Flexural and shear capacities of concrete beams reinforced with GFRP bars

This paper reports test results of 12 concrete beams reinforced with glass fibre-reinforced polymer (GFRP) bars subjected to a four point loading system. All test specimens had no transverse shear nor compression reinforcement and were classified into two groups according to the concrete compressive strength. The main parameters investigated in each group were the beam depth and amount of GFRP reinforcement. Two modes of failure were observed, namely flexural and shear. The flexural failure is mainly occurred due to tensile rupture of GFRP bars either within the mid-span region or under the applied point load. The shear failure is initiated by a major diagonal crack within the beam shear span. This diagonal crack extended horizontally at the level of the GFRP bars indicating bond failure.Simplified methods for estimating the flexural and shear capacities of beams tested are presented. The flexural capacity is estimated based on the compatibility of strains and equilibrium of forces. Comparisons between the flexural capacity obtained from the theoretical analysis and that experimentally measured in the current investigation and elsewhere show good agreement. To predict the shear capacity of the beams tested, four methods recently proposed in the literature for GFRP-reinforced concrete beams are used. These methods have been developed by modifying the ACI 318-99 shear capacity formula for steel-reinforced concrete beams to account for the difference in the axial stiffness of GFRP and steel bars. It has been shown that the theoretical predictions of the shear capacity obtained from these methods are inconsistent and further research needs to be carried out in order to establish a rational method for the shear capacity calculation of GFRP-reinforced concrete beams.     

Morphological segmenting and neighborhood pixel-based locality preserving projection on brain fMRI dataset for semantic feature extraction: an affective computing study

Two specific chemical receptive fields of brain, namely the amygdala and the orbital-frontal cortex, are related to valence and arousal in medical experiments. Functional magnetic resonance imaging (fMRI), which is a noninvasive, repeatable, and atomical tool for medical imaging in clinic system, was widely used in affective computing; however, it faces its dataset processing difficulty for dimensional reduction as well as for decreasing the computational complexity. In addition, features extraction from those de-dimensionality datasets is a challenging issue. The current work solved the de-dimensionality issue by using some preprocessing algorithms including clustering, morphological segmenting, and locality preserving projection. In order to keep useful information in fMRI dataset for reduction process, improved neighborhood pixel-based locality preserving projection (NP-LPP) algorithm was addressed and continuously for feature extraction operating using Otsu weighted sum of histogram. Furthermore, a modified covariance power spectral density (MC-PSD) separately in an fMRI Valence–Arousal experiments was measured. The results were analyzed and compared with affective norms English words system. The experiments established that the proposed methods of NP-LPP effectively simplified high complexity of fMRI, and Otsu weighted sum of histogram exhibited superior performance for features extraction compared to the MC-PSD through the calculation root mean standard error. The current proposed method provided a potential application and promising research direction on human semantic retrieval through medical imaging dataset.

     

Texture anisotropy technique in brain degenerative diseases

Structural alterations anisotropy-based measured for different areas for the most common types of dementia diseases could be a biomarker of brain impairment. The current work aims to assess whether texture anisotropy can discriminate both healthy versus Alzheimer’s and Pick’s patients based on regional evaluation while maintaining high predictive power. The investigated area is reduced from the whole-brain surface to three major lobes (i.e., frontal, temporal and parietal). A predictive model was proposed to associate a disease with a specific area in the brain based on the anisotropy values. Simultaneous analysis of 1680 measurements from 105 brain magnetic resonance images acquired as T2w and PD sequences was performed to establish the significance of the model. The cerebral calcinosis disease has been used as artificial ground truth. The association based on textural anisotropy between targeted diseases and control patients was performed by using Pearson’s correlation coefficients. A new proposed consistency index investigated the texture anisotropy relevance for all image’s types and all analyzed classes and regions. The validation study is based on area under the receiver-operating characteristic curve that depicted the overall diagnostic performance of the texture anisotropy in each region. The proposed model demonstrated that texture anisotropy is accurate solution in diagnosis of Alzheimer’s and Pick’s diseases when the investigated area is reduced to major lobes, with sensitivity >90% and specificity >80%.

     

Performance of straw bale wall: A case of study

This research aimed to evaluate a straw bale house located in Bavaria, Germany. An extensive test program was carried out. The experimental work includes compression tests, moisture content, thermal stability of bales and pH. The in situ work includes temperature and relative humidity inside the straw bale wall. The stress-strain behavior of straw bales was investigated including nonlinearity and anisotropy. Thermal stability of bales under constant temperature and relative humidity was studied considering time dependence. The moisture content of straw bale was about 11%, while pH value inside the bale was about 7.29. Moreover, the temperature and the relative humidity between the interior (inside straw bale wall) and the exterior were investigated.     

Hierarchical TiO2/ZnO Nanostructure as Novel Non-precious Electrocatalyst for Ethanol Electrooxidation

Metal oxides have a higher chemical stability in comparison to metals,so they can be utilized as electrocatalysts if the activity could be enhanced.Besides the composition,the morphology of the nanostructures has a considerable impact on the electrocatalytic activity.In this work,zinc oxide nano branches-attached titanium dioxide nanofibers were investigated as an economic and stable catalyst for ethanol electrooxidation in the alkaline media.The introduced material has been synthesized by electrospinning process followed by hydrothermal technique.Briefly,electrospinning of colloidal solution consisting of titanium isopropoxide,poly(vinyl acetate) and zinc nanoparticles was performed to produce nanofibers embedding solid nanoparticles.In order to produce TiO_2 nanofibers containing ZnO nanoparticles,the obtained electrospun nanofiber mats were calcined in air at 600 °C.The formed ZnO nanoparticles were exploited as seeds to outgrow ZnO branches around the TiO_2 nanofibers using the hydrothermal technique at sub-critical water conditions in the presence of zinc nitrate and bis-hexamethylene triamine.The morphology of the final product,as well as the electrochemical measurements indicated that zinc nanoparticles content in the original electrospun nanofibers has a significant influence on the electrocatalytic activity as the best performance was observed with the nanofibers synthesized from electrospun solution containing 0.1 g Zn,and the corresponding current density was 37 mA/cm~2.Overall,this study paves a way to titanium dioxide to be exploited to synthesize effective and stable metal oxide-based electrocatalysts.     

Saudi tests of imported cements

As the pace of development increases in Saudi Arabia so imported materials become more numerous and competitive. The Materials Testing Laboratory in Riyadh recently compared samples of cements from abroad with those produced locally. The results, though primarily directed towards the cement chemists, may also be of more than local interest.     

Essais saoudiens sur les ciments importés

Au fur et à mesure que le développement s'accélère en Arabie saoudite, les matériaux importés deviennent de plus en plus nombreux et entrent en concurrence les uns avec les autres. Le Materials Testing Laboratory de Riyad a procédé, il ny a pas très longtemps, à une étude comparative d'échantillons de ciments importés et de ciments fabriqués dans le pays. S'ils concernent avant tout les chimistes du ciment, les résultats n'en présentent pas moins un intérêt plus général.     

Effect of electrolyte characteristics on electrowinning of copper powder

This paper is concerned with studying the effect of electrolyte characteristics on the production process of electrolytic copper powder from partially depleted Cu containing synthetic electrolytes by electrowinning technique. The main electrolyte characteristics are temperature, circulation rate, Cu and H₂SO₄ concentrations, residence time in the cell, and utilization of organic bath additives. The process is positively affected by increasing the values of all of the studied parameters except for the addition of organic bath additives, which causes a negative effect. However addition of organic bath additives remarkably increases the degree of refinement of the produced powders. In most cases pure and fine copper powders were obtained with a dendritic shape, as indicated by scanning electron microscope (SEM) analysis.     

Synthesis and characterization of polyurethane – Treated waste milled light bulbs composites

In this study, polyurethane (PU)-milled light bulbs glass composites were synthesized and characterized. The main interest in this study that the polyurethane derived from renewable resources and waste glass are used to form the composite constituents as an attempt towards environmental preservation. Castor oil and polymeric diphenyl methane di-isocyanates (PMDI) were used in NCO/OH ratio = 2 for polyurethane synthesis. Milled glass with average particles size less than 300 μm were prepared based on waste light bulbs. Silane A1100 (as a compatibilizer) was used in order to improve the value of recycled milled glass beads. The adhesion force between polyurethane matrix and milled glass beads was evaluated using mechanical and physical tests. Scanning electron microscopy (SEM) was used to investigate dispersion and fracture surfaces of the composites. Infrared spectrum (IR), Differential scanning calorimetry (DSC) behavior, and Thermogravimetric analysis (TGA), were employed to characterize the developed composite materials in details. Chemical resistance (weight change, thickness swelling) was measured in oil, water and dilute acetic acid media. Furthermore, tensile strength and hardness were investigated using universal materials testing machines. A slight increase in the hardness values was reported along with the increasing in particulate fillers loading up to 10% as a considerable improvement has been detected when milled glass reached 20%. The DSC analysis showed the presence of treated milled glass beads influences the thermal behavior of pure PU and composites. This can be attributed to enhancing the physical bonding between PU and silica group. Waste milled glass showed a significant effect on the thermal degradation of the composites in the presence of coupling agent. Further analysis on the tensile strength of the composites indicated that such improved mechanical properties may be attributed to the presence of coupling agent.     

CORRELATIONS FOR ESTIMATING THE DIFFUSIVITIES OF NITROUS OXIDE IN AQUEOUS SOLUTIONS OF DIETHANOLAMINE AND N-METHYLDIETHANOLAMINE AND THE SOLUTION DENSITIES AND VISCOSITIES

Experimentally measured diffusion coefficients of nitrous oxide in water, aqueous solutions of diethanolamine, aqueous solutions of N-methyldiethanolamine, and aqueous blends of diethanolamine and N-methyldiethanolamine have been used to arrive at a modified Stokes-Einstein correlation by using nonlinear least-squares filling. The average deviation of this correlation from the experimentally measured diffusion coefficients is about 13%. Comparisons are also made to the estimated diffusivities of nitrous oxide in the amine solutions which are obtained from the Wilke-Chang and Hayduk-Minhas correlations. The average deviations of the Wilke-Chang and Hayduk-Minhas correlations from the measured values are about 13% and 19%, respectively. Correlations were also presented for estimating the solution densities and viscosities. Predicted values for the solution densities and viscosities from these correlations deviate from experimentally measured values on average by 1.2% and 4.8% respectively.