimum smoothing distance used for the entire region of interest.  相似文献   

Forward plane-wave electromagnetic model in three dimensions using hybrid finite volume–integral equation scheme     

Musa A. Bello  Rongwen Guo  Jianxin Liu 《Geophysical Prospecting》2019,67(8):2213-2226

We present a concept of the hybrid finite volume–integral equation technique for solving Maxwell's equation in a quasi-static form. The divergence correction was incorporated to improve the convergence and stability of the governing linear system equations which pose a challenge on the discretization of the curl–curl Helmholtz equation. A staggered finite volume approach is applied for discretizing the system of equations on a structured mesh and solved in a secondary field technique. The bi-conjugate gradient stabilizer was utilized with block incomplete lower-upper factorization preconditioner to solve the system of equation. To obtain the electric and magnetic fields at the receivers, we use the integral Green tensor scheme. We verify the strength of our hybrid technique with benchmark models relative to other numerical algorithms. Importantly, from the tested models, our scheme was in close agreement with the semi-analytical solution. It also revealed that the use of a quasi-analytical boundary condition helps to minimize the runtime for the linear system equation. Furthermore, the integral Green tensor approach to compute at the receivers demonstrates better accuracy compared with the conventional interpolation method. This adopted technique can be applied efficiently to the inversion procedure.  相似文献   

An application of the autoregressive extrapolation technique to enhance deconvolution results: a 2D marine data example     

Hakan Karslı 《Geophysical Prospecting》2011,59(1):56-65

Interpreting a post‐stack seismic section is difficult due to the band‐limited nature of the seismic data even post deconvolution. Deconvolution is a process that is universally applied to extend the bandwidth of seismic data. However, deconvolution falls short of this task as low and high frequencies of the deconvolved data are either still missing or contaminated by noise. In this paper we use the autoregressive extrapolation technique to recover these missing frequencies, using the high signal‐to‐noise ratio (S/N) portions of the spectrum of deconvolved data. I introduce here an algorithm to extend the bandwidth of deconvolved data. This is achieved via an autoregressive extrapolation technique, which has been widely used to replace missing or corrupted samples of data in signal processing. This method is performed in the spectral domain. The spectral band to be extrapolated using autoregressive prediction filters is first selected from the part of the spectrum that has a high signal‐to‐noise ratio (S/N) and is then extended. As there can be more than one zone of good S/N in the spectrum, the results of prediction filter design and extrapolation from three different bands are averaged. When the spectrum of deconvolved data is extended in this way, the results show higher vertical resolution to a degree that the final seismic data closely resemble what is considered to be a reflectivity sequence of the layered medium. This helps to obtain acoustic impedance with inversion by stable integration. The results show that autoregressive spectral extrapolation highly increases vertical resolution and improves horizon tracking to determine continuities and faults. This increase in coherence ultimately yields a more interpretable seismic section.  相似文献