bluuebunny/crossref_metadata_2025 huggingface dataset:
Significance of Raised Flow Velocity in Basilar Artery in Patients with Acute Ischemic Stroke: Focal Stenosis, Coexistent Stenosis, and Collateral Flow
Authors: Zhong Jingxin , Chen Xiang‐Yan , Leung Thomas Wai Hong , Ou Aihua , Shi Xiaogeng , Cai Yefeng , Huang Yan , Wong Ka Sing
Published: May 2015

BACKGROUND AND PURPOSE

Increased cerebral blood flow velocity of basilar artery (BA) is common but often neglected. By using digital subtraction angiography (DSA) to detect intracranial large artery stenosis, we performed transcranial Doppler (TCD) to evaluate cerebral hemodynamic changes of stroke patients.

METHODS

Acute stroke patients with TCD‐detected raised peak systolic velocity (PSV) in BA (≥100 cm/second) were recruited.

RESULTS

Among 91 recruited patients, BA stenosis (>50%) was confirmed by using DSA in 29 patients (32%), among which 20 patients (70.0%) had coexistent internal carotid artery (ICA) and vertebral artery (VA) stenoses. Among patients without BA stenosis (n = 62, 68%), severe stenosis or occlusion of ICA was evaluated in 22 patients (22/62, 35.4%) and severe stenosis or occlusion of VA was detected in 22 patients (22/62, 35.4%). Among the values of PSV (120, 140, 160, and 180 cm/second) and the stenotic‐to‐prestenotic ratio (SPR) (1.5, 2.0, 2.5, and 3.0), 160 cm/second was found to show the highest predictive value (area under the receiver operator characteristic curve: .75, 95% CI: .65‐.86), with a sensitivity of .70 and a specificity of .81.

CONCLUSIONS

Apart from an intrinsic BA stenosis, high‐grade steno‐occlusion of ICA or VA may contribute a lot to induce an elevated flow velocity in BA. A higher value of cutoff point may increase the accuracy of diagnosing BA stenosis.
Evaluation of Early Reperfusion Criteria in Acute Ischemic Stroke
Authors: Ozenne Brice , Cho Tae‐Hee , Mikkelsen Irene Klærke , Hermier Marc , Ribe Lars , Thomalla Götz , Pedraza Salvador , Baron Jean‐Claude , Roy Pascal , Berthezène Yves , Nighoghossian Norbert , Østergaard Leif , Maucort‐Boulch Delphine
Published: May 2015

BACKGROUND AND PURPOSE

Though still debated, early reperfusion is increasingly used as a biomarker for clinical outcome. However, the lack of a standard definition hinders the assessment of reperfusion therapies and study comparisons. The objective was to determine the optimal early reperfusion criteria that predicts clinical outcome in ischemic stroke.

METHODS

Early reperfusion was assessed voxel‐wise in 57 patients within 6 hours of symptom onset. The performance of the time to peak (TTP), the mean transit time (MTT), and the time to maximum of residue function (Tmax) at various delays thresholds in predicting the neurological response (based on the National Institutes of Health Stroke Scale) and the functional outcome (modified Rankin scale ≤1) at 1 month were compared. A receiver operating characteristics (ROC) analysis determined the optimal extent of reperfusion. A novel unsupervised classification of reperfusion using group‐based trajectory modeling (GBTM) was evaluated.

RESULTS

MTT had a lower performance than TTP andTmaxin predicting the neurological response (P= .008 vs. TTP andP= .006 vs.Tmax) or the functional outcome (P= .0006 vs. TTP;P= .002 vs.Tmax). No delay threshold had a significantly higher predictive value than another. The optimal percentage of reperfusion was dependent on the outcome scale (P< .001). The GBTM‐based classification of reperfusion was closely associated with the clinical outcome and had a similar accuracy compared to ROC‐based classification.

CONCLUSIONS

TTP andTmaxshould be preferred to MTT in defining early reperfusion. GBTM provided a clinically relevant reperfusion classification that does not require prespecified delay thresholds or clinical outcomes.
Training of neonatal cardiopulmonary resuscitation instructors
Authors: Wada Masaki , Tamura Masanori
Published: May 2015

Background

The Consensus on Science and Treatment Recommendations 2010 supported simulation‐based training for education in resuscitation. This approach has been introduced into neonatal cardiopulmonary resuscitation (NCPR) courses in Japan, but no method for teaching instructors has been established. We developed a course for training instructors of NCPR, with inclusion of an instruction practice program. The goal of the study was to evaluate the performance of instructors who completed the course.

Methods

Based on problems in the conventional instructor training course (old course 1), we developed and implemented a new course. Persons who had completed an NCPR course took the new course after developing two resuscitation scenarios. The new course included lectures and instruction practice, in which participants provided instruction using these scenarios. Instruction by participants was evaluated, and knowledge, opinions and satisfaction were examined by questionnaire after the course. Activity of the participants as instructors for 6 months after certification was also evaluated. The performance of trained instructors was compared between the old and new courses.

Results

Of 143 participants in the new course, >90% had confidence to teach NCPR, while only 50–60% of the 89 participants in the old course indicated that they could instruct on resuscitation procedures and practice (P < 0.001). All participants in the new course recognized the value of scenario practice and all were glad they had taken the course. For 6 months after certification, significantly more participants who had done the new course worked as instructors compared with those who had done the old course (60% vs 34%, P < 0.001).

Conclusion

This is the first trial of a resuscitation training course using scenarios that participants developed themselves. A new course including instruction practice for training NCPR instructors was effective for improving instructor performance.
The relationship between income and oral health among people with intellectual disabilities: a global perspective
Authors: Hughes Michael J. , Gazmararian Julie A.
Published: May 2015

Background

The scientific literature cites wide health disparities for people with intellectual disabilities compared to the general population. This study seeks to gain an understanding of the effects of income status on oral health in a global population of people with intellectual disabilities.

Methods

Eighty‐two thousand five hundred and seventy Special Olympics athletes were screened and eligible for inclusion in this study. The main exposure (income status) and selected oral health signs and symptoms (missing teeth, untreated decay, injury, gingivitis, and mouth pain) were used to conduct a cross‐sectional analysis. Prevalence odds ratios were obtained through logistic regression.

Results

Study participants from low‐income countries experienced adverse health outcomes at a lower rate than expected. Study participants from upper middle, lower middle, and low‐income countries had higher odds of mouth pain and untreated decay, yet lower odds of missing teeth, injury, and gingivitis, than participants from high‐income countries. Overall, a great number of individuals from every income group required maintenance or urgent care.

Conclusion

Oral health problems are not exclusive to low‐income study participants. Unexpectedly high odds of missing teeth, injury, and gingivitis in high‐income countries may be attributed to the high proportion of participants from the United States, which is considered a high‐income country but has large income disparities. Health‐determining circumstances in low‐income countries provide some protection from the hypothesized gradient of oral health for all measured outcomes.
Export Quality and the Dynamics of North–South Competition
Authors: Chami Batista Jorge , Liu Yan
Published: May 2015

This paper introduces and applies a new methodology to deal with competition among exporters of vertically differentiated products. The novel methodology is applied to Japanese imports of manufacturing goods at the most detailed level of classification. It is shown that the North lost market share in direct competition with the South in all of the three product segments (low, medium and high), and in every sub‐period from 1988 to 2010, except in the high segment in the 1988–91 sub‐period. Most of the North's direct loss to the South took place in the low and medium segments. China accounts for most of the South's direct gains in these two segments, while the rest of the developing countries of Asia accounts for most of these gains in the high segment.
Protocol guided bleeding management improves cardiac surgery patient outcomes
Authors: Pearse B. L. , Smith I. , Faulke D. , Wall D. , Fraser J. F. , Ryan E. G. , Drake L. , Rapchuk I. L. , Tesar P. , Ziegenfuss M. , Fung Y. L.
Published: May 2015

Background and Objectives

Excessive bleeding is a risk associated with cardiac surgery. Treatment invariably requires transfusion of blood products; however, the transfusion itself may contribute to postoperative sequelae. Our objective was to analyse a quality initiative designed to provide an evidenced‐based approach to bleeding management.

Materials and Methods

A retrospective analysis compared blood product transfusion and patient outcomes 15 months before and after implementation of a bleeding management protocol. The protocol incorporated point‐of‐care coagulation testing (POCCT) with ROTEM and Multiplate to diagnose the cause of bleeding and monitor treatment.

Results

Use of the protocol led to decreases in the incidence of transfusion of PRBCs (47·3% vs. 32·4%; P < 0·0001), FFP (26·9% vs. 7·3%; P < 0·0001) and platelets (36·1% vs. 13·5%; P < 0·0001). During the intra‐operative period, the percentage of patients receiving cryoprecipitate increased (2·7% vs. 5·1%; P = 0·002), as did the number of units transfused (248 vs. 692; P < 0·0001). The proportion of patients who received tranexamic acid increased (13·7% to 68·2%; P < 0·0001). There were reductions in re‐exploration for bleeding (5·6% vs. 3·4; P = 0·01), superficial chest wound (3·3% vs. 1·4%; P = 0·002), leg wound infection (4·6% vs. 2·0%; P < 0·0001) and a 12% reduction in mean length of stay from operation to discharge (95%: 9–16%, P < 0·0001). Acquisition cost of blood products decreased by $1 029 118 in the 15‐month period with the protocol.

Conclusions

The implementation of a bleeding management protocol supported by POCCT in a cardiac surgery programme was associated with significant reductions in the transfusion of allogeneic blood products, improved outcomes and reduced cost.
Operating Experience and Design Features of Closed Cycle Gas Turbine Power Plants
Authors: Keller Curt
Published: May 2015

This paper is the author’s third progress report in the USA on the AK-closed cycle gas turbine.
Development of a Centrifugal Compressor for a Small Gas-Turbine Engine
Authors: Balling N. R. , van Ornum V. W.
Published: May 2015

The objective of the research and development program reported by this paper was to decrease the specific fuel consumption of a small gas-turbine engine by means of an increase in pressure ratio alone. Development of a centrifugal compressor is presented, with a general description of equipment, methods, and special problems met during the tests. Results showed the required decrease in specific fuel consumption and pointed up the advantages of a straightforward development program.
Gas-Turbine Rotary Regenerator: Design and Development of Prototype Unit for 3000-HP Plant
Authors: Hammond W. E. , Evans T. C.
Published: May 2015

To exploit the regenerative gas-turbine cycle to the fullest possible extent requires an extremely high degree of heat exchange. Presently, the rotary heat exchanger is the only type which can be designed with the high thermal effectiveness necessary and yet remain practical from a size and cost standpoint. The mechanical nature of the rotary heat exchanger is such, however, that some leakage of high-pressure fluid to the low-pressure side will always occur. The fact that in the past this leakage could not be held to workable values has prevented commercial acceptance of this type unit. Consequently, The Air Preheater Corporation set up an intensive program aimed at developing an acceptable sealing means which would remove this one objection to an otherwise highly desirable piece of equipment. While this development program, at time of writing, is far from complete, results to-date have indicated that sealing of the rotary design can be accomplished, and based on quantity production, costs of a turbine plant equipped with a rotary heat exchanger would be attractive commercially. Included in the development program was the design and construction of a prototype unit for a 3000 hp turbine plant. While erection of the prototype unit is complete, no testing has been done at time of writing. The purpose of this paper is to emphasize the advantages of the regenerative cycle, generally, and more specifically, to show why the rotary type is most promising, particularly in the high effectiveness range. In addition, certain data pertaining to the design of the prototype unit are also presented. A future report will present results obtained from the prototype test program.
Design Features of New 16,500-KW Gas Turbines for Power Generation
Authors: White A. O.
Published: May 2015

The combustion gas turbine has come to be an accepted means of power generation in the world today and, as has been the case with all power generation equipment, there is a demand for ever increasing sizes. To meet this demand, late in 1954 the author’s Company embarked on the design of a unit to be rated approximately 15,000 kw.
Valveless-Gas-Turbine Combustors With Pressure Gain
Authors: Porter Carroll D.
Published: May 2015

A valveless combustor has been developed which has been tested at one to three atmospheres of pressure. It discharged combustion products at practical turbine-inlet temperatures and at a total pressure above that of the inlet. Developmental problems encountered and results are discussed. The smooth combustor cycle, a phased system of combustor tubes and pulsation traps, achieves steady flow at the inlet and outlet of the combustor system to preserve the high efficiency of today’s turbines and compressors. The combustor will soon be tested on a gas-turbine compressor to verify efficiency gain estimates.
New Gas Turbines for the Steel Industry
Authors: Stys Z. Stanley
Published: May 2015

Applications of the gas turbine in the steel industry appear attractive. Several of these units have been in operation for many years and performance and considerable operating experience already have been gained. A new type of unit has been developed based on these experiences considering newest advances in the art of engineering of a gas turbine. The historic development and layout as well as the various governing aspects of these units burning blast-furnace gas and built for use in the steel industry are described.
Development of the Bristol Proteus Turboprop to 2000 Hr Life Between Overhauls
Authors: Green P. F.
Published: May 2015

Airplane experience with the Bristol Proteus engine in the Britannia from the start of passenger services up to its present overhaul life of 2000 hr and a dsscussion of the basic reliability and safety features of the engine.
Design Considerations for Nuclear-Aircraft Gas-Turbine Engines
Authors: Riley D. R.
Published: May 2015

Many new design considerations are encountered in the design of nuclear aircraft gas-turbine engines. The effect that the power-plant configurations, the cycle, radiation level, residual radiation, and nuclear heating have on the design is discussed in this paper.
Application of Electrical Analog Theory in the Preliminary Design of Air-Cooled Turbines
Authors: Lang R. , Petrick E. N.
Published: May 2015

The demand for increased performance in turbojet engines has necessitated an increase in the operating temperatures of various engine components. To this end, metallurgical engineers have made significant improvements in the properties of high-strength metals. The metallurgical state-of-the-art, however, is not sufficient to satisfy the requirements of the propulsion engineer. The air-cooled turbine, therefore, has been developed. The higher operating temperature levels require a more critical study of temperature distribution and of the resultant operating stresses in the blading. The utilization of the analogy between heat flow and electrical flow is described herein as the basis for a method of determining the chordwise-temperature distribution and heat-transfer rates in the air-cooled turbine blades. A general review of the mathematical derivation of analog theory is included and a hypothetical problem is solved. It is to be noted that the technique is not restricted solely to the turbine problem, but can be applied to any steady-state problem which satisfies the specified conditions. Additional analog examples are cited, including techniques for determination of the velocity and pressure distribution around the turbine blade and the temperature distribution in an air-cooled turbine disk.
Operating Experience in the Petro-Chemical Industry
Authors: Stephens J. O.
Published: May 2015

The industrial gas turbine has gained acceptance in the petro-chemical industry (with its multipurpose cycle) and is now finding increasing application in this field. The reliability of this prime mover has been of paramount importance in petro-chemical applications and it is the purpose of this paper to report operating experience establishing this phase together with the improvement in thermodynamic cycle performance.
Design Considerations and Operating Experience of Regenerators for Industrial Gas Turbines
Authors: Caughill R. F.
Published: May 2015

The paper gives a brief review of the general specifications including performance requirements, operating conditions, and installation. It points out some of the design restrictions that were considered from a practical manufacturing viewpoint and some of the basic research that had taken place over a period of years. Field testing and operating experience are vital contents of the paper.
Design and Development Review of the T64 Turboprop/Turboshaft Engine
Authors: Ehrich Frederic F.
Published: May 2015

The T64 is a turboshaft/turboprop aircraft engine under development by the Small Aircraft Engine Department of the author’s company for the U. S. Navy Bureau of Weapons. A summary is given of the basic design criteria for the engine as well as a brief description of the engine configuration and highlights of engine development experience. A summary of the engine configuration is given in Table 1.
A 750-Kw Gas Turbine Generator Set for USS Oklahoma City (CGL-5)
Authors: Fowden W. M. M.
Published: May 2015

A description of a 750-kw emergency and standby electric-generator set as installed in the USS Oklahoma City. Operating experience is summarized. The 1100-hp gas turbine in this set is the largest installed in a U. S. Naval combat ship.
Overhaul and Operating Experiences JT-3 and JT-4 Jet Engines January 1, 1962
Authors: Taylor M. W.
Published: May 2015

Since the inception of Pan American’s jet operations, the JT-4 and JT-3 jet engines have logged over 1,200,000 engine hours. During the period of operation to December 1, 1961, a total of 2083 engines were changed. Seventy-eight per cent of the JT-4’s removed were planned, as were 71 per cent of JT-3 removals. The author discusses some of the experiences which have occurred in the use and overhaul of these engines.
Economics and Operating Results Prototype Aircraft Jet Engine-Electric Power Plant
Authors: Evans Robert A. , Sonntag Joseph C.
Published: May 2015

As of the date of this writing, the nation’s first aviation gas turbine in electric utiltiy service has been in operation over 500 hr with 176 startups for “on-line” operation, of which 52 have been automatic. The average startup time has been 139 sec from pushbutton actuation to full-load operation including all time steps for the operational checks designed into the starting sequence. Operation has been satisfactory and the results of the first “hot-section” inspection (after 500 hr) were excellent, showing practically no wear, erosion or corrosion of combustion chambers, nozzles, or buckets. No maintenance was required for return to full operation.
Analog Computer Study of the Transient Performance of the Orenda 600-hp Regenerative Gas Turbine
Authors: Saravanamuttoo H. I. H.
Published: May 2015

An analog computer has been used to investigate the transient performance of an advanced regenerative gas turbine. The direct simulation of the engine was a valuable tool during the design phase, giving a good understanding of the effects of regenerator time lag. The study verified the need for regenerator bypass during decelerations and permitted simplification of the control system. Use of the analog computer enabled these decisions to be made at an early stage, resulting in appreciable saving of time and money in the engine development program.
Noise Control of a Jet Engine Converted to a Fixed-Plant Installation
Authors: Galloway William J.
Published: May 2015

This paper describes the step-by-step procedure involved in solving a noise-control problem associated with the use of a J47 turbojet as a fixed-plant turbine-generator. Noise-reduction requirements for the turbine exhaust and intake are computed to satisfy both a hearing-loss criterion and a speech communication criterion. An impervious enclosure or a resilient wrapping, a lined 90-deg bend, the directive nature of one of the sources, and a muffler of acoustic baffles are utilized in solving the problem.
Analysis of Gas-Turbine Wear Data for Required Air-Cleaner Performance
Authors: Duncan S. F.
Published: May 2015

Application of gas turbines to civilian and military off-highway vehicles operating in heavy dust requires compact air filters whose performance is compatible with turbine-wear characteristics and an economical operating life. Data on turbine wear as a function of particle size and concentration of dust make possible an analysis of air-cleaner performance to determine suitability of application. A method of making such an analysis is demonstrated.
A 300-HP Recuperative Gas Turbine for EFL Energy System Application
Authors: Carlson P. G. , Pembleton T. K.
Published: May 2015

A 300-hp recuperative gas-turbine engine is described, and the results of performance tests ore presented. Factors influencing selection of principal design features are discussed. Considerations involved in arranging generator-set components and selecting a waste-heat boiler to meet installation requirements of an EFL power package application are reviewed.
Experience With Mobile Gas Turbines
Authors: Artigas R. , Bernhardt E.
Published: May 2015

The Comision Federal de Electricidad of Mexico in 1954 ordered two mobile gas-turbine sets; an additional identical set was ordered in 1955. The first two units went into service in 1955 and the third in 1956. Therefore, all three units have been operated for more than 6 years. This paper reviews briefly the operation data and the difficulties and problems involved. Finally, a few remarks are made in relation to future use of similar units.
Some Measurement Problems Encountered When Determining the Performance of Certain Turbine Stator Blades From Total Pressure Surveys
Authors: Moffitt Thomas P. , Prust Herman W. , Schum Harold J.
Published: May 2015

This paper presents some of the problems encountered in determining turbine stator blade performance from total pressure surveys downstream of the blade row. The stator blades were suitable for turbine cooling and incorprated thick trailing edges having a large included wedge angle between the suction and pressure surfaces. Blade performance was rated in terms of kinetic energy loss coefficients, which relate the frictional and mixing losses to the ideal kinetic energy that could be developed at a given overall pressure ratio. The loss coefficients were calculated from the results of total pressure surveys and flow conditions as determined by measurements at the inlet and outlet of the blade row. For the type of blading involved, it was determined that these loss coefficients were sensitive to the size of support stem of the total pressure probe used and the size and axial location of the probe sensing element. The effect of these variables on the results obtained are presented and desirable manners of taking survey data for this type of blading are discussed.
Design and Application Considerations Effecting Industrial Gas Turbine Maintenance
Authors: Fougere Louis F.
Published: May 2015

This paper is intended to provide information to users of gas turbines to compare the effects of the application and of design features on maintenance of industrial gas turbines.

A shortcoming in the prediction of part lives of gas turbines in constant-load applications is also discussed. It is pointed out that this shortcoming is inconsistent with sophisticated techniques currently available for life predictions.
Gas Turbine Heat Recovery Boiler Thermodynamics, Economics and Evaluation
Authors: Foster-Pegg R. W.
Published: May 2015

A 10,000 kw gas turbine operating open exhaust burning gas worth 30 cents per mcf will reject heat worth $25 per hour. If the gas turbine is operated more than a few hours per year, this heat will be recovered, usually in a heat recovey boiler. It is fair to say that without heat recovery systems, base loaded gas turbines would not be practical in normal industry.
Northwest Hydrofoil Line’s Hydrofoil Ship “Victoria” Gas Turbine Main Propulsion System
Authors: Niedermair William I.
Published: May 2015

The 75 passenger hydrofoil ship “Victoria” was designed for Northwest Hydrofoil Lines by Gibbs and Cox of New York and constructed by Maryland Shipbuilding and Drydock Company of Baltimore. The unique ship is equipped with General Electric twin LM100 gas turbines, transmission and gears, and flight control system. Presently the “Victoria” is in regular service between Seattle, Washington and Victoria, B.C.
Dual Mode Hydromechanical Transmission as Applied to Gas Turbines
Authors: Guedet R. H. , Louis J. E.
Published: May 2015

In applying gas turbines to vehicular applications, gas turbine designers have been faced with design restraints imposed by the limitations of conventional transmissions. Development of an automatic, infinitely variable ratio, hydromechanical transmission, the Dual Mode Transmission, now gives the designer the opportunity to concentrate on developing engine power in the most efficient, lightest, smallest, and lowest cost manner, independent of vehicle requirements. Because of the DMT characteristics, vehicle performance is similar if either a free or a fixed turbine is used. Therefore, the fixed turbine now becomes a potential candidate for many vehicle applications. Still in the development and testing stage, the DMT is presently operating in several highway trucks.
Some Aerodynamic Aspects of Turbine Blade Cooling
Authors: Barnes J. F. , Came P. M.
Published: May 2015

This paper is based mainly on theoretical and experimental work done as part of the research program on turbine blade cooling at the National Gas Turbine Establishment. After describing the effects of increased trailing edge thickness on turbine efficiency, the bulk of the paper is concerned with the losses caused by the cooling air. A simple theoretical method for calculating the pressure losses caused by discharging the spent coolant into the main gas stream is described and the available experimental results used for comparison. Reasonable agreement for the loss of efficiency is obtained. The results of some cascade tests on transportation cooled blades are also included.
Description of Propulsion Systems for DDH-280 Class Gas Turbine Destroyers
Authors: Sachs R. M.
Published: May 2015

Four helicopter carrying destroyers are being built for the Canadian Armed Forces incorporating an advanced all gas turbine COGOG propulsion system supplied by United Aircraft of Canada Ltd. The propulsion system installation described herein comprises two shaft lines, each with a Pratt & Whitney Aircraft FT4A-2 main engine and a Pratt & Whitney Aircraft FT12A-3 cruise engine, a reduction gearbox, propeller shaft and bearings, and a push rod actuated controllable pitch propeller. The associated ancillary systems, controls and monitoring instrumentation are described with comments on the underlying objectives and design philosophy.
The Response of Axial Flow Compressors to Intake Flow Distortion
Authors: Reid C.
Published: May 2015

The response of a lift engine model compressor to inlet pressure distortion is studied in detail to determine the nature and extent of the critical area of spoiling. This is found to be a sector of width between 60 and 90 deg. On this basis a simple distortion index is proposed which implies that only the circumferential pressure gradients of a complex distortion pattern are significant. The “Parallel Compressor” model satisfactorily explains surge and this experience is related to different types of compressors and to complex spoiling patterns. Comments are made on the differences in behavior between compressors operating on rig test and in engines.
An Analog Computer Simulation of a Closed Brayton Cycle System
Authors: Jordan F. D. , Hum M. R. , Carras A. N.
Published: May 2015

A summary of the Mathematical Model, Analog Computer Simulation, and experimental information comparison of a representative Closed Brayton Cycle System is presented. The foundation of the simulation, are design, experimentation, and analysis efforts performed on full-sized Closed Brayton Cycle System components. The analog computer program shows total system interaction and component behavior, both steady-state and dynamic modes, over the entire system operating range. In order to accurately describe a complete Closed Brayton Cycle System, practical details such as auxiliary components, system parasitic losses, variation of thermodynamic properties, thermal inertia, variability of pressure losses, and transient disturbances constitute an important part of the formulation. The development of the analog computer simulation provides an economical and effective method for system performance prediction, identification of critical parameters, systems integration, and component optimization.
Feasibility of Gas Bearings for Small High-Performance Aircraft Gas Turbines
Authors: Curwen P. W.
Published: May 2015

High temperatures, pressures, and speeds of future Army propulsion systems will impose severe, perhaps intolerable, operating requirements on oil-lubricated engine bearings. Accordingly, air-lubricated (gas) bearings are being investigated as a possible approach to alleviating the lubrication problems. This paper presents results of a study to apply gas bearings to a two-spool gas generator for an advanced 4.5-lb/sec engine. It is shown that gas-lubricated journal and thrust bearings can be designed to carry the maximum loads imposed by flight and landing conditions. Additionally, the resulting engine configuration has promising attributes of compactness and mechanical simplicity. Potential problem areas are identified to be rotor-bearing system stability, LP-spool balancing, and LP-spool seal leakage. One area where feasibility has not been established is durability of the bearing construction materials. Material testing at the high-temperature, high-stress operating conditions of the bearings, including the effects of momentary high-speed bearing contacts, is urgently needed so that the question of material feasibility can be critically assessed.
The Redesign and Simulated Test of a Small Closed Brayton Cycle Turbine-Compressor Set for Nuclear Application
Authors: Scott R. , Manning G. B.
Published: May 2015

The closed cycle (AK process) gas turbine power plant has been under development in Switzerland since 1940. Since the early 1950’s, within the United States, conceptual ideas have been forming around the use of this process for use within a compact, mobile nuclear power plant. The U. S. Army Corps of Engineers is a leading proponent of this concept. Today, any research and development activity concerned with closed cycle turbomachinery development is faced with one tremendous obstacle. This is true whether the activity is a private contractor or a government agency. This obstacle is the availability of a closed cycle test loop which allows the test turbine to be tested for extended periods of time under proper conditions prior to delivery to the customer. In the past, all of the Army vehicles were fabricated by contractors and, at most, tested open cycle (with compressor inlet pressure at sea level conditions) prior to shipment and installation in the closed cycle facilities in existence at only two Army locations. This has positively limited the total progress made within the closed cycle technology across the board. With the successful completion of this method of open cycle testing at closed cycle conditions (120 psia compressor inlet), this obstacle is in the process of being partially removed. Because of contamination occurring within the open cycle testing as used here, it is much more desirable to test within a true closed cycle loop. However, test data obtained in the manner described here are almost directly applicable and need almost no extrapolation.
Systematic Evaluation of Cooled Turbine Efficiency
Authors: Anderson L. R. , Heiser W. H.
Published: May 2015

This paper presents a status report of our current ability to evaluate cooled turbine performance, and is based both upon fundamental reasoning as well as our accumulated experience. During the early portion of the examination, a dimensionless entropy rise emerges as a natural quantitative measure of airfoil cascade aerodynamic performance. Later, similarity principles are used to show that reliable experiments will, at least for the time being, require the constraint of a large number of parameters. Finally, an assessment of the analytical art indicates great promise, although a substantial amount of ground remains to be covered.
Condition Monitoring
Authors: Kochanski K. B.
Published: May 2015

This paper discusses condition monitoring of jet aircraft engines intended for airline use. Some brief background information is presented to connect past programs with present developments, and the goal, objectives, and terminology for a condition monitoring system are defined. The various concepts and techniques being studied and developed by General Electric to accomplish condition monitoring are described and available results presented and discussed.
Effect of discharge polarity on the propagation of atmospheric-pressure helium plasma jets and the densities of OH, NO, and O radicals
Authors: Yonemori Seiya , Ono Ryo
Published: May 2015

The atmospheric-pressure helium plasma jet is an emerging technology for plasma biomedical applications. In this paper, the authors focus on the effect of discharge polarity on propagation of the discharge and the densities of OH, NO, and O radicals. The plasma jet is applied to a glass surface placed on a grounded metal plate. Positive or negative voltage pulses with 25 μs duration, 8 kV amplitude, and 10 kpps repetition rate are used for the plasma jet. The plasma propagation is measured using a short-gated ICCD camera. The light emission intensity of the discharge generated at the rising phase of the voltage pulse is approximately equivalent for both polarities, while that generated during the falling phase is much higher for the negative discharge than the positive one. The shape of the discharge changes with the discharge polarity. The OH, NO, and O densities in the plasma jet are also measured for both polarities. It is found that the OH density is almost the same regardless the discharge polarity. Conversely, the negative discharge produces more O atoms and the positive discharge produces more NO molecules. These results indicate that the polarity of the discharge affects the densities of some reactive species produced in the plasma jet.
A new technique to measure directional impulse responses using a 64-channel spherical microphone
Authors: Adelgren Jacob , Bradley David T.
Published: May 2015

A spherical microphone is an array consisting of numerous microphones arranged almost uniformly on the surface of a rigid sphere. Recently, spherical microphone arrays have received attention in architectural acoustics for their ability to characterize the sound field over a full sphere, which can yield additional information about the spatial characteristics of the field, including field diffusivity and directionality of individual reflections. Typically, these arrays are used as real-time analyzers to capture sound pressure information. However, in architectural acoustics, an impulse response measurement is required to adequately characterize the space. An effective approach for utilizing spherical microphones, particularly those with a large number of channels, to capture directional impulse responses has yet to be realized. The current project has utilized a 64-channel spherical microphone to carry out the integrated impulse response measurement technique using a sine-sweep signal. MATLAB has been used to evaluate sound fields in a reverberant chamber using a variety of directionality patterns (e.g., omnidirectional, cardioid, and figure-of-eight). Additionally, work is in progress to allow for arbitrary beamforming and other directionality patterns. Results and analysis will be presented.
Binaural perception of direct and reverberant sound fields rendered with mixed-order spherical harmonics
Authors: Sheaffer Jonathan , Rafaely Boaz
Published: May 2015

Binaural responses can be rendered from a plane-wave decomposition of a measured or a modeled sound field, spatially integrated with free-field head-related transfer functions. When represented in the spherical-harmonics domain, the decomposition order reflects the maximum spatial resolution, which is limited by the number of microphones in the spherical array. Recent studies suggest a direct relationship between decomposition order and perceptual attributes such as localization blur, timbre, and the sense of externalization. Insofar, studies have employed plane wave density functions in which the different components of the sound field were uniformly decomposed at a single spherical-harmonics order. This work is concerned with binaural signals in which the direct and reverberant parts of the sound field are decomposed at different spherical-harmonics orders. The direct component of the sound field carries significant directional information utilized by the auditory system. Therefore, changing the spherical-harmonics order of the direct component is expected to have a different perceptual impact compared to changing the spherical-harmonics order of the reverberant part. Listening experiments are employed to study the perception of such mixed-order representations in context of sound localization and auditory distance perception.
Spatial analysis of sound fields in rooms using spherical MIMO systems
Authors: Morgenstern Hai , Noisternig Markus , Rafaely Boaz
Published: May 2015

The perception of sound by human listeners in a room has been shown to be affected by the spatial attributes of the sound field. These spatial attributes have been studied using microphone and loudspeaker arrays separately. Systems that combine both loudspeaker and microphone arrays, termed multiple-input multiple-output (MIMO) systems, facilitate enhanced spatial analysis compared to systems with a single array, thanks to the simultaneous use of the arrays and the additional spatial diversity. Using MIMO systems, room impulse responses (RIRs) can be presented using matrix notation, which enables a unique study of a sound field’s spatial attributes, employing methods from linear algebra. For example, a matrix’s rank and null space can be studied to reveal spatial information on a room, such as the number of dominant room reflections and their direction of arrival to the microphone array and the direction of radiation from the loudspeaker array. In this contribution, a theory of the spatial analysis of a sound field using a MIMO system comprised of spherical arrays is developed and a simulation study is presented. In the study, tools proposed for processing MIMO RIRs with the aim of revealing valuable information about acoustic reflections paths are evaluated.
Bleats are universally used by ungulates for mother-offspring communication but what use do they serve for toads and pandas?
Authors: Browning David
Published: May 2015

Bleats are usually associated with sheep and goats, but are universally used by ungulates for mother-offspring communication. These short, relatively simple vocalizations are used, depending on circumstance, for localization, identification, emotion, and guidance. Interestingly, there are at least two other cases of bleat users. The Australian bleating toad appears to use them as an efficient means of continuous vocalization, while pandas use bleats as part of a repertoire of jungle talk to communicate in dense bamboo thickets.
Quantitative analysis of a frequency-domain nonlinearity indicator
Authors: Miller Kyle G. , Reichman Brent O. , Gee Kent L. , Neilsen Tracianne B.
Published: May 2015

An ensemble-averaged, frequency-domain version of the Burgers equation can be rearranged in order to directly compare the effects of nonlinearity on the sound pressure level, with the effects of atmospheric absorption and geometric spreading on a decibel scale. This nonlinear effect is calculated using the quadspectrum of the pressure and the pressure squared waveforms. A number of nonlinearity indicators have been developed based on this quadspectral term, but their use has been largely qualitative. Further analysis of the expression has resulted in a quantitative understanding of how a quadspectrum normalization, referred to as Q/S, can be tied to the frequency-dependent sound pressure level changes due to nonlinearity. This understanding is developed by analyzing how Q/S evolves for analytical scenarios—the Blackstock Bridging Function and the Mendousse Solution. The decibel change per shock formation distance calculated through Q/S accurately captures the growth and decay of the higher harmonics, indicating that the most significant changes in the normalized quadspectrum occur before sawtooth formation.
Hearing motion in motion
Authors: Carlile Simon , Leung Johahn , Locke Shannon , Burgess Martin
Published: May 2015

The acoustic cues to auditory space are referenced to the head which moves through the world, itself composed of moving sources so that our sensation convolves source with self- motion. With the head still, velocity discrimination, a perceptual process, is related to static acuity via the minimum audible movement angle (MAMA). Yet, while we can accurately localize static sounds, we are much less sensitive to velocity, resorting to distance and time cues where available. Interestingly, when velocity changes as a step function, discrimination thresholds and the amount of post-transition stimulus required for detection is greater than the corresponding MAMA. This suggests that when the head is stationary, the window of temporal integration may vary according to the sound's velocity characteristics. We also have evidence that auditory representational momentum scales with velocity, not duration or distance. Facing and following a moving auditory source is an ecologically important behavior. Tracking exhibits on-line velocity correction for slow to moderate velocities (< 80 °/s) but at higher velocities reflects a more predictive mechanism. Patients with schizophrenia are impaired in their ability to track a moving auditory target, when compared with controls, despite having normal velocity perception when the head is not moving. The presence of other efference copy dysfunctions in schizophrenia suggests a key role for motor efference copy in the disambiguation of self and target motion.
Smooth pursuit eye and gaze movements to moving auditory targets: Evidence for velocity-specific processing in the auditory system
Authors: Cloninger Christina , Fleming Justin T. , Allen Paul D. , O'Neill William E. , Paige Gary D.
Published: May 2015

Auditory motion perception remains poorly understood, in contrast with its well-established visual counterpart. Visual smooth pursuit (SP), a velocity-specific behavior, has been well-quantified during both head-fixed (ocular SP) and head-free (eye + head, or gaze SP) conditions. In contrast, auditory SP tracking has received little attention, despite its potential for demonstrating a motion-specific process in audition. We presented constant-velocity (10–40°/s), free-field auditory (0.2–20 kHz white noise), and visual (LED) targets to head-fixed or head-free subjects while recording ocular and gaze SP responses, respectively. To control for possible SP in the absence of a target, subjects were asked to recreate auditory trajectories after priming with a set of auditory ramps (practiced SP). We found that ocular auditory SP is consistently higher in gain than practiced SP, but variable and lower than visual SP. Further, the gain of auditory gaze SP exceeds ocular auditory SP. Finally, SP of periodic (triangular) motion trajectories revealed that auditory, like visual, SP improves rapidly over time, indicating predictive behavior. In sum, auditory SP closely mimics visual SP but with reduced gain. We propose that auditory motion processing exists, is robust, and recruits a velocity-dependent neural process shared with vision.
From a nonuniform brain map to motion selectivity in the owl’s midbrain
Authors: Pena Jose L. , Fischer Brian J. , Gutfreund Yoram
Published: May 2015

The owl’s midbrain displays a map of auditory space. This map is a distorted representation of the environment, where the front is magnified. In addition, sound is differently attenuated by the head depending on direction, where gain increases in the front. Because neurons in the map are functionally interconnected, the nonuniform representation influences the processing of features that rely on integration across space and time. In addition, the nonuniform gain deforms spatial receptive fields, affecting history-dependent responses. As a result, neurons become sensitive to motion direction. Previous work has explained the owl’s localizing behavior by statistical inference, where uncertainty about the sensory input and prior information can be combined optimally to guide behavior. This theory can be applied to moving targets, where sensory cues must be integrated over time. This analysis shows that the midbrain neural population can be readout to predict future positions of moving targets, a critical function for a predator species. Thus, the nonuniform representation of space can induce biased computation of a higher-order stimulus feature, allowing systematic direction-selectivity and predictive power. Because neural representations where ethologically important ranges are overrepresented, are widespread in the brain, these mechanisms are likely observed in other sensory maps that guide behavior.