bluuebunny/crossref_metadata_2025_split huggingface dataset:
Indirect Firing of Gas Turbines by Residual Coal-Water Fuel
Authors: Green Leon 
Published: April 2015

Production of low-ash, low-sulfur coal-water fuel (CWF) will yield large quantities of high-ash but still low-sulfur “residual” CWF analogous to the residual fuel oil produced by petroleum refining. Relatively low in cost compared to the premium, low-ash CWF product, “resid” CWF will thus be available for in-plant industrial generation of conventional steam power or process heat. Due to its low sulfur content, however, a higher-value use of such a compliance fuel can be the indirect firing of gas turbines for the more efficient combination of power generation plus subsequent bottoming-cycle use or process heat applications (cogeneration).
To limit NOx emissions, staged combustion will be required. Such operation can be accomplished starting with substoichiometric CWF reaction in “conventional” slurry burners followed by final combustion completed in the bottom region of a deep, intensely-mixed, fludized-bed heat exchanger. By virtue of the highly enhanced heat-transfer characteristics of the strongly-stirred bed of non-reactive particles, the normal limitation of rates of non-pressurized fire-side heat transfer is elevated. The fuel ash particles, milled fine by passage through the bed of refractory heat-transfer particles, are collected in a conventional baghouse. The conceptual design of such a combustion-driven, fluid-bed heat exchanger system fired by high-ash, residual coal-water fuel is outlined and its advantages over a conventional fluid-bed, solid-coal combustor for indirect firing of gas turbines are enumerated.
The Burning of Coal-Water Slurry Fuels in a Two-Stage Slagging Combustor
Authors: LeCren R. T. , White D. J. 
Published: April 2015

A two-stage coal-water slurry high-pressure gas turbine combustion system employing a primary zone with a hot refractory wall and an internal slag removal system has been designed, built and tested. The molten ash is removed by aerodynamic means using a form of jet impaction, a method that promises to be more effective than the more conventional cyclonic approaches. The overall combustion system is extremely flexible and can be readily configured to operate either with a lean or a rich reaction (primary) zone. In both cases a lean secondary zone is used.
Results showing emission signatures of a number of coal-water slurry fuels operating with the combustor arranged in a rich primary zone configuration are presented. Petroleum based fuels show emission trends that are very similar to those previously published. Coal-water slurry combustion, however, results in emission signatures that cover only a relatively narrow fuel-air ratio range because of the limited combustion stability. NOx emissions have been obtained that meet EPA regulations for stationary gas turbines.
Technical Evaluation of Simplified IGCC Components
Authors: Horner M. W. , Alff R. K. , Corman J. C. 
Published: April 2015

Simplified integrated gasification combined cycle (IGCC) power plants offer attractive advantages for improving the performance of coal to electricity systems. This plant configuration, which utilizes a coal gasifier, hot gas cleanup system, and gas turbine combined cycle, has the potential to reduce both capital costs for equipment and fuel costs through improved efficiency. This paper reports the results of fuel supply and gas turbine testing on actual hot low-Btu coal gas.
A pilot-scale advanced fixed-bed gasifier has been modified to supply hot coal gas to a particulate removal cyclone and then to a gas turbine simulator. The hot gas is combusted in a General Electric MS6000 combustor developed for low-Btu gas fuel. The combusted product flows through a MS6000 turbine first-stage nozzle sector. The exhaust gases from the nozzle sector pass over air-cooled cylindrical ash deposition pin specimens and then into a water quench exhaust system.
Extensive instrumentation and sampling provisions are utilized to characterize the fuel gas, the combustion gases, and the ash deposits formed on turbine components. Two regimes of nozzle metal surface temperatures have been investigated by separate testing performed including 500–600 °F with water-cooled and 1500–1650 °F with air-cooled nozzle sectors. Results from the test program have provided key data related to fuel gas cleanup and the tolerance of gas turbine hot gas path parts to the products of combustion from coal-derived fuels.
Production and Development of Secondary Flows and Losses Within a Three Dimensional Turbine Stator Cascade
Authors: Yamamoto A. , Yanagi R. 
Published: April 2015

Using five-hole pitot tubes, detailed flow measurements were made before, within and after a low-speed three-dimensional turbine stator blade row to obtain quantitative information on the aerodynamic loss mechanism. Qualitative flow visualization tests and endwall static pressure measurements were also made.
An analysis of the tests revealed that many vortical flows promote loss generation. Within a large part of the cascade, a major loss process could be explained simply as the migration of boundary layer low energy fluids from surrounding walls (endwalls and blade surfaces) to the blade suction surface near the trailing edge. On the other hand, complexity exists after the cascade and in the vortical flows near the trailing edge. The strong trailing shedding vortices affect upstream flow fields within the cascade. Detailed flow surveys within the cascade under the effects of blade tip leakage flows are also included.
Preliminary Results of a Study of the Relationship Between Free Stream Turbulence and Stagnation Region Heat Transfer
Authors: VanFossen G. James , Simoneau Robert J. 
Published: April 2015

A study is being conducted at the NASA Lewis Research Center to investigate the mechanism that causes free stream turbulence to increase heat transfer in the stagnation region of turbine vanes and blades. The work is being conducted in a wind tunnel at atmospheric conditions to facilitate measurements of turbulence and heat transfer. The model size is scaled up to simulate Reynolds numbers (based on leading edge diameter) that are to be expected on a turbine blade leading edge. Reynolds numbers from 13 000 to 177 000 were run in the present tests.
Spanwise averaged heat transfer measurements with high and low turbulence have been made with “rough” and smooth surface stagnation regions. Results of these measurements show that the boundary layer remains laminar in character even in the presence of free stream turbulence at the Reynolds numbers tested. If roughness is added the boundary layer becomes transitional as evidenced by the heat transfer increase with increasing distance from the stagnation line.
Hot wire measurements near the stagnation region downstream of an array of parallel wires has shown that vorticity in the form of mean velocity gradients is amplified as flow approaches the stagnation region. Circumferential traverses of a hot wire probe very near the surface of the cylinder have shown the fluctuating component of velocity changes in character depending on free stream turbulence and Reynolds number.
Finally smoke wire flow visualization and liquid crystal surface heat transfer visualization have been combined to show that, in the wake of an array of parallel wires, heat transfer is a minimum in the wire wakes where the fluctuating component of velocity (local turbulence) was the highest. Heat transfer was found to be the highest between pairs of vortices where the induced velocity is toward the cylinder surface.
Surface Degradation of Ductile Metal in Elevated Temperature Gas-Particle Streams
Authors: Levy Alan , Man Yong-Fa 
Published: April 2015

The mechanisms and rates of erosion and combined erosion-corrosion of 9CrlMo steel and 310SS at elevated temperatures were investigated to better understand the behavior of piping steels in fluidized bed combustor environments. Tests were performed in a partially inert gas atmosphere to study erosion behavior and in an air atmosphere to study combined erosion-corrosion behavior. It was determined that the erosion rate remained constant or decreased with temperature in nitrogen until a temperature was reached at which the tensile strength v.s. temperature curve of the alloy markedly changed its negative slope. Above this temperature the erosion rate increased rapidly with temperature.
In an erosion-corrosion environment corrosion was the dominant mechanism at all test conditions. At higher temperatures and velocities the material loss mechanism changed from low loss rate chipping of the scale to high loss rate periodic spalling. The continuous scale formed on 9CrlMo steel in air appeared to protect the metal surface, decreasing its loss rate in α=30° tests compared to that of 310SS tested at the same conditions in nitrogen where a continuous scale did not form.
A Study Concerning Performance Characteristics of Centrifugal Compressors
Authors: Mizuki Shimpei , Imai Hikaru 
Published: April 2015

A method for estimations of performance characteristics of centrifugal compressors was examined by comparing the estimated results with those by experiments. Lots of empirical and semi-empirical factors which were introduced to the losses within compressor channels in the estimations, and the experimental results for the compressors with a wide variety of configurations, operating conditions and design techniques were investigated. After the extensive comparisons, the most appropriate combinations of the factors for the present method were given.
By employing this method, the major factors which are directly related to the performance characteristics were computed and the relationships among them were discussed. Thus, the ratio of the relative velocity at the impeller exit to that at the inlet, the non-dimensional relative velocity at the impeller inlet and that at the exit were obtained as the parameters of the slip factor, the flow coefficient and the specific speed.
Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager
Authors: Liu Langechuan , Antonuk Larry E. , El‐Mohri Youcef , Zhao Qihua , Jiang Hao 
Published: April 2015

Purpose:In modern radiotherapy treatment rooms, megavoltage (MV) portal imaging and kilovoltage (kV) cone‐beam CT (CBCT) imaging are performed using various active matrix flat‐panel imager (AMFPI) designs. To expand the clinical utility of MV and kV imaging, MV AMFPIs incorporating thick, segmented scintillators and, separately, kV imaging using a beam's eye view geometry have been investigated by a number of groups. Motivated by these previous studies, it is of interest to explore to what extent it is possible to preserve the benefits of kV and MV imaging using a single AMFPI design, given the considerably different x ray energy spectra used for kV and MV imaging. In this paper, considerations for the design of such a dual energy imager are explored through examination of the performance of a variety of hypothetical AMFPIs based on x ray converters employing segmented scintillators.Methods:Contrast, noise, and contrast‐to‐noise ratio performances were characterized through simulation modeling of CBCT imaging, while modulation transfer function, Swank factor, and signal performance were characterized through simulation modeling of planar imaging. The simulations were based on a previously reported hybrid modeling technique (accounting for both radiation and optical effects), augmented through modeling of electronic additive noise. All designs employed BGO scintillator material with thicknesses ranging from 0.25 to 4 cm and element‐to‐element pitches ranging from 0.508 to 1.016 mm. A series of studies were performed under both kV and MV imaging conditions to determine the most advantageous imager configuration (involving front or rear x ray illumination and use of a mirror or black reflector), converter design (pitch and thickness), and operating mode (pitch‐binning combination).Results:Under the assumptions of the present study, the most advantageous imager design was found to employ rear illumination of the converter in combination with a black reflector, incorporate a BGO converter with a 0.508 mm pitch and a 2 cm thickness, and operate at full resolution for kV imaging and 2 × 2 binning mode for MV imaging. Such a dual energy imager design should provide soft tissue visualization at low, clinically practical doses under MV conditions, while helping to preserve the high spatial resolution and high contrast offered by kV imaging.Conclusions:The authors’ theoretical investigation suggests that a dual energy imager capable of largely preserving the desirable characteristics of both kV and MV imaging is feasible. Such an imager, when coupled to a dual energy radiation source, could facilitate simplification of current treatment room imaging systems (as well as their associated quality assurance), and facilitate more precise integration of kV and MV imaging information by virtue of reduced geometric uncertainties.
Sitting Time, Physical Activity, and Cardiorespiratory Fitness: Cooper Center Longitudinal Study Cohort
Authors: Barlow Carolyn E. , Shuval Kerem , Balasubramanian Bijal A. , Kendzor Darla E. , Gabriel Kelley Pettee 
Published: April 2015

Background:Prolonged sitting time is associated with numerous health outcomes; however, the role of cardiorespiratory fitness (CRF) in these relationships is largely unexplored. The cross-sectional association between reported sitting time and measured CRF was examined in a large study of healthy men and women.Methods:The analytic sample included 4658 men and 1737 women enrolled in the Cooper Center Longitudinal Study. Unadjusted and adjusted multivariable linear regression models were constructed to examine the association between sitting time and CRF, stratified by sex and meeting (or not) meeting physical activity (PA) guidelines.Results:In men, CRF was not associated with sitting time after adjustment for potential confounders. In contrast, for women, after adjustment there was a significant association between increased sitting time and lower CRF (P for trend <.001). When stratified by meeting or not meeting PA guidelines, there was no association between sitting time and CRF in men. In women, this relationship was statistically significant regardless of PA category (both P for trend < .05).Conclusions:These results suggest that the association between sitting time and CRF varies by sex. Further, meeting PA guidelines does not appear to modify this relation in either sex.
Structural Equation Modeling Supports a Moderating Role of Personality in the Relationship Between Physical Activity and Mental Health in College Women
Authors: Wilson Kathryn E. , Das Bhibha M. , Evans Ellen M. , Dishman Rodney K. 
Published: April 2015

Background:A positive association between physical activity and mental health is well established, particularly for lower symptoms of depression and anxiety among active adults. However, it is unclear whether the association is influenced by personality, which might moderate or otherwise explain the association. In addition, past studies have not confirmed the association using an objective measure of physical activity.Objective:Our objective was to examine whether Extraversion and Neuroticism influence the association between mental health and physical activity measured by convergent self-reports and an accelerometer.Methods:Structural equation modeling was used to test competing models of the relationships between personality, physical activity, and mental health in a sample of female undergraduates.Results:In bivariate analysis, mental health was negatively related to Neuroticism and positively related to Extraversion, self-reported physical activity (which was related only to Extraversion, positively), and objective physical activity (which was related only to Neuroticism, negatively). In structural equation modeling, a 3-way interaction indicated that objective physical activity and mental health were unrelated in extraverts, but related positively in neurotic-introverts and negatively in stable-introverts.Conclusions:Higher levels of physical activity were associated with better mental health only in neurotic-introverts, who are at higher risk for mental health problems.
Impact of Policies on Physical Activity and Screen Time Practices in 50 Child-Care Centers in North Carolina
Authors: Erinosho Temitope , Hales Derek , Vaughn Amber , Mazzucca Stephanie , Ward Dianne S. 
Published: April 2015

Background:This study assessed physical activity and screen time policies in child-care centers and their associations with physical activity and screen time practices and preschool children’s (3–5 years old) physical activity.Methods:Data were from 50 child-care centers in North Carolina. Center directors reported on the presence/absence of written policies. Trained research assistants observed physical activity and screen time practices in at least 1 preschool classroom across 3 to 4 days. Children (N = 544) wore accelerometers to provide an objective measure of physical activity.Results:Physical activity and screen time policies varied across centers. Observational data showed 82.7 min/d of active play opportunities were provided to children. Screen time provided did not exceed 30 min/d/child at 98% of centers. Accelerometer data showed children spent 38 min/d in moderate-to-vigorous physical activity and 206 min/d in sedentary activity. Policies about staff supervision of media use were negatively associated with screen time (P < .05). Contrary to expectation, policies about physical activity were associated with less time in physical activity.Conclusions:Clear strategies are needed for translating physical activity policies to practice. Further research is needed to evaluate the quality of physical activity policies, their impact on practice, and ease of operationalization.
Reduced Viral Fitness and Lack of Cross-Class Resistance with Integrase Strand Transfer Inhibitor and Nucleoside Reverse Transcriptase Inhibitor Resistance Mutations
Authors: Andreatta Kristen N. , Goodman Derrick D. , Miller Michael D. , White Kirsten L. 
Published: April 2015

ABSTRACTThe most common pattern of emergent resistance in the phase III clinical trials of coformulated elvitegravir (EVG)-cobicistat (COBI)-emtricitabine (FTC)-tenofovir disoproxil fumarate (TDF) was the EVG resistance substitution E92Q in integrase (IN) with the FTC resistance substitution M184V in reverse transcriptase (RT), with or without the tenofovir (TFV) resistance substitution K65R. In this study, the effect of these IN and RT substitutions alone and in combination in the same genome on susceptibility to antiretroviral inhibitors and viral replication fitness was characterized. Single resistance substitutions (E92Q in IN [IN-E92Q], M184V in RT [RT-M184V], and K65R in RT [RT-K65R]) specifically affected susceptibility to the corresponding inhibitor classes, with no cross-class resistance observed. The IN-E92Q mutant displayed reduced susceptibility to EVG (50-fold), which was not impacted by the addition of RT-M184V or RT-K65R/M184V. Viruses containing RT-M184V had high-level resistance to FTC (>1,000-fold) that was not affected by the addition of IN-E92Q or RT-K65R. During pairwise growth competitions, each substitution contributed to decreased viral fitness, with the RT-K65R/M184V + IN-E92Q triple mutant being the least fit in the absence of drug. In the presence of drug concentrations approaching physiologic levels, however, drug resistance offset the replication defects, resulting in single mutants outcompeting the wild type with one drug present, and double and triple mutants outcompeting single mutants with two drugs present. Taken together, these results suggest that the reduced replication fitness and phenotypic resistance associated with RT and IN resistance substitutions are independent and additive. In the presence of multiple drugs, viral growth is favored for viruses with multiple substitutions, despite the presence of fitness defects.
Encoded Library Technology Screening of Hepatitis C Virus NS4B Yields a Small-Molecule Compound Series with
In Vitro
Replicon Activity
Authors: Arico-Muendel Christopher , Zhu Zhengrong , Dickson Hamilton , Parks Derek , Keicher Jesse , Deng Jianghe , Aquilani Leah , Coppo Frank , Graybill Todd , Lind Kenneth , Peat Andrew , Thomson Michael 
Published: April 2015

ABSTRACT

To identify novel antivirals to the hepatitis C virus (HCV) NS4B protein, we utilized encoded library technology (ELT), which enables purified proteins not amenable to standard biochemical screening methods to be tested against large combinatorial libraries in a short period of time. We tested NS4B against several DNA-encoded combinatorial libraries (DEL) and identified a single DEL feature that was subsequently progressed to off-DNA synthesis. The most active of the initial synthesized compounds had 50% inhibitory concentrations (IC
50
s) of 50 to 130 nM in a NS4B radioligand binding assay and 300 to 500 nM in an HCV replicon assay. Chemical optimization yielded compounds with potencies as low as 20 nM in an HCV genotype 1b replicon assay, 500 nM against genotype 1a, and 5 μM against genotype 2a. Through testing against other genotypes and genotype 2a-1b chimeric replicons and from resistance passage using the genotype 1b replicon, we confirmed that these compounds were acting on the proposed first transmembrane region of NS4B. A single sequence change (F98L) was identified as responsible for resistance, and it was thought to largely explain the relative lack of potency of this series against genotype 2a. Unlike other published series that appear to interact with this region, we did not observe sensitivity to amino acid substitutions at positions 94 and 105. The discovery of this novel compound series highlights ELT as a valuable approach for identifying direct-acting antivirals to nonenzymatic targets.