bluuebunny/crossref_metadata_2025 huggingface dataset:
EU Labour Markets and Monetary Union
Authors: Jackman Richard , Savouri Savvas
Published: November 2003

How can European labour markets cope with a single currency? The single currency success story is the US, which has maintained low unemployment rates both in the country as a whole and in individual regions. But Richard Jackman and Savvas Savouri argue this has been achieved by massive migration of workers from depressed to prosperous areas. In Europe migration within countries is quite low and between countries essentially non‐existent. Thus in Europe, unlike in the US, the adjustment to national or regional labour market shocks will depend on wage flexibility. Unhappily wages in Europe are not very flexible, particularly in conditions of low inflation, and the single currency may make them even less so. The prospect for depressed areas is thus bleak.
Can Interest Rate Policy be Independent?
Authors: Caporale Guglielmo Maria , Williams Geoffrey
Published: November 2003

The conventional view is that interest rates are closely linked internationally and that larger countries determine monetary policy in smaller countries. In this article, Guglielmo Maria Caporale and Geoffrey Williams argue that this stylisation may not be accurate. The fundamental factors determining long‐term interest rates are likely to be national rather than international. It may therefore be possible for domestic monetary authorities to pursue an independent interest rate policy indefinitely.
Asia’s Miracle: They Think It’s All Over – It Need Not Be Yet
Authors: Crafts Nicholas
Published: November 2003

In this article Nicholas Crafts reports that the crisis in East Asia is essentially a financial crisis and, as such, reflects failures of regulation and macroeconomic policy rather than a slowdown in underlying growth potential. In the past the Tigers have been very good at factor accumulation but less strong in the effective use of investment and in productivity growth. GDP/hour worked is still well below European levels. Accordingly there remains considerable scope for strong growth based on further catch up provided that the financial crises are resolved satisfactorily. History suggests that this is quite likely. Nevertheless, the leading tigers will need to improve their productivity performance if they are to sustain rapid growth and the example of Japan shows that this is not automatic and may not be easy.
A New Paradigm? Understanding the evolving UK macroeconomics profession
Authors: Scott Andrew
Published: November 2003

In this article, Andrew Scott examines the changing incentives for macroeconomic research in the UK. The last year has seen two significant developments. The first is the ESRC’s commitment to a funding initiative encouraging a broad range of work on growth and business cycle issues. Implicit in this is a reduction in the importance of large scale macroeconometric models. The second development is the publication of the Bank of England’s Economic Models at the Bank of England (EMBE) which advocates a pluralistic approach to economic analysis. While maintaining a substantial role for large scale macroeconometric models it advocates the use of different techniques, models and methodologies when providing policy advice. This article examines the causes and reasons behind these developments and their likely implications for UK macroeconomics.
Many Models at the Bank of England
Authors: Wren‐Lewis Simon
Published: November 2003

In this article, Simon Wren‐Lewis examines why the Bank of England considers not one but a range of models when forecasting and formulating policy. He argues this reflects not so much alternative macroeconomic schools of thought, but instead alternative approaches to the nature of models themselves. In the academic literature there is now a spectrum of model types, reflecting the relative importance given to either macroeconomic theory on the one hand or explaining past data on the other. The conventional econometric model attempts a rather uneasy compromise in the middle of this spectrum, and has become distinctly unfashionable within academic circles. Despite this, the Bank retains a conventional econometric model at the core of its forecasting and policy analysis. The article discusses this model, but it also asks why the Bank places this type of model at the core of its analysis when they are now hardly used in academic macroeconomics? The answer is that the conventional model still has a number of crucial advantages for policymakers. The danger is that, in the absence of academic work on models of this type, the Bank may not be able to continue to maintain the high standard of its core model.
America's New Era
Authors: Godley Wynne , Martin Bill
Published: November 2003

In this article, Wynne Godley and Bill Martin examine the growing imbalances in the American economy and the threat they pose to continued growth. They argue that America's expansion has been, and, on present policies, will continue to be overly reliant on a rising stock market and falling private net saving. This process is unsustainable. Other countries which have experienced asset price bubbles and abnormally low and falling private saving have all been severely damaged when the process unwound with net savings rising back to and then above their historic norm. Faced with that type of shock, the same fate could easily await the United States unless its policy toward the dollar and the budget responded in a quite remarkable fashion.
The Yen as an International Currency
Authors: Breedon Francis , Williams Geoffrey
Published: November 2003

Japanese policy‐makers have spent many years attempting to increase the role of the Yen as a regional and international currency. In this article Francis Breedon and Geoffrey Williams look at its role both before and after the Asian currency crisis. Pre‐crisis they find that the Yen was of less regional importance than economic theory would suggest, so that its rapid depreciation from 1995 to 1997 did not influence regional currencies as much as it perhaps should have. Since the Asian crisis they find that its regional role has increased markedly, largely at the expense of the Dollar. This suggests that Yen volatility, which remains considerable, is likely to have more impact on regional Dollar exchange rates and thus less impact on real activity than before.
Expenditure on the NHS in Perspective
Authors: Chalkley Martin
Published: November 2003

In the wake of the recently‐announced increases in health spending, Martin Chalkley reviews the record of health spending in the UK both historically and comparatively. It is clear that prices paid by the NHS have increased more than prices in general, and once this is allowed for then it appears that real health spending today is only twice that of 50 years ago as compared with the fourfold increase suggested when using a general price deflator. Such differential inflation is obviously not a problem which is confined to the UK, and it does add considerably to problems in making proper comparisons between levels of health spending in different countries. In spite of these difficulties, it seems that compared with many other developed countries, health spending in the UK as a proportion of GDP is modest. So, looking ahead, there is some way to go before the UK attains the levels of spending achieved in many other countries. But understanding the reasons for relative price changes is vital if any proposed increases in spending is to be translated into increases in the quantity and quality of services provided.
Reviewing Bank of England Independence: The Report of the Bank of England Commission
Authors: Williams Geoffrey
Published: November 2003

In this article, Geoffrey Williams outlines the main findings and recommendations of the independent Bank of England Commission set up by the Conservative Party to review the performance of the United Kingdom’s monetary policy framework. Its final report published earlier this month, recommended that operational independence of the Bank of England should be retained but that important improvements can be made to how policy is conducted. These include even greater transparency in policy decisions, changing the inflation target and creating a new Parliamentary Committee and possibly a new Council of Economic Advisers to provide for the UK the clearest possible democratic and professional scrutiny of economic policy.
Liberalisation of Utilities and Evolving European Regulation
Authors: Coen David , Doyle Chris
Published: November 2003

In this article, David Coen and Chris Doyle provide an overview of recent liberalisation and regulatory developments affecting key utility sectors (electricity, gas, postal service, and telecommunications) in the European Union. They examine what kind of competition is suitable in the utilities, and discuss obstacles that lie in the path of competition. They address in detail the institutional design of sector specific regulation. National and supra‐national regulatory structures are analysed and these are illustrated by examples drawn from several European countries. In institutional terms, they argue that it is important regulatory regimes have a high degree of flexibilityand speed to allow for the continued evolution of the EU utility sector.
Reimagining Detroit
Authors: Eisinger Peter
Published: November 2003

Political elites and major economic development actors claim that Detroit is “coming back,” but they have rejected the former city of racial segregation and humiliation as a template for its reemergence. Instead, they are reimagining a new city, guided by three different templates: Detroit as a world‐class city, Detroit as a tourist destination, and Detroit as the vital center of a prosperous metropolitan area. Unfortunately, Detroit's circumstances and resources are inadequate to realize any of these visions. Furthermore, the expenditure of political capital and financial resources in pursuit of these visions is creating a city that will function mainly for visitors rather than residents.
Small Town Services and Facilities: The Influence of Social Networks and Civic Structure on Perceptions of Quality
Authors: Wright Morton Lois
Published: November 2003

In this research, it is posited that perceptions of the quality of services and facilities in small towns are dependent on the social organization of those places. Two components of this social organization are the social capital that inheres among individuals and the civic structure of the town. This hypothesis is tested using multi‐level models that combine individual‐level social capital and community‐level civic structure to explain variations among 99 rural towns in Iowa. I find that civic structure contributes positively and significantly to effects between communities, while individual‐level social capital is positive and a significant contributor to effects within communities. The civic structure models explain 32 percent of the variance in perceptions of the quality of core public facilities and services and 43 percent of the variance in secondary public‐private services. The strong contributions of individual social capital and civic structure suggest that investments in the micro and macro social structure of small towns can assist in strengthening perceptions of community infrastructure.
Private Lives and Public Worlds: Changes in Americans' Social Ties and Civic Attachments in the Late‐20th Century
Authors: Monti, Jr. Daniel J. , Butler Colleen , Curley Alexandra , Tilney Kirsten , Weiner Melissa F.
Published: November 2003

The tension between one's private life and larger public obligations has been the subject of much speculation, captured powerfully in works as diverse as those of Alexis de Tocqueville and Robert Putnam. This matter is explored to an extent not previously undertaken in a study of Americans' interpersonal ties and civic attachments at the end of the 20th century. Evidence from the GSS for 1974, 1984, and 1994 suggests that a person's gender, race, age, education, occupation, and mobility became a little more strongly associated with the way one socialized informally and less strongly associated with the kinds of organizations one joined. Regardless of where they live or what generation they came from, Americans have managed the tension between their private lives and broader public duties better and more creatively than we could have imagined.
Elastic-Shakedown Analysis of Axisymmetric Nozzles
Authors: Muscat Martin , Mackenzie Donald
Published: November 2003

An investigation of the shakedown behavior of axisymmetric nozzles under internal pressure is presented. The analysis is based on elastic-plastic finite element analysis and Melan’s lower bound shakedown theorem. Calculated shakedown pressures are compared with values from the literature and with the ASME Boiler and Pressure Vessel Code Section VIII Division 2 primary plus secondary stress limits. Results obtained by the lower bound method are also verified by cyclic elastic-plastic finite element analysis.
Thermoacoustically-Based Combustion Oscillation in a Gas Turbine—A Brief Note
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: November 2003

Thermoacoustic combustion oscillation and vibration experienced in a gas turbine at operation is reported. The oscillation manifested itself at two distinct frequencies representing the first and second mode frequencies of the combined hot and cold (combustion chamber/burner air) Rijke type thermoacoustic model. The first mode was a lower amplitude thermoacoustically driven free Rijke mode. The higher frequency second Rijke mode coupled with the second acoustic mode of the combustion chamber resulted in high amplitude oscillation. Modifications to the burner cold air components are considered which would eliminate the oscillation. The paper will present and discuss the principal parameters which caused the oscillation and changes which would eliminate it.
Finite Element Simulation of Bolt-Up Process of Pipe Flange Connections With Spiral Wound Gasket
Authors: Fukuoka Toshimichi , Takaki Tomohiro
Published: November 2003

It is well known that a large amount of scatter in bolt preloads is observed when bolting up a pipe flange connection, especially in the case of using a spiral wound gasket. In this study, a numerical approach is proposed, which can simulate the bolt-up process of a pipe flange connection with a spiral wound gasket inserted. The numerical approach is designed so as to predict the scatter in bolt preloads and achieve uniform bolt preloads at the completion of pipe flange assembly. To attain the foregoing purposes, the stress-strain relationship of a spiral wound gasket, which shows highly nonlinear behavior, is identified with a sixth-degree polynomial during loading and with an exponential equation during unloading and reloading. Numerical analyses are conducted by three-dimensional FEM, in which a gasket is modeled as groups of nonlinear one-dimensional elements.
Geometric Constants in Plain Cross-Bored Cylinders
Authors: Kihiu J. M. , Rading G. O. , Mutuli S. M.
Published: November 2003

A three-dimensional FEM computer program was developed to establish the stress distributions and SCFs in thick walled cylinders with flush and nonprotruding plain cross bores under internal pressure. The displacement formulation and eight-noded brick isoparametric elements were used. The Frontal solution technique was used due to the limited computing facilities. In the far field, the FEM stresses and displacements were in good agreement with the through thickness analytical values. The variation of SCF with d was established for various thickness ratios. For k>1.25, the maximum hoop stress occurred away from the crotch corner when d⩽0.2. For k=1.25, the maximum hoop stress occurred away from the crotch corner when d⩽0.15. For k⩾1.75, d was found to be a geometrical constant equal to 0.2 where the k values have a SCF of 2.734. For k<1.75, d was found to be a geometrical constant equal to 0.11 where the k values have a SCF of 2.67. A new categorization of cylinders has been proposed: thin shells, thick shells, and thick cylinders.
Analysis of Uniform Arrays of Three-Dimensional Unequal-Depth Cracks in a Thick-Walled Cylindrical Pressure Vessel
Authors: Perl M. , Ostraich B.
Published: November 2003

The effect of crack depth unevenness on the mode I stress intensity factor (SIF) distributions along the fronts of semi-elliptical surface cracks is studied. These three-dimensional radial cracks pertain to large uniform arrays of unequal-depth cracks emanating from the bore of a pressurized thick-walled cylinder. The analysis is based on the “two crack depth level model,” previously proposed, and is performed via the finite element (FE) method employing singular elements along the crack front. The distribution of KIP-the stress intensity factor due to pressurization, for numerous uneven array configurations bearing n=n1+n2=8 to 128 cracks, a wide range of crack depth to wall thickness ratios, a1/t=0.01 to 0.4, and various crack ellipticities, a1/c1=0.3 to 1.5, are evaluated for a cylinder of radii ratio Ro/Ri=2. To increase the accuracy of the evaluated SIFs an existing improved version of the displacement extrapolation method is used. The results clearly indicate that unevenness, as reflected in KIP distributions, depends on both the number of cracks in the array as well as on the cracks’ depths and ellipticities. The “interaction range” for the various configurations of uneven crack arrays is evaluated. The range of influence between adjacent cracks on the maximal SIF, KPmax, is found to be dependent on the density of the array, as reflected in the inter-crack aspect-ratio, as well as on the cracks’ elipticity.
Fatigue Crack Growth Rate of Medium and Low Sulfur Ferritic Steels in Pressurized Water Reactor Primary Water Environments
Authors: Eason Ernest D. , Nelson Edward E. , Heys Graham B.
Published: November 2003

Models of fatigue crack growth rates for medium and low sulfur ferritic pressure vessel steels in pressurized water reactor (PWR) primary environments are developed based on a recent collection of UK data and the EPRI Database for Environmentally Assisted Cracking (EDEAC). The combined UK and EDEAC database contains a broader range of experimental conditions specific to PWRs than either database by itself. Both probabilistic and conventional crack growth rate models are developed that reduce unnecessary conservatism for medium and low sulfur PWR primary water applications and eliminate the explicit dependence on rise time that caused difficulties applying prior models.
Application of Arbitrary Lagrange Euler Formulations to Flow-Induced Vibration Problems
Authors: Longatte E. , Bendjeddou Z. , Souli M.
Published: November 2003

Most classical fluid force identification methods rely on mechanical structure response measurements associated with convenient data processes providing turbulent and fluid-elastic forces responsible for possible vibrations and damage. These techniques provide good results; however, they often involve high costs as they rely on specific modelings fitted with experimental data. Owing to recent improvements in computational fluid dynamics, numerical simulation of flow-induced structure vibration problems is now practicable for industrial purposes. As far as flow structure interactions are concerned, the main difficulty consists in estimating numerically fluid-elastic forces acting on mechanical components submitted to turbulent flows. The point is to take into account both fluid effects on structure motion and conversely dynamic motion effects on local flow patterns. This requires a code coupling to solve fluid and structure problems in the same time. This ability is out of limit of most classical fluid dynamics codes. That is the reason why recently an improved numerical approach has been developed and applied to the fully numerical prediction of a flexible tube dynamic response belonging to a fixed tube bundle submitted to cross flows. The methodology consists in simulating at the same time thermo-hydraulics and mechanics problems by using an Arbitrary Lagrange Euler (ALE) formulation for the fluid computation. Numerical results turn out to be consistent with available experimental data and calculations tend to show that it is now possible to simulate numerically tube bundle vibrations in presence of cross flows. Thus a new possible application for ALE methods is the prediction of flow-induced vibration problems. The full computational process is described in the first section. Classical and improved ALE formulations are presented in the second part. Main numerical results are compared to available experimental data in section 3. Code performances are pointed out in terms of mesh generation process and code coupling method.
The Influence of Finite Three-Dimensional Multiple Axial Erosions on the Fatigue Life of Partially Autofrettaged Pressurized Cylinders
Authors: Levy C. , Perl M. , Ma Q.
Published: November 2003

Erosion geometry effects on the mode I stress intensity factor (SIF) for a crack emanating from the farthest erosion’s deepest point in a multiply, finite-length or full-length eroded, partially autofrettaged, pressurized, thick-walled cylinder is investigated. The problem is solved via the FEM method. Autofrettage, based on von Mises’ yield criterion, is simulated by thermal loading and SIFs are determined by the nodal displacement method. SIFs were evaluated for a variety of relative crack depths, a/t=0.01-0.30 and crack ellipticities, a/c=0.5-1.5 emanating from the tip of the erosion of various geometries, namely, (a) semi-circular erosions of relative depths of 1–10% of the cylinder’s wall thickness, t; (b) arc erosions for several dimensionless radii of curvature, r′/t=0.05-0.3; and (c) semi-elliptical erosions with ellipticities of d/h=0.5-1.5. In the cases of finite erosions, the semi-erosion length to the semi-crack length, Le/c, was between two and ten, erosion angular spacing, α, was between 7 and 120 degrees, whereas percent autofrettage investigated included 30%, 60%, and 100%. The normalized SIFs and the normalized effective SIFs of a crack emanating from the farthest finite erosion are found to rise sharply for values of Le/c<3. Both the normalized SIF and normalized effective SIF values are mitigated as the amount of partial autofrettage increases with the most rapid decrease occurring between 0–60% autofrettage. The purpose of this study is to detail these findings.
Effects of titanium content on sol-gel hard optical films prepared in an organic-inorganic hybrid system
Authors: Que Wenxiu , Hu X.
Published: November 2003

The effects of titanium content on the optical and mechanical properties of silica–titania hard optical films by the sol-gel technique using γ-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and tetrapropylorthotitanate as starting materials are studied. Thermal gravimetric analysis, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy are used to investigate the optical and structural properties of the films. The results indicate that crack-free and high transparency silica–titania film with a thickness more than 0.6 μm can be obtained by a single spin-coating process after a heat treatment at 500 °C. The hardness and Young’s modulus of the films are characterized by a nanoindenter and they show a linear dependence on titanium content. Hardness as high as 6.60 GPa is obtained in a 0.5 M titanium content film and heat treated at 800 °C. It is proposed that the high hardness of the film may be related to the carbon and titanium content in the film.
Mechanical and tribological properties of sub- and superstoichiometric Ti–C and Ti–Si–C films deposited by magnetron sputtering-pulsed laser deposition
Authors: Krzanowski J. E. , Nainaparampil J. J. , Phani A. R.
Published: November 2003

The magnetron sputtering–pulsed laser deposition (MSPLD) method has been used to deposit Ti–C and Ti–Si–C films with both sub- and superstoichiometric levels of carbon. The structure and composition of the films were analyzed by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. The mechanical properties were determined by nanoindentation and the tribological properties by pin-on-disk testing. Films deposited with sub- and near stoichiometric levels of carbon had good crystallinity and strong (111) texture. However, films deposited under similar conditions but with a substrate bias resulted in superstoichiometric carbon levels and nanocrystalline or near-amorphous structures. The hardness of these superstoichiometric films was generally lower than the substoichiometric films, but they also exhibited significantly better wear life. The laser power used in the MSPLD process was also found to influence hardness, where increased laser power led to higher hardness levels. Using these results, an effort was made to deposit a film with optimal mechanical and tribological properties by depositing a Ti4Si–C film with −150 V bias, maximum laser power (700 mJ/pulse) at a temperature of 400 °C. This film contained 55% carbon, had a hardness of 28 GPa, and ran for greater than 106 cycles on the pin-on-disk test.
Etching characteristics and mechanism of Au thin films in inductively coupled Cl2/Ar plasma
Authors: Efremov A. M. , Kim Dong-Pyo , Kim Chang-Il
Published: November 2003

The etching characteristics and physical/chemical mechanisms of Au thin films in Cl2/Ar plasma were investigated. It was found that an increase of the Ar content in Cl2/Ar plasma under constant pressure and input power conditions leads to an increasing etch rate of Au, which reaches a maximum value at 80%Ar/20%Cl2. X-ray photoelectron spectroscopy of the etched surfaces indicated the accumulation of reaction products in a chlorine-rich plasma. A proposed zero-dimensional model of volume kinetics, which involved the Langmuir probe data for electron temperature and electron density, showed monotonic change of both densities and fluxes of active species such as chlorine atoms and positive ions. In contrast, analyses of surface kinetics showed the possibility of nonmonotonic etch rate behavior due to the concurrence of physical and chemical factors in ion-assisted chemical reaction.
Microstructure of Mg–Ni thin film prepared by direct current magnetron sputtering and its properties as a negative electrode
Authors: Ouyang L. Z. , Chung C. Y. , Wang H. , Zhu M.
Published: November 2003

Mg–Ni thin films for nickel–metal hydride batteries electrodes were prepared by direct current magnetron sputtering from a Mg–Ni alloy target on three substrates (glass, Ni foil, and foam Ni substrates) and characterized by differential scanning calorimetry, x-ray fluorescence measurement, energy dispersive spectroscopy, x-ray diffraction, and transmission electron microscopy. The microstructure of the Mg–Ni thin films was found to be composed of an amorphous Mg–Ni phase and Mg2Ni nanocrystalline, regardless the substrates. The amorphous phase is crystallized into Mg2Ni at about 360 °C. The maximal discharge capacity of Mg–Ni thin film being 557 mA h/g was achieved in an alkaline solution.
Characterization of B–C–N hybrid prepared by ion implantation
Authors: Shimoyama Iwao , Baba Yuji , Tetsuhiro Sekiguchi , Nath Krishana G. , Sasaki Masayoshi , Okuno Kenji
Published: November 2003

Ion implantation method is applied to synthesize B–C–N hybrids and their electronic structures are characterized by x-ray photoelectron spectroscopy. A boron nitride film is deposited on a graphite target by borazine plasma implantation. At the interface between the BN film and the graphite, a variety of bonding combinations including B–N, B–C, and C–N are observed. This proved that B–C–N hybrids are formed by this method.
Effects of indium surfactant on the crystalline and optical properties of GaN during initial growth stage
Authors: Yuan Hairong , Chua Soo Jin , Tripathy Sudhiranjan , Chen Peng
Published: November 2003

In this article, we report the effects of indium doping on crystalline and optical properties of GaN grown by metalorganic chemical vapor deposition during initial growth stage. Atomic force microscopy observations revealed that the In doping enhanced the lateral growth while the c-face growth rate was reduced. X-ray diffraction (XRD) and micro-Raman scattering measurements showed that the epilayers during this growth stage are nearly strain free. From XRD measurements, we found that In doping has increased the full width at half maximum values in both (0002) and (202̄4) ω-scan. Room temperature photoluminescence measurements show that In doping has enhanced the band-edge related emission by an order of magnitude compared to that of undoped GaN. Raman spectra indicate that In doping suppressed the misorientation of crystallites. In addition, a Raman mode occurred near 710 cm−1 in the In-doped GaN and has been assigned as the Fröhlich vibration.
Formation and clustering of individual point defects in pure tungsten and its slightly dilute alloys at ion irradiation
Authors: Suvorov A. L. , Zaluzhnyi A. G. , Babaev V. P. , Zaluzhnyi A. A.
Published: November 2003

Results of field-ion microscopy investigations of formation and clustering of vacancies among themselves and intrinsic interstitial atoms with impurity atoms in tungsten and its slightly diluted alloys at irradiation by In+ or Yb+ ions of 25 keV energy and Ar+, Ni+, or Cr+ ions of 35 keV energy are presented. Distributions of vacancies complexes in irradiated samples over the number of individual vacancies associated in them have been obtained and analyzed. The noticeable difference of such distributions in areas of development of atomic displacement cascades (in depleted zones) and outside these areas has been revealed. Specific features of the distribution of identified complexes “intrinsic interstitial atom—impurity atom” (in the dumbbell configuration) over the volume of irradiated samples have been studied. The correlation between the type and concentration of components in alloys and concentration of these complexes (dumbbells) as well as dimensions and parameters of depleted zones has been established. The theoretical analysis of experimentally obtained regularities from the positions of the concept of the rupture of chains of focused replacing collisions on impurities has been carried out. Average values of chain lengths in samples with different levels and types of impurities have been measured indirectly. Effectiveness of capture of intrinsic interstitial atoms by various impurities in tungsten has been evaluated from these results.
Control of pressure rise in a vacuum chamber by boron nitride and copper composite coating
Authors: Oishi Tetsuo , Konishi Youko , Goto Masahiro , Kasahara Akira , Tosa Masahiro , Yoshihara Kazuhiro
Published: November 2003

In order to control pressure rise in a vacuum chamber, a radio-frequency magnetron cosputter deposition system has been developed and boron nitride and copper composite (BN/Cu) film was coated onto the inner surface of a vacuum chamber in the shape of a cylinder. Outgassing rate of the BN/Cu coated chamber was estimated with a pressure rise method to be about 5×10−12 Pa m s−1, which was two orders lower than that of the noncoated vacuum chamber in the same shape as the BN/Cu coated chamber. Mass spectra of the residual gas in the chamber indicated that the outgassing of various gas species, such as hydrogen gas, nitrogen gas, and oxygen gas, were reduced by the BN/Cu coating. These results concluded that the BN/Cu coating could control pressure rise in a vacuum chamber.
Formation and annealing effect for close-packed Ge/Cu(111) layers
Authors: Tsay J. S. , Chang L. W. , Yang A. B.
Published: November 2003

Growth and annealing effects of Ge/Cu(111) ultrathin films as deposited at ambient temperature have been studied using Auger electron spectroscopy and low-energy electron diffraction techniques. Ge/Cu(111) system shows a 1×1 structure up to 5 monolayers as deposited at 300 K. The kinetic energy of Cu L3M45M45 Auger electrons shifts to a lower value upon deposition of Ge overlayers. This could be explained by the electric charge transfer between Ge and Cu atoms. From the intensity ratio change of Auger signals (IGe/ICu), significant interdiffusion of Ge/Cu(111) films occurs around 375 K. Owing to the formation of a Cu-rich surface layer, the Cu L3M45M45 peak restores to the initial kinetic energy of a clean Cu(111) surface at 500 K.
Microstructure and properties of ultrathin amorphous silicon nitride protective coating
Authors: Yen Bing K. , White Richard L. , Waltman Robert J. , Dai Qing , Miller Dolores C. , Kellock Andrew J. , Marchon Bruno , Kasai Paul H. , Toney Michael F. , York Brian R. , Deng Hong , Xiao Qi-Fan , Raman Vedantham
Published: November 2003

The effect of N content on the structure and properties of rf reactively sputtered amorphous silicon nitride (a-SiNx) has been studied by Rutherford backscattering spectrometry, x-ray reflectivity, ellipsometry, and nano-indentation. The N content in the film increased with the N2 concentration in the sputtering gas until the Si3N4 stoichiometry was reached. The hardness of a-SiNx increased with density, which in turn increased with the N content. The maximum hardness of 25 GPa and density of 3.2 g/cm3 were attained at the stoichiometric Si3N4 composition. With the application of a protective overcoat for magnetic disks in mind, thin a-SiNx films were deposited on CoPtCr media to examine their coverage, pinhole density, and wear resistance. According to x-ray photoelectron spectroscopy, the minimum thickness of a-SiNx required to protect the CoPtCr alloy from oxidation was 10 Å, which was 10 Å thinner than that of the reference amorphous nitrogenated carbon (a-CNx). A statistic model showed this lower thickness required for a-SiNx can be attributed to its high density, which corresponds to 93% bulk density of Si3N4. Compared with 45 Å a-CNx coated disks, 15 Å a-SiNx coated disks had lower pinhole defect density and superior wear resistance.
Temperature profile and crater formation induced in high-current pulsed electron beam processing
Authors: Qin Ying , Dong Chuang , Wang Xiaogang , Hao Shengzhi , Wu Aimin , Zou Jianxin , Liu Yue
Published: November 2003

We study in this article the formation mechanism of craters on a metal surface during the high current pulsed electron beam processing. Based on experimental investigations and a physical model, the melting process and their temperature profiles are simulated for substrates of aluminum and steels. Initial melting positions, crater depths, and melting layer thickness are computed, the results being in a good agreement with experimental data. It is also confirmed that the temperature rises faster at a subsurface layer instead of at the outermost surface due to the maximum energy deposition located at about 1/3 of the total penetration depth of the beam. Such a subsurface layer heating and melting mechanism causes eruptions of the subsurface layer liquid matters through the outermost surface and produces the typical surface crater morphology.
Experimental and computer simulation studies of the “baffled target” reactive sputtering process
Authors: Engelmark F. , Westlinder J. , Nyberg T. , Berg S.
Published: November 2003

Reactive sputtering is a technique widely employed for deposition of compound materials. One drawback encountered with this technique is that the target normally ends up in poisoned mode at reactive gas flow levels necessary for depositing a stoichiometric film, causing a severe drop of the deposition rate. To decrease the target poisoning a reactive sputter deposition technique based on the so-called baffled target has been suggested. In this configuration a target is confined in a box having a front aperture allowing sputtered material to be deposited through the aperture onto the substrate located in the main chamber. The purpose of this box is to separate the reactive gas in the chamber from the target thereby decreasing the target poisoning. We have carried out computer simulations as well as experimental studies on the baffled target technique. The computer simulations serve to explain the reactive gas gettering and the corresponding process behavior in the box and in the chamber, respectively. The calculations also assist in finding optimum operating conditions for this novel technique. It was found that it is possible to find operating conditions where compound film formation is achieved with the target in high rate metal mode at a supply level of reactive gas far below the level required to reach the hysteresis region. This is a unique property of the baffled target technique that may not be obtained in traditional reactive sputtering system configurations.
Fluorinated amorphous carbon thin films: Analysis of the role of the plasma excitation mode on the structural and mechanical properties
Authors: Valentini L. , Bellachioma M. C. , Ahmed S. I.-U. , Bregliozzi G. , Gerbig Y. , Haefke H. , Lozzi L. , Santucci S. , Kenny J. M.
Published: November 2003

The effects of pulsed plasma enhanced chemical vapor deposition on the thermally induced gas effusion characteristics of fluorinated amorphous carbon thin films are investigated. The main contributions to the effusion spectra are found to come from hydrogen, hydrocarbons, and CF4. With a plasma excitation frequency of 10−3 s, the film produced is relatively compact and the effusion of hydrogen-related species dominate. A strong change in the effusion characteristics for the highest on-time plasma excitation (10−1 s) indicates that an interconnected network of voids is present. Strong effusion of CF4 related species is in fact found to be consistent with a surface desorption process and can only be observed when the void network dimensions are large enough. Nanoindentation measurements showed increased elasticity of the film, as well as increased hardness upon reduction of the plasma excitation period. Raman spectroscopy was applied to corroborate the effusion results, indicating a structural transition from diamond-like to polymer-like film with an increase in the plasma excitation period. Finally the microtribological properties of such types of films are presented and discussed.
Effects of air exposure on ion beam assisted TiN:O coatings to prevent multipactor
Authors: Castañeda S. I. , Dı́az N. , Raboso D. , Montero I. , Galán L. , Rueda F.
Published: November 2003

Titanium nitride films are used to prevent “multipactor” plasma in rf devices due to their low secondary electron emission coefficient (σ) in ultrahigh vacuum. This work refers to the increase of this coefficient on exposure to air and the effect of ion beam assisted deposition (IBAD) on its recovery, relevant in components for space applications. Two modes of deposition were compared: a simple sublimation of titanium in nitrogen atmosphere and a low energy (200 eV-Ar+) IBAD. The sample characterization included σ, bulk and surface compositions, by energy dispersive analysis of x rays and x-ray photoelectron spectroscopy, structure, and resistivity. When the coatings were clean they presented a low value of σ, which increases after exposure to air and recovers part of its low value by electron irradiation in ultrahigh vacuum. In IBAD samples recovery in σ, surface nitrogen content and stability were higher than in simple sublimation ones, leading to values of σ closer to one. After weeks in air, the aluminum microwave guide elements coated with IBAD TiN:O showed a “multipactor” threshold power three times higher than those coated with non-IBAD TiN:O. The coatings’ resistivities lay in the 1–7 μΩ m range.
Ion energy distributions and the density of CH3 radicals in a low pressure inductively coupled CH4/H2 plasma used for nanocrystalline diamond deposition
Authors: Okada Katsuyuki , Komatsu Shojiro , Matsumoto Seiichiro
Published: November 2003

Ion energy distributions (IEDs) and the density of CH3 radicals (n) in a 13.56 MHz radio frequency (rf) low pressure inductively coupled CH4/H2 plasma used for nanocrystalline diamond deposition have been investigated with a quadrupole mass spectrometer. The energy distributions of positive ions were measured in a CH4/H2 plasma with 50 mTorr of the gas pressure at 500 W of the plasma input power, and were compared with those of an Ar plasma. We have found that the IEDs of Ar+, CH4+, and C2H5+ have a nearly monoenergetic peak, and a hump due to a small degree of capacitive coupling. The plasma potentials obtained from the peaks are consistent with the previously reported values measured with a Langmuir probe. On the other hand, the IEDs of H+, H2+, and H3+ have a clear asymmetric double peak due to the modulation of rf driven glow discharge. The n monotonously increases with increasing pressure. The n indicates that CH3 radicals are main precursors for the growth of nanocrystalline diamond. The estimated sticking coefficient of the CH3 radical is comparable with the reported value.
Radical detection in a methane plasma
Authors: Kang H. D. , Dose V.
Published: November 2003

We present a method for detecting and quantifying the concentration of free radicals produced in a low temperature methane process plasma employing quadrupole mass spectrometry and Bayesian analysis. The latter includes a model comparison to determine species expected in the plasma and a parameter estimation of their concentrations and cracking coefficients. We find that the neutral mass spectra are best explained by incorporating the neutral molecules H2, CH4, C2H2, C2H4, and C2H6 as well as the radicals H, CH3, and C2H5 into the model.
Effects of CF4 addition on oxygen contamination of SiC films in hot filament chemical vapor deposition using CH4+SiH4+H2
Authors: Wang Guoju , Wang Bo , Huang Anping , Zhu Mankang , Wang Biben , Yan Hui
Published: November 2003

The contamination of unwanted atoms such as oxygen that may originate from residual gas in reactant chambers is common in the deposition of SiC films. In this study, CF4 was introduced into a chamber while preparing SiC films by hot filament chemical vapor deposition using CH4, SiH4, and H2, and then the films were characterized by Fourier transform infrared (FTIR) spectrometer and x-ray photoelectron spectrometry (XPS). The FTIR and XPS results showed that the CF4 addition could reduce the oxygen content in the films. It is concluded that the reduction of oxygen is due to the reaction of active F* (or CFn*), O*, Si* (or SiHn*), and C* (or CHn*) in the process. Simultaneously, the results indicate also that the addition of CF4 could improve the degree of ordering of the Si–C bonds and lead to a decrease in the growth rate. The influence of CF4 addition on the ordering of the Si–C bonds and the growth rate of the films is discussed.
Characterization of nonstoichiometric TiO2 and ZrO2 thin films stabilized by Al2O3 and SiO2 additions
Authors: Kuo Dong-Hau , Tzeng Kuo-Hwa , Chien Chi-Hung
Published: November 2003

Thin films of nonstoichiometric titanium dioxide (TiO2) and zirconium oxide (ZrO2) chemically stabilized by incorporating stoichiometric oxides of Al2O3 and SiO2, respectively, were fabricated by rf magnetron sputtering. These films deposited from ceramic targets of TiO2, TiO2–10 vol %Al2O3, ZrO2, and ZrO2–10 vol %SiO2 were designated as TiO2, TiO2–10Al2O3, ZrO2, and ZrO2–10SiO2. The dielectric and electrical properties of as-deposited and annealed TiO2 and ZrO2 films varied with the processing conditions. The addition of Al2O3 to TiO2 and SiO2 to ZrO2 films had not only reduced the dielectric loss tangent (tan δ) and increased resistivity, but also retained the competitive dielectric constant (k). The dielectric properties of the TiO2–10Al2O3 and ZrO2–10SiO2 films became stable under different deposition temperatures and annealing temperatures. The TiO2–10Al2O3 films with k=62, tan δ=0.012, resistivity of 2.5×108 Ω cm, and breakdown field of 2.2 MV/cm were obtained. ZrO2–10SiO2 films with good k values of 20–25 and low tan δ values of 0.011–0.014 can be obtained under rf power of 150 W, while k=14.5–16.4 and tan δ=0.012–0.019 under 100 W can be obtained. The advantage of adding the stoichiometric oxides of Al2O3 and SiO2 is the reduction of oxygen vacancies through the strong affinity of Al3+ and Si4+ to capture more oxygen for nonstoichiometric oxides of TiO2 and ZrO2.
Effect of vessel orientation on videodensitometry quantitative coronary arteriography
Authors: Molloi Sabee , Dang Quang , Breault John
Published: November 2003

Cross‐sectional area measurement using videodensitometry coronary arteriography is a function of the out‐of‐plane angle of the vessel segment with respect to the face of the image intensifier. Therefore, absolute cross‐sectional area measurement using videodensitometry requires correction for the out‐of‐plane angle. In this study, a simple technique to measure the out‐of‐plane angle of a vessel segment using images from two different projections is presented. The technique was tested using vessel phantoms imaged at different out‐of‐plane angles. A vessel segment with an out‐of‐plane angle of less than 20 degrees introduces less than 5% error in the cross‐sectional area measurements. However, an out‐of‐plane angle of 60 degrees can introduce more than 90% error. The results of the measurements show that correction for the out‐of‐plane angle reduces the error in cross‐sectional area measurement to less that 5%. The correction for the out‐of‐plane angle makes it possible to measure the absolute cross‐sectional area using videodensitometery, which can be used to assess a diseased vessel segment with any complex geometry.
Inverse treatment planning by physically constrained minimization of a biological objective function
Authors: Stavrev P. , Hristov D. , Warkentin B. , Sham E. , Stavreva N. , Fallone B. G.
Published: November 2003

In the current state‐of‐the art of clinical inverse planning, the design of clinically acceptable IMRT plans is predominantly based on the optimization of physical rather than biological objective functions. A major impetus for this trend is the unproven predictive power of radiobiological models, which is largely due to the scarcity of data sets for an accurate evaluation of the model parameters. On the other hand, these models do capture the currently known dose‐volume effects in tissue dose‐response, which should be accounted for in the process of optimization. In order to incorporate radiobiological information in clinical treatment planning optimization, we propose a hybrid physico‐biological approach to inverse treatment planning based on the application of a continuous penalty function method to the constrained minimization of a biological objective. The objective is defined as the weighted sum of normal tissue complication probabilities evaluated with the Lyman normal‐tissue complication probability model. Physical constraints specify the admissible minimum and maximum target dose. The continuous penalty function method is then used to find an approximate solution of the resulting large‐scale constrained minimization problem. Plans generated by our approach are compared to ones produced by a commercial planning system incorporating physical optimization. The comparisons show clinically negligible differences, with the advantage that the hybrid technique does not require specifications of any dose‐volume constraints to the normal tissues. This indicates that the proposed hybrid physico‐biological method can be used for the generation of clinically acceptable plans.