bluuebunny/crossref_metadata_2025 huggingface dataset:
A Derivation of Bending Free Toroidal Shell Shapes for Tokamak Fusion Reactors
Authors: Gray W. H. , Stoddart W. C. T. , Akin J. E.
Published: November 2010

This paper describes an extension of mathematical solutions to bending free shapes of toroidal pressure vessels. Previous work on this subject [1] derived a pure tension shape of a toroidal membrane which was subjected to a uniform internal pressure. This research was directed toward the finding of a pure tension shape of a toroidal membrane which is subjected to a pressure inversely proportional to the square of the toroidal radius. Such a relationship is possible when electromechanical forces are considered. This family of shapes, which are nearly circular for aspect ratios greater than 2.5, is derived by solving the equilibrium, constitutive, and kinematic relationships for a uniform toroidal shell using the linear membrane theory. Serious consideration should be given to these toroidal shapes, as they provide alternative methods of design for Tokamak fusion reactors.
The Calibration of Cylindrical Hot-Film Velocity Sensors
Authors: Andreas E. L.
Published: November 2010

Ten hot-film velocity sensors with aspect ratios near 20 were calibrated for Reynolds numbers from 1 to 18. This calibration required investigating the yaw angle dependence of the sensors and determining a zero-wind Nusselt number, N0, for each. Conduction heat losses to the sensors supports vary from sensor to sensor and, thus, affect both the velocity calibration and the zero-wind Nusselt numbers. Nevertheless, because these losses are velocity independent, with knowledge of N0 their effects can be eliminated from the heat transfer relation for small aspect ratio hot-films.
Hydromagnetic Flow Over a Conducting Thick Porous Plate With Hall Effects
Authors: Chhatait S. , Mandal K. K.
Published: November 2010

MHD flow of an incompressible viscous electrically conducting fluid due to a uniform stream passing over a thick, porous conducting flat plate subjected to a uniform suction at the plate under the influence of uniform transverse magnetic field has been studied taking into account the effect of Hall current. Induced magnetic field has been taken into consideration and exact solutions have been obtained for primary and secondary flows and induced magnetic field. Effects of different parameters have been illustrated using graphs. It has also been pointed out that when the magnetic Prandtl number is very small effects of Hall current, wall conductivity, and thickness of the plate are all negligible.
Flow in Straight Ducts of Arbitrary Cross Section
Authors: Duck P. W.
Published: November 2010

A method is presented for treating flows in straight ducts. The method involves the conformal mapping of the cross section on to a semicircle, and then solving the problem using Fourier series. For oscillatory flows (to which most of the paper is devoted) the method results in an infinite, coupled system of differential equations, although reliable numerical results may be obtained by truncation. For steady flows, however, the method yields a solution involving integrals of the Jacobian of the transformation.
On the Stability of Steady Motions in Free and Restrained Dynamical Systems
Authors: Hagedorn P.
Published: November 2010

In this paper the stability of the steady motions of dynamical systems with ignorable coordinates is considered. In addition to the original “free” systems “restrained” systems are defined in such a way that the ignorable velocities remain constant for all motions. The relation between the stability behavior of these two types of systems is examined in detail and several stability and instability theorems are given for damped and undamped systems. An illustrative example deals with the steady motions of a heavy gyrostat.
Longitudinal Heat Propagation in Three-Phase Laminated Composites at Low Exciting Frequencies
Authors: Gold B. , Horvay G.
Published: November 2010

In order to explore the behavior of matrix-filler bilaminate MFMFM… near the interfaces it is necessary to augment it into a trilaminate MBFBMBF… arrangement (of volume fractions fM, fB, fF), and then consider the condition that the binder layer is infinitely thin, fB → 0. In a previous paper [1] the problem was considered for high frequencies ω of the boundary temperature excitation T(0, y, t) = e−iwtχ(y), using power series representation for the eigenvalues descending in ω1/2 powers. In the first part of the present paper the low frequency regime is determined, using eigenvalue expansions in ascending powers of ω. The second part of the paper is devoted to exhibiting the interface layer as a shock layer across which there occur temperature jump and flux jump, of unexpected nature.
Transient Response of Continuous Viscoelastic Structural Members
Authors: Strenkowski J. , Pilkey W.
Published: November 2010

In this paper a comprehensive theory is formulated for the dynamic response of structural members with a constitutive relation in the form of a hereditary integral. A modal approach is taken to uncouple the response due to an arbitrary excitation force and general nonhomogeneous surface tractions. The result of this theory is a general set of formulas which may be used for both nonself-adjoint and self-adjoint systems of governing equations of motion. This general formulation is applied to the specific cases of a Voigt-Kelvin beam and a viscoelastic circular plate.
Fracture Related to a Dislocation Distribution
Authors: Vilmann C. , Mura T.
Published: November 2010

The plastic flow at the crack tip is characterized by a model compatible with slip line theory. From this model it is shown that a continuous distribution of dislocations may be derived. Then assuming that these dislocations are emitted from the crack tip and move along slip lines to their final position, the Peach-Koehler force is used to calculate the plastic work involved. Since the plastic zone size is dependent on crack length, two plastic effects are present upon propagation. Primarily the distribution of dislocations present moves along with the crack tip, secondarily new dislocations are emitted to fill the larger plastic zone. These effects yield plastic work which is dependent on both σ2 and σ4, with σ being the applied stress. This dependancy yields a critical stress relationship different from that proposed by either Irwin or Orowan. It also leads to the determination of a subcritical flaw size, i.e., one which will never become unstable.
Linearization Equations for Vibration Induced by Oscillatory Flow
Authors: Spanos P-T. D. , Chen T. W.
Published: November 2010

Equations are presented for the approximate determination through equivalent linearization of the response of a single-degree-of-freedom linear system to excitation induced by oscillatory flow with nonzero mean velocity. The reliability of the proposed methodology is examined.
Bubble Growth in a Viscous Liquid Due to a Transient Pulse
Authors: Hsieh Din-Yu
Published: November 2010

The growth of a spherical bubble in a viscous, incompressible fluid due to a transient tension is analyzed. The maximum attainable radius of the bubble is derived. The problem is closely related to the experimental study of cavitation inception by the stress wave technique. The analysis reveals clearly the role played by the viscosity and shows that for liquids of high viscosity the stress wave technique can be employed advantageously to determine the average sizes of the nuclei of cavitation.
Fluid Transient and Heat Flows in Screw Viscosity Pumps
Authors: Yang W.-J. , Chin C. L. D.
Published: November 2010

It is the objective of this paper to investigate the dynamic response of fluid and heat flows in screw viscosity pumps so that their performance may be correctly and easily predicted, the design of the pumps may be improved, and appropriate automatic control devices may be installed on them if necessary. These pumps consist essentially of a spindle threaded with screws working within a closely fitting sleeve. The analytical model consists of a viscous fluid in a stationary groove induced to flow by the sliding of a cover plate. The groove is of rectangular form or a semicircle. The effects of fluid viscosity and compressibility are included to derive transfer functions relating the pressure and velocity variables at the two cross sections of a line and the velocity of the sliding cover. The response of the fluid temperature to a deviation in the plate temperature or heat flux is also investigated. Numerical results are obtained for the frequency responses of the fluid velocity, pressure, and temperature for a screw viscosity pump with large-width rectangular groove. A phenomenon of resonance in the amplitude ratio and phase shift is disclosed. Screw viscosity pumps to which the analytical results apply include the screw pressure machine and the screw extrusion machine.
Theoretical Analysis of Flow Through Two-Dimensional Centrifugal Pump Impeller by Method of Singularities
Authors: Ayyubi S. K. , Rao Y. V. N.
Published: November 2010

The hydrodynamic method of singularities is used to analyze the flow through two-dimensional centrifugal pump impellers with blades of an arbitrary geometry. Computed values of ideal head are compared with experimental values obtained for a commercial pump. The agreement between theory and experiment is very close over a wide range of pump operation. The discrepancies that occur at other operating conditions are attributed to the effects of inlet passage and volute casing.
Evaluation of Cardiac Work by Means of the Thermodilution Technique Employing the Thermocatheter
Authors: Welland S. , Levy M. , Jacobs R. , Brancato R.
Published: November 2010

A procedure has been developed for calculating the work performed by the left ventricle during the heartbeat. This procedure involves the continuous direct measurement of fluid mixture temperature in the left ventricle during and after the controlled injection, through a catheter, of a known volume of cold saline into the left ventricle. The measured mixture temperatures are used to calculate instantaneous ventricular volumes during the entire heartbeat. The equations employed in the calculations were derived from an analysis of the flow processes through the ventricle and the application of the conservation of mass and energy principles. The procedure employs a “Thermocatheter” which is a unique device which allows for the continuous injection of cold saline into the left ventricle and the measurement of left ventricular fluid temperature. The thermocatheter consists of a specially designed fast response thermocouple and catheter assembly. The thermocouple signal is amplified by a high gain, low noise direct current amplifier The volume versus time plot calculated from the measured ventricular fluid temperatures is combined with the measured ventricular pressure trace for the heartbeat. This results in a pressure versus volume plot or work diagram for the left ventricle. Thermodilution studies performed in man, at the Saint Michael Medical Center, indicated that this approach to the evaluation of cardiac work is important in the assessment of cardiac state.
Selecting Materials to Resist Low Cycle Fatigue
Authors: Feltner C. E. , Landgraf R. W.
Published: November 2010

The selection of materials in the design of components to resist low cycle fatigue is considered in terms of reliable methods of material comparison which can be used in lieu of extensive testing programs. Specifically, a procedure is proposed for ranking candidate materials on the basis of resistance to strength loss, repeated straining, repeated stressing, and notch fatigue in the low cycle fatigue region. Easily performed tests requiring only two specimens of each material are utilized. Monotonic and cyclic stress-strain curves are determined from a standard tensile test and an incremental step test, respectively. A material’s cyclic stability is immediately apparent from comparison of the two curves. Values from these curves are then used in conjunction with empirical relations to predict fatigue resistance in terms of plastic strain amplitude, stress amplitude and a fatigue notch parameter. Examples, using practical engineering materials, are presented to illustrate the reliability of the procedure.
Two-Dimensional Diffuser Performance With Subsonic, Two-Phase, Air–Water Flow
Authors: Hench J. E. , Johnston J. P.
Published: November 2010

The pressure recovery performance of straight-wall, two-dimensional diffusers with air–water mixtures has been investigated, and their behavior as a function of gas volume flow ratio and diffuser geometry established within the limits of the experimental apparatus. The ranges of parameters investigated were: Gas volume flow ratio, β: 0 to 73 percent; area ratio, AR: 1.3 to 4; diffuser length to throat width ratio, N/W1: 3, 6, and 18. Diffusers with air–water mixtures have the same general performance characteristics as diffusers with single-phase fluids, e.g., peak pressure recovery occurs near the onset of stall and decreases again for larger area ratios in the stalled flow regimes. In stalled flow regimes, appreciable pressure recovery may be achieved in a constant-area tailpipe downstream of the diffuser. The pressure recovery of diffusers with two-phase flow deteriorates with increasing air flow, especially after the two-phase flow regime changes from bubbly to churn-turbulent.
The Effect of Axial Boundary Motion on Pressure Surge Generation
Authors: Jones S. E. , Wood D. J.
Published: November 2010

The basic relationships for transient flow in a straight tube are investigated for the case of axial boundary motion. Viscous effects and other small terms are neglected allowing the problem to be described by the wave equation subjected to a moving boundary. Using this equation the case of pressure surge generation due to instantaneous load rejection in a finite straight tube is investigated. The axial boundary motion is due to the internal pressure stretching the pipe wall along the pipe axis. A closed form analytical result is obtained using a differential difference equation and shows that the pressure surge magnitude can be significantly greater than that predicted neglecting the boundary motion. This result is used to obtain a simple expression for estimating the maximum value of the pressure surge following the load rejection. An experiment is conducted which shows the significance of the axial line motion and compares well with the prediction of this effect.
Combustion Driven Resonance Tubes
Authors: Rountree M. E. , Kranc S. C.
Published: November 2010

A small supersonic resonance tube was constructed and tested utilizing a combustion heated jet. Comparing these results to a cold jet it was found that the combustion jet has an increased frequency and a higher power output level which reflects the increased gas enthalpy.
An Experimental Study of Flows in Planar Nozzles
Authors: Owczarek J. A. , Rockwell D. O.
Published: November 2010

The paper describes an experimental investigation of the characteristics of low-Mach number flow of air from four planar nozzles. The nozzles had rectangular (rounded) inlets from a circular duct and aspect ratio of 3 at the exit. In general, two types of spiraling secondary flows were observed at nozzle exits. One type was observed in the vicinity of the midplane of the nozzles near the upper and lower walls, and the other type in the vicinity of the side walls in the corners. Experiments have shown that the secondary flows located in the vicinity of the midplane are produced by the contraction from the circular duct to the rectangular inlet, while the secondary flows located in the vicinity of the side walls are produced by the boundary layer migration toward the convex inner wall sections of the nozzles. The secondary flows have low total pressure associated with them. A comparison of discharge coefficient is made for the nozzles examined. The experiments were performed at the Reynolds numbers, based on the average flow speed at the nozzle exit and nozzle throat width, in the range of 3.4 × 103 to 2.5 × 104.
Asymptotic Rate Process Calculations of Thermal Injury to the Retina Following Laser Irradiation
Authors: Priebe L. A. , Welch A. J.
Published: November 2010

Thermal damage to the retina following laser irradiation may be predicted using impulse and steady asymptotes derived from a first-order rate process and a simple thermal model for two time domains. Effects which have been observed experimentally in the short pulse (<10−4s) region such as changes in energy per unit area for threshold damage as a function of image diameter may be explained with this model. The model allows rapid damage prediction without extensive calculations of temperature increase which normally require a large computer. Thermal damage to the ocular fundus resulting from a long pulse exposure may also be easily described with a simple steady-state model for temperature increase and damage.
Assessment of Convective Heat Loss From Humans in Cold Water
Authors: Kuehn L. A.
Published: November 2010

Convective heat loss is a primary cause of hypothermia in humans undergoing water immersion, particularly for swimmers and divers at relatively shallow depths. Various biophysical models have been advanced to account for body heat loss in water of different temperatures and cold stress, most of which have made use of physiological data obtained with easily applied classical thermometry techniques. Explicit techniques for the determination of body heat loss must involve direct calorimetry or the use of heat flow transducers, techniques which are difficult to apply in realistic simulations of actual cold water exposure. This paper describes these latter two techniques in some detail, concentrating on the accuracy to be attained and the calibration necessitated with each method. Results obtained with each method specific to heat loss determination at surface and both dry and wet hyperbaric exposures are shown, illustrating the types of data that can be attained.
Kinematics of Jaw Growth
Authors: Isaacson R. J. , Erdman A. G. , Hultgren B.
Published: November 2010

Growth of the human face occurs in unequal amounts at various areas. This results in relative motion of the upper and lower jaws. Relative motion creates changes in facial appearance and dental occlusion. Orthodontic treatment seeks to therapeutically use or alter this relative motion. Most existing orthodontic analyses have interpreted facial growth as translatory in nature. The analysis introduced in this paper is based on applying kinematic fundamentals—that is, poles of rotation and fixed and moving centrodes—as a tool for more accurately analyzing jaw motion. Reliable data is utilized and computer graphics routines are employed to help visualize output data. Several alternative approaches for analyzing relative motion due to jaw growth are presented here indicating the development of this research.
Red Cell Motion and Deformation in the Microcirculation
Authors: Sutera S. P.
Published: November 2010

The human microcirculation is taken to include all vessels with internal diameter less than 500 μm. In these small vessels the heterogeneous nature of the blood suspension becomes apparent in the external characteristics of the flow, which signifies that a continuum model of blood flow in this regime is inadequate. The motion and deformation of red cells in the capillaries is discussed in detail with emphasis on the relationship between red cell dynamics and apparent viscosity. Large scale hydraulic models of red cell motion in capillaries have yielded dimensionless correlations applicable to the microscopic prototypes. In the larger vessels the distribution of red cells across the vessel lumen is generally nonuniform and axial velocity profiles reveal the occurrence of partial plug flow. Red cells traveling near the vessel wall where the shear rate is highest may exhibit a transition to liquid droplike behavior.
Creep Failure of Rat Tail Tendon
Authors: Ellis D. G.
Published: November 2010

Creep tests were performed on rat tail tendons at each of six temperatures: 25, 30, 35, 40, 45, and 50°C. It was found that the time interval from load application to rupture was related to the applied (specific) load and the temperature. Over the range 25° to 45°C this relation was found to be reasonably approximated by a Tobolsky-Eyring rate equation, if a squared term in specific load was added to the numerator of the exponent. Deviation of the 50°C data from this equation was hypothesized to be associated with incipient “melting”. The apparent activation energy for the failure process was sufficiently high to suggest that the creep failure of tendon involves the breaking of covalent bonds.
Kinematic and Kinetic Analysis of the Human Wrist by Stereoscopic Instrumentation
Authors: Erdman A. G. , Mayfield J. K. , Dorman F. , Wallrich M. , Dahlof W.
Published: November 2010

A three-dimensional kinematic and kinetic analysis of the human wrist can lend useful data to understand carpal mechanics. This data would also be useful in implant design and evaluating surgical reconstructive procedures. A stereoscopic photographic technique using light-emitting diodes (LED’s) is described that records on film three-dimensional relative motion between two bone segments. The LED’s are inserted into the carpal bones at key ligamentous attachments. Kinetic data is generated by use of a force transducer. LED frames are mounted on both sides of the wrist joint and to the calibrated transducer so that the three-dimensional motion and force (moment) information is recorded at the same time. Wrist motion is generated both passively and dynamically by motors attached to the principle wrist tendons. The kinematic and kinetic data, recorded on film, is then digtized and analyzed by computer. Knowledge of the relative three-dimensional motion of the intercarpal and radiocarpal joints and the relative forces that are distributed through the various wrist ligaments will be produced by this instrumentation. Output computer graphics routines, including screw axis data, have been developed.
Feasibility of an Active Control Scheme for Above Knee Prostheses
Authors: Grimes D. L. , Flowers W. C. , Donath M.
Published: November 2010

The level walking process for an above knee (A/K) amputee with a conventional prosthesis greatly compromises the amputee’s mobility. The fact that conventional prostheses lock in hyperextension during the stance phase, in contrast to the extend-flexextend pattern during stance for the natural limb, has been suggested as a source of the amputee’s uncosmetic gait and high energy expenditure. While the lock in hyperextension during stance provides stability to prevent buckling, it requires the person to vault over the prosthetic limb. This vaulting during level walking may cause higher vertical displacements of the body center of gravity (c.g.) and accompanying higher energy requirements for the amputee. This investigation employs an amputee-interactive prosthesis simulator system to evaluate the viability of controlling the prosthetic knee joint to follow a normal knee position pattern. In order to insure that the amputee-interactive prosthesis simulator system does not introduce gait anomalies, the system was controlled to simulate a conventional prosthesis. This showed that the simulator system has no undesired side effects since data from walking trials with the simulator system in “conventional prosthesis mode” are very similar to data from conventional prostheses in the literature. Then, an active position control scheme which controls the prosthetic knee joint to follow a normal knee position pattern was tested by two young, active amputees in level walking trials. The subjects experienced very little difficulty in walking with the active control scheme and preferred the simulator with the active control scheme to their conventional prostheses. Measured knee power requirements for the scheme indicate that this type of control is feasible without external power sources. However, measurements of the vertical displacement of the body c.g. show little difference between gait with the active control scheme and gait with a conventional prosthesis. It appears that the increased energy requirements for A/K amputees are not due in total to the lack of the extend-flex-extend position profile at the prosthetic knee joint.
Optimal Control of Flywheel Hybrid Transmissions
Authors: Sweet L. M. , Anhalt D. A.
Published: November 2010

Selection of variable transmission ratio in a vehicle with a flywheel energy storage element to maximize the kinetic energy transfer for specified vehicle accelerations is formulated as an optimal control problem. Models for single and parallel power-flow path configurations are presented as generic hybrid propulsion system types. For both systems variation of the ratio of the continuously variable transmission results in inherently nonlinear control, with velocity trajectories found by the solution of two-point boundary value problems. For the single power-flow path system a closed loop controller is synthesized which tracks acceleration command. For the parallel path system, which is representative of conventional power split transmissions, the open loop control yields useful information, indicating tradeoffs between system energy recovery efficiency and component design parameters. Maximum energy recovery during regenerative braking is achieved by minimizing power losses to vehicle drag and transmission elements. Planetary gear geometry is shown to have the strongest influence on efficiency, maximum transmission component loading, and CVT ratio range.
Stored Response Modeling
Authors: Eichler J.
Published: November 2010

A direct “brute force” method of system identification is presented. The method is based on the definition of a deterministic system and applicable to nonlinear nonstationary systems with measurement noise. The approach is to discretize the state of the system (or equivalent measurable state), the input vector and time (in the case of a nonstationary system). For these discretized sets of values, the response i.e. the state at t + Δt is determined and stored, thus giving a “stored response” model SRM. The response for arbitrary input vector (within the class for which the model was made) is then obtained by interpolating stored responses for the current state vector, input vector and time thus yielding the state at the next Δt. Repeating this procedure produces the model’s dynamic response. The method of building the SRM table and using it is discussed and several examples are given. An optimal control problem is solved using the SRM model.
The Optimal Machine Tool Control Problem
Authors: Schlueter R. A. , Retford E. T. , Van Wieren S.
Published: November 2010

The optimal machine tool control problem is formulated for a computer-aided manufacturing facility where the costs of transmitting part program information to a continuous path numerical control machine tool should be minimized. The problem is formulated as an optimal sampled-data tracking problem with a performance index that measures both part quality (the tracking error in following a desired cutter path and the surface finish quality) and the costs for computing, storing, and transmitting the programmed control for a particular machining operation on a machine tool. The optimal sampled-data control is assumed to be a polynomial function of time over any sampling interval where the parameters of this polynomial for each sampling interval, the length of each sampling interval, and the number of sampling intervals are control variables. This optimal machine tool control problem is solved for the special case where the form of the polynomial approximation is specified and is a fixed function of the desired cutter path at the sampling times. A computation algorithm is developed and used to compute this optimal control approximation. The results for this example are used to illustrate the performance characteristics of such an optimal control approximation.
A Control Algorithm For Reactor Spatial Control During Nuclear Station Load Cycling
Authors: Cherchas D. B. , Mewdell C. G.
Published: November 2010

A multivariable reactivity control algorithm is developed to maintain acceptable reactor spatial kinetics response during reactor power cycling. A modal model for describing the space-time kinetics response of a CANDU (Canadian Deuterium Uranium) reactor is devised and ultilized in the control study. A one neutron energy group approximation and other assumptions appropriate to the CANDU reactor studied are used to derive a diffusion equation from the linearized Boltzman equation. The effects of Xe135 and I135 are incorporated in the model. The kinetics variables are expanded in terms of an infinite series of eigenfunctions which are solutions of the scalar Helmholtz equation solved on the volume of the reactor. The control reactivities are modelled as an evenly distributed reactivity for gross reactor load cycling and point reactivity devices for spatial control. The system dynamics equations are written in a bilinear state space form. An algorithm is devised to determine the control vector required to achieve a desired kinetics behaviour about the nominal response. The algorithm is illustrated for a typical load cycle by means of a digital computer program.
Lyapunov Stability of a Class of Distributed Parameter Systems
Authors: D’Souza A. Frank
Published: November 2010

The mathematical model of dynamical systems is represented as an initial-boundary value problem described by nonlinear vector-matrix valued partial differential equations. The linear partial differential operator associated with the nonlinear system is restricted to a time-invariant operator with domain dense in Hilbert space. New stability results reported in this paper show the existence of quadratic Lyapunov functions that yield both necessary and sufficient conditions for asymptotic stability of linear systems satisfying certain restrictions and the use of these forms for the stability investigation of a class of nonlinear systems. The proofs of the stability theorems employ the spectral representation of the Green’s function matrix of the associated linear differential operator. Therefore, in the earlier part of the paper well-known properties of linear operators are stated in order to express the Green’s function matrix in the form of spectral expansion.
A New Evaluation of the Mean Square Integral
Authors: Beshara R. J.
Published: November 2010

This paper gives a new evaluation of the mean square integral for an nth order, linear constant system forced by a random input. The results are explicit and literal. A comparison of Mersman’s determinant form and the results of this article show the overall superiority of this method.
Applications of Generalized Inverses to Estimation in Dynamic Systems
Authors: Prochaska B. J.
Published: November 2010

Generalized matrix inverses are used to obtain an estimation procedure for estimation of the state vector of a dynamic system. This sequential procedure is studied analytically with respect to the choice of an arbitrary vector. The covariance matrix of the estimator is determined and compared to the optimal Kalman type procedure. A numerical example illustrates the procedure and compares it to the optimal one.
A Combined Time-Frequency Condition for Stability of Time-Varying Systems With One Nonlinearity
Authors: Blodgett R. E. , Young K. P.
Published: November 2010

A means is presented for determining stability of linear time-varying systems with one feedback nonlinearity. The stability condition involves the minimization of certain time functions of the system coefficients as well as the imaginary axis behavior of a polynomial. It is required that the equation of the linear time-varying system be asymptotically stable and be in phase variable form. The nonlinearity is restricted to lie in a sector. For the limiting case of an autonomous linear system the criterion reduces to the Popov stability condition in certain cases.
Hyperconical Random Search
Authors: Wozny M. J. , Heydt G. T.
Published: November 2010

The rate of convergence of a multidimensional random search is found to improve when the search region is restricted to a directed adaptive hypercone. The convergence properties of the hyperconical search algorithm are investigated and the scheme is applied to the problem of identifying twenty-two constants of a given chemical reaction from measured data.
Model Reference Adaptive Systems—A Survey (MRAS)—What is Possible and Why?
Authors: Landau I. D.
Published: November 2010

This paper presents a survey of the model reference adaptive techniques and their applications for control and identification, based on the literature published since 1964 (171 references). Attention is focused on the basic properties and the various types of model reference adaptive systems (MRAS). The most prominent design methods are reviewed. Design methods based on optimal control, parametric optimization, stability and statistical estimation theory are presented; some unresolved questions and future areas of investigation are also discussed. A survey of the applications already accomplished and those that appear feasible in the near future concludes the paper.
A Maxmin Distance Problem
Authors: Aggarwal R. , Leitmann G.
Published: November 2010

The problem of maximizing the minimum distance of a dynamical system’s state from a given closed set, while transferring the system from a given initial state to a given terminal state, is considered. Two different methods of solution of this problem are given.
A Comparative Study of the Nonlinear and Linear Performance of Vehicle Air Cushion Suspensions Using Bond Graph Models
Authors: Wormley D. N. , Garg D. P. , Richardson H. H.
Published: November 2010

A nonlinear analytical model for the dominant low-frequency dynamic behavior of flexible-skirt air cushion suspensions is developed using bond graph notation. The model includes nonlinear fluid source and orifice characteristics, and modulation of cushion fluid capacitance and sealing gap fluid resistance by changes in geometry and cushion pressure. Bond graphs are presented for the fully nonlinear cushion and for the linearized small perturbation case. Both the nonlinear and linearized equations for the heave dynamics of an air cushion vehicle are developed and solved by machine computation for a realistic range of operating conditions. By comparing the linear and nonlinear solutions, it is concluded that the linear model is suitable for the preliminary design and optimization of air cushion vehicle suspensions. The full nonlinear simulation is prudent, however, to check a tentative design for the effects of unusually large guideway irregularities or external load disturbances.
An Algorithm for Synchronizing Entrance Ramp Vehicles and Freeway Gaps
Authors: Klee H. I.
Published: November 2010

An algorithm for synchronizing ramp vehicles into freeway gaps is developed. It is thought to be an improvement over existing synchronization algorithms because the derivation takes into account the phenomenon of vehicular interaction which is fundamental to any realistic description of the merging process. Attention is focused on identification of new platoons and characterizing gap propagations within a platoon. The probability of synchronizing a ramp vehicle with an ordered gap of a platoon is formulated in terms of the platooning freeway vehicles’ speeds and arrival times at a shoulder lane detector and is maximized to generate the optimal release time of the ramp vehicle. A numerical example is included.
Nonlinear Metabolic Dynamics of the Pancreas and Liver
Authors: Bergman R. N. , Bucolo R. J.
Published: November 2010

Organ level dynamic testing of the metabolic functions of the pancreas and liver have revealed some striking nonlinearities. Glucose provokes a biphasic response in insulin secretion, with dynamic asymmetry and time dependent gain. Amino acid stimulated insulin secretion dynamics contrasted with the dynamic response to glucose in that the gain was not time dependent, and the final phase of insulin secretion did not occur. Also, the magnitude of the amino acid response was very sensitive to the glucose level. A nonlinear model is proposed which accounts for the observed insulin secretory dynamics. The dynamic response of the net glucose balance of the liver in response to glucose was also studied and it was found that, in contrast to the pancreas, the liver can be represented simply by a first order process with a nonlinear static gain curve. These dynamic studies should help explain the nonlinear behavior of the metabolic system at the level of the whole animal.
Suboptimal Design of a Class of Nonlinear Controllers
Authors: Rouse W. B. , Garg D. P.
Published: November 2010

A systematic design procedure is presented for suboptimal nonlinear controller synthesis. Such a control yields faster response characteristics than are normally possible with a linear controller. The technique is geared to single-input linear systems where excursions of one state variable are of more importance than others. Design steps are formulated in terms of readily applicable algebraic equations. The proposed method is applied to several design examples, and the advantages are shown by comparison with the results obtained from existing techniques.
Color Television Market Penetration Dynamics
Authors: LaPadula C. A.
Published: November 2010

A mathematical model describing the dynamic relationship between value, cost, and market penetration is formulated and tested against 1954 to 1971 color television, historical data. The model contains three parameters whose values are estimated from color television ownership data available as a function of time and consumer income. Although the basic model constitutes a deterministic theory, stochastic effects are considered heuristically and forecasts to 1980 are presented together with uncertainty bounds.
Analysis and Algorithm for a Minimax Problem With Thermal Stress Applications
Authors: Bednarski Stanislaw , Shen C. N.
Published: November 2010

In some industrial processes the control transients are accompanied by thermal transients which produce damaging thermal stresses in parts of the apparatus. The steam turbine start-up may be cited as an example of such a process. The need arises to schedule the control transients so that the resulting damage be minimized while the requirements of the process are met. This problem is analyzed in the case when the measure of damage is the maximum value of the thermal stress transient at a given location and the admissible controls are constrained by two time-dependent limits. The system is assumed to be linear and time invariant with thermal stress selected at critical locations. The solution of the minimax problem is obtained for systems whose impulse response function of thermal stress satisfies certain conditions common in thermoelastic problems. The proof of the method of solution and an example of application are also given.
Algebraic Solution of the Servomechanism Problem With External Disturbances
Authors: Johnson C. D.
Published: November 2010

Previous studies of multi-variable servomechanism problems, using modern control theory, have relied almost exclusively on optimal control techniques to formulate and solve the problem. In that way, servo tracking has been obtained as a by-product of minimizing some contrived optimization functional. In this paper, a new servo theory is proposed which makes use of simple linear algebraic methods, rather than optimal control methods, to formulate, study, and solve the multi-variable linear servomechanism problem. The result is a new, algebraic procedure for designing high-performance output-feedback servo controllers for multi-input, multi-output, possibly time-varying linear plants. Moreover, when the plant is also subjected to external disturbances, the servo controllers designed by this new procedure will continue to provide consistently accurate tracking of complex servo command inputs—even though the disturbances are persistent acting, unknown and unmeasurable.
An Evaluation of Pneumatic Transmission Line Propagation Functions
Authors: Churches A. E. , Hind E. C. , Bryant R. A. A.
Published: November 2010

The results of pressure response tests are given for a wide range of dead-ended pneumatic transmission lines. The tests were conducted on lines of commercial quality PVC tubing of length 1 ft to 50 ft, inside diameter 1/8 to 3/8 in., and over a frequency range from 2Hz to 1000Hz. Air at approximately 60 deg F and a mean gauge pressure of 1.0 lb/in.2 was used as the working fluid, with input signal amplitudes of ±0.1 lb/in2. The resulting data have been used to calculate the propagation function and hence to determine best-fit values of the constants which appear in the approximate theoretical expression of F. T. Brown. While the performance of many lines of interest may be predicted accurately by using Brown’s theoretical constants, the tests have shown significant changes in the experimentally determined values of the constants as line length decreases. These changes may be due, at least in part, to the increasing significance of wall elasticity at higher frequencies, an effect which is not included in Brown’s analysis. The data are given in a form which is directly applicable to calculating transmission line response.
The Dynamics of High-Speed Sliding Power Collection Systems for Electrically Propelled Vehicles
Authors: Bain J. A.
Published: November 2010

A method is presented for estimating the contact force variation between a collector brush and a rigid third rail when the third rail has a surface with random irregularity. Results are obtained for a reference case where the third rail roughness is estimated from the roughness of other known surfaces. The surface roughness of an actual commercial third rail is measured and the results are used to estimate the performance of a collector on the measured sample at 300 mph. Conclusions are drawn about the feasibility of power collection at 300 mph.
Dynamic Whip of Elastically Restrained Plate Strips to Rapid Transit Loads
Authors: Wilson J. F.
Published: November 2010

A plate strip of infinite length and constant width is cantilevered on a uniform elastic support along one edge and free along its opposite edge. A normal line load of constant intensity applied across its width travels along the strip at constant speed. Using plate theory, steady state solutions for the flexural waves are derived in terms of the generalized Fourier integral. Superposition is used to simulate responses to distributed transit loads. Results are applicable to the design of cantilevered guidance panels for air cushion vehicles and also in the design of the metal plates for the linear induction motors sometimes used to power these vehicles.
Transportation Vehicle/Beam-Elevated Guideway Dynamic Interactions: A State-of-the-Art Review
Authors: Richardson H. H. , Wormley D. N.
Published: November 2010

The importance of elevated guideway/vehicle dynamics to the design of advanced ground transportation systems is discussed and the general vehicle-suspension-guideway interaction problem is outlined. Simplifying assumptions valid for many practical beam-type elevated guideway systems are described including the Bernoulli-Euler beam assumptions, support conditions, and simplified vehicle models. The theoretical and experimental literature on beam-guideway/vehicle dynamics is reviewed and recent computer-based analytical techniques (lumped mass, finite difference and modal analysis) are discussed. Available simulation programs are described and published results for wheeled, air cushion and magnetically levitated vehicles operating over beam-elevated guideways are reviewed. The influences of critical system parameters on guideway deflection and vehicle vibrational acceleratior (ride comfort) are illustrated through simple limiting case analyses. Low ratios of vehicle-suspension to guideway natural frequency and distribution of vehicle weight over finite pressure pads as in air or magnetic suspensions reduce guideway structural requirements for specified ride comfort. Continuous guideway beams on simple supports provide lower static deflection and greater dynamic range than simply supported single or multiple span beams. Severe resonance problems which may occur in synchronous vehicle systems are illustrated using a point-force vehicle model.
Synthesis of Optimal Feedback Control Systems With Model Feedback Observers
Authors: Ichikawa K.
Published: November 2010

This paper deals with an inaccessible control problem for a discrete time linear fixed parameter system. It is well known that when the state vector is completely detectable, an optimal feedback control system can be constructed for the so-called linear quadratic problem, at least theoretically. When the state vector is not completely detectable, the problem is not so straightforward, and many different approaches or devices have been tried. In this paper, the state vector of the controlled system is restored by an observer in order to generate optimal control. Under some appropriate assumptions, the state vector is restored within at most v stages, where v is the quotient of n divided by m (n = dimension of state vector, m = dimension of output vector, with divisibility assumed in this paper). The design method for such an observer reduces to the design of a minimum stage regulator and is explained in detail in this paper. Finally, the characteristics of the feedback control system with an observer are examined numerically and compared with those of an optimal feedback control system with complete state detectability.
Large Amplitude Pulsatile Water Flow Across an Orifice
Authors: Yellin E. L. , Peskin C. S.
Published: November 2010

The pressure-flow relations of large amplitude pulsatile water flows across an orifice have been investigated theoretically and experimentally. By retaining the unsteady term in the one-dimensional equation of motion, and by allowing the jet area to be a function of distance in the continuity equation, a lumped parameter relationship between pressure drop and flow has been developed which reflects the influence of inertia and dissipation. The results are applicable to the analysis of natural and prosthetic heart valves under normal and pathologic conditions. Within the physiologically possible conditions of frequency and flow rate, unsteady separated flows exhibit the same energy losses as comparable steady separated flows. Thus, the flow is quasi-steady, even when the waveforms and temporal relations indicate a significant inertial influence.
The International Purdue Workshop on Industrial Computer Systems and Its Work in Promoting Computer Control Guidelines and Standards
Authors: Williams T. J.
Published: November 2010

This short description is an attempt to show some of the extensive standards work now being carried out by the Purdue Workshop in the field of the applications of digital computers to plant data collection, monitoring, and other automatic control tasks. The continued success of this work will depend upon the cooperation with and acceptance of the overall results of these developments by the vendor and user company managements and the help of their personnel on the various committees involved.
Computer Applications in Urban Water Distribution System Control
Authors: Rao H. S. , Seitle R. A.
Published: November 2010

The objective of water distribution system control is to provide an adequate level of service at all points in the system economically under varying conditions of loading. With the increase in size and complexity of water systems, the need for reliable and economic operation has resulted in the use of digital computers for data acquisition and supervisory control. In this paper, the functional aspects of computer control of water systems are discussed with respect to (i) alternative system configurations for reliability and cost, and (ii) the application of mathematical models for simulation and optimization of the distribution system operation. Both on-line and off-line software requirements for computer control are discussed. Finally, examples of applications of recent developments in computer control are given together with directions for future research effort.