bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving sugarcane for biofuel: engineering for an even better feedstock
Authors: LAM ERIC , SHINE JAMES , DA SILVA JORGE , LAWTON MICHAEL , BONOS STACY , CALVINO MARTIN , CARRER HELAINE , SILVA‐FILHO MARCIO C. , GLYNN NEIL , HELSEL ZANE , MA JIONG , RICHARD EDWARD , SOUZA GLAUCIA MENDES , MING RAY
Published: June 2009

Sugarcane is a proven biofuel feedstock and accounts for about 40% of the biofuel production worldwide. It has a more favorable energy input/output ratio than that of corn, the other major biofuel feedstock. The rich resource of genetic diversity and the plasticity of autopolyploid genomes offer a wealth of opportunities for the application of genomics and technologies to address fundamental questions in sugarcane towards maximizing biomass production. In a workshop on sugarcane engineering held at Rutgers University, we identified research areas and emerging technologies that could have significant impact on sugarcane improvement. Traditional plant physiological studies and standardized phenotypic characterization of sugarcane are essential for dissecting the developmental processes and patterns of gene expression in this complex polyploid species. Breeder friendly DNA markers associated with target traits will enhance selection efficiency and shorten the long breeding cycles. Integration of cold tolerance from Saccharum spontaneum and Miscanthus has the potential to expand the geographical range of sugarcane production from tropical and subtropical regions to temperate zones. The Flex‐stock and mix‐stock concepts could be solutions for sustaining local biorefineries where no single biofuel feedstock could provide consistent year‐round supplies. The ever increasing capacities of genomics and biotechnologies pave the way for fully exploring these potentials to optimize sugarcane for biofuel production.
THE SOUTH AFRICAN AGGREGATE PRODUCTION FUNCTION: ESTIMATION OF THE CONSTANT ELASTICITY OF SUBSTITUTION FUNCTION
Authors: Bonga‐bonga Lumengo
Published: June 2009

This paper assesses the validity of the constant elasticity of substitution (CES) and the Cobb‐Douglas (CD) production functions in modelling the aggregate production function and computing the total factor productivity (TFP) in South Africa for the period 1970‐2006. The CES function is estimated with Nerlove's two‐step procedure using the autoregressive distributed lag (ARDL) cointegration and the Kalman filter estimation techniques, while the CD production function is estimated using the Kalman filter technique. The results of the forecast performance of the two model specifications show that the CD specification outperforms the CES for the period 1970‐2006, although the CD specification may be too restrictive.
THE IMPACT OF HIV/AIDS ON ECONOMIC GROWTH IN SUB‐SAHARAN AFRICA1
Authors: Lovász Enrico , Schipp Bernhard
Published: June 2009

This study investigates the hypothesis that HIV/AIDS epidemic slows down the pace of economic growth. We examine 41 Sub‐Saharan African countries by using the empirical growth equation in an augmented Solow model in which health capital serves as a determinant of human capital. Econometric analysis is based on panel data and covers the period 1997‐2005. We control for a variety of factors possibly correlated with HIV prevalence that might also influence economic growth. As a key result we prove that the epidemic has a significant negative effect on the growth rate of per capita GDP in Sub‐Saharan Africa.
AN OPEN ECONOMY NEW KEYNESIAN DSGE MODEL OF THE SOUTH AFRICAN ECONOMY
Authors: Steinbach Mr , Mathuloe Pt , Smit Bw
Published: June 2009

In this paper an open economy New Keynesian model of the South African economy is presented. The model is constructed to provide for incomplete pass‐through of exchange rate changes, external habit formation, partial indexation of domestic prices and wages to past inflation, and staggered price and wage setting. Furthermore, the model is estimated using Bayesian techniques on South African domestic and trade partner data for the period 1990Q1 to 2007Q4. The estimated model is analysed by means of impulse response functions.
HIGH AND VOLATILE TREASURY YIELDS IN TANZANIA: THE ROLE OF STRATEGIC BIDDING AND AUCTION MICROSTRUCTURE
Authors: Abbas Sm Ali , Sobolev Yuri V.
Published: June 2009

The observed increase in the level and volatility of Tanzania's Treasury yields in recent years against an otherwise benign macroeconomic backdrop presented a puzzle for policymakers, while raising concerns about the fiscal burden of rising debt interest payments and diversion of bank credit away from the private sector. Using evidence from bid‐level data, and supported by a simple theorising of bidder incentives under unorthodox issuance practices, this paper traces the recent volatility in yields to the emergence of a sharp segmentation of the T‐bill market between sophisticated financial market players (foreign‐controlled banks) and a less‐experienced group of investors (domestic pension funds and small banks). An important policy recommendation that emerges is that public debt managers should avoid micro‐managing Treasury bill auctions by issuing amounts in excess of those offered or by dipping into oversubscribed segments of the yield curve, as such practices seriously disadvantage the less‐sophisticated (but more competitive) investors vis‐à‐vis the more sophisticated players.
A STOCHASTIC ESTIMATION FRAMEWORK FOR COMPONENTS OF THE SOUTH AFRICAN CONSUMER PRICE INDEX
Authors: Aron Janine , Muellbauer John N. J. , Pretorius Coen
Published: June 2009

Under inflation targeting in South Africa, it is important to monitor and forecast changes in prices, not only for aggregate measures of the consumer price index, but also its underlying sub‐components. Hypotheses about sectoral transmission of policy and shocks are often more specific than hypotheses about overall transmission. This study employs a stochastic framework to estimate richly specified equilibrium correction models, four‐quarters‐ahead, for the 10 sub‐components of the first targeted measure of the consumer price index, CPIX. The stochastic trends are estimated by the Kalman filter, and interpreted as capturing structural breaks and institutional change, a frequent cause of forecast failure. The trends suggest the design of deterministic split trends for use in recursive forecasting models, towards more accurate overall inflation forecasting. This research also has practical use for monetary policy in allowing identification of sectoral sources of inflation.
Climate Change Adaptation, Disaster Risk Reduction and Social Protection: Complementary Roles in Agriculture and Rural Growth?
Authors: Davies Mark , Guenther Bruce , Leavy Jennifer , Mitchell Tom , Tanner Thomas
Published: June 2009

Reliance on subsistence agriculture means the impact of stresses and shocks (such as droughts or floods) are felt keenly by rural poor people, who depend directly on food system outcomes for their survival, with profound implications for the security of their livelihoods and welfare. However, such stresses and shocks will not necessarily lead to negative impacts, as risks and uncertainties, often associated with seasonality, are embedded in the practice of agriculture and there is considerable experience of coping and risk management strategies among people working in this sector. With climate change, the magnitude and frequency of stresses and shocks is changing and approaches such as social protection, disaster risk reduction (DRR) and climate change adaptation (CCA) will be needed to bolster local resilience and supplement people's experience.

This study examines the opportunities for linking social protection, CCA and DRR in the context of agriculture and rural growth, exploring whether linking these three approaches together will help enhance resilience to shocks and stresses in agriculture‐dependent rural communities. The study does this by (i) reviewing conceptual and policy‐related similarities and differences between the three disciplines, by (ii) collecting evidence from case studies where climate change‐resilient social protection approaches have been trialled and by (iii) developing an adaptive social protection framework that highlight opportunities better coordination.

This paper suggests social protection and DRR measures designed to limit damages from shocks and stresses may not be sufficient in the longer term. For social protection to be resilient to climate change impacts, it will need to consider how reducing dependence on climate sensitive livelihood activities can be part of adaptive strategies. Similarly, CCA and DRR cannot effectively address the root causes of poverty and vulnerability without taking a differentiated view of poverty, something that further integration with social protection can help with.
Transnational Agrarian Movements Struggling for Land and Citizenship Rights
Authors: Borras Saturnino M. , Franco Jennifer C.
Published: June 2009

Rural citizens have increasingly begun to invoke perceived citizenship rights at transnational level, such that rural citizen engagements today have the potential to generate new meanings of global citizenship. La Vía Campesina has advocated for, created and occupied a new citizenship space that did not exist before at the global governance terrain – a public space distinct for poor peasants and small farmers from the global South and North. La Vía Campesina's transnational campaign in protest against neoliberal land policies is a good illustration of this in the sense that rural citizens of different countries collectively invoke their rights to define what land and land reform mean to them, struggle for their rights to have rights in reframing the terms of the global land policymaking, and demand accountability from international development institutions. It has been inherently linked with campaigns for land and citizenship rights. One of the outcomes of this initiative is that the public space created and occupied by various civil society groups got expanded. Such space has also been rendered much more complex, with the subsequent creation of various layers of sub‐spaces of interactions.
Mobilising and Mediating Global Medicine and Health Citizenship: The Politics of AIDS Knowledge Production in Rural South Africa
Authors: Robins Steven
Published: June 2009

The paper investigates the ways in which global health messages and forms of health citizenship are mediated by AIDS activists in rural South Africa. It focuses on how international health agencies and NGOs engage with local communities through AIDS prevention and treatment programmes. Some critics regard such global health programmes as conduits for the medicalisation of social life and social problems. From this perspective global medicine is an all‐encompassing process that results in systematic normalisation, depoliticisation and disempowerment of patients and citizens. However, this case study draws attention to the agency of the ‘targets’ of biomedicine. It also highlights the observation that AIDS activists and treatment literacy practitioners are not only concerned with biomedical matters, but are also committed to recruiting new members into their biopolitical projects and epistemic communities. These mobilisation processes involve translating and mediating biomedical ideas and practices into vernacular forms that can be easily understood and acted upon by the ‘targets’ of these recruitment strategies. However, these processes of ‘vernacularisation’ or localisation of biomedical knowledge often occur in settings where even the most basic scientific understandings and framings of medicine can not be taken for granted. This ethnographic case study shows that global health programmes, and their local NGO and social movement mediators, often encounter considerable ‘friction’ not only from powerful national state actors, who may view such programmes as challenges to national sovereignty, but also from the most marginalised village‐level actors.
Country Classifications for a Changing World
Authors: Harris Dan , Moore Mick , Schmitz Hubert
Published: June 2009

Summary

The distinction between developing and developed countries has long been central to development studies and to debates on development policy. In earlier decades, it was in many respects accurate, and was for many purposes useful. Although the world is still very much divided between rich and poor countries, relationships among countries have changed so much that the developing–developed country distinction has become an obstacle to understanding current problems and opportunities and, even more, to thinking productively about the future. It is time to stop using it. Many alternative ways of categorising countries have been suggested. In recent years in particular, large numbers of organisations have begun annually to rank countries according to a wide variety of criteria: from economic vulnerability, bribe payers, competitiveness, digital access, ease of doing business, food insecurity, governance, and happiness to water poverty and welfare. These do not adequately capture the structural and relational changes that have occurred in our multi‐polar world with substantially altered flows of ideas, resources and influence. Focusing on the needs of European policymakers, this paper suggests two axes for classifying countries. The first is the external capacity of states to influence and work with other states. This is captured in the (measureable) concept of ‘anchor countries’ developed by the German Development Institute and beginning to be put into practice in the enlargement from the G8 to the G20. The second is internal state capacity, as shaped by the sources of government income, in particular contrasting tax, aid, and oil. Using sources of public revenue as a way of classifying countries requires more work but would help to steer the development debate toward the key issue of improving the quality of governance and thus strengthening the capacity of poor countries to help themselves.
Development of Localized Deformation in AA 2024-O
Authors: Kweon S. , Beaudoin A. J. , Kurath P. , Li M.
Published: June 2009

An experimental study is presented to (1) quantify the rate-sensitive mechanical response and (2) examine the localized deformation behavior under an applied temperature gradient in the alloy AA 2024. Isothermal flow stresses are obtained at temperatures from −100°C to 495°C and strain rates from 10−2/s to 10−5/s using routine compression tests and a novel cyclic test, which expedites the characterization. The material displays two distinct kinetic responses with both being amenable to localization phenomena. The lower temperature/high strain rate regime displays a rate-insensitive yield with Stage III/IV work hardening. At higher temperature/low strain rates, a rate-sensitive response with little work hardening is observed. In order to relate the material constitutive behavior to the development of localized deformation, a temperature gradient test is performed wherein temperature differences of approximately 30°C are enforced between the top and bottom surfaces of a cylindrical compression test specimen. Deformation heterogeneity developed in the two distinct regimes of material response is illustrative of warm and hot working conditions typical of industrial processes, such as rolling.
Effect of dc on the Formability of Ti–6Al–4V
Authors: Ross Carl D. , Kronenberger Thomas J. , Roth John T.
Published: June 2009

Recent research has demonstrated that the mechanical properties of metals are altered when an electrical current is passed through the material. These studies suggest that titanium alloys, due to their low formability and need for dramatic improvement, should be subjected to additional study. The research presented herein further investigates the use of electricity to aid in the bulk deformation of Ti–6Al–4V under tensile and compressive loads. Extensive testing is presented, which documents the changes that occur in the formability of titanium due to the presence of an electrical current at varying current densities. Using carefully designed experiments, this study also characterizes and isolates the effect of resistive heating from the overall effect due to the electrical flow. This study clearly indicates that electrical flow affects the material beyond that which can be explained through resistive heating. The results demonstrate that an applied electrical current within the material during mechanical loading can greatly decrease the force needed to deform the titanium while also dramatically enhancing the degree to which it can be worked without fracturing. Isothermal testing further demonstrates that the changes are significantly beyond that which can be accounted for due to increases in the titanium’s temperature. The results are also supported by data from tests using pulsed and discontinuously applied current. Furthermore, current densities are identified that cause an enhanced formability behavior to occur. Overall, this work fully demonstrates that an electrical current can be used to significantly improve the formability of Ti–6Al–4V and that these improvements far exceed that which can be explained by resistive heating.
Study on Erosion Response of Hybrid Composites Using Taguchi Experimental Design
Authors: Patnaik Amar , Satapathy Alok , Mahapatra S. S.
Published: June 2009

This paper describes the development of multiphase hybrid composites consisting of polyester reinforced with E-glass fiber and ceramic particulates. It further investigates the erosion wear response of these composites and presents a comparison of the influence of three different particulate fillers—fly ash, alumina (Al2O3), and silicon carbide (SiC)—on the wear characteristics of glass-polyester composites. For this purpose, the erosion test schedule in an air jet type test rig is made, following design of experiments approach using Taguchi’s orthogonal arrays. The Taguchi approach enables us to determine optimal parameter settings that lead to minimization of the erosion rate. The results indicate that erodent size, filler content, impingement angle, and impact velocity influence the wear rate significantly. The experimental results are in good agreement with the values from the theoretical model. An artificial neural network approach is also applied to predict the wear rate of the composites and compared with the theoretical results. This study reveals that addition of hard particulate fillers such as fly ash, Al2O3, and SiC improves the erosion resistance of glass-polyester composites significantly. An industrial waste such as fly ash exhibits better filler characteristics compared with those of alumina and SiC. Finally, a popular evolutionary approach known as genetic algorithm is used to generalize the method of finding out optimal factor settings for minimum wear rate.
Evolution of Damage in Near α IMI-834 Titanium Alloy Under Monotonic Loading Condition: A Continuum Damage Mechanics Approach
Authors: Kumar Jalaj , Padma S. , Srivathsa B. , Rao N. Vyaghreswara , Kumar Vikas
Published: June 2009

In the present work, a continuum damage mechanics model, based on Lemaitre’s concept of equivalent stress hypothesis (1986, “Local Approach to Fracture,” Eng. Fract. Mech., 25, pp. 523–537), has been applied to study the evolution of damage under monotonic loading condition in a near α IMI-834 titanium alloy, used for aeroengine components in compressor module. The damage model parameters have been experimentally identified by in situ measurement of damage during monotonic deformation using alternating current potential drop technique. The damage model has been applied to predict damage evolution in an axisymmetrically notched specimen using finite element analysis. A reasonably good agreement has been observed between numerically simulated and experimentally measured damage behaviors. Damage micromechanisms operative in this alloy have also been identified which show multiple damage events.
Two New Multiaxial HCF Criteria Based on Virtual Stress Amplitude and Virtual Mean Stress Concepts for Complicated Geometries and Random Nonproportional Loading Conditions
Authors: Shariyat M.
Published: June 2009

Almost all of the available multiaxial high cycle fatigue (HCF) criteria are proposed based on definition of an equivalent stress expression that is a modified version of a static equivalent stress definition or a static yield function. All the equivalent stress expressions proposed so far in the fatigue analysis field have been expressed in semistationary forms wherein the global cyclic rather than the instantaneous changes are considered. In the present paper, a new technique for instantaneous fatigue equivalent stress definition is introduced based on new concepts of instantaneous (virtual) stress amplitude and instantaneous (virtual) mean stress. Then, new HCF criteria are proposed using two approaches: (1) polynomial approach and (2) integral approach, to overcome the shortcomings of the available criteria. A relevant fatigue life assessment algorithm is also proposed, and results of the available criteria are compared with results of the proposed criteria as well as the experimental results prepared by the author. To introduce a comprehensive study, the criteria are evaluated for components with complicated geometries under proportional, nonproportional, and random nonproportional loadings. Results reveal that predictions of the proposed approaches are more accurate.
Known Residual Stress Specimens Using Opposed Indentation
Authors: Pagliaro Pierluigi , Prime Michael B. , Clausen Bjørn , Lovato Manuel L. , Zuccarello Bernardo
Published: June 2009

In order to test new theories for residual stress measurement or to test the effects of residual stress on fatigue, fracture, and stress corrosion cracking, a known stress test specimen was designed and then fabricated, modeled, and experimentally validated. To provide a unique biaxial stress state, a 60 mm diameter 10 mm thick disk of 316L stainless steel was plastically compressed through the thickness with an opposing 15 mm diameter hard steel indenters in the center of the disk. For validation, the stresses in the specimen were first mapped using time-of-flight neutron diffraction and Rietveld full pattern analysis. Next, the hoop stresses were mapped on a cross section of two disks using the contour method. The contour results were very repeatable and agreed well with the neutron results. The indentation process was modeled using the finite element method. Because of a significant Bauschinger effect, accurate modeling required testing the cyclic behavior of the steel and then modeling it using a Chaboche-type combined hardening law. The model results agreed very well with the measurements. The duplicate contour measurements demonstrated stress repeatability better than 0.01% of the elastic modulus and allowed discussion of implications of measurements of parts with complicated geometries.
Mechanical Properties of a Ceramic Coating With VEM Infiltration
Authors: Torvik Peter J. , Hansel Jason
Published: June 2009

In order to determine the mechanical properties of materials suitable for use as coatings on structural or gas turbine components, it is often necessary to conduct testing on coated specimens, with the properties of the coating then to be extracted from the response. A methodology for extracting material properties from comparisons of resonant frequencies and system loss factors for coated and uncoated beams, which is applicable even when the desired properties (storage and loss modulus) have a strong dependence on the amplitude of cyclic strain, is summarized and applied to the determination of the material properties of an air plasma sprayed alumina-titania blend ceramic to which a viscoelastic material has been added by vacuum infiltration. Tests were conducted at both room and elevated temperatures. Material properties obtained from specimens with three coating thicknesses are compared and show that values obtained for the stiffness (storage modulus) decrease with increasing coating thickness, but that values obtained for the measure of dissipative capacity (loss modulus) are essentially independent of thickness. Addition of the infiltrate was found to double the storage modulus and to increase the loss modulus at room temperature by factors of up to 3, depending on the amplitude of cyclic strain. The storage modulus of this infiltrated coating appears to diminish with increasing depth into the coating, suggesting dependence on the amount of infiltrate present. The loss modulus, however, appears to be comparatively insensitive to the amount of infiltrate present. Results from a limited investigation of the influence of increased temperature on the properties of the infiltrated coating show decreases in storage modulus with temperature, and a maximum in the loss modulus at a temperature determined by the temperature dependent properties of the specific viscoelastic material used as the infiltrate.
Mesoscopic Investigation of the Heterogeneities Induced by Channel-Die Compression
Authors: Darrieulat Michel G. , Zhani Khalid , Fillit René-Yves , Chenaoui Ahmed
Published: June 2009

Experimental techniques were applied to study the heterogeneities of deformation of metals at the mesoscopic scale (typically 100 μm in the present case). The first are fiducial carbon grids that are transferred on to the surface of the test-pieces. Here, they were used on single and polycrystals deformed in channel-die compression. They prove efficient for strains above 1. They bring out the role of the corners of the samples, which trigger bands of deformation that grow in importance as the compression goes on. They put in evidence the mesoheterogeneities that appear in the mechanical behavior of a few highly symmetric orientations such as cube. The second technique is the use of microfocused X-rays, which give the crystallographic orientation at the same scale of 100 μm and can work in the presence of the carbon grids even when there is considerable strain hardening. The gradients found in the lattice rotations are far less pronounced than the sharp localizations in the displacement field. This highlights the importance of the rotations due to the activity of the slip systems.
A Method for Estimating Uncertainty of Indentation Tensile Properties in Instrumented Indentation Test
Authors: Jeon Eun-chae , Park Joo-Seung , Choi Doo-Sun , Kim Kug-Hwan , Kwon Dongil
Published: June 2009

The instrumented indentation test, which measures indentation tensile properties, has attracted interest recently because this test can replace uniaxial tensile test. An international standard for instrumented indentation test has been recently legislated. However, the uncertainty of the indentation tensile properties has never been estimated. The indentation tensile properties cannot be obtained directly from experimental raw data as can the Brinell hardness, which makes estimation of the uncertainty difficult. The simplifying uncertainty estimation model for the indentation tensile properties proposed here overcomes this problem. Though the influence quantities are generally defined by experimental variances when estimating uncertainty, here they are obtained by calculation from indentation load-depth curves. This model was verified by round-robin test with several institutions. The average uncertainties were estimated as 18.9% and 9.8% for the indentation yield strength and indentation tensile strength, respectively. The values were independent of the materials’ mechanical properties but varied with environmental conditions such as experimental instruments and operators. The uncertainties for the indentation yield and tensile strengths were greater than those for the uniaxial tensile test. These larger uncertainties were caused by measuring local properties in the instrumented indentation test. The two tests had the same tendency to have smaller uncertainties for tensile strength than yield strength. These results suggest that the simplified model can be used to estimate the uncertainty in indentation tensile properties.
Three Dimensional Finite Element Analysis of a Split-Sleeve Cold Expansion Process
Authors: Ismonov S. , Daniewicz S. R. , Newman J. C. , Hill M. R. , Urban M. R.
Published: June 2009

A cold expansion process is used to prolong the fatigue life of a structure under cyclic loadings. The process produces a beneficial compressive residual stress zone in the hole vicinity, which retards the initiation and propagation of the crack at the hole edge. In this study, a three-dimensional finite element model of the split-sleeve cold expansion process was developed to predict the resulting residual stress field. A thin rectangular aluminum sheet with a centrally located hole was considered. A rigid mandrel and an elastic steel split sleeve were explicitly modeled with the appropriate contact elements at the interfaces between the mandrel, the sleeve, and the hole. Geometrical and material nonlinearities were included. The simulation results were compared with experimental measurements of the residual stress. The influence of friction and the prescribed boundary conditions for the sheet were studied. Differences between the split-sleeve- and the non-split-sleeve model solutions are discussed.
Relaxation of Shot-Peened Residual Stresses Under Creep Loading
Authors: Buchanan Dennis J. , John Reji , Brockman Robert A.
Published: June 2009

Shot peening is a commonly used surface treatment process that imparts compressive residual stresses into the surface of metal components. Compressive residual stresses retard initiation and growth of fatigue cracks. During the component loading history, the shot-peened residual stresses may change due to thermal exposure, creep, and cyclic loading. This paper describes a methodical approach for characterizing and modeling residual stress relaxation under elevated temperature loading, near and above the monotonic yield strength of nickel-base superalloy IN100. The model incorporates the dominant creep deformation mechanism, coupling between the creep and plasticity models, and effects of prior plastic strain. The initial room temperature residual stress and plastic strain profiles provide the initial conditions for relaxation predictions using the coupled creep-plasticity model. Model predictions correlate well with experimental results on shot-peened dogbone specimens subject to single cycle and creep loading conditions at elevated temperature. The predictions accurately capture both the shape and magnitude of the retained residual stress profile.
A Comparison of Post-buckling Behavior for FGM Cylindrical Shells With Piezoelectric Fiber Reinforced Composite Actuators
Authors: Shen Hui-Shen
Published: June 2009

Compressive post-buckling under thermal environments and thermal post-buckling due to uniform temperature field or heat conduction are presented for a shear deformable functionally graded cylindrical shell with piezoelectric fiber reinforced composite (PFRC) actuators. The material properties of functionally graded materials (FGMs) are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents, and the material properties of both FGM and PFRC layers are assumed to be temperature-dependent. The governing equations are based on a higher order shear deformation shell theory that includes thermopiezoelectric effects. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine buckling loads (temperature) and post-buckling equilibrium paths. The numerical illustrations concern the compressive and thermal post-buckling behavior of perfect and imperfect FGM cylindrical shells with fully covered PFRC actuators under different sets of thermal and electric loading conditions, from which results for monolithic piezoelectric actuators are obtained as comparators. The results reveal that, in the compressive buckling case, the control voltage only has a small effect on the post-buckling load-deflection curves of the shell with PFRC actuators, whereas in the thermal buckling case, the effect of control voltage is more pronounced for the shell with PFRC actuators, compared with the results of the same shell with monolithic piezoelectric actuators.
The Wavelike Plastic Deformation of Single Crystal Copper
Authors: McDonald Russell J. , Efstathiou Christos , Kurath Peter
Published: June 2009

The purpose of this work is to explore nonuniform plastic flow at small length- and time-scales. Pure single crystal copper tensile specimens were pulled along the [6¯ 5 6] crystal axis at three nominal strain-rates: 0.01%/s, 0.04%/s, and 0.10%/s. Simultaneously, the surface deformation was monitored with in situ digital image correlation over a length-scale of ∼100 μm and a time-scale of 0.07–0.2 s. Sequential digital image correlation strain-rate fields show compelling evidence of a wavelike plastic deformation that is proportional to the nominal strain-rate and decelerates with increasing strain hardening. While a mechanism responsible for the waves is not identified, a methodology correlating observations of multiple researchers is forwarded.
Reynolds-Averaged Navier–Stokes Equations for Turbulence Modeling
Authors: Alfonsi Giancarlo
Published: June 2009

The approach of Reynolds-averaged Navier–Stokes equations (RANS) for the modeling of turbulent flows is reviewed. The subject is mainly considered in the limit of incompressible flows with constant properties. After the introduction of the concept of Reynolds decomposition and averaging, different classes of RANS turbulence models are presented, and, in particular, zero-equation models, one-equation models (besides a half-equation model), two-equation models (with reference to the tensor representation used for a model, both linear and nonlinear models are considered), stress-equation models (with reference to the pressure-strain correlation, both linear and nonlinear models are considered) and algebraic-stress models. For each of the abovementioned class of models, the most widely-used modeling techniques and closures are reported. The unsteady RANS approach is also discussed and a section is devoted to hybrid RANS/large methods.
Continuous Collision and Interference Detection for 3D Geometric Models
Authors: Ilieş Horea T.
Published: June 2009

This paper describes a new approach to perform continuous collision and interference detection between a pair of arbitrarily complex objects moving according to general three-dimensional affine motions. Our approach, which does not require any envelope computations, recasts the problem of detecting collisions and computing the interfering subsets in terms of inherently parallel set membership classification tests of specific curves against the original (static) geometric representations. We show that our approach can compute the subsets of the moving objects that collide and interfere, as well as the times of collision, which has important applications in mechanical design and manufacturing. Our approach can be implemented for any geometric representation that supports curve-solid intersections, such as implicit and parametric representations. We describe an implementation of the proposed technique for solids given as a boundary representation (B-rep), and illustrate its effectiveness for several rigid and deformable moving objects bounded by tesselated and freeform surfaces of various complexities. Furthermore, we show that our approach can be extended to also identify the local and global self-intersections of the envelopes of the moving objects without requiring to compute these envelopes explicitly. The paper concludes by summarizing the proposed approach as well as reviewing relevant computational improvements that can decrease the computational cost of the prototype implementation by orders of magnitude.
GPU-Based Real-Time Occlusion in an Immersive Augmented Reality Environment
Authors: Lu Yuzhu , Smith Shana
Published: June 2009

In this paper, we present a prototype system, which uses CAVE-based virtual reality to enhance immersion in an augmented reality environment. The system integrates virtual objects into a real scene captured by a set of stereo remote cameras. We also present a graphic processing unit (GPU)-based method for computing occlusion between real and virtual objects in real time. The method uses information from the captured stereo images to determine depth of objects in the real scene. Results and performance comparisons show that the GPU-based method is much faster than prior CPU-based methods.
Efficient NC Simulation for Multi-Axis Solid Machining With a Universal APT Cutter
Authors: Yau Hong-Tzong , Tsou Lee-Sen
Published: June 2009

In multi-axis machining of dies and molds with complex sculptured surfaces, numerical control (NC) simulation/verification is a must for the avoidance of expensive rework and material waste. Despite the fact that NC simulation has been extensively used by industries for many years, efficient, accurate, and reliable view-independent simulation of multi-axis NC machining still remains a difficult challenge. This paper presents the use of adaptive voxel data structure in conjunction with the modeling of a universal cutter for the development of an efficient and reliable multi-axis (typically five-axis) simulation procedure. The octree-based voxel representation of the workpiece saves a significant amount of memory space without sacrificing the simulation accuracy. Rendering of the voxel-based model is view independent and does not suffer from any aliasing effect, due to the real-time triangulation of the boundary surfaces using an extended marching cube algorithm. Implicit algebraic equations are used to model the automatically programed tool geometry, which can represent a universal cutter with high precision. In addition, the proposed method allows users to perform error analysis and gouging detection by comparing the machined surfaces with the original computer-aided design (CAD) model. Illustration of the implementation and experimental results demonstrate that the proposed method is reliable, accurate, and highly efficient.
Health Management Allocation During Conceptual System Design
Authors: Hoyle Christopher , Tumer Irem Y. , Mehr Alexander F. , Chen Wei
Published: June 2009

Integrated Systems Health Management (ISHM) is an evolving technology used to detect, assess, and isolate faults in complex systems to improve safety. At the conceptual design level, system-level engineers must make decisions regarding the inclusion of ISHM and the extent and type of the sensing technologies used in various subsystems. In this paper, we propose an ISHM design tool to be used in conjunction with standard system modeling methods to help with the integration of ISHM into the system design process. The key to this analysis is the formulation of an objective function that explicitly quantifies the value derived by integrating the ISHM technology in various subsystems. Ultimately, to determine the best ISHM system configuration, an objective function is formulated, referred to as profit, which is expressed as the product of system availability (AS) and revenue per unit availability (R), minus the sum of cost of detection (CD) and cost of risk (CR). The analysis is conducted at the system functional level appropriate for conceptual design using standard system functional modeling methods, and ISHM is allocated to the functional blocks using the ISHM design tool. The proposed method is demonstrated using a simplified aerospace system design problem resulting in a configuration of sensors, which optimizes the value of the ISHM system for the given input parameters. In this problem, profit was increased by 11%, inspection interval increased by a factor of 1.5 and cost of risk reduced by a factor of 2.4 over a system with no ISHM.
Extending the Scope of Quality Assurance of CAD Systems: Putting Underlying Engineering Principles, Theories, and Methods on the Spotlight
Authors: Opiyo Eliab Z. , Horváth Imre , Vergeest Joris S. M.
Published: June 2009

This paper introduces the idea of extending quality assurance efforts in the processes of development of computer aided design (CAD) software systems to include formal review or testing of underlying engineering principles, theories, methods, or physical phenomena. It stems from the principle of disembodiment of CAD software systems and incorporates elements of existing well-established methodologies such as participatory design, extreme programming, and spiral software development. Under this approach, ideas’ generation, theories’ selection or creation, methods’ development, algorithms’ design, and pilot prototype implementation are the intermediate tasks in the early stages of the process of development of CAD software. Theories, methods, algorithms, and pilot prototypes are the deliverables of these tasks. Each task involves stepwise translation of requirements into a respective deliverable. Application experiences have shown that this procedure enlarges the scope of requirements’ acquisition and quality assurance of CAD software.
Design and Operation of an Open, Interoperable Automated Demand Response Infrastructure for Commercial Buildings
Authors: Piette Mary Ann , Ghatikar Girish , Kiliccote Sila , Watson David , Koch Ed , Hennage Dan
Published: June 2009

This paper describes the concept for and lessons from the development and field-testing of an open, interoperable communications infrastructure to support automated demand response (auto-DR). Automating DR allows greater levels of participation, improved reliability, and repeatability of the DR in participating facilities. This paper also presents the technical and architectural issues associated with auto-DR and description of the demand response automation server (DRAS), the client/server architecture-based middleware used to automate the interactions between the utilities or any DR serving entity and their customers for DR programs. Use case diagrams are presented to show the role of the DRAS between utility/ISO and the clients at the facilities.
Managing Design-Process Complexity: A Value-of-Information Based Approach for Scale and Decision Decoupling
Authors: Panchal Jitesh H. , Paredis Christiaan J. J. , Allen Janet K. , Mistree Farrokh
Published: June 2009

Design-processes for multiscale, multifunctional systems are inherently complex due to the interactions between scales, functional requirements, and the resulting design decisions. While complex design-processes that consider all interactions lead to better designs, simpler design-processes where some interactions are ignored are faster and resource efficient. In order to determine the right level of simplification of design-processes, designers are faced with the following questions: (a) How should complex design-processes be simplified without affecting the resulting product performance? (b) How can designers quantify and evaluate the appropriateness of different design-process alternatives? In this paper, the first question is addressed by introducing a method for determining the appropriate level of simplification of design-processes—specifically through decoupling of scales and decisions in a multiscale problem. The method is based on three constructs: interaction patterns to model design-processes, intervals to model uncertainty resulting from decoupling of scales and decisions, and value-of-information based metrics to measure the impact of simplification on the final design outcome. The second question is addressed by introducing a value-of-information based metric called the improvement potential for quantifying the appropriateness of design-process alternatives from the standpoint of product design requirements. The metric embodies quantitatively the potential for improvement in the achievement of product requirements by adding more information for design decision-making. The method is illustrated via a datacenter cooling system design example.
Boundary Element Methods in Dynamic Analysis
Authors: Beskos Dimitri E.
Published: June 2009

A review of boundary element methods for the numerical solution of dynamic problems of linear elasticity is presented. The integral formulation and the corresponding numerical solution of three- and two-dimensional elastodynamics from the direct boundary element method viewpoint and in both the frequency and time domains are described. The special case of the anti-plane motion governed by the scalar wave equation is also considered. In all the cases both harmonic and transient dynamic disturbances are taken into account. Special features of material behavior such as viscoelasticity, inhomogeneity, anisotropy, and poroelasticity are briefly discussed. Some other nonconventional boundary element methods as well as the hybrid scheme that results from the combination of boundary and finite elements are also reviewed. All these boundary element methodologies are applied to: soil-structure interaction problems that include the dynamic analysis of underground and above-ground structures, foundations, piles, and vibration isolation devices; problems of crack propagation and wave diffraction by cracks; and problems dealing with the dynamics of beams, plates, and shells. Finally, a brief assessment of the progress achieved so far in dynamic analysis is made and areas where further research is needed are identified.
Flow-induced Instabilities of Cylindrical Structures
Authors: Paidoussis Michael P.
Published: June 2009

A kaleidoscopic view of the many diverse and interesting instabilities are presented, to which cylindrical structures are susceptible when in contact with flowing fluids. The physical mechanisms involved are discussed in each case, to the extent that they are understood, and the degree of success of available mathematical models is assessed. Four classes of problems are dealt with, according to the disposition of the flow vis-a`-vis the cylindrical structures: (a) instabilities induced by internal flows in tubular structures; (b) instabilities of solitary or clustered cylinders due to external axial flow; (c) annular-flow-induced instabilities of coaxial beams and shells; (d) instabilities of arrays of cylinders subject to cross-flow. In the first class of problems, the stability of straight tubular beams and cylindrical shells conveying fluid is discussed first, followed by the stability of curved pipes containing flow. In the second class of problems, the instabilities of solitary and clustered cylinders subjected to an external axial flow are treated, and their dynamical behavior is compared to that of systems with internal flow. The third class of problems involves annular flow in coaxial systems of beams and/or shells. Cross-flow-induced instabilities of clustered cylinders, in the form of arrays of different geometrical patterns, are the last class of problems considered; they are fundamentally distinct from the foregoing in terms of the fluid mechanics of the problem, for in this case the flow field is not irrotational—not even approximately.
A Review of Laminated Composite Plate Buckling
Authors: Leissa Arthur W.
Published: June 2009

A brief overview is presented of considerations involved in the buckling of composite plates made of laminae having continuous, parallel fibers. Such plates are governed by orthotropic or anisotropic plate buckling theory for laminates which are symmetrically stacked with respect to the plate midplane. Unsymmetric laminates require a more complicated theory with bending-stretching coupling. Additional complicating factors are considered, including: interior holes, shear deformation, sandwich construction involving other materials, local effects, nonlinear stress-strain relationships, hygrothermal effects, and external stiffeners. Postbuckling behavior and the effects of initial imperfections are also described. Some representative results from the extensive literature (352 references) are included to aid in describing the various effects.