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Articles 13231 - 13260 of 21751
Full-Text Articles in Engineering
Gunn Oscillators Based On Shielded Dielectric Resonators With Mechanical Frequency Tuning, Sergey Kharkovsky, V. I. Lutsenko, I. V. Lutsenko, V. K. Korneenkov, A. E. Kogut
Gunn Oscillators Based On Shielded Dielectric Resonators With Mechanical Frequency Tuning, Sergey Kharkovsky, V. I. Lutsenko, I. V. Lutsenko, V. K. Korneenkov, A. E. Kogut
Electrical and Computer Engineering Faculty Research & Creative Works
The features of Gunn oscillators based on shielded dielectric resonators with whispering gallery modes and ray oscillations are investigated. Their comparative analysis for oscillators with different dielectric resonant structures is carried out.
High Q Shielded Dielectric Resonator -- The Basis Of Stable Mm-Waves Generator, V. V. Kutuzov, Sergey Kharkovsky, V. A. Solodovnik, K. A. Kutuzov
High Q Shielded Dielectric Resonator -- The Basis Of Stable Mm-Waves Generator, V. V. Kutuzov, Sergey Kharkovsky, V. A. Solodovnik, K. A. Kutuzov
Electrical and Computer Engineering Faculty Research & Creative Works
High Q-factor whispering gallery modes which are excited in a shielded hemispherical dielectric resonator by an external signal or Gunn diode are investigated. Their application as modes of an oscillator with high frequency stability is proposed. The power of the output signal and frequency tuning of an oscillator based on the investigated resonator are measured.
Improvement Of Power Quality In Vsi Drives, Badrul H. Chowdhury, Ravi Bantu
Improvement Of Power Quality In Vsi Drives, Badrul H. Chowdhury, Ravi Bantu
Electrical and Computer Engineering Faculty Research & Creative Works
The popular VSI (voltage source inverter) drives in use today are mostly PWM (pulse width modulated) drives. Harmonics produced by these drives cause heat losses, reduce the efficiency of the machine and also cause vibrations in the rotor. Active and passive filters are some of the methods to reduce the harmonics generated by these drives. A novel method is discussed which not only eliminates the 5/sup th/ harmonic but also any other negative sequence harmonics. This method, based on a reactor circuit, shows a reduction in harmonics and an improvement in the efficiency of the machine. The method can also …
Measurement And Monitoring Of Microwave Reflection And Transmission Properties Of Cement-Based Specimens, Sergey Kharkovsky, M. F. Akay, U. C. Hasar, C. D. Atis
Measurement And Monitoring Of Microwave Reflection And Transmission Properties Of Cement-Based Specimens, Sergey Kharkovsky, M. F. Akay, U. C. Hasar, C. D. Atis
Electrical and Computer Engineering Faculty Research & Creative Works
The results of measurement and monitoring of reflection and transmission properties of cement-based specimens (blocks of mortar, concrete) obtained by using a simple and an inexpensive measurement system at microwave frequencies (X-band) are presented. Dependencies of the reflection and transmission coefficients on water-to-cement (w/c) ratio, preparing and curing conditions of the specimens are demonstrated. It is shown that the amplitudes of reflection and transmission coefficients, together with thickness of the specimens, determine the complex dielectric permittivity of the hardened cement-based specimens. The expected applications of the results for the determination of physical properties of cement-based materials are discussed. The causes …
Thermogravimetric Studies Of Pmma On Silica, Bing Zhang, Frank D. Blum
Thermogravimetric Studies Of Pmma On Silica, Bing Zhang, Frank D. Blum
Chemistry Faculty Research & Creative Works
The thermal degradation of poly(methyl methacrylate) (PMMA) has been studied extensively. It is well accepted that the degradation process is a radical chain reaction involving initiation, depropagation, transfer, and termination reactions. In the degradation process, the factors having observable effects on the decomposition behavior include molecular mass, polydispersity, tacticity, and sample dimensions. The effects of tacticity on the degradation behavior of PMMA were investigated by Kashiwagi et al., Jellinek et al. And Chiamtore et al. The results indicated that both isotactic and syndiotactic PMMA have similar decomposition pathways and activation energies. Isotactic PMMA will decompose at a slightly lower temperature …
Multilevel Voltage-Source Duty-Cycle Modulation: Analysis And Implementation, Keith Corzine, J. R. Baker
Multilevel Voltage-Source Duty-Cycle Modulation: Analysis And Implementation, Keith Corzine, J. R. Baker
Electrical and Computer Engineering Faculty Research & Creative Works
Multilevel converters have become increasingly popular due to high power quality, high-voltage capability, low switching losses, and low electromagnetic compatibility concerns. Considering these advantages, the multilevel converter is a suitable candidate for implementation of future naval ship propulsion systems. This paper focuses on modulation techniques for the multilevel converter. In particular, a novel voltage-source method of multilevel modulation is introduced and compared to existing methods. The proposed method is discrete in nature and can therefore be readily implemented on a digital signal processor. The method is also readily extendable to any number of voltage levels. Results of experimental implementation are …
Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani
Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani
Chemistry Faculty Research & Creative Works
The interaction between two polymer layers, especially adhesion between them, plays an important role in polymer processing and other applications. Detailed knowledge of the molecular structure and dynamics of polymer interfaces, and how they relate to macroscopic mechanical properties, should help designers construct more functional systems. Unfortunately, there have been few studies where both molecular and macroscopic studies have been performed on similar systems. In previous studies from our group, we have probed the dynamics of poly(methyl acrylate) (PMA) and thermal behavior of poly(methyl methacrylate) (PMMA) on silica. These studies helped us paint a picture for strongly bound molecules on …
Full Binary Combination Schema For Floating Voltage Source Multilevel Inverters, Xiaomin Kou, Keith Corzine, Yakov L. Familiant
Full Binary Combination Schema For Floating Voltage Source Multilevel Inverters, Xiaomin Kou, Keith Corzine, Yakov L. Familiant
Electrical and Computer Engineering Faculty Research & Creative Works
This paper presents schema of operation for floating voltage source multilevel inverters. The primary advantage of the proposed schema is that the number of voltage levels (and thus power quality) can be increased for a given number of semiconductor devices when compared to the conventional "flying capacitor" topology. However, the new schema requires fixed floating sources instead of capacitors and therefore is more suitable for battery power applications such as electric vehicles, flexible AC transmission systems and submarine propulsion. Alternatively transformer/rectifier circuits may be used to supply the floating sources in a similar way to cascaded H-bridge inverters. Computer simulation …
Agglomerated Lubricant, Mary R. Reidmeyer
Agglomerated Lubricant, Mary R. Reidmeyer
Materials Science and Engineering Faculty Research & Creative Works
A lubricant for use in lubricating the shot sleeve of a machine for die casting molten metals is in the form of agglomerated particles. The particles have an inorganic high pressure lubricant agglomerated, with a binder material and with an organic material. The solid lubricant is resistant to dusting, caking and breakage, can be fed through an automatic dispensing machine, and combines inorganic and organic materials to achieve excellent lubrication properties. The product has low flash and low smoke release into the environment.
Normalized Natural Gradient Adaptive Filtering For Sparse And Nonsparse Systems, Steven L. Grant, S.C. Douglas
Normalized Natural Gradient Adaptive Filtering For Sparse And Nonsparse Systems, Steven L. Grant, S.C. Douglas
Electrical and Computer Engineering Faculty Research & Creative Works
This paper introduces a class of normalized natural gradient algorithms (NNG) for adaptive filtering tasks. Natural gradient techniques are useful for generating relatively simple adaptive filtering algorithms where the space of the adaptive coefficients is curved or warped with respect to Euclidean space. The advantage of normalizing gradient adaptive filters is that constant rates of convergence for signals with wide dynamic ranges may be achieved. We show that the so-called proportionate normalized least mean squares (PNLMS) algorithm, an adaptive filter that converges quickly for sparse solutions, is in fact an NNG on a certain parameter space warping. We also show …
On The Modeling Of A Gapped Power-Bus Structure Using A Hybrid Fem/Mom Approach, Yun Ji, Todd H. Hubing
On The Modeling Of A Gapped Power-Bus Structure Using A Hybrid Fem/Mom Approach, Yun Ji, Todd H. Hubing
Electrical and Computer Engineering Faculty Research & Creative Works
A hybrid finite-element-method/method-of-moments (FEM/MoM) approach is applied to the analysis of a gapped power-bus structure on a printed circuit board. FEM is used to model the details of the structure. MoM is used to provide a radiation boundary condition to terminate the FEM mesh. Numerical results exhibit significant errors when the FEM/MoM boundary is chosen to coincide with the physical boundary of the board. These errors are due to the inability of hybrid elements on the boundary to enforce the correct boundary condition at a gap edge in a strong sense. A much better alternative is to extend the MoM …
Modelling Of The Glass Phase In Fly Ashes Using Network Connectivity Theory, Mark R. Towler, Kenneth T. Stanton, Patrick Mooney, Robert G. Hill, Natalia Moreno, Xavier Querol
Modelling Of The Glass Phase In Fly Ashes Using Network Connectivity Theory, Mark R. Towler, Kenneth T. Stanton, Patrick Mooney, Robert G. Hill, Natalia Moreno, Xavier Querol
Chemical and Biochemical Engineering Faculty Research & Creative Works
The amorphous phase of fly ash dominates degradation behaviour because glass has a higher potential energy than the equivalent crystal structure and the variation of bond angles and distances in a glass make the bond breakage easier. It would be advantageous to predict the presence and subsequent degradability of glass on the basis of the solid-state chemistry of the fly ash. To this end, and inorganic polymer model was applied to a selection of European fly ashes to determine the value known as cross-link density (CLD). A cross-link density value of less than two implies that the material is amorphous …
Radiation Resistance Testing Of Mosfet And Cmos As A Means Of Risk Management, Akira Tokuhiro, Massimo F. Bertino
Radiation Resistance Testing Of Mosfet And Cmos As A Means Of Risk Management, Akira Tokuhiro, Massimo F. Bertino
Nuclear Engineering and Radiation Science Faculty Research & Creative Works
Whether for military, research (space, accelerator physics) and/or civilian use, risk avoidance against radiation-induced damage is not possible with COTS parts. Thus the sensible approach is risk management. We recommend a sensible risk management approach as follows: 1) know the radiation environment of the intended application to the extent possible; 2) know the effects of ionizing radiation on the component(s) of interest; 3) know the requirements of the application; 4) identify the candidate or chosen components; 5) test the components; 6) design-in safety factor margins to the extent possible.
Adaptive Critic Based Optimal Neurocontrol For Synchronous Generator In Power System Using Mlp/Rbf Neural Networks, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley
Adaptive Critic Based Optimal Neurocontrol For Synchronous Generator In Power System Using Mlp/Rbf Neural Networks, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley
Electrical and Computer Engineering Faculty Research & Creative Works
This paper presents a novel optimal neurocontroller that replaces the conventional controller (CONVC),which consists of the automatic voltage regulator (AVR) and turbine governor, to control a synchronous generator in a power system using a multilayer perceptron neural network (MLPN) and a radial basis function neural network (RBFN). The heuristic dynamic programming (HDP) based on the adaptive critic design (ACD) technique is used for the design of the neurocontroller. The performance of the MLPN based HDP neurocontroller (MHDPC) is compared with the RBFN based HDP neurocontroller (RHDPC) for small as well as large disturbances to a power system, and they are …
Adaptive Critic-Based Neural Network Controller For Uncertain Nonlinear Systems With Unknown Deadzones, Pingan He, Jagannathan Sarangapani, S. N. Balakrishnan
Adaptive Critic-Based Neural Network Controller For Uncertain Nonlinear Systems With Unknown Deadzones, Pingan He, Jagannathan Sarangapani, S. N. Balakrishnan
Electrical and Computer Engineering Faculty Research & Creative Works
A multilayer neural network (NN) controller in discrete-time is designed to deliver a desired tracking performance for a class of nonlinear systems with input deadzones. This multilayer NN controller has an adaptive critic NN architecture with two NNs for compensating the deadzone nonlinearity and a third NN for approximating the dynamics of the nonlinear system. A reinforcement learning scheme in discrete-time is proposed for the adaptive critic NN deadzone compensator, where the learning is performed based on a certain performance measure, which is supplied from a critic. The adaptive generating NN rejects the errors induced by the deadzone whereas a …
An Expert System Architecture To Detect System-Level Automotive Emc Problems, Sreeniwas Ranganathan, Daryl G. Beetner, R. Wiese, Todd H. Hubing
An Expert System Architecture To Detect System-Level Automotive Emc Problems, Sreeniwas Ranganathan, Daryl G. Beetner, R. Wiese, Todd H. Hubing
Electrical and Computer Engineering Faculty Research & Creative Works
Improving EMC in automobiles requires methods to detect potential problems early in the design process. Issues involved in the development of a system-level automotive EMC expert system are explored. The proposed system would help identify problems with radiation and immunity, crosstalk, placement of modules, component grounding and EMC testing. The architecture of the expert system has been developed. The system architecture is designed to allow rapid analysis of automobile designs, to point out potential problems and to suggest possible solutions.
Comparison Of Heuristic Dynamic Programming And Dual Heuristic Programming Adaptive Critics For Neurocontrol Of A Turbogenerator, Ganesh K. Venayagamoorthy, Donald C. Wunsch, Ronald G. Harley
Comparison Of Heuristic Dynamic Programming And Dual Heuristic Programming Adaptive Critics For Neurocontrol Of A Turbogenerator, Ganesh K. Venayagamoorthy, Donald C. Wunsch, Ronald G. Harley
Electrical and Computer Engineering Faculty Research & Creative Works
This paper presents the design of an optimal neurocontroller that replaces the conventional automatic voltage regulator (AVR) and the turbine governor for a turbogenerator connected to the power grid. The neurocontroller design uses a novel technique based on the adaptive critic designs (ACDs), specifically on heuristic dynamic programming (HDP) and dual heuristic programming (DHP). Results show that both neurocontrollers are robust, but that DHP outperforms HDP or conventional controllers, especially when the system conditions and configuration change. This paper also shows how to design optimal neurocontrollers for nonlinear systems, such as turbogenerators, without having to do continually online training of …
Comparison Of Mlp And Rbf Neural Networks Using Deviation Signals For Indirect Adaptive Control Of A Synchronous Generator, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley
Comparison Of Mlp And Rbf Neural Networks Using Deviation Signals For Indirect Adaptive Control Of A Synchronous Generator, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley
Electrical and Computer Engineering Faculty Research & Creative Works
This paper compares the performances of a multilayer perceptron neurocontroller and a radial basis function neurocontroller for backpropagation through time based indirect adaptive control of the synchronous generator. Also, the neurocontrollers are compared with the conventional controller for small as well as large disturbances to the power system
Decoupling Strategies For Printed Circuit Boards Without Power Planes, Todd H. Hubing, Hwan-Woo Shim, Theodore M. Zeeff
Decoupling Strategies For Printed Circuit Boards Without Power Planes, Todd H. Hubing, Hwan-Woo Shim, Theodore M. Zeeff
Electrical and Computer Engineering Faculty Research & Creative Works
Traditional decoupling capacitors connected between V/CC/ and GND traces can be relatively ineffective at frequencies above their self-resonant frequency. This paper evaluates decoupling capacitor mounting strategies on boards without power planes. Techniques for minimizing mutual inductance and improving decoupling at frequencies above resonance are investigated.
Two Separate Continually Online-Trained Neurocontrollers For Excitation And Turbine Control Of A Turbogenerator, Ganesh K. Venayagamoorthy, Ronald G. Harley
Two Separate Continually Online-Trained Neurocontrollers For Excitation And Turbine Control Of A Turbogenerator, Ganesh K. Venayagamoorthy, Ronald G. Harley
Electrical and Computer Engineering Faculty Research & Creative Works
This paper presents the design of two separate continually online trained (COT) neurocontrollers for excitation and turbine control of a turbogenerator connected to the infinite bus through a transmission line. These neurocontrollers augment/replace the conventional automatic voltage regulator and the turbine governor of a generator. A third COT artificial neural network is used to identify the complex nonlinear dynamics of the power system. Results are presented to show that the two COT neurocontrollers can control turbogenerators under steady-state as well as transient conditions and, thus, allow turbogenerators to operate more closely to their steady-state stability limits
Analysis Of A Four-Level Dc/Dc Buck Converter, Keith Corzine, J. Yuen, J. R. Baker
Analysis Of A Four-Level Dc/Dc Buck Converter, Keith Corzine, J. Yuen, J. R. Baker
Electrical and Computer Engineering Faculty Research & Creative Works
In this paper, a four-level DC/DC buck power converter is introduced. The primary application for this converter is to regulate the center capacitor voltage in a four-level inverter system. The steady-state and average-value models for the proposed converter are developed and compared in simulation. The converter was constructed in the laboratory and verified on a four-level motor drive system. It was shown that the four-level DC/DC converter provides capacitor voltage balancing and allows higher output voltage utilization from the inverter.
Optimal Placement Of Dampers And Actuators Based On Stochastic Approach, Franklin Y. Cheng, Hongping Jiang, Xiaozhe Zhang
Optimal Placement Of Dampers And Actuators Based On Stochastic Approach, Franklin Y. Cheng, Hongping Jiang, Xiaozhe Zhang
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
A general method is developed for optimal application of dampers and actuators by installing them at optimal location on seismic-resistant structures. The study includes development of a statistical criterion, formulation of a general optimization problem and establishment of a solution procedure. Numerical analysis of the seismic response in time-history of controlled structures is used to verify the proposed method for optimal device application and to demonstrate the effectiveness of seismic response control with optimal device location. This study shows that the proposed method for the optimal device application is simple and general, and that the optimally applied dampers and actuators …
Behavior Of Screw Connections In Residential Construction, Roger A. Laboube, M. A. Sokol
Behavior Of Screw Connections In Residential Construction, Roger A. Laboube, M. A. Sokol
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
Self-drilling screws are the primary means of fastening cold-formed steel members in residential construction. Because the fabrication of connections is the most labor-intensive aspect of the construction process, a better understanding of the behavior of screw connections could lead to more optimum connection design. Therefore, studies have been performed at the University of Missouri-Rolla aimed at developing a better understanding of the behavior of single-shear connections using self-drilling screws in cold-formed steel construction. The study's focus was on design parameters typically employed in residential construction. Fastener patterns, screw spacing, stripped screws, and the number of screws in a connection was …
Remediation Of Trapped Free-Phase Lnapl, T. M. Whitworth, Andrew Curtis Elmore
Remediation Of Trapped Free-Phase Lnapl, T. M. Whitworth, Andrew Curtis Elmore
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Free-phase light nonaqueous phase liquids (LNAPLs) may be trapped in certain stratigraphic and structural features near or at contaminated sites due to seasonal or other variations in the water table elevation. The purpose of this article is to point out particular subsurface conditions that are conducive to trapping of free-phase LNAPLs and to suggest approaches to remediating LNAPL-contaminated sites exhibiting similar subsurface geometry and stratigraphy. To trap free-phase LNAPL, a structure must have, in addition to closed contours, an upper boundary with pores small enough so that the LNAPL will not enter them. This boundary usually consists of clay-rich sediments. …
Best Available Treatment Technologies Applied To Groundwater Circulation Wells, Andrew Curtis Elmore, Thomas Graff
Best Available Treatment Technologies Applied To Groundwater Circulation Wells, Andrew Curtis Elmore, Thomas Graff
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Groundwater circulation wells (GCWs) are a quasi-in-situ method for remediating groundwater in areas where remediation techniques that limit the water available for municipal, domestic, industrial, or agricultural purposes are inappropriate. The inherently resource-conservative nature of groundwater circulation wells is also philosophically appealing in today's culture, which is supportive of green technologies. Groundwater circulation wells involve the circulation of groundwater through a dual screen well, with treatment occurring between the screens. The wells are specifically designed so that one well screen draws in groundwater and the second returns the groundwater after it has been treated within the well. Historically, the treatment …
Reactive Hot Pressing Of Alumina-Molybdenum Disilicide Composites, William Fahrenholtz, Ronald E. Loehman, Kevin G. Ewsuk
Reactive Hot Pressing Of Alumina-Molybdenum Disilicide Composites, William Fahrenholtz, Ronald E. Loehman, Kevin G. Ewsuk
Materials Science and Engineering Faculty Research & Creative Works
Al2O3-MoSi2 Composites Were Prepared by Reactive Hot Pressing using Molybdenum, Aluminum, and Mullite Powders as Precursors. the Gibbs Free Energy Was Highly Negative for the Composite-Forming Reaction, Which Indicated that the Products Were Stable Relative to the Reactants. after the Reaction, the Composites Had High Relative Density, ∼96%. based on the Composite-Forming Reaction, the Composites Should Have Contained 18 Vol% MoSi2 in an Al2O3 Matrix. Scanning Electron Microscopy Revealed that the MoSi2 Inclusions Were Elongated, with an Average Thickness of ∼5 Μm and Inclusion Lengths that Ranged from 5 to 50 …
Power Bus Isolation Using Power Islands In Printed Circuit Boards, J. Chen, Todd H. Hubing, Richard E. Dubroff, Thomas Van Doren
Power Bus Isolation Using Power Islands In Printed Circuit Boards, J. Chen, Todd H. Hubing, Richard E. Dubroff, Thomas Van Doren
Electrical and Computer Engineering Faculty Research & Creative Works
Power islands are often employed in printed circuit board (PCB) designs to alleviate the problem of power bus noise coupling between circuits. Good isolation can be obtained over a wide frequency band due to the large series impedance provided by the gap between the power islands. However, power bus resonances may degrade the isolation at high frequencies. The amount of isolation also depends on the type of connection between power islands and the components on the board. This paper experimentally investigates the effectiveness of several power island structures up to 3.0 GHz
Reducing Power Bus Impedance At Resonance With Lossy Components, Todd H. Hubing, Theodore M. Zeeff
Reducing Power Bus Impedance At Resonance With Lossy Components, Todd H. Hubing, Theodore M. Zeeff
Electrical and Computer Engineering Faculty Research & Creative Works
Power bus structures in printed circuit boards with solid power and ground planes exhibit resonances. When the power bus is resonant, the power bus impedance can increase dramatically. This paper explores the effect of component equivalent series resistance (ESR) on power bus resonances. General guidelines for selecting an optimum ESR are provided and are supported by laboratory measurements and numerical simulations.
Restoration Of The Lorentzian And Debye Curves Of Dielectrics And Magnetics For Fdtd Modeling, Marina Koledintseva, Konstantin Rozanov, James L. Drewniak, Gabriele Di Fazio
Restoration Of The Lorentzian And Debye Curves Of Dielectrics And Magnetics For Fdtd Modeling, Marina Koledintseva, Konstantin Rozanov, James L. Drewniak, Gabriele Di Fazio
Electrical and Computer Engineering Faculty Research & Creative Works
The algorithms of extracting the Lorentzianand Debye-curve parameters of dielectric and magnetic materials from the results of measurements at several frequency points are presented. These algorithms are based on an analytical solution of systems of non-linear equations with physical constraints that follow from the fundamental principle of causality. The extracted parameters are useful for FDTD modeling of electromagnetic structures containing such dispersive media. Some examples are presented.
Smooth Static And Dynamic Indentation Of A Cantilever Beam, Minggang Zhou, William P. Schonberg
Smooth Static And Dynamic Indentation Of A Cantilever Beam, Minggang Zhou, William P. Schonberg
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
The static and dynamic indentation of structural elements such as beams and plates continue to be intriguing problems, especially for scenarios where large area contacts are expected to occur. Standard methods of indentation analyses use a beam theory solution to obtain an overall load-displacement relationship and then a Hertzian contact solution to calculate local stresses under the indenter. However, these techniques are only applicable in a fairly limited class of problems: the stress distribution in the contact region will differ significantly from a Hertzian one when the contact length exceeds the thickness of the beam. The indentation models developed herein …