JOURNAL OF SCHOOL OF ENGINEERING
Year:2003 | Volume:15 | Issue:2|Papers Count:13

In this paper the model of permanent magnet synchronous motor drives system described by vector control approach. Because of high band width of the interior current control loop, only mechanical dynamics are used to design the outer position controller. The proposed position controller is of fuzzy sliding - mode type with rule adaptation that dose not needs the complicated model of the system and compared with the previous works, the proposed method has lesser computations and better performance. Then a simple algorithm for initial rotor position with 15 electrical degree precision is proposed. Finally the practical results are presented to verify the effectiveness of the proposed method.

To identify different radar techniques, a matrix algorithm is proposed in this paper. A systolic array is designed to do the algorithm in real time manner. Homogeneous Submatrix Systolic multiplier (HSSM) method has been used in this design. Modeling and simulation results show the processor could effectively identify different radar techniques.

Free and forced non-linear vibrations of laminated composite annular Plates are studied under ring loads in various conditions. Non-linear strains, membrane and shear forces, and bending and shear moments are established on cylindrical coordinates, then axisymmetry assumption is yielded to elminating of all angle differential equations are derived in a similar form of Von Karman equations. Finite element method is applied in analyzing and constitution of mass and stiffness matrices; and also the dynamic equations are obtained as a matrix identity through the substitution of potential and kinetic energy terms in Euler-Logrange equation. Non-linear vibration responses are computed by an iteration scheme and an initial displacement vector which resulted from linear solution. Finally mode shapes, non linear natural frequencies are ploted for a variety of boundary conditions, inner-outer radial ration, and tangential-radial of elasticity modulus. The results of the free non-linear vibration analysis closely related to solutions obtained by Ritz-kantorovich method.

This paper describes a theoretical study of the self-condensation of non-equilibrium wet steam during supersonic expansion in the Laval nozzle. The nucleation theory and exact droplet growth equations have been combined with equations of one-dimensional gas dynamics and the system integrated numerically on a computer. It has been shown that self-condensation of vapour in the divergent part of nozzle causes a jump in the flow. In order to determine the ability of this method to predict the condensation zone, a steady solution is obtained for a nozzle under supersonic flow condition and compaired with measurements. The work will be extended to predict the location of condensation jump in steam turbines.

Wherever two plates with different materials welded or bonded together there is a risk of bonding detachment near or across the interface of the plates. In order to model this phenomena the distribution of stress in a plate comprised of two different parts separated along an interface and having a middle edge crack is sought. Depending on the level and conditions of loading, plate materials may have elastic, plastic or creep types of deformation. A numerical meshless technique namely Element Free Galerkin Method (EFGM) is used for this analysis. A multi purpose EFGM computer program which is developed by authors is used to analyze Elasto-plasto-creep stress and deformation fields near a crack in a plate made up of two different parts. Prior to introducing the results a concise explanation of EFG Method and nonlinear constitutive equation modeling has been represented. Then by assuming a purely elastic behavior some of the results of the problem are compared with their similar available analytical solutions. Finally typical solutions of the problem in its complete nonlinear form are represented and assessed. j and C* integrals are used to capture the singularity of the crack tip stress in static and creep conditions respectively. The obtained results confirm that a crack taken place in the interface of two plates is more critical than a crack far from the interface.

In this research, the most important components of an obstacle-free airport design criteria such as; length and width of runway, safety area, stop way area, and dimensions of clear way, Including horizontal, conica, approach, and transitional surfaces are integrated into a mathematical model. Since high rise buildings and towers have always created problems for airport designers, in this research, a mathematical and computerized model has been developed to resolve these difficulties. The application of the developed model covers various categories of airports, including domestic and international. The methodology of research is such that all the obstacles surrounding the runway are controlled. In this way no point will be considered as an obstacle towards these surfaces. Should there be any obstacle, a solution will be recommended to resolve the problem. The standard code of practice used for this software complies with the documents of International civil Aviation organization 9ICAO). The developed software operates on Windows 98 and over platform based on Visual Basic 6.

In this paper, the semi continuum method is developed for analysis of skew bridges with arbitrary number of longitudinal girders. In this study, two assumptions are considered and in the second assumption, a larger region of the deck contributes in load distribution. Therefore, the load distribution becomes more smooth. Results are compared with the grillage analysis method. The grillage method is considered as an accurate method in OHBDC Code. This comparison shows that the error of the first assumption is 37% with respect to grillage method and for second assumption, it is 4%.

Mineral filler is the finest fraction of aggregate used in the production of asphalt paving mixed. It is essential for producing a mixture that is dense, cohesive, durable, and resistant to water penetration. In spite of the fact that filler is very small proportion of the total aggregates in the mix, due to its rather high affinity for asphalt, small changes in the amount or the character of the filler can cause the paving mixture to appear excessively dry or excessively rich. The aim of this research was to investigate the effects of using fillers of different origin on the properties of filler-asphalt and asphalt concrete mixes. A dense-graded aggregate blend, a 60-70 penetration grade asphalt and four different mineral fillers were used in the study. Fillers include a limestone filler, a siliceous filler, a siliceous filler modified by the addition of hydrated lime, and an overburden material 9soil0 filler. The results indicate that the stiffening properties of fillers in the filler-asphalt mixtures vary with the type and proportion of the filler in the mix. The mechanical and durability properties of asphalt concrete are also influenced by filler type, and can be adversely affected by the used of improper type and origin. The addition of hydrated lime to the siliceous filler and considerably improve the performance of this type of filler in the mix.

The main objective of this study is to estimate seismic demands of MDOF frames, using SDOF system demands and to presents a procedure to evaluate maximum story drift and ductility demands of MDOF Steel Moment Resisting Frames. Some modifications have been studied, in order to evaluate MDOF system demands, including higher modes. These modification factors are computed as the ratios between MDOF and the first mode SDOF seismic demands for each record, making them independent from the intensity and duration of ground motion. This permits the statistical averaging of modification factors computed for ground motions of different intensities and duration. The results of this study show that the distribution of story drift and dynamic ductility demand over the height of the frames (specially high-rise ones), have an irregular trend. The reason is attributed to higher modes and MDOF effects, which is intensified with increasing the structure height and fundamental period. It was also concluded that the amplification of deformation demands (story drift and ductility respresented by adH.M and aµH.M modification factors), are mostly increasing with fundamental period and level of ductility (µSDOF).

In this paper, finite element method is used for interaction analysis to investigate the effects of a moving mass on a surface. In analysis procedure the sliding contact effects of vehicle wheel on a bridge have been taken into account by a proposed element. At the end, the motion of a mass on a bending beam (Biggs 1964, yang and yao 1970) has been verified, and its dynamic responses have been calculated and compared with New mark-beta method.

In this study the results of an investigation carried out on radial gates for establishing the dimensionless stage-discharge relationship under submerged and free flow conditions is presented. For this purpose, indicial (power0 method of dimensional analysis and experimental data obtained from a laboratory flume was used to obtain the dimensionless equation that relates discharge (or critical depth) to upstream and downstream depth, gate width and gate opening. The fitted equations, was validated by field experimental data of some submerged radial gates of Doroodzan irrigation and drainage network in Fars province, southern Iran. Results showed that this equation can be fitted to field and laboratory data very well and can be used as a proper tool for management of radial gates in irrigation canals and dam gates.