Established Analytical Models Research Articles

Product Development Methodology Targeting Efficiency and Acoustics of E-Mobility Gearboxes

This paper presents an approach for physical/virtual coupled product development and validation. A method for studying the influence of tooth geometry on the efficiency and acoustics of an electric vehicle’s powertrain will be presented. To achieve improved acoustic characteristics the micro geometry of the teeth will be optimized. The modified gears were analysed on a gear test rig under load and at high speeds and evaluated with regard to their acoustic properties. Established analytical models are used to describe the influence of profile modifications on the gear stiffness of helical gears. The authors’ approach is to calculate the dynamic system behaviour of the gearbox using a 1D simulation. Based on this, studies of the entire gear box will be performed. For this, the results of the 1D simulation are coupled with 3D FEA analyses. This enables acoustic calculations (structure-borne and airborne sound) to be carried out.

A Methodology for the Preliminary Design of a High-Efficiency Multistage Plasma Thruster

Space electric propulsion represents a class of power-limited systems that utilize the interaction of electromagnetic fields with ionized inert gas propellants to generate thrust. This technology has emerged as a highly fuel-efficient and sustainable alternative to chemical propulsion systems, particularly for satellite constellations. However, the miniaturization potential of EP systems is impeded by certain limitations, necessitating the exploration of novel architectures. The high-efficiency multistage plasma thruster (HEMP-T) stands as a promising contender for stand-alone missions due to its employment of a cusped magnetic-field topology, which effectively mitigates plasma-wall interactions and enhances overall efficiency even at low thrust levels. Despite the growing interest in HEMP-Ts, there is a dearth of comprehensive and streamlined preliminary design procedures for these systems. Prior research has predominantly focused on extensive numerical analyses, neglecting the development of efficient and accessible design tools. To bridge this gap, this paper presents a novel preliminary design tool derived from integrating established analytical models available in the literature. The proposed design tool also incorporates an iterative procedure that refines geometric properties using a 2D magnetostatic solver. Through the application of this tool, a 4 mN HEMP thruster was analyzed. This finally exhibited a specific impulse of approximately 2000s and a good efficiency level of 23%. Also, the results obtained for a 10 mN application align closely with those achieved by other types of EP thrusters.

Instantaneous Loss Integration Method to Estimate AC Losses in Superconductors With Spatial and Time Harmonics

Estimating AC loss is an essential step in designing fully superconducting (SC) machines, which typically involves using analytical and Finite Element Analysis (FEA) models. Established analytical models are available for stationary sinusoidal and uniform rotating fields. But, the fully SC armature winding experiences a non-uniform rotating magnetic field that can result in varying losses. In this paper, we propose extended analytical methods to estimate AC losses in non-uniform rotating magnetic fields. Our proposed methods can refine the AC loss estimation process and improve the subsequent cryogenic load design. The significant advantage of our proposed method is the ability to capture the impact of AC losses due to varying field magnitude within a single cycle. We estimate losses for various scenarios and compare them to FEA analysis results to verify the accuracy of our model. We then experimentally validate the FEA models used in the analysis for uniformly rotating fields, which establishes the feasibility of our proposed models.

Diffusion least mean kurtosis algorithm and its performance analysis

Adaptive filtering algorithms developed by using the negated kurtosis of the error signal as cost function can obtain good performance in some types of sub-Gaussian noise environments. This work extends the least mean kurtosis (LMK) algorithm to a diffusion network scenario to address the distributed estimation problem. To evaluate its stochastic behavior, we analyze the transient performance using Isserlis' theorem under some statistical assumptions. In addition, the theoretical steady-state performance indicators are also derived in closed form. Our established analytical models are also applicable to the diffusion least mean fourth (DLMF) algorithm which is a special case of our proposed diffusion LMK (DLMK) algorithm. The analytical models are more universal and reliable than the existing models in the literature. Simulation results are provided to show the superiority of DLMK and to corroborate our theoretical development of transient and steady-state performance.

Development of a Sinusoidal Corrugated Dual-Axial Flexure Mechanism for Planar Nanopositioning

Taking advantage of the concurrent stretching and bending property of corrugated flexure hinges, a sinusoidal corrugated flexure linkage was proposed and applied for the construction of a corrugated dual-axial mechanism with structural symmetry and decoupled planar motion guidance. Castigliano’s second theorem was employed to derive the complete compliance for a basic sinusoidal corrugated flexure unit, and matrix-based compliance modeling was then applied to find the stiffness of the sinusoidal corrugated flexure linkage and the corrugated dual-axial mechanism. Using established analytical models, the influence of structural parameters on the stiffness of both the corrugated flexure linkage and the dual-axial mechanism were investigated, with further verification by finite element analysis, with errors less than 20% compared to the analytical results for all cases. In addition, the stiffness of the corrugated flexure mechanism was practically tested, and its deviation between practical and analytical was around 7.4%. Further, the feasibility of the mechanism was demonstrated by successfully applying it for a magnetic planar nanopositioning stage, for which both open-loop and closed-loop performances were systematically examined. The stage has a stroke around 130 μm for the two axes and a maximum cross-talk less than 2.5%, and the natural frequency is around 590 Hz.

Experimental characterization and analytical assessment of compressive behavior of carbon nanofibers enhanced UHPC

With superior mechanical and durability properties, ultra-high performance concrete (UHPC) is making strides towards revolutionizing concrete structures and the construction industry. Even though UHPC is widely known, it is still used only in small-scale elements. Recently, more advanced commercial and non-proprietary UHPC mixtures, e.g., nano-enhanced UHPC, have emerged timely to support a rapidly growing market and increased interest in expanding UHPC applications to full structural components. Thus, there is a need to comprehensively characterize the mechanical properties of such emerging mixtures using more experimental data and assess how such mixtures compare to traditional UHPC. This paper focuses on the uniaxial compression behavior of carbon nanofibers (CNF) enhanced UHPC. The literature is currently lacking any data on the combined effects of steel fibers and traditional reinforcement confinement in CNF-enhanced UHPC. The objective of this study is to experimentally characterize and analytically assess the uniaxial compressive behavior of CNF-enhanced UHPC at different ages and with varying steel fibers content and confinement reinforcement. In this study, more than 230 cylinders with 0–4 % varying steel fiber ratio and 0–4 % varying steel spiral confinement ratio were tested. Experimental results of the CNF-enhanced UHPC cylinders were assessed using established analytical models for traditional UHPC for Young's modulus and confinement effects on both stress and strain. The study first demonstrates that using accelerator in UHPC mixtures can help achieve about 80 % of the 28-day-strength only in three days after casting. Overall, the results suggest that the combined effect of steel fibers and steel spirals increases the ductility of CNF-enhanced UHPC relative to traditional UHPC. The study also concludes that current analytical models do not precisely capture the compressive and confinement behavior of this emerging type of UHPC.

Rigorous single-period micromagnetic model of stripe domains: Comparison with analytics and experiment

Stripe domains in thin films form through a complex competition of perpendicular anisotropy and demagnetizing energy and are still lacking a complete micromagnetic description, despite being investigated since 50 years. This paper elucidates the formation of stripe domains with a special focus on the dependence of stripe domain width on film thickness with varying ratio of the two major energy contributions. An overview and review of the most established analytical models for the calculation of this dependency is given with respect to experimental data. For this purpose, new measurements on epitaxial Fe-Co-C films with perpendicular anisotropy have been performed. An efficient and rigorous micromagnetic simulations method is proposed, which proved to be comparable or better than previous models in describing experimental findings, especially for films with strongly dominating demagnetizing energy. Comprehensive simulations were performed to determine thickness-dependent stripe width for various material parameters, which can serve as a benchmark for analytical theories or can be used directly for comparison with experimental results. At a given combination of exchange constant and saturation polarization there exists a specific thickness at which the stripe width is independent of the uniaxial anisotropy.

Modelling of FRP and FRCM-Confined Masonry Columns: Critical Review for Design and Intervention Strategies

This paper presents a critical review of the most established analytical models for the prediction of the compressive strength of FRP and FRCM-confined masonry columns. In particular, two types of fibres are analysed, i.e. glass and basalt. A wide dataset available in the literature is used for the application of the analytical models and for the development of parametric analyses useful for the critical comparison of FRP vs. FRCM confinement technique and glass vs. basalt fibres to be adopted as reinforcement of masonry substrate. The effects of stiffness and strength of the reinforcement, the number of reinforcing layers, the compressive strength of masonry and the cross-section shape are investigated.

Seismic evaluation and rehabilitation of G+1 corroded RC building

Reinforcing steel corrosion is one of the major cause of degradation in Reinforced Concrete (RC) construction. Corrosion is caused by the processes of carbonation and chloride attack, which results in a reduction in the structural performance of structures over time. The time-dependent corrosion process has an impact on structure safety and serviceability, and it can even lead to progressive failure. Corrosion causes reinforcing bar diameter reductions, concrete fissures, concrete cover expulsion, concrete and steel strength reductions, and the breakdown of the link between the concrete and imbedded steel. When it comes to multistory concrete buildings, corrosion is a considerably bigger issue in terms of seismic performance. As a result, accurately assessing and establishing the current corrosion degree of structural parts, as well as evaluating the local and global seismic capacity of existing corroded RC buildings, has been a major challenge around the world. The current study used a methodology in which revised properties were applied for seismic evaluation and establishing the correct restoration scheme for existing two-story RC framed buildings based on non-destructive and destructive material site as well as laboratory testing. The findings of linear seismic analysis and non-linear static pushover analysis for sound, corroded, and retrofitted buildings have been compared and analyzed and a new corrosion evaluation model is being proposed based on NDT (Non-Destructive Testing) and other established analytical models.

Stiffness analysis of a planar parallel manipulator with variable platforms

This work investigates the stiffness characteristics of a planar parallel manipulator with variable platforms. The stiffness model is established with shape variables of the base and mobile platforms based on the Jacobian matrix. By virtue of a nondimensionalization of the inhomogeneous stiffness matrix, two homogeneous submatrices are obtained. Upon which, two kinds of performance indices are derived to evaluate the manipulator’s stiffness behaviors, one for translation and the other for rotation. Stiffness performance of the considered manipulator with three types of platforms, namely variable base platform, variable mobile platform and both variable base and mobile platforms, is analyzed. To validate the stiffness models, the established analytical models are compared with the FEA based evaluations. In order to find the configurations with the best global stiffness performance, stiffness optimization with consideration of shape variables is conducted with the particle swarm optimization algorithm. Finally, a case study of platforms’ shape changing in stiffness adjustment is presented.

A simple and robust model for prediction of liquid-loading onset in gas wells

Accurate prediction of liquid loading is of great importance for production optimisation in gas wells. In this paper, the authors present a simple and accurate empirical model based on attached-film reversal for predicting liquid-loading onset in vertical and horizontal gas wells. Unlike established and complicated analytical models based on force balance, this model is developed from the empirical flooding equation by matching the experimental data from previous studies. Further, this model adopts the Belfroid angle-correction term for horizontal gas wells. Compared with the traditional entrained-droplet models, this model considers the effect of pipe diameter and liquid velocity. This study investigated the effect of pressure on the predicted critical gas velocity and scaled up low pressure by comparing some other analytical models. This model was also validated against the experimental data and field data. Results show that the presented model is capable of accurately predicting liquid-loading onset in gas wells. [Received: December 4, 2018; Accepted: December 13, 2019]

Design of composite lattice materials combined with fabrication approaches

Lattice materials can be designed through their microstructure while concurrently considering fabrication feasibility. Here, we propose two types of composite lattice materials with enhanced resistance to buckling: (a) hollow lattice materials fabricated by a newly developed bottom-up assembly technique and the previously developed thermal expansion molding technique and (b) hierarchical lattice materials with foam core sandwich trusses fabricated by interlocking assembly process. The mechanical performance of sandwich structures featuring the two types of lattice cores was tested and analyzed theoretically. For hollow lattice core material, samples from two different fabrication processes were compared and both failed by nodal rupture or debonding. In contrast, hierarchical lattice structures failed by shear buckling without interfacial failure in the sandwich struts. Calculations using established analytical models indicated that the shear strength of hollow lattice cores could be optimized by judicious selection of the thickness of patterned plates. Likewise, the shear strength of hierarchical foam core truss cores could be maximized (with minimal weight) through design of truss geometry. The bottom-up assembly technique could provide a feasible way for mass production of lattice cores, but the design about how to assembly is critical. Hierarchical lattice cores with foam sandwich trusses should be a suitable choice for future lightweight material application.

A centrifuge-based experimental verification of Soil-Structure Interaction effects

A series of prototype dynamic centrifuge experiments is carried out to investigate the influence of soil properties and structural parameters on the Soil Structure Interaction (SSI) effect. Established analytical models are herein experimentally verified, and are proven accurate in estimating the system's natural frequency characteristics. It is observed that period elongation is strongly correlated to the relative superstructure-foundation stiffness. Although the present study deals exclusively with the small-strain near-linear range, the experimental response indicates occurrence of nonlinearity. The identified damping results remarkably larger than its analytical estimate and proves highly strain-dependent, raising questions on the reliability of existing analytical methods in capturing the actual dissipation mechanisms. An extended experimental dataset is formed under realistic stress and strain soil conditions, and is implemented, for the first time, for verification of existing analytical models offering valuable insight into the theory and serving as a benchmark for engineering practice.

Theoretical and experimental evaluation of the effects of an argon gas mixture on the pressure drop through adult tracheobronchial airway replicas

Argon has the potential to be a novel inhaled therapeutic agent, owing to the neuroprotective and organoprotective properties demonstrated in preclinical studies. Before human trials are performed, an understanding of varying gas properties on airway resistance during inhalation is essential. This study predicts the effect of an 80% argon/20% oxygen gas mixture on the pressure drop through conducting airways, and by extension the airway resistance, and then verifies these predictions experimentally using 3-D printed adult tracheobronchial airway replicas.The predicted pressure drop was calculated using established analytical models of airway resistance, incorporating the change in viscosity and density of the 80% argon/20% oxygen mixture versus that of air. Predicted pressure drop for the argon mixture increased by approximately 29% compared to that for air. The experimental results were consistent with this prediction for inspiratory flows ranging from 15 to 90slpm. These results indicate that established analytical models may be used to predict increases in conducting airway resistance for argon/oxygen mixtures, compared with air. Such predictions are valuable in predicting average patient response to breathing argon/oxygen mixtures, and in selecting or designing delivery systems for use in administration of argon/oxygen mixtures to critically ill or injured patients.

Sociologia política e processos macro-históricos

Neste artigo, parto de uma breve exposição sobre algumas das muitas maneiras de se fazer sociologia política, para ilustrar a diversidade da área. Em seguida, comento uma dessas várias abordagens - aquela que privilegia as análises macro-históricas, salientando a preferência dessa perspectiva pela observação de grandes processos de transformação. Por fim, adotando essa mesma opção, discuto algumas das transformações em curso para sugerir que elas colocam desafios teóricos e metodológicos consideráveis para a sociologia política. Reconhecendo que os desafios em questão se colocam para além dela e, efetivamente, interpelam todas as ciências sociais, argumento que a justificativa para meu exercício é a convicção de que a sociologia política macro histórica é especialização vocacionada a refletir sobre tais transformações e a lançar luz sobre a obsolescência de certos esquemas analíticos consagrados pela tradição sociológica.

Design of a Large-Range Compliant Rotary Micropositioning Stage With Angle and Torque Sensing

This paper presents the design, modeling, and experimental testing of a flexure-based compliant rotary micropositioning stage with a large rotational range. The rotary stage is devised based on multistage compound radial flexures. One uniqueness lies in that it owns both a compact size and a large rotary stroke. Dominant parameters of the stage are determined based on established analytical models to cater for the requirements on rotational angle and driving torque. These models are verified by conducting finite-element analysis simulations, which also demonstrate the stage performance. A prototype rotary stage is developed using a rotary voice coil motor. A strain-gauge sensor is designed to measure both rotational angle and experienced torque of the rotary stage. The sensitivities of the two-role sensor are derived analytically and calibrated experimentally. Results show that the developed stage is capable of rotary positioning with a resolution of 20 μrad over the range of 10° under an approximately infinite fatigue-life, while keeping a compact physical size. The torque sensor exhibits a resolution of 0.128 mN-m with a measuring range of 1.23 N-m. Moreover, the reported idea can be extended to the design of multiaxis rotary stage.

Accuracy of travel time distribution (TTD) models as affected by TTD complexity, observation errors, and model and tracer selection

AbstractAnalytical models of the travel time distribution (TTD) from a source area to a sample location are often used to estimate groundwater ages and solute concentration trends. The accuracies of these models are not well known for geologically complex aquifers. In this study, synthetic data sets were used to quantify the accuracy of four analytical TTD models as affected by TTD complexity, observation errors, model selection, and tracer selection. Synthetic TTDs and tracer data were generated from existing numerical models with complex hydrofacies distributions for 1 public‐supply well and 14 monitoring wells in the Central Valley, California. Analytical TTD models were calibrated to synthetic tracer data, and prediction errors were determined for estimates of TTDs and conservative tracer ( ) concentrations. Analytical models included a new, scale‐dependent dispersivity model (SDM) for two‐dimensional transport from the water table to a well and three other established analytical models. The relative influence of the error sources (TTD complexity, observation error, model selection, and tracer selection) depended on the type of prediction. Geological complexity gave rise to complex TTDs in monitoring wells that strongly affected errors of the estimated TTDs. However, prediction errors for and median age depended more on tracer concentration errors. The SDM tended to give the most accurate estimates of the vertical velocity and other predictions, although TTD model selection had minor effects overall. Adding tracers improved predictions if the new tracers had different input histories. Studies using TTD models should focus on the factors that most strongly affect the desired predictions.

Cavitation in Block Copolymer Modified Epoxy Revealed by In Situ Small-Angle X-Ray Scattering.

Simultaneous small-angle X-ray scattering (SAXS) and tensile experiments were performed on epoxies modified with approximately 30 nm diameter rubbery and glassy core block copolymer micelles. The in situ SAXS data, interpreted using established analytical models, reveals efficient and coherent cavitation of the spherical rubbery cores coincident with yielding and absence of cavitation in the glassy nanodomains. These results are quantitatively anticipated by recent theory that accounts for cavitation in rubber toughened plastics as a function of particle size.

WASI-2D: A software tool for regionally optimized analysis of imaging spectrometer data from deep and shallow waters

An image processing software has been developed which allows quantitative analysis of multi- and hyperspectral data from oceanic, coastal and inland waters. It has been implemented into the Water Colour Simulator WASI, which is a tool for the simulation and analysis of optical properties and light field parameters of deep and shallow waters. The new module WASI-2D can import atmospherically corrected images from airborne sensors and satellite instruments in various data formats and units like remote sensing reflectance or radiance. It can be easily adapted by the user to different sensors and to optical properties of the studied area. Data analysis is done by inverse modelling using established analytical models. The bio-optical model of the water column accounts for gelbstoff (coloured dissolved organic matter, CDOM), detritus, and mixtures of up to 6 phytoplankton classes and 2 spectrally different types of suspended matter. The reflectance of the sea floor is treated as sum of up to 6 substrate types. An analytic model of downwelling irradiance allows wavelength dependent modelling of sun glint and sky glint at the water surface. The provided database covers the spectral range from 350 to 1000nm in 1nm intervals. It can be exchanged easily to represent the optical properties of water constituents, bottom types and the atmosphere of the studied area.

Fabrication and Preliminary Results for LiGA Fabricated Nickel Micro Gas Chromatograph Columns

High aspect ratio nickel microfluidic columns were fabricated using the LiGA technique. The 2-m-long 50-mum-wide high aspect ratio columns will be the separation component of a handheld gas chromatograph device for detecting semivolatile and volatile compounds. As a first step, 600-mum-deep electrodeposited nickel columns were fabricated. The serpentine columns were sealed and pressure-flow rate characteristics compared with the theoretical values. The response of the sealed columns was studied by running methane gas plugs through uncoated columns with a flame ionization detector at the exit. Negligible flow-induced dispersion was observed in the sealed metal columns. Unretained peak widths of ~15 ms were measured, and the experimental pressure and flow rate distributions matched those predicted by established analytical models within plusmn2.5%. Columns were coated with OV-1 stationary phase using static coating methods. A mixture of four hydrocarbons C6, C8, C10, and C12 was separated in a coated 50 mum by 600 mum by 0.5 m column in less than 2 s at 70 degC