bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Analysis of the Effects of Liquid Carryover on the Performance of a Two-Stage Centrifugal Compressor
Authors: Halbe Chaitanya V. , O’Brien Walter F. , Cousins William T. , Sishtla Vishnu
Published: August 2018

To extend the current understanding of the effects of liquid carryover on compressor performance, a detailed analysis including the aerothermodynamics of the compression process and the flow field within the compressor is required. This paper presents a CFD analysis of a two-stage, in-line centrifugal compressor, operating in a two-phase flow environment of a single constituent, refrigerant R134a. The computational method implemented in this analysis accounts for the real gas behavior, and also incorporates the effects of interphase heat, mass and momentum transfer, as well as the droplet dynamics. The investigations revealed that liquid carryover altered the flow field within the compressor, causing both stages to operate at off-design conditions. This effect was observed to be more pronounced for the second stage. The overall effects of liquid carryover were shown to be detrimental to the compressor performance. Increasing the amount of liquid carryover resulted in further lowering of the performance. On the other hand, the effects of the size of the ingested droplets were seen to be negligible.
Aerodynamic Optimization of Axial Fans Using the Adjoint Method
Authors: Bamberger Konrad , Carolus Thomas
Published: August 2018

This paper discusses the aerodynamic optimization of low-pressure axial fans using adjoint Computational Fluid Dynamics (CFD).

In the first part, a typical CFD-based fan optimization problem is introduced. The focus is on the CFD model and potential objective functions.

The adjoint system of equations and the adjoint boundary conditions for this optimization problem are derived in the second part. Moreover, the software implementation in the open source CFD code OpenFOAM v3.0.x is described. The existing OpenFOAM solver “adjointShapeOptimizationFoam” serves as the basis and is customized to the optimization of fans. The code solves both the primal and the adjoint incompressible Reynolds-averaged Navier-Stokes (RANS) equations from which a sensitivity map of the objective function with respect to the grid topology can be derived. The main extension of the existing code deals with the consideration of a rotating frame of reference leading to additional source terms in both the primal and the adjoint RANS equations. Moreover, the implementation of new boundary conditions is performed to handle the distinct objective functions.

In the third part, the customized adjoint solver is applied to improve an existing baseline fan. Two adjoint simulations of the baseline fan are performed aiming at maximization of pressure and efficiency, respectively. The resulting surface sensitivities on the blade are used to modify the blade shape accordingly. Eventually, the performance of the two optimized fans is predicted by RANS to quantify the improvements. The first fan features a pressure rise which is 3.6 % higher as compared to the baseline fan. The second fan features an efficiency improvement of 0.1 percentage points as compared to the baseline fan. Hence, the functionality of the adjoint method is proven. A more substantial improvement would require further optimization loops with repeated adjoint simulations that, however, are not part of this paper.
On Predictions of Fuel Effects on Lean Blow Off Limits in a Realistic Gas Turbine Combustor Using Finite Rate Chemistry
Authors: Piehl Joshua , Bravo Luis , Acosta Waldo , Kumar Gaurav , Drennan Scott , Samimi-Abianeh Omid
Published: August 2018

The demand for aviation propulsion systems with ever higher power requirements, reliability, and reduced emissions has been steadily increasing. Desirable features for next generation high-efficiency gas turbine engines include improvements in combustion efficiency, fuel economy, and stable operation in the fuel lean limit. Despite recent advances, a significant issue facing gas turbine designers is sustaining flame stability during lean operation, which could otherwise lead to global extinction events, or lean blow out (LBO), resulting in a severe loss of operability, particularly at higher altitudes. Flame stabilization is a complex physical and chemical process which is determined by the competing effects of the rates of chemical reactions and rate of turbulence advection-diffusion of species and energy to and from the flame leading to a local ignition and extinction phenomena. The goal of the present study is to perform a high fidelity numerical investigation of the turbulent diffusion flame in a realistic turbine combustor to evaluate the potential to predict the local lean-blow-off dynamics and to gain more insights of the complex physics. A comparative study on LBO characteristics is performed using Finite Rate Chemistry, Large Eddy Simulation and Adaptive Mesh Refinement, for different fuels using a realistic gas turbine combustor. The fuels investigated include a petroleum based fuel and an alternative fuel candidate. The simulation was broken down in two phases: flame stabilization and a subsequent staged ramp-down of fuel flow rate to initiate LBO. It is shown that the simulations successfully predict LBO occurring at different equivalence ratios for the two fuels. Although, the simulations predict LBO occurring at slightly smaller equivalence (fuel-to-air) ratio than the experimental data, the difference between the equivalence ratios of the two fuels at LBO is very close to the experimental observation.
Teaching Gas Turbine Technology to Undergraduate Students in Sweden
Authors: Aslanidou Ioanna , Zaccaria Valentina , Pontika Evangelia , Zimmerman Nathan , Kalfas Anestis I. , Kyprianidis Konstantinos G.
Published: August 2018

This paper addresses the teaching of gas turbine technology in a third-year undergraduate course in Sweden and the challenges encountered. The improvements noted in the reaction of the students and the achievement of the learning outcomes is discussed. The course, aimed at students with a broad academic education on energy, is focused on gas turbines, covering topics from cycle studies and performance calculations to detailed design of turbomachinery components. It also includes economic aspects during the operation of heat and power generation systems and addresses combined cycles as well as hybrid energy systems with fuel cells.

The course structure comprises lectures from academics and industrial experts, study visits, and a comprehensive assignment. With the inclusion of all of these aspects in the course, the students find it rewarding despite the significant challenges encountered. An important contribution to the education of the students is giving them the chance, stimulation, and support to complete an assignment on gas turbine design. Particular attention is given on striking a balance between helping them find the solution to the design problem and encouraging them to think on their own.

Feedback received from the students highlighted some of the challenges and has given directions for improvements in the structure of the course, particularly with regards to the course assignment. This year, an application developed for a mobile phone in the Aristotle University of Thessaloniki for the calculation of engine performance will be introduced in the course. The app will have a supporting role during discussions and presentations in the classroom and help the students better understand gas turbine operation. This is also expected to reduce the workload of the students for the assignment and spike their interest.
Additive Manufacturing of Honeycombs Seal Strips
Authors: Geisen Ole , Kersting Lisa , Masseling Lukas , Bogner Jan Pascal , Schleifenbaum Johannes Henrich
Published: August 2018

Laser-Powder Bed Fusion (L-PBF) is an additive manufacturing technique used to melt metal material into solid three-dimensional parts. While offering a high degree of design freedom, L-PBF still has technical restrictions, like the achievable surface roughness, resolution and the need for support structures in overhanging areas. [1]

Currently, L-PBF is used mainly to produce small batches of parts and prototypes. [2] In order to fully industrialize the technology, the research campus in Aachen is investigating possible future applications in turbomachinery while developing the corresponding processes with industry partners.

Sealing systems, like honeycomb seal strips in gas turbines often require time-consuming joining and assembly operations that can be avoided by building up the structure monolithically using L-PBF.

The following process development study proves the feasibility of manufacturing honeycombs with L-PBF using the Nickel-based super-alloy Inconel 718 (IN718) on an EOS M290 machine. Here, we have evaluated the economic aspects of different build orientations of the seal strips. Afterwards, we conducted a systematic parameter study with continuous and pulsed wave laser emission and investigated the resulting wall thicknesses. A reduction in wall thickness of about 30% can be observed when a modulated laser is used.
A Novel Reheat Combustor Experiment for the Analysis of High-Frequency Flame Dynamics: Concept and Experimental Validation
Authors: Berger Frederik M. , Hummel Tobias , Romero Vega Pedro , Schuermans Bruno , Sattelmayer Thomas
Published: August 2018

This paper presents a novel sequential combustor experiment for the study of reheat flame responses to high-frequency, transversal thermoacoustic oscillations. The reheat combustion chamber is of flat, quasi two-dimensional design to distinctly separate combustion areas dominated by auto-ignition and aerodynamic flame stabilization. This specific combustor setup furthermore promotes the occurrence of pressure pulsations at the first transverse resonance frequency, often referred to as screech. For investigation of combustion and acoustic properties, the reheat stage is equipped with pulsation probes at the face plate, and the entire combustion zone is optically accessible from all lateral sides to allow for (laser-) optical flame and flow diagnostics. In order to validate the qualification of the experimental setup for investigations of high-frequency flame dynamics, the reheat combustion regime and resulting transverse pressure dynamics are investigated. The desired flame shape with distinct auto-ignition and aerodynamic flame stabilization zones is achieved and can be sensibly controlled. Analyzing the frequency spectrum of the dynamic pressure measurements at the combustor face plate reveals the first transverse resonance at approximately 1600 Hz, which satisfies a key goal of the specific design. Overall, the setup qualifies for studying flame-acoustics interaction in reheat combustors and provides an experimental benchmark for modeling efforts and their validation. This will eventually contribute to design countermeasures to thermoacoustic pulsations for improved future generations of gas turbine combustors.
Implicit-LES Simulation of Variable-Speed Power Turbine Cascade for Low Free-Stream Turbulence Conditions
Authors: Ameri Ali
Published: August 2018

It is a challenge to simulate the flow in a Variable Speed Power Turbine (VSPT), or, for that matter, rear stages of low pressure turbines at low Reynolds numbers due to laminar flow separation or laminar/turbulent flow transition on the blades. At low Reynolds numbers, separation induced-transition is more prevalent which can result in efficiency lapse. LES has been used in recent years to simulate these types of flows with a good degree of success. In the present work, very low free stream turbulence flows at exit Reynolds number of 220k were simulated. The geometry was a cascade which was constructed with the midspan section of a VSPT design. Most LES simulations to date, have focused on the midspan region. As the endwall effect was significant in these simulations due to thick incoming boundary layer, full blade span computation was necessitated. Inlet flow angles representative of take-off and cruise conditions, dictated by the rotor speed in an actual design, were analyzed. This was done using a second order finite volume code and a high resolution grid. As is the case with Implicit-LES methods, no sub-grid scale model was used. Blade static pressure data, at various span locations, and downstream probe survey measurements of total pressure loss coefficient were used to verify the results. The comparisons showed good agreement between the simulations and the experimental data.
Multiphase CFD Modeling of External Oil Flow From a Journal Bearing
Authors: Berthold Martin , Morvan Hervé , Jefferson-Loveday Richard , Rothwell Benjamin C. , Young Colin
Published: August 2018

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly in a planetary configuration the kinematic conditions are complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing.

Computational Fluid Dynamics (CFD) simulations using the Volume of Fluid (VoF) method are carried out in ANSYS Fluent [1] to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing.

This paper presents an investigation of two numerical schemes that are available in ANSYS Fluent to track or capture the air-oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. Based on these simplifications, a three dimensional (3D) CFD sector model with rotationally periodic boundaries is considered.

A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regards to the accuracy of the phase interface reconstruction and the time required to reach steady state flow field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used.

With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.
A Thermoelastohydrodynamic Analysis for the Static Performance of High-Speed Heavy Load Tilting-Pad Journal Bearing Operating in the Turbulent Flow Regime and Comparisons to Test Data
Authors: Arihara Hirotoshi , Kameyama Yuki , Baba Yoshitaka , San Andrés Luis
Published: August 2018

Tilting-pad journal bearings (TPJBs) ensure rotordynamic stability that could otherwise produce dangerously large amplitude rotor oil-whirl/whip motions in high speed rotating machinery. Currently, highly efficient turbo compressors demand an ever increasing rotor surface speed and specific load on its support bearings. The accurate prediction of bearing performance is vital to guarantee reliable products, specifically with regard to reducing maximum bearing pad temperature and drag power losses, and operating with the least flow rate while still maximizing load capacity. The hydrodynamic pressure and heat generation in an oil film acting on a bearing pad produce significant mechanical and thermal deformations that change the oil film geometry (clearance and preload) to largely affect the bearing performance, static and dynamic. In addition, a high surface speed bearing often operates in the turbulent flow regime that produces a notable increase in power loss and a drop in maximum pad temperature. This paper details a thermoelastohydrodynamic (TEHD) analysis model applied to TPJBs, presents predictions for their steady-load performance, and discusses comparisons with experimental results to validate the model. The test bearing has four pads with a load between pads configuration; its length L = 76.2 mm and shaft diameter D = 101.6 mm (L/D = 0.75). The rotor top speed is 22.6 krpm, i.e. 120 m/s surface speed, and the maximum specific load is 2.94 MPa for an applied load of 23 kN. The test procedure records shaft speed and applied load, oil supply pressure/temperature and flow rate, and also measures the pads’ temperature and shaft temperature, as well as the discharge oil (sump) temperature. The TEHD model couples a generalized Reynolds equation for the hydrodynamic pressure generation with a three-dimensional energy transport equation for the film temperature. The pad mechanical deformation due to pressure utilizes the finite elemental method, whereas an analytical model estimates thermally induced pad crowning deformations. For operation beyond the laminar flow regime, the analysis incorporates the eddy viscosity concept for fully developed turbulent flow operation. Current predictions demonstrate the influence of pressure and temperature fields on the pads mechanical and thermally induced deformation fields, and also show static performance characteristics such as bearing power loss, flow rate, and pad temperatures. The comparisons of test results and analysis results reveal that turbulent flow effects significantly reduce the pads’ maximum temperature while increasing the bearing power loss. Turbulent flow mixing increases the diffusion of thermal energy and makes more uniform the temperature profile across the film.
An Improved Particle Impact Model by Accounting for Rate of Strain and Stochastic Rebound
Authors: Whitaker Steven M. , Bons Jeffrey P.
Published: August 2018

A methodology for informing physics-based impact and deposition models through the use of novel experimental and analysis techniques is presented. Coefficient of Restitution (CoR) data were obtained for Arizona Road Dust (ARD), AFRL02 dust, and each component of AFRL02 impacting a Hastelloy X plate at a variety of flow temperatures (295–866 K), surface temperatures (295–1255 K), particle velocities (0–100 m/s), and impact angles (0–90 degrees). High speed Particle Shadow Velocimetry (PSV) allowed individual impact data to be obtained for more than 8 million particles overall, corresponding to 20 combinations of particle composition, flow temperature, and surface temperature. The experimental data were applied to an existing physics-based particle impact model to assess its ability to accurately capture the physics of particle impact dynamics. Using the experimental data and model predictions, two improvements to the model were proposed. The first defined a velocity-dependent effective yield strength, designed to account for the effects of strain hardening and strain rate during impact. The second introduces statistical spread to the model output, accounting for the effect of randomizing variables such as particle shape and rotation. Both improvements were demonstrated to improve the model predictions significantly. Applying the improved model to the experimental data sets, along with known temperature-dependent material properties such as the elastic modulus and particle density, allowed the temperature dependence of the effective yield strength to be determined. It was found that the effective yield strength is not a function of temperature over the range studied, suggesting that changes in other properties are responsible for differences in rebound behavior. The improved model was incorporated into a computational simulation of an impinging flow to assess the effect of the model improvements on deposition predictions, with the improved model obtaining deposition trends that more closely match what has been observed in previous experiments. The work performed serves as a stepping stone towards further improvement of physics-based impact and deposition models through refinement of other modeled physical processes.
Meander-Like Shape Optimization of the Stator-Rotor Platform Cavity
Authors: Juangphanich Paht , Paniagua Guillermo
Published: August 2018

Recent progress in additive manufacturing has enabled opportunities to explore novel stator rim geometries which can be implemented to improve cooling strategies in turbomachinery. This paper presents a simplified stationary geometry optimization strategy to produce enhanced stator-rotor cavity sealing and highlights main driving mechanisms.

The stator and rotor rims were designed using a design strategy based on inspiration from the meandering of rivers. A minimum thickness of 2mm was maintained throughout the cavity to ensure a practical implementation. The computational domain comprised of the stator outlet, hub disk leakage cavity, and rotor platform was meshed using NUMECA Int. package, Hexpress. The numerical analysis required 3D Unsteady Reynolds Average Navier-Stokes to replicate vorticial structures using Ansys Fluent. The operating conditions were representative of engine-like conditions, exploring a wide range of massflow ratios from 1 to 3%. The optimization yielded designs that provide 30% reduction in rear platform temperature while minimizing coolant massflow. The applicability of the design was compared against 3D sector in both stationary and in rotation.
Computational Aid to AEDsys for Designing a Variable-Area Gas Turbine Nozzle
Authors: O’Dowd Devin O. , Byerley Aaron R.
Published: August 2018

This paper presents a practical approach to designing a gas turbine nozzle with the help of the Aircraft Engine Design textbook as well as the software program Nozzle, a subprogram within the Aircraft Engine Design System Analysis Software suite AEDsys. The current textbook and software allow for a variable wetted length of the converging and diverging nozzle sections. Critical feedback from industry experts has inspired an attempt to design a nozzle with fixed wetted material lengths. This paper is written to augment classroom treatment, but will also support others who use the Aircraft Engine Design text and software for a preliminary engine design capstone. This approach is further guided by the actual scaling of the Pratt & Whitney F100 variable geometry converging-diverging nozzle, where wetted lengths are fixed. The chief goal is to equip students at the United States Air Force Academy with a refined approach that is more realistic of a manufactured nozzle design, producing a graphical representation of a nozzle schedule at different speed and altitude flight conditions, both with and without afterburner.
Experimental Results on a Gaseous Jet Into a Turbulent Air Crossflow: Effect of the Shape of Injector Inlet on Fuel/Air Mixing
Authors: Song Jinkwan , Lee Jong Guen
Published: August 2018

This paper presents experimental results on a gaseous jet into an air crossflow. A plain-orifice type injectors are employed for this research. It is mounted flush with a bottom wall of a test rig with a rectangular cross-section. The main emphasis is to investigate the effect of aspect ratio of the injector on fuel/air mixing. Injector diameter is fixed at 1.59 mm and two injectors with the orifice aspect ratio (1/d) of 1 and 5 are chosen for the purpose. Velocity ratios of a fuel jet to an air crossflow, Vj/Va, are chosen as 3, 5 and 7, and the mean crossflow velocity ranges 2 to 40 m/sec, which results in a wide range of Reynolds numbers for the gaseous jet encompassing laminar to turbulent flow. Acetone planar laser-induced fluorescence measurement is used for the representation of fuel concentration. The decay rate of scalar concentration, fuel jet penetration and cross-sectional distributions of the fuel plume are determined for the two injectors. First, the effect of the aspect ratio of the injector in quiescent surroundings is considerable at low jet velocities, i.e. laminar jet flow, but not at jet velocities corresponding to turbulent jet flow. Second, the influence of the aspect ratio of the injector in the air crossflow is similar to that observed in the free jet. At the laminar jet condition, the difference in the turbulent intensity produced by the aspect ratio of the injector changes the jet core characteristics of each injector and causes a difference in jet penetration. However, in the turbulent jet flow, it is found that the effect of the aspect ratio on the jet penetration is insignificant. Third, for the concentration decay, the concentration decreases with the slope of −7/9 in the laminar jet flow and the concentration decreases with the slope of −5/9 in the turbulent jet flow.
Unsteady Turbomachinery Simulations Using Harmonic Balance on a Discontinuous Galerkin Discretization
Authors: Sharma Mayank , Wukie Nathan A. , Ugolotti Matteo , Turner Mark G.
Published: August 2018

The Harmonic Balance method is well suited for analyzing unsteadiness in turbomachinery flows comprised of a few dominant frequencies. A harmonic condition is imposed on the temporal derivatives through a Fourier transform operation. The solution is then reinterpreted as a time-domain problem, where several instances of time (lying within the largest period) are solved for simultaneously with the enforcement of the time-harmonic condition providing coupling between time instances. A discontinuous Galerkin discretization is used together with overset grids to provide higher-order spatial accuracy and flexibility in representing complex geometry. In this work, the discontinuous Galerkin infrastructure is extended for unsteady problems with a Harmonic Balance method and a Diagonally Implicit Runge-Kutta time-integrator. Verification results are presented for both time integration approaches in addition to results for a turbine blade with unsteadiness driven by a prescribed unsteady inlet boundary condition. Comparisons of results from the Harmonic Balance and Diagonally Implicit Runge-Kutta approaches are very close, with some small discrepancies that require further investigation. Significantly, rapid convergence from the Newton solver is obtained for the Harmonic Balance approach applied to the Euler equations for the turbine blade problem. Solutions converged by 8–10 orders of magnitude are obtained in between 5 and 16 Newton steps.
Investigation of the Down-Scaling Effects on the Low Swirl Burner and its Application to Microturbines
Authors: Frank Alex , Therkelsen Peter , Sierra Aznar Miguel , Rapp Vi H. , Cheng Robert K. , Chen Jyh-Yuan
Published: August 2018

About 75% of the electric power generated by centralized power plants feeds the energy needs from the residential and commercial sectors. These power plants waste about 67% of primary energy as heat emitting 2 billion tons of CO2 per year in the process (∼ 38% of total US CO2 generated per year) [1]. A study conducted by the United States Department of Energy indicated that developing small-scale combined heat and power systems to serve the commercial and residential sectors could have a significant impact on both energy savings and CO2 emissions. However, systems of this scale historically suffer from low efficiencies for a variety of reasons. From a combustion perspective, at these small scales, few systems can achieve the balance between low emissions and high efficiencies due in part to the increasing sensitivity of the system to hydrodynamic and heat transfer effects. Addressing the hydrodynamic impact, the effects of downscaling on the flowfield evolution were studied on the low swirl burner (LSB) to understand if it could be adapted to systems at smaller scales. Utilizing particle image velocimetry (PIV), three different swirlers were studied ranging from 12 mm to 25.4 mm representing an output range of less than 1 kW to over 23 kW. Results have shown that the small-scale burners tested exhibited similar flowfield characteristics to their larger-scale counterparts in the non-reacting cases studied. Utilizing this data, as a proof of concept, a 14 mm diameter LSB with an output of 3.33 kW was developed for use in microturbine operating on a recuperated Brayton cycle. Emissions results from this burner proved the feasibility of the system at sufficiently lean mixtures. Furthermore, integration of the newly developed LSB into a can style combustor for a microturbine application was successfully completed and comfortably meet the stringent emissions targets. While the analysis of the non-reacting cases was successful, the reacting cases were less conclusive and further investigation is required to gain an understanding of the flowfield evolution which is the subject of future work.
Three-Dimensional Aerodynamic Optimization of Turbine Blade Profile Considering Heat Transfer Performance
Authors: Wei Liu , Feng-bo Wen , Lei Luo , Tao Cui , Song-tao Wang
Published: August 2018

This paper presents an optimization platform for an internal-cooled gas turbine blade, using a developed simplified three-dimensional Conjugate Heat Transfer analysis method. This paper manages to improve the aerodynamic efficiency while ensuring the heat transfer performance. The simplified 3D CHT method is based on a one dimensional program for internal pipe network calculation and ANSYS CFX code. It’s for flow field prediction outside the blade and the solid region computation. Numerical verification is performed for the procedure. The platform is validated and used in aerodynamic optimization design for a turbine rotor in this study. The constraints for this optimization design is that the average and maximum temperature on the blade surface should meet the design requirement. The optimization results show that the variation in the average and maximum temperature is no more than 2K compared with the prototype. The aerodynamic efficiency is increased by 0.34%, and it the coolant mass is reduced by 7.66%.
NASA Transformational Tools and Technologies Project: 2700°F CMC/EBC Technology Challenge
Authors: Hurst Janet
Published: August 2018

Advanced gas turbine engine designs continue to push into regimes of higher operating temperatures and increased pressures. Materials capable of functioning under these extreme conditions have been sought by both government and industry. As part of its mission, the NASA Transformational Tools and Technologies (TTT) Project, under the auspices of NASA’s Aeronautics Research Mission Directorate (ARMD), has been pursuing high temperature materials development with the performance goal of 2700°F (1482°C) operation. This goal has evolved into a focused three year Technology Challenge which is nearing its conclusion. This challenge problem has sought to develop high temperature materials for turbine engines which will enable a 6% reduction in fuel burn for commercial aircraft as compared to the current generation. This ambitious effort has included ceramic matrix composite (CMC) compositions, architectures and processing as well as environmental barrier coating compositions (EBC) and processing routes. It has included collaborators and materials suppliers from both industry and academia. The development and validation of thermomechanical models and computational tools for design, analysis, and life prediction have been an important part of this effort. Evaluation of CMC/EBCs included various aspects of thermomechanical testing from coupon testing for strength and creep resistance, to materials evaluation under conditions similar to aspects of engine operation. Simulated engine testing of airfoil subcomponents in a P&W test rig is the final evaluation step following years of materials development. As this three year Technical Challenge concludes, plans are under development for continued environmental durability investigation of CMC/EBC systems accompanied by validated durability modeling.
Clinical elastography
Authors: Sporea Ioan
Published: August 2018

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Dermatophagoides farinae allergen encapsule for oral immunotherapy with HDM allergic rhinitis
Authors: Zhang Han-zhong , Xie Wei , Wang Ying , Chen Jian , Wen Ting-huan
Published: August 2018

It is well known that the house dust mites (HDMs) are the most common and potent inhalant allergens world-wide and the allergen immunotherapy (AIT) can efficaciously and safely ameliorate the allergic symptoms. Different formulations and routes of HDMs AIT have been achieved symptomatic improvement with mite allergic rhinitis (AR) and/or asthma. The object of the present article is to observe the efficacy and safety of oral immunotherapy (OIT) by enteric-coated capsules (EC) of Dermatophagoides farinae allergen (Df) with mite AR. A year of single blind placebo trial was applied. A total of 54 AR patients aged 25.8 in average with/without asthma and skin prick test (SPT) positive in HDMs were selected into either active or placebo groups. The OIT started with 5 days of dose rush induction, succeeded by a maintenance dose for 12 months. The efficacy of the treatment was assessed by symptomatic evaluation and laboratory in vivo and in vitro parameters of pre-immunotherapy (pre-IT) and post-immunotherapy (post-IT) statistically. The patients each received a total accumulative dose of 16 715BU Df protein nitrogen, and 87.5% (21/24) subjects achieved symptomatic improvement. The post-IT symptom scores decreased (t=11.07, P<0.001); visual analog scale (VAS) decreased (t=10.68, P<0.001); number of patients required symptom-medication decreased from 23/24 to 3/24 cases (c2=33.57, P<0.001); SPT wheal sizes of both Df and Dp significantly reduced (Df t=2.64, P=0.015 and Dp t=6.01, P<0.001); nasal provocation test (NPT) with the antigen tolerance elevated more than 3 times  (c2=9.65, P=0.008). The only unchanged parameter was the tIgE levels (P=0.07). The parameters of placebo group were changed but not significant statistically or negligible. There were no local or general adverse reactions in both groups happened in the one year course of OIT. It is concluded that the newly designed formulation and route of clinical administration by Df EC OIT with AR were comparable to that of Df sublingual IT. The new formulation is more convenient and promising approach to treat AR.
Improved Articulation of Incongruent Sponsor–Property Partnerships Using Analogy
Authors: King Jesse , Madrigal Robert
Published: August 2018

Sport managers are often faced with a situation where they must activate an incongruent sponsorship in which the fit between a sponsor and property is not self-evident. Existing research has shown that consumers’ perceptions of fit enhance a sponsorship’s effectiveness. Therefore, the challenge is to explain how an otherwise incongruent sponsor and property are related to one another. The current research addresses this problem and considers analogy as a means for articulating an incongruent sponsorship. We find that analogical articulation offers distinct advantages over a more common method of articulating a sponsorship by describing how a property and sponsor’s consumer base overlap.
Transfer of Content Development Across Practica in Physical Education Teacher Education
Authors: Dervent Fatih , Ward Phillip , Devrilmez Erhan , Tsuda Emi
Published: August 2018

Purpose:Instructional tasks are a form of content knowledge that can be defined as specialized content knowledge (SCK). We examined the changes in the use of instructional tasks and SCK index scores of preservice teachers from methods to final practicum.Method:Five preservice teachers were observed through the methods practicum where they taught a small group consisting of six to eight students and then through final practicum where they taught whole intact classes. A modified version of content development categories and formula to measure the depth of content development was used. SCK index scores of the preservice teachers created by the formula were used to compare the changes from methods with final practicum.Results:The results showed an increase in the mean SCK index scores of the preservice teachers from methods practicum to final practicum. The use of informing and extending-applying tasks decreased in the final practicum, while an increase occurred in the use of refining and applying tasks.Discussion/Conclusion:Increase in the mean SCK index scores seemed to reflect the strong SCK emphasis of the physical education teacher education program. It can be concluded that SCK can and should be taught to preservice teachers.
Effects of an Individualized Mental-Skills-Training Program on Golf Performance: A Single-Subject Research Design
Authors: Ashbrook Paul R. , Gillham Andrew , Barba Douglas
Published: August 2018

Using a single-subject research design, a 1-to-1 tailored mental-skills-training (MST) program was created, implemented, and evaluated. During the 20-wk intervention phase, 6 National Collegiate Athletic Association Division I college golfers received a series of individually tailored MST sessions aimed at enhancing their mental skills and athletic performance. Each athlete’s golf performance, mental-skill frequency, and response to service were evaluated using visual inspection. Despite some limitations, results suggested that the 1-to-1 training program was effective, with nearly 50% of the performance and perception metrics improving from baseline and almost 80% of the mental skills improving. Follow-up analyses indicated that the program continued to positively affect performance into the next competitive season.
Elite Canadian Women Rugby Athletes’ Attitude to and Experience of Physical Aggression
Authors: Kerr John
Published: August 2018

Elite Canadian women rugby union athletes’ (N = 10) attitude to and experience of physical aggression was investigated in this study. The methodology adopted in this postpositivist study was a deductive qualitative approach and involved theoretical thematic data analysis. The analysis and interpretation of data was informed by Kerr’s distinction between sanctioned and unsanctioned forms of aggression. Open-ended, semistructured interviews provided ample evidence that rugby provided pleasurable experiences through active physicality and sanctioned play aggression. With regard to unsanctioned aggression, backs and forwards recounted incidents of unsanctioned aggression perpetrated against them by opponents. Backs’ interview statements indicated no real involvement in unsanctioned aggression, but the majority of forwards had perpetrated acts of anger and power-unsanctioned aggression against opponents. No incidents of thrill-based unsanctioned aggression were described by the elite women athletes. Suggestions for future aggression research are discussed.
New pain drugs may lower overdose and addiction risk
Authors: Service Robert F.
Published: August 2018

By slowing action or targeting different receptors, altered opioids or alternatives aim to sidestep abuse.
Emerging scientific technologies help defend human rights
Authors: Hoy Anne Q.
Published: August 2018

Scientists leverage advancing tools to gather evidence and expand the capacity of human rights groups
Past and future global transformation of terrestrial ecosystems under climate change
Authors: Nolan Connor , Overpeck Jonathan T. , Allen Judy R. M. , Anderson Patricia M. , Betancourt Julio L. , Binney Heather A. , Brewer Simon , Bush Mark B. , Chase Brian M. , Cheddadi Rachid , Djamali Morteza , Dodson John , Edwards Mary E. , Gosling William D. , Haberle Simon , Hotchkiss Sara C. , Huntley Brian , Ivory Sarah J. , Kershaw A. Peter , Kim Soo-Hyun , Latorre Claudio , Leydet Michelle , Lézine Anne-Marie , Liu Kam-Biu , Liu Yao , Lozhkin A. V. , McGlone Matt S. , Marchant Robert A. , Momohara Arata , Moreno Patricio I. , Müller Stefanie , Otto-Bliesner Bette L. , Shen Caiming , Stevenson Janelle , Takahara Hikaru , Tarasov Pavel E. , Tipton John , Vincens Annie , Weng Chengyu , Xu Qinghai , Zheng Zhuo , Jackson Stephen T.
Published: August 2018

Future predictions from paleoecology

Terrestrial ecosystems will be transformed by current anthropogenic change, but the extent of this change remains a challenge to predict. Nolan
et al.
looked at documented vegetational and climatic changes at almost 600 sites worldwide since the last glacial maximum 21,000 years ago. From this, they determined vegetation responses to temperature changes of 4° to 7°C. They went on to estimate the extent of ecosystem changes under current similar (albeit more rapid) scenarios of warming. Without substantial mitigation efforts, terrestrial ecosystems are at risk of major transformation in composition and structure.

Science
, this issue p.
920
Cancer mutations and targeted drugs can disrupt dynamic signal encoding by the Ras-Erk pathway
Authors: Bugaj L. J. , Sabnis A. J. , Mitchell A. , Garbarino J. E. , Toettcher J. E. , Bivona T. G. , Lim W. A.
Published: August 2018

Dynamics of cell signaling and decoding

Defects in cellular signaling pathways, like those in some cancer cells, are often thought to result in increased or decreased steady-state signals that promote or inhibit cell proliferation. But Bugaj
et al.
show that dynamic changes in the duration or frequency of a signal can also alter cellular responses (see the Perspective by Kolch and Kiel). They took precise control of signaling in cultured human or mouse cells with a light-controlled mechanism for activating and inactivating the guanosine triphosphate Ras. Known cancer mutations in components of the Ras-activated signaling pathway or inhibitors of particular pathway components altered signal timing and readouts. The modified dynamics changed transcriptional outcomes and could inappropriately support cell proliferation. The ability to probe responses of signaling networks in this way may enhance understanding of biological regulation and reveal new therapeutic targets.

Science
, this issue p.
eaao3048
; see also p.
844
Quantum oscillations of electrical resistivity in an insulator
Authors: Xiang Z. , Kasahara Y. , Asaba T. , Lawson B. , Tinsman C. , Chen Lu , Sugimoto K. , Kawaguchi S. , Sato Y. , Li G. , Yao S. , Chen Y. L. , Iga F. , Singleton John , Matsuda Y. , Li Lu
Published: August 2018

Insulator or a metal?

When a metal is cooled to low temperatures and placed in an external magnetic field, its resistivity may oscillate as the magnitude of the field is varied. Seeing these so-called quantum oscillations in an insulating material would be very unusual. Xiang
et al.
report such findings in the insulator ytterbium dodecaboride (YbB
12
) (see the Perspective by Ong). In addition to oscillations in resistivity, the authors observed oscillations in the magnetic torque. The results present a challenge to theories that aim to explain the insulating state of YbB
12
.

Science
, this issue p.
65
; see also p.
32
Engineered CRISPR-Cas9 nuclease with expanded targeting space
Authors: Nishimasu Hiroshi , Shi Xi , Ishiguro Soh , Gao Linyi , Hirano Seiichi , Okazaki Sae , Noda Taichi , Abudayyeh Omar O. , Gootenberg Jonathan S. , Mori Hideto , Oura Seiya , Holmes Benjamin , Tanaka Mamoru , Seki Motoaki , Hirano Hisato , Aburatani Hiroyuki , Ishitani Ryuichiro , Ikawa Masahito , Yachie Nozomu , Zhang Feng , Nureki Osamu
Published: August 2018

Expanding the targeting space of Cas9

CRISPR-Cas9 associates with a guide RNA to target and cleave a specific DNA site next to a protospacer adjacent motif (PAM).
Streptococcus pyogenes
Cas9 (SpCas9), the one most often used for genome editing, only recognizes the NGG sequence (where N is any nucleobase) as the PAM, which restricts regions in the genome that can be targeted. To address this limitation, Nishimasu
et al.
created a SpCas9 variant that recognizes NG rather than NGG. The SpCas9-NG variant increased the targeting range, had a specificity similar to that of the wild-type enzyme, and could be used with a base editor. Thus, SpCas9-NG is a powerful addition to the CRISPR-Cas9 genome engineering toolbox and will be useful in a broad range of applications, from basic research to clinical therapeutics.

Science
, this issue p.
1259
The opium poppy genome and morphinan production
Authors: Guo Li , Winzer Thilo , Yang Xiaofei , Li Yi , Ning Zemin , He Zhesi , Teodor Roxana , Lu Ying , Bowser Tim A. , Graham Ian A. , Ye Kai
Published: August 2018

Poppy genome reveals evolution of opiates

The opium poppy has been a source of painkillers since Neolithic times. Attendant risks of addiction threaten many today. Guo
et al.
now deliver a draft of the opium poppy genome, which encompasses 2.72 gigabases assembled into 11 chromosomes and predicts more than 50,000 protein-coding genes. A particularly complex gene cluster contains many critical enzymes in the metabolic pathway that generates the alkaloid drugs noscapine and morphinan.

Science
, this issue p.
343
The spatial footprint of injection wells in a global compilation of induced earthquake sequences
Authors: Goebel Thomas H. W. , Brodsky Emily E.
Published: August 2018

Seismic limits for hard and soft rock

Induced earthquakes from oil, gas, and geothermal energy exploration projects can damage infrastructure and concern the public. However, it remains unclear how far away from an injection site an earthquake can still be triggered. Goebel and Brodsky looked at 18 different earthquake-producing injection sites around the world to address this issue. Injecting fluid into softer layers increased the range for seismic hazard, whereas harder basement rock better confined the fluid. These findings should be considered when regulating and managing projects with the potential to induce seismicity.

Science
, this issue p.
899
Joint profiling of chromatin accessibility and gene expression in thousands of single cells
Authors: Cao Junyue , Cusanovich Darren A. , Ramani Vijay , Aghamirzaie Delasa , Pliner Hannah A. , Hill Andrew J. , Daza Riza M. , McFaline-Figueroa Jose L. , Packer Jonathan S. , Christiansen Lena , Steemers Frank J. , Adey Andrew C. , Trapnell Cole , Shendure Jay
Published: August 2018

Single-cell chromatin and RNA analysis

Single-cell analyses have begun to provide insight into the differences among and within the individual cells that make up a tissue or organism. However, technological barriers owing to the small amount of material present in each single cell have prevented parallel analyses. Cao
et al.
present sci-CAR, a pooled barcode method that jointly analyzes both the RNA transcripts and chromatin profiles of single cells. By applying sci-CAR to lung adenocarcinoma cells and mouse kidney tissue, the authors demonstrate precision in assessing expression and genome accessibility at a genome-wide scale. The approach provides an improvement over bulk analysis, which can be confounded by differing cellular subgroups.

Science
, this issue p.
1380
Gene editing restores dystrophin expression in a canine model of Duchenne muscular dystrophy
Authors: Amoasii Leonela , Hildyard John C. W. , Li Hui , Sanchez-Ortiz Efrain , Mireault Alex , Caballero Daniel , Harron Rachel , Stathopoulou Thaleia-Rengina , Massey Claire , Shelton John M. , Bassel-Duby Rhonda , Piercy Richard J. , Olson Eric N.
Published: August 2018

Gene editing and muscular dystrophy

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness and a shortened life span. The disease is caused by mutations that reduce or prevent expression of dystrophin, an essential structural protein in skeletal and heart muscle. The gene editing technology CRISPR-Cas9 can correct disease-causing mutations and has yielded promising results in mouse models of DMD. In a small, short-term study, Amoasii
et al.
tested this strategy in a dog model of DMD that exhibits many features of the human disease. Intramuscular or systemic delivery of the gene editing components resulted in a substantial increase in dystrophin protein levels in skeletal and heart muscle. Restoration of dystrophin expression was accompanied by improved muscle histology.

Science
, this issue p.
86