Variation Of Geometrical Parameters Research Articles

Generalized formula for estimating the oscillation frequency response of a cantilever bar with point masses

This paper presents a study of natural oscillations of a cantilever bar with five point masses with variable geometric and stiffness parameters (distances between locations of the masses, coefficients of variability of the bending stiffness of the bar sections). Using the exact method of forces based on the Mohr formula, there have been obtained expressions in general form for calculating the main unit coefficients of the secular equation, which makes it possible to perform calculations and to determine the oscillation frequency response of natural oscillations with a wide range of changes in the initial parameters of the physical and geometric state of cantilever bars. A numerical example has been given to illustrate the proposed theoretical approaches. The results have been compared with the results based on calculating a similar can tilever bar with one( reduced by masses) degree of freedom. A graphical dependence of the oscillation frequency response value on changing the value of the bending stiffness along the length of the cantilever bar gas been obtained. The theoretical provisions and applied results presented in the work will be widely used both in the practical design of bar systems and in scientific research in the field of mechanics of a deformable solid body.

Energy and exergy analysis of microchannel central solar receivers for pressurised fluids

Within the new generation of advanced central solar receivers, microchannel pressurised gas receivers are emerging as reliable and efficient alternatives to operate at high temperatures and pressures. This paper presents an optimisation and comparative analysis of different compact plate-fin type structures, constituting the receiver’s absorber panels, classified according to the type of fin arrangement inside: plain rectangular, plain triangular, wavy, offset strip, perforated, and louvred fin. A versatile thermo-fluid receiver model is implemented, allowing simple variation of characteristic geometric parameters of each structure. Exergy efficiency is chosen as the optimisation function, as it considers both heat and pressure losses.The framework of the analysis is set by the receiver’s boundary conditions, operating at the design point conditions of a solar thermal power plant. For each compact structure, the optimal configuration is determined, providing interesting findings that have not been reported in the state-of-the-art to date. Although all geometries show good thermal performance, the perforated and plain rectangular configurations demonstrate the best exergy efficiencies of 59.21% and 58.80%, respectively, favouring taller and narrower channels. This analysis methodology could be seamlessly extrapolated to other gases and working conditions, owing to the thermo-fluid model’s versatility, to reveal the optimal configuration for each case.

Vibration analysis of rotating functionally graded graphene platelet reinforced composite shaft-disc system under various boundary conditions

A unified dynamic model of a rotating shaft-disc system with multilaminar functional graded graphene platelet reinforced composite (FG-GPLRC) disc is established in order to study the vibration characteristics of the system. Based on first-order shear deformation theory, Timoshenko Beam theory and differential quadrature finite element method, the discrete energy matrices of shaft and disc are obtained. Then the total differential equation of the system is procured by assembling the shaft and disc element matrices. The accuracy and reliability of the model are verified by comparing with the software simulation results. Besides, the influence of boundary conditions, GPL distribution types, GPL weight, disc layers and physical dimensions on the system vibration characteristics is analyzed. It reflects that the GPL distribution types and boundary conditions will make a certain difference to the frequency parameters of shaft-disc system. Furthermore, the vibration characteristics of different GPL distribution types are differently sensitive to the variation in material and geometric parameters.

Omnidirectional flat bands in chiral magnonic crystals

The magnonic band structure of two-dimensional chiral magnonic crystals is theoretically investigated. The proposed metamaterial involves a three-dimensional architecture, where a thin ferromagnetic layer is in contact with a two-dimensional periodic array of heavy-metal square islands. When these two materials are in contact, an anti-symmetric exchange coupling known as the Dzyaloshinskii–Moriya interaction (DMI) arises, which generates nonreciprocal spin waves and chiral magnetic order. The Landau–Lifshitz equation and the plane-wave method are employed to study the dynamic magnetic behavior. A systematic variation of geometric parameters, the DMI constant, and the filling fraction allows the examination of spin-wave propagation features, such as the spatial profiles of the dynamic magnetization, the isofrequency contours, and group velocities. In this study, it is found that omnidirectional flat magnonic bands are induced by a sufficiently strong Dzyaloshinskii–Moriya interaction underneath the heavy-metal islands, where the spin excitations are active. The theoretical results were substantiated by micromagnetic simulations. These findings are relevant for envisioning applications associated with spin-wave-based logic devices, where the nonreciprocity and channeling of the spin waves are of fundamental and practical scientific interest.

Design sensitivity analysis in the kinematics of the 4SS-axle guiding mechanism in Chebyshev configuration

This work deals with the design sensitivity analysis in the kinematics of the vehicle rear axle guided by four points - on four spheres (so called 4SS) in Chebyshev configuration. The study actually continues the research presented in a previous published article, which addressed the effect of variations in geometric parameters on the kinematic behavior of the 4SS guiding mechanism with Panhard bar (that is, one of the 4 bars of the mechanism was arranged transversely, while now all the guide bars of the rear axle are arranged longitudinally). The aim of the research is to identify the geometric parameters with significant influence on the kinematics of the guiding mechanism, in order to simplify the subsequent effective optimization process.

Forced and free vibration of magnetostrictive laminated sandwich beams on Kerr’s foundations

The supporting system’s influence on the dynamic behavior of the frequencies and deflection of the smart laminated composite sandwich beam with functionally graded faces is investigated according to a higher-order shear deformation theory. The graphite fiber constituent and the matrix material are distributed through the cross-section of the beam faces based on power law gradation. Kerr’s foundation is proposed to use as a variable support system for the studied structure. The proposed structure is subjected to a magnetic field and an external force in x direction. For controlling the system, a simple feedback gain control with constant distribution is applied to the embedded Terfenol-D actuators. To obtain and solve the associated dynamic equations of the studied system, Hamilton’s principle and Navier’s approach are utilized. Several numerical examples are carried out to show the forced/ free vibration response of the system with detailed illustrations of the different geometrical parameters variation.

Anatomical variations of the internal jugular vein in the context of central line placement: A visual approach to data processing.

Central line placement in the internal jugular vein (IJV) can result in complications. Previous studies that examined variations in geometric anatomical parameters in pediatric populations have reduced these risks in children. The aim of this study was to establish possible anatomical variations to improve central line placement in the adult population and demonstrate the use of a correlation heatmap in processing large amounts of data. Twenty-seven volunteers were imaged using ultrasound at three different neck levels on right and left sides and various anatomical parameters were measured. Demographic information was also collected and included in the data processing. The Pearson coefficient was derived from each possible relationship between the measured parameters and was plotted in a correlation heatmap. Strong correlations were observed between the body mass index and the depth of the IJV and common carotid artery (CCA), the relative depth of the IJV to the CCA. No significant correlations were found in the dimensions of both vessels. Anatomical variations were more common than anticipated and should be taken into account when performing central line catheterization in order to minimize post-procedure complications.

A geometric modelling framework to support the design of heterogeneous lattice structures with non-linearly varying geometry

Abstract Geometric modelling has been a crucial component of the design process ever since the introduction of the first computer-aided design systems. Additive Manufacturing (AM) pushes design freedom to previously unachievable limits. AM allows the manufacturing of lattice structures which are otherwise close to impossible to be manufactured conventionally. Yet, the geometric modelling of heterogeneous lattice structures is still greatly limited. Thus, the AM industry is now in a situation where the manufacturing capabilities exceed the geometric modelling capabilities. While there have been advancements in the modelling of heterogeneous lattice structures, the review of relevant literature revealed critical limitations of the existing approaches. These limitations include their inability to model non-linear variation of geometric parameters, as well as the limited amount of controllable geometric parameters. This work presents a novel geometric modelling methodology based on function representation as an attempt to bridge this gap. The proposed approach avoids the manual definition of geometric parameters and provides a method to control them with mathematical functions instead. A software prototype implementing the proposed approach is presented, and several use-cases are analysed.

Design of patient specific basal dental implant using Finite Element method and Artificial Neural Network technique.

The bone conditions of mandibular bone vary from patient to patient, and as a result, a patient-specific dental implant needs to be designed. The basal dental implant is implanted in the cortical region of the bone since the top surface of the bone narrows down because of aging. Taguchi designs of experiments technique are used in which 25 optimum solid models of basal dental implants are modeled with variable geometrical parameters, viz. thread length, diameter, and pitch. In the solid models the implants are placed in the cortical part of the 3D models of cadaveric mandibles, that are prepared from CT data using image processing software. Patient-specific bone conditions are varied according to the strong, weak, and normal basal bone. A compressive force of 200 N is applied on the top surface of these implants and using finite element analysis software, the microstrain on the peri-implant bone ranges from 1000 to 4000 depending on the various bone conditions. According to the finite element data, it can be concluded that weak bone microstrain is comparatively high compared with normal and strong bone conditions. A surrogate artificial neural network model is prepared from the finite element analysis data. Surrogate model assisted genetic algorithm is used to find the optimum patient-specific basal dental implant for a better osseointegration-friendly mechanical environment.

Stabilized reduced-order models for unsteady incompressible flows in three-dimensional parametrized domains

In this work we derive a parametric reduced-order model (ROM) for the unsteady three-dimensional incompressible Navier–Stokes equations without additional pre-processing on the reduced-order subspaces. Concerning the high-fidelity, full-order model, we start from a streamline-upwind Petrov–Galerkin stabilized finite element discretization of the equations using P1−P1 elements for velocity and pressure, respectively. We rely on Galerkin projection of the discretized equations onto reduced basis subspaces for the velocity and the pressure, respectively, obtained through Proper Orthogonal Decomposition on a dataset of snapshots of the full-order model. Both nonlinear and nonaffinely parametrized algebraic operators of the reduced-order system of nonlinear equations, including the projection of the stabilization terms, are efficiently assembled exploiting the Discrete Empirical Interpolation Method (DEIM), and its matrix version (MDEIM), thus obtaining an efficient offline–online computational splitting. We apply the proposed method to (i) a two-dimensional lid-driven cavity flow problem, considering the Reynolds number as parameter, and (ii) a three-dimensional pulsatile flow in stenotic vessels characterized by geometric and physiological parameter variations. We numerically show that the projection of the stabilization terms on the reduced basis subspace and their reconstruction using (M)DEIM allows to obtain a stable ROM with coupled velocity and pressure solutions, without any need for enriching the reduced velocity space, or further stabilizing the ROM. Additionally, we demonstrate that our implementation allows to compute the ROM solution about 20 times faster than the full order model.

A polarization‐insensitive dual‐band terahertz absorber using triangle graphene metamaterial structure

AbstractA polarization‐insensitive dual‐band terahertz absorber using a single‐layer periodic triangle graphene metamaterial structure is presented in this paper. Through constructing the periodic triangle graphene structure with three embedded T‐shaped graphene strips, two absorption peaks at 1.98 and 3.68 THz with high absorption rates can be obtained and tuned by the variations of geometric parameters or graphene's Fermi energy levels. Furthermore, the proposed dual‐band terahertz absorber possesses the properties of polarization insensitivity and incident angle robustness. This study will have a significant potential for the design of graphene‐based absorbers with different working frequencies at the terahertz regime.

Analysis of Compliance and Kinetostatic of a Novel Class of n-4R Compliant Parallel Micro Pointing Mechanism.

A novel class of n-4R compliant parallel pointing mechanisms is proposed, and the compliance and kinetostatic model of the mechanism are established and analyzed successively. Firstly, the compliance model of a class of n-4R compliant parallel pointing mechanism is established based on the coordinate transformation. The model is verified by finite element analysis, and the influence of geometric parameter variations on the compliance performance of the mechanism is analyzed. Secondly, the mechanism is simplified to an equivalent spring system, and the governing equation of the equivalent spring system is constructed by utilizing the established compliance model. According to the governing equation, the mapping relationship between the input force and the output displacement of the mechanism is subsequently obtained, that is, the kinetostatic model. Then, the accuracy of the kinetostatic model is verified by two simulation examples: The spiral trajectory of the mobile platform center and the spatial pointing trajectory of the mechanism. The results of the two examples show that the deviations between the analytical results and the FE-results are within 0.038% and 0.857%, with the excellent consistency indicating the accuracy of the kinetostatic model. Finally, the influence of the geometric parameter values on the mapping matrix in the kinetostatic model is studied.

Temporal Variation and Component Allocation Characteristics of Geometric and Physical Parameters of Maize Canopy for the Entire Growing Season

The accurate monitoring of crop parameters is important for crop yield prediction and canopy parameter inversion from remote sensing. Process-based and semi-empirical crop models are the main approaches to modeling the temporal changes in crop parameters. However, the former requires too many input parameters and the latter has the problem of poor portability. In this study, new semi-empirical geometric and physical parameters of the maize canopy model (GPMCM) crop model adapted to northeast China were proposed based on a time-series field datasets collected from 11 sites in the Nong’an and Changling Counties of Jilin Province, China, during DOY (day of year) 163 to DOY 278 in 2021. The allocation characteristics of and correlations between each maize canopy parameter were investigated for the whole growing season using the 22 algorithms of crop parameters, and the following conclusions were obtained. (1) The high correlation coefficient (R mean = 0.79) of LAI with other canopy parameters indicated that it was a good indicator for predicting other parameters. (2) Better performance was achieved by the regression method based on the two-stage simulation. The root-mean-squared error (RMSE) of geometric parameters including maize height, stem long radius, and short radius were 12.91 cm, 0.74 mm, and 0.73 mm, respectively, and the RMSE of the physical parameters including the FAGB, AGB, VWC, and RWC of the stems and leaves, ranged from 0.05 kg/m2 to 4.24 kg/m2 (2.0% to 12.9% for mean absolute percentage error (MAPE)). (3) The extension of the field-scale GPMCM to the 500 m MODIS-scale still provided a good accuracy (MAPE: 11% to 18.5%) and confirmed the feasibility of the large-scale application of the GPMCM. The proposed CPMCM can predict the temporal dynamics of maize geometric and physical parameters, and it is helpful to establish the forward and reverse models of remote sensing and improve the inversion accuracy of crop parameters.

Distinguishing Local Demagnetization Contribution to the Magnetization Process in Multisegmented Nanowires.

Cylindrical magnetic nanowires are promising materials that have the potential to be used in a wide range of applications. The versatility of these nanostructures is based on the tunability of their magnetic properties, which is achieved by appropriately selecting their composition and morphology. In addition, stochastic behavior has attracted attention in the development of neuromorphic devices relying on probabilistic magnetization switching. Here, we present a study of the magnetization reversal process in multisegmented CoNi/Cu nanowires. Nonstandard 2D magnetic maps, recorded under an in-plane magnetic field, produce datasets that correlate with magnetoresistance measurements and micromagnetic simulations. From this process, the contribution of the individual segments to the demagnetization process can be distinguished. The results show that the magnetization reversal in these nanowires does not occur through a single Barkhausen jump, but rather by multistep switching, as individual CoNi segments in the NW undergo a magnetization reversal. The existence of vortex states is confirmed by their footprint in the magnetoresistance and 2D MFM maps. In addition, the stochasticity of the magnetization reversal is analysed. On the one hand, we observe different switching fields among the segments due to a slight variation in geometrical parameters or magnetic anisotropy. On the other hand, the stochasticity is observed in a series of repetitions of the magnetization reversal processes for the same NW under the same conditions.

The Relationship Between the Emitter Position and the Wehnelt Cylinder Aperture Radius of the Thermionic Electron Gun

This paper includesfinding a mathematical relationship between the distance from the emitter to the width of the Wehnelt cylinder bore and the diameter of that bore, by studying the effect and correlation of these two parameterson the quality of the electron beam. A group of electron guns with identical and variable geometric parameters were designed for the values ​​of the Wehnelt cylinder aperture radius for each case from the emitter site, which represents the distance from the emitter head to the Wehnelt cylinder aperture. As well as the calculation of the electron beam diameter and the brightness and emittance, as the mathematical relationship between these two parameters was found to be linear.

Forecasting technical performance and cost estimation of designed rim wheels based on variations of geometrical parameters

Abstract Rim wheel testing through the SAE standard is necessary for driving safety. This study focused on rim wheel tests carried out using the dynamic radial fatigue test method, which has been included in the SAE standard using Fusion360 for the design and ANSYS for the simulation. With different parameters for the rim wheel type, only some parameters of the tested rim wheels were able to pass the standardization by SAE; 16 rim wheels passed the test, while the other 11 rim wheels did not pass. Simulation results suggested that variations in the thickness, geometry, and material affected the displacement of the safety factor, which was inversely proportional. In addition, the variation in the rim wheel produced a change in the safety factor due to changes in its mass and cost, which were directly proportional. The results of this study will aid in rim wheel design, not only in terms of achieving the best performance but also with regard to cost efficiency.

Static Parametric Stress-Strain Analysis for Asphaltic Concrete Core of Rockfill Dams

Abstract This study was conducted to investigate the effect of variations in the asphaltic concrete core Rockfill dam geometric parameters on the core behavior at different upper, middle, and lower points under two-dimensional static stress-strain analysis. The mentioned analysis was performed using SIGMA/W software. In the modeling and analysis process, the geometry of a large number of dams constructed around the world was studied and many numerical models with variations in eight classes of height, three dams upstream/downstream slope modes, and three different asphaltic core positions and thicknesses on a rigid foundation were created and analyzed. In addition, for each of the above models, four dam operation stages including “End of Construction”, “Full Reservoir”, “Half-Full Reservoir”, and “Rapid Drawdown” were considered. The results show, in four different stages of construction and impounding and three different slope modes, the maximum stress as well as horizontal and vertical displacements at the upper, middle, and lower points of the core increase with increasing height. In all models, increasing upstream and downstream slopes results in an increase in the amount of vertical displacement for all construction and impounding stages at the upper, middle, and lower points of the core. In the middle and lower points of the core, with increasing height, the amount of deviatoric stress increases for all construction and impounding conditions. In addition, for all operation cases, the maximum strain increases in all points of the vertical and tilted cores as the core thickness increases. Additional results are presented in the next sections.

Deep learning LSTM for predicting thermally induced geometric errors using rotary axes’ powers as input parameters

Temperature changes within a machine tool, which are partly due to internal heat sources related to the power consumption at the machine drives, result in thermally induced geometric errors of the machine. Predicting the thermally affected machine geometry facilitates the prediction of volumetric errors throughout the 5-axis machine volume. Measuring power instead of temperature is easier to implement in practice but causes drift issues. Stacked Long Short Term Memory (LSTM) with two hidden LSTM layers is applied to determine the relationship between powers and the thermal variation of geometric error parameters by remembering previous states and learning complex non-linear relationships through optimized generalized parameters of the predicting model. Optimizers Adam, RMSprop, and SGD based on exponential moving average of first order and second order moments of gradients are combined with Stacked LSTM for faster learning convergence to an optimal solution. Validation trials with various B- and C-axis motion sequences demonstrate a capability of predicting multi time steps ahead over a 40 hours period without re-measuring the geometric error parameters of the model. Stacked LSTM with the Adam optimizer has the best capability by predicting up to 93% of the main geometric error compared to the other optimizers.

Investigation of Leakage and Heat Transfer Properties of the Labyrinth Seal on Various Rotation Speed and Geometric Parameters

To investigate the influence of the variation of geometric parameters on the leakage and heat transfer characteristics of labyrinth seals at various rotational speeds, the labyrinth seal models with different geometric parameters were numerically simulated based on the control variable methods. Results show the aerodynamic mechanism of leakage characteristics changing with rotational speed, as well as the leakage characteristics of labyrinth seals under the coupling action of geometric parameters and rotating speeds. When the characteristic scale changes along the direction of centrifugal force, the variation trend of labyrinth seal leakage characteristics is consistent at different rotational speeds. However, the leakage characteristics of labyrinth seals show the difference of rotational speed when the feature scale changes along the axis. At the same time, the laws of convective heat transfer on the surface of the rotor and stator are shown by the results of the studies, which provides reference for the thermodynamic analysis of labyrinth seals.

A Literature Review on Orifice as a Flow Measuring Device

An orifice meter is one of the flow measuring devices which are more popular among all the instruments because of its simple design, less cost, and easy manufacturing to determine the discharge in single and multi-phase flow. In a multiphase flow problem such as oil and gas industry, chemical and processing industry wellhead chokes are used to control the production of oil and control, which create more fluctuation in the downstream flow due to back pressure on the reservoir and create significantly error in the measurement. To avoid the above problem orifice is an alternative device. The review paper gives an idea about single orifice consider for various applications, which will be helpful for betterment of orifice design and analysis. The review papers also produce the numerical and experimental studies on orifice to determine the pressure drop and coefficient of discharge on the variation of geometrical and flow parameters.