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  • Articles  (62)
  • 2010-2014  (62)
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  • Articles  (62)
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  • 11
    Publication Date: 2014-12-28
    Description: A new low-cost, simple and clean method for microbial monitoring sensor based on bimetallic thin film is fabricated in this research. The nanocomposite of Ag–Cu doped with PVA has been synthesized via sol–gel method and deposited on glass substrate. Ag–Cu alloy thin films with various concentrations were characterized using XRD, FTIR, UV–Vis, AFM, TEM and I – V measurement. The peaks in XRD pattern confirm the presence of Ag, Cu and Ag–Cu alloy nanoparticles in FCC structure. FTIR spectra found the O–H stretching of hydroxyl group and C–H stretching of PVA. The resonance UV–Vis absorption peaks are all sharp and lie between the wavelengths of 296–299 nm. The surface of the films has been found to be smoother as the Cu concentrations increased. The sensor performance was tested by measuring the changes of current of the film using I – V measurement. The Ag 0.2 –Cu 0.8 alloy film shows obvious changes in current when it was incubated with E. coli . The sensitivity measurement, S , shows that the high sensitivity can be observed at higher concentrations of Cu.
    Print ISSN: 1319-8025
    Electronic ISSN: 2191-4281
    Topics: Natural Sciences in General , Technology
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  • 12
    Publication Date: 2014-12-28
    Description: This paper presents an investigation of the use of recycled lightweight aggregate from waste autoclaved aerated concrete block to make lightweight pervious concrete (LWPC). The effects of fine sand (SA) and fly ash (FA) as additive materials on LWPC properties were also studied. The density, total void ratio, water permeability, compressive strength, splitting tensile strength, flexural strength, thermal conductivity, and surface abrasion of LWPC were tested. The results showed that all LWPCs had low density of 775–900 kg/m 3 and low thermal conductivity coefficient of 0.15–0.27 W/m K. The use of SA and FA improved the compressive strength, splitting tensile strength, flexural strength, and abrasion resistance of LWPC, while the total void ratio and water permeability seemed to reduce. The low thermal conductivity and low density of LWPC with reasonable 28-day compressive strength of 1.9–4.1 MPa suggested that it is suitable for use as thermal insulating concrete.
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    Electronic ISSN: 2191-4281
    Topics: Natural Sciences in General , Technology
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  • 13
    Publication Date: 2014-12-28
    Description: The earthquake-resistant design of prefabricated buildings is currently the focus of attention, especially for industrial buildings that require a high level of seismic protection. The standard design approach, based on ductility requirements, may succeed in preventing building collapse during a severe earthquake, but at the expense of accepting a high damage level at the column bases. To improve the seismic performance of such buildings, different innovative techniques have been proposed. However, these have not been widely implemented in engineering practice due, among others, to the lack of simple conceptual design methodologies. To achieve this goal, a methodology for the design of a roof isolation system is presented, where the roof isolation serves as non-conventional tuned mass damper (TMD), giving a significantly reduced response in terms of displacements and forces. To that effect, design expressions for the TMD period and damping, depending on the building and soil characteristics, are proposed: The expressions have been calibrated based on numerical parametric time history analyses considering Eurocode 8 spectrum—compatible accelerograms. The application of the proposed methodology is demonstrated for a two-story prefabricated building.
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  • 14
    Publication Date: 2014-12-25
    Description: In this paper, the effect of compacting pressure (150–450 MPa) and copper (Cu) additions (2.5, 5, 7.5 and 10 wt%) on the microstructure and physical properties of NiTi-based shape memory alloys prepared by powder metallurgy is studied. Many characterization techniques were employed in this study such as X-ray diffraction method and scanning electron microscope. The chemical composition of the prepared alloys and microstructure was achieved by using scanning electron microscope equipped with EDS. Differential scanning calorimetric is utilized to measure the transformation temperature of the prepared alloys. Several physical tests such as particle size distribution measurements, density and porosity of green compacted samples and density and porosity after sintering are achieved. XRD test shows that the master sintered samples consist of three phases at room temperature: NiTi monoclinic phase, NiTi cubic phase and Ni 3 Ti hexagonal phase. Furthermore, (CuNi 2 Ti) intermetallic compound is appeared in the samples with 2.5, 5, 7.5 and 10 wt% of Cu. According to the results, it was found that compacting pressure has an essential effect on the decreases in porosity percentage and the results show that (Cu) additions increase porosity percentage in all weight percentages of additives.
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  • 15
    Publication Date: 2014-12-25
    Description: The use of traffic crash data-based methodologies for safety evaluation is inadequate due to the shortcomings such as unavailability and low quality of historical crash data. Other than crash data-based analysis, the use of empirical vehicle maneuvers and/or the development of micro-simulation models in conjunction with surrogate safety measures has been shown to potentially complement traditional safety analysis. However, several previous works found that existing surrogate measures for intersection safety assessment, such as post-encroachment time, time to collision and speed, fail to simultaneously represent conflict probability and severity. Thus, this study proposes a measurement of the crash hazard that considers crash occurrence probability as well as expected severity. By utilizing the change in the total kinetic energy before and after the collision, angle of collision and PET, the proposed conflict index is derived and its implications are discussed. Several video-recorded signalized intersections in Nagoya, Japan, were utilized to extract vehicle trajectories, through which conflict characteristics are estimated. The relationship between the estimated distributions of the proposed index and the records of severe crashes at the corresponding sites are compared. The proposed safety measure is successful in similarly ranking different signalized intersection to the severity of crashes that occurred at each site. The author expects the new safety assessment measure can be useful in assisting policy makers in prioritizing different sites for safety improvements by identifying hazardous locations which currently lack accurate and historical crash data.
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  • 16
    Publication Date: 2014-12-25
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  • 17
    Publication Date: 2014-12-25
    Description: An artificial neural network (ANN) has a wide application field for mathematical problems. Specifically, an ANN is successfully applied to problems that are difficult to solve or do not have any information on their operating techniques. In this article, an ANN was applied to predict the concrete mix composition for steel fiber-reinforced concrete (SFRC). Thus, an ANN model was developed and trained with data collected from literature. These data have SFRC mix compositions, workability measurements of fresh SFRC, compressive strength of SFRCs, and additional information that affects concrete quality. Additionally, the ANN included steel fiber volume fraction in the SFRC and steel fiber properties. With the goal of determining the concrete mix composition, which is cement dosage, amount of water, coarse aggregate content, fine aggregate content, and chemical admixture, an ANN model was developed. The inputs for the ANN were consistency class of SFRC, compressive strength of SFRC, maximum size of aggregate, steel fiber volume fraction, steel fiber length, and diameter. At the end of the study, a feed forward ANN model with six inputs and five outputs was successfully trained and used to produce the correct responses to testing data. Designing SFRC requires more trial mixtures to obtain the desired quality than does conventional concrete. In conclusion, artificial neural networks have a strong potential for predicting concrete mix composition for SFRC such that without trial mixes and loss of time, an SFRC design is possible with the desired workability and mechanical properties.
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  • 18
    Publication Date: 2014-12-25
    Description: In the present study, ultrasonic-assisted Fenton process called sono-Fenton (SF) with low concentration of Fenton reagents was studied via degradation of Direct Blue 71. Influences of seven operational parameters including initial pH (pH 0 ), initial concentration of pollutant ( C 0 ), dose of Fenton reagents ( C Fe and C H2O2 ), ultrasound irradiation frequency (Fr S ), ultrasound irradiation power ( P S ), and treatment time ( t SF ) were investigated on the dye removal efficiency (DR). A combined design of experiments consists of full factorial for t SF , and Taguchi for other six parameters was designed, and experiments were conducted in accordance with the design. The experimental data were collected using a batch reactor equipped with controllable ultrasonic bath. The DR of 0–33.5 mg/l was achieved under experimental conditions. These results approved that the SF process can be a promising approach in terms of colored wastewater treatment. The data were used for model building by Taguchi and artificial neural network. Further statistical tests were applied to exhibit models goodness and to compare models. Finally, optimization process was carried out using Taguchi and genetic algorithm. The optimization procedure causes optimal point which gives an insight of optimal operating condition.
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  • 19
    Publication Date: 2014-12-25
    Description: Bottom intakes are frequently used as diversion structures in mountainous regions, because of their simplicity and low costs in comparison with other methods of river diversion. In this study, Flow-3D software is utilized to simulate the flow passing through the racks. Verification tests are performed on the results of numerical method by using the experimental results of Righetti and Lanzoni (J. Hydraul. Eng. 134(1), 15–22, 2008 ). Also, calibration tests and mesh sensitivity are performed on the mathematical model. The diverted discharge in the numerical model is compared with the experimental data, and a good correlation ( R 2  = 0.99) was obtained. Among the different existing turbulence models, the k ɛ RNG model performed best. Afterward, the racks with eight different cross-sectional geometries are simulated by the numerical method. The diverted discharge, velocity and pressure distributions around the racks for each cross section are obtained and compared with each other. Results revealed that lozenge shape is the most effective geometry in flow diversion.
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  • 20
    Publication Date: 2014-12-23
    Description: High flood occurrences with large environmental damages have a growing trend in Iran. Dynamic movements of water during a flood cause different environmental damages in geographical areas with different characteristics such as topographic conditions. In general, environmental effects and damages caused by a flood in an area can be investigated from different points of view. The current essay is aiming at detecting environmental effects of flood occurrences in Halilrood catchment area of Kerman province in Iran using flood zone-mapping techniques. The intended flood zone map was introduced in four steps. Steps 1–3 pave the way to calculate and estimate flood zone map in the understudy area while step 4 determines the estimation of environmental effects of flood occurrence. Based on our studies, wide range of accuracy for estimating the environmental effects of flood occurrence was introduced by using flood zone-mapping techniques. Moreover, it was identified that the existence of Jiroft dam in the study area can decrease flood zone from 260 to 225 ha and also it can decrease 20 % of flood peak intensity. As a result, 14 % of flood zone in the study area can be saved environmentally.
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