Showing papers by "Iran University of Science and Technology published in 2002"
08 Apr 2002
TL;DR: A new classification of most important and commonly used edge detection algorithms, namely ISEF, Canny, Marr-Hildreth, Sobel, Kirsch, Lapla1 and LaplA2 is introduced.
Abstract: Since edge detection is in the forefront of image processing for object detection, it is crucial to have a good understanding of edge detection algorithms. This paper introduces a new classification of most important and commonly used edge detection algorithms, namely ISEF, Canny, Marr-Hildreth, Sobel, Kirsch, Lapla1 and Lapla2. Five categories are included in our classification, and then advantages and disadvantages of some available algorithms within this category are discussed. A representative group containing the above seven algorithms are the implemented in C++ and compared subjectively, using 30 images out of 100 images. Two sets of images resulting from the application of those algorithms are then presented. It is shown that under noisy conditions, ISEF, Canny, Marr-Hildreth, Kirsch, Sobel, Lapla2, Lapla1 exhibit better performance, respectively.
324 citations
TL;DR: In this article, the microstructure of solid iron and molten aluminium couple was examined at the interface, and the phases were identified as Fe 2 Al 5 and FeAl 3.
201 citations
TL;DR: In this paper, the effect of the non-singular term of stress, often known as the T-stress, on the angle of initiation of fracture and the onset of crack growth is explored.
Abstract: There are several criteria for predicting brittle fracture in mode I and mixed mode loading. In this paper, the modified maximum tangential stress criterion originally proposed for mixed mode loading, is employed to study theoretically brittle fracture for mode I cracks. In particular, the effect of the non-singular term of stress, often known as the T-stress, on the angle of initiation of fracture and the onset of crack growth is explored. The T-stress component of the tangential stress vanishes along the crack line. Therefore, it is often postulated for linear elastic materials that the effect of T-stress on mode I brittle fracture can be ignored. However, it is shown here that the maximum tangential stress is no longer along the line of initial crack when the T-stress exceeds a critical value. Thus, a deviation in the angle of initiation of fracture can be expected for specimens having a large T-stress. It is shown that the deviation angle increases for larger values of T-stress. Theoretical results show that the apparent fracture toughness decreases significantly when a deviation in angle occurs. Earlier experimental results are used to corroborate the findings. The effect of large T-stresses is also explored for a crack specimen undergoing moderate scale yielding. The elastic-plastic investigation is conducted using finite element analysis. The finite element results reveal a similar deviation in the angle of maximum tangential stress for small to moderate scale yielding.
91 citations
TL;DR: In this paper, the force method is employed for the analysis of truss truss structures and a contraction process is developed to increase the efficiency of the GA by which an optimal design for the first sub-string associated with member cross-sections is obtained.
Abstract: In the process of discrete-sizing optimal design of truss structures by Genetic Algorithm (GA), analysis should be performed several times. In this article, the force method is employed for the analysis. The advantage of using this method lies in the fact that the matrices corresponding to particular and complementary solutions are formed independently of the mechanical properties of members. These matrices are used several times in the process of the sequential analyses, increasing the speed of optimization. The second feature of the present method is the automatic nature of the prediction of the useful range of sections for a member from a list of profiles with a large number of cross-sections. The third feature consists of a contraction process developed to increase the efficiency of the GA by which an optimal design for the first sub-string associated with member cross-sections is obtained. Improved designs are achieved in subsequent cycles by reducing the length of sub-strings. Copyright © 2002 John Wiley & Sons, Ltd.
80 citations
TL;DR: In this paper, the authors showed that the coefficient of friction was decreased from 0.8 in the uncoated copper to about 0.15 for the coated samples, which indicated that plastic deformation of the wear surfaces in coated samples decreased.
63 citations
TL;DR: In this paper, the effects of different factors such as initial anisotropic stress state, initial confining pressure, density and shear history on the stress-dilatancy relationship were studied.
47 citations
TL;DR: In this article, a simple and efficient method is developed for calculating the eigenvalues and eigen vectors of matrices having special structures, which is achieved by decomposing the matrices into specific forms.
Abstract: In this article, a simple and efficient method is developed for calculating the eigenvalues and eigen vectors of matrices having special structures. This is achieved by decomposing the matrices into specific forms. The application is extended to the eigensolution of the Laplacian matrices of symmetric graphs. Copyright © 2003 John Wiley & Sons, Ltd.
45 citations
TL;DR: In this paper, a process for synthesis of kaolin based zeolite A membrane by electrophoresis was described, which was used for ethanol/water separation. But, it was not shown how to construct the membrane.
43 citations
TL;DR: In this paper, it is shown that the variance estimate obtained from the original data is no longer an appropriate estimate to be considered for conducting process capability analyses when observations are autocorrelated.
Abstract: Process capability analysis when observations are autocorrelated is addressed using time series modelling and regression analysis. Through the use of a numerical example, it is shown that the variance estimate obtained from the original data is no longer an appropriate estimate to be considered for conducting process capability analyses. Copyright © 2002 John Wiley & Sons, Ltd.
39 citations
TL;DR: In this article, the effect of far field elastic stresses on the size and shape of the plastic zone around the crack tip and on the stresses inside the zone has been studied using a mode II boundary layer formulation.
Abstract: Studies of cracked specimens loaded in mode I have shown that the stresses near the crack tip depend significantly on the level of constraint. The stresses can be determined near the crack tip using the HRR solution, but only for high constraint specimens. For other levels of constraint, O'Dowd and Shih's Q parameter may be used to adjust the stresses derived from the HRR solution. Only limited research has been carried out to study the effect of constraint in mode II. In this paper a mode II boundary layer formulation is used to study the effect of far field elastic stresses on the size and shape of the plastic zone around the crack tip and on the stresses inside the plastic zone. It is shown that in mode II, both positive and negative values of remote T-stress influence the tangential stress along the direction of maximum tangential stress. In the spirit of O'Dowd and Shih, a dimensionless parameter QII is introduced to quantify the constraint for mode II specimens failing by brittle fracture. The relation between QII and T/σ0 is determined for different values of the strain hardening coefficient n. To investigate the range of validity of the Q−T diagram for real specimens, the constraint parameter QII is calculated directly from finite element analysis for three mode II specimens and compared with the evaluation using the Q−T diagram.
36 citations
TL;DR: In this article, the effect of milling time on reduction process in an Ar atmosphere was studied by TG-DTA, where hematite was mixed with 19.84 wt% graphite and subjected to ball milling.
Abstract: The effect of ball milling of raw materials on the reaction behavior of composite mixture of hematite and graphite have been studied. Hematite was mixed with 19.84 wt% graphite (C/O ratio was 1.1 in composite mixture) and subjected to ball milling. The milling time was changed from 6 to 100 hr with the hematite-graphite mixture. On the other hand, graphite or hematite was milled alone and then mixed with non-milled hematite or graphite, respectively. The effect of milling time on reduction process in an Ar atmosphere was studied by TG-DTA. The samples were heated by a constant heating rate of 10°C/min from room temperature up to 1 100°C and maintained for 30 min at this temperature. The rate of reaction (RTG) was obtained by the differentiation of weight loss curve. It was found that the RTG curve consisted of three reaction curves which were hematite-magnetite (HM), magnetite-wustite (MW) and wustite-metallic iron (WF) reductions. The curve corresponding to the HM reduction located in low temperature range and stood alone from other two reduction curves ( MW and WF reductions). The curves of MW and WF reductions were overlapped. The pulse-like reduction curve corresponding to WF reduction was observed in the longer milling time, which meant extremely high rate of reduction. The temperatures decreased and the reaction degrees at each peaks increased with increasing milling time. The kinetic analysis applying the single and consecutive reaction was carried out. The calculated reaction curves were in good agreement with the observations which showed that the reaction mainly occurred in this system was the solid oxide-solid carbon reaction. The variation of parameters of rate constant presented the different mechanism of reaction between shorter and longer milling time at the border of 24 hr.
TL;DR: The applicability of the synthesized reagents for softening of different water samples was studied in this article, where the quality of softened water was tested by measuring concentrations of Mg2+, Ca2+ and HCO3− ions.
TL;DR: In this paper, the Portable Flux Profiler (PFP) was used to measure the buoyancy flux of a boat in the Swan River estuary during the wet season.
Abstract: [1] More than 400 profiles of (salinity) density and velocity microstructure with 923 turbulent patches were collected over 4 days from an anchored boat with the Portable Flux Profiler (PFP) in the Swan River estuary during the wet season. By using the PFP the buoyancy flux was measured directly and estimated indirectly for this flow. Overturns were suppressed by the strong stratification, and large-scale anisotropy was correlated with turbulent Froude number. The direct measurements of the buoyancy flux exhibited both positive (downgradient) and negative (upgradient) values within the turbulent patches. The net average mixing efficiency was 0.04, less than the commonly used value of 0.17. Therefore the rate of vertical transport was small even though the dissipation levels within the turbulent patches were relatively high. The magnitude of the above mentioned competing fluxes increased with decreasing turbulent Froude numbers even though the net flux when bin-averaged with respect to turbulent Froude number remained close to zero.
23 Oct 2002
TL;DR: This article explores the use of single-channel single-trial EEG signals for natural control of prosthetic hand grasp on people with severe physical disabilities and employs the multilayer perceptron with back-propagation learning rule for EEG classification.
Abstract: This article explores the use of single-channel single-trial EEG signals for natural control of prosthetic hand grasp. It is natural in the sense of that the desired movement is what the subject intends to do. The motor tasks to be intended are the imagination of hand grasping and opening. For prosthetic hand grasp control, the discrimination of the resting state and the imagined voluntary movement is important that has been disregarded in the research area of BCI. This work provides a design for discriminating the resting state and the motor task imagery. To date most researchers have designed and test BCI system on normal subjects. In this work, the experiments were conducted on people with severe physical disabilities. One of the major problem in developing real-time BCI is the eye blink suppression. In this work, the eye blink artifact is suppressed by a neural adaptive noise canceller. This is a concern in real time application. We employ the multilayer perceptron with back-propagation learning rule for EEG classification. Preliminary results indicate that the classification accuracy of the EEG patterns at primary motor cortex and occipito-temporal recording sites is higher than that at other sites. An average correct classification rate of 83% is achieved using samples of the single-channel EEG signal.
TL;DR: In this article, the properties of AMTTO complexes [Cu(AMTTO)Cl2] (2), [CA(AMtTO)2]Cl (3), and [CA (PPh3)2Cl] (4) have been described and characterized by IR spectroscopy and elemental analyses.
Abstract: The complexes [Cu(AMTTO)Cl2] (2), [Cu(AMTTO)2]Cl (3), and [Cu(AMTTO)(PPh3)2Cl] (4) have been prepared and characterized by IR spectroscopy and elemental analyses. Also single-crystal X-ray diffraction studies on compound 2, 3 and 4 revealed that AMTTO acts in 2 as a bidentate ligand via nitrogen and sulfur atoms, in 3 and 4 as a monodentate via sulfur atoms. Complex 3 was already mentioned in literature, but the structure was not described in detail. The molecules in 2 form infinite chains through additional weak Cu—S interactions along [010] indicating the Jahn-Teller distortion of the d9 ion Cu2+. The infinite chains are connected by hydrogen bonding along [100]. Crystal data for 2 at —80°C: monoclinic, space group P21/m, a = 666.7(1), b = 609.4(1), c = 1132.6(2) pm, b = 95.46(2)°, Z = 2, R1 = 0.0365; for 3 at —80°C: orthorhombic, space group Pbcn, a = 1291.2(2), b = 1146.5(1), c = 1000.5(1) pm, Z = 4, R1 = 0.0315; for 4 at —80°C: monoclinic, space group, P21/n, a = 879.4(1), b = 1849.3(2), c = 2293.8(3) pm, β = 92.38(1)°, Z = 4, R1 = 0.0688.
25 Jul 2002
TL;DR: In this article, an iterative nonlinear algorithm is generated for optimal sizing and placement of fixed and switched capacitor banks on radial distribution lines in the presence of linear and nonlinear loads.
Abstract: An iterative nonlinear algorithm is generated for optimal sizing and placement of fixed and switched capacitor banks on radial distribution lines in the presence of linear and nonlinear loads. The HARMFLOW algorithm and the Maximum Sensitivities Selection (MSS) method are used to solve the constrained optimization problem with discrete variables. To limit the burden of calculations and improve convergence, problem is decomposed into two subproblems. Objective functions include minimum system losses and capacitor cost while IEEE-519 power quality limits are used as constrains. Results are presented and analyzed for the 18 bus IEEE distorted system. The advantage of proposed algorithm as compared to previous works is consideration of harmonic couplings and reactions of actual nonlinear loads in the distribution system.
TL;DR: In this article, the modal acoustic radiation impedance load on an infinitely long cylindrical source harmonically excited in circumferentially periodic (axially independent) spatial pattern, while positioned concentrically within a fluid cylinder, which is embedded in a fluid-saturated unbounded elastic porous medium, is computed.
Abstract: Radiation loading on a vibrating structure is best described through its radiation impedance. In the present work the modal acoustic radiation impedance load on an infinitely long cylindrical source harmonically excited in circumferentially periodic (axially independent) spatial pattern, while positioned concentrically within a fluid cylinder, which is embedded in a fluid-saturated unbounded elastic porous medium, is computed. This configuration, which is a realistic idealization of an acoustic logging tool suspended in a fluid-filled borehole within a permeable surrounding formation (White, J. E., 1983, Underground Sound Application of Seismic Waves, Elsevier, Amsterdam, Fig. 5.29, p. 183), is of practical importance with a multitude of possible applications in seismo-acoustics and noise control engineering. The formulation utilizes the Biot phenomenological model to represent the behavior of the sound in the porous, fluid-saturated, macroscopically homogeneous and isotropic surrounding medium. Employing the appropriate wave-harmonic field expansions and the pertinent boundary conditions for the given boundary configuration, a closed-form solution in the form of an infinite series is developed and the resistive and reactive components of modal radiation impedances are determined. A numerical example for a cylindrical surface excited in vibrational modes of various order, immersed in a water-filled cavity which is embedded within a water-saturated Ridgefield sandstone environment, is presented and several limiting cases are examined. Effects of porosity, frame stiffness, source size, and the interface permeability condition on the impedance values are presented and discussed. ©2002 ASME
TL;DR: The present method is based on concepts from algebraic graph theory and comprises of an efficient algorithm for calculating the Fiedler vector of the Laplacian matrix of a graph that maps the vertex ordering of graphs into nodal and element ordering of the finite element models.
TL;DR: In this paper, a phenomenological model is used to represent the behavior of sound in the fluid-saturated elastic porous medium and closed-form solution in the form of an infinite series is developed for the infinite cylindrical surface excited in vibrational modes of zeroth and first order.
TL;DR: A statistical theory is developed for the KPZ equation in (1+1) dimensions driven with a random forcing that is white in time and Gaussian-correlated in space and derived for the joint probability density function of height difference and height gradient P(h-h*, partial differential(x)h,t).
Abstract: The Kardar-Parisi-Zhang (KPZ) equation in $(1+1)$ dimensions dynamically develops sharply connected valley structures within which the height derivative is not continuous. We develop a statistical theory for the KPZ equation in $(1+1)$ dimensions driven with a random forcing that is white in time and Gaussian-correlated in space. A master equation is derived for the joint probability density function of height difference and height gradient $P(h\ensuremath{-}\overline{h},{\ensuremath{\partial}}_{x}h,t)$ when the forcing correlation length is much smaller than the system size and much larger than the typical sharp valley width. In the time scales before the creation of the sharp valleys, we find the exact generating function of $h\ensuremath{-}\overline{h}$ and ${\ensuremath{\partial}}_{x}h.$ The time scale of the sharp valley formation is expressed in terms of the force characteristics. In the stationary state, when the sharp valleys are fully developed, finite-size corrections to the scaling laws of the structure functions $〈(h\ensuremath{-}\overline{h}{)}^{n}({\ensuremath{\partial}}_{x}{h)}^{m}〉$ are also obtained.
TL;DR: In this paper, a systematic approach for the selection and physical realization of updated terms is presented, in which the discrete equilibrium equation formed by mass, and stiffness matrices is converted to a continuous form at each node.
Abstract: The selection of parameters is most important to successful updating of finite element models. When the parameters are chosen on the basis of engineering understanding the model predictions are brought into agreement with experimental observations, and the behavior of the structure, even when differently configured, can be determined with confidence. Physical phenomena may be misrepresented in the original model, or may be absent altogether. In any case the updated model should represent an improved physical understanding of the structure and not simply consist of unrepresentative numbers which happen to cause the results of the model to agree with particular test data. The present paper introduces a systematic approach for the selection and physical realization of updated terms. In the realization process, the discrete equilibrium equation formed by mass, and stiffness matrices is converted to a continuous form at each node. By comparing the resulting differential equation with governing equations known to represent physical phenomena, the updated terms and their physical effects can be recognized. The approach is demonstrated by an experimental example.
TL;DR: In this article, the authors summarize the assumptions made regarding the out-of-control process shift in the economic design of multivariate control charts and address their consequences, and study the average run length (ARL) properties of the χ 2 control chart using a numerical example.
Abstract: It is an increasingly common practice to monitor several related quality characteristics of a product or process using a multivariate control chart procedure. Several types of multivariate control charts, including Hotelling's χ 2 and T 2 control charts, have been developed in attempts to improve monitoring by using the correlation structure that exists between quality characteristics. The purpose of this paper is to summarize the assumptions made regarding the out-of-control process shift in the economic design of multivariate control charts and to address their consequences. We study the average run length (ARL) properties of the χ 2 control chart using a numerical example and show that this chart can perform ineffectively under the assumed out-of-control conditions when designed using the economic approach. Following Healy,[1] we offer an alternative procedure that has improved ARL properties and overall performance. These results can be important to researchers and practitioners who are inter...
TL;DR: In this paper, the authors proposed some seismic sensitivity indicators for tall guyed masts, which would help tower designers decide whether seismic effects are important and whether detailed dynamic analysis of the structure is required.
07 Nov 2002
TL;DR: This method exploits a DC approach for constructing a dictionary in fault diagnosis using the neural network's classification capability to provide robust diagnosis using a mechanism to deal with the problem of component tolerance and reduce testing time.
Abstract: This paper presents a method for analog circuit fault diagnosis by using neural networks. This method exploits a DC approach for constructing a dictionary in fault diagnosis using the neural network's classification capability. Also, Radial Basis Function (RBF) and backward error propagation (BEP) networks are considered and compared for analog fault diagnosis. The primary focus of the paper is to provide robust diagnosis using a mechanism to deal with the problem of component tolerance and reduce testing time. Simulation results show that the radial basis function network with reasonable dimension has double precision in fault classification but its classification is local, while the backward error propagation network with reasonable dimension has single precision in fault classification but its classification is global.
TL;DR: In this article, a numerical simulation of the evolution of the vapor-liquid interface is proposed to study the two-phase heat transfer, concerning the film boiling process on an isothermal vertical surface, through the bubble growth mechanism.
01 Jan 2002
TL;DR: In this paper, a numerical simulation of the evolution of the vapor-liquid interface is proposed to study the two-phase heat transfer, concerning the film boiling process on an isothermal vertical surface, through the bubble growth mechanism.
Abstract: The present work is aimed at studying the two-phase heat transfer, concerning the film boiling process on an isothermal vertical surface, through the bubble growth mechanism by a numerical simulation of the evolution of the vapor-liquid interface. The interface is captured by a level set method, which is modified to include the liquid-vapor phase change effect. The phase change effect and mass transfer at the interface have been considered in the continuity equation. Also, the gravity and surface tension effects have been taken into account in the momentum equation. The fluid flow adjacent to the hot surface was assumed as laminar, unsteady and two-dimensional. The governing continuity, momentum and energy equations, which include the spatial and temporal changes, and also the interface evolution equation, have been solved by a finite difference numerical method, which has implemented the TDMA algorithm and the projection method. Then, the velocity and temperature fields and also the interface location have been computed
TL;DR: In this article, the influence of induction heating on the age-hardening process of a Nickel-base cast superalloy, IN738LC, was investigated and compared with normal aging having an average heating rate of 400°C/hr.
Abstract: Influences of induction heating on the age-hardening process of a Nickel-base cast superalloy, IN738LC, was investigated. In this study cast specimens were undergone a solution treatment process in an argon atmosphere controlled furnace at 1125°C for 2 hours. Then, they were quenched in oil to room temperature to obtain supersaturated solid solution. These samples then subjected to two types of aging with equal heating rate, 30°C/Sec. One was induction aging and the other salt bath aging. Effects of these types of aging on the structure were analyzed and compared with normal aging having an average heating rate of 400°C/hr. The age-hardening behavior and microstructural characteristics were studied by hardness testing, scanning electron microscopy (SEM), electron image analyzing, X-ray diffractometery (XRD) and transmission electron microscopy (TEM) with replica method. According to the results obtained by these experiments, although the rate of heating of the specimens in induction and salt bath aging were equal, the diffusion-control process of nucleation and growth of γ′ precipitates in induction aging were considerably accelerated. Furthermore, desirable characteristics of γ′ precipitates were achieved in induction aging at lower time and temperature in comparison with times and temperatures of other types of aging. Improvement of microstructural characterization obtained in induction aging was related to the existence of an external electromagnetic force produced by induction heating. This electromagnetic force raised the effective driving force necessary for age-hardening process and intensified the nucleation and growth of γ′ precipitates remarkably.
TL;DR: In this paper, a new mixed finite element formulation is proposed to analyze transient coupled thermoelastic problems, and the non-classical (Green-Lindsay) coupled model is selected for a laminated composite and a homogeneous isotropic plate.
TL;DR: In this paper, efficient neural networks are trained for the approximate analysis and design of double layer grids using the backpropagation algorithm to reduce the non-linearity of the data and to increase the accuracy, speed, and stability of the training.
Abstract: In this paper, efficient neural networks are trained for the approximate analysis and design of double layer grids using the backpropagation algorithm. Special methods are developed for data classification and data ordering to reduce the non-linearity of the data and to increase the accuracy, speed, and stability of the training.