MODARES TECHNICAL AND ENGINEERING
Year:2006 | Volume:- | Issue:23|Papers Count:9

The objective of this research was to develop models for intercity air travel demand in Iran. The basic structure of previous demand models was based on the gravity formula, moreover, some socioeconomic and quality of service factors were used to estimate the potential for trip production and attraction of regions. Based on historical data available from civil aviation organization of Iran, a series of models were estimated. To calibrate the models, they were classified in four groups as follows: 1) models for all paired cities, 2) models with dummy variables for cities of Mashad and Tehran due to special characteristics, 3) models for paired cities based on distance criteria, and 4) models of four groups of paired cities with four cities of Mashad, Tehran, Esfahan and Shiraz being either origins or destinations. All four groups, were analyzed with and without using flight frequency parameter. In models with or without flight frequency variable, only the fourth group of these models illustrates acceptable coefficient of determination.

A variety of methods for finding hermitical shape functions are considered. Also, their weaknesses in creation of elements with necessary degrees of freedom are mentioned. After that, the method of uniform order for calculating hermitical interpolation functions is presented. In addition, shape functions for some elements are found by this technique. It is emphasized that, the suggested method is general and systematic, and does not need to guess functions.

In this paper, numerical methods are utilized to investigate the analyses of the elastic and inelastic cyclic behavior of nine reinforced concrete columns having various reinforcement configurations under cyclic compressive load. The response curves of the columns are compared with that of experimental results. In this research, tow main and important concrete mechanical properties "cohesion" and "internal friction angle" are used for the analysis. To evaluate these parameters it is possible to utilize the only one single parameter as the concrete compression strength and the relevant equation proposed in this work. The results exhibit that the specimen's behavioral model for the complete period of loading and unloading regime, is affected by the complete stress-strain curve of concrete under monotonic load.

The measuring of local strains of soils in triaxial tests is the interest of many researchers. Therefore an easy and simple method may be accepted for most investigations of strain patterns. Because of the limitations in mechanical measurements, a digital image processing method is developed here for local strain measurement. This method is a powerful technique for granular materials, in which dislocation and movement of soil grains can be recorded with an accuracy of 0.1 micron.A number of triaxial drained tests have been performed on a sandy soil sample with different relative density and confining pressures, then the local and total strains were recorded by digital video camera. Digital imaging process of results showed that the failure initiation and final deformation are the same for different specimens, whereas the maximum variation of local and total strains is happened on the upper part of specimens.

Pollution of soil around the petroleum industries with heavy metal and petroleum hydrocarbons is one of the most important environmental problems. Elektrokinetic is an effective method to treat heavy metal contaminated soil, but precipitation of heavy metals in vicinity of cathode reduces its removal efficiency.This paper proposes a new method in which degrading bacteria are inserted in the heavy metals and oil contaminated soil to be treated by electrokinetic's technology. Bacterial activities reduce pH in the soil by organic acid production and so prevent heavy metals to precipitate in the vicinity of cathode in the soil. Laboratory experiments are carried out to remove lead from clay by the proposed method.In this study clay soil spiked with lead (500 mg/Kg) and petroleum hydrocarbons (10000 mg/Kg) and then remediate by electrokinetic's using an electric gradient of 1V/cm. In all tests, nutrient solution was used as the anode reservoir fluid. Experimental results have shown that bacterial activities have 25- 35% TPHs removal and also increasing in lead removal efficiency 25-40% compares to blank.  

In this paper, Discretization of flow equations in unstructured grids has been presented. For studying these grids, numerical variables were considered at the center of volumes and vector normal components at the central points of volumes. Flow flux was obtained from upwind approximation or central differencing approximations. Considering time and computer memory, it has been shown that unstructured grids are more applicable compared to structured grids. Unstructured grids also have the advantage of repairing and local adjustment. Using the presented algorithm, both dynamic and static problems could be solved. Numerical comparison of using structured and unstructured for calculating the value of depth of flow surrounding groin, shows that unstructured grids has suitable accuracy. For calculating horizontal velocity component at surroundings of a groin, especially when the height is immediate to the free surface, assessment of the accuracy of simulation with unstructured grids showed suitable accuracy. In this state, the major error beside to information register at laboratory is 2.5%.

Attempts for reliable wave predictions for assessing the impact of waves on the natural environment, .coastal protection, offshore structures and port and harbor operations has led to the development of advanced spectral wind wave models such as SWAN over the past two decades. Geographical Information Systems (GIS) as standard tools for working with geographical data are developed which are able to manage and represent such data.In the present work, a link between GIS and the third-generation wind wave model SWAN has been implemented to ease data management and representation of inputs and outputs of the model which are geo-reference. Then, using available data for Uremia lake situated in the northwest of Iran, the effect of calculation time-step on results of wave prediction model has been investigated.As SWAN has the ability to perform the options of Ist 2nd and 3rd generation modeling, these options have been used to evaluate results obtained by applying these models. Results indicate that the 3rd generation wave model is more sensitive to higher computation al time-steps than other mode of wave generation models. Thus, the time steps should be selected relatively low to achieve reasonable accuracy. However, the convergence behavior of the 3rd-generation model is much faster than that of the other models.

Vegetation can provide an environmentally sound lining for channels, floodways, low spillways and other water conveyance structures. In this paper, the factors affecting the erosion rate in vegetated channels are addressed. A force-balance approach was developed to estimate the shear stress acting on the soil underlying a vegetative channel lining. The erosion rate was then predicted with an accepted sediment transport relationship based on this shear. The deformation of vegetation caused by the flow's momentum was accounted for by calculating the amount of bending of the vegetation using forces calculated by the force-balance method. The results are in good agreement with the experimental erosion rate data for modeled vegetated channels.