Articles in This Issue
Abstract
A computer program has been generated to calculate the optimum dimensions and the amount of reinforcements for open reinforced concrete circular cylindrical tanks rest on ground. The design is based on limit state method for both ultimate and serviceability limit states in accordance with the British Standards B.S. 8110 and B.S. 5337. The cost of concrete, steel, and formwork are considered. The procedure is based on the interior penalty method to find the optimum solution for the non-linear programming problem. The tank consists of cylindrical wall and circular base and the joint between them was considered as partially fixed. The design variables consist of tank geometric variables in addition to steel content in seven positions. The effect of the design capacity of the tank, bearing capacity of the soil, unit price of steel and concrete, and finally unit cost of formwork was studied. It is found that the reduction of the bearing capacity of the soil linearly increases the cost of the tank. The increase of concrete and steel unit costs leads to increasing the tank height while the increase of formwork unit cost enhances the tank diameter, to reach the optimal design.
Abstract
This paper is concerned with the application of finite element techniques to the nonlinear analysis of ferrocement slabs. Both material and geometric nonlinearities are considered in the analysis. Concrete compression is modelled by a plasticity model and smeared cracking approach is used for tensile cracking. Degenerated thick shell elements employing a layered discretization through the element are adopted. Analyzing of a ferrocement slab does validation of the proposed model.
Abstract
This study investigates the effect of rotating two rows of horizontal cylinders on forced convection heat transfer in cross flow. Each row consists a three rotating horizontal cylinders heated at constant temperature. The governing equations for the steady, laminar, two dimensional, incompressible flow and constant fluid properties are solved numerically using the finite element method with FlexPDE soft package for a two rows of rotating cylinders at the same direction and at opposite directions. The main parameters are: Reynolds number ( 40 10 Re − = ), Prandtl number ( 7.0 Pr = ), dimensionless longitudinal pitch (SL=1.5-2.5), dimensionless transverse pitch (ST=1.5-2.5) and the dimensionless angular velocity (Ω=0-3) (for both directions clockwise CW and counter clockwise CCW). It is found that the average Nusselt number increased with increasing Re and ST, and decreases with Ω and SL. The results are compared with other authors and give a agreement.
Abstract
In this work, a new computerized measurement system for multi-plane flexible rotor balancing has been designed and implemented. This system can be used to modernize and enhance conventional low-speed balancing machines or for field balancing applications. This system adds very important features to balancing machines such as multi-plane flexible rotor balancing, high accuracy, stability, and high dynamic range. Also, the proposed flexible rotor balancing technique permits accurate balancing of high-speed rotors utilizing low-speed balancing machines or field balancing at speeds lower than the critical speeds. The proposed digital Wattmetric technique in conjugation with advanced measurement circuitry have led to significant improvement in balancing accuracy even when the unbalance signal is buried into high level of noise.
Abstract
In this paper, the finite-element and the matlab procedures are used for the torsional analysis of large rotor system. A large rotor system of 13 discs are considered for the purpose of analysis. As a result, the finite-element and matlab procedures are good tools for the analysis of vibration analysis and design of large rotors and their results are accurate in comparison with other literatures. The normal elastic curve and T-ω diagram obtained in this study are an effective illustration for the vibration problems in large rotors, and the developed equation for drawing the normalized elastic curve reduce the need for tabulated calculation of this curve and its very essential for vibration analysts and designers.
Abstract
A two-dimensional finite element method for analysis and determination of second mode stress intensity factor (KII) of several crack configurations in plates under uniaxial compression is presented in this study. Various cases including diagonal crack (i.e. corner crack, central crack as well as at different locations on the diagonal) and central kinked crack are investigated with different crack's length, orientation and location. The influence of the contact between two crack surfaces is taken into account by applying contact element procedure with desired friction coefficient. The stress intensity factor is calculated by a crack surface displacement extrapolation technique. From the obtained results of the analysis it is found that, the corner cracked plates more dangerous than the other cracked plates, since it has the highest stress intensity factor. Also, the length and orientation of the kinked crack have significant effects on the stress intensity factor. The results of this investigation is illustrated graphically, exposing some novel knowledge about the stress intensity factor and its dependence on crack configuration.
Abstract
In this work, a portable vibration analysis and diagnosis system is designed and constructed. The system is capable of doing most of the known analysis techniques such as FFT, time waveform, cepstrum analysis, dual channel analysis, orbit, envelope detection and other techniques. Furthermore, a new fast and efficient tracking analysis algorithm, suitable for portable instruments, has been proposed. This technique provides the data required to get accurate Bode and Nyquist plots for diagnostic analysis during machine run-up and coast-down tests. Moreover, FFT waterfall and spectrogram techniques have been included. Also, single-plane and dual-plane field balancing have been implemented in this system to execute field balancing tasks.
Abstract
The current approach to cooling water treatment is to use a multi – component inhibitors. Cooling water formulations containing mixtures of inhibitors usually offer better and increased protection to ferrous metals than similar concentrations of either of the individual components. Such mixtures are synergistic in their action .But; the synergistic effects between nitrites, molybdates and inorganic phosphate were not investigated until recently. A weight loss technique was used to investigate such mixture and to optimize the concentrations of the components in the blend.Consequently; an efficient and effective blend was developed as a corrosion inhibitor for carbon steel in aerated Al–Daura refinery re-circulating cooling water in the pH range 6.75 to 7.25. The preferred concentrations of components in the multi- component inhibitor blend (as ppm ) were: (SN + SM): SHMP = 800: 20 with SN: SM weight ratio =3:2.The reduction in corrosion rate was 97.6 % .
Abstract
Obstacle avoidance and path planning are from the most important problems in mobile robots, especially in unknown environment . In this paper, we proposed an approach for mobile robot navigation combining path planning and obstacle avoidance. Methods such as obstacle avoidance are inspired from the nature, and have been developed by fuzzy logic to train an intelligent robot in unknown environment. The model of the robot has two driving wheels and the linear velocity and azimuth of the two wheels are independently controlled using PID controller. Inputs are obtained from ultrasonic sensors mounted on it.
Abstract
Sublime is considered one of the significant concepts in the recent architectural thought; it has emerged clearly as a mean of creating the highest levels of continuity in architecture, especially in contemporary architectural movements. The importance of sublime especially has emerged. Many architectural studies dealt with concept of sublime in architecture is different and various ways according to the trend of each study; this shows the importance of studying the concept of sublime in the architectural field in general. This study tries to focus on the utilization of the sublime as heritage continuity system in Islamic Architecture because it’s important in the generation of sublimity of architectural models. The paper discusses the importance of this concept and its utilization in the designs, in order to explore the particular problem which has been represented as (The absence of a specific imagination of methods and strategies for achieving sublimation).Thus the objectives of the paper has been formed by building a theoretical framework consisting of two main items of detailed theoretical field which specifies sublime as a concept ,Firstly, Then the application of the important Islamic Architectural products in Mashhad Architecture as a model, Secondly, Finally, concluding utilization of sublime as dogmatically system in Mashhad Architecture, Thirdly, after discussing the results to formulate the conclusions in the end.