Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
5 results
Search Results
Article Citation - WoS: 35Citation - Scopus: 38Historical Trends Associated With Annual Temperature and Precipitation in Aegean Turkey, Where Are We Heading?(MDPI, 2022) Mersin, Demirhan; Tayfur, Gökmen; Vaheddoost, Babak; Safari, Mir Jafar SadeghThe trend analysis of annual temperature (daily average) and total precipitation has been conducted for 14 stations located in the Aegean Region, Turkey. The Sen, Spearman’s rho, and Mann-Kendall test methods are used in the detection of the historical trends in the region. The Pettitt test is also implemented to find the significance of the trend, while the Theil-Sen approach is applied to detect the change point(s) in the time series. Findings of the following study indicate that both precipitation and temperature time series in the selected stations depict statistically significant trends with increasing nature. The rate of increase in precipitation and temperature by the Theil-Sen test is found to be 4.2–7.9 mm/year and 0.20–0.35 °C/decade, respectively. It is also found that the turn points of the temperature trends determined by the Pettitt test occurred in 1998 for all the stations. According to the results, the magnitude of the extreme events would change in the future, which may help in conceptualizing the framework and the resilience of the infrastructures against climate change.Article Citation - WoS: 33Citation - Scopus: 37Trend Analysis of Temperature and Precipitation in Trarza Region of Mauritania(IWA Publishing, 2019) Yacoub, Ely; Tayfur, GökmenTrend analysis of annual temperature and precipitation time series data collected from three stations (Boutilimit (station 1), Nouakchott (station 2) and Rosso (station 3)) has been used to detect the impacts of climate change on water resources in Trarza region, Mauritania. The Mann-Kendall, the Spearman's rho, and the Sen trend test were used for the trend identification. Pettitt's test was used to detect the change point of the series while the Theil-Sen approach was used to estimate the magnitude of the slope in the series. For precipitation, two stations (1 and 3) indicated statistically significant increase in trends. In the case of temperature, almost all the stations show statistically significant increasing trends in the maximum, minimum, and average temperatures. The magnitude of precipitation detected by the Theil-Sen test for stations 1 and 3, respectively, was found to be at the rate of 2.93 and 3.35 mm/year at 5% significance level. The magnitude trend of temperature detected by the Theil-Sen approach was found to be at the rate of 0.2-0.4 degrees C per decade for almost all the stations. The change points of temperature trends detected by Pettitt test are found to be in the same year (1995) for all the stations.Article Citation - WoS: 32Citation - Scopus: 34Spatial and Temporal of Variation of Meteorological Drought and Precipitation Trend Analysis Over Whole Mauritania(Elsevier, 2020) Yacoub, Ely; Tayfur, GökmenUsing monthly precipitation data from 15 stations, well spread over whole Mauritania, and recorded for a long period of time (1919-2016) of almost 100 years, a classification of drought is performed, based on its intensity and duration. For this purpose, the gamma-Standardized Precipitation Index (gamma-SPI) is used to detect drought events (drought frequency, duration and intensity). The Mann-Kendall Test (MK test) is employed for the trend analysis of the precipitation data at all stations and the Thiel-Sen Approach is used to calculate the magnitude of the slopes of the trends. The drought analysis results show that there were severe and extreme drought conditions seen all over the country, especially in 1970s and 1980s. This serious case seems to be emerging in early 2010s. The drought conditions in recent years seems to be more pronounced in the central and southern regions of the country. The trend analysis results reveal that there is no depletion observed in precipitation at the northern region. The total deficit in precipitation is about 100 mm or less during almost 100 year period at the western region. However, the results show that there is pronounced decrease in precipitation at the southern region, reaching to almost a total of 300 mm deficit in nearly 100-year period.Article Citation - WoS: 73Citation - Scopus: 77Zinc Oxide and Zinc Hydroxide Formation Via Aqueous Precipitation: Effect of the Preparation Route and Lysozyme Addition(Elsevier Ltd., 2015) Top, Ayben; Çetinkaya, HayrullahAqueous precipitation products of Zn(NO3)2 and NaOH obtained by changing the method of combining the reactants and by using lysozyme as an additive were investigated. In the case of single addition method, octahedral ε-Zn(OH)2 and plate-like β-Zn(OH)2 structures formed in the absence and in the presence of lysozyme, respectively. Calcination of these Zn(OH)2 samples at 700 °C yielded porous ZnO structures by conserving the template crystals. When zinc source was added dropwise into NaOH solution, predominantly clover-like ZnO crystals were obtained independent of lysozyme addition. Mixed spherical and elongated ZnO morphology was observed when NaOH was added dropwise into Zn(NO3)2 solution containing lysozyme. Lysozyme contents of the precipitation products were estimated as in the range of ∼5-20% and FTIR indicated no significant conformational change of lysozyme in the composite. These results suggest that lysozyme-ZnO/Zn(OH)2 composite materials may have a value as an antibacterial material.Article Citation - WoS: 19Citation - Scopus: 17Preparation and Characterization of Nanocrystalline Titania Powders by Sonochemical Synthesis(Elsevier Ltd., 2012) Çağlar Duvarcı, Özlem; Çiftçioğlu, MuhsinNanocrystalline mesoporous titania powders were synthesized by hydrolyzing titanium isopropoxide in ethanol-water mixtures which were ultrasonically treated without using any templates or chemicals. Titanium isopropoxide-ethanol mixture was added dropwise to a water-ethanol mixture placed in an ultrasonic bath. The properties of the sonochemically synthesized powder were compared with those of the powders prepared without ultrasonic treatment along with Degussa P-25 titania powder. The phase structure, crystallite size, surface area, particle size, powder density were determined and sintering behavior was analyzed in this work. The nanotitania powder prepared during ultrasonic induced hydrolysis (TiO 2-U) was determined to be formed from a mixture of anatase and brookite phases at 25°C. The brookite phase in nanotitania powder prepared without ultrasonic treatment (TiO 2-NoU) was detected at 70°C. The anatase-rutile phase transformation was completed in the 500-700°C range for both powders. The average crystallite sizes of the powders at 25°C were determined as 10 and 5nm for TiO 2-NoU and TiO 2-U, respectively. The surface area decreased from 238 to106m 2/g for TiO 2-NoU and from 287 to 82m 2/g for TiO 2-U when the calcination temperature was increased from 200 to 500°C. The evolution of the N 2 adsorption-desorption behavior with calcination temperature and the corresponding pore size distributions/volumes was attributed to the formation of closely packed submicron aggregates during powder synthesis and calcination. The sintering behavior was concluded to be controlled by 7-10nm crystallites and the submicron aggregates. The determination of the densification behavior of titania powders prepared by different methods with various levels of dopants may prove to be very useful for a better understanding of the phase/pore structure evolution which is crucial for a significant number of applications.