bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipid resuscitation in pediatric patients – need for caution?
Authors: Shenoy Usha , Paul John , Antony Deepu 
Published: November 2013

SummaryA 3‐year‐old child was successfully resuscitated following bupivacaine cardiotoxicity with 20% intravenous lipid emulsion (ILE). Large volume of ILE was used targeting clinically adequate perfusion. Subsequently, there were features of ventilation/perfusion (V/P) mismatch.
Multiple-Change-Point Detection for Auto-Regressive Conditional Heteroscedastic Processes
Authors: Fryzlewicz P. , Subba Rao S. 
Published: November 2013

SummaryThe emergence of the recent financial crisis, during which markets frequently underwent changes in their statistical structure over a short period of time, illustrates the importance of non-stationary modelling in financial time series. Motivated by this observation, we propose a fast, well performing and theoretically tractable method for detecting multiple change points in the structure of an auto-regressive conditional heteroscedastic model for financial returns with piecewise constant parameter values. Our method, termed BASTA (binary segmentation for transformed auto-regressive conditional heteroscedasticity), proceeds in two stages: process transformation and binary segmentation. The process transformation decorrelates the original process and lightens its tails; the binary segmentation consistently estimates the change points. We propose and justify two particular transformations and use simulation to fine-tune their parameters as well as the threshold parameter for the binary segmentation stage. A comparative simulation study illustrates good performance in comparison with the state of the art, and the analysis of the Financial Times Stock Exchange FTSE 100 index reveals an interesting correspondence between the estimated change points and major events of the recent financial crisis. Although the method is easy to implement, ready-made R software is provided.
Functional Implications of Regulatory B Cells in Human IgA Nephropathy
Authors: Wang Y.‐Y. , Zhang L. , Zhao P.‐W. , Ma L. , Li C. , Zou H.‐B. , Jiang Y.‐F. 
Published: November 2013

AbstractIgA nephropathy (IgAN) diagnosis remains largely based upon immunohistologic detection of IgA‐ and IgG‐containing glomerular deposits in renal mesangial cells, and little is known about the underlying pathogenic mechanisms. This study examines the putative contribution of B cell types, including the Breg type, to IgAN pathogenesis. Twenty‐four patients with IgAN and proteinuria (Group A: <3.5 g/24 h, n = 13; Group B: >3.5 g/24 h, n = 11) and 10 healthy controls were enrolled. The frequencies of B cell subtypes in venous blood were measured by flow cytometry. Galactose‐deficient IgA1 was measurement by ELISA. Needle biopsies were analysed by histology and immunofluorescence microscopy. Correlation between clinical features and B cell subtypes, including the regulatory B (Breg) cells, and Breg cell‐derived immunomodulatory cytokine IL‐10 was assessed by Spearman's rank correlation test. IgAN patients had significantly higher frequencies of CD27+CD19+, CD38+CD19+, CD86+CD19+ and CD5+CD19+ B cells than the healthy controls, but significantly lower levels of Breg cells and intracellular expression of IL‐10 protein in the Breg subtype. Serum IgA concentration positively correlated with CD27+CD19+ B cell frequency and negatively correlated with IL‐10+ Breg cell frequency in IgAN patients, and the percentage of CD19+CD5+CD1d+ in CD19+ cells was negatively correlated with the level of serum Gd‐IgA1. Furthermore, the frequencies of CD19+CD38+ and CD19+CD86+ in the CD19+ subpopulation negatively correlated with the estimated glomerular filtration rate of IgAN patients. Several of the CD19+ B cell subtypes and the IL‐10+ Breg cells are differentially expressed in IgAN patients and may contribute to the disease pathogenesis.
Turbocharger Synchronous Vibration Control on High Speed Balancer: Test and Prediction
Authors: Gjika Kostandin , Costeux Antoine , Mahadevan Pradeep 
Published: November 2013

Current trends for advanced automotive engines focusing on downsizing, better fuel efficiency and lower emissions have led to several changes in turbocharger bearing systems design and technology. Automotive turbochargers are running faster under high engine vibration level. Vibration control is becoming a real critical issue and turbocharger manufacturers are focusing more and more on new and improved balancing technology.
This paper deals with turbocharger synchronous vibration control on high speed balancers. In a first step the synchronous rotordynamics behavior is identified. The developed fluid bearing code predicts bearing rotational speed (in case of fully-floating design), operating inner and outer bearing film clearances and bearing force coefficients. A rotordynamics code uses this input to predict the synchronous lateral dynamic response of the rotor-bearing system by converging with bearing eccentricity ratio. The rotor-bearing system model is validated by shaft motion test data on high speed balancer (HSB). It shows that only one of the peaks seen on the synchronous G level plot collected in a high speed balancer can be explained by rotordynamics physics. A step-by-step structural dynamics model and analysis validated by experimental frequency response functions provides robust explanations for the other G level peaks. The synchronous vibration response of the system “turbocharger-HSB fixture” is predicted by integrating the predicted rotordynamics rotational bearing loads on the structural dynamics model. Numerous test data show very good correlation with the prediction, which validates the developed analytical model.
The “rotordynamics – structural dynamics model” allows deep understanding of turbocharger synchronous vibration control as well as optimization of the high speed balancer tooling.
Impact of an Optimized Power Turbine Disks Cavity on Geared Open Rotor Performance: A Multidisciplinary Approach in the Preliminary Design
Authors: Peraudo Paolo N. , Abbondanza Claudio , Pastrone Dario G. , Maggiore Paolo , De Poli Gian Paolo 
Published: November 2013

A constantly growing number of studies have been oriented to Green Aircraft and Green Engine concepts during last several years in order to reduce pollutants and carbon-dioxide production by 2020. Ultra high by-pass engines are recently getting the highest interest by academia, research centers and industries. Among the most recent research activities, many studies are focused on geared architectures, the Geared Turbofan (GTF) and the Geared Open Rotor (GOR). The GOR architecture seems to be the most promising radical architecture for short-range aircraft as climbing and landing phases interest the major part of the whole mission.
Our work refers to the most recent research activities and is focused on the preliminary design of a GOR-like engine. A multidisciplinary modular simulation environment was developed to allow researchers the chance to directly relate the considered disciplines. Introductory trade-off studies were carried on to effectively show GOR capabilities amongst the most innovative engines. A reference low-bypass turbofan was used as the core of the considered GOR engine, as previously done by General Electric for its original Open Rotor engine. GOR performance were predicted on-design and off-design, by relating to a reference short-range mission. Optimization studies of the GOR high-speed power turbine disks cavity were performed to reduce disk weight and cooling flows, complying with several engineering constraints, such as aerodynamics, structural and manufacturing constraints. Finally the optimization outcomes were linked to the performance code to capture their impact on the overall engine efficiency and specific fuel consumption. Preliminary results show that it is possible to get a remarkable improvement in the specific fuel consumption by minimizing the required cooling flows of the GOR power turbine. Moreover, for a required thrust level, engine weight may be reduced.
The Development of a New Concept for Gear Teeth Wear and Damage Detection
Authors: Chana K. S. , Cardwell M. T. , Sullivan J. S. 
Published: November 2013

Mechanical transmission systems require online health monitoring for several reasons. Gearboxes account for many of the maintenance costs due to repairs, replacements and downtime. Transmission systems feature in many applications including rotor aircraft and wind turbines.
The wind energy industry since its inception has experienced high levels of failure rates. Principal gearbox design defects and structural problems have been notably significant issues of wind turbines and have had to be addressed by the wind turbine manufacturers. Reliability and safety of conventional wind turbines has improved although rates of failures are still disappointingly high.
There still exists a lack of sufficient technology to enable reliable monitoring of the structural and operational conditions of wind turbines and this is currently a significant area of research.
Gearbox monitoring in particular lacks sensor technology to successfully detect tooth damage, high speed and low speed shaft faults. Typically, vibration measurement and spectrum analysis are chosen for gearbox monitoring but, these methods are not able to detect the faults until failure is imminent. More recently acoustic emissions sensors are being developed for early detection of stress and surface defects.
This paper presents a new concept that employs an eddy current sensor fitted to the teeth of an idler gear to detect early micro and macro pitting of the gear tooth surface. A rotating bench test has been carried out to validate the technique where simple eddy current sensors have been fitted to an idler gear. Seeded faults of three different types on an actual gear have been shown to be detectable using this technique. Eddy current sensors are used for their immunity to dust, dirt and oil contamination. Thus this technique is targeted for in-service operation where sensors have not previously been deployed to access the tooth face, flank and root shank.
Microturbine Rotational Speed Selection
Authors: Rodgers C. 
Published: November 2013

This paper delves upon the Aero-Thermodynamic performance and Mechanical design aspects of microturbines comprising a single shaft radial compressor driven by a single stage radial inflow turbine with a combustor and recuperator sized to directly drive a permanent magnet type high speed generator with an output power in the 5–10KW bracket and commensurate rotational speeds in the 100–200 krpm range.
It is initially shown that stipulation of a cycle design point output power, turbine inlet or exit temperatures, and compressor pressure ratio delivering optimum thermal efficiency inherently confines rotational speed selection, and that independent rotational speed choice away from those identified optimum speed regimes may result in cycle thermal efficiency compromises. Confining the cycle analysis within temperature limits of cost competitive superalloys and foil materials reveals that the achievement of optimum thermal efficiency is more dependent on temperature at the turbine exit rather than at inlet.
Albeit the choice of rotational speed is of particular importance in the compressor and turbine design it moreover is dominant in the mechanical design of the rotating assembly in terms of high speed bearing life and shaft dynamic stability.
As a consequence rotating assembly and bearing design options suitable for direct drive permanent magnet generators are reviewed and recommendations offered as to the prime candidate assemblies for future microturbines in the 5.0 to 10.0 kW power output range.
Electro Compression a Challenging Alternative: How and Why to Choose a Gas Turbine or an Electric Motor to Drive a Centrifugal Compressor
Authors: Alas Pascal , Noulette Eric 
Published: November 2013

In the past decade, electric motors have become a challenging alternative to gas turbines to drive centrifugal compressors [1] [7], mainly because of the progress of Variable Frequency Drives main components allowing to drive high power motors. Low Electricity prices (mainly in France) and environmental concerns have contributed to spread that technology across Europe. As flexibility needs and environmental constraints will grow in the gas transmission business, the option to drive the centrifugal compressors with an electric motor will be taken into consideration more and more often either for technical, regulatory or economic reasons in future compressor station projects [2].
GRTgaz, the main gas transmission company in France, decided in the early 2000’s to enlarge and renew its compressor fleet (42 units to be installed between 2004 and 2014 in a 5 to 14 MW power range). GRTgaz is taking that option into account for each of these projects considering the following criteria, related to 3 main considerations:
Operational needs:
• Availability, reliability
• Rangeability needs
• Flexibility needs
• Type of compressor station (head, peak, network core)
• Access to the electrical grid
• Available space for the site
• …
Environmental constraints:
• Environmental Footprint
• Air emissions
• Noise
• …
The full possession cost for a 30-year period:
• Investment cost
• Energy cost
• Maintenance cost
• CO2 quota prices
This paper is proposing to develop how these criteria are assessed, what hypotheses are made to help the decision and to share GRTgaz feedback on the projects that have already been completed. Some examples will be presented.
Comments on a Newly-Identified Destabilizing Rotordynamic Mechanism Arising in Vertical Hydraulic Turbines and the Back Shrouds of Centrifugal Impellers
Authors: Childs Dara W. , Muhammed Ameen 
Published: November 2013

In three 2010 papers, Tsujimoto, Ma, Song, and Horiguchi [1–3] discussed and explained a novel destabilizing mechanism arising in both hydraulic turbines and the back surface of vertical pump impellers. The destabilizing mechanism can be explained via a reaction force-moment model that includes both the customary radial displacement vector of an impeller plus the pitch and yaw degrees of freedom. This coupling between radial displacements and tilt plus the coupling of the shaft support structure can create negative damping. In 1993, Verhoeven, et al. [4] identified negative damping arising from U-shaped wearing-ring seals as causing a super-synchronous instability in a horizontal coke-crusher pump. However, several case studies have been presented of super-synchronously unstable pumps for which (until now) no explanation could be provided.
Tsujimoto-Song started with a 2DOF model for a disk suspended vertically via a cantilevered shaft. They used an f = ma model for the lateral displacements of the disk and used flexibility coefficients to account for reaction forces and moments from the back shroud of the impeller. The present work starts with a 4DOF model that includes the disk’s displacements and pitch and yaw degrees of freedom. Guyan reduction is used to create two reduced 2DOF models, Model A that retains the displacements and discards the rotations and Model B that retains the rotations and discards the displacements. Model A produces a requirement for instability that is inconsistent with Tsujimoto-Song’s experience and predictions. However, it is useful in predicting the reaction moments produced by a nominally planar precession of the impeller.
The instability requirement of Model B is consistent with Tsujimoto’s experience and predictions. A comparison of the predicted reaction moments of Model A and Tsujimoto’s reaction-moment data supports the instability predictions of Model B (and Tsujimoto-Song) that the instability arises due to coupling between the displacement and rotation degrees of freedom in the 4 × 4 damping matrix.
Consequential Damage of Blade Failures in Single Shaft Gas Turbines
Authors: Wettstein Hans E. 
Published: November 2013

In history of single shaft gas turbines many blade failures have happened. In most cases the consequential damage has been limited to the blading in the downstream gas path. This is unavoidable because of the impact of debris. But in some cases the related unbalance of the rotor has caused additionally extended damage during the run-down of the engine. In the worst publicly known case the result was a complete destruction of the engine with disintegration of the rotor. The general rotordynamic literature indicates features and criteria to prevent such a high sensitivity to unbalance. Some manufacturers use internal design criteria for this purpose. A sometimes mentioned criterion in this respect is: “To keep the rotation speed below the frequency of the first bending mode of the rotor”.
The aim of this paper is to track generally the history of gas turbine blade failures and to explain the design features of rotors and bearing support structures, which lead to high or low risk of secondary damages after blade failures. This is not new but a description from a gas turbine design point of view is missing so far.
Both theory and experience indicate that an exact prediction of the response amplitudes to a large unbalance from a blade failure is very difficult. On the other hand the most important criteria for a robust behavior in this respect are simple to describe. And they could easily be specified and verified by manufacturers, customers or insurers.
Modeling of Abradable Coating Removal in Aircraft Engines Through Delay Differential Equations
Authors: Salvat Nicolas , Batailly Alain , Legrand Mathias 
Published: November 2013

In modern turbomachinery, abradable materials are implemented on casings to reduce operating tip clearances and mitigate direct unilateral contact occurrences between rotating and stationary components. However, both experimental and numerical investigations revealed that blade/abradable interactions may lead to blade failures.
In order to comprehend the underlying mechanism, an accurate modeling of the abradable removal process is required. Time-marching strategies where the abradable removal is modeled through plasticity are available but another angle of attack is proposed in this work. It is assumed that the removal of abradable liners shares similarities with machine tool chatter encountered in manufacturing. Chatter is a self-excited vibration caused by the interaction between the machine and the workpiece through the cutting forces, and the corresponding dynamics are efficiently captured by delay differential equations. They differ from ordinary differential equations in that previous states of the system are involved. This mathematical framework is here employed for the exploration of the blade stability during abradable removal.
The proposed tool advantageously features a reduced computational cost and consistency with existing time-marching solution methods. Potentially dangerous interaction regimes are accurately predicted and instability lobes match both flexural and torsional modal responses. Essentially, the regenerative nature of chatter in machining processes can also be attributed to abradable coating removal in turbomachinery.
Full Design of a Highly Loaded and Compact Contra-Rotating Fan Using Multidisciplinary Evolutionary Optimization
Authors: Joly Michael , Verstraete Tom , Paniagua Guillermo 
Published: November 2013

Contra-rotation enables one to produce low-weight and high-load fans suitable for high-speed propulsion systems, such as Air Turbo Rocket engines. This paper presents a Multidisciplinary Design Optimization (MDO) methodology to achieve the full-design of highly-loaded and compact contra-rotating fans.
It utilizes a multi-objective optimization at every step of the design. Performances of the two-stage machine is first evaluated by a through-flow model to determine an optimal flow path configuration. A novel parameterization based on span-wise distributions is used to smooth the transition between the preliminary design phase and the detailed three-dimensional shape optimization. High-fidelity aero-mechanical performances are then considered to generate the detailed design of the rotors, including the section profiles along the span, as well as lean and sweep. The multi-objective optimization algorithm treats simultaneously Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM) performances of both rotors. The designed rotors satisfy a 20% safety margin to the yielding strength of titanium. A pressure ratio of 3.07 is achieved with an overall efficiency of 72.4%. A comparison between the through-flow model and the CFD-based optimized shape is made, illustrating a very close match in velocity distributions and losses. It shows that the through-flow code is able to identify an optimal configuration for highly-loaded turbomachines and only needs a small refinement in the subsequent CFD-based optimization. The developed methodology allows to produce innovative configurations at a reduced time-to-market cost compared to traditional designs.
Control of a Supercritical CO2 Recompression Brayton Cycle Demonstration Loop
Authors: Conboy T. , Pasch J. , Fleming D. 
Published: November 2013

The US Department of Energy is currently focused on the development of next-generation nuclear power reactors, with an eye towards improved efficiency and reduced capital cost. To this end, reactors using a closed-Brayton power conversion cycle have been proposed as an attractive alternative to steam turbines. The supercritical-CO2 recompression cycle has been identified as a leading candidate for this application as it can achieve high efficiency at relatively low operating temperatures with extremely compact turbomachinery.
Sandia National Laboratories has been a leader in hardware and component development for the supercritical-CO2 cycle. With contractor Barber-Nichols Inc, Sandia has constructed a megawatt-class S-CO2 cycle test-loop to investigate the key areas of technological uncertainty for this power cycle, and to confirm model estimates of advantageous thermodynamic performance. Until recently, much of the work has centered on the simple S-CO2 cycle — a recuperated Brayton loop with a single turbine and compressor. However work has recently progressed to a recompression cycle with split-shaft turbo-alternator-compressors, unlocking the potential for much greater efficiency power conversion, but introducing greater complexity in control operations.
The following sections use testing experience to frame control actions made by test loop operators in bringing the recompression cycle from cold startup conditions through transition to power generation on both turbines, to the desired test conditions, and finally to a safe shutdown. During this process, considerations regarding turbocompressor thrust state, CO2 thermodynamic state at the compressor inlet, compressor surge and stall, turbine u/c ratio, and numerous other factors must be taken into account. The development of these procedures on the Sandia test facility has greatly reduced the risk to industry in commercial development of the S-CO2 power cycle.