bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of management strategies for controlling Nassella trichotoma in modified tussock grasslands in New Zealand: a spatial and economic analysis
Authors: Lamoureaux S L , Basse B , Bourdôt G W , Saville D J
Published: May 2015

The weedy grass Nassella trichotoma (nassella tussock), historically an economically damaging invader of modified tussock grasslands in New Zealand, currently causes little if any reduction in farm production. This is a result of successful historical regional management programmes in which plants have been removed manually (by grubbing) each year before they seed. To inform a debate about the need for ongoing regional management, we developed a stage‐structured spatially explicit integrodifference equation population model and linked this to a cost analysis. We used the model to compare the weed's future population trajectories and related regional control costs over 50 years under three alternative management scenarios. The total discounted (3% p.a.) costs of no management, three‐yearly grubbing and continued annual grubbing were NZ $417 million, $736 million and $131 million respectively. These analyses indicate that annual grubbing of N. trichotoma returns a net benefit of $286 million ($417 – $131 million) compared with doing nothing and a net benefit of $605 million ($736 – $131 million) compared with a 3‐yearly grubbing programme. These results support the continuation of annual grubbing as the long‐term economically optimal management strategy for N. trichotoma on pastoral farms infested by the weed in New Zealand.
An Experimental Arrangement for the Measurement of the Pressure Distribution on High Speed Rotating Blade Rows
Authors: Leist K.
Published: May 2015

For several years past, the research staff of the Institute for Turbomachines of the Aachen Technical University has carried out measurements on rotating turbine blading. This program is part of a comprehensive effort directed toward the experimental investigation of the three-dimensional flow through axial-flow turbomachines.
Internally Fired Semi-Closed Cycle Gas Turbine Plant for Naval Propulsion
Authors: DeWitt S. H. , Boyum W. B.
Published: May 2015

An Internally fired semi-closed cycle gas turbine for Naval propulsion was designed and built for the U.S. Navy by the Westinghouse Electric Corporation. Due to a revision of the overall Navy propulsion program the plant was not tested at design conditions or mode of operation, but feasibility information for this configuration of gas turbine plant was obtained.

Plant tests indicated that this cycle configuration can be expected to attain a significant reduction in shipboard space and weight requirements while matching existing conventional propulsion plant fuel and air consumption rates over a wide load range. The plant further is simply controlled to minimize manning personnel, permit bridge control, and has a brief transient period from cruise power to full load. Plants of this cycle configuration can be expected to produce large powers such as required for main ship propulsion while employing components of the size where considerable industrial experience has been accumulated.

Fouling and corrosion of the internally fired, semi-closed cycle gas turbine were evaluated by the tests. Conventional gas turbine components are satisfactory for low sulfur fuel operation, and with additional precooler equipment development it is expected that high sulfur fuel operation will be achieved.
6200-KW Gas-Turbine-Driven Mobile Power Plant
Authors: Stys Z. Stanley
Published: May 2015

It is amazing how wide the field of application of this comparatively new machine is, because actually only slightly more than a decade has passed since it made its debut in continuous commercial service. To name a few such fields: Power generation, traction, aviation, ship propulsion, chemical industry, nuclear reactors, etc. Brown Boveri gas turbines are being used in many of these applications — and recently our company also developed a mobile power plant driven by a gas turbine. The purpose of this paper is to describe the details of such units.
The Austin Vehicle Gas Turbine
Authors: Weaving J. H.
Published: May 2015

This paper reviews the experience of the Austin Motor Company with gas-turbine development for vehicles. In particular, it considers the component efficiencies of the compressor and turbines that make up the complete unit. The present performance and fuel consumptions are reviewed and estimates made of the improvements likely to be obtained with reasonable development within a few years.
Development of Gas Turbines for Road Vehicles
Authors: Carelli A.
Published: May 2015

The experience acquired in developing an automotive gas-turbine engine is traced. Problems of design, construction, and development unique to a small gas-turbine engine and its application to an automobile are discussed. The engine performance and operational characteristics are then described. Finally, there is a discussion of the problems that must be solved before gas-turbine engines may successfully compete with reciprocating engines in automotive road transport.
A Generalized Presentation of Gas-Turbine Combustor Performance
Authors: Noreen A. E. , Martin W. T.
Published: May 2015

Experimental data on stability limits and combustion efficiency of a 3-in-diam combustor using gaseous fuel are presented. These data have been correlated by an empirical evaluation of the results of a dimensional analysis. Theories are proposed, based upon the experimental data, regarding combustor-stabilization processes. Laminar flame speed was shown to be a satisfactory index of the influence of base combustion rate on combustor performance.
Designing Thermocouples for Response Rate
Authors: Moffat R. J.
Published: May 2015

Considerable effort has been put into the study of the transient response of thermocouples. One reason for this is the growing interest in temperature-sensitive controls for jet engines. The advantage of a temperature-sensitive control is obvious — it controls by the variables which requires control. The disadvantages are chiefly in the sensing element. An ideal sensing element would be instantly aware if any change in gas temperature, and would follow accurately the temperature no matter how rapidly it changed. Unfortunately no such ideal sensing element is available. Anything which has mass requires a finite time to change its temperature, the length of time depending on its heat capacity and on how fast heat is being added to it. In terms of a thermocouple, or any other immersion element, this means that if the temperature of the gas is changing the thermocouple will “lag” and not follow the change exactly. This lag is important in control work since the control is not aware of a change in gas temperature until the signal from the sensing element changes. The lag is also important in analyzing transient temperature records made on a test engine. The recorded trace represents thermocouple temperature, not gas temperature. Due to the “lag” there may be considerable difference between gas temperature and thermocouple temperature.
The “Auris” Gas-Turbine Project
Authors: Lamb J. , Birts L.
Published: May 2015

The Auris project has as its objective the development of gas-turbine propelling machinery for medium-sized tankers and other types of merchant ships.
Accelerated Life Tests of a Pair of Naval Gas Turbines
Authors: Pasman J. S. , Miller C. L. , Fisher S. E.
Published: May 2015

This paper presents the results of a 2500-hr evaluation test performed at the U. S. Naval Engineering Experiment Station under the auspices of the Bureau of Ships. Test procedures, results, and conclusions are presented. The primary purpose of this test was to evaluate a compressor-turbine wheel with blades heavier than were in Fleet service at the time of test. This and other improvements have resulted in a forced downtime of 0.6 per cent over a thousand-hour period, and have shown justification for extension of the present 500-hr overhaul period to 1000 hr.
Rotary Regenerators for the Whirlfire Vehicular Turbines
Authors: Vickers Paul T.
Published: May 2015

The major considerations in the selection, design and development of a rotary regenerator for a vehicular gas turbine are discussed. The performance results, such as effectiveness, pressure loss and leakage of the regenerator in the General Motors Research GT-305 gas-turbine engine are presented in detail. A method for evaluating new heat-exchanger surfaces and the techniques used in developing the regenerator are also included.
A Transport Aft-Turbofan
Authors: Sells B. E. , Dodge W. R.
Published: May 2015

This paper presents the technical status of a new type aft-turbofan aircraft powerplant, designated as the General Electric CJ805-21. The successful development to date of this aft-fan engine has amply demonstrated the feasibility of a major increase in power rating and a significant improvement in altitude cruise fuel economy by converting the CJ805-3 commercial turbojet to an aft-turbofan engine. The advanced technology, performance capabilities, development and maintenance factors emphasize the importance of the CJ805-21.
Performance Analysis of Plug Nozzles for Turbojet and Rocket Exhausts
Authors: Krase W. H.
Published: May 2015

An attractive feature of the plug-type nozzle for turbojets and rocket jets is that it can automatically adjust its effective exit area with operating pressure ratio and achieve a high level of efficiency over a wide range of operating pressure ratio without variation of mechanical shape. The design and off-design performance analysis of such nozzles is described.
Seapower: Gas Turbines Add Fighting Punch
Authors: James Ralph K.
Published: May 2015

Steadily rising shipbuilding costs, approaching block obsolescence of the bulk of our active fleet, and the rapid advance of weapons technology are the major problems facing the U. S. Navy today. The ability of the gas turbine to make important contributions to combatting each of these problems has resulted in a rapid rise in its use. Specific current programs and applications are discussed.
Standby Power for Hydro-Quebec Uses Gas Turbines
Authors: Haberl H. W. , Abel D. F.
Published: May 2015

This paper covers the reasons why the standby plant was required, the selection of plant site and economic considerations governing the selection of equipment. The installation is described in some detail including building design, arrangement of equipment, significant design features and method of operation.
The Orlando Gas Turbines
Authors: Stanton C. H. , Luff H. C.
Published: May 2015

In 1958, The Orlando Utilities Commission installed two gas turbines for peaking and standby service. These units were then the largest simple-cycle gas turbines in the United States and among the largest anywhere, Fig. 1. The operating and maintenance experience with these units should be of interest to other users and potential users of large simple-cycle gas turbines.
Design and Test of a Small Turbine-Compressor Set for a Nuclear Application
Authors: Burton D. H. S. , Beck T. E. H.
Published: May 2015

This paper describes the design of a turbine-compressor set in the 400–500 kw power range for use in the ML-1 mobile nuclear power plant. The specification and design problems are discussed in terms of mechanical design and aerodynamic performance. The open-cycle test facility is also described and the results of open-cycle testing are surveyed.
Contaminated Fuel Testing of Engine Controls to MIL-E-5009B Using the USN Aeronautical Engine Laboratory Technique
Authors: Eley Myrle C.
Published: May 2015

Testing controls using fuel contaminated according to MIL-E-5009B has created problems in obtaining test equipment with satisfactory life — and also in obtaining good mixing and proper injection of the fuel contaminant mixture. The author’s company has taken the recommendations of the U. S. Navy Aeronautical Engine Laboratory in Philadelphia and developed a nonrecirculating contaminate method which has met with military approval. The method uses a concentrated fuel slurry and proportioned injection controlled by actual fuel flow rate.
A Highly Efficient Steam Turbine-Gas Turbine Cycle
Authors: Mangan J. L. , Pettit R. C.
Published: May 2015

This paper presents the approach used to select a gas turbine steam-turbine cycle of 19,000 kw with the highest efficiency attainable with commercially available equipment at reasonable costs. Mechanical integration of the equipment simplifies operation and contributes to reduced installation costs. The operating characteristics of the resulting plant are dissimilar to conventional steam-turbine plants and on application study is made to determine that significant operating cost gains are attainable when applied to a utility system.
Aircraft Turbine Power: Supporting the Prima Donna
Authors: Fisher C. A.
Published: May 2015

A discussion of recent experience with several models of gas-turbine power plants used in scheduled air-carrier operation: The causes of in-flight shutdowns and unscheduled removals; the programs to monitor performance and maintain reliability; and major problems facing the operators today.
The Gas Turbine-Air-Cleaner Dilemma
Authors: Mund Mark G. , Murphy Thomas E.
Published: May 2015

The person confronted with the selection of a gas-turbine air cleaner is faced with a dilemma because the data available to guide his selection are inconsistent and not complete. The need for air cleaners has been established. The level of air-cleaner efficiency required to protect the gas turbine from the effects of dust ingestion has not. This paper reviews the data available and relates it to Donaldson Company experience. Air-cleaner specifications and how they are influenced by gas-turbine needs and experience are discussed. Today’s gas-turbine air cleaners and what they will do are reviewed. The paper concludes that it is essential to determine the level of air-cleaner protection required by the various gas turbines and suggests programs to determine it through laboratory and field tests. Further work in air-cleaner and gas-turbine design is suggested to obtain an optimum gas-turbine air cleaner and to obtain long-life gas turbines.
Secondary-Flow Phenomena in Stator and Rotor-Blade Rows and Their Effect on Turbine Performance
Authors: Rohlik Harold E. , Kofskey Milton G.
Published: May 2015

Investigations made at the NACA Lewis Flight Propulsion Laboratory (now the NASA Lewis Research Center) on secondary-flow phenomena in stator and rotor-blade rows are interpreted, with the aid of low-speed flow visualization experiments, in order to establish sources and patterns of secondary flows there. Two stator configurations were designed to modify the stator-exit loss patterns and were investigated in conjunction with a transonic rotor to determine the effect on overall turbine performance of either reducing or eliminating stator-blade wakes and secondary-flow loss accumulations.
Description of an Operating Closed Cycle: Helium Gas Turbine
Authors: La Fleur James K.
Published: May 2015

In May of 1960 La Fleur Enterprises, later to become The La Fleur Corporation, undertook the design of a closed-cycle gas turbine utilizing helium as a working fluid. The useful output of this machine was to be in the form of a stream of helium bled from the last stage of the compressor. This stream was to be used in a low-temperature refrigeration cycle (not described in this paper) and would be returned to the compressor inlet at approximately ambient temperature and at compressor-inlet pressure. The design of this machine was completed by the end of 1960 and construction was initiated immediately. The unit was completed and initial tests were made in the Spring of 1962. This paper covers the design philosophy as it affected the conceptual and preliminary design phases of the project and describes briefly the design of the various components. Photographs of these components and a flow schematic are included.
Some Non-Simple–Equilibrium Aspects in Axisymmetric Turbomachine Flow Theory
Authors: Schroder H. J.
Published: May 2015

In turbomachines of non-free-vortex design the axisymmetric flow is mostly in a state of “disturbed equilibrium.” Methods of calculating flow fields of this kind were developed nearly 20 years ago. The examples chosen for their demonstration were rather intricate. Here, on the other hand, two very simple examples are produced which provide some insight into the — anything but self-evident — behavior of disturbed equilibrium flow. The examples serve to give some indication as to the use of definite difference methods, including the choice of boundary conditions, and a first attempt at taking incidence at the leading edges of the blades into account.
Real Gas Effects in Carbon Dioxide Cycles
Authors: Angelino G.
Published: May 2015

The potential performance of carbon dioxide as working fluid is recognized to be similar to that of steam, which justifies thorough thermodynamic analysis of possible cycles.

The substantially better results achievable with CO2 with respect to other gases are due to the real gas behaviour in the vicinity of the Andrews curve. Simple cycles benefit from the reduced compression work, but their efficiency is compromised by significant losses caused by irreversible heat transfer. Their economy, however, is appreciably better than that of perfect gas cycles. More complex cycle arrangements, six of which are proposed and analyzed in detail, reduce heat transfer losses while maintaining the advantage of low compression work and raise cycle efficiency to values attained only by the best steam practice.

Some of the cycles presented were conceived to give a good efficiency at moderate pressure which is of particular value in direct-cycle nuclear applications.

The favourable influence on heat transfer coefficients of the combined variation with pressure of mechanical, thermal and transport properties, due to real gas effects, is illustrated. Technical aspects as turbo-machines dimensions and heat transfer surfaces needed for regeneration are also considered.

Cooling water requirements are found to be not much more stringent than in steam stations.
Instrumentation Used to Define Performance of Small Size, Low Power Gas Turbines
Authors: Futral Samuel M. , Kofskey Milton , Rohlik Harold E.
Published: May 2015

Difficulties experienced in making performance measurements in small turbines resulted in the development of specialized equipment and techniques. Miniaturized probes, low pressure level transducers, precise power absorbers, and calibration methods are described. Testing of a small radial-inflow turbine at an inlet pressure of 3.4 psia is used as an example for the levels of performance variables being encountered. Accuracy of the various measurements and its effect on calculated performance numbers are included.
Design and Experience With Regenerators for Industrial Gas Turbines
Authors: Wolfe Peter , May Howard F.
Published: May 2015

This paper describes the present base load gas turbine regenerator. Covered herein are the basic design parameters, the actual physical configurations of these units along with considerable construction detail, and the service experience covering the eleven years of its existence. The evolution of the design is described.
How Thickness and Material Properties Influence Thermal Shock Stresses in Flat Plates and Cylinders
Authors: Albrecht W.
Published: May 2015

Thermal stresses in a flat plate, a solid and a hollow cylinder are calculated for sudden changes in ambient temperature using analytical solutions. The sudden temperature change from T1 to T2 is approximated by a step change and a linear change. Use of these approximations allows an evaluation of the actual stresses in close limits.

The analytical solutions for transient temperatures and stresses have been made dimensionless in order to gain general information. Thus it became possible to investigate the effect of geometry and wall thickness of a body, heat transfer characteristics and material properties on thermal shock stresses. Charts for quick evaluation of thermal shock stresses are included.
Turbomechanical Transmissions for Propulsion and Steering of Track-Laying Vehicles
Authors: Heitmann A. M. , Brassert W. L.
Published: May 2015

A novel transmission for applying the power of a gas-turbine engine to the propulsion and steering of tanks and other track-laying vehicles is described. A single gas generator supplies hot gas to three free-power turbines: two for propulsion and one for steering. The gear-train layout and calculated performance of a 2000-hp transmission for a 50-ton tank are discussed.
Distortion Tolerance: By Design Instead of by Accident
Authors: Langston C. E.
Published: May 2015

A variety of techniques are available today that may be employed by the compressor designer to minimize the adverse effects of inlet distortion. The effects of individual stage rotor matching and blade chord length have been qualitatively indicated by isolated airfoil data. These effects have been verified through testing of several multistage axial flow compressors. Matching of early compressor stages well below their peak pressure ratio has been shown to significantly reduce the sensititivty of the entire compressor-to-inlet distortion. Careful selection of blade geometry by the designer may be used to provide a favorable balance between distortion tolerance and performance. In addition, increases in rotor blade chord length and use of honeycomb blade tip shrouds have been shown to further reduce the compressor’s sensititivity to distortion. Finally, the association of inlet distortion with turbulence is established. This association assures the designer that accommodations made for time-average spatial distortion will be effective in combating the adverse effects of inlet turbulence.
NZL Gas Turbine Combustion Chamber
Authors: Sudarev A. V.
Published: May 2015

NZL designs and manufactures stationary gas turbine units with power in the 1.5–12 MW range. Eight types of gas turbine units of different use are designed, manufactured and put into operation by the Works, the main part of which is provided for operation on the main trunkline gas compression stations. At present time more than 200 units are in proper operation, duration of operation under the load is 5 million hours.
Metallurgical Studies on Gas Turbine Blade Materials After a Long Term Service
Authors: Susukida H. , Sunamoto D. , Sakumoto Y.
Published: May 2015

This paper deals with the changes of tensile, impact, and stress-rupture properties and microstructure of gas turbine blade materials due to long term heating at the temperature of 650 C (1200 F) to 800 C (1470 F) for up to 10,000 hr or due to the service operation at similar temperature range on several occasions in 34,000 hr. The relation between the above changes of the properties and the thermal fatigue strength, and the stress-rupture strength and the fatigue strength at 700 C (1292 F) and 750 C (1382 F) under corrosive environment containing vanadium and/or sulfur were also investigated. The materials involved are several heat resisting alloys such as Inconel 700, Inconel X, S816. Useful information for selection of gas turbine blade materials was obtained.
Gas Turbines: A Modern Approach to Industrial Power Plant Expansions
Authors: Elston W. D. , Bell B. A.
Published: May 2015

A major industrial complex with in-plant power generation required a large incremental expansion of steam and power production. Alternative approaches to achieve this expansion are reviewed and the gas turbine-heat recovery boiler cycle selected is described. The primary objective of this paper is to demonstrate the excellent results that can be achieved through integration of gas turbines with conventional industrial power equipment.
History of Gas Turbines Sea Salt Problems and Solutions
Authors: Kaufman R. E.
Published: May 2015

This is a presentation where you are being asked to take a look back and a look forward at the history of gas turbine sea salt problems and solutions. The implication is made that the major part of these problems now have solutions. It is believed that major efforts in sea salt sampling and separator evaluation can be greatly curtailed but not cut off. Gas turbine testing with realistically simulated sea salt ingestion must continue undiminished.
Unsteady Flow Phenomena in Rotating Centrifugal Impeller Passages
Authors: Lennemann E. , Howard J. H. G.
Published: May 2015

The phenomena of unsteady relative flow observed in a centrifugal impeller passage running at part capacity and zero flow are discussed. The mechanisms of passage stall for a shrouded and unshrouded impeller are investigated and a qualitative correlation is developed for the influence of secondary flow and inducer flow on the passage stall. The hydrogen bubble flow visualization technique is extended to higher velocities and rotating systems and provides the method for obtaining the experimental results.
The Engine Inlet on the 747
Authors: Viall W. S.
Published: May 2015

Consideration is given the manner in which inlet throat Mach number, lip losses and auxiliary passage losses affect the design of a high recovery inlet for high-bypass-ratio fan engines. Problems relating to auxiliary passage closure are discussed.
Nuclear Power Plants With High Temperature Reactor and Helium Turbine
Authors: Bammert K. , Bohm E.
Published: May 2015

The present stage of development of nuclear power plants with helium turbine and high temperature reactor is reported and a description given of the first plant of this type, the Geesthacht KSH plant (Kernkraftwerk Schleswig-Holstein) in Germany. Particular stress is laid on the control of closed-cycle gas turbines. The special cases of reactor scram, shutdown of the turbine and load release as well as starting up and turning off of the plants are taken into consideration. The design of the turboset and the arrangement of the components of helium turbines of high output are described. Furthermore results of calculations for optimum layout of helium turbine plants with regard to simultaneous power and process heat generation are given.
Gas Turbine Propulsion for LNG Tankers
Authors: Smith H. F.
Published: May 2015

This paper deals with the economic and technical aspects of using aircraft type marine gas turbines for main propulsion of LNG tankers. A general comparison of the gas turbine powered ship with a conventionally powered steam ship will be made and the advantages of the gas turbine ship from a design, construction, and operating viewpoint will be discussed.
Programs for Computation of Velocities and Streamlines on a Blade-to-Blade Surface of a Turbomachine
Authors: Katsanis Theodore , McNally W. D.
Published: May 2015

This paper describes Fortran programs that give the solution to the two-dimensional, subsonic, nonviscous flow problem on a blade-to-blade surface of revolution of a turbomachine. Flow may be axial, radial, or mixed. There may be a change in stream channel thickness in the through-flow direction. Either single, tandem, or slotted blades may be handled as well as blade rows with splitter vanes. Also, small regions may be magnified to give more detail where desired, such as around a leading or trailing edge or through a slot. The method is based on a finite difference solution of the stream function equations. Numerical examples are shown to illustrate the type of blades which can be analyzed, and to show results which can be obtained. Results are compared with experimental data.
High Bypass Ratio Compound Fan-Shaft Engines for Convertible Rotary Wing Aircraft
Authors: l’Anson L.
Published: May 2015

This paper presents design arrangements and performances of high bypass ratio compound fan-shaft engines. Helicopter rotor drive power can be obtained from the propulsion fan engine by unloading the fan. This is accomplished by using variable fan guide vanes that can be closed to reduce fan air flow or by reducing fan speed. These methods of unloading the fan are substantiated by the results of tests. The basic designs considered are for engines in the 5 to 30 lb/sec gas producer airflow size class and which have a two-spool coaxial front fan with a bypass ratio of approximately 8.0 and pressure ratio of approximately 1.4. The front fan configuration is used to superchange the gas producer. The flow of energy that results during power sharing between propulsive fan thrust and helicopter rotor drive power is discussed; in addition, fan shaft engine performance data are presented as applied to representative stowed-rotor convertiplanes of 15,000 and 60,000-lb design gross weights.
Focus on Processing Problems in Jet Engines
Authors: Wotring W. F.
Published: May 2015

An effective cost improvement program should be an integral part of the product and profit planning activity. The ideal product design configuration incorporates the functional requirements in a manner that will allow minimum manufacturing cost. Close integration of both the customer requirements and minimum manufacturing cost requirements develops a much desired philosophy of low cost design, necessary for the operation of a competitive business. This paper provides a brief summary of the product, functional requirements, design/cost philosophy, cost improvement facets, and examples of results of this concept in the General Electric jet engine business.
Noncontacting Torquemeters Utilizing Magneto-Elastic Properties of Steel Shafts
Authors: Angeid Egil
Published: May 2015

The magneto-elastic property of steel shafts makes noncontacting torquementers possible. Early magneto-elastic torquemeters suffered from excessive sensitivity to variations in airgap and shaft temperature. These drawbacks have been eliminated in the Torductor® torquemeter, which has been very successful in low-speed industrial applications. In gas turbine applications, some special problems are encountered. These problems, and ways to minimize them, are discussed.
Design of an Advanced Steam Turboalternator for Nuclear Applications
Authors: Luchter Stephen
Published: May 2015

This paper describes the results of a design study of a family of steam turboalternators for a potential terrestrial low power reactor power plant. The criteria were small size, very high reliability, and as high an efficiency as possible. The use of water lubricated bearings and of 400-Hz power were fundamental to the design. The results indicate feasibility of a single basic design over the power level range of from 30 to 2000 kwe.
Steam Injection, a Source of Incremental Power
Authors: Bultzo Charles
Published: May 2015

The performance of a gas turbine is normally guaranteed at 80 F, with derating occurring for temperatures above this point. This reduction in capability must be provided for by either installing an “oversized” turbine or means by which the horsepower lost due to derating can be provided by at least two methods. This paper reports on test work that was done to provide the incremental power and evaluates their comparative cost.
The Engine Usage Indicator
Authors: Hohenberg R.
Published: May 2015

An instrument to cumulate the exposure of a small gas turbine engine to certain deteriorating phenomena has been developed. The device displays usage in cumulative creep, low cycle fatigue, and temperature shock derived from measured gas temperature and speed. This instrument and its conceptual basis are described.
Feasibility Study of Fluidic Turbine Temperature Sensors in Gas Turbine Engines
Authors: Black J. I.
Published: May 2015

This paper is intended to introduce the reader to the subject of turbine temperature controls, and to present the results of a preliminary engine evaluation of two miniature fluidic oscillator temperature sensors. These units were installed in the air-cooled vanes of the first turbine nozzle on a Lycoming T55 L7 Engine and have successfully measured the gas temperature at the turbine inlet station for more than 8 hr. In addition to the test results, topics relating to the subject of turbine temperature controls, such as signal error compensation and temperature averaging, will be briefly discussed.
Molecular dynamics simulations of anchored viral peptide interactions
Authors: Yacoub Tyrone J. , Szleifer Igal
Published: May 2015

The authors use molecular dynamics simulations to investigate viral peptide interactions as the cause of pH-dependent fusion in liposomal drug delivery. Viral peptides (LEFN) are composed of a linker peptide (LELELELE) connected to a synthetic viral peptide (DRGWGNGCGLFGKGSI). Rather than being anchored in a lipid bilayer, the viral peptides are anchored to a neutral surface by the amino termini of the linker peptide (anchor atoms are mobile in the xy-plane). Atomistic-level peptide pair arrangement on a surface depends on pH; however, the overall propensity to cluster is independent of pH, indicating that pH-sensitive liposome fusion is not due to peptide clustering. To further investigate a molecular cause of pH-sensitive fusion, the authors treat the linker peptides as ectodomains, with the assumption that the viral peptides are already inserted into a target membrane. In these simulations, the linker peptides are elongated to encourage them to bundle. At both high and low pH, the peptides readily bundle. At high pH, however, bundling was constrained by long-range order induced by sodium ions bridging negatively charged glutamic acid residues on neighboring peptides. The authors hypothesize that this constraint hinders the ability of the linker peptides to support viral peptide insertion, resulting in decreased levels of fusion observed experimentally.
Radiological Safety and Quality: Paradigms in Leadership and Innovation
Authors: Bauer Lawrence T.
Published: May 2015

Radiological Safety and Quality: Paradigms in Leadership and Innovation. Editors: L. Lau and K.‐H. Ng, Springer Dordrecht, Heidelberg, 2014. 471 pp. Price: $179.00. ISBN: 978‐94‐007‐7255‐7 (hardcover).
Spatial aliasing study using a high-resolution radiation measurement of a violin
Authors: Shabtai Noam R. , Behler Gottfried , Vorländer Michael
Published: May 2015

Sound source radiation patterns can be employed in a virtual acoustic system in order to improve the realistic experience of the listener. Many studies were described in the literature, in which spherical microphone arrays and spherical harmonics were used to capture the radiation pattern of musical instruments. In these studies, however, a limited number of microphones is used due to technical reasons that involve a non-repeatable excitation by the human player and the corresponding requirement to capture the radiation in one single excitation. Up to now, the radiation pattern is measured without a reference that describes the degree of spatial aliasing caused by the limited number of microphones. This work presents a high-resolution spatial sampling of the radiation pattern of an electrically excited violin. An analytical measure to the degree of spatial aliasing is represented and calculated for each number of microphones, using the high-resolution measurement as a reference.
Array processing methods for the determination of reflection properties of architectural surfaces
Authors: Müller-Trapet Markus , Vorländer Michael
Published: May 2015

It has become popular in architectural acoustics to use microphone arrays, very often in spherical arrangements, to capture and analyze the sound field in rooms. This contribution will present a hemispherical receiver array, designed to obtain information about sound reflection from architectural surfaces, preferably in-situ. Similarly to previous studies, the analysis in the spherical harmonics (SH) domain is favored, with the additional challenge of data available on a hemisphere instead of a complete sphere. This problem is solved by obtaining orthonormal base functions on the hemisphere. As application cases, spherical beamforming for the determination of reflection factors will be presented as well as scattering near-field holography in order to determine the diffusion coefficient of small samples. Results from numerical and experimental case studies will be discussed.
Auditory illusion demonstrations as related to prehistoric cave art and Stonehenge
Authors: Waller Steven J.
Published: May 2015

Auditory illusions will be demonstrated, and their relevance to prehistoric cave art and Stonehenge revealed. In the ancient past, when the wave characteristics of sound were not understood, virtual sound effects arising from complex sound wave interactions (echoes, reverberations, interference patterns, etc.) were misinterpreted as invisible beings (echo spirits, thunder gods, sound absorbing bodies, etc.) as described in ancient myths around the world. In this session, live hands-on demonstrations will be given to small groups of students who can experience for themselves these types of auditory illusions. Participants will get to experience various sounds and will be given the task of interpreting what the sounds are, first blindfolded, then with visual cues. (Previous student reactions have included “Whoa!,” “Wow!,” “Amazing!,” “Cool!,” and “What??.”) These scientifically conducted experiments show how various ambiguous sounds can be interpreted in more than one way—like optical illusions—and thus can help in understanding our ancestors’ reactions to sounds they considered mysterious and spooky. These discoveries are just a few examples of research findings that are springing from the new field of Archaeoacoustics. See https://sites.google.com/site/rockartacoustics/ for further examples.
Differences in atmospheric absorption coefficients between ANSI/ASA S1.26-2014 and an updated model
Authors: Petersen Erik A. , Sparrow Victor W.
Published: May 2015

Absorption coefficient predictions from the ANSI/ASA standard S1.26-2014 and Sutherland and Bass 2004 [Sutherland, et al., J. Acoust. Soc. Am. 115(3), 2004] are compared for 125, 250, 500, and 1000 Hz pure tones ranging in elevation from 0 to 10 km. The differences in absorption mechanisms as well as the assumed atmospheric profiles are considered. Calculated using their respective profiles, the two models differ by 1–4 dB/km. Additionally, cumulative absorption over a 10 km vertical path is calculated under several conditions; ANSI with ANSI profile, ANSI with S&B profile, and S&B with S&B profile. Comparing the second and third case shows a difference of 0.5–3 dB, which characterizes model dependent differences by evaluating both models using the same profile. A comparison of the first and second cases yields a difference of 0.5 to 10 dB, indicating a strong dependence on the assumed atmospheric profile. To achieve consistent predictions over a 10 km path the layer thickness should be no greater than 1 km. [The opinions, findings, conclusions, and recommendations expressed here are those of the authors and do not necessarily reflect the views of sponsors of the ASCENT Center of Excellence including the Federal Aviation Administration.]
Comparisons between physics-based, engineering, and statistical learning models for outdoor sound propagation
Authors: Reznicek Nathan J. , Hart Carl R. , Wilson D. Keith , Pettit Chris L. , Nykaza Edward T.
Published: May 2015

Many outdoor sound propagation models exist, ranging from highly complex physics-based simulations to simplified engineering calculations. More recently, highly flexible statistical methods have become available, which offer the capability to predict outdoor sound propagation, given a training dataset. Among the variety of modeling approaches, the range of incorporated physics varies from none, as in the statistical learning methods, to comprehensive considerations for physical models. Engineering methods vary in the level of incorporated physics, oftentimes resorting to heuristic or approximate approaches. In order to compare the capability of engineering and statistical learning models, one particular physics-based model is used for outdoor sound propagation predictions, namely, a Crank-Nicholson parabolic equation (CNPE) model. Narrowband transmission loss values predicted with the CNPE, based upon a simulated dataset of meteorological, boundary, and source conditions, act as simulated observations. Among the engineering models used in the comparisons are the Harmonoise propagation model and the ISO 9613-2 method. Among the statistical learning methods used in the comparisons is a random forest regression model. Metrics such as the root-mean-square error and the skill score are computed for both the engineering models and statistical learning models.
Crank-Nicholson solution of the wide-angle parabolic equation for inhomogeneous moving media
Authors: Wilson D. K. , Ostashev Vladimir E.
Published: May 2015

Solutions of the narrow-angle parabolic equation (PE) are essentially the same in non-moving and moving media, due to the validity of the effective sound-speed approximation. However, the wide-angle PE (PE) and its numerical solution are considerably more complicated for a moving than for a non-moving medium. Starting with a rigorously derived, wide-angle PE for propagation in an inhomogeneous moving medium, the Crank-Nicholson solution of this equation is shown to involve a pentadiagonal matrix, which is relatively inefficient to calculate. However, a high-frequency approximation of this equation, valid when the wavelength is small compared to the length scale of the inhomogeneities, leads to a particularly simple wide-angle PE, the solution of which involves a tridiagonal matrix and thus can be solved with only slight extensions to existing narrow-angle PE codes. Solutions of the wide-angle PE are illustrated with examples for sound propagation in the atmosphere. Comparisons to the narrow-angle PE exhibit close agreement at low propagation angles. At higher propagation angles, the refraction effects are found to be relatively unimportant.
Chemical kinetics theory of pyrotechnic whistles
Authors: Lyons Gregory W. , Raspet Richard
Published: May 2015

Pyrotechnic whistles are sound effect devices commonly used in fireworks and consist of a particular fuel-oxidizer mixture pressed into the bottom of a tube. When ignited, a loud sound is emitted with harmonic frequencies corresponding to standing-wave modes of the tube. A theory of pyrotechnic whistles is developed for a chemical kinetics feedback mechanism in a model combustion reaction. Normal modes are obtained for a cylinder with steady, uniform axial flow. Boundary conditions are derived for a state-dependent reaction rate in an infinitesimal combustion surface. Solutions are presented for the normal modes with respect to reaction rate and tube outlet impedance.
Temporal model of edge pitch effects
Authors: Cariani Peter , Colburn H. Steven , Hartmann William M.
Published: May 2015

Musical pitches can be perceived in broadband noise stimuli near frequencies corresponding to parameter changes along the frequency dimension. For example, monaural edge pitches (MEPs) are produced by noise stimuli with sharp spectral edges. Binaural edge pitches (BEPs) are produced by dichotic noise with interaural-phase changes at frequency boundaries (e.g., 0-pi), and binaural-coherence edge pitches (BICEPs) arise from boundaries between frequency regions with different interaural coherence (such as changes from correlated to uncorrelated noises). Perceived pitches are shifted slightly in frequency away from spectral edges: MEPs are shifted into noise bands, BICEPs are shifted into the incoherent region, and BEPs are shifted bimodally. This presentation proposes a temporal model for these edge pitches based on population-wide all-order interspike interval distributions (summary autocorrelations, SACFs), computed using the Zilany-Bruce-Carney 2014 model of the auditory nerve. Pitches were estimated from mean SACF values among lags at all F0-subharmonics (0–30 ms). Binaural pitches were estimated from computations based on corresponding left and right PSTs after a binaural delay and cancellation process. Model predictions agreed well with pitch judgments in both monaural and binaural cases. [Work supported by NIDCD (R01 DC00100 and P30 DC004663) and by AFOSR FA9550-11-1-0101.]
Spectral resolution and speech recognition in noise for children with hearing loss
Authors: McCreery Ryan W. , Browning Jenna M. , Kirby Benjamin , Spratford Meredith , Brennan Marc
Published: May 2015

Better spectral resolution has been associated with higher speech recognition in noise in adults with hearing loss who use hearing aids and adults with cochlear implants. However, the role of signal audibility and age on this relationship has not been reported. The goal of this study was to evaluate the effect of aided audibility and spectral resolution on speech recognition in noise for a group of children with sensorineural hearing loss and a group of adults with hearing loss. Higher age, better aided audibility, and the ability to detect more ripples per octave in a spectral ripple discrimination task were associated with better sentence recognition in noise for children with hearing loss.
Role of high-frequency component in source segregation in multi-talkers condition
Authors: Mi Jing , Colburn H. Steven
Published: May 2015

This study explores the role of high-frequency components in generating spatial release from masking (SRM) in multiple-talker conditions. From a frequency-analysis perspective, one can fully separate multiple speech signals when their spectrograms do not overlap. The sparsity of speech can be related to spectral overlap and is explored here in the context of SRM. The interaural coherence coefficient (IACC), which is defined as the value of the cross-correlation function at the expected interaural time difference (ITD) location, can be a good indicator of sparsity for binaural signals. The sparser the stimuli in the frequency domain, the less overlap in spectrograms, which leads to higher short-term IACCs. In this study, a sound-segregation system based on binaural cues was used to separate multiple sound signals in a mixture. Then, the short-term IACC was calculated for each time-frequency slice in the segregated sound. It was shown that average IACCs for multi-speech conditions are higher than for multi-white-noise conditions, especially in high-frequency regions. Based on this result, it was hypothesized that high-frequency components, which are sparser than low-frequency components in speech, are critical for SRM in multiple-talker conditions. Psychoacoustic evidence was found to support this hypothesis. [Work supported by NIH/NIDCD: Grant R01 DC00100.]
The acoustic survey of intonation in Autism Spectrum Disorder
Authors: Azizi Zahra
Published: May 2015

The speech pattern of children with autism spectrum disorder (ASD) demonstrates a number of abnormal features, the study which can shed light on the difficulties the autistic children encounter in making meaning through speech. With regard to this stated purpose, in this article, I have scientifically examined the pattern of speech in a set of indicative and interrogative sentences as uttered by a group of autistic children and compared and contrasted the results with the pattern of speech in the same set of sentences as uttered by a group of typical development (TD) children. The specific aim of this study was to assess the intonation pattern, mean of pitch, amplitude, duration, intensity, and tilt in the ASD as compared to the TD. The data collected showed that while the amplitude in interrogative sentences, duration, intensity, mean of pitch, and tilt in ASD and TD were almost similar, the intonation pattern, the mean of pitch (with regard to severity of autism), and the amplitude in indicative sentences proved significantly different. To be more precise, with respect to these three latter features, the autistic children demonstrated monotony, an impairment that made them have difficulty making meaningful indicative and interrogative sentences.