bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite-Element Solution of Added Mass and Damping of Oscillation Rods in Viscous Fluids
Authors: Yang C.-I. , Moran T. J.
Published: November 2010

This paper presents a finite-element analysis for the cylindrical rods oscillating periodically in an incompressible viscous fluid. A system of discretized equation is obtained from the appropriate Navier-Stokes and continuity equations through Galerkin’s process. The basic unknowns are velocity and pressure. A mixed interpolation method is used. The added mass and viscous damping coefficients which characterize the fluid reaction force due to the rods oscillation can be obtained through a line integration of stress and pressure around the circumference of the rods. For the special case of a cylindrical rod oscillating in a viscous fluid enclosed by a rigid, concentric cylindrical shell, the finite-element solution agrees well with the analytical closed-form solution, which, in turn, has been verified experimentally [1].
Harmonic Holes for Nonconstant Fields
Authors: Bjorkman G. S. , Richards R.
Published: November 2010

Hole shapes which do not perturb the first invariant of the stress tensor of an isotropic stress field with superimposed linear gradients are derived. These haromonic holes, called the deloid and cardeloid, result from the solution of a nonlinear singular integral equation and can be expressed very simply in parametric form. A comparison of stresses around the boundary of a deloid with a circular hole of the same size shows that the deloid significantly reduces not only the maximum stress concentration but also the total variation of stress around the hole boundary. Deloids and cardeloids without internal boundary loading exist only in locations where the first invariant of the original field does not change sign.
The Singularity at the Apex of a Bonded Wedge-Shaped Stamp
Authors: Parihar K. S. , Keer L. M.
Published: November 2010

The problem of determining the singularity at the apex of a rigid wedge bonded to an elastic half space is formulated by considerations of Green’s functions for the loaded half space. The eigenvalue problem is reduced to finding the solution of a coupled pair of singular integral equations. A numerical solution for small wedge angles is given.
Buckling of Rectangular Cross-Ply Laminated Plates With Nonlinear Stress-Strain Behavior
Authors: Morgan Harold S. , Jones Robert M.
Published: November 2010

The Jones-Nelson-Morgan nonlinear material model is used in the derivation of a buckling criterion for laminated plates with nonlinear stress-strain behavior characteristic of many fiber-reinforced composite materials. A search procedure is developed to solve this buckling criterion which is transcendental because of interdependence of the buckling load and the coefficients relating the variations in laminate forces and moments to the variations in strains and curvatures. The effect of stress-strain curve nonlinearities on laminate buckling loads is illustrated by comparing solutions of the buckling criterion to buckling loads for laminates with linear stress-strain behavior.
Twisted-Pore Effect on Fluid Flow, Solid Deformation and Stress in a Poro-Elastic Cylinder
Authors: Kurashige M.
Published: November 2010

The linearized theory of viscous-fluid-saturated poro-elastic material proposed by Crochet and Naghdi is summarized and applied to the problem of steady fluid flow through a “twisted pore” elastic cylinder. The cylinder is encased in and bonded to an impermeable rigid tube. Deformations and stresses of the cylinder due to the flow are considered. The results of the mathematical analysis and some numerical computations cast light on the “twisted pore” effect.
Optimum Linear Tapering in the Design of Columns
Authors: Dinkoff B. , Levine M. , Luus R.
Published: November 2010

Optimum linear tapering of a simply supported solid column enables a saving of 10.4 percent of material, as compared to a nontapered column.
Polynomial Definiteness and Semidefiniteness
Authors: Chen Chiou-Shiun , Kinnen Edwin
Published: November 2010

A reduction procedure is described for determining the sign definiteness and semidefiniteness of an mth order, n dimensional real polynomial. The higher order polynomial is reduced to a quadratic form in new variables such that conditions can be obtained on the coefficients of the individual terms of the original polynomial. The procedure presents sufficient conditions only. It has been found, however, to be a relatively systematic technique for engineering stability problems where alternate effective methods for determining sign definiteness are unknown.
The Development of the Reynolds Stress Tensor in a Turbulent Shear Flow
Authors: Shamroth S. J. , Elrod H. G.
Published: November 2010

The development of the normalized Reynolds stress tensor, uiuj/q2, in the region upstream of a fully developed, turbulent shear flow is investigated. An inviscid, linear model is used to predict values of the normalized Reynolds stress tensor as a function of position. The theoretical predictions are then compared with experimental results.
On Nonuniform Flow Characteristics at the Vena Contracta
Authors: Ghazi Hassan S.
Published: November 2010

The kinetic energy correction factor for the flow at the vena contracta is calculated using experimental data and a modified Bernoulli equation. Based on an assumption of similarity of the profiles upstream and downstream of an orifice, two other nonuniformity factors, the momentum correction factor and the ratio of average velocity to center-line velocity, are also determined.
Some Solutions of the Plane Turbulent Impinging Jet
Authors: Wolfshtein M.
Published: November 2010

The impinging jet problem is solved by an iterative finite-difference technique. Reynolds stresses are assumed to be related to the mean strain by a scalar eddy viscosity. The eddy viscosity is assumed to depend on the level of energy fluctuations and a length scale. The level of energy fluctuations is obtained from a second-order differential equation, while the length scale of turbulence is prescribed on the basis of experimental information. The solutions show reasonable agreement with experiment.
Jet Reattachment to Walls of Various Shapes
Authors: Rockwell Donald O. , Fiske Preston M.
Published: November 2010

Velocity fields for jets reattaching to walls of various shapes (curved and inclined straight), setbacks, and control port conditions were examined experimentally for the case of undeveloped velocity profiles at the nozzle exit. A canting of the nozzle exit profile occurred for cases where the wall was set back from the lip of the nozzle exit. Significantly different growth characteristics were observed for the case of the inclined straight wall, relative to the curved walls, due to the sharp turning angle which the jet was required to negotiate in the vicinity of the nozzle exit. For each jet, a well-defined settling length was noted by plotting the position of the maximum velocity versus arc length from the nozzle exit. Whenever possible, results were compared with previous investigations for fully developed conditions at the nozzle exit. Off-midplane total pressure profiles were taken for the inclined straight wall and a curved wall at several arc lengths, and three-dimensional effects were found to be significant for arc lengths and nozzle aspect ratios of interest in digital flueric amplifiers.
Large Deformation Analysis of the Arterial Cross Section
Authors: Simon B. R. , Kobayashi A. S. , Strandness D. E. , Wiederhielm C. A.
Published: November 2010

Possible relations between arterial wall stresses and deformations and mechanisms contributing to atherosclerosis are discussed. Necessary material properties are determined experimentally and from available data in the literature by assuming the arterial response to be a static finite deformation of a thick-walled cylinder constrained in a state of plane strain and composed of an incompressible, nonlinear elastic, transversely isotropic material. Experimental justification from the literature and supporting theoretical considerations are presented for each assumption. The partial derivative of the strain energy density function δW1/δI , necessary for in-plane stress calculation, is determined to be of exponential form using in situ biaxial test results from the canine abdominal aorta. An axisymmetric numerical integration solution is developed and used as a check for finite element results. The large deformation finite element theory of Oden is modified to include aortic material nonlinearity and directional properties and is used for a structural analysis of the aortic cross section. Results of this investigation are: (a) Fung’s exponential form for the strain energy density function of soft tissues is found to be valid for the aorta in the biaxial states considered; (b) finite deformation analyses by the finite element method and numerical integration solution reveal that significant tangential stress gradients are present in arteries commonly assumed to be “thin-walled” tubes using linear theory.
Method of Separation of Variables for the Solution of Certain Nonlinear Partial Differential Equations
Authors: Bapat V. A. , Srinivasan P.
Published: November 2010

A method for the solution of a certain class of nonlinear partial differential equations by the method of separation of variables is presented. The method enables the nonlinear partial differential equation to be reduced to ordinary nonlinear differential equations, which can be solved by exact methods (or by approximate methods if an exact solution is not possible).
Measurements of Mean Flow Velocity Beyond a Rotating Disk
Authors: Chanaud R. C.
Published: November 2010

Measurements were made of the mean velocity components of the turbulent flow field just beyond the edge of a thin disk rotating in its own plane. An approximate analysis was made of the turbulent strongly swirling radial jet flow region by recourse to the momentum integral technique. Comparison with experiment indicated that approximate similarity of both the tangential and radial velocity components was achieved in a few disk thicknesses. The angle of the flow from radial in the disk plane compared fairly well with that predicted by the present analysis but poorly with the exact asymptotic theory. Nearly discrete frequency vortex shedding at the disk edge was detected by pressure-correlation measurements just outside the boundary layer.
Anisotropy of Fatigue Crack Propagation
Authors: Heiser F. A. , Hertzberg R. W.
Published: November 2010

The anisotropy of fatigue crack propagation in hot rolled steel plate was studied for three orientations, viz., crack arrester, crack divider, and short transverse. The dependence of crack growth rate on stress intensity factor was shown to be sensitive to the microconstituents present and their orientation relative to the fracture plane and direction. Generally, this dependence increased as the material toughness decreased and when the mechanical fibering was parallel to the facture plane and direction. The macroscopic growth rates, were considered as the summation of several macroscopic mechanisms, including striation formation and inclusion-matrix fracture. The data show that striation spacing was independent of orientation and that the fracture of inclusions was primarily responsible for the observed crack growth anisotropy.
Two-Dimensional Miter-Bend Flow
Authors: Heskestad G.
Published: November 2010

Measurements have been made of the mean flow in a two-dimensional, constant-width, ninety-degree miter bend and compared with predictions of available free-streamline theories. Agreement is quite favorable, especially with a model incorporating separation ahead of the concave corner. Reynolds number effects observed in real flows are argued to be associated with changes in the location of the outer-wall separation point. Requirements for relevancy of free-streamline models of internal flows separating at a salient edge are suggested and confirmed for cases examined.
Arbitrary Mean Flow in Adverse Pressure Gradients
Authors: Bragg G. M. , Suk J. K.
Published: November 2010

Measurements of mean velocity profiles were made in the turbulent wake behind a single cylinder as well as a row of parallel, arbitrarily spaced and arbitrarily sized cylinders with an adverse pressure gradient. Two currently available calculation methods, based on a simple superposition of momentum, and a step-by-step finite difference procedure, were applied to the prediction of mean velocity profiles in the wake. The agreement between the predicted and the observed results is good in most cases with maximum error less than 18 percent of significant velocity defects or 3 percent of local velocity.
Steady Extrusion of Superplastic Metallic Alloys
Authors: Tang S.
Published: November 2010

A three-dimensional theory of superplasticity is developed, based on the requirement that in the uniaxial case it shall reduce to the Packer-Sherby law. Analytical solutions are obtained for steady extrusions through a rectangular orifice and a circular orifice. A numerical example is given.
The Indentation of an Elastic-Perfectly-Plastic Half-Space by a Hard Sphere
Authors: Hardy C. , Baronet C.-N. , Tordion G.-V.
Published: November 2010

The indentation of hard steel spheres into the plane surface of quasi elastic-perfectly-plastic metallic materials has been investigated experimentally. It is shown in the present note that uniform results are obtained when the experimental data corresponding to some materials are reduced to a common base. These results are in fairly good agreement with the predictions of a previous finite element analysis by the same authors.
A Family of Hodograph Models for the Cross Flow Velocity Component of Three-Dimensional Turbulent Boundary Layers
Authors: Shanebrook J. R. , Hatch D. E.
Published: November 2010

A family of hodograph models for the cross flow velocity component of three-dimensional, turbulent boundary layers is presented. The principal advantage of this family is its flexibility which allows a wide variety of possible shapes for the hodograph. An integral method based on this family is developed and applied to data obtained in curved, rectangular channels. For the cases treated, the method gives acceptable results for cross flow profiles with and without flow reversal. Suggestions for refining the method are given.
Anisotropic In-Reactor Sag of Pressure Tubes
Authors: Holicky M. , Schroeder J.
Published: November 2010

A basic solution for in-reactor sag of horizontal pressure tubes is proposed in accordance with a nonlinear anisotropic creep theorem. As an example, numerical solutions for in-reactor sag of cold-worked zircaloy-2 pressure tubes supported at the ends only are given for various combinations of anisotropy coefficients. It is shown that an isotropic analysis may overestimate or underestimate the deflection due to sag by about 100 percent if hoop creep rates are about 50 percent smaller or larger than longitudinal creep rates.
Calibration and Application Techniques for Platinum Resistance Thermometers
Authors: Benedict R. P. , Russo R. J.
Published: November 2010

The International Practical Temperature Scale has been redefined recently. It follows that the interpolating equations relating platinum resistance to temperature must be reevaluated for all platinum resistance thermometers which are used as standards for calibration work. After a brief review of the former calibration procedure, the new temperature scale is discussed as it affects resistance thermometry in the temperature range from 0 C to 630.74 C. An example based on new experimental data is given to illustrate the method of determining thermometer constants for the new scale, and to indicate the magnitude of the changes required.
Analysis and Testing of Compressible Flow Ejectors With Variable Area Mixing Tubes
Authors: Hickman K. E. , Hill P. G. , Gilbert G. B.
Published: November 2010

An analytical model has been developed to predict the flow behavior within axisymmetric single-nozzle ejectors employing variable-area mixing tubes. The primary flow may be supersonic or subsonic and may have a different stagnation temperature than the subsonic secondary flow. Tests were performed on an ejector with an 800 deg F supersonic (M = 2.72) primary jet to evaluate the analytical model. Measured velocity profiles, temperature profiles, and wall static pressure distributions are presented and compared to the analytical predictions. Agreement is generally good.
A Mathematical Analog for Determination of Porous Annular Disk Squeeze Film Behavior Including the Fluid Inertia Effect
Authors: Ting L. L.
Published: November 2010

A simple mathematical analog for determination of the squeeze film behavior between two parallel annular disks, one having a porous facing, from the already available solutions of comparable nonporous disks is presented. A comparison of the analog solution with a Fourier-Bessel solution has been made and the agreement is found to be good for a range of values of the permeability parameter and the porous facing thickness. The results also have been extended to include the rotating inertia effect of the film fluid. The resulting dimensionless pressure distribution and the dimensionless squeeze film load are expressed in terms of a permeability parameter, inertia parameter, squeeze film number, and the disk dimensions. For constant squeeze film load, a relationship between squeeze time and film thickness also has been obtained. Generally, the presence of the porous facing will decrease the squeeze film load and will reduce the total squeeze time to some finite value. The inertia effect will further decrease the squeeze film load and the squeeze time, however, the squeeze time reduction due to the inertia effect will become small if the porous facing has high permeability and is thick.
A Computer-Based Electro-Optical System for Measuring Wave-Induced Sand Concentrations
Authors: Glover J. R. , Locher F. A. , Bhattacharya P. K.
Published: November 2010

A computer-based system utilizing an electro-optical instrument has been developed for generating and processing a signal proportional to the instantaneous sand concentration at a point in a flow field. Herein are described the instrumentation and techniques used in a study of sediment entrainment by periodic waves breaking on sand beaches. The instantaneous sediment concentration has been decomposed as follows: C(x,y,z,t)=C¯(x,y,z)+C′(x,y,z,t)+Cp(x,y,z,t) where C(x, y, z) is the temporal average concentration, C′(x, y, z, t) is a random component of the sediment concentration, and Cp(x, y, z, t) is a repetitive component with period equal to the period of the breaking waves. Particular attention has been given to isolating the repetitive component which was so obscured by the signal characteristics that no periodicity was apparent on either an oscilloscope trace or a strip chart recorder. Spectral analysis was not applicable because the shape of the repetitive waveform, Cp(x, y, z, t), over one wave cycle was desired.
Application of Fluid Transients to Hydraulic Mining
Authors: Contractor D. N.
Published: November 2010

Hydraulic mining involves the erosion of a material with a high speed water jet. This technique can be applied to coal mining, tunnelling for high speed ground transportation systems and drilling for deep oil wells. A high speed, unsteady jet of water is known to have a much greater potential for hydraulic mining than a steady jet of water. A comprehensive study of mining with unsteady jets would involve three aspects: (1) the hydraulic and mechanical aspects of producing an unsteady jet, (2) the study of the dispersion of the jet, and (3) the response of the material being eroded. This paper deals with the first aspect and studies three different systems for producing unsteady water jets. A computer program was written to calculate the unsteady jet velocities for each system using the method of characteristics. The unsteady jet velocity was integrated and used in a theoretical model to compare the effectiveness of the three different systems. The effect of varying certain design and operating parameters of the system was also studied. Factors affecting the choice of the appropriate system are discussed.
A Viscometer for High-Pressure Use, and Some Results
Authors: Winer W. O.
Published: November 2010

Metalworking under pressure requires viscosity data for the working fluids. A suitable viscometer is described and data on three typical hydrostatic metal working fluids presented.
Influence of Tangential Fluid Injection on the Performance of Two-Dimensional Diffusers
Authors: Fiedler R. A. , Gessner F. B.
Published: November 2010

The influence of tangential fluid injection on the performance of inherently stalled, two-dimensional diffusers is examined both analytically and experimentally. In particular, the effects of injection flow rate, slot size, and blowing system efficiency on pressure recovery characteristics are investigated. A finite-difference method of analysis based on a model suggested by Patankar and Spalding is used to predict diffuser performance with jet blowing for purposes of comparison with the experimental results. The analysis is also utilized to predict the influence of variations in injection slot location and jet velocity profile shape on overall performance. The results show that significant increases in diffuser performance can occur with fluid injection, even when jet blowing power requirements are taken into account.
Analysis of Mean Flow Characteristics of Gas-Solids Suspensions
Authors: Kramer T. J. , Depew C. A.
Published: November 2010

Solutions for the point mean flow field properties in the turbulent core for suspension flow in a vertical circular tube have been developed for the fully developed flow condition. For uniform particle density flows, the suspension velocity distribution is logarithmic and is given in terms of parameters which must be determined by experiment, but the paper shows that all flows which satisfy the conditions of the model should follow the same universal law. Analytic expressions for the gas velocity and the slip velocity are also presented. The purpose of the analysis was to produce solutions of practical utility and to provide a basis for the extrapolation and interpretation of experimental results which are presented in another paper.
Wave Propagation in Viscous, Compressible Liquids Confined in Elastic Tubes
Authors: DeArmond R. P. , Rouleau W. T.
Published: November 2010

The problem of steady-state, small amplitude, periodic wave propagation in a viscous, compressible liquid contained in an infinitely long, elastic tube is solved for the complex propagation constants of the two lowest modes of motion. One mode has a speed of propagation and decay constant characteristic of acoustic waves propagating in a liquid; the other mode corresponds to acoustic waves propagating in an elastic tube. The behavior of these two modes is investigated as a function of frequency, viscosity, and tube rigidity. A third mode of motion corresponding to edge loads on the tube is also investigated. This mode, unlike the other two modes, is characterized by a cut-off frequency above which the propagation distance is infinite and below which it is finite.
Hydrodynamic Drag of Semisubmerged Ships
Authors: Chapman R. B.
Published: November 2010

Linearized theory for wave-making resistance is applied to semisubmerged ships. Theoretical and experimental values are compared for submerged hulls, struts, and struts in tandem. Strut forms producing minimum wave-making resistance are calculated at several speeds and water plane areas for a typical submerged hull. Struts are described in terms of step functions to facilitate an investigation of multiple struts including the effect on drag of decreased wetted surface area.
Optimization of Elastic, Multilayer, Cylindrical Vessels Loaded by Pressure and Radial Thermal Gradient
Authors: Huddleston R. L. , Dewey B. R.
Published: November 2010

Radius and interference design parameters of elastic, multilayer, thick-walled cylindrical vessels are optimized on the basis of the Mises distortion energy yield criterion. Loadings are assumed uniform along cylinder length and may be independently applied or combined internal pressure and steady-state axiallysymmetric thermal gradients, as well as specified initial stresses to simulate autofrettage or other residual stresses. The optimization is effected by an accelerated, steepest-ascent, gradient projection method, subjected to constraints on loaded stress intensity, shrink stress intensity, end loading, tangential stress (e.g., for a brittle liner), and monotonic-decreasing interface pressures. Independent elastic and thermal properties are allowed for each layer; however, time-dependent phenomena are not considered. The general procedure developed is compared with several published optimization solutions for various special cases.
Nonlinear Constitutive Relations for Human Brain Tissue
Authors: Pamidi M. R. , Advani S. H.
Published: November 2010

Head injury modeling studies warrant detailed investigations into the rheological behavior of brain tissue. This paper deals with the development of the concept of a power function and employs energy principles to derive nonlinear constitutive relations for human brain tissue. Nonlinear discrete and continuum models are constructed and it is found that the model predictions compare well with experimentally determined in-vitro properties of human brain tissue under uniaxial loading conditions.
Therapeutic Effects of Postburn Cooling
Authors: Ross D. C. , Diller K. R.
Published: November 2010

The use of cooling as first aid in burn injury has been widely justified and employed although, at present, there exists no defined scientific verification of its physiological benefit or a rational therapeutic protocol to follow. The objective of this study was to identify and to quantify the primary parameters which control cooling therapy. Experiments were performed on over 200 hamster cheeckpouch preparations by creating a standard burn in the tissue resulting in the occlusion of a predictable percentage of vessels in the microcirculation. Following a delay of either 30 s or 10 min, the tissue was cooled to a temperature ranging between 3°C and 25°C for either 5, 30, or 60 min. In general, postburn cooling caused resumption of blood flow in a number of vessels which would otherwise have remained inactive. Optimum cooling temperatures were within the range of 5°C to 10°C, and were more effective when initiated immediately following the burn and maintained for times extended to 1 hr.
A Gait Analysis Subsystem for Smoothing and Differentiation of Human Motion Data
Authors: Lesh M. D. , Mansour J. M. , Simon S. R.
Published: November 2010

A computer-based subsystem has been implemented for the smoothing and differentiation of human motion data. Nonrecursive finite impulse response digital filtering has been employed for this purpose. Filter cutoff frequency was determined using a statistical error analysis. The method of data differentiation used here is compared to other methods presented in the literature.
Bioengineering Considerations in the Design of Protective Headgear
Authors: Claus W. D.
Published: November 2010

Bioengineering aspects of headgear design are surveyed to illustrate the interactions and contributions of different engineering disciplines to military headgear design. Illustrations are drawn from the fields of anthropometry, human factors, heat transfer, acoustics, and applied mechanics. In addition, a helmet design procedure is described which takes into consideration such interactions. The procedure was successfully used in the design and development of a new ballistic protective infantry helmet. This methodology is equally applicable to the design of civilian head protective devices. Possible applications are pointed out.
In-Vitro and Predicted In-Vivo Performances of a Pneumatically Regulated Artificial Ventricle
Authors: duPlessis M. P. , Tsang S.
Published: November 2010

An all-pneumatic driving system is presented which provides close duplication of the Starling’s cardiac regulation function to an artificial left ventricle in mock circulation. The system, built from commercially available fluid operated devices, uses atrial pressure feedback to adjust the ventricle pumping air pressure, with the aid of a hydraulic/pneumatic pressure transducer developed especially for the application. A simple linear mathematical model for the physiological circulatory system is used to compare the simulated in-vivo performance of the system with Starling’s response of the natural left heart for different systemic resistances and compliances. The model is valid for output flows from 1 to 10 l/min and atrial pressure from 1 to 8 mmHg. It shows close agreement in ventricle output, arterial and atrial pressure changes between the artificial ventricle and the natural left heart for systemic resistance changes from about 5 × 104 to 5 × 105 kN-s/m5 and for typical venous to arterial compliance ratios of 24 to 37.
Finite Elastic Deformation for a Class of Soft Biological Tissues
Authors: Wu Han-Chin , Reiss R.
Published: November 2010

The stress response of soft biological tissues is investigated theoretically. The treatment follows the approach of Wu and Yao [1] and is now extended for a broad class of soft tissues. The theory accounts for the anisotropy due to the presence of fibers and also allows for the stretching of fibers under load. As an application of the theory, a precise form for the strain energy function is proposed. This form is then shown to describe the mechanical behavior of annulus fibrosus satisfactorily. The constants in the strain energy function have also been approximately determined from only a uniaxial tension test.
A Motion Transducer for Use in the Intact In-Vitro Human Lumbar Spine
Authors: Koogle T. A. , Piziali R. L. , Nagel D. A. , Perkash I.
Published: November 2010

An electromechanical transducer was developed to enable measurement of the general six degree-of-freedom relative motion between lumbar vertebrae of the in-vitro human spine. The transducer system is to be used in the evaluation of various spinal fixation devices in studies of fracture dislocated spines. Preliminary testing of the system has shown it to be an accurate and general means of measuring relative spatial motion between two bodies over a limited range.
Optimal Control of On-Board and Station Flywheel Storage for Rail Transit Systems
Authors: Sweet L. M. , Keane M. J.
Published: November 2010

The energy efficiency of rail transit systems using regenerative braking is enhanced by flywheel storage elements used to store energy not accepted by the wayside power rail. In this paper three storage system control concepts are examined: armature and field control of on-board flywheels, and field control of a station-based storage device. The energy recovery efficiency and performance characteristics of each system are determined subject to optimal control laws derived to minimize energy loss. The resulting control systems are bilinear, due to the use of separately excited DC traction and flywheel motors as continuously variable transmissions. The three systems yield similar energy recovery efficiencies for deceleration, with the advantages of each for practical applications discussed.
A State-Constrained Approach to Vehicle-Follower Control for Short Headway Automated Transit Systems
Authors: Pue Alan J.
Published: November 2010

Vehicle following in an automated transit system is a longitudinal control scheme where the state of a given vehicle is determined by the behavior of the preceding vehicle. At short time headways (0.5 to 3.0 s) a kinematic constraint on vehicle operation arises as a consequence of the velocity, acceleration, and jerk limits imposed to assure passenger comfort. This constraint requires a trailing vehicle to maintain a spacing such that it may react to nominal (nonemergency) preceding vehicle maneuvers without collision and without exceeding service jerk and acceleration limits. The large initial conditions which may result preclude the use of linear time-invariant feedback. Thus a nonlinear feedback controller is designed which forces the vehicle to follow the kinematically required spacing until the desired headway is attained. The design is based upon a technique which uses an approximately optimal feedback control with state constraints. In addition, several suboptimal controls with reduced informational requirements are presented, thus producing an easily instrumentable controller which properly responds to all possible nominal maneuvers of a preceding vehicle.
Closed Loop, Knock Adaptive Spark Timing Control Based on Cylinder Pressure
Authors: Hosey R. J. , Powell J. D.
Published: November 2010

One of the important inputs to a spark ignition engine which affects nearly all engine outputs is spark advance. Spark advance not only affects fuel efficiency and exhaust emissions but is also a factor in the tendency for detonation or engine knock. Increasing pressure for reduction of emissions and better fuel economy is making effective spark advance control more important. The desire for improved efficiency is complicated by the increased use of low octane, lead-free gasoline which is an influence toward conservative, inefficient engine designs for reduction of engine knock. Conventional spark advance systems control on parameters which are inputs to the combustion process, such as manifold vacuum and engine speed. This paper describes a microprocessor based spark timing controller based on measurements of cylinder pressure history, a parameter which is a result of the combustion process. To feedback element is an experimental piezoelectric pressure transducer of an inexpensive design which would be suitable for mass production. Results are presented showing that this feedback controller is able to control spark advance to 1 percent of optimum even over fuel-air ratio changes of 40 percent. The controller also effectively controls engine knock to levels which are not harmful.
Nonlinear Wheelset Forces in Flange Contact—Part 2: Measurements Using Dynamically Scaled Models
Authors: Sweet L. M. , Sivak J. A. , Putman W. F.
Published: November 2010

This paper presents new experimental methods for the study of rail vehicle dynamics through the use of scaled models on tangent track, and the application of these techniques to the measurement of nonlinear wheelset force/displacement relations in steady-state. These relations are important to the analysis of wheelset response to track inputs, curving performance of trucks, and wheelclimb derailment. A one-fifth scale model instrumented wheelset with new wheel profiles is used, with similitude scaling of the contact forces achieved through use of a polycarbonate resin for the contact surfaces. Data are presented for wheelset lateral force and yaw moment for the nonlinear range of wheelset lateral displacements and yaw angles, including flange contact. The measured data validate the analytical model presented in Part 1 of this paper, based on nonlinear wheel/rail contact geometry, creep forces with adhesion limits, and wheelset kinematics. A criterion for wheelclimb derailment is presented and verified experimentally.
Design of a Practical Controller for a Commercial Scale Fossil Power Plant
Authors: Ray Asok , Berkowitz D. A.
Published: November 2010

To design an improved fuel controller for an operating, 386 MW(e), oil-fired power generation system, a mathematical model of the plant was developed from fundamental principles to predict thermal-hydraulic transients. This controller was successfully implemented in the actual plant by replacing a portion of the original control system. It was shown that the resulting minimum operating level of the system could be reduced from 220 MW (e) to flash tank level of 130 MW(e), and the customary load rate of change during normal operation improved from approximately 2 MW/min to 9 MW/min. Operation of the plant on automatic dispatch was subsequently demonstrated.
Some Further Contributions to the Dynamic Sensitivity of the Parameter Perturbation Process
Authors: Gupta M. M. , Nikiforuk P. N.
Published: November 2010

In a previous paper [1], the concept of the dynamic sensitivity of a system state and its performance was introduced for a continuous linear system with small arbitrary perturbations in the system parameters. In this paper this concept is extended to a class of nonlinear and linear systems. It is shown that plant and controller parameters uncertainties (internal disturbances) may be regarded as a state-dependent noise at the input of the plant. The analysis is then applied to a continuous linear situation. As an example, a satellite attitude control with randomly varying tracking signals is considered; and the dynamic sensitivity behavior of the parameter-uncertainty-transmission path, from the controller parameters to the process performance index, is studied.
Evaluation of Neuromuscular Parameters Describing Human Reflex Motion
Authors: Soechting J. F. , Stewart P. A. , Hawley R. H. , Paslay P. R. , Duffy J.
Published: November 2010

In a companion paper to the present, a model is derived to predict human reflex motion. This model contains a set of seven neuromuscular parameters which are evaluated in the present paper on the basis of results obtained from experiments performed on the human forearm. In these experiments, forearm position is studied following an abrupt change in load and the parameters are evaluated using an identification scheme which minimizes an error function containing forearm position. The relative importance of the various parameters is discussed as well as the relation between the proposed model and previous models in this field.
An Active Suspension System Design for the Lateral Dynamics of a High-Speed Wheel-Rail System
Authors: Sarma G. N. , Kozin F.
Published: November 2010

Railroad cars are known to exhibit instabilities in the lateral dynamics at high speeds. To solve some of the problems of stability, an active suspension system is studied for the high-speed rail vehicle and is compared with the passive system. The vehicle control problem is formulated as an optimization problem with an integral quadratic cost function, and the feedback law thus obtained is further simplified. For the case of the truck dynamics, with external controllers, a Lyapunov function approach is taken for considering state constraints. Stability regions are obtained by analog computer simulation.
On Systems With Coupled Chemical Reaction and Diffusion
Authors: Auslander D. M. , Oster G. F. , Perelson A. , Clifford G.
Published: November 2010

A bond graph method is described for treating nonlinear diffusion-chemical reaction processes in homogeneous or heterogeneous media. A program has been developed to study steady-state and dynamic response for a system with an arbitrary number of reactants and reactions. An experimental system selected for study is the facilitated diffusion of oxygen through a hemoglobin solution.
Dynamic Interactions of High Speed Tracked Air Cushion Vehicles With Their Guideways: Part I of a Parametric Study
Authors: Biggers S. B. , Wilson J. F.
Published: November 2010

The vehicle-guideway system is modeled as an arbitrary number of lumped, doubly-sprung vehicle mass systems traveling in tandem along simple supported beams. The vehicle load is transmitted to the guideway as a time-varying uniform pressure compatible with vehicle motion. Effects of the dimensionless system parameters on vehicle heave acceleration, and guideway deflections and bending moments at high vehicle speeds are evaluated. Results for a vehicle which includes pitching motion compare favorably with those for a vehicle without pitch where the front and rear masses are uncoupled. By proper choice of parameters, passenger compartment heave accelerations can be minimized, although to keep this acceleration below 0.05g for vehicles traveling 100–300 mph requires systems with low vehicle to beam mass and frequency ratios as well as low vehicle lower to upper mass ratios. The benefits of distributed air cushion pressure to vehicle and guideway design are shown. Also, if the ratio of lower to upper vehicle mass is low, a constant moving pressure conservatively predicts the guideway response.
A Flueric Accelerometer
Authors: Rakowsky Edward L. , Schmidlin Albertus E. , Desantis Michael J.
Published: November 2010

This paper describes a unique single-axis, analog flueric accelerometer which has undergone laboratory evaluation over a range of 0–130 g’s. The device contains essentially no moving parts since the solid proof mass has been eliminated. The accelerometer consists of a hollow, porous cylinder with porous endwalls, and encapsulated within the cylinder is a heavy non-wetting liquid such as mercury. Surface tension prevents seepage of the liquid through the cylinder walls. In response to the local acceleration, the mercury develops large hydrostatic pressure gradients which are proportional to and aligned with the acceleration vector. The output is obtained in the form of a differential gas pressure, the magnitude of which is a direct function of acceleration. Details of the input fluid power requirements and representative output characteristics are presented.
Temporal Hierarchies in the Regulation of Mammalian Fluid and Electrolyte Balance
Authors: Marsh D. J.
Published: November 2010

The hypothesis is put forth that fluid and electroylte regulation in mammals has oscillatory dynamics with several recognizeable frequencies. This view is supported by examples drawn from the physiology literature, covering a frequency spectrum from 1 Hz to 3 × 10−8 Hz. The persistence of these rhythms is used to support the theory that the system regulating fluid and electrolyte balance can be described as an ensemble of loosely coupled non-linear oscillators.
Physiological Pharmacokinetics
Authors: Dedrick R. L.
Published: November 2010

This paper reviews the physiological bases of pharmacokinetics and discusses the use of physiological and biochemical information in developing compartmental models. Pharmacokinetic principles are illustrated by reference to published work on methotrexate distribution in several animal species. Use of pharmacokinetics in predicting drug effect is cited.
On the Principle of Specific Coding
Authors: De Boer E.
Published: November 2010

In the inner ear (cochlea) the acoustical stimulus is encoded into the ensemble of pulse series occurring in each of the 40,000 nerve fibers of the auditory nerve. The cochlea exhibits, on hydrodynamic grounds, a frequency-to-space transformation with a modest amount of frequency resolution. For sinusoidal stimuli the nerve fibers show a far greater frequency selectivity. The instants at which action potentials (nerve pulses of uniform waveform) may occur in an individual nerve fiber can be predicted from a signal transformation model which contains as its most essential elements a linear filter followed by a triggerable pulse generator. This model explains frequency selectivity and phase locking for sinusoidal stimuli in a satisfactory way, provided the correct parameters are selected in accordance with the specific properties of the nerve fiber under study. Whether such, a model would represent frequency resolution in a more general sense, remains to be seen. As far as the linear circuit, part one of the model, is concerned, application of a cross-correlation technique under stimulation with white noise would yield the filter’s impulse response characteristic. However, in the physiological experiment the output of the filter is not accessible. It has been shown that with a special correlation technique, utilizing the (analog) stimulus signal and the (digital) series of action potentials of a nerve fiber, it is possible to recover the essential properties of the linear filter’s impulse response. Application of this “reverse correlation” technique in experiments on anaesthetized cats has shown that under stimulation with white noise the filter has a very sharp frequency response. This effective frequency response agrees well with the one obtained with sinusoidal signals. That this response is so much sharper than the mechanics of the cochlea would allow for, remains a puzzling, and as yet unexplainable, fact. It is concluded that frequency analysis in the cochlea proceeds as if it were realized by a linear filter and the initiation of nerve pulses is a process that operates quite independently of it. Each one of the nerve fibers of the auditory nerve is apparently excited by a specific portion of the acoustical stimulus’ frequency spectrum; the “resonance frequencies” of the fibers covering the entire range of audible frequencies. This property is referred to as the “principle of specific coding.” The findings bear an interesting relation to properties of the (human) auditory system that have been obtained by psychophysical experiments. From several problem areas one can infer that the manner of signal encoding as described by the principle of specific coding is not exhaustive. It may well be possible that finer details about the excitation pattern of nerve fibers are processed by higher auditory centers.
Thermal Control in Man: Regulation of Central Temperature or Adjustments of Heat Exchanges by Servomechanism?
Authors: Houdas Yvon , Sauvage Annie , Bonaventure Maryse , Ledru Christine , Guieu Jean-Daniel
Published: November 2010

A model of the thermoregulatory mechanisms of the human subject submitted to a heat load is presented. It is based on the hypothesis that the thermoregulatory system controls mainly the level of body heat storage but not directly the deep body temperature. The thermoregulatory system would thus appear to be a servomechanism for the heat exchanges rather than a regulator of central temperature.
Minimum Vehicle–Guideway Clearances Based on a Contact Frequency Criterion
Authors: Hullender D. A.
Published: November 2010

An important consideration in the design of air cushion and magnetic suspensions is the power required to suspend or levitate the vehicle in equilibrium. Since this power level increases with an increase in the equilibrium clearance between the base of the suspension and the guideway, it is desirable to keep the design clearance as small as possible. Ideally, the base of the vehicle would never contact the guideway. Statistically, however, contact does occur and to establish a general criteria for defining minimum clearances based on the frequency of contact would be extremely difficult since the effects of contact, such as noise, vibration, wear, etc., vary with different design configurations and materials. The criteria of a very low average contact frequency (10−3 contacts/sec) is used in this paper to define the lower bound on vehicle-guideway clearance. Results are tabulated for an optimum suspension with heave dynamics and guideway irregularity inputs only. The sensitivity of the minimum clearance to guideway irregularity amplitude and wavelength characteristics and to RMS levels of primary suspension acceleration (force) levels is demonstrated. The results indicate that equilibrium clearances on the order of 0.03 in. are tolerable for operation over guideways as smooth as welded rail and that clearances on the order of 1.5 in. may be required for operation over guideways as rough as smooth highways.
Monitoring: An Environmental State Estimation Problem
Authors: Brewer J. W. , Moore S. F.
Published: November 2010

A monitor is defined to be an estimator which minimizes the cost of taking measurements and which, simultaneously, meets constraints on accuracy. It is anticipated that the development of a monitor theory will facilitate environmental-technological system design. The authors propose that monitor synthesis can be divided into two subproblems. The “design problem” is to select the variables for measurement, to select the measurement devices, and to select the spatial distribution of the devices. The “management problem” is to select, on line, the type and sequencing of measurements. The note concludes with a simulated application of filter theory to the management of a water quality monitor. It is demonstrated that a suboptimal minimum cost monitor is, thereby, synthesized by the proper sequencing of costly measurements.