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This study investigates the factors affecting coffee exports in Cameroon. For this purpose, we employed the gravity model. Considering the sample characteristics, the model is estimated with the Poisson pseudo-maximum likelihood (PPML) method. The main material of the study is a panel data set covering the years 2001-2021 for ten countries, Cameroon’s main coffee export partners. The findings show that the GDP of importing countries, coffee export prices, and bilateral investment treaties (BITs) positively influence exports, whereas distance, exchange rates, and Cameroon’s GDP have negative impacts. The results highlight Cameroon’s logistics infrastructure deficiencies and the significance of stable, high-quality production. The Cameroonian government should implement policies to improve production quality and efficiency by expanding agricultural extension services and offering farmers input and investment incentives to address these challenges. Additionally, improving port efficiency will necessitate the digitalization of operations, implementation of data-driven planning, and strategic infrastructure investments.

 

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ECO is one of the relatively successful regional trade associations over the world and Iran is also an active member since it has been founded. After collapse of the Soviet :union:, a group of new independent Moslem countries along with Afghanistan has joined the ECO. Since Russia and China have strong economy and located in the ECO member regoin, this study examines the effects of joining these two countries in the ECO. Based on the econometric estimates of gravity models, in the first model in which the common border among countries under study is not considered, the joining of Russia will increase the volume of trade among the countries compared to the current situation. In the second model in which the common border is considered, the greatest trade will be achived when both countries, Russia and China, join the ECO. Based on the findings of three different models, if Russia and China join individualy, the average increase in the capcity of trade among the ECO members will be 74.0, 67.4, and 42.1 percentage.

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Introduction:
Fricatives not only differ in their acoustic structures from one language to another, but also they vary considerably from individual to individual. Acoustic correlates of fricatives are sensitive to the shape and size of the resonance cavity in front of the oral constriction. It is therefore conceivable that any physical change in the length and place of constriction during production of fricatives may alter the resultant acoustic signals. This research attempts to explore potential speaker-specific acoustic parameters of voiceless fricatives in Persian based on experimental phonetics. Therefore, acoustic parameters of center of gravity and fricative duration are investigated for each voiceless fricative in Persian. This research aims to discover whether voiceless fricatives and selected acoustic parameters are able to discriminate between speakers in Persian and whether these fricatives and acoustic parameters are of assistance in segregating speakers in Persian. According to the aforementioned considerations, the following questions are presented in this paper:

1. Do the selected acoustic parameters (center of gravity and duration) of voiceless fricatives have capacity to differentiate speakers in Persian?
2. Which acoustic parameters and which voiceless fricatives discriminate Persian speakers the best?

 Furthermore, we will compare the results of the present study to the findings of previous studies to see in what way Persian has been similar or different from other investigated languages.
Methodology:
In order to analyze between- and within speaker variability of voiceless fricatives, 24 Persian speakers (12 male, 12 female) on two separate occasions were recorded in the sound proof booth at phonetics laboratory of Alzahra University. Non-contemporaneous recording of speech material allows us to measure the degree of within-speaker variability across each speaker. The speech material consists of a read passage which contains 54 Persian sentences including relevant voiceless fricatives Speech tokens were acoustically measured with PRAAT version 5.2.34 and statistical analyses were carried out with SPSS version 21 and R version 3.3.3.
Results and conclusions:
Results of this study indicated that for female speakers, center of gravity of /S/ and s/  have the best performance in showing between-speaker variability. For male speakers, center of gravity of /s/ is the most highly discriminant acoustic parameters across speakers. Moreover, fricative duration was not reported as a promising acoustic parameter. Center of gravity is directly linked to the size and length of the vocal tract. The longer is the length of the vocal tract, the higher is the center of gravity and vice versa. This indicates that anatomical differences between speaker’s vocal tract influence the acoustic properties of fricatives and ultimately make them distinctive. In the future studies, additional parametric potential speaker-specific features will be examined in order to determine a set of well-established discriminant parameters for voiceless fricatives in Persian.
 

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Hydrodynamic pressure on the upstream face of the concrete dams under the effect of earthquake is one of the most important parameters, in planning dams' structure in earthquake zone. Because of the reservoir effect, dynamic analysis of concrete dams is more involved than other common structures. This problem is mostly sourced by the differences between reservoir water, dam body and foundation material behaviors. As a result, researches in this case must be able to evaluate the response of dam with consideration of dam’s interaction with reservoir and its foundation. This problem has been studied vastly by different researchers. The first research on the analysis of concrete gravity dam has been done by Westergaard in 1930 and hydrodynamic pressure on the dam face was obtained by some simplifications. There were a lot of other researches which studied the seismic behavior of the dam-reservoir system, including nonlinear behavior of the dam under pressure and also cavitation. In each research, different modeling methods are presented which are divided into two main groups. In first method which is called Eulerian method, pressure is the main unknown variable in reservoir nodes. In the second method that its main unknown variable is displacement of nodes is called lagrangian method. Each of the methods contain some advantageous and disadvantageous. The purpose of this paper is to evaluate possible advantages and disadvantages of both methods. Specifically, application of the above methods in the analysis of dam-foundationreservoir systems is leveraged to calculate the hydrodynamic pressure on dam faces. Within the frame work of dam- foundation-reservoir systems, dam displacement under earthquake for various dimensions and characteristics are also studied. To achieve this purpose, visual C#.NET 2003 computer programming language is used in this investigation that produces possibility of dynamic analysis of concrete dams under earthquake with system modeling by both methods. Nine node elements for reservoir and eight node elements for dam and foundation are used for both methods. Also newmark average acceleration method is used for solving dynamic’s equilibrium equation. Modares Civil Engineering Journal (M.C.E.L) Vol.11, No.4, Winter 2011 131 In this paper the response of the tallest, non-overflow monolith of Pine Flat dam in California, which is 122 m high, to horizontal and vertical component of earthquake is computed. A water depth of 116 m is considered in full reservoir condition, and the water has the following properties: unit mass,  1000 kg /m3 , bulk modulus, K  2.07*109 kg/m2 , and pressure wave velocity, w c 1440m/ s . The finite element model of reservoir consists of 12 isoparametric elements and it extends upstream a distance of 366 m, three times the dam height. The dam consists of 20 isoparametric elements. The concrete of dam has the unit mass of  2500kg /m3 , young’s modulus ofE  2.275*1010kg /m3, and poisson`s ratio of   0.25. The concrete of foundation has the unit mass of , young’s modulus ofE 4.45*1010 kg / m3 f  , and poisson`s ratio of  0.25 f  . The peak acceleration of S69E and vertical components are 0.18g and 0.1g, respectively. The results of both Lagrangian and Eulerian methods for Pine Flat dam are quantitatively evaluated and compared in different condition and following results are achieved: 1- In Lagrangian Method, there is only one variable in equilibrium equation and mass and stiffness matrixes are symmetric. But there is not such a condition in Eulerian method. Also, the numbers of unknown parameters are different in two methods. By considering these differentiations, needed time for analysis of Pine Flat Dam under Taft earthquake ,with mentioned characteristics, by Lagrangian method is 1.17 times more than needed time for Eulerian method. 2- The effect of material on reservoir's bottom in absorbing energy and `reducing system's response was considerable especially under vertical component of the earthquake. Results indicate that this case is not affected by reservoir modeling method. By applying this effect, the response will decrease about 15% under horizontal component and 60% under vertical component of the earthquake. 3- By evaluating the effect of reservoir bottom's slope, it is concluded that in the case of rigid foundation, the response by Lagarngian modeling is about 10% more than Eulerian one. With the increase of slope, the response will decrease under horizontal component of earthquake but it will decrease or increase about 13% under vertical component of the earthquake. In other words, reservoir bottom slope has little effect on response of the system under both vertical and horizontal component of earthquake. But this effect is not negligible. 4- It is included from the analyses that by decreasing the depth of reservoir the response will decease up to 50 percent under horizontal component of earthquake. This amount is 80 percent under vertical component. Also in the case of decreased depth, response of Lagarngian method is about 10% more than Eulerian method. 5-In all analysis, the assumption of rigid foundation results in greater answers than the cases of flexible foundation.

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Economic convergence can be considered as one of the practical reactions of the countries to globalization process. Thus, selecting a :union: or regional trade group is one of the important goals in economic planning. Studying international business cycles and their transfer from one country to another can have a great impact on regional cooperation. Investigating the relationship between trade and business cycles can also offer a proper analysis of regional integration. In this paper, such convergence is studied after Iran’s presence in Shanghai Group as an observer member and efforts which are made to join it. Econometric method and generalized gravity model for the years 1996-2009 are used to find out if there is any business convergence between Iran and member states of Shanghai Group and if synchronization of business cycles is effective to business convergence. It has been revealed that there is no business convergence between Iran and member states of Shanghai and the business relations are divergent as well. It is also found out that there is a negative and significant relationship between synchronization of business cycles and convergence (divergence) of these countries.

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The effects and actions of the two words used in the process of creating a metaphor have always been considered, how the transfer of meanings from one word to another is questioned by the researchers; there are two groups of theorists; a group forms the metaphor formation process Symmetrical and believe that the two words of the foundation and purpose play a balanced role in the process of metaphor, in contrast to the other group, they believe that in formulating the metaphor and creating the meaning of that base word, more and more, they impose their meaning on the word of the target. Slowly The main question of this article is what determines the symmetry or asymmetry of the process of metaphor? In this paper, some of the concepts in Einstein's theory of relativity such as space-time, line of world, gravity and tensor were used to study this question. Following theoretical reviews in this article, one can conclude that the "time" factor in the asymmetry of the metaphor process can be affected. In fact, in the process of metaphor, the basic word is more familiar, in other words older, more gravitational force than the meaning of its meaning on the word of the target and its meaning is affected

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One of the important aspects which may affect the seismic response of gravity dams is dam-reservoir-foundation interaction. The dam-reservoir interaction must be taken into account, since the dam undergoes deformation which influences the motion of water in the reservoir. Due to the complexity of a dam­reservoir-foundation system, the finite element method is an efficient tool for studying the dynamic response of such a system not only due to the complicated geometry of the dam-reservoir-foundation system but also due to the mechanism of incident earthquake waves and different boundary conditions which can be simulated more appropriately. In order to seismic analysis of gravity dams, a computational procedure for two-dimensional finite-element analysis of dam­reservoir­foundation systems subjected to seismic excitations is developed using Ansys software in this research. Water is assumed as a compressible, inviscid fluid with small amplitude displacements and the dam is modeled as an elastic solid. The analysis is carried out in time domain considering dynamic excitations. Newmark time integration scheme is developed to solve the time­discretized equations which are an unconditionally stable implicit method. An application of the procedure to a study of the seismic optimization of concrete gravity dams using hydrodynamic isolation layer under horizontal and vertical ground motions is presented and discussed. In this study, the hydrodynamic isolation layer is used for the geometry and seismic optimization of concrete gravity dams. For this purpose, the volume of dam body is considered as the objective function and constraints of various geometrical and structural behaviors in order to optimize the concrete gravity dam under seismic loading. To demonstrate the effectiveness of the developed numerical model, the response of Koyna dam in India due to Taft ground motion is presented as a case study to show the hydrodynamic isolation effects on seismic optimization of concrete gravity dams. The model was analyzed and compared for the cases in which the isolation layer attached along the upstream face of dam for different conditions. Consider to obtained results, it is revealed that the isolation layer can have the reducing effect on responses of dam model because of damping the induced hydrodynamic pressure due to earthquake. The layer reduces the dam response due to the hydrodynamics effect of the reservoir in essentially two different ways: (a) the layer serves as a boundary for the reservoir with a low reflection coefficient which results in reduction in the developed hydrodynamic pressure in the reservoir compared with the case of a completely reflective boundary. This effect was addressed in the previous part of the theoretical solution excluding the layer's isolation effects. (b) the isolation of the dam from the hydrodynamic pressure is the result of the layer thickness as well as its material properties which alter the amplitude of the transmitted pressure wave across the layer.

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In this paper, a method of tri-axial gravity gradient stabilization of satellite in circular orbit is proposed and investigated. In this method, only one actuator is employed. A satellite with varying-length boom is considered consisting of two rigid bodies having the freedom of moving in the boom direction. The only control input is the force between these two bodies to control the varying-length boom. The gravity gradient torque is considered as the only external torque acting on the satellite. The system is under-actuated and has Hamiltonian structure. So, the port-Hamiltonian approach is utilized. The equations of motion of the system are obtained in Hamiltonian formulation. The equilibrium points and their required control inputs are determined. The linearization around the equilibria is carried out and it can be seen that the linear dynamics of pitch-boom and roll-yaw are decoupled. Therefore, the roll-yaw dynamics is linearly uncontrollable. The method of energy shaping and damping injection is used for controller design. The conditions on the energy shaping control law to stabilize the system are determined. Further, the resulting closed-loop system is analyzed. The closed-loop system has center manifolds. Finally, the performance of the closed-loop system, convergence of state trajectory to the center manifold and its non-exponential convergence is shown by simulation.

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Performance increasing of robot-aided training in stroke elbow rehabilitation is the goal of this paper. Therapist holds on the arm of patient and guides the center of mass along a desired trajectory. In robotic rehabilitation, when the arm of patient rotate within the desired boundaries, (s)he should ideally not feel the robot. The robot needs to actively compensate for the weight of the exoskeleton and reflected mass of the motors. A nonlinear torsion spring can be used and also a counter-torque as a function of arm angle is applied by the motor. Applying the springs affords more convenience, it allows smaller motors to be used, the size of required brakes can be reduced and inherent safety is introduced in rehabilitation robots. Furthermore, the robust controller design can be used to compensator the modeling errors and gravitational force. A novel elbow rehabilitation robot is designed based on the cable actuation. The strategy is not just anti-gravitational forces because there should be joint-stiffness control. The uncertainty in the patients arm dynamic is effectively approximated. The motion of closed-loop control system in the presence of parametric uncertainties is investigated. The sliding mode controller with proportional-derivative controller is compared through computer simulation and improvement is observed.

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The present study was conducted to estimate correlations among performance and egg quality traits in Iranian native fowl. Data were collected from 21,679 birdsat the Isfahan Native Fowl Breeding Center to derive genetic parameters for performance traits and egg quality traits were measured on eggs of 1,020 birds. Genetic correlations of performance and egg quality traits were estimated with a bivariate animal model using ASREML software. Body weight at hatch, 8, and 12 weeks of age (BW₀, BW₈ and BW₁₂, respectively) positively (0.05 to 0.82) correlated with egg weight (EW), shell weight (SW), specific gravity (SG), yolk height (YH) and albumen weight (AW). BW₀ and BW₁₂ negatively (-0.10 to -0.26) correlated with shell strength (SS) and shell thickness (ST). Genetic correlations of BW₈ and BW₁₂ with albumen height (AH) and Haugh unit (HU) were highly negative (-0.45 to -0.55), whereas BW₁₂ showed positive correlation with shape index (SI) (0.22). Shell weight showed high positive genetic correlation with age at sexual maturity (ASM) (0.75), while its genetic correlation with egg number (EN) was highly negative (-0.71). EN also showed high negative correlation with yolk and albumen weight (-0.91 and -0.75, respectively). Based on the present results, selection for higher BW will lead to production of eggs with higher internal quality. In contrast, this kind of selection will reduce the shell strength and shell thickness. Therefore, selection should be based on an index including performance and egg quality traits. This will help to develop indigenous strain of meat-cum-egg type chicken.

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Heavy oil and tar sands resources comprise about 70 percent of the world's oil reserves and this reservoirs can offset the declining production from conventional reservoirs. Thermal enhanced oil recovery (EOR) methods are employed to exploit the huge reserves of heavy oil due to their high viscosity values. Thermal processes aim to increase its mobility in order to improve its production. Among these methods, the steam-assisted gravity drainage (SAGD) is one of the most efficient techniques. In this method, two horizontal wells are drilled and hot steam is injected from a well to move oil toward the other well. Optimization of operating parameters during this process is very important. The injection rate or pressure control of wells are the most common EOR methods. In this paper for the first time, in addition to the injection rate of the injector and production wells, the steam injection temperature is also optimized. It was shown that there is an optimum amount for the temperature of injected steam. In addition entropy generation analysis was performed for different cases. To simulate the process, a commercial software was used and optimization of operating parameters is performed using the pattern search algorithm. Entropy generation calculated based on the results of numerical simulations using a computational code has been written for this case. The results show that the maximum oil production corresponds with the minimum entropy generation number and thus the entropy number can be used as an appropriate objective function in order to enhance oil recovery.

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There are several quay types parallel to the shore line such as the walls constructed by piles, sheetpiles or gravity walls. Among these types of structures, the gravity quaywalls are widely used because of their simplicity of structure and ease of construction. Usually, it is the best alternative particularly in the locations with acceptable soil strengths. Weight of the blocks provide the stability of the quaywall against overturning and sliding and therefore, their dimensions are determined based on the applied loads on the quay structure. The most important load is the soil pressure that increases the lateral loads acting on the quaywall particularly during an earthquake condition. For design, the soil pressure usually converts into a static load by utilizing the seismic coefficient method. Analytical equations such as the Mononobe-Okabe formula are usually employed to calculate the applied soil pressure. However, some researchers believe that these analytical formula do not appropriately express the real behavior of the soil, and therefore, they can not be used for a proper design. There are, actually, some simplified assumptions in calculating the applied soil pressure those decrease the accuracy of the commonly used methods for quaywall design. The main assumptions are neglecting the nonlinear behavior of the soil and neglecting the flexibility of quay blocks. Due to the importance of the soil pressure in the quaywall design, these assumptions are investigated numerically in this study by making use of two well known FLAC and ANSYS softwares. For this purpose, the quaywall of Shahid Beheshti port is selected as a case study and the soil pressure around this quaywall is calculated by modeling the nonlinear behavior of the soil via using the Mohr-Coulomb constitutive model. In addition, the effect of the block rigidity on redistribution of the soil pressure beneath the quay structure is studied by a 3-D modeling of the lowest block located on linear springs (representing the supporting soil). To study the importance of each above mentioned assumption individually, two seperated models are utilized separately. According to the results, the pressure distribution under the quay wall is more uniform in the case of employing the nonlinearity of the soil. The total pressure is, however, less than the total calculated pressure by analytical formula that shows the Mononobe-Okabe formula are not accurate, but its results are overestimated for the studied problem. In addition, results show that the simplified methods can not be used for design of the lowest block because the value and the location of the maximum moment along this block changes due to its rigidity. As a result, neglecting the block deformations what is done in simplified methods is not acceptable for design purposes. It should be noted that the lowest block is so important is providing the global stability of the quaywall because its failure can lead to a total failure of the quaywall. On the other hand, all blocks are supported on this block and consequently, its repair would be too difficult even in the case of any small failure.

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Assessing factor affecting Iranian Pistachio export due to comparative advantage and share of Iran in international market of this crop is very important. In recent years, pistachio exports has faced many challenges including limitation of aflatoxin maximum of importing countries. In the present study, factors affecting on Pistachio export with emphasis on the role of aflatoxins were evaluated by gravity model. For obtained this goal, the major importing countries pistachio were determined and panel data from the years 1990-2017 were used. The results of gravity model estimation showed that the limitation of aflatoxin, GDP, population and border for selected importing countries has significant positive effect on the export of Iran Pistachio. The result suggested that Iran to maintain it is share in the Pistachio global market, pistachio with high quality and lesser aflatoxin have to be product, as well as, sanitation laws are approved based on international laws could be very useful.

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How to provide sustainable and clean sources of energy is probably the most vital question of our world today. The population growth and technology development are leading to an increase in the world energy demand and fast depletion of fuel resources. Our environment is facing critical challenges and there are serious uncertainties with the future availability of fossil fuel. The only possible remedy is to increase the share of clean and renewable energies in total energy use and to make our technology more energy efficient. Marine and offshore renewable energies are from the cleanest types that are available from the boundless energy of fluid flow in the oceans, seas, rivers and channels. In the present study, the wave energy absorption in a channel has been studied. A plate with infinite length and finite width and thickness that is placed at the bottom of a channel has been investigated to absorb the energy of gravity waves. The plate is on a viscoelastic foundation which displays linear behavior. The coupled equations of fluid and plate have been investigated to calculate the vibration characteristics of fluid surface and plate. Subsequently, a proper analysis has been done for the plate's ability to absorb wave energy.

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Density currents flow due to the density difference between the current and surrounding environment. An important category of density currents is called turbidity currents, which density difference created as a result of suspended solid particle presence in fluid. In the present study, it is tried to use both Eulerian-Eulerian and Eulerian-Lagrangian methods, to take advantage of each one. In this way, the larger particle that have a more effective role in sedimentation mechanism due to the more falling velocity are calculated as Lagrangian and smaller particles by the Eulerian method. In order to obtain a criterion for particle assortment, seven currents with different particle sizes in the Eulerian-Eulerian model have been numerically simulated in a simple channel and it is compared with no particle case, and also the Eulerian-Eulerian method has been verified with experimental results and identified when the particle sizes is less than 12 micron, the sedimentation process is not appreciable, and the presence effect of these kind of particle can be ignored. Therefore, the Eulerian-Eulerian method is a suitable method for this case. The Eulerian-Lagrangian method validation has been performed with experimental results. Finally, the current inside the channel with a spectrum of particle dimensions is simulated and described the results by the proposed method (the combination of two methods). To perform numerical simulations, the development of open-source OpenFOAM codes has been used to take into account the effect of particle. Due to the current’s turbulence, a Large Eddy Simulation method has been used for turbulent modeling.

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Abstract. One of the most vital, essential human being requirements is water, which it has become increasingly sensitive owing to population growth, the need to develop agriculture and industry, and restriction in water resources. Considering this, the need to store water and to use its potential for generating hydroelectric power, which it can be achievable by constructing dams, will be necessitated. Concrete dams play a significant role in Infrastructure in each country. One important part of dams exiting in the world are made of gravity dams and earthquake seems to be the major threat for them in earthquake-prone areas. Hence, the dam fracture, with much stored water, might have brought many conspicuous threats about in these zones. Also, any structural damage could lead to some negative economic effects. These facts have increased the scholars’ attention to the mechanical behavior of dams during the decades. The Seismic analysis of gravity concrete dams, usually, had been considered in an ideal form by means of 2D Monolith in mechanism design and an earthquake effect coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D. The numerical modelisation of huge structures such as dams is a proper tool for Seismic analysis and performance evaluation. The valley shape is one of the important parameters in the selection of the dam structure. This parameter plays a crucial role in both Seismic stimulation and its results. In this paper, a 3D finite element model of Pine-flat gravity dam, without interruption seams with a non-linear behavior of the dam’s material, is considered. . Loading has two stages: static and dynamic. In this modelisation, static loading includes both the weight of dam body and the load of filled Hydrostatic tanks. After static loading, loading of Seismic dynamic is begun. Owing to the importance of valley shape, the changes/ deformations of valley width and the dam response to every three elements of ground is investigated. The impact of the ratio changes of width in dam height, as well as the importance of the transverse component of ground motion, along the vertical and horizontal, has been explored. Interaction effects of dam-reservoir-foundation is considered in the considered analysis and ultimately, the output of which is compared with two dimensional model results. The aim of this study is comparing two and three dimensional seismic response of concrete gravity dams and also necessity of providing more realistic models for considering the effects of cross stream modes. Also, not only are interaction effects of dam-reservoir-foundation, the nonlinear behavior of concrete, studied different Valley shapes, and the effect of them on non-liner response investigated, but also the Seismic stability of gravity concrete dams under longitudinal, vertical and the chosen transverse record earthquake are separate and simultaneously studied. The effects of dam-reservoir-foundation interaction, nonlinear behavior of mass concrete, also different shapes of valley are studied and their effect on nonlinear response and seismic stability of concrete gravity dams are evaluated under two and three-component earthquake records.

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The Moving Least Square (MLS) interpolation method is proposed for approximation of adaptive fuzzy controller parameters for two degrees of freedom suspension system and each one has two inputs, one output with twenty-five linguistic fuzzy IF-THEN rules. Fuzzy systems are designed by using five Gaussian membership functions for each input, product inference engine, singleton fuzzifier and center average defuzzifier. The constructed fuzzy systems is composed with adaptation rules. For this purpose, Lyapunove approach is implemented for stability of the adaptation rules. The Gravity Search Algorithm (GSA) is implemented for achieve the optimum controller parameters. The relative displacement between sprung mass and tire and the body acceleration are two objective functions used in the optimization algorithm. Since, choose the suitable controller coefficients are important and when the parameter of the system change, Optimum coefficients of the controller will also change. In order to solve this obstacle, the MLS predictive model is purposed that is interpolation method based on a radius of the neighborhood, a basis function and a weight function for points of interest. Finally online model is implemented on the two degrees of freedom suspension system and results compared with the offline optimal systems.

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Studies have shown that compressible materials between a rigid retaining wall and backfill reduced static and dynamic forces on the wall. Nowadays, panels with low density are used. Expanded polystyrene, which is one of the geo-synthetic products known as geofoam, is a compressible material. Geofoam is one of the geo-synthetic materials that are made of foam. Geofoam is very practical in geotechnical engineering due to its low bulk weight versus soil bulk weight and high compressibility, rapid and simple implementation, thermal insulation, and resistance against water absorption. It can be used in retaining walls, road construction projects as light fillers, and to reduce stress due to vertical loads in the base and sub base layers. Geofoam is one of the geosynthetic product which is made of lightweight expanded polystyrene (EPS) or extruded polystyrene (XPS). EPS geofoam is a block or planar rigid cellular foamed polymeric material that can be used in geotechnical applications. Studies have been shown that geofoam placed directly against a rigid retaining wall can reduce static loads on the wall. This study employed a finite difference method program, FLAC (Itasca, 2007), with considering yielding and non-yielding states for retaining walls to evaluate the effectiveness of geofoam panels in improving the statically behavior of retaining walls. To determine the effects of geofoam in soil displacement and earth force acting on the rigid wall, parameters such as the height of retaining wall, density and thickness of geofoam, cross-sectional shape of geofoam panel behind the wall, and also using of two geofoam panels with four panel spacing (50, 100, 150, 200 cm) have been studied via static analysis. In this numerical study three gravity –type retaining walls at heights of 3, 6 and 9 meters and geofoam panels with densities of 15, 20 and 25 (kg/m3) at three relative thicknesses of t/H=0.05, 0.2 and 0.4, were modeled. According to the results using of EPS15 with density equal to 15(kg/m3) which has the lowest density among other geofoam panels has a significant role in reducing of lateral stresses. Although the performance of geofoam in non-yielding retaining walls is better than yielding retaining walls. The results of the present research are as follows: 1- According to results, increasing the geofoam thickness increases soil lateral displacement and reduces forces on gravity retaining walls. The same effect can be achieved by reduction of geofoam density with equal thickness. In other words, Forces on gravity retaining walls are reduced and soil lateral displacement is increased by a reduction of geofoam density with equal thickness. 2- Using two geofoam panels with distance of 50 cm, unlike 3-meter high wall, is proper in the 6 and 9 meters yielding retaining walls. 3- Trapezoidal geofoam increases soil lateral displacement and reduces forces on retaining walls compared to a rectangular geofoam panel with the same cross-sectional area. 4- Effect of geofoam on the reduction of forces on non-yielding gravity retaining walls is more than that on yielding walls. 5- According to results, stiffness of geofoam panel (K=E/t) has significant role in reducing of lateral forces acting on retaining walls. In this study, it was observed that K≤5 MN/m3 provide the most effective range for the design of these system to reduce static forces acting on yielding retaining walls.

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The Seismic analysis of concrete dams had been considered in an ideal form by means of two dimensional Monoliths in analyse and design procedures and structures had been subjected to ground motions with defining seismic coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D space. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated. The Seismic analysis of concrete dams had been considered in an ideal form by means of two dimensional Monoliths in analyse and design procedures and structures had been subjected to ground motions with defining seismic coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D space. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated. The Seismic analysis of concrete dams had been considered in an ideal form by means of two dimensional Monoliths in analyse and design procedures and structures had been subjected to ground motions with defining seismic coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D space. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated.

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Gravity dams are vital structures whose proper design and evaluation for stability are quite important. Effective issues on the stability of gravity dams are the uplift force and its distribution below the dam base. The uplift load pattern and distribution according to common codes are influenced by some factors such as head and tail water, assuming a segmented linear load distribution below the dam. In this research, to investigate the sensitivity of the load pattern to dam height, a number of gravity dams of Pine Flat type with different heights and their foundations are modeled. Coupled p-u finite element analysis is performed accounting for the seepage and stress field simultaneously. Dam body is considered to be completely impervious. The foundation rock is assumed as homogeneous and uniform, in terms of elasticity and permeability. The stresses generated in the dam interface for each case of the coupled hydro-mechanical analysis is compared against that of the conventional load pattern according to the USACE regulation for the same dam model. It was found that the error magnitude due to the conventional pattern has a direct relationship with the dam height. As the dam height increases, the amount of error of calculated stress increases. In particular, the error at the critical zones of the foundation such as at the dam heel, may raise even up to 40%. In the group of dams studied, the error increases even up to 12 times in respect to the expected error in the shorter dams. The deficiency could in some cases completely affect the safety of the dam. This research indicates the necessity of using more accurate methods of estimating uplift load under high gravity dams. Gravity dams are vital structures whose proper design and evaluation for stability are quite important. Effective issues on the stability of gravity dams are the uplift force and its distribution below the dam base. The uplift load pattern and distribution according to common codes are influenced by some factors such as head and tail water, assuming a segmented linear load distribution below the dam. In this research, to investigate the sensitivity of the load pattern to dam height, a number of gravity dams of Pine Flat type with different heights and their foundations are modeled. Coupled p-u finite element analysis is performed accounting for the seepage and stress field simultaneously. Dam body is considered to be completely impervious. The foundation rock is assumed as homogeneous and uniform, in terms of elasticity and permeability. The stresses generated in the dam interface for each case of the coupled hydro-mechanical analysis is compared against that of the conventional load pattern according to the USACE regulation for the same dam model. It was found that the error magnitude due to the conventional pattern has a direct relationship with the dam height. As the dam height increases, the amount of error of calculated stress increases. In particular, the error at the critical zones of the foundation such as at the dam heel, may raise even up to 40%. In the group of dams studied, the error increases even up to 12 times in respect to the expected error in the shorter dams. The deficiency could in some cases completely affect the safety of the dam. This research indicates the necessity of using more accurate methods of estimating uplift load under high gravity dams.