Improvement of the mechanical stability of oak by radiation-induced in-situ copolymerization of allyl glycidyl ether with acrylonitrile and methyl methacrylate

This study deals with the improvement of the mechanical stability of oak, which belongs to the hardwoods, by radiation-induced in-situ copolymerization of certain monomers. Acrylonitrile (AN), methyl methacrylate (MMA), allyl glycidyl ether/acrylonitrile (AGE/AN), and allyl glycidyl ether/methyl methacrylate (AGE/MMA) monomers and monomer mixtures were employed to conserve and consolidate the wood. After impregnating oak with these monomer mixtures, polymerization was accomplished by γ-irradiation. The relationships between the mechanical properties of the wood/(co)polymer composites and the anatomic structure of the wood, the types and the quantity of the polymer and copolymer, the irradiation dose and the aging process were explored. The fine structure of the wood/(co)polymer composites and the compatibility of wood with polymer and copolymer were investigated by scanning electron microscopy. The existence of polymer and copolymer in the wood enhanced the mechanical durability of the wood. The results of the hardness and the compressive strength tests applied in the parallel and perpendicular directions to the fibers of the wood/(co)polymer composites show that P(AGE/MMA), P(AGE/AN) copolymers are effective in raising the mechanical durability. In the case of P(AGE/MMA), the increase in the compressive strength perpendicular to the fibers in the oak wood is 179% at highest conversion. Similar results were also acquired from hardness tests. The decrease in the mechanical durability after aging for 28 d was very little.     

Improvement of mechanical stability of beechwood by radiation‐induced in situ copolymerization of allyl glycidyl ether with acrylonitrile and methyl methacrylate

Acrylonitrile (AN), methyl methacrylate (MMA), allyl glycidyl ether (AGE), AGE + AN monomer, AGE + MMA monomer, and monomer mixtures were used to conserve and consolidate beechwood. After the impregnation of these monomer mixtures in the wood, polymerization was accomplished by gamma irradiation. The fine structures of wood + polymer(copolymer) composites were investigated by scanning electron microscopy (SEM). The copolymer obtained from AGE + MMA monomer mixtures showed the optimum compatibility with the wood. The compressive strength and Brinell hardness numbers determined for untreated and treated wood samples indicated that the mechanical strength was greater in wood + polymer(copolymer) composites than in untreated wood and was greatest in the samples containing AGE + AN and AGE + MMA copolymers. All monomer couples used in this study increased the mechanical strength of the wood and protected the samples against aging. AGE + MMA copolymers were the most effective in protecting the wood against various environmental attacks. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1515–1523, 1999     

Preparation and thermal characterization of block copolymers by macroazonitriles having glycidyl azide and epichlorohydrin moieties

Poly(glycidyl azide) (PGA) an energetic polymer and polyepichlorohydrin (PECH) were condensed with 4,4′ azobis(4-cyanopentanoyl chloride) (ACPC) to prepare macro-azo-initiators. Block copolymers containing each of these polyethers as a block segment combined with polystyrene (PS) or poly(vinyl acetate) (PVAc) have been drived by the polymerization of monomers initiated with this macro-azo-initiators. Thermal properties of block copolymers were investigated with differential scanning calorimetry (DSC) and thermogravimetry. DSC traces showed single glass transition temperatures in between the related segments of copolymers. Dynamic thermogravimetric analysis revealed the individual degradation behaviors of block segments © 1996 John Wiley & Sons, Inc.     

The effect of preparation methods on the thermal properties of poly(acrylic acid) / alumina composites

Poly(acrylic acid) - alumina composites have been prepared by two different methods and thermally characterized. The glass transition temperatures (T_g) of the PAA/Al₂O₃ systems prepared by mixture and polymerization method were found to be 126°C and 130°C, respectively, irrespective of the alumina amounts involved in this work. The composites prepared by mixture and polymerization method have been investigated by using thermogravimetry (TGA) to follow the kinetics of anhyride formation and thermal degradation reactions. The activation energy of thermal anhydride formation and thermal degradation reaction was not found to change very much with the ratio of PAA/Al₂O₃ when the composites were prepared by simple mixing. For the composites prepared by the polymerization method, the activation energy of anhyride formation and thermal degradation reaction were observed to change with percentage conversion.     

The effect of pectin on the physicochemical and mechanical properties of cement containing boron

The effects of varying concentrations of pectin (0.1–1 wt% of cement) on the properties of ordinary portland cement (PC) and cement containing colemanite ore waste (CW) were investigated. Variation in setting time, compressive strength, and volume expansion of hydrated specimens were determined. It was found that pectin acts as an accelerator for PC cement and as a retarder for CW cement at a level below 0.1%. The inclusion of pectin in PC resulted in a reduction in the early strength of the mortar. However, pectin had positive contribution to the early compressive strength of the CW mortar.     

A practical approach to formulate stage–discharge relationship in natural rivers

This study proposes a new formulation technique for modeling stage–discharge relationship, as an alternative approach to standard regression techniques. An explicit neural network formulation (ENNF) is derived by using data obtained from United States Geological Survey data base. The neural network model is trained and tested using time series of daily stage and discharge data from two stations in Pennsylvania, USA. The model is compared with the standard rating curve (SRC) technique. Statistical parameters such as average, standard deviation, minimum, and maximum values, as well as criteria such as root mean square error, the efficiency coefficient (E), and determination coefficient (R ²) are used to measure the performance of the ENNF. Considerably, well performance is achieved in modeling streamflow by using ENNF. The comparison results reveal that the suggested formulations perform better than the conventional SRC.     

The synthesis of nonporous poly(isobutyl methacrylate) microspheres by suspension polymerization technique and investigation of their swelling properties

Poly(isobutyl methacrylate) (PiBMA) microspheres with different crosslinking densities were synthesized by suspension polymerization technique in aqueous medium and their characterization and swelling behaviors in different solvents were investigated. PiBMA spheres with a 800‐ to 1500‐μm‐diameter range were obtained by using benzoyl peroxide (BPO) as polymerization initiator, 1/5 ratio of monomer/water in volume, tricalcium phosphate (TCP), and poly(N vinyl‐2‐pyrrolidone) (PVP) as suspension stabilizer with 350 rpm stirring rate in nitrogen atmosphere. The influence of type and amount of crosslinking agent on the swelling properties and diffusional behavior, diffusion coefficient, and network properties of the spheres were examined in pentane, hexane, heptane, and gasoline. Dynamic swelling behaviors of crosslinked spheres were determined by measuring the diameter of the sphere as a function of time by an optical microscope. Swelling behaviors and network properties were found to be dependent on the diameter, crosslinking density of the sphere, and crosslinking agent and solvent. The results of this study indicate that the crosslinked PiBMA microsphere can be swollen in gasoline very well and retains a high ratio (1500% of its volume) of gasoline in their structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 349–356, 2002     

Estimation of Geomorphological Parameters of Lower Zab River-Basin by Using GIS-Based Remotely Sensed Image

The Lower Zab watershed is one of the most important catchment areas in the northern region of Iraq, as it includes large dam which is called Dukan Dam. Besides this, there are four other catchment areas, which are the Greater Zab (Upper Zab), Diyala, Khabur, and Uzem. During the last few decades like the other places in the world, the northern region of Iraq has been severely affected by the climatic changes, long-term drought, water shortage and some casual flood events. The former has impacted negatively on the wide range of areas in the region and continues to be a problem. However, the latter occasionally occurs during the winter season as a result of heavy rainfall and the lack of the required dams and artificial drainage. Both problems cause socio-economic damage in the region. This paper seeks to enhance water-based information in the region under study using the technique of GIS-based remotely sensed image that give us more accurate results and less time consuming to process data comparing with the GIS-based Topographic Maps (GTMs). This modern technique provides powerful and cost-effective tools for managing and processing data and creating maps for water resources. This would enable hydrologists and researchers to get better access to high quality hydrologic data. Thus, an accurate gemorphological parameters for watersheds and catchments can be calculated. Accordingly, more accurate hydraulic structures can be designed for the region under study.     

Spectroscopic and thermal studies of poly[(N‐vinylimidazole)‐co‐(maleic acid)] hydrogel and its quaternized form

BACKGROUND: In this study, poly[(N‐vinylimidazole)‐co‐(maleic acid)] (poly(VIm/MA)) hydrogels were prepared by γ‐irradiation of ternary mixtures of N‐vinylimidazole–maleic acid–water using a ⁶⁰Co γ‐source. Spectroscopic and thermal analyses of these hydrogels as a function of protonation showed that the results are consistent with the existence of an H‐bridged complex when the imidazole rings are partially protonated. Finally, the efficiency and binding trends of Cu²⁺, Co²⁺, Cd²⁺ and Pb²⁺ ions with both protonated and unprotonated poly(VIm/MA) hydrogels were determined. RESULTS: Gelation of 90% was reached at around 180 kGy dose at the end of irradiation. The poly(VIm/MA) hydrogels synthesized were further protonated in HCl solutions with different concentrations. Hydrogels originally showed 450% volumetric swelling; this ratio reached 1900% after protonation at pH = 5.0. Fourier transform infrared spectral changes in the ⁺N? H stretching region (3200–3600 and 1173 cm^?1) and the ring mode deformation at 915 cm^?1 are consistent with the formation of an H‐bridged complex between the protonated and unprotonated imidazole rings upon partial protonation. Similar changes were obtained from NMR spectra of both the protonated and unprotonated forms of the hydrogels. CONCLUSION: Protonated and unprotonated hydrogels have been used in heavy metal ion adsorption studies for environmental purposes. Adsorption decreased with decreasing pH value due to the protonation of the VIm ring. The adsorption of Me²⁺ ions decreased in the order Cu²⁺ > Co²⁺ > Cd²⁺ > Pb²⁺, which is related to the complexation stability as well as the ionic radius of the metal ions. These results show that P(VIm/MA) hydrogels can be used efficiently to remove heavy metal ions from aqueous solutions. However, the protonated form is a bad choice for heavy metal ion adsorption due to electrostatic repulsion forces; it can nevertheless be assumed to be a good choice for anion adsorption from environmental waste water systems. Copyright © 2007 Society of Chemical Industry     

Fast Computation of the Acoustic Field for Ultrasound Elements

A fast method for computing the acoustic field of ultrasound transducers is presented with application to rectangular elements that are cylindrically focused. No closed-form solutions exist for this case but several numerical techniques have been described in the ultrasound imaging literature. Our motivation is the rapid calculation of imaging kernels for physics-based diagnostic imaging for which current methods are too computationally intensive. Here, the surface integral defining the acoustic field from a baffled piston is converted to a 3-D spatial convolution of the element surface and the Green's function. A 3-D version of the overlap-save method from digital signal processing is employed to obtain a fast computational algorithm based on spatial Fourier transforms. Further efficiency is gained by using a separable approximation to the Green's function through singular value decomposition and increasing the effective sampling rate by polyphase filtering. The tradeoff between accuracy and spatial sampling rate is explored to determine appropriate parameters for a specific transducer. Comparisons with standard tools such as Field II are presented, where nearly 2 orders of magnitude improvement in computation speed is observed for similar accuracy.