Investigating the Impacts of Sea Level Rise-induced High Groundwater Table on Florida Flexible Pavement Structural Performance

This thesis evaluates the impacts of sea-level rise-induced high groundwater table on the structural performance of typical Florida interstate, arterial, and local flexible pavements. Pavement longevity was determined under rising groundwater table level conditions using two analytical methods; the mechanistic-empirical (ME) analysis software and the current Florida empirical analysis practice. Moreover, ABAQUS and KENLAYER software were utilized to analyze the impacts of stress-dependent material nonlinearity on pavement structural performance. Analysis results estimated that the pavement service life in Florida was reduced by as much as 77 percent with the effects of rising groundwater levels. The empirical method predicted higher rates of pavement deterioration than the ME method. The predominant pavement failure mode was found to be rutting, and higher class roads (interstate and arterial) were found to face more structural capacity loss than local roads. The effects of nonlinear material behavior were found to be insignificant

EFFECTS OF PH ON AGGLOMERATION STATE OF Al2O3 – ZrO2 (ZTA) NANOCOMPOSITE POWDERS SYNTHESIZED BY TARTARIC GEL METHOD

Alumina – 20 vol% zirconia (ZTA) nanocomposites were synthesized by the tartaric acid sol-gel method. The precursors gelled from solutions at different pH were prepared and then calcined from 1000 to 1500°C. Surface area measurement (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the synthesized powders. Control of agglomeration state was carried out by changing the pH of the solution. Weakly agglomerated powders were obtained at pH=6, whereas the solution at pH=1 revealed hard agglomerated powders, (agglomeration degrees, N, were found to be 16425 at pH=1 and 102 at pH=6, respectively). The pH dependence of agglomeration was explained by the dissociation behavior of tartaric acid at various pH environments. XRD results showed that the powders have been fully tetragonal phase at 1000°C, while they exhibited tetragonal zirconia with minor monoclinic phase as well as a-Al2O3 at 1500°C. The presence of a-Al2O3 in the nanocrystalline composite contributes the wide range of temperature stability for t-ZrO2 up to 1500°C. TEM micrograph confirmed that alumina and zirconia were dispersed homogenously. Mechanical properties (hardness and indentation fracture toughness) of sintered samples were also determined

The physical properties of bismuth replacement in lead halogen perovskite solar cells: CH3NH3Pb1-xBixI3 compounds by ab-initio calculations

WOS: 000476618700167The selection of elements used in the design of solar cells is crucial in terms of environmental pollution and legalization problems due to the fact that both solar energy conversion efficiency as high as possible and toxic effects when dissolved in water. Hybrid Pb halogen solar cells demonstrate promising solar cell conversion material properties with a conversion rate of approximately 20%. However, Pb is a toxic element when dissolved in water. In this study, it was aimed to design new material forms for solar cells obtained by replacing Pb with a less toxic element without disrupting the photophysical properties of the material. This approach has been exemplified by focusing on bismuth considering Goldschmidt rules (GRs), Tolerance factor concept (t) and Shockley Queisser (SQ) limits. Non-stoichiometric CH3NH3Pb(1-x)Bi(x)I3 crystal structure were formed at the ratios determined by x = 0.125, 0.25, 0.75 and 1.00 values by replacing Bi3+ with Pb2+. Using the Density Functional Theory (DFT), the effect of added Bismuth ions in the structural and electronic properties of the material was investigated. According to the Shockley Quisser (SQ) limit, the crystal form CH3NH3Pb0.875Bi0.125I3 formed with x= 0.125 ratio was determined to be the most suitable structure in terms of solar cell productivity with a direct band gap of 1.30 eV. In addition, the band gaps of CH3NH3Pb0.500Bi0.500I3 and CH3NH3Pb0.250Bi0.750I3 formed at x= 0.50 and 0.75 were calculated to be 1.0863 eV and 1.0895 eV, respectively. Band gaps of these phases were also within the SQ limit. However, the band gap of the CH3NH3PbI3 stoichiometric phase was calculated to be 1.6826 eV above the SQ limit, while the CH3NH3BiI3 phase band gap was calculated to be 0.2738 eV well below the SQ limit. According to our DFT calculations, organic halogen perovskite compounds in the form of CH3NH3Pb(1-x)Bi(x)I3 formed at ratios of x = 0.125, 0.50 and 0.75 have been found to be more efficient than CH3NH3PbI3 compounds in terms of solar energy conversion capacity, optoelectronic systems and environmental safety.TUBITAK (The Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116F073]This work was supported by TUBITAK (The Scientific and Technological Research Council of Turkey) through project number 116F073. Computations are carried out on TUBITAK-ULAKBIM clusters. Authors would like to thank the institution and agency in carrying out this work

Myositic Type of Idiopathic Orbital Pseudotumor in a 4-Year-Old Child: A Case Report

Idiopathic orbital pseudotumor is a benign, noninfectious, and nonneoplastic disease with unknown cause. It is the third most common orbital disease after thyroid orbitopathy and lymphoproliferative disorder. Idiopathic orbital pseudotumor is extremely rare in pediatric age group and may cause real diagnostic problems. This paper describes a 4-year-old girl who presented with sudden ptosis in the right eye and swollen eyelid. She recovered completely with high-dose steroid therapy. We report clinical and magnetic resonance imaging findings of orbital myositis, which is a rare subtype of idiopathic orbital pseudotumor in children and needs to be differentiated from other orbital disease especially malignancy

On the formation history of Galactic double neutron stars

Double neutron stars (DNSs) have been observed as Galactic radio pulsars, and the recent discovery of gravitational waves from the DN merger GW170817 adds to the known DNS population. We perform rapi population synthesis of massive binary stars and discuss mode predictions, including DNS formation rates, mass distributions, an delay time distributions. We vary assumptions and parameters of physica processes such as mass transfer stability criteria, supernova natal kic distributions, remnant mass prescriptions, and common-envelop eccentricity distribution of the Galactic DNS population under each o our population synthesis models, allowing us to quantitatively compar burning secondary (case BB) on to a neutron star is most likel dynamically stable. We also find that a natal kick distribution compose of both low (Maxwellian σ =30 km s^{-1}) and high (σ =265 km s^{-1} components is preferred over a single high-kick component. We conclud that the observed DNS mass distribution can place strong constraints o model assumption