Rotational Motion

The vast majority of objects in the observable universe are subject to rotational motions around an internal axis of rotation and to one or more rotational motions around external centers (or loci) of rotation. After recalling the absolute nature of all these rotations, this article demonstrates that all the rotational motions of any body A are inherited by any other body B set in motion from A. Consequently, and taking into account that the term preinertia suggests the sole inheritance of inertial motions (rectilinear and constant velocity), it is also proposed here to change the terms preinertia and preinertial respectively to the more general prekinesis and prekinetic.

This study aims to understand the behavior of connection, which holds an important key to efficient designs of the coldformed steel structure. The focus is on examining parameters that affect the rotational stiffness and behavior of the coldformed steel connection made of single-lipped channel sections with a bolt and gusset plate system. The numerical study has been conducted using component-based finite element analysis, with the studied parameters including bolt diameters, number of bolts in the group, size of the bolt group, thickness of the cold-formed steel cross-section, and thickness of the connecting plate. The effect of the variables is evaluated and explained by comparison. The result of the study reveals that the rotational behavior of the connection depends on the details of the assembly. For the given base connection, the parameters that give the greatest effect on the rotation stiffness and the moment capacity are the number of bolts and the bolt diameters, whereas the parameter that provides the least effect is the bolt spacing. On the other hand, the bolt group size is the most influential parameter for the member connection. For both types of connections, the thickness of the coldformed steel section and the thickness of the gusset plate have shown limited effect on stiffness and strength. Using different variables in assembling the connection can also lead to different failure types, either bolt failure or excessive bolt hole deformation, which leads to plate failure.

In the present paper, we introduce new models of pendulum motions for two cases: the first model consists of a pendulum with mass M moving at the end of a string with a suspended point moving on an ellipse and the second one consists of a pendulum with mass M moving at the end of a spring with a suspended point on an ellipse. In both models, we use the Lagrangian functions for deriving the equations of motions. The derived equations are reduced to a quasilinear system of the second order. We use a new mathematical technique named a large parameter method for solving both models’ systems. The analytical solutions are obtained in terms of the generalized coordinates. We use the numerical techniques represented by the fourth-order Runge–Kutta method to solve the autonomous system for both cases. The stabilities of the obtained solutions are studied using the phase diagram procedure. The obtained numerical solutions and analytical ones are compared to examine the accuracy of the mathema...

Optical control of nanoscale objects has recently developed into a thriving field of research with far-reaching promises for precision measurements, fundamental quantum physics and studies on single-particle thermodynamics. Here, we demonstrate the optical manipulation of silicon nanorods in high vacuum. Initially, we sculpture these particles into a silicon substrate with a tailored geometry to facilitate their launch into high vacuum by laser-induced mechanical cleavage. We manipulate and trace their center-of-mass and rotational motion through the interaction with an intense intra-cavity field. Our experiments show optical forces on nanorotors three times stronger than on silicon nanospheres of the same mass. The optical torque experienced by the spinning rods will enable cooling of the rotational motion and torsional opto-mechanics in a dissipation-free environment.

Introduction:
When working with a manual auger, many face the need to apply significant effort, making the process laborious and tiring. Often, recalling the school physics course, we look for ways to alleviate this task. The “Max Wheel” is not just a tool; it is a clear example of using a simple lever, which, surprisingly, is often overlooked when studying the basics of mechanics. It significantly reduces the load on the hands and back, increases productivity, and makes working with a manual auger accessible even to people with limited physical capabilities. In this article, we will thoroughly examine the theoretical basis of the “Max Wheel“‘s operating principle, its advantages over traditional methods, examples of applications in various fields, and, of course, tell you how to make this wonderful device with your own hands.

The dynamic response of a natural laminar flow airfoil undergoing harmonic small-amplitude pitching oscillations is investigated using Large-eddy simulations with a chord-based Reynolds number of Re = 750;000. Throughout the pitch cycles, large changes in the transition point are seen as well as trailingedge separation. This leads to a nonlinear response of the aerodynamic forces. Although the nature of the flow is highly nonlinear, the development of the boundary layer over the airfoil surface can be modeled using a simple phase-lag concept which suggests a quasi-steady evolution of the boundary layer. Based on this phase-lag assumption, a simple new empirical model is developed which agrees very well with the measured experimental data. With the aid of this model, the primary source of non-linearities in the unsteady aerodynamic forces is identified to be the quasi-steady term, which can be evaluated from the static airfoil characteristics. The strength of this remains unchanged with the variation of reduced frequency, but the harmonic term's strength, which models the unsteady effects, increases with increasing frequency.

By using the choline starvation process it is possible to deplete the membranes of Neurospora crassa choline auxotroph chol-1 of phosphatidylcholine, without affecting the viability of germinated spores or whole mycelium. Spin label probes were used to examine the possible dependence of the physical state of cellular lipids on the presence of phosphatidylcholine in the membranes. Increased freedom of rotational motion of lipid soluble probes was regularly detected in choline-starved mycelium. The accumulation of neutral lipids (mostly triglycerides) in bulk form was also observed during the choline starvation process. The experiments with isolated and separated lipid classes indicated that the observed increase in fluidity of lipids in choline-starved mycelium is partly due to the difference in physical properties between bulk lipids and membrane lipids. Spin label probe 2N4 (2-propyl-2,5,5-trimethyloxazolidine-N-oxyl), which can partition at the membrane-water interface, exhibited easier partitioning among membrane lipids of choline-starved mycelium.

Unlike the motion of a continuous contour, the motion of a single dot is unambiguous and immune to the aperture problem. Here we exploit this fact to explore the conditions under which unambiguous local motion signals are used to drive global percepts of an ellipse undergoing rotation. In previous work, we have shown that a thin, high aspect ratio ellipse will appear to rotate faster than a lower aspect ratio ellipse even when the two in fact rotate at the same angular velocity [

Analysis of the flow passing cylindrical obstacles is one of the basic issues in fluid dynamics and is of great importance. Many surveys have been conducted to investigate the velocity field in potential and viscous flows, as a basis for finding pressure field, and investigation of forces exerted by fluid on obstacles such as uplift and drag forces in different flow regimes. Since the nature of formation of vortexes behind the obstacles is absolutely depended on time, the conventional turbulent models which are based on average time, do not justify, and the use of direct solution of Navier Stocks equations is inevitable. One of the presented models which can solve time-dependent Navier Stocks equations in wide range of Reynolds numbers, is Random Vortex Method (RVM). Since in this method velocity field is instantly calculated, it can be used to simulate turbulent flows with a time-dependent nature. In this paper, vorticity equations gained from Navier Stocks equations are solved in both convection and diffusion phases. In this study, the flow on three cylinders with Re=140000 is investigated and field of average and instant velocity is shown along with streamlines. Also by drawing instant distribution of vortex fields and streamlines, it is possible to provide a revealing presentation of vortex behind cylinders.

In this study, the effect of replacing the elastic wall in a two-dimensional channel for forced convection flow around a circular cylinder surrounded by an incompressible flow has been studied numerically. As the current passes around the hot cylinder and the elastic wall oscillates, the rate of heat transfer changes at any time, which is a function of the vibration conditions of the elastic oscillator. Amplitude, frequency and vibration mode are the main parameters affecting the current passing through the channel. The2refore, in this study, the effect of oscillator vibration in the first, second and third modes has been investigated and in each mode, three different amplitudes and in each amplitude three different frequencies have been investigated and the calculations for two Reynolds numbers 100 and 200 have been solved. Rigid channels are compared. The results show that in the first mode, unlike the second and third modes, the elastic wall oscillation has a great effect on the average Nusselt number, average output temperature and cylinder drag coefficient. in all modes, with increasing amplitude and frequency, the average Nusselt number, the average output temperature and the drag coefficient of the cylinder increase.

The purpose of this study is to investigate the behavior of a cylinder with three fins in the presence of free air flow. This study aims to investigate the unsteady aerodynamic flow with respect to its practical significance in aviation. Considering the degree of freedom of movement within the geometry and the complexity of the vortex masses that cause instability, it is essential to accurately predict the different dynamic behaviors. We have investigated the dynamic behavior of the model with different length ratios, free flow speeds, and angles of attack. According to the results of the study, rotational and oscillating behaviors, as well as a combination of both, are observed, and they are dependent upon the geometrical characteristics of the model, such as the ratio of the length of the plates to the radius of the cylinder, as well as the angle of attack When the aspect ratio and free flow speed are low, the motion pattern is damped around 60 degrees and the motion regime is oscillatory in nature, which changes to rotational motion as the aspect ratio and flow speed increase. The maximum oscillation or rotation is related to the initial angle of attack of zero degrees. It has been observed that rotational motion regimes occur with an increase in the longitudinal ratio and free flow speed at low initial angles of attack. The angular velocity of the models and the Strouhal number in the rotational motion regime have been calculated and the results show that with the increase of the Reynolds number, the Strouhal number has a constant value.

In this paper, differential quadrature element method (DQEM) is used to analyze the free transverse vibration of multi-stepped rotors resting on multiple bearings. In order to increase the accuracy of the model, Timoshenko beam theory is used; also in order to generalization of the modeling of the bearings, each bearing is replaced with four springs; two translational and two rotational acting on two perpendicular directions. Governing equations, compatibility conditions at the each step and each bearing and external boundary conditions are derived and formulated by the differential quadrature rules. First, convergence and versatility of the proposed method are tested by the presented exact solutions. Then, the Campbell diagram is derived for a desired case study and variation of natural frequencies is investigated versus angular velocity of spin. The most advantage of the proposed method is being less time-consuming in comparison with the other methods, especially for cases with high number of steps and bearings which are unsolvable by exact methods.

Stability analysis of the polynomial characteristic equation is not easy to applied to a high-order system, in this case, it relates to search the roots of the degree n polynomial equation. It is difficult to find the roots of the equation, so stability analysis will be carried out using the stability of Routh-Hurwitz. In this study, a polynomial characteristic equation is given with a degree n with a real coefficient, then applied to the Hurwitz Matrix and a Gauss elimination procedure with a partial pivot is performed, then the growth factor is calculated. The results showed that the polynomial characteristic equation of degree n for Routh-Hurwitz conditions is said to be stable if each zero of the polynomial is located in the half left open field if and only if the elimination procedure can be performed and the optimal value of growth factor is 1.

هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 01 تشهبیدرا 1396 :شریذپ 22 دادرخ 1396 :تیاس رد هئارا 18 دادرم 1396 هب زاین لیلد هب متسیس رد لااب یدرکلمع تقد ییاهن درکلمع رب یسدنه و یداعبا یاهاطخ تارثا یسررب ،قیقد یاهدربراک رد راود یکیناکم یاه هصخشم رب رثؤم یاهرتماراپ رد اهاطخ زا یشان تارثا نیمخت رد یدیفم رازبا یسنارلت لیلحت .تسا یرورض یحارط هلحرم رد متسیس یاه یکیناکم متسیس کی یدرکلمع یم متسیس یدرکلمع تقد .دشاب متسیس فلاخ رب قیقد راود یاه یاهاطخ رب هولاع ،راودریغ یکیناکم یاه یسدنه و یداعبا هب طوبرم فاطعنا هب طوبرم یاهاطخ هب ازجا تخاس یاطخ هب نینچمه و تفش زیخ و یریذپ یگنل رد .تسا هتسباو یرارکتریغ ،هلاقم نیا یارب یدیدج شور ا یسنارلت لیلحت متسیس یکیمانید و یکیتاتس فاطعنا زا یشان تارثا ،یسدنه و یداعبا یاهاطخ دوجو اب راود یاه یم هئارا یسنارلت هیحان لدم یانبم رب یرارکتریغ یگنل یاطخ و یریذپ و یداعبا یاهاطخ ،کچوک یدازآ تاجرد موهفم زا هدافتسا اب ادتبا .ددرگ لدم بلاق رد یرارکتریغ یگنل یاطخ و یسدنه لدم یسنارلت یحاون یم یزاس لدم روظنم هب ،یدیدج یژتارتسا ساسا رب سپس .ددرگ یزاس یدرکلمع عباوت ،یسنارل...

Control of two-wheeled humanoid robots poses several challenges due to the unstable dynamics of their mobile base and the coupling between upper and lower body dynamics. The problem is often faced in the literature with methods based on linearized or simplified models that fail in exploiting the whole body dynamic capabilities of the platform in use. In this work we tackle the problem of whole-body dynamic control for a mobile wheeled unstable humanoid robot. Compared to existing approaches based on on-line optimization to guarantee respect of the constraints, we propose a control method that takes into account the nominal constrained dynamics of the robot in the quasi-velocities through an internal model, thus reducing the computational burden. A computed-torque control law in the quasi-velocities is used to stabilize the robot around the upper position. We report on preliminary experimental results and on the method effectiveness in rejecting unknown external disturbances.

optimal criteria. Then, it is augmented by a variable structure control term to guarantee the stability, as well as speeding up its convergence. Finally, simulation results demonstrate the effectiveness of the proposed scheme to trajectory control of the FWMAV.

An approach to controlling the three-link Robogymnast robotic gymnast and assessing stability is proposed and examined. In the study, a conventionally configured linear quadratic regulator is applied and compared with a fuzzy logic linear quadratic regulator hybrid approach for stabilising the Robogymnast. The Robogymnast is designed to replicate the movement of a human as they hang with both hands holding the high bar and then work to wing up into a handstand, still gripping the bar. The system, therefore has a securely attached link between the hand element and the ‘high bar’, which is mounted on ball bearings and can rotate freely. Moreover, in the study, a mathematical model for the system is linearised, investigating the means of determining the state space in the system by applying Lagrange’s equation. The fuzzy logic linear quadratic regulator controller is used to identify how far the system responses stabilise when it is implemented. This paper investigates factors affectin...

In many cases the collection of obstacles stand against water flow direction and by passing water through these obstacles, vortexes are created in downstream of them and by overlapping of these vortexes, surface waves perpendicular to the flow direction are formed. In this study the impact of obstacle shape on the characteristics of transverse waves are investigated.For this purpose, cylindrical obstacle and cubic obstacle are used. Discharges 5, 15 and 25 l/s and insertion of obstacles in parallel with ordering of 60*60,60*120,120*120 and 180*180  are considered. Totally 36 experiments were performed. The results showed that the shape of obstacles has high impact on the formation of transverse waves. The maximum amount of relative amplitude (A/H ) (A : The maximum wave amplitude , : depth of flow) was occurred for cylindrical obstacle with amount of 61.10% in arrangement of obstacles of  and discharge equal to 5 l/s and the minimum value of   was occurred for cubic obstacle for sid...

هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 3 رهم 1397 پ شریذ : 16 رذآ 1397 تیاس رد هئارا : 10 نمهب 1397 رلیوا ریت لدم زا هدافتسا اب راود روحم رضاح قیقحت رد هیبش یلونرب یم يزاس رب دراو ياهورین .دوش رثا تحت ریت هندب يروئت زا هدافتسا اب ،یلخاد نایرج تمس زا نآ تاشاعترا ) کیراب ياه Slender body theorem هیبش ( یم يزاس ارب .دوش ي اضف زا تلاداعم لاقتنا ي لحم ی غ هب ری حم یل روئت زا ي را نگنی زا هدش دراو یلخاد ياهورین اب راود روحم رب مکاح تلاداعم بیکرت اب سپس .تسا هدش هدافتسا رط یطخ تلاداعم ،نایرج ف هدش يزاس یم جارختسا متسیس ریگمه ي زا هدافتسا اب سپس .دوش شور سناکرف ،هژیو رادرب لیلحت ياه تعرس رد نآ يرادیاپ و روحم تاشاعترا یعیبط ياه ینارود ياه یم هعلاطم فلتخم ب یلخاد نایرج یمرج تبسن ،ینارود تعرس نوچ ییاهرتماراپ رثا نینچمه .دوش ه مرج روحم يرغلا بیرض ،روحم .دش دهاوخ یسررب يرادیاپ زرم رب دیلک ناگژاو رلیوا ریت یلونرب نایرج لماح راود بویت ونان تاشاعترا نگنیرا يروئت

The current location of educational institutions is generally not in the same location due to lack of land availability or educational institutions has the goal of accommodating a number of students from certain regions equally, in other words expanding the reach of these educational institutions. Generally, the institution will provide a solution by constructing a number of rooms vertically and grouping them based on the type of activity given. But the impact is the difficulty of monitoring business administrators and students when they want to conduct guidance or face-to-face counselling in addition to the teaching schedule. Thus it is deemed necessary to have a monitoring instrument regarding the presence of teachers to facilitate students and school administrators to monitor their existence. The system development method was designed using Rapid Application Development (RAD) based on observations of bourding-based elementary schools in Bogor, West Java. The system is designed ba...

This paper analyses the dynamic behavior of rigid solar panels deploying the mechanism of a spacecraft with flexible hinges. The proposed mechanism, maintaining a proper speed, guarantees the deployment synchronization of solar panels and minimizes the effects of impact and vibration applied during the final stage and after the panels lock up using torsional springs in the hinges and yoke driven assembly. The equations of the motion of the system are derived using the Lagrange an approach, and the behavior of the mechanism for constant and variable torque excitation modes is investigated. The simulation results presented, along with the dynamic simulations performed by Adams software and conventional mechanisms, show the proposed method's efficiency.

Small vibrations (Shimmy) are lateral and torsional vibrations in the aircraft wheel that excites itself and cause instability in fast functions; which can damage the aircraft's landing gear and its fuselage, as well as, in commercial aviation, this may harm passengers. Therefore, controlling and damping these vibrations is essential. For this purpose, the present study has designed a controller using the NARMA-L2 type neural method to prevent small vibrations in the aircraft's landing gear. The controller as mentioned above has a high capability against parameter uncertainties and external disturbances. To check the performance of the proposed controller, the vibration response of the system was simulated by MATLAB software, and its efficiency was measured by comparing the results obtained from RCTM and Proportional-Integral-Derivative (PID) controllers. The obtained results show a significant improvement in the performance of the closed-loop system with an effective reduction of vibrations as a result of using the proposed controller.

In this research, the free vibration of rotating tapered Timoshenko beam with piezoelectric layer has been studied. It is assumed that the beam is made of Functionally Graded Materials (FGM) through the thickness direction and the boundary condition is a cantilever attached to the hub. The first-order shear deformation theory has been used to drive governing equations. At first, the total energy of the system such as potential and kinetic energies for the beam and piezoelectric layer has been derived, and then the natural frequencies of the beam have been determined by the Ritz approach based on minimizing the total system energy. After verifying the results by comparing them with other research, the effects of some parameters such as hub radius, rotational speed, taper ratios, rotary inertia, material gradient, piezoelectric voltage, and beam thickness on the natural frequencies of the tapered Timoshenko beam have been studied in detail. The results showed that with increasing the angular velocity of the beam, the natural frequency increases so that as the increasing velocity increases, the natural frequency increases with a steeper slope.

This paper considers rotational motion of a nonlinear Mathieu equation with a narrow-band stochastic excitation. The path integration technique is utilized to obtain the joint probability density function of the response, which is used to construct domains of rotational motion in parameter space.

The Carleton University Simulator Project (CUSP) is developing a novel flight simulator that decouples typical translational motions from unlimited rotations about any axis. The new CUSP simulator, Atlas, consists of an orientable sphere, housing the cockpit, mounted on a motion platform. Atlas is not bound by the typical limitations in roll, pitch, and yaw of traditional flight simulators. This paper presents some of the systems involved with the novel flight simulator and the enrichment that undergraduates experience by developing the inter-relationships and communication paths between the multiple systems and elements.

In this study, the authors report on a novel method to estimate the total rotational velocity of a non-cooperative moving target in a multi-static Inverse Synthetic Aperture Radar (ISAR) system. The method requires a system with at least four receivers spatially distributed such that their line-of-sight vectors are not coplanar. By using least squares optimisation, estimates of the magnitude of the effective rotational velocity 'seen' by each receiver and trackfile information on the target trajectory and translational velocity are combined to determine the component due purely to the target's own rotational motion; an estimate for the total rotational velocity can thus be obtained, which can be useful for automatic target recognition. The multistatic nature of the system allows the technique to take into account the translational motion component of the total rotational velocity with some levels of robustness, which is not the case with other approaches. Simulated data results demonstrate the feasibility of the proposed method.

In the present paper, we introduce new models of pendulum motions for two cases: the first model consists of a pendulum with mass M moving at the end of a string with a suspended point moving on an ellipse and the second one consists of a pendulum with mass M moving at the end of a spring with a suspended point on an ellipse. In both models, we use the Lagrangian functions for deriving the equations of motions. The derived equations are reduced to a quasilinear system of the second order. We use a new mathematical technique named a large parameter method for solving both models’ systems. The analytical solutions are obtained in terms of the generalized coordinates. We use the numerical techniques represented by the fourth-order Runge–Kutta method to solve the autonomous system for both cases. The stabilities of the obtained solutions are studied using the phase diagram procedure. The obtained numerical solutions and analytical ones are compared to examine the accuracy of the mathema...

In this study, the authors report on a novel method to estimate the total rotational velocity of a non-cooperative moving target in a multi-static Inverse Synthetic Aperture Radar (ISAR) system. The method requires a system with at least four receivers spatially distributed such that their line-of-sight vectors are not coplanar. By using least squares optimisation, estimates of the magnitude of the effective rotational velocity 'seen' by each receiver and trackfile information on the target trajectory and translational velocity are combined to determine the component due purely to the target's own rotational motion; an estimate for the total rotational velocity can thus be obtained, which can be useful for automatic target recognition. The multistatic nature of the system allows the technique to take into account the translational motion component of the total rotational velocity with some levels of robustness, which is not the case with other approaches. Simulated data results demonstrate the feasibility of the proposed method.

In this study, the authors report on a novel method to estimate the total rotational velocity of a non-cooperative moving target in a multi-static Inverse Synthetic Aperture Radar (ISAR) system. The method requires a system with at least four receivers spatially distributed such that their line-of-sight vectors are not coplanar. By using least squares optimisation, estimates of the magnitude of the effective rotational velocity 'seen' by each receiver and trackfile information on the target trajectory and translational velocity are combined to determine the component due purely to the target's own rotational motion; an estimate for the total rotational velocity can thus be obtained, which can be useful for automatic target recognition. The multistatic nature of the system allows the technique to take into account the translational motion component of the total rotational velocity with some levels of robustness, which is not the case with other approaches. Simulated data results demonstrate the feasibility of the proposed method.

Optical control of nanoscale objects has recently developed into a thriving field of research with far-reaching promises for precision measurements, fundamental quantum physics and studies on single-particle thermodynamics. Here, we demonstrate the optical manipulation of silicon nanorods in high vacuum. Initially, we sculpture these particles into a silicon substrate with a tailored geometry to facilitate their launch into high vacuum by laser-induced mechanical cleavage. We manipulate and trace their center-of-mass and rotational motion through the interaction with an intense intra-cavity field. Our experiments show optical forces on nanorotors three times stronger than on silicon nanospheres of the same mass. The optical torque experienced by the spinning rods will enable cooling of the rotational motion and torsional opto-mechanics in a dissipation-free environment.

2 ،رایشناد اضفاوه یسدنهم ، ریبکریما یتعنص هاگشناد نارهت ، * ،نارهت قودنص یتسپ 1591634311 ، sabzeh@aut.ac.ir هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 10 رهم 1396 :شریذپ 20 ید 1396 :تیاس رد هئارا 12 نمهب 1396 دپ ی هد ی ق ی چ ی ارب داب ی پاوه ی ام اپ عافترا زاورپ رد یی ن ، سب ی را دهت و کانرطخ ی د مآ ی ز م ی هک دشاب یپاوه یریذپان لرتنک بجوم یم ام نینچمه و دوش شیپ .تسا یراوشد راک نآ صیخشت و هدیدپ ینیب قحت ی ق ا رد ی ن دب هزوح ی ن مها زئاح روظنم ی ت م ی پاوه هک دشاب ی ام ا اب ههجاوم رد ی ن دپ ی هد لرتنک ذپ ی ر .دوش کت لدم زا ،تاقیقحت رثکا هیبش یارب هطقن هدرک هدافتسا تسربورکیام اب امیپاوه ییورایور یزاس نیا .دنا تیعقوم لدم یم لامعا امیپاوه مرج زکرم هب ار تسربورکیام یارب .دوش لامعا امیپاوه مد و لاب ،هندب رساترس هب دیاب تسربورکیام نادیم هک یلاح رد ،دنک هیبش یزاس عقاو ی رت ، مان هب یدیدج لدم زا دیاب دنچ لدم لدم نیا رد .دومن هدافتسا هطقن غتم داب تارثا ی ر مرج زکرم رب هولاع ، ب طاقن هب ی رتش ی زا پاوه ی ام دراو یم دوش . تیزم زا امیپاوه هب داب نایدارگ رثا لامعا یم رامش هب لدم نیا یاه .دور ر...

Fully developed viscoelastic flows in rotating curved pipes with circular cross section are investigated theoretically and numerically employing the Oldroyd-B fluid model. Based on Dean's approximation, a perturbation solution up to the secondary order is obtained. The governing equations are also solved numerically by the finite volume method. The theoretical and numerical solutions agree with each other very well. The results indicate that the rotation, as well as the curvature and elasticity, plays an important role in affecting the friction factor, the secondary flow pattern and intensity. The co-rotation enhances effects of curvature and elasticity on the secondary flow. For the counter-rotation, there is a critical rotational number R ⍀ Ј , which can make the effect of rotation counteract the effect of curvature and elasticity. Complicated flow behaviors are found at this value. For the relative creeping flow, R ⍀ Ј can be estimated according to the expression R ⍀ Ј =−4We␦. Effects of curvature and elasticity at different rotational numbers on both relative creeping flow and inertial flow are also analyzed and discussed.

In this study, the authors report on a novel method to estimate the total rotational velocity of a non-cooperative moving target in a multi-static Inverse Synthetic Aperture Radar (ISAR) system. The method requires a system with at least four receivers spatially distributed such that their line-of-sight vectors are not coplanar. By using least squares optimisation, estimates of the magnitude of the effective rotational velocity 'seen' by each receiver and trackfile information on the target trajectory and translational velocity are combined to determine the component due purely to the target's own rotational motion; an estimate for the total rotational velocity can thus be obtained, which can be useful for automatic target recognition. The multistatic nature of the system allows the technique to take into account the translational motion component of the total rotational velocity with some levels of robustness, which is not the case with other approaches. Simulated data results demonstrate the feasibility of the proposed method.

The human vestibular system is a sensory and equilibrium system that manages and controls the human sense of balance and movement. It is the main sensor humans use to perceive rotational and linear motions. Determining an accurate mathematical model of the human vestibular system is significant for research pertaining to motion perception, as the quality and effectiveness of the motion cueing algorithm (MCA) directly depends on the mathematical model used in its design. This paper describes the history and analyses the development process of mathematical semicircular canal models. The aim of this review is to determine the most consistent and reliable mathematical semicircular canal models that agree with experimental results and theoretical analyses, and offer reliable approximations for the semicircular canal functions based on the existing studies. Selecting and formulating accurate mathematical models of semicircular canals are essential for implementation into the MCA and for e...

In this paper, we analyze and compare five imagebased visual servoing control laws. Three of them are classical while two new ones are proposed. The first new control law is based on a behavior controller to adjust the movement of the camera. It can also be used to switch between the classical methods. The second control law is designed to try to obtain the global stability of the system. An analytical study of all control schemes when translational motion along and rotational motion around the optical axis is also presented. Finally, simulation and experimental results show that the new control law with a behavior controller has a wider range of success than the other control schemes and can be used to avoid local minima and singularities.

In this work, the unsteady rotational motion of an incompressible micropolar fluid inside a right circular cylinder is investigated. The classical no-slip and no-spin boundary conditions are proposed. The problem is solved analytically using the state space approach together with Laplace transform technique. The inverse Laplace transform is carried out numerically using a numerical technique based on Fourier series expansion. Numerical results for the flow field functions are represented graphically for different values of the time and micropolarity parameters.

SUMMARYThis paper presents analysis of the dynamics and vibration of an orientation motion platform utilizing a sphere actuated by omnidirectional wheels. The purpose of the analysis is to serve as a design tool for the construction of a six-degree-of-freedom motion platform with unlimited rotational motion. The equations of motion are presented taking flexibility of the system into account. The behaviour of the system is illustrated by sample configurations with a range of omnidirectional wheel types and geometries. Vibration analysis follows, and sensitivity to various parameters is investigated. It is determined that the geometry of omnidirectional wheels has a significant effect on the behaviour of the system.

In this research the aerodynamic performance of a discrete wing capable of morphing, has been studied based on the numerical techniques. In the proposed wing the chord-wise strips have been implemented to resemble a bird wing's feathers. The morphing mechanism composed of changing the wrist angle which is equal to the partially sweep angle and the wing planform area. Here it is shown that by utilizing this proposed simple mechanism, the MAV/UAV could enhance its aerodynamic performance and also produce control power in the longitudinal and lateral maneuvers. Firstly, the benchmark geometry and a suitable numerical scheme are introduced. The results are then compared and validated against the reference available data. Consequently, the parametric study is performed by selecting the morphing wing tip sweep angle and the angle of attack as the variables and the force coefficients and efficiency as the performance indices. This kind of morphing could make the efficiency increase, up to 13 percent. Flow simulations around the wing are depicted for various morphing angles and for two angles of attack, both in the steady and unsteady manner. The results are also compared and analyzed. Based on the current research, one may continue to estimate the control forces produced by this simple mechanism to expedite the longitudinal and lateral maneuvers in a specified MAV.

The spring-back of a work-piece during machining operation causes dimensional error of the work-piece. In the present study, the spring-back of work-piece in ultrasonic-vibration assisted turning and conventional turning has been modeled. It is illustrated that the reaction of the work-piece in high frequency vibration cutting is similar to a static behavior, whereas the spring-back in this process is theoretically and experimentally smaller than the conventional cutting leading to smaller error. A method has also been proposed to obtain the errors caused by rigid assumption of the spindle assembly used for correction of the results.

The purpose of this research is to determine the simulation execution in rotational dynamics and rotational kinematics. This paper conducted two types of testing, each with two different cases: varied uses of mass distribution and pulley type. The students calculated each of the simulation's offered outcomes to see if it was precise and accurate. In this experiment, inertia had a significant impact, and it was the only factor that affected the outcome even when the inputted value was the same in each experiment. The students also discovered that there is a significant relationship between the radius multiplied by the change in angle and the change in position. The formula is denoted as. ∆θ = ∆

SUMMARYThis paper presents analysis of the dynamics and vibration of an orientation motion platform utilizing a sphere actuated by omnidirectional wheels. The purpose of the analysis is to serve as a design tool for the construction of a six-degree-of-freedom motion platform with unlimited rotational motion. The equations of motion are presented taking flexibility of the system into account. The behaviour of the system is illustrated by sample configurations with a range of omnidirectional wheel types and geometries. Vibration analysis follows, and sensitivity to various parameters is investigated. It is determined that the geometry of omnidirectional wheels has a significant effect on the behaviour of the system.

In the present paper, we introduce new models of pendulum motions for two cases: the first model consists of a pendulum with mass M moving at the end of a string with a suspended point moving on an ellipse and the second one consists of a pendulum with mass M moving at the end of a spring with a suspended point on an ellipse. In both models, we use the Lagrangian functions for deriving the equations of motions. The derived equations are reduced to a quasilinear system of the second order. We use a new mathematical technique named a large parameter method for solving both models’ systems. The analytical solutions are obtained in terms of the generalized coordinates. We use the numerical techniques represented by the fourth-order Runge–Kutta method to solve the autonomous system for both cases. The stabilities of the obtained solutions are studied using the phase diagram procedure. The obtained numerical solutions and analytical ones are compared to examine the accuracy of the mathema...

Simulation of a machine is very important before laser metal deposition is performed, as a tool to check collision detection and validate deposition result. There are several kinds of machines that are used for laser deposition and hence there is a need for a generalized concept for visual simulation of various kinds of machines. This paper presents the research conducted on describing each machine configuration in a generic format. A parent–child list and a dependency list obtained from the machine configuration are utilized to form the generic format. Such a format can be used to describe linear and rotational motion of the machines parts. This method has been tested on various examples to demonstrate its robustness and efficiency.

Do the mechanisms that underlie the perception of translational and rotational object motion show evidence of independent processing? By probing the perceived speed of translating and/or rotating objects, we find that an object's form contributes in independent ways to the processing of translational and rotational motion: In the context of translational motion, it has been shown that the more elongated an object is along its direction of motion, the faster it is perceived to translate; in the context of rotational motion, it has been shown that the sharper the maxima of curvature along an object's contour, the faster it appears to rotate. Here we demonstrate that such rotational form-motion interactions are due solely to the rotational component of combined rotational and translational motion. We conclude that the perception of rotational motion relies on form-motion interactions that are independent of the processing underlying translational motion.

The viability of using collocation methods in radius and spherical harmonics in the angular variables to calculate convective flows in full spherical geometry is examined. As a test problem the stability of the conductive state of a self-gravitating fluid sphere subject to rotation and internal heating is considered. A study of the behavior of different radial meshes previously used by several authors in polar coordinates, including or not the origin, is first performed. The presence of spurious modes due to the treatment of the singularity at the origin, to the spherical harmonics truncation, and to the initialization of the eigenvalue solver is shown, and ways to eliminate them are presented. Finally, to show the usefulness of the method, the neutral stability curves at very high Taylor and moderate and small Prandtl numbers are calculated and shown.

New helmet technologies have been developed to improve the mitigation of traumatic brain injury (TBI) in bicycle accidents. However, their effectiveness under oblique impacts, which produce more strains in the brain in comparison with vertical impacts adopted by helmet standards, is still unclear. Here we used a new method to assess the brain injury prevention effects of 27 bicycle helmets in oblique impacts, including helmets fitted with a friction-reducing layer (MIPS), a shearing pad (SPIN), a wavy cellular liner (WaveCel), an airbag helmet (Hövding) and a number of conventional helmets. We tested whether helmets fitted with the new technologies can provide better brain protection than conventional helmets. Each helmeted headform was dropped onto a 45° inclined anvil at 6.3 m/s at three locations, with each impact location producing a dominant head rotation about one anatomical axes of the head. A detailed computational model of TBI was used to determine strain distribution acros...

هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 26 دادرم 1396 :شریذپ 12 نابآ 1396 :تیاس رد هئارا 10 رذآ 1396 نیا رد هبساحم فده اب ،هلاقم هبش یکیمانیدوریآ یاهورین ی لاب یایاپ لاب اب نز و لااب هبور ندز لاب مزیناکم یکیتامنیس لیلحت هب هکتود یاه یم هتخادرپ نییاپ هبور لدم یارب بسانم مزیناکم ادتبا .دوش زاورپ یزاس نیا یم باختنا فپمک یوگلا زا هدافتسا اب ،ناگدنرپ ذم مزیناکم .دوش روک لاب تکرح ،یدازآ تاجرد دادعت رظن زا مزیناکم یگداس رب هولاع نآ ندز ریغ تکرح لماش هک ار اه مه هبور زاف هبور و لااب هکت ره نییاپ لاب ی هیبش زین ار تسا یم یزاس نیا رب .دنک هیواز باتش و تعرس ،تیعقوم ساسا هب یجراخ و یلخاد لاب رب دراو یاهورین و یا لیلحت تروص هب ی تسد یم همادا رد .دیآ طخ یروئت شیپ یارب هک ازآرب هس لاب یور آرب یورین عیزوت ینیب لاب عطاقم یکیمانیدوریآ زکرم رد هبادرگ طخ ساسارب یدعب یم هدافتسا دوش نیلوا یارب هب هکتود لاب اب ناگدنرپ یارب قیقحت نیا رد راب شیپ یروئت نیا .تسا هتفر راک ارشح یارب نیا زا کی لاب اب ت هکت هدافتسا ،یروئت نیا کمک اب .تسا هدش طسوتم یکیمانیدوریآ یاهورین هدنربولج و آرب کی ی لاب هب هک هکتود لاب...

The work described in this thesis falls into two largely unrelated categories. Part I of the thesis reports unusually fast spin 1 ? diffusion in adamantane. A calculation of the C spin-diffusion rate from first order perturbation theory is presented and compared to the experimental data. There is good agreement between calculation and experiment for relatively small mixing times. Motional averagng of 13 1. C-H dipolar coupl ing is found to be responsible for the unusual ly 13 efficient c spin-diffusion in adamantane. Further enhancement of spin-diffusion should be possible by carrying out mixing in the rota ting frame. This is experimental 1 y verified for adamantane. 13 Part II discussed C NMR of methanol adsorbed on HY zeolite. Three species were distinguished on the basis of their different spinlattice, spin-spin (spin diffusion) and chemical properties shift. These were; a species exhibiting l iquid-like mobil ity, a species chemically adsorbed onto the wall of the large cage of the zeolite, and a species chemically adsorbed onto the wall of the small cage of the zeol ite.

هدیکچ تاعبرم لضافت شور کمک هب ،قیقحت نیا رد ) DQM ( یطورخم لپوک هتسوپ دازآ تاشاعترا لیلحت هب هدش هتخادرپ یچیودناس یطورخم قیقحت نیا رد هدش یسررب یطورخم هتسوپ هسدنه .تسا ، صقان تروص هب تسا فلتخم هدام عون راهچ ،لنپ چیودناس هتسه . یلپ نوتکرتارتا ) PEEK ( تانبرک یلپ ، ) PC ( ، یلپ نلیپورپ دماج ) SPP ( و لپ موف ی مآ ی د لااب یلاگچ اب ) HDPF ( هیلا و زا یجراخ و یلخاد ياه لدم .تسا هدش رظن رد موینیمولآ سنج لوا هبترم یشرب لکش رییغت يروئت کمک هب یضایر يزاس ) FSDT ( تلاداعم و ماجنا هتسوپ رسود رد يزرم طیارش هب طوبرم تلاداعم ،هتسوپ تاشاعترا رب مکاح تکرح تلاداعم .تسا هدش جارختسا نوتلیمه شور کمک هب تکرح شور کمک هب ،هتسوپ ود لاصتا لحم رد یگتسویپ طرش هب طوبرم تلاداعم و DQ هژیو رادقم هلئسم هطبار و هدش يزاس هتسسگ جارختسا و هجیتن رد نآ ، فلتخم يزرم طیارش رثا و هتسه سنج ،طورخم سار هیواز ،تماخض ،لوط رییغت رثا .تسا هدش هبساحم یعیبط سناکرف هسیاقم ،یجنسرابتعا روظنم هب .تسا هدیدرگ یسررب یعیبط سناکرف يور و قیقحت تایبدا رد دوجوم جیاتن و هدمآ تسدب جیاتن نایم يا مرن نینچمه سوکابآ رازفا ) Abaqus ( .تسا هتفرگ تروص