bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonsimilar Solution of the Laminar Boundary Layer in an Oscillatory Flow by an Integral Matrix Method
Authors: Gastrock B. A. , Miller J. A.
Published: November 2010

The development of a numerical technique for the treatment of two-dimensional non-similar, unsteady, laminar boundary layers is presented. The method is an extension to nonsteady flows of the integral matrix procedure of Kendall. Solutions of example problems are presented demonstrating good agreement with known classical results. Core storage requirements of 130K bytes allow consideration of as many as 1250 field points and 50 time increments per oscillation cycle. Solution of oscillating Blasius flow for 8 nodal points and 16 time increments in 13.49 seconds demonstrates the practicality of the computational time required, while agreement with both the analysis and experiment of Nickerson for this flow is excellent.
On Entropy Production in Adiabatic Flow in Turbomachines
Authors: Horlock J. H.
Published: November 2010

In three recent papers, Smith [1], Marsh [2], and Novak [3] have given general equations for the flow in turbomachines and methods for their solution. Each author has worked from momentum equations for an inviscid fluid, but has introduced entropy increases in adiabatic flow. Such increases are inconsistent with the basic assumption of inviscid flow in the momentum equations, as the authors have stated. The purpose of this paper is to examine the nature of this inconsistency and to suggest modifications of the equations used by the three authors by the introduction of dissipative forces into the momentum equations. A particular example is calculated, with and without the dissipative force term, to illustrate the order of magnitude of the effect.
Transition and Mixing in the Shear Layer Produced by Tangential Injection in Supersonic Flow
Authors: Gilreath H. E. , Schetz J. A.
Published: November 2010

The interaction between a viscous mixing layer induced by tangential injection, and an external supersonic flow field is considered experimentally and analytically. Both subsonic and supersonic injection are investigated. The experiments were performed at freestream Mach numbers of 2.85 and 4.19 using air as the injectant. The principal observations are in the form of spark schlieren photographs, interferograms, and wall pressure distributions. The experiments were arranged to cross Lin’s neutral stability boundary for parallel streams. Transition occurred in all cases, but an increase in stability was noted with either a decrease in the injectant Mach number or an increase in the Mach number of the external flow. Both of these results follow the trends predicted by the stability theory. For the supersonic injection cases, it was found that simple inviscid theory is sufficient to predict the overall interaction pattern between streams, when the ratio of initial boundary layer thickness to the injection slot height is small. However, when the injection is subsonic, the injectant initial conditions in terms of either pressure or Mach number at the slot exit are determined by the downstream viscous-inviscid interaction with the external supersonic flow. A simple one-dimensional theory is applied to this problem to enable prediction of the initial conditions.
The Channel Flow of a Density-Stratified Fluid About Immersed Bodies
Authors: Droughton J. V. , Chen C. F.
Published: November 2010

The flow of a density-stratified fluid about symmetric towed bodies was investigated both experimentally and theoretically. A cylinder and a slender body were towed through a linearly stratified fluid at various depths and the resulting lee waves were observed and recorded photographically in such a manner as to show the flow tracers as streamlines of the flow. A theoretical investigation was made using an inverse method of solution in which the bodies are generated by distributions of doublets of varying strength and location within the flow field. This theoretical solution predicts that the flow field will be symmetric about the model, only if the model is at the midplane of the flow channel and will be non-symmetric at any other location of the model. This prediction is qualitatively verified by the experimental observations. Theoretical solutions corresponding to the experimental observations were generated. It was found that good agreement was obtained between the theory and experiment as long as the model was towed at a symmetric plane of the channel. At other planes of towing the quantitative agreement between theory and experiment was not good.
Isothermal Bubble Motion Through a Rotating Liquid
Authors: Schrage D. L. , Perkins H. C.
Published: November 2010

An analytical and experimental study of isothermal bubble motion through a liguid which is itself in motion is presented. Both analytical and experimental results are reported for the velocities and trajectories of oxygen bubbles moving through a liquid annulus which is rotating at angular velocities ranging from 500 to 1500 rpm. Results are presented for both distilled water and glycerin. The analytical prediction of the trajectories and velocities showed good agreement with the experimental data. It was found that the bubbles, which were injected at the exterior of the liquid annulus, spiralled inward rapidly and, due to the large pressure gradient in the radial direction, did not reach a constant or terminal velocity.
The Kinetic and Thermal Expansion of Vapor Bubbles
Authors: Gibson D. C.
Published: November 2010

The spherical expansion of vapor bubbles due to the application of either a thermal or a kinetic impulse is examined. There appears to be a wide range of initial and ambient conditions for which the vapor properties approach extremely close to ambient values at the end of the expansion, for both types of impulse. There is also a range of conditions for which the vapor is significantly subcooled at the end of the expansion for both types of impulse. It is postulated that such vapor conditions can cause a more vigorous motion in the subsequent collapse than would be expected for the prevailing ambient conditions.
An Experimental Study of Rectilinear Jet-Flap Cascades
Authors: Landsberg T. J. , Krasnoff E.
Published: November 2010

The performance of two-dimensional jet-flap cascades is determined experimentally. Stream deflection angles are presented as a function of the ratio of jet to mainstream momentum flux at chord spacing ratios of 0.375 and 0.75. Results obtained with conventional jet-flap airfoils (normal blowing near trailing edge) are in good agreement with published theoretical results. Tangential blowing jet-flap airfoils (tangential blowing over a rounded trailing edge) are shown to approximately double the turning effectiveness of the cascade.
A Note on Grounded Thermocouple Circuits
Authors: Benedict R. P. , Russo R. J.
Published: November 2010

Basic circuits involving the thermocouple as a temperature-sensing device have been described and analyzed in the literature. However, relatively little has been written on the thermocouple as part of an overall instrument circuit wherein external electrical effects are important. After reviewing the more important electrical effects which are extraneous to the basic thermocouple circuit, the problem of multiple grounds in a thermocouple proper is considered in some detail. Experiment and analysis indicate that serious errors in temperature measurement can result from the use of improper grounds in thermocouple circuits.
Secondary Flow Induced by a Transverse Resonant Acoustic Field in a Circular Duct
Authors: Hribar A. E. , Purdy K. R.
Published: November 2010

The flow field resulting from the interaction of a finite amplitude standing acoustic field and a viscous fluid was investigated analytically and experimentally. For an adiabatic wall, an analytical solution was obtained for the velocity field over the entire duct cross section. The solution predicts standing vortices in the duct cross section: their number is proportional to the resonance mode number. Similar secondary flow behavior has been found by Maslen and Moore who considered the case of an isothermal duct. The analysis is strictly valid for a characteristic Reynolds number of the order of magnitude one compared to δ, where δ ≃ 10−3. Measurements of the resonant pressure field and photographs of the induced secondary motion, using smoke as a tracer, qualitatively substantiated the analysis. Experimental data were obtained at values of the characteristic Reynolds number varying from 4.5 to 15.3.
Liquid Surface Motion Induced by Acceleration and External Pressure
Authors: Moody F. J. , Reynolds W. C.
Published: November 2010

Pressure and acceleration-induced distortion of an incompressible, inviscid liquid region is predicted numerically. The liquid is bounded by both fixed and free boundaries, and its motion is irrotational. Normal velocity is prescribed on fixed, though perhaps permeable boundaries, and the starting velocity potential is given on all free surfaces. Distortions of the liquid region are described by the motion of discrete kinematic markers assigned to each free surface. Problems are formulated on a square mesh computation field in terms of velocity potential. The liquid region interior is solved numerically by overrelaxation at every time step, which permits velocity components and potential rates to be calculated at the free surfaces. Marker positions and potentials are advanced each time step, thus preparing the computation field for further overrelaxation, and the process is repeated until finished. This technique was formulated as a Fortran IV computer program, FREESURF, for studying free surface motions. The technique can solve two-dimension rectangular or axisymmetric problems with fixed boundaries and up to three free surfaces. Bubble expansion and collapse near a free surface, dam break flows, draining of a tank, and other similar problems can be predicted with the method.
Axial Hydraulic Thrust Caused by Pump Starting
Authors: Miyashiro H. , Takada K.
Published: November 2010

A series of experiments was carried out to investigate transient axial thrust caused by pump starting. Conditions of discharge piping pressure distribution around the impellers and the relation between steady and transient operating conditions were studied. Transient pump operating conditions were calculated and compared with test data. The maximum axial thrust at starting was calculated from the measurement of axial thrust under steady operating conditions and the calculation of transient operating conditions.
On the Dynamics of Nonspherical Bubbles
Authors: Hsieh D. Y.
Published: November 2010

This study consists of three parts: the effects of heat and mass transfer on the motion of nearly spherical bubbles; the effects of compressibility of the liquid on the motion of nearly spherical bubbles; and the variational methods for dynamics of nonspherical bubbles. The programs of the linear stability of spherical bubbles become more complete with the former two parts, while the latter not only offers an alternate exact method to deal with the problem but also opens new avenues for approximate treatments. Analyses are limited entirely on the theoretical level in this study.
Transverse Oscillations of a Jet in a Jet-Splitter System
Authors: Rockwell D. O.
Published: November 2010

The fundamental transverse oscillations of a liquid jet which impinged upon a flow splitter were examined for a wide range of dimensionless splitter distance, nozzle exit Reynolds number, and dimensionless frequency. The results are presented in the form of a design map. The data, taken at low nozzle aspect ratio, reveal that fundamental (stage 1) oscillations can exist for Reynolds numbers up to at least 7000. Up to Reynolds numbers of about 3000, the jet behavior is Reynolds number dependent for all values of splitter distance. Beyond Reynolds number of 3000 the jet behavior is independent of Reynolds number. In general, the Strouhal number, based on nozzle exit-splitter distance, decreases with increasing values of splitter distance. Jets issuing from nozzles with no parallel development sections were considered. Jet nozzle shape influences the dimensionless frequency of oscillation in that the effect of a vena contracta formation outside the nozzle exit is to yield a higher value of dimensionless frequency relative to nozzles which produce parallel flow with small boundary layer thickness at the exit. Similar decreases have been found for two-dimensional jets. Of the above findings, the only comparable results for two-dimensional jets are variations in Strouhal number with nozzle exit-splitter distance.
Forced-Convection Mass Transfer From Wetted Grooves
Authors: Bressler R. G.
Published: November 2010

A wetted-wall column was used to measure liquid flow rates in capillary grooves on vertical surfaces. The test facility contained interchangeable grooved surfaces (2-in. OD) which contacted a liquid reservoir in such a way that the test surfaces were partially wetted by capillary action. The wetted portion was exposed to a forced-convection air stream, so that surface evaporation took place because of the different partial pressures of the vapor at the liquid-vapor interface and at the center of the air stream. All data were obtained in steady-state and nearly isothermal conditions. Experimental results with carbon tetrachloride on brass surfaces were in agreement with approximate predictions, which were computed for evaporative heat transfer and then related to mass transfer by using Reynolds analogy for pipe flow.
Drag Reduction by Ejecting Additive Solutions Into Pure-Water Boundary Layer
Authors: Wu Jin , Tulin M. P.
Published: November 2010

Drag reduction caused by ejecting additive solutions from a slot into a pure-water boundary layer on a flat plate has been systematically studied. Results include drag measurements for a plane boundary, smooth and rough, with various openings of the slot and with various concentrations and discharges of the ejected additive solution. Conclusions have been drawn on the additive requirement in external flows and on the ejection technique for an optimum drag reduction.
The Confined-Discharge Plasma Generator With Local Fluid Constriction
Authors: Mahan J. R. , Cremers C. J.
Published: November 2010

Normally the energy conversion efficiency of a confined-discharge plasma generator is inversely related to the mean enthalpy of the effluent plasma jet. The present paper describes a technique for increasing both the energy conversion efficiency, defined as the net fraction of the electrical power input transferred to the working fluid, and the mean enthalpy, defined as the net energy transferred to the working fluid per unit mass. A portion of the working fluid is introduced to the discharge through a narrow circumferential slit in the confining duct wall. Heat transfer and fluid dynamic effects associated with this high velocity inflow of cold gas cause the local discharge column to become highly constricted. Concomitant with this local fluid constriction (LFC) is a sharp increase in the local power density, resulting in enhanced energy transfer to the cold gas. Experimental results suggest that for optimum operation the gas injection slit should be located slightly upstream of the axial position where the discharge becomes thermally fully developed.
Closure Concepts of Large Pressure Vessels
Authors: Jorgensen S. M.
Published: November 2010

An investigation of the feasibility of fabricating and erecting very large and heavy closure structures for high pressures and in sizes presently considered beyond practical limits.
An Engineering Approach to the Design of Laminarizing Nozzle Flows
Authors: Nash-Webber J. L. , Oates G. C.
Published: November 2010

Despite intensive research into laminarization over the past twenty years, there has resulted hitherto no prediction method suitable for ab intio engineering design applications. Following a critical survey of currently proposed prediction criteria, this paper presents experimental evidence for a new prediction scheme applicable for the first time to compressible adiabatic flows. It is shown that this scheme is readily applicable for engineering design purposes. Extension to nonadiabatic flows is discussed.
A Method for Locating an Optimal “Fixed” Axis of Rotation for the Human Knee Joint
Authors: Lewis J. L. , Lew W. D.
Published: November 2010

This report describes a theoretical technique which calculates the “optimal” direction and location of a fixed axis of rotation for the human knee joint. The optimization criterion is as follows; global locations of arbitrary points on the femur as a result of flexion about the fixed axis should approximate as close as possible their positions due to an equivalent anatomical motion. For comparison, an expression for the location and direction of a screw axis describing the same anatomical movement is derived. The techniques were tested by their application to blocks of known geometry. The optimal axis for two different constraint criteria and the screw axis are located in the knee of a human subject for the range of motion of complete extension to approximately 90-deg flexion. The results for the axes are compared with each other and with a commonly utilized internal prosthetic axis on the basis of ligament length patterns obtained by flexion about the different axes.
Effect of Inhomogeneities and Finite Boundaries on Temperature Distributions in a Perfused Medium, With Application to Tumors
Authors: Jain R. K.
Published: November 2010

Analytical and numerical solutions are obtained for temperature distributions in a finite and inhomogeneous perfused medium with internal heat generation. Extensive numerical simultations are carried out using parameters characteristic of a solid tumor, Walker 256 carcinoma. The results obtained adequately describe the existing data on temperature distributions in tumors under two different conditions: (i) tumors under normal conditions, and (ii) tumors grown about and subsequently heated by a spherical heat source implanted in their center.
The Influence of Stress Frequency on the Fatigue Strength of Cortical Bone
Authors: Lafferty J. F. , Raju P. V. V.
Published: November 2010

The fatigue strength of bovine cortical bone is shown to increase with stress frequency. An analytical model provides an excellent correlation of the data and indicates that the effect of stress frequency is a result of strain rate increasing with frequency.
The Effect of Soft Tissue on Measurements of Vibrational Bone Motion by Skin-Mounted Accelerometers
Authors: Ziegert J. C. , Lewis J. L.
Published: November 2010

The effect of the soft tissue between bone and a preloaded skin surface accelerometer was studied in vivo by comparing its output with the output of an accelerometer connected directly to the bone by a needle through the soft tissue. A 34-g skin surface accelerometer gave an output with little resemblance to the bone motions, appearing to oscillate at its resonant frequency on the soft tissue. A 1.5-g skin surface accelerometer showed nearly identical output to the bone acceleration.
Skin Temperature Probe
Authors: Mahanty S. D. , Roemer R. B.
Published: November 2010

A probe which is capable of applying known, controlled pressures to the skin, and measuring the subsequent tissue deflections and skin surface temperatures has been designed and tested. This paper describes the design of the probe, with emphasis on the thermal aspects. The fin effect of the probe superstructure is compensated for by providing an appropriately sized reflective area on that portion of the probe which contacts the skin. Experimental calibration results and numerical model predictions are presented.
Determining the In-Vivo Areas of Contact in the Canine Shoulder
Authors: Scherrer P. K. , Hillberry B. M. , Van Sickle D. C.
Published: November 2010

The mathematical representation of the articular surfaces of anatomical joints can be obtained in a piecewise continuous fashion using parametric surface patches. The relative position of the anatomical bodies containing the articular surfaces can be measured with an instrumented spatial linkage. By combining the relative position data with the mathematical representations, the approximate area of contact between the articular surfaces can be determined. In this paper, the procedure for combining motion data with surface contour data is described, and in-vivo areas of contact in the canine shoulder for a normal test subject are presented.
Three-Dimensional Coordinate Data Processing in Human Motion Analysis
Authors: Andriacchi T. P. , Hampton S. J. , Schultz A. B. , Galante J. O.
Published: November 2010

A method for three-dimensional coordinate processing of human motion is presented. The method is well suited for use with opto-electronic data acquisition equipment. A resolution of one part in 500 was achieved over a viewing field of 2.4 m. This resolution was found to be adequate for human gait analysis studies.
Steady Flow in Collapsible Tubes
Authors: Shapiro Ascher H.
Published: November 2010

The one-dimensional theory of steady flow in a thin-walled tube, partially collapsed by a negative transmural pressure difference, is developed in a general way. The mechanics of the flow is closely coupled to the mechanics of the tube. The latter is characterized by a “tube law”: the relationship between cross-sectional area and transmural pressure difference. Features analogous to those in gas dynamics and free-surface flow may manifest themselves: a characteristic wave propagation speed; opposite phenomena at flow speeds, respectively, less than and greater than the wave speed; choking; and shocklike transitions. There are many practical examples of such flows, mainly in physiology and medicine. The one-dimensional, steady analysis includes the effects of friction, lengthwise variations in external pressure, variations in elevation, resting area, wall stiffness, and mechanical properties. The speed index S (ratio of flow speed to wave speed), analogous to the Mach and Froude numbers, appears naturally in the results as a controlling parameter of behavior. Various practical ways of passing continuously from subcritical (S < 1) to supercritical (S > 1)speed are suggested. A preliminary theory of shocklike, dissipative transitions is developed, the results of which depend sensitively on the tube law. Explicit working formulas are developed for several simple types of flow (friction alone; changes in rest area alone; changes in external pressure or elevation alone) for a simple, approximate tube law. Various modes of flow behavior for a flow affected by both friction and gravity are explored.
Kinetics of Thermal Injury in Cells
Authors: Moussa N. A. , McGrath J. J. , Cravalho E. G. , Asimacopoulos P. J.
Published: November 2010

HeLa cells, suspended in solution, were subjected to well-defined temperature protocols on a microscope stage specifically designed for this purpose. Simultaneously, the appearance of the first irreversible morphological change in the cells was monitored and used as an indicator of damage. For constant temperature protocols, an Arrhenius relationship was found between the measured damage time and the cell temperature, yielding an activation energy of 249 kJ/mole (59.5 kcal/mole) and a frequency factor of 9.09 × 1036 s−1. On the basis of this result and of Henriques’ damage integral concept [1], working relationships have been derived to express the damage time for two additional temperature protocols; viz., 1 a linearly increasing temperature, and 2 a linearly increasing temperature followed by a constant temperature. These relationships show the dependence of the damage time on the heating rate, the maximum attained temperature, the damage kinetics and the initial cell temperature.
Comparison of Diastolic Ventricular Mechanics for Rigid Leaflet and Caged-Ball Prosthetic Valves
Authors: Savilonis B. J. , Francis G. P.
Published: November 2010

Computer model results are reported for the diastolic behavior of blood flow and muscle stress in the left ventricle of the heart. Comparisons are made between results for a rigid-leaflet mitral valve and a caged-ball prosthetic valve. As expected, the model ball valve produces larger pressure drops, a higher wall shear, and slower opening times. In addition, the ball valve creates an abnormal distension of the heart wall. This may affect the long-term behavior of the muscle, particularly during systolic contraction.
An Analysis of the Three-Way Underlapped Hydraulic Spool Servovalve
Authors: Taft C. K. , Twill J. P.
Published: November 2010

A flow model of a three-way underlapped hydraulic servovalve is presented and used to derive a mathematical description of the flow momentum forces acting on the valve spool. The effect of these forces on valve performance is investigated by examining both the linearized system differential equations and digital computer solutions of the system nonlinear differential equations, and by experimental measurements. A three-dimensional phase space is used to display computer simulation results. Because of the oscillatory nature of system response, projections on a plane illustrate system dynamic response forms. The effects of system parameters on system stability are discussed.
A Transformation Method With Two Parameters for Constrained Optimal Control Problems
Authors: Fujii S. , Fujimoto H.
Published: November 2010

A transformation method with two parameters is described which can be applied to nonconvex optimal control problems with constraints, does not present numerical difficulties, and has a rapid convergence rate. The basic algorithm of the method is summarized for optimal control problems with equality and inequality constraints, the function of the parameters in the method is considered, one modified algorithm is proposed, and its theoretical results are proved. Finally, the method is applied successfully to both convex and nonconvex optimal control problems with a state inequality constraint.
A Parametric Study to Relate Railcar Speed to Permissible Combinations of Track Geometry Deviations
Authors: Dimasi F. , Weinstock H.
Published: November 2010

A passenger railcar was modeled using quasi-linear, frequency domain computer simulation models to compute lateral and vertical rms wheelset forces and relative displacements over a range of speeds, in response to power spectra representations of track geometry deviations in surface, alinement, and crosslevel. A simplified wheel-climb criterion (Lateral to Vertical Force Ratio, L/V) was used to estimate the margin of safety for wheel-climb and to impose limits on combined track geometry deviations which result in development of lateral and vertical forces which would cause a commonly used threshold value to be exceeded on a statistical basis. “Constant performance” contours of speed versus combined track geometry deviations are developed for selected L/V threshold values and exceedance probabilities.
Magnetic Suspension for Low-Speed Vehicles
Authors: Sinha P. K.
Published: November 2010

Several forms of novel suspension systems for passenger-carrying vehicles are currently being investigated throughout the world. Most of these, however, are aimed at high-speed, intercity transport systems, and comparatively less development work has been undertaken to provide a new form of low-speed system for urban-transportation. The possibility of using controlled direct-current electromagnets for low-speed (up to 70 kph) vehicle suspension has been explored in this paper. This system, also known as ferromagnetic or attraction suspension system, offers a very attractive combination of design simplicity, low operating and maintenance costs, high reliability and virtually silent operation. This system is also considered to have capital costs comparable with alternative forms of urban-transport systems and could be designed to fit into the existing fabric of cities and towns. The feasibility of the d-c system is illustrated here through analytical and experimental results of the ride and track-clearance characteristics for a single-degree of freedom suspension system. These results are used to formulate a procedure for designing a multimagnet vehicle suspension system. Main design and performance criteria for maglev vehicles are discussed in the context of experimental results obtained from test vehicles. Engineering aspects of some of the system components have been presented with a view to evaluating their suitability for low-speed systems.
Simulation and Control Synthesis of Manipulator in Assembling Technical Parts
Authors: Stokic´ D. , Vukobratovic´ M.
Published: November 2010

The problem of simulation and synthesis of manipulator control in the phase of joining the structural elements and subassemblies is considered in this paper. Special attention has been devoted to the complete dynamic analysis of the ensemble: manipulator – working object and external forces in the process of assembling the elements. Results of the insertion process simulation with and without feedback with respect to the forces in contact points between the working object and environment are presented.
Dynamic Interactions Between Long, High Speed Trains of Air Cushion Vehicles and Their Guideways
Authors: Wilson James F. , Biggers Sherrill B.
Published: November 2010

Trains of high speed air cushion vehicles traversing simple spans are modeled as uniform pressure segments traveling at arbitrary speeds over identical Bernoulli-Euler beams. Series solutions are found for the transient span and vehicle responses where the trains overlap several spans at a time. Elastic foundation, span tension, and span damping effects are included. Conclusions reached after studying some realistic numerical examples for constant-speed trains on elevated spans are: (a) for trains which are longer than one span length, the dynamic deflection factors (maximum ratios of dynamic to static deflection at midspan) approach 2.0 at speeds between 300 and 600 mph, and occur as the end of the train approaches, midspan; (b) these dynamic deflections may be reduced by the addition of damping, by a reduction of span length, by the addition of span tension, and by an increase in span stiffness; (c) the high vertical accelerations of the vehicles, which may approach 2 g’s at speeds of 300 mph, show the need for advanced suspension systems to insure passenger safety and comfort.
Limiting Forms of Optimum Stochastic Linear Regulators
Authors: Friedland Bernard
Published: November 2010

Of interest are the limiting forms of the optimum stochastic regulator which minimize the steady-state expectation, Es{x′Qx+u′Ru}, for the linear process, x˙=Ax+Bu+Gv, given noisy observations y = Hx+w (with v and w being independent white noise processes) as the control weighting matrix, R and/or the spectral density matrix W of the observation noise w tend to zero. It is found that as R vanishes, the optimum regulator can be synthesized by a system using at most n-k integrators, where n is the order of the system and k is the rank of B. Similarly, when W vanishes, the regulator can sometimes be realized with at most n-r integrators, where r is the rank of H. The structure of the regulator is given for each of these cases.
Interchangeability of “Inners” and “Minors”
Authors: Jury E. I. , Ahn S. M.
Published: November 2010

In this paper the concept of interchangeability of inners and principal minors is developed for the Hurwitz problem and for the aperiodicity condition simplifying the existing criteria. The connection between the inners and Lyapunov’s method for aperiodic linear continuous system is further elaborated and utilized. The application of the inners to absolute stability is also discussed. A critical view of the inner matrix representation as compared to the symmetric matrix formulation is presented.
Effects of Temperature, End-Conditions, Flow, and Branching on the Frequency Response of Pneumatic Lines
Authors: Franke M. E. , Malanowski A. J. , Martin P. S.
Published: November 2010

Experimental results are presented to show the effects of temperature, flow, end-conditions, and branching on the small-signal sinusoidal amplitude frequency response of pneumatic lines. Distributed parameter transmission line theory for uniform lines is extended to include varying conditions of pressure and temperature along the line as well as series-connected lines of different diameters and parallel branching. The experimental results are compared with the formulated theory for several test configurations. Agreement between experiment and computer solutions based on the theory is relatively good.
Approximate Nonlinear Filters and Deterministic Filter Gains
Authors: Bejczy A. K. , Sridhar R.
Published: November 2010

A simple nonlinear filter construction and performance evaluation method is described and illustrated on several examples by comparing it to more complex nonlinear filter schemes. In the new method, the filter gain is a precomputed, deterministic quantity (possibly a constant) and, the filter’s performance is (approximately) described by deterministic differential equations which can be solved off-line.
Design of a Force Feedback Chatter Control System
Authors: Nachtigal C.
Published: November 2010

The analysis of machine tool chatter from frequency domain considerations is generally accepted as a valid representation of the regenerative chatter phenomenon. However, active control of regenerative chatter is still in its embryonic stage. It was established in reference [2] that a measurement of the cutting force could be effectively used in conjunction with a controller and a tool position servo system to increase the stability of an engine lathe and to improve its transient response. This paper presents the design basis for such a system, including both analytical and experimental considerations. The design procedure stems from a real part stability criterion based on the work by Merritt [1]. Because of the unknown variability in the dynamics of a machine tool system, the controller parameters were chosen to accomodate some mismatch between structure and tool servo dynamics. Experimental tests to determine the stability zone of the controlled machine tool system qualitatively confirmed the analytical design results. The experimental results were consistent in that the transient response tests confirmed the frequency domain stability tests. It was also demonstrated experimentally that the equivalent static stiffness of a flexible work-piece system could be substantially increased.
Stability Control Analysis of Rotating Plates by Finite Element: Emphasis on Slots and Holes
Authors: Mote C. D.
Published: November 2010

Accurate finite element procedures have been developed for the vibration of plates with significant membrane stresses. Thermally stressed, rotating circular plates with peripheral edge slots are examined in detail and the influence of slots upon critical rotation speed instability is clarified. In realistic environments slots can considerably increase critical speeds through the reduction of compressive thermal stresses and the introduction of geometrical assymmetry. Optimization of critical instability speeds is discussed.
Minimum-Order Mathematical Models of Discrete Linear Dynamic Systems
Authors: Behring A. G. , Flanigan V. J.
Published: November 2010

An orthonormal filter is used to obtain minimum-order, mathematical models of linear, multivariable, discrete, time-invariant systems from input/output data. Some common problems associated with obtaining such descriptions are considered, including the problem of noise-corrupted observations.
Input Requirements and Parametric Errors for System Identification Under Periodic Excitation
Authors: Hoberock L. L. , Stewart G. W.
Published: November 2010

This paper provides the conditions on periodic system excitation necessary for unique identification using a multiple input state model of a dynamic system. Results include the minimum number of input frequencies necessary to uniquely determine all state and input matrix elements of an n dimensional linear system. It is shown that this development encompasses earlier work done on single input-output systems. A technique is provided for predicting parametric errors to be expected from identification under periodic excitation, and several examples are used to illustrate these errors.
Optimization of Constrained Dynamic Systems Using the Sequential Unconstrained Minimization Technique
Authors: Murali B. N. , Ebbesen L. R. , Sebesta H. R.
Published: November 2010

The development of a computer program for the optimization of dynamic systems subject to parameter and terminal state constraints is presented in this paper. The problem is handled by converting it to an equivalent algebraic optimization problem. The resulting problem is then solved by a modified version (D YS UMT) of the nonlinear programming method S UMT (Sequential Unconstrained Minimization Technique). The available program provides an efficient and convenient analysis tool to aid engineers in the modeling and designing of dynamic systems.
Decoupling in a Class of Nonlinear Systems by State Variable Feedback
Authors: Singh S. N. , Rugh W. J.
Published: November 2010

For a class of nonlinear systems we derive a necessary and sufficient condition for the existence of a state variable feedback control law which accomplishes decoupling, as well as some conditions which characterize the class of decoupling control laws. Several examples are presented to illustrate the application of these results. For a special subclass which includes the so-called bilinear systems, we give two equivalent forms of the necessary and sufficient condition.
A Basic Theorem on Distributed Control and Point Control
Authors: Vidyasagar M. , Higgins T. J.
Published: November 2010

This paper is concerned with linear distributed parameter systems whose input-output operators are representable in integral form. Two types of control are considered: (i) distributed control which is a function of both a spatial variable x (lying in a compact set Ω) and a time variable t, and (ii) “point” control which is applied at a specific point in Ω and is a function only of t. For such systems, a basic theorem is stated and proved, namely, that there exists a countable subset E of Ω with the following property: any state which can be attained by applying a distributed control can also be attained arbitrarily closely by applying a finite number of point controls applied at points in the set E. The theorem is applied to some specific systems, and further possible applications of the theorem are discussed.
Development of a Submerged Round Laminar Jet From an Initially Parabolic Profile
Authors: du Plessis M. P. , Wang R. L. , Tsang S.
Published: November 2010

The region near the nozzle exit of laminar free jets is of interest to those involved with the design of fluid control and free jet sensing devices often applied in low cost automation. An experimental and analytical investigation of an axially symmetric, laminar free jet with an initially parabolic profile has been carried out in the region close to the nozzle for jet Reynolds numbers of 168 and 290. Solutions using Andrade and Tsien’s theoretically derived expression for the virtual origin of an initially parabolic jet an compared with measurements and with numerical solutions of the boundary layer equations. It is shown that numerical solutions give good predictions of the velocities in the axial direction within 1 to 20 diameters from the nozzle and that the classical solution gives inaccurate predictions within 1 to 9 diameters from the nozzle even after the expression for the virtual origin has been adjusted to correspond more closely is measurements in the far region of the jet.
A Study of Feedback Fluid Jet Oscillator With a Supersonic Power Jet: Part I: Presentation and Interpretation of the Experimental Data
Authors: McGeachy J. D. , Chow W. L.
Published: November 2010

A model feedback fluid jet oscillator was constructed and run to illustrate the feasibility of producing sustained jet oscillation and provide data for analysis of such an oscillator. Experimental measurements were made on the frequency of oscillation by observing the characteristic pressures within the oscillator through oscillographic recordings. This was further confirmed by taking high speed motion pictures through a Schlieren system during jet oscillation. It was found that a certain level of primary stagnation pressure was required before jet switching and oscillation would occur. The operating frequency, which was on the order of ten cycles per sec, was dependent upon the storage volume and the feed inlet opening. The sequence of events occurring within this oscillator can be observed and interpreted from the variation of characteristic pressures. The analogy between the fluidic feedback jet oscillator and the electronic oscillator is clearly borne out from this investigation.
Computer Model of Cardiovascular Control System Responses to Exercise
Authors: Croston R. C. , Rummel J. A. , Kay F. J.
Published: November 2010

A mathematical model and digital computer simulation of the human cardiovascular system and its controls are developed to simulate transient responses to bicycle ergometer exercise. The purpose of the model is to provide a method to analyze cardiovascular control hypotheses which cannot be tested easily in an animal or human. Complex cardiovascular control hypotheses are modeled for the control of heart period, peripheral flow resistances, venous tone, and other controlled variables. Control models are based on the use of proportional neurogenic controllers and linearized systems. Metabolic control models utilize simple mathematical models of oxygen uptake, oxygen deficit, and accumulating metabolites to simulate a transient metabolic state and indicate other chemical factors. Equations describing pulsatile blood flows, pressures, and volumes for 28 model sections of the uncontrolled cardiovascular circulatory system are solved. The circulatory system model is combined with the models of the controlling systems to simulate transient responses to exercise. Other characteristics of the combined model include gravity effects, muscle pumping, venous tone, venous valves, respiratory frequency, and intrathoracic pressure effects. Transient response characteristics and steady model values are presented and compared with experimental data. It is concluded that the neurogenic proportional controller hypothesis, combined with the metabolic control factors, can simulate sub-maximal exercise responses.
Short Term Glucose Homeostasis in Man: A Systems Dynamics Model
Authors: Foster R. O. , Soeldner J. S. , Tan M. H. , Guyton J. R.
Published: November 2010

A model of glucose homeostasis whose behavior resembles clinically observed behavior is subjected to a variety of glucose stimuli. This model is used to focus attention on the mechanism of insulin secretion as related to the duration of glucose infusion during the standard intravenous glucose test (0.5 gm/kg body weight). An important clinical experiment was suggested and performed—the duration of glucose infusion was increased from 3 minutes to 12 minutes. An initial peak of insulin is observed at 4 to 6 minutes after the beginning of the infusion. This is followed by a fall in insulin levels while the glucose continues to rise. Because of this experiment, the initial model of glucose homeostasis has undergone changes to include circulatory and transport dynamics and altered mechanisms of insulin release and liver clearance of both glucose and insulin.
The Netlet Theory and Cooperative Phenomena in Neural Networks
Authors: Csermely T. J. , Harth E. , Lewis N. S.
Published: November 2010

Many of the observed oscillatory phenomena in biological systems are the result of endogenous neural activity and occur in the absence of any kind of proprioceptive feedback. In certain simple animals such activity is manifested in a stereotyped behavioral response of considerably longer duration than the evoking stimulus. For instance, in Tritonia gilberti (a slug-like nudibranch) even the briefest touch by a predator triggers a powerful escape motion consisting of alternating dorsal and ventral flections of the animal’s body. Physiological studies by A. O. D. Willows revealed that the mechanism responsible for this behaviour is a cooperative effect which requires the interaction between three small pools of neurons. In our earlier publications we have proposed a netlet theory for investigating the dynamics of interacting neuronal ensembles. We found that a variety of cooperative phenomena, such as hysteresis effects, phase transitions, resonances and entrainments exist in such structures. By a combination of mathematical analysis and computer simulation it is shown in this paper that hysteresis effects together with a known property of neurons, namely, accumulating hyperpolarization, give rise to the kind of behavior observed in Tritonia and shed light on some features found in the single unit firing records.
A Feedback Control Process in Agricultural Pest Management
Authors: Ford-Livene C.
Published: November 2010

A three-component agro-ecosystem consisting of a single prey (host), predator (parasite), and crop is described by means of a linear vector difference equation involving a control term. Deviation of the state of the system from a threshold, and the use of chemical control agents are subject to economic penalties. Dynamic Programming is used to determine the optimal pest control policy as a function of the state of the system, so that a quadratic cost function is minimized. Stratified random sampling is used to estimate the state of the system. A simulation of the model, utilizing a digital computer, is presented.
The Future Roles for Tracked Levitated Vehicle Systems
Authors: Ward J. D.
Published: November 2010

The future roles for tracked levitated vehicle (TLV) systems are identified in the context of comparison with improved passenger rail systems and short haul air systems. These new TLV systems, anticipated to be available for operational use in the 1980’s, will be capable of cruise speeds to about 300 mph, compared to 150–170 mph for high speed rail. The paper concludes that, when developed, TLV will be better than the best rail. Because of its higher speed, travel times will be shorter and operational costs per seat mile will be lower. Higher speed results in lower operating costs because it increases vehicle productivity in terms of seat-miles generated per hour. The relative preference between TLV and air systems depends on both ridership density and trip distance. TLV has much higher fixed costs than air because of the large investment in guideway and other infrastructure, so that TLV requires a larger ridership if fixed costs per passenger are to be reasonable. In operations, however, air systems lose much more time in terminal (airport) stops than TLV systems, which penalizes total trip time and vehicle productivity, especially for short trip distances. Thus air system operating costs are substantially higher than those of TLV systems for short trips. The net result is a general preference for TLV systems when ridership densities are high and trip distances are below 300–400 miles, and a preference for air systems at lower ridership densities or for longer trips. Air is distinctly superior beyond 500 miles.
The Lateral Dynamics of the Linear Induction Motor Test Vehicle
Authors: Hobbs A. E. W. , Pearce T. G.
Published: November 2010

The dynamic behavior of the LIM Test vehicle has been the subject of theoretical and experimental studies conducted for the U. S. Department of Transportation by British Rail’s Research and Development Division. Key aspects of the studies of lateral stability, curving, and response to irregular track are described showing that an adequate stability margin exists for a conicity of 0.025. Satisfactory response characteristics are available for the anticipated roughness spectrum, but the linear curving regime does not ecnompass the higher range of operating speeds on the test track curve of 2.5 miles radius. To date (October, 1973) measured performance compares well with theory but change of conicity with tire wear is an unexpected difficulty due in part to the very high track quality. This tire wear is of peculiar form and not typical of the normal high speed railway.