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Showing papers in "Arabian Journal for Science and Engineering in 2012"


Journal ArticleDOI
TL;DR: In this paper, an anchoring scheme produced with gradient materials based upon ceramics and epoxy is described for the vehicular cable-stayed Stork Bridge with 124 m span in Winterthur, Switzerland.
Abstract: Cables of suspended structures are suffering due to increased corrosion and fatigue loading. Since 1980, EMPA and BBR Ltd. in Switzerland have been developing carbon fiber-reinforced polymer (CFRP) parallel wire bundles as cables for suspended structures. The excellent properties of those bundles include corrosion resistance, very high specific strength and stiffness, superior equivalent moduli and outstanding fatigue behavior. An anchoring scheme produced with gradient materials based upon ceramics and epoxy is described. For the first time, large CFRP cables were applied in 1996 on the vehicular cable-stayed Stork Bridge with 124 m span in Winterthur, Switzerland. The performance of these cables and later applications was and still is monitored with sophisticated fiber-optical systems. Up to date, these results are fully matching the high expectations. Under the assumptions that (1) the behavior of the pilot applications of CFRP cables described in this paper will be further on fully satisfactory, (2) active systems for distributed mitigation of wind-induced vibrations are going to be successful and (3) there is a need for extremely long-span bridges to cross straits like that of Bab el Mandeb, Messina, Taiwan or Gibraltar, why should the next generation of structural engineers not use CFRP cables for such extremely long-span bridges? This would open spectacular new opportunities.

111 citations


Journal ArticleDOI
TL;DR: In this paper, the preparation and properties of relevant gold(III) compounds and the reaction conditions for employing these compounds as homogeneous catalysts and catalyst precursors are reviewed, and the synthetic chemist is introduced to the existing methods and thereby may be assisted in finding the most promising reagents and conditions that can be used in new synthetic strategies.
Abstract: There is currently a rapidly growing interest in the homogeneous catalysis of organic transformations by gold compounds. In a large number of specific studies, a wide variety of gold(I) and gold(III) complexes have been tested, and many of them have been shown to induce novel reactions or to exhibit significant advantages over conventional catalysts regarding rates and yields as well as regio- and stereoselectivity of reactions. Many of these catalysts have not been isolated and were rather prepared in situ from suitable precursor complexes, employing suitable solvents and optimized reaction conditions. While the knowledge about gold(I) catalysts has reached an advanced level, there is much less consistent information on gold(III) catalysts. In the present account, the preparation and properties of relevant gold(III) compounds and the reaction conditions for employing these compounds as homogeneous catalysts and catalyst precursors are reviewed. The synthetic chemist is introduced to the existing methods and thereby may be assisted in finding the most promising reagents and conditions that can be used in new synthetic strategies.

74 citations


Journal ArticleDOI
TL;DR: This work proposes a flexible location estimation algorithm using generalized regression neural network (GRNN) and weighted centroid localization that is remarkably good in comparison with its simplicity and requiring no additional hardware.
Abstract: Traditional received signal strength (RSS)-based localizations are often erroneous for the low-cost WSN devices. The reason is that the wireless channel is vulnerable to so many factors that deriving the appropriate propagation loss model for the WSN device is difficult. We propose a flexible location estimation algorithm using generalized regression neural network (GRNN) and weighted centroid localization. In the first phase of the proposed scheme, two GRNNs are trained separately for x and y coordinates, using RSS data gathered at the access points from the reference nodes. The networks are then used to estimate the approximate location of the target node and its close neighbors. In the second phase, the target node position is determined by calculating the weighted centroid of the Nc-closer neighbors. Performance of the proposed algorithm is compared with some existing RSS based techniques. Simulation and experimental results indicate that the location accuracy is satisfactory. The system performance is remarkably good in comparison with its simplicity and requiring no additional hardware.

73 citations


Journal ArticleDOI
TL;DR: In this article, the effect of Si/Al ratio on performance of fly ash-based geopolymer pastes at elevated temperature exposure was studied on the basis of physical appearance, weight losses, residual strength, volumetric shrinkage and water sorptivity at different temperatures.
Abstract: This paper presents the results of an experimental investigation on performance of fly ash-based geopolymer pastes at elevated temperature exposure. Geopolymer paste specimens having Si/Al in the range 1.7–2.2, manufactured by activating low calcium fly ash with a mixture of sodium hydroxide and sodium silicate solution were subjected to temperatures up to 900 °C. The effect of Si/Al ratio was studied on the basis of physical appearance, weight losses, residual strength, volumetric shrinkage and water sorptivity at different temperatures. Scanning electron microscopy along with energy dispersive X-ray and X-ray diffraction analysis were also conducted to examine changes in microstructure and mineralogy during the thermal exposure. Specimens gradually changed in colour from grey to light red accompanied by the appearance of small cracks as the temperature was increased to 900 °C. Loss of weight and volumetric strain due to elevated temperature exposure were higher in specimens manufactured with lesser Si/Al ratios. Geopolymer paste specimen containing maximum Si/Al of 2.2 performed best in terms of residual compressive strength after exposure to elevated temperatures.

55 citations


Journal ArticleDOI
TL;DR: Simulation results on IEEE 30-bus and IEEE 118-bus standard test systems show the effectiveness of the proposed approach in solving true multi-objective OPF and also finding well-distributed Pareto-optimal solutions.
Abstract: This paper presents a multi-objective differential-evolution-based approach to solve the optimal power flow (OPF) problem. The OPF problem has been treated as a true multi-objective constrained optimization problem. Different objective functions and operational constraints have been considered in the problem formulation. A clustering algorithm is applied to manage the size of the Pareto set. In addition, an algorithm based on fuzzy set theory is used to extract the best compromise solution. Simulation results on IEEE 30-bus and IEEE 118-bus standard test systems show the effectiveness of the proposed approach in solving true multi-objective OPF and also finding well-distributed Pareto-optimal solutions.

52 citations


Journal ArticleDOI
TL;DR: In this paper, the authors determined mix proportions of high-strength structural lightweight concrete (HSSLWC), which reduces the weight of concrete by using expanded aggregate clay (Leca) in order to produce HSSLWC, mineral and chemical admixtures have been used along with limestone that reduces porosity and increases strength Tests for specific gravity, and compressive, indirect tensile and flexural strengths were carried out on the specimens.
Abstract: This paper determines mix proportions of high-strength structural lightweight concrete (HSSLWC), which reduces the weight of concrete by using expanded aggregate clay (Leca) In order to produce HSSLWC, mineral and chemical admixtures have been used along with limestone that reduces porosity and increases strength Tests for specific gravity, and compressive, indirect tensile and flexural strengths were carried out on the specimens The effect of curing on the compressive strength was investigated by keeping some specimens in open air The results obtained showed that by using Leca, a lightweight structural concrete (LWSC) can be achieved, with dry density in the range of 1,610–1,965 kg/m3 and compressive strength in the range of 34–67 MPa, based on cube specimens with 100 mm side length Limestone significantly improved the mechanical properties of concrete whenever mixed with lightweight aggregates

51 citations


Journal ArticleDOI
TL;DR: The potential of Citrus sinensis (mosambi) bagasse to remove methylene blue, a cationic dye, from synthetic solutions has been investigated in batch mode as discussed by the authors.
Abstract: The potential of Citrus sinensis (mosambi) bagasse to remove methylene blue, a cationic dye, from synthetic solutions has been investigated in batch mode. Equilibrium and kinetics studies were carried out while varying the pH, biosorbent dose, biosorbent size, contact time and initial methylene blue concentration. The sorption equilibrium for methylene blue by C. sinensis bagasse was reached within 3 h at 30°C. The sorption data was analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The sorption kinetics were found to follow a pseudo-second-order kinetic model. The maximum sorption capacity of C. sinensis bagasse was found to be 96.4 mg/g under optimum conditions. The equilibrium data in synthetic solutions were well described by the Langmuir isotherm model. The thermodynamic parameters, Gibbs free energy (ΔG°), change in enthalpy (ΔH°) and change in entropy (ΔS°), for biosorption of methylene blue by C. sinensis bagasse were calculated to determine the feasibility of the process. A sorption-desorption study was also carried out using different eluents to determine the possibility of recycling the biosorbent.

49 citations


Journal ArticleDOI
TL;DR: In this article, the authors used hybrid of artificial neural networks and algorithm genetic (ANN-GA) and artificial neural network (ANNs) models for estimating reference evapotranspiration (ET0) only on the basis of the meteorological data.
Abstract: The Penman–Monteith equation (PM) is widely recommended because of its detailed and comprehensive theoretical base. This method is recommended by FAO as the sole method to calculate reference evapotranspiration (ET0) and for evaluating the other methods. The objective of this study is to compare PM using hybrid of artificial neural networks and algorithm genetic (ANN–GA) and artificial neural networks (ANNs) models for estimating ET0 only on the basis of the meteorological data. ANNs are effective tools to model nonlinear systems and require fewer inputs, and GAs are strong tools to reach the global optimal solution. The weather stations selected for this study are located in Esfahan Province (center of Iran). The monthly meteorological data from 1951 to 2005 have been used for this study. The meteorological data were maximum, average and minimum air temperatures, relative humidity, sunshine duration and wind speed. The ANNs and ANN–GA models learned to forecast PM reference evaporation (PM ET0). The results of this research indicate that ANN–GA predicted PM ET0 better than ANNs model.

44 citations


Journal ArticleDOI
TL;DR: In this paper, the authors applied the nonlinear regression (NLR) model to forecast water demand in Adana city of Turkey, where the average monthly water bill, total subscribership, atmospheric temperature, relative humidity, rainfall, global solar radiation, sunshine duration, wind speed and atmospheric pressure were selected as independent variables.
Abstract: The main objective of the present study is to apply the nonlinear regression (NLR) model in order to forecast water demand in Adana city of Turkey. The average monthly water bill, total subscribership, atmospheric temperature, relative humidity, rainfall, global solar radiation, sunshine duration, wind speed and atmospheric pressure are selected as independent variables. Meteorological parameters were taken from Adana meteorological station, and the other parameters such as water consumption, total subscribership and water bill values were supplied from Adana Water and Sewerage Administration during the periods of 2000–2009. In order to get a successful simulation, first, all independent variables were added to the “enter” regression model. Then, the method of stepwise multiple regression was applied for the selection of the “best” regression equation (model). Thus, the best independent variables were selected for the NLR model. Consequently, while water consumption in Adana city is 3.84 million m3 at the end of 2009, it will increase up to 4.99 million m3 by the year 2020.

43 citations


Journal ArticleDOI
TL;DR: In this paper, four architectures of different neural networks were used for groundwater level prediction in Shiraz Plain and their results were compared by using the statistical measures of mean square error and square of correlation coefficient.
Abstract: Groundwater level forecasting plays an important role in water resources management. Artificial neural network have been used as a robust instrument for this subject. In this paper, four architectures of different neural networks were used for groundwater level prediction in Shiraz Plain and their results were compared by using the statistical measures of mean square error and square of correlation coefficient. Effective parameters on groundwater level such as 5-month precipitation and groundwater level histories, temperature or evaporation, and runoff were utilized as the input data to forecast groundwater level at the next time step as output of the networks. All networks were trained for a ten-year period of data (from 1993 to 2003) and calibrated for an 18-month period (from Apr. 2003 to Sep. 2004). Networks were verified based on groundwater level observations in 29 wells located in the plain for another 18-month period (from Oct. 2004 to Mar. 2006). Results showed that artificial neural networks may be successfully utilized to forecast groundwater levels. Different networks forecasted groundwater level in all wells with acceptable root mean square errors of 0.6–12.17 m. Best overall performance was achieved by feed-forward neural network and the second best by Elman neural network.

40 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that black teawaste has a relatively high adsorption capacity for these heavy metals; the quantities adsorbed per a half gram of black TEWASTE at equilibrium (q e) are 15.39, 13.77, and 12.24% for Zn.
Abstract: Removal of heavy metals (Cobalt, Cadmium, and Zinc) from waste water was possible using black teawaste. Adsorption was observed for the three metals at 180 min. Under our experimental conditions, pH plays an important role in the adsorption process, particularly on the adsorption capacity of teawaste for the heavy metals under study. The pH level allowing for an optimum rate of adsorption was found to be 6 for Co, Cd, and Zn. We demonstrate that black teawaste has a relatively high adsorption capacity for these heavy metals; the quantities adsorbed per a half gram of black teawaste at equilibrium (q e) are 15.39 mg/g for Co, 13.77 mg/g for Cd, and 12.24 mg/g for Zn. It was found that the percentage of removed metal ions is inversely proportional to initial metal ions concentration, but correlates with teawaste adsorbent dosage. The adsorption of heavy metals on black teawaste is described by an isotherm of type I and is fully verified by the Freundlich and Langmuir isotherms. The kinetics of the Cobalt, Cadmium, and Zinc adsorption on the teawaste were found to follow a pseudo first-order rate equation. This method has the advantage of being applicable in developing countries due to the low cost and availability of teawaste.

Journal ArticleDOI
TL;DR: In this paper, a potential support vector machine (PSVM) is used to develop surface roughness predicted model and the validity test of the fit and adequacy of the proposed models has been carried out through analysis of variance.
Abstract: This paper is concerned with the optimization of the surface roughness when milling aluminium alloys (AA6061-T6) with carbide coated inserts. Optimization of milling is very useful to reduce cost and time for machining mould. Potential support vector machine (PSVM) is used to develop surface roughness predicted model. Design of experiments method and response surface methodology techniques are implemented. The validity test of the fit and adequacy of the proposed models has been carried out through analysis of variance. The experiments results are compared with predictive model developed by PSVM. The optimum machining conditions in favor of surface roughness are estimated and verified with proposed optimized results. It is observed that the developed model is within the limits of the agreeable error (about 2–9 %) when compared to experimental results.

Journal ArticleDOI
TL;DR: In this paper, the authors used remote sensing and geographic data to study the metropolitan expansion, land use patterns and land cover classification of Islamabad for a period of 38 years and found that the urban growth is accompanied by the loss of forest and other natural habitat in the city and has influenced the spatial patterns and structure of urban development.
Abstract: The present research relates to the exploitation of remote sensing and geographic data to study the metropolitan expansion, land use patterns and land cover classification of Islamabad. The metropolitan development based on growth direction and expansion trends from the city centre was observed for a period of 38 years. Landsat satellite data from three sensors, that is, multi-spectral sensor, thematic mapper and enhanced thematic mapper plus, were used in this study. The classification of the complex spatial assemblage of urban environment and its expanding precincts was done using temporal data collected during the period 1972–2009 and geo-referenced to a common coordinate system. The information regarding agriculture farms, bare land, dense forest, mixed vegetation, shadowy regime, sparse residential areas, thickly populated areas and water bodies was extracted. The extent of urban conurbation growth was computed and analyzed. Our results show that the urban development is expanded by 87.31 km2. In addition, the urban growth is accompanied by the loss of forest and other natural habitat in the city and has influenced the spatial patterns and structure of urban development. It is concluded that the remote sensing and GIS techniques supplemented with census data are very efficient and effective for studying the metropolitan growth patterns.

Journal ArticleDOI
TL;DR: In this paper, a simple relationship is proposed to predict free swelling potential and pressure in compacted clay, simple relationships are proposed for the different values of dry unit weight, initial water content, and plasticity index of three samples.
Abstract: In this study to predict free swelling potential and pressure in compacted clay, simple relationships are proposed. Three different clay samples were prepared with initially at constant dry unit weight and varying water contents and at constant water content and varying dry unit weights by standard compaction. In the experiment part, the free swelling technique was used. Values of free swelling potential and pressure were measured using the oedometer analysis. Analyses were repeated at least two times. To predict free swelling potential and pressure, the multiple regression analyses were performed for the different values of dry unit weight, initial water content and plasticity index of three samples. The proposed relationships and the equations in the literature were compared with the test results of these samples in optimum water content and maximum dry unit weight and of another compacted sample for the known values of the dry unit weight, initial water content, and plasticity index. The comparison was also done with a relation given in the literature. The results found that the estimated values of swelling potential and pressure obtained from the proposed relationships were in consistent with the measured ones.

Journal ArticleDOI
TL;DR: The history of the development of the Point Defect Model (PDM) for the growth of passive films that form on reactive metal and alloy surfaces when in contact with corrosive environments is presented as mentioned in this paper.
Abstract: The history of the development of the Point Defect Model (PDM) for the growth of passive films that form on reactive metal and alloy surfaces when in contact with corrosive environments is presented. Three generations of the PDM have been developed, with each addressing issues that have arisen from experiment or theory. The present review updates four previous reviews with more recent information, particularly with respect to the application of the PDM in accounting for phenomena observed in the growth of passive films under controlled electrochemical conditions. These topics include the adaptation of PDM to account for the potentiodynamic polarization of passive metals; for describing the evolution of passive systems under open circuit conditions; in the use of Mott–Schottky analysis to ascertain the electronic character of a passive film and hence to identify the dominant point defect; development of the theory of potentiostatic transients; and a description of the structures of passive films. Finally, the application of the PDM in modeling practical corrosion problems, such as the disposal of high-level nuclear waste, over ultra-long exposure times (106 years). This latter application represents one of the greatest challenges ever posed to a sector of the scientific community.

Journal ArticleDOI
TL;DR: An overview of the polymer gels technology available up-to-date with practical examples on key parameters for successful conformance improvement treatments (CITs) can be found in this paper.
Abstract: Whenever water production exceeds economic limits of a given oil or gas field, the need arises for a process by which produced water is reduced. Published data indicate that the petroleum industry spends $40 billion every year to process excessive produced water. Water also causes corrosion, scale and requires the construction of larger downstream handling facilities. Polymer gels, due to their versatile nature, are deemed suitable for reducing water production from oil and gas fields. Treatments utilizing these materials are generally referred to as conformance improvement treatments (CITs). Depending on the type of the crosslinker used, polymer gels can be classified as inorganically crosslinked or organically crosslinked. Examples on each type highlighting their capabilities and shortcomings are provided. Polymer thermal stability, compatibility with mixing waters, correct identification of the water production mechanism and gelation time are all key parameters for successful polymer-gel CITs. We will present an overview of the polymer gels technology available up-to-date with practical examples on key parameters for successful CITs. This paper will serve as a guide for scientists and engineers on the use of polymer gels for water control.

Journal ArticleDOI
TL;DR: In this article, the influence of hardness of rock material on drilling rate has been studied and the regression analyses between mean Mohs hardness and the drilling rate reveal that in soft rocks, with increase in hardness, drilling rate decreases logarithmically but in hard rock, with increasing in hardness the rate decreases linearly.
Abstract: In this paper, the influence of hardness of rock material on drilling rate has been studied. During the research, eight various rock types were subjected to drilling and hardness tests such as; Mohs hardness, Indentation Hardness Index (IHI) and L-type Schmidt hammer. Mean Mohs hardness of each rock was calculated based on the hardness of contained minerals and other two scales are carried out based on ISRM standards. For drilling studies, rock samples have been drilled using actual pneumatics top hammer drilling machine with three inches diameter cross type bit. Regression analyses between mean Mohs hardness and the drilling rate reveal that in soft rocks, with increase in hardness, drilling rate decreases logarithmically but in hard rocks, with increase in hardness, drilling rate decreases linearly. In total, with increase in Mohs hardness, drilling rate decreases exponentially. Also, with increase in Indentation Hardness Index and Schmidt hammer value, drilling rate decreases logarithmically. The regression analyses showed that Indentation Hardness Index has the best and stronger relationship with the rate of percussive drilling.

Journal ArticleDOI
TL;DR: In this paper, a modification is proposed in the existing ACI code equation which can capture accurately the mode of failure and ultimate load-carrying capacity of these hollow-core slabs.
Abstract: Prestressed, precast hollow-core slabs are used extensively for floor and roofing systems in precast concrete construction in Saudi Arabia. Design of these precast structural units is based on ultimate load-carrying capacity of these members. Full-scale load tests were conducted on prestressed precast hollow-core slabs with different shear span to depth (a/d) ratio, which were loaded to failure to ascertain the ultimate load-carrying capacity of these slabs. A total of 15 slab specimens, 5 and 2.5 m in span and having three different depths, 200, 250 and 300 mm were tested to failure using four-point load test. It was interesting to note that the failure mode of hollow-core slabs changed from pure flexure mode to flexure-shear mode for slabs with depth greater than 200 mm. The web shear cracking strength of PPHC slabs decreased with an increase in depth of the slab. A transition from flexure-shear to web shear failure as a function of a/d was noted in the load tests. The analysis of the experimental results showed that the existing ACI code equations underestimated the flexure-shear strength of these hollow-core slabs. Based on regression analysis of experimental data, a modification is proposed in the existing ACI code equation which can capture accurately the mode of failure and ultimate load-carrying capacity of these slabs.

Journal ArticleDOI
TL;DR: In this paper, a method for surface roughness identification based on the measurement of root mean square for feed vibration of the cutting tool and workpiece surface temperature for machining mild steel in turning operation is presented.
Abstract: As manufacturing requires reliable models and methods for the prediction of output performance of machining processes, the quality of surface finish is an important requirement for many turned workpieces. This paper presents a method for surface roughness identification based on the measurement of root mean square for feed vibration of the cutting tool and workpiece surface temperature for machining mild steel in turning operation. Grey relational analysis method used and developed to identify the surface roughness utilizes the grey relational coefficient and grey relational grades for combined effects of two performance characteristics, namely tool vibration and workpiece surface temperature. The method proposed has been proved by series of cutting experiments that the values of surface roughness are well identified and would ideally be able to measure the surface roughness in-process in real time and also shows the ability to specify the cutting conditions as well.

Journal ArticleDOI
TL;DR: In this article, a brief summary of the evolution of the Turkish Seismic Design Code in the last decades is presented, highlighting that the poor seismic performance of existing buildings in Turkey is not directly related to the inefficiency of the relevant seismic design codes, but rather to extremely low quality construction and the absence of a strict inspection system at the time of their construction.
Abstract: From worldwide observations made after the occurrence of earthquakes, as well as the tremendous amount of experimental, analytical and numerical studies, significant contributions have been made for a better understanding of the characteristics of earthquakes, and effects of earthquakes on existing structural systems. Consequently, seismic design codes are revised in a parallel fashion by integrating new concepts towards more realistic considerations of seismic demand, seismic response and seismic capacity. In this paper, after outlining the performance of existing buildings in Turkey during recent earthquakes (particularly Kocaeli 1999 and Duzce 1999 Earthquakes), and by focusing on the observed common structural deficiencies, a brief summary of the evolution of the Turkish Seismic Design Code in the last decades is presented. It is important to note that the poor seismic performance of existing buildings in Turkey outlined in this study is not directly related to the inefficiency of the relevant seismic design codes, but rather to extremely low quality construction and the absence of a strict inspection system at the time of their construction. It should also be highlighted that the lessons learnt from the catastrophic consequences of recent earthquakes, revisions in the seismic design code and the developments in the material and workmanship characteristics have significantly improved the quality of newer constructions in Turkey in the last decade.

Journal ArticleDOI
TL;DR: In this paper, the effect of coarse aggregates on the performance of concrete in terms of compressive strength, modulus of elasticity, and steel-corrosion penetration rate was investigated.
Abstract: This study reports the findings of an experimental investigation conducted to study the effect of two types of coarse aggregates on the performance of concrete in terms of compressive strength, modulus of elasticity, and steel-corrosion penetration rate. For this purpose, 27 concrete mixtures were prepared from each type of coarse aggregates by varying key mixture parameters, namely water/cementitious materials ratio, fine/total aggregate ratio, and cementitious materials content. In all the mixtures, 8 % cement was replaced with silica fume. Compressive strength and modulus of elasticity were determined on cylindrical concrete specimens after 28 days of water curing. Electrochemical tests for determining corrosion penetration rate were conducted on reinforced concrete specimens with 25 mm cover thickness and exposed to 3 % NaCl solution after water curing for 28 days. The test results indicate that the type of coarse aggregate significantly affects the strength, modulus of elasticity, and steel-corrosion resistance of concrete. It was also noted that it is essential to control the quality of mortar while utilizing marginal quality aggregates.

Journal ArticleDOI
TL;DR: In this article, the authors proposed an approach to assess nanostructure from the implementation of micromechanics-based scaling relations for a large array of nanoindentation tests on heterogeneous materials.
Abstract: This paper summarizes recent developments in the field of nanoindentation analysis of highly heterogeneous composites. The fundamental idea of the proposed approach is that it is possible to assess nanostructure from the implementation of micromechanics-based scaling relations for a large array of nanoindentation tests on heterogeneous materials. We illustrate this approach through the application to calcium-silicate-hydrate (C-S-H), the binding phase of all cement-based materials. For this important class of materials, we show that C-S-H exists in at least three structurally distinct but compositionally similar forms: low density, high density and ultra-high density. These three forms differ merely in the packing density of 5-nm sized particles. The proposed approach also gives access to the solid particle properties of C-S-H, which can now be compared with results from atomistic simulations. By way of conclusion, we show how this approach provides a new way of analyzing complex hydrated nanocomposites, in addition to classical microscopy techniques and chemical analysis. This approach will turn out invaluable in our quest of adding the necessary “green” value to a commodity, concrete, by nano-engineering higher strength and toughness from first principles.

Journal ArticleDOI
TL;DR: A multi-agent system has been developed to simulate a multi echelon SC and the result showed that in comparison to a traditional supply chain network, this system decreases the total cost and bullwhip effect.
Abstract: A supply chain (SC) is a coordinated system involved in moving products or services from supplier to customer. With growing focus on supply chain management, it is realized that inventories across the supply chain should be efficiently managed through greater cooperation and better coordination. Multi-agent systems (MAS) offer a new dimension for cooperation and coordination. MAS consist of a collection of automated agents who can perform a specific task intelligently without any human supervision and communicate with each other cooperatively. In this research, a multi-agent system has been developed to simulate a multi echelon SC. These agents are coordinated to control inventories and minimize the total cost of SC by sharing information, forecasting knowledge and using negotiation mechanism in special situation. The result showed that in comparison to a traditional supply chain network, this system decreases the total cost and bullwhip effect.

Journal ArticleDOI
TL;DR: In this article, the synergistic effect caused by molybdate ions and biocide on the inhibition of mild steel corrosion and scale in simulated cooling water system in the presence of a newly synthesized oxazoline derivative, namely, 2-phenyl-4-methyl-4((tetrazol-5-yl)methyl)oxazoline (OXA) has been studied using potentiodynamic polarization and electrochemical impedance spectroscopic method.
Abstract: The synergistic effect caused by molybdate ions and biocide on the inhibition of mild steel corrosion and scale in simulated-cooling water system in the presence of a newly synthesized oxazoline derivative, namely, 2-phenyl-4-methyl-4((tetrazol-5-yl)methyl)oxazoline (OXA) has been studied using potentiodynamic polarization and electrochemical impedance spectroscopic method. The obtained results show that OXA inhibits the corrosion in the considered medium. The corresponding inhibition efficiency increases with inhibitor concentration and also by addition of molybdate ions. The increase of inhibiting efficiency in the presence of $${{\rm MoO}_{4}^{2-}}$$ indicates enhancement of OXA adsorption onto the metallic surface. Moreover, the effect of biocide, namely, cetyl trimethyl ammonium bromide on biofilm formation has been studied.

Journal ArticleDOI
TL;DR: In this paper, the D-dimensional Klein-Gordon equation for a particle in a hyperspherically-symmetric potential was studied and the corresponding eigenfunctions and eigenvalues of this system were derived by using the Nikiforov-Uvarov method.
Abstract: We study the D-dimensional Klein–Gordon equation for a particle in a hyperspherically-symmetric potential. The potentials we consider here depend linearly on energy and inversely on the hyperradius. We calculate the corresponding eigenfunctions and eigenvalues of this system by using the Nikiforov–Uvarov method. The results could find interesting applications in fields such as theoretical nuclear physics if one is considering a relativistic treatment of spin-zero systems.

Journal ArticleDOI
TL;DR: In this paper, the combined effect of addition of marble sludge powder (MSP) and crusher rock dust (CRD) on the durability of self-compacting concrete (SCC) is investigated.
Abstract: Self-compacting concrete (SCC) is one of the most significant advances in concrete technology over the past two decades. SCC was developed to ensure adequate compaction through self-consolidation and facilitate placement of concrete in structures with congested reinforcement and in restricted areas. This paper aims to focus permeability study of self-compacting concrete (SCC) made with industrial wastes, i.e., marble sludge powder (MSP) from marble processing and crusher rock dust (CRD) from stone crushing industries. MSP can be used as filler and it helps to reduce the total voids content in concrete. Consequently, this contributes to improve the strength of concrete. An experimental investigation has been carried out to study the combined effect of addition of MSP and CRD on the durability of SCC. Water absorption, water permeability (flow), Ionic flow (Rapid Chloride ion penetrability) tests were conducted to measure the permeability of SCC and the results were compared with the normal concrete made up of river sand (NCRS) and the normal concrete made up of CRD (NCCRD). Test results indicate that the replacement of river sand with MSP and CRD in SCC reduces the permeability and does not affect the compressive strength.

Journal ArticleDOI
TL;DR: In this article, the effect of different components of a cement-sodium silicate grout system on the strength and moisture content of organic soils by carrying out vane shear test and scanning electron microscopy test was investigated.
Abstract: Tropical organic soils, generally formed in a natural environment and accumulates wherever the conditions are suitable, that is, the area with excess rainfall and the ground is poorly drained, irrespective of latitude or altitude. These soils commonly occur as extremely soft, unconsolidated superficial deposits with very low shear strength. Cement, sometimes with other industrial binders, is widely used for the stabilization of these soils by deep mixing method. However, these soils lack a favorable structure for the chemical reactions, coupled with a high moisture content which is acidic in nature, the efficiency of the binders is low or making it an expensive option. This paper investigates the effect of different components of cement–sodium silicate grout system on the strength and moisture content of organic soils by carrying out vane shear test and scanning electron microscopy test on samples treated and cured for up to 90 days. The study showed that cement and sodium silicate (in specific ratios) were highly effective in improvement of the shear strength along with a reduction in the moisture content of the treated soil. Further, with an increase in calcium chloride concentration in the confection, the shear strength and moisture content were observed to vacillate. The organic content present in these soils was found to have an adverse effect on the stabilization process.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of substitution of coarse aggregate by oil palm shells on compressive strength, density, modulus of elasticity, workability and water absorption.
Abstract: Oil palm shell (OPS) is a waste from the agricultural sector and is available in large quantities in the tropical regions. This paper investigates the effect of the replacement of normal weight coarse aggregate by oil palm shells on the compressive strength, density, modulus of elasticity, workability and water absorption. The gradation of substitution was 0, 28, 55, 83 and 100 %. Two mixes based on high strength concrete (HSC) with binder (cement + silica fume) content of 550 and 600 kg/m3 were used. The results show that the compressive strength, density and modulus of elasticity decrease and workability and water absorption increase by the percentage of OPS substitution increase. The results of this study show that there is a possibility of producing lightweight concretes using more than 40 % OPS in HSC mixes with adequate strength and also achieve a saving in the self-weight of about 28 %.

Journal ArticleDOI
TL;DR: Investigation results have shown that PPP provides cm-level precision quite easily by using appropriate processing parameters within a few hours of observation, and it is possible to obtain at mm to cm- level precision at the end of the 12 h observation for all the coordinate components.
Abstract: This study examines the degree of precision of precise point positioning system currently implemented in the Bernese GPS software 5.0 by zero differenced observations. The relationship between the accuracy of PPP and observation duration has been investigated using GPS data from a subset of IGS tracking stations observed over 7 days in different periods of year 2007. In the beginning, short reviews about PPP algorithm principle are given. Then, the results of several processing scenarios are presented and their respective precisions and convergence results are analyzed. Finally, with default parameters, accuracy assessments of PPP solutions are discussed. Investigation results have shown that PPP provides cm-level precision quite easily by using appropriate processing parameters within a few hours of observation. A faster convergence can be available for the north component in any case. The east component requires a convergence period more than two times longer than the north component. The east component provides a better precision than the height component after 2–3 h. For the shorter periods of observation, it is impossible to perform a reliable and accurate positioning with PPP due to the unresolved ambiguity. The repeatability and the precision ratio of the positioning are very low and unreliable for observations of a 5-min period. The mean values of RMS errors are about 0.25–0.30 m for north and east, and 0.5 m for up components. A great improvement can be achieved within a 30-min period, where mean RMS errors of 0.09 cm, 0.04 m and 0.11 m, respectively, in north, east and up were obtained. This precision could be improved up to three to five times by using, respectively, 2–8 h observations. It is possible to obtain at mm to cm-level precision at the end of the 12 h observation for all the coordinate components. Finally, 24 h data processing produced 0.0031, 0.0058 and 0.0088 m RMS errors for the north, east and up components in sequence. For all these cases, north components are more precise than up and east.

Journal ArticleDOI
İlyas Eker1
TL;DR: In this paper, a second-order sliding mode control (2-SMC) is proposed for secondorder uncertain plants using equivalent control approach to improve performance of control systems and a Proportional+Integral (PI) sliding surface is defined for the sliding mode.
Abstract: In this article, a second-order sliding mode control (2-SMC) is proposed for second-order uncertain plants using equivalent control approach to improve performance of control systems. A Proportional+Integral (PI) sliding surface is defined for the sliding mode. The sliding mode control law is derived using direct Lyapunov stability approach and asymptotic stability is proved theoretically. The second-order plant parameters are experimentally determined using input-output measured data. Performance of the closed-loop system is analysed through an experimental application to an electromechanical plant to show feasibility and effectiveness of the proposed 2-SMC and factors involved in the design. Results of the experimental application are presented to make a quantitative comparison with the traditional (first-order) sliding mode control and PID control. It is demonstrated that the proposed 2-SMC system improves performance of the closed-loop system with better tracking specifications in the case of external disturbances, better behavior of the output and faster convergence of the sliding surface while maintaining the stability.