bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Diagnosis of Mimicking Tumor Discs Using Coronal Magnetic Resonance Imaging of Three‐Dimensional Fast‐Field Echo with Water‐Selective Excitation: A Single Center Retrospective Study
Authors: Yuan Jinghong , Du Zhi , Wu Zhiwen , Yin Jianhua , Cheng Bingxue , Xiong Xi , Zheng Sikuan , Liu Xijuan , Jia Jingyu , Cheng Xigao
Published: November 2022

Objective

As disc fragment completely loses contact with the parent disc and can migrate in all directions of the epidural space, making it appear similar to schwannoma, it is fairly difficult to make a definitive diagnosis for mimicking tumor discs. The aim of this research is to differentially diagnose mimicking tumor discs and schwannomas using coronal magnetic resonance imaging (MRI) of three‐dimensional fast‐field echo with water‐selective excitation (CMRI).

Methods

Among 76 patients (38 men and 38 women; mean age, 52.88 ± 15.80 [range, 18–78 years]) who were retrospectively examined in this study, 38 were primarily diagnosed with schwannomas and pathologically diagnosed with mimicking tumor discs after surgery, and 38 were primarily diagnosed with neurogenic tumors and pathologically diagnosed with schwannomas after surgery. Open surgery was performed in all the patients between March 2016 and April 2020. The preliminary diagnosis of all patients was considered an intraspinal tumor based on conventional two‐dimensional MRI sequences. After open surgery, the final diagnosis was confirmed to mimic a tumor disc or schwannoma based on postoperative pathology reports. The sensitivity, specificity, and reliability of CMRI and conventional MRI for identifying mimicking tumor discs and schwannomas were compared. Chi‐square and McNemar tests were used for statistical analyses.

Results

Symptoms were considerably relieved in all the patients after surgery. Seven patients had grade 1 extensor digitorum longus, triceps surae, or quadriceps femoris muscle strength prior to surgery. No nerve root injury was observed in any of the patients. CMRI showed significantly higher sensitivity (94.74%) and specificity (94.74%) than conventional MRI (71.05% and 92.11%, respectively; p = 0.012 < 0.05, and p = 1 > 0.05, respectively) for differential identification between mimicking tumor discs and schwannomas. Moreover, CMRI showed a higher reliability (kappa value = 0.787) than conventional MRI (kappa value = 0.374).

Conclusions

CMRI is a better non‐invasive technology for the identification of intraspinal lesions, especially for differentiating between mimicking tumor discs and schwannomas.
A Modified Arthroscopic Outside‐in Shoulder Release Approach for Severe Shoulder Stiffness
Authors: Zhang Xu‐chao , Liu Kang , Ying Hua , Yao Gai , Fu Xia‐wei , Zhou Bo‐le , Zhou Zhi‐you , Wang Zi‐min
Published: November 2022

Objective

Arthroscopic release is effective for patients with shoulder stiffness, but the traditional inside‐out procedure cannot effectively alleviate the mobility of some severe stiff shoulder and even cause itrogenic injuries sometimes. The aim of this study is to evaluate the clinical efficacy and advantages of a modified outside‐in shoulder release approach for severe shoulder stiffness.

Methods

Included in this retrospective study were 15 patients (five male and 10 female) with severe shoulder stiffness who underwent modified outside‐in shoulder release surgery at our hospital between June 2019 and March 2021. Of them, 10 patients had a primary frozen shoulder and five had secondary shoulder stiffness, involving the right shoulder in six cases and the left shoulder in nine cases. The mean age of the 15 patients was 56.7 (34–69) years. The patients were instructed to exercise passively from second‐day post‐operation and enhance the rehabilitation exercise gradually. All patients received a range of motion (ROM) examination before and after surgery. The American Shoulder and Elbow Surgeon's Score (ASES), Constant Score (CS), and Visual Analog Scale (VAS) score for pain were recorded. All data were tested by normal distribution first and then by paired T test, otherwise by Wilcoxon rank sum test.

Results

The mean follow‐up period was 18.2 (12–33) months. Compared with the preoperative value, the mean ASES score at the final follow‐up improved from 38.4 ± 7.37 to 88.13 ± 6.33 points; the mean CS score from 43.27 ± 6.71 to 78.74 ± 6.93 points; the mean VAS score from 5.07 ± 1.03 to 0.81 ± 0.83 points; forward flexion from 81.93° ± 11.45° to 156.73° ± 9.12°; abduction from 65.93° ± 16.82° to 144.80° ± 8.83°; neutral external rotation from 13.53° ± 10.38° to 51.20° ± 4.77°; internal rotation from the buttock to waist (L3), all showing a significant difference (P < 0.0001). No serious complication was observed in any patient during the postoperative follow‐up periods.

Conclusion

The present study has demonstrated that the modified arthroscopic outside‐in shoulder release approach can improve ROM of patients and alleviate pain effectively, proving it to be an appropriate surgical option for the treatment of severe shoulder stiffness.
Robust emergency management: The role of institutional trust in organized volunteers
Authors: Krogh Andreas Hagedorn , Lo Christian
Published: November 2022

In these turbulent times of increased frequency and magnitude of emergencies caused by climate change, pandemics, and other public safety hazards, there has been a growing interest in the question of how to enhance the robustness of emergency management systems. Recent research points to integrated networks of public and non‐profit actors as a superior strategy for developing robust governance responses to turbulent problems. This article suggests that institutionally conditioned trust between professionals and volunteers is key to robust emergency management. Based on institutional trust theory and the findings of an empirical case study of local emergency management in Denmark and Norway, it shows how six institutional sources of trust condition the scalable use of organized emergency management volunteers. The study contributes with a theoretical argument and empirical insights on how institutional trust strengthens the robust governance and management of emergencies.
ABA biosynthesis gene OsNCED3 contributes to preharvest sprouting resistance and grain development in rice
Authors: Chen Yi , Xiang Zhipan , Liu Min , Wang Siyao , Zhang Lin , Cai Dan , Huang Yuan , Mao Dandan , Fu Jun , Chen Liangbi
Published: November 2022

Preharvest sprouting (PHS) is an unfavorable trait in cereal crops and causes serious yield loss. However, the molecular mechanism underlying PHS remains largely elusive. Here, we identified a member of 9‐cis‐epoxycarotenoid dioxygenase family, OsNCED3, which regulates PHS and grain development in rice (Oryza sativa L.). OsNCED3 encodes a chloroplast‐localized abscisic acid (ABA) biosynthetic enzyme highly expressed in the embryo of developing seeds. Disruption of OsNCED3 by CRISPR/Cas9‐mediated mutagenesis led to a lower ABA and higher gibberellic acid (GA) levels (thus a skewed ABA/GA ratio) in the embryo, promoting embryos growth and breaking seed dormancy before seed maturity and harvest, thus decreased seed dormancy and enhanced PHS in rice. However, the overexpression of OsNCED3 enhanced PHS resistance by regulating proper ABA/GA ratio in the embryo. Intriguingly, the overexpression of OsNCED3 resulted in increased grain size and weight, whereas the disruption of OsNCED3 function decreased grain size and weight. Nucleotide diversity analyses suggested that OsNCED3 may be selected during japonica populations adaptation of seed dormancy and germination. Taken together, we have identified a new OsNCED regulator involved rice PHS and grain development, and provide a potential target gene for improving PHS resistance and grain development in rice.
Affection deprivation is more aversive than excessive affection: A test of affection exchange theory
Authors: Hesse Colin , Floyd Kory , Mikkelson Alan C.
Published: November 2022

Affection exchange theory predicts that both excessive affection and affection deprivation are associated with poorer health, compared with receiving the level of affectionate communication that one desires. A similar yet‐untested prediction is that affection deprivation is more aversive than excessive affection. This preregistered study tested both hypotheses on a battery of mental and physical health outcomes, including depression, loneliness, stress, physical pain, frequency of nightmares, and sleep quality, using a Census‐matched sample of U.S. American adults (N = 827). As hypothesized, receiving the right amount of affection was associated with more health‐supportive scores on all outcomes than either excessive or deficient affection. Similarly, excessive affection was associated with lower depression, loneliness, stress, and pain, and higher sleep quality, than affection deprivation.
A systematic review of social determinants of health in pediatric organ transplant outcomes
Authors: Rea Kelly E. , West Kara B. , Dorste Anna , Christofferson Elizabeth S. , Lefkowitz Debra , Mudd Emily , Schneider Lauren , Smith Courtney , Triplett Kelli N. , McKenna Kristine
Published: November 2022

Background

Equitable access to pediatric organ transplantation is critical, although risk factors negatively impacting pre‐ and post‐transplant outcomes remain. No synthesis of the literature on SDoH within the pediatric organ transplant population has been conducted; thus, the current systematic review summarizes findings to date assessing SDoH in the evaluation, listing, and post‐transplant periods.

Methods

Literature searches were conducted in Web of Science, Embase, PubMed, and Cumulative Index to Nursing and Allied Health Literature databases.

Results

Ninety‐three studies were included based on pre‐established criteria and were reviewed for main findings and study quality. Findings consistently demonstrated disparities in key transplant outcomes based on racial or ethnic identity, including timing and likelihood of transplant, and rates of rejection, graft failure, and mortality. Although less frequently assessed, variations in outcomes based on geography were also noted, while findings related to insurance or SES were inconsistent.

Conclusion

This review underscores the persistence of SDoH and disparity in equitable transplant outcomes and discusses the importance of individual and systems‐level change to reduce such disparities.
Responsibility in epistemic collaborations: Is it me, is it the group or are we all to blame?
Authors: Palermos S. Orestis
Published: November 2022

According to distributed virtue reliabilism (Palermos, 2020b), epistemic collaborations—such as Transactive Memory Systems and Scientific Research Teams—can be held epistemically responsible at the collective level. This raises the question of whether participants of epistemic collaborations are exempt from being held individually responsible. In response, this paper explores two possible ways in which attributions of individual responsibility may still be appropriate within epistemic collaborations: (I) Individuals can be held epistemically responsible for their individual shortcomings, but no amount of individual epistemic responsibility can replace collective epistemic responsibility. (II) Even if it is denied that participants of epistemic collaborations can be held epistemically responsible at the individual level, they may be held structurally, perhaps morally, and even legally responsible at the individual level for breaking joint commitments necessary for the effective coordination of the epistemic collaboration.
Habituation Reflects Optimal Exploration Over Noisy Perceptual Samples
Authors: Cao Anjie , Raz Gal , Saxe Rebecca , Frank Michael C.
Published: November 2022

From birth, humans constantly make decisions about what to look at and for how long. Yet, the mechanism behind such decision‐making remains poorly understood. Here, we present the rational action, noisy choice for habituation (RANCH) model. RANCH is a rational learning model that takes noisy perceptual samples from stimuli and makes sampling decisions based on expected information gain (EIG). The model captures key patterns of looking time documented in developmental research: habituation and dishabituation. We evaluated the model with adult looking time collected from a paradigm analogous to the infant habituation paradigm. We compared RANCH with baseline models (no learning model, no perceptual noise model) and models with alternative linking hypotheses (Surprisal, KL divergence). We showed that (1) learning and perceptual noise are critical assumptions of the model, and (2) Surprisal and KL are good proxies for EIG under the current learning context.
Estimation of the intraoperative blood loss in dogs undergoing enucleation
Authors: Lenihan Emer , Baines Stephen J. , Linn‐Pearl Rose N. , Grundon Rachael A. , Carrozza Rossella , Stevens Elizabeth J. , Heinrich Christine L. , Walsh Karen
Published: November 2022

Purpose

To quantify the surgical blood loss during canine enucleation and to investigate the relationship between this and any patient, surgical, and anesthetic factors.

Methods

A prospective observational analysis was conducted on 121 client‐owned dogs (130 eyes) undergoing enucleation at a referral ophthalmology clinic. Blood loss was estimated by the gravimetric method (weight difference between dry and blood‐containing surgical materials) to provide absolute blood loss (ABL) in milliliters, expressed as a percentage of circulating blood volume, to establish relative blood loss (RBL).

Results

Median ABL was 12 ml (1.6–116 ml), and median RBL was 1.3% (0.1%–6.7%). A higher RBL was associated with the following: use of a bupivacaine splash block versus retrobulbar nerve block (1.9 vs. 1%; p < .001), transpalpebral versus subconjunctival approach (2.2 vs. 1.3%; p = .003), and small versus large breed dogs (1.7% vs. 1.1%; p = .001). Both ABL and RBL differed significantly between surgeons. There was no significant difference in hemorrhage associated with the presence of ocular hypertension, systemic illness, surgical time, administration of meloxicam or choice of pre‐medicant (acepromazine vs medetomidine). No dog required supportive intervention in response to surgical hemorrhage.

Conclusions

This study has established a surgical blood loss estimate for dogs undergoing enucleation at an ophthalmology referral centre. Subconjunctival enucleation may be preferred for patients at greater risk of haemodynamic complications.
Degradation-Aware Ensemble of Diverse Predictors for Remaining Useful Life Prediction
Authors: Nemani Venkat , Thelen Adam , Hu Chao , Daining Steve
Published: November 2022

A traditional ensemble approach to predicting the remaining useful life (RUL) of equipment and other assets has been constructing data-driven and model-based ensembles using identical predictors. This ensemble approach may perform well on quality data collected from laboratory tests but may ultimately fail when deployed in the field because of higher-than-expected noise, missing measurements, and different degradation trends. In such work environments, the high similarity of the predictors can lead to large under/overestimates of RUL, where the ensemble is only as accurate as the predictor which under/overestimated RUL the least. In response to this, we investigate whether an ensemble of diverse predictors might be able to predict RUL consistently and accurately by dynamically aggregating the predictions of various algorithms which are found to perform differently under the same conditions. We propose improving ensemble model performance by (1) using a combination of diverse learning algorithms which are found to perform differently under the same conditions and (2) training a data-driven model to adaptively estimate the prediction weight each predictor receives. The proposed methods are compared to three existing ensemble prognostics methods on open-source run-to-failure datasets from two popular systems of prognostics research: lithium-ion batteries and rolling element bearings. Results indicate the proposed ensemble method provides the most consistent prediction accuracy and uncertainty estimation quality across multiple test cases, whereas the individual predictors and ensembles of identical predictors tend to provide overconfident predictions.
The Phase Behaviors of Confined Shale Fluids Considering Adsorption Effect
Authors: Du Fengshuang , Jiang Shu
Published: November 2022

The molecular adsorption in nano-scale shale pores results in the reduction of effective pore volume and further strengthens the confinement effect. This study aims at examining the adsorption effect coupled with confinement effects on phase behaviors of shale fluids. First, a modified extended Langmuir formula was developed to calculate the adsorption amount for a multi-component shale mixture. A modified cubic Peng–Robinson equation of state was proposed, and the occupied volume by the adsorbed phase was taken into account. The saturation pressures and fluid properties under the confinement effects and adsorption isotherms were examined. In order to examine the change of phase properties during a gas injection process in a shale condensate reservoir, we gradually increase the mole fractions of N2 or CO2 in shale condensate mixtures by coupling with confinement effects. We found that the thickness of the adsorption film reduces the effective pore throat, leading to intensified confinement effects and smaller bubble point pressures. When the gas adsorption layer is considered, a more significant decrease in density and viscosity is observed. The critical pressure of the condensate fluids increases and the critical temperature decreases with the continuous N2 injection. Contrary to N2 injection, the critical pressure decreases and the critical temperature moves upwards with CO2 injection. For condensate that accumulates in nano-pores (e.g., r ≤ 6 nm), the condensate fluid always exists in gas status during the gas injection and the subsequent production processes.
An Experimental Investigation on the Dynamic Response Variability of a Turbine Blade With Mid-Span Dampers
Authors: Ferhatoglu Erhan , Botto Daniele , Zucca Stefano
Published: November 2022

This paper addresses two main subjects. Firstly, a novel test setup is described to experimentally study the nonlinear dynamic behavior of a turbine blade coupled with two mid-span dampers. To this end, a representative turbine blade and mid-span friction dampers are originally designed, and they are assembled to a special test rig which has been previously developed at Politecnico di Torino. Secondly, the variability of the dynamic response is intensively investigated with a purposely defined loading/unloading strategy. To better understand the inherent kinematics of the blade-damper interaction, contact forces are measured through the novel design of the experimental campaign. It is shown that multiple responses, which are obtained in different tests while keeping all user-controlled inputs nominally same, are due to non-unique contact forces that provide different static force equilibria on the damper. This outcome is further supported by the qualitative illustration of hysteresis cycles. The current study contributes to the understanding of the response repeatability linked to the non-uniqueness of friction forces.
Aerodynamic Forcing Models for Compressor Aeromechanics
Authors: Hernley Valerie , Jemcov Aleksandar , Morris Scott C.
Published: November 2022

The present work was focused on formalizing a mathematical description of aerodynamic forcing mechanisms relevant to compressor blade vibration. The hypothesis was that the functional form of the aerodynamic forcing functions could categorize the various aerodynamic forcing mechanisms. Based on this hypothesis, the multitude of aerodynamic forcing mechanisms relevant to compressor aeromechanics was divided into three categories: 1) external forcing, 2) blade-row aerodynamic forcing, and 3) motion-dependent forcing. Modal forcing models for each category were presented, including a novel model for rotating stall effects. Simulations for each category demonstrated distinct and unique temporal characteristics of the response to different aerodynamic forcing mechanisms. Good agreement with experimental data supports using these temporal characteristics to identify the physical forcing mechanisms present in measured blade vibration data.
Computation of the Unsteady Loading on a Fan Blade Due to Inlet Distortion Using Body Force Methodology
Authors: Bouhafid Younes , Berthelon Thomas
Published: November 2022

The latest aero-propulsion configurations are characterized by a strong aerodynamic interaction between the engine and its environment. This interaction results in unsteady loads perceived by the fan leading to vibrations. In order to ensure the mechanical integrity of the blades, engine designers must evaluate these vibration levels very early in the design phases. To do so, the classic solution consists in running full-annulus U-RANS calculations to compute unsteady loading on the blade and then deduce the fan’s forced response. However, such method can be computationally expensive and is consequently not adapted for large parametric studies conducted during the design phase of a blade. This paper presents a new method for calculating the forced response of a fan based on the use of body force calculations, which has a significantly lower computational cost compared to bladed U-RANS calculations. The main idea of the body force method is to replace the blades by source terms in the Navier-Stokes equations inside the volume swept by the fan. First, the application framework of the method is detailed. Then, the key step of the method which consists in computing the generalized aerodynamic forces from a body force calculation is presented and where the main idea involves concentrating the body force terms on the blade camber surface. A validation of the method is then proposed using a comparison with high fidelity U-RANS calculations for a BLI-like inlet distortion. It is found that the body force methodology reproduces the harmonic content of the computed generalized aerodynamic forces with a relatively good accuracy. Finally, an example of use of this method in a design context is presented as new body force calculations are run for two other inlet distortions that can occur in the takeoff phase: the ground vortex and the inlet flow separation.
Reduced Order Modeling of Forced Response in a Multistage Compressor Under Mistuning and Aerocoupling
Authors: Maroldt Niklas , Seume Joerg R. , Schwerdt Lukas , Panning von-Scheidt Lars , Wallaschek Jörg , Berger Ricarda , Rolfes Raimund
Published: November 2022

Vibration amplitudes and fatigue life in multistage turbomachinery are commonly estimated by an isolated investigation of the individual stages. Research is currently extending the scope to include inter-stage coupling of structural dynamics and aeroelasticity, i.e. aerodynamic coupling. These two effects have been shown to significantly influence blade vibrations. For safe operation of modern blisk blading with its lower structural damping due to the elimination of frictional contacts at the blade roots, an accurate prediction of the vibration behavior in multistage configurations with mistuning is necessary to avoid high cycle fatigue (HCF) failures.

In this paper, a cyclic Craig-Bampton reduction method with a priori interface reduction for multistage rotors is extended to handle aeroelastic effects. These reduced order models efficiently predict forced response in multistage applications. Aeroelastic multistage simulations are carried out using the harmonic balance method to account for the stage interactions and yield damping and stiffness coefficients, as well as modal excitation forces. Small structural mistuning is projected onto the tuned system modes of the rotor. The reduced order approach is applied to a two-stage compressor configuration. Monte Carlo simulations show the sensitivity of vibration amplitudes to the aeroelastic coupling for mistuning. The aeroelastic inter-stage coupling is found to originate mainly from acoustic mode propagation between the rotor stages. The fatigue of rotor blades is significantly affected by multistage interaction since vibration amplitudes increase due to the superposition of the vibration responses of multiple modes. This leads to the conclusion that aeroelastic multistage effects need to be incorporated in future design procedures to allow for an accurate prediction of fatigue life of compressor rotors.
Experimental Investigation of Friction Damping in Blade Root Joints
Authors: Botto Daniele , Iannotti Veronica , Cuccovillo Federica
Published: November 2022

The design of disk assemblies requires the capability to predict their dynamic behavior. To achieve this objective, knowledge of friction damping on the contact between blade and disk is of paramount importance. This paper proposes an experimental technique to measure the loss factor and the dynamics, in terms of natural frequencies, of blade-disk attachment. The free decay is used to infer the dynamic parameters from dummy blades. The identification method is based on the Hilbert transform that allows extracting the dynamic parameters from non-linear system. This paper shows the test rig utilized in the experimental analysis and details the excitation system used to displace the dummy blade. This system must be a real or a “virtual” non-contact system to avoid injecting external damping into the blade under test. Tests were performed on both a dovetail and a fir-tree type attachments. On the dovetail, tests were performed both with dry contact surfaces and with contact surfaces covered by a film of lubricant to achieve a low coefficient of friction. This low coefficient of friction better simulates dry surfaces at high temperatures, as friction coefficients decrease with temperatures. This paper presents the results obtained on the first and second bending mode. The experimental results show the loss factor and the natural frequency for different axial loads. The measured loss factor depends on the amplitude of vibrations. As predicted with theoretical analyses the loss factor shows a maximum then approaching zero for large amplitude of vibrations. As a rule, it decreases with increasing centrifugal loads.
Aerodynamic Damping Predictions During Compressor Surge: A Numerical Comparison Between a Half and Full Transient Approach
Authors: Reiber Christoph , Chenaux Virginie Anne , Belz Joachim
Published: November 2022

The prediction of the aerodynamic damping during compressor surge is a challenging task, because the flow is continuously evolving along the four surge cycle phases: Pressurization (PR), Flow-Breakdown (FB), Reversed Flow (RF) and Regeneration (RG) and complex flow conditions like shocks and separations occur.

Damping predictions with current existing methods typically consist of two steps. In the first step a modified numerical model is used to simulate transient surge cycles. In the second step, damping analyses are performed for multiple timesteps along the surge cycle phases, which are then assumed as quasi-steady. The damping simulation can be performed using nonlinear or linear approaches. If shocks or separations occur, the latter yields inaccuracies in the flow and thus in the damping predictions.

A new approach was developed to take into account and improve these inaccuracies. This new method includes the damping prediction within the transient surge simulation. Thus, all surge cycle phases and the continuously evolving flow conditions are considered and nonlinear simulations are performed to account for shocks and separations. The results of this new method are presented and compared to the former method.
Simulation and Validation of Creep Damage on Grain Boundary of Polycrystalline Alloy 247
Authors: Nguyen Tuan Duc , Mäde Lucas , Kulawinski Dirk
Published: November 2022

In this paper, the cavitation process on a grain boundary in polycrystalline Alloy 247 is simulated and modelled. The cavitation process includes mechanisms such as nucleation, growth and coalescence of creep pores and was used for characterization of polycrystalline Alloy 247 in terms of creep damage and especially creep pore sizes. Two main parameters were defined that are either responsible for pore nucleation or pore growth and that are calculated from simulation variables and material coefficients. Therefore, a Design of Experiment (DOE) was carried out to identify the effect of each material coefficient and simulation variable on the cavitation process as well as the ranges of the main parameters for pore nucleation and pore growth. As a result of the investigation, a series of Monte Carlo simulations was run with designated combinations of main parameters within the identified range. The simulation results were used as training and test data to create a model by machine learning methods. Different machine learning methods such as neural network, random forest tree and k-nearest neighbor were applied and compared to determine the best fitted model. Based on metallographic images, a first calibration of the model’s parameters has also been carried out. The resulting machine learning model allows the prediction of creep pore sizes in the grain boundary of Alloy 247 for any given temperature and stress.
Non-Linear Flutter Analysis of Labyrinth Seals
Authors: Corral Roque , Greco Michele , Matabuena Luis
Published: November 2022

A simple nonlinear model to describe labyrinth seal flutter has been developed to assess the aeromechanic stability of straight-through labyrinth seals subjected to large gap variations. The model solves the one-dimensional integral mass, momentum, and energy equations of the seal for a prescribed motion numerically until a periodic state is reached. The model accounts for the effect, previously neglected, of high clearance variations on the stability. The results show that when the vibration amplitudes are small, the work-per-cycle coincides with the prediction of the Corral and Vega model (2018, “Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models. Part I: Theoretical Background”, ASME J. Turbomach.140(10), pp. 121006) and Corral et al. (2021, “Higher-Order Conceptual Model for Seal Flutter”, ASME J. Turbomach. 143(7), pp.071006), but for large vibration amplitudes nonlinearities alter the stability limit. In realistic cases, when the discharge time of the seal is much longer than the vibration period, the nonlinear effects are significant and tend to increase the unstable range of operating conditions. Furthermore, seals supported either on the high-pressure or low-pressure sides, stable for small vibration amplitudes, can destabilise when the vibration amplitude increases. The linear stability, though close in many situations to the nonlinear threshold, is not conservative, and attention must be paid to nonlinear effects.
On the Effect of Frequency Separation, Mass Ratio, Solidity and Aerodynamic Resonances in Coupled Mode Flutter of a Linear Compressor Cascade
Authors: Schuff Matthias , Chenaux Virginie Anne
Published: November 2022

At a low mass ratio of structure to air, the work-per-cycle approach, or better known as the energy method, will lead to non-conservative results as aerodynamic coupling of modeshapes acts destabilizing. Using the p-k method to solve the aeroelastic stability equation, the effects of various structural aspects are investigated for a two-dimensional compressor cascade in subsonic and transonic flow conditions. The investigated key parameters are frequency separation, mass ratio and solidity.

Furthermore, the effect of a high frequency dependency of the aerodynamic forces is presented. Such phenomena can happen in case of aerodynamic or acoustic resonances. If the resonance peaks are close to the aeroelastic frequency, a discontinuous behavior of the frequency or damping solution can lead to a rapid destabilization of the system, once the aeroelastic frequency moves from one side to the other of the peak. In these regimes, it is crucial to have a high quality representation of the frequency-dependent generalized aerodynamic forces for an accurate prediction of the flutter onset.
Stability of a Rotor Partially-Filled With Fluid: Test Facility and Experimental Results
Authors: Kasprzyk Marie , Sentmanat John , Delgado Adolfo
Published: November 2022

Fluid trapped in a hollow, rotating component may lead to subsynchronous vibrations, resulting in high vibration amplitudes. This asynchronous response is observed around 0.55–0.9x after passing through the first critical frequency and affects large rotating equipment such as centrifuges, fluid-cooled gas turbines, and jet engines. A test rig is designed to evaluate this self-excited asynchronous vibration. The high-speed rig comprises of a flexibly-mounted rotor partially filled with fluid, with an overhung test chamber providing an unobstructed view of the liquid surface. A squeeze film damper provides external damping and allows operation through the asynchronous response when the test chamber contains a large amount of fluid. The results show the rotor response with different fluid depths and external damping values as the rotor-bearing system transverses the first critical speed (cylindrical mode). The experiments show that only a small amount of oil (∼20 mL) is required to induce asynchronous excitations, and increasing the fluid depth increases the amplitude of vibration. External damping slightly decreases the response, but it also expands the range of frequencies where asynchronous vibrations occur. At a given speed ratio, the vibrations reach a limit cycle, and subsequently, begin to drop as the rotor speed increases past the first critical speed.
Preliminary Numerical Validation of the Frequency Response Method on the Study of Aero-Damping in a Linear Oscillating Compressor Cascade
Authors: Tong Xin , Yin Fanfu , Shen Xin , Qiang Xiaoqing , Ouyang Hua
Published: November 2022

Preliminary numerical simulations are performed for validation of using the frequency response method on the study of aero-damping in a linear oscillating compressor cascade. The traveling wave method and influence coefficient method, based on the idea of the energy method, are also adopted for reference and comparison. The linearity of the unsteady pressure and the finite propagation of small flow disturbance is verified. The results of the aero-damping ratio obtained from different methods are in good agreement. Qualitative analysis is made on how the unsteady aerodynamic pressure distribution determines the overall aero-damping. When the frequency sweeps are conducted to measure aero-damping, the influence of aerodynamic stiffness cannot be ignored and the natural frequency offset caused by it should be taken into account. The existence of the two sidewalls in cascade has a certain impact on the measurement results, but it is still in an acceptable range. The application of the frequency response method on the study of aero-damping in the experiment is proved to be feasible and reliable in principle by numerical simulation.
Simulation Method of Rotor Dynamic Characteristics Considering Temperature Distribution and Aerodynamic Load
Authors: Xiang Fengguang , Chen Xi , Zhang Bo , Ren Guangming , Gan Xiaohua
Published: November 2022

When operating in a high-temperature and high-pressure environment, the high-speed rotor systems of aero-engines are inevitably subjected to thermal and aerodynamic loads. However, conventional simulations and experiments of rotor dynamics did not consider temperature distribution and aerodynamic load. Therefore, it’s necessary to investigate the influence mechanism of temperature distribution and aerodynamic loads on rotor dynamics.

Using polynomial function fitting for the continuously various parameters in elements, combined with the temperature distribution, the axial distribution of physical parameters in shaft elements was established. The stiffness coefficient matrix considering temperature load was derived based on Timoshenko beam theory. By introducing the tension (compression) potential energy, the additional stiffness coefficient matrix was derived from Lagrange equation. Using state-space vector method, the differential equations of motion for rotor-support system were solved, and dynamic characteristics of rotor system subjected to temperature distribution and aerodynamic force were analyzed. The simulation method was verified with a typical fan rotor under the maximum operating condition.

The results indicate that the rotor dynamic behavior is more sensitive to temperature distribution than aerodynamic load when operating in the temperature range of 40∼190°C. And the decrease of first two critical speeds is mainly caused by thermal load. Due to the relatively low temperature, the first-order critical speed of fan rotor considering the additional load is reduced slightly, while the second-order one is decreased by 3.42%. When a mass unbalance of 500 g·mm is located at the first disk, the resonant amplitude of unbalance response rises slightly (0.25%) with additional load. If such amount of unbalance is located at the third disk, the peak amplitude is increased by 1.28%. In addition, such a simulation method could be extended to core engines or even dual- or triple-rotor engines with higher temperature and aerodynamic load, where the dynamic characteristics and unbalance responses are expected to be significantly affected.
Active Rotor Controller Design for Vibration and Bend Mitigation Utilizing Active Magnetic Bearings and Internal Shaft Actuation
Authors: Fieux Gauthier , Bailey Nicola , Keogh Patrick
Published: November 2022

Strategies are required to reduce vibrations in machines that use rotor systems, as these disturbances reduce the life and quality of the machine. A novel low-frequency on-board counter-bend actuator topology has been designed in order to control high frequency vibrations by taking advantage of synchronous forces from the rotating frame of a rotor supported by Active Magnetic Bearings (AMBs). The AMBs ensure in return stable contact-free levitation of the rotor. A complete model of the rotor system is established, based on a finite element representation of the rotor. The feedback control forces of the AMBs are described to account for the non-collocation of the sensor and actuation, and the PD controller gains are chosen using the sensitivity function. The lowest frequency mode of the operating range is located at 2,700 RPM, and time domain analysis shows that the application of symmetric 80 N.m counter-bend moments on the rotor coupling flanges can reduce the vibration amplitude by 88% at this rotation speed.
Dynamic Characteristics of Rotor-SFD-Support System Excited by Base Harmonic Excitations Using MHB-AFT Method
Authors: Zhang Bo , Chen Xi , Xiang Fengguang , Gan Xiaohua , Ren Guangming
Published: November 2022

When operating at high speed, aeroengines mounted on the aircrafts also perform complicated maneuvering flights along with the aircrafts. The engine rotor systems will undergo forced motions excited by base movements and mass unbalance, which may lead to severe vibrations. Squeeze film damper (SFD) is generally used for vibration damping in aeroengine, but it also introduces structural nonlinearity like bistable jump. Moreover, the reliability of SFD is also affected by base excitations. Therefore, it is necessary to investigate the nonlinear dynamic behavior of rotor-SFD-support system excited by base motions.

Taking a muti-disk rotor shaft supported by two SFDs with squirrel cages as the research object to simulate a gas generator in a turboshaft engine, the steady-state responses of the rotor system were calculated by multi-dimensional harmonic balance combined with alternating frequency/time domain method (MHB-AFT). The effects of base harmonic rotations and mass unbalance on steady-state responses of rotor system were investigated. The results indicate that the time-varying parametric excitations of base motions have strong effects on amplitude-frequency response of transverse displacement of rotor system. The critical speeds and resonant amplitudes of responses change with the magnitude and frequency of several base harmonic rotations. The variation of the frequency of base harmonic motion has the most significant impact on the amplitude-frequency response of transverse displacement of rotor system. The increase of base harmonic frequency will lead to multiple local peaks in the response curves, especially in the case of base harmonic rolling motion. In addition, the combination of base harmonic rotation around pitching and yawing axes results in significantly different response characteristics. Therefore, the influence of base harmonic motions should be considered during the structural design and damping optimization of SFDs.
Robust Probabilistic Analysis of Deterioration-Induced Aeroelasticity in an Axial Turbine
Authors: Stania Lennart , Seume Joerg R.
Published: November 2022

The surface of a real-world turbine blade differs from the geometry of its model. Manufacturing tolerances, wear, and regeneration during the turbine’s lifetime impact the aerodynamic behaviour, stage efficiency, and parameters as previous probabilistic studies have shown. Aerodynamic changes lead to aeroelastic variances in downstream rows that can have a significant impact on high-cycle fatigue due to a possible increase of a blade’s vibration amplitude. The present study expands an existing tool chain to uni-directional aeroelastic full three dimensional simulations. The test object is the last stage of a low-pressure five-stage axial turbine; the geometric variances are applied to characteristic airfoil parameters of the vane by Latin hypercube sampling. A required sample size for an accurate sensitivity analysis is estimated a-priori and verified by computational simulations. The aerodynamic analysis identified the stagger angle, trailing-edge thickness, maximum thickness, and maximum camber as the most important parameters among the characteristic blade parameters. For large deviation in the stagger angle a non-monotonous influence on isentropic efficiency was found, which shows limitations of a sensitivity analysis based on the Spearman rank correlation coefficients. A variance-based sensitivity analysis was used for a more detailed analysis, which is capable to detect such non-monotonous relationships. In the aeroelastic simulations, the chord length, maximum camber, and the trailing-edge angle have the highest influence on aerodynamic forcing and damping on a downstream rotor blade of the changed stator blade. Furthermore, direct correlations between aerodynamic stage parameters and aerodynamic damping are shown, which allows reduced order modelling. The correlation between work coefficient and vibration amplitude was overlooked by the Spearman’s coefficient but identified by the variance-based approach. A maximum vibration amplitude is identified, indicating a potential of using probabilistic studies for adjusting the safety factors for high-cycle fatigue during the design process of blades.
Semi-Analytical Model for High-Speed Rotor Whirl Prediction: An Assumed Modes Formulation for an Axisymmetric Rotor With Non-Uniform Properties
Authors: Chatterjee Riju , Patel Ashutosh , Kumar Nirmal , Kumar Pramod
Published: November 2022

Most fully analytical treatments of rotor whirl are restricted to very simple rotor geometries, and have limited use while studying real-world rotors. Analysis of more complex rotors is routinely carried out in Finite Element software such as Ansys, but this is less effective at generating fundamental insights to inform the design process. This paper is motivated by the ongoing development of a Supercritical-CO2 turbine rotor, and illustrates a rotor model of intermediate complexity. Such a model, given the relative novelty of the turbine design task stemming from the very high rotational speeds required, will improve confidence in rotordynamic simulations and is expected to help with any future troubleshooting. The approach used is to consider the rotor’s rigidity and inertia to vary along its length as functions of spatial coordinate x, and obtain predictions of whirl speeds through a Lagrangian formulation with assumed modes. This method can accommodate axisymmetric rotors with variation in cross-section or material properties, or both. It is first demonstrated on a simple and analytically tractable rotor geometry. Then, it is applied to a simplified version of the turbine rotor, whose properties’ x-dependence is approximated by curves fit to a small number of datapoints obtained from simpler (non-rotordynamic) simulations.
Application of an Advanced Meta Model Selection Algorithm on the Sensitivity Analysis of a Cooled Turbine Blade
Authors: Diermeier Florian , Voigt Matthias , Mailach Ronald , Meyer Marcus
Published: November 2022

Probabilistic methods are growing more important in the aerospace industry due to the ability to describe the behaviour of complex systems in the presence of input parameter variance. Sensitivity analysis based on meta models can be utilized for this purpose. The reliability of the results is dependent on the surrogate model quality, which in turn depends on the available data. A priori the appropriate meta model type is not known.

An approach to automatically select the best fitting model for a given data set is presented in this paper. For comparison, polynomial regression with least squares fitting, moving least squares, radial basis functions, and support vector regression are used as candidate types. The selection of the best meta model type is based on two quality criteria utilizing a cross-validation (CV) scheme. The developed approach is demonstrated on the sensitivity analysis of a cooled turbine blade.
Efficient Surrogate Modeling for Turbine Blade Row Cyclic Symmetric Mode Shapes
Authors: Bhaduri Anindya , Li Jing , Ghosh Sayan , Wang Liping
Published: November 2022

In this study, we consider the Modal Cyclic Symmetric (MCS) analysis to generate the modal frequencies and mode shapes of a tip-shrouded turbine blade row. In total 87 input parameters are considered here that define the geometry of the turbine blades. The objective here is to build an efficient surrogate model which maps these input parameters to the mode shapes. The main challenge is the high dimensionality of a complex mode shape at a mesh resolution of industrial standard which is almost of the order of O(107). Thus, the idea here is to efficiently reduce the high dimensional output into a lower dimensional representation using the unsupervised deep learning architecture called the Convolutional Variational AutoEncoder (CVAE). The CVAE model helps in performing efficient surrogate model building using GE’s Bayesian Hybrid Model (BHM) in a lower dimensional output space as well as produce feasible mode shapes for new geometries after training.