bluuebunny/crossref_metadata_2025 huggingface dataset:
Social norms and female labor participation in Brazil
Authors: Codazzi Karen , Pero Valéria , Albuquerque Sant'Anna André
Published: August 2018

Over the last half‐century, the role of women in society has changed substantially. However, the gender income gap and the difference in labor force participation persist. Other authors introduced the concept of identity from sociology and social psychology at the economic analysis and, based on this, we search less traditional factors for understanding this persistence. Extending analysis of others, we analyze the impact of gender social norms, focusing on the prescription that “a man should earn more than his wife” on social and economic results. Based on the Censuses for 1991, 2000, and 2010 we observed that for only 7 percent of married couples does the wife earn more than her husband. We found evidence that the wives with greater probability of earning more than their husbands are less likely to participate in the labor force. Once she does participate in the labor force, she has a higher probability of earning less than her potential income, working fewer hours, and having an informal job.
Does economic crisis have different impact on husbands and wives? Evidence from the Asian Financial Crisis in Indonesia
Authors: Dong Sarah Xue
Published: August 2018

This paper analyzes the intra‐household allocation of risk‐coping mechanisms by testing whether the Asian financial crisis affected married men and women differently in Indonesia. It estimates the effect of the district consumption shock during the crisis on the change in married men's and women's working status and assets. It finds that the regional shock is associated with a large increase in wives’ employment and a large decrease in wives’ business assets in urban areas, and not associated with change in husbands’ working status or asset holdings in urban areas. In rural areas the regional shock is associated with a drop in women's business assets and not related to other outcomes of husbands or wives. Receiving government social safety net program aid during the crisis seems to substitute for the decrease in business assets of women as a coping strategy in both urban and rural areas.
Healthcare professionals’ lived experiences of conversations with young adults expressing existential concerns
Authors: Lundvall Maria , Lindberg Elisabeth , Hörberg Ulrica , Palmér Lina , Carlsson Gunilla
Published: August 2018

Introduction

This paper describes first‐line department healthcare professionals’ experiences of conversations with young adults (16–25 years) who express existential concerns. Existential concerns encompass questions about the meaning of life and the choices people must make, and they are sometimes expressed during the period in which a child is becoming an adult. Sometimes the transition to adulthood can be difficult, and many young adults seek support from people in first‐line departments, such as primary care providers, youth guidance centre personnel and student health service employees in high schools and universities. Conversations in which existential concerns are recognised may be important for preventing mental illness in the future.

Aim

The study aimed to describe healthcare professionals’ lived experiences of conversations with young adults who express existential concerns.

Approach and methods

This qualitative study utilises thematic meaning analysis. Interviews were conducted with healthcare professionals working in first‐line departments, and data were analysed based on the principles of reflective lifeworld research. The study followed ethical codes of conduct and conformed to the ethical guidelines adopted by the Swedish Research Council.

Findings

The results are presented in three themes of meaning: searching for innermost thoughts requires being present, uncertainty about the unpredictable and awakening of one's own existential concerns.

Conclusions and implications

Healthcare professionals are affected when young adults express their existential concerns, and they need more support to strengthen their ability to stay present and create inviting atmospheres.
Caregiver pension credits for women: Recent experience in Uruguay
Authors: Amarante Verónica , Tenenbaum Victoria
Published: August 2018

This article analyses the effects of the implementation of childcare pension credits for women in Uruguay, which were introduced as part of a social security reform in 2009. Using microdata from administrative records of the social security administration, we show that around 60% of retired women have used these credits between 2009 and 2015, computing on average 2.7 additional years of service. The use of childcare credits has been higher among more vulnerable female workers. Among women with lower pensions, childcare credits are used both to reach the required years for retirement and to improve the amount of pensions, whereas for women in the higher deciles the program mainly impacts on the amount of pensions. Using a difference in difference approach, we also show that the program has, to some extent, acted as a substitute for the mechanism of computing years of service through the declaration of witnesses, an extended practice in Uruguay to access pensions. Lastly, we show that, if these credits had not been incepted, female access to pensions would have been significantly lower, and gender gaps both in access to, and in the amount of, pensions would have been higher.
Maximum likelihood estimation framework for table‐balancing adjustments
Authors: Brent Geoffrey
Published: August 2018

Balancing problems in national accounts and similar applications may be addressed by optimization methods that aim to maximize preservation of specific characteristics of the unadjusted data, for example, levels or time‐series movements. However, published methods do not always indicate the assumptions that underpin these methods, making it hard to identify when those assumptions might be violated or how to generalize them to complex cases. Previous authors have observed that least‐squares estimation methods correspond to maximum likelihood estimation (MLE) under normality assumptions. This paper explores this relationship in the context of published “movement preservation”/“level preservation” methods, showing how the MLE interpretation identifies implicit assumptions made by these methods and, hence, helps inform decisions about their use. It also notes a case where the MLE and “preservation” approaches diverge, and gives a framework for generalizing MLE approaches to complex scenarios.
Geodynamic significance of the Santorini Detachment System (Cyclades, Greece)
Authors: Schneider David A. , Grasemann Bernhard , Lion Allan , Soukis Konstantinos , Draganits Erich
Published: August 2018

We present field and geochronologic evidence for a Miocene top‐to‐SSE detachment system on Santorini, which exhumed the Cycladic Blueschist Unit (CBU) below a package of low‐grade Upper Triassic marbles that contain well‐preserved Megalodon fossils forming a syncline with metaflysch in the core. White mica bundles from the mylonitic foliation in the CBU yield 40Ar/39Ar dates of 25–19 Ma and zircon (U–Th)/He dates are 11–8 Ma. A weakly foliated granitic intrusion that cross‐cuts the CBU is 8.5 Ma based on zircon U–Pb geochronology. Detrital white mica from the metaflysch yields Jurassic to early Palaeogene single grain 40Ar/39Ar dates, with a dominant Palaeocene signature. Zircon (U–Th)/He dating similarly reveals dispersed ages between 36 and 15 Ma suggesting Miocene metamorphic temperatures were insufficient (<200°C) to completely reset all of the zircon cooling ages. The low‐grade rocks of the hangingwall above the newly discovered Miocene low‐angle Santorini Detachment System most likely belong to the Pelagonian zone with a Triassic carbonate platform discordantly transgressed by an Eocene flysch deposit.
Phenotypic analysis of mice xenografted with canine epitheliotropic cutaneous T‐cell lymphoma cells
Authors: Ikeuchi Miho , Asahina Ryota , Nishida Hidetaka , Kamishina Hiroaki , Kitoh Katsuya , Sakai Hiroki , Maeda Sadatoshi
Published: August 2018

Background

In canine epitheliotropic cutaneous T‐cell lymphoma (ECTCL), neoplastic cells cause skin lesions and potentially metastasize to lymph nodes, blood and other organs. Murine models are potentially valuable for elucidating the molecular mechanisms responsible for regulation of ECTCL cell migration.

Hypothesis/Objectives

To describe a phenotype of mice xenografted with canine ECTCL cells (EO‐1 cells).

Animals

Four NOD.CB17‐Prkdcscid/J (NOD SCID) mice were used.

Methods and materials

EO‐1 cells were subcutaneously xenografted into NOD SCID mice. After four weeks, the development of tumour lesions in skin and other organs was investigated.

Results

Mice developed skin lesions with metastasis to the lymph nodes, spleen, lung, blood and liver.

Conclusions and clinical importance

Mice xenografted with EO‐1 cells may be useful for studying the pathogenesis of canine ECTCL.
Cytokine profiling and post‐transfusion haemoglobin increment in patients with haematological diseases
Authors: Wendelbo Øystein , Opheim Elin Netland , Egil Eide Geir , Hervig Tor , Felli Lunde Turid Helen , Bruserud Øystein , Mollnes Tom Eirik , Reikvam Håkon
Published: August 2018

Background and Objectives

In a previous pilot study, we demonstrated significantly lower haemoglobin (Hb) increment after red‐blood‐cell (RBC) transfusions in febrile patients compared to patients without fever. The aim of this study was to examine associations between inflammatory mediators and post‐transfusion haemoglobin increment in patients with haematological diseases.

Materials and Methods

Twenty‐seven patients (eight women, 19 men), median age 56 years receiving RBC transfusion, were included in the study. Hb increment per unit transfused was corrected for estimated patient blood volume and the amount of Hb transfused. A wide spectrum of inflammatory mediators was determined by multiplex technology. Association between post‐transfusion haemoglobin increment, plasma inflammatory mediators and patient characteristics was analysed using a mixed linear regression model.

Results

Febrile patients had significantly lower corrected Hb increment, significantly increased values of IL‐6, IL‐8, IL‐10 and G‐CSF, significantly reduced levels of CCL5 and CXCL10, and significantly higher pretransfusion levels of CRP. There was a significant association between pretransfusion CRP levels and corrected Hb increment for the whole patient cohort, but not within each of the two groups. Results demonstrated an association between haemoglobin increment, fever and inflammatory mediators. Febrile patients had a significantly lower corrected Hb increment compared to nonfebrile patients, when adjusting for mediators. When fever was kept constant, a significant negative association between haemoglobin increment and the proinflammatory mediators IL‐6 and IL‐8 was observed.

Conclusion

Both fever and the inflammatory mediators IL‐6 and IL‐8 were negatively associated with post‐transfusion haemoglobin increment.
Gadolinium contrast medium administration does not adversely affect T2*‐weighted gradient recalled echo magnetic resonance imaging of the canine brain at 1.5 Tesla
Authors: Bartels Janina , Hecht Silke , Conklin Gordon A. , Xiaocun Sun
Published: August 2018

As gadolinium‐based contrast agents are paramagnetic and have T2 shortening effects, they have the potential to adversely affect gradient recalled echo sequences. The aim of this prospective, cross‐sectional study was to evaluate the effects of gadolinium administration on T2*‐weighted sequence diagnostic quality and signal intensity when imaging the canine brain. A total of 100 dogs underwent brain magnetic resonance imaging (MRI) including pre‐ and postcontrast T2*‐weighted sequences acquired with a delay (Group A) or immediately (Group B) following gadolinium administration. Pre‐ and postcontrast images were subjectively compared. In dogs with intracranial enhancing masses, regions of interest were drawn on corresponding images and signal intensity ratios were calculated. The effect of degree and pattern of contrast enhancement, susceptibility artifacts, and time between contrast injection and T2*‐weighted sequence acquisition on signal intensity ratio was evaluated. Overall 31 dogs had contrast enhancing intracranial masses. Subjectively, there was no difference in image quality of T2*‐weighted sequences obtained before and after contrast medium administration. No significant signal intensity differences of intracranial contrast enhancing masses were found (Group A P = 0.9999; Group B P = 0.9992). Susceptibility artifacts did not differ in appearance, and there was no effect on calculated signal intensity ratio (P = 0.8142). Similarly, there was no effect of degree of enhancement or contrast heterogeneity on signal intensity ratio (P = 0.4413). No correlation was found between signal intensity ratio and the time to acquisition (P = 0.199). Administration of gadolinium‐based MRI contrast agents does not adversely affect T2*‐weighted imaging of the brain in dogs at 1.5 T even in the presence of contrast enhancing lesions.
Deferoxamine can prevent pressure ulcers and accelerate healing in aged mice
Authors: Bonham Clark A. , Rodrigues Melanie , Galvez Michael , Trotsyuk Artem , Stern‐Buchbinder Zachary , Inayathullah Mohammed , Rajadas Jayakumar , Gurtner Geoffrey C.
Published: August 2018

Chronic wounds are a significant medical and economic problem worldwide. Individuals over the age of 65 are particularly vulnerable to pressure ulcers and impaired wound healing. With this demographic growing rapidly, there is a need for effective treatments. We have previously demonstrated that defective hypoxia signaling through destabilization of the master hypoxia‐inducible factor 1α (HIF‐1α) underlies impairments in both aging and diabetic wound healing. To stabilize HIF‐1α, we developed a transdermal delivery system of the Food and Drug Administration–approved small molecule deferoxamine (DFO) and found that transdermal DFO could both prevent and treat ulcers in diabetic mice. Here, we demonstrate that transdermal DFO can similarly prevent pressure ulcers and normalize aged wound healing. Enhanced wound healing by DFO is brought about by stabilization of HIF‐1α and improvements in neovascularization. Transdermal DFO can be rapidly translated into the clinic and may represent a new approach to prevent and treat pressure ulcers in aged patients.
Topical inhibition of PUMA signaling mitigates radiation injury
Authors: Kowzun Maria J. , Rifkin William J , Borab Zachary M. , Ellison Trevor , Soares Marc A. , Wilson Stelios C. , Lotfi Philip , Bandekar Amey , Sofou Stavroula , Saadeh Pierre B. , Ceradini Daniel J.
Published: August 2018

Radiation therapy is an effective treatment strategy for many types of cancer but is limited by its side effects on normal tissues, particularly the skin, where persistent and progressive fibrotic changes occur and can impair wound healing. In this study, we attempted to mitigate the effects of irradiation on skin using a novel transcutaneous topical delivery system to locally inhibit p53 up‐regulated modulator of apoptosis (PUMA) gene expression with small interfering RNA (siRNA). In an isolated skin irradiation model, the dorsal skin of C57 wild‐type mice was irradiated. Prior to irradiation, PUMA and nonsense siRNA were applied via a novel hydrogel formulation to dorsal skin and reapplied weekly. Skin was harvested at multiple time points to evaluate dermal siRNA penetration, mRNA expression, protein expression, dermal thickness, subcutaneous fat, stiffness, vascular hypertrophy, SCAR index, and reactive oxygen species (ROS) generation. Murine skin treated with topical PUMA siRNA via optimized hydrogel formulation demonstrated effective PUMA inhibition in irradiated tissue at 3–4 days. Tissue stiffness, dermal thickness, vascular hypertrophy, SCAR index, ROS levels, and mRNA levels of MnSOD and TGF‐β were all significantly reduced with siPUMA treatment compared to nonsense controls. Subcutaneous fat area was significantly increased, and levels of SMAD3 and Phospho‐SMAD3 expression were unchanged. These results show that PUMA expression can be effectively silenced in vivo using a novel hydrogel lipoplex topical delivery system. Moreover, cutaneous PUMA inhibition mitigates radiation induced changes in tissue character, restoring a near‐normal phenotype independent of SMAD3 signaling.
Revisiting the Pain Resource Nurse Role in Sustaining Evidence‐Based Practice Changes for Pain Assessment and Management
Authors: Allen Emily , Williams Anne , Jennings David , Stomski Norman , Goucke Roger , Toye Christine , Slatyer Susan , Clarke Trish , McCullough Kylie
Published: August 2018

Background

Effective pain management is unlikely to occur without consistent and timely assessments. To improve assessment and management of pain, ward‐based pain resource nurses were introduced in 2007 to facilitate hospital‐wide evidence‐based practice changes using three key targets. One‐year post implementation of this quality improvement project, promising results were revealed.

Aims

The purpose of this study, 8 years post implementation, was to (a) evaluate sustained practice improvements in pain assessment and management, (b) assess current pain resource nurse knowledge and attitudes to pain, (c) explore characteristics of the pain resource nurse role, as well as (d) any perceived contextual changes regarding study findings.

Methods

A mixed‐methods approach was used to address study aims. Quantitative data were collected from documentation audits and a “Knowledge and Attitudes Survey Regarding Pain.” Qualitative interviews explored the characteristics of the pain resource nurse role, and a focus group discussion explored the context of change.

Results

Significant improvements were observed for the documentation of pain scores on admission and for each nursing shift. Survey results highlighted potential knowledge deficits in key practice areas, even though interview findings suggested that pain resource nurses provided a resource for peers, raised awareness of best practice, and imparted knowledge to other ward staff. An important facilitator for the pain resource nurse role was the ongoing collaboration and support from specific pain teams, and barriers to engage in the role were competing workload priorities, and limited awareness among other ward staff.

Linking Evidence to Action

Implementing and sustaining evidence‐based practice change in clinical practice is challenging. Ongoing evaluation is necessary for identifying the long‐term implications of practice improvement interventions and issues that influence the adoption of evidence‐based practice. Strategies to address barriers, and to increase awareness and engagement of the pain resource nurse role with wider collaboration require further investigation.
PERCEIVING NATURAL EVIL THROUGH THE LENS OF DIVINE GLORY? A CONVERSATION WITH CHRISTOPHER SOUTHGATE
Authors: Deane‐Drummond Celia
Published: August 2018

Finding a way to come to terms with the disvalues in the evolutionary world is a particular challenge in the light of Neo‐Darwinian theories. In this article I trace the shift in Christopher Southgate's work from a focus on theodicy to a theologian of glory. I am critical of his rejection of the tradition of the Fall, his incorporation of disvalues into the work of divine Glory, and the specific theological weight given to scientific content. I offer a critique of Holmes Rolston III's approach to the valuation of nature that I believe has influenced Southgate's theology. Constructively, I offer an alternative that seeks to recover an understanding of the origin of evil and the Adamic event that draws on the work of Paul Ricoeur. I also draw on the work of anthropologist Tim Ingold for an alternative philosophical approach to evolution which opens up a space for a recovery of the concepts of creaturely Sophia and shadow Sophia in the work of Sergius Bulgakov.
ESSAYS IN HONOR OF CHRISTOPHER SOUTHGATE: INTRODUCTION
Authors: Sollereder Bethany , Robinson Andrew
Published: August 2018

This article is an introduction to the special issue of Zygon in honor of Christopher Southgate. Over the years he has made many significant contributions to the field of science and religion, and contributors have gathered to celebrate him on his sixty‐fifth birthday. This introduction includes some biographical background and an outline of the issue's contents.
Customer Satisfaction: Does Player Perception of Clay Court Quality Affect Court Maintenance Requirements? Evidence from Daily Maintenance and Player Feedback
Authors: Spohn David , Plossl Tim
Published: August 2018

This paper investigates participants’ perception of the quality of clay tennis courts (i.e. satisfaction) and its effect on costly court maintenance requirements. Using unique participant data collected at a tennis facility located in Brandon, Florida from November 1, 2017 to November 30, 2017, the use of structural equation modeling techniques show that participants’ perceptions are influenced by on-court amenities. Conditional regression analysis is used to confirm the findings and reflects that participant perception of the quality of clay courts is influenced by availability of shade (for breaks) and clarity of lines. After adjusting for participant skill level, the analysis finds that more skilled players are less likely to be influenced on the quality of clay courts by on-court amenities. The analyses confirm that by focusing on customer satisfaction, maintenance cost reduction can be realized.
Deviant Behavior in School Setting
Authors: Hanımoğlu Egemen
Published: August 2018

Deviant behavior has become a daunting problem lately. More pupils are displaying abnormal behavior and thus destabilizing learning processes within school settings. It is a well-known fact that teenagers usually learn how to adapt to society and that aberrant behavior may lead to problems with conformity to societal values. Although the main causes of deviant behavior have been elucidated, the problem, despite numerous studies, deviant behavior has not been fully understood by scholars. The notion of deviance is closely related to the definition of the social norm which was defined almost a hundred years ago. The present study aims to examine causes and effects of deviant behavior, and identify main strategies to combat the issue. The research methods employed included a theoretical framework analysis, literature review, and qualitative research. A set of recommendations for the teenagers with deviant behaviour and their parents were identified to help them adjust to society.
Physical Interpretation of Machine Learning Models Applied to Film Cooling Flows
Authors: Milani Pedro M. , Ling Julia , Eaton John K.
Published: August 2018

Current turbulent heat flux models fail to predict accurate temperature distributions in film cooling flows. The present paper focuses on a machine learning (ML) approach to this problem, in which the gradient diffusion hypothesis (GDH) is used in conjunction with a data-driven prediction for the turbulent diffusivity field αt. An overview of the model is presented, followed by validation against two film cooling datasets. Despite insufficiencies, the model shows some improvement in the near-injection region. The present work also attempts to interpret the complex ML decision process, by analyzing the model features and determining their importance. These results show that the model is heavily reliant of distance to the wall d and eddy viscosity νt, while other features display localized prominence.
Machine Learning-Driven Real-Time Topology Optimization Under Moving Morphable Component-Based Framework
Authors: Lei Xin , Liu Chang , Du Zongliang , Zhang Weisheng , Guo Xu
Published: August 2018

In the present work, it is intended to discuss how to achieve real-time structural topology optimization (i.e., obtaining the optimized distribution of a certain amount of material in a prescribed design domain almost instantaneously once the objective/constraint functions and external stimuli/boundary conditions are specified), an ultimate dream pursued by engineers in various disciplines, using machine learning (ML) techniques. To this end, the so-called moving morphable component (MMC)-based explicit framework for topology optimization is adopted for generating training set and supported vector regression (SVR) as well as K-nearest-neighbors (KNN) ML models are employed to establish the mapping between the design parameters characterizing the layout/topology of an optimized structure and the external load. Compared with existing approaches, the proposed approach can not only reduce the training data and the dimension of parameter space substantially, but also has the potential of establishing engineering intuitions on optimized structures corresponding to various external loads through the learning process. Numerical examples provided demonstrate the effectiveness and advantages of the proposed approach.
Milling Bifurcations: A Review of Literature and Experiment
Authors: Honeycutt Andrew , Schmitz Tony L.
Published: August 2018

This review paper presents a comprehensive analysis of period-n (i.e., motion that repeats every n tooth periods) bifurcations in milling. Although period-n bifurcations in milling were only first reported experimentally in 1998, multiple researchers have since used both simulation and experiment to study their unique behavior in milling. To complement this work, the authors of this paper completed a three year study to answer the fundamental question “Is all chatter bad?”, where time-domain simulation and experiments were combined to: predict and verify the presence of period-2 to period-15 bifurcations; apply subharmonic (periodic) sampling strategies to the automated identification of bifurcation type; establish the sensitivity of bifurcation behavior to the system dynamics, including natural frequency and damping; and predict and verify surface location error (SLE) and surface roughness under both stable and period-2 bifurcation conditions. These results are summarized. To aid in parameter selection that yields period-n behavior, graphical tools including Poincaré maps, bifurcation diagrams, and stability maps are presented.
Numerical Modeling of Thermally-Induced Vibration in Rotor Caused by Light-Rub Against Brush Seal
Authors: Cangioli Filippo , Pennacchi Paolo , Vania Andrea , Chatterton Steven
Published: August 2018

Clearance is of paramount importance for turbomachinery manufacturers to meet today’s aggressive power output, efficiency, and operational life goals. To minimize leakages, there are various seal types used, and new sealing concepts are in development. Because of their inherent flexibility and compliance, brush seals are capable of significantly reducing the leakage, and allow sufficient geometrical margins to accommodate design and operational variations of turbomachines.

Brush seals can be assembled at very tight or zero radial clearance or even with interference on the rotor to minimize the leakage. This means that the risk of contact between the rotor and the seal bristles exists, especially in case of zero clearance or interference. If the contact occurs, a hot-spot develops on the rotor and this may cause the vibration to diverge, resulting in a synchronous instability, the so-called Newkirk effect. The friction forces generated by rotor-to-stator rubs often cause a shaft thermal bow whose main effect on the machine dynamic behavior is a progressive change of the synchronous (1X) vibration.

The development of analytical tools able to model this phenomenon is therefore important to assess the rotordynamic stability during the design phase and avoid excessive vibrations which may have severe impact on the operability and on the mechanical integrity of the machine.

The objective of this paper is the development of a numerical model to analyze the dynamic behavior of real turbomachines subject to thermally-induced vibration caused by light-rub of the rotor against brush seals. The model developed in the paper is based on the work of Bachschmid et al. [1]: the dynamics is analyzed in the frequency domain using the standard rotordynamic model, whereas the heat transfer analysis, to calculate the temperature distribution and the associated thermal bow, is studied in the time domain. The contact analysis has been deeply revised, aiming at estimating suitable normal and tangential force and the friction heating generated by the contact. The bow determined by the thermal conditions has been reproduced using suitable bending moments, which have been applied to the beam elements in the rotordynamic model.
Experimental and Numerical Design Study for a Small Scale Jet-Stabilized Micro Gas Turbine Combustor
Authors: Hasemann Stefan , Seliger Hannah , Kutne Peter , Aigner Manfred
Published: August 2018

Micro gas turbines (MGT) used as combined heat and power (CHP) systems present interesting advantages over conventional CHP systems. For low power MGTs (1–3 kWel), a single stage jet-stabilized combustor is well suited to reach low emissions despite high preheat temperatures. Although several jet stabilized combustors in this power range have already been presented in literature, the influence of single design parameters was not described yet. Therefore this paper presents a design study with different combustor geometries. Besides the number of nozzles, also the diameter of air and fuel nozzles as well as the length of the mixing zone is varied. Experiments are performed in an atmospheric combustor test rig with preheat temperatures of 730°C. Additionally RANS-CFD simulations for selected conditions are carried out. The results indicate an inverse correlation between the number of nozzles (diameter adjusted for constant inlet velocities) and the emissions, where an increase in the number of nozzles leads to lower emissions and a shorter reaction zone. Changing the air nozzle diameter and therefore the jet velocity creates a different trend. As the pressure loss decreases with smaller inlet velocities, the CO- and NOx-emission levels increase. An extension of the mixing section as well as of the diameter of the fuel nozzles have only minor effects for the examined geometries. The knowledge acquired in this work helps to evaluate the influence of design parameter changes on the behavior of small scale jet-stabilized combustors and allows an optimization of the combustor design regarding flame length and emissions.
Experimental Study of Damper Position on Instabilities in an Annular Combustor
Authors: Mazur Marek , Nygård Håkon T. , Dawson James , Worth Nicholas
Published: August 2018

The present study experimentally investigates the effects of different circumferential damper configurations on the instabilities in an annular combustor. The combustor consists of multiple bluff body swirl stabilized flames. It is operated with an ethylene-air premixture at a power of 66 kW. Combinations of Helmholtz resonators are used as dampers circumferentially arranged around the combustion chamber. The tests are performed at operating conditions where the combustor is self-excited and characterized by a strong standing mode and periodic mode switching. For each test, the dynamic pressure is measured at different locations and overhead imaging of OH* of the entire combustor is conducted simultaneously at a high sampling frequency. The measurements are then used to compare the pressure fluctuations of the different cases in order to find the best positioning of the dampers. The azimuthal modes in the chamber are determined and the phase shift between OH* and pressure is analysed. Based on the Rayleigh criterion, these investigations allow us to find out if the dampers only remove energy from the pressure oscillations, or if they also influence the instability margins of the combustor and the flame dynamics. Finally, the results are compared with the theoretical findings in literature and observed discrepancies are discussed.
A Mixed-Fidelity Numerical Study for Fan-Distortion Interaction
Authors: Ma Yunfei , Cui Jiahuan , Vadlamani Nagabhushana Rao , Tucker Paul G.
Published: August 2018

Inlet distortion often occurs at off-design points when flow separates within an intake. This unsteady phenomenon could seriously impact fan performance. Fan-distortion interaction is a highly unsteady aerodynamic phenomenon. High-fidelity simulation can provide a detailed insight into these interactions. However, due to computational resource limitations, the use of eddy resolving methods for a fully resolved fan calculation is currently infeasible for industry. To solve this problem, a mixed-fidelity CFD method is proposed. This method uses the Large Eddy Simulation (LES) to resolve the turbulence associated with separation, and the Immersed Boundary Method with Smeared Geometry (IBMSG) for the fan. The method is validated by an experiment of Darmstadt Rotor, which shows a good agreement in terms of total pressure distributions.

A detailed investigation is then conducted on a subsonic rotor with an annular beam generating inlet distortion. A range of studies are performed to investigate fan influence on distortions. Compared to the case without fan, it shows that a fan has a significant effect in reducing distortions. Three fan locations are examined. The fan nearer to the inlet tends to have a higher pressure recovery. Three beams with different heights are also tested to generate various degrees of distortions. The results indicate that the fan can suppress the distortions and its recovery effect is proportional to the degree of inlet distortion.
A Test Rig Concept to Study Fluid Structure Interactions in a Steam Turbine Valve
Authors: Wallat Stefan , Domnick Clemens B. , Musch Christian , Brillert Dieter
Published: August 2018

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate a huge amount of energy in throttled operation mode. The dissipation process generates strong pressure fluctuations and leads to high dynamic forces potentially causing valve vibrations. A brief survey of the literature dealing with valve vibrations reveals that vibrational problems and damages mostly occur in throttled operation when jets, shocks and shear layers are present. Previous investigations of the authors reveal a feedback mechanism between the dynamic flow field and the vibrating valve plug. Depending on the flow topologies either axial or lateral forces will dominate the force spectrum.

In this paper the design of a test rig including a scaled model of a steam valve is described. As it is difficult to analyse lateral forces in conventional experiments the model is designed not only to study the flow conditions but also the lateral and axial movement of the valve plug. To investigate and model the dynamic characteristic of the valve the entire periphery including the mechanical drive, sealing etc. needs to be considered.

To ensure that fluid–structure-interactions are correctly scaled, dimensionless numbers derived with the Buckingham Pi Theorem are used as design criteria. Positions of the transmitters are selected based on results of numerical simulations.
The Interaction Between Inlet Guide Vanes and the Impeller Recirculating Flow in a Centrifugal Compressor and the Resulting Impact on Flow Range
Authors: Li Xiangjun , Spence Stephen , Wu Yanhui
Published: August 2018

This paper studies the interaction between the Inlet Guide Vane (IGV) and the typical recirculation flow that occurs close to surge in a turbocharger compressor to analyse its influence on compressor performance the potential to improve the surge margin. The CFD method was first validated by experimental data, then a series of simulations were conducted to study the lengths of various part-span IGVs and also the streamwise distance between the IGV and the impeller. The results showed that, when extensive recirculating flow was generated, the IGV no longer worked in a conventional way to guide the inflow in the tip region, but instead guided the recirculation flow ejected from the impeller inducer. A three-dimensional interaction occurred at the trailing edge of the IGV where the recirculation flow turned downwards along the span of the vane and caused blockage and swirling flow below the bottom of the part span IGV. All the cases with IGVs had a similar peak efficiency to the baseline compressor but produced different impacts on the mass flow rates at the near surge point and the choke point. The IGV with shortest length placed the three-dimensional recirculating flow at a higher span-wise position. The blockage and the preswirl were thereby generated closer to the shroud and produced a different flow field at the impeller inlet. Based on the numerical surge criteria, the shortest IGV was found to improve stability at the near surge point compared to the full-span IGV, with no reduction of the mass flow rate at the choke point to give 25% more flow range. The surge margin was mainly increased because of the improved pressure recovery in the diffuser due to the blockage being distributed in the higher-span region of the impeller inflow. The beneficial impact of the three-dimensional interaction on the flow range was found to be associated with the distance between the impeller and the IGV. Both the short and the full-span IGVs achieved less improvement of surge margin when the IGV was placed further upstream of the impeller, showing that the interaction between the reverse flow and the IGV was a beneficial flow feature for overall performance.
A Multi-Fidelity Sampling Method for Efficient Design and Optimization of Centrifugal Compressor Impellers
Authors: Schemmann Christoph , Geller Marius , Kluck Norbert
Published: August 2018

The optimization of a centrifugal compressor impeller is a challenge for established strategies and algorithms, as the interactions between the geometric design parameters and the aerodynamic and structural performance of the system are highly complex. Furthermore many geometrically valid designs are unusable in terms of structure mechanics or flow physics. Due to the complex parameter correlations, a simple limitation of the parametric space is no option, as possibly beneficial parameter combinations could be ruled out. To obtain a meaningful optimization result, the complete operation range of the compressor has to be taken into account which adds further complexities in terms of the optimization process and the computational expense. The combination of these issues leads to a complicated optimization scenario.

The aim of the presented work is the reduction of the computational expense required to generate a high quality metamodel for optimization. This goal shall be achieved by the development of a multi-fidelity sampling method. The basic idea is to use preliminary of low-fidelity information from empirical data or fast analytical methods to identify promising regions of the parameter space. Then the samples of the DOE are concentrated in these areas while still maintaining a good coverage of the whole applicable design space. This ensures that no beneficial designs are ruled out which were not recommended by preliminary information. The points of the resulting DOE are computed by CFD and FEA computations and used to generate the metamodel which is used for the optimization. The method is tested by generating a metamodel used for compressor optimization. The results are compared to an optimization using a metamodel based on a conventional Latin hypercube sampling.
The Effect of Turbulent Scales on Low-Pressure Turbine Aerodynamics: Part A — An Optimized Turbulent Boundary-Condition
Authors: Müller-Schindewolffs Christoph , Herbst Florian
Published: August 2018

Exact inflow conditions for DNS and LES can be generated by resource-intensive precursor simulations of three-dimensional periodic boxes or infinite channels, in the case where a wall-bounded flow is investigated. A cheaper and much more flexible alternative is the use of synthetic boundary conditions. In the proposed paper, a modified synthetic-eddy-method will be presented, which suits the demands and specifications of turbo-machinery applications. It will further be extended to subsonic compressible flows by adding a mechanism to uncouple acoustic waves. It is applied to synthetically reproduce the wake of a turbine test case and validated against the original cascade simulation which is presented in the according Part B paper. This highly flexible approach also provides interfaces to prescribe unsteady inflow conditions, by temporally changing velocities, Reynolds stresses, and turbulent length-scales.
Analysis of Steam Turbine Blade Tip Excitation Forces by Means of Computational Fluid Dynamics and Experimental Cascade Results
Authors: aus der Wiesche Stefan , Passmann Maximilian
Published: August 2018

A semi-empirical steam excitation force model is presented for freestanding unshrouded blades. The model is resting on a superposition of the classical Thomas-Alford cross forces and additional fluid derived forces. The additional fluid derived forces are caused by static pressure modifications in the blade tip region and large-scale redistributions of the inflow velocity caused by the varying tip gap width due to eccentricity. The empirical model parameters are obtained by means of computational fluid dynamics (CFD) and experimental turbine cascade results. The Thomas-Alford cross force contribution is formulated by means of an analytical relation for the effective discharge coefficient. It is found, that the Thomas-Alford coefficient for the excitation cross-force increases if the blade tip gap decreases. That effect is caused by taking viscous flow effects into account, and it is in good agreement with available literature data. The direct force contribution results mainly from local pressure variation in the blade tip region, and it depends also on the mean tip gap width. A further effect is caused by an upstream redistribution of the velocity due to the varying tip gap width. This effect was discovered by Song and Martinez-Sanchez first, and it is confirmed experimentally by cascade measurements in the present paper.
Characterization of an Aircraft Auxiliary Power Unit Test Rig for Cycle Optimization Studies
Authors: Zanger Jan , Krummrein Thomas , Siebel Teresa , Roth Jürgen
Published: August 2018

Detailed information of the thermodynamic parameters, system performance and operating behavior of aircraft APU cycles is rarely available in literature. In order to set up numeric models and study cycle modifications, validation data with well defined boundary conditions is needed. Thus, the paper introduces an APU test rig based on a Garrett GTCP36-28 with detailed instrumentation which will be used in a further step as a demonstration platform for cycle modifications. The system is characterized in the complete feasible operating range by alternating bleed air load and electric power output. Furthermore, simulations of a validated numerical cycle model are utilized to predict the load points in the operating region which were unstable during measurements. The paper reports and discusses turbine shaft speed, compressor air mass flow, fuel mass flow, efficiencies, compressor outlet pressure and temperature, turbine inlet and outlet temperature as well as exhaust gas emissions. Furthermore, the results are discussed with respect of the difference compared to a Hamilton Sundstrand APS3200.

Though the efficiencies of the GTCP36-28 are lower compared to the APS3200, the general behavior is in good agreement. In particular, the effects of separate compressors for load and power section are discussed in contrast to the GTCP36-28 system design comprising a single compressor. In general, it was shown that the GTCP36-28 is still appropriate for the utilization as a demonstration platform for cycle modification studies.
Estimating the Drag Developed by a High Bypass Ratio Turbofan Engine
Authors: Zawislak M. S. , Cerantola D. J. , Birk A. M.
Published: August 2018

A high bypass ratio turbofan engine capable of powering the Boeing 757 was considered for thrust and drag analysis. A quasi-2D engine model applying the fundamental thermodynamics conservation equations and practical constraints determined engine performance and provided cross-sectional areas in the low-pressure system. Coupled with suggestions on boat-tail angle and curvature from literature, a representative bypass duct and primary exhaust nozzle was created. 3D steady-RANS simulations using Fluent® 18 were performed on a 1/8th axisymmetric section of the geometry. A modified 3D fan zone model forcing radial equilibrium was used to model the fan and bypass stator. Takeoff speed and cruise operating conditions were modeled and simulated to identify changes in thrust composition and intake sensitivity. Comparison between net thrust predictions by the engine model and measured in CFD were within grid uncertainty and model sensitivity at cruise. Trends observed in a published database were satisfied and calculations coincided with GasTurb™ 8.0. Verification of thrust in this manner gave confidence to the aerodynamic performance prediction of this modest CFD. Obtaining a baseline bypass design would allow rapid testing of aftermarket components and integration techniques in a realistic flow-field without reliance on proprietary engine data.
The Effects of Water Ingestion on the Tip Clearance Flow in Compressor Rotors
Authors: Yang Lu , Wu Xiaocui , Qin Desheng , Zheng Qun , Zhang Hai
Published: August 2018

As the first core component of commercial aviation engines, compressor is likely to ingest a serious amount of liquid water into its path flow during the situation of heavy rain. Under the influence of centrifugal force, the tip region of compressor rotors may be filled with water. Unfortunately, the instability of tip clearance flow is a major reason for rotating stall. In order to explore the effects of water ingestion on the steady operating boundary of compressor, the change characteristics of tip clearance flow have been investigated in this research by using numerical simulation method. In reality, the compression process after water ingestion can be regarded as a special wet compression. Therefore, on the basis of existing wet compression study, the ingested mass flow and the mean droplet diameters were set as 1% of inlet air flow as well as 100 μm respectively to investigate how does water ingestion affects the flow field at the tip clearance of rotors.

The typical trajectory of water droplet in compressor has been researched firstly to simply understand the situation of water ingestion and to verify the reliability of some special droplet breakup models. Then, the compressor performance in two states of dry and wet have been compared to indicate that the pressure ratio and adiabatic efficiency of compressor will decrease after water ingestion. Among them, the compression efficiency drops by 1∼2% as a whole compared with the dry condition, the operating point moves forward and the surge margin reduces slightly.

The simulation results show that the presence of water droplets will change the distribution of airflow parameters along span direction, which leads to the decreases of mass flow rate and flow capacity of blade row, the increase of attack angel at tip region, and the separation of boundary layer in suction surface. Furthermore, the momentum losses caused by droplet impingement and breakup cause a sharp increase in the static entropy at the blade tip region as well. On the other hand, the ingestion of droplet brings an external disturbance to the flow, although it has some dissipated effects on the turbulence kinetic energy, it aggravates the unsteady characteristic of turbulent flow seriously at the tip region of blade.