bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Si(IV) substitution on the stability of microporous ZnAPSO-44 solid acid catalysts: a combined XAS/XRD study
Authors: Sankar Gopinathan , Muncaster Gavin , Gleeson David , Catlow C. Richard A. , Thomas John Meurig , Mosselmans J. Fred W. , Harvey Ian , Dent Andrew J.
Published: July 2002

The combined XAS/XRD technique has been used to investigate the stability of the microporous structure during calcination process for a series of ZnAPSO-44 materials. Incorporation of large amounts of Zn is found to produce materials that are unstable upon removal of the structure directing organic template molecule. However, simultaneous incorporation of Si is found to increase the thermal stability of the materials, yielding catalysts that are well suited for acid catalysed reactions.
Ion exchange and fixation of rare-earth cation into expandable tetrasilicic fluorine mica
Authors: Han Yang-Su , Choi Shin-Hei , Kim Dong-Kuk
Published: July 2002

Rare-earth cation (Nd3+) are incorporated into the interlayer spaces between the silicate layers of synthetic fluorine mica, Na0.665Mg2.68(Si3.98Al0.02)O10.02F1.98, by conventional ion exchange reaction. Subsequent migration of the interlayer cations upon calcination into the vacant octahedra of 2:1 layers is followed by powder X-ray diffraction, diffuse-reflectance UV spectroscopy, and X-ray absorption spectroscopy as a function of calcination temperature. It is found from the spectroscopic analyses that the interlayer cations start to migrate into the octahedral vacant sites from 400°C through the hexagonal siloxane ring of the tetrahedral silicate layers. According to the Nd LIII-edge XANES spectra, the normalized absorption intensity gradually decreases while the FWHM increases with temperature, suggesting that the bonding character of rare-earth cations and silicate lattices evolves from ionic to covalent as the calcination temperature increases.
XAFS and X-ray reflectivity study of III–V compound native oxide/GaAs interfaces
Authors: Cheong Seong-Kyun , Bunker Bruce A. , Hall D. C. , Snider G. L. , Barrios P. J.
Published: July 2002

Fluorescence-mode XAFS has been used to study the local environment about chosen atomic species such as Ga and As in bulk oxide Al1−x
Ga
x
As (x = 0.96) and at the interface between thin (300 Å) oxidized Al1−x
Ga
x
As (x = 0.94) film and GaAs substrate in total external-reflection mode. X-ray reflectivity experiments have also been employed to investigate the density profile of the oxide film on a GaAs substrate revealing the density profile as a function of depth. It is important to find out how the As is incorporated at the interface, the interfacial strain, and related local structural parameters for understanding that may be central in developing high performance III–V MOSFET devices.
Ethylenediammonium phthalate
Authors: Edwards Selvin H. , Kahwa Ishenkumba A. , Mague Joel T.
Published: July 2002

The phthalate salt of diprotonated ethylenediamine, C2H10N2+·C8H4O4−, was obtained during ongoing studies of the hydrolytic chemistry of phthalimides for the synthesis of efficient sensitizers for EuIIIand TbIIIphotoluminescence.
R,R-(+)-Bis[(3-benzyloxazolan-4-yl)methyl] disulfide
Authors: Schulz Lang Ernesto , Burrow Robert A. , Braga Antonio Luiz , Appelt Helmoz Roseniaim , Schneider Paulo Henrique , Silveira Claudio Cruz , Wessjohann Ludger A.
Published: July 2002

R,R-Bis[(3-benzyloxazolan-4-yl)-methyl] disulfide, C22H28N2O2S2, is a chiral disulfide which is a highly effective catalyst for the enantioselective addition of diethylzinc to aldehydes, including aliphatic ones. The molecule has crystallographic twofold rotation symmetry.
2-[(2-Phenyl-1,3-oxazol-4-yl)methyl]-2H-1,2,3-benzotriazole
Authors: Swaleh Sauda , Ziemer Burkhard
Published: July 2002

The title compound, C16H12N4O, was obtained through a two-step process. There are two molecules in the asymmetric unit with essentially equal bond lengths. The phenyl and oxazole rings are essentially coplanar. Steric interactions between the two halves of the molecule produce a wide angle at the central C atom.
Tris(N-cyclohexyl-N-methyldithiocarbamato-S)antimony(III)
Authors: Baba Ibrahim , Ibrahim Sukeria , Farina Yang , Othman A. Hamid , Razak Ibrahim Abdul , Fun Hoong-Kun , Ng Seik Weng
Published: July 2002

In the title compound, [Sb(C8H14NS2)3], the dithiocarbamate groups chelate to the Sb atom in an anisobidentate manner [Sb—S = 2.530 (1) and 2.975 (1) Å]. The Sb atom lies on a threefold axis and the lone pair is also stereochemically active.
Redetermination of 1,3-thiazolidine-2,4-dione
Authors: Lynch Daniel E. , McClenaghan Ian , Light Mark E.
Published: July 2002

The structure of the title compound, C3H3NO2S, comprises flat molecules that associateviaa single N—H...O interaction and a C—H...O close contact to the second O atom. Furthermore, 10% of the molecules have S and CH2interchanged, generating disorder.
Warburg impedance ‐ basics revisited
Authors: Muralidharan V.S.
Published: July 2002

Electrochemical impedance spectroscopy has become a very important tool in the analysis of an equivalent circuit of an electrochemical cell. Recently a new model was proposed by Taylor and Gileadi for the better understanding of the Warburg process. The model describes an equivalent circuit consisting of capacitance in series with resistance to replace the conventional Warburg impedance in the Randels equivalent circuit. Discusses the above model highlighting the defects in their assumption. Attempts to find a better understanding of the Warburg impedance and discusses various possibilities.
Relationship between the molecular structure and the inhibition performance of triazole compounds using electrochemical methods
Authors: Abdennabi A.M.S. , Abdulhadi A.I. , Abu‐Orabi S.
Published: July 2002

Corrosion inhibitors represent the most cost effective and flexible means of controlling internal corrosion associated with oil and gas production. Tests were carried out to demonstrate the structure/effect relationships which are effective in controlling the inhibition efficiency. To illustrate this approach, the substituent field effect at the paraposition of 1(Benzyl)1‐H‐4,5‐Dibenzoyl‐1,2,3‐ Triazole (BDBT) on corrosion inhibition has been investigated. Mild steel rotating cylinder electrode in acid media was used in conjunction with Tafel polarization technique, AC impedance measurements and continuous linear polarization resistance method. The nitro group was found to cause a considerable decrease in the corrosion inhibition of the parent compound BDBT. Owing to the induction effects of Br on the aromatic ring the bromo derivative has better inhibition protection than the methyl derivative. The corrosion rate profiles obtained from on‐line polarization technique showed that the inhibition capacity of the studied substituents at the para‐position increases as follows: NO2 < CH3 < Br < H.
Canonical correlation analysis of customer satisfaction and future purchase of mail‐order speciality food
Authors: Mai Li‐Wei , Ness Mitchell R.
Published: July 2002

Analyses customer satisfaction with mail‐order speciality foods in the UK and examines the relationship between satisfaction with eight attributes of mail‐order speciality food and their association with overall satisfaction and likelihood of future purchase. Univariate analysis reveals that a high proportion of mail‐order customers experience satisfaction with each of the eight mail‐order attributes, reflected in a high proportion of customers who are satisfied overall and who intend to repurchase the products in the future. Canonical correlation analysis reveals a statistically significant relationship between one set of variables, overall satisfaction and likelihood of future purchase, and another set of variables, the eight mail‐order attributes. Consequently the results indicate that customer satisfaction is associated with service aspects of mail‐order such as the order process and delivery service as well as physical product attributes such as product quality.
Organizational marriage: “hard” versus
“soft” issues?
Authors: Cartwright Sue , Cooper Cary L.
Published: July 2002

Discusses the substantial increase in merger and acquisition (M
& A) activity both domestically and internationally during the 1980s
which, in contrast to previous waves of M & A activity, involved
organizational marriages between organizations in the same area of
business activity. As a result, merger synergy has become increasingly
dependent on the wide‐scale integration of people and their
organizational cultures. Examines the potential role played by people,
the so called “soft” issues in merger success. Argues that
this distinction between “hard” (financial and strategic)
and “soft” issues is extremely unhelpful in reaching any
complete understanding of such complex phenomena.
Transformational leadership and emotional intelligence: an exploratory study
Authors: Barling Julian , Slater Frank , Kevin Kelloway E.
Published: July 2002

Investigated whether emotional intelligence (EQ) is associated with the use of transformational leadership in 49 managers. Managers completed questionnaires assessing their own emotional intelligence and attributional style; their subordinates (n = 187) provided ratings of their transformational leadership. Controlling for attributional style, multivariate analyses of covariance showed that three aspects of transformational leadership (i.e. idealized influence, inspirational motivation, and individualized consideration) and constructive transactions differed according to level of emotional intelligence. In contrast, no multivariate effects emerged for transactional leadership (i.e. laissez faire or management‐by‐exception). Some suggestions for future research are offered.
European assignments: international or quasi‐domestic?
Authors: Hippler Thomas
Published: July 2002

Seeks to investigate the adjustment of business relocatees to their host environment. It explores the facets of the relocatees’ adjustment in the following three regions: Germany as the home country and destination for domestic assignments, Western Europe and other countries. It further investigates the stress levels the relocatees display and their motives for accepting or actively seeking relocation. If the results of this survey suggest the existence of Western Europe as a distinct assignment location, these findings will form a valuable basis for the development of policies for intra‐European personnel transfers, particularly in the area of selection, training, development and compensation.
Exploring Web users’ optimal flow experiences
Authors: Chen Hsiang , Wigand Rolf T. , Nilan Michael
Published: July 2002

Characterizations of users’ experiences on the Web are beginning to appear. Recently released research suggests that Internet use may reduce psychological well‐being, for instance by increasing loneliness and depression. Our current study implies that using the Internet may provoke enjoyable experiences through the flow state, which may in turn positively influence an individual’s subjective well‐being and improve a person’s happiness, life satisfaction, and positive affect. By surveying 304 Web users through an open‐ended questionnaire, this study captures a picture of Web users’ flow experiences regarding their optimal situations on the Web. Results suggest that using the World Wide Web is an activity that facilitates flow, which generates an optimal, extremely enjoyable experience with total involvement and concentration. Symptoms and dimensions of flow states on the Web are reported directly from subjects’ responses, such as merging of action and awareness, a loss of self‐consciousness, the sense of time distortion, enjoyment, and telepresence.
A conceptual framework for the analysis of vulnerability in supply chains
Authors: Svensson Göran
Published: July 2002

A conceptual framework for the analysis of vulnerability in supply chains is developed. The conceptual framework is limited to the inbound logistic flow of manufacturers. The study has been performed as a two‐step process. Step one explores the concept of vulnerability from the point of view of an inductive approach. The conceptual framework is generated and based on the empirical findings from a case study of a Swedish car manufacturer in the automotive industry. Step two is deductive in terms of testing in other industries the generated conceptual framework that originates from step one. The conceptual framework consists of two dimensions, namely categories of disturbance and sources of disturbance. Principally, categories of disturbance are divided into quantitative and qualitative disturbances. Sources of disturbance are divided into atomistic (direct) and holistic (indirect) disturbances. In addition, the specific criteria of an inbound logistic flow indicate how vulnerability in supply chains is proposed to be analysed according to the developed conceptual framework of vulnerability.
Information security awareness: educating your users effectively
Authors: Thomson M.E. , von Solms R.
Published: July 2002

This article investigates the evolution of computing, with specific reference to the security issues involved. These issues are then taken further to determine the need for education in the workplace through an information security awareness program. Techniques borrowed from the field of social psychology, which have been largely ignored in current awareness programs, are highlighted in order to show how they could be utilized to improve the effectiveness of the awareness program.
A normalized root‐mean‐spuare distance for comparing protein three‐dimensional structures
Authors: Carugo Oliviero , Pongor Sándor
Published: July 2002

The degree of similarity of two protein three‐dimensional structures is usually measured with the root‐mean‐square distance between equivalent atom pairs. Such a similarity measure depends on the dimension of the proteins, that is, on the number of equivalent atom pairs. The present communication presents a simple procedure to make the root‐mean‐square distances between pairs of three‐dimensional structures independent of their dimensions. This normalization may be useful in evolutionary and fold classification studies as well as in simple comparisons between different structural models.
Time Series Modelling of Childhood Diseases: A Dynamical Systems Approach
Authors: Finkenstädt Bärbel F. , Grenfell Bryan T.
Published: July 2002

A key issue in the dynamical modelling of epidemics is the synthesis of complex mathematical models and data by means of time series analysis. We report such an approach, focusing on the particularly well-documented case of measles. We propose the use of a discrete time epidemic model comprising the infected and susceptible class as state variables. The model uses a discrete time version of the susceptible–exposed–infected–recovered type epidemic models, which can be fitted to observed disease incidence time series. We describe a method for reconstructing the dynamics of the susceptible class, which is an unobserved state variable of the dynamical system. The model provides a remarkable fit to the data on case reports of measles in England and Wales from 1944 to 1964. Morever, its systematic part explains the well-documented predominant biennial cyclic pattern. We study the dynamic behaviour of the time series model and show that episodes of annual cyclicity, which have not previously been explained quantitatively, arise as a response to a quicker replenishment of the susceptible class during the baby boom, around 1947.
Analytical and Experimental Studies of Short-Beam Interlaminar Shear Strength of G-10CR Glass-Cloth/Epoxy Laminates at Cryogenic Temperatures
Authors: Shindo Y. , Wang R. , Horiguchi K.
Published: July 2002

Cryogenic interlaminar beam tests in the form of three-point flexure are examined both experimentally and analytically. The use of the short-beam shear test for measuring the interlaminar shear strength of glass-cloth/epoxy laminates at low temperatures is evaluated first. The interlaminar shear tests were carried out with short-beam shear specimens at room temperature, 77 K and 4 K to evaluate the interlaminar shear strength of G-10CR glass-cloth/epoxy laminates. Each specimen was placed on two roller supports that allow lateral motion and a load was applied directly at the center of the specimen. These tests were conducted in accordance with ASTM, 1984, “Standard Test Method for Apparent Interlaminar Shear Strength of Parallel Fiber Composites by Short-Beam Method,” Designation D2344-84. The effects of temperature, specimen width, and span-to-thickness ratio on the apparent interlaminar shear strength are shown graphically. Photomicrographs (scanning electron micrographs, optical micrographs) of actual failure modes were utilized to verify the failure mechanisms. A three-dimensional finite element analysis was also performed to investigate the effects of specimen width and span-to-thickness ratio on the shear stress distribution in the mid-plane. Effective elastic moduli were determined under the assumption of uniform strain inside the representative volume element. The numerical findings are then correlated with the experimental results.
Thermal Analysis of Polymer Heat Exchangers for Solar Water Heating: A Case Study
Authors: Liu Wei , Davidson Jane , Mantell Susan
Published: July 2002

The feasibility of reducing the cost of solar water heating systems by using polymer heat exchangers is illustrated by comparing thermal performance and cost of heat exchangers made of nylon, cross linked polyethylene (PEX), or copper. Both tube-in-shell heat exchangers and immersed tube banks are considered. For the thermal analysis, the tube geometry and the arrangement of tubes are fixed and the heat transfer surface areas required to provide 3000 and 6000 W are determined. Thermal performance is estimated using published heat transfer correlations. The nylon heat exchanger outperforms the PEX design, primarily because nylon is a stronger material. Consequently, the ratio of diameter to wall thickness required to withstand the operating pressure is greater and the conduction resistance across the polymer wall is less. The cost of nonoptimized nylon heat exchangers is about 80 percent of the cost of heat exchangers made of copper. Significant additional work is required to optimize the tube arrangement and geometry and to validate our initial estimates of thermal and economic performance. [S0199-6231(00)00802-9]
Elastohydrodynamic Film Collapse During Rapid Deceleration. Part I—Experimental Results
Authors: Glovnea R. P. , Spikes H. A.
Published: July 2002

This paper describes a study of the behavior of elastohydrodynamic lubricated contacts subjected to rapid halting. Experiments have been carried out using ultrathin interferometry coupled to a high-speed camera to measure the change in lubricant film thickness and shape during fast, controlled deceleration, both in pure sliding and pure rolling conditions. Film collapse is seen to occur in two stages. The first persists throughout the deceleration period and, during this stage the film geometry remains almost constant across the contact. In this stage of film collapse, the film thickness lags behind the value predicted from steady-state theory, which means that when motion ceases, a thicker than expected film is present. The second stage of film collapse ensues when the entrainment speed falls below a critical value of approximately 0.002 m/s and is characterized by the formation of a central entrapment and classical, normal approach, squeeze behavior.
Theory of Boundary Eigensolutions in Engineering Mechanics
Authors: Hadjesfandiari A. R. , Dargush G. F.
Published: July 2002

A theory of boundary eigensolutions is presented for boundary value problems in engineering mechanics. While the theory is quite general, the presentation here is restricted to potential problems. Contrary to the traditional approach, the eigenproblem is formed by inserting the eigenparameter, along with a positive weight function, into the boundary condition. The resulting spectra are real and the eigenfunctions are mutually orthogonal on the boundary, thus providing a basis for solutions. The weight function permits effective treatment of nonsmooth problems associated with cracks, notches and mixed boundary conditions. Several ideas related to the convergence characteristics are also introduced. Furthermore, the connection is made to integral equation methods and variational methods. This paves the way toward the development of new computational formulations for finite element and boundary element methods. Two numerical examples are included to illustrate the applicability.
A Scattering-Mediated Acoustic Mismatch Model for the Prediction of Thermal Boundary Resistance
Authors: Prasher Ravi S. , Phelan Patrick E.
Published: July 2002

Solid-solid thermal boundary resistance Rb plays an important role in determining heat flow, both in cryogenic and room-temperature applications, such as very large scale integrated circuitry, superlattices, and superconductors. The acoustic mismatch model (AMM) and the related diffuse mismatch model (DMM) describe the thermal transport at a solid-solid interface below a few Kelvin quite accurately. At moderate cryogenic temperatures and above, Rb is dominated by scattering caused by various sources, such as damage in the dielectric substrates and formation of an imperfect boundary layer near the interface, making Rb larger than that predicted by AMM and DMM. From a careful review of the literature on Rb, it seems that scattering near the interface plays a far more dominant role than any other mechanism. Though scattering near the interface has been considered in the past, these models are either far too complicated or are too simple (i.e., inaccurate) for engineering use. A new model, called the scattering-mediated acoustic mismatch model (SMAMM), is developed here that exploits the analogy between phonon and radiative transport by developing a damped wave equation to describe the phonon transport. Incorporating scattering into this equation and finding appropriate solutions for a solid-solid interface enable an accurate description of Rb at high temperatures, while still reducing to the AMM at low temperatures, where the AMM is relatively successful in predicting Rb.
Swirl Effects on Combustion Characteristics of Premixed Flames
Authors: Gupta A. K. , Lewis M. J. , Daurer M.
Published: July 2002

The effect of radial distribution of swirl has been examined on the thermal behavior of two different premixed flames using a double concentric premixed swirl burner. The double concentric swirl burner allowed systematic variation in the radial distribution of swirl (both co- and counter-) between the inner and outer annulus of the burner. The burner had two annular jets and a central nozzle. Information on the thermal field in two flames formed by co- or counter-swirl in the outer annulus and co-swirl in the inner annulus has been examined. Specifically mean and fluctuating temperatures, integral and micro thermal time scales, and probability density distribution of temperatures have been determined at various spatial positions in the flames. The micro-thermocouple output was compensated to provide high-frequency (about 1 kHz) response of the thermocouple. Direct flame photographs were taken to provide information about the global features of flames and flame stability. The global and thermal characteristic data presented here provided a complete insight on the thermal behavior of co- and counter-swirl flames. The results show that the direction of swirl (co- or counter-) used to stabilize a flame from annular jets provides a great influence on flame symmetry. The simultaneous combination of co- and counter-swirl in the burner showed a very nonsymmetrical behavior of the flame. The global and thermal data presented here confirmed these findings. The results suggest significant effect of co- and counter-swirl distribution in flames on the NOx emission levels.
High-Frequency Low-Loss Ultrasonic Modes in Imbedded Bars
Authors: Pavlakovic B. N. , Lowe M. J. S. , Cawley P.
Published: July 2002

The dispersion relationships of a system comprising a circular bar imbedded in a solid medium having a lower acoustic impedance than the bar have been predicted. A generic study of such systems has been undertaken, motivated by a particular interest in the case of a circular steel bar imbedded in cement grout which has application to the inspection of tendons in post-tensioned concrete bridges; measurements to confirm the predictions have been carried out for this case. The attenuation dispersion curves show a series of attenuation minima at roughly equal frequency spacing. The attenuation minima occur at the same frequencies as energy velocity maxima and they correspond to points at which the particle displacements and energy of the particular mode are concentrated towards the center of the bar so leakage of energy into the imbedding medium is minimized. The attenuation at the minima decreases with increasing frequency as the energy becomes more concentrated at the middle of the bar, until the material attenuation in the bar becomes a significant factor and the attenuation at the minima rises again. For the particular case of a steel bar in cement grout, the minimum attenuation is reached at a frequency-radius product of about 23 MHz-mm. The frequency-radius product at which the minimum attenuation is reached and the value of the minimum attenuation both increase as the acoustic impedance of the imbedding medium increases.
Microdamage Accumulation in Bovine Trabecular Bone in Uniaxial Compression
Authors: Moore T. L. Arthur , Gibson L. J.
Published: July 2002

In this study we investigated how microdamage accumulated with increasing compressive strain in bovine trabecular bone. We found that little damage is created in the linear elastic region, up to −0.4 percent strain. At an average strain of −0.76percent±0.25 percent, the stress-strain curve became nonlinear, and peaked at −1.91 percent±0.55 percent strain. Microdamage increases rapidly during the peak of the stress-strain curve, and a localized band of damage formed. At strains beyond the ultimate strain, the damaged band widened and the density of damage within the band increased. Microdamage occurred as groupings of cracks; the majority of damage occurred as regions of cross-hatching. All microdamage parameters increased with increasing maximum compressive strain. We also observed exponential relationships between crack numerical density and damage 1∘−∘Esec/E0 and between crack length density and damage.
Proton Exchange Membrane Fuel Cell System Model for Automotive
Vehicle Simulation and Control
Authors: Boettner Daisie D. , Paganelli Gino , Guezennec Yann G. , Rizzoni Giorgio , Moran Michael J.
Published: July 2002

This paper describes a proton exchange membrane (PEM) fuel cell system model for automotive applications that includes an air compressor, cooling system, and other auxiliaries. The fuel cell system model has been integrated into a vehicle performance simulator that determines fuel economy and allows consideration of control strategies. Significant fuel cell system efficiency improvements may be possible through control of the air compressor and other auxiliaries. Fuel cell system efficiency results are presented for two limiting air compressor cases: ideal control and no control. Extension of the present analysis to hybrid configurations consisting of a fuel cell system and battery is currently under study.
Flow of Two-Immiscible Fluids in Porous and Nonporous Channels
Authors: Chamkha Ali J.
Published: July 2002

This study considers steady, laminar flow of two viscous, incompressible, electrically-conducting and heat-generating or absorbing immiscible fluids in an infinitely-long, impermeable parallel-plate channel filled with a uniform porous medium. A magnetic field of uniform strength is applied normal to the flow direction. The channel walls are assumed to be electrically nonconducting and are maintained at two different temperatures. When present, the porous medium is assumed to act as an electrical insulator and that it is in local thermal equilibrium with the fluid. The transport properties of both fluids are assumed to be constant. This study is expected to be useful in understanding the influence of the presence of slag layers on the flow and heat transfer aspects of coal-fired Magnetohydrodynamic (MHD) generators when the porous medium is absent and the effects of thermal buoyancy and a magnetic field on enhanced oil recovery and filtration systems where the porous medium is present. The problem is formulated by employing the balance laws of mass, linear momentum, and energy for both phases. Continuous conditions for the velocity and temperature as well as the shear stress and heat flux of both phases at the interface are employed. The resulting governing ordinary differential equations are solved numerically subject to the boundary and interface conditions for the velocity and temperature distributions of both fluids in the channel. Analytical solutions for a special case of the problem where the porous medium is absent or only its inertia effect is neglected are obtained. Comparisons with previously reported velocity profiles are performed and excellent agreements are obtained. A parametric study illustrating the influence of the physical parameters involved in the problem is conducted and the results are presented graphically and discussed. [S0098-2202(00)02101-5]
Investigating Three-Dimensional and Rotational Effects on Wind Turbine Blades by Means of a Quasi-3D Navier-Stokes Solver
Authors: Chaviaropoulos P. K. , Hansen M. O. L.
Published: July 2002

Three-dimensional and rotational viscous effects on wind turbine blades are investigated by means of a quasi-3D Navier-Stokes model. The governing equations of the model are derived from the 3-D primitive variable Navier-Stokes equations written in cylindrical coordinates in the rotating frame of reference. The latter are integrated along the radial direction and certain assumptions are made for the mean values of the radial derivatives. The validity of these assumptions is cross-checked through fully 3-D Navier-Stokes calculations. The resulting quasi-3D model suggests that three-dimensional and rotational effects be strongly related to the local chord by radii ratio and the twist angle. The equations of the model are numerically integrated by means of a pressure correction algorithm. Both laminar and turbulent flow simulations are performed. The former is used for identifying the physical mechanism associated with the 3-D and rotational effects, while the latter for establishing semiempirical correction laws for the load coefficients, based on 2-D airfoil data. Comparing calculated and measured power curves of a stall controlled wind turbine, it is shown that the suggested correction laws may improve significantly the accuracy of the predictions. [S0098-2202(00)02702-4]
Elemental Manganese Studied by X-ray Photoemission Spectroscopy Using Mg and Zr Radiations
Authors: Chourasia A. R. , Chopra D. R.
Published: July 2002

Elemental manganese has been studied by x-ray photoelectron spectroscopy. Mg Kα and Zr Lα radiations were used as excitation sources for the study. In the literature a range of values has been reported for Mn core levels using Mg radiation. The purpose of this study is to provide spectral data obtained using Zr x-ray source in comparison with that obtained using Mg source. Such a data set will serve as a source of additional valuable information for enhancing the capability of x-ray photoelectron spectroscopy for investigating different specimens containing Mn. The XPS data in the 2p and 3p regions are presented. Significant differences are observed in the two sets of data. The data obtained using Zr source show considerable broadening of the core level spectra of Mn.
Cysteine by X-Ray Photoelectron Spectroscopy
Authors: Brizzolara Robert A.
Published: July 2002

Cysteine is one of the 20 amino acids, and one of the two sulfur-containing amino acids. The highly reactive sulfhydryl group is often used for conjugating proteins to other entities. Furthermore, in a thin film, measurement of chemical shifts of the constituent atoms of cysteine are important in determining its interaction with a surface. Also, cysteine plays an important role in determining the conformation of proteins by forming disulfide bonds. As such, spectra of bulk films of cysteine serve as an important baseline for studies of these phenomena. In this work, an aqueous solution prepared from cysteine powder was poured into a recessed sample holder and allowed to dry. This formed a block of dried cysteine approximately 1/4 in. thick. The spectra were acquired at liquid nitrogen temperature. The atomic concentrations measured with XPS agree well with those expected for cycteine, assuming the small amount of excess carbon is due to adventitious material. Predominantly zwitterionic character is observed in the O 1s and N 1s spectra. A small amount of either neutral species or condensed polypeptide is also observed. The S 2p binding energy indicates that the sulfur is predominantly disulfide, with a small amount of free sulfhydryl.
Kinetic investigation of copper film oxidation by spectroscopic ellipsometry and reflectometry
Authors: Hu Yao Zhi , Sharangpani Rahul , Tay Sing-Pin
Published: July 2002

This article presents the oxidation kinetics of Cu thin films in dry and wet oxygen at temperatures from 100 to 600 °C. Spectroscopic ellipsometry and reflectometry, which yield refractive index and thickness of the Cu oxide, were used in kinetic study of Cu film oxidation. Cabrera–Mott (C–M) theory was used for the calculation of oxidation activation energies, yielding 0.68 eV for dry oxidation and 0.43 eV for wet oxidation. The scanning electron microscopy (SEM) and Rutherford backscattering spectrometry were used to investigate the cross-sectional profile, grain size, and chemical composition of the Cu oxides. A formula for Cu oxide thickness calculation was derived from the C–M theory and experimental data. Good agreement has been observed in thickness values from formula calculation, spectroscopic reflectance and SEM has been confirmed. A study of the effect of trace O2 on Cu film anneal is also presented.
Patterning technology of carbon nanotubes for field emission displays
Authors: Cho Young-Rae , Lee Jin Ho , Song Yoon-Ho , Kang Seung-Youl , Jung Moon-Youn , Hwang Chi-Sun , Cho Kyoung Ik
Published: July 2002

Patterning technology of fine carbon nanotube (CNT) pixels on a hard metal has been developed by using photolithography process for field emission displays (FEDs). The photolithography method produced much sharper and smaller CNT pixels compared with those made by the conventional screen-printing process. The CNTs in the patterned pixels by photolithography were uniformly distributed in a 2 in. diagonal area. The density of CNT bundles in the patterned pixels was about 10/μm2. After patterning and heat treatment process below 300 °C, most of CNT bundles on the cathode were aligned perpendicular to the substrate. The turn-on field of patterned CNTs was less than 4.2 V/μm and the current density was about 2.1 mA/cm2 at 6 V/μm. This process might be applicable to field emitter arrays for high resolution FEDs.
Vibrational spectroscopy of interfaces by infrared–visible sum frequency generation
Authors: Buck M. , Himmelhaus M.
Published: July 2002

During the past decade vibrational sum frequency generation as a method to study interfaces has matured and can now be applied more routinely to systems of increasing complexity. The article provides a brief overview of technical aspects of infrared–visible sum frequency generation, compares this nonlinear technique with its linear analogs, and highlights the latest applications.
Heat transfer analysis and optimization of two-beam microelectromechanical thermal actuators
Authors: Hickey Ryan , Kujath Marek , Hubbard Ted
Published: July 2002

This article investigates rectangular two-beam microelectromechanical thermal actuators and provides a method for their optimization. The thermal actuators investigated consisted of two asymmetric parallel arms,one thin and one wide. Under an electric current load, the thin arm heats and expands more than the wide arm, thereby bending the entire structure. Simplified models of the heat transfer mechanisms are used to determine the temperature profile. From the thermal expressions for expansion of the arms, equations are derived to predict the deflection as well as the buckling loads. Measurements of the actuator deflection as a function of voltage are presented. Design guidelines are introduced for optimization of a thermal actuator.
Amorphous silicon nitride deposited at 120 °C for organic light emitting display-thin film transistor arrays on plastic substrates
Authors: Stryahilev Denis , Sazonov Andrei , Nathan Arokia
Published: July 2002

Nitrogen-rich amorphous silicon nitride (a-SiNx:H) films with [N]/[Si] ratios ranging from 1.4 to 1.7 were deposited by a 13.56 MHz plasma-enhanced chemical vapor deposition method at a temperature of 120 °C. The films’ composition, dielectric constant, electrical resistivity, and breakdown voltage were evaluated. The electrical properties of a-SiNx:H films with a [N]/[Si] ratio of more than 1.6 are superior to their lower N-content counterparts. Amorphous silicon thin film transistors (TFTs) that incorporate a-SiNx:H dielectrics were fabricated on glass and plastic substrates at a maximum processing temperature of 120 °C. The TFTs exhibit effective field effect mobility of 0.5–0.8 cm2/V s, an ON current of ∼10−5 A, an ON/OFF ratio of more than 106 and a subthreshold slope of 0.5 V/dec. The performance of the transistors seems to be compatible with application of them in active–matrix organic light emitting displays.
Primary steps in catalytic synthesis of ammonia
Authors: Ertl G.
Published: July 2002

Synthesis of ammonia from the elements (N2+3H2→2NH3) is performed over promoted iron catalysts at high pressures and temperatures (Haber–Bosch process) and represents, for about seventy years, one of the most important industrial catalytic reactions. This report is intended to demonstrate what kind of information on the nature of the catalyst surface, as well as on the microscopic reaction steps, can be obtained by the ‘‘surface science approach’’, i.e., by using a variety of surface spectroscopic techniques and by performing model studies with single crystal surfaces.
High-rate vapor deposition and large systems for coating processes
Authors: Schiller S. , Beister G. , Heisig U. , Foerster H.
Published: July 2002

In many branches of national economies the coating of large areas at high rates is a precondition for introducing new products on the market in a profitable manner. In the field of physical vapor deposition fresh ground has been opened up by the use of high-rate electron beam (EB) evaporation for about 20 yr, and by high-rate sputtering for about 10 yr. As far as metal coating of substrates at extremely high rates is concerned, high-rate EB evaporation practically has no competitor. High-rate sputtering has gained a firm hold in the deposition of alloys and compounds on large areas. Moreover, process extensions also will increase the usability of both techniques in the years to come.
Measuring the nanomechanical properties and surface forces of materials using an atomic force microscope
Authors: Burnham Nancy A. , Colton Richard J.
Published: July 2002

An atomic force microscope (AFM) has been configured so that it measures the force between a tip mounted on a cantilever beam and a sample surface as a function of the tip–surface separation. This allows the AFM to study both the nanomechanical properties of the sample and the forces associated with the tip–surface interaction. More specifically, the AFM can measure the elastic and plastic behavior and hardness via nanoindentation, van der Waals forces, and the adhesion of thin-film and bulk materials with unprecedented force and spatial resolution. The force resolution is currently 1 nanonewton, and the depth resolution is 0.02 nm. Additionally, the instrument itself is compact and relatively inexpensive.
Perspective on stresses in magnetron-sputtered thin films
Authors: Hoffman D. W.
Published: July 2002

For nearly 10 years, J. A. Thornton and the present author pursued a series of investigations on a curious and initially obscure effect of intrinsic stress reversal in magnetron-sputtered thin films. This study was first undertaken to understand the mechanical failures of decorative chromium when deposited on plastic automotive grilles. The present paper follows the evolution of these investigations in which the more than 1000 samples were mailed in small batches on a round trip between the author’s laboratory in the east and Thornton’s in the west. As the work developed it became clear that the structure-sensitive stress reversal was a phenomenon of broad generality, which reflected subtle changes in the growth microstructures and accompanying properties of magnetron sputtered films. It was postulated that these changes resulted from particle bombardment fluxes controlled by sputtering process parameters. This review recalls various experiments that were conceived to explore mechanisms and map out the stress reversal locus in parameter space.
Global model of Ar, O2, Cl2, and Ar/O2 high-density plasma discharges
Authors: Lee C. , Lieberman M. A.
Published: July 2002

We develop a global (volume averaged) model of high-density plasma discharges in molecular gases. For a specified discharge length and diameter, absorbed power, pressure, and feed gas composition, as well as the appropriate reaction rate coefficients and surface recombination constants, we solve the energy and particle balance equations to determine all species densities and the electron temperature. We use an expression for charged particle diffusive loss that is valid for low and high pressures and for electropositive and electronegative plasmas. We apply the model to Ar, O2, Cl2, and Ar/O2 discharges and compare with available experimental data. In Ar, we find that the ion density increases monotonically with increasing pressure, while for O2 and Cl2, the total positive ion density increases initially, then decreases as pressure is further increased. For a pure Cl2 discharge, we find that surface recombination processes are important in affecting the degree of dissociation and the negative-ion density of the system. For mixtures of Ar and O2, we find that at a fixed ratio of Ar to O2 flowrates, the dominant ionic species changes from Ar+ to O+ as pressure is increased. When a small amount of Ar is added to a pure O2 discharge, the overall positive-ion density increases, whereas the ratio of negative ion to electron density decreases.
Composition of the oxygen plasmas from two inductively coupled sources
Authors: Tuszewski M. , Scheuer J. T. , Tobin J. A.
Published: July 2002

The composition of the oxygen discharges from two inductively coupled plasma sources is studied experimentally with tuned cylindrical Langmuir probes, with optical emission spectroscopy, and with a compact mass spectrometer. The data show that low frequency cylindrical discharges are highly dissociated at low neutral pressures and at high powers, whereas high frequency planar discharges have less atomic content.
Nature of the use of adventitious carbon as a binding energy standard
Authors: Barr Tery L. , Seal Sudipta
Published: July 2002

It has become common practice to employ, as a binding energy reference for x-ray photoelectron spectroscopy studies on nonconductive materials, the C(1s) spectra of the ubiquitous (adventitious) carbon that seems to exhibit an instantaneous presence on all air exposed materials. Despite this commonality, surface scientists, including many practitioners, have expressed substantial concerns about the validity of this approach. A detailed discussion of the method is presented including consideration of the types of materials and the electronic energy states involved, e.g., Fermi edges, vacuum levels, etc., and the couplings that must exist for the referencing method to be correctly applied. A number of other surface environments for which the carbon referencing method may be fallacious are also presented. This leads to a consideration of the electron spectroscopy for chemical analysis results for different types of adventitious species and how the presence of some of these may confuse the use of the method. In this regard, we will also discuss the use of other methods to establish binding energy scales, such as Fermi edge coupling and select doping (e.g., the Au dot approach).
Formation of high temperature phases in sputter deposited Ti-based films below 100 °C
Authors: Musil J. , Bell A. J. , Vlček J. , Hurkmans T.
Published: July 2002

This article reports on the sputtering of pure Ti and Ti-based alloy films onto substrates where the temperature Ts was kept below 100 °C, using the magnetron sputter ion plating process. It was found that while the pure Ti film is a hexagonal low-temperature phase film (h–αTi), the Ti–Cr, and Ti–Fe alloy films, containing a relatively small amount of Cr or Fe of about 10 wt %, are cubic high-temperature beta phase Ti alloy films [c-βTi(Cr) or c-βTi(Fe)]. This finding is of immense importance both scientifically and practically. The conditions under which high-temperature phases are formed in alloy films sputtered at substrate temperatures below 100 °C, which is much lower than the temperature necessary to form these high-temperature phases (Thtp) according to the equilibrium phase diagram, will be discussed in detail. X-ray diffraction analyses of these films will also be presented.
Evaluation of correction parameters for elastic-scattering effects in x-ray photoelectron spectroscopy and Auger electron spectroscopy
Authors: Jablonski A. , Powell C. J.
Published: July 2002

We describe a relatively simple, reliable, and fast approach for quantitative surface analyses by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) that significantly improves the accuracy of analyses of polycrystalline solids. The common formalism of XPS and AES is based on the assumption, now known to be incorrect, that elastic-electron-scattering effects are negligible. These effects can be taken into account by the use of correction parameters (two for XPS and one for AES) in a modified formalism. These correction parameters can be conveniently expressed in terms of the ratio ζ of the transport mean free path to the inelastic mean free path for a particular material and electron energy, and we give an improved procedure for determining this ratio for elemental solids and compounds at electron energies ranging from 50 to 2000 eV. We test the utility and validity of the derived correction parameters for XPS based on comparisons with parameter values and photoelectron intensities derived from Monte Carlo simulations for some 400 photoelectron lines in 27 elements excited by Mg and Al characteristic x rays. It is pointed out that the systematic errors associated with the neglect of elastic-electron scattering in XPS depend on the instrumental configuration, and range from −20% to 30% for two XPS configurations investigated here. With the use of the modified XPS formalism and the two correction parameters, these errors were reduced to between −3% and 2% for most of the photoelectron lines, although with a few lines the errors were as large as −10%. Good performance of the modified formalism for AES has been reported previously. We describe and discuss the application of this approach for surface analyses of multi-component solids. The improved procedure for calculating the ratio ζ can also be used for estimation of the mean escape depth of photoelectrons and Auger electrons.