Stabilizing skateboard speed-wobble with reflex delay.

PubMed

Varszegi, Balazs; Takacs, Denes; Stepan, Gabor; Hogan, S John

2016-08-01

A simple mechanical model of the skateboard-skater system is analysed, in which the effect of human control is considered by means of a linear proportional-derivative (PD) controller with delay. The equations of motion of this non-holonomic system are neutral delay-differential equations. A linear stability analysis of the rectilinear motion is carried out analytically. It is shown how to vary the control gains with respect to the speed of the skateboard to stabilize the uniform motion. The critical reflex delay of the skater is determined as the function of the speed. Based on this analysis, we present an explanation for the linear instability of the skateboard-skater system at high speed. Moreover, the advantages of standing ahead of the centre of the board are demonstrated from the viewpoint of reflex delay and control gain sensitivity. © 2016 The Author(s).

Controls/CFD Interdisciplinary Research Software Generates Low-Order Linear Models for Control Design From Steady-State CFD Results

NASA Technical Reports Server (NTRS)

Melcher, Kevin J.

1997-01-01

The NASA Lewis Research Center is developing analytical methods and software tools to create a bridge between the controls and computational fluid dynamics (CFD) disciplines. Traditionally, control design engineers have used coarse nonlinear simulations to generate information for the design of new propulsion system controls. However, such traditional methods are not adequate for modeling the propulsion systems of complex, high-speed vehicles like the High Speed Civil Transport. To properly model the relevant flow physics of high-speed propulsion systems, one must use simulations based on CFD methods. Such CFD simulations have become useful tools for engineers that are designing propulsion system components. The analysis techniques and software being developed as part of this effort are an attempt to evolve CFD into a useful tool for control design as well. One major aspect of this research is the generation of linear models from steady-state CFD results. CFD simulations, often used during the design of high-speed inlets, yield high resolution operating point data. Under a NASA grant, the University of Akron has developed analytical techniques and software tools that use these data to generate linear models for control design. The resulting linear models have the same number of states as the original CFD simulation, so they are still very large and computationally cumbersome. Model reduction techniques have been successfully applied to reduce these large linear models by several orders of magnitude without significantly changing the dynamic response. The result is an accurate, easy to use, low-order linear model that takes less time to generate than those generated by traditional means. The development of methods for generating low-order linear models from steady-state CFD is most complete at the one-dimensional level, where software is available to generate models with different kinds of input and output variables. One-dimensional methods have been extended somewhat so that linear models can also be generated from two- and three-dimensional steady-state results. Standard techniques are adequate for reducing the order of one-dimensional CFD-based linear models. However, reduction of linear models based on two- and three-dimensional CFD results is complicated by very sparse, ill-conditioned matrices. Some novel approaches are being investigated to solve this problem.

Linear hypergeneralization of learned dynamics across movement speeds reveals anisotropic, gain-encoding primitives for motor adaptation.

PubMed

Joiner, Wilsaan M; Ajayi, Obafunso; Sing, Gary C; Smith, Maurice A

2011-01-01

The ability to generalize learned motor actions to new contexts is a key feature of the motor system. For example, the ability to ride a bicycle or swing a racket is often first developed at lower speeds and later applied to faster velocities. A number of previous studies have examined the generalization of motor adaptation across movement directions and found that the learned adaptation decays in a pattern consistent with the existence of motor primitives that display narrow Gaussian tuning. However, few studies have examined the generalization of motor adaptation across movement speeds. Following adaptation to linear velocity-dependent dynamics during point-to-point reaching arm movements at one speed, we tested the ability of subjects to transfer this adaptation to short-duration higher-speed movements aimed at the same target. We found near-perfect linear extrapolation of the trained adaptation with respect to both the magnitude and the time course of the velocity profiles associated with the high-speed movements: a 69% increase in movement speed corresponded to a 74% extrapolation of the trained adaptation. The close match between the increase in movement speed and the corresponding increase in adaptation beyond what was trained indicates linear hypergeneralization. Computational modeling shows that this pattern of linear hypergeneralization across movement speeds is not compatible with previous models of adaptation in which motor primitives display isotropic Gaussian tuning of motor output around their preferred velocities. Instead, we show that this generalization pattern indicates that the primitives involved in the adaptation to viscous dynamics display anisotropic tuning in velocity space and encode the gain between motor output and motion state rather than motor output itself.

A MHz speed wavelength sweeping for ultra-high speed FBG interrogation

NASA Astrophysics Data System (ADS)

Kim, Gyeong Hun; Lee, Hwi Don; Eom, Tae Joong; Jeong, Myung Yung; Kim, Chang-Seok

2015-09-01

We demonstrated a MHz speed wavelength-swept fiber laser based on the active mode locking (AML) technique and applied to interrogation system of an array of fiber Bragg grating (FBG) sensors. MHz speed wavelength sweeping of wavelength-swept fiber laser can be obtained by programmable frequency modulation of the semiconductor optical amplifier (SOA) without any wavelength tunable filter. Both static and dynamic strain measurement of FBG sensors were successfully characterized with high linearity of an R-square value of 0.9999 at sweeping speed of 50 kHz.

Effects of pole flux distribution in a homopolar linear synchronous machine

NASA Astrophysics Data System (ADS)

Balchin, M. J.; Eastham, J. F.; Coles, P. C.

1994-05-01

Linear forms of synchronous electrical machine are at present being considered as the propulsion means in high-speed, magnetically levitated (Maglev) ground transportation systems. A homopolar form of machine is considered in which the primary member, which carries both ac and dc windings, is supported on the vehicle. Test results and theoretical predictions are presented for a design of machine intended for driving a 100 passenger vehicle at a top speed of 400 km/h. The layout of the dc magnetic circuit is examined to locate the best position for the dc winding from the point of view of minimum core weight. Measurements of flux build-up under the machine at different operating speeds are given for two types of secondary pole: solid and laminated. The solid pole results, which are confirmed theoretically, show that this form of construction is impractical for high-speed drives. Measured motoring characteristics are presented for a short length of machine which simulates conditions at the leading and trailing ends of the full-sized machine. Combination of the results with those from a cylindrical version of the machine make it possible to infer the performance of the full-sized traction machine. This gives 0.8 pf and 0.9 efficiency at 300 km/h, which is much better than the reported performance of a comparable linear induction motor (0.52 pf and 0.82 efficiency). It is therefore concluded that in any projected high-speed Maglev systems, a linear synchronous machine should be the first choice as the propulsion means.

The high speed interconnect system architecture and operation

NASA Astrophysics Data System (ADS)

Anderson, Steven C.

The design and operation of a fiber-optic high-speed interconnect system (HSIS) being developed to meet the requirements of future avionics and flight-control hardware with distributed-system architectures are discussed. The HSIS is intended for 100-Mb/s operation of a local-area network with up to 256 stations. It comprises a bus transmission system (passive star couplers and linear media linked by active elements) and network interface units (NIUs). Each NIU is designed to perform the physical, data link, network, and transport functions defined by the ISO OSI Basic Reference Model (1982 and 1983) and incorporates a fiber-optic transceiver, a high-speed protocol based on the SAE AE-9B linear token-passing data bus (1986), and a specialized application interface unit. The operating modes and capabilities of HSIS are described in detail and illustrated with diagrams.

High-speed AFM and the reduction of tip-sample forces

NASA Astrophysics Data System (ADS)

Miles, Mervyn; Sharma, Ravi; Picco, Loren

High-speed DC-mode AFM has been shown to be routinely capable of imaging at video rate, and, if required, at over 1000 frames per second. At sufficiently high tip-sample velocities in ambient conditions, the tip lifts off the sample surface in a superlubricity process which reduces the level of shear forces imposed on the sample by the tip and therefore reduces the potential damage and distortion of the sample being imaged. High-frequency mechanical oscillations, both lateral and vertical, have been reported to reduced the tip-sample frictional forces. We have investigated the effect of combining linear high-speed scanning with these small amplitude high-frequency oscillations with the aim of reducing further the force interaction in high-speed imaging. Examples of this new version of high-speed AFM imaging will be presented for biological samples.

Tri-linear color multi-linescan sensor with 200 kHz line rate

NASA Astrophysics Data System (ADS)

Schrey, Olaf; Brockherde, Werner; Nitta, Christian; Bechen, Benjamin; Bodenstorfer, Ernst; Brodersen, Jörg; Mayer, Konrad J.

2016-11-01

In this paper we present a newly developed linear CMOS high-speed line-scanning sensor realized in a 0.35 μm CMOS OPTO process for line-scan with 200 kHz true RGB and 600 kHz monochrome line rate, respectively. In total, 60 lines are integrated in the sensor allowing for electronic position adjustment. The lines are read out in rolling shutter manner. The high readout speed is achieved by a column-wise organization of the readout chain. At full speed, the sensor provides RGB color images with a spatial resolution down to 50 μm. This feature enables a variety of applications like quality assurance in print inspection, real-time surveillance of railroad tracks, in-line monitoring in flat panel fabrication lines and many more. The sensor has a fill-factor close to 100%, preventing aliasing and color artefacts. Hence the tri-linear technology is robust against aliasing ensuring better inspection quality and thus less waste in production lines.

Electron acoustic-Langmuir solitons in a two-component electron plasma

NASA Astrophysics Data System (ADS)

McKenzie, J. F.

2003-04-01

We investigate the conditions under which ‘high-frequency’ electron acoustic Langmuir solitons can be constructed in a plasma consisting of protons and two electron populations: one ‘cold’ and the other ‘hot’. Conservation of total momentum can be cast as a structure equation either for the ‘cold’ or ‘hot’ electron flow speed in a stationary wave using the Bernoulli energy equations for each species. The linearized version of the governing equations gives the dispersion equation for the stationary waves of the system, from which follows the necessary but not sufficient conditions for the existence of soliton structures; namely that the wave speed must be less than the acoustic speed of the ‘hot’ electron component and greater than the low-frequency compound acoustic speed of the two electron populations. In this wave speed regime linear waves are ‘evanescent’, giving rise to the exponential growth or decay, which readily can give rise to non-linear effects that may balance dispersion and allow soliton formation. In general the ‘hot’ component must be more abundant than the ‘cold’ one and the wave is characterized by a compression of the ‘cold’ component and an expansion in the ‘hot’ component necessitating a potential dip. Both components are driven towards their sonic points; the ‘cold’ from above and the ‘hot’ from below. It is this transonic feature which limits the amplitude of the soliton. If the ‘hot’ component is not sufficiently abundant the window for soliton formation shrinks to a narrow speed regime which is quasi-transonic relative to the ‘hot’ electron acoustic speed, and it is shown that smooth solitons cannot be constructed. In the special case of a very cold electron population (i.e. ‘highly supersonic’) and the other population being very hot (i.e. ‘highly subsonic’) with adiabatic index 2, the structure equation simplifies and can be integrated in terms of elementary transcendental functions that provide the fully non-linear counterpart to the weakly non-linear sech(2) -type solitons. In this case the limiting soliton is comprised of an infinite compression in the cold component, a weak rarefaction in the ‘hot’ electrons and a modest potential dip.

High-Speed Digital Scan Converter for High-Frequency Ultrasound Sector Scanners

PubMed Central

Chang, Jin Ho; Yen, Jesse T.; Shung, K. Kirk

2008-01-01

This paper presents a high-speed digital scan converter (DSC) capable of providing more than 400 images per second, which is necessary to examine the activities of the mouse heart whose rate is 5–10 beats per second. To achieve the desired high-speed performance in cost-effective manner, the DSC developed adopts a linear interpolation algorithm in which two nearest samples to each object pixel of a monitor are selected and only angular interpolation is performed. Through computer simulation with the Field II program, its accuracy was investigated by comparing it to that of bilinear interpolation known as the best algorithm in terms of accuracy and processing speed. The simulation results show that the linear interpolation algorithm is capable of providing an acceptable image quality, which means that the difference of the root mean square error (RMSE) values of the linear and bilinear interpolation algorithms is below 1 %, if the sample rate of the envelope samples is at least four times higher than the Nyquist rate for the baseband component of echo signals. The designed DSC was implemented with a single FPGA (Stratix EP1S60F1020C6, Altera Corporation, San Jose, CA) on a DSC board that is a part of a high-speed ultrasound imaging system developed. The temporal and spatial resolutions of the implemented DSC were evaluated by examining its maximum processing time with a time stamp indicating when an image is completely formed and wire phantom testing, respectively. The experimental results show that the implemented DSC is capable of providing images at the rate of 400 images per second with negligible processing error. PMID:18430449

Development of two-framing camera with large format and ultrahigh speed

NASA Astrophysics Data System (ADS)

Jiang, Xiaoguo; Wang, Yuan; Wang, Yi

2012-10-01

High-speed imaging facility is important and necessary for the formation of time-resolved measurement system with multi-framing capability. The framing camera which satisfies the demands of both high speed and large format needs to be specially developed in the ultrahigh speed research field. A two-framing camera system with high sensitivity and time-resolution has been developed and used for the diagnosis of electron beam parameters of Dragon-I linear induction accelerator (LIA). The camera system, which adopts the principle of light beam splitting in the image space behind the lens with long focus length, mainly consists of lens-coupled gated image intensifier, CCD camera and high-speed shutter trigger device based on the programmable integrated circuit. The fastest gating time is about 3 ns, and the interval time between the two frames can be adjusted discretely at the step of 0.5 ns. Both the gating time and the interval time can be tuned to the maximum value of about 1 s independently. Two images with the size of 1024×1024 for each can be captured simultaneously in our developed camera. Besides, this camera system possesses a good linearity, uniform spatial response and an equivalent background illumination as low as 5 electrons/pix/sec, which fully meets the measurement requirements of Dragon-I LIA.

An extended heterogeneous car-following model accounting for anticipation driving behavior and mixed maximum speeds

NASA Astrophysics Data System (ADS)

Sun, Fengxin; Wang, Jufeng; Cheng, Rongjun; Ge, Hongxia

2018-02-01

The optimal driving speeds of the different vehicles may be different for the same headway. In the optimal velocity function of the optimal velocity (OV) model, the maximum speed vmax is an important parameter determining the optimal driving speed. A vehicle with higher maximum speed is more willing to drive faster than that with lower maximum speed in similar situation. By incorporating the anticipation driving behavior of relative velocity and mixed maximum speeds of different percentages into optimal velocity function, an extended heterogeneous car-following model is presented in this paper. The analytical linear stable condition for this extended heterogeneous traffic model is obtained by using linear stability theory. Numerical simulations are carried out to explore the complex phenomenon resulted from the cooperation between anticipation driving behavior and heterogeneous maximum speeds in the optimal velocity function. The analytical and numerical results all demonstrate that strengthening driver's anticipation effect can improve the stability of heterogeneous traffic flow, and increasing the lowest value in the mixed maximum speeds will result in more instability, but increasing the value or proportion of the part already having higher maximum speed will cause different stabilities at high or low traffic densities.

High Velocity Linear Induction Launcher with Exit-Edge Compensation for Testing of Aerospace Components

NASA Technical Reports Server (NTRS)

Kuznetsov, Stephen; Marriott, Darin

2008-01-01

Advances in ultra high speed linear induction electromagnetic launchers over the past decade have focused on magnetic compensation of the exit and entry-edge transient flux wave to produce efficient and compact linear electric machinery. The paper discusses two approaches to edge compensation in long-stator induction catapults with typical end speeds of 150 to 1,500 m/s. In classical linear induction machines, the exit-edge effect is manifest as two auxiliary traveling waves that produce a magnetic drag on the projectile and a loss of magnetic flux over the main surface of the machine. In the new design for the Stator Compensated Induction Machine (SCIM) high velocity launcher, the exit-edge effect is nulled by a dual wavelength machine or alternately the airgap flux is peaked at a location prior to the exit edge. A four (4) stage LIM catapult is presently being constructed for 180 m/s end speed operation using double-sided longitudinal flux machines. Advanced exit and entry edge compensation is being used to maximize system efficiency, and minimize stray heating of the reaction armature. Each stage will output approximately 60 kN of force and produce over 500 G s of acceleration on the armature. The advantage of this design is there is no ablation to the projectile and no sliding contacts, allowing repeated firing of the launcher without maintenance of any sort. The paper shows results of a parametric study for 500 m/s and 1,500 m/s linear induction launchers incorporating two of the latest compensation techniques for an air-core stator primary and an iron-core primary winding. Typical thrust densities for these machines are in the range of 150 kN/sq.m. to 225 kN/sq.m. and these compete favorably with permanent magnet linear synchronous machines. The operational advantages of the high speed SCIM launcher are shown by eliminating the need for pole-angle position sensors as would be required by synchronous systems. The stator power factor is also improved.

Research of rotating machinery vibration parameters - Shaft speed relationship

NASA Astrophysics Data System (ADS)

Kostyukov, V. N.; Kostyukov, A. V.; Zaytsev, A. V.; Teterin, A. O.

2017-08-01

The paper considers the relationship between the parameters of the vibration arising in rotating machinery during operation and the shaft speed. The goal of this paper is to determine the dependence of the vibration parameters on the shaft speed for solving applied engineering problems. To properly evaluate the technical condition of bearing assemblies, we should take into account the pattern of the rotating machinery vibration parameters-shaft speed relationship, which will allow creating new diagnostic features, the totality of which will ensure an increased reliability of diagnosis. We took the check for a correlation between the factor and resultative feature parameters as the correlation analysis method. A high pair linear correlation between the diagnostic features (acceleration, velocity, displacement) and the shaft speed was determined on the basis of the check for correlation between the vibration parameters and the shaft speed, and also the linear correlation coefficients can be used to solve the applied engineering problems of diagnosing the bearing assemblies of the rotating machinery.

Solving the aerodynamics of fungal flight: How air viscosity slows spore motion

PubMed Central

Fischer, Mark W. F.; Stolze-Rybczynski, Jessica L.; Davis, Diana J.; Cui, Yunluan; Money, Nicholas P.

2010-01-01

Viscous drag causes the rapid deceleration of fungal spores after high-speed launches and limits discharge distance. Stokes' law posits a linear relationship between drag force and velocity. It provides an excellent fit to experimental measurements of the terminal velocity of free-falling spores and other instances of low Reynolds number motion (Re<1). More complex, non-linear drag models have been devised for movements characterized by higher Re, but their effectiveness for modeling the launch of fast-moving fungal spores has not been tested. In this paper, we use data on spore discharge processes obtained from ultra-high-speed video recordings to evaluate the effects of air viscosity predicted by Stokes' law and a commonly used non-linear drag model. We find that discharge distances predicted from launch speeds by Stokes' model provide a much better match to measured distances than estimates from the more complex drag model. Stokes' model works better over a wide range projectile sizes, launch speeds, and discharge distances, from microscopic mushroom ballistospores discharged at <1 m/s over a distance of <0.1 mm (Re<1.0), to macroscopic sporangia of Pilobolus that are launched at >10 m/s and travel as far as 2.5 m (Re>100). PMID:21036338

High speed propeller acoustics and aerodynamics - A boundary element approach

NASA Technical Reports Server (NTRS)

Farassat, F.; Myers, M. K.; Dunn, M. H.

1989-01-01

The Boundary Element Method (BEM) is applied in this paper to the problems of acoustics and aerodynamics of high speed propellers. The underlying theory is described based on the linearized Ffowcs Williams-Hawkings equation. The surface pressure on the blade is assumed unknown in the aerodynamic problem. It is obtained by solving a singular integral equation. The acoustic problem is then solved by moving the field point inside the fluid medium and evaluating some surface and line integrals. Thus the BEM provides a powerful technique in calculation of high speed propeller aerodynamics and acoustics.

Silicon photonic transceiver circuit for high-speed polarization-based discrete variable quantum key distribution

DOE PAGES

Cai, Hong; Long, Christopher M.; DeRose, Christopher T.; ...

2017-01-01

We demonstrate a silicon photonic transceiver circuit for high-speed discrete variable quantum key distribution that employs a common structure for transmit and receive functions. The device is intended for use in polarization-based quantum cryptographic protocols, such as BB84. Our characterization indicates that the circuit can generate the four BB84 states (TE/TM/45°/135° linear polarizations) with >30 dB polarization extinction ratios and gigabit per second modulation speed, and is capable of decoding any polarization bases differing by 90° with high extinction ratios.

Silicon photonic transceiver circuit for high-speed polarization-based discrete variable quantum key distribution.

PubMed

Cai, Hong; Long, Christopher M; DeRose, Christopher T; Boynton, Nicholas; Urayama, Junji; Camacho, Ryan; Pomerene, Andrew; Starbuck, Andrew L; Trotter, Douglas C; Davids, Paul S; Lentine, Anthony L

2017-05-29

We demonstrate a silicon photonic transceiver circuit for high-speed discrete variable quantum key distribution that employs a common structure for transmit and receive functions. The device is intended for use in polarization-based quantum cryptographic protocols, such as BB84. Our characterization indicates that the circuit can generate the four BB84 states (TE/TM/45°/135° linear polarizations) with >30 dB polarization extinction ratios and gigabit per second modulation speed, and is capable of decoding any polarization bases differing by 90° with high extinction ratios.

Silicon photonic transceiver circuit for high-speed polarization-based discrete variable quantum key distribution

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

Cai, Hong; Long, Christopher M.; DeRose, Christopher T.

We demonstrate a silicon photonic transceiver circuit for high-speed discrete variable quantum key distribution that employs a common structure for transmit and receive functions. The device is intended for use in polarization-based quantum cryptographic protocols, such as BB84. Our characterization indicates that the circuit can generate the four BB84 states (TE/TM/45°/135° linear polarizations) with >30 dB polarization extinction ratios and gigabit per second modulation speed, and is capable of decoding any polarization bases differing by 90° with high extinction ratios.

A hierarchy for modeling high speed propulsion systems

NASA Technical Reports Server (NTRS)

Hartley, Tom T.; Deabreu, Alex

1991-01-01

General research efforts on reduced order propulsion models for control systems design are overviewed. Methods for modeling high speed propulsion systems are discussed including internal flow propulsion systems that do not contain rotating machinery such as inlets, ramjets, and scramjets. The discussion is separated into four sections: (1) computational fluid dynamics model for the entire nonlinear system or high order nonlinear models; (2) high order linearized model derived from fundamental physics; (3) low order linear models obtained from other high order models; and (4) low order nonlinear models. Included are special considerations on any relevant control system designs. The methods discussed are for the quasi-one dimensional Euler equations of gasdynamic flow. The essential nonlinear features represented are large amplitude nonlinear waves, moving normal shocks, hammershocks, subsonic combustion via heat addition, temperature dependent gases, detonation, and thermal choking.

Geo-spatial and log-linear analysis of pedestrian and bicyclist crashes involving school-aged children.

PubMed

Abdel-Aty, Mohamed; Chundi, Sai Srinivas; Lee, Chris

2007-01-01

There is a growing concern with the safety of school-aged children. This study identifies the locations of pedestrian/bicyclist crashes involving school-aged children and examines the conditions when these crashes are more likely to occur. The 5-year records of crashes in Orange County, Florida where school-aged children were involved were used. The spatial distribution of these crashes was investigated using the Geographic Information Systems (GIS) and the likelihoods of crash occurrence under different conditions were estimated using log-linear models. A majority of school-aged children crashes occurred in the areas near schools. Although elementary school children were generally very involved, middle and high school children were more involved in crashes, particularly on high-speed multi-lane roadways. Driver's age, gender, and alcohol use, pedestrian's/bicyclist's age, number of lanes, median type, speed limits, and speed ratio were also found to be correlated with the frequency of crashes. The result confirms that school-aged children are exposed to high crash risk near schools. High crash involvement of middle and high school children reflects that middle and high schools tend to be located near multi-lane high-speed roads. The pedestrian's/bicyclist's demographic factors and geometric characteristics of the roads adjacent to schools associated with school children's crash involvement are of interest to school districts.

Apparatus and method to pulverize rock using a superconducting electromagnetic linear motor

NASA Technical Reports Server (NTRS)

Ignatiev, Alex (Inventor)

2009-01-01

A rock pulverizer device based on a superconducting linear motor. The superconducting electromagnetic rock pulverizer accelerates a projectile via a superconducting linear motor and directs the projectile at high speed toward a rock structure that is to be pulverized by collision of the speeding projectile with the rock structure. The rock pulverizer is comprised of a trapped field superconducting secondary magnet mounted on a movable car following a track, a wire wound series of primary magnets mounted on the track, and the complete magnet/track system mounted on a vehicle used for movement of the pulverizer through a mine as well as for momentum transfer during launch of the rock breaking projectile.

Contrast effects on speed perception for linear and radial motion.

PubMed

Champion, Rebecca A; Warren, Paul A

2017-11-01

Speed perception is vital for safe activity in the environment. However, considerable evidence suggests that perceived speed changes as a function of stimulus contrast, with some investigators suggesting that this might have meaningful real-world consequences (e.g. driving in fog). In the present study we investigate whether the neural effects of contrast on speed perception occur at the level of local or global motion processing. To do this we examine both speed discrimination thresholds and contrast-dependent speed perception for two global motion configurations that have matched local spatio-temporal structure. Specifically we compare linear and radial configurations, the latter of which arises very commonly due to self-movement. In experiment 1 the stimuli comprised circular grating patches. In experiment 2, to match stimuli even more closely, motion was presented in multiple local Gabor patches equidistant from central fixation. Each patch contained identical linear motion but the global configuration was either consistent with linear or radial motion. In both experiments 1 and 2, discrimination thresholds and contrast-induced speed biases were similar in linear and radial conditions. These results suggest that contrast-based speed effects occur only at the level of local motion processing, irrespective of global structure. This result is interpreted in the context of previous models of speed perception and evidence suggesting differences in perceived speed of locally matched linear and radial stimuli. Copyright © 2017 Elsevier Ltd. All rights reserved.

Abnormal gait pattern emerges during curved trajectories in high-functioning Parkinsonian patients walking in line at normal speed

PubMed Central

Godi, Marco; Giardini, Marica; Arcolin, Ilaria; Nardone, Antonio; Giordano, Andrea; Schieppati, Marco

2018-01-01

Background Several patients with Parkinson´s disease (PD) can walk normally along straight trajectories, and impairment in their stride length and cadence may not be easily discernible. Do obvious abnormalities occur in these high-functioning patients when more challenging trajectories are travelled, such as circular paths, which normally implicate a graded modulation in the duration of the interlimb gait cycle phases? Methods We compared a cohort of well-treated mildly to moderately affected PD patients to a group of age-matched healthy subjects (HS), by deliberately including HS spontaneously walking at the same speed of the patients with PD. All participants performed, in random order: linear and circular walking (clockwise and counter-clockwise) at self-selected speed. By means of pressure-sensitive insoles, we recorded walking speed, cadence, duration of single support, double support, swing phase, and stride time. Stride length-cadence relationships were built for linear and curved walking. Stride-to-stride variability of temporal gait parameters was also estimated. Results Walking speed, cadence or stride length were not different between PD and HS during linear walking. Speed, cadence and stride length diminished during curved walking in both groups, stride length more in PD than HS. In PD compared to HS, the stride length-cadence relationship was altered during curved walking. Duration of the double-support phase was also increased during curved walking, as was variability of the single support, swing phase and double support phase. Conclusion The spatio-temporal gait pattern and variability are significantly modified in well-treated, high-functioning patients with PD walking along circular trajectories, even when they exhibit no changes in speed in straight-line walking. The increased variability of the gait phases during curved walking is an identifying characteristic of PD. We discuss our findings in term of interplay between control of balance and of locomotor progression: the former is challenged by curved trajectories even in high-functioning patients, while the latter may not be critically affected. PMID:29750815

? stability of wind turbine switching control

NASA Astrophysics Data System (ADS)

Palejiya, Dushyant; Shaltout, Mohamed; Yan, Zeyu; Chen, Dongmei

2015-01-01

In order to maximise the wind energy capture, wind turbines are operated at variable speeds. Depending on the wind speed, a turbine switches between two operating modes: a low wind speed mode and a high wind speed mode. During the low wind speed mode, the control objective is to maximise wind energy capture by controlling both the blade pitch angle and the electrical generator torque. During the high wind speed mode, the control goal is to maintain the rated power generation by only adjusting the blade pitch angle. This paper establishes the stability criteria for the switching operation of wind turbines using ? gain under the nonlinear control framework. Also, the performance of the wind turbine system is analysed by using the step response, a well-known measure for second-order linear systems.

The application of high-speed cinematography for the quantitative analysis of equine locomotion.

PubMed

Fredricson, I; Drevemo, S; Dalin, G; Hjertën, G; Björne, K

1980-04-01

Locomotive disorders constitute a serious problem in horse racing which will only be rectified by a better understanding of the causative factors associated with disturbances of gait. This study describes a system for the quantitative analysis of the locomotion of horses at speed. The method is based on high-speed cinematography with a semi-automatic system of analysis of the films. The recordings are made with a 16 mm high-speed camera run at 500 frames per second (fps) and the films are analysed by special film-reading equipment and a mini-computer. The time and linear gait variables are presented in tabular form and the angles and trajectories of the joints and body segments are presented graphically.

Linear friction welding for constructing and repairing rail for high speed and intercity passenger service rail : final report.

DOT National Transportation Integrated Search

2016-08-01

This project developed a solid-state welding process based on linear friction welding (LFW) technology. While resistance flash welding or : thermite techniques are tried and true methods for joining rails and performing partial rail replacement repai...

High Work, High-Efficiency Turbines for Uninhabited Aerial Vehicles (UAVs)

DTIC Science & Technology

2013-09-01

controlling highly loaded LP turbine blades have been demonstrated in a low speed linear cascade at the AFRL Low Speed Wind Tunnel (LSWT) facility that...34, pp. 1570-1577. [34] Selig M. S. and Mcgranahan, B. D., “ Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbines .” National...aerodynamic flows is of interest in many design domains such as air vehicles, turbomachinery, and wind turbines . Micro-air-vehicles (MAV) which have small

Ramjet Tactical Missile Propulsion Status

DTIC Science & Technology

2002-11-01

EM Linear Actuator Figure 25 - MAR C-R-282Ramjet Figure 26 - AL4RC-R-282Ramjet Testing HIGH SPEED ANTI-RADIATION MISSILE DEMONSRATION ( HSAD ) The High...Speed Anti-Radiation Demonstration ( HSAD ) Project is focused on maturing an advanced propulsion concept that is compatible with the guidance...navigation and control (GNC) section of the Air-Ground Missile-88E (AGM-88f), Advanced Anti-Radiation Guided Missile (AARGM) Program. The HSAD Project

High speed exhaust gas recirculation valve

DOEpatents

Fensom, Rod; Kidder, David J.

2005-01-18

In order to minimize pollutants such as Nox, internal combustion engines typically include an exhaust gas recirculation (EGR) valve that can be used to redirect a portion of exhaust gases to an intake conduit, such as an intake manifold, so that the redirected exhaust gases will be recycled. It is desirable to have an EGR valve with fast-acting capabilities, and it is also desirable to have the EGR valve take up as little space as possible. An exhaust gas recirculation valve is provided that includes an exhaust passage tube, a valve element pivotally mounted within the exhaust passage tube, a linear actuator; and a gear train. The gear train includes a rack gear operatively connected to the linear actuator, and at least one rotatable gear meshing with the rack gear and operatively connected to the valve element to cause rotation of the valve element upon actuation of the linear actuator. The apparatus provides a highly compact package having a high-speed valve actuation capability.

A Dynamic Range Enhanced Readout Technique with a Two-Step TDC for High Speed Linear CMOS Image Sensors.

PubMed

Gao, Zhiyuan; Yang, Congjie; Xu, Jiangtao; Nie, Kaiming

2015-11-06

This paper presents a dynamic range (DR) enhanced readout technique with a two-step time-to-digital converter (TDC) for high speed linear CMOS image sensors. A multi-capacitor and self-regulated capacitive trans-impedance amplifier (CTIA) structure is employed to extend the dynamic range. The gain of the CTIA is auto adjusted by switching different capacitors to the integration node asynchronously according to the output voltage. A column-parallel ADC based on a two-step TDC is utilized to improve the conversion rate. The conversion is divided into coarse phase and fine phase. An error calibration scheme is also proposed to correct quantization errors caused by propagation delay skew within -T(clk)~+T(clk). A linear CMOS image sensor pixel array is designed in the 0.13 μm CMOS process to verify this DR-enhanced high speed readout technique. The post simulation results indicate that the dynamic range of readout circuit is 99.02 dB and the ADC achieves 60.22 dB SNDR and 9.71 bit ENOB at a conversion rate of 2 MS/s after calibration, with 14.04 dB and 2.4 bit improvement, compared with SNDR and ENOB of that without calibration.

A parabolic model of drag coefficient for storm surge simulation in the South China Sea

PubMed Central

Peng, Shiqiu; Li, Yineng

2015-01-01

Drag coefficient (Cd) is an essential metric in the calculation of momentum exchange over the air-sea interface and thus has large impacts on the simulation or forecast of the upper ocean state associated with sea surface winds such as storm surges. Generally, Cd is a function of wind speed. However, the exact relationship between Cd and wind speed is still in dispute, and the widely-used formula that is a linear function of wind speed in an ocean model could lead to large bias at high wind speed. Here we establish a parabolic model of Cd based on storm surge observations and simulation in the South China Sea (SCS) through a number of tropical cyclone cases. Simulation of storm surges for independent Tropical cyclones (TCs) cases indicates that the new parabolic model of Cd outperforms traditional linear models. PMID:26499262

A parabolic model of drag coefficient for storm surge simulation in the South China Sea.

PubMed

Peng, Shiqiu; Li, Yineng

2015-10-26

Drag coefficient (Cd) is an essential metric in the calculation of momentum exchange over the air-sea interface and thus has large impacts on the simulation or forecast of the upper ocean state associated with sea surface winds such as storm surges. Generally, Cd is a function of wind speed. However, the exact relationship between Cd and wind speed is still in dispute, and the widely-used formula that is a linear function of wind speed in an ocean model could lead to large bias at high wind speed. Here we establish a parabolic model of Cd based on storm surge observations and simulation in the South China Sea (SCS) through a number of tropical cyclone cases. Simulation of storm surges for independent Tropical cyclones (TCs) cases indicates that the new parabolic model of Cd outperforms traditional linear models.

A parabolic model of drag coefficient for storm surge simulation in the South China Sea

NASA Astrophysics Data System (ADS)

Peng, Shiqiu; Li, Yineng

2015-10-01

Drag coefficient (Cd) is an essential metric in the calculation of momentum exchange over the air-sea interface and thus has large impacts on the simulation or forecast of the upper ocean state associated with sea surface winds such as storm surges. Generally, Cd is a function of wind speed. However, the exact relationship between Cd and wind speed is still in dispute, and the widely-used formula that is a linear function of wind speed in an ocean model could lead to large bias at high wind speed. Here we establish a parabolic model of Cd based on storm surge observations and simulation in the South China Sea (SCS) through a number of tropical cyclone cases. Simulation of storm surges for independent Tropical cyclones (TCs) cases indicates that the new parabolic model of Cd outperforms traditional linear models.

Solving the aerodynamics of fungal flight: how air viscosity slows spore motion.

PubMed

Fischer, Mark W F; Stolze-Rybczynski, Jessica L; Davis, Diana J; Cui, Yunluan; Money, Nicholas P

2010-01-01

Viscous drag causes the rapid deceleration of fungal spores after high-speed launches and limits discharge distance. Stokes' law posits a linear relationship between drag force and velocity. It provides an excellent fit to experimental measurements of the terminal velocity of free-falling spores and other instances of low Reynolds number motion (Re<1). More complex, non-linear drag models have been devised for movements characterized by higher Re, but their effectiveness for modeling the launch of fast-moving fungal spores has not been tested. In this paper, we use data on spore discharge processes obtained from ultra-high-speed video recordings to evaluate the effects of air viscosity predicted by Stokes' law and a commonly used non-linear drag model. We find that discharge distances predicted from launch speeds by Stokes' model provide a much better match to measured distances than estimates from the more complex drag model. Stokes' model works better over a wide range projectile sizes, launch speeds, and discharge distances, from microscopic mushroom ballistospores discharged at <1 m s(-1) over a distance of <0.1mm (Re<1.0), to macroscopic sporangia of Pilobolus that are launched at >10 m s(-1) and travel as far as 2.5m (Re>100). Copyright © 2010 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Ultra-high speed vacuum pump system with first stage turbofan and second stage turbomolecular pump

DOEpatents

Jostlein, Hans

2006-04-04

An ultra-high speed vacuum pump evacuation system includes a first stage ultra-high speed turbofan and a second stage conventional turbomolecular pump. The turbofan is either connected in series to a chamber to be evacuated, or is optionally disposed entirely within the chamber. The turbofan employs large diameter rotor blades operating at high linear blade velocity to impart an ultra-high pumping speed to a fluid. The second stage turbomolecular pump is fluidly connected downstream from the first stage turbofan. In operation, the first stage turbofan operates in a pre-existing vacuum, with the fluid asserting only small axial forces upon the rotor blades. The turbofan imparts a velocity to fluid particles towards an outlet at a high volume rate, but moderate compression ratio. The second stage conventional turbomolecular pump then compresses the fluid to pressures for evacuation by a roughing pump.

The Shock and Vibration Bulletin. Part 2. Modal and Impedance Analysis, Human Response to Vibration and Shock, Isolation and Damping, Dynamic Analysis

DTIC Science & Technology

1979-09-01

a " high performance fast timing" engine thrust with a mismatch between right and left SRfls...examine the dynamic behavior of a blade having a root geometry compatible with low frictional forces at high rotational speeds , somewhat like a "Christmas...Tree" root, but with a gap introduced which will close up only at high speed . Approximate non-linear equations of motion are derived and solved

Implementing a GPU-based numerical algorithm for modelling dynamics of a high-speed train

NASA Astrophysics Data System (ADS)

Sytov, E. S.; Bratus, A. S.; Yurchenko, D.

2018-04-01

This paper discusses the initiative of implementing a GPU-based numerical algorithm for studying various phenomena associated with dynamics of a high-speed railway transport. The proposed numerical algorithm for calculating a critical speed of the bogie is based on the first Lyapunov number. Numerical algorithm is validated by analytical results, derived for a simple model. A dynamic model of a carriage connected to a new dual-wheelset flexible bogie is studied for linear and dry friction damping. Numerical results obtained by CPU, MPU and GPU approaches are compared and appropriateness of these methods is discussed.

Research on fast algorithm of small UAV navigation in non-linear matrix reductionism method

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Fang, Jiancheng; Sheng, Wei; Cao, Juanjuan

2008-10-01

The low Reynolds numbers of small UAV will result in unfavorable aerodynamic conditions to support controlled flight. And as operated near ground, the small UAV will be affected seriously by low-frequency interference caused by atmospheric disturbance. Therefore, the GNC system needs high frequency of attitude estimation and control to realize the steady of the UAV. In company with the dimensional of small UAV dwindling away, its GNC system is more and more taken embedded designing technology to reach the purpose of compactness, light weight and low power consumption. At the same time, the operational capability of GNC system also gets limit in a certain extent. Therefore, a kind of high speed navigation algorithm design becomes the imminence demand of GNC system. Aiming at such requirement, a kind of non-linearity matrix reduction approach is adopted in this paper to create a new high speed navigation algorithm which holds the radius of meridian circle and prime vertical circle as constant and linearizes the position matrix calculation formulae of navigation equation. Compared with normal navigation algorithm, this high speed navigation algorithm decreases 17.3% operand. Within small UAV"s mission radius (20km), the accuracy of position error is less than 0.13m. The results of semi-physical experiments and small UAV's auto pilot testing proved that this algorithm can realize high frequency attitude estimation and control. It will avoid low-frequency interference caused by atmospheric disturbance properly.

High-Speed Linear Raman Spectroscopy for Instability Analysis of a Bluff Body Flame

NASA Technical Reports Server (NTRS)

Kojima, Jun; Fischer, David

2013-01-01

We report a high-speed laser diagnostics technique based on point-wise linear Raman spectroscopy for measuring the frequency content of a CH4-air premixed flame stabilized behind a circular bluff body. The technique, which primarily employs a Nd:YLF pulsed laser and a fast image-intensified CCD camera, successfully measures the time evolution of scalar parameters (N2, O2, CH4, and H2O) in the vortex-induced flame instability at a data rate of 1 kHz. Oscillation of the V-shaped flame front is quantified through frequency analysis of the combustion species data and their correlations. This technique promises to be a useful diagnostics tool for combustion instability studies.

Machining Chatter Analysis for High Speed Milling Operations

NASA Astrophysics Data System (ADS)

Sekar, M.; Kantharaj, I.; Amit Siddhappa, Savale

2017-10-01

Chatter in high speed milling is characterized by time delay differential equations (DDE). Since closed form solution exists only for simple cases, the governing non-linear DDEs of chatter problems are solved by various numerical methods. Custom codes to solve DDEs are tedious to build, implement and not error free and robust. On the other hand, software packages provide solution to DDEs, however they are not straight forward to implement. In this paper an easy way to solve DDE of chatter in milling is proposed and implemented with MATLAB. Time domain solution permits the study and model of non-linear effects of chatter vibration with ease. Time domain results are presented for various stable and unstable conditions of cut and compared with stability lobe diagrams.

Creation of high-energy electron tails by means of the modified two-stream instability

NASA Technical Reports Server (NTRS)

Tanaka, M.; Papadopoulos, K.

1983-01-01

Particle simulations of the modified two-stream instability demonstrate strong electron acceleration rather than bulk heating when the relative drift speed is below a critical speed Vc. A very interesting nonlinear mode transition and autoresonance acceleration process is observed which accelerates the electrons much above the phase speed of the linearly unstable modes. Simple criteria are presented that predict the value of Vc and the number density of the accelerated electrons.

Combined linear theory/impact theory method for analysis and design of high speed configurations

NASA Technical Reports Server (NTRS)

Brooke, D.; Vondrasek, D. V.

1980-01-01

Pressure distributions on a wing body at Mach 4.63 are calculated. The combined theory is shown to give improved predictions over either linear theory or impact theory alone. The combined theory is also applied in the inverse design mode to calculate optimum camber slopes at Mach 4.63. Comparisons with optimum camber slopes obtained from unmodified linear theory show large differences. Analysis of the results indicate that the combined theory correctly predicts the effect of thickness on the loading distributions at high Mach numbers, and that finite thickness wings optimized at high Mach numbers using unmodified linear theory will not achieve the minimum drag characteristics for which they are designed.

An Efficient Fuzzy Controller Design for Parallel Connected Induction Motor Drives

NASA Astrophysics Data System (ADS)

Usha, S.; Subramani, C.

2018-04-01

Generally, an induction motors are highly non-linear and has a complex time varying dynamics. This makes the speed control of an induction motor a challenging issue in the industries. But, due to the recent trends in the power electronic devices and intelligent controllers, the speed control of the induction motor is achieved by including non-linear characteristics also. Conventionally a single inverter is used to run one induction motor in industries. In the traction applications, two or more inductions motors are operated in parallel to reduce the size and cost of induction motors. In this application, the parallel connected induction motors can be driven by a single inverter unit. The stability problems may introduce in the parallel operation under low speed operating conditions. Hence, the speed deviations should be reduce with help of suitable controllers. The speed control of the parallel connected system is performed by PID controller and fuzzy logic controller. In this paper the speed response of the induction motor for the rating of IHP, 1440 rpm, and 50Hz with these controller are compared in time domain specifications. The stability analysis of the system also performed under low speed using matlab platform. The hardware model is developed for speed control using fuzzy logic controller which exhibited superior performances over the other controller.

Observations of micro-turbulence in the solar wind near the sun with interplanetary scintillation

NASA Technical Reports Server (NTRS)

Yamauchi, Y.; Misawa, H.; Kojima, M.; Mori, H.; Tanaka, T.; Takaba, H.; Kondo, T.; Tokumaru, M.; Manoharan, P. K.

1995-01-01

Velocity and density turbulence of solar wind were inferred from interplanetary scintillation (IPS) observations at 2.3 GHz and 8.5 GHz using a single-antenna. The observations were made during September and October in 1992 - 1994. They covered the distance range between 5 and 76 solar radii (Rs). We applied the spectrum fitting method to obtain a velocity, an axial ratio, an inner scale and a power-law spectrum index. We examined the difference of the turbulence properties near the Sun between low-speed solar wind and high-speed solar wind. Both of solar winds showed acceleration at the distance range of 10 - 30 Rs. The radial dependence of anisotropy and spectrum index did not have significant difference between low-speed and high-speed solar winds. Near the sun, the radial dependence of the inner scale showed the separation from the linear relation as reported by previous works. We found that the inner scale of high-speed solar wind is larger than that of low-speed wind.

Transient Vibration Prediction for Rotors on Ball Bearings Using Load-dependent Non-linear Bearing Stiffness

NASA Technical Reports Server (NTRS)

Fleming, David P.; Poplawski, J. V.

2002-01-01

Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for non-linear speed and load dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis - Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running 5 degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller beatings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.

Energy efficient fluid powered linear actuator with variable area

DOEpatents

Lind, Randall F.; Love, Lonnie J.

2016-09-13

Hydraulic actuation systems having variable displacements and energy recovery capabilities include cylinders with pistons disposed inside of barrels. When operating in energy consuming modes, high speed valves pressurize extension chambers or retraction chambers to provide enough force to meet or counteract an opposite load force. When operating in energy recovery modes, high speed valves return a working fluid from extension chambers or retraction chambers, which are pressurized by a load, to an accumulator for later use.

Effect of vanadium carbide on dry sliding wear behavior of powder metallurgy AISI M2 high speed steel processed by concentrated solar energy

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

García, C.

Mixtures of AISI M2 high speed steel and vanadium carbide (3, 6 or 10 wt.%) were prepared by powder metallurgy and sintered by concentrated solar energy (CSE). Two different powerful solar furnaces were employed to sinter the parts and the results were compared with those obtained by conventional powder metallurgy using a tubular electric furnace. CSE allowed significant reduction of processing times and high heating rates. The wear resistance of compacts was studied by using rotating pin-on-disk and linearly reciprocating ball-on-flat methods. Wear mechanisms were investigated by means of scanning electron microscopy (SEM) observations and chemical inspections of the microstructuresmore » of the samples. Better wear properties than those obtained by conventional powder metallurgy were achieved. The refinement of the microstructure and the formation of carbonitrides were the reasons for this. - Highlights: •Powder metallurgy of mixtures of M2 high speed steel and VC are studied. •Some sintering is done by concentrated solar energy. •Rotating pin-on-disk and linearly reciprocating ball-on-flat methods are used. •The tribological properties and wear mechanisms, under dry sliding, are studied.« less

Performance Optimization Design for a High-Speed Weak FBG Interrogation System Based on DFB Laser.

PubMed

Yao, Yiqiang; Li, Zhengying; Wang, Yiming; Liu, Siqi; Dai, Yutang; Gong, Jianmin; Wang, Lixin

2017-06-22

A performance optimization design for a high-speed fiber Bragg grating (FBG) interrogation system based on a high-speed distributed feedback (DFB) swept laser is proposed. A time-division-multiplexing sensor network with identical weak FBGs is constituted to realize high-capacity sensing. In order to further improve the multiplexing capacity, a waveform repairing algorithm is designed to extend the dynamic demodulation range of FBG sensors. It is based on the fact that the spectrum of an FBG keeps stable over a long period of time. Compared with the pre-collected spectra, the distorted spectra waveform are identified and repaired. Experimental results show that all the identical weak FBGs are distinguished and demodulated at the speed of 100 kHz with a linearity of above 0.99, and the range of dynamic demodulation is extended by 40%.

Performance Optimization Design for a High-Speed Weak FBG Interrogation System Based on DFB Laser

PubMed Central

Yao, Yiqiang; Li, Zhengying; Wang, Yiming; Liu, Siqi; Dai, Yutang; Gong, Jianmin; Wang, Lixin

2017-01-01

A performance optimization design for a high-speed fiber Bragg grating (FBG) interrogation system based on a high-speed distributed feedback (DFB) swept laser is proposed. A time-division-multiplexing sensor network with identical weak FBGs is constituted to realize high-capacity sensing. In order to further improve the multiplexing capacity, a waveform repairing algorithm is designed to extend the dynamic demodulation range of FBG sensors. It is based on the fact that the spectrum of an FBG keeps stable over a long period of time. Compared with the pre-collected spectra, the distorted spectra waveform are identified and repaired. Experimental results show that all the identical weak FBGs are distinguished and demodulated at the speed of 100 kHz with a linearity of above 0.99, and the range of dynamic demodulation is extended by 40%. PMID:28640187

The evolution of methods for noise prediction of high speed rotors and propellers in the time domain

NASA Technical Reports Server (NTRS)

Farassat, F.

1986-01-01

Linear wave equation models which have been used over the years at NASA Langley for describing noise emissions from high speed rotating blades are summarized. The noise sources are assumed to lie on a moving surface, and analysis of the situation has been based on the Ffowcs Williams-Hawkings (FW-H) equation. Although the equation accounts for two surface and one volume source, the NASA analyses have considered only the surface terms. Several variations on the FW-H model are delineated for various types of applications, noting the computational benefits of removing the frequency dependence of the calculations. Formulations are also provided for compact and noncompact sources, and features of Long's subsonic integral equation and Farassat's high speed integral equation are discussed. The selection of subsonic or high speed models is dependent on the Mach number of the blade surface where the source is located.

The Relationship between a Linear Combination of Intelligence, Musical Background, Rhythm Ability and Tapping Ability to Typewriting Speed and Accuracy.

ERIC Educational Resources Information Center

Fante, Cheryl H.

This study was conducted in an attempt to identify any predictor or combination of predictors of a beginning typewriting student's success. Variables of intelligence, rhythmic ability, musical background, and tapping ability were combined to study their relationship to typewriting speed and accuracy. A sample of 109 high school students was…

Wind Resource Assessment in Complex Terrain with a High-Resolution Numerical Weather Prediction Model

NASA Astrophysics Data System (ADS)

Gruber, Karin; Serafin, Stefano; Grubišić, Vanda; Dorninger, Manfred; Zauner, Rudolf; Fink, Martin

2014-05-01

A crucial step in planning new wind farms is the estimation of the amount of wind energy that can be harvested in possible target sites. Wind resource assessment traditionally entails deployment of masts equipped for wind speed measurements at several heights for a reasonably long period of time. Simplified linear models of atmospheric flow are then used for a spatial extrapolation of point measurements to a wide area. While linear models have been successfully applied in the wind resource assessment in plains and offshore, their reliability in complex terrain is generally poor. This represents a major limitation to wind resource assessment in Austria, where high-altitude locations are being considered for new plant sites, given the higher frequency of sustained winds at such sites. The limitations of linear models stem from two key assumptions in their formulation, the neutral stratification and attached boundary-layer flow, both of which often break down in complex terrain. Consequently, an accurate modeling of near-surface flow over mountains requires the adoption of a NWP model with high horizontal and vertical resolution. This study explores the wind potential of a site in Styria in the North-Eastern Alps. The WRF model is used for simulations with a maximum horizontal resolution of 800 m. Three nested computational domains are defined, with the innermost one encompassing a stretch of the relatively broad Enns Valley, flanked by the main crest of the Alps in the south and the Nördliche Kalkalpen of similar height in the north. In addition to the simulation results, we use data from fourteen 10-m wind measurement sites (of which 7 are located within valleys and 5 near mountain tops) and from 2 masts with anemometers at several heights (at hillside locations) in an area of 1600 km2 around the target site. The potential for wind energy production is assessed using the mean wind speed and turbulence intensity at hub height. The capacity factor is also evaluated, considering the frequency of wind speed between cut-in and cut-out speed and of winds with a low vertical velocity component only. Wind turbines do not turn on at wind speeds below cut-in speed. Wind turbines are taken off from the generator in the case of wind speeds higher than cut-out speed and inclination angles of the wind vector greater than 8o. All of these parameters were computed at each model grid point in the innermost domain in order to map their spatial variability. The results show that in complex terrain the annual mean wind speed at hub height is not sufficient to predict the capacity factor of a turbine; vertical wind speed and the frequency of horizontal wind speed out of the range of cut-in and cut-out speed contribute substantially to a reduction of the energy harvest and locally high turbulence may considerably raise the building costs.

MEASUREMENT OF WIND SPEED FROM COOLING LAKE THERMAL IMAGERY

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

Garrett, A; Robert Kurzeja, R; Eliel Villa-Aleman, E

2009-01-20

The Savannah River National Laboratory (SRNL) collected thermal imagery and ground truth data at two commercial power plant cooling lakes to investigate the applicability of laboratory empirical correlations between surface heat flux and wind speed, and statistics derived from thermal imagery. SRNL demonstrated in a previous paper [1] that a linear relationship exists between the standard deviation of image temperature and surface heat flux. In this paper, SRNL will show that the skewness of the temperature distribution derived from cooling lake thermal images correlates with instantaneous wind speed measured at the same location. SRNL collected thermal imagery, surface meteorology andmore » water temperatures from helicopters and boats at the Comanche Peak and H. B. Robinson nuclear power plant cooling lakes. SRNL found that decreasing skewness correlated with increasing wind speed, as was the case for the laboratory experiments. Simple linear and orthogonal regression models both explained about 50% of the variance in the skewness - wind speed plots. A nonlinear (logistic) regression model produced a better fit to the data, apparently because the thermal convection and resulting skewness are related to wind speed in a highly nonlinear way in nearly calm and in windy conditions.« less

The Development of a High Speed Exponential Function Generator for Linearization of Microwave Voltage Controlled Oscillators.

DTIC Science & Technology

1985-10-01

characteristic of a p-n junction to provide exponential linearization in a simple, thermally-stable, wide band circuit. RESME Les oscillateurs A...exponentielle (fr6quence/tension) que V’on 1 retrouve chez plusieurs oscillateurs . Ce circuit, d’une grande largeur de bande, utilise la caractfiristique

Development of a High-speed Electromagnetic Repulsion Mechanism for High-voltage Vacuum Circuit Breakers

NASA Astrophysics Data System (ADS)

Tsukima, Mitsuru; Takeuchi, Toshie; Koyama, Kenichi; Yoshiyasu, Hajimu

This paper presents a design and testing of a new high-speed electromagnetic driving mechanism for a high-voltage vacuum circuit breaker (VCB). This mechanism is based on a high-speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3d non-linear finite-elements magnetic field analysis and investigated its internal friction and eddy-current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics—contact velocity, response time and so on, required for the high-speed VCB. A prototype VCB, which was built based on the above analysis shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance.

Energy efficient fluid powered linear actuator with variable area and concentric chambers

DOEpatents

Lind, Randall F.; Love, Lonnie J.

2016-11-15

Hydraulic actuation systems having concentric chambers, variable displacements and energy recovery capabilities include cylinders with pistons disposed inside of barrels. When operating in energy consuming modes, high speed valves pressurize extension chambers or retraction chambers to provide enough force to meet or counteract an opposite load force. When operating in energy recovery modes, high speed valves return a working fluid from extension chambers or retraction chambers, which are pressurized by a load, to an accumulator for later use.

Dark-count-less photon-counting x-ray computed tomography system using a YAP-MPPC detector

NASA Astrophysics Data System (ADS)

Sato, Eiichi; Sato, Yuich; Abudurexiti, Abulajiang; Hagiwara, Osahiko; Matsukiyo, Hiroshi; Osawa, Akihiro; Enomoto, Toshiyuki; Watanabe, Manabu; Kusachi, Shinya; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

2012-10-01

A high-sensitive X-ray computed tomography (CT) system is useful for decreasing absorbed dose for patients, and a dark-count-less photon-counting CT system was developed. X-ray photons are detected using a YAP(Ce) [cerium-doped yttrium aluminum perovskite] single crystal scintillator and an MPPC (multipixel photon counter). Photocurrents are amplified by a high-speed current-voltage amplifier, and smooth event pulses from an integrator are sent to a high-speed comparator. Then, logical pulses are produced from the comparator and are counted by a counter card. Tomography is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by the linear scan. The image contrast of gadolinium medium slightly fell with increase in lower-level voltage (Vl) of the comparator. The dark count rate was 0 cps, and the count rate for the CT was approximately 250 kcps.

High-speed cylindrical collapse of two perfect fluids

NASA Astrophysics Data System (ADS)

Sharif, M.; Ahmad, Zahid

2007-09-01

In this paper, the study of the gravitational collapse of cylindrically distributed two perfect fluid system has been carried out. It is assumed that the collapsing speeds of the two fluids are very large. We explore this condition by using the high-speed approximation scheme. There arise two cases, i.e., bounded and vanishing of the ratios of the pressures with densities of two fluids given by c s , d s . It is shown that the high-speed approximation scheme breaks down by non-zero pressures p 1, p 2 when c s , d s are bounded below by some positive constants. The failure of the high-speed approximation scheme at some particular time of the gravitational collapse suggests the uncertainty on the evolution at and after this time. In the bounded case, the naked singularity formation seems to be impossible for the cylindrical two perfect fluids. For the vanishing case, if a linear equation of state is used, the high-speed collapse does not break down by the effects of the pressures and consequently a naked singularity forms. This work provides the generalisation of the results already given by Nakao and Morisawa (Prog Theor Phys 113:73, 2005) for the perfect fluid.

Photoacoustic thermal flowmetry with a single light source

NASA Astrophysics Data System (ADS)

Liu, Wei; Lan, Bangxin; Hu, Leo; Chen, Ruimin; Zhou, Qifa; Yao, Junjie

2017-09-01

We report a photoacoustic thermal flowmetry based on optical-resolution photoacoustic microscopy (OR-PAM) using a single laser source for both thermal tagging and photoacoustic excitation. When an optically absorbing medium is flowing across the optical focal zone of OR-PAM, a small volume of the medium within the optical focus is repeatedly illuminated and heated by a train of laser pulses with a high repetition rate. The average temperature of the heated volume at each laser pulse is indicated by the photoacoustic signal excited by the same laser pulse due to the well-established linear relationship between the Grueneisen coefficient and the local temperature. The thermal dynamics of the heated medium volume, which are closely related to the flow speed, can therefore be measured from the time course of the detected photoacoustic signals. Here, we have developed a lumped mathematical model to describe the time course of the photoacoustic signals as a function of the medium's flow speed. We conclude that the rising time constant of the photoacoustic signals is linearly dependent on the flow speed. Thus, the flow speed can be quantified by fitting the measured photoacoustic signals using the derived mathematical model. We first performed proof-of-concept experiments using defibrinated bovine blood flowing in a plastic tube. The experiment results have demonstrated that the proposed method has high accuracy (˜±6%) and a wide range of measurable flow speeds. We further validated the method by measuring the blood flow speeds of the microvasculature in a mouse ear in vivo.

A hierarchy for modeling high speed propulsion systems

NASA Technical Reports Server (NTRS)

Hartley, Tom T.; Deabreu, Alex

1991-01-01

General research efforts on reduced order propulsion models for control systems design are overviewed. Methods for modeling high speed propulsion systems are discussed including internal flow propulsion systems that do not contain rotating machinery, such as inlets, ramjets, and scramjets. The discussion is separated into four areas: (1) computational fluid dynamics models for the entire nonlinear system or high order nonlinear models; (2) high order linearized models derived from fundamental physics; (3) low order linear models obtained from the other high order models; and (4) low order nonlinear models (order here refers to the number of dynamic states). Included in the discussion are any special considerations based on the relevant control system designs. The methods discussed are for the quasi-one-dimensional Euler equations of gasdynamic flow. The essential nonlinear features represented are large amplitude nonlinear waves, including moving normal shocks, hammershocks, simple subsonic combustion via heat addition, temperature dependent gases, detonations, and thermal choking. The report also contains a comprehensive list of papers and theses generated by this grant.

Dynamical relationship between wind speed magnitude and meridional temperature contrast: Application to an interannual oscillation in Venusian middle atmosphere GCM

NASA Astrophysics Data System (ADS)

Yamamoto, Masaru; Takahashi, Masaaki

2018-03-01

We derive simple dynamical relationships between wind speed magnitude and meridional temperature contrast. The relationship explains scatter plot distributions of time series of three variables (maximum zonal wind speed UMAX, meridional wind speed VMAX, and equator-pole temperature contrast dTMAX), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX regime. The scatter plot distributions are qualitatively consistent with a quadratic equation obtained from a diagnostic equation of the stream function above the cloud top. The plotted points in the scatter diagrams form a linear cluster for weak wave forcing, whereas they form a small cluster for strong wave forcing. An interannual oscillation of the general circulation forming the linear cluster in the scatter diagram is apparent in the experiment of weak 5.5-day wave forcing. Although a pair of equatorial Kelvin and high-latitude Rossby waves with a same period (Kelvin-Rossby wave) produces equatorward heat and momentum fluxes in the region below 60 km, the equatorial wave does not contribute to the long-period oscillation. The interannual fluctuation of the high-latitude jet core leading to the time variation of UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

Eigenvalue assignment strategies in rotor systems

NASA Technical Reports Server (NTRS)

Youngblood, J. N.; Welzyn, K. J.

1986-01-01

The work done to establish the control and direction of effective eigenvalue excursions of lightly damped, speed dependent rotor systems using passive control is discussed. Both second order and sixth order bi-axis, quasi-linear, speed dependent generic models were investigated. In every case a single, bi-directional control bearing was used in a passive feedback stabilization loop to resist modal destabilization above the rotor critical speed. Assuming incomplete state measurement, sub-optimal control strategies were used to define the preferred location of the control bearing, the most effective measurement locations, and the best set of control gains to extend the speed range of stable operation. Speed dependent control gains were found by Powell's method to maximize the minimum modal damping ratio for the speed dependent linear model. An increase of 300 percent in stable speed operation was obtained for the sixth order linear system using passive control. Simulations were run to examine the effectiveness of the linear control law on nonlinear rotor models with bearing deadband. The maximum level of control effort (force) required by the control bearing to stabilize the rotor at speeds above the critical was determined for the models with bearing deadband.

Three-dimensional Finite Element Formulation and Scalable Domain Decomposition for High Fidelity Rotor Dynamic Analysis

NASA Technical Reports Server (NTRS)

Datta, Anubhav; Johnson, Wayne R.

2009-01-01

This paper has two objectives. The first objective is to formulate a 3-dimensional Finite Element Model for the dynamic analysis of helicopter rotor blades. The second objective is to implement and analyze a dual-primal iterative substructuring based Krylov solver, that is parallel and scalable, for the solution of the 3-D FEM analysis. The numerical and parallel scalability of the solver is studied using two prototype problems - one for ideal hover (symmetric) and one for a transient forward flight (non-symmetric) - both carried out on up to 48 processors. In both hover and forward flight conditions, a perfect linear speed-up is observed, for a given problem size, up to the point of substructure optimality. Substructure optimality and the linear parallel speed-up range are both shown to depend on the problem size as well as on the selection of the coarse problem. With a larger problem size, linear speed-up is restored up to the new substructure optimality. The solver also scales with problem size - even though this conclusion is premature given the small prototype grids considered in this study.

Fine Tuning the CJ Detonation Speed of a High Explosive products Equation of State

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

Menikoff, Ralph

For high explosive (HE) simulations, inaccuracies of a per cent or two in the detonation wave speed can result from not suficiently resolving the reaction zone width or from small inaccuracies in calibrating the products equation of state (EOS) or from variation of HE lots. More accurate detonation speeds can be obtained by ne tuning the equation of state to compensate. Here we show that two simple EOS transformations can be used to adjust the CJ detonation speed by a couple of per cent with minimal effect on the CJ release isentrope. The two transformations are (1) a shift inmore » the energy origin and (2) a linear scaling of the speci c volume. The effectiveness of the transformations is demonstrated with simulations of the cylinder test for PBX 9502 starting with a products EOS for which the CJ detonation speed is 1 per cent too low.« less

High-Speed Edge-Detecting Line Scan Smart Camera

NASA Technical Reports Server (NTRS)

Prokop, Norman F.

2012-01-01

A high-speed edge-detecting line scan smart camera was developed. The camera is designed to operate as a component in a NASA Glenn Research Center developed inlet shock detection system. The inlet shock is detected by projecting a laser sheet through the airflow. The shock within the airflow is the densest part and refracts the laser sheet the most in its vicinity, leaving a dark spot or shadowgraph. These spots show up as a dip or negative peak within the pixel intensity profile of an image of the projected laser sheet. The smart camera acquires and processes in real-time the linear image containing the shock shadowgraph and outputting the shock location. Previously a high-speed camera and personal computer would perform the image capture and processing to determine the shock location. This innovation consists of a linear image sensor, analog signal processing circuit, and a digital circuit that provides a numerical digital output of the shock or negative edge location. The smart camera is capable of capturing and processing linear images at over 1,000 frames per second. The edges are identified as numeric pixel values within the linear array of pixels, and the edge location information can be sent out from the circuit in a variety of ways, such as by using a microcontroller and onboard or external digital interface to include serial data such as RS-232/485, USB, Ethernet, or CAN BUS; parallel digital data; or an analog signal. The smart camera system can be integrated into a small package with a relatively small number of parts, reducing size and increasing reliability over the previous imaging system..

Influence of "J"-Curve Spring Stiffness on Running Speeds of Segmented Legs during High-Speed Locomotion.

PubMed

Wang, Runxiao; Zhao, Wentao; Li, Shujun; Zhang, Shunqi

2016-01-01

Both the linear leg spring model and the two-segment leg model with constant spring stiffness have been broadly used as template models to investigate bouncing gaits for legged robots with compliant legs. In addition to these two models, the other stiffness leg spring models developed using inspiration from biological characteristic have the potential to improve high-speed running capacity of spring-legged robots. In this paper, we investigate the effects of "J"-curve spring stiffness inspired by biological materials on running speeds of segmented legs during high-speed locomotion. Mathematical formulation of the relationship between the virtual leg force and the virtual leg compression is established. When the SLIP model and the two-segment leg model with constant spring stiffness and with "J"-curve spring stiffness have the same dimensionless reference stiffness, the two-segment leg model with "J"-curve spring stiffness reveals that (1) both the largest tolerated range of running speeds and the tolerated maximum running speed are found and (2) at fast running speed from 25 to 40/92 m s -1 both the tolerated range of landing angle and the stability region are the largest. It is suggested that the two-segment leg model with "J"-curve spring stiffness is more advantageous for high-speed running compared with the SLIP model and with constant spring stiffness.

Influence of “J”-Curve Spring Stiffness on Running Speeds of Segmented Legs during High-Speed Locomotion

PubMed Central

2016-01-01

Both the linear leg spring model and the two-segment leg model with constant spring stiffness have been broadly used as template models to investigate bouncing gaits for legged robots with compliant legs. In addition to these two models, the other stiffness leg spring models developed using inspiration from biological characteristic have the potential to improve high-speed running capacity of spring-legged robots. In this paper, we investigate the effects of “J”-curve spring stiffness inspired by biological materials on running speeds of segmented legs during high-speed locomotion. Mathematical formulation of the relationship between the virtual leg force and the virtual leg compression is established. When the SLIP model and the two-segment leg model with constant spring stiffness and with “J”-curve spring stiffness have the same dimensionless reference stiffness, the two-segment leg model with “J”-curve spring stiffness reveals that (1) both the largest tolerated range of running speeds and the tolerated maximum running speed are found and (2) at fast running speed from 25 to 40/92 m s−1 both the tolerated range of landing angle and the stability region are the largest. It is suggested that the two-segment leg model with “J”-curve spring stiffness is more advantageous for high-speed running compared with the SLIP model and with constant spring stiffness. PMID:28018127

A Standard for RF Modulation Factor,

DTIC Science & Technology

1979-09-01

Mathematics of Physics and Chemistry, pp. 474-477 (D. Van Nostrand Co., Inc., New York, N.Y., 1943). [23] Graybill , F. A., An Introduction to Linear ...circuit model . The primary limitation on the quadratic technique is the linearity and bandwidth of the analog multiplier. A high speed (5 MHz...o ...... . ..... 39 7.2.1. Nonlinearity Model ............................................... 41 7.2.2. Model Parameters

Investigation on Prototype Superconducting Linear Synchronous Motor (LSM) for 600-km/h Wheel-Type Railway

NASA Astrophysics Data System (ADS)

Eom, Beomyong; Lee, Changhyeong; Kim, Seokho; Lee, Changyoung; Yun, Sangwon

The existing wheel-type high-speed railway with a rotatable motor has a limit of 600 km/h speed. The normal conducting electromagnet has several disadvantages to realize 600 km/h speed. Several disadvantages are the increased space and weight, and the decreased electric efficiency to generate the required high magnetic field. In order to reduce the volume and weight, superconducting electromagnets can be considered for LSM (Linear Synchronous Motor). Prior to the fabrication of the real system, a prototype demo-coil is designed and fabricated using 2G high temperature superconducting wire. The prototype HTS coil is cooled by the conduction using a GM cryocooler. To reduce the heat penetration, thermal design was performed for the current leads, supporting structure and radiation shield considering the thermal stress. The operating temperature and current are 30∼40 K and 100 A. The coil consists of two double pancake coils (N, S pole, respectively) and it is driven on a test rail, which is installed for the test car. This paper describes the design and test results of the prototype HTS LSM system. Thermal characteristics are investigated with additional dummy thermal mass on the coil after turning off the cryocooler.

Finite element analysis of high aspect ratio wind tunnel wing model: A parametric study

NASA Astrophysics Data System (ADS)

Rosly, N. A.; Harmin, M. Y.

2017-12-01

Procedure for designing the wind tunnel model of a high aspect ratio (HAR) wing containing geometric nonlinearities is described in this paper. The design process begins with identification of basic features of the HAR wing as well as its design constraints. This enables the design space to be narrowed down and consequently, brings ease of convergence towards the design solution. Parametric studies in terms of the spar thickness, the span length and the store diameter are performed using finite element analysis for both undeformed and deformed cases, which respectively demonstrate the linear and nonlinear conditions. Two main criteria are accounted for in the selection of the wing design: the static deflections due to gravitational loading should be within the allowable margin of the size of the wind tunnel test section and the flutter speed of the wing should be much below the maximum speed of the wind tunnel. The findings show that the wing experiences a stiffness hardening effect under the nonlinear static solution and the presence of the store enables significant reduction in linear flutter speed.

Advances in CCD detector technology for x-ray diffraction applications

NASA Astrophysics Data System (ADS)

Thorson, Timothy A.; Durst, Roger D.; Frankel, Dan; Bordwell, Rex L.; Camara, Jose R.; Leon-Guerrero, Edward; Onishi, Steven K.; Pang, Francis; Vu, Paul; Westbrook, Edwin M.

2004-01-01

Phosphor-coupled CCDs are established as one of the most successful technologies for x-ray diffraction. This application demands that the CCD simultaneously achieve both the highest possible sensitivity and high readout speeds. Recently, wafer-scale, back illuminated devices have become available which offer significantly higher quantum efficiency than conventional devices (the Fairchild Imaging CCD 486 BI). However, since back thinning significantly changes the electrical properties of the CCD the high speed operation of wafer-scale, back-illuminated devices is not well understood. Here we describe the operating characteristics (including noise, linearity, full well capacity and CTE) of the back-illuminated CCD 486 at readout speeds up to 4 MHz.

Analysis of propulsion system dynamics in the validation of a high-order state space model of the UH-60

NASA Technical Reports Server (NTRS)

Kim, Frederick D.

1992-01-01

Frequency responses generated from a high-order linear model of the UH-60 Black Hawk have shown that the propulsion system influences significantly the vertical and yaw dynamics of the aircraft at frequencies important to high-bandwidth control law designs. The inclusion of the propulsion system comprises the latest step in the development of a high-order linear model of the UH-60 that models additionally the dynamics of the fuselage, rotor, and inflow. A complete validation study of the linear model is presented in the frequency domain for both on-axis and off-axis coupled responses in the hoverflight condition, and on-axis responses for forward speeds of 80 and 120 knots.

Solid-state NMR imaging system

DOEpatents

Gopalsami, Nachappa; Dieckman, Stephen L.; Ellingson, William A.

1992-01-01

An apparatus for use with a solid-state NMR spectrometer includes a special imaging probe with linear, high-field strength gradient fields and high-power broadband RF coils using a back projection method for data acquisition and image reconstruction, and a real-time pulse programmer adaptable for use by a conventional computer for complex high speed pulse sequences.

(abstract) A High Throughput 3-D Inner Product Processor

NASA Technical Reports Server (NTRS)

Daud, Tuan

1996-01-01

A particularily challenging image processing application is the real time scene acquisition and object discrimination. It requires spatio-temporal recognition of point and resolved objects at high speeds with parallel processing algorithms. Neural network paradigms provide fine grain parallism and, when implemented in hardware, offer orders of magnitude speed up. However, neural networks implemented on a VLSI chip are planer architectures capable of efficient processing of linear vector signals rather than 2-D images. Therefore, for processing of images, a 3-D stack of neural-net ICs receiving planar inputs and consuming minimal power are required. Details of the circuits with chip architectures will be described with need to develop ultralow-power electronics. Further, use of the architecture in a system for high-speed processing will be illustrated.

Analog-to-digital conversion techniques for precision photometry

NASA Technical Reports Server (NTRS)

Opal, Chet B.

1988-01-01

Three types of analog-to-digital converters are described: parallel, successive-approximation, and integrating. The functioning of comparators and sample-and-hold amplifiers is explained. Differential and integral linearity are defined, and good and bad examples are illustrated. The applicability and relative advantages of the three types of converters for precision astronomical photometric measurements are discussed. For most measurements, integral linearity is more important than differential linearity. Successive-approximation converters should be used with multielement solid state detectors because of their high speed, but dual slope integrating converters may be superior for use with single element solid state detectors where speed of digitization is not a factor. In all cases, the input signal should be tailored so that they occupy the upper part of the converter's dynamic range; this can be achieved by providing adjustable gain, or better by varying the integration time of the observation if possible.

Nonlinear effects of stretch on the flame front propagation

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

Halter, F.; Tahtouh, T.; Mounaim-Rousselle, C.

2010-10-15

In all experimental configurations, the flames are affected by stretch (curvature and/or strain rate). To obtain the unstretched flame speed, independent of the experimental configuration, the measured flame speed needs to be corrected. Usually, a linear relationship linking the flame speed to stretch is used. However, this linear relation is the result of several assumptions, which may be incorrected. The present study aims at evaluating the error in the laminar burning speed evaluation induced by using the traditional linear methodology. Experiments were performed in a closed vessel at atmospheric pressure for two different mixtures: methane/air and iso-octane/air. The initial temperaturesmore » were respectively 300 K and 400 K for methane and iso-octane. Both methodologies (linear and nonlinear) are applied and results in terms of laminar speed and burned gas Markstein length are compared. Methane and iso-octane were chosen because they present opposite evolutions in their Markstein length when the equivalence ratio is increased. The error induced by the linear methodology is evaluated, taking the nonlinear methodology as the reference. It is observed that the use of the linear methodology starts to induce substantial errors after an equivalence ratio of 1.1 for methane/air mixtures and before an equivalence ratio of 1 for iso-octane/air mixtures. One solution to increase the accuracy of the linear methodology for these critical cases consists in reducing the number of points used in the linear methodology by increasing the initial flame radius used. (author)« less

Gender difference in cycling speed and age of winning performers in ultra-cycling - the 508-mile "Furnace Creek" from 1983 to 2012.

PubMed

Rüst, Christoph Alexander; Rosemann, Thomas; Lepers, Romuald; Knechtle, Beat

2015-01-01

We analysed (i) the gender difference in cycling speed and (ii) the age of winning performers in the 508-mile "Furnace Creek 508". Changes in cycling speeds and gender differences from 1983 to 2012 were analysed using linear, non-linear and hierarchical multi-level regression analyses for the annual three fastest women and men. Cycling speed increased non-linearly in men from 14.6 (s = 0.3) km · h(-1) (1983) to 27.1 (s = 0.7) km · h(-1) (2012) and non-linearly in women from 11.0 (s = 0.3) km · h(-1) (1984) to 24.2 (s = 0.2) km · h(-1) (2012). The gender difference in cycling speed decreased linearly from 26.2 (s = 0.5)% (1984) to 10.7 (s = 1.9)% (2012). The age of winning performers increased from 26 (s = 2) years (1984) to 43 (s = 11) years (2012) in women and from 33 (s = 6) years (1983) to 50 (s = 5) years (2012) in men. To summarise, these results suggest that (i) women will be able to narrow the gender gap in cycling speed in the near future in an ultra-endurance cycling race such as the "Furnace Creek 508" due to the linear decrease in gender difference and (ii) the maturity of these athletes has changed during the last three decades where winning performers become older and faster across years.

Effect of surface tension on the dynamical behavior of bubble in rotating fluids under low gravity environment

NASA Technical Reports Server (NTRS)

Hung, R. J.; Tsao, Y. D.; Leslie, Fred W.; Hong, B. B.

1988-01-01

Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) linear functions of increasing and decreasing gravity enviroment in high and low rotating cylidner speeds, (3) step functions of spin-up and spin-down in a low gravity environment, and (4) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie (1988), and Hung et al. (1988).

Dynamical behavior of surface tension on rotating fluids in low and microgravity environments

NASA Technical Reports Server (NTRS)

Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.

1989-01-01

Consideration is given to the time-dependent evolutions of the free surface profile (bubble shapes) of a cylindrical container, partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry in low and microgravity environments. The dynamics of the bubble shapes are calculated for four cases: linear time-dependent functions of spin-up and spin-down in low and microgravity, linear time-dependent functions of increasing and decreasing gravity at high and low rotating cylinder speeds, time-dependent step functions of spin-up and spin-down in low gravity, and sinusoidal function oscillation of the gravity environment in high and low rotating cylinder speeds. It is shown that the computer algorithms developed by Hung et al. (1988) may be used to simulate the profile of time-dependent bubble shapes under variations of centrifugal, capillary, and gravity forces.

Nonlinear SVM-DTC for induction motor drive using input-output feedback linearization and high order sliding mode control.

PubMed

Ammar, Abdelkarim; Bourek, Amor; Benakcha, Abdelhamid

2017-03-01

This paper presents a nonlinear Direct Torque Control (DTC) strategy with Space Vector Modulation (SVM) for an induction motor. A nonlinear input-output feedback linearization (IOFL) is implemented to achieve a decoupled torque and flux control and the SVM is employed to reduce high torque and flux ripples. Furthermore, the control scheme performance is improved by inserting a super twisting speed controller in the outer loop and a load torque observer to enhance the speed regulation. The combining of dual nonlinear strategies ensures a good dynamic and robustness against parameters variation and disturbance. The system stability has been analyzed using Lyapunov stability theory. The effectiveness of the control algorithm is investigated by simulation and experimental validation using Matlab/Simulink software with real-time interface based on dSpace 1104. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Nonlinear waves in reaction-diffusion systems: The effect of transport memory

NASA Astrophysics Data System (ADS)

Manne, K. K.; Hurd, A. J.; Kenkre, V. M.

2000-04-01

Motivated by the problem of determining stress distributions in granular materials, we study the effect of finite transport correlation times on the propagation of nonlinear wave fronts in reaction-diffusion systems. We obtain results such as the possibility of spatial oscillations in the wave-front shape for certain values of the system parameters and high enough wave-front speeds. We also generalize earlier known results concerning the minimum wave-front speed and shape-speed relationships stemming from the finiteness of the correlation times. Analytic investigations are made possible by a piecewise linear representation of the nonlinearity.

Sparsely-sampled hyperspectral stimulated Raman scattering microscopy: a theoretical investigation

NASA Astrophysics Data System (ADS)

Lin, Haonan; Liao, Chien-Sheng; Wang, Pu; Huang, Kai-Chih; Bouman, Charles A.; Kong, Nan; Cheng, Ji-Xin

2017-02-01

A hyperspectral image corresponds to a data cube with two spatial dimensions and one spectral dimension. Through linear un-mixing, hyperspectral images can be decomposed into spectral signatures of pure components as well as their concentration maps. Due to this distinct advantage on component identification, hyperspectral imaging becomes a rapidly emerging platform for engineering better medicine and expediting scientific discovery. Among various hyperspectral imaging techniques, hyperspectral stimulated Raman scattering (HSRS) microscopy acquires data in a pixel-by-pixel scanning manner. Nevertheless, current image acquisition speed for HSRS is insufficient to capture the dynamics of freely moving subjects. Instead of reducing the pixel dwell time to achieve speed-up, which would inevitably decrease signal-to-noise ratio (SNR), we propose to reduce the total number of sampled pixels. Location of sampled pixels are carefully engineered with triangular wave Lissajous trajectory. Followed by a model-based image in-painting algorithm, the complete data is recovered for linear unmixing. Simulation results show that by careful selection of trajectory, a fill rate as low as 10% is sufficient to generate accurate linear unmixing results. The proposed framework applies to any hyperspectral beam-scanning imaging platform which demands high acquisition speed.

Temperature Prediction in High Speed Bone Grinding using Motor PWM Signal

PubMed Central

Tai, Bruce L.; Zhang, Lihui; Wang, Anthony C.; Sullivan, Stephen; Wang, Guangjun; Shih, Albert J.

2013-01-01

This research explores the feasibility of using motor electrical feedback to estimate temperature rise during a surgical bone grinding procedure. High-speed bone grinding is often used during skull base neurosurgery to remove cranial bone and approach skull base tumors through the nasal corridor. Grinding-induced heat could propagate and potentially injure surrounding nerves and arteries, and therefore, predicting the temperature in the grinding region would benefit neurosurgeons during the operation. High-speed electric motors are controlled by pulse-width-modulation (PWM) to alter the current input and thus maintain the rotational speed. Assuming full mechanical to thermal power conversion in the grinding process, PWM can be used as feedback for heat generation and temperature prediction. In this study, the conversion model was established from experiments under a variety of grinding conditions and an inverse heat transfer method to determine heat flux. Given a constant rotational speed, the heat conversion was represented by a linear function, and could predict temperature from the experimental data with less than 20% errors. Such results support the advance of this technology for practical application. PMID:23806419

Summary and recent results from the NASA advanced High Speed Propeller Research Program

NASA Technical Reports Server (NTRS)

Mitchell, G. A.; Mikkelson, D. C.

1982-01-01

Advanced high-speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. The current status of the NASA research program on high-speed propeller aerodynamics, acoustics, and aeroelastics is described. Recent wind tunnel results for five 8- to 10-blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing near-field cruise noise by dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some initial lifting line results are compared with propeller force and probe data. Some initial laser velocimeter measurements of the flow field velocities of an 8-bladed 45 deg swept propeller are shown. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller near-field noise data with linear acoustic theory indicate that the theory adequate predicts near-field noise for subsonic tip speeds but overpredicts the noise for supersonic tip speeds. Potential large gains in propeller efficiency of 7 to 11 percent at Mach 0.8 may be possible with advanced counter-rotation propellers.

High-speed technique based on a parallel projection correlation procedure for digital image correlation

NASA Astrophysics Data System (ADS)

Zaripov, D. I.; Renfu, Li

2018-05-01

The implementation of high-efficiency digital image correlation methods based on a zero-normalized cross-correlation (ZNCC) procedure for high-speed, time-resolved measurements using a high-resolution digital camera is associated with big data processing and is often time consuming. In order to speed-up ZNCC computation, a high-speed technique based on a parallel projection correlation procedure is proposed. The proposed technique involves the use of interrogation window projections instead of its two-dimensional field of luminous intensity. This simplification allows acceleration of ZNCC computation up to 28.8 times compared to ZNCC calculated directly, depending on the size of interrogation window and region of interest. The results of three synthetic test cases, such as a one-dimensional uniform flow, a linear shear flow and a turbulent boundary-layer flow, are discussed in terms of accuracy. In the latter case, the proposed technique is implemented together with an iterative window-deformation technique. On the basis of the results of the present work, the proposed technique is recommended to be used for initial velocity field calculation, with further correction using more accurate techniques.

Performance improvement for optimization of the non-linear geometric fitting problem in manufacturing metrology

NASA Astrophysics Data System (ADS)

Moroni, Giovanni; Syam, Wahyudin P.; Petrò, Stefano

2014-08-01

Product quality is a main concern today in manufacturing; it drives competition between companies. To ensure high quality, a dimensional inspection to verify the geometric properties of a product must be carried out. High-speed non-contact scanners help with this task, by both speeding up acquisition speed and increasing accuracy through a more complete description of the surface. The algorithms for the management of the measurement data play a critical role in ensuring both the measurement accuracy and speed of the device. One of the most fundamental parts of the algorithm is the procedure for fitting the substitute geometry to a cloud of points. This article addresses this challenge. Three relevant geometries are selected as case studies: a non-linear least-squares fitting of a circle, sphere and cylinder. These geometries are chosen in consideration of their common use in practice; for example the sphere is often adopted as a reference artifact for performance verification of a coordinate measuring machine (CMM) and a cylinder is the most relevant geometry for a pin-hole relation as an assembly feature to construct a complete functioning product. In this article, an improvement of the initial point guess for the Levenberg-Marquardt (LM) algorithm by employing a chaos optimization (CO) method is proposed. This causes a performance improvement in the optimization of a non-linear function fitting the three geometries. The results show that, with this combination, a higher quality of fitting results a smaller norm of the residuals can be obtained while preserving the computational cost. Fitting an ‘incomplete-point-cloud’, which is a situation where the point cloud does not cover a complete feature e.g. from half of the total part surface, is also investigated. Finally, a case study of fitting a hemisphere is presented.

Sensitivity of boundary-layer stability to base-state distortions at high Mach numbers

NASA Astrophysics Data System (ADS)

Park, Junho; Zaki, Tamer

2017-11-01

The stability diagram of high-speed boundary layers has been established by evaluating the linear instability modes of the similarity profile, over wide ranges of Reynolds and Mach numbers. In real flows, however, the base state can deviate from the similarity profile. Both the base velocity and temperature can be distorted, for example due to roughness and thermal wall treatments. We review the stability problem of high-speed boundary layer, and derive a new formulation of the sensitivity to base-state distortion using forward and adjoint parabolized stability equations. The new formulation provides qualitative and quantitative interpretations on change in growth rate due to modifications of mean-flow and mean-temperature in heated high-speed boundary layers, and establishes the foundation for future control strategies. This work has been funded by the Air Force Office of Scientific Research (AFOSR) Grant: FA9550-16-1-0103.

Physical performance characteristics of high-level female soccer players 12-21 years of age.

PubMed

Vescovi, J D; Rupf, R; Brown, T D; Marques, M C

2011-10-01

Performance assessment has become an invaluable component of monitoring player development and within talent identification programs in soccer, yet limited performance data are available for female soccer players across a wide age range. The aim of this study was to describe the physical performance characteristics of female soccer players ranging in age from 12 to 21 years. High-level female soccer players (n=414) were evaluated on linear sprinting (36.6 m with 9.1 m splits), countermovement jump (CMJ), and two agility tests. Separate one-way ANOVAs were used to compare performance characteristics between (1) each year of chronological age and (2) three age groups: 12-13 years, n=78, 14-17 years, n=223, and 18-21 years, n=113. Mean linear sprint speed over 9.1 m was similar across all chronological ages, however sprint speed over the final 9.1 m, CMJ height and agility scores improved until approximately 15-16 years. Outcomes from the group data indicated better performance on all tests for the 14-17-year-old group compared with the 12-13-year-old group. Additionally, sprint speed on the second and fourth 9.1 m splits and 36.6 m sprint speed as well as performance on the Illinois agility test was better in the 18-21-year-old group compared with the 14-17-year-old group. The findings from this study indicate that marked improvements of high intensity short duration work occur up until 15-16 years. Smaller gains in performance were observed beyond 16 years of age as evidenced by better performance on 36.6 m sprint speed, several sprint splits and the Illinois agility test in the college aged players (i.e., 18-21-year-old group). © 2010 John Wiley & Sons A/S.

Wind turbine power tracking using an improved multimodel quadratic approach.

PubMed

Khezami, Nadhira; Benhadj Braiek, Naceur; Guillaud, Xavier

2010-07-01

In this paper, an improved multimodel optimal quadratic control structure for variable speed, pitch regulated wind turbines (operating at high wind speeds) is proposed in order to integrate high levels of wind power to actively provide a primary reserve for frequency control. On the basis of the nonlinear model of the studied plant, and taking into account the wind speed fluctuations, and the electrical power variation, a multimodel linear description is derived for the wind turbine, and is used for the synthesis of an optimal control law involving a state feedback, an integral action and an output reference model. This new control structure allows a rapid transition of the wind turbine generated power between different desired set values. This electrical power tracking is ensured with a high-performance behavior for all other state variables: turbine and generator rotational speeds and mechanical shaft torque; and smooth and adequate evolution of the control variables. 2010 ISA. Published by Elsevier Ltd. All rights reserved.

Spin-wave-driven high-speed domain-wall motions in soft magnetic nanotubes

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

Yang, Jaehak; Yoo, Myoung-Woo; Kim, Sang-Koog, E-mail: sangkoog@snu.ac.kr

We report on a micromagnetic simulation study of interactions between propagating spin waves and a head-to-head domain wall in geometrically confined magnetic nanotubes. We found that incident spin waves of specific frequencies can lead to sufficiently high-speed (on the order of a few hundreds of m/s or higher) domain-wall motions in the same direction as that of the incident spin-waves. The domain-wall motions and their speed vary remarkably with the frequency and the amplitude of the incident spin-waves. High-speed domain-wall motions originate from the transfer torque of spin waves' linear momentum to the domain wall, through the partial or completemore » reflection of the incident spin waves from the domain wall. This work provides a fundamental understanding of the interaction of the spin waves with a domain wall in the magnetic nanotubes as well as a route to all-magnetic control of domain-wall motions in the magnetic nanoelements.« less

Comparisons between designs for single-sided linear electric motors: Homopolar synchronous and induction

NASA Astrophysics Data System (ADS)

Nondahl, T. A.; Richter, E.

1980-09-01

A design study of two types of single sided (with a passive rail) linear electric machine designs, namely homopolar linear synchronous machines (LSM's) and linear induction machines (LIM's), is described. It is assumed the machines provide tractive effort for several types of light rail vehicles and locomotives. These vehicles are wheel supported and require tractive powers ranging from 200 kW to 3735 kW and top speeds ranging from 112 km/hr to 400 km/hr. All designs are made according to specified magnetic and thermal criteria. The LSM advantages are a higher power factor, much greater restoring forces for track misalignments, and less track heating. The LIM advantages are no need to synchronize the excitation frequency precisely to vehicle speed, simpler machine construction, and a more easily anchored track structure. The relative weights of the two machine types vary with excitation frequency and speed; low frequencies and low speeds favor the LSM.

Ring rotational speed trend analysis by FEM approach in a Ring Rolling process

NASA Astrophysics Data System (ADS)

Allegri, G.; Giorleo, L.; Ceretti, E.

2018-05-01

Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. In this process two different deformations occur in order to reduce the width and the height of a preform hollow ring; as results a diameter expansion is obtained. In order to guarantee a uniform deformation, the preform is forced toward the Driver Roll whose aim is to transmit the rotation to the ring. The ring rotational speed selection is fundamental because the higher is the speed the higher will be the axial symmetry of the deformation process. However, it is important to underline that the rotational speed will affect not only the final ring geometry but also the loads and energy needed to produce it. Despite this importance in industrial environment, usually, a constant value for the Driver Roll angular velocity is set so to result in a decreasing trend law for the ring rotational speed. The main risk due to this approach is not fulfilling the axial symmetric constrain (due to the diameter expansion) and to generate a high localized ring section deformation. In order to improve the knowledge about this topic in the present paper three different ring rotational speed trends (constant, linearly increasing and linearly decreasing) were investigated by FEM approach. Results were compared in terms of geometrical and dimensional analysis, loads and energies required.

High-power CO(2) laser with a Gauss-core resonator for high-speed cutting of thin metal sheets.

PubMed

Takenaka, Y; Nishimae, J; Tanaka, M; Motoki, Y

1997-01-01

A novel resonator, the Gauss-core resonator, based on a stable resonator configuration designed to yield a highly focusing beam operating in a large-volume TEM(00) mode, is presented. A 6.2 kW linearly polarized output beam with an M(2) factor of 1.7 is obtained experimentally for a high-power cw CO(2) laser. The capability of the Gauss-core resonator to process laser materials is also studied. We can cut 1-mm-thick mild (soft) steel with a maximum cutting speed of 58 m/min at 5.6 kW and 0.2-mm-thick steel 145 m/min at 2.8 kW.

Generate stepper motor linear speed profile in real time

NASA Astrophysics Data System (ADS)

Stoychitch, M. Y.

2018-01-01

In this paper we consider the problem of realization of linear speed profile of stepper motors in real time. We considered the general case when changes of speed in the phases of acceleration and deceleration are different. The new and practical algorithm of the trajectory planning is given. The algorithms of the real time speed control which are suitable for realization to the microcontroller and FPGA circuits are proposed. The practical realization one of these algorithms, using Arduino platform, is given also.

High Speed and High Functional Inverter Power Supplies for Plasma Generation and Control, and their Performance

NASA Astrophysics Data System (ADS)

Uesugi, Yoshihiko; Razzak, Mohammad A.; Kondo, Kenji; Kikuchi, Yusuke; Takamura, Shuichi; Imai, Takahiro; Toyoda, Mitsuhiro

The Rapid development of high power and high speed semiconductor switching devices has led to their various applications in related plasma fields. Especially, a high speed inverter power supply can be used as an RF power source instead of conventional linear amplifiers and a power supply to control the magnetic field in a fusion plasma device. In this paper, RF thermal plasma production and plasma heating experiments are described emphasis placed on using a static induction transistor inverter at a frequency range between 200 kHz and 2.5 MHz as an RF power supply. Efficient thermal plasma production is achieved experimentally by using a flexible and easily operated high power semiconductor inverter power supply. Insulated gate bipolar transistor (IGBT) inverter power supplies driven by a high speed digital signal processor are applied as tokamak joule coil and vertical coil power supplies to control plasma current waveform and plasma equilibrium. Output characteristics, such as the arbitrary bipolar waveform generation of a pulse width modulation (PWM) inverter using digital signal processor (DSP) can be successfully applied to tokamak power supplies for flexible plasma current operation and fast position control of a small tokamak.

Relationships between coordination, active drag and propelling efficiency in crawl.

PubMed

Seifert, Ludovic; Schnitzler, Christophe; Bideault, Gautier; Alberty, Morgan; Chollet, Didier; Toussaint, Huub Martin

2015-02-01

This study examines the relationships between the index of coordination (IdC) and active drag (D) assuming that at constant average speed, average drag equals average propulsion. The relationship between IdC and propulsive efficiency (ep) was also investigated at maximal speed. Twenty national swimmers completed two incremental speed tests swimming front crawl with arms only in free condition and using a measurement of active drag system. Each test was composed of eight 25-m bouts from 60% to 100% of maximal intensity whereby each lap was swum at constant speed. Different regression models were tested to analyse IdC-D relationship. Correlation between IdC and ep was calculated. IdC was linked to D by linear regression (IdC=0.246·D-27.06; R(2)=0.88, P<.05); swimmers switched from catch-up to superposition coordination mode at a speed of ∼1.55ms(-1) where average D is ∼110N. No correlation between IdC and ep at maximal speed was found. The intra-individual analysis revealed that coordination plays an important role in scaling propulsive forces with higher speed levels such that these are adapted to aquatic resistance. Inter-individual analysis showed that high IdC did not relate to a high ep suggesting an individual optimization of force and power generation is at play to reach high speeds. Copyright © 2014 Elsevier B.V. All rights reserved.

High-Speed Research: Sonic Boom, volume 2

NASA Technical Reports Server (NTRS)

Darden, Christine M. (Compiler)

1992-01-01

A High-Speed Sonic Boom Workshop was held at NASA Langley Research Center on February 25-27, 1992. The purpose of the workshop was to make presentations on current research activities and accomplishments and to assess progress in the area of sonic boom since the program was initiated in FY-90. Twenty-nine papers were presented during the 2-1/2 day workshop. Attendees included representatives from academia, industry, and government who are actively involved in sonic-boom research. Volume 2 contains papers related to low sonic-boom design and analysis using both linear theory and higher order computational fluid dynamics (CFD) methods.

Whirl Motion of a Seal Test Rig with Squeeze-Film Dampers

NASA Technical Reports Server (NTRS)

Proctor, Margaret P.; Gunter, Edgar J.

2007-01-01

This paper presents the experimental behavior and dynamic analysis of a high speed test rig with rolling element bearings mounted in squeeze film oil damper bearings. The test rotor is a double overhung configuration with rolling element ball bearings mounted in uncentered squeeze-film oil dampers. The damper design is similar to that employed with various high-speed aircraft HP gas turbines. The dynamic performance of the test rig with the originally installed dampers with an effective damper length of length 0.23-inch was unacceptable. The design speed of 40,000 RPM could not be safely achieved as nonsynchronous whirling at the overhung seal test disk and high amplitude critical speed response at the drive spline section occurred at 32,000 RPM. In addition to the self excited stability and critical speed problems, it was later seen from FFT data analysis, that a region of supersynchronous dead band whirling occurs between 10,000 to 15,000 RPM which can lead to bearing distress and wear. The system was analyzed using both linear and nonlinear techniques. The extended length damper design resulting from the analysis eliminated the rotor subsynchronous whirling, high amplitude critical speed, and the dead band whirling region allowing the system to achieve a speed of 45,000 RPM. However, nonlinear analysis shows that damper lockup could occur with high rotor unbalance at 33,000 RPM, even with the extended squeeze-film dampers. The control of damper lockup will be addressed in a future paper.

Influence of speed and step frequency during walking and running on motion sensor output.

PubMed

Rowlands, Ann V; Stone, Michelle R; Eston, Roger G

2007-04-01

Studies have reported strong linear relationships between accelerometer output and walking/running speeds up to 10 km x h(-1). However, ActiGraph uniaxial accelerometer counts plateau at higher speeds. The aim of this study was to determine the relationships of triaxial accelerometry, uniaxial accelerometry, and pedometry with speed and step frequency (SF) across a range of walking and running speeds. Nine male runners wore two ActiGraph uniaxial accelerometers, two RT3 triaxial accelerometers (all set at a 1-s epoch), and two Yamax pedometers. Each participant walked for 60 s at 4 and 6 km x h(-1), ran for 60 s at 10, 12, 14, 16, and 18 km x h(-1), and ran for 30 s at 20, 22, 24, and 26 km x h(-1). Step frequency was recorded by a visual count. ActiGraph counts peaked at 10 km x h(-10 (2.5-3.0 Hz SF) and declined thereafter (r=0.02, P>0.05). After correction for frequency-dependent filtering, output plateaued at 10 km x h(-1) but did not decline (r=0.77, P<0.05). Similarly, RT3 vertical counts plateaued at speeds > 10 km x h(-1) (r=0.86, P<0.01). RT3 vector magnitude and anteroposterior and mediolateral counts maintained a linear relationship with speed (r>0.96, P<0.001). Step frequency assessed by pedometry compared well with actual step frequency up to 20 km x h(-1) (approximately 3.5 Hz) but then underestimated actual steps (Yamax r=0.97; ActiGraph pedometer r=0.88, both P<0.001). Increasing underestimation of activity by the ActiGraph as speed increases is related to frequency-dependent filtering and assessment of acceleration in the vertical plane only. RT3 vector magnitude was strongly related to speed, reflecting the predominance of horizontal acceleration at higher speeds. These results indicate that high-intensity activity is underestimated by the ActiGraph, even after correction for frequency-dependent filtering, but not by the RT3. Pedometer output is highly correlated with step frequency.

Visualization of high speed liquid jet impaction on a moving surface.

PubMed

Guo, Yuchen; Green, Sheldon

2015-04-17

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

PubMed Central

Guo, Yuchen; Green, Sheldon

2015-01-01

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing. PMID:25938331

Rod Has High Tensile Strength And Low Thermal Expansion

NASA Technical Reports Server (NTRS)

Smith, D. E.; Everton, R. L.; Howe, E.; O'Malley, M.

1996-01-01

Thoriated tungsten extension rod fabricated to replace stainless-steel extension rod attached to linear variable-differential transformer in gap-measuring gauge. Threads formed on end of rod by machining with special fixtures and carefully chosen combination of speeds and feeds.

Electrically Tunable Mid-Infrared Single-Mode High-Speed Semiconductor Laser

DTIC Science & Technology

2010-11-01

effective and the net tunnel rate may decrease in spite of progressing carrier density buildup in the accumulation well. Enforcing the bias current at...In te ns ity , a .u . E, eV Regular ICL Figure 4 The dependence of the electroluminescence (EL) quantum energy on the bias voltage for a...spectral maximum energy increases linearly with the bias voltage. Since the dependence is measured in the sub-threshold pumping region, the linear

High-Speed Friction-Stir Welding To Enable Aluminum Tailor-Welded Blanks

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

Hovanski, Yuri; Upadhyay, Piyush; Carsley, John

Current joining technologies for automotive aluminum alloys are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding has been traditionally applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translatemore » to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum welded components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability utilizing a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.« less

Enabling high speed friction stir welding of aluminum tailor welded blanks

NASA Astrophysics Data System (ADS)

Hovanski, Yuri

Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding (FSW) has traditionally been applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translate to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum FSW components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability using a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.

High-Speed Friction-Stir Welding to Enable Aluminum Tailor-Welded Blanks

NASA Astrophysics Data System (ADS)

Hovanski, Yuri; Upadhyay, Piyush; Carsley, John; Luzanski, Tom; Carlson, Blair; Eisenmenger, Mark; Soulami, Ayoub; Marshall, Dustin; Landino, Brandon; Hartfield-Wunsch, Susan

2015-05-01

Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and they have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high volumes. While friction-stir welding (FSW) has been traditionally applied at linear velocities less than 1 m/min, high-volume production applications demand the process be extended to higher velocities more amenable to cost-sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low-to-moderate welding velocities do not directly translate to high-speed linear FSW. Therefore, to facilitate production of high-volume aluminum FSW components, parameters were developed with a minimum welding velocity of 3 m/min. With an emphasis on weld quality, welded blanks were evaluated for postweld formability using a combination of numerical and experimental methods. An evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum TWBs, which provided validation of the numerical and experimental analysis of laboratory-scale tests.

Are the average gait speeds during the 10meter and 6minute walk tests redundant in Parkinson disease?

PubMed

Duncan, Ryan P; Combs-Miller, Stephanie A; McNeely, Marie E; Leddy, Abigail L; Cavanaugh, James T; Dibble, Leland E; Ellis, Terry D; Ford, Matthew P; Foreman, K Bo; Earhart, Gammon M

2017-02-01

We investigated the relationships between average gait speed collected with the 10Meter Walk Test (Comfortable and Fast) and 6Minute Walk Test (6MWT) in 346 people with Parkinson disease (PD) and how the relationships change with increasing disease severity. Pearson correlation and linear regression analyses determined relationships between 10Meter Walk Test and 6MWT gait speed values for the entire sample and for sub-samples stratified by Hoehn & Yahr (H&Y) stage I (n=53), II (n=141), III (n=135) and IV (n=17). We hypothesized that redundant tests would be highly and significantly correlated (i.e. r>0.70, p<0.05) and would have a linear regression model slope of 1 and intercept of 0. For the entire sample, 6MWT gait speed was significantly (p<0.001) related to the Comfortable 10 Meter Walk Test (r=0.75) and Fast 10Meter Walk Test (r=0.79) gait speed, with 56% and 62% of the variance in 6MWT gait speed explained, respectively. The regression model of 6MWT gait speed predicted by Comfortable 10 Meter Walk gait speed produced slope and intercept values near 1 and 0, respectively, especially for participants in H&Y stages II-IV. In contrast, slope and intercept values were further from 1 and 0, respectively, for the Fast 10Meter Walk Test. Comfortable 10 Meter Walk Test and 6MWT gait speeds appeared to be redundant in people with moderate to severe PD, suggesting the Comfortable 10 Meter Walk Test can be used to estimate 6MWT distance in this population. Copyright © 2016 Elsevier B.V. All rights reserved.

Are the Average Gait Speeds During the 10 Meter and 6 Minute Walk Tests Redundant in Parkinson Disease?

PubMed Central

Duncan, Ryan P.; Combs-Miller, Stephanie A.; McNeely, Marie E.; Leddy, Abigail L.; Cavanaugh, James T.; Dibble, Leland E.; Ellis, Terry D.; Ford, Matthew P.; Foreman, K. Bo; Earhart, Gammon M.

2016-01-01

We investigated the relationships between average gait speed collected with the 10 Meter Walk Test (Comfortable and Fast) and 6 Minute Walk Test (6MWT) in 346 people with Parkinson disease (PD) and how the relationships change with increasing disease severity. Pearson correlation and linear regression analyses determined relationships between 10 Meter Walk Test and 6MWT gait speed values for the entire sample and for sub-samples stratified by Hoehn & Yahr (H&Y) stage I (n=53), II (n=141), III (n=135) and IV (n=17). We hypothesized that redundant tests would be highly and significantly correlated (i.e. r > 0.70, p < 0.05) and would have a linear regression model slope of 1 and intercept of 0. For the entire sample, 6MWT gait speed was significantly (p<0.001) related to the Comfortable 10 Meter Walk Test (r=0.75) and Fast 10 Meter Walk Test (r=0.79) gait speed, with 56% and 62% of the variance in 6MWT gait speed explained, respectively. The regression model of 6MWT gait speed predicted by Comfortable 10 Meter Walk gait speed produced slope and intercept values near 1 and 0, respectively, especially for participants in H&Y stages II–IV. In contrast, slope and intercept values were further from 1 and 0, respectively, for the Fast 10 Meter Walk Test. Comfortable 10 Meter Walk Test and 6MWT gait speeds appeared to be redundant in people with moderate to severe PD, suggesting the Comfortable 10 Meter Walk Test can be used to estimate 6MWT distance in this population. PMID:27915221

Double lead spiral platen parallel jaw end effector

NASA Technical Reports Server (NTRS)

Beals, David C.

1989-01-01

The double lead spiral platen parallel jaw end effector is an extremely powerful, compact, and highly controllable end effector that represents a significant improvement in gripping force and efficiency over the LaRC Puma (LP) end effector. The spiral end effector is very simple in its design and has relatively few parts. The jaw openings are highly predictable and linear, making it an ideal candidate for remote control. The finger speed is within acceptable working limits and can be modified to meet the user needs; for instance, greater finger speed could be obtained by increasing the pitch of the spiral. The force relaxation is comparable to the other tested units. Optimization of the end effector design would involve a compromise of force and speed for a given application.

Stationarity and periodicities of linear speed of coronal mass ejection: a statistical signal processing approach

NASA Astrophysics Data System (ADS)

Chattopadhyay, Anirban; Khondekar, Mofazzal Hossain; Bhattacharjee, Anup Kumar

2017-09-01

In this paper initiative has been taken to search the periodicities of linear speed of Coronal Mass Ejection in solar cycle 23. Double exponential smoothing and Discrete Wavelet Transform are being used for detrending and filtering of the CME linear speed time series. To choose the appropriate statistical methodology for the said purpose, Smoothed Pseudo Wigner-Ville distribution (SPWVD) has been used beforehand to confirm the non-stationarity of the time series. The Time-Frequency representation tool like Hilbert Huang Transform and Empirical Mode decomposition has been implemented to unearth the underneath periodicities in the non-stationary time series of the linear speed of CME. Of all the periodicities having more than 95% Confidence Level, the relevant periodicities have been segregated out using Integral peak detection algorithm. The periodicities observed are of low scale ranging from 2-159 days with some relevant periods like 4 days, 10 days, 11 days, 12 days, 13.7 days, 14.5 and 21.6 days. These short range periodicities indicate the probable origin of the CME is the active longitude and the magnetic flux network of the sun. The results also insinuate about the probable mutual influence and causality with other solar activities (like solar radio emission, Ap index, solar wind speed, etc.) owing to the similitude between their periods and CME linear speed periods. The periodicities of 4 days and 10 days indicate the possible existence of the Rossby-type waves or planetary waves in Sun.

Aerodynamic Characteristics of the 30mm XM788E1 and XM789 projectiles

DTIC Science & Technology

1982-10-01

successfully predicted the effect of a cubic Magnus moment on the damping rates by means of an amplitude-plane analysis. However, the amplitude-plane...technique becomes cumbersome for a projectile with both Magnus and pitch-dariping moment non-linearities. The effects of changi,,y epi- cyclic...show the existence of a slow arm limit- cycle yaw at high subsonic speeds, and a limit-epicycle yaw at lower subsonic speeds. The effect of the limit

The Challenge of Evaluating the Intensity of Short Actions in Soccer: A New Methodological Approach Using Percentage Acceleration.

PubMed

Sonderegger, Karin; Tschopp, Markus; Taube, Wolfgang

2016-01-01

There are several approaches to quantifying physical load in team sports using positional data. Distances in different speed zones are most commonly used. Recent studies have used acceleration data in addition in order to take short intense actions into account. However, the fact that acceleration decreases with increasing initial running speed is ignored and therefore introduces a bias. The aim of our study was to develop a new methodological approach that removes this bias. For this purpose, percentage acceleration was calculated as the ratio of the maximal acceleration of the action (amax,action) and the maximal voluntary acceleration (amax) that can be achieved for a particular initial running speed (percentage acceleration [%] = amax,action / amax * 100). To define amax, seventy-two highly trained junior male soccer players (17.1 ± 0.6 years) completed maximal sprints from standing and three different constant initial running speeds (vinit; trotting: ~6.0 km·h-1; jogging: ~10.8 km·h-1; running: ~15.0 km·h-1). The amax was 6.01 ± 0.55 from a standing start, 4.33 ± 0.40 from trotting, 3.20 ± 0.49 from jogging and 2.29 ± 0.34 m·s-2 from running. The amax correlated significantly with vinit (r = -0.98) and the linear regression equation of highly-trained junior soccer players was: amax = -0.23 * vinit + 5.99. Using linear regression analysis, we propose to classify high-intensity actions as accelerations >75% of the amax, corresponding to acceleration values for our population of >4.51 initiated from standing, >3.25 from trotting, >2.40 from jogging, and >1.72 m·s-2 from running. The use of percentage acceleration avoids the bias of underestimating actions with high and overestimating actions with low initial running speed. Furthermore, percentage acceleration allows determining individual intensity thresholds that are specific for one population or one single player.

The Dependence of the Peak Velocity of High-Speed Solar Wind Streams as Measured in the Ecliptic by ACE and the STEREO satellites on the Area and Co-latitude of Their Solar Source Coronal Holes.

PubMed

Hofmeister, Stefan J; Veronig, Astrid; Temmer, Manuela; Vennerstrom, Susanne; Heber, Bernd; Vršnak, Bojan

2018-03-01

We study the properties of 115 coronal holes in the time range from August 2010 to March 2017, the peak velocities of the corresponding high-speed streams as measured in the ecliptic at 1 AU, and the corresponding changes of the Kp index as marker of their geoeffectiveness. We find that the peak velocities of high-speed streams depend strongly on both the areas and the co-latitudes of their solar source coronal holes with regard to the heliospheric latitude of the satellites. Therefore, the co-latitude of their source coronal hole is an important parameter for the prediction of the high-speed stream properties near the Earth. We derive the largest solar wind peak velocities normalized to the coronal hole areas for coronal holes located near the solar equator and that they linearly decrease with increasing latitudes of the coronal holes. For coronal holes located at latitudes ≳ 60°, they turn statistically to zero, indicating that the associated high-speed streams have a high chance to miss the Earth. Similarly, the Kp index per coronal hole area is highest for the coronal holes located near the solar equator and strongly decreases with increasing latitudes of the coronal holes. We interpret these results as an effect of the three-dimensional propagation of high-speed streams in the heliosphere; that is, high-speed streams arising from coronal holes near the solar equator propagate in direction toward and directly hit the Earth, whereas solar wind streams arising from coronal holes at higher solar latitudes only graze or even miss the Earth.

High-speed imaging of submerged jet: visualization analysis using proper orthogonality decomposition

NASA Astrophysics Data System (ADS)

Liu, Yingzheng; He, Chuangxin

2016-11-01

In the present study, the submerged jet at low Reynolds numbers was visualized using laser induced fluoresce and high-speed imaging in a water tank. Well-controlled calibration was made to determine linear dependency region of the fluoresce intensity on its concentration. Subsequently, the jet fluid issuing from a circular pipe was visualized using a high-speed camera. The animation sequence of the visualized jet flow field was supplied for the snapshot proper orthogonality decomposition (POD) analysis. Spatio-temporally varying structures superimposed in the unsteady fluid flow were identified, e.g., the axisymmetric mode and the helical mode, which were reflected from the dominant POD modes. The coefficients of the POD modes give strong indication of temporal and spectral features of the corresponding unsteady events. The reconstruction using the time-mean visualization and the selected POD modes was conducted to reveal the convective motion of the buried vortical structures. National Natural Science Foundation of China.

Isolated nanoinjection photo detectors for high-speed and high-sensitivity single-photon detection

NASA Astrophysics Data System (ADS)

Fathipour, V.; Memis, O. G.; Jang, S. J.; Khalid, F.; Brown, R. L.; Hassaninia, I.; Gelfand, R.; Mohseni, H.

2013-09-01

Our group has designed and developed a new SWIR single photon detector called the nano-injection detector that is conceptually designed with biological inspirations taken from the rod cells in human eye. The detector couples a nanoscale sensory region with a large absorption volume to provide avalanche free internal amplification while operating at linear regime with low bias voltages. The low voltage operation makes the detector to be fully compatible with available CMOS technologies. Because there is no photon reemission, detectors can be formed into high-density single-photon detector arrays. As such, the nano injection detectors are viable candidates for SPD and imaging at the short-wave infrared band. Our measurements in 2007 proved a high SNR and a stable excess noise factor of near unity. We are reporting on a high speed version of the detector with 4 orders of magnitude enhancement in speed as well as 2 orders of magnitude reduction in dark current (30nA vs. 10 uA at 1.5V).

Non-linear dynamic compensation system

NASA Technical Reports Server (NTRS)

Lin, Yu-Hwan (Inventor); Lurie, Boris J. (Inventor)

1992-01-01

A non-linear dynamic compensation subsystem is added in the feedback loop of a high precision optical mirror positioning control system to smoothly alter the control system response bandwidth from a relatively wide response bandwidth optimized for speed of control system response to a bandwidth sufficiently narrow to reduce position errors resulting from the quantization noise inherent in the inductosyn used to measure mirror position. The non-linear dynamic compensation system includes a limiter for limiting the error signal within preselected limits, a compensator for modifying the limiter output to achieve the reduced bandwidth response, and an adder for combining the modified error signal with the difference between the limited and unlimited error signals. The adder output is applied to control system motor so that the system response is optimized for accuracy when the error signal is within the preselected limits, optimized for speed of response when the error signal is substantially beyond the preselected limits and smoothly varied therebetween as the error signal approaches the preselected limits.

Short-term effects of meteorological factors on hand, foot and mouth disease among children in Shenzhen, China: Non-linearity, threshold and interaction.

PubMed

Zhang, Zhen; Xie, Xu; Chen, Xiliang; Li, Yuan; Lu, Yan; Mei, Shujiang; Liao, Yuxue; Lin, Hualiang

2016-01-01

Various meteorological factors have been associated with hand, foot and mouth disease (HFMD) among children; however, fewer studies have examined the non-linearity and interaction among the meteorological factors. A generalized additive model with a log link allowing Poisson auto-regression and over-dispersion was applied to investigate the short-term effects daily meteorological factors on children HFMD with adjustment of potential confounding factors. We found positive effects of mean temperature and wind speed, the excess relative risk (ERR) was 2.75% (95% CI: 1.98%, 3.53%) for one degree increase in daily mean temperature on lag day 6, and 3.93% (95% CI: 2.16% to 5.73%) for 1m/s increase in wind speed on lag day 3. We found a non-linear effect of relative humidity with thresholds with the low threshold at 45% and high threshold at 85%, within which there was positive effect, the ERR was 1.06% (95% CI: 0.85% to 1.27%) for 1 percent increase in relative humidity on lag day 5. No significant effect was observed for rainfall and sunshine duration. For the interactive effects, we found a weak additive interaction between mean temperature and relative humidity, and slightly antagonistic interaction between mean temperature and wind speed, and between relative humidity and wind speed in the additive models, but the interactions were not statistically significant. This study suggests that mean temperature, relative humidity and wind speed might be risk factors of children HFMD in Shenzhen, and the interaction analysis indicates that these meteorological factors might have played their roles individually. Copyright © 2015 Elsevier B.V. All rights reserved.

Focal plane infrared readout circuit

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor)

2002-01-01

An infrared imager, such as a spectrometer, includes multiple infrared photodetectors and readout circuits for reading out signals from the photodetectors. Each readout circuit includes a buffered direct injection input circuit including a differential amplifier with active feedback provided through an injection transistor. The differential amplifier includes a pair of input transistors, a pair of cascode transistors and a current mirror load. Photocurrent from a photodetector can be injected onto an integration capacitor in the readout circuit with high injection efficiency at high speed. A high speed, low noise, wide dynamic range linear infrared multiplexer array for reading out infrared detectors with large capacitances can be achieved even when short exposure times are used. The effect of image lag can be reduced.

Displacement monitoring of switch track and its slab on a bridge of high speed railway by FBG

NASA Astrophysics Data System (ADS)

Li, Weilai; Li, He; Cheng, Jian; Huang, Xiaomei; Pan, Jianjun; Zhou, Ciming; Yang, Minghong

2011-05-01

In a 350km/h high speed railway line, there is a seamless switch with ballastless slabs built on a bridge. 54 Fiber Bragg Grating detecting cells are employed to monitor the displacement of track and slab. The cell is of extending function of measurement range, up to 50mm displacement, and is of good linearity. Protecting methods for cells and fiber are adopted to keep them surviving from the harsh conditions. The results show that in 75 days, the displacement of the track and sleeper slab was 8-9mm, and the displacement is of high correlation with daily environmental temperature change.

Temperature prediction in high speed bone grinding using motor PWM signal.

PubMed

Tai, Bruce L; Zhang, Lihui; Wang, Anthony C; Sullivan, Stephen; Wang, Guangjun; Shih, Albert J

2013-10-01

This research explores the feasibility of using motor electrical feedback to estimate temperature rise during a surgical bone grinding procedure. High-speed bone grinding is often used during skull base neurosurgery to remove cranial bone and approach skull base tumors through the nasal corridor. Grinding-induced heat could propagate and potentially injure surrounding nerves and arteries, and therefore, predicting the temperature in the grinding region would benefit neurosurgeons during the operation. High-speed electric motors are controlled by pulse-width-modulation (PWM) to alter the current input and thus maintain the rotational speed. Assuming full mechanical to thermal power conversion in the grinding process, PWM can be used as feedback for heat generation and temperature prediction. In this study, the conversion model was established from experiments under a variety of grinding conditions and an inverse heat transfer method to determine heat flux. Given a constant rotational speed, the heat conversion was represented by a linear function, and could predict temperature from the experimental data with less than 20% errors. Such results support the advance of this technology for practical application. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

High-performance IR detector modules

NASA Astrophysics Data System (ADS)

Wendler, Joachim; Cabanski, Wolfgang; Rühlich, Ingo; Ziegler, Johann

2004-02-01

The 3rd generation of infrared (IR) detection modules is expected to provide higher video resolution, advanced functions like multi band or multi color capability, higher frame rates, and better thermal resolution. AIM has developed staring and linear high performance focal plane arrays (FPA) integrated into detector/dewar cooler assemblies (IDCA). Linear FPA"s support high resolution formats such as 1920 x 1152 (HDTV), 1280 x 960, or 1536 x 1152. Standard format for staring FPA"s is 640 x 512. In this configuration, QEIP devices sensitive in the 8 10 µm band as well as MCT devices sensitive in the 3.4 5.0 µm band are available. A 256 x 256 high speed detection module allows a full frame rate >800 Hz. Especially usability of long wavelength devices in high performance FLIR systems does not only depend on the classical electrooptical performance parameters such as NEDT, detectivity, and response homogeneity, but are mainly characterized by the stability of the correction coefficients used for image correction. The FPA"s are available in suited integrated detector/dewar cooler assemblies. The linear cooling engines are designed for maximum stability of the focal plane temperature, low operating temperatures down to 60K, high MTTF lifetimes of 6000h and above even under high ambient temperature conditions. The IDCA"s are equipped with AIM standard or custom specific command and control electronics (CCE) providing a well defined interface to the system electronics. Video output signals are provided as 14 bit digital data rates up to 80 MHz for the high speed devices.

Linear dependence of surface expansion speed on initial plasma temperature in warm dense matter

DOE PAGES

Bang, Woosuk; Albright, Brian James; Bradley, Paul Andrew; ...

2016-07-12

Recent progress in laser-driven quasi-monoenergetic ion beams enabled the production of uniformly heated warm dense matter. Matter heated rapidly with this technique is under extreme temperatures and pressures, and promptly expands outward. While the expansion speed of an ideal plasma is known to have a square-root dependence on temperature, computer simulations presented here show a linear dependence of expansion speed on initial plasma temperature in the warm dense matter regime. The expansion of uniformly heated 1–100 eV solid density gold foils was modeled with the RAGE radiation-hydrodynamics code, and the average surface expansion speed was found to increase linearly withmore » temperature. The origin of this linear dependence is explained by comparing predictions from the SESAME equation-of-state tables with those from the ideal gas equation-of-state. In conclusion, these simulations offer useful insight into the expansion of warm dense matter and motivate the application of optical shadowgraphy for temperature measurement.« less

Performance of Ti-multilayer coated tool during machining of MDN431 alloyed steel

NASA Astrophysics Data System (ADS)

Badiger, Pradeep V.; Desai, Vijay; Ramesh, M. R.

2018-04-01

Turbine forgings and other components are required to be high resistance to corrosion and oxidation because which they are highly alloyed with Ni and Cr. Midhani manufactures one of such material MDN431. It's a hard-to-machine steel with high hardness and strength. PVD coated insert provide an answer to problem with its state of art technique on the WC tool. Machinability studies is carried out on MDN431 steel using uncoated and Ti-multilayer coated WC tool insert using Taguchi optimisation technique. During the present investigation, speed (398-625rpm), feed (0.093-0.175mm/rev), and depth of cut (0.2-0.4mm) varied according to Taguchi L9 orthogonal array, subsequently cutting forces and surface roughness (Ra) were measured. Optimizations of the obtained results are done using Taguchi technique for cutting forces and surface roughness. Using Taguchi technique linear fit model regression analysis carried out for the combination of each input variable. Experimented results are compared and found the developed model is adequate which supported by proof trials. Speed, feed and depth of cut are linearly dependent on the cutting force and surface roughness for uncoated insert whereas Speed and depth of cut feed is inversely dependent in coated insert for both cutting force and surface roughness. Machined surface for coated and uncoated inserts during machining of MDN431 is studied using optical profilometer.

Compensator design for improved counterbalancing in high speed atomic force microscopy.

PubMed

Bozchalooi, I S; Youcef-Toumi, K; Burns, D J; Fantner, G E

2011-11-01

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds. © 2011 American Institute of Physics

Compensator design for improved counterbalancing in high speed atomic force microscopy

PubMed Central

Bozchalooi, I. S.; Youcef-Toumi, K.; Burns, D. J.; Fantner, G. E.

2011-01-01

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds. PMID:22128989

Compensator design for improved counterbalancing in high speed atomic force microscopy

NASA Astrophysics Data System (ADS)

Bozchalooi, I. S.; Youcef-Toumi, K.; Burns, D. J.; Fantner, G. E.

2011-11-01

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds.

The design and analysis of simple low speed flap systems with the aid of linearized theory computer programs

NASA Technical Reports Server (NTRS)

Carlson, Harry W.

1985-01-01

The purpose here is to show how two linearized theory computer programs in combination may be used for the design of low speed wing flap systems capable of high levels of aerodynamic efficiency. A fundamental premise of the study is that high levels of aerodynamic performance for flap systems can be achieved only if the flow about the wing remains predominantly attached. Based on this premise, a wing design program is used to provide idealized attached flow camber surfaces from which candidate flap systems may be derived, and, in a following step, a wing evaluation program is used to provide estimates of the aerodynamic performance of the candidate systems. Design strategies and techniques that may be employed are illustrated through a series of examples. Applicability of the numerical methods to the analysis of a representative flap system (although not a system designed by the process described here) is demonstrated in a comparison with experimental data.

Determining vehicle operating speed and lateral position along horizontal curves using linear mixed-effects models.

PubMed

Fitzsimmons, Eric J; Kvam, Vanessa; Souleyrette, Reginald R; Nambisan, Shashi S; Bonett, Douglas G

2013-01-01

Despite recent improvements in highway safety in the United States, serious crashes on curves remain a significant problem. To assist in better understanding causal factors leading to this problem, this article presents and demonstrates a methodology for collection and analysis of vehicle trajectory and speed data for rural and urban curves using Z-configured road tubes. For a large number of vehicle observations at 2 horizontal curves located in Dexter and Ames, Iowa, the article develops vehicle speed and lateral position prediction models for multiple points along these curves. Linear mixed-effects models were used to predict vehicle lateral position and speed along the curves as explained by operational, vehicle, and environmental variables. Behavior was visually represented for an identified subset of "risky" drivers. Linear mixed-effect regression models provided the means to predict vehicle speed and lateral position while taking into account repeated observations of the same vehicle along horizontal curves. Speed and lateral position at point of entry were observed to influence trajectory and speed profiles. Rural horizontal curve site models are presented that indicate that the following variables were significant and influenced both vehicle speed and lateral position: time of day, direction of travel (inside or outside lane), and type of vehicle.

High resolution optical shaft encoder for motor speed control based on an optical disk pick-up

NASA Astrophysics Data System (ADS)

Yeh, Wei-Hung; Bletscher, Warren; Mansuripur, M.

1998-08-01

Using a three-beam optical pick-up from a compact disk player and a flexible, shaft-mounted diffraction grating, we obtain information about the rotation speed and angular position of the motor's spindle. This information may be used for feedback to the motor for smooth operation. Due to the small size of the focused spot and the built-in auto-focus mechanism of the optical head, the proposed encoder can achieve submicrometer resolution. With high resolution, reliable operation, and low-cost elements, the proposed method is suitable for rotary and linear motion control where accurate positioning of an object is required.

Real-time, ultrahigh-resolution, optical coherence tomography with an all-fiber, femtosecond fiber laser continuum at 1.5 microm.

PubMed

Nishizawa, N; Chen, Y; Hsiung, P; Ippen, E P; Fujimoto, J G

2004-12-15

Real-time, ultrahigh-resolution optical coherence tomography (OCT) is demonstrated in the 1.4-1.7-microm wavelength region with a stretched-pulse, passively mode-locked, Er-doped fiber laser and highly nonlinear fiber. The fiber laser generates 100-mW, linearly chirped pulses at a 51-MHz repetition rate. The pulses are compressed and then coupled into a normally dispersive highly nonlinear fiber to generate a low-noise supercontinuum with a 180-nm FWHM bandwidth and 38 mW of output power. This light source is stable, compact, and broadband, permitting high-speed, real-time, high-resolution OCT imaging. In vivo high-speed OCT imaging of human skin with approximately 5.5-microm resolution and 99-dB sensitivity is demonstrated.

Velocity and displacement statistics in a stochastic model of nonlinear friction showing bounded particle speed

NASA Astrophysics Data System (ADS)

Menzel, Andreas M.

2015-11-01

Diffusion of colloidal particles in a complex environment such as polymer networks or biological cells is a topic of high complexity with significant biological and medical relevance. In such situations, the interaction between the surroundings and the particle motion has to be taken into account. We analyze a simplified diffusion model that includes some aspects of a complex environment in the framework of a nonlinear friction process: at low particle speeds, friction grows linearly with the particle velocity as for regular viscous friction; it grows more than linearly at higher particle speeds; finally, at a maximum of the possible particle speed, the friction diverges. In addition to bare diffusion, we study the influence of a constant drift force acting on the diffusing particle. While the corresponding stationary velocity distributions can be derived analytically, the displacement statistics generally must be determined numerically. However, as a benefit of our model, analytical progress can be made in one case of a special maximum particle speed. The effect of a drift force in this case is analytically determined by perturbation theory. It will be interesting in the future to compare our results to real experimental systems. One realization could be magnetic colloidal particles diffusing through a shear-thickening environment such as starch suspensions, possibly exposed to an external magnetic field gradient.

Performance of Simple Gas Foil Thrust Bearings in Air

NASA Technical Reports Server (NTRS)

Bruckner, Robert J.

2012-01-01

Foil bearings are self-acting hydrodynamics devices used to support high speed rotating machinery. The advantages that they offer to process fluid lubricated machines include: high rotational speed capability, no auxiliary lubrication system, non-contacting high speed operation, and improved damping as compared to rigid hydrodynamic bearings. NASA has had a sporadic research program in this technology for almost 6 decades. Advances in the technology and understanding of foil journal bearings have enabled several new commercial products in recent years. These products include oil-free turbochargers for both heavy trucks and automobiles, high speed electric motors, microturbines for distributed power generation, and turbojet engines. However, the foil thrust bearing has not received a complimentary level of research and therefore has become the weak link of oil-free turbomachinery. In an effort to both provide machine designers with basic performance parameters and to elucidate the underlying physics of foil thrust bearings, NASA Glenn Research Center has completed an effort to experimentally measure the performance of simple gas foil thrust bearing in air. The database includes simple bump foil supported thrust bearings with full geometry and manufacturing techniques available to the user. Test conditions consist of air at ambient pressure and temperatures up to 500 C and rotational speeds to 55,000 rpm. A complete set of axial load, frictional torque, and rotational speed is presented for two different compliant sub-structures and inter-pad gaps. Data obtained from commercially available foil thrust bearings both with and without active cooling is presented for comparison. A significant observation made possible by this data set is the speed-load capacity characteristic of foil thrust bearings. Whereas for the foil journal bearing the load capacity increases linearly with rotational speed, the foil thrust bearing operates in the hydrodynamic high speed limit. In this case, the load capacity is constant and in fact often decreases with speed if other factors such as thermal conditions and runner distortions are permitted to dominate the bearing performance.

Contrast affects flicker and speed perception differently

NASA Technical Reports Server (NTRS)

Thompson, P.; Stone, L. S.

1997-01-01

We have previously shown that contrast affects speed perception, with lower-contrast, drifting gratings perceived as moving slower. In a recent study, we examined the implications of this result on models of speed perception that use the amplitude of the response of linear spatio-temporal filters to determine speed. In this study, we investigate whether the contrast dependence of speed can be understood within the context of models in which speed estimation is made using the temporal frequency of the response of linear spatio-temporal filters. We measured the effect of contrast on flicker perception and found that contrast manipulations produce opposite effects on perceived drift rate and perceived flicker rate, i.e., reducing contrast increases the apparent temporal frequency of counterphase modulated gratings. This finding argues that, if a temporal frequency-based algorithm underlies speed perception, either flicker and speed perception must not be based on the output of the same mechanism or contrast effects on perceived spatial frequency reconcile the disparate effects observed for perceived temporal frequency and speed.

The circular form of the linear superconducting machine for marine propulsion

NASA Astrophysics Data System (ADS)

Rakels, J. H.; Mahtani, J. L.; Rhodes, R. G.

1981-01-01

The superconducting linear synchronous machine (LSM) is an efficient method of propulsion of advanced ground transport systems and can also be used in marine engineering for the propulsion of large commercial vessels, tankers, and military ships. It provides high torque at low shaft speeds and ease of reversibility; a circular LSM design is proposed as a drive motor. The equipment is compared with the superconducting homopolar motors, showing flexibility in design, built in redundancy features, and reliability.

On the development of HSCT tail sizing criteria using linear matrix inequalities

NASA Technical Reports Server (NTRS)

Kaminer, Isaac

1995-01-01

This report presents the results of a study to extend existing high speed civil transport (HSCT) tail sizing criteria using linear matrix inequalities (LMI). In particular, the effects of feedback specifications, such as MIL STD 1797 Level 1 and 2 flying qualities requirements, and actuator amplitude and rate constraints on the maximum allowable cg travel for a given set of tail sizes are considered. Results comparing previously developed industry criteria and the LMI methodology on an HSCT concept airplane are presented.

Use of the Azimuth Wavelength Cut-Off to Retrieve the Sea Surface Wind Speed from Sentinel 1 and COSMO-SkyMed SAR Data

NASA Astrophysics Data System (ADS)

Grieco, G.; Nirchio, F.; Montuori, A.; Migliaccio, M.; Lin, W.; Portabella, M.

2016-08-01

The dependency of the azimuth wavelength cut-off on the wind speed has been studied through a dataset of Sentinel-1 multi look SAR images co-located with wind speed measurements, significant wave height and mean wave direction from ECMWF operational output.A Geophysical Model Function (GMF) has been fitted and a retrieval exercise has been done comparing the results to a set of independent wind speed scatterometer measurements of the Chinese mission HY-2A. The preliminary results show that the dependency of the azimuth cut-off on the wind speed is linear only for fully developed sea states and that the agreement between the retrieved values and the measurements is good especially for high wind speed.A similar approach has been used to assess the dependency of the azimuth cut-off also for X-band COSMO-SkyMed data. The dataset is still incomplete but the preliminary results show a similar trend.

Deep Neural Network Emulation of a High-Order, WENO-Limited, Space-Time Reconstruction

NASA Astrophysics Data System (ADS)

Norman, M. R.; Hall, D. M.

2017-12-01

Deep Neural Networks (DNNs) have been used to emulate a number of processes in atmospheric models, including radiation and even so-called super-parameterization of moist convection. In each scenario, the DNN provides a good representation of the process even for inputs that have not been encountered before. More notably, they provide an emulation at a fraction of the cost of the original routine, giving speed-ups of 30× and even up to 200× compared to the runtime costs of the original routines. However, to our knowledge there has not been an investigation into using DNNs to emulate the dynamics. The most likely reason for this is that dynamics operators are typically both linear and low cost, meaning they cannot be sped up by a non-linear DNN emulation. However, there exist high-cost non-linear space-time dynamics operators that significantly reduce the number of parallel data transfers necessary to complete an atmospheric simulation. The WENO-limited Finite-Volume method with ADER-DT time integration is a prime example of this - needing only two parallel communications per large, fully limited time step. However, it comes at a high cost in terms of computation, which is why many would hesitate to use it. This talk investigates DNN emulation of the WENO-limited space-time finite-volume reconstruction procedure - the most expensive portion of this method, which densely clusters a large amount of non-linear computation. Different training techniques and network architectures are tested, and the accuracy and speed-up of each is given.

Linear spreading speeds from nonlinear resonant interaction

NASA Astrophysics Data System (ADS)

Faye, Grégory; Holzer, Matt; Scheel, Arnd

2017-06-01

We identify a new mechanism for propagation into unstable states in spatially extended systems, that is based on resonant interaction in the leading edge of invasion fronts. Such resonant invasion speeds can be determined solely based on the complex linear dispersion relation at the unstable equilibrium, but rely on the presence of a nonlinear term that facilitates the resonant coupling. We prove that these resonant speeds give the correct invasion speed in a simple example, we show that fronts with speeds slower than the resonant speed are unstable, and corroborate our speed criterion numerically in a variety of model equations, including a nonlocal scalar neural field model. GF received support from the project NONLOCAL (ANR-14-CE25-0013) funded by the French National Research Agency. MH was partially supported by the National Science Foundation through grant NSF-DMS-1516155. AS was partially supported by the National Science Foundation through grant NSF-DMS-1311740 and through a DAAD Fellowship.

Benzocyclobutene-based electric micromachines supported on microball bearings: Design, fabrication, and characterization

NASA Astrophysics Data System (ADS)

Modafe, Alireza

This dissertation summarizes the research activities that led to the development of the first microball-bearing-supported linear electrostatic micromotor with benzocyclobutene (BCB) low-k polymer insulating layers. The primary application of this device is long-range, high-speed linear micropositioning. The future generations of this device include rotary electrostatic micromotors and microgenerators. The development of the first generation of microball-bearing-supported micromachines, including device theory, design, and modeling, material characterization, process development, device fabrication, and device test and characterization is presented. The first generation of these devices is based on a 6-phase, bottom-drive, linear, variable-capacitance micromotor (B-LVCM). The design of the electrical and mechanical components of the micromotor, lumped-circuit modeling of the device and electromechanical characteristics, including variable capacitance, force, power, and speed are presented. Electrical characterization of BCB polymers, characterization of BCB chemical mechanical planarization (CMP), development of embedded BCB in silicon (EBiS) process, and integration of device components using microfabrication techniques are also presented. The micromotor consists of a silicon stator, a silicon slider, and four stainless-steel microballs. The aligning force profile of the micromotor was extracted from simulated and measured capacitances of all phases. An average total aligning force of 0.27 mN with a maximum of 0.41 mN, assuming a 100 V peak-to-peak square-wave voltage, was measured. The operation of the micromotor was verified by applying square-wave voltages and characterizing the slider motion. An average slider speed of 7.32 mm/s when excited by a 40 Hz, 120 V square-wave voltage was reached without losing the synchronization. This research has a pivotal impact in the field of power microelectromechanical systems (MEMS). It establishes the foundation for the development of more reliable, efficient electrostatic micromachines with variety of applications such as micropropulsion, high-speed micropumping, microfluid delivery, and microsystem power generation.

Thermoconvective flow velocity in a high-speed magnetofluid seal after it has stopped

NASA Astrophysics Data System (ADS)

Krakov, M. S.; Nikiforov, I. V.

2012-09-01

Convective flow is investigated in the high-speed (linear velocity of the shaft seal is more than 1 m/s) magnetofluid shaft seal after it has been stopped. Magnetic fluid is preliminarily heated due to viscous friction in the moving seal. After the shaft has been stopped, nonuniform heated fluid remains under the action of a high-gradient magnetic field. Numerical analysis has revealed that in this situation, intense thermomagnetic convection is initiated. The velocity of magnetic fluid depends on its viscosity. For the fluid with viscosity of 2 × 10-4 m2/s the maximum flow velocity within the volume of magnetic fluid with a characteristic size of 1 mm can attain a value of 10 m/s.

Non-linear vehicle-bridge-wind interaction model for running safety assessment of high-speed trains over a high-pier viaduct

NASA Astrophysics Data System (ADS)

Olmos, José M.; Astiz, Miguel Á.

2018-04-01

In order to properly study the high-speed traffic safety on a high-pier viaduct subject to episodes of lateral turbulent winds, an efficient dynamic interaction train-bridge-wind model has been developed and experimentally validated. This model considers the full wheel and rail profiles, the friction between these two bodies in contact, and the piers P-Delta effect. The model has been used to determine the critical train and wind velocities from which the trains cannot travel safely over the O'Eixo Bridge. The dynamic simulations carried out and the results obtained in the time domain show that traffic safety rates exceed the allowed limits for turbulent winds with mean velocities at the deck higher than 25 m/s.

Frequency control circuit for all-digital phase-lock loops

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Phase-lock loop references all its operations to fixed high-frequency service clock operating at highest speed which digital circuits permit. Wide-range control circuit provides linear control of frequency of reference signal. It requires only two counters in combination with control circuit consisting only of flip-flop and gate.

Investigation of the effects of sleeper-passing impacts on the high-speed train

NASA Astrophysics Data System (ADS)

Wu, Xingwen; Cai, Wubin; Chi, Maoru; Wei, Lai; Shi, Huailong; Zhu, Minhao

2015-12-01

The sleeper-passing impact has always been considered negligible in normal conditions, while the experimental data obtained from a High-speed train in a cold weather expressed significant sleeper-passing impacts on the axle box, bogie frame and car body. Therefore, in this study, a vertical coupled vehicle/track dynamic model was developed to investigate the sleeper-passing impacts and its effects on the dynamic performance of the high-speed train. In the model, the dynamic model of vehicle is established with 10 degrees of freedom. The track model is formulated with two rails supported on the discrete supports through the finite element method. The contact forces between the wheel and rail are estimated using the non-linear Hertz contact theory. The parametric studies are conducted to analyse effects of both the vehicle speeds and the discrete support stiffness on the sleeper-passing impacts. The results show that the sleeper-passing impacts become extremely significant with the increased support stiffness of track, especially when the frequencies of sleeper-passing impacts approach to the resonance frequencies of wheel/track system. The damping of primary suspension can effectively lower the magnitude of impacts in the resonance speed ranges, but has little effect on other speed ranges. Finally, a more comprehensively coupled vehicle/track dynamic model integrating with a flexible wheel set is developed to discuss the sleeper-passing-induced flexible vibration of wheel set.

Geostrophic adjustment in a shallow-water numerical model as it relates to thermospheric dynamics

NASA Technical Reports Server (NTRS)

Larsen, M. F.; Mikkelsen, I. S.

1986-01-01

The theory of geostrophic adjustment and its application to the dynamics of the high latitude thermosphere have been discussed in previous papers based on a linearized treatment of the fluid dynamical equations. However, a linearized treatment is only valid for small Rossby numbers given by Ro = V/fL, where V is the wind speed, f is the local value of the Coriolis parameter, and L is a characteristic horizontal scale for the flow. For typical values in the auroral zone, the approximation is not reasonable for wind speeds greater than 25 m/s or so. A shallow-water (one layer) model was developed that includes the spherical geometry and full nonlinear dynamics in the momentum equations in order to isolate the effects of the nonlinearities on the adjustment process. A belt of accelerated winds between 60 deg and 70 deg latitude was used as the initial condition. The adjustment process was found to proceed as expected from the linear formulation, but that an asymmetry between the response for an eastward and westward flow results from the nonlineawr curvature (centrifugal) terms. In general, the amplitude of an eastward flowing wind will be less after adjustment than a westward wind. For instance, if the initial wind velocity is 300 m/s, the linearized theory predicts a final wind speed of 240 m/s, regardless of the flow direction. However, the nonlinear curvature terms modify the response and produce a final wind speed of only 200 m/s for an initial eastward wind and a final wind speed of almost 300 m/s for an initial westward flow direction. Also, less gravity wave energy is produced by the adjustment of the westward flow than by the adjustment of the eastward flow. The implications are that the response of the thermosphere should be significantly different on the dawn and dusk sides of the auroral oval. Larger flow velocities would be expected on the dusk side since the plasma will accelerate the flow in a westward direction in that sector.

Control of variable speed variable pitch wind turbine based on a disturbance observer

NASA Astrophysics Data System (ADS)

Ren, Haijun; Lei, Xin

2017-11-01

In this paper, a novel sliding mode controller based on disturbance observer (DOB) to optimize the efficiency of variable speed variable pitch (VSVP) wind turbine is developed and analyzed. Due to the highly nonlinearity of the VSVP system, the model is linearly processed to obtain the state space model of the system. Then, a conventional sliding mode controller is designed and a DOB is added to estimate wind speed. The proposed control strategy can successfully deal with the random nature of wind speed, the nonlinearity of VSVP system, the uncertainty of parameters and external disturbance. Via adding the observer to the sliding mode controller, it can greatly reduce the chattering produced by the sliding mode switching gain. The simulation results show that the proposed control system has the effectiveness and robustness.

Linear dynamic coupling in geared rotor systems

NASA Technical Reports Server (NTRS)

David, J. W.; Mitchell, L. D.

1986-01-01

The effects of high frequency oscillations caused by the gear mesh, on components of a geared system that can be modeled as rigid discs are analyzed using linear dynamic coupling terms. The coupled, nonlinear equations of motion for a disc attached to a rotating shaft are presented. The results of a trial problem analysis show that the inclusion of the linear dynamic coupling terms can produce significant changes in the predicted response of geared rotor systems, and that the produced sideband responses are greater than the unbalanced response. The method is useful in designing gear drives for heavy-lift helicopters, industrial speed reducers, naval propulsion systems, and heavy off-road equipment.

Simultaneous measurement of bacterial flagellar rotation rate and swimming speed.

PubMed Central

Magariyama, Y; Sugiyama, S; Muramoto, K; Kawagishi, I; Imae, Y; Kudo, S

1995-01-01

Swimming speeds and flagellar rotation rates of individual free-swimming Vibrio alginolyticus cells were measured simultaneously by laser dark-field microscopy at 25, 30, and 35 degrees C. A roughly linear relation between swimming speed and flagellar rotation rate was observed. The ratio of swimming speed to flagellar rotation rate was 0.113 microns, which indicated that a cell progressed by 7% of pitch of flagellar helix during one flagellar rotation. At each temperature, however, swimming speed had a tendency to saturate at high flagellar rotation rate. That is, the cell with a faster-rotating flagellum did not always swim faster. To analyze the bacterial motion, we proposed a model in which the torque characteristics of the flagellar motor were considered. The model could be analytically solved, and it qualitatively explained the experimental results. The discrepancy between the experimental and the calculated ratios of swimming speed to flagellar rotation rate was about 20%. The apparent saturation in swimming speed was considered to be caused by shorter flagella that rotated faster but produced less propelling force. Images FIGURE 1 FIGURE 4 PMID:8580359

Fixed-speed and Variable-speed Pumped Storage Dispatch Model in Power Systems with High Renewable Penetration

NASA Astrophysics Data System (ADS)

Yuan, Bo; Zong, Jin; Xu, Zhicheng

2018-06-01

According to different operating characteristics of pumped storage fixed speed unit and variable speed unit, a joint dispatching model of pumped storage unit and other types of units based on mixed integer linear optimization is constructed. The model takes into account the operating conditions, reservoir capacity, cycle type and other pumped storage unit constraints, but also consider the frequent start and stop and the stability of the operation of the unit caused by the loss. Using the Cplex solver to solve the model, the empirical example of the provincial power grid shows that the model can effectively arrange the pumping storage speed and the dispatching operation of the variable speed unit under the precondition of economic life of the unit, and give full play to the function of peak shaving and accommodating new energy. Because of its more flexible regulation characteristics of power generation and pumping conditions, the variable speed unit can better improve the operating conditions of other units in the system and promote the new energy dissipation.

Analysis of High Speed Jets Produced by a Servo Tube Driven Liquid Jet Injector

NASA Astrophysics Data System (ADS)

Portaro, Rocco; Ng, Hoi Dick

2017-11-01

In today's healthcare environment many types of medication must be administered through the use of hypodermic needles. Although this practice has been in use for many years, drawbacks such as accidental needle stick injuries, transmission of deadly viruses and bio-hazardous waste are still present. This study focuses on improving a needle free technology known as liquid jet injection, through the implementation of a linear servo tube actuator for the construction of a fully closed loop liquid jet injection system. This device has the ability to deliver both micro- and macro- molecules, high viscosity fluids whilst providing real time control of the jet pressure profile for accurate depth and dispersion control. The experiments are conducted using a prototype that consists of a 3 kW servo tube actuator, coupled to a specially designed injection head allowing nozzle size and injection volume to be varied. The device is controlled via a high speed servo amplifier and FPGA. The high speed jets emanating from the injector are assessed via high speed photography and through the use of a force transducer. Preliminary results indicate that the system allows for accurate shaping of the jet pressure profile, making it possible to target different tissue depths/types accurately.

Studies on dynamic behavior of rotating mirrors

NASA Astrophysics Data System (ADS)

Li, Jingzhen; Sun, Fengshan; Gong, Xiangdong; Huang, Hongbin; Tian, Jie

2005-02-01

A rotating mirror is a kernel unit in a Miller-type high speed camera, which is both as an imaging element in optical path and as an element to implement ultrahigh speed photography. According to Schardin"s Principle, information capacity of an ultrahigh speed camera with rotating mirror depends on primary wavelength of lighting used by the camera and limit linear velocity on edge of the rotating-mirror: the latter is related to material (including specifications in technology), cross-section shape and lateral structure of rotating mirror. In this manuscript dynamic behavior of high strength aluminium alloy rotating mirrors is studied, from which it is preliminarily shown that an aluminium alloy rotating mirror can be absolutely used as replacement for a steel rotating-mirror or a titanium alloy rotating-mirror in framing photographic systems, and it could be also used as a substitute for a beryllium rotating-mirror in streak photographic systems.

A linearly frequency-swept high-speed-rate multi-wavelength laser for optical coherence tomography

NASA Astrophysics Data System (ADS)

Wang, Qiyu; Wang, Zhaoying; Yuan, Quan; Ma, Rui; Du, Tao; Yang, Tianxin

2017-02-01

We proposed and demonstrated a linearly frequency-swept multi-wavelength laser source for optical coherence tomography (OCT) eliminating the need of wavenumber space resampling in the postprocessing progress. The source consists of a multi-wavelength fiber laser source (MFS) and an optical sweeping loop. In this novel laser source, an equally spaced multi-wavelength laser is swept simultaneously by a certain step each time in the frequency domain in the optical sweeping loop. The sweeping step is determined by radio frequency (RF) signal which can be precisely controlled. Thus the sweeping behavior strictly maintains a linear relationship between time and frequency. We experimentally achieved linear time-frequency sweeping at a sweeping rate of 400 kHz with our laser source.

New method of writing long-period fiber gratings using high-frequency CO2 laser

NASA Astrophysics Data System (ADS)

Guo, Gao-Ran; Song, Ying; Zhang, Wen-Tao; Jiang, Yue; Li, Fang

2016-11-01

In the paper, the Long period fiber gratings (LPFG) were fabricated in a single-mode fiber using a high frequency CO2 laser system with the point-to-point technique. The experimental setup consists of a CO2 laser controlling system, a focusing system located at a motorized linear stage, a fiber alignment stage, and an optical spectrum analyzer to monitor the transmission spectrum of the LPFG. The period of the LPFG is precisely inscribed by periodically turning on/off the laser shutter while the motorized linear stage is driven to move at a constant speed. The efficiency of fiber writing process is improved.

Effects of fourth-order dispersion in very high-speed optical time-division multiplexed transmission.

PubMed

Capmany, J; Pastor, D; Sales, S; Ortega, B

2002-06-01

We present a closed-form expression for computation of the output pulse's rms time width in an optical fiber link with up to fourth-order dispersion (FOD) by use of an optical source with arbitrary linewidth and chirp parameters. We then specialize the expression to analyze the effect of FOD on the transmission of very high-speed linear optical time-division multiplexing systems. By suitable source chirping, FOD can be compensated for to an upper link-length limit above which other techniques must be employed. Finally, a design formula to estimate the maximum attainable bit rate limited by FOD as a function of the link length is also presented.

Progress on a Taylor weak statement finite element algorithm for high-speed aerodynamic flows

NASA Technical Reports Server (NTRS)

Baker, A. J.; Freels, J. D.

1989-01-01

A new finite element numerical Computational Fluid Dynamics (CFD) algorithm has matured to the point of efficiently solving two-dimensional high speed real-gas compressible flow problems in generalized coordinates on modern vector computer systems. The algorithm employs a Taylor Weak Statement classical Galerkin formulation, a variably implicit Newton iteration, and a tensor matrix product factorization of the linear algebra Jacobian under a generalized coordinate transformation. Allowing for a general two-dimensional conservation law system, the algorithm has been exercised on the Euler and laminar forms of the Navier-Stokes equations. Real-gas fluid properties are admitted, and numerical results verify solution accuracy, efficiency, and stability over a range of test problem parameters.

High speed intravascular photoacoustic imaging of atherosclerotic arteries (Conference Presentation)

NASA Astrophysics Data System (ADS)

Piao, Zhonglie; Ma, Teng; Qu, Yueqiao; Li, Jiawen; Yu, Mingyue; He, Youmin; Shung, K. Kirk; Zhou, Qifa; Kim, Chang-Seok; Chen, Zhongping

2016-02-01

Cardiovascular disease is the leading cause of death in the industrialized nations. Accurate quantification of both the morphology and composition of lipid-rich vulnerable atherosclerotic plaque are essential for early detection and optimal treatment in clinics. In previous works, intravascular photoacoustic (IVPA) imaging for detection of lipid-rich plaque within coronary artery walls has been demonstrated in ex vivo, but the imaging speed is still limited. In order to increase the imaging speed, a high repetition rate laser is needed. In this work, we present a high speed integrated IVPA/US imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A miniature catheter with 1.0 mm outer diameter was designed with a 200 μm multimode fiber and an ultrasound transducer with 45 MHz center frequency. The fiber was polished at 38 degree and enclosed in a glass capillary for total internal reflection. An optical/electrical rotary junction and pull-back mechanism was applied for rotating and linearly scanning the catheter to obtain three-dimensional imaging. Atherosclerotic rabbit abdominal aorta was imaged as two frame/second at 1725 nm. Furthermore, by wide tuning range of the laser wavelength from 1680 nm to 1770 nm, spectroscopic photoacoustic analysis of lipid-mimicking phantom and an human atherosclerotic artery was performed ex vivo. The results demonstrated that the developed IVPA/US imaging system is capable for high speed intravascular imaging for plaque detection.

Log-linear model based behavior selection method for artificial fish swarm algorithm.

PubMed

Huang, Zhehuang; Chen, Yidong

2015-01-01

Artificial fish swarm algorithm (AFSA) is a population based optimization technique inspired by social behavior of fishes. In past several years, AFSA has been successfully applied in many research and application areas. The behavior of fishes has a crucial impact on the performance of AFSA, such as global exploration ability and convergence speed. How to construct and select behaviors of fishes are an important task. To solve these problems, an improved artificial fish swarm algorithm based on log-linear model is proposed and implemented in this paper. There are three main works. Firstly, we proposed a new behavior selection algorithm based on log-linear model which can enhance decision making ability of behavior selection. Secondly, adaptive movement behavior based on adaptive weight is presented, which can dynamically adjust according to the diversity of fishes. Finally, some new behaviors are defined and introduced into artificial fish swarm algorithm at the first time to improve global optimization capability. The experiments on high dimensional function optimization showed that the improved algorithm has more powerful global exploration ability and reasonable convergence speed compared with the standard artificial fish swarm algorithm.

Liquid-crystal-based switchable polarizers for sensor protection.

PubMed

Wu, C S; Wu, S T

1995-11-01

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately ±10°. In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

Liquid-crystal-based switchable polarizers for sensor protection

NASA Astrophysics Data System (ADS)

Wu, Chiung-Sheng; Wu, Shin-Tson

1995-11-01

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately +/-10 deg In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

Quantification of precipitation measurement discontinuity induced by wind shields on national gauges

USGS Publications Warehouse

Yang, Daqing; Goodison, Barry E.; Metcalfe, John R.; Louie, Paul; Leavesley, George H.; Emerson, Douglas G.; Hanson, Clayton L.; Golubev, Valentin S.; Elomaa, Esko; Gunther, Thilo; Pangburn, Timothy; Kang, Ersi; Milkovic, Janja

1999-01-01

Various combinations of wind shields and national precipitation gauges commonly used in countries of the northern hemisphere have been studied in this paper, using the combined intercomparison data collected at 14 sites during the World Meteorological Organization's (WMO) Solid Precipitation Measurement Intercomparison Project. The results show that wind shields improve gauge catch of precipitation, particularly for snow. Shielded gauges, on average, measure 20–70% more snow than unshielded gauges. Without a doubt, the use of wind shields on precipitation gauges has introduced a significant discontinuity into precipitation records, particularly in cold and windy regions. This discontinuity is not constant and it varies with wind speed, temperature, and precipitation type. Adjustment for this discontinuity is necessary to obtain homogenous precipitation data for climate change and hydrological studies. The relation of the relative catch ratio (RCR, ratio of measurements of shielded gauge to unshielded gauge) versus wind speed and temperature has been developed for Alter and Tretyakov wind shields. Strong linear relations between measurements of shielded gauge and unshielded gauge have also been found for different precipitation types. The linear relation does not fully take into account the varying effect of wind and temperature on gauge catch. Overadjustment by the linear relation may occur at those sites with lower wind speeds, and underadjustment may occur at those stations with higher wind speeds. The RCR technique is anticipated to be more applicable in a wide range of climate conditions. The RCR technique and the linear relation have been tested at selected WMO intercomparison stations, and reasonable agreement between the adjusted amounts and the shielded gauge measurements was obtained at most of the sites. Test application of the developed methodologies to a regional or national network is therefore recommended to further evaluate their applicability in different climate conditions. Significant increase of precipitation is expected due to the adjustment particularly in high latitudes and other cold regions. This will have a meaningful impact on climate variation and change analyses.

Polarized Linear Motor Combined With Levitation Actuators Working in a Partial Vacuum Environment—Application to Swissmetro

NASA Astrophysics Data System (ADS)

Cassat, Alain; Espanet, Christophe; Bourquin, Vincent; Hagmann, Pascal; Jufer, Marcel

Worldwide high speed Maglev (> 400km/h) developments refer to Maglev such as the Japanese JR-Maglev MLX, the German Transrapid and the USA Inductrack Maglev. Other world projects exist such as the Japan HSST (< 300km/h) and the China HTC. The JR-Maglev, the Transrapid and the HSST have reached industrial levels. The Swissmetro Project presents a unique aspect of Maglev: it is designed to work under partial vacuum (< 10kPa) in two tunnels and for high speeds (>400km/h). The authors investigate new possibilities to combine both the propulsion and the levitation. In order to minimize the heat due to the motor levitation and guidance losses, a polarized excitation is proposed. The use of permanent magnet NdFeB for the excitation is still not applied for high speed Maglev, requiring mechanical power greater than 6MW. Such a solution only appears in Urban Rapid Transit Maglev (<160km/h), such as the USA MagneMotion M3 and the General Atomic Urban Maglev. For Swissmetro, the authors study the polarized inductors for the levitation, implying a polarized synchronous linear motor. The polarization is obtained with permanent magnets NdFeB. This paper presents some key issues related to such technical choices. The motor design is described and the power balance is presented. The thermal behavior is analyzed using a numerical platform of the complete vehicle-tunnel system, based on computation of the air flow dynamic.

How Do Tides and Tsunamis Interact in a Highly Energetic Channel? The Case of Canal Chacao, Chile

NASA Astrophysics Data System (ADS)

Winckler, Patricio; Sepúlveda, Ignacio; Aron, Felipe; Contreras-López, Manuel

2017-12-01

This study aims at understanding the role of tidal level, speed, and direction in tsunami propagation in highly energetic tidal channels. The main goal is to comprehend whether tide-tsunami interactions enhance/reduce elevation, currents speeds, and arrival times, when compared to pure tsunami models and to simulations in which tides and tsunamis are linearly superimposed. We designed various numerical experiments to compute the tsunami propagation along Canal Chacao, a highly energetic channel in the Chilean Patagonia lying on a subduction margin prone to megathrust earthquakes. Three modeling approaches were implemented under the same seismic scenario: a tsunami model with a constant tide level, a series of six composite models in which independent tide and tsunami simulations are linearly superimposed, and a series of six tide-tsunami nonlinear interaction models (full models). We found that hydrodynamic patterns differ significantly among approaches, being the composite and full models sensitive to both the tidal phase at which the tsunami is triggered and the local depth of the channel. When compared to full models, composite models adequately predicted the maximum surface elevation, but largely overestimated currents. The amplitude and arrival time of the tsunami-leading wave computed with the full model was found to be strongly dependent on the direction of the tidal current and less responsive to the tide level and the tidal current speed. These outcomes emphasize the importance of addressing more carefully the interactions of tides and tsunamis on hazard assessment studies.

Parallel network simulations with NEURON.

PubMed

Migliore, M; Cannia, C; Lytton, W W; Markram, Henry; Hines, M L

2006-10-01

The NEURON simulation environment has been extended to support parallel network simulations. Each processor integrates the equations for its subnet over an interval equal to the minimum (interprocessor) presynaptic spike generation to postsynaptic spike delivery connection delay. The performance of three published network models with very different spike patterns exhibits superlinear speedup on Beowulf clusters and demonstrates that spike communication overhead is often less than the benefit of an increased fraction of the entire problem fitting into high speed cache. On the EPFL IBM Blue Gene, almost linear speedup was obtained up to 100 processors. Increasing one model from 500 to 40,000 realistic cells exhibited almost linear speedup on 2,000 processors, with an integration time of 9.8 seconds and communication time of 1.3 seconds. The potential for speed-ups of several orders of magnitude makes practical the running of large network simulations that could otherwise not be explored.

Parallel Network Simulations with NEURON

PubMed Central

Migliore, M.; Cannia, C.; Lytton, W.W; Markram, Henry; Hines, M. L.

2009-01-01

The NEURON simulation environment has been extended to support parallel network simulations. Each processor integrates the equations for its subnet over an interval equal to the minimum (interprocessor) presynaptic spike generation to postsynaptic spike delivery connection delay. The performance of three published network models with very different spike patterns exhibits superlinear speedup on Beowulf clusters and demonstrates that spike communication overhead is often less than the benefit of an increased fraction of the entire problem fitting into high speed cache. On the EPFL IBM Blue Gene, almost linear speedup was obtained up to 100 processors. Increasing one model from 500 to 40,000 realistic cells exhibited almost linear speedup on 2000 processors, with an integration time of 9.8 seconds and communication time of 1.3 seconds. The potential for speed-ups of several orders of magnitude makes practical the running of large network simulations that could otherwise not be explored. PMID:16732488

Design and jump phenomenon analysis of an eccentric ring energy harvester

NASA Astrophysics Data System (ADS)

Wang, Yu-Jen; Chen, Chung-De

2013-10-01

This paper presents the development of a wheel-mounted eccentric ring energy harvester that is driven by centripetal and gravitational forces during wheel rotation. The natural frequency of the eccentric ring matches the wheel rotation frequency at any car speed because its character length is designed equal to the wheel radius. Consequently, the eccentric ring oscillates with a relatively large swing angle at the wheel speed to generate high levels of power. The nonlinear dynamic behavior of the eccentric ring is investigated to ensure that the proposed design produces steady swing angles, especially at high wheel speeds. Herein, the jump phenomenon of the dynamic motion of the eccentric ring is analyzed by using the Duffing equation and the linearization process. The discriminant value obtained from the analysis confirms that no jump phenomenon occurs at all wheel speeds if the eccentric ring is properly designed. In the experiment, the eccentric ring is integrated with magnets and a coil set to generate 318-442 μW at constant wheel speeds between 300 and 500 rpm. This shows that the proposed device is a potential power source for low-power wheel-mounted electronics, such as pressure sensors, accelerometers, and thermometers.

Running faster causes disaster: trade-offs between speed, manoeuvrability and motor control when running around corners in northern quolls (Dasyurus hallucatus).

PubMed

Wynn, Melissa L; Clemente, Christofer; Nasir, Ami Fadhillah Amir Abdul; Wilson, Robbie S

2015-02-01

Movement speed is fundamental to all animal behaviour, yet no general framework exists for understanding why animals move at the speeds they do. Even during fitness-defining behaviours like running away from predators, an animal should select a speed that balances the benefits of high speed against the increased probability of mistakes. In this study, we explored this idea by quantifying trade-offs between speed, manoeuvrability and motor control in wild northern quolls (Dasyurus hallucatus) - a medium-sized carnivorous marsupial native to northern Australia. First, we quantified how running speed affected the probability of crashes when rounding corners of 45, 90 and 135 deg. We found that the faster an individual approached a turn, the higher the probability that they would crash, and these risks were greater when negotiating tighter turns. To avoid crashes, quolls modulated their running speed when they moved through turns of varying angles. Average speed for quolls when sprinting along a straight path was around 4.5 m s(-1) but this decreased linearly to speeds of around 1.5 m s(-1) when running through 135 deg turns. Finally, we explored how an individual's morphology affects their manoeuvrability. We found that individuals with larger relative foot sizes were more manoeuvrable than individuals with smaller relative foot sizes. Thus, movement speed, even during extreme situations like escaping predation, should be based on a compromise between high speed, manoeuvrability and motor control. We advocate that optimal - rather than maximal - performance capabilities underlie fitness-defining behaviours such as escaping predators and capturing prey. © 2015. Published by The Company of Biologists Ltd.

Fuzzy – PI controller to control the velocity parameter of Induction Motor

NASA Astrophysics Data System (ADS)

Malathy, R.; Balaji, V.

2018-04-01

The major application of Induction motor includes the usage of the same in industries because of its high robustness, reliability, low cost, highefficiency and good self-starting capability. Even though it has the above mentioned advantages, it also have some limitations: (1) the standard motor is not a true constant-speed machine, itsfull-load slip varies less than 1 % (in high-horsepower motors).And (2) it is not inherently capable of providing variable-speedoperation. In order to solve the above mentioned problem smart motor controls and variable speed controllers are used. Motor applications involve non linearity features, which can be controlled by Fuzzy logic controller as it is capable of handling those features with high efficiency and it act similar to human operator. This paper presents individuality of the plant modelling. The fuzzy logic controller (FLC)trusts on a set of linguistic if-then rules, a rule-based Mamdani for closed loop Induction Motor model. Themotor model is designed and membership functions are chosenaccording to the parameters of the motor model. Simulation results contains non linearity in induction motor model. A conventional PI controller iscompared practically to fuzzy logic controller using Simulink.

Numerical Simulations of Laminar Air-Water Flow of a Non-linear Progressive Wave at Low Wind Speed

NASA Astrophysics Data System (ADS)

Wen, X.; Mobbs, S.

2014-03-01

A numerical simulation for two-dimensional laminar air-water flow of a non-linear progressive water wave with large steepness is performed when the background wind speed varies from zero to the wave phase speed. It is revealed that in the water the difference between the analytical solution of potential flow and numerical solution of viscous flow is very small, indicating that both solutions of the potential flow and viscous flow describe the water wave very accurately. In the air the solutions of potential and viscous flows are very different due to the effects of viscosity. The velocity distribution in the airflow is strongly influenced by the background wind speed and it is found that three wind speeds, , (the maximum orbital velocity of a water wave), and (the wave phase speed), are important in distinguishing different features of the flow patterns.

Numerical investigation on an array of Helmholtz resonators for the reduction of micro-pressure waves in modern and future high-speed rail tunnel systems

NASA Astrophysics Data System (ADS)

Tebbutt, J. A.; Vahdati, M.; Carolan, D.; Dear, J. P.

2017-07-01

Previous research has proposed that an array of Helmholtz resonators may be an effective method for suppressing the propagation of pressure and sound waves, generated by a high-speed train entering and moving in a tunnel. The array can be used to counteract environmental noise from tunnel portals and also the emergence of a shock wave in the tunnel. The implementation of an array of Helmholtz resonators in current and future high-speed train-tunnel systems is studied. Wave propagation in the tunnel is modelled using a quasi-one-dimensional formulation, accounting for non-linear effects, wall friction and the diffusivity of sound. A multi-objective genetic algorithm is then used to optimise the design of the array, subject to the geometric constraints of a demonstrative tunnel system and the incident wavefront in order to attenuate the propagation of pressure waves. It is shown that an array of Helmholtz resonators can be an effective countermeasure for various tunnel lengths. In addition, the array can be designed to function effectively over a wide operating envelope, ensuring it will still function effectively as train speeds increase into the future.

The Shock and Vibration Digest, Volume 18, Number 2

DTIC Science & Technology

1986-02-01

Bounce Response of Canadian 71. McMunn, J.C., "Multi-Parameter Optimum MAGLEV Vehicle under Guideway Excitation. . Damping in Linear Dynamical Systems...Northeast Corridor High-Speed Test Cars," J. "Suspension Bounce Response of Canadian L’,-*’-.-" Engrg. Indus., Trans. ASME, 91B (3), pp 897-907 MAGLEV

Design of a high-speed optical dark-soliton detector using a phase-shifted waveguide Bragg grating in reflection.

PubMed

Ngo, Nam Quoc

2007-12-01

A theoretical study of a new application of a simple pi-phase-shifted waveguide Bragg grating (PSWBG) in reflection mode as a high-speed optical dark-soliton detector is presented. The PSWBG consists of two concatenated identical uniform waveguide Bragg gratings with a pi phase shift between them. The reflective PSWBG, with grating reflectivities equal to 0.9, a free spectral range of 1.91 THz, and a nonlinear phase response, can convert a 40 Gbit/s noisy dark-soliton signal into a high-quality 40 Gbit/s return-to-zero signal with a peak power level of approximately 17.5 dB greater than that by the existing Mach-Zehnder interferometer with free spectral range of 1.91 THz and a linear phase response.

High speed strain measurement of active mode locking FBG laser sensor using chirped FBG cavity

NASA Astrophysics Data System (ADS)

Kim, Gyeong Hun; Kim, Joon Young; Park, Chang Hyun; Kim, Chang-Seok; Lee, Hwi Don; Chung, Youngjoo

2017-04-01

We propose a high speed strain measurement method using an active mode locking (AML) fiber Bragg grating (FBG) laser sensor with a chirped FBG cavity. The mode-locked frequency of the AML laser depends on both the position and Bragg wavelength of the FBG. Thus, the mode-locked frequency of cascaded FBGs can be detected independently along the cavity length of cascaded FBGs. The strain across FBGs can be interrogated dynamically by monitoring the change in mode-locked frequency. In this respect, the chirped FBG critically improves the frequency sensitivity to Bragg wavelength shift as a function of increasing dispersion in the AML cavity. The strain measurement of the FBG sensor shows a highly linear response, with an R-squared value of 0.9997.

Microball-bearing-supported electrostatic micromachines with polymer dielectric films for electromechanical power conversion

NASA Astrophysics Data System (ADS)

Modafe, A.; Ghalichechian, N.; Frey, A.; Lang, J. H.; Ghodssi, R.

2006-09-01

This paper presents our latest research activities toward the development of electrostatic micromotors/microgenerators with a microball-bearing support mechanism and benzocyclobutene (BCB) low-k polymer insulating layers. The primary applications of these devices are long-range, high-speed micropositioning, high-speed micro pumping and micro power generation. In this paper, we present the development of the first generation of microball-bearing-supported micromachines. This device is a 6-phase, bottom-drive, linear, variable-capacitance micromotor. The design and fabrication of the linear micromotor, and characterization of the motor capacitance, force and motion in 3-phase and 6-phase excitation modes are presented. The micromotor consists of a silicon stator, a silicon slider and four stainless-steel microballs. The aligning force profile of the micromotor was extracted from simulated and measured capacitances of all phases. An average total aligning force of 0.27 mN with a maximum of 0.41 mN at 100 V dc was measured. The ac operation of the micromotor was verified by applying square-wave voltages and characterizing the slider motion. An average slider speed of 7.32 mm s-1 at 40 Hz and 120 V P-P was reached without losing the synchronization. The design, fabrication and characterization methods presented in this paper can be used as a technology platform for developing rotary micromachines.

Proton velocity ring-driven instabilities and their dependence on the ring speed: Linear theory

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun; Gary, S. Peter

2017-08-01

Linear dispersion theory is used to study the Alfvén-cyclotron, mirror and ion Bernstein instabilities driven by a tenuous (1%) warm proton ring velocity distribution with a ring speed, vr, varying between 2vA and 10vA, where vA is the Alfvén speed. Relatively cool background protons and electrons are assumed. The modeled ring velocity distributions are unstable to both the Alfvén-cyclotron and ion Bernstein instabilities whose maximum growth rates are roughly a linear function of the ring speed. The mirror mode, which has real frequency ωr=0, becomes the fastest growing mode for sufficiently large vr/vA. The mirror and Bernstein instabilities have maximum growth at propagation oblique to the background magnetic field and become more field-aligned with an increasing ring speed. Considering its largest growth rate, the mirror mode, in addition to the Alfvén-cyclotron mode, can cause pitch angle diffusion of the ring protons when the ring speed becomes sufficiently large. Moreover, because the parallel phase speed, v∥ph, becomes sufficiently small relative to vr, the low-frequency Bernstein waves can also aid the pitch angle scattering of the ring protons for large vr. Potential implications of including these two instabilities at oblique propagation on heliospheric pickup ion dynamics are discussed.

Will women outrun men in ultra-marathon road races from 50 km to 1,000 km?

PubMed

Zingg, Matthias Alexander; Karner-Rezek, Klaus; Rosemann, Thomas; Knechtle, Beat; Lepers, Romuald; Rüst, Christoph Alexander

2014-01-01

It has been assumed that women would be able to outrun men in ultra-marathon running. The present study investigated the sex differences in running speed in ultra-marathons held worldwide from 50 km to 1,000 km. Changes in running speeds and the sex differences in running speeds in the annual fastest finishers in 50 km, 100 km, 200 km and 1,000 km events held worldwide from 1969-2012 were analysed using linear, non-linear and multi-level regression analyses. For the annual fastest and the annual ten fastest finishers, running speeds increased non-linearly in 50 km and 100 km, but not in 200 km and 1,000 km where running speeds remained unchanged for the annual fastest. The sex differences decreased non-linearly in 50 km and 100 km, but not in 200 and 1,000 km where the sex difference remained unchanged for the annual fastest. For the fastest women and men ever, the sex difference in running speed was lowest in 100 km (5.0%) and highest in 50 km (15.4%). For the ten fastest women and men ever, the sex difference was lowest in 100 km (10.0 ± 3.0%) and highest in 200 km (27.3 ± 5.7%). For both the fastest (r(2) = 0.003, p = 0.82) and the ten fastest finishers ever (r(2) = 0.34, p = 0.41) in 50 km, 100 km, 200 km and 1,000 km, we found no correlation between sex difference in performance and running speed. To summarize, the sex differences in running speeds decreased non-linearly in 50 km and 100 km but remained unchanged in 200 km and 1,000 km, and the sex differences in running speeds showed no change with increasing length of the race distance. These findings suggest that it is very unlikely that women will ever outrun men in ultra-marathons held from 50 km to 100 km.

An experimental investigation of a Mach 3.0 high-speed civil transport at supersonic speeds

NASA Technical Reports Server (NTRS)

Hernandez, Gloria; Covell, Peter F.; Mcgraw, Marvin E., Jr.

1993-01-01

An experimental study was conducted to determine the aerodynamic characteristics of a proposed high speed civil transport. This configuration was designed to cruise at Mach 3.0 and sized to carry 250 passengers for 6500 n.mi. The configuration consists of a highly blended wing body and features a blunt parabolic nose planform, a highly swept inboard wing panel, a moderately swept outboard wing panel, and a curved wingtip. Wind tunnel tests were conducted in the Langley Unitary Plan Wind Tunnel on a 0.0098-scale model. Force, moment, and pressure data were obtained for Mach numbers ranging from 1.6 to 3.6 and at angles of attack ranging from -4 to 10 deg. Extensive flow visualization studies (vapor screen and oil flow) were obtained in the experimental program. Both linear and advanced computational fluid dynamics (CFD) theoretical comparisons are shown to assess the ability to predict forces, moments, and pressures on configurations of this type. In addition, an extrapolation of the wind tunnel data, based on empirical principles, to full-scale conditions is compared with the theoretical aerodynamic predictions.

Reduced Order Modeling For High Speed Flows with Moving Shocks

DTIC Science & Technology

2001-12-03

critical values of Q are the values of U and λ such that G(y) = dQ(y) dy =   F (U) + λ dC(U) dU C(U)   = [0]. (2.28) As long as the constraints ...by adding each linear constraint as shown in equation (5.6) (the n + 1 superscript on US is dropped for convenience). This new functional Q , called...Institute of Technology, School of Engineering and Man- agement, 2001. 49. Naylor, Arch W. and Sell, George R. Linear Operator Theory in Engineering and

Hydraulic forces on a centrifugal impeller undergoing synchronous whirl

NASA Technical Reports Server (NTRS)

Allaire, P. E.; Sato, C. J.; Branagan, L. A.

1984-01-01

High speed centrifugal rotating machinery with large vibrations caused by aerodynamic forces on impellers was examined. A method to calculate forces in a two dimensional orbiting impeller in an unbounded fluid with nonuniform entering flow was developed. A finite element model of the full impeller is employed to solve the inviscid flow equations. Five forces acting on the impeller are: Coriolis forces, centripetal forces, changes in linear momentum, changes in pressure due to rotation and pressure changes due to linear momentum. Both principal and cross coupled stiffness coefficients are calculated for the impeller.

Impact of the Ability to Divide Attention on Reading Performance in Glaucoma.

PubMed

Swenor, Bonnielin K; Varadaraj, Varshini; Dave, Paulomi; West, Sheila K; Rubin, Gary S; Ramulu, Pradeep Y

2017-05-01

To determine if the ability to divide attention affects the relationship between glaucoma-related vision loss and reading speed. Better eye mean deviation (MD), contrast sensitivity (CS), and better-eye distance visual acuity (VA) were measured in 28 participants with glaucoma and 21 controls. Reading speeds were assessed using MNRead, IRest, and sustained silent reading tests (words per minute, wpm). The ability to divide attention was measured using the Brief Test of Attention (BTA; scored 0-10). Multivariable linear regression models were used to determine the relationship between visual factors and reading speeds. Effect modification by BTA score (low BTA: <7; high BTA: ≥7) was examined. Worse CS (per 0.1 log unit) was associated with slower maximum reading speed on MNRead test for participants with low BTA scores (β = -9 wpm; 95% confidence interval [CI]: -16, -2), but not for those with high BTA scores (β = -2 wpm; 95% CI: -6, +2). Similarly, for the IRest test, worse CS was associated with slower reading speeds (β = -12 wpm; 95% CI: -20, -4) among those with low, but not high BTA scores (β = -4 wpm; 95% CI: -10, +2). For the sustained silent reading test, glaucoma status (versus controls), worse visual field (VF) MD (per 5 dB), and worse CS were associated with 39%, 21%, and 19% slower reading speeds, respectively, for those with low BTA scores (P < 0.05), but these associations were not significant among those with high BTA scores (P > 0.1 for all). Decreased ability to divide attention, indicated by lower BTA scores, is associated with slower reading speeds in glaucoma with reduced CS and VF defects.

Impact of the Ability to Divide Attention on Reading Performance in Glaucoma

PubMed Central

Swenor, Bonnielin K.; Varadaraj, Varshini; Dave, Paulomi; West, Sheila K.; Rubin, Gary S.; Ramulu, Pradeep Y.

2017-01-01

Purpose To determine if the ability to divide attention affects the relationship between glaucoma-related vision loss and reading speed. Methods Better eye mean deviation (MD), contrast sensitivity (CS), and better-eye distance visual acuity (VA) were measured in 28 participants with glaucoma and 21 controls. Reading speeds were assessed using MNRead, IRest, and sustained silent reading tests (words per minute, wpm). The ability to divide attention was measured using the Brief Test of Attention (BTA; scored 0–10). Multivariable linear regression models were used to determine the relationship between visual factors and reading speeds. Effect modification by BTA score (low BTA: <7; high BTA: ≥7) was examined. Results Worse CS (per 0.1 log unit) was associated with slower maximum reading speed on MNRead test for participants with low BTA scores (β = −9 wpm; 95% confidence interval [CI]: −16, −2), but not for those with high BTA scores (β = −2 wpm; 95% CI: −6, +2). Similarly, for the IRest test, worse CS was associated with slower reading speeds (β = −12 wpm; 95% CI: −20, −4) among those with low, but not high BTA scores (β = −4 wpm; 95% CI: −10, +2). For the sustained silent reading test, glaucoma status (versus controls), worse visual field (VF) MD (per 5 dB), and worse CS were associated with 39%, 21%, and 19% slower reading speeds, respectively, for those with low BTA scores (P < 0.05), but these associations were not significant among those with high BTA scores (P > 0.1 for all). Conclusions Decreased ability to divide attention, indicated by lower BTA scores, is associated with slower reading speeds in glaucoma with reduced CS and VF defects. PMID:28460047

Design and implementation of non-linear image processing functions for CMOS image sensor

NASA Astrophysics Data System (ADS)

Musa, Purnawarman; Sudiro, Sunny A.; Wibowo, Eri P.; Harmanto, Suryadi; Paindavoine, Michel

2012-11-01

Today, solid state image sensors are used in many applications like in mobile phones, video surveillance systems, embedded medical imaging and industrial vision systems. These image sensors require the integration in the focal plane (or near the focal plane) of complex image processing algorithms. Such devices must meet the constraints related to the quality of acquired images, speed and performance of embedded processing, as well as low power consumption. To achieve these objectives, low-level analog processing allows extracting the useful information in the scene directly. For example, edge detection step followed by a local maxima extraction will facilitate the high-level processing like objects pattern recognition in a visual scene. Our goal was to design an intelligent image sensor prototype achieving high-speed image acquisition and non-linear image processing (like local minima and maxima calculations). For this purpose, we present in this article the design and test of a 64×64 pixels image sensor built in a standard CMOS Technology 0.35 μm including non-linear image processing. The architecture of our sensor, named nLiRIC (non-Linear Rapid Image Capture), is based on the implementation of an analog Minima/Maxima Unit. This MMU calculates the minimum and maximum values (non-linear functions), in real time, in a 2×2 pixels neighbourhood. Each MMU needs 52 transistors and the pitch of one pixel is 40×40 mu m. The total area of the 64×64 pixels is 12.5mm2. Our tests have shown the validity of the main functions of our new image sensor like fast image acquisition (10K frames per second), minima/maxima calculations in less then one ms.

Categorization of First-Year University Students' Interpretations of Numerical Linear Distance-Time Graphs

ERIC Educational Resources Information Center

Wemyss, Thomas; van Kampen, Paul

2013-01-01

We have investigated the various approaches taken by first-year university students (n[image omitted]550) when asked to determine the direction of motion, the constancy of speed, and a numerical value of the speed of an object at a point on a numerical linear distance-time graph. We investigated the prevalence of various well-known general…

Oasis: A high-level/high-performance open source Navier-Stokes solver

NASA Astrophysics Data System (ADS)

Mortensen, Mikael; Valen-Sendstad, Kristian

2015-03-01

Oasis is a high-level/high-performance finite element Navier-Stokes solver written from scratch in Python using building blocks from the FEniCS project (fenicsproject.org). The solver is unstructured and targets large-scale applications in complex geometries on massively parallel clusters. Oasis utilizes MPI and interfaces, through FEniCS, to the linear algebra backend PETSc. Oasis advocates a high-level, programmable user interface through the creation of highly flexible Python modules for new problems. Through the high-level Python interface the user is placed in complete control of every aspect of the solver. A version of the solver, that is using piecewise linear elements for both velocity and pressure, is shown to reproduce very well the classical, spectral, turbulent channel simulations of Moser et al. (1999). The computational speed is strongly dominated by the iterative solvers provided by the linear algebra backend, which is arguably the best performance any similar implicit solver using PETSc may hope for. Higher order accuracy is also demonstrated and new solvers may be easily added within the same framework.

High-Speed, Low-Cost Workstation for Computation-Intensive Statistics. Phase 1

DTIC Science & Technology

1990-06-20

routine implementation and performance. 5 The two compiled versions given in the table were coded in an attempt to obtain an optimized compiled version...level statistics and linear algebra routines (BSAS and BLAS) that have been prototyped in this study. For each routine, both the C code ( Turbo C...OISTRIBUTION /AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Unlimited distribution 13. ABSTRACT (Maximum 200 words) High-performance and low-cost

Phase comparator apparatus and method

DOEpatents

Coffield, F.E.

1985-02-01

This invention finds especially useful application for interferometer measurements made in plasma fusion devices (e.g., for measuring the line integral of electron density in the plasma). Such interferometers typically use very high intermediate frequencies (e.g., on the order of 10 to 70 MHz) and therefore the phase comparison circuitry should be a high speed circuit with a linear transfer characteristic so as to accurately differentiate between small fractions of interference fringes.

High-speed photoacoustic imaging using an LED-based photoacoustic imaging system

NASA Astrophysics Data System (ADS)

Sato, Naoto; Kuniyil Ajith Singh, Mithun; Shigeta, Yusuke; Hanaoka, Takamitsu; Agano, Toshitaka

2018-02-01

Recently we developed a multispectral LED-based photoacoustic/ultrasound imaging system (AcousticX) and have been continuously working on its technical/functional improvements. AcousticX is a linear array ultrasound transducer (128 elements, 10 MHz)-based system in which LED arrays (selectable wavelengths, pulse repetition frequency: 4 kHz, pulse width: tunable from 40 - 100 ns) are fixed on both sides of the transducer to illuminate the tissue for photoacoustic imaging. The ultrasound/photoacoustic data from all 128 elements can be simultaneously acquired, processed and displayed. We already demonstrated our system's capability to perform photoacoustic/ultrasound imaging for dynamic imaging of the tissue at a frame rate of 10 Hz (for example to visualize the pulsation of arteries in vivo in human subjects). In this work, we present the development of a new high-speed imaging mode in AcousticX. In this mode, instead of toggling between ultrasound and photoacoustic measurements, it is possible to continuously acquire only photoacoustic data for 1.5 seconds with a time interval of 1 ms. With this improvement, we can record photoacoustic signals from the whole aperture (38 mm) at fast rate and can be reviewed later at different speeds for analyzing dynamic changes in the photoacoustic signals. We believe that AcousticX with this new high-speed mode opens up a feasible technical path for multiple dynamic studies, for example one which focus on imaging the response of voltage sensitive dyes. We envisage to improve the acquisition speed further in future for exploring ultra-high-speed applications.

Modeling of the thermal physical process and study on the reliability of linear energy density for selective laser melting

NASA Astrophysics Data System (ADS)

Xiang, Zhaowei; Yin, Ming; Dong, Guanhua; Mei, Xiaoqin; Yin, Guofu

2018-06-01

A finite element model considering volume shrinkage with powder-to-dense process of powder layer in selective laser melting (SLM) is established. Comparison between models that consider and do not consider volume shrinkage or powder-to-dense process is carried out. Further, parametric analysis of laser power and scan speed is conducted and the reliability of linear energy density as a design parameter is investigated. The results show that the established model is an effective method and has better accuracy allowing for the temperature distribution, and the length and depth of molten pool. The maximum temperature is more sensitive to laser power than scan speed. The maximum heating rate and cooling rate increase with increasing scan speed at constant laser power and increase with increasing laser power at constant scan speed as well. The simulation results and experimental result reveal that linear energy density is not always reliable using as a design parameter in the SLM.

Full-order Luenberger observer based on fuzzy-logic control for sensorless field-oriented control of a single-sided linear induction motor.

PubMed

Holakooie, Mohammad Hosein; Ojaghi, Mansour; Taheri, Asghar

2016-01-01

This paper investigates sensorless indirect field oriented control (IFOC) of SLIM with full-order Luenberger observer. The dynamic equations of SLIM are first elaborated to draw full-order Luenberger observer with some simplifying assumption. The observer gain matrix is derived from conventional procedure so that observer poles are proportional to SLIM poles to ensure the stability of system for wide range of linear speed. The operation of observer is significantly impressed by adaptive scheme. A fuzzy logic control (FLC) is proposed as adaptive scheme to estimate linear speed using speed tuning signal. The parameters of FLC are tuned using an off-line method through chaotic optimization algorithm (COA). The performance of the proposed observer is verified by both numerical simulation and real-time hardware-in-the-loop (HIL) implementation. Moreover, a detailed comparative study among proposed and other speed observers is obtained under different operation conditions. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Growth rate of the linear Richtmyer-Meshkov instability when a shock is reflected

NASA Astrophysics Data System (ADS)

Wouchuk, J. G.

2001-05-01

An analytic model is presented to calculate the growth rate of the linear Richtmyer-Meshkov instability in the shock-reflected case. The model allows us to calculate the asymptotic contact surface perturbation velocity for any value of the incident shock intensity, arbitrary fluids compressibilities, and for any density ratio at the interface. The growth rate comes out as the solution of a system of two coupled functional equations and is expressed formally as an infinite series. The distinguishing feature of the procedure shown here is the high speed of convergence of the intermediate calculations. There is excellent agreement with previous linear simulations and experiments done in shock tubes.

A 400 KHz line rate 2048 pixel modular SWIR linear array for earth observation applications

NASA Astrophysics Data System (ADS)

Anchlia, Ankur; Vinella, Rosa M.; Wouters, Kristof; Gielen, Daphne; Hooylaerts, Peter; Deroo, Pieter; Ruythooren, Wouter; van der Zanden, Koen; Vermeiren, Jan; Merken, Patrick

2015-10-01

In this paper, we report about a family of linear imaging FPAs sensitive in the [0.9 - 1.7um] band, developed for high speed applications such as LIDAR, wavelength references and OCT analyzers and also for earth observation applications. Fast linear FPAs can also be used in a wide variety of terrestrial applications, including high speed sorting, electro- and photo-luminesce and medical applications. The arrays are based on a modular ROIC design concept: modules of 512 pixels are stitched during fabrication to achieve 512, 1024 and 2048 pixel arrays. In principle, this concept can be extended to any multiple of 512 pixels, the limiting factor being the pixel yield of long InGaAs arrays and the CTE differences in the hybrid setup. Each 512-pixel module has its own on-chip digital sequencer, analog readout chain and 4 output buffers. This modular concept enables a long-linear array to run at a high line rate of 400 KHz irrespective of the array length, which limits the line rate in a traditional linear array. The pixel has a pitch of 12.5um. The detector frontend is based on CTIA (Capacitor Trans-impedance Amplifier), having 5 selectable integration capacitors giving full well from 62x103e- (gain0) to 40x106e- (gain4). An auto-zero circuit limits the detector bias non-uniformity to 5-10mV across broad intensity levels, limiting the input referred dark signal noise to 20e-rms for Tint=3ms at room temperature. An on-chip CDS that follows the CTIA facilitates removal of Reset/KTC noise, CTIA offsets and most of the 1/f noise. The measured noise of the ROIC is 35e-rms in gain0. At a master clock rate of 60MHz and a minimum integration time of 1.4us, the FPAs reach the highest line rate of 400 KHz.

High speed line-scan confocal imaging of stimulus-evoked intrinsic optical signals in the retina

PubMed Central

Li, Yang-Guo; Liu, Lei; Amthor, Franklin; Yao, Xin-Cheng

2010-01-01

A rapid line-scan confocal imager was developed for functional imaging of the retina. In this imager, an acousto-optic deflector (AOD) was employed to produce mechanical vibration- and inertia-free light scanning, and a high-speed (68,000 Hz) linear CCD camera was used to achieve sub-cellular and sub-millisecond spatiotemporal resolution imaging. Two imaging modalities, i.e., frame-by-frame and line-by-line recording, were validated for reflected light detection of intrinsic optical signals (IOSs) in visible light stimulus activated frog retinas. Experimental results indicated that fast IOSs were tightly correlated with retinal stimuli, and could track visible light flicker stimulus frequency up to at least 2 Hz. PMID:20125743

All-optical tunable dual Fano resonance in nonlinear metamaterials in optical communication range

NASA Astrophysics Data System (ADS)

Zhou, Yi; Hu, Xiaoyong; Li, Chong; Yang, Hong; Gong, Qihuang

2018-01-01

Low-power, ultra-fast all-optical tunable dual Fano resonance was realized in a metamaterial coated with a non-linear nanocomposite layer composed of gold nanoparticle-doped polycrystalline barium strontium titanate and multilayer tungsten disulphide microsheets. A high non-linear refractive index of -2.148 × 10-11 m2/W was achieved in the nanocomposite material that originated in the non-linearity enhancement associated with the quantum confinement effect, the local-field enhancement effect, and reinforced interactions between photons and the multilayer tungsten disulphide microsheets. An ultra-low threshold pump intensity of 600 kW/cm2 was obtained. An ultra-fast response time of 25.4 ps was maintained because of the fast relaxation dynamics of the bound electrons in the nanoscale polycrystalline barium strontium titanate grains. The large third-order non-linear responses of the metamaterial were confirmed with a high third harmonic generation conversion efficiency of 5.4 × 10-5. This work may help to pave the way towards realization of ultra-high-speed information processing chips and multifunctional integrated photonic devices based on metamaterials.

New Representation of Bearings in LS-DYNA

NASA Technical Reports Server (NTRS)

Carney, Kelly S.; Howard, Samuel A.; Miller, Brad A.; Benson, David J.

2014-01-01

Non-linear, dynamic, finite element analysis is used in various engineering disciplines to evaluate high-speed, dynamic impact and vibration events. Some of these applications require connecting rotating to stationary components. For example, bird impacts on rotating aircraft engine fan blades are a common analysis performed using this type of analysis tool. Traditionally, rotating machines utilize some type of bearing to allow rotation in one degree of freedom while offering constraints in the other degrees of freedom. Most times, bearings are modeled simply as linear springs with rotation. This is a simplification that is not necessarily accurate under the conditions of high-velocity, high-energy, dynamic events such as impact problems. For this reason, it is desirable to utilize a more realistic non-linear force-deflection characteristic of real bearings to model the interaction between rotating and non-rotating components during dynamic events. The present work describes a rolling element bearing model developed for use in non-linear, dynamic finite element analysis. This rolling element bearing model has been implemented in LS-DYNA as a new element, *ELEMENT_BEARING.

Linear and Logarithmic Speed-Accuracy Trade-Offs in Reciprocal Aiming Result from Task-Specific Parameterization of an Invariant Underlying Dynamics

ERIC Educational Resources Information Center

Bongers, Raoul M.; Fernandez, Laure; Bootsma, Reinoud J.

2009-01-01

The authors examined the origins of linear and logarithmic speed-accuracy trade-offs from a dynamic systems perspective on motor control. In each experiment, participants performed 2 reciprocal aiming tasks: (a) a velocity-constrained task in which movement time was imposed and accuracy had to be maximized, and (b) a distance-constrained task in…

Applicability of linearized-theory attached-flow methods to design and analysis of flap systems at low speeds for thin swept wings with sharp leading edges

NASA Technical Reports Server (NTRS)

Carlson, Harry W.; Darden, Christine M.

1987-01-01

Low-speed experimental force and data on a series of thin swept wings with sharp leading edges and leading and trailing-edge flaps are compared with predictions made using a linearized-theory method which includes estimates of vortex forces. These comparisons were made to assess the effectiveness of linearized-theory methods for use in the design and analysis of flap systems in subsonic flow. Results demonstrate that linearized-theory, attached-flow methods (with approximate representation of vortex forces) can form the basis of a rational system for flap design and analysis. Even attached-flow methods that do not take vortex forces into account can be used for the selection of optimized flap-system geometry, but design-point performance levels tend to be underestimated unless vortex forces are included. Illustrative examples of the use of these methods in the design of efficient low-speed flap systems are included.

Fabrication of an infrared Shack-Hartmann sensor by combining high-speed single-point diamond milling and precision compression molding processes.

PubMed

Zhang, Lin; Zhou, Wenchen; Naples, Neil J; Yi, Allen Y

2018-05-01

A novel fabrication method by combining high-speed single-point diamond milling and precision compression molding processes for fabrication of discontinuous freeform microlens arrays was proposed. Compared with slow tool servo diamond broaching, high-speed single-point diamond milling was selected for its flexibility in the fabrication of true 3D optical surfaces with discontinuous features. The advantage of single-point diamond milling is that the surface features can be constructed sequentially by spacing the axes of a virtual spindle at arbitrary positions based on the combination of rotational and translational motions of both the high-speed spindle and linear slides. By employing this method, each micro-lenslet was regarded as a microstructure cell by passing the axis of the virtual spindle through the vertex of each cell. An optimization arithmetic based on minimum-area fabrication was introduced to the machining process to further increase the machining efficiency. After the mold insert was machined, it was employed to replicate the microlens array onto chalcogenide glass. In the ensuing optical measurement, the self-built Shack-Hartmann wavefront sensor was proven to be accurate in detecting an infrared wavefront by both experiments and numerical simulation. The combined results showed that precision compression molding of chalcogenide glasses could be an economic and precision optical fabrication technology for high-volume production of infrared optics.

Variable-Speed Power-Turbine Research at Glenn Research Center

NASA Technical Reports Server (NTRS)

Welch, Gerard E.; McVetta, Ashlie B.; Stevens, Mark A.; Howard, Samuel A.; Giel, Paul W.; Ameri, Ali, A.; To, Waiming; Skoch, Gary J.; Thurman, Douglas R.

2012-01-01

The main rotors of the NASA Large Civil Tilt-Rotor (LCTR) notional vehicle operate over a wide speed-range, from 100 percent at takeoff to 54 percent at cruise. The variable-speed power turbine (VSPT) offers one approach by which to effect this speed variation. VSPT aerodynamics challenges include high work factors at cruise, wide (40 to 60 ) incidence-angle variations in blade and vane rows over the speed range, and operation at low Reynolds numbers. Rotordynamics challenges include potential responsiveness to shaft modes within the 50 percent VSPT speed-range. A research effort underway at NASA Glenn Research Center, intended to address these key aerodynamic and rotordynamic challenges, is described. Conceptual design and 3-D multistage RANS and URANS analyses, conducted internally and under contract, provide expected VSPT sizing, stage-count, performance and operability information, and maps for system studies. Initial steps toward experimental testing of incidence-tolerant blading in a transonic linear cascade are described, and progress toward development/improvement of a simulation capability for multistage turbines with low Reynolds number transitional flow is summarized. Preliminary rotordynamics analyses indicate that viable concept engines with 50 percent VSPT shaft-speed range. Assessments of potential paths toward VSPT component-level testing are summarized.

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

Gearhart, Jared Lee; Adair, Kristin Lynn; Durfee, Justin David.

When developing linear programming models, issues such as budget limitations, customer requirements, or licensing may preclude the use of commercial linear programming solvers. In such cases, one option is to use an open-source linear programming solver. A survey of linear programming tools was conducted to identify potential open-source solvers. From this survey, four open-source solvers were tested using a collection of linear programming test problems and the results were compared to IBM ILOG CPLEX Optimizer (CPLEX) [1], an industry standard. The solvers considered were: COIN-OR Linear Programming (CLP) [2], [3], GNU Linear Programming Kit (GLPK) [4], lp_solve [5] and Modularmore » In-core Nonlinear Optimization System (MINOS) [6]. As no open-source solver outperforms CPLEX, this study demonstrates the power of commercial linear programming software. CLP was found to be the top performing open-source solver considered in terms of capability and speed. GLPK also performed well but cannot match the speed of CLP or CPLEX. lp_solve and MINOS were considerably slower and encountered issues when solving several test problems.« less

Relationship Between Motor Variability, Accuracy, and Ball Speed in the Tennis Serve

PubMed Central

Antúnez, Ruperto Menayo; Hernández, Francisco Javier Moreno; García, Juan Pedro Fuentes; Vaíllo, Raúl Reina; Arroyo, Jesús Sebastián Damas

2012-01-01

The main objective of this study was to analyze the motor variability in the performance of the tennis serve and its relationship to performance outcome. Seventeen male tennis players took part in the research, and they performed 20 serves. Linear and non-linear variability during the hand movement was measured by 3D Motion Tracking. Ball speed was recorded with a sports radar gun and the ball bounces were video recorded to calculate accuracy. The results showed a relationship between the amount of variability and its non-linear structure found in performance of movement and the outcome of the serve. The study also found that movement predictability correlates with performance. An increase in the amount of movement variability could affect the tennis serve performance in a negative way by reducing speed and accuracy of the ball. PMID:23486998

Analysis of sex differences in open-water ultra-distance swimming performances in the FINA World Cup races in 5 km, 10 km and 25 km from 2000 to 2012

PubMed Central

2014-01-01

Background The present study investigated the changes in swimming speeds and sex differences for elite male and female swimmers competing in 5 km, 10 km and 25 km open-water FINA World Cup races held between 2000 and 2012. Methods The changes in swimming speeds and sex differences across years were analysed using linear, non-linear, and multi-level regression analyses for the annual fastest and the annual ten fastest competitors. Results For the annual fastest, swimming speed remained stable for men and women in 5 km (5.50 ± 0.21 and 5.08 ± 0.19 km/h, respectively), in 10 km (5.38 ± 0.21 and 5.05 ± 0.26 km/h, respectively) and in 25 km (5.03 ± 0.32 and 4.58 ± 0.27 km/h, respectively). In the annual ten fastest, swimming speed remained constant in 5 km in women (5.02 ± 0.19 km/h) but decreased significantly and linearly in men from 5.42 ± 0.03 km/h to 5.39 ± 0.02 km/h. In 10 km, swimming speed increased significantly and linearly in women from 4.75 ± 0.01 km/h to 5.74 ± 0.01 km/h but remained stable in men at 5.36 ± 0.21 km/h. In 25 km, swimming speed decreased significantly and linearly in women from 4.60 ± 0.06 km/h to 4.44 ± 0.08 km/h but remained unchanged at 4.93 ± 0.34 km/h in men. For the annual fastest, the sex difference in swimming speed remained unchanged in 5 km (7.6 ± 3.0%), 10 km (6.1 ± 2.5%) and 25 km (9.0 ± 3.7%). For the annual ten fastest, the sex difference remained stable in 5 km at 7.6 ± 0.6%, decreased significantly and linearly in 10 km from 7.7 ± 0.7% to 1.2 ± 0.3% and increased significantly and linearly from 4.7 ± 1.4% to 9.6 ± 1.5% in 25 km. Conclusions To summarize, elite female open-water ultra-distance swimmers improved in 10 km but impaired in 25 km leading to a linear decrease in sex difference in 10 km and a linear increase in sex difference in 25 km. The linear changes in sex differences suggest that women will improve in the near future in 10 km, but not in 25 km. PMID:24559049

Mixed Linear/Square-Root Encoded Single-Slope Ramp Provides Low-Noise ADC with High Linearity for Focal Plane Arrays

NASA Technical Reports Server (NTRS)

Wrigley, Chris J.; Hancock, Bruce R.; Newton, Kenneth W.; Cunningham, Thomas J.

2013-01-01

Single-slope analog-to-digital converters (ADCs) are particularly useful for onchip digitization in focal plane arrays (FPAs) because of their inherent monotonicity, relative simplicity, and efficiency for column-parallel applications, but they are comparatively slow. Squareroot encoding can allow the number of code values to be reduced without loss of signal-to-noise ratio (SNR) by keeping the quantization noise just below the signal shot noise. This encoding can be implemented directly by using a quadratic ramp. The reduction in the number of code values can substantially increase the quantization speed. However, in an FPA, the fixed pattern noise (FPN) limits the use of small quantization steps at low signal levels. If the zero-point is adjusted so that the lowest column is onscale, the other columns, including those at the center of the distribution, will be pushed up the ramp where the quantization noise is higher. Additionally, the finite frequency response of the ramp buffer amplifier and the comparator distort the shape of the ramp, so that the effective ramp value at the time the comparator trips differs from the intended value, resulting in errors. Allowing increased settling time decreases the quantization speed, while increasing the bandwidth increases the noise. The FPN problem is solved by breaking the ramp into two portions, with some fraction of the available code values allocated to a linear ramp and the remainder to a quadratic ramp. To avoid large transients, both the value and the slope of the linear and quadratic portions should be equal where they join. The span of the linear portion must cover the minimum offset, but not necessarily the maximum, since the fraction of the pixels above the upper limit will still be correctly quantized, albeit with increased quantization noise. The required linear span, maximum signal and ratio of quantization noise to shot noise at high signal, along with the continuity requirement, determines the number of code values that must be allocated to each portion. The distortion problem is solved by using a lookup table to convert captured code values back to signal levels. The values in this table will be similar to the intended ramp value, but with a correction for the finite bandwidth effects. Continuous-time comparators are used, and their bandwidth is set below the step rate, which smoothes the ramp and reduces the noise. No settling time is needed, as would be the case for clocked comparators, but the low bandwidth enhances the distortion of the non-linear portion. This is corrected by use of a return lookup table, which differs from the one used to generate the ramp. The return lookup table is obtained by calibrating against a stepped precision DC reference. This results in a residual non-linearity well below the quantization noise. This method can also compensate for differential non-linearity (DNL) in the DAC used to generate the ramp. The use of a ramp with a combination of linear and quadratic portions for a single-slope ADC is novel. The number of steps is minimized by keeping the step size just below the photon shot noise. This in turn maximizes the speed of the conversion. High resolution is maintained by keeping small quantization steps at low signals, and noise is minimized by allowing the lowest analog bandwidth, all without increasing the quantization noise. A calibrated return lookup table allows the system to maintain excellent linearity.

Development of an Experimental Test Section for Forcing Unsteady Flow in a Linear Compressor Cascade using Circular Rods

DTIC Science & Technology

2003-03-01

to be moved while the tunnel was running, reducing the need for tunnel shut-down and allowing for thermal equilibrium to be maintained during the high ...rather quickly. However, for the high speed runs, the tunnel heats up greatly, so data cannot be taken until the tunnel reaches thermal steady-state...January 1992. 10. Wilson, David G. and Korakianitis, Theodosius. The Design of High - Efficiency Turbo- machinery and Gas Turbines , 317—322. Upper Saddle

Effect of pencil grasp on the speed and legibility of handwriting in children.

PubMed

Schwellnus, Heidi; Carnahan, Heather; Kushki, Azadeh; Polatajko, Helene; Missiuna, Cheryl; Chau, Tom

2012-01-01

Pencil grasps other than the dynamic tripod may be functional for handwriting. This study examined the impact of grasp on handwriting speed and legibility. We videotaped 120 typically developing fourth-grade students while they performed a writing task. We categorized the grasps they used and evaluated their writing for speed and legibility using a handwriting assessment. Using linear regression analysis, we examined the relationship between grasp and handwriting. We documented six categories of pencil grasp: four mature grasp patterns, one immature grasp pattern, and one alternating grasp pattern. Multiple linear regression results revealed no significant effect for mature grasp on either legibility or speed. Pencil grasp patterns did not influence handwriting speed or legibility in this sample of typically developing children. This finding adds to the mounting body of evidence that alternative grasps may be acceptable for fast and legible handwriting. Copyright © 2012 by the American Occupational Therapy Association, Inc.

Log-Linear Model Based Behavior Selection Method for Artificial Fish Swarm Algorithm

PubMed Central

Huang, Zhehuang; Chen, Yidong

2015-01-01

Artificial fish swarm algorithm (AFSA) is a population based optimization technique inspired by social behavior of fishes. In past several years, AFSA has been successfully applied in many research and application areas. The behavior of fishes has a crucial impact on the performance of AFSA, such as global exploration ability and convergence speed. How to construct and select behaviors of fishes are an important task. To solve these problems, an improved artificial fish swarm algorithm based on log-linear model is proposed and implemented in this paper. There are three main works. Firstly, we proposed a new behavior selection algorithm based on log-linear model which can enhance decision making ability of behavior selection. Secondly, adaptive movement behavior based on adaptive weight is presented, which can dynamically adjust according to the diversity of fishes. Finally, some new behaviors are defined and introduced into artificial fish swarm algorithm at the first time to improve global optimization capability. The experiments on high dimensional function optimization showed that the improved algorithm has more powerful global exploration ability and reasonable convergence speed compared with the standard artificial fish swarm algorithm. PMID:25691895

Secular instabilities of Keplerian stellar discs

NASA Astrophysics Data System (ADS)

Kaur, Karamveer; Kazandjian, Mher V.; Sridhar, S.; Touma, Jihad R.

2018-05-01

We present idealized models of a razor-thin, axisymmetric, Keplerian stellar disc around a massive black hole, and study non-axisymmetric secular instabilities in the absence of either counter-rotation or loss cones. These discs are prograde mono-energetic waterbags, whose phase-space distribution functions are constant for orbits within a range of eccentricities (e) and zero outside this range. The linear normal modes of waterbags are composed of sinusoidal disturbances of the edges of distribution function in phase space. Waterbags that include circular orbits (polarcaps) have one stable linear normal mode for each azimuthal wavenumber m. The m = 1 mode always has positive pattern speed and, for polarcaps consisting of orbits with e < 0.9428, only the m = 1 mode has positive pattern speed. Waterbags excluding circular orbits (bands) have two linear normal modes for each m, which can be stable or unstable. We derive analytical expressions for the instability condition, pattern speeds, growth rates, and normal mode structure. Narrow bands are unstable to modes with a wide range in m. Numerical simulations confirm linear theory and follow the non-linear evolution of instabilities. Long-time integration suggests that instabilities of different m grow, interact non-linearly, and relax collisionlessly to a coarse-grained equilibrium with a wide range of eccentricities.

A synergistic method for vibration suppression of an elevator mechatronic system

NASA Astrophysics Data System (ADS)

Knezevic, Bojan Z.; Blanusa, Branko; Marcetic, Darko P.

2017-10-01

Modern elevators are complex mechatronic systems which have to satisfy high performance in precision, safety and ride comfort. Each elevator mechatronic system (EMS) contains a mechanical subsystem which is characterized by its resonant frequency. In order to achieve high performance of the whole system, the control part of the EMS inevitably excites resonant circuits causing the occurrence of vibration. This paper proposes a synergistic solution based on the jerk control and the upgrade of the speed controller with a band-stop filter to restore lost ride comfort and speed control caused by vibration. The band-stop filter eliminates the resonant component from the speed controller spectra and jerk control provides operating of the speed controller in a linear mode as well as increased ride comfort. The original method for band-stop filter tuning based on Goertzel algorithm and Kiefer search algorithm is proposed in this paper. In order to generate the speed reference trajectory which can be defined by different shapes and amplitudes of jerk, a unique generalized model is proposed. The proposed algorithm is integrated in the power drive control algorithm and implemented on the digital signal processor. Through experimental verifications on a scale down prototype of the EMS it has been verified that only synergistic effect of controlling jerk and filtrating the reference torque can completely eliminate vibrations.

A feasibility study regarding the addition of a fifth control to a rotorcraft in-flight simulator

NASA Technical Reports Server (NTRS)

Turner, Simon; Andrisani, Dominick, II

1992-01-01

The addition of a large movable horizontal tail surface to the control system of a rotorcraft in-flight simulator being developed from a Sikorsky UH-60A Black Hawk Helicopter is evaluated. The capabilities of the control surface as a trim control and as an active control are explored. The helicopter dynamics are modeled using the Generic Helicopter simulation program developed by Sikorsky Aircraft. The effect of the horizontal tail on the helicopter trim envelope is examined by plotting trim maps of the aircraft attitude and controls as a function of the flight speed and horizontal tail incidence. The control power of the tail surface relative to that of the other controls is examined by comparing control derivatives extracted from the simulation program over the flight speed envelope. The horizontal tail's contribution as an active control is evaluated using an explicit model following control synthesis involving a linear model of the helicopter in steady, level flight at a flight speed of eighty knots. The horizontal tail is found to provide additional control flexibility in the longitudinal axis. As a trim control, it provides effective control of the trim pitch attitude at mid to high forward speeds. As an active control, the horizontal tail provides useful pitching moment generating capabilities at mid to high forward speeds.

A Study of Supersonic Surface Sources: The Ffowcs Williams-Hawkings Equation and the Kirchhoff Formula

NASA Technical Reports Server (NTRS)

Farassat, F.; Brentner, Kenneth S.; Dunn, M. H.

2004-01-01

In this paper we address the mathematical problem of noise generation from high speed moving surfaces. The problem we are solving is the linear wave equation with sources on a moving surface. The Ffowcs Williams-Hawkings (FW-H) equation as well as the govern- ing equation for deriving the Kirchhoff formula for moving surfaces are both this type of partial differential equation. We give a new exact solution of this problem here in closed form which is valid for subsonic and supersonic motion of the surface but it is particularly suitable for supersonically moving surfaces. This new solution is the simplest of all high speed formulations of Langley and is denoted formulation 4 following the tradition of numbering of our major results for the prediction of the noise of rotating blades. We show that for a smooth surface moving at supersonic speed, our solution has only removable singularities. Thus it can be used for numerical work.

A 6-bit 4 GS/s pseudo-thermometer segmented CMOS DAC

NASA Astrophysics Data System (ADS)

Yijun, Song; Wenyuan, Li

2014-06-01

A 6-bit 4 GS/s, high-speed and power-efficient DAC for ultra-high-speed transceivers in 60 GHz band millimeter wave technology is presented. A novel pseudo-thermometer architecture is proposed to realize a good compromise between the fast conversion speed and the chip area. Symmetrical and compact floor planning and layout techniques including tree-like routing, cross-quading and common-centroid method are adopted to guarantee the chip is fully functional up to near-Nyquist frequency in a standard 0.18 μm CMOS process. Post simulation results corroborate the feasibility of the designed DAC, which canperform good static and dynamic linearity without calibration. DNL errors and INL errors can be controlled within ±0.28 LSB and ±0.26 LSB, respectively. SFDR at 4 GHz clock frequency for a 1.9 GHz near-Nyquist sinusoidal output signal is 40.83 dB and the power dissipation is less than 37 mW.

A high speed implementation of the random decrement algorithm

NASA Technical Reports Server (NTRS)

Kiraly, L. J.

1982-01-01

The algorithm is useful for measuring net system damping levels in stochastic processes and for the development of equivalent linearized system response models. The algorithm works by summing together all subrecords which occur after predefined threshold level is crossed. The random decrement signature is normally developed by scanning stored data and adding subrecords together. The high speed implementation of the random decrement algorithm exploits the digital character of sampled data and uses fixed record lengths of 2(n) samples to greatly speed up the process. The contributions to the random decrement signature of each data point was calculated only once and in the same sequence as the data were taken. A hardware implementation of the algorithm using random logic is diagrammed and the process is shown to be limited only by the record size and the threshold crossing frequency of the sampled data. With a hardware cycle time of 200 ns and 1024 point signature, a threshold crossing frequency of 5000 Hertz can be processed and a stably averaged signature presented in real time.

Locomotor Recovery in Spinal Cord Injury: Insights Beyond Walking Speed and Distance.

PubMed

Awai, Lea; Curt, Armin

2016-08-01

Recovery of locomotor function after incomplete spinal cord injury (iSCI) is clinically assessed through walking speed and distance, while improvements in these measures might not be in line with a normalization of gait quality and are, on their own, insensitive at revealing potential mechanisms underlying recovery. The objective of this study was to relate changes of gait parameters to the recovery of walking speed while distinguishing between parameters that rather reflect speed improvements from factors contributing to overall recovery. Kinematic data of 16 iSCI subjects were repeatedly recorded during in-patient rehabilitation. The responsiveness of gait parameters to walking speed was assessed by linear regression. Principal component analysis (PCA) was applied on the multivariate data across time to identify factors that contribute to recovery after iSCI. Parameters of gait cycle and movement dynamics were both responsive and closely related to the recovery of walking speed, which increased by 96%. Multivariate analysis revealed specific gait parameters (intralimb shape normality and consistency) that, although less related to speed increments, loaded highly on principal component one (PC1) (58.6%) explaining the highest proportion of variance (i.e., recovery of outcome over time). Interestingly, measures of hip, knee, and ankle range of motion showed varying degrees of responsiveness (from very high to very low) while not contributing to gait recovery as revealed by PCA. The conjunct application of two analysis methods distinguishes gait parameters that simply reflect increased walking speed from parameters that actually contribute to gait recovery in iSCI. This distinction may be of value for the evaluation of interventions for locomotor recovery.

Visual control of flight speed in Drosophila melanogaster.

PubMed

Fry, Steven N; Rohrseitz, Nicola; Straw, Andrew D; Dickinson, Michael H

2009-04-01

Flight control in insects depends on self-induced image motion (optic flow), which the visual system must process to generate appropriate corrective steering maneuvers. Classic experiments in tethered insects applied rigorous system identification techniques for the analysis of turning reactions in the presence of rotating pattern stimuli delivered in open-loop. However, the functional relevance of these measurements for visual free-flight control remains equivocal due to the largely unknown effects of the highly constrained experimental conditions. To perform a systems analysis of the visual flight speed response under free-flight conditions, we implemented a 'one-parameter open-loop' paradigm using 'TrackFly' in a wind tunnel equipped with real-time tracking and virtual reality display technology. Upwind flying flies were stimulated with sine gratings of varying temporal and spatial frequencies, and the resulting speed responses were measured from the resulting flight speed reactions. To control flight speed, the visual system of the fruit fly extracts linear pattern velocity robustly over a broad range of spatio-temporal frequencies. The speed signal is used for a proportional control of flight speed within locomotor limits. The extraction of pattern velocity over a broad spatio-temporal frequency range may require more sophisticated motion processing mechanisms than those identified in flies so far. In Drosophila, the neuromotor pathways underlying flight speed control may be suitably explored by applying advanced genetic techniques, for which our data can serve as a baseline. Finally, the high-level control principles identified in the fly can be meaningfully transferred into a robotic context, such as for the robust and efficient control of autonomous flying micro air vehicles.

SU-D-213AB-06: Surface Texture and Insertion Speed Effect on Needle Friction.

PubMed

Abdullah, A; Golecki, C; Barnett, A; Moore, J

2012-06-01

High frictional forces between the needle surface and tissue cause tissue deflection which hinders accurate needle placement for procedures such as brachytherapy and needle biopsy. Accurate needle placement isimportant to maximize procedure efficacy. This work investigates how needle surface roughness and insertion speed affect the frictional forcebetween a needle and tissue. A friction experiment was conducted to measure the force of friction between bovine liver and three 11 gauge needles having Ra surface roughness of 3.43, 1.33, and 0.2 μm. Each of the three needles were mounted on a linear slide and were advanced and retracted through bovine liver at speeds of 50, 100, 150, and 200 mm/s for a total of 12 trials. In each trial the needle was advanced and retracted in 10 cycles producing a steady state insertion force and a steady state retraction force for each cycle. A force sensor connecting the needle to the linear slide recorded the resistance force of the needle sliding through the liver. The liver was mounted in a box with a pneumatic cylinder which compressed the liver sample by 11.65 kPa. The roughest needle (Ra = 3.43 μm) on average produced 68, 73, 74, and 73% lower friction force than the smoothest needle (Ra = 0.2 μm) for the speeds of 50, 100, 150, and 200mm/s, respectively. The second roughest needle (Ra = 1.33 μm) on average produced 25, 45, 60 and 64% lower friction force than the smoothest needle (Ra = 0.2 μm) for the speeds of 50, 100, 150, and 200 mm/s, respectively. Rougher needle surface texture and higher insertion speed reduced frictional forces between the tissue and the needle. Future studies will examine how frictional forces can be modeled and predicted given surface texture and insertion speed. © 2012 American Association of Physicists in Medicine.

Twin-belt continuous caster with containment and cooling of the exiting cast product for enabling high-speed casting of molten-center product

DOEpatents

Dykes, Charles D.; Daniel, Sabah S.; Wood, J. F. Barry

1990-02-20

In continuously casting molten metal into cast product by a twin-belt machine, it is desirable to achieve dramatic increases in speed (linear feet per minute) at which cast product exits the machine, particularly in installations where steel cast product is intended to feed a downstream regular rolling mill (as distinct from a planetary mill) operating in tandem with the twin-belt caster. Such high-speed casting produces product with a relatively thin shell and molten interior, and the shell tends to bulge outwardly due to metallostatic head pressure of the molten center. A number of cooperative features enable high-speed, twin-belt casting: (1) Each casting belt is slidably supported adjacent to the caster exit pulley for bulge control and enhanced cooling of cast product. (2) Lateral skew steering of each belt provides an effective increase in moving mold length plus a continuity of heat transfer not obtained with prior art belt steering apparatus. (3) The exiting slab is contained and supported downstream from the casting machine to prevent bulging of the shell of the cast product, and (4) spray cooling is incorporated in the exit containment apparatus for secondary cooling of cast product.

Application and verification of ECMWF seasonal forecast for wind energy

NASA Astrophysics Data System (ADS)

Žagar, Mark; Marić, Tomislav; Qvist, Martin; Gulstad, Line

2015-04-01

A good understanding of long-term annual energy production (AEP) is crucial when assessing the business case of investing in green energy like wind power. The art of wind-resource assessment has emerged into a scientific discipline on its own, which has advanced at high pace over the last decade. This has resulted in continuous improvement of the AEP accuracy and, therefore, increase in business case certainty. Harvesting the full potential output of a wind farm or a portfolio of wind farms depends heavily on optimizing operation and management strategy. The necessary information for short-term planning (up to 14 days) is provided by standard weather and power forecasting services, and the long-term plans are based on climatology. However, the wind-power industry is lacking quality information on intermediate scales of the expected variability in seasonal and intra-annual variations and their geographical distribution. The seasonal power forecast presented here is designed to bridge this gap. The seasonal power production forecast is based on the ECMWF seasonal weather forecast and the Vestas' high-resolution, mesoscale weather library. The seasonal weather forecast is enriched through a layer of statistical post-processing added to relate large-scale wind speed anomalies to mesoscale climatology. The resulting predicted energy production anomalies, thus, include mesoscale effects not captured by the global forecasting systems. The turbine power output is non-linearly related to the wind speed, which has important implications for the wind power forecast. In theory, the wind power is proportional to the cube of wind speed. However, due to the nature of turbine design, this exponent is close to 3 only at low wind speeds, becomes smaller as the wind speed increases, and above 11-13 m/s the power output remains constant, called the rated power. The non-linear relationship between wind speed and the power output generally increases sensitivity of the forecasted power to the wind speed anomalies. On the other hand, in some cases and areas where turbines operate close to, or above the rated power, the sensitivity of power forecast is reduced. Thus, the seasonal power forecasting system requires good knowledge of the changes in frequency of events with sufficient wind speeds to have acceptable skill. The scientific background for the Vestas seasonal power forecasting system is described and the relationship between predicted monthly wind speed anomalies and observed wind energy production are investigated for a number of operating wind farms in different climate zones. Current challenges will be discussed and some future research and development areas identified.

Spacecraft-borne long life cryogenic refrigeration: Status and trends

NASA Technical Reports Server (NTRS)

Johnson, A. L.

1983-01-01

The status of cryogenic refrigerator development intended for, or possibly applicable to, long life spacecraft-borne application is reviewed. Based on these efforts, the general development trends are identified. Using currently projected technology needs, the various trends are compared and evaluated. The linear drive, non-contacting bearing Stirling cycle refrigerator concept appears to be the best current approach that will meet the technology projection requirements for spacecraft-borne cryogenic refrigerators. However, a multiply redundant set of lightweight, moderate life, moderate reliability Stirling cycle cryogenic refrigerators using high-speed linear drive and sliding contact bearings may possibly suffice.

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

Rodriguez, George; Gilbertson, Steve Michael

Chirped fiber Bragg grating (CFBG) sensors coupled to high speed interrogation systems are described as robust diagnostic approaches to monitoring shock wave and detonation front propagation tracking events for use in high energy density shock physics applications. Taking advantage of the linear distributed spatial encoding of the spectral band in single-mode CFBGs, embedded fiber systems and associated photonic interrogation methodologies are shown as an effective approach to sensing shock and detonation-driven loading processes along the CFBG length. Two approaches, one that detects spectral changes in the integrated spectrum of the CFBG and another coherent pulse interrogation approach that fully resolvesmore » its spectral response, shows that 100-MHz–1-GHz interrogation rates are possible with spatial resolution along the CFBG in the 50 µm to sub-millimeter range depending on the combination of CFBG parameters (i.e., length, chirp rate, spectrum) and interrogator design specifics. In conclusion, results from several dynamic tests are used to demonstrate the performance of these high speed systems for shock and detonation propagation tracking under strong and weak shock pressure loading: (1) linear detonation front tracking in the plastic bonded explosive (PBX) PBX-9501; (2) tracking of radial decaying shock with crossover to non-destructive CFBG response; (3) shock wave tracking along an aluminum cylinder wall under weak loading accompanied by dynamic strain effects in the CFBG sensor.« less

Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress.

PubMed

Martin, Raleigh L; Kok, Jasper F

2017-06-01

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation-the wind-driven transport of sand in hopping trajectories-scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces.

Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress

PubMed Central

Martin, Raleigh L.; Kok, Jasper F.

2017-01-01

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation—the wind-driven transport of sand in hopping trajectories—scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces. PMID:28630907

Determination of wave speed and wave separation in the arteries.

PubMed

Khir, A W; O'Brien, A; Gibbs, J S; Parker, K H

2001-09-01

Considering waves in the arteries as infinitesimal wave fronts rather than sinusoidal wavetrains, the change in pressure across the wave front, dP, is related to the change in velocity, dU, that it induces by the "water hammer" equation, dP=+/-rhocdU, where rho is the density of blood and c is the local wave speed. When only unidirectional waves are present, this relationship corresponds to a straight line when P is plotted against U with slope rhoc. When both forward and backward waves are present, the PU-loop is no longer linear. Measurements in latex tubes and systemic and pulmonary arteries exhibit a linear range during early systole and this provides a way of determining the local wave speed from the slope of the linear portion of the loop. Once the wave speed is known, it is also possible to separate the measured P and U into their forward and backward components. In cases where reflected waves are prominent, this separation of waves can help clarify the pattern of waves in the arteries throughout the cardiac cycle.

Nonlinear optical microscopy for immunoimaging: a custom optimized system of high-speed, large-area, multicolor imaging

PubMed Central

Li, Hui; Cui, Quan; Zhang, Zhihong; Luo, Qingming

2015-01-01

Background The nonlinear optical microscopy has become the current state-of-the-art for intravital imaging. Due to its advantages of high resolution, superior tissue penetration, lower photodamage and photobleaching, as well as intrinsic z-sectioning ability, this technology has been widely applied in immunoimaging for a decade. However, in terms of monitoring immune events in native physiological environment, the conventional nonlinear optical microscope system has to be optimized for live animal imaging. Generally speaking, three crucial capabilities are desired, including high-speed, large-area and multicolor imaging. Among numerous high-speed scanning mechanisms used in nonlinear optical imaging, polygon scanning is not only linearly but also dispersion-freely with high stability and tunable rotation speed, which can overcome disadvantages of multifocal scanning, resonant scanner and acousto-optical deflector (AOD). However, low frame rate, lacking large-area or multicolor imaging ability make current polygonbased nonlinear optical microscopes unable to meet the requirements of immune event monitoring. Methods We built up a polygon-based nonlinear optical microscope system which was custom optimized for immunoimaging with high-speed, large-are and multicolor imaging abilities. Results Firstly, we validated the imaging performance of the system by standard methods. Then, to demonstrate the ability to monitor immune events, migration of immunocytes observed by the system based on typical immunological models such as lymph node, footpad and dorsal skinfold chamber are shown. Finally, we take an outlook for the possible advance of related technologies such as sample stabilization and optical clearing for more stable and deeper intravital immunoimaging. Conclusions This study will be helpful for optimizing nonlinear optical microscope to obtain more comprehensive and accurate information of immune events. PMID:25694951

Sea surface mean square slope from Ku-band backscatter data

NASA Technical Reports Server (NTRS)

Jackson, F. C.; Walton, W. T.; Hines, D. E.; Walter, B. A.; Peng, C. Y.

1992-01-01

A surface mean-square-slope parameter analysis is conducted for 14-GHz airborne radar altimeter near-nadir, quasi-specular backscatter data, which in raw form obtained by least-squares fitting of an optical scattering model to the return waveform show an approximately linear dependence over the 7-15 m/sec wind speed range. Slope data are used to draw inferences on the structure of the high-wavenumber portion of the spectrum. A directionally-integrated model height spectrum that encompasses wind speed-dependent k exp -5/2 and classical Phillips k exp -3 power laws subranges in the range of gravity waves is supported by the data.

Effects of Sea-Surface Waves and Ocean Spray on Air-Sea Momentum Fluxes

NASA Astrophysics Data System (ADS)

Zhang, Ting; Song, Jinbao

2018-04-01

The effects of sea-surface waves and ocean spray on the marine atmospheric boundary layer (MABL) at different wind speeds and wave ages were investigated. An MABL model was developed that introduces a wave-induced component and spray force to the total surface stress. The theoretical model solution was determined assuming the eddy viscosity coefficient varied linearly with height above the sea surface. The wave-induced component was evaluated using a directional wave spectrum and growth rate. Spray force was described using interactions between ocean-spray droplets and wind-velocity shear. Wind profiles and sea-surface drag coefficients were calculated for low to high wind speeds for wind-generated sea at different wave ages to examine surface-wave and ocean-spray effects on MABL momentum distribution. The theoretical solutions were compared with model solutions neglecting wave-induced stress and/or spray stress. Surface waves strongly affected near-surface wind profiles and sea-surface drag coefficients at low to moderate wind speeds. Drag coefficients and near-surface wind speeds were lower for young than for old waves. At high wind speeds, ocean-spray droplets produced by wind-tearing breaking-wave crests affected the MABL strongly in comparison with surface waves, implying that wave age affects the MABL only negligibly. Low drag coefficients at high wind caused by ocean-spray production increased turbulent stress in the sea-spray generation layer, accelerating near-sea-surface wind. Comparing the analytical drag coefficient values with laboratory measurements and field observations indicated that surface waves and ocean spray significantly affect the MABL at different wind speeds and wave ages.

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

Wolfram, Phillip J.; Ringler, Todd D.

Meridional diffusivity is assessed in this paper for a baroclinically unstable jet in a high-latitudeIdealized Circumpolar Current (ICC) using the Model for Prediction Across Scales-Ocean (MPAS-O) and the online Lagrangian In-situ Global High-performance particle Tracking (LIGHT) diagnostic via space-time dispersion of particle clusters over 120 monthly realizations of O(10 6) particles on 11 potential density surfaces. Diffusivity in the jet reaches values of O(6000 m 2 s -1) and is largest near the critical layer supporting mixing suppression and critical layer theory. Values in the vicinity of the shelf break are suppressed to O(100 m 2 s -1) due tomore » the presence of westward slope front currents. Diffusivity attenuates less rapidly with depth in the jet than both eddy velocity and kinetic energy scalings would suggest. Removal of the mean flow via high-pass filtering shifts the nonlinear parameter (ratio of the eddy velocity to eddy phase speed) into the linear wave regime by increasing the eddy phase speed via the depth-mean flow. Low-pass filtering, in contrast, quantifies the effect of mean shear. Diffusivity is decomposed into mean flow shear, linear waves, and the residual nonhomogeneous turbulence components, where turbulence dominates and eddy-produced filamentation strained by background mean shear enhances mixing, accounting for ≥ 80% of the total diffusivity relative to mean shear [O(100 m 2 s -1)], linear waves [O(1000 m 2 s -1)], and undecomposed full diffusivity [O(6000 m 2 s -1)]. Finally, diffusivity parameterizations accounting for both the nonhomogeneous turbulence residual and depth variability are needed.« less

SU-F-T-459: ArcCHECK Machine QA : Highly Efficient Quality Assurance Tool for VMAT, SRS & SBRT Linear Accelerator Delivery

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

Mhatre, V; Patwe, P; Dandekar, P

Purpose: Quality assurance (QA) of complex linear accelerators is critical and highly time consuming. ArcCHECK Machine QA tool is used to test geometric and delivery aspects of linear accelerator. In this study we evaluated the performance of this tool. Methods: Machine QA feature allows user to perform quality assurance tests using ArcCHECK phantom. Following tests were performed 1) Gantry Speed 2) Gantry Rotation 3) Gantry Angle 4)MLC/Collimator QA 5)Beam Profile Flatness & Symmetry. Data was collected on trueBEAM stX machine for 6 MV for a period of one year. The Gantry QA test allows to view errors in gantry angle,more » rotation & assess how accurately the gantry moves around the isocentre. The MLC/Collimator QA tool is used to analyze & locate the differences between leaf bank & jaw position of linac. The flatness & Symmetry test quantifies beam flatness & symmetry in IEC-y & x direction. The Gantry & Flatness/Symmetry test can be performed for static & dynamic delivery. Results: The Gantry speed was 3.9 deg/sec with speed maximum deviation around 0.3 deg/sec. The Gantry Isocentre for arc delivery was 0.9mm & static delivery was 0.4mm. The maximum percent positive & negative difference was found to be 1.9 % & – 0.25 % & maximum distance positive & negative diff was 0.4mm & – 0.3 mm for MLC/Collimator QA. The Flatness for Arc delivery was 1.8 % & Symmetry for Y was 0.8 % & X was 1.8 %. The Flatness for gantry 0°,270°,90° & 180° was 1.75,1.9,1.8 & 1.6% respectively & Symmetry for X & Y was 0.8,0.6% for 0°, 0.6,0.7% for 270°, 0.6,1% for 90° & 0.6,0.7% for 180°. Conclusion: ArcCHECK Machine QA is an useful tool for QA of Modern linear accelerators as it tests both geometric & delivery aspects. This is very important for VMAT, SRS & SBRT treatments.« less

Photoacoustic trace detection of gases at the parts-per-quadrillion level with a moving optical grating.

PubMed

Xiong, Lian; Bai, Wenyu; Chen, Feifei; Zhao, Xian; Yu, Fapeng; Diebold, Gerald J

2017-07-11

The amplitude of the photoacoustic effect for an optical source moving at the sound speed in a one-dimensional geometry increases linearly in time without bound in the linear acoustic regime. Here, use of this principle is described for trace detection of gases, using two frequency-shifted beams from a CO 2 laser directed at an angle to each other to give optical fringes that move at the sound speed in a cavity with a longitudinal resonance. The photoacoustic signal is detected with a high-[Formula: see text], piezoelectric crystal with a resonance on the order of [Formula: see text] kHz. The photoacoustic cell has a design analogous to a hemispherical laser resonator and can be adjusted to have a longitudinal resonance to match that of the detector crystal. The grating frequency, the length of the resonator, and the crystal must all have matched frequencies; thus, three resonances are used to advantage to produce sensitivity that extends to the parts-per-quadrillion level.

A 12-bit high-speed column-parallel two-step single-slope analog-to-digital converter (ADC) for CMOS image sensors.

PubMed

Lyu, Tao; Yao, Suying; Nie, Kaiming; Xu, Jiangtao

2014-11-17

A 12-bit high-speed column-parallel two-step single-slope (SS) analog-to-digital converter (ADC) for CMOS image sensors is proposed. The proposed ADC employs a single ramp voltage and multiple reference voltages, and the conversion is divided into coarse phase and fine phase to improve the conversion rate. An error calibration scheme is proposed to correct errors caused by offsets among the reference voltages. The digital-to-analog converter (DAC) used for the ramp generator is based on the split-capacitor array with an attenuation capacitor. Analysis of the DAC's linearity performance versus capacitor mismatch and parasitic capacitance is presented. A prototype 1024 × 32 Time Delay Integration (TDI) CMOS image sensor with the proposed ADC architecture has been fabricated in a standard 0.18 μm CMOS process. The proposed ADC has average power consumption of 128 μW and a conventional rate 6 times higher than the conventional SS ADC. A high-quality image, captured at the line rate of 15.5 k lines/s, shows that the proposed ADC is suitable for high-speed CMOS image sensors.

Higher Fasting Plasma Glucose Levels, within the Normal Range, are Associated with Decreased Processing Speed in High Functioning Young Elderly.

PubMed

Raizes, Meytal; Elkana, Odelia; Franko, Motty; Ravona Springer, Ramit; Segev, Shlomo; Beeri, Michal Schnaider

2016-01-01

We explored the association of plasma glucose levels within the normal range with processing speed in high functioning young elderly, free of type 2 diabetes mellitus (T2DM). A sample of 41 participants (mean age = 64.7, SD = 10; glucose 94.5 mg/dL, SD = 9.3), were examined with a computerized cognitive battery. Hierarchical linear regression analysis showed that higher plasma glucose levels, albeit within the normal range (<110 mg/dL), were associated with longer reaction times (p <  0.01). These findings suggest that even in the subclinical range and in the absence of T2DM, monitoring plasma glucose levels may have an impact on cognitive function.

High Speed All-Optical Data Distribution Network

NASA Astrophysics Data System (ADS)

Braun, Steve; Hodara, Henri

2017-11-01

This article describes the performance and capabilities of an all-optical network featuring low latency, high speed file transfer between serially connected optical nodes. A basic component of the network is a network interface card (NIC) implemented through a unique planar lightwave circuit (PLC) that performs add/drop data and optical signal amplification. The network uses a linear bus topology with nodes in a "T" configuration, as described in the text. The signal is sent optically (hence, no latency) to all nodes via wavelength division multiplexing (WDM), with each node receiver tuned to wavelength of choice via an optical de-multiplexer. Each "T" node routes a portion of the signal to/from the bus through optical couplers, embedded in the network interface card (NIC), to each of the 1 through n computers.

Non-binary LDPC-coded modulation for high-speed optical metro networks with backpropagation

NASA Astrophysics Data System (ADS)

Arabaci, Murat; Djordjevic, Ivan B.; Saunders, Ross; Marcoccia, Roberto M.

2010-01-01

To simultaneously mitigate the linear and nonlinear channel impairments in high-speed optical communications, we propose the use of non-binary low-density-parity-check-coded modulation in combination with a coarse backpropagation method. By employing backpropagation, we reduce the memory in the channel and in return obtain significant reductions in the complexity of the channel equalizer which is exponentially proportional to the channel memory. We then compensate for the remaining channel distortions using forward error correction based on non-binary LDPC codes. We propose non-binary-LDPC-coded modulation scheme because, compared to bit-interleaved binary-LDPC-coded modulation scheme employing turbo equalization, the proposed scheme lowers the computational complexity and latency of the overall system while providing impressively larger coding gains.

RQL Fuel Shifting Sector Rig Test

NASA Technical Reports Server (NTRS)

Holdeman, James D. (Technical Monitor); Haid, Daniel A.; Koopman, Frederick S.; Peschke, William O. T.; Siskind, Kenneth S.

2004-01-01

The low emissions potential of a Rich-Quench-Lean (RQL) combustor for use in the HIgh Speed Civil transport (HSCT) application was evaluated as part of the NASA Critical Propulsion Components (CPC) Program. Fuel shifting as an approach to combustor control was evaluated in a multiple bank RQL combustor, utilizing reduced scale quench technology implemented in a convoluted linear with quench plate concept.

Sound Radiated by a Wave-Like Structure in a Compressible Jet

NASA Technical Reports Server (NTRS)

Golubev, V. V.; Prieto, A. F.; Mankbadi, R. R.; Dahl, M. D.; Hixon, R.

2003-01-01

This paper extends the analysis of acoustic radiation from the source model representing spatially-growing instability waves in a round jet at high speeds. Compared to previous work, a modified approach to the sound source modeling is examined that employs a set of solutions to linearized Euler equations. The sound radiation is then calculated using an integral surface method.

High Speed Civil Transport Aircraft Simulation: Reference-H Cycle 1, MATLAB Implementation

NASA Technical Reports Server (NTRS)

Sotack, Robert A.; Chowdhry, Rajiv S.; Buttrill, Carey S.

1999-01-01

The mathematical model and associated code to simulate a high speed civil transport aircraft - the Boeing Reference H configuration - are described. The simulation was constructed in support of advanced control law research. In addition to providing time histories of the dynamic response, the code includes the capabilities for calculating trim solutions and for generating linear models. The simulation relies on the nonlinear, six-degree-of-freedom equations which govern the motion of a rigid aircraft in atmospheric flight. The 1962 Standard Atmosphere Tables are used along with a turbulence model to simulate the Earth atmosphere. The aircraft model has three parts - an aerodynamic model, an engine model, and a mass model. These models use the data from the Boeing Reference H cycle 1 simulation data base. Models for the actuator dynamics, landing gear, and flight control system are not included in this aircraft model. Dynamic responses generated by the nonlinear simulation are presented and compared with results generated from alternate simulations at Boeing Commercial Aircraft Company and NASA Langley Research Center. Also, dynamic responses generated using linear models are presented and compared with dynamic responses generated using the nonlinear simulation.

Study of microstructure and fracture properties of blunt notched and sharp cracked high density polyethylene specimens.

PubMed

Pan, Huanyu; Devasahayam, Sheila; Bandyopadhyay, Sri

2017-07-21

This paper examines the effect of a broad range of crosshead speed (0.05 to 100 mm/min) and a small range of temperature (25 °C and 45 °C) on the failure behaviour of high density polyethylene (HDPE) specimens containing a) standard size blunt notch and b) standard size blunt notch plus small sharp crack - all tested in air. It was observed that the yield stress properties showed linear increase with the natural logarithm of strain rate. The stress intensity factors under blunt notch and sharp crack conditions also increased linearly with natural logarithm of the crosshead speed. The results indicate that in the practical temperature range of 25 °C and 45 °C under normal atmosphere and increasing strain rates, HDPE specimens with both blunt notches and sharp cracks possess superior fracture properties. SEM microstructure studies of fracture surfaces showed craze initiation mechanisms at lower strain rate, whilst at higher strain rates there is evidence of dimple patterns absorbing the strain energy and creating plastic deformation. The stress intensity factor and the yield strength were higher at 25 °C compared to those at 45 °C.

Self-optimizing Pitch Control for Large Scale Wind Turbine Based on ADRC

NASA Astrophysics Data System (ADS)

Xia, Anjun; Hu, Guoqing; Li, Zheng; Huang, Dongxiao; Wang, Fengxiang

2018-01-01

Since wind turbine is a complex nonlinear and strong coupling system, traditional PI control method can hardly achieve good control performance. A self-optimizing pitch control method based on the active-disturbance-rejection control theory is proposed in this paper. A linear model of the wind turbine is derived by linearizing the aerodynamic torque equation and the dynamic response of wind turbine is transformed into a first-order linear system. An expert system is designed to optimize the amplification coefficient according to the pitch rate and the speed deviation. The purpose of the proposed control method is to regulate the amplification coefficient automatically and keep the variations of pitch rate and rotor speed in proper ranges. Simulation results show that the proposed pitch control method has the ability to modify the amplification coefficient effectively, when it is not suitable, and keep the variations of pitch rate and rotor speed in proper ranges

Relaxation approximations to second-order traffic flow models by high-resolution schemes

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

Nikolos, I.K.; Delis, A.I.; Papageorgiou, M.

2015-03-10

A relaxation-type approximation of second-order non-equilibrium traffic models, written in conservation or balance law form, is considered. Using the relaxation approximation, the nonlinear equations are transformed to a semi-linear diagonilizable problem with linear characteristic variables and stiff source terms with the attractive feature that neither Riemann solvers nor characteristic decompositions are in need. In particular, it is only necessary to provide the flux and source term functions and an estimate of the characteristic speeds. To discretize the resulting relaxation system, high-resolution reconstructions in space are considered. Emphasis is given on a fifth-order WENO scheme and its performance. The computations reportedmore » demonstrate the simplicity and versatility of relaxation schemes as numerical solvers.« less

Summary of recent NASA propeller research

NASA Technical Reports Server (NTRS)

Mikkelson, D. C.; Mitchell, G. A.; Bober, L. J.

1984-01-01

Advanced high-speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. At these speeds, studies indicate that there is a 15 to near 40 percent block fuel savings and associated operating cost benefits for advanced turboprops compared to equivalent technology turbofan powered aircraft. Recent wind tunnel results for five eight to ten blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing nearfield cruise noise by about 6 dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some results are compared with propeller force and probe data. Also, analytical predictions are compared with some initial laser velocimeter measurements of the flow field velocities of an eightbladed 45 swept propeller. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller near-field noise data with linear acoustic theory indicate that the theory adequately predicts near-field noise for subsonic tip speeds but overpredicts the noise for supersonic tip speeds.

Summary of recent NASA propeller research

NASA Technical Reports Server (NTRS)

Mikkelson, D. C.; Mitchell, G. A.; Bober, L. J.

1985-01-01

Advanced high speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. At these speeds, studies indicate that there is a 15 to near 40 percent block fuel savings and associated operating cost benefits for advanced turboprops compared to equivalent technology turbofan powered aircraft. Recent wind tunnel results for five eight to ten blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing nearfield cruise noise about 6 dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some results are compared with propeller force and probe data. Also, analytical predictions are compared with some initial laser velocimeter measurements of the flow field velocities of an eight bladed 45 swept propeller. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller nearfield noise data with linear acoustic theory indicate that the theory adequately predicts nearfield noise for subsonic tip speeds, but overpredicts the noise for supersonic tip speeds.

Acoustic Power Transmission Through a Ducted Fan

NASA Technical Reports Server (NTRS)

Envia, Ed

2016-01-01

For high-speed ducted fans, when the rotor flowfield is shock-free, the main contribution to the inlet radiated acoustic power comes from the portion of the rotor stator interaction sound field that is transmitted upstream through the rotor. As such, inclusion of the acoustic transmission is an essential ingredient in the prediction of the fan inlet noise when the fan tip relative speed is subsonic. This paper describes a linearized Euler based approach to computing the acoustic transmission of fan tones through the rotor. The approach is embodied in a code called LINFLUX was applied to a candidate subsonic fan called the Advanced Ducted Propulsor (ADP). The results from this study suggest that it is possible to make such prediction with sufficient fidelity to provide an indication of the acoustic transmission trends with the fan tip speed.

Optimization of Friction Stir Welding Tool Advance Speed via Monte-Carlo Simulation of the Friction Stir Welding Process

PubMed Central

Fraser, Kirk A.; St-Georges, Lyne; Kiss, Laszlo I.

2014-01-01

Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges), being able to model the process to determine the highest speed of advance possible that will not cause unwanted welding defects is desirable. A numerical solution to the transient two-dimensional heat diffusion equation for the friction stir welding process is presented. A non-linear heat generation term based on an arbitrary piecewise linear model of friction as a function of temperature is used. The solution is used to solve for the temperature distribution in the Al 6061-T6 work pieces. The finite difference solution of the non-linear problem is used to perform a Monte-Carlo simulation (MCS). A polynomial response surface (maximum welding temperature as a function of advancing and rotational speed) is constructed from the MCS results. The response surface is used to determine the optimum tool speed of advance and rotational speed. The exterior penalty method is used to find the highest speed of advance and the associated rotational speed of the tool for the FSW process considered. We show that good agreement with experimental optimization work is possible with this simplified model. Using our approach an optimal weld pitch of 0.52 mm/rev is obtained for 3.18 mm thick AA6061-T6 plate. Our method provides an estimate of the optimal welding parameters in less than 30 min of calculation time. PMID:28788627

Optimization of Friction Stir Welding Tool Advance Speed via Monte-Carlo Simulation of the Friction Stir Welding Process.

PubMed

Fraser, Kirk A; St-Georges, Lyne; Kiss, Laszlo I

2014-04-30

Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges), being able to model the process to determine the highest speed of advance possible that will not cause unwanted welding defects is desirable. A numerical solution to the transient two-dimensional heat diffusion equation for the friction stir welding process is presented. A non-linear heat generation term based on an arbitrary piecewise linear model of friction as a function of temperature is used. The solution is used to solve for the temperature distribution in the Al 6061-T6 work pieces. The finite difference solution of the non-linear problem is used to perform a Monte-Carlo simulation (MCS). A polynomial response surface (maximum welding temperature as a function of advancing and rotational speed) is constructed from the MCS results. The response surface is used to determine the optimum tool speed of advance and rotational speed. The exterior penalty method is used to find the highest speed of advance and the associated rotational speed of the tool for the FSW process considered. We show that good agreement with experimental optimization work is possible with this simplified model. Using our approach an optimal weld pitch of 0.52 mm/rev is obtained for 3.18 mm thick AA6061-T6 plate. Our method provides an estimate of the optimal welding parameters in less than 30 min of calculation time.

Factors affecting injury severity of vehicle occupants following road traffic collisions.

PubMed

Abu-Zidan, Fikri M; Eid, Hani O

2015-01-01

We aimed to define factors affecting injury severity of vehicle occupants following road traffic collisions (RTC). 422 vehicle occupants (343 males, 81.3%) with RTC-related injuries were prospectively studied over 18 months. General linear model was used to test the effect of age, gender, alcohol and drug use, time of injury, mechanism of injury, size and speed of the vehicle, position in the vehicle, seatbelt usage, and air bag deployment on the Injury Severity Score (ISS) of the vehicle occupants. The mean (range) age of patients was 28.2 (1-78) years and the mean (range) ISS was 7.9 (1-50). Front impact was the most common mechanism of injury (32.9%) followed by rollover (25.6%) and side impact (22.3%). 18.2% used seatbelts. The general linear model was highly significant and showed that mechanism of injury (p<0.0001), speed of the vehicle (p=0.02), and age of the vehicle occupant (p=0.03) significantly affected the Injury Severity Score. The mechanism of the RTC, the vehicle speed, and age of the vehicle occupant are the most important factors affecting the severity of road traffic collision injuries. A detailed history of the mechanism of injury is important for alerting clinicians to severity of injury, the need for admission, and workup of the patients. Furthermore, strict speed limit enforcement is an injury prevention priority in our community. Copyright © 2014 Elsevier Ltd. All rights reserved.

A high-speed scintillation-based electronic portal imaging device to quantitatively characterize IMRT delivery.

PubMed

Ranade, Manisha K; Lynch, Bart D; Li, Jonathan G; Dempsey, James F

2006-01-01

We have developed an electronic portal imaging device (EPID) employing a fast scintillator and a high-speed camera. The device is designed to accurately and independently characterize the fluence delivered by a linear accelerator during intensity modulated radiation therapy (IMRT) with either step-and-shoot or dynamic multileaf collimator (MLC) delivery. Our aim is to accurately obtain the beam shape and fluence of all segments delivered during IMRT, in order to study the nature of discrepancies between the plan and the delivered doses. A commercial high-speed camera was combined with a terbium-doped gadolinium-oxy-sulfide (Gd2O2S:Tb) scintillator to form an EPID for the unaliased capture of two-dimensional fluence distributions of each beam in an IMRT delivery. The high speed EPID was synchronized to the accelerator pulse-forming network and gated to capture every possible pulse emitted from the accelerator, with an approximate frame rate of 360 frames-per-second (fps). A 62-segment beam from a head-and-neck IMRT treatment plan requiring 68 s to deliver was recorded with our high speed EPID producing approximately 6 Gbytes of imaging data. The EPID data were compared with the MLC instruction files and the MLC controller log files. The frames were binned to provide a frame rate of 72 fps with a signal-to-noise ratio that was sufficient to resolve leaf positions and segment fluence. The fractional fluence from the log files and EPID data agreed well. An ambiguity in the motion of the MLC during beam on was resolved. The log files reported leaf motions at the end of 33 of the 42 segments, while the EPID observed leaf motions in only 7 of the 42 segments. The static IMRT segment shapes observed by the high speed EPID were in good agreement with the shapes reported in the log files. The leaf motions observed during beam-on for step-and-shoot delivery were not temporally resolved by the log files.

Increased prolactin levels are associated with impaired processing speed in subjects with early psychosis.

PubMed

Montalvo, Itziar; Gutiérrez-Zotes, Alfonso; Creus, Marta; Monseny, Rosa; Ortega, Laura; Franch, Joan; Lawrie, Stephen M; Reynolds, Rebecca M; Vilella, Elisabet; Labad, Javier

2014-01-01

Hyperprolactinaemia, a common side effect of some antipsychotic drugs, is also present in drug-naïve psychotic patients and subjects at risk for psychosis. Recent studies in non-psychiatric populations suggest that increased prolactin may have negative effects on cognition. The aim of our study was to explore whether high plasma prolactin levels are associated with poorer cognitive functioning in subjects with early psychoses. We studied 107 participants: 29 healthy subjects and 78 subjects with an early psychosis (55 psychotic disorders with <3 years of illness, 23 high-risk subjects). Cognitive assessment was performed with the MATRICS Cognitive Consensus Cognitive Battery, and prolactin levels were determined as well as total cortisol levels in plasma. Psychopathological status was assessed and the use of psychopharmacological treatments (antipsychotics, antidepressants, benzodiazepines) recorded. Prolactin levels were negatively associated with cognitive performance in processing speed, in patients with a psychotic disorder and high-risk subjects. In the latter group, increased prolactin levels were also associated with impaired reasoning and problem solving and poorer general cognition. In a multiple linear regression analysis conducted in both high-risk and psychotic patients, controlling for potential confounders, prolactin and benzodiazepines were independently related to poorer cognitive performance in the speed of processing domain. A mediation analysis showed that both prolactin and benzodiazepine treatment act as mediators of the relationship between risperidone/paliperidone treatment and speed of processing. These results suggest that increased prolactin levels are associated with impaired processing speed in early psychosis. If these results are confirmed in future studies, strategies targeting reduction of prolactin levels may improve cognition in this population.

Modeling and Analysis of CNC Milling Process Parameters on Al3030 based Composite

NASA Astrophysics Data System (ADS)

Gupta, Anand; Soni, P. K.; Krishna, C. M.

2018-04-01

The machining of Al3030 based composites on Computer Numerical Control (CNC) high speed milling machine have assumed importance because of their wide application in aerospace industries, marine industries and automotive industries etc. Industries mainly focus on surface irregularities; material removal rate (MRR) and tool wear rate (TWR) which usually depends on input process parameters namely cutting speed, feed in mm/min, depth of cut and step over ratio. Many researchers have carried out researches in this area but very few have taken step over ratio or radial depth of cut also as one of the input variables. In this research work, the study of characteristics of Al3030 is carried out at high speed CNC milling machine over the speed range of 3000 to 5000 r.p.m. Step over ratio, depth of cut and feed rate are other input variables taken into consideration in this research work. A total nine experiments are conducted according to Taguchi L9 orthogonal array. The machining is carried out on high speed CNC milling machine using flat end mill of diameter 10mm. Flatness, MRR and TWR are taken as output parameters. Flatness has been measured using portable Coordinate Measuring Machine (CMM). Linear regression models have been developed using Minitab 18 software and result are validated by conducting selected additional set of experiments. Selection of input process parameters in order to get best machining outputs is the key contributions of this research work.

Phase and speed synchronization control of four eccentric rotors driven by induction motors in a linear vibratory feeder with unknown time-varying load torques using adaptive sliding mode control algorithm

NASA Astrophysics Data System (ADS)

Kong, Xiangxi; Zhang, Xueliang; Chen, Xiaozhe; Wen, Bangchun; Wang, Bo

2016-05-01

In this paper, phase and speed synchronization control of four eccentric rotors (ERs) driven by induction motors in a linear vibratory feeder with unknown time-varying load torques is studied. Firstly, the electromechanical coupling model of the linear vibratory feeder is established by associating induction motor's model with the dynamic model of the system, which is a typical under actuated model. According to the characteristics of the linear vibratory feeder, the complex control problem of the under actuated electromechanical coupling model converts to phase and speed synchronization control of four ERs. In order to keep the four ERs operating synchronously with zero phase differences, phase and speed synchronization controllers are designed by employing adaptive sliding mode control (ASMC) algorithm via a modified master-slave structure. The stability of the controllers is proved by Lyapunov stability theorem. The proposed controllers are verified by simulation via Matlab/Simulink program and compared with the conventional sliding mode control (SMC) algorithm. The results show the proposed controllers can reject the time-varying load torques effectively and four ERs can operate synchronously with zero phase differences. Moreover, the control performance is better than the conventional SMC algorithm and the chattering phenomenon is attenuated. Furthermore, the effects of reference speed and parametric perturbations are discussed to show the strong robustness of the proposed controllers. Finally, experiments on a simple vibratory test bench are operated by using the proposed controllers and without control, respectively, to validate the effectiveness of the proposed controllers further.

Linear-constraint wavefront control for exoplanet coronagraphic imaging systems

NASA Astrophysics Data System (ADS)

Sun, He; Eldorado Riggs, A. J.; Kasdin, N. Jeremy; Vanderbei, Robert J.; Groff, Tyler Dean

2017-01-01

A coronagraph is a leading technology for achieving high-contrast imaging of exoplanets in a space telescope. It uses a system of several masks to modify the diffraction and achieve extremely high contrast in the image plane around target stars. However, coronagraphic imaging systems are very sensitive to optical aberrations, so wavefront correction using deformable mirrors (DMs) is necessary to avoid contrast degradation in the image plane. Electric field conjugation (EFC) and Stroke minimization (SM) are two primary high-contrast wavefront controllers explored in the past decade. EFC minimizes the average contrast in the search areas while regularizing the strength of the control inputs. Stroke minimization calculates the minimum DM commands under the constraint that a target average contrast is achieved. Recently in the High Contrast Imaging Lab at Princeton University (HCIL), a new linear-constraint wavefront controller based on stroke minimization was developed and demonstrated using numerical simulation. Instead of only constraining the average contrast over the entire search area, the new controller constrains the electric field of each single pixel using linear programming, which could led to significant increases in speed of the wavefront correction and also create more uniform dark holes. As a follow-up of this work, another linear-constraint controller modified from EFC is demonstrated theoretically and numerically and the lab verification of the linear-constraint controllers is reported. Based on the simulation and lab results, the pros and cons of linear-constraint controllers are carefully compared with EFC and stroke minimization.

Raindrop fall velocities from an optical array probe and 2-D video disdrometer

NASA Astrophysics Data System (ADS)

Bringi, Viswanathan; Thurai, Merhala; Baumgardner, Darrel

2018-03-01

We report on fall speed measurements of raindrops in light-to-heavy rain events from two climatically different regimes (Greeley, Colorado, and Huntsville, Alabama) using the high-resolution (50 µm) Meteorological Particle Spectrometer (MPS) and a third-generation (170 µm resolution) 2-D video disdrometer (2DVD). To mitigate wind effects, especially for the small drops, both instruments were installed within a 2/3-scale Double Fence Intercomparison Reference (DFIR) enclosure. Two cases involved light-to-moderate wind speeds/gusts while the third case was a tornadic supercell and several squall lines that passed over the site with high wind speeds/gusts. As a proxy for turbulent intensity, maximum wind speeds from 10 m height at the instrumented site recorded every 3 s were differenced with the 5 min average wind speeds and then squared. The fall speeds vs. size from 0.1 to 2 and > 0.7 mm were derived from the MPS and the 2DVD, respectively. Consistency of fall speeds from the two instruments in the overlap region (0.7-2 mm) gave confidence in the data quality and processing methodologies. Our results indicate that under low turbulence, the mean fall speeds agree well with fits to the terminal velocity measured in the laboratory by Gunn and Kinzer from 100 µm up to precipitation sizes. The histograms of fall speeds for 0.5, 0.7, 1 and 1.5 mm sizes were examined in detail under the same conditions. The histogram shapes for the 1 and 1.5 mm sizes were symmetric and in good agreement between the two instruments with no evidence of skewness or of sub- or super-terminal fall speeds. The histograms of the smaller 0.5 and 0.7 mm drops from MPS, while generally symmetric, showed that occasional occurrences of sub- and super-terminal fall speeds could not be ruled out. In the supercell case, the very strong gusts and inferred high turbulence intensity caused a significant broadening of the fall speed distributions with negative skewness (for drops of 1.3, 2 and 3 mm). The mean fall speeds were also found to decrease nearly linearly with increasing turbulent intensity attaining values about 25-30 % less than the terminal velocity of Gunn-Kinzer, i.e., sub-terminal fall speeds.

High-speed spatial scanning pyrometer

NASA Technical Reports Server (NTRS)

Cezairliyan, A.; Chang, R. F.; Foley, G. M.; Miller, A. P.

1993-01-01

A high-speed spatial scanning pyrometer has been designed and developed to measure spectral radiance temperatures at multiple target points along the length of a rapidly heating/cooling specimen in dynamic thermophysical experiments at high temperatures (above about 1800 K). The design, which is based on a self-scanning linear silicon array containing 1024 elements, enables the pyrometer to measure spectral radiance temperatures (nominally at 650 nm) at 1024 equally spaced points along a 25-mm target length. The elements of the array are sampled consecutively every 1 microsec, thereby permitting one cycle of measurements to be completed in approximately 1 msec. Procedures for calibration and temperature measurement as well as the characteristics and performance of the pyrometer are described. The details of sources and estimated magnitudes of possible errors are given. An example of measurements of radiance temperatures along the length of a tungsten rod, during its cooling following rapid resistive pulse heating, is presented.

The design of a turboshaft speed governor using modern control techniques

NASA Technical Reports Server (NTRS)

Delosreyes, G.; Gouchoe, D. R.

1986-01-01

The objectives of this program were: to verify the model of off schedule compressor variable geometry in the T700 turboshaft engine nonlinear model; to evaluate the use of the pseudo-random binary noise (PRBN) technique for obtaining engine frequency response data; and to design a high performance power turbine speed governor using modern control methods. Reduction of T700 engine test data generated at NASA-Lewis indicated that the off schedule variable geometry effects were accurate as modeled. Analysis also showed that the PRBN technique combined with the maximum likelihood model identification method produced a Bode frequency response that was as accurate as the response obtained from standard sinewave testing methods. The frequency response verified the accuracy of linear models consisting of engine partial derivatives and used for design. A power turbine governor was designed using the Linear Quadratic Regulator (LQR) method of full state feedback control. A Kalman filter observer was used to estimate helicopter main rotor blade velocity. Compared to the baseline T700 power turbine speed governor, the LQR governor reduced droop up to 25 percent for a 490 shaft horsepower transient in 0.1 sec simulating a wind gust, and up to 85 percent for a 700 shaft horsepower transient in 0.5 sec simulating a large collective pitch angle transient.

40 CFR 1066.220 - Linearity verification for chassis dynamometer systems.

Code of Federal Regulations, 2014 CFR

2014-07-01

... dynamometer speed and torque at least as frequently as indicated in Table 1 of § 1066.215. The intent of... linear regression and the linearity criteria specified in Table 1 of this section. (b) Performance requirements. If a measurement system does not meet the applicable linearity criteria in Table 1 of this...

Development Of A Dynamic Radiographic Capability Using High-Speed Video

NASA Astrophysics Data System (ADS)

Bryant, Lawrence E.

1985-02-01

High-speed video equipment can be used to optically image up to 2,000 full frames per second or 12,000 partial frames per second. X-ray image intensifiers have historically been used to image radiographic images at 30 frames per second. By combining these two types of equipment, it is possible to perform dynamic x-ray imaging of up to 2,000 full frames per second. The technique has been demonstrated using conventional, industrial x-ray sources such as 150 Kv and 300 Kv constant potential x-ray generators, 2.5 MeV Van de Graaffs, and linear accelerators. A crude form of this high-speed radiographic imaging has been shown to be possible with a cobalt 60 source. Use of a maximum aperture lens makes best use of the available light output from the image intensifier. The x-ray image intensifier input and output fluors decay rapidly enough to allow the high frame rate imaging. Data are presented on the maximum possible video frame rates versus x-ray penetration of various thicknesses of aluminum and steel. Photographs illustrate typical radiographic setups using the high speed imaging method. Video recordings show several demonstrations of this technique with the played-back x-ray images slowed down up to 100 times as compared to the actual event speed. Typical applications include boiling type action of liquids in metal containers, compressor operation with visualization of crankshaft, connecting rod and piston movement and thermal battery operation. An interesting aspect of this technique combines both the optical and x-ray capabilities to observe an object or event with both external and internal details with one camera in a visual mode and the other camera in an x-ray mode. This allows both kinds of video images to appear side by side in a synchronized presentation.

Single-mode 850-nm vertical-cavity surface-emitting lasers with Zn-diffusion and oxide-relief apertures for > 50 Gbit/sec OOK and 4-PAM transmission

NASA Astrophysics Data System (ADS)

Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jyehong; Ledentsov, N. N.; Yang, Ying-Jay

2017-02-01

Vertical-cavity surface-emitting lasers (VCSELs) has become the most important light source in the booming market of short-reach (< 300 meters) optical interconnect (OI). The next generation OI has been targeted at 56 Gbit/sec data rate per channel (CEI-56G) with the total data rate up to 400 Gbit/sec. However, the serious modal dispersion of multi-mode fiber (MMF), limited speed of VCSEL, and its high resistance (> 150 Ω) seriously limits the >50 Gbit/sec linking distance (< 10 m) by using only on-off keying (OOK) modulation scheme without any signal processing techniques. In contrast to OOK, 4-PAM modulation format is attractive for >50 Gbit/sec transmission due to that it can save one-half of the required bandwidth. Nevertheless, a 4.7 dB optical power penalty and the linearity of transmitter would become issues in the 4-PAM linking performance. Besides, in the modern OI system, the optics transreceiver module must be packaged as close as possible with the integrated circuits (ICs). The heat generated from ICs will become an issue in speed of VSCEL. Here, we review our recent work about 850 nm VCSEL, which has unique Zn-diffusion/oxide-relief apertures and special p- doping active layer with strong wavelength detuning to further enhance its modulation speed and high-temperature (85°C) performances. Single-mode (SM) devices with high-speed ( 26 GHz), reasonable resistance ( 70 Ω) and moderate output power ( 1.5 mW) can be achieved. Error-free 54 Gbit/sec OOK transmission through 1km MMF has been realized by using such SM device with signal processing techniques. Besides, the volterra nonlinear equalizer has been applied in our 4-PAM 64 Gbit/sec transmission through 2-km OM4 MMF, which significantly enhance the linearity of device and outperforms fed forward equalization (FFE) technique. Record high bit-rate distance product of 128.km is confirmed for optical-interconnect applications.

SU-E-J-28: Gantry Speed Significantly Affects Image Quality and Imaging Dose for 4D Cone-Beam Computed Tomography On the Varian Edge Platform

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

Santoso, A; Song, K; Gardner, S

Purpose: 4D-CBCT facilitates assessment of tumor motion at treatment position. We investigated the effect of gantry speed on 4D-CBCT image quality and dose using the Varian Edge On-Board Imager (OBI). Methods: A thoracic protocol was designed using a 125 kVp spectrum. Image quality parameters were obtained via 4D acquisition using a Catphan phantom with a gating system. A sinusoidal waveform was executed with a five second period and superior-inferior motion. 4D-CBCT scans were sorted into 4 and 10 phases. Image quality metrics included spatial resolution, contrast-to-noise ratio (CNR), uniformity index (UI), Hounsfield unit (HU) sensitivity, and RMS error (RMSE) ofmore » motion amplitude. Dosimetry was accomplished using Gafchromic XR-QA2 films within a CIRS Thorax phantom. This was placed on the gating phantom using the same motion waveform. Results: High contrast resolution decreased linearly from 5.93 to 4.18 lp/cm, 6.54 to 4.18 lp/cm, and 5.19 to 3.91 lp/cm for averaged, 4 phase, and 10 phase 4DCBCT volumes respectively as gantry speed increased from 1.0 to 6.0 degs/sec. CNRs decreased linearly from 4.80 to 1.82 as the gantry speed increased from 1.0 to 6.0 degs/sec, respectively. No significant variations in UIs, HU sensitivities, or RMSEs were observed with variable gantry speed. Ion chamber measurements compared to film yielded small percent differences in plastic water regions (0.1–9.6%), larger percent differences in lung equivalent regions (7.5–34.8%), and significantly larger percent differences in bone equivalent regions (119.1–137.3%). Ion chamber measurements decreased from 17.29 to 2.89 cGy with increasing gantry speed from 1.0 to 6.0 degs/sec. Conclusion: Maintaining technique factors while changing gantry speed changes the number of projections used for reconstruction. Increasing the number of projections by decreasing gantry speed decreases noise, however, dose is increased. The future of 4DCBCT’s clinical utility relies on further investigation of image optimization.« less

The Design of the Longitudinal Autopilot for the LSU-05 Unmanned Aerial Surveillance Vehicle

NASA Astrophysics Data System (ADS)

Fajar, Muhammad; Arifianto, Ony

2018-04-01

Longitudinal autopilot design for the LAPAN Surveillance Vehicle LSU-05 will be described in this paper. The LSU-05 is the most recent Unmanned Aerial Vehicle (UAV) project of the Aeronautics Technology Center (Pusat Teknologi Penerbangan – Pustekbang), LAPAN. This UAV is expected to be able to carry 30 kg of payload, four surveillance purposes. The longitudinal autopilot described in this paper consists of four modes, those are Pitch damper, Pitch Attitude Hold, Altitude Hold, and Speed Hold. The Autopilot of the UAV will be designed at four operating speeds, namely 15 m/s, 20 m/s, 25 m/s, and 30 m/. The Athena Vortex Lattice software is used to generate the aerodynamic model of the LSU-05. Non-linear longitudinal aircraft dynamics model is then developed in MATLAB/SIMULINK environment. Linearization of the non-linear model is performed using the linearization tool of SIMULINK. The controller is designed, based on the linear model of the aircraft in the state space form. A Proportional-Integral-Derivative (PID) controller structure is chosen, using root locus method to determine mainly the proportional (P) gain. Integral (I) and derivative (D) gain will only be used if the proportional gain can not achieve the desired target or if an overshoot / undershoot reduction is required. The overshoot/undershoot should not exceed 5% and settling time is less than 20 seconds. The controller designed is simulated using MATLAB and SIMULINK. Preliminary analysis of the controller performance shows that the controller can be used to stabilize the aircraft and to automatize the speed and altitude control throughout the considered speed range.

Design and Performance Improvements of the Prototype Open Core Flywheel Energy Storage System

NASA Technical Reports Server (NTRS)

Pang, D.; Anand, D. K. (Editor); Kirk, J. A. (Editor)

1996-01-01

A prototype magnetically suspended composite flywheel energy storage (FES) system is operating at the University of Maryland. This system, designed for spacecraft applications, incorporates recent advances in the technologies of composite materials, magnetic suspension, and permanent magnet brushless motor/generator. The current system is referred to as an Open Core Composite Flywheel (OCCF) energy storage system. This paper will present design improvements for enhanced and robust performance. Initially, when the OCCF prototype was spun above its first critical frequency of 4,500 RPM, the rotor movement would exceed the space available in the magnetic suspension gap and touchdown on the backup mechanical bearings would occur. On some occasions it was observed that, after touchdown, the rotor was unable to re-suspend as the speed decreased. Additionally, it was observed that the rotor would exhibit unstable oscillations when the control system was initially turned on. Our analysis suggested that the following problems existed: (1) The linear operating range of the magnetic bearings was limited due to electrical and magnetic saturation; (2) The inductance of the magnetic bearings was affecting the transient response of the system; (3) The flywheel was confined to a small movement because mechanical components could not be held to a tight tolerance; and (4) The location of the touchdown bearing magnifies the motion at the pole faces of the magnetic bearings when the linear range is crucial. In order to correct these problems an improved design of the flywheel energy storage system was undertaken. The magnetic bearings were re-designed to achieve a large linear operating range and to withstand load disturbances of at least 1 g. The external position transducers were replaced by a unique design which were resistant to magnetic field noise and allowed cancellation of the radial growth of the flywheel at high speeds. A central rod was utilized to ensure the concentricity of the magnetic bearings, the motor/generator, and the mechanical touchdown bearings. In addition, the mechanical touchdown bearings were placed at two ends of the magnetic bearing stack to restrict the motion at pole faces. A composite flywheel was made using a multi-ring interference assembled design for a high specific energy density. To achieve a higher speed and better efficiency, a permanent magnet DC brushless motor was specially designed and fabricated. A vacuum enclosure was constructed to eliminate windage losses for testing at high speeds. With the new improvements the OCCF system was tested to 20,000 RPM with a total stored energy of 15.9 WH and an angular momentum of 54.8 N-m-s (40.4 lb-ft-s). Motor current limitation, caused by power loss in the magnetic bearings, was identified as causing the limit in upper operating speed.

Intraindividual Variability in Executive Functions but Not Speed of Processing or Conflict Resolution Predicts Performance Differences in Gait Speed in Older Adults

PubMed Central

Mahoney, Jeannette; Verghese, Joe

2014-01-01

Background. The relationship between executive functions (EF) and gait speed is well established. However, with the exception of dual tasking, the key components of EF that predict differences in gait performance have not been determined. Therefore, the current study was designed to determine whether processing speed, conflict resolution, and intraindividual variability in EF predicted variance in gait performance in single- and dual-task conditions. Methods. Participants were 234 nondemented older adults (mean age 76.48 years; 55% women) enrolled in a community-based cohort study. Gait speed was assessed using an instrumented walkway during single- and dual-task conditions. The flanker task was used to assess EF. Results. Results from the linear mixed effects model showed that (a) dual-task interference caused a significant dual-task cost in gait speed (estimate = 35.99; 95% CI = 33.19–38.80) and (b) of the cognitive predictors, only intraindividual variability was associated with gait speed (estimate = −.606; 95% CI = −1.11 to −.10). In unadjusted analyses, the three EF measures were related to gait speed in single- and dual-task conditions. However, in fully adjusted linear regression analysis, only intraindividual variability predicted performance differences in gait speed during dual tasking (B = −.901; 95% CI = −1.557 to −.245). Conclusion. Among the three EF measures assessed, intraindividual variability but not speed of processing or conflict resolution predicted performance differences in gait speed. PMID:24285744

Swimming performance of a biomimetic compliant fish-like robot

NASA Astrophysics Data System (ADS)

Epps, Brenden P.; Valdivia Y Alvarado, Pablo; Youcef-Toumi, Kamal; Techet, Alexandra H.

2009-12-01

Digital particle image velocimetry and fluorescent dye visualization are used to characterize the performance of fish-like swimming robots. During nominal swimming, these robots produce a ‘V’-shaped double wake, with two reverse-Kármán streets in the far wake. The Reynolds number based on swimming speed and body length is approximately 7500, and the Strouhal number based on flapping frequency, flapping amplitude, and swimming speed is 0.86. It is found that swimming speed scales with the strength and geometry of a composite wake, which is constructed by freezing each vortex at the location of its centroid at the time of shedding. Specifically, we find that swimming speed scales linearly with vortex circulation. Also, swimming speed scales linearly with flapping frequency and the width of the composite wake. The thrust produced by the swimming robot is estimated using a simple vortex dynamics model, and we find satisfactory agreement between this estimate and measurements made during static load tests.

Design Method For Ultra-High Resolution Linear CCD Imagers

NASA Astrophysics Data System (ADS)

Sheu, Larry S.; Truong, Thanh; Yuzuki, Larry; Elhatem, Abdul; Kadekodi, Narayan

1984-11-01

This paper presents the design method to achieve ultra-high resolution linear imagers. This method utilizes advanced design rules and novel staggered bilinear photo sensor arrays with quadrilinear shift registers. Design constraint in the detector arrays and shift registers are analyzed. Imager architecture to achieve ultra-high resolution is presented. The characteristics of MTF, aliasing, speed, transfer efficiency and fine photolithography requirements associated with this architecture are also discussed. A CCD imager with advanced 1.5 um minimum feature size was fabricated. It is intended as a test vehicle for the next generation small sampling pitch ultra-high resolution CCD imager. Standard double-poly, two-phase shift registers were fabricated at an 8 um pitch using the advanced design rules. A special process step that blocked the source-drain implant from the shift register area was invented. This guaranteed excellent performance of the shift registers regardless of the small poly overlaps. A charge transfer efficiency of better than 0.99995 and maximum transfer speed of 8 MHz were achieved. The imager showed excellent performance. The dark current was less than 0.2 mV/ms, saturation 250 mV, adjacent photoresponse non-uniformity ± 4% and responsivity 0.7 V/ μJ/cm2 for the 8 μm x 6 μm photosensor size. The MTF was 0.6 at 62.5 cycles/mm. These results confirm the feasibility of the next generation ultra-high resolution CCD imagers.

Integrating solar energy and climate research into science education

NASA Astrophysics Data System (ADS)

Betts, Alan K.; Hamilton, James; Ligon, Sam; Mahar, Ann Marie

2016-01-01

This paper analyzes multi-year records of solar flux and climate data from two solar power sites in Vermont. We show the inter-annual differences of temperature, wind, panel solar flux, electrical power production, and cloud cover. Power production has a linear relation to a dimensionless measure of the transmission of sunlight through the cloud field. The difference between panel and air temperatures reaches 24°C with high solar flux and low wind speed. High panel temperatures that occur in summer with low wind speeds and clear skies can reduce power production by as much as 13%. The intercomparison of two sites 63 km apart shows that while temperature is highly correlated on daily (R2=0.98) and hourly (R2=0.94) timescales, the correlation of panel solar flux drops markedly from daily (R2=0.86) to hourly (R2=0.63) timescales. Minimum temperatures change little with cloud cover, but the diurnal temperature range shows a nearly linear increase with falling cloud cover to 16°C under nearly clear skies, similar to results from the Canadian Prairies. The availability of these new solar and climate datasets allows local student groups, a Rutland High School team here, to explore the coupled relationships between climate, clouds, and renewable power production. As our society makes major changes in our energy infrastructure in response to climate change, it is important that we accelerate the technical education of high school students using real-world data.

Influence of a Levelness Defect in a Thrust Bearing on the Dynamic Behaviour of AN Elastic Shaft

NASA Astrophysics Data System (ADS)

BERGER, S.; BONNEAU, O.; FRÊNE, J.

2002-01-01

This paper examines the non-linear dynamic behaviour of a flexible shaft. The shaft is mounted on two journal bearings and the axial load is supported by a defective hydrodynamic thrust bearing at one end. The defect is a levelness defect of the rotor. The thrust bearing behaviour must be considered to be non-linear because of the effects of the defect. The shaft is modelled with typical beam finite elements including effects such as the gyroscopic effects. A modal technique is used to reduce the number of degrees of freedom. Results show that the thrust bearing defects introduce supplementary critical speeds. The linear approach is unable to show the supplementary critical speeds which are obtained only by using non-linear analysis.

Propagation dynamics for a spatially periodic integrodifference competition model

NASA Astrophysics Data System (ADS)

Wu, Ruiwen; Zhao, Xiao-Qiang

2018-05-01

In this paper, we study the propagation dynamics for a class of integrodifference competition models in a periodic habitat. An interesting feature of such a system is that multiple spreading speeds can be observed, which biologically means different species may have different spreading speeds. We show that the model system admits a single spreading speed, and it coincides with the minimal wave speed of the spatially periodic traveling waves. A set of sufficient conditions for linear determinacy of the spreading speed is also given.

Tribological behaviour and statistical experimental design of sintered iron-copper based composites

NASA Astrophysics Data System (ADS)

Popescu, Ileana Nicoleta; Ghiţă, Constantin; Bratu, Vasile; Palacios Navarro, Guillermo

2013-11-01

The sintered iron-copper based composites for automotive brake pads have a complex composite composition and should have good physical, mechanical and tribological characteristics. In this paper, we obtained frictional composites by Powder Metallurgy (P/M) technique and we have characterized them by microstructural and tribological point of view. The morphology of raw powders was determined by SEM and the surfaces of obtained sintered friction materials were analyzed by ESEM, EDS elemental and compo-images analyses. One lot of samples were tested on a "pin-on-disc" type wear machine under dry sliding conditions, at applied load between 3.5 and 11.5 × 10-1 MPa and 12.5 and 16.9 m/s relative speed in braking point at constant temperature. The other lot of samples were tested on an inertial test stand according to a methodology simulating the real conditions of dry friction, at a contact pressure of 2.5-3 MPa, at 300-1200 rpm. The most important characteristics required for sintered friction materials are high and stable friction coefficient during breaking and also, for high durability in service, must have: low wear, high corrosion resistance, high thermal conductivity, mechanical resistance and thermal stability at elevated temperature. Because of the tribological characteristics importance (wear rate and friction coefficient) of sintered iron-copper based composites, we predicted the tribological behaviour through statistical analysis. For the first lot of samples, the response variables Yi (represented by the wear rate and friction coefficient) have been correlated with x1 and x2 (the code value of applied load and relative speed in braking points, respectively) using a linear factorial design approach. We obtained brake friction materials with improved wear resistance characteristics and high and stable friction coefficients. It has been shown, through experimental data and obtained linear regression equations, that the sintered composites wear rate increases with increasing applied load and relative speed, but in the same conditions, the frictional coefficients slowly decrease.

Maglev system concept using 20-K high-temperature superconductors and hyperconductors

NASA Astrophysics Data System (ADS)

Hull, J. R.; He, Jianliang

A magnetically levitated high-speed ground transportation concept is proposed that uses high-temperature superconductors or hyperconductors, cooled by liquid hydrogen at 20 K, to provide levitation. An on-board hydrogen-powered turbine/generator provides electricity for propulsion by linear induction motors. The liquid hydrogen is used to cool the superconductors and the windings of the generator and motors before combusting in the turbine. The principal advantage of this system is the potential to greatly reduce the cost of the guideway, which is completely passive.

Errors in Tsunami Source Estimation from Tide Gauges

NASA Astrophysics Data System (ADS)

Arcas, D.

2012-12-01

Linearity of tsunami waves in deep water can be assessed as a comparison of flow speed, u to wave propagation speed √gh. In real tsunami scenarios this evaluation becomes impractical due to the absence of observational data of tsunami flow velocities in shallow water. Consequently the extent of validity of the linear regime in the ocean is unclear. Linearity is the fundamental assumption behind tsunami source inversion processes based on linear combinations of unit propagation runs from a deep water propagation database (Gica et al., 2008). The primary tsunami elevation data for such inversion is usually provided by National Oceanic and Atmospheric (NOAA) deep-water tsunami detection systems known as DART. The use of tide gauge data for such inversions is more controversial due to the uncertainty of wave linearity at the depth of the tide gauge site. This study demonstrates the inaccuracies incurred in source estimation using tide gauge data in conjunction with a linear combination procedure for tsunami source estimation.

USSR Report, Electronics and Electrical Engineering, No. 104

DTIC Science & Technology

1983-06-13

shaping of silicon crystals during their growth is a modification of inductive contactless forming of rods and tubes directly from the melt on a...MANUFACTURING TECHNOLOGY Induction Systems for Electromagnetic Shaping of Silicon Crystal During.Growth (L. R. Lev; ELEKTROTEKHNIKA, Feb 83) • • • x...et al.; IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY: ELEKTROMEKHANIKA, Dec 82) 18 Basic Design of Linear- Induction Traction Motors for High-Speed

Infrared zone-scanning system.

PubMed

Belousov, Aleksandr; Popov, Gennady

2006-03-20

Challenges encountered in designing an infrared viewing optical system that uses a small linear detector array based on a zone-scanning approach are discussed. Scanning is performed by a rotating refractive polygon prism with tilted facets, which, along with high-speed line scanning, makes the scanning gear as simple as possible. A method of calculation of a practical optical system to compensate for aberrations during prism rotation is described.

Capillary spreading of contact line over a sinking sphere

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

Kim, Seong Jin; Fezzaa, Kamel; An, Jim

The contact line dynamics over a sinking solid sphere are investigated in comparison with classical spreading theories. Experimentally, high-speed imaging systems with optical light or x-ray illumination are employed to accurately measure the spreading motion and dynamic contact angle of the contact line. Millimetric spheres are controlled to descend with a constant speed ranging from 7.3 × 10-5 to 0.79 m/s. We observed three different spreading stages over a sinking sphere, which depends on the contact line velocity and contact angle. These stages consistently showed the characteristics of capillarity-driven spreading as the contact line spreads faster with a higher contactmore » angle. The contact line velocity is observed to follow a classical capillary-viscous model at a high Ohnesorge number (> 0.02). For the cases with a relatively low Ohnesorge number (< 0.02), the contact line velocity is significantly lower than the speed predicted by the capillary-viscous balance. This indicates the existence of an additional opposing force (inertia) for a decreasing Ohnesorge number. The capillary-inertial balance is only observed at the very beginning of the capillary rise, in which the maximum velocity is independent of the sphere’s sinking speed. Additionally, we observed the linear relation between the contact line velocity and the sphere sinking speed during the second stage, which represents capillary adjustment by dynamic contact angle.« less

Models for short-wave instability in inviscid shear flows

NASA Astrophysics Data System (ADS)

Grimshaw, Roger

1999-11-01

The generation of instability in an invsicid fluid occurs by a resonance between two wave modes, where here the resonance occurs by a coincidence of phase speeds for a finite, non-zero wavenumber. We show that in the weakly nonlinear limit, the appropriate model consists of two coupled equations for the envelopes of the wave modes, in which the nonlinear terms are balanced with low-order cross-coupling linear dispersive terms rather than the more familiar high-order terms which arise in the nonlinear Schrodinger equation, for instance. We will show that this system may either contain gap solitons as solutions in the linearly stable case, or wave breakdown in the linearly unstable case. In this latter circumstance, the system either exhibits wave collapse in finite time, or disintegration into fine-scale structures.

Physical lumping methods for developing linear reduced models for high speed propulsion systems

NASA Technical Reports Server (NTRS)

Immel, S. M.; Hartley, Tom T.; Deabreu-Garcia, J. Alex

1991-01-01

In gasdynamic systems, information travels in one direction for supersonic flow and in both directions for subsonic flow. A shock occurs at the transition from supersonic to subsonic flow. Thus, to simulate these systems, any simulation method implemented for the quasi-one-dimensional Euler equations must have the ability to capture the shock. In this paper, a technique combining both backward and central differencing is presented. The equations are subsequently linearized about an operating point and formulated into a linear state space model. After proper implementation of the boundary conditions, the model order is reduced from 123 to less than 10 using the Schur method of balancing. Simulations comparing frequency and step response of the reduced order model and the original system models are presented.

Microphysics of Waves and Instabilities in the Solar Wind and their Macro Manifestations in the Corona and Interplanetary Space

NASA Technical Reports Server (NTRS)

Habbal, Shadia R.; Gurman, Joseph (Technical Monitor)

2003-01-01

Investigations of the physical processes responsible for the acceleration of the solar wind were pursued with the development of two new solar wind codes: a hybrid code and a 2-D MHD code. Hybrid simulations were performed to investigate the interaction between ions and parallel propagating low frequency ion cyclotron waves in a homogeneous plasma. In a low-beta plasma such as the solar wind plasma in the inner corona, the proton thermal speed is much smaller than the Alfven speed. Vlasov linear theory predicts that protons are not in resonance with low frequency ion cyclotron waves. However, non-linear effect makes it possible that these waves can strongly heat and accelerate protons. This study has important implications for study of the corona and the solar wind. Low frequency ion cyclotron waves or Alfven waves are commonly observed in the solar wind. Until now, it is believed that these waves are not able to heat the solar wind plasma unless some cascading processes transfer the energy of these waves to high frequency part. However, this study shows that these waves may directly heat and accelerate protons non-linearly. This process may play an important role in the coronal heating and the solar wind acceleration, at least in some parameter space.

Study on mathematical model to predict aerated power consumption in a gas-liquid stirred tank

NASA Astrophysics Data System (ADS)

Luan, Deyu; Zhang, Shengfeng; Wei, Xing; Chen, Yiming

The aerated power consumption characteristics in a transparent tank with diameter of 0.3 m and flat bottom stirred by a Rushton impeller were investigated by means of experimental measurement. The test fluid used was tap water as liquid and air as gas. Based on Weibull model, the complete correlation of aerated power with aerated flow number was established through non-linear fit analysis. The effects of aerated rate and impeller speed on aerated power consumption were made an exploration. Results show that the changeable trend of the aerated power consumption is found to be similar under different impeller speeds and impeller diameters, i.e. the aerated power is close to dropping linear at the beginning of gas input, and then the drop tendency decreases as the aerated rate increases, at the end, the aerated power is a constant on the whole as the aerated rate reaches up the loading state. The non-linear fit curve is done using the software Origin based on the experimental data. The fairly high precision of data fit is obtained, which indicates that the mathematical model established can be used to accurately predict the aerated power consumption, comparatively. The proposed research provides a valuable instruction and reference for the design and enlargement of stirred vessel.

Hardware Neural Network for a Visual Inspection System

NASA Astrophysics Data System (ADS)

Chun, Seungwoo; Hayakawa, Yoshihiro; Nakajima, Koji

The visual inspection of defects in products is heavily dependent on human experience and instinct. In this situation, it is difficult to reduce the production costs and to shorten the inspection time and hence the total process time. Consequently people involved in this area desire an automatic inspection system. In this paper, we propose a hardware neural network, which is expected to provide high-speed operation for automatic inspection of products. Since neural networks can learn, this is a suitable method for self-adjustment of criteria for classification. To achieve high-speed operation, we use parallel and pipelining techniques. Furthermore, we use a piecewise linear function instead of a conventional activation function in order to save hardware resources. Consequently, our proposed hardware neural network achieved 6GCPS and 2GCUPS, which in our test sample proved to be sufficiently fast.

Multi-object detection and tracking technology based on hexagonal opto-electronic detector

NASA Astrophysics Data System (ADS)

Song, Yong; Hao, Qun; Li, Xiang

2008-02-01

A novel multi-object detection and tracking technology based on hexagonal opto-electronic detector is proposed, in which (1) a new hexagonal detector, which is composed of 6 linear CCDs, has been firstly developed to achieve the field of view of 360 degree, (2) to achieve the detection and tracking of multi-object with high speed, the object recognition criterions of Object Signal Width Criterion (OSWC) and Horizontal Scale Ratio Criterion (HSRC) are proposed. In this paper, Simulated Experiments have been carried out to verify the validity of the proposed technology, which show that the detection and tracking of multi-object can be achieved with high speed by using the proposed hexagonal detector and the criterions of OSWC and HSRC, indicating that the technology offers significant advantages in Photo-electric Detection, Computer Vision, Virtual Reality, Augment Reality, etc.

Flux-canceling electrodynamic maglev suspension. Part 1: Test fixture design and modeling

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

Thompson, M.T.; Thornton, R.D.; Kondoleon, A.

1999-05-01

The design and analysis of a scale-model suspension test facility for magnetic levitation (maglev) is discussed. The authors describe techniques for the design, construction, and testing of a prototype electrodynamic suspension (EDS) levitation system. The viability of future high-temperature superconducting magnet designs for maglev has been investigated with regard to their application to active secondary suspensions. In order to test the viability of a new flux-canceling EDS suspension, a 1/5-scale suspension magnet and guideway was constructed. The suspension was tested by using a high-speed rotating test wheel facility with linear peripheral speed of up to 84 m/s (300 km/h). Amore » set of approximate design tools and scaling laws has been developed in order to evaluate forces and critical velocities in the suspension.« less

VELOCITY INDICATOR FOR EXTRUSION PRESS

DOEpatents

Digney, F.J. Jr.; Bevilacqua, F.

1959-04-01

An indicator is presented for measuring the lowspeed velocity of an object in one direction where the object returns in the opposite direction at a high speed. The indicator comprises a drum having its axis of rotation transverse to the linear movement of the object and a tape wound upon the drum with its free end extending therefrom and adapted to be connected to the object. A constant torque is applied to the drum in a direction to wind the tape on the drum. The speed of the tape in the unwinding direction is indicated on a tachometer which is coupled through a shaft and clutch means to the drum only when the tape is unwinding.

Introduction to Voigt's wind power plant. [energy conversion efficiency

NASA Technical Reports Server (NTRS)

Tompkin, J.

1973-01-01

The design and operation of a 100 kilowatt wind driven generator are reported. Its high speed three-bladed turbine operates at a height of 50 meters. Blades are rigidly connected to the hub and turbine revolutions change linearly with wind velocity, maintaining a constant speed ratio of blade tip velocity to wind velocity over the full predetermined wind range. Three generators installed in the gondola generate either dc or ac current. Based on local wind conditions, the device has a maximum output of 720 kilowatts at a wind velocity of 16 meters per second. Total electrical capacity is 750 kilowatts, and power output per year is 2,135,000 kilowatt/hours.

Use of wind data for estimating horizontal dilution potential of atmosphere.

PubMed

George, K V; Verma, P; Devotta, S

2007-04-01

In this study, a new methodology is suggested for estimating horizontal dilution potential of an area using wind data. The mean wind speed and wind direction variation are used as a measure of linear and angular spread of pollutants in the atmosphere. A formula is developed for estimating the potential of horizontal spread of pollutants in an area wherein only the wind speed and direction are used. The methodology is further applied to monitor wind data of one year. It is found that there is a very smooth variation of horizontal dilution potential over a year with limited dilution during post monsoon period and a high dilution in pre monsoon period.

Frictional Torque on a Rotating Disc

ERIC Educational Resources Information Center

Mungan, Carl E.

2012-01-01

Resistance to motion often includes a dry frictional term independent of the speed of an object and a fluid drag term varying linearly with speed in the viscous limit. (At higher speeds, quadratic drag can also occur.) Here, measurements are performed for an aluminium disc mounted on bearings that is given an initial twist and allowed to spin…

A methodology for analysing lateral coupled behavior of high speed railway vehicles and structures

NASA Astrophysics Data System (ADS)

Antolín, P.; Goicolea, J. M.; Astiz, M. A.; Alonso, A.

2010-06-01

Continuous increment of the speed of high speed trains entails the increment of kinetic energy of the trains. The main goal of this article is to study the coupled lateral behavior of vehicle-structure systems for high speed trains. Non linear finite element methods are used for structures whereas multibody dynamics methods are employed for vehicles. Special attention must be paid when dealing with contact rolling constraints for coupling bridge decks and train wheels. The dynamic models must include mixed variables (displacements and creepages). Additionally special attention must be paid to the contact algorithms adequate to wheel-rail contact. The coupled vehicle-structure system is studied in a implicit dynamic framework. Due to the presence of very different systems (trains and bridges), different frequencies are involved in the problem leading to stiff systems. Regarding to contact methods, a main branch is studied in normal contact between train wheels and bridge decks: penalty method. According to tangential contact FastSim algorithm solves the tangential contact at each time step solving a differential equation involving relative displacements and creepage variables. Integration for computing the total forces in the contact ellipse domain is performed for each train wheel and each solver iteration. Coupling between trains and bridges requires a special treatment according to the kinetic constraints imposed in the wheel-rail pair and the load transmission. A numerical example is performed.

Semi-automatic mapping of linear-trending bedforms using 'Self-Organizing Maps' algorithm

NASA Astrophysics Data System (ADS)

Foroutan, M.; Zimbelman, J. R.

2017-09-01

Increased application of high resolution spatial data such as high resolution satellite or Unmanned Aerial Vehicle (UAV) images from Earth, as well as High Resolution Imaging Science Experiment (HiRISE) images from Mars, makes it necessary to increase automation techniques capable of extracting detailed geomorphologic elements from such large data sets. Model validation by repeated images in environmental management studies such as climate-related changes as well as increasing access to high-resolution satellite images underline the demand for detailed automatic image-processing techniques in remote sensing. This study presents a methodology based on an unsupervised Artificial Neural Network (ANN) algorithm, known as Self Organizing Maps (SOM), to achieve the semi-automatic extraction of linear features with small footprints on satellite images. SOM is based on competitive learning and is efficient for handling huge data sets. We applied the SOM algorithm to high resolution satellite images of Earth and Mars (Quickbird, Worldview and HiRISE) in order to facilitate and speed up image analysis along with the improvement of the accuracy of results. About 98% overall accuracy and 0.001 quantization error in the recognition of small linear-trending bedforms demonstrate a promising framework.

Stability Limits of a PD Controller for a Flywheel Supported on Rigid Rotor and Magnetic Bearings

NASA Technical Reports Server (NTRS)

Kascak, Albert F.; Brown, Gerald V.; Jansen, Ralph H.; Dever, TImothy P.

2006-01-01

Active magnetic bearings are used to provide a long-life, low-loss suspension of a high-speed flywheel rotor. This paper describes a modeling effort used to understand the stability boundaries of the PD controller used to control the active magnetic bearings on a high speed test rig. Limits of stability are described in terms of allowable stiffness and damping values which result in stable levitation of the nonrotating rig. Small signal stability limits for the system is defined as a nongrowth in vibration amplitude of a small disturbance. A simple mass-force model was analyzed. The force resulting from the magnetic bearing was linearized to include negative displacement stiffness and a current stiffness. The current stiffness was then used in a PD controller. The phase lag of the control loop was modeled by a simple time delay. The stability limits and the associated vibration frequencies were measured and compared to the theoretical values. The results show a region on stiffness versus damping plot that have the same qualitative tendencies as experimental measurements. The resulting stability model was then extended to a flywheel system. The rotor dynamics of the flywheel was modeled using a rigid rotor supported on magnetic bearings. The equations of motion were written for the center of mass and a small angle linearization of the rotations about the center of mass. The stability limits and the associated vibration frequencies were found as a function of nondimensional magnetic bearing stiffness and damping and nondimensional parameters of flywheel speed and time delay.

Efficient generation of sum-of-products representations of high-dimensional potential energy surfaces based on multimode expansions

NASA Astrophysics Data System (ADS)

Ziegler, Benjamin; Rauhut, Guntram

2016-03-01

The transformation of multi-dimensional potential energy surfaces (PESs) from a grid-based multimode representation to an analytical one is a standard procedure in quantum chemical programs. Within the framework of linear least squares fitting, a simple and highly efficient algorithm is presented, which relies on a direct product representation of the PES and a repeated use of Kronecker products. It shows the same scalings in computational cost and memory requirements as the potfit approach. In comparison to customary linear least squares fitting algorithms, this corresponds to a speed-up and memory saving by several orders of magnitude. Different fitting bases are tested, namely, polynomials, B-splines, and distributed Gaussians. Benchmark calculations are provided for the PESs of a set of small molecules.

Efficient generation of sum-of-products representations of high-dimensional potential energy surfaces based on multimode expansions.

PubMed

Ziegler, Benjamin; Rauhut, Guntram

2016-03-21

The transformation of multi-dimensional potential energy surfaces (PESs) from a grid-based multimode representation to an analytical one is a standard procedure in quantum chemical programs. Within the framework of linear least squares fitting, a simple and highly efficient algorithm is presented, which relies on a direct product representation of the PES and a repeated use of Kronecker products. It shows the same scalings in computational cost and memory requirements as the potfit approach. In comparison to customary linear least squares fitting algorithms, this corresponds to a speed-up and memory saving by several orders of magnitude. Different fitting bases are tested, namely, polynomials, B-splines, and distributed Gaussians. Benchmark calculations are provided for the PESs of a set of small molecules.

High performance waveguide-coupled Ge-on-Si linear mode avalanche photodiodes.

PubMed

Martinez, Nicholas J D; Derose, Christopher T; Brock, Reinhard W; Starbuck, Andrew L; Pomerene, Andrew T; Lentine, Anthony L; Trotter, Douglas C; Davids, Paul S

2016-08-22

We present experimental results for a selective epitaxially grown Ge-on-Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Epitaxially grown Ge-on-Si waveguide-coupled linear mode avalanche photodiodes with varying lateral multiplication regions and different charge implant dimensions are fabricated and their illuminated device characteristics and high-speed performance is measured. We report a record gain-bandwidth product of 432 GHz for our highest performing waveguide-coupled avalanche photodiode operating at 1510nm. Bit error rate measurements show operation with BER< 10^-12, in the range from -18.3 dBm to -12 dBm received optical power into a 50 Ω load and open eye diagrams with 13 Gbps pseudo-random data at 1550 nm.

A Method for Generating Reduced-Order Linear Models of Multidimensional Supersonic Inlets

NASA Technical Reports Server (NTRS)

Chicatelli, Amy; Hartley, Tom T.

1998-01-01

Simulation of high speed propulsion systems may be divided into two categories, nonlinear and linear. The nonlinear simulations are usually based on multidimensional computational fluid dynamics (CFD) methodologies and tend to provide high resolution results that show the fine detail of the flow. Consequently, these simulations are large, numerically intensive, and run much slower than real-time. ne linear simulations are usually based on large lumping techniques that are linearized about a steady-state operating condition. These simplistic models often run at or near real-time but do not always capture the detailed dynamics of the plant. Under a grant sponsored by the NASA Lewis Research Center, Cleveland, Ohio, a new method has been developed that can be used to generate improved linear models for control design from multidimensional steady-state CFD results. This CFD-based linear modeling technique provides a small perturbation model that can be used for control applications and real-time simulations. It is important to note the utility of the modeling procedure; all that is needed to obtain a linear model of the propulsion system is the geometry and steady-state operating conditions from a multidimensional CFD simulation or experiment. This research represents a beginning step in establishing a bridge between the controls discipline and the CFD discipline so that the control engineer is able to effectively use multidimensional CFD results in control system design and analysis.

Quantifying residual, eddy, and mean flow effects on mixing in an idealized circumpolar current

DOE PAGES

Wolfram, Phillip J.; Ringler, Todd D.

2017-07-13

Meridional diffusivity is assessed in this paper for a baroclinically unstable jet in a high-latitudeIdealized Circumpolar Current (ICC) using the Model for Prediction Across Scales-Ocean (MPAS-O) and the online Lagrangian In-situ Global High-performance particle Tracking (LIGHT) diagnostic via space-time dispersion of particle clusters over 120 monthly realizations of O(10 6) particles on 11 potential density surfaces. Diffusivity in the jet reaches values of O(6000 m 2 s -1) and is largest near the critical layer supporting mixing suppression and critical layer theory. Values in the vicinity of the shelf break are suppressed to O(100 m 2 s -1) due tomore » the presence of westward slope front currents. Diffusivity attenuates less rapidly with depth in the jet than both eddy velocity and kinetic energy scalings would suggest. Removal of the mean flow via high-pass filtering shifts the nonlinear parameter (ratio of the eddy velocity to eddy phase speed) into the linear wave regime by increasing the eddy phase speed via the depth-mean flow. Low-pass filtering, in contrast, quantifies the effect of mean shear. Diffusivity is decomposed into mean flow shear, linear waves, and the residual nonhomogeneous turbulence components, where turbulence dominates and eddy-produced filamentation strained by background mean shear enhances mixing, accounting for ≥ 80% of the total diffusivity relative to mean shear [O(100 m 2 s -1)], linear waves [O(1000 m 2 s -1)], and undecomposed full diffusivity [O(6000 m 2 s -1)]. Finally, diffusivity parameterizations accounting for both the nonhomogeneous turbulence residual and depth variability are needed.« less

Effect of wing planform and canard location and geometry on the longitudinal aerodynamic characteristics of a close-coupled canard wing model at subsonic speeds

NASA Technical Reports Server (NTRS)

Gloss, B. B.

1975-01-01

A generalized wind-tunnel model with canard and wing planforms typical of highly maneuverable aircraft was tested in the Langley 7- by 10-foot high-speed tunnel at a Mach number of 0.30 to determine the effect of canard location, canard size, wing sweep, and canard strake on canard-wing interference to high angles of attack. The major results of this investigation may be summarized as follows: the high-canard configuration (excluding the canard strake and canard flap), for both the 60 deg and 44 deg swept leading-edge wings, produced the highest maximum lift coefficient and the most linear pitching-moment curves; substantially larger gains in the canard lift and total lift were obtained by adding a strake to the canard located below the wing chord plane rather than by adding a strake to the canard located above the wing chord plane.

Temporal and radial variation of the solar wind temperature-speed relationship

NASA Astrophysics Data System (ADS)

Elliott, H. A.; Henney, C. J.; McComas, D. J.; Smith, C. W.; Vasquez, B. J.

2012-09-01

The solar wind temperature (T) and speed (V) are generally well correlated at ˜1 AU, except in Interplanetary Coronal Mass Ejections where this correlation breaks down. We perform a comprehensive analysis of both the temporal and radial variation in the temperature-speed (T-V) relationship of the non-transient wind, and our analysis provides insight into both the causes of the T-V relationship and the sources of the temperature variability. Often at 1 AU the speed-temperature relationship is well represented by a single linear fit over a speed range spanning both the slow and fast wind. However, at times the fast wind from coronal holes can have a different T-V relationship than the slow wind. A good example of this was in 2003 when there was a very large and long-lived outward magnetic polarity coronal hole at low latitudes that emitted wind with speeds as fast as a polar coronal hole. The long-lived nature of the hole made it possible to clearly distinguish that some holes can have a different T-V relationship. In an earlier ACE study, we found that both the compressions and rarefactions T-V curves are linear, but the compression curve is shifted to higher temperatures. By separating compressions and rarefactions prior to determining the radial profiles of the solar wind parameters, the importance of dynamic interactions on the radial evolution of the solar wind parameters is revealed. Although the T-V relationship at 1 AU is often well described by a single linear curve, we find that the T-V relationship continually evolves with distance. Beyond ˜2.5 AU the differences between the compressions and rarefactions are quite significant and affect the shape of the overall T-V distribution to the point that a simple linear fit no longer describes the distribution well. Since additional heating of the ambient solar wind outside of interaction regions can be associated with Alfvénic fluctuations and the turbulent energy cascade, we also estimate the heating rate radial profile from the solar wind speed and temperature measurements.

Ultrafast Fiber Bragg Grating Interrogation for Sensing in Detonation and Shock Wave Experiments.

PubMed

Rodriguez, George; Gilbertson, Steve M

2017-01-27

Chirped fiber Bragg grating (CFBG) sensors coupled to high speed interrogation systems are described as robust diagnostic approaches to monitoring shock wave and detonation front propagation tracking events for use in high energy density shock physics applications. Taking advantage of the linear distributed spatial encoding of the spectral band in single-mode CFBGs, embedded fiber systems and associated photonic interrogation methodologies are shown as an effective approach to sensing shock and detonation-driven loading processes along the CFBG length. Two approaches, one that detects spectral changes in the integrated spectrum of the CFBG and another coherent pulse interrogation approach that fully resolves its spectral response, shows that 100-MHz-1-GHz interrogation rates are possible with spatial resolution along the CFBG in the 50 µm to sub-millimeter range depending on the combination of CFBG parameters (i.e., length, chirp rate, spectrum) and interrogator design specifics. Results from several dynamic tests are used to demonstrate the performance of these high speed systems for shock and detonation propagation tracking under strong and weak shock pressure loading: (1) linear detonation front tracking in the plastic bonded explosive (PBX) PBX-9501; (2) tracking of radial decaying shock with crossover to non-destructive CFBG response; (3) shock wave tracking along an aluminum cylinder wall under weak loading accompanied by dynamic strain effects in the CFBG sensor.

Sequence information signal processor for local and global string comparisons

DOEpatents

Peterson, John C.; Chow, Edward T.; Waterman, Michael S.; Hunkapillar, Timothy J.

1997-01-01

A sequence information signal processing integrated circuit chip designed to perform high speed calculation of a dynamic programming algorithm based upon the algorithm defined by Waterman and Smith. The signal processing chip of the present invention is designed to be a building block of a linear systolic array, the performance of which can be increased by connecting additional sequence information signal processing chips to the array. The chip provides a high speed, low cost linear array processor that can locate highly similar global sequences or segments thereof such as contiguous subsequences from two different DNA or protein sequences. The chip is implemented in a preferred embodiment using CMOS VLSI technology to provide the equivalent of about 400,000 transistors or 100,000 gates. Each chip provides 16 processing elements, and is designed to provide 16 bit, two's compliment operation for maximum score precision of between -32,768 and +32,767. It is designed to provide a comparison between sequences as long as 4,194,304 elements without external software and between sequences of unlimited numbers of elements with the aid of external software. Each sequence can be assigned different deletion and insertion weight functions. Each processor is provided with a similarity measure device which is independently variable. Thus, each processor can contribute to maximum value score calculation using a different similarity measure.

Ultrafast Fiber Bragg Grating Interrogation for Sensing in Detonation and Shock Wave Experiments

PubMed Central

Rodriguez, George; Gilbertson, Steve M.

2017-01-01

Chirped fiber Bragg grating (CFBG) sensors coupled to high speed interrogation systems are described as robust diagnostic approaches to monitoring shock wave and detonation front propagation tracking events for use in high energy density shock physics applications. Taking advantage of the linear distributed spatial encoding of the spectral band in single-mode CFBGs, embedded fiber systems and associated photonic interrogation methodologies are shown as an effective approach to sensing shock and detonation-driven loading processes along the CFBG length. Two approaches, one that detects spectral changes in the integrated spectrum of the CFBG and another coherent pulse interrogation approach that fully resolves its spectral response, shows that 100-MHz–1-GHz interrogation rates are possible with spatial resolution along the CFBG in the 50 μm to sub-millimeter range depending on the combination of CFBG parameters (i.e., length, chirp rate, spectrum) and interrogator design specifics. Results from several dynamic tests are used to demonstrate the performance of these high speed systems for shock and detonation propagation tracking under strong and weak shock pressure loading: (1) linear detonation front tracking in the plastic bonded explosive (PBX) PBX-9501; (2) tracking of radial decaying shock with crossover to non-destructive CFBG response; (3) shock wave tracking along an aluminum cylinder wall under weak loading accompanied by dynamic strain effects in the CFBG sensor. PMID:28134819

Ultrafast Fiber Bragg Grating Interrogation for Sensing in Detonation and Shock Wave Experiments

DOE PAGES

Rodriguez, George; Gilbertson, Steve Michael

2017-01-27

Chirped fiber Bragg grating (CFBG) sensors coupled to high speed interrogation systems are described as robust diagnostic approaches to monitoring shock wave and detonation front propagation tracking events for use in high energy density shock physics applications. Taking advantage of the linear distributed spatial encoding of the spectral band in single-mode CFBGs, embedded fiber systems and associated photonic interrogation methodologies are shown as an effective approach to sensing shock and detonation-driven loading processes along the CFBG length. Two approaches, one that detects spectral changes in the integrated spectrum of the CFBG and another coherent pulse interrogation approach that fully resolvesmore » its spectral response, shows that 100-MHz–1-GHz interrogation rates are possible with spatial resolution along the CFBG in the 50 µm to sub-millimeter range depending on the combination of CFBG parameters (i.e., length, chirp rate, spectrum) and interrogator design specifics. In conclusion, results from several dynamic tests are used to demonstrate the performance of these high speed systems for shock and detonation propagation tracking under strong and weak shock pressure loading: (1) linear detonation front tracking in the plastic bonded explosive (PBX) PBX-9501; (2) tracking of radial decaying shock with crossover to non-destructive CFBG response; (3) shock wave tracking along an aluminum cylinder wall under weak loading accompanied by dynamic strain effects in the CFBG sensor.« less

Near-field acoustic radiation by high-speed turbulence: amplitude, structure, gas-stiffness, and dilatational dissipation

NASA Astrophysics Data System (ADS)

Buchta, David; Freund, Jonathan

2017-11-01

High-speed (supersonic) turbulent shear flows are well-known to radiate pressure-wave patterns that have higher positive peaks than negative valleys, which yields a notable skewness, usually with Sk > 0.4 . Direct numerical simulations (DNS) of planar turbulent mixing layers at different Mach numbers (M) are used to examine this. The baseline simulations, of an air-like gas at speeds up to M = 3.5 , reproduced the observed behavior of jets. Simulations initialized with corresponding instability modes show that Sk increases linearly with the velocity amplitude (Mt =√{ui' ui'} /co), reflecting the M dependence of the DNS, which can be related to simpler gas dynamic flows. Simulations with a stiffened-gas equation of state (often used to model liquids) show essentially the same Mach-number dependence, despite the nominally greater resistance to compressibility. Turbulence simulations with an artificial energy reallocation mechanism, imposed to alter its structure, show little change in Sk. Finally, we also consider significantly increased bulk viscosity to suppress dilatation. In this case, Sk diminishes along with the sound-field intensity, though the turbulence stresses themselves are nearly unchanged.

Small-scale rotor test rig capabilities for testing vibration alleviation algorithms

NASA Technical Reports Server (NTRS)

Jacklin, Stephen A.; Leyland, Jane Anne

1987-01-01

A test was conducted to assess the capabilities of a small scale rotor test rig for implementing higher harmonic control and stability augmentation algorithms. The test rig uses three high speed actuators to excite the swashplate over a range of frequencies. The actuator position signals were monitored to measure the response amplitudes at several frequencies. The ratio of response amplitude to excitation amplitude was plotted as a function of frequency. In addition to actuator performance, acceleration from six accelerometers placed on the test rig was monitored to determine whether a linear relationship exists between the harmonics of N/Rev control input and the least square error (LSE) identification technique was used to identify local and global transfer matrices for two rotor speeds at two batch sizes each. It was determined that the multicyclic control computer system interfaced very well with the rotor system and kept track of the input accelerometer signals and their phase angles. However, the current high speed actuators were found to be incapable of providing sufficient control authority at the higher excitation frequencies.

Pulsed photoacoustic flow imaging with a handheld system

NASA Astrophysics Data System (ADS)

van den Berg, Pim J.; Daoudi, Khalid; Steenbergen, Wiendelt

2016-02-01

Flow imaging is an important technique in a range of disease areas, but estimating low flow speeds, especially near the walls of blood vessels, remains challenging. Pulsed photoacoustic flow imaging can be an alternative since there is little signal contamination from background tissue with photoacoustic imaging. We propose flow imaging using a clinical photoacoustic system that is both handheld and portable. The system integrates a linear array with 7.5 MHz central frequency in combination with a high-repetition-rate diode laser to allow high-speed photoacoustic imaging-ideal for this application. This work shows the flow imaging performance of the system in vitro using microparticles. Both two-dimensional (2-D) flow images and quantitative flow velocities from 12 to 75 mm/s were obtained. In a transparent bulk medium, flow estimation showed standard errors of ˜7% the estimated speed; in the presence of tissue-realistic optical scattering, the error increased to 40% due to limited signal-to-noise ratio. In the future, photoacoustic flow imaging can potentially be performed in vivo using fluorophore-filled vesicles or with an improved setup on whole blood.

Feasibility study of superconducting LSM rocket launcher system

NASA Technical Reports Server (NTRS)

Yoshida, Kinjiro; Ohashi, Takaaki; Shiraishi, Katsuto; Takami, Hiroshi

1994-01-01

A feasibility study is presented concerning an application of a superconducting linear synchronous motor (LSM) to a large-scale rocket launcher, whose acceleration guide tube of LSM armature windings is constructed 1,500 meters under the ground. The rocket is released from the linear launcher just after it gets to a peak speed of about 900 kilometers per hour, and it flies out of the guide tube to obtain the speed of 700 kilometers per hour at the height of 100 meters above ground. The linear launcher is brought to a stop at the ground surface for a very short time of 5 seconds by a quick control of deceleration. Very large current variations in the single-layer windings of the LSM armature, which are produced at the higher speed region of 600 to 900 kilometers per hour, are controlled successfully by adopting the double-layer windings. The proposed control method makes the rocket launcher ascend stably in the superconducting LSM system, controlling the Coriolis force.

Increased Prolactin Levels Are Associated with Impaired Processing Speed in Subjects with Early Psychosis

PubMed Central

Montalvo, Itziar; Gutiérrez-Zotes, Alfonso; Creus, Marta; Monseny, Rosa; Ortega, Laura; Franch, Joan; Lawrie, Stephen M.; Reynolds, Rebecca M.; Vilella, Elisabet; Labad, Javier

2014-01-01

Hyperprolactinaemia, a common side effect of some antipsychotic drugs, is also present in drug-naïve psychotic patients and subjects at risk for psychosis. Recent studies in non-psychiatric populations suggest that increased prolactin may have negative effects on cognition. The aim of our study was to explore whether high plasma prolactin levels are associated with poorer cognitive functioning in subjects with early psychoses. We studied 107 participants: 29 healthy subjects and 78 subjects with an early psychosis (55 psychotic disorders with <3 years of illness, 23 high-risk subjects). Cognitive assessment was performed with the MATRICS Cognitive Consensus Cognitive Battery, and prolactin levels were determined as well as total cortisol levels in plasma. Psychopathological status was assessed and the use of psychopharmacological treatments (antipsychotics, antidepressants, benzodiazepines) recorded. Prolactin levels were negatively associated with cognitive performance in processing speed, in patients with a psychotic disorder and high-risk subjects. In the latter group, increased prolactin levels were also associated with impaired reasoning and problem solving and poorer general cognition. In a multiple linear regression analysis conducted in both high-risk and psychotic patients, controlling for potential confounders, prolactin and benzodiazepines were independently related to poorer cognitive performance in the speed of processing domain. A mediation analysis showed that both prolactin and benzodiazepine treatment act as mediators of the relationship between risperidone/paliperidone treatment and speed of processing. These results suggest that increased prolactin levels are associated with impaired processing speed in early psychosis. If these results are confirmed in future studies, strategies targeting reduction of prolactin levels may improve cognition in this population. PMID:24586772

Validity of Treadmill-Derived Critical Speed on Predicting 5000-Meter Track-Running Performance.

PubMed

Nimmerichter, Alfred; Novak, Nina; Triska, Christoph; Prinz, Bernhard; Breese, Brynmor C

2017-03-01

Nimmerichter, A, Novak, N, Triska, C, Prinz, B, and Breese, BC. Validity of treadmill-derived critical speed on predicting 5,000-meter track-running performance. J Strength Cond Res 31(3): 706-714, 2017-To evaluate 3 models of critical speed (CS) for the prediction of 5,000-m running performance, 16 trained athletes completed an incremental test on a treadmill to determine maximal aerobic speed (MAS) and 3 randomly ordered runs to exhaustion at the [INCREMENT]70% intensity, at 110% and 98% of MAS. Critical speed and the distance covered above CS (D') were calculated using the hyperbolic speed-time (HYP), the linear distance-time (LIN), and the linear speed inverse-time model (INV). Five thousand meter performance was determined on a 400-m running track. Individual predictions of 5,000-m running time (t = [5,000-D']/CS) and speed (s = D'/t + CS) were calculated across the 3 models in addition to multiple regression analyses. Prediction accuracy was assessed with the standard error of estimate (SEE) from linear regression analysis and the mean difference expressed in units of measurement and coefficient of variation (%). Five thousand meter running performance (speed: 4.29 ± 0.39 m·s; time: 1,176 ± 117 seconds) was significantly better than the predictions from all 3 models (p < 0.0001). The mean difference was 65-105 seconds (5.7-9.4%) for time and -0.22 to -0.34 m·s (-5.0 to -7.5%) for speed. Predictions from multiple regression analyses with CS and D' as predictor variables were not significantly different from actual running performance (-1.0 to 1.1%). The SEE across all models and predictions was approximately 65 seconds or 0.20 m·s and is therefore considered as moderate. The results of this study have shown the importance of aerobic and anaerobic energy system contribution to predict 5,000-m running performance. Using estimates of CS and D' is valuable for predicting performance over race distances of 5,000 m.

Intraindividual variability in executive functions but not speed of processing or conflict resolution predicts performance differences in gait speed in older adults.

PubMed

Holtzer, Roee; Mahoney, Jeannette; Verghese, Joe

2014-08-01

The relationship between executive functions (EF) and gait speed is well established. However, with the exception of dual tasking, the key components of EF that predict differences in gait performance have not been determined. Therefore, the current study was designed to determine whether processing speed, conflict resolution, and intraindividual variability in EF predicted variance in gait performance in single- and dual-task conditions. Participants were 234 nondemented older adults (mean age 76.48 years; 55% women) enrolled in a community-based cohort study. Gait speed was assessed using an instrumented walkway during single- and dual-task conditions. The flanker task was used to assess EF. Results from the linear mixed effects model showed that (a) dual-task interference caused a significant dual-task cost in gait speed (estimate = 35.99; 95% CI = 33.19-38.80) and (b) of the cognitive predictors, only intraindividual variability was associated with gait speed (estimate = -.606; 95% CI = -1.11 to -.10). In unadjusted analyses, the three EF measures were related to gait speed in single- and dual-task conditions. However, in fully adjusted linear regression analysis, only intraindividual variability predicted performance differences in gait speed during dual tasking (B = -.901; 95% CI = -1.557 to -.245). Among the three EF measures assessed, intraindividual variability but not speed of processing or conflict resolution predicted performance differences in gait speed. © The Author 2013. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Numerical algorithms for scatter-to-attenuation reconstruction in PET: empirical comparison of convergence, acceleration, and the effect of subsets.

PubMed

Berker, Yannick; Karp, Joel S; Schulz, Volkmar

2017-09-01

The use of scattered coincidences for attenuation correction of positron emission tomography (PET) data has recently been proposed. For practical applications, convergence speeds require further improvement, yet there exists a trade-off between convergence speed and the risk of non-convergence. In this respect, a maximum-likelihood gradient-ascent (MLGA) algorithm and a two-branch back-projection (2BP), which was previously proposed, were evaluated. MLGA was combined with the Armijo step size rule; and accelerated using conjugate gradients, Nesterov's momentum method, and data subsets of different sizes. In 2BP, we varied the subset size, an important determinant of convergence speed and computational burden. We used three sets of simulation data to evaluate the impact of a spatial scale factor. The Armijo step size allowed 10-fold increased step sizes compared to native MLGA. Conjugate gradients and Nesterov momentum lead to slightly faster, yet non-uniform convergence; improvements were mostly confined to later iterations, possibly due to the non-linearity of the problem. MLGA with data subsets achieved faster, uniform, and predictable convergence, with a speed-up factor equivalent to the number of subsets and no increase in computational burden. By contrast, 2BP computational burden increased linearly with the number of subsets due to repeated evaluation of the objective function, and convergence was limited to the case of many (and therefore small) subsets, which resulted in high computational burden. Possibilities of improving 2BP appear limited. While general-purpose acceleration methods appear insufficient for MLGA, results suggest that data subsets are a promising way of improving MLGA performance.

High shear rate flow in a linear stroke magnetorheological energy absorber

NASA Astrophysics Data System (ADS)

Hu, W.; Wereley, N. M.; Hiemenz, G. J.; Ngatu, G. T.

2014-05-01

To provide adaptive stroking load in the crew seats of ground vehicles to protect crew from blast or impact loads, a magnetorheological energy absorber (MREA) or shock absorber was developed. The MREA provides appropriate levels of controllable stroking load for different occupant weights and peak acceleration because the viscous stroking load generated by the MREA force increases with velocity squared, thereby reducing its controllable range at high piston velocity. Therefore, MREA behavior at high piston velocity is analyzed and validated experimentally in order to investigate the effects of velocity and magnetic field on MREA performance. The analysis used to predict the MREA force as a function of piston velocity squared and applied field is presented. A conical fairing is mounted to the piston head of the MREA in order reduce predicted inlet flow loss by 9% at nominal velocity of 8 m/s, which resulted in a viscous force reduction of nominally 4%. The MREA behavior is experimentally measured using a high speed servo-hydraulic testing system for speeds up to 8 m/s. The measured MREA force is used to validate the analysis, which captures the transient force quite accurately, although the peak force is under-predicted at the peak speed of 8 m/s.

In-process, non-destructive multimodal dynamic testing of high-speed composite rotors

NASA Astrophysics Data System (ADS)

Kuschmierz, Robert; Filippatos, Angelos; Langkamp, Albert; Hufenbach, Werner; Czarske, Jürgern W.; Fischer, Andreas

2014-03-01

Fibre reinforced plastic (FRP) rotors are lightweight and offer great perspectives in high-speed applications such as turbo machinery. Currently, novel rotor structures and materials are investigated for the purpose of increasing machine efficiency, lifetime and loading limits. Due to complex rotor structures, high anisotropy and non-linear behavior of FRP under dynamic loads, an in-process measurement system is necessary to monitor and to investigate the evolution of damages under real operation conditions. A non-invasive, optical laser Doppler distance sensor measurement system is applied to determine the biaxial deformation of a bladed FRP rotor with micron uncertainty as well as the tangential blade vibrations at surface speeds above 300 m/s. The laser Doppler distance sensor is applicable under vacuum conditions. Measurements at varying loading conditions are used to determine elastic and plastic deformations. Furthermore they allow to determine hysteresis, fatigue, Eigenfrequency shifts and loading limits. The deformation measurements show a highly anisotropic and nonlinear behavior and offer a deeper understanding of the damage evolution in FRP rotors. The experimental results are used to validate and to calibrate a simulation model of the deformation. The simulation combines finite element analysis and a damage mechanics model. The combination of simulation and measurement system enables the monitoring and prediction of damage evolutions of FRP rotors in process.

Time-delay control of a magnetic levitated linear positioning system

NASA Technical Reports Server (NTRS)

Tarn, J. H.; Juang, K. Y.; Lin, C. E.

1994-01-01

In this paper, a high accuracy linear positioning system with a linear force actuator and magnetic levitation is proposed. By locating a permanently magnetized rod inside a current-carrying solenoid, the axial force is achieved by the boundary effect of magnet poles and utilized to power the linear motion, while the force for levitation is governed by Ampere's Law supplied with the same solenoid. With the levitation in a radial direction, there is hardly any friction between the rod and the solenoid. The high speed motion can hence be achieved. Besides, the axial force acting on the rod is a smooth function of rod position, so the system can provide nanometer resolution linear positioning to the molecule size. Since the force-position relation is highly nonlinear, and the mathematical model is derived according to some assumptions, such as the equivalent solenoid of the permanently magnetized rod, so there exists unknown dynamics in practical application. Thus 'robustness' is an important issue in controller design. Meanwhile the load effect reacts directly on the servo system without transmission elements, so the capability of 'disturbance rejection; is also required. With the above consideration, a time-delay control scheme is chosen and applied. By comparing the input-output relation and the mathematical model, the time-delay controller calculates an estimation of unmodeled dynamics and disturbances and then composes the desired compensation into the system. Effectiveness of the linear positioning system and control scheme are illustrated with simulation results.

Numerical Investigation on Head and Brain Injuries Caused by Windshield Impact on Riders Using Electric Self-Balancing Scooters

PubMed Central

Zheng, Yanting; Shen, Ming; Yang, Xianfeng

2018-01-01

To investigate head-brain injuries caused by windshield impact on riders using electric self-balancing scooters (ESS). Numerical vehicle ESS crash scenarios are constructed by combining the finite element (FE) vehicle model and multibody scooter/rider models. Impact kinematic postures of the head-windshield contact under various impact conditions are captured. Then, the processes during head-windshield contact are reconstructed using validated FE head/laminated windshield models to assess the severity of brain injury caused by the head-windshield contact. Governing factors, such as vehicle speed, ESS speed, and the initial orientation of ESS rider, have nontrivial influences over the severity of a rider's brain injuries. Results also show positive correlations between vehicle speed and head-windshield impact speeds (linear and angular). Meanwhile, the time of head-windshield contact happens earlier when the vehicle speed is faster. According to the intensive study, windshield-head contact speed (linear and angular), impact location on the windshield, and head collision area are found to be direct factors on ESS riders' brain injuries during an impact. The von Mises stress and shear stress rise when relative contact speed of head-windshield increases. Brain injury indices vary widely when the head impacting the windshield from center to the edge or impacting with different areas. PMID:29770161

Fluid/Structure Interaction Studies of Aircraft Using High Fidelity Equations on Parallel Computers

NASA Technical Reports Server (NTRS)

Guruswamy, Guru; VanDalsem, William (Technical Monitor)

1994-01-01

Abstract Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft such as High Speed Civil Transport (HSCT) and Advanced Subsonic Transport (AST) which can experience complex flow/structure interactions. HSCT can experience vortex induced aeroelastic oscillations whereas AST can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional super computers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overcome the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENSAERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations.

Apparatus and method for detecting and measuring changes in linear relationships between a number of high frequency signals

DOEpatents

Bittner, J.W.; Biscardi, R.W.

1991-03-19

An electronic measurement circuit is disclosed for high speed comparison of the relative amplitudes of a predetermined number of electrical input signals independent of variations in the magnitude of the sum of the signals. The circuit includes a high speed electronic switch that is operably connected to receive on its respective input terminals one of said electrical input signals and to have its common terminal serve as an input for a variable-gain amplifier-detector circuit that is operably connected to feed its output to a common terminal of a second high speed electronic switch. The respective terminals of the second high speed electronic switch are operably connected to a plurality of integrating sample and hold circuits, which in turn have their outputs connected to a summing logic circuit that is operable to develop first, second and third output voltages, the first output voltage being proportional to a predetermined ratio of sums and differences between the compared input signals, the second output voltage being proportional to a second summed ratio of predetermined sums and differences between said input signals, and the third output voltage being proportional to the sum of signals to the summing logic circuit. A servo system that is operably connected to receive said third output signal and compare it with a reference voltage to develop a slowly varying feedback voltage to control the variable-gain amplifier in said common amplifier-detector circuit in order to make said first and second output signals independent of variations in the magnitude of the sum of said input signals. 2 figures.

Apparatus and method for detecting and measuring changes in linear relationships between a number of high frequency signals

DOEpatents

Bittner, John W.; Biscardi, Richard W.

1991-01-01

An electronic measurement circuit for high speed comparison of the relative amplitudes of a predetermined number of electrical input signals independent of variations in the magnitude of the sum of the signals. The circuit includes a high speed electronic switch that is operably connected to receive on its respective input terminals one of said electrical input signals and to have its common terminal serve as an input for a variable-gain amplifier-detector circuit that is operably connected to feed its output to a common terminal of a second high speed electronic switch. The respective terminals of the second high speed electronic switch are operably connected to a plurality of integrating sample and hold circuits, which in turn have their outputs connected to a summing logic circuit that is operable to develop first, second and third output voltages, the first output voltage being proportional to a predetermined ratio of sums and differences between the compared input signals, the second output voltage being proportional to a second summed ratio of predetermined sums and differences between said input signals, and the third output voltage being proportional to the sum of signals to the summing logic circuit. A servo system that is operably connected to receive said third output signal and compare it with a reference voltage to develop a slowly varying feedback voltage to control the variable-gain amplifier in said common amplifier-detector circuit in order to make said first and second output signals independent of variations in the magnitude of the sum of said input signals.

Electromagnetic Launchers and Guns. Phase 1

DTIC Science & Technology

1980-06-01

a high-speed maglev transportation system based on a linear synchronous motor (1,2,3). In 1975 Gerard K. O’Neill of Princeton University...fact that the very important railgun- homopolar launcher technology is already being pursued at Westinghouse and university of Texas, Austin. The...shown in Fig. 14 on the following page. There are three comparable options for energy storage: an engine-driven homopolar generator followed by an

Direct-drive field actuator motors

DOEpatents

Grahn, Allen R.

1995-01-01

A high-torque, low speed, positive-drive field actuator motor including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately.

The Steady Flow Resistance of Perforated Sheet Materials in High Speed Grazing Flows

NASA Technical Reports Server (NTRS)

Syed, Asif A.; Yu, Jia; Kwan, H. W.; Chien, E.; Jones, Michael G. (Technical Monitor)

2002-01-01

A study was conducted to determine the effects of high speed grazing air flow on the acoustic resistance of perforated sheet materials used in the construction of acoustically absorptive liners placed in commercial aircraft engine nacelles. Since DC flow resistance of porous sheet materials is known to be a major component of the acoustic resistance of sound suppression liners, the DC flow resistance of a set of perforated face-sheets and linear 'wiremesh' face-sheets was measured in a flow duct apparatus (up to Mach 0.8). Samples were fabricated to cover typical variations in perforated face-sheet parameters, such as hole diameter, porosity and sheet thickness, as well as those due to different manufacturing processes. The DC flow resistance data from perforated sheets were found to correlate strongly with the grazing flow Mach number and the face-sheet porosity. The data also show correlation against the boundary layer displacement thickness to hole-diameter ratio. The increase in resistance with grazing flow for punched aluminum sheets is in good agreement with published results up to Mach 0.4, but is significantly larger than expected above Mach 0.4. Finally, the tests demonstrated that there is a significant increase in the resistance of linear 'wiremesh' type face-sheet materials.

High-speed photon-counting x-ray computed tomography system utilizing a multipixel photon counter

NASA Astrophysics Data System (ADS)

Sato, Eiichi; Enomoto, Toshiyuki; Watanabe, Manabu; Hitomi, Keitaro; Takahashi, Kiyomi; Sato, Shigehiro; Ogawa, Akiro; Onagawa, Jun

2009-07-01

High-speed photon counting is useful for discriminating photon energy and for decreasing absorbed dose for patients in medical radiography, and the counting is usable for constructing an x-ray computed tomography (CT) system. A photon-counting x-ray CT system is of the first generation type and consists of an x-ray generator, a turn table, a translation stage, a two-stage controller, a multipixel photon counter (MPPC) module, a 1.0-mm-thick LSO crystal (scintillator), a counter card (CC), and a personal computer (PC). Tomography is accomplished by repeating the linear scanning and the rotation of an object, and projection curves of the object are obtained by the linear scanning using the detector consisting of a MPPC module and the LSO. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The lower level of the photon energy is roughly determined by a comparator circuit in the module, and the unit of the level is the photon equivalent (pe). Thus, the average photon energy of the x-ray spectra increases with increasing the lower-level voltage of the comparator. The maximum count rate was approximately 20 Mcps, and energy-discriminated CT was roughly carried out.

Computer-aided design of high-contact-ratio gears for minimum dynamic load and stress

NASA Technical Reports Server (NTRS)

Lin, Hsiang Hsi; Lee, Chinwai; Oswald, Fred B.; Townsend, Dennis P.

1990-01-01

A computer aided design procedure is presented for minimizing dynamic effects on high contact ratio gears by modification of the tooth profile. Both linear and parabolic tooth profile modifications of high contact ratio gears under various loading conditions are examined and compared. The effects of the total amount of modification and the length of the modification zone were systematically studied at various loads and speeds to find the optimum profile design for minimizing the dynamic load and the tooth bending stress. Parabolic profile modification is preferred over linear profile modification for high contact ratio gears because of its lower sensitivity to manufacturing errors. For parabolic modification, a greater amount of modification at the tooth tip and a longer modification zone are required. Design charts are presented for high contact ratio gears with various profile modifications operating under a range of loads. A procedure is illustrated for using the charts to find the optimum profile design.

Efficient Computation of Closed-loop Frequency Response for Large Order Flexible Systems

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; Giesy, Daniel P.

1997-01-01

An efficient and robust computational scheme is given for the calculation of the frequency response function of a large order, flexible system implemented with a linear, time invariant control system. Advantage is taken of the highly structured sparsity of the system matrix of the plant based on a model of the structure using normal mode coordinates. The computational time per frequency point of the new computational scheme is a linear function of system size, a significant improvement over traditional, full-matrix techniques whose computational times per frequency point range from quadratic to cubic functions of system size. This permits the practical frequency domain analysis of systems of much larger order than by traditional, full-matrix techniques. Formulations are given for both open and closed loop loop systems. Numerical examples are presented showing the advantages of the present formulation over traditional approaches, both in speed and in accuracy. Using a model with 703 structural modes, a speed-up of almost two orders of magnitude was observed while accuracy improved by up to 5 decimal places.

Validity of linear encoder measurement of sit-to-stand performance power in older people.

PubMed

Lindemann, U; Farahmand, P; Klenk, J; Blatzonis, K; Becker, C

2015-09-01

To investigate construct validity of linear encoder measurement of sit-to-stand performance power in older people by showing associations with relevant functional performance and physiological parameters. Cross-sectional study. Movement laboratory of a geriatric rehabilitation clinic. Eighty-eight community-dwelling, cognitively unimpaired older women (mean age 78 years). Sit-to-stand performance power and leg power were assessed using a linear encoder and the Nottingham Power Rig, respectively. Gait speed was measured on an instrumented walkway. Maximum quadriceps and hand grip strength were assessed using dynamometers. Mid-thigh muscle cross-sectional area of both legs was measured using magnetic resonance imaging. Associations of sit-to-stand performance power with power assessed by the Nottingham Power Rig, maximum gait speed and muscle cross-sectional area were r=0.646, r=0.536 and r=0.514, respectively. A linear regression model explained 50% of the variance in sit-to-stand performance power including muscle cross-sectional area (p=0.001), maximum gait speed (p=0.002), and power assessed by the Nottingham Power Rig (p=0.006). Construct validity of linear encoder measurement of sit-to-stand power was shown at functional level and morphological level for older women. This measure could be used in routine clinical practice as well as in large-scale studies. DRKS00003622. Copyright © 2015 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.

Using Computational Fluid Dynamics to Compare Shear Rate and Turbulence in the TIM-Automated Gastric Compartment With USP Apparatus II.

PubMed

Hopgood, Matthew; Reynolds, Gavin; Barker, Richard

2018-03-30

We use computational fluid dynamics to compare the shear rate and turbulence in an advanced in vitro gastric model (TIMagc) during its simulation of fasted state Migrating Motor Complex phases I and II, with the United States Pharmacopeia paddle dissolution apparatus II (USPII). A specific focus is placed on how shear rate in these apparatus affects erosion-based solid oral dosage forms. The study finds that tablet surface shear rates in TIMagc are strongly time dependant and fluctuate between 0.001 and 360 s -1 . In USPII, tablet surface shear rates are approximately constant for a given paddle speed and increase linearly from 9 s -1 to 36 s -1 as the paddle speed is increased from 25 to 100 rpm. A strong linear relationship is observed between tablet surface shear rate and tablet erosion rate in USPII, whereas TIMagc shows highly variable behavior. The flow regimes present in each apparatus are compared to in vivo predictions using Reynolds number analysis. Reynolds numbers for flow in TIMagc lie predominantly within the predicted in vivo bounds (0.01-30), whereas Reynolds numbers for flow in USPII lie above the predicted upper bound when operating with paddle speeds as low as 25 rpm (33). Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

The design of the Comet streamliner: An electric land speed record motorcycle

NASA Astrophysics Data System (ADS)

McMillan, Ethan Alexander

The development of the land speed record electric motorcycle streamliner, the Comet, is discussed herein. Its design process includes a detailed literary review of past and current motorcycle streamliners in an effort to highlight the main components of such a vehicle's design, while providing baseline data for performance comparisons. A new approach to balancing a streamliner at low speeds is also addressed, a system henceforth referred to as landing gear, which has proven an effective means for allowing the driver to control the low speed instabilities of the vehicle with relative ease compared to tradition designs. This is accompanied by a dynamic stability analysis conducted on a test chassis that was developed for the primary purpose of understanding the handling dynamics of streamliners, while also providing a test bed for the implementation of the landing gear system and a means to familiarize the driver to the operation and handling of such a vehicle. Data gathered through the use of GPS based velocity tracking, accelerometers, and a linear potentiometer provided a means to validate a dynamic stability analysis of the weave and wobble modes of the vehicle through linearization of a streamliner model developed in the BikeSIM software suite. Results indicate agreement between the experimental data and the simulation, indicating that the conventional recumbent design of a streamliner chassis is in fact highly stable throughout the performance envelope beyond extremely low speeds. A computational fluid dynamics study was also performed, utilized in the development of the body of the Comet to which a series of tests were conducted in order to develop a shape that was both practical to transport and highly efficient. By creating a hybrid airfoil from a NACA 0018 and NACA 66-018, a drag coefficient of 0.1 and frontal area of 0.44 m2 has been found for the final design. Utilizing a performance model based on the proposed vehicle's motor, its rolling resistance, and the body's aerodynamic drag, the top speed is predicted at 226 mph. Further design considerations are also addressed, including the development of the component level layout of the motorcycle, weighing factors such as safety and ease of fabrication with that of performance and accessibility. At the time of composition, the Comet had started the fabrication process, and it is the intent of the author that the finished product competes in the 2016 Bonneville Motorcycle Speed Trials to set the first world record for a single track electric motorcycle streamliner.

Passive wide spectrum harmonic filter for adjustable speed drives in oil and gas industry

NASA Astrophysics Data System (ADS)

Al Jaafari, Khaled Ali

Non-linear loads such as variable speed drives constitute the bulky load of oil and gas industry power systems. They are widely used in driving induction and permanent magnet motors for variable speed applications. That is because variable speed drives provide high static and dynamic performance. Moreover, they are known of their high energy efficiency and high motion quality, and high starting torque. However, these non-linear loads are main sources of current and voltage harmonics and lower the quality of electric power system. In fact, it is the six-pulse and twelve-pulse diode and thyristor rectifiers that spoil the AC power line with the dominant harmonics (5th, 7th, 11th). They provide DC voltage to the inverter of the variable speed drives. Typical problems that arise from these harmonics are Harmonic resonances', harmonic losses, interference with electronic equipment, and line voltage distortion at the Point of Common Coupling (PCC). Thus, it is necessary to find efficient, reliable, and economical harmonic filters. The passive filters have definite advantage over active filters in terms of components count, cost and reliability. Reliability and maintenance is a serious issue in drilling rigs which are located in offshore and onshore with extreme operating conditions. Passive filters are tuned to eliminate a certain frequency and therefore there is a need to equip the system with more than one passive filter to eliminate all unwanted frequencies. An alternative solution is Wide Spectrum Harmonic passive filter. The wide spectrum harmonic filters are becoming increasingly popular in these applications and found to overcome some of the limitations of conventional tuned passive filter. The most important feature of wide spectrum harmonic passive filters is that only one capacitor is required to filter a wide range of harmonics. Wide spectrum filter is essentially a low-pass filter for the harmonic at fundamental frequency. It can also be considered as a single-stage passive filter plus input and output inductors. The work proposed gives a complete analysis of wide spectrum harmonic passive filters, the methodology to choose its parameters according to the operational condition, effect of load and source inductance on its characteristics. Also, comparison of the performance of the wide band passive filter with tuned filter is given. The analyses are supported with the simulation results and were verified experimentally. The analysis given in this thesis will be useful for the selection of proper wide spectrum harmonic filters for harmonic mitigation applications in oil and gas industry.

The most important physiological constants among the Volga region long-livers

NASA Astrophysics Data System (ADS)

Malinova, L. I.; Shuvalov, S. S.; Denisova, T. P.

2012-03-01

In our research we brought out the age difference in the group of long-livers and the continuous character of the biochemical basal metabolism indexes changing. The results allowed us to carry out the polynominal high-powered approximation to study the dynamics of laboratory indexes. We revealed the progressive reduction of the cholesterol, triglycerides, glucose and creatinine levels starting from 90 years of age, and this reduction showed the non-linear character with interchange of local minimums and maximums. During the speed characteristics analysis we revealed the cooccurrence of the speed maximums of all the examined biochemical indexes, except the speed of changing the concentration of cholesterol, which maximum took the lead over the other indexes by four years. The phase-plane portrait analysis of the regulatory systems on the plane "time - speed" showed the unfulfilled attempt of system stabilization by all the searched parameters nearby the special spot - "stable focus". The standard deviation values analysis of the researched parameters showed their progressive reduction in the long-livers. That fact can be considered as the regulatory systems physiological "backlash" reduction among the centenarians.

Ultra-fast LuI{sub 3}:Ce scintillators for hard x-ray imaging

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

Marton, Zsolt, E-mail: zmarton@rmdinc.com; Miller, Stuart R.; Ovechkina, Elena

We have developed ultra-fast cerium-coped lutetium-iodide (LuI{sub 3}:Ce) films thermally evaporated as polycrystalline, structured scintillator using hot wall epitaxy (HWE) method. The films have shown a 13 ns decay compared to the 28 ns reported for crystals. The fast speed coupled with its high density (∼5.6 g/cm{sup 3}), high effective atomic number (59.7), and the fact that it can be vapor deposited in a columnar form makes LuI{sub 3}:Ce an attractive candidate for high frame rate, high-resolution, hard X-ray imaging. In crystal form, LuI{sub 3}:Ce has demonstrated bright (>100,000 photons/MeV) green (540 nm) emission, which is well matched to commercialmore » CCD/CMOS sensors and is critical for maintaining high signal to noise ratio in light starved applications. Here, we report on the scintillation properties of films and those for corresponding crystalline material. The vapor grown films were integrated into a high-speed CMOS imager to demonstrate high-speed radiography capability. The films were also tested at Advanced Photon Source, Argonne National Laboratory beamline 1-ID under hard X-ray irradiation. The data show a factor of four higher efficiency than the reference LuAG:Ce scintillators, high image quality, and linearity of scintillation response over a wide energy range. The films were employed to perform hard X-ray microtomography, the results of which will also be discussed.« less

High-resolution laser-projection display system using a grating electromechanical system (GEMS)

NASA Astrophysics Data System (ADS)

Brazas, John C.; Kowarz, Marek W.

2004-01-01

Eastman Kodak Company has developed a diffractive-MEMS spatial-light modulator for use in printing and display applications, the grating electromechanical system (GEMS). This modulator contains a linear array of pixels capable of high-speed digital operation, high optical contrast, and good efficiency. The device operation is based on deflection of electromechanical ribbons suspended above a silicon substrate by a series of intermediate supports. When electrostatically actuated, the ribbons conform to the supporting substructure to produce a surface-relief phase grating over a wide active region. The device is designed to be binary, switching between a reflective mirror state having suspended ribbons and a diffractive grating state having ribbons in contact with substrate features. Switching times of less than 50 nanoseconds with sub-nanosecond jitter are made possible by reliable contact-mode operation. The GEMS device can be used as a high-speed digital-optical modulator for a laser-projection display system by collecting the diffracted orders and taking advantage of the low jitter. A color channel is created using a linear array of individually addressable GEMS pixels. A two-dimensional image is produced by sweeping the line image of the array, created by the projection optics, across the display screen. Gray levels in the image are formed using pulse-width modulation (PWM). A high-resolution projection display was developed using three 1080-pixel devices illuminated by red, green, and blue laser-color primaries. The result is an HDTV-format display capable of producing stunning still and motion images with very wide color gamut.

Advanced Aerodynamic Design of Passive Porosity Control Effectors

NASA Technical Reports Server (NTRS)

Hunter, Craig A.; Viken, Sally A.; Wood, Richard M.; Bauer, Steven X. S.

2001-01-01

This paper describes aerodynamic design work aimed at developing a passive porosity control effector system for a generic tailless fighter aircraft. As part of this work, a computational design tool was developed and used to layout passive porosity effector systems for longitudinal and lateral-directional control at a low-speed, high angle of attack condition. Aerodynamic analysis was conducted using the NASA Langley computational fluid dynamics code USM3D, in conjunction with a newly formulated surface boundary condition for passive porosity. Results indicate that passive porosity effectors can provide maneuver control increments that equal and exceed those of conventional aerodynamic effectors for low-speed, high-alpha flight, with control levels that are a linear function of porous area. This work demonstrates the tremendous potential of passive porosity to yield simple control effector systems that have no external moving parts and will preserve an aircraft's fixed outer mold line.

High speed digital holography for density and fluctuation measurements (invited).

PubMed

Thomas, C E; Baylor, L R; Combs, S K; Meitner, S J; Rasmussen, D A; Granstedt, E M; Majeski, R P; Kaita, R

2010-10-01

The state of the art in electro-optics has advanced to the point where digital holographic acquisition of wavefronts is now possible. Holographic wavefront acquisition provides the phase of the wavefront at every measurement point. This can be done with accuracy on the order of a thousandth of a wavelength, given that there is sufficient care in the design of the system. At wave frequencies which are much greater than the plasma frequency, the plasma index of refraction is linearly proportional to the electron density and wavelength, and the measurement of the phase of a wavefront passing through the plasma gives the chord-integrated density directly for all points measured on the wavefront. High-speed infrared cameras (up to ∼40,000 fps at ∼64×4 pixels) with resolutions up to 640×512 pixels suitable for use with a CO(2) laser are readily available, if expensive.

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie

2014-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate in conditions of low Reynolds number and a wide range in incidence resulting from rotational speed variation. A comprehensive data set obtained in a linear cascade which includes the effects of Reynolds number, free-stream turbulence and incidence is now available and this paper concerns itself with the post-diction of boundary layer transitionseparation, blade pressure loading and total pressure loss pertaining to the conditions set for measurements in that data set. The distinction between the state of the measured data presented here and the earlier publications is the addition of high free-stream turbulence intensity. We will, for the purposes of the numerical post-diction, present some of the higher free stream turbulence data in this paper but defer a comprehensive presentation and treatment of the measured data will be done elsewhere.

High-speed fixed-target serial virus crystallography

DOE PAGES

Roedig, Philip; Ginn, Helen M.; Pakendorf, Tim; ...

2017-06-19

Here, we report a method for serial X-ray crystallography at X-ray free-electron lasers (XFELs), which allows for full use of the current 120-Hz repetition rate of the Linear Coherent Light Source (LCLS). Using a micropatterned silicon chip in combination with the high-speed Roadrunner goniometer for sample delivery, we were able to determine the crystal structures of the picornavirus bovine enterovirus 2 (BEV2) and the cytoplasmic polyhedrosis virus type 18 polyhedrin, with total data collection times of less than 14 and 10 min, respectively. Our method requires only micrograms of sample and should therefore broaden the applicability of serial femtosecond crystallographymore » to challenging projects for which only limited sample amounts are available. By synchronizing the sample exchange to the XFEL repetition rate, our method allows for most efficient use of the limited beam time available at XFELs and should enable a substantial increase in sample throughput at these facilities.« less

High-speed fixed-target serial virus crystallography

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

Roedig, Philip; Ginn, Helen M.; Pakendorf, Tim

Here, we report a method for serial X-ray crystallography at X-ray free-electron lasers (XFELs), which allows for full use of the current 120-Hz repetition rate of the Linear Coherent Light Source (LCLS). Using a micropatterned silicon chip in combination with the high-speed Roadrunner goniometer for sample delivery, we were able to determine the crystal structures of the picornavirus bovine enterovirus 2 (BEV2) and the cytoplasmic polyhedrosis virus type 18 polyhedrin, with total data collection times of less than 14 and 10 min, respectively. Our method requires only micrograms of sample and should therefore broaden the applicability of serial femtosecond crystallographymore » to challenging projects for which only limited sample amounts are available. By synchronizing the sample exchange to the XFEL repetition rate, our method allows for most efficient use of the limited beam time available at XFELs and should enable a substantial increase in sample throughput at these facilities.« less

A possible explanation for the present difference between linear noise theory and experimental data for supersonic helical tip speed propellers

NASA Technical Reports Server (NTRS)

Dittmar, J. H.

1983-01-01

High speed turboprops are attractive candidates for future aircraft because of their high propulsive efficiency. However, the noise of their propellers may create a cabin environment problem for the aircraft powered by these propellers. The noise of some propeller models was measured, and predictions of the noise using a method based on the Ffowcs Williams-Hawkins equation were made. The predictions and data agree well at lower helical tip Mach numbers but deviate above Mach 1.0. Some possible reasons why the theory does not predict the data and focuses on improvement of the aerodynamic inputs as the most likely remedy are investigated. In particular, it is proposed that an increase in the drag and a decrease in the lift near the tip of the blade where the majority of the noise is generated, is warranted in the input to the theory.

High-speed fixed-target serial virus crystallography

PubMed Central

Roedig, Philip; Ginn, Helen M.; Pakendorf, Tim; Sutton, Geoff; Harlos, Karl; Walter, Thomas S.; Meyer, Jan; Fischer, Pontus; Duman, Ramona; Vartiainen, Ismo; Reime, Bernd; Warmer, Martin; Brewster, Aaron S.; Young, Iris D.; Michels-Clark, Tara; Sauter, Nicholas K.; Kotecha, Abhay; Kelly, James; Rowlands, David J.; Sikorsky, Marcin; Nelson, Silke; Damiani, Daniel S.; Alonso-Mori, Roberto; Ren, Jingshan; Fry, Elizabeth E.; David, Christian; Stuart, David I.; Wagner, Armin; Meents, Alke

2017-01-01

We report a method for serial X-ray crystallography at X-ray free electron lasers (XFELs), which allows for full use of the current 120 Hz repetition rate of the Linear Coherent Light Source (LCLS). Using a micro-patterned silicon chip in combination with the high-speed Roadrunner goniometer for sample delivery we were able to determine the crystal structures of a picornavirus, bovine enterovirus 2 (BEV2), and the cytoplasmic polyhedrosis virus type 18 polyhedrin. Total data collection times were less than 14 and 10 minutes, respectively. Our method requires only micrograms of sample and will therefore broaden the applicability of serial femtosecond crystallography to challenging projects for which only limited sample amounts are available. By synchronizing the sample exchange to the XFEL repetition rate, our method allows for the most efficient use of the limited beamtime available at XFELs and should enable a substantial increase in sample throughput at these facilities. PMID:28628129

Hybrid imaging: a quantum leap in scientific imaging

NASA Astrophysics Data System (ADS)

Atlas, Gene; Wadsworth, Mark V.

2004-01-01

ImagerLabs has advanced its patented next generation imaging technology called the Hybrid Imaging Technology (HIT) that offers scientific quality performance. The key to the HIT is the merging of the CCD and CMOS technologies through hybridization rather than process integration. HIT offers exceptional QE, fill factor, broad spectral response and very low noise properties of the CCD. In addition, it provides the very high-speed readout, low power, high linearity and high integration capability of CMOS sensors. In this work, we present the benefits, and update the latest advances in the performance of this exciting technology.

Are running speeds maximized with simple-spring stance mechanics?

PubMed

Clark, Kenneth P; Weyand, Peter G

2014-09-15

Are the fastest running speeds achieved using the simple-spring stance mechanics predicted by the classic spring-mass model? We hypothesized that a passive, linear-spring model would not account for the running mechanics that maximize ground force application and speed. We tested this hypothesis by comparing patterns of ground force application across athletic specialization (competitive sprinters vs. athlete nonsprinters, n = 7 each) and running speed (top speeds vs. slower ones). Vertical ground reaction forces at 5.0 and 7.0 m/s, and individual top speeds (n = 797 total footfalls) were acquired while subjects ran on a custom, high-speed force treadmill. The goodness of fit between measured vertical force vs. time waveform patterns and the patterns predicted by the spring-mass model were assessed using the R(2) statistic (where an R(2) of 1.00 = perfect fit). As hypothesized, the force application patterns of the competitive sprinters deviated significantly more from the simple-spring pattern than those of the athlete, nonsprinters across the three test speeds (R(2) <0.85 vs. R(2) ≥ 0.91, respectively), and deviated most at top speed (R(2) = 0.78 ± 0.02). Sprinters attained faster top speeds than nonsprinters (10.4 ± 0.3 vs. 8.7 ± 0.3 m/s) by applying greater vertical forces during the first half (2.65 ± 0.05 vs. 2.21 ± 0.05 body wt), but not the second half (1.71 ± 0.04 vs. 1.73 ± 0.04 body wt) of the stance phase. We conclude that a passive, simple-spring model has limited application to sprint running performance because the swiftest runners use an asymmetrical pattern of force application to maximize ground reaction forces and attain faster speeds. Copyright © 2014 the American Physiological Society.

Wellbeing perception and the impact on external training output among elite soccer players.

PubMed

Malone, Shane; Owen, Adam; Newton, Matt; Mendes, Bruno; Tiernan, Leo; Hughes, Brian; Collins, Kieran

2018-01-01

The objective of the investigation was to observe the impact of player wellbeing on the training output of elite soccer players. Prospective cohort design. Forty-eight soccer players (age: 25.3±3.1years; height: 183±7cm; mass: 72±7kg) were involved in this single season observational study across two teams. Each morning, pre-training, players completed customised perceived wellbeing questionnaires. Global positioning technology devices were used to measure external load (total distance, total high-speed running distance, high speed running, player load, player load slow, maximal velocity, maximal velocity exposures). Players reported ratings of perceived exertion using the modified Borg CR-10 scale. Integrated training load ratios were also analysed for total distance:RPE, total high speed distance:RPE player load:RPE and player load slow:RPE respectively. Mixed-effect linear models revealed significant effects of wellbeing Z-score on external and integrated training load measures. A wellbeing Z-score of -1 corresponded to a -18±2m (-3.5±1.1%), 4±1m (-4.9±2.1%,) 0.9±0.1kmh -1 (-3.1±2.1%), 1±1 (-4.6±2.9%), 25±3AU (-4.9±3.1%) and 11±0.5AU (-8.9±2.9%) reduction in total high speed distance, high speed distance, maximal velocity, maximal velocity exposures, player load and player load slow respectively. A reduction in wellbeing impacted external:internal training load ratios and resulted in -0.49±0.12mmin -1 , -1.20±0.08mmin -1 ,-0.02±0.01AUmin -1 in total distance:RPE, total high speed distance:RPE and player load slow:RPE respectively. The results suggest that systematic monitoring of player wellbeing within soccer cohorts can provide coaches with information about the training output that can be expected from individual players during a training session. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

LQR-Based Optimal Distributed Cooperative Design for Linear Discrete-Time Multiagent Systems.

PubMed

Zhang, Huaguang; Feng, Tao; Liang, Hongjing; Luo, Yanhong

2017-03-01

In this paper, a novel linear quadratic regulator (LQR)-based optimal distributed cooperative design method is developed for synchronization control of general linear discrete-time multiagent systems on a fixed, directed graph. Sufficient conditions are derived for synchronization, which restrict the graph eigenvalues into a bounded circular region in the complex plane. The synchronizing speed issue is also considered, and it turns out that the synchronizing region reduces as the synchronizing speed becomes faster. To obtain more desirable synchronizing capacity, the weighting matrices are selected by sufficiently utilizing the guaranteed gain margin of the optimal regulators. Based on the developed LQR-based cooperative design framework, an approximate dynamic programming technique is successfully introduced to overcome the (partially or completely) model-free cooperative design for linear multiagent systems. Finally, two numerical examples are given to illustrate the effectiveness of the proposed design methods.

Investigation of frequency-response characteristics of engine speed for a typical turbine-propeller engine

NASA Technical Reports Server (NTRS)

Taylor, Burt L , III; Oppenheimer, Frank L

1951-01-01

Experimental frequency-response characteristics of engine speed for a typical turbine-propeller engine are presented. These data were obtained by subjecting the engine to sinusoidal variations of fuel flow and propeller-blade-angle inputs. Correlation is made between these experimental data and analytical frequency-response characteristics obtained from a linear differential equation derived from steady-state torque-speed relations.

A new method to measure circular runout of end-milling spindle based on cutting mark

NASA Astrophysics Data System (ADS)

Zhou, Jianlai; Liu, Shuchun

2008-12-01

A practical method is introduced to measure the circular runout of a end-milling spindle system at high speed rotations without the need of a reference sphere. A workpiece is held on a linear slide which moves along the axial direction of the spindle. The spindle is then programmed to run at a specific speed. A very sharp edge cutter must be used and the depth of cut will be very shallow in order to keep the cutting force very small. The workpiece is then fed into the end mill in order to make a cutting mark of teens μm in depth. The cutting marks are circular, and their diameters are related to the circular runout of the spindle system. The cutting mark that is generated at a specific speed is expected to contain information about the spindle circular runout at this speed. In practice the cutting marks are not perfectly circular. Therefore, a best-fit circle of a cutting mark is needed to determine its diameter. A high-resolution edge detector machine is used for this purpose. Quantitative precision analysis was carried out to confirm the accuracy and repeatability of this new measurement technique. It is demonstrated that this technique for the measurement of spindle circular runout is an effective tool in verifying the actual running accuracy of spindles at their actual operating speeds and can be accomplished without the need for a reference sphere.

Hugoniot and refractive indices of bromoform under shock compression

NASA Astrophysics Data System (ADS)

Liu, Q. C.; Zeng, X. L.; Zhou, X. M.; Luo, S. N.

2018-01-01

We investigate physical properties of bromoform (liquid CHBr3) including compressibility and refractive index under dynamic extreme conditions of shock compression. Planar shock experiments are conducted along with high-speed laser interferometry. Our experiments and previous results establish a linear shock velocity-particle velocity relation for particle velocities below 1.77 km/s, as well as the Hugoniot and isentropic compression curves up to ˜21 GPa. Shock-state refractive indices of CHBr3 up to 2.3 GPa or ˜26% compression, as a function of density, can be described with a linear relation and follows the Gladstone-Dale relation. The velocity corrections for laser interferometry measurements at 1550 nm are also obtained.

High performance waveguide-coupled Ge-on-Si linear mode avalanche photodiodes

DOE PAGES

Martinez, Nicholas J. D.; Derose, Christopher T.; Brock, Reinhard W.; ...

2016-08-09

Here, we present experimental results for a selective epitaxially grown Ge-on-Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Epitaxially grown Ge-on-Si waveguide-coupled linear mode avalanche photodiodes with varying lateral multiplication regions and different charge implant dimensions are fabricated and their illuminated device characteristics and high-speed performance is measured. We report a record gain-bandwidth product of 432 GHz for our highest performing waveguide-coupled avalanche photodiode operating at 1510nm. Bit error rate measurements show operation with BER< 10 –12, in the range from –18.3 dBm to –12 dBm received optical powermore » into a 50 Ω load and open eye diagrams with 13 Gbps pseudo-random data at 1550 nm.« less

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie B.

2014-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate at low Reynolds number and over a wide range in incidence associated with shaft speed change. A comprehensive linear cascade data set obtained includes the effects of Reynolds number, free-stream turbulence and incidence is available and this paper concerns itself with the presentation and numerical simulation of conditions resulting in a selected set of those data. As such, post-dictions of blade pressure loading, total-pressure loss and exit flow angles under conditions of high and low turbulence intensity for a single Reynolds number are presented. Analyses are performed with the three-equation turbulence models of Walters-Leylek and Walters and Cokljat. Transition, loading, total-pressure loss and exit angle variations are presented and comparisons are made with experimental data as available. It is concluded that at the low freestream turbulence conditions the Walters-Cokljat model is better suited to predictions while for high freestream conditions the two models generate similar predications that are generally satisfactory.

Technical assessment of maglev system concepts. Final report

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

Lever, J.H.

1998-10-01

The Government Maglev System Assessment Team operated from 1991 to 1993 as part of the National Maglev Initiative. They assessed the technical viability of four US Maglev system concepts, using the French TGV high speed train and the German TR07 Maglev system as assessment baselines. Maglev in general offers advantages that include high speed potential, excellent system control, high capacity, low energy consumption, low maintenance, modest land requirements, low operating costs, and ability to meet a variety of transportation missions. Further, the US Maglev concepts could provide superior performance to TR07 for similar cost or similar performance for less cost.more » They also could achieve both lower trip times and lower energy consumption along typical US routes. These advantages result generally from the use of large gap magnetic suspensions, more powerful linear synchronous motors and tilting vehicles. Innovative concepts for motors, guideways, suspension, and superconducting magnets all contribute to a potential for superior long term performance of US Maglev systems compared with TGV and TR07.« less

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie B.

2015-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate at low Reynolds number and over a wide range in incidence associated with shaft speed change. A comprehensive linear cascade data set obtained includes the effects of Reynolds number, free-stream turbulence and incidence is available and this paper concerns itself with the presentation and numerical simulation of conditions resulting in a selected set of those data. As such, post-dictions of blade pressure loading, total-pressure loss and exit flow angles under conditions of high and low turbulence intensity for a single Reynolds number are presented. Analyses are performed with the three-equation turbulence models of Walters- Leylek and Walters and Cokljat. Transition, loading, total-pressure loss and exit angle variations are presented and comparisons are made with experimental data as available. It is concluded that at the low freestream turbulence conditions the Walters-Cokljat model is better suited to predictions while for high freestream conditions the two models generate similar predications that are generally satisfactory.

Sex Differences in Anthropometrics and Heading Kinematics Among Division I Soccer Athletes

PubMed Central

Bretzin, Abigail C.; Mansell, Jamie L.; Tierney, Ryan T.; McDevitt, Jane K.

2016-01-01

Background: Soccer players head the ball repetitively throughout their careers; this is also a potential mechanism for a concussion. Although not all soccer headers result in a concussion, these subconcussive impacts may impart acceleration, deceleration, and rotational forces on the brain, leaving structural and functional deficits. Stronger neck musculature may reduce head-neck segment kinematics. Hypothesis: The relationship between anthropometrics and soccer heading kinematics will not differ between sexes. The relationship between anthropometrics and soccer heading kinematics will not differ between ball speeds. Study Design: Pilot, cross-sectional design. Level of Evidence: Level 3. Methods: Division I soccer athletes (5 male, 8 female) were assessed for head-neck anthropometric and neck strength measurements in 6 directions (ie, flexion, extension, right and left lateral flexions and rotations). Participants headed the ball 10 times (25 or 40 mph) while wearing an accelerometer secured to their head. Kinematic measurements (ie, linear acceleration and rotational velocity) were recorded at 2 ball speeds. Results: Sex differences were observed in neck girth (t = 5.09, P < 0.001), flexor and left lateral flexor strength (t = 3.006, P = 0.012 and t = 4.182, P = 0.002, respectively), and rotational velocity at both speeds (t = −2.628, P = 0.024 and t = −2.227, P = 0.048). Neck girth had negative correlations with both linear acceleration (r = −0.599, P = 0.031) and rotational velocity at both speeds (r = −0.551, P = 0.012 and r = −0.652, P = 0.016). Also, stronger muscle groups had lower linear accelerations at both speeds (P < 0.05). Conclusion: There was a significant relationship between anthropometrics and soccer heading kinematics for sex and ball speeds. Clinical Relevance: Neck girth and neck strength are factors that may limit head impact kinematics. PMID:28225689

Cognitive Processing Speed, Working Memory, and the Intelligibility of Hearing Aid-Processed Speech in Persons with Hearing Impairment

PubMed Central

Yumba, Wycliffe Kabaywe

2017-01-01

Previous studies have demonstrated that successful listening with advanced signal processing in digital hearing aids is associated with individual cognitive capacity, particularly working memory capacity (WMC). This study aimed to examine the relationship between cognitive abilities (cognitive processing speed and WMC) and individual listeners’ responses to digital signal processing settings in adverse listening conditions. A total of 194 native Swedish speakers (83 women and 111 men), aged 33–80 years (mean = 60.75 years, SD = 8.89), with bilateral, symmetrical mild to moderate sensorineural hearing loss who had completed a lexical decision speed test (measuring cognitive processing speed) and semantic word-pair span test (SWPST, capturing WMC) participated in this study. The Hagerman test (capturing speech recognition in noise) was conducted using an experimental hearing aid with three digital signal processing settings: (1) linear amplification without noise reduction (NoP), (2) linear amplification with noise reduction (NR), and (3) non-linear amplification without NR (“fast-acting compression”). The results showed that cognitive processing speed was a better predictor of speech intelligibility in noise, regardless of the types of signal processing algorithms used. That is, there was a stronger association between cognitive processing speed and NR outcomes and fast-acting compression outcomes (in steady state noise). We observed a weaker relationship between working memory and NR, but WMC did not relate to fast-acting compression. WMC was a relatively weaker predictor of speech intelligibility in noise. These findings might have been different if the participants had been provided with training and or allowed to acclimatize to binary masking noise reduction or fast-acting compression. PMID:28861009

Sex Differences in Anthropometrics and Heading Kinematics Among Division I Soccer Athletes.

PubMed

Bretzin, Abigail C; Mansell, Jamie L; Tierney, Ryan T; McDevitt, Jane K

Soccer players head the ball repetitively throughout their careers; this is also a potential mechanism for a concussion. Although not all soccer headers result in a concussion, these subconcussive impacts may impart acceleration, deceleration, and rotational forces on the brain, leaving structural and functional deficits. Stronger neck musculature may reduce head-neck segment kinematics. The relationship between anthropometrics and soccer heading kinematics will not differ between sexes. The relationship between anthropometrics and soccer heading kinematics will not differ between ball speeds. Pilot, cross-sectional design. Level 3. Division I soccer athletes (5 male, 8 female) were assessed for head-neck anthropometric and neck strength measurements in 6 directions (ie, flexion, extension, right and left lateral flexions and rotations). Participants headed the ball 10 times (25 or 40 mph) while wearing an accelerometer secured to their head. Kinematic measurements (ie, linear acceleration and rotational velocity) were recorded at 2 ball speeds. Sex differences were observed in neck girth ( t = 5.09, P < 0.001), flexor and left lateral flexor strength ( t = 3.006, P = 0.012 and t = 4.182, P = 0.002, respectively), and rotational velocity at both speeds ( t = -2.628, P = 0.024 and t = -2.227, P = 0.048). Neck girth had negative correlations with both linear acceleration ( r = -0.599, P = 0.031) and rotational velocity at both speeds ( r = -0.551, P = 0.012 and r = -0.652, P = 0.016). Also, stronger muscle groups had lower linear accelerations at both speeds ( P < 0.05). There was a significant relationship between anthropometrics and soccer heading kinematics for sex and ball speeds. Neck girth and neck strength are factors that may limit head impact kinematics.

Protograph based LDPC codes with minimum distance linearly growing with block size

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Jones, Christopher; Dolinar, Sam; Thorpe, Jeremy

2005-01-01

We propose several LDPC code constructions that simultaneously achieve good threshold and error floor performance. Minimum distance is shown to grow linearly with block size (similar to regular codes of variable degree at least 3) by considering ensemble average weight enumerators. Our constructions are based on projected graph, or protograph, structures that support high-speed decoder implementations. As with irregular ensembles, our constructions are sensitive to the proportion of degree-2 variable nodes. A code with too few such nodes tends to have an iterative decoding threshold that is far from the capacity threshold. A code with too many such nodes tends to not exhibit a minimum distance that grows linearly in block length. In this paper we also show that precoding can be used to lower the threshold of regular LDPC codes. The decoding thresholds of the proposed codes, which have linearly increasing minimum distance in block size, outperform that of regular LDPC codes. Furthermore, a family of low to high rate codes, with thresholds that adhere closely to their respective channel capacity thresholds, is presented. Simulation results for a few example codes show that the proposed codes have low error floors as well as good threshold SNFt performance.

Multi-mode phase speed measurements with array-based analysis: Application to the North American continent

NASA Astrophysics Data System (ADS)

Matsuzawa, H.; Yoshizawa, K.

2017-12-01

Recent high-density broad-band seismic networks allow us to construct improved 3-D upper mantle models with unprecedented horizontal resolution using surface waves. Such dispersion measurements have been primarily based on the analysis of fundamental mode. Higher-mode information can be of help in enhancing vertical resolution of 3-D models, but their dispersion analysis is intrinsically difficult, since wave-packets of several modes are overlapped each other in an observed seismogram. In this study, we measure phase dispersion of multi-mode surface waves with an array-based analysis. Our method is modeled on a one-dimensional frequency-wavenumber method originally developed by Nolet (1975, GRL), which can be applied to a set of broadband seismic records observed in a linear array along a great circle path. Through this analysis, we can obtain a spectrogram in c-T (phase speed - period) domain, which is characterized by mode-branch dispersion curves and relative spectral powers for each mode. Synthetic experiments indicate that we can separate the modal contribution using a long linear array with typical array length of about 2000 to 4000 km. The method is applied to a large data set from USArray using nearly 400 seismic events in 2007 - 2014 with Mw 6.5 or greater. Our phase-speed maps for the fundamental-mode Love and Rayleigh waves and the first higher-mode Rayleigh waves match well with the earlier models. The phase speed maps reflect typical large-scale features of regional seismic structure in North America, but smaller-scale variations are less constrained in our model, since our measured phase speeds represent path-average features over a long path (about a few thousands kilometers). Our multi-mode dispersion measurements can also be used for the extraction of mode-branch waveforms for the first a few modes. This can be done by applying a narrow filter around the dispersion curves of a target mode in c-T spectrogram. The mode-branch waveforms can then be reconstructed based on a linear Radon transform (e.g., Luo et al., 2015, GJI). Synthetic experiments suggest that we can successfully retrieve the mode-branch waveforms for several mode branches, which can be used in the secondary analysis for constraining local-scale heterogeneity with enhanced depth resolution.

Effects of road infrastructure and traffic complexity in speed adaptation behaviour of distracted drivers.

PubMed

Oviedo-Trespalacios, Oscar; Haque, Md Mazharul; King, Mark; Washington, Simon

2017-04-01

The use of mobile phones while driving remains a major human factors issue in the transport system. A significant safety concern is that driving while distracted by a mobile phone potentially modifies the driving speed leading to conflicts with other road users and consequently increases crash risk. However, the lack of systematic knowledge of the mechanisms involved in speed adaptation of distracted drivers constrains the explanation and modelling of the extent of this phenomenon. The objective of this study was to investigate speed adaptation of distracted drivers under varying road infrastructure and traffic complexity conditions. The CARRS-Q Advanced Driving Simulator was used to test participants on a simulated road with different traffic conditions, such as free flow traffic along straight roads, driving in urbanized areas, and driving in heavy traffic along suburban roads. Thirty-two licensed young drivers drove the simulator under three phone conditions: baseline (no phone conversation), hands-free and handheld phone conversations. To understand the relationships between distraction, road infrastructure and traffic complexity, speed adaptation calculated as the deviation of driving speed from the posted speed limit was modelled using a decision tree. The identified groups of road infrastructure and traffic characteristics from the decision tree were then modelled with a Generalized Linear Mixed Model (GLMM) with repeated measures to develop inferences about speed adaptation behaviour of distracted drivers. The GLMM also included driver characteristics and secondary task demands as predictors of speed adaptation. Results indicated that complex road environments like urbanization, car-following situations along suburban roads, and curved road alignment significantly influenced speed adaptation behaviour. Distracted drivers selected a lower speed while driving along a curved road or during car-following situations, but speed adaptation was negligible in the presence of high visual cutter, indicating the prioritization of the driving task over the secondary task. Additionally, drivers who scored high on self-reported safe attitudes towards mobile phone usage, and who reported prior involvement in a road traffic crash, selected a lower driving speed in the distracted condition than in the baseline. The results aid in understanding how driving task demands influence speed adaptation of distracted drivers under various road infrastructure and traffic complexity conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fluid flow dynamics in MAS systems

NASA Astrophysics Data System (ADS)

Wilhelm, Dirk; Purea, Armin; Engelke, Frank

2015-08-01

The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3 mm-rotor diameter has been analyzed for spinning rates up to 67 kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3 mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7 mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor.

Analog Techniques in CEBAF's RF Control System

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

Hovater, J.; Fugitt, Jock

1988-01-01

Recent developments in high-speed analog technology have progressed into the areas of traditional RF technology.Diode-related devices are being replaced by analog IC's in the CEBAF RF control system.Complex phase modulators and attenuators have been successfully tested at 70 MHz.They have three advantages over existing technology: lower cost, less temperature sensitivity, and more linearity.RF signal conditioning components and how to implement the new analog IC's will be covered in this paper.

Direct-drive field actuator motors

DOEpatents

Grahn, A.R.

1995-07-11

A high-torque, low speed, positive-drive field actuator motor is disclosed including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately. 37 figs.

High supersonic aerodynamic characteristics of five irregular planform wings with systematically varying wing fillet geometry tested in the NASA/LaRC 4-foot UPWT (LEG 2) (LA45A/B)

NASA Technical Reports Server (NTRS)

1976-01-01

An experimental and analytical aerodynamic program to develop predesign guides for irregular planform wings is reported. The benefits are linearization of subsonic lift curve slope to high angles of attack and avoidance of subsonic pitch instabilities at high lift by proper tailoring of the planform fillet wing combination while providing the desired hypersonic trim angle and stability. The two prime areas of concern are to optimize shuttle orbiter landing and entry characteristics. Basic longitudinal aerodynamic characteristics at high supersonic speeds are developed.

GLAST Burst Monitor Signal Processing System

NASA Astrophysics Data System (ADS)

Bhat, P. Narayana; Briggs, Michael; Connaughton, Valerie; Diehl, Roland; Fishman, Gerald; Greiner, Jochen; Kippen, R. Marc; von Kienlin, Andreas; Kouveliotou, Chryssa; Lichti, Giselher; Meegan, Charles; Paciesas, William; Persyn, Steven; Preece, Robert; Steinle, Helmut; Wilson-Hodge, Colleen

2007-07-01

The onboard Data Processing Unit (DPU), designed and built by Southwest Research Institute, performs the high-speed data acquisition for GBM. The analog signals from each of the 14 detectors are digitized by high-speed multichannel analog data acquisition architecture. The streaming digital values resulting from a periodic (period of 104.2 ns) sampling of the analog signal by the individual ADCs are fed to a Field-Programmable Gate Array (FPGA). Real-time Digital Signal Processing (DSP) algorithms within the FPGA implement functions like filtering, thresholding, time delay and pulse height measurement. The spectral data with a 12-bit resolution are formatted according to the commandable look-up-table (LUT) and then sent to the High-Speed Science-Date Bus (HSSDB, speed=1.5 MB/s) to be telemetered to ground. The DSP offers a novel feature of a commandable & constant event deadtime. The ADC non-linearities have been calibrated so that the spectral data can be corrected during analysis. The best temporal resolution is 2 μs for the pre-burst & post-trigger time-tagged events (TTE) data. The time resolution of the binned data types is commandable from 64 msec to 1.024 s for the CTIME data (8 channel spectral resolution) and 1.024 to 32.768 s for the CSPEC data (128 channel spectral resolution). The pulse pile-up effects have been studied by Monte Carlo simulations. For a typical GRB, the possible shift in the Epeak value at high-count rates (~100 kHz) is ~1% while the change in the single power-law index could be up to 5%.

Assessment of ultrafine particles and noise measurements using fuzzy logic and data mining techniques.

PubMed

Fernández-Camacho, R; Brito Cabeza, I; Aroba, J; Gómez-Bravo, F; Rodríguez, S; de la Rosa, J

2015-04-15

This study focuses on correlations between total number concentrations, road traffic emissions and noise levels in an urban area in the southwest of Spain during the winter and summer of 2009. The high temporal correlation between sound pressure levels, traffic intensity, particle number concentrations related to traffic, black carbon and NOx concentrations suggests that noise is linked to traffic emissions as a main source of pollution in urban areas. First, the association of these different variables was studied using PreFuRGe, a computational tool based on data mining and fuzzy logic. The results showed a clear association between noise levels and road-traffic intensity for non-extremely high wind speed levels. This behaviour points, therefore, to vehicular emissions being the main source of urban noise. An analysis for estimating the total number concentration from noise levels is also proposed in the study. The high linearity observed between particle number concentrations linked to traffic and noise levels with road traffic intensity can be used to calculate traffic related particle number concentrations experimentally. At low wind speeds, there are increases in noise levels of 1 dB for every 100 vehicles in circulation. This is equivalent to 2000 cm(-3) per vehicle in winter and 500 cm(-3) in summer. At high wind speeds, wind speed could be taken into account. This methodology allows low cost sensors to be used as a proxy for total number concentration monitoring in urban air quality networks. Copyright © 2015 Elsevier B.V. All rights reserved.

A high-accuracy optical linear algebra processor for finite element applications

NASA Technical Reports Server (NTRS)

Casasent, D.; Taylor, B. K.

1984-01-01

Optical linear processors are computationally efficient computers for solving matrix-matrix and matrix-vector oriented problems. Optical system errors limit their dynamic range to 30-40 dB, which limits their accuray to 9-12 bits. Large problems, such as the finite element problem in structural mechanics (with tens or hundreds of thousands of variables) which can exploit the speed of optical processors, require the 32 bit accuracy obtainable from digital machines. To obtain this required 32 bit accuracy with an optical processor, the data can be digitally encoded, thereby reducing the dynamic range requirements of the optical system (i.e., decreasing the effect of optical errors on the data) while providing increased accuracy. This report describes a new digitally encoded optical linear algebra processor architecture for solving finite element and banded matrix-vector problems. A linear static plate bending case study is described which quantities the processor requirements. Multiplication by digital convolution is explained, and the digitally encoded optical processor architecture is advanced.

Linear LIDAR versus Geiger-mode LIDAR: impact on data properties and data quality

NASA Astrophysics Data System (ADS)

Ullrich, A.; Pfennigbauer, M.

2016-05-01

LIDAR has become the inevitable technology to provide accurate 3D data fast and reliably even in adverse measurement situations and harsh environments. It provides highly accurate point clouds with a significant number of additional valuable attributes per point. LIDAR systems based on Geiger-mode avalanche photo diode arrays, also called single photon avalanche photo diode arrays, earlier employed for military applications, now seek to enter the commercial market of 3D data acquisition, advertising higher point acquisition speeds from longer ranges compared to conventional techniques. Publications pointing out the advantages of these new systems refer to the other category of LIDAR as "linear LIDAR", as the prime receiver element for detecting the laser echo pulses - avalanche photo diodes - are used in a linear mode of operation. We analyze the differences between the two LIDAR technologies and the fundamental differences in the data they provide. The limitations imposed by physics on both approaches to LIDAR are also addressed and advantages of linear LIDAR over the photon counting approach are discussed.

Quality evaluation of millet-soy blended extrudates formulated through linear programming.

PubMed

Balasubramanian, S; Singh, K K; Patil, R T; Onkar, Kolhe K

2012-08-01

Whole pearl millet, finger millet and decorticated soy bean blended (millet soy) extrudates formulations were designed using a linear programming (LP) model to minimize the total cost of the finished product. LP formulated composite flour was extruded through twin screw food extruder at different feed rate (6.5-13.5 kg/h), screw speed (200-350 rpm, constant feed moisture (14% wb), barrel temperature (120 °C) and cutter speed (15 rpm). The physical, functional, textural and pasting characteristics of extrudates were examined and their responses were studied. Expansion index (2.31) and sectional expansion index (5.39) was found to be was found maximum for feed rate and screw speed combination 9.5 kg/h and 250 rpm. However, density (0.25 × 10(-3) g/mm(3)) was maximum for 9.5 kg/h and 300 rpm combination. Maximum color change (10.32) was found for 9.5 kg/h feed rate and 200 rpm screw speed. The lower hardness was obtained for the samples extruded at lowest feed rate (6.5 kg/h) for all screw speed and feed rate at 9.5 kg/h for 300-350 rpm screw speed. Peak viscosity decreases with all screw speed of 9.5 kg/h feed rate.

Asymmetry in the clockwise and counterclockwise rotation of the bacterial flagellar motor

PubMed Central

Yuan, Junhua; Fahrner, Karen A.; Turner, Linda; Berg, Howard C.

2010-01-01

Cells of Escherichia coli are able to swim up gradients of chemical attractants by modulating the direction of rotation of their flagellar motors, which spin alternately clockwise (CW) and counterclockwise (CCW). Rotation in either direction has been thought to be symmetric and exhibit the same torques and speeds. The relationship between torque and speed is one of the most important measurable characteristics of the motor, used to distinguish specific mechanisms of motor rotation. Previous measurements of the torque–speed relationship have been made with cells lacking the response regulator CheY that spin their motors exclusively CCW. In this case, the torque declines slightly up to an intermediate speed called the “knee speed” after which it falls rapidly to zero. This result is consistent with a “power-stroke” mechanism for torque generation. Here, we measure the torque–speed relationship for cells that express large amounts of CheY and only spin their motors CW. We find that the torque decreases linearly with speed, a result remarkably different from that for CCW rotation. We obtain similar results for wild-type cells by reexamining data collected in previous work. We speculate that CCW rotation might be optimized for runs, with higher speeds increasing the ability of cells to sense spatial gradients, whereas CW rotation might be optimized for tumbles, where the object is to change cell trajectories. But why a linear torque–speed relationship might be optimum for the latter purpose we do not know. PMID:20615986

Relationship between speed and EEG activity during imagined and executed hand movements

NASA Astrophysics Data System (ADS)

Yuan, Han; Perdoni, Christopher; He, Bin

2010-04-01

The relationship between primary motor cortex and movement kinematics has been shown in nonhuman primate studies of hand reaching or drawing tasks. Studies have demonstrated that the neural activities accompanying or immediately preceding the movement encode the direction, speed and other information. Here we investigated the relationship between the kinematics of imagined and actual hand movement, i.e. the clenching speed, and the EEG activity in ten human subjects. Study participants were asked to perform and imagine clenching of the left hand and right hand at various speeds. The EEG activity in the alpha (8-12 Hz) and beta (18-28 Hz) frequency bands were found to be linearly correlated with the speed of imagery clenching. Similar parametric modulation was also found during the execution of hand movements. A single equation relating the EEG activity to the speed and the hand (left versus right) was developed. This equation, which contained a linear independent combination of the two parameters, described the time-varying neural activity during the tasks. Based on the model, a regression approach was developed to decode the two parameters from the multiple-channel EEG signals. We demonstrated the continuous decoding of dynamic hand and speed information of the imagined clenching. In particular, the time-varying clenching speed was reconstructed in a bell-shaped profile. Our findings suggest an application to providing continuous and complex control of noninvasive brain-computer interface for movement-impaired paralytics.

Accuracy assessment of the linear Poisson-Boltzmann equation and reparametrization of the OBC generalized Born model for nucleic acids and nucleic acid-protein complexes.

PubMed

Fogolari, Federico; Corazza, Alessandra; Esposito, Gennaro

2015-04-05

The generalized Born model in the Onufriev, Bashford, and Case (Onufriev et al., Proteins: Struct Funct Genet 2004, 55, 383) implementation has emerged as one of the best compromises between accuracy and speed of computation. For simulations of nucleic acids, however, a number of issues should be addressed: (1) the generalized Born model is based on a linear model and the linearization of the reference Poisson-Boltmann equation may be questioned for highly charged systems as nucleic acids; (2) although much attention has been given to potentials, solvation forces could be much less sensitive to linearization than the potentials; and (3) the accuracy of the Onufriev-Bashford-Case (OBC) model for nucleic acids depends on fine tuning of parameters. Here, we show that the linearization of the Poisson Boltzmann equation has mild effects on computed forces, and that with optimal choice of the OBC model parameters, solvation forces, essential for molecular dynamics simulations, agree well with those computed using the reference Poisson-Boltzmann model. © 2015 Wiley Periodicals, Inc.

An Improved Wind Speed Retrieval Algorithm For The CYGNSS Mission

NASA Astrophysics Data System (ADS)

Ruf, C. S.; Clarizia, M. P.

2015-12-01

The NASA spaceborne Cyclone Global Navigation Satellite System (CYGNSS) mission is a constellation of 8 microsatellites focused on tropical cyclone (TC) inner core process studies. CYGNSS will be launched in October 2016, and will use GPS-Reflectometry (GPS-R) to measure ocean surface wind speed in all precipitating conditions, and with sufficient frequency to resolve genesis and rapid intensification. Here we present a modified and improved version of the current baseline Level 2 (L2) wind speed retrieval algorithm designed for CYGNSS. An overview of the current approach is first presented, which makes use of two different observables computed from 1-second Level 1b (L1b) delay-Doppler Maps (DDMs) of radar cross section. The first observable, the Delay-Doppler Map Average (DDMA), is the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second, the Leading Edge Slope (LES), is the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of time delays and Doppler frequencies to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km. In the current approach, the relationship between the observable value and the surface winds is described by an empirical Geophysical Model Function (GMF) that is characterized by a very high slope in the high wind regime, for both DDMA and LES observables, causing large errors in the retrieval at high winds. A simple mathematical modification of these observables is proposed, which linearizes the relationship between ocean surface roughness and the observables. This significantly reduces the non-linearity present in the GMF that relate the observables to the wind speed, and reduces the root-mean square error between true and retrieved winds, particularly in the high wind regime. The modified retrieval algorithm is tested using GPS-R synthetic data simulated using an End-to-End Simulator (E2ES) developed for CYGNSS, and it is then applied to GPS-R data from the TechDemoSat-1 (TDS-1) GPS-R experiment. An analysis of the algorithm performances for both synthetic and real data is illustrated.

Wear behaviors of pure aluminum and extruded aluminum alloy (AA2024-T4) under variable vertical loads and linear speeds

NASA Astrophysics Data System (ADS)

Jung, Jeki; Oak, Jeong-Jung; Kim, Yong-Hwan; Cho, Yi Je; Park, Yong Ho

2017-11-01

The aim of this study was to investigate the transition of wear behavior for pure aluminum and extruded aluminum alloy 2024-T4 (AA2024-T4). The wear test was carried using a ball-on-disc wear testing machine at various vertical loads and linear speeds. The transition of wear behaviors was analyzed based on the microstructure, wear tracks, wear cross-section, and wear debris. The critical wear rates for each material are occurred at lower linear speed for each vertical load. The transition of wear behavior was observed in which abrasion wears with the generation of an oxide layer, fracture of oxide layer, adhesion wear, severe adhesion wear, and the generation of seizure occurred in sequence. In case of the pure aluminum, the change of wear debris occurred in the order of blocky, flake, and needle-like debris. Cutting chip, flake-like, and coarse flake-like debris was occurred in sequence for the extruded AA2024-T4. The transition in the wear behavior of extruded AA2024-T4 occurred slower than in pure aluminum.

Lateral Stability Simulation of a Rail Truck on Roller Rig

NASA Astrophysics Data System (ADS)

Dukkipati, Rao V.

The development of experimental facilities for rail vehicle testing is being complemented by analytic studies. The purpose of this effort has been to gain insight into the dynamics of rail vehicles in order to guide development of the Roller Rigs and to establish an analytic framework for the design and interpretation of tests to be conducted on Roller Rigs. The work described here represents initial efforts towards meeting these objectives. Generic linear models were developed of a freight car (with a characteristic North American three-piece truck) on tangent track. The models were developed using the generalized multi body dynamics software MEDYNA. Predictions were made of the theoretical linear model hunting (lateral stability) characteristics of the freight car, i. e., the critical speeds and frequencies, for five different configurations: (a) freight car on track, (b) the freight car's front truck on the roller stand and its rear truck on track, (c) freight car on the roller rig, (d) a single truck on track, and (e) single truck on the roller stand. These were compared with the Association of American Railroads' field test data for an 80-ton hopper car equipped with A-3 ride control trucks. Agreement was reached among all the analytical models, with all models indicating a range of hunting speeds of 2% from the highest to lowest. The largest discrepancy, approximately 6%, was indicated between the models and the field test data. Parametric study results using linear model of freight truck on the roller rig show that (a) increasing roller radius increases critical speed (b) increasing the wheel initial cone angle will decrease the hunting speed (c) increasing the roller cant increases hunting speed (d) decrowning of the wheelset on the rollers will not effect the hunting speed but induces longitudinal destabilizing horizontal forces at the contact and (e) lozenging of wheelset on the rollers induces a yaw moment and the hunting speed decreases with increasing wheelset yaw angle.

Sonic boom predictions using a modified Euler code

NASA Technical Reports Server (NTRS)

Siclari, Michael J.

1992-01-01

The environmental impact of a next generation fleet of high-speed civil transports (HSCT) is of great concern in the evaluation of the commercial development of such a transport. One of the potential environmental impacts of a high speed civilian transport is the sonic boom generated by the aircraft and its effects on the population, wildlife, and structures in the vicinity of its flight path. If an HSCT aircraft is restricted from flying overland routes due to excessive booms, the commercial feasibility of such a venture may be questionable. NASA has taken the lead in evaluating and resolving the issues surrounding the development of a high speed civilian transport through its High-Speed Research Program (HSRP). The present paper discusses the usage of a Computational Fluid Dynamics (CFD) nonlinear code in predicting the pressure signature and ultimately the sonic boom generated by a high speed civilian transport. NASA had designed, built, and wind tunnel tested two low boom configurations for flight at Mach 2 and Mach 3. Experimental data was taken at several distances from these models up to a body length from the axis of the aircraft. The near field experimental data serves as a test bed for computational fluid dynamic codes in evaluating their accuracy and reliability for predicting the behavior of future HSCT designs. Sonic boom prediction methodology exists which is based on modified linear theory. These methods can be used reliably if near field signatures are available at distances from the aircraft where nonlinear and three dimensional effects have diminished in importance. Up to the present time, the only reliable method to obtain this data was via the wind tunnel with costly model construction and testing. It is the intent of the present paper to apply a modified three dimensional Euler code to predict the near field signatures of the two low boom configurations recently tested by NASA.

Impacts of freeway traffic conditions on in-vehicle exposure to ultrafine particulate matter

NASA Astrophysics Data System (ADS)

Bigazzi, Alexander Y.; Figliozzi, Miguel A.

2012-12-01

There is evidence of adverse health impacts from human exposure to traffic-related ultrafine particulate matter pollution. As more commuters are spending a significant portion of their daily routine inside vehicles, it is increasingly relevant to study exposure levels to harmful pollutants inside the vehicle microenvironment. This study is one of the first research efforts to combine detailed freeway traffic data (at 20 s intervals) and in-vehicle ultrafine particulate (UFP) exposure data under varying vehicle ventilation conditions. Results show that due to negative correlation between traffic speed and density, traffic states have a small but significant impact on in-vehicle UFP concentrations, highest in high traffic flow-high speed conditions or in high traffic density-low speed conditions. Vehicle cabin barrier effects are the primary determinant of in-vehicle exposure concentrations, providing 15% protection with the windows down, 47% protection with the windows up and the vent open, and 83-90% protection with the windows up and the vent closed (more with the air conditioning on). Unique results from this study include the dominance of ventilation over traffic effects on UFP and the non-linear relationships between traffic variables and UFP concentrations. The results of this research have important implications for exposure modeling and potential exposure mitigation strategies.

Buckling of a beam extruded into highly viscous fluid

NASA Astrophysics Data System (ADS)

Gosselin, F. P.; Neetzow, P.; Paak, M.

2014-11-01

Inspired by microscopic Paramecia which use trichocyst extrusion to propel themselves away from thermal aggression, we propose a macroscopic experiment to study the stability of a slender beam extruded in a highly viscous fluid. Piano wires were extruded axially at constant speed in a tank filled with corn syrup. The force necessary to extrude the wire was measured to increase linearly at first until the compressive viscous force causes the wire to buckle. A numerical model, coupling a lengthening elastica formulation with resistive-force theory, predicts a similar behavior. The model is used to study the dynamics at large time when the beam is highly deformed. It is found that at large time, a large deformation regime exists in which the force necessary to extrude the beam at constant speed becomes constant and length independent. With a proper dimensional analysis, the beam can be shown to buckle at a critical length based on the extrusion speed, the bending rigidity, and the dynamic viscosity of the fluid. Hypothesizing that the trichocysts of Paramecia must be sized to maximize their thrust per unit volume as well as avoid buckling instabilities, we predict that their bending rigidity must be about 3 ×10-9N μ m2 . The verification of this prediction is left for future work.

High-speed extended-term time-domain simulation for online cascading analysis of power system

NASA Astrophysics Data System (ADS)

Fu, Chuan

A high-speed extended-term (HSET) time domain simulator (TDS), intended to become a part of an energy management system (EMS), has been newly developed for use in online extended-term dynamic cascading analysis of power systems. HSET-TDS includes the following attributes for providing situational awareness of high-consequence events: (i) online analysis, including n-1 and n-k events, (ii) ability to simulate both fast and slow dynamics for 1-3 hours in advance, (iii) inclusion of rigorous protection-system modeling, (iv) intelligence for corrective action ID, storage, and fast retrieval, and (v) high-speed execution. Very fast on-line computational capability is the most desired attribute of this simulator. Based on the process of solving algebraic differential equations describing the dynamics of power system, HSET-TDS seeks to develop computational efficiency at each of the following hierarchical levels, (i) hardware, (ii) strategies, (iii) integration methods, (iv) nonlinear solvers, and (v) linear solver libraries. This thesis first describes the Hammer-Hollingsworth 4 (HH4) implicit integration method. Like the trapezoidal rule, HH4 is symmetrically A-Stable but it possesses greater high-order precision (h4 ) than the trapezoidal rule. Such precision enables larger integration steps and therefore improves simulation efficiency for variable step size implementations. This thesis provides the underlying theory on which we advocate use of HH4 over other numerical integration methods for power system time-domain simulation. Second, motivated by the need to perform high speed extended-term time domain simulation (HSET-TDS) for on-line purposes, this thesis presents principles for designing numerical solvers of differential algebraic systems associated with power system time-domain simulation, including DAE construction strategies (Direct Solution Method), integration methods(HH4), nonlinear solvers(Very Dishonest Newton), and linear solvers(SuperLU). We have implemented a design appropriate for HSET-TDS, and we compare it to various solvers, including the commercial grade PSSE program, with respect to computational efficiency and accuracy, using as examples the New England 39 bus system, the expanded 8775 bus system, and PJM 13029 buses system. Third, we have explored a stiffness-decoupling method, intended to be part of parallel design of time domain simulation software for super computers. The stiffness-decoupling method is able to combine the advantages of implicit methods (A-stability) and explicit method(less computation). With the new stiffness detection method proposed herein, the stiffness can be captured. The expanded 975 buses system is used to test simulation efficiency. Finally, several parallel strategies for super computer deployment to simulate power system dynamics are proposed and compared. Design A partitions the task via scale with the stiffness decoupling method, waveform relaxation, and parallel linear solver. Design B partitions the task via the time axis using a highly precise integration method, the Kuntzmann-Butcher Method - order 8 (KB8). The strategy of partitioning events is designed to partition the whole simulation via the time axis through a simulated sequence of cascading events. For all strategies proposed, a strategy of partitioning cascading events is recommended, since the sub-tasks for each processor are totally independent, and therefore minimum communication time is needed.

Three-Minute All-Out Test in Swimming.

PubMed

Tsai, Ming-Chang; Thomas, Scott G

2017-01-01

To validate the 3-minute all-out exercise test (3MT) protocol against the traditional critical-speed (CS) model (CSM) in front-crawl swimming. Ten healthy swimmers or triathletes (mean ± SD age 35.2 ± 10.5 y, height 176.5 ± 5.4 cm, body mass 69.6 ± 8.2 kg) completed 5 tests (3MT, 100m, 200m, 400m, 800m) over 2 wk on separate days. Traditional CS and anaerobic distance capacity (D') were determined for each of the 3 traditional CSMs (linear distance-time, LIN; linear speed/time, INV; nonlinear time-speed, NLIN) from the 4 set-distance time trials. For the 3MT, CS was determined as the mean speed during the final 30 s of the test and D' was estimated as the power-time integral above the CS. Our results indicated no significant difference between the CS estimates determined from the traditional CSM and 3MT except for the INV model (P = .0311). Correlations between traditional CSMs and 3MT were high (r = .95, P < .01) However, D' differed and post hoc analysis indicated that D' estimated from 3MT was significantly lower than LIN (P = .0052) and NLIN (P < .0001). Correlations were weak (r < .55, P > .1). In addition, Bland-Altman plots between the traditional CSMs and 3MT CS estimates showed scattered points above and below the zero line, suggesting there is no consistent bias of one approach versus the other. The 3MT is a valid protocol for swimming to estimate CS. The demonstrated concurrent validity of the 3MT may allow more widespread use of CSMs to evaluate participants and responses to training.

Particle Streak Anemometry: A New Method for Proximal Flow Sensing from Aircraft

NASA Astrophysics Data System (ADS)

Nichols, T. W.

Accurate sensing of relative air flow direction from fixed-wing small unmanned aircraft (sUAS) is challenging with existing multi-hole pitot-static and vane systems. Sub-degree direction accuracy is generally not available on such systems and disturbances to the local flow field, induced by the airframe, introduce an additional error source. An optical imaging approach to make a relative air velocity measurement with high-directional accuracy is presented. Optical methods offer the capability to make a proximal measurement in undisturbed air outside of the local flow field without the need to place sensors on vulnerable probes extended ahead of the aircraft. Current imaging flow analysis techniques for laboratory use rely on relatively thin imaged volumes and sophisticated hardware and intensity thresholding in low-background conditions. A new method is derived and assessed using a particle streak imaging technique that can be implemented with low-cost commercial cameras and illumination systems, and can function in imaged volumes of arbitrary depth with complex background signal. The new technique, referred to as particle streak anemometry (PSA) (to differentiate from particle streak velocimetry which makes a field measurement rather than a single bulk flow measurement) utilizes a modified Canny Edge detection algorithm with a connected component analysis and principle component analysis to detect streak ends in complex imaging conditions. A linear solution for the air velocity direction is then implemented with a random sample consensus (RANSAC) solution approach. A single DOF non-linear, non-convex optimization problem is then solved for the air speed through an iterative approach. The technique was tested through simulation and wind tunnel tests yielding angular accuracies under 0.2 degrees, superior to the performance of existing commercial systems. Air speed error standard deviations varied from 1.6 to 2.2 m/s depending on the techniques of implementation. While air speed sensing is secondary to accurate flow direction measurement, the air speed results were in line with commercial pitot static systems at low speeds.

A Flexible Annular-Array Imaging Platform for Micro-Ultrasound

PubMed Central

Qiu, Weibao; Yu, Yanyan; Chabok, Hamid Reza; Liu, Cheng; Tsang, Fu Keung; Zhou, Qifa; Shung, K. Kirk; Zheng, Hairong; Sun, Lei

2013-01-01

Micro-ultrasound is an invaluable imaging tool for many clinical and preclinical applications requiring high resolution (approximately several tens of micrometers). Imaging systems for micro-ultrasound, including single-element imaging systems and linear-array imaging systems, have been developed extensively in recent years. Single-element systems are cheaper, but linear-array systems give much better image quality at a higher expense. Annular-array-based systems provide a third alternative, striking a balance between image quality and expense. This paper presents the development of a novel programmable and real-time annular-array imaging platform for micro-ultrasound. It supports multi-channel dynamic beamforming techniques for large-depth-of-field imaging. The major image processing algorithms were achieved by a novel field-programmable gate array technology for high speed and flexibility. Real-time imaging was achieved by fast processing algorithms and high-speed data transfer interface. The platform utilizes a printed circuit board scheme incorporating state-of-the-art electronics for compactness and cost effectiveness. Extensive tests including hardware, algorithms, wire phantom, and tissue mimicking phantom measurements were conducted to demonstrate good performance of the platform. The calculated contrast-to-noise ratio (CNR) of the tissue phantom measurements were higher than 1.2 in the range of 3.8 to 8.7 mm imaging depth. The platform supported more than 25 images per second for real-time image acquisition. The depth-of-field had about 2.5-fold improvement compared to single-element transducer imaging. PMID:23287923

A Computationally Efficient Parallel Levenberg-Marquardt Algorithm for Large-Scale Big-Data Inversion

NASA Astrophysics Data System (ADS)

Lin, Y.; O'Malley, D.; Vesselinov, V. V.

2015-12-01

Inverse modeling seeks model parameters given a set of observed state variables. However, for many practical problems due to the facts that the observed data sets are often large and model parameters are often numerous, conventional methods for solving the inverse modeling can be computationally expensive. We have developed a new, computationally-efficient Levenberg-Marquardt method for solving large-scale inverse modeling. Levenberg-Marquardt methods require the solution of a dense linear system of equations which can be prohibitively expensive to compute for large-scale inverse problems. Our novel method projects the original large-scale linear problem down to a Krylov subspace, such that the dimensionality of the measurements can be significantly reduced. Furthermore, instead of solving the linear system for every Levenberg-Marquardt damping parameter, we store the Krylov subspace computed when solving the first damping parameter and recycle it for all the following damping parameters. The efficiency of our new inverse modeling algorithm is significantly improved by using these computational techniques. We apply this new inverse modeling method to invert for a random transitivity field. Our algorithm is fast enough to solve for the distributed model parameters (transitivity) at each computational node in the model domain. The inversion is also aided by the use regularization techniques. The algorithm is coded in Julia and implemented in the MADS computational framework (http://mads.lanl.gov). Julia is an advanced high-level scientific programing language that allows for efficient memory management and utilization of high-performance computational resources. By comparing with a Levenberg-Marquardt method using standard linear inversion techniques, our Levenberg-Marquardt method yields speed-up ratio of 15 in a multi-core computational environment and a speed-up ratio of 45 in a single-core computational environment. Therefore, our new inverse modeling method is a powerful tool for large-scale applications.

A one-dimensional nonlinear problem of thermoelasticity in extended thermodynamics

NASA Astrophysics Data System (ADS)

Rawy, E. K.

2018-06-01

We solve a nonlinear, one-dimensional initial boundary-value problem of thermoelasticity in generalized thermodynamics. A Cattaneo-type evolution equation for the heat flux is used, which differs from the one used extensively in the literature. The hyperbolic nature of the associated linear system is clarified through a study of the characteristic curves. Progressive wave solutions with two finite speeds are noted. A numerical treatment is presented for the nonlinear system using a three-step, quasi-linearization, iterative finite-difference scheme for which the linear system of equations is the initial step in the iteration. The obtained results are discussed in detail. They clearly show the hyperbolic nature of the system, and may be of interest in investigating thermoelastic materials, not only at low temperatures, but also during high temperature processes involving rapid changes in temperature as in laser treatment of surfaces.

Nonlinear MHD study on the influence of E×B flow in QH-mode plasma of DIII-D

NASA Astrophysics Data System (ADS)

Liu, Feng; Huijsmans, Guido; Loarte, Alberto; Garofalo, Andrea; Solomon, Wayne; Nkonga, Boniface; Hoelzl, Matthias

2017-10-01

In QH-mode experiments with zero-net NBI torque show that there remains a finite E×B rotation in the pedestal region implying that a minimum E×B flow or flow shear is required for the plasma to develop the Edge Harmonic Oscillation (EHO), which is a saturated KPM (kink-peeling mode) characteristic of the QH-mode. To understand the roles of E×B flow and its shear in the saturation of KPMs, non-linear MHD simulations of DIII-D QH-mode plasmas including toroidal mode numbers n = 0 to 10 with different E×B rotation speed have been performed. These simulation show that ExB rotation strongly stabilizes high-n modes but destabilizes low-n modes (particularly the n =2 mode) in the linear growth phase, which is consistent experimental observations and previous linear MHD modelling. US DOE under DE-FC02-04ER54698.

Magnetic forces in high-Tc superconducting bearings

NASA Technical Reports Server (NTRS)

Moon, F. C.

1991-01-01

In September 1987, researchers at Cornell levitated a small rotor on superconducting bearings at 10,000 rpm. In April 1989, a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu307. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

Magnetic Launch Assist Experimental Track

NASA Technical Reports Server (NTRS)

1999-01-01

In this photograph, a futuristic spacecraft model sits atop a carrier on the Magnetic Launch Assist System, formerly known as the Magnetic Levitation (MagLev) System, experimental track at the Marshall Space Flight Center (MSFC). Engineers at MSFC have developed and tested Magnetic Launch Assist technologies that would use magnetic fields to levitate and accelerate a vehicle along a track at very high speeds. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, a Magnetic Launch Assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide, and about 1.5-feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

Research Technology

NASA Image and Video Library

2001-03-01

Engineers at the Marshall Space Flight Center (MSFC) have been testing Magnetic Launch Assist Systems, formerly known as Magnetic Levitation (MagLev) technologies. To launch spacecraft into orbit, a Magnetic Launch Assist system would use magnetic fields to levitate and accelerate a vehicle along a track at a very high speed. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, the launch-assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This photograph shows a subscale model of an airplane running on the experimental track at MSFC during the demonstration test. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide, and about 1.5- feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

Research Technology

NASA Image and Video Library

1999-10-01

In this photograph, a futuristic spacecraft model sits atop a carrier on the Magnetic Launch Assist System, formerly known as the Magnetic Levitation (MagLev) System, experimental track at the Marshall Space Flight Center (MSFC). Engineers at MSFC have developed and tested Magnetic Launch Assist technologies that would use magnetic fields to levitate and accelerate a vehicle along a track at very high speeds. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, a Magnetic Launch Assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide, and about 1.5-feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

A Linear Relationship between Crystal Size and Fragment Binding Time Observed Crystallographically: Implications for Fragment Library Screening Using Acoustic Droplet Ejection

PubMed Central

Birone, Claire; Brown, Maria; Hernandez, Jesus; Neff, Sherry; Williams, Daniel; Allaire, Marc; Orville, Allen M.; Sweet, Robert M.; Soares, Alexei S.

2014-01-01

High throughput screening technologies such as acoustic droplet ejection (ADE) greatly increase the rate at which X-ray diffraction data can be acquired from crystals. One promising high throughput screening application of ADE is to rapidly combine protein crystals with fragment libraries. In this approach, each fragment soaks into a protein crystal either directly on data collection media or on a moving conveyor belt which then delivers the crystals to the X-ray beam. By simultaneously handling multiple crystals combined with fragment specimens, these techniques relax the automounter duty-cycle bottleneck that currently prevents optimal exploitation of third generation synchrotrons. Two factors limit the speed and scope of projects that are suitable for fragment screening using techniques such as ADE. Firstly, in applications where the high throughput screening apparatus is located inside the X-ray station (such as the conveyor belt system described above), the speed of data acquisition is limited by the time required for each fragment to soak into its protein crystal. Secondly, in applications where crystals are combined with fragments directly on data acquisition media (including both of the ADE methods described above), the maximum time that fragments have to soak into crystals is limited by evaporative dehydration of the protein crystals during the fragment soak. Here we demonstrate that both of these problems can be minimized by using small crystals, because the soak time required for a fragment hit to attain high occupancy depends approximately linearly on crystal size. PMID:24988328

A linear relationship between crystal size and fragment binding time observed crystallographically: implications for fragment library screening using acoustic droplet ejection.

PubMed

Cole, Krystal; Roessler, Christian G; Mulé, Elizabeth A; Benson-Xu, Emma J; Mullen, Jeffrey D; Le, Benjamin A; Tieman, Alanna M; Birone, Claire; Brown, Maria; Hernandez, Jesus; Neff, Sherry; Williams, Daniel; Allaire, Marc; Orville, Allen M; Sweet, Robert M; Soares, Alexei S

2014-01-01

High throughput screening technologies such as acoustic droplet ejection (ADE) greatly increase the rate at which X-ray diffraction data can be acquired from crystals. One promising high throughput screening application of ADE is to rapidly combine protein crystals with fragment libraries. In this approach, each fragment soaks into a protein crystal either directly on data collection media or on a moving conveyor belt which then delivers the crystals to the X-ray beam. By simultaneously handling multiple crystals combined with fragment specimens, these techniques relax the automounter duty-cycle bottleneck that currently prevents optimal exploitation of third generation synchrotrons. Two factors limit the speed and scope of projects that are suitable for fragment screening using techniques such as ADE. Firstly, in applications where the high throughput screening apparatus is located inside the X-ray station (such as the conveyor belt system described above), the speed of data acquisition is limited by the time required for each fragment to soak into its protein crystal. Secondly, in applications where crystals are combined with fragments directly on data acquisition media (including both of the ADE methods described above), the maximum time that fragments have to soak into crystals is limited by evaporative dehydration of the protein crystals during the fragment soak. Here we demonstrate that both of these problems can be minimized by using small crystals, because the soak time required for a fragment hit to attain high occupancy depends approximately linearly on crystal size.

Accelerate quasi Monte Carlo method for solving systems of linear algebraic equations through shared memory

NASA Astrophysics Data System (ADS)

Lai, Siyan; Xu, Ying; Shao, Bo; Guo, Menghan; Lin, Xiaola

2017-04-01

In this paper we study on Monte Carlo method for solving systems of linear algebraic equations (SLAE) based on shared memory. Former research demostrated that GPU can effectively speed up the computations of this issue. Our purpose is to optimize Monte Carlo method simulation on GPUmemoryachritecture specifically. Random numbers are organized to storein shared memory, which aims to accelerate the parallel algorithm. Bank conflicts can be avoided by our Collaborative Thread Arrays(CTA)scheme. The results of experiments show that the shared memory based strategy can speed up the computaions over than 3X at most.

Spatial organization and Synchronization in collective swimming of Hemigrammus bleheri

NASA Astrophysics Data System (ADS)

Ashraf, Intesaaf; Ha, Thanh-Tung; Godoy-Diana, Ramiro; Thiria, Benjamin; Halloy, Jose; Collignon, Bertrand; Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH) Team; Laboratoire Interdisciplinaire des Energies de Demain (LIED) Team

2016-11-01

In this work, we study the collective swimming of Hemigrammus bleheri fish using experiments in a shallow swimming channel. We use high-speed video recordings to track the midline kinematics and the spatial organization of fish pairs and triads. Synchronizations are characterized by observance of "out of phase" and "in phase" configurations. We show that the synchronization state is highly correlated to swimming speed. The increase in synchronization led to efficient swimming based on Strouhal number. In case of fish pairs, the collective swimming is 2D and the spatial organization is characterized by two characteristic lengths: the lateral and longitudinal separation distances between fish pairs.For fish triads, different swimming patterns or configurations are observed having three dimensional structures. We performed 3D kinematic analysis by employing 3D reconstruction using the Direct Linear Transformation (DLT). We show that fish still keep their nearest neighbor distance (NND) constant irrespective of swimming speeds and configuration. We also point out characteristic angles between neighbors, hence imposing preferred patterns. At last we will give some perspectives on spatial organization for larger population. Sorbonne Paris City College of Doctoral Schools. European Union Information and Communication Technologies project ASSISIbf, FP7-ICT-FET-601074.

Speed ratio but cabin temperature positively correlated with increased heart rates among professional drivers during car races.

PubMed

Yanagida, Ryo; Takahashi, Kiichi; Miura, Masaru; Nomura, Masahiro; Ogawa, Yojiro; Aoki, Ken; Iwasaki, Ken-Ichi

2016-11-01

The present study measures heart rate (HR) on a number of professional race-car drivers during actual car races through annual seasons to test hypotheses that faster relative speed and higher cabin temperature would induce higher HR. Heart rates in fifteen male drivers (31.2 ± 5.5 years old) were obtained by chest-strap sensors during official-professional 13 races. Average HR was calculated while the driver was racing from the start to the end of each race. The average HR during races was 164.5 ± 15.1 beats min -1 and the average amount of time each driver spent driving per race was 54.2 ± 13.7 min. Average HR significantly and positively correlated with mean speed ratio (P < 0.001), but not with the average cabin temperatures (P = 0.533, range 25.6-41.8 °C) by the multiple linear regression analysis. Both average HR and mean speed ratio were significantly lower under wet, than dry conditions (151.9 ± 16.5 vs. 168.3 ± 12.5 beats min -1 , 86.9 ± 4.4 vs. 93.4 ± 1.5 %). The cardiovascular system of drivers is considerably stressed at extremely high HR. This high average HR positively correlated with mean speed ratio, suggesting that faster driving speed would induce greater cardiovascular stress to professional drivers during actual races. However, contrary to our hypothesis, cabin temperature was not significantly correlated with average HR. It is speculated that direct body cooling systems used in this professional race category work well against increases in HR by thermal stress under the temperature range found herein.

Potential impacts of climate variability on respiratory morbidity in children, infants, and adults.

PubMed

Souza, Amaury de; Fernandes, Widinei Alves; Pavão, Hamilton Germano; Lastoria, Giancarlo; Albrez, Edilce do Amaral

2012-01-01

To determine whether climate variability influences the number of hospitalizations for respiratory diseases in infants, children, and adults in the city of Campo Grande, Brazil. We used daily data on admissions for respiratory diseases, precipitation, air temperature, humidity, and wind speed for the 2004-2008 period. We calculated the thermal comfort index, effective temperature, and effective temperature with wind speed (wind-chill or heat index) using the meteorological data obtained. Generalized linear models, with Poisson multiple regression, were used in order to predict hospitalizations for respiratory disease. The variables studied were (collectively) found to show relatively high correlation coefficients in relation to hospital admission for pneumonia in children (R² = 68.4%), infants (R² = 71.8%), and adults (R² = 81.8%). Our results indicate a quantitative risk for an increase in the number of hospitalizations of children, infants, and adults, according to the increase or decrease in temperature, humidity, precipitation, wind speed, and thermal comfort index in the city under study.

Effects of vehicle power on passenger vehicle speeds.

PubMed

McCartt, Anne T; Hu, Wen

2017-07-04

During the past 2 decades, there have been large increases in mean horsepower and the mean horsepower-to-vehicle weight ratio for all types of new passenger vehicles in the United States. This study examined the relationship between travel speeds and vehicle power, defined as horsepower per 100 pounds of vehicle weight. Speed cameras measured travel speeds and photographed license plates and drivers of passenger vehicles traveling on roadways in Northern Virginia during daytime off-peak hours in spring 2013. The driver licensing agencies in the District of Columbia, Maryland, and Virginia provided vehicle information numbers (VINs) by matching license plate numbers with vehicle registration records and provided the age, gender, and ZIP code of the registered owner(s). VINs were decoded to obtain the curb weight and horsepower of vehicles. The study focused on 26,659 observed vehicles for which information on horsepower was available and the observed age and gender of drivers matched vehicle registration records. Log-linear regression estimated the effects of vehicle power on mean travel speeds, and logistic regression estimated the effects of vehicle power on the likelihood of a vehicle traveling over the speed limit and more than 10 mph over the limit. After controlling for driver characteristics, speed limit, vehicle type, and traffic volume, a 1-unit increase in vehicle power was associated with a 0.7% increase in mean speed, a 2.7% increase in the likelihood of a vehicle exceeding the speed limit by any amount, and an 11.6% increase in the likelihood of a vehicle exceeding the limit by 10 mph. All of these increases were highly significant. Speeding persists as a major factor in crashes in the United States. There are indications that travel speeds have increased in recent years. The current findings suggest the trend toward substantially more powerful vehicles may be contributing to higher speeds. Given the strong association between travel speed and crash risk and crash severity, this is cause for concern.

Speed-dependent collision effects on radar back-scattering from the ionosphere

NASA Technical Reports Server (NTRS)

Theimer, O.

1981-01-01

A computer code to accurately compute the fluctuation spectrum for linearly speed dependent collision frequencies was developed. The effect of ignoring the speed dependence on the estimates of ionospheric parameters was determined. It is shown that disagreements between the rocket and the incoherent scatter estimates could be partially resolved if the correct speed dependence of the i-n collision frequency is not ignored. This problem is also relevant to the study of ionospheric irregularities in the auroral E-region and their effects on the radio communication with satellites.

Speed of sound as a function of temperature for ultrasonic propagation in soybean oil

NASA Astrophysics Data System (ADS)

Oliveira, P. A.; Silva, R. M. B.; Morais, G. C.; Alvarenga, A. V.; Costa-Félix, R. P. B.

2016-07-01

Ultrasound has been used for characterization of liquid in several productive sectors and research. This work presents the studied about the behavior of the speed of sound in soybean oil with increasing temperature. The pulse echo technique allowed observing that the speed of sound decreases linearly with increasing temperature in the range 20 to 50 °C at 1 MHz. As result, a characteristic function capable to reproduce the speed of sound behavior in soybean oil, as a function of temperature was established, with the respective measurement uncertainty.

Cryogenic Scan Mechanism for Fourier Transform Spectrometer

NASA Technical Reports Server (NTRS)

Brasunas, John C.; Francis, John L.

2011-01-01

A compact and lightweight mechanism has been developed to accurately move a Fourier transform spectrometer (FTS) scan mirror (a cube corner) in a near-linear fashion with near constant speed at cryogenic temperatures. This innovation includes a slide mechanism to restrict motion to one dimension, an actuator to drive the motion, and a linear velocity transducer (LVT) to measure the speed. The cube corner mirror is double-passed in one arm of the FTS; double-passing is required to compensate for optical beam shear resulting from tilting of the moving cube corner. The slide, actuator, and LVT are off-the-shelf components that are capable of cryogenic vacuum operation. The actuator drives the slide for the required travel of 2.5 cm. The LVT measures translation speed. A proportional feedback loop compares the LVT voltage with the set voltage (speed) to derive an error signal to drive the actuator and achieve near constant speed. When the end of the scan is reached, a personal computer reverses the set voltage. The actuator and LVT have no moving parts in contact, and have magnetic properties consistent with cryogenic operation. The unlubricated slide restricts motion to linear travel, using crossed roller bearings consistent with 100-million- stroke operation. The mechanism tilts several arc seconds during transport of the FTS mirror, which would compromise optical fringe efficiency when using a flat mirror. Consequently, a cube corner mirror is used, which converts a tilt into a shear. The sheared beam strikes (at normal incidence) a flat mirror at the end of the FTS arm with the moving mechanism, thereby returning upon itself and compensating for the shear

Rotating elastic string loops in flat and black hole spacetimes: stability, cosmic censorship and the Penrose process

NASA Astrophysics Data System (ADS)

Natário, José; Queimada, Leonel; Vicente, Rodrigo

2018-04-01

We rederive the equations of motion for relativistic strings, that is, one-dimensional elastic bodies whose internal energy depends only on their stretching, and use them to study circular string loops rotating in the equatorial plane of flat and black hole spacetimes. We start by obtaining the conditions for equilibrium, and find that: (i) if the string’s longitudinal speed of sound does not exceed the speed of light then its radius when rotating in Minkowski’s spacetime is always larger than its radius when at rest; (ii) in Minkowski’s spacetime, equilibria are linearly stable for rotation speeds below a certain threshold, higher than the string’s longitudinal speed of sound, and linearly unstable for some rotation speeds above it; (iii) equilibria are always linearly unstable in Schwarzschild’s spacetime. Moreover, we study interactions of a rotating string loop with a Kerr black hole, namely in the context of the weak cosmic censorship conjecture and the Penrose process. We find that: (i) elastic string loops that satisfy the null energy condition cannot overspin extremal black holes; (ii) elastic string loops that satisfy the dominant energy condition cannot increase the maximum efficiency of the usual particle Penrose process; (iii) if the dominant energy condition (but not the weak energy condition) is violated then the efficiency can be increased. This last result hints at the interesting possibility that the dominant energy condition may underlie the well known upper bounds for the efficiencies of energy extraction processes (including, for example, superradiance).

Sparse distributed memory: understanding the speed and robustness of expert memory

PubMed Central

Brogliato, Marcelo S.; Chada, Daniel M.; Linhares, Alexandre

2014-01-01

How can experts, sometimes in exacting detail, almost immediately and very precisely recall memory items from a vast repertoire? The problem in which we will be interested concerns models of theoretical neuroscience that could explain the speed and robustness of an expert's recollection. The approach is based on Sparse Distributed Memory, which has been shown to be plausible, both in a neuroscientific and in a psychological manner, in a number of ways. A crucial characteristic concerns the limits of human recollection, the “tip-of-tongue” memory event—which is found at a non-linearity in the model. We expand the theoretical framework, deriving an optimization formula to solve this non-linearity. Numerical results demonstrate how the higher frequency of rehearsal, through work or study, immediately increases the robustness and speed associated with expert memory. PMID:24808842

Are Individual Differences in Reading Speed Related to Extrafoveal Visual Acuity and Crowding?

PubMed Central

Frömer, Romy; Dimigen, Olaf; Niefind, Florian; Krause, Niels; Kliegl, Reinhold; Sommer, Werner

2015-01-01

Readers differ considerably in their speed of self-paced reading. One factor known to influence fixation durations in reading is the preprocessing of words in parafoveal vision. Here we investigated whether individual differences in reading speed or the amount of information extracted from upcoming words (the preview benefit) can be explained by basic differences in extrafoveal vision—i.e., the ability to recognize peripheral letters with or without the presence of flanking letters. Forty participants were given an adaptive test to determine their eccentricity thresholds for the identification of letters presented either in isolation (extrafoveal acuity) or flanked by other letters (crowded letter recognition). In a separate eye-tracking experiment, the same participants read lists of words from left to right, while the preview of the upcoming words was manipulated with the gaze-contingent moving window technique. Relationships between dependent measures were analyzed on the observational level and with linear mixed models. We obtained highly reliable estimates both for extrafoveal letter identification (acuity and crowding) and measures of reading speed (overall reading speed, size of preview benefit). Reading speed was higher in participants with larger uncrowded windows. However, the strength of this relationship was moderate and it was only observed if other sources of variance in reading speed (e.g., the occurrence of regressive saccades) were eliminated. Moreover, the size of the preview benefit—an important factor in normal reading—was larger in participants with better extrafoveal acuity. Together, these results indicate a significant albeit moderate contribution of extrafoveal vision to individual differences in reading speed. PMID:25789812

Improving Sensitivity to Detect Mild Cognitive Impairment: Cognitive Load Dual-Task Gait Speed Assessment.

PubMed

MacAulay, Rebecca K; Wagner, Mark T; Szeles, Dana; Milano, Nicholas J

2017-07-01

Longitudinal research indicates that cognitive load dual-task gait assessment is predictive of cognitive decline and thus might provide a sensitive measure to screen for mild cognitive impairment (MCI). However, research among older adults being clinically evaluated for cognitive concerns, a defining feature of MCI, is lacking. The present study investigated the effect of performing a cognitive task on normal walking speed in patients presenting to a memory clinic with cognitive complaints. Sixty-one patients with a mean age of 68 years underwent comprehensive neuropsychological testing, clinical interview, and gait speed (simple- and dual-task conditions) assessments. Thirty-four of the 61 patients met criteria for MCI. Repeated measure analyses of covariance revealed that greater age and MCI both significantly associated with slower gait speed, ps<.05. Follow-up analysis indicated that the MCI group had significantly slower dual-task gait speed but did not differ in simple-gait speed. Multivariate linear regression across groups found that executive attention performance accounted for 27.4% of the variance in dual-task gait speed beyond relevant demographic and health risk factors. The present study increases the external validity of dual-task gait assessment of MCI. Differences in dual-task gait speed appears to be largely attributable to executive attention processes. These findings have clinical implications as they demonstrate expected patterns of gait-brain behavior relationships in response to a cognitive dual task within a clinically representative population. Cognitive load dual-task gait assessment may provide a cost efficient and sensitive measure to detect older adults at high risk of a dementia disorder. (JINS, 2017, 23, 493-501).

Perceived Shrinkage of Motion Paths

ERIC Educational Resources Information Center

Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

2009-01-01

We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require…

Protein structural similarity search by Ramachandran codes

PubMed Central

Lo, Wei-Cheng; Huang, Po-Jung; Chang, Chih-Hung; Lyu, Ping-Chiang

2007-01-01

Background Protein structural data has increased exponentially, such that fast and accurate tools are necessary to access structure similarity search. To improve the search speed, several methods have been designed to reduce three-dimensional protein structures to one-dimensional text strings that are then analyzed by traditional sequence alignment methods; however, the accuracy is usually sacrificed and the speed is still unable to match sequence similarity search tools. Here, we aimed to improve the linear encoding methodology and develop efficient search tools that can rapidly retrieve structural homologs from large protein databases. Results We propose a new linear encoding method, SARST (Structural similarity search Aided by Ramachandran Sequential Transformation). SARST transforms protein structures into text strings through a Ramachandran map organized by nearest-neighbor clustering and uses a regenerative approach to produce substitution matrices. Then, classical sequence similarity search methods can be applied to the structural similarity search. Its accuracy is similar to Combinatorial Extension (CE) and works over 243,000 times faster, searching 34,000 proteins in 0.34 sec with a 3.2-GHz CPU. SARST provides statistically meaningful expectation values to assess the retrieved information. It has been implemented into a web service and a stand-alone Java program that is able to run on many different platforms. Conclusion As a database search method, SARST can rapidly distinguish high from low similarities and efficiently retrieve homologous structures. It demonstrates that the easily accessible linear encoding methodology has the potential to serve as a foundation for efficient protein structural similarity search tools. These search tools are supposed applicable to automated and high-throughput functional annotations or predictions for the ever increasing number of published protein structures in this post-genomic era. PMID:17716377

Ultra High Resolution Linear Ion Trap Orbitrap Mass Spectrometer (Orbitrap Elite) Facilitates Top Down LC MS/MS and Versatile Peptide Fragmentation Modes*

PubMed Central

Michalski, Annette; Damoc, Eugen; Lange, Oliver; Denisov, Eduard; Nolting, Dirk; Müller, Mathias; Viner, Rosa; Schwartz, Jae; Remes, Philip; Belford, Michael; Dunyach, Jean-Jacques; Cox, Juergen; Horning, Stevan; Mann, Matthias; Makarov, Alexander

2012-01-01

Although only a few years old, the combination of a linear ion trap with an Orbitrap analyzer has become one of the standard mass spectrometers to characterize proteins and proteomes. Here we describe a novel version of this instrument family, the Orbitrap Elite, which is improved in three main areas. The ion transfer optics has an ion path that blocks the line of sight to achieve more robust operation. The tandem MS acquisition speed of the dual cell linear ion trap now exceeds 12 Hz. Most importantly, the resolving power of the Orbitrap analyzer has been increased twofold for the same transient length by employing a compact, high-field Orbitrap analyzer that almost doubles the observed frequencies. An enhanced Fourier Transform algorithm—incorporating phase information—further doubles the resolving power to 240,000 at m/z 400 for a 768 ms transient. For top-down experiments, we combine a survey scan with a selected ion monitoring scan of the charge state of the protein to be fragmented and with several HCD microscans. Despite the 120,000 resolving power for SIM and HCD scans, the total cycle time is within several seconds and therefore suitable for liquid chromatography tandem MS. For bottom-up proteomics, we combined survey scans at 240,000 resolving power with data-dependent collision-induced dissociation of the 20 most abundant precursors in a total cycle time of 2.5 s—increasing protein identifications in complex mixtures by about 30%. The speed of the Orbitrap Elite furthermore allows scan modes in which complementary dissociation mechanisms are routinely obtained of all fragmented peptides. PMID:22159718

Sperm kinematic, head morphometric and kinetic-morphometric subpopulations in the blue fox (Alopex lagopus).

PubMed

Soler, Carles; Contell, Jesús; Bori, Lorena; Sancho, María; García-Molina, Almudena; Valverde, Anthony; Segarvall, Jan

2017-01-01

This work provides information on the blue fox ejaculated sperm quality needed for seminal dose calculations. Twenty semen samples, obtained by masturbation, were analyzed for kinematic and morphometric parameters by using CASA-Mot and CASA-Morph system and principal component (PC) analysis. For motility, eight kinematic parameters were evaluated, which were reduced to PC1, related to linear variables, and PC2, related to oscillatory movement. The whole population was divided into three independent subpopulations: SP1, fast cells with linear movement; SP2, slow cells and nonoscillatory motility; and SP3, medium speed cells and oscillatory movement. In almost all cases, the subpopulation distribution by animal was significantly different. Head morphology analysis generated four size and four shape parameters, which were reduced to PC1, related to size, and PC2, related to shape of the cells. Three morphometric subpopulations existed: SP1: large oval cells; SP2: medium size elongated cells; and SP3: small and short cells. The subpopulation distribution differed between animals. Combining the kinematic and morphometric datasets produced PC1, related to morphometric parameters, and PC2, related to kinematics, which generated four sperm subpopulations - SP1: high oscillatory motility, large and short heads; SP2: medium velocity with small and short heads; SP3: slow motion small and elongated cells; and SP4: high linear speed and large elongated cells. Subpopulation distribution was different in all animals. The establishment of sperm subpopulations from kinematic, morphometric, and combined variables not only improves the well-defined fox semen characteristics and offers a good conceptual basis for fertility and sperm preservation techniques in this species, but also opens the door to use this approach in other species, included humans.

Sperm kinematic, head morphometric and kinetic-morphometric subpopulations in the blue fox (Alopex lagopus)

PubMed Central

Soler, Carles; Contell, Jesús; Bori, Lorena; Sancho, María; García-Molina, Almudena; Valverde, Anthony; Segarvall, Jan

2017-01-01

This work provides information on the blue fox ejaculated sperm quality needed for seminal dose calculations. Twenty semen samples, obtained by masturbation, were analyzed for kinematic and morphometric parameters by using CASA-Mot and CASA-Morph system and principal component (PC) analysis. For motility, eight kinematic parameters were evaluated, which were reduced to PC1, related to linear variables, and PC2, related to oscillatory movement. The whole population was divided into three independent subpopulations: SP1, fast cells with linear movement; SP2, slow cells and nonoscillatory motility; and SP3, medium speed cells and oscillatory movement. In almost all cases, the subpopulation distribution by animal was significantly different. Head morphology analysis generated four size and four shape parameters, which were reduced to PC1, related to size, and PC2, related to shape of the cells. Three morphometric subpopulations existed: SP1: large oval cells; SP2: medium size elongated cells; and SP3: small and short cells. The subpopulation distribution differed between animals. Combining the kinematic and morphometric datasets produced PC1, related to morphometric parameters, and PC2, related to kinematics, which generated four sperm subpopulations – SP1: high oscillatory motility, large and short heads; SP2: medium velocity with small and short heads; SP3: slow motion small and elongated cells; and SP4: high linear speed and large elongated cells. Subpopulation distribution was different in all animals. The establishment of sperm subpopulations from kinematic, morphometric, and combined variables not only improves the well-defined fox semen characteristics and offers a good conceptual basis for fertility and sperm preservation techniques in this species, but also opens the door to use this approach in other species, included humans. PMID:27751987

Improved Saturation Performance in High Speed Waveguide Photodetectors at 1.3 ??sing an Asymmetric InA1GaAs/InGaAsP Structure

NASA Technical Reports Server (NTRS)

Vang, T. A.; Davis, L.; Keo, S.; Forouhar, S. F.

1996-01-01

Waveguide photodetector (WGPD) results have recently been presented demonstrating the very large bandwidth-efficiency product potential of these devices. Improved saturation and linearity characteristics are realized in waveguide p-i-n photodetectors at 1.3 ??y using an asymmetric cladding structure with InA1GaAs/InGaAsP in the anode and InGaAsP in the cathode.

High-Speed Stark Wavelength Tuning of MidIR Interband Cascade Lasers

DTIC Science & Technology

2007-03-15

STARK WAVELENGTH TUNING OF MidIR ICLs 361 Fig. 2. Lasing spectra of the tunable ICL at different bias currents. injection region at before tunneling ...the energy separation between and (and hence the emission wavelength) undergoes a linear Stark shift that depends on the bias current which controls...response Fig. 3. Lasing spectra of the tunable ICL at different bias modulation frequen- cies. Fig. 4. Dependence of the intensity of the Line 2 on bias

The Experimental Study of Rayleigh-Taylor Instability using a Linear Induction Motor Accelerator

NASA Astrophysics Data System (ADS)

Yamashita, Nicholas; Jacobs, Jeffrey

2009-11-01

The experiments to be presented utilize an incompressible system of two stratified miscible liquids of different densities that are accelerated in order to produce the Rayleigh-Taylor instability. Three liquid combinations are used: isopropyl alcohol with water, a calcium nitrate solution or a lithium polytungstate solution, giving Atwood numbers of 0.11, 0.22 and 0.57, respectively. The acceleration required to drive the instability is produced by two high-speed linear induction motors mounted to an 8 m tall drop tower. The motors are mounted in parallel and have an effective acceleration length of 1.7 m and are each capable of producing 15 kN of thrust. The liquid system is contained within a square acrylic tank with inside dimensions 76 x76x184 mm. The tank is mounted to an aluminum plate, which is driven by the motors to create constant accelerations in the range of 1-20 g's, though the potential exists for higher accelerations. Also attached to the plate are a high-speed camera and an LED backlight to provide continuous video of the instability. In addition, an accelerometer is used to provide acceleration measurements during each experiment. Experimental image sequences will be presented which show the development of a random three-dimensional instability from an unforced initial perturbation. Measurements of the mixing zone width will be compared with traditional growth models.

Vibration characteristics of the HPOTP (High-Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)

NASA Technical Reports Server (NTRS)

Childs, D. W.; Moyer, D. S.

1984-01-01

Attention is given to rotor dynamic problems that have been encountered and eliminated in the course of Space Shuttle Main Engine (SSME) development, as well as continuing, subsynchronous problems which are being encountered in the development of a 109-percent power level engine. The basic model for the SSME's High Pressure Oxygen Turbopump (HPOTP) encompasses a structural dynamic model for the rotor and housing, and component models for the liquid and gas seals, turbine clearance excitation forces, and impeller diffuser forces. Linear model results are used to examine the synchronous response and stability characteristics of the HPOTP, with attention to bearing load and stability problems associated with the second critical speed. Differences between linear and nonlinear model results are discussed and explained in terms of simple models. Simulation results indicate that while synchronous bearing loads can be reduced, subsynchronous motion is not eliminated by seal modifications.

Linearized simulation of flow over wind farms and complex terrains.

PubMed

Segalini, Antonio

2017-04-13

The flow over complex terrains and wind farms is estimated here by numerically solving the linearized Navier-Stokes equations. The equations are linearized around the unperturbed incoming wind profile, here assumed logarithmic. The Boussinesq approximation is used to model the Reynolds stress with a prescribed turbulent eddy viscosity profile. Without requiring the boundary-layer approximation, two new linear equations are obtained for the vertical velocity and the wall-normal vorticity, with a reduction in the computational cost by a factor of 8 when compared with a primitive-variables formulation. The presence of terrain elevation is introduced as a vertical coordinate shift, while forestry or wind turbines are included as body forces, without any assumption about the wake structure for the turbines. The model is first validated against some available experiments and simulations, and then a simulation of a wind farm over a Gaussian hill is performed. The speed-up effect of the hill is clearly beneficial in terms of the available momentum upstream of the crest, while downstream of it the opposite can be said as the turbines face a decreased wind speed. Also, the presence of the hill introduces an additional spanwise velocity component that may also affect the turbines' operations. The linear superposition of the flow over the hill and the flow over the farm alone provided a first estimation of the wind speed along the farm, with discrepancies of the same order of magnitude for the spanwise velocity. Finally, the possibility of using a parabolic set of equations to obtain the turbulent kinetic energy after the linearized model is investigated with promising results.This article is part of the themed issue 'Wind energy in complex terrains'. © 2017 The Author(s).

Linearized simulation of flow over wind farms and complex terrains

NASA Astrophysics Data System (ADS)

Segalini, Antonio

2017-03-01

The flow over complex terrains and wind farms is estimated here by numerically solving the linearized Navier-Stokes equations. The equations are linearized around the unperturbed incoming wind profile, here assumed logarithmic. The Boussinesq approximation is used to model the Reynolds stress with a prescribed turbulent eddy viscosity profile. Without requiring the boundary-layer approximation, two new linear equations are obtained for the vertical velocity and the wall-normal vorticity, with a reduction in the computational cost by a factor of 8 when compared with a primitive-variables formulation. The presence of terrain elevation is introduced as a vertical coordinate shift, while forestry or wind turbines are included as body forces, without any assumption about the wake structure for the turbines. The model is first validated against some available experiments and simulations, and then a simulation of a wind farm over a Gaussian hill is performed. The speed-up effect of the hill is clearly beneficial in terms of the available momentum upstream of the crest, while downstream of it the opposite can be said as the turbines face a decreased wind speed. Also, the presence of the hill introduces an additional spanwise velocity component that may also affect the turbines' operations. The linear superposition of the flow over the hill and the flow over the farm alone provided a first estimation of the wind speed along the farm, with discrepancies of the same order of magnitude for the spanwise velocity. Finally, the possibility of using a parabolic set of equations to obtain the turbulent kinetic energy after the linearized model is investigated with promising results. This article is part of the themed issue 'Wind energy in complex terrains'.

Internal rotor friction instability

NASA Technical Reports Server (NTRS)

Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

1990-01-01

The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

Measurement of angular velocity in the perception of rotation.

PubMed

Barraza, José F; Grzywacz, Norberto M

2002-09-01

Humans are sensitive to the parameters of translational motion, namely, direction and speed. At the same time, people have special mechanisms to deal with more complex motions, such as rotations and expansions. One wonders whether people may also be sensitive to the parameters of these complex motions. Here, we report on a series of experiments that explore whether human subjects can use angular velocity to evaluate how fast a rotational motion is. In four experiments, subjects were required to perform a task of speed-of-rotation discrimination by comparing two annuli of different radii in a temporal 2AFC paradigm. Results showed that humans could rely on a sensitive measurement of angular velocity to perform this discrimination task. This was especially true when the quality of the rotational signal was high (given by the number of dots composing the annulus). When the signal quality decreased, a bias towards linear velocity of 5-80% appeared, suggesting the existence of separate mechanisms for angular and linear velocity. This bias was independent from the reference radius. Finally, we asked whether the measurement of angular velocity required a rigid rotation, that is, whether the visual system makes only one global estimate of angular velocity. For this purpose, a random-dot disk was built such that all the dots were rotating with the same tangential speed, irrespectively of radius. Results showed that subjects do not estimate a unique global angular velocity, but that they perceive a non-rigid disk, with angular velocity falling inversely proportionally with radius.

High strain-rate soft material characterization via inertial cavitation

NASA Astrophysics Data System (ADS)

Estrada, Jonathan B.; Barajas, Carlos; Henann, David L.; Johnsen, Eric; Franck, Christian

2018-03-01

Mechanical characterization of soft materials at high strain-rates is challenging due to their high compliance, slow wave speeds, and non-linear viscoelasticity. Yet, knowledge of their material behavior is paramount across a spectrum of biological and engineering applications from minimizing tissue damage in ultrasound and laser surgeries to diagnosing and mitigating impact injuries. To address this significant experimental hurdle and the need to accurately measure the viscoelastic properties of soft materials at high strain-rates (103-108 s-1), we present a minimally invasive, local 3D microrheology technique based on inertial microcavitation. By combining high-speed time-lapse imaging with an appropriate theoretical cavitation framework, we demonstrate that this technique has the capability to accurately determine the general viscoelastic material properties of soft matter as compliant as a few kilopascals. Similar to commercial characterization algorithms, we provide the user with significant flexibility in evaluating several constitutive laws to determine the most appropriate physical model for the material under investigation. Given its straightforward implementation into most current microscopy setups, we anticipate that this technique can be easily adopted by anyone interested in characterizing soft material properties at high loading rates including hydrogels, tissues and various polymeric specimens.

Wind tunnel test of Teledyne Geotech model 1564B cup anemometer

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

Parker, M.J.; Addis, R.P.

1991-04-04

The Department of Energy (DOE) Environment, Safety and Health Compliance Assessment (Tiger Team) of the Savannah River Site (SRS) questioned the method by which wind speed sensors (cup anemometers) are calibrated by the Environmental Technology Section (ETS). The Tiger Team member was concerned that calibration data was generated by running the wind tunnel to only 26 miles per hour (mph) when speeds exceeding 50 mph are readily obtainable. A wind tunnel experiment was conducted and confirmed the validity of the practice. Wind speeds common to SRS (6 mph) were predicted more accurately by 0--25 mph regression equations than 0--50 mphmore » regression equations. Higher wind speeds were slightly overpredicted by the 0--25 mph regression equations when compared to 0--50 mph regression equations. However, the greater benefit of more accurate lower wind speed predictions accuracy outweight the benefit of slightly better high (extreme) wind speed predictions. Therefore, it is concluded that 0--25 mph regression equations should continue to be utilized by ETS at SRS. During the Department of Energy Tiger Team audit, concerns were raised about the calibration of SRS cup anemometers. Wind speed is measured by ETS with Teledyne Geotech model 1564B cup anemometers, which are calibrated in the ETS wind tunnel. Linear regression lines are fitted to data points of tunnel speed versus anemometer output voltages up to 25 mph. The regression coefficients are then implemented into the data acquisition computer software when an instrument is installed in the field. The concern raised was that since the wind tunnel at SRS is able to generate a maximum wind speed higher than 25 mph, errors may be introduced in not using the full range of the wind tunnel.« less

Wind tunnel test of Teledyne Geotech model 1564B cup anemometer

NASA Astrophysics Data System (ADS)

Parker, M. J.; Addis, R. P.

1991-04-01

The Department of Energy (DOE) Environment, Safety, and Health Compliance Assessment (Tiger Team) of the Savannah River Site (SRS) questioned the method by which wind speed sensors (cup anemometers) are calibrated by the Environmental Technology Section (ETS). The Tiger Team member was concerned that calibration data was generated by running the wind tunnel to only 26 miles per hour (mph) when speeds exceeding 50 mph are readily obtainable. A wind tunnel experiment was conducted and confirmed the validity of the practice. Wind speeds common to SRS (6 mph) were predicted more accurately by 0-25 mph regression equations than 0-50 mph regression equations. Higher wind speeds were slightly overpredicted by the 0-25 mph regression equations when compared to 0-50 mph regression equations. However, the greater benefit of more accurate lower wind speed predictions accuracy outweigh the benefit of slightly better high (extreme) wind speed predictions. Therefore, it is concluded that 0-25 mph regression equations should continue to be utilized by ETS at SRS. During the Department of Energy Tiger Team audit, concerns were raised about the calibration of SRS cup anemometers. Wind speed is measured by ETS with Teledyne Geotech model 1564B cup anemometers, which are calibrated in the ETS wind tunnel. Linear regression lines are fitted to data points of tunnel speed versus anemometer output voltages up to 25 mph. The regression coefficients are then implemented into the data acquisition computer software when an instrument is installed in the field. The concern raised was that since the wind tunnel at SRS is able to generate a maximum wind speed higher than 25 mph, errors may be introduced in not using the full range of the wind tunnel.

Speed Profiles for Deceleration Guidance During Rollout and Turnoff (ROTO)

NASA Technical Reports Server (NTRS)

Barker, L. Keith; Hankins, Walter W., III; Hueschen, Richard M.

1999-01-01

Two NASA goals are to enhance airport safety and to improve capacity in all weather conditions. This paper contributes to these goals by examining speed guidance profiles to aid a pilot in decelerating along the runway to an exit. A speed profile essentially tells the pilot what the airplane's speed should be as a function of where the airplane is on the runway. While it is important to get off the runway as soon as possible (when striving to minimize runway occupancy time), the deceleration along a speed profile should be constrained by passenger comfort. Several speed profiles are examined with respect to their maximum decelerations and times to reach exit speed. One profile varies speed linearly with distance; another has constant deceleration; and two related nonlinear profiles delay maximum deceleration (braking) to reduce time spent on the runway.

Intelligent measurement and compensation of linear motor force ripple: a projection-based learning approach in the presence of noise

NASA Astrophysics Data System (ADS)

Liu, Yang; Song, Fazhi; Yang, Xiaofeng; Dong, Yue; Tan, Jiubin

2018-06-01

Due to their structural simplicity, linear motors are increasingly receiving attention for use in high velocity and high precision applications. The force ripple, as a space-periodic disturbance, however, would deteriorate the achievable dynamic performance. Conventional force ripple measurement approaches are time-consuming and have high requirements on the experimental conditions. In this paper, a novel learning identification algorithm is proposed for force ripple intelligent measurement and compensation. Existing identification schemes always use all the error signals to update the parameters in the force ripple. However, the error induced by noise is non-effective for force ripple identification, and even deteriorates the identification process. In this paper only the most pertinent information in the error signal is utilized for force ripple identification. Firstly, the effective error signals caused by the reference trajectory and the force ripple are extracted by projecting the overall error signals onto a subspace spanned by the physical model of the linear motor as well as the sinusoidal model of the force ripple. The time delay in the linear motor is compensated in the basis functions. Then, a data-driven approach is proposed to design the learning gain. It balances the trade-off between convergence speed and robustness against noise. Simulation and experimental results validate the proposed method and confirm its effectiveness and superiority.

Forecasting Cool Season Daily Peak Winds at Kennedy Space Center and Cape Canaveral Air Force Station

NASA Technical Reports Server (NTRS)

Barrett, Joe, III; Short, David; Roeder, William

2008-01-01

The expected peak wind speed for the day is an important element in the daily 24-Hour and Weekly Planning Forecasts issued by the 45th Weather Squadron (45 WS) for planning operations at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). The morning outlook for peak speeds also begins the warning decision process for gusts ^ 35 kt, ^ 50 kt, and ^ 60 kt from the surface to 300 ft. The 45 WS forecasters have indicated that peak wind speeds are a challenging parameter to forecast during the cool season (October-April). The 45 WS requested that the Applied Meteorology Unit (AMU) develop a tool to help them forecast the speed and timing of the daily peak and average wind, from the surface to 300 ft on KSC/CCAFS during the cool season. The tool must only use data available by 1200 UTC to support the issue time of the Planning Forecasts. Based on observations from the KSC/CCAFS wind tower network, surface observations from the Shuttle Landing Facility (SLF), and CCAFS upper-air soundings from the cool season months of October 2002 to February 2007, the AMU created multiple linear regression equations to predict the timing and speed of the daily peak wind speed, as well as the background average wind speed. Several possible predictors were evaluated, including persistence, the temperature inversion depth, strength, and wind speed at the top of the inversion, wind gust factor (ratio of peak wind speed to average wind speed), synoptic weather pattern, occurrence of precipitation at the SLF, and strongest wind in the lowest 3000 ft, 4000 ft, or 5000 ft. Six synoptic patterns were identified: 1) surface high near or over FL, 2) surface high north or east of FL, 3) surface high south or west of FL, 4) surface front approaching FL, 5) surface front across central FL, and 6) surface front across south FL. The following six predictors were selected: 1) inversion depth, 2) inversion strength, 3) wind gust factor, 4) synoptic weather pattern, 5) occurrence of precipitation at the SLF, and 6) strongest wind in the lowest 3000 ft. The forecast tool was developed as a graphical user interface with Microsoft Excel to help the forecaster enter the variables, and run the appropriate regression equations. Based on the forecaster's input and regression equations, a forecast of the day's peak and average wind is generated and displayed. The application also outputs the probability that the peak wind speed will be ^ 35 kt, 50 kt, and 60 kt.

Reliability and Validity of a New Test of Change-of-Direction Speed for Field-Based Sports: the Change-of-Direction and Acceleration Test (CODAT).

PubMed

Lockie, Robert G; Schultz, Adrian B; Callaghan, Samuel J; Jeffriess, Matthew D; Berry, Simon P

2013-01-01

Field sport coaches must use reliable and valid tests to assess change-of-direction speed in their athletes. Few tests feature linear sprinting with acute change- of-direction maneuvers. The Change-of-Direction and Acceleration Test (CODAT) was designed to assess field sport change-of-direction speed, and includes a linear 5-meter (m) sprint, 45° and 90° cuts, 3- m sprints to the left and right, and a linear 10-m sprint. This study analyzed the reliability and validity of this test, through comparisons to 20-m sprint (0-5, 0-10, 0-20 m intervals) and Illinois agility run (IAR) performance. Eighteen Australian footballers (age = 23.83 ± 7.04 yrs; height = 1.79 ± 0.06 m; mass = 85.36 ± 13.21 kg) were recruited. Following familiarization, subjects completed the 20-m sprint, CODAT, and IAR in 2 sessions, 48 hours apart. Intra-class correlation coefficients (ICC) assessed relative reliability. Absolute reliability was analyzed through paired samples t-tests (p ≤ 0.05) determining between-session differences. Typical error (TE), coefficient of variation (CV), and differences between the TE and smallest worthwhile change (SWC), also assessed absolute reliability and test usefulness. For the validity analysis, Pearson's correlations (p ≤ 0.05) analyzed between-test relationships. Results showed no between-session differences for any test (p = 0.19-0.86). CODAT time averaged ~6 s, and the ICC and CV equaled 0.84 and 3.0%, respectively. The homogeneous sample of Australian footballers meant that the CODAT's TE (0.19 s) exceeded the usual 0.2 x standard deviation (SD) SWC (0.10 s). However, the CODAT is capable of detecting moderate performance changes (SWC calculated as 0.5 x SD = 0.25 s). There was a near perfect correlation between the CODAT and IAR (r = 0.92), and very large correlations with the 20-m sprint (r = 0.75-0.76), suggesting that the CODAT was a valid change-of-direction speed test. Due to movement specificity, the CODAT has value for field sport assessment. Key pointsThe change-of-direction and acceleration test (CODAT) was designed specifically for field sport athletes from specific speed research, and data derived from time-motion analyses of sports such as rugby union, soccer, and Australian football. The CODAT features a linear 5-meter (m) sprint, 45° and 90° cuts and 3-m sprints to the left and right, and a linear 10-m sprint.The CODAT was found to be a reliable change-of-direction speed assessment when considering intra-class correlations between two testing sessions, and the coefficient of variation between trials. A homogeneous sample of Australian footballers resulted in absolute reliability limitations when considering differences between the typical error and smallest worthwhile change. However, the CODAT will detect moderate (0.5 times the test's standard deviation) changes in performance.The CODAT correlated with the Illinois agility run, highlighting that it does assess change-of-direction speed. There were also significant relationships with short sprint performance (i.e. 0-5 m and 0-10 m), demonstrating that linear acceleration is assessed within the CODAT, without the extended duration and therefore metabolic limitations of the IAR. Indeed, the average duration of the test (~6 seconds) is field sport-specific. Therefore, the CODAT could be used as an assessment of change-of-direction speed in field sport athletes.

Swimming speed alteration of Artemia sp. and Brachionus plicatilis as a sub-lethal behavioural end-point for ecotoxicological surveys.

PubMed

Garaventa, Francesca; Gambardella, Chiara; Di Fino, Alessio; Pittore, Massimiliano; Faimali, Marco

2010-03-01

In this study, we investigated the possibility to improve a new behavioural bioassay (Swimming Speed Alteration test-SSA test) using larvae of marine cyst-forming organisms: e.g. the brine shrimp Artemia sp. and the rotifer Brachionus plicatilis. Swimming speed was investigated as a behavioural end-point for application in ecotoxicology studies. A first experiment to analyse the linear swimming speed of the two organisms was performed to verify the applicability of the video-camera tracking system, here referred to as Swimming Behavioural Recorder (SBR). A second experiment was performed, exposing organisms to different toxic compounds (zinc pyrithione, Macrotrol MT-200, and Eserine). Swimming speed alteration was analyzed together with mortality. The results of the first experiment indicate that SBR is a suitable tool to detect linear swimming speed of the two organisms, since the values have been obtained in accordance with other studies using the same organisms (3.05 mm s(-1) for Artemia sp. and 0.62 mm s(-1) for B. plicatilis). Toxicity test results clearly indicate that swimming speed of Artemia sp. and B. plicatilis is a valid behavioural end-point to detect stress at sub-lethal toxic substance concentrations. Indeed, alterations in swimming speed have been detected at toxic compound concentrations as low as less then 0.1-5% of their LC(50) values. In conclusion, the SSA test with B. plicatilis and Artemia sp. can be a good behavioural integrated output for application in marine ecotoxicology and environmental monitoring programs.

Mamdani-Fuzzy Modeling Approach for Quality Prediction of Non-Linear Laser Lathing Process

NASA Astrophysics Data System (ADS)

Sivaraos; Khalim, A. Z.; Salleh, M. S.; Sivakumar, D.; Kadirgama, K.

2018-03-01

Lathing is a process to fashioning stock materials into desired cylindrical shapes which usually performed by traditional lathe machine. But, the recent rapid advancements in engineering materials and precision demand gives a great challenge to the traditional method. The main drawback of conventional lathe is its mechanical contact which brings to the undesirable tool wear, heat affected zone, finishing, and dimensional accuracy especially taper quality in machining of stock with high length to diameter ratio. Therefore, a novel approach has been devised to investigate in transforming a 2D flatbed CO2 laser cutting machine into 3D laser lathing capability as an alternative solution. Three significant design parameters were selected for this experiment, namely cutting speed, spinning speed, and depth of cut. Total of 24 experiments were performed with eight (8) sequential runs where they were then replicated three (3) times. The experimental results were then used to establish Mamdani - Fuzzy predictive model where it yields the accuracy of more than 95%. Thus, the proposed Mamdani - Fuzzy modelling approach is found very much suitable and practical for quality prediction of non-linear laser lathing process for cylindrical stocks of 10mm diameter.

A parallel and modular deformable cell Car-Parrinello code

NASA Astrophysics Data System (ADS)

Cavazzoni, Carlo; Chiarotti, Guido L.

1999-12-01

We have developed a modular parallel code implementing the Car-Parrinello [Phys. Rev. Lett. 55 (1985) 2471] algorithm including the variable cell dynamics [Europhys. Lett. 36 (1994) 345; J. Phys. Chem. Solids 56 (1995) 510]. Our code is written in Fortran 90, and makes use of some new programming concepts like encapsulation, data abstraction and data hiding. The code has a multi-layer hierarchical structure with tree like dependences among modules. The modules include not only the variables but also the methods acting on them, in an object oriented fashion. The modular structure allows easier code maintenance, develop and debugging procedures, and is suitable for a developer team. The layer structure permits high portability. The code displays an almost linear speed-up in a wide range of number of processors independently of the architecture. Super-linear speed up is obtained with a "smart" Fast Fourier Transform (FFT) that uses the available memory on the single node (increasing for a fixed problem with the number of processing elements) as temporary buffer to store wave function transforms. This code has been used to simulate water and ammonia at giant planet conditions for systems as large as 64 molecules for ˜50 ps.

Integral force feedback control with input shaping: Application to piezo-based scanning systems in ECDLs.

PubMed

Zhang, Meng; Liu, Zhigang; Zhu, Yu; Bu, Mingfan; Hong, Jun

2017-07-01

In this paper, a hybrid control system is developed by integrating the closed-loop force feedback and input shaping method to overcome the problem of the hysteresis and dynamic behavior in piezo-based scanning systems and increase the scanning speed of tunable external cavity diode lasers. The flexible hinge and piezoelectric actuators are analyzed, and a dynamic model of the scanning systems is established. A force sensor and an integral controller are utilized in integral force feedback (IFF) to directly augment the damping of the piezoelectric scanning systems. Hysteresis has been effectively eliminated, but the mechanical resonance is still evident. Noticeable residual vibration occurred after the inflection points and then gradually disappeared. For the further control of mechanical resonance, based on the theory of minimum-acceleration trajectory planning, the time-domain input shaping method was developed. The turning sections of a scanning trajectory are replaced by smooth curves, while the linear sections are retained. The IFF method is combined with the input shaping method to control the non-linearity and mechanical resonance in high-speed piezo-based scanning systems. Experiments are conducted, and the results demonstrate the effectiveness of the proposed control approach.

Integral force feedback control with input shaping: Application to piezo-based scanning systems in ECDLs

NASA Astrophysics Data System (ADS)

Zhang, Meng; Liu, Zhigang; Zhu, Yu; Bu, Mingfan; Hong, Jun

2017-07-01

In this paper, a hybrid control system is developed by integrating the closed-loop force feedback and input shaping method to overcome the problem of the hysteresis and dynamic behavior in piezo-based scanning systems and increase the scanning speed of tunable external cavity diode lasers. The flexible hinge and piezoelectric actuators are analyzed, and a dynamic model of the scanning systems is established. A force sensor and an integral controller are utilized in integral force feedback (IFF) to directly augment the damping of the piezoelectric scanning systems. Hysteresis has been effectively eliminated, but the mechanical resonance is still evident. Noticeable residual vibration occurred after the inflection points and then gradually disappeared. For the further control of mechanical resonance, based on the theory of minimum-acceleration trajectory planning, the time-domain input shaping method was developed. The turning sections of a scanning trajectory are replaced by smooth curves, while the linear sections are retained. The IFF method is combined with the input shaping method to control the non-linearity and mechanical resonance in high-speed piezo-based scanning systems. Experiments are conducted, and the results demonstrate the effectiveness of the proposed control approach.

Impact of ADC parameters on linear optical sampling systems

NASA Astrophysics Data System (ADS)

Nguyen, Trung-Hien; Gay, Mathilde; Gomez-Agis, Fausto; Lobo, Sébastien; Sentieys, Olivier; Simon, Jean-Claude; Peucheret, Christophe; Bramerie, Laurent

2017-11-01

Linear optical sampling (LOS), based on the coherent photodetection of an optical signal under test with a low repetition-rate signal originating from a pulsed local oscillator (LO), enables the characterization of the temporal electric field of optical sources. Thanks to this technique, low-speed photodetectors and analog-to-digital converters (ADCs) can be integrated in the LOS system providing a cost-effective tool for characterizing high-speed signals. However, the impact of photodetector and ADC parameters on such LOS systems has not been explored in detail so far. These parameters, including the integration time of the track-and-hold function, the effective number of bits (ENOB) of the ADC, as well as the combined limited bandwidth of the photodetector and ADC are experimentally and numerically investigated in a LOS system for the first time. More specifically, by reconstructing 10-Gbit/s non-return-to-zero on-off keying (NRZ-OOK) and 10-Gbaud NRZ-quadrature phase-shift-keying (QPSK) signals, it is shown that a short integration time provides a better recovered signal fidelity. Furthermore, an ENOB of 6 bits and an ADC bandwidth normalized to the sampling rate of 2.8 are found to be sufficient in order to reliably monitor the considered signals.

A heteroscedastic generalized linear model with a non-normal speed factor for responses and response times.

PubMed

Molenaar, Dylan; Bolsinova, Maria

2017-05-01

In generalized linear modelling of responses and response times, the observed response time variables are commonly transformed to make their distribution approximately normal. A normal distribution for the transformed response times is desirable as it justifies the linearity and homoscedasticity assumptions in the underlying linear model. Past research has, however, shown that the transformed response times are not always normal. Models have been developed to accommodate this violation. In the present study, we propose a modelling approach for responses and response times to test and model non-normality in the transformed response times. Most importantly, we distinguish between non-normality due to heteroscedastic residual variances, and non-normality due to a skewed speed factor. In a simulation study, we establish parameter recovery and the power to separate both effects. In addition, we apply the model to a real data set. © 2017 The Authors. British Journal of Mathematical and Statistical Psychology published by John Wiley & Sons Ltd on behalf of British Psychological Society.

Adaptive sound speed correction for abdominal ultrasonography: preliminary results

NASA Astrophysics Data System (ADS)

Jin, Sungmin; Kang, Jeeun; Song, Tai-Kyung; Yoo, Yangmo

2013-03-01

Ultrasonography has been conducting a critical role in assessing abdominal disorders due to its noninvasive, real-time, low cost, and deep penetrating capabilities. However, for imaging obese patients with a thick fat layer, it is challenging to achieve appropriate image quality with a conventional beamforming (CON) method due to phase aberration caused by the difference between sound speeds (e.g., 1580 and 1450m/s for liver and fat, respectively). For this, various sound speed correction (SSC) methods that estimate the accumulated sound speed for a region-of interest (ROI) have been previously proposed. However, with the SSC methods, the improvement in image quality was limited only for a specific depth of ROI. In this paper, we present the adaptive sound speed correction (ASSC) method, which can enhance the image quality for whole depths by using estimated sound speeds from two different depths in the lower layer. Since these accumulated sound speeds contain the respective contributions of layers, an optimal sound speed for each depth can be estimated by solving contribution equations. To evaluate the proposed method, the phantom study was conducted with pre-beamformed radio-frequency (RF) data acquired with a SonixTouch research package (Ultrasonix Corp., Canada) with linear and convex probes from the gel pad-stacked tissue mimicking phantom (Parker Lab. Inc., USA and Model539, ATS, USA) whose sound speeds are 1610 and 1450m/s, respectively. From the study, compared to the CON and SSC methods, the ASSC method showed the improved spatial resolution and information entropy contrast (IEC) for convex and linear array transducers, respectively. These results indicate that the ASSC method can be applied for enhancing image quality when imaging obese patients in abdominal ultrasonography.

Development and Validation of a New Method to Measure Walking Speed in Free-Living Environments Using the Actibelt® Platform

PubMed Central

Schimpl, Michaela; Lederer, Christian; Daumer, Martin

2011-01-01

Walking speed is a fundamental indicator for human well-being. In a clinical setting, walking speed is typically measured by means of walking tests using different protocols. However, walking speed obtained in this way is unlikely to be representative of the conditions in a free-living environment. Recently, mobile accelerometry has opened up the possibility to extract walking speed from long-time observations in free-living individuals, but the validity of these measurements needs to be determined. In this investigation, we have developed algorithms for walking speed prediction based on 3D accelerometry data (actibelt®) and created a framework using a standardized data set with gold standard annotations to facilitate the validation and comparison of these algorithms. For this purpose 17 healthy subjects operated a newly developed mobile gold standard while walking/running on an indoor track. Subsequently, the validity of 12 candidate algorithms for walking speed prediction ranging from well-known simple approaches like combining step length with frequency to more sophisticated algorithms such as linear and non-linear models was assessed using statistical measures. As a result, a novel algorithm employing support vector regression was found to perform best with a concordance correlation coefficient of 0.93 (95%CI 0.92–0.94) and a coverage probability CP1 of 0.46 (95%CI 0.12–0.70) for a deviation of 0.1 m/s (CP2 0.78, CP3 0.94) when compared to the mobile gold standard while walking indoors. A smaller outdoor experiment confirmed those results with even better coverage probability. We conclude that walking speed thus obtained has the potential to help establish walking speed in free-living environments as a patient-oriented outcome measure. PMID:21850254

Mobile phone use during driving: Effects on speed and effectiveness of driver compensatory behaviour.

PubMed

Choudhary, Pushpa; Velaga, Nagendra R

2017-09-01

This study analysed and modelled the effects of conversation and texting (each with two difficulty levels) on driving performance of Indian drivers in terms of their mean speed and accident avoiding abilities; and further explored the relationship between speed reduction strategy of the drivers and their corresponding accident frequency. 100 drivers of three different age groups (young, mid-age and old-age) participated in the simulator study. Two sudden events of Indian context: unexpected crossing of pedestrians and joining of parked vehicles from road side, were simulated for estimating the accident probabilities. Generalized linear mixed models approach was used for developing linear regression models for mean speed and binary logistic regression models for accident probability. The results of the models showed that the drivers significantly compensated the increased workload by reducing their mean speed by 2.62m/s and 5.29m/s in the presence of conversation and texting tasks respectively. The logistic models for accident probabilities showed that the accident probabilities increased by 3 and 4 times respectively when the drivers were conversing or texting on a phone during driving. Further, the relationship between the speed reduction patterns and their corresponding accident frequencies showed that all the drivers compensated differently; but, among all the drivers, only few drivers, who compensated by reducing the speed by 30% or more, were able to fully offset the increased accident risk associated with the phone use. Copyright © 2017 Elsevier Ltd. All rights reserved.

Age differences in change-of-direction performance and its subelements in female football players.

PubMed

Hirose, Norikazu; Nakahori, Chikako

2015-05-01

To describe cross-sectional age differences in change-of-direction performance (CODp) in female football players and investigate the relationship between CODp and linear-sprint speed, muscle power, and body size. A sample of 135 well-trained female football players was divided into 8 age groups. Anthropometry (height, body mass, and lean body mass) and athletic performance (10-m sprint speed, 10-m×5-CODp, and 5-step bounding distance) were compared to determine interage differences using ANOVA. Then, the participants were divided into 3 age groups: 12- to 14-y-olds, 15- to 17-y-olds, and ≥18 y-olds. Simple- and multiple-regression analyses were conducted to determine the correlation between CODp and the other measurement variables in each age group. Age-related differences were found for CODp (F=10.41, P<.01), sprint speed (F=3.27, P<.01), and bounding distance (F=4.20, P<.01). Post hoc analysis revealed that the CODp of 17-y-old players was faster than that of 16-y-old players (P<.01), with no interage differences in sprint speed and bounding distance. Sprint speed and bounding distance were weakly correlated with CODp in 15- to ≥18-y-old players, but only sprint speed was correlated with CODp in 12- to 14-y-old players. CODp improves from 16 to 17 y of age in female players. Linear-sprint speed, muscle power, and body size were weakly correlated with the age differences in CODp.

Developmental dyslexia and phonological processing in European Portuguese orthography.

PubMed

Moura, Octávio; Moreno, Joana; Pereira, Marcelino; Simões, Mário R

2015-02-01

This study analysed the performance of phonological processing, the diagnostic accuracy and the influence on reading in children who were native speakers of an orthography of intermediate depth. Portuguese children with developmental dyslexia (DD; N=24; aged 10-12 years), chronological age (CA)-matched controls (N=24; aged 10-12 years) and reading level (RL)-matched controls (N=24; aged 7-9 years) were tested on measures of phonological processing (phonological awareness, naming speed and verbal short-term memory) and reading. The results indicated that the children with DD performed significantly poorer in all measures compared with the CA and RL. Phonological awareness and naming speed showed a high accuracy (receiver operating characteristics curve analysis) for discriminating the children with DD from the CA and RL, whereas the presence of abnormally low scores in phonological awareness and naming speed was more frequent in the DD group than in the controls and the normative population. Hierarchical linear regression analyses revealed that phonological awareness was the most important predictor of all reading accuracy measures, whereas naming speed was particularly related to text reading fluency. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of speed matching on fundamental diagram of pedestrian flow

NASA Astrophysics Data System (ADS)

Fu, Zhijian; Luo, Lin; Yang, Yue; Zhuang, Yifan; Zhang, Peitong; Yang, Lizhong; Yang, Hongtai; Ma, Jian; Zhu, Kongjin; Li, Yanlai

2016-09-01

Properties of pedestrian may change along their moving path, for example, as a result of fatigue or injury, which has never been properly investigated in the past research. The paper attempts to study the speed matching effect (a pedestrian adjusts his velocity constantly to the average velocity of his neighbors) and its influence on the density-velocity relationship (a pedestrian adjust his velocity to the surrounding density), known as the fundamental diagram of the pedestrian flow. By the means of the cellular automaton, the simulation results fit well with the empirical data, indicating the great advance of the discrete model for pedestrian dynamics. The results suggest that the system velocity and flow rate increase obviously under a big noise, i.e., a diverse composition of pedestrian crowd, especially in the region of middle or high density. Because of the temporary effect, the speed matching has little influence on the fundamental diagram. Along the entire density, the relationship between the step length and the average pedestrian velocity is a piecewise function combined two linear functions. The number of conflicts reaches the maximum with the pedestrian density of 2.5 m-2, while decreases by 5.1% with the speed matching.

Drive Control of an Electric Vehicle by a Non-linear Controller

NASA Astrophysics Data System (ADS)

Mubin, Marizan; Ouchi, Shigeto; Anabuki, Masatoshi; Hirata, Hiroshi

The driving force of automobiles is transmitted by the frictional force between the tires and the road surface. This frictional force is a function of the weight of the car-body and the friction coefficient μ between the tires and the road surface. The friction coefficient μ is also a function of the following parameters: the slip ratio λ determined by the car-body speed and the wheel speed, and the condition of the road surface. Slippage of automobiles which causes much damage often occurs during accelerating and braking. In this paper, we propose a new drive control system which has an effect on acceleration and braking. In the drive control system, a non-linear controller designed by using a Lyapunov function is used. This non-linear controller has two functions: first one is μ control which moves the car-body, another one is λ control. The controller is designed in order that μ and λ work at noslip and with slip respectively. As another controller, a disturbance observer is used for estimating the car-body speed which is difficult to be measured. Then, this lead to the proof of the stability condition of the combined system which consists of two controllers: the non-linear controller and the disturbance observer. Finally, the effectiveness of this control system is proved by a very satisfactory simulation and experimental results for two cases.

Advanced composite structural concepts and materials technologies for primary aircraft structures: Advanced material concepts

NASA Technical Reports Server (NTRS)

Lau, Kreisler S. Y.; Landis, Abraham L.; Chow, Andrea W.; Hamlin, Richard D.

1993-01-01

To achieve acceptable performance and long-term durability at elevated temperatures (350 to 600 F) for high-speed transport systems, further improvements of the high-performance matrix materials will be necessary to achieve very long-term (60,000-120,000 service hours) retention of mechanical properties and damage tolerance. This report emphasizes isoimide modification as a complementary technique to semi-interpenetrating polymer networks (SIPN's) to achieve greater processibility, better curing dynamics, and possibly enhanced thermo-mechanical properties in composites. A key result is the demonstration of enhanced processibility of isoimide-modified linear and thermo-setting polyimide systems.

High-speed multiple sequence alignment on a reconfigurable platform.

PubMed

Oliver, Tim; Schmidt, Bertil; Maskell, Douglas; Nathan, Darran; Clemens, Ralf

2006-01-01

Progressive alignment is a widely used approach to compute multiple sequence alignments (MSAs). However, aligning several hundred sequences by popular progressive alignment tools requires hours on sequential computers. Due to the rapid growth of sequence databases biologists have to compute MSAs in a far shorter time. In this paper we present a new approach to MSA on reconfigurable hardware platforms to gain high performance at low cost. We have constructed a linear systolic array to perform pairwise sequence distance computations using dynamic programming. This results in an implementation with significant runtime savings on a standard FPGA.

A high-energy-density, high-Mach number single jet experiment

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

Hansen, J. F.; Dittrich, T. R.; Elliott, J. B.

2011-08-15

A high-energy-density, x-ray-driven, high-Mach number (M{>=} 17) single jet experiment shows constant propagation speeds of the jet and its bowshock into the late time regime. The jet assumes a characteristic mushroom shape with a stalk and a head. The width of the head and the bowshock also grow linearly in time. The width of the stalk decreases exponentially toward an asymptotic value. In late time images, the stalk kinks and develops a filamentary nature, which is similar to experiments with applied magnetic fields. Numerical simulations match the experiment reasonably well, but ''exterior'' details of the laser target must be includedmore » to obtain a match at late times.« less

Image sensor with high dynamic range linear output

NASA Technical Reports Server (NTRS)

Yadid-Pecht, Orly (Inventor); Fossum, Eric R. (Inventor)

2007-01-01

Designs and operational methods to increase the dynamic range of image sensors and APS devices in particular by achieving more than one integration times for each pixel thereof. An APS system with more than one column-parallel signal chains for readout are described for maintaining a high frame rate in readout. Each active pixel is sampled for multiple times during a single frame readout, thus resulting in multiple integration times. The operation methods can also be used to obtain multiple integration times for each pixel with an APS design having a single column-parallel signal chain for readout. Furthermore, analog-to-digital conversion of high speed and high resolution can be implemented.

The Effects of the Menstrual Cycle on Vibratory Characteristics of the Vocal Folds Investigated With High-Speed Digital Imaging.

PubMed

Kunduk, Melda; Vansant, Mathew B; Ikuma, Takeshi; McWhorter, Andrew

2017-03-01

This study investigated the effect of menstrual cycle on vocal fold vibratory characteristics in young women using high-speed digital imaging. This study examined the menstrual phase effect on five objective high-speed imaging parameters and two self-rated perceptual parameters. The effects of oral birth control use were also investigated. Thirteen subjects with no prior voice complaints were included in this study. All data were collected at three different time periods (premenses, postmenses, ovulation) over the course of one menstrual cycle. For five of the 13 subjects, data were collected for two consecutive cycles. Six of 13 subjects were oral birth control users. From high-speed imaging data, five objective parameters were computed: fundamental frequency, fundamental frequency deviation, harmonics-to-noise ratio, harmonic richness factor, and ratio of first and second harmonics. They were supplemented by two self-rated parameters: Reflux Severity Index and perceptual voice quality rating. Analysis included mixed model linear analysis with repeated measures. Results indicated no significant main effects for menstrual phase, between-cycle, or birth control use in the analysis for mean fundamental frequency, fundamental frequency deviation, harmonics-to-noise ratio, harmonic richness factor, first and second harmonics, Reflux Severity Index, and perceptual voice quality rating. Additionally, there were no interaction effects. Hormone fluctuations observed across the menstrual cycle do not appear to have direct effect on vocal fold vibratory characteristics in young women with no voice concerns. Birth control use, on the other hand, may have influence on spectral richness of vocal fold vibration. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

User Interface Developed for Controls/CFD Interdisciplinary Research

NASA Technical Reports Server (NTRS)

1996-01-01

The NASA Lewis Research Center, in conjunction with the University of Akron, is developing analytical methods and software tools to create a cross-discipline "bridge" between controls and computational fluid dynamics (CFD) technologies. Traditionally, the controls analyst has used simulations based on large lumping techniques to generate low-order linear models convenient for designing propulsion system controls. For complex, high-speed vehicles such as the High Speed Civil Transport (HSCT), simulations based on CFD methods are required to capture the relevant flow physics. The use of CFD should also help reduce the development time and costs associated with experimentally tuning the control system. The initial application for this research is the High Speed Civil Transport inlet control problem. A major aspect of this research is the development of a controls/CFD interface for non-CFD experts, to facilitate the interactive operation of CFD simulations and the extraction of reduced-order, time-accurate models from CFD results. A distributed computing approach for implementing the interface is being explored. Software being developed as part of the Integrated CFD and Experiments (ICE) project provides the basis for the operating environment, including run-time displays and information (data base) management. Message-passing software is used to communicate between the ICE system and the CFD simulation, which can reside on distributed, parallel computing systems. Initially, the one-dimensional Large-Perturbation Inlet (LAPIN) code is being used to simulate a High Speed Civil Transport type inlet. LAPIN can model real supersonic inlet features, including bleeds, bypasses, and variable geometry, such as translating or variable-ramp-angle centerbodies. Work is in progress to use parallel versions of the multidimensional NPARC code.

GLAST Burst Monitor Signal Processing System

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

Bhat, P. Narayana; Briggs, Michael; Connaughton, Valerie

The onboard Data Processing Unit (DPU), designed and built by Southwest Research Institute, performs the high-speed data acquisition for GBM. The analog signals from each of the 14 detectors are digitized by high-speed multichannel analog data acquisition architecture. The streaming digital values resulting from a periodic (period of 104.2 ns) sampling of the analog signal by the individual ADCs are fed to a Field-Programmable Gate Array (FPGA). Real-time Digital Signal Processing (DSP) algorithms within the FPGA implement functions like filtering, thresholding, time delay and pulse height measurement. The spectral data with a 12-bit resolution are formatted according to the commandablemore » look-up-table (LUT) and then sent to the High-Speed Science-Date Bus (HSSDB, speed=1.5 MB/s) to be telemetered to ground. The DSP offers a novel feature of a commandable and constant event deadtime. The ADC non-linearities have been calibrated so that the spectral data can be corrected during analysis. The best temporal resolution is 2 {mu}s for the pre-burst and post-trigger time-tagged events (TTE) data. The time resolution of the binned data types is commandable from 64 msec to 1.024 s for the CTIME data (8 channel spectral resolution) and 1.024 to 32.768 s for the CSPEC data (128 channel spectral resolution). The pulse pile-up effects have been studied by Monte Carlo simulations. For a typical GRB, the possible shift in the Epeak value at high-count rates ({approx}100 kHz) is {approx}1% while the change in the single power-law index could be up to 5%.« less

Fluid flow dynamics in MAS systems.

PubMed

Wilhelm, Dirk; Purea, Armin; Engelke, Frank

2015-08-01

The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor. Copyright © 2015 Elsevier Inc. All rights reserved.

Gliding flight in a jackdaw: a wind tunnel study.

PubMed

Rosén, M; Hedenström, A

2001-03-01

We examined the gliding flight performance of a jackdaw Corvus monedula in a wind tunnel. The jackdaw was able to glide steadily at speeds between 6 and 11 m s(-1). The bird changed its wingspan and wing area over this speed range, and we measured the so-called glide super-polar, which is the envelope of fixed-wing glide polars over a range of forward speeds and sinking speeds. The glide super-polar was an inverted U-shape with a minimum sinking speed (V(ms)) at 7.4 m s(-1) and a speed for best glide (V(bg)) at 8.3 m s(-)). At the minimum sinking speed, the associated vertical sinking speed was 0.62 m s(-1). The relationship between the ratio of lift to drag (L:D) and airspeed showed an inverted U-shape with a maximum of 12.6 at 8.5 m s(-1). Wingspan decreased linearly with speed over the whole speed range investigated. The tail was spread extensively at low and moderate speeds; at speeds between 6 and 9 m s(-1), the tail area decreased linearly with speed, and at speeds above 9 m s(-1) the tail was fully furled. Reynolds number calculated with the mean chord as the reference length ranged from 38 000 to 76 000 over the speed range 6-11 m s(-1). Comparisons of the jackdaw flight performance were made with existing theory of gliding flight. We also re-analysed data on span ratios with respect to speed in two other bird species previously studied in wind tunnels. These data indicate that an equation for calculating the span ratio, which minimises the sum of induced and profile drag, does not predict the actual span ratios observed in these birds. We derive an alternative equation on the basis of the observed span ratios for calculating wingspan and wing area with respect to forward speed in gliding birds from information about body mass, maximum wingspan, maximum wing area and maximum coefficient of lift. These alternative equations can be used in combination with any model of gliding flight where wing area and wingspan are considered to calculate sinking rate with respect to forward speed.

Experimental Determination of Linear Dynamics of Two-Spool Turbojet Engines

NASA Technical Reports Server (NTRS)

Novik, David; Heppler, Herbert

1954-01-01

Transfer functions descriptive of the response of most engine variables were determined from transient data that were obtained from approximate step inputs in fuel flow and in exhaust-nozzle area. The speed responses of both spools to fuel flow and to turbine-inlet temperature appeared as identical first-order lags. Response to exhaust-nozzle area was characterized by a first-order lag response of the outer-spool speed, accompanied by virtually no change in inner-spool speed.

Stochastic Quantitative Reasoning for Autonomous Mission Planning

DTIC Science & Technology

2014-04-09

points. Figure 4: Linear interpolation Table 1: Wind speed prediction information (ID:0-2 for Albany, ID:3-5 for Pittston, and ID:6-8 for JFK Airport ID...Pittston, and JFK Airport in Table 1, how can we estimate a reasonable wind speed for the current location at the current time? Figure 5: Example

14 CFR 29.177 - Static directional stability.

Code of Federal Regulations, 2011 CFR

2011-01-01

... pedal motion with throttle and collective controls held constant at the trim conditions specified in... control deflection for sideslip angles up to the lesser of— (1) ±25 degrees from trim at a speed of 15 knots less than the speed for minimum rate of descent varying linearly to ±10 degrees from trim at VNE...

Control of finger forces during fast, slow and moderate rotational hand movements.

PubMed

Kazemi, Hamed; Kearney, Robert E; Milner, Theodore E

2014-01-01

The goal of this study was to investigate the effect of speed on patterns of grip forces during twisting movement involving forearm supination against a torsional load (combined elastic and inertial load). For slow and moderate speed rotations, the grip force increased linearly with load torque. However, for fast rotations in which the contribution of the inertia to load torque was significantly greater than slower movements, the grip force-load torque relationship could be segmented into two phases: a linear ascending phase corresponding to the acceleration part of the movement followed by a plateau during deceleration. That is, during the acceleration phase, the grip force accurately tracked the combined elastic and inertial load. However, the coupling between grip force and load torque was not consistent during the deceleration phase of the movement. In addition, as speed increased, both the position and the force profiles became smoother. No differences in the baseline grip force, safety margin to secure the grasp during hold phase or the overall change in grip force were observed across different speeds.

Field Validation of the Stability Limit of a Multi MW Turbine

NASA Astrophysics Data System (ADS)

Kallesøe, Bjarne S.; Kragh, Knud A.

2016-09-01

Long slender blades of modern multi-megawatt turbines exhibit a flutter like instability at rotor speeds above a critical rotor speed. Knowing the critical rotor speed is crucial to a safe turbine design. The flutter like instability can only be estimated using geometrically non-linear aeroelastic codes. In this study, the estimated rotor speed stability limit of a 7 MW state of the art wind turbine is validated experimentally. The stability limit is estimated using Siemens Wind Powers in-house aeroelastic code, and the results show that the predicted stability limit is within 5% of the experimentally observed limit.

High speed and high resolution interrogation of a fiber Bragg grating sensor based on microwave photonic filtering and chirped microwave pulse compression.

PubMed

Xu, Ou; Zhang, Jiejun; Yao, Jianping

2016-11-01

High speed and high resolution interrogation of a fiber Bragg grating (FBG) sensor based on microwave photonic filtering and chirped microwave pulse compression is proposed and experimentally demonstrated. In the proposed sensor, a broadband linearly chirped microwave waveform (LCMW) is applied to a single-passband microwave photonic filter (MPF) which is implemented based on phase modulation and phase modulation to intensity modulation conversion using a phase modulator (PM) and a phase-shifted FBG (PS-FBG). Since the center frequency of the MPF is a function of the central wavelength of the PS-FBG, when the PS-FBG experiences a strain or temperature change, the wavelength is shifted, which leads to the change in the center frequency of the MPF. At the output of the MPF, a filtered chirped waveform with the center frequency corresponding to the applied strain or temperature is obtained. By compressing the filtered LCMW in a digital signal processor, the resolution is improved. The proposed interrogation technique is experimentally demonstrated. The experimental results show that interrogation sensitivity and resolution as high as 1.25 ns/με and 0.8 με are achieved.

Measurement of Non-Linear Internal Waves and Their Interaction with Surface Waves using Coherent Real Aperture Radars

DTIC Science & Technology

2010-03-08

frequencies on wind speed and direction is viable at VV polarization at much larger incidence angles than we had thought. At this polarization it works...out to 89 degree incidence angles. By contrast at HH polarization the model underpredicts the NRCS of the sea for incidence angles above about 45...degrees. ● At high grazing angles, HH polarized cross sections maximize upwind and minimize downwind; upwind they are slightly smaller than VV

Eddy current damper

NASA Technical Reports Server (NTRS)

Ellis, R. C.; Fink, R. A.; Rich, R. W.

1989-01-01

A high torque capacity eddy current damper used as a rate limiting device for a large solar array deployment mechanism is discussed. The eddy current damper eliminates the problems associated with the outgassing or leaking of damping fluids. It also provides performance advantages such as damping torque rates, which are truly linear with respect to input speed, continuous 360 degree operation in both directions of rotation, wide operating temperature range, and the capability of convenient adjustment of damping rates by the user without disassembly or special tools.

A decade of aeroacoustic research at NASA Ames Research Center

NASA Technical Reports Server (NTRS)

Schmitz, Frederic H.; Mosher, M.; Kitaplioglu, Cahit; Cross, J.; Chang, I.

1988-01-01

The rotorcraft aeroacoustic research accomplishments of the past decade at Ames Research Center are reviewed. These include an extensive sequence of flight, ground, and wind tunnel tests that have utilized the facilities to guide and pioneer theoretical research. Many of these experiments were of benchmark quality. The experiments were used to isolate the inadequacies of linear theory in high-speed impulsive noise research, have led to the development of theoretical approaches, and have guided the emerging discipline of computational fluid dynamics to rotorcraft aeroacoustic problems.

Correlated observations of three triggered lightning flashes

NASA Technical Reports Server (NTRS)

Idone, V. P.; Orville, R. E.; Hubert, P.; Barret, L.; Eybert-Berard, A.

1984-01-01

Three triggered lightning flashes, initiated during the Thunderstorm Research International Program (1981) at Langmuir Laboratory, New Mexico, are examined on the basis of three-dimensional return stroke propagation speeds and peak currents. Nonlinear relationships result between return stroke propagation speed and stroke peak current for 56 strokes, and between return stroke propagation speed and dart leader propagation speed for 32 strokes. Calculated linear correlation coefficients include dart leader propagation speed and ensuing return stroke peak current (32 strokes; r = 0.84); and stroke peak current and interstroke interval (69 strokes; r = 0.57). Earlier natural lightning data do not concur with the weak positive correlation between dart leader propagation speed and interstroke interval. Therefore, application of triggered lightning results to natural lightning phenomena must be made with certain caveats. Mean values are included for the three-dimensional return stroke propagation speed and for the three-dimensional dart leader propagation speed.

Modeling and Analysis of the Static Characteristics and Dynamic Responses of Herringbone-grooved Thrust Bearings

NASA Astrophysics Data System (ADS)

Yu, Yunluo; Pu, Guang; Jiang, Kyle

2017-12-01

This paper describes a theoretical investigation of static and dynamic characteristics of herringbone-grooved air thrust bearings. Firstly, Finite Difference Method (FDM) and Finite Volume Method (FVM) are used in combination to solve the non-linear Reynolds equation and to find the pressure distribution of the film and the total loading capacity of the bearing. The influence of design parameters on air film gap characteristics, including the air film thickness, depth of the groove and rotating speed, are analyzed based on the FDM model. The simulation results show that hydrostatic thrust bearings can achieve a better load capacity with less air consumption than herringbone grooved thrust bearings at low compressibility number; herringbone grooved thrust bearings can achieve a higher load capacity but with more air consumption than hydrostatic thrust bearing at high compressibility number; herringbone grooved thrust bearings would lose stability at high rotating speeds, and the stability increases with the depth of the grooves.

Spark Plasma Co-Sintering of Mechanically Milled Tool Steel and High Speed Steel Powders

PubMed Central

Pellizzari, Massimo; Fedrizzi, Anna; Zadra, Mario

2016-01-01

Hot work tool steel (AISI H13) and high speed steel (AISI M3:2) powders were successfully co-sintered to produce hybrid tool steels that have properties and microstructures that can be modulated for specific applications. To promote co-sintering, which is made difficult by the various densification kinetics of the two steels, the particle sizes and structures were refined by mechanical milling (MM). Near full density samples (>99.5%) showing very fine and homogeneous microstructure were obtained using spark plasma sintering (SPS). The density of the blends (20, 40, 60, 80 wt % H13) was in agreement with the linear rule of mixtures. Their hardness showed a positive deviation, which could be ascribed to the strengthening effect of the secondary particles altering the stress distribution during indentation. A toughening of the M3:2-rich blends could be explained in view of the crack deviation and crack arrest exerted by the H13 particles. PMID:28773603

Spark Plasma Co-Sintering of Mechanically Milled Tool Steel and High Speed Steel Powders.

PubMed

Pellizzari, Massimo; Fedrizzi, Anna; Zadra, Mario

2016-06-16

Hot work tool steel (AISI H13) and high speed steel (AISI M3:2) powders were successfully co-sintered to produce hybrid tool steels that have properties and microstructures that can be modulated for specific applications. To promote co-sintering, which is made difficult by the various densification kinetics of the two steels, the particle sizes and structures were refined by mechanical milling (MM). Near full density samples (>99.5%) showing very fine and homogeneous microstructure were obtained using spark plasma sintering (SPS). The density of the blends (20, 40, 60, 80 wt % H13) was in agreement with the linear rule of mixtures. Their hardness showed a positive deviation, which could be ascribed to the strengthening effect of the secondary particles altering the stress distribution during indentation. A toughening of the M3:2-rich blends could be explained in view of the crack deviation and crack arrest exerted by the H13 particles.

Aeroelastic Sizing for High-Speed Research (HSR) Longitudinal Control Alternatives Project (LCAP)

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.; Dunn, H. J.; Stroud, W. Jefferson; Barthelemy, J.-F.; Weston, Robert P.; Martin, Carl J.; Bennett, Robert M.

2005-01-01

The Longitudinal Control Alternatives Project (LCAP) compared three high-speed civil transport configurations to determine potential advantages of the three associated longitudinal control concepts. The three aircraft configurations included a conventional configuration with a layout having a horizontal aft tail, a configuration with a forward canard in addition to a horizontal aft tail, and a configuration with only a forward canard. The three configurations were aeroelastically sized and were compared on the basis of operational empty weight (OEW) and longitudinal control characteristics. The sized structure consisted of composite honeycomb sandwich panels on both the wing and the fuselage. Design variables were the core depth of the sandwich and the thicknesses of the composite material which made up the face sheets of the sandwich. Each configuration was sized for minimum structural weight under linear and nonlinear aeroelastic loads subject to strain, buckling, ply-mixture, and subsonic and supersonic flutter constraints. This report describes the methods that were used and the results that were generated for the aeroelastic sizing of the three configurations.

Resonant-type Smooth Impact Drive Mechanism (SIDM) actuator using a bolt-clamped Langevin transducer.

PubMed

Nishimura, Takuma; Hosaka, Hiroshi; Morita, Takeshi

2012-01-01

The Smooth Impact Drive Mechanism (SIDM) is a linear piezoelectric actuator that has seen practically applied to camera lens modules. Although previous SIDM actuators are easily miniaturized and enable accurate positioning, these actuators cannot actuate at high speed and cannot provide powerful driving because they are driven at an off-resonant frequency using a soft-type PZT. In the present study, we propose a resonant-type SIDM using a bolt-clamped Langevin transducer (BLT) with a hard-type PZT. The resonant-type SIDM overcomes the above-mentioned problems and high-power operation becomes possible with a very simple structure. As a result, we confirmed the operation of resonant-type SIDM by designing a bolt-clamped Langevin transducer. The properties of no-load maximum speed was 0.28m/s at driving voltages of 80V(p-p) for 44.9kHz and 48V(p-p) for 22.45kHz with a pre-load of 3.1N. Copyright © 2011 Elsevier B.V. All rights reserved.

Performance of an extended dynamic range time delay integration charge coupled device (XDR TDI CCD) for high-intrascene dynamic range scanning

NASA Astrophysics Data System (ADS)

Levine, Peter A.; Dawson, Robin M.; Andrews, James T.; Bhaskaran, Mahalingham; Furst, David; Hsueh, Fu-Lung; Meray, Grazyna M.; Sudol, Thomas M.; Swain, Pradyumna K.; Tower, John R.

2003-05-01

Many applications, such as industrial inspection and overhead reconnaissance benefit from line scanning architectures where time delay integration (TDI) significantly improves sensitivity. CCDs are particularly well suited to the TDI architecture since charge is transferred virtually noiselessly down the column. Sarnoff's TDI CCDs have demonstrated extremely high speeds where a 7200 x 64, 8 um pixel device with 120 output ports demonstrated a vertical line transfer rate greater than 800 kHz. The most recent addition to Sarnoff's TDI technology is the implementation of extended dynamic range (XDR) in high speed, back illuminated TDI CCDs. The optical, intrascene dynamic range can be adjusted in the design of the imager with measured dynamic ranges exceeding 2,000,000:1 with no degradation in low light performance. The device provides a piecewise linear response to light where multiple slopes and break points can be set during the CCD design. A description of the device architecture and measured results from fabricated XDR TDI CCDs are presented.

Vacuum-deposited polymer/silver reflector material

NASA Astrophysics Data System (ADS)

Affinito, John D.; Martin, Peter M.; Gross, Mark E.; Bennett, Wendy D.

1994-09-01

Weatherable, low cost, front surface, solar reflectors on flexible substrates would be highly desirable for lamination to solar concentrator panels. The method to be described in this paper may permit such reflector material to be fabricated for less the 50$CNT per square foot. Vacuum deposited Polymer/Silver/Polymer reflectors and Fabry-Perot interference filters were fabricated in a vacuum web coating operation on polyester substrates. Reflectivities were measured in the wavelength range from .4 micrometers to .8 micrometers . It is hoped that a low cost substrate can be used with the substrate laminated to the concentrator and the weatherable acrylic polymer coating facing the sun. This technique should be capable of deposition line speeds approaching 1500 linear feet/minute2. Central to this technique is a new vacuum deposition process for the high rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high speed polymer film deposition process has been named the PML process- for Polymer Multi- Layer.

Variation of surface ozone in Campo Grande, Brazil: meteorological effect analysis and prediction.

PubMed

Pires, J C M; Souza, A; Pavão, H G; Martins, F G

2014-09-01

The effect of meteorological variables on surface ozone (O3) concentrations was analysed based on temporal variation of linear correlation and artificial neural network (ANN) models defined by genetic algorithms (GAs). ANN models were also used to predict the daily average concentration of this air pollutant in Campo Grande, Brazil. Three methodologies were applied using GAs, two of them considering threshold models. In these models, the variables selected to define different regimes were daily average O3 concentration, relative humidity and solar radiation. The threshold model that considers two O3 regimes was the one that correctly describes the effect of important meteorological variables in O3 behaviour, presenting also a good predictive performance. Solar radiation, relative humidity and rainfall were considered significant for both O3 regimes; however, wind speed (dispersion effect) was only significant for high concentrations. According to this model, high O3 concentrations corresponded to high solar radiation, low relative humidity and wind speed. This model showed to be a powerful tool to interpret the O3 behaviour, being useful to define policy strategies for human health protection regarding air pollution.

Direct detection optical intersatellite link at 220 Mbps using AlGaAs laser diode and silicon APD with 4-ary PPM signaling

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Davidson, Frederic M.

1990-01-01

A newly developed 220 Mbps free-space 4-ary pulse position modulation (PPM) direct detection optical communication system is described. High speed GaAs integrated circuits were used to construct the PPM encoder and receiver electronic circuits. Both PPM slot and word timing recovery were provided in the PPM receiver. The optical transmitter consisted of an AlGaAs laser diode (Mitsubishi ML5702A, lambda=821nm) and a high speed driver unit. The photodetector consisted of a silicon avalanche photodiode (APD) (RCA30902S) preceded by an optical interference filter (delta lambda=10nm). Preliminary tests showed that the self-synchronized PPM receiver could achieve a receiver bit error rate of less than 10(exp -6) at 25 nW average received optical signal power or 360 photons per transmitted information bit. The relatively poor receiver sensitivity was believed to be caused by the insufficient electronic bandwidth of the APD preamplifier and the poor linearity of the preamplifier high frequency response.

Mathematical model to predict drivers' reaction speeds.

PubMed

Long, Benjamin L; Gillespie, A Isabella; Tanaka, Martin L

2012-02-01

Mental distractions and physical impairments can increase the risk of accidents by affecting a driver's ability to control the vehicle. In this article, we developed a linear mathematical model that can be used to quantitatively predict drivers' performance over a variety of possible driving conditions. Predictions were not limited only to conditions tested, but also included linear combinations of these tests conditions. Two groups of 12 participants were evaluated using a custom drivers' reaction speed testing device to evaluate the effect of cell phone talking, texting, and a fixed knee brace on the components of drivers' reaction speed. Cognitive reaction time was found to increase by 24% for cell phone talking and 74% for texting. The fixed knee brace increased musculoskeletal reaction time by 24%. These experimental data were used to develop a mathematical model to predict reaction speed for an untested condition, talking on a cell phone with a fixed knee brace. The model was verified by comparing the predicted reaction speed to measured experimental values from an independent test. The model predicted full braking time within 3% of the measured value. Although only a few influential conditions were evaluated, we present a general approach that can be expanded to include other types of distractions, impairments, and environmental conditions.

Linear and exponential TAIL-PCR: a method for efficient and quick amplification of flanking sequences adjacent to Tn5 transposon insertion sites.

PubMed

Jia, Xianbo; Lin, Xinjian; Chen, Jichen

2017-11-02

Current genome walking methods are very time consuming, and many produce non-specific amplification products. To amplify the flanking sequences that are adjacent to Tn5 transposon insertion sites in Serratia marcescens FZSF02, we developed a genome walking method based on TAIL-PCR. This PCR method added a 20-cycle linear amplification step before the exponential amplification step to increase the concentration of the target sequences. Products of the linear amplification and the exponential amplification were diluted 100-fold to decrease the concentration of the templates that cause non-specific amplification. Fast DNA polymerase with a high extension speed was used in this method, and an amplification program was used to rapidly amplify long specific sequences. With this linear and exponential TAIL-PCR (LETAIL-PCR), we successfully obtained products larger than 2 kb from Tn5 transposon insertion mutant strains within 3 h. This method can be widely used in genome walking studies to amplify unknown sequences that are adjacent to known sequences.

Linear ultrasonic motor for absolute gravimeter.

PubMed

Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

2017-05-01

Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters. Copyright © 2017 Elsevier B.V. All rights reserved.

Direct numerical simulations of premixed autoignition in compressible uniformly-sheared turbulence

NASA Astrophysics Data System (ADS)

Towery, Colin; Darragh, Ryan; Poludnenko, Alexei; Hamlington, Peter

2017-11-01

High-speed combustion systems, such as scramjet engines, operate at high temperatures and pressures, extremely short combustor residence times, very high rates of shear stress, and intense turbulent mixing. As a result, the reacting flow can be premixed and have highly-compressible turbulence fluctuations. We investigate the effects of compressible turbulence on the ignition delay time, heat-release-rate (HRR) intermittency, and mode of autoignition of premixed Hydrogen-air fuel in uniformly-sheared turbulence using new three-dimensional direct numerical simulations with a multi-step chemistry mechanism. We analyze autoignition in both the Eulerian and Lagrangian reference frames at eight different turbulence Mach numbers, Mat , spanning the quasi-isentropic, linear thermodynamic, and nonlinear compressibility regimes, with eddy shocklets appearing in the nonlinear regime. Results are compared to our previous study of premixed autoignition in isotropic turbulence at the same Mat and with a single-step reaction mechanism. This previous study found large decreases in delay times and large increases in HRR intermittency between the linear and nonlinear compressibility regimes and that detonation waves could form in both regimes.

Identifying factors affecting the safety of mid-block bicycle lanes considering mixed 2-wheeled traffic flow.

PubMed

Bai, Lu; Chan, Ching-Yao; Liu, Pan; Xu, Chengcheng

2017-10-03

Electric bikes (e-bikes) have been one of the fastest growing trip modes in Southeast Asia over the past 2 decades. The increasing popularity of e-bikes raised some safety concerns regarding urban transport systems. The primary objective of this study was to identify whether and how the generalized linear regression model (GLM) could be used to relate cyclists' safety with various contributing factors when riding in a mid-block bike lane. The types of 2-wheeled vehicles in the study included bicycle-style electric bicycles (BSEBs), scooter-style electric bicycles (SSEBs), and regular bicycles (RBs). Traffic conflict technology was applied as a surrogate measure to evaluate the safety of 2-wheeled vehicles. The safety performance model was developed by adopting a generalized linear regression model for relating the frequency of rear-end conflicts between e-bikes and regular bikes to the operating speeds of BSEBs, SSEBs, and RBs in mid-block bike lanes. The frequency of rear-end conflicts between e-bikes and bikes increased with an increase in the operating speeds of e-bikes and the volume of e-bikes and bikes and decreased with an increase in the width of bike lanes. The large speed difference between e-bikes and bikes increased the frequency of rear-end conflicts between e-bikes and bikes in mid-block bike lanes. A 1% increase in the average operating speed of e-bikes would increase the expected number of rear-end conflicts between e-bikes and bikes by 1.48%. A 1% increase in the speed difference between e-bikes and bikes would increase the expected number of rear-end conflicts between e-bikes/bikes by 0.16%. The conflict frequency in mid-block bike lanes can be modeled using generalized linear regression models. The factors that significantly affected the frequency of rear-end conflicts included the operating speeds of e-bikes, the speed difference between e-bikes and regular bikes, the volume of e-bikes, the volume of bikes, and the width of bike lanes. The safety performance model can help better understand the causes of crash occurrences in mid-block bike lanes.

General methods for determining the linear stability of coronal magnetic fields

NASA Technical Reports Server (NTRS)

Craig, I. J. D.; Sneyd, A. D.; Mcclymont, A. N.

1988-01-01

A time integration of a linearized plasma equation of motion has been performed to calculate the ideal linear stability of arbitrary three-dimensional magnetic fields. The convergence rates of the explicit and implicit power methods employed are speeded up by using sequences of cyclic shifts. Growth rates are obtained for Gold-Hoyle force-free equilibria, and the corkscrew-kink instability is found to be very weak.

General methods for determining the linear stability of coronal magnetic fields

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

Craig, I.J.D.; Sneyd, A.D.; McClymont, A.N.

1988-12-01

A time integration of a linearized plasma equation of motion has been performed to calculate the ideal linear stability of arbitrary three-dimensional magnetic fields. The convergence rates of the explicit and implicit power methods employed are speeded up by using sequences of cyclic shifts. Growth rates are obtained for Gold-Hoyle force-free equilibria, and the corkscrew-kink instability is found to be very weak. 19 references.

Magnetic Launch Assist System Demonstration Test

NASA Technical Reports Server (NTRS)

2001-01-01

Engineers at the Marshall Space Flight Center (MSFC) have been testing Magnetic Launch Assist Systems, formerly known as Magnetic Levitation (MagLev) technologies. To launch spacecraft into orbit, a Magnetic Launch Assist system would use magnetic fields to levitate and accelerate a vehicle along a track at a very high speed. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, the launch-assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This photograph shows a subscale model of an airplane running on the experimental track at MSFC during the demonstration test. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide, and about 1.5- feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

Magnetic Launch Assist Demonstration Test

NASA Technical Reports Server (NTRS)

2001-01-01

This image shows a 1/9 subscale model vehicle clearing the Magnetic Launch Assist System, formerly referred to as the Magnetic Levitation (MagLev), test track during a demonstration test conducted at the Marshall Space Flight Center (MSFC). Engineers at MSFC have developed and tested Magnetic Launch Assist technologies. To launch spacecraft into orbit, a Magnetic Launch Assist System would use magnetic fields to levitate and accelerate a vehicle along a track at very high speeds. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, a launch-assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide and about 1.5-feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

Research Technology

NASA Image and Video Library

2001-03-01

This image shows a 1/9 subscale model vehicle clearing the Magnetic Launch Assist System, formerly referred to as the Magnetic Levitation (MagLev), test track during a demonstration test conducted at the Marshall Space Flight Center (MSFC). Engineers at MSFC have developed and tested Magnetic Launch Assist technologies. To launch spacecraft into orbit, a Magnetic Launch Assist System would use magnetic fields to levitate and accelerate a vehicle along a track at very high speeds. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, a launch-assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide and about 1.5-feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed

NASA Astrophysics Data System (ADS)

Domeisen, Daniela I. V.; Martius, Olivia; Jiménez-Esteve, Bernat

2018-02-01

Sudden stratospheric warming (SSW) events are to a dominant part induced by upward propagating planetary waves. While theory predicts that the zonal phase speed of a tropospheric wave forcing affects wave propagation into the stratosphere, its relevance for SSW events has so far not been considered. This study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward, indicating that the stratosphere preselects eastward phase speeds for propagation, especially for zonal wave number 2. This also affects SSW events: Split SSW events tend to be preceded by anomalously eastward zonal phase speeds. Zonal phase speed may indeed explain part of the increased wave flux observed during the preconditioning of SSW events, as, for example, for the record 2009 SSW event.

An accurate, fast, and scalable solver for high-frequency wave propagation

NASA Astrophysics Data System (ADS)

Zepeda-Núñez, L.; Taus, M.; Hewett, R.; Demanet, L.

2017-12-01

In many science and engineering applications, solving time-harmonic high-frequency wave propagation problems quickly and accurately is of paramount importance. For example, in geophysics, particularly in oil exploration, such problems can be the forward problem in an iterative process for solving the inverse problem of subsurface inversion. It is important to solve these wave propagation problems accurately in order to efficiently obtain meaningful solutions of the inverse problems: low order forward modeling can hinder convergence. Additionally, due to the volume of data and the iterative nature of most optimization algorithms, the forward problem must be solved many times. Therefore, a fast solver is necessary to make solving the inverse problem feasible. For time-harmonic high-frequency wave propagation, obtaining both speed and accuracy is historically challenging. Recently, there have been many advances in the development of fast solvers for such problems, including methods which have linear complexity with respect to the number of degrees of freedom. While most methods scale optimally only in the context of low-order discretizations and smooth wave speed distributions, the method of polarized traces has been shown to retain optimal scaling for high-order discretizations, such as hybridizable discontinuous Galerkin methods and for highly heterogeneous (and even discontinuous) wave speeds. The resulting fast and accurate solver is consequently highly attractive for geophysical applications. To date, this method relies on a layered domain decomposition together with a preconditioner applied in a sweeping fashion, which has limited straight-forward parallelization. In this work, we introduce a new version of the method of polarized traces which reveals more parallel structure than previous versions while preserving all of its other advantages. We achieve this by further decomposing each layer and applying the preconditioner to these new components separately and in parallel. We demonstrate that this produces an even more effective and parallelizable preconditioner for a single right-hand side. As before, additional speed can be gained by pipelining several right-hand-sides.

Deep white matter hyperintensities, microstructural integrity and dual task walking in older people.

PubMed

Ghanavati, Tabassom; Smitt, Myriam Sillevis; Lord, Stephen R; Sachdev, Perminder; Wen, Wei; Kochan, Nicole A; Brodaty, Henry; Delbaere, Kim

2018-01-03

To examine neural, physiological and cognitive influences on gait speed under single and dual-task conditions. Sixty-two community-dwelling older people (aged 80.0 ± 4.2 years) participated in our study. Gait speed was assessed with a timed 20-meter walk under single and dual-task (reciting alternate letters of the alphabet) conditions. Participants also underwent tests to estimate physiological fall risk based on five measures of sensorimotor function, cognitive function across five domains, brain white matter (WM) hyperintensities and WM microstructural integrity by measuring fractional anisotropy (FA). Univariate linear regression analyses showed that global physiological and cognitive measures were associated with single (β = 0.594 and β=-0.297, respectively) and dual-task gait speed (β = 0.306 and β=-0.362, respectively). Deep WMHs were associated with dual-task gait speed only (β = 0.257). Multivariate mediational analyses showed that global and executive cognition reduced the strength of the association between deep WMHs and dual-task gait speed by 27% (β = 0.188) and 44% (β = 0.145) respectively. There was a significant linear association between single-task gait speed and mean FA values of the genu (β=-0.295) and splenium (β=-0.326) of the corpus callosum, and between dual-task gait speed and mean FA values of Superior Cerebellar Peduncle (β=-0.284), splenium of the Corpus Callosum (β=-0.286) and Cingulum (β=-0.351). Greater deep WMH volumes are associated with slower walking speed under dual-task conditions, and this relationship is mediated in part by global cognition and executive abilities specifically. Furthermore, both cerebellum and cingulum are related to dual-task walking due to their role in motor skill performance and attention, respectively.

Compressible flow at high pressure with linear equation of state

NASA Astrophysics Data System (ADS)

Sirignano, William A.

2018-05-01

Compressible flow varies from ideal-gas behavior at high pressures where molecular interactions become important. Density is described through a cubic equation of state while enthalpy and sound speed are functions of both temperature and pressure, based on two parameters, A and B, related to intermolecular attraction and repulsion, respectively. Assuming small variations from ideal-gas behavior, a closed-form solution is obtained that is valid over a wide range of conditions. An expansion in these molecular-interaction parameters simplifies relations for flow variables, elucidating the role of molecular repulsion and attraction in variations from ideal-gas behavior. Real-gas modifications in density, enthalpy, and sound speed for a given pressure and temperature lead to variations in many basic compressible flow configurations. Sometimes, the variations can be substantial in quantitative or qualitative terms. The new approach is applied to choked-nozzle flow, isentropic flow, nonlinear-wave propagation, and flow across a shock wave, all for the real gas. Modifications are obtained for allowable mass-flow through a choked nozzle, nozzle thrust, sonic wave speed, Riemann invariants, Prandtl's shock relation, and the Rankine-Hugoniot relations. Forced acoustic oscillations can show substantial augmentation of pressure amplitudes when real-gas effects are taken into account. Shocks at higher temperatures and pressures can have larger pressure jumps with real-gas effects. Weak shocks decay to zero strength at sonic speed. The proposed framework can rely on any cubic equation of state and be applied to multicomponent flows or to more-complex flow configurations.

Investigating MALDI MSI parameters (Part 1) - A systematic survey of the effects of repetition rates up to 20kHz in continuous raster mode.

PubMed

Steven, Rory T; Dexter, Alex; Bunch, Josephine

2016-07-15

Recent developments in laser performance, combined with the desire for increases in detected ion intensity and throughput, have led to the adoption of high repetition-rate diode-pumped solid-state (DPSS) lasers in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI). Previous studies have demonstrated a more complex relationship between detected ion intensity, stage raster speed and laser pulse repetition rate than the simple linear relationship between number of pulses and detected ion intensity that might be expected. Here we report, for the first time, the interrelated influence of varying laser energy, repetition rate and stage raster speed on detected ion intensity. Thin films of PC 34:1 lipid standard and murine brain tissue with CHCA are analysed by continuous stage raster MALDI MSI. Contrary to previous reports, the optimum laser repetition rate is found to be dependent on both laser energy and stage raster speed and is found to be as high as 20kHz under some conditions. The effects of different repetition rates and raster speeds are also found to vary for different ion species within MALDI MSI of tissue and so may be significant when either targeting specific molecules or seeking to minimize bias. A clear dependence on time between laser pulses is also observed indicating the underlying mechanisms may be related to on-plate hysteresis-exhibiting processes such as matrix chemical modification. Copyright © 2016 Elsevier Inc. All rights reserved.

Development of a Large Scale, High Speed Wheel Test Facility

NASA Technical Reports Server (NTRS)

Kondoleon, Anthony; Seltzer, Donald; Thornton, Richard; Thompson, Marc

1996-01-01

Draper Laboratory, with its internal research and development budget, has for the past two years been funding a joint effort with the Massachusetts Institute of Technology (MIT) for the development of a large scale, high speed wheel test facility. This facility was developed to perform experiments and carry out evaluations on levitation and propulsion designs for MagLev systems currently under consideration. The facility was developed to rotate a large (2 meter) wheel which could operate with peripheral speeds of greater than 100 meters/second. The rim of the wheel was constructed of a non-magnetic, non-conductive composite material to avoid the generation of errors from spurious forces. A sensor package containing a multi-axis force and torque sensor mounted to the base of the station, provides a signal of the lift and drag forces on the package being tested. Position tables mounted on the station allow for the introduction of errors in real time. A computer controlled data acquisition system was developed around a Macintosh IIfx to record the test data and control the speed of the wheel. This paper describes the development of this test facility. A detailed description of the major components is presented. Recently completed tests carried out on a novel Electrodynamic (EDS) suspension system, developed by MIT as part of this joint effort are described and presented. Adaptation of this facility for linear motor and other propulsion and levitation testing is described.

Oxygen consumption and gait variables of Arabian endurance horses measured during a field exercise test.

PubMed

Cottin, F; Metayer, N; Goachet, A G; Julliand, V; Slawinski, J; Billat, V; Barrey, E

2010-11-01

Arabian horses have morphological, muscular and metabolic features designed for endurance races. Their gas exchange and gait variables were therefore measured during a field exercise test. This study presents original respiratory and locomotor data recorded in endurance horses under field conditions. Respiratory gas exchange ratio (RER) of Arabian horses at the speed required to win endurance races (18 km/h for 120-160 km) are <1 and running economy (RE) is also low in order to maintain exercise intensity using aerobic metabolism for long intervals. The purpose of this study was to measure oxygen consumption and gait variables in Arabian endurance horses running in the field in order to estimate RER and RE. Five Arabian horses trained for endurance racing were test ridden at increasing speeds on the field. Their speed was recorded and controlled by the rider using a GPS logger. Each horse was equipped with a portable respiratory gas analyser, which measured breath-by-breath respiratory variables and heart rate. The gait variables were recorded using tri-axial accelerometer data loggers and software for gait analysis. Descriptive statistics and linear regressions were used to analyse the speed related changes in each variable with P < 0.05 taken as significant. At a canter speed corresponding to endurance race winning speed (18 km/h), horses presented a VO(2) = 42 ± 9 ml/min/kg bwt, RER = 0.96 ± 0.10 and RE (= VO(2) /speed) = 134 ± 27 l/km/kg bwt. Linear relationships were observed between speed and VO(2,) HR and gait variables. Significant correlations were observed between VO(2) and gait variables. The RER of 0.96 at winning endurance speed indicates that Arabian horses mainly use aerobic metabolism based on lipid oxidation and that RER may also be related to a good coordination between running speed, respiratory and gait parameters. © 2010 EVJ Ltd.

Microfabricated microengine for use as a mechanical drive and power source in the microdomain and fabrication process

DOEpatents

Garcia, Ernest J.; Sniegowski, Jeffry J.

1997-01-01

A microengine uses two synchronized linear actuators as a power source and converts oscillatory motion from the actuators into rotational motion via direct linkage connection to an output gear or wheel. The microengine provides output in the form of a continuously rotating output gear that is capable of delivering drive torque to a micromechanism. The microengine can be operated at varying speeds and its motion can be reversed. Linear actuators are synchronized in order to provide linear oscillatory motion to the linkage means in the X and Y directions according to a desired position, rotational direction and speed of said mechanical output means. The output gear has gear teeth on its outer perimeter for directly contacting a micromechanism requiring mechanical power. The gear is retained by a retaining means which allows said gear to rotate freely. The microengine is microfabricated of polysilicon on one wafer using surface micromachining batch fabrication.

Noise levels of operational helicopters of the OH-6 type designed to meet the LOH mission. [acoustic properties for various helicopter configurations

NASA Technical Reports Server (NTRS)

Wagner, R. A.

1973-01-01

Formulas relating overall sound pressure level (OASPL) to parameters such as horsepower required, tip speed, and thrust for main and tail rotors are presented for standard and quieted helicopters. Formulas relating OASPL to engine parameters such as horsepower output and percent power turbine rpm are presented for unmuffled and muffled engines. The linear scale was used in preference to any of the weighted scales because it resulted in more consistent agreement with the test data when the SPL is expressed in the usual parameters of tip speed, thrust generated and power required. It is recognized that the linear scale does not adequately reflect hearing response, and hence is not a good absolute measure for detection by humans. However, linear OASPL is believed to be useful as a relative means of comparing noise level variations of individual components in similar helicopters with reasonably modest design changes.

Stochastic sediment property inversion in Shallow Water 06.

PubMed

Michalopoulou, Zoi-Heleni

2017-11-01

Received time-series at a short distance from the source allow the identification of distinct paths; four of these are direct, surface and bottom reflections, and sediment reflection. In this work, a Gibbs sampling method is used for the estimation of the arrival times of these paths and the corresponding probability density functions. The arrival times for the first three paths are then employed along with linearization for the estimation of source range and depth, water column depth, and sound speed in the water. Propagating densities of arrival times through the linearized inverse problem, densities are also obtained for the above parameters, providing maximum a posteriori estimates. These estimates are employed to calculate densities and point estimates of sediment sound speed and thickness using a non-linear, grid-based model. Density computation is an important aspect of this work, because those densities express the uncertainty in the inversion for sediment properties.

The linear Boltzmann equation in slab geometry - Development and verification of a reliable and efficient solution

NASA Technical Reports Server (NTRS)

Stamnes, K.; Lie-Svendsen, O.; Rees, M. H.

1991-01-01

The linear Boltzmann equation can be cast in a form mathematically identical to the radiation-transport equation. A multigroup procedure is used to reduce the energy (or velocity) dependence of the transport equation to a series of one-speed problems. Each of these one-speed problems is equivalent to the monochromatic radiative-transfer problem, and existing software is used to solve this problem in slab geometry. The numerical code conserves particles in elastic collisions. Generic examples are provided to illustrate the applicability of this approach. Although this formalism can, in principle, be applied to a variety of test particle or linearized gas dynamics problems, it is particularly well-suited to study the thermalization of suprathermal particles interacting with a background medium when the thermal motion of the background cannot be ignored. Extensions of the formalism to include external forces and spherical geometry are also feasible.

Machine Learning EEG to Predict Cognitive Functioning and Processing Speed Over a 2-Year Period in Multiple Sclerosis Patients and Controls.

PubMed

Kiiski, Hanni; Jollans, Lee; Donnchadha, Seán Ó; Nolan, Hugh; Lonergan, Róisín; Kelly, Siobhán; O'Brien, Marie Claire; Kinsella, Katie; Bramham, Jessica; Burke, Teresa; Hutchinson, Michael; Tubridy, Niall; Reilly, Richard B; Whelan, Robert

2018-05-01

Event-related potentials (ERPs) show promise to be objective indicators of cognitive functioning. The aim of the study was to examine if ERPs recorded during an oddball task would predict cognitive functioning and information processing speed in Multiple Sclerosis (MS) patients and controls at the individual level. Seventy-eight participants (35 MS patients, 43 healthy age-matched controls) completed visual and auditory 2- and 3-stimulus oddball tasks with 128-channel EEG, and a neuropsychological battery, at baseline (month 0) and at Months 13 and 26. ERPs from 0 to 700 ms and across the whole scalp were transformed into 1728 individual spatio-temporal datapoints per participant. A machine learning method that included penalized linear regression used the entire spatio-temporal ERP to predict composite scores of both cognitive functioning and processing speed at baseline (month 0), and months 13 and 26. The results showed ERPs during the visual oddball tasks could predict cognitive functioning and information processing speed at baseline and a year later in a sample of MS patients and healthy controls. In contrast, ERPs during auditory tasks were not predictive of cognitive performance. These objective neurophysiological indicators of cognitive functioning and processing speed, and machine learning methods that can interrogate high-dimensional data, show promise in outcome prediction.

14 CFR 27.177 - Static directional stability.

Code of Federal Regulations, 2011 CFR

2011-01-01

... with the throttle and collective controls held constant at the trim conditions specified in § 27.175(a... for sideslip angles up to the lesser of— (1) ±25 degrees from trim at a speed of 15 knots less than the speed for minimum rate of descent varying linearly to ±10 degrees from trim at VNE; (2) The steady...

Two-Photon Imaging with Diffractive Optical Elements

PubMed Central

Watson, Brendon O.; Nikolenko, Volodymyr; Yuste, Rafael

2009-01-01

Two-photon imaging has become a useful tool for optical monitoring of neural circuits, but it requires high laser power and serial scanning of each pixel in a sample. This results in slow imaging rates, limiting the measurements of fast signals such as neuronal activity. To improve the speed and signal-to-noise ratio of two-photon imaging, we introduce a simple modification of a two-photon microscope, using a diffractive optical element (DOE) which splits the laser beam into several beamlets that can simultaneously scan the sample. We demonstrate the advantages of DOE scanning by enhancing the speed and sensitivity of two-photon calcium imaging of action potentials in neurons from neocortical brain slices. DOE scanning can easily improve the detection of time-varying signals in two-photon and other non-linear microscopic techniques. PMID:19636390

Reactive power generation in high speed induction machines by continuously occurring space-transients

NASA Astrophysics Data System (ADS)

Laithwaite, E. R.; Kuznetsov, S. B.

1980-09-01

A new technique of continuously generating reactive power from the stator of a brushless induction machine is conceived and tested on a 10-kw linear machine and on 35 and 150 rotary cage motors. An auxiliary magnetic wave traveling at rotor speed is artificially created by the space-transient attributable to the asymmetrical stator winding. At least two distinct windings of different pole-pitch must be incorporated. This rotor wave drifts in and out of phase repeatedly with the stator MMF wave proper and the resulting modulation of the airgap flux is used to generate reactive VA apart from that required for magnetization or leakage flux. The VAR generation effect increases with machine size, and leading power factor operation of the entire machine is viable for large industrial motors and power system induction generators.

Disposable pen-shaped capillary gel electrophoresis cartridge for fluorescence detection of bio-molecules

NASA Astrophysics Data System (ADS)

Amirkhanian, Varoujan; Tsai, Shou-Kuan

2014-03-01

We introduce a novel and cost-effective capillary gel electrophoresis (CGE) system utilizing disposable pen-shaped gelcartridges for highly efficient, high speed, high throughput fluorescence detection of bio-molecules. The CGE system has been integrated with dual excitation and emission optical-fibers with micro-ball end design for fluorescence detection of bio-molecules separated and detected in a disposable pen-shaped capillary gel electrophoresis cartridge. The high-performance capillary gel electrophoresis (CGE) analyzer has been optimized for glycoprotein analysis type applications. Using commercially available labeling agent such as ANTS (8-aminonapthalene-1,3,6- trisulfonate) as an indicator, the capillary gel electrophoresis-based glycan analyzer provides high detection sensitivity and high resolving power in 2-5 minutes of separations. The system can hold total of 96 samples, which can be automatically analyzed within 4-5 hours. This affordable fiber optic based fluorescence detection system provides fast run times (4 minutes vs. 20 minutes with other CE systems), provides improved peak resolution, good linear dynamic range and reproducible migration times, that can be used in laboratories for high speed glycan (N-glycan) profiling applications. The CGE-based glycan analyzer will significantly increase the pace at which glycoprotein research is performed in the labs, saving hours of preparation time and assuring accurate, consistent and economical results.

Gas film disturbance characteristics analysis of high-speed and high-pressure dry gas seal

NASA Astrophysics Data System (ADS)

Chen, Yuan; Jiang, Jinbo; Peng, Xudong

2016-08-01

The dry gas seal(DGS) has been widely used in high parameters centrifugal compressor, but the intense vibrations of shafting, especially in high-speed condition, usually result in DGS's failure. So the DGS's ability of resisting outside interference has become a determining factor of the further development of centrifugal compressor. However, the systematic researches of which about gas film disturbance characteristics of high parameters DGS are very little. In order to study gas film disturbance characteristics of high-speed and high-pressure spiral groove dry gas seal(S-DGS) with a flexibly mounted stator, rotor axial runout and misalignment are taken into consideration, and the finite difference method and analytical method are used to analyze the influence of gas film thickness disturbance on sealing performance parameters, what's more, the effects of many key factors on gas film thickness disturbance are systematically investigated. The results show that, when sealed pressure is 10.1MPa and seal face average linear velocity is 107.3 m/s, gas film thickness disturbance has a significant effect on leakage rate, but has relatively litter effect on open force; Excessively large excitation amplitude or excessively high excitation frequency can lead to severe gas film thickness disturbance; And it is beneficial to assure a smaller gas film thickness disturbance when the stator material density is between 3.1 g/cm3 to 8.4 g/cm3; Ensuring sealing performance while minimizing support axial stiffness and support axial damping can help to improve dynamic tracking property of dry gas seal. The proposed research provides the instruction to optimize dynamic tracking property of the DGS.

A comparison of linear speed, closed-skill agility, and open-skill agility qualities between backcourt and frontcourt adult semiprofessional male basketball players.

PubMed

Scanlan, Aaron T; Tucker, Patrick S; Dalbo, Vincent J

2014-05-01

The measurement of fitness qualities relevant to playing position is necessary to inform basketball coaching and conditioning staff of role-related differences in playing groups. To date, sprinting and agility performance have not been compared between playing positions in adult male basketball players. Therefore, the purpose of this study was to describe and compare linear speed, closed-skill agility, and open-skill agility qualities between backcourt (point guard and shooting guard positions) and frontcourt (small forward, power forward, and center positions) semiprofessional basketball players. Six backcourt (mean ± SD: age, 24.3 ± 7.9 years; stature, 183.4 ± 4.0 cm; body mass, 85.5 ± 12.3 kg; VO2max, 51.9 ± 4.8 ml·kg(-1)·min(-1)) and 6 frontcourt (mean ± SD: age, 27.5 ± 5.5 years; stature, 194.4 ± 7.1 cm; body mass, 109.4 ± 8.8 kg; VO2max, 47.1 ± 5.0 ml·kg(-1)·min(-1)) adult male basketball players completed 20-m sprint, closed-skill agility, and open-skill agility performance tests. Magnitude-based inferences revealed that backcourt players (5 m, 1.048 ± 0.027 seconds; 10 m, 1.778 ± 0.048 seconds; 20 m, 3.075 ± 0.121 seconds) possessed likely quicker linear sprint times than frontcourt players (5 m, 1.095 ± 0.085 seconds; 10 m, 1.872 ± 0.127 seconds; 20 m, 3.242 ± 0.221 seconds). Conversely, frontcourt players (1.665 ± 0.096 seconds) held possible superior closed-skill agility performance than backcourt players (1.613 ± 0.111 seconds). In addition, unclear positional differences were apparent for open-skill agility qualities. These findings indicate that linear speed and change of direction speed might be differently developed across playing positions. Furthermore, position-related functions might similarly depend on the aspects of open-skill agility performance across backcourt and frontcourt players. Basketball coaching and conditioning staff should consider the development of position-targeted training drills to improve speed, agility, and cognitive qualities in players.

Conjugate gradient based projection - A new explicit methodology for frictional contact

NASA Technical Reports Server (NTRS)

Tamma, Kumar K.; Li, Maocheng; Sha, Desong

1993-01-01

With special attention towards the applicability to parallel computation or vectorization, a new and effective explicit approach for linear complementary formulations involving a conjugate gradient based projection methodology is proposed in this study for contact problems with Coulomb friction. The overall objectives are focussed towards providing an explicit methodology of computation for the complete contact problem with friction. In this regard, the primary idea for solving the linear complementary formulations stems from an established search direction which is projected to a feasible region determined by the non-negative constraint condition; this direction is then applied to the Fletcher-Reeves conjugate gradient method resulting in a powerful explicit methodology which possesses high accuracy, excellent convergence characteristics, fast computational speed and is relatively simple to implement for contact problems involving Coulomb friction.

High speed, precision motion strategies for lightweight structures

NASA Technical Reports Server (NTRS)

Book, Wayne J.

1987-01-01

Abstracts of published papers and dissertations generated during the reporting period are compiled. Work on fine motion control was completed. Specifically, real time control of flexible manipulator vibrations were experimentally investigated. A linear model based on the application of Lagrangian dynamics to a rigid body mode and a series of separable flexible modes was examined with respect to model order requirements, and modal candidate selection. State feedback control laws were implemented based upon linear quadratic regulator design. Specification of the closed loop poles in the regulator design process was obtained by inclusion of a prescribed degree of stability in the manipulator model. Work on gross motion planning and control is also summarized. A systematic method to symbolically derive the full nonlinear dynamic equations of motion of multi-link flexible manipulators was developed.