bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional trait variation of Anemone nemorosa along macro‐ and microclimatic gradients close to the northern range edge
Authors: Depauw Leen , Hu Ri , Dhungana Khumanand S. , Govaert Sanne , Meeussen Camille , Vangansbeke Pieter , Strimbeck Richard , Graae Bente J. , De Frenne Pieter
Published: March 2022

Climate warming is affecting ecosystems worldwide, and slow‐colonizing forest understorey species are particularly vulnerable if they are unable to track climate change. However, species' responses to climatic conditions in terms of growth, reproduction and colonization capacity may vary with the distance to their distribution range edge. Anemone nemorosa is known to be a slow colonizing forest herb dependent on forest cover in the southern and central part of its distribution range, whereas at its northern distribution range (and at higher elevations) it also occurs in open habitats. Here, we investigated the response of plant functional traits of Anemone nemorosa in central Norway (close to its northern distribution range edge) to a macroclimatic gradient (elevation), two microclimatic gradients (forest density and distance to forest edge) and a competition treatment (removal of neighbouring vegetation). We aimed to identify which environmental conditions (light, temperature, soil pH and/or soil organic matter) drive A. nemorosa's responses. In a total of 90 plots, we measured six functional traits of A. nemorosa (plant height, biomass, specific leaf area, seed number, seed mass,and germination percentage). We found stronger variation in environmental conditions along the macroclimatic elevational gradient, than along the microclimatic gradients of forest density and distance to forest edge, and this was also reflected in A. nemorosa's responses. Light availability, in interaction with temperature, was the key environmental variable driving plant performance, while soil conditions were less important. The competition release treatment had a negative effect on A. nemorosa in our study sites, indicating that the facilitative effect of the neighbouring vegetation may be stronger than the competitive effect. Our study suggests that A. nemorosa, close to its northern distribution range edge, has the capacity to cope with climate change through phenotypic responses, and that light and temperature are the key drivers of these responses.
Retrospective evaluation of operator bias in the performance of high‐resolution anorectal manometry
Authors: Prichard David O. , Fetzer Jeffrey R.
Published: March 2022

Background

Measurements obtained during high‐resolution anorectal manometry (HRM) are subject to operator–patient interactions. For example, standardized enhanced instruction delivered by a single operator in a test–retest fashion did not consistently increase pressures generated during dynamic maneuvers. It is probable that factors other than verbal instruction effect communication during the procedure. To investigate this hypothesis, we retrospectively examined inter‐operator variance in HRM results.

Methods

The electronic health records at Mayo Clinic, Rochester, were used to identify patients who had undergone HRM in 2019 and 2020. The analysis focused on constipated patients. The instructions given to the patients they had examined, and the pressure measurements obtained during HRM, by 6 different nurse operators were compared.

Key Results

When performing HRM on their individual patients (range 126–673), the 6 nurses used similar instructions for each of the maneuvers and sensory testing thresholds. The proportion of patients with prolonged balloon expulsion tests and the rectal sensory thresholds were similar among operators. Significant variance was seen in the mean rectoanal pressures at rest, during squeeze, and during dynamic maneuvers. The proportion of patients with manometry results suggestive of a defecatory disorder differed between operators by 18% and 28% in women <50 and >50 years old, respectively.

Conclusions & Inferences

Operators obtain significantly different results during HRM despite using similar instructions to patients. Substantial differences in the proportion of patients with manometry findings suggestive of a defecatory disorder among operators may have a significant impact on the diagnoses and therapies offered to constipated patients.
Lack of hydraulic recovery as a cause of post‐drought foliage reduction and canopy decline in European beech
Authors: Arend Matthias , Link Roman Mathias , Zahnd Cedric , Hoch Günter , Schuldt Bernhard , Kahmen Ansgar
Published: March 2022

European beech (Fagus sylvatica) was among the most affected tree species during the severe 2018 European drought. It not only suffered from instant physiological stress but also showed severe symptoms of defoliation and canopy decline in the following year.

To explore the underlying mechanisms, we used the Swiss‐Canopy‐Crane II site and studied in branches of healthy and symptomatic trees the repair of hydraulic function and concentration of carbohydrates during the 2018 drought and in 2019.

We found loss of hydraulic conductance in 2018, which did not recover in 2019 in trees that developed defoliation symptoms in the year after drought. Reduced branch foliation in symptomatic trees was associated with a gradual decline in wood starch concentration throughout summer 2019. Visualization of water transport in healthy and symptomatic branches in the year after the drought confirmed the close relationship between xylem functionality and supported branch leaf area.

Our findings showed that embolized xylem does not regain function in the season following a drought and that sustained branch hydraulic dysfunction is counterbalanced by the reduction in supported leaf area. It suggests acclimation of leaf development after drought to mitigate disturbances in canopy hydraulic function.
Historical and cultural aspects of obesity: From a symbol of wealth and prosperity to the epidemic of the 21st century
Authors: Sumińska Marta , Podgórski Rafał , Bogusz‐Górna Klaudia , Skowrońska Bogda , Mazur Artur , Fichna Marta
Published: March 2022

World Health Organization defines obesity as abnormal or excess adipose tissue accumulation. Nowadays, this condition is a serious threat to the public health in most countries around the world. Obesity adversely affects physical, mental, and in most cultures, social well‐being. However, throughout the ages—from ancient times to the 21st century—this condition has been subject to various interpretations. As a matter of fact, obesity has not always been regarded as a disease. For many decades, excessive body weight has been considered rather a symbol of health. It was a marker of wealth and prosperity, as well as a sign of high social status. The centuries that passed on the development of science and medicine have gradually changed its face, but significant progress in understanding the causes and consequences of obesity has been made in the last 30 years. This paper presents the historical outline of obesity and its treatment from ancient times to the present—from its affirmation to the epidemic in the late 20th and 21st century.
Vision‐related symptoms, accommodative and binocular vision performance in young diabetics vs. normal controls
Authors: Nabovati Payam , Khabazkhoob Mehdi , Fayaz Faezeh , Rajabi Sattar , Asharlous Amir
Published: March 2022

Purpose

To compare accommodative and binocular vision performance between young diabetic subjects and normal controls, and to investigate the correlation of accommodative/binocular indices with the severity of diabetes.

Methods

Thirty young subjects with diabetes mellitus (DM) and 30 age‐matched normal controls were recruited in this hospital‐based cross‐sectional study. DM was diagnosed by a haemoglobin A1c (HbA1c) higher than 6.5%. The status of vision‐related symptoms was examined by the convergence insufficiency symptoms survey (CISS). All participants underwent a complete optometric examination including visual acuity measurement, objective and subjective refraction, accommodative and binocular vision assessments.

Results

All study participants were between 18 and 40 years of age. There were no statistically significant differences in best‐corrected visual acuity (BCVA), sphere, cylinder and spherical equivalent refraction (SE) between the diabetes and control groups. The median near point of convergence (NPC) was significantly more remote in diabetics compared with the control group. Mean accommodative amplitude (AA) and vergence facility (VF) and the median monocular accommodative facility (AF) were significantly lower in diabetic subjects compared with normal controls. In addition, the median accommodative lag in the diabetic group was significantly higher than the control group. A significantly higher percentage of the diabetic group were symptomatic (26.6%), compared with the controls (6.6%). The NPC and accommodative lag showed a significant positive correlation with the HbA1c level, while VF, AA and AF exhibited a significant negative correlation with HbA1c.

Conclusion

Aspects of accommodative and binocular vision performance are strongly affected by DM. There is also a significant correlation between accommodative and binocular disorders with the severity of DM. A significant percentage of young subjects with DM have severe vision‐related symptoms.
Exploring attention to the Canadian 24‐Hour Movement Guidelines for Children and Youth using eye‐tracking: A randomized control trial
Authors: Walters A. J. , Lithopoulos A. , Tennant E. M. , Weissman S. , Latimer‐Cheung A. E.
Published: March 2022

Background

The Canadian 24‐Hour Movement Guidelines for Children and Youth (“Guidelines”) not only pioneered the notion of an integrated movement continuum from sleep to vigorous‐intensity physical activity but also introduced a new branded Guideline visual identity.

Objectives

This study evaluated youths’ (N = 46) attention to and thoughts about the Guidelines and the brand.

Design

A cross‐sectional between‐participants randomized intervention design was used.

Sample

Canadian youth between 10 and 17 years of age comprised the study sample.

Interventions

Participants were randomly assigned to view either branded Guidelines (n = 26) or unbranded Guidelines (n = 20). Youths’ eye‐movements (e.g., dwell time, fixation count) were recorded during Guideline viewing. Participants completed a follow‐up survey assessing brand perceptions and Guideline cognitions.

Results

The branded Guidelines neither drew greater overall attention nor led to more positive brand perceptions or Guideline cognitions compared to the unbranded Guidelines.

Conclusions

Exploratory analyses provide valuable, yet preliminary insight into how branding and Guideline content may shape how Guidelines are perceived and acted upon. These findings inform an agenda for future health education resources.
Use of serum progesterone and prostaglandin F2α metabolite levels to predict onset of parturition in the bitch
Authors: Nöthling Johan Oliviette , Joonè Carolynne Jane , De Cramer Kurt G. M.
Published: March 2022

The prediction of time to onset of parturition in a preparturient bitch is of great clinical value, particularly for bitches at high risk of dystocia and those lacking relevant clinical data from the time of breeding. In a previous study, four cut‐offs for plasma progesterone levels, measured by radioimmunoassay, were shown to be useful for predicting the likelihood of a bitch entering stage one of parturition within defined time intervals. The first aim of the current study was to evaluate these cut‐offs in a clinical setting, using serum progesterone samples drawn from preparturient bitches 12‐hourly instead of 6‐hourly and assessed using chemiluminescence immunoassay. Furthermore, the use of 13,14‐dihydro‐15‐keto‐prostaglandin F2α, (PGFM), a metabolite of prostaglandin F2α, in predicting the time to onset of parturition was evaluated. Forty bitches carrying two or more foetuses were admitted to a specialist veterinary reproduction hospital 53 d after the onset of cytological dioestrus when that date was known, or 57 d after the last mating. Vaginal speculum examinations were performed every 6 hr until cervical dilatation was visualized (time of cervical dilatation; TCD). Serum samples were collected at 08h00 and 18h00 daily until TCD. All bitches underwent elective caesarean section at TCD. Results of this study show that approximately 5% and 10% of preparturient bitches will reach TCD within 12 hr despite a serum progesterone level of at least 15.8 nmol/L and 8.7 nmol/L respectively. In addition, there is a 95% probability that a preparturient bitch will reach TCD within 48 hr if her serum progesterone level is below 8.7 nmol/L, and a 91% probability of her reaching TCD within 24 hr if her serum progesterone level is below 3.18 nmol/L. Approximately 90% of bitches that demonstrate a 20% increase in PGFM over a 12‐hr period are likely to be within 36 hr of TCD. These results provide useful benchmarks for the management of canine parturition.
Recommendations from the Medical Education Editor
Authors: Lavercombe Mark
Published: March 2022

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Oral lesions and saliva alterations of COVID‐19 patients in an intensive care unit: A retrospective study
Authors: Eduardo Fernanda de Paula , Bezinelli Leticia Mello , Gobbi Marcella Ferreira , Bergamin Livia Goron , de Carvalho Danielle Lima Correa , Corrêa Luciana
Published: March 2022

Aim

To detect the type and frequency of oral lesions and clinical conditions suggestive of saliva alterations in COVID‐19 patients in an intensive care unit (ICU), as well as to describe the patient´s management in each case

Methods

Information about oral conditions and mechanical ventilation was collected from oral medicine records of COVID‐19 patients in an ICU (n = 519)

Results

From the total collected, 472 patients (90.9%) were examined by the oral medicine staff. In 242/472 patients (51.3%), alterations in the oral cavity were noted. The most frequent changes were mechanical trauma (18.1%, derived mainly from intubation), vascular/coagulation disturbances (24.1%, petechiae, bruises, varicoses, and oral bleeding), and saliva alterations (24.4%, dry mouth, and sialorrhea). Infectious lesions were mentioned in the oral medicine records (16.9%), most associated with a viral infection (15.7%), mainly herpesvirus. Improved oral change protocols included oral hygiene, use of specific medications, and laser therapy

Conclusion

COVID‐19 patients in the ICU often showed dryness in the oral and mucosa oral lesions related to vascular/coagulation disturbances, and mechanical trauma derived from orotracheal tube. An oral medicine staff must be aligned with the ICU multidisciplinary team to manage COVID‐19 patients, as well as to establish diagnoses and oral cavity treatments.
Embodied Othering Encounters with Muslim(‐Looking) Passengers: Riding across Amsterdam, Tallinn, Leipzig, and Turku1
Authors: Shaker Reza , Jungmann Annika , Zimmermann Philipp , Häkkinen Lotta , Tuvikene Tauri
Published: March 2022

Often framed in the public discourse as Europe’s ultimate Other, Muslims have been heftily debated and vastly problematized as violent, unfaithful suspect citizens, unwanted immigrants, part of a bad diversity, and refusal of modernity. Taking the Muslim Other into consideration, we explore young Muslim(‐looking) passengers’ everyday Othering encounters within the (im)mobile spaces of public transport that entangle their bodies with different imaginaries, histories, emotions, and affects. Employing qualitative research methods in a cross‐national and interurban study in Amsterdam, Tallinn, Leipzig, and Turku, which offer different dimensions of diversity, size, and history, important for understanding European cities in their complexities, we present public transport as a cross‐cultural meeting place with socio‐spatial negotiations of difference to study everyday travel experiences of 74 young Muslim(‐looking) passengers. We highlight how Othering discourses become part of their everyday travel experiences. In so doing, we investigate multiple modes through which the Muslim Other is (re)produced and Othering is lived out in the networks of their everyday embodied, that is, sensorial, corporeal, and affective, experiences of public transport. In this way, we critically position public transport at the intersection of what it means to experience European cities through riding public transport.
Absent‐Presence Present‐Absence: Places, Spaces, Rights for Young People
Authors: Skelton Tracey
Published: March 2022

Children and young people are everywhere (present) but often nowhere (absent). They can be seen but not heard, they may use their voice but not be listened to. As a substantially marginalised group of humans, they experience absence and presence in different ways to older people and are confronted with contradictory experiences and recognition. Children and youth face a range of disadvantages in relational comparison of understandings and interpretations of ‘adulthood’. They are described as unready, immature, unformed, citizens‐in‐waiting and caught in interstitial nowhere/everywhere betweenness. However, geographers of children and young people are engaging with political conceptualisations of younger people that provide space for discourse, dialogue and discussion combined with an ethics of seeing, looking, hearing, listening, supporting and including children and young people. This article spins out from the three Dossier papers and weaves a threaded analytical examination of absent/presence and present/absence.
Does the belt and road initiative stimulate Chinese exports? Evidence from micro data
Authors: Görg Holger , Mao Haiou
Published: March 2022

This paper evaluates firms' exporting responses to BRI and considers their heterogeneity in ownership types, product types, regional origin and trade mode. This is done by analysing firm–product–destination‐level customs data from 2008 to 2016. Our empirical results show that aggregate export behaviour increased significantly after BRI. However, ownership matters when evaluating firms' reactions, with SOEs and foreign firms benefitting, but privately owned domestic firms not. Furthermore, our results on regional heterogeneity suggest that ‘open through the west’, that is boosting the development of western regions in China, did not appear to work in the short term. Our findings show clearly the implications of BRI's impact from a firm‐level perspective.
Retrospective evaluation of phacoemulsification and aspiration in 182 eyes: Visual outcomes and CDE‐predictive value
Authors: Edelmann Michele L. , Mohammed Hussni O. , Ledbetter Eric C.
Published: March 2022

Objective

To determine the effect of cumulative dissipated energy (CDE) on complications and visual outcome following cataract surgery in dogs.

Animals studied

Records of 182 canine eyes that had undergone cataract surgery.

Procedures

Retrospective medical record review was conducted on dogs that underwent unilateral or bilateral elective cataract surgery by a single surgeon. Preoperative variables such as age, cataract duration, and pre‐existing conditions were recorded. Intraoperative variables such as intraocular lens (IOL) status, phacoemulsification time, average power, irrigation fluid volume, and CDE were recorded. Postoperative complications and visual status at last follow‐up were compared to these variables.

Results

Eighty‐six percent of dogs were visual in one or both eyes at last follow‐up (LFU) examination. Median follow‐up time was 186 days postoperatively. Eyes that developed glaucoma had a significantly greater mean CDE (77.73 ± 80.11) than eyes that did not develop glaucoma (49.21 ± 38.93). Eyes that remained visual at the LFU examination had a significantly lower mean CDE (48.31 ± 37.14) than eyes that were blind at LFU (82.05 ± 82.73). Significantly lower mean CDEs were found in diabetic eyes, younger eyes, early‐operated eyes (<1 month duration), and eyes with preoperative lens‐induced uveitis.

Conclusions

Higher CDE may be associated with an increased risk of postoperative glaucoma and loss of vision in dogs. Cumulative dissipated energy may be a useful prognostic indicator for success of canine cataract surgery.
Prevalence of anti‐severe acute respiratory syndrome coronavirus 2 antibodies in cats in Germany and other European countries in the early phase of the coronavirus disease‐19 pandemic
Authors: Adler Julia Maria , Weber Corinna , Wernike Kerstin , Michelitsch Anna , Friedrich Karin , Trimpert Jakob , Beer Martin , Kohn Barbara , Osterrieder Klaus , Müller Elisabeth
Published: March 2022

During the first months of the coronavirus disease (COVID‐19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), cases of human‐to‐cat transmission were reported. Seroconversion was shown in cats infected under experimental and natural conditions. This large‐scale survey of 1,005 serum samples was conducted to investigate anti‐SARS‐CoV‐2 antibody prevalence in domestic cats during the first 7 months of the pandemic in Germany and other European countries. In addition, we compared the sensitivity and specificity of two multispecies SARS‐CoV‐2 antibody enzyme‐linked immunosorbent assays (ELISA). Results were confirmed by using an indirect immunofluorescence test (iIFT) and a surrogate virus neutralization test (sVNT). Sera that were highly positive for feline coronavirus (FCoV) antibodies (n = 103) were included to correct for cross‐reactivity of the tests used. Our results showed an overall SARS‐CoV‐2 seropositivity of 1.9% (n = 19) in a receptor‐binding domain (RBD)‐based ELISA, additional 0.8% (n = 8) were giving inconclusive results. In contrast, a nucleocapsid‐based ELISA revealed 0.5% (n = 5) positive and 0.2% (n = 2) inconclusive results. While the iIFT and sVNT confirmed 100% of positive and 50%–57.1% of the doubtful results as determined in the RBD ELISA, the nucleocapsid‐based assay showed a high discrepancy and only one of the five positive results could be confirmed. The results indicate significant deficits of the nucleocapsid‐based ELISA with respect to sensitivity and specificity. Due to a significantly higher rate (5.8%) of positive results in the group of highly FCoV antibody‐positive samples, cross‐reactivity of the FCoV‐ELISA with SARS‐CoV‐2 antibodies cannot be excluded. Furthermore, we investigated the impact of direct contact of domestic cats (n = 23) to SARS‐CoV‐2 positive owners. Considering one inconclusive result, which got confirmed by iIFT, this exposure did not lead to a significantly higher prevalence (4.4%;p = .358) among tested subjects. Overall, we conclude that cats are a negligible entity with respect to virus transmission in Europe.
Controlling ion channel function with renewable recombinant antibodies
Authors: Colecraft Henry M. , Trimmer James S.
Published: March 2022

Selective ion channel modulators play a critical role in physiology in defining the contribution of specific ion channels to physiological function and as proof of concept for novel therapeutic strategies. Antibodies are valuable research tools that have broad uses including defining the expression and localization of ion channels in native tissue, and capturing ion channel proteins for subsequent analyses. In this review, we detail how renewable and recombinant antibodies can be used to control ion channel function. We describe the different forms of renewable and recombinant antibodies that have been used and the mechanisms by which they modulate ion channel function. We highlight the use of recombinant antibodies that are expressed intracellularly (intrabodies) as genetically encoded tools to control ion channel function. We also offer perspectives of avenues of future research that may be opened by the application of emerging technologies for engineering recombinant antibodies for enhanced utility in ion channel research. Overall, this review provides insights that may help stimulate and guide interested researchers to develop and incorporate renewable and recombinant antibodies as valuable tools to control ion channel function.

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UPed: A Quadruped Robot Platform to Study Directional Leg Compliance
Authors: Gurney Jason , Samare Filsoofi Ali , McClain Eric , Bolejack Chris , Aboufazeli Mahtab , John Mathews V. , Meek Sanford
Published: March 2022

This paper presents UPed, a quadruped robot platform, for studying passive, directional, leg compliance in robots. This work was motivated by the benefits provided by passively and directionally compliant legs in humans and animals. UPed uses under-actuated legs based on the bent-knee model which is capable of changing the direction and magnitude of the leg compliance by adjusting the knee angle and distal leg stiffness. Pneumatic pistons were chosen as variable compliance elements, enabling the leg compliance to be adjusted during locomotion. The platform was validated experimentally by evaluating how the robot’s pitch rate and cost of transport changed with variations in leg compliance and knee angle. Results of these experiments indicated that significant performance improvements are possible by selecting appropriate values of compliance and knee angle. They also demonstrated a unique capability to explore adjustable directional compliance and other parameters in robot legs on a physical robotic system. UPed has the potential to facilitate significant performance improvements of legged robots by enabling additional in-depth studies on directional passive leg compliance.
Design and Analysis of Both Dimensional and Geometric Tolerances in a Variational Geometry-Based Design Environment
Authors: Dong Jian
Published: March 2022

This paper describes an ongoing research on developing an analytical approach to optimal allocation of both dimensional and geometric tolerances. Current researches and industrial practices only focus on dimensional tolerances allocations, and geometric tolerances are not considered. Four major issues are discussed in this paper, they are: (1) analyzing constraint variations and tolerance sensitivity in a variational geometry-based design environment, (2) establishing an optimization model for allocating both geometric and dimensional tolerances, (3) identifying the geometric and manufacturing relationships between dimensional and geometric tolerances, (4) solving the optimization model and comparing the results. As an example, the optimal allocation of both dimensional and geometric tolerances for a precision slideway is presented.
Product Modularization for Reuse and Recycling
Authors: Sosale Swaroop , Hashemian Mehdi , Gu Peihua
Published: March 2022

Modular products consist of detachable modules, some of which may be recyclable, reusable or remanufacturable upon product retirement. This paper presents an integrated modular design methodology for environment conscious design and manufacturing. The methodology identifies the factors related to the design objectives, relates these factors to design components through interaction analysis, and clusters components into modules. An example is provided to illustrate the methodology and the algorithms.
Evaluating Reuse and Remanufacture Potential Using a Simple Model for Product Value
Authors: Sutherland John W. , Daniel Cecil M. , Vadrevu Srikanth , Olson Walter W.
Published: March 2022

Manufacturers around the world are currently evaluating new strategies to effectively utilize resources and enhance their competitiveness in the marketplace. Global concern about the environmental impacts of the manufacture and use of a multitude of products have led manufacturers to consider extensive reuse, remanufacture and recycling of products. Today, manufacturers also face legislation to “take back” their used products. Over the useful life of a product, changes occur in the mean and variance of the performance parameters. A new metric “satisfaction” has been introduced that combines the benefits and losses associated with use of the product. The change in product performance over its useful life is modeled by extending the concepts of loss and benefit over a third dimension — time. An estimate of product value may now be made at any point in the useful life of a product. A knowledge of the value could guide such decisions as the optimum time at which to remanufacture a product. Additionally, the model of product value may facilitate creation of an environmentally friendly product by raising issues such as performance degradation and reusability early in the design stage.
Analysis of Fluid-Structure Interaction by Means of Dynamic Unstructured Meshes
Authors: Blom F. J. , Leyland P.
Published: March 2022

This paper presents a computational analysis on forced vibration and fluid-structure interaction in compressible flow regimes. A so-called staggered approach is pursued where the fluid and structure are integrated in time by distinct solvers. Their interaction is then taken into account by a coupling algorithm. The unsteady fluid motion is simulated by means of an explicit time-accurate solver. For the fluid-structure interaction problems which are considered here the effects due to the viscosity can be neglected. The fluid is hence modeled by the Euler equations for compressible inviscid flow. Unstructured grids are used to discretise the fluid domain. These grids are particularly suited to simulate unsteady flows over complex geometries by their capacity of being dynamically refined and derefined. Dynamic mesh adaptation is used to enhance the computational precision with minimal CPU and memory constraints. Fluid-structure interaction involves moving boundaries. Therefore the Arbitrary Lagrange Euler method (ALE-method) is adopted to solve the Euler equations on a moving domain. The deformation of the mesh is controlled by means of a spring analogy in conjunction with a boundary correction to circumvent the principle of Saint Venant. To take advantage of the differences between fluid and structure time scales, the fluid calculation is subcycled within the structural time step. Numerical results are presented for large rotation, pitching oscillation and aeroelastic motion of the NACA0012 airfoil. The boundary deformation is validated by comparing the numerical solution for a flat plate under supersonic flow with the analytical solution.
A Finite Volume Method for the Computation of Fluid Flow With Moving Grid for Fluid-Structure Interactions
Authors: Mounsif S. , Mesquita A. L. Amarante
Published: March 2022

A finite-volume numerical method is presented for the solution of the two-dimensional incompressible, unsteady Navier-Stokes equations in general moving curvilinear co-ordinates. The method employs the semi-strong conservation form of the governing equations with pressure and physical contravariant velocity components as dependent variables. The k-ε model is utilised to describe the turbulent flow process. The SIMPLE algorithm is used to handle the pressure-velocity coupling. Results for the calculation of the fluctuating flow past an airfoil are compared with the available experimental data. As a simulation of fluid-structure interaction, the calculation of the unsteady flow-field around a stay-vane hydrofoil in forced and free vibration is presented. The numerical results obtained in this work show very good agreement with experimental observations.
Lift Coefficient Variation on a Cylinder Forced to Oscillate
Authors: Bernhardt John E. , Mihailovic Jadran , Jines Carlos F. , Abouel-Fotouh Aziz , Corke Thomas C. , Williams David R.
Published: March 2022

The instantaneous pressure distribution around the azimuth of a cylinder undergoing forced oscillations is measured using an array of 18 miniature microphones. The microphones were placed at the midspan of the cylinder with 20 degree increments between each sensor. The Reynolds number for the experiments was 13,800. The cylinder is driven in a sinusoidal motion by a printed circuit motor with an amplitude A/D = 0.18 and with bare winding numbers (Ω = f/fn) of 0 ≤ Ω ≤ 1.1. Regions of lock-in between the cylinder motion and the lift coefficient were observed at dressed winding numbers of ω = 2:3, 1:2 and 1:1. Phase diagrams show two distinctly different synchronization mechanisms, one fundamental and the other a subharmonic type, which supports the findings of Ongoren and Rockwell (1988).
A Physical Explanation of the Destabilizing Effect of Damping
Authors: Païdoussis M. P. , Semler C. , Alighanbari H.
Published: March 2022

In this paper, the destabilization due to small damping of the follower force system, known as Beck’s problem, and of the pipe conveying fluid system, two nonconservative systems, is considered. Instead of looking for a mathematical explanation, e.g. the evolution of the eigenvalues with different parameters, a more ‘physical’ explanation is provided. It is shown that it is of particular interest to focus on the different modes of vibration and to understand how they evolve when damping is varied. Also, based on energy considerations, the key factors influencing the dynamic stability are highlighted, e.g. the phase angles between the different coordinates. In the case of the pipe conveying fluid, the methodology developed and insight gained help explain the presence of ‘jumps’ in the stability curves, that are known to play an important role in the linear and nonlinear dynamics of this system.
Effect of Tube-to-Tube Ties on Fluidelastic Instability of Tube Arrays Exposed to Crossflow
Authors: Eisinger Frantisek L. , Rao Madhava M.
Published: March 2022

Tube-to-tube ties and their arrangement within the tube array are shown to affect the onset of fluidelastic instability. The influence of tie arrangement for a single tube row and for an in-line tube array is obtained by numerical simulation using S.S. Chen’s unsteady flow theory. Maps of dimensionless critical velocities for groups of tubes consisting of 2, 3, 4 and 5 tubes tied to each other are developed for several design configurations. It is shown that the stability limits can be raised by appropriate choice of tube group and tie location.
Fretting-Wear Damage of Heat Exchanger Tubes: A Proposed Damage Criterion Based on Tube Vibration Response
Authors: Yetisir M. , McKerrow E. , Pettigrew M. J.
Published: March 2022

A simple criterion is proposed to estimate fretting-wear damage in heat exchanger tubes with clearance supports. The criterion is based on parameters such as vibration frequency, mid-span vibration amplitude, span length, tube mass and an empirical wear coefficient.

It is generally accepted that fretting-wear damage is proportional to a parameter called work-rate. Work-rate is a measure of the dynamic interaction between a vibrating tube and its supports. Due to the complexity of the impact-sliding behavior at the clearance-supports, work-rate calculations for heat exchanger tubes require specialized non-linear finite element codes. These codes include contact models for various clearance-support geometries. Such non-linear finite element analyses are complex, expensive and time consuming. The proposed criterion uses the results of linear vibration analysis (i.e., vibration frequency and mid-span vibration amplitude due to turbulence) and does not require a non-linear analysis. It can be used by non-specialists for a quick evaluation of the expected work-rate, and hence, the fretting-wear damage of heat exchanger tubes.

The proposed criterion was obtained from an extensive parametric study that was conducted using a non-linear finite element program. It is shown that, by using the proposed work-rate criteria, work-rate can be estimated within a factor of two. This result, however, requires further testing with more complicated flow patterns.
Experimental Determination of Motion-Dependent Fluid Forces in Two-Phase Water-Freon Cross Flow
Authors: Delenne B. , Gay N. , Campistron R. , Banner D.
Published: March 2022

As flow-induced damage is a major concern for designers and operators of industrial heat exchangers and steam generators, some methodologies have been recently proposed to obtain a more accurate estimation of the critical flow velocity. These methodologies are based on unsteady semi-analytical models for fluid-dynamic forces, associated with dimensionless fluid force coefficients generally obtained from experiments. The present paper deals with new experiments performed on a square in-line tube bundle, subjected to two-phase water-freon cross-flow. A large range of void fractions and flow velocities has been investigated, up to fluidelastic instability threshold. Experimental results are analyzed first to derive evolution of frequency, damping ratio and tube motion amplitude evolution versus flow velocity and void fraction. Special attention is then focused on the determination of two-phase fluidelastic coefficients. Either homogeneous, slip or drift-flux models are used to describe two-phase flow characteristics and to dimensionalize the fluidelastic force coefficients. As a final step, the two-phase fluidelastic coefficients are compared to previously published data.
Improved Estimation of Fluidelastic Instability Threshold for Tube Arrays in Two-Phase Flow: Approximate Theory Based on Energy Balance in a Separated Flow Model
Authors: Nakamura Tomomichi , Kusakabe Takaya , Nishikawa Hideo
Published: March 2022

The stability boundary of tube arrays subjected to liquid-gas two-phase flow is usually estimated by a criterion similar to that for single-phase flow based on Connors’ equation. However, it has been revealed that two-phase flow instability is much more complex in our previous paper, where there exists two types of instability, intermittent instability and absolute instability.

Our theory is based on the assumption that the two phases liquid-phase and gas-phase can be separated on average. In this meaning the model is called a “separated flow model.” For each fluid phase, the energy balance between the excitation energy by fluid flow and the dissipation energy by tube vibration itself is estimated. By equating these two quantities (on average) the instability boundary is determined.

The flow distribution along the tube axis is not usually uniform. In our previous work this distribution effect was not considered. In this paper, our theory based on the energy balance in each separated flow component is expanded to include the flow-distribution effect along the tube axis.

Finally, a new criterion is for use at the practical design stage is formulated. An example showing comparison between the new criterion and the “Connors’ type formulation” is also presented.
A Theoretical Model for the Nonlinear Planar Motions of Rotors Under Fluid Confinement
Authors: Antunes José , Mendes Jorge , Grunenwald Thierry
Published: March 2022

In previous papers (Axisa & Antunes 1992, Antunes et al. 1996) the authors presented simplified theoretical models for both centered and eccentric immersed rotors, under moderate confinement (with reduced gaps δ = H/R of about 0.1, where H is the annular fluid gap and R is the rotor radius). In those papers rotor dynamics were modeled using linearised flow equations on the gap-averaged fluctuating quantities. Such simplified models enabled us to predict with reasonable success the modal parameters of the coupled system and the stability boundaries, as a function of the annulus geometry and rotor spinning velocity.

However, experiments have shown a progressive deterioration of the theoretical predictions at high spinning velocities as well as at large eccentricities. Such deterioration might be due to nonlinear effects which became significant near and beyond the stability boundaries. Hence, better predictions might be produced if the nonlinear terms of the flow equations were fully accounted — an issue which is pursued in this work. Because such nonlinear analysis is quite involved, this paper will focus on the simpler case of planar motions, in order to emphasize the main aspects of our approach.

A direct integration of the continuity and momentum equations leads to extremely lengthy formulations, which are very difficult to manipulate — even using symbolic computational tools. In this paper we discuss several strategies to obtain approximate solutions of the flow equations. Then we proceed with the actual approach used, which consists on the exact integration of the continuity equation and an approximate solution of the momentum equation, based on a Fourier representation of the azimuthal pressure gradient. We then obtain an exact formulation for the dynamic flow force.

The solution thus obtained is discussed in connection with physical phenomena. Numerical simulations of the nonlinear system dynamics are presented, which display interesting features. The linearised and the fully nonlinear models produces very similar results when the eccentricity and the spinning velocity are low. However, if such conditions are not met, the qualitative behavior stemming from these models is quite distinct. Experimental results indicate that the nonlinear flow model leads to better predictions of the rotor dynamics when the eccentricity is significant, when approaching instability and for linearly unstable regimes.
Hydroelastic and Vibroacoustic Behavior of Shells of Revolution
Authors: Berot François , Peseux Bernard
Published: March 2022

We propose two numerical models which couple the Finite Elements Method to the Boundary Elements Method. These models are designed to study the hydroelastic or vibroacoustic behavior of shells of revolution immersed in an unbounded fluid. The axisymmetric thin shell is idealized into two-node conical Ring Finite Elements. The Boundary Integral representation of the unbounded exterior fluid is discretized in two ways. The first approach uses a plane panel Boundary Element to idealize the solid-fluid interface. This quadrangular element supports constant densities of singularities. The second solution has led us to develop new Ring Boundary Elements. These elements are similar to Ring Finite Elements and make it possible to model a section of the fluid-structure interface. In this formulation, the densities of singularities are expanded in Fourier series of the circumferential variable. The coupling of Ring Finite Elements and Ring Boundary Elements widely reduces the classical numerical difficulties associated to coupled problems such as important CPU time and large storage memory.
Aeroelastic Analysis of a Trimmed Generic Hypersonic Vehicle
Authors: Nydick Ira , Friedmann Peretz P.
Published: March 2022

The aeroelastic equations of motion governing a hypersonic vehicle in free flight are derived. The equations of motion for a translating and rotating flexible body using Lagrange’s equations in terms of quasi-coordinates are presented. These equations are simplified for the case of a vehicle with pitch and plunge rigid body degrees of freedom and small elastic displacements. The displacements are approximated by a truncated series of the unrestrained mode shapes, which are obtained using equivalent plate theory. Subsequently, the nonlinear equations of motion are linearized about the trimmed vehicle state in horizontal flight. Unsteady aerodynamic loads for the vehicle and the appropriate stability derivatives are calculated from piston theory. The methodology for calculating the aeroelastic stability boundaries is also described. Numerical results are currently being generated.
Re-Engineering of an Aeroelastic Code for Solving Eigen Problems in All Flight Regimes
Authors: Lesoinne Michel , Farhat Charbel
Published: March 2022

We describe a new method for computing an arbitrary number of eigen solutions of a given aeroelastic problem. The proposed method is based on the re-engineering of a three-way coupled formulation previously developed for the solution in the time domain of nonlinear transient aeroelastic problems. It is applicable in subsonic, transonic, and supersonic flow regimes, and independently from the frequency or damping level of the target aeroelastic modes. It is based on the computation of the complex eigen solution of a carefully linearized fluid/structure interaction problem, and relies on the inverse orthogonal iteration algorithm. We illustrate this method with the stability analysis of a flat panel with infinite aspect ratio in supersonic airstreams and the AGARD 445.6 aeroelastic wing. For these aeroelastic problems, we show that the results produced by the proposed eigen solution method are in excellent agreement with those predicted analytically and numerically as well as with experimental data.
Numerical and Experimental Analyses of Segmented Modal Sensors
Authors: Sumali Hartono , Cudney Harley H. , Meissner Karsten
Published: March 2022

This paper presents results of numerical and experimental analyses to verily a new method to create modal sensors. A modal sensor is created by using rectangular segments of piezoelectric film and multiplying the segment outputs by certain gains so that the weighted combinations of the outputs approximate modal coordinates (Sumali and Cudney, 1993).

The method is tested on a beam with simple boundary conditions. The beam is covered with segments of piezoelectric film. It is shown that combining the outputs from the segments with correct weights results in a sensor that is sensitive to only a selected vibration mode of the beam and filters out other modes.
MEMS-Based Control of Structural Dynamic Instability
Authors: Chase J. Geoffrey , Yim Mark , Berlin Andrew A. , Maclean Brian. J. , Olivier Marc , Jacobsen Stephen C.
Published: March 2022

This paper describes the design, analysis and characterization of a prototype active column that applies distributed MEMS technology to a relatively new and technically challenging problem in smart structure design: the active stabilization of a buckling compressive member. The axial load bearing capacity of structural members can be increased by actively controlling the dynamic instability of buckling. Effective active stabilization is dependent on three primary factors: sensor precision, actuator authority, and control system bandwidth. A networked array of MEMS sensors, filamentary PZT actuators, and recently developed optimal control strategies are combined to demonstrate active control of an inherently unstable column. The active system, designed and simulated using finite element and optimization methods, stabilizes the column for compressive axial loads up to 2.94 times the critical buckling load. Additionally, the system is stable for all loads in the range from tension to this maximum compressive axial load.
Tensegrity Prisms as Adaptive Structures
Authors: Oppenheim Irving J. , Williams William O.
Published: March 2022

Tensegrity prisms are three-dimensional self-stressing cable systems with a relatively small number of disjoint compression members. Invented by Buckminster Fuller, they form novel structural geometries and constitute a class of mechanisms that have not been previously studied in depth. They have a number of seemingly advantageous properties — they are self-erecting, in that tensioning the final cable transforms them from a compact group of members into a large three-dimensional volume, and they are predominately tension systems. However, they have a number of properties that make them seemingly inappropriate for use — they are not conventionally rigid, they exist only under specific conditions of geometry with a corresponding prestress state, and when they exist the governing equations include singular (non-invertible) matrices. The mathematics of tensegrity geometry, statics, and kinematics have not been fully formulated, and such mathematical results must be developed and assembled before applications can be undertaken. This paper describes the physical behavior of a basic family of tensegrity prisms, presents the most useful available mathematical results, and outlines observations from an experimental study.