Journal of Advanced Materials in Engineering (Esteghlal)

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Five methods are introduced for design of castellated I beams encased in concrete. One of the methods, plastic analysis, is thoroughly explained and the relevant equations are developed. Eight castellated I beams encased in concrete are made and tested. The theoretical design methods are all compared with the test results and the safety factor for each method is calculated. The results show that the plastic method of analysis and design is the most economical, which also gives a reasonable safety factor against beam failure

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Contaminant transport analysis was performed for four selected solid waste landfill designs using the computer code POLLUTE. The diffusion coefficients were determined for the natural soils (aquitard) and compacted soils from the Urumia landfill site, using the diffusion tests. These coefficients along with the geometrical, physical, and chemical parameters of the natural soil and engineered layers, as well as the dominant boundary conditions were used in the analysis of the four selected designs for the landfill. These designs were evaluated for the contamination of the underlying aquifer in a specified period, using the drinking water standard for chloride ion. The comparisons showed that the fourth design which includes the engineered elements of a blanket type leachate collection layer and a compacted clayey liner underneath the landfill base, has more certainty in controlling the contaminant transport from the landfill base to the underlying aquifer. This type of landfill could be introduced as an optimum and semi-engineered design to be used for solid waste landfills in Iran.

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In this paper an analytical model for cold rolling of strip has been described. This model is developed based on the slab method of analysis and the hydrodynamic lubrication. The characteristics of rolling are obtained from the equations of equilibrium and the plate was allowed to strain harden assuming that the lubricant behaves as a Newtonian fluid. The shear stress to the plate is obtained by calculating the thickness of the lubricant film by employing a viscosity-pressure-temperature relation. The governing equations are obtained by composing these relations and the final differential equations have been solved. From the solution of the final equation, the rolling force، torque and shear stress to the plate are calculated. To verify the validity of the proposed model, these values are compared with experimental and analytical results of other investigators. It was also noted that by employing the proposed analytical model, a large amount of computation time and costs are saved

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Reductive leaching was used to dissolve metals, especially cobalt, present in Fars Tidar mine,. In this paper, cobalt ore was leached with sulphuric acid in the presence of phenol to determine the effects of various factors on leaching. These factors included temperature, acid concentration, time, phenol content, pulp density, and interaction between some of the parameters. The results indicated that temperature was more effective on SN ratio (Signal to Noise ratio) which was found to be about 80%. The effecst of time and acid concentration on SN ratio were also determined at about 8% and 4 %, respectively. Although the effect of phenol content on cobalt leaching was too low but dissolution of cobalt decreased in the absence of phenol. Therefore, it was concluded that phenol was one of the factors in effective the leaching process. Anyway, three parameters including temperature, acid concentration, and time were selected as more effective parameters. Consequently optimum conditions can be obtained with high levels content of temperature, acid concentration, and time with low levels of phenol and pulp density.

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The presence of defects in cold mercerizing of cotton goods led to the creation of a new method, called hot mercerizing in which caustic soda solution is used at a high temperature. Hot mercerizing is successfully used in cotton blended with some other fibers. In cotton/polyester blend fabrics, this treatment serves a dual purpose: subjectively, it imparts a silklike soft handle to the polyester and brings about mercerizing of the cotton. In this work, the mercerizing operation with caustic soda solution was performed on a 65/35 polyester/cotton fabric in sixteen different temperatures (from 15°C to 90°C), in two states: with tension and without tension. Finally, the effect of temperature of treatment on some properties of fabric such as tensile properties, weight loss, and shrinkage have been studied. Alkali treatment cause weight loss in cotton/polyester blend fabrics, the main part of the weight loss attributed to the polyester component of the blend. Increasing temperature leads to a corresponding increased in weight loss. The resulting weight loss leads to more yarn release and consequently, to the improvement of the drape and soft handle in the fabric. However, it decreases the tensile strength and causes weakness of the fabric, therefore, an optimum of temperature must be considered. In the alkali treatment, the internal stresses in the fabric can be released. Release of tension in the fabric causes shrinkage, particularly in the warp direction. The effect of tension on properties of cotton/polyester blend fabric is not considerable in alkali treatment.

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Regarding the importance of ring spinning method among spinning systems, great potentials exist for research about on the improvement of the quality and properties of ring spun yarn. This study aims to improve yarn quality by changing the shape and dimensions of spinning triangle through forming a groove in the middle zone of the front darfting roller with a curvature of 5 to 7 mm. For the top drafting roller, we used an elastic O-Ring with dimensions similar to those of the groove. With this change, the geometry of spinning triangle is expected to change as an Euclidean geometry to a half cone Riemannian shape. The results show improvement in yarn tenacity, elongation at break, yarn evenness and faults, shape of spinning baloon, decrease in yarn tension and yarn breakage, improvement in fiber packing in the yarn cross section, more evenness in the yarn count and twist, and, finally, better inter-structure compared to the normal ring spun yarn.

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Continuous welded turnouts are important for CWR track through the railway station. According to equivalent resistance and non-linear theories and the principle of force diagram, a new method of theoretical calculation for continuous welded turnouts was developed. The continuous welded turnouts designed and installed according to the new theory behaved fairly well. The data collected on sites basically agreed with those of theoretical calculation. It was proved that the calculation theory is correct and values of calculation parameters are reasonable.

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Being economical and performing well under cyclic loads, steel sections filled with concrete have been widely used in structural buildings. Extensive studies and experiments have been conducted to investigate the influence of different parameters and loadings on the behavior of these structural components. Based on the data available from previous experiments and studies, this paper discusses the behavior of composite columns. The results of 3D-non-linear finite element analysis of thin-walled steel sections filled with concrete are presented. Lastly, comparisons are made between results from finite element analysis and experimental data available about the specimens. Using a trial and error method, the finite element model was calibrated and was used to evaluate the capacity of specimens that were not tested in the laboratory. The capacities of the sections were calculated based on the LRFD design method. The results are compared to evaluate the accuracy of the proposed method. Because of the increase in the use of high strength materials in structures, the effects of increase in concrete and steel strengths on the behavior of composite columns are discussed in this paper. Also the effects that the change in the thickness of the steel shell may have on the behavior of composite columns are argued.

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Silica fume has been largely used in concrete in recent decades due to its effect on improvement of strength and durability of concrete. On the other hand, attention has been recently paid to the use of limestone powder as a substitute for part of cement in concrete, basically because of its low price and its positive effect on the durability of concrete. The aim of the current study is the investigation of the interactive effect of silica fume and limestone powder on the compressive strength of concrete and the optimization of the mix design. To do so, 27 mix designs including 3 water-to-cementitious materials ratios (W/CM=0.25, 0.3 and 0.4) 3 silica fume-to-cementitious materials ratios (SF/CM=%0, %5 and %10) and 3 limestone powder-to-cement ratios (LP/C=%0, %15 and %30) were used and 28-day compressive strength of the cubic concrete specimens were determined. Then, the interactive effect of silica fume and limestone powder on compressive strength of concrete was investigated using isoresponse curves. Furthermore, the optimization of the mix design for concretes containing silica fume and limestone powder was carried out using “cost effective factor” (CEF) which is defined compressive strength divided by cost of concrete.

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Exergy analysis is based on combined first and second laws of thermodynamics and is a useful tool to analyze the energy systems in a better and more realistic way than an energy analysis, based on the first law of thermodynamics. Combination of exergy from thermodynamics with conventional concepts from engineering economy which is referred to as thermo-economy (exergo-economy) is a valuable tool to analyze the energy systems in a better way. In this paper, efforts are made to apply the concept of thermo-economy to analyze two power cycles (a combined Gas and Steam cycle and a conventional steam power plant). In this analysis, the results of an exergy calculation are combined with the economic aspects such as investment costs, fuel costs, and also operation and maintenance costs. The goal of this study is to show how to implement the concept of thermo-economy to these cycles and also how to estimate the price of the product (electric power generated). Assessment of the components exergy destruction costs is a second objective in this study. Results obtained from this analysis clearly show the effect of the cost breakdown and the component performance on the price of the final product. Comparison of the price of the product in these cycles shows that the combined cycle is superior to the conventional steam power plant.

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A higher bustle temperature in midrex direct reduction process is always desirable due to its positive effect on the productivity and DRI quality. The limit of the bustle temperature is related to the sticking or clustering behaviour of oxide pellets during the reduction in the reactor. It has been well estabilished that coating of oxide pellets by a refractory material decreases its tendency to clustering. In this study, the clustering behaviour of oxide pellets (produced from Golegohar-Chadormalu iron ore) during redution at different temperatures was investigated. The effect of coating with different amounts of hydrated lime on the clustering behaviour was also examined. Microscopic examination of coated pellets shows a porous, non-continious layer of Ca(OH)2 being fromed on the surface of the pellets. The clustering tendency of coated pellets, measured by the standard sticking test at pilot scale, was much lower, compared with normal (uncoated) pellets, while their reducibility was the same.

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Stator flux oriented vector control of induction motor (IM) drives for speed sensorless control has several advantages. But the application of a pure integrator for the flux estimation is difficult due to the presence of measurement noise and dc offset. To overcome these problems, some have used a programmable cascaded low pass filter (PCLPF). In this paper, it is shown that some problems still exist and some new problems arise from this approach. In order to solve these problems, a novel compensation method is proposed. In this scheme, the dc offset is detected and subtracted from the estimated flux along d and q axes. The simulation results show that it works well in the low speed region as well as in the transient state. The oscillation of the torque and the estimated flux are also reduced notably when the torque reference changes rapidly.

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In the last few years, Run-to-Run (R2R) control techniques have been developed and used to control various processes in industries. These techniques combine response surface, statistical process control, and feedback control techniques. The R2R controller consists of a linear regression model that relates input variables to output variables using Exponentially Weighted Moving Average (EWMA). In this paper, we have developed a R2R controller model based on quality costs. The model consists of finding optimum weight of EWMA procedure in R2R controllers with respect to conformities and nonconformities costs. The validity and performance of the developed model were tested using a real case study in an optic industry application.

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Cohesive-frictional soils are widely used in the construction of embankment structures and due to the method of construction, i.e. applying compactive efforts in the vertical direction in these cases, the occurrence of anisotropy in the soil strength and permeability seems to be inevitable. In this study, attempts have been made to evaluate the shear strength of c-f soils through modifying a large shear box apparatus. Conducting more than 108 direct shear tests, the effects of compaction method and moisture on the shear strength anisotropy of a selected c-f soil (a clayey sand) have then been investigated. According to the test results, firstly strength anisotropy was observed in all the soil specimens and the shear strength in the vertical direction was about 14% to 21% higher than that in the horizontal direction. Secondly, it was found that an increase in the compaction moisture led to an increase in the degree of anisotropy. Furthermore, the anisotropy in the cohesive strength was more pronounced in the specimens with a moisture content higher than the optimum one. The highest degree of anisotropy was observed in the specimens compacted by impacting effort and the lowest one belonged to those with the vibratory compaction.

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A numerical simulation has been carried out to study the detonability characteristics of two- phase unconfined clouds. The parameters equivalence ratio, turbulence, shape, volume and uniformity of the cloud and the delay time distribution are recognized and introduced as the most important factors determining the reactivity of the cloud and influencing the initiation of a successful detonation. With regard to the dynamic behavior of the cloud and the changes in the magnitude of these significant characteristic parameters, the best ranges of time and position for secondary detonator action are determined. Comparisons are also performed with experimental results along with theoretical analyses to validate the numerical results obtained in this study.

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The rapid growth of space utilization requires extensive construction, and maintenance of space structures and satellites in orbit. This will, in turn, substantiate application of robotic systems in space. In this paper, a near-minimum-time optimal control law is developed for a rigid space platform with flexible links during an orientating maneuver with large angle of rotation. The time optimal control solution for the rigid-body mode is obtained as a bang-bang function and applied to the flexible system after smoothening the control inputs to avoid stimulation of the flexible modes. This will also reflect practical limitations in exerting bang-bang actuator forces/torques, due to delays and non-zero time constants of existing actuation elements. The smoothness of the input command is obtained by reshaping its profile based on consideration of additional first-order and second-order derivative constraints. The platform is modeled as a linear undamped elastic system that yields an appropriate model for the analysis of planar rotational maneuvers. The developed control law is applied on a given satellite during a slewing maneuver. The simulation results show that the modified realistic optimal input compared to the bang-bang solution agrees well with the practical limitations and also alleviates the vibrating motion of the flexible appendage, which reveals the merits of the new control law developed here.

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In this paper, an analytical method based on Modified Slab Method of analysis is presented to study the asymmetrical rolling process due to difference in work rolls radii, rolls speeds and interface frictions. The shear force imposed on material along the contact region is considered to be a function of the frictional factor and the roll gap geometry. Elastic-plastic with linear work hardening constitutive law was assumed. Asymmetric factors considered are roll diameter ratio, roll speed mismatch and differential interface friction conditions. Neutral points’ location along the contact region in relation to the variations on thickness reduction, roll speed ratios, roll diameters ratio and front and back tensions are investigated. Predicted values for rolling force and torque from the present analytical model are compared with those of other workers, which are shown to be in good agreement

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Mobile robotic systems, which include a mobile platform with one or more manipulators, mounted at specific locations on the mobile base, are of great interest in a number of applications. In this paper, after thorough kinematic studies on the platform and manipulator motions, a systematic methodology will be presented to obtain the dynamic equations for such systems without violating the base nonholonomic constraints. Combining the kinematic model with the initial dynamic equations and eliminating Lagrange multiplier with natural orthogonal complement technique lead to the comprehensive dynamic model. The variables of this model include the path of a reference point of the base and the position and orientation of the end-effector. The proposed approach will be applied on a car-like platform and a manipulator with 5 degrees-of freedom. The calculations for deriving such a model will be implemented by a program in Maple which can be used for control design and simulation purposes. The validity of the methodology is demonstrated using a second model and comparing the elements of these two models with each other. With trajectory generation for platform and manipulator generalized coordinates separately, set points for control system design will be provided. Motion generation for the platform, which due to the nonholonomic constraint has more sensitivity, will be dealt with by two motion modes. Inverting the model in terms of joint space variables, strict control of the work space variables is accomplished. Introducing state space variables and inverting the system into first order equations, the necessary preliminaries for control system design will be provided. Based on two simulation programs in Matlab, two controllers are designed with model-based algorithm (MBA) and Transposed Jacobian (TJ) control. Simulating different external conditions such as parameter perturbation, disturbances and noise, the robotic system behavior in the vicinity of real conditions will be examined. The results obtained show the merits of the TJ algorithm in controlling highly nonlinear and complex systems with multiple degrees- of freedom (DOF), without requiring a priori knowledge of plant dynamics, and with reduced computational burden which motivates further work on this algorithm

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Nanowire is a cylindrical nano-structure with nanometer dimensions. In this research, the studied nanowire was made from the magnetic triple Ni-Fe-Co alloy. We utilized ordered porous anodic aluminum oxide as a template for the nanowire deposition. The nanowire arrays were electrodeposited in the cylindrical pores of the oxide layer by AC potential in a simple sulfate bath. Then the relation of shape and composition of the nanowires with their fabrication parameters was investigated. The results showed that the barrier layer modification had an essential role in the deposition process and a composition gradient was detected in a single nanowire.

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: The CIECAM97s and its revision, as a colour appearance model, were applied for a series of fabrics with different colours and depths to explain their colour appearance coordinates in similar viewing conditions. The results show that due to some modifications which expand the scale, the modified model has improved capadilities in calculating chroma. Besides, the calculations were simpler for the revised version of CIECAM97s model while the results from the two models were the same.