Nitrogen management in reservoir catchments through constructed wetland systems.

In this study, nitrogen removal was investigated in pilot-scale subsurface flow (SSF) and in free water surface flow (FWS) constructed wetlands installed in the campus of TUBITAK-Marmara Research Center, Gebze, near Istanbul, Turkey. The main purposes of this study are to apply constructed wetlands for the protection of water reservoirs and to reuse wastewater. Experiments were carried out at continuous flow reactors. The effects of the type of plants on the removal were investigated by using emergent (Canna, Cyperus, Typhia spp., Phragmites spp., Juncus, Poaceae, Paspalum and Iris.), submerged (Elodea, Egeria) and floating (Pistia, Salvina and Lemna) marsh plants at different conditions. During the study period HLRs were 30, 50, 70, 80 and 120 L m(2)d(-1) respectively. The average annual NH4-N, NO(3)-N, organic N and TN treatment efficiencies in SSF and FWS wetlands are 81% and 68%, 37% and 49%, 75% and 68%, 47% and 53%, respectively. Nitrification, denitrification and ammonification rate constant (k20) values in SSF and FNS systems have been found as 0.898 d(-1) and 0.541 d(-1), 0.488 d(-1) and 0.502 d(-1), 0.986 d(-1) and 0.908 respectively. Two types of the models (first-order plug flow and multiple regression) were tried to estimate the system performances.     

Enhancing electrochromic properties of polypyrrole by silsesquioxane nanocages

A new monomer, octa(thiophenephenyl)silsesquioxane (OThiophenePS) was synthesized via click chemistry. The chemical structure of OThiophenePS was characterized by nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FT-IR) spectroscopies. Electrochemical polymerization of pyrrole with OThiophenePS was performed resulting in polypyrrole-attached, polyhedral oligomeric silsesquioxane (OPS–PPy). The spectroelectrochemical studies show that the electrochromic properties of (OPS–PPy) are superior to those of polypyrrole (PPy). This great improvement can be attributed to the more accessible doping sites and the facile ion movement during the redox switching brought by the loose packing of the PPy chains.     

Robust control of variable speed autonomous underwater vehicle

Set point tracking control of autonomous underwater vehicle (AUV) via robust model predictive control (RMPC) is considered. Input-constrained RMPC with integral action, which has been developed in our previous work, is used to control the AUV in this study. In order to derive a RMPC control rule, non-linear dynamics of AUV with six degree of freedom is linearized at certain operating points. So, horizontal and vertical plane dynamics of system are represented by linear models which have polytopic uncertainties. Since the derived control rule will be used in real time, the computation time should be reduced. To overcome this computational time problem and get rid of trial–error step of Algorithm 1, a new algorithm is proposed here. The simulations are carried out using the control rule based on this algorithm and these results are presented.     

Affiliated marketing

In information-intensive environments some firms may be sending their customers to other firms’ or affiliates’ websites in order to generate additional sales for their affiliates. Although this may provide a choice for the customers, from a firm’s point of view such strategies have the potential to cannibalize own sales. Hence, when customers purchase from other firms’ websites, the firm may loose its own customers. This study analyzes the optimality of such strategies using an analytical framework. The findings show that a firm may increase its prices and profit when its own customers purchase from other firm websites. An analysis of customer surplus and total welfare show that such strategies may have adverse effects. The results show that customer surplus and total welfare may decrease as a result of affiliations.     

Soft groups and normalistic soft groups

Soft set theory, proposed by Molodtsov, has been regarded as an effective mathematical tool to deal with uncertainties. In this paper, first we correct some of the problematic cases in a previous paper by Akta? and Çag˜man [H. Akta?, N. Çag˜man, Soft sets and soft groups, Inf. Sci. 177 (2007) 2726-2735]. Moreover, we introduce the concepts of normalistic soft group and normalistic soft group homomorphism, study their several related properties, and investigate some structures that are preserved under normalistic soft group homomorphisms.     

An expert system for automated recognition of patients with obstructive sleep apnea using electrocardiogram recordings

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder. The traditional diagnosis methods of the disorder are cumbersome and expensive. The ability to automatically identify OSA from electrocardiogram (ECG) recordings is important for clinical diagnosis and treatment. In this study, we proposed an expert system based on discrete wavelet transform (DWT), fast-Fourier transform (FFT) and least squares support vector machine (LS-SVM) for the automatic recognition of patients with OSA from nocturnal ECG recordings. Thirty ECG recordings collected from normal subjects and subjects with sleep apnea, each of approximately 8 h in duration, were used throughout the study. The proposed OSA recognition system comprises three stages. In the first stage, an algorithm based on DWT was used to analyze ECG recordings for the detection of heart rate variability (HRV) and ECG-derived respiration (EDR) changes. In the second stage, an FFT based power spectral density (PSD) method was used for feature extraction from HRV and EDR changes. Then, a hill-climbing feature selection algorithm was used to identify the best features that improve classification performance. In the third stage, the obtained features were used as input patterns of the LS-SVM classifier. Using the cross-validation method, the accuracy of the developed system was found to be 100% for using a subset of selected combination of HRV and EDR features. The results confirmed that the proposed expert system has potential for recognition of patients with suspected OSA by using ECG recordings.     

Conducting carbon/polymer composites as a catalyst support for proton exchange membrane fuel cells

Carbon/poly(3,4‐ethylene dioxythiophene) (C/PEDOT) composites are synthesized by in situ chemical oxidative polymerization of EDOT monomer on carbon black in order to decrease carbon corrosion that occurred in carbon‐supported catalysts used in proton exchange membrane fuel cell. The effects of different dopants including polystyrene sulfonic acid, p‐toluenesulfonic acid and camphorsulfonic acid with the addition of ethylene glycol or dimethyl sulfoxide on the properties of the composites are investigated. The synthesized composites are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, surface area analysis and scanning electron microscope. Electrical conductivity is determined by using the four‐point probe technique. Electrochemical oxidation characteristics of the synthesized C/PEDOT composites are investigated by cyclic voltammetry by applying 1.2 V for 24 h. The composite prepared at 25 °C with p‐toluenesulfonic acid and ethylene glycol shows the best carbon corrosion resistance. Platinum‐supported catalyst by using this composite was prepared using microwave irradiation technique, and it was seen that the prepared catalyst did not significantly lose its hydrogen oxidation and oxygen reduction reaction activities after electrochemical oxidation. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of Mn and Gd Co-substituted into ZnO on Structural and Magnetic Properties

We have worked on the structural and magnetic properties of Zn_0.99?xMn_0.01Gd _x O _δ (for x = 0.02, 0.03, and 0.04) compounds prepared by using a sol–gel method. The x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy were used to understand the structural properties of the samples. We observed that co-substitution of Mn (1 %) and Gd (2–4 %) into the ZnO does not change the hexagonal structure. Scanning electron microscope (SEM) images show us that the grain size decreases with the increasing amount of the Gd into the ZnO matrix. The magnetic properties of the samples have been investigated by using magnetic hysteresis and DC susceptibility measurements. The ZMG1 sample shows a weak ferromagnetic behavior at room temperature, whereas the ZMG2 and ZMG3 samples exhibit a paramagnetic nature. Furthermore, it is also found that the magnetizations of the samples decrease with increasing Gd content in the ZnMnO system due to the enhancing interaction between Gd ³⁺ ions. We summarize that the co-substitution of Mn and Gd into the ZnO generates a room-temperature ferromagnetism, but it still needs more work to obtain strong and high coercivity magnetic loops for applications.     

Ring Opening of Epoxidized Soybean Oil with Compounds Containing Two Different Functional Groups

Epoxidized vegetable oils are desirable chemicals due to their eco‐friendly characteristics and their being a major source of many green products. Ring opening is one of the ways to convert these epoxidized oils to some new intermediates. The use of mono‐functional amines, alcohols, acid anhydrides and thioethers for epoxy ring opening has been reported in the literature. In this study, thioglycolic acid (TGA) bearing thiol and carboxylic acid as two different functional groups and methyl ester of thioglycolic acid (TGAME) were used. Currently, there is no reported literature describing epoxy ring opening using chemicals bearing two different functional groups simultaneously. In this way, two new polyols were synthesized, one with TGA (polyol 1) and one with TGAME (polyol 2). FTIR and ¹H‐ and ¹³C‐NMR spectroscopy confirmed that the ring was opened by the carboxylic acid group of TGA, and the thiol group was not involved in the ring opening whereas the ring was opened by the thiol group in the case of TGAME.