Analytical Round Robin for Elastic-Plastic Analysis of Surface Cracked Plates: Phase I Results
NASA Technical Reports Server (NTRS)
Wells, D. N.; Allen, P. A.
2012-01-01
An analytical round robin for the elastic-plastic analysis of surface cracks in flat plates was conducted with 15 participants. Experimental results from a surface crack tension test in 2219-T8 aluminum plate provided the basis for the inter-laboratory study (ILS). The study proceeded in a blind fashion given that the analysis methodology was not specified to the participants, and key experimental results were withheld. This approach allowed the ILS to serve as a current measure of the state of the art for elastic-plastic fracture mechanics analysis. The analytical results and the associated methodologies were collected for comparison, and sources of variability were studied and isolated. The results of the study revealed that the J-integral analysis methodology using the domain integral method is robust, providing reliable J-integral values without being overly sensitive to modeling details. General modeling choices such as analysis code, model size (mesh density), crack tip meshing, or boundary conditions, were not found to be sources of significant variability. For analyses controlled only by far-field boundary conditions, the greatest source of variability in the J-integral assessment is introduced through the constitutive model. This variability can be substantially reduced by using crack mouth opening displacements to anchor the assessment. Conclusions provide recommendations for analysis standardization.
Vibration analysis of annular-like plates
NASA Astrophysics Data System (ADS)
Cheng, L.; Li, Y. Y.; Yam, L. H.
2003-05-01
The existence of eccentricity of the central hole for an annular plate results in a significant change in the natural frequencies and mode shapes of the structure. In this paper, the vibration analysis of annular-like plates is presented based on numerical and experimental approaches. Using the finite element analysis code Nastran, the effects of the eccentricity, hole size and boundary condition on vibration modes are investigated systematically through both global and local analyses. The results show that analyses for perfect symmetric conditions can still roughly predict the mode shapes of "recessive" modes of the plate with a slightly eccentric hole. They will, however, lead to erroneous results for "dominant" modes. In addition, the residual displacement mode shape is verified as an effective parameter for identifying damage occurring in plate-like structures. Experimental modal analysis on a clamped-free annular-like plate is performed, and the results obtained reveal good agreement with those obtained by numerical analysis. This study provides guidance on modal analysis, vibration measurement and damage detection of plate-like structures.
NASA Technical Reports Server (NTRS)
Ward, Steven N.
1988-01-01
Data obtained by Mark III VLBI measurements of radio signals from permanent and mobile VLBI sites for 5.5 years of observations, starting in October 1982, were used to derive a picture of the earth crust deformation near the North America-Pacific plate boundary. The data, which included the vector positions of the VLBI sites and their rate of change, were used for comparison with a number of lithospheric deformation models based upon the concept that the motions of points near the North America-Pacific plate boundary are a linear combination of North America and Pacific velocities. The best of these models were found to fit 95 percent of the variance in 139 VLBI length and transverse velocity observations. Instantaneous shear deformation associated with plate tectonics is apparently developing in a zone 450 km wide paralleling the San Andreas Fault; some of this deformation will be recovered through elastic rebound, while the rest will be permanently set through plastic processes. Because the VLBI data have not been collected for a significant fraction of the earthquake cycle, they cannot discriminate between elastic and plastic behaviors.
Elastic-plastic models for multi-site damage
NASA Technical Reports Server (NTRS)
Actis, Ricardo L.; Szabo, Barna A.
1994-01-01
This paper presents recent developments in advanced analysis methods for the computation of stress site damage. The method of solution is based on the p-version of the finite element method. Its implementation was designed to permit extraction of linear stress intensity factors using a superconvergent extraction method (known as the contour integral method) and evaluation of the J-integral following an elastic-plastic analysis. Coarse meshes are adequate for obtaining accurate results supported by p-convergence data. The elastic-plastic analysis is based on the deformation theory of plasticity and the von Mises yield criterion. The model problem consists of an aluminum plate with six equally spaced holes and a crack emanating from each hole. The cracks are of different sizes. The panel is subjected to a remote tensile load. Experimental results are available for the panel. The plasticity analysis provided the same limit load as the experimentally determined load. The results of elastic-plastic analysis were compared with the results of linear elastic analysis in an effort to evaluate how plastic zone sizes influence the crack growth rates. The onset of net-section yielding was determined also. The results show that crack growth rate is accelerated by the presence of adjacent damage, and the critical crack size is shorter when the effects of plasticity are taken into consideration. This work also addresses the effects of alternative stress-strain laws: The elastic-ideally-plastic material model is compared against the Ramberg-Osgood model.
Practical solution of plastic deformation problems in elastic-plastic range
NASA Technical Reports Server (NTRS)
Mendelson, A; Manson, S
1957-01-01
A practical method for solving plastic deformation problems in the elastic-plastic range is presented. The method is one of successive approximations and is illustrated by four examples which include a flat plate with temperature distribution across the width, a thin shell with axial temperature distribution, a solid cylinder with radial temperature distribution, and a rotating disk with radial temperature distribution.
Converging shocks in elastic-plastic solids.
Ortega, A López; Lombardini, M; Hill, D J
2011-11-01
We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=e(s)(I(1))+e(h)(ρ,ς), where e(s) accounts for shear through the first invariant of the Cauchy-Green tensor, and e(h) represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., e(h)=e(h)(ρ), with a power-law dependence e(h) is proportional to ρ(α), shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M is proportional to [log(1/R)](α), independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M is proportional to R(-(s-1)) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part e(h) is that of an ideal gas, is also tested, recovering the strong-shock limit M is proportional to R(-(s-1)/n(γ)) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the
Converging shocks in elastic-plastic solids
NASA Astrophysics Data System (ADS)
López Ortega, A.; Lombardini, M.; Hill, D. J.
2011-11-01
We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=es(I1)+eh(ρ,ς), where es accounts for shear through the first invariant of the Cauchy-Green tensor, and eh represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., eh=eh(ρ), with a power-law dependence eh∝ρα, shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M∝[log(1/R)]α, independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M∝R-(s-1) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part eh is that of an ideal gas, is also tested, recovering the strong-shock limit M∝R-(s-1)/n(γ) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the hydrostatic part of the energy essentially commands the strong-shock behavior, the shear
Experimental investigation of Rayleigh Taylor instability in elastic-plastic materials
NASA Astrophysics Data System (ADS)
Haley, Aaron Alan; Banerjee, Arindam
2010-11-01
The interface of an elastic-plastic plate accelerated by a fluid of lower density is Rayleigh Taylor (RT) unstable, the growth being mitigated by the mechanical strength of the plate. The instability is observed when metal plates are accelerated by high explosives, in explosive welding, and in volcanic island formation due to the strength of the inner crust. In contrast to the classical case involving Newtonian fluids, RT instability in accelerated solids is not well understood. The difficulties for constructing a theory for the linear growth phase in solids is essentially due to the character of elastic-plastic constitutive properties which has a nonlinear dependence on the magnitude of the rate of deformation. Experimental investigation of the phenomena is difficult due to the exceedingly small time scales (in high energy density experiments) and large measurement uncertainties of material properties. We performed experiments on our Two-Wheel facility to study the linear stage of the incompressible RT instability in elastic-plastic materials (yogurt) whose properties were well characterized. Rotation of the wheels imparted a constant centrifugal acceleration on the material interface that was cut with a small sinusoidal ripple. The controlled initial conditions and precise acceleration amplitudes are levied to investigate transition from elastic to plastic deformation and allow accurate and detailed measurements of flow properties.
Implementation of elastic-plastic structural analysis into NASTRAN
NASA Technical Reports Server (NTRS)
Levy, A.; Pifko, A. B.; Ogilvie, P. L.
1983-01-01
Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN.
Elastic-plastic analysis of growing cracks
Rice, J.R.; Drugan, W.J.; Sham, T.L.
1980-01-01
The elastic-plastic stress and deformation fields at the tip of a crack which grow in an ideally plastic solid under plane strain, small-scale yielding conditions is discussed. Asymptotic analysis suggests a crack-tip stress state similar to that of the classical Prandtl field, but containing elastic unloading between the centered fan region and the trailing constant stress plastic region. The near tip expression for the rate of opening displacement delta at distance r from the growing tip is found to have the same form suggested by Rice and Sorensen, delta = ..cap alpha..J/sigma/sub 0/ + ..beta..(sigma/sub 0//E)a ln (R/r), but now the presence of the elastic wedge causes ..beta.. to have the revised value of 5.08 (for Poisson ratio ..nu.. = 0.3). Here, a = crack length, sigma/sub 0/ = yield strength, E = elastic modulus, and J denotes the far-field value (1 - ..nu../sup 2/) K/sup 2//E for the small scale yielding conditions considered. The parameters ..cap alpha.. and R cannot be determined from the asymptotic analysis, but ..cap alpha.. is approximately the same for stationary and growing cracks, and R scales approximately with the size of the plastic zone, being about 15 to 30% larger. For large scale yielding, a similar form applies with possible variations in ..cap alpha.. and ..beta.., at least in cases which maintain triaxial constraint at the crack tip, but in the fully yielded case R is expected to be proportional to the dimension of the uncracked ligament. The model crack growth criterion of Rice and Sorensen, requiring a critical delta at some fixed r from the tip, is reexamined. Results suggest that the J versus ..delta..a relation describing growth will be dependent on the extent of yielding, although it is suggested that this dependency might be small for highly ductile materials, provided that a similar triaxial constraint is maintained in all cases.
3-D vibration analysis of annular sector plates using the Chebyshev-Ritz method
NASA Astrophysics Data System (ADS)
Zhou, D.; Lo, S. H.; Cheung, Y. K.
2009-02-01
The three-dimensional free vibration of annular sector plates with various boundary conditions is studied by means of the Chebyshev-Ritz method. The analysis is based on the three-dimensional small strain linear elasticity theory. The product of Chebyshev polynomials satisfying the necessary boundary conditions is selected as admissible functions in such a way that the governing eigenvalue equation can be conveniently derived through an optimization process by the Ritz method. The boundary functions guarantee the satisfaction of the geometric boundary conditions of the plates and the Chebyshev polynomials provide the robustness for numerical calculation. The present study provides a full vibration spectrum for the thick annular sector plates, which cannot be given by the two-dimensional (2-D) theories such as the Mindlin theory. Comprehensive numerical results with high accuracy are systematically produced, which can be used as benchmark to evaluate other numerical methods. The effect of radius ratio, thickness ratio and sector angle on natural frequencies of the plates with a sector angle from 120° to 360° is discussed in detail. The three-dimensional vibration solutions for plates with a re-entrant sector angle (larger than 180°) and shallow helicoidal shells (sector angle larger than 360°) with a small helix angle are presented for the first time.
Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.
Dechant, Lawrence; Smith, Justin
2016-01-01
Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by
Elastic-Plastic J-Integral Solutions or Surface Cracks in Tension Using an Interpolation Methodology
NASA Technical Reports Server (NTRS)
Allen, P. A.; Wells, D. N.
2013-01-01
No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.
NASA Astrophysics Data System (ADS)
Koduru, Jaya P.; Momeni, Sepandarmaz; Rose, Joseph L.
2013-12-01
Ultrasonic guided waves are fast emerging as a reliable tool for continuous structural health monitoring. Their multi-modal nature along with their long range propagation characteristics offer several possibilities for interrogating structures. Transducers commonly used to generate guided waves in structures excite multiple modes at any frequency; their complex scattering and reflection from defects and boundaries often complicates the extraction of useful information. Often it is desirable to control the guided wave modes propagating in a structure to take advantage of their unique properties for different applications. Earlier attempts at guided wave mode control involved developing fixed wavelength linear and annular array transducers. Their only disadvantage is that the transducer is limited to a particular wavelength and a change in wavelength necessitates a change in the transducer. In this paper, we propose the development of an annular array transducer that can generate mode controlled omnidirectional guided waves by independently controlling the amplitude and phase of the array elements. A simplified actuator model that approximates the transducer loading on the structure to a constant pressure load under the array elements is assumed and an optimization problem is set up to compute the excitation voltage and phase of the elements. A five element annular array transducer is designed utilizing 1-3 type piezocomposite materials. The theoretical computations are experimentally verified on an aluminum plate like structure by exciting A0 and S0 guided wave modes.
Cyclic loading of an elastic-plastic adhesive spherical microcontact
NASA Astrophysics Data System (ADS)
Kadin, Y.; Kligerman, Y.; Etsion, I.
2008-10-01
A previous study of a single load-unload cycle of an adhesive contact between an elastic-plastic microscopic sphere and a rigid flat is extended here for several load-unload cycles. The interacting forces between the sphere and the flat obey the Lennard-Jones potential. Kinematic hardening is assumed for the sphere material to account for possible plastic shakedown, and the difference between kinematic and isotropic hardenings is discussed. The main goal of the current work is to investigate the evolution of the load-approach curves for the elastic-plastic spherical contact during its cyclic loading-unloading. These curves are presented for different physical conditions, represented by three main dimensionless parameters, which affect the behavior of the elastic-plastic adhesive contact. A transition value of the Tabor parameter is found, below which the load-approach curves are always continuous and jump-in and jump-out instabilities are not expected.
Subwavelength focusing by binary multi-annular plates: design theory and experiment
NASA Astrophysics Data System (ADS)
Liu, Tao; Shen, Tong; Yang, Shuming; Jiang, Zhuangde
2015-03-01
Subwavelength focus can be created by one single binary multi-annular plate (MAP) through diffraction interference. Based on vectorial angular spectrum theory, a universal, efficient optimization method for designing subwavelength focusing MAPs is described using genetic algorithm and fast Hankel transform algorithm. The method can use arbitrarily polarized vector beams for illumination and can be applied to design multi-amplitude MAPs. It is shown by examples that the minimum feature size is not necessarily at subwavelength, and can be extended to several wavelengths. The longitudinally polarized electric component cannot be neglected in order to accurately reconstruct the real subwavelength focus. In the experiment, the best focal plane of MAP is precisely positioned through confocal scanning mechanism, in which a virtual confocal pinhole detection method is implemented. The wide-field, high-numerical aperture microscopic imaging system predominantly detects the transversely polarized electric components.
Elastic-plastic analysis of the SS-3 tensile specimen
Majumdar, S.
1998-09-01
Tensile tests of most irradiated specimens of vanadium alloys are conducted using the miniature SS-3 specimen which is not ASTM approved. Detailed elastic-plastic finite element analysis of the specimen was conducted to show that, as long as the ultimate to yield strength ratio is less than or equal to 1.25 (which is satisfied by many irradiated materials), the stress-plastic strain curve obtained by using such a specimen is representative of the true material behavior.
Elastic-plastic behavior of non-woven fibrous mats
NASA Astrophysics Data System (ADS)
Silberstein, Meredith N.; Pai, Chia-Ling; Rutledge, Gregory C.; Boyce, Mary C.
2012-02-01
Electrospinning is a novel method for creating non-woven polymer mats that have high surface area and high porosity. These attributes make them ideal candidates for multifunctional composites. Understanding the mechanical properties as a function of fiber properties and mat microstructure can aid in designing these composites. Further, a constitutive model which captures the membrane stress-strain behavior as a function of fiber properties and the geometry of the fibrous network would be a powerful design tool. Here, mats electrospun from amorphous polyamide are used as a model system. The elastic-plastic behavior of single fibers are obtained in tensile tests. Uniaxial monotonic and cyclic tensile tests are conducted on non-woven mats. The mat exhibits elastic-plastic stress-strain behavior. The transverse strain behavior provides important complementary data, showing a negligible initial Poisson's ratio followed by a transverse:axial strain ratio greater than -1:1 after an axial strain of 0.02. A triangulated framework has been developed to emulate the fibrous network structure of the mat. The micromechanically based model incorporates the elastic-plastic behavior of single fibers into a macroscopic membrane model of the mat. This representative volume element based model is shown to capture the uniaxial elastic-plastic response of the mat under monotonic and cyclic loading. The initial modulus and yield stress of the mat are governed by the fiber properties, the network geometry, and the network density. The transverse strain behavior is linked to discrete deformation mechanisms of the fibrous mat structure including fiber alignment, fiber bending, and network consolidation. The model is further validated in comparison to experiments under different constrained axial loading conditions and found to capture the constraint effect on stiffness, yield, post-yield hardening, and post-yield transverse strain behavior. Due to the direct connection between
ZIP3D: An elastic and elastic-plastic finite-element analysis program for cracked bodies
NASA Technical Reports Server (NTRS)
Shivakumar, K. N.; Newman, J. C., Jr.
1990-01-01
ZIP3D is an elastic and an elastic-plastic finite element program to analyze cracks in three dimensional solids. The program may also be used to analyze uncracked bodies or multi-body problems involving contacting surfaces. For crack problems, the program has several unique features including the calculation of mixed-mode strain energy release rates using the three dimensional virtual crack closure technique, the calculation of the J integral using the equivalent domain integral method, the capability to extend the crack front under monotonic or cyclic loading, and the capability to close or open the crack surfaces during cyclic loading. The theories behind the various aspects of the program are explained briefly. Line-by-line data preparation is presented. Input data and results for an elastic analysis of a surface crack in a plate and for an elastic-plastic analysis of a single-edge-crack-tension specimen are also presented.
Elastic-plastic behavior of a semicircular frame being pressed against a rigid plane
NASA Astrophysics Data System (ADS)
Zhang, X. W.; Yang, J. L.; Yu, T. X.
2008-08-01
As a simplified structural model, a semicircular frame is used to study the crashworthiness behavior of an aircraft fuselage. The quasi-static large elastic-plastic deformation of a semicircular frame in the process of its being pressed against a rigid ground is analyzed. First, based on the linear elastic assumption, the quasi-static large deformation contact process of the frame can be divided into three phases, i.e., point contact, line contact and post-buckling. By means of a shooting method, the relations between the displacement and contact force as well as the distribution of bending moment in the three phases are obtained. Then, by assuming an elastic, perfectly-plastic moment-curvature relationship for the semi-circular frame, the contact process is analyzed in detail to reveal the plastic collapse mechanism, the traveling of plastic hinge and the force-displacement relationship. In order to verify the analysis, a preliminary experiment was conducted, in which two types of half rings with clamped ends were pressed by a rigid plate. In addition, a numerical simulation is also conducted by employing ABAQUS to analyze both rectangular cross-sectional beam and I-beam. Finally, the theoretical predictions are compared with the experimental results and numerical solutions, showing that the elastic-plastic analysis can predict the contact process very well.
Engineering approach for elastic-plastic fracture analysis
Kumar, V; German, M D; Shih, C F
1981-07-01
This report for RP1237-1 presents formulas, charts, and background material that allow calculation of safety margins in ductile structures containing flaws. It is intended as a reference book for engineers who are concerned with design and analysis of flawed structures. The work extends the analysis procedures already available for brittle elastic materials to the tough and ductile steels used in the construction of pressure-boundary components. These new elastic-plastic methods more accurately describe the behavior of ductile materials and show more tolerance to flaws than the elastic methods contained in the ASME Boiler and Pressure Vessel Code and the Code of Federal Regulations.
Cyclic material properties tests supporting elastic-plastic analysis development
Hodge, S.C.; Minicucci, J.M.
1996-11-01
Correlation studies have shown that hardening models currently available in the ABAQUS finite element code (isotropic, kinematic) do not accurately capture the inelastic strain reversals that occur due to structural rebounding from a rapidly applied transient dynamic load. The purpose of the Cyclic Material properties Test program was to obtain response data for the first several cycles of inelastic strain reversal from a cyclic properties test. This data is needed to develop elastic-plastic analysis methods that can accurately predict strains and permanent sets in structures due to rapidly applied transient dynamic loading. Test specimens were cycled at inelastic strain levels typical of rapidly applied transient dynamic analyses (0.5% to 4.0%). In addition to the inelastic response data, cyclic material properties for high yield strength (80 ksi) steel were determined including a cyclic stress-strain curve for a stabilized specimen. Two test methods, the Incremental Step method and the Companion specimen Method, were sued to determine cyclic properties. The incrementally decreasing strain amplitudes in the first loading block of the Incremental Step method test is representative of the response of structures subjected to rapidly applied transient dynamic loads. The inelastic strain history data generated by this test program will be used to support development of a material model that can accurately predict inelastic material behavior including inelastic strain reversals. Additionally, this data can be used to verify material model enhancements to elastic-plastic finite element analysis codes.
Elastic plastic fracture mechanics methodology for surface cracks
NASA Technical Reports Server (NTRS)
Ernst, Hugo A.; Boatwright, D. W.; Curtin, W. J.; Lambert, D. M.
1993-01-01
The Elastic Plastic Fracture Mechanics (EPFM) Methodology has evolved significantly in the last several years. Nevertheless, some of these concepts need to be extended further before the whole methodology can be safely applied to structural parts. Specifically, there is a need to include the effect of constraint in the characterization of material resistance to crack growth and also to extend these methods to the case of 3D defects. As a consequence, this project was started as a 36 month research program with the general objective of developing an EPFM methodology to assess the structural reliability of pressure vessels and other parts of interest to NASA containing defects. This report covers a computer modelling algorithm used to simulate the growth of a semi-elliptical surface crack; the presentation of a finite element investigation that compared the theoretical (HRR) stress field to that produced by elastic and elastic-plastic models; and experimental efforts to characterize three dimensional aspects of fracture present in 'two dimensional', or planar configuration specimens.
Elastic plastic fracture mechanics methodology for surface cracks
NASA Technical Reports Server (NTRS)
Ernst, Hugo A.; Lambert, D. M.
1994-01-01
The Elastic Plastic Fracture Mechanics Methodology has evolved significantly in the last several years. Nevertheless, some of these concepts need to be extended further before the whole methodology can be safely applied to structural parts. Specifically, there is a need to include the effect of constraint in the characterization of material resistance to crack growth and also to extend these methods to the case of 3D defects. As a consequence, this project was started as a 36 month research program with the general objective of developing an elastic plastic fracture mechanics methodology to assess the structural reliability of pressure vessels and other parts of interest to NASA which may contain flaws. The project is divided into three tasks that deal with (1) constraint and thickness effects, (2) three-dimensional cracks, and (3) the Leak-Before-Burst (LBB) criterion. This report period (March 1994 to August 1994) is a continuation of attempts to characterize three dimensional aspects of fracture present in 'two dimensional' or planar configuration specimens (Chapter Two), especially, the determination of, and use of, crack face separation data. Also, included, are a variety of fracture resistance testing results (J(m)R-curve format) and a discussion regarding two materials of NASA interest (6061-T651 Aluminum alloy and 1N718-STA1 nickel-base super alloy) involving a bases for like constraint in terms of ligament dimensions, and their comparison to the resulting J(m)R-curves (Chapter Two).
Elastic plastic fracture mechanics methodology for surface cracks
NASA Astrophysics Data System (ADS)
Ernst, Hugo A.; Lambert, D. M.
1994-08-01
The Elastic Plastic Fracture Mechanics Methodology has evolved significantly in the last several years. Nevertheless, some of these concepts need to be extended further before the whole methodology can be safely applied to structural parts. Specifically, there is a need to include the effect of constraint in the characterization of material resistance to crack growth and also to extend these methods to the case of 3D defects. As a consequence, this project was started as a 36 month research program with the general objective of developing an elastic plastic fracture mechanics methodology to assess the structural reliability of pressure vessels and other parts of interest to NASA which may contain flaws. The project is divided into three tasks that deal with (1) constraint and thickness effects, (2) three-dimensional cracks, and (3) the Leak-Before-Burst (LBB) criterion. This report period (March 1994 to August 1994) is a continuation of attempts to characterize three dimensional aspects of fracture present in 'two dimensional' or planar configuration specimens (Chapter Two), especially, the determination of, and use of, crack face separation data. Also, included, are a variety of fracture resistance testing results (J(m)R-curve format) and a discussion regarding two materials of NASA interest (6061-T651 Aluminum alloy and 1N718-STA1 nickel-base super alloy) involving a bases for like constraint in terms of ligament dimensions, and their comparison to the resulting J(m)R-curves (Chapter Two).
Elastic-plastic mixed-iterative finite element analysis: Implementation and performance assessment
NASA Technical Reports Server (NTRS)
Sutjahjo, Edhi; Chamis, Christos C.
1993-01-01
An elastic-plastic algorithm based on Von Mises and associative flow criteria is implemented in MHOST-a mixed iterative finite element analysis computer program developed by NASA Lewis Research Center. The performance of the resulting elastic-plastic mixed-iterative analysis is examined through a set of convergence studies. Membrane and bending behaviors of 4-node quadrilateral shell finite elements are tested for elastic-plastic performance. Generally, the membrane results are excellent, indicating the implementation of elastic-plastic mixed-iterative analysis is appropriate.
Efficient elastic-plastic design of small foundations
NASA Astrophysics Data System (ADS)
Ohara, G. J.; Cunniff, P. F.
1982-09-01
An elastic plastic design analysis method is presented for small foundations which utilizes an energy criterion to insure against large deflections or unwanted collapse. The interaction effects from direct loads and shears are included, which has the effect of predicting a carrying capacity somewhat less than that of ordinary limit analysis. The energy storage capacity is calculated in a fashion which is conservative since the reduction of the planar moments of inertia is ignored. Several examples are worked out which use various beam like structures to illustrate the enhancement of carrying capacity from the sections contribution and of the indeterminate structural reactions. The results are worked up in detail, both theoretically and by numerical examples to show the ease of application and efficiency of this method.
Elastic-plastic analysis of crack in ductile adhesive joint
Ikeda, Toru; Miyazaki, Noriyuki; Yamashita, Akira; Munakata, Tsuyoshi
1995-11-01
The fracture of a crack in adhesive is important to the structural integrity of adhesive structures and composite materials. Though the fracture toughness of a material should be constant according to fracture mechanics, it is said that the fracture toughness of a crack in an adhesive joint depends on the bond thickness. In the present study, the elastic-plastic stress analyses of a crack in a thin adhesive layer are performed by the combination of the boundary element method and the finite element method. The effect of adhesive thickness on the J-integral, the Q`-factor which is a modified version of the Q-factor, and the crack tip opening displacement (CTOD) are investigated. It is found from the analyses that the CTOD begins to decrease at very thin bond thickness, the Q`-factor being almost constant. The decrease of the fracture toughness at very thin adhesive layer is expected by the present analysis.
NASA Astrophysics Data System (ADS)
Shi, T. F.; Wang, C. J.; Liu, C.; Liu, Y.; Dong, Y. H.; Li, X. Y.
2016-03-01
This paper presents the thermo-magneto-electro-elastic (thermo-MEE) field in an annular plate of heterogeneous multiferroic composite medium subjected to thermal loadings uniformly distributed on the main boundaries. As a prior, the temperature distribution is determined by solving the thermo-conduction equation. Then, the direct displacement method is employed to derive the coupling thermo-MEE field. Finally, numerical calculations are performed to validate the present analysis and to investigate the influence of the material heterogeneity and the multi-field coupling. The present solutions can be readily reduced to those for circular plate upon letting the inner radius tend to zero. The obtained solutions may serve as a benchmark to various numerical codes and simplified analyzes, since no ad hoc hypothesis is adopted in the present work.
Three-dimensional elastic-plastic finite-element analyses of constraint variations in cracked bodies
NASA Technical Reports Server (NTRS)
Newman, J. C., Jr.; Bigelow, C. A.; Shivakumar, K. N.
1993-01-01
Three-dimensional elastic-plastic (small-strain) finite-element analyses were used to study the stresses, deformations, and constraint variations around a straight-through crack in finite-thickness plates for an elastic-perfectly plastic material under monotonic and cyclic loading. Middle-crack tension specimens were analyzed for thicknesses ranging from 1.25 to 20 mm with various crack lengths. Three local constraint parameters, related to the normal, tangential, and hydrostatic stresses, showed similar variations along the crack front for a given thickness and applied stress level. Numerical analyses indicated that cyclic stress history and crack growth reduced the local constraint parameters in the interior of a plate, especially at high applied stress levels. A global constraint factor alpha(sub g) was defined to simulate three-dimensional effects in two-dimensional crack analyses. The global constraint factor was calculated as an average through-the-thickness value over the crack-front plastic region. Values of alpha(sub g) were found to be nearly independent of crack length and were related to the stress-intensity factor for a given thickness.
Elastic Plastic Fracture Analysis of an Aluminum COPV Liner
NASA Technical Reports Server (NTRS)
Forth, Scott; Gregg, Bradley; Bailey, Nathaniel
2012-01-01
Onboard any space-launch vehicle, composite over-wrapped pressure vessels (COPVs) may be utilized by propulsion or environmental control systems. The failure of a COPV has the potential to be catastrophic, resulting in the loss of vehicle, crew or mission. The latest COPV designs have reduced the wall-thickness of the metallic liner to the point where the material strains plastically during operation. At this time, the only method to determine the damage tolerance lifetime (safe-life) of a plastically responding metallic liner is through full-scale COPV testing. Conducting tests costs substantially more and can be far more time consuming than performing an analysis. As a result of this cost, there is a need to establish a qualifying process through the use of a crack growth analysis tool. This paper will discuss fracture analyses of plastically responding metallic liners in COPVs. Uni-axial strain tests have been completed on laboratory specimens to collect elastic-plastic crack growth data. This data has been modeled with the crack growth analysis tool, NASGRO 6.20 to predict the response of laboratory specimens and subsequently the complexity of a COPV.
Finite elastic-plastic deformation of polycrystalline metals
NASA Technical Reports Server (NTRS)
Iwakuma, T.; Nemat-Nasser, S.
1984-01-01
Applying Hill's self-consistent method to finite elastic-plastic deformations, the overall moduli of polycrystalline solids are estimated. The model predicts a Bauschinger effect, hardening, and formation of vertex or corner on the yield surface for both microscopically non-hardening and hardening crystals. The changes in the instantaneous moduli with deformation are examined, and their asymptotic behavior, especially in relation to possible localization of deformations, is discussed. An interesting conclusion is that small second-order quantities, such as shape changes of grains and residual stresses (measured relative to the crystal elastic moduli), have a first-order effect on the overall response, as they lead to a loss of the overall stability by localized deformation. The predicted incipience of localization for a uniaxial deformation in two dimensions depends on the initial yield strain, but the orientation of localization is slightly less than 45 deg with respect to the tensile direction, although the numerical instability makes it very difficult to estimate this direction accurately.
Electrical resistivity response due to elastic-plastic deformations
Stout, R.B.
1987-01-01
The electrical resistivity of many materials is sensitive to changes in the electronic band configurations surrounding the atoms, changes in the electron-phonon interaction cross-sections, and changes in the density of intrinsic defect structures. These changes are most directly dependent on interatomic measures of relative deformation. For this reason, a model for resistivity response is developed in terms of interatomic measures of relative deformation. The relative deformation consists of two terms, a continuous function to describe the recoverable displacement between two atoms in the atomic lattice structure and a functional to describe the nonrecoverable displacement between two atoms as a result of interatomic discontinuities from dislocation kinetics. This model for resistivity extends the classical piezoresistance representation and relates electric resistance change directly to physical mechanisms. An analysis for the resistivity change of a thin foil ideally embedded in a material that undergoes elastic-plastic deformation is presented. For the case of elastic deformations, stress information in the material surrounding the thin foil is inferred for the cases of pure strain coupling boundary conditions, pure stress coupling boundary conditions, and a combination of stress-strain coupling boundary conditions. 42 refs., 4 figs.
Non-Linear Vibration and Thermal Buckling of AN Orthotropic Annular Plate with a Centric Rigid Mass
NASA Astrophysics Data System (ADS)
LI, S.-R.; ZHOU, Y.-H.; SONG, X.
2002-03-01
A computational analysis of the non-linear vibration and thermal post-buckling of a heated orthotropic annular plate with a central rigid mass is examined for the cases of immovably hinged as well as clamped constraint conditions of the outer edge. First, based on von Karman's plate theory and Hamilton's principles, the governing equations, in terms of the displacements of the middle plane, of the problem are derived. Then, upon assuming that harmonic responses of the system exist, the non-linear partial differential equations are converted into the corresponding non-linear ordinary differential equations through elimination of the time variable by using the Kantorovich time-averaging method. Finally, by applying a shooting method, the fundamental responses of the non-linear vibration and thermal post-buckling of the plate are numerically obtained. For some prescribed values of the parameters, such as the material rigidity ratio, temperature rise and so on, the curves of the fundamental frequency versus specified amplitude and the thermal post-buckled equilibrium paths of the plate are numerically presented.
Application of elastic and elastic-plastic fracture mechanics methods to surface flaws
NASA Astrophysics Data System (ADS)
McCabe, Donald E.; Ernst, Hugo A.; Newman, James C., Jr.
Fuel tanks that are a part of the External Tank assembly for the Space Shuttle are made of relatively thin 2219-T87 aluminum plate. These tanks contain about 917 m of fusion weld seam, all of which is nondestructively inspected for flaws and all those found are repaired. The tanks are subsequently proof-tested to a pressure that is sufficiently severe to cause weld metal yielding in a few local regions of the weld seam. The work undertaken in the present project was to develop a capability to predict flaw growth from undetected surface flaws that are assumed to be located in the highly stressed regions. The technical challenge was to develop R-curve prediction capability for surface cracks in specimens that contain the flaws of unusual sizes and shapes deemed to be of interest. The test techniques developed and the elastic-plastic analysis concepts adopted are presented. The flaws of interest were quite small surface cracks that were narrow-deep ellipses that served to exacerbate the technical difficulties involved.
Comparison of aerogrids and punched plates for smoothing flow from short annular diffusers
NASA Technical Reports Server (NTRS)
Rumpf, R. L.; Shippen, W. B.
1972-01-01
Scale model tests were conducted to evaluate the effectiveness of aerogrids and punched plates in producing flat velocity profiles downstream of short diffusers as would be used between the compressor and combustor of advanced aircraft engines. The diffuser had an area ratio of 4.17 and a length-to-inlet-height ratio of 2.07. The aerogrids tested were plates containing 1123 contoured venturis in parallel with geometric blockages of 83, 74, and 61 percent, respectively. The punched plates contained 1123 sharp-edged orifices with blockages of 58 and 30 percent. The results show that aerogrids, with higher effective blockage for the same pressure loss, are more effective flow-smoothing devices than the punched plates. Also, the overall pressure loss decreases and the exit velocity profile becomes flatter as either type of grid is moved closer to the diffuser exit plane.
Multiaxial probabilistic elastic-plastic constitutive simulations of soils
NASA Astrophysics Data System (ADS)
Sadrinezhad, Arezoo
Fokker-Planck-Kolmogorov (FPK) equation approach has recently been developed to simulate elastic-plastic constitutive behaviors of materials with uncertain material properties. The FPK equation approach transforms the stochastic constitutive rate equation, which is a stochastic, nonlinear, ordinary differential equation (ODE) in the stress-pseudo time space into a second-order accurate, deterministic, linear FPK partial differential equation (PDE) in the probability density of stress-pseudo time space. This approach does not suffer from the drawbacks of the traditional approaches such as the Monte Carlo approach and the perturbation approach for solving nonlinear ODEs with random coefficients. In this study, the existing one dimensional FPK framework for probabilistic constitutive modeling of soils is extended to multi--dimension. However, the multivariate FPK PDEs cannot be solved using the traditional mathematical techniques such as finite difference techniques due to their high computational cost. Therefore, computationally efficient algorithms based on the Fourier spectral approach are developed for solving a class of FPK PDEs that arises in probabilistic elasto-plasticity. This class includes linear FPK PDEs in (stress) space and (pseudo) time - having space-independent but time-dependent, and both space- and time-dependent coefficients - with impulse initial conditions and reflecting boundary conditions. The solution algorithms, rely on first mapping the stress space of the governing PDE between 0 and 2pi using the change of coordinates rule, followed by approximating the solution of the PDE in the 2pi-periodic domain by a finite Fourier series in the stress space and unknown time-dependent solution coefficients. Finally, the time-dependent solution coefficients are obtained from the initial condition. The accuracy and efficiency of the developed algorithms are tested. The developed algorithms are used to simulate uniaxial and multiaxial, monotonic and cyclic
Elastic-plastic finite-element analyses of thermally cycled double-edge wedge specimens
NASA Technical Reports Server (NTRS)
Kaufman, A.; Hunt, L. E.
1982-01-01
Elastic-plastic stress-strain analyses were performed for double-edge wedge specimens subjected to thermal cycling in fluidized beds at 316 and 1088 C. Four cases involving different nickel-base alloys (IN 100, Mar M-200, NASA TAZ-8A, and Rene 80) were analyzed by using the MARC nonlinear, finite element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions obtained by using the NASTRAN and ISO3DQ computer programs. Equivalent total strain ranges at the critical locations calculated by elastic analyses agreed within 3 percent with those calculated from elastic-plastic analyses. The elastic analyses always resulted in compressive mean stresses at the critical locations. However, elastic-plastic analyses showed tensile mean stresses for two of the four alloys and an increase in the compressive mean stress for the highest plastic strain case.
Elastic-plastic finite-element analyses of thermally cycled single-edge wedge specimens
NASA Technical Reports Server (NTRS)
Kaufman, A.
1982-01-01
Elastic-plastic stress-strain analyses were performed for single-edge wedge alloys subjected to thermal cycling in fluidized beds. Three cases (NASA TAZ-8A alloy under one cycling condition and 316 stainless steel alloy under two cycling conditions) were analyzed by using the MARC nonlinear, finite-element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions that used the NASTRAN and ISO3DQ computer programs. The NASA TAZ-8A case exhibited no plastic strains, and the elastic and elastic-plastic analyses gave identical results. Elastic-plastic analyses of the 316 stainless steel alloy showed plastic strain reversal with a shift of the mean stresses in the compressive direction. The maximum equivalent total strain ranges for these cases were 13 to 22 percent greater than that calculated from elastic analyses.
Seismic elastic-plastic time history analysis and reliability study of quayside container crane
NASA Astrophysics Data System (ADS)
Jin, Yulong; Li, Zengguang
2010-06-01
Quayside container crane is a kind of huge dimension steel structure, which is the major equipment used for handling container at modern ports. With the aim to validate the safety and reliability of the crane under seismic loads, besides conventional analysis, elastic-plastic time history analysis under rare seismic intensity is carried out. An ideal finite element (FEM) elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes. Furthermore, according to elastic-plastic time history analysis theory, deformation, stress and damage pattern of the structure under rare seismic intensity are investigated. Based on the above analysis, the established reliability model according to the reliability theory, together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis. The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity, and the structure needs to be reinforced.
Finite-element formulations for problems of large elastic-plastic deformation
NASA Technical Reports Server (NTRS)
Mcmeeking, R. M.; Rice, J. R.
1975-01-01
An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is ideally suited to isotropically hardening Prandtl-Reuss materials. Further, the formulation is given in a manner which allows any conventional finite element program, for 'small strain' elastic-plastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. The paper closes with a unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures. Further, a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain, and the inadequacies of some of these are commented upon.
An Elastic Plastic Contact Model with Strain Hardening for the LAMMPS Granular Package
Kuhr, Bryan; Brake, Matthew Robert; Lechman, Jeremy B.
2015-03-01
The following details the implementation of an analytical elastic plastic contact model with strain hardening for normal im pacts into the LAMMPS granular package. The model assumes that, upon impact, the co llision has a period of elastic loading followed by a period of mixed elastic plas tic loading, with contributions to each mechanism estimated by a hyperbolic seca nt weight function. This function is implemented in the LAMMPS source code as the pair style gran/ep/history. Preliminary tests, simulating the pouring of pure nickel spheres, showed the elastic/plastic model took 1.66x as long as similar runs using gran/hertz/history.
Implementation of a trapezoidal ring element in NASTRAN for elastic-plastic analysis
NASA Technical Reports Server (NTRS)
Chen, P. C. T.; Ohara, G. P.
1980-01-01
The explicit expressions for an elastic-plastic trapezoidal ring element are presented and implemented in NASTRAN computer program. The material is assumed to obey the von Mises' yield criterion, isotropic hardening rule and the Prandtl-Reuss flow relations. For the purpose of demonstration, two elastic-plastic problems are solved and compared with previous results. The first is a plane-strain tube under uniform internal pressure and the second, a finite-length tube loaded over part of its inner surface. A very good agreement was found in both test problems.
An Elastic-Plastic Damage Model for Long-Fiber Thermoplastics
Nguyen, Ba Nghiep; Kunc, Vlastimil
2009-08-11
This article proposes an elastic-plastic damage model that combines micromechanical modeling with continuum damage mechanics to predict the stress-strain response of injection-molded long-fiber thermoplastics. The model accounts for distributions of orientation and length of elastic fibers embedded in a thermoplastic matrix whose behavior is elastic-plastic and damageable. The elastic-plastic damage behavior of the matrix is described by the modified Ramberg-Osgood relation and the three-dimensional damage model in deformation assuming isotropic hardening. Fiber/matrix debonding is accounted for using a parameter that governs the fiber/matrix interface compliance. A linear relationship between this parameter and the matrix damage variable is assumed. First, the elastic-plastic damage behavior of the reference aligned-fiber composite containing the same fiber volume fraction and length distribution as the actual composite is computed using an incremental Eshelby-Mori-Tanaka mean field approach. The incremental response of the latter is then obtained from the solution for the aligned-fiber composite by averaging over all fiber orientations. The model is validated against the experimental stress-strain results obtained for long-glass-fiber/polypropylene specimens.
Development of Advanced Life Prediction Tools for Elastic-Plastic Fatigue Crack Growth
NASA Technical Reports Server (NTRS)
Gregg, Wayne; McGill, Preston; Swanson, Greg; Wells, Doug; Throckmorton, D. A. (Technical Monitor)
2001-01-01
The objective of this viewgraph presentation is to develop a systematic approach to improving the fracture control process, including analytical tools, standards, guidelines, and awareness. Analytical tools specifically for elastic-plastic fracture analysis is a regime that is currently empirical for the Space Shuttle External Tank (ET) and is handled by simulated service testing of pre-cracked panels.
NASA Astrophysics Data System (ADS)
Tornabene, Francesco; Viola, Erasmo; Inman, Daniel J.
2009-12-01
This paper focuses on the dynamic behavior of functionally graded conical, cylindrical shells and annular plates. The last two structures are obtained as special cases of the conical shell formulation. The first-order shear deformation theory (FSDT) is used to analyze the above moderately thick structural elements. The treatment is developed within the theory of linear elasticity, when materials are assumed to be isotropic and inhomogeneous through the thickness direction. The two-constituent functionally graded shell consists of ceramic and metal that are graded through the thickness, from one surface of the shell to the other. Two different power-law distributions are considered for the ceramic volume fraction. The homogeneous isotropic material is inferred as a special case of functionally graded materials (FGM). The governing equations of motion, expressed as functions of five kinematic parameters, are discretized by means of the generalized differential quadrature (GDQ) method. The discretization of the system leads to a standard linear eigenvalue problem, where two independent variables are involved without using the Fourier modal expansion methodology. For the homogeneous isotropic special case, numerical solutions are compared with the ones obtained using commercial programs such as Abaqus, Ansys, Nastran, Straus, Pro/Mechanica. Very good agreement is observed. Furthermore, the convergence rate of natural frequencies is shown to be very fast and the stability of the numerical methodology is very good. Different typologies of non-uniform grid point distributions are considered. Finally, for the functionally graded material case numerical results illustrate the influence of the power-law exponent and of the power-law distribution choice on the mechanical behavior of shell structures.
Elastic-plastic failure analysis of pressure burst tests of thin toroidal shells
Jones, D.P.; Holliday, J.E.; Larson, L.D.
1998-07-01
This paper provides a comparison between test and analysis results for bursting of thin toroidal shells. Testing was done by pressurizing two toroidal shells until failure by bursting. An analytical criterion for bursting is developed based on good agreement between structural instability predicted by large strain-large displacement elastic-plastic finite element analysis and observed burst pressure obtained from test. The failures were characterized by loss of local stability of the membrane section of the shells consistent with the predictions from the finite element analysis. Good agreement between measured and predicted burst pressure suggests that incipient structural instability as calculated by an elastic-plastic finite element analysis is a reasonable way to calculate the bursting pressure of thin membrane structures.
On the solution of elastic-plastic static and dynamic postbuckling collapse of general structure
NASA Technical Reports Server (NTRS)
Padovan, J.; Tovichakchaikul, S.
1983-01-01
Many investigations have considered structural collapse from strictly the transient point of view. While such an approach is ideally correct, certain difficulties have to be overcome in its implementation. The present investigation is concerned with the development of self-adaptive algorithms which make it possible to conduct the analysis of both static elastic and elastic-plastic postbuckling, as well as static loading to the onset of buckling followed by subsequent dynamic postbuckling. The approach employed to solve the static portion of loading is to extend the constrained Incremental Newton-Raphson (INR) algorithm by incorporating elastic-plastic constitutive characterizations. Large deformation moderate strain theory is adopted to establish the overall strategy. Attention is given to governing field equations, aspects of algorithmic development, and numerical experiments conducted to illustrate the efficiency and stability of the developed schemes.
Weinacht, D.J.
1995-12-01
A fully coupled thermomechanical diffusion theory describing the thermal and mechanically assisted mass transport of dilute mobile constituents in an elastic solid is extended to include the effects of elastic-plastic deformation. Using the principles of modern continuum mechanics and classical plasticity theory, balance laws and constitutive equations are derived for a continuum composed of an immobile, but deformable, parent material and a dilute mobile constituent. The resulting equations are cast into a finite element formulation for incorporation into a finite element code. This code serves as a tool for modeling thermomechanically assisted phenomena in elastic-plastic solids. A number of simplified problems for which analytical solutions can be derived are used to benchmark the theory and finite element code. Potential uses of the numerical implementation of the theory are demonstrated using two problems. Specifically, tritium diffusion in a titanium alloy and hydrogen diffusion in a multiphase stainless steel are examined.
Finite element formulations for problems of large elastic-plastic deformation
NASA Technical Reports Server (NTRS)
Mcmeeking, R. M.; Rice, J. R.
1974-01-01
An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is suited to isotropically hardening Prandtl-Reuss materials. The formulation is given in a manner which allows any conventional finite element program, for "small strain" elasticplastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. A unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures, and a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain.
Elastic-plastic deformations of a beam with the SD-effect
Pavilaynen, Galina V.
2015-03-10
The results for the bending of a cantilever beam with the SD-effect under a concentrated load are discussed. To solve this problem, the standard Bernoulli-Euler hypotheses for beams and the Ilyushin model of perfect plasticity are used. The problem is solved analytically for structural steel A40X. The SD-effect for elastic-plastic deformations is studied. The solutions for beam made of isotropic material and material with the SD-effect are compared.
Elastic-plastic analysis using a triangular ring element in NASTRAN
NASA Technical Reports Server (NTRS)
Chen, P. C. T.
1980-01-01
An elastic plastic triangular ring element is implemented in NASTRAN computer program. The plane strain problem of partially plastic thick walled cylinder under internal pressure is solved and compared with the earlier finite difference solution. A very good agreement has been reached. In order to demonstrate its application to more general problems, an overloaded thread problem for the British Standard Buttress is examined. The maximum axial and principal stresses are located and their values are determined as functions of loadings.
Solution of elastic-plastic stress analysis problems by the p-version of the finite element method
NASA Technical Reports Server (NTRS)
Szabo, Barna A.; Actis, Ricardo L.; Holzer, Stefan M.
1993-01-01
The solution of small strain elastic-plastic stress analysis problems by the p-version of the finite element method is discussed. The formulation is based on the deformation theory of plasticity and the displacement method. Practical realization of controlling discretization errors for elastic-plastic problems is the main focus. Numerical examples which include comparisons between the deformation and incremental theories of plasticity under tight control of discretization errors are presented.
Solution of elastic-plastic stress analysis problems by the P-version of the finite element method
Szabo, B.A.; Holzer, S.M.; Actis, R.L.
1995-12-31
The solution of small-strain elastic-plastic stress analysis problems by the p-version of the finite element method is discussed. The formulation is based on the deformation theory of plasticity and the displacement method. Practical realization of controlling discretization errors for elastic-plastic problems is the main focus of the paper. Numerical examples, which include comparisons between the deformation and incremental theories of plasticity under tight control of discretization errors, are presented.
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NASA Astrophysics Data System (ADS)
Liang, Xu; Wang, Zhenyu; Wang, Lizhong; Liu, Guohua
2014-06-01
The three-dimensional transient analysis of functionally graded annular plates with arbitrary boundary conditions is carried out in this paper. The material properties of the FGM plate are assumed to vary smoothly in an exponential law along the thickness direction. The plate is assumed to rest on a two parameter viscoelastic foundation. A semi-analytical method, which integrates the state space method (SSM), Laplace transform and its inversion, as well as the one-dimensional differential quadrature method (DQM), is proposed to obtain the transient response of the plate. The state space method is used to obtain the analytical solution in the thickness direction. The differential quadrature method is employed to approximate the solution in the radial direction. The Laplace transform and the numerical inversion are used to obtain the solution in time domain. Numerical results show a good agreement between the response histories obtained by the present method and finite element method. The effects of the boundary conditions at the edges, the material graded index, the Winkler and shearing layer elastic coefficients, and the damping coefficient are studied. Numerical examples show that the peak response decreases as the material graded index, the Winkler and shearing layer elastic coefficients, and the damping coefficient increase. The results obtained in this paper can serve as benchmark data in further research.
NASA Astrophysics Data System (ADS)
Haddag, Badis; Abed-Meraim, Farid; Balan, Tudor
2007-05-01
In this work, an advanced anisotropic elastic-plasticity model is combined with a damage model and a strain localization criterion in the aim to describe accurately the mechanical behavior of sheet metals. Large strain, fully three-dimensional, implicit time integration algorithms are developed for this model and implemented in the finite element code Abaqus. The resulting code is used to predict the strain localization limits as well as the springback after forming of sheet steels. The impact of strain-path dependent hardening models on the limit strains and on the amount of springback is addressed.
NASA Technical Reports Server (NTRS)
Allen, Phillip A.; Wells, Douglas N.
2013-01-01
No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.
Solonick, W.
1996-11-01
Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.
An Elastic-Plastic and Strength Prediction Model for Injection-Molded Long-Fiber Thermoplastics
Nguyen, Ba Nghiep; Kunc, Vlastimil; Phelps, Jay; Tucker III, Charles L.; Bapanapalli, Satish K.
2008-09-01
This paper applies a recently developed model to predict the elastic-plastic stress/strain response and strength of injection-molded long-fiber thermoplastics (LFTs). The model combines a micro-macro constitutive modeling approach with experimental characterization and modeling of the composite microstructure to determine the composite stress/strain response and strength. Specifically, it accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length, orientation and volume fraction distributions in the composite formed by the injection-molding process. Injection-molded-long-glass-fiber/polypropylene (PP) specimens were prepared for mechanical characterization and testing. Fiber length, orientation, and volume fraction distributions were then measured at some selected locations for use in the computation. Fiber orientations in these specimens were also predicted using an anisotropic rotary diffusion model developed for LFTs. The stress-strain response of the as-formed composite was computed by an incremental procedure that uses the Eshelby’s equivalent inclusion method, the Mori-Tanaka assumption and a fiber orientation averaging technique. The model has been validated against the experimental stress-strain results obtained for these long-glass-fiber/PP specimens.
Elastic-plastic characterization of a cast stainless steep pipe elbow material
Joyce, J.A.; Hackett, E.M.; Roe, C.
1992-01-01
Tests conducted in Japan as part of the High Level Vibration Test (HLVT) program for reactor piping systems revealed fatigue crack growth in a cast stainless steel pipe elbow. The material tested was equivalent to ASME SA-351CF8M. The David Taylor Research Center (DTRC) was tasked to developed the appropriate material property data to characterize cyclic deformation, cyclic elastic-plastic crack growth and ductile tearing resistance in the pipe elbow material. It was found that the cast stainless steel was very resistant to ductile crack extension. J-R curves essentially followed a blunting behavior to very high J levels. Low cycle fatigue crack growth rate data obtained on this material using a cyclic J integral approach was consistent with the high cycle fatigue crack growth rate and with a standard textbook correlation equation typical for this type of material. Evaluation of crack closure effects was essential to accurately determine the crack driving force for cyclic elastic- plastic crack growth in this material. SEM examination of several of the cyclic J test fracture surfaces indicated that fatigue was the primary mode of fracture with ductile crack extension intervening only during the last few cycles of loading.
Hodge, S.C.; Minicucci, J.M.
1997-11-01
A test program was undertaken to demonstrate the ability of elastic-plastic finite element methods to predict dynamic inelastic response for simple structural members. Cantilever and fixed-beam specimens were tested to levels that produced plastic straining in the range of 2.0% and to 3.0% and permanent sets. Acceleration, strain, and displacement data were recorded for use in analytical correlation. Correlation analyses were performed using the ABAQUS finite element code. Results of the correlation show that current elastic-plastic analysis techniques accurately capture dynamic inelastic response (displacement, acceleration) due to rapidly applied dynamic loading. Peak elastic and inelastic surface strains are accurately predicted. To accurately capture inelastic straining near connections, a solid model, including fillet welds, is necessary. The hardening models currently available in the ABAQUS code (isotropic, kinematic) do not accurately capture inelastic strain reversals caused by specimen rebound. Analyses performed consistently underpredicted the peak strain level of the first inelastic reversal and the rebound deflection and overpredicted the permanent set of structures experiencing inelastic rebound. Based on these findings, an improved hardening model is being implemented in the ABAQUS code by the developers. The intent of this model upgrade is to improve the ability of the program to capture inelastic strain reversals and to predict permanent sets.
Analytical modeling of elastic-plastic wave behavior near grain boundaries in crystalline materials
Loomis, Eric; Greenfield, Scott; Luo, Shengnian; Swift, Damian; Peralta, Pedro
2009-01-01
It is well known that changes in material properties across an interface will produce differences in the behavior of reflected and transmitted waves. This is seen frequently in planar impact experiments, and to a lesser extent, oblique impacts. In anisotropic elastic materials, wave behavior as a function of direction is usually accomplished with the aid of velocity surfaces, a graphical method for predicting wave scattering configurations. They have expanded this method to account for inelastic deformation due to crystal plasticity. The set of derived equations could not be put into a characteristic form, but instead led to an implicit problem. to overcome this difficulty an algorithm was developed to search the parameters space defined by a wave normal vector, particle velocity vector, and a wave speed. A solution was said to exist when a set from this parameter space satisfied the governing vector equation. Using this technique they can predict the anisotropic elastic-plastic velocity surfaces and grain boundary scattering configuration for crystalline materials undergoing deformation by slip. Specifically, they have calculated the configuration of scattered elastic-plastic waves in anisotropic NiAl for an incident compressional wave propagating along a <111> direction and contacting a 45 degree inclined grain boundary and found that large amplitude transmitted waves exist owing to the fact that the wave surface geometry forces it to propagate near the zero Schmid factor direction <100>.
Development of a Practical Methodology for Elastic-Plastic and Fully Plastic Fatigue Crack Growth
NASA Technical Reports Server (NTRS)
McClung, R. C.; Chell, G. G.; Lee, Y.-D.; Russell, D. A.; Orient, G. E.
1999-01-01
A practical engineering methodology has been developed to analyze and predict fatigue crack growth rates under elastic-plastic and fully plastic conditions. The methodology employs the closure-corrected effective range of the J-integral, (Delta)J(sub eff), as the governing parameter. The methodology contains original and literature J and (Delta)J solutions for specific geometries, along with general methods for estimating J for other geometries and other loading conditions, including combined mechanical loading and combined primary and secondary loading. The methodology also contains specific practical algorithms that translate a J solution into a prediction of fatigue crack growth rate or life, including methods for determining crack opening levels, crack instability conditions, and material properties. A critical core subset of the J solutions and the practical algorithms has been implemented into independent elastic-plastic NASGRO modules. All components of the entire methodology, including the NASGRO modules, have been verified through analysis and experiment, and limits of applicability have been identified.
Development of a Practical Methodology for Elastic-Plastic and Fully Plastic Fatigue Crack Growth
NASA Technical Reports Server (NTRS)
McClung, R. C.; Chell, G. G.; Lee, Y. -D.; Russell, D. A.; Orient, G. E.
1999-01-01
A practical engineering methodology has been developed to analyze and predict fatigue crack growth rates under elastic-plastic and fully plastic conditions. The methodology employs the closure-corrected effective range of the J-integral, delta J(sub eff) as the governing parameter. The methodology contains original and literature J and delta J solutions for specific geometries, along with general methods for estimating J for other geometries and other loading conditions, including combined mechanical loading and combined primary and secondary loading. The methodology also contains specific practical algorithms that translate a J solution into a prediction of fatigue crack growth rate or life, including methods for determining crack opening levels, crack instability conditions, and material properties. A critical core subset of the J solutions and the practical algorithms has been implemented into independent elastic-plastic NASGRO modules. All components of the entire methodology, including the NASGRO modules, have been verified through analysis and experiment, and limits of applicability have been identified.
On a compressed elastic-plastic column optimized for post-buckling behaviour
NASA Astrophysics Data System (ADS)
Bielski, Jan; Bochenek, Bogdan
2008-12-01
A model of a column is proposed in order to analyse the post-buckling behaviour of a structural element in the elastic-plastic deformation range. The ideal two point I-section applied here simplifies the deformation analysis, that is, the problem of development of plastic zones in a section is eliminated, but still gives the possibility for qualitative analysis and optimization of the post-critical equilibrium paths. The coefficients of linear or parabolic variability of thickness of the flanges and their distance (web width) are accepted as model parameters and hence could be used for design variables in the optimization procedure. Moreover, the stiffness of an additional elastic support of the free end of the beam is also included as a parameter or design variable. A material model is employed with non-linear asymptotic isotropic hardening without the Bauschinger effect. Change of the tangent modulus is continuous and smooth during the transition from the elastic to plastic deformation range. The main goal of the analysis is to determine the values of the design variables for which the post-critical equilibrium paths are stable at least in the specified range of a generalized displacement. The constraints for the constant volume of the flanges and web material are applied. The inequality constraints are imposed on the flange thickness and web width. Various formulations of the optimization problem are proposed for all types of non-linear behaviour, including elastic or plastic buckling and elastic or elastic-plastic post-buckling deformation.
W.R. Solonick
2003-04-01
Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local , or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.
NASA Astrophysics Data System (ADS)
Ma, Yanling; Zhang, Shu Yan; Goodway, Chris; Done, Robert; Evans, Beth; Kirichek, Oleg; Bowden, Zoë
2012-09-01
Positions of elastic plastic interfaces play a vital role in safe design and safe use of high pressure vessels. The ENGIN-X neutron diffractometer at the ISIS facility was used to measure the residual strain profiles in a series of aluminium vessels which had been subjected to different pressure levels. The positions of elastic plastic interfaces of the autofrettaged pressure vessels were identified. The results revealed that the residual strain magnitude and the depth of the plastic region will increase with increasing autofrettage pressure level. When autofrettage pressure produces an elastic-plastic boundary at a greater depth than the geometric mean position of the vessel wall, reverse yielding will occur, hence the loss of the vessels' elastic ability to its subsequent loading. The neutron experimental results agreed well with both the suggestions from existing literatures and the results from FE simulations.
NASA Astrophysics Data System (ADS)
Proust, Gwénaëlle; Kalidindi, Surya R.
2006-08-01
Microstructure-sensitive design (MSD) is a novel mathematical framework that facilitates a rigorous consideration of the material microstructure as a continuous design variable in the engineering design enterprise [Adams, B.L., Henrie, A., Henrie, B., Lyon, M., Kalidindi, S.R., Garmestani, H., 2001. Microstructure-sensitive design of a compliant beam. J. Mech. Phys. Solids 49(8), 1639-1663; Adams, B.L., Lyon, M., Henrie, B., 2004. Microstructures by design: linear problems in elastic-plastic design. Int. J. Plasticity 20(8-9), 1577-1602; Kalidindi, S.R., Houskamp, J.R., Lyons, M., Adams, B.L., 2004. Microstructure sensitive design of an orthotropic plate subjected to tensile load. Int. J. Plasticity 20(8-9), 1561-1575]. MSD employs spectral representations of the local state distribution functions in describing the microstructure quantitatively, and these in turn enable development of invertible linkages between microstructure and effective properties using established homogenization (composite) theories. As a natural extension of the recent publications in MSD, we provide in this paper a detailed account of the methods that can be readily used by mechanical designers to construct first-order elastic-plastic property closures. The main focus in this paper is on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the elastic and yield properties of cubic (fcc and bcc) polycrystalline metals. The following specific advances are described in this paper: (i) derivation of rigorous first-order bounds for the off-diagonal terms of the effective elastic stiffness tensor and their incorporation in the MSD framework, (ii) delineation of the union of the property closures corresponding to both the upper and lower bound theories resulting in comprehensive first-order closures, (iii) development of generalized and readily usable expressions for effective anisotropic elastic-plastic properties
Elastic-plastic analysis of AS4/PEEK composite laminate using a one-parameter plasticity model
NASA Technical Reports Server (NTRS)
Sun, C. T.; Yoon, K. J.
1992-01-01
A one-parameter plasticity model was shown to adequately describe the plastic deformation of AS4/PEEK (APC-2) unidirectional thermoplastic composite. This model was verified further for unidirectional and laminated composite panels with and without a hole. The elastic-plastic stress-strain relations of coupon specimens were measured and compared with those predicted by the finite element analysis using the one-parameter plasticity model. The results show that the one-parameter plasticity model is suitable for the analysis of elastic-plastic deformation of AS4/PEEK composite laminates.
Large deflection elastic-plastic dynamic response of stiffened shells of revolution
NASA Technical Reports Server (NTRS)
Stricklin, J. A.; Haisler, W. E.; Vonriesemann, W. A.; Leick, R. D.; Hunsaker, B.; Saczalski, K. J.
1972-01-01
The formulation and check out porblems for a computer code DYNAPLAS, which analyzes the large deflection elastic-plastic dynamic response of stiffened shells of revolution, are presented. The formulation for special discretization is by the finite element method with finite differences being used for the evaluation of the pseudo forces due to material and geometric nonlinearities. Time integration is by the Houbolt method. The stiffeners may be due to concentrated or distributed eccentric rings and spring supports at arbitrary angles around the circumference of the elements. Check out porblems include the comparison of solutions from DYNAPLAS with experimental and other computer solutions for rings, conical and cylindrical shells and a curved panel. A hypothetical submarine including stiffeners and missile tube is studied under a combination of hydrostatic and dynamically applied asymmetrical pressure loadings.
Elastic-plastic cube model for ultrasonic friction reduction via Poisson's effect.
Dong, Sheng; Dapino, Marcelo J
2014-01-01
Ultrasonic friction reduction has been studied experimentally and theoretically. This paper presents a new elastic-plastic cube model which can be applied to various ultrasonic lubrication cases. A cube is used to represent all the contacting asperities of two surfaces. Friction force is considered as the product of the tangential contact stiffness and the deformation of the cube. Ultrasonic vibrations are projected onto three orthogonal directions, separately changing contact parameters and deformations. Hence, the overall change of friction forces. Experiments are conducted to examine ultrasonic friction reduction using different materials under normal loads that vary from 40 N to 240 N. Ultrasonic vibrations are generated both in longitudinal and vertical (out-of-plane) directions by way of the Poisson effect. The tests show up to 60% friction reduction; model simulations describe the trends observed experimentally. PMID:23850422
Simplified computational methods for elastic and elastic-plastic fracture problems
NASA Technical Reports Server (NTRS)
Atluri, Satya N.
1992-01-01
An overview is given of some of the recent (1984-1991) developments in computational/analytical methods in the mechanics of fractures. Topics covered include analytical solutions for elliptical or circular cracks embedded in isotropic or transversely isotropic solids, with crack faces being subjected to arbitrary tractions; finite element or boundary element alternating methods for two or three dimensional crack problems; a 'direct stiffness' method for stiffened panels with flexible fasteners and with multiple cracks; multiple site damage near a row of fastener holes; an analysis of cracks with bonded repair patches; methods for the generation of weight functions for two and three dimensional crack problems; and domain-integral methods for elastic-plastic or inelastic crack mechanics.
Loading-unloading of an elastic-plastic adhesive spherical microcontact.
Kadin, Y; Kligerman, Y; Etsion, I
2008-05-01
A numerical solution is presented for a single load-unload cycle of an adhesive contact between an elastic-plastic sphere and a rigid flat. The interacting forces between the sphere and the flat are obtained through connecting nonlinear spring elements having force-displacement behavior that obeys the Lennard-Jones potential. Kinematic, rather than isotropic, hardening is assumed for the sphere material to account for possible secondary plastification during the unloading. The well-known Tabor parameter and a plasticity parameter are shown to be the two main dimensionless parameters governing the problem. The effects of these two parameters on the load-approach curves, on the plastically deformed sphere profiles, and on the plastic strain fields inside the sphere are presented, showing different modes of separation during the unloading. PMID:18275967
Dynamic Bending Tolerance and Elastic-Plastic Material Properties of the Human Femur
Funk, J. R.; Kerrigan, J. R.; Crandall, J. R.
2004-01-01
The objective of this study was to provide data on the structural tolerance and material properties of the human femur in dynamic bending. Fifteen (15) isolated femurs from eight (8) males were tested in either posterior-to-anterior or lateral-to-medial three-point bending. The failure moment was 458 ± 95 Nm and did not differ significantly with loading direction. A method was developed to estimate the elastic-plastic material properties of the bone using both force-deflection data and strain gauge measurements. The bone material appeared to yield at about one third of the ultimate strain level prior to fracture. It is hoped that these data will aid in the development of injury criteria and finite element models for predicting injuries to pedestrians and vehicle occupants. PMID:15319127
Comparison of experiment and theory for elastic-plastic plane strain crack growth
Hermann, L; Rice, J R
1980-02-01
Recent theoretical results on elastic-plastic plane strain crack growth, and experimental results for crack growth in a 4140 steel in terms of the theoretical concepts are reviewed. The theory is based on a recent asymptotic analysis of crack surface opening and strain distributions at a quasi-statically advancing crack tip in an ideally-plastic solid. The analysis is incomplete in that some of the parameters which appear in it are known only approximately, especially at large scale yielding. Nevertheless, it suffices to derive a relation between the imposed loading and amount of crack growth, prior to general yielding, based on the assumption that a geometrically similar near-tip crack profile is maintained during growth. The resulting predictions for the variation of J with crack growth are found to fit well to the experimental results obtained on deeply cracked compact specimens.
Expansion/contraction of a spherical elastic/plastic shell revisited
NASA Astrophysics Data System (ADS)
Alexandrov, Sergei; Pirumov, Alexander; Jeng, Yeau-Ren
2015-05-01
A semi-analytic solution for the elastic/plastic distribution of stress and strain in a spherical shell subject to pressure over its inner and outer radii and subsequent unloading is presented. The Bauschinger effect is taken into account. The flow theory of plasticity is adopted in conjunction with quite an arbitrary yield criterion and its associated flow rule. The yield stress is an arbitrary function of the equivalent strain. It is shown that the boundary value problem is significantly simplified if the equivalent strain is used as an independent variable instead of the radial coordinate. In particular, numerical methods are only necessary to evaluate ordinary integrals and solve simple transcendental equations. An illustrative example is provided to demonstrate the distribution of residual stresses and strains.
Addendum to the User Manual for NASGRO Elastic-Plastic Fracture Mechanics Software Module
NASA Technical Reports Server (NTRS)
Gregg, M. Wayne (Technical Monitor); Chell, Graham; Gardner, Brian
2003-01-01
The elastic-plastic fracture mechanics modules in NASGRO have been enhanced by the addition of of the following: new J-integral solutions based on the reference stress method and finite element solutions; the extension of the critical crack and critical load modules for cracks with two degrees of freedom that tear and failure by ductile instability; the addition of a proof test analysis module that includes safe life analysis, calculates proof loads, and determines the flaw screening 1 capability for a given proof load; the addition of a tear-fatigue module for ductile materials that simultaneously tear and extend by fatigue; and a multiple cycle proof test module for estimating service reliability following a proof test.
Application of an Uncoupled Elastic-plastic-creep Constitutive Model to Metals at High Temperature
NASA Technical Reports Server (NTRS)
Haisler, W. E.
1983-01-01
A uniaxial, uncoupled constitutive model to predict the response of thermal and rate dependent elastic-plastic material behavior is presented. The model is based on an incremental classicial plasticity theory extended to account for thermal, creep, and transient temperature conditions. Revisions to he combined hardening rule of the theory allow for better representation of cyclic phenomenon including the high rate of strain hardening upon cyclic reyield and cyclic saturation. An alternative approach is taken to model the rate dependent inelastic deformation which utilizes hysteresis loops and stress relaxation test data at various temperatures. The model is evaluated and compared to experiments which involve various thermal and mechanical load histories on 5086 aluminum alloy, 304 stainless steel and Hastelloy-X.
An elastic-plastic finite element analysis of crack initiation, stable crack growth, and instability
NASA Technical Reports Server (NTRS)
Newman, J. C., Jr.
1984-01-01
Studies have been conducted to develop efficient techniques to simulate crack extension and to examine various local and global fracture criteria. Of the considered criteria, the crack-tip-opening angle (CTOA) or displacement (CTOD) at a specified distance from the crack tip was shown to be most suited for modeling stable crack growth and instability during the fracture process. The results obtained in a number of studies show the necessity for studying different crack configurations when assessing the validity of any fracture criteria. One of the objectives of the present investigation is related to a critical evaluation of the CTOD growth criterion using an elastic-plastic finite element analysis under monotonic loading to failure. The analysis was found to predict three stages of crack growth behavior under monotonic loading to failure. Calculated CTOD values agreed well with experimental values for crack growth initiation.
Elastic-Plastic Thermal Stress Analysis of a High-Pressure Cryogenic Storage Tank
NASA Technical Reports Server (NTRS)
Barker, J. Mark; Field, Robert E. (Technical Monitor)
2003-01-01
The thermal stresses on a cryogenic storage tank contribute strongly to the state of stress of the tank material and its ability to withstand operational stresses. These thermal stresses also affect the growth of any surface damage that might occur in the tank walls. These stresses are particularly of concern during the initial cooldown period for a new tank placed into service, and during any subsequent thermal cycles. A previous preliminary elastic analysis showed that the thermal stress on the inner wall would reach approximately 1,000MPa (145,000 psi). This stress far exceeds the ASTM specified room temperature values for both yield (170MPa) and ultimate (485 MPa) strength for 304L stainless steel. The present analysis determines the thermal stresses using an elastic-plastic model. The commercial software application ANSYS was used to determine the transient spatial temperature profile and the associated spatial thermal stress profiles in a segment of a thick-walled vessel during a typical cooldown process. A strictly elastic analysis using standard material properties for 304L stainless steel showed that the maximum thermal stress on the inner and outer walls was approximately 960 MPa (tensile) and - 270 MPa (compressive) respectively. These values occurred early in the cooldown process, but at different times, An elastic-plastic analysis showed significantly reducing stress, as expected due to the plastic deformation of the material. The maximum stress for the inner wall was approximately 225 MPa (tensile), while the maximum stress for the outer wall was approximately - 130 MPa (compressive).
A plane stress finite element model for elastic-plastic mode I/II crack growth
NASA Astrophysics Data System (ADS)
James, Mark Anthony
A finite element program has been developed to perform quasi-static, elastic-plastic crack growth simulations. The model provides a general framework for mixed-mode I/II elastic-plastic fracture analysis using small strain assumptions and plane stress, plane strain, and axisymmetric finite elements. Cracks are modeled explicitly in the mesh. As the cracks propagate, automatic remeshing algorithms delete the mesh local to the crack tip, extend the crack, and build a new mesh around the new tip. State variable mapping algorithms transfer stresses and displacements from the old mesh to the new mesh. The von Mises material model is implemented in the context of a non-linear Newton solution scheme. The fracture criterion is the critical crack tip opening displacement, and crack direction is predicted by the maximum tensile stress criterion at the crack tip. The implementation can accommodate multiple curving and interacting cracks. An additional fracture algorithm based on nodal release can be used to simulate fracture along a horizontal plane of symmetry. A core of plane strain elements can be used with the nodal release algorithm to simulate the triaxial state of stress near the crack tip. Verification and validation studies compare analysis results with experimental data and published three-dimensional analysis results. Fracture predictions using nodal release for compact tension, middle-crack tension, and multi-site damage test specimens produced accurate results for residual strength and link-up loads. Curving crack predictions using remeshing/mapping were compared with experimental data for an Arcan mixed-mode specimen. Loading angles from 0 degrees to 90 degrees were analyzed. The maximum tensile stress criterion was able to predict the crack direction and path for all loading angles in which the material failed in tension. Residual strength was also accurately predicted for these cases.
NASA Astrophysics Data System (ADS)
Xiao, Si; Wang, He-Ling; Liu, Bin; Hwang, Keh-Chih
2015-11-01
The J-integral based criterion is widely used in elastic-plastic fracture mechanics. However, it is not rigorously applicable when plastic unloading appears during crack propagation. One difficulty is that the energy density with plastic unloading in the J-integral cannot be defined unambiguously. In this paper, we alternatively start from the analysis on the power balance, and propose a surface-forming energy release rate (ERR), which represents the energy available for separating the crack surfaces during the crack propagation and excludes the loading-mode-dependent plastic dissipation. Therefore the surface-forming ERR based fracture criterion has wider applicability, including elastic-plastic crack propagation problems. Several formulae are derived for calculating the surface-forming ERR. From the most concise formula, it is interesting to note that the surface-forming ERR can be computed using only the stress and deformation of the current moment, and the definition of the energy density or work density is avoided. When an infinitesimal contour is chosen, the expression can be further simplified. For any fracture behaviors, the surface-forming ERR is proven to be path-independent, and the path-independence of its constituent term, so-called Js-integral, is also investigated. The physical meanings and applicability of the proposed surface-forming ERR, traditional ERR, Js-integral and J-integral are compared and discussed. Besides, we give an interpretation of Rice paradox by comparing the cohesive fracture model and the surface-forming ERR based fracture criterion.
Sachs, C; Fabritius, H; Raabe, D
2006-09-01
This study presents a novel experimental approach to the characterization of the deformation of a mineralized biological composite using arthropod cuticle as a model material. By performing tensile tests combined with a detailed strain analysis via digital image correlation, the elastic-plastic deformation behavior of the endocuticle of the American lobster Homarus americanus is examined. The test specimens originate from the pincher and crusher claws. For evaluating the effect of moisture on the deformation behavior, the samples are tested both in dry and in wet state. Sample characterization using the digital image correlation method requires a stochastic spot pattern on the sample surface. Digital images are then taken at subsequent deformation stages during the mechanical test. These images are used to calculate the displacement, the displacement gradient, and the strain fields via pattern correlation. The method is applied both, at a global scale to measure with high precision the stress-strain behavior of the bulk cuticle and at a microscopic scale to reveal strain heterogeneity, strain patterning, and strain localization phenomena. PMID:16899374
Rahman, S.
1996-12-01
A new probabilistic model was developed for predicting elastic-plastic fracture response of circumferentially cracked pipes with finite-length, constant-depth, internal surface flaws subject to remote bending loads. It involves engineering estimation of energy release rate, J-tearing theory for characterizing ductile fracture, and standard methods of structural reliability theory. The underlying J-estimation model is based on deformation theory of plasticity, constitutive law characterized by power law model for stress-strain curve, and an equivalence criterion incorporating reduced thickness analogy for simulating system compliance due to the presence of a crack. New equations were developed to predict J-integral and were evaluated by comparing with available finite-element results from the current literature. Both analytical and simulation methods were formulated to determine the probabilistic characteristics of J. The same methods were used later to predict the probability of crack initiation and net-section collapse as a function of the applied load. Numerical examples are provided to illustrate the proposed methodology.
Simple structures test for elastic-plastic strain acceptance criterion validation
Trimble, T.F.; Krech, G.R.
1997-11-01
A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens (fabricated from HY-80 steel) were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict elastic-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS finite element analysis code. The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of strain levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated. Comparison of test data to analysis results shows that displacements, accelerations, and peak strain can be predicted with a reasonable level of accuracy using detailed solid models of the tested specimens. Permanent set is overpredicted by a factor of approximately two. However, the accuracy of the prediction of permanent set is being enhanced by updating material modeling in the ABAQUS code to account for effects of strain reversal in oscillatory behavior of dynamically loaded specimens.
Three-dimensional elastic-plastic finite-element analysis of fatigue crack propagation
NASA Technical Reports Server (NTRS)
Goglia, G. L.; Chermahini, R. G.
1985-01-01
Fatigue cracks are a major problem in designing structures subjected to cyclic loading. Cracks frequently occur in structures such as aircraft and spacecraft. The inspection intervals of many aircraft structures are based on crack-propagation lives. Therefore, improved prediction of propagation lives under flight-load conditions (variable-amplitude loading) are needed to provide more realistic design criteria for these structures. The main thrust was to develop a three-dimensional, nonlinear, elastic-plastic, finite element program capable of extending a crack and changing boundary conditions for the model under consideration. The finite-element model is composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material is assumed to be elastic-perfectly plastic. The cycle stress-strain curve for the material is shown Zienkiewicz's initial-stress method, von Mises's yield criterion, and Drucker's normality condition under small-strain assumptions are used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary conditions under cyclic loading.
Elastic-Plastic Constitutive Equation of WC-Co Cemented Carbides with Anisotropic Damage
Hayakawa, Kunio; Nakamura, Tamotsu; Tanaka, Shigekazu
2007-05-17
Elastic-plastic constitutive equation of WC-Co cemented carbides with anisotropic damage is proposed to predict a precise service life of cold forging tools. A 2nd rank symmetric tensor damage tensor is introduced in order to express the stress unilaterality; a salient difference in uniaxial behavior between tension and compression. The conventional framework of irreversible thermodynamics is used to derive the constitutive equation. The Gibbs potential is formulated as a function of stress, damage tensor, isotropic hardening variable and kinematic hardening variable. The elastic-damage constitutive equation, conjugate forces of damage, isotropic hardening and kinematic hardening variable is derived from the potential. For the kinematic hardening variable, the superposition of three kinematic hardening laws is employed in order to improve the cyclic behavior of the material. For the evolution equation of the damage tensor, the damage is assumed to progress by fracture of the Co matrix - WC particle interface and by the mechanism of fatigue, i.e. the accumulation of microscopic plastic strain in matrix and particles. By using the constitutive equations, calculation of uniaxial tensile and compressive test is performed and the results are compared with the experimental ones in the literature. Furthermore, finite element analysis on cold forward extrusion was carried out, in which the proposed constitutive equation was employed as die insert material.
Elastic-Plastic Constitutive Equation of WC-Co Cemented Carbides with Anisotropic Damage
NASA Astrophysics Data System (ADS)
Hayakawa, Kunio; Nakamura, Tamotsu; Tanaka, Shigekazu
2007-05-01
Elastic-plastic constitutive equation of WC-Co cemented carbides with anisotropic damage is proposed to predict a precise service life of cold forging tools. A 2nd rank symmetric tensor damage tensor is introduced in order to express the stress unilaterality; a salient difference in uniaxial behavior between tension and compression. The conventional framework of irreversible thermodynamics is used to derive the constitutive equation. The Gibbs potential is formulated as a function of stress, damage tensor, isotropic hardening variable and kinematic hardening variable. The elastic-damage constitutive equation, conjugate forces of damage, isotropic hardening and kinematic hardening variable is derived from the potential. For the kinematic hardening variable, the superposition of three kinematic hardening laws is employed in order to improve the cyclic behavior of the material. For the evolution equation of the damage tensor, the damage is assumed to progress by fracture of the Co matrix — WC particle interface and by the mechanism of fatigue, i.e. the accumulation of microscopic plastic strain in matrix and particles. By using the constitutive equations, calculation of uniaxial tensile and compressive test is performed and the results are compared with the experimental ones in the literature. Furthermore, finite element analysis on cold forward extrusion was carried out, in which the proposed constitutive equation was employed as die insert material.
Geometry changes in the elastic-plastic analysis of steel spatial skeletal structures
NASA Astrophysics Data System (ADS)
Bondok, Hosain Mohamed H.
The principal objective is to furnish a tool for aunified formulation and numerical analysis of all the history-independent classes of response of elastic perfectly plastic space skeletal structures. We aim at determination of load domains corresponding to elastic, shakedown and collapse behavior for structures in initial and deformed configurations. Numerical program SDLAS for post-yield and inadaptation (non-shakedown) analysis of elastic-plastic space skeletal structures was prepared. It accounts for biaxial bending, torsion and axial forces contributing to yielding of beam elements. The program permits to determine a safe domain for either proportional or variable repeated loads. The proposed method accounts for nonlinear geometrical effects. In the post-yield analysis the conditions for plastic now are considered at subsequent deformed configurations. For the inadaptation analysis the similar procedure is applied. Automatic generation of all possible plastic deformation modes allows to select the most dangerous mechanisms and to determine a critical plastic deformation path. Finally, the post-yield or inadaptation curve is obtained showing the dependence of load (load domain) multiplier on the plastic deformation. These problems are formulated as a sequence of linear programming tasks and are solved by a step by step procedure. The proposed method allows to determine the limit multiplier and the shakedown (adaptation) multiplier accounting for geometric effects.
Elastic-Plastic Behavior of U6Nb under Ramp Wave Loading
Hayes, D. B.; Gray, G. T. III; Hixson, R. S.; Hall, C. A.
2006-07-28
When uranium-niobium (6 wt.%) alloy is shock loaded, the expected elastic precursor is absent. A prior model attributed this absence to shear-induced twinning and the concomitant shear stress reduction that prevented the shocked material from reaching the plastic yield point. In the present study, carefully prepared U6Nb was subjected to shock loading to verify the adequacy of the prior model. Other samples were loaded with a ramp pressure pulse with strain rate large enough so that significant twinning would not occur during the experiment. Backward integration analyses of these latter experiments' back surface motion give stress-strain loading paths in U6Nb that suggest ordinary elastic-plastic flow. Some of the U6Nb was pre-strained by cold rolling in an effort to further ensure that twinning did not affect wave propagation. Shock and ramp loadings yielded similar results to the baseline material except, as expected, they are consistent with a higher yield stress and twinning shear stress threshold.
Evolutions of elastic-plastic shock compression waves in different materials
NASA Astrophysics Data System (ADS)
Kanel, G. I.; Zaretsky, E. B.; Razorenov, S. V.; Savinykh, A. S.; Garkushin, G. V.
2015-06-01
Measurements of decay of the elastic precursor wave are used to determine the initial plastic strain rate as a function of the stress. Last years we performed large series of such kind experiments with metals and alloys at various temperatures, ceramics and glasses. In course of these measurements we observed several unexpected effects which have not got exhaustive explanations yet. In the presentation, we'll discuss a departure from self-similar development of the wave process which is accompanied with apparent sub-sonic wave propagation, changes of shape of elastic precursor wave as a result of variations in the material structure and the temperature, unexpected peculiarities of reflection of elastic-plastic waves from free surface, effects of internal friction at shock compression of glasses and some other effects. It seems the experimental data contain more information about kinetics of the time-dependent phenomena than we are able to get from their analysis now. Financial support from the Russian Science Foundation via Grant No 14-12-01127 is gratefully acknowledged.
A review of path-independent integrals in elastic-plastic fracture mechanics, task 4
NASA Technical Reports Server (NTRS)
Kim, K. S.
1985-01-01
The path independent (P-I) integrals in elastic plastic fracture mechanics which have been proposed in recent years to overcome the limitations imposed on the J integral are reviewed. The P-I integrals considered herein are the J integral by Rice, the thermoelastic P-I integrals by Wilson and Yu and by Gurtin, the J* integral by Blackburn, the J sub theta integral by Ainsworth et al., the J integral by Kishimoto et al., and the delta T sub p and delta T* sub p integrals by Atluri et al. The theoretical foundation of these P-I integrals is examined with emphasis on whether or not path independence is maintained in the presence of nonproportional loading and unloading in the plastic regime, thermal gradients, and material inhomogeneities. The similarities, differences, salient features, and limitations of these P-I integrals are discussed. Comments are also made with regard to the physical meaning, the possibility of experimental measurement, and computational aspects.
NASA Technical Reports Server (NTRS)
Knight, Norman F., Jr.; Warren, Jerry E.; Elliott, Kenny B.; Song, Kyongchan; Raju, Ivatury S.
2012-01-01
Elastic-plastic, large-deflection nonlinear thermo-mechanical stress analyses are performed for the Space Shuttle external tank s intertank stringers. Detailed threedimensional finite element models are developed and used to investigate the stringer s elastic-plastic response for different thermal and mechanical loading events from assembly through flight. Assembly strains caused by initial installation on an intertank panel are accounted for in the analyses. Thermal loading due to tanking was determined to be the bounding loading event. The cryogenic shrinkage caused by tanking resulted in a rotation of the intertank chord flange towards the center of the intertank, which in turn loaded the intertank stringer feet. The analyses suggest that the strain levels near the first three fasteners remain sufficiently high that a failure may occur. The analyses also confirmed that the installation of radius blocks on the stringer feet ends results in an increase in the stringer capability.
Nguyen, Ba Nghiep; Bapanapalli, Satish K.; Kunc, Vlastimil; Phelps, Jay; Tucker III, Charles L.
2009-01-26
This paper proposes a model to predict the elastic-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using the anisotropic rotary diffusion model recently developed by Phelps and Tucker for LFTs. An incremental procedure using the Eshelby’s equivalent inclusion method and the Mori-Tanaka model is proposed to compute the overall stress increment resulting from an overall strain increment for an aligned fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the later is then obtained from the solution for the aligned fiber composite that is averaged over all possible fiber orientations using the orientation averaging method. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The elastic-plastic and strength prediction model for LFTs was validated against the experimental stress-strain results obtained for long glass fiber/polypropylene specimens.
The ghost solid methods for the elastic-plastic solid-solid interface and the ϑ-criterion
NASA Astrophysics Data System (ADS)
Kaboudian, A.; Tavallali, P.; Khoo, B. C.
2015-12-01
Two variants of the Ghost Solid Method (GSM), namely the Original GSM (OGSM) and Modified GSM (MGSM), are proposed for the elastic-plastic solid-solid interactions in a Lagrangian framework. It is shown that the OGSM is highly problem related and can lead to large numerical errors under certain material combinations or in the presence of the wave propagation through the solid-solid interface. The ϑ-criterion, previously developed for the elastic-elastic solid-solid interactions [1], has been applied to the OGSM for the elastic-plastic interactions. It is shown that this criterion can successfully detect the onset of these large errors. Moreover, it is shown that it can be used to determine the reliability of the results obtained using the OGSM. The MGSM has been shown to be able to remove the large numerical errors that would normally arise due to the OGSM. Next, the extension of the two variants of the GSM, to two-dimensional settings, is presented for two idealized interface conditions, namely the no-slip condition, and the perfect-slip conditions. Numerous numerical experiments are provided attesting to the effectiveness and viability of the GSMs, for simulating wave propagation at the elastic-plastic solid-solid interface. The applicability of the ϑ-criterion is also studied in the numerical experiments.
Rahman, S.; Brust, F.
1995-11-01
A probabilistic fracture model was developed to analyze circumferential through-walled-cracked pipes subjected to bending loads. It involved elastic-plastic finite element analysis for estimating energy releases rates, J-tearing theory for characterizing ductile fracture, and standard methods of structural reliability theory for conduction probabilistic analysis. The evaluation of J-integral was based on the deformation theory of plasticity and power-law idealizations of the stress-strain and fracture toughness curves. This allows J to be expressed in terms of non-dimensional influence functions (F- and h{sub 1}-functions) that depend on the crack size, pipe geometry, and material hardening constant. New equations were proposed to represent these functions and were applied to conduct stochastic pipe fracture evaluations. Both analytical and simulation methods were formulated to determine the probabilistic characteristics of J. The same methods were used later to predict the failure probability of pipes as a function of the applied load. Numerical examples are provided to illustrate the proposed methodology. The validity of J-integral based on the proposed equations for predicting crack driving force in a through-wall-cracked pipe was evaluated by comparing with available results in the current literature. Probability densities of J-integral were predicted as a function of applied loads. Failure probabilities corresponding to three different performance criteria were evaluated for a stainless steel nuclear piping in the Boiling Water Reactor plant. The results suggest that large differences may exist in the failure probability estimates produced by these performance criteria.
Limitations to leading-order asymptotic solutions for ELASTIC PLASTIC crack growth
NASA Astrophysics Data System (ADS)
Drugan, W. J.
1998-12-01
Previous work has shown that there are significant discrepancies between leading-order asymptotic analytical solutions for the elastic-plastic fields near growing crack tips and detailed numerical finite element solutions of the same problems. The evidence is clearest in the simplest physically realistic case : quasi-static anti-plane shear crack growth in homogeneous, isotropic elastic-ideally plastic material. There, the sole extant asymptotic analytical solution involves a plastic loading sector of radial stress characteristics extending about 20° from ahead of the crack, followed by elastic unloading, whereas detailed numerical finite element solutions show the presence of an additional sector of plastic loading, extending from about 20 to about 50°, that is comprised of non-radial characteristics. To explore how the asymptotic analysis can completely miss this important solution feature, we derive an exact representation for the stress and deformation fields in such a propagating region of non-radial characteristics, as well as in the other allowable solution regions. These exact solutions contain arbitrary functions, which are determined by applying asymptotic analysis to the solutions and assembling a complete near-tip solution, valid through second order, that is in agreement with the numerical finite element results. In so doing, we prove that the angular extent of the sector of non-radial characteristics, while substantial until extremely close to the crack tip, vanishes in the limit as the tip is approached, and that the solution in this sector is not of variable-separable form. Beyond resolving the analytical-numerical discrepancies in this specific anti-plane shear problem, the analysis serves to caution, by explicit example, that purely leading-order asymptotic solutions to nonlinear crack growth problems cannot in general capture all essential physical features of the near-tip fields, and that the often-invoked assumption of variable
Reider, Samuel B.
1979-01-01
An industrial gas turbine engine includes an inclined annular combustor made up of a plurality of support segments each including inner and outer walls of trapezoidally configured planar configuration extents and including side flanges thereon interconnected by means of air cooled connector bolt assemblies to form a continuous annular combustion chamber therebetween and wherein an air fuel mixing chamber is formed at one end of the support segments including means for directing and mixing fuel within a plenum and a perforated header plate for directing streams of air and fuel mixture into the combustion chamber; each of the outer and inner walls of each of the support segments having a ribbed lattice with tracks slidably supporting porous laminated replaceable panels and including pores therein for distributing combustion air into the combustion chamber while cooling the inner surface of each of the panels by transpiration cooling thereof.
Gupta, Diptesh; Hess, Brian; Bachegowda, Lohith
2010-01-01
We present a case of a 77-year-old, diabetic male with a 20-year history of a migratory erythematous, asymptomatic, generalized, nonscaly, and nonitchy rash that started over the dorsum of his left hand. On examination, there were multiple annular erythematous plaques, distributed symmetrically and diffusely over his torso and arms, with central clearing and no scales. A punch biopsy of the skin helped us to arrive at the diagnosis of a generalized granuloma annulare (GA). GA is a benign, self-limiting skin condition of unknown etiology that is often asymptomatic. The cause of this condition is unknown, but it has been associated with diabetes mellitus, infections such as HIV, and malignancies such as lymphoma. These lesions typically start as a ring of flesh-colored papules that slowly progress with central clearing. Lack of symptoms, scaling, or associated vesicles helps to differentiate GA from other skin conditions such as tinea corporis, pityriasis rosea, psoriasis, or erythema annulare centrifugum. Treatment is often not needed as the majority of these lesions are self-resolving within 2 years. Treatment may be pursued for cosmetic reasons. Available options include high-dose steroid creams, PUVA, cryotherapy, or drugs such as niacinamide, infliximab, Dapsone, and topical calcineurin inhibitors. PMID:20209383
Elastic-Plastic Finite Element Analysis of Fatigue Crack Growth in Mode 1 and Mode 2 Conditions
NASA Technical Reports Server (NTRS)
Nakagaki, M.; Atluri, S. N.
1978-01-01
Presented is an alternate cost-efficient and accurate elastic-plastic finite element procedure to analyze fatigue crack closure and its effects under general spectrum loading. Both Modes 1 and 2 type cycling loadings are considered. Also presented are the results of an investigation, using the newly developed procedure, of various factors that cause crack growth acceleration or retardation and delay effects under high-to-low, low-to-high, single overload, and constant amplitude type cyclic loading in a Mode 1 situation. Further, the results of an investigation of a centercracked panel under external pure shear (Mode 2) cyclic loading, of constant amplitude, are reported.
NASA Technical Reports Server (NTRS)
Padovan, J.; Tovichakchaikul, S.
1983-01-01
This paper will develop a new solution strategy which can handle elastic-plastic-creep problems in an inherently stable manner. This is achieved by introducing a new constrained time stepping algorithm which will enable the solution of creep initiated pre/postbuckling behavior where indefinite tangent stiffnesses are encountered. Due to the generality of the scheme, both monotone and cyclic loading histories can be handled. The presentation will give a thorough overview of current solution schemes and their short comings, the development of constrained time stepping algorithms as well as illustrate the results of several numerical experiments which benchmark the new procedure.
Keimig, Emily Louise
2015-07-01
Granuloma annulare (GA) is a noninfectious granulomatous skin condition that can present with a variety of cutaneous morphologies. It is characterized by collagen degeneration, mucin deposition, and palisaded or interstitial histiocytes. Although the mechanism underlying development of GA is unknown, studies point to a cell-mediated hypersensitivity reaction to an as-yet undetermined antigen. Systemic associations with diabetes, thyroid disorders, lipid abnormalities, malignancy, and infection are described in atypical GA. Treatment is divided into localized skin-directed therapies and systemic immunomodulatory or immunosuppressive therapies. The selected treatment modality should be based on disease severity, comorbid conditions, consideration of potential side effects, and patient preference. PMID:26143416
Butsch, F; Weidenthaler-Barth, B; von Stebut, E
2015-11-01
Granuloma annulare is a benign, chronic inflammatory skin disease. Its pathogenesis is still unclear, but reports on infections as a trigger can be found. In addition, some authors reported an association with other systemic disease, e.g., cancer, trauma, and diabetes mellitus; however, these have not been verified. The clinical picture of granuloma annulare ranges from the localized form predominantly at the extremities to disseminated, subcutaneous, or perforating forms. Diagnosis is based on the typical clinical presentation which may be confirmed by a biopsy. Histologically, necrobiotic areas within granulomatous inflammation are typical. The prognosis of the disease is good with spontaneous resolution being frequently observed, especially in localized forms. Disseminated manifestations tend to persist longer, and recurrences are reported. When choosing between different therapeutic options, the benign disease character versus the individual degree of suffering and the potential therapy side effects must be considered. For local treatment, topical application of corticosteroids is most common. Disseminated forms can be treated systemically with corticosteroids for several weeks; alternatively, dapsone, hydroxychloroquine, retinoids, fumaric acid, cyclosporine, and anti-TNFα appear to be effective. PMID:26487494
Nguyen, Ba N.; Kunc, Vlastimil; Phelps, Jay H; TuckerIII, Charles L.; Bapanapalli, Satish K
2009-01-01
This paper proposes a model to predict the elastic-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using an anisotropic rotary diffusion model recently developed for LFTs. An incremental procedure using Eshelby's equivalent inclusion method and the Mori-Tanaka assumption is proposed to compute the overall stress increment resulting from an overall strain increment for an aligned-fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the latter is then obtained from the solution for the aligned-fiber composite by averaging over all fiber orientations. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The model is validated against the experimental stress-strain results obtained for long-glass-fiber/polypropylene specimens.
ML Renauld; H Lien
2004-12-13
The evolution of global and local stress/strain conditions in test fasteners under test conditions is investigated using elastic-plastic, time-dependent finite element analyses (FEA). For elastic-plastic response, tensile data from multiple specimens, material heats and test temperatures are integrated into a single, normalized flow curve from which temperature dependency is extracted. A primary creep model is calibrated with specimen- and fastener-based thermal relaxation data generated under a range of times, temperatures, stress levels and environments. These material inputs are used in analytical simulations of experimental test conditions for several types of fasteners. These fastener models are constructed with automated routines and contact conditions prescribed at all potentially mating surfaces. Thermal or mechanical room temperature pre-loading, as appropriate for a given fastener, is followed by a temperature ramp and a dwell time at constant temperature. While the amount of thermal stress relaxation is limited for the conditions modeled, local stress states are highly dependent upon geometry (thread root radius, for example), pre-loading history and thermal expansion differences between the test fastener and test fixture. Benefits of this FE approach over an elastic methodology for stress calculation will be illustrated with correlations of Stress Corrosion Cracking (SCC) initiation time and crack orientations in stress concentrations.
Jones, D.P.; Holliday, J.E.
1999-02-01
This paper provides a comparison between finite element analysis results and test data from the Pressure Vessel Research Council (PVRC) burst disk program. Testing sponsored by the PVRC over 20 years ago was done by pressurizing circular flat disks made from three different materials until failure by bursting. The purpose of this re-analysis is to investigate the use of finite element analysis (FEA) to assess the primary stress limits of the ASME Boiler and Pressure Vessel Code (1998) and to qualify the use of elastic-plastic (EP-FEA) for limit load calculations. The three materials tested represent the range of strength and ductility found in modern pressure vessel construction and include a low strength high ductility material, a medium strength medium ductility material, and a high strength low ductility low alloy material. Results of elastic and EP-FEA are compared to test data. Stresses from the elastic analyses are linearized for comparison of Code primary stress limits to test results. Elastic-plastic analyses are done using both best-estimate and elastic-perfectly plastic (EPP) stress-strain curves. Both large strain-large displacement (LSLD) and small strain-small displacement (SSSD) assumptions are used with the EP-FEA. Analysis results are compared to test results to evaluate the various analysis methods, models, and assumptions as applied to the bursting of thin disks.
NASA Astrophysics Data System (ADS)
Song, Z.; Komvopoulos, K.
2011-04-01
Adhesive interaction in spherical contacts was modeled with the Lennard-Jones (L-J) potential. Elastic adhesive contact was analyzed by the equivalent system of a rigid sphere with reduced radius of curvature and a half-space of effective elastic modulus. The critical gap at the instant of abrupt surface contact (jump-in) and separation (jump-out) was determined from the deformed surface profile of the elastic half-space and geometrical relationships. A finite element model of a rigid sphere and an elastic-plastic half-space was used to examine elastic-plastic adhesive contact. Surface adhesion was modeled by nonlinear springs with a force-displacement relationship governed by the L-J potential. The evolution of the interfacial force and the central gap distance as well as the occurrence of jump-in and jump-out instabilities were investigated in terms of the Tabor parameter, plasticity parameter, and dimensionless maximum normal displacement. The force-displacement response due to several approach-retraction cycles was interpreted in the context of elastic and plastic shakedown behaviors using dimensionless parameters.
NASA Astrophysics Data System (ADS)
Ino, Takuichiro; Hasib, M. D. Abdul; Takase, Toru; Saimoto, Akihide
2015-03-01
An embedded force doublet (EFD) model is proposed to express the presence of permanent strain in body force method (BFM). BFM is known as a boundary type method for elastic stress analysis based on the principle of superposition. In EFD model, the permanent strain is replaced by distributed force doublets. In an actual elastic-plastic analysis, the plastic region whose shape is not clear a priori, have to be discretized into elements where the magnitude of embedded force doublets is unknown to be determined numerically. In general, the determination process of magnitude of EFD is considerably difficult due to nonlinear nature of yield criterion and plastic constitutive relations. In this study, by introducing the automated Delaunay tessellation scheme for discretizing the prospective plastic region, appreciable reduction in input data was realized. Adding to this, in order to improve the computational efficiency, influence coefficients used for determining the magnitude of EFD are stored in a database. The effectiveness of these two inventions was examined by computing the elastic-plastic problem of an infinite medium with circular hole subjected to uniform internal pressure. The numerical solution was compared with Nadai’s closed form solution and found a good agreement.
Richtmyer-Meshkov instability for elastic-plastic solids in converging geometries
NASA Astrophysics Data System (ADS)
López Ortega, A.; Lombardini, M.; Barton, P. T.; Pullin, D. I.; Meiron, D. I.
2015-03-01
We present a detailed study of the interface instability that develops at the boundary between a shell of elastic-plastic material and a cylindrical core of confined gas during the inbound implosive motion generated by a shock-wave. The main instability in this configuration is the so-called Richtmyer-Meshkov instability that arises when the shock wave crosses the material interface. Secondary instabilities, such as Rayleigh-Taylor, due to the acceleration of the interface, and Kelvin-Helmholtz, due to slip between solid and fluid, arise as the motion progresses. The reflection of the shock wave at the axis and its second interaction with the material interface as the shock moves outbound, commonly known as re-shock, results in a second Richtmyer-Meshkov instability that potentially increases the growth rate of interface perturbations, resulting in the formation of a mixing zone typical of fluid-fluid configurations and the loss of the initial perturbation length scales. The study of this problem is of interest for achieving stable inertial confinement fusion reactions but its complexity and the material conditions produced by the implosion close to the axis prove to be challenging for both experimental and numerical approaches. In this paper, we attempt to circumvent some of the difficulties associated with a classical numerical treatment of this problem, such as element inversion in Lagrangian methods or failure to maintain the relationship between the determinant of the deformation tensor and the density in Eulerian approaches, and to provide a description of the different events that occur during the motion of the interface. For this purpose, a multi-material numerical solver for evolving in time the equations of motion for solid and fluid media in an Eulerian formalism has been implemented in a Cartesian grid. Equations of state are derived using thermodynamically consistent hyperelastic relations between internal energy and stresses. The resolution required
Means of manufacturing annular arrays
Day, R.A.
1985-10-10
A method is described for manufacturing an annular acoustic transducer array from a plate of transducer material, which enables production of precision aligned arrays at low cost. The circular plate is sawed along at least two lines that are radial to the axis of the plate. At steps along each radial cut, the plate is rotated first in one direction and then in an opposite direction by a predetermined angle such as slightly less than 90/sup 0/. The cuts result in the forming of several largely ring-shaped lands, each largely ring-shaped land being joined to the other rings of different radii by thin portions of the plate, and each ring being cut into segments. The bridges that join different rings hold the transducer together until it can be mounted on a lens.
Three-dimensional elastic-plastic analysis of shallow cracks in single-edge-crack-tension specimens
NASA Technical Reports Server (NTRS)
Shivakumar, Kunigal N.; Newman, James C., Jr.
1990-01-01
Three dimensional, elastic-plastic, finite element results are presented for single-edge crack-tension specimens with several shallow crack-length-to-width ratios (0.05 less than or equal to a/W less than or equal to 0.5). Results showed the need to model the initial yield plateau in the stress-strain behavior to accurately model deformation of the A36 steel specimens. The crack-tip-opening-displacement was found to be linearly proportional to the crack-mouth-opening displacement. A new deformation dependent plastic-eta factor equation is presented for calculating the J-integral from test load-displacement records. This equation was shown to be accurate for all crack lengths considered.
NASA Technical Reports Server (NTRS)
Knight, Norman F., Jr.; Song, Kyongchan; Elliott, Kenny B.; Raju, Ivatury S.; Warren, Jerry E.
2012-01-01
Elastic-plastic, large-deflection nonlinear stress analyses are performed for the external hat-shaped stringers (or stiffeners) on the intertank portion of the Space Shuttle s external tank. These stringers are subjected to assembly strains when the stringers are initially installed on an intertank panel. Four different stringer-feet configurations including the baseline flat-feet, the heels-up, the diving-board, and the toes-up configurations are considered. The assembly procedure is analytically simulated for each of these stringer configurations. The location, size, and amplitude of the strain field associated with the stringer assembly are sensitive to the assumed geometry and assembly procedure. The von Mises stress distributions from these simulations indicate that localized plasticity will develop around the first eight fasteners for each stringer-feet configuration examined. However, only the toes-up configuration resulted in high assembly hoop strains.
NASA Astrophysics Data System (ADS)
Brujan, E.-A.
2005-01-01
The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.
Subcutaneous granuloma annulare.
Requena, Luis; Fernández-Figueras, María Teresa
2007-06-01
Subcutaneous granuloma annulare is a rare clinicopathologic variant of granuloma annulare, characterized by subcutaneous nodules that may appear alone or in association with intradermal lesions. The pathogenesis of this deep variant of granuloma annulare remains uncertain. Subcutaneous granuloma annulare appears more frequently in children and young adults, and the lesions consist of subcutaneous nodules with no inflammatory appearance at the skin surface, most commonly located on the anterior aspects of the lower legs, hands, head, and buttocks. Usually, subcutaneous granuloma annulare is an authentic and exclusive panniculitic process with no dermal participation, although in 25% of the patients lesions of subcutaneous granuloma annulare coexist with the classic findings of granuloma annulare in the dermis. Histopathologically, subcutaneous granuloma annulare consist of areas of basophilic degeneration of collagen bundles with peripheral palisading granulomas involving the connective tissue septa of the subcutis. Usually, the area of necrobiosis in subcutaneous granuloma annulare is larger than in the dermal counterpart. The central necrobiotic areas contain increased amounts of connective tissue mucin and nuclear dust from neutrophils between the degenerated collagen bundles. Eosinophils are more common in subcutaneous granuloma annulare than in the dermal counterpart. There are not descriptions of subcutaneous granuloma annulare showing a histopathologic pattern of the so-called incomplete or interstitial variant. Histopathologic differential diagnosis of subcutaneous granuloma annulare includes rheumatoid nodule, necrobiosis lipoidica and epithelioid sarcoma. PMID:17544961
Elastic-Plastic Fracture Mechanics Analysis of Critical Flaw Size in ARES I-X Flange-to-Skin Welds
NASA Technical Reports Server (NTRS)
Chell, G. Graham; Hudak, Stephen J., Jr.
2008-01-01
NASA's Ares 1 Upper Stage Simulator (USS) is being fabricated from welded A516 steel. In order to insure the structural integrity of these welds it is of interest to calculate the critical initial flaw size (CIFS) to establish rational inspection requirements. The CIFS is in turn dependent on the critical final flaw size (CFS), as well as fatigue flaw growth resulting from transportation, handling and service-induced loading. These calculations were made using linear elastic fracture mechanics (LEFM), which are thought to be conservative because they are based on a lower bound, so called elastic, fracture toughness determined from tests that displayed significant plasticity. Nevertheless, there was still concern that the yield magnitude stresses generated in the flange-to-skin weld by the combination of axial stresses due to axial forces, fit-up stresses, and weld residual stresses, could give rise to significant flaw-tip plasticity, which might render the LEFM results to be non-conservative. The objective of the present study was to employ Elastic Plastic Fracture Mechanics (EPFM) to determine CFS values, and then compare these values to CFS values evaluated using LEFM. CFS values were calculated for twelve cases involving surface and embedded flaws, EPFM analyses with and without plastic shakedown of the stresses, LEFM analyses, and various welding residual stress distributions. For the cases examined, the computed CFS values based on elastic analyses were the smallest in all instances where the failures were predicted to be controlled by the fracture toughness. However, in certain cases, the CFS values predicted by the elastic-plastic analyses were smaller than those predicted by the elastic analyses; in these cases the failure criteria were determined by a breakdown in stress intensity factor validity limits for deep flaws (a greater than 0.90t), rather than by the fracture toughness. Plastic relaxation of stresses accompanying shakedown always increases the
NASA Technical Reports Server (NTRS)
Sharobeam, Monir H.
1994-01-01
Load separation is the representation of the load in the test records of geometries containing cracks as a multiplication of two separate functions: a crack geometry function and a material deformation function. Load separation is demonstrated in the test records of several two-dimensional geometries such as compact tension geometry, single edge notched bend geometry, and center cracked tension geometry and three-dimensional geometries such as semi-elliptical surface crack. The role of load separation in the evaluation of the fracture parameter J-integral and the associated factor eta for two-dimensional geometries is discussed. The paper also discusses the theoretical basis and the procedure for using load separation as a simplified yet accurate approach for plastic J evaluation in semi-elliptical surface crack which is a three-dimensional geometry. The experimental evaluation of J, and particularly J(sub pl), for three-dimensional geometries is very challenging. A few approaches have been developed in this regard and they are either complex or very approximate. The paper also presents the load separation as a mean to identify the blunting and crack growth regions in the experimental test records of precracked specimens. Finally, load separation as a methodology in elastic-plastic fracture mechanics is presented.
NASA Technical Reports Server (NTRS)
Ford, Hugh; Turner, C. E.; Fenner, R. T.; Curr, R. M.; Ivankovic, A.
1995-01-01
The objects of the first, exploratory, stage of the project were listed as: (1) to make a detailed and critical review of the Boundary Element method as already published and with regard to elastic-plastic fracture mechanics, to assess its potential for handling present concepts in two-dimensional and three-dimensional cases. To this was subsequently added the Finite Volume method and certain aspects of the Finite Element method for comparative purposes; (2) to assess the further steps needed to apply the methods so far developed to the general field, covering a practical range of geometries, work hardening materials, and composites: to consider their application under higher temperature conditions; (3) to re-assess the present stage of development of the energy dissipation rate, crack tip opening angle and J-integral models in relation to the possibilities of producing a unified technology with the previous two items; and (4) to report on the feasibility and promise of this combined approach and, if appropriate, make recommendations for the second stage aimed at developing a generalized crack growth technology for its application to real-life problems.
NASA Technical Reports Server (NTRS)
Wu, R. W.; Witmer, E. A.
1972-01-01
Assumed-displacement versions of the finite-element method are developed to predict large-deformation elastic-plastic transient deformations of structures. Both the conventional and a new improved finite-element variational formulation are derived. These formulations are then developed in detail for straight-beam and curved-beam elements undergoing (1) Bernoulli-Euler-Kirchhoff or (2) Timoshenko deformation behavior, in one plane. For each of these categories, several types of assumed-displacement finite elements are developed, and transient response predictions are compared with available exact solutions for small-deflection, linear-elastic transient responses. The present finite-element predictions for large-deflection elastic-plastic transient responses are evaluated via several beam and ring examples for which experimental measurements of transient strains and large transient deformations and independent finite-difference predictions are available.
NASA Technical Reports Server (NTRS)
Sanfeliz, Jose G.
1993-01-01
Micromechanical modeling via elastic-plastic finite element analyses were performed to investigate the effects that the residual stresses and the degree of matrix work hardening (i.e., cold-worked, annealed) have upon the behavior of a 9 vol percent, unidirectional W/Cu composite, undergoing tensile loading. The inclusion of the residual stress-containing state as well as the simulated matrix material conditions proved to be significant since the Cu matrix material exhibited plastic deformation, which affected the subsequent tensile response of the composite system. The stresses generated during cooldown to room temperature from the manufacturing temperature were more of a factor on the annealed-matrix composite, since they induced the softened matrix to plastically flow. This event limited the total load-carrying capacity of this matrix-dominated, ductile-ductile type material system. Plastic deformation of the hardened-matrix composite during the thermal cooldown stage was not considerable, therefore, the composite was able to sustain a higher stress before showing any appreciable matrix plasticity. The predicted room temperature, stress-strain response, and deformation stages under both material conditions represented upper and lower bounds characteristic of the composite's tensile behavior. The initial deformation stage for the hardened material condition showed negligible matrix plastic deformation while for the annealed state, its initial deformation stage showed extensive matrix plasticity. Both material conditions exhibited a final deformation stage where the fiber and matrix were straining plastically. The predicted stress-strain results were compared to the experimental, room temperature, tensile stress-strain curve generated from this particular composite system. The analyses indicated that the actual thermal-mechanical state of the composite's Cu matrix, represented by the experimental data, followed the annealed material condition.
Frutos, E; Cuevas, A; González-Carrasco, J L; Martín, F
2012-12-01
The purpose of this work is to study the elastoplastic properties of novel intermetallic coatings grown by hot dipping on medical steel 316 LVM and their correlation with the scratch resistance by means of instrumented ultramicroindentation techniques. Elastoplastic properties are defined by the plasticity index (PI), which correlates the hardness and the Young's modulus, and the yield strength that delimits the elastic-plastic transition. To avoid overestimations of the PI due to the so-called indentation size effect, macroscopic hardness values were determined. The PI of the coating increases from 0.6 to 0.8 with increasing immersion time. These values are always lower than those of the bare substrate (0.9) but higher than those found for ceramics (∼0.5). The increase of the PI is accompanied by a decrease in the yield strength from 0.73 to 0.34 GPa, which highlights the relevance of the compressive residual stresses and their relaxation with increasing immersion time. The higher plasticity is shown by higher apparent friction coefficients (0.159), which are always lower than those of the bare steel (0.264). Therefore, these intermetallic coatings could be considered "hard but tough" coatings, suitable for enhancing the wear resistance of the medical steel, especially when using short periods of immersion. The study provides evidence that the load-depth curve of indentation contains abundant information and that its analysis can be used to determine various mechanical properties of coatings that could be important for load bearing components. PMID:23137617
Annular feed air breathing fuel cell stack
Wilson, Mahlon S.
1996-01-01
A stack of polymer electrolyte fuel cells is formed from a plurality of unit cells where each unit cell includes fuel cell components defining a periphery and distributed along a common axis, where the fuel cell components include a polymer electrolyte membrane, an anode and a cathode contacting opposite sides of the membrane, and fuel and oxygen flow fields contacting the anode and the cathode, respectively, wherein the components define an annular region therethrough along the axis. A fuel distribution manifold within the annular region is connected to deliver fuel to the fuel flow field in each of the unit cells. In a particular embodiment, a single bolt through the annular region clamps the unit cells together. In another embodiment, separator plates between individual unit cells have an extended radial dimension to function as cooling fins for maintaining the operating temperature of the fuel cell stack.
Hutula, D.N.; Wiancko, B.E.
1980-03-01
ACCEPT is a three-dimensional finite element computer program for analysis of large-deformation elastic-plastic-creep response of Zircaloy tubes subjected to temperature, surface pressures, and axial force. A twenty-mode, tri-quadratic, isoparametric element is used along with a Zircaloy materials model. A linear time-incremental procedure with residual force correction is used to solve for the time-dependent response. The program features an algorithm which automatically chooses the time step sizes to control the accuracy and numerical stability of the solution. A contact-separation capability allows modeling of interaction of reactor fuel rod cladding with fuel pellets or external supports.
NASA Technical Reports Server (NTRS)
Wu, R. W.; Witmer, E. A.
1972-01-01
A user-oriented FORTRAN 4 computer program, called JET 3, is presented. The JET 3 program, which employs the spatial finite-element and timewise finite-difference method, can be used to predict the large two-dimensional elastic-plastic transient Kirchhoff-type deformations of a complete or partial structural ring, with various support conditions and restraints, subjected to a variety of initial velocity distributions and externally-applied transient forcing functions. The geometric shapes of the structural ring can be circular or arbitrarily curved and with variable thickness. Strain-hardening and strain-rate effects of the material are taken into account.
Annular pancreas is an abnormal ring or collar of pancreatic tissue that encircles the duodenum (the part of the ... intestine that connects to stomach). This portion of pancreas can constrict the duodenum and block or impair ...
Mechanically expandable annular seal
Gilmore, Richard F.
1983-01-01
A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluidtight barrier. A counterrotation removes the barrier.
Mechanically expandable annular seal
Gilmore, R.F.
1983-07-19
A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces is described. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluid tight barrier. A counter rotation removes the barrier. 6 figs.
Annular array and method of manufacturing same
Day, Robert A.
1989-01-01
A method for manufacturing an annular acoustic transducer array from a plate of transducer material, which enables production of precision aligned arrays at low cost. The circular plate is sawed along at least two lines that are radial to the axis of the plate. At steps along each radial cut, the plate is rotated first in one direction and then in an opposite direction by a predetermined angle such as slightly less than 90.degree.. The cuts result in the forming of several largely ring-shaped lands, each largely ring-shaped land being joined to the other rings of different radii by thin portions of the plate, and each ring being cut into segments. The bridges that join different rings, hold the transducer together until it can be mounted on a lens.
Simulation of Impact on a Ductile Polymer Plate
NASA Technical Reports Server (NTRS)
Cremona, Rebecca L.; Hinkley, Jeffrey A.
2005-01-01
Explicit finite element calculations were used to visualize the deformation and temperature rise in an elastic-plastic plate impacted by a rigid projectile. Results were compared to results of experiments involving ballistic penetration of a "self-healing" thermoplastic. The calculated temperature rise agreed well with the experimental observation, but the total energy absorbed in the penetration event was underestimated in the calculation, which neglected friction.
Erythematous Granuloma Annulare
Jang, Eun Joo; Lee, Ji Yeoun; Kim, Mi Kyeong
2011-01-01
Granuloma annulare (GA) is a common, benign, chronic inflammatory disorder, which is characterized by grouped papules in an enlarging annular shape. It has been described in several clinical subtypes, including localized, generalized, subcutaneous, perforating, and erythematous types. Even though generalized, subcutaneous, and perforating types of GA are unusual, there are several reports of those types. However, erythematous or patch GA, has not been reported yet in the Korean literature. Herein, we report a 42-year-old woman with pruritic erythematous patches, which occurred on the extremities without preceding event, and showed typical clinical and histopatologic findings of erythematous GA. PMID:21909221
P-Finite-Element Program For Analysis Of Plates
NASA Technical Reports Server (NTRS)
Smith, James P.
1995-01-01
BUCKY is p-finite-element computer program for highly accurate analysis of structures. Used to analyze buckling, bending, and in-plane stress-and-strain behaviors of plates. Provides elastic-plastic solutions for isotropic plates in states of plane stress, and axisymmetric solution sequence used to treat three-dimensional problems. Computes response of plate to variety of loading and boundary conditions by use of higher-order displacement function in p-finite-element method. Enables user to obtain results more accurate than obtained by use of traditional h-finite elements. Written in FORTRAN 77.
NASA Technical Reports Server (NTRS)
Deng, Xiaomin; Newman, James C., Jr.
1997-01-01
ZIP2DL is a two-dimensional, elastic-plastic finte element program for stress analysis and crack growth simulations, developed for the NASA Langley Research Center. It has many of the salient features of the ZIP2D program. For example, ZIP2DL contains five material models (linearly elastic, elastic-perfectly plastic, power-law hardening, linear hardening, and multi-linear hardening models), and it can simulate mixed-mode crack growth for prescribed crack growth paths under plane stress, plane strain and mixed state of stress conditions. Further, as an extension of ZIP2D, it also includes a number of new capabilities. The large-deformation kinematics in ZIP2DL will allow it to handle elastic problems with large strains and large rotations, and elastic-plastic problems with small strains and large rotations. Loading conditions in terms of surface traction, concentrated load, and nodal displacement can be applied with a default linear time dependence or they can be programmed according to a user-defined time dependence through a user subroutine. The restart capability of ZIP2DL will make it possible to stop the execution of the program at any time, analyze the results and/or modify execution options and resume and continue the execution of the program. This report includes three sectons: a theoretical manual section, a user manual section, and an example manual secton. In the theoretical secton, the mathematics behind the various aspects of the program are concisely outlined. In the user manual section, a line-by-line explanation of the input data is given. In the example manual secton, three types of examples are presented to demonstrate the accuracy and illustrate the use of this program.
El-Hachemi, Zoubir; Balaban, Teodor Silviu; Campos, J Lourdes; Cespedes, Sergio; Crusats, Joaquim; Escudero, Carlos; Kamma-Lorger, Christina S; Llorens, Joan; Malfois, Marc; Mitchell, Geoffrey R; Tojeira, Ana P; Ribó, Josep M
2016-07-01
The J aggregates of 4-sulfonatophenyl meso-substituted porphyrins are non-covalent polymers obtained by self-assembly that form nanoparticles of different morphologies. In the case of high aspect-ratio nanoparticles (bilayered ribbons and monolayered nanotubes), shear hydrodynamic forces may modify their shape and size, as observed by peak force microscopy, transmission electron microscopy of frozen solutions, small-angle X-ray scattering measurements in a disk-plate rotational cell, and cone-plate rotational viscometry. These nanoparticles either show elastic or plastic behaviour: there is plasticity in the ribbons obtained upon nanotube collapse on solid/air interfaces and in viscous concentrated nanotube solutions, whereas elasticity occurs in the case of dilute nanotube solutions. Sonication and strong shear hydrodynamic forces lead to the breaking of the monolayered nanotubes into small particles, which then associate into large colloidal particles. PMID:27238461
Granuloma annulare, patch type.
Victor, Frank C; Mengden, Stephanie
2008-01-01
A 64-year-old man was referred to the Bellevue Hospital Center Dermatology Clinic for evaluation of an asymptomatic eruption on his left inner arm, which had been present for 4 months and was unresponsive to topical anti-fungal therapy. One month after the initial eruption, 2 similar, asymptomatic lesions appeared on the right inner arm. The lesions were slowly expanding. A biopsy specimen from the left medial arm was consistent with interstitial granuloma annulare. The patient's clinical presentation was consistent with patch-type granuloma annulare. He was treated with a mid-potency topical glucocorticoid twice daily for 4 weeks without benefit. Since the eruption was asymptomatic, treatment was discontinued. PMID:18627757
Annular feed air breathing fuel cell stack
Wilson, Mahlon S.; Neutzler, Jay K.
1997-01-01
A stack of polymer electrolyte fuel cells is formed from a plurality of unit cells where each unit cell includes fuel cell components defining a periphery and distributed along a common axis, where the fuel cell components include a polymer electrolyte membrane, an anode and a cathode contacting opposite sides of the membrane, and fuel and oxygen flow fields contacting the anode and the cathode, respectively, wherein the components define an annular region therethrough along the axis. A fuel distribution manifold within the annular region is connected to deliver fuel to the fuel flow field in each of the unit cells. The fuel distribution manifold is formed from a hydrophilic-like material to redistribute water produced by fuel and oxygen reacting at the cathode. In a particular embodiment, a single bolt through the annular region clamps the unit cells together. In another embodiment, separator plates between individual unit cells have an extended radial dimension to function as cooling fins for maintaining the operating temperature of the fuel cell stack.
Kang, Yungmo
2005-10-04
An annular heat recuperator is formed with alternating hot and cold cells to separate counter-flowing hot and cold fluid streams. Each cold cell has a fluid inlet formed in the inner diameter of the recuperator near one axial end, and a fluid outlet formed in the outer diameter of the recuperator near the other axial end to evenly distribute fluid mass flow throughout the cell. Cold cells may be joined with the outlet of one cell fluidly connected to the inlet of an adjacent downstream cell to form multi-stage cells.
Burnley,P.; Zhang, D.
2008-01-01
We present synchrotron x-ray diffraction observations from a deformation experiment on fine-grained polycrystalline quartz using the newly developed deformation DIA apparatus. During deformation experiments we were able to observe the elastic strain of the (100), (101) and (112) lattice reflections. The elastic strains are typically converted into stresses and interpreted in terms of the differential stress supported by the specimen. Consistently with results from others obtained using this technique to deform monomineralic polycrystals, our results show substantial variations in stress levels between grain populations. Rather than averaging the lattice reflection stresses or choosing a single reflection to determine the macroscopic stress supported by the specimen, we explore the use of elastic-plastic self-consistent (EPSC) models. We are able to match the measured differential elastic lattice strains with an EPSC model in which basal and prism {l_angle}a{r_angle} slips are activated. An interesting outcome of the EPSC model is the prediction that the macroscopic stress experienced by the sample should be greater than the stress calculated from any of the reflections that we observed. This observation serves as a caution against using reflection stresses as a proxy for the macroscopic stress in in situ deformation experiments.
A numerical and analytical investigation of Rayleigh-Taylor instability in a solid tungsten plate
Robinson, A.C.; Swegle, J.W.
1987-07-01
The Rayleigh-Taylor instability response of an elastic-plastic tungsten plate is investigated by numerical experiments and an approximate modal analysis. The so-called ''minimum amplitude'' instability criteria derived from plasticity analyses is shown to be incomplete as a general indicator of instability or stability at very large driving pressures. Model equations are derived which are able to reproduce the basic qualitative features of the observed instability response given by the numerical calculations. 11 refs., 29 figs.
Harnoss, Jonathan M.; Harnoss, Julian C.; Diener, Markus K.; Contin, Pietro; Ulrich, Alexis B.; Büchler, Markus W.; Schmitz-Winnenthal, Friedrich H.
2014-01-01
Abstract Portal annular pancreas (PAP) is an asymptomatic congenital pancreas anomaly, in which portal and/or mesenteric veins are encased by pancreas tissue. The aim of the study was to determine the role of PAP in pancreatic surgery as well as its management and potential complication, specifically, postoperative pancreatic fistula (POPF). On the basis of a case report, the MEDLINE and ISI Web of Science databases were systematically reviewed up to September 2012. All articles describing a case of PAP were considered. In summary, 21 studies with 59 cases were included. The overall prevalence of PAP was 2.4% and the patients' mean (SD) age was 55.9 (16.2) years. The POPF rate in patients with PAP (12 pancreaticoduodenectomies and 3 distal pancreatectomies) was 46.7% (in accordance with the definition of the International Study Group of Pancreatic Surgery). Portal annular pancreas is a quite unattended pancreatic variant with high prevalence and therefore still remains a clinical challenge to avoid postoperative complications. To decrease the risk for POPF, attentive preoperative diagnostics should also focus on PAP. In pancreaticoduodenectomy, a shift of the resection plane to the pancreas tail should be considered; in extensive pancreatectomy, coverage of the pancreatic remnant by the falciform ligament could be a treatment option. PMID:25207658
Elastic-plastic deformation of Pb(Zn1/3Nb2/3)O3-(6-7)% PbTiO3 single crystals during nanoindentation
NASA Astrophysics Data System (ADS)
Wong, Meng Fei; Zeng, Kaiyang
2010-05-01
The elastic-plastic deformation behavior of (001)- and (011)-oriented single crystal solid solutions of Pb(Zn1/3Nb2/3)O3-(6-7)% PbTiO3 (PZN-PT) have been studied using a nanoindentation technique. A procedure is presented here to isolate the elastic, elastic-plastic and plastic contributions to the deformation using the unloading data, and a parameter, referred to as relaxation, is defined to characterize the elastic-plastic deformation during nanoindentations. This relaxation parameter increases with the maximum indentation load due to the higher indentation stress induced, and it also causes less recovery of the material upon indentation unloading compared to predicted pure elastic recovery. For a (001) surface, the relaxation value remains virtually unchanged within the range of the maximum indentation load of 10-50 mN, possibly due to a complete localized depoling of the non-180° domain switching. It is also found that the unpoled surface is more prone to stress-induced depolarization compared to the poled surfaces. Furthermore, by applying the continuous stiffness measurement (CSM) technique, the effects of multiple loading/unloading are studied for both (001)- and (011)-oriented PZN-PTs using the maximum indentation loads of 20 and 50 mN. With more loading/unloading cycles at higher CSM frequencies, stress-induced depolarization becomes prevalent and the contribution of the domain reorientation towards elastic recovery is significantly reduced. As a consequence, the relaxation value is increased, indicating more elastic-plastic deformation. This CSM effect is especially pronounced for poled (011) surfaces.
Reconfigurable mosaic annular arrays.
Thomenius, Kai E; Wodnicki, Robert; Cogan, Scott D; Fisher, Rayette A; Burdick, Bill; Smith, L Scott; Khuri-Yakub, Pierre; Lin, Der-Song; Zhuang, Xuefeng; Bonitz, Barry; Davies, Todd; Thomas, Glen; Woychik, Charles
2014-07-01
Mosaic annular arrays (MAA) based on reconfigurable array (RA) transducer electronics assemblies are presented as a potential solution for future highly integrated ultrasonic transducer subsystems. Advantages of MAAs include excellent beam quality and depth of field resulting from superior elevational focus compared with 1-D electronically scanned arrays, as well as potentially reduced cost, size, and power consumption resulting from the use of a limited number of beamforming channels for processing a large number of subelements. Specific design tradeoffs for these highly integrated arrays are discussed in terms of array specifications for center frequency, element pitch, and electronic switch-on resistance. Large-area RAs essentially function as RC delay lines. Efficient architectures which take into account RC delay effects are presented. Architectures for integration of the transducer and electronics layers of large-area array implementations are reviewed. PMID:24960699
Axisymmetric annular curtain stability
NASA Astrophysics Data System (ADS)
Ahmed, Zahir U.; Khayat, Roger E.; Maissa, Philippe; Mathis, Christian
2012-06-01
A temporal stability analysis was carried out to investigate the stability of an axially moving viscous annular liquid jet subject to axisymmetric disturbances in surrounding co-flowing viscous gas media. We investigated in this study the effects of inertia, surface tension, the gas-to-liquid density ratio, the inner-to-outer radius ratio and the gas-to-liquid viscosity ratio on the stability of the jet. With an increase in inertia, the growth rate of the unstable disturbances is found to increase. The dominant (or most unstable) wavenumber decreases with increasing Reynolds number for larger values of the gas-to-liquid viscosity ratio. However, an opposite tendency for the most unstable wavenumber is predicted for small viscosity ratio in the same inertia range. The surrounding gas density, in the presence of viscosity, always reduces the growth rate, hence stabilizing the flow. There exists a critical value of the density ratio above which the flow becomes stable for very small viscosity ratio, whereas for large viscosity ratio, no stable flow appears in the same range of the density ratio. The curvature has a significant destabilizing effect on the thin annular jet, whereas for a relatively thick jet, the maximum growth rate decreases as the inner radius increases, irrespective of the surrounding gas viscosity. The degree of instability increases with Weber number for a relatively large viscosity ratio. In contrast, for small viscosity ratio, the growth rate exhibits a dramatic dependence on the surface tension. There is a small Weber number range, which depends on the viscosity ratio, where the flow is stable. The viscosity ratio always stabilizes the flow. However, the dominant wavenumber increases with increasing viscosity ratio. The range of unstable wavenumbers is affected only by the curvature effect.
NASA Astrophysics Data System (ADS)
Maire, Pierre-Henri; Abgrall, Rémi; Breil, Jérôme; Loubère, Raphaël; Rebourcet, Bernard
2013-02-01
In this paper, we describe a cell-centered Lagrangian scheme devoted to the numerical simulation of solid dynamics on two-dimensional unstructured grids in planar geometry. This numerical method, utilizes the classical elastic-perfectly plastic material model initially proposed by Wilkins [M.L. Wilkins, Calculation of elastic-plastic flow, Meth. Comput. Phys. (1964)]. In this model, the Cauchy stress tensor is decomposed into the sum of its deviatoric part and the thermodynamic pressure which is defined by means of an equation of state. Regarding the deviatoric stress, its time evolution is governed by a classical constitutive law for isotropic material. The plasticity model employs the von Mises yield criterion and is implemented by means of the radial return algorithm. The numerical scheme relies on a finite volume cell-centered method wherein numerical fluxes are expressed in terms of sub-cell force. The generic form of the sub-cell force is obtained by requiring the scheme to satisfy a semi-discrete dissipation inequality. Sub-cell force and nodal velocity to move the grid are computed consistently with cell volume variation by means of a node-centered solver, which results from total energy conservation. The nominally second-order extension is achieved by developing a two-dimensional extension in the Lagrangian framework of the Generalized Riemann Problem methodology, introduced by Ben-Artzi and Falcovitz [M. Ben-Artzi, J. Falcovitz, Generalized Riemann Problems in Computational Fluid Dynamics, Cambridge Monogr. Appl. Comput. Math. (2003)]. Finally, the robustness and the accuracy of the numerical scheme are assessed through the computation of several test cases.
Concomitant occurrence of patch granuloma annulare and classical granuloma annulare.
Tsuruta, Daisuke; Sowa, Junko; Hiroyasu, Sho; Ishii, Masamitsu; Kobayashi, Hiromi
2011-05-01
Granuloma annulare (GA) is characterized clinically as annularly-distributed, erythematous papules on the extremities in children and adolescents. GA is recognized histologically as palisading granulomas with central degenerated collagen and mucin deposits. Here, we present a case of concomitant occurrence of patch GA (PGA), the most rare type of GA, and classical GA in a patient. A 60-year-old man was referred to our hospital for asymptomatic eruptions on the upper arms, forearms, right flank and right lateral chest. Clinical examination revealed annular erythematous plaques composed of numerous small papules on bilateral upper arms and forearms. Moreover, an indurative, exudative erythematous to violaceous plaque was present on the right lateral chest and right flank. Histopathology of the former was compatible with palisade-type GA, and the latter interstitial-type GA. This is the first report of PGA concomitant with "classical" annular papular lesions. PMID:21352310
Entrance and exit region friction factor models for annular seal analysis. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
Elrod, David Alan
1988-01-01
The Mach number definition and boundary conditions in Nelson's nominally-centered, annular gas seal analysis are revised. A method is described for determining the wall shear stress characteristics of an annular gas seal experimentally. Two friction factor models are developed for annular seal analysis; one model is based on flat-plate flow theory; the other uses empirical entrance and exit region friction factors. The friction factor predictions of the models are compared to experimental results. Each friction model is used in an annular gas seal analysis. The seal characteristics predicted by the two seal analyses are compared to experimental results and to the predictions of Nelson's analysis. The comparisons are for smooth-rotor seals with smooth and honeycomb stators. The comparisons show that the analysis which uses empirical entrance and exit region shear stress models predicts the static and stability characteristics of annular gas seals better than the other analyses. The analyses predict direct stiffness poorly.
Manufacture of annular cermet articles
Forsberg, Charles W.; Sikka, Vinod K.
2004-11-02
A method to produce annular-shaped, metal-clad cermet components directly produces the form and avoids multiple fabrication steps such as rolling and welding. The method includes the steps of: providing an annular hollow form with inner and outer side walls; filling the form with a particulate mixture of ceramic and metal; closing, evacuating, and hermetically sealing the form; heating the form to an appropriate temperature; and applying force to consolidate the particulate mixture into solid cermet.
Multiple plate hydrostatic viscous damper
Ludwig, L.P.
1981-02-01
A device for damping radial motion of a rotating shaft is described. The damper comprises a series of spaced plates extending in a radial direction. A hydraulic piston is utilized to place a load in these plates. Each annular plate is provided with a suitable hydrostatic bearing geometry on at least one of its faces. This structure provides a high degree of dampening in a rotor case system of turbomachinery in general. The damper is particularly useful in gas turbine engines.
Multiple plate hydrostatic viscous damper
NASA Technical Reports Server (NTRS)
Ludwig, L. P. (Inventor)
1981-01-01
A device for damping radial motion of a rotating shaft is described. The damper comprises a series of spaced plates extending in a radial direction. A hydraulic piston is utilized to place a load in these plates. Each annular plate is provided with a suitable hydrostatic bearing geometry on at least one of its faces. This structure provides a high degree of dampening in a rotor case system of turbomachinery in general. The damper is particularly useful in gas turbine engines.
Annular beam shaping and optical trepanning
NASA Astrophysics Data System (ADS)
Zeng, Danyong
surfaces of the annulus, respectively, and full Gaussian with maximum intensity within the annulus. Two refractive arrangements have been presented in this study. Geometric optics, or ray optics, describes light propagation in terms of rays. However, it is a simplification of optics, and fails to account for many important optical effects such as diffraction and polarization. The diffractive behaviors of this optical trepanning system are stimulated and analyzed based on the Fresnel diffraction integral. Diffraction patterns of the resulting optical system are measured using a laser beam analyzer and compared with the theoretical results. Based on the theoretical and experimental results, the effects of experimental parameters are discussed. We have designed the annular beam shaping optical elements and the gas delivery system to construct an optical trepanning system. Laser drilling experiments are performed on the Stainless Steel-316 (SS 316) plate and the Inconel 718 (IN 718) plate. The geometry of the trepanning holes with different sizes is presented in this study.
Development of annular targets for {sup 99}MO production.
Conner, C.; Lewandowski, E. F.; Snelgrove, J. L.; Liberatore, M. W.; Walker, D. E.; Wiencek, T. C.; McGann, D. J.; Hofman, G. L.; Vandegrift, G. F.
1999-09-30
The new annular target performed well during irradiation. The target is inexpensive and provides good heat transfer during irradiation. Based on these and previous tests, we conclude that targets with zirconium tubes and either nickel-plated or zinc-plated foils work well. We proved that we could use aluminum target tubes, which are much cheaper and easier to work with than the zirconium tubes. In aluminum target tubes nickel-plated fission-recoil barriers work well and prevent bonding of the foil to the new target tubes during irradiation. Also, zinc-plated and aluminum-foil barriers appear promising in anodized aluminum tubes. Additional tests are anticipated to address such issues as fission-recoil barrier thickness and uranium foil composition. Overall, however, the target was successful and will provide an inexpensive, efficient way to irradiate LEU metal foil for the production of {sup 99}Mo.
Annular Eclipse as Seen by Hinode
This timelapse shows an annular eclipse as seen by JAXA's Hinode satellite on Jan. 4, 2011. An annular eclipse occurs when the moon, slightly more distant from Earth than on average, moves directly...
Eosinophilic annular erythema in childhood - Case report.
Abarzúa, Alvaro; Giesen, Laura; Silva, Sergio; González, Sergio
2016-01-01
Eosinophilic annular erythema is a rare, benign, recurrent disease, clinically characterized by persistent, annular, erythematous lesions, revealing histopathologically perivascular infiltrates with abundant eosinophils. This report describes an unusual case of eosinophilic annular erythema in a 3-year-old female, requiring sustained doses of hydroxychloroquine to be adequately controlled. PMID:27579748
Eosinophilic annular erythema in childhood - Case report*
Abarzúa, Alvaro; Giesen, Laura; Silva, Sergio; González, Sergio
2016-01-01
Eosinophilic annular erythema is a rare, benign, recurrent disease, clinically characterized by persistent, annular, erythematous lesions, revealing histopathologically perivascular infiltrates with abundant eosinophils. This report describes an unusual case of eosinophilic annular erythema in a 3-year-old female, requiring sustained doses of hydroxychloroquine to be adequately controlled. PMID:27579748
Energy and Exergy Analysis of an Annular Thermoelectric Heat Pump
NASA Astrophysics Data System (ADS)
Kaushik, S. C.; Manikandan, S.; Hans, Ranjana
2016-04-01
In this paper, the concept of an annular thermoelectric heat pump (ATEHP) has been introduced. An exoreversible thermodynamic model of the ATEHP considering the Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for dimensionless heating power, optimum current at the maximum energy, exergy efficiency conditions and dimensionless irreversibilities in the ATEHP are derived. The results show that the heating power, energy and exergy efficiency of the ATEHP are lower than the flat-plate thermoelectric heat pump. The effects of annular shape parameter (S r = r 2 /r 1), dimensionless temperature ratio (θ = T h /T c) and the electrical contact resistances on the heating power, energy/exergy efficiency of an ATEHP have been studied. This study will help in the designing of actual ATEHP systems.
Energy and Exergy Analysis of an Annular Thermoelectric Heat Pump
NASA Astrophysics Data System (ADS)
Kaushik, S. C.; Manikandan, S.; Hans, Ranjana
2016-07-01
In this paper, the concept of an annular thermoelectric heat pump (ATEHP) has been introduced. An exoreversible thermodynamic model of the ATEHP considering the Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for dimensionless heating power, optimum current at the maximum energy, exergy efficiency conditions and dimensionless irreversibilities in the ATEHP are derived. The results show that the heating power, energy and exergy efficiency of the ATEHP are lower than the flat-plate thermoelectric heat pump. The effects of annular shape parameter ( S r = r 2 /r 1), dimensionless temperature ratio ( θ = T h /T c) and the electrical contact resistances on the heating power, energy/exergy efficiency of an ATEHP have been studied. This study will help in the designing of actual ATEHP systems.
Annular arc accelerator shock tube
NASA Technical Reports Server (NTRS)
Leibowitz, L. P. (Inventor)
1976-01-01
An annular arc accelerator shock tube employs a cold gas driver to flow a stream of gas from an expansion section through a high voltage electrode section to a test section, thus driving a shock wave in front of it. A glow discharge detects the shock wave and actuates a trigger generator which in turn fires spark-gap switches to discharge a bank of capacitors across a centered cathode and an annular anode in tandem electrode sections. The initial shock wave passes through the anode section from the cathode section thereby depositing energy into the flow gas without the necessity of any diaphragm opening in the gas flow from the expansion section through the electrode sections.
Behavior interrelationships in annular flow
NASA Astrophysics Data System (ADS)
Schubring, Duwayne
Two-phase gas-liquid flow occurs in many types of industrial boiling and condensing heat transfer equipment, including the reactor cores of boiling water nuclear reactors (BWRs) and the steam generators of pressurized water reactors (PWRs). In annular flow, the liquid phase often travels as both a thin film around the wall (containing disturbance waves and base film) and as entrained droplets in the central gas core. Gas bubbles are also often entrained into this film. Annular flow displays several quantifiable flow behaviors, including pressure loss, disturbance waves, and film thickness, along with micro-scale velocity profiles and fluctuations in the liquid film. The conventional approach to annular flow closely links film thickness and pressure loss, but relies on an assumed film velocity profile and does not consider disturbance waves explicitly. The present work seeks to explore a more complete range of behaviors in both horizontal and vertical flow to explore the relationships among them and thereby improve modeling of annular flow. Several of these investigations employ quantitative visualization. Modern optics and computing (in the form of non-trivial data reduction codes) are applied to the study of two-phase flow to process images of a physical experiment to quantify behavior information. Quantitative visualization allows for rapid acquisition of a large volume of flow behavior data, which allows for analysis of the flow behaviors themselves and how they relate to one another and to global modeling. By integrating behavior data from these quantitative visualizations and other conventional experimental investigations, a new two-region (base film and disturbance wave) model is proposed that can be implemented given only flow rates, external geometry, and fluid properties.
Energy Focusability of Annular Beams
NASA Astrophysics Data System (ADS)
Astadjov, Dimo N.
2010-01-01
A simulation of coherent annular flat two-level beams by two-dimensional Fast Fourier Transform is presented. After parameterization of the source beam (the `input') we examined the influence of its parameters on the shape and proportions of the output beam profile. The output pattern has a prominent central peak and faint rings concentrically surrounding it. The fraction of the central peak energy to the whole energy of beam, PF0 gives a notion of energy spread within the focal spot: PF0 is a function of beam annularity, k (i.e. `inside diameter/outside diameter' ratio) and the intensity dip, Idip of annulus central area (i.e. ring intensity minus central-bottom intensity, normalized). Up to k = 0.8 and Idip = 0.75, PF0 does not change too much—it is ⩾0.7 which is ⩾90% of PF0 maximum (0.778 at k = 0 and Idip = 0). Simulations revealed that even great changes in the shape of input beam annulus lead to small variations in the energy spread of output beam profile in the range of practical use of coherent annular beams.
Granuloma annulare in herpes zoster scars.
Ohata, C; Shirabe, H; Takagi, K; Kawatsu, T
2000-03-01
A 54-year-old Japanese female developed granuloma annulare twice in herpes zoster scars. Soon after the second event, she developed ulcerative colitis, which was well controlled by sulfonamides and corticosteroid suppository. She had no history of diabetes mellitus. There was no recurrence of granuloma annulare by June of 1999. Granuloma annulare might have contributed to the complications of ulcerative colitis, although this had not been noticed before. PMID:10774142
Annular Solar Eclipse of 10 May 1994
NASA Technical Reports Server (NTRS)
Espenak, Fred; Anderson, Jay
1993-01-01
An annular eclipse of the Sun will be widely visible from the Western Hemisphere on 10 May 1994. The path of the Moon's shadow passes through Mexico, the United States of America, maritime Canada, the North Atlantic, the Azores and Morocco. Detailed predictions for this event are presented and include tables of geographic coordinates of the annular path, local circumstances for hundreds of cities, maps of the path of annular and partial eclipse, weather prospects, and the lunar limb profile.
Na, Shuai; Chen, Albert I H; Wong, Lawrence L P; Li, Zhenhao; Macecek, Mirek; Yeow, John T W
2016-09-01
A novel design of an air-coupled capacitive micromachined ultrasonic transducer (CMUT) with annular cell geometry (annular CMUT) is proposed. Finite element analysis shows that an annular cell has a ratio of average-to-maximum displacement (RAMD) of 0.52-0.58 which is 58-76% higher than that of a conventional circular cell. The increased RAMD leads to a larger volume displacement which results in a 48.4% improved transmit sensitivity and 127.3% improved power intensity. Single-cell annular CMUTs were fabricated with 20-μm silicon plates on 13.7-μm deep and 1.35-mm wide annular cavities using the wafer bonding technique. The measured RAMD of the fabricated CMUTs is 0.54. The resonance frequency was measured to be 94.5kHz at 170-V DC bias. The transmit sensitivity was measured to be 33.83Pa/V and 25.85Pa/V when the CMUT was excited by a continuous wave and a 20-cycle burst, respectively. The receive sensitivity at 170-V DC bias was measured to be 7.7mV/Pa for a 20-cycle burst, and 15.0mV/Pa for a continuous incident wave. The proposed annular CMUT design demonstrates a significant improvement in transmit efficiency, which is an important parameter for air-coupled ultrasonic transducers. PMID:27352025
Numerical Analysis of Residual Stress for Copper Base Brazed Stainless Steel Plate-Fin Structure
NASA Astrophysics Data System (ADS)
Xie, Qiaoyun; Ling, Xiang
2010-07-01
Copper base stainless steel plate-fin structure has been widely used as a heat exchanger in many fields. The nonlinear thermal reaction on the residual stress in brazing process of the plate-fin structure was studied in this paper. A finite element model (FEM) was proposed to simulate the heat transfer and the sequential residual stress generated in the plate-fin and filler metals based on thermal elastic-plastic theory. By the stress distribution in four paths marked in the structure obtained from FEM results, it is found that the maximum residual tensile stress occurs in the brazed joint next to the plate side and a crack would initiate in this region. Also, the first principle stresses of reference nodes were calculated and the conclusion is consistent with the simulation results. These results would provide some constructive instructions in the practical brazing procedure.
Confocal Annular Josephson Tunnel Junctions
NASA Astrophysics Data System (ADS)
Monaco, Roberto
2016-04-01
The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.
Confocal Annular Josephson Tunnel Junctions
NASA Astrophysics Data System (ADS)
Monaco, Roberto
2016-09-01
The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.
Bistability and hysteresis of annular impinging jets
NASA Astrophysics Data System (ADS)
Tisovsky, Tomas
2016-06-01
In present study, the bistability and hysteresis of annular impinging jets is investigated. Annular impinging jets are simulated using open source CFD code - OpenFOAM. Both flow field patterns of interest are obtained and hysteresis is found by means of dynamic mesh simulation. Effect of nozzle exit velocity on resulting hysteresis loop is also illustrated.
Digital controller design: Analysis of the annular suspension pointing system
NASA Technical Reports Server (NTRS)
Kuo, B. C.
1979-01-01
The Annular Suspension and Pointing System (ASPS) is a payload auxiliary pointing device of the Space Shuttle. The ASPS is comprised of two major subassemblies, a vernier and a coarse pointing subsystem. The experiment is attached to a mounting plate/rim combination which is suspended on magnetic bearing/actuators (MBA) strategically located about the rim. Fine pointing is achieved by gimballing the plate/rim within the MBA gaps. Control about the experiment line-of-sight is obtained through the use of a non-contacting rim drive and positioning torquer. All sensors used to close the servo loops on the vernier system are noncontacting elements. Therefore, the experiment is a free-flyer constrained only by the magnetic forces generated by the control loops.
Granuloma annulare with prominent lymphoid infiltrates ("pseudolymphomatous" granuloma annulare).
Cota, Carlo; Ferrara, Gerardo; Cerroni, Lorenzo
2012-05-01
Granuloma annulare (GA) is characterized histopathologically by 3 patterns: necrobiotic granuloma, interstitial incomplete form and, rarely, sarcoidal or tuberculoid granuloma. The amount of lymphoid infiltrate in GA is usually limited. We describe 10 cases of GA with prominent "pseudolymphomatous" lymphoid infiltrates mimicking cutaneous lymphoid hyperplasia. Patients were 6 males and 4 females (mean age 49.9 years, median age 47 years, age range 25-70). Lesions were localized to a limited area of the body (n = 6), or involved the entire trunk (n = 3), or were generalized (n = 1). The correct clinical diagnosis of GA was provided only in 30% of the cases. In all cases, histopathologic features were characterized by dense, nodular, superficial, and deep infiltrates of lymphocytes. Immunohistology revealed predominance of T lymphocytes in 7 of 7 tested cases. This "pseudolymphomatous" variant of GA represents a pitfall in the histopathologic diagnosis of the disease and may be misinterpreted as other types of cutaneous lymphoproliferative disorders. PMID:22207445
NASA Technical Reports Server (NTRS)
Anderson, W. W.; Joshi, S. M.
1975-01-01
An annular suspension and pointing system consisting of pointing assemblies for coarse and vernier pointing is described. The first assembly is attached to a carrier spacecraft (e.g., the space shuttle) and consists of an azimuth gimbal and an elevation gimbal which provide 'coarse' pointing. The second or vernier pointing assembly is made up of magnetic actuators of suspension and fine pointing, roll motor segments, and an instrument or experiment mounting plate around which is attached a continuous annular rim similar to that used in the annular momentum control device. The rim provides appropriate magnetic circuits for the actuators and the roll motor segments for any instrument roll position. The results of a study to determine the pointing accuracy of the system in the presence of crew motion disturbances are presented. Typical 3 sigma worst-case errors are found to be of the order of 0.001 arc-second.
Etizolam-induced superficial erythema annulare centrifugum.
Kuroda, K; Yabunami, H; Hisanaga, Y
2002-01-01
Erythema annulare centrifugum (EAC) is characterized by slowly enlarging annular erythematous lesions. Although the origin is not clear in most cases, EAC has been associated with infections, medications, and in rare cases, underlying malignancy. We describe a patient who developed annular erythematous lesions after etizolam administration. The eruptions were typical of the superficial form of EAC, both clinically and histopathologically. The lesions disappeared shortly after discontinuation of the medication. Patch testing with etizolam gave positive results. To our knowledge this is the first reported case of etizolam-induced superficial EAC. PMID:11952667
Sealing arrangement with annular flexible disc
Pennell, William E.; Honigsberg, Charles A.
1983-01-01
Fluid sealing arrangements including an annular shaped flexible disc having enlarged edges disposed within channel-shaped annular receptacles which are spaced from one another. The receptacles form an annular region for contacting and containing the enlarged edges of the disc, and the disc is preloaded to a conical configuration. The disc is flexibly and movably supported within the receptacles so that unevenly distributed relative motion between the components containing the receptacles is accommodated without loss of sealing contact between the edges of the disc and the walls of the receptacles.
NASA Astrophysics Data System (ADS)
Mahmood, Tahir; Kanapathipillai, Sangarapillai; Chowdhury, Mahiuddin
2013-06-01
This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-creep and elastic-plastic-creep finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.
Method and apparatus for continuous annular electrochromatography
Scott, Charles D.
1987-01-01
Separation of complex mixtures and solutions can be carried out using a method and apparatus for continuous annular electrochromatography. Solutes are diverted radially by an imposed electrical field as they move downward in a rotating chromatographic column.
Granuloma Annulare Treated with Excimer Laser
Ragi, Jennifer; Milgraum, Sandy
2012-01-01
Objective: To review the current therapy for granuloma annulare and report a case of refractory generalized granuloma annulare successfully treated with excimer laser. A discussion about the characteristics of excimer laser and the mechanism of its effectiveness is presented. Design: Patient case report and literature review. Setting: Outpatient dermatology practice. Participants: A 73-year-old woman suffering from generalized granuloma annulare for more than 40 years. Measurements: Change in clinical appearance of lesions. Results: Use of excimer laser therapy resulted in prompt and complete resolution in treated areas with no residual skin changes or side effects. Conclusion: Excimer laser therapy is a powerful treatment modality with minimal side effects for patients with granuloma annulare. Further study is necessary to elucidate optimal dosing, long-term efficacy, and safety profile. PMID:23198013
[Treatment of disseminated granuloma annulare with anthralin].
Jantke, M E; Bertsch, H-P; Schön, M P; Fuchs, T
2011-12-01
Granuloma annulare is a benign, often asymptomatic and self-limiting granulomatous skin disease. In cases of disseminated granuloma annulare, spontaneous regression is considerably less frequent than in localized forms so that therapy is often desired. Systemic treatments should always be assessed critically and reserved for patients who are severely affected and in whom treatment approaches with few side effects such as local application of anthralin do not suffice to achieve a satisfactory effect. PMID:21656108
Annular-Cross-Section CFE Chamber
NASA Technical Reports Server (NTRS)
Sharnez, Rizwan; Sammons, David W.
1994-01-01
Proposed continuous-flow-electrophoresis (CFE) chamber of annular cross section offers advantages over conventional CFE chamber, and wedge-cross-section chamber described in "Increasing Sensitivity in Continuous-Flow Electrophoresis" (MFS-26176). In comparison with wedge-shaped chamber, chamber of annular cross section virtually eliminates such wall effects as electro-osmosis and transverse gradients of velocity. Sensitivity enhanced by incorporating gradient maker and radial (collateral) flow.
Adaptive optics scanning ophthalmoscopy with annular pupils
Sulai, Yusufu N.; Dubra, Alfredo
2012-01-01
Annular apodization of the illumination and/or imaging pupils of an adaptive optics scanning light ophthalmoscope (AOSLO) for improving transverse resolution was evaluated using three different normalized inner radii (0.26, 0.39 and 0.52). In vivo imaging of the human photoreceptor mosaic at 0.5 and 10° from fixation indicates that the use of an annular illumination pupil and a circular imaging pupil provides the most benefit of all configurations when using a one Airy disk diameter pinhole, in agreement with the paraxial confocal microscopy theory. Annular illumination pupils with 0.26 and 0.39 normalized inner radii performed best in terms of the narrowing of the autocorrelation central lobe (between 7 and 12%), and the increase in manual and automated photoreceptor counts (8 to 20% more cones and 11 to 29% more rods). It was observed that the use of annular pupils with large inner radii can result in multi-modal cone photoreceptor intensity profiles. The effect of the annular masks on the average photoreceptor intensity is consistent with the Stiles-Crawford effect (SCE). This indicates that combinations of images of the same photoreceptors with different apodization configurations and/or annular masks can be used to distinguish cones from rods, even when the former have complex multi-modal intensity profiles. In addition to narrowing the point spread function transversally, the use of annular apodizing masks also elongates it axially, a fact that can be used for extending the depth of focus of techniques such as adaptive optics optical coherence tomography (AOOCT). Finally, the positive results from this work suggest that annular pupil apodization could be used in refractive or catadioptric adaptive optics ophthalmoscopes to mitigate undesired back-reflections. PMID:22808435
Annular gel reactor for chemical pattern formation
Nosticzius, Zoltan; Horsthemke, Werner; McCormick, William D.; Swinney, Harry L.; Tam, Wing Y.
1990-01-01
The present invention is directed to an annular gel reactor suitable for the production and observation of spatiotemporal patterns created during a chemical reaction. The apparatus comprises a vessel having at least a first and second chamber separated one from the other by an annular polymer gel layer (or other fine porous medium) which is inert to the materials to be reacted but capable of allowing diffusion of the chemicals into it.
Multiple Granuloma Annulare in a 2-year-old Child
Siddalingappa, Karjigi; Murthy, Sambasiviah Chidambara; Herakal, Kallappa; Kusuma, Marganahalli Ramachandra
2015-01-01
Granuloma annulare is a benign, self-limiting, inflammatory and granulomatous disease of unknown etiology occurring in both adults and children. An 18-month-old male child had multiple progressive annular plaques over the lower extremities. Clinical and histopathological features were consistent with granuloma annulare. Localized granuloma annulare is the most common form in children. We report a young child with multiple, progressive granuloma annulare over the lower extremities. PMID:26677301
Annular flow optimization: A new integrated approach
Maglione, R.; Robotti, G.; Romagnoli, R.
1997-07-01
During the drilling stage of an oil and gas well the hydraulic circuit of the mud assumes great importance with respect to most of the numerous and various constituting parts (mostly in the annular sections). Each of them has some points to be satisfied in order to guarantee both the safety of the operations and the performance optimization of each of the single elements of the circuit. The most important tasks for the annular part of the drilling hydraulic circuit are the following: (1) Maximum available pressure to the last casing shoe; (2) avoid borehole wall erosions; and (3) guarantee the hole cleaning. A new integrated system considering all the elements of the annular part of the drilling hydraulic circuit and the constraints imposed from each of them has been realized. In this way the family of the flow parameters (mud rheology and pump rate) satisfying simultaneously all the variables of the annular section has been found. Finally two examples regarding a standard and narrow annular section (slim hole) will be reported, showing briefly all the steps of the calculations until reaching the optimum flow parameters family (for that operational condition of drilling) that satisfies simultaneous all the flow parameters limitations imposed by the elements of the annular section circuit.
Aerodynamic performance of an annular classical airfoil cascade
NASA Technical Reports Server (NTRS)
Bergsten, D. E.; Stauter, R. C.; Fleeter, S.
1983-01-01
Results are presented for a series of experiments that were performed in a large-scale subsonic annular cascade facility that was specifically designed to provide three-dimensional aerodynamic data for the verification of numerical-calculation codes. In particular, the detailed three-dimensional aerodynamic performance of a classical flat-plate airfoil cascade is determined for angles of incidence of 0, 5, and 10 deg. The resulting data are analyzed and are correlated with predictions obtained from NASA's MERIDL and TSONIC numerical programs. It is found that: (1) at 0 and 5 deg, the airfoil surface data show a good correlation with the predictions; (2) at 10 deg, the data are in fair agreement with the numerical predictions; and (3) the two-dimensional Gaussian similarity relationship is appropriate for the wake velocity profiles in the mid-span region of the airfoil.
NASA Technical Reports Server (NTRS)
Wu, R. W. H.; Stagliano, T. R.; Witmer, E. A.; Spilker, R. L.
1978-01-01
These structural ring deflections lie essentially in one plane and, hence, are called two-dimensional (2-d). The structural rings may be complete or partial; the former may be regarded as representing a fragment containment ring while the latter may be viewed as a 2-d fragment-deflector structure. These two types of rings may be either free or supported in various ways (pinned-fixed, locally clamped, elastic-foundation supported, mounting-bracket supported, etc.). The initial geometry of each ring may be circular or arbitrarily curved; uniform-thickness or variable-thickness rings may be analyzed. Strain-hardening and strain-rate effects of initially-isotropic material are taken into account. An approximate analysis utilizing kinetic energy and momentum conservation relations is used to predict the after-impact velocities of each fragment and of the impact-affected region of the ring; this procedure is termed the collision-imparted velocity method (CIVM) and is used in the CIVM-JET 5 B program. This imparted-velocity information is used in conjunction with a finite-element structural response computation code to predict the transient, large-deflection, elastic-plastic responses of the ring. Similarly, the equations of motion of each fragment are solved in small steps in time. Provisions are made in the CIVM-JET 5B code to analyze structural ring response to impact attack by from 1 to 3 fragments, each with its own size, mass, translational velocity components, and rotational velocity. The effects of friction between each fragment and the impacted ring are included.
Annular bilayer magnetoelectric composites: theoretical analysis.
Guo, Mingsen; Dong, Shuxiang
2010-01-01
The laminated bilayer magnetoelectric (ME) composites consist of magnetostrictive and piezoelectric layers are known to have giant ME coefficient due to the high coupling efficiency in bending mode. In our previous report, the bar-shaped bilayer composite has been investigated by using a magnetoelectric-coupling equivalent circuit. Here, we propose an annular bilayer ME composite, which consists of magnetostrictive and piezoelectric rings. This composite has a much lower resonance frequency of bending mode compared with its radial mode. In addition, the annular bilayer ME composite is expected to respond to vortex magnetic field as well as unidirectional magnetic field. In this paper, we investigate the annular bilayer ME composite by using impedance-matrix method and predict the ME coefficients as a function of geometric parameters of the composites. PMID:20178914
Laser-Launched Flyer Plates and Direct Laser Shocks for Dynamic Material Property Measurements
NASA Astrophysics Data System (ADS)
Paisley, D. L.; Swift, D. C.; Johnson, R. P.; Kopp, R. A.; Kyrala, G. A.
2002-07-01
The Trident laser at Los Alamos was used to impart known and controlled shocks in various materials by launching flyer plates or by irradiating the sample directly. Materials investigated include copper, gold, NiTi, SS316, and other metals and alloys. Tensile spall strength, elastic-plastic transition, phase boundaries, and equation of state can be determined with small samples. Using thin samples (0.1 - 1.0 mm thick) as targets, high pressure gradients can be generated with relatively low pressures, resulting in high tensile strain rates (105 to 108 s-1). Free surface and interface velocities are recorded with point- and line-imaging VISARs. The flexible spatial and temporal pulse profiles of Trident, coupled with the use of laser-launched flyer plates, provides capabilities which complement experiments conducted using gas guns and tensile bars.
NASA Astrophysics Data System (ADS)
Patil, Mayuri Suresh
Plates or members containing plate elements have been used in the offshore, aerospace and construction industry. Cutouts are often located to lighten the weight of the structure, but these cutouts reduce the ultimate strength of the plate. A number of studies have taken place for determining the buckling strength of a perforated plated but few discuss the effect of material strain hardening on the buckling strength of a perforated plate. Buckling strength is often considered as an important criterial to determine the serviceable limit of the perforated plate in the offshore structure. The aim of the present study is to investigate the effect of material strain hardening on the strength characteristic of a perforated plate under uniaxial loading. This load at some point could lead to a possibility of instability. A square plate with perforation is considered here. The plate is considered to be simply supported at all four edges and has been kept straight. The perforation is located at the center of the plate. A number of ANSYS static nonlinear analysis are undertaken with different strain hardening material properties for AL7075. The Ramberg-Osgood method is used to determine the stress-strain curve for different strain hardening values. The plate thickness and the cutout size of the perforation are varied to determine the effect on the strength. The study covers the behavior of the system in the elastic buckling and the elastic-plastic region.
Miller, M.P.; Barton, N.R.
2000-01-01
Rolled aluminum alloys are known to be anisotropic due to their processing histories. This paper focuses on measuring and modeling monotonic and cyclic strength anisotropies as well as the associated anisotropy of the elastic/elastic-plastic transition of a commercially-available rolled plate product. Monotonic tension tests were conducted on specimens in the rolling plane of 25.4 mm thick AA 7075-T6 plate taken at various angles to the rolling direction (RD). Fully-reversed tension/compression cyclic experiments were also conducted. As expected, the authors found significant anisotropy in the back-extrapolated yield strength. They also found that the character of the elastic/elastic-plastic transition (knee of the curve) to be dependent on the orientation of the loading axis. The tests performed in RD and TD (transverse direction) had relatively sharp transitions compared to the test data from other orientations. They found the cyclic response of the material to reflect the monotonic anisotropy. The material response reached cyclic stability in 10 cycles or less with very little cyclic hardening or softening observed. For this reason, they focused their modeling effort on predicting the monotonic response. Reckoning that the primary source of anisotropy in the rolled plate is the processing-induced crystallographic texture, they employed the experimentally-measured texture of the undeformed plate material in continuum slip polycrystal plasticity model simulations of the monotonic experiments. Three types of simulations were conducted, upper and lower bound analyses and a finite element calculation that associates an element with each crystal in the aggregate. They found that all three analyses predicted anisotropy of the back-extrapolated yield strength and post-yield behavior with varying degrees of success in correlating the experimental data.
Azimuthally forced flames in an annular combustor
NASA Astrophysics Data System (ADS)
Worth, Nicholas; Dawson, James; Mastorakos, Epaminondas
2015-11-01
Thermoacoustic instabilities are more likely to occur in lean burn combustion systems, making their adoption both difficult and costly. At present, our knowledge of such phenomena is insufficient to produce an inherently stable combustor by design, and therefore an improved understanding of these instabilities has become the focus of a significant research effort. Recent experimental and numerical studies have demonstrated that the symmetry of annular chambers permit a range of self-excited azimuthal modes to be generated in annular geometry, which can make the study of isolated modes difficult. While acoustic forcing is common in single flame experiments, no equivalent for forced azimuthal modes in an annular chamber have been demonstrated. The present investigation focuses on the novel application of acoustic forcing to a laboratory scale annular combustor, in order to generate azimuthal standing wave modes at a prescribed frequency and amplitude. The results focus on the ability of the method to isolate the mode of oscillation using experimental pressure and high speed OH* measurements. The successful excitation of azimuthal modes demonstrated represents an important step towards improving our fundamental understanding of this phenomena in practically relevant geometry.
Paisley, D.L.; Warnes, R.H.; Kopp, R.A.
1991-01-01
Miniature laser-driven flat plates (<1-mm diam {times} 0.5--10{mu}m thick, typical) of aluminum, cooper, tungsten, and other materials are accelerated to {le}5 km/s. These miniature plates are used to generate one-dimensional shock waves in solids, liquids, and crystals. Dynamic measurements of spall strength at strain rates {le}10{sup 7} s{sup {minus}1}, elastic-plastic shock wave profiles in 10-{mu}m-thick targets, shocked free-surface acceleration of 10{sup 12} m/s{sup 2}, and laser-driven plate launch accelerations of 10{sup 10} m/s{sup 2} are routinely obtained. The small size of the sample of and projectile mass permits recovery of targets without additional unintended damage or energy deposited into the test specimen. These miniature plates can be launched with conventional 1-J laboratory lasers. 10 refs., 5 figs.
Experimental equipment for measuring physical properties of the annular hydrostatic thrust bearing
NASA Astrophysics Data System (ADS)
Kozdera, Michal; Drábková, Sylva; Bojko, Marian
2014-03-01
The hydraulic circuit, through which the mineral oil is brought, is an important part of hydrostatic bearings. The annular hydrostatic thrust bearing consists of two sliding plates divided by a layer of mineral oil. In the lower plate, there are oil grooves which distribute the liquid between the sliding areas. The hydraulic circuit is made of two basic parts: the energy source and the controlling part. The hydraulic pump, which brings the liquid into the sliding bearing, is the source of the pressure energy. The sliding bearing is weighted down by axial force, which can be changed during the process. That's why in front of the particular oil grooves control components adjusting pressure and flow size are located. This paper deals with a project of a hydraulic circuit for regulation of fluid layer in the annular hydrostatic thrust bearing and the testing equipment for measuring its physical properties. It will include the issue of measuring loading capacity and height of the fluid layer in the annular hydrostatic thrust bearing.
NASA Technical Reports Server (NTRS)
Juhasz, A. J.
1975-01-01
The effect of wall edge suction on the performance of a short annular dump diffuser having a perforated plate flow resistance device in the exit passage was evaluated. Testing was conducted with air at near ambient pressure and temperature at inlet Mach numbers of 0.18 and 0.27 with suction rates up to 13.5 percent. Results show that pressure recovery downstream of the perforated plate was improved significantly by suction. Optimum performance was obtained with the flow resistance plate located at one inlet passage height downstream of the dump plane.
Gordon, R.G. )
1991-01-01
The motion of tectonic plates on the earth is characterized in a critical review of U.S. research from the period 1987-1990. Topics addressed include the NUVEL-1 global model of current plate motions, diffuse plate boundaries and the oceanic lithosphere, the relation between plate motions and distributed deformations, accelerations and the steadiness of plate motions, the distribution of current Pacific-North America motion across western North America and its margin, plate reconstructions and their uncertainties, hotspots, and plate dynamics. A comprehensive bibliography is provided. 126 refs.
Management of Periocular Granuloma Annulare Using Topical Dapsone
Patel, Mayha; Shitabata, Paul; Horowitz, David
2015-01-01
Granuloma annulare is a disease characterized by granulomatous inflammation of the dermis. Localized granuloma annulare may resolve spontaneously, while generalized granuloma annulare may persist for decades. The authors present the case of a 41-year-old Hispanic man with a two-week history of periocular granuloma annulare. Due to previously reported success in the use of systemic dapsone for the treatment of granuloma annulare, and the periocular proximity of the patient’s lesion, topical dapsone was used for treatment. Various additional therapies for the management of granuloma annulare have been reported, such as topical and systemic steroids, isotretinoin, pentoxifylline, cyclosporine, Interferon gamma, potassium iodide, nicotinamide, niacinamide, salicylic acid, fumaric acid ester, etanercept, infliximab, and hydroxychloroquine. Additional clinical trials are necessary to further evaluate the effectiveness of topical dapsone in the management of granuloma annulare. PMID:26203321
LDV measurements in an annular combustor model
NASA Astrophysics Data System (ADS)
Barron, Dean A.
1986-08-01
The design and setup of a Laser Doppler Velocimeter (LDV) system used to take velocity measurements in an annular combustor model are covered. The annular combustor model is of contemporary design using 60 degree flat vane swirlers, producing a strong recirculation zone. Detailed measurements are taken of the swirler inlet air flow and of the downstream enclosed swirling flow. The laser system used is a two color, two component system set up in forward scatter. Detailed are some of the special considerations needed for LDV use in the confined turbulent flow of the combustor model. The LDV measurements in a single swirler rig indicated that the flow changes radically in the first duct height. After this, a flow profile is set up and remains constant in shape. The magnitude of the velocities gradually decays due to viscous damping.
Development of an Advanced Annular Combustor
NASA Technical Reports Server (NTRS)
Rusnak, J. P.; Shadowen, J. H.
1969-01-01
The objective of the effort described in this report was to determine the structural durability of a full-scale advanced annular turbojet combustor using ASTM A-1 type fuel and operating at conditions typical of advanced supersonic aircraft. A full-scale annular combustor of the ram-induction type was fabricated and subjected to a 325-hour cyclic endurance test at conditions representative of operation in a Mach 3.0 aircraft. The combustor exhibited extensive cracking and scoop burning at the end of the test program. But these defects had no appreciable effect on combustor performance, as performance remained at a high level throughout the endurance program. Most performance goals were achieved with pressure loss values near 6% and 8%, and temperature rise variation ratio (deltaTVR) values near 1.25 and l.22 at takeoff and cruise conditions, respectively. Combustion efficiencies approached l004 and the exit radial temperature profiles were approximately as desired.
LDV Measurements in an Annular Combustor Model
NASA Technical Reports Server (NTRS)
Barron, Dean A.
1996-01-01
This thesis covers the design and setup of a laser doppler velocimeter (LDV) system used to take velocity measurements in an annular combustor model. The annular combustor model is of contemporary design using 60 degree flat vane swirlers, producing a strong recirculation zone. Detailed measurements are taken of the swirler inlet air flow and of the downstream enclosed swirling flow. The laser system used is a two color, two component system set up in forward scatter. Detailed are some of the special considerations needed for LDV use in the confined turbulent flow of the combustor model. LDV measurements in a single swirler rig indicated that the flow changes radically in the first duct height. After this, a flow profile is set up and remains constant in shape. The magnitude of the velocities gradually decays due to viscous damping.
Annular and Total Solar Eclipses of 2003
NASA Technical Reports Server (NTRS)
Espenak, Fred; Anderson, Jay
2002-01-01
On Saturday, 2003 May 31, an annular eclipse of the Sun will be visible from a broad corridor that traverses the North Atlantic. The path of the Moon's antumbral shadow begins in northern Scotland, crosses Iceland and central Greenland, and ends at sunrise in Baffin Bay (Canada). A partial eclipse will be seen within the much broader path of the Moon's penumbral shadow, which includes most of Europe, the Middle East, central and northern Asia, and northwestern North America. The trajectory of the Moon's shadow is quite unusual during this event. The shadow axis passes to the far north where it barely grazes Earth's surface. In fact, the northern edge of the antumbra actually misses Earth so that one path limit is defined by the day/night terminator rather than by the shadow's upper edge. As a result, the track of annularity has a peculiar "D" shape that is nearly 1200 kilometers wide. Since the eclipse occurs just three weeks prior to the northern summer solstice, Earth's northern axis is pointed sunwards by 22.8 deg. As seen from the Sun, the antumbral shadow actually passes between the North Pole and the terminator. As a consequence of this extraordinary geometry, the path of annularity runs from east to west rather than the more typical west to east. The event transpires near the Moon's ascending node in Taurus five degrees north of Aldebaran. Since apogee occurs three days earlier (May 28 at 13 UT), the Moon's apparent diameter (29.6 arc-minutes) is still too small to completely cover the Sun (31.6 arc-minutes) resulting in an annular eclipse.
Atypical scabies presenting as annular patches.
Hossain, Delwar
2014-01-01
Scabies is a common parasitic disease that can be recognized by the development of itchy lesions and a predilection for certain places on the body. It may infrequently present with patchy lesions. We report a patient with well-defined annular patches. Histopathology showed an egg of the scabies mite in the epidermis. Treatment with permethrin cream resulted in complete resolution of her disease. PMID:22967356
The Annular Suspension and Pointing System /ASPS/
NASA Technical Reports Server (NTRS)
Anderson, W. W.; Woolley, C. T.
1978-01-01
The Annular Suspension and Pointing System (ASPS) may be attached to a carrier vehicle for orientation, mechanical isolation, and fine pointing purposes applicable to space experiments. It has subassemblies for both coarse and vernier pointing. A fourteen-degree-of-freedom simulation of the ASPS mounted on a Space Shuttle has yielded initial performance data. The simulation describes: the magnetic actuators, payload sensors, coarse gimbal assemblies, control algorithms, rigid body dynamic models of the payload and Shuttle, and a control system firing model.
Annular Alopecia Areata: Report of Two Cases
Bansal, Manish; Manchanda, Kajal; Pandey, SS
2013-01-01
Alopecia areata (AA) is an auto-immune disorder characterized by the appearance of non-scarring bald patches affecting the hair bearing areas of the body. Scalp is the most common site of involvement. AA can affect any age group. The usual pattern of the hair loss is oval or round. We hereby, report two cases of annular and circinate pattern of AA due to its unusual morphology. PMID:24403774
Neoclassical transport in an annular penning trap
Robertson, S.
1997-07-01
A modified Penning trap is described with an annular confinement region and a toroidal magnetic field. A non-neutral electron plasma is confined axially by an electrostatic field and, in the radial direction, particles are constrained to lie within a small drift distance of a cylindrical flux surface. Drift orbits of all particles are banana-shaped and collisions cause neoclassical transport. {copyright} {ital 1997 American Institute of Physics.}
Endoscopic measurements using a panoramic annular lens
NASA Technical Reports Server (NTRS)
Gilbert, John A.; Matthys, Donald R.
1992-01-01
The objective of this project was to design, build, demonstrate, and deliver a prototype system for making measurements within cavities. The system was to utilize structured lighting as the means for making measurements and was to rely on a stationary probe, equipped with a unique panoramic annular lens, to capture a cylindrical view of the illuminated cavity. Panoramic images, acquired with a digitizing camera and stored in a desk top computer, were to be linearized and analyzed by mouse-driven interactive software.
Performance of annular high frequency thermoacoustic engines
NASA Astrophysics Data System (ADS)
Rodriguez, Ivan A.
This thesis presents studies of the behavior of miniature annular thermoacoustic prime movers and the imaging of the complex sound fields using PIV inside the small acoustic wave guides when driven by a temperature gradient. Thermoacoustic engines operating in the standing wave mode are limited in their acoustic efficiency by a high degree of irreversibility that is inherent in how they work. Better performance can be achieved by using traveling waves in the thermoacoustic devices. This has led to the development of an annular high frequency thermoacoustic prime mover consisting of a regenerator, which is a random stack in-between a hot and cold heat exchanger, inside an annular waveguide. Miniature devices were developed and studied with operating frequencies in the range of 2-4 kHz. This corresponds to an average ring circumference of 11 cm for the 3 kHz device, the resonator bore being 6 mm. A similar device of 11 mm bore, length of 18 cm was also investigated; its resonant frequency was 2 kHz. Sound intensities as high as 166.8 dB were generated with limited heat input. Sound power was extracted from the annular structure by an impedance-matching side arm. The nature of the acoustic wave generated by heat was investigated using a high speed PIV instrument. Although the acoustic device appears symmetric, its performance is characterized by a broken symmetry and by perturbations that exist in its structure. Effects of these are observed in the PIV imaging; images show axial and radial components. Moreover, PIV studies show effects of streaming and instabilities which affect the devices' acoustic efficiency. The acoustic efficiency is high, being of 40% of Carnot. This type of device shows much promise as a high efficiency energy converter; it can be reduced in size for microcircuit applications.
Annular flow film characteristics in variable gravity.
MacGillivray, Ryan M; Gabriel, Kamiel S
2002-10-01
Annular flow is a frequently occurring flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space systems. Annular two-phase flow occurs in the mining and transportation of oil and natural gas, petrochemical processes, and boilers and condensers in heating and refrigeration systems. The flow regime is also anticipated during the refueling of space vehicles, and thermal management systems for space use. Annular flow is mainly inertia driven with little effect of buoyancy. However, the study of this flow regime is still desirable in a microgravity environment. The influence of gravity can create an unstable, chaotic film. The absence of gravity, therefore, allows for a more stable and axisymmetric film. Such conditions allow for the film characteristics to be easily studied at low gas flow rates. Previous studies conducted by the Microgravity Research Group dealt with varying the gas or liquid mass fluxes at a reduced gravitational acceleration.(1,2) The study described here continues this work by examining the effect of changing the gravitational acceleration (hypergravity) on the film characteristics. In particular, the film thickness and the associated pressure drops are examined. The film thickness was measured using a pair of two-wire conductance probes. Experimental data was collected over a range of annular flow set points by changing the liquid and gas mass flow rates, the liquid-to-gas density ratio and the gravitational acceleration. The liquid-to-gas density ratio was varied by collecting data with helium-water and air-water at the same flow rates. The gravitational effect was examined by collecting data during the microgravity and pull-up (hypergravity) portions of the parabolic flights. PMID:12446332
Gorman, Jhana; Hales, Jason Dean; Corona, Edmundo
2010-05-01
This report considers the calculation of the quasi-static nonlinear response of rectangular flat plates and tubes of rectangular cross-section subjected to compressive loads using quadrilateralshell finite element models. The principal objective is to assess the effect that the shell drilling stiffness parameter has on the calculated results. The calculated collapse load of elastic-plastic tubes of rectangular cross-section is of particular interest here. The drilling stiffness factor specifies the amount of artificial stiffness that is given to the shell element drilling Degree of freedom (rotation normal to the plane of the element). The element formulation has no stiffness for this degree of freedom, and this can lead to numerical difficulties. The results indicate that in the problems considered it is necessary to add a small amount of drilling tiffness to obtain converged results when using both implicit quasi-statics or explicit dynamics methods. The report concludes with a parametric study of the imperfection sensitivity of the calculated responses of the elastic-plastic tubes with rectangular cross-section.
Impact and Blast Resistance of Sandwich Plates
NASA Astrophysics Data System (ADS)
Dvorak, George J.; Bahei-El-Din, Yehia A.; Suvorov, Alexander P.
Response of conventional and modified sandwich plate designs is examined under static load, impact by a rigid cylindrical or flat indenter, and during and after an exponential pressure impulse lasting for 0.05 ms, at peak pressure of 100 MPa, simulating a nearby explosion. The conventional sandwich design consists of thin outer (loaded side) and inner facesheets made of carbon/epoxy fibrous laminates, separated by a thick layer of structural foam core. In the three modified designs, one or two thin ductile interlayers are inserted between the outer facesheet and the foam core. Materials selected for the interlayers are a hyperelas-tic rate-independent polyurethane;a compression strain and strain rate dependent, elastic-plastic polyurea;and an elastomeric foam. ABAQUS and LS-Dyna software were used in various response simulations. Performance comparisons between the enhanced and conventional designs show that the modified designs provide much better protection against different damage modes under both load regimes. After impact, local facesheet deflection, core compression, and energy release rate of delamination cracks, which may extend on hidden interfaces between facesheet and core, are all reduced. Under blast or impulse loads, reductions have been observed in the extent of core crushing, facesheet delaminations and vibration amplitudes, and in overall deflections. Similar reductions were found in the kinetic energy and in the stored and dissipated strain energy. Although strain rates as high as 10-4/s1 are produced by the blast pressure, peak strains in the interlayers were too low to raise the flow stress in the polyurea to that in the polyurethane, where a possible rate-dependent response was neglected. Therefore, stiff polyurethane or hard rubber interlayers materials should be used for protection of sandwich plate foam cores against both impact and blast-induced damage.
The terminal effects of chisel-shape projectile penetrating into metallic target plates
NASA Astrophysics Data System (ADS)
Tao, Xu; Yao, Xiaohu; Ma, Wei
2015-09-01
This work performs the analysis and simulation investigations of penetration behaviors of chisel-shape projectile. In analysis, the projectile is assumed to be a rigid body and the target plate is elastic-plastic material. By introducing the velocity potential function, the velocity field in target is first obtained. Then, the momentum equation is solved for determining the pressure and stress fields in the elastic and plastic regions in target. The variation of the resultant force subjected by the projectiles with the penetration depth is studied. The approximate expressions of penetration depth and the residual velocity with the initial impacting velocity are obtained for the exploration of the penetration mechanisms of the chisel-shape projectile. In numerical simulation, the main attention focuses on the dissipation mechanisms of the kinetic energy of the chisel-shape projectile in penetration process.
Functional specifications of the annular suspension pointing system, appendix A
NASA Technical Reports Server (NTRS)
Edwards, B.
1980-01-01
The Annular Suspension Pointing System is described. The Design Realization, Evaluation and Modelling (DREAM) system, and its design description technique, the DREAM Design Notation (DDN) is employed.
Design and fabrication of a 40-MHz annular array transducer
Ketterling, Jeffrey A.; Lizzi, Frederic L.; Aristizábal, Orlando; Turnbull, Daniel H.
2006-01-01
This paper investigates the feasibility of fabricating a 5-ring, focused annular array transducer operating at 40 MHz. The active piezoelectric material of the transducer was a 9-μm thick polyvinylidene fluoride (PVDF) film. One side of the PVDF was metallized with gold and forms the ground plane of the transducer. The array pattern of the transducer and electrical traces to each annulus were formed on a copper-clad polyimide film. The PVDF and polyimide were bonded with a thin layer of epoxy, pressed into a spherically curved shape, and then back filled with epoxy. A 5-ring transducer with equal area elements and 100 μm kerfs between annuli was fabricated and tested. The transducer had a total aperture of 6 mm and a geometric focus of 12 mm. The pulse/echo response from a quartz plate located at the geometric focus, two-way insertion loss (IL), complex impedance, electrical cross-talk, and lateral beamwidth were all measured for each annulus. The complex impedance data from each element were used to perform electrical matching and the measurements were repeated. After impedance matching, fc ≈ 36 MHz and BWs ranged from 31 to 39%. The ILs for the matched annuli ranged from −28 to −38 dB. PMID:16060516
Experiment of rocket-ram annular combustor
NASA Astrophysics Data System (ADS)
Yatsuyanagi, N.; Sakamoto, H.; Sato, K.; Ono, F.; Sasaki, M.; Takahashi, M.
In this experiment, the double-nozzle type of rocket-ram annular combustor with a total thrust of 5kN was designed and tested with varying ratios of thrust produced by rocket and ram. Thrust and pressure distribution along the common expansion nozzle, i.e., the ram combustor nozzle, were measured to investigate the effect of interaction of the two expansion gases on thrust. Enhancement of specific impulse was verified by the experiments. That is, the specific impulse gains in rocket-ram parallel operation, the ratio of rocket thrust to ram thrust being 50 to 50, were found to be 190 percent of gains in pure rocket operation.
Duration test of an annular colloid thruster.
NASA Technical Reports Server (NTRS)
Perel, J.; Mahoney, J. F.; Daley, H. L.
1972-01-01
An annular colloid thruster was continuously operated for 1023 hours. Performance was stable with no sparking and negligible drain currents observed. An average thrust of 25.1 micropounds and an average specific impulse of 1160 seconds were obtained at an accelerating voltage of 15 k he thruster exhaust beam was continuously neutralized using electrons and electrostatic vectoring was demonstrated periodically. The only clear trend with time was an increase in specific impulse during the last third of the test period. From these results the thruster lifetime was estimated to be over an order of magnitude greater than the test duration.
Wave turbulence in annular wave tank
NASA Astrophysics Data System (ADS)
Onorato, Miguel; Stramignoni, Ettore
2014-05-01
We perform experiments in an annular wind wave tank at the Dipartimento di Fisica, Universita' di Torino. The external diameter of the tank is 5 meters while the internal one is 1 meter. The tank is equipped by two air fans which can lead to a wind of maximum 5 m/s. The present set up is capable of studying the generation of waves and the development of wind wave spectra for large duration. We have performed different tests including different wind speeds. For large wind speed we observe the formation of spectra consistent with Kolmogorv-Zakharov predictions.
Tank evaluation system shielded annular tank application
Freier, D.A.
1988-10-04
TEST (Tank Evaluation SysTem) is a research project utilizing neutron interrogation techniques to analyze the content of nuclear poisons and moderators in tank shielding. TEST experiments were performed on an experimental SAT (Shielded Annular Tank) at the Rocky Flats Plant. The purpose of these experiments was threefold: (1) to assess TEST application to SATs, (2) to determine if Nuclear Safety inspection criteria could be met, and (3) to perform a preliminary calibration of TEST for SATs. Several experiments were performed, including measurements of 11 tank shielding configurations, source-simulated holdup experiments, analysis of three detector modes, resolution studies, and TEST scanner geometry experiments. 1 ref., 21 figs., 4 tabs.
Thread-annular flow in vertical pipes
NASA Astrophysics Data System (ADS)
Frei, Ch.; Lüscher, P.; Wintermantel, E.
2000-05-01
Thread injection is a promising method for different minimally invasive medical applications. This paper documents an experimental study dealing with an axially moving thread in annular pipe flow. Mass flow and axial force on the thread are measured for a 0.46 mm diameter thread in pipes with diameters between 0.55 and 1.35 mm. The experiments with thread velocities of up to 1.5 ms[minus sign]1 confirm the findings of theoretical studies that for clinical requirements the radius ratio between thread and pipe is crucial for the adjustments of mass ow and force on the thread.
Pseudomonas aeruginosa infection mimicking erythema annulare centrifugum.
Czechowicz, R T; Warren, L J; Moore, L; Saxon, B
2001-02-01
A 3-year-old girl receiving chemotherapy for acute lymphocytic leukaemia developed a rapidly expanding red annular plaque on her thigh, initially without signs of systemic toxicity or local pain. Subsequently she developed Pseudomonas aeruginosa sepsis and purpura at the leading edge of the plaque. Skin biopsy showed an extensive necrotizing vasculitis with numerous Gram-negative bacilli in the blood vessel walls. In immunocompromised individuals, skin biopsy and culture of cutaneous lesions for bacteria and fungi should be considered even in the absence of signs of systemic toxicity or multiple lesions. PMID:11233725
Endoscopic inspection using a panoramic annular lens
NASA Technical Reports Server (NTRS)
Gilbert, John A.; Matthys, Donald R.
1991-01-01
The objective of this one year study was to design, build, and demonstrate a prototype system for cavity inspection. A cylindrical view of the cavity interior was captured in real time through a compound lens system consisting of a unique panoramic annular lens and a collector lens. Images, acquired with a digitizing camera and stored in a desktop computer, were manipulated using image processing software to aid in visual inspection and qualitative analysis. A detailed description of the lens and its applications is given.
Interfacial friction in cocurrent upward annular flow
NASA Astrophysics Data System (ADS)
Hossfeld, L. M.; Bharathan, D.; Wallis, G. B.; Richter, H. J.
1982-03-01
Cocurrent upward annular flow is investigated, with an emphasis on correlating and predicting pressure drop. Attention is given to the characteristics of the liquid flow in the film, and the interaction of the core with the film. Alternate approaches are discussed for correlating suitably defined interfacial friction factors. Both approaches are dependent on knowledge of the entrainment in order to make predictions. Dimensional analysis is used to define characteristic parameters of the flow and an effort is made to determine, to the extent possible, the influences of these parameters on the interfacial friction factor.
Optical manipulation using optimal annular vortices.
Paez-Lopez, Rafael; Ruiz, Ulises; Arrizon, Victor; Ramos-Garcia, Ruben
2016-09-01
We discuss a simple method to generate a configurable annular vortex beam (AVB) with the maximum possible peak intensity, employing a phase hologram whose transmittance is the phase of a Bessel beam. Due to its maximum intensity, the AVB provides the optimal density of the orbital angular moment. Another attribute of the generated AVB is the relatively high invariance of the intensity profile when the topological charge is changed. We demonstrate the advantages and flexibility of these AVBs for optical trapping applications. PMID:27607992
Nonlinear features of Northern Annular Mode variability
NASA Astrophysics Data System (ADS)
Fu, Zuntao; Shi, Liu; Xie, Fenghua; Piao, Lin
2016-05-01
Nonlinear features of daily Northern Annular Mode (NAM) variability at 17 pressure levels are quantified by two different measures. One is nonlinear correlation, and the other is time-irreversible symmetry. Both measures show that there are no significant nonlinear features in NAM variability at the higher pressure levels, however as the pressure level decreases, the strength of nonlinear features in NAM variability becomes predominant. This indicates that in order to reach better prediction of NAM variability in the lower pressure levels, nonlinear features must be taken into consideration to build suitable models.
Laminar heat transfer in annular sector ducts
Soliman, H.M. )
1987-02-01
The continuing interest in compact heat exchangeers has created the need for friction factor and Nusselt number data for different passage shapes. It has long been recognized that circular tube results are generally not applicable to noncircular passages even when the hydraulic diameter is used as the characteristic dimension. Hence, design data should be generated for each passage individually, and a good source of such information is Shah and London. One duct geometry for which complete design information does not appear to be available in the open literature is that of annular sector ducts. Such configuration is encountered in multipassage internally finned tubes and many other compact het exchanger applications. The fluid flow problem for this configuration has been solved by Sparrow et al., and more recently by Niida. However, to the beest of the author's knowledge, the heat transfer results are not available yet. The purpose of this note is to summarize the analysis and results of fluid flow and heat transfer in annular sector ducts.
Detonation diffraction from an annular channel
NASA Astrophysics Data System (ADS)
Meredith, James; Ng, Hoi Dick; Lee, John H. S.
2010-12-01
In this study, gaseous detonation diffraction from an annular channel was investigated with a streak camera and the critical pressure for transmission of the detonation wave was obtained. The annular channel was used to approximate an infinite slot resulting in cylindrically expanding detonation waves. Two mixtures, stoichiometric acetylene-oxygen and stoichiometric acetylene-oxygen with 70% Ar dilution, were tested in a 4.3 and 14.3 mm channel width ( W). The undiluted and diluted mixtures were found to have values of the critical channel width over the cell size around 3 and 12 respectively. Comparing these results to values of the critical diameter ( d c ), in which a spherical detonation occurs, a value of critical d c / W c near 2 is observed for the highly diluted mixture. This value corresponds to the geometrical factor of the curvature term between a spherical and cylindrical diverging wave. Hence, the result is in support of Lee's proposed mechanism [Lee in Dynamics of Exothermicity, pp. 321, Gordon and Breach, Amsterdam, 1996] for failure due to diffraction based on curvature in stable mixtures such as those highly argon diluted with very regular detonation cellular patterns.
Annular and Total Solar Eclipses of 2010
NASA Technical Reports Server (NTRS)
Espenak, Fred; Anderson, J.
2008-01-01
While most NASA eclipse bulletins cover a single eclipse, this publication presents predictions for two solar eclipses during 2010. This has required a different organization of the material into the following sections. Section 1 -- Eclipse Predictions: The section consists of a general discussion about the eclipse path maps, Besselian elements, shadow contacts, eclipse path tables, local circumstances tables, and the lunar limb profile. Section 2 -- Annular Solar Eclipse of 2010 Ja n 15: The section covers predictions and weather prospects for the annular eclipse. Section 3 -- Total Solar Eclipse of 2010 Jul 11: The se ction covers predictions and weather prospects for the total eclipse. Section 4 -- Observing Eclipses: The section provides information on eye safety, solar filters, eclipse photography, and making contact timings from the path limits. Section 5 -- Eclipse Resources: The final section contains a number of resources including information on the IAU Working Group on Eclipses, the Solar Eclipse Mailing List, the NASA eclipse bulletins on the Internet, Web sites for the two 2010 eclipses, and a summary identifying the algorithms, ephemerides, and paramete rs used in the eclipse predictions.
NWIS MEASUREMENTS FOR URANIUM METAL ANNULAR CASTINGS
MATTINGLY, J.K.; VALENTINE, T.E.; MIHALCZO, J.T.
1998-03-13
This report describes measurements performed with annular uranium metal castings of different enrichments to investigate the use of {sup 252}Cf-source-driven noise analysis measurements as a means to quantify the amount of special nuclear material (SNM) in the casting. This work in FY 97 was sponsored by the Oak Ridge Y-12 Plant and the DOE Office of Technology Development Programs. Previous measurements and calculational studies have shown that many of the signatures obtained from the source-driven measurement are very sensitive to fissile mass. Measurements were performed to assess the applicability of this method to standard annular uranium metal castings at the Oak Ridge Y-12 plant under verification by the International Atomic Energy Agency (IAEA) using the Nuclear Weapons Identification System (NWIS) processor. Before the measurements with different enrichments, a limited study of source-detector-casting moderator configurations was performed to enhance the correlated information. These configurations consisted of a casting with no reflector and with various thicknesses of polyethylene reflectors up to 10.16 cm in 2.54 cm steps. The polyethylene moderator thickness of 7.62 cm was used for measurements with castings of different enrichments reported here. The sensitivity of the measured parameters to fissile mass was investigated using four castings each with a different enrichment. The high sensitivity of this measurement method to fissile mass and to other material and configurations provides some advantages over existing safeguards methods.
Non-elastic Plate Weakening at Tonga, Costa Rica and Japanese Subduction Zones
NASA Astrophysics Data System (ADS)
Arredondo, K.; Billen, M. I.
2010-12-01
Traditionally studies of plate bending in subduction zones have utilized elastic, viscous or elastic-plastic rheologies to model the deformation of subducting plates, yet they are based on averaged plate properties and do not take into account variations in plate strength. Direct measurements of plate strength at subduction zones could permit more detailed models of how plates deform during subduction and may allow differentiation between the elastic and viscous or plastic rheologies. Additionally, weakening of the subducting plate is important for understanding the degree of coupling of the surface plate to the negative buoyancy of descending slabs. To obtain quantitative measurements of changes in plate strength along profiles parallel to the trench, we use analysis of the gravity-topography admittance in three subduction zones: Tonga, Costa Rica and Japan. We show that the plate flexural rigidity decreases near and inside the trench of the Tonga and Japan subduction zones, in agreement with previous results for the Kermadec subduction zone (1). Near the trench the flexural rigidity values are consistently smaller than those predicted by an elastic rheology and the plate age (2). This degree of weakening, by up to 3 orders magnitude, suggests that the plate does not act elastically as it is subducted, possibly due to lithospheric-scale weakening by extensional faulting and plastic yielding at depth. In contrast lithospheric-scale weakening in the Costa Rica subduction zone is less clear. This may be due to the younger age of the subducting plate and the small age difference between the seamounts and surrounding plate, which limits the sensitivity of the gravity field to changes in the non-isostatic support of topographic feature. These results suggest that this technique is only applicable to older plates with large seamounts that are appreciably younger than the subducting plate. Comparison of the flexural rigidity results to the tectonic characteristics of all
75 FR 23582 - Annular Casing Pressure Management for Offshore Wells
Federal Register 2010, 2011, 2012, 2013, 2014
2010-05-04
... published the proposed rule Annular Casing Pressure Management for Offshore Wells (74 FR 38147). The comment... the published proposed rule 1010-AD47 Annular Casing Pressure Management for Offshore Wells (74 FR... subsea wellhead. (3) hybrid well, a riser or the production casing pressure is greater than 100...
Controlling the pressure within an annular volume of a wellbore
Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.
2010-06-29
A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.
Controlling the pressure within an annular volume of a wellbore
Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.; Coates, Don M.
2011-05-31
A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.
Controlling the pressure within an annular volume of a wellbore
Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.
2008-10-28
A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.
Controlling the pressure within an annular volume of a wellbore
Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.
2011-01-18
A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.
Controlling the pressure within an annular volume of a wellbore
Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.; Coates, Don M.
2011-06-21
A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.
Localized interstitial granuloma annulare induced by subcutaneous injections for desensitization.
Spring, Philipp; Vernez, Maxime; Maniu, Christa-Maria; Hohl, Daniel
2013-06-01
We describe a patient with interstitial granuloma annulare associated with subcutaneous injection therapy (SIT) for desensitization to a type I allergy. Asymptomatic, erythematous, violaceous annular patches were located at the injection sites on both her arms. Medical history revealed perennial rhinoconjonctivitis treated with SIT (Phostal Stallergen® cat 100% and D. pteronyssinus/D.farinae 50%:50%). PMID:24011321
Annular pancreas intra operatively discovered: a case report
Zeineb, Mzoughi; Sadri, Ben Abid; Nizar, Miloudi; Hassen, Hentati; Nafaa, Arfa; Taher, Khalfallah
2011-01-01
Annular pancreas is a rare congenital abnormality. This entity can rarely be symptomatic. Patients can present with gastrointestinal obstruction or acute pancreatitis. We report a case with a rich iconography, of an annular pancreas discovered intraoperatively. A 46-year-old woman was operated with the diagnosis of acute cholecystitis with common bile duct stones. At operation, a strip of pancreatic tissue (2 cm) completely encircled the second duodenum. Open cholecytectomy with choledocotomy and stones extractionwas done. Postoperatively, she developed an acute pancreatitis. The post-operative cholangiography showed the annular duct surrounding the second duodenum. Annular pancreas is rare. Symptoms may occur in newborn children. In adults, annular pancreas discovering is radiological or intra operatively. PMID:24765382
Virtual cathode microwave generator having annular anode slit
Kwan, T.J.T.; Snell, C.M.
1988-03-08
A microwave generator using an oscillating virtual cathode is described comprising: a cathode for emitting electrons; an anode for accelerating emitted electrons from the cathode, the anode having an annular slit therethrough effective for forming the virtual cathode and having at least one range thickness relative to electrons reflected from the virtual cathode; and magnet means for producing a magnetic field having a field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit and to enable the electrons reflected from the virtual cathode to axially diverge from the annular beam. The reflected electrons return toward the cathode diverge from the annular beam and are absorbed by the anode to substantially eliminate electrons reflexing between the cathode and the virtual cathode.
Eccentric annular crack under general nonuniform internal pressure
NASA Astrophysics Data System (ADS)
Moeini-Ardakani, S.; Kamali, M. T.; Shodja, H. M.
2016-08-01
For a better approximation of ring-shaped and toroidal cracks, a new eccentric annular crack model is proposed and an analytical approach for determination of the corresponding stress intensity factors is given. The crack is subjected to arbitrary mode I loading. A rigorous solution is provided by mapping the eccentric annular crack to a concentric annular crack. The analysis leads to two decoupled Fredholm integral equations of the second kind. For the sake of verification, the problem of a conventional annular crack is examined. Furthermore, for various crack configurations of an eccentric annular crack under uniform tension, the stress intensity factors pertaining to the inner and outer crack edges are delineated in dimensionless plots.
NASA Astrophysics Data System (ADS)
Morrow, T. A.; Mittelstaedt, E. L.; Olive, J. A. L.
2015-12-01
Observations along oceanic fracture zones suggest that some mid-ocean ridge transform faults (TFs) previously split into multiple strike-slip segments separated by short (<~50 km) intra-transform spreading centers and then reunited to a single TF trace. This history of segmentation appears to correspond with changes in plate motion direction. Despite the clear evidence of TF segmentation, the processes governing its development and evolution are not well characterized. Here we use a 3-D, finite-difference / marker-in-cell technique to model the evolution of localized strain at a TF subjected to a sudden change in plate motion direction. We simulate the oceanic lithosphere and underlying asthenosphere at a ridge-transform-ridge setting using a visco-elastic-plastic rheology with a history-dependent plastic weakening law and a temperature- and stress-dependent mantle viscosity. To simulate the development of topography, a low density, low viscosity 'sticky air' layer is present above the oceanic lithosphere. The initial thermal gradient follows a half-space cooling solution with an offset across the TF. We impose an enhanced thermal diffusivity in the uppermost 6 km of lithosphere to simulate the effects of hydrothermal circulation. An initial weak seed in the lithosphere helps localize shear deformation between the two offset ridge axes to form a TF. For each model case, the simulation is run initially with TF-parallel plate motion until the thermal structure reaches a steady state. The direction of plate motion is then rotated either instantaneously or over a specified time period, placing the TF in a state of trans-tension. Model runs continue until the system reaches a new steady state. Parameters varied here include: initial TF length, spreading rate, and the rotation rate and magnitude of spreading obliquity. We compare our model predictions to structural observations at existing TFs and records of TF segmentation preserved in oceanic fracture zones.
Intraorbital granuloma annulare in an elderly patient.
Barrett, Dianne; Petris, Carisa; Garrido Hermosilla, Antonio Manuel; Oktavec, Kathleen; Mansukhani, Mahesh; Kazim, Michael
2016-06-01
Classically, granuloma annulare (GA) is a cutaneous disorder localized to the dorsum of the hands and/or feet in children and young adults. Very rarely it can present on the face and rarer still on periorbital structures such as the eyelid and orbital rim. Diagnosis hinges on clinical presentation and histological features, such as palisading granulomas with central destruction of collagen, presence of mucin and lymphohistiocytic infiltration. The etiology of this condition remains unknown, but may involve a delayed-type hypersensitivity reaction, malignancy and/or infection. Herein is the first reported case of an intraorbital GA in an 86-year-old male patient who presented with right eye proptosis. PMID:27163779
The liquid annular reactor system (LARS) propulsion
Maise, G.; Lazareth, O.W.; Horn, F.; Powell, J.R.; Ludewig, H. ); Lenard, R.X. )
1991-01-05
A new concept for very high specific impulse ({gt}2000 seconds) direct nuclear propulsion is described. The concept, termed LARS (Liquid Annular Reactor System) uses liquid nuclear fuel elements to heat hydrogen propellant to very high temperatures ({similar to}6000 K). Operating pressure is moderate ({similar to}10 atm), with the result that the outlet hydrogen is virtually 100% dissociated to monatomic H. The molten fuel is contained in a solid container of its own material, which is rotated to stabilize the liquid layer by centripetal force. LARS reactor designs are described, together with neutronic and thermal-hydraulic analyses. Power levels are on the order of 200 megawatts. Typically, LARS designs use 7 rotating fuel elements, are beryllium moderated and have critical radii of {similar to}100 cm (core L/D{approx}1.5).
Facility modernization Annular Core Research Reactor
Morris, F.M.; Luera, T.F.; McCrory, F.M.; Nelson, D.A.; Trowbridge, F.R.; Wold, S.A.
1990-07-01
The Annular Core Research Reactor (ACRR) has undergone numerous modifications since its conception in response to program needs. The original reactor fuel, which was special U-ZrH TRIGA fuel designed primarily for pulsing, has been replaced with a higher pulsing capacity BeO fuel. Other advanced operating modes which use this increased capability, in addition to the pulse and steady state, have been incorporated to tailor power histories and fluences to the experiments. Various experimental facilities have been developed that range from a radiography facility to a 50 cm diameter External Fuel Ring Cavity (FREC) using 180 of the original ZrH fuel elements. Currently a digital reactor console is being produced with GA, which will give enhanced monitoring capabilities of the reactor parameters while leaving the safety-related shutdown functions with analog technology. (author)
Annular MHD Physics for Turbojet Energy Bypass
NASA Technical Reports Server (NTRS)
Schneider, Steven J.
2011-01-01
The use of annular Hall type MHD generator/accelerator ducts for turbojet energy bypass is evaluated assuming weakly ionized flows obtained from pulsed nanosecond discharges. The equations for a 1-D, axisymmetric MHD generator/accelerator are derived and numerically integrated to determine the generator/accelerator performance characteristics. The concept offers a shockless means of interacting with high speed inlet flows and potentially offers variable inlet geometry performance without the complexity of moving parts simply by varying the generator loading parameter. The cycle analysis conducted iteratively with a spike inlet and turbojet flying at M = 7 at 30 km altitude is estimated to have a positive thrust per unit mass flow of 185 N-s/kg. The turbojet allowable combustor temperature is set at an aggressive 2200 deg K. The annular MHD Hall generator/accelerator is L = 3 m in length with a B(sub r) = 5 Tesla magnetic field and a conductivity of sigma = 5 mho/m for the generator and sigma= 1.0 mho/m for the accelerator. The calculated isentropic efficiency for the generator is eta(sub sg) = 84 percent at an enthalpy extraction ratio, eta(sub Ng) = 0.63. The calculated isentropic efficiency for the accelerator is eta(sub sa) = 81 percent at an enthalpy addition ratio, eta(sub Na) = 0.62. An assessment of the ionization fraction necessary to achieve a conductivity of sigma = 1.0 mho/m is n(sub e)/n = 1.90 X 10(exp -6), and for sigma = 5.0 mho/m is n(sub e)/n = 9.52 X 10(exp -6).
Recurrent Annular Peripheral Choroidal Detachment after Trabeculectomy
Liu, Shaohui; Sun, Lisa L.; Kavanaugh, A. Scott; Langford, Marlyn P.; Liang, Chanping
2013-01-01
We report a challenging case of recurrent flat anterior chamber without hypotony after trabeculectomy in a 54-year-old Black male with a remote history of steroid-treated polymyositis, cataract surgery, and uncontrolled open angle glaucoma. The patient presented with a flat chamber on postoperative day 11, but had a normal fundus exam and intraocular pressure (IOP). Flat chamber persisted despite treatment with cycloplegics, steroids, and a Healon injection into the anterior chamber. A transverse B-scan of the peripheral fundus revealed a shallow annular peripheral choroidal detachment. The suprachoroidal fluid was drained. The patient presented 3 days later with a recurrent flat chamber and an annular peripheral choroidal effusion. The fluid was removed and reinforcement of the scleral flap was performed with the resolution of the flat anterior chamber. A large corneal epithelial defect developed after the second drainage. The oral prednisone was tapered quickly and the topical steroid was decreased. One week later, his vision decreased to count fingers with severe corneal stromal edema and Descemet's membrane folds that improved to 20/50 within 24 h of resumption of the oral steroid and frequent topical steroid. The patient's visual acuity improved to 20/20 following a slow withdrawal of the oral and topical steroid. Eight months after surgery, the IOP was 15 mm Hg without glaucoma medication. The detection of a shallow anterior choroidal detachment by transverse B-scan is critical to making the correct diagnosis. Severe cornea edema can occur if the steroid is withdrawn too quickly. Thus, steroids should be tapered cautiously in steroid-dependent patients. PMID:24348402
NASA Technical Reports Server (NTRS)
Babecki, A. J. (Inventor); Haehner, C. L.
1973-01-01
A process for metal plating which comprises spraying a mixture of metallic powder and small peening particles at high velocity against a surface is described. The velocity must be sufficient to impact and bond metallic powder onto the surface. In the case of metal surfaces, the process has as one of its advantages providing mechanical working (hardening) of the surface simultaneously with the metal plating.
Results of fracture mechanics tests on PNC SUS 304 plate
Mills, W.J.; James, L.A.; Blackburn, L.D.
1985-08-01
PNC provided SUS 304 plate to be irradiated in FFTF at about 400/sup 0/C to a target fluence of 5 x 10/sup 21/ n/cm/sup 2/ (E > 0.1 MeV). The actual irradiation included two basically different exposure levels to assure that information would be available for the exposure of interest. After irradiation, tensile properties, fatigue-crack growth rates and J-integral fracture toughness response were determined. These same properties were also measured for the unirradiated material so radiation damage effects could be characterized. This report presents the results of this program. It is expected that these results would be applicable for detailed fracture analysis of reactor components. Recent advances in elastic-plastic fracture mechanics enable reasonably accurate predictions of failure conditions for flawed stainless steel components. Extensive research has focused on the development of J-integral-based engineering approach for assessing the load carrying capacity of low-strength, high-toughness structural materials. Furthermore, Kanninen, et al., have demonstrated that J-integral concepts can accurately predict the fracture response for full-scale cracked structures manufactured from Type 304 stainless steel.
Principle of radial transport in low temperature annular plasmas
Zhang, Yunchao Charles, Christine; Boswell, Rod
2015-07-15
Radial transport in low temperature annular plasmas is investigated theoretically in this paper. The electrons are assumed to be in quasi-equilibrium due to their high temperature and light inertial mass. The ions are not in equilibrium and their transport is analyzed in three different situations: a low electric field (LEF) model, an intermediate electric field (IEF) model, and a high electric field (HEF) model. The universal IEF model smoothly connects the LEF and HEF models at their respective electric field strength limits and gives more accurate results of the ion mobility coefficient and effective ion temperature over the entire electric field strength range. Annular modelling is applied to an argon plasma and numerical results of the density peak position, the annular boundary loss coefficient and the electron temperature are given as functions of the annular geometry ratio and Paschen number.
Virtual cathode microwave generator having annular anode slit
Kwan, Thomas J. T.; Snell, Charles M.
1988-01-01
A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit therethrough effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators.
Annular elastolytic giant cell granuloma: A report of 10 cases
Arora, Sandeep; Malik, Ajay; Patil, Chetan; Balki, Anil
2015-01-01
Annular elastolytic giant cell granuloma initially described by O’Brien in 1975 is a disorder of uncertain etiopathogenesis presenting with annular erythematous plaques predominantly on the sun-exposed areas. Hisptopathologically, it is characterized by elastin degenration, multinucleate giant cells, and elastophagocytosis. The authors came across 10 such cases, which were managed with hydroxychloroquine resulting in complete resolution in 4–6 months. PMID:26904442
Experimental Results for an Annular Aerospike with Differential Throttling
NASA Technical Reports Server (NTRS)
Ruf, Joseph H.; McDaniels, David M.
2005-01-01
A) MSFC funded an internal study on Altitude Compensating Nozzles: 1) Develop an ACN design and performance prediction tool. 2) Design, build and test cold flow ACN nozzles. 3) An annular aerospike nozzle was designed and tested. 4) Incorporated differential throttling to assess Thrust Vector Control. B) Objective of the test hardware: 1) Provide design tool verification. 2) Provide benchmark data for CFD calculations. 3) Experimentally measure side force, or TVC, for a differentially throttled annular aerospike.
Annular Arrays Of Solar Cells For Spinning Spacecraft
NASA Technical Reports Server (NTRS)
Spilker, Thomas R.
1995-01-01
Report proposes annular arrays of solar photovoltaic cells installed on spin-stabilized spacecraft. Annular array faces Sun. Typical array consists of two stacked annuli of solar cells: one annulus fixed about spin axis, while other divided into deployable sectors mounted on dual swing arms and stowed by folding them atop fixed annulus. Once released, deployable sectors swing outward under spring or centrifugal force and expose fixed array so it generates additional power.
Skov, Søren Nielsen; Røpcke, Diana Mathilde; Ilkjær, Christine; Rasmussen, Jonas; Tjørnild, Marcell Juan; Jimenez, Jorge H; Yoganathan, Ajit P; Nygaard, Hans; Nielsen, Sten Lyager; Jensen, Morten Olgaard
2016-03-21
Limited knowledge exists about the forces acting on mitral valve annuloplasty repair devices. The aim of this study was to develop a new mitral annular force transducer to measure the forces acting on clinically used mitral valve annuloplasty devices. The design of an X-shaped transducer in the present study was optimized for simultaneous in- and out-of-plane force measurements. Each arm was mounted with strain gauges on four circumferential elements to measure out-of-plane forces, and the central parts of the X-arms were mounted with two strain gauges to measure in-plane forces. A dedicated calibration setup was developed to calibrate isolated forces with tension and compression for in- and out-of-plane measurements. With this setup, it was possible with linear equations to isolate and distinguish measured forces between the two planes and minimize transducer arm crosstalk. An in-vitro test was performed to verify the crosstalk elimination method and the assumptions behind it. The force transducer was implanted and evaluated in an 80kg porcine in-vivo model. Following crosstalk elimination, in-plane systolic force accumulation was found to be in average 4.0±0.1N and the out-of-plane annular segments experienced an average force of 1.4±0.4N. Directions of the systolic out-of-plane forces indicated movements towards a saddle shaped annulus, and the transducer was able to measure independent directional forces in individual annular segments. Further measurements with the new transducer coupled with clinical annuloplasty rings will provide a detailed insight into the biomechanical dynamics of these devices. PMID:26903412
Experiment of rocket-ram annular combustor
NASA Astrophysics Data System (ADS)
Yatsuyanagi, Nobuyuki; Sakamoto, Hiroshi; Sato, Kazuo; Sasaki, Masaki; Ono, Fumiei
Superiority in specific impulse of the double-nozzle type of rocket-ram combined engine over the ducted type of combined engine was shown by performance calculations. Then, a double-nozzle type of rocket-ram annular combustor with a total thrust of 5 kN was designed and experimentally tested with varying ratios of thrust produced by rocket and ram. With the combustor having different diverging half-angles, namely 10 deg 18 arcmin, and 6 deg 40 arcmin, thrust and pressure distribution along the common expansion nozzle were measured to investigate the effect of interaction of the two expansion gases on thrust. Enhancement of specific impulse was experimentally verified. That is, the specific impulse gained in rocket-ram parallel operations, the ratio of rocket thrust to ram thrust being 50 to 50, were found to be 190 percent of those in pure rocket operations. However, in the downstream region of the common nozzle, the flow might separate due to the generation of shock waves in either type of nozzle configuration.
Mechanical properties of stapedial annular ligament.
Gan, Rong Z; Yang, Fan; Zhang, Xiangming; Nakmali, Don
2011-04-01
Stapedial annular ligament (SAL) provides a sealed but mobile boundary between the stapes footplate and oval window bony wall. Mechanical properties of the SAL affect the transmission of ossicular movement into the cochlea in sound conduction. However, the mechanical properties of this tissue have never been investigated due to its complexity. In this paper, we report measurement of the viscoelastic properties of SAL on human cadaver temporal bones using a micro-material testing system with digital image correlation analysis. The measured load-deformation relations of SAL samples were converted into shear stress-shear strain relationship, stress relaxation function, and ultimate shear stress and shear strain of the SAL. The hyperelastic Ogden model was used to describe constitutive behavior of the SAL and a 3D finite element model of the experimental setup with SAL was created for assessing the effects of loading variation and measurement errors on results. The study demonstrates that the human SAL is a typical viscoelastic material with hysteresis, nonlinear stress-strain relationship and stress relaxation function. The shear modulus changes from 3.6 to 220 kPa when the shear stress increases from 2 to 140 kPa. These results provide useful information on quasi-static behavior of the SAL. PMID:21112232
Simulation of cryogenic turbopump annular seals
NASA Astrophysics Data System (ADS)
Palazzolo, Alan B.
1993-11-01
San Andres employed the NBS software package MIPROPS to account for density's dependence on pressure in the simulation of liquid annular seals. His example on a LH2 seal showed a significant change in the mass coefficient compared to a constant density model. San Andres, Yang, and Childs extended this analysis by including the pressure and temperature dependence of density, specific heat, viscosity, volumetric expansion, and thermal conductivity in a coupled solution of the energy, momentum, and continuity equations. Their example showed very significant changes in stiffness and inertia for a high speed (38,000 rpm), large L/D ratio (0.5) LOX seal, as compared to their constant temperature results. The current research rederived the San Andres-Yang-Childs (SYC) analysis and extended it to include not only the Moody friction model of SYC but also the Hir's friction model. The derivation begins with obtaining the local differential equations of continuity, momentum, and energy conservation in the seal. These equations are averaged across the film thickness to obtain the resulting 'bulk flow' differential equations. Shear stress and convective heat loss through the stator (seal) and rotor are related to the Moody and Hir's friction factor model. The Holman analogy is employed to relate heat conduction in or out of the fluid film's boundary layer to the friction induced shear stress.
Fluxon Dynamics in Elliptic Annular Josephson Junctions
NASA Astrophysics Data System (ADS)
Monaco, Roberto; Mygind, Jesper
2016-04-01
We analyze the dynamics of a magnetic flux quantum (current vortex) trapped in a current-biased long planar elliptic annular Josephson tunnel junction. The system is modeled by a perturbed sine-Gordon equation that determines the spatial and temporal behavior of the phase difference across the tunnel barrier separating the two superconducting electrodes. In the absence of an external magnetic field, the fluxon dynamics in an elliptic annulus does not differ from that of a circular annulus where the stationary fluxon speed merely is determined by the system losses. The interaction between the vortex magnetic moment and a spatially homogeneous in-plane magnetic field gives rise to a tunable periodic non-sinusoidal potential which is strongly dependent on the annulus aspect ratio. We study the escape of the vortex from a well in the tilted potential when the bias current exceeds the depinning current. The smallest depinning current as well as the lowest sensitivity of the annulus to the external field is achieved when the axes ratio is equal to √{2}. The presented extensive numerical results are in good agreement with the findings of the perturbative approach. We also probe the rectifying properties of an asymmetric potential implemented with an egg-shaped annulus formed by two semi-elliptic arcs.
Solar cycle modulation of Southern Annular Mode
NASA Astrophysics Data System (ADS)
Kuroda, Yuhji
2016-04-01
Climate is known to be affected by various factors, including oceanic changes and volcanic eruptions. 11-year solar cycle change is one of such important factors. Observational analysis shows that the winter-mean North Atlantic Oscillation (NAO) and late-winter/spring Southern Annular Mode (SAM) show structural modulation associated with 11-year solar cycle. In fact, these signals tend to extend from surface to upper stratosphere and persistent longer period only in the High Solar (HS) years. In the present study, we used 35-year record of ERA-Interim reanalysis data and performed wave-energy and momentum analysis on the solar-cycle modulation of the SAM to examine key factors to create such solar-SAM relationship. It is found that enhanced wave-mean flow interaction tends to take place in the middle stratosphere in association with enhanced energy input from diabatic heating on September only in HS years. The result suggests atmospheric and solar conditions on September are keys to create solar-SAM relationship.
Granuloma annulare: another manifestation of Bartonella infection?
Smoller, B R; Madhusudhan, K T; Scott, M A; Horn, T D
2001-12-01
Granuloma annulare (GA) is a common cutaneous eruption whose pathogenesis remains unknown. Recent literature has suggested a relation between Borrelia infection and GA, a relation that has not been widely accepted. Earlier works attempted unsuccessfully to implicate various other infectious agents. Some reports have demonstrated the increased frequency of GA in patients with human immunodeficiency virus infection, again raising the possibility of an infectious etiology. Using polymerase chain reaction amplification, we examined 19 biopsy specimens from 19 patients with GA (14 with classic palisading GA and 5 with an interstitial pattern) for the presence of a 153-base pair sequence specific for Bartonella henselae or Bartonella quintana. None of our patients were known to be human immunodeficiency virus-positive. These primers failed to detect B. henselae and B. quintana DNA in any of the specimens examined. Our findings do not support the hypothesis that GA represents a granulomatous reaction pattern to cutaneous Bartonella infection. Nevertheless, we cannot exclude the possibility that there may be a relation in other geographic locations or in immunocompromised patients or that GA represents an autosensitization reaction in response to a distant site of infection. Additional studies are needed to address these hypotheses. PMID:11801791
NASA Astrophysics Data System (ADS)
Sun, Shufeng; Wu, Yuyuan; Zhao, Rongyi
2001-04-01
According to a separated phase flow model for vertical annular two-phase flow in an annular channel, the liquid film thickness, distributions of velocities and temperatures in the liquid layer are predicted in the range of heat fluxes: 6000-12000 W/m 2, mass flux: 500-1100 kg/m2 s. The pressure drop along the flow channel and heat transfer coefficient are also calculated. The liquid film thickness is in the order of micrometers and heat transfer coefficient is 2800-7800 W/m2 K of liquid nitrogen boiling in narrow annular channels. The measured heat transfer coefficient is 29% higher than the calculated values. With the mass flux increasing and the gap of the annular channel decreasing, pressure drop and heat transfer coefficient increase.
Internal combustion engine with a central crankshaft and integral tandem annular pistons
NASA Astrophysics Data System (ADS)
Esparbes, Bernard
1993-08-01
An internal combustion engine with tandem annular pistons and a central crankshaft is disclosed, based on that found in British patent 11027 of 11 May 1914. The piston block formed by the two pistons presents, at each axial extremity, a double axial skirt fitted with an outer crown forming the head of the piston as such, and an inner crown forming an inlet pump with a holding chamber radially located at the inside of the corresponding annular cylinder, in which the piston head delimits a combustion chamber. Radial fingers, crossing axial openings of the crankcase and radial holes of the piston block, have their inner radial ends engaged within wavy sinusoidal peripheral slots arranged in a bulging central portion of the central crankshaft set into rotation by alternating axial movements of the piston block. The admission of fuel or combustion sustaining gas is ensured axially by the extremities, valves, and openings in the end plates closing the holding chambers in which the inner crowns slide, fitted with valves to act as an inlet pump. The invention is particularly applicable to aircraft engines in view of the ease in which the shaft rotation can be adapted to such a use.
Sea Carousel—A benthic, annular flume
NASA Astrophysics Data System (ADS)
Amos, Carl L.; Grant, J.; Daborn, G. R.; Black, K.
1992-06-01
A benthic annular flume (Sea Carousel) has been developed and tested to measure in situ the erodibility of cohesive sediments. The flume is equipped with three optical backscatter sensors, a lid rotation switch, and an electromagnetic (EM) flow meter capable of detecting azimuthal and vertical components of flow. Data are logged at rates up to 10·66 Hz. Erodibility is inferred from the rate of change in suspended sediment concentration detected in the annulus. The energy-density/wave number spectrum of azimuthal flow showed peaks in the energy spectrum at paddle rotation wave numbers (k) of 14 and 7 m -1 (macroturbulent time scales) but were not significant. Friction velocity ( U*), measured (1) at 1 Hz using a flush-mounted hot-film sensor, and (2) derived from measured velocity profiles in the inner part of the logarithmic layer gave comparable results for Ū* < 0·064 m s -1. At higher values of U*, method (2) underpredicted by up to 20%. Method (1) showed radial increases in Ū* in the annulus for Ū y > 0·32 m s -1. Radial velocity gradients were proportional to ( Ū y - 0·32 m s -1). Maximum radial differences in U* were 10% for Ū y = 0·5 ms -1. Suspended sediment mass concentration ( S) in the annulus resulted in a significant decrease (10·5%) in Ū* derived by method (1) over the range 0< S<208 mg l -1. These decreases were not evident in method (2). Method (1) may, therefore, be subject to changes in stress sensor calibration with changes in S. Subaerial deployments of Sea Carousel caused severe substrate disturbance, water losses, and aeration of the annulus. Submarine deployments produced stable results, though dispersion of turbid flume water took place. Results clearly demonstrated the existence of 'Type I' and 'Type II' erosion documented from laboratory studies.
The modeling and design of the Annular Suspension and Pointing System /ASPS/. [for Space Shuttle
NASA Technical Reports Server (NTRS)
Kuo, B. C.; Lin, W. C. W.
1979-01-01
The Annular Suspension and Pointing System (ASPS) is a payload auxiliary pointing device of the Space Shuttle. The ASPS is comprised of two major subassemblies, a vernier and a coarse pointing subsystem. The three functions provided by the ASPS are related to the pointing of the payload, centering the payload in the magnetic actuator assembly, and tracking the payload mounting plate and shuttle motions by the coarse gimbals. The equations of motion of a simplified planar model of the ASPS are derived. Attention is given to a state diagram of the dynamics of the ASPS with position-plus-rate controller, the nonlinear spring characteristic for the wire-cable torque of the ASPS, the design of the analog ASPS through decoupling and pole placement, and the time response of different components of the continuous control system.
Mechanical Analysis of High Power Internally Cooled Annular Fuel
Zhao Jiyun; No, Hee Cheon; Kazimi, Mujid S.
2004-05-15
Annular fuel with internal flow is proposed to allow higher power density in pressurized water reactors. The structural behavior issues arising from the higher flow rate required to cool the fuel are assessed here, including buckling, vibrations, and potential wear problems. Five flow-induced vibration mechanisms are addressed: buckling instability, vortex-induced vibration, acoustic resonance, fluid-elastic instability, and turbulence-induced vibration. The structural behavior of the 17 x 17 traditional solid fuel array is compared with that of two types of annular fuels, a 15 x 15 array, and a 13 x 13 array.It is seen that the annular fuels are superior to the reference fuel in avoiding vibration-induced damage, even at a 50% increase in flow velocity above today's reactors. The higher resistance to vibration is mainly due to their relatively larger cross section area making them more rigid. The 13 x 13 annular fuel shows better structural performance than the 15 x 15 one due to its higher rigidity. Analysis of acoustic resonance of the inner channel cladding with pump blade passing frequencies showed that the acoustic frequencies are within 120% of the pulsation frequency. The annular fuel exhibits reduced impact, sliding, and fretting wear than the solid fuel, even at 150% flow rate of today's reactors.
New method of annular sub-apertures stitching
NASA Astrophysics Data System (ADS)
Su, Yun; Wang, Kai; Ruan, Ningjuan; Li, Bo
2009-05-01
Annular sub-apertures stitching technology is a feasible method for testing asphere without assistant equipment. The overlap area of two annular sub-apertures is needed to sample in traditional stitching way. The size of overlap area influences the accuracy and efficiency of annular sub-apertures stitching, since small area will deduce the error of calculation, otherwise, more sub-apertures will be needed. Based on the principle of annular sub-apertures interference, a model is built to calculate the parameters of sub-apertures according to equal thickness interference in this paper firstly; then two clear-cut interference areas near the center of asphere and annular sub-apertures are figured out by theory and simulation. A new method is presented to use interference area near the center of asphere as the overlap area to sample. The results of simulation in the paper reveal that this new method can reduce stitching error relatively and improve efficiency availably, solving the inconsistency of error and efficiency consequently.
Nematic polymer liquid-crystal wave plate for high-power lasers at 1054 nm
Kreuzer, F. ); Korenic, E.M.; Jacobs, S.D.; Houghton, J.K.; Schmid, A. )
1994-04-01
A nematic polymer liquid crystal is used to construct wave plates for use at 1054 nm. Three methods of wave-plate construction are discussed: double substrate with fiber spacers in homogeneous distribution, double substrate with fiber spacers in annular distribution, and single substrate. The polymer liquid crystal shows high laser-damage resistance, making it particularly useful for high-peak-power laser applications. Alignment techniques and measurement of birefringence for the highly viscous polymer are described.
Non-axisymmetric annular curtain stability
NASA Astrophysics Data System (ADS)
Ahmed, Zahir U.; Khayat, Roger E.; Maissa, Philippe; Mathis, Christian
2013-08-01
A stability analysis of non-axisymmetric annular curtain is carried out for an axially moving viscous jet subject in surrounding viscous gas media. The effect of inertia, surface tension, gas-to-liquid density ratio, inner-to-outer radius ratio, and gas-to-liquid viscosity ratio on the stability of the jet is studied. In general, the axisymmetric disturbance is found to be the dominant mode. However, for small wavenumber, the non-axisymmetric mode is the most unstable mode and the one likely observed in reality. Inertia and the viscosity ratio for non-axisymmetric disturbances show a similar stability influence as observed for axisymmetric disturbances. The maximum growth rate in non-axisymmetric flow, interestingly, appears at very small wavenumber for all inertia levels. The dominant wavenumber increases (decreases) with inertia for non-axisymmetric (axisymmetric) flow. Gas-to-liquid density ratio, curvature effect, and surface tension, however, exhibit an opposite influence on growth rate compared to axisymmetric disturbances. Surface tension tends to stabilize the flow with reductions of the unstable wavenumber range and the maximum growth rate as well as the dominant wavenumber. The dominant wavenumber remains independent of viscosity ratio indicating the viscosity ratio increases the breakup length of the sheet with very little influence on the size of the drops. The range of unstable wavenumbers is affected only by curvature in axisymmetric flow, whereas all the stability parameters control the range of unstable wavenumbers in non-axisymmetric flow. Inertia and gas density increase the unstable wavenumber range, whereas the radius ratio, surface tension, and the viscosity ratio decrease the unstable wavenumber range. Neutral curves are plotted to separate the stable and unstable domains. Critical radius ratio decreases linearly and nonlinearly with the wavenumber for axisymmetric and non-axisymmetric disturbances, respectively. At smaller Weber numbers, a
Cohen, Philip R; Carlos, Casey A
2015-07-01
Granuloma annulare, a benign dermatosis of undetermined etiology, typically presents in a localized or generalized form. It has 3 distinctive histologic patterns: an infiltrative (interstitial) pattern, a palisading granuloma pattern, and an epithelioid nodule (sarcoidal granuloma) pattern. A man whose granuloma annulare skin lesions mimicked sarcoidosis is described. His localized granuloma annulare presented with a total of 3 lesions that each had a distinctive clinical morphology: an annular lesion of individual papules, a dermal nodule, and a linear arrangement of 3 papules. Two of his lesions showed a palisading granuloma histology pattern of granuloma annulare; however, the linear papules on his posterior neck lesion demonstrated noncaseating granulomas consistent with either the epithelioid nodule histology pattern of granuloma annulare or sarcoidal granuloma compatible with sarcoidosis. A comprehensive evaluation excluded the diagnosis of systemic sarcoidosis. Using the PubMed database, an extensive literature search was performed on granuloma annulare, epithelioid nodule, sarcoidal granuloma, and sarcoidosis. The histology patterns of granuloma annulare-emphasizing the history and differentiating features of the epithelioid nodule pattern from cutaneous sarcoidosis-were reviewed. The epithelioid nodule (sarcoidal granuloma) histology pattern of granuloma annulare is uncommon and may mimic the histology changes observed in sarcoidosis skin lesions; the absence of asteroid or other giant cell inclusions and an increase in mucin deposition between the collagen bundles favor the diagnosis of granuloma annulare. In addition, the epithelioid nodule pattern of granuloma annulare can rarely also show other histologic patterns of granuloma annulare in the same biopsy specimen or concurrently present with other clinical lesions of granuloma annulare that demonstrate a palisading granuloma, or possibly an infiltrative, histology pattern. However, the presence of an
Derivation of anisotropic diffusion coefficients in a large annular cavity
Eiichi Suetomi; Hiroshi Sekimoto )
1993-06-01
A small reactor for a spacecraft or a small liquid-metal reactor for urban siting, decentralized electrical units, or seawater desalination is designed for a large leakage of neutrons from the reactor core. In these reactors, a movable annular reflector is used for reactivity control. Therefore, a large annular cavity exists between the core and the shielding materials. In this paper, anisotropic diffusion coefficients for a large annular cavity are derived by equating the neutron currents obtained by the diffusion equation and by the transport equation. These diffusion coefficients depend only on the geometrical configuration of the cavity. A numerical comparison of diffusion calculations using these diffusion coefficients and transport calculations shows good agreement.
Annular subaperture interferometric testing technique for large aspheric surfaces
NASA Astrophysics Data System (ADS)
Hou, Xi; Wu, Fan; Wu, Shibin; Chen, Qiang
2005-02-01
A new method to test large aspheric surface by using Annular Sub-aperture Interferometric Testing (ASIT) is described in this paper. It solves the two main difficulties, which are manufacture difficulty and high cost of auxiliary elements (optics compensator, CGH, large reflector) used generally in testing the large aspheric mirror. The method reduces departure between the reference wavefront and tested wavefront to the measurement range of the interferometer by testing annular subaperture of aspheric surface, which makes reference wavefronts with different curvature radius match corresponding annular subaperture, then sews all sub-aperture datum together with a suitable algorithm to get the whole information of the surface. A stitching mathematics model is provided. The feasibility of the technique has been demonstrated by comparing test results from an autocollimation test and ASIT of an 152-mm diameter paraboloidal mirror. This method extends the dynamic range of interferometric measurements, by which the large, fast aspheric surface can be directly tested without additional optical elements.
Imaging performance of annular apertures. II - Line spread functions
NASA Technical Reports Server (NTRS)
Tschunko, H. F. A.
1978-01-01
Line images formed by aberration-free optical systems with annular apertures are investigated in the whole range of central obstruction ratios. Annular apertures form lines images with central and side line groups. The number of lines in each line group is given by the ratio of the outer diameter of the annular aperture divided by the width of the annulus. The theoretical energy fraction of 0.889 in the central line of the image formed by an unobstructed aperture increases for centrally obstructed apertures to 0.932 for the central line group. Energy fractions for the central and side line groups are practically constant for all obstruction ratios and for each line group. The illumination of rectangular secondary apertures of various length/width ratios by apertures of various obstruction ratios is discussed.
Design and analysis of annular antenna arrays with different reflectors.
Shi, G; Joines, W T
2004-09-01
The design and performance of annular antenna arrays with reflectors is presented. Arrays with three shapes of reflectors are analysed and simulated. These include the corner reflector, the circular reflector and the elliptical reflector. Power-density distributions within the annular arrays with and without reflectors are obtained by using the FDTD method. Also, the image theory method is used to verify the FDTD results in one case. By comparing the power-density distribution pattern of all four of the array designs (three with different reflectors, one without reflector), it is readily seen in each case that the array with reflectors yields better power-efficiency than the array without reflectors and the elliptical reflector yields the best performance. Comparisons of each array are made using 4, 6 and 8 antennae in the annular array. By using the optimized results of the elliptical reflector, the requirement for the input-power level to each antenna is greatly reduced. PMID:15370818
The Annular Gap: Gamma-Ray & Radio Emission of Pulsars
NASA Astrophysics Data System (ADS)
Qiao, G. J.; Du, Y. J.; Han, J. L.; Xu, R. X.
2013-01-01
Pulsars have been found more than 40 years. Observations from radio to gamma-rays present abundant information. However, the radiation mechanism is still an open question. It is found that the annular gap could be formed in the magnetosphere of pulsars (neutron stars or quark stars), which combines the advantages of the polar cap, slot gap and outer gap models. It is emphasized that observations of some radio pulsars, normal and millisecond gamma-ray pulsars (MSGPs) show that the annular gap would play a very important role. Here we show some observational and theoretical evidences about the annular gap. For example, bi-drifting sub-pulses; radio and gamma-ray millisecond pulsars and so on.
Annular elastolytic giant cell granuloma in association with Hashimoto's thyroiditis.
Hassan, Rishi; Arunprasath, P; Padmavathy, L; Srivenkateswaran, K
2016-01-01
Annular elastolytic giant cell granuloma (AEGCG) is a rare granulomatous skin disease characterized clinically by annular plaques with elevated borders and atrophic centers found mainly on sun-exposed skin and histologically by diffuse granulomatous infiltrates composed of multinucleated giant cells, histiocytes and lymphocytes in the dermis along with phagocytosis of elastic fibers by multinucleated giant cells. We report a case of AEGCG in a 50-year-old woman and is highlighted for the classical clinical and histological findings of the disease and its rare co-existence with Hashimoto's thyroiditis. PMID:27057492
Portal annular pancreas: the pancreatic duct ring sign on MRCP.
Lath, Chinar O; Agrawal, Dilpesh S; Timins, Michael E; Wein, Melissa M
2015-12-01
Portal annular pancreas is a rare pancreatic variant in which the uncinate process of the pancreas extends and fuses to the dorsal surface of the body of the pancreas by surrounding the portal vein. It is asymptomatic, but it can be mistaken for a pancreatic head mass on imaging and could also have serious consequences during pancreatic surgery, if unrecognized. We report this case of a 53-year-old female patient who was diagnosed to have portal annular pancreas on the basis of an unusual course (ring appearance) of the main pancreatic duct on magnetic resonance cholangiopancreatography, not described earlier in the radiology literature. PMID:26649117
Annular elastolytic giant cell granuloma in association with Hashimoto's thyroiditis
Hassan, Rishi; Arunprasath, P.; Padmavathy, L.; Srivenkateswaran, K.
2016-01-01
Annular elastolytic giant cell granuloma (AEGCG) is a rare granulomatous skin disease characterized clinically by annular plaques with elevated borders and atrophic centers found mainly on sun-exposed skin and histologically by diffuse granulomatous infiltrates composed of multinucleated giant cells, histiocytes and lymphocytes in the dermis along with phagocytosis of elastic fibers by multinucleated giant cells. We report a case of AEGCG in a 50-year-old woman and is highlighted for the classical clinical and histological findings of the disease and its rare co-existence with Hashimoto's thyroiditis. PMID:27057492
Polarization-independent waveguiding with annular photonic crystals.
Cicek, Ahmet; Ulug, Bulent
2009-09-28
A linear waveguide in an annular photonic crystal composed of a square array of annular dielectric rods in air is demonstrated to guide transverse electric and transverse magnetic modes simultaneously. Overlapping of the guided bands in the full band gap of the photonic crystal is shown to be achieved through an appropriate set of geometric parameters. Results of Finite-Difference Time-Domain simulations to demonstrate polarization-independent waveguiding with low loss and wavelength-order confinement are presented. Transmission through a 90 degrees bend is also demonstrated. PMID:19907629
Predictions for the annular solar eclipse of 1984
NASA Technical Reports Server (NTRS)
Espenak, F.
1984-01-01
Predictions for the path of the annular solar eclipse of 30 May 1984 are presented. Local circumstances for cities in and along the path are discussed as well as the Saros history of this eclipse. The author investigates the possibility of observing the solar corona during maximum eclipse but concludes that the prospects are remote. Finally, the appearance of the eclipse during annularity, and beading phenomena, are discussed, with the help of a lunar-limb analysis and observations made at previous eclipses of this Saros series.
Portal annular pancreas: the pancreatic duct ring sign on MRCP
Lath, Chinar O.; Agrawal, Dilpesh S.; Timins, Michael E.; Wein, Melissa M.
2015-01-01
Portal annular pancreas is a rare pancreatic variant in which the uncinate process of the pancreas extends and fuses to the dorsal surface of the body of the pancreas by surrounding the portal vein. It is asymptomatic, but it can be mistaken for a pancreatic head mass on imaging and could also have serious consequences during pancreatic surgery, if unrecognized. We report this case of a 53-year-old female patient who was diagnosed to have portal annular pancreas on the basis of an unusual course (ring appearance) of the main pancreatic duct on magnetic resonance cholangiopancreatography, not described earlier in the radiology literature. PMID:26649117
Preceding Annular Skin Lesions in a Patient with Hemophagocytic Lymphohistiocytosis
Jun, Hee Jin; Kim, Hyung Ok; Lee, Jun Young
2015-01-01
The cutaneous manifestations of hemophagocytic lymphohistiocytosis (HLH) are variable and nonspecific. A 42-year-old man presented with multiple annular, erythematous patches on the trunk for 3 months. Two months later, he presented with bullae along with high fever. The laboratory examination showed pancytopenia, hypertriglyceridemia, and hypofibrinogenemia. The bone marrow biopsy specimen showed an active hemophagocytosis. On the basis of these findings, a diagnosis of HLH was concluded. After five cycles of chemotherapy, his skin lesion completely resolved. Taking the results together, we suggest that annular skin lesion can be added to the list of cutaneous manifestations of HLH. PMID:26512177
Laser-launched flyer plates and direct laser shocks for dynamic material property measurements
NASA Astrophysics Data System (ADS)
Paisley, Dennis; Swift, Damian; Johnson, Randall; Kopp, Roger; Kyrala, George
2001-06-01
The Trident laser at Los Alamos was used to impart known and controlled shocks in various materials by launching flyer plates or by irradiating the sample directly. Materials investigated include copper, gold, NiTi, SS316, and other metals and alloys. Tensile spall strength, elastic-plastic transition, phase boundaries, and equation of state can be determined with small samples. Using thin samples (0.1 - 1.0 mm thick) as targets, high pressure gradients can be generated with relatively low pressures, resulting in high tensile strain rates (10^5 to 10^8 s-1). Free surface and interface velocities are recorded with point- and line-imaging VISARs. The flexible spatial and temporal pulse profiles of Trident, coupled with the use of laser-launched flyer plates, provides capabilities which complement experiments conducted using gas guns and tensile bars. These samples spalled at high strain rates will be compared with samples spalled at lower strain rates to elucidate mechanisms for the initiation and growth of spall.
Ultrasonic guided waves in eccentric annular pipes
Pattanayak, Roson Kumar; Balasubramaniam, Krishnan; Rajagopal, Prabhu
2014-02-18
This paper studies the feasibility of using ultrasonic guided waves to rapidly inspect tubes and pipes for possible eccentricity. While guided waves are well established in the long range inspection of structures such as pipes and plates, studies for more complex cross sections are limited and analytical solutions are often difficult to obtain. Recent developments have made the Semi Analytical Finite Element (SAFE) method widely accessible for researchers to study guided wave properties in complex structures. Here the SAFE method is used to study the effect of eccentricity on the modal structures and velocities of lower order guided wave modes in thin pipes of diameters typically of interest to the industry. Results are validated using experiments. The paper demonstrates that even a small eccentricity in the pipe can strongly affect guided wave mode structures and velocities and hence shows potential for pipe eccentricity inspection.
Ultrasonic guided waves in eccentric annular pipes
NASA Astrophysics Data System (ADS)
Pattanayak, Roson Kumar; Balasubramaniam, Krishnan; Rajagopal, Prabhu
2014-02-01
This paper studies the feasibility of using ultrasonic guided waves to rapidly inspect tubes and pipes for possible eccentricity. While guided waves are well established in the long range inspection of structures such as pipes and plates, studies for more complex cross sections are limited and analytical solutions are often difficult to obtain. Recent developments have made the Semi Analytical Finite Element (SAFE) method widely accessible for researchers to study guided wave properties in complex structures. Here the SAFE method is used to study the effect of eccentricity on the modal structures and velocities of lower order guided wave modes in thin pipes of diameters typically of interest to the industry. Results are validated using experiments. The paper demonstrates that even a small eccentricity in the pipe can strongly affect guided wave mode structures and velocities and hence shows potential for pipe eccentricity inspection.
Multi-functional annular fairing for coupling launch abort motor to space vehicle
NASA Technical Reports Server (NTRS)
Camarda, Charles J. (Inventor); Scotti, Stephen J. (Inventor); Buning, Pieter G. (Inventor); Bauer, Steven X. S. (Inventor); Engelund, Walter C. (Inventor); Schuster, David M. (Inventor)
2011-01-01
An annular fairing having aerodynamic, thermal, structural and acoustic attributes couples a launch abort motor to a space vehicle having a payload of concern mounted on top of a rocket propulsion system. A first end of the annular fairing is fixedly attached to the launch abort motor while a second end of the annular fairing is attached in a releasable fashion to an aft region of the payload. The annular fairing increases in diameter between its first and second ends.
Subsonic annular wing theory with application to flow about nacelles
NASA Technical Reports Server (NTRS)
Mann, M. J.
1974-01-01
A method has recently been developed for calculating the flow over a subsonic nacelle at zero angle of attack. The method makes use of annular wing theory and boundary-layer theory and has shown good agreement with both experimental data and more complex theoretical solutions. The method permits variation of the mass flow by changing the size of a center body.
Annular linear induction pump with an externally supported duct
Craig, Edwin R.; Semken, Robert S.
1979-01-01
Several embodiments of an annular linear induction pump for pumping liquid metals are disclosed having the features of generally one pass flow of the liquid metal through the pump and an increased efficiency resulting from the use of thin duct walls to enclose the stator. The stator components of this pump are removable for repair and replacement.
Design curves for circular and annular duct silencers
NASA Technical Reports Server (NTRS)
Watson, Willie R.; Ramakrishnan, R.
1989-01-01
Conventional models of sound propagation between porous walls (Scott, 1946) are adapted in order to calculate design curves for the lined circular and annular-duct silencers used in HVAC systems. The derivation of the governing equations is outlined, and results for two typical cases are presented graphically. Good agreement with published experimental data is demonstrated.
PARTICLE TRANSMISSION CHARACTERISTICS OF AN ANNULAR DENUDER AMBIENT SAMPLING SYSTEM
Transmission measurements have been performed on URG 2000-30B glass annular denuders at 10 LPM using monodisperse particles in the 0.01 - 1 um dia size range. hrough control of the aerosol charge state, particle losses due to diffusion and electrostatic effects were separately me...
An experimental investigation of straight and curved annular wall jets
NASA Technical Reports Server (NTRS)
Rodman, L. C.; Wood, N. J.; Roberts, L.
1987-01-01
Accurate turbulence measurements taken in wall jet flows are difficult to obtain, due to high intensity turbulence and problems in achieving two-dimensionality. The problem is compounded when streamwise curvature of the flow is introduced, since the jet entrainment and turbulence levels are greatly increased over the equivalent planar values. In this experiment, two-dimensional straight and curved incompressible wall jet flows are simulated by having a jet blow axially over a cylinder. Hot wire measurements and some Laser Doppler Velocimetry measurements are presented for straight and curved wall jet flows. The results for the straight wall showed good agreement between the annular flow data and the rectangular data taken by previous researchers. For the jets with streamwise curvature, there was agreement between the annular and corresponding rectangular jets for the flow region closest to the slot exit. An integral analysis was used as a simple technique to interpret the experimental results. Integral momentum calculations were performed for both straight and curved annular and two dimensional wall jets. The results of the calculation were used to identify transverse curvature parameters and to predict the values of those parameters which would delineate the region where the annular flow can satisfactorily simulate two dimensional flow.
RESIDENCE TIME DISTRIBUTION OF FLUIDS IN STIRRED ANNULAR PHOTOREACTORS
When gases flow through an annular photoreactor at constant rate, some of the gas spends more or less than the average residence time in the reactor. This spread of residence time can have an important effect on the performance of the reactor. this study tested how the residence...
Vibrational mode and sound radiation of electrostatic speakers using circular and annular diaphragms
NASA Astrophysics Data System (ADS)
Huang, Yu-Hsi; Chiang, Hsin-Yuan
2016-06-01
This study modeled two diaphragms comprising a pair of indium tin oxide (ITO) transparent plates sandwiching a vibrating diaphragm to create circular (30 mm radius) and annular (30 mm outer and 3 mm inner radius) push-pull electrostatic speakers. We then measured the displacement amplitudes and mode shapes produced by the devices. Vibration characteristics were used to predict sound pressure levels (SPLs) using the lumped parameter method (LPM) and distributed parameter method (DPM). The two measurement results obtained using a laser system were compared to the SPLs obtained using traditional acoustic measurement (AM) from 20 Hz to 20 kHz in order to verify our predictions. When using LPM and DPM, the SPL prediction results in the first three symmetric modes were in good agreement with the AM results. Under the assumption of linear operations, the DPM and amplitude-fluctuation electronic speckle pattern interferometry (ESPI) techniques proved effective in determining the visualization of mode shape (0,1)-(0,3). The use of ITO plates is a practical technique for the prediction of SPL, as well as measurement of mode shapes. The four evaluation methods, i.e. LPM, DPM, ESPI and AM, present a high degree of consistency with regard to vibrational mode and sound radiation characteristics.
Hou Xi; Wu Fan; Yang Li; Wu Shibin; Chen Qiang
2006-05-20
We propose a more accurate and efficient reconstruction method used in testing large aspheric surfaces with annular subaperture interferometry. By the introduction of the Zernike annular polynomials that are orthogonal over the annular region, the method proposed here eliminates the coupling problem in the earlier reconstruction algorithm based on Zernike circle polynomials. Because of the complexity of recurrence definition of Zernike annular polynomials, a general symbol representation of that in a computing program is established. The program implementation for the method is provided in detail. The performance of the reconstruction algorithm is evaluated in some pertinent cases, such as different random noise levels, different subaperture configurations, and misalignments.
NASA Astrophysics Data System (ADS)
Kuang, Zheng; Perrie, Walter; Edwardson, Stuart P.; Fearon, Eamonn; Dearden, Geoff
2014-03-01
Ultrafast laser parallel microdrilling using diffractive multiple annular beam patterns is demonstrated in this paper. The annular beam was generated by diffractive axicon computer generated holograms (CGHs) using a spatial light modulator. The diameter of the annular beam can be easily adjusted by varying the radius of the smallest ring in the axicon. Multiple annular beams with arbitrary arrangement and multiple annular beam arrays were generated by superimposing an axicon CGH onto a grating and lenses algorithm calculated multi-beam CGH and a binary Dammann grating CGH, respectively. Microholes were drilled through a 0.03 mm thick stainless steel foil using the multiple annular beams. By avoiding huge laser output attenuation and mechanical annular scanning, the processing is ˜200 times faster than the normal single beam processing.
A simplified method for elastic-plastic-creep structural analysis
NASA Technical Reports Server (NTRS)
Kaufman, A.
1985-01-01
A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.
A simplified method for elastic-plastic-creep structural analysis
NASA Technical Reports Server (NTRS)
Kaufman, A.
1984-01-01
A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.
Accurate direct Eulerian simulation of dynamic elastic-plastic flow
Kamm, James R; Walter, John W
2009-01-01
The simulation of dynamic, large strain deformation is an important, difficult, and unsolved computational challenge. Existing Eulerian schemes for dynamic material response are plagued by unresolved issues. We present a new scheme for the first-order system of elasto-plasticity equations in the Eulerian frame. This system has an intrinsic constraint on the inverse deformation gradient. Standard Godunov schemes do not satisfy this constraint. The method of Flux Distributions (FD) was devised to discretely enforce such constraints for numerical schemes with cell-centered variables. We describe a Flux Distribution approach that enforces the inverse deformation gradient constraint. As this approach is new and novel, we do not yet have numerical results to validate our claims. This paper is the first installment of our program to develop this new method.
THE RESPONSE OF SOLIDS TO ELASTIC/ PLASTIC INDENTATION
Chiang, S. S.; Marshall, D. B.; Evans, A. G.
1980-11-01
A new approach for analysing indentation plasticity and indentation fracture is presented, The analysis permits relations to be established between material properties (notably hardness, yield strength and elastic modulus) and the dimensions of the indentation and plastic zone. The predictions are demonstrated to be fully consistent with observations performed on a wide range of materials. The indentation stress fields can also be adapted to generate predictions of indentation fracture thresholds for the three dominant crack types: radial, median and lateral cracks. The predictions are generally consistent with experimental observations.
Elastic-plastic fracture mechanics of strength-mismatching
Parks, D.M.; Ganti, S.; McClintock, F.A.
1996-12-31
Approximate solutions to stress-fields are provided for a strength-mismatched interface crack in small-scale yielding (SSY) for non-hardening and low hardening materials. Variations of local deformation intensities, characterized by a J-type contour integral, are proposed. The softer material experiences a higher deformation intensity level, J{sub S}, while the harder material sees a much lower deformation intensity level, J{sub H}, compared to that obtained from the applied J near the respective homogeneous crack-tips. For a low hardening material, the stress fields are obtained by scaling from an elastic/perfectly-plastic problem, based on an effective mismatch, M{sub eff}, which is a function of mismatch, M, and the hardening exponent, n. Triaxial stress build-up is discussed quantitatively in terms of M. The influence of strength-mismatch on cleavage fracture is discussed using Weibull statistics.
Annular fuel and air co-flow premixer
Stevenson, Christian Xavier; Melton, Patrick Benedict; York, William David
2013-10-15
Disclosed is a premixer for a combustor including an annular outer shell and an annular inner shell. The inner shell defines an inner flow channel inside of the inner shell and is located to define an outer flow channel between the outer shell and the inner shell. A fuel discharge annulus is located between the outer flow channel and the inner flow channel and is configured to inject a fuel flow into a mixing area in a direction substantially parallel to an outer airflow through the outer flow channel and an inner flow through the inner flow channel. Further disclosed are a combustor including a plurality of premixers and a method of premixing air and fuel in a combustor.
Annular hypopigmented mycosis fungoides: a novel ringed variant.
Uhlenhake, Elizabeth E; Mehregan, Darius M
2012-05-01
Hypopigmented mycosis fungoides (MF) is a relatively uncommon variant of cutaneous lymphoma that is mostly seen in darker skin types. We present a novel and unique clinical presentation in an African-American female patient, consisting of regular hypopigmented annular rings in areas of normal skin and in more typical hypopigmented patches of MF. The lesions appeared diffusely on all extremities, anterior chest and back. Histopathologic examination showed an atypical lymphocytic infiltrate at the dermal-epidermal junction with epidermotropism and few Pautrier's collections. The patient was otherwise healthy and improved with narrowband ultraviolet (UV)-B. This case represents a presentation of a most unusual variant of hypopigmented MF, for which we propose the name 'annular hypopigmented MF'. PMID:22515225
Electroosmotic flow and Joule heating in preparative continuous annular electrochromatography.
Laskowski, René; Bart, Hans-Jörg
2015-09-01
An openFOAM "computational fluid dynamic" simulation model was developed for the description of local interaction of hydrodynamics and Joule heating in annular electrochromatography. A local decline of electrical conductivity of the background eluent is caused by an electrokinetic migration of ions resulting in higher Joule heat generation. The model equations consider the Navier-Stokes equation for incompressible fluids, the energy equation for stationary temperature fields, and the mass transfer equation for the electrokinetic flow. The simulations were embedded in commercial ANSYS Fluent software and in open-source environment openFOAM. The annular gap (1 mm width) contained an inorganic C8 reverse-phase monolith as stationary phase prepared by an in situ sol-gel process. The process temperature generated by Joule heating was determined by thermal camera system. The local hydrodynamics in the prototype was detected by a gravimetric contact-free measurement method and experimental and simulated values matched quite well. PMID:25997390
Axisymmetric buckling of laminated thick annular spherical cap
NASA Astrophysics Data System (ADS)
Dumir, P. C.; Dube, G. P.; Mallick, A.
2005-03-01
Axisymmetric buckling analysis is presented for moderately thick laminated shallow annular spherical cap under transverse load. Buckling under central ring load and uniformly distributed transverse load, applied statically or as a step function load is considered. The central circular opening is either free or plugged by a rigid central mass or reinforced by a rigid ring. Annular spherical caps have been analysed for clamped and simple supports with movable and immovable inplane edge conditions. The governing equations of the Marguerre-type, first order shear deformation shallow shell theory (FSDT), formulated in terms of transverse deflection w, the rotation ψ of the normal to the midsurface and the stress function Φ, are solved by the orthogonal point collocation method. Typical numerical results for static and dynamic buckling loads for FSDT are compared with the classical lamination theory and the dependence of the effect of the shear deformation on the thickness parameter for various boundary conditions is investigated.
Erythema migrans and the differential diagnosis of annular erythema.
Grau, Renee H; Allen, Pamela S; Cornelison, Raymond L
2002-04-01
The diagnosis of Lyme disease (LD) or Lyme borreliosis is often based on the recognition of erythema migrans (EM) because its clinical appearance precedes systemic manifestations of the disease and the antibody response. The clinical basis and variable presentation of EM leave room for diagnostic error and, as a consequence, potential long-term repercussions such as rheumatic, cardiac, ophthalmic, or neurologic complications. Most cases are reported in the Northcentral and Northeastern states. In areas where LD is not endemic, the differential diagnosis of annular erythema may not list EM highly, although all the features of a lesion may fit the typical description of EM. Therefore, a complete understanding of LD and its clinical presentation are key in making a diagnosis, especially in areas with low incidence. We present a hypothetical case report of EM from Oklahoma, a state with low incidence of LD, for the purposes of review of this entity and the differential diagnosis of annular erythema. PMID:11957843
Analysis of Enriched Uranyl Nitrate in Nested Annular Tank Array
John D. Bess; James D. Cleaver
2009-06-01
Two series of experiments were performed at the Rocky Flats Critical Mass Laboratory during the 1980s using highly enriched (93%) uranyl nitrate solution in annular tanks. [1, 2] Tanks were of typical sizes found in nuclear production plants. Experiments looked at tanks of varying radii in a co-located set of nested tanks, a 1 by 2 array, and a 1 by 3 array. The co-located set of tanks had been analyzed previously [3] as a benchmark for inclusion within the International Handbook of Evaluated Criticality Safety Benchmark Experiments. [4] The current study represents the benchmark analysis of the 1 by 3 array of a series of nested annular tanks. Of the seventeen configurations performed in this set of experiments, twelve were evaluated and nine were judged as acceptable benchmarks.
Evaluation of the performance of an annular diffusion denuder
Fan, B.J.; Cheng, Y.S.; Yeh, Hsu-Chi
1994-11-01
In air sampling, an annular diffusion denuder (ADD) is often used to trap specific gases from an air sample stream. The efficiency of an ADD in collecting a gas was considered in this study. A dimensional analysis showed that the collection efficiency depended on two parameters: the Peclet number and the annulus radii ratio. To determine collection efficiency, we calculated the fractional loss of the gas inside the denuder. In the calculation, the governing equations for gas concentration and flow field inside the annulus were solved numerically. After validating the methodology, a parameteric calculation of the collection efficiency was made, and a one-equation model based on the calculation was developed. A comparison of the model and experimental data showed a variance coefficient of 3.26%. This confirmed that the performance of an annular denuder could be evaluated by this model.
High Thrust-to-Power Annular Engine Technology
NASA Technical Reports Server (NTRS)
Patterson, Michael J.; Thomas, Robert E.; Crofton, Mark W.; Young, Jason A.; Foster, John E.
2015-01-01
Gridded ion engines have the highest efficiency and total impulse of any mature electric propulsion technology, and have been successfully implemented for primary propulsion in both geocentric and heliocentric environments with excellent ground/in-space correlation of performance. However, they have not been optimized to maximize thrust-to-power, an important parameter for Earth orbit transfer applications. This publication discusses technology development work intended to maximize this parameter. These activities include investigating the capabilities of a non-conventional design approach, the annular engine, which has the potential of exceeding the thrust-to-power of other EP technologies. This publication discusses the status of this work, including the fabrication and initial tests of a large-area annular engine. This work is being conducted in collaboration among NASA Glenn Research Center, The Aerospace Corporation, and the University of Michigan.
High Thrust-to-Power Annular Engine Technology
NASA Technical Reports Server (NTRS)
Patterson, Michael; Thomas, Robert; Crofton, Mark; Young, Jason A.; Foster, John E.
2015-01-01
Gridded ion engines have the highest efficiency and total impulse of any mature electric propulsion technology, and have been successfully implemented for primary propulsion in both geocentric and heliocentric environments with excellent ground-in-space correlation of performance. However, they have not been optimized to maximize thrust-to-power, an important parameter for Earth orbit transfer applications. This publication discusses technology development work intended to maximize this parameter. These activities include investigating the capabilities of a non-conventional design approach, the annular engine, which has the potential of exceeding the thrust-to-power of other EP technologies. This publication discusses the status of this work, including the fabrication and initial tests of a large-area annular engine. This work is being conducted in collaboration among NASA Glenn Research Center, The Aerospace Corporation, and the University of Michigan.
Dual annular rotating "windowed" nuclear reflector reactor control system
Jacox, Michael G.; Drexler, Robert L.; Hunt, Robert N. M.; Lake, James A.
1994-01-01
A nuclear reactor control system is provided in a nuclear reactor having a core operating in the fast neutron energy spectrum where criticality control is achieved by neutron leakage. The control system includes dual annular, rotatable reflector rings. There are two reflector rings: an inner reflector ring and an outer reflector ring. The reflectors are concentrically assembled, surround the reactor core, and each reflector ring includes a plurality of openings. The openings in each ring are capable of being aligned or non-aligned with each other. Independent driving means for each of the annular reflector rings is provided so that reactor criticality can be initiated and controlled by rotation of either reflector ring such that the extent of alignment of the openings in each ring controls the reflection of neutrons from the core.
System design of the annular suspension and pointing system /ASPS/
NASA Technical Reports Server (NTRS)
Cunningham, D. C.; Gismondi, T. P.; Wilson, G. W.
1978-01-01
This paper presents the control system design for the Annular Suspension and Pointing System. Actuator sizing and configuration of the system are explained, and the control laws developed for linearizing and compensating the magnetic bearings, roll induction motor and gimbal torquers are given. Decoupling, feedforward and error compensation for the vernier and gimbal controllers is developed. The algorithm for computing the strapdown attitude reference is derived, and the allowable sampling rates, time delays and quantization of control signals are specified.
Hydraulic forces caused by annular pressure seals in centrifugal pumps
NASA Technical Reports Server (NTRS)
Iino, T.; Kaneko, H.
1980-01-01
The hydraulic forces caused by annular pressure seals were investigated. The measured inlet and exit loss coefficients of the flow through the seals were much smaller than the conventional values. The results indicate that the damping coefficient and the inertia coefficient of the fluid film in the seal are not affected much by the rotational speed or the eccentricity of the rotor, though the stiffness coefficient seemed to be influenced by the eccentricity.
Granuloma annulare: Clinical and histologic variants, epidemiology, and genetics.
Piette, Evan W; Rosenbach, Misha
2016-09-01
Granuloma annulare (GA) is a poorly understood condition characterized by a set of clinical morphologic variants with 2 predominant histopathologic patterns of inflammation. This review provides a comprehensive overview of the available information about the clinical variants and histopathologic features, current epidemiologic data, and potential genetic underpinnings of GA. Much of the current understanding of GA is based on retrospective studies, case series, and case reports; this review aims to synthesize the available information and present it clearly for practicing dermatologists. PMID:27543209
Persistent currents in Bose gases confined in annular traps
Bargi, S.; Malet, F.; Reimann, S. M.; Kavoulakis, G. M.
2010-10-15
We examine the problem of stability of persistent currents in a mixture of two Bose gases trapped in an annular potential. We evaluate the critical coupling for metastability in the transition from quasi-one- to two-dimensional motion. We also evaluate the critical coupling for metastability in a mixture of two species as a function of the population imbalance. The stability of the currents is shown to be sensitive to the deviation from one-dimensional motion.
Annular Momentum Control Device (AMCD). Volume 1: Laboratory model development
NASA Technical Reports Server (NTRS)
1975-01-01
The annular momentum control device (AMCD) a thin hoop-like wheel with neither shaft nor spokes is described. The wheel floats in a magnetic field and can be rotated by a segmented motor. Potential advantages of such a wheel are low weight, configuration flexibility, a wheel that stiffens with increased speed, vibration isolation, and increased reliability. The analysis, design, fabrication, and testing is described of the laboratory model of the AMCD.
Guided Wave Annular Array Sensor Design for Improved Tomographic Imaging
NASA Astrophysics Data System (ADS)
Koduru, Jaya Prakash; Rose, Joseph L.
2009-03-01
Guided wave tomography for structural health monitoring is fast emerging as a reliable tool for the detection and monitoring of hotspots in a structure, for any defects arising from corrosion, crack growth etc. To date guided wave tomography has been successfully tested on aircraft wings, pipes, pipe elbows, and weld joints. Structures practically deployed are subjected to harsh environments like exposure to rain, changes in temperature and humidity. A reliable tomography system should take into account these environmental factors to avoid false alarms. The lack of mode control with piezoceramic disk sensors makes it very sensitive to traces of water leading to false alarms. In this study we explore the design of annular array sensors to provide mode control for improved structural tomography, in particular, addressing the false alarm potential of water loading. Clearly defined actuation lines in the phase velocity dispersion curve space are calculated. A dominant in-plane displacement point is found to provide a solution to the water loading problem. The improvement in the tomographic images with the annular array sensors in the presence of water traces is clearly illustrated with a series of experiments. An annular array design philosophy for other problems in NDE/SHM is also discussed.
Slim hole MWD tool accurately measures downhole annular pressure
Burban, B.; Delahaye, T. )
1994-02-14
Measurement-while-drilling of downhole pressure accurately determines annular pressure losses from circulation and drillstring rotation and helps monitor swab and surge pressures during tripping. In early 1993, two slim-hole wells (3.4 in. and 3 in. diameter) were drilled with continuous real-time electromagnetic wave transmission of downhole temperature and annular pressure. The data were obtained during all stages of the drilling operation and proved useful for operations personnel. The use of real-time measurements demonstrated the characteristic hydraulic effects of pressure surges induced by drillstring rotation in the small slim-hole annulus under field conditions. The interest in this information is not restricted to the slim-hole geometry. Monitoring or estimating downhole pressure is a key element for drilling operations. Except in special cases, no real-time measurements of downhole annular pressure during drilling and tripping have been used on an operational basis. The hydraulic effects are significant in conventional-geometry wells (3 1/2-in. drill pipe in a 6-in. hole). This paper describes the tool and the results from the field test.
Linearization of an annular image by using a diffractive optic
NASA Technical Reports Server (NTRS)
Matthys, Donald R.
1996-01-01
The goal for this project is to develop the algorithms for fracturing the zones defined by the mapping transformation, and to actually produce the binary optic in an appropriate setup. In 1984 a side-viewing panoramic viewing system was patented, consisting of a single piece of glass with spherical surfaces which produces a 360 degree view of the region surrounding the lens which extends about 25 degrees in front of and 20 degrees behind the lens. The system not only produces images of good quality, it is also afocal, i.e., images stay in focus for objects located right next to the lens as well as those located far from the lens. The lens produced a panoramic view in an annular shaped image, and so the lens was called a PAL (panoramic annular lens). When applying traditional measurements to PAL images, it is found advantageous to linearize the annular image. This can easily be done with a computer and such a linearized image can be produced within about 40 seconds on current microcomputers. However, this process requires a frame-grabber and a computer, and is not real-time. Therefore, it was decided to try to perform this linearization optically by using a diffractive optic.
The annular flow electrothermal ramjet. M.S. Thesis
NASA Technical Reports Server (NTRS)
Shaw, B. D.
1984-01-01
The annular flow, electrothermal, plug ramjet is examined as a possible means of achieving rapid projectile acceleration to velocities for such applications as direct launch of spacebound payloads. The performance of this ramjet operating with hydrogen propellant is examined for cases where this working fluid is treated: (1) as a perfect gas, and (2) as a gas that is allowed to dissociate and ionize and then recombine with finite reaction rates in the nozzle. Performance results for these cases are compared to the performance of a conventional ramjet operating with perfect gas hydrogen propellant. The performance of the conventional ramjet is superior to that of the annular flow, electrothermal ramjet. However, it is argued that the mechanical complexities associated with conventional ramjet operation are difficult to attain, and for this reason the annular flow, electrothermal ramjet is more desirable as a launch system. Models are presented which describe both electrothermal plug ramjet and conventional ramjet operation, and it is shown that for a given flight velocity there is a rate of heat addition per unit propellant mass for which ramjet operation is optimized.
Treatment of generalized granuloma annulare - a systematic review.
Lukács, J; Schliemann, S; Elsner, P
2015-08-01
Granuloma annulare (GA) is a benign inflammatory skin disease. Localized GA is likely to resolve spontaneously, while generalized GA (GGA) is rare and may persist for decades. GGA usually is resistant to a variety of therapeutic modalities and takes a chronic course. The objective of this study was to summarize all reported treatments of generalized granuloma annulare. This is a systematic review based on MEDLINE, Embase and Cochrane Central Register search of articles in English and German and a manual search, between 1980 and 2013, to summarize the treatment of generalized granuloma annulare. Most medical literature on treatment of GGA is limited to individual case reports and small series of patients treated without a control group. Randomized controlled clinical studies are missing. Multiple treatment modalities for GGA were reported including topical and systemic steroids, PUVA, isotretinoin, dapsone, pentoxifylline, hydroxychloroquine, cyclosporine, IFN-γ, potassium iodide, nicotinamide, niacinamide, salicylic acid, dipyridamole, PDT, fumaric acid ester, etanercept, infliximab, adalimumab. While there are numerous case reports of successful treatments in the literature including surgical, medical and phototherapy options, well-designed, randomized, controlled clinical trials are required for an evidence-based treatment of GGA. PMID:25651003
Free vortex theory for efficiency calculations from annular cascade data
Main, A.J.; Oldfield, M.L.G.; Lock, G.D.; Jones, T.V.
1997-04-01
This paper describes a new three-dimensional theory to calculate the efficiency or loss of nozzle guide vane annular cascades from experimental area traverse measurements of the compressible downstream flow. To calculate such an efficiency, it is necessary to mix out the measured flow computationally to either a uniform state or one that is a function of radius only. When this is done by conserving momentum, mass, and energy flow, there is a remaining degree of freedom in that the radial distribution of circumferential velocity can be chosen. This extra freedom does not arise in two-dimensional cascades. The new method mixes the flow out to a free (i.e., irrotational) vortex. This is preferred to existing methods in that it gives a physically realistic flow and also provides a unique, lossless, isentropic reference flow. The annular cascade efficiency is then uniquely defined as the ratio of the mixed-out experimental kinetic energy flux to the ideal isentropic kinetic energy flux at the same mean radius static pressure. The mathematical derivation of this method is presented. This new theory has been used to process data obtained from a large, transonic, annular cascade in a blowdown tunnel. A four-hole pyramid probe, mounted on a computer-controlled traverse, has been used to map the passage flowfield downstream of the nozzle guide vanes. Losses calculated by the new method are compared with those calculated from the same data using earlier analysis methods.
Droplet sizes, dynamics and deposition in vertical annular flow
Lopes, J C.B.; Dukler, A E
1985-10-01
The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data.
Allopurinol induced granuloma annulare in a patient of lepromatous leprosy
Singh, Satyendra Kumar; Manchanda, Kajal; Bhayana, Aakash Amar; Verma, Anurag
2013-01-01
Granuloma annulare (GA) is a benign, inflammatory dermatosis involving dermis or subcutis with unknown etiology and poorly understood pathology. GA has characteristic histological features of necrobiosis, granuloma formation and abundant mucin deposition. Various predisposing factors, systemic diseases and drugs have been implicated in the etiology. We hereby describe a case of 70 year old male who was a known case of lepromatous leprosy, taking multidrug therapy for 6 months presented with multiple discrete, annular, firm, non tender, smooth surfaced skin colored papular lesions ranging in size from 0.5-1 cm over back for 1 month. There was past history of intake of allopurinol for hyperuricemia which was started 1 year back. There was history of similar lesions 6 months back which healed within 1 month of stopping allopurinol and he started taking the drug for the past 4 months on his own without any medical advice. Histopathological examination showed superficial and deep perivascular lymphocytic infiltrate with numerous histiocytes scattered in the intersititum of reticular dermis and abundant mucin in between the histiocytes. Allopurinol was implicated as an etiological agent and dramatic improvement was seen after stopping the drug for a period of 4 weeks. Naranjo's algorithm showed a probable association with a score of 6. Thus the final diagnosis of allopurinol induced generalised interstitial granuolma annulare was made. Patient was advised to continue antileprotic drugs, low purine diet and avoid allopurinol intake. PMID:23761716
Allopurinol induced granuloma annulare in a patient of lepromatous leprosy.
Singh, Satyendra Kumar; Manchanda, Kajal; Bhayana, Aakash Amar; Verma, Anurag
2013-04-01
Granuloma annulare (GA) is a benign, inflammatory dermatosis involving dermis or subcutis with unknown etiology and poorly understood pathology. GA has characteristic histological features of necrobiosis, granuloma formation and abundant mucin deposition. Various predisposing factors, systemic diseases and drugs have been implicated in the etiology. We hereby describe a case of 70 year old male who was a known case of lepromatous leprosy, taking multidrug therapy for 6 months presented with multiple discrete, annular, firm, non tender, smooth surfaced skin colored papular lesions ranging in size from 0.5-1 cm over back for 1 month. There was past history of intake of allopurinol for hyperuricemia which was started 1 year back. There was history of similar lesions 6 months back which healed within 1 month of stopping allopurinol and he started taking the drug for the past 4 months on his own without any medical advice. Histopathological examination showed superficial and deep perivascular lymphocytic infiltrate with numerous histiocytes scattered in the intersititum of reticular dermis and abundant mucin in between the histiocytes. Allopurinol was implicated as an etiological agent and dramatic improvement was seen after stopping the drug for a period of 4 weeks. Naranjo's algorithm showed a probable association with a score of 6. Thus the final diagnosis of allopurinol induced generalised interstitial granuolma annulare was made. Patient was advised to continue antileprotic drugs, low purine diet and avoid allopurinol intake. PMID:23761716
The influence of annular seal clearance to the critical speed of the multistage pump
NASA Astrophysics Data System (ADS)
Wang, J.; Shen, H. P.; Y Ye, X.; Hu, J. N.; Feng, Y. N.
2013-12-01
In the multistage pump of high head, pressure difference in two ends of annular seal clearance and rotor eccentric would produce the sealing fluid force, the effect of which can be expressed by a damping and stiffness coefficient. It has a great influence on the critical speed of the rotor system. In order to research the influence of the annular seal to the rotor system, this paper used CFD method to conduct the numerical simulation for the flow field of annular seal clearance. The radial and tangential forces were obtained to calculate the annular dynamic coefficients. Also dynamic coefficient were obtained by Matlab. The rotor system was modeled using ANSYS finite software and the critical speed with and without annular seal clearance were calculated. The result shows: annular seal's fluid field is under the comprehensive effect of pressure difference and rotor entrainment. Due to the huge pressure difference in front annular seal, fluid flows under pressure difference; the low pressure difference results in the more obvious effect on the clearance field in back annular seal. The first order critical speed increases greatly with the annular seal clearance; while the average growth rate of the second order critical speed is only 3.2%; the third and fourth critical speed decreases little. Based on the above result, the annular seal has great influence to the first order speed, while has little influence on the rest.
Streit, R.D.
1981-01-01
A double-ended guillotine break in the primary coolant loop of a pressurized water reactor (PWR) is a postulated loss of coolant accient which can result in extreme dynamic loads (i.e., the asymmetric blowdown load) on the reactor pressure vessel (RPV) an vessel intervals. Design and construction of the RPV and support systems to withstand these extreme dynamic loads is very difficult. Similar high loading would also be experienced in a boiling water reactor given a similar accident. Although such a break would be an extremely rare event, its obvious safety and design implications demand that it is carefully evaluated. The work discussed here is part of the Load Combinations Program at Lawrence Livermore National Laboratory to estimate the probability of a double-ended guillotine break in the primary reactor coolant loop of a selected PWR. The program employs a fracture mechanics based fatigue model to propagate cracks from an initial flaw distribution. It was found that while most of the large cracks grew into leaks, a complete (or nearly complete) circumferential crack could lead to a double-ended pipe break with prior leaking and thus, without warning. It is important to assess under what loads such a crack will result in complete pipe severance. The loads considered in this evaluation result from pressure, dead weight and seismic stresses. For the PWR hot leg considered in this investigation the internal pressure contributes the most to the load controlled stresses (i.e., stresses which can cause piping failure) and thus, the problem is treated as axisymmetric with uniform axial loading.
NASA Technical Reports Server (NTRS)
1972-01-01
The proceedings of a conference on sputtering and ion plating are presented. Subjects discussed are: (1) concepts and applications of ion plating, (2) sputtering for deposition of solid film lubricants, (3) commercial ion plating equipment, (4) industrial potential for ion plating and sputtering, and (5) fundamentals of RF and DC sputtering.
NASA Astrophysics Data System (ADS)
Liu, T.; Fleck, N. A.; Wadley, H. N. G.; Deshpande, V. S.
2013-08-01
The impact of a slug of dry sand particles against a metallic sandwich beam or circular sandwich plate is analysed in order to aid the design of sandwich panels for shock mitigation. The sand particles interact via a combined linear-spring-and-dashpot law whereas the face sheets and compressible core of the sandwich beam and plate are treated as rate-sensitive, elastic-plastic solids. The majority of the calculations are performed in two dimensions and entail the transverse impact of end-clamped monolithic and sandwich beams, with plane strain conditions imposed. The sand slug is of rectangular shape and comprises a random loose packing of identical, circular cylindrical particles. These calculations reveal that loading due to the sand is primarily inertial in nature with negligible fluid-structure interaction: the momentum transmitted to the beam is approximately equal to that of the incoming sand slug. For a slug of given incoming momentum, the dynamic deflection of the beam increases with decreasing duration of sand-loading until the impulsive limit is attained. Sandwich beams with thick, strong cores significantly outperform monolithic beams of equal areal mass. This performance enhancement is traced to the "sandwich effect" whereby the sandwich beams have a higher bending strength than that of the monolithic beams. Three-dimensional (3D) calculations are also performed such that the sand slug has the shape of a circular cylindrical column of finite height, and contains spherical sand particles. The 3D slug impacts a circular monolithic plate or sandwich plate and we show that sandwich plates with thick strong cores again outperform monolithic plates of equal areal mass. Finally, we demonstrate that impact by sand particles is equivalent to impact by a crushable foam projectile. The calculations on the equivalent projectile are significantly less intensive computationally, yet give predictions to within 5% of the full discrete particle calculations for the
Electron beam diagnostic system using computed tomography and an annular sensor
Elmer, John W.; Teruya, Alan T.
2014-07-29
A system for analyzing an electron beam including a circular electron beam diagnostic sensor adapted to receive the electron beam, the circular electron beam diagnostic sensor having a central axis; an annular sensor structure operatively connected to the circular electron beam diagnostic sensor, wherein the sensor structure receives the electron beam; a system for sweeping the electron beam radially outward from the central axis of the circular electron beam diagnostic sensor to the annular sensor structure wherein the electron beam is intercepted by the annular sensor structure; and a device for measuring the electron beam that is intercepted by the annular sensor structure.
Electron beam diagnostic system using computed tomography and an annular sensor
Elmer, John W.; Teruya, Alan T.
2015-08-11
A system for analyzing an electron beam including a circular electron beam diagnostic sensor adapted to receive the electron beam, the circular electron beam diagnostic sensor having a central axis; an annular sensor structure operatively connected to the circular electron beam diagnostic sensor, wherein the sensor structure receives the electron beam; a system for sweeping the electron beam radially outward from the central axis of the circular electron beam diagnostic sensor to the annular sensor structure wherein the electron beam is intercepted by the annular sensor structure; and a device for measuring the electron beam that is intercepted by the annular sensor structure.
A granuloma annulare-like eruption associated with the use of amlodipine.
Lim, Adrian C; Hart, Kim; Murrell, Dédée
2002-02-01
A granuloma annulare-like drug reaction is a rarely encountered clinical entity. A 64-year-old Caucasian female developed a granuloma annulare-like reaction 13 days after starting amlodipine and cleared within 3 months after drug cessation. The eruption consisted of multiple erythematous pruritic papules, distributed symmetrically over the lateral aspects of the legs and thighs, as well as on both palms. Histology showed focal collagen degeneration and significant interstitial histiocytic dermal infiltrate suggestive of granuloma annulare. We review previously reported cases of granuloma annulare-like drug reactions, in the context of a recently proposed classification for drug-induced interstitial granulomatous reactions. PMID:11869204
A grillage model for predicting wrinkles in annular graphene under circular shearing
Zhang, Z.; Duan, W. H.; Wang, C. M.
2013-01-07
This paper is concerned with a Timoshenko grillage model for modeling the wrinkling phenomenon in annular graphene under circular shearing applied at its inner edge. By calibrating the grillage model results against the molecular mechanics (MM) results, the grillage model comprising beams of elliptical cross-section orientated along the carbon-carbon bond has section dimensions of 0.06 nm for the major axis length and 0.036 nm for the minor axis length. Moreover, the beams are connected to one another at 0.00212 nm from the geometric centric. This eccentric connection of beams allows the proposed grillage model to cater for the cross-couplings among bonds that produce the out-of-plane wrinkling pattern. The out-of-plane to in-plane bending stiffnesses' ratio is 0.36, and the cross bending stiffness provided by the ellipse eccentricity is 0.025 times that of the in-plane bending stiffness. Besides furnishing identical wave numbers as well as amplitudes and wavelengths that are in good agreement with MM results, the grillage model can capture wrinkling patterns with a boundary layer, whereas plate and membrane models could not mimic the boundary layer.
Numerical analysis of the flows in annular slinger combustors
NASA Astrophysics Data System (ADS)
Huebner, S.; Exley, T.
1990-07-01
Improved gas-turbine combustor design techniques are developed through the application of CFD flow predictions. The conservation equations of mass, momentum, and energy are solved using the finite-volume approach of Spalding. The geometry is a three-dimensional region of cyclic symmetry for a selected annular slinger combustor of reasonable performance. The flow is assumed nonreacting, isothermal, and turbulent. Mixing of the dilution jet stream with the bulk combustor flow is simulated by assuming different inlet temperatures for the two mass sources and noting the temperature profile at the combustor exit plane. A flow visualization experiment is performed on cold flow conditions and reasonably corroborates the CFD predictions.
Parametric Investigations of Miniaturized Cylindrical and Annular Hall Thrusters
A. Smirnov; Y. Raitses; N.J. Fisch
2001-10-16
A cylindrical geometry Hall thruster may overcome certain physical and technological limitations in scaling down of Hall thrusters to miniature sizes. The absence of the inner wall and use of the cusp magnetic field can potentially reduce heating of the thruster parts and erosion of the channel. A 2.6 cm miniaturized Hall thruster of a flexible design was built and successfully operated in the power range of 50-300 W. Comparison of preliminary results obtained for cylindrical and annular thruster configurations is presented.
Identification of dynamic coefficients of annular turbulent seals
NASA Technical Reports Server (NTRS)
Nordmann, R.; Massmann, H.
1984-01-01
An identification procedure to determine dynamic coefficients of annular turbulent seals in turbopumps is presented. Measurements were carried out at a built test rig with two symmetrical arranged seals. A rigid rotating shaft is surrounded by an elastically supported housing, which is excited by impact forces. The relative radial motion between the rotating parts and the housing, respectively between the seal surfaces, is measured by displacement pick-ups and from the time signals complex frequency response functions can be calculated. Finally an analytical model, depending on the seal parameters, is fitted to the measured data, to find the dynamic coefficients.
Analytic vortex dynamics in an annular Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Toikka, L. A.; Suominen, K.-A.
2016-05-01
We consider analytically the dynamics of an arbitrary number and configuration of vortices in an annular Bose-Einstein condensate obtaining expressions for the free energy and vortex precession rates to logarithmic accuracy. We also obtain lower bounds for the lifetime of a single vortex in the annulus. Our results enable a closed-form analytic treatment of vortex-vortex interactions in the annulus that is exact in the incompressible limit. The incompressible hydrodynamics that is developed here paves the way for more general analytical treatments of vortex dynamics in non-simply-connected geometries.
Dynamically adjustable annular laser trapping based on axicons
Shao, Bing; Esener, Sadik C.; Nascimento, Jaclyn M.; Botvinick, Elliot L.; Berns, Michael W
2006-09-01
To study the chemotactic response of sperm to an egg and to characterize sperm motility, an annular laser trap based on axicons is designed, simulated with the ray-tracing tool, and implemented. The diameter of the trapping ring can be adjusted dynamically for a range of over 400 {mu}m by simply translating one axicon along the optical axis. Trapping experiments with microspheres and dog sperm demonstrate the feasibility of the system,and the power requirement agrees with theoretical expectation. This new type of laser trapping could provide a prototype of a parallel, objective, and quantitative tool for animal fertility and biotropism study.
Laser window with annular grooves for thermal isolation
Warner, B.E.; Horton, J.A.; Alger, T.W.
1983-07-13
A laser window or other optical element which is thermally loaded, heats up and causes optical distortions because of temperature gradients between the center and the edge. A number of annular grooves, one to three or more, are formed in the element between a central portion and edge portion, producing a web portion which concentrates the thermal gradient and thermally isolates the central portion from the edge portion, producing a uniform temperature profile across the central portion and therefore reduce the optical distortions. The grooves are narrow and closely spaced with respect to the thickness of the element, and successive grooves are formed from alternate sides of the element.
Annular self-similar solutions in ideal magnetogasdynamics
NASA Astrophysics Data System (ADS)
Lock, R. M.; Mestel, A. J.
2008-08-01
We consider the possibility of self-similar solutions describing the implosion of hollow cylindrical annuli driven by an azimuthal magnetic field, in essence a self-similar imploding liner z-pinch. We construct such solutions for gasdynamics, for ideal ‘β=0’ plasma and for ideal magnetogasdynamics (MGD). In the latter two cases some quantities are singular at the annular boundaries. Numerical solutions of the full ideal MGD initial value problem indicate that the self-similar solutions are not attractive for arbitrary initial conditions, possibly as a result of flux-freezing.
Granuloma annulare: Pathogenesis, disease associations and triggers, and therapeutic options.
Piette, Evan W; Rosenbach, Misha
2016-09-01
Granuloma annulare (GA) represents a cutaneous reaction pattern of unknown cause with a variety of previously described potential disease associations and triggers. This review attempts to synthesize the available data regarding potential etiopathogenesis, reviews the available data on potential GA disease associations and work-up indicated for patients with GA, and discusses potential inciting triggers. In the final part, this article describes the available treatments options and supporting data, and provides a framework for approaching management of patients with GA. The previous accompanying article provided a comprehensive overview of the available information known about the clinical variants, epidemiology, genetics, and histology of GA. PMID:27543210
Annular Suspension and Pointing System (ASPS) magnetic rotary joint
NASA Technical Reports Server (NTRS)
Smith, W. E.; Quach, W.; Thomas, W.
1993-01-01
The Annular Suspension and Pointing System (ASPS) is a prototype of flight hardware for a high-accuracy space payload pointing mount. The long term project objective is to perform modifications and implement improvements to the existing ASPS in hopes of recommission. Also, new applications will be investigated for this technology. This report will focus on the first aspect of this overall goal, to establish operation of a single bearing station. Presented is an overview of the system history and bearing operation followed by the processes, results, and status of the single bearing study.
Photoacoustic Imaging of Animals with an Annular Transducer Array
NASA Astrophysics Data System (ADS)
Yang, Di-Wu; Zhou, Zhi-Bin; Zeng, Lv-Ming; Zhou, Xin; Chen, Xing-Hui
2014-07-01
A photoacoustic system with an annular transducer array is presented for rapid, high-resolution photoacoustic tomography of animals. An eight-channel data acquisition system is applied to capture the photoacoustic signals by using multiplexing and the total time of data acquisition and transferring is within 3 s. A limited-view filtered back projection algorithm is used to reconstruct the photoacoustic images. Experiments are performed on a mouse head and a rabbit head and clear photoacoustic images are obtained. The experimental results demonstrate that this imaging system holds the potential for imaging the human brain.
Exhaust emissions of a double annular combustor: Parametric study
NASA Technical Reports Server (NTRS)
Schultz, D. F.
1974-01-01
A full scale double-annular ram-induction combustor designed for Mach 3.0 cruise operation was tested. Emissions of oxides of nitrogen, carbon monoxide, unburned hydrocarbons, and smoke were measured over a range of combustor operating variables including reference velocity, inlet air temperature and pressure, and exit average temperature. ASTM Jet-A fuel was used for these tests. An equation is provided relating oxides of nitrogen emissions as a function of the combustor, operating variables. A small effect of radial fuel staging on reducing exhaust emissions (which were originally quite low) is demonstrated.
Final Technical Report for the MIT Annular Fuel Research Project
Mujid S. Kazimi; Pavel Hejzlar
2008-01-31
MIT-NFC-PR-082 (January 2006) Abstract This summary provides an overview of the results of the U.S. DOE funded NERI (Nuclear Research ENergy Initiative) program on development of the internally and externally cooled annular fuel for high power density PWRs. This new fuel was proposed by MIT to allow a substantial increase in poer density (on the order of 30% or higher) while maintaining or improving safety margins. A comprehensive study was performed by a team consisting of MIT (lead organization), Westinghuse Electric Corporation, Gamma Engineering Corporation, Framatome ANP(formerly Duke Engineering) and Atomic Energy of Canada Limited.
Cylindrical plasmas generated by an annular beam of ultraviolet light
Thomas, D. M.; Allen, J. E.
2015-07-15
We investigate a cylindrical plasma system with ionization, by an annular beam of ultraviolet light, taking place only in the cylinder's outer region. In the steady state, both the outer and inner regions contain a plasma, with that in the inner region being uniform and field-free. At the interface between the two regions, there is an infinitesimal jump in ion density, the magnitude approaching zero in the quasi-neutral (λ{sub D} → 0) limit. The system offers the possibility of producing a uniform stationary plasma in the laboratory, hitherto obtained only with thermally produced alkali plasmas.
Generalized granuloma annulare with open comedones in photoexposed areas.
Bhushan, P; Aggarwal, A; Yadav, R; Baliyan, V
2011-07-01
Granuloma annulare (GA) is a noninfectious necrobiotic granuloma, which can present as localized or generalized patterns. We present a case of generalized GA with multiple large open comedones over the lesions in a woman with hypothyroidism and diabetes mellitus. GA is associated with collagen and elastic-fibre damage, which may lead to loss of follicular support and resultant open comedone formation, analogous to solar elastosis or senile comedones. The rapid recovery of our patient after treatment with of oral hypoglycaemics supports the role of insulin resistance as a predisposing factor for GA. PMID:21392084
A high efficiency annular dark field detector for STEM.
Kirkland, E J; Thomas, M G
1996-01-01
A new high efficiency annular dark field (ADF) detector for an HB501 STEM (Scanning Transmission Electron Microscope) has been constructed and tested. This detector uses a single crystal YAP scintillator and a solid quartz light pipe extending from the scintillator (inside the vacuum) to the photomultiplier tube (outside the vacuum). A factor of approximately 100 improvement in signal relative to the original detector has been obtained. This has substantially improved the signal to noise ratio in the recorded high resolution ADF-STEM images. PMID:22666919
Performance of a K-band superconducting annular ring antenna
NASA Technical Reports Server (NTRS)
Richard, M. A.; Bhasin, K. B.; Lee, R. Q.; Claspy, P. C.
1992-01-01
Superconducting annular ring antennas operating in the TM12 mode at 21 GHz are designed and fabricated on a lanthanum aluminate substrate using a YBCO high-temperature superconducting thin film. The efficiencies and far-field antenna patterns are measured and compared with an identical antenna patterned with silver. The resonant frequencies and experimental far-field patterns agree well with published models, and efficiency measurements show a maximum improvement of 6 percent at 20 K in the efficiency of the HTS antenna when compared to the silver ring at the same temperature.
Earth's Decelerating Tectonic Plates
Forte, A M; Moucha, R; Rowley, D B; Quere, S; Mitrovica, J X; Simmons, N A; Grand, S P
2008-08-22
Space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions are employed to determine a new global map of present-day rates of change of plate velocities. This map shows that Earth's largest plate, the Pacific, is presently decelerating along with several other plates in the Pacific and Indo-Atlantic hemispheres. These plate decelerations contribute to an overall, globally averaged slowdown in tectonic plate speeds. The map of plate decelerations provides new and unique constraints on the dynamics of time-dependent convection in Earth's mantle. We employ a recently developed convection model constrained by seismic, geodynamic and mineral physics data to show that time-dependent changes in mantle buoyancy forces can explain the deceleration of the major plates in the Pacific and Indo-Atlantic hemispheres.
Groh, E.F.; Lennox, D.H.
1963-04-23
This invention is concerned with a rigid assembly of parallel plates in which keyways are stamped out along the edges of the plates and a self-retaining key is inserted into aligned keyways. Spacers having similar keyways are included between adjacent plates. The entire assembly is locked into a rigid structure by fastening only the outermost plates to the ends of the keys. (AEC)
Anderson, D L
1975-03-21
The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence. PMID:17799689
NASA Astrophysics Data System (ADS)
Lee, Joon Sang
The compressible filtered Navier-Stokes equations were solved using a second order accurate finite volume method with low Mach number preconditioning. A dynamic subgrid-scale stress model accounted for the subgrid-scale turbulence. The study focused on the effects of buoyancy and rotation on the structure of turbulence and transport processes including heat transfer. Several different physical arrangements were studied as outlined below. The effects of buoyancy were first studied in a vertical channel using large eddy simulation (LES). The walls were maintained at constant temperatures, one heated and the other cooled. Results showed that aiding and opposing buoyancy forces emerge near the heated and cooled walls, respectively. In the aiding flow, the turbulent intensities and heat transfer were suppressed at large values of Grashof number. In the opposing flow, however, turbulence was enhanced with increased velocity fluctuations. Another buoyancy study considered turbulent flow in a vertically oriented annulus. Isoflux wall boundary conditions with low and high heating were imposed on the inner wall while the outer wall was adiabatic. The results showed that the strong heating and buoyancy force caused distortions of the flow structure resulting in reduction of turbulent intensities, shear stress, and turbulent heat flux, particularly near the heated wall. Flow in an annular pipe with and without an outer wall rotation about its axis was first investigated at moderate Reynolds numbers. When the outer pipe wall was rotated, a significant reduction of turbulent kinetic energy was realized near the rotating wall. Secondly, a large eddy simulation has been performed to investigate the effect of swirl on the heat and momentum transfer in an annular pipe flow with a rotating inner wall. The simulations indicated that the Nusselt number and the wall friction coefficient increased with increasing rotation speed of the wall. It was also observed that the axial velocity
Energy Science and Technology Software Center (ESTSC)
1998-03-01
The Plating Tank Control Software is a graphical user interface that controls and records plating process conditions for plating in high aspect ratio channels that require use of low current and long times. The software is written for a Pentium II PC with an 8 channel data acquisition card, and the necessary shunt resistors for measuring currents in the millampere range.
Rotatable shear plate interferometer
Duffus, Richard C.
1988-01-01
A rotatable shear plate interferometer comprises a transparent shear plate mounted obliquely in a tubular supporting member at 45.degree. with respect to its horizontal center axis. This tubular supporting member is supported rotatably around its center axis and a collimated laser beam is made incident on the shear plate along this center axis such that defocus in different directions can be easily measured.
Investigation of azimuthal staging concepts in annular gas turbines
NASA Astrophysics Data System (ADS)
Noiray, Nicolas; Bothien, Mirko; Schuermans, Bruno
2011-10-01
In this work, the influence of azimuthal staging concepts on the thermoacoustic behavior of annular combustion chambers is assessed theoretically and numerically. Staging is a well-known and effective method to abate thermoacoustic pulsations in combustion chambers. However, in the case of, for example, fuel staging the associated inhomogeneity of equivalence ratio may result in increased levels of NOx emissions. In order to minimize this unwanted effect a staging concept is required in which the transfer functions of the burners are changed while affecting the equivalence ratio as little as possible. In order to achieve this goal, a theoretical framework for predicting the influence of staging concepts on pulsations has been developed. Both linear and nonlinear analytical approaches are presented and it is shown that the dynamics of azimuthal modes can be described by coupled Van der Pol oscillators. A criterion based on the thermoacoustic coupling strength and on the asymmetry degree provides the modal behavior in the annular combustor, i.e. standing or traveling waves. The model predictions have been verified by numerical simulations of a heavy-duty gas turbine using an in-house thermoacoustic network-modeling tool. The interaction between the heat release of the flame and the acoustic field was modeled using measured transfer functions and source terms. These numerical simulations confirmed the original theoretical considerations.
Non-null annular subaperture stitching interferometry for aspheric test
NASA Astrophysics Data System (ADS)
Zhang, Lei; Liu, Dong; Shi, Tu; Yang, Yongying; Chong, Shiyao; Miao, Liang; Huang, Wei; Shen, Yibing; Bai, Jian
2015-10-01
A non-null annular subaperture stitching interferometry (NASSI), combining the subaperture stitching idea and non-null test method, is proposed for steep aspheric testing. Compared with standard annular subaperture stitching interferometry (ASSI), a partial null lens (PNL) is employed as an alternative to the transmission sphere, to generate different aspherical wavefronts as the references. The coverage subaperture number would thus be reduced greatly for the better performance of aspherical wavefronts in matching the local slope of aspheric surfaces. Instead of various mathematical stitching algorithms, a simultaneous reverse optimizing reconstruction (SROR) method based on system modeling and ray tracing is proposed for full aperture figure error reconstruction. All the subaperture measurements are simulated simultaneously with a multi-configuration model in a ray-tracing program, including the interferometric system modeling and subaperture misalignments modeling. With the multi-configuration model, full aperture figure error would be extracted in form of Zernike polynomials from subapertures wavefront data by the SROR method. This method concurrently accomplishes subaperture retrace error and misalignment correction, requiring neither complex mathematical algorithms nor subaperture overlaps. A numerical simulation exhibits the comparison of the performance of the NASSI and standard ASSI, which demonstrates the high accuracy of the NASSI in testing steep aspheric. Experimental results of NASSI are shown to be in good agreement with that of Zygo® VerifireTM Asphere interferometer.
Magnetohydrodynamics stability of a streaming annular cylindrical liquid surface
NASA Astrophysics Data System (ADS)
Radwan, Ahmed E.; Elazab, Samia S.; Hydia, Wafaa M.
1997-08-01
The instability of a streaming annular magnetized fluid jet surrounding a solid mantle subject to capillary, inertia, fluid kinetic pressure gradient and Lorentz forces has been developed for all kind of perturbations. Several recent works are recovered as limiting cases from the present result. The analytical discussion results are confirmed along with numerical and asymptotic analysis methods. The streaming has a strong destabilizing influence in hydrodynamic, magnetodynamic and hydromagnetics versions. That influence is found to be independent of the kind of perturbation and idem the stabilizing effect of the magnetic field pervaded the interior of the annular fluid jet model. An external longitudinal magnetic field is strongly stabilizing in both axisymmetric and non-axisymmetric perturbation modes. An external transverse varying magnetic field is destabilizing or stabilizing according to restrictions. Large values for the parameter of the transverse field is needed so that stability due to this transverse field may arise and thence the model stability states are modified. The streaming destabilizing influence may be overcome if the intensity of the axials fields interior and exterior the model is so strong that the Alfvén magnetic velocity is much larger than the basic streaming velocity of the fluid in the unperturbed initial state.
Annular bullous lesions with atypical erythema multiforme in leprosy.
Shah, Aishani; Mahajan, Rashmi; Ninama, Kishan; Bilimoria, Freny
2014-09-01
Erythema nodosum leprosum (ENL) is an immune complex-mediated reaction that may complicate the course of multibacillary leprosy. Bullous lesions in Type II reaction, though reported, are exceedingly rare. We report the case of a 32 year old female patient who presented initially at our OPD with erythema nodosum. Cutaneous examination revealed impaired sensation over dorsum of right foot and thickened right lateral popliteal nerve. Slit skin smear (SSS) from ear lobes revealed AFB with a bacteriological index of 2+. She was started on MDT, tablet ofloxacin 200 mg twice a day, and 30 mg oral prednisolone. Two months later, she presented with generalised pruritus, large target lesions over the back, and hemorrhagic bullae over lower extremities and annular pattern of bullae, over both arms. A SSS was repeated which was positive for AFB. Histopathology from bullous lesions was consistent with ENL. Direct Immunofluorescence (DIF) study was negative. Our patient improved rapidly after she was started on thalidomide 100 mg twice daily, with withdrawal of ofloxacin. Erythema Multiforme (EMF) and annular bullous lesions have been reported in patients on treatment with ofloxacin. This case is being presented due to the unusual and varied manifestation of Type II lepra reaction in a 34 year old female patient. PMID:25509721
Electrorheological damper with annular ducts for seismic protection applications
NASA Astrophysics Data System (ADS)
Makris, Nicos; Burton, Scott A.; Taylor, Douglas P.
1996-10-01
This paper presents the design, analysis, testing and modeling of an electrorheological (ER) fluid damper developed for vibration and seismic protection of civil structures. The damper consists of a main cylinder and a piston rod that pushes an ER fluid through a stationary annular duct. The behavior of the damper can be approximated with Hagen - Poiseuille flow theory. The basic equations that describe the fluid flow across an annular duct are derived. Experimental results on the damper response with and without the presence of electric field are presented. As the rate of deformation increases, viscous stresses prevail over field-induced yield stresses and a smaller fraction of the total damper force can be controlled. Simple physically motivated phenomenological models are considered to approximate the damper response with and without the presence of electric field. Subsequently, the performance of a multilayer neural network constructed and trained by an efficient algorithm known as the Dependence Identification Algorithm is examined to predict the response of the electrorheological damper. A combination of a simple phenomenological model and a neural network is then proposed as a practical tool to approximate the nonlinear and velocity-dependent damper response.
Coupled counterrotating polariton condensates in optically defined annular potentials.
Dreismann, Alexander; Cristofolini, Peter; Balili, Ryan; Christmann, Gabriel; Pinsker, Florian; Berloff, Natasha G; Hatzopoulos, Zacharias; Savvidis, Pavlos G; Baumberg, Jeremy J
2014-06-17
Polariton condensates are macroscopic quantum states formed by half-matter half-light quasiparticles, thus connecting the phenomena of atomic Bose-Einstein condensation, superfluidity, and photon lasing. Here we report the spontaneous formation of such condensates in programmable potential landscapes generated by two concentric circles of light. The imposed geometry supports the emergence of annular states that extend up to 100 μm, yet are fully coherent and exhibit a spatial structure that remains stable for minutes at a time. These states exhibit a petal-like intensity distribution arising due to the interaction of two superfluids counterpropagating in the circular waveguide defined by the optical potential. In stark contrast to annular modes in conventional lasing systems, the resulting standing wave patterns exhibit only minimal overlap with the pump laser itself. We theoretically describe the system using a complex Ginzburg-Landau equation, which indicates why the condensate wants to rotate. Experimentally, we demonstrate the ability to precisely control the structure of the petal condensates both by carefully modifying the excitation geometry as well as perturbing the system on ultrafast timescales to reveal unexpected superfluid dynamics. PMID:24889642
The annular hematoma of the shrew yolk-sac placenta.
King, B F; Enders, A C; Wimsatt, W A
1978-05-01
The annular hematoma of the shrew, Blarina brevicauda, is a specialized portion of the yolk-sac wall. In this study, we have examined the fine structure of the different cellular components of the anular hematoma. Small pieces of the gestation sacs from seven pregnant shrews were fixed in glutaraldehyde and osmium tetroxide and processed for transmission electron microscopy. In the area of the trophoblastic curtain, the maternal capillary endothelial cells were hypertrophied and syncytial trophoblast surrounded the capillaries. Cellular trophoblast covered part of the luminal surface of the curtain region, whereas masses of apparently degenerating syncytium were present on other areas of the surface. Maternal erythrocytes, released into the uterine lumen from the curtain region, were phagocytized and degraded by the columnar cells of the trophoblastic annulus. No evidence of iron or pigment accumulation was evident in the parietal endodermal cells underlying the annular trophoblast. Parietal endodermal cells were characterized by cuboidal shape, widely dilated intercellular spaces, and cytoplasm containing granular endoplasmic reticulum. Endodermal cells of the visceral yolk-sac accumulated large numbers of electron-dense granules as well as glycogen in their cytoplasm. Hemopoietic areas and vitelline capillaries were found subjacent to the visceral endoderm. The various portions of the yolk-sac wall of Blarina appear to perform complementary functions which are probably important in maternal-fetal iron transfer. PMID:677046
The Growth of Instabilities in Annular Liquid Sheets
Duke, Daniel J.; Honnery, Damon R; Soria, Julio
2015-11-01
An annular liquid sheet surrounded by parallel co-flowing gas is an effective atomiser. However, the initial instabilities which determine the primary break-up of the liquid sheet are not well understood. Lack of agreement on the influence of the boundary conditions and the non-dimension scaling of the initial instability persists between theoretical stability analyses and experiments. To address this matter, we have undertaken an experimental parametric study of an aerodynamically-driven, non-swirling annular water sheet. The effects of sheet thickness, inner and outer gas-liquid momentum ratio were investigated over an order of magnitude variation in Reynolds and Weber number. From high-speed image correlation measurements in the near-nozzle region, we propose new empirical correlations for the frequency of the instability as a function of the total gas-liquid momentum ratio, with good non-dimensional collapse. From analysis of the instability velocity probability densities, we find two persistent and distinct superimposed instabilities with different growth rates. The first is a short-lived, rapidly saturating sawtooth-like instability. The second is a slower-growing stochastic instability which persists through the break-up of the sheet. The presence of multiple instabilities whose growth rates do not strongly correlate with the shear velocities may explain some of the discrepancies between experiments and stability analyses.
Oscillation Characteristics of Thermocapillary Convection in An Open Annular Pool
NASA Astrophysics Data System (ADS)
Duan, Li; Kang, Qi; Zhang, Di
2016-07-01
Temperature oscillation characteristics and free surface deformation are essential phenomena in fluids with free surface. We report experimental oscillatory behaviors for hydrothermal wave instability in thermocapillary-driven flow in an open annular pool of silicone oil. The annular pool is heated from the inner cylindrical wall with the radius 4mm and cooled at the outer wall with radius 20mm, and the depth of the silicone oil layer is in the range of 0.8mm-3mm.Temperature difference between the two sidewalls was increased gradually, and the flow will become unstable via a super critical temperature difference. In the present paper we used T-type thermocouple measuring the single-point temperature inside the liquid layer and captured the tiny micrometer wave signal through a high-precision laser displacement sensor. The critical temperature difference and critical Ma number of onset of oscillation have been obtained. We discussed the critical temperature difference and critical Marangoni number varies with the change of the depth of liquid layer, and the relationship between the temperature oscillation and surface oscillation has been discussed. Experimental results show that temperature oscillation and surface oscillation start almost at the same time with similar spectrum characteristic.
A compact annular ring microstrip antenna for WSN applications.
Wang, Daihua; Song, Linli; Zhou, Hanchang; Zhang, Zhijie
2012-01-01
A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN) application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna's performance of a steel installation base. By using a chip resistor of large resistance (120 Ω) the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and -2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels. PMID:23012510
Coupled counterrotating polariton condensates in optically defined annular potentials
Dreismann, Alexander; Cristofolini, Peter; Balili, Ryan; Christmann, Gabriel; Pinsker, Florian; Berloff, Natasha G.; Hatzopoulos, Zacharias; Savvidis, Pavlos G.; Baumberg, Jeremy J.
2014-01-01
Polariton condensates are macroscopic quantum states formed by half-matter half-light quasiparticles, thus connecting the phenomena of atomic Bose–Einstein condensation, superfluidity, and photon lasing. Here we report the spontaneous formation of such condensates in programmable potential landscapes generated by two concentric circles of light. The imposed geometry supports the emergence of annular states that extend up to 100 μm, yet are fully coherent and exhibit a spatial structure that remains stable for minutes at a time. These states exhibit a petal-like intensity distribution arising due to the interaction of two superfluids counterpropagating in the circular waveguide defined by the optical potential. In stark contrast to annular modes in conventional lasing systems, the resulting standing wave patterns exhibit only minimal overlap with the pump laser itself. We theoretically describe the system using a complex Ginzburg–Landau equation, which indicates why the condensate wants to rotate. Experimentally, we demonstrate the ability to precisely control the structure of the petal condensates both by carefully modifying the excitation geometry as well as perturbing the system on ultrafast timescales to reveal unexpected superfluid dynamics. PMID:24889642
A Compact Annular Ring Microstrip Antenna for WSN Applications
Wang, Daihua; Song, Linli; Zhou, Hanchang; Zhang, Zhijie
2012-01-01
A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN) application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna's performance of a steel installation base. By using a chip resistor of large resistance (120 Ω) the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and –2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels. PMID:23012510
Annular beam-driven high-gradient accelerators
Keinigs, R.; Jones, M.E.
1988-01-01
During the past several years there has been an increasing interest in using wakefield acceleration techniques as a means for achieving TeV energies with the next generation of linear colliders. The principal design goals for a wakefield accelerator that is to be sued in this context are high accelerating gradients and large transformer ratios. Fundamentally any slow wave structure can function as a wakefield accelerator, and several interesting concepts have been proposed. In this paper we consider for the slow wave structure a dielectrically loaded waveguide. The Dielectric Wakefield Accelerator is a very simple device. The geometry consists of a gapless cavity filled with a dielectric. The dielectric may fill all or just part of the cavity. Here we investigate driving the system with an intense annular beam, so the dielectric is separated from the wall by a vacuum region in which this beam is propagated. The primary advantage of driving with an annular beam is that larger currents can be achieved, and thus larger accelerating gradients can be generated. The drive beam is stabilized by a strong, axial magnetic field. The wall is coated with a dielectric liner to provide for better coupling. A small hole is drilled in the center of the dielectric to allow for the passage of a low current, witness beam.
Design Attributes and Scale Up Testing of Annular Centrifugal Contactors
David H. Meikrantz; Jack D. Law
2005-04-01
Annular centrifugal contactors are being used for rapid yet efficient liquid- liquid processing in numerous industrial and government applications. Commercialization of this technology began eleven years ago and now units with throughputs ranging from 0.25 to 700 liters per minute are readily available. Separation, washing, and extraction processes all benefit from the use of this relatively new commercial tool. Processing advantages of this technology include: low in-process volume per stage, rapid mixing and separation in a single unit, connection-in-series for multi-stage use, and a wide operating range of input flow rates and phase ratios without adjustment. Recent design enhancements have been added to simplify maintenance, improve inspection ability, and provide increased reliability. Cartridge-style bearing and mechanical rotary seal assemblies that can include liquid-leak sensors are employed to enhance remote operations, minimize maintenance downtime, prevent equipment damage, and extend service life. Clean-in-place capability eliminates the need for disassembly, facilitates the use of contactors for feed clarification, and can be automated for continuous operation. In nuclear fuel cycle studies, aqueous based separations are being developed that efficiently partition uranium, actinides, and fission products via liquid-liquid solvent extraction. Thus, annular centrifugal contactors are destined to play a significant role in the design of such new processes. Laboratory scale studies using mini-contactors have demonstrated feasibility for many such separation processes but validation at an engineering scale is needed to support actual process design.
Effects of Gravity on Bubble Formation in an Annular Jet
NASA Technical Reports Server (NTRS)
Koepp, R. A.; Parthasarathy, R. N.; Gollahalli, S. R.
2004-01-01
The effects of gravity on the bubble formation in an annular jet were studied. The experiments were conducted in the 2.2-second drop tower at the NASA Glenn Research Center. Terrestrial gravity experiments were conducted at the Fluid Dynamics Research Laboratory at the University of Oklahoma. Stainless steel tubing with inner diameters of 1/8" (gas inner annulus) and 5/16" (liquid outer annulus) served as the injector. A rectangular test section, 6" x 6" x 14" tall, made out of half-inch thick Lexan was used. Images of the annular jet were acquired using a high-speed camera. The effects of gravity and varying liquid and gas flow rates on bubble size, wavelength, and breakup length were documented. In general, the bubble diameter was found to be larger in terrestrial gravity than in microgravity for varying Weber numbers (0.05 - 0.16 and 5 - 11) and liquid flow rates (1.5 ft/s - 3.0 ft/s). The wavelength was found to be larger in terrestrial gravity than in microgravity, but remained constant for varying Weber numbers. For low Weber numbers (0.05 - 0.16), the breakup length in microgravity was significantly higher than in terrestrial gravity. Comparison with linear stability analysis showed estimated bubble sizes within 9% of experimental bubble sizes. Bubble size compared to other terrestrial gravity experiments with same flow conditions showed distinct differences in bubble size, which displayed the importance of injector geometry on bubble formation.
Investigating an annular nozzle on combustion products of hydrocarbon fuels
NASA Astrophysics Data System (ADS)
Levin, V. A.; Afonina, N. E.; Gromov, V. G.; Smekhov, G. D.; Khmelevsky, A. N.; Markov, V. V.
2013-09-01
Full-scale and computational experiments were used to investigate the flows in the jet thrust unit with annular nozzle and deflector in the form of a spherical segment. The used working gas was the combustion products of air mixtures with acetylene, gas-phase aviation kerosene, and natural gas. Experimental studies were carried out in a hot-shot wind tunnel in the range of stagnation pressure from 0.48 to 2.05 MPa. The calculations for the cases of combustion products outflow in terrestrial and high altitude conditions were performed with the original computer program that used the Euler and Navier-Stokes systems supplemented by equations of chemical kinetics. It was found that the thrust of the jet module with an annular nozzle at high altitude almost twice exceeds the sound nozzle thrust, but is lesser (about 25 %) than the thrust of the ideal calculated Laval nozzle; the difference therewith decreases markedly with the decrease of flight altitude and stagnation pressure.
Annular Flow Liquid Film Dynamics in Pipes and Bod Bundle
NASA Astrophysics Data System (ADS)
Ju, Peng
Average liquid film thickness is important for detailed mechanistic modeling of annular two-phase flow in engineering applications. The existing models and correlations either have large relative errors or narrow application range. Because of this, a new liquid film thickness model has been developed for vertical annular flow in pipes based on three databases. The model includes the pressure, liquid and gas velocities, diameter, and viscosity effects on liquid film thickness. Analysis indicates the film thickness to be a function of Weber numbers for both liquid and gas, and the viscosity number. The model is compared with film thickness data which considers a wide range of liquid and gas superficial velocities, system pressure, fluid properties, as well as several pipe diameters. The trend in the current and available film thickness models at various system conditions are analyzed, highlighting the improvement and widening applicability of the new model. The newly proposed film thickness model results in an average relative error of 14% considering the complete database. Interfacial friction factor in annular two-phase flow is essential both for detailed modeling of two-fluid model and the calculation of pressure gradient. Most of the existing correlations on interfacial friction factor are based on Wallis 1969's correlation, which considers the interfacial friction factor as a function of film thickness. In this research, a new correlation of interfacial friction factor that is based on the wave characteristics has been proposed. The wave characteristics is considered to be a function of a group of non-dimensional numbers. Since the effects of wave characteristics for ripples waves and disturbance waves on interfacial friction factors are different, the correlation is divided into two sub-correlations based on these two wave regimes. The new correlation has been compared with a wide range of data. From the data comparison, the new correlation shows significant
NASA Technical Reports Server (NTRS)
Groom, N. J.
1979-01-01
An analytical model of an Annular Momentum Control Device (AMCD) laboratory test model magnetic bearing actuator with permanent magnet fluxbiasing is presented. An AMCD consists of a spinning annular rim which is suspended by a noncontacting linear electromagnetic spin motor. The actuator is treated as a lumped-parameter electromechanical system in the development of the model.
A collapse surface for a perforated plate with an equilateral triangular array of penetrations
Gordon, J.L.; Jones, D.P.; Hutula, D.N.; Banas, D.
1999-02-01
This paper describes the development of incipient yield and subsequent collapse surfaces for a plate containing a large number of small circular penetrations arranged in an equilateral triangular array. The collapse surface developed here is appropriate for formulating a generic elastic-plastic flow theory for perforated materials. A unit cell is defined to characterize the mechanical response of an equilateral triangular array of penetrations. An elastic-perfectly plastic [EPP] finite element analysis [FEA] computer program is used to calculate the EPP response of the unit cell. A sufficient number of load cases are solved to define the complete incipient yield and collapse surfaces for the unit cell. A fourth order yield function is defined by squaring the Von Mises quadratic yield function and retaining only those terms that are required for the symmetry dictated by the triangular array. Curve fitting is used to determine the coefficients of the fourth order function to match the incipient yield and collapse data calculated for the unit cell by FEA. The incipient yield function in the plane of the plate incorporating the penetration pattern is shown to be almost rhomboidal in shape while the collapse curve is more elliptical. The fourth order yield function which passes through the incipient yield data possess regions where the surface is concave--a concern when developing a plasticity theory based on the function. Fitting the coefficients of the fourth order function to the collapse data results in a curve which is shown to be always convex thus having all positive outward normal vectors which is a required property for the development of plasticity flow theories.
NASA Technical Reports Server (NTRS)
Askew, John C.
1994-01-01
An alternative to the immersion process for the electrodeposition of chromium from aqueous solutions on the inside diameter (ID) of long tubes is described. The Vessel Plating Process eliminates the need for deep processing tanks, large volumes of solutions, and associated safety and environmental concerns. Vessel Plating allows the process to be monitored and controlled by computer thus increasing reliability, flexibility and quality. Elimination of the trivalent chromium accumulation normally associated with ID plating is intrinsic to the Vessel Plating Process. The construction and operation of a prototype Vessel Plating Facility with emphasis on materials of construction, engineered and operational safety and a unique system for rinse water recovery are described.
Annular core liquid-salt cooled reactor with multiple fuel and blanket zones
Peterson, Per F.
2013-05-14
A liquid fluoride salt cooled, high temperature reactor having a reactor vessel with a pebble-bed reactor core. The reactor core comprises a pebble injection inlet located at a bottom end of the reactor core and a pebble defueling outlet located at a top end of the reactor core, an inner reflector, outer reflector, and an annular pebble-bed region disposed in between the inner reflector and outer reflector. The annular pebble-bed region comprises an annular channel configured for receiving pebble fuel at the pebble injection inlet, the pebble fuel comprising a combination of seed and blanket pebbles having a density lower than the coolant such that the pebbles have positive buoyancy and migrate upward in said annular pebble-bed region toward the defueling outlet. The annular pebble-bed region comprises alternating radial layers of seed pebbles and blanket pebbles.
Modeling corrosion rates in non-annular gas condensate wells containing CO{sub 2}
Garber, J.D.; Polaki, V.; Adams, C.; Varanasi, N.R.
1998-12-31
New gas condensate wells are typically producing in annular flow. As the water production increases, the flow dynamics of these wells change to a non-annular flow regime. The flow regime could become chum or slug. A mathematical model has been developed to physically describe this condition. Corrosion rates have been measured in the laboratory and the corrosion rate in slug flow was consistently higher than in churn flow regardless of the experimental conditions selected. A number of non-annular flow wells from the field have been physically described using the new non-annular flow model. There appears to be a correlation between the Taylor bubble length and the corrosion rate. A corrosion rate model has been developed which uses 4 parameters from the non-annular flow model.
Carrilho, Emanuel; Phillips, Scott T; Vella, Sarah J; Martinez, Andres W; Whitesides, George M
2009-08-01
This paper describes 96- and 384-microzone plates fabricated in paper as alternatives to conventional multiwell plates fabricated in molded polymers. Paper-based plates are functionally related to plastic well plates, but they offer new capabilities. For example, paper-microzone plates are thin (approximately 180 microm), require small volumes of sample (5 microL per zone), and can be manufactured from inexpensive materials ($0.05 per plate). The paper-based plates are fabricated by patterning sheets of paper, using photolithography, into hydrophilic zones surrounded by hydrophobic polymeric barriers. This photolithography used an inexpensive formulation photoresist that allows rapid (approximately 15 min) prototyping of paper-based plates. These plates are compatible with conventional microplate readers for quantitative absorbance and fluorescence measurements. The limit of detection per zone loaded for fluorescence was 125 fmol for fluorescein isothiocyanate-labeled bovine serum albumin, and this level corresponds to 0.02 the quantity of analyte per well used to achieve comparable signal-to-noise in a 96-well plastic plate (using a solution of 25 nM labeled protein). The limits of detection for absorbance on paper was approximately 50 pmol per zone for both Coomassie Brilliant Blue and Amaranth dyes; these values were 0.4 that required for the plastic plate. Demonstration of quantitative colorimetric correlations using a scanner or camera to image the zones and to measure the intensity of color, makes it possible to conduct assays without a microplate reader. PMID:19572563
Multicolor printing plate joining
NASA Technical Reports Server (NTRS)
Waters, W. J. (Inventor)
1984-01-01
An upper plate having ink flow channels and a lower plate having a multicolored pattern are joined. The joining is accomplished without clogging any ink flow paths. A pattern having different colored parts and apertures is formed in a lower plate. Ink flow channels each having respective ink input ports are formed in an upper plate. The ink flow channels are coated with solder mask and the bottom of the upper plate is then coated with solder. The upper and lower plates are pressed together at from 2 to 5 psi and heated to a temperature of from 295 F to 750 F or enough to melt the solder. After the plates have cooled and the pressure is released, the solder mask is removed from the interior passageways by means of a liquid solvent.
Detection of cracks on a plate by piezoelectric interdigital transducers
NASA Astrophysics Data System (ADS)
Roh, Yongrae; Kim, Junho
2011-04-01
Much work has been reported on the use of piezoceramic patch sensors in structural health monitoring due to their simple structure and moderate performance. However, the patch uses the inherent electromechanical properties of a piezoceramic element itself. Once the piezoceramic element is given, not much controllability is available on its operation frequency, directionality, and sensitivity. This paper proposes and verifies the feasibility of a new ultrasonic sensor to estimate the quantitative configuration of cracks on a plate: an inter-digital transducer (IDT) type Lamb wave sensor. This IDT sensor is more readily controllable than conventional patch sensors in terms of its operation frequency and directionality by altering the IDT pattern on a given piezoceramic element. In this work, two different types of IDT sensors are designed and fabricated: annular IDT and rectangular IDT sensors. The IDT sensors are implemented in the experiments to investigate the length, the number and the inclination angle of the cracks artificially imposed on an aluminum plate. The variation of amplitude and time-of-flight (TOF) of Lamb waves are measured and analyzed to estimate the crack configurations. The results show that the annular IDT sensor is similar to the conventional patch sensors in terms of its omni-directional beam pattern. The rectangular IDT sensor is highly directional, thus the sensor has superior sensitivity to a particular direction, which means more robust to environmental noise coming from arbitrary directions. The measured configuration shows excellent correlation with real configuration of the cracks, which confirms the efficacy of the IDT sensors.
Enhanced simulation software for rocket turbopump, turbulent, annular liquid seals
NASA Technical Reports Server (NTRS)
Padavala, Satya; Palazzolo, Alan
1994-01-01
One of the main objectives of this work is to develop a new dynamic analysis for liquid annular seals with arbitrary profile and to analyze a general distorted interstage seal of the space shuttle main engine high pressure oxygen turbopump (SSME-ATD-HPOTP). The dynamic analysis developed is based on a method originally proposed by Nelson and Nguyen. A simpler scheme based on cubic splines is found to be computationally more efficient and has better convergence properties at higher eccentricities. The first order solution of the original analysis is modified by including a more exact solution that takes into account the variation of perturbed variables along the circumference. A new set of equations for dynamic analysis are derived based on this more general model. A unified solution procedure that is valid for both Moody's and Hirs' friction models is presented. Dynamic analysis is developed for three different models: constant properties, variable properties, and thermal effects with variable properties. Arbitrarily varying seal profiles in both axial and circumferential directions are considered. An example case of an elliptical seal with varying degrees of axial curvature is analyzed in detail. A case study based on predicted clearances of an interstage seal of the SSME-ATD-HPOTP is presented. Dynamic coefficients based on external specified load are introduced to analyze seals that support a preload. The other objective of this work is to study the effect of large rotor displacements of SSME-ATD-HPOTP on the dynamics of the annular seal and the resulting transient motion. One task is to identify the magnitude of motion of the rotor about the centered position and establish limits of effectiveness of using current linear models. This task is accomplished by solving the bulk flow model seal governing equations directly for transient seal forces for any given type of motion, including motion with large eccentricities. Based on the above study, an equivalence is
Theory of low voltage annular beam free-electron lasers
Blank, M.; Freund, H.P.; Jackson, R.H.
1995-12-31
An nonlinear analysis of an annular beam propagating through a cylindrical waveguide in the presence of a helical wiggler and an axial guide field is presented. The analysis is based upon the ARACHNE simulation which is a non-wiggler-averaged slow-time-scale simulation code in which the electromagnetic field is represented as a superposition of the TE and TM modes in a vacuum waveguide, and the beam space-charge waves are represented as a superposition of Gould-Trivelpiece modes. The DC self-electric and self-magnetic fields are also included in the model. ARACHNE has been extensively benchmarked against experiments at MIT and NRL in the past with good agreement, but all of these experiments have dealt with solid electron beams and beam voltages in excess of 200 kV. In seeking to reduce the beam voltage requirements we now consider the effect of operation with an annular beam. One advantage to be obtained by using an annular beam is that, for a fixed beam current, the effect of the DC selffields (i.e., the space-charge depression in beam voltage) will be reduced relative to that of a solid beam. This facilitates beam transport in short period wigglers in which the transverse dimensions are also small. A specific example is under study which makes use of 55 kV/5A electron beam with inner and outer radii of 0.27 cm and 0.33 cm respectively. The wiggler amplitude is 250 G with a period of 0.9 cm. and guide fields up to 3 kG corresponding to Group I trajectories. The waveguide radius is chosen to correspond to grazing incidence for the fundamental mode in Ku-Band (12-18 GHz). Preliminary results indicate that efficiencies upwards of 10% are possible with no wiggler taper. In addition, the energy spread must be held below 0.1%, and the instantaneous bandwidth is found to be greater than 20%.
Measurements in an annular combustor-diffuser system
NASA Astrophysics Data System (ADS)
Srinivasan, R.; Freeman, W. G.; Mozumdar, S.; Grahmann, J. W.
1990-07-01
Results of three-component Laser Doppler Velocimeter (LDV) measurements in an annular combustor-diffuser system are presented in this paper. The LDV measurements were made at several locations in the prediffuser and dump regions of the combustor-diffuser test rig for three different inlet velocity profiles. The prediffuser average inlet Mach number was maintained at 0.305 during these tests. The LDV data are compared with predictions obtained from a boundary-fitted, two-dimensional elliptic analytical model. The agreement between the LDV data and the predicted results is very good for mean velocities. However, measured turbulence intensities are higher than the predicted values in the region adjacent to the prediffuser walls.
Non-axisymmetric instability of core-annular flow
NASA Astrophysics Data System (ADS)
Hu, Howard H.; Patankar, Neelesh
1995-05-01
Stability of core-annular flow of water and oil in a vertical circular pipe is studied with respect to non-axisymmetric disturbances. Results show that when the oil core is thin, the flow is most unstable to the asymmetric sinuous mode of disturbance, and the core moves in the form of corkscrew waves as observed in experiments. The asymmetric mode of disturbance is the most dangerous mode for quite a wide range of material and flow parameters. This asymmetric mode persists in vertical pipes with upward and downward flows and in horizontal pipes. The analysis also applies to the instability of freely rising axisymmetric cigarette smoke or a thermal plume. The study predicts a unique wavelength for the asymmetric meandering waves.
Core/corona modeling of diode-imploded annular loads
NASA Astrophysics Data System (ADS)
Terry, R. E.; Guillory, J. U.
1980-11-01
The effects of a tenuous exterior plasma corona with anomalous resistivity on the compression and heating of a hollow, collisional aluminum z-pinch plasma are predicted by a one-dimensional code. As the interior ("core") plasma is imploded by its axial current, the energy exchange between core and corona determines the current partition. Under the conditions of rapid core heating and compression, the increase in coronal current provides a trade-off between radial acceleration and compression, which reduces the implosion forces and softens the pitch. Combined with a heuristic account of energy and momentum transport in the strongly coupled core plasma and an approximate radiative loss calculation including Al line, recombination and Bremsstrahlung emission, the current model can provide a reasonably accurate description of imploding annular plasma loads that remain azimuthally symmetric. The implications for optimization of generator load coupling are examined.
Annular dark field transmission electron microscopy for protein structure determination.
Koeck, Philip J B
2016-02-01
Recently annular dark field (ADF) transmission electron microscopy (TEM) has been advocated as a means of recording images of biological specimens with better signal to noise ratio (SNR) than regular bright field images. I investigate whether and how such images could be used to determine the three-dimensional structure of proteins given that an ADF aperture with a suitable pass-band can be manufactured and used in practice. I develop an approximate theory of ADF-TEM image formation for weak amplitude and phase objects and test this theory using computer simulations. I also test whether these simulated images can be used to calculate a three-dimensional model of the protein using standard software and discuss problems and possible ways to overcome these. PMID:26656466
Design for a One-Gigawatt, Annular-Beam Klystron
Arfin, Bernard
2001-01-23
A one-gigawatt, annular beam klystron (ABK) is being developed by Los Alamos National Laboratory in collaboration with the Stanford Linear Accelerator Center (SLAC). The pulse length is 1 {micro}s, the pulse repetition frequency is 5 Hz, and the operating frequency is 1.3 GHz. The beam voltage and current are 800 kV and 4 kA. Since the electron beam parameters are considerably beyond the state-of the-art, an aggressive cathode and electron gun design is required. The magnetron injection gun (MIG) configuration was chosen over the standard Pierce geometry that is typically used in klystrons. The tube design, design issues, and status are presented.
Hyperthermia and inhomogeneous tissue effects using an Annular Phased Array
Turner, P.F.
1984-08-01
A regional hyperthermia Annular Phased Array (APA) applicator is described, and examples of its various heating patterns, obtained by scanning the electric fields with a small E-field sensor, are illustrated. Also shown are the effects of different frequencies of an elliptical phantom cylinder having a 1-cm-thick artificial fat wall and the general dimensions of the human trunk. These studies show the APA's ability to achieve uniform heating at lower frequencies (below 70 MHz) or to focus central heating at moderately higher frequencies (above 70 MHz). The influence of human anatomical contours in altering heating patterns is discussed using results obtained with a female mannequin having a thin latex shell filled with tissue-equivalent phantom. Field perturbations caused by internally embedded low-dielectric structures are presented, showing the localized effects of small objects whose surfaces are perpendicular to the electric field.
Vortex shedding from struts in an annular exhaust diffuser
Fric, T.F.; Villarreal, R.; Auer, R.O.; James, M.L.; Ozgur, D.; Staley, T.K.
1998-01-01
Results from scale-model experiments and industrial gas turbine tests show that strut vortex shedding in an annular exhaust diffuser can effectively be modified by adding tapered chord to the struts. The struts are bluff bodies at full-speed, no-load conditions, when inlet swirl is close to 60 deg. Data from wind tunnel tests show that wake Strouhal number is 0.47, larger than that expected for an isolated cylinder wake. This value of Strouhal number agrees with those measured in full-scale exhaust diffusers. Wind tunnel tests showed that a strut with tapered chord most effectively reduced wake amplitudes and shifted shedding frequency. The tapered strut was also effective in reducing shedding amplitude in a scale-model diffuser. Finally, gas turbine tests employing a tapered strut showed significant reductions in unsteady pressure and noise. A major benefit of strut taper is a reduction of noise by uncoupling of vortex shedding from acoustic resonant response.
Annular billiard dynamics in a circularly polarized strong laser field
NASA Astrophysics Data System (ADS)
Kamor, A.; Mauger, F.; Chandre, C.; Uzer, T.
2012-01-01
We analyze the dynamics of a valence electron of the buckminsterfullerene molecule (C60) subjected to a circularly polarized laser field by modeling it with the motion of a classical particle in an annular billiard. We show that the phase space of the billiard model gives rise to three distinct trajectories: “whispering gallery orbits,” which hit only the outer billiard wall; “daisy orbits,” which hit both billiard walls (while rotating solely clockwise or counterclockwise for all time); and orbits that only visit the downfield part of the billiard, as measured relative to the laser term. These trajectories, in general, maintain their distinct features, even as the intensity is increased from 1010 to 1014Wcm-2. We attribute this robust separation of phase space to the existence of twistless tori.
Thermo-electrohydrodynamic internal waves in annular geometry
NASA Astrophysics Data System (ADS)
Yoshikawa, Harunori; Meyer, Antoine; Crumeyrolle, Olivier; Mutabazi, Innocent
2014-11-01
An electric field applied to a dielectric fluid with a temperature gradient generates a body force on the fluid, which can be regarded as thermal buoyancy associated with an electric effective gravity. We consider the internal waves due to this thermoelectric force in annular geometry, where the force field is centro-symmetric. The Earth's gravity is neglected. This configuration is of relevance to large-scale geophysical flows. The dispersion relation of the waves is determined by a spectral method, with or without taking into account the fluid viscosity. The effects of geometry curvature and of a thermoelectric feedback are discussed. The oscillatory instability of the circular Couette flow under the thermoelectric body force and its relation with the waves will also be discussed. Authors acknowledge the financial support from the CNRS under the program PEPS-PTI OndInterGE.
Interfacial shear modeling in two-phase annular flow
Kumar, R.; Edwards, D.P.
1996-07-01
A new interfacial shear stress model called the law of the interface model, based on the law of the wall approach in turbulent flows, has been developed and locally applied in a fully developed, adiabatic, two-phase annular flow in a duct. Numerical results have been obtained using this model in conjunction with other models available in the literature that are required for the closure of the continuity and momentum equations. These results have been compared with droplet velocity data (using laser Doppler velocimetry and hot film anemometry), void fraction data (using gamma densitometry) and pressure drop data obtained in a R-134A refrigerant test facility. Droplet velocity results match the experimental data well, however, the prediction of the void fraction is less accurate. The poor prediction of void fraction, especially for the low void fraction cases, appears to be due to the lack of a good mechanistic model for entrainment.
An in-house developed annular bright field detection system
NASA Astrophysics Data System (ADS)
Lari, Leonardo; Wright, Ian; Pingstone, Daniel; Steward, Jonathan; Gilks, Daniel; Lazarov, Vlado K.
2014-06-01
Annular bright field (ABF) detectors have been developed in the last few years allowing the direct imaging of low-Z atoms from oxygen down to hydrogen. These types of detectors are now available as standard attachments for the latest generation of top-end electron microscopes. However these systems cannot always be installed in previous generation microscopes. In this paper we report the preliminary results of an in-house implementation of a ABF detection system on a CEOS aberration corrected JEOL 2200FS STEM. This has been obtained by exploiting the standard BF detector coupled with a high vacuum compatible, X-ray tight and retractable shadowing mechanism. This results in the acquisition of near zero-angle scattered electrons with inner collection semi-angle from 2.0 mrad to 23 mrad and outer semi-angle in the range from 3.0 mrad to 35 mrad. The characteristics and performances of this ABF detection system are discussed.
Fuel Injector Design Optimization for an Annular Scramjet Geometry
NASA Astrophysics Data System (ADS)
Steffen, Christopher J., Jr.
2003-01-01
A four-parameter, three-level, central composite experiment design has been used to optimize the configuration of an annular scramjet injector geometry using computational fluid dynamics. The computational fluid dynamic solutions played the role of computer experiments, and response surface methodology was used to capture the simulation results for mixing efficiency and total pressure recovery within the scramjet flowpath. An optimization procedure, based upon the response surface results of mixing efficiency, was used to compare the optimal design configuration against the target efficiency value of 92.5%. The results of three different optimization procedures are presented and all point to the need to look outside the current design space for different injector geometries that can meet or exceed the stated mixing efficiency target.
Investigation of a low NOx full-scale annular combustor
NASA Technical Reports Server (NTRS)
1982-01-01
An atmospheric test program was conducted to evaluate a low NOx annular combustor concept suitable for a supersonic, high-altitude aircraft application. The lean premixed combustor, known as the vortex air blast (VAB) concept, was tested as a 22.0-cm diameter model in the early development phases to arrive at basic design and performance criteria. Final demonstration testing was carried out on a full scale combustor of 0.66-m diameter. Variable geometry dilution ports were incorporated to allow operation of the combustor across the range of conditions between idle (T(in) = 422 K, T(out) = 917 K) and cruise (T(in) = 833 K, T(out) - 1778 K). Test results show that the design could meet the program NOx goal of 1.0 g NO2/kg fuel at a one-atmospheric simulated cruise condition.
Two-phase flow instabilities in a vertical annular channel
Babelli, I.; Nair, S.; Ishii, M.
1995-09-01
An experimental test facility was built to study two-phase flow instabilities in vertical annular channel with emphasis on downward flow under low pressure and low flow conditions. The specific geometry of the test section is similar to the fuel-target sub-channel of the Savannah River Site (SRS) Mark 22 fuel assembly. Critical Heat Flux (CHF) was observed following flow excursion and flow reversal in the test section. Density wave instability was not recorded in this series of experimental runs. The results of this experimental study show that flow excursion is the dominant instability mode under low flow, low pressure, and down flow conditions. The onset of instability data are plotted on the subcooling-Zuber (phase change) numbers stability plane.
Annular plaques on the tongue: what is your diagnosis?
Kayhan, Tuba Çelebĺ; Bĺlaç, Cemal; Bĺlaç, Dilek Bayraktar; Ecemĺş, Talat; Ermertcan, Aylin Türel
2011-11-01
Geographic tongue is an inflammatory disorder of the tongue characterized by asymptomatic erythematous patches with serpiginous borders. Candidiasis of the tongue may be confused with geographic tongue. A 63-year-old male patient with painful white annular lesions localized to the left side of his tongue is presented. He applied topical corticosteroid and antiinflammatory agents, but his lesions did not respond to those therapies. Using direct mycologic examination and culture, the patient was diagnosed with candidiasis. After systemic and topical antifungal therapy, clinical improvement was observed. With this case, the clinical forms of oral candidiasis were discussed, and it was suggested that the clinical presentation of mucosal candidiasis may vary according to the stage of infection and individual immunity. PMID:22148032
Annular modes and apparent eddy feedbacks in the Southern Hemisphere
NASA Astrophysics Data System (ADS)
Byrne, Nicholas J.; Shepherd, Theodore G.; Woollings, Tim; Plumb, R. Alan
2016-04-01
Lagged correlation analysis is often used to infer intraseasonal dynamical effects but is known to be affected by nonstationarity. We highlight a pronounced quasi 2 year peak in the anomalous zonal wind and eddy momentum flux convergence power spectra in the Southern Hemisphere, which is prima facie evidence for nonstationarity. We then investigate the consequences of this nonstationarity for the Southern Annular Mode and for eddy momentum flux convergence. We argue that positive lagged correlations previously attributed to the existence of an eddy feedback are more plausibly attributed to nonstationary interannual variability external to any potential feedback process in the midlatitude troposphere. The findings have implications for the diagnosis of feedbacks in both models and reanalysis data as well as for understanding the mechanisms underlying variations in the zonal wind.
Periocular granuloma annulare: a case report and review of literature.
Chiang, Katherine; Bhalla, Rohan; Mesinkovska, Natasha A; Piliang, Melissa P; Tamburro, Joan E
2014-01-01
Granuloma annulare (GA) is a granulomatous dermatosis that rarely presents on the face and is extremely uncommon in the periocular region. We report our experience with the presentation and management of GA lesions on the eyelids of a 17-year-old girl. We performed a review of published literature and identified 13 cases of pediatric periocular GA. One additional case was identified upon review of all pediatric GA cases at the Cleveland Clinic Foundation. Review of these cases suggests that periocular GA is a benign condition that spontaneously regresses within a few months. GA nodules have a predilection for the upper eyelids. A greater incidence is noted in African American children. Awareness of the self-resolving nature of this condition can prevent unnecessary surgical excisions in affected children. PMID:23551387
Mathematical model for multicomponent separations on the continuous annular chromatograph
Bratzler, R.L.; Begovich, J.M.
1980-12-01
A model for multicomponent separations on ion exchange columns has been adapted for use in studying the performance of the continuous annular chromatograph. The model accurately predicts solute peak positions in the column effluent and qualitatively predicts trends in solute effluent resolution as a function of increasing bandwidth of the solute feed pulse. The major virtues of the model are its simplicity in terms of the calculations involved and the fact that it incorporates the nonlinear solute-resin binding isotherms common in many ion exchange separations. Because dispersion effects are not accounted for in the model, discrepancies exist between the shapes of the effluent peaks predicted by the model and those determined experimentally.
Orbital Granuloma Annulare as Presentation of Systemic Sarcoidosis
Kang, Joann J.; Aakalu, Vinay K.; Lin, Amy; Setabutr, Pete
2014-01-01
Purpose: To report a unique case of an orbital mass with atypical histopathologic features that although overlap with other granulomatous disorders, likely represents orbital involvement of systemic sarcoidosis. Methods: Observational case report. Results: A 51-year-old woman presented with an orbital mass and was found to have mild proptosis and restriction of ocular motility. The remainder of her ophthalmic exam was unremarkable. Excisional biopsy revealed ill-defined granulomas with central necrosis, chronic inflammation and sclerotic collagen; several features consistent with granuloma annulare. Further systemic workup including laboratory and radiologic studies were compatible with a diagnosis of systemic sarcoidosis. Conclusion: Our case emphasizes the importance of a complete systemic workup with the detection of an orbital granuloma to ensure accurate diagnosis and appropriate management. PMID:23895369
Annular suspension and pointing system with controlled DC electromagnets
NASA Technical Reports Server (NTRS)
Vu, Josephine Lynn; Tam, Kwok Hung
1993-01-01
The Annular Suspension and Pointing System (ASPS) developed by the Flight System division of Sperry Corporation is a six-degree of freedom payload pointing system designed for use with the space shuttle. This magnetic suspension and pointing system provides precise controlled pointing in six-degrees of freedom, isolation of payload-carrier disturbances, and end mount controlled pointing. Those are great advantages over the traditional mechanical joints for space applications. In this design, we first analyzed the assumed model of the single degree ASPS bearing actuator and obtained the plant dynamics equations. By linearizing the plant dynamics equations, we designed the cascade and feedback compensators such that a stable and satisfied result was obtained. The specified feedback compensator was computer simulated with the nonlinearized plant dynamics equations. The results indicated that an unstable output occurred. In other words, the designed feedback compensator failed. The failure of the design is due to the Taylor's series expansion not converging.
Simulation study with arbitrary profile liquid annular seals
Padavala, S.; Palazzolo, A.B.
1994-10-01
This paper presents an improved dynamic analysis for liquid annular seals with arbitrary profile based on a method first proposed by Nelson and Nguyen. An improved first-order solution that incorporates a continuous interpolation of perturbed quantities in the circumferential direction is presented. The original method uses an approximation scheme for circumferential gradients of zeroth order solution based on Fast Fourier Transforms (FFT). A simpler scheme based on cubic splines is found to be computationally more efficient, with better convergence at higher eccentricities. Arbitrarily varying seal profiles in both axial and circumferential directions are considered. A procedure for computing dynamic coefficients based on external specific load is discussed. An example case of an elliptical seal with varying degrees of axial curvature is analyzed. A case study based on actual operating clearances (6 axial planes with 68 clearances/plane) of an interstage seal of the Space Shuttle Main Engine High Pressure Oxygen Turbopump (SSME-ATD-HPOTP) is presented.
Intermittent Flow of Granular Matter in an Annular Geometry
NASA Astrophysics Data System (ADS)
Brzinski, Ted; Daniels, Karen E.
Granular solids can be subjected to a finite stress below which the response is elastic. Above this yield stress, however, the material fails catastrophically, undergoing a rapid plastic deformation. In the case of a monotonically increasing stress the material exhibits a characteristic stick-slip response. We investigate the statistics of this intermittent failure in an annular shear geometry, driven with a linear-ramp torque in order to generate the stick-slip behavior. The apparatus is designed to allow visual access to particle trajectories and inter-particle forces (through the use of photoelastic materials). Additionally, twelve piezoelectric sensors at the outer wall measure acoustic emissions due to the plastic deformation of the material. We vary volume fraction, and use both fixed and deformable boundaries. We measure how the distribution of slip size and duration are related to the bulk properties of the packing, and compare to systems with similar governing statistics.
Existence of non zero modes in an annular lined duct
NASA Astrophysics Data System (ADS)
Balint, Agneta M.; Balint, Stefan; Tanasie, Loredana
2012-11-01
The purpose is to extend Vilenski - Rienstra's [32] results concerning mainly the general aspects of the existence of non zero modes in annular lined ducts. The case, when the radial and circumferential components of the mean flow are equal to zero and the axial component depends only on the distance to the duct axis, is investigated. Conditions for the existence of non zero modes, which satisfy the linearized homogeneous Euler equations (obtained by linearization around the mean flow) and the boundary conditions, (corresponding to the perturbation - liner interaction of mass-spring-damper type) are found. The first condition, called dispersion relation, is expressed in terms of the solutions of two normalized initial value problems and is equivalent to the linear dependence of these solutions. It is shown that the set of non zero modes, corresponding to a given frequency and given axial and circumferential wave number, is either the null space, either is a one dimensional function space. It is shown also that if the mean flow is symmetric with respect to the "center of the ring", then neither symmetric, nor anti-symmetric modes exist. This difference between the annular and rectangular or circular lined duct models explains while one of the boundary conditions can not be transferred in the center of symmetry. For symmetric flow, being constant in the "central part of the ring", new dispersion relations are derived. The new relations beside the solutions of the two normalized initial value problems incorporate also modified Bessel functions or additional Bessel functions. The Lyapunov stability of the mean flow with respect to the initial value perturbation by mode type perturbations is discussed in terms of the zero's of the dispersion relation.
NASA Astrophysics Data System (ADS)
Falahatgar, S. R.; Salehi, Manouchehr
2011-12-01
Nonlinear bending analysis of polymeric laminated composite plate is examined considering material nonlinearity for viscoelastic matrix material through a Micro-macro approach. The micromechanical Simplified Unit Cell Method (SUCM) in three-dimensional closed-form solution is used for the overall behavior of the unidirectional composite in any combination of loading conditions. The elastic fibers are transversely isotropic where Schapery single integral equation in multiaxial stress state describes the matrix material by recursive-iterative formulation. The finite difference Dynamic Relaxation (DR) method is utilized to study the bending behavior of Mindlin annular sector plate including geometric nonlinearity under uniform lateral pressure with clamped and hinged edge constraints. The unsymmetrical laminated plate deflection is predicted for different thicknesses and also various pressures in different time steps and they are compared with elastic finite element results. As a main objective, the deflection results of viscoelastic laminated sector plate are obtained for various fiber volume fractions in the composite system.
Feasibility development program LEU-foil plate type target for the production of Mo-99
Allen, C.W.; Butler, R.A.; Jarousse, C.; Falgoux, J.L.
2008-07-15
The University of Missouri Research Reactor and AREVA-CERCA have recently signed a Memorandum of Understanding to cooperate in a program to determine the feasibility of manufacturing a prototype LEU-foil target in a plate geometry for the production of molybdenum-99. The concept of a plate type target consists of transitioning Argonne National Laboratory's existing LEU-foil annular target design from a concentric tube geometry to a plate geometry. The objectives of the feasibility determination are: 1) Evaluate the structural integrity and geometric stability of a foil plate target during irradiation and post-irradiation by finite element analysis modeling. 2) Evaluate the heat transfer characteristics of a foil plate target with respect to thermal contact resistance at the foil / plate interfaces. 3) Determine the economics of manufacturing an LEU-foil plate target in comparison to that of a LEU dispersion plate type target on a commercial scale basis. 4) Determine the most effective and efficient method of disassembling the target to remove the foil component of the target for chemical processing. The results of the structural and thermal analyses will be used to determine if a comprehensive set of Safety Case documentation can be developed to support the irradiation and disassembly of a 'mini' (i.e., small scale) LEU-foil plate target as a trial demonstration. (author)
Hypervelocity plate acceleration
Marsh, S.P.; Tan, T.H.
1991-01-01
Shock tubes have been used to accelerate 1.5-mm-thick stainless steel plates to high velocity while retaining their integrity. The fast shock tubes are 5.1-cm-diameter, 15.2-cm-long cylinders of PBX-9501 explosive containing a 1.1-cm-diameter cylindrical core of low-density polystyrene foam. The plates have been placed directly in contact with one face of the explosive system. Plane-wave detonation was initiated on the opposite face. A Mach disk was formed in the imploding styrofoam core, which provided the impulse required to accelerate the metal plate to high velocity. Parametric studies were made on this system to find the effect of varying plate metal, plate thickness, foam properties, and addition of a barrel. A maximum plate velocity of 9.0 km/s has been observed. 6 refs., 17 figs.
WFPDB: European Plate Archives
NASA Astrophysics Data System (ADS)
Tsvetkov, Milcho
2007-08-01
The Wide-Field Plate Database (WFPDB) gives an inventory of all wide-field (>~ 1 sq. deg) photographic observations archived in astronomical institutions over the world. So it facilitates and stimulates their use and preservation as a valuable source of information for future investigations in astronomy. At present WFPDB manages plate-index information for 25% of all existing plates providing on-line access from Sofia (http://www.skyarchive.org/search) and in CDS, Strasbourg. Here we present the new development of WFPDB as an instrument for searching of long term brightness variations of different sky objects stressing on the European photographic plate collections (from existing 2 million wide-field plates more than 55% are in Europe: Germany, Russia, Ukraine, Italy, Czech Republic, etc.). We comment examples of digitization (with flatbed scanners) of the European plate archives in Sonneberg, Pulkovo, Asiago, Byurakan, Bamberg, etc. and virtual links of WFPDB with European AVO, ADS, IBVS.
Seegmiller, R.
1957-08-01
An improved bath is reported for plating gold on other metals. The composition of the plating bath is as follows: Gold cyanide from about 15 to about 50 grams, potassium cyanide from about 70 to about 125 grams, and sulfonated castor oil from about 0.1 to about 10 cc. The gold plate produced from this bath is smooth, semi-hard, and nonporous.
NASA Technical Reports Server (NTRS)
Berkowitz, J. B.; Emerson, N. H.
1972-01-01
Results are presented of a comprehensive search of the literature available, much of which has been generated by the research centers of NASA and its contractors, on plating and coating methods and techniques. Methods covered included: (1) electroplating from aqueous solutions; (2) electroplating from nonaqueous solutions; (3) electroplating from fused-salt baths; (4) electroforming; (5) electroless plating, immersion plating, and mirroring; (6) electroplating from gaseous plasmas; and (7) anodized films and conversion coatings.
NASA Astrophysics Data System (ADS)
Peng, Yufeng; Peng, Fang; Han, Junpeng
2013-02-01
Based on the laser field from a positive confocal unstable resonator, considering the influence of thermal distortion of the internal resonator mirror on the annular beam, the propagation characteristics of the annular beam through turbulent atmosphere are investigated by means of the fast Fourier transform algorithm (FFT). The intensity distributions of the output laser far-field are obtained to analyze the propagation characteristics of laser annular beam through the turbulent atmosphere, which is a function about different propagation distances. The results show that the peak intensity of the laser pattern becomes depressed and the spread of the far field diagram patterns is broadened under the increasing of the transmission distance and the thermal distortion of the laser resonator. β-parameter and strehl ratio are introduced to estimate the annular beam quality characteristics. It is found that the annular beam through strong turbulence influences much less obviously than the annular beam through weak turbulence on the quality characteristics with thermal distortion. In the same atmospheric conditions with a certain distance, the greater the mirror thermal distortion is, the worse the annular beam quality characteristics is.
Laser-induced retinal damage thresholds for annular retinal beam profiles
NASA Astrophysics Data System (ADS)
Kennedy, Paul K.; Zuclich, Joseph A.; Lund, David J.; Edsall, Peter R.; Till, Stephen; Stuck, Bruce E.; Hollins, Richard C.
2004-07-01
The dependence of retinal damage thresholds on laser spot size, for annular retinal beam profiles, was measured in vivo for 3 μs, 590 nm pulses from a flashlamp-pumped dye laser. Minimum Visible Lesion (MVL)ED50 thresholds in rhesus were measured for annular retinal beam profiles covering 5, 10, and 20 mrad of visual field; which correspond to outer beam diameters of roughly 70, 160, and 300 μm, respectively, on the primate retina. Annular beam profiles at the retinal plane were achieved using a telescopic imaging system, with the focal properties of the eye represented as an equivalent thin lens, and all annular beam profiles had a 37% central obscuration. As a check on experimental data, theoretical MVL-ED50 thresholds for annular beam exposures were calculated using the Thompson-Gerstman granular model of laser-induced thermal damage to the retina. Threshold calculations were performed for the three experimental beam diameters and for an intermediate case with an outer beam diameter of 230 μm. Results indicate that the threshold vs. spot size trends, for annular beams, are similar to the trends for top hat beams determined in a previous study; i.e., the threshold dose varies with the retinal image area for larger image sizes. The model correctly predicts the threshold vs. spot size trends seen in the biological data, for both annular and top hat retinal beam profiles.
Brobeck, W.M.
1959-08-25
The construction of a removable cover plate for a calutron tank is described. The plate is fabricated of a rectangular frame member to which is welded a bowed or dished plate of thin steel, reinforced with transverse stiffening ribs. When the tank is placed between the poles of a magnet, the plate may be pivoted away from the tank and magnet and is adapted to support the ion separation mechanism secured to its inner side as well as the vacuum load within the tank.
West, J.M.; Schumar, J.F.
1958-06-10
Planar-type fuel assemblies for nuclear reactors are described, particularly those comprising fuel in the oxide form such as thoria and urania. The fuel assembly consists of a plurality of parallel spaced fuel plate mennbers having their longitudinal side edges attached to two parallel supporting side plates, thereby providing coolant flow channels between the opposite faces of adjacent fuel plates. The fuel plates are comprised of a plurality of longitudinally extending tubular sections connected by web portions, the tubular sections being filled with a plurality of pellets of the fuel material and the pellets being thermally bonded to the inside of the tubular section by lead.
Filoux, Erwan; Sampathkumar, Ashwin; Chitnis, Parag V; Aristizábal, Orlando; Ketterling, Jeffrey A
2013-05-01
This paper presents a combined ultrasound and photoacoustic (PA) imaging (PAI) system used to obtain high-quality, co-registered images of mouse-embryo anatomy and vasculature. High-frequency ultrasound (HFU, >20 MHz) is utilized to obtain high-resolution anatomical images of small animals while PAI provides high-contrast images of the vascular network. The imaging system is based on a 40 MHz, 5-element, 6 mm aperture annular-array transducer with a 800 μm diameter hole through its central element. The transducer was integrated in a cage-plate assembly allowing for a collimated laser beam to pass through the hole so that the optical and acoustic beams were collinear. The assembly was mounted on a two-axis, motorized stage to enable the simultaneous acquisition of co-registered HFU and PA volumetric data. Data were collected from all five elements in receive and a synthetic-focusing algorithm was applied in post-processing to beamform the data and increase the spatial resolution and depth-of-field (DOF) of the HFU and PA images. Phantom measurements showed that the system could achieve high-resolution images (down to 90 μm for HFU and 150 μm for PAI) and a large DOF of >8 mm. Volume renderings of a mouse embryo showed that the scanner allowed for visualizing morphologically precise anatomy of the entire embryo along with corresponding co-registered vasculature. Major head vessels, such as the superior sagittal sinus or rostral vein, were clearly identified as well as limb bud vasculature. PMID:23742556
NASA Astrophysics Data System (ADS)
Filoux, Erwan; Sampathkumar, Ashwin; Chitnis, Parag V.; Aristizábal, Orlando; Ketterling, Jeffrey A.
2013-05-01
This paper presents a combined ultrasound and photoacoustic (PA) imaging (PAI) system used to obtain high-quality, co-registered images of mouse-embryo anatomy and vasculature. High-frequency ultrasound (HFU, >20 MHz) is utilized to obtain high-resolution anatomical images of small animals while PAI provides high-contrast images of the vascular network. The imaging system is based on a 40 MHz, 5-element, 6 mm aperture annular-array transducer with a 800 μm diameter hole through its central element. The transducer was integrated in a cage-plate assembly allowing for a collimated laser beam to pass through the hole so that the optical and acoustic beams were collinear. The assembly was mounted on a two-axis, motorized stage to enable the simultaneous acquisition of co-registered HFU and PA volumetric data. Data were collected from all five elements in receive and a synthetic-focusing algorithm was applied in post-processing to beamform the data and increase the spatial resolution and depth-of-field (DOF) of the HFU and PA images. Phantom measurements showed that the system could achieve high-resolution images (down to 90 μm for HFU and 150 μm for PAI) and a large DOF of >8 mm. Volume renderings of a mouse embryo showed that the scanner allowed for visualizing morphologically precise anatomy of the entire embryo along with corresponding co-registered vasculature. Major head vessels, such as the superior sagittal sinus or rostral vein, were clearly identified as well as limb bud vasculature.
High-power test of annular-ring coupled structures for the J-PARC linac energy upgrade
NASA Astrophysics Data System (ADS)
Tamura, Jun; Ao, Hiroyuki; Nemoto, Yasuo; Asano, Hiroyuki; Suzuki, Takahiro
2015-02-01
Annular-ring coupled structures (ACSs) will increase the beam energy of the Japan proton accelerator research complex (J-PARC) linac from 181 to 400 MeV to achieve a beam power of 1 MW for a materials and life science experimental facility. The mass production of the ACS cavities commenced in March 2009. Before the installation, all cavities require power testing. High-power testing is essential not only for confirming the cavity's design performance but also for preventing delays in cavity conditioning schedule. However, the 2011 Tohoku earthquake damaged J-PARC facilities, including the ACS power-test area, and cavity conditioning was interrupted for two years. After the facility's restoration, two ACS cavities (M01 and M11) were conditioned. They performed 15-20% above the designed accelerating field of 4.2 MV/m. As M01 was initially conditioned six years ago, the most recent conditioning time required for M01 was drastically reduced. From this result, we confirmed that long-term stored ACS cavities purged with nitrogen gas do not produce critical cavity performance issues. During high-power operation of M11, which is a unique cavity equipped with a capacitive iris in a waveguide, no significant increases in the temperature and the discharge rate around the capacitive iris were observed. Even considering beam loss due to residual gas scattering, the vacuum pressure was sufficiently low (4 × 10-6 Pa). More stable operation can be expected following a month-long conditioning process before the beam is commissioned. M11's conditioning successfully demonstrated an auto-conditioning program, and we established the conditioning scheme using this auto-conditioning program for all ACS cavities in a limited time and with limited manpower.
Apparatus for tensile testing plate-type ceramic specimens
Liu, K.C.
1993-08-24
Apparatus is described for gripping a plate-type tensile specimen having generally T-shaped end regions in a dynamic tension fatigue testing apparatus comprising an annular housing having an open-ended elongated cavity therein, a plurality of hydraulic piston means supported by the housing in a spaced array about the cavity, and a specimen-supporting plate means overlying the piston means at one end of the elongated cavity and displaceable by said piston means in a longitudinal direction with respect to the longitudinal axis of the cavity, said apparatus for gripping a flat plate-type tensile specimen comprising: a pair of elongated pull rods each having oppositely disposed first and second end regions; a pair of mounting means carried by said plate means with each mounting means for pivotally attaching the first end region of each of said pull rods in a central region of said plate means for supporting said pair of elongated pull rods in a side-by-side relationship along a common longitudinal centerline within said cavity; recess means in the second end region of each of said pull rods in adjacently disposed surface regions thereof with said recess means facing one another and each adapted to receive one side of one of the generally T-shaped end regions of the plate-type tensile specimen; and load-bearing means positionable in each of said recess means and adapted to bear against a shoulder on each side of the generally T-shaped end region of the plate-type tensile specimen when a tensile loading is applied thereon.
Characterization of annular two-phase gas-liquid flows in microgravity
NASA Technical Reports Server (NTRS)
Bousman, W. Scott; Mcquillen, John B.
1994-01-01
A series of two-phase gas-liquid flow experiments were developed to study annular flows in microgravity using the NASA Lewis Learjet. A test section was built to measure the liquid film thickness around the perimeter of the tube permitting the three dimensional nature of the gas-liquid interface to be observed. A second test section was used to measure the film thickness, pressure drop and wall shear stress in annular microgravity two-phase flows. Three liquids were studied to determine the effects of liquid viscosity and surface tension. The result of this study provide insight into the wave characteristics, pressure drop and droplet entrainment in microgravity annular flows.
On the Motion of an Annular Film in Microgravity Gas-Liquid Flow
NASA Technical Reports Server (NTRS)
McQuillen, John B.
2002-01-01
Three flow regimes have been identified for gas-liquid flow in a microgravity environment: Bubble, Slug, and Annular. For the slug and annular flow regimes, the behavior observed in vertical upflow in normal gravity is similar to microgravity flow with a thin, symmetrical annular film wetting the tube wall. However, the motion and behavior of this film is significantly different between the normal and low gravity cases. Specifically, the liquid film will slow and come to a stop during low frequency wave motion or slugging. In normal gravity vertical upflow, the film has been observed to slow, stop, and actually reverse direction until it meets the next slug or wave.
ERIC Educational Resources Information Center
Fontes, Kris
2009-01-01
In the December 1997 issue of "SchoolArts" is a lesson titled "Blue Willow Story Plates" by Susan Striker. In this article, the author shares how she used this lesson with her middle-school students many times over the years. Here, she describes a Blue Willow plate painting project that her students made.
Earthquakes and plate tectonics
Spall, H.
1977-01-01
An explanation is to be found in plate tectonics, a concept which has revolutionized thinking in the Earth sciences in the last 10 years. The theory of plate tectonics combines many of the ideas about continental drift (originally proposed in 1912 by Alfred Wegener in Germany) and sea-floor spreading (suggested originally by Harry Hess of Princeton University).
Add-on unidirectional elastic metamaterial plate cloak
Lee, Min Kyung; Kim, Yoon Young
2016-01-01
Metamaterial cloaks control the propagation of waves to make an object invisible or insensible. To manipulate elastic waves in space, a metamaterial cloak is typically embedded in a base system that includes or surrounds a target object. The embedding is undesirable because it structurally weakens or permanently alters the base system. In this study, we propose a new add-on metamaterial elastic cloak that can be placed over and mechanically coupled with a base structure without embedding. We designed an add-on type annular metamaterial plate cloak through conformal mapping, fabricated it and performed cloaking experiments in a thin-plate with a hole. Experiments were performed in a thin plate by using the lowest symmetric Lamb wave centered at 100 kHz. As a means to check the cloaking performance of the add-on elastic plate cloak, possibly as a temporary stress reliever or a so-called “stress bandage”, the degree of stress concentration mitigation and the recovery from the perturbed wave field due to a hole were investigated. PMID:26860896
Add-on unidirectional elastic metamaterial plate cloak
NASA Astrophysics Data System (ADS)
Lee, Min Kyung; Kim, Yoon Young
2016-02-01
Metamaterial cloaks control the propagation of waves to make an object invisible or insensible. To manipulate elastic waves in space, a metamaterial cloak is typically embedded in a base system that includes or surrounds a target object. The embedding is undesirable because it structurally weakens or permanently alters the base system. In this study, we propose a new add-on metamaterial elastic cloak that can be placed over and mechanically coupled with a base structure without embedding. We designed an add-on type annular metamaterial plate cloak through conformal mapping, fabricated it and performed cloaking experiments in a thin-plate with a hole. Experiments were performed in a thin plate by using the lowest symmetric Lamb wave centered at 100 kHz. As a means to check the cloaking performance of the add-on elastic plate cloak, possibly as a temporary stress reliever or a so-called “stress bandage”, the degree of stress concentration mitigation and the recovery from the perturbed wave field due to a hole were investigated.
Add-on unidirectional elastic metamaterial plate cloak.
Lee, Min Kyung; Kim, Yoon Young
2016-01-01
Metamaterial cloaks control the propagation of waves to make an object invisible or insensible. To manipulate elastic waves in space, a metamaterial cloak is typically embedded in a base system that includes or surrounds a target object. The embedding is undesirable because it structurally weakens or permanently alters the base system. In this study, we propose a new add-on metamaterial elastic cloak that can be placed over and mechanically coupled with a base structure without embedding. We designed an add-on type annular metamaterial plate cloak through conformal mapping, fabricated it and performed cloaking experiments in a thin-plate with a hole. Experiments were performed in a thin plate by using the lowest symmetric Lamb wave centered at 100 kHz. As a means to check the cloaking performance of the add-on elastic plate cloak, possibly as a temporary stress reliever or a so-called "stress bandage", the degree of stress concentration mitigation and the recovery from the perturbed wave field due to a hole were investigated. PMID:26860896
Schiavo Jr., Anthony L.
2006-01-10
A turbine vane assembly includes a turbine vane having first and second shrouds with an elongated airfoil extending between. Each end of the airfoil transitions into a shroud at a respective junction. Each of the shrouds has a plurality of cooling passages, and the airfoil has a plurality of cooling passages extending between the first and second shrouds. A substantially flat inner plate and an outer plate are coupled to each of the first and second shrouds so as to form inner and outer plenums. Each inner plenum is defined between at least the junction and the substantially flat inner plate; each outer plenum is defined between at least the substantially flat inner plate and the outer plate. Each inner plenum is in fluid communication with a respective outer plenum through at least one of the cooling passages in the respective shroud.
A deployable, annular, 30m telescope, space-based observatory
NASA Astrophysics Data System (ADS)
Rey, Justin J.; Wirth, Allan; Jankevics, Andrew; Landers, Franklin; Rohweller, David; Chen, C. Bill; Bronowicki, Allen
2014-08-01
High resolution imaging from space requires very large apertures, such as NASA's current mission the James Webb Space Telescope (JWST) which uses a deployable 6.5m segmented primary. Future missions requiring even larger apertures (>>10m) will present a great challenge relative to the size, weight and power constraints of launch vehicles as well as the cost and schedule required to fabricate the full aperture. Alternatively, a highly obscured annular primary can be considered. For example, a 93.3% obscured 30m aperture having the same total mirror area (91m2) as a 10.7m unobscured telescope, can achieve ~3X higher limiting resolution performance. Substantial cost and schedule savings can be realized with this approach compared to fully filled apertures of equivalent resolution. A conceptual design for a ring-shaped 30m telescope is presented and the engineering challenges of its various subsystems analyzed. The optical design consists of a 20X annular Mersenne form beam compactor feeding a classical 1.5m TMA telescope. Ray trace analysis indicates the design can achieve near diffraction limited images over a 200μrad FOV. The primary mirror consists of 70 identical rectangular 1.34x1.0m segments with a prescription well within the demonstrated capabilities of the replicated nanolaminate on SiC substrate technology developed by AOA Xinetics. A concept is presented for the deployable structure that supports the primary mirror segments. A wavefront control architecture consisting of an optical metrology subsystem for coarse alignment and an image based fine alignment and phasing subsystem is presented. The metrology subsystem is image based, using the background starfields for distortion and pointing calibration and fiducials on the segments for measurement. The fine wavefront control employs a hill climbing algorithm operating on images from the science camera. The final key technology required is the image restoration algorithm that will compensate for the highly
Effect of the annular region on the performance of a cylindrical Hall plasma thruster
Seo, Mihui; Lee, Jongsub; Choe, Wonho; Seon, Jongho; June Lee, Hae
2013-02-15
Performance characteristics of a cylindrical Hall thruster depending on the depth of the annular region (L{sub a}) in front of the anode were investigated. The effect of the annular region was examined by operating thrusters corresponding to four different values of L{sub a} (0, 4, 6, and 10 mm) and a fixed length of the cylindrical region (25 mm). Various measurements such as electron and ion currents, thrust, anode efficiency, current and propellant utilizations, and ion energy distribution functions were performed. Such measurements lead to an interpretation that (1) a considerable potential difference may exist between the anode and the ionization region, which is presumably located near the end of the annular region where magnetic field lines converge; (2) this potential difference increases with respect to increasing L{sub a}; and (3) the presence of the annular region near the anode reduces the specific impulse and anode efficiency for the examined thrusters.
Method of improving image sharpness for annular-illumination scanning electron microscopes
NASA Astrophysics Data System (ADS)
Enyama, Momoyo; Hamada, Koichi; Fukuda, Muneyuki; Kazumi, Hideyuki
2016-06-01
Annular illumination is effective in enhancing the depth of focus for scanning electron microscopes (SEMs). However, owing to high side lobes of the point-spread function (PSF), annular illumination results in poor image sharpness. The conventional deconvolution method, which converts the PSF to a delta function, can improve image sharpness, but results in artifacts due to noise amplification. In this paper, we propose an image processing method that can reduce the deterioration of image sharpness. With this method, the PSF under annular illumination is converted to that under standard illumination. Through simulations, we verified that the image sharpness of SEM images under annular illumination with the proposed method can be improved without noise amplification.
Myers, N.J.
1994-12-31
The author gives a hybrid method for the iterative solution of linear systems of equations Ax = b, where the matrix (A) is nonsingular, sparse and nonsymmetric. As in a method developed by Starke and Varga the method begins with a number of steps of the Arnoldi method to produce some information on the location of the spectrum of A. This method then switches to an iterative method based on the Faber polynomials for an annular sector placed around these eigenvalue estimates. The Faber polynomials for an annular sector are used because, firstly an annular sector can easily be placed around any eigenvalue estimates bounded away from zero, and secondly the Faber polynomials are known analytically for an annular sector. Finally the author gives three numerical examples, two of which allow comparison with Starke and Varga`s results. The third is an example of a matrix for which many iterative methods would fall, but this method converges.
Annular reactors (ARs) were used to study biofilm community succession and provide an ecological insight during nitrification arrestment through simultaneously increasing monochloramine (NH2Cl) and chlorine to nitrogen mass ratios, resulting in four operational periods (I to IV)....
Free transverse vibration of a wrinkled annular thin film by using finite difference method
NASA Astrophysics Data System (ADS)
Wang, C. G.; Liu, Y. P.; Lan, L.; Tan, H. F.
2016-02-01
This paper investigates the free transverse vibration of a wrinkled annular thin film. The non-dimensional Hamilton motion equation of the wrinkled annular thin film is established, which is solved by using the finite difference method to acquire the vibration frequency and mode. The predicted vibration characteristics are verified by the experimental measurements based on the digital image correlation (DIC) technique. The results show that wrinkles have great effects on the vibration of the annular thin film. Especially for the heavily wrinkled cases, the local-global interactive mode dominates the vibration of the annular thin film. The frequency increases as the wrinkling level increases which is mainly due to the increased nonlinear geometric stiffness. The results provide favorable supports for understanding the role of nonlinear wrinkling on the vibration of thin films.
Large Eddy Simulation of ignition in an annular multi-injector combustor
NASA Astrophysics Data System (ADS)
Vicquelin, Ronan; Philip, Maxime; Boileau, Matthieu; Schmitt, Thomas; Bourgoin, Jean-François; Durox, Daniel; Candel, Sébastien
2013-11-01
The present work deals with validating the LES methodology for transient ignition simulations, and in particular elucidating the mechanisms that control the light round sequence in a laboratory annular combustor, representative of many practical industrial systems. The simulation benefits from the unique experimental database built at EM2C on a fully transparent annular chamber equipped with 16 premixed swirled injectors. The F-TACLES combustion model is used for its ability to properly represent the flame propagation.
The numerical solution of flow field of short-annular combustion chamber
NASA Astrophysics Data System (ADS)
Xu, H.; Ning, H.
1986-05-01
The recirculating flow field of a short-annular combustion chamber has been studied. The body-fitting coordinate system and the 'simple' method combined with a constant viscosity model have been employed to solve the Navier-Stokes equations in a regime containing a complicated curved boundary. The result could provide the theoretical reference for the design and improvement of short-annular combustion chambers.
Kim, Gwan Sic; Beom, Min Sun; Kim, Sung Ryong; Kim, Na Rae; Jang, Ji Wook; Jang, Mi Hee; Ryu, Sang Wan
2016-01-01
The concomitant presence of posterior mitral annular calcification and infectious mitral valve lesions poses a technical challenge with considerable perioperative risk when using previously proposed techniques for mitral valve surgery. Herein, we report a case of the use of a modified surgical technique to successfully treat a patient with mitral infective endocarditis complicated by a subendocardial abscess and extensive posterior mitral annular calcification. PMID:26889447
An X-band high-impedance relativistic klystron amplifier with an annular explosive cathode
NASA Astrophysics Data System (ADS)
Zhu, Danni; Zhang, Jun; Zhong, Huihuang; Qi, Zumin
2015-11-01
The feasibility of employing an annular beam instead of a solid one in the X-band high-impedance relativistic klystron amplifier (RKA) is investigated in theory and simulation. Small-signal theory analysis indicates that the optimum bunching distance, fundamental current modulation depth, beam-coupling coefficient, and beam-loaded quality factor of annular beams are all larger than the corresponding parameters of solid beams at the same beam voltage and current. An annular beam RKA and a solid beam RKA with almost the same geometric parameters are compared in particle-in-cell simulation. Output microwave power of 100 MW, gain of 50 dB, and power conversion efficiency of 42% are obtained in an annular beam RKA. The annular beam needs a 15% lower uniform guiding magnetic field than the solid beam. Our investigations demonstrate that we are able to use a simple annular explosive cathode immersed in a lower uniform magnetic field instead of a solid thermionic cathode in a complicated partially shielding magnetic field for designing high-impedance RKA, which avoids high temperature requirement, complicated electron-optical system, large area convergence, high current density, and emission uniformity for the solid beam. An equivalent method for the annular beam and the solid beam on bunching features is proposed and agrees with the simulation. The annular beam has the primary advantages over the solid beam that it can employ the immersing uniform magnetic field avoiding the complicated shielding magnetic field system and needs a lower optimum guiding field due to the smaller space charge effect.
An X-band high-impedance relativistic klystron amplifier with an annular explosive cathode
Zhu, Danni; Zhang, Jun Zhong, Huihuang; Qi, Zumin
2015-11-15
The feasibility of employing an annular beam instead of a solid one in the X-band high-impedance relativistic klystron amplifier (RKA) is investigated in theory and simulation. Small-signal theory analysis indicates that the optimum bunching distance, fundamental current modulation depth, beam-coupling coefficient, and beam-loaded quality factor of annular beams are all larger than the corresponding parameters of solid beams at the same beam voltage and current. An annular beam RKA and a solid beam RKA with almost the same geometric parameters are compared in particle-in-cell simulation. Output microwave power of 100 MW, gain of 50 dB, and power conversion efficiency of 42% are obtained in an annular beam RKA. The annular beam needs a 15% lower uniform guiding magnetic field than the solid beam. Our investigations demonstrate that we are able to use a simple annular explosive cathode immersed in a lower uniform magnetic field instead of a solid thermionic cathode in a complicated partially shielding magnetic field for designing high-impedance RKA, which avoids high temperature requirement, complicated electron-optical system, large area convergence, high current density, and emission uniformity for the solid beam. An equivalent method for the annular beam and the solid beam on bunching features is proposed and agrees with the simulation. The annular beam has the primary advantages over the solid beam that it can employ the immersing uniform magnetic field avoiding the complicated shielding magnetic field system and needs a lower optimum guiding field due to the smaller space charge effect.
Polarization state modifications in the propagation of high azimuthal order annular beams.
Lapucci, A; Ciofini, M
2001-12-01
Using a vector Fresnel diffraction propagator we investigate the far-field distributions obtained from guided annular modes with different polarization states. Furthermore we demonstrate that a pure azimuthal polarization transforms into a mainly radial one in the propagation of annular beams with azimuthal mode number higher than 0. This property could enhance the performance of a laser metal-cutting system based on these kind of beams. PMID:19424296
NASA Astrophysics Data System (ADS)
Al-Kayiem, A. H. H.; Ibrahim, M. A.
2015-12-01
The flow behaviour and the pressure drop throughout an annular flow test section was investigated in order to evaluate and justify the reliability of experimental flow loop for wax deposition studies. The specific objective of the present paper is to assess and highlight the influence of the equivalent diameter method on the analysis of the hydrodynamic behaviour of the flow and the pressure drop throughout the annular test section. The test section has annular shape of 3 m length with three flow passages, namely; outer thermal control jacket, oil annular flow and inner pipe flow of a coolant. The oil annular flow has internal and external diameters of 0.0422 m and 0.0801 m, respectively. Oil was re-circulated in the annular passage while a cold water-glycol mixture was re-circulated in the inner pipe counter currently to the oil flow. The experiments were carried out at oil Reynolds number range of 2000 to 17000, covering laminar, transition and turbulent flow regimes. Four different methods of equivalent diameter of the annulus have been considered in this hydraulic analysis. The correction factor model for frictional pressure drop was also considered in the investigations. All methods addressed the high deviation of the prediction from the experimental data, which justified the need of a suitable pressure prediction correlation for the annular test section. The conventional hydraulic diameter method is a convenient substitute for characterizing physical dimension of a non-circular duct, and it leads to fairly good correlation between turbulent fluid flow and heat transfer characteristic of annular ducts.
Earthquakes and plate tectonics.
Spall, H.
1982-01-01
Earthquakes occur at the following three kinds of plate boundary: ocean ridges where the plates are pulled apart, margins where the plates scrape past one another, and margins where one plate is thrust under the other. Thus, we can predict the general regions on the earth's surface where we can expect large earthquakes in the future. We know that each year about 140 earthquakes of magnitude 6 or greater will occur within this area which is 10% of the earth's surface. But on a worldwide basis we cannot say with much accuracy when these events will occur. The reason is that the processes in plate tectonics have been going on for millions of years. Averaged over this interval, plate motions amount to several mm per year. But at any instant in geologic time, for example the year 1982, we do not know, exactly where we are in the worldwide cycle of strain build-up and strain release. Only by monitoring the stress and strain in small areas, for instance, the San Andreas fault, in great detail can we hope to predict when renewed activity in that part of the plate tectonics arena is likely to take place. -from Author
Lohse's historic plate archive
NASA Astrophysics Data System (ADS)
Tsvetkov, M.; Tsvetkova, K.; Richter, G.; Scholz, G.; Böhm, P.
The description and the analysis of Oswald Lohse's astrophotographic plates, collected at the Astrophysical Observatory Potsdam in the period 1879 - 1889, are presented. 67 plates of the archive, taken with the greatest instrument of the observatory at that time - the refractor (D = 0.30 m, F = 5.40 m, scale = 38''/mm) and with the second heliographic objective (D = 0.13 m, F = 1.36 m, scale = 152''/mm) - - survived two world wars in relative good condition. The plate emulsions are from different manufacturers in the beginning of astrophotography (Gädicke, Schleussner, Beernaert, etc.). The sizes of the plates are usually 9x12 cm2, which corresponds to fields of 1.2deg and 5deg respectively for each instrument mentioned above. The average limiting magnitude is 13.0(pg). Besides of the plates received for technical experiments (work on photographic processes, testing of new instruments and methods of observations), the scientific observations follow programs for studies of planet surfaces, bright stars, some double stars, stellar clusters and nebulous objects. Lohse's archive is included into the Wide Field Plate Database (http://www.skyarchive.org) as the oldest systematic one, covering the fields of Orion (M42/43), Pleiades, h & chi Persei, M37, M3, M11, M13, M92, M31, etc. With the PDS 2020 GM+ microdensitometer of Münster University 10 archive plates were digitized.
NASA Technical Reports Server (NTRS)
Bain, D. B.; Smith, C. E.; Holdeman, J. D.
1995-01-01
Three dimensional turbulent reacting CFD analyses were performed on transverse jets injected into annular and cylindrical (can) confined crossflows. The goal was to identify and assess mixing differences between annular and can geometries. The approach taken was to optimize both annular and can configurations by systematically varying orifice spacing until lowest emissions were achieved, and then compare the results. Numerical test conditions consisted of a jet-to-mainstream mass-flow ratio of 3.2 and a jet-to-mainstream momentum-flux ratio (J) of 30. The computational results showed that the optimized geometries had similar emission levels at the exit of the mixing section although the annular configuration did mix-out faster. For lowest emissions, the density correlation parameter (C = (S/H) square root of J) was 2.35 for the annular geometry and 3.5 for the can geometry. For the annular geometry, the constant was about twice the value seen for jet mixing at low mass-flow ratios (i.e., MR less than 0.5). For the can geometry, the constant was about 1 1/2 times the value seen for low mass-flow ratios.
NASA Astrophysics Data System (ADS)
Jiang, Wei; Wang, Langping; Wang, Xiaofeng
2016-08-01
In order to irradiate circular components with high current pulsed electron beam (HCPEB), an annular cathode based on carbon fiber bunches was designed and fabricated. Using an acceleration voltage of 25 kV, the maximum pulsed irradiation current and energy of this annular cathode can reach 7.9 kA and 300 J, respectively. The irradiation current density distribution of the annular cathode HCPEB source measured along the circumferential direction shows that the annular cathode has good emission uniformity. In addition, four 9310 steel substrates fixed uniformly along the circumferential direction of a metal ring substrate were irradiated by this annular cathode HCPEB source. The surface and cross-section morphologies of the irradiated samples were characterized by scanning electron microscopy (SEM). SEM images of the surface reveal that crater and surface undulation have been formed, which hints that the irradiation energy of the HCPEB process is large enough for surface modification of 9310 steel. Meanwhile, SEM cross-section images exhibit that remelted layers with a thickness of about 5.4 μm have been obtained in all samples, which proves that a good practical irradiation uniformity can be achieved by this annular cathode HCPEB source.
Depth-targeted transvascular drug delivery by using annular-shaped photomechanical waves
NASA Astrophysics Data System (ADS)
Akiyama, Takuya; Sato, Shunichi; Ashida, Hiroshi; Terakawa, Mitsuhiro
2011-02-01
Laser-based drug delivery is attractive for the targeting capability due to high spatial controllability of laser energy. Recently, we found that photomechanical waves (PMWs) can transiently increase the permeability of blood vessels in skin, muscle and brain of rats. In this study, we examined the use of annular-shaped PMWs to increase pressure at target depths due to superposition effect of pressure waves. This can increase the permeability of blood vessels located in the specific depth regions, enabling depth-targeted transvascular drug delivery. Annular PMWs were produced by irradiating a laser-absorbing material with annular-shaped pulsed laser beams that were produced by using an axicon lens. We first examined propagation and pressure characteristics of annular PMWs in tissue phantoms and confirmed an increased pressure at a target depth, which can be controlled by changing laser parameters. We injected Evans blue (EB) into a rat tail vein, and annular PMWs (inner diameter, 3 mm; outer diameter, 5 mm) were applied from the myofascial surface of the anterior tibialis muscle. After perfusion fixation, we observed fluorescence originating from EB in the tissue. We observed intense fluorescence at a target depth region of around 5 mm. These results demonstrate the capability of annular PMWs for depth-targeted transvascular drug delivery.
Molecular mechanisms regulating formation, trafficking and processing of annular gap junctions.
Falk, Matthias M; Bell, Cheryl L; Kells Andrews, Rachael M; Murray, Sandra A
2016-01-01
Internalization of gap junction plaques results in the formation of annular gap junction vesicles. The factors that regulate the coordinated internalization of the gap junction plaques to form annular gap junction vesicles, and the subsequent events involved in annular gap junction processing have only relatively recently been investigated in detail. However it is becoming clear that while annular gap junction vesicles have been demonstrated to be degraded by autophagosomal and endo-lysosomal pathways, they undergo a number of additional processing events. Here, we characterize the morphology of the annular gap junction vesicle and review the current knowledge of the processes involved in their formation, fission, fusion, and degradation. In addition, we address the possibility for connexin protein recycling back to the plasma membrane to contribute to gap junction formation and intercellular communication. Information on gap junction plaque removal from the plasma membrane and the subsequent processing of annular gap junction vesicles is critical to our understanding of cell-cell communication as it relates to events regulating development, cell homeostasis, unstable proliferation of cancer cells, wound healing, changes in the ischemic heart, and many other physiological and pathological cellular phenomena. PMID:27230503
An optical system design that converts a Gaussian to a flattop annular beam
NASA Astrophysics Data System (ADS)
Li, Chaochen; Wu, Tengfei; Wang, Yu
2015-10-01
Flattop annular beam has been predicted with good character over an increasing application, but the generating of flattop annular beam is rarely mentioned by academic article. In our paper, an optical refractive system, which is designed to achieve flattop annular beam, are proposed. The cone prism is commonly used to get an annular beam, however, the beam intensity distribution is non-uniform. In our design, an additional aspheric lens is placed in front of the cone prism along the optical axis. The lens parameters are theoretically analyzed and well optimized to homogenize the optical field. Furthermore, to lower the requirement of machining accuracy, a pair of aspheric lenses is also designed, which can be used independently to generate flattop annular beam. It combines the function of cone prism and aspheric lens, so as to replace them both. The performance of the implementations has been demonstrated in detail. Simulation result shows that the proposed design is effective and feasible. It is hope that our work would be helpful in related fields. Flattop annular beam, Aspheric lens, Cone prism
Modeling and analysis of thermoacoustic instabilities in an annular combustor
NASA Astrophysics Data System (ADS)
Murthy, Sandeep; Sayadi, Taraneh; Le Chenadec, Vincent; Schmid, Peter
2015-11-01
A simplified model is introduced to study thermo-acoustic instabilities in axisymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber's geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al., 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.
Criticality Benchmark Analysis of the HTTR Annular Startup Core Configurations
John D. Bess
2009-11-01
One of the high priority benchmarking activities for corroborating the Next Generation Nuclear Plant (NGNP) Project and Very High Temperature Reactor (VHTR) Program is evaluation of Japan's existing High Temperature Engineering Test Reactor (HTTR). The HTTR is a 30 MWt engineering test reactor utilizing graphite moderation, helium coolant, and prismatic TRISO fuel. A large amount of critical reactor physics data is available for validation efforts of High Temperature Gas-cooled Reactors (HTGRs). Previous international reactor physics benchmarking activities provided a collation of mixed results that inaccurately predicted actual experimental performance.1 Reevaluations were performed by the Japanese to reduce the discrepancy between actual and computationally-determined critical configurations.2-3 Current efforts at the Idaho National Laboratory (INL) involve development of reactor physics benchmark models in conjunction with the International Reactor Physics Experiment Evaluation Project (IRPhEP) for use with verification and validation methods in the VHTR Program. Annular cores demonstrate inherent safety characteristics that are of interest in developing future HTGRs.
Experimental investigation of the low NOx vortex airblast annular combustor
NASA Technical Reports Server (NTRS)
Johnson, S. M.; Biaglow, J. A.; Smith, J. M.
1984-01-01
A low oxides of nitrogen vortex airblast annular combustor was evaluated which has attained the goal of 1 gm NO2/kg fuel or less during operation. The experimental combustor test conditions were a nominal inlet-air temperature of 703 K, inlet total pressures between 0.52 to 0.83 MPa, and a constant inlet Mach number of 0.26. Exit temperature pattern factors for all test points were between 0.16 and 0.20 and exit swirl flow angles were 47 degrees at isothermal conditions and 23 degrees during combustion. Oxides of nitrogen did not exceed 1.05 gm NO2/kg fuel at the highest inlet pressure and exhaust temperature tested. Previous correlations have related NOx proportionally to the combustor inlet pressure raised to some exponent. In this experiment, a band of exponents between 0.5 and 1.0 resulted for fuel-air ratios from 0.023 to 0.027 and inlet pressures from 0.52 to 0.83 MPa. Previously announced in STAR as N84-22567
Operational verification of a 40-MHz annular array transducer
Ketterling, Jeffrey A.; Ramachandran, Sarayu; Aristizäbal, Orlando
2006-01-01
An experimental system to take advantage of the imaging capabilities of a 5-ring polyvinylidene fluoride (PVDF) based annular array is presented. The array has a 6 mm total aperture and a 12 mm geometric focus. The experimental system is designed to pulse a single element of the array and then digitize the received data of all array channels simultaneously. All transmit/receive pairs are digitized and then the data are post-processed with a synthetic focusing technique to achieve an enhanced depth of field (DOF). The performance of the array is experimentally tested with a wire phantom consisting of 25-μm diameter wires diagonally spaced at 1 mm by 1 mm intervals. The phantom permitted the efficacy of the synthetic focusing algorithm to be tested and was also used for two-way beam characterization. Experimental results are compared to a spatial impulse response method beam simulation. After synthetic focusing, the two-way echo amplitude was enhanced over the range of 8 to 19 mm and the 6-dB DOF spanned from 9 to 15 mm. For a wire at a fixed axial depth, the relative time delays between transmit/receive ring pairs agreed with theoretical predictions to within ± 2 ns. To further test the system, B-mode images of an excised bovine eye are rendered. PMID:16555771
Acoustic modal analysis of a full-scale annular combustor
NASA Technical Reports Server (NTRS)
Karchmer, A. M.
1982-01-01
An acoustic modal decomposition of the measured pressure field in a full scale annular combustor installed in a ducted test rig is described. The modal analysis, utilizing a least squares optimization routine, is facilitated by the assumption of randomly occurring pressure disturbances which generate equal amplitude clockwise and counter-clockwise pressure waves, and the assumption of statistical independence between modes. These assumptions are fully justified by the measured cross spectral phases between the various measurement points. The resultant modal decomposition indicates that higher order modes compose the dominant portion of the combustor pressure spectrum in the range of frequencies of interest in core noise studies. A second major finding is that, over the frequency range of interest, each individual mode which is present exists in virtual isolation over significant portions of the spectrum. Finally, a comparison between the present results and a limited amount of data obtained in an operating turbofan engine with the same combustor is made. The comparison is sufficiently favorable to warrant the conclusion that the structure of the combustor pressure field is preserved between the component facility and the engine.
Pollution technology program, can-annular combustor engines
NASA Technical Reports Server (NTRS)
Roberts, R.; Fiorentino, A. J.; Greene, W.
1976-01-01
A Pollution Reduction Technology Program to develop and demonstrate the combustor technology necessary to reduce exhaust emissions for aircraft engines using can-annular combustors is described. The program consisted of design, fabrication, experimental rig testing and assessment of results and was conducted in three program elements. The combustor configurations of each program element represented increasing potential for meeting the 1979 Environmental Protection Agency (EPA) emission standards, while also representing increasing complexity and difficulty of development and adaptation to an operational engine. Experimental test rig results indicate that significant reductions were made to the emission levels of the baseline JT8D-17 combustor by concepts in all three program elements. One of the Element I single-stage combustors reduced carbon monoxide to a level near, and total unburned hydrocarbons (THC) and smoke to levels below the 1979 EPA standards with little or no improvement in oxides of nitrogen. The Element II two-stage advanced Vorbix (vortex burning and mixing) concept met the standard for THC and achieved significant reductions in CO and NOx relative to the baseline. Although the Element III prevaporized-premixed concept reduced high power NOx below the Element II results, there was no improvement to the integrated EPA parameter relative to the Vorbix combustor.
Flow Pressure Loss through Straight Annular Corrugated Pipes
NASA Technical Reports Server (NTRS)
Sargent, Joseph R.; Kirk, Daniel R.; Marsell, Brandon; Roth, Jacob; Schallhorn, Paul A.; Pitchford, Brian; Weber, Chris; Bulk, Timothy
2016-01-01
Pressure loss through annular corrugated pipes, using fully developed gaseous nitrogen representing purge pipes in spacecraft fairings, was studied to gain insight into a friction factor coefficient for these pipes. Twelve pipes were tested: four Annuflex, four Masterflex and two Titeflex with ¼”, 3/8”, ½” and ¾” inner diameters. Experimental set-up was validated using smooth-pipe and showed good agreement to the Moody diagram. Nitrogen flow rates between 0-200 standard cubic feet per hour were used, producing approximate Reynolds numbers from 300-23,000. Corrugation depth varied from 0.248 = E/D = 0.349 and relative corrugation pitch of 0.192 = P/D = 0.483. Differential pressure per unit length was measured and calculated using 8-9 equidistant pressure taps. A detailed experimental uncertainty analysis, including correlated bias error terms, is presented. Results show larger differential pressure losses than smooth-pipes with similar inner diameters resulting in larger friction factor coefficients.
NB-UVB phototherapy for generalized granuloma annulare.
Pavlovsky, Mor; Samuelov, Liat; Sprecher, Eli; Matz, Hagit
2016-05-01
Granuloma annulare (GA) is a benign, usually self-limited, granulomatous skin disease of unknown etiology. The generalized form of the disease shows a more chronic, relapsing course, rare spontaneous resolution, and poorer response to therapy. Psoralen plus UVA phototherapy has been reported to be effective for GA. However, little is known regarding the efficacy of narrowband UVB phototherapy. Our goal was to determine the efficacy of NB-UVB phototherapy in generalized GA. We carried out a retrospective study of patients with generalized GA treated with NB-UVB phototherapy over a period of 3 years. On completion of treatment, outcome was assessed as complete response (complete clearance of the lesions), partial response (>50% clearance of the lesions), and poor response (<50% clinical response). Therapy was stopped if no improvement was seen after 20 treatments. Thirteen patients were included in the study. 54% of patients treated with NB-UVB had a complete/partial response by the end of the treatment period. NB-UVB phototherapy was well-tolerated, with no serious adverse effects. NB-UVB phototherapy is effective in a substantial portion of patients with generalized GA. To determine the true efficacy of this therapeutic modality, a prospective study comparing it to PUVA is warranted. PMID:26626163
On the motion of an annular viscous jet
NASA Astrophysics Data System (ADS)
Smolka, Linda; North, Justin; Guerra, Bree
2006-11-01
We experimentally examine the motion of an annular jet of viscous fluid flowing down the outside of a thin, vertical fiber. As other authors have observed, perturbations develop along the free surface of the jet; our focus is on the instability that leads to the formation of these perturbations. We observe a striking transition in the perturbation dynamics at a critical flow rate, Qc. Above Qc, the distance from the orifice that perturbations form oscillates in time, and the spacing between perturbations varies, typically leading to the coalescence of neighboring perturbations. For fixed Q below Qc, the distance from the orifice that perturbations form is constant, and the spacing between consecutive perturbations remains fixed as they travel down the length of the fiber (2 meters). We find the growth of the perturbations is initially rapid followed by a slower phase as they saturate in size. We compare the nascent perturbation growth to theoretical predictions developed from a long-wave model (Craster & Matar, J. Fluid Mech. 553, 85-105 (2006)).
MCNP/MCNPX model of the annular core research reactor.
DePriest, Kendall Russell; Cooper, Philip J.; Parma, Edward J., Jr.
2006-10-01
Many experimenters at the Annular Core Research Reactor (ACRR) have a need to predict the neutron/gamma environment prior to testing. In some cases, the neutron/gamma environment is needed to understand the test results after the completion of an experiment. In an effort to satisfy the needs of experimenters, a model of the ACRR was developed for use with the Monte Carlo N-Particle transport codes MCNP [Br03] and MCNPX [Wa02]. The model contains adjustable safety, transient, and control rods, several of the available spectrum-modifying cavity inserts, and placeholders for experiment packages. The ACRR model was constructed such that experiment package models can be easily placed in the reactor after being developed as stand-alone units. An addition to the 'standard' model allows the FREC-II cavity to be included in the calculations. This report presents the MCNP/MCNPX model of the ACRR. Comparisons are made between the model and the reactor for various configurations. Reactivity worth curves for the various reactor configurations are presented. Examples of reactivity worth calculations for a few experiment packages are presented along with the measured reactivity worth from the reactor test of the experiment packages. Finally, calculated neutron/gamma spectra are presented.
Development of an annular arc accelerator shock tube driver
NASA Technical Reports Server (NTRS)
Leibowitz, L. P.
1973-01-01
An annular arc accelerator (ANAA) shock tube driver has been developed that deposits the energy of an arc discharge into a flowing gas, which then expands and cools without any delay for the opening of a diaphragm. A simplified one-dimensional flow analysis of the ANAA shock tube has been performed, which indicates that shock velocities greater than 40 km/sec may be obtained using a 300-kJ capacitor bank. The ANAA driver consists of a high-pressure driver, an expansion section, and an electrode section. In operation, the cold gas driver is pressurized until the diaphragm bursts, sending a pressure front down the expansion tube to the arc section. When the accelerated flow arrives at the electrode section, a 100-capacitor, 300-kJ capacitor bank is discharged either by breaking an insulating diaphragm between the electrodes or by the triggering of a series of external switches. Shock velocities of 28 km/sec have been obtained, and modifications are described that are expected to improve performance.
Acoustic modal analysis of a full-scale annular combustor
NASA Technical Reports Server (NTRS)
Karchmer, A. M.
1983-01-01
An acoustic modal decomposition of the measured pressure field in a full scale annular combustor installed in a ducted test rig is described. The modal analysis, utilizing a least squares optimization routine, is facilitated by the assumption of randomly occurring pressure disturbances which generate equal amplitude clockwise and counter-clockwise pressure waves, and the assumption of statistical independence between modes. These assumptions are fully justified by the measured cross spectral phases between the various measurement points. The resultant modal decomposition indicates that higher order modes compose the dominant portion of the combustor pressure spectrum in the range of frequencies of interest in core noise studies. A second major finding is that, over the frequency range of interest, each individual mode which is present exists in virtual isolation over significant portions of the spectrum. Finally, a comparison between the present results and a limited amount of data obtained in an operating turbofan engine with the same combustor is made. The comparison is sufficiently favorable to warrant the conclusion that the structure of the combustor pressure field is preserved between the component facility and the engine. Previously announced in STAR as N83-21896
Adaptive control system for large annular momentum control device
NASA Technical Reports Server (NTRS)
Montgomery, R. C.; Johnson, C. R., Jr.
1981-01-01
A dual momentum vector control concept, consisting of two counterrotating rings (each designated as an annular momentum control device), was studied for pointing and slewing control of large spacecraft. In a disturbance free space environment, the concept provides for three axis pointing and slewing capabilities while requiring no expendables. The approach utilizes two large diameter counterrotating rings or wheels suspended magnetically in many race supports distributed around the antenna structure. When the magnets are energized, attracting the two wheels, the resulting gyroscopic torque produces a rate along the appropriate axis. Roll control is provided by alternating the radiative rotational velocity of the two wheels. Wheels with diameters of 500 to 800 m and with sufficient momentum storage capability require rims only a few centimeters thick. The wheels are extremely flexible; therefore, it is necessary to account for the distributed nature of the rings in the design of the bearing controllers. Also, ring behavior is unpredictably sensitive to ring temperature, spin rate, manufacturing imperfections, and other variables. An adaptive control system designed to handle these problems is described.
Characterization of Novel Calorimeters in the Annular Core Research Reactor
NASA Astrophysics Data System (ADS)
Hehr, Brian D.; Parma, Edward J.; Peters, Curtis D.; Naranjo, Gerald E.; Luker, S. Michael
2016-02-01
A series of pulsed irradiation experiments have been performed in the central cavity of Sandia National Laboratories' Annular Core Research Reactor (ACRR) to characterize the responses of a set of elemental calorimeter materials including Si, Zr, Sn, Ta, W, and Bi. Of particular interest was the perturbing effect of the calorimeter itself on the ambient radiation field - a potential concern in dosimetry applications. By placing the calorimeter package into a neutron-thermalizing lead/polyethylene (LP) bucket and irradiating both with and without a cadmium wrapper, it was demonstrated that prompt capture gammas generated inside the calorimeters can be a significant contributor to the measured dose in the active disc region. An MCNP model of the experimental setup was shown to replicate measured dose responses to within 10%. The internal (n,γ) contribution was found to constitute as much as 50% of the response inside the LP bucket and up to 20% inside the nominal (unmodified) cavity environment, with Ta and W exhibiting the largest enhancement due to their sizable (n,γ) cross sections. Capture reactions in non-disc components of the calorimeter were estimated to be responsible for up to a few percent of the measured response. This work was supported by the United States Department of Energy under Contract DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy.
Current Density Measurements of an Annular-Geometry Ion Engine
NASA Technical Reports Server (NTRS)
Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.
2012-01-01
The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential nonuniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to 10% of the average current density in the discharge and 5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.
Current Density Measurements of an Annular-Geometry Ion Engine
NASA Technical Reports Server (NTRS)
Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.
2012-01-01
The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential non-uniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to +/-10% of the average current density in the discharge and +/-5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 - 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.
Predicting Activation of Experiments Inside the Annular Core Research Reactor
Greenberg, Joseph Isaac
2015-11-01
The objective of this thesis is to create a program to quickly estimate the radioactivity and decay of experiments conducted inside of the Annular Core Research Reactor at Sandia National Laboratories and eliminate the need for users to write code. This is achieved by model the neutron fluxes in the reactor’s central cavity where experiments are conducted for 4 different neutron spectra using MCNP. The desired neutron spectrum, experiment material composition, and reactor power level are then input into CINDER2008 burnup code to obtain activation and decay information for every isotope generated. DREAD creates all of the files required for CINDER2008 through user selected inputs in a graphical user interface and executes the program for the user and displays the resulting estimation for dose rate at various distances. The DREAD program was validated by weighing and measuring various experiments in the different spectra and then collecting dose rate information after they were irradiated and comparing it to the dose rates that DREAD predicted. The program provides results with an average of 17% higher estimates than the actual values and takes seconds to execute.
DEP thermal convection in annular geometry under microgravity conditions
NASA Astrophysics Data System (ADS)
Yoshikawa, Harunori; Crumeyrolle, Olivier; Mutabazi, Innocent
2012-11-01
Thermal convection driven by the dielectrophoretic force is investigated in annular geometry in microgravity environments. A radial heating and a radial alternating electric field are imposed on a dielectric fluid layer filling the gap of two concentric infinite-length cylinders. The resulting dielectric force field is regarded as spatially varying radial gravity that can develop thermal convection. The linear stability problem of a purely conductive basic state is solved by a spectral-collocation method for both axisymmetric and non-axisymmetric disturbances. A stationary non-axisymmetric mode becomes first unstable at a critical Rayleigh number to develop convection. The stability boundary shows asymmetry with respect to heating direction. For an outward heating the critical value approaches that of the Rayleigh-Bénard problem (1708) as the gap size decreases, while it converges to larger values in the narrow gap limit. For an inward heating the instability occurs only when the gap is narrower than a certain value. The critical number diverges with increasing the gap size. Instability mechanism is examined from energetic viewpoints. The feedback of electric field to temperature disturbances is found to stabilize the conductive state for narrow gaps. This work has been partly supported by the CNES, the CNRS and the FEDER.
Visual Measurements of Droplet Size in Gas Liquid Annular Flow
Fore, L.B.; Ibrahim, B.B.; Beus, S.G.
2000-07-01
Drop size distributions have been measured for nitrogen-water annular flow in a 9.67 mm hydraulic diameter duct, at system pressures of 3.4 and 17 atm and a temperature of 38 C. These new data extend the range of conditions represented by existing data in the open literature, primarily through an increase in system pressure. Since most existing correlations were developed from data obtained at lower pressures, it should be expected that the higher-pressure data presented in this paper would not necessarily follow those correlations. The correlation of Tatterson, et al. (1977) does not predict the new data very well, while the correlation of Kataoka, et al. (1983) only predicts those data taken at the lower pressure of 3.4 atm. However, the maximum drop size correlation of Kocamustafaogullari, et al. (1994) does predict the current data to a reasonable approximation. Similarly, their correlation for the Sauter mean diameter can predict the new data, provided the coefficient in the equation is adjusted.
Studies of falling annular films, Parts I and II
Roidt, R.M.; Evans, R.A.
1989-01-01
New environmental requirements and restrictions necessitate exploration of new methods for controlling and containing various chemicals and chemical reactions. A novel method of exercising such control is based upon the cylindrical film reactor, a device originally studied as a confinement for a fusion reactor. The films used in these confinement models were quite thick relative to the radius of the cylindrical film so that the experimental work was generally not relevant to the design of chemical reactors where, for purposes of efficiency, the minimum confinement flowrate is desired. An annular, cylindrical, falling film converges into a single stream due to surface tension forces; this convergence length determines the volume of the reactor. Entrainment of gases from within the film volume to the exit stream allows a constant feed of gas into the reactor volume so that gas phase reactions may be carried out without contact with surrounding atmosphere. The present work is an experimental investigation of the pertinent parameters and stability criteria for thin, falling, cylindrical films. We find that, while only for relatively restricted ratios of gas to liquid flow rates do stable reaction volumes exist, most of this range lies within flow rate limits which may be of use in gas-liquid chemical reactors. 12 refs., 33 figs.
Eruptive xanthoma: a microscopic simulant of granuloma annulare.
Cooper, P H
1986-06-01
The microscopic appearance of eruptive xanthoma (EX) presents the potential for misinterpretation as granuloma annulare (GA). Both exhibit one or multiple lesions in the superficial reticular dermis. Both have a perivascular and interstitial inflammatory cell infiltrate. Extracellular lipid in EX separates and disrupts the reticular dermis, simulating necrobiosis. There are several useful differential diagnostic features. The perivascular infiltrate is histiocytic in EX and lymphoid in GA. The histiocytes of EX have translucent, finely stippled cytoplasm, whereas those of GA have denser eosinophilic cytoplasm. EX lacks a distinctly granulomatous appearance, whereas epithelioid and multinuclear cells are typical of GA. The semilucent extracellular deposits of lipid in EX are associated with only minimal fragmentation of collagen and no evidence of cellular necrosis. Necrobiotic material stains more deeply eosinophilic or basophilic; degradation of collagen is discernable, and there is often evidence of cell death. Both EX and GA exhibit deposits of hyaluronic acid. They tend to be concentrated at the borders of lesions in EX and in the centers of lesions in GA. Elastolysis was not appreciated in EX. It was present in some cases of GA. PMID:3734221
NASA Astrophysics Data System (ADS)
Yankovskii, A. P.
2014-07-01
Deformation of annular plates with different structures of helical reinforcement is studied. It is demonstrated that the use of the classical theory for calculating steady-state creep for thick reinforced plates subjected to bending leads to underprediction of the compliance of thin-walled metal-composite structures. It is also shown that there are significant shear strain rates in the binder of such plates, which has to be taken into account and which is mainly responsible for creep strain accumulation. Results calculated by two different models, which take into account the composite structure, are compared.
ERIC Educational Resources Information Center
Landalf, Helen
1998-01-01
Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)
Parikh, M.
1981-01-01
The construction of an Indian Rs. 186 (US $20.33) flat-plate solar oven is described. Detailed drawings are provided and relevant information on cooking times and temperature for different foods is given.
Plate tectonics: Metamorphic myth
NASA Astrophysics Data System (ADS)
Korenaga, Jun
2016-01-01
Clear evidence for subduction-induced metamorphism, and thus the operation of plate tectonics on the ancient Earth has been lacking. Theoretical calculations indicate that we may have been looking for something that cannot exist.
Gough, Colin
2015-01-01
As the first step toward developing a generic model for the acoustically radiating vibrational modes of the violin and related instruments, the modes of both freely supported and edge-constrained top and back plates have been investigated as functions of shape, arching height, elastic anisotropy, the f-holes and associated island area, thickness graduations, and the additional boundary constraints of the ribs, soundpost, and bass-bar present in the assembled instrument. Comsol shell structure finite element software has been used as a quasi-experimental tool, with physical and geometric properties varied smoothly, often over several orders of magnitude, allowing the development of the plate modes to be followed continuously from those of an initially square plate to those of doubly-arched, guitar-shaped, orthotropic plates and their dependence on all the above factors. PMID:25618046
Improvement of Vacuum Pressure in the Annular-Ring Coupled Structures for the J-PARC Linac
NASA Astrophysics Data System (ADS)
Ao, Hiroyuki; Nemoto, Yasuo; Oozone, Akira; Tamura, Jun
The accelerating cavities of the J-PARC linac, additionally comprising an annular-ring-coupled structure (ACS), went into operation in 2014. To further improve the vacuum pressure of the ACS, an additional nonevaporable getter (NEG) pump was designed so that it could be installed independent of the vacuum chamber of the ACS cavity. We confirmed that the NEG pump can be appropriately activated by using a small pumping station and that purging with noble gases reduces the saturation of the NEG surface. In the evacuation test of the prototype ACS cavity with the NEG pump, the partial pressure of H2 and the total pressure were reduced from 4.8 × 10-7 and 6.8 × 10-7 Pa to 2.5 × 10-7 and 4.5 × 10-7 Pa, respectively. The additional NEG pump will be installed in the ACS cavity in the fall of 2014, after which any decrease in pressure and NEG-pump lifetime will be confirmed by long-term-operation experiments.
Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere
NASA Astrophysics Data System (ADS)
Kim, Junsu; Reichler, Thomas
2015-10-01
The proper simulation of the annular mode time scale may be regarded as an important benchmark for climate models. Previous research demonstrated that this time scale is systematically overestimated by climate models. As suggested by the fluctuation-dissipation theorem, this may imply that climate models are overly sensitive to external forcings. Previous research also made it clear that calculating the AM time scale is a slowly converging process, necessitating relatively long time series and casting doubts on the usefulness of the historical reanalysis record to constrain climate models in terms of the annular mode time scale. Here, we use long control simulations with the coupled and uncoupled version of the GFDL climate model, CM2.1 and AM2.1, respectively, to study the effects of internal atmospheric variability and forcing from the lower boundary on the stability of the annular mode time scale. In particular, we ask whether a model's annular mode time scale and dynamical sensitivity can be constrained from the 50-year-long reanalysis record. We find that internal variability attaches large uncertainty to the annular mode time scale when diagnosed from decadal records. Even under the fixed forcing conditions of our long control run at least 100 years of data are required in order to keep the uncertainty in the annular mode time scale of the Northern Hemisphere to 10 %; over the Southern Hemisphere, the required length increases to 200 years. If nature's annular mode time scale over the Northern Hemisphere is similarly variable, there is no guarantee that the historical reanalysis record is a fully representative target for model evaluation. Over the Southern Hemisphere, however, the discrepancies between model and reanalysis are sufficiently large to conclude that the model is unable to reproduce the observed time scale structure correctly. The effects of ocean coupling lead to a considerable increase in time scale and uncertainty in time scale, effects which
Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere
NASA Astrophysics Data System (ADS)
Kim, Junsu; Reichler, Thomas
2016-07-01
The proper simulation of the annular mode time scale may be regarded as an important benchmark for climate models. Previous research demonstrated that this time scale is systematically overestimated by climate models. As suggested by the fluctuation-dissipation theorem, this may imply that climate models are overly sensitive to external forcings. Previous research also made it clear that calculating the AM time scale is a slowly converging process, necessitating relatively long time series and casting doubts on the usefulness of the historical reanalysis record to constrain climate models in terms of the annular mode time scale. Here, we use long control simulations with the coupled and uncoupled version of the GFDL climate model, CM2.1 and AM2.1, respectively, to study the effects of internal atmospheric variability and forcing from the lower boundary on the stability of the annular mode time scale. In particular, we ask whether a model's annular mode time scale and dynamical sensitivity can be constrained from the 50-year-long reanalysis record. We find that internal variability attaches large uncertainty to the annular mode time scale when diagnosed from decadal records. Even under the fixed forcing conditions of our long control run at least 100 years of data are required in order to keep the uncertainty in the annular mode time scale of the Northern Hemisphere to 10 %; over the Southern Hemisphere, the required length increases to 200 years. If nature's annular mode time scale over the Northern Hemisphere is similarly variable, there is no guarantee that the historical reanalysis record is a fully representative target for model evaluation. Over the Southern Hemisphere, however, the discrepancies between model and reanalysis are sufficiently large to conclude that the model is unable to reproduce the observed time scale structure correctly. The effects of ocean coupling lead to a considerable increase in time scale and uncertainty in time scale, effects which
NASA Technical Reports Server (NTRS)
Rowlette, John R. (Inventor)
1985-01-01
The power characteristics of a lead acid battery are improved by incorporating a dispersion of 1 to 10% by weight of a thermodynamically stable conductivity additive, such as conductive tin oxide coated glass fibers (34) of filamentary glass wool (42) in the positive active layer (32) carried on the grid (30) of the positive plate (16). Positive plate potential must be kept high enough to prevent reduction of the tin oxide to tin by utilizing an oversized, precharged positive paste.
Fractal multifiber microchannel plates
NASA Technical Reports Server (NTRS)
Cook, Lee M.; Feller, W. B.; Kenter, Almus T.; Chappell, Jon H.
1992-01-01
The construction and performance of microchannel plates (MCPs) made using fractal tiling mehtods are reviewed. MCPs with 40 mm active areas having near-perfect channel ordering were produced. These plates demonstrated electrical performance characteristics equivalent to conventionally constructed MCPs. These apparently are the first MCPs which have a sufficiently high degree of order to permit single channel addressability. Potential applications for these devices and the prospects for further development are discussed.
Wu, Tsung-Tsong; Hsu, Jin-Chen; Sun, Jia-Hong
2011-10-01
In the past two decades, phononic crystals (PCs) which consist of periodically arranged media have attracted considerable interest because of the existence of complete frequency band gaps and maneuverable band structures. Recently, Lamb waves in thin plates with PC structures have started to receive increasing attention for their potential applications in filters, resonators, and waveguides. This paper presents a review of recent works related to phononic plate waves which have recently been published by the authors and coworkers. Theoretical and experimental studies of Lamb waves in 2-D PC plate structures are covered. On the theoretical side, analyses of Lamb waves in 2-D PC plates using the plane wave expansion (PWE) method, finite-difference time-domain (FDTD) method, and finite-element (FE) method are addressed. These methods were applied to study the complete band gaps of Lamb waves, characteristics of the propagating and localized wave modes, and behavior of anomalous refraction, called negative refraction, in the PC plates. The theoretical analyses demonstrated the effects of PC-based negative refraction, lens, waveguides, and resonant cavities. We also discuss the influences of geometrical parameters on the guiding and resonance efficiency and on the frequencies of waveguide and cavity modes. On the experimental side, the design and fabrication of a silicon-based Lamb wave resonator which utilizes PC plates as reflective gratings to form the resonant cavity are discussed. The measured results showed significant improvement of the insertion losses and quality factors of the resonators when the PCs were applied. PMID:21989878
Fluid and structural dynamic design considerations of the HYLIFE nozzle plate
Pitts, J.H.; Ojalvo, I.U.
1981-02-01
The basic concept of the High Yield Lithium Injection Fusion Energy (HYLIFE) reaction chamber involves a falling liquid-metal (lithium) jet array that absorbs 90% of the energy released from inertial confinement fusion reactions. The key element of the chamber that produces the jet array is the nozzle plate. This paper describes the design and analysis of a nozzle plate which can withstand the structural loads and permit the fluid jet array to be reestablished for a 1-Hz fusion reaction frequency. The shape of the nozzle plate and jet array is dictated by considerations of fluid dynamics and neutron-shielding. A vertical jet array, rather than a single annulus, is used because this design enhances fluid momentum interchange and dissipation of the kinetic energy that occurs when the jets disassemble. Less net outward-directed momentum results than with a single liquid annular flow configuration, thus producing lower stresses in the structural components.
Exploring flocculation of suspended burned sediment using an annular flume
NASA Astrophysics Data System (ADS)
Blake, W. H.; Clarke, P.; Manning, A. J.; Fitzsimons, M. F.
2010-05-01
The frequency and severity of wildfire events are predicted to increase in many fire-prone areas of the world with implications for erosion, sediment transport and sedimentation. While cohesive suspended sediment is known to be transported primarily as flocculated material in river channels, with important implications for catchment nutrient and contaminant fluxes, there has been little work to date to explore the effect of burning on suspended sediment flocculation processes. Since heating has profound effects on surface soil biogeochemistry, it can be hypothesised that in-channel flocculation processes may also be affected as burned eroded material is transported through the catchment system. Using an annular flume and LISST-ST (Laser in Situ Scatter and Transmissometry with Settling Tube) particle size analyser, short-term suspended sediment flocculation dynamics were examined in burned and unburned sediment collected from a wildfire-impacted catchment, Southern Peloponnese, Greece. Fine sediment (< 63 μm) samples were introduced to a small annular flume (45 L capacity) which was operated at range of turbulent shear stresses (0.1, 0.3, 0.6 and 0.9 Pa). Experiments were undertaken for a range of suspended sediment concentrations (111, 222 and 333 mg l-1) of burned and unburned material. For each shear and sediment concentration scenario, the flume was operated for 30 minutes to induce a theoretical equilibrium between flocs and fluid shear stress after which 5 replicate subsamples were collected and analysed for effective particle size using the LISST-ST. Material was also analysed for absolute particle size following chemical and ultrasonic dispersion. At the two higher sediment concentrations, the effective particle size distribution of unburned material notably coarsened at shear stresses of 0.1-0.3 Pa in comparison to the absolute particle size distribution. This is reflected in a reduction of the percentage of 250 μm) e.g. from 14.4 ± 4.1 % to 5.9 ± 2
Uninstrumented assembly airflow testing in the Annular Flow Distribution facility
Kielpinski, A.L.
1992-02-01
During the Emergency Cooling System phase of a postulated large-break loss of coolant accident (ECS-LOCA), air enters the primary loop and is pumped down the reactor assemblies. One of the experiments performed to support the analysis of this accident was the Annular Flow Distribution (AFD) experiment, conducted in a facility built for this purpose at Babcock and Wilcox Alliance Research Center in Alliance, Ohio. As part of this experiment, a large body of airflow data were acquired in a prototypical mockup of the Mark 22 reactor assembly. This assembly was known as the AFD (or the I-AFD here) reference assembly. The I-AFD assembly was fully prototypical, having been manufactured in SRS`s production fabrication facility. Similar Mark 22 mockup assemblies were tested in several test facilities in the SRS Heat Transfer Laboratory (HTL). Discrepancies were found. The present report documents further work done to address the discrepancy in airflow measurements between the AFD facility and HTL facilities. The primary purpose of this report is to disseminate the data from the U-AFD test, and to compare these test results to the I-AFD data and the U-AT data. A summary table of the test data and the B&W data transmittal letter are included as an attachment to this report. The full data transmittal volume from B&W (including time plots of the various instruments) is included as an appendix to this report. These data are further analyzed by comparing them to two other HTL tests, namely, SPRIHTE 1 and the Single Assembly Test Stand (SATS).
Rotating annular chromatograph for continuous metal separations and recovery
Begovich, J.M.; Sisson, W.G.
1981-01-01
Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. By continuously introducing the feed material to be separated at a stationary point at the top of the bed and eluent everywhere else around the annulus, elution chromatography occurs. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence, the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effect of annulus width and diameter has recently been studied using the same device with a 50.8-mm-wide annulus and another 0.6-m-long chromatograph with an 89-mm diameter and annulus widths of 6.4, 12.7, and 22.2 mm. These columns have been constructed of Plexiglas and typically operate at a gauge pressure of 175 kPa. To further study the effect of size and pressure, a new 445-mm-diam by 1-m-long column with a 31.8-mm-wide annulus has been fabricated. Its metal construction allows preparative-scale operation with a wide variety of liquids at pressures to 1.3 MPa. Three metal recovery systems have been explored: (1) separation of iron and aluminum in ammonium sulfate-sulfuric acid solutions; (2) separation of hafnium from zirconium in sulfuric acid solutions; and (3) the separation of copper, nickel, and cobalt in ammonium carbonate solutions. This last system simulates the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. It has been studied, using similar conditions, on each of the chromatographs, and the results demonstrate the effect of column dimensions on the quality and quantity of the separation. 8 figures, 1 table.
Successful outcome of cryosurgery in patients with granuloma annulare.
Blume-Peytavi, U; Zouboulis, C C; Jacobi, H; Scholz, A; Bisson, S; Orfanos, C E
1994-04-01
Several therapeutic methods have been employed in the management of localized granuloma annulare (GA), with varying degrees of success. We performed a prospective trial to evaluate the efficacy, cosmetic results, and safety of cryosurgical treatment in GA. Thirty-one patients with localized GA were treated by cryosurgery, using the contact method. Nitrous oxide (-86 degrees C) or liquid nitrogen (-196 degrees C) were used as refrigerants, and were applied with closed probes; each lesion was treated with one freeze-thaw cycle of 10-60 s per session. If necessary, treatment was repeated after 20-30 days. Resolution of the lesions was obtained in all patients, and in 25 of 31 patients (80.6%) they resolved after a single freeze-thaw cycle. Relapse occurred in only one of 11 patients who were followed for more than 2 years, and this occurred 16 months after treatment. Excellent cosmetic results were obtained in 14 of 28 patients who were eligible for evaluation (50%), and good results in 11 (39.3%). The cosmetic result obtained by cryosurgery with nitrous oxide was independent of the size of the lesion, whereas in the group of patients treated with liquid nitrogen a better cosmetic result was obtained with smaller lesions (comparison of lesions < or = 2.40 cm2 with those > 2.40 cm2; P = 0.04). The duration of the lesion, its location, previous treatment with another method, and the number of treatment sessions, did not have any influence on the cosmetic result. The treatment was generally well tolerated. Blister formation occurred in all patients.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8186116
Two-phase gas-liquid flow characteristics inside a plate heat exchanger
Nilpueng, Kitti; Wongwises, Somchai
2010-11-15
In the present study, the air-water two-phase flow characteristics including flow pattern and pressure drop inside a plate heat exchanger are experimentally investigated. A plate heat exchanger with single pass under the condition of counter flow is operated for the experiment. Three stainless steel commercial plates with a corrugated sinusoidal shape of unsymmetrical chevron angles of 55 and 10 are utilized for the pressure drop measurement. A transparent plate having the same configuration as the stainless steel plates is cast and used as a cover plate in order to observe the flow pattern inside the plate heat exchanger. The air-water mixture flow which is used as a cold stream is tested in vertical downward and upward flow. The results from the present experiment show that the annular-liquid bridge flow pattern appeared in both upward and downward flows. However, the bubbly flow pattern and the slug flow pattern are only found in upward flow and downward flow, respectively. The variation of the water and air velocity has a significant effect on the two-phase pressure drop. Based on the present data, a two-phase multiplier correlation is proposed for practical application. (author)
Ball, M. )
1993-02-01
Vector analysis of plate motions, derived from studies of Atlantic magnetic lineations and fracture zone trends, indicates the following relative movements between the Caribbean, North American, and South American Plates. (1) During Early Jurassic to Early Cretaceous, the North American Plate moved 1900 km westward and 900 km northward relative to the South American Plate. A broad zone including the Caribbean region, i.e., the zone between the North and South America Plates, was a site of left-lateral shear and north-south extension. (2) During Early Cretaceous to Late Cretaceous, the North American Mate moved an additional 1200 km westward relative to South America across this zone. (3) During Late Cretaceous to the end of the Eocene, the North American Plate moved 200 km westward and 400 km northward relative to the South American Plate. (4) From the end of the Eocene to near the end of the Miocene, North America converged on South America some 200 km and moved 100 km eastward relative to it. Through the Mesozoic and earliest Tertiary history of the Caribbean, the region was a shear zone within which left-lateral displacement exceeded 3000 km and north-south extension exceeded 1300 km. In regard to time, 80% of the history of the Caribbean region is one of north-south extension and left-lateral shear. In terms of space, 97% of the shear is left-lateral and the ratio of divergence versus convergence is 7 to 1. Thus, characterizing the Caribbean region, and the Atlantic to its east, as a zone of north-south extension and left-lateral shear, is a fair generalization.
Using Plate Mapping to Examine Portion Size and Plate Composition for Large and Small Divided Plates
Sharp, David E.; Sobal, Jeffery; Wansink, Brian
2015-01-01
Does the size of a plate influence the serving of all items equally, or does it influence the serving of some foods – such as meat versus starch versus vegetables – very differently? To examine this, we utilize a promising new plate mapping method where people drew a meal on a paper plate to examine sensitivity to small versus large three-compartment divided plates in portion size and meal composition in a sample of 109 university students. The total drawn meal area was 37% bigger on large plates than small plates, that is, the portion of plate coverage did not differ by plate size. Men and women drew bigger vegetable portions and men drew bigger meat portions on large plates when compared to small plates. These results suggest that men and women are differentially sensitive to plate size for overall meal size and for meal composition. Implications for decreasing portion size and improving meal balance are discussed. PMID:25280373
Nelson, M.J.; Groshart, E.C.
1995-03-01
The Boeing Company has been searching for replacements to cadmium plate. Two alloy plating systems seem close to meeting the needs of a cadmium replacement. The two alloys, zinc-nickel and tin-zinc are from alloy plating baths; both baths are neutral pH. The alloys meet the requirements for salt fog corrosion resistance, and both alloys excel as a paint base. Currently, tests are being performed on standard fasteners to compare zinc-nickel and tin-zinc on threaded hardware where cadmium is heavily used. The Hydrogen embrittlement propensity of the zinc-nickel bath has been tested, and just beginning for the tin-zinc bath. Another area of interest is the electrical properties on aluminum for tin-zinc and will be discussed. The zinc-nickel alloy plating bath is in production in Boeing Commercial Airplane Group for non-critical low strength steels. The outlook is promising that these two coatings will help The Boeing Company significantly reduce its dependence on cadmium plating.
NASA Technical Reports Server (NTRS)
Nelson, Mary J.; Groshart, Earl C.
1995-01-01
The Boeing Company has been searching for replacements to cadmium plate. Two alloy plating systems seem close to meeting the needs of a cadmium replacement. The two alloys, zinc-nickel and tin-zinc are from alloy plating baths; both baths are neutral pH. The alloys meet the requirements for salt fog corrosion resistance, and both alloys excel as a paint base. Currently, tests are being performed on standard fasteners to compare zinc-nickel and tin-zinc on threaded hardware where cadmium is heavily used. The Hydrogen embrittlement propensity of the zinc-nickel bath has been tested, and just beginning for the tin-zinc bath. Another area of interest is the electrical properties on aluminum for tin-zinc and will be discussed. The zinc-nickel alloy plating bath is in production in Boeing Commercial Airplane Group for non-critical low strength steels. The outlook is promising that these two coatings will help The Boeing Company significantly reduce its dependence on cadmium plating.
Estimates of elastic plate thicknesses beneath large volcanos on Venus
NASA Technical Reports Server (NTRS)
Mcgovern, Patrick J.; Solomon, Sean C.
1992-01-01
Megellan radar imaging and topography data are now available for a number of volcanos on Venus greater than 100 km in radius. These data can be examined to reveal evidence of the flexural response of the lithosphere to the volcanic load. On Earth, flexure beneath large hotspot volcanos results in an annual topographic moat that is partially to completely filled in by sedimentation and mass wasting from the volcano's flanks. On Venus, erosion and sediment deposition are considered to be negligible at the resolution of Magellan images. Thus, it may be possible to observe evidence of flexure by the ponding of recent volcanic flows in the moat. We also might expect to find topographic signals from unfilled moats surrounding large volcanos on Venus, although these signals may be partially obscured by regional topography. Also, in the absence of sedimentation, tectonic evidence of deformation around large volcanos should be evident except where buried by very young flows. We use analytic solutions in axisymmetric geometry for deflections and stresses resulting from loading of a plate overlying an inviscid fluid. Solutions for a set of disk loads are superimposed to obtain a solution for a conical volcano. The deflection of the lithosphere produces an annular depression or moat, the extent of which can be estimated by measuring the distance from the volcano's edge to the first zero crossing or to the peak of the flexural arch. Magellan altimetry data records (ARCDRs) from data cycle 1 are processed using the GMT mapping and graphics software to produce topographic contour maps of the volcanos. We then take topographic profiles that cut across the annular and ponded flows seen on the radar images. By comparing the locations of these flows to the predicted moat locations from a range of models, we estimate the elastic plate thickness that best fits the observations, together with the uncertainty in that estimate.
NASA Astrophysics Data System (ADS)
Woehl, Taylor; White, Ryan; Keller, Robert
A multichannel plate was used as an ion sensitive transmission detector in a commercial helium ion microscope for annular dark-field imaging of nanomaterials, i.e. scanning transmission ion microscopy. In contrast to previous transmission helium ion microscopy approaches that used secondary electron conversion holders, our new approach directly detects transmitted helium ions on an annular detector. Monte Carlo simulations are used to predict detector collection angles at which annular dark-field images with atomic number contrast are obtained. We demonstrate atomic number contrast imaging via scanning transmission ion imaging of silica-coated gold nanoparticles and magnetite nanoparticles. While the resolution of this transmission technique is limited by beam broadening in the substrate, we image magnetite nanoparticles with high contrast on a relatively thick silicon nitride substrate. We expect this new approach to annular dark-field scanning transmission ion microscopy will open avenues for more quantitative ion imaging techniques, such as direct mass-thickness determination, and advance fundamental understanding of underlying ion scattering mechanisms leading to image formation.
NASA Astrophysics Data System (ADS)
Hou, Xi; Wu, Fan; Yang, Li; Wu, Shi-bin; Chen, Qiang
2006-02-01
Annular sub-aperture stitching technique has been developed for low cost and flexible testing rotationally symmetric aspherical surfaces, of which combining accurately the sub-aperture measurement data corrupted by misalignments into a complete surface figure is the key problem. An existed stitching algorithm of annular sub-apertures can convert sub-aperture Zernike coefficients into full-aperture Zernike coefficients, in which use of Zernike circle polynomials represents sub-aperture data over both circle and annular domain. Since Zernike circle polynomials are not orthogonal over annular dominion, the fitting results may give wrong results. In this paper, the Zernike polynomials and existed stitching algorithm have been reviewed, and a modified stitching algorithm with Zernike annular polynomials is provided. The performances of a modified algorithm on the reconstruction precision are studied by comparing with the algorithm existed. The results of computer simulation show that the sub-aperture data reduction with the modified algorithm is more accurate than that obtained with the existed algorithm based on Zernike circle polynomials, and the undergoing matrix manipulation is simpler.
NASA Technical Reports Server (NTRS)
Rowlette, John J. (Inventor)
1987-01-01
A liquid-impermeable plate (10) having through-plate conductivity with essentially zero resistance comprises an insulator sheet (12) having a series of spaced perforations (14) each of which contains a metal element (16) sealingly received into the perforation (14). A low-cost plate can readily be manufactured by punching a thermoplastic sheet (40) such as polypropylene with a punching tool (52), filling the apertures with led spheres (63) having a diameter smaller than the holes (50) but larger than the thickness of the sheet, sweeping excess spheres (62) off the sheet with a doctor blade (60) and then pressing a heated platen (74) onto the sheet to swage the spheres into a cylindrical shape and melt the surrounding resin to form a liquid-impermeable collar (4) sealing the metal into the sheet.
Nitrided Metallic Bipolar Plates
Brady, Michael P; Tortorelli, Peter F; Pihl, Josh A; Toops, Todd J; More, Karren Leslie; Meyer III, Harry M; Vitek, John Michael; Wang, Heli; Turner, John; Wilson, Mahlon; Garzon, Fernando; Rockward, Tommy; Connors, Dan; Rakowski, Jim; Gervasio, Don
2008-01-01
The objectives are: (1) Develop and optimize stainless steel alloys amenable to formation of a protective Cr-nitride surface by gas nitridation, at a sufficiently low cost to meet DOE targets and with sufficient ductility to permit manufacture by stamping. (2) Demonstrate capability of nitridation to yield high-quality stainless steel bipolar plates from thin stamped alloy foils (no significant stamped foil warping or embrittlement). (3) Demonstrate single-cell fuel cell performance of stamped and nitrided alloy foils equivalent to that of machined graphite plates of the same flow-field design ({approx}750-1,000 h, cyclic conditions, to include quantification of metal ion contamination of the membrane electrode assembly [MEA] and contact resistance increase attributable to the bipolar plates). (4) Demonstrate potential for adoption in automotive fuel cell stacks. Thin stamped metallic bipolar plates offer the potential for (1) significantly lower cost than currently-used machined graphite bipolar plates, (2) reduced weight/volume, and (3) better performance and amenability to high volume manufacture than developmental polymer/carbon fiber and graphite composite bipolar plates. However, most metals exhibit inadequate corrosion resistance in proton exchange membrane fuel cell (PEMFC) environments. This behavior leads to high electrical resistance due to the formation of surface oxides and/or contamination of the MEA by metallic ions, both of which can significantly degrade fuel cell performance. Metal nitrides offer electrical conductivities up to an order of magnitude greater than that of graphite and are highly corrosion resistant. Unfortunately, most conventional coating methods (for metal nitrides) are too expensive for PEMFC stack commercialization or tend to leave pinhole defects, which result in accelerated local corrosion and unacceptable performance.
Plate-mantle coupling from post-Pangea plate kinematics
NASA Astrophysics Data System (ADS)
Zahirovic, Sabin; Dietmar Müller, R.; Seton, Maria; Flament, Nicolas
2015-04-01
Convection in the Earth's mantle that involves plates at the surfaces gives rise to plate velocities that vary through time and depend on the balance of plate boundary forces, with the present-day providing a snapshot of this ongoing process. However, present-day plate velocities do not capture plate behaviour over geologically representative timeframes and thus cannot be used to evaluate factors limiting plate velocities. Previous studies investigated the effects of continental keels on plate speeds by either using the present-day snapshot or a limited number of reconstructed plate configurations, often leading to conflicting results. For example, an early assumption was that continental keels (especially cratons) were unlikely to impede fast plate motions because India's velocity approached ~20 cm/yr in the Eocene prior to the collision with Eurasia. We employ a modern plate reconstruction approach with evolving global topological plate boundaries for the post-Pangea timeframe (since 200 Ma) to evaluate factors controlling plate velocities. Plate boundary configurations and plate velocities are extracted from the open-source and cross-platform plate reconstruction package GPlates (www.gplates.org) at 1 Myr intervals. For each plate, at each timestep, the area of continental and cratonic lithosphere is calculated to evaluate the effect on plate velocities. Our results support that oceanic plates tend to be 2-3 times faster than plates with large portion of continental plate area, consistent with predictions of numerical models of mantle convection. The fastest plates (~8.5 cm/yr RMS) are dominated by oceanic plate area and high subducting portion of plate perimeter, while the slowest plates (~2.6-2.8 cm/yr RMS) are dominated by continental plate area and bounded by transforms and mid-oceanic ridge segments. Importantly, increasing cratonic fractions (both Proterozoic and Archean lithosphere) significantly impede plate velocities, suggesting that deep continental
Enhancing VVER Annular Proliferation Resistance Fuel with Minor Actinides
G. S. Chang
2007-06-01
Key aspects of the Global Nuclear Energy Partnership (GNEP) are to significantly advance the science and technology of nuclear energy systems and the Advanced Fuel Cycle (AFC) program. The merits of nuclear energy are the high-density energy, and low environmental impacts i.e. almost zero greenhouse gas emission. Planned efforts involve near-term and intermediate-term improvements in fuel utilization and recycling in current LWR as well as the longer-term development of new nuclear energy systems that offer much improved fuel utilization and proliferation resistance, along with continued advances in operational safety. The challenges are solving the energy needs of the world, protection against nuclear proliferation, the problem of nuclear waste, and the global environmental problem. To reduce the spent fuel for storage and enhance the proliferation resistance for the intermediate-term, there are two major approaches (a) increase the discharged spent fuel burnup in the advanced LWR (Gen-III Plus), which not only can reduce the spent fuel for storage, but also increase the 238Pu and 240Pu isotopes ratio to enhance the proliferation resistance, (b) use of transuranic nuclides (237Np and 241Am) in the high burnup fuel, which can drastically increase the proliferation resistance isotope 238Pu /Pu ratio. For future advanced nuclear systems, the minor actinides are viewed more as a resource to be recycled, or transmuted to less hazardous and possibly more useful forms, rather than simply as a waste stream to be disposed of in expensive repository facilities. In this paper, a typical pressurized water reactor (PWR) VVER-1000 annular fuel unit lattice cell model with UO2 fuel pins will be used to investigate the effectiveness of minor actinide reduction approach (MARA) for enhancing proliferation resistance and improving the fuel cycle performance. We concluded that the concept of MARA, involves the use of transuranic nuclides (237Np and/or 241Am), can not only drastically
Turbulent structure at the midsection of an annular flow
NASA Astrophysics Data System (ADS)
Ghaemi, S.; Rafati, S.; Bizhani, M.; Kuru, E.
2015-10-01
The turbulent flow in the midsection of an annular gap between two concentric tubes at Reynolds number of 59 200-90 800 based on hydraulic diameter (dh = 57 mm) and average velocity is experimentally investigated. Measurements are carried out using particle tracking velocimetry (PTV) and planar particle image velocimetry (PIV) with spatial resolution of 0.0068dh (size of the binning window) and 0.0129dh (size of the interrogation window), respectively. Both PTV and PIV results show that the location of maximum mean streamwise velocity (yU) does not coincide with the locations of zero shear stress (yuv), minimum streamwise velocity fluctuation (yu2), and minimum radial velocity fluctuation (yv2). The separation between yU and yuv is 0.013dh based on PTV while PIV underestimates the separation distance as 0.0063dh. Conditional averages of turbulent fluctuations based on the four quadrants across the annulus demonstrate that the inner and outer wall flows overlap in the midsection. In the midsection, the flow is subject to opposing sweep/ejection events originating from both the inner and outer walls. The opposite quadrant events of the two boundary layers cancel out at yuv while the local minimum of spatial correlation of u (maximum mixing of the two wall flows) occurs at yU. Investigation of the budget of Reynolds shear stress showed that production and advection terms act towards the coincidence of the yU and yuv while the dissipation term works against the coincidence of the two points. The location of max also overlaps with zero dissipation of
Beyond the Cosmological: Numerical Scenarios underneath Ancient Annular Architectural Structures
NASA Astrophysics Data System (ADS)
Ranieri, M.
2009-08-01
``Cecì est la regle du carré et du cercle. Pour toutes choses, la circonférence (tcheou) est en usage, et les figures circulaire et carrée sont employées. L'officier dit ta-tsiang (grand charpentier, titre du Tcheou-li) prend ses mesures. Le compass et le règle sont apprêtés. Tantot on rompt le carré et on fait un cercle. Tantot on brise le cercle et on fait un carré. Au milieu d'un carré, quand on fait un cercle, on appelle cette figure cercle-carré. Au milieu d'un cercle, quand on fait un carré, on appelle cette figure carré-cercle.'' (Tcheou-Pei-Souan-King, book one, trad. E.Biot, Journal Asiatique, Juin 1841 p. 614 Circles and squares, as geometrical representations of the cosmos, are frequent in ancient cultures, mainly with the earth represented by the square and the sky by the circle. Quite many are the circular or circle-and-square architectures of the past that are to be interpreted as related to the cosmologies of the cultures to which they belong. In this paper we focus on those relevant annular geometries (CQC) where the square inscribable into the external circumference in turn perfectly circumscribes the internal one. Beyond the possible cosmological significances, a CQC geometry bears underneath a strict numerical structure that can be put in relation to the length-units used by the builders. Results are presented of CAD (Computer Aided Drawing) analyses performed on the plans of ancient structures where the CQC geometry was suspected to exist. A large repertory of such structures has been found, from Nuragic Sardinia to Mesoamerica including Minoans, Greeks, Romans and others. In many cases the found length-units coincide with known ancient units. The large variety presented at CAC 2000 cannot be shown in this paper for reasons of space and only a smaller but significant selection is presented.
Transverse bed slope effects in an annular flume
NASA Astrophysics Data System (ADS)
Baar, Anne; Kleinhans, Maarten; de Smit, Jaco; Uijttewaal, Wim
2016-04-01
Large scale morphology, in particular bar dimensions and bifurcation dynamics, are greatly affected by the deflection of sediment transport on transverse bed slopes due to gravity and by helical flows. However, existing transverse bed slope predictors are based on a small set of experiments with a minor range of flow conditions and sediment sizes, and do not account for the presence of bedforms. In morphological modelling the deflection angle is therefore often calibrated on measured morphology. Our objective is to experimentally quantify the transverse slope effect for a large range of near-bed flow conditions and sediment sizes (0.17 - 4 mm) to test existing predictors, in order to improve morphological modelling of rivers and estuaries. We have conducted about 400 experiments in an annular flume, which functions as an infinitely long bended flume and therefore avoids boundary effects. Flow is generated by rotating the lid of the flume, while the intensity of the helical flow can be decreased by counterrotating the bottom of the flume. The equilibrium transverse slope that develops during the experiments is a balance between the transverse bed slope effect and the bed shear stress caused by the helical flow. We obtained sediment mobilities from no motion to sheet flow, ranging across bedload and suspended load. Resulting equilibrium transverse slopes show a clear trend with varying sediment mobilities and helical flow intensities that deviate from typical power relations with Shields number. As an end member we found transversely horizontal beds by counterrotation that partially cancelled the helical flow near the bed, which allows us to quantify helical flow. The large range in sediment mobilities caused different bed states from ripples and dunes to sheet flow that affect near-bed flow, which cause novel nonlinear relations between transverse slope and Shields number. In conclusion, our results show for a wide range of conditions and sediments that transverse
Panoramic Imaging and Holographic Interferometry Using a Panoramic Annular Lens.
NASA Astrophysics Data System (ADS)
Puliparambil, Joseph Thomas
1992-01-01
Ideally, a device for making measurements of the inner surface of a cavity should be rugged, compact, and capable of obtaining an unobstructed, complete, and comprehensive image of the cavity space in every direction. The first attempt to patent a system for panoramic imaging was made by Mangin in 1878 and since that time several other devices have been patented. Most of these devices depend on a scanning system or on a complex set of lenses and mirrors and as such they are not very practical for use. However, in 1984 Dr. Pal Greguss invented a simple lens known as a Panoramic Annular Lens (PAL) capable of giving a full 360 degree surround image of the area around the lens. This lens can be utilized along with digital cameras and computer programs to inspect and measure the interior walls of cavities. If a cavity can be regarded as a cylindrical rather than a spherical volume, the image information can be transformed, using stretching methods, onto a flat surface creating a two-dimensional representation of a three-dimensional cylindrical surface. This phenomenon called Flat Cylindrical Perspective (FCP) forms the basis for the image produced by a PAL. To apply standard methods of analysis on an image and also for visual interpretation, image processing algorithms were developed to linearize a PAL image. These programs can be used for endoscopy which is a technique for imaging the inner part of a volume or cavity. Such techniques have applications in the fields of medicine, civil engineering and aerospace; indeed, anywhere tubes and pipes are involved. Holographic interferometry has become an important diagnostic tool in non-destructive testing, but due to lack of panoramic imaging systems this work could not be effectively used for the analysis of cavities. Now, the PAL can be used for panoramic holographic interferometry which can be used to measure submicron deformations of cavity walls caused by small perturbations in temperature, pressured and mechanical loads
NASA Technical Reports Server (NTRS)
Polzin, Kurt A (Inventor); Pearson, J Boise (Inventor)
2014-01-01
An ignitron apparatus has an airtight tubular housing having a first sealed end and a second sealed end. An anode is connected at the first sealed end, projecting into the housing, and a recess at the second sealed and forms a well which contains a quantity of liquid gallium or gallium alloy making up the cathode. An ignitor projects through the liquid metal and into the housing. The inner surface of the housing includes at least one plating-reduction structure to prevent electrical shorting of the apparatus caused by plating of the liquid metal.
Hoover, T.B.; Zava, T.E.
1959-05-12
A simplified process is presented for plating nickel by the vapor decomposition of nickel carbonyl. In a preferred form of the invention a solid surface is nickel plated by subjecting the surface to contact with a mixture containing by volume approximately 20% nickel carbonyl vapor, 2% hydrogen sulfide and .l% water vapor or 1% oxygen and the remainder carbon dioxide at room temperature until the desired thickness of nickel is obtained. The advantage of this composition over others is that the normally explosive nickel carbonyl is greatly stabilized.
Analytic wave solution with helicon and Trivelpiece-Gould modes in an annular plasma
NASA Astrophysics Data System (ADS)
Carlsson, Johan; Pavarin, Daniele; Walker, Mitchell
2009-11-01
Helicon sources in an annular configuration have applications for plasma thrusters. The theory of Klozenberg et al. [J. P. Klozenberg B. McNamara and P. C. Thonemann, J. Fluid Mech. 21 (1965) 545-563] for the propagation and absorption of helicon and Trivelpiece-Gould modes in a cylindrical plasma has been generalized for annular plasmas. Analytic solutions are found also in the annular case, but in the presence of both helicon and Trivelpiece-Gould modes, a heterogeneous linear system of equations must be solved to match the plasma and inner and outer vacuum solutions. The linear system can be ill-conditioned or even exactly singular, leading to a dispersion relation with a discrete set of discontinuities. The coefficients for the analytic solution are calculated by solving the linear system with singular-value decomposition.
Pressure drop in fully developed, turbulent, liquid-vapor annular flows in zero gravity
NASA Technical Reports Server (NTRS)
Sridhar, K. R.; Chao, B. T.; Soo, S. L.
1992-01-01
The prediction of frictional pressure drop in fully developed, turbulent, annular liquid-vapor flows in zero gravity using simulation experiments conducted on earth is described. The scheme extends the authors' earlier work on dispersed flows. The simulation experiments used two immiscible liquids of identical density, namely, water and n-butyl benzoate. Because of the lack of rigorous analytical models for turbulent, annular flows, the proposed scheme resorts to existing semiempirical correlations. Results based on two different correlations are presented and compared. Others may be used. It was shown that, for both dispersed and annular flow regimes, the predicted frictional pressure gradients in 0-g are lower than those in 1-g under otherwise identical conditions. The physical basis for this finding is given.
Key messages from a rare case of annular sarcoidosis of scalp
Bhushan, Premanshu; Thatte, Sarvesh S.; Singh, Avninder
2016-01-01
Sarcoidosis, a multisystem disease of obscure etiology, is characterized by the formation of noncaseating epithelioid cell granulomas in several organs or tissues. The diagnosis of sarcoidosis requires a compatible clinical picture, histologic demonstration of noncaseating granulomas, and exclusion of other diseases capable of producing similar histology or clinical features. The lung is the most commonly affected organ, but the skin is frequently involved. Sarcoidosis occurs worldwide and affects all ages and races with female predominance. Scalp involvement is decidedly rare among the myriad cutaneous manifestations of sarcoidosis. Alopecia is common in sarcoidosis and is generally scarring in nature. Annular sarcoidosis is a rare morphology and annular sarcoid of scalp is seldom reported. Herein we present a case of annular scalp sarcoid with systemic involvement and without alopecia. PMID:27294057
Key messages from a rare case of annular sarcoidosis of scalp.
Bhushan, Premanshu; Thatte, Sarvesh S; Singh, Avninder
2016-01-01
Sarcoidosis, a multisystem disease of obscure etiology, is characterized by the formation of noncaseating epithelioid cell granulomas in several organs or tissues. The diagnosis of sarcoidosis requires a compatible clinical picture, histologic demonstration of noncaseating granulomas, and exclusion of other diseases capable of producing similar histology or clinical features. The lung is the most commonly affected organ, but the skin is frequently involved. Sarcoidosis occurs worldwide and affects all ages and races with female predominance. Scalp involvement is decidedly rare among the myriad cutaneous manifestations of sarcoidosis. Alopecia is common in sarcoidosis and is generally scarring in nature. Annular sarcoidosis is a rare morphology and annular sarcoid of scalp is seldom reported. Herein we present a case of annular scalp sarcoid with systemic involvement and without alopecia. PMID:27294057
An experimental technique for performing 3-D LDA measurements inside whirling annular seals
NASA Astrophysics Data System (ADS)
Morrison, Gerald L.; Johnson, Mark C.; Deotte, Robert E., Jr.; Thames, H. Davis, III; Wiedner, Brian G.
1992-09-01
During the last several years, the Fluid Mechanics Division of the Turbomachinery Laboratory at Texas A&M University has developed a rather unique facility with the experimental capability for measuring the flow field inside journal bearings, labyrinth seals, and annular seals. The facility consists of a specially designed 3-D LDA system which is capable of measuring the instantaneous velocity vector within 0.2 mm of a wall while the laser beams are aligned almost perpendicular to the wall. This capability was required to measure the flow field inside journal bearings, labyrinth seals, and annular seals. A detailed description of this facility along with some representative results obtained for a whirling annular seal are presented.
Annular Ligament Reconstruction With Triceps Autograft for Chronic Radial Head Instability.
Marinello, Patrick G; Wagner, Timothy; Styron, Joseph; Maschke, Steven; Evans, Peter J
2016-03-01
We present a modification and revisit of the Bell Tawse technique for annular ligament reconstruction with triceps autograft for chronic radial head instability. In patients with instability stemming from an incompetent annular ligament, this technique has proved successful to restore stability to the proximal radial capitellar joint as an augment after ensuring normal boney anatomy. Through a lateral Kocher approach, an approximately 10 cm × 4 mm strip of lateral triceps tendon is harvested as a free graft for the reconstruction. Following passing of the triceps autograft around the radial neck, it is sutured to a mini-Mitek suture anchor and is placed into a decorticated portion of the proximal ulna to recreate the annular ligament. Finally, we present 2 case illustrations where this technique was successfully used for chronic radial head instability. PMID:26709571
Wardle, K.E.
2013-07-01
Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup.
Igawa, K; Maruyama, R; Katayama, I; Nishioka, K
1997-05-01
A 72-year-old fisherman who was positive for the HCV antibody developed an annular, erythematous, infiltrated lesions on sun-exposed areas. The lesions were diagnosed as annular elastolytic giant cell granuloma both clinically and histologically. Topical corticosteroid and cryotherapy with liquid nitrogen for several months failed to improve the lesions. We then started dapsone, a known anti-oxidant, at 50 mg/day. A month later, the margins of the erythematous lesions faded, and the infiltration gradually decreased. No recurrence has been observed for one year after the start of the therapy. Anti-oxidative therapy appears to be effective for annular elastolytic giant cell granuloma and could be an alternate therapy for refractory granulomatous disease. PMID:9198323