bluuebunny/crossref_metadata_2025 huggingface dataset:
From Informal Recreation to a Geography of Achievement: Women's Soccer in South Australia
Authors: ROSSO EDOARDO
Published: December 2009

Since its inclusion amongst Olympic sports in the 1990s, women's soccer has grown impressively worldwide. Despite its rapid global expansion and growth in the number of playing participants, the sport has been neglected by geographers. In Australia, which is currently the fifth women's soccer country in the world as per registered players, the popularity of the sport has grown significantly in recent years. Perhaps even more strikingly, however, the approach to the sport has changed, to focus on the achievement of results. The shift in the purpose of women's soccer, from a solely social and recreational activity to an achievement sport, is a result of the increasing links between the local women's soccer systems and the global world of sport. The paper examines an exemplar of South Australia, and in particular the Adelaide metropolitan region. Here, in the last 30 years, women's soccer has evolved from a geography of foundation, defined by informal organisation and localised scope, to a geography of achievement, characterised by an institutionalised focus on the production of players, the introduction of higher‐profile ‘sportscapes’, a broader pattern of clubs distribution, and a new set of connections with global women's soccer. The current geography of achievement links local and global women's soccer scenes. On the other hand, it funnels access to the achievement level of South Australian women's soccer to a limited central area of Adelaide's metropolitan region. The paper also draws attention to the part that social capital, and especially ‘bridging’ social capital, played in enabling the evolution of Adelaide women's soccer. The role of social capital as a contributing element of the development of sporting systems is a topic that deserves further investigation.
Development Imperative, Terrae Incognitae: a Pioneer Soil Scientist 1912–1951
Authors: POWELL J.M.
Published: December 2009

James Arthur Prescott was a prominent soil scientist whose career responded to an increasingly complex, recognisably Australian web of interpenetrating spatial scales, served to promote revolutionary global advances in his chosen field, and in the process negotiated the blurred boundaries between ‘pure’ and ‘applied’ research. Encounters with this instructive life suggest that, while resolutions of pivotal anxieties might turn on ineluctably personal qualities, they also reflect a dynamic interplay between international, imperial, national and state contexts. Prescott's innovative contributions to soil science, fruits of a tenaciously consolidated career, influenced resource appraisal and environmental management across a prodigious continental expanse. A sustained focus on local and regional development brought him into contact with a wide range of contemporaries, including pioneering geographers, and culminated in his election to a Fellowship of the Royal Society.
The Multifunctional Transition in Australia's Tropical Savannas: the Emergence of Consumption, Protection and Indigenous Values
Authors: HOLMES JOHN
Published: December 2009

As elsewhere in affluent, western nations, the direction, complexity and pace of rural change in Australia can be conceptualised as a multifunctional transition in which a variable mix of consumption and protection values has emerged, contesting the former dominance of production values, and leading to greater complexity and heterogeneity in rural occupance at all scales. This transition has been explored in accessible, high‐amenity landscapes driven by enhanced consumption values. Less attention has been directed to remote, marginal lands where a flimsy mode of productivist occupance can, in part, be displaced by alternative modes with the transitions being facilitated by low transfer costs. Such is the case in Australia's northern tropical savannas where an extensive mode of pastoral occupance is selectively displaced by alternative consumption, protection and Indigenous values. This transition towards multifunctional occupance is most readily documented by mapping changes in land tenure and ownership over the last three decades. Tenure changes have been accompanied by new regimes of property rights and land ownership, including: native titles derived from common law; non‐transferable, common‐property Aboriginal freehold tenures; transfers of pastoral leases to Indigenous and conservation interests; expansion of conservation lands under public tenures; and revisions of the rights and duties of pastoral lessees. Future occupance scenarios remain unclear, given the sensitivity of this frontier zone to national and global driving forces.
Efficacy and Safety of Efalizumab in Patients with Moderate‐to‐Severe Plaque Psoriasis Resistant to Previous Anti‐Psoriatic Treatment: Results of a Multicentre, Open‐label, Phase IIIb/IV Trial
Authors: Lotti Torello , Chimenti Sergio , Katsambas Andreas , Ortonne Jean‐Paul , Dubertret Louis , Licu Daiana , Simon Jan
Published: December 2009

Objectives.  To evaluate the efficacy and safety of efalizumab in continuous or interrupted therapy of adults with moderate‐to‐severe plaque psoriasis who had failed to respond to or were intolerant of other systemic therapies, including methotrexate, ciclosporin and psoralen plus UVA phototherapy, or for whom such therapies were contraindicated.

Methods.  Patients received a conditioning dose of efalizumab 0.7 mg/kg followed by once‐weekly open‐label efalizumab 1.0 mg/kg for 11 weeks. Responders (Physician Global Assessment [PGA] score of “good” or better at Week 12) could continue efalizumab for a further 8 weeks (continuous‐treatment period). Nonresponders transitioned to alternative anti‐psoriasis medication or stopped treatment. Responders who discontinued efalizumab could restart treatment if symptoms worsened. PGA response was evaluated at Weeks 12 (primary endpoint) and 20, as were the proportions of patients achieving an improvement from baseline of ≥50%, ≥75% and ≥90% in Psoriasis Area and Severity Index (PASI) (PASI 50, PASI 75 and PASI 90, respectively).

Results.  A total of 1,255 patients were included in the intention‐to‐treat population. At Week 12, 68.0% of patients had a PGA rating of “good” or better. Of 688 patients who entered the continuous‐treatment period, 79.5% had a PGA rating of “good” or better at Week 20. At Week 12, median improvement in PASI score was 68.4%. PASI 50/75/90 was achieved by 65.5%/35.9%/13.0% of patients at Week 12, and by 78.2%/52.9%/24.3% of responders at Week 20. Of the 127 responders at Week 12 who discontinued efalizumab, 11% experienced rebound and 56.7% relapsed within 8 weeks after stopping therapy. Efalizumab was well tolerated during the study.

Conclusions.  Efalizumab provided effective control of psoriasis in the majority of patients during the initial treatment period. The high response rates were maintained in initial responders when treatment was continued beyond 12 weeks.
Epidemiology of exfoliation syndrome in the Reykjavik Eye Study
Authors: Arnarsson Ársæll Már
Published: December 2009

Exfoliation syndrome (XFS) is a major risk factor for glaucoma. It is characterized by a pathological accumulation of polymorphic fibrillar material in the anterior segment of the eye. It is likely that the increase in intraocular pressure (IOP) seen in XFS patients is at least in part because of flakes of material clogging up the trabecular meshwork, and thereby increasing the resistance to outflow and increasing IOP. XFS glaucoma progresses more rapidly, is more resistant to medical treatment and has worse prognosis than other glaucomas. The prevalence of XFS has been found to vary greatly between different studies, raising the possibility of racial and/or environmental modulators. XFS has also been linked to other changes in ophthalmological structures such as; changes in central corneal thickness (CCT), steeper corneal curvature (CC) and nuclear lens opacifications. Some studies have found XFS to be associated with systemic diseases, mostly cardiovascular and cerebrovascular. Exposure to ultra‐violet (UV) light has also been investigated as a possible culprit, along with several other plausible factors. The aim of the present study was to determine the prevalence and 5‐year incidence of XFS, to establish possible risk factors and/or concomitant symptoms and finally to investigate the relationship between XFS and glaucomatous changes.

The Reykjavík Eye Study (RES) is a prospective study based on a random sample from the Icelandic national population sample. The baseline examination was performed in the autumn of 1996, when 1045 persons older than 50 years participated. Of these, 846 (88.2% of survivors) participated in a follow‐up 5 years later. All participants went through a standard examination protocol, and answered a comprehensive questionnaire on health and life style.

In the prevalence study, XFS was found in 10.7% of subjects, more frequently in women and older persons. Five years later, a further 5.2% of those that participated in the follow‐up study and had no signs of XFS at baseline were diagnosed having XFS. We found a strong correlation between IOP and XFS. No difference was found in the anterior segment parameters measured, but there was a significant loss of neural tissue in the XFS as demonstrated by measurements of cup/disk ratio.

In conclusion, we find XFS to be frequent among Icelanders, increasing with age and more in women. Our diagnostic criteria are reliable over time. We have also identified possible risk factors that point to a role of antioxidants in the development of XFS. We find changes in corneal curvature and thickness more related to age than XFS.
Comparative Evaluation of Antioxidant Reactivity between Ovariectomized and Control Urinary Bladder Tissue Using Ferric Reducing Ability of Plasma and Cupric Ion Reducing Antioxidant Capacity Assays
Authors: RADU Florian , BEAN Holly , SCHULER Catherine , LEGGETT Robert E. , LEVIN Robert M.
Published: December 2009

Objectives:In rabbits, ovariectomy has been shown to cause reduced blood flow to the bladder, increased free radical generation, and oxidative damage to the bladder. Thus, the antioxidant status of rabbits may play an important role in the damaging effects of ovariectomy. The present study analyzed total antioxidant content (TAC) in control, 14‐ and 28‐day ovariectomized (Ovx) female rabbit bladders using both ferric reducing ability of plasma (FRAP) and cupric ion reducing antioxidant capacity (CURPAC) assays.

Methods:Twelve weight‐ and age‐matched virgin female New Zealand White rabbits (∼ 4.0 kg) were separated into three groups of four rabbits each. Group 1 received ovariectomy surgery for 14 days. Group 2 received ovariectomy surgery for 28 days. Group 3 received sham operations.

Results:FRAP did not show any significant differences between either muscle and mucosa or control and Ovx samples. CUPRAC revealed higher TAC in the control mucosa compared to muscle and significantly decreased antioxidant levels in 14‐ and 28‐day Ovx mucosal layers compared to the mucosa of the control rabbits.

Conclusion:The CUPRAC method proved to be superior to the FRAP method for accuracy.
Biochemical and genomic comparison of inorganic phosphate solubilization in Pseudomonas species
Authors: Miller Simon H. , Browne Patrick , Prigent‐Combaret Claire , Combes‐Meynet Emeline , Morrissey John P. , O'Gara Fergal
Published: December 2009

Mobilization of insoluble soil inorganic phosphate by plant beneficial rhizobacteria is a trait of key importance to the development of microbial biofertilizers. In this study, the ability of several Pseudomonas spp. to solubilize Ca3(PO4)2 was compared. While all Pseudomonas spp. were found to facilitate a decrease in pH and solubilize inorganic phosphate by the production of extracellular organic acids, strains varied by producing either gluconic or 2‐ketogluconic acid. Furthermore, comparison between the Pseudomonas spp. of the genes involved in oxidative glucose metabolism revealed variations in genomic organization. To further investigate the genetic mechanisms involved in inorganic phosphate solubilization by Pseudomonas spp., a transposon mutant library of P. fluorescens F113 was screened for mutants with reduced Ca3(PO4)2 solubilization ability. Mutations in the gcd and pqqE genes greatly reduced the solubilization ability, whereas mutations in the pqqB gene only moderately reduced this ability. The combination of biochemical analysis and genomic comparisons revealed that alterations in the pqq biosynthetic genes, and the presence/absence of the gluconate dehydrogenase (gad) gene, fundamentally affect phosphate solublization in strains of P. fluorescens.
Intelligent Procedures for Intra‐Day Updating of Call Center Agent Schedules
Authors: Mehrotra Vijay , Ozlük Ozgür , Saltzman Robert
Published: December 2009

For nearly all call centers, agent schedules are typically created several days or weeks before the time that agents report to work. After schedules are created, call center resource managers receive additional information that can affect forecasted workload and resource availability. In particular, there is significant evidence, both among practitioners and in the research literature, suggesting that actual call arrival volumes early in a scheduling period (typically an individual day or week) can provide valuable information about the call arrival pattern later in the same scheduling period. In this paper, we develop a flexible and powerful heuristic framework for managers to make intra‐day resource adjustment decisions that take into account updated call forecasts, updated agent requirements, existing agent schedules, agents' schedule flexibility, and associated incremental labor costs. We demonstrate the value of this methodology in managing the trade‐off between labor costs and service levels to best meet variable rates of demand for service, using data from an actual call center.
On the parity of ranks of Selmer groups IV. With an appendix by Jean-Pierre Wintenberger
Authors: Nekovář Jan
Published: December 2009

We prove the parity conjecture for the ranks of p-power Selmer groups (p⁄=2) of a large class of elliptic curves defined over totally real number fields.
Noncrossing partitions and representations of quivers
Authors: Ingalls Colin , Thomas Hugh
Published: December 2009

We situate the noncrossing partitions associated with a finite Coxeter group within the context of the representation theory of quivers. We describe Reading’s bijection between noncrossing partitions and clusters in this context, and show that it extends to the extended Dynkin case. Our setup also yields a new proof that the noncrossing partitions associated with a finite Coxeter group form a lattice. We also prove some new results within the theory of quiver representations. We show that the finitely generated, exact abelian, and extension-closed subcategories of the representations of a quiverQwithout oriented cycles are in natural bijection with the cluster tilting objects in the associated cluster category. We also show that these subcategories are exactly the finitely generated categories that can be obtained as the semistable objects with respect to some stability condition.
Whittaker unitary dual of affine graded Hecke algebras of type E
Authors: Barbasch Dan , Ciubotaru Dan
Published: December 2009

This paper gives the classification of the Whittaker unitary dual for affine graded Hecke algebras of type E. By the Iwahori–Matsumoto involution, this is also equivalent to the classification of the spherical unitary dual for type E. Together with some results of Barbasch and Moy (D. Barbasch and A. Moy, Unitary spherical spectrum for p-adic classical groups, Acta Appl. Math. 44 (1996), 3–37; D. Barbasch, The spherical unitary spectrum of split classical real and p-adic groups, Preprint (2006), math/0609828) and Ciubotaru (D. Ciubotaru, The Iwahori spherical unitary dual of the split group of type F4, Represent. Theory 9 (2005), 94–137), this work completes the classification of the Whittaker Iwahori-spherical unitary dual or, equivalently, the spherical unitary dual of any split p-adic group.
Sums of smooth squares
Authors: Blomer V. , Brüdern J. , Dietmann R.
Published: December 2009

LetR(n,θ) denote the number of representations of the natural numbernas the sum of four squares, each composed only with primes not exceedingnθ/2. Whenθ>e−1/3 a lower bound forR(n,θ) of the expected order of magnitude is established, and whenθ>365/592, it is shown thatR(n,θ)>0 holds for largen. A similar result is obtained for sums of three squares. An asymptotic formula is obtained for the related problem of representing an integer as the sum of two squares and two squares composed of small primes, as above, for any fixedθ>0. This last result is the key to boundR(n,θ) from below.
On volumes of arithmetic line bundles
Authors: Yuan Xinyi
Published: December 2009

We show an arithmetic generalization of the recent work of Lazarsfeld–Mustaţǎ which uses Okounkov bodies to study linear series of line bundles. As applications, we derive a log-concavity inequality on volumes of arithmetic line bundles and an arithmetic Fujita approximation theorem for big line bundles.
On the Performance of Very High Temperature Reactor Plants With Direct and Indirect Closed Brayton Cycles
Authors: El-Genk Mohamed S. , Tournier Jean-Michel
Published: December 2009

The performance of very high temperature reactor plants with direct and indirect closed Brayton cycles (CBCs) is compared and the effects of the molecular weight of the CBC working fluid on the number of stages and sizes of the axial flow, single shaft compressor and turbine are investigated. The working fluids considered are helium (4 g/mole), He–Xe, and He–N2 binary mixtures (15 g/mole). Also investigated are the effects of using low and high pressure compressors with intercooling, instead of a single compressor, and changing the reactor exit temperature from 700°C to 950°C on the plant thermal efficiency, the CBC pressure ratio, and the number of stages in and size of the turbomachines. For plants with direct CBCs, the effect of cooling the reactor pressure vessel with He bled off at the exit of the compressor is also investigated. The present analyses are performed for a reactor thermal power of 600 MW, shaft rotation speed of 3000 rpm, and intermediate heat exchanger temperature pinch of 50°C.
Simulating the Concentration Equations and the Gas-Wall Interface for One-Dimensional Based Diesel Particulate Filter Models
Authors: Depcik Christopher
Published: December 2009

This paper enhances an earlier publication by including the concentration equations of motion into the area-conserved one-dimensional based diesel particulate filter model. A brief historical review of the species equations is accomplished to describe this model and the pertinent physics involved. In the species equations through the wall and soot layers, the diffusion constants are modified to account for the close proximity of the porous walls and the particulate matter to the gas flowing through the accompanying layers. In addition, a review of potential options involving the diffusion velocity is accomplished to determine the effect of pressure gradients on this phenomenon. In the previous paper, the model formulation illustrated that a common assumption to make for an enthalpy difference is the use of constant pressure specific heat times a temperature difference. Because of the different heats of formation and sensible enthalpies associated with the chemical species, this assumption reviewed is found to have a related error. Finally, because each channel is treated as an open system, making the common assumption of dilute mixture simplification is reviewed and found to have an associated error.
Synchronous Response to Rotor Imbalance Using a Damped Gas Bearing
Authors: Ertas Bugra H. , Camatti Massimo , Mariotti Gabriele
Published: December 2009

One type of test performed for evaluating bearings for application into turbomachinery is the synchronous bearing response to rotor imbalance. This paper presents rotordynamic tests on a rotor system using a 70 mm diameter damped gas bearing reaching ultra-high speeds of 50,000 rpm. The main objective of the study was to experimentally evaluate the ability of the damped gas bearing to withstand large rotor excursions and provide adequate damping through critical speed transitions. Two critical speeds were excited through varying amounts and configurations of rotor imbalance while measuring the synchronous rotordynamic response at two different axial locations. The results indicated a well-damped rotor system and demonstrated the ability of the gas bearing to safely withstand rotor vibration levels while subjected to severe imbalance loading. Also, a waterfall plot was used to verify ultra-high-speed stability of the rotor system throughout the speed range of the test vehicle. In addition to the experimental tests, a rotordynamic computer model was developed for the rotor-bearing system. Using the amplitude/frequency dependent stiffness and damping coefficients for the ball bearing support and the damped gas-bearing support, a pseudononlinear rotordynamic response to imbalance was performed and compared with the experiments.
Application of Bayesian Forecasting to Change Detection and Prognosis of Gas Turbine Performance
Authors: Lipowsky Holger , Staudacher Stephan , Bauer Michael , Schmidt Klaus-Juergen
Published: December 2009

The performance of gas turbines degrades over time due to deterioration mechanisms and single fault events. While deterioration mechanisms occur gradually, single fault events are characterized by occurring accidentally. In the case of single events, abrupt changes in the engine parameters are expected. Identifying these changes as soon as possible is referred to as detection. State-of-the-art detection algorithms are based on expert systems, neural networks, special filters, or fuzzy logic. This paper presents a novel detection technique, which is based on Bayesian forecasting and dynamic linear models (DLMs). Bayesian forecasting enables the calculation of conditional probabilities, whereas DLMs are a mathematical tool for time series analysis. The combination of the two methods can be used to calculate probability density functions prior to the next observation, or the so called forecast distributions. The change detection is carried out by comparing the current model with an alternative model, where the mean value is shifted by a prescribed offset. If the forecast distribution of the alternative model better fits the actual observation, a potential change is detected. To determine whether the respective observation is a single outlier or the first observation of a significant change, a special logic is developed. In addition to change detection, the proposed technique has the ability to perform a prognosis of measurement values. The developed method was run through an extensive test program. Detection rates >92% have been achieved for changed heights, as small as 1.5 times the standard deviation of the observed signal (sigma). For changed heights greater than 2 sigma, the detection rates have proven to be 100%. It could also be shown that a high detection rate is gained by a high false detection rate (∼2%). An optimum must be chosen between a high detection rate and a low false detection rate, by choosing an appropriate uncertainty limit for the detection. Increasing the uncertainty limit decreases both detection rate and false detection rate. In terms of prognostic abilities, the proposed technique not only estimates the point of time of a potential limit exceedance of respective parameters, but also calculates confidence bounds, as well as probability density and cumulative distribution functions for the prognosis. The conflictive requirements of a high degree of smoothing and a quick reaction to changes are fulfilled in parallel by combining two different detection conditions.
Mapping the Density Fluctuations in a Pulsed Air-Methane Flame Using Laser-Vibrometry
Authors: Giuliani Fabrice , Leitgeb Thomas , Lang Andreas , Woisetschläger Jakob
Published: December 2009

Laser vibrometry (LV) is originally a laser-based, line-of-sight measurement technique dedicated to the analysis of surface vibrations. It was lately adapted at TU Graz for monitoring the stability of an air-methane flame (Giuliani, et al., 2006, ASME Turbo Expo, ASME Paper No. GT2006-90413). This paper reports on the mapping of density fluctuations measured with LV in a premixed air-methane flame (free jet; swirl stabilized) with a forced flow modulation (quarter-wave resonator; amplification with a siren). In order to correlate the density fluctuations with the jet aerodynamics and turbulent flame shape, stereoscopic particle image velocimetry and high-speed schlieren visualizations were used. This paper addresses issues regarding the estimate of density fluctuations, the transform from line-of-sight to local measurement with tomographic methods, and the potential of the method for detailed description of thermoacoustic couplings. One emphasized application of LV is its ability to perform precise and low-cost benchmark stability tests on a combustor during the design phase (time-resolved measurement, high frequency and phase resolution on the 5 Hz–20 kHz range with the present equipment and settings, near-constant spectral sensitivity over a large bandwidth, and no seeding required; measurement possible over the whole combustion volume).
Aerodynamic Design and Numerical Investigation on Overall Performance of a Microradial Turbine With Millimeter-Scale
Authors: Fu Lei , Shi Yan , Deng Qinghua , Feng Zhenping
Published: December 2009

For millimeter-scale microturbines, the principal challenge is to achieve a design scheme to meet the aerothermodynamics, geometry restriction, structural strength, and component functionality requirements while in consideration of the applicable materials, realizable manufacturing, and installation technology. This paper mainly presents numerical investigations on the aerothermodynamic design, geometrical design, and overall performance prediction of a millimeter-scale radial turbine with a rotor diameter of 10 mm. Four kinds of turbine rotor profiles were designed, and they were compared with one another in order to select the suitable profile for the microradial turbine. The leaving velocity loss in microgas turbines was found to be a large source of inefficiency. The approach of refining the geometric structure of rotor blades and the profile of diffuser were adopted to reduce the exit Mach number, thus improving the total-static efficiency. Different from general gas turbines, microgas turbines are operated in low Reynolds numbers (104–105), which has significant effect on flow separation, heat transfer, and laminar to turbulent flow transition. Based on the selected rotor profile, several microgas turbine configurations with different tip clearances of 0.1 mm, 0.2 mm, and 0.3 mm, two different isothermal wall conditions, and two laminar-turbulent transition models were investigated to understand the particular influences of low Reynolds numbers. These influences on the overall performance of the microgas turbine were analyzed in detail. The results indicate that these configurations should be included and emphasized during the design process of the millimeter-scale microradial turbines.
Measurement of Structural Stiffness and Damping Coefficients in a Metal Mesh Foil Bearing
Authors: San Andrés Luis , Chirathadam Thomas Abraham , Kim Tae-Ho
Published: December 2009

Engineered metal mesh foil bearings (MMFBs) are a promising low cost bearing technology for oil-free microturbomachinery. In a MMFB, a ring shaped metal mesh provides a soft elastic support to a smooth arcuate foil wrapped around a rotating shaft. This paper details the construction of a MMFB and the static and dynamic load tests conducted on the bearing for estimation of its structural stiffness and equivalent viscous damping. The 28.00 mm diameter 28.05 mm long bearing, with a metal mesh ring made of 0.3 mm copper wire and compactness of 20%, is installed on a test shaft with a slight preload. Static load versus bearing deflection measurements display a cubic nonlinearity with large hysteresis. The bearing deflection varies linearly during loading, but nonlinearly during the unloading process. An electromagnetic shaker applies on the test bearing loads of controlled amplitude over a frequency range. In the frequency domain, the ratio of applied force to bearing deflection gives the bearing mechanical impedance, whose real part and imaginary part give the structural stiffness and damping coefficients, respectively. As with prior art published in the literature, the bearing stiffness decreases significantly with the amplitude of motion and shows a gradual increasing trend with frequency. The bearing equivalent viscous damping is inversely proportional to the excitation frequency and motion amplitude. Hence, it is best to describe the mechanical energy dissipation characteristics of the MMFB with a structural loss factor (material damping). The experimental results show a loss factor as high as 0.7 though dependent on the amplitude of motion. Empirically based formulas, originally developed for metal mesh rings, predict bearing structural stiffness and damping coefficients that agree well with the experimentally estimated parameters. Note, however, that the metal mesh ring, after continuous operation and various dismantling and re-assembly processes, showed significant creep or sag that resulted in a gradual decrease in its structural force coefficients.
An Engineering Approach to Improve the Stamping Robustness of High Strength Steels
Authors: Wang Wu-rong , Hou Bo , Lin Zhong-qin , Xia Z. Cedric
Published: December 2009

High strength steels (HSSs) are one of the light-weight sheet metals well suited for reducing vehicle weight due to their higher strength-to-weight ratio. However, HSS tend to have bigger variations in their mechanical properties due to more complex rolling techniques involved in the steel-making process. Such uncertainties, when combined with variations in the process parameters such as friction and blank holder force, pose a significant challenge in maintaining the robustness of HSS sheet metal stamping. The paper presents a systematic and robust approach, combining the power of the finite element method and stochastic statistics to decrease the sensitivity of HSS stamping in the presence of above-mentioned uncertainties. First, the statistical distribution of sheet metal properties of selected HSS is characterized from a material sampling database. Then a separate interval adaptive response surface methodology (RSM) is applied in modeling sheet metal stamping. The new method significantly improves the model accuracy when compared with the conventional RSM within a single interval. Finally, the Monte Carlo method is employed to simulate the stochastic response of material/process variations to stamping quality and to provide optimal process parameter designs to reduce the sensitivity of these effects. The experiment with the obtained optimal process design demonstrates the improvements of stamping robustness using small-batch experiments.
A Parametric Analysis of the Undeformed Chip Geometry in Gear Hobbing
Authors: Vedmar Lars , Andersson Carin , Ståhl Jan-Eric
Published: December 2009

Hobbing is a common manufacturing method when producing helical, involute gears. In order to increase tool life and surface finish, an accurate method to determine chip geometry is needed. Although this accurateness may involve numeric solutions, the geometric description must, as far as possible, be analytic and give a description of the continuously changing chip geometry. In this report, the cutting edges of the tool are mathematically described using parametric and analytically differentiable functions. This gives the possibility to determine the geometry of the three-dimensional surface on the blank each cutting edge will cut with numeric approximations kept to a minimum. By comparing successively cut surfaces, the chip geometry is determined using the tool and process parameters. The mathematical description gives the possibility to calculate the required characteristic properties of the chips. These are needed for increasing the tool life in order to develop more efficient tools and processes. An example is given in which characteristics, as the maximum chip thickness, the chip cross-section area, and the mean chip thickness are calculated. The reported theory describes in detail how the chip geometry is determined.
Surface Texturing of Tribological Interfaces Using the Vibromechanical Texturing Method
Authors: Greco Aaron , Raphaelson Steven , Ehmann Kornel , Wang Q. Jane , Lin Chih
Published: December 2009

Modifying the surface topography of tribological interfaces has the potential to improve the friction performance of certain mechanical components that experience sliding contact. Vibromechanical texturing (VMT), an improved texturing method based on the convenient turning process, is introduced. This process is performed on a standard computer numeric controlled (CNC) lathe, which is retrofitted with a piezoelectric-actuated tool positioning stage. Controlled vibratory motion of the tool is used to cut microsized dimples into the surface of the workpiece. Two types of workpiece materials are used: aluminum and hardened steel, with three forms of workpiece geometries: outer cylinder, inner cylinder, and flat/end face. The accuracy of the texturing method is compared with a basic surface topography model, which predicts texture dimensions within an 11% error for aluminum and up to 90% error for hardened steel, using the current open-loop control system. Further analysis of the textured samples shows no significant signs of process-induced damage. It is demonstrated that this VMT method is a versatile, accurate technique that has potential to be a cost-effective means for surface texturing of tribological components.
Environment-Friendly Strategies for Efficient Utilization of Cutting Tools in Finish Turning
Authors: Sarma D. K. , Dixit U. S.
Published: December 2009

A number of experiments was conducted on the dry and air-cooled turning of steel with TiN coated carbide tool, and Weibull distribution was fitted on the tool life data. It is observed that the tool life (based on surface roughness) in dry turning is more than that in air-cooled turning. However, the tool consumed in air-cooled turning can be reused in dry turning. Further utilization of tool is possible by reusing the failed tool at reduced feed. These strategies of enhancing the tool life require only compressed air as a coolant, and hence, they are environment-friendly. A simple heuristic method is proposed for optimizing the finish turning process that is not dependent on a priori knowledge of tool life.
Experimental Investigation of Microcutting Mechanisms in Marble Grinding
Authors: Tanovic LJ. , Bojanic P. , Puzovic R. , Klimenko S.
Published: December 2009

This paper offers an experimental study of the microcutting mechanisms in marble grinding to aid the optimization of the marble grinding process. The necessity for investigating these mechanisms is dictated by the increased use of marble in many applications and the fact that grinding and polishing processes are the dominant technologies used to meet surface finish requirements in this natural material. The experiments are aimed at the determination of the normal component of the cutting force and of the grain traces in microcutting with a single diamond grain. The investigations carried out make provisions for establishing critical grain penetration and cutting depths and allow the prediction of the normal cutting force component as a function of grain penetration speed and depth.
Investigation of surface roughness of poly(methylmethacrylate) developed at reduced temperatures
Authors: Yan M. , Choi S. , Lee J. , Subramanian K. R. V. , Adesida I.
Published: December 2009

The surface roughness of poly(methylmethacrylate) (PMMA) with various molecular weights, using 50 keV electron beam, has been investigated at reduced developer temperatures. As the developer temperature decreased, the magnitude of the surface roughness increased rapidly while the contrast curves merged into a single curve below 0 °C. A sharp drop in roughness at the bottom of the resist was observed for all temperatures investigated. At each temperature, the higher molecular weight PMMA had higher maximum roughness.
Pushing extreme ultraviolet lithography development beyond 22 nm half pitch
Authors: Naulleau Patrick P. , Anderson Christopher N. , Baclea-an Lorie-Mae , Denham Paul , George Simi , Goldberg Kenneth A. , Goldstein Michael , Hoef Brian , Jones Gideon , Koh Chawon , La Fontaine Bruno , Montgomery Warren , Wallow Tom
Published: December 2009

Microfield exposure tools (METs) have and continue to play a dominant role in the development of extreme ultraviolet resists and masks. One of these tools is the SEMATECH Berkeley 0.3 numerical aperture (NA) MET. Here, the authors investigate the possibilities and limitations of using the 0.3 NA MET for sub-22-nm half-pitch development. They consider mask resolution limitations and present a method unique to the centrally obscured MET, allowing mask patterning resolution limitations to be overcome. The method, however, comes at the cost of increased sensitivity to mask surface roughness. They also explore projection optics resolution limits and describe various illumination schemes allowing resolution enhancement. At 0.3 NA, the 0.5k1 factor resolution limit is 22.5 nm, meaning that conventional illumination is of limited utility for sub-22-nm development. In general, resolution enhancing illumination encompasses increased coherence. They study the effect of this increased coherence on line-edge roughness (LER), which, along with resolution, is another crucial factor in sub-22-nm resist development. Due to coherence induced LER limitations, addressing the development at 16 nm half pitch and beyond will ultimately require higher NA systems.
Preparation of diamond-shaped channels in SU-8 for optical control of the filling state
Authors: Möllenbeck S. , Bogdanski N. , Mayer A. , Scheer H.-C. , Zajadacz J. , Zimmer K.
Published: December 2009

To improve control during the filling of the channels of a microfluidic device with the fluid under investigation, a new concept is presented: channels with a diamond-shaped cross section. These channels easily allow one to distinguish an unfilled channel from a filled channel by simple optical microscopy. The idea is based on the fact that incident light is totally reflected with unfilled channels, whereas it is mostly transmitted with filled channels. Preparation of such channels in thin SU-8 layers on a glass was performed via a double replication of a Si template with undercut trenches. Functionality tests with filling materials spanning the range of refractive indices of typical organic media provided an excellent contrast between filled and unfilled channels, thus demonstrating the capacity of this concept.
Self-aligned fabrication of 10 nm wide asymmetric trenches for Si/SiGe heterojunction tunneling field effect transistors using nanoimprint lithography, shadow evaporation, and etching
Authors: Wang Chao , Chou Stephen Y.
Published: December 2009

Fabrication of an asymmetric source/drain structure is important to heterojunction tunneling transistors but is extremely difficult to achieve reliably due to the stringent requirement of nanometer overlay alignment. Here the authors propose and demonstrate a simple self-aligned asymmetric nanotrench fabrication method, which has achieved a 10 nm wide (35 nm deep) trench in source region with an alignment accuracy better than 3 nm. The method is based on asymmetric shadow evaporation of the metal with the gate as a mask, creating an area uncovered by the metal only in the source but not in the drain, and a subsequent reactive ion etching with the evaporated metal as the etching mask. The accuracy of this method was found experimentally and theoretically to be within 5 nm.
Fabrication of a seamless roll mold by direct writing with an electron beam on a rotating cylindrical substrate
Authors: Taniguchi Jun , Aratani Masao
Published: December 2009

The fabrication of a seamless roll mold is difficult because of its cylindrical shape. However, seamless nanoscale patterns are in great demand for optical film applications. The authors have therefore developed a method for producing a seamless roll mold by direct writing with an electron beam (EB) onto a layer of resist material coated on a cylindrical substrate as the substrate is rotated in a vacuum. The resist layer is applied to the roll mold substrate by dipping the substrate in poly(methyl methacrylate) (PMMA) solution and then slowly withdrawing it; this coating method gives a uniform layer of resist. The resulting sample is mounted on rotating equipment and installed in an EB writing machine. The developed patterns produced in this case were seamless submicron striped patterns. The mold was used for ultraviolet nanoimprint lithography to give replica pattern that showed that the height of the striped pattern in the PMMA resist almost corresponded to the thickness of the resist. Furthermore, increasing the angle of incidence of the EB increased the sensitivity of the resist because of the resulting increase in the yield of secondary electrons.
Positioning Pd catalyst particles for carbon nanotube growth using charge patterns created with a scanning electron microscope
Authors: Zonnevylle A. C. , Hagen C. W. , Kruit P. , Valenti M. , Schmidt-Ott A.
Published: December 2009

Positioning of charged nanoparticles with the help of charge patterns in an insulator substrate is a known method. However, the creation of charge patterns with a scanning electron microscope for this is relatively new. Here a scanning electron microscope is used for the creation of localized charge patterns in an insulator, while a glowing wire generator is used as the nanoparticle source. The deposited palladium nanoparticles are used as catalysts for the localized growth of carbon nanotubes in a chemical vapor deposition oven. The authors show first the results on local carbon nanotube growth using this procedure.
Direct indium tin oxide patterning using thermal nanoimprint lithography for highly efficient optoelectronic devices
Authors: Yang Ki-Yeon , Yoon Kyung-Min , Lim SangWoo , Lee Heon
Published: December 2009

Indium tin oxide (ITO) is the most commonly used transparent conducting oxide (TCO) material on account of its high conductivity and transmittance in a visible range. In order to improve the efficiency of optoelectronic devices using TCO materials, the transmittance and conductivity of the TCO layers need to be improved. Recently, various techniques, which use nanostructures on the surface to improve the transmittance, have attracted considerable attention. In this study, a direct ITO nanopatterning technique using thermal nanoimprint lithography was presented. An ITO nanoparticle solution is used as an imprint resin and postimprint annealing process was followed. The optical transmittance of the ITO glass was increased by forming periodic ITO dot patterns on the ITO glass. UV-visible near infrared spectra showed that the transmittance at 485nm of the ITO glass with the directly patterned ITO layer was 5% higher than that of ordinary ITO glass.
Recovery prevention via pressure control in thermal nanoimprint lithography
Authors: Scheer Hella-Christin , Bogdanski Nicolas , Möllenbeck Saskia , Mayer Andre
Published: December 2009

In order to investigate the nonuniformity occurring below wider patterns during thermal nanoimprint lithography, the pressure situation is analyzed in detail. A balance of vertical forces shows that the gas pressure within the cavities is negligible, whereas the effective pressure acting on the stamp structures in contact to the polymer is increased compared to the externally applied pressure. This effective pressure has a high hydrostatic component, which may result in local stamp deformation. Imprint with a low molecular weight polymer provides evidence that the stamp structures become compressed under high pressure, resulting in a nonuniform residual layer beneath the imprinted patterns. In contrast, bending deformation of single stamp structures is found to be negligible. Pressure reduction is effective to reduce stamp compression, improving the uniformity of the residual layer. With typical imprint polymers of medium molecular weight, however, pressure reduction reduces the overall imprint depth.
Comparison of fast three-dimensional simulation and actinic inspection for extreme ultraviolet masks with buried defects and absorber features
Authors: Clifford Chris H. , Wiraatmadja Sandy , Chan Tina T. , Neureuther Andrew R. , Goldberg Kenneth A. , Mochi Iacopo , Liang Ted
Published: December 2009

The printability of buried extreme ultraviolet (EUV) defects near absorber features is studied using aerial images from the actinic inspection tool (AIT) and the fast EUV mask simulation program RADICAL. This work begins by comparing the printability of isolated defects through focus predicted by RADICAL and measured by the AIT. Then, images of defects near features from both simulation and experiment are investigated for different defect sizes and positions through focus. Finally, RADICAL is used to assess the expected defect printability levels in the less in coherent conditions which are expected to be used for production. Defect printability will be investigated as a function of defect size, position, and focus for the small absorber lines critical to 22nm imaging using a top-hat illumination condition of sigma=0.75. Here, defects as small as 0.8nm surface height cause a critical dimension (CD) change greater than 10% at best focus when located in the worst case position. Defects as small as 2.2nm cause a CD change greater than 10% even when located under the center of the absorber.
Embedded vertical nanosheets of SiO2 in PDMS using an alternative nanopatterning process
Authors: Jalabert L. , Bottier C. , Kumemura M. , Fujita H.
Published: December 2009

The authors demonstrate for the first time the embedding of vertical nanosheets of thermal silicon dioxide into the surface of polydimethylsiloxane (PDMS). The generic process is suitable for embedding a wide range of thin film nanosheets into PDMS-like polymers. The nanosheets are fabricated on a silicon template, and transferred into the PDMS by molding and releasing the nanosheets from the template during the peel-off of the cured PDMS. Since the template is fully fabricated using semiconductor and compatible processes, the presented technique aims at considerably expanding the range of materials that can be embedded in PDMS, thereby increasing the possible applications. As the width of the nanosheets is defined by the thickness of the deposited materials, nanoscale features can be directly embedded without relying on expensive nanolithography tools.
Evaluation of nanoimprint lithography as a fabrication process of phase-shifted diffraction gratings of distributed feedback laser diodes
Authors: Yanagisawa Masaki , Tsuji Yukihiro , Yoshinaga Hiroyuki , Kono Naoya , Hiratsuka Kenji
Published: December 2009

The authors have succeeded in employing nanoimprint lithography (NIL) to form diffraction gratings of distributed feedback laser diodes (DFB LDs) used in optical communication. Uniform gratings and phase-shifted gratings with periods of 232 nm have been formed by using a reversal NIL with a step-and-repeat imprint tool. Line edge roughness has been sufficiently low with the fabricated gratings. DFB LDs fabricated by NIL have indicated comparable characteristics with LDs fabricated by electron beam lithography. LDs show high long-term stability in threshold current. The authors have also demonstrated that phase-shifted DFB LDs show better uniformity in characteristics than uniform-grating DFB LDs. The results of this study indicate that NIL has high potential for fabricating DFB LDs.