bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Efficiency and Water Recovery in Steam Injected Gas Turbines
Authors: De Paepe M. , Dick E. 
Published: December 2014

The study presented in this paper has two objectives. The first objective is to analyse the efficiency of the steam injected gas turbine by modelling the thermodynamic cycle. This is done by adapting a calculation model for turbine blade cooling proposed by El Masri (1986). The expansion path is divided into small subintervals, to take into account the changing gas properties during the expansion. This model is then verified for four different industrial machines.
The basic cycle as well as cycles with thermodynamic improvements as intercooling, heat recuperation by heat exchanger and blade cooling using steam are studied. The calculations are done for a range of pressure ratios (PR) and turbine inlet temperatures (TIT), with methane (CH4) as fuel being representative of natural gas. A comparison is made with a simple cycle gas turbine and with a combined cycle system. The maximum efficiency of the basic cycle is found to be around 49 % with current gas turbine technology. Steam blade cooling is extremely simple to implement in a steam injected gas turbine and is found to be thermodynamically very attractive, bringing the maximum efficiency to about 52 %.
Secondly the water recuperation in the condenser is analysed. Due to the combustion of the fuel, water is formed. As a result, the dew point temperature of the combustion gas without steam injection can be rather high, i.e. around 45 °C. As a consequence, the amount of water corresponding to the injected steam can be recuperated by cooling the gas mixture to the original dew point temperature. Closing the cycle for water is in this case thermodynamically possible. The practical recuperation of water in the condenser is studied on a test rig with a simulated gas turbine augmented with a condenser and steam injection. This proves that complete recuperation of the injected water is technically possible.
The conclusion of the study is that a steam injected gas turbine with complete water recuperation is possible and has a high efficiency.
Mixing of Multiple Jets With a Confined Subsonic Crossflow: Part II — Opposed Rows of Orifices in Rectangular Ducts
Authors: Holdeman James D. , Liscinsky David S. , Bain Daniel B. 
Published: December 2014

This paper summarizes experimental and computational results on the mixing of opposed rows of jets with a confined subsonic crossflow in rectangular ducts. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex 3-D flowfield in the combustion chambers in gas turbine engines.
The principal observation was that the momentum-flux ratio, J, and the orifice spacing, S/H, were the most significant flow and geometric variables. Jet penetration was critical, and penetration decreased as either momentum-flux ratio or orifice spacing decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the orifice spacing was inversely proportional to the square-root of the momentum-flux ratio. It was also seen that planar averages must be considered in context with the distributions. Note also that the mass-flow ratios and the orifices investigated were often very large (jet-to-mainstream mass-flow ratio >1 and the ratio of orifices-area-to-mainstream-cross-sectional-area up to 0.5 respectively), and the axial planes of interest were often just downstream of the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations.
The Influence of Film-Cooling on the Aerodynamic Performance of a Turbine Nozzle Guide Vane
Authors: Osnaghi C. , Perdichizzi A. , Savini M. , Harasgama P. , Lutum E. 
Published: December 2014

The paper presents the results of an investigation on the aerodynamic performance of a full coverage film-cooled nozzle guide vane. The blading is a typical high pressure turbine vane of advanced design, working in the high subsonic regime.
Tests have been carried out for a wide range of conditions, including variations in Mach number, coolant to mainstream mass flow rate ratio and location of the coolant injection. Both air and carbon dioxide at ambient conditions have been utilized, as coolant flow. Measurements have been performed in a plane located at 0.5 axial chord downstream of the trailing edge by means of a miniaturized five-hole pressure probe.
Performances, in terms of losses, flow angles and profile pressure distributions, for different cooling mass flow rates are presented and compared to the results of the solid blade tests (i.e. with no cooling holes). The results showed a significant increase of the losses with blowing. Test with air and carbon dioxide provided almost equal losses if carried out at the same global momentum flux ratio; however the density ratio was found to influence slightly the share of the coolant fluid among the injection rows and the local momentum flux ratio as well.
In order to define the individual contributions of groups of cooling rows on the performance of the blade, three different modes of injection have been tested, namely full, trailing edge and shower head injection. The main trend observed is that trailing edge injection produces the least amount of additional losses at high blowing rates. Full-coverage film-cooling injection did not lead to marked variations in the blade pressure distribution and/or outlet flow angle.
Aspirated Compressors
Authors: Kerrebrock J. L. , Reijnen D. P. , Ziminsky W. S. , Smilg L. M. 
Published: December 2014

The performance of compressors can be improved in two ways by judicious removal from the flow path of the viscous flow in the boundary layers. First, removal of the boundary layer fluid just prior to or in a region of rapid pressure rise, either at shock incidence or more generally at the point of rapid pressure rise on the suction surface of the airfoil, can enable significant increases in the diffusion, hence in the work done by a stage for any given blade speed. Second, removal of the high entropy fluid in the boundary layer minimizes the required compression work in subsequent stages of compression, thereby raising the compression efficiency. Analysis has shown that the latter effect can result in approximately one half point increase in efficiency for each percent of (high entropy) fluid removal. Design studies have been carried out for two different stages to assess the increase in pressure ratio that may be achieved. One stage that has been designed would produce a pressure ratio of 2 at a tip speed of 1000 ft/sec, and may be very attractive for the fan stage of high-bypass turbofan engines. The other stage would produce a pressure ratio of 3 at a tip speed of 1500 ft/sec, and should be attractive as the first stage of a core compressor or the fan stage of a low-bypass ratio engine. An experiment has been completed, to examine the effect of boundary layer removal just prior to shock impingement on the suction surface of blades in a transonic rotor. The suction was implemented on 5 of the 23 blades of the rotor, providing a direct comparison of the flow behavior with and without suction. Analysis of the data has shown that the blades with suction have increased mass flow and that the flow more closely followed the suction surface near the trailing edge. The differences between aspirated and normal blades were most pronounced when the rotor was very close to stall. The third and fourth of the blades in the group with suction appear to be representative of the behavior to be expected of a rotor with suction on all blades. They exhibited improved efficiency and increased mass flow. The rotor as a whole with suction showed different stall behavior than its counterpart without boundary layer control. Future plans include the fabrication and experimental evaluation in the MIT Blowdown Compressor, of one of the two stages discussed above. In this experiment suction will be applied to all the blades in both rotor and stator, so that the increased work enabled by suction can be realized.
This research was supported by AFOSR, Dr. James McMichael, and by AlliedSignal Aircraft Engines, Dr. Arun Sehra.
Assessment of the dose reduction potential of a model‐based iterative reconstruction algorithm using a task‐based performance metrology
Authors: Samei Ehsan , Richard Samuel 
Published: December 2014

Purpose:Different computed tomography (CT) reconstruction techniques offer different image quality attributes of resolution and noise, challenging the ability to compare their dose reduction potential against each other. The purpose of this study was to evaluate and compare the task‐based imaging performance of CT systems to enable the assessment of the dose performance of a model‐based iterative reconstruction (MBIR) to that of an adaptive statistical iterative reconstruction (ASIR) and a filtered back projection (FBP) technique.Methods:The ACR CT phantom (model 464) was imaged across a wide range of mA setting on a 64‐slice CT scanner (GE Discovery CT750 HD, Waukesha, WI). Based on previous work, the resolution was evaluated in terms of a task‐based modulation transfer function (MTF) using a circular‐edge technique and images from the contrast inserts located in the ACR phantom. Noise performance was assessed in terms of the noise‐power spectrum (NPS) measured from the uniform section of the phantom. The task‐based MTF and NPS were combined with a task function to yield a task‐based estimate of imaging performance, the detectability index (d′). The detectability index was computed as a function of dose for two imaging tasks corresponding to the detection of a relatively small and a relatively large feature (1.5 and 25 mm, respectively). The performance of MBIR in terms of the d′ was compared with that of ASIR and FBP to assess its dose reduction potential.Results:Results indicated that MBIR exhibits a variability spatial resolution with respect to object contrast and noise while significantly reducing image noise. The NPS measurements for MBIR indicated a noise texture with a low‐pass quality compared to the typical midpass noise found in FBP‐based CT images. At comparable dose, the d′ for MBIR was higher than those of FBP and ASIR by at least 61% and 19% for the small feature and the large feature tasks, respectively. Compared to FBP and ASIR, MBIR indicated a 46%–84% dose reduction potential, depending on task, without compromising the modeled detection performance.Conclusions:The presented methodology based on ACR phantom measurements extends current possibilities for the assessment of CT image quality under the complex resolution and noise characteristics exhibited with statistical and iterative reconstruction algorithms. The findings further suggest that MBIR can potentially make better use of the projections data to reduce CT dose by approximately a factor of 2. Alternatively, if the dose held unchanged, it can improve image quality by different levels for different tasks.
Cost of unintended pregnancy in Norway: a role for long-acting reversible contraception
Authors: Henry Nathaniel , Schlueter Max , Lowin Julia , Lekander Ingrid , Filonenko Anna , Trussell James , Skjeldestad Finn Egil 
Published: December 2014

ObjectivesThe objective of this study was to quantify the cost burden of unintended pregnancies (UPs) in Norway, and to estimate the proportion of costs due to imperfect contraceptive adherence. Potential cost savings that could arise from increased uptake of long-acting reversible contraception (LARC) were also investigated.MethodsAn economic model was constructed to estimate the total number of UPs and associated costs in women aged 15–24 years. Adherence-related UP was estimated using ‘perfect use’ and ‘typical use’ contraceptive failure rates. Potential savings from increased use of LARC were projected by comparing current costs to projected costs following a 5% increase in LARC uptake.ResultsTotal costs from UP in women aged 15–24 years were estimated to be 164 million Norwegian Kroner (NOK), of which 81.7% were projected to be due to imperfect contraceptive adherence. A 5% increase in LARC uptake was estimated to generate cost savings of NOK 7.2 million in this group.ConclusionsThe cost of UP in Norway is substantial, with a large proportion of this cost arising from imperfect contraceptive adherence. Increased LARC uptake may reduce the UP incidence and generate cost savings for both the health care payer and contraceptive user.
Interactive Learning of Pattern Rankings
Authors: Dzyuba Vladimir , Leeuwen Matthijs van , Nijssen Siegfried , De Raedt Luc 
Published: December 2014

Pattern mining provides useful tools for exploratory data analysis. Numerous efficient algorithms exist that are able to discover various types of patterns in large datasets. Unfortunately, the problem of identifying patterns that are genuinely interesting to a particular user remains challenging. Current approaches generally require considerable data mining expertise or effort from the data analyst, and hence cannot be used by typical domain experts. To address this, we introduce a generic framework for interactive learning of userspecific pattern ranking functions. The user is only asked to rank small sets of patterns, while a ranking function is inferred from this feedback by preference learning techniques. Moreover, we propose a number of active learning heuristics to minimize the effort required from the user, while ensuring that accurate rankings are obtained. We show how the learned ranking functions can be used to mine new, more interesting patterns. We demonstrate two concrete instances of our framework for two different pattern mining tasks, frequent itemset mining and subgroup discovery. We empirically evaluate the capacity of the algorithm to learn pattern rankings by emulating users. Experiments demonstrate that the system is able to learn accurate rankings, and that the active learning heuristics help reduce the required user effort. Furthermore, using the learned ranking functions as search heuristics allows discovering patterns of higher quality than those in the initial set. This shows that machine learning techniques in general, and active preference learning in particular, are promising building blocks for interactive data mining systems.
Five-Year Outcome of Catheter Ablation of Persistent Atrial Fibrillation Using Termination of Atrial Fibrillation as a Procedural Endpoint
Authors: Scherr Daniel , Khairy Paul , Miyazaki Shinsuke , Aurillac-Lavignolle Valerie , Pascale Patrizio , Wilton Stephen B. , Ramoul Khaled , Komatsu Yuki , Roten Laurent , Jadidi Amir , Linton Nick , Pedersen Michala , Daly Matthew , O’Neill Mark , Knecht Sebastien , Weerasooriya Rukshen , Rostock Thomas , Manninger Martin , Cochet Hubert , Shah Ashok J. , Yeim Sunthareth , Denis Arnaud , Derval Nicolas , Hocini Meleze , Sacher Frederic , Haissaguerre Michel , Jais Pierre 
Published: December 2014

Background—
This study aimed to determine 5-year efficacy of catheter ablation for persistent atrial fibrillation (AF) using AF termination as a procedural end point.

Methods and Results—

One hundred fifty patients (57±10 years) underwent persistent AF ablation using a stepwise ablation approach (pulmonary vein isolation, electrogram-guided, and linear ablation) with the desired procedural end point being AF termination. Repeat ablation was performed for recurrent AF or atrial tachycardia. AF was terminated by ablation in 120 patients (80%). Arrhythmia-free survival rates after a single procedure were 35.3%±3.9%, 28.0%±3.7%, and 16.8%±3.2% at 1, 2, and 5 years, respectively. Arrhythmia-free survival rates after the last procedure (mean 2.1±1.0 procedures) were 89.7%±2.5%, 79.8%±3.4%, and 62.9%±4.5%, at 1, 2, and 5 years, respectively. During a median follow-up of 58 (interquartile range, 43–73) months after the last ablation procedure, 97 of 150 (64.7%) patients remained in sinus rhythm without antiarrhythmic drugs. Another 14 (9.3%) patients maintained sinus rhythm after reinitiation of antiarrhythmic drugs, and an additional 15 (10.0%) patients regressed to paroxysmal recurrences only. Failure to terminate AF during the index procedure (hazard ratio 3.831; 95% confidence interval, 2.070–7.143;
P
<0.001), left atrial diameter ≥50 mm (hazard ratio 2.083; 95% confidence interval, 1.078–4.016;
P
=0.03), continuous AF duration ≥18 months (hazard ratio 1.984; 95% confidence interval, 1.024–3.846;
P
<0.04), and structural heart disease (hazard ratio 1.874; 95% confidence interval, 1.037–3.388;
P
=0.04) predicted arrhythmia recurrence.

Conclusions—
In patients with persistent AF, an ablation strategy aiming at AF termination is associated with freedom from arrhythmia recurrence in the majority of patients over a 5-year follow-up period. Procedural AF nontermination and specific baseline factors predict long-term outcome after ablation.
Elevated Placental Adenosine Signaling Contributes to the Pathogenesis of Preeclampsia
Authors: Iriyama Takayuki , Sun Kaiqi , Parchim Nicholas F. , Li Jessica , Zhao Cheng , Song Anren , Hart Laura A. , Blackwell Sean C. , Sibai Baha M. , Chan Lee-Nien L. , Chan Teh-Sheng , Hicks M. John , Blackburn Michael R. , Kellems Rodney E. , Xia Yang 
Published: December 2014

Background—
Preeclampsia is a prevalent hypertensive disorder of pregnancy and a leading cause of maternal and neonatal morbidity and mortality worldwide. This pathogenic condition is speculated to be caused by placental abnormalities that contribute to the maternal syndrome. However, the specific factors and signaling pathways that lead to impaired placentas and maternal disease development remain elusive.

Methods and Results—

Using 2 independent animal models of preeclampsia (genetically engineered pregnant mice with elevated adenosine exclusively in placentas and a pathogenic autoantibody-induced preeclampsia mouse model), we demonstrated that chronically elevated placental adenosine was sufficient to induce hallmark features of preeclampsia, including hypertension, proteinuria, small fetuses, and impaired placental vasculature. Genetic and pharmacological approaches revealed that elevated placental adenosine coupled with excessive A
2B
adenosine receptor (ADORA2B) signaling contributed to the development of these features of preeclampsia. Mechanistically, we provided both human and mouse evidence that elevated placental CD73 is a key enzyme causing increased placental adenosine, thereby contributing to preeclampsia.

Conclusions—
We determined that elevated placental adenosine signaling is a previously unrecognized pathogenic factor for preeclampsia. Moreover, our findings revealed the molecular basis underlying the elevation of placental adenosine and the detrimental role of excess placental adenosine in the pathophysiology of preeclampsia, and thereby, we highlight novel therapeutic targets.
an Exhibit/an Aesthetic: Richard Hamilton and Postwar Exhibition Design
Authors: Lotery Kevin 
Published: December 2014

The story, as Richard Hamilton told it years later, begins with something of an insult. Upon viewing Hamilton's 1955 exhibition Man, Machine, and Motion, Victor Pasmore, the Constructivist sculptor and Hamilton's then-colleague at King's College in Newcast le, delivered a snide quasi-compliment, dismissing the iconographical content (and main attraction) of the project only to praise the mere apparatus of exhibiting—the bracket and framing system that Hamilton had invented to exhibit his imposing photographic enlargements of men and their technical prostheses. “It would have been very good,” Pasmore is purport-ed to have said, “if it hadn't been for all those photographs.”2But clearly the exhibition intrigued Pasmore, who would approach Hamilton later in the hope of collaborating with the younger artist. Hamilton recalls:Remembering his comment on Man, Machine and Motion I proposed that we might make a show which would be its own justification: no theme, no subject, not a display of things or ideas—pure abstract exhibition.3
2DVD Data Revisited: Multifractal Insights into Cuts of the Spatiotemporal Rainfall Process
Authors: Gires Auguste , Tchiguirinskaia Ioulia , Schertzer Daniel , Berne Alexis 
Published: December 2014

Abstract
Data collected during four heavy rainfall events that occurred in Ardèche (France) with the help of a 2D video disdrometer (2DVD) are used to investigate the structure of the raindrop distribution in both space and time. A first type of analysis is based on the reconstruction of 36-m-height vertical rainfall columns above the measuring device. This reconstruction is obtained with the help of a ballistic hypothesis applied to 1-ms time step series. The corresponding snapshots are analyzed with the help of universal multifractals. For comparison, a similar analysis is performed on the time series with 1-ms time steps, as well as on time series of accumulation maps of N consecutive recorded drops (therefore with variable time steps). It turns out that the drop distribution exhibits a good scaling behavior in the range 0.5–36 m during the heaviest portion of the events, confirming the lack of empirical evidence of the widely used homogenous assumption for drop distribution. For smaller scales, drop positions seem to be homogeneously distributed. The notion of multifractal singularity is well illustrated by the very high-resolution time series.
Should Drivers Be Operating Within an Automation-Free Bandwidth? Evaluating Haptic Steering Support Systems With Different Levels of Authority
Authors: Petermeijer Sebastiaan M. , Abbink David A. , de Winter Joost C. F. 
Published: December 2014

Objective: The aim of this study was to compare continuous versus bandwidth haptic steering guidance in terms of lane-keeping behavior, aftereffects, and satisfaction. Background: An important human factors question is whether operators should be supported continuously or only when tolerance limits are exceeded. We aimed to clarify this issue for haptic steering guidance by investigating costs and benefits of both approaches in a driving simulator. Methods: Thirty-two participants drove five trials, each with a different level of haptic support: no guidance (Manual); guidance outside a 0.5-m bandwidth (Band1); a hysteresis version of Band1, which guided back to the lane center once triggered (Band2); continuous guidance (Cont); and Cont with double feedback gain (ContS). Participants performed a reaction time task while driving. Toward the end of each trial, the guidance was unexpectedly disabled to investigate aftereffects. Results: All four guidance systems prevented large lateral errors (>0.7 m). Cont and especially ContS yielded smaller lateral errors and higher time to line crossing than Manual, Band1, and Band2. Cont and ContS yielded short-lasting aftereffects, whereas Band1 and Band2 did not. Cont yielded higher self-reported satisfaction and faster reaction times than Band1. Conclusions: Continuous and bandwidth guidance both prevent large driver errors. Continuous guidance yields improved performance and satisfaction over bandwidth guidance at the cost of aftereffects and variability in driver torque (indicating human–automation conflicts). Application: The presented results are useful for designers of haptic guidance systems and support critical thinking about the costs and benefits of automation support systems.