bluuebunny/crossref_metadata_2025 huggingface dataset:
A temporal refuge from predation can change the outcome of prey species competition
Authors: Slade Andrew , White Andy , Lurz Peter W. W. , Shuttleworth Craig , Lambin Xavier
Published: July 2022

Generalist predators whose primary prey undergoes cyclic fluctuations, will predate on alternate food sources when the abundance of their primary prey is low. In this paper we have developed a general model of a predator that switches predation between its primary prey and two alternative, competing, prey species. When the predators primary prey is at high abundance, predation of the alternate, competing, prey species is low, which provides periods of temporal refuge for the alternate prey from predation. When the inter‐specific interactions between the competing prey species lead to different dynamical outcomes in the presence and absence of predation, increasing the duration of the temporal refuge promotes dominance of a competitively superior species that is vulnerable to predation. The general theoretical framework was extended to consider a key case study system of pine marten predation on red and grey squirrels. In the absence of predation, grey squirrels out‐compete red squirrels but preferential predation by pine marten on grey squirrels can suppress grey squirrel density and allow red squirrel recovery. A temporal refuge for both squirrel species can arise due to prey switching by pine marten in years when field voles, their primary prey in the UK, are abundant. The duration of the temporal refuge, quantified as the relative length of the multi‐annual vole population cycle where vole density is above a population threshold, is a critical factor determining the persistence of red and grey squirrels. Our findings therefore provide insights for the conservation of the endangered red squirrel in the UK and the Republic of Ireland and more generally on the influence of the population dynamics of primary prey species in determining community composition.
Distress factors of voice‐hearing in young people and social relating: Exploring a cognitive‐interpersonal voice‐hearing model
Authors: Rammou Aikaterini , Berry Clio , Fowler David , Hayward Mark
Published: July 2022

Objectives

Little is known about the factors that can maintain the distress related to voice‐hearing experiences in youth. Building upon understandings developed with adults, this study aimed to explore the associations between negative relating between hearer and voices, persecutory beliefs about voices and voice‐related distress in a clinical sample of adolescents. The study also aimed to investigate associations between relating to voices and wider patterns of social relating.

Design

This was an observational, cross‐sectional, survey study.

Methods

Thirty‐four young people (age 14–18 years) who were hearing voices completed measures about voices (characteristics, relating and beliefs) and relating to social others (negative relating styles, social connectedness and belongingness). Participants were patients of NHS mental health services. Bivariate correlations explored associations between relating to voices and distress, beliefs about voices and distress, and between relating to voices and social relating variables.

Results

Perceiving the voices as dominant, intrusive, and persecutory and resisting them was significantly associated with distress. Adjusting for loudness and negative content rendered the association between persecutory beliefs and distress non‐significant. Fear of separation and of being alone in relation to social others was associated with distancing from voices. Being suspicious, uncommunicative and self‐reliant and/or being sadistic and intimidating towards social others was significantly associated with dependence towards the voices. Greater hearer‐to‐voice dependence was associated with lower perceived social belongingness and connectedness.

Conclusions

Beliefs about voices being persecutory, dominant, intrusive and resisting voices seem to be significant contributors of distress in young people. In terms of proximity and power, relating to voices and social others appears to be contrasting.
Net Radiation in the Semiarid Region of the States of Paraíba and Rio Grande do Norte Using the MODIS Sensor
Authors: Silva Madson Tavares , Oliveira Verônica Gabriella de , Santos Carlos Antonio Costa dos , Da Silva Lindenberg Lucena , Santos Francineide Amorim Costa , Serrão Edivaldo Afonso de Oliveira
Published: July 2022

This study aimed to estimate the surface net radiation (Rn) for the States of Paraíba and Rio Grande do Norte and validate the results with data measured in validate the results with measurements in experimental recovering (CRec), degraded (CDeg), and preserved (CPres) areas of Caatinga. Seventeen images of the MODIS sensor on board the Terra satellite were selected for CRec and CDeg in the State of Paraíba and twenty-eight images for CPres in the state of Rio Grande do Norte, corresponding to the period of January to December 2014. The MODIS-Terra MOD09A1 and MOD11A2 products were used. Parametric (Shapiro-Wilk) and non-parametric (Kolmogorov-Smirnov and Wilcoxon-Mann-Whitney) tests were applied to understand the patterns. Statistical error indices were applied to verify the accuracy of the estimates in relation to the observed values. Only the measured albedo (α_meas) met the assumption of normality. According to mean absolute percentage error statistics, the model used to estimate the albedo was classified as inappropriate for CPres and CRec ( 25%), while it was satisfactory for CDeg (15-25%). Significant differences between observed and estimated values were absent only for the variable Rn in the three observation sites. The good performance of Rn estimates confirms the efficiency of the application of the method in semiarid regions.
Piping-Flexibility Analysis
Authors: Markl A. R. C.
Published: July 2022

A steadily expanding literature bears testimony to the growing recognition of the importance of the problem of providing flexibility in piping and to the many difficulties besetting efforts at establishing a simple rational approach for its solution. This paper aims to outline the various phases of the problem, with particular emphasis on the phenomena of plastic flow and fatigue which distinguish the behavior of piping systems under thermal expansion from the ordinary room-temperature steady-state structural problem and lead to the concept of a limiting-stress range rather than an allowable stress as the criterion of the adequacy of a layout. In treating his subject, the author has sought to present the consensus of the Task Force on Flexibility charged with reformulating Chapter 3 of Section 6 of the Code for Pressure Piping. Their Proposed Rules are included as a focal point on which it is hoped broad discussion will center.
Manpower and Other Factors Affecting Operating Costs in Steam Generating Stations
Authors: Estcourt V. F.
Published: July 2022

The tremendous gains in thermal efficiency which have been achieved by going to higher steam pressures and temperatures with increasingly larger units are now approaching a point where the returns are diminishing at an impressive rate. As these rates of improvement continue to diminish with still further increases in temperature and pressure, it becomes increasingly important to give closer attention to the effect of basic plant design upon the total station payroll. Various philosophies of centralized control are reviewed and evaluated in some detail. Consideration also is given to the interrelation between design and operating concepts and the effect of plant management policies upon operating costs. It is shown that many of these problems are adaptable to economic evaluation and the need for such an approach is greatly emphasized in the light of the present trend of technological advances and changing economic conditions. The effect of the changing requirements in the type of plant operating organization also is discussed in relation to the control of operating costs.

[Following Mr. Estcourt’s paper will be found the individual contributions of the panel members.—Editor.]
Consolidated Edison Looks at the Manpower Situation
Authors: Falkner J. C.
Published: July 2022

The quest of the public utilities to decrease over-all costs is apparently endless. In the past, effort has been made in individual fields, i.e., design, construction, and operation. Now the industry is co-ordinating two or more fields—specifically, endeavoring to design plants so that manpower will be at a minimum. We are now thinking of how each man must function as we design. This is progress.
Economic Determination of Condenser and Turbine-Exhaust Sizes
Authors: Miller E. H. , Sidun A.
Published: July 2022

There are many combinations of condensers and turbine exhaust-annulus areas available to the engineer studying alternate large steam-station designs. The proper selection from among these many combinations is a broad economic problem which can best be solved by considering initially only those few basic variables that apply directly to the problem. It is the purpose of this paper to present these basic data on turbine and condenser performance in a form that will help the user to determine quickly the most economical turbine-condenser combination for a given situation.
Effect of Viscosity of Car-Journal Oils on Running Temperature and Other Characteristics of Journal-Bearing Performance
Authors: Keller W. M.
Published: July 2022

The effect of viscosity in journal oil has been the subject of discussion for many years. Until recent years no data had been obtained with sufficient accuracy and in sufficient quantity to establish the optimum viscosity for oils in the journal box. In more recent years with laboratory test equipment, it has been possible with controlled conditions to isolate the oil as a variable and obtain reliable data on this subject. A consideration of this problem shows that with full hydrodynamic lubrication the asperities of journal and the bearing are separated by a film of oil. While there may be minor areas in which this condition does not obtain, the general separation of the two surfaces must take place, as it is evident that if large areas of the bearing were in metal-to-metal contact the wear which results would be of a much higher order and bearing failure more frequent. When bearings have a hydrodynamic film and the metal surfaces are not in contact, the heat developed in a journal box is from two sources, i.e., the pressure of the waste against the bottom of the journal and the viscous shear of the oil film between the bearing and the journal.
Action of Boiler Water on Steel—Attack by Bonded Oxygen
Authors: Kaufman C. E. , Trautman W. H. , Schnarrenberger W. R.
Published: July 2022

This paper includes information relating to attack by boiler water on steel of boilers and superheaters. Emphasis is placed on the power of water itself, in the absence of dissolved oxygen, to oxidize metal, causing substantial damage under some conditions. Examples of aggressive action drawn from field experience are explored by metallographic study of damaged specimens. Laboratory results show that hydrogen embrittlement can be produced and controlled in test bombs. It is concluded that the power of bonded oxygen of water to react with steel can be curbed by making both chemical and physical changes in boiler systems.
An Introduction to the Thermal Problems of Turbojet Engines for Supersonic Propulsion
Authors: Gardner A. J.
Published: July 2022

An introductory summary of what temperature ranges are to be expected in planning the design of turbojet engines for use at supersonic flight speeds, and the effect of the expected temperatures on various basic engine components. The source and magnitude of the heat is first considered. The general effects of the high temperatures on engine materials, compressor performance, and energy, added in the form of fuel, are outlined. General requirements and possible design considerations for supersonic turbojets are summarized briefly.
Human Problems Associated With High-Speed and High-Altitude Flight
Authors: McFarland R. A.
Published: July 2022

Human tolerance for heat and cold is outlined so that aeronautical engineers may have a better understanding of design problems related to cabin atmosphere. The hazards resulting from noxious gases and vapors also are considered. The need for air-crew indoctrination in the effective use of equipment is emphasized as well as the need for airmen to understand their own physical limitations while in flight. Finally, the need for more effective collaboration between the biological and engineering sciences is stressed in regard to improving the man-machine systems in high-speed, high-altitude flying.
Carbon-Molybdenum Steel Steam Pipe After 100,000 Hours of Service
Authors: Sinnott R. J. , Rohrig I. A. , Freeman J. W. , Rush A. I.
Published: July 2022

Rarely does the engineer or metallurgist have an opportunity to evaluate design considerations and laboratory data in terms of creep in service. Carbon-molybdenum steam pipe, carefully measured for service creep during 100,000 hr of operation at 900 F, was subjected to laboratory examination after removal from service. The purpose was to check calculated service creep rates, assess creep damage, and to compare long-time performance prediction based on short-time laboratory data. Remarkable correlation was observed between calculated service creep rates and those established by subsequent laboratory creep testing. Full agreement with average values used by the Subgroup on Allowable Stresses for Ferrous Materials of the ASME Boiler Code Committee in setting allowable stresses for this material was established for both creep and stress-rupture properties.
Resistance of Tubular Materials to Sulphide-Corrosion Cracking
Authors: Fraser J. P. , Treseder R. S.
Published: July 2022

A typical sulphide-corrosion cracking failure of tubing in a sour gas-condensate well is described in detail. A laboratory test procedure is described which allows alloys to be rated as to their resistance to sulphide-corrosion cracking. Using this rating, based on the critical stress to cause cracking in a standard laboratory test, a study has been made of the relative susceptibility to cracking of a large number of heats of commercial tubular alloys (e.g., N-80, J-55, 5 per cent nickel steel, and 9 per cent nickel steel). It has been shown that significant improvement in the resistance to cracking of commercial N-80 tubing can be effected by means of a simple tempering heat-treatment.
The Design of Vertical Pressure Vessels Subjected to Applied Forces
Authors: Bergman E. O.
Published: July 2022

Pressure-vessel codes do not give design methods except for the relatively simple case of cylindrical shells with standard-type heads and openings under uniform pressure. The designer must apply engineering principles when he deals with more complicated structures and loading systems. This paper discusses some design principles that are not covered in the codes. It deals with vessels that are subjected to various applied forces acting in combination with internal or external pressure. The type of vessels considered is limited to cylindrical shells with the longitudinal axis vertical.
Hydrazine for Boiler-Feedwater Treatment
Authors: Harshman R. C. , Woodward E. R.
Published: July 2022

The physical and chemical properties of hydrazine are discussed, particularly, as they relate to its use for scavenging dissolved oxygen in boiler feedwater. The amount of hydrazine to use, the methods of application, and the methods of control of dosage are described. The results of use of hydrazine for boiler-feedwater treatment in several central power stations are summarized.
Suppression of Burner Oscillations by Acoustical Dampers
Authors: Putnam A. A. , Dennis W. R.
Published: July 2022

Tests on the suppression of burner oscillations are described. The work was not all inclusive but did produce several positive conclusions which may help in quieting particular combustion installations, or may be of help in preventing waste of effort in trying ineffective methods. The effectiveness of a quarter-wave tube was found to be critically dependent on length, but relatively insensitive to location, as long as the tube is placed in the region of the pressure antinode. Similarly, the effectiveness of a Helmholtz resonator depended critically on volume for a particular neck, but is quite insensitive to location. In neither case did the suppressor have to be placed near the particular antinode where energy was fed into the oscillation. The degree of suppression obtained was approximately proportional to the cross-sectional area of the tube; the same conclusion appears to be warranted with regard to the cross-sectional area of the throat of a Helmholtz resonator. Almost complete suppression was obtained with holes drilled in the side of the tube and placed within 10 per cent of a wave length from a pressure antinode. It was found that the diameter of the hole need not be greater than about 1/10 to 1/15 of the diameter of the combustion chamber, but should be greater than the wall thickness for best suppression.
The Assembly-Line Balancing Problem
Authors: Salveson M. E.
Published: July 2022

An increasing number of industrial problems in programming and scheduling now are being solved by analytic procedures. Yet, the almost universal problem of balancing an assembly line does not appear heretofore to have been so treated, even though the first known assembly line was established as early as the War of the Revolution by Eli Whitney for the manufacture of muskets. Efficient procedures for handling this problem are highly desirable. A very large percentage of all commodities, both civilian and military, are manufactured by assembly-line methods, so that any improvement in these procedures would have a very broad area of impact, in both peacetime and wartime production. This paper reports initial results in attempting to develop such a procedure. While refinements are expected with increasing experience and further research, it is believed the practical usefulness of the analytical, engineering approach to this manufacturing problem is demonstrated by present results. Indeed, substantial improvements in productivity have been achieved in each of several cases in which it was used. In addition, the present procedure lends itself to machine computation, such that it likely will be possible to compute optimum balances for assembly lines for many different levels of output in advance and thereby permit reduction by two to three weeks the lead time required to change the rate of production when required by changes in sales.
The Evaluation of Corrosion Resistance for Gas-Turbine-Blade Materials
Authors: Young W. E. , Hershey A. E. , Hussey C. E.
Published: July 2022

Surface analysis of gas-turbine-blade material before and after exposure to the combustion products of residual fuel oils, demonstrates the corrosive effect of these products, and a measurable indication may be obtained in a fraction of the testing time required to produce appreciable weight loss. Surface analysis has the further advantage that it is possible to measure corrosion in specific regions on a specimen where the specimen has been exposed to a gas-flow pattern with a well-defined temperature profile. Weight-loss measurements following long-time tests have shown good agreement with this method of analysis. The fusion temperature of the fuel ash appears to be a reliable criterion for judging the potential corrosivity of residual fuel oil, and good correlation has been obtained between ash-fusion temperatures and corrosion both for untreated oils and oils with additives.
Thermal Conductivity and Its Variability With Temperature and Pressure
Authors: Kowalczyk L. S.
Published: July 2022

This paper gives a summary of the present status of the theory of thermal conductivity and attempts to explain its variability with temperature and pressure by means of the nature of heat, structure of matter, and resistances offered by matter to heat conduction at various physical states. Experimental data are used to illustrate theoretical considerations; long mathematical derivations are thoroughly avoided.
Residual Grinding Stresses in Hardened Steel
Authors: Letner H. R.
Published: July 2022

Residual stresses resulting from surface grinding a hardened ball-bearing-type steel under closely controlled conditions were measured by the deflection method and the effects of wheel grade, unit downfeed, and grinding fluid upon the stresses generated were studied. The stress gradients close to the surface were found to be quite steep and, in a number of instances, both components of the biaxial stress were compressive at the surface. This behavior contrasts with previous dry-grinding experiments on annealed steel and indicates the possibility of generating compressive surface stresses in hardened steel by grinding.
Cutter Design and Application for Face-Milling Cast Iron and Steel
Authors: Boston O. W. , Gilbert W. W.
Published: July 2022

This paper summarizes an extensive research program sponsored by the Office of Production Research and Development during World War II. Two previous papers have presented the results of power and cutter life, respectively. These results, relating to cutter design, are averaged for various grades of cast iron, tool materials, feed, depth, width of bar, number of teeth in the cutter, and the cutting speed. General effects of each variable are obtained from final tool shapes for steel and cast iron which are given for recommended practice.
The Influence of Curvature on Heat Transfer to Incompressible Fluids
Authors: Kreith Frank
Published: July 2022

The analogy between momentum transfer and heat transfer has been extended to flow channels with heating surfaces of either a convex or a concave curvature in the direction of flow. Using experimental results of wall shear and velocity distribution obtained by Wattendorf, Nusselt numbers have been calculated for Reynolds numbers ranging from 104 to 106 and Prandtl numbers ranging from 0.01 to 100, and for radii of curvature ranging from 0.12 to 1.2 ft. It was found that the heat-transfer coefficient from a heating surface with a concave curvature is considerably higher than for a heating surface of the same curvature in a convex configuration under similar conditions of flow-cross-sectional area and flow rate. The calculated results are in agreement with results from heat-transfer experiments using flow channels with convex and concave heating surfaces in the direction of flow.
Free-Convection Heat Transfer From a Rotating Horizontal Cylinder to Ambient Air With Interferometric Study of Flow
Authors: Etemad G. A.
Published: July 2022

Free-convection heat-transfer correlation for a rotating horizontal cylinder in air was evaluated experimentally for a range of Reynolds numbers from 0 to 65,400. The stability of flow around the rotating cylinder and the transition from laminar Couette flow to fully developed secondary flow were investigated with the aid of a Zehnder-Mach interferometer. The heat-transfer data obtained agree well with the experimental results of Anderson and Saunders (1). The experimental results for the models in the stationary state exhibited substantial correlation with published data.
Through-Flow in Concentric and Eccentric Annuli of Fine Clearance With and Without Relative Motion of the Boundaries
Authors: Tao L. N. , Donovan W. F.
Published: July 2022

The problem of the through-flow across annuli of fine clearance has been investigated both theoretically and experimentally. The study includes the effects due to the relative motion of the walls and to varying degrees of eccentricity of the bounding surface. The experimental work was carried up to a Reynolds number, based on the diametral clearance, of 30,000. The theoretical results are presented both graphically and in the form of equations. Nomographs are included for rapid solution of certain engineering problems.
Predictor Control Optimalizes Control-System Performance
Authors: Silva L. M.
Published: July 2022

A new technique for the design of automatic-control systems with nearly optimum transient response has been developed. The fundamental concept in the new method is that the control or forcing of the output member must be performed in such a manner that the error or deviation and its derivatives should be reduced to zero in three steps for third and higher-order systems. These three steps consist of a single period of maximum corrective action which forces the controlled variable in the direction of decreasing error or deviation, a single period of maximum corrective action in the opposite sense to decelerate the controlled variable, and finally a force-free period at the end of which the error and its derivatives simultaneously go to zero. In the practical embodiment of this mode of control a proportional control action exists during the final phase. During this proportional control period, the controller corrects any errors introduced by the instrumentation during the initial phases. In addition to the superior transient performance, a predictor-control system has the advantage that its response is not affected by variations in gain, if the gain is sufficiently large, and that the allowable gain in the proportional region is considerably in excess of that permitted in conventional linear-type systems. As a result, the steady-state accuracy which can be obtained is not dependent on a critical gain setting and the system response and accuracy are not degraded by the incorporation of variable gain elements.
The Effect of Wheel-Work Conformity in Precision Grinding
Authors: Hahn R. S.
Published: July 2022

The conformity between wheel and work is defined in terms of the trochoidal work surface at the region of engagement. Experimental results are presented for a variety of wheels which show that the rate of metal removal varies as the 0.18 power of the curvature difference. Two modes of grinding action are recognized, one in which stock removal is proportional to work speed and independent of wheel speed and the other where the reverse is true. A mechanism of grinding action is proposed and a theoretical formula relating rate of stock removal to normal force and curvature difference is derived which in certain respects agrees remarkably well with experiment.
Possibilities of Burning Lower-Cost Diesel Fuels
Authors: McBrian Ray
Published: July 2022

The question of getting the most out of diesel fuel and the possibilities of burning lower-cost diesel fuels involves more than the operational price savings. It requires a knowledge and understanding of the facts of combustion as related to engine performance and the effects of the characteristics of fuels and means by which undesirable features can be recognized and corrections made so that fuels may be burned satisfactorily in service. The paper outlines the research carried out by the Denver and Rio Grande Western Railroad on lower-cost fuels and the resulting economies.
Phase-Plane Analysis—A General Method of Solution for Two-Position Process Control
Authors: Eckman D. P.
Published: July 2022

The phase-plane method of analysis requires transforming the differential equations for the closed loop into coordinates of rate of change of deviation versus deviation. Then, by integral equations the period and amplitude of oscillation of process control may be evaluated. Five interesting problems in process control are discussed. The limitations of the analysis are that process-control problems involving differential equations of higher order than second cannot be evaluated exactly. For process-control problems, an approximation of the response by a Ziegler-Nichols method of approach can be used in a very simple manner. Problems involving various nonlinearities also may be solved.
Proposal for a Standard Design for General Industrial Coarse-Pitch Cylindrical Worm Gearing
Authors: East F. G.
Published: July 2022

This paper suggests a method of standardizing general industrial coarse-pitch cylindrical worm gear drives, particularly the worm diameter and tooth proportions, to eliminate the present situation where no recognized standard exists. The suggestions contained in this paper do not insist on a single worm diameter for each pitch or center distance but rather a limited group of worms that will cover the range of good design.
A Plastic-Flow Problem Arising in the Theory of Discontinuous Machining
Authors: Lee E. H.
Published: July 2022

Plastic flow is analyzed adjacent to the nose of the tool in the initial stages of the formation of a discontinuous-chip segment. It is assumed on the basis of experimental evidence that fracture of the previous chip segment occurred across a plane through the cutting edge of the tool. The present solution applies only while the fracture surface is being deformed, before plastic flow spreads to the initial work surface. The solution demonstrates the influence of the plastic-stress distribution in determining the chip-formation process. It shows that simple shear across a plane between two undeforming regions cannot satisfy stress conditions in typical cases. It is shown that the inclination of the plane of equivalent simple shear is remarkably insensitive to the coefficient of friction at the tool face. The variation to be expected as a result of spread of plastic flow to the initial work surface is discussed briefly. The choice between alternative types of slip-line fields which arise in certain cases is considered.
Predicting the Angle of Chip Flow for Single-Point Cutting Tools
Authors: Colwell L. V.
Published: July 2022

Current practice for predicting tool life is entirely empirical; consequently, a prohibitive number of tests must be conducted in order to take all influential factors into consideration in predicting tool performance for a specific set of cutting conditions. One of these factors is the direction of chip flow across the tool face. This determines the effective rake angle which in turn affects the tool life. The usefulness and application of present tool-life data and that to be obtained will be greatly expanded if they can be correlated with the rake angle in the direction of chip flow. However, such a correlation, once established, will be useful only if it is possible to predict the direction of chip flow for a given tool used with any combination of cutting conditions. This paper presents a method for predicting the direction of chip flow over a range of tool shape and cutting conditions, thus establishing a necessary basis for the successful completion of the second phase of the over-all objective.
Heat Transfer to Constant-Property Laminar Boundary-Layer Wedge Flows With Stepwise and Arbitrary Wall-Temperature Variation
Authors: Scesa Steve , Levy Solomon
Published: July 2022

The analysis for the determination of the heat transfer for bodies in constant-property two-dimensional laminar flow with a free-stream velocity variation as u1 = Kxm and a stepwise wall-temperature variation is presented. The general theory may be applied to a gas of any Prandtl number although numerical results have been computed herein for Prandtl numbers of 0.7 and 1 for the values of m equal to —1/13, 0, 1/9, 1/3, 1, and 4. The method of investigation is such that the temperature profile may be obtained if so desired. Results of local Nusselt number are compared with the more approximate investigations of Bond and Lighthill which indicate an increasing deviation as m increases or decreases from zero. However, comparison of the ratio of the local Nusselt number with a stepwise wall-temperature variation to the local Nusselt number for a constant wall temperature indicates good agreement with the results of Bond and Lighthill. Extension to the problem of an arbitrary wall-temperature variation is indicated. The theoretical investigation neglects the effect of heat generated by friction since this effect may be considered by superposition of proper solutions.
The Dynamics and Lubrication of a Miniature Turbine Rotor on Porous Bushings
Authors: Sines George
Published: July 2022

A miniature air turbine was designed to investigate the lubrication and dynamic action of the rotor shaft within the bearing clearance. An optical apparatus was used to observe the time-position history of the shaft. Several different mechanisms of lubrication were identified at various speeds; at higher speeds boundary lubrication may occur. Under certain conditions the shaft moves in a very irregular pattern characterized by low friction and long bearing life. The conditions for the onset of this motion are discussed.
On the Solution of the Reynolds Equation for Slider-Bearing Lubrication—VII: The Nonsteady-State Operation of Tilting-Pad Slider Bearings
Authors: Osterle F. , Charnes A. , Saibel E.
Published: July 2022

The Reynolds equation in hydrodynamic lubrication theory, modified to take into account nonsteady-state effects, is applied to the problem of the tilting-pad slider bearing subject to a sinusoidal pivot oscillation in the direction normal to the bearing surface. Relationships are developed giving the load-supporting capacity and coefficient of friction as functions of the amplitude and frequency of the oscillation.
Study of Cubic Characteristic Equation by Root-Locus Method
Authors: Chu Yaohan , Yeh V. C. M.
Published: July 2022

It is shown in this paper that all possible roots of a cubic characteristic equation lie on a portion of a hyperbola and of its axis. This hyperbola may be sketched readily from the values of the coefficients of the cubic equation. Hence the change of the roots of the cubic equation due to any change in its coefficients may be visualized. The discussion of the transient response in relation to possible root configurations is included. A root-locus chart is provided for “universal” use. Results from an analog computer are shown to be agreeable with those in this paper.
The Study of Transients in Linear Feedback System by Conformal Mapping and the Root-Locus Method
Authors: Yeh Victor C. M.
Published: July 2022

The correlation between frequency and transient analysis of linear feedback systems, either degenerative or regenerative, through conformal mapping is pointed out. The root locus is a special case of the conformal mapping obtained by transforming the real axis of the inverse Y(s)-plane onto the s-plane. A method for deriving the equations of root loci is presented, and the basic shapes of root loci are shown. The shifting and reshaping of root locus by means of controller adjustments are discussed.
Heat-Transfer and Friction Characteristics for Gas Flow Normal to Tube Banks—Use of a Transient-Test Technique
Authors: Kays W. M. , London A. L. , Lo R. K.
Published: July 2022

Heat-transfer and flow-friction design data are presented for flow normal to circular tube bundles for the Reynolds-number range, 500 to 20,000 (based on tube diameter). Six staggered circular tube patterns and one in-line arrangement were tested. Tentative correlations are presented for the staggered arrangements allowing interpolation of the test results to obtain design data partially covering a transverse pitch-ratio range from 1.25 to 2.50, and a longitudinal pitch-ratio range from 0.75 to 1.50. Data also are provided so that the influence of the number of tube rows on the mean coefficient may be estimated accurately. These results are of interest in applications involving small-diameter tubes and low-density fluids, as, for example, the gas-turbine regenerator. They supplement the high Reynolds-number data of Pierson, Huge, and Grimison, and the low Reynolds-number viscous-flow-range data of Bergelin, Colburn, et al., by providing needed information for the intermediate range. A transient-test technique was employed in obtaining these data. Several tests employing a conventional steady-state technique also were made to demonstrate the validity of the transient method. The advantages and limitations of the transient method are considered in detail.
Erosion by Melting and Evaporation
Authors: Berman Kurt
Published: July 2022

This work represents an investigation of the erosion of solid bodies placed in an air stream. The test specimens were formed into cylindrical and conical shapes. Ice, acetophenone, and para-dichloro-benzene were used as the materials for the solid models. It was possible to correlate the rate of erosion as a function of the Reynolds number.
Calculation of Transient Temperatures in Pipes and Heat Exchangers by Numerical Methods
Authors: Dusinberre G. M.
Published: July 2022

An interest has been shown in the prediction of transient phenomena in pipes and heat exchangers. The numerical methods for the solution of such problems exist in a general form in the literature, but it may be of service to research workers and designers to have these methods developed into explicit iteration formulas and computation guides. This is done for a number of cases.
Effect of Exhaust Pressure on the Economy of Condensing Turbines
Authors: Keller A. , Downs J. E.
Published: July 2022

The purpose of this paper is to provide quick and accurate methods of determining the change in heat rate, nonextraction steam rate, or turbine capability, resulting from changes in the exhaust pressure of condensing turbines. The methods are applicable for turbines from 25,000 kw to the maximum size built by the authors’ company. It is believed that these data will be useful to the power-station designer in selecting between alternative turbine designs with different last-stage-bucket annulus areas available in the larger ratings, and also helpful in the selection of condenser size. It also will be useful to the operating engineer in determining when condenser maintenance is advisable, for correcting test data to base exhaust pressure for comparison with guarantee or expected information, and showing the desirability of operation with less than maximum condenser circulating-water pump capacity in cold weather.
Convective Heat Transfer for Mixed, Free, and Forced Flow Through Tubes
Authors: Eckert E. R. G. , Diaguila A. J.
Published: July 2022

This paper presents current knowledge on heat transfer caused by simultaneously occurring free and forced convection in tubes. It discusses the results of experiments that have been conducted by the NACA on mixed, free, and forced-convection heat transfer in turbulent flow through a vertical tube with a length-to-diameter ratio of 5. In these studies, forced air flow was directed parallel or opposite to the flow direction which free-convection flow alone would have under the same temperature conditions. Results of experiments made by other investigators, when analyzed in the same way as the NACA experiments, make it possible to generalize and extend the heat-transfer relations established. A calculation by R. C. Martinelli and L. M. K. Boelter for laminar mixed, free, and forced flow in parallel direction, and its extension to flow in opposite direction furnish information on heat transfer in the laminar-flow range.
Heat Transfer to Lead-Bismuth and Mercury in Laminar and Transition Pipe Flow
Authors: Johnson H. A. , Hartnett J. P. , Clabaugh W. J.
Published: July 2022

Experimental heat-transfer results in the low Reynolds modulus range of 1000 to 10,000 are reported for two different liquid metals, lead-bismuth eutectic and mercury. The single heat exchanger used in both series of tests was a ¾-in., 18-gage, 4-ft-long mild-steel tube. Similar heat-transfer tests with water in laminar and turbulent flow were performed with this same tube before and after each liquid-metal series, and the agreement of the turbulent-water tests with previous published results supports the liquid-metals test procedure. The data for both liquid metals, including flow in the upward and downward directions, are correlated on a Nusselt-Peclet basis with a single curve representing all experimental results with a maximum deviation of 20 per cent. The experimental Nusselt values decrease from approximately 6 at Reynolds number of 10,000 down to 1 at a Reynolds number of 1200, and consequently are considerably lower than the theoretical constant heat-rate laminar-flow Nusselt value of 4.36 (6). Possible causes for this behavior which have been investigated and found to be inadequate when considered independently include: (a) Insulating gas-layer or oxide-film fouling at the heated surface; (b) nonwetting; (c) uncertainties in property values; (d) axial-conduction effects. Although no supporting data are available, a distortion of the velocity profile from the parabolic distribution appears to be the most plausible explanation.
Heat Transfer in a Gas-Fired Furnace
Authors: Genna S. J. , Nolan E. J. , Furczyk A. A.
Published: July 2022

The general problem of heat transfer in a gas-fired furnace is examined. A method of analysis is introduced for determining the contributions of the various modes of heat transfer. A particular furnace, gas-fired with non-luminous flames, is investigated in the temperature range of 1750 to 2110 F. The results indicate that approximately 80 per cent of the heat is transferred by radiation from the furnace walls to the charge being heated and the remainder by gas convection and gas radiation.
Electronic-Control Method for the Precision Expanding of Tubes
Authors: Dudley F. E.
Published: July 2022

As conditions of temperature and pressure become more severe in modern heat-transfer equipment, the art of expanding tubes must keep abreast of this progress in engineering. This is especially true with tubes being expanded at both ends where metal-to-metal fixed joints are required to maintain absolute leaktight integrity and mechanical stability for safe and efficient operation. Overexpanding imposes excessive cold-work stresses in tubes and sheets, resulting in early failures. Underexpanding carries its burden of leakage and added nonproductive hours for correction in the field. This paper relates to progress in the precision expanding of tubes during the past few years.
Measurement of Stresses Imposed on Wheels in Diesel-Locomotive Service
Authors: Olson L. L.
Published: July 2022

The dieselization of railroads has been accompanied by many reports of locomotive-wheel failures. Laboratory tests by wheel manufacturers have been helpful but inadequate, since actual operating conditions were not duplicated. This paper describes a test program, now in its preliminary stages, which will undertake to secure necessary data. The objectives, test procedures, and instrumentation of the proposed program are outlined.
A Short Method for the Evaluation of the Effect of Some Thermal-Cycle Variations on Steam-Turbine Heat Rates
Authors: Fulton S. D.
Published: July 2022

The purpose of this paper is to present a short method of evaluating the effect of several thermal-cycle variations on steam-turbine heat rates, utilizing the data given in a heat balance. The method is based on the fact that the product of the input to a cycle and its thermal efficiency equals the output. To use this fact a method for determining the thermal efficiency from any extraction point to the turbine exhaust is presented. Equations derived for the various changes in the cycle make determination of heat-rate changes quite simple. A high order of accuracy is obtained by computing only changes in input and output.
The Controlled-Circulation Boiler
Authors: Armacost W. H.
Published: July 2022

From the standpoint of circulation there are two general types of boilers in operation in this country. These are natural circulation based on the conventional “thermal circulation head,” and controlled circulation based on the use of a pump to distribute and circulate the water through the heat-absorption areas. The author’s company supplies both types, having pioneered in the design and development of natural-circulation as well as controlled-circulation boilers. With the trend toward larger high-pressure units, industry is directing more and more attention to the controlled-circulation type. Therefore it appears desirable to summarize the information regarding these boilers. This paper deals largely with (a) the development of these boilers, (b) presently preferred designs, (c) operating features, results, and characteristics, and (d) brief reference to installations in this country.
Mechanical Features of the Tandem Helicopter Drive System
Authors: Plume W. F.
Published: July 2022

In the shaft-driven helicopter, drive-system reliability plays a large part in the safety of the helicopter. Drive-system reliability is established by extensive development testing and is maintained by quality control and production load runs. This paper describes in detail the transmissions and clutches of two types of tandem-rotor helicopters and the methods used for testing.
Evaluation of Transient Temperatures and Stresses
Authors: Fritz R. J.
Published: July 2022

Solutions to the one-dimensional, heat-conduction equation for arbitrary surface temperature transients are treated by superposition of other solutions and by a concept of thermal reflections. The maximum thermal stresses are given for a flat plate due to a given surface temperature change at a linear rate. Thermal stresses in thin cylindrical shells are discussed, and an example is evaluated.

Design factors are discussed briefly, mainly by citing critical problems and giving references. A comprehensive bibliography is presented.
Evaluation of Bandsaw Performance
Authors: Colwell L. V. , McKee R. E.
Published: July 2022

Methods of evaluating bandsaw performance are presented and typical performance characteristics are discussed. Tests indicate that bandsawing has orderly and predictable machinability characteristics very similar to other machining operations. Cutting speed and feed rate or feeding force are the more important variables requiring careful selection and control. Tests on sawing titanium show that positive power feed is almost a necessity to prevent premature breakdown of the band.
The Tabulation of Imperfect-Gas Properties for Air, Nitrogen, and Oxygen
Authors: Hall Newman A. , Ibele Warren E.
Published: July 2022

Recent theoretical developments of intermolecular forces have established a basis upon which a valid extension of gas-property data may be prepared. This paper establishes the fact that deviation from perfect-gas behavior may be expressed fundamentally by the compressibility factor. Tables of virial coefficients and temperature derivatives for air, nitrogen, and oxygen are given, as well as tables of compressibility factors for these three gases.
Cyclic Heating Test of Main Steam Piping Materials and Welds at the Sewaren Generating Station
Authors: Weisberg H. , Soldan H. M.
Published: July 2022

This paper describes a continuation of previously reported cyclic heating tests of austenitic and ferritic piping and welds, representing the main steam piping installed at Sewaren Generating Station. In the current test, a section made up of these materials was subjected to thermal cycling from room temperature to 1100 F, and from atmospheric pressure to the operating pressure of 1500 psi. The heating and cooling rates were somewhat more severe than are experienced during regular starting and shutting-down conditions in the actual piping systems. The results show that 100 cycles did not produce any cracking. It is proposed to continue the test to destruction by further cycling and the addition of external bending forces.
Some 12 Per Cent Chromium Alloys for 1000 F to 1200 F Operation
Authors: Newhouse D. L. , Seguin B. R. , Lape E. M.
Published: July 2022

This paper presents a discussion of important engineering properties of some martensitic 12 per cent Cr alloys for use at temperatures up to 1200 F. Detailed high-temperature creep-relaxation and stress-rupture data are given for 12 per cent Cr (Type 403) and for six alloy modifications including 12 per cent Cr-Co-W-V, 12 per cent Cr-W-V, 12 per cent Cr-Mo-V, 12 per cent Cr-Mo-W-V, 12 per cent Cr-Cb, and 12 per cent Cr-Ni-W. Other properties such as thermal expansion, modulus of elasticity, resistance to stress corrosion, and so forth, are discussed. Some of the modified 12 per cent Cr alloys offer a combination of properties which makes them attractive for a number of high-temperature applications.