Failure analysis of unidirectional polymeric matrix composites with two serial pin loaded-holes

The objective of this study is to investigate the effects of geometrical and physical parameters on failure modes and failure loads in unidirectional polymeric matrix composites with two serial pin loaded holes, analytically and experimentally. It is assumed that all of unidirectional fibers in the laminate lie in one direction while loaded by a load p ₀ at infinity, parallel to the direction of the fibers. To derive equilibrium equations based on a Shear-Lag theory, a rectangular arrangement of fibers is considered and with the proper use of boundary and boundness conditions, stress and displacement fields are computed within the laminate, along with the surrounding pinholes. Finally by using the Hashin criterion failure modes and failure loads are estimated. To validate analytical results based on shear-lag theory, an experimental program is carried out. A very good agreement is observed between two procedures. Based on results, in small sizes of two pins, the dominant failure mode is bearing and with the increasing of hole sizes, failure modes are changed to tension and shear modes.     

The preparation of activated carbon from macadamia nutshell by chemical activation

Different structured activated carbons were prepared from macadamia nutshell by chemical activation with potassium hydroxide and zinc chloride. The influence of process variables on the carbons' pore structure was studied in order to optimise these parameters. The results were also compared with those previously obtained on the chemical activation of coal. The most important parameter in chemical activation with both chemical agents was found to be the impregnation ratio. Carbonization temperature is the second important variable which had significant effect on pore volume evolution. Under the experimental circumstances studied, the optimum conditions in preparation of carbons with high surface area and pore volumes with both chemical agents are identified.     

Human leukocyte derived interferon-alpha in a hydrophilic gel for the treatment of intravaginal warts in women: a placebo-controlled, double-blind study

Persistent polychlorinated biphenyl (PCB) metabolites were studied with respect to their interaction with the human glucocorticoid receptor (GR). 3-Methylsulphonyl-2,5,6,2',4',5'-hexachlorobiphenyl (3-MeSO2-CB149) was shown to compete with 3H-dexamethasone for binding to the GR, with an IC50 (concentration that inhibits 50%) of approximately 1 microM. Using GRAF cells expressing human GR, glucocorticoid responsive element, and a reporter enzyme, we demonstrated that 3-MeSO2-CB149 functionally acts as an antagonist at the GR (IC50 = 2.7 microM). In accordance with the receptor binding, the antagonism mainly appeared to be of a competitive nature. When studying the competitive binding of 24 methylsulfonyl PCBs (relative to dexamethasone) to GR from mouse liver cytosol, seven compounds had a higher affinity to GR than 3-MeSO2-CB149. Structure-activity relationship studies indicated that the presence of three chlorine atoms in the ortho-position and chlorine and methyl sulfone groups on either end of the molecule (4 and 4'-position) increased the affinity to GR. The relevance of this finding for human health is not known, but PCB methyl sulfones are ubiquitous pollutants present in mother's milk. The results stress the need for studying endocrine disruptors that affect hormonal systems other than sex and thyroidogenic hormones.     

An extended discrete autoregressive model for variable bit rate video traffic encoded by scalable video codec

Designing an effective and high performance network requires accurate characterization and modeling of network traffic. This paper provides a study of the transmission, modeling, and analysis of variable bit rate (VBR) video, which is fundamental for designing protocols and for effective utilization of networks in video transmission. To meet the specified requirements of future networks, the scalable video codec (SVC) was chosen as the video compression standard. The main objective of this work was to propose a statistical model that will allow better coordination between generated SVC video traffic and original video traffic. The performance of the proposed model was evaluated by comparing the model with three existing low‐complex statistical models using graphical and statistical measurements as well as cross‐validation. For all evaluation techniques, the accuracy of the proposed model was evaluated, and the frame size distribution of the modeled traffic was found to match that of the original video traffic better than other existing models. Copyright © 2015 John Wiley & Sons, Ltd.     

Surface modification of commercial carbon black by silane coupling agents for improving dispersibility in rubber compounds

The dispersion of a filler in a rubber matrix is a crucial parameter affecting the mechanical and dynamical properties of a rubber compound. It is the current issue of the rubber compounding industry because, most fillers are categorized as a mineral, while the rubber is an organic material. The surface modification of the filler has been accepted as an effective technique for the improvement of the abovementioned parameter. First, the surface premodification of commercial carbon black with a grade of N660 (CB) was implemented by four different oxidation methods. After that, among of used methods, the oxidation method using citric acid was selected to produce modified carbon black (CB-Oxi) for further treatment. Subsequently, the coupling agent, Bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) was functionalized on the surface of CB-Oxi to produce modified-CB-Oxi. Also, for comparison purposes, the TESPT functionalization was accomplished on untreated CB to form modified-CB. The FTIR spectra of CB-Oxi showed using the premodification method introduced the hydroxyl and carboxyl groups on the surface of CB. The correspondent spectra for modified-CB-Oxi confirmed the existence of silane groups on the surface of the carbon black. However, the mentioned silane groups were not observed on the surface of modified-CB. The findings were strengthened by several characteristic techniques including, FESEM, XRD, EDS, CHNS elemental analysis, and RAMAN spectra. The FESEM graphs and elemental mapping showed homogeneous dispersion and uniform distribution of sulfur and silicon elements on the modified-CB-Oxi surface. According to RAMAN spectra, the disturbance in the structure of carbon black graphite was reduced after surface modification. modified-CB-Oxi is proposed as a potential substitute filler for current commercial carbon black in rubber compounding.     

Numerical simulation of two-phase mass transport in three-dimensional naturally fractured reservoirs using discrete streamlines

Simulation of multiphase mass transport in large field-scale heterogeneous, naturally fractured reservoirs with common grid-based methods is very time consuming and costly. An in-house streamline-based simulator is extended to simulate two-phase flow of oil and water in 3D heterogeneous, naturally fractured reservoirs. Different waterflooding problems have been simulated in 2D and 3D fractured reservoirs, and their results are compared with those of the grid-based commercial software. It has been shown that the streamline-based simulator can predict the results of the grid-based software with an acceptable accuracy, while its computational time and required memory is exceptionally less than the grid-based method.     

Model predictive control optimisation using the metaheuristic optimisation for blood pressure control

Given the importance of high blood pressure, it is important to control and maintain a constant blood pressure level in the normal state. The main aim of this article is to design a model predictive controller with a genetic algorithm (GA) for the regulation of arterial blood pressure. The present study is an applied cross‐sectional study. In order to do this research, studies related to designing mathematical models for blood pressure regulation and mechanical models for heart muscle and pressure sensors are investigated. Then, a model predictive controller with GA is designed for blood pressure control. All control and design operations are performed in the MATLAB software. According to the viscoelasticity of blood, transducer, and injection set, we can assume the mechanical model as Mass, Spring, and Damper. Initially, the patient''s blood pressure is lower than normal, and after controlling, the patient''s blood pressure returned to normal. By using a GA‐based model predictive control (MPC), mathematical validation, and mechanical model, the patient''s blood pressure can be adjusted and maintained. The simulation result shows that the GA‐based MPC offers acceptable response and speed of operation and the proposed controller can achieve good tracking and disturbance rejection.     

Effect of stirring on behaviour of double oxide film defects in A356 aluminium melt

The effect of stirring of melt on the behaviour of double oxide film (bifilm) defects in A356 melt was investigated using a reduced pressure test (RPT) technique. The melt was poured from a height into a crucible to introduce bifilms into the melt. The melt was then either remained stagnant or mechanically stirred, and RPT samples were taken from the melt at 8 min intervals. The RPT samples were then characterised by determination of their porosity parameters and examination of the internal surfaces of the pores using a scanning electron microscope. The results showed that stirring of the melt facilitated the diffusion of H in the melt into the atmosphere of the defects and hence accelerated the removal of the defects from the melt by floatation. This effect was attributed to the increase in the stress induced to the defects, which increased the rate of formation of cracks on their layers.