Time filter

Source Type

Dincer H.,stanbul Technical University | Mert H.,Hitit University | Caliskan E.,Hitit University | Atmaca G.Y.,Yildiz Technical University | Erdomus A.,Yildiz Technical University
Journal of Molecular Structure | Year: 2015

Synthesis and characterization of poly(ethylene glycol) conjugated symmetrical and asymmetrical zinc phthalocyanines (ZnPcs) is described. Copper (I) catalyzed azide-alkyne cycloaddition (CuAAC) click reaction between azide functional methoxypoly(ethylene glycol) (mPEG-N3) and tetra terminal alkynyl substituted ZnPc yields star polymer with ZnPc core. Furthermore, CuAAC click reaction between asymmetrically terminal alkynyl substituted zinc phthalocyanine (aZnPc) and mPEG-N3 yields aZnPc end functionalized PEG. Spectral, photophysical (fluorescence quantum yield), photochemical (singlet oxygen (ΦΔ), and photodegradation quantum yield (Φd) properties of the symmetrically, and asymmetrically PEGylated ZnPcs are investigated to be used as sensitizers in photodynamic therapy (PDT). The quantum yield values of fluorescence (ΦF) and singlet oxygen generation (ΦΔ) for water soluble symmetrically PEGylated ZnPc in aqueous solution are calculated as 0.01 and 0.14 respectively, suggesting its potential as photosensitizer in PDT treatment. © 2015 Elsevier B.V. Source

Kaya H.,Yildiz Technical University | Kahraman C.,stanbul Technical University
Expert Systems with Applications | Year: 2011

Process performance can be analyzed by using process capability indices (PCIs), which are summary statistics to depict the process location and dispersion successfully. Traditional PCIs are generally used for a process which has a symmetric tolerance when the target value (T) locates on the midpoint of the specification interval (m). When this is not the case (T ≠ m), there are serious disadvantages in the casual use and interpretation of traditional PCIs. To overcome these problems, PCIs with asymmetric tolerances have been developed and applied successfully. Although PCIs are very usable statistics, they have some limitations which prevent a deep and flexible analysis because of the crisp definitions for specification limits (SLs), mean, and variance. In this paper, the fuzzy set theory is used to add more information and flexibility to PCIs with asymmetric tolerances. For this aim, fuzzy process mean, μ̃ and fuzzy variance, σ̃2, which are obtained by using the fuzzy extension principle, are used together with fuzzy specification limits (SLs) and target value (T) to produce fuzzy PCIs with asymmetric tolerances. The fuzzy formulations of the indices Cpk″,Cpm,Cpmk″, which are the most used PCIs with asymmetric tolerances, are developed. Then a real case application from an automotive company is given. The results show that fuzzy estimations of PCIs with asymmetric tolerances include more information and flexibility to evaluate the process performance when it is compared with the crisp case. © 2011 Elsevier Ltd. All rights reserved. Source

Yasar E.,Uludag University | Ozer T.,stanbul Technical University
International Journal of Non-Linear Mechanics | Year: 2011

This study deals with symmetry group properties and conservation laws of the foam-drainage equation. Firstly, we study the classical Lie symmetries, optimal systems, similarity reductions and similarity solutions of the foam-drainage equation which are obtained through the Lie group method of infinitesimal transformations. Secondly, using the new general theorem on non-local conservation laws and partial Lagrangian approach, local and non-local conservation laws are also studied and, finally, non-classical symmetries are derived. © 2010 Elsevier Ltd. All rights reserved. Source

The shallow-marine Eocene Soǧucak Limestone and Oligocene Ceylan Formation were studied in the northern and eastern parts of the Thrace Basin with detailed biometric analysis of the full spectrum of larger benthic foraminifera (mainly nummulitids and orthophragmines). This allows us to establish a high-resolution biostratigraphy in the context of the shallow benthic zonation (with SBZ zones) of the Tethyan Palaeogene since larger foraminiferal assemblages show a very strong Western Tethyan af nity Only two species (Heterostegina armenica and Orbitoclypeus haynesi) are unknown so far to the west of the Thrace Basin. The age of particular larger foraminiferal sites is determined based on (i) the occurrence and developmental stage of different species of Heterostegina (H. armenica hacimasliensis n. ssp. is introduced here), (ii) the presence/absence of giant Nummulites, (iii) the presence/absence of Spiroclypeus, (iv) the developmental stage of reticulate Nummulites, (v) the occurrence and developmental stage of orthophragmines, (vi) the occurrence of particular Operculina and radiate Nummulites. Six larger foraminiferal horizons could be established. They correspond to (i) the vicinity of the early/late Bartonian boundary (SBZ 17/18), (ii) the middle late Bartonian (SBZ 18B), (iii) the latest Bartonian (SBZ 18C), (iv) the early Priabonian (SBZ 19), (v) the late Priabonian (SBZ 20) and (vi) the early Rupelian (SBZ 21). Three main shallow-water depositional environments could be recognized in both the late Bartonian and Priabonian: two of them took place in the middle shelf; one with low and another with high water-energy (back-bank and Nummulites-bank facies) whereas the third one refers to the outer shelf (fore-bank facies). Biostratigraphical and palaeoenvironmental observations allow us to reconstruct three subregions in the northern and eastern parts of the Thrace Basin with different depositional histories: (i) The eastern part of the territory, with an İstanbul Zone basement was fooded at the beginning of the middle late Bartonian (SBZ 18B), but the carbonate platform was drowned in the latest Bartonian (SBZ 18C). (ii) The Çatalca block, lying on the Istranca Massif, formed a palaeohigh in whose peripheries a similar depositional history to for the former sub-region can be reconstructed, although the central part was transgressed only in the late Priabonian and was not drowned at all. (iii) The northern margin of the recent Thrace Basin (also lying on the Istranca Massif) was fooded only in the latest Bartonian (SBZ 18C) or in the early Priabonian (SBZ 19) and the Priabonian carbonate platform had only partly and shallowly been drowned. This subregion very probably formed the real northern margin of the whole Thrace Basin in the Palaeogene. © TÜBİTAK. Source

Turkay B.E.,stanbul Technical University | Telli A.Y.,stanbul Technical University
Renewable Energy | Year: 2011

A pilot region was selected and cost analysis of using renewable energy sources with a hydrogen system for that region's energy demand is introduced, in a techno-economic perspective, in this paper. The renewable energy potential for the region was evaluated by implementing energy cost analysis. The study also evaluates the feasibility of utilizing solar and wind energy with hydrogen as a storage unit to meet the electricity requirements of the pilot region as a standalone system and in conjunction with the conventional grid based electricity. In order to simulate the operation of the system and to calculate the technical and economic parameters, micropower optimization program Homer (NREL, US) was used in this study. Homer requires some input values, such as technological options, cost of components, and resource compliance; and then the program ranges the feasible system configurations according to the net present cost (system cost) by using these inputs. The pilot region in this study, where the renewable based energy will be used, is determined to be Electrics & Electronics Faculty, Istanbul Technical University. © 2010 Elsevier Ltd. Source

Discover hidden collaborations