INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE (ENGLISH)
Year:2004 | Volume:15 | Issue:1|Papers Count:14

A parametric study is undertaken to examine the effects of tension and compression reinforcement ratios and steel yield strengths, loading types and stages, concrete compressive strength, craking and tension-stiffening, using the nonlinear layered finite element method. The effects of the above parameters on different behavioral aspects including the load-deflection and moment-curvature characteristics, failure load and flexured rigidity, El. Of R.C. beams are reviewed along with a comparison with the ACI code and ABA code and experimental data where available. To account for the influencing parameters, new models are proposed for estimating the felxural rigidity and the deflection of R.C. beams. The accuracy and efficiency of the proposed model is verified by comparing the analytical results with the experimental data from five different investigations. Reasonably close agreement was obtained between the test data and the computed results.

Ductility, or deformation energy, is by far the largest source of energy dissipation of structures, since normal levels of internal damping represent only a small portion of energy dissipation. However, large material deformations such as that required in building components to perform in a ductile manner, are often associated with cracking and degradation of its strength, particularly in concrete structures. Added Damping and Stiffness (ADAS) elements are mechanical devices that design to be installed in either new or existing buildings. ADAS elements, if properly designed and installed, can increase the strength, stiffness and usable energy dissipation capacity of a moment resistant frame (MRF), in addition the energy dissipation is concentrated to locations, which have been specifically designed for this purpose. This paper proposes a new alternative design approach for buildings with the application of ADAS elements and determining of ductility and response modification factor of structures by the use of nonlinear static analysis and capacity spectrum method (CSM). Also ductility and response modification factor of ordinary moment resistant frames with and or without ADAS elements have been compared. The results of these investigations indicated that equal viscose damping of moment resistant frames with ADAS elements is more than moment resistant frames. Therefore base shear forces of these structures are less than MRF and the weight of steel used and foundation construction costs of these structures are less.

Bilinear Subspace algorithms are a generalization of a previously presented paper that considered bilinear systems with white inputs [9]. They are also a direct extension of linear subspace identification. To illustrate the practical use of the method, it has been compared with linear subspace methods when applied to the same data obtained from an industrial winding process. This process represents a subsystem of complex industrial processes, which make more difficult their identification and control design.

The aim of this work is to find the important parameters, that include impact velocity of tube to plug, the dynamic angle, the pressure of the explosion at the point of connection between explosive material and tube, the amount of stress and strain in the tube during the deformation, and the kinetic energy and strain energy that remain in the tube. Our simulation of this mode ling is done with ABAQUS software in two dimensions.With these parameters, and with change of the geometric condition similar to the standoff distance, boundary condition, initial condition and the use of specific geometry of the impactor, it is possible to achieve a good joint in this process.

Active control of sinusoidal acoustic noise in an experimental phone kiosk is investigated. This is performed by implementation of a single-channel and a 1x2x2 multiple channel FXLMS active noise control (ANC) system in a 1X 1X2 m phone kiosk. The secondary path transfer functions are identified using an offline technique. The results show that both ANC systems generate a quiet zone with 15 dB noise attenuation in each error microphone. In this way, using the multiple-channel one, two quiet zones are produced at two locations in the kiosk. Further experiments also revealed that the multiple-channel system is stable for a wider range of noise frequencies, and therefore, more appropriate for multi-tonal noise cancellation.

The partial oxidation of natural gas with oxygen at different independent variables such as fuel equivalence ratios from 2 to 4, preheat temperatures of feed gas streams up to 200ºC and space velocities from 40 to 100hr-1 was studied. Experiments were carried out using a bench-scale syngas generator mainly consisted of preheats sections, a water cooled swirling jet burner, a combustion chamber and a water quenching chamber. Evaluation parameters were selected to be H2/CO ratio, CO selectivity, natural gas conversion and syngas yield. Results show that the fuel equivalence ratio is the most important factor for syngas production. Preheating the feed gas streams was generally made better conditions and by increasing the space velocity the better operating conditions achieved. The operation of the system showed successful obtaining of syngas from natural gas using noncatalytic partial oxidation.

High-hazardous materials transportation can be extremely harmful to the environment and human health upon the occurrence of accidents. Contacts with these materials can cause damage and even death to human lives and animals. Hazardous materials include explosives, gases, flammable liquids and solids, along with oxidizing substances, poisonous, and radioactive materials and any other dangerous substance. When these substances are moved on the roads, special precautionary measures should have been taken.In this article, the framework of risk evaluation and modeling has been discussed, and then this framework is used to make a mathematical model for finding the optimum path for transporting the hazardous materials. Finally a risk oriented optimization algorithm is developed for solving the mathematical model.

In this paper we use interval functions to solve the nonlinear Fred, Holm integral equation of the second kind of the form: y(x)- b a∫g(x,t,y(x),y(t)dt=ƒ(x), xÎ[a,b] For solving above equation with arithmetic functions, we know if integral operator has some special properties, e.g. if integral operator has monotonicity property, equation will be easy solved. In this paper we will consider a general computational scheme, which does not assume any special properties of integral operator.

Saponification reaction of fatty acids in palm oil sodium hydroxide results soap. Addition of ethanol, sugar, glycerine and ethylene glycol to the saponification of fatty acids form transparent soap. Various compositions of sodium hydroxide were incorporated in different batches of experiment at 70°C to determine its effect on the conversion rate, pH and percentage of transparency in the final product. The experiment was then carried out with different compositions of ethanol and sugar to achieve a unique and high transparency of palm oil based glycerine soap.An 82 percent glossy honey colour transparent soap bar was formulated by addition of 8.8 percent of sodium hydroxide, 8.5 percent of ethanol and 8 percent of sugar to the palm oil, at reaction temperature of 75°C. The reaction temperature affected the conversion rate and percentage of transparency in the final product. A concentration of 0.02 percent of free alkali yielded 99.6 percent of conversion within 120 minutes of reaction time. An attractive honey soap bar with excellent transparency was produced when reaction temperature rose to slightly higher than 75ºC .

In every engineering field, rational methods of design, in which the strengths of all materials employed are utilized on unit of strength, is an ultimate objective. A rational procedure of design requires that a general mode of failure under assumed service conditions be determined or assumed. Also, a quantity such as stress, strain, or energy may be chosen as a critical value to limit the loading that can be applied to the member. Further more, suitable testes of material must be adopted for determination of the critical value. In this study triaxial test and Mohr-Coulomb failure criterion is utilized to characterize asphalt concrete mixture. Also, a relationship is proposed by which the asphalt concrete mixture strength could be determined based on loading geometry including surface shear and interface adhesion (bonding) between asphalt surface course and underlying layer as well as mixture strength parameters.To develop the equation of asphalt concrete mixture strength, it is assumed that an adequate thickness of base and subbase layers are provided to prevent subgrade failure, and that the base and subbase course materials will not fail under the shear stresses imposed by the loads applied.

This paper presents a new method to determine an accurate position by using a low cost GPS receiver and proposes a neurofuzzy system for better accuracy in GPS positioning. At first a fix position parameters, such as Dilution of Precision (DOP) and Signal to Noise Ratio (SNR), are measured. Then those are applied to fuzzy system. Fuzzy system output defines as Reliable Factor (R.F.). Based on the R.F. values, the more accurate positions are selected. Calculating the errors of fuzzy selected position components, real and dynamic patterns of the errors will be created and feed in to neural network. The neural network is trained with such real data to predict the later seconds errors. The steps of design and implementation of the neurofuzzy system are presented and the experimental result of the tests are stated with real data, before and after Selective Availability (S/A) is turned off. Those show that the errors of position components decrease due to using of the neurofuzzy system. Also, it is shown that the positioning accuracy with adaptive neurofuzzy system is independent of the absence of S/A or its presence.

Taking into account the fact that a -large amount of the nation's budget is used in new projects such as petrochemical plants, power plants, airports, freeways and so on, it-is essential to focus on the optimum allocation of funds to these projects. At the same time increasing the level of quality and productivity of the projects or products are of prime importance to both owners and customers.Value engineering as an organized systematic approach has been used effectively in engineering projects to reduce cost or enhance the quality of the work. This method, which mainly concentrates on "Basic Function" is highly efficient in analyzing various big projects.In this paper a new methodology for increasing the effectiveness of the project management process using value-engineering approach is presented. The method uses Value Engineering Job Plan.This method is applied in a project and the results are presented in this article. The application of the model resulted in a 22% cost reduction in the project.

In addition to some practical limitations, for instance, the storage of low-density natural gas even at high storage pressures of I 50 bar, emission reduction of natural gas engines is a major constraint in urban transportation, especially with new and strict emission standards. Methane, as the most oxidation-resistive hydrocarbon, constitutes the main part of the unburned hydrocarbon in the exhaust and must be well reduced, with other pollutants such as carbon monoxide. On the other hand, catalytic converters have been widely used on gasoline engines since 1976, with the most commonly used catalyst at present being the three-way catalyst (TWC), which oxidizes CO and HC, and reduces NOx. Many experimental and mode ling studies have been reported for automobile catalytic converters. The performance and operating conditions for the catalytic converter of dedicated natural gas engine have not been widely studied. The engine operation is well controlled using an advanced electronic controller system. This control system is in charge of exact metering of fuel injection, as a function of operating conditions, to minimize the emission, while producing maximum power output, as the-basic duty of the engine.In this paper, a transient Model for natural gas catalytic converter is developed to investigate the performance and operation of the catalytic converter, including chemical kinetics. The type of chemical kinetic applied is selected, based on the exhaust conditions and main components and has a non-linear structure. This model also includes transfer phenomena and temperature and composition-dependant physical properties for main components. Results are then presented and analyzed. As evident, this model must be verified and improved with future experiments. The dynamic nature of the model generalizes its outputs and accounts for engine start-up, shutdown and changes in its operational mode.