bluuebunny/crossref_metadata_2025 huggingface dataset:
Salicylic acid‐dependent immunity contributes to resistance against Rhizoctonia solani, a necrotrophic fungal agent of sheath blight, in rice and Brachypodium distachyon
Authors: Kouzai Yusuke , Kimura Mamiko , Watanabe Megumi , Kusunoki Kazuki , Osaka Daiki , Suzuki Tomoko , Matsui Hidenori , Yamamoto Mikihiro , Ichinose Yuki , Toyoda Kazuhiro , Matsuura Takakazu , Mori Izumi C. , Hirayama Takashi , Minami Eiichi , Nishizawa Yoko , Inoue Komaki , Onda Yoshihiko , Mochida Keiichi , Noutoshi Yoshiteru
Published: October 2017

Rhizoctonia solani is a soil‐borne fungus causing sheath blight. In consistent with its necrotrophic life style, no rice cultivars fully resistant to R. solani are known, and agrochemical plant defense activators used for rice blast, which upregulate a phytohormonal salicylic acid (SA)‐dependent pathway, are ineffective towards this pathogen. As a result of the unavailability of genetics, the infection process of R. solani remains unclear.

We used the model monocotyledonous plants Brachypodium distachyon and rice, and evaluated the effects of phytohormone‐induced resistance to R. solani by pharmacological, genetic and microscopic approaches to understand fungal pathogenicity.

Pretreatment with SA, but not with plant defense activators used in agriculture, can unexpectedly induce sheath blight resistance in plants. SA treatment inhibits the advancement of R. solani to the point in the infection process in which fungal biomass shows remarkable expansion and specific infection machinery is developed. The involvement of SA in R. solani resistance is demonstrated by SA‐deficient NahG transgenic rice and the sheath blight‐resistant B. distachyon accessions, Bd3‐1 and Gaz‐4, which activate SA‐dependent signaling on inoculation.

Our findings suggest a hemi‐biotrophic nature of R. solani, which can be targeted by SA‐dependent plant immunity. Furthermore, B. distachyon provides a genetic resource that can confer disease resistance against R. solani to plants.
Effects of probiotics on body weight, body mass index, fat mass and fat percentage in subjects with overweight or obesity: a systematic review and meta‐analysis of randomized controlled trials
Authors: Borgeraas H. , Johnson L. K. , Skattebu J. , Hertel J. K. , Hjelmesæth J.
Published: October 2017

A systematic review and meta‐analysis of randomized controlled trials was conducted to examine the effects of probiotic supplementation on body weight, body mass index (BMI), fat mass and fat percentage in subjects with overweight (BMI 25–29.9 kg m−2) or obesity (BMI ≥30 kg m−2). MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were searched for studies published between 1946 and September 2016. A meta‐analysis, using a random effects model, was performed to calculate the weighted mean difference between the intervention and control groups. Of 800 studies identified through the literature search, 15 were finally included. The studies comprised a total of 957 subjects (63% women), with the mean BMI being 27.6 kg m−2 and the duration of the interventions ranging from 3 to 12 weeks. Administration of probiotics resulted in a significantly larger reduction in body weight (weighted mean difference [95% confidence interval]; −0.60 [−1.19, −0.01] kg, I2 = 49%), BMI (−0.27 [−0.45, −0.08] kg m−2, I2 = 57%) and fat percentage (−0.60 [−1.20, −0.01] %, I2 = 19%), compared with placebo; however, the effect sizes were small. The effect of probiotics on fat mass was non‐significant (−0.42 [−1.08, 0.23] kg, I2 = 84%).
IRF‐1 SNPs influence the risk for childhood allergic asthma: A critical role for pro‐inflammatory immune regulation
Authors: Landgraf‐Rauf Katja , Boeck Andreas , Siemens Diana , Klucker Elisabeth , Vogelsang Vanessa , Schmidt Susanne , Kunze Sonja , Weissenbacher Claudia , Graessel Anke , Schmidt‐Weber Carsten , von Mutius Erika , Schedel Michaela , Schaub Bianca
Published: October 2017

Background

Allergic and non‐allergic childhood asthma has been characterized by distinct immune mechanisms. While interferon regulating factor 1 (IRF‐1) polymorphisms (SNPs) influence atopy risk, the effect of SNPs on asthma phenotype‐specific immune mechanisms is unclear. We assessed whether IRF‐1 SNPs modify distinct immune‐regulatory pathways in allergic and non‐allergic childhood asthma (AA/NA).

Methods

In the CLARA study, asthma was characterized by doctor's diagnosis and AA vs NA by positive or negative specific IgE. Children were genotyped for four tagging SNPs within IRF‐1 (n = 172). mRNA expression was measured with qRT‐PCR. Gene expression was analyzed depending on genetic variants within IRF‐1 and phenotype including haplotype estimation and an allelic risk score.

Results

Carrying the risk alleles of IRF‐1 in rs10035166, rs2706384, or rs2070721 was associated with increased risk for AA. Carrying the non‐risk allele in rs17622656 was associated with lower risk for AA but not NA. In AA carrying the risk alleles, an increased pro‐inflammatory expression of ICAM3, IRF‐8, XBP‐1, IFN‐γ, RGS13, RORC, and TSC2 was observed. NOD2 expression was decreased in AA with risk alleles in rs2706384 and rs10035166 and with risk haplotype. Further, AA with risk haplotype showed increased IL‐13 secretion. NA with risk allele in rs2070721 compared to non‐risk allele in rs17622656 showed significantly upregulated calcium, innate, mTOR, neutrophil, and inflammatory‐associated genes.

Conclusion

IRF‐1 polymorphisms influence the risk for childhood allergic asthma being associated with increased pro‐inflammatory gene regulation. Thus, it is critical to implement IRF‐1 genetics in immune assessment for childhood asthma phenotypes.
Vessel diameter is related to amount and spatial arrangement of axial parenchyma in woody angiosperms
Authors: Morris Hugh , Gillingham Mark A.F. , Plavcová Lenka , Gleason Sean M. , Olson Mark E. , Coomes David A. , Fichtler Esther , Klepsch Matthias M. , Martínez‐Cabrera Hugo I. , McGlinn Daniel J. , Wheeler Elisabeth A. , Zheng Jingming , Ziemińska Kasia , Jansen Steven
Published: October 2017

Parenchyma represents a critically important living tissue in the sapwood of the secondary xylem of woody angiosperms. Considering various interactions between parenchyma and water transporting vessels, we hypothesize a structure–function relationship between both cell types. Through a generalized additive mixed model approach based on 2,332 woody angiosperm species derived from the literature, we explored the relationship between the proportion and spatial distribution of ray and axial parenchyma and vessel size, while controlling for maximum plant height and a range of climatic factors. When factoring in maximum plant height, we found that with increasing mean annual temperatures, mean vessel diameter showed a positive correlation with axial parenchyma proportion and arrangement, but not for ray parenchyma. Species with a high axial parenchyma tissue fraction tend to have wide vessels, with most of the parenchyma packed around vessels, whereas species with small diameter vessels show a reduced amount of axial parenchyma that is not directly connected to vessels. This finding provides evidence for independent functions of axial parenchyma and ray parenchyma in large vesselled species and further supports a strong role for axial parenchyma in long‐distance xylem water transport.
Seed bank dynamics in restored grassland following the sowing of high‐ and low‐diversity seed mixtures
Authors: Wagner Markus , Walker Kevin J. , Pywell Richard F.
Published: October 2017

Soil seed banks on ex‐arable land are dominated by undesirable ruderal species that compete with “desirable” target species during grassland restoration. At the same time, for continued regeneration, the latter often functionally depend on gap colonization from the seed bank, which serves as a buffer against local extinction. Nonetheless, few studies have so far investigated the effects of restoration practices on seed bank dynamics. Using a multisite experiment investigating techniques for restoring lowland mesotrophic grassland, we studied the effects of seedbed preparation (shallow cultivation using harrows or discs vs. deep cultivation using a plow) and of seed mixtures (species‐rich grass–forb mixes vs. species‐poor grass‐only mixes vs. unseeded natural regeneration) on 7 years of post‐restoration seed bank dynamics. We assessed how these practices affected density and diversity of sown and unsown species in the seed bank. Seed bank dynamics were much more strongly affected by seed sowing than by cultivation. Grass sowing resulted in stronger seed bank decline of unsown grasses, and additional forb sowing in stronger decline of unsown forbs. Higher seed densities and species richness of sown forbs colonizing from neighboring plots sown with the grass–forb mix were observed under natural regeneration than in the grass‐only sown treatment, reflecting grass priority effects on sown forb colonization in the latter. Sowing of diverse target species mixtures was associated with the greatest shift in seed bank composition away from extant ruderal species towards sown target species. Our results illustrate the usefulness of seed bank monitoring for assessing restoration progress.
Instability of Economic Systems: Signals, Asymmetric Reactions, Corrections
Authors: Cossiga Giovanni Antonio
Published: October 2017

An economic system becomes unstable when it’s deviating from the compatible growth course, because of human errors. Systems have a natural tendency to linear growth so that if they deviate, the growth and price profile takes a cyclical trend. The cyclical rhythm of the economy is not an end, but it’s a natural order trying to bring the economy back to its lost stability, over time. The unstable system, in promoting this return to stability, has a whole range of tools, including the spread of implicit perceptions about the economy state among companies and families: a sort of signal widespread by the sick economy. So, every common man is perceiving the country system malaise, nevertheless without having a direct knowledge of the problems and their causes. Starting from this implicit perception, the democratic process and the periodic use of polls are to be considered not only as the exercise of civic rights, but also as a test for the choice of a good government that would implement the program to balance again the unstable system. The collective wisdom of the people in selecting their own rulers, thus is moving in the context of the economy’s general tendency to the stability and to the compatibility with the natural environment.  Moreover, the asymmetric market reaction is also reported. The system reacts to a prolonged instability with speculative waves inexorably converging towards the financial crisis, to clean up the corrupt system. Finally, a mention to the Euro theme is also made.
Physics-Based Dynamic Models of Three SOFC/GT Emulator Test Rigs
Authors: Rossi Iacopo , Traverso Alberto , Hohloch Martina , Huber Andreas , Tucker David
Published: October 2017

This paper presents the development, implementation, and validation of a simplified dynamic modeling approach to describe solid oxide fuel cell gas turbine (SOFC/GT) hybrid systems (HSs) in three real emulator test rigs installed at University of Genoa (Italy), German Aerospace Center (DLR, Germany), and National Energy Technology Laboratory (NETL, USA), respectively. The proposed modeling approach is based on an experience-based simplification of the physical problem to reduce model computational efforts with minimal expense of accuracy. Traditional high fidelity dynamic modeling requires specialized skills and significant computational resources. This innovative approach, on the other hand, can be easily adapted to different plant configurations, predicting the most relevant dynamic phenomena with a reduced number of states: such a feature will allow, in the near future, the model deployment for monitoring purposes or advanced control scheme applications (e.g., model predictive control). The three target systems are briefly introduced and dynamic situations analyzed for model tuning, first, and validation, then. Relevance is given to peculiar transients where the model shows its reliability and its weakness. Assumptions introduced during model definition for the three different test rigs are discussed and compared. The model captured significant dynamic behavior in all analyzed systems (in particular those regarding the GT) and showed influence of signal noise on some of the SOFC computed outputs.
Interface Reduction in Craig–Bampton Component Mode Synthesis by Orthogonal Polynomial Series
Authors: Carassale Luigi , Maurici Mirko
Published: October 2017

The component mode synthesis (CMS) based on the Craig–Bampton (CB) method has two strong limitations that appear when the number of the interface degrees-of-freedom (DOFs) is large. First, the reduced-order model (ROM) obtained is overweighed by many unnecessary DOF. Second, the reduction step may become extremely time consuming. Several interface reduction (IR) techniques addressed successfully the former problem, while the latter remains open. In this paper, we tackle this latter problem through a simple IR technique based on an a-priory choice of the interface modes. An efficient representation of the interface displacement field is achieved adopting a set of orthogonal basis functions determined by the interface geometry. The proposed method is compared with other existing IR methods on a case study regarding a rotor blade of an axial compressor.
Anticipated Operational Occurrences That Could Develop into Serious
Accidents
Authors: Miranda Samuel
Published: October 2017

Nuclear safety analysis and licensing criteria are based upon the concept that plant situations that are expected to have a high frequency of occurrence must not pose a danger to the public, and that plant situations that could pose a danger to the public must be limited to situations that have a very low expected frequency of occurrence. This concept is implemented by grouping postulated plant situations (or events) into categories that are defined according to their expected frequencies of occurrence (i.e., high-frequency, low-consequence events, and low-frequency, high consequence events). In plant licensing basis analyses, events in each category must be shown to yield consequences that remain within the limits that are specified for that category. To protect the integrity of this categorization scheme, events must not be allowed to develop into the more serious events that belong in other, higher-consequence categories. In other words, nuclear plant designs must not allow high-frequency, low-consequence events to degrade into high-frequency, high-consequence events. The development of this system of frequency-based categorization is discussed, followed by an evaluation of various methods that could, and could not be used to demonstrate, for licensing purposes, that benign events are prevented from becoming serious accidents.
Trapped Cylindrical Flow With Multiple Inlets for Savonius Vertical Axis Wind Turbines
Authors: Alexander Aaron S. , Santhanakrishnan Arvind
Published: October 2017

Savonius vertical axis wind turbines (VAWTs) typically suffer from low efficiency due to detrimental drag production during one half of the rotational cycle. The present study examines a stator assembly created with the objective of trapping cylindrical flow for application in a Savonius VAWT. While stator assemblies have been studied in situ around Savonius rotors in the past, they have never been isolated from the rotor to determine the physics of the flow field, raising the likelihood that a moving rotor could cover up deficiencies attributable to the stator design. The flow field created by a stator assembly, sans rotor, is studied computationally using three-dimensional (3D) numerical simulations in the commercial computational fluid dynamics (CFD) package Star-CCM+. Examination of the velocity and pressure contours at the central stator plane shows that the maximum induced velocity exceeded the freestream velocity by 65%. However, flow is not sufficiently trapped in the stator assembly, with excess leakage occurring between the stator blades due to adverse pressure gradients and momentum loss from induced vorticity. A parametric study was conducted on the effect of the number of stator blades with simulations conducted with 6, 12, and 24 blades. Reducing the blade number resulted in a reduction in the cohesiveness of the internal swirling flow structure and increased the leakage of flow through the stator. Two unique energy loss mechanisms have been identified with both caused by adverse pressure gradients induced by the stator.
Free-Form Versus Ruled Inducer Design in a Transonic Centrifugal Impeller
Authors: Hazby Hamid , Robinson Chris , Casey Michael , Rusch Daniel , Hunziker Rene
Published: October 2017

The detailed design of the inducer of a high pressure ratio transonic radial compressor impeller with a design inlet tip relative Mach number of 1.4 is considered. Numerical analysis has been used to compare a datum impeller with ruled inducer design with a number of different free-form design concepts, generated following the same aerodynamic design philosophy. The datum stage and one with a free-form inducer, referred to as “barrelled forward swept,” with forward swept leading edge near the tip and increased chord at midspan, have been manufactured and tested. The tests were performed with the same stationary components, including the casing, vaned diffuser, and the volute. The design with a barrelled forward sweep of the inducer allows the designer more control of the strength and position of the passage shock at the inlet while meeting mechanical constraints. Interestingly, the performance is also enhanced at off-design points at lower tip-speeds. The measurements show that the stage tested with the swept impeller achieves higher efficiency of between 0.5% and 1.6% compared to the datum design, depending on the operating speed. The computational fluid dynamics (CFD) simulations are used to further study the flow at part speeds, in order to explain the causes of the observed performance differences at off design conditions.
Experimental Evaluation of Thermal and Mass Transfer Techniques to Measure Adiabatic Effectiveness With Various Coolant to Freestream Property Ratios
Authors: Wiese Connor J. , Rutledge James L. , Polanka Marc D.
Published: October 2017

Experimentally evaluating gas turbine cooling schemes is generally prohibitive at engine conditions. Thus, researchers conduct film cooling experiments near room temperature and attempt to scale the results to engine conditions. An increasingly popular method of evaluating adiabatic effectiveness employs pressure sensitive paint (PSP) and the heat–mass transfer analogy. The suitability of mass transfer methods as a substitute for thermal methods is of interest in the present work. Much scaling work has been dedicated to the influence of the coolant-to-freestream density ratio (DR), but other fluid properties also differ between experimental and engine conditions. Most notably in the context of an examination of the ability of PSP to serve as a proxy for thermal methods are the properties that directly influence thermal transport. That is, even with an adiabatic wall, there is still heat transfer between the freestream flow and the coolant plume, and the mass transfer analogy would not be expected to account for the specific heat or thermal conductivity distributions within the flow. Using various coolant gases (air, carbon dioxide, nitrogen, and argon) and comparing with thermal experiments, the efficacy of the PSP method as a direct substitute for thermal measurements was evaluated on a cylindrical leading edge model with compound coolant injection. The results thus allow examination of how the two methods respond to different property variations. Overall, the PSP technique was found to overpredict the adiabatic effectiveness when compared to the results obtained from infrared (IR) thermography, but still reveals valuable information regarding the coolant flow.
An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser
Authors: Galloway Lee , Spence Stephen , In Kim Sung , Rusch Daniel , Vogel Klemens , Hunziker René
Published: October 2017

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser (PTD). Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio (PR) compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilizing mechanism of the porous throat diffuser. The nonuniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure nonuniformity at various locations through the compressor stage and diffuser subcomponent analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser, and the stability limit is mainly governed by this element.
Large Amplitude Oscillatory Shear From Viscoelastic Model With Stress Relaxation
Authors: Garinei Alberto , Castellani Francesco , Astolfi Davide , Pucci Edvige , Scappaticci Lorenzo
Published: October 2017

The analytic response for the Cauchy extra stress in large amplitude oscillatory shear (LAOS) is computed from a constitutive model for isotropic incompressible materials, including viscoelastic contributions, and relaxation time. Three cases of frame invariant derivatives are considered: lower, upper, and Jaumann. In the first two cases, the shear stress at steady-state includes the first and third harmonics, and the difference of normal stresses includes the zeroth, second, and fourth harmonics. In the Jaumann case, the stress components are obtained in integral form and are approximated with a Fourier series. The behavior of the coefficients is studied parametrically, as a function of relaxation time and constitutive parameters. Further, the shear stress and the difference of normal stresses are studied as functions of shear strain and shear rate, and are visualized by means of the elastic and viscous Lissajous–Bowditch (LB) plots. Sample results in the Pipkin plane are reported, and the influence of the constitutive parameters in each case is discussed.
Discussion of “Measuring and Understanding Contact Area at the Nanoscale: A Review” (Jacobs, T. D. B., and Ashlie Martini, A., 2017, ASME Appl. Mech. Rev., 69(6), p. 060802)
Authors: Ciavarella M. , Papangelo A.
Published: October 2017

Jacobs and Martini (JM) give a nice review of direct measurement methods (in situ electron microscopy), as well as indirect methods (which are based on contact resistance, contact stiffness, lateral forces, and topography) for measurement of the contact area, mostly at nanoscale. They also discuss simulation techniques and theories from single-contact continuum mechanics, to multicontact continuum mechanics and atomistic accounting. As they recognize, even at very small scales, “multiple-contacts” case occurs, and a returning problem is that the “real contact area” is often an ill-defined, “magnification” dependent quantity. The problem remains to introduce a truncation to the fractal roughness process, what was called in the 1970s “functional filtering.” The truncation can be “atomic roughness” or can be due to adhesion, or could be the resolution of the measuring instrument. Obviously, this also means that the strength (hardness) at the nanoscale is ill-defined. Of course, it is perfectly reasonable to fix the magnification and observe the dependence of contact area, and strength, on any other variable (speed, temperature, time, etc.).
Free Convection in an Open Triangular Cavity Filled With a Nanofluid Under the Effects of Brownian Diffusion, Thermophoresis and Local Heater
Authors: Bondareva Nadezhda S. , Sheremet Mikhail A. , Oztop Hakan F. , Abu-Hamdeh Nidal
Published: October 2017

Natural convection of a water-based nanofluid in a partially open triangular cavity with a local heat source of constant temperature under the effect of Brownian diffusion and thermophoresis has been analyzed numerically. Governing equations formulated in dimensionless stream function and vorticity variables on the basis of two-phase nanofluid model with corresponding initial and boundary conditions have been solved by finite difference method. Detailed study of the effect of Rayleigh number, buoyancy-ratio parameter, and local heater location on fluid flow and heat transfer has been carried out. It has been revealed that an increase in the buoyancy force magnitude leads to homogenization of nanoparticles distribution inside the cavity. A growth of a distance between the heater and the cavity corner illustrates the heat transfer enhancement.
In-Plane Stiffness of Additively Manufactured Hierarchical Honeycomb Metamaterials With Defects
Authors: Rahman Kazi Moshiur , Hu Zhong , Letcher Todd
Published: October 2017

Cellular metamaterials are of interest for many current engineering applications. The incorporation of hierarchy to cellular metamaterials enhances the properties and introduces novel tailorable metamaterials. For many complex cellular metamaterials, the only realistic manufacturing process is additive manufacturing (AM). The use of AM to manufacture large structures may lead to several types of manufacturing defects, such as imperfect cell walls, irregular thickness, flawed joints, partially missing layers, and irregular elastic–plastic behavior due to toolpath. It is important to understand the effect of defects on the overall performance of the structures to determine if the manufacturing defect(s) are significant enough to abort and restart the manufacturing process or whether the material can still be used in its nonperfect state. In this study, the performance of hierarchical honeycomb metamaterials with defects has been investigated through simulations and experiments, and hierarchical honeycombs were shown to demonstrate more sensitivity to missing cell walls than regular honeycombs. On average, the axial elastic modulus decreased by 45% with 5.5% missing cell walls for regular honeycombs, 60% with 4% missing cell walls for first-order hierarchical honeycomb and 95% with 4% missing cell walls for second-order hierarchical honeycomb. The transverse elastic modulus decreased by about 45% with more than 5.5% missing cell walls for regular honeycomb, about 75% with 4% missing cell walls for first-order and more than 95% with 4% missing cell walls for second-order hierarchical honeycomb.
Design for Manufacturing of Variable Microgeometry Cutting Tools
Authors: Yussefian N. Z. , Hosseini A. , Hosseinkhani K. , Kishawy H. A.
Published: October 2017

Cutting edge microgeometry has gained special attention of late in the machining research community. Machine tool vibration, tool life, and workpiece surface integrity are all influenced by cutting edge size/shape. To optimize the machining process, variable microgeometry (VMG) cutting tools, in which the edge microgeometry varies along the edgeline with respect to specific variables (such as machining parameters or expected tool wear), are manufactured. Despite the advantages of VMG tools, a major hindrance in their development is the manufacturing complexity that demands high precision multi-axis edge preparation processes following extensive machine setup, fixturing, and programming. This paper details the proof of concept of a design criterion, which leads to the manufacturing of VMG cutting tools by only traditional edge preparation processes. The present method relies on the existing relationship between the edge radius subsequent to the edge preparation process and the tool wedge angle. The validity of the proposed method is first examined by a numerical simulation of the edge preparation. Carbide cutting tool inserts are then designed based on the proposed idea. Robust VMG generation subsequent to edge preparation by microblasting is demonstrated through microgeometric measurements. VMG chemical vapor deposition-coated carbide tools manufactured by the proposed approach are evaluated for turning hardened steel, and optimal designs are identified with respect to tool life and workpiece surface roughness. To address the design consideration, finite element (FE) modeling provides valuable insight into the machining process. FE modeled stress and temperature distribution clarify the experimental observations and reveal the design constraints.
Shape and Form Optimization of On-Line Pressure-Compensating Drip Emitters to Achieve Lower Activation Pressure
Authors: Shamshery Pulkit , Winter Amos G.
Published: October 2017

This study presents the design and validation of on-line pressure-compensating (PC) drip irrigation emitters with a substantially lower minimum compensating inlet pressure (MCIP) than commercially available products. A reduced MCIP, or activation pressure, results in a drip irrigation system that can operate at a reduced pumping pressure, has lower power and energy requirements, requires a lower initial capital cost, and facilitates solar-powered irrigation systems. The technology presented herein can help spread drip irrigation to remote regions and contribute to reducing poverty, particularly in developing countries. The activation pressures of drip emitters at three flow rates were minimized using a genetic algorithm (GA)-based optimization method coupled with a recently published fluid–structure interaction analytical model of on-line PC drip emitter performance. The optimization took into account manufacturing constraints and the need to economically retrofit existing machines to manufacture new emitters. Optimized PC drip emitter designs with flow rates of 3.3, 4.2, and 8.2 lph were validated using precision machined prototype emitters. The activation pressure for all was ≤0.2 bar, which is as low as 16.7% that of commercial products. A limited production run of injection molded 8.2 lph dripper prototypes demonstrated they could be made with conventional manufacturing techniques. These drippers had an activation pressure of 0.15 bar. A cost analysis showed that low MCIP drip emitters can reduce the cost of solar-powered drip irrigation systems by up to 40%.
Reliability Analysis of Nonlinear Vibratory Systems Under Non-Gaussian Loads
Authors: Geroulas Vasileios , Mourelatos Zissimos P. , Tsianika Vasiliki , Baseski Igor
Published: October 2017

A general methodology is presented for time-dependent reliability and random vibrations of nonlinear vibratory systems with random parameters excited by non-Gaussian loads. The approach is based on polynomial chaos expansion (PCE), Karhunen–Loeve (KL) expansion, and quasi Monte Carlo (QMC). The latter is used to estimate multidimensional integrals efficiently. The input random processes are first characterized using their first four moments (mean, standard deviation, skewness, and kurtosis coefficients) and a correlation structure in order to generate sample realizations (trajectories). Characterization means the development of a stochastic metamodel. The input random variables and processes are expressed in terms of independent standard normal variables in N dimensions. The N-dimensional input space is space filled with M points. The system differential equations of motion (EOM) are time integrated for each of the M points, and QMC estimates the four moments and correlation structure of the output efficiently. The proposed PCE–KL–QMC approach is then used to characterize the output process. Finally, classical MC simulation estimates the time-dependent probability of failure using the developed stochastic metamodel of the output process. The proposed methodology is demonstrated with a Duffing oscillator example under non-Gaussian load.
Effects of Surface Waviness on the Interaction of Oblique Shock Wave With Turbulent Boundary Layer
Authors: Hossain Joy Md. Saddam , Rahman Saeedur , Toufique Hasan A. B. M.
Published: October 2017

Present investigation deals with the interaction of an incident oblique shock wave on a turbulent boundary layer over a wavy surface. The oblique shock wave was generated by an 8 deg wedge in a freestream Mach number of 2.0. Three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations with k–ω shear stress transport (SST) turbulence model were used for numerical computation. The computed results are in good agreement with the experimental measurement and direct numerical simulation (DNS) data in case of the interaction of an oblique shock with plain flat plate. To identify the effect of surface waviness on shock wave/turbulent boundary layer interaction (SWBLI), a section of the flat plate was replaced by a wavy surface. Computations have been conducted for different magnitudes of wavy amplitude. Further, the wavelength of the wavy surface has been varied. Results showed that the presence of wavy surface induces supplementary shock and expansion waves in the flow field, which are referred as topographic waves. This supplementary system of waves interacts with the counterpart of intrinsic SWBLI in a complex manner. Flow structure, separation behavior, and aerodynamic characteristics are studied. It is revealed that the amplitude is dominant than the wavelength of waviness in case of SWBLI on a wavy surface.
Preliminary Design and Testing of a Cavo-Arterial Pump Utilizing Axial Magnetic Couplings
Authors: Valdovinos John , Chris Bouwmeester J. , Bonde Pramod
Published: October 2017

Right ventricular (RV) dysfunction has limited the effectiveness of mechanical circulatory support (MCS) therapy in some heart failure (HF) patients. Intravascular pumps can provide adequate circulatory support without the need for extensive operations. The development of an intravascular right ventricular assist device (RVAD), called the cavo-arterial pump (CAP), is presented. Two prototypes of the CAP were developed to demonstrate the feasibility of providing adequate pulmonary support and to demonstrate the feasibility of using axial magnetic couplings for contactless torque transmission from the motor shaft to the pump impeller. The CAP utilizing a direct drive mechanism produced a maximum pressure of 100 mm Hg and a maximum flow of 2.25 L/min when operated at 24 kRPM. When a magnetic drive mechanism was used, the overall flowrate decreased due to a loss in torque transmission. The magnetic drive CAP was able to operate up to 18.5 kRPM and produce a maximum flowrate of 1.35 L/min and a maximum pressure difference of 40 mm Hg. These results demonstrate that the CAP produces sufficient output for partial circulatory support of the pulmonary circulation, and that axial magnetic couplings can help to eliminate the sealing system needed to isolate the miniature motor and bearings from blood contact.
Design and Evaluation of a Mechanically Driven Artificial Speech Device
Authors: Tuttle Tyler G. , Erath Byron D.
Published: October 2017

This paper presents the design of a mechanically driven artificial speech device to be used by laryngectomees as an affordable alternative to an electrolarynx (EL). Design objectives were based on feedback from potential end users. The device implements a mainspring powered gear train that drives a striker. The striker impacts a suspended drum-like head, producing sound. When pressed against the neck, the head transmits sound into the oral cavity, allowing the user to produce intelligible speech. The dynamics of the vibrating head and sound pressure levels (SPLs) produced at the mouth were measured to compare performance between the device and a common, commercially available EL. The results showed comparable performance and sound output.
Research Works on Iodine and Ruthenium Behavior in Severe Accident Conditions
Authors: Cantrel Laurent , Albiol Thierry , Bosland Loïc , Colombani Juliette , Cousin Frédéric , Grégoire Anne-Cécile , Leroy Olivia , Morin Sandrine , Mun Christian , Ohnet Marie-Noëlle , Souvi Sidi , Monsanglant-Louvet Céline , Louis Florent , Azambre Bruno , Volkringer Christophe
Published: October 2017

This paper deals with near past, ongoing, and planned R&D works on fission products (FPs) behavior in reactor cooling system (RCS), containment building and in filtered containment venting systems (FCVS) for severe accident (SA) conditions. All the researches are collaborative works; the overall objective is to develop confident models to be implemented in simulation software. After being initiated in 2004, researches on iodine transport through the RCS are still ongoing and for containment, the last advances are linked to the source term (ST) evaluation and mitigation (STEM) OECD/NEA project. The objective is to improve the evaluation of ST for a SA on a nuclear power plant and to reduce uncertainties on specific phenomena dealing with the chemistry of two major FPs: iodine and ruthenium. For ruthenium attention has been paid to study the amount and nature (gas/aerosol partition) of ruthenium species along the RCS. A follow-up, called STEM2, has started to reduce some remaining issues and be closer to reactor conditions. For FCVS works, the efficiencies for trapping iodine covering scrubbers and dry filters are examined to get a clear view of their abilities in SA conditions. Another part is focused on specific porous materials able to trap volatile iodine. Influence of zeolite materials parameters (nature of the counter-ions, structure, Si/Al ratio…) are tested as well as new kind of porous materials constituted by Metal organic Frameworks will also be looked at.
Modeling and Measuring Residual Stress in Autofrettaged Hollow Cylinders Through the Initial Strain Distribution Method
Authors: Loffredo Matteo , Bagattini Andrea , Monelli Bernardo D. , Beghini Marco
Published: October 2017

The paper presents a method for modeling and measuring the residual stress (RS) field in axisymmetric autofrettaged elements. The method is based on the assumption that an Initial Strain Distribution (ISD), originated by the plastic strain previously induced during the autofrettage process, is the source of RSs. The ISD is the quantity to be evaluated and, after being determined, it can be used, by means of a dedicated finite element (FE) model, to evaluate the RS field in the component or in any part extracted from it. The ISD is obtained by elaborating the relaxed strains produced by cutting the autofrettaged component in incremental steps. The elaboration is based on solving a set of Fredholm's integral equations in which the unknown function is the ISD and the kernel is an Influence Function (IF) correlating the measured relaxed strain to the ISD. After a general discussion of the RS induced by the autofrettage and the effect of the plastic properties of the material under process, the methods for obtaining the relaxed strains by a rational experimental setup and the procedures for obtaining the IFs are presented and discussed. The whole methodology is applied to evaluate the RS field in a hollow cylinder for which the autofrettage was modeled by a FE simulation. The consistency of the method is verified and useful indications for the experimental activities were obtained.
Air Cooling Concepts for Li-Ion Battery Pack in Cell Level
Authors: Chen Kuo-Huey , Han Taeyoung , Khalighi Bahram , Klaus Philip
Published: October 2017

Computational Fluid Dynamics (CFD) modeling is used to study different cooling architectures for the next generation (Gen-2) EREV Li-Ion battery package. There might be advantages of air cooled batteries with respect to complexity, cost and reliability compared to liquid cooled systems like the EREV (Extended Range Electric Vehicle) GEN1 battery. Therefore, the feasibility of air cooling architectures is investigated first and later liquid cooling strategies. In this study, the thermal performance and pressure drop of the cell level for two of the core product designs are reported. The parameters considered in this study include two different heat generations (heat sources) by the battery pack and three cooling flow rates. The heat generations used are 500 W and 1500 W representing the normal driving and peak load conditions, respectively. The cooling flow rates are 100, 200 and 600 m3/h. The battery cell temperatures, both in terms of absolute value and the variation within the cell, and the pressure drop which is related to the required pumping power, are evaluated and presented.
Numerical Evaluation of Clearance Requirements Around Obstructions in Finned Heat Sinks
Authors: Miner Steven
Published: October 2017

This study uses CFD to consider the effects of obstructions (bosses) on the fluid flow and heat transfer in finned heat sinks used for cooling electronic components. In particular, the effect of bosses, used for mounting components, on the fluid flow distribution and temperature distribution in the heat sink are evaluated. A typical heat sink has fins sandwiched between top and bottom plates, with electronic components mounted on the plates. The top and bottom plates spread the heat generated in the components to reduce the local heat flux. The fins substantially increase the heat transfer area, reducing the temperature rise from the coolant to the top and bottom plates. In this case a uniform distribution of flow across the heat sink can be achieved and there will be no localized hot spots. Ideally there are no protrusions into the finned portion of the heat sink which would cause disruptions in the uniform flow through the heat sink. However, a boss may be needed to bolt a component to the heat sink. The presence of the boss has three effects on the heat sink performance. The boss disrupts the flow in its immediate vicinity, increasing the thermal resistance. This will cause an increase in operating temperature at that location. In addition, the boss will change the flow distribution in the heat sink. Locations upstream and downstream of the boss may see reduced flow due to the obstruction, which in turn will cause an increase in operating temperature for these areas of the heat sink. Finally, the change in flow distribution may increase the pressure drop through the entire heat sink, increasing the power required to operate the system. The purpose of this study is to numerically evaluate the clearance requirements around circular bosses. Comparisons between an unobstructed heat sink and a heat sink with an obstruction are made for the maximum component temperature rise, the pressure drop and the flow distribution. Clearance ratios, diameter of the fin cut out to boss diameter, were varied from 1.1 to 3.3. The Reynolds number for the flow was varied from roughly 3000 to 70,000 based on the hydraulic diameter of flow passage.
Air-Side Heat Transfer Enhancement and Pumping Power Penalty in Air-Cooled Heat Exchangers With Dimpled Fins
Authors: Vu Tung X. , Mohanta Lokanath , Dhir Vijay K.
Published: October 2017

In this work, we focus exclusively on heat transfer enhancement techniques for the air-side heat transfer in air-cooled heat exchangers/condensers. An innovative dimpled fin configuration is explored. Experiments, in which both heat transfer and drag are measured, are conducted with flat tubes in three configurations: without fins, with plain fins and with dimpled fins. Reynolds numbers based on the hydraulic diameter of the finned passages are varied between 600 and 7000. Results indicate that fins are more advantageous at lower Reynolds numbers since the increase in drag at higher Reynolds numbers quickly erases any advantage due to an increase in heat transfer rate. As an example, for the plain fins versus a bare tube at a Reynolds number of 600, there is a 7 fold increase in heat transfer with only a 5 fold increase in drag. However, at a Reynolds number of 7000, both heat transfer and drag increase by approximately 6 times, indicating that the increase in drag has caught up with the heat transfer enhancement. Similarly, while dimpled fins do result in higher heat transfer compared with the plain fins, the advantage is also more prominent at lower Reynolds numbers where heat transfer enhancement is higher than the associated increase in pumping power.
Simultaneous Measurements of Unsteady Thermal and Flow Fluctuations Using High-Speed Infrared Thermography and PIV Over a Backward Facing Step
Authors: Yamada Shunsuke , Nakamura Hajime
Published: October 2017

In order to investigate the flow and heat transfer fluctuations in the near-wall region downstream a backward facing step, a Time-resolved Stereoscopic Particle Image Velocimetry (TS-PIV) and a high-speed infrared thermography (IRT) combined system was constructed. Using this measurement system, the time series of the velocity in the vicinity of the heated wall and the heat transfer on the heated wall were measured at Reynolds number, which is based on the step height and inlet mainstream velocity, of 2.5 × 103. It confirmed the validity of the velocity fluctuation obtained by using TS-PIV. The results showed that the forward and downwash flows correspond to the enhancement of the heat transfer in the near-wall region. Also, the vortex structure in the yz plane was detected by Qyz-criterion, and the locational relationship between the vortex structure and the heat transfer enhancement was investigated.
Computational Study of Enhanced Convection and Effects of Geometrical Features in Offset Strip Fin Cores
Authors: Bhave Chittatosh C. , Manglik Raj M. , Jog Milind
Published: October 2017

Offset strip fin channels promote higher heat transfer rate than plain fins due to the periodic disruption of boundary layers in the offset channels and downstream flow mixing. The enhanced convection heat transfer in laminar air flows (50 < Re < 2000; Pr = 0.7) is computationally investigated. By considering the fin height h to be much larger than the inter-fin spacing s (or s/h <<1) which is representative of many practical applications, a two-dimensional flow channel is modeled. With thin fins (t/s) < 20%, the effect of fin offset length l (1 ≤ l/s ≤ 35) on the convective enhancement is explored. Higher heat transfer coefficients are found to be obtained with shorter fin lengths and higher flow Reynolds number Re. This effect, however, diminishes for low Re and very large fin offset length and performance asymptotically approaches that of plain rectangular fin channels. The frictional loss also increases correspondingly, and is primarily due to flow acceleration and boundary-layer disruption. This penalty is offset by a 2.5–3 times higher heat transfer rate capacity for fixed pressure drop condition relative to plain fins. For a fixed heat transfer rate application, offset-strip fins are shown to yield 40%–50% smaller surface area cores.