bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Electric-Analog Computers to Heat-Transfer and Fluid-Flow Problems
Authors: McCann G. D. , Wilts C. H. 
Published: April 2021

Abstract
There are two general classes of mathematical problems encountered in science and engineering for which high-speed mechanical computation is required. One of these embraces those problems of such complexity that it is impractical to obtain even a few solutions by conventional analysis. In the other class are problems which may be of only moderate complexity, but in which it is necessary to obtain a large number of solutions before the results become of practical value. It is the intent of this paper to discuss some of the applications that have been made of the California Institute of Technology “electric-analog computer” to heat-transfer and fluid-flow problems of both of the classes mentioned.
Compliance of Elastic Bodies in Contact
Authors: Mindlin R. D. 
Published: April 2021

Abstract
A small tangential force and a small torsional couple are applied across the elliptic contact surface of a pair of elastic bodies which have been pressed together. If there is no slip at the contact surface, considerations of symmetry and continuity lead to the conclusion that there is no change in the normal component of traction across the surface and, aside from warping of the surface, there is no relative displacement of points on the contact surface. The problem is thus reduced to a “problem of the plane” in which the tangential displacements and normal component of traction are given over part of the boundary and the three components of traction are given over the remainder. In the case of the tangential force it is observed that, when Poisson’s ratio is zero, the problem is a simple one, in potential theory, which is then generalized by means of a special device. An expression for tangential compliance is found as a linear combination of complete elliptic integrals. In general, the compliance is greater in the direction of the major axis of the elliptic contact surface than in the direction of the minor axis. Both components of tangential compliance increase as Poisson’s ratio decreases and become equal when Poisson’s ratio is zero. Over the practical range of Poisson’s ratio, the tangential compliance is greater than the normal compliance, but never more than twice as great as long as there is no slip. The tangential traction on the contact surface is everywhere parallel to the applied force. Contours of constant traction are ellipses homothetic with the elliptic boundary. The magnitude of the traction rises from one half the average at the center of the contact surface to infinity at the edge. Due to this infinity, there will be slip, the effect of which is studied for the circular contact surface. In the case of the torsional couple, the solution is obtained by generalizing a solution by H. Neuber pertaining to a hyperbolic groove in a twisted shaft. The torsional compliance is expressed in terms of complete elliptic integrals and, for the circular contact area, reduces to that found by E. Reissner and H. F. Sagoci. The resultant traction at a point rises from zero at the center to infinity at the edge of the contact surface, but is constant along and parallel to homothetic ellipses only in the case of the circular contact area.
Supersonic Flow Past Airfoil Tips
Authors: Beskin Leon 
Published: April 2021

Abstract
Airfoils examined in this paper are constituted by developable surfaces with arbitrary cross sections, all the generators of the surfaces, including the sharp leading and trailing edges, being supersonic. The tips are constituted by supersonic sections, which are generally blunt. The flow past an airfoil is determined by application of linearized equations, by means of Busemann’s conical flow theory. The two fundamental cases are that of a plate at a small angle of attack, and that of a slender wedge at zero angle of attack. In both cases, the supersonic leading edge and the subsonic tip may have arbitrary directions. The tip, particularly, may be either parallel to the flow, or acting as a leading edge, or else acting as a trailing edge, and each condition must be considered separately. All other conditions are solved by superposition of the two fundamental cases, antisymmetrical conditions resulting from the first case, and symmetrical conditions, from the second. Thus the general solution for the flow about a developable surface with arbitrary thickness and camber distributions, limited to a plane subsonic tip, is simply obtained under the conventional restrictions of the linear theory. While the absolutely general case of a developable surface, constituted by the tangents to an arbitrary edge of retrogradation, appears to be of limited interest, major applications correspond to special cases of developable surfaces; cylindrical, prismatical, conical, and pyramidal airfoils.
Discontinuities of Stress in Plane Plastic Flow
Authors: Winzer Alice , Carrier G. F. 
Published: April 2021

Abstract
This paper presents a method of discussing the stress distribution in the neighborhood of a surface of discontinuity of stress in a field of plane plastic flow. The plastic material under consideration is supposed to obey the laws of the Saint Venant-Mises theory; the surface of discontinuity is assumed to be plane, but the intensity of the discontinuity is allowed to vary along the trace of this plane in the plane of flow.
Vibration of Multifrequency Systems During Acceleration Through Critical Speeds
Authors: McCann G. D. , Bennett R. R. 
Published: April 2021

Abstract
This paper presents generalized solutions for the response of a linear two-degree-of-freedom system excited by a single constant-magnitude sinusoidal force whose frequency varies uniformly with time. These solutions were obtained with the Cal Tech “electric-analog computer” which is described briefly since it has wide application to problems of this type.
Transverse Vibration of a Two-Span Beam Under Action of a Moving Constant Force
Authors: Ayre R. S. , Ford George , Jacobsen L. S. 
Published: April 2021

Abstract
The problem relates to the transient vibration of a symmetrical, continuous, simply supported two-span beam which is traversed by a constant force moving with constant velocity. The beam is of slender proportions, flexure alone being considered. Damping is zero, and there is no mass associated with the moving force. Exact theoretical solutions for bending stress have been derived in general form. They consist of three infinite series, each related to one of three time eras as follows: (a) Where force is crossing first span; (b) is crossing second span; (c) has left the beam. Each term of a series is related to a natural mode of vibration. Quantitative theoretical studies show the variation in individual terms of the series, and also in summations of the first five terms, as the traversing velocity is varied. A mechanical model with electrical recording of stress was employed to obtain a more complete quantitative solution than was feasible analytically. The agreement between theory and experiment was reasonably good. Large magnifications of stress (of the order of 2.5) were found in the neighborhood of resonance with the fundamental mode.
Use of an Optical Property of Glycerine-Water Solutions to Study Viscous Fluid-Flow Problems
Authors: Hagerty W. W. 
Published: April 2021

Abstract
It is a property of certain concentrations of glycerine-water solutions, when in a state of steady flow, that the planes of equal shear in the liquid become visible in ordinary light, if viewed along a path tangent to the shear plane. This phenomenon has been used successfully to study a fluid-flow problem at the University of Michigan. The nature and scope of application of this optical property is currently being studied further. This report gives details of what may prove to be a useful tool in certain phases of experimental fluid-flow problems.
Stress Studies on Piping Expansion Bellows
Authors: Feely F. J. , Goryl W. M. 
Published: April 2021

Abstract
As a result of numerous and costly failures of the stainless-steel bellows used to take up thermal expansion in the piping of petroleum and chemical processing equipment, a basis has been developed for designing these bellows to operate within reasonable stresses. A formula has been derived to show the total stress induced in the material as a result of the combined effects of pressure and movement. The validity of the approximations used in this formula has been verified by laboratory strain-gage measurements on an experimental bellows. A relationship between several variables in the design of the disks has also been determined and serves as a basis for dimensioning them to achieve the most economical proportions. When this relationship is satisfied, the maximum permissible movement per disk can be obtained. This is shown graphically. Several supplementary formulas are given for determining bellows characteristics which may affect the design of adjacent piping. The problem of designing an expansion joint for high-pressure service is discussed briefly, and some preliminary laboratory data are presented on a commercial joint of this type.
An Approximate Solution for Incompressible Flow About an Ellipsoid Near a Plane Wall
Authors: Eisenberg Phillip 
Published: April 2021

Abstract
Using the method of successive images, an approximate solution for the velocity potential is obtained in closed form for incompressible flow about an ovary ellipsoid near a plane wall. The velocity distribution is computed from this solution in two ways. The first computation properly predicts differences in velocities on opposite half-meridians of the ellipsoid. A second method results in a symmetric velocity distribution but is useful for rapid estimates of the average wall effect. Pressure distributions calculated by this theory are compared with values measured on 4:1 and 6:1 ellipsoid models.
Free Periodic Motions of an Undamped Two-Degree-of-Freedom Oscillatory System With Nonlinear Unsymmetrical Elasticity
Authors: Soroka Walter W. 
Published: April 2021

Abstract
Precise solutions are presented for a two-degree-of-freedom oscillatory system containing a preset spring. Such a system is characteristic of an aircraft propeller-engine-supercharger installation. The periodic free motions obtained indicate the possibility of highly unconventional motions when the nonlinearity is pronounced, motions which may be easily overlooked in the usual approximate treatment of nonlinear systems. The results presented in this paper show that one mass may oscillate several times while the other mass is going through one oscillation. The ratio of oscillations of one mass with respect to the other changes with amplitude.
By considering the load-deflection curve for the nonlinear spring to be a broken line, periodic motions may be obtained to any desired degree of precision by combining conventional general solutions for two-degree-of-freedom linear systems.
A Method for Determining Mode Shapes and Frequencies Above the Fundamental by Matrix Iteration
Authors: Flomenhoft H. I. 
Published: April 2021

Abstract
Recently, an increasing use has been made of the matrix-iteration method for determining mode shapes and frequencies, particularly with regard to dynamic problems in aircraft design. Its particular advantage is the relative ease with which it handles complex discontinuous structures whose elastic properties can be defined adequately only in terms of influence coefficients. The disadvantage of tedious calculations has been alleviated greatly by an “acceleration method” for convergence which has been described by Isakson. The predominant disadvantage to matrix iteration, however, has been the difficulty in obtaining mode shapes and frequencies higher than the fundamental. The purpose of this paper is to establish a technique for accomplishing this in a manner that is practical for use in industry, as proved by its successful application to many problems of this type in the Aero-Elastic and Structures Research Laboratory at the Massachusetts Institute of Technology. This is accomplished by applying a device worked out by L. A. Pipes, and extending it to the general case, at the same time organizing the computations in tabular form. Only a basic knowledge of matrix notation and dynamic systems is necessary to understand this development, and this can be obtained easily by a review of von Kármán and Biot’s work on this subject.
Soap-Film and Sandbed-Mapper Techniques
Authors: Moore A. D. 
Published: April 2021

Abstract
A new photographic method for indirect measurement of a soap film is presented. Only one photograph is taken of a spiderweb grid as reflected by the film; the picture is analyzed to find contour lines and lines of maximum slope. Thus the film need last only long enough to be photographed. A fluid mapper of the isolated sandbed type is shown to be an analog for the soap film and, therefore, for the torsional stress situation in a shaft of like boundary. Thus sandbed techniques might replace soap-film techniques. The sandbed mapper also is an analog for other noncircular two-dimensional distributed source situations, such as the following: Field of a space charge; heat flow, with uniform heat production in the volume, the boundary being an isothermal; eddy currents in a plate (or section of lamination) uniformly pierced by a changing flux; magnetic flux in a volume of iron of constant permeability, the iron being (axially) a conductor of uniformly distributed current; streamline fluid flow in a long straight tube (sandbed isopressure lines corresponding to the tube’s isovelocity lines); and chemical diffusion, with the diffusing material uniformly appearing or disappearing throughout the volume. Since the sandbed is an analog for the soap film, the soap film is also an analog for these other situations.
Crushing of Aluminum Tubes Under Hydrostatic and Localized Pressure
Authors: Creutz E. 
Published: April 2021

Abstract
In the theory of elasticity equations have been derived by Sturm and Timoshenko for the crushing strength of long tubes subjected to external hydrostatic pressure. These equations have been found to fit experimental data on steel tubes, provided the length is several times the diameter, and the ratio of diameter to wall thickness exceeds about 30. No similar test data had been taken on aluminum tubes so an experimental study was carried out to determine whether the equations mentioned would apply. No satisfactory correlation was found to exist, but a simple equation was derived which is well within the reproducibility of the test results.
Impact on a Multispan Beam
Authors: Hoppmann W. H. 
Published: April 2021

Abstract
In this paper a study is made of impact on a continuous beam on four supports. The impact is produced by collision of a solid sphere with the beam at the mid-point of the center span. The spans are of equal length and of constant cross section. Formulas are obtained for the deflections and strains. A numerical example illustrating the theory is worked out in detail.
Characteristics of Irrotational Flow Through Axially Symmetric Orifices
Authors: Rouse Hunter , Abul-Fetouh Abdel-Hadi 
Published: April 2021

Abstract
Although an exact analytical solution of the orifice problem has not yet proved feasible, use of the method of relaxation has permitted a numerical determination of the flow characteristics to be made with sufficient precision for the problem to be considered solved. The coefficient of contraction is found to be practically identical with that evaluated by von Mises for two-dimensional flow from slots over the entire range of area ratio, and reasonable agreement is shown to exist between measurement and computation. Co-ordinates of the jet profiles are presented in tabular and graphical form, and are found to differ appreciably from those previously adapted from the two-dimensional case. A composite dimensionless chart is also provided showing the distribution of pressure along the boundary and center line and across the efflux section for the various area ratios.
Effect of Sinusoidally Varying Flow of Yield Stress Fluid on Heat Transfer From a Cylinder
Authors: Gupta S. , Patel S. A. , Chhabra R. P. 
Published: April 2021

Abstract
The effect of pulsating laminar flow of a Bingham plastic fluid on heat transfer from a constant temperature cylinder is studied numerically over wide ranges of conditions as Reynolds number (0.1 ≤ Re ≤ 40) and Bingham number (0.01 ≤ Bn ≤ 50) based on the mean velocity, Prandtl number (10 ≤ Pr ≤ 100), pulsation frequency (0 ≤ ω* ≤ π), and amplitude (0 ≤ A ≤ 0.8). Results are visualized in terms of instantaneous streamlines, isotherms, and apparent yield surfaces at different instants of time during a pulsation cycle. The overall behavior is discussed in terms of the instantaneous and time-averaged values of the drag coefficient and Nusselt number. The size of the yielded zone is nearly in phase with the pulsating velocity, whereas the phase shift has been observed in both drag coefficient and Nusselt number. The maximum augmentation (∼30%) in Nusselt number occurs at Bn = 1, Re = 40, Pr = 100, ω* = π, and A = 0.8 with respect to that for uniform flow. However, the increasing yield stress tends to suppress the potential for heat transfer enhancement. Conversely, this technique of process intensification is best suited for Newtonian fluids in the limit of Bn → 0. Finally, a simple expression consolidates the numerical values of the time-averaged Nusselt number as a function of the pertinent dimensionless parameters, which is consistent with the widely accepted scaling of the Nusselt number with ∼Pe1/3 under these conditions.
The Past and Future of the Monte Carlo Method in Thermal Radiation Transfer
Authors: Howell John R. , Daun Kyle J. 
Published: April 2021

Abstract
Since its initial development as a specialty technique for modeling neutron transport in fissile materials almost 80 years ago, the Monte Carlo method has since been deployed in almost every area of science and engineering, including radiative transfer. This paper reviews the history and progress in Monte Carlo methods for simulating radiative energy transfer, with emphasis on advances over the past 25 years. A short historical review that emphasizes the probabilistic foundations of the method, is followed by discussions of recent extensions and applications, including variance reduction techniques, high fidelity simulations in complex media, and a discussion of unresolved issues. The article concludes with an outlook for the method as impacted by advancements in algorithm development as well as massively parallel and quantum computing.
Optimization-Driven Controller Design for a High-Performance Electro-Hydrostatic Asymmetric Actuator Operating in All Quadrants
Authors: Butt Khurram , Costa Gustavo Koury , Sepehri Nariman 
Published: April 2021

Abstract
This paper presents an optimization-driven controller design for smooth and accurate position control of a single-rod electrohydrostatic actuator. The design approach uses logically guided iterative runs of the electrohydrostatic actuator to determine the optimal gain and poles' locations of a low-bandwidth controller. The optimization algorithm used in the paper is the globalized bounded Nelder–Mead algorithm with deterministic restarts for improved globalization and lower numerical cost. The design also incorporates a prefilter to ensure minimum jerk in the system's step input response in the beginning and while approaching steady-state. The step response of the filter is a seventh-deg polynomial curve that ensures the minimum change in acceleration in both states. Experimental results reveal that the addition of the proposed prefilter reduces jerk in the system by up to 90%. Results also indicate that the controller performs very well in all quadrants with external load uncertainty of up to 367 kg and thus proves the effectiveness of the design approach.
Evaluation of the Kinematic Biofidelity and Inter-Test Repeatability of Global Accelerations and Brain Parenchyma Pressure for a Head–Brain Physical Model
Authors: Li Yizhao , Ouellet Simon , Vette Albert H. , Raboud Don , Martin Ashton , Dennison Christopher R. 
Published: April 2021

Abstract
Head surrogates are widely used in biomechanical research and headgear assessment. They are designed to approximate the inertial and mechanical properties of the head and are instrumented to measure global head kinematics. Due to the recent interest in studying disruption to the brain, some head models include internal fluid layers and brain tissue, and instrumentation to measure head intracranial biomechanics. However, it is unknown whether such models exhibit realistic human responses. Therefore, this study aims to assess the biofidelity and repeatability of a head model, the Blast Injury Protection Evaluation Device (BIPED), that can measure both global head kinematics and intraparenchymal pressure (IPP) for application in blunt impact, a common loading scenario in civilian life. Drop tests were conducted with the BIPED and the widely used Hybrid III headform. BIPED measures were compared to the Hybrid III data and published cadaveric data, and the biofidelity level of the global linear acceleration was quantified using CORrelation and Analysis (CORA) ratings. The repeatability of the acceleration and IPP measurements in multiple impact scenarios was evaluated via the coefficient of variation (COV) of the magnitudes and pulse durations. BIPED acceleration peaks were generally not significantly different from cadaver and Hybrid III data. The CORA ratings for the BIPED and Hybrid III accelerations ranged from 0.50 to 0.61 and 0.51 to 0.77, respectively. The COVs of acceleration and IPP were generally below 10%. This study is an important step toward a biofidelic head surrogate measuring both global kinematics and IPP in blunt impact.
The Design and Development of an Eye Drop Aid for Glaucoma Patients
Authors: Srihirun Janyut , Poowaruttanawiwit Prayuth 
Published: April 2021

Abstract
Visual impairment is an important public health problem. A cataract is the most common eye disease, and surgical methods are mostly used. Unlike a cataract, glaucoma may lead to permanent loss of vision and can be treated appropriately using eye drops. In this study, the researchers aimed to create, design, and develop a device called “Eye Drop Aid of Naresuan University (EDANU).” This research employed mixed methods using an in-depth interview and questionnaire, which were conducted with a group of 10 experts to provide preliminary data for the design and a group of 20 volunteers to test the efficacy and safety of the EDANU compared with the instructions of the Xal-Ease™ eye drop administration and instructions as recommended by the Pharmacy Council of Thailand in the laboratory. It was found that the EDANU, which was designed and developed as a prototype using thermoplastic polyurethane, which is a highly flexible material, was more accurate, reliable, and safer than the Xal-Ease eye drop administration. The EDANU displayed efficient statistical significance and proved to be safe for using in the laboratory.This was a device that could help glaucoma patients and their caregivers have a better quality of life because this device was more accurate, reliable, and safer than the other two methods. However, the EDANU is still in the process of prototype development, and, in the future, it would still be necessary to study with a human clinical trial.