Analytical Simulation Research Articles

Nonlinear dynamical and harvesting characteristics of bistable energy harvester under hybrid base vibration and galloping

To harvest wind energy and vibration energy simultaneously, the nonlinear dynamical and harvesting characteristics of a bistable piezoelectric energy harvester (BPEH) under hybrid excitations are studied in this manuscript. A distributed model of BPEH is established by the generalized Hamilton’s principle, Kirchhoff’s law, and the quasi-steady hypothesis. The influences of wind speed, base excitation level, magnetic distance and resistance are studied by the harmonic balance method (HBM). The results show that the structure can be optimized to reach the best harvesting performance for wind energy and vibration energy. The analytical prediction and simulation results are verified by the experiments. The coexisting solutions appear while the BPEH is under a hybrid excitation of wind galloping and base vibration. The dynamical response will approach different branches for different initial conditions, by which the system can be intentionally designed to attain the high energy orbit. The experimental results show that the BPEH could reach the highest output efficiency while it undergoes the motion of inter-well period-1. Thus, a high energy output can be realized by controlling the initial conditions to the desired range. This study could provide a comprehensive insight into the promotion of harvesting performance for hybrid ambient excitations.

Improvement of the Airflow Energy Harvester Based on the New Diamagnetic Levitation Structure.

This paper presents an improved solution for the airflow energy harvester based on the push-pull diamagnetic levitation structure. A four-notch rotor is adopted to eliminate the offset of the floating rotor and substantially increase the energy conversion rate. The new rotor is a centrally symmetrical-shaped magnet, which ensures that it is not subjected to cyclically varying unbalanced radial forces, thus avoiding the rotor's offset. Considering the output voltage and power of several types of rotors, the four-notch rotor was found to be optimal. Furthermore, with the four-notch rotor, the overall average increase in axial magnetic spring stiffness is 9.666% and the average increase in maximum monostable levitation space is 1.67%, but the horizontal recovery force is reduced by 3.97%. The experimental results show that at an airflow rate of 3000 sccm, the peak voltage and rotation speed of the four-notch rotor are 2.709 V and 21,367 rpm, respectively, which are 40.80% and 5.99% higher compared to the three-notch rotor. The experimental results were consistent with the analytical simulation. Based on the improvement, the energy conversion factor of the airflow energy harvester increased to 0.127 mV/rpm, the output power increased to 138.47 mW and the energy conversion rate increased to 58.14%, while the trend of the levitation characteristics also matched the simulation results. In summary, the solution proposed in this paper significantly improves the performance of the airflow energy harvester.

ENERGY CONSUMPTION ANALYSIS FOR AN EV POWERTRAIN USING THREE BLDC IDENTICAL MOTORS

Using more than one motor in an EV (Electric Vehicle) powertrain enhances the vehicle’s torque, acceleration, and speed capabilities. A more tractive force produced by the electric powertrain requires more electric current from the battery. In modern EVs, mechanical power production can be approached to the wheels reducing the mechanical losses in the transmissions. It is the case with multiple-motor powertrains. Several advantages regarding vehicle control, physical performance, and energy efficiency improvement are obtained. In the current study, a BLDC (brushless dc) motor is investigated from the efficiency point of view to build a multiple-motor powertrain. A new methodology uses analytic calculations, simulations, and physical measurements. A powertrain with three identical motors results in a new vehicle configuration. Each motor's energy consumption improvements are analyzed following a normalized testing procedure. The results are compared with those of a single-motor powertrain.

Inversion in binary gas mixtures in rarefied flow conditions: Direct simulation Monte Carlo solution and comparison with the analytical solutions at free molecular regime

This paper analyzes the mixing of gases in a plane channel at rarefied conditions. The direct simulation Monte Carlo method is employed to simulate gas mixing in parallel mixers working at different Knudsen numbers and having different values of wall accommodation coefficient. Results show that the normal-to-wall component of the mole fraction gradient may have the same sign as the corresponding component of the diffusive mass flux vector near the diffuse solid walls in contrast to the predictions of Fick's law for continuum conditions. This non-continuum behavior, which is called “inversion” in the present study, will become more pronounced at higher Knudsen numbers, whereas it will become less evident for smaller wall accommodation coefficients. To confirm that the observed phenomenon is consistent with the basic physical laws governing the rarefied gas dynamics and it is not an artifact of the numerical method, a new analytical model based on the kinetic theory of gases is developed for the parallel mixers that have diffuse walls and are working in the free-molecular regime. Excellent agreement is observed between the analytical and direct simulation Monte Carlo results in the free molecular flow regime. Both methods predict the occurrence of inversion near the diffuse walls at highly rarefied flow conditions.

Constructing a Digital Thread to Support Mission Analysis & System of Systems Engineering

AbstractTo keep pace with growing system complexity, Digital Engineering (DE) Model Based Systems Engineering (MBSE) capabilities must be expanded. A digital thread based approach is required to holistically evaluate measures of effectiveness/performance for missions. This paper describes the approach taken to connect requirements, SysML‐based architecture, and analytical Modeling and Simulation (M&S) yielding an interdisciplinary digital thread supporting mission analysis. The analysis was conducted in support of a multi‐domain (land, air, sea, and space) multi‐platform mission to detect, track, and engage the enemy. The approach used commercially available tools, strategically connected to establish an Authoritative Source of Truth (ASOT) for each piece of data, and gain insights about the System of Systems (SoS) beyond that which the component models could provide on their own. The results of these efforts produced a multipurpose SoS MBSE toolset enabling semi‐automated trade study analysis, while more importantly serving as a basis from which to expand systems engineering activities during subsequent phases of the systems' lifecycle. This paper concludes by identifying further opportunities for MBSE research and development to expand the developed capability.

Scalar dark matter vortex stabilization with black holes

Galaxies and their dark-matter halos are commonly presupposed to spin. But it is an open question how this spin manifests in halos and soliton cores made of scalar dark matter (SDM, including fuzzy/wave/ultralight-axion dark matter). One way spin could manifest in a necessarily irrotational SDM velocity field is with a vortex. But recent results have cast doubt on this scenario, finding that vortices are generally unstable except with substantial repulsive self-interaction. In this paper, we introduce an alternative route to stability: in both (non-relativistic) analytic calculations and simulations, a black hole or other central mass at least as massive as a soliton can stabilize a vortex within it. This conclusion may also apply to AU-scale halos bound to the sun and stellar-mass-scale Bose stars.

Insights into an analytical simulation of a natural convection flow controlled by Arrhenius kinetics in a micro-channel

The focus of this paper is the investigation of an Arrhenius-driven chemical reaction in an upstanding micro-channel over an imposed transverse magnetic field with fully developed constant free convection flow. Subject to suitable boundary conditions, the temperature and velocity equations are resolved in non-dimensional form employing the homotopy perturbation method (HPM). the fundamental flow behaviors of temperature, velocity, and volumetric flow are explored as a consequence of regulating characteristics such as fluid-wall interaction parameter, rarefaction parameter, chemical reaction parameters, wall-ambient temperature difference ratio, and Hartman number. The findings are carefully investigated and graphically represented in several mesh grid graphs. It was established that increasing the values of the rarefaction parameters and chemical reaction results in an upsurge in the fluid velocity and volume flow rate, respectively, whereas increasing the Hartman number results in observable flow retardation. Additionally, when the chemical reactant parameter is ignored, the numerical comparison is in excellent agreement with the previously published results.

BEYONDPLANCK

We presentPlanckLow Frequency Instrument (LFI) frequency sky maps derived within the BEYONDPLANCKframework. This framework draws samples from a global posterior distribution that includes instrumental, astrophysical, and cosmological parameters, and the main product is an entire ensemble of frequency sky map samples, each of which corresponds to one possible realization of the various modeled instrumental systematic corrections, including correlated noise, time-variable gain, as well as far sidelobe and bandpass corrections. This ensemble allows for computationally convenient end-to-end propagation of low-level instrumental uncertainties into higher-level science products, including astrophysical component maps, angular power spectra, and cosmological parameters. We show that the two dominant sources of LFI instrumental systematic uncertainties are correlated noise and gain fluctuations, and the products presented here support – for the first time – full Bayesian error propagation for these effects at full angular resolution. We compared our posterior mean maps with traditional frequency maps delivered by the Planck Collaboration, and find generally good agreement. The most important quality improvement is due to significantly lower calibration uncertainties in the new processing, as we find a fractional absolute calibration uncertainty at 70 GHz of Δg0/g0 = 5 × 10−5, which is nominally 40 times smaller than that reported byPlanck2018. However, we also note that the originalPlanck2018 estimate has a nontrivial statistical interpretation, and this further illustrates the advantage of the new framework in terms of producing self-consistent and well-defined error estimates of all involved quantities without the need of ad hoc uncertainty contributions. We describe how low-resolution data products, including dense pixel-pixel covariance matrices, may be produced from the posterior samples directly, without the need for computationally expensive analytic calculations or simulations. We conclude that posterior-based frequency map sampling provides unique capabilities in terms of low-level systematics modeling and error propagation, and may play an important role for future Cosmic Microwave Background (CMB)B-mode experiments aiming at nanokelvin precision.

Microstructural insights into the enigmatic network of random fibers: van Wyk’s notions revisited

Understanding the structure–property relationships of random materials is a long-standing problem of great interest as their applications span one of the most diverse fields of science and engineering. Polycrystals, polymer blends, foams, fluidized beds, cermets, rocks, fibrous materials, and composites are notable examples of these materials. In random fiber networks, the apparent disconnect between size effects, intricate porous characteristics, and the stochastic nature of constituents, leading to quasi-heterogeneous features, emphasizes the need to explore beyond their microstructure. Herein, we revisit the pioneering work of van Wyk on the architectural-based interfiber spacing model for random fiber networks established via the excluded area and excluded volume approaches. In van Wyk’s original work, the discrepancy between the excluded area and excluded volume frameworks has been ascertained and is now addressed by correlating with classical Bertrand’s paradox. Subsequently, the excluded area and excluded volume approaches of the interfiber spacing model have been modified to account for low-aspect-ratio fibers by including the side-side, end-end, and side-end interactions. van Wyk’s modified interfiber spacing model for low-aspect-ratio fibers has been compared with the other analytical model, developed for random fiber networks. A simple relationship between the maximum volume fraction and aspect ratio has also been deduced for cylindrical fibers. To demonstrate our analytical model’s versatility and wide-ranging applicability, the maximum volume fraction and aspect ratio relationship has been benchmarked with a plethora of analytical models, simulations, and experiments obtained from the literature that resulted in a reasonable agreement.

Evaluation of the load distribution of timber slab bridge and the efficiency of the retrofit methods

Timber slab bridges are commonly used in rural regions because of their simple construction and low costs. However, a review of the bridge manual indicates that there is no specific guidance or very similar guidance to the current nationwide bridge codes with respect to the calculation of wheel load distribution and strengthening/enhancing methods. The objective of this research is to evaluate the load distribution for timber slab bridges and the efficiency of the retrofit methods. To achieve this objective, ten timber slab bridges were identified for a program of bridge live load tests. Three of them were tested twice, once before and once after bridge strengthening measures were employed. The data collected from the field test program was utilized to calculate the equivalent strip width (ESW), and the results were compared with the codified values. In addition, a series of finite element (FE) models were created based on these ten field-tested bridges and validated against the field-collected data. The validated FE models were utilized for a parametric study to evaluate the wheel load distribution and the performance of various retrofit methods on the bridges with different truck loading, bridge geometry, and retrofit approaches. Based on the results from the field tests and analytical simulation, an equation to predict the equivalent strip width for the timber slab bridges was developed with consideration of numerous variables.

Influence of rheological behavior of low-melting alloy on instability and control method for sheet metal

The wrinkling-free forming method for sheet metal forming based on the low-melting alloy (LMA) is a novel sheet forming method. However, the wrinkling phenomenon is affected by the transmission of loading force depending on the rheological behavior of material LMA. The effect of the rheological behavior of LMA medium on the wrinkling mechanism needs to be deeply studied. The blank holder force exerted by the LMA medium on the edge of the sheet is analyzed using the plane strain method. The critical stress of sheet deformation and wrinkling is studied by combining the classical energy method. The range of blank holder force was computed at the critical wrinkling stage. The flow resistance of the sheet material flowing into the plastic region is affected by the stress angle in the transition zone through numerical simulation and experimental methods. The influence of different forming process conditions on stress angle on the transition area is studied, and the evolution law of the stress angle and the material flowing status are revealed. The effect of the upper layer thickness of LMA, the temperature of LMA, and the dimension of LMA in the flange region on wrinkling occurrence are performed. Experiments are carried out to verify the results for analytical and FE simulation. The experimental results indicated that research results show that a decrease in the stress angle will increase the resistance of the sheet flowing to the plastic deformation region.

Analytical simulation of vibration demeanor of robotic arm immersed in incompressible dynamic fluid

The use of underwater mechanical arms is extensively considered to be the most suitable tool for performing mechanical operations underwater. These mechanical arms can transport samples and patterns in water environments. A simulation of the fluid flow provoked vibrations in the arm of the robot is presented in this paper. Under the influence of the force generated through the surrounding fluid flow and considering the flexibility of the robotic arm, the governing forced vibration equations are derivative of the Rayleigh beam hypothesis. With the displacement couple pattern, the force from the surrounding fluid is tested for the arm. For analyzing the equations of movement, MATLAB software has been utilized to examine the influence of variables like the mechanical and geometric features and the liquid flow rate on the forced vibration the responding robot arm. Numerical simulations indicate that fluid inertial forces increase with increasing fluid velocity. Therefore, at higher levels of the fluid, the result of extra mass-produced by the fluid causes the range of oscillations to increase suddenly, which decreases the performance and accuracy of the arm. By identifying the lock-in area, the system parameters should be selected in such a way as to prevent the arm from entering the lock-in area.

REDUCING PROTOTYPE FABRICATION TIME THROUGH ENHANCED MATERIAL EXTRUSION PROCESS CAPABILITY

Abstract3D printing is a widely used technology for automating the fabrication of prototypes. The benefits are wide reaching, and include low required expertise, accurate geometric form and the processibility of many materials. However, production of certain forms – especially large forms – can be slow. From review of the sub-systems, the hotend is commonly found to be the limiting factor. To improve this, a modified nozzle design is considered that incorporates a flat copper plate within the flow stream. Analytical simulation was used to guide this design before experimental methods validated the modifications. The maximum volumetric rate for the standard hotend nozzle is 14 mm3/s. The best performing modified nozzle increased the maximum volumetric flow rate to 26 mm3/s – an 86% increase. A series of popular parts were further considered, demonstrating a maximum ∼48% fabrication time reduction, and a mean of ∼23%. This enables 3D printed prototypes to be made more efficiently – both with regards to the design cycle and energy use – and allows designers to use the technology more rapidly than previously possible. By extension, this improves the efficiency of the design process.

Resource Allocation in Quantum-Key-Distribution- Secured Datacenter Networks With Cloud–Edge Collaboration

Datacenter networks (DCNs) with cloud-edge collaboration are emerging to satisfy the communication, computation, and caching (3C) requirements of future services such as cloud-based IoT services. However, the enroute data over DCNs with cloud-edge collaboration is likely to suffer from cyberattacks such as eavesdropping. A large number of services require not only 3C resources, but also cryptographic resources for encryption to ensure high security. Quantum key distribution (QKD) is a practical approach to provide secret keys for remote users with information-theoretic security against eavesdropping attacks from quantum computing. A QKD-secured DCN (QKD-DCN) with cloud-edge collaboration can be deployed to satisfy the communication, computation, caching, and cryptographic (4C) requirements of services. This paper innovatively solves the new 4C resource-allocation (4CRA) problem in the network to minimize the cryptographic resource consumption. It formulates an integer linear programming (ILP) model and proposes a heuristic cryptographic-dependent 4C resource-allocation algorithm to find optimal solutions. The proposed algorithm is compared with two baseline 4CRA algorithms which respectively consider the minimized service delivery latency and the first-fit resource availability. Analytical simulations show that the proposed algorithm minimizes the key-resource-consumption ratio and the average key-resource consumption under static and dynamic traffic scenarios in different network topologies.

The Dynamics and Energetics of Remnant and Restarting RLAGN

In this article, I review past, current, and future advances on the study of radio-loud AGN (RLAGN; radio-loud quasars and radio galaxies) lifecycles exclusively in the remnant and restarting phases. I focus on their dynamics and energetics as inferred from radio observations while discussing their radiative lifetimes, population statistics, and trends in their physical characteristics. I briefly summarise multi-wavelength observations, particularly X-rays, that have enabled studies of the large-scale environments of RLAGN in order to understand their role in feedback. Furthermore, I discuss analytic and numerical simulations that predict key properties of remnant and restarting sources as found in wide-area surveys, and discuss the prospects of future surveys that may shed further light on these elusive subpopulations of RLAGN.

Hybrid optimal design method for magnetic field coils under magnetic shielding boundary

A novel strategy for designing uniform magnetic field and gradient magnetic field coils considering the boundary effect of magnetic shielding is proposed in this study. This strategy uses intelligent optimization algorithm to skillfully transform the complex coil design problem into the spatial optimization problem of individual population. The mirror method is combined with Green’s function to accurately calculate the magnetic field, and the target field method (TFM) is combined with the whale optimization algorithm to optimize the stream functions using adaptive ridge regression. The minimum fitness function is defined as the real-time magnetic field relative error, and the optimal ridge coefficient is continuously obtained by determining the current density coefficient. The proposed method significantly reduces the magnetic field deviation in the target area compared to the conventional TFM, with reductions ranging from 12.2% to 0.11% (Bx coil), 0.3% to 0.02% (Bz coil), 20% to 10% (dBx/dz coil) and 2.9% to 2.4% (dBz/dz coil). The strategy has been effectively validated by analytical simulations and experimental results, and is expected to be applied to the design of uniform field coils and gradient coils for ultra-high precision atomic sensors.

Quantum scattering of spinless particles in Riemannian manifolds

Quantum mechanics is sensitive to the geometry of the underlying space. Here we present a framework for quantum scattering of a nonrelativistic particle confined to a two-dimensional space. When the motion manifold hosts localized curvature modulations, scattering occurs from an emergent geometric potential and the metric tensor field. Analytical and full numerical simulations identify the geometric potential as the primary source for low-energy scattering, while the metric tensor field of the curved space governs high-energy diffraction. Compared to flat spaces, important differences in the validity range of perturbation approaches are found and demonstrated by full numerical simulations using combined finite element and boundary element methods. As an illustration, we consider a Gaussian-shaped dent leading to effects known as gravitational lensing. Experimentally, the considered setup is realizable based on geometrically engineered two-dimensional materials.

A New Cable-Driven Model for Under-Actuated Force–Torque Sensitive Mechanisms

Force–torque sensors are used in many and different domains (i.e., space, medicine, biology, etc.). Design solutions of force–torque sensors can be conceived by using many types of connections or components; however, there are only a few sensors designed using cable-driven systems. This could be related to many reasons, one of which being that cables are able only to pull and not push. In this paper, a new cable-driven model for under-actuated force–torque sensing mechanisms is proposed, simulated, and tested, underlining the novelty of using cables for force–torque sensing. Analytical formulations, simulations, and physical implementations are presented in this paper. Results confirm that the new proposed model can be used for force–torque sensing mechanisms in micro- and macro- applications where under-actuation is a fundamental requirement, as in robotic surgery. The proposed model and mechanism can be used in the design of sensors and actuators. The innovative model is validated with two different test benches, opening new challenges in the design and development of under-actuated force–torque transducers.

Effect of the local energy distribution of x-ray beams generated through inverse Compton scattering in dual-energy imaging applications.

X-ray sources based on the inverse Compton interaction between a laser and a relativistic electron beam are emerging as a promising compact alternative to synchrotron for the production of intense monochromatic and tunable radiation. The emission characteristics enable several innovative imaging techniques, including dual-energy K-edge subtraction (KES) imaging. The performance of these techniques is optimal in the case of perfectly monochromatic x-ray beams, and the implementation of KES was proven to be very effective with synchrotron radiation. Nonetheless, the features of inverse Compton scattering (ICS) sources make them good candidates for a more compact implementation of KES techniques. The energy and intensity distribution of the emitted radiation is related to the emission direction, which means different beam qualities in different spatial positions. In fact, as the polar angle increases, the average energy decreases, while the local energy bandwidth increases and the emission intensity decreases. The scope of this work is to describe the impact of the local energy distribution variations on KES imaging performance. By means of analytical simulations, the reconstructed signal, signal-to-noise ratio, and background contamination were evaluated as a function of the position of each detector pixel. The results show that KES imaging is possible with ICS x-ray beams, even if the image quality slightly degrades at the detector borders for a fixed collimation angle and, in general, as the beam divergence increases. Finally, an approach for the optimization of specific imaging tasks is proposed by considering the characteristics of a given source.

Analytical modelling to study the magnetic field-assisted growth of graphene in the reactive plasma

A theoretical model has been developed to study the impact of a magnetic field on the growth of vertically aligned graphene sheets using plasma deposition techniques. The present model incorporates the dynamics of negatively charged electrons and positively charged ions and active neutral radicals of reactive gases in the complex plasma comprising Ar, C2H2, and H2 gases and deposition of these gaseous phase plasma species in the form of vertically aligned graphene sheets. The dynamics and deposition of the plasma particles can be controlled or enhanced by various process parameters and use of external magnetic field is one of the most promising way to enhance the deposition of species. In the present work, the growth of vertical graphene in a plasma environment has been studied with and without external magnetic field. The analytical simulations of the developed model revealed the significant enhancement in the growth of vertically aligned graphene sheets when magnetic field is applied in the plasma reactor. Our findings of the analytical simulations are in line with existing experimental observations.