Ant colony optimization approach to estimate energy demand of Turkey

This paper attempts to shed light on the determinants of energy demand in Turkey. Energy demand model is first proposed using the ant colony optimization (ACO) approach. It is multi-agent systems in which the behavior of each ant is inspired by the foraging behavior of real ants to solve optimization problem. ACO energy demand estimation (ACOEDE) model is developed using population, gross domestic product (GDP), import and export. All equations proposed here are linear and quadratic. Quadratic_ACOEDE provided better-fit solution due to fluctuations of the economic indicators. The ACOEDE model plans the energy demand of Turkey until 2025 according to three scenarios. The relative estimation errors of the ACOEDE model are the lowest when they are compared with the Ministry of Energy and Natural Resources (MENR) projection.     

Thermodynamic analysis of solar photovoltaic cell systems

The thermodynamic characteristics of solar photovoltaic (PV) cells are investigated from a perspective based on exergy. A new efficiency is developed that is useful in studying PV performance and possible improvements. Exergy analysis is applied to a PV system and its components, and exergy flows, losses and efficiencies are evaluated. Energy efficiency is seen to vary between 7% and 12% during the day. In contrast, exergy efficiencies, which incorporate the second law of thermodynamics and account for solar irradiation exergy values, are lower for electricity generation using the considered PV system, ranging from 2% to 8%. Values of “fill factors” are determined for the system and observed to be similar to values of exergy efficiency.     

Low-noise properties of dry gate recess etched InP HEMTs

Lattice-matched InAlAs-InGaAs HEMTs with dry etched and wet etched gate recesses have been fabricated and both high-frequency and noise measurements have been carried out. The highly selective dry etching process ensures uniform device parameters. The small signal and noise performance shows only minor differences between the two transistor types. There is no evidence of detrimental effects caused by dry etching that reduce the electrical and noise performance of the device at high frequencies. These results show that dry etched InP HEMT's have suitable characteristics for the fabrication of MM-wave integrated circuits     

Heat evolution of high-volume fly ash concrete

In this paper, the results of a laboratory investigation conducted with heat evolution of high-volume fly ash (HVFA) concrete are presented. Heat evolution of concrete was studied by measuring the temperature increase in concrete under adiabatic curing condition. Characteristic of heat evolution of fly ash concrete was found to be strongly dependent on the replacement level of fly ash and dosage of superplasticizer used to maintain workability. It was also found that using fly ash as cement replacement resulted in a reduction on the maximum temperature rise. Increasing the replacement level of fly ash caused lower temperature rise in concrete. Superplasticizer caused a delay in peak temperature rise time; this is taken as an indicator that high-dosage superplasticizer used in concrete caused retardation in hydration of cement. Concretes having similar ingredients showed similar peak temperature rise whether they are superplasticized or not.     

Preparation and sintering behaviour of submicronic Bi4Ti3O12 powders

Submicronic powders of Bi₄Ti₃O₁₂ with different morphologies were prepared by both the oxalate coprecipitation and the conventional mixing oxides methods. Compacts of the two calcined powders were sintered at 850–1100 °C in air, and the densification process was studied by non-isothermal and dilatometric experiments. A rapid densification (> 97% theoretical density) below 875 °C took place in the Bi₄Ti₃O₁₂ oxalate powder which was attributed to an extremely uniform pore-size distribution in the green compact. The possible formation of a transient liquid which promotes densification also was taken into account. The development of plate-like morphology in the conventional Bi₄Ti₃O₁₂ powder, broad pore-size distribution, and the plate-like colony formation, hindered rapid densification of the green compacts at low temperature. Microstructural development was studied; preliminary dielectric and electrical results are also reported.     

Effect of Aluminum Content on the Dynamic Recrystallization of Fe18MnxAl0.74C Steels During Hot-Forging Treatments

Metallurgical and Materials Transactions A - In the present work, the dynamic recrystallization and microstructural evolution of the family of advanced high-strength steels Fe18MnxAl0.74C are...     

Synthesis of copolymers of tert‐butyl vinyl ether with maleic and citraconic anhydrides

In the present study, the effects of charge‐transfer complex formation and intramolecular fragmentation (side‐chain lactonization) in radical copolymerization of tert‐butyl vinyl ether (t‐BVE) with anhydrides of maleic (MA) and citraconic (CA) acids and the structure–thermal behavior relationships of the resulting copolymers were examined using the ¹H‐NMR, FTIR, DSC, and TGA analysis methods. It was shown that copolymerization under the chosen conditions proceeded through intramolecular fragmentation with the formation of γ‐lactone units. Side‐chain fragmentation of t‐BVE–MA and t‐BVE–CA copolymers also was confirmed by TGA and DSC analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2455–2463, 2006 2006     

Synthesis,characterization, and antitumor activity of poly(maleic anhydride‐co‐vinyl acetate‐co‐acrylic acid)

The ternary copolymerization of maleic anhydride (MA), vinyl acetate (VA), and acrylic acid (AA) [P(MA‐co‐VA‐co‐AA)], which is considered to be an acceptor–donor–acceptor system, was carried out in 1,4‐dioxane with benzoyl peroxide as an initiator at 70°C under a nitrogen atmosphere. Constants of complex formation for the monomer systems in the study were determined by UV–visible (hydrogen‐bonding complex) and ¹H‐NMR (charge transfer complex) methods, respectively. The results show that polymerization of the P(MA‐co‐VA‐co‐AA) system proceeds by an alternating terpolymerization mechanism. It is shown that the synthesized copolymers have typical polyelectrolyte behavior, ability for reversible hydrolysis–anhydrization reactions, and semicrystalline structures. In these cases, including radical polymerization, and formation of semicrystalline structures, the hydrogen‐bonding effect plays a significant role. The in vitro cytotoxicities of the synthesized terpolymer and alternating copolymer were evaluated using Raji cells (human Burkitt lymphoma cell line). The antitumor activities of prepared anion‐active copolymers were studied using methyl–thiazol–tetrazolium colorimetric assay and 50% of the cytotoxic dose of each copolymer and terpolymer were calculated. Hydrolyzed P(MA‐co‐VA‐co‐AA) and P(MA‐alt‐AA) copolymers have sufficiently high antitumor activity, which depends on the amount of hydrogen‐bonding carboxylic groups and their regular distribution in the side chain of functional macromolecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3425–3432, 2006     

Taylor series approach to fuzzy multiobjective linear fractional programming

This paper presents the use of a Taylor series for fuzzy multiobjective linear fractional programming problems (FMOLFP). The Taylor series is a series expansion that a representation of a function. In the proposed approach, membership functions associated with each objective of fuzzy multiobjective linear fractional programming problem transformed by using a Taylor series are unified. Thus, the problem is reduced to a single objective. Practical applications and numerical examples are used in order to show the efficiency and superiority of the proposed approach.