Showing 17 results for Lapping
Volume 9, Issue 2 (5-2018)
Abstract
Aim:
This paper tries to apply Raskin’s (1985) script-based semantic theory to regional anecdotes in Zakani’s (1999) Risala-ye Delgosha (Joyous Treaties).
Theoretical Framework
In his theory, Raskin tries to examine the mechanisms of both generating as well as receiving by the audiences those verbally expressed humor he calls a joke-carrying-text. In this sense, a text is humors if three of the following conditions are satisfied: 1) The text has at least two different scripts; 2) The two scripts are compatible with each other; 3) The two scripts are opposite. A text is non-bona fide/humorous if these conditions are followed; bona- fide/non-humorous, if not followed.
Question:
Is there any meaningful compatibility between SSTH and Zakani's regional anecdotes?
Hypothesis:
Zakani's regional anecdotes are in compatible with the conditions as proposed by Raskin (1985).
Methodology:
As for the corpus, 16 regional anecdotes and or Qazvini-related anecdotes were chosen out of the total 256 anecdotes of the whole version edited by Mahjoob (1999). Then the five anecdotes were discussed in detail, and the rest was generally taken into consideration. Having followed Propp (1928) and Bremond (1973), the Qazvini's behaviors were mapped onto the three functions resulting in a model to show that the Qazvini's foolish action defines his role as the fool and his role as the fool generates his foolish action.
Findings and Results:
Some results show that the regional humor get high frequency in the book thereby they emphasis on the Qazvin's functions. Totally, the application of the SSTH shows that all the kinds of humor are in compatible with the conditions as proposed by Raskin (1985).
Volume 12, Issue 3 (1-2005)
Abstract
Arguments for the recognition of cultural diversity have led to a fundamental question in political theory: On what basis the process of political decision making should be formed to accommodate cultural diversity as a permanent feature of contemporary societies?
The aim of this paper is to examine whether 'dialogue' can be employed as a means in such a process. The first section of this paper is concerned with the nature and sources of cultural diversity. It is also important to see in what way cultural diversity implies problems which concern political theory. This is the concern of the second section. Next, I shall examine ways in which dialogue can be employed to aid the formation of political decision making process to accommodate cultural differences. In particular, I shall suggest that interpretations of dialogue such as Brenda Dervin's and David J. Schaefer's interesting discussion, which aims to transfer the burden of dialogue as a discipline from participants to procedures, may be useful so far as dialogue among cultures and civilizations is concerned.
Ali Alavi Nia, Hamid Omidvar, Hassan Nourbakhsh,
Volume 13, Issue 15 (3-2014)
Abstract
Friction stir process is one of the severe plastic deformation techniques which causes microstructure refinement and hence change in mechanical properties of the specimen. Temperature, strain and strain rate which are the results of this process, causing dynamic recrystallization and followed by shift in mechanical properties. Magnesium is the lightest structural alloy which is used in a wide range, in the automobile and aerospace industries. In this research, the overlapping friction stir process is applied on the surface of AZ31 alloy. The overlapping is conducted in 50 and 0 percentages. In order to reduce the temperature which is generated in the process, rapid cooling was used. After friction stir processing in the 0 percent overlapping the grains refine from 18 micrometer in the base metal to 7 micrometer with a uniformer structure than the base metal, ultimate tensile strength and elongation increased 29.9% and 19.8%, respectively with respect to the base metal. The structural uniformity of 50 percent overlapping was less than that of 0 percent overlapping, ultimate tensile strength and elongation increased 19.98% and 3.9%, respectively with respect to the base metal.
Ali Heydari, Mahmud Pasandidehfard,
Volume 14, Issue 2 (5-2014)
Abstract
The purpose of this paper is to investigate the effect of unsteady trailing edge flapping on lift generation for fixed airfoils at low angles of attack. To do this, a 2D unsteady compressible flow around a fixed airfoil is analyzed at different angles of incidence by means of Coarse Grid CFD (CGCFD) method with spring dynamic network. In this method Euler system of equation is solved with coarse Grid and no slip boundary condition using vorticity confinement technique. At first for code validation, the results of fixed airfoil at different angles of attack and also pitching airfoil are compared with experiments. Further, the CGCFD consequences are compared with the results of RANS with SA turbulent model in the quasi steady case. Then trailing edge flapping (TEF) is added to the fixed airfoil at low angles of attack. The effects of unsteady parameters such as the amplitude and the frequency of TEF are investigated at different low angles of attack. The results show that in a specific low angle of attack, adding TEF results in increasing the lift coefficient comparing with the fixed airfoil without TEF.
Saeed Karimian, Abbas Ebrahimi,
Volume 14, Issue 9 (12-2014)
Abstract
A new complete system model of a flapping wing has been derived which consists of all effective parameters. Flapping mechanism can deliver maneuverability as well as low speed flight capability in MAVs. Here a validated aeroelastic model is being developed based on the wing torsional deformation assumption. Based on the proposed model complete parameter study could be performed and consequently the optimization requirements can be extracted. Experimental results of a static test stand have been used for validation. Performance indices, composed of force generated, power consumption and efficiency are depicted in terms of stiffness and kinematic properties. The average behavior is being referred. It is revealed that by changing frequency and speed, the optimum values for stiffness and amplitude are independent. Therefore using suitable kinematics one can utilize specified constant stiffness to optimize the flapping robot flight.
Ali Ashrafizadeh, Ali Akbar Hosseinjani,
Volume 14, Issue 16 (3-2015)
Abstract
In this paper an improved immersed boundary method is used for simulating sinusoidal pitching oscillations of a symmetric airfoil. Immersed boundary methods because of using a fixed Cartsian grid are well suited for such moving boundary problems. Two test cases are used to validate the proposed method and the effects of oscillation frequency and amplitude on the flow field are investigated. Flow field vorticity and kinetic energy contours are reported in this paper. It is found that the deflected wake start to be appeared for Strouhal number more than 0.4 at a fixed pitching amplitude 0.71. A chaotic flow can be observed at oscillation amplitude 2.80, for a fixed Strouhal number, 0.22. Kintic energy contour shows that for Strouhal number 0.1, the airfoil performs work and transfers momentum to flow but the fluid energy loss due to the enlargement of flow separation zone decreases the momentum and kinetic energy behind the airfoil. Deficit momentum and kinetic energy behind the airfoil results in drag force increasing. By increasing the oscillation frequency and amplitude more momentum transfers to flow filed behind the airfoil which results in drag force decreasing.
Amir Hossein Zaree, Mohammad Hassan Javareshkian,
Volume 15, Issue 10 (1-2016)
Abstract
In first part of this study the methods of direct and indirect entering the effect of induced velocity in blade element theory to achieve lift force in hover flight of Drosophila flapping insect are investigated. Then a new algorithm for Induced velocity correction based on Rankin-Froude jet theory and direct method is presented. The results of previous and new methods to aerodynamic simulation of this insect in hovering flight with combined flapping and pitching angles were compared with published experimental results. The results of this comparison indicate that one of the models based on the indirect method as the best way to predict the experimental results. In second part of this work, the sensitivity of the instantaneous and mean force, produced by insect modeled wing, is examined with change in six wing important motion parameters. This parameters Includes: flapping frequency, phase difference between flapping and pitching angle, flapping and pitching amplitudes and flapping and pitching variations with respect to time in flapping cycle. The results show that with increasing frequency and flapping amplitude lift increasingly increases. Also, range of phase difference percent between flapping and pitching angle that lead to maximum lift of the wings is introduced. Results also show that with tending variation of flapping angle in cycle to sinusoidal trend, the lift force increases.
Ahmad Reza Haghighi, Soraya Asadi Chalak,
Volume 16, Issue 3 (5-2016)
Abstract
In this paper a mathematical model of pulsatile, unsteady and non-Newtonian blood flow through elastic tapered artery with overlapping stenosis is proposed. The blood flow has been assumed to be non-Linear, fully developed, laminar, axisymmetric, two-dimensional. The non-Newtonian model chosen is characterized by Sisko model for discribe the rheology of blood. The artery has been assumed to be elastic and time-dependent stenosis is considered. Due to the blood flow depends on the pumping action of the heart, the blood flow has been assumed pulsate. The stenosed artery change in to a rectangular and rigid artery, using a radial coordinate transformation on the continuity and the nonlinear momentum equations and boundary conditions. The discretization of the continuity and the non-linear momentum equations and boundary conditions are obtained by finite difference scheme. The radial and axial velocity profiles are obtained and the blood flow characteristics such a resistive impedances and volumetric flow rate and the severity of the stenosis are discussed. The volumetric flow rate is minimum in the case of converging tapered arteries and the resistive impedances is maximum in the case of converging tapered arteries by effect of tapering angle.
Volume 17, Issue 5 (9-2015)
Abstract
The aim of this study was to investigate the effects of preslaughter shackling durations on some blood parameters, breast and thigh meat quality traits, and muscle metabolites in broilers. The effects of shackling were determined in a group of Ross 308 broilers (240 birds) aged 42 days. Four shackling treatments were used in experimental tests: shackling of broilers for 10 (Group G10; as control), 30 (G30), 60 (G60), and 120 seconds (G120). Results showed that corticosterone (CORT) level (2314.79 pg ml-1) at 120 seconds shackling group increased (P< 0.01). Results indicated that kinase (CK) activity was the highest (2265.69 U I-1) in the 120 seconds shackling group while it was the lowest (1970.64 U I-1) in 10 s group according to the shackling duration (P< 0.05). The breast meat redness value increased due to increase in shackling duration (P< 0.05). It was revealed that shackling duration had decreased breast muscle glycogen level in all treatment groups (P< 0.001). Conversely, breast lactate level increased according to increase in shackling duration (P< 0.05). It was revealed that there was a negative relationship (r= -0.466) between breast meat ultimate pH and cooking loss (CL) value in male broilers (P< 0.01). These results indicated that the preslaughter shackling procedure might be a considerably stressful procedure for broilers, particularly exceeding 60 s. This study suggested that broilers could be at disadvantage due to more struggle during long duration shackling and accelerated postmortem glycolysis, which is detrimental to the quality of breast meat.
Mohammad Reza Pilehchian, Mohammad Hossein Abolbashari,
Volume 17, Issue 5 (7-2017)
Abstract
In this paper, the effect of new control tools on the behavior of the parachute and its performance is studied by applying a compulsive stimulus in flow field. Modeling simulation and analysis performed with Ansys Fluent. A general geometry is proposed and simulations are carried out to indicate the effect of those stimuli on the flow behavior, parachute performance and high pressure areas on parachute. For the simplicity, the assumptions of axisymmetric and rigid wall of the parachute are used. Due to the large range of motion of fins compared to adjacent cells and also the importance of quality of mesh in the vicinity of the solid boundary, spring-based smoothing method for local and area remeshing are employed. In this way, the mesh quality for presenting the boundary layer and vortex generated in the solid surface are enhanced. The results depicted that using spherical arch geometries versus circular sector or parabolic geometries lead to some advantages. Permittivity of disk at the end of the parachute, has been triggered to increase the general drag coefficient dramatically up to around two times larger. Despite the existence of stimulation on a large area, flow field experience a total pressure drop. On the other hand if the stimulus does not exist the area is much smaller.
Mohammad Hossein Khalesi, Hassan Salarieh, Mahmoud Saadat Foumani,
Volume 17, Issue 8 (10-2017)
Abstract
According to numerous capabilities and increasingly military and commercial applications of radio controlled helicopters, many investigations are being performed on these unmanned aircraft vehicles. Due to nonlinear, complex, unstable and coupled dynamic system and also existing limitations on manual control, the ability of automatic control of these vehicles has gained great importance. In this paper, in addition to investigating different methods of unmanned helicopters dynamic modeling, a multi-level simulator environment has been designed and implemented for flight performance analysis and effects of different parameters have been investigated. The main importance and innovation of present simulator is in possibility of dynamic flight simulation of helicopter using different theories for applications like control system design, performance analysis and real flight simulation. The main difference of the utilized methods is in theories and assumptions applied in main rotor and its flapping dynamics modeling. For each level, Kalman filter and control system design have been performed and preliminary results show the acceptable performance of estimator and controller systems. Considering the complexity of real unmanned helicopter behavior compared to previously performed models, the proposed multi-level simulator can be used as an appropriate tool for the first step before real flight tests.
Mohammad Shafiei Alavijeh, Hossein Amirabadi,
Volume 17, Issue 8 (10-2017)
Abstract
The most essential problem in lapping process is low material removal rate which leads to increase in production costs and time. Thus, in this process, it's essential to select a condition that besides producing pieces with required flatness and roughness, has a high material removal rate. In this research, effects of parameters such as abrasive particle size, abrasive particles concentration in slurry, and lapping pressure on material removal rate, flatness and surface roughness were studied by experimental method in single sided lapping of flat workpieces made of 440c steel. In the following, effect of aforementioned parameters on material removal rate, flatness and surface roughness of lapped surface has been modeled using artificial neural network. Finally, by exerting multi-objective particle swarm optimization, simultaneous optimization of material removal rate, surface roughness and flatness of lapping pieces has been conducted and related Pareto front has been obtained. Obtained results show that by using Multi-objective particle swarm optimization algorithm we can produce workpieces with required surface roughness and flatness with high material removal rate. Consequently, by using this method moreover producing workpieces with desired quality, production cost and time would decrease.
Mohammad Reza Darmiyani, Hossein Amirabadi,
Volume 18, Issue 1 (3-2018)
Abstract
Among the pieces are ceramic balls that are special because of the physical and mechanical properties that have been the industry's attention. Ceramic balls are produced by powder metallurgy way. Finally, by grinding, lapping and polishing processes is reached to surface smoothness, roundness and diameter of the desired. Since the required finishing process to ceramic finishing for surface quality and geometry accuracy of the desired is Time consuming and expensive, creating an economical finishing way is an important issue in the application of ceramic balls. In this article, a mechanism for ceramic balls lapping is proposed. Proposed mechanism consist of two lap plates. Lower lap plate has an eccentric v-shaped groove and placed on out of upper lap plate rotation center. Kinematic analysis of proposed mechanism has been done and lapping trajectory has been investigated on the ball surface. The results of kinematic analysis and lapping trajectory show that the proposed mechanism increases removal rate and roundness of the ball. In general, efficiency and productivity of balls lapping process will improve to achieve the desired surface smoothness and roundness. It can increase the speed of operation and reduce the process time by increasing removal rate.
Volume 19, Issue 2 (7-2019)
Abstract
Local scour around bridge pier is one of the important problem in bridge stability against water flow that is created due to hole scour around bridge pier and castrates its stability. So as, providing methods for control and scour reduction around bridge pier have very importance. Yet different methods have been proposed for preventing and reducing the local scouring around the bridge pier. Use of Submerged Vanes is one of the methods that researchers are interested in. Submerged plates are thin rectangular structures that because of having angle with the flow direction, is created high pressure and low pressure region on both sides. These structures create a secondary vortex and change the flow pattern in the river bed and as a result, change the sediment and scour transmission. Submerged vanes performance to reduce the bridge pier scouring the sediment movement around the vanes due to the downward flow in front of them, are affected by the layout of the plates. These vanes are designed in cross section of the channel and fixed with a little angle relative to flow direction perpendicularly on bed. In this research, submerged vanes were used to reduce the local scour around the single bridged pier located in bend head. Effective variables in this study were vanes overlapping length, space of submerged vanes from bridge pier center and space of submerged vanes from each other perpendicular state on flow direction. For this purpose, a cylindrical bridge pier to diameter 5 cm in the laboratory was performed with a sharp bend 180 degree with central radius to channel width ratio equal 2, a width 1 meter and height 90 cm with straight direction length of bend upstream 6.5m and straight direction length of bend downstream 5m in clear water conditions( u)⁄u_c =0/98 with water discharge of 70 liters per second and depth 18cm. The submerged vanes were Plexi Glass with width 1.5 equal pier diagonal (7.5cm), thickness equal 20% pier diagonal and located in 25 angle relative to horizon with height of out of bed 4.5cm (submergence percent 0.75) with sitting vanes center in the middle of channel (50% channel width from inner shore, with overlapping length (Lcv) 80 and 100% and intervals of submerged vanes from each other perpendicularly on flow direction 5 and 10cm (Lvv/D)=1.2 in position 83 and 79.5 degree from beginning of the bend (interval equal 5 and 7.5 pier diameter toward upstream from located pier site) (Lvp/D=5, 7.5). According to the results of this study, the 20 percent reduction in the overlapping length of the submerged vanes decreases the depth of the scour hole around the bridge pier about 30 percent. Also use of submerged vanes, is transferred location of maximum scour depth to a place near than pier and limited width of scour hole around pier. Furthermore, submerged vanes limit sedimentation region to 0-12% channel width from inner shore and in 70-127 degree from the beginning of the bend. Minimum and maximum scour in hole around pier with submerged vanes is created 0.53 and 0.65 equal flow depth in the beginning of the bend in V80-5-2 and V100-7.5-1 Tests, respectively. The discussion about the results of this research is from the other parts of this article.
Volume 19, Issue 4 (1-2016)
Abstract
With an increasing population growth and subsequent physical expansion of cities and their tendency toward consumerism, waste generation and disposal of solid waste have increased and this non-normative and non-professional disposal has left deleterious effects of the environment. and far to reduce the quality of the urban environment has led. In Ardebil, the current location of waste disposal is in its north, i.e. the east side of Ardebil- Meshkinshar road. The present study is an attempt to analyze land suitability of the site with its current situation using a descriptive- analytical approach. It proposes an optimal location for the disposal of solid waste. Based on library studies and field observations, the parameters affecting the subject of the research were determined and the research criteria maps were produced using the Arcgis 10.2 software. All these effective parameters were evaluated and standardized using Fuzzy membership and Fuzzy overlay functions; therefore, all Layers were combined by taking advantage of fuzzy overlapping method. After overlapping the criteria maps in the software environment, the obtained results showed that locating the current landfill has not been in compliance with the standards. Hence, the optimal place to locate the landfill was proposed at 32 km southwest of Ardebil city
M. Navabi, H. Ghaffari,
Volume 19, Issue 10 (10-2019)
Abstract
The helicopter rotor blade flapping results in a helicopter rotor symmetry lift and has a significant impact on stability and control. In this paper, the modeling of helicopter flapping in the presence of aerodynamic forces and moments and the effect of offset, blade torque, hinge resistant spring, blade geometry, natural frequency effect, and forward ratio to achieve reliable relief from flapping was investigated. In the simulation, the effects of small and large flapping angles and the role of offset on the momentum entered on the blade, as well as the role of the forward ratio in moments were investigated. Different models of flapping dynamics and equations for the flight of a hover and are fully presented and all of the important issues are examined for a numerical example. Also, the effect of non-uniform flow in the flapping equations of the blade is the effect of the natural frequency of the flapping motion with the blade offset. This leads to increasing the accuracy in modeling the phenomenon of on a helicopter. Simulation results show the importance and impact of offsets, moments and forces imposed on the blade in the motion of the flapping, which leads to an increase of accuracy in modeling.
A. Mehrabi, A. Davari,
Volume 20, Issue 6 (6-2020)
Abstract
In this study, multipurpose testing equipment with a sub-scale model of a specific tandem rotor helicopter constructed to conduct a number of experiments to accurate understanding from the tandem rotor's outwash in ground effect. The experiments conducted as measuring rakes were positioned at two distances equal to 1.5 R and 3R from the rotor(s). Unlike the experiments that have been performed in wind tunnels or in special hover chambers, these experiments were performed in an open environment with fewer side walls effects. The results show that when the single rotor operates in a fixed altitude, and the blades tip velocity of 0.2M, the outwash velocities reduces as the flow moving away and vice versa, but for tandem rotors, increasing the rack distance from the model does not have a noticeable effect on the average values of the flow velocity. A comparison of the results of these measurements with the CH-47D helicopter outwash patterns confirms the accuracy of the obtained patterns and showed that the overlap between the rotors increases the velocity values and causes to the occurrence of maximum outwash velocity at lower altitudes. No overlap between the tandem rotors makes the outwash flow pattern of each of them similar to a single rotor. Increase in ground effect as the height of the rotor(s) decreases to 1R, changes the flow pattern in the forward and aft of the model helicopter. In this altitude, unlike their operation in altitude of 2R, the outwash flow increases when moving away from the rotor(s).