Oil decolorization properties of the Emirler clinoptilolite (Bigadiç, Turkey)     

I. Girgin  M. N. Gündoğdu  S. Ata  A. Yörükoğlu 《Mineralium Deposita》1996,31(6):584-588

Oil decolorization properties of the Emirler clinoptilolite and its acid-activated forms were studied using neutralized cottonseed oil. Although the oil decolorization capacity of natural clinoptilolite is low, it can be improved by a factor of 1.8 after HCl activation under the optimized conditions (1M HCl, solid/liquid ratio = 1/20, T = 25°C, t = 1 hour). Acid activation increases the total specific surface area from 40 to 70 m²/g which is mostly realized with a pore diameter range smaller than 15 nm. The bleaching capacity of acid-activated clinoptilolite is comparable to that of natural bentonitic clays but it is 1.6 times lower than the capacity of activated bleaching earths such as Tonsil and others. However, the amount of oil absorbed by clinoptilolite during the bleaching process is almost half that compared with the commonly used natural and acid-activated clays.  相似文献   

Modelling groundwater level variations by learning from multiple models using fuzzy logic     

Ata Allah Nadiri  Keyvan Naderi  Maryam Gharekhani 《水文科学杂志》2019,64(2):210-226

Modelling time series of groundwater levels is investigated by three fuzzy logic (FL) models, Sugeno (SFL), Mamdani (MFL) and Larsen (LFL), using data from observation wells. One novelty in the study is the re-use of these three models as multiple models through the following strategies: (a) simple averaging, (b) weighted averaging and (c) committee machine techniques; these are implemented using artificial neural networks (ANN). These strategies provide some evidence that (i) multiple models improve on the performance of individual models and those using committee machines perform better than the other two options; and (ii) committee machine models produce defensible modelling results to develop management scenarios. The study investigates water table declines through management scenarios and shows that in this aquifer water use has higher impacts on water table variations than climatic variations. This provides evidence of the need for planned management in the study area.  相似文献   

Ages and metallicities of five intermediate-age star clusters projected towards the Small Magellanic Cloud     

Andrés E. Piatti  João F. C. SantosJr  Juan J. Clariá  Eduardo Bica  Ata Sarajedini  Doug Geisler 《Monthly notices of the Royal Astronomical Society》2001,325(2):792-802

Colour–magnitude diagrams are presented for the first time for L32, L38, K28 (L43), K44 (L68) and L116, which are clusters projected on to the outer parts of the Small Magellanic Cloud (SMC). The photometry was carried out in the Washington system C and T ₁ filters, allowing the determination of ages by means of the magnitude difference between the red giant clump and the main-sequence turn-off, and metallicities from the red giant branch locus. The clusters have ages in the range 2–6 Gyr , and metallicities in the range −1.65<[Fe/H]<−1.10, increasing the sample of intermediate-age clusters in the SMC. L116, the outermost cluster projected on to the SMC, is a foreground cluster, and somewhat closer to us than the Large Magellanic Cloud. Our results, combined with those for other clusters in the literature, show epochs of sudden chemical enrichment in the age–metallicity plane, which favour a bursting star formation history as opposed to a continuous one for the SMC.  相似文献   

Statistical relationship between sunspots and major flares     

T. Ataç 《Astrophysics and Space Science》1987,129(1):203-208

In this study, the statistical relationship between sunspots and major flares observed in the descending branch of the 20th and in the ascending branch of the 21st solar cycle is evaluated. It is found that the sunspots which produced these major flares are of the type Dki or Eki with magnetic class D and the largest magnetic field strength between 1600 and 2500 G.  相似文献   

Constraining the LMC cluster age gap: Washington photometry of NGC 2155 and SL 896 (LW 480)     

Andrés E. Piatti  Ata Sarajedini  Doug Geisler  Eduardo Bica  Juan J. Clariá 《Monthly notices of the Royal Astronomical Society》2002,329(3):556-566

We carried out Washington system photometry of the intermediate-age Large Magellanic Cloud (LMC) star clusters NGC 2155 and SL 896 (LW 480). We derive ages and metallicities from the T ₁ versus     colour–magnitude diagrams (CMDs). For the first time an age has been obtained for SL 896,     . For NGC 2155 we derive     . The two clusters basically define the lower age limit of the LMC age gap. In particular, NGC 2155 is confirmed as the oldest intermediate-age LMC cluster so far studied. The derived metallicities are     and     for NGC 2155 and SL 896, respectively. We also studied the CMDs of the surrounding fields, which have a dominant turn-off comparable to that of the clusters themselves, and similar metallicity, showing that one is dealing with an intermediate-age disc where clusters and field stars have the same origin. We inserted the present clusters in the LMC and Small Magellanic Cloud (SMC) age–metallicity relations, using a set of homogeneous determinations with the same method as in our previous studies, now totalling 15 LMC clusters and four SMC clusters, together with some additional values from the literature. The LMC and SMC age–metallicity relations appear to be remarkably complementary, since the SMC was actively star-forming during the LMC quiescent age gap epoch.  相似文献   

Overview of the Solar Activity During Solar Cycle 23     

Tamer Ataç  Atila Özgüç 《Solar physics》2006,233(1):139-153

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A data-driven Bayesian approach for finding young stellar populations in early-type galaxies from their ultraviolet–optical spectra     

Louisa A. Nolan  Markus O. Harva  Ata Kabán  Somak Raychaudhury 《Monthly notices of the Royal Astronomical Society》2006,366(1):321-338

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Supervised committee fuzzy logic model to assess groundwater intrinsic vulnerability in multiple aquifer systems     

Dara Faeq Hamamin  Ata Allah Nadiri 《Arabian Journal of Geosciences》2018,11(8):176

Groundwater vulnerability modeling is an alternative approach to evaluate groundwater contamination especially in areas affected by intensive anthropogenic activities. However, the DRASTIC model as a well-known method to assess groundwater vulnerability suffers from the inherent uncertainty associated with its seven essential parameters. In this study, three different fuzzy logic (FL) models (Sugeno fuzzy logic, Mamdani fuzzy logic, and Larsen fuzzy logic) are adopted to improve the DRASTIC system to be more realistic. The vulnerability map of groundwater from multiple aquifer systems (i.e., karstic, alluvium, and complex) in Basara basin, Iraq, was created using the FL models. Validation of the FL models results using NO₃-N concentration obtained from wells and springs of the study area indicating that all of the three FL models are applicable for improving the DRASTIC model. However, each of the FL models has its own advantages for groundwater vulnerability estimation in different types of aquifer systems in the Basara basin. Therefore, this study proposes the supervised committee fuzzy logic (SCFL) as a multimodel method to combine the advantages of individual FL models. The SCFL method confirms that no water well with high NO₃-N levels would be classified as low risk and vice versa. The study suggests that this approach has provided a convenient estimation of pollution risk in the study area and therefore, a more accurate prediction of the intrinsic vulnerability to pollution in the multiple aquifer system can be achieved through SCFL method.  相似文献   

Seven young star clusters in the inner region of the Small Magellanic Cloud     

Andrés E. Piatti  Doug Geisler  Ata Sarajedini  Carme Gallart  Marina Wischnjewsky † 《Monthly notices of the Royal Astronomical Society》2008,389(1):429-440

We present CCD photometry in the Washington system C and T ₁ passbands down to   T ₁∼ 22  in the fields of L35, L45, L49, L50, L62, L63 and L85, seven poorly studied star clusters in the inner region of the Small Magellanic Cloud (SMC). We measured T ₁ magnitudes and   C − T ₁  colours for a total of 114 826 stars distributed throughout cluster areas of 13.7 × 13.7 arcmin² each. Cluster radii were estimated from star counts distributed throughout the entire observed fields. The seven clusters are generally characterized by a relatively small angular size and by a high field star contamination. We performed an in-depth analysis of the field star contamination of the colour–magnitude diagrams (CMDs), and statistically cleaned the cluster CMDs. Based on the best fits of isochrones computed by the Padova group to the  ( T ₁,  C − T ₁)  CMDs, we derive ages for the sample, assuming Z = 0.004, finding ages between 25 Myr and 1.2 Gyr. We then examined different relationships between positions in the SMC, age and metallicity of a larger sample of clusters including our previous work whose ages and metallicities are on the same scale used in this paper. We confirm previous results in the sense that the further a cluster is from the centre of the galaxy, the older and more metal poor it is, with some dispersion; although clusters associated with the Magellanic Bridge clearly do not obey the general trend. The number of clusters within ∼ 2° of the SMC centre appears to have increased substantially after ∼2.5 Gyr ago, hinting at a burst.  相似文献   

A Global Review of Wind Power Installations and their Development in Turkey     

Mehmet Bilgili 《洁净——土壤、空气、水》2009,37(3):195-202

The development of wind power installations globally and in Turkey is reviewed here. Firstly, the growth of global installed wind power capacity between 1996 and 2007 is reviewed, and the top countries in terms of total installed wind power capacity by region are identified. Then, wind power installation and its development in Europe are discussed. In addition, the current status and development of Turkey's wind power plants are investigated in detail.  相似文献