bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital Projector Calibration for 3-D Active Vision Systems
Authors: Shen Tzung-Sz , Menq Chia-Hsiang
Published: July 2002

3-D active vision systems that project artificial structured light for coordinate measurements have been adopted in many industrial applications. With advances of electronic projection display technology, the digital projector is becoming an important component of various 3-D active vision systems. However, current projector models or structured light calibration techniques for 3-D active vision systems are limited to stripe-type structured light and the majority of them do not consider projector lens distortion. In order to overcome these limitations, a digital projector calibration method is developed to calibrate light beams projected from all pixel elements of a digital projector. Since the digital projector is fully programmable, various structured light patterns can be projected for coordinate acquisition, whose models can be obtained by interpolating parameters of light beams that synthesize the structured light patterns. With proper interpolation functions, experimental results indicate that the projector lens distortion can be successfully compensated and measurement errors are significantly reduced. When the digital projector is moved, a simple rigid body transformation calibration method is developed to rapidly obtain the transformation without re-calibrating the projector. The precision of the 3-D active vision system using the proposed digital projector calibration method and rigid body transformation calibration technique is experimentally evaluated.
Local and Average Characteristics of Heat/Mass Transfer Over Flat Tube Bank Fin With Four Vortex Generators per Tube
Authors: Wang L. B. , Ke F. , Gao S. D. , Mei Y. G.
Published: July 2002

The analogy between heat and mass transfer has been used to obtain local and average heat transfer characteristics over a complete flat tube-fin element with four vortex generators (VGs) per tube. Several types of surfaces involved in heat transfer process such as fin surface mounted with VGs, its back surface (mounted without VGs) and flat tube surface are considered. The mass transfer experiments are performed using naphthalene sublimation method. The effects of the fin spacing and VG parameters such as height and attack angle on heat transfer and pressure drop are investigated. The comparisons of heat transfer enhancement with flat tube-fin element without VG enhancement under three constraints are carried out. The local Nusselt number distribution reveals that VGs can efficiently enhance the heat transfer in the region near flat tube on fin surface mounted with VGs. On its back surface the enhancement is almost the same as on the fin surface mounted with VGs but enhanced region is away from flat tube wall with some distance. Average results reveal that increasing of VG height and attack angle increases the enhancement of heat transfer and pressure drop, whereas small fin spacing causes greater increase of pressure drop. The heat transfer performance, correlations of Nusselt number and friction factor are also given.
Numerical Analysis of Flow Through a Severely Stenotic Carotid Artery Bifurcation
Authors: Stroud J. S. , Berger S. A. , Saloner D.
Published: July 2002

The results of computational simulations may supplement MR and other in vivo diagnostic techniques to provide an accurate picture of the hemodynamics in particular vessels, which may help demonstrate the risks of embolism or plaque rupture posed by particular plaque deposits. In this study, a model based on an endarterectomy specimen of the plaque in a carotid bifurcation was examined. The flow conditions include steady flow at Reynolds numbers of 300, 600, and 900 as well as unsteady, pulsatile flow. Both dynamic pressure and wall shear stress are very high, with shear values up to 70 N/m2, proximal to the stenosis throat in the internal carotid artery, and both vary significantly through the flow cycle. The wall shear stress gradient is also strong along the throat. Vortex shedding is observed downstream of the most severe occlusion. Two turbulence models, the Chien and Goldberg varieties of k-ε, are tested and evaluated for their relevance in this geometry. The Chien model better captures phenomena such as vortex shedding. The flow distal to stenosis is likely transitional, so a model that captures both laminar and turbulent behavior is needed.
Time-Dependent Mechanical Behavior of Sheep Digital Tendons, Including the Effects of Preconditioning
Authors: Sverdlik A. , Lanir Y.
Published: July 2002

The time-dependent mechanical properties of sheep digital extensor tendons were studied by sequences of stress-relaxation tests. The results exhibited irreversible preconditioning and reversible viscoelasticity. Preconditioning effects were manifested by stress decay during consecutive stretch cycles to the same strain level, accompanied by elongation of the tendon’s reference length. They intensified with increased strain level, and were reduced or became negligible as the strain decreased. The significance of intrinsic response mechanisms was studied via a structural model that includes viscoelasticity, preconditioning, and morphology of the tendon’s collagen fibers. Model/data comparisons showed good agreement and good predictive power, suggesting that preconditioning can be integrated into comprehensive material characterization of tendons.
Fitting Manifold Surfaces to Three-Dimensional Point Clouds
Authors: Grimm Cindy M. , Crisco Joseph J. , Laidlaw David H.
Published: July 2002

We present a technique for fitting a smooth, locally parameterized surface model (called the manifold surface model) to unevenly scattered data describing an anatomical structure. These data are acquired from medical imaging modalities such as CT scans or MRI. The manifold surface is useful for problems which require analyzable or parametric surfaces fitted to data acquired from surfaces of arbitrary topology (e.g., entire bones). This surface modeling work is part of a larger project to model and analyze skeletal joints, in particular the complex of small bones within the wrist and hand. To demonstrate the suitability of this model we fit to several different bones in the hand, and to the same bone from multiple people.
“Loop-at-a-Time” Design of Dynamic Surface Controllers for Nonlinear Systems
Authors: Gerdes J. Christian , Hedrick J. Karl
Published: July 2002

The use of multiple surface sliding controllers for robust control of nonlinear systems with mismatched uncertainties has produced a number of impressive applications, but also raised a few theoretical questions. Among the latter are the use of numerical differencing to obtain derivatives of desired trajectories, robustness to uncertainties in the gain terms and the common practice of filtering desired trajectories for implementation. This paper seeks to address these issues through the concept of a Dynamic Surface Controller, in which filters form an integral part of the structure. This filtering removes the need for numerical differencing and guarantees a certain smoothness, enabling other assumptions of smoothness to be relaxed. In this paper, the Dynamic Surface Controller is coupled with a sequential design procedure that carves a system workspace out of the state space. Within this bounded region, bounded tracking performance can be rigorously guaranteed in the presence of uncertainties and constraints such as rate limits and saturation can be systematically avoided. The design of a Dynamic Surface Controller and the advantages of the workspace concept are demonstrated in the context of engine speed control.
Modified Skyhook Control of Semi-Active Suspensions: A New Model, Gain Scheduling, and Hardware-in-the-Loop Tuning
Authors: Hong Keum-Shik , Sohn Hyun-Chul , Hedrick J. Karl
Published: July 2002

In this paper, a road adaptive modified skyhook control for the semi-active Macpherson strut suspension system of hydraulic type is investigated. A new control-oriented model, which incorporates the rotational motion of the unsprung mass, is introduced. The control law extends the conventional skyhook-groundhook control scheme and schedules its gains for various road conditions. Using the vertical acceleration data measured, the road conditions are estimated by using the linearized new model developed. Two filters for estimating the absolute velocity of the sprung mass and the relative velocity in the rattle space are also designed. The hydraulic semi-active actuator dynamics are incorporated in the hardware-in-the-loop tuning stage of the control algorithm developed. The optimal gains for the ISO road classes are discussed. Experimental results are included.
Return Air Leakage Impact on Air Conditioner Performance in Humid Climates
Authors: O’Neal Dennis L. , Rodriguez Angel , Davis Michael , Kondepudi Sekhar
Published: July 2002

An experimental study was conducted to quantify the effect of return air leakage from hot/humid attic spaces on the performance of a residential air conditioner. Tests were conducted in psychrometric facilities where temperatures and humidities could be controlled closely. The test air conditioner had a nominal cooling capacity of 12.3 kW and a seasonal coefficient of performance of 3.8. Return air leakage from hot attic spaces was simulated by assuming adiabatic mixing of the indoor air at normal conditions with the attic air at high temperatures. Effective capacity and coefficient of performance both decreased with increased return air leakage, leakage air temperature, and air humidity. Under attic conditions of 54.4°C and 20 percent relative humidity, 10% return leakage reduced the effective cooling capacity and coefficient of performance of the air conditioner by approximately 30%. Power consumption was relatively constant for all variables except outdoor temperature. The sensible heat ratio (SHR), which is a measure of the dehumidification performance, increased with increasing leakage.
Design and Analysis of a Spherical Continuously Variable Transmission
Authors: Kim Jungyun , Park F. C. , Park Yeongil , Shizuo Mishima
Published: July 2002

In this article we propose the design of a novel continuously variable transmission, the spherical continuously variable transmission (S-CVT). The S-CVT consists of a sphere, input and output discs, and variators. The rotating input and output discs are connected to the power source and output shafts, respectively, while the sphere is situated between the input and output discs. The transmission ratio is controlled by adjusting the location of the contact point between the variators and the sphere, which in turn controls the axis of rotation of the sphere. The S-CVT can smoothly transit between the forward, neutral, and reverse states without any brakes or clutches, and its compact and simple design and its relatively simple control make it particularly effective for mechanical systems in which excessively large torques are not required (e.g., mobile robots, household appliances, small-scale machining centers). We describe the operating principles behind the S-CVT, including a kinematic and dynamic analysis. Simulations and experiments with a constructed prototype are conducted to assess the performance of the S-CVT, including a study of its energy efficiency vis-a´-vis reduction gears.
Transient Thermal Bubble Formation on Polysilicon Micro-Resisters
Authors: Tsai Jr-Hung , Lin Liwei
Published: July 2002

Transient bubble formation experiments are investigated on polysilicon micro-resisters having dimensions of 95 μm in length, 10 μm or 5 μm in width, and 0.5 μm in thickness. Micro resisters act as both resistive heating sources and temperature transducers simultaneously to measure the transient temperature responses beneath the thermal bubbles. The micro bubble nucleation processes can be classified into three groups depending on the levels of the input current. When the input current level is low, no bubble is nucleated. In the middle range of the input current, a single spherical bubble is nucleated with a waiting period up to 2 sec while the wall temperature can drop up to 8°C depending on the magnitude of the input current. After the formation of a thermal bubble, the resister temperature rises and reaches a steady state eventually. The bubble growth rate is found proportional to the square root of time that is similar to the heat diffusion controlled model as proposed in the macro scale boiling experiments. In the group of high input current, a single bubble is nucleated immediately after the current is applied. A first-order model is proposed to characterize the transient bubble nucleation behavior in the micro-scale and compared with experimental measurements.
Influence of Processing on Microstructure and Performance of Electron Beam Physical Vapor Deposition (EB-PVD) Thermal Barrier Coatings
Authors: Schulz U. , Fritscher K. , Leyens C. , Peters M.
Published: July 2002

The paper addresses the effect of processing parameters on microstructure and lifetime of electron beam physical vapor deposition, partially yttria-stabilized zirconia (EB-PVD PYSZ) coatings deposited onto NiCoCrAlY-coated Ni-base superalloys. In particular, the formation of a thermally grown oxide layer, an equi-axed zone, and various columnar arrangements of the highly textured PYSZ layers are discussed with respect to processing conditions. Three different microstructures were cyclically tested at 1100°C. The intermediate columnar structure was superior with respect to cyclic life times to a fine and to a coarse columnar structure which was mainly attributed to differences in the elastic properties. The effect of PYSZ microstructure on hot corrosion behavior of the thermal barrier coating (TBC) system at 950°C is briefly discussed.
Thermometry and Thermal Transport in Micro/Nanoscale Solid-State Devices and Structures
Authors: Cahill David G. , Goodson Kenneth , Majumdar Arunava
Published: July 2002

We review recent advances in experimental methods for high spatial-resolution and high time-resolution thermometry, and the application of these and related methods for measurements of thermal transport in low-dimensional structures. Scanning thermal microscopy (SThM) achieves lateral resolutions of 50 nm and a measurement bandwidth of 100 kHz; SThM has been used to characterize differences in energy dissipation in single-wall and multi-wall carbon nanotubes. Picosecond thermoreflectance enables ultrahigh time-resolution in thermal diffusion experiments and characterization of heat flow across interfaces between materials; the thermal conductance G of interfaces between dissimilar materials spans a relatively small range, 20<G<200 MW m−2K−1 near room temperature. Scanning thermoreflectance microscopy provides nanosecond time resolution and submicron lateral resolution needed for studies of heat transfer in microelectronic, optoelectronic and micromechanical systems. A fully-micromachined solid immersion lens has been demonstrated and achieves thermal-radiation imaging with lateral resolution at far below the diffraction limit, <2 μm. Microfabricated metal bridges using electrical resistance thermometry and joule heating give precise data for thermal conductivity of single crystal films, multilayer thin films, epitaxial superlattices, polycrystalline films, and interlayer dielectrics. The room temperature thermal conductivity of single crystal films of Si is strongly reduced for layer thickness below 100 nm. The through-thickness thermal conductivity of Si-Ge and GaAs-AlAs superlattices has recently been shown to be smaller than the conductivity of the corresponding alloy. The 3ω method has been recently extended to measurements of anisotropic conduction in polyimide and superlattices. Data for carbon nanotubes measured using micromachined and suspended heaters and thermometers indicate a conductivity near room temperature greater than diamond.
Hopf Bifurcation in PD Controlled Pendulum or Manipulator
Authors: Bucklaew Tom , Liu Ching-Shi
Published: July 2002

In this brief the dynamic behavior of a parametrically forced manipulator, or pendulum, system with PD control is examined. For an excitation of sufficient amplitude or frequency a Hopf bifurcation to a steady-state limit cycle is shown to result, appearing as a precursor to instability. The parameter space is mapped in order to illustrate regions where control failure will likely occur, even in the strongly damped case. For weakly damped systems, the Hopf bifurcation can additionally exhibit a dependence on initial conditions. The resulting case of competing point and periodic attractors is discussed.
Vibration Behavior of Rotated Triangular Tube Bundles in Two-Phase Cross Flows
Authors: Pettigrew M. J. , Taylor C. E. , Janzen V. P. , Whan T.
Published: July 2002

The results of a series of tests describing the vibration behavior of several rotated triangular tube bundles subjected to two-phase cross flows are presented. Tube bundles with a pitch-to-diameter ratio of approximately 1.5 were tested over a broad range of void fractions and mass fluxes. Fluidelastic instability, random turbulence excitation, hydrodynamic mass, two-phase damping and local void-fraction were investigated. Well-defined fluidelastic instabilities were observed in continuous two-phase flow regimes. However, intermittent two-phase flow regimes had a dramatic effect on fluidelastic instability leading to lower than expected threshold flow velocities for instability. This effect was more pronounced in Freon two-phase flow than in air-water, and appeared well correlated to the transition between continuous and intermittent flow regimes. Generally, random turbulence excitation forces were much lower in Freon than in air-water. Although very dependent on void fraction, as expected, damping was quite similar in air-water and Freon.
Representative Terrestrial Solar Brightness Profiles
Authors: Neumann Andreas , Witzke Andreas , Jones Scott A. , Schmitt Gregor
Published: July 2002

Solar thermal energy systems often use optical imaging concentrators. The image size and shape produced in the focal plane of the concentrator system depends on the solar brightness distribution. Therefore, the forward scattering of solar radiation by the Earth’s atmosphere modifies the solar brightness distribution and creates a circumsolar aureole. The circumsolar ratio, the energy contained in the solar aureole compared to total energy, can impact the performance of these concentrating systems. Based on about 2300 sunshape measurements from sites in France, Germany, and Spain made with a camera system developed by the German Aerospace Center (DLR), average solar brightness profiles with a circumsolar ratio of about 0%, 5%, 10%, 20%, 30%, and 40% were generated. These profiles are compared to the measurements taken by the Lawrence Berkeley Laboratory (LBL) in the late 1970s and a commonly used limb-darkened solar brightness profile, as known from astronomy. A statistical analysis gives information on the frequency of occurrence of each of the average profiles. The profiles combined with the statistical weight should offer a numerical database for calculating the influence of variable conditions of the sunlight scattering on solar concentrating systems. Furthermore, a single average profile was calculated from the DLR data.
Controlling the Transition From Stable Resting to Tracking Control of an Unstable System
Authors: Yang Pai-Hsueh , Auslander David M.
Published: July 2002

This paper discusses the control problem of launching an open-loop unstable system from its resting state on a mechanical hard stop. Smooth state transition with the appropriate control mode is accomplished by fuzzy transition logic. A “soft tracking” algorithm with on-line trajectory planning is then employed to manage the system stabilization immediately following the launch. The strategies have been successfully applied to an experimental system consisting of a hydraulically balanced beam pivoted at its center.
A Robust Tracking Controller Design With Hierarchical Perturbation Compensation
Authors: Kwon SangJoo , Chung Wan Kyun
Published: July 2002

A robust tracking controller for mechanical systems is proposed by combining the robust perturbation compensator which effectively attenuates the perturbation to the plant with the nominal tracking controller designed using the sliding surface. This approach enables a smooth sliding mode in tracking control loop without chattering problem. A unified view is given on a class of perturbation observers. Three kinds of equivalent expressions for the perturbation of a plant is described. In terms of the equivalents, we propose the feedforward perturbation observer (FFPO), the feedback perturbation observer (FBPO), and the sliding mode perturbation observer (SMPO). Successively, by hierarchically adopting these three observers to attenuate the residual perturbation, the hierarchical perturbation compensator (HPC) is constructed with stability analysis. The adaptive and integral property of the HPC greatly enhances the robust performance with minimal control effort. The actuator saturation issue is also considered. Experimental results demonstrate the effectiveness of the proposed controller.
Bending of Cord Composite Cylindrical Shells
Authors: Paris A. J. , Costello G. A.
Published: July 2002

An analytical method for determining the load-deformation behavior of cord composite cylindrical shells is developed by considering the mechanics of the matrix, the cords, and the shell. To illustrate the method, a circular cylindrical shell with a single ply of uniformly spaced cords parallel to the shell axis is considered. The differential equations for the displacements are derived. These equations are solved analytically in closed form for a shell with the cords on the middle surface and subjected to axisymmetric loading. The deformations are strongly dependent upon the properties of the constituents, including the extension-twist coupling of the cords, and the geometry, boundary conditions, and loading. [S0021-8936(00)02701-X]
A Numerical Tool for Periodic Heterogeneous Media: Application to Interface in Al/SiC Composites
Authors: Dumont D. , Lebon F. , Khaoua A. Ould
Published: July 2002

A wavelet-Galerkin method for periodic heterogeneous media is presented. The advantages are to remove the mesh and to make adaptivity easier. Numerical results are presented. A specific study of interfaces in a Al-SiC composite is given. [S0021-8936(00)00301-9]
Nondestructive Evaluation of Ceramic Substrate With Embedded Passive Components by SAM
Authors: Yu Z. Q. , Chan Y. C. , Webb D. P. , Li G. Y.
Published: July 2002

Delaminations of embedded passive components are often associated with reliability problems. Understanding the delamination can help us quickly identify the failure caused at an early stage of failure analysis. In this work, defects in buried capacitors have been detected by use of scanning acoustic microscopy (SAM). Defects in buried capacitors caused by thermal shock have also been clearly observed. The results show that SAM can be a powerful analytical tool for the nondestructive evaluation of delaminations in buried passive components. Through transmission scan (THRU-scan) is a fast method to detect the existence of internal defects, while Tomographic Acoustic Multiple Imaging scan (TAMI-scan) is shown to be capable of detecting the location and size of delaminations and voids. [S1043-7398(00)01102-6]
Full Load and Part-Load Performance Prediction for Integrated SOFC and Microturbine Systems
Authors: Campanari Stefano
Published: July 2002

During the last years, two new subjects among the others have raised interest in the field of small scale electric power generation: advanced microturbines and solid oxide fuel cells. This paper investigates the thermodynamic potential of the integration of the solid oxide fuel cell technology with microturbine systems, in order to obtain ultra-high efficiency small capacity plants, generating electric power in the range of 250 kW with 65 percent LHV net electrical efficiency and with the possibility of cogenerating heat. A detailed description of the calculation model is presented, capable of full and part-load performance analysis of the microturbine and of the integrated SOFC+microturbine system. [S0742-4795(00)01702-6]
Modeling of Ball-End Milling Forces With Cutter Axis Inclination
Authors: Lazoglu Ismail , Liang Steven Y.
Published: July 2002

In the machining of sculpture surfaces with ball-end mill, the cutter axis or workpiece is often inclined to generate an admissible orientation. This paper primarily presents an enhanced cutting force model for ball-end milling with cutter axis inclination. It involves the kinematic reasoning of cutting edge geometry, local helix angle and average chip thickness followed by the analysis of effects of axis inclination in the contact zone between cutter and workpiece. Thereupon, development of the analytical force model for inclined-axis machining is achieved using cutter angle domain convolution method. Experimental evaluation of the model is discussed, and experimental results and model predictions under various cutting conditions are compared in the frequency as well as in the angular domain. [S1087-1357(00)70601-0]
Use of Cavitating Jet for Introducing Compressive Residual Stress
Authors: Soyama H. , Park J. D. , Saka M.
Published: July 2002

In an attempt to strengthen the surface of materials, the potential of using a cavitating jet to form compressive residual stress has been investigated. Introducing compressive residual stress to a material surface provides improvement of the fatigue strength and resistance to stress corrosion cracking. In general, cavitation causes damage to hydraulic machinery. However, cavitation impact can be used to form compressive residual stress in the same way as shot peening. In the initial stage, when cavitation erosion progresses, only plastic deformation, without mass loss, takes place on the material surface. Thus, it is possible to form compressive residual stress without any damage by considering the intensity and exposure time of the cavitation attack. Cavitation is also induced by ultrasonic, high-speed water tunnel and high-speed submerged water jet, i.e., a cavitating jet. The great advantage of a cavitating jet is that the jet causes the cavitation wherever the cavitation impact is required. To obtain the optimum condition for the formation of compressive residual stress by using a cavitating jet, the residual stresses on stainless steel (JIS SUS304 and SUS316) and also copper (JIS C1100) have been examined by changing the exposure time of the cavitating jet. The in-plane normal stresses were measured in three different directions on the surface plane using the X-ray diffraction method, allowing for the principal stresses to be calculated. Both of the principal stresses are found changing from tension to compression within a 10 s exposure to the cavitating jet. The compressive residual stress as a result of the cavitating jet was found to be saturated after a certain time, but it starts decreasing, and finally, it approaches zero asymptotically. It could be verified in the present study that it was possible to form compressive residual stress by using a cavitating jet, and the optimum processing time could also be realized. The great difference between the water jet in water and air has also been shown in this regard. [S1087-1357(00)00501-3]
Structure and Properties of Coatings Deposited by High Velocity Arc Spray Technique
Authors: Xu Binshi , Zhang Wei , Ma Shining , Tian Baohong , Liang Xiubing
Published: July 2002

The microstructure of spray coatings using a newly developed thermal spray technique, High Velocity Arc Spray (HVAS), was studied and compared with those of regular arc sprayed coatings. The mechanical and wear properties of HVAS coatings were also investigated. The test results showed that HVAS coatings had better mechanical properties than those of regular arc sprayed coatings. The bonding strength of HVAS Al and 3Cr13 coatings was increased by 114 percent and 51.8 percent; the relative wear resistance of HVAS coatings was about twice that of regular arc sprayed coatings. The difference of microstructure and tribological properties between HVAS and regular arc sprayed coatings was discussed. [S0742-4787(00)00203-4]
Fitness for Service Evaluation of Ring Joint Groove Cracking
Authors: Brown R. G. , Buchheim G. M. , Osage D. A. , Janelle J. L.
Published: July 2002

Cracking of ring joint style flanges has been a recurring problem in the petrochemical industry, particularly in high-pressure hydrogen processing vessels. The cracking of the ring joint groove region is an inherent problem with the design. The ring groove is subjected to high stresses from the wedging action of the gasket and the ring groove radii are not substantial enough to effectively reduce the stress concentrating effect. A fitness for service assessment was conducted for a hydrogen processing vessel containing cracks in the ring groove radius region of a ring joint style flange. The flange was forged 2-1/4Cr-1Mo material with a Type 347 SS overlay. Results of an elastic-plastic numerical fracture mechanics assessment showed that the driving force for crack propagation was high for a very localized region near the ring groove radius. However, the driving force decreased significantly for deeper cracks as the crack tip became removed from the very localized high stress region of the ring groove. The assessment also showed that the highest stresses occurred during the bolt-up operation. Metallurgical tests were performed on a small sample removed from the flange. The chemistry, grain size, microstructure, and hardness of the material indicated that the probability that this material had very low resistance to hydrogen-assisted crack growth during downtime was quite small and that the resistance to crack advance during service was good. Therefore, the combined results of the fracture assessment and metallurgical testing were used to justify continued operation without repair of the cracks present in the flange. [S0094-9930(00)01901-6]
Flaw Stability in Mild Steel Tanks in the Upper-Shelf Ductile Range—Part II: J-Integral-Based Fracture Analysis
Authors: Lam Poh-Sang , Sindelar Robert L.
Published: July 2002

The J-integral fracture methodology was applied to evaluate the stability of postulated flaws in mild steel storage tanks. The material properties and the J-resistance JR curve were obtained from the archival A285 Grade B carbon steel test data. The J-integral calculation was based on the center-cracked panel (CCP) solution of Shih and Hutchinson (1976, ASME J. Eng. Mater. Technol. 98, pp. 289–295). A curvature correction was applied to account for the cylindrical shell configuration. A finite element analysis of an arbitrary flaw in the storage tank demonstrated that the curvature-corrected CCP solution is a close approximation. The maximum storage tank fluid level for a postulated flaw size can be established based on the J-integral flaw stability methodology. [S0094-9930(00)00502-3]
Use of CDM in Materials Modeling and Component Creep Life Prediction
Authors: Dyson Brian
Published: July 2002

Physically based continuum creep damage mechanics (CDM) has been reviewed and shown to provide a unifying framework for some seemingly diverse methods of predicting design and remanent creep lifetimes. These methods—theta projection, omega parameter, Larson-Miller parameter, and Robinson’s life fraction rule—exhibit certain strengths in common with CDM, but also weaknesses which CDM identifies and avoids. CDM consists of sets of coupled rate equations for inelastic strain, internal stress, and microstructural evolution (damage) which can then be integrated under boundary conditions appropriate to the test or service operating conditions: constant load/temperature for creep; constant total strain for stress-relaxation, variable stress/temperature, etc. Other state-variable approaches to creep and cyclic plasticity (for example, those due to Bodner, Miller, Chaboche, and Robinson), differ from CDM mainly in concentrating on the primary/secondary stages of creep (or cyclic work-hardening) and/or by their introduction of damage in an empirical Kachanov manner. The application of physically based CDM to LCF/thermal fatigue and its potential for predicting lifetimes of welded joints are also discussed. [S0094-9930(00)00903-3]
CuCl by XPS
Authors: Vasquez Richard P.
Published: July 2002

X-ray photoemission measurements of high purity CuCl are presented. XPS studies of Cu compounds have been motivated in this laboratory by the need to identify species on high temperature superconductor surfaces which have been chemically etched [see R. P. Vasquez, M. C. Foote, and B. D. Hunt, J. Appl. Phys. 66, 4866 (1989)].
Vacuum beam studies of photoresist etching kinetics
Authors: Greer Frank , Coburn J. W. , Graves David B.
Published: July 2002

One factor limiting the development of reliable models of high density, low pressure oxide etch plasmas is the relatively poor understanding of the plasma-photoresist surface interactions. In particular, the relatively high rates of photoresist (PR) loss experienced in high density fluorocarbon plasmas is a significant problem. It has long been accepted that fluorine plays a key role in controlling the oxide to PR etch rate selectivity. The addition of hydrogen has been shown to improve this selectivity, presumably by scavenging fluorine from the tool by forming HF. By reducing the fluorine to carbon ratio in the plasma and more specifically at the PR surface itself, the rate of polymer deposition increases causing the net PR etch rate to decrease. In this work, the complex surface chemistry of fluorocarbon plasmas is simplified to facilitate the study of the interaction of fluorine atoms and hydrogen atoms on the PR surface. This chemistry is modeled in vacuum beam experiments with argon ions and independent fluxes of neutral deuterium and fluorine atoms intersecting at the surface of photoresist samples. We present experimental evidence that the etch yield of photoresist (carbon atoms removed per incident argon ion) under these conditions is high compared to that of silicon and silicon dioxide. The presence of a simultaneous flux of deuterium atoms on the photoresist surface does not affect the etch yield despite the fact that DF is formed during the etching process.
Variable angle spectroscopic ellipsometry of fluorocarbon films from hot filament chemical vapor deposition
Authors: Lau Kenneth K. S. , Caulfield Jeffrey A. , Gleason Karen K.
Published: July 2002

Hot filament chemical vapor deposition using hexafluoropropylene oxide as the precursor gas yielded two sets of fluorocarbon films, one with varying OH/COOH content and the other with varying grain aspect ratio, as revealed by Fourier transform infrared spectroscopy and atomic force microscopy, respectively. Variable angle spectroscopic ellipsometry was performed to derive film thickness and film optical constants. A uniaxial Cauchy–Urbach dispersion layer, with separate in-plane and out-of-plane dispersion parameters, was found to realistically describe the films. Derived film thickness agreed well with profilometry measurements. Anisotropy in index of refraction n and extinction coefficient k was on the order of 10−2 and 10−5 to 10−3, respectively. The relationship between the complex index of refraction and the dielectric function allowed the optical dielectric constant ε1 to be calculated. The presence of OH did not affect the film optical dielectric constant significantly. Even though OH/COOH groups are considered to contribute adversely by increasing the dielectric constant, their effect may have been masked by the dominance of F atoms. The optical dielectric constant decreased linearly with increasing grain aspect ratio. The presence of voids was thought to lower the effective index of refraction and optical dielectric constant, and the increase in grain asymmetry created more of these voids due to less efficient packing. By assuming a linear contribution from bulk grains and voids to the effective optical dielectric constant, film porosity was derived. A maximum film porosity of 33%, corresponding to an optical dielectric constant of 1.74, was observed.
Kinematic sample mounting system for accurate positioning of transferrable samples
Authors: Lapicki Adam , Boyd Kevin J. , Anderson Scott L.
Published: July 2002

A design is reported for a system of transferrable sample holders and mating experimental stations, that allows samples to be transferred between preparation and analysis tools with high positional accuracy. The sample holders are designed to be manipulated/transported using standard “ESCA stub” compatible hardware. Provisions are made for heating, cooling, and temperature measurement.
Optical properties of bulk and thin-film SrTiO3 on Si and Pt
Authors: Zollner Stefan , Demkov A. A. , Liu R. , Fejes P. L. , Gregory R. B. , Alluri Prasad , Curless J. A. , Yu Z. , Ramdani J. , Droopad R. , Tiwald T. E. , Hilfiker J. N. , Woollam J. A.
Published: July 2002

We have studied the optical properties (complex dielectric function) of bulk SrTiO3 and thin films on Si and Pt using spectroscopic ellipsometry over a very broad spectral range, starting at 0.03 eV [using Fourier transform infrared (FTIR) ellipsometry] to 8.7 eV. In the bulk crystals, we analyze the interband transitions in the spectra to determine the critical-point parameters. To interpret these transitions, we performed band structure calculations based on ab initio pseudopotentials within the local-density approximation. The dielectric function was also calculated within this framework and compared with our ellipsometry data. In the FTIR ellipsometry data, we notice a strong lattice absorption peak due to oxygen-related vibrations. Two longitudinal optic (LO) phonons were also identified. In SrTiO3 films on Si, the refractive index below the band gap decreases with decreasing thickness because of the increasing influence of the amorphous interfacial layer between the SrTiO3 film and the Si substrate. There is also a decrease in amplitude and an increase in broadening of the critical points with decreasing thickness. In SrTiO3 films on Pt, there is a strong correlation between the crystallinity and texture of the films (mostly aligned with the Pt pseudosubstrate) and the magnitude of the refractive index, the Urbach tail below the bulk band edge, and the critical-point parameters. FTIR reflectance measurements of SrTiO3 on Pt (reflection–absorption spectroscopy) show absorption peaks at the LO phonon energies, a typical manifestation of the Berreman effect for thin insulating films on a metal. The Urbach tail in our ellipsomety data and the broadening of the optical phonons in SrTiO3 on Pt are most likely caused by oxygen vacancy clusters.
Time-stability measurement and compensation of a scanning probe microscope instrument
Authors: Huang Wenhao , Wang Wenwei , Xia Andong , Jin Nong , Hu ZhiQiang
Published: July 2002

The scanning probe microscope (SPM) is a kind of superprecision instrument with nanometer and even atomic resolution. The time stability of a SPM instrument is an important parameter. We measured the time stability and obtained the drift speed of a commercial SPM instrument quantitatively by using the method of image correlation. Then the drift was fed to the scanning piezotube to compensate. The experiment showed that the drift speed of our instrument was decreased by an order of magnitude during the scanning of 16 images. The possible causes of the drift are also discussed in the article.
PREVAIL Alpha system: Status and design considerations
Authors: Golladay S. D. , Pfeiffer H. C. , Rockrohr J. D. , Stickel W.
Published: July 2002

An overview is given of the PREVAIL Alpha system program, a joint project of IBM and Nikon to develop a production-level electron project lithography system. The Alpha system program is based on the successful completion of an initial feasibility phase conducted by the IBM/Nikon alliance team and on the PREVAIL proof of concept results reported at EIPBN 1999. The electron beam column and associated electronics and software are under development at IBM’s Semiconductor R&D Center in East Fishkill, New York, while the high speed, high precision stages for both reticle and wafer as well as the overall systems architecture are being developed at Nikon’s facilities. A key architectural objective is the combination of leading edge stepper technology with state-of-the-art PREVAIL electron optics. The design of the electron optics is based on carefully balancing geometric aberrations and Coulomb interactions for optimum resolution at the required high beam current. Cornerstones of the design are the high emittance gun and the curvilinear variable axis lens concept developed for PREVAIL. Design considerations of the Alpha column are emphasized including a detailed treatment of space-charge lens aberrations.
Relationship between Substrate Surface Chemistry and Adhesion of Thin Films
Authors: Sundahl Robert C.
Published: July 2002

The surface chemical compositions of high purity Al2O3 substrates have been characterized by Auger electron spectroscopy. It was found that when a ground ceramic surface, essentially free of inorganic impurities, is annealed at a high temperature, the bulk impurities Ca and Si tend to segregate at the surface. With extended annealing, however, the surfaces become depleted of impurities, possibly due to evaporation. The adhesion of Ta2N–TiPdAu films on the same surfaces were characterized by the results of 90 ° peel tests performed on leads which were thermocompression-bonded to the films. These results demonstrate that the poor adhesion observed on ground surfaces is significantly improved when Ca and/or Si appear at the surface in significant quantities. A subsequent etching treatment, which was found to remove the Ca and Si from the surface, also degraded adhesion, while a post-etch anneal again led to the recovery of both the impurities and adhesion. It was concluded that a necessary requirement for good adherence of Ta2N–TiPdAu films to alumina substrates is the presence of a minimum amount of Ca and/or Si at the surface.
The Influence of Ion Bombardment on the Microstructure of Thick Deposits Produced by High Rate Physical Vapor Deposition Processes
Authors: Bunshah R. F. , Juntz R. S.
Published: July 2002

The structure of massive deposits produced by high rate physical vapor deposition processes above 0.3 Tm substrate temperature consists of columnar grains. The length and width of the columnar grains increases with substrate temperature. Ion bombardment of the deposit during deposition by biasing the substrate negatively to 5 kV produces a marked refinement in grain size. A possible mechanism is nucleation of new grains by localized temperature spikes at the vapor–solid interface due to ion bombardment.
Miniaturizing the Cold Cathode Vacuum Gauge
Authors: Woods Robert O.
Published: July 2002

It is possible to greatly reduce the physical dimensions of cold cathode vacuum gauges by increasing the efficiency of the magnetic circuit. The work described in this paper was undertaken to establish the limit to which miniaturization could be carried. It is concluded that a gauge 18.5 mm high and weighing 25 g is close to the practical lower limit for gauges of the geometry tested.
Thermal Diffuse Scattering of Low-Energy Electrons at Low Temperature
Authors: Dennis Robin L. , Webb Maurice B.
Published: July 2002

A very precise low-energy electron diffractometer capable of operating from near liquid He temperatures to near 1000 K has been developed. As a first experiment, the Debye-Waller factor and the thermal diffuse scattering from a Ag(111) crystal have been studied. In earlier experiments, owing to the large multiphonon scattering, the one-phonon scattering could be determined only in the central part of the Brillouin zone. At low temperatures the one-phonon scattering is relatively much larger. Hence, using their known temperature dependences in the high temperature limit, the zero-, one-, and multiphonon contributions have been separated all the way to the zone boundary. Near the zone boundary the deviation from a continuum model due to the phonon dispersion in a discrete lattice is observed, and the angular, energy penetration, and temperature dependences have been observed.
Stencil reticle repair for electron beam projection lithography
Authors: Okada Masashi , Shimizu Sumito , Kawata Shintaro , Kaito Takashi
Published: July 2002

Repair of stencil reticles for electron beam projection lithography system is one of the critical issues on reticle manufacturing. Focused ion beam deposition is studied as the method for repairing the clear defects of stencil reticle. The film deposition of diamondlike carbon (DLC) across the stencil pattern, on the sidewall of the stencil, and on the pre-etched slot pattern is demonstrated. The deposited DLC films have good properties as the repair material. Deposited patterns across the stencil pattern are imaged on the resist with the Nikon 100 kV experimental projection column. When the thickness of the deposited DLC film is more than 0.5 μm and the contrast aperture size of the projection column is 1.5 mrad, the thickness of the deposited pattern does not affect the critical dimension of the resist pattern imaged the repaired patterns. The profiles, the pattern size, and the electron scattering properties of DLC films are stable for 100 kV electron beam continuous irradiation (2 C/cm2 dosage; corresponding to half-year dosage on electron beam stepper). Moreover, the repaired pattern is not damaged by the wet megasonic cleaning.
Quantification of a radical beam source for methyl radicals
Authors: Schwarz-Selinger T. , Dose V. , Jacob W. , von Keudell A.
Published: July 2002

A radical beam source for methyl radicals (CH3) was characterized applying ionization-threshold mass spectrometry. The beam source is based on thermal dissociation of methane (CH4) or azomethane (N2(CH3)2) in a heated tungsten capillary. A flux of (3±1)×1013 cm−2 s−1 CH3 radicals is produced using methane as precursor gas and a capillary temperature of 1650 K. Alternatively, a flux of (3±1)×1014 cm−2 s−1 CH3 is produced using azomethane as precursor gas and a capillary temperature of 1150 K. The dominant production of methyl from the precursor methane occurs due to reaction 2 CH4+M→2 CH3+H2+M at the hot tungsten surface. The dominant production of methyl from azomethane occurs due to the reaction N2(CH3)2→2 CH3+N2. Besides methyl radicals, only stable molecules contribute to the emitted flux; within the detection limit, no atomic hydrogen is observed. From the comparison of ionization-threshold mass spectrometry and standard mass spectrometry, it is concluded that the cracking pattern of methane varies with the methane gas temperature. This is explained by the vibrational assisted dissociation of methane.
Influence of diamond film thickness on field emission characteristics
Authors: Ji H. , Jin Z. S. , Gu C. Z. , Wang J. Y. , Lu X. Y. , Liu B. B. , Gao C. X. , Yuan G. , Wang W. B.
Published: July 2002

Diamond films with various thicknesses (0.15–9 μm) were grown by microwave plasma chemical vapor deposition. The lowest threshold field strength for electron emission was 4 V/μm for the ∼1.5-μm-thick diamond film. The results were analyzed by effective emission areas and effective work function according to Fowler–Nordheim theory. It was found that the threshold voltage was strongly affected by the ratio of (111) and (110) oriented grains in the films. The larger the fraction of (111) oriented grains, the lower the effective work function in agreement with the reported negative electron affinity of (111) surfaces.