Browsing Fakülteler by Author "Bilge, Ayşe Hümeyra"
Now showing items 1-20 of 26
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(3+3+2) warped-like product manifolds with Spin(7) holonomy
Uğuz, Selman; Bilge, Ayşe Hümeyra (Elsevier Science Bv, 2011)We consider a generalization of eight-dimensional multiply warped product manifolds as a special warped product by allowing the fiber metric to be non-block diagonal. We define this special warped product as a (3 + 3 + 2) ... -
An analysis of price spikes and deviations in the deregulated Turkish power market
Gayretli, Gizem; Yücekaya, Ahmet; Bilge, Ayşe Hümeyra (Elsevier, 2019)The successful operation of a real time market is related to the planning in the day ahead market. We analyze the day ahead and real time market data for the Turkish power market for the period 2012-2015 to classify price ... -
Application of epidemic models to phase transitions
Bilge, Ayşe Hümeyra; Pekcan, Önder; Gürol, M. V. (Taylor & Francis Ltd, 2012)The Susceptible-Infected-Recovered (SIR) and Susceptible-Exposed-Infected-Recovered (SEIR) models describe the spread of epidemics in a society. In the typical case, the ratio of the susceptible individuals fall from a ... -
Canonical forms for families of anti-commuting diagonalizable linear operators
Kumbasar, Yalcin; Bilge, Ayşe Hümeyra (Elsevier Science Inc, 2012)It is well known that a commuting family of diagonalizable linear operators on a finite dimensional vector space is simultaneously diagonalizable. In this paper we consider a family A = {A(a)} A(a) : V -> V a = 1... N of ... -
The critical point of a sigmoidal curve
Bilge, Ayşe Hümeyra; Özdemir, Yunus (Babeș-Bolyai University, 2020)Let y(t) be a monotone increasing curve with lim(t ->+/-infinity) y((n))(t) = 0 for all n and let t(n) be the location of the global extremum of the nth derivative y((n))(t). Under certain assumptions on the Fourier and ... -
Determination of epidemic parameters from early phase fatality data: A case study of the 2009 A(H1N1) pandemic in Europe
Bilge, Ayşe Hümeyra; Samanlıoğlu, Funda (World Scientific Publ Co Pte Ltd, 2018)This paper demonstrates that the susceptible-infected-removed (SIR) model applied to the early phase of an epidemic can be used to determine epidemic parameters reliably. As a case study the SIR model is applied to the ... -
Epidemic models for phase transitions: application to a physical gel
Bilge, Ayşe Hümeyra; Pekcan, Önder; Kara, Selim; Öğrenci, Arif Selçuk (Taylor & Francis Ltd, 2017)Carrageenan gels are characterized by reversible sol-gel and gel-sol transitions under cooling and heating processes and these transitions are approximated by generalized logistic growth curves. We express the transitions ... -
An equivalence class decomposition of finite metric spaces via Gromov products
Bilge, Ayşe Hümeyra; Çelik, Derya; Koçak, Şahin (Elsevier Science Bv, 2017)Let (X, d) be a finite metric space with elements P-i, i = 1,..., n and with the distance functions d(ij) The Gromov Product of the "triangle" (P-i, P-j, P-k) with vertices P-t, P-j and P-k at the vertex Pi is defined by ... -
Forecasting electricity demand for Turkey: Modeling periodic variations and demand segregation
Yükseltan, Ergün; Yücekaya, Ahmet; Bilge, Ayşe Hümeyra (Elsevier, 2017)In deregulated electricity markets the independent system operator (ISO) oversees the power system and manages the supply and demand balancing process. In a typical day the ISO announces the electricity demand forecast for ... -
Forecasting Models For Daily Natural Gas Consumption Considering Periodic Variations And Demand Segregation
Yükseltan, Ergün; Yücekaya, Ahmet; Bilge, Ayşe Hümeyra; Ağca Aktunç, Esra (Elsevier Ltd, 2020)Due to expensive infrastructure and the difficulties in storage, supply conditions of natural gas are different from those of other traditional energy sources like petroleum or coal. To overcome these challenges, supplier ... -
'Level grading' a new graded algebra structure on differential polynomials: application to the classification of scalar evolution equations
Mizrahi, Eti; Bilge, Ayşe Hümeyra (IOP Publishing Ltd, 2013)We define a new grading which we call the 'level grading' on the algebra of polynomials generated by the derivatives u(k+i) over the ring K-(k) of C-infinity functions of x t u u(1) ... u(k) where . This grading has the ... -
Managing natural gas demand for free consumers under uncertainty and limited storage capacity
Aktunç, Esra Ağca; Yükseltan, Ergün; Yücekaya, Ahmet; Bilge, Ayşe Hümeyra (Elsevier, 2020)Demand for energy sources depends on several factors such as population growth, urbanization, industrialization, and climate. Among fundamental energy sources, natural gas is characterized by storage limitations and ... -
A mathematical characterization of the gel point in sol-gel transition
Bilge, Ayşe Hümeyra; Pekcan, Önder (IOP Publishing Ltd, 2015)We model the sol-gel transition in terms of Susceptible-Infected-Removed (SIR) and Susceptible-Exposed-Infected-Removed (SEIR) models and compare with experimental results. We show, numerically, that the "gel point" described ... -
Mathematical Characterization of Thermo-reversible Phase Transitions of Agarose Gels
Öğrenci, Arif Selçuk; Pekcan, Önder; Kara, Selim; Bilge, Ayşe Hümeyra (Taylor & Francis Inc, 2018)The thermal phase transition temperatures of high (HMP) and low melting point (LMP) agarose gels were investigated by using UV-vis spectroscopy techniques. Transmitted light intensities from the gel samples with different ... -
A MATHEMATICAL DESCRIPTION OF THE CRITICAL POINT IN PHASE TRANSITIONS
Bilge, Ayşe Hümeyra; Pekcan, Önder (World Scientific Publ Co Pte Ltd, 2013)Let y(x) be a smooth sigmoidal curve, y((n)) be its nth derivative and {x(m,i)} and {x(a,i)}, i = 1, 2, ... , be the set of points where respectively the derivatives of odd and even order reach their extreme values. We ... -
Mathematical models for phase transitions in biogels
Bilge, Ayşe Hümeyra; Öğrenci, Arif Selçuk; Pekcan, Önder (World Scientific Publ Co Pte Ltd, 2019)It has been shown that reversible and irreversible phase transitions of biogels can be represented by epidemic models. The irreversible chemical sol-gel transitions are modeled by the Susceptible-Exposed-Infected-Removed ... -
Maximal linear subspaces of strong self-dual 2-forms and the Bonan 4-form
Bilge, Ayşe Hümeyra; Dereli, Tekin; Koçak, Şahin (Elsevier Science Inc, 2011)The notion of self-duality of 2-forms in 4-dimensions plays an eminent role in many areas of mathematics and physics, but although the 2-forms have a genuine meaning related to curvature and gauge-field-strength in higher ... -
Modeling of Wind Effects on Stratified Flows in Open Channels: A Model for the Istanbul Strait (Bosphorus)
Stratified flows in open channels arise as a result of density or surface level differences. If the channel is connected to a basin at one or both ends, strong winds originating from the basin cause the "wind setup" effect ... -
On the Classification of Fifth Order Quasi-linear Non-constant Separant Scalar Evolution Equations of the KdV-Type
Özkum, Gülcan; Bilge, Ayşe Hümeyra (Physical Soc Japan, 2012)Fifth order, quasi-linear, non-constant separant evolution equations are of the form u(t) = A(partial derivative(5)u/partial derivative x(5)) + (B) over tilde, where A and (B) over tilde are functions of x, t, u and of the ... -
On the classification of scalar evolution equations with non-constant separant
Bilge, Ayşe Hümeyra; Mizrahi, Eti (IOP Publishing Ltd, 2017)The ` separant' of the evolution equation u(t) = F where F is some differentiable function of the derivatives of u up to order m is the partial derivative partial derivative F/partial derivative u(m) where um u(m) = partial ...