AMIRKABIR
Year:2002 | Volume:13 | Issue:50|Papers Count:17

The tip displacement variance of an articulated robotic manipulator to simultaneous horizontal and vertical stochastic base excitation is studied. The dynamic equations for an n- links manipulator subjected to both horizontal and vertical stochastic excitations are derived by Lagrangian method and decoupled for small displacement of joints. The dynamic response covariance of the manipulator links is computed in the coordinate frame attached to the base and then the principal variance of tip displacement is determined. Finally, simulation for a two-link planner robotic manipulator under base excitation is developed. Then sensitivity of the principal variance of tip displacement and tip velocity to manipulator configuration, damping, excitation parameters and manipulator links length are investigated.

Historical buildings and ancient monuments are valuable cultural heritage of nations, that are unfortunately being damged due to human interference, weather conditions and environmental pollution. So, it is necessary to record all of them in a rapid and easy manner, in order that archaeological studies and establishment of a National Heritage Archive becomes i possible. Close Range Photogrammetry (CRP) with interesting and unique capabilities is the most useful tool for this purpose. The difficulty in traditional photogrammetry is the necessity of metric camera that is expensive, hard to access (especially in countries such as Iran that are rich in cultural heritage), far from user - friendliness and needs special processing instruments. Such factors reduce the degree of usefulness and easiness of CRP technology. There are a lot of historical monuments in Iran (which many of them are in the level of the most important cultural heritage of the world) and in the present project one of them i.e. the relief of Driush I, the Great (500 B. C.) on the rocks of Bisotun was choosen as the test field. This splendid monument is, nationally and internationally, highly discussed and there is an Emergent propgramme in hand for its conservation and restoration. The present project is concentrated on the application of professional and amateur non metric cameras. These cameras have unknown calibration parameters that are usually photo variant. The kernel of ths research is firsty to have a survey on the calibration elements of non metric cameras (that are easily available) and secondly to show the photogrammetric capabilities of a precise non metric (Hasselblad), an amateur (Yashica), and a digital (Minolta) camera from the stereoplotting and rectification point of view.

An efficient method for two-dimensional dynamic interaction analysis of gravity dam-reservoir systems is presented. The Euler-Lagrangian approach, based on BEM-FEM formulation in the frequency domain, is adopted. Displacement-based finite elements for the structure and velocity potential-based boundary elements for the fluid domain are developed. Compressibility of the fluid is considered. In this formulation, symmetry of the equations system could only be achieved once the fluid domain is circular and interaction absent. The results show that this method can be offered as an appropriate method for dam-reservoir interaction analysis and indeed extendable to time-domain analysis.

Distribution of thermal stresses in dams, especially concrete gravity dams is a complex and significant subject in designing the dams. Although by the use of a simplified assumption, the temperature distribution along the cross section of a dam can be considered linearly, because of the low thermal diffusion coefficient for concrete and variance of atmospheric conditions with time, temperature distribution along the dam cross section is nonlinear. So, the assumption of linear distribution of temperature will not be an accurate one. A number of factors influence the temperature distribution along the dam cross section that can be divided into two groups internal factors due to hydration of cement and external factors due to atmospheric variation. The temperature distribution along the dam cross section has a significant effect on the thermal stresses.In the present paper a concrete gravity dam by the use of 2D finite element analysis in a climate condition similar to Mashhad were analyzed. In this analysis concreting in hot and cold weather with different types of cements (type I and type IV) were investigated. At the first step, the results of thermal analysis were obtained and then normal stresses and displacements at different nodes were extracted. The results show that the critical stresses are produced in the case of hot weather; with high thermal hydration for cement and high expansion coefficient for the materials. These stresses in the core of a dam cross-section and away from the drainage gallery and also adjacent to the toe and heel of the dam are maximum.

The paper represents a physical blasting model in laboratory scale along with a photographic approach to describe the distribution of blasted rock materials. For this purpose, based on we bull probability distribution function, eight samples each weighted 100 kg, were obtained. Four pictures from four different section of each sample were taken. Then, pictures were converted into graphic files with characterizing boundary of each piece of rocks in the samples. Error caused due to perspective were eliminated. Volume of each piece of the blasted rock materials and hence the required sieve size, each piece of rock to pass through, were calculated. Finally, original blasted rock size distribution was compared with that obtained from the photographic method. The paper concludes with presenting an approach to convert the results of photographic technique into size distribution obtained by seive analysis with sufficient verification.

Direct conversion of methane to methanol is a newly developed technique by which the intermediate and expensive process of formation of synthesis gas is eliminated.The main aim of the present study is to develop a generally applicable mathematical model to predict the behavior of the direct oxidation of methane to methanol. The interesting point concerning this work may be the task of simultaneous solution of the reacting species mass balances equations both inside the catalysts pores (microscopic relations) and within the bulk of fluid (macroscopic relations).A large number of the studies performed in this area are solely experimental investigations without pertinent interpretation of the results. While, those considered the theoretical aspects of such a process have not gone into details of the reactions inside the catalysts pores. , In the present investigation, a dynamic model for the partial oxidation of methane to methanol, utilizing oxygen in a fixed, bed reactor packed with V2O5 /SiO2 particles as the reaction catalyst has been developed.Considering an appropriate rate equation, the kinetic scheme of the process and the catalysts effectiveness factor have been deter mea. It has been observed that an increase m methane conversion improves the selectivity's of both CO and formaldehyde, while those of CO2; and methanol are decreased. In addition; the effects of temperature, pressure, oxygen concentration in feed and gas hourly space velocity (GHSV) on the conversion of methane and selectivity of the products have been investigated. The results obtained applying this model, were adequately correlated with the experimental data available in the literature.

In this paper a novel efficient method for reliability assessment of radial distribution systems using Monte Carlo simulation is proposed For specification of appropriate probability distribution function and its parameters to generation of random variables in Monte Carlo simulation, an efficient method is introduced. Also loads in distribution networks are considered as time varying. In computation procedure load modeling is based on maximum and minimum consumption of load points using fuzzy numbers. Case studies in IEEE-RBTS are presented to show the effectiveness of the proposed method.

The present facusos on the performance of mesmeric indices in relation to visual, , assessments. To this end, 98 real pairs of metameric samples were prepared using computer colour match predictions and the differences between the pairs were assessed visually against a prepared Grey scale under three different light sources. The correlation of these data obtained from two different kinds of metameric indices (one based on colour differences under different illuminates and the other based on the difference in spectral reflectance data) were obtained using statistical parameters. For each metameric pair the parametric correction using the matrix-R decomposition were also carried out. The results show that the maximum correlation between the indices and visual assessments were approximately 35% (PF/4 = 36). All indices per famed similarly, but the CIE94 index in the colour difference group of indices and M 16 in the specral difference group of indices gave maximum correlation and hence best performances. Parametric correction led to poorer correlation with the least effect on the MI6 index.

The Mouteh area is located 270-km southwest of Tehran. It is a part of Sanandaj-sirjan Zone and contains metamorphosed igneous-sedimentary complex (predominantly composed of mica-schist, mylonitic felsic met igneous rocks), granitoids and sedimentary assemblage. A progressive deformation affected on these lithologic assemblage. This process contains three deformation stages including: D1, D2 and D3. Result of the first deformation stage (D1) is production of a compositional layering in different parts of this area containing alteration of layers rich in felsic (quartz and feldpar) and mafic (biotite and amphibol) minerals. Structural event that produced this compositional layering (s1) has been overprinted by following stages. The second stage of deformation that is the most important event of deformation in the Mouteh and adjacent areas developed a penetrative mylonitic foliation (S2 =Sm) and stretching/ mineral lineation (Lm). Folds that are related to this stage, have high amplitude and low wavelegth and their inter-limb angle is less than 30 (tight to isoclinal).Many of these folds of this stage (fold axes and stretching lineation) have shallowly plunging in different parts of the area. Trend of deformation produced open folds that has changed position of the second structural elements development of dextral en-echelon fault system with sinistral-revers sense of movement is the main character of this stage. Several joint systems are related to this event. The most activity of magmatism occurred during this stage. The mouteh granitoid appears to intruded after DJ & D2 deformations along "transtension shear zones". This deformation was accompanied by remobilization of quartz pyrite and chalcopyrite(hosting gold)from granitoid intrusion.

In this study, seismic response of an idealized single storey structure with sliding support to three directional (i.e.two horizontal and the vertical components) earthquake ground motion is investigated. The frictional forces mobilized at the sliding support are assumed to have ideal Coulomb-friction characteristics. A circular interaction curve between stresses in two orthogonal directions is assumed and the vertical stresses in base are affected by vertical component earthquake. The effects of bidirectional interaction and vertical components of stress in base on the response are investigated by comparing the responses to three components earthquake excitations with the corresponding responses produced by two components earthquake excitation and the application of single component excitation in each direction independently. The results indicated that effects of verical component are significant and should be considered in low period structures.

Three-Dimensional elasticity solutions are obtained for finite length, cross-ply cylindrical panels, simply supported at four edges and subjected to dynamic transverse loading. Displacements are assumed in the form of trigonometric function expansion in the circumferential and axial directions which satisfy the boundary conditions at each edges of panel. By these assumption the boundary value problem is reduced to a set of ordinary differential equations with variable coefficients. The resulting equations of motion are solved by using Galerkin finite element method. Numerical results are presented for [0 deg], [0/90 deg] and [0/90/0 deg] laminations. Finally radial displacement obtained by this method is compared with classic shell theory (CST) result.

Explosive forming of cone was investigated from some new analytical, numerical and experimental aspects. In the analytical modelling, it is supposed that deformation profile of plate is a truncated cone during process which will be deformed to a fully formed cone at the end of process. The variation of plate thickness was also neglected. Analysis required equations for determining cone dimensions, distribution of plate center velocity and displacement, distribution of hoop strain during process and required charge mass to produce fully formed cone are also given in this analytical model. ABAQUS/Explicit package was used fo FEM simulation. The results of analytical model given in this paper are in agreement with experimental and numerical (FEM) results.

This paper presents a dynamic model to simulate the high power single-phase "Written Pole" motors. The base of this modelling is the generalized theory of electrical machines Based on this theory, first, the required equations governing the dynamic behavior of these motors are obtained. Next, the equations are solved in a special reference frame which is valid for the unique properties of single-phase Written Pole motors. Finally, the comparison of simulation modelling with the experimental results shows very good agreement.

Daring recent years, voltage stability has received attention in literarure. Reactive power resources while influencing voltage Stability, affect voltage profile A the grid. In this paper, a new approach based on Genetic Algorithm is proposed in which proper rective resources are allocated throughout the system so that both voltage profile and stability are optimized. Due to their important effects, optimal allocation of ULTC'S are also considered

A numerical model based on the laboratory testing method for buried pipeline is presented to study the effect the effect of some parameters such as static & dynamic stiffness, damping and added mass for pipe and surrounding material. The model set up is based on the theory of structural dynamic and mechanical vibration with application of the extension of fourier transfer in time and frequency domain.The loading system through the Servo-hydraulic, actuator and load cell which all are connected to the computer provide the control of laborator testing procedure. The pipe and surrounding material is modeled by box with a suitable scale and is equipped with some measuring system for controlling the effect of damping and relative longitudinal displacement for different section of the pipo. Comparison of the laboratory results with the other references confirms the testing procedure. However, the investigation shows that some parameters such as static and dynamic stiffness, added mass for different conditions can be estimated for different buried depth and diameter of pipeline. The effect of pipe materials, soil compactness, soil water content, frequency and amplitude of the harmoniuc loading are studied in this paper.

In the present paper, the response of orthotropic plates to transverse impact load due to moving body have been studied theoretically in terms of the induced impact load and the impulse imparted to the plate. The analysis assumes linear elastic behavior of the material. The impulse is directly proportional to the deflection under the point of impact. The results, obtained shown that the complete response is described by a single parameter called impact, parameterl. The coefficient of restitution, maximum impact force, and time of contact between , the impactor and the plate can be easily determined in term of l. The variation of the energy of impact is also considered and the approximate expressions used by others discussed. Finally, for a glass fibre reinforced epoxy amina, the roles of the volume fraction of fibres and the, impactor parameters such as its mass, velocity and kinetic energy are ascertained and useful, conclusions drawn

The characteristics of earthquake ground motion have great influences on the response of structures to the earthquakes. Peak ground motions, duration of strong motions and frequency content are important characteristics of earthquakes, which are studied in this paper. The relation between peak ground acceleration, velocity and displacement have been taken into account and the effects of magnitude, epicentral distance and recorded duration of earthquakes on peak ground acceleration have been presented as graphs. The frequency content of ground motion can be examined by power spectral density of accelerograms. In this study the power spectral density of the records have been determined and normalized power spectral densities are compared. There are different formulas for the smoothed power spectral density function such as Kanai-Tajimi's model. In this study, comparing with Kanai- Tajim s formula, the extreme value model is suggested for the spectral density function. This model is evaluated for accelerograms on different soil conditions and the smoothed mean power spectral density function are determined for each soil groups. The central frequency and predominant period of earthquakes are also estimated. .