bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling and Bumpless Learning Control of Position and Pressure for an Electropneumatic Actuator
Authors: Ng Han Wee , Alleyne Andrew 
Published: November 2021

Abstract
This paper presents the modeling, simulation and control of a pneumatic cylinder actuator driven by a high-performance pneumatic servovalve. The modeling is done via a combination of first principles and empirically identified system characteristics. A stick-slip friction model is incorporated as a necessary component of the overall system description. The model is verified against experimental data and shown to be quite accurate over a range of operating conditions. Two separate Iterative Learning Controllers (ILC’s) are applied to the system to improve the overall sequential tracking of position and pressure reference inputs. In addition, a bumpless transfer technique is used to transition between the position and pressure control loops in a smooth manner. The profiles chosen are similar to those found in certain manufacturing processes such as blow molding. It is show via simulation and experiment that the ILC can provide an improvement in the system tracking capabilities and the bumpless transfer can be used very effectively to minimize transients in the changeover from position to pressure.
Trade-Off Analysis for the Design of a High Performance Hydrostatic Actuation System
Authors: Habibi S. R. 
Published: November 2021

Abstract
This paper considers the design of a high performance hydrostatic actuation system referred to as the ElectroHydraulic Actuator (EHA). The expected performance of EHA and its dominant design parameters are identified by using mathematical modeling. The design parameters are classified into Direct and Indirect categories based on the measure of their accessibility to the designer. The Direct parameters are directly quantifiable and, can be linked to the performance of EHA through a set of mathematical functions.
A prototype of EHA has been produced and described. The mathematical functions linking performance to design parameters are used to investigate design trade-offs. Design improvements to the prototype are suggested by using constrained quadratic programming.
Free Vibration of Stepped and Restrained Cantilever Beams Connected With a Rigid Body: Exact and Numerical Solutions
Authors: Kwon Hyuck-Dong , Park Young-Pil , Yang Hyun Seok 
Published: November 2021

Abstract
The object of this work is to analyze the dynamic characteristics of the portal closed frame which consists of two stepped beams including a torsional spring at the discontinuous point and a rigid body connecting each beam tips. This system is available in a lot of cases that need higher stiffness and linear motion of the tip mass. For example, it might be used for an optical pick-up actuator, using piezoelectric materials, of the high areal density CD, DVD or the next generation of optical memory devices, which requires super rigidity and linear motion in focusing. The mathematical modeling and the derivation of the equation of motion are given for the beam that is identically paralleled and stepped cantilevers. The equation of motion and the associated boundary and the continuous conditions are analytically obtained by using variational Hamilton’s principle. The exact solutions are presented and compared with the results obtained by the use of the FEM Tool (IDEAS).
Study of In-Plane Motions in a Thin Rotating Disk
Authors: Deshpande Moreshwar , Mote C. D. 
Published: November 2021

Abstract
A model for the in-plane oscillations of a thin rotating disk has been derived using a nonlinear strain measure to calculate the disk energy. This accounts for the stiffening of the disk due the radial expansion resulting from its rotation. The corresponding non-dimensionalized natural frequencies are seen to depend only on rotation speed and have been calculated. The radially expanded disk configuration is linearly stable over the range of rotation speeds studied here. The sine and cosine modes for all nodal diameters couple to each other at all nonzero rotation speeds and the strength of this coupling increases with rotation speed. This coupling causes the reported frequencies of the stationary disk to split. The zero, one and two nodal diameter in-plane modes do not have a critical speed corresponding to the vanishing of the backward travelling wave frequency. The use of a linear strain measure in earlier work incorrectly predicts instability of the rotating equilibrium and the existence of critical speeds in these modes.
Nonlinear Resonant Motion of Traveling Waves in Rotating Disks
Authors: Luo Albert C. J. , Tan Chin An 
Published: November 2021

Abstract
The resonant conditions for traveling waves in rotating disks are derived. The nonlinear resonant spectrum of a rotating disk is computed from the resonant conditions. Such a resonant spectrum is useful for the disk drive industry to determine the range of operational rotation speed. The resonant wave motions for linear and nonlinear, rotating disks are simulated numerically for a 3.5-inch diameter computer memory disk.
Influence of Core on Face/Core Debond Toughness
Authors: Viana Camps Gilmer M. , Carlsson Leif A. , Li Xiaoming 
Published: November 2021

Abstract
The influence of mechanical properties and fracture toughness of the core on debond fracture toughness of foam core sandwich has been examined. It was found that the fracture toughness for debonding was larger than the core toughness. The observed difference between core fracture toughness and face/core debonding toughness was analyzed using plastic zone size and mode mixity arguments. The difference in toughness can not be explained by plastic zone size and mode mixity effects. It is possible that the core displays a gradient in properties and fracture resistance, and anisotropic behavior which might explain the difference in toughness.
Effects of Interfacial Delaminations in Curved Sandwich Beams
Authors: Layne Andrew M. , Carlsson Leif A. 
Published: November 2021

Abstract
The influence of face/core debonding on the structural integrity of curved sandwich beams subjected to opening bending moments has been examined experimentally. The sandwich beams consisted of glass/polyester faces over a PVC H30 foam core. Debonds of various sizes were implanted by inserting thin teflon sheets at the outer face/core interface in the curved region of the beam prior to processing. A test fixture for flexure testing of curved sandwich beams was designed and manufactured, and evaluated using homogeneous isotropic beams. The surface strains at the middle of the curve were recorded to examine the response. Buckling of the debonded face sheet occurred followed by face/core propagation of the debond. Strength reduction of the beams under opening moments due to face/core debonding was substantial.
An Asymptotic Solution for the Response of Face-Sheet Delaminations/Debonds Under Compression
Authors: Kardomateas George A. , Huang Haiying 
Published: November 2021

Abstract
The buckling and initial postbuckling behavior of face-sheet delaminations or face-sheet/core debonds is studied by a perturbation procedure. The procedure is based on the nonlinear beam equation with transverse shear included, and an asymptotic expansion of the load and deformation quantities. First the characteristic equation for the critical load is formulated and this is a nonlinear algebraic equation. Subsequently, the first order load is found from a system of linear equations and the initial postbuckling behavior can thus be studied. The procedure can be easily expanded to the higher order terms. The effect of transverse shear is illustrated with results on the critical strain and the initial postbuckling displacement.
Sandwich Shell Finite Element for Dynamic Explicit Analysis
Authors: Tabiei Ala , Tanov Romil , Birman Victor 
Published: November 2021

Abstract
This work presents the finite element (FE) formulation and implementation of a higher order shear deformable shell element for dynamic explicit analysis of composite and sandwich shells. The formulation is developed using a displacement based third order shear deformation shell theory. Using the differential equilibrium equations and the interlayer requirements, a treatment is developed for the transverse shear, resulting in a continuous, piecewise quartic distribution of the transverse shear stresses through the shell thickness. The FE implementation is cast into a 4-noded quadrilateral shell element with 9 degrees of freedom (DOF) per node. Only C0 continuity of the displacement functions is required in the shell plane, which makes the present formulation applicable to the most common 4-noded bilinear isoparametric shell elements. Expressions are developed for the critical time step of the explicit time integration for orthotropic homogeneous and layered shells based on the developed third order formulation. To assess the performance of the present shell element it is implemented in the general nonlinear explicit dynamic FE code DYNA3D. Several problems are solved and results are compared to other theoretical and numerical results. The developed sandwich shell element is much more computationally efficient for modeling sandwich shells than solid elements.
A Novel Non-Intrusive Probe of Particle Motion and Gas Generation in the Feed Injection Zone of the Feed Riser of a Fluidized Bed Catalytic Cracking Unit
Authors: Cody G. D. , Bellows R. J. , Goldfarb D. J. , Wolf H. A. , Storch G. V. 
Published: November 2021

Abstract
We define a non-intrusive Acoustic Shot, Noise, ASN, probe of particle velocity at the wall of fluidized beds and transfer lines, and demonstrate how it can be used to obtain quantitative data on changes in particle velocity at the wall through changes in the mean squared wall acceleration of the wall vibrational energy produced by random particle impact or ASN. We note that the probe can be simply calibrated if any two of the following quantities are known for the transfer line: (1) average Axial Velocity of particles; (2) average Axial Mass Density of particles; (3) average Mass Flux of particles. We present the first field data on simultaneous measurements of ASN excited wall vibrational energy along the feed riser of Fluidized Catalytic Cracking Units where catalyst particle flow is produced by the gas generated in the catalytic and thermal cracking of injected oil. We define the Feed Riser Profile as the curve of RMS acceleration along the feed riser and show that changes in its magnitude and shape can be correlated with changes in the product yield of the catalytic and thermal cracking process.
Mean Flow and Turbulent Stress Estimation Using DPIV in Pulsatile Flow Through Mechanical Heart Valve
Authors: Subramanian Amirthaganesh , Mu Haining , Kadambi Jaikrishnan R. , Harasaki Hiroaki , Wernet Mark P. 
Published: November 2021

Abstract
Accurate estimation of turbulent stresses in pulsatile flows is very important in the design of mechanical heart valves to reduce thromboembolism and hemolysis. The flow within the lumen of a fully transparent bileaflet mechanical heart valve model, in the “mitral” position of an in-vitro pulsatile flow loop, is characterized using digital particle image velocimetry (DPIV). A phase-averaging technique is used to obtain the mean velocities and turbulent stresses. The results are compared with those obtained using laser Doppler anemometry which shows good agreement between the two measurement techniques, thereby validating the integrity of the DPIV measurements in the conditionally sampled time dependent flow. Convergence and accuracy issues involving turbulent stress measurements with DPIV in pulsatile flows are addressed in this paper.
Scale Effects on the Non-Newtonian Behaviour of Blood: A Numerical Study
Authors: Sørensen Lotte T. , Rosendahl Lasse A. , Condra Thomas J. , Madsen Jens I. 
Published: November 2021

Abstract
The commonly used assumption that blood behaves as a Newtonian fluid in the large vessels and the heart and as a non-Newtonian fluid in the smaller vessels is questioned in this paper. A numerical simulation of three characteristic vessels (aorta, arterie, and arteriole) in the human cardiovascular system has been carried out using three constitutive equations for human blood. The constitutive equations are proposed by other researchers, one depending on the composition of blood, a general non-Newtonian model, and a Newtonian model. The calculations carried out shows that the prediction of the shear stresses varies with the constitutive equation used, and the deviation is more pronounced for the aorta than for the smaller vessels.
An Eulerian Model for Free-Shear Multiphase Turbulent Diffusion
Authors: Loth Eric 
Published: November 2021

Abstract
A closed-form Eulerian model was constructed for longtime diffusion of heavy or buoyant particles. This model is based on incorporation of experimentally observed turbulent diffusion features: Stokes number, crossing-trajectory, inertial limit, and continuity effects. The anisotropic model was formulated using a Csanady-based approximation for the particle diffusion ratio as equal to the ratio of the particle interaction time to local eddy integral time scale. The model favorably compares with experimental free-shear measurements and numerical Lagrangian turbulent diffusion results for a range of particle density ratios (including solid particles in gas and gas bubbles in liquid). The model for turbulent diffusion effects is suited for inclusion within multi-phase Reynolds-Averaged Navier-Stokes methods which treat the particle distribution as a continuous Eulerian concentration field.
Drag-Reduction and Slip: An Investigation of Size Scale and Hydrophobicity Effects
Authors: Gordon Timothy D. , McCarthy Thomas J. 
Published: November 2021

Abstract
Experiments indicate that hydrodynamic drag may be reduced by using ultrahydrophobic substrates to induce slip at the solid-liquid interface. The connection between drag-reduction and slip is explored, and these previously isolated fields are joined into a single, more comprehensive area of research.
We present data from two experimental techniques indicating the role of hydrophobicity and size scale in drag-reduction. In one series of studies, water was directed through a channel containing two rectangular plates of smooth silicon. Flow rates for smooth non-hydrophobic plates and smooth hydrophobic plates were identical.
In another series of studies, a rheometer was used to measure the relative drag experienced by a polypropylene-coated disk as it was rotated in water. The polypropylene (PP) was ultrahydrophobized (water contact angles were θa/θr = 167°/166°) by argon plasma etching in the presence of poly(tetrafluoroethylene). Drag was reduced by over 20% by using the roughened PP instead of the virgin PP.
Contact angle hysteresis is isolated as a critical factor in the drag-reduction mechanism proposed.
A Laboratory Study of the Velocity Structure in an Intrusive Gravity Current
Authors: Lowe Ryan J. 
Published: November 2021

Abstract
Laboratory experiments were performed in which an intrusive gravity current was observed using shadowgraph and particle tracking methods. The intrusion was generated in a two-layer fluid with a sharp interface by mixing the fluid behind a vertical lock-gate and then suddenly withdrawing the gate from the tank. The purpose of the experiments is to determine the structure of the velocity field inside the intrusion as well as the stability characteristics of the interface. Soon after the removal of the lock-gate the speed of the front of the intrusive gravity current reached a constant speed. The observed structure of the flow inside the intrusion shows a “head region” where the flow is nearly uniform, followed by a region of intense mixing and high velocities and finally followed by another region of fairly uniform velocity with a speed slightly faster than the front speed. The results show that the maximum centerline velocity is about 50% greater than the front speed and corresponds to the position in the intrusion where the strongest Kelvin- Helmholtz billows form. Closer to the front, the relative flow within the head is weak, which explains why Benjamin’s (1968) energy-conserving gravity current theory accurately predicts the behavior of dissipative gravity currents.
A Computational Study on Airfoils at a Low Reynolds Number
Authors: Singh Ajit Pal , Winoto S. H. , Shah D. A. , Lim K. G. , Goh Robert E. K. 
Published: November 2021

Abstract
Performance characteristics of some low Reynolds number airfoils for the use in micro air vehicles (MAVs) are computationally studied using XFOIL at a Reynolds number of 80,000. XFOIL, which is based on linear-vorticity stream function panel method coupled with a viscous integral formulation, is used for the analysis. In the first part of the study, results obtained from the XFOIL have been compared with available experimental data at low Reynolds numbers. XFOIL is then used to study relative aerodynamic performance of nine different airfoils. The computational analysis has shown that the S1223 airfoil has a relatively better performance than other airfoils considered for the analysis.
A Nested-Grid Computational Study of Jets in Crossflow
Authors: Zheng Z. Charlie , Zhang N. , Lim S. H. 
Published: November 2021

Abstract
In this paper, a nested grid technique is used to accommodate the smaller scale structures near the jet hole and the larger structures downstream. Flow physics resolved by the nested-grid computation is discussed in the context of vorticity transport and vortex dynamics. Pitch and skew angle effects of the jet are studied. Quantitative comparisons with available experimental data have been made.
Fluid Flows Through Two-Dimensional Irregular Composite Channels
Authors: Al-Hadhrami A. K. , Elliott L. , Ingham D. B. , Wen X. 
Published: November 2021

Abstract
The present analysis is concerned with the study of two-dimensional fluid flow problems through channels of irregular composite materials. The fluid is assumed to be steady, incompressible, with a negligible gravitational force, and is constrained to flow in an infinite long channel in which the height assumes a series of piecewise constant values. An analytical study in the fully developed section of the composite channel is presented when the channel is of constant height and composed of several layers of porous media, each of uniform porosity. Numerical solutions are utilised using CFD based on the control volume method to solve the Brinkman equation, which governs fluid flow through porous media. In the fully developed flow regime the analytical and numerical solutions are graphically indistinguishable. A geometrical configuration involving several discontinuities of channel height, and where the entry and exit sections are layered, is considered and the effect of different permeabilities is demonstrated. Several numerical investigations which form a first attempt to mathematically model some geological structures, e.g. a fault or a fracture, are performed. Further, flow through fractures composed of randomly generated permeability values are also discussed and the effect on the overall pressure gradient is considered.
Numerical Study of Density-Currents Using the Non-Staggered Grid Fractional-Step-Method
Authors: Pacheco J. Rafael , Pacheco-Vega Arturo , Pacheco-Vega Sigfrido 
Published: November 2021

Abstract
A new approach for the solution of time-dependent calculations of buoyancy driven currents is presented. This method employs the idea that density variation can be pursued by using markers distributed in the flow field. The analysis based on the finite difference technique with the non-staggered grid fractional step method is used to solve the flow equations written in terms of primitive variables. The physical domain is transformed to a rectangle by means of a numerical mapping technique. The problems analyzed include two-fluid flow in a tank with sloping bottom and colliding density currents. The numerical experiments performed show that this approach is efficient and robust.
Railroad Wheel Rotundity
Authors: Van Overveen Joseph P. , Grosser Joseph 
Published: November 2021

Abstract
This paper is based on wheel data collected by the authors at the Bay Area Rapid Transit (BART). The wheel data is examined to determine the rotundity in a new condition and after three levels of accumulated service mileage. Analysis of this data points to the need for investigating Wheel/Rail reaction under various conditions of wheel rail rotundity and rail irregularities.
The authors suggest a method of investigation that should show that the interaction of wheel and rail can result in rail corrugation.
Consolequip Steering Bogie for the Société Nationale Industrielle et Minière ‘SNIM’ de la Mauritanie
Authors: Khatchadourian Varoujan 
Published: November 2021

Abstract
This paper describes in detail the design, engineering and testing conducted for 260 self-steering bogies in response to a bid from SNIM (Société Nationale Industrielle et Minière), in Mauritania, Africa.
Severe environmental conditions in Mauritania, caused by the presence of sand, contribute to accelerated wheel tread wear. This in combination with asymmetric wheel wear typically experienced with the standard three-piece bogie, results in poor wheel life. A steering bogie improves wheel life by allowing the axles to self-align, thus reducing asymmetric wheel wear occurrence.
Bogie behavior is explained by comparing the stiffness characteristics of self-steering bogies and standard three-piece bogies. High bogie stiffness keeps a truck square as it travels on the track, thus improving its dynamic response on tangent track. Split type friction wedges are used together with heavy-duty suspension system to obtain high bogie shear stiffness and vertical damping characteristics. An elastic shear pad between the roller bearings and the side frame pedestal roof allows the axles to self-align in curves, giving the truck its self-steering characteristic.
The truck design is unique as the standard AAR unit guide bracket construction point and angle were changed to provide the alignment for the unique combination of axle spacing and wheel diameter. It utilizes 1000 mm diameter wheels and a wheel base of 1800 mm.
The Consolequip steering bogie has been engineered to improve dynamic response on tangent track. This is done by increasing bogie interaxle shear stiffness which increases the threshold of truck hunting. Stability tests with service worn wheels confirmed stability speed to exceed operating speeds used by SNIM network. Preliminary projections have estimated an improvement of up to 50% in wheel life by reducing asymmetric wheel wear and the number of times they are re-profiled.
Comparing U.S. and European Freight Car Design Specifications: What Can We Learn?
Authors: Richmond Shaun 
Published: November 2021

Abstract
Railroads in the U.S. and Europe have evolved to perform the same functions but have developed different specification and regulatory environments. In the U.S., AAR rules apply while in Europe the UIC code is followed. This paper compares selected parts of both specifications with a view to understanding the differences in philosophy between them and pointing out areas where we in the U.S. might gain from adopting the methods used in Europe.
Clearly, the volume of regulation prohibits a comprehensive review and so discussion is limited to three key areas: Trackability—which includes ride quality and safety from derailment, Structural Integrity and Gauging—the calculation of the maximum permitted profile of the car. It is the author’s belief that improved performance could be obtained from the existing railroad environment by adopting certain UIC methodologies.