bluuebunny/crossref_metadata_2025 huggingface dataset:
Disease Progression and Treatment Response of Idiopathic Epilepsy inAustralianShepherd Dogs
Authors: Weissl J. , Hülsmeyer V. , Brauer C. , Tipold A. , Koskinen L.L. , Kyöstilä K. , Lohi H. , Sauter‐Louis C. , Wolf M. , Fischer A.
Published: December 2011

Background

Idiopathic epilepsy (IE) in Australian Shepherds (ASs) occurs worldwide but there is a lack of description of the epilepsy syndrome in this breed. TheABCB1‐1Δ mutation is more prevalent inASs than in many other dog breeds.

Hypothesis

Australian Shepherds suffer from a poorly controlledIEsyndrome with prevailing severe courses. Seizure control andABCB1‐1Δ mutation might be related in this breed.

Animals

Fifty ASs diagnosed with IE and 50 unaffected ASs.

Methods

Predominant study design is a longitudinal cohort study. Pedigrees, medical records, seizure, and treatment data ofASs withIEwere analyzed descriptively. Sex, color, and theABCB1‐1Δ genotype were compared between case and control groups andASs with poorly or well‐controlled seizures. Differences in survival times were assessed by logrank tests andCox regression analysis.

Results

Idiopathic epilepsy inASs is dominated by moderate and severe clinical courses with the occurrence of cluster seizures and status epilepticus and a high seizure frequency. Poor seizure control and a high initial seizure frequency (≥10 seizure days/first 6 months) are associated with shorter survival times (P < .05). Poor seizure control, unrelated to theABCB1(MDR1) genotype, is evident in 56% of epilepticASs. Pedigree analysis suggests a genetic basis.

Conclusion and Clinical Importance

Frequent severe clinical courses, poor seizure control unrelated to theABCB1(MDR1) genotype, and a young age at death compromise animal welfare and warrant further genetic studies to unravel the underlaying molecular mechanisms ofIEand seizure control in the breed.
BUILDING A LATINO‐ENGAGED ACTION‐RESEARCH COLLABORATIVE: A CHALLENGING UNIVERSITY–COMMUNITY ENCOUNTER
Authors: Contreras Ricardo , Griffith David
Published: December 2011

This article discusses the experience of the Nuevo South Action‐Research Collaborative, a university–community collaborative involving an interdisciplinary group of faculty and students from East Carolina University and Latino community organizations. The article describes the collaborative formation process and places it within the context of the southeast as a new destination for Latino immigration. The collaborative formation process is discussed from the point of view of a complex encounter characterized by concurrences and tensions.
AN ACADEMIC IN AN ACTIVIST COALITION: RECOGNIZING AND BRIDGING ROLE CONFLICTS
Authors: Heyman Josiah
Published: December 2011

On the basis of participant‐observation in an immigrant human rights coalition, this contribution offers reflections on the opportunities and challenges of being an academic in a politically active coalition. It first examines the ways in which university scholars can encounter rich fields for social scientific learning by engagement with coalitions in the communities that surround them, offering an alternative to the ivory tower model of anthropology done in distant fields. It then explores the challenges of coalition involvement through the theme of role expectations and conflicts. Among the topics examined through participant‐observation are role expectations conflicts, time or schedule conflicts, resource tensions, legal and bureaucratic limits, social status inequalities, reduction of name visibility and ego gratification, and complex negotiations and compromises. It finishes with observations on commitment and objectivity, and proposes that coalitions shape particular forms of knowledge creating and communicating processes. These are real issues, but not insurmountable ones, and an honest accounting of them will result in more effective and rewarding coalitions between activists and academics.
Spatial Motions I—Point Paths of Mechanisms With Four or Fewer Links
Authors: Primrose E. J. F. , Freudenstein F.
Published: December 2011

Algebraic, geometric and some kinematic properties are derived for the paths generated by points on representative single degree-of-freedom spatial motions of four and fewer members. The motions considered are spherical rolling, spatial three-link motion, spherical four-bar motion, skew four-bar motion (three types), Bennett’s mechanism, and one type of spatial four-bar motion.
On a General Method of Spatial Kinematic Synthesis by Means of a Stretch-Rotation Tensor
Authors: Sandor G. N. , Bisshopp K. E.
Published: December 2011

One of the key concepts in a general method of spatial kinematic synthesis is a stretch-rotation operator applied to members of a general spatial kinematic chain. The latter consists of one or more interconnected loops of successively ball-jointed bar-slideball members. Each member is represented by a vector free to stretch-rotate with the motion of the chain. In the mathematical model of the general chain, displacement is simulated by means of stretch-rotation tensors operating on each member vector. Appropriate mathematical constraints render the general chain and its mathematical model equivalent to a particular mechanism. With this approach and by taking derivatives, first, second, and higher-order loop equations can be developed which form the basis for a general method of spatial kinematic synthesis, applicable to path, function and motion generation (body guidance) with first, second, and higher-order as well as for combined “point-order” approximations.
Generalized Cardan Motion
Authors: Tesar D. , Anderson H.
Published: December 2011

Cardan motion has been treated in the literature principally in terms of infinitesimally separated positions. Here Cardan motion is synthesized for all combinations of up to five infinitesimally and finitely separated positions of the moving plane. For each of the five distinct combinations which exist for four positions, the circle point curve is shown to degenerate into a circle and a line and the center point curve into a line at infinity and a hyperbola. Elementary analytical and graphical design procedures are provided and supported by examples. The five position problem is shown to be constrained only by the well-known Scott-Russell mechanism or a double-slider mechanism.
On the Spherical Oscillating Cylinder Mechanism
Authors: Veldkamp G. R.
Published: December 2011

If a plane oscillating cylinder mechanism is in the position where the slider and the crank are aligned, it has a Ball point on the slider. This Ball point coincides with the inflexion-pole. The said point has the excess two if and only if the mechanism is suitably dimensioned. In this paper, extensions of these theorems are given for a spherical oscillating cylinder mechanism. It is shown that the theorems for the plane mechanism can be obtained from the spherical ones by a limiting process. Moreover, some theorems on the spherical mechanism are given without proofs.
Acceleration Axes and Acceleration Distribution in Spatial Motion
Authors: Veldkamp G. R.
Published: December 2011

In plane kinematics there is in general in a given position of the moving plane one point J in this plane (the acceleration pole) which has the acceleration zero. Moreover, if A ≠ J is a point in the moving plane, the angle γ between AJ→ and the acceleration AA→j of A does not depend on the choice of A. We give in this paper a generalization of this theorem to spatial motions.
Symmetric Overconstrained Linkages
Authors: Waldron K. J.
Published: December 2011

A study is made of the mobility of linkages with line and plane symmetry. The symmetry conditions are shown to give rise to several very general classes of overconstrained linkages.
Synthesis of 4-Bar Linkages Adjustable for Several Approximate Straight-Line Motions of a Coupler Point
Authors: Beaudrot C. B.
Published: December 2011

A design technique which makes use of the unique inflection circles that result when the instant center (pole) falls at a fixed pivot or at a link pivot is developed to synthesize a 4-bar linkage which has a point or points on its coupler plane which trace two straight-line motions of specified angular displacements for two adjustments of a “fixed” pivot. When combined with an adaptation of the Euler-Savary equation, this technique can be used to synthesize a 4-bar linkage having a coupler point which traces three straight-line motions for three specified adjustments of a fixed pivot.
Automatic Design of Four Bar Function Generators
Authors: Bussell William H.
Published: December 2011

A method intended for programming on a computer is presented for designing four bar function generators based on infinitesimal kinematic synthesis. By using the outlined procedure, one can obtain mechanism linkage specifications and tables of performance of a large number of the possible mechanisms for a single design point. Selection of the most suitable mechanism by inspection of the tables is then possible.
Design Equations for the Finitely and Infinitesimally Separated Position Synthesis of Binary Links and Combined Link Chains
Authors: Chen P. , Roth B.
Published: December 2011

A general method for synthesizing spatial linkages (derived in a previous paper [1]) is applied to the design of various types of binary links and combined link chains. Equations governing those special points and lines which define the link dimensions are derived. Types and order of loci of such special points and lines and the maximum number of design positions for each link are given. Numerical method for computing these special points and lines are discussed, and a numerical example is presented.
Structural Synthesis of a Four-Bit Binary Adding Mechanism
Authors: Haas S. L. , Crossley F. R. E.
Published: December 2011

The structural permutation method (the “number” synthesis) of linkages is used to produce a collection of linkage forms with mobility 4. The steps of the procedure are carefully explained in detail; Franke’s notation is used. From the collection, a few promising forms are selected for dimensional sizing, so that the mechanism be capable of adding any of the numbers 1, 2, 4, and 8 to obtain a sum N with 0 ≤ N ≤ 15. The study provides an example of this design procedure.
Dynamic Behavior of Spatial Linkages: Part 1—Exact Equations of Motion, Part 2—Small Oscillations About Equilibrium
Authors: Uicker J. J.
Published: December 2011

Part 1: Over the past several years, the matrix method of linkage analysis has been developed to give the kinematic, static and dynamic force, error, and equilibrium analyses of three-dimensional mechanical linkages. This two-part paper is an extension of these methods to include some aspects of dynamic analysis. In Part 1, expressions are developed for the kinetic and potential energies of a system consisting of a multiloop, multi-degree-of-freedom spatial linkage having springs and damping devices in any or all of its joints, and under the influence of gravity as well as time varying external forces. Using the Lagrange equations, the exact differential equations governing the motion of such a system are derived. Although these equations cannot be solved directly, they form the basis for the solution of more restricted problems, such as a linearized small oscillation analysis which forms Part 2 of the paper. Part 2: This paper is a direct extension of Part 1 and it is assumed that the reader has a thorough knowledge of the previous material. Assuming that the spatial linkage has a stable position of static equilibrium and oscillates with small displacements and small velocities about this position, the general differential equations of motion are linearized to describe these oscillations. The equations lead to an eigenvalue problem which yields the resonant frequencies and associated damping constants of the system for the equilibrium position. Laplace transformations are then used to solve the linearized equations. Digital computer programs have been written to lest these methods and an example solution dealing with a vehicle suspension is presented.
Three-Dimensional Deformation and Buckling of a Circular Ring of Arbitrary Section
Authors: Meck H. R.
Published: December 2011

Solutions are developed for bending and buckling of a circular ring with an arbitrary section under several types of loading. It is found that in-plane and out-of-plane deformations are coupled. In-plane loads cause out-of-plane deformations, and loads normal to the plane of the ring cause in-plane deformations. The solutions reduce to known results from strength of materials in special cases.
Analysis of Bolt Spacing for Flange Sealing
Authors: Meck H. R.
Published: December 2011

A solution based upon the theory of elasticity is found for the maximum allowable bolt spacing in a flange assembly. The flanges are assumed to have flat faces and no gasket.
Inverted Slider Crank, Coupled in Tandem to Another Four Bar, to Generate a Constant Velocity Ratio
Authors: Meyer zur Capellen W.
Published: December 2011

Combinations of the inverted slider-crank linkage (i.e., the Whitworth quick-return mechanism) with another of the same sort, with a scotch-yoke mechanism or with a planetary gear, are able to produce excellent function generators having a stationary value of velocity ratio. Various forms are discussed, and graphs of their characteristic motions are shown.
Coordination of Coupler-Point Positions and Crank Rotations in Connection With Roberts’ Configuration
Authors: Dijksman E. A.
Published: December 2011

In this paper a geometrical solution is given to the problem of finding four-bar linkages having 5 given coupler-point positions coordinated with 4 given crank angles. It may also be possible to find solutions if one given coupler-point position together with a given crank angle, corresponding to this position, is replaced by two given link lengths. It has been found thus far that four-bar linkages, satisfying the stated conditions, are easy to obtain if the problem is related to Roberts’ law. To get a view of the possibilities, the degenerations of cognate circle-point curves and cognate center-point curves, linked to each other by the configuration (CR) of Roberts, are investigated. As an example at the end of the paper a straight-line mechanism has been designed so that the coupler point moves along this line with an approximately uniform velocity.
Some Characteristic Qualities of Powder Materials
Authors: Bruff W.
Published: December 2011

Is it possible to tell in advance if a material has a tendency to flood, or not? Powder materials often behave like liquids when aerated. There are engineers who still have not heard about these, even though they are used in solving material handling problems. Bad experiences are often their first meeting with the problem, a meeting characterized by surprise and trouble. At Fiskaa Verk, Elektrokemisk A/S, a particular problem with flooding of ground calcined anthracite was successfully solved by Dr. Jenike, and the method is described in [1]. Problems of this type are common, and in order to prevent such incidents in the future, some tests were made to find out if it is possible in advance to decide whether a material has a tendency to flood or not. A simple method was arrived at. Some characteristic qualities helping to clarify the problems of powder materials are also described.
Effect of Injected Air on the Rate of Flow of Solids
Authors: Engh T. A.
Published: December 2011

Injected air facilitates flow of a noncohesive powder through an orifice. The effect of injected air on the flow rate of raw-mix powder (used in cement production) through an orifice has been measured. It is shown that the flow rate of noncohesive solids may be determined by an energy balance that includes the expansion energy of the air.
On the Theory of Bin Loads
Authors: Jenike A. W. , Johanson J. R.
Published: December 2011

It is proposed that three loading conditions should be considered in the analysis of loads acting on a bin: Initial loading which occurs when bulk solid is charged without any of it being withdrawn, flow loading which occurs after flow has been established, and switch loading which occurs during the switch from initial to flow loading. The last is transient but, while it acts, it exerts large concentrated forces. The importance of the flow pattern is outlined and an expression is given for the high local force which frequently acts at the transition from the vertical part to the converging part of a bin.
Theory of the Formation of Arches in Bins
Authors: Peschl I. A. S. Z.
Published: December 2011

The flowing of the granular materials in bins is governed, particularly in the case of small ratios of aperture diameter to particle size, by the constant formation and breaking down of arches, known as dynamical arches. In unfavorable circumstances the arches may become stable and the aperture clogged. By building up a mechanical model of the arch the fields have been found in which a stable and a dynamical arch, respectively, may be formed, enabling a bin to be judged with respect to the danger of stable arch formation. A stable field allows of studying the interaction of arch stresses and deformation of materials starting from the stress curve of the arch as a function of the curvature, and from the curve of deformation of the material as a function of the stress. It is, therefore, possible that the elasticity of the material diminishes the stable field or even reduces it to zero. In the case of nonelastic materials, the collapse of the arch may be introduced by making the lower part of the aperture wall elastic. Stable arches can now be prevented from forming by choosing the elasticity of the resilient aperture wall in such a way that if the stress increases the wall expands sufficiently to cause the required collapse. The theory underlying this solution enables the elasticity constant and the required expansion to be calculated.
Pressures on Silo Walls
Authors: Deutsch G. P. , Schmidt L. C.
Published: December 2011

Overpressures up to four times the static pressure have been measured during discharge of sand from a model silo. The overpressures can be associated with the fundamental flow patterns. Design and calibration of the pressure cells ensured that underegistration and arching did not occur. The work suggests that previous pressure measurements may be unreliable due to inadequate pressure measuring devices. The measured overpressures were generally greater than those recommended for use in design by the recently revised German and Russian codes. A more conservative design approach is suggested herein.
Flow of Dry Bulk Solids on Bin Walls
Authors: Bernache P. L.
Published: December 2011

The assumption that a smooth wall finish, such as stainless-steel mill finish as opposed to carbon steel, will give mass flow in a less steep cone is not always valid. This paper presents case studies of how the kinematic angle of friction (φ′) between dry bulk solids and bin walls affects the design of mass flow hoppers and how it varies for different materials.
Pressure Attenuation in Long Rarefaction Wave Tubes
Authors: Levy M. J. , Gerecke H. , Potter J. H.
Published: December 2011

This paper reports upon an experimental investigation of gas dynamic rarefaction waves in rarefaction wave tubes to determine effects of large length to diameter ratios. A fitted equation is presented from which reasonable predictions can be made on the pressure deviation between a real and an ideal rarefaction wave. Transient boundary-layer effects cause an attenuation of the pressure which becomes more pronounced as the length to diameter ratio is increased. At a length to diameter ratio of 895, the pressure damping was essentially complete in one cycle for initial pressure ratios in excess of 1.6.
What Sound Can Be Expected From a Worn Tool?
Authors: Weller E. J. , Schrier H. M. , Weichbrodt Bjorn
Published: December 2011

This paper describes an electronic-mechanical system which utilizes sonic signals to detect the degree of cutting edge wear in metalworking tools and automatically trigger a cutting edge change. A packaged electronic unit reads out sonic vibrations from an instrumented machine-tool workpiece cutting-tool system to determine degree of cutting edge wear during a turning cut. At a predetermined comparative sonic ratio, the electronic unit commands stoppage of the machine tool feed, retraction of the tool and automatic index of the cemented carbide insert to the next good cutting edge. The latter function is performed by a prototype mechanical device. The paper describes the system and cites data generated during use of the sonic detection system with five grades of cemented carbide cutting AISI 1045 steel. Results under varying cutting conditions are reported. The authors speculate on the possibility of combining such a wear detection and cutting edge indexing arrangement with a computer to provide a complete system for optimum productivity and economy in a completely automatic operation.
Tools and Engineering Materials with Hard, Wear-Resistant Infusions
Authors: Schmidt Alfred O.
Published: December 2011

Development and evaluation of improved cutting tool materials which combine the high-strength properties of alloy tool steels with the higher hardness and increased wear resistance of metallic carbides by infusion of the latter into selected areas of an HSS tool tip are reported.
Application of Primary Sealing Criteria to a Self Energized Gasket
Authors: Mikesell W. R. , Brown R. T.
Published: December 2011

The seal on a metal-to-metal gasketed joint is effected by the imposition of bearing stresses, shearing stresses, or a combination of the two at the interface of the gasket and its mating seating surface. The required initial load to establish this seal for a given leak rate is greatly influenced by the gasket geometry and the type of sealing stress inherent to it. The retention of the seal under operating conditions is affected by the ability of the gasket to maintain contact with its mating surfaces through “springback” from the initial bolt-up deformations until the pressure loading is sufficient to take over. Theoretical investigations using the finite element method have been employed to determine suitable gasket geometry. Test data obtained from a full scale model are presented for comparison with the predicted values.
Solutions for Distributed Loads on Long Cylinders
Authors: Patel P. D. , Melworm R. F. , Berman I.
Published: December 2011

Previously unavailable solutions of the elastic behavior of a long cylinder subjected to balanced radial loads are obtained. The circumferentially distributed radial load solution is extended to obtain the solution in which the load is also distributed, not necessarily uniformly, in the axial direction. All displacement and stress results are written in a single expression with tabulated coefficients. Comparison to several limiting cases is made to check the validity of results. The graphical results presented herein provide an engineer with more adequate means of designing long cylinders subjected to local loads.
The Modulation of Chatter Vibrations
Authors: Thompson R. A.
Published: December 2011

The results of several experimental investigations concerning the nature of machining chatter are discussed. They indicate that chatter vibrations are generally amplitude modulated and that the chatter frequency may or may not vary from the free vibrational frequency of the chattering component. Of the several results considered each is explained in terms of an extension of the empirically derived lag equation for the machining process of Doi and Kato whereby the characteristic frequencies of the lag equation are determined. The fact that the frequency related phenomena of several independent tests are confirmed by the lag equation, which was not derived from frequency considerations, seems to justify it as a valid mathematical model for the machining process.
Generalizing the Analysis of Shoe-Type Brake-Clutch Systems
Authors: Offner D. H.
Published: December 2011

The equations used in the analysis of asymmetrically pivoted shoe-type brake-clutch systems are derived. The equations include the pressure function, average pressure, torque, energizing effect, and parameters for locating the resultant force center. These equations are shown to be valid also in the analysis of both symmetrically pivoted and “floating” shoe type systems as well as short shoe systems, thus providing the designer with one set of equations that can be used for these common types of shoes used in brake-clutch systems. A table summarizing derived equations is given and typical graphical representations of relationships are shown.
A New Upper-Bound Method for Analysis of Some Steady-State Plastic Deformation Processes
Authors: Lambert E. R. , Mehta H. S. , Kobayashi S.
Published: December 2011

A method of obtaining admissible velocity fields without velocity discontinuities is described, and applied to plane-strain extrusion, tube extrusion, and axisymmetric piercing. In plane-strain extrusion, the flow lines, grid distortions, and extrusion pressures were obtained and the values were compared with those found in previous solutions. For tube extrusion and axisymmetric piercing, the solutions are presented as examples in terms of flow lines and velocity component distributions; these solutions await experimental confirmation.
Prediction of the One-Dimensional Equilibrium Cutting Gap in Electrochemical Machining
Authors: Hopenfeld J. , Cole R. R.
Published: December 2011

In electrochemical machining the evolution of gas and heat in the electrolyte results in local variation of the gap between the electrodes. The ability to predict these variations for any given operating condition is a prerequisite of proper design of the cathode tool. This paper provides analytical predictions of the change in gap geometry for the one-dimensional steady-state case. Employing the basic conservation laws, a system of coupled nonlinear differential equations is derived for the gas-electrolyte mixture which flows between the electrodes. The assumption of homogeneity of the two-phase mixture is employed throughout the analysis. Numerical results from the solution of the equations are presented graphically and compared with experimental data. The local variation in gap and the relation between current, gap, and applied voltage compare favorably with the experimental data within the ranges of parameters investigated: current density 45–400 amps per sq in., electrolyte flow rate 0.22–0.98 gpm, entrance gap size 0.015–0.020 in., potassium chloride electrolyte normality 0.67–1.14.
Shakedown as a Guide to the Design of Pressure Vessels
Authors: Leckie F. A. , Penny R. K.
Published: December 2011

Using the theorems of plasticity lower bound estimates of shakedown loadings have been calculated for a number of shell-like structures commonly found in the pressure vessel industry. These have been determined by making use of elastic solutions, already available, in conjunction with standard linear programming techniques. Combinations of loadings and temperatures have been considered with a view to illustrating how calculations of these types can help in making design decisions.
A Computer Study of Dynamic Loads Caused by Vehicle-Track Interaction
Authors: Meacham H. C. , Ahlbeck D. R.
Published: December 2011

Computer analyses of vehicle and track are producing enlightening results regarding actual dynamic loads and the manner in which various parameters of vehicle and track structure affect these loads. Using this information, it is possible to decide more intelligently how to alleviate the high wheel-rail stresses caused by today’s unique traffic and track conditions. Possible solutions range from better track maintenance to different wheel-rail geometries to changes in stiffness and damping of trucks and the track structure itself.
Dynamic Measurement of Absolute Track Properties
Authors: Cass R. , Berthiaume P. P. , Kalita R. E. , St-Louis L.
Published: December 2011

A transducer developed to mount on the truck of a standard railway coach is the basis of a special track evaluation car. The practical application of this facility to track maintenance is described.
General Aspects of the Lateral Dynamics of Railway Vehicles
Authors: Wickens A. H.
Published: December 2011

Recent developments in research into the lateral dynamics of railway vehicles are reviewed with particular reference to dynamic stability, dynamic response, and curving. Two engineering aspects of this work are stressed—namely, the advantages of applying linear theory to a comprehensive study of vehicle dynamics, and the choice of basic assumptions required to make such studies realistic for design purposes.
A New Transit Propulsion Unit Suspension—Proved on Northeast Corridor High-Speed Test Cars
Authors: Nelson J. A. , Hapeman M. J.
Published: December 2011

A new concept in the suspension of transit propulsion units has evolved from the emphasis on new developments, such as the San Francisco BART and the Northeast Corridor high-speed projects. Designed for the new generation of transit cars, battered and modified during operation at speeds up to 150 mph on Department of Transportation cars, this suspension arrangement has proved itself at speeds up to 150 mph. It reached fruition in time to be applied to the transit cars now being built for operation at 100 mph. Correcting deficiencies in the old design for lightweight, inboard journal trucks—motor and gear unit bolted solidly together, driving the axle through, and supported on rubber around the axle—yet retaining the principle of floating the motor in rubber to isolate it from rail shocks, this new propulsion-unit arrangement has successfully permitted car operating speeds to double, from 75 to 150 mph, in one jump. Propulsion units and lightweight trucks should never again be considered separately for speeds over 75 mph. They are married into a system and must be analyzed as a system. This paper tells how and why.
Transfer Functions for Helical Springs
Authors: Johnson B. L. , Stewart E. E.
Published: December 2011

This study reports the results of an analytical and experimental investigation of helical springs subjected to vibratory motion. Transfer functions are presented for both displacement and transmitted force as outputs with force as the input. Steady-state sinusoidal Magnitude Ratio (displacement—force) and Transmittance Ratio (force—force) are plotted along with substantiating experimental data. It is shown that an actual spring displays frequency response characteristics over most of the frequency spectrum that would render its function useless in many cases.
An Application of Diakoptics in the Determination of Turbine Bucket Frequencies by the Use of Perturbations
Authors: Tuncel O. , Bueckner H. F. , Koplik B.
Published: December 2011

The method of Diakoptics, originally designed for the computation of linear electrical network, is also applicable to those linear systems of mechanics, where major subsystems are not too strongly coupled with one another. The method deals with the subsystems individually in a first step and takes care of the effects of weak coupling in a second one. If the systems are represented by a set of simultaneous algebraic equations, the procedure of Diakoptics manifests itself in various additive and multiplicative matrix decompositions. Diakoptics in combination with a method of perturbation is applied to determine the natural frequencies of a group of buckets coupled by tie-wires and/or a cover. Starting with the natural frequency and corresponding mode shape of the single bucket we obtain the frequency of the coupled system by a method of perturbation. An algorithm is derived in order to compute perturbation coefficients as they appear in a series expansion of a certain matrix. It is found that the proper representation of the single bucket is of utmost importance in obtaining accurate coupling frequencies. The results for the coupling frequencies of various groups of buckets calculated using this procedure correlate well with test results. Different mode shape combinations and the coupling effect of the cover, and cover and tie-wire combination are also considered. Comparison of our results with those obtained by the Prohl-Myklestad method as well as with experiments indicates that both methods are compatible with one another. It appears, however, that the method of Diakoptics in combination with a perturbation on the Prohl-Myklestad method requires much less numerical work.
Balancing Criteria and Their Relationship to Current American Practice
Authors: Muster D. , Flores B.
Published: December 2011

The results of a survey on acceptable residual specific unbalance are discussed in the context of existing balancing criteria. The study includes a statistical analysis of the data received. The results are divided in two subclasses of information according to rotor-use and rotor-weight for the purpose of grouping quantitative data for similar rotors.
Response and Stability of a Self-Sustained Two-Degrees-of-Freedom System With Nonlinear Damping
Authors: Huang T. C.
Published: December 2011

A self-sustained two-degrees-of-freedom system with nonlinear damping is investigated. The analysis, which involves the application of the van der Pol method and the Andronow and Witt method, leads to the equation of response and stability classification. The novel feature of this analysis is that the form of the resulting equation is such that the classification of singularities of first-order differential equations can be applied. Three-dimensional response surfaces and stability regions for harmonic oscillations are presented.
Analog Simulation of a Bilinear Hysteretic System Undergoing Random Vibration
Authors: Brown R. N.
Published: December 2011

An analog computer simulation is used to substantiate an equivalent linearization analysis of a bilinear hysteretic system undergoing random vibration. An interpretation of the physical behavior of the system is presented. Quantities useful in failure prediction—the average level crossing rate and the probability distribution of the displacement—are also measured, and it is shown that the hysteretic system can have a longer life than a linear system based on a low level approximation.
Application of Controlled Mechanical Impedance for Reducing Machine Tool Vibrations
Authors: Comstock T. R. , Tse F. S. , Lemon J. R.
Published: December 2011

A feedback loop that instantaneously controls the tool-work motion is successfully applied to an engine lathe for the purpose of reducing vibrations. The extent to which chatter-free performance can be obtained is predicted using linear systems theory. Although the results are strictly valid for single-point turning, the basic approach is applicable to more complex machining processes.
On the Response of a Structure Moving Through a Random Load Field
Authors: Beer F. P. , Trevino G.
Published: December 2011

A method is given for determining the effect of spacewise variations in a homogeneous, frozen, random load field on the response of a structure moving through the field. The proposed method is based on the determination of the response of the structure to a few simple deterministic loadings and does not require the use of multidimensional power spectral analysis. The method is applied to the analysis of the response of a beam moving first longitudinally and then transversely through the load field.
Actual Popping Pressure of a Relief Valve With a Real Helical Spring Under Dynamic Load
Authors: Johnson B. L. , Wandling D. E.
Published: December 2011

This paper presents the describing equations of a poppet-type relief valve with a real helical spring, that is, a spring having distributed mass. The sinusoidal analysis shows that the actual popping pressure is very frequency dependent and may occur at pressures that are a fraction of the static popping pressure to twice that value. Experimental data which verify the theory are also presented.
Metal Forming With Vibrated Tools
Authors: Kristoffy Ivan
Published: December 2011

The results of superimposed 20- and 20,000-cps tool vibration in deep drawing, ironing, and cold-forging are presented. Equipment and instrumentation are discussed. The importance of proper dynamic force measurement is emphasized. It was found that: (a) punch vibration resulted in only an apparent force reduction proportional to the workpiece stiffness and vibration amplitude; (b) die vibration caused a true forming force reduction either by changing the direction of friction force or by altering the state of stress; (c) material properties were not affected, although in cold-forging, with superimposed 20,000 cps punch vibration, an apparent force drop of up to 60 percent was achieved; (d) surface finish and deep drawability of the material, under certain conditions, were slightly improved. It is recommended to use superimposed tool vibration only in continuous forming operations, and then only if certain necessary conditions can be satisfied.
Dynamic Stability of a Vibrating Hammer
Authors: Fu C. C. , Paul B.
Published: December 2011

This paper deals with the stability of motion of an elastically suspended vibrating hammer that impacts upon an energy absorbing surface. The energy absorber could represent, for example, a rock drill bit or drill steel, or a spike being driven by the hammer. The problem is intrinsically nonlinear because the instant of impact depends upon the motion of the hammer. “Simple steady-state solutions” are derived, and their asymptotic stability is examined. Regions in which the analytically constructed simple solutions are asymptotically stable are determined in parameter space. Results have been checked by a digital computer simulation.
The Inception of Nucleate Boiling With Liquid Nitrogen
Authors: Almgren D. W. , Smith J. L.
Published: December 2011

The phenomena of patchwise boiling are discussed, and the significant parameters restricting the growth of a boiling patch are analytically determined to be: (a) a high nucleate-boiling heat-transfer coefficient, (b) a low total heat flux, (c) the absence of cavities with a trapped liquid vapor interface outside the boiling patch, (d) an appropriate value of wall thermal conductivity, and (e) a high vapor enthalpy per bubble. A qualitative agreement between theory and experiment was observed for items (a), (b), and (d). A surface finish was developed and tested in pool boiling of liquid nitrogen which eliminated the observed, stable temperature hysteresis at inception of nucleate boiling and maintained a low-temperature difference (Tw−Tsat) for the entire nucleate-boiling curve.
The Influence of Surface Characteristics on the Boiling of Cryogenic Fluids
Authors: Smith R. V.
Published: December 2011

This paper reviews the influence of the characteristics of the solid surface on the boiling of cryogenic fluids. Particular emphasis is placed on papers presented in the cryogenics section of the 1968 Annual ASME meeting. Hysteresis, boiling-site spreading, and the influence of radiation on the surface are discussed in detail.
On the Response of a Beam Subjected to a Cyclic Moving Load
Authors: Kessel P. G. , Schlack A. L.
Published: December 2011

A theoretical analysis is presented on the damped steady state response of a simply supported beam on an elastic foundation subjected to a cyclic moving load that oscillates longitudinally along the beam about a fixed point. Loadings of this type have been recently shown to yield an infinite number of load movement frequencies that will excite resonance of a given natural frequency of an elastic member or system of members. It is the purpose of this investigation to introduce damping into the problem in order to determine both the absolute and relative importance of this infinite number of load movement frequencies that will excite a given natural frequency of a beam. The mathematical analogy between the problem of a beam resting on an elastic foundation and that of a long circular cylindrical shell with axial and rotatory inertia neglected is noted. Hence the results obtained are applicable to either problem. Numerical results are presented to illustrate the effects of damping, frequency of oscillation of load movement and amplitude of load movement on the dynamic deflection of the beam.
Periodic Motions of a Two-Body System Subjected to Repetitive Impact
Authors: Sikarskie David L. , Paul Burton
Published: December 2011

The dynamics of a widely used class of hammer impact machines are investigated on the basis of a two-degree-of-freedom idealization. The difficulty in the problem is due to the repetitive impact which introduces a nonlinearity in the system. It is the purpose of the analysis to develop a solution for the steady-state behavior of the system. There are several ways this can be done. One of the most efficient ways, from the point of view of ease of parametric studies of the system, is to convert the problem to a “boundary” value problem. With this technique, the system is governed by the equations of motion between impacts, and further satisfies additional conditions at the beginning and end of each impact cycle. Since the solution is obtained in only one cycle, it thus represents a straightforward method of studying the effect of various system parameters. A fundamental assumption in the analysis is that the steady-state response of the system has a period equal to the forcing period. This is verified for one set of parameters through the use of high-speed movies of an actual machine. There are several other interesting features in the analysis, including multivaluedness of the solution, allowable solution domain, and stability of solution, which have not been completely resolved to date.
Limit Cycles and Stability of a Nonlinear Two-Degree-of-Freedom Autonomous Vibratory System
Authors: Senator M.
Published: December 2011

A perturbation technique based on small reciprocal of rotational inertia is used to find limit cycles for a system consisting of a spring, dashpot, and mass upon which is mounted an eccentric driven by a motor with a linear torque-speed characteristic. This technique, which is carried to second order, gives significantly different results from those of previous investigators using averaging techniques and is not limited to small eccentric mass, departure from resonant speed, and translational damping as they are. The linearized variational equations which govern stability are of fourth order with periodic coefficients. Instead of working with these equations, a modified averaging technique is developed which predicts limit cycles that agree with those of the zeroth-order perturbation solution and which allows a simpler stability determination to be made. The predicted limit cycles and their stability are verified by an analog computer simulation of the system.
Response of Linear Systems to Magnitude Limited Random Excitation
Authors: Hu P. Y.
Published: December 2011

In many situations, encountered both in the field and in the laboratory, the excitation produced by a broadband random source has many of the characteristics of a signal having a Gaussian distribution of instantaneous values except that the higher values predicted by the theory do not appear. Therefore, in all cases, physical systems are really excited by a magnitude limited Gaussian random vibration rather than a strictly Gaussian random vibration. Analytical as well as experimental results on the response of the single-degree-of-freedom system subject to magnitude limited random vibration are presented.
Design of Surface Grinding Dynamometers
Authors: Yang C. T.
Published: December 2011

This paper discusses the application of some basic elastic theory of thin circular rings used as transducers and equations generally used in the design of a surface grinding dynamometer. Octagonal strain rings and their approximation in design application to dynamometers are presented. Examples of calculations are demonstrated. The wiring diagrams of strain gages on the dynamometer are also shown. The calibration setup, curves, and equations of calibration are dealt with. The author has a dual purpose in writing this paper: He wishes to have a record of his design experience for later reference and to share some valuable information with engineers and scientists in the field.
Flow-Induced Vibration and Noise in Tube-Bank Heat Exchangers Due to von Karman Streets
Authors: Chen Y. N.
Published: December 2011

This paper treats the problem of vibration and noise in tube-bank heat exchangers. The frequency of vortex shedding has been investigated by many authors, and their results have varied considerably. The author, in previous works, correlated these different data into a curve group of his own, and now proceeds to further analyze the problem. Results of experiments performed in a small wind tunnel are given, accompanied by typical graphs. Based on his findings, the author concludes with some design proposals for suppressing vibrations.
The New Electric Locomotive Type Re 4/4II of the Swiss Federal Railways and the Problems Related to the Development of Its Mechanical Part
Authors: Borgeaud G. , Loosli H.
Published: December 2011

Some three years ago, the Swiss Federal Railways introduced the prototype of a very efficient, high-power electric locomotive type Re 4/4II of the wheel arrangement Bo′Bo′. The locomotive weighs 80 tons overall and has a 1-hr rating of 6340 hp, and it had to be especially designed for small lateral forces between wheel and rail and good adhesion properties. In the first part of the paper, the basic theoretical problems related to the development of the mechanical part of the locomotive are outlined. The technical solutions of the various mechanical problems are described in the second part of the paper, which concludes with a few remarks on the numerous tests carried out with the completed locomotive.
Accuracy of the Taut-Line Position-Indicator for Offshore Drilling Vessels
Authors: Adams R. B.
Published: December 2011

The taut-line system measures horizontal position of a drilling vessel by using trigonometric relations with the assumption that a steel line is essentially straight from vessel to sea floor. This paper examines mathematically the accuracy of this assumption under a variety of operational circumstances. A convenient method to estimate error as a function of equipment and environment parameters is developed. Further, an on-site procedure is suggested for estimating and reducing error by use of only the taut-line system itself.
Vibration Problems With High-Speed Turbomachinery
Authors: Sternlicht B. , Lewis Paul
Published: December 2011

The paper presents several examples of vibrational problems recently experienced by several turbine manufacturers. These problems include stability, system critical speeds, rotor response to unbalance, and balancing of high-speed compressors and turbines. The effects of fluid-film bearings and seals, bearing pedestals, and other parts of support structure on rotor response and critical speeds are discussed. The effects of rotor stiffness, mass, and inertia distribution are presented. The paper gives a comparison between theory and practice and provides guidelines to machinery designers.