Equivalent Elements Research Articles

A method for converting the existing mechanical zoom optical system to the focus tunable lens zoom optical system

The focus tunable lens (FTL), an emerging device, has brought a new development direction for the research of zoom optical systems, and the zoom lens designed with this lens has more advantages in response speed and mechanical vibration control than the conventional mechanical zoom system. However, there is a relative lack of design methods and computational theories for this type of system at present, and there is a lack of initial structure patents for reference. To solve this problem, this paper proposes a method that can convert the existing conventional mechanical zoom system into an FTL zoom system, and we first introduce the equivalent group element substitution theory for optical systems, then we design a computational screening algorithm for the equivalent FTL group element. We performed an example demonstration to illustrate the details of this method, and we finally obtain one FTL zoom optical system with an F/# of 4, a total length of 120 mm, and an 8 mm image plane. The whole design process is smooth, and the system structure is stable.

Crystal plasticity based homogenized model for lamellar colonies of near-α and titanium alloys

The microstructure of near α and Ti-alloys consists of globular α grains, and transformed β colonies, which have a lamellar structure with alternating α hexagonal close packed and β body centered cubic laths. Due to the disparate length scales between the laths of the colonies and the globular α grains, a homogenized representation of the lath microstructure is necessary for computationally feasible and efficient crystal plasticity (CP) based full-field simulations of polycrystalline aggregates of these alloys. Thus, equivalent models of the lath microstructure based on iso-strain and virtual crystal (consisting of both α and β slip systems) assumptions were developed. However, these models fail to capture the response of the lath aggregate (colony), the individual phases (α and β laths), and slip systems, accurately. The deficiencies in the earlier models have been overcome in the equivalent model developed in this work in which the individual laths are allowed independent iso-stress and iso-strain conditions, while strain compatibility and stress equilibrium of the lath aggregate is ensured by enforcing periodic motion of the laths and traction balance at the interface. Additionally, an anisotropic size dependent CP constitutive model, due to the semi-coherent nature of the lath interfaces, is also developed for the α and β laths in the colony. The improvements of the present model are elucidated by comparing its response with the existing equivalent models and periodic CP finite element method simulations of a lath representative volume element for two different sets of Euler angles and four different deformation histories. The comparisons clearly show that the present model is significantly more accurate than the existing models in predicting the stress–strain response of the lath aggregate and the individual phases, as well as the slip activities on the various systems. The formulation of the developed model is generic and can also be applied to other materials with lamellar microstructure.

Beam based rotordynamics modelling for preloaded Hirth, Curvic and butt couplings

Gas turbine and other machinery rotating assemblies are frequently manufactured as multiple components for cost and component alignment reasons. Butt joint, Hirth, and Curvic coupling are widely used for this purpose. Localized joint flexibility in these preloaded couplings introduce non-beamlike behavior which affects rotordynamic critical speeds, imbalance response and stability, rendering a conventional beam model inadequate. 3D solid finite element models of the couplings with Greenwood Williamson (GW) asperity interface features provide accurate representations of the couplings, however computational costs are impractical for use in an industrial design setting, which are limited to beam element models. A novel modeling approach for the coupling is developed that derives equivalent beam element Young's modulus and shear form factor properties, that replicate the bending behavior of the high fidelity 3D solid models, including GW based interface asperity stiffness. The equivalent beam models for butt, Hirth and Curvic couplings are validated using measured natural frequencies as a benchmark, for a range of through-bolt preloads. The equivalent beam model and the 3D solid model in this correlation incorporate GW contact models derived with experimentally measured surface roughness parameters. An Ecoupling sensitivity study for GW surface roughness parameters was conducted and showed a significant level of sensitivity. The effect of the coupling on an industrial class rotor's critical speed is included to illustrate usage of the approach.

CULTURAL DIFFERENCES INFLUENCE ON LITERARY TRANSLATION

Objective. The objective of the article is to study the components of the influence of cultural differences on literary translation; analyze the problems that arise when translating culturally specific elements and propose methods and strategies used to achieve accuracy and adequacy of literary translation. Methods. The main scientific results are obtained with the help of such methods as the analysis and generalization of scientific and educational and methodological literature on the problems of literary translation; system analysis; combination of cultural and logical methods in research; separation of subsystems of complex objects and their systematic analysis, an integral approach to the study of linguistic phenomena. Results. Based on the latest research, the article provides new ideas and approaches to solving problems related to the rendering of cultural differences in the process of fiction texts translation. The authors emphasize the importance of the dissemination of literary works among the representatives of other cultures, namely: transfer of cultural heritage; increasing the level of intercultural understanding; expanding the audience of recipients; preservation of literary value. Cultural differences require a translator to have a deep understanding and sensitivity to different aspects of culture. This allows us to preserve and transmit not only the linguistic content, but also the wealth of cultural heritage, which is an integral part of artistic works. Therefore, understanding cultural characteristics and context is important for accurate and adequate translation of literary works. The following requirements for this type of translation are noted: accuracy of the transfer of values; adaptation of the cultural context; transfer of nuances and styles; respect for cultural identity. Considerable attention is paid to methods and strategies used to convey cultural information in translation: selection of equivalent cultural elements; explanation and adaptation; specification and generalization; localization; contextual translation. The authors conclude that modern trends and challenges in literary translation require translators to take into account cultural differences, intercultural collaboration, use of new media and the development of cultural sensitivity.

On the modelling of ground-board mounted microphones for outdoor noise measurements

This paper presents a boundary element method for calculating the sound pressure level on and above a ground-board placed on an infinite ground plane with constant impedance. This method uses the Green's function for the Helmholtz equation in a half-space bounded by an infinite impedance plane and therefore avoids the complications which occur when modeling the ground as a finite impedance plane (which results in diffraction from the edges of the ground plane). Two formulations are presented: the first one models a finite thickness ground-board, whilst the second one models a zero-thickness ground-board with the upper surface coplanar with the ground plane. The method is validated against an equivalent finite element method simulation and example calculations are presented for typical ground-board designs used for outdoor noise measurements on different ground impedance planes and incidence angles. It is shown that the sound pressure level on the upper surface of a ground-board placed on a non-rigid ground can vary significantly and that this variation is dependant on the ground impedance, angle of incidence and frequency. These findings are consistent with previous investigations and highlight the fact that noise measurements made using ground-board mounted microphones on a non-rigid ground are dependant on the impedance of the surrounding ground surface. The method presented in this paper could be used to develop corrections to straightforwardly account for this effect.

Near-field vibration induced by single-hole blasting under different initiation modes

In drilling and blasting, initiation modes determine the propagation direction of detonation wave, which affects the distribution of blast vibration field. In this study, the near-field distribution characteristics of peak particle velocity (PPV) induced by different initiation modes were obtained based on the solution model of the Heelan equivalent elements. The influence law of the initiation mode on the transmission of explosion energy was determined. Through onsite single-hole blasting experiments, the PPV resulting from different initiation modes, such as top initiation, bottom initiation, midpoint initiation, and two-point initiation, were compared and analyzed. The influence of the initiation mode on the transmission of explosion energy was also discussed. The results revealed that the PPV are positively proportional to the blasting load amplitude and the charge length, but inversely proportional to the duration and rising time of the blasting load. The PPV induced by the different initiation modes has the following relationship: bottom initiation > midpoint initiation > two-point initiation > top initiation. The effect of initiation mode on PPV gradually decreased with increasing distance from the blasting centre.

Effect of tuning of charge defects by K, Ba, La doping on structural and electrical behaviour of NaNbO3

The aim of this study is to highlight the impact of monovalent, divalent and trivalent substitutions on structural, and electrical properties. Creation of defects and its impact on phase transition behaviour reflected in dielectric properties makes it more interesting. Compositions (x) in the material system Na1-xAxNbO3 (where, x = 0.0 abbreviated as S0, and x = 0.05 for K1+, Ba2+, and La3+ doped samples abbreviated as S1, S2, and S3 respectively) are prepared by the conventional solid-state reaction method. Rietveld refinement of diffraction data has confirmed single-phase formation with an orthorhombic structure having Pbcm space group symmetry. FTIR spectra show the shifting of vibrational modes towards higher wave number sides with increasing valence states of dopants. SEM images of these samples show a decrease in average grain size for S1, S2, and S3, respectively. Dielectric plots from room temperature to 773K at 1 kHz, 10 kHz, and 100 kHz for x = 0.0 have shown two prominent anomalies, one at 404K and the other one at 610K. The low-temperature anomaly has disappeared in samples S1, S2, and S3, whereas the high-temperature sharp anomaly at 610K for sample S0 has shifted to 618K for sample S1 and vanished for samples S2 and S3. Tanδ with temperature plots show two anomalies for samples S0, S1, and S2, whereas for S3, only one broad anomaly is observed. Conductivity has been found to increase with doping through the equivalent concentration of iso-valent K1+ and graded off-valent Ba2+ and La3+ cations. Impedance analysis has proposed an electronic circuit model containing two parallel equivalent RC elements.

End diaphragm and interior cross frame modeling in steel tub girder superstructures

Composite steel tub girders are proven to be an economical choice for long span bridges. However, detailed analysis of such superstructures requires extensive Finite Element (FE) modeling that includes many internal and external diaphragms. This paper is an attempt to study diaphragms and interior cross frames in tub girders and present simplified FE modeling details for the tub girder superstructures under gravity and seismic loadings incorporating accurate end diaphragm and interior cross frame stiffness equations. The simplified model is applicable to design of new tub girder bridges as well as load rating, health monitoring and retrofitting of existing bridges which require more sophisticated models. To this end, first a parametric study using 18 different FE models was carried out to better understand the behavior of tub girder superstructure and its components such as end diaphragms, the composite concrete deck and interior cross frames. Second, the stiffness equations for the end diaphragms and interior cross frames were derived analytically. These were associated with equivalent beam elements, which were used in combination with girder/deck elements to arrive at the simplified model. The resultant FE modeling was validated against detailed 3D FE models under gravity and seismic loads as well as the fundamental modes of vibration. Results indicated that the modeling approach is able to efficiently simulate different component behaviors and estimate the static and dynamic demands on the girders with remarkable accuracy.

A novel gas spring based negative stiffness mechanism for seismic protection of structures

The integration of negative stiffness (NS) elements in the concept of seismic base isolation constitutes an innovative and highly effective approach for ensuring the safety of structures against the damaging effects of earthquakes. With these isolators, the system’s natural frequency is significantly decreased and thus the transmissibility of seismic forces for all the frequencies above the natural one is reduced. The KDamper is such a representative device that has been implemented in many types of structures improving their dynamic performance due to its superior damping and isolation properties. This study investigates the performance of a variant of the KDamper, referred to as SBA (Seismic Base Absorber), which is equipped with a novel NS element. The SBA combines an extended version of the KDamper with a parallel-connected inerter used to further decrease the structure’s natural frequency without reducing its static stiffness. The NS element of this device is selected to be realized with a modified Scott-Russell mechanism with an extension link that is connected through a revolute joint with a vertical pre-compressed gas spring. This configuration enables the NS element to keep the pre-tension of the spring internally without transmitting it to the superstructure. Additionally, the gas springs provide high and undiminished values of NS in the entirety of motion and are capable of supporting heavy oscillating structural masses without running into issues like buckling or yielding, unlike the conventional compression springs. The performance of the SBA equipped with this NS element is evaluated through numerical simulations both in frequency and time domains, considering a single degree of freedom (SDOF) system and having as excitation input 30 artificial and 20 real accelerograms. To draw the necessary conclusions these simulations are also conducted for a conventional and a highly damped base isolation system as well as a linear SBA system. In addition, a comparative analysis is performed between the proposed NS element and an equivalent element that incorporates linear springs. The results highlight the effectiveness of the SBA in reducing the maximum dynamic responses and the superiority of gas springs over the linear ones in terms of stability and feasibility of the system.

A Coaxial Pulsed Plasma Thruster Model with Efficient Flyback Converter Approaches for Small Satellites

Pulsed plasma thrusters (PPT) have demonstrated enormous potential since the 1960s. One major shortcoming is their low thrust efficiency, typically <30%. Most of these losses are due to joule heating, while some can be attributed to poor efficiency of the power processing units (PPUs). We model PPTs to improve their efficiency, by exploring the use of power electronic topologies to enhance the power conversion efficiency from the DC source to the thruster head. Different control approaches are considered, starting off with the basic approach of a fixed frequency flyback converter. Then, the more advanced critical conduction mode (CrCM) flyback, as well as other optimized solutions using commercial off-the-shelf (COTS) components, are presented. Variations of these flyback converters are studied under different control regimes, such as zero voltage switching (ZVS), valley voltage switching (VVS), and hard switched, to enhance the performance and efficiency of the PPU. We compare the max voltage, charge time, and the overall power conversion efficiency for different operating regimes. Our analytical results show that a more dynamic control regime can result in fewer losses and enhanced performance, offering an improved power conversion efficiency for PPUs used with PPTs. An efficiency of 86% was achieved using the variable frequency approach. This work has narrowed the possible PPU options through analytical analysis and has therefore identified a strategic approach for future investigations. In addition, a new low-power coaxial micro-thruster model using equivalent circuit model elements is developed.This is referred to as the Carlow–Stuttgart model and has been validated against experimental data from vacuum chamber tests in Stuttgart’s Pulsed Plasma Laboratory. This work serves as a valuable precursor towards the implementation of highly optimized PPU designs for efficient PPT thrusters for the next PETRUS (pulsed electrothermal thruster for the University of Stuttgart) missions.

Modeling and Analysis of Spike Signal Sequence for Memristor Crossbar Array in Neuromorphic Chips

This paper presents the efficient systematic methods for modeling and analysis of spike signal sequence in crossbar arrays for neuromorphic computing chips. A novel spike signal sequence is proposed, where the ideal spike sequence with only spike time information in the original spiking neural network (SNN) algorithm is mapped onto actual spike waveform by stitching neighboring sequential spikes together with certain overlaps. We thoroughly investigate and analyze the performance of the input encoding as well as the implementation of spike timing dependent plasticity (STDP)-based SNN on memristor crossbar arrays with the proposed spike signal sequence. A detailed circuit model of a crossbar array, consisting of resistance, capacitance and inductance derived by the partial equivalent element circuit (PEEC) method, is created to simulate the training process of SNN. The proposed spike signal sequence is demonstrated that is able to achieve accurate input encoding as well as high recognition accuracy when it is used to perform the classification task on MNIST handwritten digits. The spike signal sequence is further analyzed and assessed in terms of the main factors affecting its encoding accuracy and the parasitic effects of crossbar arrays on its robustness.

Research on Electromagnetic Vibration Characteristics of a Permanent Magnet Synchronous Motor Based on Multi-Physical Field Coupling

Background and Purpose: The stator vibration characteristics are comprehensively mastered by considering the influence of winding and the housing structure on the stator modes. This effect is neglected in the research field of electromagnetic vibration of permanent magnet synchronous motors (PMSMs). Methods: The radial air-gap flux density equations and PMSM’s electromagnetic force density are derived, and then the harmonic characteristics of electromagnetic force density are studied. An equivalent finite element model of the stator is proposed that investigates the impacts of the winding and stator housing rules on the stator modal frequency. Finally, the harmonic response and acoustic analyses of electromagnetic vibration are carried out based on multi-physics field coupling. Results: The equivalent radiated power distribution laws and acoustic field of motor electromagnetic vibration under transient operating conditions are obtained. The theoretical analysis results are consistent with the experimental results. Conclusion: The obtained results show that the spatial order of the radial electromagnetic force is not equal to the order of the radial mode of the motor stator. The reason for this is that structural resonance is induced when the frequency components of the spatial radial electromagnetic force are coupled with the intrinsic frequency of the stator.

An equivalent line element approach for free surface flow through two-dimensional rock mass including fracture networks

In this paper, an equivalent line element method is established to analyze seepage problems with free surface through two-dimensional rock mass, including fracture networks. Low-permeablity rock matrix is characterized by the line elements as well as the high-permeablity fracture networks. Unlike the conventional equivalent continuum model, water flow in a rock mass is restricted to the line elements, and the equivalent hydraulic conductivity is determined according to Darcy's law and flux equivalence principle. As a result, uniform expressions of governing equations and boundary conditions are formulated, and the corresponding numerical procedure is developed by introducing the local coordinate and continuous Heaviside function. Satisfactory agreements with the existing test and numerical data verify this proposed line element method. The numerical solutions on the fractured slope indicate that the geological features of fractures have a substantial effect on locating the free surface. In addition, the proposed line element method can efficiently achieve accurate results with less computing time, iteration, and storage.

Research on a high-frequency unfilled layered symmetrical piezoelectric material with a high effective electromechanical coupling coefficient

As the demand for high-performance hydrophones for marine communication systems grows, this paper develops a high-frequency unfilled layered symmetrical piezoelectric material with high effective electromechanical coupling coefficient. The vibration mode of piezoelectric material is converted into vibration mode of the piezoelectric pillar to improve the effective electromechanical coupling coefficient of the material. The material is determined by the equivalent circuit method and ANSYS finite element simulation method. Test results show that the resonant frequency is 117.8 kHz and the effective electromechanical coupling coefficient is 0.67, which shows that the developed material has a good electromechanical conversion performance.

A Front-End CMOS Interface Circuit With High Voltage Charge Pump and Oscillator for Capacitive Micromachined Ultrasonic Transducers

Label-free biosensors, combined with miniaturized micro-electromechanical sensory platforms, offer an attractive solution for real-time and facile monitoring of biomolecules due to their high sensitivity and selectivity without the need for specifically labeling. Resonators have been acknowledged as an efficient technology for measuring biomolecular binding events including those involving nucleic acid and antibody. Among these, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as a promising candidate for biosensing. However, their usage is often limited by the requirement for high voltage supply and continuous frequency tracking, which can result in significant parasitic effects and measurement errors. In this paper, we present a novel front-end interface circuit for a CMUTs-based biosensor. The circuit, fabricated using TSMC 0.18-μX;Jm Bipolar-CMOS-DMOS (BCD) technology, incorporates an on-chip high voltage charge pump and feedback frequency monitoring. The CMUTs array features 20×20 circular cells, fabricated using a low-temperature direct bonding technology, with an experimental parallel-resonant frequency of 1.724 MHz and a high quality factor of up to 40.9. To fit the measured electrical characteristics, a five-element equivalent lumped element model is proposed. The high voltage charge pump provides an output voltage of 20 V, while the feedback oscillator has a ms-level start-up time and a total power dissipation of 3.8 mW. The proposed front-end interface is designed to function as a stand-alone chip for CMUTs-based resonant biodetection.

Seismic performance of RC frame structure across the earth fissure based on pushover analysis

This study aims to investigate the seismic performance and failure mechanism of reinforced concrete frame structures across the earth fissure. A five-story reinforced concrete frame structure across the earth fissure was tested by shaking table and the test equivalent finite element model was established by simulation software, the seismic performance of the reinforced concrete frame structure across the earth fissure was carried out and analyzed by these two methods. The results showed that the earth fissure has an amplification effect on the structure displacement response, the damage indexes and internal forces of the structure across the earth fissure were always larger than the structure on the ordinary site. The maximum damage index deviation increases from 6.1% to 11.4% under 0.2 g and 0.4 g seismic waves, and the maximum axial and shear forces deviation of column increases from 29% to 50% and 11.7% to 15.2% during 0.2 g to 0.6 g Cape Mendocino waves, respectively. With the increase of seismic intensity, the deviation of damage indexes and internal forces increased. The damage to the structure of the hanging wall were earlier and more seriously, and the first floor was the most vulnerable floor. The research in this paper has practical significance for seismic performance evaluation and provides reference for reinforced concrete frame structure across the earth fissure seismic design.

Extended multiscale isogeometric analysis for mechanical simulation of two-dimensional periodic heterogeneous materials

Periodic heterogeneous material (PHM) is widely used in the design of multi-functional composite structures. Embedded particles or void holes with smooth boundaries are common in PHM, and the simulation of such material needs novel multiscale simulation method. Thus, extended multiscale isogeometric analysis (EmsIGA) is developed for the mechanical analysis of planar PHM, particularly for heterogeneous materials with smooth inclusions or voids. The non-uniform rational B-spline basis function is used for geometrical description and also mechanical simulation of the fine-scale unit cells to obtain numerical heterogeneity function. By calculating the numerical heterogeneity function as a static basis function, the equivalent element stiffness matrix of the sub-grids in the coarse scale is obtained and the structural problem can be solved. Downscaling computation is applied to obtain the stress and strain of the structure. Numerical examples validate the efficiency and accuracy of the proposed EmsIGA method in the simulation of heterogeneous structures. Compared with the results of the traditional and multi-scale finite element method, the proposed method can precisely capture the geometry and concentrated stress state of the smooth inclusions and calculate the microscopic stress and strain with improved efficiency.

Effects of equivalent composition on superconducting properties of high-entropy REOBiS2 (RE = La, Ce, Pr, Nd, Sm, Gd) single crystals

Superconductors are influenced by high-entropy alloys (HEAs); these have been investigated in various functional materials. REOBiS2 (RE = La, Ce, Pr, Nd, Sm, and Gd in different combinations) single crystals with HEAs at the RE-site were successfully grown using the flux method. The obtained crystals were plate-shaped (∼1 mm2) with a well-developed c-plane. Ce was present in both trivalent (Ce3+) and tetravalent (Ce4+) electronic configurations; the concentration of Ce4+ at the RE-site was approximately 10 at% in all single crystals. The single crystals showed superconducting transition temperature with zero resistivity within 1.2–4.2 K. The superconducting transition temperature, superconducting anisotropy, electronic specific heat coefficient, and Debye temperature of the crystals were not correlated with the mixed entropy at the RE-site. Except for the electronic specific heat coefficient, the variation of these parameters as a function of mixed entropy showed different trends for equivalent and non-equivalent RE element compositions. Thus, the configuration of RE elements influences the superconducting properties of REOBiS2 single crystals, alluding to a method of modulating transition temperatures.

Single-track thermal analysis of laser powder bed fusion process: Parametric solution through physics-informed neural networks

Modelling the highly localised and rapid phenomena occurring during metal additive manufacturing (MAM) processes such as the laser powder bed fusion (LPBF) demands the adoption of very fine time- and space-discretisation and therefore high computational cost for the classical simulation approaches, namely the finite element method (FEM). Particularly, when the solution is required for a range of scenarios, e.g. in sensitivity or optimisation analyses, computation costs of such simulations are not affordable. As an alternative strategy, this study explores the application of physics informed neural networks (PINNs) as a low-cost physics-based simulation approach for the thermal analysis of the LPBF process, through which reliable transient and steady-state temperature profiles for single-track LPBF depositions are achieved. An unsupervised learning strategy is employed for PINNs to parametrically solve the heat transfer equation for the LPBF process. The trained PINNs calculate the temperature profiles and the melt-pool dimensions evolving during the LPBF process for any given set of material’s thermal properties and process conditions at practically zero computational cost. The reliability of the PINNs outcomes is verified through ground-truth data generated based on several benchmark equivalent finite element simulations.

A modified conductive network used to characterize the conductivity of carbon fibre reinforced polymers in eddy current testing

Carbon fibre reinforced polymers (CFRPs) are prone to various defects during production and service due to their special composite structures. These defects alter the electrical properties of CFRPs, so they are often be analyzed by eddy current testing (ECT). However, owing to the low conductivity of CFRPs, ECT must operate at high frequencies. And the conductivity mechanism of CFRPs at high frequencies is more complex than that at low frequencies, which makes the electrical properties of CFRPs difficult to be determined. Based on the conductivity characteristics of unidirectional CFRP laminates under high-frequency excitation, a modified conductive network model and a unique non-destructive calibration method are proposed in this paper. By introducing density characteristic parameters of equivalent impedance element, the analytical relationship between characteristic parameters and transverse conductivity of CFRPs is established in the proposed model. And the impedance parameters of CFRPs specimens are calibrated by eddy-current induction experiment and Monte Carlo method. The experimental results show that the proposed model is more accurate than the traditional tensor conductivity model in determining the conductivity characteristics of CFRPs at high frequencies. In addition, the proposed method can effectively determine the internal conductive elements of unidirectional CFRP laminates with different fabrication processes.