WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 53Citation - Scopus: 63Effective Stress Principle for Saturated Fractured Porous Media(Wiley-Blackwell, 1995) Tuncay, Kağan; Çorapçıoğlu, M. YavuzAn effective stress principle for saturated fractured porous media is proposed based On the double-porosity representation. Both the solid grains and the fractured porous medium are assumed to be linearly elastic materials. The derivation employs volume averaging technique to obtain macroscopic scale expressions. Two parameters, the bulk modulus of the fractured medium and bulk modulus of the porous matrix, are introduced in the formulation. The final expression reduces to the one obtained by Blot and Willis [1957], Skempton [1960], Nur and Byeerle [1971], and Verruijt [1984] when the volume fraction of the fractures vanishes, that is, for a nonfractured porous medium.Article Citation - WoS: 8Hydrogen Sulfide Determination by Solid Surface Luminescence(Springer Verlag, 1996) Eroğlu, Ahmet Emin; Volkan, Mürvet; Bayramlı, Erdal; Ataman, O. Yavuz; Mark, Harry B.In the analytical system suggested, atmospheric hydrogen sulfide reacts with the surface of a filter paper treated with aqueous cadmium chloride and yields a luminescent species whose intensity can be correlated with the analyte concentration in ambient air. It was shown that the luminescent species are CdS solid particles which were formed in a well defined size. The paper luminescence was also tried on polymeric surfaces; polyethyleneoxide, polyvinyl alcohol, ethylcellulose and carboxymethylcellulose were found to give a similar luminescence signal. The system can be used on the tip of an optical fiber for an irreversible, cumulative type of analytical device for hydrogen sulfide determination. The 3s detection limit for the paper luminescence detection system was 7.8 ppb H2S.Article Citation - WoS: 36Citation - Scopus: 47Perceptions of Process Quality in Building Projects(American Society of Civil Engineers (ASCE), 1999) Arditi, David; Günaydın, Hüsnü MuratA Delphi process and a questionnaire survey are conducted to investigate the differences in the perceptions of entry-level professionals and long-time practitioners with regard to process quality in building projects. The factors that affect process quality in the three phases (design, construction, and operation) of a building project's life cycle are identified and ranked by the respondents' perceived degree of importance. The findings indicate that the perceptions of entry-level professionals and long-time practitioners are in agreement for most (74%) of the factors. Given the differences in the respondents' background, expectations, and experience, differences in perceptions are to be expected in the remaining 26% of the factors. Analyzing these differences helps in revising and improving existing training courses and academic programs. It is recommended that college programs include courses that treat the administrative aspects involved in the building project in great detail and that continuing education programs cover quality training and life cycle cost analysis.Article Citation - WoS: 18Citation - Scopus: 22Application of Inverse Gas Chromatography To the Measurement of Diffusion and Phase Equilibria in Polyacrylate-Solvent Systems(Elsevier Ltd., 1999) Tıhmınlıoğlu, Funda; Danner, Ronald P.The inverse gas chromatography technique (IGC) was used to determine the partition and diffusion coefficients of ethyl acetate and 2-ethylhexyl acrylate in polyacrylate for both infinite dilution and finite concentrations of solvent. Experiments were performed over a temperature range of 60 to 100°C, more than 100°C above the glass transition temperature of the polymer. The capillary column IGC model previously developed for determining partition and diffusion coefficients of infinitely dilute solvent has been modified to account for the concentration of the solvent in the polymer phase. Thermodynamic data obtained from retention theory and the modified capillary column IGC model are comparedArticle Citation - WoS: 200Citation - Scopus: 212Predominantly Superconducting Origin of Large Energy Gaps in Underdoped Bi2sr2cacu2o8+? From Tunneling Spectroscopy(American Physical Society, 1999) Miyakawa, Nobuaki; Zasadzinski, John F.; Özyüzer, Lütfi; Guptasarma, Prasenjit; Hinks, David G.; Kendziora, Christopher A.; Gray, Kenneth E.New tunneling data are reported in Bi2Sr2CaCu2O8+δ which show quasiparticle excitation gaps, Δ, reaching values as high as 60 meV for underdoped crystals with Tc = 70 K. These energy gaps are nearly 3 times larger than those of overdoped crystals with similar Tc. Despite the large differences in gap magnitude, the tunneling spectra display qualitatively similar characteristics over the entire doping range. Detailed examination of the spectra, including the Josephson IcRn product measured in break junctions, indicates that these energy gaps are predominantly of superconducting origin.Article 1/Nc Expansion and Anomaly Cancellation in the Presence of Electroweak Interactions(IOP Publishing Ltd., 1998) Erdem, RecaiWe study the question of a consistent formulation of the 1/Nc expansion in the presence of electroweak interactions. We show that in some cases the previous formulation leads to an unrealistic picture. We improve the scheme. We derive the corresponding hypercharge and electric charge values of fermions under the requirement that the standard model in the large-Nc limit should be free of chiral gauge anomalies. We find that the resulting hypercharge and the electric charge values for quarks are the same as for the standard model.Article Citation - WoS: 12Citation - Scopus: 17Dynamics of Water Vapor Adsorption on Humidity-Indicating Silica Gel(Elsevier Ltd., 1998) Balköse, Devrim; Ulutan, Sevgi; Çakıcıoğlu Özkan, Seher Fehime; Çelebi, Sedat; Ülkü, SemraWell-defined CoCl2-containing silica gels were prepared by impregnation of the aqueous solution of the salt to silica hydrogel, drying and aging methods. Silica gels having 392-437 m2 g-1 surface area and 0.21-0.37 cm3 g-1 pore volume and having an average particle size of 3 mm were obtained. Aging in CoCl2 solutions decreased the surface area of silica gels from 540 cm2 g-1 to 392-430 m2 g-1 and pore volume from 0.27 to 0.21-0.23 cm3 g-1 for CoCl2 concentration smaller than 0.28 mol dm-3 in silica gel. Adsorbed water desorbed from the gels absorbing 1917-2555 J g-1 energy as determined by differential scanning calorimetry. The CoCl2-containing gels were successfully used in dynamic column experiments, with linear relation between velocities of inlet air and movement of blue to pink boundary. The colour change also makes the detection of the defects in column filling which causes air channellingArticle Citation - WoS: 8Citation - Scopus: 9Calculation of the Wavelength Filter Properties of the Fiber-Slab Waveguide Structure Using Vector Mode Expansion(Institute of Electrical and Electronics Engineers Inc., 1998) Dinleyici, Mehmet Salih; Patterson, David B.A vectorial solution technique is applied to investigate the dispersion characteristics of the ridge modes of a waveguide structure comprising a slab and optical fiber. The power transmission characteristics of the device with respect to wavelength are calculated under various device parameters, such as slab index and fiber-slab separation. We discuss the effects of such parameters on the bandwidth and rejection of the notch filter produced by this structure.Article Citation - WoS: 12Citation - Scopus: 12Oil Mound Spreading and Migration With Ambient Groundwater Flow in Coarse Porous Media(John Wiley and Sons Inc., 1996) Çorapçıoplu, M. Yavuz; Tuncay, Kağan; Ceylan, B. KağanWhen a light, immiscible oil leaks above an unconfined aquifer, it spreads and forms a floating mound on the table. The oil mound migrates in the direction of ambient ground flow. In this study we present a governing equation for the migrating mound thickness by averaging the oil phase mass balance equation. Analytical and numerical solutions to an advective- dispersive type equation are presented to estimate the temporal and spatial distribution of the migrating oil mound thickness for two problems of practical importance: formation, spreading, and migration of an oil mound on the table and spreading and migration of an established layer of oil with ambient ground flow. The model results compare favorably with test data obtained by laboratory flume experiments. Although the model has some simplifying assumptions such as the absence of capillary pressure gradients, sharp saturation changes across the phase interfaces, and single mobile phase (i.e., oil flow only), it can be useful as a screening or site assessment tool because of its relative simplicity.Article Citation - WoS: 5Citation - Scopus: 4Prolactin Receptor Expression by Splenocytes From Rats in Various Hormonal States(John Wiley and Sons Inc., 1997) Güneş, Hatice; Zawilla, S.; Mastro, Andrea M.Prolactin (PRL) is mitogenic for lymphocytes in vitro, but the responsiveness of lymphocytes depends on the in vivo hormonal status of the rats from which the cells were obtained. Lymphocytes from ovariectomized (OVX) rats, but not from rats in oestrus or from male rats, respond to prolactin; administration of oestradiol to OVX rats diminishes the response. In order to determine if a correlation exists between lymphocyte responsiveness to prolactin and levels of cell surface prolactin receptors (PRL-R) expression, the percentage of splenocytes and each splenocyte subpopulation expressing surface PRL-R from rats of various hormonal states (OVX, oestradiol-injected OVX, oestrus and male) was analysed by single-colour and dual-colour flow cytometric analysis. We found that approximately 20% of splenocytes expressed surface PRL-R regardless of hormonal states (n = 16). The majority (85%) of PRL-R positive splenocytes were B lymphocytes whereas 11.1% and 4.8% of splenocytes expressing the PRL-R were CD4 positive T-helper (TH) and CD8 positive T-cytotoxic (TC) lymphocytes, respectively. B lymphocytes also stained more brightly than T lymphocytes. This distribution of PRL-R expression did not show significant alterations on total splenocytes or TH and TC lymphocytes during various hormonal stages. However, the percentage of PRL-R-positive B lymphocytes increased markedly in OVX rats (twofold), compared to rats at oestrus. In summary, no correlation was found between the responsiveness to prolactin as a mitogen and levels of PRL-R expression by lymphocytes from rats at different hormonal states. This result suggests that sex steroid hormones may control prolactin responsiveness of lymphocytes by affecting the signal transduction pathway through PRL-R rather than by altering the level of the cell surface receptor expression.