Time-Dependent Diffusion Coefficient of Fe in MgB<Subscript>2</Subscript> Superconductors

The iron (Fe) diffusion in superconducting MgB₂ bulk samples has been studied for sintering time durations of 15 min, 30 min, 1 h, 2 h, and 4 h at 900^°C. Fe coating bulk polycrstalline superconducting MgB₂ samples for Fe coating were prepared by pelletizing and used in the diffusion experiments with initial sintering at 800^°C for 1 h. A thin layer of Fe was coated on MgB₂ pellets by evaporation in vacuum. Effects of Fe diffusion on the structural, electrical, and superconducting properties of MgB₂ have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), energy-dispersive X-ray spectroscopy (EDS), and resistivity measurements. Fe diffused samples have slightly increased critical transition temperatures and have larger lattice parameter c values, in comparison with bare samples. Fe diffusion coefficients were calculated from depth profiles of c parameter and room temperature resistivity values. Depth profiles were obtained by successive removal of thin layers from Fe diffused surfaces of the samples. Our results have shown that the Fe diffusion coefficient decreases with increasing sintering time and resistivity measurements can be utilized for determination of diffusion coefficient.     

Design and implementation of a distributed teleradiaography system: DIPACS

Medical imaging informatics has origins spanning back over two or more decades. Currently, sharing of radiological images for diagnosis, collaborative and administrative purposes is one of the challenging issues in both medicine and computer science. In this study, we designed and implemented a distributed PACS system, namely DIPACS, for small and medium scale medical networks. DIPACS forms a virtual organization by combining the storage of health centers and providing transparent access to images. In this study, we introduce the DIPACS architecture together with the implementation details.     

A study on modeling and performance assessment of a heat pump system for utilizing low temperature geothermal resources in buildings

Low and moderate geothermal resources are found in most areas of the world. A very efficient way to heat and air-condition homes and buildings is the utilization of ground source heat pumps (GSHPs), also known as geothermal heat pump (GHPs), to obtain heat energy from low temperature geothermal resources.     

Sustainability SI: Multimode Multicommodity Network Design Model for Intermodal Freight Transportation with Transfer and Emission Costs

Intermodal freight transportation is concerned with the shipment of commodities from their origin to destination using combinations of transport modes. Traditional logistics models have concentrated on minimizing transportation costs by appropriately determining the service network and the transportation routing. This paper considers an intermodal transportation problem with an explicit consideration of greenhouse gas emissions and intermodal transfers. A model is described which is in the form of a non-linear integer programming formulation, which is then linearized. A hypothetical but realistic case study of the UK including eleven locations forms the test instances for our investigation, where uni-modal with multi-modal transportation options are compared using a range of fixed costs.     

Single password authentication

Users frequently reuse their passwords when authenticating to various online services. Combined with the use of weak passwords or honeypot/phishing attacks, this brings high risks to the security of the user’s account information. In this paper, we propose several protocols that can allow a user to use a single password to authenticate to multiple services securely. All our constructions provably protect the user from dictionary attacks on the password, and cross-site impersonation or honeypot attacks by the online service providers.     

Mineral content of some herbs and herbal teas by infusion and decoction

Sage (Salvia fruticosa L.), anise (Pimpinella anisum L.), Hawthorn (Crataegus orientalis), rosemary (Rosmarinus officinalis L.), mountain tea (Sideritis spp), basil (Ocimum basilicum L.), lime flower (Tilia cordata), nettle (Urtica dioica L.), thyme (Thymbra spicata), coriander (Coriandrum sativum L.), rosehip (Rosa canina L.), mentha (Mentha piperita L.), balm (Melissa officinalis L.), tea (Camelia sinensis L.) (Black and green), sena leaf (Casia angustifolia), camomile (Matricaria chamomilla), tarragon (Artemisia dracunculus L.), cinnamon (Cinnamomum casia) and fennel (Foeniculum vulgare L.) were used as plant material in this study. Decoction was applied to R. canina, A. dracunculus and C. casia, and infusion was applied to other plant materials. Ten, 15 and 20 min were used as a time parameter for both infusion and decection. Inductive coupled plasma atomic emission spectrometry (ICP-AEs) has been used for the determination of the elements in all infusions, decoctions and plant material.     

The effects of ethanol–unleaded gasoline blends on engine performance and exhaust emissions in a spark-ignition engine

Alcohols have been used as a fuel for engines since 19th century. Among the various alcohols, ethanol is known as the most suited renewable, bio-based and ecofriendly fuel for spark-ignition (SI) engines. The most attractive properties of ethanol as an SI engine fuel are that it can be produced from renewable energy sources such as sugar, cane, cassava, many types of waste biomass materials, corn and barley. In addition, ethanol has higher evaporation heat, octane number and flammability temperature therefore it has positive influence on engine performance and reduces exhaust emissions. In this study, the effects of unleaded gasoline (E0) and unleaded gasoline–ethanol blends (E50 and E85) on engine performance and pollutant emissions were investigated experimentally in a single cylinder four-stroke spark-ignition engine at two compression ratios (10:1 and 11:1). The engine speed was changed from 1500 to 5000 rpm at wide open throttle (WOT). The results of the engine test showed that ethanol addition to unleaded gasoline increase the engine torque, power and fuel consumption and reduce carbon monoxide (CO), nitrogen oxides (NO_x) and hydrocarbon (HC) emissions. It was also found that ethanol–gasoline blends allow increasing compression ratio (CR) without knock occurrence.     

Comparison of electrolyte effects for poly(3,4-ethylenedioxythiophene) and poly(3-octylthiophene) by electrochemical impedance spectroscopy and polymerization parameters with morphological analyses on coated films

3,4-Ethylenedioxythiophene and 3-octylthiophene were electropolymerized on glassy carbon electrodes (GCE) to compare with four different electrolytes [lithium perchlorate (LiClO₄), sodium perchlorate, tetraethylammonium tetrafluoroborate, and tetrabutylammonium tetrafluoroborate] in a solvent of acetonitrile (CH₃CN). Modified electrodes were characterized by cyclic voltammetry, attenuated total reflectance–Fourier transform IR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, atomic force microscopy, and electrochemical impedance spectroscopy (EIS). Nyquist and Bode plots for magnitude, phase, admittance, and capacitance on both polymer-modified electrodes were comparatively investigated in detail. The highest low-frequency capacitance (C _LF) and double-layer capacitance (C _dl) were obtained in 0.1 M LiClO₄/CH₃CN for poly(3,4-ethylenedioxythiophene) and poly(octylthiophene)/GCE. EIS data were fitted to the equivalent circuit model of R(Q(R(C(R(C(RW))))))(CR), which is used to investigate circuit parameters.     

Adsorption kinetics of malachite green onto activated carbon prepared from Tunçbilek lignite

Adsorbent (T₃K618) has been prepared from Tunçbilek lignite by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N₂ adsorption isotherm. The N₂ adsorption isotherm of malachite green on T₃K618 is type I. The BET surface area of the adsorbent which was primarily contributed by micropores was determined 1000 m²/g. T₃K618 was used to adsorb malachite green (MG) from an aqueous solution in a batch reactor. The effects of initial dye concentration, agitation time, initial pH and adsorption temperature have been studied. It was also found that the adsorption isotherm followed both Freundlich and Dubinin–Radushkevich models. However, the Freundlich gave a better fit to all adsorption isotherms than the Dubinin–Radushkevich. The kinetics of adsorption of MG has been tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Results show that the adsorption of MG from aqueous solution onto micropores T₃K618 proceeds according to the pseudo-second-order model. The intraparticle diffusion of MG molecules within the carbon particles was identified to be the rate-limiting step. The adsorption of the MG was endothermic (ΔH° = 6.55–62.37 kJ/mol) and was accompanied by an increase in entropy (ΔS° = 74–223 J/mol K) and a decrease in mean value of Gibbs energy (ΔG° = −6.48 to −10.32 kJ/mol) in the temperature range of 20–50 °C.     

Use of Fenton oxidation to improve the biodegradability of a pharmaceutical wastewater

The applicability of Fenton's oxidation to improve the biodegradability of a pharmaceutical wastewater to be treated biologically was investigated. The wastewater was originated from a factory producing a variety of pharmaceutical chemicals. Treatability studies were conducted under laboratory conditions with all chemicals (having COD varying from 900 to 7000 mg/L) produced in the factory in order to determine the operational conditions to utilize in the full-scale treatment plant. Optimum pH was determined as 3.5 and 7.0 for the first (oxidation) and second stage (coagulation) of the Fenton process, respectively. For all chemicals, COD removal efficiency was highest when the molar ratio of H(2)O(2)/Fe(2+) was 150-250. At H(2)O(2)/Fe(2+) ratio of 155, 0.3M H(2)O(2) and 0.002 M Fe(2+), provided 45-65% COD removal. The wastewater treatment plant that employs Fenton oxidation followed by aerobic degradation in sequencing batch reactors (SBR), built after these treatability studies provided an overall COD removal efficiency of 98%, and compliance with the discharge limits. The efficiency of the Fenton's oxidation was around 45-50% and the efficiency in the SBR system which has two reactors each having a volume of 8m(3) and operated with a total cycle time of 1 day, was around 98%, regarding the COD removal.