Endüstri Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12469/48

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Citation - WoS: 11
Citation - Scopus: 11
Application of Epidemic Models To Phase Transitions
(Taylor & Francis Ltd, 2012) Bilge, Ayşe Hümeyra; Pekcan, Önder; Gürol, M. V.
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 value S-0 close to 1 to a final value S-f, while the ratio of recovered individuals rise from 0 to R-f = 1 - S-f. The sharp passage from the level zero to the level R-f allows also the modeling of phase transitions by the number of "recovered" individuals R(t) of the SIR or SEIR model. In this article, we model the sol-gel transition for polyacrylamide-sodium alginate (SA) composite with different concentrations of SA as SIR and SEIR dynamical systems by solving the corresponding differential equations numerically and we show that the phase transitions of "classical" and "percolation" types are represented, respectively, by the SEIR and SIR models.
Chebyshev Nets Formed by Ricci Curves in a 3-Dimensional Weyl Space
(Elsevier Science Bv, 2005) Yıldırım, Gülçin Çivi; Özdeğer, Abdülkadir
In this paper Ricci curves in a 3-dimensional Weyl space W-3(g T) are defined and it is shown that any 3-dimensional Chebyshev net formed by the three families of Ricci curves in a W-3(g T) having a definite metric and Ricci tensors is either a geodesic net or it consists of a geodesic subnet the members of which have vanishing second curvatures. In the case of in indefinite Ricci tensor only one of the members of the geodesic subnet under consideration has a vanishing second curvature. (c) 2004 Elsevier B.V. All rights reserved.
Chelate Extraction of Transition Metal Ions by Ethylene Diamine Diacetic Acid With N-Substituted Octadecyl Groups
(Taylor & Francis Inc, 2002) Bıçak, Niyazi; Şungur, Şana Kutun; Tan, Nükhet; Gazi, Mustafa
An organic-soluble chelating agent NN'-di-n-octadecyl ethylenediamine-NN'-diacetic acid (DOED) has been synthesized in two steps by (i) condensation of dibromoethane with 1-amino octadecane (octadecylamine) and (ii) subsequent reaction with sodium chloro acetate in alcohol-water mixture. The chelating agent in 2-ethylhexanol-cyclohexanol (1:1) solutions shows extremely high chelating ability for Ni(II) Co(II) Cu(II) Fe(111) Cr(III) and Cd(II) ions in neutral aqueous solutions. Extractions take place by the formation of (1:1) ligand-to-metal complexes and extraction coefficients are in the range 0.74-0.99. The ligand can be regenerated almost quantitatively by washing its complexes with 1M HCl and 0.2 M NaOH solutions successively. In each extraction step the organic solution exhibits a clear-cut phase separation and does not need salting out. The chelating agent can be regenerated and recycled more than 24 times without losing its extracting ability due to nonhydrolyzability of linkages in its structure. Experiments indicate that in high metal concentrations (more than 1 M) the solvent mixture itself is able to extract appreciable amounts of metal ions (33-53%). The solubility in organic solvents induced by long aliphatic chains seems to be general and the method presented offers possibility of large scale chelate extraction of metal ions of relatively low concentrations.
Citation - WoS: 2
Citation - Scopus: 2
Determination of Epidemic Parameters From Early Phase Fatality Data: a Case Study of the 2009 A(h1n1) Pandemic in Europe
(World Scientific Publ Co Pte Ltd, 2018) Bilge, Ayşe Hümeyra; Samanlıoğlu, Funda
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 fatality data of the 2009 fall wave cycle of the A(H1N1) pandemic in 12 European countries. It is observed that the best estimates of the basic reproduction number R-0 and the mean duration of the infection period 1/eta lie on a curve in the scatterplots indicating the existence of a nearly-invariant quantity which corresponds to the duration of the epidemic. Spline interpolation applied to the early phase of the epidemic an approximately 10-week period together with a future control point in the stabilization region is sufficient to estimate model parameters. The SIR model is run over a wide range of parameters and estimates of R0 in the range 1.2-2.0 match the values in the literature. The duration of the infection period 1/eta is estimated to be in the range 2.0-7.0 days. Longer infection periods are tied to spatial characteristics of the spread of the epidemic.
Citation - WoS: 5
Citation - Scopus: 5
Epidemic Models for Phase Transitions: Application To a Physical Gel
(Taylor & Francis Ltd, 2017) Bilge, Ayşe Hümeyra; Pekcan, Önder; Kara, Selim; Öğrenci, Arif Selçuk
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 of carrageenan-water system as a representative of reversible physical gels in terms of a modified Susceptible-Infected-Susceptible epidemic model as opposed to the Susceptible-Infected-Removed model used to represent the (irreversible) chemical gel formation in the previous work. We locate the gel point T-c of sol-gel and gel-sol transitions and we find that for the sol-gel transition (cooling) T-c > T-sg (transition temperature) i.e. T-c is earlier in time for all carrageenan contents and moves forward in time and gets closer to T-sg as the carrageenan content increases. For the gel-sol transition (heating) T-c is relatively closer to T-gs
Citation - WoS: 5
Citation - Scopus: 9
Managing Fuel Coal Supply Chains With Multiple Objectives and Multimode Transportation
(AMER SOC ENGINEERING MANAGEMENT, 2013) Yücekaya, Ahmet; Yücekaya, Ahmet
Power companies require sophisticated tools to manage fuel-coal supply chains which include multiple suppliers coal contracts and multimode transportation routes. In this article a multi-objective model which is integrated with multi-attribute decision-making for the selection of suppliers transportation routes and coal orders is developed. The model simultaneously optimizes multiple objectives such as minimizing purchase costs transportation costs and ash output and it also presents a decision framework on the selection of suppliers transportation routes and coal products that will achieve these objectives. The network and capacity constraints of suppliers and transportation routes are included in the model. The study utilizes multi-objective linear programming and well-known decision rules such as minimax maximin and compromise programming and Analytic Hierarchy Process is employed to determine preferred solutions. The methodology for the solution is illustrated via a case study and an alternative evaluation process is presented. The study demonstrates that the model can be used by power companies to find desired solutions as it provides an opportunity for the inclusion of the preferences of decision-makers and adjustments of the weights for each objective.
Citation - WoS: 15
Citation - Scopus: 21
A Multi-Objective Stochastic Model for an Earthquake Relief Network
(Wiley-Hindawi, 2020) Yenice, Zeren D.; Samanlıoğlu, Funda
Earthquake relief network involves storage and distribution of relief aid to people in need. In this paper, a new stochastic multi-objective mixed integer mathematical model is developed and implemented in Kadikoy municipality of Istanbul, Turkey in order to configure part of the earthquake relief network. The aim of the model is to help decision makers decide on the locations of storage areas for shelters pre-earthquake and distribution of shelters from these areas to temporary shelter areas post-earthquake while minimizing earthquake scenario-specific total expected distribution distance, total expected earthquake damage risk factor of storage areas and expected total penalty cost related to unsatisfied demand at temporary shelter areas, simultaneously. In the model, storage area capacity and coverage distance restrictions are taken into consideration. The data related to potential storage areas and shelter locations were obtained from Kadikoy municipality of Istanbul and Istanbul Metropolitan Municipality (IMM). The earthquake damage risk factors were determined based on possible earthquake scenarios given in Japan International Cooperation Agency's (JICA) report. Four event scenarios with two different earthquake scenario likelihoods were considered and sample efficient solutions from the Pareto frontier were obtained implementing the normalized (scaled) weighted sum method.
Citation - WoS: 26
Citation - Scopus: 30
Nutrient Dynamics in Flooded Wetlands. I: Model Development
(ASCE-AMER SOC CIVIL ENGINEERS, 2013) Hantush, Mohamed M.; Kalın, Latif; Işık, Sabahattin; Yücekaya, Ahmet
Wetlands are rich ecosystems recognized for ameliorating floods improving water quality and providing other ecosystem benefits. This part of a two-paper series presents a relatively detailed process-based model for nitrogen and phosphorus retention cycling and removal in flooded wetlands. The model captures salient features of nutrient dynamics and accounts for complex interactions among various physical biogeochemical and physiological processes. The model simulates oxygen dynamics and the impact of oxidizing and reducing conditions on nitrogen transformation and removal and approximates phosphorus precipitation and releases into soluble forms under aerobic and anaerobic conditions respectively. Nitrogen loss pathways of volatilization and denitrification are explicitly accounted for on a physical basis. Processes in surface water and the bottom-active soil layer are described by a system of coupled ordinary differential equations. A finite-difference numerical scheme is implemented to solve the coupled system of ordinary differential equations for various multiphase constituents' concentrations in the water column and wetland soil. The numerical solution algorithm is verified against analytical solutions obtained for simplified transport and fate scenarios. Quantitative global sensitivity analysis revealed consistent model performance with respect to critical parameters and dominant nutrient processes. A hypothetical phosphorus loading scenario shows that the model is capable of capturing the phenomenon of phosphorus precipitation and release under oxic and anoxic conditions respectively.
Citation - WoS: 9
Citation - Scopus: 11
Nutrient Dynamics in Flooded Wetlands. Ii: Model Application
(ASCE-AMER SOC CIVIL ENGINEERS, 2013) Kalın, Latif; Hantush, Mohamed M.; Işık, Sabahattin; Yücekaya, Ahmet; Jordan, T.
In this paper the authors applied and evaluated the wetland nutrient model that was described in Paper I. Hydrologic and water quality data from a small restored wetland located on Kent Island Maryland which is part of the Delmarva Peninsula on the eastern shores of the Chesapeake Bay was used for this purpose. The model was assessed through various methods against the observed data in simulating nitrogen (N) phosphorus (P) and total suspended sediment (TSS) dynamics. Time series plots of observed and simulated concentrations and loads generally compared well
Citation - WoS: 22
Citation - Scopus: 22
Selective Liquid-Liquid Extraction of Mercuric Ions by Octyl Methane Sulfonamide
(Marcel Dekker Inc, 2003) Bıçak, Niyazi; Sungur, Sana; Gazi, Mustafa; Tan, Nükhet
N-octyl methane sulfonamide (OMSA) has been demonstrated to be a very efficient reagent for selective extraction of Hg(II) ions from aqueous solutions. The extraction bases on rapid reaction of OMSA with Hg(II) ions yielding mono and disulfonamido mercury compounds in ordinary conditions. Solubility of OMSA and its mercury compounds in 2-ethyl hexanol provide a clear-cut phase separation in the extraction. The solution of OMSA in 2-ethyl hexanol (0.4 mol L-1) is able to extract 82.2% of mercuric-acetate (0.4 mol L-1) in non-buffered conditions. Although the process depends on the nature of accompanying anions the distribution coefficient is reasonably high (k(d) greater than or equal to 1.27) even in the presence of chloride ions. The extraction is strictly selective and the presence of Cd(II) Zn(II) Pb(II) do not bring any interference. The extraction system works in moderate concentrations. Extracted mercury in the organic phase can be recovered by back-extraction with concentrated HCl or H2SO4 solutions. After acid treatment the organic solution of OMSA becomes regenerated without losing its activity due to reasonable hydrolytic stability of the sulfonamide linkage and it can be recycled for further extractions.

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