bluuebunny/crossref_metadata_2025 huggingface dataset:
Chusquea septentrionalis sp. nov. (Poaceae: Bambusoideae) from the Madrean region in Durango, Mexico
Authors: Ruiz‐Sanchez Eduardo , Castro‐Castro Arturo , Clark Lynn G.
Published: October 2017

Chusquea is a monophyletic genus divided into five subgenera. Chusquea subg. Swallenochloa is recognized based on the combination of a more or less shrubby and clumping habit, often relatively short internodes, and the usual presence of intravaginal branching. It is distributed from Mexico to Chile, with species also in the mountains of eastern and southeastern Brazil, commonly occupying high elevation grasslands, although a few species inhabit montane forests. Based on the review of herbarium specimens and fieldtrips to the Sierra Madre Occidental in the state of Durango, Mexico, we here describe and illustrate Chusquea septentrionalis, the newest species to be classified within subgen. Swallenochloa. This novelty is compared with the rare, high elevation Mexican endemics C. matlatzinca and C. perotensis, from which it can be separated by its thick‐walled, hollow culms, intravaginal branching pattern, central bud slightly larger than the subsidiary buds, subsidiary buds axillary and arranged linearly, and the long inner ligule of the foliage leaves. Chusquea septentrionalis is referred to Chusquea subgen. Swallenochloa sect. Swallenochloa, because of the morphological characters that it shares with the rest of the species in this section, especially the branching pattern. With the description of this new species, the diversity of native Chusquea and woody bamboos overall in Mexico increases to 22 and 52 species, respectively. Due to the reduced distribution of this new species, we propose to include it in the Norma Oficial Mexicana (NOM‐059‐SEMARNAT‐2010) and IUCN red list for its protection. A morphological key to the species of C. sect. Swallenochloa known from Mexico is provided.
Aerophagia in adolescents is associated with exposure to adverse life events and psychological maladjustment
Authors: Rajindrajith S. , Hettige S. , Gulegoda I. , Jayawickrama N. , De Silva S. C. , Samarakoon H. K. , de Silva R. L. , Abeyagunawardena S. , Devanarayana N. M.
Published: October 2017

Background

Aerophagia is a common childhood functional gastrointestinal disorder. We studied the association between adverse life events (ALEs), psychological maladjustment, somatization, and aerophagia (AP) in adolescents. We also assessed the impact of AP on their health‐related quality of life (HRQoL).

Methods

A cross‐sectional survey was conducted on 2500 subjects of 13‐18 years in 8 randomly selected schools in Sri Lanka. Translated, validated, and self‐administered questionnaires were used to collect data. Aerophagia was diagnosed using Rome III criteria.

Key Results

A total of 2453 questionnaires were analyzed (males 1200 [48.9%], mean age 14.8 years, SD 1.6 years). Of them, 371 adolescents had AP (15.1%). Aerophagia was associated with exposure to physical abuse (20.4% vs. 12.7% in controls, P < .0001), emotional abuse (20.3% vs. 8.2% in controls, P < .0001), and other ALEs (22% vs. 10.2% in controls, P < .001). One hundred and ninety (51.2%) adolescents with AP and 775 (37.2%) controls had a personality score above the international cutoff value of 105, indicating psychological maladjustment (odds ratio 1.77, 95% confidence interval 1.42‐2.21, P < .0001). Those with AP had higher somatization (16.4 vs. 8.9) and lower overall HRQoL scores (77.0 vs. 85.1, P < .0001). HRQoL scores of adolescents with AP were lower in all domains, namely, physical (80.6 vs. 86.9), emotional (69.1 vs. 80.3), social (83.8 vs. 90.5), and school (72.6 vs. 82.5) functioning (P < .0001).

Conclusions and Inferences

Aerophagia was associated with exposure to ALEs and psychological maladjustment. Affected teenagers suffer from more somatic symptoms and has a poor HRQoL.
Identification of genes encoding glycosyltransferases involved in lipopolysaccharide synthesis in Porphyromonas gingivalis
Authors: Shoji M. , Sato K. , Yukitake H. , Kamaguchi A. , Sasaki Y. , Naito M. , Nakayama K.
Published: October 2017

Porphyromonas gingivalis can synthesize both A‐LPS and O‐LPS lipopolysaccharides, which contain anionic O‐polysaccharides and conventional O‐polysaccharides, respectively. A‐LPS can anchor virulence proteins to the cell surface, so elucidating the mechanism of A‐LPS synthesis is important for understanding the pathogenicity of this bacterium. To identify the genes involved in LPS synthesis, we focused on uncharacterized genes encoding the glycosyltransferases, PGN_0361, PGN_1239, PGN_1240 and PGN_1668, which were tentatively named gtfC, gtfD, gtfE and gtfF, respectively, and characterized their mutants. We found that disruption of gtfC and gtfF resulted in A‐LPS deficiency. In addition, a gtfD mutant had abnormal A‐LPS synthesis, and a gtfE mutant exhibited a rough‐type LPS that possesses a short oligosaccharide with lipid A‐core. We then constructed a gtfC and gtfD double mutant, because their amino acid sequences were very similar, and this mutant similarly possessed a rough‐type LPS. Cross‐complementation analysis revealed that the GtfD protein is a functional homologue of the Escherichia coli WbbL protein, which is a rhamnosyltransferase. These results suggested that the GtfE protein is essential for the synthesis of both O‐LPS and A‐LPS, and that GtfC and GtfD proteins may work together to synthesize the two kinds of LPS. In addition, the GtfF protein was essential for A‐LPS synthesis, although this may be achieved in a strain‐specific manner.
Optimising mobility through the sit‐to‐stand activity for older people living in residential care facilities: A qualitative interview study of healthcare aide experiences
Authors: Kagwa Sharon A. , Boström Anne‐Marie , Ickert Carla , Slaughter Susan E.
Published: October 2017

Aims and objectives

To explore the experience of HCAs encouraging residents living in residential care to complete the sit‐to‐stand activity and to identify the strategies HCAs used to integrate the activity into their daily work routines.

Background

Decreased mobility in advanced ageing is further reduced when entering a residential care facility. Interventions such as the sit‐to‐stand activity have been shown to have a positive effect on the mobility of older people. There is evidence to suggest that healthcare aides are able to support residents to complete the sit‐to‐stand activity as part of their daily work routines; however, little is known about how healthcare aides actually do this with residents living in residential care.

Design

A qualitative interview study included seven purposively sampled HCAs working in residential care facilities. Semistructured interviews were analysed using inductive qualitative content analysis.

Results

The HCAs’ experience with the sit‐to‐stand activity was represented by the following four categories: Resident participation, Feeling misunderstood and disrespected, Time and workload, and Management involvement. HCAs identified three strategies to help them support residents to complete the sit‐to‐stand activity: Motivating residents, Completing activity in a group and Using time management skills.

Conclusions

HCAs reported some encouragement from managers and cooperation from residents to complete the sit‐to‐stand activity with residents; however, they also felt constrained by time limitations and workload demands and they felt misunderstood and disrespected. HCAs were able to identify several strategies that helped them to integrate the sit‐to‐stand activity into their daily routines.

Implications for practice

This study highlights the challenges and supportive factors of implementing the sit‐to‐stand activity into the daily work routine of HCAs. The study also identifies the strategic role of nurse managers when implementing interventions in residential care facilities.
Quantifying rapid changes in cardiovascular state with a moving ensemble average
Authors: Cieslak Matthew , Ryan William S. , Babenko Viktoriya , Erro Hannah , Rathbun Zoe M. , Meiring Wendy , Kelsey Robert M. , Blascovich Jim , Grafton Scott T.
Published: October 2017

MEAP, the moving ensemble analysis pipeline, is a new open‐source tool designed to perform multisubject preprocessing and analysis of cardiovascular data, including electrocardiogram (ECG), impedance cardiogram (ICG), and continuous blood pressure (BP). In addition to traditional ensemble averaging, MEAP implements a moving ensemble averaging method that allows for the continuous estimation of indices related to cardiovascular state, including cardiac output, preejection period, heart rate variability, and total peripheral resistance, among others. Here, we define the moving ensemble technique mathematically, highlighting its differences from fixed‐window ensemble averaging. We describe MEAP's interface and features for signal processing, artifact correction, and cardiovascular‐based fMRI analysis. We demonstrate the accuracy of MEAP's novel B point detection algorithm on a large collection of hand‐labeled ICG waveforms. As a proof of concept, two subjects completed a series of four physical and cognitive tasks (cold pressor, Valsalva maneuver, video game, random dot kinetogram) on 3 separate days while ECG, ICG, and BP were recorded. Critically, the moving ensemble method reliably captures the rapid cyclical cardiovascular changes related to the baroreflex during the Valsalva maneuver and the classic cold pressor response. Cardiovascular measures were seen to vary considerably within repetitions of the same cognitive task for each individual, suggesting that a carefully designed paradigm could be used to capture fast‐acting event‐related changes in cardiovascular state.
Using structured decision‐making to set restoration objectives when multiple values and preferences exist
Authors: Guerrero Angela M. , Shoo Luke , Iacona Gwenllian , Standish Rachel J. , Catterall Carla P. , Rumpff Libby , de Bie Kelly , White Zoe , Matzek Virginia , Wilson Kerrie A.
Published: October 2017

Achieving global targets for restoring native vegetation cover requires restoration projects to identify and work toward common management objectives. This is made challenging by the different values held by concerned stakeholders, which are not often accounted for. Additionally, restoration is time‐dependent and yet there is often little explicit acknowledgment of the time frames required to achieve outcomes. Here, we argue that explicitly incorporating value and time considerations into stated objectives would help to achieve restoration goals. We reviewed the peer‐reviewed literature on restoration of terrestrial vegetation and found that while there is guidance on how to identify and account for stakeholder values and time considerations, there is little evidence these are being incorporated into decision‐making processes. In this article, we explore how a combination of stakeholder surveys and workshops can be used within a structured decision‐making framework to facilitate the integration of diverse stakeholder values and time frame considerations to set restoration objectives. We demonstrate this approach with a case of restoration decision‐making at a regional scale (southeast Queensland, Australia) with a view to this experience supporting similar restoration projects elsewhere.
Bounding Analysis of Drinking Water Health Risks from a Spill of Hydraulic Fracturing Flowback Water
Authors: Rish William R. , Pfau Edward J.
Published: October 2017

A bounding risk assessment is presented that evaluates possible human health risk from a hypothetical scenario involving a 10,000‐gallon release of flowback water from horizontal fracturing of Marcellus Shale. The water is assumed to be spilled on the ground, infiltrates into groundwater that is a source of drinking water, and an adult and child located downgradient drink the groundwater. Key uncertainties in estimating risk are given explicit quantitative treatment using Monte Carlo analysis. Chemicals that contribute significantly to estimated health risks are identified, as are key uncertainties and variables to which risk estimates are sensitive. The results show that hypothetical exposure via drinking water impacted by chemicals in Marcellus Shale flowback water, assumed to be spilled onto the ground surface, results in predicted bounds between 10−10 and 10−6 (for both adult and child receptors) for excess lifetime cancer risk. Cumulative hazard indices (HICUMULATIVE) resulting from these hypothetical exposures have predicted bounds (5th to 95th percentile) between 0.02 and 35 for assumed adult receptors and 0.1 and 146 for assumed child receptors. Predicted health risks are dominated by noncancer endpoints related to ingestion of barium and lithium in impacted groundwater. Hazard indices above unity are largely related to exposure to lithium. Salinity taste thresholds are likely to be exceeded before drinking water exposures result in adverse health effects. The findings provide focus for policy discussions concerning flowback water risk management. They also indicate ways to improve the ability to estimate health risks from drinking water impacted by a flowback water spill (i.e., reducing uncertainty).
Supply‐ versus Demand‐Side Policies in the Presence of Carbon Leakage and the Green Paradox
Authors: Hagem Cathrine , Storrøsten Halvor Briseid
Published: October 2017

We consider a climate coalition that seeks to reduce global emissions in the presence of carbon leakage and resource exhaustibility. We show that a credible announcement of future unilateral supply‐side policies delays foreign emissions, and we derive the optimal combination of consumer taxes and producer taxes when we consider leakages from free riders, both within periods and across periods. The tax shares generally differ over time. A decline in the present value of the social cost of carbon over time supports a time path where the consumers’ tax share of the total carbon tax also declines over time. We illustrate our findings with a numerical model.
Multilingualism and European Identification
Authors: Medrano Juan Díez
Published: October 2017

The literature on ethnicity and nationalism notes the centrality of language in group formation. Developments connected to globalization have simultaneously propitiated learning more than one language and the emergence of post‐national and pan‐ethnic identifications. This article brings the literature on ethnicity and nationalism to bear on the analysis of these changes to assess the causal relationship between multilingualism (ML) and European identification (EI). Sociology and social psychology provide solid theoretical arguments for why they should be related. The article tests this relationship withEurobarometerdata from 2010. I show thatMLhas a causal impact onEIand that interaction helps mediate this relationship. The effect of language onEIis modest, however, and interaction does not appear to be the main mechanism mediating it. The article concludes with speculation as to the role of low relative cross‐national mobility in Europe as the main explanation for some of the findings.
Chemical and Phase Composition of the Friction Surfaces Fe–Mn–C–B–Si–Ni–Cr Hardfacing Coatings
Authors: Pashechko Mykhaylo I. , Dziedzic Krzysztof , Mendyk Ewaryst , Jozwik Jerzy
Published: October 2017

The paper presents the results of an X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) study of chemical and phase composition of the friction surfaces Fe–Mn–C–B–Si–Ni–Cr hardfacing coatings. The alloy was used as a core mixture to produce flux-cored wire of 2.4 mm in diameter. The coating was deposited by gas metal arc welding using CO2 as a shielding gas. The tribological examination was conducted in a ball on disk system with a load of 20 N under dry friction conditions. A XPS were used to examine the structures on the friction surface and depend on depth 5, 10, 15, 20, 50, 100, 200, and 6000 nm. The segregation of C, B, and Si atoms was observed in the process of the friction. The presence of compounds such as oxides (B2O3, SiO2, Cr2O3), carbides (Fe3C, Cr7C3), and borides (FeB, Fe2B) was detected on the surface and in the subsurface layer of the Fe–Mn–C–B–Si–Ni–Cr coating. The formation of these structures increases the wear resistance of composite coatings.
Normal Damping Model of Mechanical Joints Interfaces Considering Asperities in Lateral Contact
Authors: Gao Zhiqiang , Fu Weiping , Wang Wen , Lou Leiting , Wu Jiebei
Published: October 2017

A mechanical interface behaves as the stiffness and damping when the interface is bearing a static normal force and a sine normal exciting force. For the interfacial normal damping, a calculating model was proposed. This proposed model studied the lateral contact (shoulder–shoulder contact) between upper and lower asperities in the elastic and elastic-perfectly plastic stages, which is neglected by other classical models. The normal force can be divided into a normal component and a tangential component when two asperities are contacting in dislocation. The relation between the loading–unloading normal component forces and deformation can be calculated, and then the strain energy dissipation between asperities can be gotten by integral. The friction energy dissipation also can be calculated based on the relation between loading–unloading tangential component forces and the slippage. Furthermore, the total interfacial energy dissipation can be obtained according to the statistical theory. Finally, the equivalent viscous damping is estimated using the vibration theory. The proposed model and classical models are compared by simulation and experiment, and it was found that the interfacial damping of the proposed model is more than the damping of the classical models. Moreover, the proposed model is consistent with the experimental results.
Active Control of Viscoelastic Systems by the Method of Receptance
Authors: Singh Kumar V. , Ling Xiaoxuan
Published: October 2017

Viscoelastic materials have frequency and temperature-dependent properties and they can be used as passive controlling devices in wide range of vibration applications. In order to design active control for viscoelastic systems, an accurate mathematical modeling is needed. In practice, various material models and approximation techniques are used to model the dynamic behavior of viscoelastic systems. These models are then transformed into approximating state-space models, which introduces several challenges such as introduction of nonphysical internal state variables and requirement of observer/state estimator design. In this paper, it is shown that the active control for viscoelastic structures can be designed accurately by only utilizing the available receptance transfer functions (RTF) and hence eliminating the need for state-space modeling for control design. By using the recently developed receptance method, it is shown that active control for poles and zeros assignment of the viscoelastic systems can be achieved. It is also shown that a nested active controller can also be designed for continuous structures (beams/rods) supported by viscoelastic elements. It is highlighted that such a controller design requires modest size of RTF and solution of the set of linear system of equations.
Mixed Acoustic-Entropy Combustion Instabilities in a Model Aeronautical Combustor: Large Eddy Simulation and Reduced Order Modeling
Authors: Lacombe Florent , Méry Yoann
Published: October 2017

This article focuses on combustion instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, and outlet nozzle), while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, and circular nozzle at the outlet). A large eddy simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, dynamic mode decomposition (DMD) is used to visualize, analyze, and model the complex phasing between different processes affecting the reacting zones. Using these data, a zero-dimensional (0D) modeling of the premixed flame and of the diffusion flame is proposed. These models provide an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.
Friction Effects on the Edge-of-Contact Stresses for Sliding Contact Between a Flat Punch With Rounded Corners and a Half Space
Authors: Sinclair G. B.
Published: October 2017

For the title problem, the punch is assumed to be pressed vertically into the horizontal upper surface of the half space, then slide horizontally sideways. A range of such configurations is identified that permit Shtaerman’s solution for the contact pressure for a rigid frictionless punch to be modified so that it applies to a deformable punch and also yields the contact stresses when the punch slides in the presence of friction. Closed-form expressions are obtained for the peak edge-of-contact stresses. These edge-of-contact stresses can fluctuate significantly with even modest amounts of sliding.
Computational Fluid Dynamics Analysis of a Radial Turbine During Load Step Operation of an Automotive Turbocharger
Authors: Roclawski Harald , Gugau Marc , Böhle Martin
Published: October 2017

A method for evaluating the transient performance of a turbocharger (TC) is so-called load step tests. In these tests, the load of the engine is increased at constant engine speed and the time measured from the start to the end of the load step is measured. Usually, these tests can be run relatively late in the development process, since hardware needs to be already available. In order to judge the transient TC performance at an earlier stage, engine process simulations are run using maps of compressor and turbine. For the turbine, these maps usually need to be extrapolated, since only a certain range of each speed line can be measured on a standard gas stand. Furthermore, because of the exhaust gas pulsation of the engine, it is known that the turbine performance differs from the steady-state case which the maps rely on. This has to be respected by additional models. Using computational fluid dynamics (CFD) simulations, the transient performance of the turbine can be analyzed independent from steady-state maps. So far, these investigations have been usually performed with a constant turbine speed. In this paper, a method is presented which includes the speed fluctuations of the TC caused by the exhaust pulsations as well as the change in mean speed during the load step by including compressor and engine in the CFD analysis with User-Fortran models. Results for a load step from 21,000 rpm to 196,400 rpm are discussed.
Comparison of Moment-Based Methods for Representing Droplet Size Distributions in Supersonic Nucleating Flows of Steam
Authors: Afzalifar Ali , Turunen-Saaresti Teemu , Grönman Aki
Published: October 2017

This paper investigates the performance of moment-based methods and a monodispersed model (Mono) in predicting the droplet size distribution and behavior of wet-steam flows. The studied moment-based methods are a conventional method of moments (MOM) along with its enhanced version using Gaussian quadrature, namely the quadrature method of moments (QMOM). The comparisons of models are based on the results of an Eulerian–Lagrangian (E–L) method, as the benchmark calculations, providing the full spectrum of droplet size. In contrast, for the MOM, QMOM, and Mono an Eulerian reference frame is chosen to cast all the equations governing the phase transition and fluid motion. This choice of reference frame is essential to draw a meaningful comparison regarding complex flows in wet-steam turbines as the most important advantage of the moment-based methods is that the moment-transport equations can be conveniently solved in an Eulerian frame. Thus, the moment-based method can avoid the burdensome challenges in working with a Lagrangian framework for complicated flows. The main focus is on the accuracy of the QMOM and MOM in representing the water droplet size distribution. The comparisons between models are made for two supersonic low-pressure nozzle experiments reported in the literature. Results show that the QMOM, particularly inside the nucleation zone, predicts moments closer to those of the E–L method. Therefore, for the test case in which the nucleation is significant over a large proportion of the domain, the QMOM provides results in clearly better agreements with the E–L method in comparison with the MOM.
Numerical Simulation of a Pump–Turbine Transient Load Following Process in Pump Mode
Authors: Pavesi Giorgio , Cavazzini Giovanna , Ardizzon Guido
Published: October 2017

This paper presents the simulation of the dynamic behavior of variable speed pump–turbine. A power reduction scenario at constant wicket gate opening was numerically analyzed from 100% to 93% rpm corresponding to a power reduction from full load to about 70% with a ramp rate of 1.5% per second. The flow field analysis led to the onset and development of unsteady phenomena progressively evolving in an organized rotating partial stall during the pump power reduction. These phenomena were characterized by frequency and time–frequency analyses of several numerical signals (pressure, blade torque, and flow rate in blade passages). The unsteady pattern in return channel strengthened emphasizing its characteristic frequency with the rotational velocity decreasing reaching a maximum and then disappearing. At lower rotational speed, the flow field into the wickets gates channel starts to manifest a full three-dimensional (3D) flow structure. This disturbance was related to the boundary layer separation and stall, and it was noticed by a specific frequency.
Numerical Analysis of Suppression Effect of Asymmetric Slit on Cavitation Instabilities in Cascade
Authors: Kobayashi Hiroki , Hagiwara Ryosuke , Kawasaki Satoshi , Uchiumi Masaharu , Yada Kazuyuki , Iga Yuka
Published: October 2017

In this study, numerical analysis is carried out around the cyclic flat-plate cascade with symmetric and asymmetric slit, so as to examine the suppressing or controlling effect of the slit on cavitation instabilities such as cavitation oscillation (CO) which resembles cavitation surge, and rotating cavitation. These instabilities cause various problems for the turbomachinery, for example, rotating cavitation causes an asynchronous shaft vibration, and CO causes an oscillation of column of working fluid as a result of the resonance phenomenon of the system. In liquid propellant rocket engine, suppression device for these instabilities bring increase in cost of the launch. Therefore, it is thought that to develop effective suppression technique is important for turbopumps. Especially, in this paper, two types of the flat-plate three blades cascade which have symmetric slit on each blade and three types of the cascade which have asymmetric slit were analyzed, and the results are compared with those of cascade without slit. As a result, the CO is perfectly suppressed in both of two types cascade with asymmetric slit. Also, other examined cascades have suppression effect of CO These results indicate the possibility of suppressing cavitation instabilities in actual inducers or controlling the type of the cavitation instabilities by the arrangement of the slit. Moreover, the head performance is equal or slightly increased by arranging slit.
Deformation Compensation During Buoyancy-Enabled Inkjet Printing of Three-Dimensional Soft Tubular Structures
Authors: Christensen Kyle , Zhang Zhengyi , Xu Changxue , Huang Yong
Published: October 2017

Of various tissues being fabricated using bioprinting, three-dimensional (3D) soft tubular structures have often been the focus since they address the need for printable vasculature throughout a thick tissue and offer potential as perfusable platforms for biological studies. Drop-on-demand inkjetting has been favored as an effective technique to print such 3D soft tubular structures from various hydrogel bioinks. During the buoyancy-enabled inkjet fabrication of hydrogel-based soft tubular structures, they remain submerged in a solution, which crosslinks the printed structures and provides a supporting buoyant force. However, because of the low stiffness of the structures, the structural deformation of printed tubes poses a significant challenge to the process effectiveness and efficiency. To overcome this structural deformation during buoyancy-enabled inkjet printing, predictive compensation approaches are developed to incorporate deformation allowance into the designed shape. Circumferential deformation is addressed by a four-zone approach, which includes base, circular, vertical, and spanning zones for the determination of a designed cross section or compensated printing path. Axial deformation is addressed by the modification of the proposed circumferential compensation based on the distance of a given cross section to the junction of a branching tube. These approaches are found to enable the successful fabrication of straight and branching alginate tubular structures with nearly ideal geometry, providing a good foundation for the wide implementation of the buoyancy-enabled inkjetting technique. While inkjetting is studied herein as a model bioprinting process, the resulting knowledge also applies to other buoyancy-enabled bioprinting techniques.
Effect of Internal Crossflow Velocity on Film Cooling Effectiveness—Part I: Axial Shaped Holes
Authors: McClintic John W. , Anderson Joshua B. , Bogard David G. , Dyson Thomas E. , Webster Zachary D.
Published: October 2017

The effect of feeding shaped film cooling holes with an internal crossflow is not well understood. Previous studies have shown that internal crossflow reduces film cooling effectiveness from axial shaped holes, but little is known about the mechanisms governing this effect. It was recently shown that the crossflow-to-mainstream velocity ratio is important, but only a few of these crossflow velocity ratios have been studied. This effect is of concern because gas turbine blades typically feature internal passages that feed film cooling holes in this manner. In this study, film cooling effectiveness was measured for a single row of axial shaped cooling holes fed by an internal crossflow with crossflow-to-mainstream velocity ratio varying from 0.2 to 0.6 and jet-to-mainstream velocity ratios varying from 0.3 to 1.7. Experiments were conducted in a low speed flat plate facility at coolant-to-mainstream density ratios of 1.2 and 1.8. It was found that film cooling effectiveness was highly sensitive to crossflow velocity at higher injection rates while it was much less sensitive at lower injection rates. Analysis of the jet shape and lateral spreading found that certain jet characteristic parameters scale well with the crossflow-to-coolant jet velocity ratio, demonstrating that the crossflow effect is governed by how coolant enters the film cooling holes.
A Design Tool for a Single Vertex Compliant-Facet Origami Mechanism Including Torsional Hinge Lines
Authors: Rommers Jelle , Radaelli Giuseppe , Herder Just L.
Published: October 2017

Principles from origami art are applied in the design of mechanisms and robotics increasingly frequent. A large part of the application driven research of these origami-like mechanisms focuses on devices where the creases (hinge lines) are actuated and the facets are constructed as stiff elements. In this paper, a design tool is proposed in which hinge lines with torsional stiffness and flexible facets are used to design passive, instead of active mechanisms. The design tool is an extension of a model of a single vertex compliant facet origami mechanism (SV-COFOM) and is used to approximate a desired moment curve by optimizing the design variables of the mechanism. Three example designs are presented: a constant moment joint (CMJ), a gravity compensating joint (GCJ) and a zero moment joint (ZMJ). The CMJ design has been evaluated experimentally, resulting in a root-mean-squared error (RMSE) of 6.4 × 10−2 N·m on a constant moment value of 0.39 N·m. This indicates that the design tool is suitable for a course estimation of the moment curve of the SV-COFOM in early stages of a design process.
Design and Development of a Dual-Axis Force Sensing MEMS Microgripper
Authors: Yang Sijie , Xu Qingsong , Nan Zhijie
Published: October 2017

This paper presents the design, simulation, fabrication, and testing processes of a new microelectromechanical systems (MEMS) microgripper, which integrates an electrostatic actuator and a capacitive force sensor. One advantage of the presented gripper is that the gripping force and interaction force in two orthogonal directions can be, respectively, detected by a single force sensor. The whole gripper structure consists of the left actuating part and right sensing part. It owns a simple structure and compact footprint. The actuator and sensor are fixed and linearly guided by four leaf flexures, respectively. The left arm of the gripper is driven through a lever amplification mechanism. By this structure, the displacement from the electrostatic actuator is transmitted and enlarged at the gripper tip. The right arm of the gripper is designed to detect the gripping and interaction forces using a capacitive sensor. The MEMS gripper is manufactured by SOIMUMPs process. The performance of the designed gripper is verified by conducting finite element analysis (FEA) simulation and experimental studies. Moreover, the demonstration of biocellulose gripping confirms the feasibility of the developed gripper device.
Effectiveness of Rack-Level Fans—Part II: Control Strategies and System Redundancy
Authors: Fernandes John Edward , Eiland Richard , Nagendran Bharath , Mulay Veerendra , Agonafer Dereje
Published: October 2017

Fan efficiency is known to increase with size. In part I of this study, savings in server fan power on the order of 50% were reported by replacing server-enclosed 60 mm fans with a rear-mounted wall of larger fans (80 mm or 120 mm in size). A methodology for row-wise control of such rack-level fans, with the purpose of simulating an actual product, is previewed and savings comparable to part I are reported. Performance under real-life scenarios such as nonuniform computational loads and fan failure is investigated. Each rack-level setup has distinct advantages. Selecting between configurations would necessitate a compromise between efficiency, redundancy, and cost.
Modeling and Simulation of Material Removal Rates and Profile Accuracy Control in Abrasive Flow Machining of the Integrally Bladed Rotor Blade and Experimental Perspectives
Authors: Cheng Kai , Shao Yizhi , Bodenhorst Rodrigo , Jadva Mitul
Published: October 2017

Abrasive flow machining (AFM) technology is getting more and more interest by the industry and research community particularly in the context of increasing demands for postprocessing of the additively manufactured and complex components. It is essentially important to develop an industrial feasible approach to controlling and improving the profile accuracy (form and dimensional) of components as well as their surface roughness. In this paper, a multiscale multiphysics simulation-based approach is presented to model and simulate the AFM process against the component form and dimensional accuracy control in particular. The simulation is developed in comsol which is a multiphysics computational environment. Well-designed AFM experiment trials are carried out on a purposely configured blade “coupon” to further evaluate and validate the simulations. The AFM machine and specific machining media for the experiments are provided by the industrial collaboration company, with their further industrial inputs. Both the simulation and experimental trial results illustrate that the approach is applicable to the blade profile prediction and accuracy control, which is used as a foundation for developing the simulation-based AFM virtual machining system.
Characterization of Different Actuator Designs for the Control of the Precessing Vortex Core in a Swirl-Stabilized Combustor
Authors: Lückoff Finn , Sieber Moritz , Paschereit Christian Oliver , Oberleithner Kilian
Published: October 2017

The precessing vortex core (PVC) represents a helical-shaped coherent flow structure typically occurring in both reacting and nonreacting swirling flows. Until now, the fundamental impact of the PVC on flame dynamics, thermoacoustic instabilities, and pollutant emissions is still unclear. In order to identify and investigate these mechanisms, the PVC needs to be controlled effectively with a feedback control system. A previous study successfully applied feedback control in a generic swirling jet setup. The next step is to transfer this approach into a swirl-stabilized combustor, which poses big challenges on the actuator and sensor design and placement. In this paper, different actuator designs are investigated with the goal of controlling the PVC dynamics. The actuation strategy aims to force the flow near the origin of the instability—the so-called wavemaker. To monitor the PVC dynamics, arrays of pressure sensors are flush-mounted at the combustor inlet and the combustion chamber walls. The best sensor placement is evaluated with respect to the prediction of the PVC dynamics. Particle image velocimetry (PIV) is used to evaluate the passive impact of the actuator shape on the mean flow field. The performance of each actuator design is evaluated from lock-in experiments showing excellent control authority for two out of seven actuators. All measurements are conducted at isothermal conditions in a prototype of a swirl-stabilized combustor.
A Flow Starvation Model for Tilting Pad Journal Bearings and Evaluation of Frequency Response Functions: A Contribution Toward Understanding the Onset of Low Frequency Shaft Motions
Authors: San Andrés Luis , Koo Bonjin , Hemmi Makoto
Published: October 2017

Direct lubrication tilting pad journal bearings (TPJBs) require less oil flow, reduce power consumption, and offer cooler pad temperatures for operation at high surface speeds. Although apparently free of hydrodynamic instability, the literature shows that direct lubrication TPJBs exhibit unexpected shaft vibrations with a broadband low frequency range, albeit small in amplitude. Published industrial practice demonstrates the inlet lubrication type, a reduced supply flow rate causing film starvation, and the bearing discharge conditions (evacuated or end sealed) affect the onset, gravity, and persistency of the subsynchronous vibration (SSV) hash motions. The paper presents a physical model to predict the performance of TPJBs with flow conditions ranging from over flooded to extreme starvation. Lubricant starvation occurs first on an unloaded pad, thus producing a (beneficial) reduction in drag power. As the supplied flowrate decreases further, fluid starvation moves toward the loaded pads and affects the film temperature and power loss, increases the journal eccentricity, and modifies the dynamic force coefficients of each tilting pad and thus the whole bearing. For a point mass rotor supported on a TPJB, the analysis produces eigenvalues and frequency response functions (FRFs) from three physical models for lateral rotor displacements: one with frequency reduced (4 × 4) bearing stiffness (K) and damping (C) coefficients and another with constant K–C–M (inertia) coefficients over a frequency range. The third model keeps the degrees of freedom (DOF) (tilting) of each pad and incorporates the full matrices of force coefficients including fluid inertia. Predictions of rotordynamic performance follow for two TPJBs: one bearing with load between pads (LBP) configuration, and the other with a load on a pad (LOP) configuration. For both examples, under increasingly poor lubricant flow conditions, the damping ratio for the rotor-bearing low frequency (SSV) modes decreases, thus producing an increase in the amplitude of the FRFs. For the LOP bearing, a large static load produces a significant asymmetry in the force coefficients; the rotor bearing has a small stiffness and damping for shaft displacements in the direction orthogonal to the load. A reduction in lubricant flow only exacerbates the phenomenon; starvation reaches the loaded pad to eventually cause the onset of low frequency (SSV) instability. The bearing analyzed showed similar behavior in a test bench. The predictions thus show a direct correlation between lubricant flow starvation and the onset of SSV.
Use of Silicone Oil and Coconut Oil as Liquid Spectrum Filters for BSPVT: With Emphasis on Degradation of Liquids by Sunlight
Authors: Joshi Sandeep S. , Dhoble Ashwinkumar S.
Published: October 2017

The solar photovoltaic thermal system (PVT) facilitates conversion of incoming solar radiations into heat and electricity simultaneously. The beam split photovoltaic thermal system (BSPVT) is one of the PVT systems. In this system, the incoming solar beam is splitted and used separately for PV and thermal system. The feasibility of water, silicone oil, and coconut oil as spectrum filter for C–Si solar photovoltaic system is reported in the literature recently. However, the changes in the optical behavior of the liquids due to extended exposure to sunlight (aging effect) had not been considered in most of the previous studies. The current study includes the methodology for the selection of liquids for BSPVT systems, estimation of external quantum efficiency (EQE) of a solar cell using liquids, and the aging effect on the liquid spectrum filters. The spectral response of the solar cell is analyzed using BENTHAM, (PVE 300) for 300–1100 nm. In this study, it has been observed that the aging of silicone oil reduces the electrical performance of the solar cell. On the other hand, the aged coconut oil improves the electrical performance of the solar cell as compared to the fresh coconut oil spectrum filter.
Stochastic Analysis of Microgrinding Tool Topography and Its Role in Surface Generation
Authors: Anandita S. , Mote Rakesh G. , Singh Ramesh
Published: October 2017

With the rising trend of miniaturization in modern industries, micro manufacturing processes have made a significant position in the manufacturing domain. Demands of high precision along with super finish of the final machined product have started rising. Grinding, being largely considered as a finishing operation, has large potential to cater to such requirements of micro manufacturing. However, stochastic nature of the grinding wheel topography results in a high degree of variation in the output responses especially in the case of microgrinding. With an aim to obtain a good and predictable surface finish in brittle materials, the current study aims at developing a surface generation model for wall grinding of hard and brittle materials using a microgrinding tool. Tool topographical features such as grit protrusion height, intergrit spacing, and grit distribution on the tool tip of a microgrinding pin have been calculated from the known mesh size of the grits used during tool manufacturing. Kinematic analysis of surface grinding has been extended to the case of wall grinding and each grit trajectory has been predicted. The kinematic analysis has been done by taking into consideration the effect of tool topographical features and the process parameters on the ground surface topography. Detailed analysis of the interaction of the grit trajectories is done to predict the final surface profile. The predicted surface roughness has been validated with the experimental results to provide an insight to the surface quality that can be produced for a given tool topography.
Numerical Simulation Research on the Performance of SCWR Fuel Rod
Authors: Tang Changbing , Xing Shuo , Pang Hua , Chen Ping , Zhou Yi
Published: October 2017

Because of the high temperature and high pressure characteristics of supercritical water-cooled reactor (SCWR), the thermal hydraulic performance of SCWR is greatly different from pressurized water reactor (PWR), which makes the current PWR fuel rod performance analysis codes are no longer applicable to SCWR. In this research, the irradiation swelling, irradiation densification, thermal expansion, thermal creep, plastic deformation, irradiation creep and irradiation hardening of UO2 pellet, and stainless steel cladding were considered; the gas conductance and radiant conductance of gap heat transfer were considered, the forced convective heat transfer on the outer surface of cladding was considered. Meanwhile, the irradiation effects and the thermal effects on the materials parameters such as thermal conductivity, specific heat, and young’s modulus were also considered in this research. With the help of abaqus software, the related user-defined subroutines were developed, and the irradiation effects and thermal effects of SCWR fuel were introduced into the numerical simulation, and then completed the analysis of SCWR fuel rods’ performance under steady power conditions. Some reference suggestions for the design and development of SCWR fuel could be provided by the establishment of this numerical simulation method.
Fukushima Unit 2 Accident Simulation With MELCOR 2.1
Authors: Bocanegra Rafael , Di Marcello Valentino , Sánchez-Espinoza Victor H. , Jiménez Gonzalo
Published: October 2017

A VTT Fukushima Daiichi Unit 3 (1F3) method for estimation of liquids and consequences of releases (MELCOR) model was modified to simulate the Fukushima Daiichi Unit 2 (1F2) accident. Five simulations were performed using different modeling approaches. The model 1F2 v1 includes only the basic modifications to reproduce the 1F2 accident. The model 1F2 v2 includes the same modifications used in 1F2 v1 plus the wet well (WW) improvement. In the 1F2 v3 model, the reactor core isolation cooling (RCIC) system logic was modified to avoid the use of tabular functions for the mass flow inlet and outlet. Because of this analysis, it is concluded that there is a strong dependency on parameters that still have many uncertainties, such as the RCIC two-phase flow operation, the alternative water injection, the suppression pool (SP) behavior, the rupture disk behavior and the containment failure modes, which affect the final state of the reactor core.
Buckling of a Pressurized Hemispherical Shell Subjected to a Probing Force
Authors: Marthelot Joel , López Jiménez Francisco , Lee Anna , Hutchinson John W. , Reis Pedro M.
Published: October 2017

We study the buckling of hemispherical elastic shells subjected to the combined effect of pressure loading and a probing force. We perform an experimental investigation using thin shells of nearly uniform thickness that are fabricated with a well-controlled geometric imperfection. By systematically varying the indentation displacement and the geometry of the probe, we study the effect that the probe-induced deflections have on the buckling strength of our spherical shells. The experimental results are then compared to finite element simulations, as well as to recent theoretical predictions from the literature. Inspired by a nondestructive technique that was recently proposed to evaluate the stability of elastic shells, we characterize the nonlinear load-deflection mechanical response of the probe for different values of the pressure loading. We demonstrate that this nondestructive method is a successful local way to assess the stability of spherical shells.