Pulvirenti F. | Aloisi M. | Jin S.
Makale | 2017 | Journal of Volcanology and Geothermal Research344 , pp.185 - 196
In this paper, the relationship between the dike-forming magmatic intrusions and the faulting process at Mount Etna is investigated in terms of Coulomb stress changes. As case study, a complete time-dependent 3-D finite element model for the 2002–2003 eruption at Mount Etna is presented. In the model, which takes into account the topography, medium heterogeneities and principal fault systems in a viscoelastic/plastic rheology, we sequentially activated three dike-forming processes and looked at the induced temporal evolution of the Coulomb stress changes, during the co-intrusive and post-intrusive periods, on Pernicana and Santa Ven . . .erina faults. We investigated where and when fault slips were encouraged or not, and consequently how earthquakes may have been triggered. Results show positive Coulomb stress changes for the Pernicana Fault in accordance to the time, location and depth of the 27th October 2002 Pernicana earthquake (Md = 3.5). The amount of Coulomb stress changes in the area of Santa Venerina Fault, as induced by dike-forming intrusions only, is instead almost negligible and, probably, not sufficient to trigger the 29th October Santa Venerina earthquake (Md = 4.4), occurred two days after the start of the eruption. The necessary Coulomb stress change value to trigger this earthquake is instead reached if we consider it as induced by the 27th October Pernicana biggest earthquake, combined with the dike-induced stresses. © 2016 Elsevier B.V Daha fazlası Daha az
Pekdemir F. | Orman E.B. | Selçuki N.A. | Özkaya A.R. | Salih B. | Şengül A.
Makale | 2019 | Journal of Photochemistry and Photobiology A: Chemistry379 , pp.54 - 62
In this study, four new perylene diimide (PDI)derivatives incorporating 2-(2'-pyridyl)-1H-benzimidazole (2PBI)chromophores at the imide positions, in which 1 bearing non-bay-substituted perylene core, and those having four substituents at 1,6,7,12-bay positions of the perylene core, namely 2 bearing electron-withdrawing chlorine atoms, 3 bearing electron-donating 4-methoxyphenoxy groups and 4 bearing non-electron-donating 4-tert-butylphenoxy groups, respectively were synthesized and fully characterized by FT-IR, 1 H NMR, 13 C NMR, MALDI-TOF mass spectrometry and UV/Vis spectroscopy. The thermal properties were measured by thermograv . . .imetric analysis (TGA)which showed that the materials (1-4)are thermally very stable (T d > 450 °C). DFT was performed for geometry optimizations, and TDDFT was used to compare the calculated and the experimental UV/Vis electronic spectra at the B3LYP/6–311 G(d)level. Detailed measurements were carried out by the use of electroanalytical, spectroscopic and colorimetric techniques in order to understand redox natures, color changes and optoelectronic characters of the novel compounds. These 2PBI-functionalized PDI triads showed reversible reduction processes, chemically stable reduced species and considerably low HOMO-LUMO band gaps, as the new worthy members of photoactive charge transport materials for optoelectronic and photovoltaic systems. In addition, with distinct color changes associated with their redox processes in the solution, these new triads displayed great capacity for application in electrochromic devices. The emission maxima of the compounds were found to be red shifted in the solid state. © 2019 Elsevier B.V Daha fazlası Daha az
Efe Y.K. | Ugurbas S.C. | Alpay A. | Ugurbas S.H.
Gözden Geçirme | 2012 | Canadian Journal of Ophthalmology47 ( 2 ) , pp.150 - 154
Objective: To determine concurrent changes in corneal thickness, intraocular pressure (IOP), and corneal topography measurements during normal pregnancy. Design: Prospective cohort study. Participants: We studied 50 eyes from 25 healthy women whose ages ranged from 21 to 35 years and who were first seen during the 10th week of pregnancy. Methods: Measurements included IOP (noncontact tonometry); corneal thickness (ultrasound pachymetry); and corneal topography (TMS 2N, TOMEY, Nagoya, Japan). Changes in IOP, central corneal thickness (CCT), and corneal power were calculated at 4 time periods: first trimester, second trimester, third . . .trimester, and 3 months postpartum. Results: The mean IOPs in the second and third trimesters of pregnancy were found to be lower than those in the first trimester and at 3 months postpartum (p = 0.001). The mean CCT in the second and third trimester of pregnancy was measured to be higher than in the first trimester and at 3 months postpartum (p < 0.001). Both IOP and CCT returned to first-trimester levels following delivery. In the third trimester, a 3.1% increase in CCT was associated with a 9.5 % decrease in IOP. Topographic measurements did not show statistically significant changes throughout the trimesters or after pregnancy. Conclusions: An increase in CCT was accompanied by a decrease in IOP in the second and third trimesters. Physiologic changes occurring in CCT and IOP should be considered in the management of glaucoma during pregnancy. © 2012 Canadian Ophthalmological Society Daha fazlası Daha az
Makale | 2019 | Journal of Power Sources435 , pp.150 - 154
In this study, a novel 1–10 phenanthroline and 1–10 phenanthroline 5,6 diol based metal complex sensitizers for dyes sensitized solar cells applications is investigated. The 1–10 phenanthroline 5,6 diol structure is formed by the addition of two –OH groups to 1–10 phenanthroline, which has higher cell yields due to binding sites of TiO2. The 1–10 phenanthroline 5,6 diol metal complexes are prepared with Cu and Fe at different pH values. Additionally, these metal complexes are mixed at different ratio to prepare cocktail dyes. The maximum cell efficiency value of dyes sensitized solar cells based on 1–10 phenanthroline 5,6 diol prepa . . .red with Cu:Fe 2:1 ratio cocktail dyes is 3.70%. The phen-ol based DSSC containing Cu-complex dye exhibits 2.80% conversion efficiency value, which shows an 25% lower than cocktail phen-ol based dyes sensitized solar cells. The solar cell efficiency values are demonstrated decrement by increasing of Fe-complex ratio. However, the Fe-complexes exhibit more stable complex structures than Cu-complexes. This phenomenon also gives a new way to the use of the environmentally friendly metal complex-based dyes sensitized solar cells. Additionally, these transition metal-based sensitizers will be an alternative to synthetic organic dyes and noble metal-based solar cells. © 2019 Elsevier B.V Daha fazlası Daha az
Makale | 2013 | Energy for Sustainable Development17 ( 1 ) , pp.13 - 23
Ventilation air methane (VAM) emissions from underground coal mines have become important in the mining community worldwide recently since they constitute the major part of greenhouse gas emissions from coal mining and are a so-called wasted resource. As demonstrated in important coal producers such as the United States, China, Australia and the United Kingdom, it has become possible to use methane in ventilation air to generate energy. However, there has been no study concerning the feasibility of application of VAM technologies in Turkey. This study was, therefore, conducted to evaluate the applicability of VAM mitigation and util . . .ization options for an underground coal mine in Turkey. The Kozlu mine, owned by the Turkish Hardcoal Enterprises (TTK) was chosen for the study since it is known that the mine has gassy coal seams and high coal production. The paper analyzes the data from a computerized continuous monitoring system and from manual readings to quantify VAM emission characteristics of the mine. In addition to a technical assessment, a detailed preliminary economic analysis was performed for the technology alternatives proposed for the mine. The technical and economic analyses revealed that any of the technologies for VAM mitigation/utilization could be used for the mine but economically there must be a carbon credit of 19.8 US$/ tCO2e or more to provide incentive for using the technology. This requires that a legislative framework be put in place in Turkey. © 2012 Elsevier Ltd Daha fazlası Daha az
Panigrahi M. | Grabda M. | Kozak D. | Dorai A. | Shibata E. | Kawamura J. | Nakamura T.
Makale | 2016 | Separation and Purification Technology171 , pp.263 - 269
A protocol for the recovery of rare earth elements based on the dissolution of an aqueous solution of a rare earth metal chloride in an ionic liquid (IL) followed by stripping of the dissolved metal ions into an aqueous phase is proposed. The use of ILs is a departure from the traditional strategies employed for extraction. Liquid–liquid extraction of neodymium (Nd) ions from an aqueous solution of NdCl3 with and without hydrochloric acid (HCl) was carried out using phosphonium-based ILs, namely trihexyl(tetradecyl)phosphonium benzoate [T66614][BA] and trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide [T66614][TFSA]. . . . The extraction was also conducted using a mixture of the aforementioned ILs and toluene. The efficiency of the extraction decreased with increasing concentrations of Nd in the aqueous solution. Furthermore, increasing the concentration of HCl in the aqueous phase decreased the percentage of extracted Nd ions. It indicates that the extraction followed a neutral or ion-pair extraction type of mechanism. Stripping of Nd ions from the metal-loaded organic phase using different acids revealed that HCl and HNO3 were the most effective stripping agents for complete re-extraction of the metal ions. Trihexyl(tetradecyl)phosphonium-based IL with a benzoate counter anion was more effective for Nd extraction than the congener with the bis(trifluoromethylsulfonyl)imide anion. © 2016 Elsevier B.V Daha fazlası Daha az
Ndah A.B. | Dagar L. | Becek K. | Odihi J.O.
Makale | 2019 | Regional Studies in Marine Science29 , pp.263 - 269
The sea-surface distribution of four phytoplankton functional groups in the South China Sea (SCS) namely Coccolithophores (Coc), Diatoms (Dia), Cyanobacteria (Cya) and Chlorophytes (Chlo) was studied across spatial and temporal scales. The time-series datasets derived from the National Aeronautic and Space Administration (NASA) Ocean Biogeochemical Model and retrieved via the Giovanni Portal were analysed statistically with well-known methods including Pearson's correlation coefficient, ordinary least square regression (OLR), Maximum Entropy Spectral Analysis (MESA) and Principal Components Analysis (PCA). The data were analysed for . . . relative abundance, seasonality, cyclicity, long-term trends, spatial variability, inter-relationships, and relative contributions of individual phytoplankton groups to primary production (PP, using Chl-a as a proxy). The results reveal that the numerically dominant phytoplankton group in terms of relative abundance is Cya, comprising about 57% of the planktonic biomass, followed closely by Coc (about 40%), while Dia constitutes almost 3% of the total abundance. Dia was found to have the strongest annual cycle, and hence displayed the highest rate of seasonal variability. Clear spatial segregation patterns have also been uncovered; Coc and Dia are strongly correlated in the Northern SCS (NSCS) while Cya dominate in Southern SCS (SSCS). Coc and Dia display a strong positive correlation with PP, whereas the seasonal relationships between Cya and Chlo with PP are non-linear, and hence appear statistically non-significant. The rise in the trend of Cya and decrease in Coc, since 2004, may be indicative of changes in successional patterns of phytoplankton functional groups in the SCS. This study, therefore, sets the precedence for more robust research to uncover the immediate and remote causes of the observed spatiotemporal changes in marine phytoplankton dynamics and to develop predictive models of marine primary productivity (MPP) and ecological health. © 201 Daha fazlası Daha az
Ergen S. | Yılmaz F. | Gul S. | Kolemen U. | Kilicaslan M.F. | Uzun O.
Makale | 2018 | Advanced Powder Technology29 ( 3 ) , pp.563 - 572
In this study, the effect of Si amount on the microstructure, crystal structure and some mechanical properties of Al-(20,25,30 wt%)Si–5Fe powder mixtures produced by high energy ball milling method was investigated by determining the sintering temperature. In the X-ray diffraction analysis, no inter-metallic phases were found except for the Al, Si and Fe phases of the powder mixtures. The X-ray diffraction patterns were analyzed by the Rietveld method to determine amounts of the Al, Si and Fe elements in the powder mixtures. From the scanning electron microscopy analysis, it is seen that as the amount of Si increases, there is a mar . . .ked decrease in the grain size of powders. In the micro-indentation tests performed at room temperature, the hardness and elastic modulus values of the pelletized powders were found to increase with the amount of Si. It was also found that the Al-20Si-5Fe powder mixture with the lowest Si content had the highest damping capability. The high temperature micro-indentation tests showed that the resulting Al-(20,25,30 wt%) Si-5 Fe powder mixtures started to consolidation at 200 °C and completed the consolidation at 400 °C. This method can be used as an alternative method in the determination of the sintering temperature of materials. © 201 Daha fazlası Daha az
Yalçn Z. | Içelli O. | Okutan M. | Boncukçuoglu R. | Artun O. | Orak S.
Makale | 2012 | Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment686 , pp.43 - 47
In this study, the effective atomic number (Zeff)has been calculated for some boron compounds, such as concentrate colemanite, tincal, ulexite, boric acid, probertite and TSW (Trommel Sieve Waste) by means of ZXCOM at incident beam energy (E0=59.543 keV) and scattering angle (?=35°). We present and discuss the (Zeff) obtained by Rayleigh/Compton (R/C) ratio and evaluated for the purpose of radiation shielding which contains boron compounds, which are commonly used as shield materials. © 2012 Elsevier B.V. All rights reserved.
Baysal, Veli | Yılmaz, Ergin
Makale | 2020 | Physica A: Statistical Mechanics and its Applications537 , pp.43 - 47
In this paper, Vibrational Resonance (VR), in which the response of some dynamical systems to a weak, low frequency signal can be enhanced by the optimal amplitude of high frequency signal, is investigated under the effects of electromagnetic induction in both single neurons and small-world networks. We find that the occurrence of VR in single neurons requires less energy in the presence of electromagnetic induction, although the resonant peak of the response reduces. Besides, VR can be obtained in small-world networks both with and without electromagnetic induction. In small-world neuronal networks, the highest resonance peak of VR . . . enhances with an increase in the probability of adding link in case of without electromagnetic induction. On the other hand, with the increasing of the probability of adding link, VR disappears in the presence of relatively strong electromagnetic induction, while it enhances in the presence of relatively weak electromagnetic induction. © 2019 Elsevier B.V Daha fazlası Daha az
Jin S. | Zou F.
Makale | 2015 | Global and Planetary Change135 , pp.170 - 178
The Gravity Recovery and Climate Experiment (GRACE) satellites can estimate the high-precision time-varying gravity field and the changes of Earth's surface mass, which have been widely used in water cycle and glacier mass balance. However, one of larger errors in GRACE measurements, land-ocean leakage effects, restricts high precision retrieval of ocean mass and terrestrial water storage variations along the coasts, particularly estimation of mass loss in Greenland. The land-ocean leakage effect along the coasts in Greenland will contaminate the mass loss signals with significant signal attenuation. In this paper, the precise glaci . . .er mass loss in Greenland from GRACE is re-estimated with correction of land-ocean leakage effects using the forward gravity modeling. The loss of Greenland ice-sheets is -102.8±9.01Gt/a without removing leakage effect, but -183.0±19.91Gt/a after removing the leakage effect from September 2003 to March 2008, which has a good agreement with ICESat results of -184.8±28.2Gt/a. From January 2003 to December 2013, the total Greenland ice-sheet loss is at -261.54±6.12Gt/a from GRACE measurements with removing the leakage effect by 42.4%, while two-thirds of total glacier melting in Greenland occurred in southern Greenland in the past 11years. The secular leakage effects on glacier melting estimate is mainly located in the coastal areas, where larger glacier signals are significantly attenuated due to leaking out into the ocean. Furthermore, the leakage signals also have remarkable effects on seasonal and acceleration variations of glacier mass loss in Greenland. More significantly accelerated loss of glacier mass in Greenland is found at -26.19Gt/a2 after correcting for leakage effects. © 2015 Elsevier B.V Daha fazlası Daha az
Onur Y.A. | İmrak C.E. | Onur T.Ö.
Makale | 2019 | Measurement: Journal of the International Measurement Confederation142 , pp.163 - 169
In this paper, theoretical and experimental studies are conducted to exhibit the discarding fatigue lifetime of a rotation resistant rope exposed to alternate bending over sheave (BoS) fatigue. Experimental studies are fulfilled to determine discarding lifetimes of a rotation resistant rope exposed to BoS fatigue. Multiple linear regression analysis is performed and novel theoretical discarding lifetime prediction formula is determined by using the least square method. Furthermore, discarding lifetimes of rotation resistant ropes exposed to BoS fatigue is predicted by using artificial neural network (ANN). There is a vigorous correl . . .ation among the results acquired by regression model, ANN and experimental data. © 2019 Elsevier Lt Daha fazlası Daha az