Evaluation of Centrifugal Casting Process Parameters for In Situ Fabricated Functionally Gradient Fe-TiC Composite

A gradient Fe-TiC composite was successfully produced via combination of in situ reaction with centrifugal casting techniques. Additionally, some of the effective parameters of the centrifugal casting process have been studied. Cast iron and ferrotitanium, which were used as raw materials, were melted using a high-frequency induction furnace coupled with centrifugal equipment. The microstructure and phase characterization of the fabricated composite was studied by scanning electron microscopy, optical microscopy, and X-ray diffraction. The results show that the production of a pearlite matrix composite reinforced by TiC particles is feasible. The distribution of TiC in the pearlitic matrix is completely uneven as a result of density difference between molten medium and TiC in the centrifugal casting process.     

Investigating correlations between crack width,corrosion level and anchorage capacity

In assessing existing structures, inspection results need to be linked to the effects on load-carrying capacity; to provide such information, this study has investigated the correlation between splitting crack width, corrosion level and anchorage capacity. The study was based on 13 reinforced concrete beams that had been exposed to natural corrosion for 32 years, 11 beams with splitting cracks and 2 without. The crack pattern and widths were documented before undergoing structural testing of anchorage capacity. Thereafter, the reinforcement bars were extracted and their corrosion levels measured using two methods, gravimetric weight loss and 3D scanning. The corrosion level from the weight loss method was approximately twice as large; possible reasons are horizontal or subsurface corrosion pits, and the cleaning method. Further, for the same corrosion level, the specimens in this study had much larger crack widths and slightly lower bond capacity than the artificially corroded tests in the literature; a possible reason is that these specimens had been subjected to combined corrosion and freezing. However, the corrosion level and reduction in bond capacity related to crack width were both lower in the present than in previous studies in the literature. Thus, by formulating a damage indicator from the damage visible in the form of crack widths from artificial test data, the structural capacity is estimated to be on the safe side.     

Optimum lipid production using agro-industrial wastewater treated microalgae as biofuel substrate

Abundant wastewater discharges from palm oil industries in tropical nations being a valuable resource of biodiesel need proper exploration. Research hinted that such wastewater as economical nutrient source or substrate can support the cultivation of microalgae. In this experiment, we have tested the growth and lipid production of five different microalgal strains in palm oil mill effluent (POME). POME as a biofuel substrate is demonstrated to be lucrative for microalgae-assisted lipids production. POME is rich in macro- and micronutrients can be used as a growth medium for algal growth in order to reduce the growth medium cost and environmental pollutions. Among the five microalgal strains tested, Chlorella sorokiniana revealed optimum biomass and lipid production. The productivity was evaluated in terms of chlorophyll content, growth rate, biomass, and lipid content, which discerned to be 0.099/day, 8.0 mg/L day and 2.68 mg/mg cell dry weight (CDW). Furthermore, in this study, an optimization study was carried out to enhance the microalgae to produce high lipid content using carbon-to-nitrogen ratio and different light/dark periods. The presence of nitrogen combined glucose (with a carbon-to-nitrogen ratio 100:7) as an alternative source to carbon displayed higher lipid production of 2.68 (mg/mg CDW) by C. sorokiniana. This study confirms that 8:16 h light/dark condition at C:TN ratio of 100:7 supported to produce high lipid content of 17 mg lipid/mg CDW. The above results revealed that POME could be a suitable growth media for the alga C. sorokiniana to improve the maximum lipid yield for biofuels production.     

Calculation of equilibrium composition in combustion products

For a specific combustion problem involving calculations of several species at equilibrium, it is much simpler to write a special computer program and calculate the concentrations, rather than to use a generalized computer program. To calculate these concentrations, one must solve a set of non-linear algebraic equations. This work describes a procedure in which the Newton-Raphson method and the successive substitution method are combined. It is was found that for these types of problems the value of unknowns and the nature of the equations are such that by adopting the two procedures simultaneously a much faster and reliable convergence is achieved. This study also shows what possible species should be considered for these calculations.     

Aggregation and clogging phenomena of rigid microparticles in microfluidics

We developed a numerical tool to investigate the phenomena of aggregation and clogging of rigid microparticles suspended in a Newtonian fluid transported through a straight microchannel. In a first step, we implement a time-dependent one-way coupling Discrete Element Method (DEM) technique to simulate the movement and effect of adhesion on rigid microparticles in two- and three-dimensional computational domains. The Johnson–Kendall–Roberts (JKR) theory of adhesion is applied to investigate the contact mechanics of particle–particle and particle–wall interactions. Using the one-way coupled solver, the agglomeration, aggregation and deposition behavior of the microparticles is studied by varying the Reynolds number and the particle adhesion. In a second step, we apply a two-way coupling CFD–DEM approach, which solves the equation of motion for each particle, and transfers the force field corresponding to particle–fluid interactions to the CFD toolbox OpenFOAM. Results for the one-way (DEM) and two-way (CFD–DEM) coupling techniques are compared in terms of aggregate size, aggregate percentages, spatial and temporal evaluation of aggregates in 2D and 3D. We conclude that two-way coupling is the more realistic approach, which can accurately capture the particle–fluid dynamics in microfluidic applications.     

A cubic dual band near-field focused array antenna using composite right/left handed transmission lines

This paper proposes a new method for design of a dual-frequency near field-focused (NFF) antenna. A 4 × 4 array of dual-band patches and a dual-band feed network are designed to provide a phase distribution at 2.4 and 5.8 GHz. Rectangular patches with U-shaped slot be used as the double-band patches. The composite right/left handed transmission lines (CRLH TL) are used in design of a dual-band phase distribution network for the patches. Finally, a three-dimensional cubic structure is proposed to isolate the feed network and thereby improve the antenna performance. A prototype of a cubic dual band 4 × 4 near field focused array antenna is fabricated and tested. The measurement results have good agreement with simulation results.     

Radiation dose to neonates undergoing X-ray imaging in special care baby units in Iran

Radiographic imaging has a significant role in the timely diagnosis of the diseases of neonates in intensive care units. The estimation of the dose received by the infants undergoing radiographic examination is of great importance, due to greater more radiosensitivity and longer life expectancy of the neonates and premature babies. In this study, the values of entrance skin dose (ESD), dose area products (DAPs), energy imparted (EI), whole-body dose, effective dose and risk of childhood cancer were estimated using three methods including direct method [using thermoluminescence dosimetry (TLD) chips], indirect method (using tube output) and Monte Carlo (MC) method (using MCNP4C code). In the first step, the ESD of the neonates was directly measured using TLD-100 chips. Fifty neonates, mostly premature, with different weights and gestational ages in five hospitals mostly suffering from respiratory distress syndrome and pneumonia were involved in this study. In the second step, the values of ESD to neonates were indirectly obtained from the tube output in different imaging techniques. The imaging room, incubator, neonates and other components were then simulated in order to obtain the ESD values using the MCNP4C code. Finally, the values of ESD assessed by the three methods were used for calculation of DAP, EI, whole-body dose, effective dose and risk of childhood cancer. The results indicate that the mean ESD per radiograph estimated by the direct, indirect and MC methods are 56.6±4.1, 50.1±3.1 and 54.5±3.3 μGy, respectively. The mean risk of childhood cancer estimated in this study varied between 4.21×10(-7) and 2.72×10(-6).     

Analytical cracking load estimation of Laminated Veneer Lumber (LVL) beams with holes

Predicting the load-carrying capacity of timber beams with holes cannot be performed by usual analysis methods if the failure of the beam is governed by the crack initiation and propagation around the hole at low load levels. Predicting the cracking load is an important design issue because it corresponds to the load-carrying capacity of the timber beam before the crack propagation. One of the models that can be used for the fracture formulation is that of a beam on elastic foundation. In this model a part of the beam is assumed to follow the conditions of beam with elastic foundation which has spring stiffness equal to the fracture properties of the material in the crack surface. Based on beam on elastic foundation model, the cracking load prediction is the target of the paper. Some closed form solutions for the beam with hole are presented. The formulation has been derived for two cases of pure shear and pure bending moment. Finally a semi-empirical formulation for combination of shear and bending moment in the section is presented. The model predictions are compared with the results of an experimental program showing good correlation. The analytical model can therefore be proposed for future revisions of codes of practice such as the Eurocode 5.     

An algorithm on sign words extraction and recognition of continuous Persian sign language based on motion and shape features of hands

Sign language is the most important means of communication for deaf people. Given the lack of familiarity of non-deaf people with the language of deaf people, designing a translator system which facilitates the communication of deaf people with the surrounding environment seems to be necessary. The system of translating the sign language into spoken languages should be able to identify the gestures in sign language videos. Consequently, this study provides a system based on machine vision to recognize the signs in continuous Persian sign language video. This system generally consists of two main phases of sign words extraction and their classification. Several stages, including tracking and separating the sign words, are conducted in the sign word extraction phase. The most challenging part of this process is separation of sign words from video sequences. To do this, a new algorithm is presented which is capable of detecting accurate boundaries of words in the Persian sign language video. This algorithm decomposes sign language video into the sign words using motion and hand shape features, leading to more favorable results compared to the other methods presented in the literature. In the classification phase, separated words are classified and recognized using hidden Markov model and hybrid KNN-DTW algorithm, respectively. Due to the lack of proper database on Persian sign language, the authors prepared a database including several sentences and words performed by three signers. Simulation of proposed words boundary detection and classification algorithms on the above database led to the promising results. The results indicated an average rate of 93.73 % for accurate words boundary detection algorithm and the average rate of 92.4 and 92.3 % for words recognition using hands motion and shape features, respectively.     

Alteration of ADP-ribosylation in aging rat brain astrocytes

DNA damage and the enzyme poly (ADP-ribose) polymerase (PARP) associated with the pathogenesis of numerous age-related neurodegenerative disorders. Astrocytes play crucial roles in both support metabolic functions and cell viability of the brain. PARP regulates DNA damage and repair in the brain cells. In this study PARP activity and DNA strand break were investigated in the astrocytes isolated from young and aged rat brain. Three and 30-month-old rats were killed by decapitation and brains were removed onto an ice cooled glass plate. Astrocytes were isolated by sucrose density gradient centrifugation and glutamine synthetase (GS) served as a marker of the astrocytes lineage. The specific activity of PARP was assayed in permeabilized cells by measuring the incorporation of the ADPribose moiety of [3H]NAD into the nuclear acceptor proteins. The rate of DNA strand breaks was determined using a fluorescent dye and monitored spectrofluorimetry. An increase (about 75%) in the PARP activity was observed in the whole homogenates of aged rats, whereas this rise was more pronounced (about 360%) when the reaction was measured in the purified astrocyte preparations. The amount of DNA strand breaks was also higher in the astrocytes isolated from the aged brain as compared to that of young levels. The close relationship between the level of DNA strand breaks and PARP activity in the astrocytes suggest that these cells are susceptible to the metabolic alterations in aging. It is concluded that the astrocytes PARP might be considered as a therapeutic target for combating age related neurodegenerative disorders.