bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of the Bore Honing Process
Authors: Lee J. , Malkin S.
Published: April 2010

A fundamental investigation is reported on the mechanics of the bore honing process. An experimental test rig was developed consisting of a honing machine instrumented with sensors to measure spindle power, expansion pressure, and honing head displacement and interfaced to a computer for data acquisition and analysis. Experimental results are presented, which show the effects of applied normal force and grit size on the power, removal rate, specific energy, stone wear, honing ratio, and surface roughness for honing of cast iron bores with silicon carbide abrasive stones. Considerable variability in honing behavior was observed due to stone inconsistency and differences in stone properties from different manufactures, but the results are reasonably consistent when cross-plotted versus removal rate rather than applied normal force. Slower removal rates, obtained with smaller applied normal forces and effectively harder stones, resulted in relatively less stone wear and smoother surfaces, and finer abrasive grit sizes led to relatively more stone wear and smoother surfaces. An analysis of the results indicates that the forces and specific energy associated with the process can be separated into chip formation, plowing, and sliding components, which is similar to what is found for grinding processes.
Experimental Investigations in Cutting Dynamics
Authors: Marchelek K. , Tomko´w J.
Published: April 2010

This paper presents the results of an investigation of cutting process transfer functions in orthogonal cutting. An empirical model of cutting process dynamics with respect to the inner modulation of the chip thickness has been developed. The hypothesis about the independent and additive influence of both inner and outer modulation on the cutting force components has been confirmed.
Thermodynamic Analysis of Buoyancy-Induced Flow in Rotating Cavities
Authors: Owen J. Michael
Published: April 2010

Buoyancy-induced flow occurs in the rotating cavities between the adjacent disks of a gas-turbine compressor rotor. In some cases, the cavity is sealed, creating a closed system; in others, there is an axial throughflow of cooling air at the center of the cavity, creating an open system. For the closed system, Rayleigh–Bénard (RB) flow can occur in which a series of counter-rotating vortices, with cyclonic and anticyclonic circulation, form in the r-ϕ plane of the cavity. For the open system, the RB flow can occur in the outer part of the cavity, and the core of the fluid containing the vortices rotates at a slower speed than the disks: that is, the rotating core “slips” relative to the disks. These flows are examples of self-organizing systems, which are found in the world of far-from-equilibrium thermodynamics and which are associated with the maximum entropy production (MEP) principle. In this paper, these thermodynamic concepts are used to explain the phenomena that were observed in rotating cavities, and expressions for the entropy production were derived for both open and closed systems. For the closed system, MEP corresponds to the maximization of the heat transfer to the cavity; for the open system, it corresponds to the maximization of the sum of the rates of heat and work transfer. Some suggestions, as yet untested, are made to show how the MEP principle could be used to simplify the computation of buoyancy-induced flows.
Film Cooling in a Separated Flow Field on a Novel Lightweight Turbine Blade
Authors: Okita Yoji , Nakamata Chiyuki , Kumada Masaya , Ikeda Masahiro
Published: April 2010

The primary contribution of this research is to clarify the feasibility of a novel lightweight turbine blade with internal and external cooling, which is invented, aiming at drastic reduction in weight. With a considerably thinner airfoil, an extensive separation bubble is formed on the pressure side, and film cooling performance in such a flow field has to be investigated. Experimental results with a curved duct setup, which simulates the flow field around the proposed airfoil, show that a film cooling is still an effective measure of cooling even in the vastly separated region, and it behaves quite similarly to the conventional correlation, except for lower blowing ratios, where the thermal field is strongly affected by the intense recirculation flow. Comparisons between the experimental and numerical results verify that an affordable Reynolds-averaged Navier–Stokes simulation is useful to investigate the detailed physics of this flow field. With the numerical modeling, a cooling performance of the proposed blade under a typical engine operating condition is simulated, and the metal temperatures of the blade are also predicted with a fluid-solid conjugate calculation. The resultant thermal distribution in the airfoil suggests that the trailing edge portion is inevitably most critical in the temperature, and also a considerable thermal gradient across the blade is induced. Thermal profile, however, is partly recovered with some of the film coolant being bypassed from the pressure side to the suction side.
Internal Losses and Flow Behavior of a Turbofan Stage at Windmill
Authors: Prasad Dilip , Lord Wesley K.
Published: April 2010

The flow through a high-bypass ratio fan stage during engine-out conditions is investigated, with the objective of quantifying the internal losses when the rotor is at “windmill.” An analysis of altitude test data at various simulated flight Mach numbers shows that the fan rotational speed scales with the engine mass flow rate. Making use of the known values of the nozzle coefficients, we deduce the stagnation pressure loss of the fan stage, which rises significantly as the mass flow rate increases. In order to better understand this behavior, numerical simulations of the fan stage were carried out. The calculated losses agree well with the test data, and it is found that the bulk of the stagnation pressure loss occurs in the stator. A detailed examination of the flow field reveals that the relative flow leaves the rotor at very nearly the metal angle. Moreover, the rotational speed of the fan is such that the inboard sections of the fan blade add work to the flow, while the outboard sections extract work from it. The overall work is essentially zero so that the absolute swirl angle at the rotor exit is small, causing the stator to operate at a severely negative incidence. A gross separation ensues, and the resulting blockage of the stator passage accelerates the flow to high Mach numbers. The highly separated flow in the vane, together with the mixing of the large wakes behind it are responsible for the high losses in the vane. Based on the simulation results for the flow behavior, a simple physical model to estimate the windmill speed of the rotor is developed and is found to be in good agreement with the test data. The utility of this model is that it enables the development of a procedure to predict the internal drag at engine-out conditions, which is discussed.
Study on Advanced Internal Cooling Technologies for the Development of Next-Generation Small-Class Aircraft Engines
Authors: Fujimoto Shu , Okita Yoji , Fukuyama Yoshitaka , Yamane Takashi , Mimura Fujio , Matsushita Masahiro , Yoshida Toyoaki
Published: April 2010

An innovative internal cooling structure named multislot cooling has been invented for high-pressure turbine (HPT) nozzles and blades. This cooling structure has been designed to be simple and inexpensive and to exhibit good cooling performance. In order to confirm the cooling performance of this structure, test pieces of dummy turbine nozzles were manufactured. Three geometric parameters (width of slots, overall height of cooling channel, and height of jet impingement) are associated with these test pieces. The cooling performance tests were conducted by using these test pieces for several Reynolds numbers of the mainstream hot gas [2.2×105–3.4×105] and cooling airflow [3×103–1×104]. Infrared images of the heated surfaces of the test pieces were captured for every Reynolds number in the tests, and then the distributions of the cooling effectiveness were obtained. Simultaneously, the pressure losses were measured. This paper describes the hot gas flow tests performed to confirm the effects of the geometric parameters on the cooling performance and pressure loss, and to obtain data of Nusselt number and pressure loss coefficient for the design of turbine nozzles in the future by applying this new cooling structure to next-generation small-class aircraft engines. Additionally a preliminary analysis of airfoil cooling was performed to evaluate both cooling performance of conventional impingement cooling and multislot cooling when applied to a HPT nozzle. As a result it was found that the multislot cooling is well applicable to cooling of HPT airfoils.
Aerodynamic Performance of Suction-Side Gill Region Film Cooling
Authors: Chappell Justin , Ligrani Phil , Sreekanth Sri , Lucas Terry , Vlasic Edward
Published: April 2010

The performance of suction-side gill region film cooling is investigated using the University of Utah transonic wind tunnel and a simulated turbine vane in a two-dimensional cascade. The effects of film cooling hole orientation, shape, and number of rows, and their resulting effects on the aerodynamic losses, are considered for four different hole configurations: round axial (RA), shaped axial (SA), round radial (RR), and round compound (RC). The mainstream Reynolds number based on axial chord is 500,000, exit Mach number is 0.35, and the tests are conducted using the first row of holes, or both rows of holes at blowing ratios of 0.6 and 1.2. Carbon dioxide is used as the injectant to achieve density ratios of 1.77–1.99 similar to values present in operating gas turbine engines. Presented are the local distributions of total pressure loss coefficient, local normalized exit Mach number, and local normalized exit kinetic energy. Integrated aerodynamic losses (IAL) increase anywhere from 4% to 45% compared with a smooth blade with no film injection. The performance of each hole type depends on the airfoil configuration, film cooling configuration, mainstream flow Mach number, number of rows of holes, density ratio, and blowing ratio, but the general trend is an increase in IAL as either the blowing ratio or the number of rows of holes increase. In general, the largest total pressure loss coefficient Cp magnitudes and the largest IAL are generally present at any particular wake location for the RR or SA configurations, regardless of the film cooling blowing ratio and number of holes. The SA holes also generally produce the highest local peak Cp magnitudes. IAL magnitudes are generally lowest with the RA hole configuration. A one-dimensional mixing loss correlation for normalized IAL values is also presented, which matches most of the both rows data for RA, SA, RR, and RC hole configurations. The equation also provides good representation of the RA, RC, and RR first row data sets.
Method of Initial Functions in Two-Dimensional Elastodynamic Problems
Authors: Das Y. C. , Setlur A. V.
Published: April 2010

The method of initial functions is formulated for the two-dimensional elastodynamic problems both in plane stress and plane strain. Knowing the stresses and displacements on a given layer of an elastic body in a plane state, the stresses and displacements at any other layer or point can be obtained by the method developed in this paper. The method is illustrated in the case of a deep beam subjected to time-dependent transverse loads. A particular solution for a straight-crested wave traveling along an infinite beam is obtained. Exact value of the dynamic shear coefficient for the well-known Timoshenko beam equation is derived. This method is also applied to the dynamic analysis of layered beams.
Exponentially Decaying Pressure Pulse Moving With Constant Velocity on the Surface of a Layered Elastic Material (Superseismic Layer, Subseismic Half Space)
Authors: Wright J. P. , Baron M. L.
Published: April 2010

The response of a layered elastic half space to a progressing exponentially decaying normal surface pressure is evaluated for a case in which the constant velocity V of the moving pressure is greater than that of the P and S waves, respectively, in the upper layer (superseismic) and smaller than these wave speeds in the underlying half space (subseismic). It is assumed that a steady state exists with respect to coordinate axis attached to the moving load. The superseismic-subseismic geometry results in a stress field that extends over the entire plane, with sharp shocks possible only in that portion of the layer that lies behind the front of the progressing normal loading. A computer program for evaluating stresses and velocities at points in the medium was developed and results are presented for a typical configuration of interest.
The Mechanics of Ferroelastic Plates in a Uniform Magnetic Field
Authors: Moon F.
Published: April 2010

The stability and vibration of two-dimensional ferroelastic plates in a uniform, static oblique magnetic field are investigated. It is shown that for either clamped or simply supported boundary conditions, the plate remains either undeformed or unstable. Buckling instability is found to occur only when the field is near normal to the plate. The buckling magnetic field and frequency field dispersion relation is found for a simply supported circular plate. At near-normal field incidence the lowest mode plate frequency decreases with magnetic field. Otherwise an increase in field strength is found to increase the natural frequency. The propagation of transverse waves down an infinite simply supported panel in a magnetic field is also studied.
Plastic Flow Buckling of Cylindrical Shells Due to Impulsive Loading
Authors: Vaughan Henry , Florence A. L.
Published: April 2010

A theory is postulated to explain the plastic buckling of cylindrical shells caused by uniform radially inward impulses. Experimental results are presented which show that the number of buckles increases with the shell length. A simple formula is derived which predicts preferred mode numbers in agreement with the experimental results for shells with lengths up to about 1 1/2 dia. For longer shells, mode numbers may be obtained by numerical integration of the equation of motion. The increase in mode number with shell length is attributed to the relative effects of the “directional” and hardening contributions to the reactive bending moment, the former stemming from yielding in a biaxial plastic state of stress. In short shells (length < dia), it is shown that the directional moment dominates, whereas in long shells (length > 3 dia) the hardening moment dominates. The mode prediction formula just mentioned applies whenever the directional moment dominates and the difficulty in treating cases where the hardening moment is significant is indicated. Again, for the former case, a simple threshold impulse formula is derived conforming to the experiments.
Velocity Profiles in the Skewed Boundary Layers on Some Rotating Bodies in Axial Flow
Authors: Furuya Y. , Nakamura I.
Published: April 2010

Velocity distributions in incompressible boundary layers on the various rotating bodies in axial flow were investigated experimentally. The rotating bodies consisted of a cylinder with nose section of three forms. Tests were run with two Reynolds numbers and the ratio of peripheral velocity of the body to main-stream velocity was in the range 0–4. The centrifugal force of the rotation considerably affected the meridian velocity profiles. Momentum thicknesses calculated from a theory with assumption of the quasi-two-dimensional velocity profile agreed well with the experiments except in the case of high rotating speed. The local shearing stress in the rotating direction is discussed.
Impact of an Indenter on a Large Plate
Authors: Conway H. D. , Lee H. C.
Published: April 2010

This Note is concerned with the impact between an indenter and a plate through a linear spring. The plate is sufficiently large to ignore reflections from its boundaries. Calculations are made on the duration of impact, the coefficient of restitution and the force-time and displacement-time characteristics. Analysis of the direct impact of a flat-ended, rigid indenter with a plate, yields the interesting result that the coefficient of restitution is independent of the elastic moduli of the plate.
Settling Length for Turbulent Flow of Air in Smooth Annuli With Square-Edged or Bellmouth Entrances
Authors: Sridhar K. , Nicol A. A. , Padmanabha A. V. A.
Published: April 2010

Settling or hydrodynamic entrance lengths have been determined for turbulent flow of air in three smooth concentric annuli of diameter ratios 0.306, 0.527, and 0.842. Both square-edged and bellmouth entrances were investigated for Reynolds number ranging from 7000–47,500. Flow separation caused by the abrupt change in area of the square-edged entrance resulted in skewed (distorted) velocity profiles near the entrance. This skewness was modified further downstream and finally fully developed velocity profiles were established. The settling lengths for the annuli with the square-edged entrances were between 25 and 35 dia. With the bellmouth entrance, the velocity profile developed conventionally from the nearly flat profile at the inlet. The settling lengths for the bellmouth entrances were about 10–15 equivalent diameters more than those for the square-edged entrances.
Velocity Profiles of Flow at Low Reynolds Numbers
Authors: Abarbanel S. , Bennett S. , Brandt A. , Gillis J.
Published: April 2010

Earlier numerical work on viscous flow in the inlet region of a straight channel indicated some curious features in the velocity profiles. These are now investigated further to establish that they are not merely a numerical effect and that, moreover, they persist, even if the initial conditions are modified so as to remove the singularity at the inlet. The method used is to consider a physically similar problem of Stokes flow in a quarter-plane which can be solved analytically.
Thermal Damping in Gas-Filled Composite Materials During Impact Loading
Authors: Otis David R.
Published: April 2010

Damping during impact loading of gas-filled composites can occur because of heat transport between the compressed gas and the solid structure of the composite. This “thermal damping” can be optimized so as to dissipate a significant fraction of the impact energy. It is suggested that damping in many common structures such as plastic foams and wood may under certain conditions be largely due to this mechanism. Calculations based on a heat transport model show the effects on thermal damping of certain geometrical and thermal properties of the composite and of the mass and velocity of the impacting mass.
Finite Deflections of a Nonlinearly Elastic Bar
Authors: Oden J. T. , Childs S. B.
Published: April 2010

The problem of finite deflections of a nonlinearly elastic bar is investigated as an extension of the classical theory of the elastica to include material nonlinearities. A moment-curvature relation in the form of a hyperbolic tangent law is introduced to simulate that of a class of elastoplastic materials. The problem of finite deflections of a clamped-end bar subjected to an axial force is given special attention, and numerical solutions to the resulting system of nonlinear differential equations are obtained. Tables of results for various values of the parameters defining the material are provided and solutions are compared with those of the classical theory of the elastica.
Flow in a Circular Pipe With Recessed Walls
Authors: Friedman Menahem
Published: April 2010

We are concerned with the flow of a homogeneous viscous fluid in a straight circular pipe with recessed walls. A study is made of the streamlines, separation phenomena, vorticities, and other features of the flow. We also compare our results with those obtained by a different approach for the case of a viscous flow in a straight channel with recessed walls.
Stress Concentration Around Spheroidal Inclusions and Cavities in a Transversely Isotropic Material Under Pure Shear
Authors: Chen W. T.
Published: April 2010

This paper presents an exact solution for the stress distribution around an elastic spheroidal inclusion in an infinite transversely isotropic elastic body which is otherwise under a pure shear stress. The stresses and displacements are expressed in terms of elementary functions. The technically important consideration of the stress concentrations around a spheroidal cavity is discussed. Numerical results are given for a number of hexagonal crystals.
Nonlinear Vibrations of a Beam Under Harmonic Excitation
Authors: Tseng W. Y. , Dugundji J.
Published: April 2010

A straight beam with fixed ends, excited by the periodic motion of its supporting base in a direction normal to the beam span, was investigated analytically and experimentally. By using Galerkin’s method (one mode approximation) the governing partial differential equation reduces to the well-known Duffing equation. The harmonic balance method is applied to solve the Duffing equation. Besides the solution of simple harmonic motion (SHM), many other branch solutions, involving superharmonic motion (SPHM) and subharmonic motion (SBHM), are found experimentally and analytically. The stability problem is analyzed by solving a corresponding variational Hill-type equation. The results of the present analysis agree well with the experiments.
Safe Impact Speed for Hollow Circular Cylinders
Authors: Wambold J. C. , Ju F. D.
Published: April 2010

An analog simulation of stress wave propagation in hollow circular cylinders with, and without, end caps for the purpose of determining safe impact velocity. The results were checked with experimental tests run by Sandia Corporation.
On the Longitudinal Impact of Two, Thin, Viscoelastic Rods
Authors: Behring A. G. , Oetting R. B.
Published: April 2010

A one-dimensional representation of the distribution of stress and strain resulting from the longitudinal impact of two elastic rods is developed. A form of the “correspondence principle” is then used to obtain series solutions for stress and strain distributions resulting from the longitudinal impact of two rods of a “Maxwell material.” Results of the viscoelastic solutions, obtained by use of nondimensional variables, are presented graphically.
Interaction of Horizontal Shear Waves With a Running Crack
Authors: Sih G. C. , Loeber J. F.
Published: April 2010

An analysis of the scattering of horizontally polarized shear waves by a finite crack extending uniformly is carried out. It is based on the extension of the integral equation method used by the authors in wave diffraction problems dealing with stationary lines or surfaces of discontinuity. The distortion of the local stress pattern due to the motion of the crack is determined for incident waves impinging on the crack in an arbitrary direction. It is found that the intensity factor of the singular stresses depends sensitively upon the speed of crack propagation, the frequency of the incoming waves, and the angle of incidence. As the crack speed is increased at normal incidence, the peaks of the intensity-factor curves tend to decrease and to occur at lower wave numbers. Quantitative assessment of the effect of the aforementioned system parameters on the stress and displacement fields is made by displaying the numerical results graphically.
Optical Stress Analysis of Flexural Waves in a Bar
Authors: Clark J. A. , Durelli A. J.
Published: April 2010

A complete, direct, full-field optical determination of dynamic stress distributions by a combination of photoelastic and interferometric measurements is illustrated. The method is applied to the study of flexural waves propagating in a photoelastic, urethane rubber bar. A displacement type of transverse, dynamic loading (which has approximately the form of a decaying sine wave) is applied at one end of the bar. The loading pulse can be repeated with good precision. Individual isochromatics and isoclinics are obtained, using a still camera with a short duration (0.5 micro sec) flash. A series of isochromatics have also been obtained with a Fastax high-speed motion picture camera. Photoelastic data are supplemented by isopachic patterns obtained by a modified method of holographic interferometry recently developed by the authors. As an example of complete determination of stress distributions, a vectorial representation of the principal stresses at one instant is given. Comparisons are made with approximate theories.
Thermal Stresses Near a Prolate Spheroidal Inclusion
Authors: Hussain M. A. , Pu S. L.
Published: April 2010

In this paper, we have studied the intensification of thermal stresses due to a transverse flow of heat in a fiber of prolate spheroidal shape embedded in an unbounded medium. The analysis shows that for a stiff fiber the shearing stress at the tip becomes unbounded as ξ−1.61 as the shape ratio ξ becomes small. The analysis has been extended to the case of a cavity and the results show that, as the cavity becomes a “needle-shaped” crack, there is no intensification of stress whatsoever. This result is at wide variance with either a two-dimensional or a “penny-shaped” crack.
Local Yielding Around a Crack Tip in Plexiglas
Authors: Theocaris P. S.
Published: April 2010

An optical method was developed to study the highly strained region surrounding small edge cracks in brittle transparent materials loaded in tension. Interference of the partially reflected coherent monochromatic light beam from the front and back surfaces of the specimen prepared from an optically isotropic and inert material, gave a fringe pattern which depicted the thickness variation of the plate in the neighborhood of the crack. The fringe pattern consisted of a dense pattern surrounding the crack tip which was separated from the rest by a distinct bright envelope. It was shown for the material studied that the limiting envelope was a circle which, when projected to a screen, became an epicycloid. The evolution of the geometric characteristics of the highly strained zone with increasing load was studied, up to the critical load for a rapid crack propagation. The data obtained yielded an insight on the mechanism of fracture in brittle materials.
Low-Speed Slip Flow Over a Wedge
Authors: Kasza K. E. , Chow W. L.
Published: April 2010

The problem of low-speed slip flow of a rarefied gas over a wedge has been solved using Meksyn’s asymptotic method of integrating the boundary-layer equations. Detailed results are given for slip velocity and developing velocity profiles for various wedge angles. The solution tends far downstream asymptotically to the Falkner and Skan profiles of conventional nonslip flow. In addition, the first correction to the skin friction due to velocity slip is found to be of the order of the first power of the molecular mean free path of the gas.
Nonadiabatic Flow Around Blunt Bodies at Hyperbolic Speeds
Authors: Bluston H. S.
Published: April 2010

This investigation applies Belotserkovskii’s method of integral relations to the nonadiabatic, self-absorbing radiative flow of a gray gas about a sharp-cornered blunt body. The radiative quantities are represented by means of the “differential approximation.” Nonadiabatic effects are included both in the energy equation and in the shock layer temperature profiles. Numerical results are presented for flow about an Apollo-type capsule reentering the Earth’s atmosphere at an altitude of 190,000 ft and a velocity of 48,000 fps.
A Three-Dimensional Hypersonic Viscous Interaction
Authors: Hurley F. X.
Published: April 2010

The displacement-interacting boundary layer in the symmetry plane region of a flat hypersonic delta wing is studied through a method of control volume balances for mass, momentum, and energy. Free-parameter-bearing expressions for the velocity components, density, and boundary-layer thickness are postulated and substituted into the integral balance equations. The resulting algebraic system for the free parameters is a very complicated one, but solutions are readily extracted by means of iterative machine computations. Answers for the assumed set of flight conditions indicate that the inboard drift of boundary-layer fluid from both sides gives rise to a center-plane region which is three-dimensional in character and which exhibits increased boundary-layer thickness, elevated pressures, and reduced skin-friction and heat-transfer coefficients.
Transient Excitation of a Liquid Half Space by a Decelerating Load
Authors: Myers M. K.
Published: April 2010

Wave propagation from a two-dimensional expanding load on a liquid half space is considered for the case in which the fronts of the load decelerate monotonically from an initial supersonic speed. The pressure on the surface is taken to be of constant magnitude. Particular attention is paid to the pressure field near the surface during the transonic period of motion of the expanding pulse. It is found that rapid variations in the field occur near the wave front during this period. Results are computed for the special case of a uniformly decelerating load.
Characteristic Functional of Nonstationary Shot Noise
Authors: Srinivasan S. K. , Kumaraswamy S.
Published: April 2010

An explicit expression for the characteristic functional of nonstationary shot noise is obtained with the help of Lin’s formulation. This enables us to obtain moments and correlations of all orders by appropriate functional differentiation.
Lattice strain and in situ chemical depth profiling of nanometer-thick molecular beam epitaxy grown Y2O3 epitaxial films on Si (111)
Authors: Lee Y. J. , Lee W. C. , Huang M. L. , Wu S. Y. , Nieh C. W. , Hong M. , Kwo J. , Hsu C.-H.
Published: April 2010

The strain/relaxation behavior of nanometer thick Y2O3 (111) epitaxially grown on Si (111) has been investigated with x-ray diffraction using synchrotron radiation. The authors systematically measured a series of Bragg reflections to determine the lattice parameters of Y2O3 films with thickness ranging from 1.6 to 9.5 nm. The strain state of the oxide lattice along surface normal and lateral directions is analyzed as a function of the oxide thickness. The spectra of Si 2p and Y 3d, obtained with in situ angle-resolved x-ray photoelectron spectroscopy on Y2O3 5 nm thick, showed no Y silicide but a very small incorporation of Si into the Y2O3 films at the interface.
dc and rf characteristics of self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors using molecular beam epitaxy-Al2O3/Ga2O3(Gd2O3) as gate dielectrics
Authors: Lin T. D. , Chang P. , Chiu H. C. , Hong M. , Kwo J. , Lin Y. S. , Hsu Shawn S. H.
Published: April 2010

dc and rf characteristics of self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors (MOSFETs) using molecular beam epitaxy (MBE) deposited Al2O3/Ga2O3(Gd2O3) (GGO) high κ dielectrics and TiN metal gates are reported. MOSFETs with various oxide thicknesses were fabricated. The In0.53Ga0.47As MOSFETs using Al2O3(2 nm)/GGO (5 nm) gate dielectric demonstrated a maximum drain current of 1.05 mA/μm and a peak transconductance of 714 μS/μm, both are the highest values ever reported for enhancement-mode InGaAs MOSFETs with 1 μm gate length. In addition, the same transistors exhibited excellent embedded rf properties and achieved a fT of 17.9 GHz and a fmax of 12.1 GHz. The high-quality in situ MBE growth of high κ dielectrics/InGaAs has attributed to the high device performance.
Growth and structural characterization of epitaxial (La1−xLux)2O3 layers grown on Si(111)
Authors: Watahiki Tatsuro , Grosse Frank , Kaganer Vladimir M. , Proessdorf André , Braun Wolfgang
Published: April 2010

The authors study the growth and structure of epitaxial (La1−xLux)2O3 alloy layers on Si(111) in either homogeneous or digital alloy form. Layer-by-layer growth is achieved by thermal evaporation from La and Lu oxides at a substrate temperature of 700 °C. The grown structures have an abrupt Si/oxide interface as observed by grazing incidence x-ray diffraction and transmission electron microscopy. The in-plane lattice parameter of the (La1−xLux)2O3 reaches values within 0.2% of Si. In-plane lattice constants determined by density functional theory are only slightly off Vegard’s law whereas larger deviations are found for the out-of-plane direction. This may explain the different in-plane lattice constants they measure for digitally or randomly grown (La1−xLux)2O3.
Three-dimensional force spectroscopy of KBr(001) by tuning fork-based cryogenic noncontact atomic force microscopy
Authors: Such Bartosz , Glatzel Thilo , Kawai Shigeki , Koch Sascha , Meyer Ernst
Published: April 2010

A tuning fork-based noncontact atomic force microscopy was used to collect three-dimensional (3D) frequency shift data set over the cleaved KBr(001) surface at 5 K. The results suggest that significant tip relaxation is present, especially at the smallest tip-surface separations. The analysis of the shape of force versus distance curves and the cross sections of the 3D frequency shift data set allows for identification of chemical identity of the tip apex as K+ ion.
SU‐AA‐BRD‐01: Update On AAPM State Licensing Efforts
Authors: Bevan M , Limmer J
Published: April 2010

The AAPM and ACMP are sponsoring state licensing efforts in 5 states: Pennsylvania, Missouri, Massachusetts, Michigan, and Ohio. This part of the session will provide an update from the lobbying firm with whom we have contracted.
SU‐FF‐I‐01: Automated Differential Diagnoses of CT Images From Healthy Lung and Three Pulmonary Diseases Using a Simple Statistical Transform and a Probabilistic Neural Network
Authors: Newman F , Rosskamm S
Published: April 2010

Purpose: The viability of automated differential diagnosis of pulmonary diseases and healthy lungs in CT images using a simple statistical transform and a probabilistic neural network is demonstrated. Method and Materials: We use statistical components and a probabilistic neural network (PNN) toward automated differential diagnosis of pulmonary alveolar proteinosis (PAP), cystic fibrosis (CF), sarcoidosis (SAR) and healthy lung (HL) CTs. Training is performed by selecting 50 points in a single representative image from the 4 categories and forming a 16 by 16 pixel ROI around each training point. The statistical components forming the feature vector are the mean, minimum and standard deviation of intensities from the 16 by 16 pixel ROIs. The feature vectors are then used to train a PNN. One patient image from each category is the only image from which all training vectors are drawn. Results: The simple statistical feature vectors from a single patient image for each category perform surprisingly well using the PNN. Since PAP is a rare condition, only one patient was available. Training on one image from this patient produced perfect classification on the remaining images. There were 5 patients used for HL, 5 for CF and 3 for SAR. Twenty test vectors were then input to the PNN for classification. The 20 test vectors were drawn from the remaining patient images. Training on only 1 image from 1 patient for each category produced 80%, 65% and 90% classification success for HL, SAR and CF respectively for the remaining patient images. CF classified as SAR 35% of the time. Conclusions: The results indicate that a statistical transform and a PNN may offer substantial advantage toward an automated differential diagnosis system in CTs of the tested lung diseases. Training on more patients while elaborating the feature space should continue to improve the classification success.
SU‐FF‐I‐22: Enhancement of Image Quality From Cone Beam Computed Tomography Images Using Entropy Criteria
Authors: Krishnan K , Ramaseshan R , Kohli K , Harrop S
Published: April 2010

Purpose: To improve the image quality of small low contrast objects and overall image quality from Cone Beam Computed Tomography using a new entropy technique. Materials and Methods: Cone Beam CT (CBCT) images were acquired using the Catphan phantom in an Acuity Simulator. The images were acquired at 125 kVp, 80mA with 2.5 mm slice thickness. All the images were acquired in a full fan configuration. A new criterion for image enhancement was developed based on entropy behavior. For some of the images we have applied a noise reduction technique before applying the criteria. Results and discussion: Visualization of small low contrast objects is of significant importance for clinical treatment planning and verification. In this paper, we propose a new technique to enhance the quality of images obtained from CBCT. The technique involves measuring the entropy of the image using its histogram at different contrast levels using the definition , where Pn represents the relative frequencies of occurrence of gray levels in the image with . The behavior of the entropy has been analyzed and studied on the phantom CATPHAN 500/600 and various types of CT images for the quality of image. Significant improvement in the quality of image was observed at the point of maximum entropy. We were able to observe low contrast objects which were not observed in the original image. Quantitative analysis of detectability, signal to noise ratio, contrast to noise ratio shows significant changes for the processed image. The method operates directly on the raw data with significantly lower computational time of 5–10 seconds per slice. We are hoping to improve this computational time. Conclusion: We have demonstrated that using entropy criteria it is possible to improve the CBCT image quality.
SU‐FF‐I‐29: Comparison of Dedicated Cone‐Beam Breast CT with Conventional CT for Detection of Micro‐Calcification
Authors: Ge S , Lai C , Pan T , Han T , Chen L , Shen Y , Liu X , Zhong Y , Wang T , Yi Y , Zhang H , You Z , Shaw C
Published: April 2010

Purpose: To compare the visibility of micro‐calcifications in cone‐beam breast CT with that in conventional CT. Material and method: Calcium Carbonate grains (ranging from 180–200 to 250–280 microns) were used to simulate calcifications. Two bowl shaped plastic containers filled with paraffin were used to simulate a breast. The phantom was scanned with a bench‐top experimental CBCT system, configured for breast imaging. The system consists of a conventional tungsten target x‐ray tube (G‐1592) and an a‐Si:H/CsI flat panel detector (Paxscan 4030CB). The source to image and source to iso‐center distances are 100 and 75 cm, corresponding to a magnification factor of 1.33 at the iso‐center. A conventional CT system (GE Discovery STE PET/CT Scanner) was used to scan one phantom by itself and with two phantoms on an anthropomorphic chest phantom. Result: The visibility of the calcifications in CBCT images was found to be significantly better than that in the conventional CT images. Calcifications as small as 180–200μm were visible in the CBCT images. While calcifications of 212–224μm were visible in the conventional CT images when only breast phantom was scanned. None of the calcifications studied (280 μm or smaller) were visible when the two breast phantoms were placed on the anthropomorphic chest phantom for scan. Conclusion: Our results indicated that CBCT is capable of imaging calcifications as small as 180 μm. This is due to the intrinsic high spatial resolution of the detector used and the pendant geometry used which allowed the breast to be scanned and imaged by itself. The conventional CT is intrinsically lower in spatial resolution. An important disadvantage is the inclusion of the entire chest in the scan which results in degraded spatial resolution as well as overall higher radiation dose to the patient.
SU‐FF‐I‐36: Comparison of Vendor Estimated CTDIvol and Physicist Calculated CTDIvol
Authors: Johnson P , Stenroos K , Davros W
Published: April 2010

Purpose: To determine if CT unit's estimated CTDIvol is statistically similar to values obtained using conventional medical physics testing and instrumentation. The ACR calculation spreadsheet was used to calculate the CTDIvol for each unit tested. Method and Materials: Exposure measurements were obtained from the center and 12 o'clock position for both a 32 cm diameter abdominal and 16 cm diameter acrylic head phantom. The measurements were made using axial scans for typical patient abdominal and head protocols. Five CT units were evaluated. Results: Examination of the results indicate good statistical agreement between the CT unit CTDIvol estimates and the ACR dose spreadsheet calculated CTDIvol. Conclusion: This work indicates that estimating patient dose (i.e., CTDIvol) using CT unit values may be an accepted alternative to performing traditional measurements using acrylic phantoms.
SU‐FF‐I‐44: Iterative Image Reconstruction for CBCT Using Edge‐Preserving Prior
Authors: Wang J , Li T , Xing L
Published: April 2010

Purpose: To improve the image quality of low‐dose cone‐beam CT (CBCT) using an iterative image reconstruction algorithm with an edge‐preserving prior. Method and Materials: We reconstructed CBCT image by minimizing the objective function based on the penalized weighted least‐squares (PWLS) criterion with an anisotropic quadratic penalty. The penalty or the prior constraint is applied on neighboring voxels in the image domain, where the gradient of image intensity controls the degree of smoothness in the reconstructed image. For neighbors associated with large gradient, such as the region around sharp edges, equivalence between them will be discouraged. CBCT projection data of a quality assurance phantom was acquired by a Varian Acuity simulator (Varian Medical Systems, Palo Alto, CA). Contrast‐to‐noise ratio (CNR) and modulation transfer function (MTF), which characterizes the spatial resolution of the reconstructed image, are used to quantitatively evaluate the proposed algorithm. Results: At matched spatial resolution, CNR of a low‐contrast region‐of‐interest in the image reconstructed by the proposed algorithm is 2 times higher than that in the corresponding image reconstructed by the analytical FDK algorithm. Compared with the projection domain smoothing algorithm, the iterative image reconstruction algorithm based on the image domain PWLS criterion produces higher resolution image at matched noise level. Comparison studies with conventional isotropic quadratic penalty and Huber penalty also show that the proposed anisotropic penalty generates images of better spatial resolution at matched noise level. Conclusion: CNR in the low‐dose CBCT image can be significantly improved without loss of spatial resolution by using the proposed iterative image reconstruction algorithm. Imaging dose of CBCT can be lowered using statistical image reconstruction algorithms.
SU‐FF‐I‐47: A Hybrid Algebraic/Inverse Radon Transform Method for Region of Interest Reconstruction of Computed Tomography Images
Authors: Manciu M , Cruz M Barrera , Estrada E Valdes
Published: April 2010

Purpose: To obtain good ROI image reconstructions from few projections, by mixing a global Inverse Radon Transform (IRT) algorithm with a local algebraic reconstruction algorithm. Method and Materials: Algebraic methods are very efficient for small images; however, for large images the system of equations is prohibitively large. On the other hand, IRT works very well if sufficient low‐noise projections are obtained, but is not accurate for a reduced number of projections. The basic idea of the present approach is to use IRT to generate an approximate image; the contributions to the projections from the ROI and from the rest of the image are subsequently separated; and the former are used for the algebraic reconstruction of the ROI. Various existing algebraic algorithms have been employed for the latter purpose (SVD, ART, EM, and TVR). Results: Assuming that 20 projections are used, and a ROI of 10×10 (from an initial image of 256×256 pixels) is selected, the matrix of the system is reduced to only ∼30,000 coefficients (instead of ∼475,000,000); the linear system, that has been severely underdetermined (∼7000 equations for 65,536 unknowns) becomes now overdetermined (∼ 300 equations for 100 unknowns). The method have been tested for a Shepp‐Logan phantom and 10, 20 and 30 projections; the Figure of Merit of the ROI reconstruction is sometimes better by orders of magnitude that the IRT reconstruction. A priori knowledge is easier to introduce in algebraic reconstruction; we will show the capabilities of the algorithm to detect a region of constant adsorption coefficient in a background of constant (but different) adsorption coefficient by using a hybrid IRT/TV algebraic reconstruction. Conclusion: The hybrid Algebraic/IRT algorithm for ROI reconstruction has the potential to improve drastically the quality of the ROI images obtained from few projections. Acknowledgement: This work was supported by the NIH Grant♯P20‐CA126201
SU‐FF‐I‐56: Radiation Dose Estimation From Pediatric Cone Beam Computed Tomography
Authors: Kim S , Yoshizumi T , Toncheva G , Yin F , Frush D
Published: April 2010

Purpose: To estimate absorbed doses and effective dose (ED) from cone beam computed tomography (CBCT) with metal oxide semiconductor field effect transistor (MOSFET) detectors in an anthropomorphic phantom, and to estimate the risk of cancer incidence from CBCT. Method and Materials: CBCT was performed in the abdominal region of a 5‐year old anthropomorphic phantom using a Varian On‐Board Imager with standard (125kVp, 80mA, 25msec) and low dose mode (125kVp, 40mA, 10msec). Full‐fan mode was employed as scanning protocol and 20 MOSFET dosimeters were used to measure the absorbed doses at various organ locations. We evaluated the effective doses, the lifetime attributable risks (LAR) and relative risk (RR) of cancer induction for both standard and low dose mode. Results: Highest absorbed doses were founded in the skin, ascending colon and stomach. EDs of CBCT were 37.8±0.7 mSv for standard dose mode and 8.1±0.2 mSv for low dose mode. LAR of cancer incidence ranged from 23 to 144 for standard dose mode and from 5 to 31 for low dose mode per 100,000 exposed persons. RR of cancer incidence ranged from 1.003 to 1.053 for standard dose mode and from 1.001 to 1.012 for low dose mode. Conclusion: ED from pediatric CBCT for standard dose mode was considerably higher than that of MDCT, while the ED for low dose mode was comparable. For abdominal CBCT in the pediatric phantom, the highest LARs were for incidence of colon and bladder cancer and the highest RRs were for incidence of stomach and liver cancer.