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In this paper, the behavior of the double pendulums has been studied by considering the effect of initial conditions (angular displacement of the outer pendulum for four cases 12, 30, 90, and 150 degrees) and the influence of system geometry (increasing rod length and mass of the second pendulum), also. After extracting motion equations using the Lagrangian method, in order to deal with the frequency spectrum, traces of bobs, and understanding the system behavior for every case, the Fast Fourier Transform (FFT) technique and Poincare sections have been applied. The obtained results show that the consequence of the rising angular displacement the outer pendulum is to increase the energy level of the system and the change of its behavior from quasi-periodic for angular displacement is less than 90 degrees to chaotic when it is 150 degrees. Therefore, the energy level, in this case, has increased more than twice compared to the first. In addition, it seems a quasi-periodic behavior is forming at the heart of chaotic behavior. On the other hand, the results indicate a very significant effect of geometrics on a system's behavior. According to the calculations, the consequence of increasing the length of the rod of the second pendulum has only led to a different behavior from its similar case (case number 3) completely. however, their energy level is the same. Increasing the mass of the outer by twice not only to lead decrease energy level of the system by 330J but also has shown chaotic behavior (in comparison to the case3).

Knowing the behavior of thick-walled cylinders, due to their numerous applications is important. There are numerous relationships for cylinders and spheres containing explosives which have been found, based mainly on other experimental models. Hence, developing an analytical model of the behavior of structures under internal and high-rate loading, like explosion in the cylinders, is of great importance. The main objective of this paper is to derive a mathematical model of isotropic thick-walled aluminum cylinder containing TNT in which JWL equation of state is considered for behavior of explosive expansion. The present analysis is based on the Cowper-Symonds material model, in which strain rate at each moment is used for calculation of dynamic strength. Therefore, given the instantaneous explosive pressure boundary conditions as well as instantaneous strain rate and its impact on the dynamic strength of the material, is of significant technique in this paper. By employing equations of equilibrium in thick-walled cylinders, the equations of radial and circumferential stresses and radial velocities were derived. The instantaneous geometric and boundary conditions and corrected dynamic stress of material with respect to the strain rate used to calculate radial velocity through solving the differential equation of motion. After extraction of radial velocity, other stress equations will be evaluated. Furthermore, by considering the assumptions and in order to assess the overall results of the analytical modeling, computer simulation was done using Autodyn software, which shows good agreement with the analytical results. [ABSTRACT FROM AUTHOR]

Slip factor is one of the most important parameters used in centrifugal pumps performance prediction. Knowing this parameter as a function of flow rate seems essential for off-design performance prediction. In this paper, it is intended to establish the slip factor dependence upon flow rate for a centrifugal pump using computational fluid dynamics. For this purpose, the full 3DRANS equations in coupled with RNG k - ε turbulence model were solved for several flow rates ranging from 45% to 120% of rated condition by means of a commercial code, CFX. In the steady state, this simulation is defined by means of the multi-reference frame technique, in which the impeller is situated in the rotating reference frame, and the volute is in the fixed reference frame. The validity of the numerical model was confirmed by matching the calculated characteristic curves with the associated experimental data. It was found that there is a good coincidence between the numerical results and available experimental data of global performance, local velocity distribution and slip factors. A comparison was performed among the well-known slip models which reveals, that the slip factor variations can be predicted very well using CFD analysis. [ABSTRACT FROM AUTHOR]

In this paper, the problem of the navigation error effect for the optimal and constraint Trajectory de of the UAVs that are required to fly at low altitude over terrains has been discussed. Due to the increasing deviation problem of inertial navigation systems in terms of time, having a safe flight and collision avoidance with terrain at low altitude is the main point in the trajectory design of this type of the vehicles. On the other hand, some of these vehicles use Terrain Contour Matching (TERCOM) as a navigation aiding system. This system is more efficient in rough terrains, and providing the requirements of this system beside other constraints is a complex task. In this paper is tried to meet these constraints in the trajectory design process. For this purpose, an algorithm based on the layered network flow on the digital terrain maps used in a manner that has a high potential in adoption of various constraints and optimal trajectory is generated. Then, using equations of motion on a terrain digital data in 3D space with the dynamical constraints and different optimality criteria, a complete model of navigation error and also parameters affecting TERCOM has been developed to generate feasible path reducing terrain collision probability to zero. The resulting algorithm applying initial conditions and in the least time possible, produces the trajectory. Numerical results show validity of this issue. [ABSTRACT FROM AUTHOR]

In the single-mode resource-constrained project scheduling problem, it is assumed that each activity has a specified known execution time and resource consumption can be done only in one way. In practice, there are many cases in which the make span can be reduced by providing additional resources activities. In this case, each activity can be done in one of the procedures, which is called the multi-mode resource-constrained project scheduling. In this paper, the problem includes determination of the basic schedule for the project activities which may be done in several models and the precedence relations are met, While the project make-span, cost and resource fluctuations are minimal. In this research project scheduling problem network will model using ED simulation software and the results of the simulation and a meta-heuristic algorithm has been compared. Finally, management strategies to optimize the scheduling, i.e such minimize total time, cost and resource leveling, will be offered. [ABSTRACT FROM AUTHOR]

Efforts to reduce the ballistic effects and achieve the good results have always been important. In this article, perforated targets were used in order to reduce the penetration depth of projectile. The use of these targets in the case of high-speed projectiles reduces the number of parameters, such as penetration depth, cost of target products, and target area density. The goal of this paper was to present a new and complete analytical model for projectile penetration in ceramic/metal semi-infinite perforated targets, based on the Fellows analytical model, one of the most important models for penetration. First, the Fellows model was modified for ceramic/ metal semi-infinite none-perforated targets. This modified model, while perfectly improving the results of the penetration depth at low speeds and had a better fit with experimental results at high speeds. In the new analytical model, 7 different states were considered for the projectile to impact the perforated target. In each of these states, the angle of oblique and the speed of the projectile after reaching the metal varied with respect to the ceramic thickness and the speed of the projectile’s impact. Regarding the oblique impact on the metal, corrected relations were rewritten for new conditions. Finally, the depth of penetration was achieved according to the target conditions. The numerical simulation in Abaqus software was used to compare the results. The results of the new analytical model has good agreement with numerical simulation. [ABSTRACT FROM AUTHOR]

Microgrid can operate in both grid-connected and islanded modes. Islanding can be scheduled or unscheduled. In the event of unscheduled islanding, the microgrid should be able to maintain its sustainability. Therefore, it is necessary to determine and supply the amount of required spinning reserve for stable islanding. In this paper, a two-stage strategy for optimal scheduling of the microgrid is proposed while uncertainties of renewable generations and demand are considered. In the first stage, co-optimization of power and reserve is carried out with the presence of distributed generations and batteries. Therefore, in the second stage, the demand is also used as reserve to provide required reserve for stable islanding. In order to determine the optimal amount of reserve of demand, a novel objective function is proposed. The objective function minimizes the sum of the standby reserve cost, expected cost of called reserve, and expected cost of emergency curtailment. One of the salient features of the proposed model is its modularity. That is, it can be added easily to any scheduling model in which the demand is not considered as reserve. Mathematical analysis and numerical simulations show the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

Introduction: The queue is one of the most complex social systems in which human lives are inevitably ‎associated with the activities of organizations. Due to the characteristics of healthcare ‎organizations and the critical role that planning plays in such organizations, research in this regard ‎can be of great help. This paper was an attempt to demonstrate the role and use of the branches ‎of the operations research discipline in healthcare centers. Methods: The current research was a cross-sectional study conducted on‏ ‏‎2614‎‏ ‏patients referred to the ‎paraclinic ward of Hafez Hospital, Shiraz, Iran. In order to collect data, the patient code, time of arrival, work start time, serving start and end time were recorded with the help of staff and two assistants at the time of arrival of the patients. Then, modeling and optimization of patient flow were conducted using queues and simulation techniques. The data was analyzed using SPSS software and Input Analyzer ‎Software and the system was simulated using Arena software. Results: The results showed that 30% of the patients no longer wished to be referred back to the center. ‎The findings also revealed that there was a significant difference between the standard waiting ‎time and the time spent in the hospital to recive a service. Among the 6 different scenarios, the ‎mixed scenario reduced waiting time of the first service for‏ ‏sonography patients to 75.04 minutes ‎and for radiology patients to 65.573 minutes. Conclusion: The results showed that the suggested model, in comparison to the current model of health ‎centers, can improve the‏ ‏quality of services and reduce the duration of time patients must wait ‎until receiving the first service‏.

Background and Aims: Improving dental implantation conditions in order to reduce the failure is always desirable for researchers. The aim of this study was to compare two different materials of dental implants from the viewpoint of biomechanical effect after placement and loading in the mandible. Materials and Methods: A 3D model of mandible was designed in the MIMICS 10.01 software. Then, by using the obtained model, the end part of the mandible was designed in CATIA V5 software and a drilling operation was performed on the cortical bone of mandible by finite element analysis simulation method in DEFORM-3D V6.1 software. Thereafter, the 3D model of created hole was extract from the drilled site and an ITI dental implant model designed in the CATIA V5 software, was placed in the hole. The space remained between the implant and cavity was considered as a newly-formed cortical bone in drilled site after 6 weeks of dental implant placement and the mechanical properties of newly-formed bone were entered to DEFORM-3D V6.1 software. Then, a load was applied on the top surfaces of two dental implant models with the materials titanium and zirconium-2.5% niobium. Results: The emerged volume changes in newly formed cortical bone around Ti and Zr-2.5 Nb dental implants were measured 0.238 and 0.242 percent, respectively. Furthermore, micro-motion of Ti and Zr-2.5 Nb dental implants were measured 0.00514 and 0.00538 mm, respectively. Conclusion: The results of this study showed that Ti dental implant created better conditions than Zr-2.5 Nb dental implant in the mandible. [ABSTRACT FROM AUTHOR]

Numerical and experimental models have been developed to investigate the effect of implementing in-line and staggered arrangement of dimple on heat transfer augmentation and pressure drop of the air flow through a multilouvered fin bank. Three-dimensional simulations of single row of louvers have been conducted for the aforementioned geometry. Simulations are performed for different Reynolds number. The simulation revealed that heat transfer and temperature augmentations occur due to existence of a circulation region created by dimple. Additionally, continuous temperature gradients have been observed over the louver surface with the highest temperature at the base of the louver and the lowest temperature at the middle of the louver. Besides, the difference between these two points is more obvious in higher Reynolds numbers, especially in the first louvers. Fin efficiency and fin effectiveness have been calculated to assess the louver performance. The air-side performance of heat exchanger is evaluated by calculating Colburn j factor and Fanning friction f factor. Results show that implementing dimples on the louver surface increase j factor and f factor. The present results indicated the staggered arrangement, in comparison with in-line arrangement, could effectively enhance the heat transfer performance. The results show that both fin bank performance and louver effectiveness will be increased against an acceptable increase in pressure drop. [ABSTRACT FROM AUTHOR]

In this study, spray behavior of bio-ethanol as a regenerative fuel that reduces emissions such as NOx and CO is investigated in a combustion chamber and compared to its different blends with gasoline. For this purpose, microscopic and macroscopic spray characteristics and also evaporated fuel mass after the injection are modeled and investigated using Fire 2013. It is concluded by increasing bio-ethanol content in the fuel, evaporated fuel mass, spray cone angle, spray area and sauter mean diameter increases, however spray tip penetration remains roughly constant. Increase of injection pressure, decreases spray cone angle and suater mean diameter and increases evaporated fuel mass, spray area and spray tip penetration. If the energy content and time of injection of bio-ethanol and gasoline be equivalent the results vary significantly compared to previous cases. In this case bio-ethanol has a longer spray tip penetration and spray area, higher fuel mass evaporated and smaller spray cone angle and sauter mean diameter compared to gasoline. The increased spray tip penetration and spray area in this case may lead to piston impingement and bore wetting resulting increased hydrocarbon emissions and decreasing engine efficiency. [ABSTRACT FROM AUTHOR]

At moderate Reynolds numbers, perturbations may be intensified and laminar flow regime will change to turbulent flow regime. In transition process from laminar to turbulence, the flow tends to separate from a surface and then reattaches to it. As a result, some bubbles are formed which are called laminar separation bubbles. Understanding the physics of the separation bubble phenomenon and controlling them are necessary for proper aerodynamic devices design at moderate Reynolds numbers. This study has tried to enhance the aerodynamic efficiency of a low speed UAV airfoil and wing by using geometric heterogeneity like groove and bump. In this study, firstly, around CLARK-Y airfoil a proper turbulence model is proposed and effective value of Reynolds numbers on bubbles is obtained. Secondly, a geometric heterogeneity is built and moved from leading edge to trailing edge on the airfoil and the performance of this airfoil is evaluated. Thirdly, geometric heterogeneity around the transition zone is changed and its effect on the performance of this airfoil is evaluated. Finally, some grooves and bumps are arranged on the wing and their aerodynamic performance is compared relative to the clean wing. The results show that, the K - Kl - ω turbulence model is more accurate than the others, higher Reynolds number results in lower bubble size, nearby transition point position is a good option for building heterogeneity, grooves enhance aerodynamic performance more than bumps, and a continuous groove obtained higher aerodynamic performance than clean wing but discontinuous aligned grooves obtained lower aerodynamic performance than clean wing. [ABSTRACT FROM AUTHOR]

In this research, experiment and computational fluid dynamics (CFD) are used to assess the performance of UAV with variable-span and sweep morphing wing under low speed conditions. Both wing area and aspect ratio are changed due to variations in span and sweep, whereas structure of the variable-span and sweep morphing wing remains constant. In this study, the numerical results of Fluent software and experimental data are presented. Results are achieved under a low wind speed (50, 60 and 70 m/s). In this case, full extension represents a 30% (10 cm) increase in wing span and 36% (12 deg.) in sweep angle relative to the original wing, with no extension. The results of this study show that the morphing wing is capable to improved aerodynamic efficiency, increased both range and endurance, reduced induced drag and in general reduced thrust required. According to experimental and numerical results, the use of morphing wing can increase the range by 13.6% and 13.5%, also, endurance of the vehicle by approximately 8.855 and 8.17%, respectively. The results of this study show that the maximum value of lift-to-drag ratio occurred at 6 degrees angle of attack and a speed of 70m/s. These results demonstrate that the use of morphing wing improve the lift-to-drag ratio by 10% compared to original wing. Finally, the numerical simulations are compared and show good agreement with the experimental results. This research also showed how morphing concept can be used as an alternative method for roll control instead of the traditional method of roll control (Aileron control surfaces). [ABSTRACT FROM AUTHOR]

Nowadays, computer simulations are becoming more and more important in performance investigation of thermal systems. In this article, radiator from a cooling system of a diesel engine of ER24PC locomotive is simulated. The radiator is composed of parallel and series arrangement of compact heat exchangers with offset strip fins. It also has two high and low temperature sections. Due to the complexity and compactness of heat transfer plates implemented in the radiator, the simulation is carried out in two steps. First, a relation for coolant-side and air-side heat transfer coefficient is correlated using computational fluid dynamics. Due to vortex shedding phenomenon in the staggered fin arrays, governing equations are solved transiently in twodimensional space. Appropriate timestep for the transient solution is chosen according to time period of vortex shedding from the surface. In the second step, using the developed computational code, the overall thermal performance of the radiator is simulated as a heat exchanger. Consequently, temperature distribution inside the radiator and its thermal performance are studied. Amount of heat released from the radiator in different flow rates and temperatures of fluid flowing out of the radiator are among the outputs of the developed code. Finally, thermal performance curve of radiator is obtained. [ABSTRACT FROM AUTHOR]

In this study, considering slippage between a robot end-effector and an object, adaptive control of a one-finger hand manipulating an object is explored. This system is a good sample to develop different techniques such as grasp analysis, grasp synthesis, stability analysis and designing different types of controller for cooperative manipulator systems. Due to the presence of inequality equations in frictional point contact modeling, a novel formulation is developed to replace the equality and inequality equations with a single second order differential equation with switching coefficients. Introducing this new friction contact model, an input-output conventional form is derived using the equality and inequality equations of motion of the system. Using this new form of motion equations, two adaptive controllers with simple update laws are proposed that both of them ensure the asymptotic convergence of the object position tracking as well as slippage control while compensating the system uncertainties. The first controller compensates the uncertain masses of the manipulator links and the object while the second one compensates the uncertain coefficients of friction. Numerical simulation is utilized to evaluate performance of the proposed controllers. [ABSTRACT FROM AUTHOR]

In this research, a Mach reflection and its effect on explosive free forming of confined cylindrical shells are studied numerically. This shells were manufactured from extruded 6063-T5 Aluminum alloy. The diameter of shell was 1.5 times larger than its length. Its ends were sealed with rigid sheets. The simulation of formation of Mach reflection and plastic response of shell were done with Autodyne hydrocode and coupled Lagrangian-Eulrian spatial discretization. Formation of Mach reflection occurred on end plates. It is observed that the generated pressure in an area that is affected by Mach stem is higher than elsewhere. This phenomena causes rupture in boundaries area of shell to plate connections, before forming process. The maximum of transverse deformation that obtained from this study compared with experimental results which done in explosion mechanic laboratory in K. N. Toosi university of technology. The experimental and numerical results shows more than 93% agreement. Meanwhile, because of blast waves reflection and interaction of waves, coupled Lagrangian-Eulrian method is suitable method for investigation of internal explosion problems. In addition failure modes was simulated with finite element software Abaqus and good agreement was found between the results. [ABSTRACT FROM AUTHOR]