bluuebunny/crossref_metadata_2025_split huggingface dataset:
Factors associated with delivery outside a health facility: cross‐sectional study in rural Malawi
Authors: Mazalale Jacob , Kambala Christabel , Brenner Stephan , Chinkhumba Jobiba , Lohmann Julia , Mathanga Don P. , Robberstad Bjarne , Muula Adamson S. , De Allegri Manuela 
Published: February 2015

AbstractObjectiveTo identify factors associated with delivery outside a health facility in rural Malawi.MethodA cross‐sectional survey was conducted in Balaka, Dedza, Mchinji and Ntcheu districts in Malawi in 2013 among women who had completed a pregnancy 12 months prior to the day of the survey. Multilevel logistic regression was used to assess factors associated with delivery outside a facility.ResultsOf the 1812 study respondents, 9% (n = 159) reported to have delivered outside a facility. Unmarried women were significantly more likely [OR = 1.88; 95% CI (1.086–3.173)] to deliver outside a facility, while women from households with higher socio‐economic status [third‐quartile OR = 0.51; 95% CI (0.28–0.95) and fourth‐quartile OR = 0.48; 95% CI (0.29–0.79)] and in urban areas [OR = 0.39; 95%‐CI (0.23–0.67)] were significantly less likely to deliver outside a facility. Women without formal education [OR 1.43; 95% CI (0.96–2.14)] and multigravidae [OR = 1.14; 95% CI (0.98–1.73)] were more likely to deliver outside a health facility at 10% level of significance.ConclusionAbout 9% of women deliver outside a facility. Policies to encourage facility delivery should not only focus on health systems but also be multisectoral to address women's vulnerability and inequality. Facility‐based delivery can contribute to curbing the high maternal illness burden if authorities provide incentives to those not delivering at the facility without losing existing users.
Menstrual cycle phase does not affect sympathetic neural activity in women with postural orthostatic tachycardia syndrome
Authors: Stickford Abigail S.L. , VanGundy Tiffany B. , Levine Benjamin D. , Fu Qi 
Published: February 2015

Key points
Women with the postural orthostatic tachycardia syndrome (POTS) report fluctuations in orthostatic tolerance throughout the menstrual cycle.
The mechanism(s) underlying blood pressure control across the menstrual cycle in women with POTS are unknown.
The findings of the present study indicate that the menstrual cycle does not affect muscle sympathetic nerve activity but modulates blood pressure and vasoconstriction in POTS women during orthostatic stress.
Factors other than sympathetic neural activity are likely responsible for the symptoms of orthostatic intolerance across the menstrual cycle in women with POTS.
AbstractPatients with the postural orthostatic tachycardia syndrome (POTS) are primarily premenopausal women, which may be attributed to female sex hormones. We tested the hypothesis that hormonal fluctuations of the menstrual cycle alter sympathetic neural activity and orthostatic tolerance in POTS women. Ten POTS women were studied during the early follicular (EF) and mid‐luteal (ML) phases of the menstrual cycle. Haemodynamics and muscle sympathetic nerve activity (MSNA) were measured when supine, during 60 deg upright tilt for 45 min or until presyncope, and during the cold pressor test (CPT) and Valsalva manoeuvres. Blood pressure and total peripheral resistance were higher during rest and tilting in the ML than EF phase; however, heart rate, stroke volume and cardiac output were similar between phases. There were no mean ± SD differences in MSNA burst frequency (8 ± 8 EF phase vs. 10 ± 10 bursts min–1 ML phase at rest; 34 ± 15 EF phase vs. 36 ± 16 bursts min–1 ML phase at 5 min tilt), burst incidence or total activity, nor any differences in the cardiovagal and sympathetic baroreflex sensitivities between phases under any condition. The incidence of presyncope was also the same between phases. There were no differences in haemodynamic or sympathetic responses to CPT or Valsalva. These results suggest that the menstrual cycle does not affect sympathetic neural activity but modulates blood pressure and vasoconstriction in POTS women during tilting. Thus, factors other than sympathetic neural activity are probably responsible for the symptoms of orthostatic intolerance across the menstrual cycle in women with POTS.
H Gas Turbine Combined Cycle Technology and Development Status
Authors: Corman James C. 
Published: February 2015

A revolutionary step has been taken in the development of the Next Advance in Power Generation Systems — “H” Technology Combined Cycle. This new gas turbine combined cycle system increases thermal performance to the 60% level by increasing gas turbine operating conditions to 2600°F (1430°C) at a pressure ratio of 23 to 1. This represents a significant increase in operating temperature for the gas turbine. However, the potential for single digit NOx levels (based upon 15% O2 in the exhaust) has been retained. The combined effect of performance increase and environmental control is achieved by an innovative closed loop steam cooling system which tightly integrated the gas turbine and steam turbine cycles.
Although a significant advance has been taken in performance, the new power generation system has been configured with a substantial number of proven concepts and technology programs are ongoing to validate the new features. The technical activities which support the introduction of the new turbine system have reached a point in the development cycle where the results are integrated into the design methods. This has permitted the “H” Technology to achieve a design readiness status and the first unit will be under test in late 1997.
Simple Instrumentation Rake Designs for Gas Turbine Engine Testing
Authors: Smout Peter D. , Cook Steven C. 
Published: February 2015

The determination of gas turbine engine performance relies heavily on intrusive rakes of pilot tubes and thermocouples for gas path pressure and temperature measurement. For over forty years, Kiel-shrouds mounted on the rake body leading edge have been used as the industry standard to de-sensitise the instrument to variations in flow incidence and velocity. This results in a complex rake design which is expensive to manufacture, susceptible to mechanical damage, and difficult to repair.
This paper describes an exercise aimed at radically reducing rake manufacture and repair costs. A novel ’common cavity rake’ (CCR) design is presented where the pressure and/or temperature sensors are housed in a single slot let into the rake leading edge. Aerodynamic calibration data is included to show that the performance of the CCR design under uniform flow conditions and in an imposed total pressure gradient is equivalent to that of a conventional Kiel-shrouded rake.
Three-Dimensional Inverse Method for Turbomachinery Blading Design
Authors: Demeulenaere Alain , Van den Braembussche René 
Published: February 2015

An iterative procedure for 3D blade design is presented. The three-dimensional blade shape is modified using a physical algorithm, based on the transpiration model. The transpiration flux is computed by means of a modified Euler solver, in which the target pressure distribution is imposed along the blade surfaces. Only a small number of modifications is needed to obtain the final geometry.
The method is based on a high resolution three-dimensional Euler solver. An upwind biased evaluation of the advective fluxes allows for a very low numerical entropy generation, and sharp shock capturing.
The method is first validated, by redesigning an existing geometry, starting from a different one. It is further used to redesign a transonic compressor blade, to achieve, for the same mass flow and outlet flow angle, a shock free deceleration along the suction side. The last example concerns the design of a low aspect ratio turbine blade, with a positive compound lean to reduce the intensity of the passage vortices. The final blade is designed for an optimized pressure distribution, taking into account the forces resulting from the blade lean angle.
Externally Fired Combined Cycles (EFCC): Part A — Thermodynamics and Technological Issues
Authors: Consonni Stefano , Macchi Ennio , Farina Francesco 
Published: February 2015

Externally Fired Combined Cycles (EFCC) are one of the options allowing the use of “dirty” fuels like coal, biomass or waste in conjunction with modern, high efficiency gas turbines. The plant concept comprises an indirect-contact ceramic heat exchanger where compressed air exiting the gas turbine compressor is heated by hot combustion gases; the combustor is placed downstream the turbine and operates at nearly atmospheric pressure.
From a thermodynamic standpoint, the cycle is equivalent to a combined cycle with supplementary firing. Attainable efficiencies are higher than those achievable by steam cycles (even the most advanced ultra-supercritical), as well as those of most other coal-based technologies (PFBC and IGCC). These efficiency advantages must be weighted against the uncertainty (and risk) of the realization of high temperature ceramic heat exchangers, and the challenges for the design of the combustor.
This two-part paper discusses thermodynamic, technological and economic issues crucial to the success of EFCCs, both for large scale utility service (3–400 MWe1 and more) and for medium/low scale applications (down to 30–50 MWe1). Part A addresses the most relevant thermodynamic and technological issues, performing comparisons with the technologies which will presumably dominate the coal-based power generation market of the next century.
Externally Fired Combined Cycles (EFCC): Part B — Alternative Configurations and Cost Projections
Authors: Consonni Stefano , Macchi Ennio 
Published: February 2015

Externally Fired Combined Cycles (EFCC) constitute one of the options allowing the use of “dirty” fuels like coal, biomass or waste in conjunction with modern, high efficiency gas turbines. This two-part paper discusses thermodynamic, technological and economic issues crucial to the successful realization of EFCCs.
Part B discusses the cycle arrangement, its implications for the design and the cost of the high temperature heat exchangers, the effects of scale and the economic prospects. An “enhanced” configuration whereby the excess air sent to the combustor is limited to the minimum required for complete combustion can reach net LHV efficiencies above 50%, with relatively low high-temperature heat transfer surface requirements. Cost projections are hindered by the uncertainty on the cost of the high temperature heat exchangers. Estimates based on published and proprietary data collected by the authors indicate that EFCCs should be cost-competitive with IGCCs, especially at medium-low power outputs.
Turbomachinery Diagnostic System: SNAM Cortemaggiore Compressor Station as a Typical Application
Authors: Pulicani Paolo , Zampieri Giuliano 
Published: February 2015

The development in the computer networking area has been growing in the past few years in connection with the prevaling of the open system concepts and with the improvement in microcomputers as opposed to minicomputers technology. Compared to the structure of a centralized system, a distribuited structure gives the following advantages: functional flexibility, maintainability, software rangeability and friendly interface with the operator.
Based on several years of field experience. Nuovo Pignone has developed an on-line diagnostic system for turbomachines made up of integrated hardware and software modules designed for optimum management of information coming from turbomachines. The system controls the mechanical and thermodynamic behaviour of the machines, thus providing an effective support to their operation and maintenance. This results in an increased availability lower maintainance costs and improved plant efficiency.
A mathematical model, based on Gas Path Analysis (G.P.A.) methodology, has been implemented in the system and has already been successfully tested in several industrial applications, quite similar to Cortemaggiore plant.
The experience gained in the Cortemaggiore gas compression station indicates that the main problem arises in interpretation of the data coming from the system. The Diagnostic System gives plenty of data, suitably arranged, to support the maintenance staff in their duties. Nevertheless is the operator who had to interpretate data, correlate thermodynamic information with mechanical data and decide on the best course of action. Taking into account that many plants are not continuously attended by highly experienced technicians in this domain, Nuovo Pignone has developed an Expert System, integrated with the Diagnostic Packages, that incorporates all the information acquired from skilled field engineers during years of activities.
Analysis and Validation of Turbine Disc Cooling
Authors: Hannis John M. , Maltson John D. , Corry Robert J. , Johnson Nigel 
Published: February 2015

Design and analysis of the turbine disc cooling and secondary air systems, thermal analysis of the rotor structure and subsequent validation of the temperature levels are described for a 4.9 MW industrial gas turbine.
A general purpose air flow network solver specifically developed for GT air systems is used to analyse and optimise the disc cooling air flows and determine the interaction between disc air, rotor blade cooling air and leakage.
Analysis of the individual wheelspace cavities is undertaken accounting for windage heating, rim sealing and potential for ingestion, heat transfer levels and cooling air temperature rise. This involves both simple 1D methods based on conservation of angular momentum and CFD analysis to determine flow recirculation mechanisms in the disc wheelspace.
The thermal boundary conditions from the above are applied to a finite difference thermal analysis model of the turbine rotor to predict temperature distributions at both steady state and transient conditions.
Test validation on the engine provides air system pressures and temperatures to validate the airflow analysis and rotor temperatures from thermal paints to validate the thermal analysis.
Experimental Study of Tip Clearance Effects Under Transonic Flow Conditions
Authors: Wehner M. , Bölcs A. , Bütikofer J. 
Published: February 2015

An idealized 3 blade test section has been used to study tip clearance effects which occur in transonic axial turbines. At subsonic inlet conditions (Mis1 = 0.56) the flow leaves the test section supersonic (Mis2 = 1.26). The tip clearance was varied from 0 to 15% of the chord length.
Extensive laser-2-focus anemometry was used to determine the tip gap mass flow based on the velocity vectors for gaps with 6, 10 and 15% chord. At small clearances the tip gap flow is mainly influenced by the pressure drop between pressure and suction side, while for larger gaps the main flow field dominates the tip gap flow.
The variation of the blade loading with the tip clearance was measured by static pressure tappings at 50% and 90% Span. Furthermore the static pressure along the tip surface was measured for varying tip clearances.
Pitot probe traverses in the tip vortex region at different downstream positions revealed the vortex structures and vortex core evolution. For tip gaps of 3 and 6%, multiple vortices were detected which were not fully mixed downstream. The origin of these vortices moves towards the trailing edge for larger gaps.
The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals
Authors: Kleynhans George F. , Childs Dara W. 
Published: February 2015

A two-control-volume model is employed for honeycomb-stator/smooth-rotor seals, with a conventional control-volume used for the through flow and a “capacitance-accumulator” model for the honeycomb cells. The control volume for the honeycomb cells is shown to cause a dramatic reduction in the effective acoustic velocity of the main flow, dropping the lowest acoustic frequency into the frequency range of interest for rotordynamics. In these circumstances, the impedance functions for the seals can not be modeled with conventional (frequency-independent) stiffness, damping, and mass coefficients. More general transform functions are required to account for the reaction forces, and the transfer functions calculated here are a lead-lag term for the direct force function and a lag term for the cross-coupled function. Experimental measurements verify the magnitude and phase trends of the proposed transfer functions.
These first-order functions are simple, compared to transfer functions for magnetic bearings or foundations. For synchronous response due to imbalance, they can be approximated by running-speed-dependent stiffness and damping coefficients in conventional rotordynamics codes. Correct predictions for stability and transient response will require more general algorithms, presumably using a state-space format.
The Maximum Factor by Which Forced Vibration of Blades Can Increase due to Mistuning
Authors: Whitehead Denis S. 
Published: February 2015

In 1966 it was shown that the maximum factor by which the amplitude of forced vibration of blades can increase due 10 mistuning is, with certain assumptions, 1/2(1+√N), where N is the number of blades in the row. This report gives a further investigation of the circumstances when this factor can be obtained. These are, small damping, and a relationship must hold between the mistuning distribution γ(s) and the interblade coupling function c(r), where r is the mode number. The mistuning distribution must be symmetrical about the blade on which maximum amplitude is to occur, s=0. The coupling function must be symmetrical about r=R, where R is the mode number of the excitation.
If the coupling is purely mechanical, additional conditions apply. The coupling function c(r) must consist of a number of identical symmetrical sub-strips. A 1976 result for mechanical coupling is amended.
Comparison Between Complete Hilbert Transform and Simplified Solutions of the Moore Rotating Stall Model
Authors: Arnulfi Gianmario L. , Ghiglino Fabio L. , Massardo Aristide F. 
Published: February 2015

The main objective of this work is the analysis and the comparison between different methods utilised to solve the Moore rotating stall model. To date only simplified relations between the axial flow perturbation g and the transverse one h have been utilised and presented in literature, such as h′ = −g or the truncated Fourier series. On the contrary, in this paper the accurate relation given by the Hilbert Transform is utilised, and to improve the numerical stability of the method a new expression of the first derivative of transverse flow coefficient perturbation is proposed and utilised.
A complete and detailed comparison between the results of the simplified methods and the solution proposed here is presented. This comparison is extended to a wide range of geometrical and physical compressor parameters, and it allows the accuracy of simplified approaches to be tested.
Finally, a correlative approach estimating overall rotating stall effects based on the complete solution proposed here is presented. It allows rotating stall influence to be quickly and easily taken into account in several axial compressor areas (design, optimisation, active control, etc.).
Anchored CCD for Gas Turbine Combustor Design and Data Correlation
Authors: Danis Allen M. , Burrus David L. , Mongia Hukam C. 
Published: February 2015

Correlations based on design database, combined with multi-dimensional computational combustion dynamics (CCD) models are used in the combustion design process. However, because of limitations in the current turbulent combustion models, numerics, and boundary conditions, CCD has provided mainly qualitative trends for aerothermal performance, emissions and liner wall temperature levels and gradients. To overcome these deficiencies, hybrid modeling approaches have been proposed to analyze existing combustors. A typical hybrid modeling approach combines empirical and semianalytical correlations with CCD to give quantitatively accurate predictions of NOx, CO, HC, smoke, lean blowout, ignition, pattern factor and liner wall temperatures.
An alternate approach, anchored CCD, is described in this paper. First, the models were anchored with one of the five modern turbopropulsion engine combustors. The anchored models were then run for the other four combustors. The predicted results correlated well with measured NOx, CO, HC, LBO and exit temperature quality data, demonstrating a broader applicability of the anchored method. The models were also used for designing a new combustion concept. The pre-test prediction agreed well with sector rig data from development hardware, showing the feasibility of using the anchored methodology as a design tool.
Next-Generation Integration Concepts for Air Separation Units and Gas Turbines
Authors: Smith Arthur R. , Klosek Joseph , Woodward Donald W. 
Published: February 2015

The commercialization of Integrated Gasification Combined Cycle (IGCC) power has been aided by concepts involving the integration of a cryogenic air separation unit (ASU) with the gas turbine combined-cycle module. Other processes, such as coal-based ironmaking and combined power/industrial gas production facilities, can also benefit from the integration. It is known and now widely accepted that an ASU designed for “elevated pressure” service and optimally integrated with the gas turbine can increase overall IGCC power output, increase overall efficiency, and decrease the net cost of power generation when compared to non-integrated facilities employing low pressure ASU’s. The specific gas turbine, gasification technology. NOx emission specification, and other site specific factors determine the optimal degree of compressed air and nitrogen stream integration.
Continuing advancements in both air separation and gas turbine technologies offer new integration opportunities to improve performance and reduce costs. This paper reviews basic integration principles and describes next-generation concepts based on advanced high pressure ratio gas turbines, Humid Air Turbine (HAT) cycles and integration of compression heat and refrigeration sources from the ASU. Operability issues associated with integration are reviewed and control measures are described for the safe, efficient and reliable operation of these facilities.