Thermo-mechanical properties of concrete containing high-volume mineral admixtures

This paper reports the results of a study conducted to evaluate the influence of high-volume class C fly ash (FA), blast furnace slag (BFS) and both FA+BFS on the thermal conductivity (TC), compressive strength, water absorption and density of concrete. TC decreased with the increase of FA, BFS and FA+BFS as replacement for Portland cement. The reductions in TC due to FA, BFS and FA+BFS were, respectively, up to 39%, 18% and 31%. The addition of FA, BFS and FA+BFS in the concrete had a decreasing effect on TC. Their addition also decreased compressive strength as a function of replacement percent. However, this reduction in compressive strength decreased with increasing curing period.     

Development of a New Methodology for Indirect Determination of Nitrite,Nitrate, and Total Nitrite in the Selected Two Groups of Foods by Spectrophotometry

A new indirect preconcentration procedure was developed for micellar sensitive detection of trace nitrite as analyte by spectrophotometry. The method is based on ion association of triiodide ion, I₃ ^? or I₂, produced by the reaction of nitrite at low concentrations with excess iodide in presence of ion-pairing agent, Coomassie brilliant blue R 250 (CBB), and electrophilic attack of nitrosyl cation produced by disproportionation of nitrite depending on concentration to ion-pairing agent at higher concentrations than 5 μg L^?1 in acidic medium, and then extraction of the ion-pairing complex formed from aqueous solution into the micelles of Triton X-114 at sodium acetate medium. The calibration graphs were rectilinear in the range of 0.5–5 and 5–200 μg L^?1 with increasing and decreasing slopes in micellar phase, respectively. The detection and quantification limits of the method were 0.15 and 0.50 μg L^?1, and the precision (as RSD) for five replicate measurements of different concentrations of nitrite was in the range of 2.3–4.8%. The average recoveries of spiked nitrite residues ranged from 97 to 104%. The method is free of matrix interferences and successfully applied to the indirect determination of nitrite, nitrate, and total nitrite in selected two groups of foods. Also, the accuracy was validated by analysis of a certified reference material as well as recoveries of spiked samples. The objective of the study is to provide an alternate economical method to determine the contents of nitrite, nitrate, and total nitrite after homogenization, extraction, reduction, and preconcentration from sample matrix.

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Effect of inhibitor treatment on corrosion of steel in a salt solution

This study examined experimentally different chemicals for inhibition of steel corrosion in a simulated aqueous solution for the industrial marine atmosphere of the Arabian Gulf region. The literature reported various inhibitors that can help in protection against metal corrosion in aqueous environments. Among them, 10 inhibitors (calcium silicate, cyclohexylamine, n-methylcyclohexylamine, dicyclohexylamine nitrite, sodium benzoate, sodium nitrate, sodium nitrite, sodium phosphate, sodium dihydrogen orthophosphate, and magnesium nitrate hexahydrate) were obtained and corrosion resistance of inhibitor applied steel specimens were examined in the simulated solution (2 wt.% NaCl and 1 wt.% Na₂SO₄). Test specimens were prepared from locally produced reinforcing steel products. Treatment of steel with either dicyclohexylamine nitrite or sodium dihydrogen orthophosphate both at 10 mM concentration for 1 day at room temperature resulted in significant inhibition of corrosion. No significant improvement in corrosion inhibition was observed either with an increase in inhibitor concentration at room temperature or with an increase in inhibitor application temperature at 10 mM concentration. A further study is planned to examine the inhibition performances of the two inhibitors under actual atmospheric conditions in the Arabian Gulf region (industrial marine environment).     

Mill-knurling as an alternative to laser welding for automotive drivetrain assembly

A novel technique for drivetrain assembly -“mill-knurling and press-fitting (MKPF)” is proposed as an alternative to laser welding or bolting. This joining technique involves the press fitting of two mating surfaces, one with mill-knurled teeth and the other which is of a relatively softer material, enabling it to flow over the teeth making a joint. This process is applied within the rear axle differential subjected to fluctuating torque loads. Experimental analysis and simulation is used to compare the functional feasibility and the potential benefits of mill knurled joints with laser welded and bolted joints currently used in differential/bevel gear assembly.     

A fuzzy controller design for nuclear research reactors using the particle swarm optimization algorithm

In this paper, a closed-loop fuzzy logic controller based on the particle swarm optimization algorithm is proposed for controlling the power level of nuclear research reactors. The principle of the fuzzy logic controller is based on the rules constructed from numerical experiments made by means of a computer code for the core dynamics calculation and from human operator's experience and knowledge. In addition to these intuitive and experimental design efforts, consequent parts of the fuzzy rules are optimally (or near optimally) determined using the particle swarm optimization algorithm. The contribution of the proposed algorithm to a reactor control system is investigated in details. The performance of the controller is also tested with numerical simulations in numerous operating conditions from various initial power levels to desired power levels, as well as under disturbance. It is shown that the proposed control system performs satisfactorily under almost all operating conditions, even in the case of very small initial power levels.     

Air permeability of electrospun polyacrylonitrile nanoweb

Ultrafine fibers were spun from polyacrylonitrile (PAN) solution in N,N‐dimethylformamide using a homemade electrospinning setup. Fibers with diameter ranging from 80 to 340 nm were obtained. Fiber size and fiber size distribution were investigated for various concentration, applied voltage, and tip‐to‐collector distance using image analysis. The diameters of the electrospun fibers increase when increasing the solution concentration and decrease slightly when increasing the voltage and needle tip‐to‐collector distance. Porosity and air permeability are vital properties in applications of electrospun nanofibrous structures. In this study, effects of process parameters on the porosity and air permeability of electrospun nanoweb were investigated as well. Results of statistical analysis showed that solution concentration and applied voltage have significant influences on pore diameters. It was concluded that nanofiber diameter played an important role on the diameter of pores formed by the intersections of nanofibers. A more realistic understanding of porosity was obtained and a quantitative relationship between nanoweb parameters and its air permeability was established by regression analysis. Two separate models were constructed for predicting air permeability in relation to process parameters. Optimization of electrospinning process for producing nanoweb with desirable air permeability is well achieved by these models. The models presented in this study are of high importance for their ability to predict the air permeability of PAN nanoweb both by process or structure parameters. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Seawater effect on impact behavior of glass–epoxy composite pipes

The effect of seawater immersion on impact behavior of glass–epoxy composite pipes is experimentally investigated. Glass–epoxy pipes with [±55°]₃ orientation were fabricated using filament winding method. Composite pipes were selected for four different diameters as 50 mm, 75 mm, 100 mm, and 150 mm. The pipes were immersed in artificial seawater having a salinity of about 3.5% for 3, 6, 9, and 12 months in laboratory conditions. At the end of the conditioning period, the specimens were impacted at three distinct energy levels as 15 J, 20 J, and 25 J at ambient temperature of 20 °C. The comparisons between the dry and immersed cases were carried out by using contact force, deflection and absorbed energy data of the impact tests. Results show that moisture absorption, salt in seawater, diameter of specimen and residual stresses produced by manufacturing process of the composite pipe have significant effect on maximum contact force, maximum deflection, absorbed energy and failure of composite pipes according to exposure time to seawater.     

Development of a real time energy monitoring platform

This study introduces development of a user-friendly and quite effectual energy monitoring system which has been installed in Electrical Education Department of Gazi University in Turkey and in use since November 2007. The system developed monitors data in real time using a powerful energy analyzer which is capable of measuring many parameters of energy consumed in the building. The real time data measured by the power analyzer are transferred to a host computer via RS485 serial communication protocol and then collected in a database continuously. Thus, parameters of energy measured are successfully followed, archived, and presented as graphical forms.The monitoring system presented in the study integrates to quite visual and quite user friendly interface with powerful and flexible hardware. Therefore, several functions can be performed easily and safely by simple actions. On the other hand, the system presented in our paper is developed in a university, so it can be used by students to learn energy systems and parameters.     

S2S: structural-to-syntactic matching similar documents

Management of large collection of replicated data in centralized or distributed environments is important for many systems that provide data mining, mirroring, storage, and content distribution. In its simplest form, the documents are generated, duplicated and updated by emails and web pages. Although redundancy may increase the reliability at a level, uncontrolled redundancy aggravates the retrieval performance and might be useless if the returned documents are obsolete. Document similarity matching algorithms do not provide the information on the differences of documents, and file synchronization algorithms are usually inefficient and ignore the structural and syntactic organization of documents. In this paper, we propose the S2S matching approach. The S2S matching is composed of structural and syntactic phases to compare documents. Firstly, in the structural phase, documents are decomposed into components by its syntax and compared at the coarse level. The structural mapping processes the decomposed documents based on its syntax without actually mapping at the word level. The structural mapping can be applied in a hierarchical way based on the structural organization of a document. Secondly, the syntactic matching algorithm uses a heuristic look-ahead algorithm for matching consecutive tokens with a verification patch. Our two-phase S2S matching approach provides faster results than currently available string matching algorithms.

Educational interface agents as social models to influence learner achievement,attitude and retention of learning

This study examined the impacts of educational interface agents with different attributes on achievement, attitude and retention of elementary school students in their science and technology courses. The study was implemented in four different eighth- grade classes (aged 13–14) of an elementary school. Four different types of educational software, covering living things and life unit of 8th graders, were developed to analyze the impacts of educational software agents with different attributes on the results of learning. The study was conducted according to experimental model with pretest and posttest control group, which is one of the quasi-experimental designs. For five consecutive weeks experimental and control group students used the software designed for this research. The students were asked to fill an attitude scale on science and technology both before and after the implementation. And following completion, an achievement test was applied. The results of the study revealed that students who used a human-like educational interface agent were more successful than both the rest of the experimental groups and the control group in terms of achievement, attitude and retention of learning in science and technology classes. It is also revealed that the software to be developed for elementary school 8th graders (aged 13–14) should be supported with human-like educational interface agents.