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With the use of ANSYS Fluent software and ANSYS ICEM CFD calculation grid generator, the flows past a wing airfoil, an infinite cylinder, and 3D blunted bodies located in the open and closed test sections of low-speed wind tunnels were calculated. The mathematical model of the flows included the Reynolds equations and the SST model of turbulence. It was found that the ratios between the aerodynamic coefficients in the test section and in the free (unbounded) stream could be fairly well approximated with a piecewise-linear function of the blockage factor, whose value weakly depended on the angle of attack. The calculated data and data gained in the analysis of previously reported experimental studies proved to be in a good agreement. The impact of the extension of the closed test section on the airfoil lift force is analyzed.

The objective of this paper is to perform a hybrid design for an Adaptive Neuro-Fuzzy Inference System (ANFIS) optimized by Particle Swarm Optimization (PSO) to improve the dynamic voltage stability of a grid-connected wind power system. An onshore 99.2MW wind farm using Doubly Fed Induction Generator (DFIG) is studied. To compensate the reactive power absorbed from the power grid of the wind farm, a Static VAR Compensator (SVC) is proposed. To demonstrate the performance of the proposed hybrid PSO–ANFIS controller, simulations of the voltage response in time-domain are performed in Matlab to evaluate the effectiveness of the designed controller. From the results, it can be concluded that the proposed hybrid PSO-optimized ANFIS-based model can be applied to enhance the dynamic voltage stability of the studied grid-connected wind power system.

In this paper, a 99.2-MW grid-connected Bac Lieu wind farm using Doubly Fed Induction Generator (DFIG) is studied. For improving the voltage stability of the wind connected bus, a Static VAR Compensator (SVC) is proposed and an Adaptive Neuro Fuzzy Inference System (ANFIS) controller for SVC is also designed. Simulation results of the voltage response in time-domain are performed using MATLAB software to evaluate the effectiveness of the designed controller for SVC. From these results, it can be concluded that the proposed ANFIS controller can be applied to enhance the voltage stability of Bac Lieu power system.

The flow around a model in the closed test section of a low-speed wind tunnel has been analyzed in 2D approximation. As the contour of the nozzle, test section, and diffuser, the contour of the T-324 wind tunnel, of the Khristianovich Institute of Theoretical and Applied Mechanics (ITAM SB RAS, Novosibirsk), in its symmetry plane was adopted. A comparison of experimental with calculated data on the distribution of velocities and dynamic pressures in the test section is given. The effect due to the sizes of a model installed in the test section on the values of the aerodynamic coefficients of the model is analyzed. As the aerodynamic model, the NASA0012 airfoil and the circular cylinder were considered. For the airfoil chord length b = 20 % of nozzle height, the values of the aerodynamic coefficients of the airfoil in the free stream and in the test section proved to be close to each other up to the angle of attack a = 7°, which configuration corresponds to blockage-factor value ξ ≈ 7 %. The obtained data are indicative of the expedience of taking into account, in choosing the model scale, not only the degree of flow passage area blockage by the model but, also, the length of the well-streamlined model. In the case of a strongly blunted body with a high drag-coefficient value, the admissible blockage factor ξ may reach a value of 10 %.

The paper considers a problem of sizing a model and converting the balance test results in the low speed open-jet wind tunnel to free-flow conditions. The ANSYS Fluent commercial code performs flow model calculations in the test section and in the free flow, and the ANSYS ICEM CFD module is used to provide grid generation. A structured grid is generated in the free flow and an unstructured one is provided in the test section. The changes of aerodynamic coefficients are determined at the different values of the blockage factor for the segmental-conical and hemisphere cylinder-cone shapes of the model. The blockage factor values are found at which the interference of the test section – model is neglected. The paper presents a technique to convert the wind tunnel test results to the free flow conditions.

The present work proposes applying polyurethane coatings as an additional barrier in the design of Canadian nuclear waste disposal containers. The goal of the present research is to investigate the physico-mechanical integrity of a natural castor oil-based polyurethane (COPU) to be used as a coating material in pH–radiation–temperature environments. As the first part to these inquiries, the present paper investigates the effect of a mixed radiation field supplied by a SLOWPOKE-2 nuclear research reactor on COPUs that differ only by their isocyanate structure. FTIR, DSC, DMA, WAXS, and MALDI are used to characterize the changes that occur as a result of radiation and to relate these changes to polymer structure and composition. The COPUs used in the present work have demonstrated sustained physico-mechanical properties up to accumulated doses of 2.0 MGy and are therefore suitable for end-uses in radiation environments such as those expected in the deep geological repository.

Thermally cured polyurethanes were prepared from castor oil and hexamethylene diisocyanate (HMDI). Due to the long aliphatic chain of the castor oil component of polyurethane, thermal curing of castor oil based polyurethane (COPU) is limited by increasing polymer viscosity. To enhance further crosslinking, COPUs were exposed to doses up to 3.0 MGy produced by the mixed ionizing radiation field of a SLOWPOKE-2 research nuclear reactor. The physico-mechanical properties of castor oil based polyurethanes (COPU), unirradiated and irradiated, were characterized by mechanical tensile tests. A four-fold increase in modulus and tensile strength values from 0.930 to 4.365 MPa and 0.149 to 0.747 MPa, respectively, suggests improved physico-mechanical properties resulting from radiation. The changing areas of the carbonyl and the NH absorbance peaks and the disappearance of the isocyanate peak in the FTIR spectra as radiation progressed, indicates increased hydrogen bonding and intermolecular crosslinking, which is in agreement with the mechanical tests. Unchanging 13C solid state NMR spectra imply limited sample degradation with increasing radiation.

The disposal of Canada’s radioactive waste materials has been the focus of ongoing research at the Royal Military College of Canada, in the use of polymer-based composite materials for the fabrication of disposal containers. An evaluation of the performance of polyamide 6,6 after exposure to radiation and acidic aqueous solutions provides the basis for the assessment of the lifetime performance of a polymeric-based storage container. This work demonstrates the importance of the combined effects of aqueous solution diffusion and radiation exposure on the mechanical performance and molecular structure of polyamide 6,6. Irradiation of dry samples initially results in a marked reduction of mechanical performance, however, post-irradiation aging allows for the return to pre-irradiation mechanical strength. Samples irradiated after exposure to either distilled water or 0.1 M sulfuric acid solutions exhibited increases in mechanical performance upon exposure to a mixed field radioactive environment.

Nylon 6,6 is an excellent material for the study of the diffusion mechanism and associated mechanical performance of polymers saturated with aqueous solutions of varying pH at different temperatures. The diffusion profile was studied for samples saturated at temperatures ranging from 20 to 90°C in solutions decreasing in pH from distilled water to 1.0M sulfuric acid. The presence of sulfuric acid molecules within the diffusing solutions acts to promote hydrolysis of the polyamide molecules. The degree of hydrolysis is dependent on saturation temperature and solution pH. The extent of degradation was evaluated via changes to mechanical performance and inherent viscosity and often results in a reduction of the stress at yield, flexural modulus, and inherent viscosity on increasing temperature and decreasing pH. The use of neutron activation analysis allowed for an evaluation of the sulfur content within the samples as a function of diffusing time. This demonstrated that although the mechanical performance decreases rapidly on initial exposure to the aqueous medium, this is likely due to plasticization. As diffusion time progresses, the sulfur content within the sample continues to rise to a level where the acid/water molar ratio is much higher in the sample than that of the bulk. This results in an enhancement of the degradation process as time progresses. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2476–2487, 2005

Indentation tests were performed on flat coupons of poly(formaldehyde), three types of reinforced nylon and reinforced poly(ethyl terephthalate) using a device developed for a typical universal tensile testing machine. Spherical, conical and cylindrical indenters were selected for this study and the effects of indenter shape combined with the rate of indentation on the behavior of these materials were examined. The load-depth relationship during the indentation process revealed the emergence of step-like transitions at high indentation rates. The effects of the assessed parameters on the indentation resistance, as defined in this study, were analyzed. Interest was also focused on the investigation of the deformation work as well as the plastic work taking place for a total depth that incorporated both the skin and part of the bulk of the material. The modeling of the data was based on a previously developed approach and the introduction of a modified parameter that took not only the geometrical characteristics of the indenter into account but also the indentation depth. The proposed method has proven to be useful since a steady state of the indentation pressure was observed for all materials after a certain depth of indentation. This was valid for the results obtained using both conical and cylindrical indenters. Polym. Eng. Sci. 44:1439–1447, 2004. © 2004 Society of Plastics Engineers.

The thermodynamic behavior of ternary solutions containing one cyclic (CYC10 and CYC20) and one linear (LIN10 and LIN20) poly(methylene) ester oligomer, respectively, in p-dioxan and chloroform were investigated through vapor-pressure measurements. Experiments were carried out at 25, 30, 35, and 40 °C. The ring-chain interaction parameters χ were evaluated using the Leonard's equation for a ternary polymer solution containing one ring polymer. Results indicated that the values of χ are concentration and solvent dependent, and they vary with molecular size and slightly with temperature. All χ values were positive for both CYC10/LIN10 and CYC20/LIN20 blends, with the higher values for the former system, indicating that both ring-chain oligomer blends are nearly immiscible, and the difference between cyclic and linear oligomers decreases as molecular size increases. The positive χ agrees with differential scanning calorimetric measurements performed on ring-chain oligomer blends that show two distinct endotherms for the blends.

Differential vapor pressures were measured for mixtures of two cyclic polymethylene ester oligomers in p-dioxane and chloroform at 25, 30, 35, and 40 °C at five different concentrations ranging from 1 to 20 wt %. The Flory-Huggins interaction parameter ( X ) as well as Leonard's interaction parameter ( X' ) for flexible and semiflexible rings were calculated and compared to one another. A new method for the estimation of the number of segments of a cyclic polymer is proposed that allows Leonard's equations to be applied correctly to a particular cyclic compound. Consistent differences between X and X' were observed for all studied mixtures, and the differences became smaller if the cyclic oligomers were considered semiflexible. Interestingly, the enthalpic parameter (K) deduced from values of X and X' did not differ within their uncertainties. This supports the prediction that mixing cyclic polymer compared to its linear counterpart is mainly due to a molecular configurational entropy difference and that this difference should become less pronounced as the cyclic compound becomes larger.

The synthesis and characterization of semi-II interpenetrating polymer networks (IPN) based on poly(methyl methacrylate) (PMMA) and on castor oil polyurethane (PU) of composition 70/30 are reported. Various degrees of crosslinking of the PU phase were obtained by varying the weight ratio of HDI/N-100 while maintaining the NCO/OH ratio fixed at 1.5. Thermal characterization was performed by thermomechanical analysis (TMA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two distinct glass transition temperatures were observed, indicating a two-phase morphology. This was also supported by scanning electron microscopy (SEM) observations. Rheological characterization was performed using a capillary rheometer. Shear thinning flow behaviour and reprocessing were confirmed for all semi-II IPN. All the results demonstrate that a higher crosslinking level leads to better overall properties.

The synthesis and characterization of simultaneous interpenetrating polymer networks (SINs) based on methyl methacrylate and castor oil are reported. A mixture of 50/50 in weight of HDI/N-100 was employed for the polymerization and crosslinking of the polyurethane phase. The SINs over the whole composition range have only one single glass transition temperature T g, as determined by TMA (thermomechanical analysis) which suggests a single phase morphology even though the linear chain blends are completely immiscible. This is also supported by scanning electron microscopy observations. The SINs exhibit a higher heat resistance than pure PMMA but lower than N-100. They also exhibit a maximum tensile strength and impact strength at a composition of PU around 30%. This synergistic effect resulted from a strong entanglement between two networks as well as chain transfer phenomenon.

Une methode approximative et simple pour les essais mecaniques des polymeres a basse temperature est frequemment utilisee. Elle consiste a tremper l'echantillon de polymere dans l'azote liquide et ensuite l'installer dans l'appareil servant aux essais. La temperature desiree pour l'essai est determinee par le temps ou l'essai est commence. Les historiques de temps-temperature de deux echantillons pour essai d'impact, en polyethylene a haute densite et polyurethane, etaient d'abord mesures et par la suite compares avec les valeurs obtenues d'une methode graphique concue pour la conduction thermique a l'etat non-stationnaire. L'accord entre les valeurs experimentales et calculees est meilleur que 8% en terme d'erreur relative

The Flory-Huggins polymer solution theory can be extended to be applicable to a binary liquid mixture, yielding a parameter which represents the interactive behaviour of the mixture over the entire concentration range. Static vapour pressures of α-methylstyrene-toluene mixture were measured from 20 to 40°C by using a MKS Baratron manometer. The interaction parameter was then computed by means of the Wilson's equation. Positive values of the parameter and its concentration dependence may be explained by a lack of intermolecular interaction as well as by the free volume effect on mixing. These findings can also be supported by positive volume excess of the mixture, deduced from density measurements using a SODEV densimeter. The interactive pattern of the present mixture will be compared with that of other mixtures of α-methylstyrene in tetrahydrofuran, cyclohexane and p-dioxan. La theorie des solutions de polymere de Flory-Huggins peut aussi etre applicable a une solution binaire de deux liquides pour produire un parametre qui represente le comportement interactif de cette solution a travers toute la gamme de concentration. Les pressions de vapeur statiques du melange α-methylstyrene-toluene ont ete mesurees a des temperatures variant entre 20 et 40°C en utilisant un manometre du type MKS Baratron. Avec ces valeurs, le parametre d'interaction a ete calcule a l'aide de l'equation Wilson. Les valeurs positives de ce parametre ainsi que sa dependance sur la concentration peuvent etre interpretes par un manque d'interaction intermoleculaire combine a l'effet du volume libre sur le melange. Ces observations peuvent aussi etre supportees par les valeurs positives de volume d'exces du melange deduit a partir des mesures de densite utilisant un densimetre SODEV. L'aspect interactif de ce present melange sera compare avec celui des autres melanges de α-methylstyrene dans tetrahydrofurane, cyclohexane et p-dioxane.

Generalement l’occlusion coronaire aigue se traduit par des modifications electriques a type de sus decalage de ST, plus rarement un sous decalage de ST. Mais il arrive que ces signes electriques fassent defaut ou sont trompeuses rendant ainsi le diagnostic d’infarctus un peu plus difficile. L’occlusion de l’artere coronaire circonflexe est le plus souvent en cause dans ces atypies d’expressions electriques de l’infarctus du myocarde aigu. Nous rapportons ici trois formes inhabituelles d’expression electrique d’occlusion de l’artere circonflexe: un cas ou les criteres electriques orientent vers une occlusion de la coronaire droite alors que c’est la circonflexe qui est retrouvee occluse, un cas ou l’electrogramme de surface reste normal et c’est l’elevation de la troponine qui pose l’indication d’une coronarographie en urgence qui objective l’occlusion thrombotique de la circonflexe et enfin un troisieme cas ou la coronarographie est motivee par des fibrillations ventriculaires iteratives recuperees par des chocs electriques externes, les ECG inter critiques et post-angioplastie restent normaux, la desobstruction de la circonflexe a fait regresser les troubles de rythme ventriculaires graves.

A numerical method for calculation of vapor-liquid equilibrium data for ternary systems, from total pressure measurements, is developed. The proposed method is applied to the ternary systems benzene-n heptane-n propanol and acetone-methanol-water. Une methode numerique pour le calcul des donnees d'equilibre liquide-vapeur pour des systemes ternaires, a partir de mesures de pression totale, est mise au point. La methode est appliquee aux systemes ternaires benzene-n heptane-n propanol et acetone-methanol-eau.