bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuel-Flexible Combined Cycles for Utility Power and Cogeneration
Authors: Roberts P. B. , Duffy T. E. , Schreiber H.
Published: April 2015

Two combustion turbine combined cycle power plants have been studied for performance and operating economics. Both power plants are in the size range that will be suitable for small utility application and use less than 106 GJ/hr (100 million Btu/hr). The Powerplant and Industrial Fuel Use Act of 1978 has exempted power plants of this size from the requirement to use coal. The first power plant is based on the Solar Turbines International (STI) Mars industrial gas turbine. The combined gas turbine/steam cycle is direct fired with No. 2 diesel fuel. A net plant efficiency of 39.7 percent (HHV) is obtained at the 11.56-mW growth rating of the Mars engine for a turbine rotor inlet temperature of 1331 K (1935 F). A total installed cost for the system is estimated to be within the band 545 to 660 $/kW. The second power plant is based on STI’s Centaur industrial gas turbine. The combined gas turbine/steam cycle is indirectly fired with solid fuel although it is intended that the installation can be initially fired with a liquid fuel. A net plant efficiency of 25.0 percent (HHV) is obtained burning Illinois No. 6 coal at a rating of 3.78 mW with a turbine inlet gas temperature of 1117 K (1550 F).
A Gas Turbine Maintenance Information System for the Saudi Arabian East-West Crude Oil Pipeline
Authors: Temple T. W. , Foltz F. L. , Jamalallail H. R.
Published: April 2015

The 747-mile East-West Crude Oil Pipeline across Saudi Arabia employs 60 gas turbines for pumping and power generation. Mainline pump drives are three United Technologies Corporation FT4A-9 modular industrial gas turbines at each of 11 pumping stations. Two of the three mainline gas turbines are required for maximum throughput, while the third is an operational spare. High reliability and availability constraints and the remote unmanned station concept underscore the need for a modern maintenance information system. This paper describes an independent multiple-fault diagnostic/prognostic system, employing a patented gas path analysis technique.
Engine Condition Monitoring Using Fibreoptic Probes
Authors: McCord R. M.
Published: April 2015

With the advent of U.S. military aviation changing from the fixed-cycle inspection concept to the On-Condition Maintenance (OCM) concept, it has become readily apparent to the aircraft maintenance people that their existing inspection methods and diagnostic tools are not adequate to keep pace with the new concept. Some of those components which required removal and disassembly to facilitate inspection should now be inspected on-the-wing to maintain the inspection flow time. Some means of gaining visual access to those components is required. A method has been developed to inspect the gas path of a turbine engine with sufficient accuracy to provide the user with the decisive information on whether to continue the engine in service or remove it for repair. The genesis of using controlled light and vision for engine internal inspection is presented and progress from the early days on the flightline to the future is discussed.
Digital Controls for Helicopter Engines
Authors: Eccles E. S.
Published: April 2015

The paper describes a digital electronic engine control system being built by Dowty and Smiths Industries Controls Limited (DSIC) to demonstrate the control features required for the next generation of helicopters and their power plants. It is engine mounted, fuel cooled and of lightweight design. The paper describes the mechanical design, the installation and the cooling of the system including the choice of the basic packaging concept. It also discusses the safety of flight aspects of system operation. Finally, the paper discusses how the design can be modulated to increase/reduce the capability of the system and thus, the more effectively to cover a range of requirements.
Digital Control for V/Stol Powerplants
Authors: Eccles E. S.
Published: April 2015

The author describes the evolution of his company’s digital control approach to the Pegasus engine as applied to a single engined VTOL aircraft. The paper describes the digital control system being built by Dowty and Smiths Industries Controls Limited (DSIC). The design is based on extensive engine evaluation of different control configuration with electronic and hydromechanical back-up system. The paper describes the mechanical design, installation on the engine and the cooling of the system including the choice of basic packaging concept. It also discusses the rationale for the particular choice of back-up system and the reliability/safety of flight trade-offs involved.
Experiments of the Vibration Characteristics of the Rotor With Flexible, Damped Support
Authors: Tong Y. L. , Han L. Q.
Published: April 2015

Experiments were operated on a model rotor test rig with a disk located at the mid span and a squeeze film damper and/or flexible support at one end and a rigid support at the other end. The damping effects of the flexible support and stress variation of the support itself have been tested. Emphasis was placed on the steady-state characteristics and the damping effects of the flexible supports and dampers with different radial clearances under various level of rotor unbalance. The dampers are without end seals and oil grooves. Comparative tests of the damping effects of the flexible, damped support were done during passing through the 1st and second critical speeds. Simulating tests of the vibration of the bearing housing excited by non-rotor exciting sources have been carried out and the damping effects of the oil film dampers on this type of vibrations were examined.
The Control of Hot Corrosion in Marine Gas Turbines
Authors: Condé J. F. G. , McCreath C. G.
Published: April 2015

Ingestion of sea salt and sulphur from fuel can lead to aggressive environments in gas turbines operating in marine conditions resulting in corrosion damage to hot end components, even in well-filtered engines. The nature of the environment in the engine and the factors which influence this are indicated. The chemistry of salt contaminant particles in the engine and combustion environments and temperature levels prevailing in naval engines are described in relation to the normal operating profile and the incidence of corrosion effects in relation to temperature. Results of rig evaluation of materials and coatings are given. Erosion resistance, the combined effects of erosion/corrosion and the mechanisms of hot corrosion are discussed together with the effects of material composition and the use of inhibition as a control procedure. The effects of a salt environment on the creep and stress-rupture behavior of superalloys are covered briefly.
Closed-Cycle Gas Turbine Working Fluids
Authors: Lee J. C. , Campbell J. , Wright D. E.
Published: April 2015

Characteristic requirements of a closed-cycle gas turbine (CCGT) working fluid were identified and the effects of their thermodynamic and transport properties on the CCGT cycle performance, required heat exchanger surface area and metal operating temperature, cycle operating pressure levels, and the turbomachinery design were investigated. Material compatibility, thermal and chemical stability, safety, cost, and availability of the working fluid were also considered in the study. This paper also discusses CCGT working fluids utilizing mixtures of two or more pure gases. Some mixtures of gases exhibit pronounced synergetic effects on their characteristic properties including viscosity, thermal conductivity and Prandtl number, resulting in desirable heat transfer properties and high molecular weights. Typical examples of such synergetic gas mixture are helium-xenon and helium-carbon dioxide.
On the Pressure Losses due to the Tip Clearance of Centrifugal Blowers
Authors: Ishida M. , Senoo Y.
Published: April 2015

The pressure distribution along the shroud is measured for three types of centrifugal impeller at seven different values of tip clearance each. The change of input power due to a change of tip clearance is related to the effective blockage at the impeller tip. Since the change of input power is little for the test cases, the variation of local pressure gradient along the shroud is mostly attributed to the change of local pressure loss. The local pressure loss is related to the local tip clearance ratio and to the local pressure gradient based on the decleration of relative velocity in the impeller. Since the local pressure gradient is largest near the throat of impeller is used as the representative value. The tip clearance loss is related to the clearance ratio and the pressure rise based on the deceleration of relative velocity in the impeller. A good correlation is observed in all cases at various flow rate.
Vorticity Modelling of Blade Wakes Behind Isolated Annular Blade-Rows: Induced Disturbances in Swirling Flows
Authors: Tan C. S.
Published: April 2015

A general analysis is proposed for studying the fluid-mechanical behavior of blade wakes from an annular blade-row in highly swirling flow. The coupling between the centrifugal force and the vorticity, which is inherent to highly swirling flows, can significantly modify the wake behavior from that in a two-dimensional situation. In steady flow, theoretical considerations show that a blade wake consists primarily of two distinct types of vorticity: a) trailing vorticity shed from the blade due to a span wise variation in blade circulation, and b) vorticity associated with defects in stagnation pressure (or rotary stagnation in relative coordinate system). Three types of disturbances can be identified in the resulting three-dimensional disturbance field: a) the exponentially decaying type (potential, irrotational), b) the purely convected type (rotational), and c) the non-convected type (both rotational and irrotational parts).
Testing of Ceramic Rotors: Hot Spin Test Rig and Rotor Preparation
Authors: DeBell G. C. , Swank L. R.
Published: April 2015

A series of duo-density silicon nitride gas turbine rotors have been prepared for testing and tested at Ford Motor Company. The paper reviews the duo-density fabrication process, and covers in detail the rotor preparation process, which includes machining, inspection, and cold proof spinning. The paper describes the hot spin test rig used for the hot testing of the rotors, and summarizes the results of the hot spin test program.
Operating Experience of the General Electric LM2500 Gas Turbines in Navy Ships: Second Report
Authors: Reid R. E. , Klemm V. P.
Published: April 2015

LM2500 Engines have been in operation in U.S. Navy ships since September, 1975. This is an update of a previous ASME paper given in March, 1977, which presented the operational experience of the LM2500 to that time. Included in this paper will be the reliability achieved thus far plus the improvements that are projected from the ongoing component improvement program. The application of the engine to a wide spectrum of ships in 11 foreign navies is also covered.
Results From Tests on a High Work Transonic Turbine for an Energy Efficient Engine
Authors: Crow D. E. , Vanco M. R. , Welna H. , Singer I. D.
Published: April 2015

This paper will present the experimental results of the evaluation of two high work, transonic, single-stage turbines investigated under the Energy Efficient Engine Program. The objective of the E3 program, a joint P&WA/NASA program (NAS3-20646) is to provide an advanced technology base for a new generation of fuel-conservative turbofan engines. A single-stage turbine required fewer cooled airfoils, a reduced number of leakage paths and no interstage seals. These advanced energy efficient engines require high engine pressure ratios resulting in high expansion ratio, transonic, turbine designs which must have high aerodynamic efficiency. The goal of the turbine program is to develop a high pressure turbine that is compatible with the overall engine design and has an uncooled efficiency of 90.8 percent.
The Determination of Deviation Angles at Exit From the Nozzles of an Inward Flow Radial Turbine
Authors: Fairbanks F.
Published: April 2015

A method for predicting the deviation angle at exit from the nozzles of an inward flow radial turbine using a streamline curvature method is given. Measurements of flow angles and stagnation and static pressures across the nozzle exit span of a small turbine have been made. The accuracy of the analysis is shown by comparison with experimental results. Finally, the developed theory has been used to show the possible effect on the deviation angle at exit from the nozzles of reducing the number of stator blades.
Organic Rankine-Cycle Turbine Power Plant Utilizing Low Temperature Heat Sources
Authors: Maizza V.
Published: April 2015

Utilizing and converting of existing low temperature and waste heat sources by the use of a high efficiency bottoming cycle is attractive and should be possible for many locations. This paper presents a theoretical study on possible combination of an organic Rankine-cycle turbine power plant with the heat pump supplied by waste energy sources. Energy requirements and system performances are analyzed using realistic design operating condition for a middle town. Some conversion systems employing working fluids other than water are being studied for the purpose of proposed application. Thermodynamic efficiencies, with respect to available resource, have been calculated by varying some system operating parameters at various reference temperature. With reference to proposed application equations and graphs are presented which interrelate the turbine operational parameters for some possible working fluids with computation results.
Cycle Optimization for a 10,000 SHP High Efficiency Gas Turbine System
Authors: Hendriks Rolf , Levine Philip
Published: April 2015

A new gas turbine system is under development by Thomassen Holland b. v. and Fern Engineering. The machine features a two-stage inter-cooled centrifugal compressor, a regenerator and an annular combustor. Prototype units will be operating in 1982. Cycle optimization results are presented which lead to the selection of a rotor inlet temperature of 2042 F, an overall compression ratio of 9.5 and a thermal efficiency of 44 percent.
Preliminary Evaluation of Coal-Fired Fluid Bed Combustion-Augmented Compressed Air Energy Storage Power Plants
Authors: Lessard R. D. , Giramonti A. J. , Merrick David
Published: April 2015

This paper presents highlights of an ongoing study program to assess the technical and economic feasibility of advanced concepts for generating peak-load electric power from a compressed air energy storage (CAES) power plant incorporating a coal-fired fluid bed combustor (FBC). It reviews the analyses performed to select an FBC/CAES power plant system configuration for the subsequent conceptual design phase of the study. Included in this review are: the design and operating considerations involved with integrating either an atmospheric or a pressurized fluid bed combustor with a CAES system to yield practical system configurations; the integration of system configurations; the parametric performance of these system configurations; and the preliminary screening which considered performance, cost, and technical risk and led to the identification of an open-bed PFBC/CAES system as having the greatest near-term commercialization potential.
Redesign of Structural Vibration Modes by Finite-Element Inverse Perturbation
Authors: Stetson K. A. , Harrison I. R.
Published: April 2015

A previously developed technique for redesigning the vibrational properties of structures, by inverting the first-order perturbation analysis of the equations of motion, has been applied to a NASTRAN finite element analysis for plates and shells. The program finds the minimal changes to the thicknesses of the plate elements necessary to effect a given set of changes in the modal frequencies and shapes. Results have been obtained for a flat cantilever plate, a cantilever segment of a cylinder, and for a compressor blade for a jet engine.
Low Btu Coal Gas Combustion in High Temperature Turbines
Authors: Vogt R. L.
Published: April 2015

This paper defines the combustion consequences of burning low Btu coal gas in high temperature gas turbines. It identifies the limits of their application regarding the heating value and its thermodynamic constraints on turbine firing temperature, operating flammability limits, product carbon monoxide, oxides of nitrogen and combustor turndown ratio. Sensitivity to reaction zone radiation and effects on combustor hot gas path flow area are discussed. The effect of these constraints on the conceptual design of a combustor is described herein. The example discussed is the sectoral combustor which was designed under contract to the Department of Energy for use in the High Temperature Turbine Technology program. The sectoral combustor is to be fired on coal gas to within 250 C of the homogeneous, adiabatic, stoichiometric flame temperature limit.
Heat Transfer Phenomena in Gas Turbines
Authors: Taylor J. R.
Published: April 2015

A discussion of the problems encountered in prediction of heat transfer in the turbine section of a gas turbine engine is presented. Areas of current gas turbine engine is presented. Areas of current concern to designers where knowledge is deficient or lacking are elucidated. Consideration is given to methods and problems associated with determination of heat transfer coefficients, external gas temperatures, and, where applicable, film cooling effectiveness. The paper is divided into parts dealing with turbine airfoil heat transfer, endwall heat transfer, and heat transfer in the internal cavities of cooled turbine blades. Recent literature dealing with these topics is listed.
Creep Rupture Behavior of Selected Turbine Materials in Air, Ultra-High Purity Helium, and Simulated Closed Cycle Brayton Helium Working Fluids
Authors: Ammon R. L. , Eisenstatt L. R. , Yatsko G. O.
Published: April 2015

Five turbine materials, IN100, 713LC, MAR-M-509, MA-754 and TZM were selected as candidate materials for use in a Compact Closed Cycle Brayton System (CCCBS) study in which helium served as the working fluid. The suitability of the alloys to serve in the CCCBS environment at 927 C (1700 F) was evaluated on the basis of creep-rupture tests conducted in air, ultra-high purity helium (> 99.9999 percent), and a controlled impurity helium environment. Baseline reference creep rupture properties for times up to 10,000 hr were established in a static ultra-high purity helium enviroment.
Development of a High Temperature Turbine for Operation on Coal-Derived Fuel
Authors: Wolf J. C. , Moskowitz S. , Manning G. B.
Published: April 2015

The efficiency of an integrated coal gasification-combined cycle powerplant can be improved above that of conventional coal-fired steam powerplants by increasing the gas turbine component firing temperature and pressure ratio while limiting component cooling requirements. A stage of the development of a transpiration-air-cooled turbine for operation at 2600 F (1427 C) and above in a combusted coal-derived fuel environment is presented. Results are presented from 300 hr of turbine cascade and 400 hr of rig-engine tests conducted at up to 3000 F (1649 C) using a jet fuel “doped” with aluminum oxide or fly ash to simulate the potentially erosive and corrosive nature of coal derived fuels. The metallographic examinations and flow permeability discussed in terms of the effects from particle deposition.
A User Programmable General Purpose Microprocessor Control System
Authors: Mann D. E.
Published: April 2015

This paper describes the hardware structure and design of a general-purpose microprocessor based controller intended for the full authority control of gas turbine and diesel engines in ground based vehicle and industrial applications. Particular attention is paid to the digital processor and how it’s design was influenced by the user requirements of a general purpose, real-time system. The system is currently being manufactured in production form. An accompanying paper describes the supporting software and user program facilities (Ref 1). Such systems based on the use of microprocessors must not only provide general purpose hardware, but also software structured so that a wide range of control algorithms may be programmed and performed within strict limits of real-time. This paper describes the development of the Type C4E87 General Purpose Controller (REF Fig. 1) with particular reference to its hardware structure and design within a system intended primarily for application as a full authority control of gas turbine and diesel engines etc.
Protection and Specification of Clutches to be Used With Gas Turbine Generators
Authors: Burns K. H. , Kearsey R. P.
Published: April 2015

The use of self-actuating clutches in gas tubine driven electrical power generators is examined, in relation to operation of the clutch during fault conditions. Clutches are employed in the main shaft between the power turbine and the electrical generator, to enable the unit to operate as a synchronous compensator. Five particular fault conditions are identified which could cause overstressing of the clutch. Protection is not universally provided to protect the clutch under all five conditions, and methods of providing protection are suggested. Analysis of the fault conditions is developed to identify the differential acceleration requirement for the clutch. The analysis is extended to demonstrate the limited capability of a gas turbine generator, when operating as a synchronous compensator, to provide spinning reserve capacity for an electrical system.
Time Between Overhaul vs Premature Removal Rates as Turbine Design Considerations
Authors: Curry C. E. , Wei A. C.
Published: April 2015

A general knowledge of aviation practices constituted the background for the identification of three distinct variables as the major drivers for engine removals in the operation of an aircraft. This study provides an insight into the interrelationships of the major drivers which determine engine removals for an aircraft: utilization rate (U), time between overhaul (TBO), and premature removal rate (PRR). Each of these elements is of concern to nearly every aircraft operator. For this study, it was assumed to be the same as aircraft flight hours per month.
Streakline Flow Visualization Study of a Horseshoe Vortex in a Large-Scale, Two-Dimensional Turbine Stator Cascade
Authors: Gaugler R. E. , Russell L. M.
Published: April 2015

Neutrally buoyant helium-filled bubbles were observed as they followed the streamlines in a horseshoe vortex system around the vane leading edge in a large-scale, two-dimensional, turbine stator cascade. Inlet Reynolds number, based on true chord, ranged between 1.0 × 10 ⅝ to 3.0 × 10 ⅝. Bubbles were introduced into the endwall boundary layer through a slot upstream of the vane leading edge. The paths of the bubbles were recorded photographically as streaklines on 16-mm movie film. Individual frames from the film have been selected, and overlayed to show the details of the horseshoe vortex around the leading edge, the transport of the vortex across the passage near the leading edge is clearly seen when compared to the streaks formed by bubbles carried in the main stream. Limiting streamlines on the endwall surface were traced by the flow of oil drops.
The Influence on the Meridional Impeller Shape on the Energy-Transfer in Centrifugal Compressors
Authors: Bammert K. , Rautenberg M. , Knapp P.
Published: April 2015

Three radial flow impellers were tested having an elliptic blade shape and identical blade geometry at inlet and exit but different shapes of the meridional contours. The compressor maps with pressure ratios up to 2.9:1 are compared using time-dependent measurements of the static pressure at the shroud and of the flow angles closely downstream of the impeller. From these measurements, the influence of impeller shap on the jet-and-wake flow is discussed. It is shown that with increasing impeller length, the wake zone at the suction side of the blades can be only partially influenced and friction losses become dominant with respect to compressor performance. A smooth curvature of the meridional cross section of the impeller channel leads to a better jet-wake ratio at impeller exit. Accordingly, the performance characteristic shows higher values especially when the mass flow is increased.
Fuel Property Effects on Life Characteristics of Aircraft Turbine Engine Combustors
Authors: Gleason C. C. , Bahr D. W.
Published: April 2015

Results of a program to determine the effects of fuel properties on the life characteristics of two USAF/General Electric aircraft turbine engine combustors are presented. Thirteen test fuels were evaluated in an older technology cannular combustion system (J79) and in an advanced technology, virtually smokeless, compact, annular combustion system (F101) over wide ranges of simulated engine operating conditions. Fuel variables were hydrogen content, aromatic structure, volatility and distillation end point. Significant increases in combustor liner temperatures were observed as fuel hydrogen content was decreased. With fuel hydrogen contents of 14.5, 14.0, 13.0 and 12.0, the resulting relative combustor liner cyclic life predictions are 1.00, 0.78, 0.52, and 0.35 for the J79 combustor and 1.00, 0.72, 0.52 and 0.47 for the F101 combustor, respectively. Based on these findings, it is concluded that improved liner cooling design features will be needed in most current technology combustors to accommodate the projected lower hydrogen contents of future fuels.
An Analytical Study of Nitrogen Oxides and Carbon Monoxide Emissions in Hydrocarbon Combustion With Added Nitrogen: Preliminary Results
Authors: Bittker D. A.
Published: April 2015

This work is one part of a four-part Critical Research and Technology Fuels Combustion Program funded by the Department of Energy. The primary objective of this part of the program is to analytically determine the effect of combustor operating conditions on the conversion of fuel-bound nitrogen (FBN) to nitrogen oxides (NOx). The effect of FBN and of operating conditions on carbon monoxide (CO) formation was also studied.
Combustion Effects of Coal Liquid and Other Synthetic Fuels in Gas Turbine Combustors: Part II — Full Scale Combustor and Corrosion Tests
Authors: Bauserman G. W. , Spengler C. J. , Cohn A.
Published: April 2015

Combustion tests on over twelve types of coal derived liquid fuels from the EDS, H-coal, SRC-I and SRC-II processes and three shale oil fuels have been conducted in gas turbine type combustors. Emission measurements wre made of NOx, smoke, CO, and unburned hydrocarbons. Combustor wall temperature profiles were measured. The results are correlated with the fuel properties — percent nitrogen, hydrogen and aromaticity. This paper (Part II) describes the results of full scale combustor testing and of a long-term corrosion/deposition test. A companion paper by Cohn, et al. Part I discusses the fuels used in the program and the subscale combustor test results.
Airblast Atomization: The Effect of Linear Scale on Mean Drop Size
Authors: El-Shanawany M. S. , Lefebvre A. H.
Published: April 2015

Experimental and analytical studies are made of the factors governing the mean drop size of sprays produced by prefilming airblast atomizers. Three geometrically similar atomizers, having cross-sectional areas in the ratio of 1:4:16, and with prefilmer lip diameters of 19.05, 38.10 and 76.20 mm, are employed. It is found that spray quality declines with increase in atomizer size. Analysis of the experimental data shows that the relationship between the key variables and mean drop size is described satisfactorily by the following dimensionally correct expression: SMD=0.073(σLρAUA2)0.6(ρLρA)0.1Dp0.4(1+WLWA)+0.015(μL2DPσLρL)0.5(1+WLWA)
Isothermal Roll Forging of Compressor Blades
Authors: Metcalfe A. G. , Rose F. K. , Gagne R. A.
Published: April 2015

Isothermal roll forging is being applied to the manufacture of gas turbine compressor blades. The process can produce a compressor blade to net section in a single roll forge pass from simple barstock using force feed to gather the metal for the root section. Heating is performed with simultaneous electrical resistance heating of precision molybdenum alloy dies and the blade to a set forging temperature. Good surfaces are produced together with thin flash thereby minimizing final operations for clean-up and inspection. A manufacturing process has been selected and demonstrated under the U. S. Army’s Manufacturing Methods and Technology Program. Projected costs show potential for significant cost reduction. Establishment of this manufacturing process is in progress.
Preliminary Evaluation of a Combustor for Use in Modeling and Diagnostics Development
Authors: Roquemore W. M. , Bradley R. P. , Stutrud J. S. , Reeves C. M. , Krishnamurthy L.
Published: April 2015

This paper reports on the preliminary results of an evaluation of a bluff-body combustor that is suitable for use in modeling and diagnostics development. To facilitate modeling studies and the evaluation of diagnostic techniques, the combustor is designed with simple axisymmetric geometry and easy measurement access to the reaction zone. The combustor configuration consists of a 14-cm-dia shrouded disk centered in a 25.4-cm-dia duct with gaseous propane injection at the center of the disk through a 4.8-mm-dia tube. The combustor is operated at atmospheric pressure and room air inlet temperatures and burns gaseous propane. Measurements of flame lengths and the rich and lean blow-off limits are presented. Combustion inefficiencies are presented at selected air and fuel flow rates. For a constant airflow rate, the combustion inefficiency passes through a minimum as the fuel flow rate increases. Photographs show that the shape of the flame changes dramatically as the air and fuel flow rates are varied.
Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO
3
films
Authors: Tang Y. L. , Zhu Y. L. , Ma X. L. , Borisevich A. Y. , Morozovska A. N. , Eliseev E. A. , Wang W. Y. , Wang Y. J. , Xu Y. B. , Zhang Z. D. , Pennycook S. J.
Published: April 2015

Getting closure in ferroelectric films

Ferroelectric materials have a spontaneous electric polarization that can be manipulated for applications. The polarization is usually not uniform throughout the material, and for nanosized ferroelectrics, polarization can be quite complex. Using scanning transmission electron microscopy, Tang
et al.
found that in thin films of the ferroelectric PbTiO
3
, the polarization vector rotated in space, forming a closed loop, the so-called flux closure. The flux closure structures formed an array, with the period dependent on the width of the thin film, and caused the buildup of considerable strain within the crystal lattice of the material

Science, this issue p.
547
Whole-Genome Sequences of Five Burkholderia pseudomallei Isolates from Australian Cystic Fibrosis Patients
Authors: Viberg Linda T. , Price Erin P. , Kidd Timothy J. , Bell Scott C. , Currie Bart J. , Sarovich Derek S.
Published: April 2015

We report here five improved high-quality draft genomes of
Burkholderia pseudomallei
isolated from Australian cystic fibrosis (CF) patients. This pathogen is rarely seen in CF patients. These genomes will be used to better understand chronic carriage of
B. pseudomallei
in the CF lung and the within-host evolution of longitudinal isolates from these patients.
Draft Genome Sequences of Lactobacillus plantarum Strain 90sk and Lactobacillus brevis Strain 15f: Focusing on Neurotransmitter Genes
Authors: Yunes Roman A. , Klimina Ksenia M. , Emelyanov Kirill V. , Zakharevich Natalia V. , Poluektova Elena U. , Danilenko Valery N.
Published: April 2015

The genomes of
Lactobacillus plantarum
strain 90sk and
Lactobacillus brevis
strain 15f were isolated from human intestinal microbiota. Both strains synthesize gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter. Detailed genome analyses will help to understand the role of GABA in the interaction of bacteria with human intestinal cells.
Genome Sequence of Mushroom Soft-Rot Pathogen Janthinobacterium agaricidamnosum
Authors: Graupner Katharina , Lackner Gerald , Hertweck Christian
Published: April 2015

Janthinobacterium agaricidamnosum
causes soft-rot disease of the cultured button mushroom
Agaricus bisporus
and is thus responsible for agricultural losses. Here, we present the genome sequence of
J. agaricidamnosum
DSM 9628. The 5.9-Mb genome harbors several secondary metabolite biosynthesis gene clusters, which renders this neglected bacterium a promising source for genome mining approaches.
Draft Genome Sequence of Lysinibacillus fusiformis Strain SW-B9, a Novel Strain for Biotransformation of Isoeugenol to Vanillin
Authors: Zhao Liqing , Bao Guanhui , Geng Beibei , Song Jiangning , Li Yin
Published: April 2015

Lysinibacillus fusiformis
SW-B9 was the first reported strain in
L. fusiformis
showing effective biotransformation of isoeugenol to vanillin. Here, we report the annotated genome of strain SW-B9, which has special pathways for producing vanillin. The genome will provide a genetic basis for better understanding the physiology of this species.
Draft Genome Sequence of
Lachancea lanzarotensis
CBS 12615
T
,
an Ascomycetous Yeast Isolated from Grapes
Authors: Sarilar Véronique , Devillers Hugo , Freel Kelle C. , Schacherer Joseph , Neuvéglise Cécile
Published: April 2015

We report the genome sequencing of the yeast
Lachancea lanzarotensis
CBS 12615
T
. The assembly comprises 24 scaffolds, for a total size of 11.46 Mbp. The annotation revealed 5,058 putative protein-coding genes. Detection of seven centromeres supports a chromosome fusion, which occurred after divergence from
Lachancea thermotolerans
and
Lachancea kluyveri.
Draft Genome Sequences of Marine Isolates of Thalassomonas viridans and Thalassomonas actiniarum
Authors: Olonade Israel , van Zyl Leonardo Joaquim , Trindade Marla
Published: April 2015

Thalassomonas viridans
and
Thalassomonas actiniarum
are aerobic Gram-negative bacilli which belong to a genus that has not received much attention, even though, as demonstrated here by the sequencing of their genomes, they are quite different from their closest relatives in current databases. Their genomes are relatively large at 7.7 and 7.4 Mb, respectively. This brief report describes the first draft genomes for any
Thalassomonas
species.
Genome Sequence of Ureaplasma diversum Strain ATCC 49782
Authors: Marques Lucas M. , Guimarães Ana M. S. , Martins Hellen B. , Rezende Izadora S. , Barbosa Maysa S. , Campos Guilherme B. , do Nascimento Naíla C. , dos Santos Andrea P. , Amorim Aline T. , Santos Verena M. , Messick Joanne B. , Timenetsky Jorge
Published: April 2015

Here, we report the complete genome sequence of
Ureaplasma diversum
strain ATCC 49782. This species is of bovine origin, having an association with reproductive disorders in cattle, including placentitis, fetal alveolitis, abortion, and birth of weak calves. It has a small circular chromosome of 975,425 bp.
Multimorbidity and healthcare utilisation among high-cost patients in the US Veterans Affairs Health Care System
Authors: Zulman Donna M , Pal Chee Christine , Wagner Todd H , Yoon Jean , Cohen Danielle M , Holmes Tyson H , Ritchie Christine , Asch Steven M
Published: April 2015

Objectives

To investigate the relationship between multimorbidity and healthcare utilisation patterns among the highest cost patients in a large, integrated healthcare system.

Design

In this retrospective cross-sectional study of all patients in the U.S. Veterans Affairs (VA) Health Care System, we aggregated costs of individuals’ outpatient and inpatient care, pharmacy services and VA-sponsored contract care received in 2010. We assessed chronic condition prevalence, multimorbidity as measured by comorbidity count, and multisystem multimorbidity (number of body systems affected by chronic conditions) among the 5% highest cost patients. Using multivariate regression, we examined the association between multimorbidity and healthcare utilisation and costs, adjusting for age, sex, race/ethnicity, marital status, homelessness and health insurance status.

Setting

USA VA Health Care System.

Participants

5.2 million VA patients.

Measures

Annual total costs; absolute and share of costs generated through outpatient, inpatient, pharmacy and VA-sponsored contract care; number of visits to primary, specialty and mental healthcare; number of emergency department visits and hospitalisations.

Results

The 5% highest cost patients (n=261 699) accounted for 47% of total VA costs. Approximately two-thirds of these patients had chronic conditions affecting ≥3 body systems. Patients with cancer and schizophrenia were less likely to have documented comorbid conditions than other high-cost patients. Multimorbidity was generally associated with greater outpatient and inpatient utilisation. However, increased multisystem multimorbidity was associated with a higher outpatient share of total costs (1.6 percentage points per affected body system, p<0.01) but a lower inpatient share of total costs (−0.6 percentage points per affected body system, p<0.01).

Conclusions

Multisystem multimorbidity is common among high-cost VA patients. While some patients might benefit from disease-specific programmes, for most patients with multimorbidity there is a need for interventions that coordinate and maximise efficiency of outpatient services across multiple conditions.
Type III functional response in the zebra mussel,Dreissena polymorpha
Authors: Sarnelle Orlando , White Jeffrey D. , Geelhoed Theresa E. , Kozel Carrie L.
Published: April 2015

Distinguishing between functional response types requires observations at low food concentrations, but surprisingly these tend to be rare. A paucity of feeding observations at low food concentrations is especially acute for dreissenid mussels, despite their importance as invading species in fresh waters. We assessed the functional response of zebra mussels (Dreissena polymorpha) via feeding experiments and behavioral observations conducted at low food levels. Critically, food levels were chosen to be in the vicinity of minimum concentrations found in lakes with established D. polymorpha populations. Results of two feeding experiments show clear evidence of a Type III functional response for D. polymorpha feeding on Ankistrodesmus falcatus — clearance rate increased with increasing food concentration at low food levels. Mussels were always open and feeding during these experiments. An independent set of behavioral observations further showed that the fraction of mussels actively feeding (valves open, siphons extended) decreased as food concentrations decreased. We also measured somatic growth of juvenile mussels at varying levels of A. falcatus over 27 days and found that mussels were able to grow at food levels where Type III behavior was observed in the feeding experiments.
On a model of a population with variable motility
Authors: Turanova Olga
Published: April 2015

We study a reaction–diffusion equation with a nonlocal reaction term that models a population with variable motility. We establish a global supremum bound for solutions of the equation. We investigate the asymptotic (long-time and long-range) behavior of the population. We perform a certain rescaling and prove that solutions of the rescaled problem converge locally uniformly to zero in a certain region and stay positive (in some sense) in another region. These regions are determined by two viscosity solutions of a related Hamilton–Jacobi equation.
Gravitational collapse with rotating thin shells and cosmic censorship
Authors: Rocha Jorge V.
Published: April 2015

Gravitational collapse of matter in the presence of rotation is a mostly unexplored topic but it might have important implications for cosmic censorship. Recently a convenient setup was identified to address this problem, by considering thin matter shells at the interface between two equal angular momenta Myers–Perry spacetimes in five dimensions. This note provides more details about the matching of such cohomogeneity-1 spacetimes and extends the results obtained therein to arbitrary higher odd dimensions. It is also pointed out that oscillatory orbits for shells in asymptotically flat spacetimes can be naturally obtained if the matter has a negative pressure component.
Large deviations for SPDEs of jump type
Authors: Yang Xue , Zhai Jianliang , Zhang Tusheng
Published: April 2015

In this paper, we establish a large deviation principle for a fully nonlinear stochastic evolution equation driven by both Brownian motions and Poisson random measures on a given Hilbert space H. The weak convergence method plays an important role.
Determinants of Knowledge Sharing in Virtual Network Communities in Organizational Context
Authors: Al Muzaffar Aisha Y. , Alshare Khaled A.
Published: April 2015

This paper attempts to examine factors that affect knowledge sharing by individuals in virtual network communities (VNCs) from an organisational context. A research model based on the theory of planned behaviour (TPB) was developed and empirically tested using a web-based survey questionnaire. Antecedent variables are considered as organisational support, organisational culture, subjective norm, web-self-efficacy, attitude towards knowledge sharing, and intention to sharing knowledge. The results showed that attitude towards knowledge sharing, organisational culture, and subjective norm have significant positive effects on knowledge sharing intention which in turns has a significant positive impact on knowledge sharing. Additionally, organisational support indirectly impact intention through attitude. Additionally, the results revealed that web-self-efficacy gender, age, educational level, and firm's age were not significant. Implications for researchers and managers were reported.
Creating Sparks: Comparing Search Results Using Discriminatory Search Term Word Co-Occurrence to Facilitate Serendipity in the Enterprise
Authors: Cleverley Paul Hugh , Burnett Simon
Published: April 2015

Categories or tags that appear in faceted search interfaces which are representative of an information item, rarely convey unexpected or non-obvious associated concepts buried within search results. No prior research has been identified which assesses the usefulness of discriminative search term word co-occurrence to generate facets to act as catalysts to facilitate insightful and serendipitous encounters during exploratory search. In this study, 53 scientists from two organisations interacted with semi-interactive stimuli, 74% expressing a large/moderate desire to use such techniques within their workplace. Preferences were shown for certain algorithms and colour coding. Insightful and serendipitous encounters were identified. These techniques appear to offer a significant improvement over existing approaches used within the study organisations, providing further evidence that insightful and serendipitous encounters can be facilitated in the search user interface. This research has implications for organisational learning, knowledge discovery and exploratory search interface design.
Factors Impacting the Implementation of Enterprise Content Management Systems
Authors: Horne Stephanie Burnett , Hawamdeh Suliman
Published: April 2015

Enterprise content management (ECM) is a new and fast growing area. It is still undergoing the same defining process as predecessor systems such as decision support and enterprise resource systems. A qualitative case study was conducted to identify key factors that impact the success of ECM systems implementations. A theoretical framework was developed from the information systems (ISs) literature resulting in a research model defining five categories of factors that impact ECM implementation success with these questions: Are there managerial, user, task, technological and content related factors that impact ECM implementation success? The research model was tested using a mix methods approach. Content analysis of the project documentations and interviews of 15 team leads and members that implemented ECM systems within their departments in their organization. The results included 12 factors that were supported by the interview data as well as the content analysis of related project documents.
Distribution of x ⋅ p for quantum states on a circle
Authors: Liu Q. H. , Qin L. , Huang X. L. , Zhang D. Y. , Xun D. M.
Published: April 2015

We first give the proper definition of the particle's position-momentum dot product, the so-called posmomx ⋅ p, to quantum states on a circular circle, in which the momentum turns out to be the geometric one that is recently intensively studied. Second, we carry out the posmom distributions for eigenstates of the free motion on the circle, i.e. [Formula: see text], (m = 0, ±1, ±2, …). The results are not only potentially experimentally testable, but also reflect a fact that the embedding of the circle S1 in two-dimensional flat space R2 is physically reasonable.
The crustal architecture of the Faroe–Shetland Basin: insights from a newly merged gravity and magnetic dataset
Authors: Rippington Stephen , Mazur Stanislaw , Warner Jamie
Published: April 2015

Seismic imaging beneath shallow (<5 km) Palaeogene basaltic volcanic successions on the Faroe–Shetland Margin is very challenging with conventional seismic methods. Consequently, the interpretational uncertainty that surrounds the sub-basalt structure of the region is a major source of exploration risk. This study uses gravity and magnetic data in conjunction with seismic data to map the sub-basalt structure of the Faroe–Shetland Basin and model the crustal architecture of this part of the Atlantic margin. Four crustal types are recognized using gravity data: oceanic, intruded transitional, stretched continental and normal continental crust. Map-based interpretation of the gravity and magnetic data helps redefine the basins, highs and faults in the region. The structural interpretation suggests that the boundary between normal and stretched continental crust is coincident with the long-lived left-lateral ‘West Shetland Shear Zone’, which partitioned strain during rifting of the margin. 2D/2.5D gravity and magnetic models are shown for two seismic profiles from the PGS FSB MegaSurveyPlus. The models suggest highly thinned crust, which was intruded by mafic magma beneath the Flett sub-basin, and an asymmetry to the rifting, which is consistent with a process of Wernicke simple shear.
MCALIB
Authors: Frechtling Michael , Leong Philip H. W.
Published: April 2015

Runtime analysis provides an effective method for measuring the sensitivity of programs to rounding errors. To date, implementations have required significant changes to source code, detracting from their widespread application. In this work, we present an open source system that automates the quantitative analysis of floating point rounding errors through the use of C-based source-to-source compilation and a Monte Carlo arithmetic library. We demonstrate its application to the comparison of algorithms, detection of catastrophic cancellation, and determination of whether single precision floating point provides sufficient accuracy for a given application. Methods for obtaining quantifiable measurements of sensitivity to rounding error are also detailed.
A Survey of TDMA Scheduling Schemes in Wireless Multihop Networks
Authors: Sgora Aggeliki , Vergados Dimitrios J. , Vergados Dimitrios D.
Published: April 2015

One of the major problems in wireless multihop networks is the scheduling of transmissions in a fair and efficient manner. Time Division Multiple Access (TDMA) seems to be one of the dominant solutions to achieve this goal since it is a simple scheme and can prolong the devices’ lifetime by allowing them to transmit only a portion of the time during conversation. For that reason, several TDMA scheduling algorithms may be found in the literature. The scope of this article is to classify the existing TDMA scheduling algorithms based on several factors, such as the entity that is scheduled, the network topology information that is needed to produce or maintain the schedule, and the entity or entities that perform the computation that produces and maintains the schedules, and to discuss the advantages and disadvantages of each category.