Acoustic levitation of an object larger than the acoustic wavelength.

PubMed

Andrade, Marco A B; Okina, Fábio T A; Bernassau, Anne L; Adamowski, Julio C

2017-06-01

Levitation and manipulation of objects by sound waves have a wide range of applications in chemistry, biology, material sciences, and engineering. However, the current acoustic levitation techniques are mainly restricted to particles that are much smaller than the acoustic wavelength. In this work, it is shown that acoustic standing waves can be employed to stably levitate an object much larger than the acoustic wavelength in air. The levitation of a large slightly curved object weighting 2.3 g is demonstrated by using a device formed by two 25 kHz ultrasonic Langevin transducers connected to an aluminum plate. The sound wave emitted by the device provides a vertical acoustic radiation force to counteract gravity and a lateral restoring force that ensure horizontal stability to the levitated object. In order to understand the levitation stability, a numerical model based on the finite element method is used to determine the acoustic radiation force that acts on the object.

Predicting vertical jump height from bar velocity.

PubMed

García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

2015-06-01

The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance.

Predicting Vertical Jump Height from Bar Velocity

PubMed Central

García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

2015-01-01

The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s-2). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r2 = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r2 = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key points Vertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer. The relationship between the point at which bar acceleration is less than -9.81 m·s-2 and the real take-off is affected by the velocity of movement. Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance. PMID:25983572

A microelectromechanical systems (MEMS) force-displacement transducer for sub-5 nm nanoindentation and adhesion measurements

NASA Astrophysics Data System (ADS)

Zhang, Youfeng; Oh, Yunje; Stauffer, Douglas; Polycarpou, Andreas A.

2018-04-01

We present a highly sensitive force-displacement transducer capable of performing ultra-shallow nanoindentation and adhesion measurements. The transducer utilizes electrostatic actuation and capacitive sensing combined with microelectromechanical fabrication technologies. Air indentation experiments report a root-mean-square (RMS) force resolution of 1.8 nN and an RMS displacement resolution of 0.019 nm. Nanoindentation experiments on a standard fused quartz sample report a practical RMS force resolution of 5 nN and an RMS displacement resolution of 0.05 nm at sub-10 nm indentation depths, indicating that the system has a very low system noise for indentation experiments. The high sensitivity and low noise enables the transducer to obtain high-resolution nanoindentation data at sub-5 nm contact depths. The sensitive force transducer is used to successfully perform nanoindentation measurements on a 14 nm thin film. Adhesion measurements were also performed, clearly capturing the pull-on and pull-off forces during approach and separation of two contacting surfaces.

An ergonomic handheld ultrasound probe providing contact forces and pose information.

PubMed

Yohan Noh; Housden, R James; Gomez, Alberto; Knight, Caroline; Garcia, Francesca; Hongbin Liu; Razavi, Reza; Rhode, Kawal; Althoefer, Kaspar

2015-08-01

This paper presents a handheld ultrasound probe which is integrated with sensors to measure force and pose (position/orientation) information. Using an integrated probe like this, one can relate ultrasound images to spatial location and create 3D ultrasound maps. The handheld device can be used by sonographers and also easily be integrated with robot arms for automated sonography. The handheld device is ergonomically designed; rapid attachment and removal of the ultrasound transducer itself is possible using easy-to-operate clip mechanisms. A cable locking mechanism reduces the impact that gravitational and other external forces have (originating from data and power supply cables connected to the probe) on our measurements. Gravitational errors introduced by the housing of the probe are compensated for using knowledge of the housing geometry and the integrated pose sensor that provides us with accurate orientation information. In this paper, we describe the handheld probe with its integrated force/pose sensors and our approach to gravity compensation. We carried out a set of experiments to verify the feasibility of our approach to obtain accurate spatial information of the handheld probe.

Features calibration of the dynamic force transducers

NASA Astrophysics Data System (ADS)

Sc., M. Yu Prilepko D.; Lysenko, V. G.

2018-04-01

The article discusses calibration methods of dynamic forces measuring instruments. The relevance of work is dictated by need to valid definition of the dynamic forces transducers metrological characteristics taking into account their intended application. The aim of this work is choice justification of calibration method, which provides the definition dynamic forces transducers metrological characteristics under simulation operating conditions for determining suitability for using in accordance with its purpose. The following tasks are solved: the mathematical model and the main measurements equation of calibration dynamic forces transducers by load weight, the main budget uncertainty components of calibration are defined. The new method of dynamic forces transducers calibration with use the reference converter “force-deformation” based on the calibrated elastic element and measurement of his deformation by a laser interferometer is offered. The mathematical model and the main measurements equation of the offered method is constructed. It is shown that use of calibration method based on measurements by the laser interferometer of calibrated elastic element deformations allows to exclude or to considerably reduce the uncertainty budget components inherent to method of load weight.

A functional TOC complex contributes to gravity signal transduction in Arabidopsis

PubMed Central

Strohm, Allison K.; Barrett-Wilt, Greg A.; Masson, Patrick H.

2014-01-01

Although plastid sedimentation has long been recognized as important for a plant's perception of gravity, it was recently shown that plastids play an additional function in gravitropism. The Translocon at the Outer envelope membrane of Chloroplasts (TOC) complex transports nuclear-encoded proteins into plastids, and a receptor of this complex, Toc132, was previously hypothesized to contribute to gravitropism either by directly functioning as a gravity signal transducer or by indirectly mediating the plastid localization of a gravity signal transducer. Here we show that mutations in multiple genes encoding TOC complex components affect gravitropism in a genetically sensitized background and that the cytoplasmic acidic domain of Toc132 is not required for its involvement in this process. Furthermore, mutations in TOC132 enhance the gravitropic defect of a mutant whose amyloplasts lack starch. Finally, we show that the levels of several nuclear-encoded root proteins are altered in toc132 mutants. These data suggest that the TOC complex indirectly mediates gravity signal transduction in Arabidopsis and support the idea that plastids are involved in gravitropism not only through their ability to sediment but also as part of the signal transduction mechanism. PMID:24795735

A functional TOC complex contributes to gravity signal transduction in Arabidopsis.

PubMed

Strohm, Allison K; Barrett-Wilt, Greg A; Masson, Patrick H

2014-01-01

Although plastid sedimentation has long been recognized as important for a plant's perception of gravity, it was recently shown that plastids play an additional function in gravitropism. The Translocon at the Outer envelope membrane of Chloroplasts (TOC) complex transports nuclear-encoded proteins into plastids, and a receptor of this complex, Toc132, was previously hypothesized to contribute to gravitropism either by directly functioning as a gravity signal transducer or by indirectly mediating the plastid localization of a gravity signal transducer. Here we show that mutations in multiple genes encoding TOC complex components affect gravitropism in a genetically sensitized background and that the cytoplasmic acidic domain of Toc132 is not required for its involvement in this process. Furthermore, mutations in TOC132 enhance the gravitropic defect of a mutant whose amyloplasts lack starch. Finally, we show that the levels of several nuclear-encoded root proteins are altered in toc132 mutants. These data suggest that the TOC complex indirectly mediates gravity signal transduction in Arabidopsis and support the idea that plastids are involved in gravitropism not only through their ability to sediment but also as part of the signal transduction mechanism.

Plasma momentum meter for momentum flux measurements

DOEpatents

Zonca, F.; Cohen, S.A.; Bennett, T.; Timberlake, J.R.

1993-08-24

An apparatus is described for measuring momentum flux from an intense plasma stream, comprising: refractory target means oriented normal to the flow of said plasma stream for bombardment by said plasma stream where said bombardment by said plasma stream applies a pressure to said target means, pendulum means for communicating a translational displacement of said target to a force transducer where said translational displacement of said target is transferred to said force transducer by an elongated member coupled to said target, where said member is suspended by a pendulum configuration means and where said force transducer is responsive to said translational displacement of said member, and force transducer means for outputting a signal representing pressure data corresponding to said displacement.

Introduction: an overview of gravity sensing, perception, and signal transduction in animals and plants

NASA Technical Reports Server (NTRS)

Halstead, T. W.

1994-01-01

The antiquity of biological sensitivity and response to gravity can be traced through the ubiquity of morphology, mechanisms, and cellular events in gravity sensing biological systems in the most diverse species of both plants and animals. Further, when we examine organisms at the cellular level to elucidate the molecular mechanism by which a gravitational signal is transduced into a biochemical response, the distinction between plants and animals becomes blurred.

Amorphous ribbon transducers

NASA Astrophysics Data System (ADS)

Meydan, T.; Overshott, K. J.

1984-02-01

Amorphous ribbon transducers have been investigated which consist of toroidally wound amorphous ribbon with a primary (magnetizing) winding and secondary (search coil) windings. The application of a force to the ribbon gives a linear search coil voltage against applied force characteristic. The positioning of the windings with respect to the applied force has been studied, and it is shown that the effect of the applied force is localized. Domain studies have shown that the applied force produces domain wall motion which can be correlated to the performance. These results have elucidated the operation of ac amorphous ribbon transducers and enabled improved designs to be produced.

Dual-Use Transducer for Use with a Boundary-Stiffened Panel and Method of Using the Same

NASA Technical Reports Server (NTRS)

Schiller, Noah H. (Inventor); Cabell, Randolph H. (Inventor)

2011-01-01

A transducer for use with a boundary-stiffened panel has an inter-digitated electrode (IDE) and a piezoelectric wafer portion positioned therebetween. The IDE and/or the wafer portion are triangular, with one edge or side aligned with a boundary edge of the panel. The transducer generates and transmits an output force to the panel in response to an input voltage signal from a sensor, which can be another transducer as described above or an accelerometer. A controller can generate an output force signal in response to the input voltage signal to help cancel the input voltage signal. A method of using the transducer minimizes vibration in the panel by connecting multiple transducers around a perimeter thereof. Motion is measured at different portions of the panel, and a voltage signal determined from the motion is transmitted to the transducers to generate an output force at least partially cancelling or damping the motion.

Acoustic levitation of a large solid sphere

NASA Astrophysics Data System (ADS)

Andrade, Marco A. B.; Bernassau, Anne L.; Adamowski, Julio C.

2016-07-01

We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.

An approach to improve the spatial resolution of a force mapping sensing system

NASA Astrophysics Data System (ADS)

Negri, Lucas Hermann; Manfron Schiefer, Elberth; Sade Paterno, Aleksander; Muller, Marcia; Luís Fabris, José

2016-02-01

This paper proposes a smart sensor system capable of detecting sparse forces applied to different positions of a metal plate. The sensing is performed with strain transducers based on fiber Bragg gratings (FBG) distributed under the plate. Forces actuating in nine squared regions of the plate, resulting from up to three different loads applied simultaneously to the plate, were monitored with seven transducers. The system determines the magnitude of the force/pressure applied on each specific area, even in the absence of a dedicated transducer for that area. The set of strain transducers with coupled responses and a compressive sensing algorithm are employed to solve the underdetermined inverse problem which emerges from mapping the force. In this configuration, experimental results have shown that the system is capable of recovering the value of the load distributed on the plate with a signal-to-noise ratio better than 12 dB, when the plate is submitted to three simultaneous test loads. The proposed method is a practical illustration of compressive sensing algorithms for the reduction of the number of FBG-based transducers used in a quasi-distributed configuration.

Role of membrane sterols and cortical microtubules in gravity resistance in plants

NASA Astrophysics Data System (ADS)

Hoson, T.; Koizumi, T.; Matsumoto, S.; Kumasaki, S.; Soga, K.; Wakabayashi, K.; Sakaki, T.

Resistance to the gravitational force is a principal graviresponse in plants comparable to gravitropism Nevertheless only limited information has been obtained for this graviresponse We have examined mechanisms of signal perception transformation and transduction of the perceived signal and response to the transduced signal in gravity resistance using hypergravity conditions produced by centrifugation In Arabidopsis hypocotyls hypergravity treatment greatly increased the expression level of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase HMGR which catalyzes a reaction producing mevalonic acid a key precursor of terpenoids such as membrane sterols Geranyl diphosphate synthase gene was also up-regulated by hypergravity whereas the expression of other genes involved in membrane lipid metabolism was not influenced Hypergravity caused an increase in sterol content in azuki bean epicotyls but not in phospholipid glycolipid or fatty acid content Also hypergravity did not influence fatty acid composition in any lipid class Thus the effect of hypergravity on membrane lipid metabolism was specific for sterol synthesis On the other hand alpha- and beta-tubulin genes were up-regulated by hypergravity treatment in Arabidopsis hypocotyls Hypergravity also induced reorientation of cortical microtubules in azuki epicotyls the percentage of epidermal cells with transverse microtubles was decreased whereas that with longitudinal microtubules was increased Inhibitors of HMGR action and microtubule-disrupting agents completely prevented the gravity resistance

A Force Transducer from a Junk Electronic Balance

ERIC Educational Resources Information Center

Aguilar, Horacio Munguia; Aguilar, Francisco Armenta

2009-01-01

It is shown how the load cell from a junk electronic balance can be used as a force transducer for physics experiments. Recovering this device is not only an inexpensive way of getting a valuable laboratory tool but also very useful didactic work on electronic instrumentation. Some experiments on mechanics with this transducer are possible after a…

Simultaneous in- and out-of-plane Mitral Valve Annular Force Measurements.

PubMed

Skov, Søren N; Røpcke, Diana M; Telling, Kristine; Ilkjær, Christine; Tjørnild, Marcell J; Nygaard, Hans; Nielsen, Sten L; Jensen, Morten O

2015-06-01

Mitral valve repair with annuloplasty is often favoured over total valve replacement. In order to develop and optimize new annuloplasty ring designs, it is important to study the complex biomechanical behaviour of the valve annulus and the subvalvular apparatus with simultaneous in- and out-of-plane restraining force measurements. A new flat D-shaped mitral valve annular force transducer was developed. The transducer was mounted with strain gauges to measure strain and calibrated to provide simultaneous restraining forces in- and out of the mitral annular plane. The force transducer was implanted and evaluated in an 80 kg porcine experimental model. Accumulation of out-of-plane restraining forces, creating strain in the anterior segment were 0.7 ± 0.0 N (towards apex) and an average force accumulation of 1.5 ± 0.3 N, creating strain in the commissural segments (away from apex). The accumulations of in-plane restraining forces, creating strain on the inner side of the ring were 1.7 ± 0.2 N (away from ring center). A new mitral annular force transducer was successfully developed and evaluated in vivo. The transducer was able to measure forces simultaneously in different planes. Initial indications point towards overall agreement with previous individual force measurements in- and out-of the mitral annular plane. This can provide more detailed insight into the annular force distribution, and could potentially improve the level of evidence based mitral valve repair and support the development of future mitral annuloplasty devices.

Instrument for controlling the application of mechanical loads to biological and bicompatible test subjects

DOEpatents

Lintilhac, Phillip M.; Vesecky, Thompson B.

1995-01-01

Apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user.

Instrument for controlling the application of mechanical loads to biological and bicompatible test subjects

DOEpatents

Lintilhac, P.M.; Vesecky, T.B.

1995-09-19

An apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user. 8 figs.

Influence of bending stress on flux distribution in toroidal transducers

NASA Astrophysics Data System (ADS)

Goktepe, M.; Meydan, T.

1994-05-01

Amorphous transducers consisting of toroidally wound amorphous ribbon with a magnetising winding and search coil windings have been investigated. The application of displacement to the toroid gives a linear search coil voltage against the applied force characteristics. The position of the search coils with respect to the applied force has been studied and it is shown that the effect of applied force is localised. These results have elucidated the operation of ac amorphous ribbon transducers and enabled improved designs to be produced.

Cell proliferation and plant development under novel altered gravity environments.

PubMed

Herranz, R; Medina, F J

2014-01-01

Gravity is a key factor for life on Earth. It is the only environmental factor that has remained constant throughout evolution, and plants use it to modulate important physiological activities; gravity removal or alteration produces substantial changes in essential functions. For root gravitropism, gravity is sensed in specialised cells, which are capable of detecting magnitudes of the g vector lower than 10(-3) . Then, the mechanosignal is transduced to upper zones of the root, resulting in changes in the lateral distribution of auxin and in the rate of auxin polar transport. Gravity alteration has consequences for cell growth and proliferation rates in root meristems, which are the basis of the developmental programme of a plant, in which regulation via auxin is involved. The effect is disruption of meristematic competence, i.e. the strict coordination between cell proliferation and growth, which characterises meristematic cells. This effect can be related to changes in the transport and distribution of auxin throughout the root. However, similar effects of gravity alteration have been found in plant cell cultures in vitro, in which neither specialised structures for gravity sensing and signal transduction, nor apparent gravitropism have been described. We postulate that gravity resistance, a general mechanism of cellular origin for developing rigid structures in plants capable of resisting the gravity force, could also be responsible for the changes in cell growth and proliferation parameters detected in non-specialised cells. The mechanisms of gravitropism and graviresistance are complementary, the first being mostly sensitive to the direction of the gravity vector, and the second to its magnitude. At a global molecular level, the consequence of gravity alteration is that the genome should be finely tuned to counteract a type of stress that plants have never encountered before throughout evolution. Multigene families and redundant genes present an advantage in that they can experience changes without the risk of being deleterious and, for this reason, they should play a key role in the response to gravitational stress. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

Acoustic levitation of a large solid sphere

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

Andrade, Marco A. B., E-mail: marcobrizzotti@gmail.com; Bernassau, Anne L.; Adamowski, Julio C.

2016-07-25

We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setupmore » consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.« less

Effect of Surface Pressure Integration Methodology on Launch Vehicle Buffet Forcing Functions

NASA Technical Reports Server (NTRS)

Sekula, Martin K.; Piatak, David J.; Rausch, Russ D.

2016-01-01

The 2014 test of the Space Launch System (SLS) Rigid Buffet Model conducted at the NASA Langley Transonic Dynamics Tunnel employed an extremely high number of unsteady pressure transducers. The high channel count provided an opportunity to examine the effect of transducer placement on the resulting buffet forcing functions (BFFs). Rings of transducers on the forward half of the model were employed to simulate a single-body vehicle. The impact of transducer density, circumferential distribution, and loss of a single transducer on the resulting BFFs were examined. Rings of transducers on the aft half of the SLS model were employed to examine the effect of transducer density and circumferential distribution on BFFs for a multi-body configuration. Transducer placement considerations with respect to model size, facility infrastructure, and data acquisition system capabilities, which affect the integration process, are also discussed.

Electromechanical Nerve Stimulator

NASA Technical Reports Server (NTRS)

Tcheng, Ping; Supplee, Frank H., Jr.; Prass, Richard L.

1993-01-01

Nerve stimulator applies and/or measures precisely controlled force and/or displacement to nerve so response of nerve measured. Consists of three major components connected in tandem: miniature probe with spherical tip; transducer; and actuator. Probe applies force to nerve, transducer measures force and sends feedback signal to control circuitry, and actuator positions force transducer and probe. Separate box houses control circuits and panel. Operator uses panel to select operating mode and parameters. Stimulator used in research to characterize behavior of nerve under various conditions of temperature, anesthesia, ventilation, and prior damage to nerve. Also used clinically to assess damage to nerve from disease or accident and to monitor response of nerve during surgery.

New devices for measuring forces on the kayak foot bar and on the seat during flat-water kayak paddling: a technical report.

PubMed

Nilsson, Johnny E; Rosdahl, Hans G

2014-03-01

The purpose was to develop and validate portable force-measurement devices for recording push and pull forces applied by each foot to the foot bar of a kayak and the horizontal force at the seat. A foot plate on a single-point force transducer mounted on the kayak foot bar underneath each foot allowed the push and pull forces to be recorded. Two metal frames interconnected with 4 linear ball bearings, and a force transducer allowed recording of horizontal seat force. The foot-bar-force device was calibrated by loading each foot plate with weights in the push-pull direction perpendicular to the foot plate surface, while the seat-force device was calibrated to horizontal forces with and without weights on the seat. A strong linearity (r2 = .99-1.0) was found between transducer output signal and load force in the push and pull directions for both foot-bar transducers perpendicular to the foot plate and the seat-force-measuring device. Reliability of both devices was tested by means of a test-retest design. The coefficient of variation (CV) for foot-bar push and pull forces ranged from 0.1% to 1.1%, and the CV for the seat forces varied from 0.6% to 2.2%. The current study opens up a field for new investigations of the forces generated in the kayak and ways to optimize kayak-paddling performance.

How cells (might) sense microgravity

NASA Technical Reports Server (NTRS)

Ingber, D.

1999-01-01

This article is a summary of a lecture presented at an ESA/NASA Workshop on Cell and Molecular Biology Research in Space that convened in Leuven, Belgium, in June 1998. Recent studies are reviewed which suggest that cells may sense mechanical stresses, including those due to gravity, through changes in the balance of forces that are transmitted across transmembrane adhesion receptors that link the cytoskeleton to the extracellular matrix and to other cells (e.g., integrins, cadherins, selectins). The mechanism by which these mechanical signals are transduced and converted into a biochemical response appears to be based, in part, on the finding that living cells use a tension-dependent form of architecture, known as tensegrity, to organize and stabilize their cytoskeleton. Because of tensegrity, the cellular response to stress differs depending on the level of pre-stress (pre-existing tension) in the cytoskeleton and it involves all three cytoskeletal filament systems as well as nuclear scaffolds. Recent studies confirm that alterations in the cellular force balance can influence intracellular biochemistry within focal adhesion complexes that form at the site of integrin binding as well as gene expression in the nucleus. These results suggest that gravity sensation may not result from direct activation of any single gravioreceptor molecule. Instead, gravitational forces may be experienced by individual cells in the living organism as a result of stress-dependent changes in cell, tissue, or organ structure that, in turn, alter extracellular matrix mechanics, cell shape, cytoskeletal organization, or internal pre-stress in the cell-tissue matrix.--Ingber, D. How cells (might) sense microgravity.

United in Diversity: Mechanosensitive Ion Channels in Plants

PubMed Central

Hamilton, Eric S.; Schlegel, Angela M.; Haswell, Elizabeth S.

2015-01-01

Mechanosensitive (MS) ion channels are a common mechanism for perceiving and responding to mechanical force. This class of mechanoreceptors is capable of transducing membrane tension directly into ion flux. In plant systems, MS ion channels have been proposed to play a wide array of roles, from the perception of touch and gravity to the osmotic homeostasis of intracellular organelles. Three families of plant MS ion channels have been identified: the MscS-like (MSL), Mid1-complementing activity (MCA), and two-pore potassium (TPK) families. Channels from these families vary widely in structure and function, localize to multiple cellular compartments, and conduct chloride, calcium, and/or potassium ions. However, they are still likely to represent only a fraction of the MS ion channel diversity in plant systems. PMID:25494462

Fluid force transducer

DOEpatents

Jendrzejczyk, Joseph A.

1982-01-01

An electrical fluid force transducer for measuring the magnitude and direction of fluid forces caused by lateral fluid flow, includes a movable sleeve which is deflectable in response to the movement of fluid, and a rod fixed to the sleeve to translate forces applied to the sleeve to strain gauges attached to the rod, the strain gauges being connected in a bridge circuit arrangement enabling generation of a signal output indicative of the magnitude and direction of the force applied to the sleeve.

Radii effect on the translation spring constant of force transducer beams

NASA Technical Reports Server (NTRS)

Scott, C. E.

1992-01-01

Multi-component strain-gage force transducer design requires the designer to determine the spring constant of the numerous beams or flexures incorporated in the transducer. The classical beam deflection formulae that are used in calculating these spring constants typically assume that the beam has a uniform moment of inertia along the entire beam length. In practice all beams have a radius at the end where the beam interfaces with the shoulder of the transducer, and on short beams in particular this increases the beam spring constant considerably. A Basic computer program utilizing numerical integration is presented to determine this effect.

Adhesion promoters for large scale fabrication of dielectric elastomer stack transducers (DESTs) made of pre-fabricated dielectric films

NASA Astrophysics Data System (ADS)

Grotepaß, T.; Förster-Zügel, F.; Mößinger, H.; Schlaak, H. F.

2015-04-01

Multilayer dielectric elastomer stack transducers (DESTs) are a promising new transducer technology with many applications in different industry sectors, like medical devices, human-machine-interaction, etc. Stacked dielectric elastomer transducers show larger thickness contraction driven by lower voltages than transducers made from a single dielectric layer. Traditionally multilayered DESTs are produced by repeatedly cross-linking a liquid elastomeric pre-polymer into the required shape. Our recent research focusses on a novel fabrication method for large scale stack transducers with a surface area over 200 x 300 mm by processing pre-fabricated elastomeric thin films of less than 50 μm thicknesses. The thin films are provided as two- or three-layer composites, where the elastomer is sandwiched between one or two sacrificial liners. Separating the elastomeric film from the residual layers and assembling them into dielectric elastomer stack transducers poses many challenges concerning adhesion, since the dielectric film merely separates from the liner if the adhesive forces between them are overcome. Conversely, during the assembly of a dielectric elastomer stack transducer, adhesive forces have to be established between two elastomeric layers or between the dielectric and the electrode layer. The very low Young's modulus of at least one adhesion partner requires suitable means of increasing the adhesive forces between the different adhesive layers of a dielectric elastomer stack transducer to prevent a delamination of the transducer during its lifetime. This work evaluates different surface activation treatments - corona, low-pressure plasma and UV-light - and their applicability in the production of large scale DESTs made from pre-fabricated elastomeric films.

High-Sensitivity Encoder-Like Micro Area-Changed Capacitive Transducer for a Nano-g Micro Accelerometer

PubMed Central

Zheng, Panpan; Liu, Jinquan; Li, Zhu; Liu, Huafeng

2017-01-01

Encoder-like micro area-changed capacitive transducers are advantageous in terms of their better linearity and larger dynamic range compared to gap-changed capacitive transducers. Such transducers have been widely applied in rectilinear and rotational position sensors, lab-on-a-chip applications and bio-sensors. However, a complete model accounting for both the parasitic capacitance and fringe effect in area-changed capacitive transducers has not yet been developed. This paper presents a complete model for this type of transducer applied to a high-resolution micro accelerometer that was verified by both simulations and experiments. A novel optimization method involving the insertion of photosensitive polyimide was used to reduce the parasitic capacitance, and the capacitor spacing was decreased to overcome the fringe effect. The sensitivity of the optimized transducer was approximately 46 pF/mm, which was nearly 40 times higher than that of our previous transducer. The displacement detection resolution was measured as 50 pm/√Hz at 0.1 Hz using a precise capacitance detection circuit. Then, the transducer was applied to a sandwich in-plane micro accelerometer, and the measured level of the accelerometer was approximately 30 ng/√Hz at 1Hz. The earthquake that occurred in Taiwan was also detected during a continuous gravity measurement. PMID:28930176

Genetic analysis of gravity signal transduction in roots

NASA Astrophysics Data System (ADS)

Masson, Patrick; Strohm, Allison; Baldwin, Katherine

To grow downward into the soil, roots use gravity as a guide. Specialized cells, named stato-cytes, enable this directional growth response by perceiving gravity. Located in the columella region of the cap, these cells sense a reorientation of the root within the gravity field through the sedimentation of, and/or tension/pressure exerted by, dense amyloplasts. This process trig-gers a gravity signal transduction pathway that leads to a fast alkalinization of the cytoplasm and a change in the distribution of the plasma membrane-associated auxin-efflux carrier PIN3. The latter protein is uniformly distributed within the plasma membrane on all sides of the cell in vertically oriented roots. However, it quickly accumulates at the bottom side upon gravis-timulation. This process correlates with a preferential transport of auxin to the bottom side of the root cap, resulting in a lateral gradient across the tip. This gradient is then transported to the elongation zone where it promotes differential cellular elongation, resulting in downward curvature. We isolated mutations that affect gravity signal transduction at a step that pre-cedes cytoplasmic alkalinization and/or PIN3 relocalization and lateral auxin transport across the cap. arg1 and arl2 mutations identify a common genetic pathway that is needed for all three gravity-induced processes in the cap statocytes, indicating these genes function early in the pathway. On the other hand, adk1 affects gravity-induced PIN3 relocalization and lateral auxin transport, but it does not interfere with cytoplasmic alkalinization. ARG1 and ARL2 encode J-domain proteins that are associated with membranes of the vesicular trafficking path-way whereas ADK1 encodes adenosine kinase, an enzyme that converts adenosine derived from nucleic acid metabolism and the AdoMet cycle into AMP, thereby alleviating feedback inhibi-tion of this important methyl-donor cycle. Because mutations in ARG1 (and ARL2) do not completely eliminate gravitropism, we sought genetic enhancers of arg1 as a way to identify new gravity signal transducers. Two of these modifiers, named mar1 and mar2, were found to affect genes that encode two subunits of the plastidic outer-membrane protein import complex, TOC75 and TOC132, respectively. mar2 did not affect the ultrastructure of amyloplasts in the statocytes nor did it alter their ability to sediment in response to gravistimulation, suggesting a role for the outer membrane of the amyloplasts in gravity signal transduction (reviewed in Stanga et al., 2009, Plant Signal Behavior 4(10): 1-9). The contribution of TOC132 in gravity signal transduction is being investigated by analyzing the regions of this protein that are needed for the pathway, and investigating the contribution of a putative TOC132-interacting protein in gravity signal transduction. We have also isolated additional putative enhancers of arg1-2 in the hope of identifying new plastid-associated gravity signal transducers, and have initiated a screen for genetic enhancers of mar2 to seek new transducers in the ARG1 branch of the pathway.

Localize and identify the gravity sensing mechanism of plants

NASA Technical Reports Server (NTRS)

Bandurski, Robert S.

1990-01-01

The machinery by which a plant transduces the gravity stimulus into a growth response is localized and identified at the cellular level. The fact that a plant grows unequally on the lower side of a horizontally placed stem implies that there must be an asymmetric distribution of some of the chemical substances involved in the growth response. The three most likely chemicals to cause this growth were determined to be potassium, calcium, or the growth hormone, indole-3-acetic acid (IAA). IAA was chosen for this study and the results present a fairly complete understanding of the transduction of the gravity stimulus.

PRESSURE TRANSDUCER

DOEpatents

Sander, H.H.

1959-10-01

A pressure or mechanical force transducer particularly adaptable to miniature telemetering systems is described. Basically the device consists of a transistor located within a magnetic field adapted to change in response to mechanical force. The conduction characteristics of the transistor in turn vary proportionally with changes in the magnetic flux across the transistor such that the output (either frequency of amplitude) of the transistor circuit is proportional to mechanical force or pressure.

Experimental Investigation of a Piezo-Optical Transducer for Highly Sensitive Strain Gauges

NASA Astrophysics Data System (ADS)

Paulish, A. G.; Zagubisalo, P. S.; Barakov, V. N.; Pavlov, M. A.

2018-03-01

The characteristics of a piezo-optical transducer of a new design with high strain sensitivity at compact size have been studied.The original form of the photoelastic element provides a considerable increase in the stress in its working area at a given external force, resulting in an increase in the sensitivity of the transducer. The main characteristics of the transducer were measured using a specially designed device. The strain at a given applied force was calculated using a developed mathematical model of the transducer. As a result, the sensitivity to the relative strain was Δ x/ x=3 · 10-10, the dynamic range was at least four orders of magnitude higher and the gauge factor three orders of magnitude higher than those of strain-resistive gauges.

Vehicle brake testing system

DOEpatents

Stevens, Samuel S [Harriman, TN; Hodgson, Jeffrey W [Lenoir City, TN

2002-11-19

This invention relates to a force measuring system capable of measuring forces associated with vehicle braking and of evaluating braking performance. The disclosure concerns an invention which comprises a first row of linearly aligned plates, a force bearing surface extending beneath and beside the plates, vertically oriented links and horizontally oriented links connecting each plate to a force bearing surface, a force measuring device in each link, a transducer coupled to each force measuring device, and a computing device coupled to receive an output signal from the transducer indicative of measured force in each force measuring device. The present invention may be used for testing vehicle brake systems.

Does flowpath alteration by centrifugal force cause deviation from Darcy's law?

NASA Astrophysics Data System (ADS)

Nimmo, J. R.; Turturro, A. C.; MA, B.; Caputo, M. C.; Perkins, K. S.

2016-12-01

Though driving force much larger than gravity is unnatural, centrifugal force has proven useful for investigating flow in soil and rock. It affords practical measurement techniques, as well as a means of perturbation that can provide insights into the fundamentals of flow. Many centrifugally-driven flow experiments have been carried out in the USGS Menlo Park facility since 1980. Notable developments include the Steady-State Centrifuge (SSC) method and the Quasi-Steady Centrifuge (QSC) method for accurate measurements of unsaturated hydraulic properties over a wide range of water content. Centrifugal force can affect flowpaths in at least two ways: (1) deformation of pores by compression, and (2) distortion of air-water interfaces. Compression reduces the hydraulic conductivity K. We have measured this effect on saturated K of several core samples from several m depth. For forces over a 50X (factor-of-50) range, saturated K varied by as much as 10X. In unsaturated soil, the effect is less because much of the pore size reduction occurs in large pores and in air-filled space. A complication is that some portion of the compressional strain is elastic, and its rebound after centrifugation prevents easy determination of how much strain occurred at the time of measurement. Experiments with a linear displacement transducer inside a centrifuge bucket showed for a silty soil of massive structure that about one-third of the strain is elastic. Centrifugal force affords rigorous tests of Darcy's law. If flux measured at a single water content varies in direct proportion to driving force, Darcy's law is confirmed for the conditions tested. The SSC and QSC methods are ideally suited to this purpose as they allow great force variation with minimal effect on water content. Our tests at forces up to 1000 or more times normal gravity in a sandy soil at low water content, and in a porous sandstone (calcarenite) at intermediate water content, show strong agreement with Darcy's law. Further tests are needed because deviation would be more likely in cases such as higher water contents or greater heterogeneity. The observed good agreement, perhaps surprisingly, indicates that any force-caused alterations of the shape of air-water interfaces do not significantly affect unsaturated K.

Traceable calibration and demonstration of a portable dynamic force transfer standard

NASA Astrophysics Data System (ADS)

Vlajic, Nicholas; Chijioke, Ako

2017-08-01

In general, the dynamic sensitivity of a force transducer depends upon the mechanical system in which it is used. This dependence serves as motivation to develop a dynamic force transfer standard, which can be used to calibrate an application transducer in situ. In this work, we SI-traceably calibrate a hand-held force transducer, namely an impact hammer, by using a mass suspended from a thin line which is cut to produce a known dynamic force in the form of a step function. We show that this instrument is a promising candidate as a transfer standard, since its dynamic response has small variance between different users. This calibrated transfer standard is then used to calibrate a secondary force transducer in an example application setting. The combined standard uncertainty (k  =  2) in the calibration of the transfer standard was determined to be 2.1% or less, up to a bandwidth of 5 kHz. The combined standard uncertainty (k  =  2) in the performed transfer calibration was less than 4%, up to 3 kHz. An advantage of the transfer calibration framework presented here, is that the transfer standard can be used to transfer SI-traceable calibrations without the use of any SI-traceable voltage metrology instrumentation.

A new method to include the gravitational forces in a finite element model of the scoliotic spine.

PubMed

Clin, Julien; Aubin, Carl-Éric; Lalonde, Nadine; Parent, Stefan; Labelle, Hubert

2011-08-01

The distribution of stresses in the scoliotic spine is still not well known despite its biomechanical importance in the pathomechanisms and treatment of scoliosis. Gravitational forces are one of the sources of these stresses. Existing finite element models (FEMs), when considering gravity, applied these forces on a geometry acquired from radiographs while the patient was already subjected to gravity, which resulted in a deformed spine different from the actual one. A new method to include gravitational forces on a scoliotic trunk FEM and compute the stresses in the spine was consequently developed. The 3D geometry of three scoliotic patients was acquired using a multi-view X-ray 3D reconstruction technique and surface topography. The FEM of the patients' trunk was created using this geometry. A simulation process was developed to apply the gravitational forces at the centers of gravity of each vertebra level. First the "zero-gravity" geometry was determined by applying adequate upwards forces on the initial geometry. The stresses were reset to zero and then the gravity forces were applied to compute the geometry of the spine subjected to gravity. An optimization process was necessary to find the appropriate zero-gravity and gravity geometries. The design variables were the forces applied on the model to find the zero-gravity geometry. After optimization the difference between the vertebral positions acquired from radiographs and the vertebral positions simulated with the model was inferior to 3 mm. The forces and compressive stresses in the scoliotic spine were then computed. There was an asymmetrical load in the coronal plane, particularly, at the apices of the scoliotic curves. Difference of mean compressive stresses between concavity and convexity of the scoliotic curves ranged between 0.1 and 0.2 MPa. In conclusion, a realistic way of integrating gravity in a scoliotic trunk FEM was developed and stresses due to gravity were explicitly computed. This is a valuable improvement for further biomechanical modeling studies of scoliosis.

Nonstationary Gravity Wave Forcing of the Stratospheric Zonal Mean Wind

NASA Technical Reports Server (NTRS)

Alexander, M. J.; Rosenlof, K. H.

1996-01-01

The role of gravity wave forcing in the zonal mean circulation of the stratosphere is discussed. Starting from some very simple assumptions about the momentum flux spectrum of nonstationary (non-zero phase speed) waves at forcing levels in the troposphere, a linear model is used to calculate wave propagation through climatological zonal mean winds at solstice seasons. As the wave amplitudes exceed their stable limits, a saturation criterion is imposed to account for nonlinear wave breakdown effects, and the resulting vertical gradient in the wave momentum flux is then used to estimate the mean flow forcing per unit mass. Evidence from global, assimilated data sets are used to constrain these forcing estimates. The results suggest the gravity-wave-driven force is accelerative (has the same sign as the mean wind) throughout most of the stratosphere above 20 km. The sense of the gravity wave forcing in the stratosphere is thus opposite to that in the mesosphere, where gravity wave drag is widely believed to play a principal role in decelerating the mesospheric jets. The forcing estimates are further compared to existing gravity wave parameterizations for the same climatological zonal mean conditions. Substantial disagreement is evident in the stratosphere, and we discuss the reasons for the disagreement. The results suggest limits on typical gravity wave amplitudes near source levels in the troposphere at solstice seasons. The gravity wave forcing in the stratosphere appears to have a substantial effect on lower stratospheric temperatures during southern hemisphere summer and thus may be relevant to climate.

Detecting the gravitational sensitivity of Paramecium caudatum using magnetic forces

NASA Astrophysics Data System (ADS)

Guevorkian, Karine; Valles, James M., Jr.

2006-03-01

Under normal conditions, Paramecium cells regulate their swimming speed in response to the pN level mechanical force of gravity. This regulation, known as gravikinesis, is more pronounced when the external force is increased by methods such as centrifugation. Here we present a novel technique that simulates gravity fields using the interactions between strong inhomogeneous magnetic fields and cells. We are able to achieve variable gravities spanning from 10xg to -8xg; where g is earth's gravity. Our experiments show that the swimming speed regulation of Paramecium caudatum to magnetically simulated gravity is a true physiological response. In addition, they reveal a maximum propulsion force for paramecia. This advance establishes a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.

Gravity brake

DOEpatents

Lujan, Richard E.

2001-01-01

A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

PubMed

Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

2014-01-01

The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method.

Three-Dimensional Mid-Air Acoustic Manipulation by Ultrasonic Phased Arrays

PubMed Central

Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

2014-01-01

The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

Can vibratory feedback be used to improve postural stability in persons with transtibial limb loss?

PubMed

Rusaw, David; Hagberg, Kerstin; Nolan, Lee; Ramstrand, Nerrolyn

2012-01-01

The use of vibration as a feedback modality to convey motion of the body has been shown to improve measures of postural stability in some groups of patients. Because individuals using transtibial prostheses lack sensation distal to the amputation, vibratory feedback could possibly be used to improve their postural stability. The current investigation provided transtibial prosthesis users (n = 24, mean age 48 yr) with vibratory feedback proportional to the signal received from force transducers located under the prosthetic foot. Postural stability was evaluated by measuring center of pressure (CoP) movement, limits of stability, and rhythmic weight shift while participants stood on a force platform capable of rotations in the pitch plane (toes up/toes down). The results showed that the vibratory feedback increased the mediolateral displacement amplitude of CoP in standing balance and reduced the response time to rapid voluntary movements of the center of gravity. The results suggest that the use of vibratory feedback in an experimental setting leads to improvements in fast open-loop mechanisms of postural control in transtibial prosthesis users.

Direct force-measuring transducer used in blood pressure research

NASA Technical Reports Server (NTRS)

Eige, J. J.; Newgard, P. M.; Pressman, G. L.

1965-01-01

Direct force measuring transducer acts as an arterial tonometer, gives a direct readout to instrumentation, and is unaffected by ambient noise. It uses a semiconductor strain gage which is deflected by pressure pulses in the artery. The deflection changes the resistance of the gage and alters the voltage reading on the associated instrumentation.

Stability and Heat Transfer Characteristics of Condensing Films

NASA Astrophysics Data System (ADS)

Hermanson, J. C.; Pedersen, P. C.; Allen, J. S.; Shear, M. A.; Chen, Z. Q.; Alexandrou, A. N.

2002-11-01

The overall objective of this research is to investigate the fundamental physics of film condensation in reduced gravity. The condensation of vapor on a cool surface is important in many engineering problems,including spacecraft thermal control and also the behavior of condensate films that may form on the interior surfaces of spacecraft. To examine the effects of body force on condensing films, two different geometries have been tested in the laboratory: (1) a stabilizing gravitational body force (+1g, or condensing surface facing 'upwards') and (2) de-stabilizing gravitational body force (-1g, or 'downwards'). For each geometry, different fluid configurations are employed to help isolate the fluid mechanical and thermal mechanisms operative in condensing films. The fluid configurations are (a) a condensing film, and (b) a non-condensing film with film growth by mass addition by through the plate surface. Condensation experiments are conducted in a test cell containing a cooled copper or brass plate with an exposed diameter of 12.7 cm. The metal surface is polished to allow for double-pass shadowgraph imaging, and the test surface is instrumented with imbedded heat transfer gauges and thermocouples. Representative shadowgraph images of a condensing, unstable (-1g) n-pentane film are shown. The interfacial disturbances associated with the de-stabilizing body force leading to droplet formation and break-off can be clearly seen. The heat transfer coefficient associated with the condensing film is shown. The heat transfer coefficient is seen to initially decrease, consistent with the increased thermal resistance due to layer growth. For sufficiently long time, a steady value of heat transfer is observed, accompanied by continuous droplet formation and break-off. The non-condensing cell consists of a stack of thin stainless steel disks 10 cm in diameter mounted in a brass enclosure. The disks are perforated with a regular pattern of 361 holes each 0.25 mm in diameter. Non-condensing experiments in -1g have employed 50 cSt and 125 cSt silicone oil pumped through the perforated disks at a specified rate by a syringe micropump. The time to droplet break-off and the disturbance wavelengths appear to decrease with increasing pumping rate. The ability to reliably perform multi-point, ultrasonic measurements of the film thickness has been demonstrated. A linear array of eight transducers of 6 mm diameter (with a beam footprint of comparable size) are pulsed with a square-wave signal at a frequency of 5 MHz and a pulse duration of approximately 0.3 s. For thin films (60 m to 2-3 mm in thickness) the layer thickness is determined by frequency analysis, where the received ultrasound pulse is Fourier transformed and the spacing between the peaks in the frequency spectrum is analyzed. For thicker layers (up to at least 1 cm in thickness), time-domain analysis is performed of the received ultrasound pulses to generate directly the layer thickness. A time-trace of the film thickness at a point using a single transducer in the linear array is shown for the case of an unstable (-1g) n-pentane film. The oscillations in film thickness are evidently due to the passage and/or shedding of droplets from the cooled plate surface. The entire transducer array was used to measure the changes in film thickness resulting from the passage of gravity waves generated either by an oscillating wall or the impact of a single droplet on the free surface of a film. The enclosure in both cases was 14 cm square and the transducer spacing was 12 mm. Best results were obtained using as test fluid a mixture of 50% glycerol and 50% water with a fluid layer thickness of 3-5 mm. In both cases the measured wavelengths and wave propagation speeds using the ultrasound technique compared reasonably well with those observed by optical imaging. Additional information can be found in the original extended abstract.

Stability and Heat Transfer Characteristics of Condensing Films

NASA Technical Reports Server (NTRS)

Hermanson, J. C.; Pedersen, P. C.; Allen, J. S.; Shear, M. A.; Chen, Z. Q.; Alexandrou, A. N.

2002-01-01

The overall objective of this research is to investigate the fundamental physics of film condensation in reduced gravity. The condensation of vapor on a cool surface is important in many engineering problems,including spacecraft thermal control and also the behavior of condensate films that may form on the interior surfaces of spacecraft. To examine the effects of body force on condensing films, two different geometries have been tested in the laboratory: (1) a stabilizing gravitational body force (+1g, or condensing surface facing 'upwards') and (2) de-stabilizing gravitational body force (-1g, or 'downwards'). For each geometry, different fluid configurations are employed to help isolate the fluid mechanical and thermal mechanisms operative in condensing films. The fluid configurations are (a) a condensing film, and (b) a non-condensing film with film growth by mass addition by through the plate surface. Condensation experiments are conducted in a test cell containing a cooled copper or brass plate with an exposed diameter of 12.7 cm. The metal surface is polished to allow for double-pass shadowgraph imaging, and the test surface is instrumented with imbedded heat transfer gauges and thermocouples. Representative shadowgraph images of a condensing, unstable (-1g) n-pentane film are shown. The interfacial disturbances associated with the de-stabilizing body force leading to droplet formation and break-off can be clearly seen. The heat transfer coefficient associated with the condensing film is shown. The heat transfer coefficient is seen to initially decrease, consistent with the increased thermal resistance due to layer growth. For sufficiently long time, a steady value of heat transfer is observed, accompanied by continuous droplet formation and break-off. The non-condensing cell consists of a stack of thin stainless steel disks 10 cm in diameter mounted in a brass enclosure. The disks are perforated with a regular pattern of 361 holes each 0.25 mm in diameter. Non-condensing experiments in -1g have employed 50 cSt and 125 cSt silicone oil pumped through the perforated disks at a specified rate by a syringe micropump. The time to droplet break-off and the disturbance wavelengths appear to decrease with increasing pumping rate. The ability to reliably perform multi-point, ultrasonic measurements of the film thickness has been demonstrated. A linear array of eight transducers of 6 mm diameter (with a beam footprint of comparable size) are pulsed with a square-wave signal at a frequency of 5 MHz and a pulse duration of approximately 0.3 s. For thin films (60 m to 2-3 mm in thickness) the layer thickness is determined by frequency analysis, where the received ultrasound pulse is Fourier transformed and the spacing between the peaks in the frequency spectrum is analyzed. For thicker layers (up to at least 1 cm in thickness), time-domain analysis is performed of the received ultrasound pulses to generate directly the layer thickness. A time-trace of the film thickness at a point using a single transducer in the linear array is shown for the case of an unstable (-1g) n-pentane film. The oscillations in film thickness are evidently due to the passage and/or shedding of droplets from the cooled plate surface. The entire transducer array was used to measure the changes in film thickness resulting from the passage of gravity waves generated either by an oscillating wall or the impact of a single droplet on the free surface of a film. The enclosure in both cases was 14 cm square and the transducer spacing was 12 mm. Best results were obtained using as test fluid a mixture of 50% glycerol and 50% water with a fluid layer thickness of 3-5 mm. In both cases the measured wavelengths and wave propagation speeds using the ultrasound technique compared reasonably well with those observed by optical imaging. Additional information can be found in the original extended abstract.

In-plane ultrasonic velocity measurement of longitudinal and shear waves in the machine direction with transducers in rotating wheels

DOEpatents

Hall, M.S.; Jackson, T.G.; Knerr, C.

1998-02-17

An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like. In addition to velocity measurements of ultrasonic signals in the plane of the web in the MD and CD, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web. 37 figs.

In-plane ultrasonic velocity measurement of longitudinal and shear waves in the machine direction with transducers in rotating wheels

DOEpatents

Hall, Maclin S.; Jackson, Theodore G.; Knerr, Christopher

1998-02-17

An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like. In addition to velocity measurements of ultrasonic signals in the plane of the web in the MD and CD, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web.

Sensor tip for a robotic gripper and method of manufacture

NASA Technical Reports Server (NTRS)

Lorenz, Robert D. (Inventor); Jackson, Gregory T. (Inventor)

1991-01-01

A sensor tip (10) for use in a robotic hand has a three-dimensional compliant elastomeric body (12) with an outer boundary (22) having a circular base (24) and a convex surface (26) extending therefrom. Four strain transducers (14, 16, 18, and 20) produce electrical signals indicative of the strain at various positions near the boundary of the elastomeric body (12) resulting from forces exerted upon the sensor tip (10) by an object which the robotic hand is manipulating. The transducers (14, 16, 18, and 20) are positioned about the convex surface (26) so as to produce signals that may be decoupled to determine the normal and tangential forces and the applied torque. A buffer amplifier circuit (34), one for each of the transducers (14, 16, 18, and 20), receives the signals and provides quasi-steady state force information. The circuit (34) connects the respective transducer (40) in a feedback loop around an amplifier (36) and has desirable attributes for static charge buffering. The sensor tip (10) is calibrated to determine proportionality constants for the decoupling algorithm for use of a force delivering system (60), which uses voice coils (74) to apply a force that is linearly related to the current introduced to each of the coils (74). A method of manufacture of the sensor tip (10) results in improved bonding between the transducers (14, 16, 18, and 20) and the elastomeric body (12) for better performance and longer life of the sensor tip (10).

Sensor tip for a robotic gripper and method of manufacture

NASA Technical Reports Server (NTRS)

Lorenz, Robert D. (Inventor); Jackson, Gregory T. (Inventor)

1993-01-01

A sensor tip (10) for use in a robotic hand has a three-dimensional compliant elastomeric body (12) with an outer boundary (22) having a circular base (24) and a convex surface (26) extending therefrom. Four strain transducers (14, 16, 18, and 20) produce electrical signals indicative of the strain at various positions near the boundary of the elastomeric body (12) resulting from forces exerted upon the sensor tip (10) by an object which the robotic hand is manipulating. The transducers (14, 16, 18, and 20) are positioned about the convex surface (26) so as to produce signals that may be decoupled to determine the normal and tangential forces and the applied torque. A buffer amplifier circuit (34), one for each of the transducers (14, 16, 18, and 20), receives the signals and provides quasi-steady state force information. The circuit (34) connects the respective transducer (40) in a feedback loop around an amplifier (36) and has desirable attributes for static charge buffering. The sensor tip (10) is calibrated to determine proportionality constants for the decoupling algorithm for use of a force delivering system (60), which uses voice coils (74) to apply a force that is linearly related to the current introduced to each of the coils (74). A method of manufacture of the sensor tip (10) results in improved bonding between the transducers (14, 16, 18, and 20) and the elastomeric body (12) for better performance and longer life of the sensor tip (10).

Precise Determination of the Zero-Gravity Surface Figure of a Mirror without Gravity-Sag Modeling

NASA Technical Reports Server (NTRS)

Bloemhof, Eric E.; Lam, Jonathan C.; Feria, V. Alfonso; Chang, Zensheu

2007-01-01

The zero-gravity surface figure of optics used in spaceborne astronomical instruments must be known to high accuracy, but earthbound metrology is typically corrupted by gravity sag. Generally, inference of the zero-gravity surface figure from a measurement made under normal gravity requires finite-element analysis (FEA), and for accurate results the mount forces must be well characterized. We describe how to infer the zero-gravity surface figure very precisely using the alternative classical technique of averaging pairs of measurements made with the direction of gravity reversed. We show that mount forces as well as gravity must be reversed between the two measurements and discuss how the St. Venant principle determines when a reversed mount force may be considered to be applied at the same place in the two orientations. Our approach requires no finite-element modeling and no detailed knowledge of mount forces other than the fact that they reverse and are applied at the same point in each orientation. If mount schemes are suitably chosen, zero-gravity optical surfaces may be inferred much more simply and more accurately than with FEA.

Cross-shaped torsional spring

DOEpatents

Williamson, Matthew M.; Pratt, Gill A.

1999-06-08

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section.

All about Forces & Gravity. Physical Science for Children[TM]. Schlessinger Science Library. [Videotape].

ERIC Educational Resources Information Center

2000

A force is a push or a pull. In All About Forces and Gravity, kids will join our host on a parasailing adventure to investigate how forces impact and shape everything that happens in the world around us. Learn about gravity and the work of Sir Isaac Newton, the English scientists whose scientific principles forever changed the way people looked at…

Intravascular ultrasound catheter to enhance microbubble-based drug delivery via acoustic radiation force.

PubMed

Kilroy, Joseph P; Klibanov, Alexander L; Wamhoff, Brian R; Hossack, John A

2012-10-01

Previous research has demonstrated that acoustic radiation force enhances intravascular microbubble adhesion to blood vessels in the presence of flow for moleculartargeted ultrasound imaging and drug delivery. A prototype acoustic radiation force intravascular ultrasound (ARFIVUS) catheter was designed and fabricated to displace a microbubble contrast agent in flow representative of conditions encountered in the human carotid artery. The prototype ARFIVUS transducer was designed to match the resonance frequency of 1.4- to 2.6-μm-diameter microbubbles modeled by an experimentally verified 1-D microbubble acoustic radiation force translation model. The transducer element was an elongated Navy Type I (hard) lead zirconate titanate (PZT) ceramic designed to operate at 3 MHz. Fabricated devices operated with center frequencies of 3.3 and 3.6 MHz with -6-dB fractional bandwidths of 55% and 50%, respectively. Microbubble translation velocities as high as 0.86 m/s were measured using a high-speed streak camera when insonating with the ARFIVUS transducer. Finally, the prototype was used to displace microbubbles in a flow phantom while imaging with a commercial 45-MHz imaging IVUS transducer. A sustained increase of 31 dB in average video intensity was measured following insonation with the ARFIVUS, indicating microbubble accumulation resulting from the application of acoustic radiation force.

Cylindrical acoustic levitator/concentrator

DOEpatents

Kaduchak, Gregory; Sinha, Dipen N.

2002-01-01

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow cylindrical piezoelectric crystal which has been modified to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. The cylinder does not require accurate alignment of a resonant cavity. Water droplets having diameters greater than 1 mm have been levitated against the force of gravity using; less than 1 W of input electrical power. Concentration of aerosol particles in air is also demonstrated.

Gravity Functions of Circumnutation by Hypocotyls of Helianthus annuus in Simulated Hypogravity 12

PubMed Central

Chapman, David K.; Venditti, Allen L.; Brown, Allan H.

1980-01-01

For more than a decade research on the botanical mechanism responsible for circumnutation has centered on whether or not these nearly ubiquitous oscillations can be attributed to a hunting process whereby the plant organ continuously responds to the gravity force and, by overshooting each stimulus, initiates a sustained oscillation or, driven by a not yet defined autogenic mechanism, performs oscillatory activities that require no external reinforcement to maintain the observed rhythms of differential growth. We explore here the effects of altered gravity force on parameters of circumnutation. Following our earlier publication on circumnutation in hypergravity we report here an exploration of circumnutation in hypogravity. Parameters of circumnutation are recorded as functions of the axially imposed gravity force. The same method was used (two-axes clinostat rotation) to produce sustained gravity forces referred to as hypergravity (1 < g), hypogravity (0 [unk] g < 1), and negative gravity (−1 < g < 0). In these three regions of the g-parameter nutational frequency and nutational amplitude were influenced in different ways. The results of our tests describe the gravity dependence of circumnutation over the full range of real or simulated gravity levels that are available in an earth laboratory. Our results demonstrated that nutational parameters are indeed gravity-dependent but are not inconsistent with the postulate that circumnutation can proceed in the absence of a significant gravity force. PMID:16661229

Simultaneous muscle force and displacement transducer

NASA Technical Reports Server (NTRS)

Feldstein, C.; Lewis, G. W.; Culler, V. H. (Inventor)

1980-01-01

A myocardial transducer for simultaneously measuring force and displacement within a very small area of myocardium is disclosed. The transducer comprised of an elongated body forked at one end to form an inverted Y shaped beam with each branch of the beam constituting a low compliant tine for penetrating the myocardium to a predetermined depth. Bonded to one of the low compliance tines is a small piezoresistive element for converting a force acting on the beam into an electrical signal. A third high compliant tine of the transducer, which measures displacement of the myocardium in a direction in line with the two low compliant tines, is of a length that just pierces the surface membrane. A small piezoresistive element is bonded to the third tine at its upper end where its bending is greatest. Displacement of the myocardium causes a deformation in curvature of the third tine, and the second small piezoresistive element bonded to the surface of its curved end converts its deformation into an electrical signal.

Einstein's 1919 View

NASA Astrophysics Data System (ADS)

Goradia, Shantilal

2012-10-01

When Rutherford discovered the nuclear force in 1919, he felt the force he discovered reflected some deviation of Newtonian gravity. Einstein too in his 1919 paper published the failure of the general relativity and Newtonian gravity to explain nuclear force and, in his concluding remarks, he retracted his earlier introduction of the cosmological constant. Consistent with his genius, we modify Newtonian gravity as probabilistic gravity using natural Planck units for a realistic study of nature. The result is capable of expressing both (1) nuclear force [strong coupling], and (2) Newtonian gravity in one equation, implying in general, in layman's words, that gravity is the cumulative effect of all quantum mechanical forces which are impossible to measure at long distances. Non discovery of graviton and quantum gravity silently support our findings. Continuing to climb on the shoulders of the giants enables us to see horizons otherwise unseen, as reflected in our book: ``Quantum Consciousness - The Road to Reality,'' and physics/0210040, where we derive the fine structure constant as a function of the age of the universe in Planck times consistent with Gamow's hint, using natural logarithm consistent with Feynman's hint.

Observation of infrasonic and gravity waves at Soufrière Hills Volcano, Montserrat

NASA Astrophysics Data System (ADS)

Ripepe, Maurizio; De Angelis, Silvio; Lacanna, Giorgio; Voight, Barry

2010-04-01

The sudden ejection of material during an explosive eruption generates a broad spectrum of pressure oscillations, from infrasonic to gravity waves. An infrasonic array, installed at 3.5 km from the Soufriere Hills Volcano has successfully detected and located, in real-time, the infrasound generated by several pyroclastic flows (PF) estimating mean flow speeds of 30-75 m/s. On July 29 and December 3, 2008, two differential pressure transducers, co-located with the array, recorded ultra long-period (ULP) oscillations at frequencies of 0.97 and 3.5 mHz, typical of atmospheric gravity waves, associated with explosive eruptions. The observation of gravity waves in the near-field (<6 km) at frequencies as low as about 1 mHz is unprecedented during volcanic eruptions.

40 CFR 1065.310 - Torque calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... reference force is measured. The lever arm must be perpendicular to gravity (i.e., horizontal), and it must... known distance along a lever arm. Make sure the weights' lever arm is perpendicular to gravity (i.e... gravity (using this equation: force = mass · acceleration). The local acceleration of gravity, a g, at...

40 CFR 1065.310 - Torque calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

... reference force is measured. The lever arm must be perpendicular to gravity (i.e., horizontal), and it must... known distance along a lever arm. Make sure the weights' lever arm is perpendicular to gravity (i.e... gravity (using this equation: force = mass · acceleration). The local acceleration of gravity, a g, at...

May the Forces Be with You!

ERIC Educational Resources Information Center

Sirola, Christopher

2018-01-01

In everyday life, we usually directly note two basic forces: gravity and electromagnetism. Gravity--as in the acceleration due to Earth's gravity--tends to be a background force of sorts, something that is always present and always the same. We don't always see electricity and/or magnetism as such, but their subsidiaries are all around…

Elastic actuator for precise force control

DOEpatents

Pratt, G.A.; Williamson, M.M.

1997-07-22

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section. 30 figs.

Elastic actuator for precise force control

DOEpatents

Pratt, Gill A.; Williamson, Matthew M.

1997-07-22

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section.

Transducer technology transfer to bio-engineering applications. [aerospace stress transducer for heart function analysis

NASA Technical Reports Server (NTRS)

Duran, E. N.; Lewis, G. W.; Feldstein, C.; Corday, E.; Meerbaum, S.; Lang, T.

1973-01-01

The results of a technology transfer of a miniature unidirectional stress transducer, developed for experimental stress analysis in the aerospace field, to applications in bioengineering are reported. By modification of the basic design and innovations in attachment techniques, the transducer was successfully used in vivo on the myocardium of large dogs to record the change in contractile force due to coronary occlusion, reperfusion, and intervention.

Long term performance of wearable transducer for motion energy harvesting

NASA Astrophysics Data System (ADS)

McGarry, Scott A.; Behrens, Sam

2010-04-01

Personal electronic devices such as cell phones, GPS and MP3 players have traditionally depended on battery energy storage technologies for operation. By harvesting energy from a person's motion, these devices may achieve greater run times without increasing the mass or volume of the electronic device. Through the use of a flexible piezoelectric transducer such as poly-vinylidene fluoride (PVDF), and integrating it into a person's clothing, it becomes a 'wearable transducer'. As the PVDF transducer is strained during the person's routine activities, it produces an electrical charge which can then be harvested to power personal electronic devices. Existing wearable transducers have shown great promise for personal motion energy harvesting applications. However, they are presently physically bulky and not ergonomic for the wearer. In addition, there is limited information on the energy harvesting performance for wearable transducers, especially under realistic conditions and for extended cyclic force operations - as would be experienced when worn. In this paper, we present experimental results for a wearable PVDF transducer using a person's measured walking force profile, which is then cycled for a prolonged period of time using an experimental apparatus. Experimental results indicate that after an initial drop in performance, the transducer energy harvesting performance does not substantially deteriorate over time, as less than 10% degradation was observed. Longevity testing is still continuing at CSIRO.

Design of a phased array for the generation of adaptive radiation force along a path surrounding a breast lesion for dynamic ultrasound elastography imaging.

PubMed

Ekeom, Didace; Hadj Henni, Anis; Cloutier, Guy

2013-03-01

This work demonstrates, with numerical simulations, the potential of an octagonal probe for the generation of radiation forces in a set of points following a path surrounding a breast lesion in the context of dynamic ultrasound elastography imaging. Because of the in-going wave adaptive focusing strategy, the proposed method is adapted to induce shear wave fronts to interact optimally with complex lesions. Transducer elements were based on 1-3 piezocomposite material. Three-dimensional simulations combining the finite element method and boundary element method with periodic boundary conditions in the elevation direction were used to predict acoustic wave radiation in a targeted region of interest. The coupling factor of the piezocomposite material and the radiated power of the transducer were optimized. The transducer's electrical impedance was targeted to 50 Ω. The probe was simulated by assembling the designed transducer elements to build an octagonal phased-array with 256 elements on each edge (for a total of 2048 elements). The central frequency is 4.54 MHz; simulated transducer elements are able to deliver enough power and can generate the radiation force with a relatively low level of voltage excitation. Using dynamic transmitter beamforming techniques, the radiation force along a path and resulting acoustic pattern in the breast were simulated assuming a linear isotropic medium. Magnitude and orientation of the acoustic intensity (radiation force) at any point of a generation path could be controlled for the case of an example representing a heterogeneous medium with an embedded soft mechanical inclusion.

Characterization of a small Terfenol-D transducer in mechanically blocked configuration

NASA Astrophysics Data System (ADS)

Faidley, LeAnn E.; Dapino, Marcelo J.; Flatau, Alison B.

2001-08-01

In numerous applications, smart material transducers are employed to actuate upon virtually immovable structures, that is, structures whose stiffness approaches infinity in comparison with that of the transducer itself. Such mechanically blocked transducer configurations can be found in applications ranging from seismic testing and isolation of civil structures, to clamping mechanisms in linear or rotational inchworm motors. In addition to providing high blocking forces, smart materials for this type of applications must often be small in size and lightweight in order for design constraints to be met. This paper provides a characterization of the force produced by a 0.9 cm (0.35 in) diameter, 2.0 cm (0.79i in) long Terfenol-D operated under mechanically blocked conditions. Experimental results are shown for several mechanical preloads as well as various magnetic field intensities, waveforms, and frequencies. Optimal levels are deduced and discussed and the results are compared to published data for a PZT transducer of similar size operated in mechanically blocked configuration. The comparison reveals that the Terfenol-D rod provides higher blocking forces than its PZT counterpart. It is thus feasible to employ small magnetostrictive drivers in applications involving zero or near-zero displacement, particularly those based on hybrid magnetostrictive/piezoelectric designs in which high efficiencies are achieved by driving the two electrically complementary transducer materials at electrical resonance.

Intramuscular pressures in antigravity muscles using gravity-independent, pneumatic hardware.

PubMed

Macias, Brandon R; Minocha, Ranjeet; Cutuk, Adnan A; Hill, James; Shiau, Jonathon; Hargens, Alan R

2008-08-01

Resistive exercise helps prevent muscle atrophy in microgravity, but better exercise equipment is needed. Therefore, the purpose of this study was to determine if a pneumatic, gravity-independent leg-press device (LPD) provides sufficient force to leg musculature. We hypothesized that intramuscular pressure (IMP), a quantitative index of muscle force, is greater in the antigravity superficial posterior and deep posterior compartments than in the non-antigravity anterior compartment during bilateral leg-press exercise. Millar pressure transducers were inserted into the anterior, lateral, superficial posterior, and deep posterior muscle compartments of the left leg of eight healthy subjects (three women, five men). Subjects were supine on the Keiser SX-1, a pneumatic LPD. Then maximal voluntary contraction (MVC) was determined; each subject performed three consecutive voluntary contractions at approximately 18%, 50%, and 100% MVC while continuously measuring IMP. Repeated measures ANOVA were used to determine differences of IMPs between compartments and loads. The magnitudes of IMP (mean +/- SEM) at 18 - 3% (abbreviated approximately 18%), 50%, and 100% MVC in the superficial and deep posterior compartments were significantly greater than that in the anterior compartment during exercise (P < 0.05). Additionally, IMPs in all four compartments significantly rose as resistance increased at approximately 18%, 50%, and 100% MVC (P < 0.05). The LPD provides significantly increased resistance to all four compartments, but with greater loading of the antigravity compartments as compared to the non-antigravity compartment. Since antigravity muscles of the leg are contained primarily in the superficial and deep posterior compartments, the LPD may help prevent muscle atrophy associated with microgravity.

Characteristics of receptor- and transducer-coupled activation of the intracellular signalling in sensory neuron revealed by atomic force microscopy

NASA Astrophysics Data System (ADS)

Khalisov, M. M.; Penniyaynen, V. A.; Esikova, N. A.; Ankudinov, A. V.; Krylov, B. V.

2017-01-01

The mechanical properties of sensory neurons upon activation of intracellular cascade processes by comenic acid binding to a membrane opioid-like receptor (receptor-coupled), as well as a very low (endogenous) concentration of ouabain (transducer-coupled), have been investigated. Using atomic force microscopy, it is established that exposure to ouabain, in contrast to the impact of comenic acid, leads to a hardening of the neuron soma. This suggests that the receptor-coupled signal transmission to the cell genome is carried out through mechanisms that are different from the transducer-coupled signal pathways.

Method and system of measuring ultrasonic signals in the plane of a moving web

DOEpatents

Hall, Maclin S.; Jackson, Theodore G.; Wink, Wilmer A.; Knerr, Christopher

1996-01-01

An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like. In addition to velocity measurements of ultrasonic signals in the plane of the web in the machine direction, MD, and a cross direction, CD, generally perpendicular to the direction of the traveling web, therefor, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web.

Method and system of measuring ultrasonic signals in the plane of a moving web

DOEpatents

Hall, M.S.; Jackson, T.G.; Wink, W.A.; Knerr, C.

1996-02-27

An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like is disclosed. In addition to velocity measurements of ultrasonic signals in the plane of the web in the machine direction, MD, and a cross direction, CD, generally perpendicular to the direction of the traveling web, therefore, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web. 37 figs.

Flexural Fillet Geometry Optimization for Design of Force Transducers Used in Aeronautics Testing

NASA Technical Reports Server (NTRS)

Lynn, Keith C.; Dixon, Genevieve

2014-01-01

Force transducer designs used in the ground testing aeronautics community have seen minimal change over the last few decades. With increased focus on data quality and long- term performance capabilities over the life of these instruments, it is critical to investigate new methods that improve these designs. One area of focus in the past few years at NASA has been on the design of the exural elements of traditional force balance transducers. Many of the heritage balances that have been heavily used over the last few decades have started to develop fatigue cracks. The recent focus on the exural design of traditional single-piece force balances revolves around the design of these elements such that stress concentrations are minimized, with the overall goal of increasing the fatigue life of the balance. Recent research in the area of using conic shaped llets in the highly stressed regions of traditional force balances will be discussed, with preliminary numerical and experimental data results. A case study will be presented which discusses integration of this knowledge into a new high-capacity semi-span force balance

Flexural Fillet Geometry Optimization for Design of Force Transducers Used in Aeronautics Testing

NASA Technical Reports Server (NTRS)

Lynn, Keith C.; Dixon, Genevieve

2015-01-01

Force transducer designs used in the ground testing aeronautics community have seen minimal change over the last few decades. With increased focus on data quality and long-term performance capabilities over the life of these instruments, it is critical to investigate new methods that improve these designs. One area of focus in the past few years at NASA has been on the design of the flexural elements of traditional force balance transducers. Many of the heritage balances that have been heavily used over the last few decades have started to develop fatigue cracks. The recent focus on the flexural design of traditional single-piece force balances revolves around the design of these elements such that stress concentrations are minimized, with the overall goal of increasing the fatigue life of the balance. Recent research in the area of using conic shaped fillets in the highly stressed regions of traditional force balances will be discussed, with preliminary numerical and experimental data results. A case study will be presented which discusses integration of this knowledge into a new high-capacity semi-span force balance.

Tunable optical lens array using viscoelastic material and acoustic radiation force

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

Koyama, Daisuke, E-mail: dkoyama@mail.doshisha.ac.jp; Kashihara, Yuta; Matsukawa, Mami

2015-10-28

A movable optical lens array that uses acoustic radiation force was investigated. The lens array consists of a glass plate, two piezoelectric bimorph transducers, and a transparent viscoelastic gel film. A cylindrical lens array with a lens pitch of 4.6 mm was fabricated using the acoustic radiation force generated by the flexural vibration of the glass plate. The focal point and the positioning of the lenses can be changed using the input voltage and the driving phase difference between the two transducers, respectively.

A Parametric Study for the Design of an Optimized Ultrasonic Percussive Planetary Drill Tool.

PubMed

Li, Xuan; Harkness, Patrick; Worrall, Kevin; Timoney, Ryan; Lucas, Margaret

2017-03-01

Traditional rotary drilling for planetary rock sampling, in situ analysis, and sample return are challenging because the axial force and holding torque requirements are not necessarily compatible with lightweight spacecraft architectures in low-gravity environments. This paper seeks to optimize an ultrasonic percussive drill tool to achieve rock penetration with lower reacted force requirements, with a strategic view toward building an ultrasonic planetary core drill (UPCD) device. The UPCD is a descendant of the ultrasonic/sonic driller/corer technique. In these concepts, a transducer and horn (typically resonant at around 20 kHz) are used to excite a toroidal free mass that oscillates chaotically between the horn tip and drill base at lower frequencies (generally between 10 Hz and 1 kHz). This creates a series of stress pulses that is transferred through the drill bit to the rock surface, and while the stress at the drill-bit tip/rock interface exceeds the compressive strength of the rock, it causes fractures that result in fragmentation of the rock. This facilitates augering and downward progress. In order to ensure that the drill-bit tip delivers the greatest effective impulse (the time integral of the drill-bit tip/rock pressure curve exceeding the strength of the rock), parameters such as the spring rates and the mass of the free mass, the drill bit and transducer have been varied and compared in both computer simulation and practical experiment. The most interesting findings and those of particular relevance to deep drilling indicate that increasing the mass of the drill bit has a limited (or even positive) influence on the rate of effective impulse delivered.

Students' Understanding on Newton's Third Law in Identifying the Reaction Force in Gravity Interactions

ERIC Educational Resources Information Center

Zhou, Shaona; Zhang, Chunbin; Xiao, Hua

2015-01-01

In the past three decades, previous researches showed that students had various misconceptions of Newton's Third Law. The present study focused on students' difficulties in identifying the third-law force pair in gravity interaction situations. An instrument involving contexts with gravity and non-gravity associated interactions was designed and…

Centrifuges in gravitational physiology research

NASA Technical Reports Server (NTRS)

Ballard, Rodney W.; Davies, Phil; Fuller, Charles A.

1993-01-01

Data from space flight and ground based experiments have clearly demonstrated the importance of Earth gravity for normal physiological function in man and animals. Gravitational Physiology is concerned with the role and influence of gravity on physiological systems. Research in this field examines how we perceive and respond to gravity and the mechanisms underlying these responses. Inherent in our search for answers to these questions is the ability to alter gravity, which is not physically possible without leaving Earth. However, useful experimental paradigms have been to modify the perceived force of gravity by changing either the orientation of subjects to the gravity vector (i.e., postural changes) or by applying inertial forces to augment the magnitude of the gravity vector. The later technique has commonly been used by applying centripetal force via centrifugation.

40 CFR 1065.310 - Torque calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... maintenance. Use good engineering judgment to repeat the calibration. Follow the torque transducer... the U.S. National Oceanographic and Atmospheric Administration's surface gravity prediction Web site at http://www.ngs.noaa.gov/cgi-bin/grav_pdx.prl. If this Web site is unavailable, you may use the...

40 CFR 1065.310 - Torque calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... maintenance. Use good engineering judgment to repeat the calibration. Follow the torque transducer... the U.S. National Oceanographic and Atmospheric Administration's surface gravity prediction Web site at http://www.ngs.noaa.gov/cgi-bin/grav_pdx.prl. If this Web site is unavailable, you may use the...

Cross-shaped torsional spring

DOEpatents

Williamson, M.M.; Pratt, G.A.

1999-06-08

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section. 30 figs.

Anti-gravity and galaxy rotation curves

NASA Astrophysics Data System (ADS)

Sanders, R. H.

1984-07-01

A modification of Newtonian gravitational attraction which arises in the context of modern attempts to unify gravity with the other forces in nature can produce rotation curves for spiral galaxies which are nearly flat from 10 to 100 kpc, bind clusters of galaxies, and close the universe with the density of baryonic matter consistent with primordial nucleosynthesis. This is possible if a very low mass vector boson carries an effective anti-gravity force which on scales smaller than that of galaxies almost balances the normal attractive gravity force.

Physics of Artificial Gravity

NASA Technical Reports Server (NTRS)

Bukley, Angie; Paloski, William; Clement, Gilles

2006-01-01

This chapter discusses potential technologies for achieving artificial gravity in a space vehicle. We begin with a series of definitions and a general description of the rotational dynamics behind the forces ultimately exerted on the human body during centrifugation, such as gravity level, gravity gradient, and Coriolis force. Human factors considerations and comfort limits associated with a rotating environment are then discussed. Finally, engineering options for designing space vehicles with artificial gravity are presented.

Force Measurement Services at Kebs: AN Overview of Equipment, Procedures and Uncertainty

NASA Astrophysics Data System (ADS)

Bangi, J. O.; Maranga, S. M.; Nganga, S. P.; Mutuli, S. M.

This paper describes the facilities, instrumentation and procedures currently used in the force laboratory at the Kenya Bureau of Standards (KEBS) for force measurement services. The laboratory uses the Force Calibration Machine (FCM) to calibrate force-measuring instruments. The FCM derives its traceability via comparisons using reference transfer force transducers calibrated by the Force Standard Machines (FSM) of a National Metrology Institute (NMI). The force laboratory is accredited to ISO/IEC 17025 by the Germany Accreditation Body (DAkkS). The accredited measurement scope of the laboratory is 1 MN to calibrate force transducers in both compression and tension modes. ISO 376 procedures are used while calibrating force transducers. The KEBS reference transfer standards have capacities of 10, 50, 300 and 1000 kN to cover the full range of the FCM. The uncertainty in the forces measured by the FCM were reviewed and determined in accordance to the new EURAMET calibration guide. The relative expanded uncertainty of force W realized by FCM was evaluated in a range from 10 kN-1 MN, and was found to be 5.0 × 10-4 with the coverage factor k being equal to 2. The overall normalized error (En) of the comparison results was also found to be less than 1. The accredited Calibration and Measurement Capability (CMC) of the KEBS force laboratory was based on the results of those intercomparisons. The FCM enables KEBS to provide traceability for the calibration of class ‘1’ force instruments as per the ISO 376.

Experimental studies of protozoan response to intense magnetic fields and forces

NASA Astrophysics Data System (ADS)

Guevorkian, Karine

Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar rates as the motile ones. It was established that the magneto-orientation is mostly due to the magnetic torques acting on rigid structures in the cell body and therefore the response is a non-biological, passive response. From the orientation rate of paramecia in various magnetic field strengths, the average anisotropy of the diamagnetic susceptibility of the cell was estimated. It has also been demonstrated that magnetic forces can be used to create increased, decreased and even inverted simulated gravity environments for the investigation of the gravi-responses of single cells. Since the mechanisms by which Earth's gravity affects cell functioning are still not fully understood, a number of methods to simulate different strength gravity environments, such as centrifugation, have been employed. Exploiting the ability to exert magnetic forces on weakly diamagnetic constituents of the cells, we were able to vary the gravity from -8 g to 10 g, where g is Earth's gravity. Investigations of the swimming response of paramecia in these simulated gravities revealed that they actively regulate their swimming speed to oppose the external force. This result is in agreement with centrifugation experiments, confirming the credibility of the technique. Moreover, the Paramecium's swimming ceased in simulated gravity of 10 g, indicating a maximum possible propulsion force of 0.7 nN. The magnetic force technique to simulate gravity is the only earthbound technique that can create increased and decreased simulated gravities in the same experimental setup. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.

A flex-compressive-mode piezoelectric transducer for mechanical vibration/strain energy harvesting.

PubMed

Li, Xiaotian; Guo, Mingsen; Dong, Shuxiang

2011-04-01

A piezoelectric transducer for harvesting energy from ambient mechanical vibrations/strains under pressure condition was developed. The proposed transducer was made of two ring-type piezoelectric stacks, one pair of bow-shaped elastic plates, and one shaft that pre-compresses them. This transducer works in flex-compressive (F-C) mode, which is different from a conventional flex-tensional (F-T) one, to transfer a transversely applied force F into an amplified longitudinal force N pressing against the two piezo-stacks via the two bowshaped elastic plates, generating a large electric voltage output via piezoelectric effect. Our experimental results show that without an electric load, an F-C mode piezo-transducer could generate a maximum electric voltage output of up to 110 Vpp, and with an electric load of 40 κΩ, it a maximum power output of 14.6 mW under an acceleration excitation of 1 g peak-peak at the resonance frequency of 87 Hz. © 2011 IEEE

Fundamental Experiments at Liquid Helium Temperatures (Low Temperature Studies of Anomalous Surface Shielding and Related Phenomena).

DTIC Science & Technology

1984-09-30

EXPERIMENT BACKGROUND Motivated by the desire to measure for the first time the force of 27 gravity on antimatter , Witteborn and Fairbank (WF...and antimatter . There are, however, no direct experimental tests of the gravitational forces on antimatter . Having measured the force of gravity on...electrons, a measurement using positrons would give the first measurement of the force of gravity on antimatter as well as giving a definitive value for

Microhydraulic transducer technology for actuation and power generation

NASA Astrophysics Data System (ADS)

Hagood, Nesbitt W.; Roberts, David C.; Saggere, Laxminarayana; Breuer, Kenneth S.; Chen, Kuo-Shen; Carretero, Jorge A.; Li, Hanqing; Mlcak, Richard; Pulitzer, Seward W.; Schmidt, Martin A.; Spearing, S. Mark; Su, Yu-Hsuan

2000-06-01

The paper introduces a novel transducer technology, called the solid-state micro-hydraulic transducer, currently under development at MIT. The new technology is enabled through integration of micromachining technology, piezoelectrics, and microhydraulic concepts. These micro-hydraulic transducers are capable of bi-directional electromechanical energy conversion, i.e., they can operate as both an actuator that supplies high mechanical force in response to electrical input and an energy generator that transduces electrical energy from mechanical energy in the environment. These transducers are capable of transducing energy at very high specific power output in the order of 1 kW/kg, and thus, they have the potential to enable many novel applications. The concept, the design, and the potential applications of the transducers are presented. Present efforts towards the development of these transducers, and the challenges involved therein, are also discussed.

A parametric symmetry breaking transducer

NASA Astrophysics Data System (ADS)

Eichler, Alexander; Heugel, Toni L.; Leuch, Anina; Degen, Christian L.; Chitra, R.; Zilberberg, Oded

2018-06-01

Force detectors rely on resonators to transduce forces into a readable signal. Usually, these resonators operate in the linear regime and their signal appears amidst a competing background comprising thermal or quantum fluctuations as well as readout noise. Here, we demonstrate a parametric symmetry breaking transduction method that leads to a robust nonlinear force detection in the presence of noise. The force signal is encoded in the frequency at which the system jumps between two phase states which are inherently protected against phase noise. Consequently, the transduction effectively decouples from readout noise channels. For a controlled demonstration of the method, we experiment with a macroscopic doubly clamped string. Our method provides a promising paradigm for high-precision force detection.

The effects of gravity on human walking: a new test of the dynamic similarity hypothesis using a predictive model.

PubMed

Raichlen, David A

2008-09-01

The dynamic similarity hypothesis (DSH) suggests that differences in animal locomotor biomechanics are due mostly to differences in size. According to the DSH, when the ratios of inertial to gravitational forces are equal between two animals that differ in size [e.g. at equal Froude numbers, where Froude = velocity2/(gravity x hip height)], their movements can be made similar by multiplying all time durations by one constant, all forces by a second constant and all linear distances by a third constant. The DSH has been generally supported by numerous comparative studies showing that as inertial forces differ (i.e. differences in the centripetal force acting on the animal due to variation in hip heights), animals walk with dynamic similarity. However, humans walking in simulated reduced gravity do not walk with dynamically similar kinematics. The simulated gravity experiments did not completely account for the effects of gravity on all body segments, and the importance of gravity in the DSH requires further examination. This study uses a kinematic model to predict the effects of gravity on human locomotion, taking into account both the effects of gravitational forces on the upper body and on the limbs. Results show that dynamic similarity is maintained in altered gravitational environments. Thus, the DSH does account for differences in the inertial forces governing locomotion (e.g. differences in hip height) as well as differences in the gravitational forces governing locomotion.

49 CFR 572.177 - Test conditions and instrumentation.

Code of Federal Regulations, 2012 CFR

2012-10-01

...) except as noted, with channel frequency classes as follows: (1) Pendulum acceleration, CFC 180, (2) Pendulum D-plane rotation (if transducer is used), CFC 60, (3) Torso flexion pulling force (if transducer...

49 CFR 572.177 - Test conditions and instrumentation.

Code of Federal Regulations, 2014 CFR

2014-10-01

...) except as noted, with channel frequency classes as follows: (1) Pendulum acceleration, CFC 180, (2) Pendulum D-plane rotation (if transducer is used), CFC 60, (3) Torso flexion pulling force (if transducer...

49 CFR 572.177 - Test conditions and instrumentation.

Code of Federal Regulations, 2013 CFR

2013-10-01

...) except as noted, with channel frequency classes as follows: (1) Pendulum acceleration, CFC 180, (2) Pendulum D-plane rotation (if transducer is used), CFC 60, (3) Torso flexion pulling force (if transducer...

Transient Intervals of Hyper-Gravity Enhance Endothelial Barrier Integrity: Impact of Mechanical and Gravitational Forces Measured Electrically

PubMed Central

Szulcek, Robert; van Bezu, Jan; Boonstra, Johannes; van Loon, Jack J. W. A.; van Nieuw Amerongen, Geerten P.

2015-01-01

Background Endothelial cells (EC) guard vascular functions by forming a dynamic barrier throughout the vascular system that sensitively adapts to ‘classical’ biomechanical forces, such as fluid shear stress and hydrostatic pressure. Alterations in gravitational forces might similarly affect EC integrity, but remain insufficiently studied. Methods In an unique approach, we utilized Electric Cell-substrate Impedance Sensing (ECIS) in the gravity-simulators at the European Space Agency (ESA) to study dynamic responses of human EC to simulated micro- and hyper-gravity as well as to classical forces. Results Short intervals of micro- or hyper-gravity evoked distinct endothelial responses. Stimulated micro-gravity led to decreased endothelial barrier integrity, whereas hyper-gravity caused sustained barrier enhancement by rapid improvement of cell-cell integrity, evidenced by a significant junctional accumulation of VE-cadherin (p = 0.011), significant enforcement of peripheral F-actin (p = 0.008) and accompanied by a slower enhancement of cell-matrix interactions. The hyper-gravity triggered EC responses were force dependent and nitric-oxide (NO) mediated showing a maximal resistance increase of 29.2±4.8 ohms at 2g and 60.9±6.2 ohms at 4g vs. baseline values that was significantly suppressed by NO blockage (p = 0.011). Conclusion In conclusion, short-term application of hyper-gravity caused a sustained improvement of endothelial barrier integrity, whereas simulated micro-gravity weakened the endothelium. In clear contrast, classical forces of shear stress and hydrostatic pressure induced either short-lived or no changes to the EC barrier. Here, ECIS has proven a powerful tool to characterize subtle and distinct EC gravity-responses due to its high temporal resolution, wherefore ECIS has a great potential for the study of gravity-responses such as in real space flights providing quantitative assessment of a variety of cell biological characteristics of any adherent growing cell type in an automated and continuous fashion. PMID:26637177

Gravity. Physical Science in Action[TM]. Schlessinger Science Library. [Videotape].

ERIC Educational Resources Information Center

2000

All kids are familiar with the basic idea of gravity--it's why things fall to the ground. Gravity uses exciting visuals and clear, colorful graphics to take students beyond the basics to explain that gravity is really a force of attraction between objects. They'll discover that all objects--no matter how large or small--have gravitational force,…

Optical Interferometric Micrometrology

NASA Technical Reports Server (NTRS)

Abel, Phillip B.; Lauer, James R.

1989-01-01

Resolutions in angstrom and subangstrom range sought for atomic-scale surface probes. Experimental optical micrometrological system built to demonstrate calibration of piezoelectric transducer to displacement sensitivity of few angstroms. Objective to develop relatively simple system producing and measuring translation, across surface of specimen, of stylus in atomic-force or scanning tunneling microscope. Laser interferometer used to calibrate piezoelectric transducer used in atomic-force microscope. Electronic portion of calibration system made of commercially available components.

Cooperative unfolding of distinctive mechanoreceptor domains transduces force into signals

PubMed Central

Ju, Lining; Chen, Yunfeng; Xue, Lingzhou; Du, Xiaoping; Zhu, Cheng

2016-01-01

How cells sense their mechanical environment and transduce forces into biochemical signals is a crucial yet unresolved question in mechanobiology. Platelets use receptor glycoprotein Ib (GPIb), specifically its α subunit (GPIbα), to signal as they tether and translocate on von Willebrand factor (VWF) of injured arterial surfaces against blood flow. Force elicits catch bonds to slow VWF–GPIbα dissociation and unfolds the GPIbα leucine-rich repeat domain (LRRD) and juxtamembrane mechanosensitive domain (MSD). How these mechanical processes trigger biochemical signals remains unknown. Here we analyze these extracellular events and the resulting intracellular Ca2+ on a single platelet in real time, revealing that LRRD unfolding intensifies Ca2+ signal whereas MSD unfolding affects the type of Ca2+ signal. Therefore, LRRD and MSD are analog and digital force transducers, respectively. The >30 nm macroglycopeptide separating the two domains transmits force on the VWF–GPIbα bond (whose lifetime is prolonged by LRRD unfolding) to the MSD to enhance its unfolding, resulting in unfolding cooperativity at an optimal force. These elements may provide design principles for a generic mechanosensory protein machine. DOI: http://dx.doi.org/10.7554/eLife.15447.001 PMID:27434669

Ultra-sensitive transducer advances micro-measurement range

NASA Technical Reports Server (NTRS)

Rogallo, V. L.

1964-01-01

An ultrasensitive piezoelectric transducer, that converts minute mechanical forces into electrical impulses, measures the impact of micrometeoroids against space vehicles. It has uniform sensitivity over the entire target area and a high degree of stability.

Forced and natural convection in laminar-jet diffusion flames. [normal-gravity, inverted-gravity and zero-gravity flames

NASA Technical Reports Server (NTRS)

Haggard, J. B., Jr.

1981-01-01

An experimental investigation was conducted on methane, laminar-jet, diffusion flames with coaxial, forced-air flow to examine flame shapes in zero-gravity and in situations where buoyancy aids (normal-gravity flames) or hinders (inverted-gravity flames) the flow velocities. Fuel nozzles ranged in size from 0.051 to 0.305 cm inside radius, while the coaxial, convergent, air nozzle had a 1.4 cm inside radius at the fuel exit plane. Fuel flows ranged from 1.55 to 10.3 cu cm/sec and air flows from 0 to 597 cu cm/sec. A computer program developed under a previous government contract was used to calculate the characteristic dimensions of normal and zero-gravity flames only. The results include a comparison between the experimental data and the computed axial flame lengths for normal gravity and zero gravity which showed good agreement. Inverted-gravity flame width was correlated with the ratio of fuel nozzle radius to average fuel velocity. Flame extinguishment upon entry into weightlessness was studied, and it was found that relatively low forced-air velocities (approximately 10 cm/sec) are sufficient to sustain methane flame combustion in zero gravity. Flame color is also discussed.

Runners do not push off the ground but fall forwards via a gravitational torque.

PubMed

Romanov, Nicholas; Fletcher, Graham

2007-09-01

The relationship between the affect and timing of the four forces involved in running (gravity, ground reaction force, muscle force, and potential strain energy) is presented. These forces only increase horizontal acceleration of the centre of mass during stance but not flight. The current hierarchical models of running are critiqued because they do not show gravity, a constant force, in affect during stance. A new gravitational model of running is developed, which shows gravity as the motive force. Gravity is shown to cause a torque as the runner's centre of mass moves forward of the support foot. Ground reaction force is not a motive force but operates according to Newton's third law; therefore, the ground can only propel a runner forward in combination with muscle activity. However, leg and hip extensor muscles have consistently proven to be silent during leg extension (mid-terminal stance). Instead, high muscle-tendon forces at terminal stance suggest elastic recoil regains most of the centre of mass's height. Therefore, the only external motive force from mid-terminal stance is gravity via a gravitational torque, which causes a horizontal displacement. The aim of this paper is to establish a definitive biomechanical technique (Pose method) that is easily taught to runners (Romanov, 2002): falling forwards via a gravitational torque while pulling the support foot rapidly from the ground using the hamstring muscles.

Statolith positioning by microfilaments in Chara rhizoids and protonemata

NASA Astrophysics Data System (ADS)

Hodick, Dieter; Buchen, Brigitte; Sievers, Andreas

The rhizoids of the green alga Chara are tip-growing cells with a precise positive gravitropism. In rhizoids growing downwards the statoliths never sediment upon the cell wall at the very tip but keep a minimal distance of approximately 10 μm from the cell vertex. It has been argued that this position is attained by a force acting upon the statoliths in the basal direction and that this force is generated by an interaction between actin microfilaments and myosin on the statolith membrane. This hypothesis received experimental support from (1) effects of the actin-attacking drug cytochalasin, (2) experiments under microgravity conditions, and (3) clinostat experiments. Using video-microscopy it is now shown that this basipetal force also acts on statoliths during sedimentation. As a result, many statoliths in Chara rhizoids do not simply fall along the plumb line while sedimenting during gravistimulation, but move basipetally. This statolith movement is compared to the ones occurring in the unicellular Chara protonemata during gravistimulation. Dark-grown protonemata morphologically closely resemble the rhizoids but respond negatively gravitropic. In contrast to the rhizoids a gravistimulation of the protonemata induces a transport of statoliths towards the tip. This transport is mainly along the cell axis and not parallel to the gravity vector. It is stressed that the sedimentation of statoliths in Chara rhizoids and protonemata as well as in gravity sensing cells in mosses and higher plants is accompanied by statolith movements based on interactions with the cytoskeleton. In tip-growing cells these movements direct the statoliths to a definite region of the cell where they can sediment and elicit a gravitropic curvature. In the statocytes of higher plants the interactions of the statoliths with the cytoskeleton probably do not serve primarily to move the statoliths but to transduce mechanical stresses from the sedimenting statoliths to the plasma membrane.

Statolith positioning by microfilaments in Chara rhizoids and protonemata.

PubMed

Hodick, D; Buchen, B; Sievers, A

1998-01-01

The rhizoids of the green alga Chara are tip-growing cells with a precise positive gravitropism. In rhizoids growing downwards the statoliths never sediment upon the cell wall at the very tip but keep a minimal distance of approximately 10 micrometers from the cell vertex. It has been argued that this position is attained by a force acting upon the statoliths in the basal direction and that this force is generated by an interaction between actin microfilaments and myosin on the statolith membrane. This hypothesis received experimental support from (1) effects of the actin-attacking drug cytochalasin, (2) experiments under microgravity conditions, and (3) clinostat experiments. Using video-microscopy it is now shown that this basipetal force also acts on statoliths during sedimentation. As a result, many statoliths in Chara rhizoids do not simply fall along the plumb line while sedimenting during gravistimulation, but move basipetally. This statolith movement is compared to the ones occurring in the unicellular Chara protonemata during gravistimulation. Dark-grown protonemata morphologically closely resemble the rhizoids but respond negatively gravitropic. In contrast to the rhizoids a gravistimulation of the protonemata induces a transport of statoliths towards the tip. This transport is mainly along the cell axis and not parallel to the gravity vector. It is stressed that the sedimentation of statoliths in Chara rhizoids and protonemata as well as in gravity sensing cells in mosses and higher plants is accompanied by statolith movements based on interactions with the cytoskeleton. In tip-growing cells these movements direct the statoliths to a definite region of the cell where they can sediment and elicit a gravitropic curvature. In the statocytes of higher plants the interactions of the statoliths with the cytoskeleton probably do not serve primarily to move the statoliths but to transduce mechanical stresses from the sedimenting statoliths to the plasma membrane.

Effects of Transducer Installation on Unsteady Pressure Measurements on Oscillating Blades

NASA Technical Reports Server (NTRS)

Lepicovsky, Jan

2006-01-01

Unsteady pressures were measured above the suction side of a blade that was oscillated to simulate blade stall flutter. Measurements were made at blade oscillation frequencies up to 500 Hz. Two types of miniature pressure transducers were used: surface-mounted flat custom-made, and conventional miniature, body-mounted transducers. The signals of the surface-mounted transducers are significantly affected by blade acceleration, whereas the signals of body-mounted transducers are practically free of this distortion. A procedure was introduced to correct the signals of surface-mounted transducers to rectify the signal distortion due to blade acceleration. The signals from body-mounted transducers, and corrected signals from surface-mounted transducers represent true unsteady pressure signals on the surface of a blade subjected to forced oscillations. However, the use of body-mounted conventional transducers is preferred for the following reasons: no signal corrections are needed for blade acceleration, the conventional transducers are noticeably less expensive than custom-made flat transducers, the survival rate of body-mounted transducers is much higher, and finally installation of body-mounted transducers does not disturb the blade surface of interest.

Foot-ground reaction force during resistive exercise in parabolic flight

NASA Technical Reports Server (NTRS)

Lee, Stuart M C.; Cobb, Kendall; Loehr, James A.; Nguyen, Daniel; Schneider, Suzanne M.

2004-01-01

INTRODUCTION: An interim resistance exercise device (iRED) was designed to provide resistive exercise as a countermeasure to spaceflight-induced loss of muscle strength and endurance as well as decreased bone mineral density. The purpose of this project was to compare foot-ground reaction force during iRED exercise in normal gravity (1 G) vs. microgravity (0 G) achieved during parabolic flight. METHODS: There were four subjects who performed three exercises (squat, heel raise, and deadlift) using the iRED during 1 G and 0 G at a moderate intensity (60% of maximum strength during deadlift exercise). Foot-ground reaction force was measured in the three orthogonal axes (x, y, z) using a force plate, and the magnitude of the resultant force vector was calculated (r = square root(x2 + y2 + z2)). Linear displacement (LD) was measured using a linear transducer. Peak force (Fpeak) and an index of total work (TWi) were calculated using a customized computer program. Paired t-tests were used to test if significant differences (p < or = 0.05) were observed between 1 G and 0 G exercise. RESULTS: Fpeak and TWi measured in the resultant axis were significantly less in 0 G for each of the exercises tested. During 0 G, Fpeak was 42-46% and TWi was 33-37% of that measured during 1 G. LD and average time to complete each repetition were not different from 1 G to 0 G. CONCLUSIONS: Crewmembers who perform resistive exercises during spaceflight that include the movement of a large portion of their body mass will require much greater external resistive force during 0 G than 1 G exercise to provide a sufficient stimulus to maintain muscle and bone mass.

Vacuum force

NASA Astrophysics Data System (ADS)

Han, Yongquan

2015-03-01

To study on vacuum force, we must clear what is vacuum, vacuum is a space do not have any air and also ray. There is not exist an absolute the vacuum of space. The vacuum of space is relative, so that the vacuum force is relative. There is a certain that vacuum vacuum space exists. In fact, the vacuum space is relative, if the two spaces compared to the existence of relative vacuum, there must exist a vacuum force, and the direction of the vacuum force point to the vacuum region. Any object rotates and radiates. Rotate bend radiate- centripetal, gravity produced, relative gravity; non gravity is the vacuum force. Gravity is centripetal, is a trend that the objects who attracted wants to Centripetal, or have been do Centripetal movement. Any object moves, so gravity makes the object curve movement, that is to say, the radiation range curve movement must be in the gravitational objects, gravity must be existed in non vacuum region, and make the object who is in the region of do curve movement (for example: The earth moves around the sun), or final attracted in the form gravitational objects, and keep relatively static with attract object. (for example: objects on the earth moves but can't reach the first cosmic speed).

Magnetic levitation-based Martian and Lunar gravity simulator

NASA Technical Reports Server (NTRS)

Valles, J. M. Jr; Maris, H. J.; Seidel, G. M.; Tang, J.; Yao, W.

2005-01-01

Missions to Mars will subject living specimens to a range of low gravity environments. Deleterious biological effects of prolonged exposure to Martian gravity (0.38 g), Lunar gravity (0.17 g), and microgravity are expected, but the mechanisms involved and potential for remedies are unknown. We are proposing the development of a facility that provides a simulated Martian and Lunar gravity environment for experiments on biological systems in a well controlled laboratory setting. The magnetic adjustable gravity simulator will employ intense, inhomogeneous magnetic fields to exert magnetic body forces on a specimen that oppose the body force of gravity. By adjusting the magnetic field, it is possible to continuously adjust the total body force acting on a specimen. The simulator system considered consists of a superconducting solenoid with a room temperature bore sufficiently large to accommodate small whole organisms, cell cultures, and gravity sensitive bio-molecular solutions. It will have good optical access so that the organisms can be viewed in situ. This facility will be valuable for experimental observations and public demonstrations of systems in simulated reduced gravity. c2005 Published by Elsevier Ltd on behalf of COSPAR.

Magnetic levitation-based Martian and Lunar gravity simulator.

PubMed

Valles, J M; Maris, H J; Seidel, G M; Tang, J; Yao, W

2005-01-01

Missions to Mars will subject living specimens to a range of low gravity environments. Deleterious biological effects of prolonged exposure to Martian gravity (0.38 g), Lunar gravity (0.17 g), and microgravity are expected, but the mechanisms involved and potential for remedies are unknown. We are proposing the development of a facility that provides a simulated Martian and Lunar gravity environment for experiments on biological systems in a well controlled laboratory setting. The magnetic adjustable gravity simulator will employ intense, inhomogeneous magnetic fields to exert magnetic body forces on a specimen that oppose the body force of gravity. By adjusting the magnetic field, it is possible to continuously adjust the total body force acting on a specimen. The simulator system considered consists of a superconducting solenoid with a room temperature bore sufficiently large to accommodate small whole organisms, cell cultures, and gravity sensitive bio-molecular solutions. It will have good optical access so that the organisms can be viewed in situ. This facility will be valuable for experimental observations and public demonstrations of systems in simulated reduced gravity. c2005 Published by Elsevier Ltd on behalf of COSPAR.

Calcium mobilizations in response to changes in the gravity vector in Arabidopsis seedlings

PubMed Central

Tatsumi, Hitoshi; Toyota, Masatsugu; Furuichi, Takuya; Sokabe, Masahiro

2014-01-01

Gravity influences the growth direction of higher plants. Changes in the gravity vector (gravistimulation) immediately promote the increase in the cytoplasmic free calcium ion concentration ([Ca2+]c) in Arabidopsis (Arabidopsis thaliana) seedlings. When the seedlings are gravistimulated by reorientation at 180°, a transient two peaked (biphasic) [Ca2+]c-increase arises in their hypocotyl and petioles. Parabolic flights (PFs) can generate a variety of gravity-stimuli, and enables us to measure gravity-induced [Ca2+]c-increases without specimen rotation, which demonstrate that Arabidopsis seedlings possess a rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes into Ca2+ signals on a sub-second timescale. Hypergravity by centrifugation (20 g or 300 g) also induces similar transient [Ca2+]c-increases. In this review, we propose models for possible cellular processes of the garavi-stimulus-induced [Ca2+]c-increase, and evaluate those by examining whether the model fits well with the kinetic parameters derived from the [Ca2+]c-increases obtained by applying gravistimulus with different amplitudes and time sequences. PMID:25763612

Calcium mobilizations in response to changes in the gravity vector in Arabidopsis seedlings: possible cellular mechanisms.

PubMed

Tatsumi, Hitoshi; Toyota, Masatsugu; Furuichi, Takuya; Sokabe, Masahiro

2014-01-01

Gravity influences the growth direction of higher plants. Changes in the gravity vector (gravistimulation) immediately promote the increase in the cytoplasmic free calcium ion concentration ([Ca(2+)]c) in Arabidopsis (Arabidopsis thaliana) seedlings. When the seedlings are gravistimulated by reorientation at 180°, a transient two peaked (biphasic) [Ca(2+)]c-increase arises in their hypocotyl and petioles. Parabolic flights (PFs) can generate a variety of gravity-stimuli, and enables us to measure gravity-induced [Ca(2+)]c-increases without specimen rotation, which demonstrate that Arabidopsis seedlings possess a rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes into Ca(2+) signals on a sub-second timescale. Hypergravity by centrifugation (20 g or 300 g) also induces similar transient [Ca(2+)]c-increases. In this review, we propose models for possible cellular processes of the garavi-stimulus-induced [Ca(2+)]c-increase, and evaluate those by examining whether the model fits well with the kinetic parameters derived from the [Ca(2+)]c-increases obtained by applying gravistimulus with different amplitudes and time sequences.

Constant Applied Force Stimulates Osteoblast Proliferation Via Matrix-Integrin-Signaling Pathways

NASA Technical Reports Server (NTRS)

Vercoutere, W.; Parra, M.; Roden, C.; DaCosta, M.; Wing, A.; Damsky, C.; Holton, E.; Searby, N.; Globus, R.; Almeida, E. A. C.

2003-01-01

Reduced weight-bearing caused by immobilization, bed-rest or microgravity leads to atrophy in mechanosensitive tissue such as muscle and bone. We hypothesize that bone tissue requires earth s gravity (1-g) for the maintenance of extracellular matrix, integrin, and kinase-mediated cell growth and survival pathways. We investigate the role of matrix-integrin signaling in bone cells using cell culture centrifugation to provide different levels of hypergravity mechanostimulation. The 10-50-g range we use also mimics physiological intermedullary pressure (1.2 - 5 kPa). 24 hours at 50-g increased primary rat osteoblast proliferation on collagen Type I and fibronectin, but not laminin or uncoated plastic. BrdU incorporation in primary osteoblasts over 24 h showed hypergravity increased the number of cells actively synthesizing DNA from about 60% at 1-g to over 90% at 25-g. Primary rat fibroblasts grown at 50-g (24 h) showed no proliferation increase, suggesting this is a tissue-specific phenomenon. These results suggest that the betal and alpha4 integrins may be involved. To further test this, we used osteocytic-like MLO-Y4 cells that showed increased proliferation at 1-g with stable expression of a betal integrin cytoplasmic tail and transmembrane domain construct. At 50-g, MLO-Y4/betal cells showed greater MAPK activation than MLO-Y4 vector controls, suggesting that betal integrin is involved in transducing mitogenic signals in response to hypergravity. Preliminary results also show that interfering with the alpha4 integrin in primary osteoblasts grown on fibronectin blocked the proliferation response. These results indicate that cells from mechanosensitive bone tissue can respond to gravity-generated forces, and this response involves specific matrix and integrin-dependent signaling pathways.

The Validity and Reliability of the Gymaware Linear Position Transducer for Measuring Counter-Movement Jump Performance in Female Athletes

ERIC Educational Resources Information Center

O'Donnell, Shannon; Tavares, Francisco; McMaster, Daniel; Chambers, Samuel; Driller, Matthew

2018-01-01

The current study aimed to assess the validity and test-retest reliability of a linear position transducer when compared to a force plate through a counter-movement jump in female participants. Twenty-seven female recreational athletes (19 ± 2 years) performed three counter-movement jumps simultaneously using the linear position transducer and…

Development of a bi-directional standing wave linear piezoelectric actuator with four driving feet.

PubMed

Liu, Yingxiang; Shi, Shengjun; Li, Chunhong; Chen, Weishan; Wang, Liang; Liu, Junkao

2018-03-01

A bi-directional standing wave linear piezoelectric ultrasonic actuator with four driving feet is proposed in this work. Two sandwich type transducers operated in longitudinal-bending hybrid modes are set parallelly. The working mode of the transducer is not simple hybrid vibrations of a longitudinal one and a bending one, but a special coupling vibration mode contained both longitudinal and bending components. Two transducers with the same structure and unsymmetrical boundary conditions are set parallelly to accomplish the bi-directional driving: the first transducer can push the runner forward, while the other one produces the backward driving. In the experiments, two voltages with different amplitudes are applied on the two transducers, respectively: the one with higher voltage serves as the actuator, whereas the other one applied with lower voltage is used to reduce the frictional force. The prototype achieves maximum no-load speed and thrust force of 244 mm/s and 9.8 N. This work gives a new idea for the construction of standing wave piezoelectric ultrasonic actuator with bi-directional driving ability. Copyright © 2017 Elsevier B.V. All rights reserved.

Flowmeter for Clear and Translucent Fluids

NASA Technical Reports Server (NTRS)

White, P. R.

1985-01-01

Transducer with only three moving parts senses flow of clear or translucent fluid. Displacement of diaphragm by force of flow detected electrooptically and displayed by panel meter or other device. Transducer used to measure flow of gasoline to automobile engine.

Physics of direct-contact ultrasonic cloth drying process

DOE PAGES

Peng, Chang; Ravi, Saitej; Patel, Viral K.; ...

2017-02-27

Existing methods of drying fabrics involve energy-intensive thermal evaporation of moisture from clothes. Drying fabrics using high-frequency vibrations of piezoelectric transducers can substantially reduce drying time and energy consumption. In this method, vibrational energy generates instability on the liquid-air interface and mechanically ejects water from a wet fabric. For the first time, the physics of the ultrasonic fabric drying process in direct-contact mode is studied. The kinematic and thermal responses of water droplets and fabrics on piezoelectric crystal transducers and metal mesh–based transducers are studied. The results suggest that on piezoelectric crystal transducers, the response of a droplet subjected tomore » ultrasonic excitation is dictated by the relative magnitude of the surface tension and the ultrasonic excitation forces. The drying process for a fabric on the studied transducers consists of two regimes—vibrational and thermal. When the water content is high, the vibrational forces can eject bulk water rapidly. But the more strongly bound water within the smaller fabric pores evaporates by the thermal energy generated as a result of the viscous losses. Our study finds that a metal mesh–based transducer is more suitable for dewatering fabrics, as it facilitates the ejection of water from the fabric–transducer interface to the opposite side of the mesh. A demonstration unit developed consumes 10–20% of the water latent heat energy at water contents greater than 20%.« less

Physics of direct-contact ultrasonic cloth drying process

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

Peng, Chang; Ravi, Saitej; Patel, Viral K.

Existing methods of drying fabrics involve energy-intensive thermal evaporation of moisture from clothes. Drying fabrics using high-frequency vibrations of piezoelectric transducers can substantially reduce drying time and energy consumption. In this method, vibrational energy generates instability on the liquid-air interface and mechanically ejects water from a wet fabric. For the first time, the physics of the ultrasonic fabric drying process in direct-contact mode is studied. The kinematic and thermal responses of water droplets and fabrics on piezoelectric crystal transducers and metal mesh–based transducers are studied. The results suggest that on piezoelectric crystal transducers, the response of a droplet subjected tomore » ultrasonic excitation is dictated by the relative magnitude of the surface tension and the ultrasonic excitation forces. The drying process for a fabric on the studied transducers consists of two regimes—vibrational and thermal. When the water content is high, the vibrational forces can eject bulk water rapidly. But the more strongly bound water within the smaller fabric pores evaporates by the thermal energy generated as a result of the viscous losses. Our study finds that a metal mesh–based transducer is more suitable for dewatering fabrics, as it facilitates the ejection of water from the fabric–transducer interface to the opposite side of the mesh. A demonstration unit developed consumes 10–20% of the water latent heat energy at water contents greater than 20%.« less

The Strong Nuclear Force

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

Lincoln, Don

Scientists are aware of four fundamental forces- gravity, electromagnetism, and the strong and weak nuclear forces. Most people have at least some familiarity with gravity and electromagnetism, but not the other two. How is it that scientists are so certain that two additional forces exist? In this video, Fermilab’s Dr. Don Lincoln explains why scientists are so certain that the strong force exists.

The Strong Nuclear Force

ScienceCinema

Lincoln, Don

2018-01-16

Scientists are aware of four fundamental forces- gravity, electromagnetism, and the strong and weak nuclear forces. Most people have at least some familiarity with gravity and electromagnetism, but not the other two. How is it that scientists are so certain that two additional forces exist? In this video, Fermilab’s Dr. Don Lincoln explains why scientists are so certain that the strong force exists.

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet.

PubMed

Liu, Yingxiang; Liu, Junkao; Chen, Weishan; Shi, Shengjun

2012-05-01

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).

The Detection of Gravitational Waves

NASA Astrophysics Data System (ADS)

Blair, David G.

2005-10-01

Part I. An Introduction to Gravitational Waves and Methods for their Detection: 1. Gravitational waves in general relativity D. G. Blair; 2. Sources of gravitational waves D. G. Blair; 3. Gravitational wave detectors D. G. Blair; Part II. Gravitational Wave Detectors: 4. Resonant-bar detectors D. G. Blair; 5. Gravity wave dewars W. O. Hamilton; 6. Internal friction in high Q materials J. Ferreirinko; 7. Motion amplifiers and passive transducers J. P. Richard; 8. Parametric transducers P. J. Veitch; 9. Detection of continuous waves K. Tsubono; 10. Data analysis and algorithms for gravitational wave-antennas G. V. Paalottino; Part III. Laser Interferometer Antennas: 11. A Michelson interferometer using delay lines W. Winkler; 12. Fabry-Perot cavity gravity-wave detectors R. W. P. Drever; 13. The stabilisation of lasers for interferometric gravitational wave detectors J. Hough; 14. Vibration isolation for the test masses in interferometric gravitational wave detectors N. A. Robertson; 15. Advanced techniques A. Brillet; 16. Data processing, analysis and storage for interferometric antennas B. F. Schutz; 17. Gravitational wave detection at low and very low frequencies R. W. Hellings.

Familiar trajectories facilitate the interpretation of physical forces when intercepting a moving target.

PubMed

Mijatović, Antonija; La Scaleia, Barbara; Mercuri, Nicola; Lacquaniti, Francesco; Zago, Myrka

2014-12-01

Familiarity with the visual environment affects our expectations about the objects in a scene, aiding in recognition and interaction. Here we tested whether the familiarity with the specific trajectory followed by a moving target facilitates the interpretation of the effects of underlying physical forces. Participants intercepted a target sliding down either an inclined plane or a tautochrone. Gravity accelerated the target by the same amount in both cases, but the inclined plane represented a familiar trajectory whereas the tautochrone was unfamiliar to the participants. In separate sessions, the gravity field was consistent with either natural gravity or artificial reversed gravity. Target motion was occluded from view over the last segment. We found that the responses in the session with unnatural forces were systematically delayed relative to those with natural forces, but only for the inclined plane. The time shift is consistent with a bias for natural gravity, in so far as it reflects an a priori expectation that a target not affected by natural forces will arrive later than one accelerated downwards by gravity. Instead, we did not find any significant time shift with unnatural forces in the case of the tautochrone. We argue that interception of a moving target relies on the integration of the high-level cue of trajectory familiarity with low-level cues related to target kinematics.

Energetics and mechanics for partial gravity locomotion.

PubMed

Newman, D J; Alexander, H L; Webbon, B W

1994-09-01

The role of gravitational acceleration on human locomotion is not clearly understood. It is hypothesized that the mechanics and energetics of locomotion depend upon the prevailing gravity level. A unique human-rated underwater treadmill and an adjustable ballasting harness were used to stimulate partial gravity environments. This study has two research aspects, biomechanics and energetics. Vertical forces which are exerted by subjects on the treadmill-mounted, split-plate force platform show that peak vertical force and stride frequency significantly decrease (p < 0.05) as the gravity level is reduced, while ground contact time is independent of gravity level. A loping gait is employed over a wide range of speeds (approximately 1.5 m/s to approximately 2.3 m/s) suggesting a change in the mechanics for lunar (1/6 G) and Martian (3/8 G) locomotion. As theory predicts, locomotion energy requirements for partial gravity levels are significantly less than at 1 G (p < 0.05).

Measuring mitotic forces.

PubMed

Ye, Anna A; Maresca, Thomas J

2018-01-01

Productive chromosome movements require that a large multiprotein complex called the kinetochore assemble on sister centromeres. The kinetochore fulfills two critical functions as (1) the physical linkage between chromosomes and spindle microtubules and (2) a mechanomolecular sensor that relays a spindle assembly checkpoint signal delaying anaphase onset until chromosomes are attached to spindle microtubules and bioriented. Given its central roles in such a vital process, the kinetochore is one of the most important force-transducing structures in cells; yet it has been technically challenging to measure kinetochore forces. Barriers to measuring cellular forces have begun to be broken by the development of fluorescence-based tension sensors. In this chapter, two methods will be described for measuring kinetochore forces in living cells and strategies for applying these sensors to other force-transducing processes and molecules will be discussed. © 2018 Elsevier Inc. All rights reserved.

A correlation between extensional displacement and architecture of ionic polymer transducers

NASA Astrophysics Data System (ADS)

Akle, Barbar J.; Duncan, Andrew; Leo, Donald J.

2008-03-01

Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain and a moderate stress at low applied voltages (<5V). Bending actuators have limited engineering applications due to the low forcing capabilities and the need for complicated external devices to convert the bending action into rotating or linear motion desired in most devices. Recently Akle and Leo reported extensional actuation in ionic polymer transducers. In this study, extensional IPTs are characterized as a function of transducer architecture. In this study 2 actuators are built and there extensional displacement response is characterized. The transducers have similar electrodes while the middle membrane in the first is a Nafion / ionic liquid and an aluminum oxide - ionic liquid in the second. The first transducer is characterized for constant current input, voltage step input, and sweep voltage input. The model prediction is in agreement in both shape and magnitude for the constant current experiment. The values of α and β used are within the range of values reported in Akle and Leo. Both experiments and model demonstrate that there is a preferred direction of applying the potential so that the transducer will exhibit large deformations. In step response the model well predicted the negative potential and the early part of the step in the positive potential and failed to predict the displacement after approximately 180s has elapsed. The model well predicted the sweep response, and the observed 1st harmonic in the displacement further confirmed the existence of a quadratic in the charge response. Finally the aluminum oxide based transducer is characterized for a step response and compared to the Nafion based transducer. The second actuator demonstrated electromechanical extensional response faster than that in the Nafion based transducer. The Aluminum oxide based transducer is expected to provide larger forces and hence larger energy density.

Conformal invariance and the metrication of the fundamental forces

NASA Astrophysics Data System (ADS)

Mannheim, Philip D.

2016-07-01

We revisit Weyl’s metrication (geometrization) of electromagnetism. We show that by making Weyl’s proposed geometric connection be pure imaginary, not only are we able to metricate electromagnetism, an underlying local conformal invariance makes the geometry be strictly Riemannian and prevents observational gravity from being complex. Via torsion, we achieve an analogous metrication for axial-vector fields. We generalize our procedure to Yang-Mills theories, and achieve a metrication of all the fundamental forces. Only in the gravity sector does our approach differ from the standard picture of fundamental forces, with our approach requiring that standard Einstein gravity be replaced by conformal gravity. We show that quantum conformal gravity is a consistent and unitary quantum gravitational theory, one that, unlike string theory, only requires four spacetime dimensions.

Nanomechanical force transducers for biomolecular and intracellular measurements: is there room to shrink and why do it?

PubMed

Sirbuly, Donald J; Friddle, Raymond W; Villanueva, Joshua; Huang, Qian

2015-02-01

Over the past couple of decades there has been a tremendous amount of progress on the development of ultrasensitive nanomechanical instruments, which has enabled scientists to peer for the first time into the mechanical world of biomolecular systems. Currently, work-horse instruments such as the atomic force microscope and optical/magnetic tweezers have provided the resolution necessary to extract quantitative force data from various molecular systems down to the femtonewton range, but it remains difficult to access the intracellular environment with these analytical tools as they have fairly large sizes and complicated feedback systems. This review is focused on highlighting some of the major milestones and discoveries in the field of biomolecular mechanics that have been made possible by the development of advanced atomic force microscope and tweezer techniques as well as on introducing emerging state-of-the-art nanomechanical force transducers that are addressing the size limitations presented by these standard tools. We will first briefly cover the basic setup and operation of these instruments, and then focus heavily on summarizing advances in in vitro force studies at both the molecular and cellular level. The last part of this review will include strategies for shrinking down the size of force transducers and provide insight into why this may be important for gaining a more complete understanding of cellular activity and function.

What is the best method for assessing lower limb force-velocity relationship?

PubMed

Giroux, C; Rabita, G; Chollet, D; Guilhem, G

2015-02-01

This study determined the concurrent validity and reliability of force, velocity and power measurements provided by accelerometry, linear position transducer and Samozino's methods, during loaded squat jumps. 17 subjects performed squat jumps on 2 separate occasions in 7 loading conditions (0-60% of the maximal concentric load). Force, velocity and power patterns were averaged over the push-off phase using accelerometry, linear position transducer and a method based on key positions measurements during squat jump, and compared to force plate measurements. Concurrent validity analyses indicated very good agreement with the reference method (CV=6.4-14.5%). Force, velocity and power patterns comparison confirmed the agreement with slight differences for high-velocity movements. The validity of measurements was equivalent for all tested methods (r=0.87-0.98). Bland-Altman plots showed a lower agreement for velocity and power compared to force. Mean force, velocity and power were reliable for all methods (ICC=0.84-0.99), especially for Samozino's method (CV=2.7-8.6%). Our findings showed that present methods are valid and reliable in different loading conditions and permit between-session comparisons and characterization of training-induced effects. While linear position transducer and accelerometer allow for examining the whole time-course of kinetic patterns, Samozino's method benefits from a better reliability and ease of processing. © Georg Thieme Verlag KG Stuttgart · New York.

The moon-Earth system...As a vacuum gravity energy machine? A Hint about the Nature of Universal Gravity that May Have Been Overlooked

NASA Astrophysics Data System (ADS)

Masters, Roy

2011-10-01

We revisit the theories describing the moon raising the tides by virtue of pull gravity combined with the moon's centripetal angular momentum. We show that if gravity is considered as the attractive interaction between individual bodies, then a laboring moon doing work would have fallen to earth eons ago. Isaac Newton's laws of motion cannot work with pull gravity, but they do with Einstein's gravity as a property of the universe, which produces a continuous infusion of energy. In other words, the moon-Earth system becomes the first observable vacuum gravity energy machine. In other words the dynamics of what appears to be a closed system has been producing energy that continues raising the tides into perpetuity along with the force needed for the moon to escape the Earth's gravitational pull 4cm per year. All this is in defiance of Newton's first law which says ``If no force is added to a body it cannot accelerate.'' In this theory, a flowing space-time curves with three dimensions of force. A (flowing) spatial fabric bends around mass and displaces the inverse square field vanishing point property of matter with the appearance of a push-force square of the distance. In other words, the immeasurable universal gravity field appears as measurable local gravitation, concentrating universal gravitational pressure with the square of the distance from the very point was supposed to have disappeared. Needless to say such ``gravity'' necessitates a different beginning.

Pressure Profiles in a Loop Heat Pipe Under Gravity Influence

NASA Technical Reports Server (NTRS)

Ku, Jentung

2015-01-01

During the operation of a loop heat pipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed.

Pressure Profiles in a Loop Heat Pipe under Gravity Influence

NASA Technical Reports Server (NTRS)

Ku, Jentung

2015-01-01

During the operation of a loop heat pipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity-neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed.

Techniques of Force and Pressure Measurement in the Small Joints of the Wrist.

PubMed

Schreck, Michael J; Kelly, Meghan; Canham, Colin D; Elfar, John C

2018-01-01

The alteration of forces across joints can result in instability and subsequent disability. Previous methods of force measurements such as pressure-sensitive films, load cells, and pressure-sensing transducers have been utilized to estimate biomechanical forces across joints and more recent studies have utilized a nondestructive method that allows for assessment of joint forces under ligamentous restraints. A comprehensive review of the literature was performed to explore the numerous biomechanical methods utilized to estimate intra-articular forces. Methods of biomechanical force measurements in joints are reviewed. Methods such as pressure-sensitive films, load cells, and pressure-sensing transducers require significant intra-articular disruption and thus may result in inaccurate measurements, especially in small joints such as those within the wrist and hand. Non-destructive methods of joint force measurements either utilizing distraction-based joint reaction force methods or finite element analysis may offer a more accurate assessment; however, given their recent inception, further studies are needed to improve and validate their use.

Recording forces exerted on the bowel wall during colonoscopy: in vitro evaluation.

PubMed

Dogramadzi, S; Virk, G S; Bell, G D; Rowland, R S; Hancock, J

2005-12-01

A novel system for distributed force measurement between the bowel wall and the shaft of a colonoscope is presented. The system, based on the piezoresistive method, involves the integration of soft miniature transducers to a colonoscope to enable a wide range of forces to be sensed. The attached sensing sheath does not restrict the propulsion of the colonoscope nor notably alter its flexibility. The addition of the sensor sheath increases the colonoscope diameter by 15-20% depending on the type of the colonoscope (adult or paediatric). The transducer's accuracy is +/-20 grammes if it is not subjected to extensive static forces. Under large static force conditions the errors may increase to +/-50 grammes. The tactile force measuring sensors have provided preliminary results from experiments on a model of the large bowel. The force measurements confirm the predictions on the location and magnitude of the forces and that most of the forces are exerted whilst the instrument is looping. Copyright 2005 John Wiley & Sons, Ltd.

A generalised multiple-mass based method for the determination of the live mass of a force transducer

NASA Astrophysics Data System (ADS)

Montalvão, Diogo; Baker, Thomas; Ihracska, Balazs; Aulaqi, Muhammad

2017-01-01

Many applications in Experimental Modal Analysis (EMA) require that the sensors' masses are known. This is because the added mass from sensors will affect the structural mode shapes, and in particular its natural frequencies. EMA requires the measurement of the exciting forces at given coordinates, which is often made using piezoelectric force transducers. In such a case, the live mass of the force transducer, i.e. the mass as 'seen' by the structure in perpendicular directions must be measured somehow, so that compensation methods like mass cancelation can be performed. This however presents a problem on how to obtain an accurate measurement for the live mass. If the system is perfectly calibrated, then a reasonably accurate estimate can be made using a straightforward method available in most classical textbooks based on Newton's second law. However, this is often not the case (for example when the transducer's sensitivity changed over time, when it is unknown or when the connection influences the transmission of the force). In a self-calibrating iterative method, both the live mass and calibration factor are determined, but this paper shows that the problem may be ill-conditioned, producing misleading results if certain conditions are not met. Therefore, a more robust method is presented and discussed in this paper, reducing the ill-conditioning problems and the need to know the calibration factors beforehand. The three methods will be compared and discussed through numerical and experimental examples, showing that classical EMA still is a field of research that deserves the attention from scientists and engineers.

Two Curriculum-Relevant/Open Day Physics Experiments Concerning Gravity

ERIC Educational Resources Information Center

Sosabowski, Michael Hal; Young, Clive; Matkin, Judy; Ponikwer, Fiona

2013-01-01

Gravity is an intangible abstract force when considered theoretically and yet we are affected by it constantly. The apparently "strong" nature of gravity, which in the layperson's mind causes him or her to stick to the Earth, is belied by the fact that it is the weakest of the fundamental forces. Demonstrations that allow pupils,…

The effects of capillary forces on the axisymmetric propagation of two-phase, constant-flux gravity currents in porous media

NASA Astrophysics Data System (ADS)

Golding, Madeleine J.; Huppert, Herbert E.; Neufeld, Jerome A.

2013-03-01

The effects of capillary forces on the propagation of two-phase, constant-flux gravity currents in a porous medium are studied analytically and numerically in an axisymmetric geometry. The fluid within a two-phase current generally only partially saturates the pore space it invades. For long, thin currents, the saturation distribution is set by the vertical balance between gravitational and capillary forces. The capillary pressure and relative permeability of the fluid in the current depend on this saturation. The action of capillary forces reduces the average saturation, thereby decreasing the relative permeability throughout the current. This results in a thicker current, which provides a steeper gradient to drive flow, and a more blunt-nose profile. The relative strength of gravity and capillary forces remains constant within a two-phase gravity current fed by a constant flux and spreading radially, due to mass conservation. For this reason, we use an axisymmetric representation of the framework developed by Golding et al. ["Two-phase gravity currents in porous media," J. Fluid Mech. 678, 248-270 (2011)], 10.1017/jfm.2011.110, to investigate the effect on propagation of varying the magnitude of capillary forces and the pore-size distribution. Scaling analysis indicates that axisymmetric two-phase gravity currents fed by a constant flux propagate like t1/2, similar to their single-phase counterparts [S. Lyle, H. E. Huppert, M. Hallworth, M. Bickle, and A. Chadwick, "Axisymmetric gravity currents in a porous medium," J. Fluid Mech. 543, 293-302 (2005)], 10.1017/S0022112005006713, with the effects of capillary forces encapsulated in the constant of proportionality. As a practical application of our new concepts and quantitative evaluations, we discuss the implications of our results for the process of carbon dioxide (CO2) sequestration, during which gravity currents consisting of supercritical CO2 propagate in rock saturated with aqueous brine. We apply our two-phase model including capillary forces to quantitatively assess seismic images of CO2 spreading at Sleipner underneath the North Sea.

Acoustic radiation force optical coherence elastography using vibro-acoustography

NASA Astrophysics Data System (ADS)

Qu, Yueqiao (.; Ma, Teng; Li, Rui; Qi, Wenjuan; Zhu, Jiang; He, Youmin; Shung, K. K.; Zhou, Qifa; Chen, Zhongping

2015-03-01

High-resolution elasticity mapping of tissue biomechanical properties is crucial in early detection of many diseases. We report a method of acoustic radiation force optical coherence elastography (ARF-OCE) based on the methods of vibroacoustography, which uses a dual-ring ultrasonic transducer in order to excite a highly localized 3-D field. The single element transducer introduced previously in our ARF imaging has low depth resolution because the ARF is difficult to discriminate along the entire ultrasound propagation path. The novel dual-ring approach takes advantage of two overlapping acoustic fields and a few-hundred-Hertz difference in the signal frequencies of the two unmodulated confocal ring transducers in order to confine the acoustic stress field within a smaller volume. This frequency difference is the resulting "beating" frequency of the system. The frequency modulation of the transducers has been validated by comparing the dual ring ARF-OCE measurement to that of the single ring using a homogeneous silicone phantom. We have compared and analyzed the phantom resonance frequency to show the feasibility of our approach. We also show phantom images of the ARF-OCE based vibro-acoustography method and map out its acoustic stress region. We concluded that the dual-ring transducer is able to better localize the excitation to a smaller region to induce a focused force, which allows for highly selective excitation of small regions. The beat-frequency elastography method has great potential to achieve high-resolution elastography for ophthalmology and cardiovascular applications.

Piezoelectric Composites by Solid Freeform Fabrication: A Nature-Inspired Approach

NASA Astrophysics Data System (ADS)

Safari, A.; Akdoğan, E. K.

Piezoelectrics and electrostrictors are indispensable materials for use in transducer technology, as they inherently possess both direct (sensing) and converse (actuation) effects. A piezoelectric/electrostrictive sensor converts a mechanical input (displacement or force) into a measurable electrical output through piezoelectric/electrostrictive energy conversion. In the case of a piezoelectric, an applied mechanical force (stress) induces a voltage across the terminals of the transducer. On the other hand, an applied mechanical force induces a change in the capacitance of an electrostrictive transducer that could be electrically detected. Hence, the mechanical to electrical energy conversion is accomplished directly when a piezoelectric is used, while the same is obtained indirectly if the electroactive material of choice is an electrostrictor. Conversely, both piezoelectric and electrostrictive materials develop an elastic strain under an applied electric field. The said elastic strain is linearly proportional to the applied field in a piezoelectric, whereas electrostrictive coupling involves the second-order (quadratic) coupling of electric field with elastic strain. While piezoelectricity is possible only in noncentrosymetric point groups, electrostriction is observed in all solids, which make it a much more general solid-state phenomenon. Sensing and actuation functions can coexist in a given transducer by the intelligent use of such materials. Piezoelectrics and electrostrictors, therefore, constitute the backbone of modern transducer technology, as mechanical to electric energy (and vice versa) conversion can be accomplished with great efficiency in a way that is second to none among all phenomena known to date [1,2].

Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer

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

Qi, Wenjuan; Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, California 92697; Li, Rui

2014-03-24

We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.

Floating Ultrasonic Transducer Inspection System and Method for Nondestructive Evaluation

NASA Technical Reports Server (NTRS)

Johnston, Patrick H. (Inventor); Zalameda, Joseph N. (Inventor)

2016-01-01

A method for inspecting a structural sample using ultrasonic energy includes positioning an ultrasonic transducer adjacent to a surface of the sample, and then transmitting ultrasonic energy into the sample. Force pulses are applied to the transducer concurrently with transmission of the ultrasonic energy. A host machine processes ultrasonic return pulses from an ultrasonic pulser/receiver to quantify attenuation of the ultrasonic energy within the sample. The host machine detects a defect in the sample using the quantified level of attenuation. The method may include positioning a dry couplant between an ultrasonic transducer and the surface. A system includes an actuator, an ultrasonic transducer, a dry couplant between the transducer the sample, a scanning device that moves the actuator and transducer, and a measurement system having a pulsed actuator power supply, an ultrasonic pulser/receiver, and a host machine that executes the above method.

A novel ultrasonic clutch using near-field acoustic levitation.

PubMed

Chang, Kuo-Tsi

2004-10-01

This paper investigates design, fabrication and drive of an ultrasonic clutch with two transducers. For the two transducers, one serving as a driving element of the clutch is connected to a driving shaft via a coupling, and the other serving as a slave element of the clutch is connected to a slave shaft via another coupling. The principle of ultrasonic levitation is first expressed. Then, a series-resonant inverter is used to generate AC voltages at input terminals of each transducer, and a speed measuring system with optic sensors is used to find the relationship between rotational speed of the slave shaft and applied voltage of each transducer. Moreover, contact surfaces of the two transducers are coupled by the frictional force when both the two transducers are not energized, and separated using the ultrasonic levitation when at least one of the two transducers is energized at high voltages at resonance.

Einstein's Elevator in Class: A Self-Construction by Students for the Study of the Equivalence Principle

NASA Astrophysics Data System (ADS)

Kapotis, Efstratios; Kalkanis, George

2016-10-01

According to the principle of equivalence, it is impossible to distinguish between gravity and inertial forces that a noninertial observer experiences in his own frame of reference. For example, let's consider an elevator in space that is being accelerated in one direction. An observer inside it would feel as if there was gravity force pulling him toward the opposite direction. The same holds for a person in a stationary elevator located in Earth's gravitational field. No experiment enables us to distinguish between the accelerating elevator in space and the motionless elevator near Earth's surface. Strictly speaking, when the gravitational field is non-uniform (like Earth's), the equivalence principle holds only for experiments in elevators that are small enough and that take place over a short enough period of time (Fig. 1). However, performing an experiment in an elevator in space is impractical. On the other hand, it is easy to combine both forces on the same observer, i.e., gravity and a fictitious inertial force due to acceleration. Imagine an observer in an elevator that falls freely within Earth's gravitational field. The observer experiences gravity pulling him down while it might be said that the inertial force due to gravity acceleration g pulls him up. Gravity and inertial force cancel each other, (mis)leading the observer to believe there is no gravitational field. This study outlines our implementation of a self-construction idea that we have found useful in teaching introductory physics students (undergraduate, non-majors).

Analysis and numerical study of inertia-gravity waves generated by convection in the tropics

NASA Astrophysics Data System (ADS)

Evan, Stephanie

2011-12-01

Gravity waves transport momentum and energy upward from the troposphere and by dissipation affect the large-scale structure of the middle atmosphere. An accurate representation of these waves in climate models is important for climate studies, but is still a challenge for most global and climate models. In the tropics, several studies have shown that mesoscale gravity waves and intermediate scale inertia-gravity waves play an important role in the dynamics of the upper atmosphere. Despite observational evidence for the importance of forcing of the tropical circulation by inertia-gravity waves, their exact properties and forcing of the tropical stratospheric circulation are not fully understood. In this thesis, properties of tropical inertia-gravity waves are investigated using radiosonde data from the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE), the European Centre for Medium-Range Weather Forecasts (ECMWF) dataset and high-resolution numerical experiments. Few studies have characterized inertia-gravity wave properties using radiosonde profiles collected on a campaign basis. We first examine the properties of intermediate-scale inertia-gravity waves observed during the 2006 TWP-ICE campaign in Australia. We show that the total vertical flux of horizontal momentum associated with the waves is of the same order of magnitude as previous observations of Kelvin waves. This constitutes evidence for the importance of the forcing of the tropical circulation by intermediate-scale inertia-gravity waves. Then, we focus on the representation of inertia-gravity waves in analysis data. The wave event observed during TWP-ICE is also present in the ECMWF data. A comparison between the characteristics of the inertia-gravity wave derived with the ECMWF data to the properties of the wave derived with the radiosonde data shows that the ECMWF data capture similar structure for this wave event but with a larger vertical wavelength. The Weather Research and Forecasting (WRF) modeling system is used to understand the representation of the wave event in the ECMWF data. The model is configured as a tropical channel with a high top at 1 hPa. WRF is used with the same horizontal resolution (˜ 40 km) as the operational ECMWF in 2006 while using a finer vertical grid-spacing than ECMWF. Different experiments are performed to determine the sensitivity of the wave structure to cumulus schemes, initial conditions and vertical resolution. We demonstrate that high vertical resolution would be required for ECMWF to accurately resolve the vertical structure of inertia-gravity waves and their effect on the middle atmosphere circulation. Lastly we perform WRF simulations in January 2006 and 2007 to assess gravity wave forcing of the tropical stratospheric circulation. In these simulations a large part of the gravity wave spectrum is explicitly simulated. The WRF model is able to reproduce the evolution of the mean tropical stratospheric zonal wind when compared to observational data and the ECMWF reanalysis. It is shown that gravity waves account for 60% up to 80% of the total wave forcing of the tropical stratospheric circulation. We also compute wave forcing associated with intermediate-scale inertiagravity waves. In the WRF simulations this wave type represents ˜ 30% of the total gravity wave forcing. This suggests that intermediate-scale inertia-gravity waves can play an important role in the tropical middle-atmospheric circulation. In addition, the WRF high-resolution simulations are used to provide some guidance for constraining gravity wave parameterizations in coarse-grid climate models.

Cylindrical acoustic levitator/concentrator having non-circular cross-section

DOEpatents

Kaduchak, Gregory; Sinha, Dipen N.

2003-11-11

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow piezoelectric crystal which has been formed with a cylindrical cross-section to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. By deforming the circular cross-section of the transducer, the acoustic force is concentrated along axial regions parallel to the axis of the transducer. The cylinder does not require accurate alignment of a resonant cavity. The concentrated regions of acoustic force cause particles in the fluid to concentrate within the regions of acoustic force for separation from the fluid.

Research on new dynamic force calibration system

NASA Astrophysics Data System (ADS)

Zhang, Li

2008-06-01

Sinusoidal force calibration method based on electrodynamic shaker and interferometric system was studied several years before at Physikalisch-Technische Bundesanstalt (PTB). In that system a load mass are screwed on the top of force transducer, the sinusoidal forces realized by accelerated load masses are traceable to acceleration and mass according to the force definition F(t) = ma(t), where m is the total mass acting on the sensing element of the force transducer and a is the time and spatial-dependent acceleration of the mass, which is directly measured by a laser interferometer. This paper will introduce a new dynamic force calibration system developed at Changcheng Institute of Metrology and Measurement (CIMM). It uses electrodynamic shakers to generate dynamic force in the range from 1N to 20kN, and heterodyne laser interferometers are used for acceleration measurement. A new air bearing system is developed to increase the performance of shakers and an active vibration isolator is used to reduce enviromental disturbance to the interferometric system.

Development and testing of a unique carousel wind tunnel to experimentally determine the effect of gravity and the interparticle force on the physics of wind-blown particles

NASA Technical Reports Server (NTRS)

Leach, R. N.; Greeley, Ronald; White, Bruce R.; Iversen, James D.

1987-01-01

In the study of planetary aeolian processes the effect of gravity is not readily modeled. Gravity appears in the equations of particle motion along with the interparticle forces but the two are not separable. A wind tunnel that perimits multiphase flow experiments with wind blown particles at variable gravity was built and experiments were conducted at reduced gravity. The equations of particle motion initiation (saltation threshold) with variable gravity were experimentally verified and the interparticle force was separated. A uniquely design Carousel Wind Tunnel (CWT) allows for the long flow distance in a small sized tunnel since the test section if a continuous loop and develops the required turbulent boundary layer. A prototype model of the tunnel where only the inner drum rotates was built and tested in the KC-135 Weightless Wonder 4 zero-g aircraft. Future work includes further experiments with walnut shell in the KC-135 which sharply graded particles of widely varying median sizes including very small particles to see how interparticle force varies with particle size, and also experiments with other aeolian material.

Objectives, Outlines, and Preparation for the Resist Tubule Space Experiment to Understand the Mechanism of Gravity Resistance in Plants

NASA Astrophysics Data System (ADS)

Hoson, Takayuki; Akamatsu, Haruhiko; Soga, Kouichi; Wakabayashi, Kazuyuki; Hashimoto, Hirofumi; Yamashita, Masamichi; Hasegawa, Katsuya; Yano, Sachiko; Omori, Katsunori; Ishioka, Noriaki; Matsumoto, Shohei; Kasahara, Haruo; Shimazu, Toru; A. Baba, Shoji; Hashimoto, Takashi

Gravity resistance is a principal graviresponse in plants. In resistance to hypergravity, the gravity signal may be perceived by the mechanoreceptors located on the plasma membrane, and then transformed and transduced via the structural continuum or physiological continuity of cortical microtubules-plasma membrane-cell wall, leading to an increase in the cell wall rigidity as the final response. The Resist Tubule experiment, which will be conducted in the Kibo Module on the International Space Station, aims to confirm that this hypothesis is applicable to resistance to 1 G gravity. There are two major objectives in the Resist Tubule experiment. One is to quantify the contributions of cortical microtubules to gravity resistance using Arabidopsis tubulin mutants with different degrees of defects. Another objective is to analyze the modifications to dynamics of cortical microtubules and membrane rafts under microgravity conditions on-site by observing green fluorescent protein (GFP)-expressing Arabidopsis lines with the fluorescence microscope in the Kibo. We have selected suitable mutants, developed necessary hardware, and fixed operation procedure for the experiment.

[Gravity resistance, another graviresponse in plants--function of anti-gravitational polysaccharides].

PubMed

Hoson, Takayuki; Wakabayashi, Kazuyuki; Soga, Kouichi

2003-08-01

The involvement of anti-gravitational polysaccharides in gravity resistance, one of two major gravity responses in plants, was discussed. In dicotyledons, xyloglucans are the only cell wall polysaccharides, whose level, molecular size, and metabolic turnover were modified under both hypergravity and microgravity conditions, suggesting that xyloglucans act as anti-gravitational polysaccharides. In monocotyledonous Poaceae, (1-->3),(1-->4)-beta glucans, instead of xyloglucans, were shown to play a role as anti-gravitational polysaccharides. These polysaccharides are also involved in plant responses to other environmental factors, such as light and temperature, and to some phytohormones, such as auxin and ethylene. Thus, the type of anti-gravitational polysaccharides is different between dicotyledons and Poaceae, but such polysaccharides are universally involved in plant responses to environmental and hormonal signals. In gravity resistance, the gravity signal may be received by the plasma membrane mechanoreceptors, transformed and transduced within each cell, and then may modify the processes of synthesis and secretion of the anti-gravitational polysaccharides and the cell wall enzymes responsible for their degradation, as well as the apoplastic pH, leading to the cell wall reinforcement. A series of events inducing gravity resistance are quite independent of those leading to gravitropism.

Inertia coupling analysis of a self-decoupled wheel force transducer under multi-axis acceleration fields.

PubMed

Feng, Lihang; Lin, Guoyu; Zhang, Weigong; Dai, Dong

2015-01-01

Wheel force transducer (WFT), which measures the three-axis forces and three-axis torques applied to the wheel, is an important instrument in the vehicle testing field and has been extremely promoted by researchers with great interests. The transducer, however, is typically mounted on the wheel of a moving vehicle, especially on a high speed car, when abruptly accelerating or braking, the mass/inertia of the transducer/wheel itself will have an extra effect on the sensor response so that the inertia/mass loads will also be detected and coupled into the signal outputs. The effect which is considered to be inertia coupling problem will decrease the sensor accuracy. In this paper, the inertia coupling of a universal WFT under multi-axis accelerations is investigated. According to the self-decoupling approach of the WFT, inertia load distribution is solved based on the principle of equivalent mass and rotary inertia, thus then inertia impact can be identified with the theoretical derivation. The verification is achieved by FEM simulation and experimental tests. Results show that strains in simulation agree well with the theoretical derivation. The relationship between the applied acceleration and inertia load for both wheel force and moment is the approximate linear, respectively. All the relative errors are less than 5% which are within acceptable and the inertia loads have the maximum impact on the signal output about 1.5% in the measurement range.

Inertia Coupling Analysis of a Self-Decoupled Wheel Force Transducer under Multi-Axis Acceleration Fields

PubMed Central

Feng, Lihang; Lin, Guoyu; Zhang, Weigong; Dai, Dong

2015-01-01

Wheel force transducer (WFT), which measures the three-axis forces and three-axis torques applied to the wheel, is an important instrument in the vehicle testing field and has been extremely promoted by researchers with great interests. The transducer, however, is typically mounted on the wheel of a moving vehicle, especially on a high speed car, when abruptly accelerating or braking, the mass/inertia of the transducer/wheel itself will have an extra effect on the sensor response so that the inertia/mass loads will also be detected and coupled into the signal outputs. The effect which is considered to be inertia coupling problem will decrease the sensor accuracy. In this paper, the inertia coupling of a universal WFT under multi-axis accelerations is investigated. According to the self-decoupling approach of the WFT, inertia load distribution is solved based on the principle of equivalent mass and rotary inertia, thus then inertia impact can be identified with the theoretical derivation. The verification is achieved by FEM simulation and experimental tests. Results show that strains in simulation agree well with the theoretical derivation. The relationship between the applied acceleration and inertia load for both wheel force and moment is the approximate linear, respectively. All the relative errors are less than 5% which are within acceptable and the inertia loads have the maximum impact on the signal output about 1.5% in the measurement range. PMID:25723492

Gravity-dependent estimates of object mass underlie the generation of motor commands for horizontal limb movements.

PubMed

Crevecoeur, F; McIntyre, J; Thonnard, J-L; Lefèvre, P

2014-07-15

Moving requires handling gravitational and inertial constraints pulling on our body and on the objects that we manipulate. Although previous work emphasized that the brain uses internal models of each type of mechanical load, little is known about their interaction during motor planning and execution. In this report, we examine visually guided reaching movements in the horizontal plane performed by naive participants exposed to changes in gravity during parabolic flight. This approach allowed us to isolate the effect of gravity because the environmental dynamics along the horizontal axis remained unchanged. We show that gravity has a direct effect on movement kinematics, with faster movements observed after transitions from normal gravity to hypergravity (1.8g), followed by significant movement slowing after the transition from hypergravity to zero gravity. We recorded finger forces applied on an object held in precision grip and found that the coupling between grip force and inertial loads displayed a similar effect, with an increase in grip force modulation gain under hypergravity followed by a reduction of modulation gain after entering the zero-gravity environment. We present a computational model to illustrate that these effects are compatible with the hypothesis that participants partially attribute changes in weight to changes in mass and scale incorrectly their motor commands with changes in gravity. These results highlight a rather direct internal mapping between the force generated during stationary holding against gravity and the estimation of inertial loads that limb and hand motor commands must overcome. Copyright © 2014 the American Physiological Society.

Wave Dynamics and Transport in the Stratosphere

NASA Technical Reports Server (NTRS)

Holton, James R.; Alexander, M. Joan

1999-01-01

The report discusses: (1) Gravity waves generated by tropical convection: A study in which a two-dimensional cloud-resolving model was used to examine the possible role of gravity waves generated by a simulated tropical squall line in forcing the quasi-biennial oscillation was completed. (2) Gravity wave ray tracing studies:It was developed a linear ray tracing model of gravity wave propagation to extend the nonlinear storm model results into the mesosphere and thermosphere. (3) tracer filamentation: Vertical soundings of stratospheric ozone often exhibit laminated tracer structures characterized by strong vertical tracer gradients. (4) Mesospheric gravity wave modeling studies: Although our emphasis in numerical simulation of gravity waves generated by convection has shifted from simulation of idealized two-dimensional squall lines to the most realistic (and complex) study of wave generation by three-dimensional storms. (5) Gravity wave climatology studies: Mr. Alexander applied a linear gravity wave propagation model together with observations of the background wind and stability fields to compute climatologies of gravity wave activity for comparison to observations. (6) Convective forcing of gravity waves: Theoretical study of gravity wave forcing by convective heat sources has completed. (7) Gravity waves observation from UARS: The objective of this work is to apply ray tracing, and other model technique, in order to determine to what extend the horizontal and vertical variation in satellite observed distribution of small-scale temperature variance can be attributed to gravity waves from particular sources. (8) The annual and interannual variations in temperature and mass flux near the tropical tropopause. and (9) Three dimensional cloud model.

CFD modeling of an ultrasonic separator for the removal of lipid particles from pericardial suction blood.

PubMed

Trippa, Giuliana; Ventikos, Yiannis; Taggart, David P; Coussios, Constantin-C

2011-02-01

A computational fluid dynamics (CFD) model is presented to simulate the removal of lipid particles from blood using a novel ultrasonic quarter-wavelength separator. The Lagrangian-Eulerian CFD model accounts for conservation of mass and momentum, for the presence of lipid particles of a range of diameters, for the acoustic force as experienced by the particles in the blood, as well as for gravity and other particle-fluid interaction forces. In the separator, the liquid flows radially inward within a fluid chamber formed between a disc-shaped transducer and a disc-shaped reflector. Following separation of the lipid particles, blood exits the separator axially through a central opening on the disc-shaped reflector. Separator diameters studied varied between 12 and 18 cm, and gap sizes between the discs of 600 μm, 800 μm and 1 mm were considered. Results show a strong effect of residence time of the particles within the chamber on the separation performance. Different separator configurations were identified, which could give a lipid removal performance of 95% or higher when processing 62.5 cm (3)/min of blood. The developed model provides a design method for the selection of geometric and operating parameters for the ultrasonic separator.

Simple-structured capillary-force-dominated tunable-focus liquid lens based on the higher-order-harmonic resonance of a piezoelectric ring transducer.

PubMed

Feng, Guo-Hua; Liu, Jun-Hao

2013-02-01

This paper proposes a tunable-focus liquid lens implemented with a simple cylindrical container structure and liquid as the lens material. The cylindrical container was constructed using a Pb [Zr(0.52)Ti(0.48)]O(3) (PZT) ring transducer and a polydimethylsiloxane membrane that was attached to a flat side of the transducer. The free surface of the liquid in the cylindrical container can be driven as a static-like convex lens with different curvatures because the higher-order harmonic resonance of the PZT transducer was electrically controlled. Based on a capillary-force-dominant design, the activated liquid lens maintained surface curvature in an arbitrary orientation without a gravitational effect. Profiles of the liquid lenses were characterized with the driving voltages of the transducer ranging from 12 to 60 V peak-to-peak (Vpp) at a resonant frequency of 460 kHz. The temperature effects on the lenses caused by the continuous operation of the transducer were measured. Images showed the various curvatures of the lenses with a range of actuation voltages. A change in focal length of eight times (5.72 to 46.03 cm) was demonstrated within the 10 Vpp variation of the driving voltage. For the characterized liquid lenses, the distortion was less than 2%, and the modulation transfer function reached 63 line pairs per mm (lp/mm) using ZEMAX analysis.

Grip Force Adjustments Reflect Prediction of Dynamic Consequences in Varying Gravitoinertial Fields

PubMed Central

White, Olivier; Thonnard, Jean-Louis; Lefèvre, Philippe; Hermsdörfer, Joachim

2018-01-01

Humans have a remarkable ability to adjust the way they manipulate tools through a genuine regulation of grip force according to the task. However, rapid changes in the dynamical context may challenge this skill, as shown in many experimental approaches. Most experiments adopt perturbation paradigms that affect only one sensory modality. We hypothesize that very fast adaptation can occur if coherent information from multiple sensory modalities is provided to the central nervous system. Here, we test whether participants can switch between different and never experienced dynamical environments induced by centrifugation of the body. Seven participants lifted an object four times in a row successively in 1, 1.5, 2, 2.5, 2, 1.5, and 1 g. We continuously measured grip force, load force and the gravitoinertial acceleration that was aligned with body axis (perceived gravity). Participants adopted stereotyped grasping movements immediately upon entry in a new environment and needed only one trial to adapt grip forces to a stable performance in each new gravity environment. This result was underlined by good correlations between grip and load forces in the first trial. Participants predictively applied larger grip forces when they expected increasing gravity steps. They also decreased grip force when they expected decreasing gravity steps, but not as much as they could, indicating imperfect anticipation in that condition. The participants' performance could rather be explained by a combination of successful scaling of grip force according to gravity changes and a separate safety factor. The data suggest that in highly unfamiliar dynamic environments, grip force regulation is characterized by a combination of a successful anticipation of the experienced environmental condition, a safety factor reflecting strategic response to uncertainties about the environment and rapid feedback mechanisms to optimize performance under constant conditions. PMID:29527176

Design of a 7-DOF slave robot integrated with a magneto-rheological haptic master

NASA Astrophysics Data System (ADS)

Hwang, Yong-Hoon; Cha, Seung-Woo; Kang, Seok-Rae; Choi, Seung-Bok

2017-04-01

In this study, a 7-DOF slave robot integrated with the haptic master is designed and its dynamic motion is controlled. The haptic master is made using a controllable magneto-rheological (MR) clutch and brake and it provides the surgeon with a sense of touch by using both kinetic and kinesthetic information. Due to the size constraint of the slave robot, a wire actuating is adopted to make the desired motion of the end-effector which has 3-DOF instead of a conventional direct-driven motor. Another motions of the link parts that have 4-DOF use direct-driven motor. In total system, for working as a haptic device, the haptic master need to receive the information of repulsive forces applied on the slave robot. Therefore, repulsive forces on the end-effector are sensed by using three uniaxial torque transducer inserted in the wire actuating system and another repulsive forces applied on link part are sensed by using 6-axis transducer that is able to sense forces and torques. Using another 6-axis transducer, verify the reliability of force information on final end of slave robot. Lastly, integrated with a MR haptic master, psycho-physical test is conducted by different operators who can feel the different repulsive force or torque generated from the haptic master which is equivalent to the force or torque occurred on the end-effector to demonstrate the effectiveness of the proposed system.

A new topological structure for the Langevin-type ultrasonic transducer.

PubMed

Lu, Xiaolong; Hu, Junhui; Peng, Hanmin; Wang, Yuan

2017-03-01

In this paper, a new topological structure for the Langevin-type ultrasonic transducer is proposed and investigated. The two cylindrical terminal blocks are conically shaped with four supporting plates each, and two cooling fins are disposed at the bottom of terminal blocks, adjacent to the piezoelectric rings. Experimental results show that it has larger vibration velocity, lower temperature rise and higher electroacoustic energy efficiency than the conventional Langevin transducer. The reasons for the phenomena can be well explained by the change of mass, heat dissipation surface and force factor of the transducer. The proposed design may effectively improve the performance of ultrasonic transducers, in terms of the working effect, energy consumption and working life. Copyright © 2016 Elsevier B.V. All rights reserved.

Gas pressure in sealed electrochemical cells measured externally

NASA Technical Reports Server (NTRS)

Sherfey, J. M.

1967-01-01

Piezoresistive transducer measures gas pressure inside sealed secondary electrochemical cells without breaking the seal. This method is based on the observed fact that the force exerted by the cell faces on the clamp tightening them against the transducer is a function of the gas pressure inside the cell.

Methodological concerns for determining power output in the jump squat.

PubMed

Cormie, Prue; Deane, Russell; McBride, Jeffrey M

2007-05-01

The purpose of this study was to investigate the validity of power measurement techniques during the jump squat (JS) utilizing various combinations of a force plate and linear position transducer (LPT) devices. Nine men with at least 6 months of prior resistance training experience participated in this acute investigation. One repetition maximums (1RM) in the squat were determined, followed by JS testing under 2 loading conditions (30% of 1RM [JS30] and 90% of 1RM [JS90]). Three different techniques were used simultaneously in data collection: (a) 1 linear position transducer (1-LPT); (b) 1 linear position transducer and a force plate (1-LPT + FP); and (c) 2 linear position transducers and a force place (2-LPT + FP). Vertical velocity-, force-, and power-time curves were calculated for each lift using these methodologies and were compared. Peak force and peak power were overestimated by 1-LPT in both JS30 and JS90 compared with 2-LPT + FP and 1-LPT + FP (p

The effects of dimensional parameters on sensing and energy harvesting of an embedded PZT in a total knee replacement

NASA Astrophysics Data System (ADS)

Safaei, Mohsen; Anton, Steven R.

2016-04-01

Total Knee Replacement (TKR), one of the most common surgeries in the United States, is performed when the patient is experiencing significant amounts of pain or when knee functionality has become substantially degraded. Despite impressive recent developments, only about 85% of patients are satisfied with the pain reduction after one year. Therefore, structural health and performance monitoring are integral for intraoperative and postoperative feedback. In extension of the author's previous work, a new configuration for implementation of piezoelectric transducers in total knee replacement bearings is proposed and FEA modeling is performed to attain appropriate sensing and energy harvesting ability. The predicted force transmission ratio to the PZT (ratio of force applied to the bearing to force transferred to the embedded piezoelectric transducer) is about 6.2% compared to about 5% found for the previous encapsulated design. Dimensional parameters of the polyethylene bearing including the diameter and depth of the PZT pocket as well as the placement geometry of the PZT transducer within the bearing are hypothesized as the most influential parameters on the performance of the designed system. The results show a small change of 1% and 2.3% in the output of the system as a result of variation in the PZT location and pocket diameter, respectively. Whereas, the output of the system is significantly sensitive to the pocket depth; a pocket 0.01 mm deeper than the PZT transducer leads to no force transmission, and a pocket 0.15 mm shallower leads to full load transmission to the PZT. In order to develop a self-powered sensor, the amount of energy harvested from tibial forces for the proposed geometry is investigated.

Association between gravitational force and tissue metabolism in periparturient rats

NASA Technical Reports Server (NTRS)

Zakrzewska, E. I.; Maple, R.; Lintault, L.; Wade, C.; Baer, L.; Ronca, A.; Plaut, K.

2004-01-01

Recently, interest in mammalian reproduction and offspring survival in altered gravity has been growing. Because successful lactation is critical for mammalian neonate survival, we have been studying the effect of gravity metabolism. We have shown an exponential relationship between glucose metabolic rate in mammary tissue of periparturient rats and an increase in gravity load. In this study we showed that changes in mammary metabolic rate due to gravity force were accompanied by a decrease in glucose metabolism in adipose tissue and by a reduced size of adipocytes. We assume that these changes are likely due to changes in prolactin or leptin levels related to altered gravity load.

Development of a novel configuration for a MEMS transducer for low bias and high resolution imaging applications

NASA Astrophysics Data System (ADS)

Emadi, Tahereh Arezoo; Buchanan, Douglas A.

2014-03-01

A robust capacitive micromachined ultrasonic transducer has been developed. In this novel configuration, a stack of two deflectable membranes are suspended over a fixed bottom electrode. Similar to conventional capacitive ultrasonic transducers, a generated electrostatic force between the electrodes causes the membranes to deflect and vibrate. However, in this new configuration the transducer effective cavity height is reduced due to the deflection of two membranes. Therefore, the transducer spring constant is more susceptible to bias voltage, which in return reduces the required bias voltage. The transducers have been produced employing a MEMS sacrificial technique where two different membrane anchoring (curved- and flat- anchors) structures, with similar membrane radii were fabricated. Highly doped polysilicon was used as the membrane material. The resonant frequencies of the two transducers have been investigated. It was found that the transducers with curved membrane anchors exhibits a larger resonant frequency shift compared to the transducers with flat membranes for a given bias voltage. Comparison has been made between the spring constant of the flat membrane transducer and that of a conventional single membrane transducer. It is shown that the multiple moving membrane transducer exhibits a larger reduction in the spring constant compared to the conventional transducer, when driven with the same bias voltage. This results in a transducer with a higher power generation capability and sensitivity.

Escaping the maze: micro-swimmers using acoustic forces to navigate

NASA Astrophysics Data System (ADS)

Louf, Jean-Francois; Dollet, Benjamin; Stephan, Olivier; Marmottant, Philippe

2017-11-01

The goal of this study is to make 3D micro-swimmers containing a bubble that can be stimulated with acoustic waves emitted by a transducer, and whose direction is accurately controlled. By using 3D micro-fabrication techniques, we designed 40x40 μm swimmers with a trapped air bubble. We then applied acoustic vibration to the bubble, which generates a strong steady flow (1-100 mm/s) behind it, an effect referred as acoustic streaming. However, independently from the orientation of the bubble and thus from the flow, the motion of the swimmer is found to be towards the transducer. This suggests that primary Bjerknes forces, i.e. acoustic radiation forces, are involved. Subsequently, using different transducers located at different points, we could be able to navigate the swimmer in a chosen direction. The next step of our study is to use a stationary wave and Bjerknes forces to bring encapsulated objects in a pressure node. Without bubbles, the effect of acoustic streaming on big objects of more than a micrometer is not sufficient to generate motion. However, with the presence of bubbles, our swimmers should be able to move. ERC BUBBLEBOOST.

Catheter tip force transducer for cardiovascular research

NASA Technical Reports Server (NTRS)

Feldstein, C.; Lewis, G. W.; Silver, R. H.; Culler, V. H. (Inventor)

1976-01-01

A force transducer for measuring dynamic force activity within the heart of a subject essentially consists of a U-shaped beam of low elastic compliance material. Two lines extend from the beams's legs and a long coil spring is attached to the beam. A strain gauge is coupled to one of the beam's legs to sense deflections thereof. The beam with the tines and most of the spring are surrounded by a flexible tube, defining a catheter, which is insertable into a subject's heart through an appropriate artery. The tines are extractable from the catheter for implantation into the myocardium by pushing on the end of the spring which extends beyond the external end of the catheter.

Helmet weight simulator

NASA Technical Reports Server (NTRS)

Ashworth, B. R.; Hall, A. C.; Clark, C. E. (Inventor)

1981-01-01

A device for providing acceleration cues to the helmet of a simulator pilot is described. Pulleys are attached to both shoulders of the pilot. A cable is attached to both sides of the helmet and extends through the pulleys to a takeup reel that is controlled by a torque motor. Control signals are applied to a servo system including the torque motor, the takeup reel and a force transducer which supplies the feedback signal. In one embodiment of the invention the force transducer is in the cable and in another it is in the takeup reel.

Some physiological effects of alternation between zero gravity and one gravity

NASA Technical Reports Server (NTRS)

Graybiel, A.

1977-01-01

The anatomy and physiology of the healthy vestibular system and the history of its study, maintenance of muskuloskeletal fitness under low-gravity conditions, tests of motion sickness, and data and techniques on testing subjects in a slow rotation room, are covered. Components of the inner ear labyrinth and their behavior in relation to equilibrium, gravity and inertial forces, motion sickness, and dizziness are discussed. Preventive medicine, the biologically effective force environment, weightlessness per se, activity in a weightless spacecraft, exercizing required to maintain musculoskeletal function, and ataxia problems are dealt with.

Gravitational Radiation

NASA Astrophysics Data System (ADS)

Schutz, B.; Murdin, P.

2000-11-01

Gravity is one of the fundamental forces of nature, and it is the dominant force in most astronomical systems. In common with all other phenomena, gravity must obey the principles of SPECIAL RELATIVITY. In particular, gravitational forces must not be transmitted or communicated faster than light. This means that, when the gravitational field of an object changes, the changes ripple outwards throu...

Dynamic behavior of microscale particles controlled by standing bulk acoustic waves

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

Greenhall, J.; Raeymaekers, B., E-mail: bart.raeymaekers@utah.edu; Guevara Vasquez, F.

2014-10-06

We analyze the dynamic behavior of a spherical microparticle submerged in a fluid medium, driven to the node of a standing bulk acoustic wave created by two opposing transducers. We derive the dynamics of the fluid-particle system taking into account the acoustic radiation force and the time-dependent and time-independent drag force acting on the particle. Using this dynamic model, we characterize the transient and steady-state behavior of the fluid-particle system as a function of the particle and fluid properties and the transducer operating parameters. The results show that the settling time and percent overshoot of the particle trajectory are dependentmore » on the ratio of the acoustic radiation force and time-independent damping force. In addition, we show that the particle oscillates around the node of the standing wave with an amplitude that depends on the ratio of the time-dependent drag forces and the particle inertia.« less

Modeling of Vapor Bubble Growth Under Nucleate Boiling Conditions in Reduced Gravity

NASA Technical Reports Server (NTRS)

Buyevich, Yu A.; Webbon, Bruce W.

1995-01-01

A dynamic model is developed to describe the evolution of a vapor bubble growing at a nucleation site on a superheated surface under arbitrary gravity. The bubble is separated from the surface by a thin microlayer and grows due to the evaporation from the microlayer interface. The average thickness of the microlayer increases as the bubble expands along the surface if the evaporation rate is lower than some critical value. The corresponding threshold value of the surface temperature has to be associated with the burn-out crisis. Two main reasons make for bubble separation, which are the buoyancy force and a force caused by the vapor momentum that comes to the bubble with vapor molecules. The latter force is somewhat diminished if condensation takes place at the upper bubble surface in subcooled liquids. The action of the said forces is opposed by inertia of the additional mass of liquid as the bubble center rises above the surface and by inertia of liquid being expelled by the growing bubble in radial directions. An extra pressure force arises due to the liquid inflow into the microlayer with a finite velocity. The last force helps in holding the bubble close to the surface during an initial stage of bubble evolution. Two limiting regimes with distinctly different properties can be singled out, depending on which of the forces that favor bubble detachment dominates. Under conditions of moderately reduced gravity, the situation is much the same as in normal gravity, although the bubble detachment volume increases as gravity diminishes. In microgravity, the buoyancy force is negligible. Then the bubble is capable of staying near the surface for a long time, with intensive evaporation from the microlayer. It suggests a drastic change in the physical mechanism of heat removal as gravity falls below a certain sufficiently low level. Inferences of the model and conclusions pertaining to effects caused on heat transfer processes by changes in bubble hydrodynamics induced by gravity are discussed in connection with experimental evidence, both available in current and in as yet unpublished literature.

21 CFR 888.1240 - AC-powered dynamometer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... neuromuscular function or degree of neuromuscular blockage by measuring, with a force transducer (a device that translates force into electrical impulses), the grip-strength of a patient's hand. (b) Classification. Class...

21 CFR 888.1240 - AC-powered dynamometer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... neuromuscular function or degree of neuromuscular blockage by measuring, with a force transducer (a device that translates force into electrical impulses), the grip-strength of a patient's hand. (b) Classification. Class...

Short Range Tests of Gravity

NASA Astrophysics Data System (ADS)

Cardenas, Crystal; Harter, Andrew; Hoyle, C. D.; Leopardi, Holly; Smith, David

2014-03-01

Gravity was the first force to be described mathematically, yet it is the only fundamental force not well understood. The Standard Model of quantum mechanics describes interactions between the fundamental strong, weak and electromagnetic forces while Einstein's theory of General Relativity (GR) describes the fundamental force of gravity. There is yet to be a theory that unifies inconsistencies between GR and quantum mechanics. Scenarios of String Theory predicting more than three spatial dimensions also predict physical effects of gravity at sub-millimeter levels that would alter the gravitational inverse-square law. The Weak Equivalence Principle (WEP), a central feature of GR, states that all objects are accelerated at the same rate in a gravitational field independent of their composition. A violation of the WEP at any length would be evidence that current models of gravity are incorrect. At the Humboldt State University Gravitational Research Laboratory, an experiment is being developed to observe gravitational interactions below the 50-micron distance scale. The experiment measures the twist of a parallel-plate torsion pendulum as an attractor mass is oscillated within 50 microns of the pendulum, providing time varying gravitational torque on the pendulum. The size and distance dependence of the torque amplitude provide means to determine deviations from accepted models of gravity on untested distance scales. undergraduate.

The effect of an extraluminal transducer on the reproductive capability of the rabbit.

PubMed

Fromm, E; Garcia, C R; Jeutter, D C; Anid, A; Epstein, S

1976-12-01

An extraluminally attached microminiature force transducer, designed for reproductive tract contractility measurements, was investigated in terms of its effects on the physiology of the uterotubal junction in the rabbit. The presence or attachment process of the extraluminal force transducer (EFT) did not affect the rate of pregnancy or the number of embryonic implantation sites whether the attached device was silicone rubber or polyethylene-encased. The uterotubal junction was able to retain the blastocyst for the required time after mating, while an examination of postembryonic mortality revealed a rate of one resorption in some experimental groups. The gestation period was unaffected by the EFT, ranging from 30 to 40 days with a mode of 32, while histologic examinations revealed formation of a thin fibroblastic layer, some increased vascularity, and no abnormal leukocytic accumulation.

Effect of reduced gravity on the preferred walk-run transition speed

NASA Technical Reports Server (NTRS)

Kram, R.; Domingo, A.; Ferris, D. P.

1997-01-01

We investigated the effect of reduced gravity on the human walk-run gait transition speed and interpreted the results using an inverted-pendulum mechanical model. We simulated reduced gravity using an apparatus that applied a nearly constant upward force at the center of mass, and the subjects walked and ran on a motorized treadmill. In the inverted pendulum model for walking, gravity provides the centripetal force needed to keep the pendulum in contact with the ground. The ratio of the centripetal and gravitational forces (mv2/L)/(mg) reduces to the dimensionless Froude number (v2/gL). Applying this model to a walking human, m is body mass, v is forward velocity, L is leg length and g is gravity. In normal gravity, humans and other bipeds with different leg lengths all choose to switch from a walk to a run at different absolute speeds but at approximately the same Froude number (0.5). We found that, at lower levels of gravity, the walk-run transition occurred at progressively slower absolute speeds but at approximately the same Froude number. This supports the hypothesis that the walk-run transition is triggered by the dynamics of an inverted-pendulum system.

The influence of cadence and power output on force application and in-shoe pressure distribution during cycling by competitive and recreational cyclists.

PubMed

Sanderson, D J; Hennig, E M; Black, A H

2000-03-01

The aim of this study was to determine the response of cyclists to manipulations of cadence and power output in terms of force application and plantar pressure distribution. Two groups of cyclists, 17 recreational and 12 competitive, rode at three nominal cadences (60, 80, 100 rev x min(-1)) and four power outputs (100, 200, 300, 400 W) while simultaneous force and in-shoe pressure data were collected. Two piezoelectric triaxial force transducers mounted in the right pedal measured components of the pedal force and orientation, and a discrete transducer system with 12 transducers recorded the in-shoe pressures. Force application was characterized by calculating peak resultant and peak effective pedal forces and positive and negative impulses. In-shoe pressures were analysed as peak pressures and as the percent relative load. The force data showed no significant group effect but there was a cadence and power main effect. The impulse data showed a significant three-way interaction. Increased cadence resulted in a decreased positive impulse, while increased power output resulted in an increased impulse. The competitive group produced less positive impulse but the difference became less at higher cadences. Few between-group differences were found in pressure, notable only in the pressure under the first metatarsal region. This showed a consistent pattern of in-shoe pressure distribution, where the primary loading structures were the first metatarsal and hallux. There was no indication that pressure at specific sites influenced the pedal force application. The absence of group differences indicated that pressure distribution was not the result of training, but reflected the intrinsic relationship between the foot, the shoe and the pedal.

Clausewitz’s Elusive Center of Gravity

DTIC Science & Technology

1987-09-01

compel our enemy to do our will. Force, to counter opposing force, equips itself with the inventions of art and science . . . . Force-that is...relationship to the concentration of force. In his Summary o f the Art o f War (1838), Jomini defined the fundamental principle of war as...will to resist that provides the cohesion, the coherence, to these centers of gravity in collision. But the essence of operational art is the

Using FOCUS to determine the radiation impedance for square transducers

NASA Astrophysics Data System (ADS)

Jennings, Matthew R.; McGough, Robert J.

2012-10-01

The power radiated by an ultrasound transducer is calculated with the radiation resistance, which is the real part of the radiation impedance. For circular transducers, an analytical solution for the radiation impedance is known, but an analytical expression for the radiation impedance is not available for rectangular or square transducers. To determine the radiation resistance in FOCUS, the pressure on the surface of a square transducer is computed with the fast nearfield method, and then the force on the transducer face is computed by integrating the pressure. Results using this approach are numerically evaluated for a range of ka values from 0.1 to 16. The pressure on the transducer face is also computed with the Rayleigh-Sommerfeld integral, and the results are compared. The numerical value of the radiation resistance computed with FOCUS and with the Rayleigh-Sommerfeld integral converge to the same value, although FOCUS calculates the same result in about one-quarter of the time.

Normal values of spleen stiffness in healthy children assessed by acoustic radiation force impulse imaging (ARFI): comparison between two ultrasound transducers.

PubMed

Cañas, Teresa; Fontanilla, Teresa; Miralles, María; Maciá, Araceli; Malalana, Ana; Román, Enriqueta

2015-08-01

Portal hypertension, a major complication of hepatic fibrosis, can affect the stiffness of the spleen. To suggest normal values of spleen stiffness determined by acoustic radiation force impulse imaging in healthy children and to compare measurements using two different US probes. In a prospective study, 60 healthy children between 1 day and 14 years of age were assigned to four age groups with 15 children in each. Measurements were performed using two transducers (convex 4C1 and linear 9L4), and 10 measurements were obtained in each child, 5 with each probe. The mean splenic shear wave velocities were 2.17 m/s (SD 0.35, 95% CI 2.08-2.26) with the 4C1 probe and 2.15 m/s (SD 0.23, 95% CI 2.09-2.21) with the 9L4 probe (not significant). We found normal values for spleen stiffness with no difference in the mean values obtained using two types of US transducers, but with higher variability using a convex compared to a linear transducer.

Design, analysis, and fabrication of a piezoelectric force plate

NASA Astrophysics Data System (ADS)

Hoummadi, Elias; Safaei, Mohsen; Anton, Steven R.

2017-04-01

Force plates are used to detect static and dynamic reaction forces due to presence of stationary or moving objects as well as the location of applied forces. The application of force plates in various biomechanical fields, such as gait analysis, has been widely suggested and investigated in the past. Several sensor technologies like piezoelectrics, capacitance gauges, and piezoresistive sensors are utilized to develop force plates with special characteristics. Among the technologies employed in force plate designs, piezoelectrics present the ability of providing a self-powered sensory system. Recently, it has been suggested to implement piezoelectric transducers as sensors in the tibial bearing of total knee replacement (TKR) implants in order to transform the knee bearing into a force plate with the ability to detect force and contact point location for in vivo knee load analysis. Considering this application, a simplified design of a force plate instrumented with six piezoelectric transducers is presented in this study. The force plate is modeled using a finite element (FE) model to investigate the sensing performance of the system. In order to validate the simulation, a prototype force plate is fabricated and tested under the same loading condition applied on the FE model. The results are presented in terms of measured location and amplitude of applied force measured by the piezoelectric transducers. For the FE simulation, the deviation of the measured location of the applied force from the actual location is obtained as 0.62 mm in the x-direction and 0.13 mm in the y-direction, and the error in the amplitude of the measured force is 0.03% of the applied force. On the other hand, the deviation in the measured location of the force from the experimental test is 0.53 mm in the x-direction and 0.1 mm in the y-direction, while the error in force is 3.6% of the applied force. The small quantities of error in both sensed location and amplitude of applied force obtained from the FE simulation and experimental test results demonstrates the potential of the proposed design to be utilized as the sensor in the knee bearing of TKR implants.

Gravity wave forcing in the middle atmosphere due to reduced ozone heating during a solar eclipse

NASA Technical Reports Server (NTRS)

Fritts, David C.; Luo, Zhangai

1993-01-01

We present an analysis of the gravity wave structure and the associated forcing of the middle atmosphere induced by the screening of the ozone layer from solar heating during a solar eclipse. Fourier integral techniques and numerical evaluation of the integral solutions were used to assess the wave field structure and to compute the gravity wave forcing of the atmosphere at greater heights. Our solutions reveal dominant periods of a few hours, characteristic horizontal and vertical scales of about 5000 to 10,000 km and 200 km, respectively, and an integrated momentum flux in the direction of eclipse motion of about 5.6 x 10 exp 8 N at each height above the forcing level. These results suggest that responses to solar eclipses may be difficult to detect above background gravity wave and tidal fluctuations until well into the thermosphere. Conversely, the induced body forces may penetrate to considerable heights because of the large wave scales and will have significant effects at levels where the wave field is dissipated.

Vibration Control via Stiffness Switching of Magnetostrictive Transducers

NASA Technical Reports Server (NTRS)

Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

2016-01-01

This paper presents a computational study of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magnetomechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.25; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping.

Multifunctional transducer

NASA Technical Reports Server (NTRS)

Feldstein, C.; Lewis, G. W.; Culler, V. H.; Merrbaum, S. (Inventor)

1981-01-01

Several parameters of a small region of a muscle tissue or other object, can be simultaneously measured using with minimal traumatizing or damage of the object, a trifunctional transducer which can determine the force applied by a muscle fiber, the displacement of the fiber, and the change in thickness of the fiber. The transducer has three legs with inner ends joined together and outer ends formed to piece the tissue and remain within it. Two of the legs are relatively stiff, to measure force applied by the tissue, and a third leg is relatively flexible to measure displacement of the tissue relative to one or both stiff legs, and with the three legs lying in a common plane so that the force and displacement measurements all relate to the same direction of muscle movements. A flexible loop is attached to one of the stiff legs to measure changes in muscle thickness, with the upper end of the loop fixed to the leg and the lower end of the loop bearing against the surface of the tissue and being free to slide on the leg.

Gravity Responsive NADH Oxidase of the Plasma Membrane

NASA Technical Reports Server (NTRS)

Morre, D. James (Inventor)

2002-01-01

A method and apparatus for sensing gravity using an NADH oxidase of the plasma membrane which has been found to respond to unit gravity and low centrifugal g forces. The oxidation rate of NADH supplied to the NADH oxidase is measured and translated to represent the relative gravitational force exerted on the protein. The NADH oxidase of the plasma membrane may be obtained from plant or animal sources or may be produced recombinantly.

Microgravity research in plant biological systems: Realizing the potential of molecular biology

NASA Technical Reports Server (NTRS)

Lewis, Norman G.; Ryan, Clarence A.

1993-01-01

The sole all-pervasive feature of the environment that has helped shape, through evolution, all life on Earth is gravity. The near weightlessness of the Space Station Freedom space environment allows gravitational effects to be essentially uncoupled, thus providing an unprecedented opportunity to manipulate, systematically dissect, study, and exploit the role of gravity in the growth and development of all life forms. New and exciting opportunities are now available to utilize molecular biological and biochemical approaches to study the effects of microgravity on living organisms. By careful experimentation, we can determine how gravity perception occurs, how the resulting signals are produced and transduced, and how or if tissue-specific differences in gene expression occur. Microgravity research can provide unique new approaches to further our basic understanding of development and metabolic processes of cells and organisms, and to further the application of this new knowledge for the betterment of humankind.

Detecting chameleons through Casimir force measurements

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

Brax, Philippe; Bruck, Carsten van de; Davis, Anne-Christine

2007-12-15

The best laboratory constraints on strongly coupled chameleon fields come not from tests of gravity per se but from precision measurements of the Casimir force. The chameleonic force between two nearby bodies is more akin to a Casimir-like force than a gravitational one: The chameleon force behaves as an inverse power of the distance of separation between the surfaces of two bodies, just as the Casimir force does. Additionally, experimental tests of gravity often employ a thin metallic sheet to shield electrostatic forces; however, this sheet masks any detectable signal due to the presence of a strongly coupled chameleon field.more » As a result of this shielding, experiments that are designed to specifically test the behavior of gravity are often unable to place any constraint on chameleon fields with a strong coupling to matter. Casimir force measurements do not employ a physical electrostatic shield and as such are able to put tighter constraints on the properties of chameleons fields with a strong matter coupling than tests of gravity. Motivated by this, we perform a full investigation on the possibility of testing chameleon models with both present and future Casimir experiments. We find that present-day measurements are not able to detect the chameleon. However, future experiments have a strong possibility of detecting or rule out a whole class of chameleon models.« less

Digital holographic microscopy long-term and real-time monitoring of cell division and changes under simulated zero gravity.

PubMed

Pan, Feng; Liu, Shuo; Wang, Zhe; Shang, Peng; Xiao, Wen

2012-05-07

The long-term and real-time monitoring the cell division and changes of osteoblasts under simulated zero gravity condition were succeed by combing a digital holographic microscopy (DHM) with a superconducting magnet (SM). The SM could generate different magnetic force fields in a cylindrical cavity, where the gravitational force of biological samples could be canceled at a special gravity position by a high magnetic force. Therefore the specimens were levitated and in a simulated zero gravity environment. The DHM was modified to fit with SM by using single mode optical fibers and a vertically-configured jig designed to hold specimens and integrate optical device in the magnet's bore. The results presented the first-phase images of living cells undergoing dynamic divisions and changes under simulated zero gravity environment for a period of 10 hours. The experiments demonstrated that the SM-compatible DHM setup could provide a highly efficient and versatile method for research on the effects of microgravity on biological samples.

Mechanism of dynamic reorientation of cortical microtubules due to mechanical stress.

PubMed

Muratov, Alexander; Baulin, Vladimir A

2015-12-01

Directional growth caused by gravitropism and corresponding bending of plant cells has been explored since 19th century, however, many aspects of mechanisms underlying the perception of gravity at the molecular level are still not well known. Perception of gravity in root and shoot gravitropisms is usually attributed to gravisensitive cells, called statocytes, which exploit sedimentation of macroscopic and heavy organelles, amyloplasts, to sense the direction of gravity. Gravity stimulus is then transduced into distal elongation zone, which is several mm far from statocytes, where it causes stretching. It is suggested that gravity stimulus is conveyed by gradients in auxin flux. We propose a theoretical model that may explain how concentration gradients and/or stretching may indirectly affect the global orientation of cortical microtubules, attached to the cell membrane and induce their dynamic reorientation perpendicular to the gradients. In turn, oriented microtubule arrays direct the growth and orientation of cellulose microfibrils, forming part of the cell external skeleton and determine the shape of the cell. Reorientation of microtubules is also observed in reaction to light in phototropism and mechanical bending, thus suggesting universality of the proposed mechanism. Copyright © 2015 Elsevier B.V. All rights reserved.

Feasibility Study of TRISCAN Landing System.

DTIC Science & Technology

1977-10-01

as inclinometers, tiltmeters , vertical sensors , level sensors , pendulums, and gravity sensing electrolytic transducers. Of course, the common...5.0 NAVTOLAND SENSOR REQUIREMENTS 5.1 TRISCAN PERFORMANCE _ --* L 5.2 SHIPS MOTION SENSING 5.3 DATA LINK Dit.S.ia 6.0 CONCLUSIONS AND RECOMMENDATIONS...involved in enabling the pilot to fly V/STOL Aircraft onto Navy Ships and Marine Corps tactical sites. Guidance sensors have been identified as being

A new method for acoustic containerless processing of materials

NASA Technical Reports Server (NTRS)

Barmatz, M.

1984-01-01

The development of an acoustic positioner, which uses only one acoustic mode in chambers of rectangular, cylindrical, and spherical geometries, for high-temperature containerless processing of materials in space is described. The objective of the single-mode positioner is to develop sufficient acoustic forces to stably localize and manipulate molten materials. In order to attain this goal the transducer power, energy transfer medium, and chamber geometry and dimensions need to be optimized. The use of a variable frequency compression driver or solid-state piezoelectric transducer to optimize these properties is investigated; it is determined that a solid-state transducer would be most applicable for optimizing the positioner. The positioning capabilities of this single-mode positioner are discussed. The dependence of the acoustic forces on temperature and ambient pressure is studied. The development of a levitator to process a molten sample at 1500 C in the space environment using the cylindrical (011) mode is illustrated.

A New Electromagnetic Acoustic Transducer Design for Generating and Receiving S0 Lamb Waves in Ferromagnetic Steel Plate

PubMed Central

He, Jianpeng; Dixon, Steve; Hill, Samuel; Xu, Ke

2017-01-01

Electromagnetic acoustic transducers (EMATs) are non-contact, ultrasonic transducers that are usually kept within 5 mm from the sample surface to obtain a sufficient signal-to-noise ratio (SNR). One important issue associated with operation on a ferromagnetic plate is that the strong attraction force from the magnet can affect measurements and make scanning difficult. This paper investigates a method to generate fundamental, symmetric Lamb waves on a ferromagnetic plate. A coil-only, low-weight, generation EMAT is designed and investigated, operating at lift-offs of over 5 mm. Another design of an EMAT is investigated using a rectangular magnet with a much higher lift-off than the coil, of up to 19 mm. This results in a much lower force between the EMAT and sample, making scanning the EMAT much easier. PMID:28471377

Mechanosensory calcium-selective cation channels in epidermal cells

NASA Technical Reports Server (NTRS)

Ding, J. P.; Pickard, B. G.

1993-01-01

This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is sychronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 micromole at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 micromoles promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

Baroclinic instability with variable gravity: A perturbation analysis

NASA Technical Reports Server (NTRS)

Giere, A. C.; Fowliss, W. W.; Arias, S.

1980-01-01

Solutions for a quasigeostrophic baroclinic stability problem in which gravity is a function of height were obtained. Curvature and horizontal shear of the basic state flow were omitted and the vertical and horizontal temperature gradients of the basic state were taken as constant. The effect of a variable dielectric body force, analogous to gravity, on baroclinic instability for the design of a spherical, baroclinic model for Spacelab was determined. Such modeling could not be performed in a laboratory on the Earth's surface because the body force could not be made strong enough to dominate terrestrial gravity. A consequence of the body force variation and the preceding assumptions was that the potential vorticity gradient of the basic state vanished. The problem was solved using a perturbation method. The solution gives results which are qualitatively similar to Eady's results for constant gravity; a short wavelength cutoff and a wavelength of maximum growth rate were observed. The averaged values of the basic state indicate that both the wavelength range of the instability and the growth rate at maximum instability are increased. Results indicate that the presence of the variable body force will not significantly alter the dynamics of the Spacelab experiment. The solutions are also relevant to other geophysical fluid flows where gravity is constant but the static stability or Brunt-Vaisala frequency is a function of height.

Effective utilization of gravity during arm downswing in keystrokes by expert pianists.

PubMed

Furuya, S; Osu, R; Kinoshita, H

2009-12-01

The present study investigated a skill-level-dependent interaction between gravity and muscular force when striking piano keys. Kinetic analysis of the arm during the downswing motion performed by expert and novice piano players was made using an inverse dynamic technique. The corresponding activities of the elbow agonist and antagonist muscles were simultaneously recorded using electromyography (EMG). Muscular torque at the elbow joint was computed while excluding the effects of gravitational and motion-dependent interaction torques. During descending the forearm to strike the keys, the experts kept the activation of the triceps (movement agonist) muscle close to the resting level, and decreased anti-gravity activity of the biceps muscle across all loudness levels. This suggested that elbow extension torque was produced by gravity without the contribution of agonist muscular work. For the novices, on the other hand, a distinct activity in the triceps muscle appeared during the middle of the downswing, and its amount and duration were increased with increasing loudness. Therefore, for the novices, agonist muscular force was the predominant contributor to the acceleration of elbow extension during the downswing. We concluded that a balance shift from muscular force dependency to gravity dependency for the generation of a target joint torque occurs with long-term piano training. This shift would support the notion of non-muscular force utilization for improving physiological efficiency of limb movement with respect to the effective use of gravity.

Bounds on quantum communication via Newtonian gravity

NASA Astrophysics Data System (ADS)

Kafri, D.; Milburn, G. J.; Taylor, J. M.

2015-01-01

Newtonian gravity yields specific observable consequences, the most striking of which is the emergence of a 1/{{r}2} force. In so far as communication can arise via such interactions between distant particles, we can ask what would be expected for a theory of gravity that only allows classical communication. Many heuristic suggestions for gravity-induced decoherence have this restriction implicitly or explicitly in their construction. Here we show that communication via a 1/{{r}2} force has a minimum noise induced in the system when the communication cannot convey quantum information, in a continuous time analogue to Bell's inequalities. Our derived noise bounds provide tight constraints from current experimental results on any theory of gravity that does not allow quantum communication.

Visual analysis of flow boiling at different gravity levels in 4.0 mm tube

NASA Astrophysics Data System (ADS)

Valencia-Castillo, C. M.; Celata, G. P.; Saraceno, L.; Zummo, G.

2014-11-01

The aim of the present paper is to describe the results of flow boiling heat transfer at low gravity and compare them with those obtained at earth gravity, evaluating possible differences. The experimental campaigns at low gravity have been performed during the parabolic flight campaign of October-November 2013. The paper will show the analysis of differences between the heat transfer coefficients and vapour bubble parameters at normal and at zero gravity. The results of 4.0 mm tube are presented and discussed. With respect to terrestrial gravity, heat transfer is systematically lower at microgravity in the range of the experimental conditions. Heat transfer differences for the two gravity conditions are related to the different bubble size in each of them. The size of a bubble in flow boiling is affected by the gravity level, being larger at low gravity, unless inertial forces are largely predominant over buoyancy and other forces acting on the bubble itself when detaching from a heated wall. Vapour bubble parameters (bubble diameter, bubble length, width, and nose velocity) have been measured.

Experimental measure of retinal impact force resulting from intraocular foreign body dropped onto retina through media of differing viscosity.

PubMed

Ernst, Benjamin J; Velez-Montoya, Raul; Kujundzic, Damir; Kujundzic, Elmira; Olson, Jeffrey L

2013-07-01

To evaluate and compare the perfluorocarbon liquid, silicone oil, and viscoelastic against standard saline, in their ability to dampen the impact force of a foreign body, dropped within the eye. In an experimental surgical model in where cohesive and adhesive forces of the substances are not enough to float heavy-than-water foreign bodies. A model of ophthalmic surgery was constructed. A BB pellet was dropped from 24 mm onto a force transducer through four different fluids: balanced salt solution, perfluoro-n-octane, viscoelastic, and silicone oil. The impact energy (force) for each case was measured and recorded by the force transducer. The mean force of impact for each fluid was compared using the Student t-test. Silicone oil resulted in the lowest force of impact. Both silicone oil and viscoelastic dampened the impact an order of magnitude more than perfluoro-n-octane and balanced salt solution. Silicone oil and viscoelastic cushioned the force from a dropped BB. They may be useful adjuncts to prevent iatrogenic retinal injury during vitrectomy for intraocular foreign body removal. © 2012 The Authors. Clinical and Experimental Ophthalmology © 2012 Royal Australian and New Zealand College of Ophthalmologists.

Transducer-actuator systems and methods for performing on-machine measurements and automatic part alignment

DOEpatents

Barkman, William E.; Dow, Thomas A.; Garrard, Kenneth P.; Marston, Zachary

2016-07-12

Systems and methods for performing on-machine measurements and automatic part alignment, including: a measurement component operable for determining the position of a part on a machine; and an actuation component operable for adjusting the position of the part by contacting the part with a predetermined force responsive to the determined position of the part. The measurement component consists of a transducer. The actuation component consists of a linear actuator. Optionally, the measurement component and the actuation component consist of a single linear actuator operable for contacting the part with a first lighter force for determining the position of the part and with a second harder force for adjusting the position of the part. The actuation component is utilized in a substantially horizontal configuration and the effects of gravitational drop of the part are accounted for in the force applied and the timing of the contact.

Root gravitropism: an experimental tool to investigate basic cellular and molecular processes underlying mechanosensing and signal transmission in plants

NASA Technical Reports Server (NTRS)

Boonsirichai, K.; Guan, C.; Chen, R.; Masson, P. H.

2002-01-01

The ability of plant organs to use gravity as a guide for growth, named gravitropism, has been recognized for over two centuries. This growth response to the environment contributes significantly to the upward growth of shoots and the downward growth of roots commonly observed throughout the plant kingdom. Root gravitropism has received a great deal of attention because there is a physical separation between the primary site for gravity sensing, located in the root cap, and the site of differential growth response, located in the elongation zones (EZs). Hence, this system allows identification and characterization of different phases of gravitropism, including gravity perception, signal transduction, signal transmission, and curvature response. Recent studies support some aspects of an old model for gravity sensing, which postulates that root-cap columellar amyloplasts constitute the susceptors for gravity perception. Such studies have also allowed the identification of several molecules that appear to function as second messengers in gravity signal transduction and of potential signal transducers. Auxin has been implicated as a probable component of the signal that carries the gravitropic information between the gravity-sensing cap and the gravity-responding EZs. This has allowed the identification and characterization of important molecular processes underlying auxin transport and response in plants. New molecular models can be elaborated to explain how the gravity signal transduction pathway might regulate the polarity of auxin transport in roots. Further studies are required to test these models, as well as to study the molecular mechanisms underlying a poorly characterized phase of gravitropism that is independent of an auxin gradient.

Big Mysteries: Extra Dimensions

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

Lincoln, Don

2014-06-10

The weakness of gravity compared to the other subatomic forces is a real mystery. While nobody knows the answer, one credible solution is that gravity has access to more spatial dimensions than the other three known forces. In this video, Fermilab's Dr. Don Lincoln describes this idea, with the help of some very urbane characters.

Big Mysteries: Extra Dimensions

ScienceCinema

Lincoln, Don

2018-01-16

The weakness of gravity compared to the other subatomic forces is a real mystery. While nobody knows the answer, one credible solution is that gravity has access to more spatial dimensions than the other three known forces. In this video, Fermilab's Dr. Don Lincoln describes this idea, with the help of some very urbane characters.

Droplet Depinning on Inclined Surfaces at High Reynolds Numbers

NASA Astrophysics Data System (ADS)

White, Edward; Singh, Natasha; Lee, Sungyon

2017-11-01

Contact angle hysteresis enables a sessile liquid drop to adhere to a solid surface when the surface is inclined, the drop is exposed to gas-phase flow, or the drop is exposed to both forcing modalities. Previous work by Schmucker and White (2012.DFD.M4.6) identified critical depinning Weber numbers for water drops subject to gravity- and wind-dominated forcing. This work extends the Schmucker and White data and finds the critical depinning Weber number obeys a two-slope linear model. Under pure wind forcing at Reynolds numbers above 1500 and with zero surface inclination, Wecrit = 8.0 . For non-zero inclinations, α, Wecrit decreases proportionally to A Bo sinα where A is the drop aspect ratio and Bo is its Bond number. The same relationship holds for α < 0 when gravity resists depinning by wind. Above We 4 , depinning is dominated by wind forcing; at We < 4 , depinning is gravity dominated. While Wecrit depends linearly on A Bo sinα in both forcing regimes, the slopes of the the limit lines depend on the forcing regime. The difference is attributed to different drop shapes and contact angle distributions that arise depending on whether wind or gravity dominates the depinning behavior. Supported by the National Science Foundation through Grant CBET-1605947.

Design and calibration of the carousel wind tunnel

NASA Technical Reports Server (NTRS)

Leach, R. N.; Greeley, R.; Iversen, J.; White, B.; Marshall, J. R.

1986-01-01

In the study of planetary aeolian processes the effect of gravity is not readily modeled. Gravity appears in the equations of particle motion along with interparticle forces but the two terms are not separable. A wind tunnel that would permit variable gravity would allow separation of the forces and aid greatly in understanding planetary aeolian processes. The design Carousel Wind Tunnel (CWT) allows for a long flow distance in a small sized tunnel since the test section is a continuo us circuit and allows for a variable pseudo gravity. A prototype design was built and calibrated to gain some understanding of the characteristics of the design and the results presented.

Design and calibration of the carousel wind tunnel

NASA Technical Reports Server (NTRS)

Leach, R. N.; Greeley, Ronald; Iversen, James D.; White, Bruce R.; Marshall, John R.

1987-01-01

In the study of planetary aeolian processes the effect of gravity is not readily modeled. Gravity appears in the equations of particle motion along with interparticle forces but the two terms are not separable. A wind tunnel that would permit variable gravity would allow separation of the forces and aid greatly in understanding planetary aeolian processes. The design of the Carousel Wind Tunnel (CWT) allows for a long flow distance in a small sized tunnel since the test section is a continuous circuit and allows for a variable pseudo-gravity. A prototype design was built and calibrated to gain some understanding of the characteristics of the design and the results presented.

Static Footprint Local Forces, Areas, and Aspect Ratios for Three Type 7 Aircraft Tires

NASA Technical Reports Server (NTRS)

Howell, William E.; Perez, Sharon E.; Vogler, William A.

1991-01-01

The National Tire Modeling Program (NTMP) is a joint NASA/industry effort to improve the understanding of tire mechanics and develop accurate analytical design tools. This effort includes fundamental analytical and experimental research on the structural mechanics of tires. Footprint local forces, areas, and aspect ratios were measured. Local footprint forces in the vertical, lateral, and drag directions were measured with a special footprint force transducer. Measurements of the local forces in the footprint were obtained by positioning the transducer at specified locations within the footprint and externally loading the tires. Three tires were tested: (1) one representative of those used on the main landing gear of B-737 and DC-9 commercial transport airplanes, (2) a nose landing gear tire for the Space Shuttle Orbiter, and (3) a main landing gear tire for the Space Shuttle Orbiter. Data obtained for various inflation pressures and vertical loads are presented for two aircraft tires. The results are presented in graphical and tabulated forms.

Acoustic force mapping in a hybrid acoustic-optical micromanipulation device supporting high resolution optical imaging† †Electronic supplementary information (ESI) available: Additional information about 1D model calculations for a piezoelectric transducer. See DOI: 10.1039/c6lc00182c Click here for additional data file.

PubMed Central

McDougall, Craig; MacDonald, Michael Peter; Ritsch-Marte, Monika

2016-01-01

Many applications in the life-sciences demand non-contact manipulation tools for forceful but nevertheless delicate handling of various types of sample. Moreover, the system should support high-resolution optical imaging. Here we present a hybrid acoustic/optical manipulation system which utilizes a transparent transducer, making it compatible with high-NA imaging in a microfluidic environment. The powerful acoustic trapping within a layered resonator, which is suitable for highly parallel particle handling, is complemented by the flexibility and selectivity of holographic optical tweezers, with the specimens being under high quality optical monitoring at all times. The dual acoustic/optical nature of the system lends itself to optically measure the exact acoustic force map, by means of direct force measurements on an optically trapped particle. For applications with (ultra-)high demand on the precision of the force measurements, the position of the objective used for the high-NA imaging may have significant influence on the acoustic force map in the probe chamber. We have characterized this influence experimentally and the findings were confirmed by model simulations. We show that it is possible to design the chamber and to choose the operating point in such a way as to avoid perturbations due to the objective lens. Moreover, we found that measuring the electrical impedance of the transducer provides an easy indicator for the acoustic resonances. PMID:27025398

Adhesion enhancement methods for a roll-to-sheet fabrication process of DE stack-transducers and their influences on the electric properties

NASA Astrophysics Data System (ADS)

Bochmann, Helge; von Heckel, Benedikt; Maas, Jürgen

2017-04-01

Transducers made of dielectric elastomers (DE) offer versatile opportunities for many different applications. To gain large strains and forces a multilayer topology is commonly used. DE stack-transducers represent one multilayer topology and can be operated as a sensor, a generator or an actuator simultaneously. They are made of many layers of DE films, like silicone (PDMS) and polyurethane (PUR), stacked on top of each other. The single layers are several micrometers thin and coated with a compliant electrode on both sides. Depending on the application a DE transducer has to withstand tensile forces, which may lead to a delamination of the layers and a ripping of the stack-transducer. This can be prevented by enhancing the adhesion among the layers. Within this contribution a surface plasma jet treatment with an atmospheric plasma beam as well as an adhesive utilized as electrode material was investigated to obtain an adhesion enhancement. The effects of these methods to enhance the adhesion are introduced briefly. Furthermore, various investigations were made to determine the benefits of the enhancement methods with respect to the electromechanical properties of the electrode. Therefore, certain tests regarding the surface resistance of the electrode and the dielectric breakdown strength (DBS) of the DE film were conducted. The tests indicate that the influences are strongly dependent on the composition of the electrode and the used DE material. Finally, improvements for a dry deposition roll-to-sheet manufacturing process for DE stack-transducers are derived from the obtained results.

Near-field multiple traps of paraxial acoustic vortices with strengthened gradient force generated by sector transducer array

NASA Astrophysics Data System (ADS)

Wang, Qingdong; Li, Yuzhi; Ma, Qingyu; Guo, Gepu; Tu, Juan; Zhang, Dong

2018-01-01

In order to improve the capability of particle trapping close to the source plane, theoretical and experimental studies on near-field multiple traps of paraxial acoustic vortices (AVs) with a strengthened acoustic gradient force (AGF) generated by a sector transducer array were conducted. By applying the integration of point source radiation, numerical simulations for the acoustic fields generated by the sector transducer array were conducted and compared with those produced by the circular transducer array. It was proved that strengthened AGFs of near-field multiple AVs with higher peak pressures and smaller vortex radii could be produced by the sector transducer array with a small topological charge. The axial distributions of the equivalent potential gradient indicated that the AGFs of paraxial AVs in the near field were much higher than those in the far field, and the distances at the near-field vortex antinodes were also proved to be the ideal trapping positions with relatively higher AGFs. With the established 8-channel AV generation system, theoretical studies were also verified by the experimental measurements of pressure and phase for AVs with various topological charges. The formation of near-field multiple paraxial AVs was verified by the cross-sectional circular pressure distributions with perfect phase spirals around central pressure nulls, and was also proved by the vortex nodes and antinodes along the center axis. The favorable results demonstrated the feasibility of generating near-field multiple traps of paraxial AVs with strengthened AGF using the sector transducer array, and suggested the potential applications of close-range particle trapping in biomedical engineering.

Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space

NASA Astrophysics Data System (ADS)

Baryshev, Yurij

2006-03-01

Thirring-Feynman's tensor field approach to gravitation opens new understanding on the physics of gravitational interaction and stimulates novel experiments on the nature of gravity. According to Field Gravity, the universal gravity force is caused by exchange of gravitons - the quanta of gravity field. Energy of this field is well-defined and excludes the singularity. All classical relativistic effects are the same as in General Relativity. The intrinsic scalar (spin 0) part of gravity field corresponds to ``antigravity'' and only together with the pure tensor (spin 2) part gives the usual Newtonian force. Laboratory and astrophysical experiments which may test the predictions of FG, will be performed in near future. In particular, observations at gravity observatories with bar and interferometric detectors, like Explorer, Nautilus, LIGO and VIRGO, will check the predicted scalar gravitational waves from supernova explosions. New types of cosmological models in Minkowski space are possible too.

Partial gravity simulation using a pneumatic actuator with closed loop mechanical amplification

NASA Technical Reports Server (NTRS)

Ray, David M.

1994-01-01

To support future manned missions to the surface of the Moon and Mars or missions requiring manipulation of payloads and locomotion in space, a training device is required to simulate the conditions of both partial and microgravity as compared to the gravity on Earth. The focus of this paper is to present the development, construction, and testing of a partial gravity simulator which uses a pneumatic actuator with closed loop mechanical amplification. Results of the testing show that this type of simulator maintains a constant partial gravity simulation with a variation of the simulated body force between 2.2 percent and 10 percent, depending on the type of locomotion inputs. The data collected using the simulator show that mean stride frequencies at running speeds at lunar and Martian gravity levels are 12 percent less than those at Earth gravity. The data also show that foot/ground reaction forces at lunar and Martian gravity are, respectively, 62 percent and 51 percent less than those on Earth.

Vibration Control via Stiffness Switching of Magnetostrictive Transducers

NASA Technical Reports Server (NTRS)

Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

2016-01-01

In this paper, a computational study is presented of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

Gravitropism in Higher Plant Shoots 1

PubMed Central

Mueller, Wesley J.; Salisbury, Frank B.; Blotter, P. Thomas

1984-01-01

Dimensional changes during gravitropic bending of cocklebur (Xanthium strumarium L.) dicot stems were measured using techniques of stereo photogrammetry. The differential growth is from an increased growth rate on the bottom of the stem and a stopping or contraction of the top. Contraction of the top was especially evident upon release and immediate bending of horizontal stems that had been restrained between stiff wires for 36 hours. The energy for this could have been stored in both the top and bottom, since the bottom elongated, and the top contracted. Forces developed during bending were measured by fastening a stem tip to the end of a bar with attached strain gauges and recording electrical output from the strain gauges. Restrained mature cocklebur stems continued to accumulate potential energy for bending for about 120 hours, after which the recorded force reached a maximum. Pressures within castor bean (Ricinus communis L.) stems were also measured with 3.5-millimeter diameter pressure transducers. As expected, the pressure on the bottom of the restrained plants increased with time; pressures decreased in vertical controls, tops of restrained stems, and bottoms of free-bending stems. Pressures increased in tops of free-bending stems. When restrained plants were released, pressure on the bottom decreased and pressure on the top increased. Results suggest a possible role for cell contraction in the top of stems bending upward in response to gravity. Images Fig. 5 Fig. 11 PMID:16663987

Atmospheric gravity waves with small vertical-to-horizotal wavelength ratios

NASA Astrophysics Data System (ADS)

Song, I. S.; Jee, G.; Kim, Y. H.; Chun, H. Y.

2017-12-01

Gravity wave modes with small vertical-to-horizontal wavelength ratios of an order of 10-3 are investigated through the systematic scale analysis of governing equations for gravity wave perturbations embedded in the quasi-geostrophic large-scale flow. These waves can be categorized as acoustic gravity wave modes because their total energy is given by the sum of kinetic, potential, and elastic parts. It is found that these waves can be forced by density fluctuations multiplied by the horizontal gradients of the large-scale pressure (geopotential) fields. These theoretical findings are evaluated using the results of a high-resolution global model (Specified Chemistry WACCM with horizontal resolution of 25 km and vertical resolution of 600 m) by computing the density-related gravity-wave forcing terms from the modeling results.

Using Magnetic Forces to Probe the Gravi-response of Swimming Paramecium

NASA Astrophysics Data System (ADS)

Guevorkian, Karine; Valles, James M., Jr.

2004-03-01

Paramecium Caudatum, a single celled ciliate, alters its swimming behavior when subjected to different gravity environments (e.g. centrifugation and micro-gravity). To dissect the mechanisms behind this gravi-response and that of other biological systems, we are developing the use of magnetic body forces as a means of creating a rapidly tunable, simulated variable gravity environment. Since biological materials are weakly diamagnetic, we must subject them to intense inhomogeneous magnetic fields with characteristic field-field gradient products on the order of 16 T^2/cm. We will describe experiments on Paramecium Caudatum in which we adjust their net buoyancy with magnetic forces and measure the resulting changes in their swimming behavior.

Magnetic compensation of gravity forces in (p-) hydrogen near its critical point: Application to weightless conditions

NASA Astrophysics Data System (ADS)

Wunenburger, R.; Chatain, D.; Garrabos, Y.; Beysens, D.

2000-07-01

We report a study concerning the compensation of gravity forces in two-phase (p-) hydrogen. The sample is placed near one end of the vertical z axis of a superconducting coil, where there is a near-uniform magnetic field gradient. A variable effective gravity level g can thus be applied to the two-phase fluid system. The vanishing behavior of the capillary length lC at the critical point is compensated by a decrease in g and lC is kept much smaller than the cell dimension. For g ranging from 1 to 0.25 times Earth's gravity (modulus g0) we compare the actual shape of the meniscus to the expected shape in a homogeneous gravity field. We determine lC in a wide range of reduced temperature τ=(TC-T)/TC=[10-4-0.02] from a fit of the meniscus shape. The data are in agreement with previous measurements further from TC performed in n-H2 under Earth's gravity. The effective gravity is homogeneous within 10-2g0 for a 3 mm diameter and 2 mm thickness sample and is in good agreement with the computed one, validating the use of the apparatus as a variable gravity facility. In the vicinity of the levitation point (where magnetic forces exactly compensate Earth's gravity), the computed axial component of the acceleration is found to be quadratic in z, whereas its radial component is proportional to the distance to the axis, which explains the gas-liquid patterns observed near the critical point.

Magnetic compensation of gravity forces in (p-) hydrogen near its critical point: application to weightless conditions

PubMed

Wunenburger; Chatain; Garrabos; Beysens

2000-07-01

We report a study concerning the compensation of gravity forces in two-phase (p-) hydrogen. The sample is placed near one end of the vertical z axis of a superconducting coil, where there is a near-uniform magnetic field gradient. A variable effective gravity level g can thus be applied to the two-phase fluid system. The vanishing behavior of the capillary length l(C) at the critical point is compensated by a decrease in g and l(C) is kept much smaller than the cell dimension. For g ranging from 1 to 0.25 times Earth's gravity (modulus g(0)) we compare the actual shape of the meniscus to the expected shape in a homogeneous gravity field. We determine l(C) in a wide range of reduced temperature tau=(T(C)-T)/T(C)=[10(-4)-0.02] from a fit of the meniscus shape. The data are in agreement with previous measurements further from T(C) performed in n-H2 under Earth's gravity. The effective gravity is homogeneous within 10(-2)g(0) for a 3 mm diameter and 2 mm thickness sample and is in good agreement with the computed one, validating the use of the apparatus as a variable gravity facility. In the vicinity of the levitation point (where magnetic forces exactly compensate Earth's gravity), the computed axial component of the acceleration is found to be quadratic in z, whereas its radial component is proportional to the distance to the axis, which explains the gas-liquid patterns observed near the critical point.

Numerical study of gravity effects on phase separation in a swirl chamber.

PubMed

Hsiao, Chao-Tsung; Ma, Jingsen; Chahine, Georges L

2016-01-01

The effects of gravity on a phase separator are studied numerically using an Eulerian/Lagrangian two-phase flow approach. The separator utilizes high intensity swirl to separate bubbles from the liquid. The two-phase flow enters tangentially a cylindrical swirl chamber and rotate around the cylinder axis. On earth, as the bubbles are captured by the vortex formed inside the swirl chamber due to the centripetal force, they also experience the buoyancy force due to gravity. In a reduced or zero gravity environment buoyancy is reduced or inexistent and capture of the bubbles by the vortex is modified. The present numerical simulations enable study of the relative importance of the acceleration of gravity on the bubble capture by the swirl flow in the separator. In absence of gravity, the bubbles get stratified depending on their sizes, with the larger bubbles entering the core region earlier than the smaller ones. However, in presence of gravity, stratification is more complex as the two acceleration fields - due to gravity and to rotation - compete or combine during the bubble capture.

New improvement of the combined optical fiber transducer for landslide monitoring

NASA Astrophysics Data System (ADS)

Zhu, Z.-W.; Yuan, Q.-Y.; Liu, D.-Y.; Liu, B.; Liu, J.-C.; Luo, H.

2014-08-01

Landslide monitoring is important in predicting the behavior of landslides, thereby ensuring environmental, life, and property safety. On the basis of our previous studies, we conducted the double shear test by using a third-generation optical fiber transducer that uses expandable polystyrene (EPS) as base material. However, the third-generation transducer has poor performance when cohesive force is present between the grout and capillary stainless steel pipe of the transducer. Thus, the fourth-generation optical fiber transducer was invented. Similar to the third-generation transducer, the fourth-generation transducer also used EPS as its base material. Single shear test was conducted on the fourth-generation transducer after being grouted with cement mortar (1 : 1 mix ratio). The micro-bend loss mechanism of the optical fiber was considered, and the optical time domain reflectometry instrument was used. The fact that the loss sequence of optical fibers subjected to loading is different at various locations is found. The relationship of the loading-point displacement vs. optical fiber sliding distance and optical loss were measured. Results show that the maximum initial measurement precision of the newly proposed device is 1 mm, the corresponding sliding distance is 21 mm, and the dynamic range is 0-20 mm. The fourth-generation transducer can measure the movement direction of loadings, thus making this transducer applicable for landslide monitoring.

Method and apparatus for determining material structural integrity

DOEpatents

Pechersky, M.J.

1994-01-01

Disclosed are a nondestructive method and apparatus for determining the structural integrity of materials by combining laser vibrometry with damping analysis to determine the damping loss factor. The method comprises the steps of vibrating the area being tested over a known frequency range and measuring vibrational force and velocity vs time over the known frequency range. Vibrational velocity is preferably measured by a laser vibrometer. Measurement of the vibrational force depends on the vibration method: if an electromagnetic coil is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by the coil current. If a reciprocating transducer is used, the vibrational force is determined by a force gauge in the transducer. Using vibrational analysis, a plot of the drive point mobility of the material over the preselected frequency range is generated from the vibrational force and velocity data. Damping loss factor is derived from a plot of the drive point mobility over the preselected frequency range using the resonance dwell method and compared with a reference damping loss factor for structural integrity evaluation.

Nanofibre optic force transducers with sub-piconewton resolution via near-field plasmon–dielectric interactions

PubMed Central

Huang, Qian; Lee, Joon; Arce, Fernando Teran; Yoon, Ilsun; Angsantikul, Pavimol; Liu, Justin; Shi, Yuesong; Villanueva, Josh; Thamphiwatana, Soracha; Ma, Xuanyi; Zhang, Liangfang; Chen, Shaochen; Lal, Ratnesh; Sirbuly, Donald J.

2018-01-01

Ultrasensitive nanomechanical instruments, including the atomic force microscope (AFM)1–4 and optical and magnetic tweezers5–8, have helped shed new light on the complex mechanical environments of biological processes. However, it is difficult to scale down the size of these instruments due to their feedback mechanisms9, which, if overcome, would enable high-density nanomechanical probing inside materials. A variety of molecular force probes including mechanophores10, quantum dots11, fluorescent pairs12,13 and molecular rotors14–16 have been designed to measure intracellular stresses; however, fluorescence-based techniques can have short operating times due to photo-instability and it is still challenging to quantify the forces with high spatial and mechanical resolution. Here, we develop a compact nanofibre optic force transducer (NOFT) that utilizes strong near-field plasmon–dielectric interactions to measure local forces with a sensitivity of <200 fN. The NOFT system is tested by monitoring bacterial motion and heart-cell beating as well as detecting infrasound power in solution. PMID:29576804

Forced Gravity Waves and the Tropospheric Response to Convection

NASA Astrophysics Data System (ADS)

Halliday, O. J.; Griffiths, S. D.; Parker, D. J.; Stirling, A.

2017-12-01

It has been known for some time that gravity waves facilitate atmospheric adjustment to convective heating. Further, convectively forced gravity waves condition the neighboring atmosphere for the initiation and / or suppression of convection. Despite this, the radiation of gravity waves in macro-scale models (which are typically forced at the grid-scale, by existing parameterization schemes) is not well understood. We present here theoretical and numerical work directed toward improving our understanding of convectively forced gravity wave effects at the mesoscale. Using the linear hydrostatic equations of motion for an incompressible (but non-Boussinesq) fluid with vertically varying buoyancy frequency, we find a radiating solution to prescribed sensible heating. We then interrogate the spatial and temporal sensitivity of the vertical velocity and potential temperature response to different heating functions, considering the remote and near-field forced response both to steady and pulsed heating. We find that the meso-scale tropospheric response to convection is significantly dependent on the upward radiation characteristics of the gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and stratification of the domain. Moving from a trapped to upwardly-radiating solution there is a 50% reduction in tropospherically averaged vertical velocity, but significant perturbations persist for up to 4 hours in the far-field. We find the tropospheric adjustment to be sensitive to the horizontal length scale which characterizes the heating, observing a 20% reduction in vertical velocity when comparing the response from a 10 km to a 100 km heat source. We assess the implications for parameterization of convection in coarse-grained models in the light of these findings. We show that an idealized `full-physics' nonlinear simulation of deep convection in the UK Met Office Unified Model is qualitatively described by the linear solution: departures are quantified and explored.

Plasma momentum meter for momentum flux measurements

DOEpatents

Zonca, Fulvio; Cohen, Samuel A.; Bennett, Timothy; Timberlake, John R.

1993-01-01

Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

Study of toluene rotary fluid management device and shear flow condenser performance for a space-based organic Rankine power system

NASA Technical Reports Server (NTRS)

Havens, Vance; Ragaller, Dana

1988-01-01

Management of two-phase fluid and control of the heat transfer process in microgravity is a technical challenge that must be addressed for an orbital Organic Rankine Cycle (ORC) application. A test program was performed in 1-g that satisfactorily demonstrated the two-phase management capability of the rotating fluid management device (RFMD) and shear-flow condenser. Operational tests of the RFMD and shear flow condenser in adverse gravity orientations, confirmed that the centrifugal forces in the RFMD and the shear forces in the condenser were capable of overcoming gravity forces. In a microgravity environment, these same forces would not have to compete against gravity and would therefore be dominant. The specific test program covered the required operating range of the Space Station Solar Dynamic Rankine Cycle power system. Review of the test data verified that: fluid was pumped from the RFMD in all attitudes; subcooled states in the condenser were achieved; condensate was pushed uphill against gravity; and noncondensible gases were swept through the condenser.

Learning on Jupiter, learning on the Moon: the dark side of the G-force. Effects of gravity changes on neurovascular unit and modulation of learning and memory

PubMed Central

Porte, Yves; Morel, Jean-Luc

2012-01-01

On earth, gravity vector conditions the development of all living beings by physically imposing an axis along which to build their organism. Thus, during their whole life, they have to fight against this force not only to maintain their architectural organization but also to coordinate the communication between organs and keep their physiology in a balanced steady-state. In space, astronauts show physiological, psychological, and cognitive deregulations, ranging from bone decalcification or decrease of musculature, to depressive-like disorders, and spatial disorientation. Nonetheless, they are confronted to a great amount of physical changes in their environment such as solar radiations, loss of light-dark cycle, lack of spatial landmarks, confinement, and obviously a dramatic decrease of gravity force. It is thus very hard to selectively discriminate the strict role of gravity level alterations on physiological, and particularly cerebral, dysfunction. To this purpose, it is important to design autonomous models and apparatuses for behavioral phenotyping utilizable under modified gravity environments. Our team actually aims at working on this area of research. PMID:23015785

Liquid phase sintered compacts in space

NASA Technical Reports Server (NTRS)

Mookherji, T. K.; Mcanelly, W. B.

1974-01-01

A model that will explain the effect of gravity on liquid phase sintering was developed. Wetting characteristics and density segregation which are the two important phenomena in liquid phase sintering are considered in the model development. Experiments were conducted on some selected material combinations to study the gravity effects on liquid phase sintering, and to verify the validity of the model. It is concluded that: (1) The surface tension forces acting on solid particles in a one-g environment are not appreciably different from those anticipated in a 0.00001g/g sub 0 (or lower) environment. (2) The capillary forces are dependent on the contact angle, the quantity of the liquid phase, and the distance between solid particles. (3) The pores (i.e., bubbles) do not appear to be driven to the surface by gravity-produced buoyancy forces. (4) The length of time to produce the same degree of settling in a low-gravity environment will be increased significantly. (5) A low gravity environment would appear to offer a unique means of satisfactorily infiltrating a larger and/or complex shaped compact.

The Tai Chi in Star Formation

NASA Astrophysics Data System (ADS)

Li, Hua-bai

2017-10-01

Tai Chi, a Chinese martial art developed based on the laws of nature, emphasises how 'to conquer the unyielding with the yielding'. The recent observation of star formation shows that stars result from the interaction between gravity, turbulence and magnetic fields. This interaction again follows the nature rules that inspired Tai Chi. For example, if self-gravity is the force that dominates, the molecular cloud will collapse isotropically, which compresses magnetic field lines. The density of the yielding field lines increases until magnetic pressure reaches the critical value to support the cloud against the gravitational force in directions perpendicular to the field lines (Lorentz force). Then gravity gives way to Lorentz force, accumulating gas only along the field lines till the gas density achieves the critical value to again compress the field lines. The Tai Chi goes on in a self-similar way.

Gravity enhanced acoustic levitation method and apparatus

NASA Technical Reports Server (NTRS)

Barmatz, M. B.; Allen, J. L.; Granett, D. (Inventor)

1985-01-01

An acoustic levitation system is provided for acoustically levitating an object by applying a single frequency from a transducer into a resonant chamber surrounding the object. The chamber includes a stabilizer location along its height, where the side walls of the chamber are angled so they converge in an upward direction. When an acoustic standing wave pattern is applied between the top and bottom of the chamber, a levitation surface within the stabilizer does not lie on a horizontal plane, but instead is curved with a lowermost portion near the vertical axis of the chamber. As a result, an acoustically levitated object is urged by gravity towards the lowermost location on the levitation surface, so the object is kept away from the side walls of the chamber.

Centrifuge in Free Fall: Combustion at Partial Gravity

NASA Technical Reports Server (NTRS)

Ferkul, Paul

2017-01-01

A centrifuge apparatus is developed to study the effect of variable acceleration levels in a drop tower environment. It consists of a large rotating chamber, within which the experiment is conducted. NASA Glenn Research Center 5.18-second Zero-Gravity Facility drop tests were successfully conducted at rotation rates up to 1 RPS with no measurable effect on the overall Zero-Gravity drop bus. Arbitrary simulated gravity levels from zero to 1-g (at a radius of rotation 30 cm) were produced. A simple combustion experiment was used to exercise the capabilities of the centrifuge. A total of 23 drops burning a simulated candle with heptane and ethanol fuel were performed. The effect of gravity level (rotation rate) and Coriolis force on the flames was observed. Flames became longer, narrower, and brighter as gravity increased. The Coriolis force tended to tilt the flames to one side, as expected, especially as the rotation rate was increased. The Zero-Gravity Centrifuge can be a useful tool for other researchers interested in the effects of arbitrary partial gravity on experiments, especially as NASA embarks on future missions which may be conducted in non-Earth gravity.

Comparison of Gait During Treadmill Exercise While Supine in Lower Body Negative Pressure (LBNP), Supine with Bungee Resistance and Upright in Normal Gravity

NASA Technical Reports Server (NTRS)

Boda, Wanda; Hargens, Alan R.; Aratow, Michael; Ballard, Richard E.; Hutchinson, Karen; Murthy, Gita; Campbell, James

1994-01-01

The purpose of this study is to compare footward forces, gait kinematics, and muscle activation patterns (EMG) generated during supine treadmill exercise against LBNP with the same parameters during supine bungee resistance exercise and upright treadmill exercise. We hypothesize that the three conditions will be similar. These results will help validate treadmill exercise during LBNP as a viable technique to simulate gravity during space flight. We are evaluating LBNP as a means to load the musculoskeletal and cardiovascular systems without gravity. Such loading should help prevent physiologic deconditioning during space flight. The best ground-based simulation of LBNP treadmill exercise in microgravity is supine LBNP treadmill exercise on Earth because the supine footward force vector is neither directed nor supplemented by Earth's gravity. Previous results from HR-95 ("Dynamics of footward force and leg intramuscular pressure during exercise against supine LBNP and upright standing in normal gravity") indicate that supine plantar-/dorsiflexion exercise in LBNP at 100 mm Hg produces similar ground reaction forces, musculoskeletal stress, and VO2 to those during upright exercise against Earth's gravity. However, elevations of leg volume and heart rate indicate that cardiovascular stress during 100 mm Hg LBNP exercise exceeds that during 1 g exercise. Therefore, the need arose to reduce the cardiovascular stress of LBNP, while maintaining LBNP-induced reaction forces. To this end, we determined that mild plantar-/dorsiflexion exercise during LBNP significantly improves tolerance to LBNP via musculovenous pumping and sympathoexcitation; more intense exercise such as walking and running may further improve LBNP tolerance. In addition, two methodological advances have permited us to simulate upright 1 g exercise better with supine LBNP exercise. First, a newly-designed waist seal allows decreased levels of LBNP (50-60 mm Hg) to produce a footward force equaling one body weight

Porous media matric potential and water content measurements during parabolic flight

NASA Technical Reports Server (NTRS)

Norikane, Joey H.; Jones, Scott B.; Steinberg, Susan L.; Levine, Howard G.; Or, Dani

2005-01-01

Control of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications.

Behind the Mosaic: Insurgent Centers of Gravity and Counterinsurgency

DTIC Science & Technology

2011-12-01

centers of gravity vary by time, space , and purpose. While Clausewitz’s key statement on a center of gravity defines a single center of gravity, he...explicitly or implicitly, that multiple centers of gravity can vary with time, space , and purpose. Shimon Naveh Retired Israeli Reserve Brigadier...century military forces, which in turn expanded operations in time and space . The integration of operations distributed in time and space distributed

Role of the plant cell wall in gravity resistance.

PubMed

Hoson, Takayuki; Wakabayashi, Kazuyuki

2015-04-01

Gravity resistance, mechanical resistance to the gravitational force, is a principal graviresponse in plants, comparable to gravitropism. The cell wall is responsible for the final step of gravity resistance. The gravity signal increases the rigidity of the cell wall via the accumulation of its constituents, polymerization of certain matrix polysaccharides due to the suppression of breakdown, stimulation of cross-link formation, and modifications to the wall environment, in a wide range of situations from microgravity in space to hypergravity. Plants thus develop a tough body to resist the gravitational force via an increase in cell wall rigidity and the modification of growth anisotropy. The development of gravity resistance mechanisms has played an important role in the acquisition of responses to various mechanical stresses and the evolution of land plants. Copyright © 2014 Elsevier Ltd. All rights reserved.

Gravity, black holes, and the universe

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

Nicolson, I.

1981-01-01

The book treats current understandings of the nature and properties of gravity, with particular emphasis on its role in the physics of black holes and the structure and evolution of the universe as a whole. The development of modern ideas on force, motion and gravity is traced from the systems of Aristotle and Ptolemy through the work of Copernicus, Galileo and Kepler to Newton's law of universal gravitation and Einstein's general theory of relativity. Particular attention is then given to the role of gravity in stellar motions and to the phenomena determined by the immense gravitational forces associated with bodiesmore » of such great density, including relativistic effects, tidal forces, space-time effects, event horizons, rotation, mass and electrical charge, the existence of naked singularities and white holes, and black-hole thermodynamics. The existence of actual black holes in the universe is considered, and various black-hole candidates in the Galaxy, quasars and galactic nuclei are indicated. The role of gravity in cosmology is then examined, with attention given to the implications of general relativity, the Hubble law, the age of the universe, the density of the universe and its eventual fate. Possible alternative to general relativity as a theory of gravitation are considered, including theories of variable gravitational constant, grand unified theories, and quantum gravity.« less

Gravity, black holes and the universe

NASA Astrophysics Data System (ADS)

Nicolson, I.

The book treats current understandings of the nature and properties of gravity, with particular emphasis on its role in the physics of black holes and the structure and evolution of the universe as a whole. The development of modern ideas on force, motion and gravity is traced from the systems of Aristotle and Ptolemy through the work of Copernicus, Galileo and Kepler to Newton's law of universal gravitation and Einstein's general theory of relativity. Particular attention is then given to the role of gravity in stellar motions and to the phenomena determined by the immense gravitational forces associated with bodies of such great density, including relativistic effects, tidal forces, space-time effects, event horizons, rotation, mass and electrical charge, the existence of naked singularities and white holes, and black-hole thermodynamics. The existence of actual black holes in the universe is considered, and various black-hole candidates in the Galaxy, quasars and galactic nuclei are indicated. The role of gravity in cosmology is then examined, with attention given to the implications of general relativity, the Hubble law, the age of the universe, the density of the universe and its eventual fate. Possible alternative to general relativity as a theory of gravitation are considered, including theories of variable gravitational constant, grand unified theories, and quantum gravity.

What Makes a Superhero "Super"? Graphic Novels Inspire a Gravity Investigation

ERIC Educational Resources Information Center

Gross, Lisa A.; Bradbury, Leslie Upson; Frye, Elizabeth M.; Watkins, Bonnie

2016-01-01

To further students' understanding about gravity, forces, and motion, multiple types of text were integrated into instruction. As part of a 5E lesson (Bybee et al. 2006), the authors used a selection from Capstone Press's Graphic Science series, "A Crash Course in Forces and Motion with Max Axiom" (Sohn and Barnett 2007) to support…

Why Do Things Fall? How to Explain Why Gravity Is Not a Force

ERIC Educational Resources Information Center

Stannard, Warren B.

2018-01-01

In most high school physics classes, gravity is described as an attractive force between two masses as formulated by Newton over 300 years ago. Einstein's general theory of relativity implies that gravitational effects are instead the result of a "curvature" of space-time. However, explaining why things fall without resorting to Newton's…

A Fifth Force: Generalized through Superconductors

NASA Technical Reports Server (NTRS)

Robertson, Glen A.

1999-01-01

The connection between the Biefield-Brown Effect, the recent repeat of the 1902 Trouton-Noble (TN) experiments, and the gravity shielding experiments was explored. This connection is visualized through high capacitive electron concentrations. From this connection, a theory is proposed that connects mass energy to gravity and a fifth force. The theory called the Gravi-Atomic Energy theory presents two new terms: Gravi-atomic energy and quantum vacuum pressure (QVP). Gravi-atomic energy is defined as the radiated mass energy, which acts on vacuum energy to create a QVP about a mass, resulting in gravity and the fifth force. The QVP emission from a superconductor was discussed followed by the description of a test for QVP from a superconductor using a Cavendish balance.

Bouncing on Mars and the Moon-the role of gravity on neuromuscular control: correlation of muscle activity and rate of force development.

PubMed

Ritzmann, Ramona; Freyler, Kathrin; Krause, Anne; Gollhofer, Albert

2016-11-01

On our astronomical neighbors Mars and the Moon, bouncing movements are the preferred locomotor techniques. During bouncing, the stretch-shortening cycle describes the muscular activation pattern. This study aimed to identify gravity-dependent changes in kinematic and neuromuscular characteristics in the stretch-shortening cycle. Hence, neuromuscular control of limb muscles as well as correlations between the muscles' pre-activation, reflex components, and force output were assessed in lunar, Martian, and Earth gravity. During parabolic flights, peak force (F max ), ground-contact-time, rate of force development (RFD), height, and impulse were measured. Electromyographic (EMG) activities in the m. soleus (SOL) and gastrocnemius medialis (GM) were assessed before (PRE) and during bounces for the reflex phases short-, medium-, and long-latency response (SLR, MLR, LLR). With gradually decreasing gravitation, F max , RFD, and impulse were reduced, whereas ground-contact time and height increased. Concomitantly, EMG_GM decreased for PRE, SLR, MLR, and LLR, and in EMG_SOL in SLR, MLR, and LLR. For SLR and MLR, F max and RFD were positively correlated to EMG_SOL. For PRE and LLR, RFD and F max were positively correlated to EMG_GM. Findings emphasize that biomechanically relevant kinematic adaptations in response to gravity variation were accompanied by muscle- and phase-specific modulations in neural control. Gravitational variation is anticipated and compensated for by gravity-adjusted muscle activities. Importantly, the pre-activation and reflex phases were differently affected: in SLR and MLR, SOL is assumed to contribute to the decline in force output with a decreasing load, and, complementary in PRE and LLR, GM seems to be of major importance for force generation. Copyright © 2016 the American Physiological Society.

Force That Increases at Larger Distance Has Some Psychological and Astronomical Evidence Supporting its Existence

NASA Astrophysics Data System (ADS)

Struck, James

2011-09-01

Force that Increases with distance is different than dark energy as I am arguing for existence of force based on psychological and astronomical bases. Hubble shift, doppler shift, comet return, quasar zoo and quasars and psychological evidence of interest in distant objects lends support to a force like gravity, nuclear, weak, strong, virtual, decay, biological, growth forces which increases its intensity with distance unlike gravity which decreases in intensity with distance. Jane Frances Back Struck contributed to this finding with her request that her grandparents have "perfect justice" even though her grandparents had died before she was born; interest increasing with distance from grandparents.

A Model Study of Zonal Forcing in the Equatorial Stratosphere by Convectively Induced Gravity Waves

NASA Technical Reports Server (NTRS)

Alexander, M. J.; Holton, James R.

1997-01-01

A two-dimensional cloud-resolving model is used to examine the possible role of gravity waves generated by a simulated tropical squall line in forcing the quasi-biennial oscillation (QBO) of the zonal winds in the equatorial stratosphere. A simulation with constant background stratospheric winds is compared to simulations with background winds characteristic of the westerly and easterly QBO phases, respectively. In all three cases a broad spectrum of both eastward and westward propagating gravity waves is excited. In the constant background wind case the vertical momentum flux is nearly constant with height in the stratosphere, after correction for waves leaving the model domain. In the easterly and westerly shear cases, however, westward and eastward propagating waves, respectively, are strongly damped as they approach their critical levels, owing to the strongly scale-dependent vertical diffusion in the model. The profiles of zonal forcing induced by this wave damping are similar to profiles given by critical level absorption, but displaced slightly downward. The magnitude of the zonal forcing is of order 5 m/s/day. It is estimated that if 2% of the area of the Tropics were occupied by storms of similar magnitude, mesoscale gravity waves could provide nearly 1/4 of the zonal forcing required for the QBO.

Suggested Procedures for Installing Strain Gauges on Langley Research Center Wind Tunnel Balances, Custom Force Measuring Transducers, Metallic and Composite Structural Test Articles

NASA Technical Reports Server (NTRS)

Moore, Thomas C., Sr.

2004-01-01

The character of force and strain measurement testing at LaRC is such that the types of strain gauge installations, the materials upon which the strain gauges are applied, and the test environments encountered, require many varied approaches. In 1997, a NASA Technical Memorandum (NASA TM 110327) was generated to provide the strain gauge application specialist with a listing of recommended procedures for strain gauging various transducers and test articles at LaRC. The technical memorandum offered here is an effort to keep the strain gauge user informed of new technological enhancements in strain-gauging methodology while preserving the strain-gauging guidelines set forth in the 1997 TM. This document provides detailed recommendations for strain gauging LaRC-designed balances and custom transducers, composite materials, cryogenic and high-temperature test articles, and selected non-typical or unique materials or test conditions. Additionally, one section offers details for installing Bragg-Grating type fiber-optic strain sensors for non-typical test scenarios.

Load apparatus and method for bolt-loaded compact tension test specimen

DOEpatents

Buescher, B.J. Jr.; Lloyd, W.R.; Ward, M.B.; Epstein, J.S.

1997-02-04

A bolt-loaded compact tension test specimen load apparatus includes: (a) a body having first and second opposing longitudinal ends, the first end comprising an externally threaded portion sized to be threadedly received within the test specimen threaded opening; (b) a longitudinal loading rod having first and second opposing longitudinal ends, the loading rod being slidably received in a longitudinal direction within the body internally through the externally threaded portion and slidably extending longitudinally outward of the body first longitudinal end; (c) a force sensitive transducer slidably received within the body and positioned to engage relative to the loading rod second longitudinal end; and (d) a loading bolt threadedly received relative to the body, the loading bolt having a bearing end surface and being positioned to bear against the transducer to forcibly sandwich the transducer between the loading bolt and loading rod. Also disclosed is a method of in situ determining applied force during crack propagation in a bolt-loaded compact tension test specimen. 6 figs.

Load apparatus and method for bolt-loaded compact tension test specimen

DOEpatents

Buescher, Jr., Brent J.; Lloyd, W. Randolph; Ward, Michael B.; Epstein, Jonathan S.

1997-01-01

A bolt-loaded compact tension test specimen load apparatus includes: a) a body having first and second opposing longitudinal ends, the first end comprising an externally threaded portion sized to be threadedly received within the test specimen threaded opening; b) a longitudinal loading rod having first and second opposing longitudinal ends, the loading rod being slidably received in a longitudinal direction within the body internally through the externally threaded portion and slidably extending longitudinally outward of the body first longitudinal end; c) a force sensitive transducer slidably received within the body and positioned to engage relative to the loading rod second longitudinal end; and d) a loading bolt threadedly received relative to the body, the loading bolt having a bearing end surface and being positioned to bear against the transducer to forcibly sandwich the transducer between the loading bolt and loading rod. Also disclosed is a method of in situ determining applied force during crack propagation in a bolt-loaded compact tension test specimen.

Measurement of Forces and Moments Transmitted to the Residual Limb

DTIC Science & Technology

2009-08-01

prosthesis alignment, socket pressure, gait, force and moment sensors 16. SECURITY CLASSIFICATION OF: U 17. LIMITATION OF ABSTRACT 18. NUMBER... prosthesis to measure the forces and moments at the base of the socket and to use these measurements to estimate the forces transmitted to the residual limb...BODY – EACH TASK IN STATEMENT OF WORK Task 1. To instrument a transtibial prosthesis with a tri-axial transducer to measure the forces and

A rectangle-type linear ultrasonic motor using longitudinal vibration transducers with four driving feet.

PubMed

Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

2013-04-01

To make full use of the vibrational energy of a longitudinal transducer, a rectangle-type linear ultrasonic motor with four driving feet is proposed in this paper. This new motor consists of four longitudinal vibration transducers which are arranged in a rectangle and form an enclosed construction. Lead zirconate titanate ceramics are embedded into the middle of the transducer and fastened by a wedge-caulking mechanism. Each transducer includes an exponentially shaped horn located on each end. The horns of the vertical transducers intersect at the base of the horizontal transducers' horns; the tip ends of the horizontal transducers' horns are used as the driving feet. Longitudinal vibrations are superimposed in the motor and generate elliptical movements at the tip ends of the horns. The working principle of the proposed motor is analyzed. The resonance frequencies of two working modes are tuned to be close to each other by adjusting the structural parameters. Transient analysis is developed to gain the vibration characteristics of the motor. A prototype motor is fabricated and measured. The vibration test results verify the feasibility of the proposed design. Typical output of the prototype is a no-load speed of 928 mm/s and maximum thrust force of 60 N at a voltage of 200 Vrms.

Intracardiac ultrasound scanner using a micromachine (MEMS) actuator.

PubMed

Zara, J M; Bobbio, S M; Goodwin-Johansson, S; Smith, S W

2000-01-01

Catheter-based intracardiac ultrasound offers the potential for improved guidance of interventional cardiac procedures. The objective of this research is the development of catheter-based mechanical sector scanners incorporating high frequency ultrasound transducers operating at frequencies up to 20 MHz. The authors' current transducer assembly consists of a single 1.75 mm by 1.75 mm, 20 MHz, PZT element mounted on a 2 mm by 2 mm square, 75 mum thick polyimide table that pivots on 3-mum thick gold plated polyimide hinges. The hinges also serve as the electrical connections to the transducer. This table-mounted transducer is tilted using a miniature linear actuator to produce a sector scan. This linear actuator is an integrated force array (IFA), which is an example of a micromachine, i.e., a microelectromechanical system (MEMS). The IFA is a thin (2.2 mum) polyimide membrane, which consists of a network of hundreds of thousands of micron scale deformable capacitors made from pairs of metallized polyimide plates. IFAs contract with an applied voltage of 30-120 V and have been shown to produce strains as large as 20% and forces of up to 8 dynes. The prototype transducer and actuator assembly was fabricated and interfaced with a GagePCI analog to digital conversion board digitizing 12 bit samples at a rate of 100 MSamples/second housed in a personal computer to create a single channel ultrasound scanner. The deflection of the table transducer in a low viscosity insulating fluid (HFE 7100, 3M) is up to +/-10 degrees at scan rates of 10-60 Hz. Software has been developed to produce real-time sector scans on the PC monitor.

Effects of stinger axial dynamics and mass compensation methods on experimental modal analysis

NASA Astrophysics Data System (ADS)

Hu, Ximing

1992-06-01

A longitudinal bar model that includes both stinger elastic and inertia properties is used to analyze the stinger's axial dynamics as well as the mass compensation that is required to obtain accurate input forces when a stinger is installed between the excitation source, force transducer, and the structure under test. Stinger motion transmissibility and force transmissibility, axial resonance and excitation energy transfer problems are discussed in detail. Stinger mass compensation problems occur when the force transducer is mounted on the exciter end of the stinger. These problems are studied theoretically, numerically, and experimentally. It is found that the measured Frequency Response Function (FRF) can be underestimated if mass compensation is based on the stinger exciter-end acceleration and can be overestimated if the mass compensation is based on the structure-end acceleration due to the stinger's compliance. A new mass compensation method that is based on two accelerations is introduced and is seen to improve the accuracy considerably. The effects of the force transducer's compliance on the mass compensation are also discussed. A theoretical model is developed that describes the measurement system's FRD around a test structure's resonance. The model shows that very large measurement errors occur when there is a small relative phase shift between the force and acceleration measurements. These errors can be in hundreds of percent corresponding to a phase error on the order of one or two degrees. The physical reasons for this unexpected error pattern are explained. This error is currently unknown to the experimental modal analysis community. Two sample structures consisting of a rigid mass and a double cantilever beam are used in the numerical calculations and experiments.

A Novel Strategy for landslide displacement and its direction monitoring

NASA Astrophysics Data System (ADS)

Zhu, Z.-W.; Yuan, Q.-Y.; Liu, D.-Y.; Liu, B.; Liu, J.-C.; Luo, H.

2013-12-01

Landslide monitoring is important in predicting the behavior of landslides, thereby ensuring environmental, life, and property safety. On the basis of our previous studies, we conducted the double shear test by using a third-generation optical fiber transducer that uses expandable polystyrene (EPS) as base material. However, the third-generation transducer has poor performance when cohesive force is present between the grout and capillary stainless steel pipe of the transducer. Thus, the fourth-generation optical fiber transducer was invented. Similar to the third-generation transducer, the fourth-generation transducer also used EPS as its base material. Single shear test was conducted on the fourth-generation transducer after being grouted with cement mortar (1:1 mix ratio). The micro-bend loss mechanism of the optical fiber was considered, and the optical time domain reflectometry instrument was used. The fact that the loss sequence of optical fibers subjected to loading is different at various locations is found. The relationship of the loading-point displacement VS. optical fiber sliding distance and optical loss were measured. Results show that the maximum initial measurement precision of the newly proposed device is 1mm, the corresponding sliding distance is 21 mm, and the dynamic range is 0-20 mm. The fourth-generation transducer can measure the movement direction of loadings, thus making this transducer applicable for landslide monitoring.

Synchronous monitoring of muscle dynamics and muscle force for maximum isometric tetanus

NASA Astrophysics Data System (ADS)

Zakir Hossain, M.; Grill, Wolfgang

2010-03-01

Skeletal muscle is a classic example of a biological soft matter . At both macro and microscopic levels, skeletal muscle is exquisitely oriented for force generation and movement. In addition to the dynamics of contracting and relaxing muscle which can be monitored with ultrasound, variations in the muscle force are also expected to be monitored. To observe such force and sideways expansion variations synchronously for the skeletal muscle a novel detection scheme has been developed. As already introduced for the detection of sideways expansion variations of the muscle, ultrasonic transducers are mounted sideways on opposing positions of the monitored muscle. To detect variations of the muscle force, angle of pull of the monitored muscle has been restricted by the mechanical pull of the sonic force sensor. Under this condition, any variation in the time-of-flight (TOF) of the transmitted ultrasonic signals can be introduced by the variation of the path length between the transducers. The observed variations of the TOF are compared to the signals obtained by ultrasound monitoring for the muscle dynamics. The general behavior of the muscle dynamics and muscle force shows almost an identical concept. Since muscle force also relates the psychological boosting-up effects, the influence of boosting-up on muscle force and muscle dynamics can also be quantified form this study. Length-tension or force-length and force-velocity relationship can also be derived quantitatively with such monitoring.

The mean zonal flow response to Rossby wave and gravity wave forcing in the equatorial lower stratosphere - Relationship to the QBO

NASA Technical Reports Server (NTRS)

Takahashi, Masaaki; Holton, James R.

1991-01-01

Observations show that the westerly acceleration of the equatorial quasi-biennial oscillation (QBO) can be accounted for by Kelvin waves, but that there is a deficiency in the easterly acceleration due to Rossby-gravity waves. Rossby waves and westward propagating gravity waves have been suggested as alternative sources for the easterly acceleration. The possible role of these two wave modes has been tested in a two-dimensional model of the QBO. When the easterly acceleration is due to Rossby waves, the zonal-mean response is steady; when it is due to gravity waves, an oscillation with some features similar to the QBO occurs, but it is of short period and weak amplitude. A similar result occurs when a standing-wave forcing pattern is imposed. These results suggest that Rossby waves play only a minor role in the QBO, and that while the Rossby-gravity mode is essential, other gravity modes may also be important for the easterly phase.

Gauge Bosons--The Ties That Bind.

ERIC Educational Resources Information Center

Hill, Christopher T.

1982-01-01

Discusses four basic forces/interactions in nature (strong force, weak force, electromagnetic force and gravity), associated with elementary particles. Focuses on "gauge bosons" (for example, photons), thought to account for strong, weak, and electromagnetic forces. (Author/JN)

Investigating gravity waves evidences in the Venus upper atmosphere

NASA Astrophysics Data System (ADS)

Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

2014-05-01

We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

Gravitational force and torque on a solar power satellite considering the structural flexibility

NASA Astrophysics Data System (ADS)

Zhao, Yi; Zhang, Jingrui; Zhang, Yao; Zhang, Jun; Hu, Quan

2017-11-01

The solar power satellites (SPS) are designed to collect the constant solar energy and beam it to Earth. They are traditionally large in scale and flexible in structure. In order to obtain an accurate model of such system, the analytical expressions of the gravitational force, gravity gradient torque and modal force are investigated. They are expanded to the fourth order in a Taylor series with the elastic displacements considered. It is assumed that the deformation of the structure is relatively small compared with its characteristic length, so that the assumed mode method is applicable. The high-order moments of inertia and flexibility coefficients are presented. The comprehensive dynamics of a large flexible SPS and its orbital, attitude and vibration evolutions with different order gravitational forces, gravity gradient torques and modal forces in geosynchronous Earth orbit are performed. Numerical simulations show that an accurate representation of the SPS‧ dynamic characteristics requires the retention of the higher moments of inertia and flexibility. Perturbations of orbit, attitude and vibration can be retained to the 1-2nd order gravitational forces, the 1-2nd order gravity gradient torques and the 1-2nd order modal forces for a large flexible SPS in geosynchronous Earth orbit.

Investigation of the free flow electrophoretic process. Volume 2: Technical analysis

NASA Technical Reports Server (NTRS)

Weiss, R. A.; Lanham, J. W.; Richman, D. W.; Walker, C. D.

1979-01-01

The effect of gravity on the free flow electrophoretic process was investigated. The demonstrated effects were then compared with predictions made by mathematical models. Results show that the carrier buffer flow was affected by gravity induced thermal convection and that the movement of the separating particle streams was affected by gravity induced buoyant forces. It was determined that if gravity induced buoyant forces were included in the mathematical models, then effective predictions of electrophoresis chamber separation performance were possible. The results of tests performed using various methods of electrophoresis using supportive media show that the mobility and the ability to separate were essentially independent of concentration, providing promise of being able to perform electrophoresis with higher inlet concentrations in space.

Dark Energy and Dark Matter from Emergent Gravity Picture

NASA Astrophysics Data System (ADS)

Seok Yang, Hyun

2018-01-01

We suggest that dark energy and dark matter may be a cosmic uroboros of quantum gravity due to the coherent vacuum structure of spacetime. We apply the emergent gravity to a large N matrix model by considering the vacuum in the noncommutative (NC) Coulomb branch satisfying the Heisenberg algebra. We observe that UV fluctuations in the NC Coulomb branch are always paired with IR fluctuations and these UV/IR fluctuations can be extended to macroscopic scales. We show that space-like fluctuations give rise to the repulsive gravitational force while time-like fluctuations generate the attractive gravitational force. When considering the fact that the fluctuations are random in nature and we are living in the (3+1)-dimensional spacetime, the ratio of the repulsive and attractive components will end in ¾ : ¼= 75 : 25 and this ratio curiously coincides with the dark composition of our current Universe. If one includes ordinary matters which act as the attractive gravitational force, the emergent gravity may explain the dark sector of our Universe more precisely.

Plasma membrane NADH oxidase of maize roots responds to gravity and imposed centrifugal forces

NASA Technical Reports Server (NTRS)

Bacon, E.; Morre, D. J.

2001-01-01

NADH oxidase activities measured with excised roots of dark-grown maize (Zea mays) seedlings and with isolated plasma membrane vesicles from roots of dark-grown maize oscillated with a regular period length of 24 min and were inhibited by the synthetic auxin 2,4-dichlorophenoxyacetic [correction of dichorophenoxyacetic] acid. The activities also responded to orientation with respect to gravity and to imposed centrifugal forces. Turning the roots upside down resulted in stimulation of the activity with a lag of about 10 min. Returning the sections to the normal upright position resulted in a return to initial rates. The activity was stimulated reversibly to a maximum of about 2-fold with isolated plasma membrane vesicles, when subjected to centrifugal forces of 25 to 250 x g for 1 to 4 min duration. These findings are the first report of a gravity-responsive enzymatic activity of plant roots inhibited by auxin and potentially related to the gravity-induced growth response. c2001 Editions scientifiques et medicales Elsevier SAS.

Rotor systems research aircraft risk-reduction shake test

NASA Technical Reports Server (NTRS)

Wellman, J. Brent

1990-01-01

A shake test and an extensive analysis of results were performed to evaluate the possibility of and the method for dynamically calibrating the Rotor Systems Research Aircraft (RSRA). The RSRA airframe was subjected to known vibratory loads in several degrees of freedom and the responses of many aircraft transducers were recorded. Analysis of the transducer responses using the technique of dynamic force determination showed that the RSRA, when used as a dynamic measurement system, could predict, a posteriori, an excitation force in a single axis to an accuracy of about 5 percent and sometimes better. As the analysis was broadened to include multiple degrees of freedom for the excitation force, the predictive ability of the measurement system degraded to about 20 percent, with the error occasionally reaching 100 percent. The poor performance of the measurement system is explained by the nonlinear response of the RSRA to vibratory forces and the inadequacy of the particular method used in accounting for this nonlinearity.

Reduction of Effective Acceleration to Microgravity Levels

NASA Technical Reports Server (NTRS)

Downey, James P.

2000-01-01

Acceleration due to earth's gravity causes buoyancy driven convection and sedimentation in solutions. In addition. pressure gradients occur as a function of the height within a liquid column. Hence gravity effects both equilbria conditions and phase transitions as a result of hydrostatic pressure gradients. The affect of gravity on the rate of heat and man transfer in solutal processes can be particularly important in polymer processing due to the high sensitivity of polymeric materials to processing conditions. The term microgravity has been coined to describe an environment in which the affects of gravitational acceleration am greatly reduced. It may seem odd to talk in term of reducing the effects of gravitational acceleration since gravitational attraction is a basic property of matter. However, die presence of gravity on in situ processing or measurements can be negated by achieving conditions in which the laboratory, or more specifically the container of the experimental materials, a subjected to the same acceleration as the materials themselves. With regard to the laboratory reference frame, there is virtually no force on the experimental solutions. This is difficult to achieve but can be done. A short review of Newtonian physics provides an explanation on both how processes we affected by gravity and how microgravity conditions are achieved. The fact that fluids deform when subject to a force bid solids do not indicates that solids have a structure able to exert an opposing force that negates an externally applied force. Liquids deform when a force is applied, indicating that a liquid structure cannot completely negate an applied force. Just how easily a liquid resists deformation is related to its viscosity. Spaceflight provides an environment in which the laboratory reference frame i.e. the spacecraft and all the equipment therein an experiencing virtually identical forces. There is no solid foundation underneath such a laboratory, so the laboratory accelerates according to the force of gravity as do the experimental fluids within the lab. Hence, the magnitude of the form excited by the laboratory on the experimental solutions within are greatly reduced. When compared with a laboratory on the ground and averaged over time, the fluids in a spaceflight laboratory experience approximately a 10 (sup -6)decrease in acceleration relative to their laboratory reference frame hence the term microgravity.

Evaluation method for acoustic trapping performance by tracking motion of trapped microparticle

NASA Astrophysics Data System (ADS)

Lim, Hae Gyun; Ham Kim, Hyung; Yoon, Changhan

2018-05-01

We report a method to evaluate the performances of a single-beam acoustic tweezer using a high-frequency ultrasound transducer. The motion of a microparticle trapped by a 45-MHz single-element transducer was captured and analyzed to deduce the magnitude of trapping force. In the proposed method, the motion of a trapped microparticle was analyzed from a series of microscopy images to compute trapping force; thus, no additional equipment such as microfluidics is required. The method could be used to estimate the effective trapping force in an acoustic tweezer experiment to assess cell membrane deformability by attaching a microbead to the surface of a cell and tracking the motion of the trapped bead, which is similar to a bead-based assay that uses optical tweezers. The results showed that the trapping force increased with increasing acoustic intensity and duty factor, but the force eventually reached a plateau at a higher acoustic intensity. They demonstrated that this method could be used as a simple tool to evaluate the performance and to optimize the operating conditions of acoustic tweezers.

Spit-Hole Effects on the Ballistics of a 7.62-mm Cartridge

DTIC Science & Technology

2014-02-01

barrel retains 0.50 in (12.7 mm) of rifling. The midchamber pressure transducer, Kistler Model 6215 (8), is consistent with previous experiments...Nemours and Company. 2 Kistler Model 9031A Load Washer (9). Force transducer selection was driven by the anticipated load and the necessity of an...Development and Engineering Center, Picatinny Arsenal, NJ, January 1986. 8. Kistler Operating Instructions, Quartz High-Pressure Sensor Type 6215

Nonlinear Effects in Ultrasound Fields of Diagnostic-type Transducers Used for Kidney Stone Propulsion: Characterization in Water

PubMed Central

Karzova, M.; Cunitz, B.; Yuldashev, P.; Andriyakhina, Y.; Kreider, W.; Sapozhnikov, O.; Bailey, M.; Khokhlova, V.

2016-01-01

Newer imaging and therapeutic ultrasound technologies require higher in situ pressure levels compared to conventional diagnostic values. One example is the recently developed use of focused ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe is used to deliver the acoustic pushing pulses. The probe comprises 128 elements equally spaced at the 55 mm long convex cylindrical surface with 38 mm radius of curvature. The efficacy of the treatment can be increased by using higher transducer output to provide stronger pushing force; however, nonlinear acoustic saturation effect can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the 3D Westervelt equation; the boundary condition was set to match low power pressure beam scans. Focal waveforms simulated for increased output power levels were compared with the fiber-optic hydrophone measurements and were found in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of the transducer. This work has application to standard diagnostic probes and imaging. PMID:27087711

Matrix method for acoustic levitation simulation.

PubMed

Andrade, Marco A B; Perez, Nicolas; Buiochi, Flavio; Adamowski, Julio C

2011-08-01

A matrix method is presented for simulating acoustic levitators. A typical acoustic levitator consists of an ultrasonic transducer and a reflector. The matrix method is used to determine the potential for acoustic radiation force that acts on a small sphere in the standing wave field produced by the levitator. The method is based on the Rayleigh integral and it takes into account the multiple reflections that occur between the transducer and the reflector. The potential for acoustic radiation force obtained by the matrix method is validated by comparing the matrix method results with those obtained by the finite element method when using an axisymmetric model of a single-axis acoustic levitator. After validation, the method is applied in the simulation of a noncontact manipulation system consisting of two 37.9-kHz Langevin-type transducers and a plane reflector. The manipulation system allows control of the horizontal position of a small levitated sphere from -6 mm to 6 mm, which is done by changing the phase difference between the two transducers. The horizontal position of the sphere predicted by the matrix method agrees with the horizontal positions measured experimentally with a charge-coupled device camera. The main advantage of the matrix method is that it allows simulation of non-symmetric acoustic levitators without requiring much computational effort.

Einstein's Elevator in Class: A Self-Construction by Students for the Study of the Equival

ERIC Educational Resources Information Center

Kapotis, Efstratios; Kalkanis, George

2016-01-01

According to the principle of equivalence, it is impossible to distinguish between gravity and inertial forces that a noninertial observer experiences in his own frame of reference. For example, let's consider an elevator in space that is being accelerated in one direction. An observer inside it would feel as if there was gravity force pulling him…

Life of the onion not knowing up from down

NASA Technical Reports Server (NTRS)

Gordeyev, A.

1980-01-01

The absence of the force of gravity has a negative effect on plant life. Plants grown on spacecraft have died prematurely. Tests are being made to discover whether or not electricity will compensate for the absence of gravitation. It was found that an onion under current is not subject to the force of gravity. Tremendous possibilities are opened up by these experiments.

Particle manipulation by a non-resonant acoustic levitator

NASA Astrophysics Data System (ADS)

Andrade, Marco A. B.; Pérez, Nicolás; Adamowski, Julio C.

2015-01-01

We present the analysis of a non-resonant acoustic levitator, formed by an ultrasonic transducer and a concave reflector. In contrast to traditional levitators, the geometry presented herein does not require the separation distance between the transducer and the reflector to be a multiple of half wavelength. The levitator behavior is numerically predicted by applying a numerical model to calculate the acoustic pressure distribution and the Gor'kov theory to obtain the potential of the acoustic radiation force that acts on a levitated particle. We also demonstrate that levitating particles can be manipulated by controlling the reflector position while maintaining the transducer in a fixed position.

Nano-optomechanical transducer

DOEpatents

Rakich, Peter T; El-Kady, Ihab F; Olsson, Roy H; Su, Mehmet Fatih; Reinke, Charles; Camacho, Ryan; Wang, Zheng; Davids, Paul

2013-12-03

A nano-optomechanical transducer provides ultrabroadband coherent optomechanical transduction based on Mach-wave emission that uses enhanced photon-phonon coupling efficiencies by low impedance effective phononic medium, both electrostriction and radiation pressure to boost and tailor optomechanical forces, and highly dispersive electromagnetic modes that amplify both electrostriction and radiation pressure. The optomechanical transducer provides a large operating bandwidth and high efficiency while simultaneously having a small size and minimal power consumption, enabling a host of transformative phonon and signal processing capabilities. These capabilities include optomechanical transduction via pulsed phonon emission and up-conversion, broadband stimulated phonon emission and amplification, picosecond pulsed phonon lasers, broadband phononic modulators, and ultrahigh bandwidth true time delay and signal processing technologies.

An Investigation of the Posterior Component of Occlusal Force

DTIC Science & Technology

1994-05-01

of the hemostat allowed subjects to consistently orient the bite force transducer parallel to the occIusal plane , thus allowing the bite force to be...the anterior component of occlusal force was influenced by the steepness of the occlusal plane . Southard et al (1989) was the first to quantify the...young adult males yielded higher mean maximum bite forces at 20 mm opening and at 40 mm opening. The authors suggested that orientation and function of

Prediction of Bubble Diameter at Detachment from a Wall Orifice in Liquid Cross Flow Under Reduced and Normal Gravity Conditions

NASA Technical Reports Server (NTRS)

Nahra, Henry K.; Kamotani, Y.

2003-01-01

Bubble formation and detachment is an integral part of the two-phase flow science. The objective of the present work is to theoretically investigate the effects of liquid cross-flow velocity, gas flow rate embodied in the momentum flux force, and orifice diameter on bubble formation in a wall-bubble injection configuration. A two-dimensional one-stage theoretical model based on a global force balance on the bubble evolving from a wall orifice in a cross liquid flow is presented in this work. In this model, relevant forces acting on the evolving bubble are expressed in terms of the bubble center of mass coordinates and solved simultaneously. Relevant forces in low gravity included the momentum flux, shear-lift, surface tension, drag and inertia forces. Under normal gravity conditions, the buoyancy force, which is dominant under such conditions, can be added to the force balance. Two detachment criteria were applicable depending on the gas to liquid momentum force ratio. For low ratios, the time when the bubble acceleration in the direction of the detachment angle is greater or equal to zero is calculated from the bubble x and y coordinates. This time is taken as the time at which all the detaching forces that are acting on the bubble are greater or equal to the attaching forces. For high gas to liquid momentum force ratios, the time at which the y coordinate less the bubble radius equals zero is calculated. The bubble diameter is evaluated at this time as the diameter at detachment from the fact that the bubble volume is simply given by the product of the gas flow rate and time elapsed. Comparison of the model s predictions was also made with predictions from a two-dimensional normal gravity model based on Kumar-Kuloor formulation and such a comparison is presented in this work.

The behavior of surface tension on steady-state rotating fluids in the low gravity environments

NASA Technical Reports Server (NTRS)

Hung, R. J.; Leslie, Fred W.

1987-01-01

The effect of surface tension on steady-state rotating fluids in a low gravity environment is studied. All the values of the physical parameters used in these calculations, except in the low gravity environments, are based on the measurements carried out by Leslie (1985) in the low gravity environment of a free-falling aircraft. The profile of the interface of two fluids is derived from Laplace's equation relating the pressure drop across an interface to the radii of curvature which has been applied to a low gravity rotating bubble that contacts the container boundary. The interface shape depends on the ratio of gravity to surface tension forces, the ratio of centrifugal to surface tension forces, the contact radius of the interface to the boundary, and the contact angle. The shape of the bubble is symmetric about its equator in a zero-gravity environment. This symmetry disappears and gradually shifts to parabolic profiles as the gravity environment becomes non-zero. The location of the maximum radius of the bubble moves upward from the center of the depth toward the top boundary of the cylinder as gravity increases. The contact radius of interface to the boundary r0 at the top side of cylinder increases and r0 at the bottom side of the cylinder decreases as the gravity environment increases from zero to 1 g.

Bolt-Tension Sensor

NASA Technical Reports Server (NTRS)

Goldie, James H.; Bushko, Dariusz A.; Gerver, Michael J.

1995-01-01

In technique for measuring tensile force of bolt, specially fabricated magnetostrictive washer used as force transducer. Compact, portable inductive electronic sensor placed against washer to measure tension force. New system provides accurate, economical, and convenient way to measure bolt tension in field. Measurements on test assembly shows that tension can be measured to accuracy of about plus or minus 1 percent of load capacity of typical bolt.

Transducer-based evaluation of tremor

PubMed Central

Haubenberger, Dietrich; Abbruzzese, Giovanni; Bain, Peter G; Bajaj, Nin; Benito-León, Julián; Bhatia, Kailash P; Deuschl, Günther; Forjaz, Maria João; Hallett, Mark; Louis, Elan D; Lyons, Kelly E; Mestre, Tiago A; Raethjen, Jan; Stamelou, Maria; Tan, Eng-King; Testa, Claudia M; Elble, Rodger J

2016-01-01

The Movement Disorder Society (MDS) established a task force on tremor that reviewed the use of transducer-based measures in the quantification and characterization of tremor. Studies of accelerometry, electromyography, activity monitoring, gyroscopy, digitizing tablet-based measures, vocal acoustic analysis, and several other transducer-based methods were identified by searching PubMed.gov. The availability, use, acceptability, reliability, validity, and responsiveness were reviewed for each measure using the following criteria: 1) used in the assessment of tremor, 2) used in published studies by people other than the developers, and 3) adequate clinimetric testing. Accelerometry, gyroscopy, electromyography, and digitizing tablet-based measures fulfilled all three criteria. Compared to rating scales, transducers are far more sensitive to changes in tremor amplitude and frequency, but they do not appear to be more capable of detecting a change that exceeds random variability in tremor amplitude (minimum detectable change). The use of transducer-based measures requires careful attention to their limitations and validity in a particular clinical or research setting. PMID:27273470

Space truss zero gravity dynamics

NASA Technical Reports Server (NTRS)

Swanson, Andy

1989-01-01

The Structural Dynamics Branch of the Air Force Flight Dynamics Laboratory in cooperation with the Reduced Gravity Office of the NASA Lyndon B. Johnson Space Center (JSC) plans to perform zero-gravity dynamic tests of a 12-meter truss structure. This presentation describes the program and presents all results obtained to date.

40 CFR 1065.310 - Torque calibration.

Code of Federal Regulations, 2014 CFR

2014-07-01

... force is measured. The lever arm must be perpendicular to gravity (i.e., horizontal), and it must be... known distance along a lever arm. Make sure the weights' lever arm is perpendicular to gravity (i.e... Earth's gravity, as described in § 1065.630. Calculate the reference torque as the weights' reference...

Ground Reaction Forces During Reduced Gravity Running in Parabolic Flight.

PubMed

Cavanagh, Peter; Rice, Andrea; Glauberman, Molly; Sudduth, Amanda; Cherones, Arien; Davis, Shane; Lewis, Michael; Hanson, Andrea; Wilt, Grier

2017-08-01

Treadmills have been employed as both a form of exercise and a countermeasure to prevent changes in the musculoskeletal system on almost all NASA missions and many Russian missions since the early Space Shuttle flights. It is possible that treadmills may also be part of exercise programs on future Mars missions and that they may be a component of exercise facilities in lunar or Martian habitats. In order to determine if the ambient gravity on these destinations will provide osteogenic effects while performing exercise on a treadmill, ground reactions forces (GRFs) were measured on eight subjects (six women and two men) running at 6 mph during parabolic flight in Martian and lunar gravity conditions. On average, stride length increased as gravity decreased. The first and second peaks of the GRFs decreased by 0.156 and 0.196 bodyweights, respectively, per 1/10 g change in ambient gravity. Based on comparisons with previously measured GRF during loaded treadmill running on the International Space Station, we conclude that unloaded treadmill running under lunar and Martian conditions during exploration missions is not likely to be an osteo-protective exercise.Cavanagh P, Rice A, Glauberman M, Sudduth A, Cherones A, Davis S, Lewis M, Hanson A, Wilt G. Ground reaction forces during reduced gravity running in parabolic flight. Aerosp Med Hum Perform. 2017; 88(8):730-736.

Bubble Formation from Wall Orifice in Liquid Cross-Flow Under Low Gravity

NASA Technical Reports Server (NTRS)

Nahra, Henry K.; Kamotani, Y.

2000-01-01

Two-phase flows present a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two phase flow science. The objective of the present work is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation in a wall-bubble injection configuration. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter, the gas flow rate, and the liquid cross-flow velocity. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small, the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle.

Altered vestibular function in fetal and newborn rats gestated in space

NASA Technical Reports Server (NTRS)

Ronca, A. E.; Alberts, J. R.

1997-01-01

Researchers evaluated vestibular development and function in rat pups flown during gestation on the NASA-NIH R1 and R2 missions. Fetal and postnatal vestibular function were examined. Altered vestibular-mediated responses in the experimental fetal pups are attributed to either direct effect of gravity on the vestibular system or indirect effects of microgravity transduced through the mother. The postnatal tests confirmed the hypothesis that the vestibular system continually adapts and responds to tonic stimulation.

Otolith-Canal Convergence In Vestibular Nuclei Neurons

NASA Technical Reports Server (NTRS)

Dickman, J. David; Si, Xiao-Hong

2002-01-01

The current final report covers the period from June 1, 1999 to May 31, 2002. The primary objective of the investigation was to determine how information regarding head movements and head position relative to gravity is received and processed by central vestibular nuclei neurons in the brainstem. Specialized receptors in the vestibular labyrinths of the inner ear function to detect angular and linear accelerations of the head, with receptors located in the semicircular canals transducing rotational head movements and receptors located in the otolith organs transducing changes in head position relative to gravity or linear accelerations of the head. The information from these different receptors is then transmitted to central vestibular nuclei neurons which process the input signals, then project the appropriate output information to the eye, head, and body musculature motor neurons to control compensatory reflexes. Although a number of studies have reported on the responsiveness of vestibular nuclei neurons, it has not yet been possible to determine precisely how these cells combine the information from the different angular and linear acceleration receptors into a correct neural output signal. In the present project, rotational and linear motion stimuli were separately delivered while recording responses from vestibular nuclei neurons that were characterized according to direct input from the labyrinth and eye movement sensitivity. Responses from neurons receiving convergent input from the semicircular canals and otolith organs were quantified and compared to non-convergent neurons.

Self-similar gravity wave spectra resulting from the modulation of bound waves

NASA Astrophysics Data System (ADS)

Michel, Guillaume; Semin, Benoît; Cazaubiel, Annette; Haudin, Florence; Humbert, Thomas; Lepot, Simon; Bonnefoy, Félicien; Berhanu, Michaël; Falcon, Éric

2018-05-01

We experimentally study the properties of nonlinear surface gravity waves in a large-scale basin. We consider two different configurations: a one-dimensional (1D) monochromatic wave forcing, and a two-dimensional (2D) forcing with bichromatic waves satisfying resonant-wave interaction conditions. For the 1D forcing, we find a discrete wave-energy spectrum dominated at high frequencies by bound waves whose amplitudes decrease as a power law of the frequency. Bound waves (e.g., to the carrier) are harmonics superimposed on the carrier wave propagating with the same phase velocity as the one of the carrier. When a narrow frequency random modulation is applied to this carrier, the high-frequency part of the wave-energy spectrum becomes continuous with the same frequency-power law. Similar results are found for the 2D forcing when a random modulation is also applied to both carrier waves. Our results thus show that all these nonlinear gravity wave spectra are dominated at high frequencies by the presence of bound waves, even in the configuration where resonant interactions occur. Moreover, in all these configurations, the power-law exponent of the spectrum is found to depend on the forcing amplitude with the same trend as the one found in previous gravity wave turbulence experiments. Such a set of bound waves may thus explain this dependence that was previously poorly understood.

Gravity resistance, another graviresponse in plants - role of microtubule-membrane-cell wall continuum

NASA Astrophysics Data System (ADS)

Hoson, T.; Saito, Y.; Usui, S.; Soga, K.; Wakabayashi, K.

Resistance to the gravitational force has been a serious problem for plants to survive on land, after they first went ashore more than 400 million years ago. Thus, gravity resistance is the principal graviresponse in plants comparable to gravitropism. Nevertheless, only limited information has been obtained for this second gravity response. We have examined the mechanism of gravity resistance using hypergravity conditions produced by centrifugation. The results led a hypothesis on the mechanism of plant resistance to the gravitational force that the plant constructs a tough body by increasing the cell wall rigidity, which are brought about by modification of the cell wall metabolism and cell wall environment, especially pH. The hypothesis was further supported by space experiments during the Space Shuttle STS-95 mission. On the other hand, we have shown that gravity signal may be perceived by mechanoreceptors (mechanosensitive ion channels) on the plasma membrane and amyloplast sedimentation in statocytes is not involved in gravity resistance. Moreover, hypergravity treatment increased the expression levels of genes encoding alpha-tubulin, a component of microtubules and 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMGR), which catalyzes a reaction producing mevalonic acid, a key precursor of terpenoids such as membrane sterols. The expression of HMGR and alpha- and beta-tubulin genes increased within several hours after hypergravity treatment, depending on the magnitude of gravity. The determination of levels of gene products as well as the analysis with knockout mutants of these genes by T-DNA insertions in Arabidopsis supports the involvement of both membrane sterols and microtubules in gravity resistance. These results suggest that structural or physiological continuum of microtubule-cell membrane-cell wall is responsible for plant resistance to the gravitational force.

Bubble Formation at a Submerged Orifice in Reduced Gravity

NASA Technical Reports Server (NTRS)

Buyevich, Yu A.; Webbon, Bruce W.

1994-01-01

The dynamic regime of gas injection through a circular plate orifice into an ideally wetting liquid is considered, when successively detached bubbles may be regarded as separate identities. In normal gravity and at relatively low gas flow rates, a growing bubble is modeled as a spherical segment touching the orifice perimeter during the whole time of its evolution. If the flow rate exceeds a certain threshold value, another stage of the detachment process takes place in which an almost spherical gas envelope is connected with the orifice by a nearly cylindrical stem that lengthens as the bubble rises above the plate. The bubble shape resembles then that of a mushroom and the upper envelope continues to grow until the gas supply through the stem is completely cut off. Such a stage is always present under conditions of sufficiently low gravity, irrespective of the flow rate. Two major reasons make for bubble detachment: the buoyancy force and the force due to the momentum inflow into the bubble with the injected gas. The former force dominates the process at normal gravity whereas the second one plays a key role under negligible gravity conditions. It is precisely this fundamental factor that conditions the drastic influence on bubble growth and detachment that changes in gravity are able to cause. The frequency of bubble formation is proportional to and the volume of detached bubbles is independent of the gas flow rate in sufficiently low gravity, while at normal and moderately reduced gravity conditions the first variable slightly decreases and the second one almost linearly increases as the flow rate grows. Effects of other parameters, such as the orifice radius, gas and liquid densities, and surface tension are discussed.

Astronaut Edwin Aldrin undergoes zero-gravity training aboard KC-135

NASA Image and Video Library

1969-07-15

S69-39269 (10 July 1969) --- Astronaut Edwin E. Aldrin Jr., lunar module pilot of the Apollo 11 lunar landing mission, undergoes zero-gravity training aboard a U.S. Air Force KC-135 jet aircraft from nearby Patrick Air Force Base, Florida. Aldrin is wearing an Extravehicular Mobility Unit (EMU), the type of equipment which he will wear on the lunar surface.

Centrifuge Testing of a Partially-Confined FC-72 Spray

DTIC Science & Technology

2006-11-01

induced body forces. Heat transfer associated with closed - loop spray cooling will be affected by acceleration body forces, the extent of which is not...impingement cooling, spray cooling, heat pipes , loop heat pipes , carbon foam impregnated with phase-change materials, and combinations of the above...reduced gravity and elevated gravity experiments to help prove viability of pulsating heat pipes (PHPs) for space applications. The PHPs, filled

Measurement of Forces and Moments Transmitted to the Residual Limb

DTIC Science & Technology

2010-10-01

forces, moments, and alignments. 15. SUBJECT TERMS Amputees, prosthesis alignment, socket pressure, gait, force and moment sensors 16. SECURITY...evaluate the feasibility of using a tri-axial transducer mounted to the pylon of a lower limb prosthesis directly below the socket to a.) Characterize...weighing up to nearly 500lbs, or activities which involve deceleration or acceleration forces of up to 500 lbs along the pylon of a prosthesis . Diameter

Early Detection of Clinically Significant Prostate Cancer Using Ultrasonic Acoustic Radiation Force Impulse (ARFI) Imaging

DTIC Science & Technology

2017-10-01

Toolkit for rapid 3D visualization and image volume interpretation, followed by automated transducer positioning in a user-selected image plane for... Toolkit (IGSTK) to enable rapid 3D visualization and image volume interpretation followed by automated transducer positioning in the user-selected... careers in science, technology, and the humanities. What do you plan to do during the next reporting period to accomplish the goals? If this

Active Response Gravity Offload System

NASA Technical Reports Server (NTRS)

Valle, Paul; Dungan, Larry; Cunningham, Thomas; Lieberman, Asher; Poncia, Dina

2011-01-01

The Active Response Gravity Offload System (ARGOS) provides the ability to simulate with one system the gravity effect of planets, moons, comets, asteroids, and microgravity, where the gravity is less than Earth fs gravity. The system works by providing a constant force offload through an overhead hoist system and horizontal motion through a rail and trolley system. The facility covers a 20 by 40-ft (approximately equals 6.1 by 12.2m) horizontal area with 15 ft (approximately equals4.6 m) of lifting vertical range.

Three-dimensional cellular deformation analysis with a two-photon magnetic manipulator workstation.

PubMed

Huang, Hayden; Dong, Chen Y; Kwon, Hyuk-Sang; Sutin, Jason D; Kamm, Roger D; So, Peter T C

2002-04-01

The ability to apply quantifiable mechanical stresses at the microscopic scale is critical for studying cellular responses to mechanical forces. This necessitates the use of force transducers that can apply precisely controlled forces to cells while monitoring the responses noninvasively. This paper describes the development of a micromanipulation workstation integrating two-photon, three-dimensional imaging with a high-force, uniform-gradient magnetic manipulator. The uniform-gradient magnetic field applies nearly uniform forces to a large cell population, permitting statistical quantification of select molecular responses to mechanical stresses. The magnetic transducer design is capable of exerting over 200 pN of force on 4.5-microm-diameter paramagnetic particles and over 800 pN on 5.0-microm ferromagnetic particles. These forces vary within +/-10% over an area 500 x 500 microm2. The compatibility with the use of high numerical aperture (approximately 1.0) objectives is an integral part of the workstation design allowing submicron-resolution, three-dimensional, two-photon imaging. Three-dimensional analyses of cellular deformation under localized mechanical strain are reported. These measurements indicate that the response of cells to large focal stresses may contain three-dimensional global deformations and show the suitability of this workstation to further studying cellular response to mechanical stresses.

Quantifying anti-gravity torques for the design of a powered exoskeleton.

PubMed

Ragonesi, Daniel; Agrawal, Sunil K; Sample, Whitney; Rahman, Tariq

2013-03-01

Designing an upper extremity exoskeleton for people with arm weakness requires knowledge of the joint torques due to gravity and joint stiffness, as well as, active residual force capabilities of users. The objective of this research paper is to describe the characteristics of the upper limb of children with upper limb impairment. This paper describes the experimental measurements of the torque on the upper limb due to gravity and joint stiffness of three groups of subjects: able-bodied adults, able-bodied children, and children with neuromuscular disabilities. The experiment involves moving the arm to various positions in the sagittal plane and measuring the resultant force at the forearm. This force is then converted to torques at the elbow and shoulder. These data are compared to a two-link lumped mass model based on anthropomorphic data. Results show that the torques based on anthropometry deviate from experimentally measured torques as the arm goes through the range. Subjects with disabilities also maximally pushed and pulled against the force sensor to measure maximum strength as a function of arm orientation. For all subjects, the maximum voluntary applied torque at the shoulder and elbow in the sagittal plane was found to be lower than gravity torques throughout the disabled subjects' range of motion. This experiment informs designers of upper limb orthoses on the contribution of passive human joint torques due to gravity and joint stiffness and the strength capability of targeted users.

Production of Gas Bubbles in Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Oguz, Hasan N.; Takagi, Shu; Misawa, Masaki

1996-01-01

In a wide variety of applications such as waste water treatment, biological reactors, gas-liquid reactors, blood oxygenation, purification of liquids, etc., it is necessary to produce small bubbles in liquids. Since gravity plays an essential role in currently available techniques, the adaptation of these applications to space requires the development of new tools. Under normal gravity, bubbles are typically generated by forcing gas through an orifice in a liquid. When a growing bubble becomes large enough, the buoyancy dominates the surface tension force causing it to detach from the orifice. In space, the process is quite different and the bubble may remain attached to the orifice indefinitely. The most practical approach to simulating gravity seems to be imposing an ambient flow to force bubbles out of the orifice. In this paper, we are interested in the effect of an imposed flow in 0 and 1 g. Specifically, we investigate the process of bubble formation subject to a parallel and a cross flow. In the case of parallel flow, we have a hypodermic needle in a tube from which bubbles can be produced. On the other hand, the cross flow condition is established by forcing bubbles through an orifice on a wall in a shear flow. The first series of experiments have been performed under normal gravity conditions and the working fluid was water. A high quality microgravity facility has been used for the second type and silicone oil is used as the host liquid.

On the Hydrogranular Dynamics of Magmatic Gravity Currents

NASA Astrophysics Data System (ADS)

McIntire, M. Z.; Bergantz, G. W.; Schleicher, J.; Burgisser, A.

2016-12-01

Magmatic processes are generally governed by multi-phase interactions of silicate liquid, crystals, and bubbles. However, the modes of dissipation and the manner that stress is transmitted are poorly understood. We use a model of a simple but widely applicable gravity current as a means to exemplify the hydrogranular dynamics in crystal-rich magmas. Viscous and lubrication forces are of special interest because they have a dual role in dispersal and mixing in a crystal-rich gravity current. For example, lubrication forces provide an initial apparent yield strength by inducing a negative pore pressure as crystals move apart. However, once the gravity current is underway, lubrication forces reduce the dissipation due to collision and frictional contact.The gravity current is initiated by a combination of toppling and sliding along a well-defined granular fault. This produces three distinct regimes: a quasi-static base, an overlying particle hump that translates in a quasi-plastic fashion by grain-passing and rolling until the angle of repose is reached, and a viscous particle current. The current initially forms a leading vortex at the head, but the loss of crystals by sedimentation-assisted granular capture by an upward growing particle front drains energy from the flow. The vortex is soon abandoned, but persists in the reservoir as a fossil feature of orphaned crystals in a smear of previous intercumulate fluid. The kinetic energy of the most active crystals decays in a dual fashion, initially linearly, then parabolically with a near symmetrical increase and loss of kinetic energy.There is very little entrainment and mixing between intercumulate and reservoir fluids from magmatic gravity currents. Only a thin seam of reservoir melt is captured by the base of the flow as it descends across the floor. Hence magmatic gravity currents, while producing modest amounts of crystal sorting, are not effective agents of mixing as lubrication and viscous forces inhibit interpenetration of reservoir fluid.

Bubble Detachment in Variable Gravity Under the Influence of a Non-Uniform Electric Field

NASA Technical Reports Server (NTRS)

Chang, Shinan; Herman, Cila; Iacona, Estelle

2002-01-01

The objective of the study reported in this paper is to investigate the effects of variable, reduced gravity on the formation and detachment behavior of individual air bubbles under the influence of a non-uniform electric field. For this purpose, variable gravity experiments were carried out in parabolic nights. The non-uniform electric field was generated by a spherical electrode and a plate electrode. The effect of the magnitude of the non-uniform electric field and gravity level on bubble formation, development and detachment at an orifice was investigated. An image processing code was developed that allows the measurement of bubble volume, dimensions and contact angle at detachment. The results of this research can be used to explore the possibility of enhancing boiling heat transfer in the variable and low gravity environments by substituting the buoyancy force with a force induced by the electric field. The results of experiments and measurements indicate that the level of gravity significantly affects bubble shape, size and frequency. The electric field magnitude also influences bubble detachment, however, its impact is not as profound as that of variable gravity for the range of electric field magnitudes investigated in the present study.

On Calculating the Zero-Gravity Surface Figure of a Mirror

NASA Technical Reports Server (NTRS)

Bloemhof, Eric E.

2010-01-01

An analysis of the classical method of calculating the zero-gravity surface figure of a mirror from surface-figure measurements in the presence of gravity has led to improved understanding of conditions under which the calculations are valid. In this method, one measures the surface figure in two or more gravity- reversed configurations, then calculates the zero-gravity surface figure as the average of the surface figures determined from these measurements. It is now understood that gravity reversal is not, by itself, sufficient to ensure validity of the calculations: It is also necessary to reverse mounting forces, for which purpose one must ensure that mountingfixture/ mirror contacts are located either at the same places or else sufficiently close to the same places in both gravity-reversed configurations. It is usually not practical to locate the contacts at the same places, raising the question of how close is sufficiently close. The criterion for sufficient closeness is embodied in the St. Venant principle, which, in the present context, translates to a requirement that the distance between corresponding gravity-reversed mounting positions be small in comparison to their distances to the optical surface of the mirror. The necessity of reversing mount forces is apparent in the behavior of the equations familiar from finite element analysis (FEA) that govern deformation of the mirror.

Finger forces in fastball baseball pitching.

PubMed

Kinoshita, Hiroshi; Obata, Satoshi; Nasu, Daiki; Kadota, Koji; Matsuo, Tomoyuki; Fleisig, Glenn S

2017-08-01

Forces imparted by the fingers onto a baseball are the final, critical aspects for pitching, however these forces have not been quantified previously as no biomechanical technology was available. In this study, an instrumented baseball was developed for direct measurement of ball reaction force by individual fingers and used to provide fundamental information on the forces during a fastball pitch. A tri-axial force transducer with a cable having an easily-detachable connector were installed in an official baseball. Data were collected from 11 pitchers who placed the fingertip of their index, middle, ring, or thumb on the transducer, and threw four-seam fastballs to a target cage from a flat mound. For the index and middle fingers, resultant ball reaction force exhibited a bimodal pattern with initial and second peaks at 38-39ms and 6-7ms before ball release, and their amplitudes were around 97N each. The ring finger and thumb produced single-peak forces of approximately 50 and 83N, respectively. Shear forces for the index and middle fingers formed distinct peak at 4-5ms before release, and the peaks summed to 102N; a kinetic source for backspin on the ball. An additional experiment with submaximal pitching effort showed a linear relationship of peak forces with ball velocity. The peak ball reaction force for fastballs exceeded 80% of maximum finger strength measured, suggesting that strengthening of the distal muscles is important both for enhancing performance and for avoiding injuries. Copyright © 2017 Elsevier B.V. All rights reserved.

Calcium dependent current recordings in Xenopus laevis oocytes in microgravity

NASA Astrophysics Data System (ADS)

Wuest, Simon L.; Roesch, Christian; Ille, Fabian; Egli, Marcel

2017-12-01

Mechanical unloading by microgravity (or weightlessness) conditions triggers profound adaptation processes at the cellular and organ levels. Among other mechanisms, mechanosensitive ion channels are thought to play a key role in allowing cells to transduce mechanical forces. Previous experiments performed under microgravity have shown that gravity affects the gating properties of ion channels. Here, a method is described to record a calcium-dependent current in native Xenopus laevis oocytes under microgravity conditions during a parabolic flight. A 3-voltage-step protocol was applied to provoke a calcium-dependent current. This current increased with extracellular calcium concentration and could be reduced by applying extracellular gadolinium. The custom-made ;OoClamp; hardware was validated by comparing the results of the 3-voltage-step protocol to results obtained with a well-established two-electrode voltage clamp (TEVC). In the context of the 2nd Swiss Parabolic Flight Campaign, we tested the OoClamp and the method. The setup and experiment protocol worked well in parabolic flight. A tendency that the calcium-dependent current was smaller under microgravity than under 1 g condition could be observed. However, a conclusive statement was not possible due to the small size of the data base that could be gathered.

Wavelength dependence of eddy dissipation and Coriolis force in the dynamics of gravity wave driven fluctuations in the OH nightglow

NASA Technical Reports Server (NTRS)

Hickey, M. P.

1988-01-01

This paper examines the effect of inclusion of Coriolis force and eddy dissipation in the gravity wave dynamics theory of Walterscheid et al. (1987). It was found that the values of the ratio 'eta' (where eta is a complex quantity describing the ralationship between the intensity oscillation about the time-averaged intensity, and the temperature oscillation about the time-averaged temperature) strongly depend on the wave period and the horizontal wavelength; thus, if comparisons are to be made between observations and theory, horizontal wavelengths will need to be measured in conjunction with the OH nightglow measurements. For the waves with horizontal wavelengths up to 1000 km, the eddy dissipation was found to dominate over the Coriolis force in the gravity wave dynamics and also in the associated values of eta. However, for waves with horizontal wavelengths of 10,000 km or more, the Coriolis force cannot be neglected; it has to be taken into account along with the eddy dissipation.

Standing surface acoustic wave technology applied for micro-particle concentration in oil

NASA Astrophysics Data System (ADS)

Wang, Ziping; Xue, Xian; Luo, Ying; Yuan, Fuh-Gwo

2018-03-01

Oil lubrication plays an important role in a variety of mechanical equipment. The traditional purification method is difficult to remove the tiny impurity size of 5-15 μm. Three different types of the transducers and its preparation methods were used in the experiment. The phenomenon that the impurity particles in viscous fluid by the acoustic radiation force was moved the wave node position and focused on the center line was observed by the super-depth microscope. The influence factors of the produced SSAW, particle force condition and movement track were analyzed. The experimental results show that the interdigital transducer can be used to generate SSAW, so as to achieve the separation effect of oil and suspended particles.

Novel approach to tensile testing of micro- and nanoscale fibers

NASA Astrophysics Data System (ADS)

Tan, E. P. S.; Lim, C. T.

2004-08-01

Due to the strength and size of the micro- and nanoscale fibers, larger conventional universal testing machines are not suitable in performing stretch test of such fibers. Existing microtensile testing machines are custom-made and are complex and expensive to construct. Here, a novel method of using an existing atomic force microscope (AFM)-based nanoindenation system for the tensile testing of microscale or bundled nanoscale fibers is proposed. The microscale poly (L-lactic-co-glycolic acid) fiber (˜25 μm diameter) was used as an example to illustrate this technique. The microfiber was first attached to a nanoindenter tip and the base via a custom-made holder to ensure that the microfiber was taut and vertically aligned. The force transducer of the nanoindenter was used to measure the tensile force required to stretch the microfiber. The microfiber was stretched using the stepper motor of the AFM system. The elongation of the microfiber was measured by subtracting the elongation of the transducer spring from the total elongation of the microfiber and transducer spring. A plot of the load against elongation of the microfiber was then obtained. The stress and strain of the microfiber was measured by subtracting the elongation of the transducer spring from the total elongation of the microfiber was then obtained. The stress and strain of the microfiber was obtained by dividing the load and elongation by cross-sectional area and gauge length, respectively. With this data, the mechanical behavior of the sample at small strains can be studied. This system is able to provide a high load resolution of 80 nN and displacement resolution of 0.5 nm. However, maximum load and sample elongation is limited and handling of the sample still remains a challenge.

Limitation of Gravitational Wave Detector Niobè Sensitivity by the Frequency Tracking Noise

NASA Astrophysics Data System (ADS)

Frajuca, Carlos; Bortoli, Fabio Da Silva

The gravity wave detector at the University of Western Australia was based on a bending flap of 0.45kg tuned near the fundamental resonant frequency of a 1.5ton resonant-bar of 710Hz at a temperature of 5K. The displacement of the bending flap was monitored with a 9.5GHz superconducting re-entrant cavity transducer. The performance of the transducer is related to the development of a low noise microwave pump oscillator to drive the transducer. This work studies the influence of the frequency tracking noise of Niobè. It had a burst sensitivity of h ≈ 7 × 10-19 with a long term operation from 1993 to early 1998. It had the lowest observed noise temperature. Using the characteristics of the detector, NIOBÈ should had reached a much better sensitivity that the one measure. It seems that the noise introduced in the system by the frequency tracking device was not taken into account at the time of operation, this noise gives a value of ≈ 2.5 × 10-18m/(Hz)-1/2, what is the value that limited the detector sensitivity to the one measured at the time of operation.

The mean zonal flow response to Rossby wave and gravity wave forcing in the equatorial lower stratosphere: Relationship to the QBO. [QBO (quasi-biennial oscillation)

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

Takahashi, M.; Holton, J.R.

1991-09-15

Observations show that the westerly acceleration of the equatorial quasi-biennial oscillation (QBO) can be accounted for by Kelvin waves, but that there is a deficiency in the easterly acceleration due to Rossby-gravity waves. Rossby waves and westward propagating gravity waves have been suggested as alternative sources for the easterly acceleration. We have tested the possible role of these two wave modes in a two-dimensional model of the QBO. When the easterly acceleration is due to Rossby waves, the zonal-mean response is steady; when it is due to gravity waves, an oscillation with some features similar to the QBO occurs, butmore » it is of short period and weak amplitude. A similar result occurs when a standing-wave forcing pattern is imposed. These results suggest that Rossby waves play only a minor role in the QBO, and that while the Rossby-gravity mode is essential, other gravity modes may also be important for the easterly phase. 12 refs., 22 figs.« less

Acoustic levitator for structure measurements on low temperature liquid droplets.

PubMed

Weber, J K R; Rey, C A; Neuefeind, J; Benmore, C J

2009-08-01

A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

Combined targeting of lentiviral vectors and positioning of transduced cells by magnetic nanoparticles.

PubMed

Hofmann, Andreas; Wenzel, Daniela; Becher, Ulrich M; Freitag, Daniel F; Klein, Alexandra M; Eberbeck, Dietmar; Schulte, Maike; Zimmermann, Katrin; Bergemann, Christian; Gleich, Bernhard; Roell, Wilhelm; Weyh, Thomas; Trahms, Lutz; Nickenig, Georg; Fleischmann, Bernd K; Pfeifer, Alexander

2009-01-06

Targeting of viral vectors is a major challenge for in vivo gene delivery, especially after intravascular application. In addition, targeting of the endothelium itself would be of importance for gene-based therapies of vascular disease. Here, we used magnetic nanoparticles (MNPs) to combine cell transduction and positioning in the vascular system under clinically relevant, nonpermissive conditions, including hydrodynamic forces and hypothermia. The use of MNPs enhanced transduction efficiency of endothelial cells and enabled direct endothelial targeting of lentiviral vectors (LVs) by magnetic force, even in perfused vessels. In addition, application of external magnetic fields to mice significantly changed LV/MNP biodistribution in vivo. LV/MNP-transduced cells exhibited superparamagnetic behavior as measured by magnetorelaxometry, and they were efficiently retained by magnetic fields. The magnetic interactions were strong enough to position MNP-containing endothelial cells at the intima of vessels under physiological flow conditions. Importantly, magnetic positioning of MNP-labeled cells was also achieved in vivo in an injury model of the mouse carotid artery. Intravascular gene targeting can be combined with positioning of the transduced cells via nanomagnetic particles, thereby combining gene- and cell-based therapies.

Novel approaches to optomechanical transduction

NASA Astrophysics Data System (ADS)

Cernotik, Ondrej; Hammerer, Klemens

In recent years, mechanical oscillators received attention as a promising tool for frequency conversion between microwaves and light. A general, bi-directional transducer with high efficiency is still far from reach of current technology; finding new strategies for optomechanical transduction allows us to relax the requirements and bring these systems closer to an experimental realization. An interesting example is generation of entanglement between two superconducting qubits using measurement and postselection. Here, the mechanical oscillators interacts directly with the superconducting transmon qubit in such a way that it feels a qubit-state dependent force. This force can then be read out using a cavity field; reading out two such systems sequentially realizes an effective total spin measurement. Starting from a suitable initial state and employing postselection, entanglement can be generated. Another interesting approach is to use an array of optomechanical transducers in which the output fields of one transducer are fed into the input of the next. The periodicity of the array results in a joint dispersion relation for the propagating microwave and optical fields. The resulting structure can be used to control the conversion bandwidth and forward and backward scattering.

Acoustic levitator for structure measurements on low temperature liquid droplets

NASA Astrophysics Data System (ADS)

Weber, J. K. R.; Rey, C. A.; Neuefeind, J.; Benmore, C. J.

2009-08-01

A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 °C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of ˜22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

Transducer selection and application in magnetoacoustic tomography with magnetic induction

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

Zhou, Yuqi; Wang, Jiawei; Ma, Qingyu, E-mail: maqingyu@njnu.edu.cn

2016-03-07

As an acoustic receiver, transducer plays a vital role in signal acquisition and image reconstruction for magnetoacoustic tomography with magnetic induction (MAT-MI). In order to optimize signal acquisition, the expressions of acoustic pressure detection and waveform collection are theoretically studied based on the radiation theory of acoustic dipole and the reception pattern of transducer. Pressure distributions are simulated for a cylindrical phantom model using a planar piston transducer with different radii and bandwidths. The proposed theory is also verified by the experimental measurements of acoustic waveform detection for an aluminum foil cylinder. It is proved that acoustic pressure with sharpmore » and clear boundary peaks can be detected by the large-radius transducer with wide bandwidth, reflecting the differential of the induced Lorentz force accurately, which is helpful for precise conductivity reconstruction. To detect acoustic pressure with acceptable pressure amplitude, peak pressure ratio, amplitude ratio, and improved signal to noise ratio, the scanning radius of 5–10 times the radius of the object should be selected to improve the accuracy of image reconstruction. This study provides a theoretical and experimental basis for transducer selection and application in MAT-MI to obtain reconstructed images with improved resolution and definition.« less

The effect of oblateness and gravity darkening on the radiation driving in winds from rapidly rotating B stars

NASA Technical Reports Server (NTRS)

Cranmer, Steven R.; Owocki, Stanley P.

1995-01-01

We calculate the radiative driving force for winds around rapidly rotating oblate B stars, and we estimate the impact these forces should have on the production of a wind compressed disk. The effects of limb darkening, gravity darkening, oblateness, and an arbitrary wind velocity field are included in the computation of vector 'oblate finite disk' (OFD) factors, which depend on both radius and colatitude in the wind. The impact of limb darkening alone, with or without rotation, can increase the mass loss by as much as 10% over values computed using the standard uniformly bright spherical finite disk factor. For rapidly rotating stars, limb darkening makes 'sub-stellar' gravity darkening the dominant effect in the radial and latitudinal OFD factors, and lessens the impact of gravity darkening at other visible latitudes (nearer to the oblate limb). Thus, the radial radiative driving is generally stronger over the poles and weaker over the equator, following the gravity darkening at these latitudes. The nonradial radiative driving is considerably smaller in magnitude than the radial component, but is directed both away from the equatorial plane and in a retrograde azimuthal direction, acting to decrease the effective stellar rotation velocity. These forces thus weaken the equatorward wind compression compared to wind models computed with nonrotating finite disk factors.

Unstructured High-Order Galerkin-Temporal- Boundary Methods for the Klein-Gordon Equation with Non-Reflecting Boundary Conditions

DTIC Science & Technology

2010-06-01

9 C. Conservation of Momentum . . . . . . . . . . . . . . . . . . . . . 11 1. Gravity Effects . . . . . . . . . . . . . . . . . . . . . . . . . 12 2...describe the high-order spectral element method used to discretize the problem in space (up to 16th order polynomials ) in Chapter IV. Chapter V discusses...inertial frame. Body forces are those acting on the fluid volume that are proportional to the mass. The body forces considered here are gravity and

Dynamic regimes of buoyancy-affected two-phase flow in unconsolidated porous media.

PubMed

Stöhr, M; Khalili, A

2006-03-01

The invasion and subsequent flow of a nonwetting fluid (NWF) in a three-dimensional, unconsolidated porous medium saturated with a wetting fluid of higher density and viscosity have been studied experimentally using a light-transmission technique. Distinct dynamic regimes have been found for different relative magnitudes of viscous, capillary, and gravity forces. It is shown that the ratio of viscous and hydrostatic pressure gradients can be used as a relevant dimensionless number K for the characterization of the different flow regimes. For low values of K, the invasion is characterized by the migration and fragmentation of isolated clusters of the NWF resulting from the prevalence of gravity and capillary forces. At high values of K, the dominance of viscous and gravity forces leads to an anisotropic fingerlike invasion. When the invasion stops after the breakthrough of the NWF at the open upper boundary, the invasion structure retracts under the influence of gravity and transforms into stable vertical channels. It is shown that the stability of these channels is the result of a balance between hydrostatic and viscous pressure gradients.

Plasma Component of Self-gravitating Disks and Relevant Magnetic Configurations

NASA Astrophysics Data System (ADS)

Bertin, G.; Coppi, B.

2006-04-01

Astrophysical disks in which the disk self-gravity is more important than the gravity force associated with the central object can have significant plasma components where appreciable toroidal current densities are produced. When the vertical confinement of the plasma rotating structures that can form is kept by the Lorentz force rather than by the vertical component of the gravity force, the disk self-gravity remains important only in the radial equilibrium condition, modifying the rotation curve from the commonly considered Keplerian rotation. The equilibrium equations that are solved involve the vertical and the horizontal components of the total momentum conservation equations, coupled with the lowest order form of the gravitational Poisson's equation. The resulting poloidal field configuration can be visualized as a sequence [1] of Field Reverse Configurations, in the radial direction, consisting of pairs of oppositely directed current channels. The plasma density thus acquires a significant radial modulation that may grow to the point where plasma rings can form [2]. [1] B. Coppi, Phys. Plasmas, 12, 057302 (2005) [2] B. Coppi and F. Rousseau, to be published in Astrophys. J. (April 2006)

Ensemble average theory of gravity

NASA Astrophysics Data System (ADS)

Khosravi, Nima

2016-12-01

We put forward the idea that all the theoretically consistent models of gravity have contributions to the observed gravity interaction. In this formulation, each model comes with its own Euclidean path-integral weight where general relativity (GR) has automatically the maximum weight in high-curvature regions. We employ this idea in the framework of Lovelock models and show that in four dimensions the result is a specific form of the f (R ,G ) model. This specific f (R ,G ) satisfies the stability conditions and possesses self-accelerating solutions. Our model is consistent with the local tests of gravity since its behavior is the same as in GR for the high-curvature regime. In the low-curvature regime the gravitational force is weaker than in GR, which can be interpreted as the existence of a repulsive fifth force for very large scales. Interestingly, there is an intermediate-curvature regime where the gravitational force is stronger in our model compared to GR. The different behavior of our model in comparison with GR in both low- and intermediate-curvature regimes makes it observationally distinguishable from Λ CDM .

A novel experimental mechanics method for measuring the light pressure acting on a solar sail membrane

NASA Astrophysics Data System (ADS)

Shi, Aiming; Jiang, Li; Dowell, Earl H.; Qin, Zhixuan

2017-02-01

Solar sail is a high potential `sailing craft' for interstellar exploration. The area of the first flight solar sail demonstrator named "IKAROS" is 200 square meters. Future interplanetary missions will require solar sails at least on the order of 10000 square meters (or larger). Due to the limitation of ground facilities, the size of experimental sample should not be large. Furthermore the ground experiments have to be conducted in gravitational field, so the gravity effect must be considered in a ground test. To obtain insight into the solar sail membrane dynamics, a key membrane flutter (or limit cycle oscillations) experiment with light forces acting on it must be done. But one big challenge is calibrating such a tiny light force by as a function of the input power. In this paper, a gravity-based measuring method for light pressure acting on membrane is presented. To explain the experimental principle, an ideal example of a laser beam with expanders and a metal film is studied. Based on calculations, this experimental mechanics method for calibrating light pressure with an accuracy of 0.01 micro-Newton may be realized by making the light force balance the gravity force on the metal films. This gravity-based measuring method could not only be applied to study the dynamics characteristics of solar sail membrane structure with different light forces, but could also be used to determine more accurate light forces/loads acting on solar sail films and hence to enhance the determination of the mechanical properties of the solar sail membrane structure.

Influence of Berdan and Boxer Primer Spit-Hole Diameter on 7.62-mm Cartridge Performance

DTIC Science & Technology

2014-06-01

pressure transducer, Kistler Model 6215 (4), is consistent with previous experiments. Pressure is measured through a 3/32-in hole drilled into the...cartridge case forward of the midpoint, and case holes are sealed with 1-mil- thick DuPont Kapton* tape. The force transducer selected is the Kistler ...April 1986. 3. M14 Barrel, Drawing 7790190, Rev R, January 1986. 4. Kistler Operating Instructions, Quartz High-Pressure Sensor Type 6215, Kistler

Techniques For Mass Production Of Tunneling Electrodes

NASA Technical Reports Server (NTRS)

Kenny, Thomas W.; Podosek, Judith A.; Reynolds, Joseph K.; Rockstad, Howard K.; Vote, Erika C.; Kaiser, William J.

1993-01-01

Techniques for mass production of tunneling electrodes developed from silicon-micromachining, lithographic patterning, and related microfabrication processes. Tunneling electrodes named because electrons travel between them by quantum-mechanical tunneling; tunneling electrodes integral parts of tunneling transducer/sensors, which act in conjunction with feedback circuitry to stabilize tunneling currents by maintaining electrode separations of order of 10 Angstrom. Essential parts of scanning tunneling microscopes and related instruments, and used as force and position transducers in novel microscopic accelerometers and infrared detectors.

The dynamical simulation of transient three-dimensional cryogenic liquid sloshing oscillations under low-gravity and microgravity

NASA Astrophysics Data System (ADS)

Chi, Yong Mann

A numerical simulation model has been developed for the dynamical behavior of spacecraft propellant, both during the draining and the closing of the tank outlet at the onset of suction dip affected by the asymmetric combined gravity gradient and gravity jitter accelerations. In particular the effect of the surface tension of the fluids in the partially filled dewar (applicable to the Gravity Probe-B spacecraft dewar tank and fuel tanks for a liquid rocket) with rotation has been simulated and investigated. Two different cases of accelerations, one with gravity jitter dominated and the other equally weighted between gravity gradient and gravity jitter accelerations, are studied. In the development of this numerical simulation model, the NASA-VOF3D has been used as a supplement to the numerical program of this dissertation. The NASA-VOF3D code has been used for performing the three-dimensional incompressible flows with free surface. This is also used for controlling liquid sloshing inside the tank when the spacecraft is orbiting. To keep track of the location of the liquid, the fractional volume of fluid (VOF) technique was used. The VOF is based on the indicator function of the region occupied by the liquid with an Eulerian approach to solve the free surface phenomena between liquid and gas phases. For the calculation of surface tension force, the VOF model is also used. The newly developed simulation model is used to investigate the characteristics of liquid hydrogen draining in terms of the residual amount of trapped liquid at the onset of the suction dip and residual liquid volume at the time the dip of the liquid-vapor interface formed. This investigation simulates the characteristics of liquid oscillations due to liquid container outlet shut-off at the onset of suction dip. These phenomena checked how these mechanisms affected the excitation of slosh waves during the course of liquid draining and after shut-off tank outlet. In the present study, the dynamical evolution of sloshing dynamics excited by fluid stress forces, fluid stress moments, and the arm of fluid moment exerted on the dewar container, is considered. This excitation was driven by the combined gravity gradient and gravity jitter acceleration inside the tank during the draining process and closing the tank outlet. The time evolution of the liquid-vapor interface profiles and the bubble mass center fluctuation, as well as liquid mass center and fluctuations of angular momentum caused by slosh wave excitations with 0.1 rpm in a reduced gravity, are also investigated and simulated. Force, angular momentum, and torque vector time histories and Power Spectral Density (PSD) are also plotted and discussed. The results of this investigation may be applied to determine the magnitude and nature of control forces and torques needed to minimize influence of slosh on the dynamics of liquid fueled vehicles in near earth orbit. Results show that induced fluid forces (or angular momentum) exerted on the container wall along x and y-axes, which are non-existent at the beginning, are introduced by the slosh waves excited by asymmetric gravity gradient and the gravity jitter acceleration.

Real-time Focused Ultrasound Surgery (FUS) Monitoring Using Harmonic Motion Imaging (HMI)

NASA Astrophysics Data System (ADS)

Maleke, Caroline; Konofagou, Elisa E.

2009-04-01

Monitoring changes in tissue mechanical properties to optimally control thermal exposure is important in thermal therapies. The amplitude-modulated (AM) harmonic motion imaging (HMI) for focused ultrasound (HMIFU) technique is a radiation force technique, which has the capability of tracking tissue stiffness during application of an oscillatory force. The feasibility of HMIFU for assessing mechanical tissue properties has been previously demonstrated. In this paper, a confocal transducer, combining a 4.5 MHz FUS transducer and a 3.3 MHz phased array imaging transducer, was used. The FUS transducer was driven by AM wave at 15 Hz with an acoustic intensity (Ispta) was equal to 1050 W/cm2. A lowpass digital filter was used to remove the spectrum of the higher power beam prior to displacement estimation. The resulting axial tissue displacement was estimated using 1D cross-correlation with a correlation window of 2 mm and a 92.5% overlap. A thermocouple was also used to measure the temperature near the ablated region. 2D HMI-images from six-bovine-liver specimens indicated the onset of coagulation necrosis through changes in amplitude displacement after coagulation due to its simultaneous probing and heating capability. The HMI technique can thus be used to monitor temperature-related stiffness changes of tissues during thermal therapies in real-time, i.e., without interrupting or modifying the treatment protocol.

Real-time Focused Ultrasound Surgery (FUS) Monitoring Using Harmonic Motion Imaging (HMI)

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

Maleke, Caroline; Konofagou, Elisa E.; Department of Radiology, Columbia University, New York, NY

2009-04-14

Monitoring changes in tissue mechanical properties to optimally control thermal exposure is important in thermal therapies. The amplitude-modulated (AM) harmonic motion imaging (HMI) for focused ultrasound (HMIFU) technique is a radiation force technique, which has the capability of tracking tissue stiffness during application of an oscillatory force. The feasibility of HMIFU for assessing mechanical tissue properties has been previously demonstrated. In this paper, a confocal transducer, combining a 4.5 MHz FUS transducer and a 3.3 MHz phased array imaging transducer, was used. The FUS transducer was driven by AM wave at 15 Hz with an acoustic intensity (I{sub spta}) wasmore » equal to 1050 W/cm{sup 2}. A lowpass digital filter was used to remove the spectrum of the higher power beam prior to displacement estimation. The resulting axial tissue displacement was estimated using 1D cross-correlation with a correlation window of 2 mm and a 92.5% overlap. A thermocouple was also used to measure the temperature near the ablated region. 2D HMI-images from six-bovine-liver specimens indicated the onset of coagulation necrosis through changes in amplitude displacement after coagulation due to its simultaneous probing and heating capability. The HMI technique can thus be used to monitor temperature-related stiffness changes of tissues during thermal therapies in real-time, i.e., without interrupting or modifying the treatment protocol.« less

Hybrid gravity survey to search for submarine ore deposit

NASA Astrophysics Data System (ADS)

Araya, A.; Kanazawa, T.; Fujimoto, H.; Shinohara, M.; Yamada, T.; Mochizuki, K.; Iizasa, K.; Ishihara, T.; Omika, S.

2011-12-01

Along with seismic surveys, gravity survey is a useful method to profile the underground density structure. We propose a hybrid gravity survey using gravimeters and gravity gradiometers to detect submarine ore deposits as density anomalies by towing the instruments using an AUV (Autonomous Underwater Vehicle) or an ROV (Remotely Operated Vehicle). Gravimeters measure the regional density structure below the seafloor, whereas gravity gradiometers are sensitive to localized mass distribution. A gravity gradiometer comprises two accelerometers arranged with a vertical separation, and a gravity gradient can be obtained from the acceleration difference. Compared to gravimeters, gravity gradiometers are insensitive to common disturbances such as parallel acceleration, thermal drift, and apparent gravity effect (Eötvös effect). We made two accelerometers using astatic pendulums, and obtained common acceleration reduction more than two orders of magnitude. With these pendulums of 500-mm separation, resolution of 7E (=7x10^{-9}(1/s^2)), enough to detect a typical ore deposit buried 50m below the seafloor, was evaluated. During measurements using a submersible mobile object, instrument orientation is required to be controlled to keep verticality and to reduce centrifugal force associated with rotation of the instrument. Using a gyro and a tiltmeter, angular rotation was shown to be controlled within 0.001deg/s which corresponds to 0.3E in effective gravity gradient due to the centrifugal force. In this paper, target of this research, details of the instruments and their performance, and development for the submarine gravity survey using an AUV will be presented.

Equivalent mechanical model of large-amplitude liquid sloshing under time-dependent lateral excitations in low-gravity conditions

NASA Astrophysics Data System (ADS)

Nan, Miao; Junfeng, Li; Tianshu, Wang

2017-01-01

Subjected to external lateral excitations, large-amplitude sloshing may take place in propellant tanks, especially for spacecraft in low-gravity conditions, such as landers in the process of hover and obstacle avoidance during lunar soft landing. Due to lateral force of the order of gravity in magnitude, the amplitude of liquid sloshing becomes too big for the traditional equivalent model to be accurate. Therefore, a new equivalent mechanical model, denominated the "composite model", that can address large-amplitude lateral sloshing in partially filled spherical tanks is established in this paper, with both translational and rotational excitations considered. The hypothesis of liquid equilibrium position following equivalent gravity is first proposed. By decomposing the large-amplitude motion of a liquid into bulk motion following the equivalent gravity and additional small-amplitude sloshing, a better simulation of large-amplitude liquid sloshing is presented. The effectiveness and accuracy of the model are verified by comparing the slosh forces and moments to results of the traditional model and CFD software.

Comparison of Gait During Treadmill Exercise While Supine in Lower Body Negative Pressure (LBNP), Supine with Bungee Resistance and Upright in Normal Gravity

NASA Technical Reports Server (NTRS)

Boda, Wanda; Hargens, Alan R.; Aratow, Michael; Ballard, Richard E.; Hutchinson, Karen; Murthy, Gita; Campbell, James

1994-01-01

The purpose of this study is to compare footward forces, gait kinematics, and muscle activation patterns (EMG) generated during supine treadmill exercise against LBNP with the same parameters during supine bungee resistance exercise and upright treadmill exercise. We hypothesize that the three conditions will be similar. These results will help validate treadmill exercise during LBNP as a viable technique to simulate gravity during space flight. We are evaluating LBNP as a means to load the musculoskeletal and cardiovascular systems without gravity. Such loading should help prevent physiologic deconditioning during space flight. The best ground-based simulation of LBNP treadmill exercise in microgravity is supine LBNP treadmill exercise on Earth because the supine footward force vector is neither directed nor supplemented by Earth's gravity.

Lateral bending of tapered piezo-semiconductive nanostructures for ultra-sensitive mechanical force to voltage conversion.

PubMed

Araneo, Rodolfo; Falconi, Christian

2013-07-05

Quasi-1D piezoelectric nanostructures may offer unprecedented sensitivity for transducing minuscule input mechanical forces into high output voltages due to both scaling laws and increased piezoelectric coefficients. However, until now both theoretical and experimental studies have suggested that, for a given mechanical force, lateral bending of piezoelectric nanowires results in lower output electric potentials than vertical compression. Here we demonstrate that this result only applies to nanostructures with a constant cross-section. Moreover, though it is commonly believed that the output electric potential of a strained piezo-semiconductive device can only be reduced by the presence of free charges, we show that the output piezopotential of laterally bent tapered nanostructures, with typical doping levels and very small input forces, can be even increased up to two times by free charges.Our analyses confirm that, though not optimal for piezoelectric energy harvesting, lateral bending of tapered nanostructures with typical doping levels can be ideal for transducing tiny input mechanical forces into high and accessible piezopotentials. Our results provide guidelines for designing high-performance piezo-nano-devices for energy harvesting, mechanical sensing, piezotronics, piezo-phototronics, and piezo-controlled chemical reactions, among others.

Light-regulated root gravitropism: a role for, and characterization of, a calcium/calmodulin-dependent protein kinase homolog

NASA Technical Reports Server (NTRS)

Lu, Y. T.; Feldman, L. J.

1997-01-01

Roots of many species grow downward (orthogravitropism) only when illuminated. Previous work suggests that this is a calcium-regulated response and that both calmodulin and calcium/calmodulin-dependent kinases participate in transducing gravity and light stimuli. A genomic sequence has been obtained for a calcium/calmodulin-dependent kinase homolog (MCK1) expressed in root caps, the site of perception for both light and gravity. This homolog consists of 7265 base pairs and contains 11 exons and 10 introns. Since MCK1 is expressed constitutively in both light and dark, it is unlikely that the light directly affects MCK1 expression, though the activity of the protein may be affected by light. In cultivars showing light-regulated gravitropism, we hypothesize that MCK1, or a homolog, functions in establishing the auxin asymmetry necessary for orthogravitropism.

Compact Tactile Sensors for Robot Fingers

NASA Technical Reports Server (NTRS)

Martin, Toby B.; Lussy, David; Gaudiano, Frank; Hulse, Aaron; Diftler, Myron A.; Rodriguez, Dagoberto; Bielski, Paul; Butzer, Melisa

2004-01-01

Compact transducer arrays that measure spatial distributions of force or pressure have been demonstrated as prototypes of tactile sensors to be mounted on fingers and palms of dexterous robot hands. The pressure- or force-distribution feedback provided by these sensors is essential for the further development and implementation of robot-control capabilities for humanlike grasping and manipulation.

The Effects of Partial Mechanical Loading and Ibandronate on Skeletal Tissues in the Adult Rat Hindquarter Suspension Model for Microgravity

NASA Technical Reports Server (NTRS)

Schultheis, Lester W.

1999-01-01

We report initial data from a suspended rat model that quantitatively relates chronic partial weightbearing to bone loss. Chronic partial weightbearing is our simulation of the effect of limited artificial gravity aboard spacecraft or reduced planetary gravity. Preliminary analysis of bone by PQCT, histomorphometry, mechanical testing and biochemistry suggest that chronic exposure to half of Earth gravity is insufficient to prevent severe bone loss. The effect of episodic full weightbearing activity (Earth Gravity) on rats otherwise at 50% weightbearing was also explored. This has similarity to treatment by an Earth G-rated centrifuge on a spacecraft that normally maintained artificial gravity at half of Earth G. Our preliminary evidence, using the above techniques to analyze bone, indicate that 2 hours daily of full weightbearing was insufficient to prevent the bone loss observed in 50% weightbearing animals. The effectiveness of partial weightbearing and episodic full weightbearing as potential countermeasures to bone loss in spaceflight was compared with treatment by ibandronate. Ibandronate, a long-acting potent bisphosphonate proved more effective in preventing bone loss and associated functionality based upon structure than our first efforts at mechanical countermeasures. The effectiveness of ibandronate was notable by each of the testing methods we used to study bone from gross structure and strength to tissue and biochemistry. These results appear to be independent of generalized systemic stress imposed by the suspension paradigm. Preliminary evidence does not suggest that blood levels of vitamin D were affected by our countermeasures. Despite the modest theraputic benefit of mechanical countermeasures of partial weightbearing and episodic full weightbearing, we know that some appropriate mechanical signal maintains bone mass in Earth gravity. Moreover, the only mechanism that correctly assigns bone mass and strength to oppose regionally specific force applied to bone is mechanical, a process based upon bone strain. Substantial evidence indicates that the specifics of dynamic loading i.e. time-varying forces are critical. Bone strain history is a predictor of the effect that mechanical conditions have on bone structure mass and strength. Using servo-controlled force plates on suspended rats with implanted strain gauges we manipulated impact forces of ambulation in the frequency (Fourier) domain. Our results indicate that high frequency components of impact forces are particularly potent in producing bone strain independent of the magnitude of the peak force or peak energy applied to the leg. Because a servo-system responds to forces produced by the rat's own muscle activity during ambulation, the direction of ground-reaction loads act on bone through the rat's own musculature. This is in distinction to passive vibration of the floor where forces reach bone through the natural filters of soft tissue and joints. Passive vibration may also be effective, but it may or may not increase bone in the appropriate architectural pattern to oppose the forces of normal ambulatory activity. Effectiveness of high frequency mechanical stimulation in producing regional (muscle directed) bone response will be limited by 1. the sensitivity of bone to a particular range of frequencies and 2. the inertia of the muscles, limiting their response to external forces by increasing tension along insertions. We have begun mathematical modeling of normal ambulatory activity. Effectiveness of high frequency mechanical stimulation in producing regional (muscle directed) bone response will be limited by 1. the sensitivity of bone to a particular range of frequencies and 2. the inertia of the muscles, limiting their response to external forces by increasing tension along insertions. We have begun mathematical modeling of the rat forelimb as a transfer function between impact force and bone strain to predict optimal dynamic loading conditions for this system. We plan additional studies of mechanical counter-measures that incorporate improved dynamic loading, features relevant to anticipated evaluation of artificial gravity, exercise regimens and exposure to Martian gravity, The combination of mechanical countermeasures with ibandronate will also be investigated for signs of synergy.

The Investigation of the Effects of Gravity on Single Bubble Sonoluminescence

NASA Technical Reports Server (NTRS)

Dzikowicz, Ben; Thiessen, David B.; Marston, Philip

2000-01-01

In single bubble following it's rapid collapse each cycle of oscillation of an ultrasonic field. Since widely varying length and time scales affect the bubble dynamics and optical emission processes, it is difficult to anticipate the importance of the effects of gravity present for observations on earth. Our bubble is driven in an acoustically resonating cavity at it's first harmonic mode. The acoustical radiation pressure (Bjerknes force) will then keep it suspended in the center near the pressure antinode. When driven in a region where the diffusive processes balance the bubble it acts in a nonlinear but regular way, emitting a short (approx. 200ps) burst of light each acoustic cycle. Balancing the Bjerknes force with buoyancy, as in, we can see that the bubble should be displaced from the velocity node approximately 20m at normal gravity. Therefore, water flows past the bubble at the time of collapse. Gravitation also changes the ambient pressure at the bubble's location, as Delta.P = rho.g.h this gives a change of approximately -0.5% in our experiment when going from 1.8g to 0g. Studies of ambient pressure changes were also done in order to assess these effects. Inside a pressure sealed chamber a spherical glass cell is filled with distilled water which has been degassed to 120mmHg. A bubble is then trapped in the center and driven by a piezoelectric transducer at 32.2kHz attached to the side of the cell. An optical system is then set up to take strobbed video images along and light emission data simultaneously. Temperature, pressure, drive voltage, and listener voltage are also monitored. PMT output in Volts The radii of the bubbles for both experiment s are fit using the Rayleigh-Plesset equation and the acoustic drive amplitude and the ambient bubble radius are found. There is little change in the acoustic drive amplitude as we expect, since we are not varying the drive voltage. However. the ambient bubble radius goes up considerably. These changes (increased light output, increased maximum bubble radius, and increased ambient bubble radius) are also observed when the ambient pressure is varied in the laboratory by an amount similar to that due to gravitation. The changes in the ambient bubble radius and light output with a change in ambient pressure are predicted by the "dissociation hypothesis" and have been observed by other groups in the laboratory. It seems clear that buoyancy's effect on light output and bubble radius, are at best on the same order as the effects of ambient pressure.

Postural hypotension and the anti-gravity suit.

PubMed

Brook, W H

1994-10-01

An air force anti-gravity suit, as used by fighter pilots to prevent loss of consciousness, has been successfully employed to treat severe postural hypotension in a patient with Shy-Drager syndrome. The definition of postural hypotension is reviewed, and reference is made to the previous use of the anti-gravity suit in the treatment of this condition.

The "Gravity-Powered Calculator," a Galilean Exhibit

ERIC Educational Resources Information Center

Cerreta, Pietro

2014-01-01

The Gravity-Powered Calculator is an exhibit of the Exploratorium in San Francisco. It is presented by its American creators as an amazing device that extracts the square roots of numbers, using only the force of gravity. But if you analyze his concept construction one can not help but recall the research of Galileo on falling bodies, the inclined…

jsc2018m000256_Rooting_for_Answers

NASA Image and Video Library

2018-03-22

Rooting for Answers: Simulating G-Force in Plants---------On Earth, plants use gravity and light to orient their roots and shoots, but in space, microgravity is too weak to provide a growth cue. The Gravity Perception Systems (Plant Gravity Perception) investigation germinates normal and variant forms of thale cress, a model research plant, to study the plants’ gravity and light perception. Results provide new information about plants’ ability to detect gravity and adapt to an environment without it. The investigation continues efforts to grow plants for food on future missions.

Why do things fall? How to explain why gravity is not a force

NASA Astrophysics Data System (ADS)

Stannard, Warren B.

2018-03-01

In most high school physics classes, gravity is described as an attractive force between two masses as formulated by Newton over 300 years ago. Einstein’s general theory of relativity implies that gravitational effects are instead the result of a ‘curvature’ of space-time. However, explaining why things fall without resorting to Newton’s gravitational force can be difficult. This paper introduces some simple graphical and visual analogies and models which are suitable for the introduction of Einstein’s theory of general relativity at a high school level. These models provide an alternative to Newton’s gravitational force and help answer the simple question: why do things fall?

The Kadomtsev-Petviashvili equation under rapid forcing

NASA Astrophysics Data System (ADS)

Moroz, Irene M.

1997-06-01

We consider the initial value problem for the forced Kadomtsev-Petviashvili equation (KP) when the forcing is assumed to be fast compared to the evolution of the unforced equation. This suggests the introduction of two time scales. Solutions to the forced KP are sought by expanding the dependent variable in powers of a small parameter, which is inversely related to the forcing time scale. The unforced system describes weakly nonlinear, weakly dispersive, weakly two-dimensional wave propagation and is studied in two forms, depending upon whether gravity dominates surface tension or vice versa. We focus on the effect that the forcing has on the one-lump solution to the KPI equation (where surface tension dominates) and on the one- and two-line soliton solutions to the KPII equation (when gravity dominates). Solutions to second order in the expansion are computed analytically for some specific choices of the forcing function, which are related to the choice of initial data.

Method and apparatus for determining material structural integrity

DOEpatents

Pechersky, Martin

1996-01-01

A non-destructive method and apparatus for determining the structural integrity of materials by combining laser vibrometry with damping analysis techniques to determine the damping loss factor of a material. The method comprises the steps of vibrating the area being tested over a known frequency range and measuring vibrational force and velocity as a function of time over the known frequency range. Vibrational velocity is preferably measured by a laser vibrometer. Measurement of the vibrational force depends on the vibration method. If an electromagnetic coil is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by the amount of coil current used in vibrating the magnet. If a reciprocating transducer is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by a force gauge in the reciprocating transducer. Using known vibrational analysis methods, a plot of the drive point mobility of the material over the preselected frequency range is generated from the vibrational force and velocity measurements. The damping loss factor is derived from a plot of the drive point mobility over the preselected frequency range using the resonance dwell method and compared with a reference damping loss factor for structural integrity evaluation.

Material test machine for tension-compression tests at high temperature

DOEpatents

Cioletti, Olisse C.

1988-01-01

Apparatus providing a device for testing the properties of material specimens at high temperatures and pressures in controlled water chemistries includes, inter alia, an autoclave housing the specimen which is being tested. The specimen is connected to a pull rod which couples out of the autoclave to an external assembly which includes one or more transducers, a force balance chamber and a piston type actuator. The pull rod feeds through the force balance chamber and is compensated thereby for the pressure conditions existing within the autoclave and tending to eject the pull rod therefrom. The upper end of the push rod is connected to the actuator through elements containing a transducer comprising a linear variable differential transformer (LVDT). The housing and coil assembly of the LVDT is coupled to a tube which runs through a central bore of the pull rod into the autoclave where it is connected to one side of the specimen. The movable core of the LVDT is coupled to a stem which runs through the tube where it is then connected to the other side of the specimen through a coupling member. A transducer in the form of a load cell including one or more strain gages is located on a necked-down portion of the upper part of the pull rod intermediate the LVDT and force balance chamber.

Measurement of total ultrasonic power using thermal expansion and change in buoyancy of an absorbing target

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

Dubey, P. K., E-mail: premkdubey@gmail.com; Kumar, Yudhisther; Gupta, Reeta

2014-05-15

The Radiation Force Balance (RFB) technique is well established and most widely used for the measurement of total ultrasonic power radiated by ultrasonic transducer. The technique is used as a primary standard for calibration of ultrasonic transducers with relatively fair uncertainty in the low power (below 1 W) regime. In this technique, uncertainty comparatively increases in the range of few watts wherein the effects such as thermal heating of the target, cavitations, and acoustic streaming dominate. In addition, error in the measurement of ultrasonic power is also caused due to movement of absorber at relatively high radiated force which occursmore » at high power level. In this article a new technique is proposed which does not measure the balance output during transducer energized state as done in RFB. It utilizes the change in buoyancy of the absorbing target due to local thermal heating. The linear thermal expansion of the target changes the apparent mass in water due to buoyancy change. This forms the basis for the measurement of ultrasonic power particularly in watts range. The proposed method comparatively reduces uncertainty caused by various ultrasonic effects that occur at high power such as overshoot due to momentum of target at higher radiated force. The functionality of the technique has been tested and compared with the existing internationally recommended RFB technique.« less

Measurement of total ultrasonic power using thermal expansion and change in buoyancy of an absorbing target

NASA Astrophysics Data System (ADS)

Dubey, P. K.; Kumar, Yudhisther; Gupta, Reeta; Jain, Anshul; Gohiya, Chandrashekhar

2014-05-01

The Radiation Force Balance (RFB) technique is well established and most widely used for the measurement of total ultrasonic power radiated by ultrasonic transducer. The technique is used as a primary standard for calibration of ultrasonic transducers with relatively fair uncertainty in the low power (below 1 W) regime. In this technique, uncertainty comparatively increases in the range of few watts wherein the effects such as thermal heating of the target, cavitations, and acoustic streaming dominate. In addition, error in the measurement of ultrasonic power is also caused due to movement of absorber at relatively high radiated force which occurs at high power level. In this article a new technique is proposed which does not measure the balance output during transducer energized state as done in RFB. It utilizes the change in buoyancy of the absorbing target due to local thermal heating. The linear thermal expansion of the target changes the apparent mass in water due to buoyancy change. This forms the basis for the measurement of ultrasonic power particularly in watts range. The proposed method comparatively reduces uncertainty caused by various ultrasonic effects that occur at high power such as overshoot due to momentum of target at higher radiated force. The functionality of the technique has been tested and compared with the existing internationally recommended RFB technique.

Mathematical modeling of the flow field and particle motion in a rotating bioreactor at unit gravity and microgravity

NASA Technical Reports Server (NTRS)

Boyd, Ernest J.

1990-01-01

The biotechnology group at NASA Johnson Space Center is developing systems for culturing mammalian cells that stimulate some aspect of microgravity and provide a low shear environment for microgravity-based studies on suspension and anchorage dependent cells. The design of these vessels for culturing cells is based on the need to suspend cells and aggregates of cells and microcarrier beads continually in the culturing medium. The design must also provide sufficient circulation for adequate mass transfer of nutrients to the cells and minimize the total force on the cells. Forces, resulting from sources such as hydrodynamic fluid shear and collisions of cells and walls of the vessels, may damage delicate cells and degrade the formation of three dimensional structures. This study examines one particular design in both unit gravity and microgravity based on two concentric cylinders rotating in the same direction at different speeds to create a Couette flow between them. A numerical simulation for the flow field and the trajectories of particles in the vessel. The flow field for the circulation of the culturing medium is modeled by the Navier-Stokes equations. The forces on a particle are assumed to be drag from the fluid's circulation, buoyancy from the gravitational force and centrifugal force from the rotation of the vessel. The problem requires first solving the system of partial differential equations for the fluid flow by a finite difference method and then solving the system of ordinary differential equations for the trajectories by Gear's stiff method. Results of the study indicate that the trajectories in unit gravity and microgravity are very similar except for small spatial deviations on the fast time scale in unit gravity. The total force per unit cross sectional area on a particle in microgravity, however, is significantly smaller than the corresponding value in unit gravity, which is also smaller than anticipated. Hence, this study indicates that this design for a bioreactor with optimal rates of rotation can provide a good environment for culturing cells in microgravity with adequate circulation and minimal force on the cells.

Longitudinal Variations of Low-Latitude Gravity Waves and Their Impacts on the Ionosphere

NASA Astrophysics Data System (ADS)

Cullens, C. Y.; England, S.; Immel, T. J.

2014-12-01

The lower atmospheric forcing has important roles in the ionospheric variability. However, influences of lower atmospheric gravity waves on the ionospheric variability are still not clear due to the simplified gravity wave parameterizations and the limited knowledge of gravity wave distributions. In this study, we aim to study the longitudinal variations of gravity waves and their impacts of longitudinal variations of low-latitude gravity waves on the ionospheric variability. Our SABER results show that longitudinal variations of gravity waves at the lower boundary of TIME-GCM are the largest in June-August and January-February. We have implemented these low-latitude gravity wave variations from SABER instrument into TIME-GCM model. TIME-GCM simulation results of ionospheric responses to longitudinal variations of gravity waves and physical mechanisms will be discussed.

Simulating reduced gravity: a review of biomechanical issues pertaining to human locomotion.

PubMed

Davis, B L; Cavanagh, P R

1993-06-01

In the decade preceding Apollo missions to the Moon, extensive studies were conducted on human locomotion in reduced gravity. These investigations focused primarily on issues of maneuverability and energy expenditure and not on musculoskeletal loading, which is of more interest to planners of long-duration space missions. The techniques have included water immersion, parabolic aircraft flights, supine and erect cable suspension and centrifugal methods. The practical implications of the findings from these studies are: 1) the present shuttle treadmill running surface would not suffice if one wanted to run with a natural style at levels greater than 0.6 G; 2) in terms of attempting to replicate typical ground reaction force profiles during locomotor exercise at reduced gravity levels, it appears as though it is easier to match the peak rates of change of force (maxDFDT) than it is to match values for the peak force magnitudes (maxGRF).

A visualization study on two-phase gravity drainage in porous media by using magnetic resonance imaging.

PubMed

Teng, Ying; Liu, Yu; Jiang, Lanlan; Song, Yongchen; Zhao, Jiafei; Zhang, Yi; Wang, Dayong

2016-09-01

Gravity drainage characteristics are important to improve our understanding of gas-liquid or liquid-liquid two-phase flow in porous media. Stable or unstable displacement fronts that controlled by the capillary force, viscous force, gravitational force, etc., are relevant features of immiscible two-phase flow. In this paper, three dimensionless parameters, namely, the gravity number, the capillary number and the Bond number, were used to describe the effect of the above mentioned forces on two-phase drainage features, including the displacement front and final displacing-phase saturation. A series of experiments on the downward displacement of a viscous fluid by a less viscous fluid in a vertical vessel that is filled with quartz beads are performed by using magnetic resonance imaging (MRI). The experimental results indicate that the wetting properties at both high and low capillary numbers exert remarkable control on the fluid displacement. When the contact angle is lower than 90°, i.e., the displaced phase is the wetting phase, the average velocity Vf of the interface of the two phases (displacement front velocity) is observably lower than when the displaced phase is the non-wetting phase (contact angle higher than 90°). The results show that a fingering phenomenon occurs when the gravity number G is less than the critical gravity number G'=Δμ/μg. Moreover, the higher Bond number results in higher final displacing-phase saturation, whereas the capillary number has an opposite effect. Copyright © 2016 Elsevier Inc. All rights reserved.

Mass Wasting

NASA Image and Video Library

2011-12-06

Mass Wasting is the term given to the process of change on a surface due to gravity things moving downhill due to the force of gravity. Dark streaks mark the slopes of craters and hills in this region of Amazonis Planitia.

14 CFR 29.733 - Tires.

Code of Federal Regulations, 2013 CFR

2013-01-01

... static ground reaction corresponding to the critical center of gravity; and (3) A load on nose wheel... gravity and exerts a force of 1.0 g downward and 0.25 g forward, the reactions being distributed to the...

14 CFR 29.733 - Tires.

Code of Federal Regulations, 2012 CFR

2012-01-01

... static ground reaction corresponding to the critical center of gravity; and (3) A load on nose wheel... gravity and exerts a force of 1.0 g downward and 0.25 g forward, the reactions being distributed to the...

Transducer-based evaluation of tremor.

PubMed

Haubenberger, Dietrich; Abbruzzese, Giovanni; Bain, Peter G; Bajaj, Nin; Benito-León, Julián; Bhatia, Kailash P; Deuschl, Günther; Forjaz, Maria João; Hallett, Mark; Louis, Elan D; Lyons, Kelly E; Mestre, Tiago A; Raethjen, Jan; Stamelou, Maria; Tan, Eng-King; Testa, Claudia M; Elble, Rodger J

2016-09-01

The International Parkinson and Movement Disorder Society established a task force on tremor that reviewed the use of transducer-based measures in the quantification and characterization of tremor. Studies of accelerometry, electromyography, activity monitoring, gyroscopy, digitizing tablet-based measures, vocal acoustic analysis, and several other transducer-based methods were identified by searching PubMed.gov. The availability, use, acceptability, reliability, validity, and responsiveness were reviewed for each measure using the following criteria: (1) used in the assessment of tremor; (2) used in published studies by people other than the developers; and (3) adequate clinimetric testing. Accelerometry, gyroscopy, electromyography, and digitizing tablet-based measures fulfilled all three criteria. Compared to rating scales, transducers are far more sensitive to changes in tremor amplitude and frequency, but they do not appear to be more capable of detecting a change that exceeds random variability in tremor amplitude (minimum detectable change). The use of transducer-based measures requires careful attention to their limitations and validity in a particular clinical or research setting. © 2016 International Parkinson and Movement Disorder Society. © 2016 International Parkinson and Movement Disorder Society.

On the effect of pressure, oxygen concentration, air flow and gravity on simulated pool fires

NASA Technical Reports Server (NTRS)

Torero, J. L.; Most, J. M.; Joulain, P.

1995-01-01

The initial development of a fire is characterized by the establishment of a diffusion flame over the surface of a the condensed fuel and is particularly influenced by gravity, with most of the gaseous flow induced by natural convection. Low initial momentum of the fuel vapor, strong buoyant flows induced by the hot post-combustion gases and consequently low values of the Froude number (inertia-gravity forces ratio) are typical of this kind of scenario. An experimental study is conducted by using a porous burner to simulate the burning of a horizontal combustible surface. Ethane is used as fuel and different mixtures of oxygen and nitrogen as oxidizer. The magnitude of the fuel injection velocities is restricted to values that will keep the Froude number on the order of 10-5, when calculated at normal gravity and pressure, which are characteristic of condensed fuel burning. Two different burners are used, a circular burner (62 mm diameter) placed inside a cylindrical chamber (0.3 m diameter and 1.0 m height) and a rectangular burner (50 mm wide by 200 mm long) placed in a wind tunnel (350 mm long) of rectangular cross section (120 mm wide and 90 mm height). The first burner is used to study the effect of pressure and gravity in the absence of a forced flow parallel to the surface. The second burner is used to study the effect of a forced flow parallel to the burner surface as well as the effect of oxygen concentration in the oxidizer flow. In this case experiments are also conducted at different gravity levels (micro-gravity, 0.2 g(sub 0), g(sub 0) and 1.8 g(sub 0)) to quantify the relative importance of buoyancy.

Results from a U.S. Absolute Gravity Survey,

DTIC Science & Technology

1982-01-01

National Bureau of Standards. La . ... ,., 831A08 NOV -2- 1. Introduction We have recently completed an absolute gravity survey at twelve sites in the...Air Force Geophysics Laboratory (AFGL) and the Istituto di Metrologia -7- "G. Colonnetti" (IMGC) [Marson and Alasia, 1978, 19801. All three...for ab- solute measurements of the earth’s gravity, Metrologia , in press, 1982. L 4 !" Table 1. Gravity values transferred to the floor in gal (cm

Sensing And Force-Reflecting Exoskeleton

NASA Technical Reports Server (NTRS)

Eberman, Brian; Fontana, Richard; Marcus, Beth

1993-01-01

Sensing and force-reflecting exoskeleton (SAFiRE) provides control signals to robot hand and force feedback from robot hand to human operator. Operator makes robot hand touch objects gently and manipulates them finely without exerting excessive forces. Device attaches to operator's hand; comfortable and lightweight. Includes finger exoskeleton, cable mechanical transmission, two dc servomotors, partial thumb exoskeleton, harness, amplifier box, two computer circuit boards, and software. Transduces motion of index finger and thumb. Video monitor of associated computer displays image corresponding to motion.

Mechanics of a gaseous film barrier to lubricant wetting of elastohydrodynamically lubricated conjunctions

NASA Technical Reports Server (NTRS)

Prahl, J. M.; Hamrock, B. J.

1985-01-01

Two analytical models, one based on simple hydrodynamic lubrication and the other on soft elastohydrodynamic lubrication, are presented and compared to delineate the dominant physical parameters that govern the mechanics of a gaseous film between a small droplet of lubricant and the outer race of a ball bearing. Both models are based on the balance of gravity forces, air drag forces, and air film lubrication forces and incorporate a drag coefficient C sub D and a lubrication coefficient C sub L to be determined from experiment. The soft elastohydrodynamic lubrication (EHL) model considers the effects of droplet deformation and solid-surface geometry; the simpler hydrodynamic lubrication (HL) model assumes that the droplet remains essentially spherical. The droplet's angular position depended primarily on the ratio of gas inertia to droplet gravity forces and on the gas Reynolds number and weakly on the ratio of droplet gravity forces to surface tension forces (Bond number) and geometric ratios for the soft EHL. An experimental configuration in which an oil droplet is supported by an air film on the rotating outer race of a ball bearing within a pressure-controlled chamber produced measurements of droplet angular position as a function of outer-race velocity droplet size and type, and chamber pressure.

The mean Evershed flow

NASA Astrophysics Data System (ADS)

Hu, W.-R.

1984-09-01

The paper gives a theoretical analysis of the overall characteristics of the Evershed flow (one of the main features of sunspots), with particular attention given to its outward flow from the umbra in the photosphere, reaching a maximum somewhere in the penumbra, and decreasing rapidly further out, and its inward flow of a comparable magnitude in chromosphere. Because the inertial force of the flow is small, the relevant dynamic process can be divided into a base state and a perturbation. The base-state solution yields the equilibrium relations between the pressure gradient, the Lorentz force, and gravity, and the flow law. The perturbation describes the force driving the Evershed flow. Since the pressure gradient in the base state is already in equilibrium with the Lorentz force and the gravity, the driving force of the mean Evershed flow is small.

Energetic balance in an ultrasonic reactor using focused or flat high frequency transducers.

PubMed

Hallez, L; Touyeras, F; Hihn, J Y; Klima, J

2007-09-01

In order to undertake irradiation of polymer blocks or films by ultrasound, this paper deals with the measurements of ultrasonic power and its distribution within the cell by several methods. The electric power measured at the transducer input is compared to the ultrasonic power input to the cell evaluated by calorimetry and radiation force measurement for different generator settings. Results obtained in the specific case of new transducer types (composites and focused composites i.e., HIFU: high intensity focused ultrasound) provide an opportunity to conduct a discussion about measurement methods. It has thus been confirmed that these measurement techniques can be applied to HIFU transducers. For all cases, results underlined the fact that measurement of radiation pressure for power evaluation is more adapted to low powers (<15 W) and that measurement by calorimetry is a valid technique for global energy measurements. Composites and monocomponent transducers were compared and it appears that the presence of an adaptation glass plate reduces the efficiency of the monocomponent transducers. The distribution of ultrasonic intensity is qualitatively depicted by sono-chemiluminescence of luminol. Finally, the quantity of energy absorbed by samples placed in the sound field is determined and the temperature distribution monitored as a function of wall distance. This energetic balance allows us to understand the global behaviour of all experimental set-ups made up of a generator-transducer-liquid and sample.

Using Passive Two-Port Networks to Study the Forced Vibrations of Piezoceramic Transducers

NASA Astrophysics Data System (ADS)

Karlash, V. L.

2017-09-01

A generalization and subsequent development of experimental techniques, including methods of studying the phase-frequency relations between the measured components of admittance and instantaneous power are considered. The conditions of electric loading where electric currents, voltages, or instantaneous powers of constant amplitude in the piezoresonators are specified are numerically modeled. It is particularly established that the advanced Mason circuit with additional switch allows acquiring much more data on the forced vibrations of piezoceramic transducers than the classical circuit. The measured (at an arbitrary frequency) voltage drop across the piezoelement, its pull-up resistor, and at the input of the measuring circuit allow determining, with high accuracy, the current, conductivity, impedance, instantaneous power, and phase shifts when the amplitudes of electric current and voltage are given.

Atomic force microscope based on vertical silicon probes

NASA Astrophysics Data System (ADS)

Walter, Benjamin; Mairiaux, Estelle; Faucher, Marc

2017-06-01

A family of silicon micro-sensors for Atomic Force Microscope (AFM) is presented that allows to operate with integrated transducers from medium to high frequencies together with moderate stiffness constants. The sensors are based on Micro-Electro-Mechanical-Systems technology. The vertical design specifically enables a long tip to oscillate perpendicularly to the surface to be imaged. The tip is part of a resonator including quasi-flexural composite beams, and symmetrical transducers that can be used as piezoresistive detector and/or electro-thermal actuator. Two vertical probes (Vprobes) were operated up to 4.3 MHz with stiffness constants 150 N/m to 500 N/m and the capability to oscillate from 10 pm to 90 nm. AFM images of several samples both in amplitude modulation (tapping-mode) and in frequency modulation were obtained.

Industrial processes influenced by gravity

NASA Technical Reports Server (NTRS)

Ostrach, Simon

1988-01-01

In considering new directions for low gravity research with particular regard to broadening the number and types of industrial involvements, it is noted that transport phenomena play a vital role in diverse processes in the chemical, pharmaceutical, food, and biotech industries. Relatively little attention has been given to the role of gravity in such processes. Accordingly, numerous industrial processes and phenomena are identified which involve gravity and/or surface tension forces. Phase separations and mixing are examples that will be significantly different in low gravity conditions. A basis is presented for expanding the scope of the low gravity research program and the potential benefits of such research is indicated.

Scientific management and implementation of the geophysical fluid flow cell for Spacelab missions

NASA Technical Reports Server (NTRS)

Hart, J.; Toomre, J.

1980-01-01

Scientific support for the spherical convection experiment to be flown on Spacelab 3 was developed. This experiment takes advantage of the zero gravity environment of the orbiting space laboratory to conduct fundamental fluid flow studies concerned with thermally driven motions inside a rotating spherical shell with radial gravity. Such a system is a laboratory analog of large scale atmospheric and solar circulations. The radial body force necessary to model gravity correctly is obtained by using dielectric polarization forces in a radially varying electric field to produce radial accelerations proportional to temperature. This experiment will answer fundamental questions concerned with establishing the preferred modes of large scale motion in planetary and stellar atmospheres.

Force-sensed interface for control and training space robot

NASA Astrophysics Data System (ADS)

Moiseev, O. S.; Sarsadskikh, A. S.; Povalyaev, N. D.; Gorbunov, V. I.; Kulakov, F. M.; Vasilev, V. V.

2018-05-01

A method of positional and force-torque control of robots is proposed. Prototypes of the system and the master handle have been created. Algorithm of bias estimation and gravity compensation for force-torque sensor and force-torque trajectory correction are described.

Material fabrication using acoustic radiation forces

DOEpatents

Sinha, Naveen N.; Sinha, Dipen N.; Goddard, Gregory Russ

2015-12-01

Apparatus and methods for using acoustic radiation forces to order particles suspended in a host liquid are described. The particles may range in size from nanometers to millimeters, and may have any shape. The suspension is placed in an acoustic resonator cavity, and acoustical energy is supplied thereto using acoustic transducers. The resulting pattern may be fixed by using a solidifiable host liquid, forming thereby a solid material. Patterns may be quickly generated; typical times ranging from a few seconds to a few minutes. In a one-dimensional arrangement, parallel layers of particles are formed. With two and three dimensional transducer arrangements, more complex particle configurations are possible since different standing-wave patterns may be generated in the resonator. Fabrication of periodic structures, such as metamaterials, having periods tunable by varying the frequency of the acoustic waves, on surfaces or in bulk volume using acoustic radiation forces, provides great flexibility in the creation of new materials. Periodicities may range from millimeters to sub-micron distances, covering a large portion of the range for optical and acoustical metamaterials.

Nonlinear characterization of a single-axis acoustic levitator.

PubMed

Andrade, Marco A B; Ramos, Tiago S; Okina, Fábio T A; Adamowski, Julio C

2014-04-01

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jump phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.

Nonlinear characterization of a single-axis acoustic levitator

NASA Astrophysics Data System (ADS)

Andrade, Marco A. B.; Ramos, Tiago S.; Okina, Fábio T. A.; Adamowski, Julio C.

2014-04-01

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jump phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.

Gravity in a Mine Shaft.

ERIC Educational Resources Information Center

Hall, Peter M.; Hall, David J.

1995-01-01

Discusses the effects of gravity, local density compared to the density of the earth, the mine shaft, centrifugal force, and air buoyancy on the weight of an object at the top and at the bottom of a mine shaft. (JRH)

Inclination not force is sensed by plants during shoot gravitropism.

PubMed

Chauvet, Hugo; Pouliquen, Olivier; Forterre, Yoël; Legué, Valérie; Moulia, Bruno

2016-10-14

Gravity perception plays a key role in how plants develop and adapt to environmental changes. However, more than a century after the pioneering work of Darwin, little is known on the sensing mechanism. Using a centrifugal device combined with growth kinematics imaging, we show that shoot gravitropic responses to steady levels of gravity in four representative angiosperm species is independent of gravity intensity. All gravitropic responses tested are dependent only on the angle of inclination from the direction of gravity. We thus demonstrate that shoot gravitropism is stimulated by sensing inclination not gravitational force or acceleration as previously believed. This contrasts with the otolith system in the internal ear of vertebrates and explains the robustness of the control of growth direction by plants despite perturbations like wind shaking. Our results will help retarget the search for the molecular mechanism linking shifting statoliths to signal transduction.

Inclination not force is sensed by plants during shoot gravitropism

NASA Astrophysics Data System (ADS)

Chauvet, Hugo; Pouliquen, Olivier; Forterre, Yoël; Legué, Valérie; Moulia, Bruno

2016-10-01

Gravity perception plays a key role in how plants develop and adapt to environmental changes. However, more than a century after the pioneering work of Darwin, little is known on the sensing mechanism. Using a centrifugal device combined with growth kinematics imaging, we show that shoot gravitropic responses to steady levels of gravity in four representative angiosperm species is independent of gravity intensity. All gravitropic responses tested are dependent only on the angle of inclination from the direction of gravity. We thus demonstrate that shoot gravitropism is stimulated by sensing inclination not gravitational force or acceleration as previously believed. This contrasts with the otolith system in the internal ear of vertebrates and explains the robustness of the control of growth direction by plants despite perturbations like wind shaking. Our results will help retarget the search for the molecular mechanism linking shifting statoliths to signal transduction.

On the detection and attribution of gravity waves generated by the 20 March 2015 solar eclipse

PubMed Central

2016-01-01

Internal gravity waves are generated as adjustment radiation whenever a sudden change in forcing causes the atmosphere to depart from its large-scale balanced state. Such a forcing anomaly occurs during a solar eclipse, when the Moon’s shadow cools part of the Earth’s surface. The resulting atmospheric gravity waves are associated with pressure and temperature perturbations, which in principle are detectable both at the surface and aloft. In this study, surface pressure and temperature data from two UK sites at Reading and Lerwick are examined for eclipse-driven gravity wave perturbations during the 20 March 2015 solar eclipse over northwest Europe. Radiosonde wind data from the same two sites are also analysed using a moving parcel analysis method, to determine the periodicities of the waves aloft. On this occasion, the perturbations both at the surface and aloft are found not to be confidently attributable to eclipse-driven gravity waves. We conclude that the complex synoptic weather conditions over the UK at the time of this particular eclipse helped to mask any eclipse-driven gravity waves. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’. PMID:27550763

On the detection and attribution of gravity waves generated by the 20 March 2015 solar eclipse.

PubMed

Marlton, G J; Williams, P D; Nicoll, K A

2016-09-28

Internal gravity waves are generated as adjustment radiation whenever a sudden change in forcing causes the atmosphere to depart from its large-scale balanced state. Such a forcing anomaly occurs during a solar eclipse, when the Moon's shadow cools part of the Earth's surface. The resulting atmospheric gravity waves are associated with pressure and temperature perturbations, which in principle are detectable both at the surface and aloft. In this study, surface pressure and temperature data from two UK sites at Reading and Lerwick are examined for eclipse-driven gravity wave perturbations during the 20 March 2015 solar eclipse over northwest Europe. Radiosonde wind data from the same two sites are also analysed using a moving parcel analysis method, to determine the periodicities of the waves aloft. On this occasion, the perturbations both at the surface and aloft are found not to be confidently attributable to eclipse-driven gravity waves. We conclude that the complex synoptic weather conditions over the UK at the time of this particular eclipse helped to mask any eclipse-driven gravity waves.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'. © 2016 The Authors.

Thermosyphon Flooding Limits in Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Gibson, Marc A.; Jaworske, Donald A.; Sanzi, James L.; Ljubanovic, Damir

2012-01-01

Fission Power Systems have long been recognized as potential multi-kilowatt power solutions for lunar, Martian, and extended planetary surface missions. Current heat rejection technology associated with fission surface power systems has focused on titanium water thermosyphons embedded in carbon composite radiator panels. The thermosyphons, or wickless heat pipes, are used as a redundant and efficient way to spread the waste heat from the power conversion unit(s) over the radiator surface area where it can be rejected to space. It is well known that thermosyphon performance is reliant on gravitational forces to keep the evaporator wetted with the working fluid. One of the performance limits that can be encountered, if not understood, is the phenomenon of condenser flooding, otherwise known as evaporator dry out. This occurs when the gravity forces acting on the condensed fluid cannot overcome the shear forces created by the vapor escaping the evaporator throat. When this occurs, the heat transfer process is stalled and may not re-stabilize to effective levels without corrective control actions. The flooding limit in earth's gravity environment is well understood as experimentation is readily accessible, but when the environment and gravity change relative to other planetary bodies, experimentation becomes difficult. An innovative experiment was designed and flown on a parabolic flight campaign to achieve the Reduced Gravity Environments (RGE) needed to obtain empirical data for analysis. The test data is compared to current correlation models for validation and accuracy.

Gravity and Nonconservative Force Model Tuning for the GEOSAT Follow-On Spacecraft

NASA Technical Reports Server (NTRS)

Lemoine, Frank G.; Zelensky, Nikita P.; Rowlands, David D.; Luthcke, Scott B.; Chinn, Douglas S.; Marr, Gregory C.; Smith, David E. (Technical Monitor)

2000-01-01

The US Navy's GEOSAT Follow-On spacecraft was launched on February 10, 1998 and the primary objective of the mission was to map the oceans using a radar altimeter. Three radar altimeter calibration campaigns have been conducted in 1999 and 2000. The spacecraft is tracked by satellite laser ranging (SLR) and Doppler beacons and a limited amount of data have been obtained from the Global Positioning Receiver (GPS) on board the satellite. Even with EGM96, the predicted radial orbit error due to gravity field mismodelling (to 70x70) remains high at 2.61 cm (compared to 0.88 cm for TOPEX). We report on the preliminary gravity model tuning for GFO using SLR, and altimeter crossover data. Preliminary solutions using SLR and GFO/GFO crossover data from CalVal campaigns I and II in June-August 1999, and January-February 2000 have reduced the predicted radial orbit error to 1.9 cm and further reduction will be possible when additional data are added to the solutions. The gravity model tuning has improved principally the low order m-daily terms and has reduced significantly the geographically correlated error present in this satellite orbit. In addition to gravity field mismodelling, the largest contributor to the orbit error is the non-conservative force mismodelling. We report on further nonconservative force model tuning results using available data from over one cycle in beta prime.

Strain Gage

NASA Technical Reports Server (NTRS)

1995-01-01

HITEC Corporation developed a strain gage application for DanteII, a mobile robot developed for NASA. The gage measured bending forces on the robot's legs and warned human controllers when acceptable forces were exceeded. HITEC further developed the technology for strain gage services in creating transducers out of "Indy" racing car suspension pushrods, NASCAR suspension components and components used in motion control.

Generation of Acoustic Self-bending and Bottle Beams by Phase Engineering

DTIC Science & Technology

2014-07-03

projectile under the action of gravity . We synthesize an acoustic beam propagating along a free-form Bézier curve in air33 by employing a planar speaker...the axial radiation force can be negative, indicating the existence of a pulling force against the beam propagation direction as well as the gravity ...use Legendre transformations to construct the geometric wavefront from a preset beam trajectory. Assume that the geometric wavefront W corresponding to

Hybrid Electrostatic/Acoustic Levitator

NASA Technical Reports Server (NTRS)

Rhim, Won K.; Trinh, Eugene H.; Chung, Sang K.; Elleman, Daniel D.

1987-01-01

Because electrostatic and acoustic forces independent of each other, hybrid levitator especially suitable for studies of drop dynamics. Like all-acoustic or all-electrostatic systems, also used in studies of containerless material processing. Vertical levitating force applied to sample by upper and lower electrodes. Torques or vibrational forces in horizontal plane applied by acoustic transducers. Electrically charged water drop about 4 mm in diameter levitated electrostatically and rotated acoustically until it assumed dumbell shape and broke apart.

Force characteristic analysis of a magnetic gravity compensator with annular magnet array for magnetic levitation positioning system

NASA Astrophysics Data System (ADS)

Zhou, Yiheng; Kou, Baoquan; Liu, Peng; Zhang, He; Xing, Feng; Yang, Xiaobao

2018-05-01

Magnetic levitation positioning system (MLPS) is considered to be the state of the art in inspection and manufacturing systems in vacuum. In this paper, a magnetic gravity compensator with annular magnet array (AMA-MGC) for MLPS is proposed. Benefiting from the double-layer annular Halbach magnet array on the stator, the proposed AMA-MGC possesses the advantages of symmetrical force, high force density and small force fluctuation. Firstly, the basic structure and operation principle of the AMA-MGC are introduced. Secondly, the basic characteristics of the AMA-MGC such as magnetic field distribution, levitation force, parasitic force and parasitic torque are analyzed by the three-dimensional finite element analysis (3-D FEA). Thirdly, the influence of structural parameters on force density and force fluctuation is investigated, which is conductive to the design and optimization of the AMA-MGC. Finally, a prototype of the AMA-MGC is constructed, and the experiment shows good agreement with the 3-D FEA results.

Strong anti-gravity Life in the shock wave

NASA Astrophysics Data System (ADS)

Fabbrichesi, Marco; Roland, Kaj

1992-12-01

Strong anti-gravity is the vanishing of the net force between two massive particles at rest, to all orders in Newton's constant. We study this phenomenon and show that it occurs in any effective theory of gravity which is obtained from a higher-dimensional model by compactification on a manifold with flat directions. We find the exact solution of the Einstein equations in the presence of a point-like source of strong anti-gravity by dimensional reduction of a shock-wave solution in the higher-dimensional model.

The Electrical Network of Maize Root Apex is Gravity Dependent

PubMed Central

Masi, Elisa; Ciszak, Marzena; Comparini, Diego; Monetti, Emanuela; Pandolfi, Camilla; Azzarello, Elisa; Mugnai, Sergio; Baluška, Frantisek; Mancuso, Stefano

2015-01-01

Investigations carried out on maize roots under microgravity and hypergravity revealed that gravity conditions have strong effects on the network of plant electrical activity. Both the duration of action potentials (APs) and their propagation velocities were significantly affected by gravity. Similarly to what was reported for animals, increased gravity forces speed-up APs and enhance synchronized electrical events also in plants. The root apex transition zone emerges as the most active, as well as the most sensitive, root region in this respect. PMID:25588706

The electrical network of maize root apex is gravity dependent.

PubMed

Masi, Elisa; Ciszak, Marzena; Comparini, Diego; Monetti, Emanuela; Pandolfi, Camilla; Azzarello, Elisa; Mugnai, Sergio; Baluška, Frantisek; Mancuso, Stefano

2015-01-15

Investigations carried out on maize roots under microgravity and hypergravity revealed that gravity conditions have strong effects on the network of plant electrical activity. Both the duration of action potentials (APs) and their propagation velocities were significantly affected by gravity. Similarly to what was reported for animals, increased gravity forces speed-up APs and enhance synchronized electrical events also in plants. The root apex transition zone emerges as the most active, as well as the most sensitive, root region in this respect.

Four theorems on the psychometric function.

PubMed

May, Keith A; Solomon, Joshua A

2013-01-01

In a 2-alternative forced-choice (2AFC) discrimination task, observers choose which of two stimuli has the higher value. The psychometric function for this task gives the probability of a correct response for a given stimulus difference, Δx. This paper proves four theorems about the psychometric function. Assuming the observer applies a transducer and adds noise, Theorem 1 derives a convenient general expression for the psychometric function. Discrimination data are often fitted with a Weibull function. Theorem 2 proves that the Weibull "slope" parameter, β, can be approximated by β(Noise) x β(Transducer), where β(Noise) is the β of the Weibull function that fits best to the cumulative noise distribution, and β(Transducer) depends on the transducer. We derive general expressions for β(Noise) and β(Transducer), from which we derive expressions for specific cases. One case that follows naturally from our general analysis is Pelli's finding that, when d' ∝ (Δx)(b), β ≈ β(Noise) x b. We also consider two limiting cases. Theorem 3 proves that, as sensitivity improves, 2AFC performance will usually approach that for a linear transducer, whatever the actual transducer; we show that this does not apply at signal levels where the transducer gradient is zero, which explains why it does not apply to contrast detection. Theorem 4 proves that, when the exponent of a power-function transducer approaches zero, 2AFC performance approaches that of a logarithmic transducer. We show that the power-function exponents of 0.4-0.5 fitted to suprathreshold contrast discrimination data are close enough to zero for the fitted psychometric function to be practically indistinguishable from that of a log transducer. Finally, Weibull β reflects the shape of the noise distribution, and we used our results to assess the recent claim that internal noise has higher kurtosis than a Gaussian. Our analysis of β for contrast discrimination suggests that, if internal noise is stimulus-independent, it has lower kurtosis than a Gaussian.

Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly†

PubMed Central

Hill, Richard J. A.; Larkin, Oliver J.; Dijkstra, Camelia E.; Manzano, Ana I.; de Juan, Emilio; Davey, Michael R.; Anthony, Paul; Eaves, Laurence; Medina, F. Javier; Marco, Roberto; Herranz, Raul

2012-01-01

Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity. PMID:22219396

Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly.

PubMed

Hill, Richard J A; Larkin, Oliver J; Dijkstra, Camelia E; Manzano, Ana I; de Juan, Emilio; Davey, Michael R; Anthony, Paul; Eaves, Laurence; Medina, F Javier; Marco, Roberto; Herranz, Raul

2012-07-07

Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity.

Low Stretch PMMA Burning in Microgravity: Status of the Ground-Based Program and New ISS Glovebox Experiment SALSA

NASA Technical Reports Server (NTRS)

Olson, S. L.; T'ien, J. S.; Armstrong, J. B.

2001-01-01

The objective of this ground-based program is to study low stretch diffusion flames burning PMMA as the solid fuel to determine the relationship between buoyant low stretch burning in normal gravity and forced flow low stretch burning in microgravity. The low stretch is generated in normal gravity by using the buoyant convection induced by burning the bottom of a large radius of curvature sample. Low stretch is also generated using the Combustion Tunnel drop tower rig (2.2 and 5.2 second facilities), which provides a forced convective low velocity flow past smaller radius of curvature samples. Lastly, an ISS glovebox investigation is being developed to study low stretch burning of PMMA spheres to obtain long duration testing needed to accurately assess the flammability and burning characteristics of the material in microgravity. A comparison of microgravity experiment results with normal gravity test results allows us to establish a direct link between a material's burning characteristics in normal gravity (easily measured) with its burning characteristics in extraterrestrial environments, including microgravity forced convective environments. Theoretical predictions and recent experimental results indicate that it should be possible to understand a material's burning characteristics in the low stretch environment of spacecraft (non-buoyant air movement induced by fans and crew disturbances) by understanding its burning characteristics in an equivalent Earth-based low stretch environment (induced by normal gravity buoyancy). Similarly, Earth-based stretch environments can be made equivalent to those in Lunar- and Martian-surface stretch environments (which would induce partial-gravity buoyancy).

Sensitivity of Middle Atmospheric Temperature and Circulation in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking

NASA Technical Reports Server (NTRS)

Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.

2003-01-01

The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General Circulation Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and circulation. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger meridional transport circulation that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport circulation in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In the tropics, only with the AD parameterization can the model produce realistic semiannual oscillations.

Critical consideration on the relationship between auxin transport and calcium transients in gravity perception of Arabidopsis seedlings

PubMed Central

Toyota, Masatsugu; Furuichi, Takuya; Tatsumi, Hitoshi

2008-01-01

Plants regulate their growth and morphogenesis in response to gravity field, known as gravitropism. In the early process of gravitropism, changes in the gravity vector (gravistimulation) are transduced into certain intracellular signals, termed gravity perception. The plant hormone auxin is not only a crucial factor to represent gravitropism but also a potential signaling molecule for gravity perception. Another strong candidate for the signaling molecule is calcium ion of which cytoplasmic concentration ([Ca2+]c) is known to increase in response to gravistimulation. However, relationship between these two factors, say which is in the first place, has been controversial. This issue is addressed here mainly based on recent progress including our latest studies. Gravistimulation by turning plants 180° induced a two-peaked [Ca2+]c-increase lasting for several minutes in Arabidopsis seedlings expressing apoaequorin; only the second peak was sensitive to the gravistimulation. Peak amplitudes of the [Ca2+]c-increase were attenuated by the 10 µM auxin transport inhibitor (TIBA) and vesicle trafficking inhibitor (BFA), whereas the onset time and rate of rise of the second peak were not significantly altered. This result indicates that polar auxin transport is not involved in the initial phase of the second [Ca2+]c-increase. It is likely that the gravi-induced [Ca2+]c-increase constitutes an upstream event of the auxin transport, but may positively be modulated by auxin since its peak amplitude is attenuated by the inhibition of auxin transport. PMID:19513245

Cantilever Beam Natural Frequencies in Centrifugal Inertia Field

NASA Astrophysics Data System (ADS)

Jivkov, V. S.; Zahariev, E. V.

2018-03-01

In the advanced mechanical science the well known fact is that the gravity influences on the natural frequencies and modes even for the vertical structures and pillars. But, the condition that should be fulfilled in order for the gravity to be taken into account is connected with the ration between the gravity value and the geometrical cross section inertia. The gravity is related to the earth acceleration but for moving structures there exist many other acceleration exaggerated forces and such are forces caused by the centrifugal accelerations. Large rotating structures, as wind power generators, chopper wings, large antennas and radars, unfolding space structures and many others are such examples. It is expected, that acceleration based forces influence on the structure modal and frequency properties, which is a subject of the present investigations. In the paper, rotating beams are subject to investigations and modal and frequency analysis is carried out. Analytical dependences for the natural resonances are derived and their dependences on the angular velocity and centrifugal accelerations are derived. Several examples of large rotating beams with different orientations of the rotating shaft are presented. Numerical experiments are conducted. Time histories of the beam tip deflections, that depict the beam oscillations are presented.

Orbit Stability of OSIRIS-REx in the Vicinity of Bennu Using a High-Fidelity Solar Radiation Model

NASA Technical Reports Server (NTRS)

Williams, Trevor W.; Hughes, Kyle M.; Mashiku, Alinda K.; Longuski, James M.

2015-01-01

Solar radiation pressure is one of the largest perturbing forces on the OSIRISRex trajectory as it orbits the asteroid Bennu. In this work, we investigate how forces due to solar radiation perturb the OSIRIS-REx trajectory in a high-fidelity model. The model accounts for Bennu's non-spherical gravity field, third-body gravity forces from the Sun and Jupiter, as well as solar radiation forces acting on a simplified spacecraft model. Such high-fidelity simulations indicate significant solar radiation pressure perturbations from the nominal orbit. Modifications to the initial design of the nominal orbit are found using a variation of parameters approach that reduce the perturbation in eccentricity by a factor of one-half.

40 CFR 1066.255 - Parasitic loss verification.

Code of Federal Regulations, 2013 CFR

2013-07-01

... following the dynamometer manufacturer's specifications to establish a parasitic loss curve, taking data at.... Parasitic loss forces may never be negative. Note that the torque transducers must be zeroed and spanned...

40 CFR 1066.255 - Parasitic loss verification.

Code of Federal Regulations, 2012 CFR

2012-07-01

... following the dynamometer manufacturer's specifications to establish a parasitic loss curve, taking data at.... Parasitic loss forces may never be negative. Note that the torque transducers must be zeroed and spanned...

What every physicist should know about string theory

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

Witten, Edward

2015-11-15

Some of nature’s rhymes—the appearance of similar structures in different areas of physics—underlie the way that string theory potentially unifies gravity with the other forces of nature and eliminates the ultraviolet divergences that plague quantum gravity.

Dark Energy and Gravity: Yin and Yang of the Universe Artist Concept

NASA Image and Video Library

2011-05-19

New results from NASA Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy is a smooth, uniform force that now dominates over the effects of gravity.

Precision Mechanical Measurement Using the Levitation Mass Method (LMM)

NASA Astrophysics Data System (ADS)

Fujii, Yusaku; Jin, Tao; Maru, Koichi

2010-12-01

The present status and the future prospects of a method for precision mass and force measurement, the levitation mass method (LMM), are reviewed. The LMM has been proposed and improved by the authors. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects under test, such as force transducers, materials or structures. The inertial force of the levitated mass is measured using an optical interferometer. The three typical applications of the LMM, i.e. the dynamic force calibration, the micro force material tester and the space scale, are reviewed in this paper.

Model of a Piezoelectric Transducer

NASA Technical Reports Server (NTRS)

Goodenow, Debra

2004-01-01

It's difficult to control liquid and gas in propellant tanks in zero gravity. A possible a design would utilize acoustic liquid manipulation (ALM) technology which uses ultrasonic beams conducted through a liquid and solid media, to push gas bubbles in the liquid to desirable locations. We can propel and control the bubble with acoustic radiation pressure by aiming the acoustic waves on the bubble s surface. This allows us to design a so called smart tank in which the ALM devices transfer the gas to the outer wall of the tank and isolating the liquid in the center. Because the heat transfer rate of a gas is lower of that of the liquid it would substantially decrease boil off and provide of for a longer storage life. The ALM beam is composed of little wavelets which are individual waves that constructively interfere with each other to produce a single, combined acoustic wave front. This is accomplished by using a set of synchronized ultrasound transducers arranged in an array. A slight phase offset of these elements allows us to focus and steer the beam. The device that we are using to produce the acoustic beam is called the piezoelectric transducer. This device converts electrical energy to mechanical energy, which appears in the form of acoustic energy. Therefore the behavior of the device is dependent on both the mechanical characteristics, such as its density, cross-sectional area, and its electrical characteristics, such as, electric flux permittivity and coupling factor. These devices can also be set up in a number of modes which are determined by the way the piezoelectric device is arranged, and the shape of the transducer. For this application we are using the longitudinal or thickness mode for our operation. The transducer also vibrates in the lateral mode, and one of the goals of my project is to decrease the amount of energy lost to the lateral mode. To model the behavior of the transducers I will be using Pspice, electric circuit modeling tool, to determine the transducer's electrical characteristics at the frequency of interest. This will also help me determine the characteristics of an impedance matching network to operate the transducer at its optimum efficiency. For this I will use ABMs (analog behavioral modeling) to model dependent current and voltage sources that represent the transducer. I have also been working on the Labview control software for the phased array used to control the bubbles, and will begin testing on that before the end of my internship.

Ground Based Investigation of Electrostatic Accelerometer in HUST

NASA Astrophysics Data System (ADS)

Bai, Y.; Zhou, Z.

2013-12-01

High-precision electrostatic accelerometers with six degrees of freedom (DOF) acceleration measurement were successfully used in CHAMP, GRACE and GOCE missions which to measure the Earth's gravity field. In our group, space inertial sensor based on the capacitance transducer and electrostatic control technique has been investigated for test of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, and satellite Earth's field recovery. The significant techniques of capacitive position sensor with the noise level at 2×10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are carried out and all the six servo loop controls by using a discrete PID algorithm are realized in a FPGA device. For testing on ground, in order to compensate one g earth's gravity, the fiber torsion pendulum facility is adopt to measure the parameters of the electrostatic controlled inertial sensor such as the resolution, and the electrostatic stiffness, the cross couple between different DOFs. A short distance and a simple double capsule equipment the valid duration about 0.5 second is set up in our lab for the free fall tests of the engineering model which can directly verify the function of six DOF control. Meanwhile, high voltage suspension method is also realized and preliminary results show that the horizontal axis of acceleration noise is about 10-8m/s2/Hz1/2 level which limited mainly by the seismic noise. Reference: [1] Fen Gao, Ze-Bing Zhou, Jun Luo, Feasibility for Testing the Equivalence Principle with Optical Readout in Space, Chin. Phys. Lett. 28(8) (2011) 080401. [2] Z. Zhu, Z. B. Zhou, L. Cai, Y. Z. Bai, J. Luo, Electrostatic gravity gradiometer design for the advanced GOCE mission, Adv. Sp. Res. 51 (2013) 2269-2276. [3] Z B Zhou, L Liu, H B Tu, Y Z Bai, J Luo, Seismic noise limit for ground-based performance measurements of an inertial sensor using a torsion balance, Class. Quantum Grav. 27 (2010) 175012. [4] H B Tu, Y Z Bai, Z B Zhou, L Liu, L Cai, and J Luo, Performance measurements of an inertial sensor with a two-stage controlled torsion pendulum, Class Quantum. Grav. 27 (2010) 205016.

Revisiting the "thermospheric spoon" mechanism of the thermosphere and ionosphere semiannual oscillation

NASA Astrophysics Data System (ADS)

Emmert, J. T.; Jones, M., Jr.; Picone, J. M.; Drob, D. P.; Siskind, D. E.

2017-12-01

The thermosphere-ionosphere (T-I) exhibits a strong ( ±20%) semiannual oscillation (SAO) in globally averaged mass and electron density; the source of the SAO is still unclear. Two prominent proposed mechanisms are: (1) the "thermospheric spoon" mechanism (TSM) [Fuller-Rowell, 1998], which is a resolved-scale, seasonally dependent mixing process that drives an SAO through interhemispheric meridional and vertical transport of constituents and (2) seasonal variations in eddy diffusion (Kzz) associated with breaking gravity waves ("Kzz hypothesis") [Qian et al. 2009]. In this study, we use the National Center for atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM), to investigate the source of the T-I SAO. We performed numerical experiments over a continuous calendar year assuming constant solar and geomagnetic forcing and several configurations of lower atmospheric tidal forcing, lower atmospheric gravity wave forcing, and the obliquity of Earth's rotational axis with respect to the ecliptic plane. The prominent results are as follows: (1) In the absence of lower atmospheric gravity wave and tidal forcing a 30% SAO in globally averaged mass density (with respect to its global annual average) is simulated in the TIME-GCM, suggesting that seasonally-varying Kzz driven by breaking gravity waves is not the primary driver of the T-I SAO; (2) When the Earth's obliquity is set to zero (i.e., perpetual equinox) the T-I SAO is reduced to 2%; (3) When Earth's obliquity is set to 11.75° (i.e., half its actual value), the mass density SAO is 10%; (4) The meridional and vertical transport patterns in the simulations are consistent with the TSM, except that coupling with the upper mesospheric circulation also contributes to the T-I SAO; and (5) Inclusion of lower atmospheric tidal and gravity wave forcing weakens the TSM and thus damps the T-I SAO. These results suggest that the TSM accurately describes the primary source of the T-I SAO.

Nucleate pool boiling: High gravity to reduced gravity; liquid metals to cryogens

NASA Technical Reports Server (NTRS)

Merte, Herman, Jr.

1988-01-01

Requirements for the proper functioning of equipment and personnel in reduced gravity associated with space platforms and future space station modules introduce unique problems in temperature control; power generation; energy dissipation; the storage, transfer, control and conditioning of fluids; and liquid-vapor separation. The phase change of boiling is significant in all of these. Although both pool and flow boiling would be involved, research results to date include only pool boiling because buoyancy effects are maximized for this case. The effective application of forced convection boiling heat transfer in the microgravity of space will require a well grounded and cogent understanding of the mechanisms involved. Experimental results are presented for pool boiling from a single geometrical configuration, a flat surface, covering a wide range of body forces from a/g = 20 to 1 to a/g = 0 to -1 for a cryogenic liquid, and from a/g = 20 to 1 for water and a liquid metal. Similarities in behavior are noted for these three fluids at the higher gravity levels, and may reasonably be expected to continue at reduced gravity levels.

Study of fluid behaviour under gravity compensated by a magnetic field

NASA Astrophysics Data System (ADS)

Chatain, D.; Beysens, D.; Madet, K.; Nikolayev, V.; Mailfert, A.

2006-09-01

Fluids, and especially cryogenic fluids like hydrogen and oxygen, are widely used in space technology for propulsion and cooling. The knowledge of fluid behaviour during the acceleration variation and under reduced gravity is necessary for an efficient management of fluids in space. Such a management also rises fundamental questions about thermo-hydrodynamics and phase change once buoyancy forces are cancelled. For security reasons, it is nearly impossible to use the classical microgravity means to experiment with such cryofluids. However, it is possible to counterbalance gravity by using the paramagnetic (O2) or diamagnetic (H2) properties of fluids. By applying a magnetic field gradient on these materials, a volume force is created that is able to impose to the fluid a varying effective gravity, including microgravity. We have set up a magnetic levitation facility for H2 in which numerous experiments have been performed. A new facility for O2 is under construction. It will enable fast change in the effective gravity by quenching down the magnetic field. The facilities and some particularly representative experimental results are presented.

Regulation of the position of statoliths in Chara rhizoids.

PubMed

Hejnowicz, Z; Sievers, A

1981-01-01

The behavior of statoliths in rhizoids differently oriented with respect to the gravity vector indicates that there are cytoskeleton elements which exert forces on the statoliths, mostly in the longitudinal directions. Compared to the sum of the forces acting on a statolith, the gravitational force is a relatively small component, i.e., less than 1/5 of the cytoskeleton force. The balance is disturbed by displacing the rhizoid from the normal vertical orientation. It is also reversibly disturbed by cytochalasin B such that some statoliths move against the gravity force. Phalloidin stabilizes the position of the statoliths against cytochalasin B. We infer that microfilaments are involved in controlling the position of statoliths, and that there is a considerable tension on these microfilaments. The vibration frequency of the microfilaments corresponding to this tension is in the ultrasonic range.

Combined targeting of lentiviral vectors and positioning of transduced cells by magnetic nanoparticles

PubMed Central

Hofmann, Andreas; Wenzel, Daniela; Becher, Ulrich M.; Freitag, Daniel F.; Klein, Alexandra M.; Eberbeck, Dietmar; Schulte, Maike; Zimmermann, Katrin; Bergemann, Christian; Gleich, Bernhard; Roell, Wilhelm; Weyh, Thomas; Trahms, Lutz; Nickenig, Georg; Fleischmann, Bernd K.; Pfeifer, Alexander

2009-01-01

Targeting of viral vectors is a major challenge for in vivo gene delivery, especially after intravascular application. In addition, targeting of the endothelium itself would be of importance for gene-based therapies of vascular disease. Here, we used magnetic nanoparticles (MNPs) to combine cell transduction and positioning in the vascular system under clinically relevant, nonpermissive conditions, including hydrodynamic forces and hypothermia. The use of MNPs enhanced transduction efficiency of endothelial cells and enabled direct endothelial targeting of lentiviral vectors (LVs) by magnetic force, even in perfused vessels. In addition, application of external magnetic fields to mice significantly changed LV/MNP biodistribution in vivo. LV/MNP-transduced cells exhibited superparamagnetic behavior as measured by magnetorelaxometry, and they were efficiently retained by magnetic fields. The magnetic interactions were strong enough to position MNP-containing endothelial cells at the intima of vessels under physiological flow conditions. Importantly, magnetic positioning of MNP-labeled cells was also achieved in vivo in an injury model of the mouse carotid artery. Intravascular gene targeting can be combined with positioning of the transduced cells via nanomagnetic particles, thereby combining gene- and cell-based therapies. PMID:19118196

Development of the sonic pump levitation

NASA Technical Reports Server (NTRS)

Dunn, S. A.

1984-01-01

A prototype levitating/positioning device termed the Sonic Pump Levitator was designed, built and successfully tested in full gravity and in the reduced gravity of the parabolic flight regime of the KC-135. Positioning is achieved by timely and appropriate application of gas momentum from one or more of six sonic pumps. The sonic pumps, which are arranged orthogonally in opposed pairs about the levitation region, are activated by an electro-optical, computer controlled, feedback system. The sonic pump is a transducer which is capable of converting sound energy into a directed flow of gas. It consists of a loudspeaker whose face is sealed by a closure perforated by one or more orifices. The diaphragm of the loudspeaker is the only moving part of the sonic pump, no valves being needed. This very low inertia electromechanical device was developed to provide the short response time necessary to keep pace with the demands of computerized position keeping.

Analysis of Cell Biomechanics Response to Gravity:A Fluids for Biology Study Utilizing NASA Glenns Zero Gravity Research Facility

NASA Technical Reports Server (NTRS)

Bomani, Bilal M. M.; Kassemi, Mohammad; Neumann, Eric S.

2016-01-01

It remains unclear how biological cells sense and respond to gravitational forces. Leading scientists state that a large gap exists in the understanding of physiological and molecular adaptation that occurs as biology enters the spaceflight realm. We are seeking a method to fully understand how cells sense microgravity/gravity and what triggers their response.

BOILING HEAT TRANSFER IN ZERO GRAVITY

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

Zara, E.A.

1964-01-01

The preliminary results of a research program to determine the effects of zero and near zero gravity on boiling heat transfer are presented. Zero gravity conditions were obtained on the ASD KC-135 zero gravity test aircraft, capable of providing 30-seconds of zero gravity. Results of the program to date indicate that nucleate (bubble) boiling heat transfer rates are not greatly affected by the absence of gravity forces. However, radical pressure increases were observed that will dictate special design considerations to space vehicle systems utilizing pool boiling processes, such as cryogenic or other fluid storage vessels where thermal input to themore » fluid is used for vessel pressurization. (auth)« less

Tribology experiment in zero gravity

NASA Technical Reports Server (NTRS)

Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.

1984-01-01

A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates studies of the motion of liquid lubricants over solid surfaces as controlled by interfacial and capillary forces. Observations were made of phenomena associated with the liquid on one solid surface and also with the liquid between a pair of closely spaced surfaces. Typical photographic records obtained on Spacelab 1 are described.

Mathematical Modelling of the Behavior of the Lacoste and Romberg ’G’ Gravity Meter for Use in Gravity Network Adjustments and Data Analyses,

DTIC Science & Technology

1981-11-01

Geodetic Science and Surveying 62101F The Ohio State University 760003AL Columbus, Ohio 43210 11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE Air ... Air Force Contract No. F19628-79-C-9975, The Ohio State University Research Foundation, Project No. 711715, Project Supervisor, Urho A. Uotila...Professor, Department of Geodetic Science and Surveying. The contract covering this research is administered by the Air Force Geophysics Laboratory (AFGL

Testing the Cubic Galileon Gravity Model by the Milky Way Rotation Curve and SPARC Data

NASA Astrophysics Data System (ADS)

Chan, Man Ho; Hui, Hon Ka

2018-04-01

Recently, the cubic Galileon gravity (CGG) model has been suggested as an alternative gravity theory to general relativity. The model consists of an extra field potential term that can serve as the “fifth force.” In this article, we examine the possibility of whether or not this extra force term can explain the missing mass problem in galaxies without the help of dark matter. By using the Milky Way rotation curve and the Spitzer Photomery and Accurate Rotation Curves data, we show that this CGG model can satisfactorily explain the shapes of these rotation curves without dark matter. The CGG model can be regarded as a new alternative theory to challenge the existing dark matter paradigm.

Application of electrohydrodynamic phenomena to space processing

NASA Technical Reports Server (NTRS)

Jones, T. B.

1975-01-01

The capabilities of electrohydrodynamic (EHD) unit separation, liquid handling/control, and mixing are introduced to industrial chemists and metallurgists, working on specific zero-gravity processes. Previously proposed zero-gravity applications of EHD are presented along with the prominent electrohydrodynamical force effects.

Effect of Heat Generation of Ultrasound Transducer on Ultrasonic Power Measured by Calorimetric Method

NASA Astrophysics Data System (ADS)

Uchida, Takeyoshi; Kikuchi, Tsuneo

2013-07-01

Ultrasonic power is one of the key quantities closely related to the safety of medical ultrasonic equipment. An ultrasonic power standard is required for establishment of safety. Generally, an ultrasonic power standard below approximately 20 W is established by the radiation force balance (RFB) method as the most accurate measurement method. However, RFB is not suitable for high ultrasonic power because of thermal damage to the absorbing target. Consequently, an alternative method to RFB is required. We have been developing a measurement technique for high ultrasonic power by the calorimetric method. In this study, we examined the effect of heat generation of an ultrasound transducer on ultrasonic power measured by the calorimetric method. As a result, an excessively high ultrasonic power was measured owing to the effect of heat generation from internal loss in the transducer. A reference ultrasound transducer with low heat generation is required for a high ultrasonic power standard established by the calorimetric method.

The Common Forces: Conservative or Nonconservative?

ERIC Educational Resources Information Center

Keeports, David

2006-01-01

Of the forces commonly encountered when solving problems in Newtonian mechanics, introductory texts usually limit illustrations of the definitions of conservative and nonconservative forces to gravity, spring forces, kinetic friction and fluid resistance. However, at the expense of very little class time, the question of whether each of the common…

Tolerance of Snakes to Hypergravity

NASA Technical Reports Server (NTRS)

Lillywhite, H. B.; Ballard, R. E.; Hargens, A. R.

1994-01-01

Sensitivity of carotid blood flow to +Gz (head-to-tail) acceleration was studied in six species of snakes hypothesized to show varied adaptive cardiovascular responses to gravity. Blood flow in the proximal carotid artery was measured in 15 snakes before, during and following stepwise increments of +0.25Gz force produced on a 2.4 m diameter centrifuge. During centrifugation each snake was confined to a straight position within an individually- fitted acrylic tube with the head facing the center of rotation. We measured the centrifugal force at the tail of the snake in order to quantify the maximum intensity of force gradient promoting antero-posterior pooling of blood. Tolerance to increased gravity was quantified as the acceleration force at which carotid blood flow ceased. This parameter varied according to the gravitational adaptation of species defined by their ecology and behavior. At the extremes, carotid blood flow decreased in response to increasing gravity and approached zero near +1Gz in aquatic and ground-dwelling species, whereas in climbing species carotid flow was maintained at forces in excess of +2Gz. Surprisingly, tolerant (arboreal) species withstood hypergravic forces of +2 to +3 G. for periods up to 1 h without cessation of carotid blood flow or apparent loss of consciousness. Data suggest that relatively tight skin of the tolerant species provides a natural antigravity suit which is of prime importance in counteracting Gz stress on blood circulation.

A beamforming study for implementation of vibro-acoustography with a 1.75-D array transducer.

PubMed

Urban, Matthew W; Chalek, Carl; Haider, Bruno; Thomenius, Kai E; Fatemi, Mostafa; Alizad, Azra

2013-03-01

Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using 1-D linear-array transducers. In this article, we discuss VA beamforming and image formation using a 1.75-D array transducer. A 1.75-D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75-D array over a 1-D linear-array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75-D array transducer offers several advantages over scanning with a linear-array transducer, including improved image resolution and contrast resulting from better elevation focusing of the imaging point-spread function.

A Beamforming Study for Implementation of Vibro-acoustography with a 1.75D Array Transducer

PubMed Central

Urban, Matthew W.; Chalek, Carl; Haider, Bruno; Thomenius, Kai E.; Fatemi, Mostafa; Alizad, Azra

2013-01-01

Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using one-dimensional (1D) linear array transducers. In this article, we discuss VA beamforming and image formation using a 1.75D array transducer. A 1.75D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75D array over a 1D linear array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75D array transducer offers several advantages over scanning with a linear array transducer including improved image resolution and contrast due to better elevation focusing of the imaging point-spread function. PMID:23475919

Toric focusing for radiation force applications using a toric lens coupled to a spherically focused transducer.

PubMed

Arnal, Bastien; Nguyen, Thu-Mai; O'Donnell, Matthew

2014-12-01

Dynamic elastography using radiation force requires that an ultrasound field be focused during hundreds of microseconds at a pressure of several megapascals. Here, we address the importance of the focal geometry. Although there is usually no control of the elevational focal width in generating a tissue mechanical response, we propose a tunable approach to adapt the focus geometry that can significantly improve radiation force efficiency. Several thin, in-house-made polydimethylsiloxane lenses were designed to modify the focal spot of a spherical transducer. They exhibited low absorption and the focal spot widths were extended up to 8-fold in the elevation direction. Radiation force experiments demonstrated an 8-fold increase in tissue displacements using the same pressure level in a tissue-mimicking phantom with a similar shear wave spectrum, meaning it does not affect elastography resolution. Our results demonstrate that larger tissue responses can be obtained for a given pressure level, or that similar response can be reached at a much lower mechanical index (MI). We envision that this work will impact 3-D elastography using 2-D phased arrays, where such shaping can be achieved electronically with the potential for adaptive optimization.

Optical Trap Loading of Dielectric Microparticles In Air.

PubMed

Park, Haesung; LeBrun, Thomas W

2017-02-05

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

Nonlinear characterization of a single-axis acoustic levitator

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

Andrade, Marco A. B.; Ramos, Tiago S.; Okina, Fábio T. A.

2014-04-15

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jumpmore » phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.« less

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker.

PubMed

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Marty, Jean Louis; Hayat, Akhtar

2016-10-06

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer-Emmett- Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker

PubMed Central

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Louis Marty, Jean; Hayat, Akhtar

2016-01-01

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications. PMID:27782067

A large motion zero-gravity suspension system for experimental simulation of orbital construction and deployment. M.S. Thesis

NASA Technical Reports Server (NTRS)

Straube, Timothy Milton

1993-01-01

The design and implementation of a vertical degree of freedom suspension system is described which provides a constant force off-load condition to counter gravity over large displacements. By accommodating motions up to one meter for structures weighing up to 100 pounds, the system is useful for experiments which simulate orbital construction events such as docking, multiple component assembly, or structural deployment. A unique aspect of this device is the combination of a large stroke passive off-load device augmented by electromotive torque actuated force feedback. The active force feedback has the effect of reducing break-away friction by a factor of twenty over the passive system alone. The thesis describes the development of the suspension hardware and the control algorithm. Experiments were performed to verify the suspensions system's effectiveness in providing a gravity off-load and simulating the motion of a structure in orbit. Additionally, a three dimensional system concept is presented as an extension of the one dimensional suspension system which was implemented.

Biomedical technical transfer. Applications of NASA science and technology

NASA Technical Reports Server (NTRS)

1976-01-01

Lower body negative pressure testing in cardiac patients has been completed as well as the design and construction of a new leg negative unit for evaluating heart patients. This technology is based on NASA research, using vacuum chambers to stress the cardiovascular system during space flight. Additional laboratory tests of an intracranial pressure transducer, have been conducted. Three new biomedical problems to which NASA technology is applicable are also identified. These are: a communication device for the speech impaired, the NASA development liquid-cooled garment, and miniature force transducers for heart research.

Assessment on the methods of measuring the tyre-road contact patch stresses

NASA Astrophysics Data System (ADS)

Anghelache, G.; Moisescu, A.-R.; Buretea, D.

2017-08-01

The paper reviews established and modern methods for investigating tri-axial stress distributions in the tyre-road contact patch. The authors used three methods of measuring stress distributions: strain gauge method; force sensing technique; acceleration measurements. Four prototypes of instrumented pins transducers involving mentioned measuring methods were developed. Data acquisitions of the contact patch stresses distributions were performed using each transducer with instrumented pin. The results are analysed and compared, underlining the advantages and drawbacks of each method. The experimental results indicate that the three methods are valuable.

Real time control for NASA robotic gripper

NASA Technical Reports Server (NTRS)

Salter, Carole A.; Baras, John S.

1990-01-01

The ability to easily manipulate objects in a zero gravity environment will pay a key role in future space activities. Emphasis will be placed on robotic manipulation. This will serve to increase astronaut safety and utility in addition to several other benefits. The aim is to develop control laws for the zero gravity robotic end effectors. A hybrid force/position controller will be used. Sensory data available to the controller are obtained from an array of strain gauges and a linear potentiometer. Applying well known optimal control theoretical principles, the control which minimizes the transition time between positions is obtained. A robust force control scheme is developed which allows the desired holding force to be achieved smoothly without oscillation. In addition, an algorithm is found to determine contact force and contact location.

Systems and Methods for Gravity-Independent Gripping and Drilling

NASA Technical Reports Server (NTRS)

Thatte, Nitish (Inventor); King, Jonathan P. (Inventor); Parness, Aaron (Inventor); Frost, Matthew A. (Inventor)

2016-01-01

Systems and methods for gravity independent gripping and drilling are described. The gripping device can also comprise a drill or sampling devices for drilling and/or sampling in microgravity environments, or on vertical or inverted surfaces in environments where gravity is present. A robotic system can be connected with the gripping and drilling devices via an ankle interface adapted to distribute the forces realized from the robotic system.

Theoretical regime diagrams for thermally driven flows in a beta-plane channel in the presence of variable gravity

NASA Technical Reports Server (NTRS)

Geisler, J. E.; Fowlis, W. W.

1980-01-01

The effect of a power law gravity field on baroclinic instability is examined, with a focus on the case of inverse fifth power gravity, since this is the power law produced when terrestrial gravity is simulated in spherical geometry by a dielectric force. Growth rates are obtained of unstable normal modes as a function of parameters of the problem by solving a second order differential equation numerically. It is concluded that over the range of parameter space explored, there is no significant change in the character of theoretical regime diagrams if the vertically averaged gravity is used as parameter.

Tidal Forces: A Different Theory

NASA Astrophysics Data System (ADS)

Masters, Roy

2010-10-01

We revisit the theories describing the moon raising the tides by virtue of pull gravity combined with the moon's centripetal angular momentum. We show that if gravity is considered as the attractive interaction between individual bodies, then the moon would have fallen to earth eons ago. Isaac Newton's laws of motion cannot work with pull gravity. However, they do with gravity as a property of the universe as Einstein said with a huge energy bonus. In other words, the moon-Earth system becomes the first observable vacuum gravity energy machine, meaning that it not only produces energy, but provides also escape momentum for the moon's centripetal motion at 4cm per year.

Hydrogen Burning in Low Mass Stars Constrains Scalar-Tensor Theories of Gravity.

PubMed

Sakstein, Jeremy

2015-11-13

The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity and find that it is always significantly larger than the general relativity prediction. The observation of several low mass red dwarf stars therefore rules out a large class of scalar-tensor gravity theories and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy.

The Biomechanics of Exercise Countermeasures

NASA Technical Reports Server (NTRS)

Cavanagh, Peter R.; Arnold, Steven; Derr, Janice; Sharkey, Neil; Wu, Ge

1999-01-01

The Penn State Zero-gravity Simulator (PSZS) is a device developed by the Center for Locomotion Studies (CELOS) to enable ground studies of exercise countermeasures for the bone loss that has been shown to occur during long-term exposure to zero gravity (0G). The PSZS simulates 0G exercise by providing a suspension system that holds an individual in a horizontal (supine) position above the floor in order to enable exercise on a wall-mounted treadmill. Due to this orientation, exercise performed in the PSZS is free of the force of -ravity in the direction that would normally contribute to ground reaction forces. In order for movements to be more similar to those in 0G, a constant force suspension of each segment (equal to the segment weight) is provided regardless of limb position. During the preliminary development of the PSZS, CELOS researchers also designed an optional gravity-replacement simulation feature for the PSZS. This feature was a prototype tethering system that consisted of a spring tension system to pull an exercising individual toward the treadmill. The immediate application of the tethering system was to be the provision of gravity-replacement loading so that exercise in 0G- and 1G-loading conditions could be compared, and the PSZS could then be used to evaluate exercise countermeasures for bone loss during space flight. This tethering system would also be a model for the further refinement of gravity-replacement systems provided for astronaut usage while performing prescribed exercise countermeasures for bone loss during long-term space flights.

The Myosuit: Bi-articular Anti-gravity Exosuit That Reduces Hip Extensor Activity in Sitting Transfers.

PubMed

Schmidt, Kai; Duarte, Jaime E; Grimmer, Martin; Sancho-Puchades, Alejandro; Wei, Haiqi; Easthope, Chris S; Riener, Robert

2017-01-01

Muscle weakness-which can result from neurological injuries, genetic disorders, or typical aging-can affect a person's mobility and quality of life. For many people with muscle weakness, assistive devices provide the means to regain mobility and independence. These devices range from well-established technology, such as wheelchairs, to newer technologies, such as exoskeletons and exosuits. For assistive devices to be used in everyday life, they must provide assistance across activities of daily living (ADLs) in an unobtrusive manner. This article introduces the Myosuit, a soft, wearable device designed to provide continuous assistance at the hip and knee joint when working with and against gravity in ADLs. This robotic device combines active and passive elements with a closed-loop force controller designed to behave like an external muscle (exomuscle) and deliver gravity compensation to the user. At 4.1 kg (4.6 kg with batteries), the Myosuit is one of the lightest untethered devices capable of delivering gravity support to the user's knee and hip joints. This article presents the design and control principles of the Myosuit. It describes the textile interface, tendon actuators, and a bi-articular, synergy-based approach for continuous assistance. The assistive controller, based on bi-articular force assistance, was tested with a single subject who performed sitting transfers, one of the most gravity-intensive ADLs. The results show that the control concept can successfully identify changes in the posture and assist hip and knee extension with up to 26% of the natural knee moment and up to 35% of the knee power. We conclude that the Myosuit's novel approach to assistance using a bi-articular architecture, in combination with the posture-based force controller, can effectively assist its users in gravity-intensive ADLs, such as sitting transfers.

The Myosuit: Bi-articular Anti-gravity Exosuit That Reduces Hip Extensor Activity in Sitting Transfers

PubMed Central

Schmidt, Kai; Duarte, Jaime E.; Grimmer, Martin; Sancho-Puchades, Alejandro; Wei, Haiqi; Easthope, Chris S.; Riener, Robert

2017-01-01

Muscle weakness—which can result from neurological injuries, genetic disorders, or typical aging—can affect a person's mobility and quality of life. For many people with muscle weakness, assistive devices provide the means to regain mobility and independence. These devices range from well-established technology, such as wheelchairs, to newer technologies, such as exoskeletons and exosuits. For assistive devices to be used in everyday life, they must provide assistance across activities of daily living (ADLs) in an unobtrusive manner. This article introduces the Myosuit, a soft, wearable device designed to provide continuous assistance at the hip and knee joint when working with and against gravity in ADLs. This robotic device combines active and passive elements with a closed-loop force controller designed to behave like an external muscle (exomuscle) and deliver gravity compensation to the user. At 4.1 kg (4.6 kg with batteries), the Myosuit is one of the lightest untethered devices capable of delivering gravity support to the user's knee and hip joints. This article presents the design and control principles of the Myosuit. It describes the textile interface, tendon actuators, and a bi-articular, synergy-based approach for continuous assistance. The assistive controller, based on bi-articular force assistance, was tested with a single subject who performed sitting transfers, one of the most gravity-intensive ADLs. The results show that the control concept can successfully identify changes in the posture and assist hip and knee extension with up to 26% of the natural knee moment and up to 35% of the knee power. We conclude that the Myosuit's novel approach to assistance using a bi-articular architecture, in combination with the posture-based force controller, can effectively assist its users in gravity-intensive ADLs, such as sitting transfers. PMID:29163120

Demonstrating Electrical Activity in Nerve and Muscle. Part I

ERIC Educational Resources Information Center

Robinson, D. J.

1975-01-01

Describes a demonstration for showing the electrical activity in nerve and muscle including action potentials, refractory period of a nerve, and fatigue. Presents instructions for constructing an amplifier, electronic stimulator, and force transducer. (GS)

Analyses of a Gravistimulation-Specific Ca2+ Signature in Arabidopsis using Parabolic Flights1[W][OPEN

PubMed Central

Toyota, Masatsugu; Furuichi, Takuya; Sokabe, Masahiro; Tatsumi, Hitoshi

2013-01-01

Gravity is a critical environmental factor affecting the morphology and functions of organisms on the Earth. Plants sense changes in the gravity vector (gravistimulation) and regulate their growth direction accordingly. In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation, achieved by rotating the specimens under the ambient 1g of the Earth, is known to induce a biphasic (transient and sustained) increase in cytoplasmic calcium concentration ([Ca2+]c). However, the [Ca2+]c increase genuinely caused by gravistimulation has not been identified because gravistimulation is generally accompanied by rotation of specimens on the ground (1g), adding an additional mechanical signal to the treatment. Here, we demonstrate a gravistimulation-specific Ca2+ response in Arabidopsis seedlings by separating rotation from gravistimulation by using the microgravity (less than 10−4g) conditions provided by parabolic flights. Gravistimulation without rotating the specimen caused a sustained [Ca2+]c increase, which corresponds closely to the second sustained [Ca2+]c increase observed in ground experiments. The [Ca2+]c increases were analyzed under a variety of gravity intensities (e.g. 0.5g, 1.5g, or 2g) combined with rapid switching between hypergravity and microgravity, demonstrating that Arabidopsis seedlings possess a very rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes (0.5g–2g) into Ca2+ signals on a subsecond time scale. PMID:23835410

Analyses of a gravistimulation-specific Ca2+ signature in Arabidopsis using parabolic flights.

PubMed

Toyota, Masatsugu; Furuichi, Takuya; Sokabe, Masahiro; Tatsumi, Hitoshi

2013-10-01

Gravity is a critical environmental factor affecting the morphology and functions of organisms on the Earth. Plants sense changes in the gravity vector (gravistimulation) and regulate their growth direction accordingly. In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation, achieved by rotating the specimens under the ambient 1g of the Earth, is known to induce a biphasic (transient and sustained) increase in cytoplasmic calcium concentration ([Ca(2+)]c). However, the [Ca(2+)]c increase genuinely caused by gravistimulation has not been identified because gravistimulation is generally accompanied by rotation of specimens on the ground (1g), adding an additional mechanical signal to the treatment. Here, we demonstrate a gravistimulation-specific Ca(2+) response in Arabidopsis seedlings by separating rotation from gravistimulation by using the microgravity (less than 10(-4)g) conditions provided by parabolic flights. Gravistimulation without rotating the specimen caused a sustained [Ca(2+)]c increase, which corresponds closely to the second sustained [Ca(2+)]c increase observed in ground experiments. The [Ca(2+)]c increases were analyzed under a variety of gravity intensities (e.g. 0.5g, 1.5g, or 2g) combined with rapid switching between hypergravity and microgravity, demonstrating that Arabidopsis seedlings possess a very rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes (0.5g-2g) into Ca(2+) signals on a subsecond time scale.

U-PHOS Project: Development of a Large Diameter Pulsating Heat Pipe Experiment on board REXUS 22

NASA Astrophysics Data System (ADS)

Nannipieri, P.; Anichini, M.; Barsocchi, L.; Becatti, G.; Buoni, L.; Celi, F.; Catarsi, A.; Di Giorgio, P.; Fattibene, P.; Ferrato, E.; Guardati, P.; Mancini, E.; Meoni, G.; Nesti, F.; Piacquadio, S.; Pratelli, E.; Quadrelli, L.; Viglione, A. S.; Zanaboni, F.; Mameli, M.; Baronti, F.; Fanucci, L.; Marcuccio, S.; Bartoli, C.; Di Marco, P.; Bianco, N.; Marengo, M.; Filippeschi, S.

2017-01-01

U-PHOS Project aims at analysing and characterising the behaviour of a large diameter Pulsating Heat Pipe (PHP) on board REXUS 22 sounding rocket. A PHP is a passive thermal control device where the heat is efficiently transported by means of the self-sustained oscillatory fluid motion driven by the phase change phenomena. Since, in milli-gravity conditions, buoyancy forces become less intense, the PHP diameter may be increased still maintaining the slug/plug typical flow pattern. Consequently, the PHP heat power capability may be increased too. U-PHOS aims at proving that a large diameter PHP effectively works in milli-g conditions by characterizing its thermal response during a sounding rocket flight. The actual PHP tube is made of aluminum (3 mm inner diameter, filled with FC-72), heated at the evaporator by a compact electrical resistance, cooled at the condenser by a Phase Change Material (PCM) embedded in a metallic foam. The tube wall temperatures are recorded by means of Fibre Bragg Grating (FBG) sensors; the local fluid pressure is acquired by means of a pressure transducer. The present work intends to report the actual status of the project, focusing in particular on the experiment improvements with respect to the previous campaign.

Applicability of the Newtonian gravity concept inventory to introductory college physics classes

NASA Astrophysics Data System (ADS)

Williamson, Kathryn; Prather, Edward E.; Willoughby, Shannon

2016-06-01

The study described here extends the applicability of the Newtonian Gravity Concept Inventory (NGCI) to college algebra-based physics classes, beyond the general education astronomy courses for which it was originally developed. The four conceptual domains probed by the NGCI (Directionality, Force Law, Independence of Other Forces, and Threshold) are well suited for investigating students' reasoning about gravity in both populations, making the NGCI a highly versatile instrument. Classical test theory statistical analysis with physics student responses pre-instruction (N = 1,392) and post-instruction (N = 929) from eight colleges and universities across the United States indicate that the NGCI is composed of items with appropriate difficulty and discrimination and is reliable for this population. Also, expert review and student interviews support the NGCI's validity for the physics population. Emergent similarities and differences in how physics students reason about gravity compared to astronomy students are discussed, as well as future directions for analyzing the instrument's item parameters across both populations.

Effect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experiments.

PubMed

Chrysikopoulos, Constantinos V; Syngouna, Vasiliki I

2014-06-17

The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition.

Bioprocessing: Prospects for space electrophoresis

NASA Technical Reports Server (NTRS)

Bier, M.

1977-01-01

The basic principles of electrophoresis are reviewed in light of its past contributions to biology and medicine. The near-zero gravity environment of orbiting spacecraft may present some unique advantages for a variety of processes, by abolishing the major source of convection in fluids. As the ground-based development of electrophoresis was heavily influenced by the need to circumvent the effects of gravity, this process should be a prime candidate for space operation. Nevertheless, while a space facility for electrophoresis may overcome the limitations imposed by gravity, it will not necessarily overcome all problems inherent in electrophoresis. These are, mainly, electroosmosis and the dissipation of the heat generated by the electric field. The NASA program has already led to excellent coatings to prevent electroosmosis, while the need for heat dissipation will continue to impose limits on the actual size of equipment. It is also not excluded that, once the dominant force of gravity is eliminated, disturbances in fluid stability may originate from weaker forces, such as surface tension.

QBO Modulation of the Mesopause Gravity Wave Momentum Flux over Tierra del Fuego

NASA Technical Reports Server (NTRS)

De Wit, R. J.; Janches, D.; Fritts, D. C.; Hibbins, R. E.

2016-01-01

The interannual variability of the mesosphere and lower thermosphere (MLT) gravity wave momentum flux over southern mid latitudes (53.7degS) has been studied using more than 7 years of meteor radar observations at Ro Grande, Argentina. A modulation, with periods similar to that of the equatorial stratospheric quasi-biennial oscillation (QBO), is observed in the vertical flux of zonal as well as meridional momentum. The QBO signal is largest in the zonal component during summer and is in phase with the stratospheric QBO at 50 hPa (approx. 21 km). The relation between the stratospheric QBO and the QBO modulation in the MLT gravity wave forcing (derived from the divergence of the momentum flux) was found to be consistent with that expected from the Holton-Tan effect coupled to the interhemispheric coupling mechanism. These results provide the first observational support for the existence of the midlatitude gravity wave forcing anomalies as hypothesized in the interhemispheric coupling mechanism.

Kinematic and EMG Comparison of Gait in Normal and Microgravity

NASA Technical Reports Server (NTRS)

DeWitt, John K.; Edwards, W. Brent; Perusek, Gail P.; Lewandowski, Beth E.; Samorezov, Sergey

2009-01-01

Astronauts regularly perform treadmill locomotion as a part of their exercise prescription while onboard the International Space Station. Although locomotive exercise has been shown to be beneficial for bone, muscle, and cardiovascular health, astronauts return to Earth after long duration missions with net losses in all three areas [1]. These losses might be partially explained by fundamental differences in locomotive performance between normal gravity (NG) and microgravity (MG) environments. During locomotive exercise in MG, the subject must wear a waist and shoulder harness that is attached to elastomer bungees. The bungees are attached to the treadmill, and provide forces that are intended to replace gravity. However, unlike gravity, which provides a constant force upon all body parts, the bungees provide a spring force only to the harness. Therefore, subjects are subjected to two fundamental differences in MG: 1) forces returning the subject to the treadmill are not constant, and 2) forces are only applied to the axial skeleton at the waist and shoulders. The effectiveness of the exercise may also be affected by the magnitude of the gravity replacement load. Historically, astronauts have difficulty performing treadmill exercise with loads that approach body weight (BW) due to comfort and inherent stiffness in the bungee system. Although locomotion can be executed in MG, the unique requirements could result in performance differences as compared to NG. These differences may help to explain why long term training effects of treadmill exercise may differ from those found in NG. The purpose of this investigation was to compare locomotion in NG and MG to determine if kinematic or muscular activation pattern differences occur between gravitational environments.

Fitting unanchored puzzle pieces in the skeleton: appropriate 3D scapular positions for the quadrupedal support in tetrapods.

PubMed

Fujiwara, Shin-Ichi

2018-05-01

Deducing the scapular positions of extinct tetrapod skeletons remains difficult, because the scapulae and rib cage are connected with each other not directly by skeletal joint, but by thoracic muscles. In extant non-testudine quadrupedal tetrapods, the top positions of the scapulae/suprascapulae occur at the anterior portion of the rib cage, above the vertebral column and near the median plane. The adequacy of this position was tested using three-dimensional mechanical models of Felis, Rattus and Chamaeleo that assumed stances on a forelimb on a single side and the hindlimbs. The net moment about the acetabulum generated by the gravity force and the contractive forces of the anti-gravity thoracic muscles, and the resistance of the rib to vertical compression between the downward gravity and upward lifting force from the anti-gravity thoracic muscle depend on the scapular position. The scapular position common among quadrupeds corresponds to the place at which the roll and yaw moments of the uplifted portion of the body are negligible, where the pitch moment is large enough to lift the body, and above the ribs having high strength against vertical compression. These relationships between scapular position and rib cage morphology should allow reliable reconstruction of limb postures of extinct taxa. © 2018 Anatomical Society.

Stem sap flow in plants under low gravity conditions

NASA Astrophysics Data System (ADS)

Tokuda, Ayako; Hirai, Hiroaki; Kitaya, Yoshiaki

2016-07-01

A study was conducted to obtain a fundamental knowledge for plant functions in bio-regenerative life support systems in space. Stem sap flow in plants is important indicators for water transport from roots to atmosphere through leaves. In this study, stem sap flow in sweetpotato was assessed at gravity levels from 0.01 to 2 g for about 20 seconds each during parabolic airplane flights. Stem sap flow was monitored with a heat balance method in which heat generated with a tiny heater installed in the stem was transferred upstream and downstream by conduction and upstream by convection with the sap flow through xylems of the vascular tissue. Thermal images of stem surfaces near heated points were captured using infrared thermography and the internal heat convection corresponding to the sap flow was analyzed. In results, the sap flow in stems was suppressed more at lower gravity levels without forced air circulation. No suppression of the stem sap flow was observed with forced air circulation. Suppressed sap flow in stems would be caused by suppression of transpiration in leaves and would cause restriction of water and nutrient uptake in roots. The forced air movement is essential to culture healthy plants at a high growth rate under low gravity conditions in space.

Beyond the growth rate of cosmic structure: Testing modified gravity models with an extra degree of freedom

NASA Astrophysics Data System (ADS)

Burrage, Clare; Parkinson, David; Seery, David

2017-08-01

In "modified" gravity the observed acceleration of the universe is explained by changing the gravitational force law or the number of degrees of freedom in the gravitational sector. Both possibilities can be tested by measurements of cosmological structure formation. In this paper we elaborate the details of such tests using the Galileon model as a case study. We pay attention to the possibility that each new degree of freedom may have stochastically independent initial conditions, generating different types of potential well in the early universe and breaking complete correlation between density and velocity power spectra. This "stochastic bias" can confuse schemes to parametrize the predictions of modified gravity models, such as the use of the growth parameter f alone. Using data from the WiggleZ Dark Energy Survey we show that it will be possible to obtain constraints using information about the cosmological-scale force law embedded in the multipole power spectra of redshift-space distortions. As an example, we obtain an upper limit on the strength of the conformal coupling to matter in the cubic Galileon model, giving |1 /M |≲200 /MP . This allows the fifth-force to be stronger than gravity, but is consistent with zero coupling.

Contact Angle Influence on Geysering Jets in Microgravity Investigated

NASA Technical Reports Server (NTRS)

Chato, David J.

2004-01-01

Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquid-free vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, surface tension forces must be used to contain jets. To model this phenomenon, a numerical method that tracks the fluid motion and the surface tension forces is required. Jacqmin has developed a phase model that converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly away. Previous attempts at this formulation were criticized for smearing the interface. This can be overcome by sharpening the phase function, double gridding the fluid function, and using a higher-order solution for the fluid function. The solution of this equation can be rewritten as two coupled Poisson equations that also include the velocity.

High-precision gravimetric survey in support of lunar laser ranging at Haleakala, Maui, 1976 - 1978

NASA Technical Reports Server (NTRS)

Schenck, B. E.; Laurila, S. H.

1978-01-01

The planning, observations and adjustment of high-precision gravity survey networks established on the islands of Maui and Oahu as part of the geodetic-geophysical program in support of lunar laser ranging at Haleakala, Maui, Hawaii are described. The gravity survey networks include 43 independently measured gravity differences along the gravity calibration line from Kahului Airport to the summit of Mt. Haleakala, together with some key points close to tidal gauges on Maui, and 40 gravity differences within metropolitan Honolulu. The results of the 1976-1978 survey are compared with surveys made in 1961 and in 1964-1965. All final gravity values are given in the system of the international gravity standardization net 1971 (IGSN 71); values are obtained by subtracting 14.57 mgal from the Potsdam value at the gravity base station at the Hickam Air Force Base, Honolulu.

Four Theorems on the Psychometric Function

PubMed Central

May, Keith A.; Solomon, Joshua A.

2013-01-01

In a 2-alternative forced-choice (2AFC) discrimination task, observers choose which of two stimuli has the higher value. The psychometric function for this task gives the probability of a correct response for a given stimulus difference, . This paper proves four theorems about the psychometric function. Assuming the observer applies a transducer and adds noise, Theorem 1 derives a convenient general expression for the psychometric function. Discrimination data are often fitted with a Weibull function. Theorem 2 proves that the Weibull “slope” parameter, , can be approximated by , where is the of the Weibull function that fits best to the cumulative noise distribution, and depends on the transducer. We derive general expressions for and , from which we derive expressions for specific cases. One case that follows naturally from our general analysis is Pelli's finding that, when , . We also consider two limiting cases. Theorem 3 proves that, as sensitivity improves, 2AFC performance will usually approach that for a linear transducer, whatever the actual transducer; we show that this does not apply at signal levels where the transducer gradient is zero, which explains why it does not apply to contrast detection. Theorem 4 proves that, when the exponent of a power-function transducer approaches zero, 2AFC performance approaches that of a logarithmic transducer. We show that the power-function exponents of 0.4–0.5 fitted to suprathreshold contrast discrimination data are close enough to zero for the fitted psychometric function to be practically indistinguishable from that of a log transducer. Finally, Weibull reflects the shape of the noise distribution, and we used our results to assess the recent claim that internal noise has higher kurtosis than a Gaussian. Our analysis of for contrast discrimination suggests that, if internal noise is stimulus-independent, it has lower kurtosis than a Gaussian. PMID:24124456

Reflector-based phase calibration of ultrasound transducers.

PubMed

van Neer, Paul L M J; Vos, Hendrik J; de Jong, Nico

2011-01-01

Recently, the measurement of phase transfer functions (PTFs) of piezoelectric transducers has received more attention. These PTFs are useful for e.g. coding and interference based imaging methods, and ultrasound contrast microbubble research. Several optical and acoustic methods to measure a transducer's PTF have been reported in literature. The optical methods require a setup to which not all ultrasound laboratories have access to. The acoustic methods require accurate distance and acoustic wave speed measurements. A small error in these leads to a large error in phase, e.g. an accuracy of 0.1% on an axial distance of 10cm leads to an uncertainty in the PTF measurement of ±97° at 4MHz. In this paper we present an acoustic pulse-echo method to measure the PTF of a transducer, which is based on linear wave propagation and only requires an estimate of the wave travel distance and the acoustic wave speed. In our method the transducer is excited by a monofrequency sine burst with a rectangular envelope. The transducer initially vibrates at resonance (transient regime) prior to the forcing frequency response (steady state regime). The PTF value of the system is the difference between the phases deduced from the transient and the steady state regimes. Good agreement, to within 7°, was obtained between KLM simulations and measurements on two transducers in a 1-8MHz frequency range. The reproducibility of the method was ±10°, with a systematic error of 2° at 1MHz increasing to 16° at 8MHz. This work demonstrates that the PTF of a transducer can be measured in a simple laboratory setting. Copyright © 2010 Elsevier B.V. All rights reserved.

Tiltmeter studies in earthquake prediction

USGS Publications Warehouse

Johnston, M.

1978-01-01

tilt measurements give us a means of monitoring vertical displacements or local uplift of the crust. The simplest type of tiltmeter is a stationary pendulum (fig. 1). As the Earth's surface distorts locally, the pendulum housing is tilted while, of course, the pendulum continues to hang vertically (that is, in the direction of the gravity vector). The tilt angle is the angle through which the pendulum housing is tilted. The pendulum is the inertial reference (the force of gravity remains unchanged at the site), and tilting of the instrument housing represents the moving reference frame. We note in passing that the tiltmeter could also be used to measure the force of gravity by using the pendulum in the same way as Henry Kater did in his celebrated measurement of g in 1817. 

Microgravity Fluid Separation Physics: Experimental and Analytical Results

NASA Technical Reports Server (NTRS)

Shoemaker, J. Michael; Schrage, Dean S.

1997-01-01

Effective, low power, two-phase separation systems are vital for the cost-effective study and utilization of two-phase flow systems and flow physics of two-phase flows. The study of microgravity flows have the potential to reveal significant insight into the controlling mechanisms for the behavior of flows in both normal and reduced gravity environments. The microgravity environment results in a reduction in gravity induced buoyancy forces acting on the discrete phases. Thus, surface tension, viscous, and inertial forces exert an increased influence on the behavior of the flow as demonstrated by the axisymmetric flow patterns. Several space technology and operations groups have studied the flow behavior in reduced gravity since gas-liquid flows are encountered in several systems such as cabin humidity control, wastewater treatment, thermal management, and Rankine power systems.

Liquid jet impingement normal to a disk in zero gravity. Ph.D. Thesis Toledo Univ.

NASA Technical Reports Server (NTRS)

Labus, T. L.

1977-01-01

The free surface shapes of circular liquid jets impinging normal to sharp-edged disks in zero gravity are determined. Zero gravity drop tower experiments yielded three distinct flow patterns that were classified in terms of the relative effects of surface tension and inertial forces. An order of magnitude analysis was conducted that indicated regions where viscous forces were not significant in the computation of free surface shapes. The free surface analysis was simplified by transforming the governing potential flow equations and boundary conditions into the inverse plane, where the stream function and velocity potential became the coordinates. The resulting nonlinear equations were solved by standard finite difference methods, and comparisons were made with the experimental data for the inertia dominated regime.

Gravity Reception and Cardiac Function in the Spider

NASA Technical Reports Server (NTRS)

Finck, A.

1985-01-01

The following features of the arachnid gravity system were studied. (1) the absolute threshold to hyper-gz is quite low indicating fine proprioreceptive properties of the lyriform organ, the Gz/vibration detector; (2) the neurogenic heart of the spider is a good dependent variable for assessing its behavior to Gz and other stimuli which produce mechanical effects on the exoskeleton; (3) Not only is the cardiac response useful but it is now understood to be an integral part of the system which compensates for the consequences of gravity in the spider (an hydraulic leg extension); and (4) a theoretical model was proposed in which a mechanical amplifier, the leg lever, converts a weak force (at the tarsus) to a strong force (at the patella), capable of compressing the exoskeleton and consequently the lyriform receptor.

Tsunami-Generated Atmospheric Gravity Waves and Their Atmospheric and Ionospheric Effects: a Review and Some Recent Modeling Results

NASA Astrophysics Data System (ADS)

Hickey, M. P.

2017-12-01

Tsunamis propagate on the ocean surface at the shallow water phase speed which coincides with the phase speed of fast atmospheric gravity waves. The forcing frequency also corresponds with those of internal atmospheric gravity waves. Hence, the coupling and effective forcing of gravity waves due to tsunamis is particularly effective. The fast horizontal phase speeds of the resulting gravity waves allows them to propagate well into the thermosphere before viscous dissipation becomes strong, and the waves can achieve nonlinear amplitudes at these heights resulting in large amplitude traveling ionospheric disturbances (TIDs). Additionally, because the tsunami represents a moving source able to traverse large distances across the globe, the gravity waves and associated TIDs can be detected at large distances from the original tsunami (earthquake) source. Although it was during the mid 1970s when the tsunami source of gravity waves was first postulated, only relatively recently (over the last ten to fifteen years) has there has been a surge of interest in this research arena, driven largely by significant improvements in measurement technologies and computational capabilities. For example, the use of GPS measurements to derive total electron content has been a particularly powerful technique used to monitor the propagation and evolution of TIDs. Monitoring airglow variations driven by atmospheric gravity waves has also been a useful technique. The modeling of specific events and comparison with the observed gravity waves and/or TIDs has been quite revealing. In this talk I will review some of the most interesting aspects of this research and also discuss some interesting and outstanding issues that need to be addressed. New modeling results relevant to the Tohoku tsunami event will also be presented.

Optimal integration of gravity in trajectory planning of vertical pointing movements.

PubMed

Crevecoeur, Frédéric; Thonnard, Jean-Louis; Lefèvre, Philippe

2009-08-01

The planning and control of motor actions requires knowledge of the dynamics of the controlled limb to generate the appropriate muscular commands and achieve the desired goal. Such planning and control imply that the CNS must be able to deal with forces and constraints acting on the limb, such as the omnipresent force of gravity. The present study investigates the effect of hypergravity induced by parabolic flights on the trajectory of vertical pointing movements to test the hypothesis that motor commands are optimized with respect to the effect of gravity on the limb. Subjects performed vertical pointing movements in normal gravity and hypergravity. We use a model based on optimal control to identify the role played by gravity in the optimal arm trajectory with minimal motor costs. First, the simulations in normal gravity reproduce the asymmetry in the velocity profiles (the velocity reaches its maximum before half of the movement duration), which typically characterizes the vertical pointing movements performed on Earth, whereas the horizontal movements present symmetrical velocity profiles. Second, according to the simulations, the optimal trajectory in hypergravity should present an increase in the peak acceleration and peak velocity despite the increase in the arm weight. In agreement with these predictions, the subjects performed faster movements in hypergravity with significant increases in the peak acceleration and peak velocity, which were accompanied by a significant decrease in the movement duration. This suggests that movement kinematics change in response to an increase in gravity, which is consistent with the hypothesis that motor commands are optimized and the action of gravity on the limb is taken into account. The results provide evidence for an internal representation of gravity in the central planning process and further suggest that an adaptation to altered dynamics can be understood as a reoptimization process.

Ultrasound imparted air-recoil resonance (UIAR) method for acoustic power estimation: theory and experiment.

PubMed

Kaiplavil, Sreekumar; Rivens, Ian; ter Haar, Gail

2013-07-01

Ultrasound imparted air-recoil resonance (UIAR), a new method for acoustic power estimation, is introduced with emphasis on therapeutic high-intensity focused ultrasound (HIFU) monitoring applications. Advantages of this approach over existing practices include fast response; electrical and magnetic inertness, and hence MRI compatibility; portability; high damage threshold and immunity to vibration and interference; low cost; etc. The angle of incidence should be fixed for accurate measurement. However, the transducer-detector pair can be aligned in any direction with respect to the force of gravity. In this sense, the operation of the device is orientation independent. The acoustic response of a pneumatically coupled pair of Helmholtz resonators, with one of them acting as the sensor head, is used for the estimation of acoustic power. The principle is valid in the case of pulsed/ burst as well as continuous ultrasound exposure, the former being more sensitive and accurate. An electro-acoustic theory has been developed for describing the dynamics of pressure flow and resonance in the system considering various thermo- viscous loss mechanisms. Experimental observations are found to be in agreement with theoretical results. Assuming the window damage threshold (~10 J·mm(-2)) and accuracy of RF power estimation are the upper and lower scale-limiting factors, the performance of the device was examined for an RF power range of 5 mW to 100 W with a HIFU transducer operating at 1.70 MHz, and an average nonlinearity of ~1.5% was observed. The device is also sensitive to sub-milliwatt powers. The frequency response was analyzed at 0.85, 1.70, 2.55, and 3.40 MHz and the results are presented with respective theoretical estimates. Typical response time is in the millisecond regime. Output drift is about 3% for resonant and 5% for nonresonant modes. The principle has been optimized to demonstrate a general-purpose acoustic power meter.

Indirect Blood Pressure Measuring Device

NASA Technical Reports Server (NTRS)

Hum, L.; Cole, C. E.

1973-01-01

Design and performance of a blood pressure recording device for pediatric use are reported. A strain gage transducer with a copper-beryllium strip as force sensing element is used to monitor skin movements and to convert them into electrical signals proportional to those displacements. Experimental tests with this device in recording of force developed above the left femoral artery of a dog accurately produced a blood pressure curve.

Reversible Solid Adhesion for Defense Applications

DTIC Science & Technology

2008-01-31

sensitive. Referring to Fig. 2(a), using the two closed-loop piezoelectric ( PZT ) actuators, the vertical and horizontal velocities of the...approaching/retracting contacting surfaces can be independently controlled. The displacement resolution of the vertical PZT actuator is 0.6 nm, and the total...interfacial forces are measured using the prototype custom-made capacity-type force transducer which is attached directly on the upper PZT actuator. In order

State of Technology Report for Force Main Rehabilitation

EPA Science Inventory

Force mains that carry sewage flows under pressure represent a special set of challenges for sewer rehabilitation. Force mains represent about 7.5% of the wastewater system and they typically use materials that are not commonly used in gravity sewer systems. Ductile iron (DI), ...

Nuclear Posture Review

DTIC Science & Technology

2018-02-01

SLBM); land- based intercontinental ballistic missiles (ICBM); and strategic bombers carrying gravity bombs and air-launched cruise missiles (ALCMs...capable bomber force beginning in the mid-2020s. The B83-1 and B61-11 gravity bombs can hold at risk a variety of protected targets. As a result...both will be retained in the stockpile, at least until there is sufficient confidence in the B61-12 gravity bomb that will be available in 2020

Liquid management in low gravity using baffled rotating containers

NASA Technical Reports Server (NTRS)

Gans, R. F.

1985-01-01

Possible static configurations of liquids in rotating cylindrical containers with baffles evenly spaced in the axial direction are found. The force balance is among surface tension, centrifugal force and gravity. Two instabilities are found in this parameter space: type 1 is the inability of the liquid to form an interface attached to the baffles; type 2 is the inability for multi-baffled configurations to sustain interfaces between each pair of baffles. The type 1 analysis is confirmed through laboratory based equipment. Applications to orbiting containers are discussed.

Liquid management in low gravity using baffled rotating containers

NASA Technical Reports Server (NTRS)

Gans, R. F.

1984-01-01

Possible static configurations of liquids in rotating cylindrical containers with baffles evenly spaced in the axial direction are found. The force balance is among surface tension, centrifugal force and gravity. Two instabilities are found in this parameter space: type 1 is the inability of the liquid to form an interface attached to the baffles; type 2 is the inability for multi-baffled configurations to sustain interfaces between each pair of baffles. The type 1 analysis is confirmed through laboratory based equipment. Applications to orbiting containers are discussed.

A ray tracing model of gravity wave propagation and breakdown in the middle atmosphere

NASA Technical Reports Server (NTRS)

Schoeberl, M. R.

1985-01-01

Gravity wave ray tracing and wave packet theory is used to parameterize wave breaking in the mesosphere. Rays are tracked by solving the group velocity equations, and the interaction with the basic state is determined by considering the evolution of the packet wave action density. The ray tracing approach has a number of advantages over the steady state parameterization as the effects of gravity wave focussing and refraction, local dissipation, and wave response to rapid changes in the mean flow are more realistically considered; however, if steady state conditions prevail, the method gives identical results. The ray tracing algorithm is tested using both interactive and noninteractive models of the basic state. In the interactive model, gravity wave interaction with the polar night jet on a beta-plane is considered. The algorithm produces realistic polar night jet closure for weak topographic forcing of gravity waves. Planetary scale waves forced by local transfer of wave action into the basic flow in turn transfer their wave action into the zonal mean flow. Highly refracted rays are also found not to contribute greatly to the climatology of the mesosphere, as their wave action is severely reduced by dissipation during their lateral travel.

Dynamics of flexural gravity waves: from sea ice to Hawking radiation and analogue gravity

NASA Astrophysics Data System (ADS)

Das, S.; Sahoo, T.; Meylan, M. H.

2018-01-01

The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity. Between the blocking and buckling limit of the compressive force, the dispersion relation possesses three positive real roots, contrary to an earlier observation of having a single positive real root. Negative energy waves, in which the phase and group velocity point in opposite directions, are also shown to exist. In the presence of an opposing current and certain critical ranges of compressive force, the second blocking point shifts from the positive to the negative branch of the dispersion relation. Such a shift is known as the Hawking effect from the analogous behaviour in the theory of relativity which leads to Hawking radiation. The theory we develop is illustrated with simulations of linear waves in the time domain.

Βiocolloid and colloid transport through water-saturated columns packed with glass beads: Effect of gravity

NASA Astrophysics Data System (ADS)

Chrysikopoulos, C. V.; Syngouna, V. I.

2013-12-01

The role of gravitational force on biocolloid and colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with biocolloids (bacteriophages: ΦΧ174, MS2) and colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q=1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one dimensional, colloid transport model, accounting for gravity effects. The results revealed that flow direction has a significant influence on particle deposition. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for biocolloid and colloid deposition. Schematic illustration of a packed column with up-flow velocity having orientation (-i) with respect to gravity. The gravity vector components are: g(i)= g(-z) sinβ i, and g(-j)= -g(-z) cosβ j. Experimental setup showing the various column arrangements: (a) horizontal, (b) diagonal, and (c) vertical.

Observing human movements helps decoding environmental forces.

PubMed

Zago, Myrka; La Scaleia, Barbara; Miller, William L; Lacquaniti, Francesco

2011-11-01

Vision of human actions can affect several features of visual motion processing, as well as the motor responses of the observer. Here, we tested the hypothesis that action observation helps decoding environmental forces during the interception of a decelerating target within a brief time window, a task intrinsically very difficult. We employed a factorial design to evaluate the effects of scene orientation (normal or inverted) and target gravity (normal or inverted). Button-press triggered the motion of a bullet, a piston, or a human arm. We found that the timing errors were smaller for upright scenes irrespective of gravity direction in the Bullet group, while the errors were smaller for the standard condition of normal scene and gravity in the Piston group. In the Arm group, instead, performance was better when the directions of scene and target gravity were concordant, irrespective of whether both were upright or inverted. These results suggest that the default viewer-centered reference frame is used with inanimate scenes, such as those of the Bullet and Piston protocols. Instead, the presence of biological movements in animate scenes (as in the Arm protocol) may help processing target kinematics under the ecological conditions of coherence between scene and target gravity directions.

Extending Newton's Universal Theory of Gravity

NASA Astrophysics Data System (ADS)

Aisenberg, Sol

2011-11-01

This should remove the mystery of Dark Matter. Newton's universal theory of gravity only used the observations of the motion of planets in our solar system. Hubble later used observations of fixed stars in the universe, and showed that the fixed stars were actually galaxies with very large numbers of stars. Newton's universal law of gravity could not explain these new observations without the mystery of dark matter for the additional gravity. In science, when a theory is not able to explain new observations it is necessary to modify the theory or abandon the theory. Rubin observed flat (constant velocity) rotation curves for stars in spiral galaxies. Dark matter was proposed to provide the missing gravity. The equation balancing gravitational force and centripetal force is M*G=v*v*r and for the observed constant velocity v this requires M*G to be a linear function of distance r. If the linear dependence is instead assigned to G instead of M to give a new value for Gn as G+A*r, this will explain the observations in the cosmos and also in our solar system for small r. See ``The Misunderstood Universe'' for more details.

DIY Astrophysics: Examining diurnal and seasonal fluctuations in the effects of solar gravity using a three-axis accelerometer

NASA Astrophysics Data System (ADS)

Romich, Kristine; Kruger, Andrew

On the surface of the Earth, the acceleration due to the influence of the Sun's gravity is approximately 0.06% of that due to the Earth's own gravity (0.0006g). Nevertheless, it may be detected using a sensitive three-axis accelerometer such as the InvenSense MPU-6050, which is compatible with low-cost microcontrollers such as the Arduino and Raspberry Pi and hence provides an affordable means of investigation. Unlike the gravitational force between the Earth and an object on its surface, the x-, y-, and z-components of the gravitational force between the Sun and an earthbound observer are not constant: the vector direction of the gravitational acceleration caused by the Sun - denoted g⊙ - fluctuates as a function of the Earth's rotation (i.e., the time of day) and position in orbit (i.e., the time of year). The present investigation derives mathematical expressions for the instantaneous value of each component of g⊙ in terms of both quantities. It also outlines a method of using the InvenSense MPU-6050 to detect the corresponding fluctuations in total gravity (and, thus, the influence of the Sun's gravity) experimentally.

DIY Astrophysics: Examining diurnal and seasonal fluctuations in the effects of solar gravity using a three-axis accelerometer

NASA Astrophysics Data System (ADS)

Romich, Kristine; Kruger, Andrew

2017-01-01

On the surface of the Earth, the acceleration due to the influence of the Sun's gravity is approximately 0.06% of that due to the Earth's own gravity (0.0006g). Nevertheless, it may be detected using a sensitive three-axis accelerometer such as the InvenSense MPU-6050, which is compatible with low-cost microcontrollers such as the Arduino and Raspberry Pi and hence provides an affordable means of investigation. Unlike the gravitational force between the Earth and an object on its surface, the x-, y-, and z-components of the gravitational force between the Sun and an earthbound observer are not constant: the vector direction of the gravitational acceleration caused by the Sun — denoted g⊙ — fluctuates as a function of the Earth's rotation (i.e., the time of day) and position in orbit (i.e., the time of year). The present investigation derives mathematical expressions for the instantaneous value of each component of g⊙ in terms of both quantities. It also outlines a method of using the InvenSense MPU-6050 to detect the corresponding fluctuations in total gravity (and, thus, the influence of the Sun's gravity) experimentally.

Dynamics of flexural gravity waves: from sea ice to Hawking radiation and analogue gravity.

PubMed

Das, S; Sahoo, T; Meylan, M H

2018-01-01

The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity. Between the blocking and buckling limit of the compressive force, the dispersion relation possesses three positive real roots, contrary to an earlier observation of having a single positive real root. Negative energy waves, in which the phase and group velocity point in opposite directions, are also shown to exist. In the presence of an opposing current and certain critical ranges of compressive force, the second blocking point shifts from the positive to the negative branch of the dispersion relation. Such a shift is known as the Hawking effect from the analogous behaviour in the theory of relativity which leads to Hawking radiation. The theory we develop is illustrated with simulations of linear waves in the time domain.

Physics for First-Graders.

ERIC Educational Resources Information Center

Hagerott, Steven G.

1997-01-01

A Lockheed flight controls engineer describes how, as an undergraduate, he taught first graders basic lessons in physics and engineering by using slides, monkey bars, and other playground equipment to demonstrate principles like gravity, friction, force, and inertia. The children learned more about lift and gravity by constructing and flying paper…

A Prototype Tactile Sensor Array.

DTIC Science & Technology

1982-09-15

Active Touch Sensing. Technical Report, MIT Artificial Inteligence Laboratory, 1981. (9] Larcombe, M. Carbon Fibre Tactile Sensors. Technical Report...thesis, Carnegie-Mellon University, 1981. [13] Purbrick, John A. A Force Transducer Employing Conductive Silicone Rubber. Technical Report, MIT Artificial

Steerable vertical to horizontal energy transducer for mobile robots

DOEpatents

Spletzer, Barry L.; Fischer, Gary J.; Feddema, John T.

2001-01-01

The present invention provides a steerable vertical to horizontal energy transducer for mobile robots that less complex and requires less power than two degree of freedom tilt mechanisms. The present invention comprises an end effector that, when mounted with a hopping actuator, translates along axis (typically vertical) actuation into combined vertical and horizontal motion. The end effector, or foot, mounts with an end of the actuator that moves toward the support surface (typically a floor or the earth). The foot is shaped so that the first contact with the support surface is off the axis of the actuator. Off-axis contact with the support surface generates an on-axis force (typically resulting in vertical motion) and a moment orthogonal to the axis. The moment initiates a horizontal tumbling motion, and tilts the actuator so that its axis is oriented with a horizontal component and continued actuation generates both vertical and horizontal force.

Cosmos 2229

NASA Technical Reports Server (NTRS)

Edgerton, V. Reggie; Roy, Roland R.; Hodgson, John A.

1993-01-01

The 6 weeks preflight activities of the Cosmos project during 1993 included: modification of EMG connector to improve the reliability of EMG recording; 24 hour cage activity recording from all but two of the flight animals (monkeys); attempts to record from flight candidates during foot lever task; and force transducer calibrations on all flight candidate animals. The 4 week postflight recordings included: postflight recordings from flight animals; postflight recordings on 3 control (non-flight) animals; postflight recalibration of force transducers on 1 flight and 4 control (non-flight) animals; and attempts to record EMG and video data from the flight animals during postflight locomotion and postural activity. The flight EMG recordings suggest that significant changes in muscle control may occur in spaceflight. It is also clear from recordings that levels of EMG recorded during spaceflight can attain values similar to those measured on earth. Amplifier gain settings should therefore probably not be changed for spaceflight.

A comparison of Lorentz, planetary gravitational, and satellite gravitational resonances

NASA Technical Reports Server (NTRS)

Hamilton, Douglas P.

1994-01-01

We consider a charged dust grain whose orbital motion is dominated by a planet's point-source gravity, but perturbed by higher-order terms in the planet's gravity field as well as by the Lorentz force arising from an asymmetric planetary magnetic field. Perturbations to Keplerian orbits due to a nonspherical gravity field are expressed in the traditional way: in terms of a disturbing function which can be expanded in a series of spherical harmonics (W. M. Kaula, 1966). In order to calculate the electromagnetic perturbation, we first write the Lorentz force in terms of the orbital elements and then substitute it into Gauss' perturbation equations. We use our result to derive strengths of Lorentz resonances and elucidate their properties. In particular, we compare Lorentz resonances to two types of gravitational resonances: those arising from periodic tugs of a satellite and those due to the attraction of an arbitrarily shaped planet. We find that Lorentz resonances share numerous properties with their gravitational counterparts and show, using simple physical arguments, that several of these patterns are fundamental, applying not only to our expansions, but to all quantities expressed in terms of orbital elements. Some of these patterns have been previously called 'd'Alembert rules' for satellite resonances. Other similarities arise because, to first-order in the perturbing force, the three problems share an integral of the motion. Yet there are also differences; for example, first-order inclination resonances exist for perturbations arising from planetary gravity and from the Lorentz force, but not for those due to an orbiting satellite. Finally, we provide a heuristic treatment of a particle's orbital evolution under the influence of drag and resonant forces. Particles brought into mean-motion resonances experience either trapping or resonant 'jumps,' depending on the direction from which the resonance is approached. We show that this behavior does not depend on the details of the perturbing force but rather is fundamental to all mean-motion resonances.

Modeling of Piezoelectric Energy Harvesting Using Cymbal Transducers

NASA Astrophysics Data System (ADS)

Kim, Hyeoungwoo; Priya, Shashank; Uchino, Kenji

2006-07-01

This study reports the experimental and analytical results on a piezoelectric cymbal with 29 mm diameter and 1 mm thickness operating under force of 70 N in the frequency range of 10-200 Hz. It was found that the generated power increases with the frequency and around 100 mW can be harvested at frequency of 200 Hz across a 200 kΩ resistor. Power generation from the cymbal transducer was modeled by using the theory developed for the Belleville spring. The calculated results were found to be in good agreement with the experimental results. The results indicate that the metal-ceramic composite transducer “CYMBAL” is the most promising structure for harvesting the electric energy from automobile engine vibrations. The metal cap enhances the endurance of the ceramic to sustain high loads along with stress amplification.

Chameleon vector bosons

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

Nelson, Ann E.; Instituto de Fisica Teorica UAM/CSIC, Facultad de Ciencias, C-XVI Universidad Autonoma de Madrid Cantoblanco, Madrid 28049; Walsh, Jonathan

2008-05-01

We show that for a force mediated by a vector particle coupled to a conserved U(1) charge, the apparent range and strength can depend on the size and density of the source, and the proximity to other sources. This chameleon effect is due to screening from a light charged scalar. Such screening can weaken astrophysical constraints on new gauge bosons. As an example we consider the constraints on chameleonic gauged B-L. We show that although Casimir measurements greatly constrain any B-L force much stronger than gravity with range longer than 0.1 {mu}m, there remains an experimental window for a long-rangemore » chameleonic B-L force. Such a force could be much stronger than gravity, and long or infinite range in vacuum, but have an effective range near the surface of the earth which is less than a micron.« less

Acoustic levitation in the presence of gravity

NASA Technical Reports Server (NTRS)

Collas, P.; Barmatz, M.; Shipley, C.

1989-01-01

The method of Gor'kov (1961) has been applied to derive general expressions for the total potential and force on a small spherical object in a resonant chamber in the presence of both acoustic and gravitational force fields. The levitation position is also determined in rectangular resonators for the simultaneous excitation of up to three acoustic modes, and the results are applied to the triple-axis acoustic levitator. The analysis is applied to rectangular, spherical, and cylindrical single-mode levitators that are arbitrarily oriented relative to the gravitational force field. Criteria are determined for isotropic force fields in rectangular and cylindrical resonators. It is demonstrated that an object will be situated within a volume of possible levitation positions at a point determined by the relative strength of the acoustic and gravitational fields and the orientation of the chamber relative to gravity.

Force Required to Cinch the Tricuspid Annulus: An Ex-Vivo Study

PubMed Central

Adkins, Amy; Aleman, Jesus; Boies, Lori; Sako, Edward; Bhattacharya, Shamik

2016-01-01

Background and aim of the study Tricuspid annuloplasty is the most preferred technique for the treatment of functional tricuspid regurgitation (FTR). However, high incidences of recurrent regurgitation and risky reoperation demands a deeper insight into the technique. The cinching force required to bring a dilated annulus back to the original size is unknown. The study aim was to quantify the cinching force in the tricuspid annulus which can contribute to the long-term durability of tricuspid annuloplasty and percutaneous device design. Methods In ten ovine hearts, a suture was anchored around the free wall of the tricuspid annulus with the free end attached to a force transducer. The force transducer was mounted on a slider system which pulled the suture at regular intervals. Closure of the tricuspid valve was achieved by pressurizing the right ventricle at 30 mmHg through the pulmonary valve. The suture was pulled to cinch the tricuspid annulus. The tricuspid annulus area was measured from images taken at each increment, and the corresponding force was recorded. The hearts were tested for three conditions: (i) non-pressurized (NP); (ii) pressurized (P; normal), and (iii) dilated-pressurized (DP; diseased). Leakage data were also collected for pressurized and dilated pressurized conditions. Annulus dilation was created by injecting phenol into the annulus. Results The maximum annulus dilation obtained was 8.82%, and the maximum cinching force was 0.38 ± 0.09 N. Leakage was increased by 81.73% from the pressurized to dilated condition. Conclusion The minimal force required to cinch a tricuspid annulus with severe FTR (23.98% dilation) can be approximated to 0.25 N. The required cinching force can play a major role in the long-term durability of the tricuspid annuloplasty. PMID:26897846

Nonlinear effects in ultrasound fields of diagnostic-type transducers used for kidney stone propulsion: Characterization in water

NASA Astrophysics Data System (ADS)

Karzova, M.; Cunitz, B.; Yuldashev, P.; Andriyakhina, Y.; Kreider, W.; Sapozhnikov, O.; Bailey, M.; Khokhlova, V.

2015-10-01

Newer imaging and therapeutic ultrasound technologies require higher in situ pressure levels compared to conventional diagnostic values. One example is the recently developed use of focused ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe is used to deliver the acoustic pushing pulses. The probe comprises 128 elements equally spaced at the 55 mm long convex cylindrical surface with 38 mm radius of curvature. The efficacy of the treatment can be increased by using higher intensity at the focus to provide stronger pushing force; however, nonlinear acoustic saturation can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the 3D Westervelt equation; the boundary condition was set to match the focal geometry of the beam as measured at a low power output. Focal waveforms simulated for increased output power levels were compared with the fiber-optic hydrophone measurements and were found in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of the transducer. This work has application to standard diagnostic probes and imaging.

An Investigation of Energy Transmission Due to Flexural Wave Propagation in Lightweight, Built-Up Structures. Thesis

NASA Technical Reports Server (NTRS)

Mickol, John Douglas; Bernhard, R. J.

1986-01-01

A technique to measure flexural structure-borne noise intensity is investigated. Two accelerometers serve as transducers in this cross-spectral technique. The structure-borne sound power is obtained by two different techniques and compared. In the first method, a contour integral of intensity is performed from the values provided by the two-accelerometer intensity technique. In the second method, input power is calculated directly from the output of force and acceleration transducers. A plate and two beams were the subjects of the sound power comparisons. Excitation for the structures was either band-limited white noise or a deterministic signal similar to a swept sine. The two-accelerometer method was found to be sharply limited by near field and transducer spacing limitations. In addition, for the lightweight structures investigated, it was found that the probe inertia can have a significant influence on the power input to the structure. In addition to the experimental investigation of structure-borne sound energy, an extensive study of the point harmonically forced, point-damped beam boundary value problem was performed to gain insight into measurements of this nature. The intensity formulations were also incorporated into the finite element method. Intensity mappings were obtained analytically via finite element modeling of simple structures.

The Comfortable Roller Coaster--on the Shape of Tracks with a Constant Normal Force

ERIC Educational Resources Information Center

Nordmark, Arne B.; Essen, Hanno

2010-01-01

A particle that moves along a smooth track in a vertical plane is influenced by two forces: gravity and normal force. The force experienced by roller coaster riders is the normal force, so a natural question to ask is, what shape of the track gives a normal force of constant magnitude? Here we solve this problem. It turns out that the solution is…

A computer-based servo system for controlling isotonic contractions of muscle.

PubMed

Smith, J P; Barsotti, R J

1993-11-01

We have developed a computer-based servo system for controlling isotonic releases in muscle. This system is a composite of commercially available devices: an IBM personal computer, an analog-to-digital (A/D) board, an Akers AE801 force transducer, and a Cambridge Technology motor. The servo loop controlling the force clamp is generated by computer via the A/D board, using a program written in QuickBASIC 4.5. Results are shown that illustrate the ability of the system to clamp the force generated by either skinned cardiac trabeculae or single rabbit psoas fibers down to the resolution of the force transducer within 4 ms. This rate is independent of the level of activation of the tissue and the size of the load imposed during the release. The key to the effectiveness of the system consists of two algorithms that are described in detail. The first is used to calculate the error signal to hold force to the desired level. The second algorithm is used to calculate the appropriate gain of the servo for a particular fiber and the size of the desired load to be imposed. The results show that the described computer-based method for controlling isotonic releases in muscle represents a good compromise between simplicity and performance and is an alternative to the custom-built digital/analog servo devices currently being used in studies of muscle mechanics.

Thermosyphon Flooding in Reduced Gravity Environments Test Results

NASA Technical Reports Server (NTRS)

Gibson, Marc A.; Jaworske, Donald A.; Sanzi, Jim; Ljubanovic, Damir

2013-01-01

The condenser flooding phenomenon associated with gravity aided two-phase thermosyphons was studied using parabolic flights to obtain the desired reduced gravity environment (RGE). The experiment was designed and built to test a total of twelve titanium water thermosyphons in multiple gravity environments with the goal of developing a model that would accurately explain the correlation between gravitational forces and the maximum axial heat transfer limit associated with condenser flooding. Results from laboratory testing and parabolic flights are included in this report as part I of a two part series. The data analysis and correlations are included in a follow on paper.

Vertebrate gravity sensors as dynamic systems

NASA Technical Reports Server (NTRS)

Ross, M. D.

1985-01-01

This paper considers verterbrate gravity receptors as dynamic sensors. That is, it is hypothesized that gravity is a constant force to which an acceleration-sensing system would readily adapt. Premises are considered in light of the presence of kinocilia on hair cells of vertebrate gravity sensors; differences in loading of the sensors among species; and of possible reduction in loading by inclusion of much organic material in otoconia. Moreover, organic-inorganic interfaces may confer a piezoelectric property upon otoconia, which increase the sensitivity of the sensory system to small accelerations. Comparisons with man-made accelerometers are briefly taken up.

Direction-dependent arm kinematics reveal optimal integration of gravity cues.

PubMed

Gaveau, Jeremie; Berret, Bastien; Angelaki, Dora E; Papaxanthis, Charalambos

2016-11-02

The brain has evolved an internal model of gravity to cope with life in the Earth's gravitational environment. How this internal model benefits the implementation of skilled movement has remained unsolved. One prevailing theory has assumed that this internal model is used to compensate for gravity's mechanical effects on the body, such as to maintain invariant motor trajectories. Alternatively, gravity force could be used purposely and efficiently for the planning and execution of voluntary movements, thereby resulting in direction-depending kinematics. Here we experimentally interrogate these two hypotheses by measuring arm kinematics while varying movement direction in normal and zero-G gravity conditions. By comparing experimental results with model predictions, we show that the brain uses the internal model to implement control policies that take advantage of gravity to minimize movement effort.

Reproductive cell separation: A concept

NASA Technical Reports Server (NTRS)

Cutaia, A. J.

1973-01-01

Attempt has been made to separate mammalian male (Y) bearing sperm from female (X) bearing sperm. Both types of sperm are very dependent on gravity for their direction of movement. Proposed concept suggests electrophoretic force of suitable magnitude and direction may be effective means of separating X and Y sperm under zero gravity.

14 CFR 29.733 - Tires.

Code of Federal Regulations, 2011 CFR

2011-01-01

... static ground reaction corresponding to the critical center of gravity; and (3) A load on nose wheel tires (to be compared with the dynamic rating established for those tires) equal to the reaction... gravity and exerts a force of 1.0 g downward and 0.25 g forward, the reactions being distributed to the...

14 CFR 29.733 - Tires.

Code of Federal Regulations, 2010 CFR

2010-01-01

... static ground reaction corresponding to the critical center of gravity; and (3) A load on nose wheel tires (to be compared with the dynamic rating established for those tires) equal to the reaction... gravity and exerts a force of 1.0 g downward and 0.25 g forward, the reactions being distributed to the...

The Secret Siphon

ERIC Educational Resources Information Center

Hughes, Stephen W.

2011-01-01

Although the siphon has been in use since ancient times, the exact mechanism of operation is still under discussion. For example, most dictionaries assert that atmospheric pressure is essential to the operation of a siphon rather than gravity. Although there is general agreement that gravity is the motivating force in a siphon, there is…

The AFGL (Air Force Geophysics Laboratory) Absolute Gravity System’s Error Budget Revisted.

DTIC Science & Technology

1985-05-08

also be induced by equipment not associated with the system. A systematic bias of 68 pgal was observed by the Istituto di Metrologia "G. Colonnetti...Laboratory Astrophysics, Univ. of Colo., Boulder, Colo. IMGC: Istituto di Metrologia "G. Colonnetti", Torino, Italy Table 1. Absolute Gravity Values...measurements were made with three Model D and three Model G La Coste-Romberg gravity meters. These instruments were operated by the following agencies

Correlation of Normal Gravity Mixed Convection Blowoff Limits with Microgravity Forced Flow Blowoff Limits

NASA Technical Reports Server (NTRS)

Marcum, Jeremy W.; Olson, Sandra L.; Ferkul, Paul V.

2016-01-01

The axisymmetric rod geometry in upward axial stagnation flow provides a simple way to measure normal gravity blowoff limits to compare with microgravity Burning and Suppression of Solids - II (BASS-II) results recently obtained aboard the International Space Station. This testing utilized the same BASS-II concurrent rod geometry, but with the addition of normal gravity buoyant flow. Cast polymethylmethacrylate (PMMA) rods of diameters ranging from 0.635 cm to 3.81 cm were burned at oxygen concentrations ranging from 14 to 18% by volume. The forced flow velocity where blowoff occurred was determined for each rod size and oxygen concentration. These blowoff limits compare favorably with the BASS-II results when the buoyant stretch is included and the flow is corrected by considering the blockage factor of the fuel. From these results, the normal gravity blowoff boundary for this axisymmetric rod geometry is determined to be linear, with oxygen concentration directly proportional to flow speed. We describe a new normal gravity 'upward flame spread test' method which extrapolates the linear blowoff boundary to the zero stretch limit in order to resolve microgravity flammability limits-something current methods cannot do. This new test method can improve spacecraft fire safety for future exploration missions by providing a tractable way to obtain good estimates of material flammability in low gravity.

Time-dependent computational studies of flames in microgravity

NASA Technical Reports Server (NTRS)

Oran, Elaine S.; Kailasanath, K.

1989-01-01

The research performed at the Center for Reactive Flow and Dynamical Systems in the Laboratory for Computational Physics and Fluid Dynamics, at the Naval Research Laboratory, in support of the NASA Microgravity Science and Applications Program is described. The primary focus was on investigating fundamental questions concerning the propagation and extinction of premixed flames in Earth gravity and in microgravity environments. The approach was to use detailed time-dependent, multispecies, numerical models as tools to simulate flames in different gravity environments. The models include a detailed chemical kinetics mechanism consisting of elementary reactions among the eight reactive species involved in hydrogen combustion, coupled to algorithms for convection, thermal conduction, viscosity, molecular and thermal diffusion, and external forces. The external force, gravity, can be put in any direction relative to flame propagation and can have a range of values. A combination of one-dimensional and two-dimensional simulations was used to investigate the effects of curvature and dilution on ignition and propagation of flames, to help resolve fundamental questions on the existence of flammability limits when there are no external losses or buoyancy forces in the system, to understand the mechanism leading to cellular instability, and to study the effects of gravity on the transition to cellular structure. A flame in a microgravity environment can be extinguished without external losses, and the mechanism leading to cellular structure is not preferential diffusion but a thermo-diffusive instability. The simulations have also lead to a better understanding of the interactions between buoyancy forces and the processes leading to thermo-diffusive instability.

Conception of the system for traffic measurements based on piezoelectric foils

NASA Astrophysics Data System (ADS)

Płaczek, M.

2016-08-01

A concept of mechatronic system for traffic measurements based on the piezoelectric transducers used as sensors is presented. The aim of the work project is to theoretically and experimentally analyse the dynamic response of road infrastructure forced by vehicles motion. The subject of the project is therefore on the borderline of civil engineering and mechanical and covers a wide range of issues in both these areas. To measure the dynamic response of the tested pieces of road infrastructure application of piezoelectric, in particular piezoelectric transducers in the form of piezoelectric films (MFC - Macro Fiber Composite) is proposed. The purpose is to verify the possibility to use composite piezoelectric transducers as sensors used in traffic surveillance systems - innovative methods of controlling the road infrastructure and traffic. Presented paper reports works that were done in order to receive the basic information about analysed systems and their behaviour under excitation by passing vehicles. It is very important to verify if such kind of systems can be controlled by the analysis of the dynamic response of road infrastructure measured using piezoelectric transducers. Obtained results show that it could be possible.

Thin film strain transducer. [in-flight measurement of stress or strain in walls of high altitude balloons

NASA Technical Reports Server (NTRS)

Rand, J. L.

1981-01-01

Previous attempts to develop an appropriate sensor for measuring the stress or strain of high altitude balloons during flight are reviewed as well as the various conditions that must be met by such a device. The design, development and calibration of a transducer which promises to satisfy the necessary design constraints are described. The thin film strain transducer has a low effective modulus so as not to interfere with the strain that would naturally occur in the balloon. In addition, the transducer has a high sensitivity to longitudinal strain (7.216 mV/V/unit strain) which is constant for all temperature from room temperature to -80 C and all strains from 5 percent compression to 10 percent tensile strain. At the same time, the sensor is relatively insensitive (0.27 percent) to transverse forces. The device has a standard 350 ohm impedance which is compatible with available bridge balance, amplification and telemetry instrumentation now available for balloon flight. Recommendations are included for improved coatings to provide passive thermal control as well as model, tethered and full scale flight testing.

Validity of the Myotest® in measuring force and power production in the squat and bench press.

PubMed

Comstock, Brett A; Solomon-Hill, Glenn; Flanagan, Shawn D; Earp, Jacob E; Luk, Hui-Ying; Dobbins, Kathryn A; Dunn-Lewis, Courtenay; Fragala, Maren S; Ho, Jen-Yu; Hatfield, Disa L; Vingren, Jakob L; Denegar, Craig R; Volek, Jeff S; Kupchak, Brian R; Maresh, Carl M; Kraemer, William J

2011-08-01

The purpose of this study was to verify the concurrent validity of a bar-mounted Myotest® instrument in measuring the force and power production in the squat and bench press exercises when compared to the gold standard of a computerized linear transducer and force platform system. Fifty-four men (bench press: 39-171 kg; squat: 75-221 kg) and 43 women (bench press: 18-80 kg; squat: 30-115 kg) (age range 18-30 years) performed a 1 repetition maximum (1RM) strength test in bench press and squat exercises. Power testing consisted of the jump squat and the bench throw at 30% of each subject's 1RM. During each measurement, both the Myotest® instrument and the Celesco linear transducer of the directly interfaced BMS system (Ballistic Measurement System [BMS] Innervations Inc, Fitness Technology force plate, Skye, South Australia, Australia) were mounted to the weight bar. A strong, positive correlation (r) between the Myotest and BMS systems and a high correlation of determination (R2) was demonstrated for bench throw force (r = 0.95, p < 0.05) (R2 = 0.92); bench throw power (r = 0.96, p < 0.05) (R2 = 0.93); squat jump force (r = 0.98, p < 0.05) (R2 = 0.97); and squat jump power (r = 0.91, p < 0.05) (R2 = 0.82). In conclusion, when fixed on the bar in the vertical axis, the Myotest is a valid field instrument for measuring force and power in commonly used exercise movements.

Plastic Muscles TM as lightweight, low voltage actuators and sensors

NASA Astrophysics Data System (ADS)

Bennett, Matthew; Leo, Donald; Duncan, Andrew

2008-03-01

Using proprietary technology, Discover Technologies has developed ionomeric polymer transducers that are capable of long-term operation in air. These "Plastic Muscle TM" transducers are useful as soft distributed actuators and sensors and have a wide range of applications in the aerospace, robotics, automotive, electronics, and biomedical industries. Discover Technologies is developing novel fabrication methods that allow the Plastic Muscles TM to be manufactured on a commercial scale. The Plastic Muscle TM transducers are capable of generating more than 0.5% bending strain at a peak strain rate of over 0.1 %/s with a 3 V input. Because the Plastic Muscles TM use an ionic liquid as a replacement solvent for water, they are able to operate in air for long periods of time. Also, the Plastic Muscles TM do not exhibit the characteristic "back relaxation" phenomenon that is common in water-swollen devices. The elastic modulus of the Plastic Muscle TM transducers is estimated to be 200 MPa and the maximum generated stress is estimated to be 1 MPa. Based on these values, the maximum blocked force at the tip of a 6 mm wide, 35 mm long actuator is estimated to be 19 mN. Modeling of the step response with an exponential series reveals nonlinearity in the transducers' behavior.

Mesoscale disturbances in the tropical stratosphere excited by convection - Observations and effects on the stratospheric momentum budget

NASA Technical Reports Server (NTRS)

Pfister, Leonhard; Scott, Stanley; Loewenstein, Max; Bowen, Stuart; Legg, Marion

1993-01-01

Aircraft temperature and pressure measurements as well as satellite imagery are used to establish the amplitudes and the space and time scale of potential temperature disturbances over convective systems. A conceptual model is proposed for the generation of mesoscale gravity waves by convection. The momentum forcing that a reasonable distribution of convection might exert on the tropical stratosphere through convectively excited mesoscale gravity waves of the observed amplitudes is estimated. Aircraft measurements show that presence of mesoscale disturbances in the lower stratospheric temperature, disturbances that appear to be associated with underlying convection. If the disturbances are convectively excited mesoscale gravity waves, their amplitude is sufficient that their breakdown in the upper stratosphere will exert a zonal force comparable to but probably smaller than the planetary-scale Kelvin waves.

Methods for quantifying simple gravity sensing in Drosophila melanogaster.

PubMed

Inagaki, Hidehiko K; Kamikouchi, Azusa; Ito, Kei

2010-01-01

Perception of gravity is essential for animals: most animals possess specific sense organs to detect the direction of the gravitational force. Little is known, however, about the molecular and neural mechanisms underlying their behavioral responses to gravity. Drosophila melanogaster, having a rather simple nervous system and a large variety of molecular genetic tools available, serves as an ideal model for analyzing the mechanisms underlying gravity sensing. Here we describe an assay to measure simple gravity responses of flies behaviorally. This method can be applied for screening genetic mutants of gravity perception. Furthermore, in combination with recent genetic techniques to silence or activate selective sets of neurons, it serves as a powerful tool to systematically identify neural substrates required for the proper behavioral responses to gravity. The assay requires 10 min to perform, and two experiments can be performed simultaneously, enabling 12 experiments per hour.