bluuebunny/crossref_metadata_2025 huggingface dataset:
The Relationship Between Fracture Toughness and Stress Concentration Factors for Several High-Strength Aluminum Alloys
Authors: Mulherin J. H. , Armiento D. F. , Markus H.
Published: November 2011

For the case of an elliptical notch in an infinite solid, a relationship between the stress concentration factor and the fracture toughness parameter was examined. Edge-notched specimens from three high-strength aluminum alloys were tensile loaded to failure. The resulting data were analyzed in the light of this relationship. It was indicated that a predicted proportionality between the fracture toughness parameter and the square root of the notch root radius exists. Further examination of the relationship based upon the proportionality showed that fracture occurs at a fixed state of strain within a plastic zone having a size proportional to the original root radius. However, a departure from the predicted behavior was evident with the introduction of plane strain components at the notch root. It was also demonstrated that the use of specimens with intermediate root radii for either the evaluation of a single material or as a basis of comparison between materials can lead to invalid conclusions. The reversion of fracture toughness data from blunt notch specimens to stress concentration factors is shown for one alloy. Due to a constancy in the ratio of the fracture parameter to the nominal stress, the resulting factor lacks sensitivity.
On the Tendency to Self-Preservation in Axisymmetric Ducted Jets
Authors: Curtet R. , Ricou F. P.
Published: November 2011

If it is assumed that the mean-velocity profiles of a ducted jet are similar in form sufficiently for downstream of the orifice it is possible, as shown in earlier papers [1, 2, 3], to integrate the equations of motion using the boundary-layer approximation and assuming a constant-energy secondary stream. It is necessary to know when and how this limiting profile is reached, and whether a similar tendency to self-preservation of the components of the velocity fluctuations is observed before the jet reaches the duct-wall boundary layer. Measurements have been made in an axisymmetric ducted air jet of the mean and fluctuating velocities, jet width, secondary-stream velocity, ductwall static pressure, and the boundary layer thickness. Results are compared with values predicted by the approximate jet theory. The authors define form factors calculated from measured profiles of mean velocities, of radial and longitudinal components of the velocity fluctuations, and of the shear stress. The variation of these form factors indicates a definite tendency to similarity for the mean velocity profiles; however, departures from similarity persist for the velocity fluctuations to the limit of measurements, about three duct diameters (40 nozzle diameters).
Establishment of the Wake Behind a Disk
Authors: Carmody Thomas
Published: November 2011

An air-tunnel study of the establishment of the wake behind a disk at a Reynolds number of approximately 7 × 104 was undertaken. On the basis of the measured data, such a wake is fully established, that is, similarity profiles of the flow characteristics are formed, within 15 diameters of the disk, and approximately 95 percent of the transfer of energy from the mean motion to the turbulence motion takes place within 3 diameters of the disk, in the region of the mean standing eddy. The measured mean ambient-pressure and mean total-pressure distributions, mean velocity distributions, turbulence-intensity and shear-stress distributions, and the mean streamline pattern are presented in graphical form, as are the quantitative balances of the integrated momentum and mean-energy relationships. A stream function consisting of a continuous distribution of doublets is introduced to extend the radial limit of understanding of the flow characteristics to a very large if not infinite radius. Considerable attention is given to the problem of obtaining and interpreting turbulence shear-stress data immediately downstream from the point of flow separation. The applicability of a local diffusion coefficient or virtual viscosity of the Boussinesq or Prandtl type for relating the turbulence shear stress to the radial gradient of mean axial velocity is discussed. The Bernoulli sum and the energy changes along individual streamlines investigated in an associated study are incorporated herein to obtain a quantitative estimate of the local errors involved in the turbulence-shear-stress measurements.
Hydrodynamic Lubrication of Narrow Press-Fitted Porous Metal Bearings
Authors: Rouleau W. T.
Published: November 2011

An analysis is made of the performance of narrow porous metal bearings (e.g., sintered bronze powder) which operate with a full film of lubricant. The configuration considered is that in which the bearings are pressed tightly into housings with their ends remaining open to the atmosphere. A solution for the lubricant pressure is obtained which satisfies Reynolds’ equation in the film and Laplace’s equation in the porous metal. Expressions are developed which give the Sommerfeld and Ocvirk numbers, attitude angle, and coefficient of friction as functions of eccentricity ratio, permeability parameter, and thickness-to-length ratio. The results are shown graphically for situations of practical importance.
A General Solution for Linear, Sampled-Data Control
Authors: Gunckel T. L. , Franklin Gene F.
Published: November 2011

If system performance can be adequately measured by a quadratic function of the error, it is possible to present a single optimum design procedure that encompasses almost all linear, sampled-data control problems of interest. This development includes both random and deterministic inputs, the random parameter problem, and a general time-varying system. The results are in the form of iterative equations which specify the optimum linear feedback coefficients. The method constitutes a generalization of the work by Kalman, Koepcke, Bellman, and others, and presumes the availability of a digital computer to solve the final equations.
Optimal Control of Systems With Generalized Poisson Inputs
Authors: Florentin J. J.
Published: November 2011

This paper discusses the optimal control of systems having known dynamics with command and disturbance inputs which may be described as generalized Poisson processes. An engineering interpretation of the physical nature of Poisson processes is given, with brief comments on their use as mathematical models of practical situations. Representative examples of partial differential equations of optimal control are quoted. Explicit solutions of the control equations are given for the following systems with quadratic performance indexes: (a) The general linear system with linear Poisson inputs; (b) a linear regulator with a quadratically nonlinear Poisson disturbance; (c) a linear regulator with a random step-wave disturbance.
Squeeze Films for Rectangular Plates
Authors: Hays Donald F.
Published: November 2011

A theoretical analysis is made of the normal approach of flat and curved rectangular plates which are separated by a thin film of lubricant. Load capacity curves are presented and some typical pressure distributions are shown. The effect of surface curvature on the squeeze film generation is investigated.
Characteristics of an Externally Pressurized Bearing Having Variable External Flow Restrictors
Authors: Mayer J. E. , Shaw M. C.
Published: November 2011

An externally pressurized bearing having variable external flow restrictors has been investigated and compared to a conventional externally pressurized journal bearing having fixed external restrictors. The variable restrictor considered was adjusted by means of a journal load sensing device and its resistance to flow varied linearly with load. Use of this variable resistance was found to greatly increase the bearing stiffness compared to that for a bearing equipped with conventional fixed external restrictors. For the bearing geometry and supply pressure employed, a bearing stiffness of at least 50 × 105 lb/in. was achieved. A design procedure that provides a given stiffness is presented.
Cavitation Damage to Centrifugal Pump Impellers During Operation With Liquid Metals and Molten Salt at 1050–1400 F
Authors: Smith P. G. , DeVan J. H. , Grindell A. G.
Published: November 2011

Three centrifugal pump impellers fabricated of Inconel were subjected to endurance testing under cavitating conditions with sodium and with molten salt (fused fluorides) at temperatures of 1050–1400 F. The tests were run (one with sodium and two with molten salt) at or near pump design head and flow conditions to establish the extent of impeller damage sustained during long periods of operation and to observe the effects upon performance. Descriptions are provided of the test impellers and volutes, of the experimental apparatus, and of the test operations. The cavitation damage is described by the effects on hydraulic performance and with photomicrographs and metallurgical analyses. Damage was manifested by the formation of pits in excess of 1/4 in. in depth. No change in performance was detected.
On Cumulative Damage in Impulse Fatigue Tests
Authors: Tanaka S.
Published: November 2011

Experimental results are presented for fatigue failure of mild steel specimens under repeated application of lateral impulses; the cumulative damage effect as a result of stresses arising from free-damped vibration of the specimen in the intervals between the repeated impulses is studied. A discussion on the conformity of these results with Miner’s hypothesis is given.
Geometrical Effects in Strain Cycled Aluminum
Authors: Raymond M. H. , Coffin L. F.
Published: November 2011

Dimensional changes in the form of necking and bulging occur in the shape of cylindrical and hourglass commercially pure aluminum specimens subjected to axial push-pull cyclic loading. The present report deals with the effect of these changes on the resistance to deformation and fracture by fatigue. It is found that the change in shape due to instability affects the stress range response of the material during cycling. The control of shape permits a steady-state response with cycling regardless of the prior state of strain in the material. With an appropriate correction for the shape constraint effect, the steady-state stress range achieved is the same with or without shape control. Frequent removal of the surface material to control the specimen profile during cycling leads to a stabilized hysteresis loop and an indeterminate extension in the fatigue life.
The Clamped Plate Analogy for Thermoelasticity
Authors: Ross A. L.
Published: November 2011

A method is described for determining the thermal stresses in plane systems with free boundaries. The method makes use of the analogy between the problems of the bending stresses in clamped plates and those of plane thermoelasticity. The analogy is illustrated for both simply and multiply connected regions. The method allows the simple solution of thermal stress problems for which the analogous plate bending problem has already been solved; and provides a means of easily visualizing the distribution and magnitude of thermal stresses in terms more familiar to many engineers.
Measurements of Auto-Oscillation in a Hydroelectric Supply Tunnel and Penstock System
Authors: Abbott H. F. , Gibson W. L. , McCaig I. W.
Published: November 2011

Severe sustained vibration of a closed hydraulic-turbine penstock valve was associated with accidentally inadequate inflation of the valve service seal. The vibration stopped when the valve bypass was opened or full seal pressure was applied. Theory indicates that intermittent valve leakage and corresponding oscillating penstock pressure can be self-sustaining in some instances, and that opening a bypass around the leaking valve can suppress them. Field tests were performed to confirm the general theory and prove the reliability of utilizing the bypass to prevent future vibration.
Counterrotating Journal Bearings
Authors: Pinkus O.
Published: November 2011

A theoretical derivation is given showing that whenever the center of curvature of a bearing does not coincide with its center of rotation, synchronous counterrotation will produce a load capacity. Test results are given for a number of bearing designs that operated successfully under synchronous counterrotation with load capacities beyond 1500 psi. The only bearing that scored under counterrotation was a perfectly circular ungrooved bearing, as predicted by theory.
Theoretical Contributions to the Study of Gas-Lubricated Journal Bearings
Authors: Katto Y. , Soda N.
Published: November 2011

As a theoretical study of the hydrodynamic, gas-lubricated journal bearings, the paper presents approximate solutions with fair accuracy for high values of eccentricity ratio. In addition, an approximate solution available for clarifying the characteristics of journal bearing operating at low revolution speeds is reported. Comparison with experimental data reveals the fact that actual bearings operate under an intermediate condition between isothermal and adiabatic when running at high revolution speeds, while under the isothermal condition at low speeds.
A Successive Approximation Technique for Optimal Control Systems Subject to Input Saturation
Authors: Ho Yu-Chi
Published: November 2011

A class of problems that has received considerable attention in recent years from both control theorists and engineers is the following: Givenx˙=Fx+du,x(0)=cDetermine|u(t)|≤1suchthatx(T)=0andx(t)≠0for0≤t<TandwhereTisaminimum(P-1) A related and perhaps more practical class of problems can be stated as Givenx˙=Fx+du,x(0)=cDetermine|u(t)|≤1suchthat‖x(T)‖2PisaminimumforgivenT(P-2) Although a considerable amount of effort has been expended on (P-1), and to a lesser extent on (P-2), yet computational techniques which enable one to solve numerically the above problems are still lacking except in restricted cases [7, 8]. This paper presents such a technique which completely solves this problem by successive approximation. The convergence of this solution is proved, and it is shown to satisfy all known properties of the problems.
Stability of a Nonlinear Feedback System in the Presence of Gaussian Noise
Authors: Sridhar Rangasami , Oldenburger Rufus
Published: November 2011

A stability criterion for certain types of nonlinear feedback systems in the presence of Gaussian noise is established here. This criterion may be considered as a natural extension of the describing function method. It is assumed that the lowest frequency component in the power spectral density of the noise is at least ten times higher than the highest significant frequency of the system. The method developed here is applicable to feedback systems with just one instantaneous, nonmemory type nonlinearity in the loop. The results mentioned in this paper have been experimentally verified on an analog computer. The theory explained here may be used by the designer to predict the manner in which noise will affect the performance of a system.
Flow Regimes in Curved Subsonic Diffusers
Authors: Fox R. W. , Kline S. J.
Published: November 2011

An extension and refinement of the work of Moore and Kline (NACA TN 4080) is presented for the flow regimes found in straight-walled diffusers. A systematic map of flow regimes in curved diffusing passages is presented, in steps of ten degrees, for a range of flow turning angles from 0 to 90 degrees. Each curved diffuser geometry tested had a circular arc center line and a linear area distribution normal to the center line. The line of first appreciable stall showed a peak in divergence angle as a function of the ratio of center line length to throat width for all values of turning angle equal to, or greater than, fifty degrees. The divergence angle at the transition to the fully developed stall regime was found to decrease monotonically with increase in turning angle at fixed values of the ratio of center line length to throat width in all cases.
Cavitation in Turbopumps—Part 1
Authors: Stripling L. B. , Acosta A. J.
Published: November 2011

A free-streamline flow through a cascade of semi-infinite flat plates is taken as a simplified model of the cavitation process in a helical inducer pump. The length and thickness of the resulting cavity is determined as a function of blade geometry and cavitation parameter. Loss coefficients resulting from the cavitation are estimated and representative cavity shapes are calculated to aid in designing the leading edge shape of the blades.
Design of Pressure Vessels for Low-Cycle Fatigue
Authors: Langer B. F.
Published: November 2011

Methods are described for constructing a fatigue curve based on strain-fatigue data for use in pressure vessel design. When this curve is used, the same fatigue strength-reduction factor should be used for low-cycle as for high-cycle conditions. When evaluating the effects of combined mean and alternating stress, the fatigue strength-reduction factor should be applied to both the mean and the alternating component, but then account must be taken of the reduction in mean stress which can be produced by yielding. The complete fatigue evaluation of a pressure vessel can be a major task for the designer, but it can be omitted, or at least drastically reduced, if certain requirements can be met regarding design details, inspection, and magnitude of transients. Although the emphasis in this paper is on pressure vessel design, the same principles could be applied to any structure made of ductile metal and subjected to limited numbers of load cycles.
Rotor-Bearing Dynamics With Emphasis on Attenuation
Authors: Lund J. W. , Sternlicht B.
Published: November 2011

This paper presents a theoretical analysis of the dynamics of a rotor-bearing system. The analysis is quite general but because of space limitations only the symmetrical rotor supported in two plain cylindrical journal bearings is considered. Furthermore, the rotor mass is concentrated at midspan giving the rotor only one degree of freedom. Limiting the analysis to small amplitudes of rotor motion the components of the fluid film force are made linear with respect to journal amplitude and velocity. The resulting 8 coefficients, denoted spring and damping coefficients, are calculated from Reynolds equation and by coupling them with the rotor, the motion and the force transmitted to the bearing pedestal are obtained. Results are presented in dimensionless form for transmitted force and for critical speed.
Experimental Support for Generalized Equation Predicting Low Cycle Fatigue
Authors: Tavernelli J. F. , Coffin L. F.
Published: November 2011

Experimental data from cyclic strain fatigue tests on twelve structural materials are compared on the basis of a low cycle fatigue equation as suggested by an ASME task group. This equation S=Ec2N1/2+Se where Se is the endurance limit, E the modulus of elasticity, N the cycles to failure, and c a constant derived from reported values of reduction in area, gives the stress amplitude S for comparison with elastically computed stresses. A satisfactory or good correlation with experiments for up to 105 cycles of failure is found.
An Experimental Investigation of the Crack Tip Stress Intensity Factors in Plates Under Cylindrical Bending
Authors: Erdogan Fazil , Tuncel Ozcan , Paris Paul C.
Published: November 2011

This experimental study was undertaken to investigate the validity of the theory based on the crack tip stress intensity factors to explain the fracture of thin cracked plates subjected to static bending moments. Plexiglas sheets were used as specimens and the loading was pure cylindrical bending. The results indicate that there is in fact a critical value of the stress intensity factor at which the crack starts growing. It was found that, while in static tensile tests the crack growth was unstable, in the case of bending, the external load (here, the bending moment) which starts the crack growing is not sufficient for the complete fracture of the plate if it is maintained constant. That is, when the critical value of the stress intensity factor is reached, the crack starts growing on the tensile side of the plate whereupon the crack tip takes a triangular shape and the system again becomes stable. In order to make the crack grow further, a considerable increase in the load is required.
Dynamic Behavior of a Simple Pneumatic Pressure Reducer
Authors: Tsai D. H. , Cassidy E. C.
Published: November 2011

This paper presents an analysis of the dynamic behavior of a simple pneumatic pressure reducer. Both the nonlinear and the linearized problems were studied. Some experimental results also were obtained on a working reducer model to check the validity of the analysis. The agreement between the nonlinear solutions and the experimental results was satisfactory. The nonlinear and the linearized solutions were compared in detail so as to bring out the essential features of the dynamic behavior in both cases. The stability problem was studied also, and a set of stability criteria for the linearized case was formulated in terms of the design and operating parameters of the reducer. In the few sample cases studied, these criteria gave correct qualitative predictions of the stability of the reducer in both the linearized case and the nonlinear case. The flow forces on three typical flowmetering values were determined by experimental measurements (Appendix 2). These results were used in the analytical part of the paper.
The Jet-Flap Compressor Cascade
Authors: Brocher Eric F.
Published: November 2011

Scholz’s method for measurements on a two-dimensional cascade has been extended to include mass and energy input into the main flow by trailing-edge jets. Pressure recovery and mixing losses downstream of the cascade have been theoretically investigated and the need of low jet velocities has been emphasized. Improvements which can be expected by increasing the jet width but keeping the jet coefficient constant have been demonstrated. The airfoil tested was the NACA 65-(12)10 compressor blade with a thickened trailing edge. A stagger angle of 45 deg and a solidity of 0.915 were used throughout. Results are given in the form of wake profiles, axial and tangential force coefficients, and cascade polars.
Application of a Cumulative Damage Concept to Fatigue
Authors: Gatts R. R.
Published: November 2011

A general concept of the accumulation of damage is described. This concept is combined with a particular hypothesis for the accumulation of fatigue damage. Initial and failure conditions are established for use with the equation and the solution for constant stress amplitude is discussed. Simple algebraic expressions are developed in terms of the nominal stresses and cycles commonly associated with machine design and stress analysis. These expressions are compared with data from rotating bending tests of steel specimens and found to be in good agreement. Nondimensional co-ordinates are used to provide a composite plot of S-N data from a wide range of steels.
Effects of Interrupted Quenching Procedures on Properties of Type 410 Stainless Steel
Authors: Bressanelli J. , Hoke J.
Published: November 2011

The impact strength of hardened Type 410 stainless steel is known to be adversely affected when the steel is tempered between 750 and 1050 F. However, a desirable combination of other properties may be obtained by tempering within this range. An investigation was performed to determine the extent of improvement in impact strength that may result from certain variations in heat-treating procedures. The hardening operation was studied thoroughly, and a large number of commercial heats was included in the program to establish the consistency of results. It was found that the cooling rate through the martensite transformation range has a significant effect upon the impact properties after subsequent tempering. Rapid cooling such as that which occurs during oil quenching is detrimental, but air cooling of 0.4-in-diameter bar samples was sufficiently slow to bring about a marked improvement. This improvement was present for samples tempered at all temperatures through 1000 F with the greatest degree of improvement occurring for samples tempered in the range of 700 to 900 F. No improvement was observed for samples tempered at 1100 F and above. Martempering procedures are particularly suited for taking advantage of this phenomenon.
An Analysis of the Time and Temperature Dependence of the Upper Yield Point in Iron
Authors: Bennett P. E. , Sinclair G. M.
Published: November 2011

The influence of temperature and strain rate on the upper yield point of ingot iron was studied. Torsion tests were conducted using strain rates of 12.5/sec, 0.25/sec, and 0.0001/sec over the temperature range 77 to 525 deg K. The upper yield point showed a rapid increase as the temperature was lowered. An increase in the strain rate also caused an increase in the yield point. An apparent activation energy can be associated with the strain rate and temperature dependence of the yield point. This energy is influenced by stress level, and it appears from the present study that the relationship can be described by an equation of the form ΔH=ΔH¯τ¯−ττ¯b. If this relationship is substituted for ΔH in a modification of the Boltzmann relation, the following result is obtained: logγ˙γ˙1=MΔH¯RT1τ¯−τ1τ¯b1−T1Tτ¯−ττ¯−τ1b. This equation describes the experimental data within ± 3000 psi. The results of this investigation compared with tensile test data from other investigators confirm that state of stress is an important factor in determining whether a material will behave in a ductile or brittle fashion.
On the Mechanism of Cavitation Damage by Nonhemispherical Cavities Collapsing in Contact With a Solid Boundary
Authors: Naude´ Charl F. , Ellis Albert T.
Published: November 2011

A perfect fluid theory, which neglects the effect of gravity, and which assumes that the pressure inside a cavitation bubble remains constant during the collapse process, is given for the case of a nonhemispherical, but axially symmetric cavity which collapses in contact with a solid boundary. The theory suggests the possibility that such a cavity may deform to the extent that its wall strikes the solid boundary before minimum cavity volume is reached. High-speed motion pictures of cavities generated by spark methods are used to test the theory experimentally. Agreement between theory and experiment is good for the range of experimental cavities considered, and the phenomenon of the cavity wall striking the solid boundary does indeed occur. Studies of damage by cavities of this type on soft aluminum samples reveals that pressures caused by the cavity wall striking the bounda y are higher than those resulting from a compression of gases inside the cavity, and are responsible for the damage.
Pressure Losses in Smooth Pipe Bends
Authors: Ito¯ H.
Published: November 2011

The results of extensive experimental studies to determine the pressure losses for turbulent flow in smooth pipe bends of circular cross section are presented in this paper. To make the data usable in practical design problems, the results are discussed in relation to those found by previous investigators, and empirical formulas for the bend-loss coefficient are given. The general correlation of the test data appears to be as good as our present test information will permit.
Separation Prediction for Conical Diffusers
Authors: Robertson James M. , Fraser Harvey R.
Published: November 2011

A method of incompressible turbulent boundary-layer analysis based on the D parameter introduced by D. Ross is applied to conical-diffuser flow. The separation conditions are shown to depend on the initial momentum-thickness Reynolds number and a distance parameter involving the initial momentum thickness, the initial radius, and the diffuser length. Comparison with experimental information on diffuser separation indicates that the predictions are reliable, but conservative.
On the Three-Dimensional Turbulent Boundary Layer Generated by Secondary Flow
Authors: Johnston J. P.
Published: November 2011

A study of the secondary flow type of three-dimensional turbulent boundary layer is presented. Two objectives are achieved: (a) A mathematical model of the relationship between the cross-flow and main-flow components of the velocity vectors of the layer is established. (b) By utilization of the model some of the relationships required to carry out a boundary-layer problem solution by the use of the momentum-integral equations are developed.
The Measurement of Oil-Film Thickness in Gear Teeth
Authors: MacConochie I. O. , Cameron A.
Published: November 2011

The voltage drop across thin oil films when a constant current of 1 amp is passed, i.e., the discharge voltage, is used to measure the oil-film thickness between loaded gear teeth while running. It is found that the thickness at the pitch line is between 1 and 4 × 10−4 in., which varies slightly with the viscosity and rather more strongly with load. The thickness at the tips and roots is very dependent on the tip relief. The conditions here may explain the difference between disk and gear tests. These experimental values are compared with theoretical work and are shown to be of the same order of magnitude.
Relations Between the Notch Tensile Strength of Cylindrical and Prismatic Specimens of Titanium Alloys and Heat-Treated Steels
Authors: Sachs G. , Sessler J. G. , Pray R. F. , Yeh T. H.
Published: November 2011

The basic relations which govern the behavior of titanium alloys in the presence of stress concentrations, as caused by notching, were investigated for cylindrical and prismatic tension test specimens. Notch tensile strengths were determined, at room temperature, for 4340 steel heat-treated to various strength levels, and for the titanium alloys 6Al-4V and 5Al-1.5Fe-1.4Cr-1.2Mo (Ti-155A). Some effects of notch geometry, specimen shape, type of loading, material history, and test temperature were included in the investigation. The information acquired from these studies leads to recommendations pertaining to the design of notch tensile specimens for evaluating the relative notch sensitivity of titanium sheet alloys.
A Generalization of Cumulative Damage
Authors: Mains R. M.
Published: November 2011

In the application of various damage accumulation hypotheses to shock and vibration problems, a pattern of results was observed. A plot of allowable response (for the largest of a sequence of excitations) versus the number of excitations in the sequence produced straight lines on log-log paper for each value of damping. It seemed likely that a generalization could be found which would relate the allowable response to the largest excitations with a load-distribution factor, a material-and-structure factor, and the material constants from fatigue tests. One form of this generalization is presented, together with some numerical examples of its use, and a discussion of its possible significance.
Cyclic Operation of Pressure Piping With γ Heating
Authors: Merckx K. R.
Published: November 2011

An elastic-plastic analysis is developed for an internally cooled pressure tube with uniform heat generation. This analysis extends the method of calculating the location of the elastic-plastic boundary reported by Barrie [4] to account for the change in the plastic zone due to residual stresses which occur during cyclic operation. Numerical calculations are made for operating conditions expected to be encountered in a pressure tube in a loop through the Engineering Test Reactor Core. The numerical results show that the radius of the initial plastic boundary decreases during subsequent loading cycles. Also, for equal maximum pressure and volumetric heat generation, the total plastic strain per operational cycle on the inner tube surface and the residual tensile stress on the outer tube surface increase when the tube wall is thickened.
Dynamics of Heat Exchangers and Their Models
Authors: Thal-Larsen Herman
Published: November 2011

The author rejects, momentarily, actual experimentation with real heat exchangers for logical cogitation and arm-chair experiments. Observed as mental images or models, these heat exchangers reveal their basic characteristics—characteristics that will be partially obscured in an actual experiment by secondary effects inherent in the equipment. These basic characteristics, once perceived, may be used to correlate by means of frequency-response diagrams many results heretofore diverse and seemingly unrelated, that have been reported in the literature. Included among such results are not only the dynamics of various types of heat exchangers but also the thermal dynamic interaction between fluids and the confining pipe used for their transport. In addition, the author warns that all too frequently the use of the average temperature in heat-exchanger dynamics is based on faulty logic.
Radial Distributions of Temporal-Mean Peripheral Velocity and Pressure for Fully Developed Turbulent Flow in Curved Channels
Authors: Marris A. W.
Published: November 2011

Experimental results are presented for the radial distributions of pressure and peripheral velocity for the turbulent flow of water in two closed curved channels of rectangular cross section and large depth-to-width ratio. The traverses were taken at the equatorial section of the channel and sufficiently far around the curve for the effect of curvature on the mean motion to be fully established. The two channels employed had widely differing mean-radius-to-width ratios n. The data obtained for a wide range of flow rates in the channel with a larger n indicated that Reynolds similarity existed between the flows in this channel. These data are compared with the pressure and velocity profiles predicted by potential flow theory and with a semiempirical logarithmic velocity distribution. Results obtained for the channel with smaller n showed that at above a certain Reynolds number an anomaly occurred in the flow, manifesting itself as an unstable “belt” of faster moving fluid, which moved outward from the inner wall as the Reynolds number was increased. This effect, considered to be the consequence of upstream stall, was accompanied by an adverse longitudinal-pressure gradient at the inner wall of the channel. It appeared to be eliminated by the insertion of an upstream splitter vane.
Cycle-Dependent Stress Relaxation of A-286 Alloy
Authors: Ross A. S. , Morrow JoDean
Published: November 2011

When an axial fatigue specimen is subjected to repeated strain cycling about a fixed mean strain value, the mean stress decreases with the number of strain cycles. To explore this type of material behavior, tubular fatigue specimens of A-286 alloy have been axially tested under conditions of controlled strain, and the cycle-dependent relaxation of mean stress measured. Fatigue data for five initial mean stresses are also reported. It was found that, in the case of A-286 alloy, most of the relaxation occurred early in the fatigue life, especially during the first ten cycles.
The Creep-Rupture Properties of 80 Ni-20 Cr Alloys
Authors: Widmer Robert , Grant Nicholas J.
Published: November 2011

The creep-rupture properties and the creep behavior of a series of 80 Ni-20 Cr alloys were investigated over the 1200 to 1800-F range. In the group were two vacuum-melted and three air-melted alloys. Among these five heats there were small but important differences in minor constituents such as silicon, manganese, sulfur, and possible tramp elements, primarily as a result of the melting practice in each case. Of particular interest in this study was the variation in ductility which the various alloys exhibited in creep-rupture tests which lasted from a few minutes to more than 1000 hr. A close examination of ductility behavior was undertaken by breaking down the creep curve into primary, secondary, and third-stage creep as a function of stress and temperature. It is shown that the stress-rupture properties are not affected over a wide temperature and stress range by a change in minor constituents, whereas the ductility behavior can vary considerably.
Falling Film of Ionic Liquid-Water Binary Solutions on a Uniformly Heated Vertical Wall
Authors: Peng Jing , Wang Ming-Ming , Geng Jiao , Wu You-Ting , Zhang Zhi-Bing
Published: November 2011

The flow characteristics of falling film of amino acid ionic liquid (AAIL) aqueous solution on a uniformly heated vertical plane have been experimentally studied. The infrared images and temperature profiles have been determined and used to analyze the fluid flow. It is proven that the Marangoni effect exists widely and has significant influence on the flow region of falling film. A novel flow pattern is additionally observed when the mass fraction of AAIL is 30%. The flow patterns are also shown to be affected by the wall-liquid temperature differential, the flow rate and the concentration of solute. The experimental results of AAIL falling film are expected to be helpful for the further industrial application of ionic liquids.
Which Way Out?
Authors: Adler Elizabeth M.
Published: November 2011

Adenomatous polyposis coli determines the apical or basal site of cell extrusion from epithelia.
Repeated Exposure to Aspergillus fumigatus Conidia Results in CD4+T Cell-Dependent and -Independent Pulmonary Arterial Remodeling in a Mixed Th1/Th2/Th17 Microenvironment That Requires Interleukin-4 (IL-4) and IL-10
Authors: Shreiner Andrew B. , Murdock Benjamin J. , Sadighi Akha Amir A. , Falkowski Nicole R. , Christensen Paul J. , White Eric S. , Hogaboam Cory M. , Huffnagle Gary B.
Published: November 2011

Pulmonary arterial remodeling is a pathological process seen in a number of clinical disease states, driven by inflammatory cells and mediators in the remodeled artery microenvironment. In murine models, Th2 cell-mediated immune responses to inhaled antigens, such as purifiedAspergillusallergen, have been reported to induce remodeling of pulmonary arteries. We have previously shown that repeated intranasal exposure of healthy C57BL/6 mice to viable, restingAspergillus fumigatusconidia leads to the development of chronic pulmonary inflammation and the coevolution of Th1, Th2, and Th17 responses in the lungs. Our objective was to determine whether repeated intranasal exposure toAspergillusconidia would induce pulmonary arterial remodeling in this mixed Th inflammatory microenvironment. Using weekly intranasal conidial challenges, mice developed robust pulmonary arterial remodeling after eight exposures (but not after two or four). The process was partially mediated by CD4+T cells and by interleukin-4 (IL-4) production, did not require eosinophils, and was independent of gamma interferon (IFN-γ) and IL-17. Furthermore, remodeling could occur even in the presence of strong Th1 and Th17 responses. Rather than serving an anti-inflammatory function, IL-10 was required for the development of the Th2 response toA. fumigatusconidia. However, in contrast to previous studies of pulmonary arterial remodeling driven by theA. fumigatusallergen, viable conidia also stimulated pulmonary arterial remodeling in the absence of CD4+T cells. Remodeling was completely abrogated in IL-10−/−mice, suggesting that a second, CD4+T cell-independent, IL-10-dependent pathway was also driving pulmonary arterial remodeling in response to repeated conidial exposure.
Defining the Roles of Human Carcinoembryonic Antigen-Related Cellular Adhesion Molecules during Neutrophil Responses to Neisseria gonorrhoeae
Authors: Sarantis Helen , Gray-Owen Scott D.
Published: November 2011

Symptomatic infection of humans withNeisseria gonorrhoeaeis characterized by a neutrophil-rich cervical or urethral exudate, suggesting that neutrophils are important both for the clearance of these bacteria and for the pathogenesis of gonorrhea.Neisseriainteracts with neutrophils through ligation of human carcinoembryonic antigen related-cellular adhesion molecules (CEACAMs) by their surface-expressed Opa proteins, resulting in bacterial binding, engulfment, and neutrophil activation. Multiple CEACAMs are expressed by human neutrophils, and yet their coexpression has precluded understanding of the relative contribution of each CEACAM to functional responses of neutrophils during neisserial infection. In this work, we directly address the role of each CEACAM during infection by introducing individual human CEACAMs into a differentiated murine MPRO cell line-derived neutrophil model. Murine neutrophils cannot bind the human-restrictedNeisseria; however, we show that introducing any of the Opa-binding CEACAMs of human neutrophils (CEACAM1, CEACAM3, and CEACAM6) allows binding and entry ofNeisseriainto murine neutrophils. While CEACAM1- and CEACAM6-expressing neutrophils bind more bacteria, neisserial uptake via these two receptors unexpectedly proceeds without appreciable neutrophil activation. In stark contrast, neisserial engulfment via CEACAM3 recapitulates the oxidative burst and intracellular granule release seen during human neutrophil infection. Finally, by coexpressing multiple CEACAMs in our model, we show that the expression of CEACAM1 and CEACAM6 potentiate, rather than hinder, CEACAM3-dependent responses of neutrophils, exposing a cooperative role for this family of proteins during neisserial infection of neutrophils. These observations illustrate a divergence in function of CEACAMs in neutrophils and implicate the human-restricted CEACAM3 in the neutrophil innate response to neisserial infection.
Macrophages Are Critical for Cross-Protective Immunity Conferred by Babesia microti against Babesia rodhaini Infection in Mice
Authors: Li Yan , Terkawi Mohamad Alaa , Nishikawa Yoshifumi , Aboge Gabriel Oluga , Luo Yuzi , Ooka Hideo , Goo Youn-Kyoung , Yu Longzheng , Cao Shinuo , Sun Yongfeng , Yamagishi Junya , Masatani Tatsunori , Yokoyama Naoaki , Igarashi Ikuo , Xuan Xuenan
Published: November 2011

Although primary infection of mice withBabesia microtihas been shown to protect mice against subsequent lethal infection byBabesia rodhaini, the mechanism behind the cross-protection is unknown. To unravel this mechanism, we investigated the influence of primary infection of mice with nonlethalB. microtiusing different time courses on the outcome of subsequent lethalB. rodhainiinfection. Simultaneous infections of mice with these parasites resulted in rapid increases in parasitemia, with 100% mortality in BALB/c mice, as observed with control mice infected withB. rodhainialone. In contrast, mice with acute, resolving, and chronic-phaseB. microtiinfections were completely protected againstB. rodhaini, resulting in low parasitemia and no mortalities. Mice immunized with deadB. microtiwere not protected fromB. rodhainiinfection, although high antibody responses were induced. Interestingly, the protected mice had significantly decreased levels of antibody response, cytokines (including gamma interferon [IFN-γ], interleukin-2 [IL-2], IL-8, IL-10, and IL-12), and nitric oxide levels after infection withB. rodhaini. SCID mice and IFN-γ-deficient mice with chronicB. microtiinfections demonstrated protective responses comparable to those of immunocompetent mice. Likewise,in vivoNK cell depletion did not significantly impair the protective responses. Conversely, macrophage depletion resulted in increased susceptibility toB. rodhainiinfection associated with changes in their antibody and cytokines profiles, indicating that macrophages contribute to the protection against this challenge infection. We conclude that future development of vaccines againstBabesiashould include a strategy that enhances the appropriate activation of macrophages.
Use of genetic markers to aid in re-establishing migratory connectivity in a fragmented metapopulation of bull trout (Salvelinus confluentus)
Authors: DeHaan Patrick W. , Bernall Shana R. , DosSantos Joseph M. , Lockard Lawrence L. , Ardren William R.
Published: November 2011

Dams and other barriers fragment important migratory corridors for bull trout ( Salvelinus confluentus ) across the species range. Three dams constructed without fish passage facilities prevented migratory bull trout in the Lake Pend Oreille and Clark Fork River system in Idaho and Montana, USA, from returning to their natal spawning tributaries for nearly 100 years. We genotyped bull trout from 39 spawning tributaries to assemble a baseline data set that we used to develop a real-time genotyping and analysis protocol to assist with upstream fish transport decisions. Self-assignment tests and analysis of blind samples indicated that unknown individuals could be assigned to their region of origin with a high degree of confidence. From 2004 to 2010, genetic assignments were conducted for 259 adult bull trout collected below mainstem dams. Based on genetic assignments, 203 fish were transported upstream above one or more dams. This protocol has helped re-establish connectivity in a fragmented system, providing increased numbers of spawning adults for numerically depressed populations above the dams. We discuss the utility of genetic data for assisting with upstream passage decisions.
Fishing power increases from technological development in the Faroe Islands longline fishery
Authors: Eigaard Ole Ritzau , Thomsen Bjarti , Hovgaard Holger , Nielsen Anders , Rijnsdorp Adriaan D.
Published: November 2011

During an effort-regulated period from 1996 to 2002, unregistered annual increases of 0.3% of hooks fished per day were demonstrated for the Faroe Islands longline fishery. However, annual increases were higher (1.5%) during a preceding total allowable catch regulated period, thereby invalidating an expectation of the 1996 shift in regulations (output to input control) to have induced increases in the number of hooks set per day. Underlying this result is a substantial increase in total yearly effort (fishing days) and a shift in targeting behaviour from secondary to primary (high value) target species in response to the transition from output to input control. Interview data on technology were combined with logbook data and analysed with generalized linear modelling to demonstrate haddock ( Melanogrammus aeglefinus ) and Atlantic cod ( Gadus morhua ) catch-per-unit-effort increases of 51% and 26%, respectively, following the introduction of skewed hooks and swivel line. The technological introductions were not correlated to regulation shifts. So, rather than the management system in force, an ongoing technological development seems to be the principal driver of fishing power trends. The results highlight the need to explicitly address technological development and targeting behaviour when attempting to meet conservation objectives through input control of fisheries.
Effects of size and diet on stable hydrogen isotope values (δD) in fish: implications for tracing origins of individuals and their food sources
Authors: Soto David X. , Wassenaar Leonard I. , Hobson Keith A. , Catalan Jordi
Published: November 2011

Recent studies suggest that stable hydrogen isotope ratios (δD) of fish can be used to track their watershed origin and the relative contributions of source material. Both applications assume that there is no metabolic or trophic effect on tissue δD. We studied the local variation of δD values in four fish species of contrasting size and feeding habits in an isotopically homogenous reservoir (Flix, Spain). Other isotopic values (δ15N, δ13C) and trace metal content were measured as indicators of trophic and bioaccumulation patterns. In addition, isotopic values (δD, δ15N, δ13C) of other food web components were measured for comparison. Muscle δD values differed greatly among fish species: European catfish, Silurus glanis (–131‰); common carp, Cyprinus carpio (–141‰); rudd, Scardinius erythrophthalmus (–158‰); and roach, Rutilus rutilus (–163‰). The influence of fish size and trophic position affected the fish δD values. Possible mechanisms that drive δD variation among fish might be a metabolic effect and (or) the compounding effect of ambient water δD on exchangeable H at each trophic stage. Our findings showed that size and feeding habits are factors that should be controlled when tracing origins of fish or their dependence on nutrient inputs using δD measurements.