Active Piezoelectric Structures for Tip Clearance Management Assessed

NASA Technical Reports Server (NTRS)

1995-01-01

Managing blade tip clearance in turbomachinery stages is critical to developing advanced subsonic propulsion systems. Active casing structures with embedded piezoelectric actuators appear to be a promising solution. They can control static and dynamic tip clearance, compensate for uneven deflections, and accomplish electromechanical coupling at the material level. In addition, they have a compact design. To assess the feasibility of this concept and assist the development of these novel structures, the NASA Lewis Research Center developed in-house computational capabilities for composite structures with piezoelectric actuators and sensors, and subsequently used them to simulate candidate active casing structures. The simulations indicated the potential of active casings to modify the blade tip clearance enough to improve stage efficiency. They also provided valuable design information, such as preliminary actuator configurations (number and location) and the corresponding voltage patterns required to compensate for uneven casing deformations. An active ovalization of a casing with four discrete piezoceramic actuators attached on the outer surface is shown. The center figure shows the predicted radial displacements along the hoop direction that are induced when electrostatic voltage is applied at the piezoceramic actuators. This work, which has demonstrated the capabilities of in-house computational models to analyze and design active casing structures, is expected to contribute toward the development of advanced subsonic engines.

Testing of a Microwave Blade Tip Clearance Sensor at the NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Woike, Mark R.; Roeder, James W.; Hughes, Christopher E.; Bencic, Timothy J.

2009-01-01

The development of new active tip clearance control and structural health monitoring schemes in turbine engines and other types of rotating machinery requires sensors that are highly accurate and can operate in a high-temperature environment. The use of a microwave sensor to acquire blade tip clearance and tip timing measurements is being explored at the NASA Glenn Research Center. The microwave blade tip clearance sensor works on principles that are very similar to a short-range radar system. The sensor sends a continuous microwave signal towards a target and measures the reflected signal. The phase difference of the reflected signal is directly proportional to the distance between the sensor and the target being measured. This type of sensor is beneficial in that it has the ability to operate at extremely high temperatures and is unaffected by contaminants that may be present in turbine engines. The use of microwave sensors for this application is a new concept. Techniques on calibrating the sensors along with installation effects are not well quantified as they are for other sensor technologies. Developing calibration techniques and evaluating installation effects are essential in using these sensors to make tip clearance and tip timing measurements. As a means of better understanding these issues, the microwave sensors were used on a benchtop calibration rig, a large axial vane fan, and a turbofan. Background on the microwave tip clearance sensor, an overview of their calibration, and the results from their use on the axial vane fan and the turbofan will be presented in this paper.

Testing of a Microwave Blade Tip Clearance Sensor at the NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Woike, Mark R.; Roeder, James W.; Hughes, Christopher E.; Bencic, Timothy J.

2009-01-01

The development of new active tip clearance control and structural health monitoring schemes in turbine engines and other types of rotating machinery requires sensors that are highly accurate and can operate in a high temperature environment. The use of a microwave sensor to acquire blade tip clearance and tip timing measurements is being explored at the NASA Glenn Research Center. The microwave blade tip clearance sensor works on principles that are very similar to a short range radar system. The sensor sends a continuous microwave signal towards a target and measures the reflected signal. The phase difference of the reflected signal is directly proportional to the distance between the sensor and the target being measured. This type of sensor is beneficial in that it has the ability to operate at extremely high temperatures and is unaffected by contaminants that may be present in turbine engines. The use of microwave sensors for this application is a new concept. Techniques on calibrating the sensors along with installation effects are not well quantified as they are for other sensor technologies. Developing calibration techniques and evaluating installation effects are essential in using these sensors to make tip clearance and tip timing measurements. As a means of better understanding these issues, the microwave sensors were used on a bench top calibration rig, a large axial vane fan, and a turbofan. Background on the microwave tip clearance sensor, an overview of their calibration, and the results from their use on the axial vane fan and the turbofan will be presented in this paper.

JT9D-70/59 Improved High Pressure Turbine Active Clearance Control System. [for specific fuel consumption improvement

NASA Technical Reports Server (NTRS)

Gaffin, W. O.

1979-01-01

The JT9D-70/59 high pressure turbine active clearance control system was modified to provide reduction of blade tip clearance when the system is activated during cruise operation. The modification increased the flow capacity and air impingement effectiveness of the cooling air manifold to augment turbine case shrinkage capability, and increased responsiveness of the airseal clearance to case shrinkage. The simulated altitude engine testing indicated a significant improvement in specific fuel consumption with the modified system. A 1000 cycle engine endurance test showed no unusual wear or performance deterioration effects on the engine or the clearance control system. Rig tests indicated that the air impingement and seal support configurations used in the engine tests are near optimum.

Improved Temperature Dynamic Model of Turbine Subcomponents for Facilitation of Generalized Tip Clearance Control

NASA Technical Reports Server (NTRS)

Kypuros, Javier A.; Colson, Rodrigo; Munoz, Afredo

2004-01-01

This paper describes efforts conducted to improve dynamic temperature estimations of a turbine tip clearance system to facilitate design of a generalized tip clearance controller. This work builds upon research previously conducted and presented in and focuses primarily on improving dynamic temperature estimations of the primary components affecting tip clearance (i.e. the rotor, blades, and casing/shroud). The temperature profiles estimated by the previous model iteration, specifically for the rotor and blades, were found to be inaccurate and, more importantly, insufficient to facilitate controller design. Some assumptions made to facilitate the previous results were not valid, and thus improvements are presented here to better match the physical reality. As will be shown, the improved temperature sub- models, match a commercially validated model and are sufficiently simplified to aid in controller design.

Method to improve the blade tip-timing accuracy of fiber bundle sensor under varying tip clearance

NASA Astrophysics Data System (ADS)

Duan, Fajie; Zhang, Jilong; Jiang, Jiajia; Guo, Haotian; Ye, Dechao

2016-01-01

Blade vibration measurement based on the blade tip-timing method has become an industry-standard procedure. Fiber bundle sensors are widely used for tip-timing measurement. However, the variation of clearance between the sensor and the blade will bring a tip-timing error to fiber bundle sensors due to the change in signal amplitude. This article presents methods based on software and hardware to reduce the error caused by the tip clearance change. The software method utilizes both the rising and falling edges of the tip-timing signal to determine the blade arrival time, and a calibration process suitable for asymmetric tip-timing signals is presented. The hardware method uses an automatic gain control circuit to stabilize the signal amplitude. Experiments are conducted and the results prove that both methods can effectively reduce the impact of tip clearance variation on the blade tip-timing and improve the accuracy of measurements.

Shape memory alloy adaptive control of gas turbine engine compressor blade tip clearance

NASA Astrophysics Data System (ADS)

Schetky, Lawrence M.; Steinetz, Bruce M.

1998-06-01

The ambient air ingested through the inlet of a gas turbine is first compressed by an axial compressor followed by further compression in a centrifugal compressor and then fed into the combustion chamber where ignition and expansion take place to produce the engine thrust. The axial compressor typically has five or more stages which consist of revolving blades and stators and the overall performance of the turbine is strongly affected by the compressor efficiency. When the turbine is turned on, to accommodate the rapid initial increase in the compressor blade length due to centrifugal force, the cold turbine has a built in clearance between the turbine blade tip and the casing. As the turbine reached its operating temperature there is a further increase in the blade length due to thermal expansion and, at the same time, the diameter of the casing increases. The net result is that when these various components have reached their equilibrium temperatures, the initial cold build clearance is reduced, but there remains a residual clearance. The magnitude of this clearance has a direct effect on the compressor efficiency and can be stated as: Δη/Δ CLR equals 0.5 where η is efficiency and CLR is the tip clearance. The concept of adaptive tip clearance control is based on the ability of a shape memory alloy ring to shrink to a predetermined diameter when heated to the temperature of a particular stage, and thus reducing the tip clearance. The ring is fabricated from a CuAlNi shape memory alloy and is mounted in the casing so as to be coaxial with the rotating blades of the particular stage. When cold, the ring dimensions are such as to provide the required cold build clearance, but when at operating temperature the reduced diameter creates a very small tip clearance. The clearance provided by this concept is much smaller than the clearance normally obtained for a turbine of the size being studied.

Energy efficient engine high pressure turbine test hardware detailed design report

NASA Technical Reports Server (NTRS)

Halila, E. E.; Lenahan, D. T.; Thomas, T. T.

1982-01-01

The high pressure turbine configuration for the Energy Efficient Engine is built around a two-stage design system. Moderate aerodynamic loading for both stages is used to achieve the high level of turbine efficiency. Flowpath components are designed for 18,000 hours of life, while the static and rotating structures are designed for 36,000 hours of engine operation. Both stages of turbine blades and vanes are air-cooled incorporating advanced state of the art in cooling technology. Direct solidification (DS) alloys are used for blades and one stage of vanes, and an oxide dispersion system (ODS) alloy is used for the Stage 1 nozzle airfoils. Ceramic shrouds are used as the material composition for the Stage 1 shroud. An active clearance control (ACC) system is used to control the blade tip to shroud clearances for both stages. Fan air is used to impinge on the shroud casing support rings, thereby controlling the growth rate of the shroud. This procedure allows close clearance control while minimizing blade tip to shroud rubs.

Advanced turbine blade tip seal system

NASA Technical Reports Server (NTRS)

Zelahy, J. W.

1981-01-01

An advanced blade/shroud system designed to maintain close clearance between blade tips and turbine shrouds and at the same time, be resistant to environmental effects including high temperature oxidation, hot corrosion, and thermal cycling is described. Increased efficiency and increased blade life are attained by using the advanced blade tip seal system. Features of the system include improved clearance control when blade tips preferentially wear the shrouds and a superior single crystal superalloy tip. The tip design, joint location, characterization of the single crystal tip alloy, the abrasive tip treatment, and the component and engine test are among the factors addressed. Results of wear testing, quality control plans, and the total manufacturing cycle required to fully process the blades are also discussed.

Analysis, design, fabrication and testing of an optical tip clearance sensor. [turbocompressor blade tips

NASA Technical Reports Server (NTRS)

Poppel, G. L.; Marple, D. T. F.; Kingsley, J. D.

1981-01-01

Analyses and the design, fabrication, and testing of an optical tip clearance sensor with intended application in aircraft propulsion control systems are reported. The design of a sensor test rig, evaluation of optical sensor components at elevated temperatures, sensor design principles, sensor test results at room temperature, and estimations of sensor accuracy at temperatures of an aircraft engine environment are discussed. Room temperature testing indicated possible measurement accuracies of less than 12.7 microns (0.5 mils). Ways to improve performance at engine operating temperatures are recommended. The potential of this tip clearance sensor is assessed.

Overview of NASA Glenn Seal Developments

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Proctor, Margaret P.; Dunlap, Patrick H., Jr.; Delgado, Irebert; DeMange, Jeffrey J.; Daniels, Christopher C.; Lattime, Scott B.

2004-01-01

Turbine engine studies have shown that reducing high pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin and increase range. Dr. Lattime presented the design and development status of a new Active Clearance Control Test rig aimed at demonstrating advanced ACC approaches and sensors. Mr. Melcher presented controls considerations for turbine active clearance control. Mr. Geisheimer of Radatech presented an overview of their microwave blade tip sensor technology. Microwave tip sensors show promise of operation in the extreme gas temperatures present in the HPT location. Mr. Justak presented an overview of non-contacting seal developments at Advanced Technologies Group. Dr. Braun presented investigations into a non-contacting finger seal under development by NASA GRC and University of Akron. Dr. Stango presented analytical assessments of the effects of flow-induced radial loads on brush seal behavior. Mr. Flaherty presented innovative seal and seal fabrication developments at FlowServ. Mr. Chappel presented abradable seal developments at Technetics. Dr. Daniels presented an overview of NASA GRC s acoustic seal developments. NASA is investigating the ability to harness high amplitude acoustic waves, possible through a new field of acoustics called Resonant Macrosonic Synthesis, to effect a non-contacting, low leakage seal. Dr. Daniels presented early results showing the ability to restrict flow via acoustic pressures. Dr. Athavale presented numerical results simulating the flow blocking capability of a pre-prototype acoustic seal.

Test Rig for Evaluating Active Turbine Blade Tip Clearance Control Concepts

NASA Technical Reports Server (NTRS)

Lattime, Scott B.; Steinetz, Bruce M.; Robbie, Malcolm G.; Erker, Arthur H.

2004-01-01

The objectives of the research presented in this viewgraph presentation are to 1) Design a mechanical ACC system for HPT tip seal clearance management; 2) Design a test rig to evaluate ACC system concepts. We have focused our efforts on designing mechanical ACC systems that articulate the seal shroud via mechanical linkages connected to actuators that reside outside the extreme environment of the HPT. We opted for this style of design due to a lack of high temperature/low profile actuators that are presently available. We have also selected multiple hydraulic actuators for this first generation ACC system. Fuel-draulic actuators are already a well established technology.

Seal Investigations of an Active Clearance Control System Concept

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Taylor, Shawn; Oswald, Jay; DeCastro, Jonathan A.

2006-01-01

In an effort to improve upon current thermal active clearance control methods, a first generation, fast-acting mechanically actuated, active clearance control system has been designed and installed into a non-rotating test rig. In order to harvest the benefit of tighter blade tip clearances, low-leakage seals are required for the actuated carrier segments of the seal shroud to prevent excessive leakage of compressor discharge (P3) cooling air. The test rig was designed and fabricated to facilitate the evaluation of these types of seals, identify seal leakage sources, and test other active clearance control system concepts. The objective of this paper is to present both experimental and analytical investigations into the nature of the face-seal to seal-carrier interface. Finite element analyses were used to examine face seal contact pressures and edge-loading under multiple loading conditions, varied E-seal positions and two new face seal heights. The analyses indicated that moving the E-seal inward radially and reducing face seal height would lead to more uniform contact conditions between the face seal and the carriers. Lab testing confirmed that moving the balance diameter inward radially caused a decrease in overall system leakage.

Gas turbine engine active clearance control

NASA Technical Reports Server (NTRS)

Deveau, Paul J. (Inventor); Greenberg, Paul B. (Inventor); Paolillo, Roger E. (Inventor)

1985-01-01

Method for controlling the clearance between rotating and stationary components of a gas turbine engine are disclosed. Techniques for achieving close correspondence between the radial position of rotor blade tips and the circumscribing outer air seals are disclosed. In one embodiment turbine case temperature modifying air is provided in flow rate, pressure and temperature varied as a function of engine operating condition. The modifying air is scheduled from a modulating and mixing valve supplied with dual source compressor air. One source supplies relatively low pressure, low temperature air and the other source supplies relatively high pressure, high temperature air. After the air has been used for the active clearance control (cooling the high pressure turbine case) it is then used for cooling the structure that supports the outer air seal and other high pressure turbine component parts.

Effects of Double-Leakage Tip Clearance Flow on the Performance of a Compressor Stage with a Large Rotor Tip Gap

NASA Technical Reports Server (NTRS)

Hah, Chunill

2016-01-01

Effects of a large rotor tip gap on the performance of a one and half stage axial compressor are investigated in detail with a numerical simulation based on LES and available PIV data. The current paper studies the main flow physics, including why and how the loss generation is increased with the large rotor tip gap. The present study reveals that when the tip gap becomes large, tip clearance fluid goes over the tip clearance core vortex and enters into the next blade's tip gap, which is called double-leakage tip clearance flow. As the tip clearance flow enters into the adjacent blade's tip gap, a vortex rope with a lower pressure core is generated. This vortex rope breaks up the tip clearance core vortex of the adjacent blade, resulting in a large additional mixing. This double-leakage tip clearance flow occurs at all operating conditions, from design flow to near stall condition, with the large tip gap for the current compressor stage. The double-leakage tip clearance flow, its interaction with the tip clearance core vortex of the adjacent blade, and the resulting large mixing loss are the main flow mechanism of the large rotor tip gap in the compressor. When the tip clearance is smaller, flow near the end wall follows more closely with the main passage flow and this double-leakage tip clearance flow does not happen near the design flow condition for the current compressor stage. When the compressor with a large tip gap operates at near stall operation, a strong vortex rope is generated near the leading edge due to the double-leakage flow. Part of this vortex separates from the path of the tip clearance core vortex and travels from the suction side of the blade toward the pressure side of the blade. This vortex is generated periodically at near stall operation with a large tip gap. As the vortex travels from the suction side to the pressure side of the blade, a large fluctuation of local pressure forces blade vibration. Nonsynchronous blade vibration occurs due to this vortex as the frequency of this vortex generation is not the same as the rotor. The present investigation confirms that this vortex is a part of separated tip clearance vortex, which is caused by the double-leakage tip clearance flow.

Numerical investigation of tip clearance effects on the performance of ducted propeller

NASA Astrophysics Data System (ADS)

Ding, Yongle; Song, Baowei; Wang, Peng

2015-09-01

Tip clearance loss is a limitation of the improvement of turbomachine performance. Previous studies show the Tip clearance loss is generated by the leakage flow through the tip clearance, and is roughly linearly proportional to the gap size. This study investigates the tip clearance effects on the performance of ducted propeller. The investigation was carried out by solving the Navier-Stokes equations with the commercial Computational Fluid Dynamic (CFD) code CFX14.5. These simulations were carried out to determine the underlying mechanisms of the tip clearance effects. The calculations were performed at three different chosen advance ratios. Simulation results showed that the tip loss slope was not linearly at high advance due to the reversed pressure at the leading edge. Three type of vortical structures were observed in the tip clearance at different clearance size.

Influence of blade tip rounding on tip leakage vortex cavitation of axial flow pump

NASA Astrophysics Data System (ADS)

Wu, S. Q.; Shi, W. D.; Zhang, D. S.; Yao, J.; Cheng, C.

2013-12-01

Tip leakage flow in axial flow pumps is mainly caused by the tip clearance, which is the main cause of tip leakage vortex cavitation and blade tip cavitation erosion. In order to improve tip clearance flow and reduce TLV cavitation, four schemes were adopted to the round blade tip. These are: no tip rounding, one time tip clearance tip rounding, two times tip clearance tip rounding, four times tip clearance tip rounding. Using SST k-ω turbulence model and Zwart cavitation model in CFX software, this simulation obtained four kinds of inner flow field results. The numerical results indicated that with the increase of r*, NPSHc gradually increased and the cavitation performance reduced. However, corner vortex was eliminated so that cavitation in gap was restrained. But TLV vorticity increased and cavitation's range here had a little expansion. Combined with the research of this paper and the different analyses of four schemes, we recommend adopting the two times of the tip clearance rounding.

On the development of a magnetoresistive sensor for blade tip timing and blade tip clearance measurement systems

NASA Astrophysics Data System (ADS)

Tomassini, R.; Rossi, G.; Brouckaert, J.-F.

2014-05-01

The accurate control of the gap between static and rotating components is vital to preserve the mechanical integrity and ensure a correct functioning of any rotating machinery. Moreover, tip leakage above the airfoil tip results in relevant aerodynamic losses. One way to measure and to monitor blade tip gaps is by the so-called Blade Tip Clearance (BTC) technique. Another fundamental phenomenon to control in the turbomachines is the vibration of the blades. For more than half a century, this has been performed by installing strain gauges on the blades and using telemetry to transmit the signals. The Blade Tip Timing (BTT) technique, (i.e. measuring the blade time of arrival from the casing at different angular locations with proximity sensors) is currently being adopted by all manufacturers as a replacement for the classical strain gauge technique because of its non-intrusive character. This paper presents a novel magnetoresistive sensor for blade tip timing and blade tip clearance systems, which offers high temporal and high spatial resolution simultaneously. The sensing element adopted is a Wheatstone bridge of Permalloy elements. The principle of the sensor is based on the variation of magnetic field at the passage of ferromagnetic objects. Two different configurations have been realized, a digital and an analogue sensor. Measurements of tip clearance have been performed in an high speed compressor and the calibration curve is reported. Measurements of blade vibration have been carried out in a dedicated calibration bench; results are presented and discussed. The magnetoresistive sensor is characterized by high repeatability, low manufacturing costs and measurement accuracy in line with the main probes used in turbomachinery testing. The novel sensor has great potential and is capable of fulfilling the requirements for a simultaneous BTC and BTT measurement system.

Tip Clearance Control Using Plasma Actuators

DTIC Science & Technology

2007-03-01

Clearance Control Using Plasma Actuators 4 posed by Denton (1993). A number of investigators have used partial shrouds, or " winglet " designs to...main molded blade with a span of 3.42 in., a removable molded blade segment with a span of 0.1875 in., and removable blade tip winglets made of glass...segment and the main blade to vary the distance between the blade end and the front wall of the cascade section. The winglets were machined using a

Rate-Based Model Predictive Control of Turbofan Engine Clearance

NASA Technical Reports Server (NTRS)

DeCastro, Jonathan A.

2006-01-01

An innovative model predictive control strategy is developed for control of nonlinear aircraft propulsion systems and sub-systems. At the heart of the controller is a rate-based linear parameter-varying model that propagates the state derivatives across the prediction horizon, extending prediction fidelity to transient regimes where conventional models begin to lose validity. The new control law is applied to a demanding active clearance control application, where the objectives are to tightly regulate blade tip clearances and also anticipate and avoid detrimental blade-shroud rub occurrences by optimally maintaining a predefined minimum clearance. Simulation results verify that the rate-based controller is capable of satisfying the objectives during realistic flight scenarios where both a conventional Jacobian-based model predictive control law and an unconstrained linear-quadratic optimal controller are incapable of doing so. The controller is evaluated using a variety of different actuators, illustrating the efficacy and versatility of the control approach. It is concluded that the new strategy has promise for this and other nonlinear aerospace applications that place high importance on the attainment of control objectives during transient regimes.

ADAPTIVE CLEARANCE CONTROL SYSTEMS FOR TURBINE ENGINES

NASA Technical Reports Server (NTRS)

Blackwell, Keith M.

2004-01-01

The Controls and Dynamics Technology Branch at NASA Glenn Research Center primarily deals in developing controls, dynamic models, and health management technologies for air and space propulsion systems. During the summer of 2004 I was granted the privilege of working alongside professionals who were developing an active clearance control system for commercial jet engines. Clearance, the gap between the turbine blade tip and the encompassing shroud, increases as a result of wear mechanisms and rubbing of the turbine blades on shroud. Increases in clearance cause larger specific fuel consumption (SFC) and loss of efficient air flow. This occurs because, as clearances increase, the engine must run hotter and bum more fuel to achieve the same thrust. In order to maintain efficiency, reduce fuel bum, and reduce exhaust gas temperature (EGT), the clearance must be accurately controlled to gap sizes no greater than a few hundredths of an inch. To address this problem, NASA Glenn researchers have developed a basic control system with actuators and sensors on each section of the shroud. Instead of having a large uniform metal casing, there would be sections of the shroud with individual sensors attached internally that would move slightly to reform and maintain clearance. The proposed method would ultimately save the airline industry millions of dollars.

Investigation of Unsteady Tip Clearance Flow in a Low-Speed One and Half Stage Axial Compressor with LES And PIV

NASA Technical Reports Server (NTRS)

Hah, Chunill; Hathaway, Michael; Katz, Joseph; Tan, David

2015-01-01

The primary focus of this paper is to investigate how a rotor's unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor when the rotor tip gap size is increased from 0.5 mm (0.49% of rotor tip blade chord, 2% of blade span) to 2.4 mm (2.34% chord, 4% span) at the design condition are investigated. The changes in unsteady tip clearance flow with the 0.62 % tip gap as the flow rate is reduced to near stall condition are also investigated. A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at these three flow conditions. Detailed Stereoscopic PIV (SPIV) measurements of the current flow fields were also performed at the Johns Hopkins University in a refractive index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. Unsteady tip clearance flow fields from LES are compared with the PIV measurements and both LES and PIV results are used to study changes in tip clearance flow structures. The current study shows that the tip clearance vortex is not a single structure as traditionally perceived. The tip clearance vortex is formed by multiple interlaced vorticities. Therefore, the tip clearance vortex is inherently unsteady. The multiple interlaced vortices never roll up to form a single structure. When phased-averaged, the tip clearance vortex appears as a single structure. When flow rate is reduced with the same tip gap, the tip clearance vortex rolls further upstream and the tip clearance vortex moves further radially inward and away from the suction side of the blade. When the tip gap size is increased at the design flow condition, the overall tip clearance vortex becomes stronger and it stays closer to the blade suction side and the vortex core extends all the way to the exit of the blade passage. Measured and calculated unsteady flow fields inside the tip gap agree fairly well. Instantaneous velocity vectors inside the tip gap from both the PIV and LES do show flow separation and reattachment at the entrance of tip gap as some earlier studies suggested. This area at the entrance of tip gap flow (the pressure side of the blade) is confined very close to the rotor tip section. With a small tip gap (0.5mm), the gap flow looks like a simple two-dimensional channel flow with larger velocity near the casing for both flow rates. A small area with a sharp velocity gradient is observed just above the rotor tip. This strong shear layer is turned radially inward when it collides with the incoming flow and forms the core structure of the tip clearance vortex. When tip gap size is increased to 2.4 mm at the design operation, the radial profile of the tip gap flow changes drastically. With the large tip gap, the gap flow looks like a two-dimensional channel flow only near the casing. Near the rotor top section, a bigger region with very large shear and reversed flow is observed.

Materials for advanced turbine engines. Volume 1: Advanced blade tip seal system

NASA Technical Reports Server (NTRS)

Zelahy, J. W.; Fairbanks, N. P.

1982-01-01

Project 3, the subject of this technical report, was structured toward the successful engine demonstration of an improved-efficiency, long-life, tip-seal system for turbine blades. The advanced tip-seal system was designed to maintain close operating clearances between turbine blade tips and turbine shrouds and, at the same time, be resistant to environmental effects including high-temperature oxidation, hot corrosion, and thermal cycling. The turbine blade tip comprised an environmentally resistant, activated-diffussion-bonded, monocrystal superalloy combined with a thin layer of aluminium oxide abrasive particles entrapped in an electroplated NiCr matrix. The project established the tip design and joint location, characterized the single-crystal tip alloy and abrasive tip treatment, and established the manufacturing and quality-control plans required to fully process the blades. A total of 171 blades were fully manufactured, and 100 were endurance and performance engine-tested.

Axial compressor blade design for desensitization of aerodynamic performance and stability to tip clearance

NASA Astrophysics Data System (ADS)

Erler, Engin

Tip clearance flow is the flow through the clearance between the rotor blade tip and the shroud of a turbomachine, such as compressors and turbines. This flow is driven by the pressure difference across the blade (aerodynamic loading) in the tip region and is a major source of loss in performance and aerodynamic stability in axial compressors of modern aircraft engines. An increase in tip clearance, either temporary due to differential radial expansion between the blade and the shroud during transient operation or permanent due to engine wear or manufacturing tolerances on small blades, increases tip clearance flow and results in higher fuel consumption and higher risk of engine surge. A compressor design that can reduce the sensitivity of its performance and aerodynamic stability to tip clearance increase would have a major impact on short and long-term engine performance and operating envelope. While much research has been carried out on improving nominal compressor performance, little had been done on desensitization to tip clearance increase beyond isolated observations that certain blade designs such as forward chordwise sweep, seem to be less sensitive to tip clearance size increase. The current project aims to identify through a computational study the flow features and associated mechanisms that reduces sensitivity of axial compressor rotors to tip clearance size and propose blade design strategies that can exploit these results. The methodology starts with the design of a reference conventional axial compressor rotor followed by a parametric study with variations of this reference design through modification of the camber line and of the stacking line of blade profiles along the span. It is noted that a simple desensitization method would be to reduce the aerodynamic loading of the blade tip which would reduce the tip clearance flow and its proportional contribution to performance loss. However, with the larger part of the work on the flow done in this region, this approach would entail a nominal performance penalty. Therefore, the chosen rotor design philosophy aims to keep the spanwise loading constant to avoid trading performance for desensitization. The rotor designs that resulted from this exercise are simulated in ANSYS CFX at different tip clearance sizes. The change in their performance with respect to tip clearance size (sensitivity) is compared both on an integral level in terms of pressure ratio and adiabatic efficiency, as well as on a detailed level in terms of aerodynamic losses and blockage associated with tip clearance flow. The sensitivity of aerodynamic stability is evaluated either directly through the simulations of the rotor characteristics up to the stall point (expensive in time and resources) for a few designs or indirectly through the position of the interface between the incoming and tip clearance flow with respect to the rotor leading edge plane. The latter approach is based on a generally observed stall criteria in modern axial compressors. The rotor designs are then assessed according to their sensitivity in comparison to that of the reference rotor design to detect features that can explain the trend in sensitivity to tip clearance size. These features can then be validated and the associated flow mechanisms explained through numerical simulations and modelling. Analysis of the database from the rotor parametric study shows that the observed trend in sensitivity cannot be explained by the shifting of the aerodynamic loading along the blade chord, as initially hypothesized based on the literature review. Instead, two flow features are found to reduce sensitivity of performance and stability to tip clearance, namely an increase in incoming meridional momentum in the tip region and a reduction/elimination of double leakage flow. Double leakage flow is the flow that exits the tip clearance of one blade and proceeds into the clearance of the adjacent blade rather than convecting downstream out of the local blade passage. These flow features are isolated and validated based on the reference rotor design through changes in the inlet total pressure condition to alter incoming flow momentum and blade number count to change double leakage rate. In terms of flow mechanism, double leakage is shown to be detrimental to performance and stability, and its proportional increase with tip clearance size explains the sensitivity increase in the presence of double leakage and, conversely, the desensitization effect of reducing or eliminating double leakage. The increase in incoming meridional momentum in the tip region reduces sensitivity to tip clearance through its reduction of double leakage as well as through improved mixing with tip clearance flow, as demonstrated by an analytical model without double leakage flow. The above results imply that any blade design strategy that exploits the two desensitizing flow features would reduce the performance and stability sensitivity to tip clearance size. The increase of the incoming meridional momentum can be achieved through forward chordwise sweep of the blade. The reduction of double leakage without changing blade pitch can be obtained by decreasing the blade stagger angle in the tip region. Examples of blade designs associated with these strategies are shown through CFX simulations to be successful in reducing sensitivity to tip clearance size.

Cold-air performance of a 12.766-centimeter-tip-diameter axial-flow cooled turbine. 3: Effect of rotor tip clearance on overall performance of a solid blade configuration

NASA Technical Reports Server (NTRS)

Haas, J. E.; Kofskey, M. G.

1977-01-01

Two tip clearance configurations, one with a recess in the casing and the other with a reduced rotor blade height, were investigated at design equivalent speed over a range of tip clearance from about 2.0 to 5.0 percent of the stator blade height. The optimum configuration with a recess in the casing was the one where the rotor tip diameter was equal to the stator tip diameter (zero blade extension). For this configuration there was an approximate 1.5 percent decrease in total efficiency for an increase in tip clearance of 1 percent of stator blade height. For the reduced blade height configurations there was an approximate 2.0 percent decrease in total efficiency for an increase in tip clearance of 1 percent of stator blade height.

Measurement of Rotating Blade Tip Clearance with Fibre-Optic Probe

NASA Astrophysics Data System (ADS)

Cao, S. Z.; Duan, F. J.; Zhang, Y. G.

2006-10-01

This paper described a tip clearance measuring system with fibre-optic probe. The system is based on a novel tip clearance sensor of optical fibre-bundle mounted on the casing, rotating speed synchronization sensor mounted on the rotating shaft, the tip clearance preamplification processing circuit followed by high speed data-acquisition unit. A novel tip clearance sensor of trifurcated optical fibre bundle was proposed and demonstrated. It is independent of material of measured surface but capacitive probe demands target conductive. Measurements can be taken under severe conditions such as ionization. Sensor circuitry and data acquisition circuit were successfully designed. With the help of Rotation synchronized sensor, all the blades can be detected in real-time. Because of fibre-optic sensor, the measuring system has commendably frequency response, which can work well in high rotating speed from 0-15000rpm.The measurement range of tip clearance is 0-3mm with 25um precision.

Removable inner turbine shell with bucket tip clearance control

DOEpatents

Sexton, Brendan F.; Knuijt, Hans M.; Eldrid, Sacheverel Q.; Myers, Albert; Coneybeer, Kyle E.; Johnson, David Martin; Kellock, Iain R.

2000-01-01

A turbine includes a plurality of inner shell sections mounting first and second stage nozzle and shroud portions. The inner shell sections are pinned to an outer containment shell formed of sections to preclude circumferential movement of the inner shell relative to the outer shell and enable thermal expansion and contraction of the inner shell relative to the outer shell. Positive bucket tip clearance control is afforded by passing a thermal medium about the inner shell in heat transfer relation with the shrouds about the first and second stage bucket tips, the thermal medium being provided from a source of heating/cooling fluid independent of the turbine. Access is provided to the rotor and turbine buckets by removing the outer and inner shell sections.

Compressor airfoil tip clearance optimization system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Little, David A.; Pu, Zhengxiang

2015-08-18

A compressor airfoil tip clearance optimization system for reducing a gap between a tip of a compressor airfoil and a radially adjacent component of a turbine engine is disclosed. The turbine engine may include ID and OD flowpath boundaries configured to minimize compressor airfoil tip clearances during turbine engine operation in cooperation with one or more clearance reduction systems that are configured to move the rotor assembly axially to reduce tip clearance. The configurations of the ID and OD flowpath boundaries enhance the effectiveness of the axial movement of the rotor assembly, which includes movement of the ID flowpath boundary.more » During operation of the turbine engine, the rotor assembly may be moved axially to increase the efficiency of the turbine engine.« less

Advanced optical blade tip clearance measurement system

NASA Technical Reports Server (NTRS)

Ford, M. J.; Honeycutt, R. E.; Nordlund, R. E.; Robinson, W. W.

1978-01-01

An advanced electro-optical system was developed to measure single blade tip clearances and average blade tip clearances between a rotor and its gas path seal in an operating gas turbine engine. This system is applicable to fan, compressor, and turbine blade tip clearance measurement requirements, and the system probe is particularly suitable for operation in the extreme turbine environment. A study of optical properties of blade tips was conducted to establish measurement system application limitations. A series of laboratory tests was conducted to determine the measurement system's operational performance characteristics and to demonstrate system capability under simulated operating gas turbine environmental conditions. Operational and environmental performance test data are presented.

Effect of rotor tip clearance and configuration on overall performance of a 12.77-centimeter tip diameter axial-flow turbine

NASA Technical Reports Server (NTRS)

Haas, J. E.; Kofskey, M. G.

1978-01-01

The rotor tip clearance was obtained by use of a recess in the casing above the rotor blades and also by use of a reduced blade height. For the recessed casing configuration, the optimum rotor blade height was found to be the one where the rotor tip diameter was equal to the stator tip diameter. The tip clearance loss associated with this optimum recessed casing configuration was less than that for the reduced blade height configuration.

Investigation of Unsteady Flow Field in a Low-Speed One and a Half Stage Axial Compressor. Part 2; Effects of Tip Gap Size On the Tip Clearance Flow Structure at Near Stall Operation

NASA Technical Reports Server (NTRS)

Hah, Chunill; Hathaway, Michael; Katz, Joseph

2014-01-01

The primary focus of this paper is to investigate the effect of rotor tip gap size on how the rotor unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor at near stall operation (for example, where maximum pressure rise is obtained). A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at this flow condition with both a small and a large tip gaps. The numerically obtained flow fields at the small clearance matches fairly well with the available initial measurements obtained at the Johns Hopkins University with 3-D unsteady PIV in an index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. The numerical results are also compared with previously published measurements in a low speed single stage compressor (Maerz et al. [2002]). The current study shows that, with the smaller rotor tip gap, the tip clearance vortex moves to the leading edge plane at near stall operating condition, creating a nearly circumferentially aligned vortex that persists around the entire rotor. On the other hand, with a large tip gap, the clearance vortex stays inside the blade passage at near stall operation. With the large tip gap, flow instability and related large pressure fluctuation at the leading edge are observed in this one and a half stage compressor. Detailed examination of the unsteady flow structure in this compressor stage reveals that the flow instability is due to shed vortices near the leading edge, and not due to a three-dimensional separation vortex originating from the suction side of the blade, which is commonly referred to during a spike-type stall inception. The entire tip clearance flow is highly unsteady. Many vortex structures in the tip clearance flow, including the sheet vortex system near the casing, interact with each other. The core tip clearance vortex, which is formed with the rotor tip gap flows near the leading edge, is also highly unsteady or intermittent due to pressure oscillations near the leading edge and varies from passage to passage. For the current compressor stage, the evidence does not seem to support that a classical vortex breakup occurs in any organized way, even with the large tip gap. Although wakes from the IGV influence the tip clearance flow in the rotor, the major characteristics of rotor tip clearance flows in isolated or single stage rotors are observed in this one and a half stage axial compressor.

Study of blade clearance effects on centrifugal pumps

NASA Technical Reports Server (NTRS)

Hoshide, R. K.; Nielson, C. E.

1972-01-01

A program of analysis, design, fabrication, and testing has been conducted to develop and experimentally verify analytical models to predict the effects of impeller blade clearance on centrifugal pumps. The effect of tip clearance on pump efficiency, and the relationship between the head coefficient and torque loss with tip clearance was established. Analysis were performed to determine the cost variation in design, manufacture, and test that would occur between unshrouded and shrouded impellers. An impeller, representative of typical rocket engine impellers, was modified by removing its front shroud to permit variation of its blade clearances. It was tested in water with special instrumentation to provide measurements of blade surface pressures during operation. Pump performance data were obtained from tests at various impeller tip clearances. Blade pressure data were obtained at the nominal tip clearance. Comparisons of predicted and measured data are given.

Experimental Study of Unshrouded Impeller Pump Stage Sensitivity to Tip Clearance

NASA Technical Reports Server (NTRS)

Williams, Robert W.; Zoladz, Thomas; Storey, Anne K.; Skelley, Stephen E.

2002-01-01

This viewgraph presentation provides information on an experiment. Its objective is to experimentally determine unshrouded impeller performance sensitivity to tip clearance. The experiment included: Determining impeller efficiency at scaled operating conditions in water at MSFC's Pump Test Equipment (PTE) Facility; Testing unshrouded impeller at three different tip clearances; Testing each tip clearance configuration at on- and off-design conditions, and collecting unsteady- and steady-state data in each configuration; Determining impeller efficiency directly using drive line torquemeter and pump inlet and exit total pressure measurements.

Axial compressor gas path design for desensitization of aerodynamic performance and stability to tip clearance

NASA Astrophysics Data System (ADS)

Cevik, Mert

Tip clearance is the necessary small gap left between the moving rotor tip and stationary shroud of a turbomachine. In a compressor, the pressure driven flow through this gap, called tip clearance flow, has a major and generally detrimental impact on compressor performance (pressure ratio and efficiency) and aerodynamic stability (stall margin). The increase in tip clearance, either temporary during transient engine operations or permanent from wear, leads to a drop in compressor performance and aerodynamic stability which results in a fuel consumption increase and a reduced operating envelope for a gas turbine engine. While much research has looked into increasing compressor performance and stall margin at the design (minimum or nominal) tip clearance, very little attention has been paid for reducing the sensitivity of these parameters to tip clearance size increase. The development of technologies that address this issue will lead to aircraft engines whose performance and operating envelope are more robust to operational demands and wear. The current research is the second phase of a research programme to develop design strategies to reduce the sensitivity of axial compressor performance and aerodynamic stability to tip clearance. The first phase had focused on blade design strategies and had led to the discovery and explanation of two flow features that reduces tip sensitivity, namely increased incoming meridional momentum in the rotor tip region and reduction/elimination of double leakage. Double leakage is the flow that exits one tip clearance and enters the tip clearance of the adjacent blade instead of convecting downstream out of the rotor passage. This flow was shown to be very detrimental to compressor performance and stall margin. Two rotor design strategies involving sweep and tip stagger reduction were proposed and shown by CFD simulations to exploit these features to reduce sensitivity. As the second phase, the objectives of the current research project are to develop gas path design strategies for axial compressors to achieve the same goal, to assess their ability to be combined with desensitizing axial compressor blade design strategies and to be applied to non-axial compressors. The search for gas path design strategies was based on the exploitation of the two flow desensitizing features listed above. Two gas path design strategies were proposed and analyzed. The first was gas path contouring in the form of a concave gas path to increase incoming tip meridional momentum.

Local Mass and Heat Transfer on a Turbine Blade Tip

DOE PAGES

Jin, P.; Goldstein, R. J.

2003-01-01

Locmore » al mass and heat transfer measurements on a simulated high-pressure turbine blade-tip surface are conducted in a linear cascade with a nonmoving tip endwall, using a naphthalene sublimation technique. The effects of tip clearance (0.86–6.90% of chord) are investigated at various exit Reynolds numbers (4–7 × 10 5 ) and turbulence intensities (0.2 and 12.0%). The mass transfer on the tip surface is significant along its pressure edge at the smallest tip clearance. At the two largest tip clearances, the separation bubble on the tip surface can cover the whole width of the tip on the second half of the tip surface. The average mass-transfer rate is highest at a tip clearance of 1.72% of chord. The average mass-transfer rate on the tip surface is four and six times as high as on the suction and the pressure surface, respectively. A high mainstream turbulence level of 12.0% reduces average mass-transfer rates on the tip surface, while the higher mainstream Reynolds number generates higher local and average mass-transfer rates on the tip surface.« less

Rotor tip clearance effects on overall and blade-element performance of axial-flow transonic fan stage

NASA Technical Reports Server (NTRS)

Moore, R. D.

1982-01-01

The effects of tip clearance on the overall and blade-element performance of an axial-flow transonic fan stage are presented. The 50-centimeter-diameter fan was tested at four tip clearances (nonrotating) from 0.061 to 0.178 centimeter. The calculated radial growth of the blades was 0.040 centimeter at design conditions. The decrease in overall stage performance with increasing clearance is attributed to the loss in rotor performance. For the rotor the effects of clearance on performance parameters extended to about 70 percent of blade span from the tip. The stage still margin based on an assumed operating line decreased from 15.3 to 0 percent as the clearance increased from 0.061 to 0.178 centimeter.

Experimental short-duration techniques. [gas turbine engine tests

NASA Technical Reports Server (NTRS)

Dunn, Michael G.

1986-01-01

Short-duration facilities used for gas turbine studies are described. Data recording techniques; and instruments (thin-film heat flux gages, high-frequency response pressure measurements, total temperature probes, measurement of rotor tip speed, active measurement of tip clearance) are presented.

Fiber-optic laser Doppler turbine tip clearance probe

NASA Astrophysics Data System (ADS)

Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

2006-05-01

A laser Doppler based method for in situ single blade tip clearance measurements of turbomachines with high precision is presented for what we believe is the first time. The sensor is based on two superposed fanlike interference fringe systems generated by two laser wavelengths from a fiber-coupled, passive, and therefore compact measurement head employing diffractive optics. Tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm (833 Hz, 586 m/s tip speed) are reported. At these speeds the measured uncertainty of the tip position was less than 20 μm, a factor of 2 more accurate than that of capacitive probes. The sensor offers great potential for in situ and online high-precision tip clearance measurements of metallic and nonmetallic turbine blades.

Fiber-optic laser Doppler turbine tip clearance probe.

PubMed

Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

2006-05-01

A laser Doppler based method for in situ single blade tip clearance measurements of turbomachines with high precision is presented for what we believe is the first time. The sensor is based on two superposed fanlike interference fringe systems generated by two laser wavelengths from a fiber-coupled, passive, and therefore compact measurement head employing diffractive optics. Tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm (833 Hz, 586 m/s tip speed) are reported. At these speeds the measured uncertainty of the tip position was less than 20 microm, a factor of 2 more accurate than that of capacitive probes. The sensor offers great potential for in situ and online high-precision tip clearance measurements of metallic and nonmetallic turbine blades.

Turbine Engine Clearance Control Systems: Current Practices and Future Directions

NASA Astrophysics Data System (ADS)

Lattime, Scott B.; Steinetz, Bruce M.

2002-09-01

Improved blade tip sealing in the high pressure compressor (HPC) and high pressure turbine (HPT) can provide dramatic reductions in specific fuel consumption (SFC), time-on-wing, compressor stall margin, and engine efficiency as well as increased payload and mission range capabilities. Maintenance costs to overhaul large commercial gas turbine engines can easily exceed 1M. Engine removal from service is primarily due to spent exhaust gas temperature (EGT) margin caused mainly by the deterioration of HPT components. Increased blade tip clearance is a major factor in hot section component degradation. As engine designs continue to push the performance envelope with fewer parts and the market drives manufacturers to increase service life, the need for advanced sealing continues to grow. A review of aero gas turbine engine HPT performance degradation and the mechanisms that promote these losses are discussed. Benefits to the HPT due to improved clearance management are identified. Past and present sealing technologies are presented along with specifications for next generation engine clearance control systems.

Turbine Engine Clearance Control Systems: Current Practices and Future Directions

NASA Technical Reports Server (NTRS)

Lattime, Scott B.; Steinetz, Bruce M.

2002-01-01

Improved blade tip sealing in the high pressure compressor (HPC) and high pressure turbine (HPT) can provide dramatic reductions in specific fuel consumption (SFC), time-on-wing, compressor stall margin, and engine efficiency as well as increased payload and mission range capabilities. Maintenance costs to overhaul large commercial gas turbine engines can easily exceed $1M. Engine removal from service is primarily due to spent exhaust gas temperature (EGT) margin caused mainly by the deterioration of HPT components. Increased blade tip clearance is a major factor in hot section component degradation. As engine designs continue to push the performance envelope with fewer parts and the market drives manufacturers to increase service life, the need for advanced sealing continues to grow. A review of aero gas turbine engine HPT performance degradation and the mechanisms that promote these losses are discussed. Benefits to the HPT due to improved clearance management are identified. Past and present sealing technologies are presented along with specifications for next generation engine clearance control systems.

Calculation of tip clearance effects in a transonic compressor rotor

NASA Technical Reports Server (NTRS)

Chima, R. V.

1996-01-01

The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearance model. Recommendations were made concerning the use of the simple clearance model. Detailed comparisons were made between the gridded clearance gap solution and the laser anemometer data near the tip at two operating points. The computer results agreed fairly well with the data but overpredicted the extent of the casing separation and underpredicted the wake decay rate. The computations were then used to describe the interaction of the tip vortex, the passage shock, and the casing boundary layer.

Tip clearance effects on loads and performances of semi-open impeller centrifugal pumps at different specific speeds

NASA Astrophysics Data System (ADS)

Boitel, G.; Fedala, D.; Myon, N.

2016-11-01

Relevant industrial standards or customer's specifications could strictly forbid any device adjusting the axial rotor/stator position, so that tip clearance between semi-open impeller and casing might become a result of the pump machining tolerances and assembling process, leading to big tip clearance variations compared to its nominal value. Consequently, large disparities of global performances (head, power, efficiency) and axial loads are observed with high risk of both specifications noncompliance and bearing damages. This work aims at quantifying these variations by taking into account tip clearance value and pump specific speed. Computational Fluid Dynamics is used to investigate this phenomenon by means of steady simulations led on a semi-open centrifugal pump numerical model including secondary flows, based on a k-omega SST turbulence model. Four different specific speed pump sizes are simulated (from 8 to 50, SI units), with three tip clearances for each size on a wide flow range (from 40% to 120% of the best efficiency point). The numerical results clearly show that head, power and efficiency increase as the tip clearance decreases for the whole flow range. This effect is more significant when the specific speed is low. Meanwhile, the resulting axial thrust on the impeller is very sensitive to the tip clearance and can even lead to direction inversion.

Rotating coherent flow structures as a source for narrowband tip clearance noise from axial fans

NASA Astrophysics Data System (ADS)

Zhu, Tao; Lallier-Daniels, Dominic; Sanjosé, Marlène; Moreau, Stéphane; Carolus, Thomas

2018-03-01

Noise from axial fans typically increases significantly as the tip clearance is increased. In addition to the broadband tip clearance noise at the design flow rate, narrowband humps also associated with the tip flow are observed in the far-field acoustic spectra at lower flow rate. In this study, both experimental and numerical methods are used to shed more light on the noise generation mechanism of this narrowband tip clearance noise and provide a unified description of this source. Unsteady aeroacoustic predictions with the Lattice-Boltzmann Method (LBM) are successfully compared with experiment. Such a validation allows using LBM data to conduct a detailed modal analysis of the pressure field for detecting rotating coherent flow structures which might be considered as noise sources. As previously found in ring fans the narrowband humps in the far-field noise spectra are found to be related to the tip clearance noise that is generated by an interaction of coherent flow structures present in the tip region with the leading edge of the impeller blades. The visualization of the coherent structures shows that they are indeed part of the unsteady tip clearance vortex structures. They are hidden in a complex, spatially and temporally inhomogeneous flow field, but can be recovered by means of appropriate filtering techniques. Their pressure trace corresponds to the so-called rotational instability identified in previous turbomachinery studies, which brings a unified picture of this tip-noise phenomenon for the first time.

Time-of-Flight Tip-Clearance Measurements

NASA Technical Reports Server (NTRS)

Dhadwal, H. S.; Kurkov, A. P.; Janetzke, D. C.

1999-01-01

In this paper a time-of-flight probe system incorporating the two integrated fiber optic probes which are tilted equally relative to the probe holder centerline, is applied for the first time to measure the tip clearance of an advanced fan prototype. Tip clearance is largely independent of the signal amplitude and it relies on timing measurement. This work exposes optical effects associated with the fan blade stagger angle that were absent during the original spin-rig experiment on the zero stagger rotor. Individual blade tip clearances were measured with accuracy of +/- 127-mm (+/- 0.005-in). Probe features are discussed and improvements to the design are suggested.

Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines

NASA Technical Reports Server (NTRS)

Ameri, A. A.; Steinthorsson, E.; Rigby, David L.

1998-01-01

Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E 3 first stage turbine, which represents a modem gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.

Turbomachinery Clearance Control

NASA Technical Reports Server (NTRS)

Chupp, Raymond E.; Hendricks, Robert C.; Lattime, Scott B.; Steinetz, Bruce M.; Aksit, Mahmut F.

2007-01-01

Controlling interface clearances is the most cost effective method of enhancing turbomachinery performance. Seals control turbomachinery leakages, coolant flows and contribute to overall system rotordynamic stability. In many instances, sealing interfaces and coatings are sacrificial, like lubricants, giving up their integrity for the benefit of the component. They are subjected to abrasion, erosion, oxidation, incursive rubs, foreign object damage (FOD) and deposits as well as extremes in thermal, mechanical, aerodynamic and impact loadings. Tribological pairing of materials control how well and how long these interfaces will be effective in controlling flow. A variety of seal types and materials are required to satisfy turbomachinery sealing demands. These seals must be properly designed to maintain the interface clearances. In some cases, this will mean machining adjacent surfaces, yet in many other applications, coatings are employed for optimum performance. Many seals are coating composites fabricated on superstructures or substrates that are coated with sacrificial materials which can be refurbished either in situ or by removal, stripping, recoating and replacing until substrate life is exceeded. For blade and knife tip sealing an important class of materials known as abradables permit blade or knife rubbing without significant damage or wear to the rotating element while maintaining an effective sealing interface. Most such tip interfaces are passive, yet some, as for the high-pressure turbine (HPT) case or shroud, are actively controlled. This work presents an overview of turbomachinery sealing. Areas covered include: characteristics of gas and steam turbine sealing applications and environments, benefits of sealing, types of standard static and dynamics seals, advanced seal designs, as well as life and limitations issues.

A similitude method and the corresponding blade design of a low-speed large-scale axial compressor rotor

NASA Astrophysics Data System (ADS)

Yu, Chenghai; Ma, Ning; Wang, Kai; Du, Juan; Van den Braembussche, R. A.; Lin, Feng

2014-04-01

A similitude method to model the tip clearance flow in a high-speed compressor with a low-speed model is presented in this paper. The first step of this method is the derivation of similarity criteria for tip clearance flow, on the basis of an inviscid model of tip clearance flow. The aerodynamic parameters needed for the model design are then obtained from a numerical simulation of the target high-speed compressor rotor. According to the aerodynamic and geometric parameters of the target compressor rotor, a large-scale low-speed rotor blade is designed with an inverse blade design program. In order to validate the similitude method, the features of tip clearance flow in the low-speed model compressor are compared with the ones in the high-speed compressor at both design and small flow rate points. It is found that not only the trajectory of the tip leakage vortex but also the interface between the tip leakage flow and the incoming main flow in the high-speed compressor match well with that of its low speed model. These results validate the effectiveness of the similitude method for the tip clearance flow proposed in this paper.

Experimental and computational investigation of the tip clearance flow in a transonic axial compressor rotor

NASA Astrophysics Data System (ADS)

Suder, Kenneth L.; Celestina, Mark L.

1995-06-01

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with primary flow downstream of the rotor at both design and part speed conditions is also discussed.

Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor

NASA Technical Reports Server (NTRS)

Suder, Kenneth L.; Celestina, Mark L.

1995-01-01

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with primary flow downstream of the rotor at both design and part speed conditions is also discussed.

75 FR 17375 - Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-06

... submit to the Office of Management and Budget (OMB) for clearance the following proposal for collection... Papers to the Technology Innovation Program (TIP). OMB Control Number: None. Form Number(s): None. Type... develop new areas for future competitions for the Technology Innovation Program (TIP) by offering ideas in...

2003 NASA Seal/Secondary Air System Workshop. Volume 1

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Editor); Hendricks, Robert C. (Editor)

2004-01-01

The following reports were included in the 2003 NASA Seal/Secondary Air System Workshop:Low Emissions Alternative Power (LEAP); Overview of NASA Glenn Seal Developments; NASA Ultra Efficient Engine Technology Project Overview; Development of Higher Temperature Abradable Seals for Industrial Gas Turbines; High Misalignment Carbon Seals for the Fan Drive Gear System Technologies; Compliant Foil Seal Investigations; Test Rig for Evaluating Active Turbine Blade Tip Clearance Control Concepts; Controls Considerations for Turbine Active Clearance Control; Non-Contacting Finger Seal Developments and Design Considerations; Effect of Flow-Induced Radial Load on Brush Seal/Rotor Contact Mechanics; Seal Developments at Flowserve Corporation; Investigations of High Pressure Acoustic Waves in Resonators With Seal-Like Features; Numerical Investigations of High Pressure Acoustic Waves in Resonators; Feltmetal Seal Material Through-Flow; "Bimodal" Nuclear Thermal Rocket (BNTR) Propulsion for Future Human Mars Exploration Missions; High Temperature Propulsion System Structural Seals for Future Space Launch Vehicles; Advanced Control Surface Seal Development for Future Space Vehicles; High Temperature Metallic Seal Development for Aero Propulsion and Gas Turbine Applications; and BrazeFoil Honeycomb.

A Blade Tip Timing Method Based on a Microwave Sensor

PubMed Central

Zhang, Jilong; Duan, Fajie; Niu, Guangyue; Jiang, Jiajia; Li, Jie

2017-01-01

Blade tip timing is an effective method for blade vibration measurements in turbomachinery. This method is increasing in popularity because it is non-intrusive and has several advantages over the conventional strain gauge method. Different kinds of sensors have been developed for blade tip timing, including optical, eddy current and capacitance sensors. However, these sensors are unsuitable in environments with contaminants or high temperatures. Microwave sensors offer a promising potential solution to overcome these limitations. In this article, a microwave sensor-based blade tip timing measurement system is proposed. A patch antenna probe is used to transmit and receive the microwave signals. The signal model and process method is analyzed. Zero intermediate frequency structure is employed to maintain timing accuracy and dynamic performance, and the received signal can also be used to measure tip clearance. The timing method uses the rising and falling edges of the signal and an auto-gain control circuit to reduce the effect of tip clearance change. To validate the accuracy of the system, it is compared experimentally with a fiber optic tip timing system. The results show that the microwave tip timing system achieves good accuracy. PMID:28492469

A Blade Tip Timing Method Based on a Microwave Sensor.

PubMed

Zhang, Jilong; Duan, Fajie; Niu, Guangyue; Jiang, Jiajia; Li, Jie

2017-05-11

Blade tip timing is an effective method for blade vibration measurements in turbomachinery. This method is increasing in popularity because it is non-intrusive and has several advantages over the conventional strain gauge method. Different kinds of sensors have been developed for blade tip timing, including optical, eddy current and capacitance sensors. However, these sensors are unsuitable in environments with contaminants or high temperatures. Microwave sensors offer a promising potential solution to overcome these limitations. In this article, a microwave sensor-based blade tip timing measurement system is proposed. A patch antenna probe is used to transmit and receive the microwave signals. The signal model and process method is analyzed. Zero intermediate frequency structure is employed to maintain timing accuracy and dynamic performance, and the received signal can also be used to measure tip clearance. The timing method uses the rising and falling edges of the signal and an auto-gain control circuit to reduce the effect of tip clearance change. To validate the accuracy of the system, it is compared experimentally with a fiber optic tip timing system. The results show that the microwave tip timing system achieves good accuracy.

Compressor blade clearance measurement using capacitance and phase lock techniques

NASA Astrophysics Data System (ADS)

Demers, Rosario N.

1986-11-01

The clearance measurement system has several unique features which mimimize problems plaguing earlier systems. These include tuning stability and sensitivity drift. Both these problems are intensified by the environmental factors present in compressors i.e., wide temperature fluctuations, vibrations, and conductive contamination of probe tips. The circuitry in this new system provides phase lock feedback to control tuning and shut calibration to measure sensitivity. The use of high frequency excitation lowers the probe tip impedance, thus miminizing the effects of contamination. A prototype has been built and tested. The ability to calibrate has been demonstrated. An eight channel system is now being constructed for use in the Compressor Research Facility at Wright-Patterson AFB. The efficiency of a turbine engine is to a large extent dependent upon the mechanical tolerances maintained between its moving parts. On critical tolerance is the blade span. Although this tolerance may not appear severe, the impact on compressor efficiency is dramatic. The penalty in percent efficiency has been shown to be three times the percent clearance to blade span ratio. In addition, each percent loss in compressor efficiency represents one half percent loss in specific fuel consumption. Factors which affect blade tip clearance are identified.

Aerodynamic Inner Workings of Circumferential Grooves in a Transonic Axial Compressor

NASA Technical Reports Server (NTRS)

Hah, Chunill; Mueller, Martin; Schiffer, Heinz-Peter

2007-01-01

The current paper reports on investigations of the fundamental flow mechanisms of circumferential grooves applied to a transonic axial compressor. Experimental results show that the compressor stall margin is significantly improved with the current set of circumferential grooves. The primary focus of the current investigation is to advance understanding of basic flow mechanics behind the observed improvement of stall margin. Experimental data and numerical simulations of a circumferential groove were analyzed in detail to unlock the inner workings of the circumferential grooves in the current transonic compressor rotor. A short length scale stall inception occurs when a large flow blockage is built on the pressure side of the blade near the leading edge and incoming flow spills over to the adjacent blade passage due to this blockage. The current study reveals that a large portion of this blockage is created by the tip clearance flow originating from 20% to 50% chord of the blade from the leading edge. Tip clearance flows originating from the leading edge up to 20% chord form a tip clearance core vortex and this tip clearance core vortex travels radially inward. The tip clearance flows originating from 20% to 50% chord travels over this tip clearance core vortex and reaches to the pressure side. This part of tip clearance flow is of low momentum as it is coming from the casing boundary layer and the blade suction surface boundary layer. The circumferential grooves disturb this part of the tip clearance flow close to the casing. Consequently the buildup of the induced vortex and the blockage near the pressure side of the passage is reduced. This is the main mechanism of the circumferential grooves that delays the formation of blockage near the pressure side of the passage and delays the onset of short length scale stall inception. The primary effect of the circumferential grooves is preventing local blockage near the pressure side of the blade leading edge that directly determines flow spillage around the leading edge. The circumferential grooves do not necessarily reduce the over all blockage built up at the rotor tip section.

Application of chromatic confocal displacement sensor in measurement of tip clearance

NASA Astrophysics Data System (ADS)

Bi, Chao; Li, Di; Fang, Jianguo; Zhang, Bin

2016-10-01

In the field of aeronautics, the tip clearance of rotor exerts a crucial influence on the performance of the aero engine. As defined as the radial distance between the top of the blade and the inner wall of the casing, the tip clearance of too large or small size will adversely affect the normal running of the engine. In order to realize accurate measurement of the tip clearance in a simple way, a non-contact measuring method by the chromatic confocal displacement sensor is proposed in the paper. The sensor possesses the advantages such as small volume, good signal-to-noise ratio, high accuracy and response frequency etc., which make it be widely used in engineering and industry. For testing the performance and potential application of the sensor, a simulation testing platform is established. In the platform, a simulation blisk is installed on the air bearing spindle and a chromatic confocal displacement sensor is fixed on the platform to measure the displacement variation of the blade tip, which can be used to characterize the variation of the tip clearance. In the simulation experiments, both of single and continuous measurement of the tip clearance of the 36 blades on the blisk is executed. As the results of experiments show, the chromatic confocal displacement sensor can meet the requirements of measuring task, in which both of high measuring efficiency and accuracy could be achieved. Therefore, the measuring method proposed in the paper can be utilized in the actual assembling sites of the aero engine.

A Novel Approach for Reducing Rotor Tip-Clearance Induced Noise in Turbofan Engines

NASA Technical Reports Server (NTRS)

Khorrami, Mehdi R.; Li, Fei; Choudhari, Meelan

2001-01-01

Rotor tip-clearance induced noise, both in the form of rotor self noise and rotor-stator interaction noise , constitutes a significant component of total fan noise. Innovative yet cost effective techniques to suppress rotor-generated noise are, therefore, of foremost importance for improving the noise signature of turbofan engines. To that end, the feasibility of a passive porous treatment strategy to positively modify the tip-clearance flow field is addressed. The present study is focused on accurate viscous flow calculations of the baseline and the treated rotor flow fields. Detailed comparison between the computed baseline solution and experimental measurements shows excellent agreement. Tip-vortex structure, trajectory, strength, and other relevant aerodynamic quantities are extracted from the computed database. Extensive comparison between the untreated and treated tip-clearance flow fields is performed. The effectiveness of the porous treatment for altering the rotor-tip vortex flow field in general and reducing the intensity of the tip vortex, in particular, is demonstrated. In addition, the simulated flow field for the treated tip clearly shows that substantial reduction in the intensity of both the shear layer roll-up and boundary layer separation on the wall is achieved.

An optical fiber bundle sensor for tip clearance and tip timing measurements in a turbine rig.

PubMed

García, Iker; Beloki, Josu; Zubia, Joseba; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Jiménez, Felipe

2013-06-05

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions.

An Optical Fiber Bundle Sensor for Tip Clearance and Tip Timing Measurements in a Turbine Rig

PubMed Central

García, Iker; Beloki, Josu; Zubia, Joseba; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Jiménez, Felipe

2013-01-01

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions. PMID:23739163

The influences of tip clearance on the performance of nozzle blades of radial turbines - Experiment and performance prediction at three nozzle angles

NASA Astrophysics Data System (ADS)

Hyun, Yong-Ik; Yamaguchi, Michiteru; Hayami, Hiroshi; Senoo, Yasutoshi

1988-05-01

In order to study the influence of tip clearance on the turning angle and pressure loss of turbine nozzles, experimental results were obtained for nozzle angles at which the throat area was 0.8 and 1.4 times the rated condition. Contour maps of the total pressure loss and of the spanwise distributions of the mean exit-flow angle have been obtained. Although the two-layer flow model of Senoo et al., (1987) is shown to accurately predict the effects of tip clearance, it underestimates the clearance effect for a lightly loaded condition.

An Experimental Characterization of Tip Leakage Flows and Corresponding Effects on Multistage Compressor Performance

NASA Astrophysics Data System (ADS)

Berdanier, Reid Adam

The effect of rotor tip clearances in turbomachinery applications has been a primary research interest for nearly 80 years. Over that time, studies have shown increased tip clearance in axial flow compressors typically has a detrimental effect on overall pressure rise capability, isentropic efficiency, and stall margin. With modern engine designs trending toward decreased core sizes to increase propulsive efficiency (by increasing bypass ratio) or additional compression stages to increase thermal efficiency by increasing the overall pressure ratio, blade heights in the rear stages of the high pressure compressor are expected to decrease. These rear stages typically feature smaller blade aspect ratios, for which endwall flows are more important, and the rotor tip clearance height represents a larger fraction of blade span. As a result, data sets collected with large relative rotor tip clearance heights are necessary to facilitate these future small core design goals. This research seeks to characterize rotor tip leakage flows for three tip clearance heights in the Purdue three-stage axial compressor facility (1.5%, 3.0%, and 4.0% as a percentage of overall annulus height). The multistage environment of this compressor provides the unique opportunity to examine tip leakage flow effects due to stage matching, stator-rotor interactions, and rotor-rotor interactions. The important tip leakage flow effects which develop as a result of these interactions are absent for previous studies which have been conducted using single-stage machines or isolated rotors. A series of compressor performance maps comprise points at four corrected speeds for each of the three rotor tip clearance heights. Steady total pressure and total temperature measurements highlight the effects of tip leakage flows on radial profiles and wake shapes throughout the compressor. These data also evaluate tip clearance effects on efficiency, stall margin, and peak pressure rise capability. An emphasis of measurements collected at these part-speed and off-design conditions provides a unique data set for calibrating computational models and predictive algorithms. Further investigations with detailed steady total pressure traverses provide additional insight to tip leakage flow effects on stator performance. A series of data on the 100% corrected speedline further characterize the tip leakage flow using time-resolved measurements from a combination of instrumentation techniques. An array of high-frequency-response piezoresistive pressure transducers installed over the rotors allows quantification of tip leakage flow trajectories. These data, along with measurements from a fast-response total pressure probe downstream of the rotors, evaluate the development of tip leakage flows and assess the corresponding effects of upstream stator wakes. Finally, thermal anemometry measurements collected using the single slanted hot-wire technique evaluate three-dimensional velocity components throughout the compressor. These data facilitate calculations of several flow metrics, including a blockage parameter and phase-locked streamwise vorticity.

Recommendations for Achieving Accurate Numerical Simulation of Tip Clearance Flows in Transonic Compressor Rotors

NASA Technical Reports Server (NTRS)

VanZante, Dale E.; Strazisar, Anthony J.; Wood, Jerry R,; Hathaway, Michael D.; Okiishi, Theodore H.

2000-01-01

The tip clearance flows of transonic compressor rotors are important because they have a significant impact on rotor and stage performance. While numerical simulations of these flows are quite sophisticated. they are seldom verified through rigorous comparisons of numerical and measured data because these kinds of measurements are rare in the detail necessary to be useful in high-speed machines. In this paper we compare measured tip clearance flow details (e.g. trajectory and radial extent) with corresponding data obtained from a numerical simulation. Recommendations for achieving accurate numerical simulation of tip clearance flows are presented based on this comparison. Laser Doppler Velocimeter (LDV) measurements acquired in a transonic compressor rotor, NASA Rotor 35, are used. The tip clearance flow field of this transonic rotor was simulated using a Navier-Stokes turbomachinery solver that incorporates an advanced k-epsilon turbulence model derived for flows that are not in local equilibrium. Comparison between measured and simulated results indicates that simulation accuracy is primarily dependent upon the ability of the numerical code to resolve important details of a wall-bounded shear layer formed by the relative motion between the over-tip leakage flow and the shroud wall. A simple method is presented for determining the strength of this shear layer.

Numerical analysis of the blade tip-timing signal of a fiber bundle sensor probe

NASA Astrophysics Data System (ADS)

Guo, Haotian; Duan, Fajie; Cheng, Zhonghai

2015-03-01

Blade tip-timing is the most effective method for online blade vibration measurement of large rotating machines like turbine engines. Fiber bundle sensors are utilized in tip-timing system to measure the arrival time of the blade. The model of the tip-timing signal of the fiber bundle sensor is established. Experiments are conducted and the results are in concordance with the model established. The rising speed of the tip-timing signal is analyzed. To minimize the tip-timing error, the effects of the clearance change between the sensor and the blade and the deflection of the tip surface are analyzed. Simulation results indicate that the variable gain amplifier, which amplifies the signals to a similar level, can eliminate the measurement error caused by the variation of the clearance between the sensor and blade. Increasing the clearance between the sensor and blade can reduce the measurement error introduced by deflection of the tip surface.

An Experimental Investigation of the Flow Physics Associated With End Wall Losses and Large Rotor Tip Clearances as Found in the Rear Stages of a High Pressure Compressor

NASA Technical Reports Server (NTRS)

Berdanier, Reid A.; Key, Nicole L.

2015-01-01

The focus of this work was to characterize the fundamental flow physics and the overall performance effects due to increased rotor tip clearance heights in axial compressors. Data have been collected in the three-stage axial research compressor at Purdue University with a specific focus on analyzing the multistage effects resulting from the tip leakage flow. Three separate rotor tip clearance heights were studied with nominal tip clearance heights of 1.5%, 3.0%, and 4.0% based on a constant annulus height. Overall compressor performance was investigated at four corrected speedlines (100%, 90%, 80%, and 68%) for each of the three tip clearance configurations using total pressure and total temperature rakes distributed throughout the compressor. The results have confirmed results from previous authors showing a decrease of total pressure rise, isentropic efficiency, and stall margin which is approximately linear with increasing tip clearance height. The stall inception mechanisms have also been evaluated at the same corrected speeds for each of the tip clearance configurations. Detailed flow field measurements have been collected at two loading conditions, nominal loading (NL) and high loading (HL), on the 100% corrected speedline for the smallest and largest tip clearance heights (1.5% and 4.0%). Steady detailed radial traverses of total pressure at the exit of each stator row have been supported by flow visualization techniques to identify regions of flow recirculation and separation. Furthermore, detailed radial traverses of time-resolved total pressures at the exit of each rotor row have been measured with a fast-response pressure probe. These data have helped to quantify the size of the leakage flow at the exit of each rotor. Thermal anemometry has also been implemented to evaluate the time-resolved three-dimensional components of velocity throughout the compressor and calculate blockage due to the rotor tip leakage flow throughout the compressor. These measurements have also been used to calculate streamwise vorticity. Time-resolved static pressure measurements have been collected over the rotor tips for all rotors with each of the three tip clearance configurations for up to five loading conditions along the 100% corrected speedline using fast-response piezoresistive pressure sensors. These time-resolved static pressure measurements, as well as the time-resolved total pressures and velocities have helped to reveal a profound influence of the upstream stator vane on the size and shape of the rotor tip leakage flow. Finally, a novel particle image velocimetry (PIV) technique has been developed as a proof-of- concept. In contrast to PIV methods that have been typically been utilized for turbomachinery applications in the past, the method used for this study introduced the laser light through the same access window that was also used to image the flow. This new method addresses potential concerns related to the intrusive laser-introducing techniques that have typically been utilized by other authors in the past. Ultimately, the data collected for this project represent a unique data set which contributes to build a better understanding of the tip leakage flow field and its associated loss mechanisms. These data will facilitate future engine design goals leading to small blade heights in the rear stages of high pressure compressors and aid in the development of new blade designs which are desensitized to the performance penalties attributed to rotor tip leakage flows.

A Reduced Model for Prediction of Thermal and Rotational Effects on Turbine Tip Clearance

NASA Technical Reports Server (NTRS)

Kypuros, Javier A.; Melcher, Kevin J.

2003-01-01

This paper describes a dynamic model that was developed to predict changes in turbine tip clearance the radial distance between the end of a turbine blade and the abradable tip seal. The clearance is estimated by using a first principles approach to model the thermal and mechanical effects of engine operating conditions on the turbine sub-components. These effects are summed to determine the resulting clearance. The model is demonstrated via a ground idle to maximum power transient and a lapse-rate takeoff transient. Results show the model demonstrates the expected pinch point behavior. The paper concludes by identifying knowledge gaps and suggesting additional research to improve the model.

Electrical capacitance clearanceometer

NASA Technical Reports Server (NTRS)

Hester, Norbert J. (Inventor); Hornbeck, Charles E. (Inventor); Young, Joseph C. (Inventor)

1992-01-01

A hot gas turbine engine capacitive probe clearanceometer is employed to measure the clearance gap or distance between blade tips on a rotor wheel and its confining casing under operating conditions. A braze sealed tip of the probe carries a capacitor electrode which is electrically connected to an electrical inductor within the probe which is inserted into a turbine casing to position its electrode at the inner surface of the casing. Electrical power is supplied through a voltage controlled variable frequency oscillator having a tuned circuit in which the probe is a component. The oscillator signal is modulated by a change in electrical capacitance between the probe electrode and a passing blade tip surface while an automatic feedback correction circuit corrects oscillator signal drift. A change in distance between a blade tip and the probe electrode is a change in capacitance therebetween which frequency modulates the oscillator signal. The modulated oscillator signal which is then processed through a phase detector and related circuitry to provide an electrical signal is proportional to the clearance gap.

CF6 High Pressure Compressor and Turbine Clearance Evaluations

NASA Technical Reports Server (NTRS)

Radomski, M. A.; Cline, L. D.

1981-01-01

In the CF6 Jet Engine Diagnostics Program the causes of performance degradation were determined for each component of revenue service engines. It was found that a significant contribution to performance degradation was caused by increased airfoil tip radial clearances in the high pressure compressor and turbine areas. Since the influence of these clearances on engine performance and fuel consumption is significant, it is important to accurately establish these relatonships. It is equally important to understand the causes of clearance deterioration so that they can be reduced or eliminated. The results of factory engine tests run to enhance the understanding of the high pressure compressor and turbine clearance effects on performance are described. The causes of clearance deterioration are indicated and potential improvements in clearance control are discussed.

Robust Optimization Design for Turbine Blade-Tip Radial Running Clearance using Hierarchically Response Surface Method

NASA Astrophysics Data System (ADS)

Zhiying, Chen; Ping, Zhou

2017-11-01

Considering the robust optimization computational precision and efficiency for complex mechanical assembly relationship like turbine blade-tip radial running clearance, a hierarchically response surface robust optimization algorithm is proposed. The distribute collaborative response surface method is used to generate assembly system level approximation model of overall parameters and blade-tip clearance, and then a set samples of design parameters and objective response mean and/or standard deviation is generated by using system approximation model and design of experiment method. Finally, a new response surface approximation model is constructed by using those samples, and this approximation model is used for robust optimization process. The analyses results demonstrate the proposed method can dramatic reduce the computational cost and ensure the computational precision. The presented research offers an effective way for the robust optimization design of turbine blade-tip radial running clearance.

Microwave Sensor for Blade Tip Clearance and Structural Health Measurements

NASA Technical Reports Server (NTRS)

Woike, Mark R.; Bencic, Timothy J.

2008-01-01

The use of microwave based sensors for the health monitoring of rotating machinery is being explored at the NASA Glenn Research Center. The microwave sensor works on the principle of sending a continuous signal towards a rotating component and measuring the reflected signal. The phase shift of the reflected signal is proportional to the distance between the sensor and the component that is being measured. This type of sensor is beneficial in that it has the ability to operate at extremely high temperatures and is unaffected by contaminants that may be present in the rotating machinery. It is intended to use these probes in the hot sections of turbine engines for closed loop turbine clearance control and structural health measurements. Background on the sensors, an overview of their calibration and preliminary results from using them to make blade tip clearance and health measurements on a large axial vane fan will be presented.

Investigating Dynamics of Eccentricity in Turbomachines

NASA Technical Reports Server (NTRS)

Baun, Daniel

2010-01-01

A methodology (and hardware and software to implement the methodology) has been developed as a means of investigating coupling between certain rotordynamic and hydrodynamic phenomena in turbomachines. Originally, the methodology was intended for application in an investigation of coupled rotordynamic and hydrodynamic effects postulated to have caused high synchronous vibration in the space shuttle s high-pressure oxygen turbopump (HPOTP). The methodology can also be applied in investigating (for the purpose of developing means of suppressing) undesired hydrodynamic rotor/stator interactions in turbomachines in general. The methodology and the types of phenomena that can be investigated by use of the methodology are best summarized by citing the original application as an example. In that application, in consideration of the high synchronous vibration in the space-shuttle main engine (SSME) HPOTP, it was determined to be necessary to perform tests to investigate the influence of inducer eccentricity and/or synchronous whirl motion on inducer hydrodynamic forces under prescribed flow and cavitation conditions. It was believed that manufacturing tolerances of the turbopump resulted in some induced runout of the pump rotor. Such runout, if oriented with an inducer blade, would cause that blade to run with tip clearance smaller than the tip clearances of the other inducer blades. It was hypothesized that the resulting hydraulic asymmetry, coupled with alternating blade cavitation, could give rise to the observed high synchronous vibration. In tests performed to investigate this hypothesis, prescribed rotor whirl motions have been imposed on a 1/3-scale water-rig version of the SSME LPOTP inducer (which is also a 4-biased inducer having similar cavitation dynamics as the HPOTP) in a magnetic-bearing test facility. The particular magnetic-bearing test facility, through active vibration control, affords a capability to impose, on the rotor, whirl orbits having shapes and whirl rates prescribed by the user, and to simultaneously measure the resulting hydrodynamic forces generated by the impeller. Active control also made it possible to modulate the inducer-blade running tip clearance and consequently effect alternating blade cavitation. The measured hydraulic forces have been compared and correlated with shroud dynamic-pressure measurements.

Design, analysis, optimization and control of rotor tip flows

NASA Astrophysics Data System (ADS)

Maesschalck, Cis Guy M. De

Developments in turbomachinery focus on efficiency and reliability enhancements, while reducing the production costs. In spite of the many noteworthy experimental and numerical investigations over the past decades, the turbine tip design presents numerous challenges to the engine manufacturers, and remains the primary factor defining the machine durability for the periodic removal of the turbine components during overhaul. Due to the hot gases coming from the upstream combustion chamber, the turbine blades are subjected to temperatures far above the metal creep temperature, combined with severe thermal stresses induced within the blade material. Inadequate designs cause early tip burnouts leading to considerable performance degradations, or even a catastrophic turbine failure. Moreover, the leakage spillage, nowadays often exceeding the transonic regime, generates large aerodynamic penalties which are responsible for about one third of the turbine losses. In this view, the current doctoral research exploits the potential through the modification and optimization of the blade tip shape as a means to control the tip leakage flow aerodynamics and manage the heat load distribution over the blade profile to improve the turbine efficiency and durability. Three main design strategies for unshrouded turbine blade tips were analyzed and optimized: tight running clearances, blade tip contouring and the use of complex squealer-like geometries. The altered overtip flow physics and heat transfer characteristics were simulated for tight gap sizes as low as 0.5% down to 0.1% of the blade height, occurring during engine transients and soon to be expected due to recent developments in active clearance control strategies. The potential of fully 3D contoured blade top surfaces, allowing to adapt the profile locally to the changing flow conditions throughout the camberline, is quantified. First adopting a quasi-3D approach and subsequently using a full 3D optimization. For the industrial rub-safe squealer profiles featuring cavities separated by upstanding rims, a topology-like multi-objective 3D optimization strategy is used to identify so far undiscovered, optimal blade tip profiles. Furthermore, the additional potential of the widely adopted shroud coolant injection just upstream of the rotor blade is examined. Specifically, the possibility of combining the beneficial effect of the purge flow in the overtip region while minimizing the detrimental influence on the upper passage vortex is explored. Eventually, a high-speed rotating turbine facility at the von Karman Institute was redesigned, allowing simultaneous testing of multiple distinct blade (tip) profiles mounted in separate sectors around the rotor annulus. Important considerations related with the balancing and precise clearance design are highlighted, arising from the complexity of such rainbow-rotor configuration. Moreover, approaches are described to integrate Reynolds-Averaged Navier-Stokes simulations to a priori estimate the errors induced by the finite spatial sampling and inherent limited sensor bandwidth. This research effort provided new insights into the overtip flow topology and aerothermal characteristics, identified new design strategies to create future turbines with enhanced aerodynamic efficiencies and reduced thermal loads, and paved the way for an elaborate experimental validation in a rotating turbine facility, at engine-matched conditions.

Capacitance-type blade-tip clearance measurement system using a dual amplifier with ramp/dc inputs and integration

NASA Technical Reports Server (NTRS)

Sarma, Garimella R.; Barranger, John P.

1992-01-01

The analysis and prototype results of a dual-amplifier circuit for measuring blade-tip clearance in turbine engines are presented. The capacitance between the blade tip and mounted capacitance electrode within a guard ring of a probe forms one of the feedback elements of an operational amplifier (op amp). The differential equation governing the circuit taking into consideration the nonideal features of the op amp was formulated and solved for two types of inputs (ramp and dc) that are of interest for the application. Under certain time-dependent constraints, it is shown that (1) with a ramp input the circuit has an output voltage proportional to the static tip clearance capacitance, and (2) with a dc input, the output is proportional to the derivative of the clearance capacitance, and subsequent integration recovers the dynamic capacitance. The technique accommodates long cable lengths and environmentally induced changes in cable and probe parameters. System implementation for both static and dynamic measurements having the same high sensitivity is also presented.

Capacitance-type blade-tip clearance measurement system using a dual amplifier with ramp/dc inputs and integration

NASA Astrophysics Data System (ADS)

Sarma, Garimella R.; Barranger, John P.

1992-10-01

The analysis and prototype results of a dual-amplifier circuit for measuring blade-tip clearance in turbine engines are presented. The capacitance between the blade tip and mounted capacitance electrode within a guard ring of a probe forms one of the feedback elements of an operational amplifier (op amp). The differential equation governing the circuit taking into consideration the nonideal features of the op amp was formulated and solved for two types of inputs (ramp and dc) that are of interest for the application. Under certain time-dependent constraints, it is shown that (1) with a ramp input the circuit has an output voltage proportional to the static tip clearance capacitance, and (2) with a dc input, the output is proportional to the derivative of the clearance capacitance, and subsequent integration recovers the dynamic capacitance. The technique accommodates long cable lengths and environmentally induced changes in cable and probe parameters. System implementation for both static and dynamic measurements having the same high sensitivity is also presented.

Comparison of Various Supersonic Turbine Tip Designs to Minimize Aerodynamic Loss and Tip Heating

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Ameri, Ali

2012-01-01

The rotor tips of axial turbines experience high heat flux and are the cause of aerodynamic losses due to tip clearance flows, and in the case of supersonic tips, shocks. As stage loadings increase, the flow in the tip gap approaches and exceeds sonic conditions. This introduces effects such as shock-boundary layer interactions and choked flow that are not observed for subsonic tip flows that have been studied extensively in literature. This work simulates the tip clearance flow for a flat tip, a diverging tip gap and several contoured tips to assess the possibility of minimizing tip heat flux while maintaining a constant massflow from the pressure side to the suction side of the rotor, through the tip clearance. The Computational Fluid Dynamics (CFD) code GlennHT was used for the simulations. Due to the strong favorable pressure gradients the simulations assumed laminar conditions in the tip gap. The nominal tip gap width to height ratio for this study is 6.0. The Reynolds number of the flow is 2.4 x 10(exp 5) based on nominal tip width and exit velocity. A wavy wall design was found to reduce heat flux by 5 percent but suffered from an additional 6 percent in aerodynamic loss coefficient. Conventional tip recesses are found to perform far worse than a flat tip due to severe shock heating. Overall, the baseline flat tip was the second best performer. A diverging converging tip gap with a hole was found to be the best choice. Average tip heat flux was reduced by 37 percent and aerodynamic losses were cut by over 6 percent.

Local measurement and numerical modeling of mass/heat transfer from a turbine blade in a linear cascade with tip clearance

NASA Astrophysics Data System (ADS)

Jin, Peitong

2000-11-01

Local mass/heat transfer measurements from the turbine blade near-tip and the tip surfaces are performed using the naphthalene sublimation technique. The experiments are conducted in a linear cascade consisting of five high-pressure blades with a central test-blade configuration. The incoming flow conditions are close to those of the gas turbine engine environment (boundary layer displacement thickness is about 0.01 of chord) with an exit Reynolds number of 6.2 x 105. The effects of tip clearance level (0.86%--6.90% of chord), mainstream Reynolds number and turbulence intensity (0.2 and 12.0%) are investigated. Two methods of flow visualization---oil and lampblack, laser light sheet smoke wire---as well as static pressure measurement on the blade surface are used to study the tip leakage flow and vortex in the cascade. In addition, numerical modeling of the flow and heat transfer processes in the linear cascade with different tip clearances is conducted using commercial software incorporating advanced turbulence models. The present study confirms many important results on the tip leakage flow and vortex from the literature, contributes to the current understanding in the effects of tip leakage flow and vortex on local heat transfer from the blade near-tip and the tip surfaces, and provides detailed local and average heat/mass transfer data applicable to turbine blade tip cooling design.

Facilitating higher-fidelity simulations of axial compressor instability and other turbomachinery flow conditions

NASA Astrophysics Data System (ADS)

Herrick, Gregory Paul

The quest to accurately capture flow phenomena with length-scales both short and long and to accurately represent complex flow phenomena within disparately sized geometry inspires a need for an efficient, high-fidelity, multi-block structured computational fluid dynamics (CFD) parallel computational scheme. This research presents and demonstrates a more efficient computational method by which to perform multi-block structured CFD parallel computational simulations, thus facilitating higher-fidelity solutions of complicated geometries (due to the inclusion of grids for "small'' flow areas which are often merely modeled) and their associated flows. This computational framework offers greater flexibility and user-control in allocating the resource balance between process count and wall-clock computation time. The principal modifications implemented in this revision consist of a "multiple grid block per processing core'' software infrastructure and an analytic computation of viscous flux Jacobians. The development of this scheme is largely motivated by the desire to simulate axial compressor stall inception with more complete gridding of the flow passages (including rotor tip clearance regions) than has been previously done while maintaining high computational efficiency (i.e., minimal consumption of computational resources), and thus this paradigm shall be demonstrated with an examination of instability in a transonic axial compressor. However, the paradigm presented herein facilitates CFD simulation of myriad previously impractical geometries and flows and is not limited to detailed analyses of axial compressor flows. While the simulations presented herein were technically possible under the previous structure of the subject software, they were much less computationally efficient and thus not pragmatically feasible; the previous research using this software to perform three-dimensional, full-annulus, time-accurate, unsteady, full-stage (with sliding-interface) simulations of rotating stall inception in axial compressors utilized tip clearance periodic models, while the scheme here is demonstrated by a simulation of axial compressor stall inception utilizing gridded rotor tip clearance regions. As will be discussed, much previous research---experimental, theoretical, and computational---has suggested that understanding clearance flow behavior is critical to understanding stall inception, and previous computational research efforts which have used tip clearance models have begged the question, "What about the clearance flows?''. This research begins to address that question.

Investigation of the tip clearance flow inside and at the exit of a compressor rotor passage

NASA Technical Reports Server (NTRS)

Pandya, A.; Lakshminarayana, B.

1982-01-01

The nature of the tip clearance flow in a moderately loaded compressor rotor is studied. The measurements were taken inside the clearance between the annulus-wall casing and the rotor blade tip. These measurements were obtained using a stationary two-sensor hot-wire probe in combination with an ensemble averaging technique. The flowfield was surveyed at various radial locations and at ten axial locations, four of which were inside the blade passage in the clearance region and the remaining six outside the passage. Variations of the mean flow properties in the tangential and the radial directions at various axial locations were derived from the data. Variation of the leakage velocity at different axial stations and the annulus-wall boundary layer profiles from passage-averaged mean velocities were also estimated.

Task II: Three-dimensional Rotating Stall Inception and Effects of Rotating Tip Clearance Asymmetry in Axial Compressors

NASA Technical Reports Server (NTRS)

Suder, Kenneth (Technical Monitor); Tan, Choon-Sooi

2003-01-01

The effects of two types of flow non-uniformity on stall inception behavior were assessed with linearized stability analyses of two compressor flow models. Response to rotating tip clearance asymmetries induced by a whirling rotor shaft or rotor height variations were investigated with a two-dimensional flow model. A 3-D compressor model was also developed to study the stability of both full-span and part-span rotating stall modes in annular geometries with radial flow variations. The studies focussed on (1) understanding what compressor designs were sensitive to these types of circumferential and spanwise flow non-uniformities, and (2) situations where 2-D stability theories were inadequate because of 3-D flow effects. Rotating tip clearance non-uniformity caused the greatest performance loss for shafts whirling at the rotating stall frequency. A whirling shaft displacement of 1 percent chord caused the stalling mass flow to rise by as much as 10 percent and the peak pressure rise to decrease by 6 percent. These changes were an order of magnitude larger than for equivalent-sized stationary or rotor-locked clearance asymmetries. Spanwise flow non-uniformity always destabilized the compressor, so that 2-D models over-predicted that stall margin compared to 3-D theory. The difference increased for compressors with larger spanwise variations of characteristic slope and reduced characteristic curvature near the peak. Differences between 2-D and 3-D stall point predictions were generally unacceptable (2 - 4 percent of flow coefficient) for single-stage configurations, but were less than 1 percent for multistage compressors. 2-D analyses predicted the wrong stall mode for specific cases of radial inlet flow distortion, mismatching and annulus area contraction, where higher-order radial modes led to stall. The stability behavior of flows with circumferential or radial non-uniformity was unified through a single stability criterion. The stall point for both cases was set by the integral around the annulus of the pressure rise characteristic slope, weighted by the amplitude of the mode shape. For the case of steady circumferential variations, this criterion reduced to the integrated mean slope (IMS) condition associated with steady inlet distortions. The rotating tip clearance asymmetry model was also used to demonstrate the feasibility of actively controlling the shaft position to suppress rotating stall. In axisymmetric mean flow, this method only stabilized the first harmonic mode, increasing the operating range until surge or higher harmonic modes became unstable.

High-Speed, capacitance-based tip clearance sensing

NASA Astrophysics Data System (ADS)

Haase, W. C.; Haase, Z. S.

This paper discusses recent advances in tip clearance measurement systems for turbine engines using capacitive probes. Real time measurements of individual blade pulses are generated using wideband signal processing providing 3 dB bandwidths of typically 5 MHz. Subsequent mixed-signal processing circuitry provide real-time measurements of maximum, minimum, and average clearance with latencies of one blade-to-blade time interval. Both guarded and unguarded probe configurations are possible with the system. Calibration techniques provide high accuracy measurements.

Numerical investigation of tip clearance cavitation in Kaplan runners

NASA Astrophysics Data System (ADS)

Nikiforova, K.; Semenov, G.; Kuznetsov, I.; Spiridonov, E.

2016-11-01

There is a gap between the Kaplan runner blade and the shroud that makes for a special kind of cavitation: cavitation in the tip leakage flow. Two types of cavitation caused by the presence of clearance gap are known: tip vortex cavitation that appears at the core of the rolled up vortex on the blade suction side and tip clearance cavitation that appears precisely in the gap between the blade tip edge and the shroud. In the context of this work numerical investigation of the model Kaplan runner has been performed taking into account variable tip clearance for several cavitation regimes. The focus is put on investigation of structure and origination of mechanism of cavitation in the tip leakage flow. Calculations have been performed with the help of 3-D unsteady numerical model for two-phase medium. Modeling of turbulent flow in this work has been carried out using full equations of Navier-Stokes averaged by Reynolds with correction for streamline curvature and system rotation. For description of this medium (liquid-vapor) simplification of Euler approach is used; it is based on the model of interpenetrating continuums, within the bounds of this two- phase medium considered as a quasi-homogeneous mixture with the common velocity field and continuous distribution of density for both phases. As a result, engineering techniques for calculation of cavitation conditioned by existence of tip clearance in model turbine runner have been developed. The detailed visualization of the flow was carried out and vortex structure on the suction side of the blade was reproduced. The range of frequency with maximum value of pulsation was assigned and maximum energy frequency was defined; it is based on spectral analysis of the obtained data. Comparison between numerical computation results and experimental data has been also performed. The location of cavitation zone has a good agreement with experiment for all analyzed regimes.

Numerical analysis of turbine blade tip treatments

NASA Technical Reports Server (NTRS)

Gopalaswamy, Nath S.; Whitaker, Kevin W.

1992-01-01

Three-dimensional solutions of the Navier-Stokes equations for a turbine blade with a turning angle of 180 degrees have been computed, including blade tip treatments involving cavities. The geometry approximates a preliminary design for the GGOT (Generic Gas Oxidizer Turbine). The data presented here will be compared with experimental data to be obtained from a linear cascade using original GGOT blades. Results have been computed for a blade with 1 percent clearance, based on chord, and three different cavity sizes. All tests were conducted at a Reynolds number of 4 x 10 exp 7. The grid contains 39,440 points with 10 spanwise planes in the tip clearance region of 5.008E-04 m. Streamline plots and velocity vectors together with velocity divergence plots reveal the general flow behavior in the clearance region. Blade tip temperature calculations suggest placement of a cavity close to the upstream side of the blade tip for reduction of overall blade tip temperature. The solutions do not account for the relative motion between the endwall and the turbine blade. The solutions obtained are generally consistent with previous work done in this area,

Evaluation of a Microwave Blade Tip Clearance Sensor for Propulsion Health Monitoring

NASA Technical Reports Server (NTRS)

Woike, Mark R.

2013-01-01

The NASA Glenn Research Center has investigated a microwave blade tip clearance system for the structural health monitoring of gas turbine engines. This presentation describes the sensors and the experiments that have been conducted to evaluate their performance along with future plans for their use on an engine ground test.

Supersonic cruise research aircraft structural studies: Methods and results

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, J.; Gross, D.; Kurtze, W.; Newsom, J.; Wrenn, G.; Greene, W.

1981-01-01

NASA Langley Research Center SCAR in-house structural studies are reviewed. In methods development, advances include a new system of integrated computer programs called ISSYS, progress in determining aerodynamic loads and aerodynamically induced structural loads (including those due to gusts), flutter optimization for composite and metal airframe configurations using refined and simplified mathematical models, and synthesis of active controls. Results given address several aspects of various SCR configurations. These results include flutter penalties on composite wing, flutter suppression using active controls, roll control effectiveness, wing tip ground clearance, tail size effect on flutter, engine weight and mass distribution influence on flutter, and strength and flutter optimization of new configurations. The ISSYS system of integrated programs performed well in all the applications illustrated by the results, the diversity of which attests to ISSYS' versatility.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Astrophysics Data System (ADS)

Sarma, Garimella R.; Barranger, John P.

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solution shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects for environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and a typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Astrophysics Data System (ADS)

Sarma, G. R.; Barranger, J. P.

1986-05-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solutions shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects the environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Technical Reports Server (NTRS)

Sarma, Garimella R.; Barranger, John P.

1986-01-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solution shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects for environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and a typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Technical Reports Server (NTRS)

Sarma, G. R.; Barranger, J. P.

1986-01-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solutions shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects the environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and typical application are included.

Study of tip clearance flow in a turbomachinery cascade using large eddy simulation

NASA Astrophysics Data System (ADS)

You, Donghyun

In liquid handling systems like pumps and ducted propulsors, low pressure events in the vicinity and downstream of the rotor tip gap can induce tip-leakage cavitation which leads to noise, vibration, performance loss, and erosions of blade and casing wall. In order to analyze the dynamics of the tip-clearance flow and determine the underlying mechanism for the low pressure events, a newly developed large-eddy simulation (LES) solver which combines an immersed-boundary method with a generalized curvilinear structured grid has been employed. An analysis of the LES results has been performed to understand the mean flow field, turbulence characteristics, vortex dynamics, and pressure fluctuations in the turbomachinery cascade with tip gap. In the cascade passage, the tip-leakage jet, which is generated by the pressure difference between the pressure and suction sides of the blade tip, is found to produce highly enhanced vorticity magnitude and significant levels of turbulent kinetic energy. Based on the understanding of the flow field, a guideline for reducing viscous loss in the cascade is provided. Analyses of the energy spectra and space-time correlations of the velocity fluctuations suggest that the tip-leakage vortex is subject to pitchwise wandering motion. The largest pressure drop and most intense pressure fluctuations due to the formation of the tip-leakage vortex are found at the location where the strongest portion of the tip-leakage vortex is found. Present study suggests that the tip-leakage vortex needs to be controlled in its origin to reduce cavitation in the present configuration. The effects of tip-gap size on the end-wall vortical structures and on the velocity and pressure fields have been investigated. The present analysis indicates that the mechanism for the generation of the vorticity and turbulent kinetic energy is mostly unchanged by the tip-gap size variation. However, larger tip-gap sizes are found to be more inductive to tip-leakage cavitation judged by the levels of negative mean pressure and pressure fluctuations.

Tip-leakage cavitation in the clearance of a 2D hydrofoil with fillets: high-speed visualization and PIV/PTV measurements

NASA Astrophysics Data System (ADS)

Zapryagaev, Ivan I.; Timoshevskiy, Mikhail V.; Pervunin, Konstantin S.

2017-09-01

Tip-clearance cavitation is one of the most aggressive forms of cavitation as it can cause surface erosion of hydraulic machinery elements and, as a result, their fatigue damage and disturb designed operating conditions. At present, the literature lacks for detailed experimental data on the inception and development of this type of cavitation at various flow conditions. In the paper, a tip-leakage cavitation occurring in the clearance between an end face of a 2D hydrofoil (a scaled-down model of guide vanes (GV) of a Francis turbine) and a transparent wall of the test section was studied. The experiments were carried out for different cavitating regimes on the cavitation number and two attack angles of 3° and 9°, with the gap size (tip clearance width) varied in the range from 0.4 to 0.8 mm. In order to determine the cavitation inception conditions and investigate the dynamics of the tip-leakage cavitation, a high-speed visualization was applied. A modified PIV/PTV technique with a diverging laser beam instead of a laser light sheet was used to measure the mean velocity distributions within the gap. It was shown that the cavitation pattern on the suction side of the GV model impacts the dynamics of the leakage flow in the gap but does not affect the sheet cavity formed close to the foil leading edge in the clearance as well as its size and dynamics. When the gap size is increased, the tip-leakage cavitation initiates at higher cavitation numbers or, in other words, conditions for the cavitation occurrence become more favorable.

Hover and Wind-Tunnel Testing of Shrouded Rotors for Improved Micro Air Vehicle Design

DTIC Science & Technology

2008-01-01

and the shroud surface pressure distributions. The uniformity of the wake was improved by the presence of the shrouds and by decreasing the blade tip...213 3.35 Effect of blade tip clearance on shrouded-rotor exit-plane wake profiles215 3.36 Effects of changing blade tip clearance on induced...Wright [139] developed a vortex wake model for heavily loaded ducted fans, in which the “inner vortex sheets [shed from the blades ] move at a different

An investigation of rotor tip leakage flows in the rear-block of a multistage compressor

NASA Astrophysics Data System (ADS)

Brossman, John Richard

An effective method to improve gas turbine propulsive efficiency is to increase the bypass ratio. With fan diameter reaching a practical limit, increases in bypass ratio can be obtained from reduced core engine size. Decreasing the engine core, results in small, high pressure compressor blading, and large relative tip clearances. At general rule of 1% reduction in compressor efficiency with a 1% increase in tip clearance, a 0.66% change in SFC indicates the entire engine is sensitive to high pressure compressor tip leakage flows. Therefore, further investigations and understanding of the rotor tip leakage flows can help to improve gas turbine engine efficiency. The objectives of this research were to investigate tip leakage flows through computational modeling, examine the baseline experimental steady-stage performance, and acquire unsteady static pressure, over-the rotor to observe the tip leakage flow structure. While tip leakage flows have been investigated in the past, there have been no facilities capable of matching engine representative Reynolds number and Mach number while maintaining blade row interactions, presenting a unique and original flow field to investigate at the Purdue 3-stage axial compressor facility. To aid the design of experimental hardware and determine the influence of clearance geometry on compressor performance, a computational model of the Purdue 3-stage compressor was investigated using a steady RANS CFD analysis. A cropped rotor and casing recess design was investigated to increase the rotor tip clearance. While there were small performance differences between the geometries, the tip leakage flow field was found independent of the design therefore designing future experimental hardware around a casing recess is valid. The largest clearance with flow margin past the design point was 4% tip clearance based on the computational model. The Purdue 3-stage axial compressor facility was rebuilt and setup for high quality, detailed flow measurements during this investigation. A detailed investigation and sensitivity analysis of the inlet flow field found the influence by the inlet total temperature profile was important to performance calculations. This finding was significant and original as previous investigations have been conducted on low-speed machines where there is minimal temperature rise. The steady state performance of the baseline 1.5% tip clearance case was outlined at design speed and three off-design speeds. The leakage flow from the rear seal, the inlet flow field and a thermal boundary condition over the casing was recorded at each operating point. Stage 1 was found to be the limiting stage independent of speed. Few datasets exist on multistage compressor performance with full boundary condition definitions, especially with off-design operating points presenting this as a unique dataset for CFD comparison. The detailed unsteady pressure measurements were conducted over Rotor 1 at design and a near-stall operating condition to characterize the leakage trajectory and position. The leakage flow initial point closer to the leading edge and trajectory angle increased at the higher loading condition. The over-the-rotor static pressure field on Rotor 1 indicated similar trends between the computational model and the leakage trajectory.

An on-line calibration technique for improved blade by blade tip clearance measurement

NASA Astrophysics Data System (ADS)

Sheard, A. G.; Westerman, G. C.; Killeen, B.

A description of a capacitance-based tip clearance measurement system which integrates a novel technique for calibrating the capacitance probe in situ is presented. The on-line calibration system allows the capacitance probe to be calibrated immediately prior to use, providing substantial operational advantages and maximizing measurement accuracy. The possible error sources when it is used in service are considered, and laboratory studies of performance to ascertain their magnitude are discussed. The 1.2-mm diameter FM capacitance probe is demonstrated to be insensitive to variations in blade tip thickness from 1.25 to 1.45 mm. Over typical compressor blading the probe's range was four times the variation in blade to blade clearance encountered in engine run components.

Discrete-Layer Piezoelectric Plate and Shell Models for Active Tip-Clearance Control

NASA Technical Reports Server (NTRS)

Heyliger, P. R.; Ramirez, G.; Pei, K. C.

1994-01-01

The objectives of this work were to develop computational tools for the analysis of active-sensory composite structures with added or embedded piezoelectric layers. The targeted application for this class of smart composite laminates and the analytical development is the accomplishment of active tip-clearance control in turbomachinery components. Two distinct theories and analytical models were developed and explored under this contract: (1) a discrete-layer plate theory and corresponding computational models, and (2) a three dimensional general discrete-layer element generated in curvilinear coordinates for modeling laminated composite piezoelectric shells. Both models were developed from the complete electromechanical constitutive relations of piezoelectric materials, and incorporate both displacements and potentials as state variables. This report describes the development and results of these models. The discrete-layer theories imply that the displacement field and electrostatic potential through-the-thickness of the laminate are described over an individual layer rather than as a smeared function over the thickness of the entire plate or shell thickness. This is especially crucial for composites with embedded piezoelectric layers, as the actuating and sensing elements within these layers are poorly represented by effective or smeared properties. Linear Lagrange interpolation polynomials were used to describe the through-thickness laminate behavior. Both analytic and finite element approximations were used in the plane or surface of the structure. In this context, theoretical developments are presented for the discrete-layer plate theory, the discrete-layer shell theory, and the formulation of an exact solution for simply-supported piezoelectric plates. Finally, evaluations and results from a number of separate examples are presented for the static and dynamic analysis of the plate geometry. Comparisons between the different approaches are provided when possible, and initial conclusions regarding the accuracy and limitations of these models are given.

Numerical investigation of influence of tip leakage flow on secondary flow in transonic centrifugal compressor at design condition

NASA Astrophysics Data System (ADS)

Kaneko, Masanao; Tsujita, Hoshio

2015-04-01

In a centrifugal compressor, the leakage flow through the tip clearance generates the tip leakage vortex by the interaction with the main flow, and consequently makes the flow in the impeller passage more complex by the interaction with the passage vortex. In addition, the tip leakage vortex interacts with the shock wave on the suction surface near the blade tip in the transonic centrifugal compressor impeller. Therefore, the detailed examination for the influence of the tip leakage vortex becomes seriously important to improve the aerodynamic performance especially for the transonic centrifugal compressor. In this study, the flows in the transonic centrifugal compressor with and without the tip clearance at the design condition were analyzed numerically by using the commercial CFD code. The computed results revealed that the tip leakage vortex induced by the high loading at the blade tip around the leading edge affected the loss generation by the reduction or the suppression of the shock wave on the suction surface of the blade.

Toward Understanding Tip Leakage Flows in Small Compressor Cores Including Stator Leakage Flow

NASA Technical Reports Server (NTRS)

Berdanier, Reid A.; Key, Nicole L.

2017-01-01

The focus of this work was to provide additional data to supplement the work reported in NASA/CR-2015-218868 (Berdanier and Key, 2015b). The aim of that project was to characterize the fundamental flow physics and the overall performance effects due to increased rotor tip clearance heights in axial compressors. Data have been collected in the three-stage axial research compressor at Purdue University with a specific focus on analyzing the multistage effects resulting from the tip leakage flow. Three separate rotor tip clearances were studied with nominal tip clearance gaps of 1.5 percent, 3.0 percent, and 4.0 percent based on a constant annulus height. Overall compressor performance was previously investigated at four corrected speedlines (100 percent, 90 percent, 80 percent, and 68 percent) for each of the three tip clearance configurations. This study extends the previously published results to include detailed steady and time-resolved pressure data at two loading conditions, nominal loading (NL) and high loading (HL), on the 100 percent corrected speedline for the intermediate clearance level (3.0 percent). Steady detailed radial traverses of total pressure at the exit of each stator row are supported by flow visualization techniques to identify regions of flow recirculation and separation. Furthermore, detailed radial traverses of time-resolved total pressures at the exit of each rotor row have been measured with a fast-response pressure probe. These data were combined with existing three-component velocity measurements to identify a novel technique for calculating blockage in a multistage compressor. Time-resolved static pressure measurements have been collected over the rotor tips for all rotors with each of the three tip clearance configurations for up to five loading conditions along the 100 percent corrected speedline using fast-response piezoresistive pressure sensors. These time-resolved static pressure measurements reveal new knowledge about the trajectory of the tip leakage flow through the rotor passage. Further, these data extend previous measurements identifying a modulation of the tip leakage flow due to upstream stator wake propagation. Finally, a novel instrumentation technique has been implemented to measure pressures in the shrouded stator cavities. These data provide boundary conditions relating to the flow across the shrouded stator knife seal teeth. Moreover, the utilization of fast-response pressure sensors provides a new look at the time-resolved pressure field, leading to instantaneous differential pressures across the seal teeth. Ultimately, the data collected for this project represent a unique data set which contributes to build a better understanding of the tip leakage flow field and its associated loss mechanisms. These data will facilitate future engine design goals leading to small blade heights in the rear stages of high pressure compressors and aid in the development of new blade designs which are desensitized to the performance penalties attributed to rotor tip leakage flows.

Gas turbine blade film cooling and blade tip heat transfer

NASA Astrophysics Data System (ADS)

Teng, Shuye

The detailed heat transfer coefficient and film cooling effectiveness distributions as well as the detailed coolant jet temperature profiles on the suction side of a gas turbine blade were measured using a transient liquid crystal image method and a traversing cold wire and thermocouple probe, respectively. The blade has only one row of film holes near the gill hole portion on the suction side of the blade. The hole geometries studied include standard cylindrical holes and holes with diffuser shaped exit portion (i.e. fanshaped holes and laidback fanshaped holes). Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity was 5.3 x 105. The upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The wake Strouhal number was kept at 0 and 0.1. The coolant blowing ratio was varied from 0.4 to 1.2. Results show that both expanded holes have significantly improved thermal protection over the surface downstream of the ejection location, particularly at high blowing ratios. However, the expanded hole injections induce earlier boundary layer transition to turbulence and enhance heat transfer coefficients at the latter part of the blade suction surface. In general, the unsteady wake tends to reduce film cooling effectiveness. Measurements of detailed heat transfer coefficient distributions on a turbine blade tip were performed in the same wind tunnel facility as above. The central blade had a variable tip gap clearance. Measurements were made at three different tip gap clearances of about 1.1%, 2.1%, and 3% of the blade span. Static pressure distributions were measured in the blade mid-span and on the shroud surface. Detailed heat transfer coefficient distributions were measured on the blade tip surface. Results show that reduced tip clearance leads to reduced heat transfer coefficient over the blade tip surface. Results also show that reduced tip clearance tends to weaken the unsteady wake effect on blade tip heat transfer.

Low-coherence interferometric tip-clearance probe

NASA Astrophysics Data System (ADS)

Kempe, Andreas; Schlamp, Stefan; Rösgen, Thomas; Haffner, Ken

2003-08-01

We propose an all-fiber, self-calibrating, economical probe that is capable of near-real-time, single-port, simultaneous blade-to-blade tip-clearance measurements with submillimeter accuracy (typically <100 μm, absolute) in the first stages of a gas turbine. Our probe relies on the interference between backreflected light from the blade tips during the 1-μs blade passage time and a frequency-shifted reference with variable time delay, making use of a low-coherence light source. A single optical fiber of arbitrary length connects the self-contained optics and electronics to the turbine.

Flow fields behind a variable-area nozzle for radial turbines

NASA Astrophysics Data System (ADS)

Hayami, Hiroshi; Hyun, Yong-Ik; Senoo, Yasutoshi; Yamaguchi, Michiteru

The flow fields behind a variable-area nozzle for radial turbines were measured in detail using a three-hole cobra probe in 15 cases, which are a combination of three nozzle throat areas (0.8, 1.0, and 1.4 times the rated area) and five values of the tip-clearance to blade-height ratio (between 0.0 to 0.099). The flow fields at different tip clearances are presented in contour maps, and the pitch mean values are discussed as spanwise distributions of total pressure loss, flow angle, and radial and tangential velocity components. It is shown that the intensity of swirl behind the nozzle is decreased and the pressure loss is increased with the tip clearance, and the effect is magnified as the blade loading is higher.

Research turbine for high-temperature core engine application. 2: Effect of rotor tip clearance on overall performance

NASA Technical Reports Server (NTRS)

Szanca, E. M.; Behning, F. P.; Schum, H. J.

1974-01-01

A 25.4-cm (10-in) tip diameter turbine was tested to determine the effect of rotor radial tip clearance on turbine overall performance. The test turbine was a half-scale model of a 50.8-cm-(20-in.-) diameter research turbine designed for high-temperature core engine application. The test turbine was fabricated with solid vanes and blades with no provision for cooling air and tested at much reduced inlet conditions. The tests were run at design speed over a range of pressure ratios for three different rotor clearances ranging from 2.3 to 6.7 percent of the annular blade passage height. The results obtained are compared to the results obtained with three other turbines of varying amounts of reaction.

On the development of a magnetoresistive sensor for blade tip timing and blade tip clearance measurement systems.

PubMed

Tomassini, R; Rossi, G; Brouckaert, J-F

2016-10-01

A simultaneous blade tip timing (BTT) and blade tip clearance (BTC) measurement system enables the determination of turbomachinery blade vibrations and ensures the monitoring of the existing running gaps between the blade tip and the casing. This contactless instrumentation presents several advantages compared to the well-known telemetry system with strain gauges, at the cost of a more complex data processing procedure. The probes used can be optical, capacitive, eddy current as well as microwaves, everyone with its dedicated electronics and many existing different signal processing algorithms. Every company working in this field has developed its own processing method and sensor technology. Hence, repeating the same test with different instrumentations, the answer is often different. Moreover, rarely it is possible to achieve reliability for in-service measurements. Developments are focused on innovative instrumentations and a common standard. This paper focuses on the results achieved using a novel magnetoresistive sensor for simultaneous tip timing and tip clearance measurements. The sensor measurement principle is described. The sensitivity to gap variation is investigated. In terms of measurement of vibrations, experimental investigations were performed at the Air Force Institute of Technology (ITWL, Warsaw, Poland) in a real aeroengine and in the von Karman Institute (VKI) R2 compressor rig. The advantages and limitations of the magnetoresistive probe for turbomachinery testing are highlighted.

On the development of a magnetoresistive sensor for blade tip timing and blade tip clearance measurement systems

NASA Astrophysics Data System (ADS)

Tomassini, R.; Rossi, G.; Brouckaert, J.-F.

2016-10-01

A simultaneous blade tip timing (BTT) and blade tip clearance (BTC) measurement system enables the determination of turbomachinery blade vibrations and ensures the monitoring of the existing running gaps between the blade tip and the casing. This contactless instrumentation presents several advantages compared to the well-known telemetry system with strain gauges, at the cost of a more complex data processing procedure. The probes used can be optical, capacitive, eddy current as well as microwaves, everyone with its dedicated electronics and many existing different signal processing algorithms. Every company working in this field has developed its own processing method and sensor technology. Hence, repeating the same test with different instrumentations, the answer is often different. Moreover, rarely it is possible to achieve reliability for in-service measurements. Developments are focused on innovative instrumentations and a common standard. This paper focuses on the results achieved using a novel magnetoresistive sensor for simultaneous tip timing and tip clearance measurements. The sensor measurement principle is described. The sensitivity to gap variation is investigated. In terms of measurement of vibrations, experimental investigations were performed at the Air Force Institute of Technology (ITWL, Warsaw, Poland) in a real aeroengine and in the von Karman Institute (VKI) R2 compressor rig. The advantages and limitations of the magnetoresistive probe for turbomachinery testing are highlighted.

Structural Health Monitoring on Turbine Engines Using Microwave Blade Tip Clearance Sensors

NASA Technical Reports Server (NTRS)

Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle

2014-01-01

The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA) has taken a lead role in the investigation of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. As part of this effort, microwave sensor technology has been investigated as a means of making high temperature non-contact blade tip clearance, blade tip timing, and blade vibration measurements for use in gas turbine engines. This paper presents a summary of key results and findings obtained from the evaluation of two different types of microwave sensors that have been investigated for use possible in structural health monitoring applications. The first is a microwave blade tip clearance sensor that has been evaluated on a large scale Axial Vane Fan, a subscale Turbofan, and more recently on sub-scale turbine engine like disks. The second is a novel microwave based blade vibration sensor that was also used in parallel with the microwave blade tip clearance sensors on the experiments with the sub-scale turbine engine disks.

Structural health monitoring on turbine engines using microwave blade tip clearance sensors

NASA Astrophysics Data System (ADS)

Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle

2014-04-01

The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to the aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA) has taken a lead role in the investigation of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. As part of this effort, microwave sensor technology has been investigated as a means of making high temperature non-contact blade tip clearance, blade tip timing, and blade vibration measurements for use in gas turbine engines. This paper presents a summary of key results and findings obtained from the evaluation of two different types of microwave sensors that have been investigated for possible use in structural health monitoring applications. The first is a microwave blade tip clearance sensor that has been evaluated on a large scale Axial Vane Fan, a subscale Turbofan, and more recently on sub-scale turbine engine like disks. The second is a novel microwave based blade vibration sensor that was also used in parallel with the microwave blade tip clearance sensors on the same experiments with the sub-scale turbine engine disks.

Numerical investigation & comparison of a tandem-bladed turbocharger centrifugal compressor stage with conventional design

NASA Astrophysics Data System (ADS)

Danish, Syed Noman; Qureshi, Shafiq Rehman; EL-Leathy, Abdelrahman; Khan, Salah Ud-Din; Umer, Usama; Ma, Chaochen

2014-12-01

Extensive numerical investigations of the performance and flow structure in an unshrouded tandem-bladed centrifugal compressor are presented in comparison to a conventional compressor. Stage characteristics are explored for various tip clearance levels, axial spacings and circumferential clockings. Conventional impeller was modified to tandem-bladed design with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison with conventional design. Performance degradation is observed for both the conventional and tandem designs with increase in tip clearance. Linear-equation models for correlating stage characteristics with tip clearance are proposed. Comparing two designs, it is clearly evident that the conventional design shows better performance at moderate flow rates. However; near choke flow, tandem design gives better results primarily because of the increase in throat area. Surge point flow rate also seems to drop for tandem compressor resulting in increased range of operation.

Experimental performance of a 13.65-centimeter-tip-diameter tandem-bladed sweptback centrifugal compressor designed for a pressure ratio of 6

NASA Technical Reports Server (NTRS)

Klassen, H. A.; Wood, J. R.; Schumann, L. F.

1977-01-01

A 13.65 cm tip diameter backswept centrifugal impeller having a tandem inducer and a design mass flow rate of 0.907 kg/sec was experimentally investigated to establish stage and impeller characteristics. Tests were conducted with both a cascade diffuser and a vaneless diffuser. A pressure ratio of 5.9 was obtained near surge for the smallest clearance tested. Flow range at design speed was 6.3 percent for the smallest clearance test. Impeller exit to shroud axial clearance at design speed was varied to determine the effect on stage and impeller performance.

In-place recalibration technique applied to a capacitance-type system for measuring rotor blade tip clearance

NASA Technical Reports Server (NTRS)

Barranger, J. P.

1978-01-01

The rotor blade tip clearance measurement system consists of a capacitance sensing probe with self contained tuning elements, a connecting coaxial cable, and remotely located electronics. Tests show that the accuracy of the system suffers from a strong dependence on probe tip temperature and humidity. A novel inplace recalibration technique was presented which partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction. This technique, when applied to a commercial system significantly reduced errors under varying conditions of humidity and temperature. Equations were also found that characterize the important cable and probe design quantities.

2005 NASA Seal/Secondary Air System Workshop, Volume 1

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Editor); Hendricks, Robert C. (Editor)

2006-01-01

The 2005 NASA Seal/Secondary Air System workshop covered the following topics: (i) Overview of NASA s new Exploration Initiative program aimed at exploring the Moon, Mars, and beyond; (ii) Overview of the NASA-sponsored Propulsion 21 Project; (iii) Overview of NASA Glenn s seal project aimed at developing advanced seals for NASA s turbomachinery, space, and reentry vehicle needs; (iv) Reviews of NASA prime contractor, vendor, and university advanced sealing concepts including tip clearance control, test results, experimental facilities, and numerical predictions; and (v) Reviews of material development programs relevant to advanced seals development. Turbine engine studies have shown that reducing high-pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin, and increase range. Several organizations presented development efforts aimed at developing faster clearance control systems and associated technology to meet future engine needs. The workshop also covered several programs NASA is funding to develop technologies for the Exploration Initiative and advanced reusable space vehicle technologies. NASA plans on developing an advanced docking and berthing system that would permit any vehicle to dock to any on-orbit station or vehicle. Seal technical challenges (including space environments, temperature variation, and seal-on-seal operation) as well as plans to develop the necessary "androgynous" seal technologies were reviewed. Researchers also reviewed tests completed for the shuttle main landing gear door seals.

Free-Space Oscillating Pressures Near the Tips of Rotating Propellers

NASA Technical Reports Server (NTRS)

Hubbard, Harvey H; Regier, Arthur A

1950-01-01

The theory is given for calculating the free-space oscillating pressures associated with a rotating propeller, at any point in space. Because of its complexity this analysis is convenient only for use in the critical region near the propeller tips where the assumptions used by Gutin to simplify his final equations are not valid. Good agreement was found between analytical and experimental results in the tip Mach number range 0.45 to two, three, four, five, six, on eight-blade propellers and for a range of tip clearances from 0.04 to 0.30 times the propeller diameter. If the power coefficient, tip Mach number, and the tip clearance are known for a given propeller, the designer may determine from these charts the average maximum free-space oscillating pressure in the critical region near the plane of rotation. A section of the report is devoted to the fuselage response to these oscillating pressures and indicates some of the factors to be considered in solving the problems of fuselage vibration and noise.

Analysis of middle bearing failure in rotor jet engine using tip-timing and tip-clearance techniques

NASA Astrophysics Data System (ADS)

Rzadkowski, R.; Rokicki, E.; Piechowski, L.; Szczepanik, R.

2016-08-01

The reported problem is the failure of the middle bearing in an aircraft rotor engine. Tip-timing and tip-clearance and variance analyses are carried out on a compressor rotor blade in the seventh stage above the middle bearing. The experimental analyses concern both an aircraft engine with a middle bearing in good working order and an engine with a damaged middle bearing. A numerical analysis of seventh stage blade free vibration is conducted to explain the experimental results. This appears to be an effective method of predicting middle bearing failure. The results show that variance first increases in the initial stages of bearing failure, but then starts to decrease and stabilize, and then again decrease shortly before complete bearing failure.

Reynolds-averaged Navier-Stokes computation on tip clearance flow in a compressor cascade using an unstructured grid

NASA Astrophysics Data System (ADS)

Shin, Sangmook

2001-07-01

A three-dimensional unstructured incompressible RANS code has been developed using artificial compressibility and Spalart-Allmaras eddy viscosity model. A node-based finite volume method is used in which all flow variables are defined at the vertices of tetrahedrons in an unstructured grid. The inviscid fluxes are computed by using the Roe's flux difference splitting method, and higher order accuracy is attained by data reconstruction based on Taylor series expansion. Gauss theorem is used to formulate necessary gradients. For time integration, an implicit scheme based on linearized Euler backward method is used. A tetrahedral unstructured grid generation code has been also developed and applied to the tip clearance flow in a highly staggered cascade. Surface grids are first generated in the flow passage and blade tip by using several triangulation methods including Delaunay triangulation, advancing front method and advancing layer method. Then the whole computational domain including tip gap region is filled with prisms using the surface grids. The code has been validated by comparisons with available computational and experimental results for several test cases: inviscid flow around NACA section, laminar and turbulent flow over a flat plate, turbulent flow through double-circular arc cascade and laminar flow through a square duct with 90° bend. Finally the code is applied to a linear cascade that has GE rotor B section with tip clearance and a high stagger angle of 56.9°. The overall structure of the tip clearance flow is well predicted. Loss of loading due to tip leakage flow and reloading due to tip leakage vortex are presented. On the end wall, separation line of the tip leakage vortex and reattachment line of passage vortex are identified. Prediction of such an interaction presents a challenge to RANS computations. The effects of blade span on the flow structure have been also investigated. Two cascades with blades of aspect ratios of 0.5 and 1.0 are considered. By comparing pressure distributions on the blade, it is shown that the aspect ratio has strong effects on loading distribution on the blade although the tip gap height is very small (0.016 chord). Grid convergence study has been carried out with three different grids for pressure distributions and limiting streamlines on the end wall. (Abstract shortened by UMI.)

Navier-Stokes analysis of an oxidizer turbine blade with tip clearance with and without a mini-shroud

NASA Technical Reports Server (NTRS)

Chan, Tony; Dejong, Frederik J.

1993-01-01

The Gas Generator Oxidizer Turbine (GGOT) Blade is being analyzed by various investigators under the NASA MSFC-sponsored Turbine Stage Technology Team design effort. The present work concentrates on the tip clearance region flow and associated losses; however, flow details for the passage region are also obtained in the simulations. The present calculations simulate the rotor blade row in a rotating reference frame with the appropriate coriolis and centrifugal acceleration term included in the momentum equations. The upstream computational boundary is located about one axial chord from the blade leading edge. The boundary conditions at this location have been determined by Pratt & Whitney using an Euler analysis without the vanes to obtain approximately the same flow profiles at the rotor as were obtained with the Euler stage analysis including the vanes. Inflow boundary layer profiles are then constructed assuming the skin friction coefficient at both the hub and the casing. The downstream computational boundary is located about one axial chord from the blade trailing edge, and the circumferentially averaged static pressure at this location was also obtained from the P&W Euler analysis. Results obtained for the 3-D baseline GGOT geometry at the full scale design Reynolds number show a region of high loss in the region near the casing. Particle traces in the near tip region show vortical flow behavior of the fluid which passes through the clearance region and exits at the downstream edge of the gap. In an effort to reduce clearance flow losses, the mini-shroud concept was proposed by the Pratt & Whitney design team. Calculations were performed on the GGO geometry with the mini-shroud. Results of these calculations indicate that the mini-shroud does not significantly affect the flow in the passage region, and although the tip clearance flow is different, the mini-shroud does not seem to prevent the above-mentioned vortical flow behavior. Since both flow distortion and total pressure losses are similar for both geometries, the addition of the mini-shroud does not seem to reduce the tip clearance flow effects.

CF6 jet engine diagnostics program. High pressure turbine roundness/clearance investigation

NASA Technical Reports Server (NTRS)

Howard, W. D.; Fasching, W. A.

1982-01-01

The effects of high pressure turbine clearance changes on engine and module performance was evaluated in addition to the measurement of CF6-50C high pressure turbine Stage 1 tip clearance and stator out-of-roundness during steady-state and transient operation. The results indicated a good correlation of the analytical model of round engine clearance response with measured data. The stator out-of-roundness measurements verified that the analytical technique for predicting the distortion effects of mechanical loads is accurate, whereas the technique for calculating the effects of certain circumferential thermal gradients requires some modifications. A potential for improvement in roundness was established in the order of 0.38 mm (0.015 in.), equivalent to 0.86 percent turbine efficiency which translates to a cruise SFC improvement of 0.36 percent. The HP turbine Stage 1 tip clearance performance derivative was established as 0.44 mm (17 mils) per percent of turbine efficiency at take-off power, somewhat smaller, therefore, more sensitive than predicted from previous investigations.

Energy efficient engine. Low pressure turbine test hardware detailed design report

NASA Technical Reports Server (NTRS)

Cherry, D. G.; Gay, C. H.; Lenahan, D. T.

1982-01-01

The low pressure turbine for the energy efficient engine is a five-stage configuration with moderate aerodynamic loading incorporating advanced features of decambered airfoils and extended blade overlaps at platforms and shrouds. Mechanical integrity of 18,000 hours on flowpath components and 36,000 hours on all other components is achieved along with no aeromechanical instabilities within the steady-state operating range. Selection of a large number (156) of stage 4 blades, together with an increased stage 4 vane-to-blade gap, assists in achieving FAR 36 acoustic goals. Active clearance control (ACC) of gaps at blade tips and interstage seals is achieved by fan air cooling judiciously applied at responsive locations on the casing. This ACC system is a major improvement in preventing deterioration of the 0.0381 cm (0.015 in.) clearances required to meet the integrated-core/low-spool turbine efficiency goal of 91.1% and the light propulsion system efficiency goal of 91.7%.

Turbine-blade tip clearance and tip timing measurements using an optical fiber bundle sensor

NASA Astrophysics Data System (ADS)

Garcia, Iker; Beloki, Josu; Zubia, Joseba; Durana, Gaizka; Aldabaldetreku, Gotzon

2013-04-01

Traditional limitations of capacitive, inductive or discharging probe sensor for tip timing and tip clearance measurements are overcome by reflective intensity modulated optical fiber sensors. This paper presents the signals and results corresponding to a one stage turbine rig which rotor has 146 blades, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on turbine casing. It is composed of a central illuminating fiber that guides the light from a laser to the turbine blade, and two concentric rings of receiving fibers that collect the reflected light. Two photodetectors turn this reflected light signal from the receiving rings into voltage. The electrical signals are acquired and saved by a high-sample-rate oscilloscope. In tip clearance calculations the ratio of the signals provided by each ring of receiving fibers is evaluated and translated into distance. In the case of tip timing measurements, only one of the signals is considered to get the arrival time of the blade. The differences between the real and theoretical arrival times of the blades are used to obtain the deflections amplitude. The system provides the travelling wave spectrum, which presents the average vibration amplitude of the blades at a certain nodal diameter. The reliability of the results in the turbine rig testing facilities suggests the possibility of performing these measurements in real turbines under real working conditions.

Rotary-Wing Relevant Compressor Aero Research and Technology Development Activities at Glenn Research Center

NASA Technical Reports Server (NTRS)

Welch, Gerard E.; Hathaway, Michael D.; Skoch, Gary J.; Snyder, Christopher A.

2012-01-01

Technical challenges of compressors for future rotorcraft engines are driven by engine-level and component-level requirements. Cycle analyses are used to highlight the engine-level challenges for 3000, 7500, and 12000 SHP-class engines, which include retention of performance and stability margin at low corrected flows, and matching compressor type, axial-flow or centrifugal, to the low corrected flows and high temperatures in the aft stages. At the component level: power-to-weight and efficiency requirements impel designs with lower inherent aerodynamic stability margin; and, optimum engine overall pressure ratios lead to small blade heights and the associated challenges of scale, particularly increased clearance-to-span ratios. The technical challenges associated with the aerodynamics of low corrected flows and stability management impel the compressor aero research and development efforts reviewed herein. These activities include development of simple models for clearance sensitivities to improve cycle calculations, full-annulus, unsteady Navier-Stokes simulations used to elucidate stall, its inception, and the physics of stall control by discrete tip-injection, development of an actuator-duct-based model for rapid simulation of nonaxisymmetric flow fields (e.g., due inlet circumferential distortion), advanced centrifugal compressor stage development and experimentation, and application of stall control in a T700 engine.

Blade tip clearance measurement of the turbine engines based on a multi-mode fiber coupled laser ranging system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Haotian; Duan, Fajie; Wu, Guoxiu

2014-11-15

The blade tip clearance is a parameter of great importance to guarantee the efficiency and safety of the turbine engines. In this article, a laser ranging system designed for blade tip clearance measurement is presented. Multi-mode fiber is utilized for optical transmission to guarantee that enough optical power is received by the sensor probe. The model of the tiny sensor probe is presented. The error brought by the optical path difference of different modes of the fiber is estimated and the length of the fiber is limited to reduce this error. The measurement range in which the optical power receivedmore » by the probe remains essentially unchanged is analyzed. Calibration experiments and dynamic experiments are conducted. The results of the calibration experiments indicate that the resolution of the system is about 0.02 mm and the range of the system is about 9 mm.« less

Distributed collaborative probabilistic design for turbine blade-tip radial running clearance using support vector machine of regression

NASA Astrophysics Data System (ADS)

Fei, Cheng-Wei; Bai, Guang-Chen

2014-12-01

To improve the computational precision and efficiency of probabilistic design for mechanical dynamic assembly like the blade-tip radial running clearance (BTRRC) of gas turbine, a distribution collaborative probabilistic design method-based support vector machine of regression (SR)(called as DCSRM) is proposed by integrating distribution collaborative response surface method and support vector machine regression model. The mathematical model of DCSRM is established and the probabilistic design idea of DCSRM is introduced. The dynamic assembly probabilistic design of aeroengine high-pressure turbine (HPT) BTRRC is accomplished to verify the proposed DCSRM. The analysis results reveal that the optimal static blade-tip clearance of HPT is gained for designing BTRRC, and improving the performance and reliability of aeroengine. The comparison of methods shows that the DCSRM has high computational accuracy and high computational efficiency in BTRRC probabilistic analysis. The present research offers an effective way for the reliability design of mechanical dynamic assembly and enriches mechanical reliability theory and method.

2007 NASA Seal/Secondary Air System Workshop. Volume 1

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Hendricks, Robert C.; Delgado, Irebert

2008-01-01

The 2007 NASA Seal/Secondary Air System workshop covered the following topics: (i) Overview of NASA's new Orion project aimed at developing a new spacecraft that will fare astronauts to the International Space Station, the Moon, Mars, and beyond; (ii) Overview of NASA's fundamental aeronautics technology project; (iii) Overview of NASA Glenn s seal project aimed at developing advanced seals for NASA's turbomachinery, space, and reentry vehicle needs; (iv) Reviews of NASA prime contractor, vendor, and university advanced sealing concepts, test results, experimental facilities, and numerical predictions; and (v) Reviews of material development programs relevant to advanced seals development. Turbine engine studies have shown that reducing seal leakage as well as high-pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin, and increase range. Turbine seal development topics covered include a method for fast-acting HPT blade tip clearance control, noncontacting low-leakage seals, intershaft seals, and a review of engine seal performance requirements for current and future Army engine platforms.

2008 NASA Seal/Secondary Air System Workshop

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Editor); Hendricks, Robert C. (Editor); Delgado, Irebert R. (Editor)

2009-01-01

The 2008 NASA Seal/Secondary Air System Workshop covered the following topics: (i) Overview of NASA s new Orion project aimed at developing a new spacecraft that will fare astronauts to the International Space Station, the Moon, Mars, and beyond; (ii) Overview of NASA s fundamental aeronautics technology project; (iii) Overview of NASA Glenn s seal project aimed at developing advanced seals for NASA s turbomachinery, space, and reentry vehicle needs; (iv) Reviews of NASA prime contractor, vendor, and university advanced sealing concepts, test results, experimental facilities, and numerical predictions; and (v) Reviews of material development programs relevant to advanced seals development. Turbine engine studies have shown that reducing seal leakage as well as high-pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin, and increase range. Turbine seal development topics covered include a method for fast-acting HPT blade tip clearance control, noncontacting low-leakage seals, intershaft seals, and a review of engine seal performance requirements for current and future Army engine platforms.

2006 NASA Seal/Secondary Air System Workshop; Volume 1

NASA Technical Reports Server (NTRS)

Steinetz, Bruce, M. (Editor); Hendricks, Robert C. (Editor); Delgado, Irebert (Editor)

2007-01-01

The 2006 NASA Seal/Secondary Air System workshop covered the following topics: (i) Overview of NASA s new Exploration Initiative program aimed at exploring the Moon, Mars, and beyond; (ii) Overview of NASA s new fundamental aeronautics technology project; (iii) Overview of NASA Glenn Research Center s seal project aimed at developing advanced seals for NASA s turbomachinery, space, and reentry vehicle needs; (iv) Reviews of NASA prime contractor, vendor, and university advanced sealing concepts including tip clearance control, test results, experimental facilities, and numerical predictions; and (v) Reviews of material development programs relevant to advanced seals development. Turbine engine studies have shown that reducing seal leakages as well as high-pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin, and increase range. Several organizations presented development efforts aimed at developing faster clearance control systems and associated technology to meet future engine needs. The workshop also covered several programs NASA is funding to develop technologies for the Exploration Initiative and advanced reusable space vehicle technologies. NASA plans on developing an advanced docking and berthing system that would permit any vehicle to dock to any on-orbit station or vehicle. Seal technical challenges (including space environments, temperature variation, and seal-on-seal operation) as well as plans to develop the necessary "androgynous" seal technologies were reviewed. Researchers also reviewed seal technologies employed by the Apollo command module that serve as an excellent basis for seals for NASA s new Crew Exploration Vehicle (CEV).

Investigation of tip clearance flow physics in axial flow turbine rotors

NASA Astrophysics Data System (ADS)

Xiao, Xinwen

In axial turbines, the tip clearance between casing wall and rotating blades results in a tip leakage flow, which significantly affects loss production, heat protection, vibration and noise. It is important to minimize these effects for a better turbine engine performance and higher reliability. Most of previous efforts were concentrated on turbine cascades that however may not completely and correctly simulate the flow physics in practical turbine rotors. An investigation has to be performed in turbine rotors to reveal the real tip leakage flow physics in order to provide a scientific basis for minimizing its effects. This is the objective of this thesis research. The three dimensional flow field near the end wall/tip clearance region in a turbine rotor has been investigated experimentally, complemented by a numerical simulation to study the influences of inlet turbulence intensities on the development of the tip leakage flow. The experimental investigation is carried out in a modern unshrouded high pressure turbine stage. The survey region covers 20% span near the end wall, and extends axially from 10% chord upstream of the leading edge, through the rotor passage, and to 20% chord downstream of the trailing edge. It has been found that the tip leakage effects extend only to the surveyed region. The three dimensional LDV technique is used to measure the velocity and turbulence field upstream of the rotor, inside the rotor passage, and near the trailing edge. The static pressure on blade surfaces is surveyed from the rotating frame. The transient pressure on the casing wall is measured using a dynamic pressure sensor with a shaft encoder. A rotating Five Hole Probe is employed to measure the losses as well as the pressure and the three dimensional velocity field at 20% chord downstream of the rotor. The unsteady flow field is also investigated at this location by using a slanted single-element Hot Wire technique. The physics of the tip leakage flow and vortex in turbine rotors, including its inception location, development, interaction with the main stream and the passage vortex, and decay, are revealed. The rotation effects on the boundary layer flow and the turbulence structure are discussed. The effects of the relative motion between the blade and the casing wall on the flow field near the tip clearance region are also investigated. The structure of the rotor wake, the nozzle wake, and their interaction are interpreted based on the instantaneous Hot Wire data. The numerical simulation on the influence of the inlet turbulence intensity on the development of the tip leakage flow is based on previous efforts. The results indicate that the tip leakage vortex diffuses very quickly under a high inlet turbulence intensity, resulting in a very weak tip leakage vortex and less losses.

Investigation of Turbulent Tip Leakage Vortex in an Axial Water Jet Pump with Large Eddy Simulation

NASA Technical Reports Server (NTRS)

Hah, Chunill; Katz, Joseph

2012-01-01

Detailed steady and unsteady numerical studies were performed to investigate tip clearance flow in an axial water jet pump. The primary objective is to understand physics of unsteady tip clearance flow, unsteady tip leakage vortex, and cavitation inception in an axial water jet pump. Steady pressure field and resulting steady tip leakage vortex from a steady flow analysis do not seem to explain measured cavitation inception correctly. The measured flow field near the tip is unsteady and measured cavitation inception is highly transient. Flow visualization with cavitation bubbles shows that the leakage vortex is oscillating significantly and many intermittent vortex ropes are present between the suction side of the blade and the tip leakage core vortex. Although the flow field is highly transient, the overall flow structure is stable and a characteristic frequency seems to exist. To capture relevant flow physics as much as possible, a Reynolds-averaged Navier-Stokes (RANS) calculation and a Large Eddy Simulation (LES) were applied for the current investigation. The present study reveals that several vortices from the tip leakage vortex system cross the tip gap of the adjacent blade periodically. Sudden changes in local pressure field inside tip gap due to these vortices create vortex ropes. The instantaneous pressure filed inside the tip gap is drastically different from that of the steady flow simulation. Unsteady flow simulation which can calculate unsteady vortex motion is necessary to calculate cavitation inception accurately even at design flow condition in such a water jet pump.

A Probabilistic System Analysis of Intelligent Propulsion System Technologies

NASA Technical Reports Server (NTRS)

Tong, Michael T.

2007-01-01

NASA s Intelligent Propulsion System Technology (Propulsion 21) project focuses on developing adaptive technologies that will enable commercial gas turbine engines to produce fewer emissions and less noise while increasing reliability. It features adaptive technologies that have included active tip-clearance control for turbine and compressor, active combustion control, turbine aero-thermal and flow control, and enabling technologies such as sensors which are reliable at high operating temperatures and are minimally intrusive. A probabilistic system analysis is performed to evaluate the impact of these technologies on aircraft CO2 (directly proportional to fuel burn) and LTO (landing and takeoff) NO(x) reductions. A 300-passenger aircraft, with two 396-kN thrust (85,000-pound) engines is chosen for the study. The results show that NASA s Intelligent Propulsion System technologies have the potential to significantly reduce the CO2 and NO(x) emissions. The results are used to support informed decisionmaking on the development of the intelligent propulsion system technology portfolio for CO2 and NO(x) reductions.

Numerical simulation of steady and unsteady viscous flow in turbomachinery using pressure based algorithm

NASA Astrophysics Data System (ADS)

Lakshminarayana, B.; Ho, Y.; Basson, A.

1993-07-01

The objective of this research is to simulate steady and unsteady viscous flows, including rotor/stator interaction and tip clearance effects in turbomachinery. The numerical formulation for steady flow developed here includes an efficient grid generation scheme, particularly suited to computational grids for the analysis of turbulent turbomachinery flows and tip clearance flows, and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, and is applicable to both viscous and inviscid flows. The values of these artificial dissipation is optimized to achieve accuracy and convergency in the solution. The numerical model is used to investigate the structure of tip clearance flows in a turbine nozzle. The structure of leakage flow is captured accurately, including blade-to-blade variation of all three velocity components, pitch and yaw angles, losses and blade static pressures in the tip clearance region. The simulation also includes evaluation of such quantities of leakage mass flow, vortex strength, losses, dominant leakage flow regions and the spanwise extent affected by the leakage flow. It is demonstrated, through optimization of grid size and artificial dissipation, that the tip clearance flow field can be captured accurately. The above numerical formulation was modified to incorporate time accurate solutions. An inner loop iteration scheme is used at each time step to account for the non-linear effects. The computation of unsteady flow through a flat plate cascade subjected to a transverse gust reveals that the choice of grid spacing and the amount of artificial dissipation is critical for accurate prediction of unsteady phenomena. The rotor-stator interaction problem is simulated by starting the computation upstream of the stator, and the upstream rotor wake is specified from the experimental data. The results show that the stator potential effects have appreciable influence on the upstream rotor wake. The predicted unsteady wake profiles are compared with the available experimental data and the agreement is good. The numerical results are interpreted to draw conclusions on the unsteady wake transport mechanism in the blade passage.

Effect of tip clearance on performance of small axial hydraulic turbine

NASA Technical Reports Server (NTRS)

Boynton, J. L.; Rohlik, H. E.

1976-01-01

The first two stages of a six stage liquid oxygen turbine were tested in water. One and two stage performance was determined for one shrouded and two unshrouded blade end configurations over ranges of clearance and blade-jet speed ratio. First stage, two stage, and second stage efficiencies are included as well as the effect of clearance on mass flow for two stage operation.

Experimental analysis of the flow in a two stage axial compressor at off-design conditions

NASA Astrophysics Data System (ADS)

Massardo, Aristide; Satta, Antonio

1987-05-01

The experimental analysis of the flow that develops in a two-stage axial flow compressor at off-design conditions is presented. The measurements are performed upstream, between, and downstream of the four blade rows of the compressor. The analysis shows the off-design effects on the local conditions of the flow field. Low-energy flow zones are identified, and the development of annulus-boundary-layer, secondary, and tip-clearance flows is shown. The tip-clearance flows are also present in the stator rows with various outlying conditions (stationary or rotating hub).

Effects of Impeller-Diffuser Interaction on Centrifugal Compressor Performance

NASA Technical Reports Server (NTRS)

Tan, Choon S.

2003-01-01

This research program focuses on characterizing the effect of impeller-diffuser interactions in a centrifugal compressor stage on its performance using unsteady threedimensional Reynolds-averaged Navier-Stokes simulations. The computed results show that the interaction between the downstream diffuser pressure field and the impeller tip clearance flow can account for performance changes in the impeller. The magnitude of performance change due to this interaction was examined for an impeller with varying tip clearance followed by a vaned or vaneless diffuser. The impact of unsteady impeller-diffuser interaction, primarily through the impeller tip clearance flow, is reflected through a time-averaged change in impeller loss, blockage and slip. The results show that there exists a tip clearance where the beneficial effect of the impeller-diffuser interaction on the impeller performance is at a maximum. A flow feature that consists of tip flow back leakage was shown to occur at design speed for the centrifugal compressor stage. This flow phenomenon is described as tip flow that originates in one passage, flows downstream of the impeller trailing edge and then returns to upstream of the impeller trailing edge of a neighboring passage. Such a flow feature is a source of loss in the impeller. A hypothesis is put forth to show that changing the diffuser vane count and changing impeller-diffuser gap has an analogous effect on the impeller performance. The centrifugal compressor stage was analyzed using diffusers of different vane counts, producing an impeller performance trend similar to that when the impeller-diffuser gap was varied, thus supporting the hypothesis made. This has the implication that the effect impeller performance associated with changing the impeller-diffuser gap and changing diffuser vane count can be described by the non-dimensional ratio of impeller-diffuser gap to diffuser vane pitch. A procedure is proposed and developed for isolating impeller passage blockage change without the need to define the region of blockage generation (which may incur a certain degree of arbitrariness). This method has been assessed for its applicability and utility.

Boeing 18-Inch Fan Rig Broadband Noise Test

NASA Technical Reports Server (NTRS)

Ganz, Ulrich W.; Joppa, Paul D.; Patten, Timothy J.; Scharpf, Daniel F.

1998-01-01

The purposes of the subject test were to identify and quantify the mechanisms by which fan broadband noise is produced, and to assess the validity of such theoretical models of those mechanisms as may be available. The test was conducted with the Boeing 18-inch fan rig in the Boeing Low-Speed Aeroacoustic Facility (LSAF). The rig was designed to be particularly clean and geometrically simple to facilitate theoretical modeling and to minimize sources of interfering noise. The inlet is cylindrical and is equipped with a boundary layer suction system. The fan is typical of modern high-by-pass ratio designs but is capable of operating with or without fan exit guide vanes (stators), and there is only a single flow stream. Fan loading and tip clearance are adjustable. Instrumentation included measurements of fan performance, the unsteady flow field incident on the fan and stators, and far-field and in-duct acoustic fields. The acoustic results were manipulated to estimate the noise generated by different sources. Significant fan broadband noise was found to come from the rotor self-noise as measured with clean inflow and no boundary layer. The rotor tip clearance affected rotor self-noise somewhat. The interaction of the rotor with inlet boundary layer turbulence is also a significant source, and is strongly affected by rotor tip clearance. High level noise can be generated by a high-order nonuniform rotating at a fraction of the fan speed, at least when tip clearance and loading are both large. Stator-generated noise is the loudest of the significant sources, by a small margin, at least on this rig. Stator noise is significantly affected by propagation through the fan.

Numerical Analysis of the Acoustic Field of Tip-Clearance Flow

NASA Astrophysics Data System (ADS)

Alavi Moghadam, S. M.; M. Meinke Team; W. Schröder Team

2015-11-01

Numerical simulations of the acoustic field generated by a shrouded axial fan are studied by a hybrid fluid-dynamics-acoustics method. In a first step, large-eddy simulations are performed to investigate the dynamics of tip clearance flow for various tip gap sizes and to determine the acoustic sources. The simulations are performed for a single blade out of five blades with periodic boundary conditions in the circumferential direction on a multi-block structured mesh with 1.4 ×108 grid points. The turbulent flow is simulated at a Reynolds number of 9.36 ×105 at undisturbed inflow condition and the results are compared with experimental data. The diameter and strength of the tip vortex increase with the tip gap size, while simultaneously the efficiency of the fan decreases. In a second step, the acoustic field on the near field is determined by solving the acoustic perturbation equations (APE) on a mesh for a single blade consisting of approx. 9.8 ×108 grid points. The overall agreement of the pressure spectrum and its directivity with measurements confirm the correct identification of the sound sources and accurate prediction of the acoustic duct propagation. The results show that the longer the tip gap size the higher the broadband noise level. Senior Scientist, Institute of Aerodynamics, RWTH Aachen University.

Study of the capacitance technique for measuring high-temperature blade tip clearance on ceramic rotors

NASA Technical Reports Server (NTRS)

Barranger, John P.

1993-01-01

Higher operating temperatures required for increased engine efficiency can be achieved by using ceramic materials for engine components. Ceramic turbine rotors are subject to the same limitations with regard to gas path efficiency as their superalloy predecessors. In this study, a modified frequency-modulation system is proposed for the measurement of blade tip clearance on ceramic rotors. It is expected to operate up to 1370 C (2500 F), the working temperature of present engines with ceramic turbine rotors. The design of the system addresses two special problems associated with nonmetallic blades: the capacitance is less than that of a metal blade and the effects of temperature may introduce uncertainty with regard to the blade tip material composition. To increase capacitance and stabilize the measurement, a small portion of the rotor is modified by the application of 5-micron-thick platinum films. The platinum surfaces on the probe electrodes and rotor that are exposed to the high-velocity gas stream are coated with an additional 10-micron-thick protective ceramic topcoat. A finite-element method is applied to calculate the capacitance as a function of clearance.

76 FR 78081 - Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-15

... examination of returns filed by tipped employees large food or beverage establishments are required to report annually information concerning food or beverage operations receipts, tips, reported by employees, and in... Management and Budget (OMB) for review and clearance in accordance with the Paperwork Reduction Act of 1995...

Novel sensors to enable closed-loop active clearance control in gas turbine engines

NASA Astrophysics Data System (ADS)

Geisheimer, Jonathan; Holst, Tom

2014-06-01

Active clearance control within the turbine section of gas turbine engines presents and opportunity within aerospace and industrial applications to improve operating efficiencies and the life of downstream components. Open loop clearance control is currently employed during the development of all new large core aerospace engines; however, the ability to measure the gap between the blades and the case and close down the clearance further presents as opportunity to gain even greater efficiencies. The turbine area is one of the harshest environments for long term placement of a sensor in addition to the extreme accuracy requirements required to enable closed loop clearance control. This paper gives an overview of the challenges of clearance measurements within the turbine as well as discusses the latest developments of a microwave sensor designed for this application.

Small axial compressor technology, volume 1

NASA Technical Reports Server (NTRS)

Holman, F. F.; Kidwell, J. R.; Ware, T. C.

1976-01-01

A scaled single-stage, highly-loaded, axial-flow transonic compressor was tested at speeds from 70 to 110% design equivalent speed to evaluate the effects of scaling compromises and the individual and combined effects of rotor tip running clearance and rotor shroud casing treatment on the overall and blade element performance. At design speed and 1% tip clearance the stage demonstrated an efficiency of 83.2% at 96.4% design flow and a pressure ratio of 1.865. Casing treatment increased design speed surge margin 2.0 points to 12.8%. Overall performance was essentially unchanged. An increase in rotor running clearance to 2.2%, with smooth casing, reduced design speed peak efficiency 5.7 points, flow by 7.4%, pressure ratio to 1.740, and surge margin to 5.4%. Reinstalling casing treatment regained 3.5 points in design speed peak efficiency, 4.7% flow, increased pressure ratio to 1.800 and surge margin to 8.7%.

A Visualization Study of Secondary Flows in Cascades

NASA Technical Reports Server (NTRS)

Herzig, Howard Z; Hansen, Arthur G; Costello, George R

1954-01-01

Flow-visualization techniques are employed to ascertain the streamline patterns of the nonpotential secondary flows in the boundary layers of cascades, and thereby to provide a basis for more extended analyses in turbomachines. The three-dimensional deflection of the end-wall boundary layer results in the formation of a vortex within each cascade passage. The size and tightness of the vortex generated depend upon the main-flow turning in the cascade passage. Once formed, a vortex resists turning in subsequent blade rows, with consequent unfavorable angles of attack and possible flow disturbances on the pressure surfaces of subsequent blade rows when the vortices impinge on these surfaces. Two major tip-clearance effects are observed, the formation of a tip-clearance vortex and the scraping effect of a blade with relative motion past the wall boundary layer. The flow patterns indicate methods for improving the blade tip-loading characteristics of compressors and of low- and high-speed turbulence.

Optimization of an Active Twist Rotor Blade Planform for Improved Active Response and Forward Flight Performance

NASA Technical Reports Server (NTRS)

Sekula, Martin K; Wilbur, Matthew L.

2014-01-01

A study was conducted to identify the optimum blade tip planform for a model-scale active twist rotor. The analysis identified blade tip design traits which simultaneously reduce rotor power of an unactuated rotor while leveraging aeromechanical couplings to tailor the active response of the blade. Optimizing the blade tip planform for minimum rotor power in forward flight provided a 5 percent improvement in performance compared to a rectangular blade tip, but reduced the vibration control authority of active twist actuation by 75 percent. Optimizing for maximum blade twist response increased the vibration control authority by 50 percent compared to the rectangular blade tip, with little effect on performance. Combined response and power optimization resulted in a blade tip design which provided similar vibration control authority to the rectangular blade tip, but with a 3.4 percent improvement in rotor performance in forward flight.

JT9D performance deterioration results from a simulated aerodynamic load test

NASA Technical Reports Server (NTRS)

Stakolich, E. G.; Stromberg, W. J.

1981-01-01

The results of testing to identify the effects of simulated aerodynamic flight loads on JT9D engine performance are presented. The test results were also used to refine previous analytical studies on the impact of aerodynamic flight loads on performance losses. To accomplish these objectives, a JT9D-7AH engine was assembled with average production clearances and new seals as well as extensive instrumentation to monitor engine performance, case temperatures, and blade tip clearance changes. A special loading device was designed and constructed to permit application of known moments and shear forces to the engine by the use of cables placed around the flight inlet. The test was conducted in the Pratt & Whitney Aircraft X-Ray Test Facility to permit the use of X-ray techniques in conjunction with laser blade tip proximity probes to monitor important engine clearance changes. Upon completion of the test program, the test engine was disassembled, and the condition of gas path parts and final clearances were documented. The test results indicate that the engine lost 1.1 percent in thrust specific fuel consumption (TSFC), as measured under sea level static conditions, due to increased operating clearances caused by simulated flight loads. This compares with 0.9 percent predicted by the analytical model and previous study efforts.

Integrated fiber optic light probe: Measurement of static deflections in rotating turbomachinery

NASA Astrophysics Data System (ADS)

Dhadwal, Harbans S.; Mehmud, Ali; Khan, Romel; Kurkov, Anatole

1996-02-01

This paper describes the design, fabrication, and testing of an integrated fiber optic light probe system for monitoring blade tip deflections, vibrational modes, and changes in blade tip clearances in the compressor stage of rotating turbomachinery. The system comprises a set of integrated fiber optic light probes which are positioned to detect the passing blade tip at the leading and the trailing edges. In this configuration measurements of both blade vibrations and steady-state blade deflection can be obtained from the timing information provided by each light probe, which comprises an integrated fiber optic transmitting channel and a number of high numerical aperture receiving fibers, all mounted in the same cylindrical housing. A spatial resolution of 50 μm is possible with the integrated fiber optic technology, while keeping the outer diameter below 2.5 mm. Additionally, one fiber sensor provides a capability of monitoring changes in the blade tip clearance of the order of 10 μm. Measurements from a single stage compressor facility and an engine-fan rig in a 9 ft×15 ft subsonic wind tunnel are presented.

Energy Efficient Engine: High-pressure compressor test hardware detailed design report

NASA Technical Reports Server (NTRS)

Howe, David C.; Marchant, R. D.

1988-01-01

The objective of the NASA Energy Efficient Engine program is to identify and verify the technology required to achieve significant reductions in fuel consumption and operating cost for future commercial gas turbine engines. The design and analysis is documented of the high pressure compressor which was tested as part of the Pratt and Whitney effort under the Energy Efficient Engine program. This compressor was designed to produce a 14:1 pressure ratio in ten stages with an adiabatic efficiency of 88.2 percent in the flight propulsion system. The corresponding expected efficiency for the compressor component test rig is 86.5 percent. Other performance goals are a surge margin of 20 percent, a corrected flow rate of 35.2 kg/sec (77.5 lb/sec), and a life of 20,000 missions and 30,000 hours. Low loss, highly loaded airfoils are used to increase efficiency while reducing the parts count. Active clearance control and case trenches in abradable strips over the blade tips are included in the compressor component design to further increase the efficiency potential. The test rig incorporates variable geometry stator vanes in all stages to permit maximum flexibility in developing stage-to-stage matching. This provision precluded active clearance control on the rear case of the test rig. Both the component and rig designs meet or exceed design requirements with the exception of life goals, which will be achievable with planned advances in materials technology.

In-situ position and vibration measurement of rough surfaces using laser Doppler distance sensors

NASA Astrophysics Data System (ADS)

Czarske, J.; Pfister, T.; Günther, P.; Büttner, L.

2009-06-01

In-situ measurement of distances and shapes as well as dynamic deformations and vibrations of fast moving and especially rotating objects, such as gear shafts and turbine blades, is an important task at process control. We recently developed a laser Doppler distance frequency sensor, employing two superposed fan-shaped interference fringe systems with contrary fringe spacing gradients. Via two Doppler frequency evaluations the non-incremental position (i.e. distance) and the tangential velocity of rotating bodies are determined simultaneously. The distance uncertainty is in contrast to e.g. triangulation in principle independent of the object velocity. This unique feature allows micrometer resolutions of fast moved rough surfaces. The novel sensor was applied at turbo machines in order to control the tip clearance. The measurements at a transonic centrifugal compressor were performed during operation at up to 50,000 rpm, i.e. 586 m/s velocity of the blade tips. Due to the operational conditions such as temperatures of up to 300 °C, a flexible and robust measurement system with a passive fiber-coupled sensor, using diffractive optics, has been realized. Since the tip clearance of individual blades could be temporally resolved an analysis of blade vibrations was possible. A Fourier transformation of the blade distances results in an average period of 3 revolutions corresponding to a frequency of 1/3 of the rotary frequency. Additionally, a laser Doppler distance sensor using two tilted fringe systems and phase evaluation will be presented. This phase sensor exhibits a minimum position resolution of σz = 140 nm. It allows precise in-situ shape measurements at grinding and turning processes.

Techniques for blade tip clearance measurements with capacitive probes

NASA Astrophysics Data System (ADS)

Steiner, Alexander

2000-07-01

This article presents a proven but advantageous concept for blade tip clearance evaluation in turbomachinery. The system is based on heavy duty probes and a high frequency (HF) and amplifying electronic unit followed by a signal processing unit. Measurements are taken under high temperature and other severe conditions such as ionization. Every single blade can be observed. The signals are digitally filtered and linearized in real time. The electronic set-up is highly integrated. Miniaturized versions of the electronic units exist. The small and robust units can be used in turbo engines in flight. With several probes at different angles in one radial plane further information is available. Shaft eccentricity or blade oscillations can be calculated.

Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade

NASA Technical Reports Server (NTRS)

Azad, Gm S.; Han, Je-Chin; Boyle, Robert J.

2000-01-01

Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modem first stage gas turbine rotor blade with a blade tip profile of a GE-E(sup 3) aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1 x 10(exp 6). A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. 'Me heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1 % case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.

Intelligent Engine Systems: HPT Clearance Control

NASA Technical Reports Server (NTRS)

2008-01-01

The Advanced Thermally Actuated Clearance Control System underwent several studies. Improved flow path isolation quantified what can be gained by making the HPT case nearly adiabatic. The best method of heat transfer was established, and finally two different borrowed air cooling circuits were evaluated to be used for the HPT Active Clearance Control System.

Emergency Department Medical Clearance of Patients with Psychiatric or Behavioral Emergencies, Part 1.

PubMed

Tucci, Veronica Theresa; Moukaddam, Nidal; Alam, Al; Rachal, James

2017-09-01

Patients presenting to the emergency department with mental illness or behavioral complaints merit workup for underlying physical conditions that can trigger, mimic, or worsen psychiatric symptoms. However, interdisciplinary consensus on medical clearance is lacking, leading to wide variations in quality of care and, quite often, poor medical care. Psychiatry and emergency medicine specialty guidelines support a tailored, customized approach. This article summarizes best-practice approaches to the medical clearance of patients with psychiatric illness, tips on history taking, system reviews, clinical or physical examination, and common pitfalls in the medical clearance process. Copyright © 2017 Elsevier Inc. All rights reserved.

Performance of a Splittered Transonic Rotor with Several Tip Clearances

DTIC Science & Technology

2015-06-15

θ Ratio of inlet to reference pressure and γ [-] ρ Density [kg/m3] ω Humidity ratio [-] Subscripts 1 Inlet 3 Outlet a Air gas l Water liquid ...has a large influence on the performance and efficiency of compressors and fans during operation. In a gas turbine engine the ratio of tip-gap to...of compressors and fans during operation. In a gas turbine engine the ratio of tip-gap to blade height or span usually increases in the direction of

A Microwave Blade Tip Clearance Sensor for Propulsion Health Monitoring

NASA Technical Reports Server (NTRS)

Woike, Mark R.; Abdul-Aziz, Ali; Bencic, Timothy J.

2010-01-01

Microwave sensor technology is being investigated by the NASA Glenn Research Center as a means of making non-contact structural health measurements in the hot sections of gas turbine engines. This type of sensor technology is beneficial in that it is accurate, it has the ability to operate at extremely high temperatures, and is unaffected by contaminants that are present in turbine engines. It is specifically being targeted for use in the High Pressure Turbine (HPT) and High Pressure Compressor (HPC) sections to monitor the structural health of the rotating components. It is intended to use blade tip clearance to monitor blade growth and wear and blade tip timing to monitor blade vibration and deflection. The use of microwave sensors for this application is an emerging concept. Techniques on their use and calibration needed to be developed. As a means of better understanding the issues associated with the microwave sensors, a series of experiments have been conducted to evaluate their performance for aero engine applications. This paper presents the results of these experiments.

78 FR 22020 - Agency Information Collection Activities: Requests for Comments; Clearance of New Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-12

... Control Number: 2120-XXXX. Title: Safety Awareness, Feedback, and Evaluation (SAFE) Program. Form Numbers: No FAA forms are associated with this collection. Type of Review: Clearance of a new information... Activities: Requests for Comments; Clearance of New Approval of Information Collection: Safety Awareness...

Further Characterization of an Active Clearance Control Concept

NASA Technical Reports Server (NTRS)

Taylor, Shawn C.; Steinetz, Bruce M.; Oswald, Jay J.

2007-01-01

A new test chamber and precision hydraulic actuation system were incorporated into an active clearance control (ACC) test rig at NASA Glenn Research Center. Using the improved system, a fast-acting, mechanically-actuated, ACC concept was evaluated at engine simulated temperatures and pressure differentials up to 1140 F and 120 psig, on the basis of secondary seal leakage and kinematic controllability. During testing, the ACC concept tracked a simulated flight clearance transient profile at 1140 F, 120 psig, with a maximum error of only 0.0012 in. Comparison of average dynamic leakage of the system with average static leakage did not show significant differences between the two operating conditions. Calculated effective clearance values for the rig were approximately 0.0002 in. at 120 psig, well below the industry specified effective clearance threshold of 0.001 in.

Progress on Shape Memory Alloy Actuator Development for Active Clearance Control

NASA Technical Reports Server (NTRS)

DeCastro, Jonathan; Melcher, Kevin; Noebe, Ronald

2006-01-01

Results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine has been conducted. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 in. Design results show that an actuator comprised of 10 wires 2 in. in length is adequate for control at critical engine operating points and still exhibit acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

Emergency Department Medical Clearance of Patients with Psychiatric or Behavioral Emergencies, Part 2: Special Psychiatric Populations and Considerations.

PubMed

Alam, Al; Rachal, James; Tucci, Veronica Theresa; Moukaddam, Nidal

2017-09-01

Patients who present to the emergency department (ED) with mental illness or behavioral complaints merit workup for underlying physical conditions that can trigger, mimic, or worsen psychiatric symptoms. However, there are wide variations in quality of care for these individuals. Psychiatry and emergency medicine specialty guidelines support a tailored, customized approach to patients. Our group has long advocated a dynamic comanagement approach for medical clearance in the ED, and this article summarizes best-practice approaches to the medical clearance of patients with psychiatric illness, tips on history taking, system reviews, clinical/physical examination, and common pitfalls in the medical clearance process. Copyright © 2017 Elsevier Inc. All rights reserved.

Application of winglets and/or wing tip extensions with active load control on the Boeing 747

NASA Technical Reports Server (NTRS)

Allison, R. L.; Perkin, B. R.; Schoenman, R. L.

1978-01-01

The application of wing tip modifications and active control technology to the Boeing 747 airplane for the purpose of improving fuel efficiency is considered. Wing tip extensions, wing tip winglets, and the use of the outboard ailerons for active wing load alleviation are described. Modest performance improvements are indicated. A costs versus benefits approach is taken to decide which, if any, of the concepts warrant further development and flight test leading to possible incorporation into production airplanes.

78 FR 5855 - Agency Information Collection Activities: Requests for Comments; Clearance of a New Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-28

... generic clearance for the purpose of gathering customer satisfaction data directly from customers for a... Activities: Requests for Comments; Clearance of a New Approval of Information Collection: FAA Customer... INFORMATION: OMB Control Number: 2120-XXXX Title: FAA Customer Service Surveys Form Numbers: There are no FAA...

Navier-Stokes analysis of an oxidizer turbine blade with tip clearance

NASA Technical Reports Server (NTRS)

Gibeling, Howard J.; Sabnis, Jayant S.

1992-01-01

The Gas Generator Oxidizer Turbine (GGOT) Blade is being analyzed by various investigators under the NASA MSFC sponsored Turbine Stage Technology Team design effort. The present work concentrates on the tip clearance region flow and associated losses; however, flow details for the passage region are also obtained in the simulations. The present calculations simulate the rotor blade row in a rotating reference frame with the appropriate coriolis and centrifugal acceleration terms included in the momentum equation. The upstream computational boundary is located about one axial chord from the blade leading edge. The boundary conditions at this location were determined by using a Euler analysis without the vanes to obtain approximately the same flow profiles at the rotor as were obtained with the Euler stage analysis including the vanes. Inflow boundary layer profiles are then constructed assuming the skin friction coefficient at both the hub and the casing. The downstream computational boundary is located about one axial chord from the blade trailing edge, and the circumferentially averaged static pressure at this location was also obtained from the Euler analysis. Results were obtained for the 3-D baseline GGOT geometry at the full scale design Reynolds number. Details of the clearance region flow behavior and blade pressure distributions were computed. The spanwise variation in blade loading distributions are shown, and circumferentially averaged spanwise distributions of total pressure, total temperature, Mach number, and flow angle are shown at several axial stations. The spanwise variation of relative total pressure loss shows a region of high loss in the region near the casing. Particle traces in the near tip region show vortical behavior of the fluid which passes through the clearance region and exits at the downstream edge of the gap.

Recent advances in capacitance type of blade tip clearance measurements

NASA Technical Reports Server (NTRS)

Barranger, John P.

1988-01-01

Two recent electronic advances at NASA-Lewis that meet the blade tip clearance needs of a wide class of fans, compressors, and turbines are described. The first is a frequency modulated (FM) oscillator that requires only a single low cost ultrahigh frequency operational amplifier. Its carrier frequency is 42.8 MHz when used with a 61 cm long hermetically sealed coaxial cable. The oscillator can be calibrated in the static mode and has a negative peak frequency deviation of 400 kHz for a typical rotor blade. High temperature performance tests of the probe and 13 cm of the adjacent cable show good accuracy up to 600 C, the maximum which produces a clearance error of + or - 10 microns at a clearance of 500 microns. In the second advance, a guarded probe configuration allows a longer cable capacitance. The capacitance of the probe is part of a small time constant feedback in a high speed operational amplifier. The solution of the governing differential equation is applied to a ramp type of input. The results show an amplifier output that contains a term which is proportional to the derivative of the feedback capacitance. The capacitance is obtained by subtracting a balancing reference channel followed by an integration stage.

Control of the Water Transport Activity of Barley HvTIP3;1 Specifically Expressed in Seeds.

PubMed

Utsugi, Shigeko; Shibasaka, Mineo; Maekawa, Masahiko; Katsuhara, Maki

2015-09-01

Tonoplast intrinsic proteins (TIPs) are involved in the transport and storage of water, and control intracellular osmotic pressure by transporting material related to the water potential of cells. In the present study, we focused on HvTIP3;1 during the periods of seed development and desiccation in barley. HvTIP3;1 was specifically expressed in seeds. An immunochemical analysis showed that HvTIP3;1 strongly accumulated in the aleurone layers and outer layers of barley seeds. The water transport activities of HvTIP3;1 and HvTIP1;2, which also accumulated in seeds, were measured in the heterologous expression system of Xenopus oocytes. When they were expressed individually, HvTIP1;2 transported water, whereas HvTIP3;1 did not. However, HvTIP3;1 exhibited water transport activity when co-expressed with HvTIP1;2 in oocytes, and this activity was higher than when HvTIP1;2 was expressed alone. This is the first report to demonstrate that the water permeability of a TIP aquaporin was activated when co-expressed with another TIP. The split-yellow fluorescent protein (YFP) system in onion cells revealed that HvTIP3;1 interacted with HvTIP1;2 to form a heterotetramer in plants. These results suggest that HvTIP3;1 functions as an active water channel to regulate water movement through tissues during the periods of seed development and desiccation. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

System-Level Design of a Shape Memory Alloy Actuator for Active Clearance Control in the High-Pressure Turbine

NASA Technical Reports Server (NTRS)

DeCastro, Jonathan A.; Melcher, Kevin J.; Noebe, Ronald D.

2005-01-01

This paper describes results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 inches. Design results show that an actuator comprised of 10 wires 2 inches in length is adequate for control at critical engine operating points and still exhibits acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

Annulus wall boundary layer development in a compressor stage, including the effects of tip clearance

NASA Technical Reports Server (NTRS)

Lakshminarayana, B.; Murthy, K. N. S.; Pouagare, M.; Govindan, T. R.

1983-01-01

The end-wall boundary layer development in a compressor stage, including the inlet guide vane (IGV) passage and the rotor passage, was measured. The measurement upstream of the rotor and inside the IGV passage were carried out with a five-hole probe. The data (blade-to-blade) inside the IGV passage were carried out with a five-hole probe. The data (blade-to-blade) inside the rotor passage were measured using a three-sensor rotating hot-wire below the tip clearance region and "V' configuration probe inside the clearance region. The rotor exit measurements (blade-to-blade) were acquired with a laser Doppler velocimeter. The velocity profiles and the integral properties are presented and interpreted. The boundary layer is comparatively well behaved up to the leading edge of the rotor, beyond which complex interactions result in very unconventional profiles. The momentum thicknesses decrease in the leakage flow region of the rotor. The momentum thicknesses and the limiting streamline angles predicted from a momentum integral technique agree well with the data up to the leading edge of the rotor.

Laser Doppler position sensor for position and shape measurements of fast rotating objects

NASA Astrophysics Data System (ADS)

Czarske, Jürgen; Pfister, Thorsten; Büttner, Lars

2006-08-01

We report about a novel optical method based on laser Doppler velocimetry for position and shape measurements of moved solid state surfaces with approximately one micrometer position resolution. 3D shape measurements of a rotating cylinder inside a turning machine as well as tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm and 586 m/s blade tip velocity are presented. All results are in good agreement with conventional reference probes. The measurement accuracy of the laser Doppler position sensor is investigated in dependence of the speckle pattern. Furthermore, it is shown that this sensor offers high temporal resolution and high position resolution simultaneously and that shading can be reduced compared to triangulation. Consequently, the presented laser Doppler position sensor opens up new perspectives in the field of real-time manufacturing metrology and process control, for example controlling the turning and the grinding process or for future developments of turbo machines.

Visualisation of the flow at the tip of a high speed axial flow turbine rotor: An assessment of flow visualisation techniques and the requirement of the experimental turbine

NASA Astrophysics Data System (ADS)

Bindon, J.; Alder, D.; Ianovici, I.

1987-11-01

The field of flow visualization has been reviewed and its application to the study of the flow near the tip of an unshrouded axial turbine rotor discussed in detail. The logical conceptualization of experiments which could lead to a final understanding of the flow structure was developed and how this leads to test turbine design philosophy is suggested. The rotor periodicity shed by the stator requires that particle of pulse tracing is needed rather than the more universal continuous streamline trace which arises from a continuous tracer injection at a point in a flow. While the whole field of flow visualization at a rotor tip is demanding because of its very nature, pulse tracking will place a greater demand on the development of new skills and techniques. Since streamline tracking is somewhat more standard, these demands will not be as great. A fundamental choice does however need to be made between the two methods. The suggested experimental turbine should thus, always with the facility of infinitely variable Mach number, model the following: (1) Stationary annular cascade with tip clearance inside a stationary outer endwall; (2) Stationary annular cascade with tip clearance inside a moving endwall; (3) The transfer of flow visualization techniques developed into the rotating frame; (4) Fully rotating rotor with no inlet periodicity; (5) Fully rotating rotor with inlet periodicity.

Kaplan turbine tip vortex cavitation - analysis and prevention

NASA Astrophysics Data System (ADS)

Motycak, L.; Skotak, A.; Kupcik, R.

2012-11-01

The work is focused on one type of Kaplan turbine runner cavitation - a tip vortex cavitation. For detailed description of the tip vortex, the CFD analysis is used. On the basis of this analysis it is possible to estimate the intensity of cavitating vortex core, danger of possible blade surface and runner chamber cavitation pitting. In the paper, the ways how to avoid the pitting effect of the tip vortex are described. In order to prevent the blade surface against pitting, the following possibilities as the change of geometry of the runner blade, dimension of tip clearance and finally the installation of the anti-cavitation lips are discussed. The knowledge of the shape and intensity of the tip vortex helps to design the anti-cavitation lips more sophistically. After all, the results of the model tests of the Kaplan runner with or without anti-cavitation lips and the results of the CFD analysis are compared.

Performance Optimization of a Rotor Alone Nacelle for Acoustic Fan Testing

NASA Technical Reports Server (NTRS)

Cunningham, C. C.; Thompson, W. K.; Hughes, C. E.

2000-01-01

This paper describes the techniques, equipment, and results from the optimization of a two-axis traverse actuation system used to maintain concentricity between a sting-mounted fan and a wall-mounted nacelle in the 9 x 15 (9 Foot by 15 Foot Test Section) Low Speed Wind Tunnel (LSWT) at the NASA Glenn Research Center (GRC). The Rotor Alone Nacelle (RAN) system, developed at GRC by the Engineering Design and Analysis Division (EDAD) and the Acoustics Branch, used nacelle-mounted lasers and an automated control system to maintain concentricity as thermal and thrust operating loads displace the fan relative to the nacelle. This effort was critical to ensuring rig/facility safety and experimental consistency of the acoustic data from a statorless, externally supported nacelle configuration. Although the tip clearances were originally predicted to be about 0.020 in. at maximum rotor (fan) operating speed, proximity probe measurements showed that the nominal clearance was less than 0.004 in. As a result, the system was optimized through control-loop modifications, active laser cooling, data filtering and averaging, and the development of strict operational procedures. The resultant concentricity error of RAN was reduced to +/- 0.0031 in. in the Y-direction (horizontal) and +0.0035 in./-0.001 3 in. in the Z-direction (vertical), as determined by error analysis and experimental results. Based on the success of this project, the RAN system will be transitioned to other wind tunnel research programs at NASA GRC.

Low-cost FM oscillator for capacitance type of blade tip clearance measurement system

NASA Technical Reports Server (NTRS)

Barranger, John P.

1987-01-01

The frequency-modulated (FM) oscillator described is part of a blade tip clearance measurement system that meets the needs of a wide class of fans, compressors, and turbines. As a result of advancements in the technology of ultra-high-frequency operational amplifiers, the FM oscillator requires only a single low-cost integrated circuit. Its carrier frequency is 42.8 MHz when it is used with an integrated probe and connecting cable assembly consisting of a 0.81 cm diameter engine-mounted capacitance probe and a 61 cm long hermetically sealed coaxial cable. A complete circuit analysis is given, including amplifier negative resistance characteristics. An error analysis of environmentally induced effects is also derived, and an error-correcting technique is proposed. The oscillator can be calibrated in the static mode and has a negative peak frequency deviation of 400 kHz for a rotor blade thickness of 1.2 mm. High-temperature performance tests of the probe and 13 cm of the adjacent cable show good accuracy up to 600 C, the maximum permissible seal temperature. The major source of error is the residual FM oscillator noise, which produces a clearance error of + or - 10 microns at a clearance of 0.5 mm. The oscillator electronics accommodates the high rotor speeds associated with small engines, the signals from which may have frequency components as high as 1 MHz.

Effect of area ratio on the performance of a 5.5:1 pressure ratio centrifugal impeller

NASA Technical Reports Server (NTRS)

Schumann, L. F.; Clark, D. A.; Wood, J. R.

1986-01-01

A centrifugal impeller which was initially designed for a pressure ratio of approximately 5.5 and a mass flow rate of 0.959 kg/sec was tested with a vaneless diffuser for a range of design point impeller area ratios from 2.322 to 2.945. The impeller area ratio was changed by successively cutting back the impeller exit axial width from an initial value of 7.57 mm to a final value of 5.97 mm. In all, four separate area ratios were tested. For each area ratio a series of impeller exit axial clearances was also tested. Test results are based on impeller exit surveys of total pressure, total temperature, and flow angle at a radius 1.115 times the impeller exit radius. Results of the tests at design speed, peak efficiency, and an exit tip clearance of 8 percent of exit blade height show that the impeller equivalent pressure recovery coefficient peaked at a design point area ratio of approximately 2.748 while the impeller aerodynamic efficiency peaked at a lower value of area ratio of approximately 2.55. The variation of impeller efficiency with clearance showed expected trends with a loss of approximately 0.4 points in impeller efficiency for each percent increase in exit axial tip clearance for all impellers tested.

Ebola (Ebola Virus Disease): Q&As on Transmission

MedlinePlus

... Response Planning Tips Managing and Preventing Cases of Malaria in Areas with Ebola Phone Numbers for State ... the Ebola outbreak due to the risk of malaria. In addition, plasma derived products have viral clearance ...

Study of Near-Stall Flow Behavior in a Modern Transonic Fan with Composite Sweep

NASA Technical Reports Server (NTRS)

Hah, Chunill; Shin, Hyoun-Woo

2011-01-01

Detailed flow behavior in a modern transonic fan with a composite sweep is investigated in this paper. Both unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) methods are applied to investigate the flow field over a wide operating range. The calculated flow fields are compared with the data from an array of high-frequency response pressure transducers embedded in the fan casing. The current study shows that a relatively fine computational grid is required to resolve the flow field adequately and to calculate the pressure rise across the fan correctly. The calculated flow field shows detailed flow structure near the fan rotor tip region. Due to the introduction of composite sweep toward the rotor tip, the flow structure at the rotor tip is much more stable compared to that of the conventional blade design. The passage shock stays very close to the leading edge at the rotor tip even at the throttle limit. On the other hand, the passage shock becomes stronger and detaches earlier from the blade passage at the radius where the blade sweep is in the opposite direction. The interaction between the tip clearance vortex and the passage shock becomes intense as the fan operates toward the stall limit, and tip clearance vortex breakdown occurs at near-stall operation. URANS calculates the time-averaged flow field fairly well. Details of measured RMS static pressure are not calculated with sufficient accuracy with URANS. On the other hand, LES calculates details of the measured unsteady flow features in the current transonic fan with composite sweep fairly well and reveals the flow mechanism behind the measured unsteady flow field.

Numerical simulation of steady three-dimensional flows in axial turbomachinery bladerows

NASA Astrophysics Data System (ADS)

Basson, Anton Herman

The formulation for and application of a numerical model for low Mach number steady three-dimensional flows in axial turbomachinery blade rows is presented. The formulation considered here includes an efficient grid generation scheme (particularly suited to computational grids for the analysis of turbulent turbomachinery flows) and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, applicable to viscous and inviscid flows. The grid generation technique uses a combination of algebraic and elliptic methods, in conjunction with the Minimal Residual Method, to economically generate smooth structured grids. For typical H-grids in turbomachinery bladerows, when compared to a purely elliptic grid generation scheme, the presented grid generation scheme produces grids with much improved smoothness near the leading and trailing edges, allows the use of small near wall grid spacing required by low Reynolds number turbulence models, and maintains orthogonality of the grid near the solid boundaries even for high flow angle cascades. A specialized embedded H-grid for application particularly to tip clearance flows is presented. This topology smoothly discretizes the domain without modifying the tip shape, while requiring only minor modifications to H-grid flow solvers. Better quantitative modeling of the tip clearance vortex structure than that obtained with a pinched tip approximation is demonstrated. The formulation of artificial dissipation terms for a semi-implicit, pressure-based (SIMPLE type) flow solver, is presented. It is applied to both the Euler and the Navier-Stokes equations, expressed in generalized coordinates using a non-staggered grid. This formulation is compared to some SIMPLE and time marching formulations, revealing the artificial dissipation inherent in some commonly used semi-implicit formulations. The effect of the amount of dissipation on the accuracy of the solution and the convergence rate is quantitatively demonstrated for a number of flow cases. The ability of the formulation to model complex steady turbomachinery flows is demonstrated, e.g. for pressure driven secondary flows, turbine nozzle wakes, turbulent boundary layers. The formulation's modeling of blade surface heat transfer is assessed. The numerical model is used to investigate the structure of phenomena associated with tip clearance flows in a turbine nozzle.

Smart helicopter rotor with active blade tips

NASA Astrophysics Data System (ADS)

Bernhard, Andreas Paul Friedrich

2000-10-01

The smart active blade tip (SABT) rotor is an on-blade rotor vibration reduction system, incorporating active blade tips that can be independently pitched with respect to the main blade. The active blade tip rotor development included an experimental test program culminating in a Mach scale hover test, and a parallel development of a coupled, elastic actuator and rotor blade analysis for preliminary design studies and hover performance prediction. The experimental testing focussed on a small scale rotor on a bearingless Bell-412 hub. The fabricated Mach-scale active-tip rotor has a diameter of 1.524 m, a blade chord of 76.2 mm and incorporated a 10% span active tip. The nominal operating speed is 2000 rpm, giving a tip Mach number of 0.47. The blade tips are driven by a novel piezo-induced bending-torsion coupled actuator beam, located spanwise in the hollow mid-cell of the main rotor blade. In hover at 2000 rpm, at 2 deg collective, and for an actuation of 125 Vrms, the measured blade tip deflection at the first four rotor harmonics is between +/-1.7 and +/-2.8 deg, increasing to +/-5.3 deg at 5/rev with resonant amplification. The corresponding oscillatory amplitude of the rotor thrust coefficient is between 0.7 · 10-3 and 1.3 · 10-1 at the first four rotor harmonics, increasing to 2.1 · 10-3 at 5/rev. In general, the experimental blade tip frequency response and corresponding rotor thrust response are well captured by the analysis. The flexbeam root flap bending moment is predicted in trend, but is significantly over-estimated. The blade tips did not deflect as expected at high collective settings, because of the blade tip shaft locking up in the bearing. This is caused by the high flap bending moment on the blade tip shaft. Redesign of the blade tip shaft assembly and bearing support is identified as the primary design improvement for future research. The active blade tip rotor was also used as a testbed for the evaluation of an adaptive neural-network based control algorithm. Effective background vibration reduction of an intentional 1/rev hover imbalance was demonstrated. The control algorithm also showed the capability to generate desired multi-frequency control loads on the hub, based on artificial signal injection into the vibration measurement. The research program demonstrates the technical feasibility of the active blade tip concept for vibration reduction and warrants further investigation in terms of closed loop forward flight tests in the windtunnel and full scale design studies.

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Heat transfer and flow characteristics on a gas turbine shroud.

PubMed

Obata, M; Kumada, M; Ijichi, N

2001-05-01

The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.

Controlled Ascent From the Surface of an Asteroid

NASA Technical Reports Server (NTRS)

Shen, Haijun; Roithmayr, Carlos M.; Cornelius, David M.

2014-01-01

The National Aeronautics and Space Administration (NASA) is currently investigating a conceptual robotic mission to collect a small boulder up to 4 m in diameter resting on the surface of a large Near Earth Asteroid (NEA). Because most NEAs are not well characterized, a great range of uncertainties in boulder mass properties and NEA surface characteristics must be considered in the design of this mission. These uncertainties are especially significant when the spacecraft ascends with the boulder in tow. The most important requirement during ascent is to keep the spacecraft in an upright posture to maintain healthy ground clearances for the two large solar arrays. This paper focuses on the initial stage (the first 50 m) of ascent from the surface. Specifically, it presents a sensitivity study of the solar array ground clearance, control authority, and accelerations at the array tips in the presence of a variety of uncertainties including various boulder sizes, densities, shapes and orientations, locations of the true center of mass, and push-off force distributions. Results are presented, and appropriate operations are recommended in the event some of the off-nominal cases occur.

Prediction of destabilizing blade tip forces for shrouded and unshrouded turbines

NASA Technical Reports Server (NTRS)

Qiu, Y. J.; Martinezsanchez, M.

1985-01-01

The effect of a nonuniform flow field on the Alford force calculation is investigated. The ideas used here are based on those developed by Horlock and Greitzer. It is shown that the nonuniformity of the flow field does contribute to the Alford force calculation. An attempt is also made to include the effect of whirl speed. The values predicted by the model are compared with those obtained experimentally by Urlicks and Wohlrab. The possibility of using existing turbine tip loss correlations to predict beta is also exploited. The nonuniform flow field induced by the tip clearnance variation tends to increase the resultant destabilizing force over and above what would be predicted on the basis of the local variation of efficiency. On the one hand, the pressure force due to the nonuniform inlet and exit pressure also plays a part even for unshrouded blades, and this counteracts the flow field effects, so that the simple Alford prediction remains a reasonable approximation. Once the efficiency variation with clearance is known, the presented model gives a slightly overpredicted, but reasonably accurate destabilizing force. In the absence of efficiency vs. clearance data, an empirical tip loss coefficient can be used to give a reasonable prediction of destabilizing force. To a first approximation, the whirl does have a damping effect, but only of small magnitude, and thus it can be ignored for some purposes.

CF6 Jet Engine Performance Improvement: High Pressure Turbine Active Clearance Control

NASA Technical Reports Server (NTRS)

Rich, S. E.; Fasching, W. A.

1982-01-01

An active clearance control system was developed which reduces fuel consumption and performance degradation. This system utilizes compressor discharge air during takeoff and fan discharge air during cruise to impinge on the shroud structure to improve the thermal response. The system was evaluated in component and engine tests. The test results demonstrated a performance improvement of 0.7 percent in cruise SFC.

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Tip Vortex and Wake Characteristics of a Counterrotating Open Rotor

NASA Technical Reports Server (NTRS)

VanZante, Dale E.; Wernet, Mark P.

2012-01-01

One of the primary noise sources for Open Rotor systems is the interaction of the forward rotor tip vortex and blade wake with the aft rotor. NASA has collaborated with General Electric on the testing of a new generation of low noise, counterrotating Open Rotor systems. Three-dimensional particle image velocimetry measurements were acquired in the intra-rotor gap of the Historical Baseline blade set. The velocity measurements are of sufficient resolution to characterize the tip vortex size and trajectory as well as the rotor wake decay and turbulence character. The tip clearance vortex trajectory is compared to results from previously developed models. Forward rotor wake velocity profiles are shown. Results are presented in a form as to assist numerical modeling of Open Rotor system aerodynamics and acoustics.

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Thermal Response Turbine Shroud.

DTIC Science & Technology

1979-11-01

AD-AO82 754. GENERAL ELECTRIC CO CINCINNATI OH AIRCRAFT ENGINE GROUP F/G 21/5 THERMAL RESPONSE TURBINE SHROUO.(UI NOV 79 C N GAY F33615-7B-C-2071...SUPPLEMENTARY NOTES IS. IEV WORDS (C..tIam. ON guinea 80410 Itf08M 8". 1~0 &VU~ b lma n-M-) Clearance Shroud Clearance Control Turbine Shroud engine / aircrafte ...compressor Active Clearance Control Systems (ACC) de-signed for aircraft gas turbine engine applications. The study vas conducted by personnel of the

Design of Single Stage Axial Turbine with Constant Nozzle Angle Blading for Small Turbojet

NASA Astrophysics Data System (ADS)

Putra Adnan, F.; Hartono, Firman

2018-04-01

In this paper, an aerodynamic design of a single stage gas generator axial turbine for small turbojet engine is explained. As per design requirement, the turbine should be able to deliver power output of 155 kW at 0.8139 kg/s gas mass flow, inlet total temperature of 1200 K and inlet total pressure of 335330 Pa. The design phase consist of several steps, i.e.: determination of velocity triangles in 2D plane, 2D blading design and 3D flow analysis at design point using Computational Fluid Dynamics method. In the determination of velocity triangles, two conditions are applied: zero inlet swirl (i.e. the gas flow enter the turbine at axial direction) and constant nozzle angle design (i.e. the inlet and outlet angle of the nozzle blade are constant from root to tip). The 2D approach in cascade plane is used to specify airfoil type at root, mean and tip of the blade based on inlet and outlet flow conditions. The 3D approach is done by simulating the turbine in full configuration to evaluate the overall performance of the turbine. The observed parameters including axial gap, stagger angle, and tip clearance affect its output power. Based on analysis results, axial gap and stagger angle are positively correlated with output power up to a certain point at which the power decreases. Tip clearance, however, gives inversely correlation with output power.

Shroud leakage flow discouragers

DOEpatents

Bailey, Jeremy Clyde; Bunker, Ronald Scott

2002-01-01

A turbine assembly includes a plurality of rotor blades comprising a root portion, an airfoil having a pressure sidewall and a suction sidewall, and a top portion having a cap. An outer shroud is concentrically disposed about said rotor blades, said shroud in combination with said tip portions defining a clearance gap. At least one circumferential shroud leakage discourager is disposed within the shroud. The leakage discourager(s) increase the flow resistance and thus reduce the flow of hot gas flow leakage for a given pressure differential across the clearance gap to improve overall turbine efficiency.

Feasibility Study for a Practical High Rotor Tip Clearance Turbine.

DTIC Science & Technology

GAS TURBINE BLADES ), (* TURBINE BLADES , TOLERANCES(MECHANICS)), (* TURBOFAN ENGINES , GAS TURBINES , AXIAL FLOW TURBINES , AXIAL FLOW TURBINE ROTORS...AERODYNAMIC CONFIGURATIONS, LEAKAGE(FLUID), MEASUREMENT, TEST METHODS, PERFORMANCE( ENGINEERING ), MATHEMATICAL PREDICTION, REDUCTION, PRESSURE, PREDICTIONS, NOZZLE GAS FLOW, COMBUSTION CHAMBER GASES, GAS FLOW.

A tip-localized RhoGAP controls cell polarity by globally inhibiting Rho GTPase at the cell apex.

PubMed

Hwang, Jae-Ung; Vernoud, Vanessa; Szumlanski, Amy; Nielsen, Erik; Yang, Zhenbiao

2008-12-23

Highly elongated eukaryotic cells (e.g., neuronal axons, fungal hyphae, and pollen tubes) are generated through continuous apically restricted growth (tip growth), which universally requires tip-localized Rho GTPases. We used the oscillating pollen tube as a model system to determine the function and regulation of Rho GTPases in tip growth. Our previous work showed that the spatiotemporal dynamics of the apical cap of the activated Rho-like GTPase from Plant 1 (ROP1) are critical for tip growth in pollen tubes. However, the underlying mechanism for the generation and maintenance of this dynamic apical cap is poorly understood. A screen for mutations that enhance ROP1-overexpression-induced depolarization of pollen-tube growth identified REN1 (ROP1 enhancer 1) in Arabidopsis, whose null mutations turn elongated pollen tubes into bulbous cells. REN1 encodes a novel Rho GTPase-activating protein (RhoGAP) required for restricting the ROP1 activity to the pollen-tube tip. REN1 was localized to exocytic vesicles accumulated in the pollen-tube apex, as well as to the apical plasma membrane at the site of ROP1 activation. The apical localization of REN1 and its function in controlling growth polarity was compromised by disruption of ROP1-dependent F-actin and vesicular trafficking, which indicates that REN1 targeting and function is regulated by ROP1 downstream signaling. Our findings suggest that the REN1 RhoGAP controls a negative-feedback-based global inhibition of ROP1. This function provides a critical self-organizing mechanism, by which ROP signaling is spatially limited to the growth site and temporally oscillates during continuous tip growth. Similar spatiotemporal control of Rho GTPase signaling may also play an important role in cell-polarity control in other systems, including tip growth in fungi and cell movement in animals.

A Numerical Analysis of Heat Transfer and Effectiveness on Film Cooled Turbine Blade Tip Models

NASA Technical Reports Server (NTRS)

Ameri, A. A.; Rigby, D. L.

1999-01-01

A computational study has been performed to predict the distribution of convective heat transfer coefficient on a simulated blade tip with cooling holes. The purpose of the examination was to assess the ability of a three-dimensional Reynolds-averaged Navier-Stokes solver to predict the rate of tip heat transfer and the distribution of cooling effectiveness. To this end, the simulation of tip clearance flow with blowing of Kim and Metzger was used. The agreement of the computed effectiveness with the data was quite good. The agreement with the heat transfer coefficient was not as good but improved away from the cooling holes. Numerical flow visualization showed that the uniformity of wetting of the surface by the film cooling jet is helped by the reverse flow due to edge separation of the main flow.

Flow visualization for investigating stator losses in a multistage axial compressor

NASA Astrophysics Data System (ADS)

Smith, Natalie R.; Key, Nicole L.

2015-05-01

The methodology and implementation of a powder-paint-based flow visualization technique along with the illuminated flow physics are presented in detail for application in a three-stage axial compressor. While flow visualization often accompanies detailed studies, the turbomachinery literature lacks a comprehensive study which both utilizes flow visualization to interrupt the flow field and explains the intricacies of execution. Lessons learned for obtaining high-quality images of surface flow patterns are discussed in this study. Fluorescent paint is used to provide clear, high-contrast pictures of the recirculation regions on shrouded vane rows. An edge-finding image processing procedure is implemented to provide a quantitative measure of vane-to-vane variability in flow separation, which is approximately 7 % of the suction surface length for Stator 1. Results include images of vane suction side corner separations from all three stages at three loading conditions. Additionally, streakline patterns obtained experimentally are compared with those calculated from computational models. Flow physics associated with vane clocking and increased rotor tip clearance and their implications to stator loss are also investigated with this flow visualization technique. With increased rotor tip clearance, the vane surface flow patterns show a shift to larger separations and more radial flow at the tip. Finally, the effects of instrumentation on the flow field are highlighted.

Investigation of Unsteady Flow Behavior in Transonic Compressor Rotors with LES and PIV Measurements

NASA Technical Reports Server (NTRS)

Hah, Chunill; Voges, Melanie; Mueller, Martin; Schiffer, Heinz-Peter

2009-01-01

In the present study, unsteady flow behavior in a modern transonic axial compressor rotor is studied in detail with large eddy simulation (LES) and particle image velocimetry (PIV). The main purpose of the study is to advance the current understanding of the flow field near the blade tip in an axial transonic compressor rotor near the stall and peak-efficiency conditions. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. Casing-mounted unsteady pressure transducers have been widely applied to investigate steady and unsteady flow behavior near the casing. Although many aspects of flow have been revealed, flow structures below the casing cannot be studied with casing-mounted pressure transducers. In the present study, unsteady velocity fields are measured with a PIV system and the measured unsteady flow fields are compared with LES simulations. The currently applied PIV measurements indicate that the flow near the tip region is not steady even at the design condition. This self-induced unsteadiness increases significantly as the compressor rotor operates near the stall condition. Measured data from PIV show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics of the flow from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The present study indicates that stall inception is heavily dependent on unsteady behavior of the flow field near the leading edge of the blade tip section for the present transonic compressor rotor.

Tip-Clearance Measurement in the First Stage of the Compressor of an Aircraft Engine.

PubMed

García, Iker; Przysowa, Radosław; Amorebieta, Josu; Zubia, Joseba

2016-11-11

In this article, we report the design of a reflective intensity-modulated optical fiber sensor for blade tip-clearance measurement, and the experimental results for the first stage of a compressor of an aircraft engine operating in real conditions. The tests were performed in a ground test cell, where the engine completed four cycles from idling state to takeoff and back to idling state. During these tests, the rotational speed of the compressor ranged between 7000 and 15,600 rpm. The main component of the sensor is a tetrafurcated bundle of optical fibers, with which the resulting precision of the experimental measurements was 12 µm for a measurement range from 2 to 4 mm. To get this precision the effect of temperature on the optoelectronic components of the sensor was compensated by calibrating the sensor in a climate chamber. A custom-designed MATLAB program was employed to simulate the behavior of the sensor prior to its manufacture.

Tip-Clearance Measurement in the First Stage of the Compressor of an Aircraft Engine

PubMed Central

García, Iker; Przysowa, Radosław; Amorebieta, Josu; Zubia, Joseba

2016-01-01

In this article, we report the design of a reflective intensity-modulated optical fiber sensor for blade tip-clearance measurement, and the experimental results for the first stage of a compressor of an aircraft engine operating in real conditions. The tests were performed in a ground test cell, where the engine completed four cycles from idling state to takeoff and back to idling state. During these tests, the rotational speed of the compressor ranged between 7000 and 15,600 rpm. The main component of the sensor is a tetrafurcated bundle of optical fibers, with which the resulting precision of the experimental measurements was 12 µm for a measurement range from 2 to 4 mm. To get this precision the effect of temperature on the optoelectronic components of the sensor was compensated by calibrating the sensor in a climate chamber. A custom-designed MATLAB program was employed to simulate the behavior of the sensor prior to its manufacture. PMID:27845709

Imaging contrast and tip-sample interaction of non-contact amplitude modulation atomic force microscopy with Q-control

NASA Astrophysics Data System (ADS)

Shi, Shuai; Guo, Dan; Luo, Jianbin

2017-10-01

Active quality factor (Q) exhibits many promising properties in dynamic atomic force microscopy. Energy dissipation and image contrasts are investigated in the non-contact amplitude modulation atomic force microscopy (AM-AFM) with an active Q-control circuit in the ambient air environment. Dissipated power and virial were calculated to compare the highly nonlinear interaction of tip-sample and image contrasts with different Q gain values. Greater free amplitudes and lower effective Q values show better contrasts for the same setpoint ratio. Active quality factor also can be employed to change tip-sample interaction force in non-contact regime. It is meaningful that non-destructive and better contrast images can be realized in non-contact AM-AFM by applying an active Q-control to the dynamic system.

Experimental performance of a 16.10-centimeter-tip-diameter sweptback centrifugal compressor designed for a 6:1 pressure ratio

NASA Technical Reports Server (NTRS)

Klassen, H. A.; Wood, J. R.; Schumann, L. F.

1977-01-01

A backswept impeller with design mass flow rate of 1.033 kg/sec was tested with both a vaned diffuser and a vaneless diffuser to establish stage and impeller characteristics. Design stage pressure ratio of 5.9:1 was attained at a flow slightly lower than the design value. Flow range at design speed was 6 percent of choking flow. Impeller axial tip clearance at design speed was varied to determine effect on stage and impeller performance.

Endovascular Catheter for Magnetic Navigation under MR Imaging Guidance: Evaluation of Safety in Vivo at 1.5T

PubMed Central

Hetts, S.W.; Saeed, M.; Martin, A.J.; Evans, L.; Bernhardt, A.F.; Malba, V.; Settecase, F.; Do, L.; Yee, E.J.; Losey, A.; Sincic, R.; Roy, S.; Arenson, R.L.; Wilson, M.W.

2013-01-01

BACKGROUND AND PURPOSE: Endovascular navigation under MR imaging guidance can be facilitated by a catheter with steerable microcoils on the tip. Not only do microcoils create visible artifacts allowing catheter tracking, but also they create a small magnetic moment permitting remote-controlled catheter tip deflection. A side product of catheter tip electrical currents, however, is the heat that might damage blood vessels. We sought to determine the upper boundary of electrical currents safely usable at 1.5T in a coil-tipped microcatheter system. MATERIALS AND METHODS: Alumina tubes with solenoid copper coils were attached to neurovascular microcatheters with heat shrink-wrap. Catheters were tested in carotid arteries of 8 pigs. The catheters were advanced under x-ray fluoroscopy and MR imaging. Currents from 0 mA to 700 mA were applied to test heating and potential vascular damage. Postmortem histologic analysis was the primary endpoint. RESULTS: Several heat-mitigation strategies demonstrated negligible vascular damage compared with control arteries. Coil currents ≤300 mA resulted in no damage (0/58 samples) compared with 9 (25%) of 36 samples for > 300-mA activations (P = .0001). Tip coil activation ≤1 minute and a proximal carotid guide catheter saline drip > 2 mL/minute also had a nonsignificantly lower likelihood of vascular damage. For catheter tip coil activations ≤300 mA for ≤1 minute in normal carotid flow, 0 of 43 samples had tissue damage. CONCLUSIONS: Activations of copper coils at the tip of microcatheters at low currents in 1.5T MR scanners can be achieved without significant damage to blood vessel walls in a controlled experimental setting. Further optimization of catheter design and procedure protocols is necessary for safe remote control magnetic catheter guidance. PMID:23846795

Selected advanced aerodynamics and active controls technology concepts development on a derivative B-747 aircraft

NASA Technical Reports Server (NTRS)

1983-01-01

Analytical design and wind tunnel test evaluations covering the feasibility of applying wing tip extensions, winglets, and active control wing had alleviation to the model B747 are described. Aerodynamic improvement offered by wing tip extension and winglet individually, and the combined aerodynamic and weight improvements when wing load alleviation is combined with the tip extension or the winglet are evaluated. Results are presented in the form of incremental effects on weight mission range, fuel usage, cost, and airline operating economics.

Understanding and Mitigating Tip Leakage and Endwall Losses in High Pressure Ratio Cores

NASA Technical Reports Server (NTRS)

Christophel, Jesse

2015-01-01

Reducing endwall and tip secondary flow losses will be a key enabler for the next generation of commercial and military air transport and will be an improvement on the state-of-the-art in turbine loss reduction strategies. The objective of this research is three-fold: 1) To improve understanding of endwall secondary flow and tip clearance losses 2) To develop novel technologies to mitigate these losses and test them in low-speed cascade and rig environments 3) To validate predictive tools To accomplish these objectives, Pratt & Whitney (P&W) has teamed with Pennsylvania State University (PSU) to experimentally test new features designed by P&W. P&W will create new rim-cavity features to reduce secondary flow loss and improve purge flow cooling effectiveness and new blade tip features to manage leakage flows and reduce tip leakage secondary flow loss. P&W is currently developing technologies in these two areas that expect to be assimilated in the N+2/N+3 generation of commercial engines.

The CF6 Jet Engine Performance Improvement - Low Pressure Turbine Active Clearance Control

NASA Technical Reports Server (NTRS)

Beck, B. D.; Fasching, W. A.

1982-01-01

A low pressure turbine (LPT) active clearance control (ACC) cooling system was developed to reduce the fuel consumption of current CF6-50 turbofan engines for wide bodied commercial aircraft. The program performance improvement goal of 0.3% delta sfc was determined to be achievable with an improved impingement cooling system. The technology enables the design of an optimized manifold and piping system which is capable of a performance gain of 0.45% delta sfc.

Effect of tip flange on tip leakage flow of small axial flow fans

NASA Astrophysics Data System (ADS)

Zhang, Li; Jin, Yingzi; Jin, Yuzhen

2014-02-01

Aerodynamic performance of an axial flow fan is closely related to its tip clearance leakage flow. In this paper, the hot-wire anemometer is used to measure the three dimensional mean velocity near the blade tips. Moreover, the filtered N-S equations with finite volume method and RNG k-ɛ turbulence model are adopted to carry out the steady simulation calculation of several fans that differ only in tip flange shape and number. The large eddy simulation and the FW-H noise models are adopted to carry out the unsteady numerical calculation and aerodynamic noise prediction. The results of simulation calculation agree roughly with that of tests, which proves the numerical calculation method is feasible.The effects of tip flange shapes and numbers on the blade tip vortex structure and the characteristics are analyzed. The results show that tip flange of the fan has a certain influence on the characteristics of the fan. The maximum efficiencies for the fans with tip flanges are shifted towards partial flow with respect to the design point of the datum fan. Furthermore, the noise characteristics for the fans with tip flanges have become more deteriorated than that for the datum fan. Tip flange contributes to forming tip vortex shedding and the effect of the half-cylinder tip flange on tip vortex shedding is obvious. There is a distinct relationship between the characteristics of the fan and tip vortex shedding. The research results provide the profitable reference for the internal flow mechanism of the performance optimization of small axial flow fans.

New digital capacitive measurement system for blade clearances

NASA Astrophysics Data System (ADS)

Moenich, Marcel; Bailleul, Gilles

This paper presents a totally new concept for tip blade clearance evaluation in turbine engines. This system is able to detect exact 'measurands' even under high temperature and severe conditions like ionization. The system is based on a heavy duty probe head, a miniaturized thick-film hybrid electronic circuit and a signal processing unit for real time computing. The high frequency individual measurement values are digitally filtered and linearized in real time. The electronic is built in hybrid technology and therefore can be kept extremely small and robust, so that the system can be used on actual flights.

77 FR 2131 - Submission for OMB Review; Comment Request

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.... Abstract: Employers in food or beverage establishments where tipping is customary can claim an income tax... Management and Budget (OMB) for review and clearance in accordance with the Paperwork Reduction Act of 1995... burden, to (1) Office of Information and Regulatory Affairs, Office of Management and Budget, Attention...

Cerebrospinal Fluid Clearance in Alzheimer Disease Measured with Dynamic PET.

PubMed

de Leon, Mony J; Li, Yi; Okamura, Nobuyuki; Tsui, Wai H; Saint-Louis, Les A; Glodzik, Lidia; Osorio, Ricardo S; Fortea, Juan; Butler, Tracy; Pirraglia, Elizabeth; Fossati, Silvia; Kim, Hee-Jin; Carare, Roxana O; Nedergaard, Maiken; Benveniste, Helene; Rusinek, Henry

2017-09-01

Evidence supporting the hypothesis that reduced cerebrospinal fluid (CSF) clearance is involved in the pathophysiology of Alzheimer disease (AD) comes primarily from rodent models. However, unlike rodents, in which predominant extracranial CSF egress is via olfactory nerves traversing the cribriform plate, human CSF clearance pathways are not well characterized. Dynamic PET with 18 F-THK5117, a tracer for tau pathology, was used to estimate the ventricular CSF time-activity as a biomarker for CSF clearance. We tested 3 hypotheses: extracranial CSF is detected at the superior turbinates; CSF clearance is reduced in AD; and CSF clearance is inversely associated with amyloid deposition. Methods: Fifteen subjects, 8 with AD and 7 normal control volunteers, were examined with 18 F-THK5117. Ten subjects additionally underwent 11 C-Pittsburgh compound B ( 11 C-PiB) PET scanning, and 8 were 11 C-PiB-positive. Ventricular time-activity curves of 18 F-THK5117 were used to identify highly correlated time-activity curves from extracranial voxels. Results: For all subjects, the greatest density of CSF-positive extracranial voxels was in the nasal turbinates. Tracer concentration analyses validated the superior nasal turbinate CSF signal intensity. AD patients showed ventricular tracer clearance reduced by 23% and 66% fewer superior turbinate CSF egress sites. Ventricular CSF clearance was inversely associated with amyloid deposition. Conclusion: The human nasal turbinate is part of the CSF clearance system. Lateral ventricle and superior nasal turbinate CSF clearance abnormalities are found in AD. Ventricular CSF clearance reductions are associated with increased brain amyloid depositions. These data suggest that PET-measured CSF clearance is a biomarker of potential interest in AD and other neurodegenerative diseases. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Cold-air performance of a tip turbine designed to drive a lift fan

NASA Technical Reports Server (NTRS)

Haas, J. E.; Kofskey, M. G.; Hotz, G. M.

1978-01-01

Performance was obtained over a range of speeds and pressure ratios for a 0.4 linear scale version of the LF460 lift fan turbine with the rotor radial tip clearance reduced to about 2.5 percent of the rotor blade height. These tests covered a range of speeds from 60 to 140 percent of design equivalent speed and a range of scroll inlet total to diffuser exit static pressure ratios from 2.6 to 4.2. Results are presented in terms of equivalent mass flow, equivalent torque, equivalent specific work, and efficiency.

The challenge of stereo PIV measurements in the tip gap of a transonic compressor rotor with casing treatment

NASA Astrophysics Data System (ADS)

Voges, Melanie; Willert, Christian E.; Mönig, Reinhard; Müller, Martin W.; Schiffer, Heinz-Peter

2012-03-01

This contribution is aimed at summarizing the effort taken to apply stereoscopic PIV (SPIV) measurements in the tip clearance of a transonic compressor rotor equipped with a casing treatment. A light sheet probe was placed downstream of the stator and aligned to pass the light sheet through a stator passage into the blade tip clearance of the rotor. A setup with three cameras has been used in order to record the entire 2C velocity field and the smaller area of 3C field of view at the same time instance for comparison with earlier 2C PIV results. A homogeneous seeding distribution was achieved by means of a smoke generator. The main emphasis of the SPIV measurement was to establish a data set with high spatial resolution close to the compressor casing, where the aerodynamic effects of a CT are known to be strong. The paper will discuss some major aspects of the utilized PIV data processing and point out a variety of frequently underestimated error sources that influence the overall quality of the recovered data in spite of the fact that the individual PIV recordings seemed to be of very good quality. Thus, the authors will not focus on the PIV results and related interpretation of the flow field, but on the optimization and procedures applied during setup of the experiment and data processing, respectively.

The CF6 engine performance improvement

NASA Technical Reports Server (NTRS)

Fasching, W. A.

1982-01-01

As part of the NASA-sponsored Engine Component Improvement (ECI) Program, a feasibility analysis of performance improvement and retention concepts for the CF6-6 and CF6-50 engines was conducted and seven concepts were identified for development and ground testing: new fan, new front mount, high pressure turbine aerodynamic performance improvement, high pressure turbine roundness, high pressure turbine active clearance control, low pressure turbine active clearance control, and short core exhaust nozzle. The development work and ground testing are summarized, and the major test results and an enomic analysis for each concept are presented.

Dual clearance squeeze film damper

NASA Technical Reports Server (NTRS)

Fleming, D. P. (Inventor)

1985-01-01

A dual clearance hydrodynamic liquid squeeze film damper for a gas turbine engine is described. Under normal operating conditions, the device functions as a conventional squeeze film damper, using only one of its oil films. When an unbalance reaches abusive levels, as may occur with a blade loss or foreign object damage, a second, larger clearance film becomes active, controlling vibration amplitudes in a near optimum manner until the engine can be safely shut down and repaired.

78 FR 21118 - Agency Information Collection Activities; Comment Request; Streamlined Clearance Process for...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-09

...; Comment Request; Streamlined Clearance Process for Discretionary Grants AGENCY: Department of Education... also helps the public understand the Department's information collection requirements and provide the... for Discretionary Grants OMB Control Number: 1894-0001 Type of Review: An extension of an existing...

Physiological and Microfluorometric Studies of Reduction and Clearance of Retinal in Bleached Rod Photoreceptors

PubMed Central

Tsina, Efthymia; Chen, Chunhe; Koutalos, Yiannis; Ala-Laurila, Petri; Tsacopoulos, Marco; Wiggert, Barbara; Crouch, Rosalie K.; Cornwall, M. Carter

2004-01-01

The visual cycle comprises a sequence of reactions that regenerate the visual pigment in photoreceptors during dark adaptation, starting with the reduction of all-trans retinal to all-trans retinol and its clearance from photoreceptors. We have followed the reduction of retinal and clearance of retinol within bleached outer segments of red rods isolated from salamander retina by measuring its intrinsic fluorescence. Following exposure to a bright light (bleach), increasing fluorescence intensity was observed to propagate along the outer segments in a direction from the proximal region adjacent to the inner segment toward the distal tip. Peak retinol fluorescence was achieved after ∼30 min, after which it declined very slowly. Clearance of retinol fluorescence is considerably accelerated by the presence of the exogenous lipophilic substances IRBP (interphotoreceptor retinoid binding protein) and serum albumin. We have used simultaneous fluorometric and electrophysiological measurements to compare the rate of reduction of all-trans retinal to all-trans retinol to the rate of recovery of flash response amplitude in these cells in the presence and absence of IRBP. We find that flash response recovery in rods is modestly accelerated in the presence of extracellular IRBP. These results suggest such substances may participate in the clearance of retinoids from rod photoreceptors, and that this clearance, at least in rods, may facilitate dark adaptation by accelerating the clearance of photoproducts of bleaching. PMID:15452202

Off-Design Performance of Radial-Inflow Turbines

NASA Technical Reports Server (NTRS)

Meitner, P. L.; Glassman, A. J.

1986-01-01

Computer code determines rotor exit flow from hub to tip. RTOD (Radial Turbine Off-Design), computes off-design performance of radial turbine by modeling flow with stator viscous and trailing-edge losses, and with vaneless space loss between stator and rotor, and with rotor incidence, viscous, clearance, trailing-edge, and disk friction losses.

New sensors and techniques for the structural health monitoring of propulsion systems.

PubMed

Woike, Mark; Abdul-Aziz, Ali; Oza, Nikunj; Matthews, Bryan

2013-01-01

The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA), through the Aviation Safety Program (AVSP), has taken a lead role in the development of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. This paper presents a summary of key results and findings obtained from three different structural health monitoring approaches that have been investigated. This includes evaluating the performance of a novel microwave blade tip clearance sensor; a vibration based crack detection technique using an externally mounted capacitive blade tip clearance sensor; and lastly the results of using data driven anomaly detection algorithms for detecting cracks in a rotating disk.

Optical Tip Clearance Measurements as a Tool for Rotating Disk Characterization

PubMed Central

García, Iker; Zubia, Joseba; Beloki, Josu; Arrue, Jon; Durana, Gaizka; Aldabaldetreku, Gotzon

2017-01-01

An experimental investigation on the vibrational behavior of a rotating disk by means of three optical fiber sensors is presented. The disk, which is a scale model of the real disk of an aircraft engine, was assembled in a wind tunnel in order to simulate real operation conditions. The pressure difference between the upstream and downstream sides of the disk causes an airflow that might force the disk to vibrate. To characterize this vibration, a set of parameters was determined by measuring the tip clearance of the disk: the amplitude, the frequency and the number of nodal diameters in the disk. All this information allowed the design of an upgraded prototype of the disk, whose performance was also characterized by the same method. An optical system was employed for the measurements, in combination with a strain gauge mounted on the disk surface, which served to confirm the results obtained. The data of the strain gauge coincided closely with those provided by the optical fiber sensors, thus demonstrating the suitability of this innovative technique to evaluate the vibrational behavior of rotating disks. PMID:28098845

New Sensors and Techniques for the Structural Health Monitoring of Propulsion Systems

PubMed Central

2013-01-01

The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA), through the Aviation Safety Program (AVSP), has taken a lead role in the development of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. This paper presents a summary of key results and findings obtained from three different structural health monitoring approaches that have been investigated. This includes evaluating the performance of a novel microwave blade tip clearance sensor; a vibration based crack detection technique using an externally mounted capacitive blade tip clearance sensor; and lastly the results of using data driven anomaly detection algorithms for detecting cracks in a rotating disk. PMID:23935425

In Vitro Comparison of a Novel Single Probe Dual-Energy Lithotripter to Current Devices.

PubMed

Carlos, Evan C; Wollin, Daniel A; Winship, Brenton B; Jiang, Ruiyang; Radvak, Daniela; Chew, Ben H; Gustafson, Michael R; Simmons, W Neal; Zhong, Pei; Preminger, Glenn M; Lipkin, Michael E

2018-06-01

The LithoClast Trilogy is a novel single probe, dual-energy lithotripter with ultrasonic (US) vibration and electromagnetic impact forces. ShockPulse and LithoClast Select are existing lithotripters that also use a combination of US and mechanical impact energies. We compared the efficacy and tip motion of these devices in an in vitro setting. Begostones, in the ratio 15:3, were used in all trials. Test groups were Trilogy, ShockPulse, Select ultrasound (US) only, and Select ultrasound with pneumatic (USP). For clearance testing, a single investigator facile with each lithotripter fragmented 10 stones per device. For drill testing, a hands-free apparatus with a submerged balance was used to apply 1 or 2 lbs of pressure on a stone in contact with the device tip. High-speed photography was used to assess Trilogy and ShockPulse's probe tip motion. Select-USP was slowest and Trilogy fastest on clearance testing (p < 0.01). On 1 lbs drill testing, Select-US was slowest (p = 0.001). At 2 lbs, ShockPulse was faster than Select US (p = 0.027), but did not significantly outpace Trilogy nor Select-USP. At either weight, there was no significant difference between Trilogy and ShockPulse. During its US function, Trilogy's maximum downward tip displacement was 0.041 mm relative to 0.0025 mm with ShockPulse. Trilogy had 0.25 mm of maximum downward displacement during its impactor function while ShockPulse had 0.01 mm. Single probe dual-energy devices, such as Trilogy and ShockPulse, represent the next generation of lithotripters. Trilogy more efficiently cleared stone than currently available devices, which could be explained by its larger probe diameter and greater downward tip displacement during both US and impactor functions.

Floating wind turbine system

NASA Technical Reports Server (NTRS)

Viterna, Larry A. (Inventor)

2009-01-01

A floating wind turbine system with a tower structure that includes at least one stability arm extending therefrom and that is anchored to the sea floor with a rotatable position retention device that facilitates deep water installations. Variable buoyancy for the wind turbine system is provided by buoyancy chambers that are integral to the tower itself as well as the stability arm. Pumps are included for adjusting the buoyancy as an aid in system transport, installation, repair and removal. The wind turbine rotor is located downwind of the tower structure to allow the wind turbine to follow the wind direction without an active yaw drive system. The support tower and stability arm structure is designed to balance tension in the tether with buoyancy, gravity and wind forces in such a way that the top of the support tower leans downwind, providing a large clearance between the support tower and the rotor blade tips. This large clearance facilitates the use of articulated rotor hubs to reduced damaging structural dynamic loads. Major components of the turbine can be assembled at the shore and transported to an offshore installation site.

Sensing mode atomic force microscope

DOEpatents

Hough, Paul V. C.; Wang, Chengpu

2003-01-01

An atomic force microscope utilizes a pulse release system and improved method of operation to minimize contact forces between a probe tip affixed to a flexible cantilever and a specimen being measured. The pulse release system includes a magnetic particle affixed proximate the probe tip and an electromagnetic coil. When energized, the electromagnetic coil generates a magnetic field which applies a driving force on the magnetic particle sufficient to overcome adhesive forces exhibited between the probe tip and specimen. The atomic force microscope includes two independently displaceable piezo elements operable along a Z-axis. A controller drives the first Z-axis piezo element to provide a controlled approach between the probe tip and specimen up to a point of contact between the probe tip and specimen. The controller then drives the first Z-axis piezo element to withdraw the cantilever from the specimen. The controller also activates the pulse release system which drives the probe tip away from the specimen during withdrawal. Following withdrawal, the controller adjusts the height of the second Z-axis piezo element to maintain a substantially constant approach distance between successive samples.

Heat Transfer and Flow on the First Stage Blade Tip of a Power Generation Gas Turbine. Part 1; Experimental Results

NASA Technical Reports Server (NTRS)

Bunker, Ronald S.; Bailey, Jeremy C.; Ameri, Ali A.

1999-01-01

A combined computational and experimental study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first stage blade tip surface for a geometry typical of large power generation turbines(>100MW). This paper is concerned with the design and execution of the experimental portion of the study. A stationary blade cascade experiment has been run consisting of three airfoils, the center airfoil having a variable tip gap clearance. The airfoil models the aerodynamic tip section of a high pressure turbine blade with inlet Mach number of 0.30, exit Mach number of 0.75, pressure ratio of 1.45, exit Reynolds number based on axial chord of 2.57 x 10(exp 6), and total turning of about 110 degrees. A hue detection based liquid crystal method is used to obtain the detailed heat transfer coefficient distribution on the blade tip surface for flat, smooth tip surfaces with both sharp and rounded edges. The cascade inlet turbulence intensity level took on values of either 5% or 9%. The cascade also models the casing recess in the shroud surface ahead of the blade. Experimental results are shown for the pressure distribution measurements on the airfoil near the tip gap, on the blade tip surface, and on the opposite shroud surface. Tip surface heat transfer coefficient distributions are shown for sharp-edge and rounded-edge tip geometries at each of the inlet turbulence intensity levels.

Phosphorylation regulates the water channel activity of the seed-specific aquaporin alpha-TIP.

PubMed

Maurel, C; Kado, R T; Guern, J; Chrispeels, M J

1995-07-03

The vacuolar membrane protein alpha-TIP is a seed-specific protein of the Major Intrinsic Protein family. Expression of alpha-TIP in Xenopus oocytes conferred a 4- to 8-fold increase in the osmotic water permeability (Pf) of the oocyte plasma membrane, showing that alpha-TIP forms water channels and is thus a new aquaporin. alpha-TIP has three putative phosphorylation sites on the cytoplasmic side of the membrane (Ser7, Ser23 and Ser99), one of which (Ser7) has been shown to be phosphorylated. We present several lines of evidence that the activity of this aquaporin is regulated by phosphorylation. First, mutation of the putative phosphorylation sites in alpha-TIP (Ser7Ala, Ser23Ala and Ser99Ala) reduced the apparent water transport activity of alpha-TIP in oocytes, suggesting that phosphorylation of alpha-TIP occurs in the oocytes and participates in the control of water channel activity. Second, exposure of oocytes to the cAMP agonists 8-bromoadenosine 3',5'-cyclic monophosphate, forskolin and 3-isobutyl-1-methylxanthine, which stimulate endogenous protein kinase A (PKA), increased the water transport activity of alpha-TIP by 80-100% after 60 min. That the protein can be phosphorylated by PKA was demonstrated by phosphorylating alpha-TIP in isolated oocyte membranes with the bovine PKA catalytic subunit. Third, the integrity of the three sites at positions 7, 23 and 99 was necessary for the cAMP-dependent increase in the Pf of oocytes expressing alpha-TIP, as well as for in vitro phosphorylation of alpha-TIP. These findings demonstrate that the alpha-TIP water channel can be modulated via phosphorylation of Ser7, Ser23 and Ser99.(ABSTRACT TRUNCATED AT 250 WORDS)

Fitness: Tips for Staying Motivated

MedlinePlus

... life. Review these tips whenever you feel your motivation slipping. Identifying your fitness goals. American Heart Association. ... prescription. Primary Care. 2013;40:801. Physical activity: Motivation. Centers for Disease Control and Prevention. http://www. ...

Evaluation of a low aspect ratio small axial compressor stage, volume 1

NASA Technical Reports Server (NTRS)

Sawyer, C. W., III

1977-01-01

A program was conducted to evaluate the effects of scaling, tip clearance, and IGV reset on the performance of a low aspect ratio compressor stage. Stage design was obtained by scaling an existing single stage compressor by a linear factor of 0.304. The design objective was to maintain the meanline velocity field of the base machine in the smaller size. Adjustments were made to account for predicted blockage differences and to chord lengths and airfoil edge radii to obtain reasonable blade geometries. Meanline velocity diagrams of the base stage were not maintained at the scaled size. At design speed and flowrate the scaled stage achieved a pressure ratio of 1.423, adiabatic efficiency of 0.822, and surge margin of 18.5%. The corresponding performance parameters for the base stage were 1.480, 0.872, and 25.2%, respectively. The base stage demonstrated a peak efficiency at design speed of 0.872; the scaled stage achieved a level of 0.838. When the scaled stage rotor and stator tip clearances were doubled, the stage achieved a pressure ratio of 1.413, efficiency of 0.799, and surge margin of 16.0% at the design flowrate. The peak stage efficiency at design speed was 0.825 with the increased clearance. Increased prewhirl lowered the stage pressure ratio as expected. Stage efficiency was maintained with ten degrees of increased prewhirl and then decreased substantially with ten additional degrees of reset.

Influence of Finite Span and Sweep on Active Flow Control Efficacy

NASA Technical Reports Server (NTRS)

Greenblatt, David; Washburn, Anthony E.

2008-01-01

Active flow control efficacy was investigated by means of leading-edge and flap-shoulder zero mass-flux blowing slots on a semispan wing model that was tested in unswept (standard) and swept configurations. On the standard configuration, stall commenced inboard, but with sweep the wing stalled initially near the tip. On both configurations, leading-edge perturbations increased CL,max and post stall lift, both with and without deflected flaps. Without sweep, the effect of control was approximately uniform across the wing span but remained effective to high angles of attack near the tip; when sweep was introduced a significant effect was noted inboard, but this effect degraded along the span and produced virtually no meaningful lift enhancement near the tip, irrespective of the tip configuration. In the former case, control strengthened the wingtip vortex; in the latter case, a simple semi-empirical model, based on the trajectory or "streamline" of the evolving perturbation, served to explain the observations. In the absence of sweep, control on finite-span flaps did not differ significantly from their nominally twodimensional counterpart. Control from the flap produced expected lift enhancement and CL,max improvements in the absence of sweep, but these improvements degraded with the introduction of sweep.

Experiment measurement of Alford's force in axial-flow turbomachinery

NASA Technical Reports Server (NTRS)

Vance, J. M.; Laudadio, F. J.

1982-01-01

Results of experimental measurements made on a small high speed, axial flow test apparatus are presented to verify the existence of Alford's force (that circumferential variation of blade-tip clearances in axial-flow turbomachinery will produce cross-coupled (normal to the eccentricity) aerodynamic forces on the rotor) and to investigate the validity of his mathematical prediction model.

Self-excited rotor whirl due to tip-seal leakage forces

NASA Technical Reports Server (NTRS)

Leie, B.; Thomas, H. J.

1980-01-01

The limitations in the performance of turbomachines which arise as a result of selfexcited vibration were investigated. Bearing forces, elastic hysteresis, and forces from fluid flow through clearances were considered as possible origins. A theoretical evaluation was made to determine the dependence of the forces form the leakage losses and from rotating flow in radial gaps.

Multitip scanning bio-Kelvin probe

NASA Astrophysics Data System (ADS)

Baikie, I. D.; Smith, P. J. S.; Porterfield, D. M.; Estrup, P. J.

1999-03-01

We have developed a novel multitip scanning Kelvin probe which can measure changes in biological surface potential ΔVs to within 2 mV and, quasisimultaneously monitor displacement to <1 μm. The control and measurement subcomponents are PC based and incorporate a flexible user interface permitting software control of each individual tip, measurement, and scan parameters. We review the mode of operation and design features of the scanning bio-Kelvin probe including tip steering, signal processing, tip calibration, and novel tip tracking/dithering routines. This system uniquely offers both tip-to-sample spacing control (which is essential to avoid spurious changes in ΔVs due to variations in mean spacing) and a dithering routine to maintain tip orientation to the biological specimen, irrespective of the latter's movement. These features permit long term (>48 h) "active" tracking of the displacement and biopotentials developed along and around a plant shoot in response to an environmental stimulus, e.g., differential illumination (phototropism) or changes in orientation (gravitropism).

Magnetic force microscopy with frequency-modulated capacitive tip-sample distance control

NASA Astrophysics Data System (ADS)

Zhao, X.; Schwenk, J.; Mandru, A. O.; Penedo, M.; Baćani, M.; Marioni, M. A.; Hug, H. J.

2018-01-01

In a step towards routinely achieving 10 nm spatial resolution with magnetic force microscopy, we have developed a robust method for active tip-sample distance control based on frequency modulation of the cantilever oscillation. It allows us to keep a well-defined tip-sample distance of the order of 10 nm within better than +/- 0.4 nm precision throughout the measurement even in the presence of energy dissipative processes, and is adequate for single-passage non-contact operation in vacuum. The cantilever is excited mechanically in a phase-locked loop to oscillate at constant amplitude on its first flexural resonance mode. This frequency is modulated by an electrostatic force gradient generated by tip-sample bias oscillating from a few hundred Hz up to a few kHz. The sum of the side bands’ amplitudes is a proxy for the tip-sample distance and can be used for tip-sample distance control. This method can also be extended to other scanning probe microscopy techniques.

Energy Efficient Engine: Control system preliminary definition report

NASA Technical Reports Server (NTRS)

Howe, David C.

1986-01-01

The object of the Control Preliminary Definition Program was to define a preliminary control system concept as a part of the Energy Efficient Engine program. The program was limited to a conceptual definition of a full authority digital electronic control system. System requirements were determined and a control system was conceptually defined to these requirements. Areas requiring technological development were identified and a plan was established for implementing the identified technological features, including a control technology demonstration. A significant element of this program was a study of the potential benefits of closed-loop active clearance control, along with laboratory tests of candidate clearance sensor elements for a closed loop system.

Tip clearance noise of axial flow fans operating at design and off-design condition

NASA Astrophysics Data System (ADS)

Fukano, T.; Jang, C.-M.

2004-08-01

The noise due to tip clearance (TC) flow in axial flow fans operating at a design and off-design conditions is analyzed by an experimental measurement using two hot-wire probes rotating with the fan blades. The unsteady nature of the spectra of the real-time velocities measured by two hot-wire sensors in a vortical flow region is investigated by using cross-correlation coefficient and retarded time of the two fluctuating velocities. The results show that the noise due to TC flow consists of a discrete frequency noise due to periodic velocity fluctuation and a broadband noise due to velocity fluctuation in the blade passage. The peak frequencies in a vortical flow are mainly observed below at four harmonic blade passing frequency. The discrete frequency component of velocity fluctuation at the off-design operating conditions is generated in vortical flow region as well as in reverse flow region. The peak frequency can be an important noise source when the fans are rotated with a high rotational speed. The authors propose a spiral pattern of velocity fluctuation in the vortical flow to describe the generation mechanism of the peak frequency in the vortical flow. In addition, noise increase due to TC flow at low flow rate condition is analyzed with relation to the distribution of velocity fluctuation due to the interference between the tip leakage vortex and the adjacent pressure surface of the blade.

A Numerical Analysis on the Effects of Self-Excited Tip Flow Unsteadiness and Upstream Blade Row Interactions on the Performance Predictions of a Transonic Compressor

NASA Astrophysics Data System (ADS)

Heberling, Brian

Computational fluid dynamics (CFD) simulations can offer a detailed view of the complex flow fields within an axial compressor and greatly aid the design process. However, the desire for quick turnaround times raises the question of how exact the model must be. At design conditions, steady CFD simulating an isolated blade row can accurately predict the performance of a rotor. However, as a compressor is throttled and mass flow rate decreased, axial flow becomes weaker making the capturing of unsteadiness, wakes, or other flow features more important. The unsteadiness of the tip clearance flow and upstream blade wake can have a significant impact on a rotor. At off-design conditions, time-accurate simulations or modeling multiple blade rows can become necessary in order to receive accurate performance predictions. Unsteady and multi- bladerow simulations are computationally expensive, especially when used in conjunction. It is important to understand which features are important to model in order to accurately capture a compressor's performance. CFD simulations of a transonic axial compressor throttling from the design point to stall are presented. The importance of capturing the unsteadiness of the rotor tip clearance flow versus capturing upstream blade-row interactions is examined through steady and unsteady, single- and multi-bladerow computations. It is shown that there are significant differences at near stall conditions between the different types of simulations.

Use of radioisotopic esophageal transit in the assessment of patients with symptoms of reflux and non-specific esophageal motor disorders.

PubMed

Iascone, C; Di Giulio, E; Maffi, C; Ruperto, M

2004-01-01

The purposes of this study were to assess the esophageal clearance of a radioisotopic bolus in patients with symptoms of reflux and evaluate the impact of manometric abnormalities on scintigraphic esophageal transit. Esophageal clearance was assessed in a supine position and indicated by the retained radioactivity in the esophagus at 10, 20, 30 and 40 s after the ingestion of a liquid bolus labeled with 2 mCi 99 mTc-SC. The study included 214 consecutive patients with symptoms of reflux and 11 normal controls. The results were compared to the motility findings detected on manometry performed on a separate occasion. Esophageal manometry was normal in 93 patients. Nonspecific esophageal motor disorders were identified in 121 patients and were classified into: 'predominantly nonpropagated activity', 'predominantly low-amplitude peristaltic contractions' and 'miscellaneous disorders' diagnosed in 27, 47 and 47 patients, respectively. The radionuclide clearance was significantly delayed in the overall group of patients compared with that of normal controls (P < 0.001); in patients with reflux symptoms and nonspecific esophageal motor disorders compared with patients with reflux symptoms and 'normal manometry' (P < 0.01 at 20 s); and in patients with reflux symptoms and 'normal manometry' compared with the control group (P < 0.01 at 20 s). Abnormal radioisotope clearances were detected in 88% of patients with 'predominantly nonpropagated activity', in 70% of patients with 'predominantly low-amplitude peristaltic contractions' and in 57% of patients with 'miscellaneous disorders'. Radioisotopic esophageal clearance abnormalities are frequently observed in patients with reflux symptoms and are more likely to be associated to hypomotility disorders, i.e. nonpropagated motor activity or low-amplitude contractions.

Tip off the HAT– Epigenetic control of learning and memory by Drosophila Tip60

PubMed Central

Xu, Songjun; Elefant, Felice

2015-01-01

Disruption of epigenetic gene control mechanisms involving histone acetylation in the brain causes cognitive impairment, a debilitating hallmark of most neurodegenerative disorders. Histone acetylation regulates cognitive gene expression via chromatin packaging control in neurons. Unfortunately, the histone acetyltransferases (HATs) that generate such neural epigenetic signatures and their mechanisms of action remain unclear. Our recent findings provide insight into this question by demonstrating that Tip60 HAT action is critical for morphology and function of the mushroom body (MB), the learning and memory center in the Drosophila brain. We show that Tip60 is robustly produced in MB Kenyon cells and extending axonal lobes and that targeted MB Tip60 HAT loss results in axonal outgrowth disruption. Functional consequences of loss and gain of Tip60 HAT levels in the MB are evidenced by defects in memory. Tip60 ChIP-Seq analysis reveals enrichment for genes that function in cognitive processes and accordingly, key genes representing these pathways are misregulated in the Tip60 HAT mutant fly brain. Remarkably, increasing levels of Tip60 in the MB rescues learning and memory deficits resulting from Alzheimer's disease associated amyloid precursor protein (APP) induced neurodegeneration. Our studies highlight the potential of HAT activators as a therapeutic option for cognitive disorders. PMID:26327426

Measurements of the tip leakage vortex structures and turbulence in the meridional plane of an axial water-jet pump

NASA Astrophysics Data System (ADS)

Wu, Huixuan; Miorini, Rinaldo L.; Katz, Joseph

2011-04-01

Particle image velocimetry (PIV) measurements at varying resolutions focus on the flow structures in the tip region of a water-jet pump rotor, including the tip-clearance flow and the rollup process of a tip leakage vortex (TLV). Unobstructed views of these regions are facilitated by matching the optical refractive index of the transparent pump with that of the fluid. High-magnification data reveal the flow non-uniformities and associated turbulence within the tip gap. Instantaneous data and statistics of spatial distributions and strength of vortices in the rotor passage reveal that the leakage flow emerges as a wall jet with a shear layer containing a train of vortex filaments extending from the tip of the blade. These vortices are entrained into the TLV, but do not have time to merge. TLV breakdown in the aft part of the blade passage further fragments these structures, increasing their number and reducing their size. Analogy is made between the circumferential development of the TLV in the blade passage and that of the starting jet vortex ring rollup. Subject to several assumptions, these flows display similar trends, including conditions for TLV separation from the shear layer feeding vorticity into it.

Energy dissipation in the blade tip region of an axial fan

NASA Astrophysics Data System (ADS)

Bizjan, B.; Milavec, M.; Širok, B.; Trenc, F.; Hočevar, M.

2016-11-01

A study of velocity and pressure fluctuations in the tip clearance flow of an axial fan is presented in this paper. Two different rotor blade tip designs were investigated: the standard one with straight blade tips and the modified one with swept-back tip winglets. Comparison of integral sound parameters indicates a significant noise level reduction for the modified blade tip design. To study the underlying mechanisms of the energy conversion and noise generation, a novel experimental method based on simultaneous measurements of local flow velocity and pressure has also been developed and is presented here. The method is based on the phase space analysis by the use of attractors, which enable more accurate identification and determination of the local flow structures and turbulent flow properties. Specific gap flow energy derived from the pressure and velocity time series was introduced as an additional attractor parameter to assess the flow energy distribution and dissipation within the phase space, and thus determines characteristic sources of the fan acoustic emission. The attractors reveal a more efficient conversion of the pressure to kinetic flow energy in the case of the modified (tip winglet) fan blade design, and also a reduction in emitted noise levels. The findings of the attractor analysis are in a good agreement with integral fan characteristics (efficiency and noise level), while offering a much more accurate and detailed representation of gap flow phenomena.

The sensitivity and negative predictive value of a pediatric cervical spine clearance algorithm that minimizes computerized tomography.

PubMed

Arbuthnot, Mary; Mooney, David P

2017-01-01

It is crucial to identify cervical spine injuries while minimizing ionizing radiation. This study analyzes the sensitivity and negative predictive value of a pediatric cervical spine clearance algorithm. We performed a retrospective review of all children <21years old who were admitted following blunt trauma and underwent cervical spine clearance utilizing our institution's cervical spine clearance algorithm over a 10-year period. Age, gender, International Classification of Diseases 9th Edition diagnosis codes, presence or absence of cervical collar on arrival, Injury Severity Score, and type of cervical spine imaging obtained were extracted from the trauma registry and electronic medical record. Descriptive statistics were used and the sensitivity and negative predictive value of the algorithm were calculated. Approximately 125,000 children were evaluated in the Emergency Department and 11,331 were admitted. Of the admitted children, 1023 patients arrived in a cervical collar without advanced cervical spine imaging and were evaluated using the cervical spine clearance algorithm. Algorithm sensitivity was 94.4% and the negative predictive value was 99.9%. There was one missed injury, a spinous process tip fracture in a teenager maintained in a collar. Our algorithm was associated with a low missed injury rate and low CT utilization rate, even in children <3years old. IV. Published by Elsevier Inc.

Component Performance Investigation of J71 Experimental Turbine. Part 2; Internal-Flow Conditions with 97-Percent-Design Stator Areas

NASA Technical Reports Server (NTRS)

Rebeske, John J., Jr.; Petrash, Donald A.

1956-01-01

An experimental investigation of the internal-flow conditions of a J71 experimental turbine equipped with 97-percent-design stator areas was conducted at equivalent design speed and near equivalent design work. The results of the investigation indicate that the stage work distribution closely approximates design, the actual distribution being 44.1, 33.4, and 22.5 percent for the first, second, and third stages, respectively. The first-, second-, and third-stage efficiencies were 0.894, 0.858, and 0.792, respectively. The first and second stages exhibited loss regions near the hub and tip at the rotor blade outlets. The hub loss region is attributed to stator secondary flows, and a contributing factor to the tip loss region may be the high design diffusion on the rotor blade suction surface near the tip. The loss in the third stage is appreciably greater than that in the first or second stage. The fact that the third rotor is unshrouded and has a nominal tip clearance of 0.120 inch may contribute to the higher loss in the tip region of the third stage.

Development and experimental characterization of a new non contact sensor for blade tip timing

NASA Astrophysics Data System (ADS)

Brouckaert, Jean-Francois; Marsili, Roberto; Rossi, Gianluca; Tomassini, Roberto

2012-06-01

Performances of blade tip timing measurement systems (BTT), recently used for non contact turbine blade vibration measurements, in terms of uncertainty and resolution are strongly affected by sensor characteristics. The sensors used for BTT generate pulses, to be used also for precise measurements of turbine blades time of arrival. All the literature on this measurement techniques do not address this problem in a clear way, defining the relevant dynamic and static sensor characteristics, fundamental for this application. Till now proximity sensors used are based on optical, capacitive, eddy current and microwave measuring principle. Also pressure sensors has been used. In this paper a new sensing principle is proposed. A proximity sensor based on magnetoresistive sensing element has been assembled end tested. A simple and portable test bench with variable speed, blade tip width, variable clearance was built and used in order to characterize the main sensor performances.

A prediction of 3-D viscous flow and performance of the NASA Low-Speed Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Moore, John; Moore, Joan G.

1990-01-01

A prediction of the three-dimensional turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation of high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modeling. Recommendations are made for future flow studies in the NASA impeller.

A prediction of 3-D viscous flow and performance of the NASA low-speed centrifugal compressor

NASA Technical Reports Server (NTRS)

Moore, John; Moore, Joan G.

1989-01-01

A prediction of the 3-D turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation for high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modelling. Recommendations are made for future flow studies in the NASA impeller.

JT8D high pressure compressor performance improvement

NASA Technical Reports Server (NTRS)

Gaffin, W. O.

1981-01-01

An improved performance high pressure compressor with potential application to all models of the JT8D engine was designed. The concept consisted of a trenched abradable rubstrip which mates with the blade tips for each of the even rotor stages. This feature allows tip clearances to be set so blade tips run at or near the optimum radius relative to the flowpath wall, without the danger of damaging the blades during transients and maneuvers. The improved compressor demonstrated thrust specific fuel consumption and exhaust gas temperature improvements of 1.0 percent and at least 10 C over the takeoff and climb power range at sea level static conditions, compared to a bill-of-material high pressure compressor. Surge margin also improved 4 percentage points over the high power operating range. A thrust specific fuel consumption improvement of 0.7 percent at typical cruise conditions was calculated based on the sea level test results.

Pre-Stall Behavior of a Transonic Axial Compressor Stage via Time-Accurate Numerical Simulation

NASA Technical Reports Server (NTRS)

Chen, Jen-Ping; Hathaway, Michael D.; Herrick, Gregory P.

2008-01-01

CFD calculations using high-performance parallel computing were conducted to simulate the pre-stall flow of a transonic compressor stage, NASA compressor Stage 35. The simulations were run with a full-annulus grid that models the 3D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation demonstrates the development of the rotating stall from the growth of instabilities. Pressure-rise performance and pressure traces are compared with published experimental data before the study of flow evolution prior to the rotating stall. Spatial FFT analysis of the flow indicates a rotating long-length disturbance of one rotor circumference, which is followed by a spike-type breakdown. The analysis also links the long-length wave disturbance with the initiation of the spike inception. The spike instabilities occur when the trajectory of the tip clearance flow becomes perpendicular to the axial direction. When approaching stall, the passage shock changes from a single oblique shock to a dual-shock, which distorts the perpendicular trajectory of the tip clearance vortex but shows no evidence of flow separation that may contribute to stall.

Rational design and validation of a Tip60 histone acetyltransferase inhibitor

NASA Astrophysics Data System (ADS)

Gao, Chunxia; Bourke, Emer; Scobie, Martin; Famme, Melina Arcos; Koolmeister, Tobias; Helleday, Thomas; Eriksson, Leif A.; Lowndes, Noel F.; Brown, James A. L.

2014-06-01

Histone acetylation is required for many aspects of gene regulation, genome maintenance and metabolism and dysfunctional acetylation is implicated in numerous diseases, including cancer. Acetylation is regulated by histone acetyltransferases (HATs) and histone deacetylases and currently, few general HAT inhibitors have been described. We identified the HAT Tip60 as an excellent candidate for targeted drug development, as Tip60 is a key mediator of the DNA damage response and transcriptional co-activator. Our modeling of Tip60 indicated that the active binding pocket possesses opposite charges at each end, with the positive charges attributed to two specific side chains. We used structure based drug design to develop a novel Tip60 inhibitor, TH1834, to fit this specific pocket. We demonstrate that TH1834 significantly inhibits Tip60 activity in vitro and treating cells with TH1834 results in apoptosis and increased unrepaired DNA damage (following ionizing radiation treatment) in breast cancer but not control cell lines. Furthermore, TH1834 did not affect the activity of related HAT MOF, as indicated by H4K16Ac, demonstrating specificity. The modeling and validation of the small molecule inhibitor TH1834 represents a first step towards developing additional specific, targeted inhibitors of Tip60 that may lead to further improvements in the treatment of breast cancer.

Radioaerosol lung clearance in patients with active pulmonary sarcoidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, M.P.; Baughman, R.P.; Hughes, J.

1985-05-01

Pulmonary radioaerosol clearance rate of /sup 99m/Tc diethylenetriamine pentacetate (DTPA) in 14 patients with untreated sarcoidosis was compared with /sup 67/Ga lung scan and increased lymphocytes in the bronchoalveolar lavage (BAL) fluid. Nine healthy nonsmoking subjects had a mean DTPA clearance rate of 1.18%/min (range, 0.54 to 1.60%/min). Eight of 14 patients with sarcoidosis had clearance rates greater than 1.60%/min. Of those 8 patients with abnormal DTPA clearance, 4 had positive gallium scans, 4 had more than 17% lymphocytes in the BAL fluid, and 3 had both tests positive. To study the cause of abnormal DTPA clearance, 23 subjects (includingmore » 3 normal controls, all 14 patients with sarcoidosis, and 6 patients with localized disease on chest roentgenogram) underwent both DTPA clearance studies and BAL for quantitation of the amount of albumin in lung fluid. There was a positive correlation between the rate of DTPA clearance and the albumin concentration in lung fluid (r = 0.87, p less than 0.01).« less

Development of Active Catheter,Active Guide Wire and Micro Sensor Systems

PubMed Central

Haga, Y.; Mineta, T.; Totsu, K.; Makishi, W.; Esashi, M.

2001-01-01

Summary Active catheters and active guide wires which move like a snake have been developed for catheter-based minimally invasive diagnosis and therapy. Communication and control IC chips in the active catheter reduce the number of lead wires for control. The active catheter can be not only bent but also torsioned and extended. An ultra minature fiber-optic pressure sensor; a forward-looking ultrasonic probe and a magnetic position and orientation sensor have been developed for catheters and guide wires. These moving mechanisms and several sensors which are fitted near the tip of the catheter and the guide wire will provide detailed information near the tip and enable delicate and effective catheter intervention. PMID:20663389

Rotor whirl forces induced by the tip clearance effect in axial flow compressors

NASA Astrophysics Data System (ADS)

Ehrich, F.

1993-10-01

It is now widely recognized that destabilizing forces, tending to generate forward rotor whirl, are generated in axial flow turbines as a result of the nonuniform torque induced by the nonuniform tip-clearance in a deflected rotor-the so called Thomas/Alford force (Thomas, 1958, and Alford, 1965). It is also recognized that there will be a similar effect in axial flow compressors, but qualitative considerations cannot definitively establish the magnitude or even the direction of the induced whirling forces-that is, if they will tend to forward or backward whirl. Applying a 'parallel compressor' model to simulate the operation of a compressor rotor deflected radially in its clearance, it is possible to derive a quantitative estimate of the proportionality factor which relates the Thomas/Alford force in axial flow compressors (i.e., the tangential force generated by a radial deflection of the rotor) to the torque level in the compressor. The analysis makes use of experimental data from the GE Aircraft Engines Low Speed Research Compressor facility comparing the performance of three different axial flow compressors, each with four stages (typical of a mid-block of an aircraft gas turbine compressor) at two different clearances (expressed as a percent of blade length) - CL/L = 1.4 percent and CL/L = 2.8 percent. It is found that the value of Beta is in the range of + 0.27 to - 0.71 in the vicinity of the stages' nominal operating line and + 0.08 to - 1.25 in the vicinity of the stages' operation at peak efficiency. The value of Beta reaches a level of between - 1.16 and - 3.36 as the compressor is operated near its stalled condition. The final result bears a very strong resemblance to the correlation obtained by improvising a normalization of the experimental data of Vance and Laudadio (1984) and a generic relationship to the analytic results of Colding-Jorgensen (1990).

DDT spray for control of the ponderosa pine tip moth (Rhyacionia zozana [Kearfott])

Treesearch

Robert E. Stevens

1965-01-01

A water emulsion spray of DDT applied by hand sprayer to young trees infested with eggs and early-instar larvae of the ponderosa pine tip moth halted further larval activity and effectively prevented all damage.

Propulsion Health Monitoring of a Turbine Engine Disk Using Spin Test Data

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Woike, Mark R.; Oza, Nikunj; Matthews, Bryan; Baaklini, George Y.

2010-01-01

This paper considers data collected from an experimental study using high frequency capacitive sensor technology to capture blade tip clearance and tip timing measurements in a rotating turbine engine-like-disk-to predict the disk faults and assess its structural integrity. The experimental results collected at a range of rotational speeds from tests conducted at the NASA Glenn Research Center s Rotordynamics Laboratory are evaluated using multiple data-driven anomaly detection techniques to identify abnormalities in the disk. Further, this study presents a select evaluation of an online health monitoring scheme of a rotating disk using high caliber sensors and test the capability of the in-house spin system.

Multiple roles of filopodial dynamics in particle capture and phagocytosis and phenotypes of Cdc42 and Myo10 deletion

PubMed Central

Horsthemke, Markus; Bachg, Anne C.; Groll, Katharina; Moyzio, Sven; Müther, Barbara; Hemkemeyer, Sandra A.; Wedlich-Söldner, Roland; Sixt, Michael; Tacke, Sebastian; Bähler, Martin; Hanley, Peter J.

2017-01-01

Macrophage filopodia, finger-like membrane protrusions, were first implicated in phagocytosis more than 100 years ago, but little is still known about the involvement of these actin-dependent structures in particle clearance. Using spinning disk confocal microscopy to image filopodial dynamics in mouse resident Lifeact-EGFP macrophages, we show that filopodia, or filopodia-like structures, support pathogen clearance by multiple means. Filopodia supported the phagocytic uptake of bacterial (Escherichia coli) particles by (i) capturing along the filopodial shaft and surfing toward the cell body, the most common mode of capture; (ii) capturing via the tip followed by retraction; (iii) combinations of surfing and retraction; or (iv) sweeping actions. In addition, filopodia supported the uptake of zymosan (Saccharomyces cerevisiae) particles by (i) providing fixation, (ii) capturing at the tip and filopodia-guided actin anterograde flow with phagocytic cup formation, and (iii) the rapid growth of new protrusions. To explore the role of filopodia-inducing Cdc42, we generated myeloid-restricted Cdc42 knock-out mice. Cdc42-deficient macrophages exhibited rapid phagocytic cup kinetics, but reduced particle clearance, which could be explained by the marked rounded-up morphology of these cells. Macrophages lacking Myo10, thought to act downstream of Cdc42, had normal morphology, motility, and phagocytic cup formation, but displayed markedly reduced filopodia formation. In conclusion, live-cell imaging revealed multiple mechanisms involving macrophage filopodia in particle capture and engulfment. Cdc42 is not critical for filopodia or phagocytic cup formation, but plays a key role in driving macrophage lamellipodial spreading. PMID:28289096

Inhaled nano- and microparticles for drug delivery

PubMed Central

El-Sherbiny, Ibrahim M.; El-Baz, Nancy M.; Yacoub, Magdi H.

2015-01-01

The 21st century has seen a paradigm shift to inhaled therapy, for both systemic and local drug delivery, due to the lung's favourable properties of a large surface area and high permeability. Pulmonary drug delivery possesses many advantages, including non-invasive route of administration, low metabolic activity, control environment for systemic absorption and avoids first bypass metabolism. However, because the lung is one of the major ports of entry, it has multiple clearance mechanisms, which prevent foreign particles from entering the body. Although these clearance mechanisms maintain the sterility of the lung, clearance mechanisms can also act as barriers to the therapeutic effectiveness of inhaled drugs. This effectiveness is also influenced by the deposition site and delivered dose. Particulate-based drug delivery systems have emerged as an innovative and promising alternative to conventional inhaled drugs to circumvent pulmonary clearance mechanisms and provide enhanced therapeutic efficiency and controlled drug release. The principle of multiple pulmonary clearance mechanisms is reviewed, including mucociliary, alveolar macrophages, absorptive, and metabolic degradation. This review also discusses the current approaches and formulations developed to achieve optimal pulmonary drug delivery systems. PMID:26779496

Effect of ultrasonic tip designs on intraradicular post removal.

PubMed

Aguiar, Anny Carine Barros; de Meireles, Daniely Amorim; Marques, André Augusto Franco; Sponchiado Júnior, Emílio Carlos; Garrido, Angela Delfina Bitencourt; Garcia, Lucas da Fonseca Roberti

2014-11-01

To evaluate the effect of different ultrasonic tip designs on intraradicular post removal. The crowns of forty human canine teeth were removed, and after biomechanical preparation and filling, the roots were embedded in acrylic resin blocks. The post spaces were made, and root canal molding was performed with self-cured acrylic resin. After casting (Cu-Al), the posts were cemented with zinc phosphate cement. The specimens were randomly separated into 4 groups (n = 10), as follows: G1 - no ultrasonic vibration (control); G2 - ultrasonic vibration using an elongated cylindrical-shaped and active rounded tip; G3 - ultrasonic vibration with a flattened convex and linear active tip; G4 - ultrasonic vibration with active semicircular tapered tip. Ultrasonic vibration was applied for 15 seconds on each post surface and tensile test was performed in a Universal Testing Machine (Instron 4444 - 1 mm/min). G4 presented the highest mean values, however, with no statistically significant difference in comparison to G3 (P > 0.05). G2 presented the lowest mean values with statistically significant difference to G3 and G4 (P < 0.05). Ultrasonic vibration with elongated cylindrical-shaped and active rounded tip was most effective in reducing force required for intraradicular post removal.

Epigenetic Regulation of Axonal Growth of Drosophila Pacemaker Cells by Histone Acetyltransferase Tip60 Controls Sleep

PubMed Central

Pirooznia, Sheila K.; Chiu, Kellie; Chan, May T.; Zimmerman, John E.; Elefant, Felice

2012-01-01

Tip60 is a histone acetyltransferase (HAT) enzyme that epigenetically regulates genes enriched for neuronal functions through interaction with the amyloid precursor protein (APP) intracellular domain. However, whether Tip60-mediated epigenetic dysregulation affects specific neuronal processes in vivo and contributes to neurodegeneration remains unclear. Here, we show that Tip60 HAT activity mediates axonal growth of the Drosophila pacemaker cells, termed “small ventrolateral neurons” (sLNvs), and their production of the neuropeptide pigment-dispersing factor (PDF) that functions to stabilize Drosophila sleep–wake cycles. Using genetic approaches, we show that loss of Tip60 HAT activity in the presence of the Alzheimer’s disease-associated APP affects PDF expression and causes retraction of the sLNv synaptic arbor required for presynaptic release of PDF. Functional consequence of these effects is evidenced by disruption of the sleep–wake cycle in these flies. Notably, overexpression of Tip60 in conjunction with APP rescues these sleep–wake disturbances by inducing overelaboration of the sLNv synaptic terminals and increasing PDF levels, supporting a neuroprotective role for dTip60 in sLNv growth and function under APP-induced neurodegenerative conditions. Our findings reveal a novel mechanism for Tip60 mediated sleep–wake regulation via control of axonal growth and PDF levels within the sLNv-encompassing neural network and provide insight into epigenetic-based regulation of sleep disturbances observed in neurodegenerative diseases like Alzheimer’s disease. PMID:22982579

Epigenetic control of learning and memory in Drosophila by Tip60 HAT action.

PubMed

Xu, Songjun; Wilf, Rona; Menon, Trisha; Panikker, Priyalakshmi; Sarthi, Jessica; Elefant, Felice

2014-12-01

Disruption of epigenetic gene control mechanisms in the brain causes significant cognitive impairment that is a debilitating hallmark of most neurodegenerative disorders, including Alzheimer's disease (AD). Histone acetylation is one of the best characterized of these epigenetic mechanisms that is critical for regulating learning- and memory- associated gene expression profiles, yet the specific histone acetyltransferases (HATs) that mediate these effects have yet to be fully characterized. Here, we investigate an epigenetic role for the HAT Tip60 in learning and memory formation using the Drosophila CNS mushroom body (MB) as a well-characterized cognition model. We show that Tip60 is endogenously expressed in the Kenyon cells, the intrinsic neurons of the MB, and in the MB axonal lobes. Targeted loss of Tip60 HAT activity in the MB causes thinner and shorter axonal lobes while increasing Tip60 HAT levels cause no morphological defects. Functional consequences of both loss and gain of Tip60 HAT levels in the MB are evidenced by defects in immediate-recall memory. Our ChIP-Seq analysis reveals that Tip60 target genes are enriched for functions in cognitive processes, and, accordingly, key genes representing these pathways are misregulated in the Tip60 HAT mutant fly brain. Remarkably, we find that both learning and immediate-recall memory deficits that occur under AD-associated, amyloid precursor protein (APP)-induced neurodegenerative conditions can be effectively rescued by increasing Tip60 HAT levels specifically in the MB. Together, our findings uncover an epigenetic transcriptional regulatory role for Tip60 in cognitive function and highlight the potential of HAT activators as a therapeutic option for neurodegenerative disorders. Copyright © 2014 by the Genetics Society of America.

An analysis of the viscous flow through a compact radial turbine by the average passage approach

NASA Technical Reports Server (NTRS)

Heidmann, James D.; Beach, Timothy A.

1990-01-01

A steady, three-dimensional viscous average passage computer code is used to analyze the flow through a compact radial turbine rotor. The code models the flow as spatially periodic from blade passage to blade passage. Results from the code using varying computational models are compared with each other and with experimental data. These results include blade surface velocities and pressures, exit vorticity and entropy contour plots, shroud pressures, and spanwise exit total temperature, total pressure, and swirl distributions. The three computational models used are inviscid, viscous with no blade clearance, and viscous with blade clearance. It is found that modeling viscous effects improves correlation with experimental data, while modeling hub and tip clearances further improves some comparisons. Experimental results such as a local maximum of exit swirl, reduced exit total pressures at the walls, and exit total temperature magnitudes are explained by interpretation of the flow physics and computed secondary flows. Trends in the computed blade loading diagrams are similarly explained.

The effect of insulin deficiency on the plasma clearance and exchange of high-density-lipoprotein phosphatidylcholine in rats.

PubMed Central

Martins, I J; Redgrave, T G

1992-01-01

Triolein/cholesteryl oleate/cholesterol/phosphatidylcholine emulsions designed to model the lipid composition of chylomicrons were injected intravenously into control and streptozotocin-treated insulin-deficient rats. As previously described for lymph chylomicrons, the emulsion triolein was hydrolysed and phosphatidylcholine was transferred to the plasma high-density lipoproteins (HDL). This mechanism was used to introduce a phospholipid label into HDL in vivo. The subsequent clearance of phospholipid radioactivity from the plasma of insulin-deficient rats was significantly slower than in controls (P less than 0.025). Plasma clearance was similarly slower in insulin-deficient rats after injection of HDL that was previously labelled with radioactive phospholipids. After injection, the phospholipid label redistributed rapidly between the large-particle fraction of plasma lipoproteins (very-low- and low-density lipoproteins), and the lighter and heavier fractions of HDL. Compared with control rats, in insulin-deficient rats less of the phospholipid label was distributed to the lighter HDL fraction and more to the heavier HDL fraction, and this difference was not due to changes in activity of lecithin: cholesterol acyltransferase or in the apparent activity of phospholipid transfer protein. In insulin-deficient rats the changes in HDL phospholipid clearance and exchange appeared to be secondary to the associated hypertriglyceridaemia and the related changes in distribution of phospholipids between classes of plasma lipoproteins. PMID:1536661

Traffic control concepts for incident clearance

DOT National Transportation Integrated Search

2009-01-01

This document discusses various aspects of traffic control for incidents with the focus on the traffic control roles and responsibilities of the responders as well as the safety of the responders and the motoring public. It also recognizes that activ...

Clearance of polonium-210-enriched cigarette smoke from the rat trachea and lung

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohen, B.S.; Harley, N.H.; Tso, T.C.

The distribution and clearance of alpha radioactivity in the lungs of rats were measured after inhalation of smoke from cigarettes highly enriched in /sup 210/Po. Female Fischer rats were exposed daily for 6 months to smoke from cigarettes with 500 times the normal content of /sup 210/Po. Control rats were exposed to standard cigarette smoke. Animals were serially withdrawn and killed. After necropsy the trachea, major bronchi, larynx, and nasopharynx were examined for surface alpha activity by an etched track technique utilizing cellulose nitrate detectors. Areas of accumulated activity were seen on samples of larynx from rats exposed to themore » /sup 210/Po-enriched cigarettes. No other local accumulations were seen on the airways. The lower lungs were analyzed radiochemically for /sup 210/Po. Both radiochemical analysis and track measurements showed highly elevated activity concentrations in rats exposed to the /sup 210/Po-enriched cigarettes. Following withdrawal from smoking, both short- and long-term clearance components were seen. The parameters which fit the postexposure data for clearance of the lung burden cannot fit the buildup during the exposure period.« less

Clearance of polonium-210-enriched cigarette smoke from the rat trachea and lung.

PubMed

Cohen, B S; Harley, N H; Tso, T C

1985-06-30

The distribution and clearance of alpha radioactivity in the lungs of rats were measured after inhalation of smoke from cigarettes highly enriched in 210Po. Female Fischer rats were exposed daily for 6 months to smoke from cigarettes with 500 times the normal content of 210Po. Control rats were exposed to standard cigarette smoke. Animals were serially withdrawn and killed. After necropsy the trachea, major bronchi, larynx, and nasopharynx were examined for surface alpha activity by an etched track technique utilizing cellulose nitrate detectors. Areas of accumulated activity were seen on samples of larynx from rats exposed to the 210Po-enriched cigarettes. No other local accumulations were seen on the airways. The lower lungs were analyzed radiochemically for 210Po. Both radiochemical analysis and track measurements showed highly elevated activity concentrations in rats exposed to the 210Po-enriched cigarettes. Following withdrawal from smoking, both short- and long-term clearance components were seen. The parameters which fit the postexposure data for clearance of the lung burden cannot fit the buildup during the exposure period.

Optical Strain and Crack-Detection Measurements on a Rotating Disk

NASA Technical Reports Server (NTRS)

Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle; Fralick, Gustave

2013-01-01

The development of techniques for the in-situ measurement and structural health monitoring of the rotating components in gas turbine engines is of major interest to NASA. As part of this on-going effort, several experiments have been undertaken to develop methods for detecting cracks and measuring strain on rotating turbine engine like disks. Previous methods investigated have included the use of blade tip clearance sensors to detect the presence of cracks by monitoring the change in measured blade tip clearance and analyzing the combined disk-rotor system's vibration response. More recently, an experiment utilizing a novel optical Moiré based concept has been conducted on a subscale turbine engine disk to demonstrate a potential strain measurement and crack detection technique. Moiré patterns result from the overlap of two repetitive patterns with slightly different spacing. When this technique is applied to a rotating disk, it has the potential to allow for the detection of very small changes in spacing and radial growth in a rotating disk due to a flaw such as a crack. This investigation was a continuation of previous efforts undertaken in 2011-2012 to validate this optical concept. The initial demonstration attempted on a subscale turbine engine disk was inconclusive due to the minimal radial growth experienced by the disk during operation. For the present experiment a new subscale Aluminum disk was fabricated and improvements were made to the experimental setup to better demonstrate the technique. A circular reference pattern was laser etched onto a subscale engine disk and the disk was operated at speeds up to 12 000 rpm as a means of optically monitoring the Moiré created by the shift in patterns created by the radial growth due the presence of the simulated crack. Testing was first accomplished on a clean defect free disk as a means of acquiring baseline reference data. A notch was then machined in to the disk to simulate a crack and testing was repeated for the purposes of demonstrating the concept. Displacement data was acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the optical data and for validating other sensor based crack detection techniques.

Optical Strain and Crack-Detection Measurements on a Rotating Disk

NASA Technical Reports Server (NTRS)

Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle M.; Fralick, Gustave

2013-01-01

The development of techniques for the in-situ measurement and structural health monitoring of the rotating components in gas turbine engines is of major interest to NASA. As part of this on-going effort, several experiments have been undertaken to develop methods for detecting cracks and measuring strain on rotating turbine engine like disks. Previous methods investigated have included the use of blade tip clearance sensors to detect the presence of cracks by monitoring the change in measured blade tip clearance and analyzing the combined disk-rotor system's vibration response. More recently, an experiment utilizing a novel optical Moiré based concept has been conducted on a subscale turbine engine disk to demonstrate a potential strain measurement and crack detection technique. Moiré patterns result from the overlap of two repetitive patterns with slightly different spacing. When this technique is applied to a rotating disk, it has the potential to allow for the detection of very small changes in spacing and radial growth in a rotating disk due to a flaw such as a crack. This investigation was a continuation of previous efforts undertaken in 2011 to 2012 to validate this optical concept. The initial demonstration attempted on a subscale turbine engine disk was inconclusive due to the minimal radial growth experienced by the disk during operation. For the present experiment a new subscale Aluminum disk was fabricated and improvements were made to the experimental setup to better demonstrate the technique. A circular reference pattern was laser etched onto a subscale engine disk and the disk was operated at speeds up to 12 000 rpm as a means of optically monitoring the Moiré created by the shift in patterns created by the radial growth due the presence of the simulated crack. Testing was first accomplished on a clean defect free disk as a means of acquiring baseline reference data. A notch was then machined in to the disk to simulate a crack and testing was repeated for the purposes of demonstrating the concept. Displacement data was acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the optical data and for validating other sensor based crack detection techniques.

Cellular functions of TIP60.

PubMed

Sapountzi, Vasileia; Logan, Ian R; Robson, Craig N

2006-01-01

TIP60 was originally identified as a cellular acetyltransferase protein that interacts with HIV-1 Tat. As a consequence, the role of TIP60 in transcriptional regulation has been investigated intensively. Recent data suggest that TIP60 has more divergent functions than originally thought and roles for TIP60 in many processes, such as cellular signalling, DNA damage repair, cell cycle and checkpoint control and apoptosis are emerging. TIP60 is a tightly regulated transcriptional coregulator, acting in a large multiprotein complex for a range of transcription factors including androgen receptor, Myc, STAT3, NF-kappaB, E2F1 and p53. This usually involves recruitment of TIP60 acetyltransferase activities to chromatin. Additionally, in response to DNA double strand breaks, TIP60 is recruited to DNA lesions where it participates both in the initial as well as the final stages of repair. Here, we describe how TIP60 is a multifunctional enzyme involved in multiple nuclear transactions.

Application of a multi-block CFD code to investigate the impact of geometry modeling on centrifugal compressor flow field predictions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hathaway, M.D.; Wood, J.R.

1997-10-01

CFD codes capable of utilizing multi-block grids provide the capability to analyze the complete geometry of centrifugal compressors. Attendant with this increased capability is potentially increased grid setup time and more computational overhead with the resultant increase in wall clock time to obtain a solution. If the increase in difficulty of obtaining a solution significantly improves the solution from that obtained by modeling the features of the tip clearance flow or the typical bluntness of a centrifugal compressor`s trailing edge, then the additional burden is worthwhile. However, if the additional information obtained is of marginal use, then modeling of certainmore » features of the geometry may provide reasonable solutions for designers to make comparative choices when pursuing a new design. In this spirit a sequence of grids were generated to study the relative importance of modeling versus detailed gridding of the tip gap and blunt trailing edge regions of the NASA large low-speed centrifugal compressor for which there is considerable detailed internal laser anemometry data available for comparison. The results indicate: (1) There is no significant difference in predicted tip clearance mass flow rate whether the tip gap is gridded or modeled. (2) Gridding rather than modeling the trailing edge results in better predictions of some flow details downstream of the impeller, but otherwise appears to offer no great benefits. (3) The pitchwise variation of absolute flow angle decreases rapidly up to 8% impeller radius ratio and much more slowly thereafter. Although some improvements in prediction of flow field details are realized as a result of analyzing the actual geometry there is no clear consensus that any of the grids investigated produced superior results in every case when compared to the measurements. However, if a multi-block code is available, it should be used, as it has the propensity for enabling better predictions than a single block code.« less

Trials of Improved Practices (TIPs) to Enhance the Dietary and Iron-Folate Intake during Pregnancy- A Quasi Experimental Study among Rural Pregnant Women of Varanasi, India.

PubMed

Shivalli, Siddharudha; Srivastava, Ratan Kumar; Singh, Gyan Prakash

2015-01-01

Behavior Change Communications (BCC) play a decisive role in modifying socio-cultural norms affecting the perception and nutritional practices during pregnancy. To examine the effectiveness of 'Trials of Improved Practices' (TIPs) on dietary and iron-folate intake during pregnancy. Community based quasi experimental study with a control group. Four villages of Chiraigaon Community Development Block of Varanasi, India from May 2010 and recruited from August 2010. End line assessment, after 12 weeks of intervention, was completed in April 2011. Pregnant women in 13-28 weeks of gestation. TIPs was implemented in addition to ongoing essential obstetric care services in two villages through 3 home (assessment, negotiation and evaluation) visits and only assessment and evaluation visits in the other two control villages. Interpersonal communication, endorsing the active participation of family members and home based reminder materials were the TIPs based strategies. The effect of TIPs was assessed by comparing key outcome variables at baseline and after 12 weeks of intervention. Hemoglobin%, anemia prevalence, weight gain, compliance for iron-folate supplementation and dietary intake of calorie, protein, calcium and iron. A total of 86 participants completed the study. At the end, mean hemoglobin levels were 11.5±1.24 g/dl and 10.37±1.38 g/dl in the TIPs and control groups, respectively. The prevalence of anemia reduced by half in TIPs group and increased by 2.4% in the control group. Weight gain (grams/week) was significantly (p<0.01) higher in TIPs group (326.9±91.8 vs. 244.6±97.4). More than 85% of the PW in TIPs group were compliant for Iron-folate and only 38% were compliant among controls. The mean intake of protein increased by 1.78gm in intervention group and decreased by 1.81 gm in controls (p<0.05). More than two thirds of PW in TIPs group were taking one extra meal and only one third of controls were doing the same. TIPs found to be an effective approach to improve the nutritional status of pregnant women in the study area. TIPs strategy could be further explored on larger sample representing different socio-cultural and geographical areas. Clinical Trial Registry of India CTRI/2015/02/005517.

MicroRNA-3178 ameliorates inflammation and gastric carcinogenesis promoted by Helicobacter pylori new toxin, Tip-α, by targeting TRAF3.

PubMed

Zou, Meijuan; Wang, Fang; Jiang, Aiqin; Xia, Anliang; Kong, Siya; Gong, Chun; Zhu, Mingxia; Zhou, Xin; Zhu, Jun; Zhu, Wei; Cheng, Wenfang

2017-04-01

Helicobacter pylori infection is the main cause of chronic gastritis, peptic ulcer, and gastric cancer. Tip-α is a newly identified carcinogenic factor present in H. pylori. TRAF3 can activate NF-κB by both canonical and noncanonical signaling pathways. In this study, we found that the expression of TRAF3 and NF-κB was upregulated, while microRNA-3178 (miR-3178) was decreased in H. pylori-positive gastric tissues but not in H. pylori-negative tissues. GES-1 cells were incubated with 12.5 μg/mL recombinant Tip-α (rTip-α) in RPMI1640 for 2 hours. After another 24 hours, the supernatant medium was designed as inflammatory-conditioned medium (ICM) and that from the untreated control cells was designed as untreated control medium. The release of proinflammatory cytokines from GES-1 cells and proliferation of gastric cancer cells was determined by ELISA and CCK-8 kits. Cells were transfected with the mimic, inhibitor, negative control of miR-3178, or TRAF3 siRNA control siRNA. The medium was then replaced with RPMI1640, 12.5 μg/mL rTip-α, and collected, and the total cellular RNA and protein were extracted for the following detection. MiR-3178 mimic prevented the increasement of TRAF3 and hence decreased activation of NF-κB signals, whereas miR-3178 inhibitor could not, in GES-1 cells with Tip-α treatment. The condition medium from miR-3178 mimic transfected GES-1 cells could inhibit proliferation and induce apoptosis of inflammation-related gastric cancer cells SGC7901 and MGC803 by decreasing the production of inflammatory cytokines TNF-α and IL-6, which were secreted by GES-1 cells. Taken all together, Tip-α might activate NF-κB to promote inflammation and carcinogenesis by inhibiting miR-3178 expression, which directly targeting TRAF3, during H. pylori infection in gastric mucosal epithelial cells. © 2016 John Wiley & Sons Ltd.

Modulating p56Lck in T-Cells by a Chimeric Peptide Comprising Two Functionally Different Motifs of Tip from Herpesvirus saimiri

PubMed Central

Vernot, Jean-Paul; Perdomo-Arciniegas, Ana María; Pérez-Quintero, Luis Alberto; Martínez, Diego Fernando

2015-01-01

The Lck interacting protein Tip of Herpesvirus saimiri is responsible for T-cell transformation both in vitro and in vivo. Here we designed the chimeric peptide hTip-CSKH, comprising the Lck specific interacting motif CSKH of Tip and its hydrophobic transmembrane sequence (hTip), the latter as a vector targeting lipid rafts. We found that hTip-CSKH can induce a fivefold increase in proliferation of human and Aotus sp. T-cells. Costimulation with PMA did not enhance this proliferation rate, suggesting that hTip-CSKH is sufficient and independent of further PKC stimulation. We also found that human Lck phosphorylation was increased earlier after stimulation when T-cells were incubated previously with hTip-CSKH, supporting a strong signalling and proliferative effect of the chimeric peptide. Additionally, Lck downstream signalling was evident with hTip-CSKH but not with control peptides. Importantly, hTip-CSKH could be identified in heavy lipid rafts membrane fractions, a compartment where important T-cell signalling molecules (LAT, Ras, and Lck) are present during T-cell activation. Interestingly, hTip-CSKH was inhibitory to Jurkat cells, in total agreement with the different signalling pathways and activation requirements of this leukemic cell line. These results provide the basis for the development of new compounds capable of modulating therapeutic targets present in lipid rafts. PMID:26539553

Modulating p56Lck in T-Cells by a Chimeric Peptide Comprising Two Functionally Different Motifs of Tip from Herpesvirus saimiri.

PubMed

Vernot, Jean-Paul; Perdomo-Arciniegas, Ana María; Pérez-Quintero, Luis Alberto; Martínez, Diego Fernando

2015-01-01

The Lck interacting protein Tip of Herpesvirus saimiri is responsible for T-cell transformation both in vitro and in vivo. Here we designed the chimeric peptide hTip-CSKH, comprising the Lck specific interacting motif CSKH of Tip and its hydrophobic transmembrane sequence (hTip), the latter as a vector targeting lipid rafts. We found that hTip-CSKH can induce a fivefold increase in proliferation of human and Aotus sp. T-cells. Costimulation with PMA did not enhance this proliferation rate, suggesting that hTip-CSKH is sufficient and independent of further PKC stimulation. We also found that human Lck phosphorylation was increased earlier after stimulation when T-cells were incubated previously with hTip-CSKH, supporting a strong signalling and proliferative effect of the chimeric peptide. Additionally, Lck downstream signalling was evident with hTip-CSKH but not with control peptides. Importantly, hTip-CSKH could be identified in heavy lipid rafts membrane fractions, a compartment where important T-cell signalling molecules (LAT, Ras, and Lck) are present during T-cell activation. Interestingly, hTip-CSKH was inhibitory to Jurkat cells, in total agreement with the different signalling pathways and activation requirements of this leukemic cell line. These results provide the basis for the development of new compounds capable of modulating therapeutic targets present in lipid rafts.

The effects of topical agents of fluticasone propionate, oxymetazoline, and 3% and 0.9% sodium chloride solutions on mucociliary clearance in the therapy of acute bacterial rhinosinusitis in vivo.

PubMed

Inanli, Selçuk; Oztürk, Ozmen; Korkmaz, Mukadder; Tutkun, Alper; Batman, Cağlar

2002-02-01

The aims of the study were to determine: 1) how mucociliary activity in acute bacterial rhinosinusitis is affected; 2) how this activity is changed by therapy; 3) the effects of topical agents on mucociliary clearance, and 4) the most appropriate topical agent(s) to be used in the therapy of sinusitis. Five groups of patients with acute bacterial rhinosinusitis were studied prospectively. All patients had 500 mg oral amoxicillin and 125 mg oral clavulanic acid preparations given three times daily for 3 weeks. According to the topical agent applications, these groups included: group I (n = 12), no topical treatment was given; group II (n = 14), two puffs for each nostril once daily of 50 microg/100 mL fluticasone propionate was given; group III (n = 9), one puff for each nostril three times daily of 0.05% oxymetazoline was given; group IV (n =12), 3% sodium chloride (NaCl) (buffered to pH 6.5-7 at room temperature) was given; and group V (n =13), 10-mL solutions of 0.9% NaCl (buffered to pH 6.5--7 at room temperature) were given for nasal irrigations three times daily. All patients had medication for 3 weeks and were controlled each week. The saccharin method was used to measure nasal mucociliary clearance. To investigate the early effects of the topical agents for groups II to V, an additional test was repeated 20 minutes after the basal mucociliary clearance recordings. The test was repeated in the first, second, and third weeks of the treatment. The mucociliary clearance was significantly slower in the acute bacterial rhinosinusitis group than in the control group. There was no significant difference between the basal mucociliary clearance and the 20th minute mucociliary clearance of the fluticasone propionate and 0.9% NaCl solution groups. The mean values of the basal and the 20 minute's mucociliary clearance of the oxymetazoline group were 24.72 +/- 6.16 and 15.5 +/- 7.45 minutes, respectively, which were statistically significant. The mean values of the basal and the 20th minute mucociliary clearance of the 3% NaCl solution groups were 19.45 +/- 9.35 and 15.45 +/- 8.20 minutes, respectively, which were also statistically significant. In the first group (without topical treatment), the basal mucociliary clearance became significantly shorter after the second week of treatment. In the first and second weeks of the treatment of the oxymetazoline group, the mucociliary clearance did not change significantly, but after the third week the mucociliary clearance was significantly shorter. In the 3% NaCl solution group, significant improvement began from the first week and continued through the third week. Comparing the basal and the third weeks' mucociliary clearance values among the groups, the oxymetazoline and 3% NaCl solution groups revealed more significant improvement than the other groups, but this improvement was not different from the improvement of group I. There was still a statistically significant difference in the mucociliary clearance of the post-treatment sinusitis groups from the control group. The oxymetazoline and 3% NaCl solution groups seemed to be more effective in mucociliary clearance, but there was no significant difference in improvement among the groups. The improvement of acute bacterial rhinosinusitis takes more than 3 weeks, according to the mucociliary clearance values of the groups.

Root Border Cells and Their Role in Plant Defense.

PubMed

Hawes, Martha; Allen, Caitilyn; Turgeon, B Gillian; Curlango-Rivera, Gilberto; Minh Tran, Tuan; Huskey, David A; Xiong, Zhongguo

2016-08-04

Root border cells separate from plant root tips and disperse into the soil environment. In most species, each root tip can produce thousands of metabolically active cells daily, with specialized patterns of gene expression. Their function has been an enduring mystery. Recent studies suggest that border cells operate in a manner similar to mammalian neutrophils: Both cell types export a complex of extracellular DNA (exDNA) and antimicrobial proteins that neutralize threats by trapping pathogens and thereby preventing invasion of host tissues. Extracellular DNases (exDNases) of pathogens promote virulence and systemic spread of the microbes. In plants, adding DNase I to root tips eliminates border cell extracellular traps and abolishes root tip resistance to infection. Mutation of genes encoding exDNase activity in plant-pathogenic bacteria (Ralstonia solanacearum) and fungi (Cochliobolus heterostrophus) results in reduced virulence. The study of exDNase activities in plant pathogens may yield new targets for disease control.

Status of E-ELT M5 scale-one demonstrator

NASA Astrophysics Data System (ADS)

Barriga, Pablo; Sedghi, Babak; Dimmler, Martin; Kornweibel, Nick

2014-07-01

The fifth mirror of the European Extremely Large Telescope optical train is a field stabilization tip/tilt unit responsible for correcting the dynamical tip and tilt caused mainly by wind load on the telescope. A scale-one prototype including the inclined support, the fixed frame and a basic control system was designed and manufactured by NTE-SENER (Spain) and CSEM (Switzerland) as part of the prototyping and design activities. All interfaces to the mirror have been reproduced on a dummy structure reproducing the inertial characteristics of the optical element. The M5 unit is required to have sufficient bandwidth for tip/tilt reference commands coming from the wavefront control system. Such a bandwidth can be achieved using local active damping loop to damp the low frequency mechanical modes before closing a position loop. Prototyping on the M5 unit has been undertaken in order to demonstrate the E-ELT control system architecture, concepts and development standards and to further study active damping strategies. The control system consists of two nested loops: a local damping loop and a position loop. The development of this control system was undertaken following the E-ELT control system development standards in order to determine their applicability and performance and includes hardware selection, communication, synchronization, configuration, and data logging. In this paper we present the current status of the prototype M5 control system and the latest results on the active damping control strategy, in particular the promising results obtained with the method of positive position feedback.

'On Your Feet to Earn Your Seat', a habit-based intervention to reduce sedentary behaviour in older adults: study protocol for a randomized controlled trial.

PubMed

Gardner, Benjamin; Thuné-Boyle, Ingela; Iliffe, Steve; Fox, Kenneth R; Jefferis, Barbara J; Hamer, Mark; Tyler, Nick; Wardle, Jane

2014-09-20

Many older adults are both highly sedentary (that is, spend considerable amounts of time sitting) and physically inactive (that is, do little physical activity). This protocol describes an exploratory trial of a theory-based behaviour change intervention in the form of a booklet outlining simple activities ('tips') designed both to reduce sedentary behaviour and to increase physical activity in older adults. The intervention is based on the 'habit formation' model, which proposes that consistent repetition leads to behaviour becoming automatic, sustaining activity gains over time. The intervention is being developed iteratively, in line with Medical Research Council complex intervention guidelines. Selection of activity tips was informed by semi-structured interviews and focus groups with older adults, and input from a multidisciplinary expert panel. An ongoing preliminary field test of acceptability among 25 older adults will inform further refinement. An exploratory randomized controlled trial will be conducted within a primary care setting, comparing the tips booklet with a control fact sheet. Retired, inactive and sedentary adults (n = 120) aged 60 to 74 years, with no physical impairments precluding light physical activity, will be recruited from general practices in north London, UK. The primary outcomes are recruitment and attrition rates. Secondary outcomes are changes in behaviour, habit, health and wellbeing over 12 weeks. Data will be used to inform study procedures for a future, larger-scale definitive randomized controlled trial. Current Controlled Trials ISRCTN47901994.

ATM Mediates pRB Function To Control DNMT1 Protein Stability and DNA Methylation

PubMed Central

Suzuki, Misa; Hayashi, Naoyuki; Kobayashi, Masahiko; Sasaki, Nobunari; Nishiuchi, Takumi; Doki, Yuichiro; Okamoto, Takahiro; Kohno, Susumu; Muranaka, Hayato; Kitajima, Shunsuke; Yamamoto, Ken-ichi

2013-01-01

The retinoblastoma tumor suppressor gene (RB) product has been implicated in epigenetic control of gene expression owing to its ability to physically bind to many chromatin modifiers. However, the biological and clinical significance of this activity was not well elucidated. To address this, we performed genetic and epigenetic analyses in an Rb-deficient mouse thyroid C cell tumor model. Here we report that the genetic interaction of Rb and ATM regulates DNMT1 protein stability and hence controls the DNA methylation status in the promoters of at least the Ink4a, Shc2, FoxO6, and Noggin genes. Furthermore, we demonstrate that inactivation of pRB promotes Tip60 (acetyltransferase)-dependent ATM activation; allows activated ATM to physically bind to DNMT1, forming a complex with Tip60 and UHRF1 (E3 ligase); and consequently accelerates DNMT1 ubiquitination driven by Tip60-dependent acetylation. Our results indicate that inactivation of the pRB pathway in coordination with aberration in the DNA damage response deregulates DNMT1 stability, leading to an abnormal DNA methylation pattern and malignant progression. PMID:23754744

Energy Loss, Velocity Distribution, and Temperature Distribution for a Baffled Cylinder Model

NASA Technical Reports Server (NTRS)

Brevoort, Maurice J

1937-01-01

A study has been made of the important principles involved in the operation of a baffle for an engine cylinder and shows that cooling can be improved by 20 percent by using a correctly designed baffle. Such a gain is as effective as a 65 percent increase in pressure drop across the standard baffle, which had a 1/4 inch clearance between baffle and fin tips.

Unsteady numerical simulation of the flow in the U9 Kaplan turbine model

NASA Astrophysics Data System (ADS)

Javadi, Ardalan; Nilsson, Håkan

2014-03-01

The Reynolds-averaged Navier-Stokes equations with the RNG k-ε turbulence model closure are utilized to simulate the unsteady turbulent flow throughout the whole flow passage of the U9 Kaplan turbine model. The U9 Kaplan turbine model comprises 20 stationary guide vanes and 6 rotating blades (696.3 RPM), working at best efficiency load (0.71 m3/s). The computations are conducted using a general finite volume method, using the OpenFOAM CFD code. A dynamic mesh is used together with a sliding GGI interface to include the effect of the rotating runner. The clearance is included in the guide vane. The hub and tip clearances are also included in the runner. An analysis is conducted of the unsteady behavior of the flow field, the pressure fluctuation in the draft tube, and the coherent structures of the flow. The tangential and axial velocity distributions at three sections in the draft tube are compared against LDV measurements. The numerical result is in reasonable agreement with the experimental data, and the important flow physics close to the hub in the draft tube is captured. The hub and tip vortices and an on-axis forced vortex are captured. The numerical results show that the frequency of the forced vortex in 1/5 of the runner rotation.

Experimental Investigation of Centrifugal Compressor Stabilization Techniques

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

2003-01-01

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.

Tip-localized Ca2+ -permeable channels control pollen tube growth via kinase-dependent R- and S-type anion channel regulation.

PubMed

Gutermuth, Timo; Herbell, Sarah; Lassig, Roman; Brosché, Mikael; Romeis, Tina; Feijó, José Alberto; Hedrich, Rainer; Konrad, Kai Robert

2018-05-01

Pollen tubes (PTs) are characterized by having tip-focused cytosolic calcium ion (Ca 2+ ) concentration ([Ca 2+ ] cyt ) gradients, which are believed to control PT growth. However, the mechanisms by which the apical [Ca 2+ ] cyt orchestrates PT growth are not well understood. Here, we aimed to identify these mechanisms by combining reverse genetics, cell biology, electrophysiology, and live-cell Ca 2+ and anion imaging. We triggered Ca 2+ -channel activation by applying hyperpolarizing voltage pulses and observed that the evoked [Ca 2+ ] cyt increases were paralleled by high anion channel activity and a decrease in the cytosolic anion concentration at the PT tip. We confirmed a functional correlation between these patterns by showing that inhibition of Ca 2+ -permeable channels eliminated the [Ca 2+ ] cyt increase, resulting in the abrogation of anion channel activity via Ca 2+ -dependent protein kinases (CPKs). Functional characterization of CPK and anion-channel mutants revealed a CPK2/20/6-dependent activation of SLAH3 and ALMT12/13/14 anion channels. The impaired growth phenotypes of anion channel and CPK mutants support the physiological significance of a kinase- and Ca 2+ -dependent pathway to control PT growth via anion channel activation. Other than unveiling this functional link, our membrane hyperpolarization method allows for unprecedented manipulation of the [Ca 2+ ] cyt gradient or oscillations in the PT tips and opens an array of opportunities for channel screenings. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Active clearance control system for a turbomachine

NASA Technical Reports Server (NTRS)

Johnston, R. P.; Knapp, M. H.; Coulson, C. E. (Inventor)

1982-01-01

An axial compressor is provided with a cooling air manifold surrounding a portion of the shroud, and means for bleeding air from the compressor to the manifold for selectively flowing it in a modulating manner axially along the outer side of the stator/shroud to cool and shrink it during steady state operating conditions so as to obtain minimum shroud/rotor clearance conditions. Provision is also made to selectively divert the flow of cooling air from the manifold during transient periods of operation so as to alter the thermal growth or shrink rate of the stator/shroud and result in adequate clearance with the compressor rotor.

Endothelial Notch signalling limits angiogenesis via control of artery formation

PubMed Central

Hasan, Sana S.; Tsaryk, Roman; Lange, Martin; Wisniewski, Laura; Moore, John C.; Lawson, Nathan D.; Wojciechowska, Karolina; Schnittler, Hans; Siekmann, Arndt F.

2017-01-01

Angiogenic sprouting needs to be tightly controlled. It has been suggested that the Notch ligand dll4 expressed in leading tip cells restricts angiogenesis by activating Notch signalling in trailing stalk cells. Here, we show using live imaging in zebrafish that activation of Notch signalling is rather required in tip cells. Notch activation initially triggers expression of the chemokine receptor cxcr4a. This allows for proper tip cell migration and connection to the pre-existing arterial circulation, ultimately establishing functional arterial-venous blood flow patterns. Subsequently, Notch signalling reduces cxcr4a expression, thereby preventing excessive blood vessel growth. Finally, we find that Notch signalling is dispensable for limiting blood vessel growth during venous plexus formation that does not generate arteries. Together, these findings link the role of Notch signalling in limiting angiogenesis to its role during artery formation and provide a framework for our understanding of the mechanisms underlying blood vessel network expansion and maturation. PMID:28714969

Activation of the serratus anterior and upper trapezius in a population with winged and tipped scapulae during push-up-plus and diagonal shoulder-elevation.

PubMed

Park, Se-Yeon; Yoo, Won-Gyu

2015-01-01

Scapular winging and tipping are types of abnormal scapular kinematics, which is caused by not only the entrapment of peripheral nerve, but also imbalance of the scapulothoracic musculatures. The purpose of this study was to investigate the presence of muscular imbalance in the middle and lower parts of the serratus anterior and upper trapezius in people with scapular winging and tipping. Twenty male participants (age, 23.0 ± 1.92 y) were placed into symptomatic group (n = 10) and control group (n = 10). Participants completed two individual trials of a push-up plus, and a diagonal shoulder elevation, while electromyography (EMG) recorded muscle activity of the low and middle serratus anterior and upper trapezius. The root mean squared EMG values for three muscles were normalized using maximum voluntary isometric contractions (%MVIC). The value was calculated using modified isolation equation for comparing activation of middle and lower serratus anterior (%isolation). During a diagonal shoulder elevation, the % maximal voluntary isometric contraction (%MVIC) data showed that the symptomatic participants had significantly greater activation of the middle serratus anterior compared to the control group (P = 0.01). During a diagonal shoulder elevation, the symptomatic participants had not only significantly increased %isolation of the middle serratus anterior, but also significantly decreased for the lower serratus anterior compare with the control group (p = 0.00). Present result indicated that different muscle activation between middle and lower serratus anterior could represent in group with scapular dyskinesis, and need for selective activation of the lower serratus anterior in patients with scapular winging and tipping.

System for Centering a Turbofan in a Nacelle During Tests

NASA Technical Reports Server (NTRS)

Cunningham, Cameron C.; Thompson, William K.; Hughes, Christopher E.; Shook, Tony D.

2003-01-01

A feedback position-control system has been developed for maintaining the concentricity of a turbofan with respect to a nacelle during acoustic and flow tests in a wind tunnel. The system is needed for the following reasons: Thermal and thrust loads can displace the fan relative to the nacelle; In the particular test apparatus (see Figure 1), denoted as a rotor-only nacelle (RAN), the struts, vanes, and other stator components of a turbofan engine that ordinarily maintain the required concentricity in the face of thermal and thrust loads are not present; and The struts and stator components are not present because it is necessary to provide a flow path that is acoustically clean in the sense that the measured noise can be attributed to the fan alone. The system is depicted schematically in Figure 2. The nacelle is supported by two struts attached to a two-axis traverse table located outside the wind-tunnel wall. Two servomotors acting through 100:1 gearboxes drive the table along the Y and Z axes, which are perpendicular to the axis of rotation. The Y and Z components of the deviation from concentricity are measured by four laser displacement sensors mounted on the nacelle and aimed at reflective targets on the center body, which is part of the fan assembly. The outputs of the laser displacement sensors are digitized and processed through a personal computer programmed with control software. The control output of the computer commands the servomotors to move the table as needed to restore concentricity. Numerous software and hardware travel limits and alarms are provided to maximize safety. A highly ablative rub strip in the nacelle minimizes the probability of damage in the event that a deviation from concentricity exceeds the radial clearance [<0.004 in. (<0.1 mm)] between the inner surface of the nacelle and the tips of the fan blades. To be able to prevent an excursion in excess of the tip clearance, the system must be accurate enough to control X and Y displacements to within 0.001 in. (.0.025 mm). One characteristic essential to such accuracy is sufficient rigidity in the mechanical components of the system to prevent excitation of vibrations in the strut/ nacelle subsystem. The need for such a high degree of accuracy prompted a comprehensive analysis of sources of measurement and control errors, followed by rigorous design efforts to minimize these errors. As a result, the design of the system incorporates numerous improvements in hardware, software, and operational procedures.

Trials of Improved Practices (TIPs) to Enhance the Dietary and Iron-Folate Intake during Pregnancy- A Quasi Experimental Study among Rural Pregnant Women of Varanasi, India

PubMed Central

Shivalli, Siddharudha; Srivastava, Ratan Kumar; Singh, Gyan Prakash

2015-01-01

Background Behavior Change Communications (BCC) play a decisive role in modifying socio-cultural norms affecting the perception and nutritional practices during pregnancy. Objective To examine the effectiveness of ‘Trials of Improved Practices’ (TIPs) on dietary and iron-folate intake during pregnancy. Design Community based quasi experimental study with a control group Setting Four villages of Chiraigaon Community Development Block of Varanasi, India from May 2010 and recruited from August 2010. End line assessment, after 12 weeks of intervention, was completed in April 2011. Participants Pregnant women in 13–28 weeks of gestation Intervention TIPs was implemented in addition to ongoing essential obstetric care services in two villages through 3 home (assessment, negotiation and evaluation) visits and only assessment and evaluation visits in the other two control villages. Interpersonal communication, endorsing the active participation of family members and home based reminder materials were the TIPs based strategies. The effect of TIPs was assessed by comparing key outcome variables at baseline and after 12 weeks of intervention. Outcome Measures Hemoglobin%, anemia prevalence, weight gain, compliance for iron-folate supplementation and dietary intake of calorie, protein, calcium and iron. Results A total of 86 participants completed the study. At the end, mean hemoglobin levels were 11.5±1.24 g/dl and 10.37±1.38 g/dl in the TIPs and control groups, respectively. The prevalence of anemia reduced by half in TIPs group and increased by 2.4% in the control group. Weight gain (grams/week) was significantly (p<0.01) higher in TIPs group (326.9±91.8 vs. 244.6±97.4). More than 85% of the PW in TIPs group were compliant for Iron-folate and only 38% were compliant among controls. The mean intake of protein increased by 1.78gm in intervention group and decreased by 1.81 gm in controls (p<0.05). More than two thirds of PW in TIPs group were taking one extra meal and only one third of controls were doing the same. Conclusion TIPs found to be an effective approach to improve the nutritional status of pregnant women in the study area. TIPs strategy could be further explored on larger sample representing different socio-cultural and geographical areas. Trial Registration Clinical Trial Registry of India CTRI/2015/02/005517 PMID:26367775

The PDZ protein tax-interacting protein-1 inhibits beta-catenin transcriptional activity and growth of colorectal cancer cells.

PubMed

Kanamori, Mutsumi; Sandy, Peter; Marzinotto, Stefania; Benetti, Roberta; Kai, Chikatoshi; Hayashizaki, Yoshihide; Schneider, Claudio; Suzuki, Harukazu

2003-10-03

Wnt signaling is essential during development while deregulation of this pathway frequently leads to the formation of various tumors including colorectal carcinomas. A key component of the pathway is beta-catenin that, in association with TCF-4, directly regulates the expression of Wnt-responsive genes. To identify novel binding partners of beta-catenin that may control its transcriptional activity, we performed a mammalian two-hybrid screen and isolated the Tax-interacting protein (TIP-1). The in vivo complex formation between beta-catenin and TIP-1 was verified by coimmunoprecipitation, and a direct physical association was revealed by glutathione S-transferase pull-down experiments in vitro. By using a panel of deletion mutants of both proteins, we demonstrate that the interaction is mediated by the PDZ (PSD-95/DLG/ZO-1 homology) domain of TIP-1 and requires primarily the last four amino acids of beta-catenin. TIP-1 overexpression resulted in a dose-dependent decrease in the transcriptional activity of beta-catenin when tested on the TOP/FOPFLASH reporter system. Conversely, siRNA-mediated knock-down of endogenous TIP-1 slightly increased endogenous beta-catenin transactivation function. Moreover, we show that overexpression of TIP-1 reduced the proliferation and anchorage-independent growth of colorectal cancer cells. These data suggest that TIP-1 may represent a novel regulatory element in the Wnt/beta-catenin signaling pathway.

Methods and apparatus for controlling rotary machines

DOEpatents

Bagepalli, Bharat Sampathkumaran [Niskayuna, NY; Jansen, Patrick Lee [Scotia, NY; Barnes, Gary R [Delanson, NY; Fric, Thomas Frank [Greer, SC; Lyons, James Patrick Francis [Niskayuna, NY; Pierce, Kirk Gee [Simpsonville, SC; Holley, William Edwin [Greer, SC; Barbu, Corneliu [Guilderland, NY

2009-09-01

A control system for a rotary machine is provided. The rotary machine has at least one rotating member and at least one substantially stationary member positioned such that a clearance gap is defined between a portion of the rotating member and a portion of the substantially stationary member. The control system includes at least one clearance gap dimension measurement apparatus and at least one clearance gap adjustment assembly. The adjustment assembly is coupled in electronic data communication with the measurement apparatus. The control system is configured to process a clearance gap dimension signal and modulate the clearance gap dimension.

Aircraft turbofans: new economic and environmental benefits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sampl, F.R.; Shank, M.E.

1985-09-01

This article describes turbofan and turboprop engines. Advanced turbofans and turboprop engines, by continuing to reduce the velocities of the jet exhaust and fan tip speed, can provide significant noise reductions. New combustors incorporated into these engines have reduced smoke, hydrocarbons and carbon monoxide to levels below the current requirements. The third generation of turbofans will continue to increase fuel efficiency and reduce aircraft operating costs. They are more modular in design and consist of half as many parts as the earlier engines, reducing maintenance time by half. Some of the key features of the new turbofan concept include: amore » very high bypass ratio/compression ratio cycle; swept fan blades; a thin, low-loss nacelle; low-loss reduction gearing; new materials; advanced compressor/turbine airfoils; and high-speed rotors with improved clearance control.« less

An Experimental and Analytical Study of TIP Clearance Effects in Axial Flow Compressors

DTIC Science & Technology

1991-12-01

increasingly being used for design insight into the flow field. Implementations of the Navier Stokes equations using interacting grids or similar schemes...analytical reason for the existence of a pressure minimum locus lving away from the suction corner is provided by Barclay (1982) in a solution for the...relief at the leading edge on the suction side, grid Sensitivity and similar computational concerns, the computations predict %khat the blade loading

Selection of a turbine cooling system applying multi-disciplinary design considerations.

PubMed

Glezer, B

2001-05-01

The presented paper describes a multi-disciplinary cooling selection approach applied to major gas turbine engine hot section components, including turbine nozzles, blades, discs, combustors and support structures, which maintain blade tip clearances. The paper demonstrates benefits of close interaction between participating disciplines starting from early phases of the hot section development. The approach targets advancements in engine performance and cost by optimizing the design process, often requiring compromises within individual disciplines.

Performance deterioration of commercial high-bypass ratio turbofan engines

NASA Technical Reports Server (NTRS)

Mehalic, C. M.; Ziemianski, J. A.

1980-01-01

The results of engine performance deterioration investigations based on historical data, special engine tests, and specific tests to define the influence of flight loads and component clearances on performance are presented. The results of analyses of several damage mechanisms that contribute to performance deterioration such as blade tip rubs, airfoil surface roughness and erosion, and thermal distortion are also included. The significance of these damage mechanisms on component and overall engine performance is discussed.

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Material Constitutive Models for Creep and Rupture of SiC/SiC Ceramic-Matrix Composites (CMCs) Under Multiaxial Loading

NASA Astrophysics Data System (ADS)

Grujicic, Mica; Galgalikar, R.; Snipes, J. S.; Ramaswami, S.

2016-05-01

Material constitutive models for creep deformation and creep rupture of the SiC/SiC ceramic-matrix composites (CMCs) under general three-dimensional stress states have been developed and parameterized using one set of available experimental data for the effect of stress magnitude and temperature on the time-dependent creep deformation and rupture. To validate the models developed, another set of available experimental data was utilized for each model. The models were subsequently implemented in a user-material subroutine and coupled with a commercial finite element package in order to enable computational analysis of the performance and durability of CMC components used in high-temperature high-stress applications, such as those encountered in gas-turbine engines. In the last portion of the work, the problem of creep-controlled contact of a gas-turbine engine blade with the shroud is investigated computationally. It is assumed that the blade is made of the SiC/SiC CMC, and that the creep behavior of this material can be accounted for using the material constitutive models developed in the present work. The results clearly show that the blade-tip/shroud clearance decreases and ultimately becomes zero (the condition which must be avoided) as a function of time. In addition, the analysis revealed that if the blade is trimmed at its tip to enable additional creep deformation before blade-tip/shroud contact, creep-rupture conditions can develop in the region of the blade adjacent to its attachment to the high-rotational-speed hub.

Development and Validation of High Performance Unshrouded Centrifugal Impeller

NASA Technical Reports Server (NTRS)

Chen, Wei-Chung; Williams, M.; Paris, John K.; Prueger, G. H.; Williams, Robert; Turner, James E. (Technical Monitor)

2001-01-01

The feasibility of using a two-stage unshrouded impeller turbopump to replace the current three-stage reusable launch vehicle engine shrouded impeller hydrogen pump has been evaluated from the standpoint of turbopump weight reduction and overall payload improvement. These advantages are a by-product of the higher tip speeds that an unshrouded impeller can sustain. The issues associated with the effect of unshrouded impeller tip clearance on pump efficiency and head have been evaluated with one-dimensional tools and full three-dimensional rotordynamic fluid reaction forces and coefficients have been established through time dependent computational fluid dynamics (CFD) simulation of the whole 360 degree impeller with different rotor eccentricities and whirling ratios. Unlike the shrouded impeller, the unshrouded impeller forces are evaluated as the sum of the pressure forces on the blade and the pressure forces on the hub using the CFD results. The turbopump axial thrust control has been optimized by adjusting the first stage impeller backend wear ring seal diameter and diverting the second stage backend balance piston flow to the proper location. The structural integrity associated with the high tip speed has been checked by analyzing a 3D-Finite Element Model at maximum design conditions (6% higher than the design speed). This impeller was fabricated and tested in the NASA Marshall Space Flight Center water-test rig. The experimental data will be compared with the analytical predictions and presented in another paper. The experimental data provides validation data for the numerical design and analysis methodology. The validated numerical methodology can be used to help design different unshrouded impeller configurations.

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Ducted fan inlet/exit and rotor tip flow improvements for vertical lift systems

NASA Astrophysics Data System (ADS)

Akturk, Ali

The current research utilized experimental and computational techniques in 5" and 22" diameter ducted fan test systems that have been custom designed and manufactured. Qualitative investigation of flow around the ducted fan was also performed using smoke flow visualizations. Quantitative measurements consisted of 2D and 3D velocity measurements using planar and Stereoscopic Particle Image Velocimetry (PIV and SPIV), high resolution total pressure measurements using Kiel total pressure probes and real time six-component force and torque measurements. The computational techniques used in this thesis included a recently developed radial equilibrium based rotor model(REBRM) and a three dimensional Reynolds-Averaged Navier Stokes (RANS) based CFD model. A radial equilibrium based rotor model (REBRM) developed by the author was effectively integrated into a three-dimensional RANS based computational system. The PIV measurements and computational flow predictions using (REBRM) near the fan inlet plane were in a good agreement at hover and forward flight conditions. The aerodynamic modifications resulting from the fan inlet flow distortions in forward flight regime were clearly captured in 2D PIV results. High resolution total pressure measurements at the downstream of the fan rotor showed that tip leakage, rotor hub separation, and passage flow related total pressure losses were dominant in hover condition. However, the losses were dramatically increased in forward flight because of inlet lip separation and distortion. A novel ducted fan inlet flow conditioning concept named "Double Ducted Fan" (DDF) was developed. The (DDF) concept has a potential to significantly improve the performance and controllability of VTOL UAVs and many other ducted fan based vertical lift systems. The new concept that will significantly reduce the inlet lip separation related performance penalties used a secondary stationary duct system to control "inlet lip separation" occurring especially at elevated forward flight velocities. The (DDF) is self-adjusting in a wide forward flight velocity range. DDFs corrective aerodynamic in influence becomes more pronounced with increasing flight velocity due to its inherent design properties. RANS simulations of the flow around rotor blades and duct geometry in the rotating frame of reference provided a comprehensive description of the tip leakage and passage flow in the flow environment of the two ducted fan research facilities developed throughout this thesis. The aerodynamic measurements and results of the RANS simulation showed good agreement especially near the tip region. A number of novel tip treatments based on custom designed pressure side extensions were introduced. Various tip leakage mitigation schemes were introduced by varying the chordwise location and the width of the extension in the circumferential direction. The current study showed that a proper selection of the pressure side bump location and width were the two critical parameters in influencing the success of the tip leakage mitigation approach. Significant gains in axial mean velocity component were observed when a proper pressure side tip extension was used. It is also observed that an effective tip leakage mitigation scheme significantly reduced the tangential velocity component near the tip of the axial fan blade. Reduced tip clearance related flow interactions were essential in improving the energy efficiency and range of ducted fan based vehicle. Full and inclined pressure side tip squealers were designed. Squealer tips were effective in changing the overall trajectory of the tip vortex to a higher path in radial direction. The interaction of rotor blades and tip vortex was effectively reduced and aerodynamic performance of the rotor blades was improved. The overall aerodynamic gain was a measurable reduction in leakage mass flow rate. This leakage reduction increased thrust significantly. Full and inclined pressure side tip squealers increased thrust obtained in hover condition by 9.1 % and 9.6 % respectively. A reduction or elimination of the momentum deficit in tip vortices is essential to reduce the adverse performance effects originating from the unsteady and highly turbulent tip leakage flows rotating against a stationary casing. The novel tip treatments developed throughout this thesis research are highly effective in reducing the adverse performance effects of ducted fan systems developed for VTOL vehicles. (Abstract shortened by UMI.)

Coupled Aerodynamic-Thermal-Structural (CATS) Analysis

NASA Technical Reports Server (NTRS)

1995-01-01

Coupled Aerodynamic-Thermal-Structural (CATS) Analysis is a focused effort within the Numerical Propulsion System Simulation (NPSS) program to streamline multidisciplinary analysis of aeropropulsion components and assemblies. Multidisciplinary analysis of axial-flow compressor performance has been selected for the initial focus of this project. CATS will permit more accurate compressor system analysis by enabling users to include thermal and mechanical effects as an integral part of the aerodynamic analysis of the compressor primary flowpath. Thus, critical details, such as the variation of blade tip clearances and the deformation of the flowpath geometry, can be more accurately modeled and included in the aerodynamic analyses. The benefits of this coupled analysis capability are (1) performance and stall line predictions are improved by the inclusion of tip clearances and hot geometries, (2) design alternatives can be readily analyzed, and (3) higher fidelity analysis by researchers in various disciplines is possible. The goals for this project are a 10-percent improvement in stall margin predictions and a 2:1 speed-up in multidisciplinary analysis times. Working cooperatively with Pratt & Whitney, the Lewis CATS team defined the engineering processes and identified the software products necessary for streamlining these processes. The basic approach is to integrate the aerodynamic, thermal, and structural computational analyses by using data management and Non-Uniform Rational B-Splines (NURBS) based data mapping. Five software products have been defined for this task: (1) a primary flowpath data mapper, (2) a two-dimensional data mapper, (3) a database interface, (4) a blade structural pre- and post-processor, and (5) a computational fluid dynamics code for aerothermal analysis of the drum rotor. Thus far (1) a cooperative agreement has been established with Pratt & Whitney, (2) a Primary Flowpath Data Mapper has been prototyped and delivered to General Electric Aircraft Engines and Pratt & Whitney for evaluation, (3) a collaborative effort has been initiated with the National Institute of Standards and Testing to develop a Standard Data Access Interface, and (4) a blade tip clearance capability has been implemented into the Structural Airfoil Blade Engineering Routine (SABER) program. We plan to continue to develop the data mappers and data management tools. As progress is made, additional efforts will be made to apply these tools to propulsion system applications.

Esophageal Acid Clearance During Random Swallowing Is Faster in Patients with Barrett’s Esophagus Than in Healthy Controls

PubMed Central

Lottrup, Christian; Krarup, Anne L; Gregersen, Hans; Ejstrud, Per; Drewes, Asbjørn M

2016-01-01

Background/Aims Impaired esophageal acid clearance may be a contributing factor in the pathogenesis of Barrett’s esophagus. However, few studies have measured acid clearance as such in these patients. In this explorative, cross-sectional study, we aimed to compare esophageal acid clearance and swallowing rate in patients with Barrett’s esophagus to that in healthy controls. Methods A total of 26 patients with histology-confirmed Barrett’s esophagus and 12 healthy controls underwent (1) upper endoscopy, (2) an acid clearance test using a pH-impedance probe under controlled conditions including controlled and random swallowing, and (3) an ambulatory pH-impedance measurement. Results Compared with controls and when swallowing randomly, patients cleared acid 46% faster (P = 0.008). Furthermore, patients swallowed 60% more frequently (mean swallows/minute: 1.90 ± 0.74 vs 1.19 ± 0.58; P = 0.005), and acid clearance time decreased with greater random swallowing rate (P < 0.001). Swallowing rate increased with lower distal esophageal baseline impedance (P = 0.014). Ambulatory acid exposure was greater in patients (P = 0.033), but clearance times assessed from the ambulatory pH-measurement and acid clearance test were not correlated (all P > 0.3). Conclusions More frequent swallowing and thus faster acid clearance in Barrett’s esophagus may constitute a protective reflex due to impaired mucosal integrity and possibly acid hypersensitivity. Despite these reinforced mechanisms, acid clearance ability seems to be overthrown by repeated, retrograde acid reflux, thus resulting in increased esophageal acid exposure and consequently mucosal changes. PMID:27557545

Imaging Lung Clearance of Radiolabeled Tumor Cells to Study Mice with Normal, Activated or Depleted Natural Killer (NK) Cells

NASA Astrophysics Data System (ADS)

Kulkarni, P. V.; Bennett, M.; Constantinescu, A.; Arora, V.; Viguet, M.; Antich, P.; Parkey, R. W.; Mathews, D.; Mason, R. P.; Oz, O. K.

2003-08-01

Lung clearance of 51CR and 125I iododeoxyuridine (IUDR) labeled cancer cells assess NK cell activity. It is desirable to develop noninvasive imaging technique to assess NK activity in mice. We labeled target YAC-1 tumor cells with 125I, 111In, 99mTc, or 67Ga and injected I.V. into three groups of BALB/c mice. Animals were treated with medium (group I), 300mg/kg cyclophosmamide (CY) to kill NK cell (group II), or anti-LY49C/1) (ab')2 mAb to augment NK function (group III). Lungs were removed 15 min or 2 h later for tissue counting. Control and treated mice were imaged every 5 min with a scintillating camera for 1 h after 15 min of infusion of the 111In labeled cells. Lung clearance increased after 15 min (lodging: 60-80%) and (2 h retention: 3-7%). Similar results were obtained with all the isotopes studied. Images distinguished the control and treated mice for lung activity. Cells labeled with 111In, 99mTc or 67Ga are cleared similar to those labeled with 51Cr or 125I. NK cell destruction of tumor cells may be assessed by noninvasive imaging method either by SPECT (99mTc, 111In, 67Ga) or by PET (68Ga).

Investigation of a Moire Based Crack Detection Technique for Propulsion Health Monitoring

NASA Technical Reports Server (NTRS)

Woike, Mark R.; Abudl-Aziz, Ali; Fralick, Gustave C.; Wrbanek, John D.

2012-01-01

The development of techniques for the health monitoring of the rotating components in gas turbine engines is of major interest to NASA s Aviation Safety Program. As part of this on-going effort several experiments utilizing a novel optical Moir based concept along with external blade tip clearance and shaft displacement instrumentation were conducted on a simulated turbine engine disk as a means of demonstrating a potential optical crack detection technique. A Moir pattern results from the overlap of two repetitive patterns with slightly different periods. With this technique, it is possible to detect very small differences in spacing and hence radial growth in a rotating disk due to a flaw such as a crack. The experiment involved etching a circular reference pattern on a subscale engine disk that had a 50.8 mm (2 in.) long notch machined into it to simulate a crack. The disk was operated at speeds up to 12 000 rpm and the Moir pattern due to the shift with respect to the reference pattern was monitored as a means of detecting the radial growth of the disk due to the defect. In addition, blade displacement data were acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the data obtained from the optical technique. The results of the crack detection experiments and its associated analysis are presented in this paper.

Electrostatic precipitation is a novel way of maintaining visual field clarity during laparoscopic surgery: a prospective double-blind randomized controlled pilot study.

PubMed

Ansell, James; Warren, Neil; Wall, Pete; Cocks, Kim; Goddard, Stuart; Whiston, Richard; Stechman, Michael; Scott-Coombes, David; Torkington, Jared

2014-07-01

Ultravision™ is a new device that utilizes electrostatic precipitation to clear surgical smoke. The aim was to evaluate its performance during laparoscopic cholecystectomy. Patients undergoing laparoscopic cholecystectomy were randomized into "active (device on)" or "control (device off)." Three operating surgeons scored the percentage effective visibility and three reviewers scored the percentage of the procedure where smoke was present. All assessors also used a 5-point scale (1 = imperceptible/excellent and 5 = very annoying/bad) to rate visual impairment. Secondary outcomes were the number of smoke-related pauses, camera cleaning, and pneumoperitoneum reductions. Mean results are presented with 95% confidence intervals (CI). In 30 patients (active 13, control 17), the effective visibility was 89.2% (83.3-95.0) for active cases and 71.2% (65.7-76.7) for controls. The proportion of the procedure where smoke was present was 41.1% (33.8-48.3) for active cases and 61.5% (49.0-74.1) for controls. Operating surgeons rated the visual impairment as 2.2 (1.7-2.6) for active cases and 3.2 (2.8-3.5) for controls. Reviewers rated the visual impairment as 2.3 (2.0-2.5) for active cases and 3.2 (2.8-3.7) for controls. In the active group, 23% of procedures were paused to allow smoke clearance compared to 94% of control cases. Camera cleaning was not needed in 85% of active procedures and 35% of controls. The pneumoperitoneum was reduced in 0% of active cases and 88% of controls. Ultravision™ improves visibility during laparoscopic surgery and reduces delays in surgery for smoke clearance and camera cleaning.

Characterization of Aeromechanics Response and Instability in Fans, Compressors, and Turbine Blades

NASA Technical Reports Server (NTRS)

Tan, Choon S.

2003-01-01

This study investigated the effect of interaction between tip clearance flow, steady and unsteady upstream wakes in rotor and stator blade rows in terms of blade forced response. In a stator blade row, the interaction of steady wakes in the upstream rotor frame with the stator imply a blade forced response whose spectrum contains the Blade passing frequency (BPF) and its harmonics, with a decaying amplitude as the frequency increases. When the incoming wakes are unsteady, however, the spectrum of blade excitation exhibits unexpectedly amplified high frequencies due to the modulation of BPF with the fluctuation frequency. In a rotor blade row, a tip flow instability has been demonstrated with a frequency (TVF) equal to 0.45 times the Blade Passing frequency corresponding to a reduced frequency (F(sub c) (sup +)) of 0.7. Under uniform inlet flow conditions, the frequency and spatial content of the tip flow region have been characterized. The disturbance TVF was the dominant disturbance in the flow field and was found to imply variations of the pressure coefficient of more than 30% on the blade tip (between 35% to 90% chord) and in the rotor-generated wake (from 75% to 100% hub-to-tip position). In an attempt to better understand the origin of the instability, the structure of the tip flow has also been analyzed. The interface between the tip flow region and the core flow has been found to have periodical wave-like flow patterns which proceed downstream at a speed of approximately 0.42 times the core flow speed at a frequency corresponding to TVF. A list of conclusions derived from these interactions is presented.

Acute Effects of Walking Exercise on Stair Negotiation in Sedentary and Physically Active Older Adults.

PubMed

Kunzler, Marcos R; da Rocha, Emmanuel S; Bobbert, Maarten F; Duysens, Jacques; Carpes, Felipe P

2017-07-01

In negotiating stairs, low foot clearance increases the risk of tripping and a fall. Foot clearance may be related to physical fitness, which differs between active and sedentary participants, and be acutely affected by exercise. Impaired stair negotiation could be an acute response to exercise. Here we determined acute changes in foot clearances during stair walking in sedentary (n = 15) and physically active older adults (n = 15) after prolonged exercise. Kinematic data were acquired during negotiation with a 3-steps staircase while participants walked at preferred speed, before and after 30 min walking at preferred speed and using a treadmill. Foot clearances were compared before and after exercise and between the groups. Sedentary older adults presented larger (0.5 cm for lead and 2 cm for trail leg) toe clearances in ascent, smaller (0.7 cm) heel clearance in the leading foot in descent, and larger (1 cm) heel clearance in the trailing foot in descent than physically active. Sedentary older adults negotiate stairs in a slightly different way than active older adults, and 30 min walking at preferred speed does not affect clearance in stair negotiation.

DNA-binding activity of TNF-{alpha} inducing protein from Helicobacter pylori

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuzuhara, T.; Suganuma, M.; Oka, K.

2007-11-03

Tumor necrosis factor-{alpha} (TNF-{alpha}) inducing protein (Tip{alpha}) is a carcinogenic factor secreted from Helicobacter pylori (H. pylori), mediated through both enhanced expression of TNF-{alpha} and chemokine genes and activation of nuclear factor-{kappa}B. Since Tip{alpha} enters gastric cancer cells, the Tip{alpha} binding molecules in the cells should be investigated. The direct DNA-binding activity of Tip{alpha} was observed by pull down assay using single- and double-stranded genomic DNA cellulose. The surface plasmon resonance assay, indicating an association between Tip{alpha} and DNA, revealed that the affinity of Tip{alpha} for (dGdC)10 is 2400 times stronger than that of del-Tip{alpha}, an inactive Tip{alpha}. This suggestsmore » a strong correlation between DNA-binding activity and carcinogenic activity of Tip{alpha}. And the DNA-binding activity of Tip{alpha} was first demonstrated with a molecule secreted from H. pylori.« less

The Three Dimensional Flow Field at the Exit of an Axial-Flow Turbine Rotor

NASA Technical Reports Server (NTRS)

Lakshminarayana, B.; Ristic, D.; Chu, S.

1998-01-01

A systematic and comprehensive investigation was performed to provide detailed data on the three dimensional viscous flow phenomena downstream of a modem turbine rotor and to understand the flow physics such as origin, nature, development of wakes, secondary flow, and leakage flow. The experiment was carried out in the Axial Flow Turbine Research Facility (AFTRF) at Penn State, with velocity measurements taken with a 3-D LDV System. Two radial traverses at 1% and 10% of chord downstream of the rotor have been performed to identify the three-dimensional flow features at the exit of the rotor blade row. Sufficient spatial resolution was maintained to resolve blade wake, secondary flow, and tip leakage flow. The wake deficit is found to be substantial, especially at 1% of chord downstream of the rotor. At this location, negative axial velocity occurs near the tip, suggesting flow separation in the tip clearance region. Turbulence intensities peak in the wake region, and cross- correlations are mainly associated with the velocity gradient of the wake deficit. The radial velocities, both in the wake and in the endwall region, are found to be substantial. Two counter-rotating secondary flows are identified in the blade passage, with one occupying the half span close to the casino and the other occupying the half span close to the hub. The tip leakage flow is well restricted to 10% immersion from the blade tip. There are strong vorticity distributions associated with these secondary flows and tip leakage flow. The passage averaged data are in good agreement with design values.

Triacylglycerol kinetics in endotoxic rats with suppressed lipoprotein lipase activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagby, G.J.; Corll, C.B.; Martinez, R.R.

1987-07-01

Hypertriglyceridemia observed in animals after bacterial endotoxin administration and some forms of sepsis can result from increased hepatic triacylglycerol (TG) output or decreased TG clearance by extrahepatic tissues. To differentiate between these two possibilities, TG and free fatty acid (FFA) kinetics were determined in control and endotoxin-injected rats 18 h after treatment. Plasma TG and FFA kinetics were assessed by a constant intravenous infusion with (9,10-/sup 3/H)palmitate-labeled very low-density lipoprotein and (1-/sup 14/C)palmitate bound to albumin, respectively. In addition, lipoprotein lipase (LPL) activity was determined in heart, skeletal muscle, and adipose tissue as well as in postheparin plasma of functionallymore » hepatectomized, adrenalectomized, and gonadectomized rats. Plasma FFA acid concentrations were slightly increased in endotoxin-treated rats but their turnover did not differ from control. Endotoxin-treated rats had a threefold increase in plasma TG concentrations and decreased heart, skeletal muscle, and post-heparin plasma LPL activity. Plasma TG turnover was decreased, indicating that hypertriglyceridemia was not due to an increased TG output by the liver. Instead, the endotoxin-induced increase in plasma TG concentration was consequence of the 80% reduction in TG metabolic clearance rate. Thus, suppression of LPL activity in endotoxic animals impairs TG clearance resulting in hypertriglyceridemia. Furthermore, endotoxin administration reduced the delivery of TG-FFA to extrahepatic tissues because hepatic synthesis and secretion of TG from plasma FFA was decreased and LPL activity was suppressed.« less

Control means for a gas turbine engine

NASA Technical Reports Server (NTRS)

Beitler, R. S.; Sellers, F. J.; Bennett, G. W. (Inventor)

1982-01-01

A means is provided for developing a signal representative of the actual compressor casing temperature, a second signal representative of compressor inlet gas temperature, and a third signal representative of compressor speed. Another means is provided for receiving the gas temperature and compressor speed signals and developing a schedule output signal which is a representative of a reference casing temperature at which a predetermined compressor blade stabilized clearance is provided. A means is also provided for comparing the actual compressor casing temperature signal and the reference casing temperature signal and developing a clearance control system representative of the difference. The clearance control signal is coupled to a control valve which controls a flow of air to the compressor casing to control the clearance between the compressor blades and the compressor casing. The clearance control signal can be modified to accommodate transient characteristics. Other embodiments are disclosed.

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Fan Noise Source Diagnostic Test: LDV Measured Flow Field Results

NASA Technical Reports Server (NTRS)

Podboy, Gary C.; Krupar, Martin J.; Hughes, Christopher E.; Woodward, Richard P.

2003-01-01

Results are presented of an experiment conducted to investigate potential sources of noise in the flow developed by two 22-in. diameter turbofan models. The R4 and M5 rotors that were tested were designed to operate at nominal take-off speeds of 12,657 and 14,064 RPMC, respectively. Both fans were tested with a common set of swept stators installed downstream of the rotors. Detailed measurements of the flows generated by the two were made using a laser Doppler velocimeter system. The wake flows generated by the two rotors are illustrated through a series of contour plots. These show that the two wake flows are quite different, especially in the tip region. These data are used to explain some of the differences in the rotor/stator interaction noise generated by the two fan stages. In addition to these wake data, measurements were also made in the R4 rotor blade passages. These results illustrate the tip flow development within the blade passages, its migration downstream, and (at high rotor speeds) its merging with the blade wake of the adjacent (following) blade. Data also depict the variation of this tip flow with tip clearance. Data obtained within the rotor blade passages at high rotational speeds illustrate the variation of the mean shock position across the different blade passages.

Integrated Fiber-Optic Light Probe: Measurement of Static Deflections in Rotating Turbomachinery

NASA Technical Reports Server (NTRS)

Kurkov, Anatole P.

1998-01-01

At the NASA Lewis Research Center, in cooperation with Integrated Fiber Optic Systems, Inc., an integrated fiber-optic light probe system was designed, fabricated, and tested for monitoring blade tip deflections, vibrations, and to some extent, changes in the blade tip clearances of a turbomachinery fan or a compressor rotor. The system comprises a set of integrated fiber-optic light probes that are positioned to detect the passing blade tip at the leading and trailing edges. In this configuration, measurements of both nonsynchronous blade vibrations and steady-state blade deflections can be made from the timing information provided by each light probe-consisting of an integrated fiber-optic transmitting channel and numerical aperture receiving fibers, all mounted in the same cylindrical housing. With integrated fiber-optic technology, a spatial resolution of 50 mm is possible while the outer diameter is kept below 2.5 mm. To evaluate these probes, we took measurements in a single-stage compressor facility and an advanced fan rig in Lewis' 9- by 15-Foot Low-Speed Wind Tunnel.

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Effect of photon-initiated photoacoustic streaming, passive ultrasonic, and sonic irrigation techniques on dentinal tubule penetration of irrigation solution: a confocal microscopic study.

PubMed

Akcay, Merve; Arslan, Hakan; Mese, Merve; Durmus, Nazlı; Capar, Ismail Davut

2017-09-01

The aim of this in vitro study was to evaluate the efficacy of different irrigation techniques including laser-activated irrigation using an erbium:yttrium-aluminum-garnet (Er:YAG) laser with a novel tip design (photon-induced photoacoustic streaming (PIPS)), Er:YAG laser with Preciso tip, sonic activation, and passive ultrasonic activation on the final irrigation solution penetration into dentinal tubules by using a laser scanning confocal microscope. In this study, 65 extracted single-rooted human mandibular premolars were instrumented up to size 40 and randomly divided into 5 groups (n = 13) based on the activation technique of the final irrigation solution as follows: conventional irrigation (control group), sonic activation, passive ultrasonic activation, Er:YAG-PIPS tip activation, and Er:YAG-Preciso tip activation. In each group, 5 mL of 5% NaOCl labeled with fluorescent dye was used during the activation as the final irrigation solution. Specimens were sectioned at 2.5 and 8 mm from the apex and then examined under a confocal microscope to calculate the dentinal tubule penetration area. Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's post hoc tests (P = 0.05). Both Er:YAG laser (Preciso/PIPS) activations exhibited a significantly higher penetration area than the other groups (P < 0.05). Additionally, passive ultrasonic activation had significantly higher penetration than the sonic activation group and the control group. Statistically significant differences were also found between each root canal third (coronal > middle > apical) (P < 0.001). The results from the present study support the use of Er:YAG laser activation (Preciso/PIPS) to improve the effectiveness of the final irrigation procedure by increasing the irrigant penetration area into the dentinal tubules. The activation of the irrigant and the creation of the streaming with the Er:YAG laser have a positive effect on the irrigant penetration.

Turbine rotor disk health monitoring assessment based on sensor technology and spin tests data.

PubMed

Abdul-Aziz, Ali; Woike, Mark

2013-01-01

The paper focuses on presenting data obtained from spin test experiments of a turbine engine like rotor disk and assessing their correlation to the development of a structural health monitoring and fault detection system. The data were obtained under various operating conditions such as the rotor disk being artificially induced with and without a notch and rotated at a rotational speed of up to 10,000 rpm under balanced and imbalanced state. The data collected included blade tip clearance, blade tip timing measurements, and shaft displacements. Two different sensor technologies were employed in the testing: microwave and capacitive sensors, respectively. The experimental tests were conducted at the NASA Glenn Research Center's Rotordynamics Laboratory using a high precision spin system. Disk flaw observations and related assessments from the collected data for both sensors are reported and discussed.

Optical Fiber Sensors for Aircraft Structural Health Monitoring

PubMed Central

García, Iker; Zubia, Joseba; Durana, Gaizka; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Villatoro, Joel

2015-01-01

Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel. PMID:26134107

Optical Fiber Sensors for Aircraft Structural Health Monitoring.

PubMed

García, Iker; Zubia, Joseba; Durana, Gaizka; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Villatoro, Joel

2015-06-30

Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel.

Rotorcraft In-Plane Noise Reduction Using Active/Passive Approaches with Induced Vibration Tracking

NASA Astrophysics Data System (ADS)

Chia, Miang Hwee

A comprehensive study of the use of active and passive approaches for in-plane noise reduction, including the vibrations induced during noise reduction, was conducted on a hingeless rotor configuration resembling the MBB BO-105 rotor. First, a parametric study was performed to examine the effects of rotor blade stiffness on the vibration and noise reduction performance of a 20%c plain trailing edge flap and a 1.5%c sliding microflap. This was accomplished using a comprehensive code AVINOR (for Active VIbration and NOise Reduction). A two-dimensional unsteady reduced order aerodynamic model (ROM), using the Rational Function Approximation approach and CFD-based oscillatory aerodynamic load data, was used in the comprehensive code. The study identified a hingeless blade configuration with torsional frequency of 3.17/rev as an optimum configuration for studying vibration and noise reduction using on-blade control devices such as flaps or microflaps. Subsequently, a new suite of computational tools capable of predicting in-plane low frequency sound pressure level (LFSPL) rotorcraft noise and its control was developed, replacing the acoustic module WOPWOP in AVINOR with a new acoustic module HELINOIR (for HELIcopter NOIse Reduction), which overcomes certain limitations associated with WOPWOP. The new suite, consisting of the AVINOR/HELINOIR combination, was used to study active flaps, as well as microflaps operating in closed-loop mode for in-plane noise reduction. An alternative passive in-plane noise reduction approach using modification to the blade tip in the 10%R outboard region was also studied. The new suite consisting of the AVINOR/HELINOIR combination based on a compact aeroacoustic model was validated by comparing with wind tunnel test results, and subsequently verified by comparing with computational results. For active control, the in-plane noise reduction obtained with a single 20%c plain trailing edge flap during level flight at a moderate advance ratio was examined. Different configurations of far-field and near-field feedback microphone locations were examined to develop a fundamental understanding of the feedback microphone locations on the noise reduction process A near-field microphone located on the tip of a nose boom was found to produce a LFSPL reduction of up to 6dB. However, this noise reduction was accompanied by an out-of-plane noise increase of 18dB and 60% increase in vertical hub shear. For passive control, three tip geometries having sweep, dihedral, and anhedral, were considered. The tip dihedral reduced LFSPL by up to 2dB without a vibratory load penalty. However, this was accompanied by an increase in the mid frequency sound pressure levels (MFSPL). The tip sweep and tip anhedral produced an increase in in-plane LFSPL below the horizon. A comparison of the active and passive approaches indicated that active approaches implemented by a plain flap with a feedback microphone located on the nose boom is superior to the passive control approaches. However, there is a general trade-off between LFSPL reduction, MFSPL generation and vibratory hub loads induced by noise control.

Tip60 HAT Action Mediates Environmental Enrichment Induced Cognitive Restoration

PubMed Central

Xu, Songjun; Panikker, Priyalakshmi; Iqbal, Sahira; Elefant, Felice

2016-01-01

Environmental enrichment (EE) conditions have beneficial effects for reinstating cognitive ability in neuropathological disorders like Alzheimer’s disease (AD). While EE benefits involve epigenetic gene control mechanisms that comprise histone acetylation, the histone acetyltransferases (HATs) involved remain largely unknown. Here, we examine a role for Tip60 HAT action in mediating activity- dependent beneficial neuroadaptations to EE using the Drosophila CNS mushroom body (MB) as a well-characterized cognition model. We show that flies raised under EE conditions display enhanced MB axonal outgrowth, synaptic marker protein production, histone acetylation induction and transcriptional activation of cognition linked genes when compared to their genotypically identical siblings raised under isolated conditions. Further, these beneficial changes are impaired in both Tip60 HAT mutant flies and APP neurodegenerative flies. While EE conditions provide some beneficial neuroadaptive changes in the APP neurodegenerative fly MB, such positive changes are significantly enhanced by increasing MB Tip60 HAT levels. Our results implicate Tip60 as a critical mediator of EE-induced benefits, and provide broad insights into synergistic behavioral and epigenetic based therapeutic approaches for treatment of cognitive disorder. PMID:27454757

Tip60 HAT Action Mediates Environmental Enrichment Induced Cognitive Restoration.

PubMed

Xu, Songjun; Panikker, Priyalakshmi; Iqbal, Sahira; Elefant, Felice

2016-01-01

Environmental enrichment (EE) conditions have beneficial effects for reinstating cognitive ability in neuropathological disorders like Alzheimer's disease (AD). While EE benefits involve epigenetic gene control mechanisms that comprise histone acetylation, the histone acetyltransferases (HATs) involved remain largely unknown. Here, we examine a role for Tip60 HAT action in mediating activity- dependent beneficial neuroadaptations to EE using the Drosophila CNS mushroom body (MB) as a well-characterized cognition model. We show that flies raised under EE conditions display enhanced MB axonal outgrowth, synaptic marker protein production, histone acetylation induction and transcriptional activation of cognition linked genes when compared to their genotypically identical siblings raised under isolated conditions. Further, these beneficial changes are impaired in both Tip60 HAT mutant flies and APP neurodegenerative flies. While EE conditions provide some beneficial neuroadaptive changes in the APP neurodegenerative fly MB, such positive changes are significantly enhanced by increasing MB Tip60 HAT levels. Our results implicate Tip60 as a critical mediator of EE-induced benefits, and provide broad insights into synergistic behavioral and epigenetic based therapeutic approaches for treatment of cognitive disorder.

Active cycle of breathing technique for cystic fibrosis.

PubMed

Mckoy, Naomi A; Wilson, Lisa M; Saldanha, Ian J; Odelola, Olaide A; Robinson, Karen A

2016-07-05

People with cystic fibrosis experience chronic airway infections as a result of mucus build up within the lungs. Repeated infections often cause lung damage and disease. Airway clearance therapies aim to improve mucus clearance, increase sputum production, and improve airway function. The active cycle of breathing technique (also known as ACBT) is an airway clearance method that uses a cycle of techniques to loosen airway secretions including breathing control, thoracic expansion exercises, and the forced expiration technique. This is an update of a previously published review. To compare the clinical effectiveness of the active cycle of breathing technique with other airway clearance therapies in cystic fibrosis. We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles and reviews.Date of last search: 25 April 2016. Randomised or quasi-randomised controlled clinical studies, including cross-over studies, comparing the active cycle of breathing technique with other airway clearance therapies in cystic fibrosis. Two review authors independently screened each article, abstracted data and assessed the risk of bias of each study. Our search identified 62 studies, of which 19 (440 participants) met the inclusion criteria. Five randomised controlled studies (192 participants) were included in the meta-analysis; three were of cross-over design. The 14 remaining studies were cross-over studies with inadequate reports for complete assessment. The study size ranged from seven to 65 participants. The age of the participants ranged from six to 63 years (mean age 22.33 years). In 13 studies, follow up lasted a single day. However, there were two long-term randomised controlled studies with follow up of one to three years. Most of the studies did not report on key quality items, and therefore, have an unclear risk of bias in terms of random sequence generation, allocation concealment, and outcome assessor blinding. Due to the nature of the intervention, none of the studies blinded participants or the personnel applying the interventions. However, most of the studies reported on all planned outcomes, had adequate follow up, assessed compliance, and used an intention-to-treat analysis.Included studies compared the active cycle of breathing technique with autogenic drainage, airway oscillating devices, high frequency chest compression devices, conventional chest physiotherapy, and positive expiratory pressure. Preference of technique varied: more participants preferred autogenic drainage over the active cycle of breathing technique; more preferred the active cycle of breathing technique over airway oscillating devices; and more were comfortable with the active cycle of breathing technique versus high frequency chest compression. No significant difference was seen in quality of life, sputum weight, exercise tolerance, lung function, or oxygen saturation between the active cycle of breathing technique and autogenic drainage or between the active cycle of breathing technique and airway oscillating devices. There was no significant difference in lung function and the number of pulmonary exacerbations between the active cycle of breathing technique alone or in conjunction with conventional chest physiotherapy. All other outcomes were either not measured or had insufficient data for analysis. There is insufficient evidence to support or reject the use of the active cycle of breathing technique over any other airway clearance therapy. Five studies, with data from eight different comparators, found that the active cycle of breathing technique was comparable with other therapies in outcomes such as participant preference, quality of life, exercise tolerance, lung function, sputum weight, oxygen saturation, and number of pulmonary exacerbations. Longer-term studies are needed to more adequately assess the effects of the active cycle of breathing technique on outcomes important for people with cystic fibrosis such as quality of life and preference.

Lipoprotein lipase activity in surgical patients: influence of trauma and infection.

PubMed

Robin, A P; Askanazi, J; Greenwood, M R; Carpentier, Y A; Gump, F E; Kinney, J M

1981-08-01

Hypertriglyceridemia commonly accompanies clinical sepsis and may be caused by increased hepatic production or decreased clearance of triglyceride from the bloodstream. In contrast, enhanced lipid clearing capacity is usually seen after uncomplicated trauma. The purpose of the study was to determine the role of lipoprotein lipase (LPL) in effecting the above changes. Enzyme activity was assayed in skeletal muscle and adipose tissue biopsy samples from 11 normal subjects and from 17 injured and 11 infected surgical patients. Normal subjects after 4 days of 5% dextrose infusion (D5) showed a significant decrease in adipose tissue LPL activity but no change in skeletal muscle activity. Trauma patients after several days of D5 had higher activity in adipose tissue and higher plasma insulin levels than diet-matched control subjects but showed no change in skeletal muscle activity. Infected patients with high plasma triglyceride levels had significantly decreased LPL activity in both tissues. A linear relationship was found between insulin concentration and adipose tissue LPL activity in normal subjects. We conclude that: (1) low tissue LPL activity in sepsis may result in diminished lipid clearance and contribute to hypertriglyceridemia, (2) after trauma, changes in tissue LPL activity as well as other factors such as altered hemodynamics play a role in determining in vivo lipid clearance, and (3) adipose tissue LPL activity is related to the plasma insulin concentration in normal subjects.

Facile synthesis, pharmacokinetic and systemic clearance evaluation, and positron emission tomography cancer imaging of 64Cu-Au alloy nanoclusters

NASA Astrophysics Data System (ADS)

Zhao, Yongfeng; Sultan, Deborah; Detering, Lisa; Luehmann, Hannah; Liu, Yongjian

2014-10-01

Gold nanoparticles have been widely used for oncological applications including diagnosis and therapy. However, the non-specific mononuclear phagocyte system accumulation and potential long-term toxicity have significantly limited clinical translation. One strategy to overcome these shortcomings is to reduce the size of gold nanoparticles to allow renal clearance. Herein, we report the preparation of 64Cu alloyed gold nanoclusters (64CuAuNCs) for in vivo evaluation of pharmacokinetics, systemic clearance, and positron emission tomography (PET) imaging in a mouse prostate cancer model. The facile synthesis in acqueous solution allowed precisely controlled 64Cu incorporation for high radiolabeling specific activity and stability for sensitive and accurate detection. Through surface pegylation with 350 Da polyethylene glycol (PEG), the 64CuAuNCs-PEG350 afforded optimal biodistribution and significant renal and hepatobiliary excretion. PET imaging showed low non-specific tumor uptake, indicating its potential for active targeting of clinically relevant biomarkers in tumor and metastatic organs.Gold nanoparticles have been widely used for oncological applications including diagnosis and therapy. However, the non-specific mononuclear phagocyte system accumulation and potential long-term toxicity have significantly limited clinical translation. One strategy to overcome these shortcomings is to reduce the size of gold nanoparticles to allow renal clearance. Herein, we report the preparation of 64Cu alloyed gold nanoclusters (64CuAuNCs) for in vivo evaluation of pharmacokinetics, systemic clearance, and positron emission tomography (PET) imaging in a mouse prostate cancer model. The facile synthesis in acqueous solution allowed precisely controlled 64Cu incorporation for high radiolabeling specific activity and stability for sensitive and accurate detection. Through surface pegylation with 350 Da polyethylene glycol (PEG), the 64CuAuNCs-PEG350 afforded optimal biodistribution and significant renal and hepatobiliary excretion. PET imaging showed low non-specific tumor uptake, indicating its potential for active targeting of clinically relevant biomarkers in tumor and metastatic organs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04569f

Salicylic Acid Regulates Pollen Tip Growth through an NPR3/NPR4-Independent Pathway.

PubMed

Rong, Duoyan; Luo, Nan; Mollet, Jean Claude; Liu, Xuanming; Yang, Zhenbiao

2016-11-07

Tip growth is a common strategy for the rapid elongation of cells to forage the environment and/or to target to long-distance destinations. In the model tip growth system of Arabidopsis pollen tubes, several small-molecule hormones regulate their elongation, but how these rapidly diffusing molecules control extremely localized growth remains mysterious. Here we show that the interconvertible salicylic acid (SA) and methylated SA (MeSA), well characterized for their roles in plant defense, oppositely regulate Arabidopsis pollen tip growth with SA being inhibitory and MeSA stimulatory. The effect of SA and MeSA was independent of known NPR3/NPR4 SA receptor-mediated signaling pathways. SA inhibited clathrin-mediated endocytosis in pollen tubes associated with an increased accumulation of less stretchable demethylated pectin in the apical wall, whereas MeSA did the opposite. Furthermore, SA and MeSA alter the apical activation of ROP1 GTPase, a key regulator of tip growth in pollen tubes, in an opposite manner. Interestingly, both MeSA methylesterase and SA methyltransferase, which catalyze the interconversion between SA and MeSA, are localized at the apical region of pollen tubes, indicating of the tip-localized production of SA and MeSA and consistent with their effects on the apical cellular activities. These findings suggest that local generation of a highly diffusible signal can regulate polarized cell growth, providing a novel mechanism of cell polarity control apart from the one involving protein and mRNA polarization. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

Control of Flap Vortices

NASA Technical Reports Server (NTRS)

Greenblatt, David

2005-01-01

A wind tunnel investigation was carried out on a semi-span wing model to assess the feasibility of controlling vortices emanating from outboard flaps and tip-flaps by actively varying the degree of boundary layer separation. Separation was varied by means of perturbations produced from segmented zero-efflux oscillatory blowing slots, while estimates of span loadings and vortex sheet strengths were obtained by integrating wing surface pressures. These estimates were used as input to inviscid rollup relations as a means of predicting changes to the vortex characteristics resulting from the perturbations. Surveys of flow in the wake of the outboard and tip-flaps were made using a seven-hole probe, from which the vortex characteristics were directly deduced. Varying the degree of separation had a marked effect on vortex location, strength, tangential velocity, axial velocity and size for both outboard and tip-flaps. Qualitative changes in vortex characteristics were well predicted by the inviscid rollup relations, while the failure to account for viscosity was presumed to be the main reason for observed discrepancies. Introducing perturbations near the outboard flap-edges or on the tip-flap exerted significant control over vortices while producing negligible lift excursions.

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High-speed noncontacting instrumentation for jet engine testing

NASA Astrophysics Data System (ADS)

Scotto, M. J.; Eismeier, M. E.

1980-03-01

This paper discusses high-speed, noncontacting instrumentation systems for measuring the operating characteristics of jet engines. The discussion includes optical pyrometers for measuring blade surface temperatures, capacitance clearanceometers for measuring blade tip clearance and vibration, and optoelectronic systems for measuring blade flex and torsion. In addition, engine characteristics that mandate the use of such unique instrumentation are pointed out as well as the shortcomings of conventional noncontacting devices. Experimental data taken during engine testing are presented and recommendations for future development discussed.

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The Microtubule-Associated Protein MAP18 Affects ROP2 GTPase Activity during Root Hair Growth1[OPEN

PubMed Central

Kang, Erfang; Zheng, Mingzhi; Zhang, Yan; Yuan, Ming; Fu, Ying

2017-01-01

Establishment and maintenance of the polar site are important for root hair tip growth. We previously reported that Arabidopsis (Arabidopsis thaliana) MICROTUBULE-ASSOCIATED PROTEIN18 (MAP18) functions in controlling the direction of pollen tube growth and root hair elongation. Additionally, the Rop GTPase ROP2 was reported as a positive regulator of both root hair initiation and tip growth in Arabidopsis. Both loss of function of ROP2 and knockdown of MAP18 lead to a decrease in root hair length, whereas overexpression of either MAP18 or ROP2 causes multiple tips or a branching hair phenotype. However, it is unclear whether MAP18 and ROP2 coordinately regulate root hair growth. In this study, we demonstrate that MAP18 and ROP2 interact genetically and functionally. MAP18 interacts physically with ROP2 in vitro and in vivo and preferentially binds to the inactive form of the ROP2 protein. MAP18 promotes ROP2 activity during root hair tip growth. Further investigation revealed that MAP18 competes with RhoGTPase GDP DISSOCIATION INHIBITOR1/SUPERCENTIPEDE1 for binding to ROP2, in turn affecting the localization of active ROP2 in the plasma membrane of the root hair tip. These results reveal a novel function of MAP18 in the regulation of ROP2 activation during root hair growth. PMID:28314794

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Medical catheters thermally manipulated by fiber optic bundles

DOEpatents

Chastagner, Philippe

1992-01-01

A maneuverable medical catheter comprising a flexible tube having a functional tip. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts.

Servo-control of water and sodium homeostasis during renal clearance measurements in conscious rats.

PubMed

Thomsen, Klaus; Shirley, David G

2007-01-01

Servo-controlled fluid and sodium replacement during clearance studies is used in order to prevent loss of body fluid and sodium following diuretic/natriuretic procedures. However, even under control conditions, the use of this technique is sometimes associated with increases in proximal tubular fluid output (assessed by lithium clearance) and excretion rates. The present study examined the reason for these increases. The first series of experiments showed that one cause is volume overloading. This can occur if the servo system is activated from the start, i.e., during the establishment of a suitably high urine flow rate by constant infusion of hypotonic glucose solution. The second series of experiments showed that replacement of blood samples with donor blood can also lead to increases in fractional lithium excretion and accompanying increases in water and sodium excretion, a problem not seen when blood samples are replaced with the animal's own red blood cells resuspended in isotonic saline. When these pitfalls are avoided, servo-controlled sodium and fluid replacement is a reliable technique that makes it possible to study the effects of natriuretic and/or diuretic stimuli without interference from unwanted changes in extracellular volume. 2007 S. Karger AG, Basel

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Sealing in Turbomachinery

NASA Technical Reports Server (NTRS)

Chupp, Raymond E.; Hendricks, Robert C.; Lattime, Scott B.; Steinetz, Bruce M.

2006-01-01

Clearance control is of paramount importance to turbomachinery designers and is required to meet today's aggressive power output, efficiency, and operational life goals. Excessive clearances lead to losses in cycle efficiency, flow instabilities, and hot gas ingestion into disk cavities. Insufficient clearances limit coolant flows and cause interface rubbing, overheating downstream components and damaging interfaces, thus limiting component life. Designers have put renewed attention on clearance control, as it is often the most cost effective method to enhance system performance. Advanced concepts and proper material selection continue to play important roles in maintaining interface clearances to enable the system to meet design goals. This work presents an overview of turbomachinery sealing to control clearances. Areas covered include: characteristics of gas and steam turbine sealing applications and environments, benefits of sealing, types of standard static and dynamics seals, advanced seal designs, as well as life and limitations issues.

Evaluation of lung epithelial permeability in the volatile substance abuse using Tc-99m DTPA aerosol scintigraphy.

PubMed

Cayir, Derya; Demirel, Koray; Korkmaz, Meliha; Koca, Gokhan

2011-10-01

Chronic inhalant use is associated with significant toxic effects, including neurological, renal, hepatic, and pulmonary damage. However, there is a paucity of reports regarding respiratory complications in inhalant abusers. The aim of this study was to evaluate pulmonary epithelial permeability in the volatile substance abuse (VSA) using Tc-99m DTPA aerosol scintigraphy. This study included 18 patients with volatile substance abuse and 18 volunteer controls. All of patients and controls were smokers. Tc-99m DTPA aerosol scintigraphy was performed in all cases. Time-activity curves from each lung were generated and clearance half-time (T(1/2)) of Tc-99m DTPA were calculated. T(1/2) of whole lung was calculated as a mean of the T(1/2) of left and right lung. The T(1/2) values of Tc-99m DTPA clearance in the substance abusers were significantly decreased as compared to the control group with respective mean values of 28.86 ± 8.44, and 62.14 ± 26.12 min (p = 0.001). It was seen Tc-99m DTPA clearance from lung was faster as the duration of substance abuse was increased. Tc-99m DTPA pulmonary clearance is markedly accelerated in the volatile substance abuse. This suggests that inhalant abuse of substance may produce abnormalities in pulmonary alveolo-capillary membrane function.

The Effect of a Six-Month Dancing Program on Motor-Cognitive Dual-Task Performance in Older Adults.

PubMed

Hamacher, Dennis; Hamacher, Daniel; Rehfeld, Kathrin; Hökelmann, Anita; Schega, Lutz

2015-10-01

Dancing is a complex sensorimotor activity involving physical and mental elements which have positive effects on cognitive functions and motor control. The present randomized controlled trial aims to analyze the effects of a dancing program on the performance on a motor-cognitive dual task. Data of 35 older adults, who were assigned to a dancing group or a health-related exercise group, are presented in the study. In pretest and posttest, we assessed cognitive performance and variability of minimum foot clearance, stride time, and stride length while walking. Regarding the cognitive performance and the stride-to-stride variability of minimum foot clearance, interaction effects have been found, indicating that dancing lowers gait variability to a higher extent than conventional health-related exercise. The data show that dancing improves minimum foot clearance variability and cognitive performance in a dual-task situation. Multi-task exercises (like dancing) might be a powerful tool to improve motor-cognitive dual-task performance.

Automation for "Direct-to" Clearances in Air-Traffic Control

NASA Technical Reports Server (NTRS)

Erzberger, Heinz; McNally, David

2006-01-01

A method of automation, and a system of computer hardware and software to implement the method, have been invented to assist en-route air-traffic controllers in the issuance of clearances to fly directly to specified waypoints or navigation fixes along straight paths that deviate from previously filed flight plans. Such clearances, called "direct-to" clearances, have been in use since before the invention of this method and system.

Adaptive Engine Technologies for Aviation CO2 Emissions Reduction

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R.; Haller, William J.; Tong, Michael T.

2006-01-01

Adaptive turbine engine technologies are assessed for their potential to reduce carbon dioxide emissions from commercial air transports.Technologies including inlet, fan, and compressor flow control, compressor stall control, blade clearance control, combustion control, active bearings and enabling technologies such as active materials and wireless sensors are discussed. The method of systems assessment is described, including strengths and weaknesses of the approach. Performance benefit estimates are presented for each technology, with a summary of potential emissions reduction possible from the development of new, adaptively controlled engine components.

76 FR 17181 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-28

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Association of KIR genotypes and haplotypes with susceptibility to chronic hepatitis B virus infection in Chinese Han population.

PubMed

Lu, Zhiming; Zhang, Bingchang; Chen, Shijun; Gai, Zhongtao; Feng, Zhaolei; Liu, Xiangdong; Liu, Yiqing; Wen, Xin; Li, Li; Jiao, Yulian; Ma, Chunyan; Shao, Song; Cui, Xiangfa; Chen, Guojian; Li, Jianfeng; Zhao, Yueran

2008-12-01

Killer immunoglobulin-like receptor (KIR) genes can regulate the activation of NK and T cells upon interaction with HLA class I molecules. Hepatitis B virus (HBV) infection has been regarded as a multi-factorial disorder disease. Previous studies revealed that KIRs were involved in HCV and HIV infection or clearance. The aim of this study was to explore the possibility of the inheritance of KIR genotypes and haplotypes as a candidate for susceptibility to persistent HBV infection or HBV clearance. The sequence specific primer polymerase chain reaction (SSP-PCR) was employed to identify the KIR genes and pseudogenes in 150 chronic hepatitis B (CHB) patients, 251 spontaneously recovered (SR) controls, and 412 healthy controls. The frequencies of genotype G, M, FZ1 increased in CHB patients compared with healthy control subjects. The frequency of genotype AH was higher in SR controls than that in both CHB patients and healthy controls. The carriage frequencies of genotype G and AH were higher; while, the frequencies of AF and AJ were lower in SR controls than those in healthy control subjects. The frequency of A haplotype was lower, whereas, the frequency of B haplotype was higher in CHB patients and SR controls than those in healthy controls. In healthy controls, haplotype 4 was found lower compared with that in CHB patients and SR controls and the frequency of haplotype 5 was higher in SR controls than that in other two groups. Based on these findings, it seems that the genotypes M and FZ1 are HBV susceptive genotypes; AH, on the other hand, may be protective genotypes that facilitate the clearance of HBV. It appears that the haplotype 4 is HBV susceptive haplotype, whereas, haplotype 5 may be the protective haplotype that facilitates the clearance of HBV.

Microtubule plus-end tracking of end-binding protein 1 (EB1) is regulated by CDK5 regulatory subunit-associated protein 2

PubMed Central

Fong, Ka-Wing; Au, Franco K. C.; Jia, Yue; Yang, Shaozhong; Zhou, Liying; Qi, Robert Z.

2017-01-01

Microtubules are polar cytoskeleton filaments that extend via growth at their plus ends. Microtubule plus-end-tracking proteins (+TIPs) accumulate at these growing plus ends to control microtubule dynamics and attachment. The +TIP end-binding protein 1 (EB1) and its homologs possess an autonomous plus-end-tracking mechanism and interact with other known +TIPs, which then recruit those +TIPs to the growing plus ends. A major +TIP class contains the SXIP (Ser-X-Ile-Pro, with X denoting any amino acid residue) motif, known to interact with EB1 and its homologs for plus-end tracking, but the role of SXIP in regulating EB1 activities is unclear. We show here that an interaction of EB1 with the SXIP-containing +TIP CDK5 regulatory subunit-associated protein 2 (CDK5RAP2) regulates several EB1 activities, including microtubule plus-end tracking, dynamics at microtubule plus ends, microtubule and α/β-tubulin binding, and microtubule polymerization. The SXIP motif fused with a dimerization domain from CDK5RAP2 significantly enhanced EB1 plus-end-tracking and microtubule-polymerizing and bundling activities, but the SXIP motif alone failed to do so. An SXIP-binding-deficient EB1 mutant displayed significantly lower microtubule plus-end tracking than the wild-type protein in transfected cells. These results suggest that EB1 cooperates with CDK5RAP2 and perhaps other SXIP-containing +TIPs in tracking growing microtubule tips. We also generated plus-end-tracking chimeras of CDK5RAP2 and the adenomatous polyposis coli protein (APC) and found that overexpression of the dimerization domains interfered with microtubule plus-end tracking of their respective SXIP-containing chimeras. Our results suggest that disruption of SXIP dimerization enables detailed investigations of microtubule plus-end-associated functions of individual SXIP-containing +TIPs. PMID:28320860

The active control devices of the size of products based on sapphire measuring tips with three degrees of freedom

NASA Astrophysics Data System (ADS)

Leun, E. V.; Leun, V. I.; Sysoev, V. K.; Zanin, K. A.; Shulepov, A. V.; Vyatlev, P. A.

2018-01-01

The article presents the results of the calculation of the load capacity of the active control devices (ACD) sapphire tip, which showed nearly 30-fold margin of safety to shock loads and experimental researches in mechanical contact with 5 cogs cutter 15 mm in diameter rotating with a frequency of 1000 rpm, which confirmed the calculations, determined the surface roughness Rz of the contact area of no more than 0.15 μm. Conditions have been created for recording without distortion of the image through a sapphire tip in contact with the processed article. A ACD design with new functionality is proposed: with one, two and three degrees of freedom of the sapphire tip and allows measuring the taper of the article and measurements on the chord. It is shown that with the implementation of their fixed head like the frame of the gyroscope with the rotations around the axes OY and OZ. It is shown that the rotation of the tip around the axis OX can be replaced more convenient for the implementation of the angular offset of the transferred image due to rotation of the output end of the flexible optical waveguide relative to the input. This makes it possible to reduce the "blurring of the image" during registration of the fast moving product profile when the slope of the recorder lines coincides with the slope of the edges of the image elements of the selected moving elements of the article.

Alternative blade materials for technical and ecological optimization of a hydraulic pressure machine

NASA Astrophysics Data System (ADS)

Schwyzer, Olivier; Saenger, Nicole

2016-11-01

The Hydraulic Pressure Machine (HPM) is an energy converter to exploit head differences between 0.5 and 2.5 m in small streams and irrigation canals. Previous investigations show that efficiencies above 60% are possible. Several case studies indicate good continuity for aquatic life (e.g. fish) and bed load for the technology. The technology is described as an economically and ecologically viable option for small scale hydropower generation. Primary goal of this research is to improve the HPM blade design regarding its continuity properties by maintaining good efficiency rates. This is done by modifying the blade tip and testing within a large physical model under laboratory condition. Blade tips from steel (conventional - reference case) and a combination of EPDM rubber and steel as sandwich construction (rubber, steel, rubber - adhesive layered) are tested and compared. Both materials reach similar values for hydraulic efficiency (approx. 58%) and mechanical power output (approx. 220 W). The variation of different gap sizes pointed out the importance of small clearance gaps to reach high efficiencies. For assessing the two blade tip materials regarding continuity for aquatic life, fish dummies were led through the wheel. Analysis of slow motion video of dummies hit by the blade show significant advantages for the EPDM blade tip. The EPDM rubber allows to bend and thus reduces the shock and the probability for cuts on the fish dummy. It was shown that blade tips from EPDM have certain advantages regarding continuity compared to standard blade tips from steel. No compromise regarding energy production had to be made. These results from the HPM can be transferred to breast shot water wheel and may be applied for new and retrofitting projects.

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78 FR 73192 - Agency Information Collection Activities; Submission for OMB Review; Comment Request

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2013-12-05

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2013-04-19

... Dependent Surveillance--Broadcast (ADS-B) Out Performance Requirements To Support Air Traffic Control (ATC.... The final rule titled ``Automatic Dependent Surveillance-- Broadcast (ADS-B) Equipage Mandate To... System. The rule facilitates the use of ADS-B for aircraft surveillance by FAA air traffic controllers to...

A transport model for the deterministic stresses associated with turbomachinery blade row interactions

NASA Astrophysics Data System (ADS)

van de Wall, Allan George

The unsteady process resulting from the interaction of upstream vortical structures with a downstream blade row in turbomachines can have a significant impact on the machine efficiency. A transport model assuming incompressible flow and using linear theory was developed to take this process into account in the computation of time-average multistage turbomachinery flows. The upstream vortical structures are transported by the mean flow of the downstream blade row, redistributing the time-average unsteady kinetic energy (Uke ) associated with the incoming disturbance. The model was applied to compressor and turbine geometry. For compressors, the Uke associated with upstream 2-D wakes and 3-D tip clearance flows is reduced as a result of the interaction with a downstream blade row. This reduction results from inviscid effects as well as viscous effects and reduces the loss associated with the upstream disturbance. Any disturbance passing through a compressor blade row results in a smaller loss than if the disturbance was mixed-out prior to entering the blade row. For turbines, the Uke associated with upstream 2-D wakes and 3-D tip clearance flows are significantly amplified by inviscid effects as a result of the interaction with a downstream turbine blade row. Viscous effects act to reduce the amplification of the Uke by inviscid effects but results in a substantial loss. Any disturbance passing through a turbine blade row results in a larger loss than if the disturbance was mixedout prior to entering the blade row.

Vibration Based Crack Detection in a Rotating Disk. Part 2; Experimental Results

NASA Technical Reports Server (NTRS)

Gyekenyesi, Andrew L.; Sawicki, Jerzy T.; Martin, Richard E.; Haase, Wayne C.; Baaklini, George

2005-01-01

This paper describes the experimental results concerning the detection of a crack in a rotating disk. The goal was to utilize blade tip clearance and shaft vibration measurements to monitor changes in the system's center of mass and/or blade deformation behaviors. The concept of the approach is based on the fact that the development of a disk crack results in a distorted strain field within the component. As a result, a minute deformation in the disk's geometry as well as a change in the system's center of mass occurs. Here, a notch was used to simulate an actual crack. The vibration based experimental results failed to identify the existence of a notch when utilizing the approach described above, even with a rather large, circumferential notch (l.2 in.) located approximately mid-span on the disk (disk radius = 4.63 in. with notch at r = 2.12 in.). This was somewhat expected, since the finite element based results in Part 1 of this study predicted changes in blade tip clearance as well as center of mass shifts due to a notch to be less than 0.001 in. Therefore, the small changes incurred by the notch could not be differentiated from the mechanical and electrical noise of the rotor system. Although the crack detection technique of interest failed to identify the existence ofthe notch, the vibration data produced and captured here will be utilized in upcoming studies that will focus on different data mining techniques concerning damage detection in a disk.

Aerodynamic and heat transfer analysis of the low aspect ratio turbine using a 3D Navier-Stokes code

NASA Astrophysics Data System (ADS)

Choi, D.; Knight, C. J.

1991-06-01

The single-stage, high-pressure ratio Garrett Low Aspect Ratio Turbine (LART) test data obtained in a shock tunnel are employed as a basis for evaluating a new three-dimensional Navier Stokes code based on the O-H grid system. It uses Coakley's two-equation turbulence modeling with viscous sublayer resolution. For the nozzle guide vanes, calculations were made based on two grid zones: an O-grid zone wrapping around airfoil and an H-grid zone outside of the O-grid zone, including the regions upstream of the leadig edge and downstream of the trailing edge. For the rotor blade row, a third O-grid zone was added for the tip-gap region leakage flow. The computational results compare well with experiment. These comparisons include heat transfer distributions on the airfoils and end-walls. The leakage flow through the tip-gap clearance is well resolved.

Turbine Rotor Disk Health Monitoring Assessment Based on Sensor Technology and Spin Tests Data

PubMed Central

2013-01-01

The paper focuses on presenting data obtained from spin test experiments of a turbine engine like rotor disk and assessing their correlation to the development of a structural health monitoring and fault detection system. The data were obtained under various operating conditions such as the rotor disk being artificially induced with and without a notch and rotated at a rotational speed of up to 10,000 rpm under balanced and imbalanced state. The data collected included blade tip clearance, blade tip timing measurements, and shaft displacements. Two different sensor technologies were employed in the testing: microwave and capacitive sensors, respectively. The experimental tests were conducted at the NASA Glenn Research Center's Rotordynamics Laboratory using a high precision spin system. Disk flaw observations and related assessments from the collected data for both sensors are reported and discussed. PMID:23844396

CF6 jet engine performance improvement: New fan

NASA Technical Reports Server (NTRS)

Fasching, W. A.

1980-01-01

As part of the NASA sponsored engine component improvement program, and fan package was developed to reduce fuel consumption in current CF6 turbofan aircraft engine. The new fan package consist of an improved fan blade, reduced fan tip clearance due to a fan case stiffener, and a smooth fan casing tip shroud. CF6 engine performance and acoustic tests demonstrated the predicted 1.8% improvement in cruise sfc without an increase in engine noise. Power management thrust/fan speed characteristics were defined. Mechanical and structural integrity was demonstrated in model fan rotor photoelastic stress tests, full-size fan blade bench fatigue tests, and CF6 engine bird ingestion, crosswind, and cyclic endurance tests. The fan was certified in the CF6-500c2/E2 engines and is in commerical service on the Boeing 747-200, Douglas DC-10-30, and Atrbus industrie A300B aircraft.

Reduced Cortisol Metabolism during Critical Illness

PubMed Central

Boonen, Eva; Vervenne, Hilke; Meersseman, Philippe; Andrew, Ruth; Mortier, Leen; Declercq, Peter E.; Vanwijngaerden, Yoo-Mee; Spriet, Isabel; Wouters, Pieter J.; Perre, Sarah Vander; Langouche, Lies; Vanhorebeek, Ilse; Walker, Brian R.; Van den Berghe, Greet

2015-01-01

BACKGROUND Critical illness is often accompanied by hypercortisolemia, which has been attributed to stress-induced activation of the hypothalamic–pituitary–adrenal axis. However, low corticotropin levels have also been reported in critically ill patients, which may be due to reduced cortisol metabolism. METHODS In a total of 158 patients in the intensive care unit and 64 matched controls, we tested five aspects of cortisol metabolism: daily levels of corticotropin and cortisol; plasma cortisol clearance, metabolism, and production during infusion of deuterium-labeled steroid hormones as tracers; plasma clearance of 100 mg of hydrocortisone; levels of urinary cortisol metabolites; and levels of messenger RNA and protein in liver and adipose tissue, to assess major cortisol-metabolizing enzymes. RESULTS Total and free circulating cortisol levels were consistently higher in the patients than in controls, whereas corticotropin levels were lower (P<0.001 for both comparisons). Cortisol production was 83% higher in the patients (P=0.02). There was a reduction of more than 50% in cortisol clearance during tracer infusion and after the administration of 100 mg of hydrocortisone in the patients (P≤0.03 for both comparisons). All these factors accounted for an increase by a factor of 3.5 in plasma cortisol levels in the patients, as compared with controls (P<0.001). Impaired cortisol clearance also correlated with a lower cortisol response to corticotropin stimulation. Reduced cortisol metabolism was associated with reduced inactivation of cortisol in the liver and kidney, as suggested by urinary steroid ratios, tracer kinetics, and assessment of liver-biopsy samples (P≤0.004 for all comparisons). CONCLUSIONS During critical illness, reduced cortisol breakdown, related to suppressed expression and activity of cortisol-metabolizing enzymes, contributed to hypercortisolemia and hence corticotropin suppression. The diagnostic and therapeutic implications for critically ill patients are unknown. (Funded by the Belgian Fund for Scientific Research and others; ClinicalTrials.gov numbers, NCT00512122 and NCT00115479; and Current Controlled Trials numbers, ISRCTN49433936, ISRCTN49306926, and ISRCTN08083905.) PMID:23506003

Controlled deposition of palladium nanodendrites on the tips of gold nanorods and their enhanced catalytic activity.

PubMed

Su, Gaoxing; Jiang, Huaqiao; Zhu, Hongyan; Lv, Jing-Jing; Yang, Guohai; Yan, Bing; Zhu, Jun-Jie

2017-08-31

Plasmonic Au-Pd nanostructures have drawn significant attention for use in heterogeneous catalysis. In this study, palladium nanodendrite-tipped gold nanorods (PdND-T-AuNRs) were subjected to a facile fabrication under mild reaction conditions. The palladium amounts on the two tips were tunable. In the preparation of PdND-T-AuNRs, dense capped AuNRs, a low reaction temperature, and suitable stabilizing agents were identified as critical reaction parameters for controlling palladium nanodendrites deposited on both ends of AuNRs. After overgrowth with palladium nanodendrites, the longitudinal surface plasmonic resonance peaks of PdND-T-AuNRs were red-shifted from 810 nm to 980 nm. The electrocatalytic activity of PdND-T-AuNRs for ethanol oxidation was examined, which was a bit weaker than that of cuboid core-shell Au-Pd nanodendrites; however, PdND-T-AuNRs were more stable in ethanol electrooxidation. Moreover, the photocatalytic activity of PdND-T-AuNRs for Suzuki cross-coupling reactions was investigated. At room temperature, nearly 100% yield was obtained under laser irradiation. The results can further enhance our capability of fine-tuning the optical, electronic, and catalytic properties of the bimetallic Au-Pd nanostructures.

76 FR 45573 - Agency Information Collection Activities: Proposed Collection; Comment Request; Generic Clearance...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-29

... Technology Research Center survey. Abstract: The information collection activity will garner qualitative.... This type of generic clearance for qualitative information will not be used for quantitative... Collection; Comment Request; Generic Clearance for the Collection of Qualitative Feedback on Agency Service...

PRMT5-Dependent Methylation of the TIP60 Coactivator RUVBL1 Is a Key Regulator of Homologous Recombination.

PubMed

Clarke, Thomas L; Sanchez-Bailon, Maria Pilar; Chiang, Kelly; Reynolds, John J; Herrero-Ruiz, Joaquin; Bandeiras, Tiago M; Matias, Pedro M; Maslen, Sarah L; Skehel, J Mark; Stewart, Grant S; Davies, Clare C

2017-03-02

Protein post-translation modification plays an important role in regulating DNA repair; however, the role of arginine methylation in this process is poorly understood. Here we identify the arginine methyltransferase PRMT5 as a key regulator of homologous recombination (HR)-mediated double-strand break (DSB) repair, which is mediated through its ability to methylate RUVBL1, a cofactor of the TIP60 complex. We show that PRMT5 targets RUVBL1 for methylation at position R205, which facilitates TIP60-dependent mobilization of 53BP1 from DNA breaks, promoting HR. Mechanistically, we demonstrate that PRMT5-directed methylation of RUVBL1 is critically required for the acetyltransferase activity of TIP60, promoting histone H4K16 acetylation, which facilities 53BP1 displacement from DSBs. Interestingly, RUVBL1 methylation did not affect the ability of TIP60 to facilitate ATM activation. Taken together, our findings reveal the importance of PRMT5-mediated arginine methylation during DSB repair pathway choice through its ability to regulate acetylation-dependent control of 53BP1 localization. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Design and analysis of axial aspirated compressor stages

NASA Astrophysics Data System (ADS)

Merchant, Ali A.

The pressure ratio of axial compressor stages can be significantly increased by controlling the development of blade and endwall boundary layers in regions of adverse pressure gradient by means of boundary layer suction. This concept is validated and demonstrated through the design and analysis of two unique aspirated compressor stages: a low-speed stage with a design pressure ratio of 1.6 at a tip speed of 750 ft/s, and a high-speed stage with a design pressure ratio of 3.5 at a tip speed of 1500 ft/s. The aspirated compressor stages were designed using a new procedure which is a synthesis of low speed and high speed blade design techniques combined with a flexible inverse design method which enabled precise independent control over the shape of the blade suction and pressure surfaces. Integration of the boundary layer suction calculation into the overall design process is an essential ingredient of the new procedure. The blade design system consists of two axisymmetric through-flow codes coupled with a quasi three-dimensional viscous cascade plane code with inverse design capability. Validation of the completed designs were carried out with three-dimensional Euler and Navier-Stokes calculations. A single spanwise slot on the blade suction surface is used to bleed the boundary layer. The suction mass flow requirement for the low-speed and high-speed stages are 1% and 4% of the inlet mass flow, respectively. Additional suction between 1-2% is also required on the compressor endwalls near shock impingement locations. The rotor is modeled with a tip shroud to eliminate tip clearance effects and to discharge the suction flow radially from the flowpath. Three-dimensional viscous evaluation of the designs showed good agreement with the quasi three-dimensional design intent, except in the endwall regions. The suction requirements predicted by the quasi three-dimensional calculation were confirmed by the three-dimensional viscous calculations. The three-dimensional viscous analysis predicted a peak pressure ratio of 1.59 at an isentropic efficiency of 89% for the low-speed stage, and a peak pressure ratio of 3.68 at an isentropic efficiency of 94% for the high-speed rotor. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

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2011-07-13

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Regulation Of Hypothalamic Signaling By Tuberoinfundibular Peptide Of 39 Residues Is Critical For The Response To Cold: A Novel Peptidergic Mechanism Of Thermoregulation

PubMed Central

Dimitrov, Eugene L.; Kim, Yoon Yi; Usdin, Ted B.

2012-01-01

Euthermia is critical for mammalian homeostasis. Circuits within the preoptic hypothalamus regulate temperature, with fine control exerted via descending GABAergic inhibition of presympathetic motor neurons that control brown adipose tissue (BAT) thermogenesis and cutaneous vascular tone. The thermoregulatory role of hypothalamic excitatory neurons is less clear. Here we report peptidergic regulation of preoptic glutamatergic neurons that contributes to temperature regulation. Tuberoinfundibular peptide of 39 residues (TIP39) is a ligand for the parathyroid hormone 2 receptor (PTH2R). Both peptide and receptor are abundant in the preoptic hypothalamus. Based on PTH2R and vesicular glutamate transporter 2 (VGlut2) immunolabeling in animals with retrograde tracer injection, PTH2R containing glutamatergic fibers are presynaptic to neurons projecting from the median preoptic nucleus (MnPO) to the dorsomedial hypothalamus. Transneuronal retrograde pathway tracing with pseudorabies virus revealed connectivity between MnPO VGlut2 and PTH2R neurons and BAT. MnPO injection of TIP39 increased body temperature by 2° C for several hours. Mice lacking TIP39 signaling, either because of PTH2R null mutation or brain delivery of a PTH2R antagonist had impaired heat production upon cold exposure, but no change in basal temperature and no impairment in response to a hot environment. Thus, TIP39 appears to act on PTH2Rs present on MnPO glutamatergic terminals to regulate their activation of projection neurons and subsequent sympathetic BAT activation. This excitatory mechanism of heat production appears to be activated on demand, during cold exposure, and parallels the tonic inhibitory GABAergic control of body temperature. PMID:22159128

Unsteady Turbine Blade and Tip Heat Transfer Due to Wake Passing

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Rigby, David L.; Steinthorsson, Erlendur; Heidmann, James; Fabian, John C.

2007-01-01

The geometry and the flow conditions of the first stage turbine blade of GE s E3 engine have been used to obtain the unsteady three-dimensional blade and tip heat transfer. The isothermal wall boundary condition was used. The effect of the upstream wake of the first stage vane was of interest and was simulated by provision of a gust type boundary condition upstream of the blades. A one blade periodic domain was used. The consequence of this choice was explored in a preliminary study which showed little difference in the time mean heat transfer between 1:1 and 2:3 vane/blade domains. The full three-dimensional computations are of the blade having a clearance gap of 2 percent the span. Comparison between the time averaged unsteady and steady heat transfer is provided. It is shown that there is a significant difference between the steady and time mean of unsteady blade heat transfer in localized regions. The differences on the suction side of the blade in the near hub and near tip regions were found to be rather significant. Steady analysis underestimated the blade heat transfer by as much as 20 percent as compared to the time average obtained from the unsteady analysis. As for the blade tip, the steady analysis and the unsteady analysis gave results to within 2 percent.

Fiber optics for aircraft engine/inlet control

NASA Technical Reports Server (NTRS)

Baumbick, R. J.

1981-01-01

NASA programs that focus on the use of fiber optics for aircraft engine/inlet control are reviewed. Fiber optics for aircraft control is attractive because of its inherent immunity to EMI and RFI noise. Optical signals can be safely transmitted through areas that contain flammable or explosive materials. The use of optics also makes remote sensing feasible by eliminating the need for electrical wires to be connected between sensors and computers. Using low-level optical signals to control actuators is also feasible when power is generated at the actuator. Each application of fiber optics for aircraft control has different requirements for both the optical cables and the optical connectors. Sensors that measure position and speed by using slotted plates can use lossy cables and bundle connectors if data transfer is in the parallel mode. If position and speed signals are multiplexed, cable and connector requirements change. Other sensors that depend on changes in transmission through materials require dependable characteristics of both the optical cables and the optical connectors. A variety of sensor types are reviewed, including rotary position encoders, tachometers, temperature sensors, and blade tip clearance sensors for compressors and turbines. Research on a gallium arsenide photoswitch for optically switched actuators that operate at 250 C is also described.

Magnetic Catheter Manipulation in the Interventional MRI Environment

PubMed Central

Wilson, Mark W.; Martin, Alastair B.; Lillaney, Prasheel; Losey, Aaron D.; Yee, Erin J.; Bernhardt, Anthony; Malba, Vincent; Evans, Lee; Sincic, Ryan; Saeed, Maythem; Arenson, Ronald L.; Hetts, Steven W.

2013-01-01

Purpose To evaluate deflection capability of a prototype endovascular catheter, which is remotely magnetically steerable, for use in the interventional MRI environment. Materials and Methods Copper coils were mounted on the tips of commercially available 2.3 – 3.0 Fr microcatheters. The coils were fabricated in a novel manner by plasma vapor deposition of a copper layer followed by laser lithography of the layer into coils. Orthogonal helical (solenoid) and saddle-shaped (Helmholtz) coils were mounted on a single catheter tip. Microcatheters were tested in water bath phantoms in a 1.5T clinical MRI scanner, with variable simultaneous currents applied to the coils. Catheter tip deflection was imaged in the axial plane utilizing a “real-time” steady-state free precession (SSFP) MRI sequence. Degree of deflection and catheter tip orientation were measured for each current application. Results The catheter tip was clearly visible in the longitudinal and axial planes. Magnetic field artifacts were visible when the orthogonal coils at the catheter tip were energized. Variable amounts of current applied to a single coil demonstrated consistent catheter deflection in all water bath experiments. Changing current polarity reversed the observed direction of deflection, whereas current applied to two different coils resulted in deflection represented by the composite vector of individual coil activations. Microcatheter navigation through the vascular phantom was successful through control of applied current to one or more coils. Conclusion Controlled catheter deflection is possible with laser lithographed multi-axis coil tipped catheters in the MRI environment. PMID:23707097

Endpoint Accuracy in Manual Control of a Steerable Needle.

PubMed

van de Berg, Nick J; Dankelman, Jenny; van den Dobbelsteen, John J

2017-02-01

To study the ability of a human operator to manually correct for errors in the needle insertion path without partial withdrawal of the needle by means of an active, tip-articulated steerable needle. The needle is composed of a 1.32-mm outer-diameter cannula, with a flexure joint near the tip, and a retractable stylet. The bending stiffness of the needle resembles that of a 20-gauge hypodermic needle. The needle functionality was evaluated in manual insertions by steering to predefined targets and a lateral displacement of 20 mm from the straight insertion line. Steering tasks were conducted in 5 directions and 2 tissue simulants under image guidance from a camera. The repeatability in instrument actuations was assessed during 100 mm deep automated insertions with a linear motor. In addition to tip position, tip angles were tracked during the insertions. The targeting error (mean absolute error ± standard deviation) during manual steering to 5 different targets in stiff tissue was 0.5 mm ± 1.1. This variability in manual tip placement (1.1 mm) was less than the variability among automated insertions (1.4 mm) in the same tissue type. An increased tissue stiffness resulted in an increased lateral tip displacement. The tip angle was directly controlled by the user interface, and remained unaffected by the tissue stiffness. This study demonstrates the ability to manually steer needles to predefined target locations under image guidance. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

Rhodamine B induces long nucleoplasmic bridges and other nuclear anomalies in Allium cepa root tip cells.

PubMed

Tan, Dehong; Bai, Bing; Jiang, Donghua; Shi, Lin; Cheng, Shunchang; Tao, Dongbing; Ji, Shujuan

2014-03-01

The cytogenetic toxicity of rhodamine B on root tip cells of Allium cepa was investigated. A. cepa were cultured in water (negative control), 10 ppm methyl methanesulfonate (positive control), and three concentrations of rhodamine B (200, 100, and 50 ppm) for 7 days. Rhodamine B inhibited mitotic activity; increased nuclear anomalies, including micronuclei, nuclear buds, and bridged nuclei; and induced oxidative stress in A. cepa root tissues. Furthermore, a substantial amount of long nucleoplasmic bridges were entangled together, and some nuclei were simultaneously linked to several other nuclei and to nuclear buds with nucleoplasmic bridges in rhodamine B-treated cells. In conclusion, rhodamine B induced cytogenetic effects in A. cepa root tip cells, which suggests that the A. cepa root is an ideal model system for detecting cellular interactions.

Comparing Phlebotomy by Tail Tip Amputation, Facial Vein Puncture, and Tail Vein Incision in C57BL/6 Mice by Using Physiologic and Behavioral Metrics of Pain and Distress

PubMed Central

Moore, Elizabeth S; Cleland, Thomas A; Williams, Wendy O; Peterson, Christine M; Singh, Bhupinder; Southard, Teresa L; Pasch, Bret; Labitt, Rachael N; Daugherity, Erin K

2017-01-01

Tail tip amputation with minimal restraint is not widely used for mouse phlebotomy. In part, this infrequency may reflect policies influenced by tail tip amputation procedures for genotyping, which involve greater handling and tissue removal. To assess tail tip amputation with minimal restraint as a phlebotomy technique, we compared it with 2 more common methods: scruffing with facial vein puncture and lateral tail vein incision with minimal restraint. Blood glucose levels, audible and ultrasonic vocalizations, postphlebotomy activity and grooming behavior, open field and elevated plus maze behaviors, nest-building scores, and histologic changes at the phlebotomy site were evaluated. Mice in the facial vein phlebotomy group produced more audible vocalizations, exhibited lower postphlebotomy activity in the open field, and had more severe histologic changes than did mice in the tail incision and tail tip amputation groups. Facial vein phlebotomy did not affect grooming behavior relative to sham groups, whereas tail vein incision—but not tail tip amputation—increased tail grooming compared with that in control mice. Blood glucose levels, nest-building scores, and elevated plus maze behavior did not differ between groups, and no mice in any group produced ultrasonic vocalizations. Tail tip amputation mice did not perform differently than sham mice in any metric analyzed, indicating that this technique is a potentially superior method of blood collection in mice in terms of animal wellbeing. PMID:28535866

Comparing Phlebotomy by Tail Tip Amputation, Facial Vein Puncture, and Tail Vein Incision in C57BL/6 Mice by Using Physiologic and Behavioral Metrics of Pain and Distress.

PubMed

Moore, Elizabeth S; Cleland, Thomas A; Williams, Wendy O; Peterson, Christine M; Singh, Bhupinder; Southard, Teresa L; Pasch, Bret; Labitt, Rachael N; Daugherity, Erin K

2017-05-01

Tail tip amputation with minimal restraint is not widely used for mouse phlebotomy. In part, this infrequency may reflect policies influenced by tail tip amputation procedures for genotyping, which involve greater handling and tissue removal. To assess tail tip amputation with minimal restraint as a phlebotomy technique, we compared it with 2 more common methods: scruffing with facial vein puncture and lateral tail vein incision with minimal restraint. Blood glucose levels, audible and ultrasonic vocalizations, postphlebotomy activity and grooming behavior, open field and elevated plus maze behaviors, nest-building scores, and histologic changes at the phlebotomy site were evaluated. Mice in the facial vein phlebotomy group produced more audible vocalizations, exhibited lower postphlebotomy activity in the open field, and had more severe histologic changes than did mice in the tail incision and tail tip amputation groups. Facial vein phlebotomy did not affect grooming behavior relative to sham groups, whereas tail vein incision-but not tail tip amputation-increased tail grooming compared with that in control mice. Blood glucose levels, nest-building scores, and elevated plus maze behavior did not differ between groups, and no mice in any group produced ultrasonic vocalizations. Tail tip amputation mice did not perform differently than sham mice in any metric analyzed, indicating that this technique is a potentially superior method of blood collection in mice in terms of animal wellbeing.

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2011-06-28

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Auditory Localization Performance with Gamma Integrated Eye and Ear Protection

DTIC Science & Technology

2016-12-01

is unlimited. v List of Figures Fig. 1 IEEP device under test: shown with clear ballistic lens and Comply foam earphone tips...conducted with the system active. Fig. 1 IEEP device under test: shown with clear ballistic lens and Comply foam earphone tips. 1.2 Auditory...controlled acoustic facilities with large loudspeaker arrays. Method 1 has 2 listener orientations (0° and 45°) and specifies the use of 8

Tip Vortex Cavitation

NASA Astrophysics Data System (ADS)

Maines, Brant H.; Arndt, Roger E. A.

2000-11-01

Cavitation in vortical flows is a problem of practical importance, that is relatively unexplored. Vortical structures of importance range from the eddies occurring randomly in space and time in turbulent flows to the developed vortices that occur at the tips of lifting surfaces and at the hubs of propellers and hydraulic turbines. A variety of secondary flow phenomena such as the horse shoe vortices that form around bridge piers, chute blocks and struts, and the secondary vortices found in the clearance passages of turbomachinery are also important cavitation sites. Tip vortex cavitation can be viewed as a canonical problem that captures many of the essential physics associated with vortex cavitation in general. This paper describes the inception process and focuses on the high levels of tension that can be sustained in the flow, which appears to scale with the blade loading. High speed video visualization indicates that the details of how free stream nuclei are ingested plays a major role in the nucleation and inception process. A new photographic technique was used to obtain high quality images of the bubble growth process at framing rates as high as 40,000 fps. Sponsored by the Office of Naval Research

The effects of 2100-MHz radiofrequency radiation on nasal mucosa and mucociliary clearance in rats.

PubMed

Aydoğan, Filiz; Aydın, Emine; Koca, Gökhan; Özgür, Elçin; Atilla, Pergin; Tüzüner, Arzu; Demirci, Şule; Tomruk, Arin; Öztürk, Göknur Güler; Seyhan, Nesrin; Korkmaz, Meliha; Müftüoğlu, Sevda; Samim, Ethem Erdal

2015-07-01

Nasal mucociliary clearance has an important role in voiding the airways from inhaled foreign substances. This activity could be disturbed by environmental factors such as radiofrequency radiation. The aim of the present study was to investigate short-term and relatively long-term effects of 2100-MHz radiofrequency radiation emitted by a generator, simulating a 3G-mobile phone, on the nasal septal mucosa and mucociliary clearance in rats. Thirty Wistar albino rats were divided into 4 groups. There were 6 rats in Group A and Group B, which served as the control groups (10-day and 40-day groups, respectively). Groups C (10-day exposure) and D (40-day exposure) were both composed of 9 rats; they comprised the radiofrequency radiation exposure groups. The rats in groups C and D were exposed to 2100-MHz radiofrequency radiation emitted by a generator, simulating a 3G-mobile phone, 6 hours/day, for 10 or 40 days, respectively. After exposure, nasal mucociliary clearance was measured by rhinoscintigraphy. After euthanization, the nasal septa of the animals were removed, and tissue samples of the nasal mucosa were examined using a transmission electron microscope. The differences in mucociliary clearances between groups A and C, groups B and D, and groups C and D were found to be statistically significant (p = 0.005, p < 0.001, p < 0.001, respectively). Although there were no histopathological abnormalities in the control groups, the exposure groups showed a number of degenerated and apoptotic cells, ciliary disorganization and ciliary loss in the epithelial cells, epithelial metaplasia, alteration of normal chromatin distribution and karyolysis in nuclei, changes in the basal cells, and lymphocytic infiltration. The histopathological changes were more severe in group D. Radiofrequency radiation at 2100 MHz damaged the nasal septal mucosa, and disturbed the mucociliary clearance. Ciliary disorganization and ciliary loss in the epithelial cells resulted in deterioration of nasal mucociliary clearance. © 2015 ARS-AAOA, LLC.

CF6 jet engine performance improvement program. Task 1: Feasibility analysis

NASA Technical Reports Server (NTRS)

Fasching, W. A.

1979-01-01

Technical and economic engine improvement concepts selected for subsequent development include: (1) fan improvement; (2) short core exhaust; (3) HP turbine aerodynamic improvement; (4) HP turbine roundness control; (5) HP turbine active clearance control; and (6) cabin air recirculation. The fuel savings for the selected engine modification concepts for the CF6 fleet are estimated.

77 FR 24492 - Agency Information Collection Activities; Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-24

... requirements contained in the Pay-Per-Call Rule (Rule). That clearance expires on May 31, 2012 (OMB Control No...''), 16 CFR part 308. OMB Control Number: 3084-0102. Type of Review: Extension of a currently approved...-call service, that they will not be liable for unauthorized non-toll charges on their telephone bills...

IL-5-stimulated eosinophils adherent to periostin undergo stereotypic morphological changes and ADAM8-dependent migration.

PubMed

Johansson, M W; Khanna, M; Bortnov, V; Annis, D S; Nguyen, C L; Mosher, D F

2017-10-01

IL-5 causes suspended eosinophils to polarize with filamentous (F)-actin and granules at one pole and the nucleus in a specialized uropod, the "nucleopod," which is capped with P-selectin glycoprotein ligand-1 (PSGL-1). IL-5 enhances eosinophil adhesion and migration on periostin, an extracellular matrix protein upregulated in asthma by type 2 immunity mediators. Determine how the polarized morphology evolves to foster migration of IL-5-stimulated eosinophils on a surface coated with periostin. Blood eosinophils adhering to adsorbed periostin were imaged at different time points by fluorescent microscopy, and migration of eosinophils on periostin was assayed. After 10 minutes in the presence of IL-5, adherent eosinophils were polarized with PSGL-1 at the nucleopod tip and F-actin distributed diffusely at the opposite end. After 30-60 minutes, the nucleopod had dissipated such that PSGL-1 was localized in a crescent or ring away from the cell periphery, and F-actin was found in podosome-like structures. The periostin layer, detected with monoclonal antibody Stiny-1, shown here to recognize the FAS1 4 module, was cleared in wide areas around adherent eosinophils. Clearance was attenuated by metalloproteinase inhibitors or antibodies to disintegrin metalloproteinase 8 (ADAM8), a major eosinophil metalloproteinase previously implicated in asthma pathogenesis. ADAM8 was not found in podosome-like structures, which are associated with proteolytic activity in other cell types. Instead, immunoblotting demonstrated proteoforms of ADAM8 that lack the cytoplasmic tail in the supernatant. Anti-ADAM8 inhibited migration of IL-5-stimulated eosinophils on periostin. Migrating IL-5-activated eosinophils on periostin exhibit loss of nucleopodal features and appearance of prominent podosomes along with clearance of the Stiny-1 periostin epitope. Migration and epitope clearance are both attenuated by inhibitors of ADAM8. We propose, therefore, that eosinophils remodel and migrate on periostin-rich extracellular matrix in the asthmatic airway in an ADAM8-dependent manner, making ADAM8 a possible therapeutic target. © 2017 John Wiley & Sons Ltd.

Performance of a tandem-rotor/tandem-stator conical-flow compressor designed for a pressure ratio of 3

NASA Technical Reports Server (NTRS)

Wood, J. R.; Owen, A. K.; Schumann, L. F.

1982-01-01

A conical-flow compressor stage with a large radius change through the rotor was tested at three values of rotor tip clearance. The stage had a tandem rotor and a tandem stator. Peak efficiency at design speed was 0.774 at a pressure ratio of 2.613. The rotor was tested without the stator, and detailed survey data were obtained for each rotor blade row. Overall peak rotor efficiency was 0.871 at a pressure ratio of 2.952.

A Study on Aircraft Structure and Jet Engine

NASA Astrophysics Data System (ADS)

Park, Gil Moon; Park, Hwan Kyu; Kim, Jong Il; Kim, Jin Won; Kim, Jin Heung; Lee, Moo Seok; Chung, Nak Kyu

1985-12-01

The one of critical factor in gas turbine engine performance is high turbine inlet gas temperature. Therefore, the turbine rotor has so many problems which must be considered such as the turbine blade cooling, thermal stress of turbine disk due to severe temperature gradient, turbine rotor tip clearance, under the high operation temperature. The purpose of this study is to provide the temperature distribution and heat flux in turbine disk which is required to considered premensioned problem by the Finite Difference Method and the Finite Element Methods on the steady state condition.

Role of atrial receptors in the control of sodium excretion. [pressure breathing and antinatiuretic effects in dogs

NASA Technical Reports Server (NTRS)

Meehan, J. R.; Henry, J. P.

1973-01-01

Responses of an innervated and a contralateral chronically denervated kidney to mild positive pressure breathing are compared for saline volume expansions in chloralose anesthetized dogs. It is shown that mild pressure breathing significantly reduces sodium excretion, urine flow, free water clearance, and PAH clearance. After 20 minutes of positive pressure breathing, both kidney responses are identical suggesting the release of natriuretic hormone which reduces renal function in addition to the demonstrated change in renal nerve activity. Increase of the left atrial pressure through balloon obstruction of the mitral orifice increases urine flow, sodium excretion and PAH clearance; inflation of the balloon and positive pressure breathing again depresses renal function. Preliminary evidence indicates that receptors in the right atrium are more severely affected by pressure breathing than those in the left atrium.

Active hexagonally segmented mirror to investigate new optical phasing technologies for segmented telescopes.

PubMed

Gonté, Frédéric; Dupuy, Christophe; Luong, Bruno; Frank, Christoph; Brast, Roland; Sedghi, Baback

2009-11-10

The primary mirror of the future European Extremely Large Telescope will be equipped with 984 hexagonal segments. The alignment of the segments in piston, tip, and tilt within a few nanometers requires an optical phasing sensor. A test bench has been designed to study four different optical phasing sensor technologies. The core element of the test bench is an active segmented mirror composed of 61 flat hexagonal segments with a size of 17 mm side to side. Each of them can be controlled in piston, tip, and tilt by three piezoactuators with a precision better than 1 nm. The context of this development, the requirements, the design, and the integration of this system are explained. The first results on the final precision obtained in closed-loop control are also presented.

Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips.

PubMed

Tewari, Sumit; Bastiaans, Koen M; Allan, Milan P; van Ruitenbeek, Jan M

2017-01-01

Scanning tunneling microscopes (STM) are used extensively for studying and manipulating matter at the atomic scale. In spite of the critical role of the STM tip, procedures for controlling the atomic-scale shape of STM tips have not been rigorously justified. Here, we present a method for preparing tips in situ while ensuring the crystalline structure and a reproducibly prepared tip structure up to the second atomic layer. We demonstrate a controlled evolution of such tips starting from undefined tip shapes.

Blood lactate clearance after maximal exercise depends on active recovery intensity.

PubMed

Devlin, J; Paton, B; Poole, L; Sun, W; Ferguson, C; Wilson, J; Kemi, O J

2014-06-01

High-intensity exercise is time-limited by onset of fatigue, marked by accumulation of blood lactate. This is accentuated at maximal, all-out exercise that rapidly accumulates high blood lactate. The optimal active recovery intensity for clearing lactate after such maximal, all-out exercise remains unknown. Thus, we studied the intensity-dependence of lactate clearance during active recovery after maximal exercise. We constructed a standardized maximal, all-out treadmill exercise protocol that predictably lead to voluntary exhaustion and blood lactate concentration>10 mM. Next, subjects ran series of all-out bouts that increased blood lactate concentration to 11.5±0.2 mM, followed by recovery exercises ranging 0% (passive)-100% of the lactate threshold. Repeated measurements showed faster lactate clearance during active versus passive recovery (P<0.01), and that active recovery at 60-100% of lactate threshold was more efficient for lactate clearance than lower intensity recovery (P<0.05). Active recovery at 80% of lactate threshold had the highest rate of and shortest time constant for lactate clearance (P<0.05), whereas the response during the other intensities was graded (100%=60%>40%>passive recovery, P<0.05). Active recovery after maximal all-out exercise clears accumulated blood lactate faster than passive recovery in an intensity-dependent manner, with maximum clearance occurring at active recovery of 80% of lactate threshold.

Medical catheters thermally manipulated by fiber optic bundles

DOEpatents

Chastagner, P.

1992-10-06

A maneuverable medical catheter comprising a flexible tube having a functional tip is described. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts. 10 figs.

77 FR 47492 - Agency Information Collection Activities: Requests for Comments; Clearance of a New Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-08

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Hepatobiliary Clearance Prediction: Species Scaling From Monkey, Dog, and Rat, and In Vitro-In Vivo Extrapolation of Sandwich-Cultured Human Hepatocytes Using 17 Drugs.

PubMed

Kimoto, Emi; Bi, Yi-An; Kosa, Rachel E; Tremaine, Larry M; Varma, Manthena V S

2017-09-01

Hepatobiliary elimination can be a major clearance pathway dictating the pharmacokinetics of drugs. Here, we first compared the dose eliminated in bile in preclinical species (monkey, dog, and rat) with that in human and further evaluated single-species scaling (SSS) to predict human hepatobiliary clearance. Six compounds dosed in bile duct-cannulated (BDC) monkeys showed biliary excretion comparable to human; and the SSS of hepatobiliary clearance with plasma fraction unbound correction yielded reasonable predictions (within 3-fold). Although dog SSS also showed reasonable predictions, rat overpredicted hepatobiliary clearance for 13 of 24 compounds. Second, we evaluated the translatability of in vitro sandwich-cultured human hepatocytes (SCHHs) to predict human hepatobiliary clearance for 17 drugs. For drugs with no significant active uptake in SCHH studies (i.e., with or without rifamycin SV), measured intrinsic biliary clearance was directly scalable with good predictability (absolute average fold error [AAFE] = 1.6). Drugs showing significant active uptake in SCHH, however, showed improved predictability when scaled based on extended clearance term (AAFE = 2.0), which incorporated sinusoidal uptake along with a global scaling factor for active uptake and the canalicular efflux clearance. In conclusion, SCHH is a useful tool to predict human hepatobiliary clearance, whereas BDC monkey model may provide further confidence in the prospective predictions. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

NFκB is a central regulator of protein quality control in response to protein aggregation stresses via autophagy modulation

PubMed Central

Nivon, Mathieu; Fort, Loïc; Muller, Pascale; Richet, Emma; Simon, Stéphanie; Guey, Baptiste; Fournier, Maëlenn; Arrigo, André-Patrick; Hetz, Claudio; Atkin, Julie D.; Kretz-Remy, Carole

2016-01-01

During cell life, proteins often misfold, depending on particular mutations or environmental changes, which may lead to protein aggregates that are toxic for the cell. Such protein aggregates are the root cause of numerous diseases called “protein conformational diseases,” such as myofibrillar myopathy and familial amyotrophic lateral sclerosis. To fight against aggregates, cells are equipped with protein quality control mechanisms. Here we report that NFκB transcription factor is activated by misincorporation of amino acid analogues into proteins, inhibition of proteasomal activity, expression of the R120G mutated form of HspB5 (associated with myofibrillar myopathy), or expression of the G985R and G93A mutated forms of superoxide dismutase 1 (linked to familial amyotrophic lateral sclerosis). This noncanonical stimulation of NFκB triggers the up-regulation of BAG3 and HspB8 expression, two activators of selective autophagy, which relocalize to protein aggregates. Then NFκB-dependent autophagy allows the clearance of protein aggregates. Thus NFκB appears as a central and major regulator of protein aggregate clearance by modulating autophagic activity. In this context, the pharmacological stimulation of this quality control pathway might represent a valuable strategy for therapies against protein conformational diseases. PMID:27075172

Active Chest Tube Clearance After Cardiac Surgery Is Associated With Reduced Reexploration Rates.

PubMed

Grieshaber, Philippe; Heim, Nicolas; Herzberg, Moritz; Niemann, Bernd; Roth, Peter; Boening, Andreas

2018-06-01

Ineffective evacuation of intrathoracic fluid after cardiac surgery (retained blood syndrome [RBS]) might increase postoperative complications, morbidity, and mortality. Active tube clearance (ATC) technology using an intraluminal clearing apparatus aims at increasing chest tube drainage efficiency. This study evaluated whether ATC reduces RBS in an all-comers collective undergoing scheduled cardiac surgery with cardiopulmonary bypass and full or partial median sternotomy. In this nonrandomized prospective trial, 581 consecutive patients undergoing scheduled cardiac surgery with median sternotomy between January 2016 and December 2016 were assigned to receive conventional chest tubes (control group) or a combination of conventional tubes and as many as two ATC devices (ATC group), depending on their operation date. Postoperative occurrence of RBS (one or more of the following: reexploration for bleeding or tamponade, pericardial drainage procedure, pleural drainage procedure) and other endpoints were compared. Propensity score matching was applied. In 222 ATC patients and 222 matched control patients, RBS occurrence did not differ between the groups (ATC 16%, control 22%; p = 0.15). However, reexploration rate for bleeding or tamponade was significantly reduced in the ATC group compared with the control group (4.1% versus 9.1%, respectively; p = 0.015). The mortality of RBS patients (21%) was higher compared with patients without RBS (3.9%, p < 0.001). Among the RBS components, only reexploration (odds ratio 16, 95% confidence interval: 5.8 to 43, p < 0.001) was relevant for inhospital mortality (ATC 6.8%, control 7.7%; p = 0.71). Active tube clearance is associated with reduced reexploration rates in an all-comers collective undergoing cardiac surgery. Reexploration is the only RBS component relevant for mortality. The ATC effect does not translate into improved overall survival. Copyright © 2018 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Circadian Clearance of a Fungal Pathogen from the Lung Is Not Based on Cell-intrinsic Macrophage Rhythms.

PubMed

Chen, Shan; Fuller, Kevin K; Dunlap, Jay C; Loros, Jennifer J

2018-02-01

Circadian rhythms govern immune cell function, giving rise to time-of-day variation in the recognition and clearance of bacterial or viral pathogens; to date, however, no such regulation of the host-fungal interaction has been described. In this report, we use murine models to explore circadian control of either fungal-macrophage interactions in vitro or pathogen clearance from the lung in vivo. First, we show that expression of the important fungal pattern recognition receptor Dectin-1 ( clec7a), from either bone marrow-derived or peritoneum-derived macrophages, is not under circadian regulation at either the level of transcript or cell surface protein expression. Consistent with this finding, the phagocytic activity of macrophages in culture against spores of the pathogen Aspergillus fumigatus also did not vary over time. To account for the multiple cell types and processes that may be coordinated in a circadian fashion in vivo, we examined the clearance of A. fumigatus from the lungs of immunocompetent mice. Interestingly, animals inoculated at night demonstrated a 2-fold enhancement in clearance compared with animals inoculated in the morning. Taken together, our data suggest that while molecular recognition of fungi by immune cells may not be circadian, other processes in vivo may still allow for time-of-day differences in fungal clearance from the lung.

Environmental Assessment: 2005 Base Realignment and Closure Seymour Johnson Air Force Base Goldsboro, North Carolina

DTIC Science & Technology

2007-07-01

clearance criteria is being prepared. Expected completion date: __ _ A temporary waiver for construction activity in the airfield vacinity was approved on...space clearance criteria is being prepared. Expected completion date: __ _ A temporary waiver for construction activity in the airfield vacinity was...construction activity in the airfield vacinity was approved on ____ (date). A permanent waiver of airfield/airspace clearance criteria was obtained on

76 FR 30680 - Notice of Submission for OMB Review

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-26

... Clearance for the Collection of Qualitative Feedback on Agency Service Delivery. OMB Control Number: 1880.... Abstract: The information collection activity will garner qualitative customer and stakeholder feedback in... delivery. By qualitative feedback we mean information that provides useful insights on perceptions and...

Enhanced Performance Consistency in Nanoparticle/TIPS Pentacene-Based Organic Thin Film Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Zhengran; Xiao, Kai; Durant, William Mark

2011-01-01

In this study, inorganic silica nanoparticles are used to manipulate the morphology of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS pentacene) thin films and the performance of solution-processed organic thin-film transistors (OTFTs). This approach is taken to control crystal anisotropy, which is the origin of poor consistency in TIPS pentacene based OTFT devices. Thin film active layers are produced by drop-casting mixtures of SiO{sub 2} nanoparticles and TIPS pentacene. The resultant drop-cast films yield improved morphological uniformity at {approx}10% SiO{sub 2} loading, which also leads to a 3-fold increase in average mobility and nearly 4 times reduction in the ratio of measured mobility standard deviationmore » ({mu}{sub Stdev}) to average mobility ({mu}{sub Avg}). Grazing-incidence X-ray diffraction, scanning and transmission electron microscopy as well as polarized optical microscopy are used to investigate the nanoparticle-mediated TIPS pentacene crystallization. The experimental results suggest that the SiO{sub 2} nanoparticles mostly aggregate at TIPS pentacene grain boundaries, and 10% nanoparticle concentration effectively reduces the undesirable crystal misorientation without considerably compromising TIPS pentacene crystallinity.« less

The results of a wind tunnel investigation of a model rotor with a free tip

NASA Technical Reports Server (NTRS)

Stroub, Robert H.; Young, Larry A.

1985-01-01

The results of a wind-tunnel test of the free tip rotor are presented. The free tip extended over the outer 10% of the rotor blade and included a simple, passive controller mechanism. Wind-tunnel test hardware is described. The free-tip assembly, which includes the controller, functioned flawlessly throughout the test. The tip pitched freely and responded to airflow perturbation in a sharp, quick, and stable manner. Tip pitch-angle responses are presented for an advance ratio range of 0.1 to 0.397 and for a thrust coefficient range of 0.038 to 0.092. The free tip reduced power requirements, loads going into the control system, and some flatwise blade-bending moments. Chordwise loads were not reduced by the free tip.

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2011-04-07

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2011-09-06

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Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-25

... Request; Generic Clearance for the Collection of Qualitative Feedback on Agency Service Delivery AGENCY... Clearance for the Collection of Qualitative Feedback on Agency Service Delivery'' to OMB for approval under...: Title: Generic Clearance for the Collection of Qualitative Feedback on Agency Service Delivery. Abstract...

Magnetic catheter manipulation in the interventional MR imaging environment.

PubMed

Wilson, Mark W; Martin, Alastair B; Lillaney, Prasheel; Losey, Aaron D; Yee, Erin J; Bernhardt, Anthony; Malba, Vincent; Evans, Lee; Sincic, Ryan; Saeed, Maythem; Arenson, Ronald L; Hetts, Steven W

2013-06-01

To evaluate deflection capability of a prototype endovascular catheter, which is remotely magnetically steerable, for use in the interventional magnetic resonance (MR) imaging environment. Copper coils were mounted on the tips of commercially available 2.3-3.0-F microcatheters. The coils were fabricated in a novel manner by plasma vapor deposition of a copper layer followed by laser lithography of the layer into coils. Orthogonal helical (ie, solenoid) and saddle-shaped (ie, Helmholtz) coils were mounted on a single catheter tip. Microcatheters were tested in water bath phantoms in a 1.5-T clinical MR scanner, with variable simultaneous currents applied to the coils. Catheter tip deflection was imaged in the axial plane by using a "real-time" steady-state free precession MR imaging sequence. Degree of deflection and catheter tip orientation were measured for each current application. The catheter tip was clearly visible in the longitudinal and axial planes. Magnetic field artifacts were visible when the orthogonal coils at the catheter tip were energized. Variable amounts of current applied to a single coil demonstrated consistent catheter deflection in all water bath experiments. Changing current polarity reversed the observed direction of deflection, whereas current applied to two different coils resulted in deflection represented by the composite vector of individual coil activations. Microcatheter navigation through the vascular phantom was successful through control of applied current to one or more coils. Controlled catheter deflection is possible with laser lithographed multiaxis coil-tipped catheters in the MR imaging environment. Copyright © 2013 SIR. Published by Elsevier Inc. All rights reserved.

Fluctuating Pressure Environments and Hydrodynamic Radial Force Mitigation for a Two Blade Unshrouded Inducer

NASA Technical Reports Server (NTRS)

Mulder, Andrew; Skelley, Stephen

2011-01-01

Fluctuating pressure data from water flow testing of an unshrouded two blade inducer revealed a cavitation induced oscillation with the potential to induce a radial load on the turbopump shaft in addition to other more traditionally analyzed radial loads. Subsequent water flow testing of the inducer with a rotating force measurement system confirmed that the cavitation induced oscillation did impart a radial load to the inducer. After quantifying the load in a baseline configuration, two inducer shroud treatments were selected and tested to reduce the cavitation induced load. The first treatment was to increase the tip clearance, and the second was to introduce a circumferential groove near the inducer leading edge. Increasing the clearance resulted in a small load decrease along with some steady performance degradation. The groove greatly reduced the hydrodynamic load with little to no steady performance loss. The groove did however generate some new, relatively high frequency, spatially complex oscillations to the environment.

Vismodegib Therapy for Basal Cell Carcinoma in an 8-Year-Old Chinese Boy with Xeroderma Pigmentosum.

PubMed

Fife, Douglas; Laitinen, Marko A; Myers, David J; Landsteiner, Pamela B

2017-03-01

Vismodegib is an oral inhibitor of the Hedgehog signaling pathway and has been used to treat basal cell carcinoma (BCC) in adults. This article reports clearance of a nodular BCC of the nasal tip in an 8-year-old boy with xeroderma pigmentosum (XP). BCC can pose therapeutic challenges when located in areas that are not amenable to traditional therapies such as Mohs micrographic surgery or topical agents. Vismodegib was used at a dose of 150 mg/day to treat the boy's BCC. After 4 months of therapy, we achieved complete clinical clearance. During 21 months of follow-up, the patient's nose remained clinically clear of tumor. Vismodegib was successfully used to treat a child with XP and nodular BCC. Our goal in using vismodegib was tumor regression while avoiding cosmetic and functional disfigurement. Vismodegib was effective in clinically clearing the tumor, and the patient has shown no signs of recurrence. Further studies are warranted. © 2017 Wiley Periodicals, Inc.

Fluctuating Pressure Environments and Hydrodynamic Radial Force Mitigation for a Two Blade Unshrouded Inducer

NASA Technical Reports Server (NTRS)

Mulder, Andrew; Skelley, Stephen

2011-01-01

Fluctuating pressure data from water flow testing of an unshrouded two blade inducer revealed a cavitation induced oscillation with the potential to induce a radial load on the turbopump shaft in addition to other more traditionally analyzed radial loads. Subsequent water flow testing of the inducer with a rotating force measurement system confirmed that the cavitation induced oscillation did impart a radial load to the inducer. After quantifying the load in a baseline configuration, two inducer shroud treatments were selected and tested to reduce the cavitation induced load. The first treatment was to increase the tip clearance, and the second was to introduce a circumferential groove near the inducer leading edge. Increasing the clearance resulted in a small decrease in radial load along with some steady performance degradation. The groove greatly reduced the hydrodynamic load with little to no steady performance loss. The groove did however generate some new, relatively high frequency, spatially complex oscillations to the flow environment.

Numerical Study of the Performance Effect of Varying Vaneless Space in He Turboexpander Nozzles

NASA Astrophysics Data System (ADS)

Meng, Y. R.; Xiong, L. Y.; Liu, L. Q.; Peng, N.; Ke, C. L.; Li, K. R.; Wang, H. R.

2017-02-01

A numerical analysis has been carried out on a 16 mm tip diameter radial-axial flow cryogenic turboexpander using He, in order to directly compare performance characteristics by varying the vaneless space. A reference nozzle with radial clearance 0.1 mm was used in the helium liquefaction system, and six other nozzles were designed with radial clearance of 0.3 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm and 1.5 mm. As part of the design process a series of CFD simulations were carried out in order to guide design iterations towards achieving a matched flow capacity for each design. In this way the variations in the stage efficiency could be attributed to the different vaneless space only, thus allowing direct comparisons to be made. The variation in computed efficiency was used to recommend optimum value of the ratio of the nozzle vane trailing edge radius to the rotor leading edge radius (R te/r le).

Composition and Antioxidant Activity of Water-Soluble Polysaccharides from Tuber indicum

PubMed Central

Luo, Qiang; Zhang, Jie; Yan, Liang; Tang, Yuanlin; Ding, Xiang; Yang, Zhirong

2011-01-01

Abstract Crude water-soluble Chinese truffle Tuber indicum polysaccharide (TIP) was extracted from the fruiting bodies with water and then successively purified by DEAE–cellulose 52 and Sephadex G-100 column chromatography, yielding two major polysaccharide fractions: TIP1-1 and TIP2-1. High-performance gel permeation chromatography analysis showed that the average molecular sizes of TIP1-1 and TIP2-1 were approximately 1.75×104 Da and 5.73×103 Da, respectively. Monosaccharide component analysis by gas chromatography indicated that TIP1-1 was composed of mannose, glucose, galactose, and rhamannose in the respective molar ratio of 3.93:1.24:0.75:1.26 and that TIP2-1 contained mannose, glucose, and arabinose in the respective molar ratio of 5.27:1.44:0.43. The antioxidant activity analyses revealed that TIP1-1 and TIP2-1 possessed considerable antioxidant activity. Compared with TIP1-1, which has a higher molecular weight and contains no uronic acid, TIP2-1 exhibited a protective effect on PC12 cells injured by H2O2 and a higher scavenging activity against free radicals. The relative effects of the lower molecular size, the presence of uronic acid, and the antioxidant activity of TIP2-1 appear to be significant. Accordingly, the Chinese truffle T. indicum might serve as an effective antioxidative healthcare food and source of natural antioxidants. PMID:21877953

76 FR 59185 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-23

... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Agency Information Collection... Registration Renewal AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice and request for... 8050-1 (approved under OMB control number 2120- 0042). The updated registration database will then be...

75 FR 26889 - Airworthiness Directives; Arrow Falcon Exporters, Inc. (previously Utah State University) et al...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-13

... the forward tip weight retention block (tip block) or aft tip closure (tip closure), loss of the blade...) forward tip weight retention block (tip block) and the aft tip closure (tip closure) for adhesive bond... prevent loss of a tip block or tip closure, loss of a blade, and subsequent loss of control of the...

Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller

NASA Technical Reports Server (NTRS)

Skoch, G. J.; Prahst, P. S.; Wernet, M. P.; Wood, J. R.; Strazisar, A. J.

1997-01-01

A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller.

Multi-objective shape optimization of runner blade for Kaplan turbine

NASA Astrophysics Data System (ADS)

Semenova, A.; Chirkov, D.; Lyutov, A.; Chemy, S.; Skorospelov, V.; Pylev, I.

2014-03-01

Automatic runner shape optimization based on extensive CFD analysis proved to be a useful design tool in hydraulic turbomachinery. Previously the authors developed an efficient method for Francis runner optimization. It was successfully applied to the design of several runners with different specific speeds. In present work this method is extended to the task of a Kaplan runner optimization. Despite of relatively simpler blade shape, Kaplan turbines have several features, complicating the optimization problem. First, Kaplan turbines normally operate in a wide range of discharges, thus CFD analysis of each variant of the runner should be carried out for several operation points. Next, due to a high specific speed, draft tube losses have a great impact on the overall turbine efficiency, and thus should be accurately evaluated. Then, the flow in blade tip and hub clearances significantly affects the velocity profile behind the runner and draft tube behavior. All these features are accounted in the present optimization technique. Parameterization of runner blade surface using 24 geometrical parameters is described in details. For each variant of runner geometry steady state three-dimensional turbulent flow computations are carried out in the domain, including wicket gate, runner, draft tube, blade tip and hub clearances. The objectives are maximization of efficiency in best efficiency and high discharge operation points, with simultaneous minimization of cavitation area on the suction side of the blade. Multiobjective genetic algorithm is used for the solution of optimization problem, requiring the analysis of several thousands of runner variants. The method is applied to optimization of runner shape for several Kaplan turbines with different heads.

The effectiveness of triclosan-incorporated plastic against bacteria on beef surfaces.

PubMed

Cutter, C N

1999-05-01

Triclosan is a nonionic, broad-spectrum, antimicrobial agent that has been incorporated into a variety of personal hygiene products, including hand soaps, deodorants, shower gels, mouthwashes, and toothpastes. In this study, plastic containing 1,500 ppm of triclosan was evaluated in plate overlay assays and meat experiments as a means of reducing populations of bacteria. Plate overlay assays indicated that the triclosan-incorporated plastic (TIP) inhibited the following organisms: Brochothrix thermosphacta ATCC 11509, Salmonella Typhimurium ATCC 14028, Staphylococcus aureus ATCC 12598, Bacillus subtilis ATCC 6051, Shigella flexneri ATCC 12022, Escherichia coli ATCC 25922, and several strains of E. coli O157:H7. In meat experiment 1, irradiated, lean beef surfaces inoculated with B. thermosphacta, Salmonella Typhimurium, E. coli O157:H7, or B. subtilis were covered with TIP, vacuum packaged, and stored for 24 h at 4 degrees C. Of the organisms tested, only populations of B. thermosphacta were slightly reduced. In meat experiment 2, prerigor beef surfaces were inoculated with E. coli O157: H7, Salmonella Typhimurium, or B. thermosphacta incubated at 4 degrees C for 24 h, wrapped in TIP or control plastic, vacuum packaged, and stored at 4 degrees C for up to 14 days. There was a slight reduction in the population of the organisms after initial application with TIP. However, bacterial populations following long-term, refrigerated (4 degrees C), vacuum-packaged storage up to 14 days were not statistically (P< or =0.05) or numerically different than controls. In meat experiment 3, even TIP-wrapped, vacuum-packaged beef samples that were temperature abused at 12 degrees C did not exhibit significant (P< or =0.05) or sustainable reductions after 14 days of 4 degrees C storage. Another study indicated that populations of E. coli O157:H7 or B. thermosphacta added directly to TIP were not affected after 2 h of refrigerated storage or that the antimicrobial activity could be extracted from the plastic. Additional experiments suggest that presence of fatty acids or adipose may diminish the antimicrobial activity of TIP on meat surfaces. This study demonstrates that while antimicrobial activity is detected against bacterial cultures in antimicrobial plate assays, plastic containing 1,500 ppm of triclosan does not effectively reduce bacterial populations on refrigerated, vacuum-packaged meat surfaces.

The role of tip deflection on the thrust produced by rigid flapping fins

NASA Astrophysics Data System (ADS)

Huera-Huarte, Francisco; Gharib, Morteza

2015-11-01

It is well known that flexibility plays an important role in the propulsion performance and efficiency of oscillating fin based propulsion systems. Compliance is one of the aspects that has received more attention, as it seems to be a common feature in nature's flyers and swimmers. Active control strategies are also common in nature. We will show how by deflecting only the last 10% of length of a rigid fin, at the tip, the thrust can be changed dramatically. This can be thought as an alternative to passive flexibility for controlling very efficiently the momentum transfer in the wake and therefore the thrust generation when flapping. A series of experiments have been carried with a robotic fin that allowed the control of its flapping kinematics as well as the control of the motions of its tip independently. We will be showing situations in which the tip was kept at a certain fixed position during a power stroke, and others in which it moved either in-phase or out-of-phase with the fin. The observed thrust and wake dynamics will be discussed for all these situations. The authors would like to acknowledge the financial support provided by the Gordon and Betty Moore Foundation and by the Spanish Ministerio de Economia y competitividad (MINECO) through grant DPI2012-37904. Visiting Associate in Aerospace, California Institute of Technology.

Overview of NASA Glenn Seal Program

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Proctor, Margaret P.; Dunlap, Patrick H., Jr.; Delgado, Irebert; DeMange, Jeffrey J.; Daniels, Christopher C.; Lattime, Scott B.

2003-01-01

The Seal Team is divided into four primary areas. These areas include turbine engine seal development, structural seal development, acoustic seal development, and adaptive seal development. The turbine seal area focuses on high temperature, high speed shaft seals for secondary air system flow management. The structural seal area focuses on high temperature, resilient structural seals required to accommodate large structural distortions for both space- and aero-applications. Our goal in the acoustic seal project is to develop non-contacting, low leakage seals exploiting the principles of advanced acoustics. We are currently investigating a new acoustic field known as Resonant Macrosonic Synthesis (RMS) to see if we can harness the large acoustic standing pressure waves to form an effective air-barrier/seal. Our goal in the adaptive seal project is to develop advanced sealing approaches for minimizing blade-tip (shroud) or interstage seal leakage. We are planning on applying either rub-avoidance or regeneration clearance control concepts (including smart structures and materials) to promote higher turbine engine efficiency and longer service lives.

An interactive grid generation procedure for axial and radial flow turbomachinery

NASA Technical Reports Server (NTRS)

Beach, Timothy A.

1989-01-01

A combination algebraic/elliptic technique is presented for the generation of three dimensional grids about turbo-machinery blade rows for both axial and radial flow machinery. The technique is built around use of an advanced engineering workstation to construct several two dimensional grids interactively on predetermined blade-to-blade surfaces. A three dimensional grid is generated by interpolating these surface grids onto an axisymmetric grid. On each blade-to-blade surface, a grid is created using algebraic techniques near the blade to control orthogonality within the boundary layer region and elliptic techniques in the mid-passage to achieve smoothness. The interactive definition of bezier curves as internal boundaries is the key to simple construction. This procedure lends itself well to zonal grid construction, an important example being the tip clearance region. Calculations done to date include a space shuttle main engine turbopump blade, a radial inflow turbine blade, and the first stator of the United Technologies Research Center large scale rotating rig. A finite Navier-Stokes solver was used in each case.

Functional localization of a "Time Keeper" function separate from attentional resources and task strategy.

PubMed

Tracy, J I; Faro, S H; Mohamed, F B; Pinsk, M; Pinus, A

2000-03-01

The functional neuroanatomy of time estimation has not been well-documented. This research investigated the fMRI measured brain response to an explicit, prospective time interval production (TIP) task. The study tested for the presence of brain activity reflecting a primary time keeper function, distinct from the brain systems involved either in conscious strategies to monitor time or attentional resource and other cognitive processes to accomplish the task. In the TIP task participants were given a time interval and asked to indicate when it elapsed. Two control tasks (counting forwards, backwards) were administered, in addition to a dual task format of the TIP task. Whole brain images were collected at 1.5 Tesla. Analyses (n = 6) yielded a statistical parametric map (SPM ¿z¿) reflecting time keeping and not strategy (counting, number manipulation) or attention resource utilization. Additional SPM ¿z¿s involving activation associated with the accuracy and magnitude the of time estimation response are presented. Results revealed lateral cerebellar and inferior temporal lobe activation were associated with primary time keeping. Behavioral data provided evidence that the procedures for the explicit time judgements did not occur automatically and utilized controlled processes. Activation sites associated with accuracy, magnitude, and the dual task provided indications of the other structures involved in time estimation that implemented task components related to controlled processing. The data are consistent with prior proposals that the cerebellum is a repository of codes for time processing, but also implicate temporal lobe structures for this type of time estimation task. Copyright 2000 Academic Press.

Histaminergic regulation of natural killer cell-mediated clearance of tumour cells in mice.

PubMed

Asea, A; Hermodsson, S; Hellstrand, K

1996-01-01

Treatment of Swiss albino mice with histamine enhanced the clearance of natural killer (NK)-cell sensitive YAC-1 lymphoma and B16/F10 melanoma cells from lung tissue in vivo, but did not affect the elimination of NK-cell-insensitive P815 mastocytoma cells. The effect of histamine was apparently mediated by H2-type histamine receptors (H2R) since it was blocked by ranitidine, and H2R antagonist. Histamine did not affect clearance of tumour cells in animals depleted of NK cells in vivo by treatment with antibodies to asialo-GM1 or NK1.1. The effect of histamine was time-dependent: pretreatment with histamine for 3 h significantly augmented the clearance of YAC-1 cells, whereas, pretreatment with histamine for 5 min was ineffective. Histamine potentiated the anti-tumour properties of NK-cell activators such as interleukin-2 (IL-2) or interferon-alpha (IFN-alpha) in vivo. None of these lymphokines significantly affected the clearance of YAC-1 cells unless animals were concomitantly treated with histamine. Treatment with ranitidine alone reduced the in vivo clearance of YAC-1 cells from lungs but did not affect the clearance of NK-cell-insensitive P815 cells. Effects of ranitidine on NK-cell function in vivo were not shared by a chemical control to ranitidine, AH20239AA, thus indicating that the inhibition of NK-cells results from H2R antagonism rather than non-specific toxicity. It is concluded that histaminergic mechanisms may be involved in the regulation of NK cell function in vivo.

Changes in extracellular calcium activity during gravity sensing in maize roots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bjoerkman, T.; Cleland, R.E.

1990-05-01

A redistribution of calcium downward across the root cap has been proposed as an essential part of gravitropism in roots. Exogenous {sup 45}Ca moves preferentially downward across gravistimulated maize root tips. However, because of the many calcium-binding sites in the apoplast, this might not result in a physiologically effect change in the apoplasmic calcium activity. To test whether there is such a change, we measured the effect of gravistimulation on the calcium activity with calcium-specific microelectrodes. Decapped maize roots (Zea mays L. cv. Golden Cross Bantam) were grown for 31 h to regenerate gravitropic sensitivity, but not root caps. Themore » calcium activity in the apoplasm surrounding the gravity-sensing cells could then be measured. The initial pCa was 2.60 {plus minus} 0.28 (approx 2.5 mM). The calcium activity on the upper side of the root tip remained constant for about five minutes after gravistimulation, then decreased by about one half. On the lower side, after a similar lag the calcium activity doubled. Control roots, which were decapped but measured before recovering gravisensitivity (19 h), showed no change in calcium activity. We have found a distinct and rapid differential in the apoplasmic calcium activity between the upper and lower sides of gravistimulated maize root tips.« less

Comparison of Two Alternate Methods for Tracking Toe Clearance

NASA Technical Reports Server (NTRS)

Miller, Christopher A.; Feiveson, Alan H.; Bloomberg, Jacob J.

2007-01-01

Analyses of toe clearance during the swing phase of locomotion has often been utilized in determining a subject s propensity to trip while either walking or stepping over an obstacle. In the literature, toe clearance has been studied using a marker on the superior aspect of the second toe (rtoe), a marker on the lateral aspect of the fifth metatarsal head (mth5), or a virtual marker positioned at the anterior tip of the toe (vtoe). The purpose of this study was to compute toe clearance and associated parameters using a fifth metatarsal marker and a virtual toe marker, and compare the results with those of the standard toe marker. Subjects walked on a motorized treadmill at five different speeds while performing a visual acuity task at two separate target distances (ten 60-second trials). The minimum vertical height (TCl) was determined for each stride, along with its point of occurence in the gait cycle, and the angles of the foot and ankle at that time. A regression analysis was performed on the vtoe and mth5 results versus rtoe individually. For all TCl parameters, the mth5 marker did not correlate well with rtoe; the vtoe marker showed better agreement. Most importantly, the mth5 marker predicted a later occurence of TCl than rtoe and vtoe - thereby missing the most dangerous point in swing phase for a trip. From this analysis, the vtoe marker proved to be a better analog to rtoe than mth5, especially for determining a subject s propensity to trip.

28 CFR 524.74 - Activities clearance.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., AND TRANSFER CLASSIFICATION OF INMATES Central Inmate Monitoring (CIM) System § 524.74 Activities... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Activities clearance. 524.74 Section 524... authority on all transfers, temporary releases, community activities, and escorted trips. (b) Witness...

28 CFR 524.74 - Activities clearance.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., AND TRANSFER CLASSIFICATION OF INMATES Central Inmate Monitoring (CIM) System § 524.74 Activities... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Activities clearance. 524.74 Section 524... authority on all transfers, temporary releases, community activities, and escorted trips. (b) Witness...

28 CFR 524.74 - Activities clearance.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., AND TRANSFER CLASSIFICATION OF INMATES Central Inmate Monitoring (CIM) System § 524.74 Activities... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Activities clearance. 524.74 Section 524... authority on all transfers, temporary releases, community activities, and escorted trips. (b) Witness...

28 CFR 524.74 - Activities clearance.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., AND TRANSFER CLASSIFICATION OF INMATES Central Inmate Monitoring (CIM) System § 524.74 Activities... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Activities clearance. 524.74 Section 524... authority on all transfers, temporary releases, community activities, and escorted trips. (b) Witness...

Analysis of foot clearance in firefighters during ascent and descent of stairs.

PubMed

Kesler, Richard M; Horn, Gavin P; Rosengren, Karl S; Hsiao-Wecksler, Elizabeth T

2016-01-01

Slips, trips, and falls are a leading cause of injury to firefighters with many injuries occurring while traversing stairs, possibly exaggerated by acute fatigue from firefighting activities and/or asymmetric load carriage. This study examined the effects that fatigue, induced by simulated firefighting activities, and hose load carriage have on foot clearance while traversing stairs. Landing and passing foot clearances for each stair during ascent and descent of a short staircase were investigated. Clearances decreased significantly (p < 0.05) post-exercise for nine of 12 ascent parameters and increased for two of eight descent parameters. Load carriage resulted in significantly decreased (p < 0.05) clearance over three ascent parameters, and one increase during descent. Decreased clearances during ascent caused by fatigue or load carriage may result in an increased trip risk. Increased clearances during descent may suggest use of a compensation strategy to ensure stair clearance or an increased risk of over-stepping during descent. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Control of submersible vortex flows

NASA Technical Reports Server (NTRS)

Bushnell, D. M.; Donaldson, C. D.

1990-01-01

Vortex flows produced by submersibles typically unfavorably influence key figures of merit such as acoustic and nonacoustic stealth, control effectiveness/maneuverability, and propulsor efficiency/body drag. Sources of such organized, primarily longitudinal, vorticity include the basic body (nose and sides) and appendages (both base/intersection and tip regions) such as the fairwater, dive planes, rear control surfaces, and propulsor stators/tips. Two fundamentally different vortex control approaches are available: (1) deintensification of the amplitude and/or organization of the vortex during its initiation process; and (2) downstream vortex disablement. Vortex control techniques applicable to the initiation region (deintensification approach) include transverse pressure gradient minimization via altered body cross section, appendage dillets, fillets, and sweep, and various appendage tip and spanload treatment along with the use of active controls to minimize control surface size and motions. Vortex disablement can be accomplished either via use of control vortices (which can also be used to steer the vortices off-board), direct unwinding, inducement of vortex bursting, or segmentation/tailoring for enhanced dissipation. Submersible-applicable vortex control technology is also included derived from various aeronautical applications such as mitigation of the wing wake vortex hazard and flight aircraft maneuverability at high angle of attack as well as the status of vortex effects upon, and mitigation of, nonlinear control forces on submersibles. Specific suggestions for submersible-applicable vortex control techniques are presented.

Constitutive androstane receptor activation promotes bilirubin clearance in a murine model of alcoholic liver disease.

PubMed

Wang, Xiuyan; Zheng, Liyu; Wu, Jinming; Tang, Binbin; Zhang, Mengqin; Zhu, Debin; Lin, Xianfan

2017-06-01

Increased plasma levels of bilirubin have been reported in rat models and patients with alcoholic liver disease (ALD). The constitutive androstane receptor (CAR) is a known xenobiotic receptor, which induces the detoxification and transport of bilirubin. In the present study, the bilirubin transport regulatory mechanisms, and the role of CAR activation in hepatic and extrahepatic bilirubin clearance were investigated in a murine model of ALD. The mice were fed a Lieber-DeCarli ethanol diet or an isocaloric control diet for 4 weeks, followed by the administration of CAR agonists, 1,4-bis-[2‑(3,5-dichlorpyridyloxy)]benzene (TCPOBOP) and phenobarbital (PB), and their vehicles to examine the effect of the pharmacological activation of CAR on serum levels of bilirubin and on the bilirubin clearance pathway in ALD by serological survey, western blotting and reverse transcription‑quantitative polymerase chain reaction. The results showed that chronic ethanol ingestion impaired the nuclear translocation of CAR, which was accompanied by elevated serum levels of bilirubin, suppression of the expression of hepatic and renal organic anion transporting polypeptide (OATP) 1A1 and hepatic multidrug resistance‑associated protein 2 (MRP2), and induction of the expression of UDP-glucuronosyltransferase (UGT) 1A1. The activation of CAR by TCPOBOP and PB resulted in downregulation of the serum levels of bilirubin followed by selective upregulation of the expression levels of OATP1A1, OATP1A4, UGT1A1 and MRP2 in ALD. These results revealed the bilirubin transport regulatory mechanisms and highlighted the importance of CAR in modulating the bilirubin clearance pathway in the ALD mouse model.

Repeated swim impairs serotonin clearance via a corticosterone-sensitive mechanism: organic cation transporter 3, the smoking gun.

PubMed

Baganz, Nicole; Horton, Rebecca; Martin, Kathryn; Holmes, Andrew; Daws, Lynette C

2010-11-10

Activation of the hypothalamic-pituitary-adrenal (HPA) axis is associated with increased extracellular serotonin (5-HT) in limbic brain regions. The mechanism through which this occurs remains unclear. One way could be via HPA axis-dependent impairment of serotonin transporter (SERT) function, the high-affinity uptake mechanism for 5-HT. Consistent with this idea, we found that 5-HT clearance rate in hippocampus was dramatically reduced in mice exposed to repeated swim, a stimulus known to activate the HPA axis. However, this phenomenon also occurred in mice lacking SERT, ruling out SERT as a mechanism. The organic cation transporter 3 (OCT3) is emerging as an important regulator of brain 5-HT. Moreover, corticosterone, which is released upon HPA axis activation, blocks 5-HT uptake by OCT3. Repeated swim produced a persistent elevation in plasma corticosterone, and, consistent with prolonged blockade by corticosterone, we found that OCT3 expression and function were reduced in these mice. Importantly, this effect of repeated swim to reduce 5-HT clearance rate was corticosterone dependent, as evidenced by its absence in adrenalectomized mice, in which plasma corticosterone levels were essentially undetectable. Behaviorally, mice subjected to repeated swim spent less time immobile in the tail suspension test than control mice, but responded similarly to SERT- and norepinephrine transporter-selective antidepressants. Together, these results show that reduced 5-HT clearance following HPA axis activation is likely mediated, at least in part, by the corticosterone-sensitive OCT3, and that drugs developed to selectively target OCT3 (unlike corticosterone) may be candidates for the development of novel antidepressant medications.

Performance and power regulation characteristics of two aileron-controlled rotors and a pitchable tip-controlled rotor on the Mod-O turbine

NASA Technical Reports Server (NTRS)

Corrigan, Robert D.; Ensworth, Clinton B. F., III; Miller, Dean R.

1987-01-01

Tests were conducted on the DOE/NASA mod-0 horizontal axis wind turbine to compare and evaluate the performance and the power regulation characteristics of two aileron-controlled rotors and a pitchable tip-controlled rotor. The two aileron-controlled rotor configurations used 20 and 38 percent chord ailerons, while the tip-controlled rotor had a pitchable blade tip. The ability of the control surfaces to regulate power was determined by measuring the change in power caused by an incremental change in the deflection angle of the control surface. The data shows that the change in power per degree of deflection angle for the tip-controlled rotor was four times the corresponding value for the 2- percent chord ailerons. The root mean square power deviation about a power setpoint was highest for the 20 percent chord aileron, and lowest for the 38 percent chord aileron.

Experimental demonstration of using divergence cost-function in SPGD algorithm for coherent beam combining with tip/tilt control.

PubMed

Geng, Chao; Luo, Wen; Tan, Yi; Liu, Hongmei; Mu, Jinbo; Li, Xinyang

2013-10-21

A novel approach of tip/tilt control by using divergence cost function in stochastic parallel gradient descent (SPGD) algorithm for coherent beam combining (CBC) is proposed and demonstrated experimentally in a seven-channel 2-W fiber amplifier array with both phase-locking and tip/tilt control, for the first time to our best knowledge. Compared with the conventional power-in-the-bucket (PIB) cost function for SPGD optimization, the tip/tilt control using divergence cost function ensures wider correction range, automatic switching control of program, and freedom of camera's intensity-saturation. Homemade piezoelectric-ring phase-modulator (PZT PM) and adaptive fiber-optics collimator (AFOC) are developed to correct piston- and tip/tilt-type aberrations, respectively. The PIB cost function is employed for phase-locking via maximization of SPGD optimization, while the divergence cost function is used for tip/tilt control via minimization. An average of 432-μrad of divergence metrics in open loop has decreased to 89-μrad when tip/tilt control implemented. In CBC, the power in the full width at half maximum (FWHM) of the main lobe increases by 32 times, and the phase residual error is less than λ/15.

TNF-α-inducing protein of Helicobacter pylori induces epithelial-mesenchymal transition (EMT) in gastric cancer cells through activation of IL-6/STAT3 signaling pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Guodong; Tang, Na; Wang, Chao

Tumor necrosis factor (TNF)-α-inducing protein (Tipα) is a newly identified carcinogenic factor secreted by Helicobacter pylori (H. pylori). Although it has been proved that Tipα is a strong inducer of epithelial-mesenchymal transition (EMT), a crucial process of migration, the exact molecular mechanism is unknown. Current evidence indicates that the oncogenic transcription factor signal transducers and activators of transcription 3 (STAT3) is inappropriately activated in multiple malignancies, including gastric cancer. In this study, we showed that Tipα significantly down-regulated the expression of EMT-related markers E-cadherin as well as up-regulated N-cadherin and vimentin in SGC7901 cells, with typical morphological changes of EMT. Tipα alsomore » promoted proliferation and migration of SGC7901 cells. Furthermore, Tipα activated interleukin-6 (IL-6)/STAT3 signaling pathway in SGC7901 cells. The effects of Tipα treatment observed was abolished when we block IL-6/STAT3 signaling pathway. Altogether, our data demonstrated that Tipα may accelerate tumor aggressiveness in gastric cancer by promoting EMT through activation of IL-6/STAT3 pathway. - Highlights: • Tipα induces EMT and activates IL-6/STAT3 pathway in gastric cancer cells. • IL-6/STAT3 pathway inhibition reverses Tipα-induced proliferation and migration in gastric cancer cells. • Tipα induces EMT in gastric cancer cells via IL-6/STAT3 pathway activation.« less

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2011-12-27

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2012-06-04

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Tip-localized receptors control pollen tube growth and LURE sensing in Arabidopsis.

PubMed

Takeuchi, Hidenori; Higashiyama, Tetsuya

2016-03-10

Directional control of tip-growing cells is essential for proper tissue organization and cell-to-cell communication in animals and plants. In the sexual reproduction of flowering plants, the tip growth of the male gametophyte, the pollen tube, is precisely guided by female cues to achieve fertilization. Several female-secreted peptides have recently been identified as species-specific attractants that directly control the direction of pollen tube growth. However, the method by which pollen tubes precisely and promptly respond to the guidance signal from their own species is unknown. Here we show that tip-localized pollen-specific receptor-like kinase 6 (PRK6) with an extracellular leucine-rich repeat domain is an essential receptor for sensing of the LURE1 attractant peptide in Arabidopsis thaliana under semi-in-vivo conditions, and is important for ovule targeting in the pistil. PRK6 interacted with pollen-expressed ROPGEFs (Rho of plant guanine nucleotide-exchange factors), which are important for pollen tube growth through activation of the signalling switch Rho GTPase ROP1 (refs 7, 8). PRK6 conferred responsiveness to AtLURE1 in pollen tubes of the related species Capsella rubella. Furthermore, our genetic and physiological data suggest that PRK6 signalling through ROPGEFs and sensing of AtLURE1 are achieved in cooperation with the other PRK family receptors, PRK1, PRK3 and PRK8. Notably, the tip-focused PRK6 accumulated asymmetrically towards an external AtLURE1 source before reorientation of pollen tube tip growth. These results demonstrate that PRK6 acts as a key membrane receptor for external AtLURE1 attractants, and recruits the core tip-growth machinery, including ROP signalling proteins. This work provides insights into the orchestration of efficient pollen tube growth and species-specific pollen tube attraction by multiple receptors during male-female communication.

Clearance of Aspergillus fumigatus is impaired in the airway in allergic inflammation.

PubMed

Fukahori, Susumu; Matsuse, Hiroto; Tsuchida, Tomoko; Kawano, Tetsuya; Nishino, Tomoya; Fukushima, Chizu; Kohno, Shigeru

2014-08-01

Aspergillus fumigatus (Af) sometimes colonizes and persists within the respiratory tree in some patients with asthma. To date, the precise reasons why the clearance of Af is impaired in patients with asthma remain unknown. To characterize the effects of allergic airway inflammation on clearance of Af. Control and Dermatophagoides farinae (Df) allergen-sensitized BALB/c mice were intranasally infected with Af. After 2 and 9 days of infection, the pathology, fungal burden, and cytokine profile in lung tissue were compared. In a different set of experiments, the phagocytotic activity of alveolar macrophages and the expression of their pathogen recognition receptors also were determined. The Af conidia and neutrophilic airway inflammation disappeared by day 9 after infection in control mice. In Df-sensitized mice, Af conidia and neutrophilic and eosinophilic airway inflammation persisted at day 9 after infection. Compared with control mice, Df allergen-sensitized mice showed significant increases in interleukin (IL)-5 and decreases in IL-12 and interferon-γ in lung tissues at day 2 after infection. Most importantly, compared with Af-infected non-Df-sensitized mice, IL-17 in lung tissues was significantly decreased in Df allergen-sensitized Af-infected mice at day 2 after infection but was significantly increased at day 9. Alveolar macrophages isolated from Df allergen-sensitized mice exhibited significant decreases in phagocytotic activity and expression of Toll-like receptor-4 and dectin-1 compared with those from control mice. In the airway of patients with allergy, T-helper cell type 2-dominant immunity potentially affects the expression of pathogen recognition receptors and attenuates cellular defense against Af. Prolonged IL-17 production also could play an important role. Copyright © 2014 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Early lactate clearance for predicting active bleeding in critically ill patients with acute upper gastrointestinal bleeding: a retrospective study.

PubMed

Wada, Tomoki; Hagiwara, Akiyoshi; Uemura, Tatsuki; Yahagi, Naoki; Kimura, Akio

2016-08-01

Not all patients with upper gastrointestinal bleeding (UGIB) require emergency endoscopy. Lactate clearance has been suggested as a parameter for predicting patient outcomes in various critical care settings. This study investigates whether lactate clearance can predict active bleeding in critically ill patients with UGIB. This single-center, retrospective, observational study included critically ill patients with UGIB who met all of the following criteria: admission to the emergency department (ED) from April 2011 to August 2014; had blood samples for lactate evaluation at least twice during the ED stay; and had emergency endoscopy within 6 h of ED presentation. The main outcome was active bleeding detected with emergency endoscopy. Classification and regression tree (CART) analyses were performed using variables associated with active bleeding to derive a prediction rule for active bleeding in critically ill UGIB patients. A total of 154 patients with UGIB were analyzed, and 31.2 % (48/154) had active bleeding. In the univariate analysis, lactate clearance was significantly lower in patients with active bleeding than in those without active bleeding (13 vs. 29 %, P < 0.001). Using the CART analysis, a prediction rule for active bleeding is derived, and includes three variables: lactate clearance; platelet count; and systolic blood pressure at ED presentation. The rule has 97.9 % (95 % CI 90.2-99.6 %) sensitivity with 32.1 % (28.6-32.9 %) specificity. Lactate clearance may be associated with active bleeding in critically ill patients with UGIB, and may be clinically useful as a component of a prediction rule for active bleeding.

Hepatic Stellate Cells Orchestrate Clearance of Necrotic Cells in a HIF-1α-dependent Manner by Modulating Macrophage Phenotype in Mice

PubMed Central

Rockwell, Cheryl E.; Roth, Katherine J.; Chow, Aaron; O'Brien, Kate M; Albee, Ryan; Kelly, Kara; Towery, Keara; Luyendyk, James P.; Copple, Bryan L.

2014-01-01

Hypoxia-inducible factor-1α (HIF-1α) is activated in hepatic stellate cells (HSCs) by hypoxia, and regulates genes important for tissue repair. Whether HIF-1α is activated in HSCs after acute injury and contributes to liver regeneration, however, is not known. To investigate this, mice were generated with reduced levels of HIF-1α in HSCs by crossing HIF-1α floxed mice with mice that express Cre recombinase under control of the glial fibrillary acidic protein (GFAP) promoter (i.e., HIF-1α-GFAP Cre+ mice). These mice and control mice (i.e., HIF-1α-GFAP Cre- mice) were treated with a single dose of carbon tetrachloride, and liver injury and repair were assessed. After carbon tetrachloride, HIF-1α was activated in HSCs. Although liver injury was not different between the two strains of mice, during resolution of injury, clearance of necrotic cells was decreased in HIF-1α-GFAP Cre+ mice. In these mice, the persistence of necrotic cells stimulated a fibrotic response characterized by extensive collagen deposition. Hepatic accumulation of macrophages, which clear necrotic cells from the liver after carbon tetrachloride, was not affected by HIF-1α deletion in HSCs. Conversion of macrophages to M1-like, pro-inflammatory macrophages, which have increased phagocytic activity, however, was reduced in HIF-1α-GFAP Cre+ mice as indicated by a decrease in pro-inflammatory cytokines, and a decrease in the percentage of Gr1hi macrophages. Collectively, these studies have identified a novel function for HSCs and HIF-1α in orchestrating the clearance of necrotic cells from the liver, and demonstrated a key role for HSCs in modulating macrophage phenotype during acute liver injury. PMID:24639359

Controllable activation of nanoscale dynamics in a disordered protein alters binding kinetics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callaway, David J. E.; Matsui, Tsutomu; Weiss, Thomas

The phosphorylation of specific residues in a flexible disordered activation loop yields precise control of signal transduction. One paradigm is the phosphorylation of S339/S340 in the intrinsically disordered tail of the multi-domain scaffolding protein NHERF1, which affects the intracellular localization and trafficking of NHERF1 assembled signaling complexes. Using neutron spin echo spectroscopy (NSE), we show salt-concentration-dependent excitation of nanoscale motion at the tip of the C-terminal tail in the phosphomimic S339D/S340D mutant. The “tip of the whip” that is unleashed is near the S339/S340 phosphorylation site and flanks the hydrophobic Ezrin-binding motif. The kinetic association rate constant of the bindingmore » of the S339D/S340D mutant to the FERM domain of Ezrin is sensitive to buffer salt concentration, correlating with the excited nanoscale dynamics. The results suggest that electrostatics modulates the activation of nanoscale dynamics of an intrinsically disordered protein, controlling the binding kinetics of signaling partners. Furthermore NSE can pinpoint the nanoscale dynamics changes in a highly specific manner.« less

Controllable activation of nanoscale dynamics in a disordered protein alters binding kinetics

DOE PAGES

Callaway, David J. E.; Matsui, Tsutomu; Weiss, Thomas; ...

2017-03-08

The phosphorylation of specific residues in a flexible disordered activation loop yields precise control of signal transduction. One paradigm is the phosphorylation of S339/S340 in the intrinsically disordered tail of the multi-domain scaffolding protein NHERF1, which affects the intracellular localization and trafficking of NHERF1 assembled signaling complexes. Using neutron spin echo spectroscopy (NSE), we show salt-concentration-dependent excitation of nanoscale motion at the tip of the C-terminal tail in the phosphomimic S339D/S340D mutant. The “tip of the whip” that is unleashed is near the S339/S340 phosphorylation site and flanks the hydrophobic Ezrin-binding motif. The kinetic association rate constant of the bindingmore » of the S339D/S340D mutant to the FERM domain of Ezrin is sensitive to buffer salt concentration, correlating with the excited nanoscale dynamics. The results suggest that electrostatics modulates the activation of nanoscale dynamics of an intrinsically disordered protein, controlling the binding kinetics of signaling partners. Furthermore NSE can pinpoint the nanoscale dynamics changes in a highly specific manner.« less

Using rainfall simulators to test wood shreddings for erosion control

Treesearch

James Gronier; Randy Foltz; Charlie Showers

2005-01-01

The U.S. Department of Agriculture Forest Service is considering alternative methods of erosion control when constructing roads, decommissioning roads, protecting lands burned by wildland fires, and reclaiming lands disturbed by other activities. This article is the second in a series of tech tips that discuss the use of wood shreddings for erosion control. The first...

75 FR 4809 - Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-29

... ENVIRONMENTAL PROTECTION AGENCY [EPA-HQ-OECA-2009-0494; FRL-9108-2] Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment Request; Tips and Complaints Regarding Environmental Violations; EPA ICR No. 2219.03, OMB Control No. 2020- 0032 AGENCY: Environmental Protection...

Modifiable risk factors for typhoid intestinal perforations during a large outbreak of typhoid fever, Kampala Uganda, 2015.

PubMed

Bulage, Lilian; Masiira, Ben; Ario, Alex R; Matovu, Joseph K B; Nsubuga, Peter; Kaharuza, Frank; Nankabirwa, Victoria; Routh, Janell; Zhu, Bao-Ping

2017-09-25

Between January and June, 2015, a large typhoid fever outbreak occurred in Kampala, Uganda, with 10,230 suspected cases. During the outbreak, area surgeons reported a surge in cases of typhoid intestinal perforation (TIP), a complication of typhoid fever. We conducted an investigation to characterize TIP cases and identify modifiable risk factors for TIP. We defined a TIP case as a physician-diagnosed typhoid patient with non-traumatic terminal ileum perforation. We identified cases by reviewing medical records at all five major hospitals in Kampala from 2013 to 2015. In a matched case-control study, we compared potential risk factors among TIP cases and controls; controls were typhoid patients diagnosed by TUBEX TF, culture, or physician but without TIP, identified from the outbreak line-list and matched to cases by age, sex and residence. Cases and controls were interviewed using a standard questionnaire from 1st -23rd December 2015. We used conditional logistic regression to assess risk factors for TIP and control for confounding. Of the 88 TIP cases identified during 2013-2015, 77% (68/88) occurred between January and June, 2015; TIPs sharply increased in January and peaked in March, coincident with the typhoid outbreak. The estimated risk of TIP was 6.6 per 1000 suspected typhoid infections (68/10,230). The case-fatality rate was 10% (7/68). Cases sought care later than controls; Compared with 29% (13/45) of TIP cases and 63% (86/137) of controls who sought treatment within 3 days of onset, 42% (19/45) of cases and 32% (44/137) of controls sought treatment 4-9 days after illness onset (OR adj  = 2.2, 95%CI = 0.83-5.8), while 29% (13/45) of cases and 5.1% (7/137) of controls sought treatment ≥10 days after onset (OR adj  = 11, 95%CI = 1.9-61). 68% (96/141) of cases and 23% (23/100) of controls had got treatment before being treated at the treatment centre (OR adj  = 9.0, 95%CI = 1.1-78). Delay in seeking treatment increased the risk of TIPs. For future outbreaks, we recommended aggressive community case-finding, and informational campaigns in affected communities and among local healthcare providers to increase awareness of the need for early and appropriate treatment.

HPT Clearance Control: Intelligent Engine Systems-Phase 1

NASA Technical Reports Server (NTRS)

2005-01-01

The following work has been completed to satisfy the Phase I Deliverables for the "HPT Clearance Control" project under NASA GRC's "Intelligent Engine Systems" program: (1) Need for the development of an advanced HPT ACC system has been very clearly laid out, (2) Several existing and potential clearance control systems have been reviewed, (3) A scorecard has been developed to document the system, performance (fuel burn, range, payload, etc.), thermal, and mechanical characteristics of the existing clearance control systems, (4) Engine size and flight cycle selection for the advanced HPT ACC system has been reviewed with "large engine"/"long range mission" combination showing the most benefit, (5) A scoring criteria has been developed to tie together performance parameters for an objective, data driven comparison of competing systems, and (6) The existing HPT ACC systems have been scored based on this scoring system.

Clearance of amyloid-β peptide across the choroid plexus in Alzheimer's disease.

PubMed

Alvira-Botero, Ximena; Carro, Eva M

2010-12-01

Aging and several neurodegenerative diseases bring about changes in the anatomy and physiology of the choroid plexus. The identification of specific membrane receptors that bind and internalize extracellular ligands has revolutionized the traditional roles of this tissue. Amyloid beta peptide (Aβ), the major constituent of the amyloid core of senile plaques in patients with Alzheimer's disease (AD) is known to contribute to disease neuropathology and progression. Recent emphasis on comorbidity of AD and a deficient clearance of Aβ across the blood-brain barrier and blood-cerebrospinal fluid barrier have highlighted the importance of brain Aβ clearance in AD. The megalin receptor has also been implicated in the pathogenesis of AD. Faulty Aβ clearance from the brain across the choroid plexus epithelium by megalin appears to mediate focal Aβ accumulation in AD. Patients with AD have reduced levels of megalin at the choroid plexus, which in turn seem to increase brain levels of Aβ through a decreased efflux of brain Aβ. Therapies that increase megalin expression at the choroid plexus could potentially control accumulation of brain Aβ. This review covers in depth the anatomy and function of the choroid plexus, focusing on the brain barrier at the choroid plexus, as it actively participates in Aβ clearance. In addition, we describe the role of the choroid plexus in brain functions, aging and AD, as well as the role of megalin in the process of Aβ clearance. Finally, we present current data on the use of choroid plexus cells to repair the damaged brain.

Turbine blade-tip clearance excitation forces

NASA Technical Reports Server (NTRS)

Martinez-Sanchez, M.; Greitzer, E. M.

1985-01-01

The results of an effort to assess the existing knowledge and plan the required experimentation in the area of turbine blade tip excitation forces is summarized. The work was carried out in three phases. The first was a literature search and evaluation, which served to highlight the state of the art and to expose the need for an articulated theoretical experimental effort to provide not only design data, but also a rational framework for their extrapolation to new configurations and regimes. The second phase was a start in this direction, in which several of the explicit or implicit assumptions contained in the usual formulations of the Alford force effect were removed and a rigorous linearized flow analysis of the behavior of a nonsymmetric actuator disc was carried out. In the third phase a preliminary design of a turbine test facility that would be used to measure both the excitation forces themselves and the flow patterns responsible for them were conducted and do so over a realistic range of dimensionless parameters.

Numerical Investigation on the Effects of Self-Excited Tip Flow Unsteadiness and Blade Row Interactions on the Performance Predictions of Low Speed and Transonic Compressor Rotors

NASA Astrophysics Data System (ADS)

Lee, Daniel H.

The impact blade row interactions can have on the performance of compressor rotors has been well documented. It is also well known that rotor tip clearance flows can have a large effect on compressor performance and stall margin and recent research has shown that tip leakage flows can exhibit self-excited unsteadiness at near stall conditions. However, the impact of tip leakage flow on the performance and operating range of a compressor rotor, relative to other important flow features such as upstream stator wakes or downstream potential effects, has not been explored. To this end, a numerical investigation has been conducted to determine the effects of self-excited tip flow unsteadiness, upstream stator wakes, and downstream blade row interactions on the performance prediction of low speed and transonic compressor rotors. Calculations included a single blade-row rotor configuration as well as two multi-blade row configurations: one where the rotor was modeled with an upstream stator and a second where the rotor was modeled with a downstream stator. Steady-state and time accurate calculations were performed using a RANS solver and the results were compared with detailed experimental data obtained in the GE Low Speed Research Compressor and the Notre Dame Transonic Rig at several operating conditions including near stall. Differences in the performance predictions between the three configurations were then used to determine the effect of the upstream stator wakes and the downstream blade row interactions. Results obtained show that for both the low speed and transonic research compressors used in this investigation time-accurate RANS analysis is necessary to accurately predict the stalling character of the rotor. Additionally, for the first time it is demonstrated that capturing the unsteady tip flow can have a larger impact on rotor performance predictions than adjacent blade row interactions.

Planar rigid-flexible coupling spacecraft modeling and control considering solar array deployment and joint clearance

NASA Astrophysics Data System (ADS)

Li, Yuanyuan; Wang, Zilu; Wang, Cong; Huang, Wenhu

2018-01-01

Based on Nodal Coordinate Formulation (NCF) and Absolute Nodal Coordinate Formulation (ANCF), this paper establishes rigid-flexible coupling dynamic model of the spacecraft with large deployable solar arrays and multiple clearance joints to analyze and control the satellite attitude under deployment disturbance. Considering torque spring, close cable loop (CCL) configuration and latch mechanisms, a typical spacecraft composed of a rigid main-body described by NCF and two flexible panels described by ANCF is used as a demonstration case. Nonlinear contact force model and modified Coulomb friction model are selected to establish normal contact force and tangential friction model, respectively. Generalized elastic force are derived and all generalized forces are defined in the NCF-ANCF frame. The Newmark-β method is used to solve system equations of motion. The availability and superiority of the proposed model is verified through comparing with numerical co-simulations of Patran and ADAMS software. The numerical results reveal the effects of panel flexibility, joint clearance and their coupling on satellite attitude. The effects of clearance number, clearance size and clearance stiffness on satellite attitude are investigated. Furthermore, a proportional-differential (PD) attitude controller of spacecraft is designed to discuss the effect of attitude control on the dynamic responses of the whole system.

Oil-flow study of a Space Shuttle orbiter tip-fin controller

NASA Technical Reports Server (NTRS)

Helms, V. T., III

1983-01-01

Possible use of tip-fin controllers instead of a vertical tail on advanced winged entry vehicles was examined. Elimination of the vertical tail and using tip-fins offers the advantages of positive yaw control at high angles of attack and a potential weight savings. Oil-flow technique was used to obtain surface flow patterns on a tip-fin installed on a 0.01-scale Space Shuttle orbiter model for the purpose of assessing the extent of flow interference effects on the wing and tip-fin which might lead to serious heating problems. Tests were conducted in air at Mach 10 for a free-stream Reynolds numbers of .000113 at 20, 30, and 40 degree angle of attack and sideslip angles of 0 and 2 degree. Elevon deflections of -10, 0, and 10 degree and tip-fin control-surface deflections of 0, 20, and 40 degree were employed. Test results were also used to aid in the interpretation of heating data obtained on a Shuttle orbiter tip-fin on another model in a different facility. A limited comparison of oil-flow patterns and heat-transfer data is included. It was determined that elevon deflection angles from -10 to 10 degree and sideslip angles up to 2 degree have very little effect on tip-fin surface flow patterns. Also, there is a minimum of interference between the tip-fin and the wing. The most significant flow interactions occur on the tip-fin onboard surface as a result of its control-surface deflections.

77 FR 29748 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-18

... for Commercial Space Transportation (AST), that a license applicant's proposed activities meet... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of Information Collection: Commercial Space...

Microparticles in the blood of patients with systemic lupus erythematosus (SLE): phenotypic characterization and clinical associations

PubMed Central

Mobarrez, Fariborz; Vikerfors, Anna; Gustafsson, Johanna T.; Gunnarsson, Iva; Zickert, Agneta; Larsson, Anders; Pisetsky, David S.; Wallén, Håkan; Svenungsson, Elisabet

2016-01-01

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by circulating autoantibodies and the formation of immune complexes. In these responses, the selecting self-antigens likely derive from the remains of dead and dying cells, as well as from disturbances in clearance. During cell death/activation, microparticles (MPs) can be released to the circulation. Previous MP studies in SLE have been limited in size and differ regarding numbers and phenotypes. Therefore, to characterize MPs more completely, we investigated 280 SLE patients and 280 individually matched controls. MPs were measured with flow cytometry and phenotyped according to phosphatidylserine expression (PS+/PS−), cellular origin and inflammatory markers. MPs, regardless of phenotype, are 2–10 times more abundant in SLE blood compared to controls. PS− MPs predominated in SLE, but not in controls (66% vs. 42%). Selectively in SLE, PS− MPs were more numerous in females and smokers. MP numbers decreased with declining renal function, but no clear association with disease activity was observed. The striking abundance of MPs, especially PS− MPs, suggests a generalized disturbance in SLE. MPs may be regarded as “liquid biopsies” to assess the production and clearance of dead, dying and activated cells, i.e. pivotal events for SLE pathogenesis. PMID:27777414

Dynamic frequency-domain interferometer for absolute distance measurements with high resolution

NASA Astrophysics Data System (ADS)

Weng, Jidong; Liu, Shenggang; Ma, Heli; Tao, Tianjiong; Wang, Xiang; Liu, Cangli; Tan, Hua

2014-11-01

A unique dynamic frequency-domain interferometer for absolute distance measurement has been developed recently. This paper presents the working principle of the new interferometric system, which uses a photonic crystal fiber to transmit the wide-spectrum light beams and a high-speed streak camera or frame camera to record the interference stripes. Preliminary measurements of harmonic vibrations of a speaker, driven by a radio, and the changes in the tip clearance of a rotating gear wheel show that this new type of interferometer has the ability to perform absolute distance measurements both with high time- and distance-resolution.

Three-dimensional multigrid Navier-Stokes computations for turbomachinery applications

NASA Astrophysics Data System (ADS)

Subramanian, S. V.

1989-07-01

The fully three-dimensional, time-dependent compressible Navier-Stokes equations in cylindrical coordinates are presently used, in conjunction with the multistage Runge-Kutta numerical integration scheme for solution of the governing flow equations, to simulate complex flowfields within turbomechanical components whose pertinent effects encompass those of viscosity, compressibility, blade rotation, and tip clearance. Computed results are presented for selected cascades, emphasizing the code's capabilities in the accurate prediction of such features as airfoil loadings, exit flow angles, shocks, and secondary flows. Computations for several test cases have been performed on a Cray-YMP, using nearly 90,000 grid points.

The "Hoover" (vacuum cleaner) technique for calcifying tendonitis deposits excision and removal of the calcific debris.

PubMed

Ehud, Atoun; Ehud, Rath; Alexander, Van Tongel; Ali, Narvani; Giusseppe, Sforza; Ofer, Levy

2012-07-01

A new technical tip for the improvement of the arthroscopic treatment of symptomatic calcifying tendinitis is described. Arthroscopic excision of calcifying tendonitis may result with multiple minute calcific debris in the subacromial bursa, causing severe post operative pain due to chemical irritation of the bursa. We suggest the use of a bladeless shaver barrel as a "Hoover" (vacuum cleaner) for arthroscopic clearance of these miniature calcific debris from the subacromial space after resection of the major deposits. The use of this technique resulted in good clinical outcome with improved post operative pain.

Turbomachinery design and tonal acoustics computations

NASA Technical Reports Server (NTRS)

Rangwalla, Akil A.

1995-01-01

The objective of this research was two-fold. The first objective was to complete the three-dimensional unsteady calculations of the flow through a new transonic turbine and study the effects of secondary flows due to the hub and casing, tip clearance vortices, and the inherent three-dimensional mixing of the flow. It should be noted that this turbine was and is still in the design phase and the results of the calculations have formed an integral part of the design process. The second objective of this proposal was to evaluate the capability of rotor-stator interaction codes to calculate tonal acoustics.

Numerical investigation on the self-induced unsteadiness in tip leakage flow of a micro-axial fan rotor

NASA Astrophysics Data System (ADS)

Chen, Jinxin; Lai, Huanxin

2015-06-01

The self-induced unsteadiness in tip leakage flow (TLF) of a micro-axial fan rotor is numerically studied by solvingReynolds-averaged Navier-Stokes equations. The micro-axial fan, which is widely used in cooling systems of electronic devices, has a tip clearance of 6% of the axial chord length of the blade. At the design rotation speed, four cases near the peak efficiency point (PEP) with self-induced unsteadiness and four steady cases which have much weaker pressure fluctuations are investigated Using the "interface" separating the incoming main flow and the TLF defined by Du et al. [1], an explanation based on the propagation of the low energy spot and its multi-passing through the high gradient zone of the relativetotal pressure, is proposed to clarify the originating mechanism of the unsteadiness. At the operating points near the PEP, the main flow is weaker than the TLF and the interface moves upstream. The low energy spot which propagates along in the close behind of the interface has opportunity to circulate in the circumferential direction and passes through the sensitive interfaces several times, a slight perturbation therefore may be magnified significantlyand develops into the self-induced unsteadiness. The explanation is demonstrated by numerical results

Computational Study on the Effect of Shroud Shape on the Efficiency of the Gas Turbine Stage

NASA Astrophysics Data System (ADS)

Afanas'ev, I. V.; Granovskii, A. V.

2018-03-01

The last stages of powerful power gas turbines play an important role in the development of power and efficiency of the whole unit as well as in the distribution of the flow parameters behind the last stage, which determines the efficient operation of the exhaust diffusers. Therefore, much attention is paid to improving the efficiency of the last stages of gas turbines as well as the distribution of flow parameters. Since the long blades of the last stages of multistage high-power gas turbines could fall into the resonance frequency range in the course of operation, which results in the destruction of the blades, damping wires or damping bolts are used for turning out of resonance frequencies. However, these damping elements cause additional energy losses leading to a reduction in the efficiency of the stage. To minimize these losses, dampening shrouds are used instead of wires and bolts at the periphery of the working blades. However, because of the strength problems, designers have to use, instead of the most efficient full shrouds, partial shrouds that do not provide for significantly reducing the losses in the tip clearance between the blade and the turbine housing. In this paper, a computational study is performed concerning an effect that the design of the shroud of the turbine-working blade exerted on the flow structure in the vicinity of the shroud and on the efficiency of the stage as a whole. The analysis of the flow structure has shown that a significant part of the losses under using the shrouds is associated with the formation of vortex zones in the cavities on the turbine housing before the shrouds, between the ribs of the shrouds, and in the cavities at the outlet behind the shrouds. All the investigated variants of a partial shrouding are inferior in efficiency to the stages with shrouds that completely cover the tip section of the working blade. The stage with a unshrouded working blade was most efficient at the values of the relative tip clearance less than 0.9%.

Neural adaptive control for vibration suppression in composite fin-tip of aircraft.

PubMed

Suresh, S; Kannan, N; Sundararajan, N; Saratchandran, P

2008-06-01

In this paper, we present a neural adaptive control scheme for active vibration suppression of a composite aircraft fin tip. The mathematical model of a composite aircraft fin tip is derived using the finite element approach. The finite element model is updated experimentally to reflect the natural frequencies and mode shapes very accurately. Piezo-electric actuators and sensors are placed at optimal locations such that the vibration suppression is a maximum. Model-reference direct adaptive neural network control scheme is proposed to force the vibration level within the minimum acceptable limit. In this scheme, Gaussian neural network with linear filters is used to approximate the inverse dynamics of the system and the parameters of the neural controller are estimated using Lyapunov based update law. In order to reduce the computational burden, which is critical for real-time applications, the number of hidden neurons is also estimated in the proposed scheme. The global asymptotic stability of the overall system is ensured using the principles of Lyapunov approach. Simulation studies are carried-out using sinusoidal force functions of varying frequency. Experimental results show that the proposed neural adaptive control scheme is capable of providing significant vibration suppression in the multiple bending modes of interest. The performance of the proposed scheme is better than the H(infinity) control scheme.

Noncontact Capacitive Clearance Control System For Laser Cutting Machines

NASA Astrophysics Data System (ADS)

Topkaya, Ahmet; Schmall, Karl-Heinz; Majoli, Ralf

1989-03-01

For a continuous high quality laser cut, it is necessary among other things to position the focal point of the laser beam correctly. This means that a constant clearance between the cutting head and the workpiece with a tolerance of +/- 0.Imm must he ensured. When cutting corrugated automobile bodysheet for example, a good quality cut can only be achieved with automatic clearance control. In the following, a method of automatic clearance control is described using the assistance of a noncontact capacitive sensor system. The copper nozzle of the laser cutting head acts as the electrode of the clearance sensor. The nozzle electrode and the workpiece build a small variable capacitance depending on the clearance. A change of clearance also changes the capacitance, which in turn influences a high frequency oscillator circuit. This shift in frequency is then converted into an analogue DC signal, which can be used to operate a servo motor control for the positioning of the laser cutting head in a closed loop servo system. Laser cutting heads with clearance sensor nozzles of different shapes, suited fur most applications in the industry, with focal lengths from 2.5" to 5" have been developed. They are capable to cut metal sheet from 0.2 to 12 mm of thickness, using CO2-lasers with output power up to 2.5 kW. For special applications involving difficult workpiece topographies in automobile production applications special "trunk" nozzles have been developed. For 5-axis cutting machines and robots, new laser cutting heads with integrated nozzle sensors in combination with a high dynamic Z-axis motor drive are in a stage of development.

76 FR 65777 - Proposed Agency Information Collection Activities; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... the regulations governing freight power brakes and equipment in October 2008 by adding a new Subpart... being submitted for clearance by OMB as required by the PRA. Title: Inspection Brake System Safety Standards for Freight and Other Non-Passenger Trains and Equipment (Power Brakes and Drawbars). OMB Control...

78 FR 2379 - Agency Information Collection Activities; Comment Request; Impact Evaluation of Math Professional...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-11

...; Comment Request; Impact Evaluation of Math Professional Development AGENCY: IES/NCES, Department of... of Math Professional Development. OMB Control Number: 1850-NEW. Type of Review: New information... requests clearance to recruit and collect data from districts, schools, and teachers for a study of math...

75 FR 52802 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-27

...: Mechanics, Repairmen, and Parachute Riggers, FAR 65 AGENCY: Federal Aviation Administration (FAA), DOT...) approval to renew an information collection. FAR part 65 prescribes requirements for mechanics, repairmen... Control Number: 2120-0022. Title: Certification: Mechanics, Repairmen, and Parachute Riggers, FAR 65. Form...

75 FR 81710 - Proposed Agency Information Collection Activities; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-28

... clearance by OMB as required by the PRA. Title: Safety Integration Plans. OMB Control Number: 2130-0557... for the development and implementation of safety integration plans (``SIPs'' or ``plans'') by a Class... affected railroads (Class Is and some Class IIs) address critical safety issues unique to the amalgamation...

78 FR 48540 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-08

... collection. Background: Information to be collected will focus on pilot, controller, or vehicle driver practices and/or feedback on specific runway safety initiatives, such as training programs, Runway Safety... incursions. Respondents: An estimated 8,900 pilots, aircraft support vehicle drivers, airport/airfield...

76 FR 59184 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-23

... Airmen for the Operation of Light-Sport Aircraft AGENCY: Federal Aviation Administration (FAA), DOT... airworthiness representatives to support the certification of new light-sport aircraft, pilots, flight...: OMB Control Number: 2120-0690. Title: Certification of Airmen for the Operation of Light-Sport...

Microsomal quercetin glucuronidation in rat small intestine depends on age and segment

USDA-ARS?s Scientific Manuscript database

UDP-glucuronosyltransferase (UGT) activity toward the flavonoid quercetin and UGT protein were characterized in 3 equidistant small intestine (SI) segments from 4, 12, 18, and 28 mo male F344 rats, n=8/age using villin to control for enterocyte content. SI microsomal intrinsic clearance of quercetin...

78 FR 51807 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-21

... Permits for Reusable Suborbital Rockets AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice... INFORMATION: OMB Control Number: 2120-0722. Title: Experimental Permits for Reusable Suborbital Rockets. Form... experimental permits for reusable suborbital rockets to authorize launches for the purpose of research and...

78 FR 76153 - Agency Information Collection Activities: Comment Request; Extension of an Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-16

... Notice of Information Collection for review; Electronic Bonds Online (eBonds) Access; OMB Control No... submitting the following information collection request for review and clearance in accordance [[Page 76154... information collection. (2) Title of the Form/Collection: Electronic Bonds Online (eBonds) Access. (3) Agency...

77 FR 5802 - Proposed Agency Information Collection Activities; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-06

.... Federal Reserve Board Clearance Officer--Cynthia Ayouch--Division of Research and Statistics, Board of... Survey on Bank Lending Practices. Agency form number: FR 2018. OMB control number: 7100-0058. Frequency... respondent bank, generally through electronic submission, up to six times a year. The purpose of the survey...

76 FR 53023 - Agency Information Collection Activities: Requests for Comments; Clearance of New Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-24

... Activities: Requests for Comments; Clearance of New Approval of Information Collection: Activation of Ice... requirement imposed by the new rule ``Part 121 Activation of Ice Protection''. The NPRM for that rule was...: Activation of Ice Protection Rule--Flight Manual Requirements. Form Numbers: There are no FAA forms...

Application of an in vitro OAT assay in drug design and optimization of renal clearance.

PubMed

Soars, Matthew G; Barton, Patrick; Elkin, Lisa L; Mosure, Kathleen W; Sproston, Joanne L; Riley, Robert J

2014-07-01

1. Optimization of renal clearance is a complex balance between passive and active processes mediated by renal transporters. This work aimed to characterize the interaction of a series of compounds with rat and human organic anion transporters (OATs) and develop quantitative structure-activity relationships (QSARs) to optimize renal clearance. 2. In vitro inhibition assays were established for human OAT1 and rat Oat3 and rat in vivo renal clearance was obtained. Statistically significant quantitative relationships were explored between the compounds' physical properties, their affinity for OAT1 and oat3 and the inter-relationship with unbound renal clearance (URC) in rat. 3. Many of the compounds were actively secreted and in vitro analysis demonstrated that these were ligands for rat and human OAT transporters (IC50 values ranging from <1 to >100 µM). Application of resultant QSAR models reduced renal clearance in the rat from 24 to <0.1 ml/min/kg. Data analysis indicated that the properties associated with increasing affinity at OATs are the same as those associated with reducing URC but orthogonal in nature. 4. This study has demonstrated that OAT inhibition data and QSAR models can be successfully used to optimize rat renal clearance in vivo and provide confidence of translation to humans.

76 FR 36168 - Agency Information Collection Activities; Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-21

... Transportation (FAA/AST) that the proposed activity meets applicable public safety, national security, and... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Agency Information Collection Activities; Requests for Comments; Clearance of Renewed Approval of Information Collection; Commercial Space...

77 FR 51608 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-24

... Administrator for Commercial Space Transportation (AST), that a license applicant's proposed activities meet... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of Information Collection: Commercial Space...

Parametric modeling and stagger angle optimization of an axial flow fan

NASA Astrophysics Data System (ADS)

Li, M. X.; Zhang, C. H.; Liu, Y.; Y Zheng, S.

2013-12-01

Axial flow fans are widely used in every field of social production. Improving their efficiency is a sustained and urgent demand of domestic industry. The optimization of stagger angle is an important method to improve fan performance. Parametric modeling and calculation process automation are realized in this paper to improve optimization efficiency. Geometric modeling and mesh division are parameterized based on GAMBIT. Parameter setting and flow field calculation are completed in the batch mode of FLUENT. A control program is developed in Visual C++ to dominate the data exchange of mentioned software. It also extracts calculation results for optimization algorithm module (provided by Matlab) to generate directive optimization control parameters, which as feedback are transferred upwards to modeling module. The center line of the blade airfoil, based on CLARK y profile, is constructed by non-constant circulation and triangle discharge method. Stagger angles of six airfoil sections are optimized, to reduce the influence of inlet shock loss as well as gas leak in blade tip clearance and hub resistance at blade root. Finally an optimal solution is obtained, which meets the total pressure requirement under given conditions and improves total pressure efficiency by about 6%.

Reversible mechano-electrochemical writing of metallic nanostructures with the tip of an atomic force microscope.

PubMed

Obermair, Christian; Kress, Marina; Wagner, Andreas; Schimmel, Thomas

2012-01-01

We recently introduced a method that allows the controlled deposition of nanoscale metallic patterns at defined locations using the tip of an atomic force microscope (AFM) as a "mechano-electrochemical pen", locally activating a passivated substrate surface for site-selective electrochemical deposition. Here, we demonstrate the reversibility of this process and study the long-term stability of the resulting metallic structures. The remarkable stability for more than 1.5 years under ambient air without any observable changes can be attributed to self-passivation. After AFM-activated electrochemical deposition of copper nanostructures on a polycrystalline gold film and subsequent AFM imaging, the copper nanostructures could be dissolved by reversing the electrochemical potential. Subsequent AFM-tip-activated deposition of different copper nanostructures at the same location where the previous structures were deleted, shows that there is no observable memory effect, i.e., no effect of the previous writing process on the subsequent writing process. Thus, the four processes required for reversible information storage, "write", "read", "delete" and "re-write", were successfully demonstrated on the nanometer scale.

Reversible mechano-electrochemical writing of metallic nanostructures with the tip of an atomic force microscope

PubMed Central

Kress, Marina; Wagner, Andreas; Schimmel, Thomas

2012-01-01

Summary We recently introduced a method that allows the controlled deposition of nanoscale metallic patterns at defined locations using the tip of an atomic force microscope (AFM) as a “mechano-electrochemical pen”, locally activating a passivated substrate surface for site-selective electrochemical deposition. Here, we demonstrate the reversibility of this process and study the long-term stability of the resulting metallic structures. The remarkable stability for more than 1.5 years under ambient air without any observable changes can be attributed to self-passivation. After AFM-activated electrochemical deposition of copper nanostructures on a polycrystalline gold film and subsequent AFM imaging, the copper nanostructures could be dissolved by reversing the electrochemical potential. Subsequent AFM-tip-activated deposition of different copper nanostructures at the same location where the previous structures were deleted, shows that there is no observable memory effect, i.e., no effect of the previous writing process on the subsequent writing process. Thus, the four processes required for reversible information storage, “write”, “read”, “delete” and “re-write”, were successfully demonstrated on the nanometer scale. PMID:23365795

Initial, Cockpit Anthropometric Assessment of U.S. Navy T-6 Life Support Equipment

DTIC Science & Technology

2007-11-05

DEP was not specified. Zone 1, 2, and 3 reach conditions to controls and pedals and clearances were in accordance with military standard...functional leg reach as operation of pedals ; cockpit volume clearances, including ejection clearances not striking objects unintention-ally; and overhead...was measured from knee to any obstruction. Reach to pedals was measured from a position where full control was achieved. Arm reach was measured for

48 CFR 952.204-73 - Facility clearance.

Code of Federal Regulations, 2014 CFR

2014-10-01

....204-73 Section 952.204-73 Federal Acquisition Regulations System DEPARTMENT OF ENERGY CLAUSES AND... granted by the Secretary of Energy. In addition, a Facility Clearance and foreign ownership, control and... Department of Energy Facility Clearance generally need not resubmit the following foreign ownership...

48 CFR 952.204-73 - Facility clearance.

Code of Federal Regulations, 2011 CFR

2011-10-01

....204-73 Section 952.204-73 Federal Acquisition Regulations System DEPARTMENT OF ENERGY CLAUSES AND... granted by the Secretary of Energy. In addition, a Facility Clearance and foreign ownership, control and... Department of Energy Facility Clearance generally need not resubmit the following foreign ownership...

48 CFR 952.204-73 - Facility clearance.

Code of Federal Regulations, 2012 CFR

2012-10-01

....204-73 Section 952.204-73 Federal Acquisition Regulations System DEPARTMENT OF ENERGY CLAUSES AND... granted by the Secretary of Energy. In addition, a Facility Clearance and foreign ownership, control and... Department of Energy Facility Clearance generally need not resubmit the following foreign ownership...

48 CFR 952.204-73 - Facility clearance.

Code of Federal Regulations, 2013 CFR

2013-10-01

....204-73 Section 952.204-73 Federal Acquisition Regulations System DEPARTMENT OF ENERGY CLAUSES AND... granted by the Secretary of Energy. In addition, a Facility Clearance and foreign ownership, control and... Department of Energy Facility Clearance generally need not resubmit the following foreign ownership...

48 CFR 952.204-73 - Facility clearance.

Code of Federal Regulations, 2010 CFR

2010-10-01

....204-73 Section 952.204-73 Federal Acquisition Regulations System DEPARTMENT OF ENERGY CLAUSES AND... granted by the Secretary of Energy. In addition, a Facility Clearance and foreign ownership, control and... Department of Energy Facility Clearance generally need not resubmit the following foreign ownership...

Auxin, ethylene and the regulation of root growth under mechanical impedance

NASA Astrophysics Data System (ADS)

Sharma, Rameshwar; Santisree, Parankusam; Nongmaithem, Sapana; Sreelakshmi, Yellamaraju

2012-07-01

Among the multitude functions performed by plant roots, little information is available about the mechanisms that allow roots to overcome the soil resistance, in order to grow in the soil to obtain water and nutrient. Tomato (Solanum lycopersicum) seedlings grown on horizontally placed agar plates showed a progressive decline in the root length with the increasing impedance of agar media. The incubation with 1-methylcyclopropane (1-MCP), an inhibitor of ethylene perception, led to aerial growth of roots. In contrast, in absence of 1-MCP control roots grew horizontally anchored to the agar surface. Though 1-MCP-treated and control seedlings showed differential ability to penetrate in the agar, the inhibition of root elongation was nearly similar for both treatments. While increased mechanical impedance also progressively impaired hypocotyl elongation in 1-MCP treated seedlings, it did not affect the hypocotyl length of control seedlings. The decline in root elongation was also associated with increased expression of DR5::GUS activity in the root tip signifying accumulation of auxin at the root tip. The increased expression of DR5::GUS activity in the root tip was also observed in 1-MCP treated seedlings, indicating independence of this response from ethylene signaling. Our results indicate operation of a sensing mechanism in root that likely operates independently of ethylene but involves auxin to determine the degree of impedance of the substratum.

The aircraft energy efficiency active controls technology program

NASA Technical Reports Server (NTRS)

Hood, R. V., Jr.

1977-01-01

Broad outlines of the NASA Aircraft Energy Efficiency Program for expediting the application of active controls technology to civil transport aircraft are presented. Advances in propulsion and airframe technology to cut down on fuel consumption and fuel costs, a program for an energy-efficient transport, and integrated analysis and design technology in aerodynamics, structures, and active controls are envisaged. Fault-tolerant computer systems and fault-tolerant flight control system architectures are under study. Contracts with leading manufacturers for research and development work on wing-tip extensions and winglets for the B-747, a wing load alleviation system, elastic mode suppression, maneuver-load control, and gust alleviation are mentioned.

Tissue dissolution ability of sodium hypochlorite activated by photon-initiated photoacoustic streaming technique.

PubMed

Guneser, Mehmet Burak; Arslan, Dilara; Usumez, Aslihan

2015-05-01

The aim of this study was to evaluate the effect of the photon-initiated photoacoustic streaming (PIPS) technique on the pulp tissue-dissolving capacity of sodium hypochlorite (NaOCl) and compare it with the EndoActivator System (Dentsply Tulsa Dental Specialties, Tulsa, OK) and the Er:YAG laser with an endodontic fiber tip. Bovine pulp tissue samples (45 ± 15 mg) and dentin powder (10 mg) were placed in 1.5-mL Eppendorf tubes with 1 mL 5.25% NaOCl (Wizard; Rehber Kimya, Istanbul, Turkey) or distilled water (control) for 5 minutes with activation by the EndoActivator System, the Er:YAG laser with an endodontic fiber tip, and the PIPS technique. Nonactivated NaOCl served as the positive control. All testing procedures were performed at room temperature. The tissue samples were weighed before and after treatment, and the percentage of weight loss was calculated. The differences were statistically analyzed. The highest rate of tissue dissolution was observed in the NaOCl + Er:YAG group (P < .05). The NaOCl + PIPS group dissolved more bovine pulp tissue than the nonactivated NaOCl group (P < .05). There was no statistically significant difference between the rates of tissue dissolution of the NaOCl + EA and the nonactivated NaOCl groups (P > .05). NaOCl activation with the Er:YAG laser with an endodontic fiber tip was the most effective in bovine pulp tissue dissolution. The PIPS technique also promoted superior tissue-dissolving effects when compared with no activation. However, the EndoActivator System had no direct effect on tissue dissolution. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

76 FR 54285 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-31

... to the FAA Office of Commercial Space Transportation (FAA/ AST) that the proposed activity meets... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of Information Collection: Commercial Space...

Transient FTY720 treatment promotes immune-mediated clearance of a chronic viral infection.

PubMed

Premenko-Lanier, Mary; Moseley, Nelson B; Pruett, Sarah T; Romagnoli, Pablo A; Altman, John D

2008-08-14

For a wide variety of microbial pathogens, the outcome of the infection is indeterminate. In some individuals the microbe is cleared, but in others it establishes a chronic infection, and the factors that tip this balance are often unknown. In a widely used model of chronic viral infection, C57BL/6 mice clear the Armstrong strain of lymphocytic choriomeningitis virus (LCMV), but the clone 13 strain persists. Here we show that the Armstrong strain induces a profound lymphopenia at days 1-3 after infection, but the clone 13 strain does not. If we transiently augment lymphopenia by treating the clone-13-infected mice with the drug FTY720 at days 0-2 after infection, the mice successfully clear the infection by day 30. Clearance does not occur when CD4 T cells are absent at the time of treatment, indicating that the drug is not exerting direct antiviral effects. Notably, FTY720 treatment of an already established persistent infection also leads to viral clearance. In both models, FTY720 treatment preserves or augments LCMV-specific CD4 and CD8 T-cell responses, a result that is counter-intuitive because FTY720 is generally regarded as a new immunosuppressive agent. Because FTY720 targets host pathways that are completely evolutionarily conserved, our results may be translatable into new immunotherapies for the treatment of chronic microbial infections in humans.

An Active Smart Material Control System for F/A-18 Buffet Alleviation

NASA Technical Reports Server (NTRS)

Sheta, Essam F.; Moses, Robert W.; Huttsell, Lawrence J.; Harrand, Vincent J.

2003-01-01

The vertical tail buffet problem of fighter aircraft occurs at high angles of attack when the vortical flow breaks down ahead of the vertical tails resulting in unsteady and unbalanced pressure loads on the vertical tails. The buffet loads imposed upon the vertical tails resulted in a premature fatigue failure of the tails, and consequently limits the performance and super maneuverability of twin-tail fighter aircraft. An active smart material control system using distributed piezoelectric actuators has been developed for buffet alleviation and is presented. The inboard and outboard surfaces of the vertical tail are equipped with piezoelectric actuators to control the buffet responses in the first bending and torsion modes. The electrodynamics of the piezoelectric actuators are expressed with a three-dimensional finite-element model. A single-input-single-output controller is designed to drive the active piezoelectric actuators. High-fidelity multidisciplinary analysis modules for the fluid dynamics, structure dynamics, electrodynamics of the piezoelectric actuators, control law, fluid structure interfacing, and grid motion are integrated into a multidisciplinary computing environment that controls the temporal synchronization of the analysis modules. At 30 degree angle of attack, RMS values of tip acceleration are reduced by as much as 12%. The peak values of the power spectral density of tail-tip acceleration are reduced by as much as 22% in the first bending mode and by as much as 82% in the first torsion mode. The actively controlled piezoelectric actuators were also effective in adding damping at wide range of angles of attack.

Expanding torque possibilities: A skeletally anchored torqued cantilever for uprighting "kissing molars".

PubMed

Barros, Sérgio Estelita; Janson, Guilherme; Chiqueto, Kelly; Ferreira, Eduardo; Rösing, Cassiano

2018-04-01

Several uprighting mechanics and devices have been used for repositioning tipped molars. "Kissing molars" (KMs) are an uncommon tooth impaction involving 2 severely tipped mandibular molars with their occlusal surfaces positioned crown to crown, with the roots pointing in opposite directions. Orthodontic uprighting of KMs has not been a usual treatment protocol, and it can be a challenging task due to the severe tipping and double impaction, requiring efficient and well-controlled uprighting mechanics. An innovative skeletally anchored cantilever, which uses the torque principle for uprighting tipped molars, is suggested. This torqued cantilever is easy to manufacture, install, and activate; it is a well-known torque that is effective for producing root movement. A successful treatment of symptomatic KMs, involving the first and second molars, was achieved with this cantilever. Thus, clinicians should consider the suggested uprighting mechanics and orthodontic device as a more conservative alternative to extraction of KMs, depending on the patient's age, involved teeth in KMs, tipping severity, and impaction positions. Copyright © 2018 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Zinc supplementation leads to immune modulation and improved survival in a juvenile model of murine sepsis.

PubMed

Ganatra, Hammad A; Varisco, Brian M; Harmon, Kelli; Lahni, Patrick; Opoka, Amy; Wong, Hector R

2017-01-01

Children with severe sepsis are known to have altered zinc homeostasis and decreased circulating zinc levels, suggesting a role for zinc supplementation to improve outcomes. We tested the hypothesis that zinc supplementation would improve survival in a juvenile model of polymicrobial sepsis. Juvenile (13-14-d-old) C57BL/6 mice were treated with 10 mg/kg of zinc via i.p. injections (or vehicle) for 3 d prior to induction of polymicrobial sepsis via i.p. cecal slurry injections. Survival after sepsis was followed for 3 d, and bacterial clearance, ex vivo phagocytosis, systemic inflammatory markers and neutrophil extracellular trap (NET) formation were quantified. We found a significant survival benefit and decreased bacterial burden among zinc supplemented mice when compared with the control group. Zinc supplementation also resulted in enhanced phagocytic activity, greater neutrophil recruitment in the peritoneal cavity and NET formation, suggesting a possible mechanism for improved bacterial clearance and survival. We also noted decreased serum cytokine levels and decreased myeloperoxidase activity in lung tissue following zinc supplementation, suggesting attenuation of the systemic inflammatory response. In conclusion, zinc supplementation improves bacterial clearance, and hence survival, in juvenile mice with polymicrobial sepsis.