bluuebunny/crossref_metadata_2025 huggingface dataset:
Rice sucrose transporter1 (OsSUT1) up‐regulation in xylem parenchyma is caused by aphid feeding on rice leaf blade vascular bundles
Authors: Ibraheem O. , Botha C. E. J. , Bradley G. , Dealtry G. , Roux S.
Published: November 2013

The role of the sucrose transporter OsSUT1 in assimilate retrieval via the xylem, as a result of damage to and leakage from punctured phloem was examined after rusty plum aphid (Hysteroneura setariae, Thomas) infestation on leaves from 3‐week‐old rice (Oryza sativa L. cv Nipponbare) plants. Leaves were examined over a 1‐ to 10‐day infestation time course, using a combination of gene expression and β‐glucuronidase (GUS) reporter gene analyses. qPCR and Western blot analyses revealed differential expression of OsSUT1 during aphid infestation. Wide‐field fluorescence microscopy was used to confirm the expression of OsSUT1‐promoter::GUS reporter gene in vascular parenchyma associated with xylem elements, as well as in companion cells associated with phloem sieve tubes of large, intermediate and small vascular bundles within the leaf blade, in regions where the aphids had settled and were feeding. Of great interest was up‐regulation of OsSUT1 expression associated with the xylem parenchyma cells, abutting the metaxylem vessels, which confirmed that OsSUT1 was not only involved in loading of sugars into the phloem under normal physiological conditions, but was apparently involved in the retrieval of sucrose leaked into the xylem conduits, which occurred as a direct result of aphid feeding, probing and puncturing of vascular bundles. The up‐regulation of OsSUT1 in xylem vascular parenchyma thus provides evidence in support of the location within the xylem parenchyma cells of an efficient mechanism to ensure sucrose recovery after loss to the apoplast (xylem) after aphid‐related feeding damage and its transfer back to the symplast (phloem) in O. sativa leaves.
Playing It Straight: Framing Strategies Among Reparative Therapists
Authors: Arthur Elizabeth , McGill Dillon , Essary Elizabeth H.
Published: November 2013

Reparative therapy, a form of counseling that seeks to help individuals get rid of their homosexual desires, has been an important component of the ex‐gay movement, but the controversy surrounding the practice has been growing since the 1990s. As a result, the therapy has been effectively relegated to a deviant status by both mainstream society and the mental health profession. Nevertheless, a number of reparative therapists continue to offer their services. This article uses the sociological concepts of deviance and framing to identify both the factors that constitute the deviant status of reparative therapy and the frames practitioners use to legitimate the therapy within an increasingly hostile social environment. A content analysis of reparative therapy Web sites highlights differences between two types of reparative therapists: professional therapists who emphasize the client's right to pursue change and religious counselors who prioritize biblical teachings prohibiting homosexual acts. The results contribute to the sparse sociological literature on reparative therapy and the use of frames by individuals who have experienced marginalization.
The novel HLA‐C*03:02:02:03 identified by cloning and genomic full‐length sequencing
Authors: Ko S.‐Y. , Oh H.‐B. , Jun J. H. , Kwon O.‐J.
Published: November 2013

The sequence of the C*03:02:02:03 differs from that of C*03:02:02:01 by one nucleotide substitution in the 5′ UTR at position −57 (C>A).
Systematic review of the proportion of pregnancy‐related deaths attributed to HIV in population‐based studies in sub‐Saharan Africa
Authors: Grollman C. , Ronsmans C.
Published: November 2013

Objectives

To estimate the proportion of pregnancy‐related deaths attributed to HIV in population‐based studies in sub‐Saharan Africa, and to document the methods used to make such attribution.

Methods

Four databases were searched for studies on causes of maternal and pregnancy‐related mortality published from 2003 to June 2013. Data were extracted, and meta‐analysis of proportions with random effects was used to obtain summary estimates.

Results

In the 19 studies found, the proportion of deaths attributed to HIV ranged from 0.0% to 27.0%. The summary proportion was 3.4% (95% confidence interval: 1.8–6.3), with high heterogeneity. Subregionally, the summary proportions were 1.1% (0.4–3.3%) in West Africa, 4.5% (1.7–11.2%) in East Africa and 26.1% (21.9–30.7%) in Southern Africa. Criteria for assigning HIV as a cause of maternal death were rarely reported, and overall, methods were poor.

Conclusions

The proportion of pregnancy‐related/maternal deaths attributed to HIV is substantially lower than modelled estimates, but comparisons are hampered by the absence of standard approaches. Clear guidelines on how to classify pregnancy‐related deaths as attributable to HIV are urgently needed, so that the effect of the HIV epidemic on pregnancy‐related mortality can be monitored and action taken accordingly.
Physiological mechanisms of sex differences in exertional dyspnoea: role of neural respiratory motor drive
Authors: Schaeffer Michele R. , Mendonca Cassandra T. , Levangie Marc C. , Andersen Ross E. , Taivassalo Tanja , Jensen Dennis
Published: November 2013

New Findings

What is the central question of this study?

Does the combination of a higher neural respiratory drive and greater dynamic mechanical ventilatory constraints during exercise in healthy women versus men form the mechanistic basis of sex differences in activity‐related dyspnoea?

What is the main finding and its importance?

Sex differences in activity‐related dyspnoea in health primarily reflected the awareness of a higher neural respiratory drive needed to achieve any given ventilation during exercise in the setting of relatively greater dynamic mechanical ventilatory constraints in women. These findings may have implications for our understanding of the mechanisms of sex differences in exertional dyspnoea in variants of health (e.g. the elderly) and in patients with cardiorespiratory disease.

The purpose of this study was to elucidate the physiological mechanisms of sex differences in exertional dyspnoea. We compared detailed measures of neural respiratory motor drive [diaphragmatic EMG (EMGdi) expressed as a percentage of maximal EMGdi (EMGdi%max)], breathing pattern, operating lung volumes, dynamic respiratory mechanics [tidal oesophageal (Poes,tidal%peak) and transdiaphragmatic pressure swings (Pdi,tidal%peak) expressed as a percentage of their respective peak values] and sensory intensity and unpleasantness ratings of dyspnoea during symptom‐limited incremental cycle exercise in healthy young women (n = 25) and men (n = 25). The tidal volume to forced vital capacity ratio (VT%FVC), breathing frequency, EMGdi%max, Poes,tidal%peak, Pdi,tidal%peak and sensory intensity and unpleasantness ratings of dyspnoea were higher, while dynamic inspiratory capacity and inspiratory reserve volume were lower at a standardized absolute ventilation of 55 l min−1 during submaximal exercise in women versus men (all P < 0.05). In contrast, sex had no demonstrable effect on the inter‐relationships between exercise‐induced increases in VT%FVC, EMGdi%max and sensory intensity and unpleasantness ratings of dyspnoea. The results of this study suggest that sex differences in the intensity and unpleasantness of exertional dyspnoea in health are likely to reflect the awareness of a relatively higher neural respiratory motor drive (or EMGdi%max) needed to achieve any given ventilation during exercise in the setting of relatively greater dynamic mechanical constraints on VT expansion in women.
Modifiers of heart and muscle function: where genetics meets physiology
Authors: Swaggart Kayleigh A. , McNally Elizabeth M.
Published: November 2013

New Findings

What is the topic of this review?

Genetic modifiers act on many different physiological aspects of muscle disease. Understanding and identifying such modifiers is important because their discovery may help to predict the course of muscle disease and also indicate pathways to be exploited in designing new therapeutics.

What advances does it highlight?

Genetic modifiers have been identified that act primarily on limb skeletal muscles. Newer modifiers, where the responsible gene has yet to be identified, alter the course of cardiopulmonary dysfunction in muscular dystrophy. Distinct modifiers that act differentially on limb skeletal muscles versus heart and respiratory muscles reflect underlying physiological differences of these muscle groups.

Many single‐gene disorders are associated with a range of symptoms that cannot be explained solely by the primary genetic mutation. Muscular dystrophy is a genetic disorder associated with variable outcomes that arise from both the primary genetic mutation and the contribution from environmental and genetic modifiers. Disruption of the dystrophin complex occurs in Duchenne muscular dystrophy and limb girdle muscular dystrophy, producing heart and muscle disease through a cellular injury process characterized by plasma membrane disruption and fibrosis. Multiple modifier loci have been mapped by using a mouse model of muscular dystrophy. These modifiers exert their effect often on specific muscle groups targeted by the muscular dystrophy process, possibly reflecting distinct pathophysiological processes among muscle groups. Genetic modifiers act on both cardiac and respiratory muscle parameters, suggesting genetic and physiological integration of cardiopulmonary function. Skeletal muscles of the limbs are modified by a locus on mouse chromosome 7. This region of chromosome 7 harbours an insertion/deletion polymorphism in Ltbp4, the gene encoding latent transforming growth factor β binding protein 4. LTBP4 exerts its effect in muscle disease by acting on plasma membrane stability and fibrosis, thereby linking instability of the sarcolemma directly to fibrosis. In the human muscle disease Duchenne muscular dystrophy, protein coding single‐nucleotide polymorphisms in LTBP4 associate with prolonged ambulation, demonstrating that modifiers identified from mouse studies translate to human disease.
Attenuated Fractional Wave Equations With Anisotropy
Authors: Meerschaert Mark M. , McGough Robert J.
Published: November 2013

This paper develops new fractional calculus models for wave propagation. These models permit a different attenuation index in each coordinate to fully capture the anisotropic nature of wave propagation in complex media. Analytical expressions that describe power law attenuation and anomalous dispersion in each direction are derived for these fractional calculus models.
Lower Bound Methods in Elastic-Plastic Shakedown Analysis
Authors: Reinhardt Wolf , Adibi-Asl Reza
Published: November 2013

Several methods were proposed in recent years that allow the efficient calculation of elastic and elastic-plastic shakedown limits. This paper establishes a uniform framework for such methods that are based on perfectly-plastic material behavior, and demonstrates the connection to Melan's theorem of elastic shakedown. The paper discusses implications for simplified methods of establishing shakedown, such as those used in the ASME Code. The framework allows a clearer assessment of the limitations of such simplified approaches. Application examples are given.
Simulation and Analysis of Residual Stress and Microstructure Transformation for Post Weld Heat Treatment of a Welded Pipe
Authors: Han Yi , Yu Enlin , Huang Daochen , Zhang Liang
Published: November 2013

With the characteristics of the sandglass-shaped temperature field generated during welding of high-frequency induction longitudinally welded pipe taken into consideration, this paper focuses on the rules of influence of a post weld medium-frequency heat treatment process on microstructural change and the rules of residual stress distribution, and proposes a quantitative analysis method for studies on heating mechanisms of on-line heat treatment. The microstructural evolution process respect to time, and the rules of post weld axial, circumferential, radial, and residual von Mises stresses changing by path were quantitatively analyzed, respectively. It was found from comparison between a metallographic test and a microhardness test that on-line heat treatment is significantly effective in improving microstructures and reducing residual stress of the outer surface of a welded pipe. By controlling the distribution types of the microstructural field and the stress field through appropriate selection of heat treatment process parameters and distributing heat more reasonable heat distribution, it is expected that the residual stress of the inner surface of a welded pipe can be further reduced and the quality and efficiency of on-line heat treatment can be improved.
High Temperature, Low Cycle Fatigue Characterization of P91 Weld and Heat Affected Zone Material
Authors: Farragher T. P. , Scully S. , O'Dowd N. P. , Hyde C. J. , Leen S. B.
Published: November 2013

The high temperature low cycle fatigue behavior of P91 weld metal (WM) and weld joints (cross-weld) is presented. Strain-controlled tests have been carried out at 400 °C and 500 °C. The cyclic behavior of the weld material (WM) and cross-weld (CW) specimens are compared with previously published base material (BM) tests. The weld material is shown to give a significantly harder and stiffer stress–strain response than both the base material and the cross-weld material. The cross-weld tests exhibited a cyclic stress–strain response, which was similar to that of the base material. All specimen types exhibited cyclic softening but the degree of softening exhibited by the cross-weld specimens was lower than that of the base material and all-weld tests. Finite element models of the base metal, weld metal and cross-weld test specimens are developed and employed for identification of the cyclic viscoplasticity material parameters. Heat affected zone (HAZ) cracking was observed for the cross-weld tests.
A Data-Driven Approach for Condition Monitoring of Reciprocating Compressor Valves
Authors: Guerra Christopher J. , Kolodziej Jason R.
Published: November 2013

This paper focuses on condition-monitoring of three different valve failure modes common in reciprocating compressors. They are missing valve poppets, valve spring fatigue, and valve seat wear. First, a targeted instrumentation study is performed on a Dresser–Rand ESH-1 industrial reciprocating compressor to investigate detection methods for these failures. This is followed by the development of a novel health classification methodology based on frequency analysis and Bayes theorem. The method is shown to successfully classify the condition of the valves to a high degree of accuracy when applied to actual seeded valve faults in the compressor.
Positive Flow Response Characteristic in Vertical Tube Furnace of Supercritical Once-Through Boiler
Authors: Wang Huan , Che Defu
Published: November 2013

Positive flow response characteristic in vertical tube furnace of supercritical once-through boiler provides a feasible and effective way to alleviate the thermal maldistribution to some extent. In the present paper, theoretical derivation and simulations were performed to investigate the mechanism and forming conditions of positive flow response characteristic systematically. Two types of transition criterions were built up to judge positive or negative flow response characteristic. Parametric study was carried out to analyze the influencing factors. Both the operating conditions (mass flux, pressure, temperature or quality, heat flux) and the geometric parameters (inside diameter, length, pitch and type of tube) were investigated. In addition, thermal-hydraulic simulation of a 600 MW supercritical W-flame boiler has been carried out to take all these factors into account simultaneously. The conclusions drawn from this study will be of help to the design of large capacity supercritical once-through boilers as well as the refurbishment of existing supercritical or subcritical boilers.
Effect of Nozzle Guide Vane Lean Under Influence of Inlet Temperature Traverse
Authors: Rahim A. , Khanal B. , He L. , Romero E.
Published: November 2013

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e., the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under nonuniform temperature conditions (commonly referred to as a “hot-streak”) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the nozzle guide vane (NGV) blades are shaped. In the present work, a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier–Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analyzed. After confirming the typical NGV loading and aeroloss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. While the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favorable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.
Development of a Turning Mid Turbine Frame With Embedded Design—Part II: Unsteady Measurements
Authors: Spataro Rosario , Göttlich Emil , Lengani Davide , Faustmann Christian , Heitmeir Franz
Published: November 2013

This paper, the second of two parts, presents a new setup for the two-stage two-spool facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed to reproduce the flow behavior of a transonic turbine followed by a counter-rotating low pressure stage such as those in high bypass aero-engines. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. The role of wide chord vanes placed into the mid turbine frame is to lead the flow towards the low pressure (LP) rotor with appropriate swirl. Experimental and numerical investigations performed on this setup showed that the wide chord struts induce large wakes and extended secondary flows at the LP inlet flow. Moreover, large deterministic fluctuations of pressure, which may cause noise and blade vibrations, were observed downstream of the LP rotor. In order to minimize secondary vortices and to damp the unsteady interactions, the mid turbine frame was redesigned to locate two zero-lift splitters into each vane passage. While in the first part of the paper the design process of the splitters and the time-averaged flow field were presented, in this second part the measurements performed by means of a fast response probe will support the explanation of the time-resolved field. The discussion will focus on the comparison between the baseline case (without splitters) and the embedded design.
Endwall Loss Reduction of High Lift Low Pressure Turbine Airfoils Using Profile Contouring—Part I: Airfoil Design
Authors: Eric Lyall M. , King Paul I. , Clark John P. , Sondergaard Rolf
Published: November 2013

This paper presents the reasoning for and the design process of contouring a high lift front-loaded low pressure turbine (LPT) airfoil near the endwall to reduce the endwall loss. The test airfoil, L2F, was designed to the approximate gas angles with 38% larger pitchwise spacing than the widely studied Pack B airfoil. Being more front-loaded with a higher stagger angle, L2F is shown to produce more endwall losses than Pack B. It is suggested that the high endwall loss of L2F is due to the high stagger angle, not front-loading, as usually suggested in the literature. A procedure is presented to approximate the front-loading and stall resistance of L2F and obtain a low stagger version of that airfoil, designated as L2F-LS. A contoured airfoil is then designed by transitioning L2F into L2F-LS at the endwall to obtain a benefit from the reduced stagger angle at the endwall. Due to the contouring process generating a fillet, the contoured airfoil is referred to as L2F-EF (“endwall fillet”). Predictions in this paper suggest endwall loss reductions between 17% and 24% at Re = 100,000. Linear cascade experiments in Part II of this paper indicate that L2F-EF reduces endwall losses more than 20% compared to L2F. The overall conclusion is that the stagger angle has a significant effect on endwall loss and should be considered for designing high lift LPT airfoils at the endwall.
End Wall Loss Reduction of High Lift Low Pressure Turbine Airfoils Using Profile Contouring—Part II: Validation
Authors: Sangston Keith , Little Jesse , Lyall M. Eric , Sondergaard Rolf
Published: November 2013

The hypothesis, posed in Part I, that excessive end wall loss of high lift low pressure turbine (LPT) airfoils is due to the influence of high stagger angles on the end wall pressure distribution and not front loading is evaluated in a linear cascade at Re = 100,000 using both experimental and computational studies. A nominally high lift and high stagger angle front-loaded profile (L2F) with aspect ratio 3.5 is contoured at the end wall to reduce the stagger angle while maintaining the front loading. The contouring process effectively generates a fillet at the end wall, so the resulting airfoil is referred to as L2F-EF (end wall fillet). Although referred to as a fillet, this profile contouring process is novel in that it is designed to isolate the effect of stagger angle on end wall loss. Total pressure loss measurements downstream of the blade row indicate that the use of the lower stagger angle at the end wall reduces mixed out mass averaged end wall and passage losses approximately 23% and 10%, respectively. This is in good agreement with computational results used to design the contour which predict 18% and 7% loss reductions. The end wall flow field of the L2F and L2F-EF models is measured using stereoscopic particle image velocimetry (PIV) in the passage. These data are used to quantify changes in the end wall flow field due to the contouring. PIV results show that this loss reduction is characterized by reduced inlet boundary layer separation as well as a change in strength and location of the suction side horseshoe vortex (SHV) and passage vortex (PV). The end wall profile contouring also produces a reduction in all terms of the Reynolds stress tensor consistent with a decrease in deformation work and overall flow unsteadiness. These results confirm that the stagger angle has a significant effect on high-lift front-loaded LPT end wall loss. Low stagger profiling is successful in reducing end wall loss by limiting the development and migration of the low momentum fluid associated with the SHV and PV interaction.
Stochastic Averaging for Quasi-Integrable Hamiltonian Systems With Variable Mass
Authors: Wang Yong , Jin Xiaoling , Huang Zhilong
Published: November 2013

Variable-mass systems become more and more important with the explosive development of micro- and nanotechnologies, and it is crucial to evaluate the influence of mass disturbances on system random responses. This manuscript generalizes the stochastic averaging technique from quasi-integrable Hamiltonian systems to stochastic variable-mass systems. The Hamiltonian equations for variable-mass systems are firstly derived in classical mechanics formulation and are approximately replaced by the associated conservative Hamiltonian equations with disturbances in each equation. The averaged Itô equations with respect to the integrals of motion as slowly variable processes are derived through the stochastic averaging technique. Solving the associated Fokker–Plank–Kolmogorov equation yields the joint probability densities of the integrals of motion. A representative variable-mass oscillator is worked out to demonstrate the application and effectiveness of the generalized stochastic averaging technique; also, the sensitivity of random responses to pivotal system parameters is illustrated.
A New Loss and Deviation Model for Axial Compressor Inlet Guide Vanes
Authors: Banjac Milan , Petrovic Milan V. , Wiedermann Alexander
Published: November 2013

This paper describes a new universal algebraic model for the estimation of flow deflection and losses in axial compressor inlet guide vane devices. The model deals with nominal flow and far-off-design operating conditions in connection with large stagger angle adjustments. The first part of the model considers deflection and losses in 2D cascades, taking into account the main cascade geometry parameters and operating conditions, such as Mach number and stagger adjustment. The second part of the model deals with additional deviation and losses due to secondary flow caused by the end wall viscous effects and by the trailing vortices. The model is developed for NACA65 airfoils, NACA63-A4K6 airfoils, and airfoils having an NACA65 thickness distribution on a circular-arc camber line. It is suitable for application in 1D or 2D through-flow calculations for design and analysis cases. The development of the method is based on systematic computational fluid dynamics (CFD) flow calculations for various cascade geometries and operating parameters. The comparison of correlation results with experimental data for several test cases shows good agreement.
A Compartmental Model for Supercritical Coal-Fired Boiler Systems
Authors: Qi Longzhou , Huang Shuhong , Zhang Yanping , Xu Xing , Li Yu , Wang Yong
Published: November 2013

A compartmental furnace model for supercritical coal-fired boiler systems is presented in this paper. Instead of the traditional lumped parameter method, the furnace is divided to seven compartments along the height based on the positions of the burner groups. The lower six compartments correspond to the six groups of burners, respectively. This model provides the possibility to connect the pulverization system and the furnace, the variability of the combustion property caused by changes of the pulverization system can be studied by switching the operating conditions. To evaluate the proposed model, simulation results are compared with available data from a 600 MW supercritical coal-fired boiler and reasonably good agreement is achieved. The simulation results also show that the compartmental model features a better precision than the lumped parameter modeling. This model allows for evaluating different control strategies and subsequently proposing optimization strategies for boiler system operation.
Technology Characterization Models and Their Use in Systems Design
Authors: Parker Robert R. , Galvan Edgar , Malak Richard J.
Published: November 2013

Prior research suggests that set-based design representations can be useful for facilitating collaboration among engineers in a design project. However, existing set-based methods are limited in terms of how the sets are constructed and in their representational capability. The focus of this article is on the problem of modeling the capabilities of a component technology in a way that can be communicated and used in support of system-level decision making. The context is the system definition phases of a systems engineering project, when engineers still are considering various technical concepts. The approach under investigation requires engineers familiar with the component- or subsystem-level technologies to generate a set-based model of their achievable technical attributes, called a technology characterization model (TCM). Systems engineers then use these models to explore system-level alternatives and choose the combination of technologies that are best suited to the design problem. Previously, this approach was shown to be theoretically sound from a decision making perspective under idealized circumstances. This article is an investigation into the practical effectiveness of different TCM representational methods under realistic conditions such as having limited data. A power plant systems engineering problem is used as an example, with TCMs generated for different technical concepts for the condenser component. Samples of valid condenser realizations are used as inputs to the TCM representation methods. Two TCM representation methods are compared based on their solution accuracy and computational effort required: a Kriging-based interpolation and a machine learning technique called support vector domain description (SVDD). The results from this example hold that the SVDD-based method provides the better combination of accuracy and efficiency.
A Scheme for Numerical Representation of Graph Structures in Engineering Design
Authors: Wyatt David F. , Wynn David C. , Clarkson P. John
Published: November 2013

Graph structures are fundamental in many aspects of design. This paper discusses a way to improve access to design spaces of graph structures, by converting graph structures into numerical values and vice versa. Mathematical properties of such conversions are described, and those that are desirable are identified. A candidate conversion algorithm, Indexed Stacked Blocks, is proposed. Its use and benefits are illustrated through an example graph-structure design problem. The example demonstrates that such conversions allow design spaces of graph structures to be visualized, sampled, and evaluated. In principle, they also allow other powerful numerical techniques to be applied to the design of graph-structure-based systems.
Advanced Robust Optimization With Interval Uncertainty Using a Single-Looped Structure and Sequential Quadratic Programming
Authors: Zhou Jianhua , Li Mian
Published: November 2013

Uncertainty is inevitable and has to be taken into consideration in engineering optimization; otherwise, the obtained optimal solution may become infeasible or its performance can degrade significantly. Robust optimization (RO) approaches have been proposed to deal with this issue. Most existing RO algorithms use double-looped structures in which a large amount of computational efforts have been spent in the inner loop optimization to determine the robustness of candidate solutions. In this paper, an advanced approach is presented where no optimization run is required for robustness evaluation in the inner loop. Instead, a concept of Utopian point is proposed and the corresponding maximum variable/parameter variation will be obtained just by performing matrix operations. The obtained robust optimal solution from the new approach may be conservative, but the deviation from the true robust optimal solution is small enough and acceptable given the significant improvement in the computational efficiency. Six numerical and engineering examples are tested to show the applicability and efficiency of the proposed approach, whose solutions and computational efforts are compared to those from a previously proposed double-looped approach, sequential quadratic program-robust optimization (SQP-RO).
Computational Optimization and Experimental Evaluation of Grasp Quality for Tendon-Driven Hands Subject to Design Constraints
Authors: Inouye Joshua M. , Valero-Cuevas Francisco J.
Published: November 2013

The chief tasks of robotic and prosthetic hands are grasping and manipulating objects, and size and weight constraints are very influential in their design. In this study, we use computational modeling to both predict and optimize the grasp quality of a reconfigurable, tendon-driven hand. Our computational results show that grasp quality, measured by the radius of the largest ball in wrench space, could be improved up to 259% by simply making some pulleys smaller and redistributing the maximal tensions of the tendons. We experimentally evaluated several optimized and unoptimized designs, which had either 4, 5, or 6 tendons and found that the theoretical calculations are effective at predicting grasp quality, with an average friction loss in this system of around 30%. We conclude that this optimization can be a very useful design tool and that using biologically inspired asymmetry and parameter adjustments can be used to maximize performance.
A High Ratio Power Dense Planetary Drive for Rotorcraft Applications
Authors: Ai Xiaolan , Orkin Curtis , Kruse Randy
Published: November 2013

Epicyclic geartrains are known to provide high power density and have become the geartrain of choice for the main power flow in virtually all rotorcraft designs. This paper presents a unique compound planetary design targeting a helicopter main gearbox transmission application. The design significantly improves power density over conventional geartrains through its innovative planet gear load-sharing configuration along with the utilization of high-performance materials for gears and bearings. Design studies were conducted comparing the power density of this new design to a baseline gearbox design. The results of these studies demonstrate an estimated 38% power density improvement over the baseline configuration. Of the total improvement, 86% is attributed to the novel load-sharing configuration while 14% is attributed to utilization of advanced materials and processes.
A Simplified Morphing Blade for Horizontal Axis Wind Turbines
Authors: Wang Weijun , Caro Stéphane , Bennis Fouad , Salinas Mejia Oscar Roberto
Published: November 2013

The aim of designing wind turbine blades is to improve the power capture ability. Since rotor control technology is currently limited to controlling rotational speed and blade pitch, an increasing concern has been given to morphing blades. In this paper, a simplified morphing blade is introduced, which has a linear twist distribution along the span and a shape that can be controlled by adjusting the twist of the blade's root and tip. To evaluate the performance of wind turbine blades, a numerical code based on the blade element momentum theory is developed and validated. The blade of the NREL Phase VI wind turbine is taken as a reference blade and has a fixed pitch. The optimization problems associated with the control of the morphing blade and a blade with pitch control are formulated. The optimal results show that the morphing blade gives better results than the blade with pitch control in terms of produced power. Under the assumption that at a given site, the annual average wind speed is known and the wind speed follows a Rayleigh distribution, the annual energy production of wind turbines was evaluated for three types of blade, namely, morphing blade, blade with pitch control and fixed pitch blade. For an annual average wind speed varying between 5 m/s and 15 m/s, it turns out that the annual energy production of the wind turbine containing morphing blades is 24.5% to 69.7% higher than the annual energy production of the wind turbine containing pitch fixed blades. Likewise, the annual energy production of the wind turbine containing blades with pitch control is 22.7% to 66.9% higher than the annual energy production of the wind turbine containing pitch fixed blades.
Integration of Solar Gasification With Conventional Fuel Production: The Roles of Storage and Hybridization
Authors: Hathaway Brandon J. , Kittelson David B. , Davidson Jane H.
Published: November 2013

The use of concentrated solar radiation as the source of process heat to drive biomass gasification offers potential increases in yield and efficiency over conventional approaches to gasification but requires that temporal variations in output be alleviated with thermal storage or hybridization. The impacts of thermal storage and degree of hybridization on the efficiency, specific yield, and variation in output of a solar gasification facility are explored through parametric simulations of a generalized 100 MWth solar receiver facility. Nominal syngas yield rates from 1.5 to 50 tonnes/h are considered along with molten carbonate salt storage volumes from 200 to 6500 m3. High solar fractions (95%) result in a maximum thermal efficiency of 79% and specific syngas yield of 139 GJ/ha while low solar fractions (10%) for highly hybridized facilities reduce the thermal efficiency to 72% and specific yield to 88 GJ/ha, akin to conventional gasification processes. Solar fractions greater than 95% result in large variation in synthesis gas yield rate, varying as much as 30:1 throughout the year. This variation can be reduced to below a 4:1 ratio, more acceptable for downstream processes, through either hybridization to achieve solar fractions less than 50% with little to no thermal storage, or alternately the use of 5600 m3 of molten carbonate salt to allow for solar fractions up to 87%.
Fracture Analysis and Distribution of Surface Cracks in Multicrystalline Silicon Wafers
Authors: Saffar S. , Gouttebroze S. , Zhang Z. L.
Published: November 2013

Solar silicon wafers are mainly produced through multiwire sawing. The sawing process induces micro cracks on the wafer surface, which are responsible for brittle fracture. Hence, it is important to scrutinize the crack geometries most commonly generated in silicon wafer sawing or handling process and link the surface crack to the fracture of wafers. The fracture of a large number of multicrystalline silicon wafers has been investigated by means of 4-point bending and twisting tests and a failure probability function is presented. By neglecting the material property variation and assuming that one surface crack is dominating the wafer breakage, 3D finite element models with various crack sizes (depth, length, and orientation) have been analyzed to identify the distribution of surface crack geometries by fitting the failure probability from the experiments. With respect to the 63% probability, the existing surface cracks in the wafers studied appear to have depth and length ratios less than 0.042 and 0.19, respectively. Furthermore, it has been shown that the surface cracks with depth in the range from 10 to 20 μm, length up to 10 mm and angles in the range of 30 deg–60 deg, can be considered as the most common crack geometries in wafers we tested. Finally, it has been found that the mechanical strength of the wafers tested parallel to the sawing direction is approximately 15 MPa smaller than those tested perpendicular to the sawing direction.
Numerical Simulation of Heat Pipe-Assisted Latent Heat Thermal Energy Storage Unit for Dish-Stirling Systems
Authors: Shabgard Hamidreza , Faghri Amir , Bergman Theodore L. , Andraka Charles E.
Published: November 2013

A two-dimensional numerical model is developed to simulate the transient response of a heat pipe-assisted latent heat thermal energy storage (LHTES) unit integrated with dish-Stirling solar power generation systems. The unit consists of a container which houses a phase change material (PCM) and two sets of interlaced input and output heat pipes (HPs) embedded in the PCM. The LHTES unit is exposed to time-varying concentrated solar irradiance. A three-stage operating scenario is investigated that includes: (i) charging only, (ii) simultaneous charging and discharging, and (iii) discharging only. In general, it was found that the PCM damps the temporal variations of the input solar irradiance, and provides relatively smooth thermal power to the engine over a time period that can extend to after-sunset hours. Heat pipe spacing was identified as a key parameter to control the dynamic response of the unit. The system with the greatest (smallest) heat pipe spacing was found to have the greatest (smallest) temperature drops across the LHTES, as well as the maximum (minimum) amount of PCM melting and solidification. Exergy analyses were also performed, and it was found that the exergy efficiencies of all the systems considered were greater than 97%, with the maximum exergy efficiency associated with the system having the minimum heat pipe spacing.
Effect of Initial Texture on Rollability of Mg-3Al-1Zn Alloy Sheet
Authors: Dai Q. , Lan W. , Chen X.
Published: November 2013

The influence of initial texture on rollability is investigated using cuneal AZ31 Mg alloy sheets. Upon large thickness reduction, the sheet with initial basal texture has many edge cracks, whereas the sheet is crack-free if its normal direction is orthogonal to c-axis of hexagonal close packed (HCP) lattice. Microstructural analysis shows that the former one has heterogeneous grain structure owing to grain-boundary-related recrystallization, and by contrast the later one has a more uniform microstructure for the twin-related recrystallization. The initial nonbasal texture can lead to excellent rollability and anisotropic deformation, based on which a new iterative approach of rolling is proposed, which may achieve large reduction in few passes.
Parametric Investigation Into the Fabrication of Disk Microelectrodes by Electrochemical Micromachining
Authors: Rathod Vijaysing , Doloi B. , Bhattacharyya B.
Published: November 2013

In electrochemical micromachining (EMM) of microfeatures using straight cylindrical microtools, sidewalls of the structure tapers as depth increases. Disk microtool electrodes are used to minimize the taper formation during the machining of microfeatures. At present disk microtool electrodes are fabricated by wire electrical discharge grinding, reverse electro discharge machining (EDM), and microwire electro discharge machining method, which needs separate EDM machine as well as fabricated microtools suffer from thermal defects like microcracks on surface, residual stress, deformation, and needs careful handling. To overcome these limitations, new method is proposed to fabricate disk microtool electrode by EMM. Also the influences of EMM process parameters like applied voltage, pulse frequency, duty ratio, electrolyte concentration on shank diameter, material removal rate, and surface quality are investigated. Disk microtool electrode of disk height 70 μm, disk diameter 175 μm, shank diameter 93 μm, and shank height 815 μm have been fabricated from tungsten microrod of 300 μm diameter by proposed method and used to machine microfeatures like cylindrical hole with reduced taper angle, reverse taper hole, taper free microgroove, and 3D microstructure with plane surfaces on stainless steel by EMM. Effects of disk height on machining accuracy during generation of microhole, in the form of taper angle are also presented in the paper. Proposed method of developing disk electrode by EMM will be very useful for fabricating disk microtool electrodes with different disk diameters, disk heights, shank diameter, and shank height with desired surface quality by controlling various process parameters. Disk microtools with lower disk heights are more effective to generate microfeatures with minimum taper.
Roll Molding of Microchannel Arrays on Al and Cu Sheet Metals: A Method for High-Throughput Manufacturing
Authors: Lu Bin , Meng W. J.
Published: November 2013

The method of roll molding is proposed as an alternative to compression molding for low-cost, high-throughput manufacturing of metal-based microchannel structures. Elemental aluminum- and copper- based microchannel arrays with depths of ∼600 μm and depth:width ratios ≥2:1 were successfully fabricated by roll molding at room temperature. Morphologies of roll molded Al and Cu microchannels were examined in detail. Response of roll molding was characterized by measuring depths of roll molded microchannels as a function of the normal loading force per width. This response of roll molding was further shown to scale with the flow stress of roll molded material. Roll molding offers the potential of fabricating microchannel structures with large footprints in a continuous manner.
Influence of Lapping Residual Stress on Machining Precision of Elastic Deformation Molding Method
Authors: Yuan Julong , Wu Zhe , Zhao Ping , Lv Binghai , Lin Wangpiao
Published: November 2013

Elastic deformation molding method is a newly developed aspheric machining technology which can convert complex aspherical surface machining to simple flat surface machining. The residual stress induced in lapping process of elastic deformation molding method has significant influence on machining precision. In this paper, the influence of residual stress induced lapping process on machining accuracy is analyzed and discussed through experiment. An experiment with elimination of residual stress is carried out. The machining result shows that distortion amount has reduced form 2 μm to 0.8 μm, which means the residual stress can be effectively eliminated. A machining form accuracy of P-V 0.56 μm is obtained.
The Vascular Model Repository: A Public Resource of Medical Imaging Data and Blood Flow Simulation Results
Authors: Wilson Nathan M. , Ortiz Ana K. , Johnson Allison B.
Published: November 2013

Patient-specific blood flow simulations may provide insight into disease progression, treatment options, and medical device design that would be difficult or impossible to obtain experimentally. However, publicly available image data and computer models for researchers and device designers are extremely limited. The National Heart, Lung, and Blood Institute sponsored Open Source Medical Software Corporation (contract nos. HHSN268200800008C and HHSN268201100035C) and its university collaborators to build a repository (www.vascularmodel.org) including realistic, image-based anatomic models and related hemodynamic simulation results to address this unmet need.
Harnessing Genetic Diversity in Saccharomyces cerevisiae for Fermentation of Xylose in Hydrolysates of Alkaline Hydrogen Peroxide-Pretreated Biomass
Authors: Sato Trey K. , Liu Tongjun , Parreiras Lucas S. , Williams Daniel L. , Wohlbach Dana J. , Bice Benjamin D. , Ong Irene M. , Breuer Rebecca J. , Qin Li , Busalacchi Donald , Deshpande Shweta , Daum Chris , Gasch Audrey P. , Hodge David B.
Published: November 2013

The fermentation of lignocellulose-derived sugars, particularly xylose, into ethanol by the yeast
Saccharomyces cerevisiae
is known to be inhibited by compounds produced during feedstock pretreatment. We devised a strategy that combined chemical profiling of pretreated feedstocks, high-throughput phenotyping of genetically diverse
S. cerevisiae
strains isolated from a range of ecological niches, and directed engineering and evolution against identified inhibitors to produce strains with improved fermentation properties. We identified and quantified for the first time the major inhibitory compounds in alkaline hydrogen peroxide (AHP)-pretreated lignocellulosic hydrolysates, including Na
+
, acetate, and
p
-coumaric (
p
CA) and ferulic (FA) acids. By phenotyping these yeast strains for their abilities to grow in the presence of these AHP inhibitors, one heterozygous diploid strain tolerant to all four inhibitors was selected, engineered for xylose metabolism, and then allowed to evolve on xylose with increasing amounts of
p
CA and FA. After only 149 generations, one evolved isolate, GLBRCY87, exhibited faster xylose uptake rates in both laboratory media and AHP switchgrass hydrolysate than its ancestral GLBRCY73 strain and completely converted 115 g/liter of total sugars in undetoxified AHP hydrolysate into more than 40 g/liter ethanol. Strikingly, genome sequencing revealed that during the evolution from GLBRCY73, the GLBRCY87 strain acquired the conversion of heterozygous to homozygous alleles in chromosome VII and amplification of chromosome XIV. Our approach highlights that simultaneous selection on xylose and
p
CA or FA with a wild
S. cerevisiae
strain containing inherent tolerance to AHP pretreatment inhibitors has potential for rapid evolution of robust properties in lignocellulosic biofuel production.