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  Increasing overall liberalization and improving reliability indexes are the two prime but often conflicting objectives of electricity markets. Proper embedding of regulatory intervention of price caps provides an effective means to tradeoff between these two objectives. Surprisingly, in the context of the infinitely repeated game paradigm, as in the case of actual electricity markets, the dominance of tacit collusion and capacity withholding highlights the role of non-pivotal firms in frustrating price caps and deteriorating reliability indexes. An agent-based simulation framework is proposed to evaluate both individual behavior of non-pivotal firms within the market and the emergent collusive behavior arising from interaction between firms. Mathematically speaking, to put the capacity withholding into action, we propose embedding a hybrid-control problem in the supply function equilibrium (SFE) modeling assumptions. As a consequence, non-pivotal firms are granted supply curves with vertical segments that obviate the slope constraint of the SFE modeling. A simulation using the generation portfolio of the Iranian electricity industry illuminates the impacts of tacit collusion on reliability indexes.

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This article investigates experimental study of the flow field on a blunt airfoil. For this purpose, PIV technique based on instantaneous flow structures is used in order to view and two dimensional investigation of flow field around unmodified and blunt airfoil and at different times. This study is performed on flows at very low Reynolds number(Reynolds number lower than 4500). This flow regime is very similar to dominant condition on micro air vehicles (MAVs). In order to validate the method used in this study, flow field around cylinder is considered and in continue, instantaneous and mean velocities fields, streamlines and mean vortices field around unmodified and blunt airfoils are obtained. The results show that there are prominent differences on the structure of wake around airfoils and sizes of separation region for blunt and simple airfoils. Meanwhile separation of the flow for both blunt and simple airfoils at this very low Reynolds number, is occurred at angle of attack 5 (at low angle of attack). Also generation of vortex at wake region and their position and circulation at different times, are discussed.

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In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration.

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 System evaluations were performed on 48 center pivots in different parts of Saudi Arabia. These systems, located on different farms in four different regions of the country, namely: Riyadh, Jouf, Qassim and Eastern regions, were evaluated to study the effect of lateral configuration on water application uniformity as regards the original vs. modified laterals. Lateral configuration modifications have been made by the local farmers through a chang of the position of the lateral and spray nozzles from the original design. Depths of water distribution along the lateral, Coefficient of uniformity (Cu) and Distribution uniformity of the low quarter (Du) were determined and compared for the original and modified laterals under field conditions. The average values of Cu for original systems ranged between 71.81 and 89.46% with an overall average of 82.69%, whereas the average values of Cu for modified systems rangingbetween 61.35 and 84.33% with an overall average of 78.05%. Also, the values of Du ranged between 54.14 and 81.81% with an overallaverage of 73.24% for the original systems, while these values for the modified systems ranging between 31.45 and 77.07% with an overall average of 66.87%. The results finally indicated that the values of uniformity for original vs. modified laterals were significantly different indicating that there existed a noticble adverse effect of center pivot lateral configuration on the uniformity of water application.

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The study of wave transmission over submerged obstacles and the flow pattern that formed around the obstacle has been always an important subject because of the affect directly on wave and the changes in wave energy that is crucial in the design of devices, which absorb wave’s energy and coastal breakwaters. In this research, the flow pattern induced by solitary wave passing over a submerged vertical thin plate has been studied. A wave maker piston has been used to generate the solitary wave and particle image velocimetry (PIV) technique has been used to flow visualization that this technique is non- introsire optic method, which can measure the fluid velocity with any changes in flow pattern. The study of the flow pattern visualization, velocity values and vorticity shows, at first the flow separation shear layer forms and the clockwise vortex generate at the rear edge of the obstacle before the wave arrives to the barrier. Then the vortex grows in size and cussed the water move upward like vertical jet on upstream. Then the fluid enters to the downstream and generates the counterclockwise vortex in this region, which is less than the first clockwise vortex in power that makes an important difference with the thick geometry researches. In addition, the non-dimensional horizontal components of fluid velocity at the time of shear layer formation at the rear edge of the plate have been studied and it has been compared with the case that the barrier is rectangular.

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In this paper, the results obtained from experimental measurements of average and turbulence quantities of a turbulent rectangular impinging jet hitting a fixed wall is reported using the laser doppler anemometry (LDA) method. The nozzle to plate distance is 10 times the nozzle width, and the tests are repeated for three different Reynolds numbers, namely Re=3000, 6000 and 9000. The aim of the current research was to investigate and comparise of flow in different Re and also to determine the two effective experimental errors on average velocities, namely data sampling and residence time in measurement volume. The results reveal that the previous stated correlation for prediction of the number of data required for ensuring independence of the average flow variables on the number of the sampled data is not sufficient by itself, and depending on the turbulence intensity of the flow, this correlation could become ineffective. Further, in the present study, the residence time is used for calculation of average velocities, and the results are compared with those obtained by particle image velocimetry (PIV) method. The comparison shows good agreement between the results from LDA and PIV when considering effect of residence time within the avaraging equations in the former method. The results show that the behavior and quantity of the dimensionless average velocities for various Reynolds numbers are identical at most cross sections of the flow domain while the dimensionless turbulent stresses have different quantities at different values of the Reynolds number.

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Particle image velocimetry (PIV) is an optical flow measurement technique, which is capable of measuring instantaneous flow velocity. In this method, visualized flow patterns by small tracer particles, which follow the fluid flow and reflect an incident light, is recorded by a camera successively, and an analysis of particle movements in the recorded images results in the velocity of flow field. Correlation analysis is commonly used for the analysis of particle shift images, in which the images are divided into smaller windows called interrogation windows. The common displacement vector of particles in each interrogation window is determined by correlation analysis, which in turn results in the displacement vectors for the entire image. The accuracy of this method is dependent on the estimation of the location of the maximum value of correlation with subpixel accuracy. The objective of this research is the evaluation of function fit methods to estimate of the correlation peak location with subpixel accuracy. For this purpose, parabolic curve and second order surface fitting are investigated theoretically and experimentally. To achieve definite displacements, deformation of a solid part under uniform loading is investigated instead of fluid flow and the displacement of point patterns painted on the solid surface are analyzed. The results show that both function fit methods are capable of resolving subpixel movements with the accuracy of 0.035 pixel or one micrometer in this research.

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Water increases in slope layers induced failure of slopes. Water is the most important factor in most of the slope stability analysis. Although water does not directly lead to the slopes displacement, but is an important factor for the following reasons: (1) water increases due to rainfall and snow melt will lead to increases slope weight. (2) Water can change the angle of slope (angle of slope is an angle that slope is stable in this angle). (3) Water can be absorbed or excreted by minerals are available in the soil. After adding the water, the weight of the rock and soil increases. (4) Water can dissolve the cement between the seeds and cohesion between the seeds is lost. In this paper, the feasibility of using piles to stabilize layered earth slopes were studied. A set of physical modeling of foundations was performed adjacent to layered slopes. The deformation pattern and shear strains of soil near slope and below surcharge load were studied. For this purpose, a comprehensive set of tests and numerical analysis were undertaken on different slope models. In each step of loading, digital image of deformed soil was captured and image processing was applied with GeoPIV software for investigation of soil deformation on slope and below the footing. the effect of pile and saturated conditions effects on improvement ratio (safety factor of stabilized slope with pile / safety factor of the slope stability without piles), bearing capacity of foundations, slope stability and slip surface shape in layered slope were investigated. The results show that the slip surface of layered slopes differs depending strongly on the installed pile positions and layered saturation conditions. In consideration of the model tests and numerical analysis results, it is found that, when clayey layer was near ground surface, changes in clayey layers water content significantly affected on slip surface and layered slope stability. Consideration of slipe surface shape for different layers saturation canditions, it is found, saturation of below layers which is located below the slip surface, has not significant effects on slope stability and slip surface shape. But with increasing upper layers water content, large volume of soil were failed. Experimental and numerical results show, for stable slope before applied surcharge load or before water content increases, critical slipe surface occurred in front the installed pile. But for unstable slope, critical slip surface positions depend on layers saturation and soil properties and occurred in front or behind or in upper and lower part of pile. In general The critical slip surface location dependent on water table level conditions and location of pile. Also from the experimental and numerical results it is found, the optimum location of pile for increasing bearing capacity of foundation which is located on slope crest, is near slope crest and maximum magnitude of Bearing capacity ratio ((bearing capacity of reinforced slope/ bearing capacity of non- reinforced slope)(BCR)) was obtained when piles installed near slope crest. Also optimum location of pile for increasing slope stability are found near mid of slope. A close agreement between the experimental and numerical results in Failure mechanism and the critical values of the studied parameters is observed