bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing the use of vibrations and strobe lights at fish screens as enhanced deterrents for two estuarine fishes
Authors: Mussen Timothy D. , Cech Joseph J.
Published: August 2018

The role of vision and the lateral‐line system in fish‐screen avoidance behaviours was investigated in shiner surfperch Cymatogaster aggregata and staghorn sculpin Leptocottus armatus. Avoidance experiments were conducted in front of water‐diversion‐type wedge‐wire fish screens in a laboratory flume with a 0.3 m s−1 water velocity. Fish contacted the screens less frequently during the day than night, indicating that fish screen avoidance is visually mediated during the day. Input from the fishes' lateral‐line systems was also blocked with streptomycin‐sulphate treatments during the night to determine if these fishes use mechanoreceptive cues to guide screen avoidance in darkened conditions. Streptomycin‐treated and untreated fish had similar contact rates suggesting that mechanoreceptive guidance was not increasing the fishes' abilities to avoid contact with non‐vibrating screens at night. Fishes were stained with 2‐(4‐(dimethylamino)styryl)‐N‐ethylpyridinium iodide (DASPEI) to assess the streptomycin treatment's effectiveness. We also tested the fishes' ability to avoid contact with the screens at night, when a strobe light or industrial vibrator was operated on the screens, to respectively increase the screen's visual and mechanoreceptory guidance potential. Cymatogaster aggregata contacted the screens significantly less frequently when they were vibrating, compared with their night‐time controls, suggesting useful mechanoreceptive guidance. Leptocottus armatus contacted the screens significantly less frequently under strobe‐light illumination, compared with their night‐time controls, suggesting useful visual guidance. This research should benefit fishery and water‐resource managers, regarding the development of future fish‐protection decisions at screened water diversions.
Genetic and molecular evidence that brown trout Salmo trutta belonging to the Danubian lineage are a single biological species
Authors: Kalayci Gokhan , Ozturk Rafet C. , Capkin Erol , Altinok Ilhan
Published: August 2018

We tested for reproductive isolation between Salmo trutta abanticus, S.t. labrax, S.t. caspius and S.t. fario by conducting crosses to produce F1 and F2 offspring. We also estimated the extent of genetic divergence between all three entities by examining sequence variation across the coI, d‐loop and cytb mitochondrial genes. All of the F1 cross‐types were successfully produced. After 2 years of culturing, F2 generation were produced as well. Fertilization, hatching and survival rates and hatching performance of F1 and F2 generations were evaluated. F2 generation had similar performance to their parent. Fertilization, hatching, larval survival rate and hatchery performance of F1 and F2 generation were similar except pure bred F2 S.t. abanticus. Purebred F1 individuals shared similar coloration patterns and spots with their parents but direction of the hybridization appeared to be decisive on morphology of hybrids. Some of the hybrids exhibit different morphological characters than their parents. Based on partial alignments of the three genes, phylogenetic analysis showed that these S. trutta are gathering within the same clade and appeared as monophyletic group. We found that there were some morphologic and genetic variation among S. trutta subspecies but the degree of variation does not warrant species level recognition. These findings indicate that the four subspecies constitute a single biological entity, corresponding to different morphs of the Danubian lineage. We therefore recommend that S. trutta belonging to Danubian lineage in Turkey be referred to as Salmo trutta and that strains be named according to location, such as Abant, Caspian, Black Sea and Anatolian.
Stuck in the Middle: Indigenous Interpreters and the Politics of Vernacularizing Prior Consultation in Peru
Authors: Flemmer Riccarda
Published: August 2018

Las consultas previas no deberían ser concebidas como diálogos interculturales sino como luchas sobre la interpretación de derechos. Un aspecto no atendido ni por la política, ni por la literatura es que en estos procesos, los intermediarios—en este caso intérpretes indígenas—tienen la posición de ser mucho más que traductores lingüísticos. Applicando la idea de vernacularization entendido como la traducción de derechos de Sally Engle Merry a este nuevo ámbito, la presión política sobre las personas quienes contribuyen a estas interpretaciones vernáculas de derechos es evidente: son actores políticos en posiciones de brokerage para el entendimiento de derechos. Basado en trabajo de campo etnográfico en la Amazonía Peruana (2013–2014), muestro que los intérpretes indígenas están atascados “en el medio” de las tensiones políticas y simultáneamente tienen que ser intermediarios de conocimientos, cultura y poder. Sin saberlo, llevan todo el peso de la disputa (inter)nacional sobre las interpretaciones estatales e indígenas de la consulta previa. [Amazonia, derechos humanos, pueblos indígenas, ley, Perú, consulta previa]
What is the cognitive basis of the side‐effect effect? An experimental test of competing theories
Authors: Proft Marina , Dieball Alexander , Rakoczy Hannes
Published: August 2018

Recent work on the side‐effect effect has shown that subjects' intentionality judgments are influenced by moral evaluations. In six experiments, we tested four different candidates for the cognitive foundation derived from prominent explanatory accounts (prescriptiveness, [un‐]expectedness, blame and a shift in default attitudes) against each other in three steps. First, Study 1 showed that the effect even extends to certain descriptive norms. Second, Studies 2–5 investigated the candidates more directly. Results reveal that intentionality judgments could best be explained by underlying shifts in default attitudes. Third, Study 6 experimentally manipulated this default attitude, leading to the predicted change in intentionality judgments.
The link between self‐compassion and psychotic‐like experiences: A matter of distress?
Authors: Scheunemann Jakob , Schlier Björn , Ascone Leonie , Lincoln Tania M.
Published: August 2018

Objectives

Self‐shaming and self‐criticism have been shown to contribute to the emergence of distressing psychotic symptoms and psychotic‐like experiences (PLEs). In contrast, a self‐compassionate mindset may protect against negative evaluations in response to PLEs leading to less distress. This study explores the association between self‐compassion, the frequency of PLEs, and their associated distress.

Design

The study used a correlational, cross‐sectional design on a German community sample.

Methods

A total of 234 participants completed the self‐compassion scale (SCS), the Peters’ Delusions Inventory, and a modified version of the Launay–Slade Hallucination Scale that measures frequency and distress of hallucinatory experiences. Pearson correlations between SCS and frequency of PLEs as well as between SCS and PLE‐distress were compared. Additionally, network analyses of SCS and PLE‐measures were calculated.

Results

Self‐compassion was associated with less‐frequent PLEs and with less PLE‐distress, with stronger correlations between self‐compassion and PLE‐distress. The network analysis showed the self‐compassion facets isolation and overidentification to be the closest links to PLE‐distress.

Conclusions

Self‐compassion is associated with less PLE related distress. Prevention programmes and interventions that target the negative facets associated with lack of self‐compassion may be promising. However, future studies need to explore the causal role of self‐compassion facets in the formation of PLE‐distress.

Practitioner points

Low levels of self‐compassion are associated with being more distressed by psychotic experiences.

As the self‐compassion facets isolation and overidentification are most strongly related to distress, prevention and intervention programmes may benefit from focusing on these negative facets.
Feasibility and safety of arthroscopic medial glenohumeral ligament and subscapularis tendon repair with knotless anchors: A cadaveric study in dogs
Authors: Penelas Alexandra , Gutbrod Andreas , Kühn Karolin , Pozzi Antonio
Published: August 2018

Objective

To test the feasibility and safety of an arthroscopic imbrication of the medial glenohumeral ligament (MGHL) and the subscapularis tendon with knotless anchors in dogs.

Study design

Cadaveric study.

Sample population

Ten limbs.

Methods

Cranial and caudal arms of the MGHL were imbricated with a 2.9‐ or a 2.4‐mm knotless anchor. A horizontal mattress suture secured with a 3.5‐mm knotless anchor was used to imbricate the subscapularis tendon. Computed tomography measurements included (1) the bone stock around the anchors, (2) the angle between the anchor and the joint surface (insertion angle), and (3) the angle formed by lines tangent to the cortices of the bones (safety angle). Limbs were dissected to assess the position of anchors. Safety and insertion angles and bone stock were compared among anchors with a Kruskal‐Wallis test (P < .05).

Results

Surgical repairs were achieved in all limbs, with only 2 of 30 anchors incorrectly placed, both in the glenoid. The safety angle of the humeral anchor (HA; median, 89°) was greater than that of the cranial glenoid anchor (CrGA; P = .0017) and the caudal glenoid anchor (CdGA; P < .001). The insertion angle of the HA (median, 68°) was also greater than that of the other anchors (P < .001 and P = .001). The insertion angle of the CrGA (median, 26°) was greater (P = .0191) than that of the CdGA (median, 7°). All anchors were inserted at the MGHL and subscapularis footprint.

Conclusion

Arthroscopic imbrication of MGHL and subscapularis tendon was feasible. HA were safer to place than glenoid anchors.

Clinical significance

The results of this feasibility study justify further evaluation of the indications and outcomes of this technique in dogs with shoulder instability.
Sensors and signals: the role of reactive oxygen species in hypoxic pulmonary vasoconstriction
Authors: Smith Kimberly A. , Schumacker Paul T.
Published: August 2018

When lung cells experience hypoxia, the functional response, termed hypoxic pulmonary vasoconstriction, activates a multitude of pathways with the goal of optimizing gas exchange. While previously controversial, overwhelming evidence now suggests that increased reactive oxygen species – produced at complex III of the mitochondrial electron transport chain and released into the intermembrane space – is the cellular oxygen signal responsible for triggering hypoxic pulmonary vasoconstriction. The increased reactive oxygen species (ROS) activate many downstream targets that ultimately lead to increased intracellular ionized calcium concentration and contraction of pulmonary arterial smooth muscle cells. While the specific targets of ROS signals are not completely understood, it is clear that this signalling pathway is critical for development and for normal lung function in newborns and adults.

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Wall Temperature Measurements in Gas Turbine Combustors With Thermographic Phosphors
Authors: Nau Patrick , Yin Zhiyao , Lammel Oliver , Meier Wolfgang
Published: August 2018

Phosphor thermometry has been developed for wall temperature measurements in gas turbines and gas turbine model combustors. An array of phosphors has been examined in detail for spatially and temporally resolved surface temperature measurements. Two examples are provided, one at high pressure (8 bar) and high temperature and one at atmospheric pressure with high time resolution. To study the feasibility of this technique for full-scale gas turbine applications, a high momentum confined jet combustor at 8 bar was used. Successful measurements up to 1700 K on a ceramic surface are shown with good accuracy. In the same combustor, temperatures on the combustor quartz walls were measured, which can be used as boundary conditions for numerical simulations. An atmospheric swirl-stabilized flame was used to study transient temperature changes on the bluff body. For this purpose, a high-speed setup (1 kHz) was used to measure the wall temperatures at an operating condition where the flame switches between being attached (M-flame) and being lifted (V-flame) (bistable). The influence of a precessing vortex core (PVC) present during M-flame periods is identified on the bluff body tip, but not at positions further inside the nozzle.
Modeling the Effect of Infrared Opacifiers on Coupled Conduction-Radiation Heat Transfer in Expanded Polystyrene
Authors: Akolkar A. , Rahmatian N. , Unterberger S. , Petrasch J.
Published: August 2018

Heat transfer properties of two expanded polystyrene (EPS) samples of similar density, one without (white) and one with graphite opacifier particles (gray), are compared. Tomographic scans are used to obtain cell sizes of the foams. Using established models for closed-cell polymer foams, the extinction coefficient and the effective thermal conductivity are obtained. The effect of opacifiers is modeled using (1) an effective refractive index for the polystyrene walls within a cell model for the EPS and (2) a superposition of extinction due to a particle cloud upon extinction predicted by the cell model, where particles are modeled as oblate spheroids, or equivalent volume, surface, or hydraulic diameter spheres. Modeled effective conductivities are compared with measurements done on a guarded hot-plate apparatus at sample mean temperatures in the range from 0 °C to 40 °C. Typically, cells of the gray EPS are about 40% larger than those of the white EPS and the cell walls in the gray EPS are thicker. The refractive index mixing model and the model with graphite opacifier particles as oblate spheroids overpredict extinction, however, the mean error in the effective conductivity predicted by the oblate spheroids model is only 2.7%. Equivalent volume/surface sphere models underpredict extinction, but still yield a low mean error in effective conductivity of around 4%. While the oblate spheroids model has a lower mean error, the computationally less expensive equivalent volume or equivalent surface models can also be recommended to model the inclusions.
Rotational Speed-Dependent Contact Formulation for Nonlinear Blade Dynamics Prediction
Authors: Heinze Torsten , Scheidt Lars Panning-von , Wallaschek Jörg , Hartung Andreas
Published: August 2018

Considering rotational speed-dependent stiffness for vibrational analysis of friction-damped bladed disk models has proven to lead to significant improvements in nonlinear frequency response curve computations. The accuracy of the result is driven by a suitable choice of reduction bases. Multimodel reduction combines various bases, which are valid for different parameter values. This composition reduces the solution error drastically. The resulting set of equations is typically solved by means of the harmonic balance method. Nonlinear forces are regularized by a Lagrangian approach embedded in an alternating frequency/time domain method providing the Fourier coefficients for the frequency domain solution. The aim of this paper is to expand the multimodel approach to address rotational speed-dependent contact situations. Various reduction bases derived from composing Craig–Bampton, Rubin–Martinez, and hybrid interface methods will be investigated with respect to their applicability to capture the changing contact situation correctly. The methods validity is examined based on small academic examples as well as large-scale industrial blade models. Coherent results show that the multimodel composition works successfully, even if multiple different reduction bases are used per sample point of variable rotational speed. This is an important issue in case that a contact situation for a specific value of the speed is uncertain forcing the algorithm to automatically choose a suitable basis. Additionally, the randomized singular value decomposition is applied to rapidly extract an appropriate multimodel basis. This approach improves the computational performance by orders of magnitude compared to the standard singular value decomposition, while preserving the ability to provide a best rank approximation.
An Efficient Method for Numerical Solutions of Distributed-Order Fractional Differential Equations
Authors: Jibenja N. , Yuttanan B. , Razzaghi M.
Published: August 2018

This paper presents an efficient numerical method for solving the distributed fractional differential equations (FDEs). The suggested framework is based on a hybrid of block-pulse functions and Taylor polynomials. For the first time, the Riemann–Liouville fractional integral operator for the hybrid of block-pulse functions and Taylor polynomials has been derived directly and without any approximations. By taking into account the property of this operator, the problem under consideration is converted into a system of algebraic equations. The present method can be applied to both linear and nonlinear distributed FDEs. Easy implementation, simple operations, and accurate solutions are the essential features of the proposed hybrid functions. Illustrative examples are examined to demonstrate the performance and effectiveness of the developed approximation technique, and a comparison is made with the existing results.
Modeling of Heat Transfer in an Aluminum X-Ray Anode Employing a Chemical Vapor Deposited Diamond Heat Spreader
Authors: Stupple David J. , Kemp Victor , Oldfield Matthew J. , Watts John F. , Baker Mark A.
Published: August 2018

X-ray sources are used for both scientific instrumentation and inspection applications. In X-ray photoelectron spectroscopy (XPS), aluminum Kα X-rays are generated through electron beam irradiation of a copper-based X-ray anode incorporating a thin surface layer of aluminum. The maximum power operation of the X-ray anode is limited by the relatively low melting point of the aluminum. Hence, optimization of the materials and design of the X-ray anode to transfer heat away from the aluminum thin film is key to maximizing performance. Finite element analysis (FEA) has been employed to model the heat transfer of a water-cooled copper-based X-ray anode with and without the use of a chemical vapor deposited (CVD) diamond heat spreader. The modeling approach was to construct a representative baseline model, and then to vary different parameters systematically, solving for a steady-state thermal condition, and observing the effect on the maximum temperature attained. The model indicates that a CVD diamond heat spreader (with isotropic thermal properties) brazed into the copper body reduces the maximum temperature in the 4 μm aluminum layer from 613 °C to 301 °C. Introducing realistic anisotropy and inhomogeneity in the thermal conductivity (TC) of the CVD diamond has no significant effect on heat transfer if the aluminum film is on the CVD diamond growth face (with the highest TC). However, if the aluminum layer is on the CVD diamond nucleation face (with the lowest TC), the maximum temperature is 575 °C. Implications for anode design are discussed.
Cluster-Based Optimization of Cellular Materials and Structures for Crashworthiness
Authors: Liu Kai , Detwiler Duane , Tovar Andres
Published: August 2018

The objective of this work is to establish a cluster-based optimization method for the optimal design of cellular materials and structures for crashworthiness, which involves the use of nonlinear, dynamic finite element models. The proposed method uses a cluster-based structural optimization approach consisting of four steps: conceptual design generation, clustering, metamodel-based global optimization, and cellular material design. The conceptual design is generated using structural optimization methods. K-means clustering is applied to the conceptual design to reduce the dimensional of the design space as well as define the internal architectures of the multimaterial structure. With reduced dimension space, global optimization aims to improve the crashworthiness of the structure can be performed efficiently. The cellular material design incorporates two homogenization methods, namely, energy-based homogenization for linear and nonlinear elastic material models and mean-field homogenization for (fully) nonlinear material models. The proposed methodology is demonstrated using three designs for crashworthiness that include linear, geometrically nonlinear, and nonlinear models.
Comparison of Different Model-Free Control Methods Concerning Real-Time Benchmark
Authors: Madadi Elmira , Dong Yao , Söffker Dirk
Published: August 2018

The design of accurate model often appears as the most challenging tasks for control engineers especially focusing to the control of nonlinear system with unknown parameters or effects to be identified in parallel. For this reason, development of model-free control methods is of increasing importance. The class of model-free control approaches is defined by the nonuse of any knowledge about the underlying structure and/or related parameters of the dynamical system. Therefore, the major criteria to evaluate model-free control performance are aspects regarding robustness against unknown inputs and disturbances and related achievable tracking performance. In this contribution, a detailed comparison of three different model-free control methods (intelligent proportional-integral-derivative (iPID) using second-order sliding differentiator and two variations of model-free adaptive control (using modified compact form dynamic linearization (CFDL) as well as modified partial form) is given. Using a three-tank system benchmark, the experimental results are validated concerning the performance behavior. The results obtained demonstrate the effectiveness of the methods introduced.
Electrohydrodynamic Pump Supplied by Unipolar Direct Current Voltage With Both Positive and Negative Corona Discharge
Authors: Podliński Janusz , Danowska Magdalena , Izdebski Tomasz , Dors Mirosław
Published: August 2018

Strong electric field applied between the two electrodes initiates a corona discharge, which results in ionization of gas molecules and induces ionic wind, also known as the electrohydrodynamic (EHD) flow. If an electric field is asymmetric, then a unidirectional gas flow can be formed causing so-called EHD gas pumping. In spite of many experiments with different electrode shapes and configurations such as needle-to-mesh, needle-to-ring, wire-to-rod, wire-to-non-parallel plates, etc., aimed at production of intensive gas pumping, the investigated EHD pumps were most often unsatisfactory. In our research, we proposed a new configuration of electrodes for the EHD pump, where all electrodes (excluding the first one and the last one) are simultaneously the discharge (on one side) and the collecting (on the other side) electrodes. Our electrodes configuration can be easily multiplied without additional space between consecutive electrodes. In such a case, a high ratio of pumping efficiency to pump size can be obtained. The Time-Resolved Particle Image Velocimetry technique was used to investigate the EHD flow generated by our EHD pump.
Robust and Optimal Output-Feedback Control for Interval State-Space Model: Application to a Two-Degrees-of-Freedom Piezoelectric Tube Actuator
Authors: Hammouche Mounir , Lutz Philippe , Rakotondrabe Micky
Published: August 2018

The problem of robust and optimal output feedback design for interval state-space systems is addressed in this paper. Indeed, an algorithm based on set inversion via interval analysis (SIVIA) combined with interval eigenvalues computation and eigenvalues clustering techniques is proposed to seek for a set of robust gains. This recursive SIVIA-based algorithm allows to approximate with subpaving the set solutions [K] that satisfy the inclusion of the eigenvalues of the closed-loop system in a desired region in the complex plane. Moreover, the LQ tracker design is employed to find from the set solutions [K] the optimal solution that minimizes the inputs/outputs energy and ensures the best behaviors of the closed-loop system. Finally, the effectiveness of the algorithm is illustrated by a real experimentation on a piezoelectric tube actuator.
Operational
Time and Melt Fraction Based Optimization of a Phase Change Material Longitudinal Fin Heat
Sink
Authors: Jaya
    Krishna D.
Published: August 2018

In the present study, the numerical investigation has been performed for a phase change material (PCM)-based longitudinal fin heat sink. The fins are taken as an integral part of the heat sink and are made up of aluminum. The PCM considered in the study is RT44HC. Heat is transferred to the heat sink through its horizontal base. In order to simulate the melting behavior of the PCM, volume of fluid model has been used. To attain the best configuration with optimum operational time, Taguchi method has been used followed by analysis of melt fraction and maximum base temperature. The optimized heat sink configuration with maximum operational time has been obtained at the critical temperatures of 54.8 °C, 63 °C, and 72.6 °C.
Numerical Analysis of Conjugated Convection-Conduction Heat Transfer in a Microtube Gas Flow
Authors: Ramadan K. M.
Published: August 2018

Numerical solutions for conjugate heat transfer of a hydro-dynamically fully developed, thermally developing, steady, incompressible laminar gas flow in a microtube with uniform wall heat flux boundary condition are presented. The mathematical model takes into account effects of rarefaction, viscous dissipation, flow work, shear work, and axial conduction in both the wall and the fluid. The effect of the tube wall thickness, the wall-to-fluid thermal conductivity ratio, as well as other factors on heat transfer parameters is investigated, and comparisons with the case of zero wall thickness are presented as appropriate. The results illustrate the significance of heat conduction in the tube wall on convective heat transfer and disclose the significant deviation from those with no conjugated effects. Increasing the wall thickness lowers the local Nusselt number. Increasing the wall-to-fluid thermal conductivity ratio also results in lower Nusselt number. In relatively long and thick microtubes with high wall-to-fluid thermal conductivity ratio, the local Nusselt number exhibits minimum values in the entrance regions and at the end sections due to axial conduction effects. The analysis presented also demonstrate the significance of rarefaction, shear work, axial conduction, as well as the combined viscous dissipation and flow work effects on heat transfer parameters in a microtube gas flow. The combined flow work and viscous dissipation effects on heat transfer parameters are significant and result in a reduction in the Nusselt number. The shear work lowers the Nusselt number when heat is added to the fluid.
Mistuning Identification Approach With Focus on High-Speed Centrifugal Compressors
Authors: Weber Robby , Kühhorn Arnold
Published: August 2018

Blade vibrations are one of the main cost drivers in turbomachinery. Computational blade vibration analysis facilitates an enormous potential to increase the productivity in the design of bladed components. Increasing computing power as well as improved modeling and simulation methods leads to comprehensive calculation results. This allows for a more precise prediction and assessment of experimental data. Usually, in the field of turbomachinery, identical blades are assumed to lower the required computational resources. However, mistuning is unavoidable, since small deviations due to the manufacturing process will lead to slightly different blade behavior. Potential effects such as mode localization and amplification can be treated statistically and have been thoroughly studied in the past. Since then, several reduced order models (ROMs) have been invented in order to calculate the maximum vibration amplitude of a fleet of mistuned blisks. Most commonly, mistuning is thereby modeled by small material deviations from blade to blade, e.g., Young's modulus or density. Nowadays, it is common knowledge that the level of manufacturing imperfection (referred as level of mistuning) significantly influences mode localization as well as vibration amplification effects. Optical measurements of the geometric deviations of manufactured blades and converting to a high-fidelity finite element (FE) model make huge progress. However, to the knowledge of the authors, there is no reliable method that derives a characteristic quantity from the geometric mistuning, that fits into the mentioned statistically approaches. Therefore, experimental data are needed to quantify the level of mistuning. Several approaches, which isolate blade individual parameters, are used to identify the dynamic behavior of axial compressors and turbines. These methods can be applied to medium-speed centrifugal turbine wheels but tend to fail to evaluate high-speed compressor with splitter blades. This paper briefly presents the original approach and discusses the reasons for failure. Thereafter, a new approach is proposed. Finally, the level of mistuning and important quantities to perform a statistical evaluation of a high-speed compressor is shown.
Gas Turbine Fouling Offshore: Effective Online Water Wash Through High Water-to-Air Ratio
Authors: Madsen Stian , Bakken Lars E.
Published: August 2018

Optimized operation of gas turbines is discussed for a fleet of 11 GE LM2500PE engines at a Statoil North Sea offshore field in Norway. Three engines are generator drivers, and eight engines are compressor drivers. Several of the compressor drive engines are running at peak load (T5.4 control), hence, the production rate is limited by the available power from these engines. The majority of the engines discussed run continuously without redundancy, hence, the gas turbine uptime is critical for the field's production and economy. The performance and operational experience with online water wash at high water-to-air ratio (w.a.r.), as well as successful operation at longer maintenance intervals and higher average engine performance are described. The water-to-air ratio is significantly increased compared to the original equipment manufacturer (OEM) limit (OEM limit is 17 l/min which yields approximately 0.5% water-to-air ratio). Today the engines are operated at a water rate of 50 l/min (three times the OEM limit) which yields a 1.4% water-to-air ratio. Such a high water-to-air ratio has been proven to be the key parameter for obtaining good online water wash effectiveness. Possible downsides of high water-to-air ratio have been thoroughly studied.
Mechanical Properties and Structure of Laser Beam and Wide Gap Brazed Joints Produced Using Mar M247–Amdry DF3 Powders
Authors: Gontcharov Alexandre , Tian Yuan , Lowden Paul , Brochu Mathieu
Published: August 2018

The microstructure and mechanical properties of materials produced by wide gap brazing (WGB) and laser beam (LBW) cladding with different blends of Mar M247 and Amdry DF-3 brazing powders were studied. It was shown that LBW Mar M247-based materials comprised of 0.6 to 1 wt % B were weldable. The weld properties were superior to WGB deposits with the same bulk chemical composition, due to the formation of a dendritic structure typical for welded joints, and the precipitation of cuboidal borides of Cr, Mo, and W in the ductile Ni–Cr based matrix. Both materials were found to have useful properties for three-dimensional (3D) additive manufacturing (AM) and repair components manufactured from high gamma prime precipitation hardened superalloys.
Wear and Mechanical Contact Behavior of Polymer Gears
Authors: Alharbi Khalid Abdulkhaliq M.
Published: August 2018

Extensive investigations have been carried out in the present paper to understand polymer gear performance, i.e., wear and contact behaviors. The experimental results and possible wear mechanisms for polymer gears run against themselves have been presented, especially the wear rate of the polymer gears under different running speeds and loads. The tested samples were made of three different materials (acetal, nylon, and polycarbonate (PC)) and the effects of two different manufacturing techniques were also investigated (i.e., machine-cut and injection-molded polymer gears). The polymer gear performances (wear and life) were recorded using a uniquely designed and built test rig for this purpose. The testing results have been compared with the existing literature for polymer fatigue and wear theory. Further extensive investigations have been carried out to understand the wear phenomena on tooth flank surface profile of these gears and the data obtained have been discussed.
Versatile Absolute Nodal Coordinate Formulation Model for Dynamic Folding Wing Deployment and Flutter Analyses
Authors: Otsuka Keisuke , Wang Yinan , Makihara Kanjuro
Published: August 2018

Aircraft performance can be improved using morphing wing technologies, in which the wing can be deployed and folded under flight conditions, providing a wide flight envelope, good fuel efficiency, and reducing the space required to store the aircraft. Because the deployment of the wing is a nonlinear-coupled motion comprising large rigid body motion and large elastic deformation, a nonlinear folding-wing model is required to perform the necessary time-domain deployment simulation, while a linear model is required to perform the frequency-domain flutter analysis. The objective of this paper is to propose a versatile model that can be applied to both the time-domain and frequency-domain analyses of a folding wing, based on flexible multibody dynamics (MBD) using absolute nodal coordinate formulation (ANCF) and unsteady aerodynamics. This new versatile model expands the application range of the flexible MBD using ANCF in time-domain simulation, allowing it to express the coupled motion of extremely large elastic deformations and large rigid body motions that arise in next-generation aircraft. The time-domain deployment simulation conducted using the proposed model is useful for parametric deployment-system design because the model has improved calculation time. In the frequency-domain flutter analysis of a folding wing, the flutter speed obtained from the proposed model agrees with that obtained from an experiment, with an error of 4.0%, showing promise for application in next-generation aircraft design.
A Method and Apparatus for Direct Enthalpy Rise Measurement for Gas Compression
Authors: Brun Klaus , Simons Sarah , Katcher Kelsi , Cater Ryan , Ridens Brandon , Kurz Rainer
Published: August 2018

Gas property prediction is necessary for proper design of compressors. Equations of state are utilized to predict the thermo-physical gas properties needed for such calculations. These are semi-empirical models that allow the calculation of thermodynamic properties such as density, enthalpy, and speed of sound of gas mixtures for known pressures and temperature. Currently, there is limited or no data publically available to verify the results of these equation of state calculations for the range of pressures, temperatures, and gas compositions relevant to many oil and gas applications. Especially for isentropic enthalpy head (i.e., the enthalpy rise along constant entropy lines), which is a critical parameter required to accurately design and performance test compressors, limited public domain data are available for equation of state validation. In this paper, a method and test apparatus is described to measure compression enthalpy rise directly. In this apparatus, a test gas is compressed using a fast acting piston inside an adiabatic autoclave. Test results are then corrected using calibration efficiencies from a known reference gas compression process at a similar Reynolds number. The paper describes the test apparatus, calibration, measurement methodology, and test results for one complex hydrocarbon gas composition at elevated temperatures and pressures. An uncertainty analysis of the new measurement method is also presented and results are compared to several equations of state. The results show that commonly used equations of state significantly underpredicted the compression enthalpy rise for the test gas case by more than 6%.
A Comparative Study of the Dissipative Contact Force Models for Collision Under External Spring Forces
Authors: Xiang Dong , Shen Yinhua , Wei Yaozhong , You Mengxing
Published: August 2018

The dissipative contact force model plays a key role in predicting the response of multibody mechanical systems. Contact-impact event can frequently take place in multibody systems and the impact pair is often affected by supporting forces which are treated as external spring forces. However, the external spring forces are ignored during the derivation process of existing dissipative contact force models. Considering the influences of external spring forces, the fact is discussed that the crucial issues, including relative velocity and energy loss, in modeling dissipative contact force are different compared to the same issues analyzed in existing literatures. These differences can result in obvious errors in describing the collision response in multibody systems. Thus, a comparative study is carried out for examining the performances of several popular dissipative contact force models in multibody dynamics. For this comparison, a method associated with Newton's method is proposed to calculate the contact force that meets the Strong's law of energy loss and this force is used as reference. The comparative results show that the models suitable for both hard and soft contact exhibit good accuracy when contact equivalent stiffness is far larger than external spring stiffness by two orders of magnitude. Conversely, these models can cause varying degree and obvious errors in contact force, number of collisions, etc., especially when the difference in stiffness is close to or less than one order of magnitude.
A Novel Method for Designing Fan-Shaped Holes With Short Length-to-Diameter Ratio in Producing High Film Cooling Performance for Thin-Wall Turbine Airfoil
Authors: Li Weihong , Li Xueying , Ren Jing , Jiang Hongde
Published: August 2018

An experimental investigation of the geometrical parameter effects on the film cooling performance of a fan-shaped hole was conducted on a low speed flat-plate facility. The pressure sensitive paint (PSP) technique and steady liquid crystal (SLC) technique were employed to determine the adiabatic film cooling effectiveness and heat transfer coefficients, respectively, for a blowing ratio ranging from 0.3 to 3 and a density ratio of DR = 1.5. Several geometrical parameters were investigated, including lateral expansion angle, length-to-diameter ratio, and hole entrance shape. Local, laterally averaged, and area-averaged adiabatic film cooling effectiveness, heat transfer coefficients, and net heat flux reduction (NHFR) were shown to provide a comprehensive understanding on the geometrical parameter effects on the thermal performance. A novel method was proposed for designing a fan-shaped hole with short length-to-diameter ratio to design to achieve high film cooling performance. The original and optimized fan-shaped holes were compared in terms of adiabatic film cooling effectiveness, heat transfer coefficients, and NHFR. Results showed that the optimized fan-shaped hole with short length-to-diameter ratio, large lateral diffusion angle, and slot hole entrance shape obtained highest overall thermal performance. It demonstrated the feasibility of adopting the proposed design method to design fan-shaped holes applied in thin wall gas turbine blades.
Experimental Deposition of NaCl Particles From Turbulent Flows at Gas Turbine Temperatures
Authors: Forsyth Peter R. , Gillespie David R. H. , McGilvray Matthew
Published: August 2018

The ingestion and deposition of solid particulates within gas turbine engines has become a very significant concern for both designers and operators in recent times. Frequently aircraft are operated in environments where sand, ash, dust, and salt are present, which can drive damage mechanisms from long term component degradation to in-flight flame-out. Experiments are presented to assess deposition characteristics of sodium chloride (NaCl) at gas turbine secondary air system temperature conditions in horizontal pipe flow. Monodisperse NaCl particles were generated in the size range 2.0–6.5 µm, with gas temperatures 390–480 °C, and metal temperatures 355–730 °C. Two engine-representative surface roughnesses were assessed. An experimental technique for the measurement of deposited NaCl based on solution conductivity was developed and validated. Experiments were carried out under isothermal and nonisothermal/thermophoretic conditions. An initial experimental campaign was conducted under ambient and isothermal conditions; high temperature isothermal results showed good similarity. Under thermophoretic conditions, deposition rates varied by up to several orders of magnitude compared to isothermal rates.
Impact of Predicted Combustor Outlet Conditions on the Aerothermal Performance of Film-Cooled High Pressure Turbine Vanes
Authors: Cubeda S. , Mazzei L. , Bacci T. , Andreini A.
Published: August 2018

Turbine inlet conditions in lean-burn aeroengine combustors are highly swirled and present nonuniform temperature distributions. Uncertainty and lack of confidence associated with combustor-turbine interaction affect significantly engine performance and efficiency. It is well known that only Large-eddy and scale-adaptive simulations (SAS) can overcome the limitations of Reynolds-averaged Navier–Stokes (RANS) in predicting the combustor outlet conditions. However, it is worth investigating the impact of such improvements on the predicted aerothermal performance of the nozzle guide vanes (NGVs), usually studied with RANS-generated boundary conditions. Three numerical modelling strategies were used to investigate a combustor-turbine module designed within the EU Project FACTOR: (i) RANS model of the NGVs with RANS-generated inlet conditions; (ii) RANS model of the NGVs with scale-adaptive simulation (SAS)-generated inlet conditions; (iii) SAS model inclusive of both combustor and NGVs. It was shown that estimating the aerodynamics through the NGVs does not demand particularly complex approaches, in contrast to situations where turbulent mixing is key. High-fidelity predictions of the turbine entrance conditions proved very beneficial to reduce the discrepancies in the estimation of adiabatic temperature distributions. However, a further leap forward can be achieved with an integrated simulation, capable of reproducing the transport of unsteady fluctuations generated from the combustor through the turbine, which play a key role in presence of film cooling. This work, therefore, shows how separate analysis of combustor and NGVs can lead to a poor estimation of the thermal loads and ultimately to a wrong thermal design of the cooling system.
Finite Element Formulation of Multiphasic Shell Elements for Cell Mechanics Analyses in FEBio
Authors: Hou Jay C. , Maas Steve A. , Weiss Jeffrey A. , Ateshian Gerard A.
Published: August 2018

With the recent implementation of multiphasic materials in the open-source finite element (FE) software FEBio, three-dimensional (3D) models of cells embedded within the tissue may now be analyzed, accounting for porous solid matrix deformation, transport of interstitial fluid and solutes, membrane potential, and reactions. The cell membrane is a critical component in cell models, which selectively regulates the transport of fluid and solutes in the presence of large concentration and electric potential gradients, while also facilitating the transport of various proteins. The cell membrane is much thinner than the cell; therefore, in an FE environment, shell elements formulated as two-dimensional (2D) surfaces in 3D space would be preferred for modeling the cell membrane, for the convenience of mesh generation from image-based data, especially for convoluted membranes. However, multiphasic shell elements are yet to be developed in the FE literature and commercial FE software. This study presents a novel formulation of multiphasic shell elements and its implementation in FEBio. The shell model includes front- and back-face nodal degrees-of-freedom for the solid displacement, effective fluid pressure and effective solute concentrations, and a linear interpolation of these variables across the shell thickness. This formulation was verified against classical models of cell physiology and validated against reported experimental measurements in chondrocytes. This implementation of passive transport of fluid and solutes across multiphasic membranes makes it possible to model the biomechanics of isolated cells or cells embedded in their extracellular matrix (ECM), accounting for solvent and solute transport.
Performance Evaluation of a Respirator Vortex Cooling Device
Authors: Elizondo Ashley D. , Iacovone Robert K.
Published: August 2018

The United States Department of Energy's Savannah River Site (SRS) in Aiken, South Carolina, is dedicated to promoting site-level, risk-based inspection practices to maintain a safe and productive work environment. Protective suits are worn by personnel working in contaminated environments. These suits require that cooling be applied to keep the interior temperature within safe and comfortable limits. A vortex tube, also known as the Ranque-Hilsch vortex tube (RHVT), can provide the necessary cooling. As mechanical devices void of moving components, vortex tubes separate a compressed gas into hot and cold streams—the air emerging from the “hot” end reaching a temperature of 433.2 K and the air emerging from the “cold” end reaching a temperature of 241.5 K (Hilsch, 1946, “Die Expansion Von Gasen Im Zentrifugalfeld Als Kälteprozeß,” Z. Für Naturforsch., 1, pp. 208–214). Routing the cold stream of the vortex tube to the user's protective suit facilitates the required cooling. Vortex tubes currently in use at SRS are preset, through modification solely by and within the SRS respiratory equipment facility (REF), to provide a temperature reduction between 22.2 and 25.0 K. When a new model of vortex tube capable of user adjustment during operation recently became available, prototype testing was conducted for product comparison. Ultimately, it was identified that similar cooling performance between the old and new models is achievable. Production units were acquired to be subjected to complete product analysis at SRS utilizing a statistical test plan. The statistical test plan, data, thermodynamic calculations, and conclusions were reviewed to determine acceptability for site use.
Visualization of Thermal Fatigue Damage Distribution With Simplified Stress Range Calculations
Authors: Miura Junya , Fujioka Terutaka , Shindo Yasuhiro
Published: August 2018

This paper proposes simplified methods to evaluate fatigue damage in a component subjected to cyclic thermal loads to visualize damage distribution by using typical computer-aided engineering systems. The objective is to perform the evaluations on a standard desktop PC within a reasonably short computation time. Three simplified methods for defining elastic stress ranges are proposed in place of the method in the ASME Subsection NH procedures. A thermal fatigue test that was previously performed using a type-304 stainless steel (304SS) cylinder is simulated to validate the proposed methods. Heat transfer and elastic analyses are conducted. Simultaneously with the analyses, fatigue usage factors are calculated using user subroutines formulated in this study, including the three simplified methods and the ASME NH-based method. The calculated values of the fatigue usage factor are visualized using a graphical user interface (GUI) incorporated into a commercial finite-element analysis (FEA) code. The fatigue usage factor distribution obtained using the simplified methods could be calculated without requiring large amounts of memory and long computation time. In addition, the distribution of the fatigue usage factor was consistent with the distribution of cracks observed in the test.