Preparation of hyperbranched polyester polyol-based urethane acrylates and applications on UV-curable wood coatings

In the present study, hyperbranched urethane acrylates (UA/HB-PEs) were synthesized by modifying the hydroxyl groups of hyperbranched polyester polyols (HB-PEs). The structure of oligomers were characterized by FTIR and ¹H NMR spectroscopic techniques. Formulations containing UA/HB-PEs, reactive diluents, and photoinitiator were applied onto wood substrates and successfully polymerized under UV-irradiation. The coating performances and thermal properties of UV-cured films were evaluated. The studies on film characteristics reveal that the incorporation of UA/HB-PE afforded coatings with good adhesion and high gloss properties. It is observed that UV-cured coatings originated from [2,2-bis(4-??-hydroxyethoxy) phenyl propane] (HB-HEPA)- and [2,2-bis(4-??-hydroxyethoxy) phenyl 6F propane] (HB-HEPFA)-based oligomers possessed better surface and mechanical properties.     

Improvement of PEMFC performance with Nafion/inorganic nanocomposite membrane electrode assembly prepared by ultrasonic coating technique

Membrane electrode assemblies with Nafion/nanosize titanium silicon dioxide (TiSiO₄) composite membranes were manufactured with a novel ultrasonic-spray technique and tested in proton exchange membrane fuel cell (PEMFC). Nafion/TiO₂ and Nafion/SiO₂ nanocomposite membranes were also fabricated by the same technique and their characteristics and performances in PEMFC were compared with Nafion/TiSiO₄ mixed oxide membrane. The composite membranes have been characterized by thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, water uptake, and proton conductivity. The composite membranes gained good thermal resistance with insertion of inorganic oxides. Uniform and homogeneous distribution of inorganic oxides enhanced crystalline character of these membranes. Gas diffusion electrodes (GDE) were fabricated by Ultrasonic Coating Technique. Catalyst loading was 0.4 mg Pt/cm² for both anode and cathode sides. Fuel cell performances of Nafion/TiSiO₄ composite membrane were better than that of other membranes. The power density obtained at 0.5 V at 75 °C was 0.456 W cm⁻², 0.547 W cm⁻², 0.477 W cm⁻² and 0.803 W cm⁻² for Nafion, Nafion/TiO₂, Nafion/SiO₂, and Nafion/TiSiO₄ composite membranes, respectively.     

Electroinitiated polymerization of 2-allylphenol

Summary Redox behaviour of 2-allylphenol (2APhOH) was studied by using cyclic voltammetry (CV) and electroinitiated polymerization was conducted at the measured peak potentials. Constant potential electrolysis (CPE) of the monomer was carried out in acetonitrile-sodium perchlorate, solvent-electrolyte couple, at room temperature. Polymerization of the monomer yielded insoluble polymer films on the surface of the electrode together with the low molecular weight polymers in the bulk of the solution. The structural analysis of the polymers were carried by ¹H-NMR and FTIR spectroscopy. Molecular weight of the soluble polymer was determined by GPC. Thermal properties of the polymer film and soluble polymer were studied by DSC. The course of electroinitiated polymerization was monitored by in-situ UV-VIS spectroscopy. Received: 10 April 2000/Revised version: 21 June 2000/Accepted: 5 July 2000     

High rate compression of CAD meshes based on subdivision inversion

In this paper we present a new framework, based on subdivision surface approximation, for efficient compression and coding of 3D models represented by polygonal meshes. Our algorithm fits the input 3D model with a piecewise smooth subdivision surface represented by a coarse control polyhedron, near optimal in terms of control points number and connectivity. Our algorithm, which remains independent of the connectivity of the input mesh, is particularly suited for meshes issued from mechanical or cad parts. The found subdivision control polyhedron is much more compact than the original mesh and visually represents the same shape after several subdivision steps, without artifacts or cracks, like traditional lossy compression schemes. This control polyhedron is then encoded specifically to give the final compressed stream. Experiments conducted on several cad models have proven the coherency and the efficiency of our algorithm, compared with existing methods.     

Equivalent Roughness Height for Plane Bed under Steady Flow

This paper presents a new relationship between the roughness height and the main hydrodynamic and sediment parameters for plane beds under steady current conditions. In order to derive such a formula, a large data base involving plane-bed experiments was compiled from previous investigations and analyzed. Comparisons between the data and different existing predictive formulas for the bed roughness obtained from the literature were also made. A relationship with the Shields parameter only, which is commonly proposed, appeared to be insufficient. The roughness was also found to be a function of a Froude number and a dimensionless settling velocity. A critical Shields parameter was identified up to which the equivalent roughness ratio is proportional to the Shields parameter. The new empirical equation that was developed yields the best results for all conditions investigated, and should improve the understanding of the total shear stress.     

Anodic polymerization of 2,5-di-(2-thienyl)-furan in ethanol

Poly(2,5-di-(2-thienyl)-furan) (PSOS) was synthesized via anodic polymerization of 2,5-di-(2-thienyl)-furan (SOS) in ethanol solution containing 0.2 M LiClO₄ as supporting electrolyte. The electrochemical and spectroelectrochemical properties were investigated using electroanalytical and UV–vis spectroscopic techniques, respectively. The band gap of the polymer film was found as 2.22 eV and the film was successfully switched between black oxidized state and orange neutral state. Fluorescence and electrochemical impedance spectroscopy (EIS) studies were also performed.     

The Interaction of Sheep Genomic DNA with a Cobalt(II) Complex Containing p-Nitrobenzoate and N,N′-Diethylnicotinamide Ligands

The synthesized cobalt(II) complex, CoPNBDENA and the binding of this complex with sheep genomic DNA were investigated by UV–Visible absorption and viscosity techniques. Also the interaction of sheep genomic DNA with the complex was studied using the agarose gel electrophoresis method. The results indicated that the complex interacted with DNA. The nature of the binding seemed to be mainly an electrostatic interaction between DNA and the cobalt(II) complex. Other binding modes such as hydrogen bonds may also exist in this system. In this study, after the interaction of DNA–CoPNBDENA, it was observed that the migration of the DNA band became slow as the amount of cobalt(II) complex was increased. This clearly demonstrates that the CoPNBDENA complex neutralizes the negative charges of DNA.     

Adsorption of heavy metal cations from aqueous solutions by wool fibers

Adsorption of metal cations by kivircik wool from aqueous NiCl₂, CuCl₂, ZnCl₂, CdCl₂, HgCl₂ and Pb(NO₃)₂ solutions at 25°C and 50°C was investigated using atomic absorption spectroscopy. A fiber diffusion controlled adsorption rate model was used to predict the effective diffusion coefficients of metal ions in wool. It has been shown that wool is a potential adsorbent for removing toxic metal ions from contaminated water.     

The effects of ethanol–unleaded gasoline blends and ignition timing on engine performance and exhaust emissions

In this study, the effects of using unleaded gasoline (E0) and unleaded gasoline–ethanol blends (E10, E20 E40 and E60) on engine performance and exhaust emissions have been experimentally investigated. The investigation was conducted on a Hydra single-cylinder, four-stroke, spark ignition engine. The experiments were performed by varying the compression ratio (8:1, 9:1 and 10:1) and ignition timing at a constant speed of 2000 rpm at wide open throttle (WOT). The experimental results showed that blending unleaded gasoline with ethanol slightly increased the brake torque and decreased carbon monoxide (CO) and hydrocarbon (HC) emissions. It was also found that blending with ethanol allows increasing the compression ratio without knock occurrence.     

Measurements and model calculations of activation cross sections for 232Th(n,2n)231Th reaction between 13.57 and 14.83 MeV neutrons

In this study, activation cross sections were measured for the reaction of ²³²Th(n,2n)²³¹Th (T_1/2 = 25.5 h) by using neutron activation technique at six different neutron energies from 13.57 and 14.83 MeV. Neutrons were produced via the ³H(²H,n)⁴He reaction using SAMES T-400 neutron generator. Irradiated and activated high purity Thorium foils were measured by a high-resolution γ-ray spectrometer with a high-purity Germanium (HpGe) detector. In cross section measurements, the corrections were made for the effects of γ-ray self-absorption in the foils, dead-time, coincidence summing, fluctuation of neutron flux, low energy neutrons. For this reaction, statistical model calculation, which the pre-equilibrium emission effects were taken into consideration, were also performed between 13.57 and 14.83 MeV energy range. The cross sections were compared with previous works in literature, with model calculation results, and with evaluation data bases (ENDF/B-VII, ENDF/B-VI, JEFF-3.1, JENDL-4.0, JENDL-3.3, and ROSFOND-2010).