Neural network modelling for shear strength of concrete members reinforced with FRP bars

This paper investigates the feasibility of using artificial neural networks (NNs) to predict the shear capacity of concrete members reinforced longitudinally with fibre reinforced polymer (FRP) bars, and without any shear reinforcement. An experimental database of 138 test specimens failed in shear is created and used to train and test NNs as well as to assess the accuracy of three existing shear design methods. The created NN predicted to a high level of accuracy the shear capacity of FRP reinforced concrete members.Garson index was employed to identify the relative importance of the influencing parameters on the shear capacity based on the trained NNs weightings. A parametric analysis was also conducted using the trained NN to establish the trend of the main influencing variables on the shear capacity. Many of the assumptions made by the shear design methods are predicted by the NN developed; however, few are inconsistent with the NN predictions.     

Crack growth rates of Inconel 600 in aqueous solutions at elevated temperature

The effect of sulfate ions on the crack growth rates (CGRs) of notched specimens (CT) of Inconel 600 under constant load has been investigated in chloride containing aqueous solutions at 250 °C. The intergranular stress corrosion crack growth rates increased in chloride solutions while its hinder with increasing sulfate concentrations. Stress intensity factor (k) for stress corrosion cracking decreased with increasing of aggressivity of chloride ions while increased in the presence of sulfate solutions. At very low concentration of chloride (0.001 m), k-value retardation was observed. It is clear from the results that hydrogen in the aqueous solutions has a deleterious effect on crack propagation. The difference in crack growth rates in chloride ions and in chloride containing sulfate solution at high temperature can be recognized as caused by the difference in local environment conditions at a crack tip. The results indicate that the crack don't propagate under this conditions in the presence of sulfate ions. It is mainly due to a hinderance of chloride ions adsorption on active sites of the fracture surfaces and the formation of chromium oxide layer which is stable at higher temperature.     

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.     

Multivariate determinants of the need for postoperative ventilation in myasthenia gravis

PURPOSE: Following transsternal thymectomy, up to 50% of patients may require postoperative ventilation. The aim of this study was to identify the variables most useful in predicting the myasthenic patient who needs postoperative mechanical ventilation. METHODS: We applied multivariate discriminant analysis to preoperative physical, historical, laboratory and intraoperative data of 51 myasthenic patients who underwent transcervical-transsternal thymectomy to select those variables most useful in predicting the postoperative need for mechanical ventilation. The receiver operating characteristic (ROC) curve was also used to describe the discrimination abilities and to explore the trade-offs between sensitivity and specificity of the model. RESULTS: Discriminant analysis identified seven risk factors that correlated with the need for postoperative ventilation: FVC, FEF25-75%, MEF50% and their percentages of the predicted values, as well as, sex. The model correctly predicted the actual ventilatory outcome in 88.2% of patients. The area under the ROC curve verified that our model correctly predicted the actual ventilatory outcome with a probability of 88.2%. CONCLUSIONS: This model can be used for predicting the need for postoperative mechanical ventilation in myasthenia gravis patients.     

Discrete cuckoo search algorithms for two-sided robotic assembly line balancing problem

Neural Computing and Applications - Robotics are extensively utilized in modern industry to replace human labor and achieve high automation and flexibility. In order to produce large-size products,...     

Influence of pressurized carbon dioxide on ketoprofen-incorporated hot-melt extruded low molecular weight hydroxypropylcellulose

Objectives: The aim of the current research project was to investigate the effect of pressurized carbon dioxide (P-CO₂) on the physico-mechanical properties of ketoprofen (KTP)-incorporated hydroxypropylcellulose (HPC) (Klucel? ELF, EF, and LF) produced using hot-melt extrusion (HME) techniques and to assess the plasticization effect of P-CO₂ on the various polymers tested.

Methods: The physico-mechanical properties of extrudates with and without injection of P-CO₂ were examined and compared with extrudates with the addition of 5% liquid plasticizer of propylene glycol (PG). The extrudates were milled and compressed into tablets. Tablet characteristics of the extrudates with and without injection of P-CO₂ were evaluated.

Results and conclusion: P-CO₂ acted as a plasticizer for tested polymers, which allowed for the reduction in extrusion processing temperature. The microscopic morphology of the extrudates was changed to a foam-like structure due to the expansion of the CO₂ at the extrusion die. The foamy extrudates demonstrated enhanced KTP release compared with the extrudates processed without P-CO₂ due to the increase of porosity and surface area of those extrudates. Furthermore, the hardness of the tablets prepared by foamy extrudates was increased and the percent friability was decreased. Thus, the good binding properties and compressibility of the extrudates were positively influenced by utilizing P-CO₂ processing.     

La~(3+) doped LiCo_(0.25)Zn_(0.25)Fe_2O_4 spinel ferrite nanocrystals:Insights on structural,optical and magnetic properties

This paper addresses the manipulation of structural,morphology,optical and magnetic properties of LiCo_(0.25)Zn_(0.25)Fe_2 O_4 ferrite via incorporation of different proportions of La~(3+) at the expense of iron ions using a sol-gel method.The samples were characterized using the X-ray diffraction technique(XRD),Fourier transform infrared(FT-IR) spectroscopy,the energy dispersive X-ray spectra(EDX),inductively coupled plasma optical emission spectroscopy(ICP-OES),high resolution scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET) surface area analysis,ultraviolet-diffuse reflectance spectroscopy(UV-DRS),and vibrating sample magnetometer(VSM) technique.The Rietveld refinements of the samples indicate that at higher concentrations of La3+,nanostructures with dual phase,i.e.cubic spinel and orthorhombic LaFeO_3 perovskite with space group(Pbnm) appear.Optical studies show that the energy band gap(E_g) of the bare LiCo_(0.25)Zn_(0.25)Fe_2 O_4 ferrite sample(2.18 eV) reaches up to 2.47 eV at x=0.06 and above this concentration,it drops sharply to 2.00 eV.Although the saturation magnetization and the coercivity of LiCo_(0.25)Zn_(0.25)La_xFe_(2-x)O_4 are lower than that of LiCo_(0.25)Zn_(0.25)Fe_2 O_4 NPs.Overall,the superparamagnetic nature and low values of saturation magnetization and coercivity of LiCo_(0.25)Zn_(0.25)La_xFe_(2-x)O_4 NPs are suitable to be applied in transformers core.     

Optimization of hot melt extrusion parameters for sphericity and hardness of polymeric face-cut pellets

The aim of this study was to formulate face-cut, melt-extruded pellets, and to optimize hot melt process parameters to obtain maximized sphericity and hardness by utilizing Soluplus^® as a polymeric carrier and carbamazepine (CBZ) as a model drug. Thermal gravimetric analysis (TGA) was used to detect thermal stability of CBZ. The Box–Behnken design for response surface methodology was developed using three factors, processing temperature (?°C), feeding rate (%), and screw speed (rpm), which resulted in 17 experimental runs. The influence of these factors on pellet sphericity and mechanical characteristics was assessed and evaluated for each experimental run. Pellets with optimal sphericity and mechanical properties were chosen for further characterization. This included differential scanning calorimetry, drug release, hardness friability index (HFI), flowability, bulk density, tapped density, Carr’s index, and fourier transform infrared radiation (FTIR) spectroscopy. TGA data showed no drug degradation upon heating to 190?°C. Hot melt extrusion processing conditions were found to have a significant effect on the pellet shape and hardness profile. Pellets with maximum sphericity and hardness exhibited no crystalline peak after extrusion. The rate of drug release was affected mainly by pellet size, where smaller pellets released the drug faster. All optimized formulations were found to be of superior hardness and not friable. The flow properties of optimized pellets were excellent with high bulk and tapped density.