bluuebunny/crossref_metadata_2025 huggingface dataset:
Enforcing Model Validity by Automatic Adjustment
Authors: Noort Alex , Bronsvoort Willem F.
Published: July 2002

In current modeling systems, all dimensions in a model have to be fully specified by the user. It is desirable that systems become more flexible in this respect, i.e. that non-critical dimensions in a model can be declared variant, and that the model can be automatically adjusted to enforce its validity when it is invalid. A method to realize this in feature modeling systems is described. The underlying feature model definition and validation approach are introduced. Validation is done by a collection of constraint solvers. An overview of invalid situations in which automatic model adjustment can be applied is given. The constraint solving scheme and, in particular, the automatic model adjustment strategies for different types of constraints are elaborated. Applications to enforce model validity are given for the areas of design by features, creating a member of a family of products, and feature conversion. These illustrate that automatic model adjustment is a very useful concept.
Application of Boundary Layer Fences and Vortex Generators in Improving Performance of S-Duct Diffusers
Authors: Sullerey R. K. , Mishra Sourabh , Pradeep A. M.
Published: July 2002

An experimental investigation was undertaken to study the effect of various fences and vortex generator configurations in reducing the exit flow distortion and improving total pressure recovery in two-dimensional S-duct diffusers of different radius ratios. Detailed measurements including total pressure and velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken in a uniform inlet flow at a Reynolds number of 7.8×105. These measurements are presented here along with static pressure rise, distortion coefficient, and the transverse velocity vectors at the duct exit determined from the measured data. The results indicate that substantial improvement in static pressure rise and flow quality is possible with judicious deployment of fences and vortex generators.
Evaluation of Multiaxial Fatigue Life Prediction Methodologies for Ti-6Al-4V
Authors: Kallmeyer Alan R. , Krgo Ahmo , Kurath Peter
Published: July 2002

Many critical engineering components are routinely subjected to cyclic multiaxial stress states, which may include non-proportional loading and multidimensional mean stresses. Existing multiaxial fatigue models are examined to determine their suitability at estimating fatigue damage in Ti-6Al-4V under complex, multiaxial loading, with an emphasis on long-life conditions. Both proportional and non-proportional strain-controlled tension/torsion experiments were conducted on solid specimens. Several multiaxial fatigue damage parameters are evaluated based on their ability to correlate the biaxial fatigue data and uniaxial fatigue data with tensile mean stresses (R>−1) to a fully-reversed (R=−1) uniaxial baseline. Both equivalent stress-based models and critical plane approaches are evaluated. Only one equivalent stress model and two critical plane models showed promise for the range of loadings and material considered.
Thermal Charge Conditioning for Optimal HCCI Engine Operation
Authors: Martinez-Frias Joel , Aceves Salvador M. , Flowers Daniel , Smith J. Ray , Dibble Robert
Published: July 2002

This work investigates a purely thermal control system for HCCI engines, where thermal energy from exhaust gas recirculation (EGR) and compression work in the supercharger are either recycled or rejected as needed. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), which has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficiency, while meeting the restrictions of low NOx and peak cylinder pressure. The results show the values of the operating conditions that yield optimum efficiency as a function of torque for a constant engine speed (1800 rpm). For zero torque (idle), the optimizer determines operating conditions that result in minimum fuel consumption. The optimizer is also used for determining the maximum torque that can be obtained within the operating restrictions of NOx and peak cylinder pressure. The results show that a thermally controlled HCCI engine can successfully operate over a wide range of conditions at high efficiency and low emissions.
Hydraulic Axial Thrust in Multistage Pumps—Origins and Solutions
Authors: Gantar Marjan , Florjancic Dusan , Sirok Brane
Published: July 2002

In this paper, axial thrust problems of multistage pumps are presented. The entire investigation has been focused on the pump design concept having all impellers in series (facing in one direction) and is valid for barrel casing type as well as for segmental type. The major part of the investigation has been experimental on one stage testing arrangement, using also Laser Doppler Anemometry (LDA) for determination of fluid rotation in the impeller side chamber. Numerical flow analysis (NFA) has been applied for some flow variants in order to verify whether a numerical approach could simulate the test results. The phenomenon of fluid rotation in side chambers and its effect on impeller hydraulic axial thrust have been determined for different leakage flow regimes. The influence of increased wear ring radial clearance on axial thrust has been analyzed together with the solutions for pump hydraulic axial thrust reduction.
Solid Third Body Analysis Using a Discrete Approach: Influence of Adhesion and Particle Size on Macroscopic Properties
Authors: Iordanoff I. , Seve B. , Berthier Y.
Published: July 2002

The dynamics of solid third bodies sheared between two rubbing bodies is far from being understood. Yet, this interface plays a prominent role in the velocity accommodation and in the load transmission. In the present paper, a simple model, which uses the Distinct Element Method, is operated in order to understand phenomena occurring in dry contact. In this model, the solid third body is considered as an aggregate of discrete interacting particles. Inter-particle forces are determined by force-displacement law and trajectories are calculated using the Newton’s second law. The global behavior of the simulated contact can be analyzed through the evolution versus time of characteristic parameters calculated by averaging over all the particles. The model is used to study the effect of particle size and inter-particle forces. The influence of particle size is studied in presence of repulsive force (based on Hertz contact model), and in presence of adhesive force (based on JKR contact model). Some promising results are highlighted. In particular, with the boundary conditions chosen in this paper, it is shown that the particle size has a weak influence when inter-particle forces are repulsive but has a dramatic influence when inter-particle adhesion is considered: solid third body goes from a quasi-fluid to a quasi-solid behavior.
Computational and Mathematical Modeling of Turbine Rim Seal Ingestion
Authors: Hills Nicholas J. , Chew John W. , Turner Alan B.
Published: July 2002

Understanding and modeling of main annulus gas ingestion through turbine rim seals is considered and advanced in this paper. Unsteady three-dimensional computational fluid dynamics (CFD) calculations and results from a more elementary model are presented and compared with experimental data previously published by Hills et al. (1997). The most complete CFD model presented includes both stator and rotor in the main annulus and the interdisk cavity. The k-ε model of turbulence with standard wall function approximations is assumed in the model which was constructed in a commercial CFD code employing a pressure correction solution algorithm. It is shown that considerable care is needed to ensure convergence of the CFD model to a periodic solution. Compared to previous models, results from the CFD model show encouraging agreement with pressure and gas concentration measurements. The annulus gas ingestion is shown to result from a combination of the stationary and rotating circumferential pressure asymmetries in the annulus. Inertial effects associated with the circumferential velocity component of the flow have an important effect on the degree of ingestion. The elementary model used is an extension of earlier models based on orifice theory applied locally around the rim seal circumference. The new model includes a term accounting for inertial effects. Some good qualitative and fair quantitative agreement with data is shown.
Autoregressive Model-Based Gear Fault Diagnosis
Authors: Wang Wenyi , Wong Albert K.
Published: July 2002

This paper presents a model-based technique for the detection and diagnosis of gear faults. Based on the signal averaging technique, the proposed technique first establishes an autoregressive (AR) model on the vibration signal of the gear of interest in its healthy-state. The model is then used as a linear prediction error filter to process the future-state signal from the same gear. The health condition of the gear is diagnosed by characterizing the error signal between the filtered and unfiltered signals. The technique is validated using both numerical simulation and experimental data. The results show that the AR model technique is an effective tool in the detection and diagnosis of gear faults and it may lead to an effective solution for in-flight diagnosis of helicopter transmissions.
Development of a High-Temperature, Long-Shafted, Molten-Salt Pump for Power Tower Applications
Authors: Barth Daniel L. , Pacheco James E. , Kolb William J. , Rush Earl E.
Published: July 2002

A new hot-salt pump has been developed for molten-salt solar power tower applications that will reduce the capital cost of the plant, eliminate many of the piping, valve and sump problems associated with the handling of molten salt, and improve the reliability of a critical part of the operating system of the plant. Previous systems required that the pumps in these plants be housed in shallow sumps that were gravity fed by the storage tanks. This new pump arrangement will eliminate the sump level-control valves and the potential for overflowing the pump sump vessels. Until now, only cantilever pumps were qualified for hot molten-salt service because no suitable bearing materials had been tested. This paper describes the successful qualification of a long-shafted pump with salt-lubricated bearings tested for over 5000 hours with nitrate salt at 565°C.
Underwater Pipeline Inspection Using Guided Waves
Authors: Na Won-Bae , Kundu Tribikram
Published: July 2002

Underwater pipeline inspections are conducted using ultrasonic cylindrical guided waves in the laboratory environment. Three different types of mechanical defects—gouge, removed metal, and dent—are fabricated in small-diameter, 22.22-mm, aluminum pipes and tested. To efficiently propagate the antisymmetric (flexural) cylindrical guided waves through the aluminum pipe in water, a new transducer holder device is designed. The device uses commercially available ultrasonic transducers that generate compressional ultrasonic waves in the water. The device can change the striking angle of the incident beam from 0 to 51 deg. With the help of this device, the incident angle adjustment and frequency sweeping can be carried out. This is necessary for obtaining the time history of the received signals for various incident angles and signal frequencies; then these time histories are converted to Vf curves, or received signal amplitude versus frequency curves. From the amplitude of these Vf curves, the type and extent of the mechanical defects can be estimated. This investigation shows that the new coupler device can be effectively used for health monitoring of underwater pipelines using guided waves.
Particle Entrainment in Elastohydrodynamic Point Contacts and Related Risks of Oil Starvation and Surface Indentation
Authors: Nikas George K.
Published: July 2002

This theoretical study concentrates on the mathematical analysis of the motion of small (5–50 μm) spherical solid particles in the inlet zone of elastohydrodynamic point contacts, found in various machine elements as, for example, in ball bearings, in order to compute the particle trajectories in the fluid flow. Particles may collide on a moving element of the contact (e.g., a ball in a bearing) or bypass it. For those particles that collide on another element, a fluid and mechanical force analysis reveals if they will be entrapped and, possibly, cause surface damage, or temporarily or finally expelled. Particle rejection is associated with the risk of inlet blockage and fluid starvation, which may further cause film collapse and scuffing. The study gives useful evidence of the probabilities of particle entrapment or rejection, extending the concept to evaluate the probabilities of oil starvation, surface indentation, or both, under various operating conditions.
Effects of Diaphragm Compliance on Spring-Diaphragm Pressure Regulator Dynamics
Authors: Hubbard Mont
Published: July 2002

A dynamical model is derived for a spring-diaphragm type automotive pressure regulator containing an annular membrane. Previous studies have generally assumed that the diaphragm was of constant area and that it remained flat. Central features of the model presented are the calculation of the deformed shape of the annular diaphragm and the effects of its resulting fluid compliance and force on the drain orifice cover plate. Elasticity theory is used to derive the diaphragm two-port compliance relation that is integrated into an overall regulator dynamic model. Effects of diaphragm elastic modulus on system dynamic response are studied. The model and its results may be used in other design parameter studies and as a component of a fueling system dynamic model.
A Sliding Mode Control of a Full-Car Electrorheological Suspension System Via Hardware in-the-Loop Simulation
Authors: Choi S. B. , Choi Y. T. , Park D. W.
Published: July 2002

This paper presents a feedback control performance of a full-car suspension system featuring electrorheological (ER) dampers for a passenger vehicle. A cylindrical ER damper is designed and manufactured by incorporating a Bingham model of an ER fluid which is commercially available. After evaluating field-dependent damping characteristics of the ER damper, a full-car suspension system installed with four independent ER dampers is then constructed and its governing equation of motion, which includes vertical, pitch, and roll motions, is derived. A sliding mode controller, which has inherent robustness against system uncertainties, is then formulated by treating the sprung mass as uncertain parameter. For the demonstration of a practical feasibility, control characteristics for vibration suppression of the proposed ER suspension system are evaluated under various road conditions through the hardware-in-the-loop simulation (HILS). [S0022-0434(00)02801-X]
Numerical Analysis of Welding Residual Stress and Its Verification Using Neutron Diffraction Measurement
Authors: Mochizuki Masahito , Hayashi Makoto , Hattori Toshio
Published: July 2002

Direct measurements and computed distributions of through-thickness residual stress in a pipe butt-welded joint and a pipe socket-welded joint are compared. The analytical evaluation methods used were inherent strain analysis and thermal elastic-plastic analysis. The experimental methods were neutron diffraction for the internal residual stress, and X-ray diffraction and strain-gauge measurement for the surface stress. The residual stress distributions determined using these methods agreed well with each other, both for internal stress and surface stress. The characteristics of the evaluation methods and the suitability of these methods for each particular welded object to be evaluated are discussed. [S0094-4289(00)01501-2]
Combustion System Damping Augmentation With Helmholtz Resonators
Authors: Gysling D. L. , Copeland G. S. , McCormick D. C. , Proscia W. M.
Published: July 2002

This paper describes an analytical and experimental investigation to enhance combustion system operability using side branch resonators. First, a simplified model of the combustion system dynamics is developed in which the large amplitude pressure oscillations encountered at the operability limit are viewed as limit cycle oscillations of an initially linear instability. Under this assumption, increasing the damping of the small amplitude combustion system dynamics will increase combustor operability. The model is then modified to include side branch resonators. The parameters describing the side branch resonators and their coupling to the combustion system are identified, and their influence on system stability is examined. The parameters of the side branch resonator are optimized to maximize damping augmentation and frequency robustness. Secondly, the model parameters for the combustor and side branch resonator dynamics are identified from experimental data. The analytical model predicts the observed trends in combustor operability as a function of the resonator parameters and is shown to be a useful guide in developing resonators to improve the operability of combustion systems. [S0742-4795(00)00602-5]
An Experimental Investigation of Cavitation Inception and Development on a Two-Dimensional Eppler Hydrofoil
Authors: Astolfi J.-A. , Dorange P. , Billard J.-Y. , Tomas I. Cid
Published: July 2002

Cavitation inception and development on a two-dimensional foil with an Eppler E817 cross section issued from an inverse calculus have been experimentally investigated. The foil is theoretically designed to have a wide cavitation-free bucket allowing a large range of cavitation-free angle of incidence (Eppler, R., 1990, Airfoil Design and Data, Springer-Verlag, Berlin). The inception cavitation numbers, the noise level, the velocity distribution, the minimum pressure coefficient, the cavitation patterns (bubble, leading edge “band type” cavitation, attached sheet cavity), together with the sheet cavity length have been experimentally determined. Effects on the velocity field have been studied too with a slightly developed cavitation. For angles of incidence larger than 1 deg, a great difference exists between the inception cavitation number and the theoretical minimum pressure coefficient. However it is in agreement with the measured one obtained from velocity measurements (for 0 deg<α<6 deg). Discrepancy between theory and experiment on scale models is generally attributed to a flow separation at the leading edge. Although there are some indications of a separated flow at the leading edge, the velocity measurements do not show reverse flow with clearly detected negative velocities excepted for a large angle of incidence equal to 10 deg. Concerning sheet cavity development, the length cavity is found to scale as [σ/2α−αiσ]−m with m close to 2, for length cavities that do not exceed half the foil chord and for σ/2α−αiσ larger than about 30. [S0098-2202(00)00201-7]
Passive Boundary Layer Control With Slots in Short Diffusers
Authors: Raghunathan S. , Cooper R. K.
Published: July 2002

Experiments were conducted in short wide-angle diffusers. The control surface was made of slots and a plenum chamber underneath and on both diverging walls of the diffusers. The experiments included slots normal to the surface and a combination of slots normal and inclined to the surface. Passive control with inclined slots produced modest improvement in pressure recovery but significant increases in the stall angle. [S0098-2202(00)01501-7]
Theoretical Analysis of Cavitation in Inducers With Unequal Blades With Alternate Leading Edge Cutback: Part II—Effects of the Amount of Cutback
Authors: Horiguchi Hironori , Watanabe Satoshi , Tsujimoto Yoshinobu
Published: July 2002

In Part I, it was found that the alternate blade cutback of the leading edge causes a peculiar behavior in the development of steady cavitation. A stability analysis showed that the alternate blade cutback can reduce the onset region of rotating cavitation by enhancing the stability of alternate blade cavitation. In this report, we examine the effects of the amount of cutback. It was found that the development of steady cavity is significantly different depending on the amount of cutback. Those steady cavity developments are explained by the interaction of local flow near the cavity closure with the leading edge of the opposing blade just in the same way as for the development of alternate blade cavitation. It is also shown that the range of cavitation number with stable cavitation can be increased by increasing the amount of cutback. [S0098-2202(00)00502-2]
Toward Improved Rotor-Only Axial Fans—Part I: A Numerically Efficient Aerodynamic Model for Arbitrary Vortex Flow
Authors: So̸rensen D. N. , So̸rensen J. N.
Published: July 2002

A numerically efficient mathematical model for the aerodynamics of rotor-only axial fans has been developed. The model is based on a blade-element principle whereby the rotor is divided into a number of annular streamtubes. For each of these streamtubes relations for velocity, pressure, and radial position are derived from the incompressible conservation laws for mass, tangential momentum, and energy. The resulting system of equations is nonlinear and, due to mass conservation and pressure equilibrium far downstream of the rotor, strongly coupled. The equations are solved using the Newton-Raphson method, and solutions converged to machine accuracy are found at small computing costs. Calculations are found to agree well with published measurements. [S0098-2202(00)01502-9]
Analytical Description of Meshing of Constant Pressure Angle Teeth Profiles on a Variable Radius Gear and its Applications
Authors: Danieli Guido A.
Published: July 2002

This paper presents a method for determining the profile of the gear teeth on a variable radius wheel characterized by a constant pressure angle. The method can generate special gears using numerically controlled milling machines. As will be shown, the method, applied to a constant radius gear, generates an involute profile. The method is based on the integration of a differential equation describing the mesh between gears of variable radius, where the mesh point position is computed during rotation starting from the point, freely selected, where the tooth crosses the pitch line. The individual point is subsequently rotated in the opposite direction by an angle equal to the angle of rotation from the initial pitch line point, thereby generating the tooth profile. The method, applied to a wheel of variable radius, defined analytically or numerically, can compute teeth profiles on pairs of pitch lines of any shape. In particular, the motion of a slotted rotating link mechanism has been reproduced, but for the sign. Teeth profiles of other variable radius wheels have also been obtained. The results are more than satisfactory and are presented below. A numerically controlled milling machine has been programmed to actually build the antirotating slotted link equivalent gear. The present method, however, has much broader application, such as assigning the speed law to consequentially determine the gear form, as can be done with cams. Furthermore, a special planetary gear train makes it also possible to obtain reciprocating motion driven solely by gears. This has been built and its picture and scheme are presented in the paper. However, due to the low efficiency of the said mechanism, the best way to utilize this new technology seems to be to couple a crank and a rod to the pair of variable radius gears, as has been done at Hanover University. Some possible applications are presented. The special feature of these gears is the programmability of the shape of the pitch lines during the design phase, and thus of the velocity and acceleration profiles. In this way velocity profiles that could formerly only be obtained electro-pneumatically can be produced from purely mechanical components, with the added advantage of being able to control the level of inertia forces during the design phase. [S1050-0472(00)01601-9]
A Hybrid Film Thickness Evaluation Scheme Based on Multi-Channel Interferometry and Contact Mechanics
Authors: Lord J. , Jolkin A. , Larsson R. , Marklund O.
Published: July 2002

A hybrid evaluation scheme for EHL film thickness determination is proposed and discussed. The film thickness profile in the contact region is measured using interferograms produced with a novel multi channel interferometry method. Since the refractive index distribution in the contact is pressure-dependent, and the initial film thickness profile will be evaluated assuming atmospheric pressure, a refractive index correction scheme is employed. The correction scheme is based on the Lorenz-Lorentz equation and a pressure-density relation together with a numerical pressure solver taking the initial film thickness measurement as input. The film thickness determination scheme is applied to an interesting phenomenon that can be observed at sliding conditions when the discrepancy occurred in the form of a deep and large dimple in the conjunction. Such a dimple appeared instead of the conventional plateau. The phenomenon was studied under different degrees of sliding. The detailed film thickness maps and pressure distributions for highly loaded EHL conjunctions at high degrees of sliding are produced using a hybrid evaluation scheme. The results are analyzed and discussed. [S0742-4787(00)00301-5]
Lubricant Film Thickness in Rough Surface, Mixed Elastohydrodynamic Contact
Authors: Guangteng G. , Cann P. M. , Olver A. V. , Spikes H. A.
Published: July 2002

A spacer layer imaging method has been employed to map lubricant film thickness in very thin film, rough surface, rolling elastohydrodynamic (EHD) contacts. A series of model roughnesses have been produced by depositing tiny ridges and bumps on a steel ball surface and the influence of these features on film thickness has been investigated at a range of rolling speeds. It has been shown that all the model surface features studied form speed-dependent, micro-EHD lubricating films, but the detailed shape and thickness of these films depends upon the geometry of the feature and the rolling speed. All model surface features also produce a net increase in mean film thickness, compared to the smooth surface, under operating conditions where the film thickness is less than the out-of-contact height of the surface feature studied. For a real, random, rough surface, however, mean film thickness is less than the smooth surface case. The film thickness mapping technique has also been used to measure the effective roughness of surfaces in lubricated contact. This shows that surfaces based on 2-D array of tiny circular bumps become rougher as the rolling speed and thus film thickness increases. However, real, rough surfaces appear to show a decrease of in-contact roughness with increasing rolling speed. [S0742-4787(00)01001-8]
Analysis of Controllable Stress Distribution and Optimal Design of Flat Steel Ribbon Wound Pressure Vessel
Authors: Chuanxiang Zheng
Published: July 2002

Stress distribution of high pressure vessel wall is not even. How to appropriately distribute stresses on high pressure vessel wall is our goal. It can be realized in flat steel ribbon wound pressure vessel (FSRWPV). The paper shows that stress can be distributed in someway on FSRWPV wall by controlling prestress and winding angle of its flat steel ribbon. An example is given at the end. [S0094-9930(00)00902-1]
Highly Oriented Pyrolytic Graphite by XPS
Authors: Vasquez Richard P.
Published: July 2002

High resolution XPS measurements of the C 1s, including energy losses, and the valence band regions are presented for freshly cleaved highly oriented pyrolytic graphite. These spectra are useful for comparison to the diamond and C60 forms of carbon.
Elemental Palladium by XPS
Authors: Militello Maria C. , Simko Steven J.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) spectra of elemental palladium (Pd) are presented. The specimen is a polycrystalline foil and was analyzed after chemical cleaning and ion-sputtering to remove surface contamination. The spectra were collected with a Surface Science Instruments SSX-101 M-Probe ESCA instrument using monochromatized Al Kα x rays. Spectra include a survey scan and the Pd 3d, 3p, 3s, 4s, 4p, and valence band regions. Also included are the Pd MNN and MNV Auger transitions.
Factors affecting the adherence of chemically vapor-deposited coatings
Authors: Bryant W. A. , Meier G. H.
Published: July 2002

The causes of nonadherence of chemically vapor-deposited coatings are considered. The absence of substrate attack by the gases present in the system is shown to be a necessary criterion, in addition to those usually cited, for coating adherence. The importance of this criterion is illustrated for a number of coating experiments from the literature. The use of standard free-energy data for predicting substrate attack is also illustrated. Cases in which standard free-energy data alone are not sufficient are also considered and illustrated for the adherence of tungsten coatings on tantalum substrates.
Columnar grains and twins in high-purity sputter-deposited copper
Authors: Dahlgren S. D.
Published: July 2002

Columnar grains were normal to the substrate in thick, high-purity copper deposits made by high-rate (80–110 Å/sec) sputter deposition. The grains contained a high density of stacking faults and twin boundaries parallel to the substrate. The columnar grains for a deposit made at 6 °C, 80 Å/sec, and with a −75 V substrate to anode bias were uniformly about 700 Å in diameter, but a deposit made at 100 °C, 110 Å/sec, and with a −20 V bias had a few large grains with diameters up to 13 000 Å and many smaller grains with diameters of about 2500 Å. Deposits made at 100 °C did not recrystallize, but deposits made at −196 °C and at about 10 °C recrystallized at room temperature. Recrystallized regions had annealing twins that were 1000–10 000 Å across. The deposits had (111) crystallographic planes parallel to the substrate before recrystallization, but after recrystallization (100) planes were parallel to the substrate. Chemical analyses for impurity elements in the sputtering target material and a deposit showed four elements not detected in the target material were detectable in the deposit. Krypton gas pickup in the deposits during sputtering was estimated to be less than 5 ppm.
Vacuum Deposition of Stainless-Steel Coating onto Titanium Alloy Plate and Cryogenic and Mechanical Properties of the Coated Product
Authors: Wan C. T. , Chambers D. L. , Carmichael D. C.
Published: July 2002

Stainless-steel coatings were deposited on titanium alloy (Ti-5Al-2.5Sn) plates by electron-beam vacuum evaporation of stainless-steel source materials. The effect of source material feeding on the composition of the coating is reported. The effects of the substrate surface condition and temperature, the deposition rate, and heat treatment on the adherence and quality of the coating are presented and discussed. The function of the stainless-steel coating is to protect the titanium alloy from reaction in a liquid oxygen environment. Both cryogenic and room-temperature properties of the stainless-steel-coated titanium are reported. Results of investigations of the effectiveness of the coating in protecting the alloy from liquid oxygen showed excellent protection in mechanical impact tests of purposely defected specimens. The effects of the coating on the mechanical properties of the substrate material, including tensile strength and fatigue, are presented.
Ion-Plated Copper—Steel Graded Interface
Authors: Swaroop B. , Adler I.
Published: July 2002

Copper was ion plated onto a steel substrate to form a highly adherent surface coating. Electron probe examination of the copper/steel interfacial region showed that the ion-plated copper had penetrated the steel substrate to a depth of about 7–8 μ to form a graded, diffuse interface. The excellent adhesion of the coating to the substrate, which was examined by a 90° bend test and the standard Scotch Tape Test, can be attributed to the diffused interface formed by ion plating.
Adsorption of Simple Particles onto a One Dimensional Lattice with Nearest Neighbor Interaction
Authors: McQuistan R. B. , Lichtman S. J.
Published: July 2002

Using an exact expression for the occupied nearest neighbor degeneracy, the adsorption isotherm for a one dimensional lattice is calculated taking into account nearest neighbor interactions between adsorbing particles. The equation of state is also determined. It is also shown that the influence of coverage on the heat of adsorption is exactly that obtained using the Bethe approximation.
LSI Pattern Generation and Replication by Electron Beams
Authors: Malmberg P. R. , O'Keeffe T. W. , Sopira M. M. , Levi M. W.
Published: July 2002

The combined use of the digitally controlled single electron beam pattern generator to make micron-scale LSI patterns and the 1:1 electron image projection system to replicate these patterns on device substrates represents a practical means for realizing high-density integrated circuits in large volume production. After six years of research and development at Westinghouse, most of the obstacles to successful use of these methods have been removed. Among the problems solved are uniform exposure of points, lines, and areas in a device pattern, fabrication of high-resolution electromasks for the electron image projector, and registration of successive device patterns in both electron beams systems, used in combination. In the most recent work, a 1024-bit random access memory was used as a test vehicle. Eight mask levels were involved, including a buried diffusion. In both machines, alignment of a new pattern with a preexisting pattern on the substrate was obtained through electron beam probing of fiducial mark areas. An automatic alignment system developed for the electron image projection system made possible alignment within a few seconds and subsequent controlled exposure. Including alignment errors originating in the electron beam mask generator, over-all pattern registrations were within ±1.5μ.
A new approach for computing diode sputter-ion pump characteristics
Authors: Hartwig H. , Kouptsidis J. S.
Published: July 2002

By using theoretical considerations combined with experimental results, a general approach for computing sputter-ion pump characteristics is given. This approach can be successfully applied to optimal design of distributed sputter-ion pumps in high energy accelerators. The deviation between computed and measured pumping speed values is less than 30%.
Plasma etching endpoint detection using multiple wavelengths for small open-area wafers
Authors: Yue H. Henry , Qin S. Joe , Wiseman Joseph , Toprac Anthony
Published: July 2002

This article proposes a new approach for etch endpoint detection of small open area wafers. The traditional endpoint detection technique uses a few manually selected wavelengths, which are adequate for large open areas. As the integrated circuit devices continue to shrink in geometry and increase in device density, detecting the endpoint for small open areas presents a serious challenge to process engineers. In this work, a high-resolution optical emission spectroscopy (OES) system is used to provide the necessary sensitivity for detecting subtle endpoint signals. Principal component analysis is used to analyze the OES data and extract key components that capture the endpoint signal. Data analysis from many wafers shows that the endpoint pattern in the principal components is repeatable. Two methods are used to select wavelengths so as to improve reliability and reduce susceptibility to noise. The first method is to remove those spectrum windows that contain no endpoint information. The second method is to use a “sphere” criterion to select the most relevant wavelengths. The final endpoint algorithm using a much-reduced number of wavelengths shows more distinguishable and reliable endpoint features.
Observation and characteristics of mechanical vibration in three-dimensional nanostructures and pillars grown by focused ion beam chemical vapor deposition
Authors: Fujita J. , Ishida M. , Sakamoto T. , Ochiai Y. , Kaito T. , Matsui S.
Published: July 2002

The Young’s modulus of diamond-like carbon (DLC) pillars was measured by means of mechanical vibration using scanning electron microscopy. The DLC pillars were grown using Ga+ focused ion beam-induced chemical vapor deposition with a precursor of phenanthrene vapor. The Young’s modulus of the DLC pillars was around 100 GPa at vapor pressure of 5×10−5 Pa and it had a quality (Q) value of resonance exceeding 1200. There seemed to be a balance between the DLC growth rate and surface bombardment by the ions, and this played an important role in the stiffness of the pillars. Some of the DLC pillars showed a very large Young’s modulus over 600 GPa at low gas pressure conditions.
Performance analysis and optimization considerations for a Knudsen compressor in transitional flow
Authors: Muntz E. P. , Sone Y. , Aoki K. , Vargo S. , Young M.
Published: July 2002

The Knudsen compressor can be applied as either a vacuum pump or compressor for gases. Earlier investigations have indicated that there are several interesting potential applications of the Knudsen compressor because it has no moving parts and requires no lubricants or supplementary working fluids. However, its energy efficiency tends to be low, so that careful optimization is necessary. An important aspect of the optimization is an understanding of the Knudsen compressor’s operating characteristics in the transitional flow regime of rarefied gas dynamics. This article presents a formulation of Knudsen compressor operation in transitional, rarefied flow. In certain simplified but meaningful situations the formulation provides essentially analytical results for the sensitivity of key performance indicators, such as the energy use and device volume per unit of upflow, to changes in operating and geometric parameters. A numerical study of more complicated situations, using the most general form of the formulation developed here, is substantiated by the analytical investigation. The numerical results also extend the understanding of the Knudsen compressor’s performance characteristics to conditions that cannot be addressed by the simplified analytical form. Specifically, minimization of the device’s volume per unit of upflow is found when the entire cascade operates in transitional flow, which can only be studied using the complete formulation. The results make clear that operation in the transitional flow regime can lead to very significant (factor of 5 to 10) reductions of energy use and device volume for a given task.
Dry etching of polydimethylsiloxane for microfluidic systems
Authors: Garra J. , Long T. , Currie J. , Schneider T. , White R. , Paranjape M.
Published: July 2002

A fluorine-based reactive ion etch (RIE) process has been developed to anisotropically dry etch the silicone elastomer polydimethylsiloxane (PDMS). This technique complements the standard molding procedure that makes use of forms made of thick SU-8 photoresist to produce features in the PDMS. Total gas pressure and the ratio of O2 to CF4 were varied to optimize etch rate. The RIE recipe developed in this study uses a 1:3 mixture of O2 to CF4 gas resulting in a highly directional and stable etch rate of approximately 20 μm per hour. Selective dry etching can be performed through a photolithographically patterned metal etch mask providing greater precision and alignment with preexisting molded features. The dry etch process is presented in this article along with a brief comparison to recently reported wet etch approaches.
Nanophase films deposited from a high-rate, nanoparticle beam
Authors: Urban F. K. , Hosseini-Tehrani A. , Griffiths P. , Khabari A. , Kim Y.-W. , Petrov I.
Published: July 2002

The early efforts to form nanoparticles beams were characterized by unsuccessful nanoparticle formation, synthesis for only a few “high vapor pressure” solids, or prohibitively low deposition rates. A new type of deposition system described here overcomes these impediments and is demonstrated to produce at high rates nanostructured films of diverse materials. It employs ion sputtering of target materials and gas phase condensation into an inert gas atmosphere at pressures ⩽1 Torr. The condensed nanoparticles are then swept out of a 3 mm diameter converging–diverging exit nozzle, forming a low velocity beam. The beam is directed on a substrate on which a film is deposited. Nanostructured films were successfully grown using Al, Cr, Fe, Ni, Cu1−xCox, Cu, Zr, Mo, Ag, Ta, W, Pt, and Au targets at rates in the interval of 0.15–0.91 nms−1 with metal-atom deposition fluxes in the interval 1.45–11.9×1014 cm−2 s−1. Rutherford backscattering spectrometry revealed that metal-atom densities of the films ranged from 11% to 24% from the corresponding bulk metals and that films contained a significant fraction of oxygen and carbon, indicating high reactivity with atmosphere gases. Transmission electron microscopy showed successful formation of nanostructured layers from all materials studied with average sizes (standard deviations) ranging from 0.7 (0.4) to 15.6 (8.2) nm.
Etching of polysilicon in inductively coupled Cl2 and HBr discharges. I. Experimental characterization of polysilicon profiles
Authors: Mahorowala Arpan P. , Sawin Herbert H. , Jones Richard , Labun Andrew H.
Published: July 2002

Photoresist and oxide masked polysilicon samples were etched in a Lam TCP 9400SE, using both Cl2 and HBr discharges. A three variable (inductive power/rf bias power/flow rate) fractional factorial set of experiments was performed for the photoresist and oxide masked polysilicon samples. Complete experimental sets of profiles for polysilicon etching with both photoresist and oxide masks using Cl2 and HBr are presented. Additional experimental profiles showing the profile evolution with time are documented. The most striking features exhibited in the profiles are: (1) the greater polysilicon-to-photoresist selectivity exhibited by HBr over Cl2; (2) the increased sidewall deposition associated with photoresist over oxide masks; (3) the greater curvature or bowing of the sidewalls associated with the combination of photoresist masking, spacing, and Cl2 plasmas; (4) the more vertical sidewalls achieved with HBr; (5) the double faceting of the feature sidewalls under etching conditions accompanied by significant deposition; (6) the variation of photoresist facet angle associated with product deposition; (7) the delay in the onset of microtrenching while etching photoresist-masked samples with Cl2; (8) the greater microtrenching exhibited with oxide masking and Cl2 plasmas; and (9) the lack of microtrenching for the HBr etching.
Vacuum-deposited CuInTe2 thin films: Growth, structural, and electrical properties
Authors: Kazmerski L. L. , Juang Y. J.
Published: July 2002

The growth, structural, and electrical characterization of vacuum-deposited n- and p-type CuInTe2 thin films utilizing a high-evaporation-rate technique (≳100 Å/s) are reported. Complementary transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) are used to investigate the films’ crystalline (grain size, orientation, structure) and compositional (elemental) properties. The effects of substrate temperature on these quantities are presented. A substrate temperature range (400<Tsub<525 K) has been identified for the growth of single phase, chalcopyrite CuInTe2 thin films which have a preferred (112) orientation. Selected area diffraction and Auger analyses have detected Te inclusions at low Tsub and In inclusions for Tsub≳525 K. Annealing of the films in argon is used to increase grain size from ∠1000 Å for as-deposited films to the 2000–6000 Å range. The as-deposited films have characteristically high resistivities, in excess of 103 Ω cm. The effects of a low-temperature (673 K) annealing procedure on the films’ electrical characteristics are indicated and are correlated with the corresponding structural changes. The temperature dependences of the mobilities, conductivities, and carrier concentrations of both n- and p-type annealed films are presented and explained in terms of a grain-boundary scattering mechanism. Film mobilities, μn∠20–30 cm2 V−1 s−1 and μp∠5–12 cm2 V−1 s−1 have been measured. The majority-carrier type is found to depend on Tsub for these vacuum-deposited ternary films, and a range, 443<Tsub<463 K, has been identified over which the change from n (lower Tsub) to p (higher Tsub) occurs.
Doping superlattices
Authors: Döhler G. H.
Published: July 2002

The MBE technique has made feasible the growth of periodic semiconductor structures composed of ultrathin layers with alternating p- and n-doping. This kind of superlattice, in contrast to familiar heterostructure systems, does not contain any interfaces, and, therefore, does not show the problems related to those. Doping superlattices, on the contrary, are crystallographically only slightly perturbed by a relatively small amount of dopants (typically 1017 to 1019 cm−3 for the most interesting range). The periodic potential in this type of superlattice is due to the electrostatic potential of fixed ionized impurities, which may be partly compensated by mobile electrons and holes confined to the n- and p-doped layers, respectively. In addition to the features related to the subband formation as known from heterostructure superlattices, crystals with doping superstructure show intriguing pecularities which originate from the fact that electron and hole states are more or less separated from each other in local space. As a first consequence the electron and hole concentration in the crystal can be varied within a wide range either by optical excitation or by carrier injection or extraction via appropriate lateral electrodes. By the internal space charge fields the electrons and holes are always collected in the n- and p-layers, respectively. At sufficiently large superlattice period and low temperatures even large deviations from the equilibrium electron and hole concentration are quasistable. Secondly, the amplitude of the periodic potential, which may amount up to more than half of the energy gap of the pure semiconductor in the ground state, is gradually reduced with increasing carrier concentration by compensation of ionized impurity charges. As a consequence, a semiconductor with doping superstructure, in fact, represents a crystal with variable band gap and with variable carrier concentration. These unique features open a new field for both scientific research and device application. By appropriate choice of doping concentration and superlattice period, for instance, one may ’’design’’ crystals in which the conductivity parallel to the doping layers for both types of carriers may be modulated from zero up to typical values for low resistivity semiconductors (field effect transistor as a bulk device!) crystals with variable optical absorption coefficient for h/ω< and ≳Eg, or with variable photo- or electroluminescence frequency and intensity (tunable infrared laser with the whole bulk as active material and with low threshold intensity), and many kinds of other crystals with unusual properties.
An axial-emission ultra-high vacuum gauge
Authors: Chen J. Z. , Suen C. D.
Published: July 2002

The BA gauge has been widely used in ultra-high vacuum systems for many years. However, it has some well-known disadvantages. In this paper a new ionization gauge structure, the Axial-Emission gauge (AEG) is described. The filament and the ion collector plate of the AEG are located on the two terminals of a spiral grid, respectively. The sensitivity (for N2) of the AEG is 0.281 Pa−1 (37.5 Torr−1). The distance between electrodes in the AEG has only a slight effect on the gauge sensitivity. The variation in sensitivity from gauge to gauge is less than ±5%. The ’’x-ray’’ limit of the AEG is 2.67×10−9 Pa (2×10−11 Torr). The upper limit of linearity (±5%) has been ascertained to be 5.3×10−2 Pa (4×10−4 Torr). The electrodes in the AEG are quite simple. Therefore it is easy to degas and can be used on any general purpose UHV system.