bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional variation in contribution of myenteric and intramuscular interstitial cells of Cajal to generation of slow waves in mouse gastric antrum
Authors: Hirst G. D. S. , Beckett E. A. H. , Sanders K. M. , Ward S. M.
Published: July 2002

When intracellular recordings were made from the antral region of murine stomach, cells with three different patterns of electrical activity were detected. One group of cells generated follower potentials, the second group generated pacemaker potentials and the third group generated slow waves that consisted of primary and secondary components. Slow waves recorded in different regions of the gastric antrum had similar amplitudes but different characteristic shapes. At the greater curvature, slow waves had large initial components. Midway between the greater and lesser curvature, the amplitude of the initial component was reduced and at the lesser curvature an initial component was difficult to detect. When the distributions of myenteric (ICC‐MY) and intramuscular interstitial cells of Cajal (ICC‐IM) were determined, using an antibody to Kit, ICC‐MY were found to be present at the greater curvature but were greatly reduced in density at the lesser curvature. In contrast, ICC‐IM were found in the circular layer of each region. When recordings were made from the antrum of W/WV mice, which lack ICC‐IM, incomplete slow waves were detected and their amplitudes fell from the greater to the lesser curvature. Again, a corresponding fall in the density of ICC‐MY was detected. The observations indicate that the contribution of ICC‐MY and ICC‐IM to the generation of slow waves varies in different regions of the mouse gastric antrum.
Regenerative component of slow waves in the guinea‐pig gastric antrum involves a delayed increase in [Ca2+]i and Cl− channels
Authors: Hirst G. D. S. , Bramich N. J. , Teramoto N. , Suzuki H. , Edwards F. R.
Published: July 2002

Regenerative potentials were initiated by depolarizing short segments of single bundles of circular muscle isolated from the gastric antrum of guinea‐pigs. When changes in [Ca2+]i and membrane potential were recorded simultaneously, regenerative potentials were found to be associated with an increase in [Ca2+]i, with the increase starting after a minimum latency of about 1 s. Although the increase in [Ca2+]i was reduced by nifedipine, the amplitudes of the regenerative responses were little changed. Regenerative responses and associated changes in [Ca2+]i were abolished by loading the preparations with the Ca2+ chelator MAPTA‐AM. Regenerative potentials were abolished by 2‐aminoethoxydiphenyl borate (2APB), an inhibitor of IP3 induced Ca2+ release, by N‐ethylamaleimide (NEM), an alkylating agent which blocks activation of G‐proteins and were reduced in amplitude by two agents which block chloride (Cl−)‐selective channels in many tissues. The observations suggest that membrane depolarization triggers IP3 formation. This causes Ca2+ release from intracellular stores which activates Ca2+‐dependent Cl− channels.
An Investigation of Material Removal Mechanisms in Lapping with Grain Size Transition
Authors: Chang Y. P. , Hashimura M. , Dornfeld D. A.
Published: July 2002

The mechanical material removal (MRR) mechanisms in lapping were investigated, using concepts of two-body vs. three-body abrasion and ductile vs. brittle machining. The statistical nature of the depth of cut in the lapping process was described using distribution of abrasive sizes in the slurry. Through the change in abrasive size distribution, the time dependent characteristic of MRR was captured in the model. Experiments were conducted for model verification. It was found that a constant 60 deg effective inclusion angle allowed the model to fit measurement well. [S1087-1357(00)00504-9]
Natural Gas Fired Combined Cycles With Low CO2 Emissions
Authors: Chiesa Paolo , Consonni Stefano
Published: July 2002

This paper assesses performances and economic viability of CO2 removal by chemical absorption from the flue gases of natural gas-fired Combined Cycles, more specifically for two configurations: one where CO2 is removed ahead of the stack without modifying the power cycle; the other where part of the flue gases is recirculated to the gas turbine, thereby reducing the flow to be treated by chemical absorption. In both cases sequestered CO2 is made available at conditions suitable to storage into deep oceanic waters. Performances and cost of electricity are evaluated for systems based on large, heavy-duty turbines representative of state-of-the-art “FA” technology. Carbon sequestration reduces net plant efficiency and power output by about 10 percent and increases the cost of electricity from 36 to about 50 mills/kWh. Flue gas recirculation warrants slightly higher efficiencies and lower costs. CO2 removal is eventually compared with other strategies for the reduction of CO2 emissions, like switching existing coal-fired steam plants to natural gas or replacing existing steam plants with conventional CCs. At current fuel prices the latter appears the option of choice, with a cost of about $25 per tonn of avoided CO2 emission. [S0742-4795(00)02803-9]
Handling of a Semiclosed Cycle Gas Turbine With a Carbon Dioxide-Argon Working Fluid
Authors: Ulizar Inaki , Pilidis Pericles
Published: July 2002

This paper outlines the handling of a semi-closed cycle gas turbine, its working fluid is carbon dioxide and the fuel is low heating value gas from coal; however, at startup air and natural gas are used. The objective of the machine is to produce clean electricity with the smallest efficiency penalty. Many aspects of the operation of the engine are examined in this paper; these include starting requirements, stator vane and bleed valve scheduling, and the working fluid transition from air to carbon dioxide. Other features highlighted are the compressor operating lines and surge margins. The present paper describes the salient features of the three main stages into which the engine operation has been divided. These stages are: startup to synchronous idle, change of working fluid (from air to Carbon Dioxide-Argon) and fuel (from natural gas to coal synthetic gas) at synchronous idle, and part load operation. Preliminary findings show that engine handling can be carried out effectively with variable stators. This is possible because of the two-shaft gas generator. Another point of interest is the large increase of corrected speed relative to rotational speed experienced when the working fluid changes from air to carbon dioxide. In general the control of the engine does not seem to present any insurmountable problems despite the complexities arising from the need to change working fluid and fuel. [S0742-4795(00)02903-3]
Effect of Coating Geometry on Contact Stresses in Two-Dimensional Discontinuous Coatings
Authors: Ramachandra Sunil , Ovaert Timothy C.
Published: July 2002

Recent experimental investigations have shown that discontinuous coatings, characterized by island-like coating deposits on dissimilar substrates, can exhibit improved tribological performance over equivalent continuously-coated substrates. In this analysis, the effect of coating geometry on the normal contact pressure profile was examined for several two-dimensional discontinuous coatings using a numerical elastic stress model. Normal pressure singularities were found for discontinuous coatings having both sharp and rounded edges. However, when crowned discontinuous regions were examined, the normal pressure singularities were reduced or eliminated. Interfacial tensile stress, due to an imposed tangential friction force, was also investigated. The magnitude of this tensile stress (and stress singularities due to edge configuration) was most affected by the friction coefficient and by the discontinuous coating geometry in the middle of the contact region, where the normal contact pressure was the highest. The discontinuous coating has the potential to provide reservoirs of sacrificial solid lubricants, which wear away with the coating itself, providing a friction-reduction mechanism over the life of the coating reducing the interfacial tensile stress which can lead to premature coating failure. [S0742-4787(00)01504-6]
Closure to “Discussion of ‘Turbulent Gas Injections’ ” (2000, ASME J. Fluids Eng., 122, p. 752)
Authors: Ouellette and P. , Hill P. G.
Published: July 2002

[S0098-2202(00)02604-3]
Optimum Active Vehicle Suspensions With Actuator Time Delay
Authors: Jalili Nader , Esmailzadeh Ebrahim
Published: July 2002

A new approach to optimal control of vehicle suspension systems, incorporating actuator time delay, is presented. The inclusion of time delay provides a more realistic model for the actuators, and the problem is viewed from a different perspective rather than the conventional optimal control techniques. The objective here is to select a set of feedback gains such that the maximum vertical acceleration of the sprung mass is minimized, over a wide band frequency range and when subjected to certain constraints. The constraints are dictated by the vehicle stability characteristics and the physical bounds placed on the feedback gains. Utilizing a Simple Quarter Car model, the constrained optimization is then carried out in the frequency domain with the road irregularities described as random processes. Due to the presence of the actuator time delay, the characteristic equation is found to be transcendental rather than algebraic, which makes the stability analysis relatively complex. A new scheme for the stability chart strategy with fixed time delay is introduced in order to address the stability issue. The stability characteristics are also verified utilizing other conventional methods such as the Michailov technique. Results demonstrate that the suspension system, when considering the effect of the actuator time delay, exhibits a completely different behavior.
Precise Solutions for Surface Wave Propagation in Stratified Material
Authors: Zhong Wanxie , Howson W. P. , Williams F. W.
Published: July 2002

A precise integration algorithm is proposed to solve the differential equation of surface wave propagation for stratified anisotropic material. The method can easily be extended to 3D wave problems. The numerical result is exact in the sense that it depends only on the precision of the host computer.
Transfer Matrix Method of Wave Propagation in a Layered Medium With Multiple Interface Cracks: Antiplane Case
Authors: Wang Y.-S. , Gross D.
Published: July 2002

The paper develops a universal method for SH-wave propagation in a multilayered medium with an arbitrary number of interface cracks. The method makes use of the transfer matrix and Fourier integral transform techniques to cast the mixed boundary value problem to a set of Cauchy singular integral equations of the first type which can be solved numerically. The paper calculates the dynamic stress intensity factors for some simple but typical examples.
Performance Characteristics of a Low Heat Rejection Direct-Injection Military Diesel Engine Retrofitted With Thermal Barrier Coated Pistons
Authors: Schihl P. , Schwarz E. , Bryzik W.
Published: July 2002

A special two-cylinder military specific power plant was employed to evaluate the effect of thermal barrier coated pistons on overall engine performance at simulated low heat rejection-type operating conditions. This study focused on three combustion systems including a noncoated baseline ductile iron piston along with zirconia and chrome-oxide sealed zirconia coated analogs. For the test matrix encompassing ten full and half-load operating conditions, both coated piston combustion systems yielded a detrimental effect on fuel economy in comparison to the baseline combustion system at constant fueling and air consumption rates. These performance differences were attributed to a combination of combustion phasing modulations, injection timing discrepancies, and sluggish combustion associated with the zirconia coated piston configurations.
Temperature Distribution in Advanced Power Electronics Systems and the Effect of Phase Change Materials on Temperature Suppression During Power Pulses
Authors: Evans A. G. , He M. Y. , Hutchinson J. W. , Shaw M.
Published: July 2002

A thermal analysis has been performed for a package design pertinent to power electronics. The objective has been the derivation of straightforward expressions that relate the materials used and their physical dimensions to the power input and the junction temperature. This has been done for both steady-state operating conditions and for pulses. The role of phase change materials (PCMs) in suppressing temperature elevations during pulses is also addressed.
Modern Wind Power Plant in Minnesota
Authors: Dunlop John
Published: July 2002

Wind on Minnesota’s southwestern prairie supplies electricity to Minneapolis and St. Paul. At the time this 143-wind turbine, 107 MW project was brought on line in 1998, it was the largest in the U.S. It was superceded by a project in Iowa that began operating in June of 1999. The turbine blades are 50 meters in diameter and mounted on towers 50 meters high. Each 750 kW turbine generates enough electricity for 260 homes. The 143 turbines are expected to produce about 300 GWhr of electricity per year. Minnesota has led the nation in new wind power installations over the past decade, followed closely by Iowa. California still has the largest installed capacity of any state due to the installation of numerous projects in the early 1980s.
Fracture Toughness Requirements for ASME Section VIII Vessels for Temperatures Colder Than 77K
Authors: Rana Mahendra D. , Doty W. D. , Yukawa Sumio , Zawierucha Robert
Published: July 2002

Earlier research work conducted at MIT and NIST indicated that CVN specimens with an initial temperature at or near 4K (−452°F) actually fracture at temperatures significantly above 4K due to adiabatic heating. As a result of this work, ASTM E-23 test method on CVN testing was revised to incorporate a restriction that CVN tests are valid only at 77K (−320°F) and warmer. ASME requested PVRC to assess the above CVN issue and provide an appropriate recommendation for the Code change or for a further Code change, if needed for vessels with MDMT colder than 77K. PVRC formed a Task Group under the Committee on Failure Modes. The TG undertook a program which included a review of the existing data and an experimental program to develop new KIcJ data at 4K and 77K and CVN data at 77K. In the experimental program, a total of four 1-in-thick weldments were prepared from SA 240, Type 304 stainless steel plate using the SMAW process and E316L-15 electrodes. The electrodes purchased permitted the preparation of the weldments with four progressively higher levels of ferrite. The PVRC data and existing data were utilized in developing the recommendations to ASME. The recommendations are: use CVN tests (with 316L S.S. weld filler metal with FN⩽5) at 77K with increased acceptance criterion of 21 mils lateral expansion; for welds not meeting the foregoing requirements, use ASTM E1820 JIc tests at MDMT and the acceptance criterion for KIcJ has been set at 120 ksi√in. This paper presents the test data, analysis and technical basis for the PVRC recommendations to ASME.
Theoretical Analysis of Transitional and Partial Cavity Instabilities
Authors: Watanabe Satoshi , Tsujimoto Yoshinobu , Furukawa Akinori
Published: July 2002

This paper describes a new time marching calculation of blade surface cavitation based on a linearized free streamline theory using a singularity method. In this calculation, closed cavity models for partial and super cavities are combined to simulate the transitional cavity oscillation between partial and super cavities. The results for an isolated hydrofoil located in a 2-D channel are presented. Although the re-entrant jet is not taken into account, the transitional cavity oscillation with large amplitude, which is known to occur when the cavity length exceeds 75 percent of the chord length, was simulated fairly well. The partial cavity oscillation with relatively high frequency was simulated as damping oscillations. The frequency of the damping oscillation agrees with that of a stability analysis and of experiments. The present calculation can be easily extended to simulate other cavity instabilities in pumps or cascades.
Development of Constrained Equilibrium Codes and Their Applications in Nonequilibrium Thermodynamics
Authors: Bishnu Partha S. , Hamiroune Djamel , Metghalchi Mohamad
Published: July 2002

Two constrained equilibrium codes, GNASA and GSTANJAN, have been developed which determine the composition of constrained equilibrium gas mixture. These codes use NASA and STANJAN equilibrium programs as the basis for generalized equilibrium routines. Gas mixture composition is determined by minimizing Gibbs free energy of the mixture subject to any specified constraints in addition to elemental constraints. Performances of these two codes have been compared to each other, and it has been found that GSTANJAN converges over a wider range of constraints, while the convergence of GNASA is limited. These codes have been applied in nonequilibrium evolution process of hydrogen-oxygen mixture. The nonequilibrium process has been modeled by using only two constraints in addition to elemental constraints. The results are in good agreement with detailed kinetic solution.
Computational Design of Vibration Pumping Device for Artificial Heart
Authors: Kawano Satoyuki , Yamakami Junko , Kamijo Kenjiro , Hashimoto Hiroyuki , Yambe Tomoyuki , Nitta Shin-ichi
Published: July 2002

To develop the prototype vibration pumping device for an artificial heart (Hashimoto et al., 1994, ASME J. Fluids Eng., 116, pp. 741–745), the flow patterns in the casing were analyzed experimentally and numerically from the viewpoint of biomechanical engineering. Considering not only the mechanical performance of the pump, but also the hemolysis, was very important to design the artificial heart. In the present study, the curvilinear coordinate transformation technique and the finite difference technique were used to numerically solve the unsteady, incompressible, and axisymmetric Navier-Stokes equations for the flow field in the various casing configurations of the vibration pumping device. The validity of numerical analysis was confirmed by comparison with the experimental data obtained by the flow visualization technique. Furthermore, the strong dependence of the hemolysis on the flow patterns in the casing was recognized. In particular, the relationship between the vorticity field in the casing and the hemolysis was elucidated. The results obtained here would provide the useful suggestions for future research and the basic design concept of vibration pumping device for the left ventricular assist device.
Design Optimization of Cementless Femoral Hip Prostheses Using Finite Element Analysis
Authors: Kowalczyk Piotr
Published: July 2002

Implant separation from bone tissue, resulting in the necessity for revision surgery, is a serious drawback of cementless total joint replacement. Unnatural stress distribution around the implant is considered the main reason for the failure. Optimization of the implant properties, especially its geometric parameters, is believed to be the right way to improve reliability of joint prosthetics. An efficient numerical model of the femur–implant system is presented in the paper, including the finite element formulation featuring computation of sensitivity gradients, parametric mesh generator, and a gradient-based optimization scheme. Numerical examples show results of shape optimization of an implant for two sets of design parameters and for the initial stability criterion taken as the optimization goal. The optimum shape appears to be relatively long and proximally porous-coated on about half of its length. The method can be flexibly adjusted to various implant types, stress- and displacement-based optimum criteria, and geometric design parameters.
Experimental Evaluation of a High-Gain Control for Compressor Surge Suppression
Authors: Blanchini Franco , Giannattasio Pietro , Micheli Diego , Pinamonti Piero
Published: July 2002

The present paper considers the suppression of surge instability in compression systems by means of active control strategies based on a high-gain approach. A proper sensor-actuator pair and a proportional controller are selected that, in theory, guarantee system stabilization in any operating condition for a sufficiently high value of the gain. Furthermore, an adaptive control strategy is introduced that allows the system automatically to detect a suitable value of the gain needed for stabilization, without requiring any knowledge of the compressor and plant characteristics. The control device is employed to suppress surge in an industrial compression system based on a four-stage centrifugal blower. An extensive experimental investigation has been performed in order to test the control effectiveness in various operating points on the stalled branch of the compressor characteristic and at different compressor speeds. On one hand, the experimental results confirm the good performance of the proposed control strategy; on the other, they show some inherent difficulties in stabilizing the system at high compressor speeds due to the measurement disturbances and to the limited operation speed of the actuator.
Extension of the STEP Standard for Parametric CAD Models
Authors: Pratt Michael J.
Published: July 2002

The first Technical Note in this series [1] introduced the international standard ISO 10303, informally known as STEP, and the second [2] dealt with some practical aspects of using the standard for the exchange of CAD models. It was noted in [1] that the current published parts of the standard are restricted to the representation and exchange of non-parameterized models. The present contribution discusses the implications of that restriction and describes the progress of the ISO TC184/SC4 committee towards its removal. As will be shown, this extension of the STEP standard will lead to considerable benefits for industry.
Laminar Mixed Convection Adjacent to Three-Dimensional Backward-Facing Step
Authors: Li and A. , Armaly B. F.
Published: July 2002

Simulations of three-dimensional laminar buoyancy-assisting mixed convection adjacent to a backward-facing step in a vertical rectangular duct are presented to demonstrate the influence of Grashof number on the distributions of the Nusselt number, and the reverse flow regions that develop adjacent to the duct’s walls. The Reynolds number, and duct’s geometry are kept constant: heat flux at the wall downstream from the step is kept uniform but its magnitude varied to cover a Grashof number range of 0–4000; all the other walls in the duct are kept at adiabatic condition; and the flow, upstream of the step, is treated as fully developed and isothermal. Increasing the Grashof number results in increasing the Nusselt number; the size of the secondary recirculation flow region adjacent to the stepped wall; the size of the reverse flow region adjacent to the sidewall and the flat wall; and the spanwise flow from the sidewall toward the center of the duct. On the other hand, the size of the primary recirculation flow region adjacent to the stepped wall decreases and detaches partially from the heated stepped wall as the Grashof number increases. Details are presented and discussed.
Large Eddy Simulation of Turbulent Wake Behind a Square Cylinder With a Nearby Wall
Authors: Liou Tong-Miin , Chen Shih-Hui , Hwang Po-Wen
Published: July 2002

Computations of the time-averaged and phase-averaged fluid flow and heat transfer based on large eddy simulation (LES) are presented for turbulent flows past a square cylinder with and without a nearby wall at a fixed Reynolds number of 2.2×104. The finite-volume technique was used to solve the time-dependent filtered compressible Navier-Stokes equations with a dynamic subgrid-scale turbulence model, and the numerical fluxes were computed using alternating in time the second-order, explicit MacCormack’s and the modified Godunov’s scheme. Results show some improvements in predicting the streamwise evolutions of the long-time-averaged streamwise mean velocity and total fluctuation intensity along the centerline over those predicted by using Reynolds stress models. A better overall centerline streamwise mean velocity distribution is also predicted by the present LES than by other LES. The wall proximity effect is studied through the comparison of turbulent wake flow past one free standing cylinder and one with a nearby wall, and is illustrated by the phase-averaged spanwise vorticity components and the vortex celerity of spanwise vortices. Moreover, documentation is given on the mechanisms responsible for the augmentation of heat transfer through the spanwise and longitudinal vortices as well as periodic and random fluctuations.
A Quantitative Model of Cellular Elasticity Based on Tensegrity
Authors: Stamenovic´ Dimitrije , Coughlin Mark F.
Published: July 2002

A tensegrity structure composed of six struts interconnected with 24 elastic cables is used as a quantitative model of the steady-state elastic response of cells, with the struts and cables representing microtubules and actin filaments, respectively. The model is stretched uniaxially and the Young’s modulus E0 is obtained from the initial slope of the stress versus strain curve of an equivalent continuum. It is found that E0 is directly proportional to the pre-existing tension in the cables (or compression in the struts) and inversely proportional to the cable (or strut) length square. This relationship is used to predict the upper and lower bounds of E0 of cells, assuming that the cable tension equals the yield force of actin (∼400 pN) for the upper bound, and that the strut compression equals the critical buckling force of microtubules for the lower bound. The cable (or strut) length is determined from the assumption that model dimensions match the diameter of probes used in standard mechanical tests on cells. Predicted values are compared to reported data for the Young’s modulus of various cells. If the probe diameter is greater than or equal to 3 μm, these data are closer to the lower bound than to the upper bound. This, in turn, suggests that microtubules of the CSK carry initial compression that exceeds their critical buckling force (order of 100-101 pN), but is much smaller than the yield force of actin. If the probe diameter is less than or equal to 2 μm, experimental data fall outside the region defined by the upper and lower bounds. [S0148-0731(00)00101-1]
Numerical Simulation of a Heat-Treated Ring Gear Blank
Authors: Mgbokwere C. , Callabresi M.
Published: July 2002

Carburization and quenching of steels in general has been and continues to be an important commercial manufacturing process for steel components. The minimization of distortion, cracking, and residual stresses are major issues that need to be properly understood in order to efficiently produce high quality components. To assist process engineers in understanding the effect process parameters have on these major issues, a numerical study was conducted on an automotive transmission ring gear. The ring gear has substantial ovaling distortion, which cannot always be straightened within the design tolerances of the part thereby leading to a 3–5 percent rejection rate. The purpose of this report is to predict the distortions, microstructural phase changes, residual stresses, and hardness that occur during quenching using finite element techniques. The ABAQUS model from the NCMS Heat Treatment Prediction Program was used to perform the simulations. This report describes a two-dimensional simulation of the gear blank with the wall thinned where the teeth would have been located to represent the proper thermal mass. The gear blank geometry is essentially the same as the gear geometry without the teeth; moreover it has the same dimensions exhibited by the gear. Even though the ovaling caused by distortion is a three-dimensional problem the two-dimensional representation was chosen as an initial step before simulating the more complex three-dimensional gear geometry. The symmetry of the blank can be exploited by allowing fewer elements to be used for the finite element analysis which in turn will decrease the simulation times of the problem. [S0094-4289(00)01103-8]
Vectoring Thrust in Multiaxes Using Confined Shear Layers
Authors: Alvi F. S. , Strykowski P. J. , Krothapalli A. , Forliti D. J.
Published: July 2002

A fluidic scheme is described which exploits a confined countercurrent shear layer to achieve multiaxis thrust vector response of supersonic jets in the absence of moving parts. Proportional and continuous control of jet deflection is demonstrated at Mach numbers up to 2, for pitch vectoring in rectangular nozzles and multiaxis vectoring in axisymmetric nozzles. Secondary mass flow rates less than approximately 2% of the primary flow are used to achieve thrust vector angles exceeding 15 degrees. Jet slew rates up to 180 degrees per second are shown, and the fluidic scheme is examined in both static and wind-on configurations. Thrust performance is studied for external coflow velocities between Mach 0.3 and 0.7. [S0098-2202(00)02601-8]
Editorial
Authors: Bergman Larry
Published: July 2002

[S0739-3717(00)01302-7]
A Study of Solid CO2 by XPS
Authors: Dillingham T. R. , Cornelison D. M. , Galle K. , Tegler S. C. , Lutz B. L.
Published: July 2002

High quality solid CO2 films have been grown on a stainless steel cold-finger using a continuous flow liquid nitrogen system. The solid was formed from research grade (99.995% min. purity) CO2 gas using a gas nozzle placed directly over the cold-finger (at a temperature of approximately 77 K). The base pressure in the chamber was less than 5 × 10−10 T prior to deposition and upon gas introduction was increased, using a precision leak valve, to approximately 5 × 10−8 T. Films were grown in this pressure for 1 h. Gas purity was monitored using a Balzers Prisma QMS 300 quadrapole mass spectrometer. The solid CO2 films were characterized using x-ray photolelectron spectroscopy (XPS). The reported spectra include survey and high resolution scans for the major photoelectron peaks.
Commercially Pure Titanium and Ti6Al4V: XPS Comparison Between Different Commercial Ti Dental Implants and Foils Prepared by Various Oxidation Procedures
Authors: Aronsson B.-O. , Krozer A. , Lausmaa J. , Kasemo B.
Published: July 2002

Commercially pure (c.p., 99.6%) titanium and the Ti6Al4V alloy are widely used in biomedical applications. The surface (oxide) properties of these materials play a key role for their function in biomaterial applications, and it is therefore important to analyze their surface composition. XPS survey and high resolution spectra (Ti 2p, O 1s, and C 1s) are presented from three commercially available dental implants, all manufactured by machining but with different post treatments (grit blasting, cleaning, sterilizing, and packaging). Comparison is made with a TiO2 single crystal (rutile (110)) reference sample, and with Ti and Ti6Al4V foils prepared by the following treatments commonly used for titanium biomaterials: ASTM F86/B600 passivation, electropolishing in perchloric acid based electrolyte, anodization in sulfuric acid and phosphoric acid, and glow discharge plasma oxidation. Survey spectra from the implants are qualitatively similar but quantitatively different, with Ti, O, and C as the main elements and trace amounts of preparation-specific impurities. The high resolution spectra show differences in oxide composition (varying deviations from pure TiO2 stoichiometry), thickness, and carbon overlayer composition. Spectra from the differently prepared Ti and Ti6Al4V foils showed preparation-specific differences mainly with respect to oxide composition, oxide thickness, and trace impurities. For the Ti6Al4V the different preparations lead to various amounts of detected Al. A general difference between the differently prepared Ti and Ti6Al4V foils was that Al and V were always detected on the latter, but only sporadically on the Ti. These results clearly show that the composition of titanium surfaces varies considerably depending on the surface preparation used. Important implications are: (i) surface preparation and characteristics need to be considered when results from biological studies on Ti surfaces are interpreted and compared, (ii) Ti and Ti6Al4V form oxides with different composition, and (iii) different commercial Ti implants cannot a priori be assumed to have similar surface composition.
Stability of Schottky contacts with Ta–Si–N amorphous diffusion barriers and Au overlayers on 6H–SiC
Authors: Shalish I. , Shapira Yoram
Published: July 2002

The thermal stability of two sputter-deposited Schottky contact metallizations incorporating Ta–Si–N amorphous diffusion barriers and Au overlayers are compared using depth profiling by backscattering spectrometry and secondary ion mass spectrometry as well as current–voltage measurements. A 〈6H–SiC〉/TaSi2/Ta20Si40N40/Au metallization changes its Schottky barrier height from 0.71 to 0.62 eV upon annealing at 600 °C for 30 min, while its ideality factor improves from an initial value of 1.55 to 1.16. Both Schottky barrier height and ideality factor remain stable upon successive annealing of the sample at 700 °C for 30 min and for an additional 90 min. The observed stability is attributed to the thermal stability of TaSi2 with SiC and to the effectiveness of the Ta–Si–N diffusion barrier evidenced in backscattering depth profiles. On the other hand, a 〈6H–SiC〉/Ta36Si14N40/Au metallization that does not include the silicide contacting layer becomes ohmic after vacuum annealing at 600 °C for 30 min, while no signs of metallurgical interaction are observed in its backscattering spectra. Using secondary ion mass spectrometry, diffusion of nitrogen is observed from the Ta–Si–N layer into the 6H–SiC substrate. It is tentatively suggested that nitrogen penetrates the substrate through defects, induced in the sputter-deposition process.
Enhancement of resolution of DNA on silylated mica using atomic force microscopy
Authors: Tang Jing , Li Junwei , Wang Chen , Bai Chunli
Published: July 2002

It is demonstrated that the mica surface covered with a nanometer-thick, well connected silane film can appreciably improve the lateral resolution of DNA molecules in comparison with that on bare mica using atomic force microscopy. A typical value width of 4 nm can be obtained. We propose that the nanometer dimensioned porous surface provides an approach to eliminate the hydrated salt layer associated with the condensation of DNA strands, and leads to the enhancement of lateral resolution.
Insulator Films and Their Interfaces in Semiconductor Devices
Authors: Nicollian E. H.
Published: July 2002

Grown thin films of SiO2 play an important role in the performance and stability of silicon insulated gate field effect transistors, bipolar transistors, and diodes used in modern integrated circuits. The principal properties of the Si–SiO2 system which can influence device characteristics are fixed charge, interface states and drift. Fixed charge and interface states can adversely affect device characteristics like gain, noise, junction reverse currents, and junction breakdown voltage, while drift undermines the stability of these device characteristics. Our present understanding of some of the chemistry and physics of the Si–SiO2 system pertaining to device performance and stability will be reviewed. The metal-oxide–silicon capacitor has been the principal measurement tool used in this work. Its operation and how it was used to determine the oxide growth conditions, annealing treatments, and other processing required to get low fixed charge and interface state densities and minimum drift will be emphasized.
Surface Segregation Studies in Alloys Using Auger Electron Spectroscopy
Authors: Dooley George J.
Published: July 2002

Several metals used in the nuclear field are found to be lacking in one or more respects when these metals are employed in their pure or unalloyed state. For a variety of reasons, minor alloying additions are often added to these pure metals. However, the basic role played by these alloying elements is not well understood. By utilizing the technique of Auger electron spectroscopy on zircaloy-2 and zircaloy-4, it has been possible to make correlations between observed surface phenomena (of both impurity and alloy species) and previously established mechanical properties, such as a strain rate sensitivity around 300 °C in the zircaloys, and also chemical properties such as the build-up of an oxide layer above 300 °C in these same zirconium alloys.
Experimental Investigation of the Cylindrical Mirror Analyzer with a 2π-Thermionic Electron Source
Authors: Bas E. B. , Bänninger U. , Keller P.
Published: July 2002

An experimental setup for the investigation of a cylindrical mirror analyzer is described. It makes possible precise displacements of the analyzing slit in the axial direction and of the electron source in the axial and two radial directions under operational conditions. A special spherical electron gun construction is used for the realization of a virtual electron source of small radial extension and with an isotropic emission in the hemispheric solid angle of 2π. The preliminary results show that for each axial position of the source close to the injection angle of α=42.3° there can be found a best-focus position of the slit with approximately the same half-height-width resolution of about 0.7% (for Δα=6°). If the meridional opening angle of the electron beam is reduced from Δφ=2π to Δφ=8°, the resolution improves to 0.5%. However, the axial position of the focus is dependent on the meridional position of the Δφ slit. This indicates that the residual magnetic field in the mumetal screened analyzer and other assymetries are affecting the electron paths. The radial displacement of the source can disturb considerably the electron density distribution at the focus.
Ion Implantation and Analysis of Thin Film Structures by Backscattering of MeV Particles
Authors: Mayer James W.
Published: July 2002

Ion implantation has been developed to the point where it is used in production of silicon devices for integrated circuit applications. This paper reviews the basic factors influencing the electrical behavior of dopant species implanted in silicon. Implantation in compound semiconductors, primarily III–V compounds, is not as well defined, but clear guidelines can be established. One of the key factors in untangling implanation phenomena was the use of backscattering and channeling effect measurements with MeV particles to determine the amount and anneal behavior of lattice disorder and the lattice position of dopant atoms. This technique has now been applied to the analysis of layer structures, because it provides both mass information and depth distributions (≈200 Å resolution down to ≈1 μ). We have investigated properties of dielectric layers [SiO2, Si2N4, and Al2O3), magnetic films, and diffusion in both semiconductors and oxide layers.
Vacuum Problems on a 5-GeV Electron Synchrotron
Authors: Halliday B. S. , Trickett B. A.
Published: July 2002

A number of problems arise in the design, commissioning and subsequent running of the vacuum system of a large synchrotron. The problems dealt with are (a) high water desorption from ferrite materials, (b) the use of a data logging computer for ion pump starting and pressure monitoring, (c) the protection of the system due to turbomolecular pump set failure when running unattended, (d) the reconditioning of ion pumps, and (e) radiation damage to early design vacuum chambers and outgassing due to synchrotron radiation.
Vacuum System for Irradiation Studies
Authors: Basham S. J. , Zielenbach W. J.
Published: July 2002

An oil-free vacuum system capable of achieving vacuum levels of 10−6 Torr for in-pile experiments has been constructed at the pool-type Battelle Research Reactor (BRR). The pumping system which is mounted on a moveable bridge above the pool surface, consists of a 7500 liter/sec titanium sublimation pump and two 350-liter/sec triode-type ion pumps; system roughing is accomplished with a roots-type blower with a double-walled liquid nitrogen trap. Nine meters of 20.3-cm (8-in.) diam vacuum piping connect the pumping system to a test chamber at the core level. Test chamber geometry can be varied to fit either a 7.62×7.62-cm test cell or the core face. Neutron fluxes of 2×1013 neutron/cm2⋅sec (thermal) and 1×1013 neutron/cm2⋅sec (fast) are available and the maximum gamma rate is 108 R/h. Adjustments of desired gamma/neutron ratio are made by employing appropriate shielding at the core face. Irradiation effects on the performance of electro-mechanical components for space nuclear power systems have been studied at elevated temperatures (620–820 K) and a full-scale nuclear fueled thermionic diode is currently being prepared for irradiation in the system.
Thermal Transpiration Error in Absolute Pressure Measurement with Capacitance Manometers
Authors: Baldwin George C. , Gaerttner Martin R.
Published: July 2002

Readings of two Baratron capacitance manometers with sensors at unequal temperatures, when compared over a wide range of pressures in helium and nitrogen, demonstrate appreciable nonlinearity caused by thermal transpiration. The asymptotic indication ratio at low pressure, 1.026±0.002, is approximately double the value reported by Bromberg, but considerably less than the Knudsen ratio for apertures. The data can be fitted to the Liang Equation, but the coefficients are sensitive to the geometry of the apparatus in the region of temperature transition.
Access to Uncombined Titanium through an Inhibiting Film in Sublimation Pumping of Deuterium
Authors: Steinberg Robert , Alger Donald L.
Published: July 2002

In principle, titanium bulk sublimator pumping should be ideal for removing large quantities of deuterium from a vacuum system. In practice, much of the depositied titanium remains uncombined and is wasted. We have demonstrated, through a series of experiments, that it is possible (by the addition of a thin layer of titanium to an apparently occluded surface) to gain access to previsouly deposited sublayers of uncombined titanium in spite of the presence of an inhibiting film (such as an oxide) on the surface.
Spatial Distribution of CO2 and H2O Molecules on Reflection and Sublimation from a Cold Surface
Authors: Bryson C. E. , Cazcarra V. , Levenson L. L.
Published: July 2002

An effusive molecular beam, a copper target, and several quartz crystal microbalances were used to measure the spatial distributions of reflected and sublimated CO2 and H2O molecules. These spatial distributions were found to be identical for surface temperatures ranging from 55 to 210 K for CO2 and from 55 to 160 K for H2O, and for gas temperatures below 300 K. Experimental results agreed with the diffuse cosine law spatial distribution within the accuracy of the measurement.
CNDO model and interpretation of the photoelectron spectrum of CO chemisorbed on Ni
Authors: Blyholder G.
Published: July 2002

CNDO calculations for CO chemisorbed on a cluster of 10 Ni atoms produce a pattern of valence orbital energy levels that agrees well with the experimental photoelectron spectrum of CO adsorbed on Ni; thus allowing the experimental energies to be assigned to specific orbitals. The bonding of the carbon atom to the Ni atom largely involves nickel s and p orbitals, with little contribution from the d orbitals.
Design and Analysis of a Laser Oriented, Automatic Dimensional Inspection System for High-Speed Process Control
Authors: Ward Steven M. , Brew Patrick H.
Published: July 2002

Recent advances in the technology of high-speed manufacturing systems have introduced the need for a new approach in the design of process control systems. Computerized process control systems require automatic quality inspection stations which are capable of converting measures of product attributes into electronic information. In this study, a noncontact, electro-optic inspection system was developed which automatically measures product outer dimension at high speeds. Two approaches were taken in the system design. One approach required a photodetector as an analog measuring device, and the other utilized a photodiode matrix as a digital measuring device. The performance capability of each system was in the order of 100% detection of outer dimensions that were 0.01 in. out of specification to 97% for 0.001 in. variations. Both design approaches resulted in fast, accurate, and inexpensive inspection systems which could easily be adapted to most production environments.
The Fabrication of Bipolar Transistors using Electron Lithography, Ion Implantation, and Nickel-Masked Gold Metallization
Authors: Shackle P. W. , Payne R. S.
Published: July 2002

Bipolar microwave transistors have been fabricated using ion implantation and electron lithography, with a sputter-etched nickel-masked gold metallization process as originally developed by Herb and Labuda. The resulting devices showed the fine definition associated with the latter two technologies, together with the uniformity of electrical properties associated with ion implantation. The electrical properties of the transistors were found to be comparable to similar devices also made with ion implantation but employing conventional photolithography and electroplated gold metallization. It is suggested that the combination of technologies illustrated in the work will be generally applicable to bipolar integrated circuits.
Integrated atomic force microscopy array probe with metal–oxide–semiconductor field effect transistor stress sensor, thermal bimorph actuator, and on-chip complementary metal–oxide–semiconductor electronics
Authors: Akiyama T. , Staufer U. , de Rooij N. F. , Lange D. , Hagleitner C. , Brand O. , Baltes H. , Tonin A. , Hidber H. R.
Published: July 2002

A microfabricated 2×1 array of active and self-detecting cantilevers is presented for applications in atomic force microscopy (AFM). The integrated deflection sensor is based on a stress sensing metal–oxide–semiconductor transistor. Full custom complementary metal–oxide–semiconductor amplifiers for signal readout are combined on the same chip. A sensor sensitivity of 2.25 mV/nm, or a change in current ΔId/Id=2.8×10−6/nm, was obtained at the final output stage. Three Al–Si thermal bimorph actuators are integrated on each cantilever for self-excitation and feedback actuation. The efficiencies of the heaters are 2.4–4.7 K/mW. In the experimental setup, a maximum displacement of 8 μm was achieved at 45 mW input. A pair of parallel AFM images in the constant height mode, a typical tapping mode image, and a constant force image with 1.3 μm high features have been successfully taken with the array probe.
Oxide phosphor thin-film electroluminescent devices fabricated by magnetron sputtering with rapid thermal annealing
Authors: Minami Tadatsugu , Toda Hidenobu , Miyata Toshihiro
Published: July 2002

A procedure for producing high-luminance thin-film electroluminescent (TFEL) devices with an oxide phosphor thin-film emitting layer prepared without high-temperature postannealing is described. The TFEL devices were fabricated by depositing an oxide phosphor thin film onto a thick BaTiO3 ceramic sheet insulator using magnetron sputtering and in situ rapid thermal annealing (RTA). The oxide phosphor thin films were deposited by rf magnetron sputtering onto an insulating ceramic sheet mounted on a rotating platform; a thin film was deposited onto the ceramic sheet when it passed over the target, and subsequent in situ RTA was performed on the deposited film when it passed over the halogen lamps. High-luminance green emissions were obtained in TFEL devices using either a Ga2O3:Mn or a ZnGa2O4:Mn thin-film emitting layer prepared under optimized deposition conditions. A ZnGa2O4:Mn TFEL device driven at 1 kHz exhibited a luminance of 200 cd/m2.