Search results for: powder fine recycled aggregate

Authors: Naruemon Prapasuwannakul, Supitcha Boonchai, Nawapat Pengpengpit

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The aim of this study was to determine physicochemical and sensory properties of germinated brown rice ice cream as affected by replacement of cream, milk, stabilizer, and emulsifier with green coconut pulp. Five different formulations of ice cream were performed. Regular formulation of ice cream consisted of GBR juice, milk cream, milk powder, stabilizer, emulsifier, sucrose and salt. Replacing of cream, milk, stabilizer, and emulsifier with coconut pulp resulted in an increase in viscosity and overrun, but a decrease in hardness, melting rate, lightness (l*) and redness (a*). However, there was no significant difference among all formulations on any sensory attributes. The results also showed that the ice cream with replacement of coconut pulp contained less fat and protein than those of the regular ice cream. The findings suggested that green coconut pulp can be used as alternative ingredient to replace fat, milk stabilizer and emulsifier even in a high carbohydrate ice cream formulation.

Keywords: ice cream, germinated brown rice, coconut pulp, milk, cream

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Authors: Nicolò Vaiana, Giorgio Serino

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In this paper, an advanced Nonlinear Exponential Model (NEM), able to simulate the uniaxial dynamic behavior of seismic isolators having a continuously decreasing tangent stiffness with increasing displacement in the relatively large displacements range and a hardening or softening behavior at large displacements, is presented. The mathematical model is validated by comparing the experimental force-displacement hysteresis loops obtained during cyclic tests, conducted on a helical wire rope isolator and a recycled rubber-fiber reinforced bearing, with those predicted analytically. Good agreement between the experimental and simulated results shows that the proposed model can be an effective numerical tool to predict the force-displacement relationship of seismic isolation devices within the large displacements range. Compared to the widely used Bouc-Wen model, unable to simulate the response of seismic isolators at large displacements, the proposed one allows to avoid the numerical solution of a first order nonlinear ordinary differential equation for each time step of a nonlinear time history analysis, thus reducing the computation effort. Furthermore, the proposed model can simulate the smooth transition of the hysteresis loops from small to large displacements by adopting only one set of five parameters determined from the experimental hysteresis loops having the largest amplitude.

Keywords: base isolation, hardening behavior, nonlinear exponential model, seismic isolators, softening behavior

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Authors: Y. Galerkin, A. Rekstin, K. Soldatova

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Universal modeling method well proven for industrial compressors was applied for design of the high flow rate supersonic stage. Results were checked by ANSYS CFX and NUMECA Fine Turbo calculations. The impeller appeared to be very effective at transonic flow velocities. Stator elements efficiency is acceptable at design Mach numbers too. Their loss coefficient versus inlet flow angle performances correlates well with Universal modeling prediction. The impeller demonstrated ability of satisfactory operation at design flow rate. Supersonic flow behavior in the impeller inducer at the shroud blade to blade surface Φdes deserves additional study.

Keywords: centrifugal compressor stage, supersonic impeller, inlet flow angle, loss coefficient, return channel, shock wave, vane diffuser

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Authors: Tse-An Pan, Sheng-Long Lee

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The effect of non-isothermal aging on the mechanical properties and corrosion resistance of Al-9Zn-2.3Mg-1.9Cu (AA7056) alloys was investigated. The results revealed that thick materials were limited to retrogression and re-aging treatment (RRA). It could not reach the retrogression temperature in the RRA treatment. Compared with the RRA treatment, the non-isothermal aging (NIA) treatment produced discontinuous precipitates at grain boundaries, while the intragranular precipitates were fine and dense. The strength was similar to that of the RRA treatment; the corrosion resistance of the alloy was significantly improved by NIA aging. NIA treatment was less affected by the thickness of the alloy. The difference between the actual temperature and the setting temperature of the alloy is minimal during the aging process. The combination of properties could overcome the fact that RRA treatment cannot handle thick materials.

Keywords: Al-Zn-Mg-Cu alloy, corrosion, retrogression, re-aging, non-isothermal aging

Procedia PDF Downloads 181

Authors: I. A. Ibrahim, T. A. Elbarbary, N. Abdelaty, A. T. Kandil, H. K. Farhan

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The present work aims to study the leaching of Abu Ghalaga ilmenite ore by hydrochloric acid and simultaneous reduction by iron powder method to dissolve its titanium and iron contents. Iron content in the produced liquor is separated by solvent extraction using TBP as a solvent. All parameters affecting the efficiency of the dissolution process were separately studied including the acid concentration, solid/liquid ratio which controls the ilmenite/acid molar ratio, temperature, time and grain size. The optimum conditions at which maximum leaching occur are 30% HCl acid with a solid/liquid ratio of 1/30 at 80 °C for 4 h using ore ground to -350 mesh size. At the same time, all parameters affecting on solvent extraction and stripping of iron content from the produced liquor were studied. Results show that the best extraction is at solvent/solution 1/1 by shaking at 240 RPM for 45 minutes at 30 °C whereas best striping of iron at H₂O/solvent 2/1.

Keywords: ilmenite ore, leaching, titanium solvent extraction, Abu Ghalaga ilmenite ore

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Authors: Gurbir Kaur, Surinder Pal Singh

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The present study is a part of the research work on the effect of limestone powder (LP), silica fume (SF) and metakaolin (MK), on the flexural fatigue performance of steel fibre reinforced concrete (SFRC). Corrugated rectangular steel fibres of size 0.6x2.0x35 mm at a constant volume fraction of 1.0% have been incorporated in all mix combinations as the reinforcing material. Three mix combinations were prepared by replacing 30% of ordinary Portland cement (OPC) by weight with these cement additives in binary and ternary fashion to demonstrate their contribution. An experimental programme was conducted to obtain the fatigue lives of all mix combinations at various stress levels. The fatigue life data have been analysed as an attempt to determine the relationship between stress level ‘S’, number of cycles to failure ‘N’ and probability of failure ‘Pf’ for all mix combinations. The experimental coefficients of the fatigue equation have also been obtained from the fatigue data to represent the S-N-Pf curves analytically.

Keywords: cement additives, fatigue life, probability of failure, steel fibre reinforced concrete

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Authors: Sira Suren, Soorathep Kheawhom

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This work investigates the development of a high energy density zinc-air battery. Printed and flexible thin film zinc-air battery with an overall thickness of about 350 μm was fabricated by an inexpensive screen-printing technique. Commercial nano-silver ink was used as both current collectors and catalyst layer. Carbon black ink was used to fabricate cathode electrode. Polypropylene membrane was used as the cathode substrate and separator. 9 M KOH was used as the electrolyte. A mixture of Zn powder, ZnO, and Bi2O3 was used to prepare the anode electrode. The suitable concentration of Bi2O3 and types of binders (styrene-butadiene and sodium silicate) were investigated. Results showed that battery using 20% Bi2O3 and sodium silicate binder provided the best performance. The open-circuit voltage and energy density observed were 1.59 V and 690 Wh/kg, respectively. When the battery was discharged at 20 mA/cm2, the potential voltage observed was 1.3 V. Furthermore, the battery was tested for its flexibility. Upon bending, no significant loss in performance was observed.

Keywords: flexible, printed battery, screen printing, Zn-air

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Authors: Olakunle M. Makanjuola, Adebola Ajayi

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Effect of the dehydrated method on proximate, functional and mineral properties of corn starch was evaluated. The study was carried and to determine the proximate, functional and mineral properties of corn starch produced using three different drying methods namely (sun) (oven) and (cabinet) drying methods. The corn starch was obtained by cleaning, steeping, milling, sieving, dewatering and drying corn starch was evaluated for proximate composition, functional properties, and mineral properties to determine the nutritional properties, moisture, crude protein, crude fat, ash, and carbohydrate were in the range of 9.35 to 12.16, 6.5 to 10.78 1.08 to 2.5, 1.08 to 2.5, 4.0 to 5.2, 69.58 to 75.8% respectively. Bulk density range between 0.610g/dm3 to 0.718 g/dm3, water, and oil absorption capacities range between 116.5 to 117.25 and 113.8 to 117.25 ml/g respectively. Swelling powder had value varying from 1.401 to 1.544g/g respectively. The results indicate that the cabinet method had the best result item of the quality attribute.

Keywords: starch flour, maize, dehydration, cabinet dryer

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Authors: Mahera Abdulrahman

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Objective: Healthcare transformation from traditional to modern in the country recently prompted the need to address career choices, accreditation perception and satisfaction among medical residents. However, a concerted nationwide study to understand and address burnout in the medical residency program has not been conducted in the UAE and the region. Methods: A nationwide, multicenter, cross-sectional study was designed to evaluate professional burnout and depression among medical residents in order to address the gap. Results: Our results indicate that 75.5% (216/286) of UAE medical residents had moderate to high emotional exhaustion, 84% (249/298) had high depersonalization, and 74% (216/291) had a low sense of personal accomplishment. In aggregate, 70% (212/302) of medical residents were considered to be experiencing at least one symptom of burnout based on a high emotional exhaustion score or a high depersonalization score. Depression ranging from 6-22%, depending on the specialty was also striking given the fact the Arab culture lays high emphasis on family bonding. Interestingly 83% (40/48) of medical residents who had high scores for depression also reported burnout. Conclusion: Our data indicate that burnout and depression among medical residents is epidemic. There is an immediate need to address burnout through effective interventions at both the individual and institutional levels. It is imperative to reconfigure the approach to medical training for the well-being of the next generation of physicians in the Arab world.

Keywords: mental health, Gulf, Arab, residency training, burnout, depression

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Authors: M. Tang, S. M. Wen, D. W. Liu

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This paper presents the influences on the entrainment of serpentines by grinding and reagents during copper–nickel sulfide flotation. The previous bench flotation tests were performed to extract the metallic values from the ore in Yunnan Mine, China and the relatively satisfied results with recoveries of 86.92% Cu, 54.92% Ni, and 74.73% Pt+Pd in the concentrate were harvested at their grades of 4.02%, 3.24% and 76.61 g/t, respectively. However, the content of MgO in the concentrate was still more than 19%. Micro-flotation tests were conducted with the objective of figuring out the influences on the entrainment of serpentines into the concentrate by particle size, flocculants or depressants and collectors, as well as visual observations in suspension by OLYMPUS camera. All the tests results pointed to the presences of both “entrapped-in” serpentines and its coating on the hydrophobic flocs resulted from strong collectors (combination of butyl xanthate, butyl ammonium dithophosphate, even after adding carboxymethyl cellulose as effective depressant. And fine grinding may escalate the entrainment of serpentines in the concentrate.

Keywords: serpentine, copper and nickel sulfides, flotation, entrainment

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Authors: P. C. Chiu, Jehnming Lin

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In this study, a 50-W CO₂ laser was used for the clad of 304L powders on the stainless steel substrate with a temperature sensor and image monitoring system. The laser power and cladding speed and focal position were modified to achieve the requirement of the workpiece flatness and mechanical properties. The numerical calculation is based on ANSYS to analyze the temperature change of the moving heat source at different surface positions when coating the workpiece, and the effect of the process parameters on the bath size was discussed. The temperature of stainless steel powder in the nozzle outlet reacting with the laser was simulated as a process parameter. In the experiment, the difference of the thermal conductivity in three-dimensional space is compared with single-layer cladding and multi-layer cladding. The heat dissipation pattern of the single-layer cladding is the steel plate and the multi-layer coating is the workpiece itself. The relationship between the multi-clad temperature and the profile was analyzed by the temperature signal from an IR pyrometer.

Keywords: laser cladding, temperature, profile, microstructure

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Authors: S. A. Naeini, M. Ghorbani Tochaee

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The aim of this study is to assess the influence of plastic fines content on sand-clay mixtures on maximum shear modulus and liquefaction resistance using a series of resonant column tests. A high plasticity clay called bentonite was added to 161 Firoozkooh sand at the percentages of 10, 15, 20, 25, 30 and 35 by dry weight. The resonant column tests were performed on the remolded specimens at constant confining pressure of 100 KPa and then the values of G_max and liquefaction resistance were investigated. The maximum shear modulus and cyclic resistance ratio (CRR) are examined in terms of fines content. Based on the results, the maximum shear modulus and liquefaction resistance tend to decrease within the increment of fine contents.

Keywords: Gmax, liquefaction, plastic fines, resonant column, sand-clay mixtures, bentonite

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Authors: M. Alsaadi, A. Erkliğ, M. Bulut

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This paper experimentally investigates the flexural and tensile properties of the industrial wastes sewage sludge ash (SSA) and fly ash (FA), and conventional ceramic powder silicon carbide (SiC) filled polyester composites. Four weight fractions (5, 10, 15 and 20 wt%) for each micro filler were used for production of composites. Then, test samples were produced according to ASTM. The resulting degree of particle dispersion in the polymer matrix was visualized by using scanning electron microscope (SEM). Results from this study showed that the tensile strength increased up to its maximum value at filler content 5 wt% of SSA, FA and SiC. Flexural strength increased with addition of particulate filler up to its maximum value at filler content 5 wt% of SSA and FA while for SiC decreased for all weight fractions gradually. The addition of SSA, FA and SiC fillers resulted in increase of tensile and flexural modulus for all the particulate composites. Industrial waste SSA can be used as an additive with polymer to produce composite materials.

Keywords: particle-reinforcement, sewage sludge ash, polymer matrix composites, mechanical properties

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Authors: Sara Soltanpour, Adolfo Foriero

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Frost heave is arguably the most problematic adverse phenomenon in cold region areas. Frost heave is a complex process that depends on heat and water transfer. These coupled physical fields generate considerable heave stresses as well as deformations. In the present study, a coupled thermal-hydraulic-mechanical (THM) model using COMSOL Multiphysics in frozen unsaturated soils, such as fine sand, is investigated. Particular attention to the frost heave and temperature distribution, as well as the water migrating during soil freezing, is assessed. The results obtained from the numerical simulations are consistent with the results measured in the full-scale tests conducted by Cold Regions Research and Engineering Laboratory (CRREL).

Keywords: frost heave, numerical simulations, COMSOL software, unsaturated freezing soil

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Authors: Arjun, A. D. Singh

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Concrete the basic material using in construction across the global these days. The purpose of this special concrete is to provide extra strength and stability for irregular structure where the center of gravity is disturbed. In this paper an effort has been made to use different type of material aggregates has been discussed. We named As "STAR Aggregates" which has qualities to resist Shear, tension and compression forces. We have been divided into coarse aggregates and fine aggregates according to their sizes. Star Aggregates has interlocking behavior and cutting edge technology. Star aggregates had been draft and deign in Auto CAD and then analysis in ANSYS software. by using special aggregates we deign concrete grade of M40 for mega structures and irregular structure. This special concrete with STAR aggregates use in construction for irregular structure like Bridges, Skyscrapers or in deigned buildings.

Keywords: star aggregates, high performance concrete, material aggregates, interlocking

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Authors: Mlk. Khouadjia, B. Mezghiche

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The environment protection has led to a growing interest in the use of crushed sand, which is not correctly exploited due to the high rate of fine particles that it contains and which affect concrete properties. This study will examine the variation of the compressive strength of concrete with several local areas of sand exposed to freeze-thaw cycles and chemical solutions. The experiments have been realized on crushed, river, and dune sands. We use software (MATLAB) to find the coefficient of particle shape. Finally, we have found a relationship between the reference concrete without modification and concrete modified with river and dune sands to predict the variations of resistance after curing in different environments. The results showed that the behavior of concrete is different according to the types of sand and the environment of exposition.

Keywords: crushed sand, compressive strength, freeze-thaw, MATLAB, dune sand, river sand

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Authors: P. Venkata Karthik, B. Kranthi Kumar

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Fly ash is a solid waste product of coal based electric power generating plants. Fly ash is the finest of coal ash particles and it is transported from the combustion chamber by exhaust gases. Fly ash is removed by particulate emission control devices such as electrostatic precipitators or filter fabric bag-houses. It is a fine material with spherical particles. Large quantities of fly ash discharged from coal-fired power stations are a major problem not only in terms of scarcity of land available for its disposal, but also in environmental aspects. Fly ash can be one of the alternatives and can be a viable option to use as a filling material. This paper contains the problems associated with fly ash generation, need for its management and the efficacy of fly ash composite as a backfilling material. By conducting suitable geotechnical investigations and numerical modelling techniques, the fly ash composite material was tested. It also contains case studies of typical Indian opencast and underground coal mines.

Keywords: backfilling, fly ash, high concentration slurry disposal, power plant, void infilling

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Authors: C. A. Roberts, S. L. Mascaro, J. R. Gerrish, J. L. Horner

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Management-intensive Grazing (MiG) is a practice that rotates livestock through paddocks in a way that best matches the nutrient requirements of the animal to the yield and quality of the pasture. In the USA, MiG has been taught to livestock producers throughout the state of Missouri in 2- and 3-day workshops called “Missouri Grazing Schools.” The economic impact of these schools was quantified using IMPLAN software. The model included hectares of adoption, animal performance, carrying capacity, and input costs. To date, MiG, as taught in the Missouri Grazing Schools, has been implemented on more than 70,000 hectares in Missouri. The economic impact of these schools is presently $125 million USD per year added to the state economy. This magnitude of impact is the result not only of widespread adoption but also because of increased livestock carrying capacity; in Missouri, a capacity increase of 25 to 30% has been well documented. Additional impacts have been MiG improving forage quality and reducing the cost of feed and fertilizer. The environmental impact of MiG in the state of Missouri is currently being estimated. Environmental impact takes into account the reduction in the application of commercial fertilizers; in MiG systems, nitrogen is supplied by N fixation from legumes, and much of the P and K is recycled naturally by well-distributed manure. The environmental impact also estimates carbon sequestration and methane production; MiG can increase carbon sequestration and reduce methane production in comparison to default grazing practices and feedlot operations in the USA.

Keywords: agricultural education, forage quality, management-intensive grazing, nutrient cycling, stock density, sustainable agriculture

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Authors: U. V. S. Seshavatharam, S. Lakshminarayana

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In a unified approach observed cosmic red shift can be re-interpreted as an index of cosmological galactic atomic light emission phenomenon. By increasing the applications of Hubble volume in cosmology as well as in quantum physics, concepts of ‘Black Hole Cosmology’ can be well-confirmed. Clearly speaking ‘quantum mechanics’ can be shown to be a branch of ‘black hole cosmology’. In Big Bang Model, confirmation of all the observations directly depend on the large scale galactic distances that are beyond human reach and raise ambiguity in all respects. The subject of modern black hole physics is absolutely theoretical. Advantage of Black hole cosmology lies in confirming its validity through the ground based atomic and nuclear experimental results.

Keywords: Hubble volume, black hole cosmology, CMBR energy density, Planck’s constant, fine structure ratio, cosmic time, nuclear charge radius, unification

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Authors: T. S. Sidhu

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Amongst the existing coatings methods, the cold spray is new upcoming process to deposit coatings. As from the name itself, the cold spray coating takes place at very low temperature as compare to other thermal spray coatings. In all other thermal spray coating process the partial melting of the coating powder particles takes place before deposition, but cold spray process takes place in solid state. In cold spray process, the bonding of coating power with substrate is not metallurgical as in other thermal spray processes. Due to supersonic speed and less temperature of spray particles, solid state, dense, and oxide free coatings are produced. Due to these characteristics, the cold spray coatings have been used to protect the materials against hot corrosion. In the present study, the cold spray process, cold spray fundaments, its types, and its applications for high temperatures are discussed in the light of presently available literature. In addition, the assessment of cold spray with the competitive technologies has been conferred with available literature.

Keywords: cold spray coating, hot corrosion, thermal spray coating, high-temperature materials

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Authors: Sello Mokwena, Monyepao Thabang

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In this study, we propose a comprehensive approach to address the challenges in person re-identification models. By combining a centroid tracking algorithm with a Siamese convolutional neural network model, our method excels in detecting, tracking, and capturing robust person features across non-overlapping camera views. The algorithm efficiently identifies individuals in the camera network, while the neural network extracts fine-grained global features for precise cross-image comparisons. The approach's effectiveness is further accentuated by leveraging the camera network topology for guidance. Our empirical analysis on benchmark datasets highlights its competitive performance, particularly evident when background subtraction techniques are selectively applied, underscoring its potential in advancing person re-identification techniques.

Keywords: camera network, convolutional neural network topology, person tracking, person re-identification, siamese

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Authors: Anup Kumar Keshri, Arvind Agarwal

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Carbon nanotube (CNT) reinforced aluminum oxide (Al2O3) composite coating was synthesized on the steel substrate using plasma spraying technique. Three different compositions of coating such as Al2O3, Al2O¬3-4 wt. % CNT and Al2O3-8 wt. % CNT were synthesized and the fracture strength was determined using the four point bend test. Uniform dispersion of CNTs over Al2O3 powder particle was successfully achieved. With increasing CNT content, porosity in the coating showed decreasing trend and hence contributed towards enhanced mechanical properties such as hardness (~12% increased) and elastic modulus (~34 % increased). Fracture strength of the coating was found to be increasing with the CNT additions. By reinforcement of 8 wt. % of CNT, fracture strength increased by ~2.5 times. The improvement in fracture strength of Al2O3-CNT coating was attributed to three competitive phenomena viz. (i) lower porosity (ii) higher hardness and elastic modulus (iii) CNT bridging between splats.

Keywords: aluminum oxide, carbon nanotube, fracture strength, plasma spraying

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Authors: Badr M. Thamer

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The use of hydrogels as adsorbents for pollutants removal from wastewater is limited due to their high swelling properties and the difficulty in recovering them after the adsorption process. To overcome these problems, a new hydrogel nanocomposite based on chitosan-g-polyacrylic acid/oxidized electrospun carbon nanofibers (CT-g-PAA/O-ECNFs) was prepared by in-situ grafting polymerization process. The prepared hydrogel nanocomposite was used as a novel effective and highly reusable adsorbent for the removal of methylene blue (MB) from polluted water with low cost. The morphology and the structure of CT-g-PAA/O-ECNFs were investigated by numerous techniques. The effect of incorporating O-ECNFs on the swelling capability of the prepared hydrogel was explored in distillated water and MB solution at normal pH. The effect of parameters including the ratio of O-ECNFs, contact time, pH, initial concentration, and temperature on the adsorption process were explored. The adsorption isotherm and kinetic were studied by numerous non-linear models. The obtained results confirmed that the incorporation of O-ECNFs into the hydrogel network improved its ability towards MB dye removal with decreasing their swelling capacity. The adsorption process depends on the pH value of the dye solution. Additionally, the adsorption and kinetic results were fitted using the Freundlich isotherm model and pseudo second order model (PSO), respectively. Moreover, the new adsorbents can be recycled for at least five cycles keeping its adsorption capacity and can be easily recovered without loss in its initial weight.

Keywords: carbon nanofibers, hydrogels, nanocomposites, water treatment

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Authors: Ji Sun Kim, Jae Ho Baek, Kyeong Ho Kim, Ji Hae Ha, Seong Soo Hong, Jung-Wook Park, Man Sig Lee

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Carbon supported palladium catalysts have been used in many industrial reactions, especially for hydrogenation in the fine chemical industry. Porous carbons had been widely used as catalyst supports due to its higher surface area and larger pore volume. The specific surface area, pore structure and surface chemical functional groups of porous carbon affects metal dispersion and particle size. In this paper, we confirm the effect of support texture on the dispersion of Pd. Pd catalyst supported on activated carbon having various specific surface area were characterized by BET, XRD and FE-TEM. Catalyst activity and dispersion of prepared catalyst were evaluated on the basis of the CO adsorption capacity by CO-chemisorption. As concluding remark to this part of our study, let us note that specific area of carbon play important role on the synthesis of Pd/C catalyst/.

Keywords: carbon, dispersion, Pd/C, specific are, support

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Authors: Amandeep Singh, Niraj Bala

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In the last decades, light-weight materials such as magnesium matrix composites have become hot topic for material research due to their excellent mechanical and physical properties. However, relatively very less work has been done related to the wear behavior of these composites. Magnesium matrix composites have wide applications in automobile and aerospace sector. In this review, attempt has been done to collect the literature related to wear behavior of magnesium matrix composites fabricated through various processing techniques such as stir casting, powder metallurgy, friction stir processing etc. Effect of different reinforcements, reinforcement content, reinforcement size, wear load, sliding speed and time have been studied by different researchers in detail. Wear mechanism under different experimental condition has been reviewed in detail. The wear resistance of magnesium and its alloys can be enhanced with the addition of different reinforcements. Wear resistance can further be enhanced by increasing the percentage of added reinforcements. Increase in applied load during wear test leads to increase in wear rate of magnesium composites.

Keywords: hardness, magnesium matrix composites, reinforcement, wear

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Authors: Sahar Heidary, Ramin Ghasemi Shayan

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The overall goal Monte Carlo N-atom radioactivity transference PC program (MCNP4C) was done for the regeneration of x-ray groups in diagnostic radiology and mammography. The electrons were transported till they slow down and stopover in the target. Both bremsstrahlung and characteristic x-ray creation were measured in this study. In this issue, the x-ray spectra forecast by several computational models recycled in the diagnostic radiology and mammography energy kind have been calculated by appraisal with dignified spectra and their outcome on the scheming of absorbed dose and effective dose (ED) told to the adult ORNL hermaphroditic phantom quantified. This comprises practical models (TASMIP and MASMIP), semi-practical models (X-rayb&m, X-raytbc, XCOMP, IPEM, Tucker et al., and Blough et al.), and Monte Carlo modeling (EGS4, ITS3.0, and MCNP4C). Images got consuming synchrotron radiation (SR) and both screen-film and the CR system were related with images of the similar trials attained with digital mammography equipment. In sight of the worthy feature of the effects gained, the CR system was used in two mammographic inspections with SR. For separately mammography unit, the capability acquiesced bilateral mediolateral oblique (MLO) and craniocaudal(CC) mammograms attained in a woman with fatty breasts and a woman with dense breasts. Referees planned the common groups and definite absences that managed to a choice to miscarry the part that formed the scientific imaginings.

Keywords: mammography, monte carlo, effective dose, radiology

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Authors: Bounar Nedjemeddine

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Materials with the pyrochlore lattice structure have attracted much recent attention due to their wide applications in ceramic thermal barrier coatings, high-permittivity dielectrics, and potential solid electrolytes in solid-oxide fuel cells. The work described in this paper is devoted to the synthesis and characterization of a pyrochlore structure based on lanthanum (La₂O₃) and tin (SnO₂) oxides of general formula La₂Sn₂O₇, substituted by Sr at the site La. Their structures were determined from X-ray powder diffraction using CELFER analysis. All the compositions present the space group Fd-3m. The substitution of La by Sr in the La₂Sn₂O₇ compound causes a variation of the cell parameters. The difference in charge between La³⁺ and Sr²⁺ and the difference in size cause the cell parameters to decrease from a=10.7165 A° to a=10.6848 A° for the substitution rates (x = 0.05, 0.1, 0.15 ...), which leads to a decrease in the volume of the mesh. For a substitution rate x = 0.25, there is an increase in the cell parameters (a=10.7035A°), which can be explained by a competitiveness of the size effect and the presence of a gap in the structure which go in the opposite direction.

Keywords: solid-oxide fuel cells, structure, pyrochlore, X-ray diffraction

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Authors: Hamid Alihosseini, Kamran Dehghani

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In this study, the effects of grain size of AA6061 aluminum on the bake hardening have been investigated. The grains of sample sheets refined by applying 4, 8, and 12 passes of ECAP and their microstructures and mechanical properties were investigated. EBSD and TEM studies of the sheets showed grain refinement, and the EBSD micrograph of the alloy ECAPed for 12 passes showed nano-grained (NG) ∼95nm in size. Then, the bake hardenability of processed sheet was compared by pre-straining to 6% followed by baking at 200°C for 20 min. The results show that in case of baking at 200°C, there was an increase about 108%, 93%, and 72% in the bake hardening for 12, 8, and 4 passes, respectively. The maximum in bake hardenability (120 MPa) and final yield stress (583 MPa) were pertaining to the ultra-fine grain specimen pre-strained 6% followed by baking at 200◦C.

Keywords: bake hardening, ultrafine grain, nano grain, AA6061 aluminum,

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Authors: Millicent N. Khumalo, Phesheya E. Dlamini

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Shrub-encroachment leads to a gain or loss of soil organic carbon (SOC) in previously open rangelands. The stabilization mechanisms controlling the storage of soil organic carbon (SOC) within aggregates of shrub-encroached grassland soils are poorly understood, especially in shallow plinthic soils. In this study, physical fractionation of surface soils (0- 10 cm) collected from open and shrub-encroached grasslands was conducted to determine the distribution of SOC within macro-and- microaggregates. Soil aggregates were classified into four fractions by a wet-sieving procedure, namely >2000 (large macro-aggregates), 212-2000 (small macro-aggregates), 50-212 (microaggregates) and < 50µm (silt+clay). In both shrub-encroached and open grassland soils, SOC was greater in the silt+clay fraction. In this fraction, SOC was on average 133% greater in shrub-encroached compared to open grassland. The greater SOC within the silt+clay fraction is due to the greater surface area and thus more exchange sites for carbon absorption. This implies that the SOC physically protected within the silt+clay is stored long-term.

Keywords: aggregate fractions, shrub-encroachment, soil organic carbon, stabilization

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Authors: Nükhet Konuk, N. Gamze Turan, Yüksel Ardalı

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Solid waste management is the most environmental problem in Turkey as a result of the rapid increase in solid waste generation caused by the rapid population growth, urbanization, rapid industrialization and economic development. The large quantity of waste generated necessitates system of collection, transportation and disposal. The landfill method for the ultimate disposal of solid waste continues to be widely accepted and used due to its economic advantages. In Turkey, most of the disposal sites open dump areas. Open dump sites may result in serious urban, sanitary and environmental problems such as an unpleasant odor and the risk of explosion as well as groundwater contamination because of leachate percolation. Unsuitable management practices also result in the loss of resources and energy, which could be recycled and produced from a large part of the solid waste. Therefore, over the past few decades, particular attention has been drawn to the sustainable solid waste management as a response to the increase in environmental problems related to the disposal of waste. The objective of this paper is to assess the situation of landfilling practices in Turkey as a developing country and to identify any gaps in the system as currently applied. The results show that approximately 25 million tons of MSW are generated annually in Turkey. The percentage of MSW disposed to sanitary landfill is only 45% whereas more than 50% of MSW is disposed without any control.

Keywords: developing countries, open dumping, solid waste management, sustainable landfilling, sustainable solid waste management

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