bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Red Cell Modulus of Elasticity by in-Vitro and Model Cell Experiments
Authors: Hoeber T. W. , Hochmuth R. M.
Published: November 2010

Because of the small size of the human red blood cell, it is difficult to measure the elasticity of the cell membrane. Previous techniques of measuring membrane elasticity involve high stress and strain and therefore do not adequately characterize the membrane’s elasticity near its equilibrium (biconcave) shape. In order to determine elasticity at low stress and strain, an experiment was designed to involve minimal membrane stress. In the experiment, the red cells are expelled from glass micropipettes on the order of 3 microns in internal diameter. The cell is in a folded deformed shape within the confines of the tip but once it leaves the pipette the cell returns to its biconcave shape. With the use of dimensional analysis, the characteristic relaxation times of the red cells and of geometrically similar, fluid-filled model cells are compared and a modulus of elasticity of approximately 106 dynes/cm2 is calculated.
Stress-Corrosion Cracking and the Interaction Between Crack-Tip Stress Field and Solute Atoms
Authors: Liu H. W.
Published: November 2010

Based on the elastic interaction between a solute atom and a tensile crack-tip stress field, a mechanism of stress-corrosion cracking was proposed and analyzed. This elastic interaction provides a potential for solute atoms to migrate toward the tip of a crack. The elastic interaction and the equilibrium concentration of solute atoms near a crack tip were calculated. The solute atom concentration increases rapidly toward the crack tip if the solute atom is interstitial or if it relaxes the crack-tip stress field. The high concentration of solute atoms at the tip of a crack will enhance the reaction between solute and solvent atoms. The weak fracture strength of the reaction product may cause crack growth. Two crack growth models were analyzed: One is based on the assumption of the “homogeneity” of the fracture and deformation properties of a material, and the other takes a structural size of a material into consideration. The proposed models are compared with available data on magnesium-aluminum alloy, 4340 steel, and soda-lime glass.
Mechanisms of Metal Removal by Impacting Dust Particles
Authors: Smeltzer C. E. , Gulden M. E. , Compton W. A.
Published: November 2010

This is a two-part paper, which stresses the materials science approach to understanding dust erosion mechanisms. The first part is an experimental phase, studying the effects upon solid-particle erosion, of such material and environmental variables as target alloy composition and heat-treat condition; dust particle velocity, size, concentration, velocity, and kinetic energy; carrier-gas true temperature and impingement angle. All test variables and their limits were chosen to simulate the range of engineering conditions and erosive environments encountered in helicopter turbine service. Actual erosion data are compared with erosion levels predicted by existing theories on particulate erosion. The second part is a diagnostic phase, programmed to detect and study visible phenomena associated with the erosion processes, using high-magnification electron microscopy. Phenomenological evidence obtained from the erosion surfaces and erosion products are used to define probable physical models of the erosion mechanisms.
Lift Fluctuations Associated With Unsteady Chordwise Flow Past an Airfoil
Authors: Morfey C. L.
Published: November 2010

A simple theory is given for unsteady lift on a flat-plate airfoil due to chordwise velocity perturbations. Horlock’s theory for a frozen gust pattern convected at the free-stream velocity is included as a special case, and a distinction is drawn between streamwise and chordwise velocity perturbations.
Behavior of Liquid Sodium in a Sinusoidal Pressure Field
Authors: Nystrom R. E. , Hammitt F. G.
Published: November 2010

Utilizing an ultrasonic vibratory cavitation facility, the onset of cavitation was observed in liquid sodium for different liquid sodium temperatures and at various sinusoidal pressure field frequencies. It was observed that the pressure oscillation required to initiate cavitation decreases linearly as the temperature of the sodium is increased from 500 to 1500 deg F. For frequencies below 20 kHz the cavitation threshold pressure amplitude is essentially independent of frequency. For frequencies above 20 kHz the cavitation threshold begins to increase sharply. Using the onset of cavitation data and the saturation temperature-pressure data for liquid sodium, the superheat required to produce nucleate boiling in liquid sodium was calculated. As the saturation temperature of liquid sodium is increased the calculated superheat decreases. For frequencies below 20 kHz the calculated sodium superheat requirements, which are independent of frequency, are in good agreement with steady-state sodium superheat data reported in the literature.
Bubble Formation Due to a Submerged Capillary Tube in Quiescent and Coflowing Streams
Authors: Chuang S. C. , Goldschmidt V. W.
Published: November 2010

The case of bubble formation in both quiescent and moving streams due to the injection of a constant gas flow through a small tube is considered. Relationships predicting the expected size and quantity of bubbles generated are proposed. These are compared with measurements taken with stream velocities up to 9 ft/sec, while generating gas bubbles from 40 to 700 microns in diameter. For the case of generation in a quiescent stream the forces due to the virtual mass, surface tension, viscous drag, buoyancy, and the wake formed by the preceding bubble are accounted for. There still remains some question (only partly answered by a comparison with measurements) as to the proper added mass coefficient and the geometry of the bubble previous to detachment, as well as an adequate estimate of the interaction with a preceding bubble’s wake. The proposed model for generation in a moving stream is in good agreement with actual measurements for co-flowing velocities between 1 and 9 fps and capillary tubes in the order of 10−3 cm in dia.
Cavitation Erosion in Nonaqueous Liquids
Authors: Plesset M. S.
Published: November 2010

Cavitation erosion rates in the organic liquids formamide, ethanol, acetone, and glycerol are compared with the rate in distilled water. As is to be expected, these non-ionizing liquids, which are chemically less reactive with metals than water, show lower damage rates. The cavitation damage rates have also been measured for solutions of these organic liquids in water and all these solutions show a monotonic decrease in going from pure water to the pure organic liquid except glycerol. The water-glycerol solutions go through a minimum damage rate for a solution with molecular ratio of glycerol to water of approximately 1 to 1. Solutions of ethanol in glycerol show a maximum in damage rate for a solution with molecular ratio, glycerol/ethanol, of about 2 to 1. Qualitative differences in the cavitation bubble cloud in the various liquids studied are indicated by short-exposure photographs.
Experimental Study of Through-Flowing Pneumatic Lines
Authors: Orner P. A. , Cooley W. C.
Published: November 2010

The complete linear two-port admittance parameters of a short uniform pneumatic line are experimentally determined as functions of driving frequency and the steady through-flow in the line. The measured through-flow influence (c.f. the driving point admittance increase) is found to be much greater than that predicted by known one-dimensional acoustic models (frequency dependent phase velocity and attenuation factor) with mean velocity Doppler shift correction. More satisfactory agreement is found with a model which considers the first-order effects of the through-flow velocity profile. High-frequency (up to 2500 Hz) laminar dynamic flow and pressure data is presented for lines on the order of 6 in. long and 1/8 in. ID, with Mach numbers from zero to 0.16. The experimental aspects of quantitative dynamic flow measurement with a hot-wire anemometer are discussed in detail. Details and calibration of the high-frequency line flow and pressure probes, and the low Reynolds number—high Mach number flow test setup are presented.
A Boundary-Layer Theory for Transient Viscous Losses in Turbulent Flow
Authors: Wood D. J. , Funk J. E.
Published: November 2010

A laminar boundary-layer model is proposed to account for viscous losses during the transient turbulent flow of a liquid in a tube. In this model, inviscid slug flow is assumed for the core and all viscous effects are assumed to occur in the boundary layer. The transient boundary-layer velocity distribution is determined as a function of a prescribed variation in core velocity and the associated pressure gradient. Both analytical and numerical solutions are presented. This transient flow information is used to calculate local and integrated energy dissipation rates which are then combined, with one-dimensional energy analyses. The result is a prediction of the decrease in pressure-wave magnitude due to viscous dissipation, and a comparison is made with experimental data for rapid flow extinction. Good agreement between the observed and predicted results is obtained.
Interaction of a Two-Dimensional Sonic Jet With a Supersonic Stream
Authors: Srinivasan G. , Diab T. A. , Krishna Murthy M. , Ravindran R. , Narasimha R.
Published: November 2010

Experiments were conducted in a 1-in. × 3-in. supersonic wind tunnel on two-dimensional secondary fluid injection into a uniform primary supersonic stream. Both primary and secondary fluids were air at the same stagnation temperature, but the secondary stagnation pressure was varied from about 0.2 to 2 times the primary value; injection was sonic and the jet issued into the primary stream through a slit of constant width at 0 deg, 8 deg, 23 deg, and 50 deg upstream (the angle being measured from the normal to the primary flow). Primary stream Mach number covered the range from 1.64 to 2.96 in the tests. The shape of the leading shock shows similarity in modified blast variables at all angles of injection. It is also found that the separation shock in front of the main shock corresponds to a nearly constant flow deflection of about 10 deg. Estimates of the interaction force obtained from the measured pressure field show rough agreement with the calculations of Broadwell and of Spaid and Zukoski, and while supplementing the experimental data given by the latter, they bring out the dependence of the amplification factor on injection angle.
Acoustic Interactions With Turbulent Jets
Authors: Simcox C. D. , Hoglund R. F.
Published: November 2010

The interaction of a monochromatic acoustic wave with a fluctuating vorticity field is considered. The vorticity is first considered as varying harmonically both in time and space. The results show that significant changes in the time-averaged vorticity can occur. The changes are found to result from a rapid and repeated stretching and convection of the existing vorticity field by the applied acoustic field. By Fourier analysis this is extended to spectral relations to account for acoustic-turbulent interactions. The results of the study provide a consistent explanation of experimentally observed acoustic-turbulent interactions in jets, which at first appear to be contradictory.
A Reassessment of Fracture-Safe Operating Criteria for Reactor Vessel Steels Based on Charpy-V Performance
Authors: Loss F. J. , Hawthorne J. R. , Serpan C. Z.
Published: November 2010

Fracture-safe operating criteria for commercial nuclear pressure vessels based on fracture analysis diagram procedures and Charpy-V energy trends are reappraised with respect to the effects of thick section mechanical constraint and low Charpy - V shelf energies resulting from neutron irradiation. Comparisons of the Charpy-V test with the more definitive dynamic tear test procedures indicate the former to be an acceptable means of assessing the fracture toughness of A533-B steel. The mechanical constraint associated with 12-in. thicknesses of this steel suggests the addition of 70 F (39 C) to the existing criterion requiring vessel operation above NDT + 60 F (33 C). Ratio analysis diagram procedures are shown to be useful in interpreting Charpy-V shelf level data obtained from vessel surveillance programs in terms of critical toughness levels relating to brittle fracture.
Fracture Safety Analysis Concepts for Nuclear Pressure Vessels, Considering the Effects of Irradiation
Authors: Merkle J. G.
Published: November 2010

One of the most important aspects of the growth of nuclear power has been the development and use of quantitative methods of analysis for insuring the reliability of plant components and for protecting the public health and safety. Nuclear pressure vessels have always received close attention with regard to their structural strength and reliability. This paper summarizes some of the fracture mechanics concepts now being considered for application to the safety analysis of nuclear pressure vessels. The effects of thickness, temperature, strain rate, and irradiation on fracture toughness are discussed in terms of their relevance to a safety analysis. The amount of neutron irradiation likely to be received by a light water reactor pressure vessel is examined in terms of reactor type and the thermal power level. The ranges of temperature and fluence that are of most importance with regard to irradiation effects data on pressure vessel steels are identified. An example safety analysis problem is included to illustrate the application of the concepts discussed.
Shear Strength of Beryllium, Uranium, and Tungsten as a Function of Strain, Strain Rate, and Pressure
Authors: Abey A. E. , Stromberg H. D.
Published: November 2010

The shear strengths of beryllium, uranium, and tungsten were measured at strain rates of 3.5 × 10−5, 3.6 × 10−3, and 3.7 × 10−1 sec−1. The measurements were taken under nearly hydrostatic pressures of 21, 44, and 63 × 108 N/m2. The shear strength versus shear strain curves are presented along with the pressure and in strain rate derivatives of the experimental parameters.
Low Reynolds Number Turbulent Flow in Large Aspect Ratio Rectangular Ducts
Authors: Beavers G. S. , Sparrow E. M. , Lloyd J. R.
Published: November 2010

Experiments are reported on fully developed turbulent flows at low Reynolds numbers in rectangular ducts of large aspect ratio. Six ducts, with aspect ratios between 15.5:1 and 35.0:1, were employed for the investigation, covering a Reynolds number range from 5,000 to 27,000. A friction factor, Reynolds number relation expressed as f = 0.507 R−0.30 was found to be an excellent representation of the experimental data when the equivalent diameter was used as the characteristic length dimension. The Blasius and Prandtl circular tube friction factor relations, generalized by use of the equivalent diameter, gave results within 5 percent or better of the aforementioned correlation over the Reynolds number range of this investigation.
Evaluation of Angle to Be Subtended by the Spiral of Semispiral Casings
Authors: Raghunathan S. , Kar S.
Published: November 2010

A hydrodynamic model is considered for estimating the angle to be subtended by the spiral portion of high specific speed axial flow water turbine casings. The results are correlated with the design parameters of turbines.
Chemical Nonequilibrium in Supersonic Nozzle Flow
Authors: Wang Roa-Ling
Published: November 2010

An experimental and theoretical study has been made on chemical nonequilibrium flows in a supersonic nozzle for a mixture of dissociated gases and inert diluent. In the calculations, four different flow behaviors were assumed: one-dimensional non-equilibrium, two-dimensional nonequilibrium, two-dimensional equilibrium, and two-dimensional frozen flows. These were compared with measurements of the static pressure and NO2 concentration in the supersonic nozzle flow of the NO2-N4O2-N2 reactive system. Relatively good agreement demonstrates the applicability of the proposed calculation methods and the validity of the assumed reaction mechanisms and their rate constants.
Mode II Fatigue Crack Propagation
Authors: Roberts R. , Kibler J. J.
Published: November 2010

Fatigue crack propagation rates were obtained for 2024-T3 bare aluminum plates subjected to in-plane, mode I, extensional loads and transverse, mode II, bending loads. These results were compared to the results of Iida and Kobayashi for in-plane mode I-mode II extensional loads. The engineering significance of mode I-mode II fatigue crack growth is considered in view of the present results. A fatigue crack growth equation for handling mode I-mode II fatigue crack growth rates from existing mode I data is also discussed.
Liquid-Vapor Interactions in a Constant-Area Condensing Ejector
Authors: Levy E. K. , Brown G. A.
Published: November 2010

The performance of a condensing ejector depends on the interactions occurring between the liquid and vapor streams in the mixing section. Axial static and liquid-vapor stagnation pressure profiles were measured in a constant-area mixing section using steam and water over a limited range of inlet vapor conditions and a wide range of inlet liquid velocities. Three flow regimes were identified based on inlet liquid velocity. Complete vapor condensation due to a “condensation shock” occurred only in the High Inlet Liquid Velocity Regime. The presence of supersonic vapor flow was found to be a necessary but not a sufficient condition for the existence of the “condensation shock.” In addition, breakup of the liquid jet was found to play an important role in the mixing section processes. A quasi one-dimensional analytical model of the annular liquid-vapor flow patterns occurring in the upstream portion of the mixing section was formulated. Though it was not possible to predict sufficiently accurately the interfacial heat transfer rates from any currently available analyses or data, interfacial heat transfer coefficients of approximately 100 Btu/sec ft2 deg F were found to produce good agreement between the experimentally measured and computed analytical axial static pressure variations. These values compare favorably with other data on the heat transfer rates to turbulent water jets with condensation.
The Effect of Strain Rate and Temperature on Yielding in Steels
Authors: Kendall D. P.
Published: November 2010

The effect of elastic strain rates ranging from 10−14 to 10 sec−1 and temperatures ranging from 200 K (−100 F) to 590 K (600 F) on the yield strength of several steels is reported. The steels utilized are a 1018 mild steel, 4340 steel, H-11 tool steel, and 300 grade maraging steel. The results are interpreted in terms of the Cottrell-Bilby yielding model based on release of dislocations from locking carbon atmospheres. The results for all of the materials except the maraging steel are consistent with this model if it is modified to account for relocking of dislocations by migration of carbon atoms. The maraging steel shows a constant strain rate sensitivity at a constant temperature, over the range of strain rates investigated. This rate sensitivity decreases with increasing temperature and at 590 K (600 F) a decreasing strength with increasing strain rate is found. This is attributed to stress aging effects.
Punching of Copper Under Pressure
Authors: Kaneda H. , Bobrowsky A. R.
Published: November 2010

Punching of copper sheet at atmospheric pressure and under environmental pressures up to about 160,000 psi showed the following: The fraction of slug thickness that is burnished is essentially independent of the thickness of the metal specimen; finite pressures can be used for complete burnished punching (about 70,000 to 110,000 psi for the soft copper and about 70,000 to 120,000 psi for the hard copper); hard copper requires higher pressure to achieve the same fraction of burnished zone as soft copper at the lower pressures, but requires the same pressure at higher pressures; and, the effect of clearance is complex inasmuch as small clearance yields larger burnished zones at atmospheric pressure, but the reverse is true at the highest pressures, with a crossover in between at about 70,000 psi.
“DANUTA,” A Three-Dimensional Finite Element Program Used in the Analysis of Turbomachinery
Authors: Chacour S.
Published: November 2010

A three-dimensional structural analysis program (DANUTA), using newly developed subparametric finite elements, is described and applied to the analysis of turbo-machinery components. The hexahedron-shaped element has twelve generalized displacements concentrated at each of the eight corner nodes. The displacement components are represented by a complete third degree polynomial, with some selected terms of the fourth and fifth degree, while the geometry is described by a set of second order parametric interpolation functions. The derivation of the stiffness and consistent load matrices (surface and body forces) is outlined. Numerical results, for cases where a classical solution is available, illustrate the high accuracy of the element. Application of the program to the analysis of spherical valves, turbine runners and wicket gates, as well as machine requirements, automatic data generation and possible further developments are discussed.
Studies on Cavitation Erosion
Authors: Suezawa Y. , Matsumura M. , Nakajima M. , Tsuda K.
Published: November 2010

Cavitation damage tests of iron and steel have been carried out using two types of experimental facilities. One is a water tunnel system which presumably simulates the field conditions fairly closely and the other is a magnetostriction vibratory unit commonly used for accelerated cavitation erosion testing of metals. A comparison between water tunnel and vibratory tests shows a difference in mechanism of cavitation damage. Consequently, it has been concluded that the application of the test results obtained in a magnetostriction vibratory apparatus should be limited to provide rough data for the primary selection of proper materials to be used in the construction of hydraulic units and other industrial systems, unless damage is caused under similar conditions to that of the vibratory apparatus.
Temperature Effects in Cavitation Damage
Authors: Plesset M. S.
Published: November 2010

Cavitation damage is studied for several materials over a range of temperatures in the cavitating liquid from 0 C to 90 deg C. The cavitating liquids used were distilled water, distilled water buffered to pII 8, and a 3 percent solution of NaCl in distilled water. The cavitation damage was produced by continuous oscillation of the test specimens with a magnetostrictive transducer so that long term chemical effects tended to be suppressed. It is found that the maximum in the damage rate occurs at temperatures in the range 40 C to 50 deg C. The decrease in the damage observed at the higher temperatures is to be expected as a consequence of the increase in vapor pressure. The rise in damage at the lower temperatures has a less obvious interpretation and may be due to an increase in chemical activity with temperature.
Hydrodynamic Transition in Electrolysis
Authors: Bhattacharya A. , Lienhard J. H.
Published: November 2010

The gas removal process during electrolysis is studied with the aim of identifying hydrodynamic transitions, analogous to those which occur in boiling. The local peak in the electrolysis gas flux is observed during electrolysis from a horizontal cylindrical cathode. This transition point is shown to correspond with Moissis and Berenson’s “first transition” in nucleate pool boiling. A prediction of the transition, applicable to either boiling or electrolysis, is developed for the cylindrical heater (or cathode) arrangement. It is compared with 12 experimental data for boiling and electrolysis, and its limitations are discussed. Finally, some attributes of the regime of film electrolysis are identified and discussed.
Response of a Realistic Human Head-Neck Model to Impact
Authors: Goldsmith W. , Sackman J. L. , Ouligian G. , Kabo M.
Published: November 2010

A structurally realistic model of the human head-neck system, consisting of a water-filled human cadaver skull and an artificial neck was subjected to pendulum impact under nondestructive conditions. The neck consisted of a series of neoprene and aluminum rings fabricated so as to faithfully reproduce the head motion of living persons in the saggital plane. Both an aluminum spherical shell and a solid steel sphere were employed to produce contact durations of the order of 1–6 ms and 0.2–1 ms, respectively, depending upon whether the impact occurred against the bare skull or against one of several scalp simulators used. Both frontal and occipital blows were produced on the system. A series of pressure transducers were suspended along the impact axis that measured the history of this parameter for the various conditions employed, and a crystal transducer arrangement ascertained the force input to the system. A displacement gage was utilized to record the excursion of the head-neck junction. Significant differences in pressure response were noted between frontal and occipital blows without protective covers that disappeared when scalp simulators were employed. The response characteristics in the present tests were much simpler than in corresponding tests using an acrylic shell for the head model, where pressures under similar impulsive loading conditions were at least an order of magnitude larger; this difference is attributed to the layering effect of the real skull relative to the homogeneous shell previously used.
Mechanical Response of the Lungs at High Frequencies
Authors: Fredberg J. J. , Hoenig A.
Published: November 2010

We put forward an efficient method for computing the input impedance of complex asymmetrically branching duct networks, and apply this method to simulation of the dynamic response of the lungs of normal adult humans in the frequency range extending to 10,000 Hz. The results indicate that the response of comparable symmetric and asymmetric branching networks differ at high frequency (> 2 kHz in air), and that the airway wall response is an important factor in determining system damping and resonant frequencies.
Use of Optimization Techniques to Predict Muscle Forces
Authors: Crowninshield R. D.
Published: November 2010

Optimization solutions to the indeterminate distribution problem of determining muscle forces are discussed. A method of predicting muscle force during joint function is presented which encourages the prediction of synergistic muscle action with physiologically reasonable individual muscle forces. The method uses limits on muscle strength that are a set portion of the lowest muscle strength that will permit a solution at the particular joint moment. The method is shown to correlate well with recorded EMG activity.
Measurements of Temperature Distributions at Electro-Surgical Dispersive Electrode Sites
Authors: Overmyer K. M. , Pearce J. A. , DeWitt D. P.
Published: November 2010

The superficial temperature distribution for various types of dispersive electrodes applied to human subjects and a surrogate medium are presented. Typical temperature distributions on the human thigh display a high temperature perimeter and cooler central area, with the temperature extremes and contours peculiar to the electrode design. These patterns persist for several minutes after electrode removal. A series of experiments was conducted on a surrogate medium to determine the extent of volumetric (ohmic) heating, to evaluate influence of media properties on the temperature distribution, and to evaluate the use of the medium for simulation of the human system. It was found that volumetric heating is appreciable and that appropriate alteration of the medium resistivity with depth produced patterns having similar characteristics to those obtained with the same electrode on a human thigh. A simplified model to analytically predict the temperature distribution is presented and the results are similar to those observed on human subjects.
A Model of a Sac-Type Artificial Ventricle in Mock Circulation
Authors: Tsang S. , duPlessis M. P.
Published: November 2010

A mathematical model of a sac-type artificial ventricle is presented. The model, derived from the mass conservation and energy equations of a deformable control volume, is used in a digital simulation study of a latex ventricle in mock circulation. The hinged disk valves mounted within the ventricle are modelled as nonlinear resistive elements with flow regurgitation. The simulation results are compared with experimental measurements.
In-Vivo Bone Strain Telemetry in Monkeys (M. Nemestrina)
Authors: Young D. R. , Howard W. H. , Orne D.
Published: November 2010

A new method for collecting in-vivo bone strain data in monkeys has been developed and tested. The method includes a system which consists of a new design of implantable strain transducer and its companion telemetry package. The transducer fits into a hole drilled in a monkey tibia and is threaded for subsequent bone ingrowth. The transducers and telemetry package are biocompatible for over 503 days. The telemetry package uses Pulse Interval Ratio Modulation (PIRM) to transmit strain information to receiving equipment located outside the animal housing cage.
Compliance of the Human Ankle Joint
Authors: Agarwal G. C. , Gottlieb C. L.
Published: November 2010

The dynamic response of the human ankle joint to a band-limited (0 to 50 Hz) gaussian torque disturbance superimposed on a constant bias torque is observed at different levels of voluntary contraction of the leg muscles acting about the ankle. The compliance of the ankle joint, defined as the ratio of the joint rotation and applied torque is modeled by a second-order, linear dynamic model. The visco-elastic properties of the joint are shown to be linear functions of the muscle activation.
Steering Controller Design For Automated Guideway Transit Vehicles
Authors: Shladover S. E. , Wormley D. N. , Richardson H. H. , Fish R.
Published: November 2010

The fundamental lateral performance capabilities of rubber-tired automated guideway transit (AGT) vehicles operating under automatic steering control on exclusive guideways are discussed. Control is achieved by steering the front wheels in response to signals derived from the position errors between the vehicle and a guideway-based reference containing random irregularities. Optimal control techniques are used to synthesize controllers which minimize a performance index consisting of mean square lateral acceleration and tracking error, defining a frontier which limits the performance of vehicles steered by a broad class of controllers. Simple single-sensor proportional steering controllers are found to achieve near-optimum performance for a typical AGT vehicle. The degradations in performance arising from dynamic lags in the steering actuator and operation at off-design speeds are shown.
A Novel Pressure Transducer Using Mechanical Resonance
Authors: Ohga J. , Mizushima Y.
Published: November 2010

A novel electromechanical pressure transducer, suitable for telemetering, is proposed. It transforms an absolute static pressure into a frequency signal, using acoustical resonance due to the stiffness of a fluid in a cavity and the mass of a vibrating plate. The relation between the period of the output frequency T and the normalized input pressure p is theoretically given by T2 = A + B/p, where A and B are constants. This relation is verified experimentally by constructing two kinds of models. The advantages and disadvantages of the transducer are discussed.
Optimum Design of Control System Compensators
Authors: Afimiwala K. A. , Mayne R. W.
Published: November 2010

Compensators are designed for a plant to optimize its transient response during load disturbances and changes in reference input, and subject to constraints on plant input, peak displacements during the transients, and speed of response. Optimum controller parameters are determined here by making a sequence of 2D minimizations, approximating the design criterion and constraints with polynomials, and using contour plots for estimating the 2D minimums. Contour plots generated help identify the feasible design region and show the influence of the design variables and constraints on the system performance. Finally, sensitivity curves are generated at the optimum to aid the designer in making trade-offs between competing objectives and to select a new design when system requirements are modified.
Rail Passenger Vehicle Lateral Dynamic Performance Improvement Through Active Control
Authors: Sinha P. K. , Wormley D. N. , Hedrick J. K.
Published: November 2010

High speed operation of conventional rail vehicles is limited by a number of dynamic problems including ride quality, curve negotiation, and hunting. Active control is investigated as a technique for improving rail vehicle performance at high speeds. An automatic controller of specified configuration and structure is defined based on the physics of the wheel-rail interaction dynamics which allow a decomposition of dynamic constraints into selected frequency bands and a methodology for selecting the controller parameters is presented. Two controller case studies are examined to demonstrate the effectiveness of controller configuration on rail vehicle performance in terms of ride quality and tracking errors on tangent track while allowing specified curve negotiation requirements to be met. Estimates of control power requirements are also obtained which show that the controller configurations considered produce improvements in vehicle performance—reduction of rms vehicle accelerations by a factor of between 5 and 6 and reduction of rms tracking errors by a factor of between 4 and 5—with modest expenditures of control—power between 1.5 and 2 kw per truck at a vehicle speed of 68.58m/s.
Longitudinal Control of Automated Guideway Transit Vehicles Within Platoons
Authors: Shladover S. E.
Published: November 2010

This paper demonstrates, via analysis and simulation, the feasibility of a vehicle-follower control system which maintains intervehicular spacings of 30–60 cm within platoons of automated guideway transit (AGT) vehicles. Asymptotic stability of the platoon is shown to be achievable when each vehicle references its speed to that of the platoon leader. Jerk limiting, which is regarded as essential for all AGT longitudinal controllers, is shown to be potentially destabilizing. The nonlinear effects produced by the jerk limiter are analyzed by use of describing functions, and it is demonstrated how the undesirable effects can be avoided.
Discrete Parts Assembly Automation—an Overview
Authors: Whitney D. E.
Published: November 2010

The research problems in automated assembly are discussed. They are broken down into ten problem areas. The major theoretical issues are described and examples of different approaches are cited and commented on.
Optimal Control of Sun Tracking Solar Concentrators
Authors: Hughes R. O.
Published: November 2010

Using the disciplines of Modern Control Theory, an optimal tracking control for a point focusing solar concentrator is derived. By converting the tracking problem into a regulator problem with a sun rate input a very low pointing error is achieved. A representative example with a corresponding computer simulation is presented.
The Application of Model-Referenced Adaptive Control to Robotic Manipulators
Authors: Dubowsky S. , DesForges D. T.
Published: November 2010

The achievement of quality dynamic performance in manipulator systems is difficult using conventional control methods because of both the inherent geometric nonlinearities of these systems and the dependence of the system dynamics on the characteristics of manipulated objects. A model-referenced adaptive control law is developed for maintaining uniformly good performance over a wide range of motions and payloads. The effectiveness of the approach is demonstrated in several simulations and the system stability as a function of input is investigated. Also developed is a “learning signal” approach designed to minimize initial transients arising from abrupt changes in the inertial payload.
Guaranteed Asymptotic Stability for Some Linear Systems With Bounded Uncertainties
Authors: Leitmann G.
Published: November 2010

We consider a class of linear dynamical systems in which the system and input matrices, as well as the input, are uncertain. The nominal system is time-invariant, while the uncertainties are assumed to be measurable functions of time whose values may range in given compact sets. Utilizing solely the knowledge of the sets from which uncertain quantities take their values, we derive a state feedback controller that guarantees global uniform asymptotic (Lyapunov) stability of the zero state in the presence of admissible uncertainties. The controller is nonlinear, namely componentwise switching; however, its construction requires only the solution of a linear matrix equation. Unlike linear feedback, this nonlinear controller assures asymptotic stability for any admissible realization of the system; this is illustrated by means of a simple example.
Application of Sensitivity Analysis to Car-Trailer Stability
Authors: Mikulcik E. C.
Published: November 2010

Sensitivity coefficients relating to the oscillatory stability of the equations for simplified automobile-trailer combinations are defined and calculated. These coefficients show that variations in the automobile’s parameters have very little influence on a stable combination, but their influence on a combination which is on the verge of instability is just as important as the parameters of the trailer. The sensitivity coefficients give a quantitative indication of the importance of parameter changes made in attempting to improve the characteristics of a vehicle.
Initial Condition Sensitivity Functions and Their Applications
Authors: Leondes Cornelius T. , Wu C. A.
Published: November 2010

The well-known method of obtaining sensitivity functions is usually restricted by the condition of continuity imposed on the functions of the coordinates in system equations. For the case of discontinuous functions, more elaborate procedures are required to give a good linear approximation. It is shown that sensitivity functions are discontinuous at the discontinuous points. Also, relations between elements of sensitivity functions at these points are shown to be linear for a given nominal solution of the system. The switching time of the desired Bang-Bang control can be estimated if variations in initial conditions are known. The changes in terminal states and cost function due to deviations in initial conditions can be determined, to first order, by the use of sensitivity functions. Bounds on the deviations in initial conditions can be found by a worst case approach so that the desired terminal conditions are satisfied within given tolerances. The fundamental importance of these techniques in a number of areas of application, for instance, guidance and control of aerospace vehicles, is well known.
Lagrangian Bond Graphs
Authors: Brown F. T.
Published: November 2010

Two types of bond graphs which imbed Lagrange’s equations and variables are found for systems conceived in terms of energy and power. The basic form also imbeds simpler transformed equations and more primitive variables. The graphs enhance one’s grasp of both energetic structure and functional behavior, including nonlinearities, and give state space formulations.
Bond Graph Models for Fluid Dynamic Systems
Authors: Karnopp D.
Published: November 2010

The modeling process whereby distributed parameter fluid systems are described approximately by lumped parameter models is discussed using bond graph techniques. It is shown that despite the analogies which exist between some fluid systems and other physical systems, the lumping process for fluid systems introduces forms of nonlinear behavior not often encountered in other types of systems. Many such effects may be traced to the desire to use control volumes and Eulerian rather than Lagrangian descriptions of the fluid systems.
Direct Application of the Loop Rule to Bond Graphs
Authors: Brown F. T.
Published: November 2010

The Shannon-Mason loop rule permits direct reduction of a linear constant-parameter signal flow graph to a transfer function. Signal flow graphs can be constructed from bond graphs or sets of equations. Application of the loop rule to the parent bond graphs, however, with the aid of certain rules, is shown to be quicker and less prone to error. Also, four invariant classes of bond graph meshes are distinguished, with implications in physical analogies and in computation.
Jet-Driven Cylindrical Cavity Oscillators
Authors: Franke M. E. , Jones G. , Olsen W. A.
Published: November 2010

The effects of cavity diameter, jet-exit distance, and flow rate on the performance of a jet-driven cylindrical cavity oscillator are investigated experimentally in this study. The cavity oscillator is driven by an air jet that enters the cavity radially through a nozzle located on the periphery of the cavity. The air leaves the cavity perpendicularly to the entering flow through a tube that has its axis parallel to the axis of the cavity. The operating frequencies are found to agree with the eigenfrequencies of the cavity; however, the regions of operation at these frequencies are shown to depend on the flow rate and to exhibit characteristics similar to those of a multistage, jet-edge resonator. The results for several cavity diameters are correlated in terms of a dimensionless frequency and a cavity Reynolds number. Schlieren still photographs and high-speed motion pictures are used to observe the motions of the jet.
Recent Developments in Numerical Integration
Authors: Smith J. M.
Published: November 2010

Classical and even modern developments of numerical integration have not been directly concerned with the frequency-response of integration algorithms. The frequency-response characteristics of an integrator are usually presented only as a property of the integrator. When numerical integration is used in all digital (or hybrid) simulation, digital computer controlled systems or other discrete information systems, much care is given to selecting a numerical integration formula with well-behaved frequency-response characteristics. This paper is concerned with the development of a set of numerical integrators suited for application in information systems. These integrators are synthesized in such a way that they have well-defined frequency-response characteristics WHICH CAN BE VARIED; thus, each of these integrators can be tailored to integrate accurately and efficiently in many different applications. These methods of numerical integration have stability, accuracy, and noise-controlling parameters. Analytical and empirical methods of selecting the values of these parameters are discussed in detail.
Dynamic Interaction Aspects of Cable-Stayed Guideways for High Speed Ground Transportation
Authors: Meisenholder S. G. , Weidlinger P.
Published: November 2010

This paper describes the dynamic considerations in the design of a long span (200 to 600 ft) cable-stayed guideways for future tracked levitated vehicles (TLV’s) which will be used for high speed ground transportation. A design approach is described in which a cable-stayed guideway structure can be synthesized to simulate the behavior of a beam on elastic foundation. This result is achieved by the “cable-tuning” approach, in which the cable stays are selected to achieve an equivalent uniform elastic foundation. The design approach insures that the live load deflection of the trackway beam is manifested as a traveling wave which moves horizontally at the same velocity as the vehicle, thereby minimizing dynamic interaction problems. Parametric results are presented for the dynamic response of a beam on elastic foundation. Optimum cable and tower configurations are developed for this guideway concept and a typical conceptual design is described.
Computation of Approximately Optimal Control Signals for Systems With Time Delays
Authors: Horwitz L. B.
Published: November 2010

A computational algorithm is presented for a class of optimal control problems involving time delays. The approach is to restrict the control signal to a class of piecewise constant time functions with a prescribed number of switching times, compute the optimal member of this class, and then repeat with a larger number of switching times. By allowing the number of switching times to increase beyond bound a sequence of restricted optimal control signals is developed whose limit approaches the unrestricted optimal control signal. In practice the computations are terminated after a finite number of repeats, thus leading to the approximate nature of the solution. The results of two examples are included to illustrate the technique.
Arbitrary Pole Placement With Limited Number of Inputs and Outputs
Authors: Loscutoff W. V.
Published: November 2010

In controller design problems, the quantitative description of the desired controlled system behavior is often given by specifying the closed loop poles. An output-variable, feedback control policy for a linear system of order n, with m outputs and p inputs, is described by u = −Gy. Matrix G contains p × m parameters which may be used to dictate the locations of the closed loop poles. The limiting condition for arbitrary pole placement, without some form of state estimation, is p × m = n since the p × m independent controller parameters may be used to specify the n poles. However, there is no systematic procedure for the design of controllers subject to limiting condition. In this paper, a technique based on modal system description is used to design static output-variable feedback controllers with limited number of inputs and outputs. It is shown that arbitrary closed loop pole placement is possible if p + m ⩾ n + 1 for sufficiently well coupled systems.
Flow Saturated Step Response of a Hydraulic Servo
Authors: Martin K. F.
Published: November 2010

This paper reports a theoretical and experimental investigation of the displacement and pressure responses of a closed loop hydraulic servo to a very large step input. The latter ensures that the servovalve ports are fully open and the servo flow-saturated for substantial periods. The nonlinear equations are solved by both analogue and digital computation with analytical solutions in particular situations. Approximations for the displacement response and the maximum pressure attained are evaluated and shown to be acceptable. Experimental values compare reasonably well with predictions An important conclusion is that such a servo cannot cavitate during a step response
A Variational Method for Approximating the Response of Nonlinear Stochastic Systems
Authors: Zirkle L. D. , Clark L. G.
Published: November 2010

A method is introduced for determining approximate properties of the response of nonlinear stochastic systems. The method is based in concept on the variational methods of mechanics and allows the consideration of classes of systems not readily subject to analysis by existing techniques. Three examples are presented illustrating the application to nonlinear systems with non-stationary inputs, non-Gaussian inputs and with time delay. The main limitation of the technique is the necessity for assuming a meaningful form for the approximate solution in terms of arbitrary random variables.
Recent Development in France of Stochastic Filtering and Its Application to Identification
Authors: Martin J. A. , de Larminat Ph.
Published: November 2010

The objective of this paper is to describe some typical contributions to theory and practice on stochastic filtering and identification in France. Attention is focused on the problems related to the noise characteristics in linear filtering, and the application of nonlinear filtering to system parameter identification.