Three-axis accelerometer package for slimhole and microhole seismic monitoring and surveys

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

Hunter, S.L.; Harben, P.E.

1997-01-07

The development of microdrilling technology, nominally defined as drilling technology for 1-in.-diameter boreholes, shows potential for reducing the cost of drilling monitoring wells. A major question that arises in drilling microholes is if downhole logging and monitoring in general--and downhole seismic surveying in particular--can be conducted in such small holes since the inner working diameter of such a seismic tool could be as small as 0.31 in. A downhole three-component accelerometer package that fits within a 031-in. inner diameter tube has been designed, built, and tested. The package consists of three orthogonally mounted Entran EGA-125-5g piezoresistive silicon micromachined accelerometers withmore » temperature compensation circuitry, downhole amplification, and line drivers mounted in a thin-walled aluminum tube. Accelerometers are commercially available in much smaller package sizes than conventional geophones, but the noise floor is significantly higher than that for the geophones. Cross-well tests using small explosives showed good signal-to-noise ratio in the recorded waveform at various receiver depths with a 1,50-ft source-receiver well separation. For some active downhole surveys, the accelerometer unit would clearly be adequate. It can be reasonably assumed, however, that for less energetic sources and for greater well separations, the high accelerometer noise floor is not acceptable. By expanding the inner working diameter of a microhole seismic tool to 0.5 in., other commercial accelerometers can be used with substantially lower noise floors.« less

Description of the three axis low-g accelerometer package

NASA Technical Reports Server (NTRS)

Amalavage, A. J.; Fikes, E. H.; Berry, E. H.

1978-01-01

The three axis low-g accelerometer package designed for use on the Space Processing Application Rocket (SPAR) Program is described. The package consists of the following major sections: (1) three Kearfott model 2412 accelerometers mounted in an orthogonal triad configuration on a temperature controlled, thermally isolated cube, (2) the accelerometer servoelectronics (printed circuit cards PC-6 through PC-12), and (3) the signal conditioner (printed circuit cards PC-15 and PC-16). The measurement range is 0 + or - 0.031 g with a quantization of 1.1 x 10 to the 7th power g. The package was flown successfully on six SPAR launches with the Black Brant booster. These flights provide approximately 300 s of free fall or zero-g environment.

Mechanical design optimization of a single-axis MOEMS accelerometer based on a grating interferometry cavity for ultrahigh sensitivity

NASA Astrophysics Data System (ADS)

Lu, Qianbo; Bai, Jian; Wang, Kaiwei; Lou, Shuqi; Jiao, Xufen; Han, Dandan; Yang, Guoguang

2016-08-01

The ultrahigh static displacement-acceleration sensitivity of a mechanical sensing chip is essential primarily for an ultrasensitive accelerometer. In this paper, an optimal design to implement to a single-axis MOEMS accelerometer consisting of a grating interferometry cavity and a micromachined sensing chip is presented. The micromachined sensing chip is composed of a proof mass along with its mechanical cantilever suspension and substrate. The dimensional parameters of the sensing chip, including the length, width, thickness and position of the cantilevers are evaluated and optimized both analytically and by finite-element-method (FEM) simulation to yield an unprecedented acceleration-displacement sensitivity. Compared with one of the most sensitive single-axis MOEMS accelerometers reported in the literature, the optimal mechanical design can yield a profound sensitivity improvement with an equal footprint area, specifically, 200% improvement in displacement-acceleration sensitivity with moderate resonant frequency and dynamic range. The modified design was microfabricated, packaged with the grating interferometry cavity and tested. The experimental results demonstrate that the MOEMS accelerometer with modified design can achieve the acceleration-displacement sensitivity of about 150μm/g and acceleration sensitivity of greater than 1500V/g, which validates the effectiveness of the optimal design.

Identification of capacitive MEMS accelerometer structure parameters for human body dynamics measurements.

PubMed

Benevicius, Vincas; Ostasevicius, Vytautas; Gaidys, Rimvydas

2013-08-22

Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model's response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments.

Micromachined Fluid Inertial Sensors

PubMed Central

Liu, Shiqiang; Zhu, Rong

2017-01-01

Micromachined fluid inertial sensors are an important class of inertial sensors, which mainly includes thermal accelerometers and fluid gyroscopes, which have now been developed since the end of the last century for about 20 years. Compared with conventional silicon or quartz inertial sensors, the fluid inertial sensors use a fluid instead of a solid proof mass as the moving and sensitive element, and thus offer advantages of simple structures, low cost, high shock resistance, and large measurement ranges while the sensitivity and bandwidth are not competitive. Many studies and various designs have been reported in the past two decades. This review firstly introduces the working principles of fluid inertial sensors, followed by the relevant research developments. The micromachined thermal accelerometers based on thermal convection have developed maturely and become commercialized. However, the micromachined fluid gyroscopes, which are based on jet flow or thermal flow, are less mature. The key issues and technologies of the thermal accelerometers, mainly including bandwidth, temperature compensation, monolithic integration of tri-axis accelerometers and strategies for high production yields are also summarized and discussed. For the micromachined fluid gyroscopes, improving integration and sensitivity, reducing thermal errors and cross coupling errors are the issues of most concern. PMID:28216569

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument

PubMed Central

Huang, Xiangqing; Deng, Zhongguang; Xie, Yafei; Fan, Ji; Hu, Chenyuan

2018-01-01

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δO and δP respectively, called the misalignment angles. The angle δO, coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δP would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δP component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δP is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10−7 g/√Hz (1 g ≈ 9.8 m/s2). PMID:29670021

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument.

PubMed

Huang, Xiangqing; Deng, Zhongguang; Xie, Yafei; Fan, Ji; Hu, Chenyuan; Tu, Liangcheng

2018-04-18

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δ O and δ P respectively, called the misalignment angles. The angle δ O , coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δ P would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δ P component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δ P is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10 −7 g/√Hz (1 g ≈ 9.8 m/s²).

Terrestrial Applications of a Nano-g Accelerometer

NASA Technical Reports Server (NTRS)

Hartley, Frank T.

1996-01-01

The ultra-sensitive accelerometer, developed for NASA to monitor the microgravity environments of Space Shuttle, five orbiters and Space Station, needed to measure accelerations up to 10 mg with an absolute accuracy of 10 nano-g (10(exp -8)g) for at least two orbits (10(exp 4) seconds) to resolve accelerations associated with orbital drag. Also, the accelerometers needed to have less than 10(exp -9) F.S. off-axis sensitivity; to be thermally and magnetically inert; to be immune to quiescent shock, and to have an in-situ calibration capability. Multi-axis compact seismometers, designs that have twelve decades of dynamic range will be described. Density profilometers, precision gradiometers, gyros and vibration isolation designs and applications will be discussed. Finally, examples of transformations of the accelerometer into sensitive anemometers and imaging spectrometers will be presented.

Single-Axis Accelerometer

NASA Technical Reports Server (NTRS)

Tucker, Dennis Stephen (Inventor); Capo-Lugo, Pedro A. (Inventor)

2016-01-01

A single-axis accelerometer includes a housing defining a sleeve. An object/mass is disposed in the sleeve for sliding movement therein in a direction aligned with the sleeve's longitudinal axis. A first piezoelectric strip, attached to a first side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The first piezoelectric strip includes a first strip of a piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A second piezoelectric strip, attached to a second side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The second piezoelectric strip includes a second strip of the piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A voltage sensor is electrically coupled to at least one of the first and second piezoelectric strips.

Extracting Time-Accurate Acceleration Vectors From Nontrivial Accelerometer Arrangements.

PubMed

Franck, Jennifer A; Blume, Janet; Crisco, Joseph J; Franck, Christian

2015-09-01

Sports-related concussions are of significant concern in many impact sports, and their detection relies on accurate measurements of the head kinematics during impact. Among the most prevalent recording technologies are videography, and more recently, the use of single-axis accelerometers mounted in a helmet, such as the HIT system. Successful extraction of the linear and angular impact accelerations depends on an accurate analysis methodology governed by the equations of motion. Current algorithms are able to estimate the magnitude of acceleration and hit location, but make assumptions about the hit orientation and are often limited in the position and/or orientation of the accelerometers. The newly formulated algorithm presented in this manuscript accurately extracts the full linear and rotational acceleration vectors from a broad arrangement of six single-axis accelerometers directly from the governing set of kinematic equations. The new formulation linearizes the nonlinear centripetal acceleration term with a finite-difference approximation and provides a fast and accurate solution for all six components of acceleration over long time periods (>250 ms). The approximation of the nonlinear centripetal acceleration term provides an accurate computation of the rotational velocity as a function of time and allows for reconstruction of a multiple-impact signal. Furthermore, the algorithm determines the impact location and orientation and can distinguish between glancing, high rotational velocity impacts, or direct impacts through the center of mass. Results are shown for ten simulated impact locations on a headform geometry computed with three different accelerometer configurations in varying degrees of signal noise. Since the algorithm does not require simplifications of the actual impacted geometry, the impact vector, or a specific arrangement of accelerometer orientations, it can be easily applied to many impact investigations in which accurate kinematics need to be extracted from single-axis accelerometer data.

A novel determination of energy expenditure efficiency during a balance task using accelerometers. A pilot study.

PubMed

Caña-Pino, Alejandro; Apolo-Arenas, Maria Dolores; Moral-Blanco, Javier; De la Cruz-Sánchez, Ernesto; Espejo-Antúnez, Luis

2017-08-18

The objectives of this study are to determine the displacement of the center of pressure (CoP) and its association with the spectral energy density of the acceleration required for the maintenance of postural balance in different standing positions in healthy participants using design observational and setting laboratorial studies. Participants were 30 healthy university students aged between 18 and 32 years old (mean [M] ± standard deviation [SD] = 21,57 ± 3,31 years). Triaxial accelerometer and a pressure platform were used in order to obtain energy spectral density and CoP sway measurements during four balance tasks. Statistically significant differences were found for anteroposterior (p = 0.002) and mediolateral (p = 0.009) CoP displacement between the conditions eyes closed and stable surface and the conditions eyes closed and unstable surface. A statistically significant correlation was also observed between Z-axis (anterior-posterior) of the accelerometer and mediolateral axis of the CoP (r = 0.465; p = 0.01) and between Y-axis accelerometer (mediolateral) and displacement of the CoP in the anteroposterior axis (r = 0.413; p = 0.023). Spectral energy density appears to be associated with the displacement of CoP in healthy participants.

Micro-optoelectromechanical systems accelerometer based on intensity modulation using a one-dimensional photonic crystal.

PubMed

Sheikhaleh, Arash; Abedi, Kambiz; Jafari, Kian; Gholamzadeh, Reza

2016-11-10

In this paper, we propose what we believe is a novel sensitive micro-optoelectromechanical systems (MOEMS) accelerometer based on intensity modulation by using a one-dimensional photonic crystal. The optical sensing system of the proposed structure includes an air-dielectric multilayer photonic bandgap material, a laser diode (LD) light source, a typical photodiode (1550 nm) and a set of integrated optical waveguides. The proposed sensor provides several advantages, such as a relatively wide measurement range, good linearity in the whole measurement range, integration capability, negligible cross-axis sensitivity, high reliability, and low air-damping coefficient, which results in a wider frequency bandwidth for a fixed resonance frequency. Simulation results show that the functional characteristics of the sensor are as follows: a mechanical sensitivity of 119.21 nm/g, a linear measurement range of ±38g and a resonance frequency of 1444 Hz. Thanks to the above-mentioned characteristics, the proposed MOEMS accelerometer is suitable for a wide spectrum of applications, ranging from consumer electronics to aerospace and inertial navigation.

NASA Ultra-Sensitive Miniature Accelerometer

NASA Technical Reports Server (NTRS)

Zavracky, Paul M.; Hartley, Frank T.

1994-01-01

Using micro-machined silicon technology, an ultra-sensitive miniature acce.,rometer can be constructed which meets the requirements for microgravity experiments in the space environment.Such an accelerometer will have a full scale sensitivity of 1C2 g a resolution of lC8 g, low cross axis sensitivity, and low temperature sensitivity. Mass of the device is approximately five grams and its footprint is 2 cm x 2 cm. Innovative features of the accelerometer, which are patented, are: electrostatic caging to withstand handling shock up to 150 g, in-situ calibration, in situ performance characterization, and both static and dynamic compensation. The transducer operates on a force balance principle wherein the displacement of the proof mass is monitored by measuring tunneling electron current flow between a conductive tip, and a fixed platen. The four major parts of the accelerometer are tip die, incorporating the tunneling tip and four field plates for controlling pitch and roll of the proof mass; two proof mass dies, attached to the surrounding frame by sets of four leg" springs; and a force plate die. The four parts are fuse-bonded into a complete assembly. External electrical connections are made at bond pads on the front surface of the force plate die. Materials and processes used in the construction of the transducer are compatible with volume production.

An Accelerometer as an Alternative to a Force Plate for the Step-Up-and-Over Test.

PubMed

Bailey, Christopher A; Costigan, Patrick A

2015-12-01

The step-up-and-over test has been used successfully to examine knee function after knee injury. Knee function is quantified using the following variables extracted from force plate data: the maximal force exerted during the lift, the maximal impact force at landing, and the total time to complete the step. For various reasons, including space and cost, it is unlikely that all clinicians will have access to a force plate. The purpose of the study was to determine if the step-up-and-over test could be simplified by using an accelerometer. The step-up-and-over test was performed by 17 healthy young adults while being measured with both a force plate and a 3-axis accelerometer mounted at the low back. Results showed that the accelerometer and force plate measures were strongly correlated for all 3 variables (r = .90-.98, Ps < .001) and that the accelerometer values for the lift and impact indices were 6-7% higher (Ps < .01) and occurred 0.07-0.1 s later than the force plate (Ps < .05). The accelerometer returned values highly correlated to those from a force plate. Compared with a force plate, a wireless, 3-axis accelerometer is a less expensive and more portable system with which to measure the step-up-and-over test.

Laparoscopic surgery skills evaluation: analysis based on accelerometers.

PubMed

Sánchez, Alexis; Rodríguez, Omaira; Sánchez, Renata; Benítez, Gustavo; Pena, Romina; Salamo, Oriana; Baez, Valentina

2014-01-01

Technical skills assessment is considered an important part of surgical training. Subjective assessment is not appropriate for training feedback, and there is now increased demand for objective assessment of surgical performance. Economy of movement has been proposed as an excellent alternative for this purpose. The investigators describe a readily available method to evaluate surgical skills through motion analysis using accelerometers in Apple's iPod Touch device. Two groups of individuals with different minimally invasive surgery skill levels (experts and novices) were evaluated. Each group was asked to perform a given task with an iPod Touch placed on the dominant-hand wrist. The Accelerometer Data Pro application makes it possible to obtain movement-related data detected by the accelerometers. Average acceleration and maximum acceleration for each axis (x, y, and z) were determined and compared. The analysis of average acceleration and maximum acceleration showed statistically significant differences between groups on both the y (P = .04, P = .03) and z (P = .04, P = .04) axes. This demonstrates the ability to distinguish between experts and novices. The analysis of the x axis showed no significant differences between groups, which could be explained by the fact that the task involves few movements on this axis. Accelerometer-based motion analysis is a useful tool to evaluate laparoscopic skill development of surgeons and should be used in training programs. Validation of this device in an in vivo setting is a research goal of the investigators' team.

MEMS SoC: observer-based coplanar gyro-free inertial measurement unit

NASA Astrophysics Data System (ADS)

Chen, Tsung-Lin; Park, Sungsu

2005-09-01

This paper presents a novel design of a coplanar gyro-free inertial measurement unit (IMU) that consists of seven to nine single-axis linear accelerometers, and it can be utilized to perform the six DOF measurements for an object in motion. Unlike other gyro-fee IMUs, this design uses redundant accelerometers and state estimation techniques to facilitate the in situ and mass fabrication for the employed accelerometers. The alignment error from positioning accelerometers onto a measurement unit and the fabrication cost of an IMU can greatly be reduced. The outputs of the proposed design are three linear accelerations and three angular velocities. As compared to other gyro-free IMUs, the proposed design uses less integral operation and thus improves its sensing resolution and drifting problem. The sensing resolution of a gyro-free IMU depends on the sensing resolution of the employed accelerometers as well as the size of the measurement unit. Simulation results indicate that the sensing resolution of the proposed design is 2° s-1 for the angular velocity and 10 μg for the linear acceleration when nine single-axis accelerometers, each with 10 μg sensing resolution, are deployed on a 4 inch diameter disc. Also, thanks to the iterative EKF algorithm, the angle estimation error is within 10-3 deg at 2 s.

Development of the German A-4 guidance and control system, 1939 - 1945: A memoir

NASA Technical Reports Server (NTRS)

Steinhoff, E. A.

1977-01-01

The development by 1943 of a fully inertial navigational system for the German A-4 (V-2) missile is detailed. This flight control system used a triple-axis stabilized platform with two longitudinal accelerometers and one lateral accelerometer.

The microgravity environment of the Space Shuttle Columbia middeck during STS-32

NASA Technical Reports Server (NTRS)

Dunbar, Bonnie J.; Thomas, Donald A.; Schoess, Jeff N.

1991-01-01

Four hours of three-axis microgravity accelerometer data were successfully measured at the MA9F locker location in the Orbiter middeck of Columbia as part of the Microgravity Disturbances Experiment (MDE) on STS-32. These data were measured using the Honeywell In-Space Accelerometer, a small three-axis accelerometer that was hard-mounted onto the Fluid Experiment Apparatus to record the microgravity environment at the exact location of the MDE. Data were recorded during specific mission events such as Orbiter quiescent periods, crew exercise on the treadmill, and numerous Orbiter engine burns. Orbiter background levels were measured to be in the 3 x 10(exp -5) to 2 x 10(exp -4) G range, treadmill operations in the 6 x 10(exp -4) to 5 x 10(exp -3) G range, and Orbiter engine burns from 4 x 10(exp -3) to in excess of 1 x 10(exp -2) G. These data represent some of the first microgravity accelerometer data ever recorded in the middeck area of the Orbiter.

Acoustic Sensing of Ocean Turbulence

DTIC Science & Technology

1991-12-01

quantities and of fast varying quantities, requiring high spatial resolution, fast response sensors and stable observation platforms. A classical approach to...with this type of sensor . Moum et.al. [Ref.l0] performed upper ocean observations with this instrument where they were able to 60 characterize the fine...platform orientation using the 3 axis accelerometer as tiltmeters . E. NON-ACOUSTIC DATA The non-acoustic channels on the CDV package are: 3 component

High Risk Behaviors in Marine Mammals: Linking Behavioral Responses to Anthropogenic Disturbance to Biological Consequences

DTIC Science & Technology

2014-09-30

98) Prescribed by ANSI Std Z39-18 2 injury via cardiovascular performance during submergence. Neuro -protection through globin deposition and...relationships for stroking costs, aerobic dive limits, types of neuro -protection (globin deposition, capillarity), and cardiac risk factors that will be mapped...Greenland. A custom built ECG recorder with 3- axis accelerometer recorder and pressure transducer was combined with retrieval transmitters (Argos

Multiple-stage integrating accelerometer

DOEpatents

Devaney, H.F.

1984-06-27

An accelerometer assembly is provided for use in activating a switch in response to multiple acceleration pulses in series. The accelerometer includes a housing forming a chamber. An inertial mass or piston is slidably disposed in the chamber and spring biased toward a first or reset position. A damping system is also provided to damp piston movement in response to first and subsequent acceleration pulses. Additionally, a cam, including a Z-shaped slot, and cooperating follower pin slidably received therein are mounted to the piston and the housing. The middle or cross-over leg of the Z-shaped slot cooperates with the follower pin to block or limit piston movement and prevent switch activation in response to a lone acceleration pulse. The switch of the assembly is only activated after two or more separate acceleration pulses are sensed and the piston reaches the end of the chamber opposite the reset position.

Self Diagnostic Accelerometer Testing on the C-17 Aircraft

NASA Technical Reports Server (NTRS)

Tokars, Roger P.; Lekki, John D.

2013-01-01

The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. To demonstrate the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The SDA attachment conditions were varied from fully tight to loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first.

Fabrication and characterization of monolithic piezoresistive high-g three-axis accelerometer

NASA Astrophysics Data System (ADS)

Jung, Han-Il; Kwon, Dae-Sung; Kim, Jongbaeg

2017-12-01

We report piezoresistive high-g three-axis accelerometer with a single proof mass suspended by thin eight beams. This eight-beam design allows load-sharing at high-g preventing structural breakage, as well as the symmetric arrangement of piezoresistors. The device chip size is 1.4 mm × 1.4 mm × 0.51 mm. Experimental results show that the sensitivity in X-, Y- and Z-axes are 0.2433, 0.1308 and 0.3068 mV/g/V under 5 V applied and the resolutions are 24.2, 29.9 and 25.4 g, respectively.

Proceedings of an ESA-NASA Workshop on a Joint Solid Earth Program

NASA Technical Reports Server (NTRS)

Guyenne, T. Duc (Editor); Hunt, James J. (Editor)

1987-01-01

The NASA geodynamics program; spaceborne magnetometry; spaceborne gravity gradiometry (characterizing the data type); terrestrial gravity data and comparisons with satellite data; GRADIO three-axis electrostatic accelerometers; gradiometer accommodation on board a drag-free satellite; gradiometer mission spectral analysis and simulation studies; and an opto-electronic accelerometer system were discussed.

Parabrachial nucleus neuronal responses to off-vertical axis rotation in macaques

PubMed Central

McCandless, Cyrus H.; Balaban, Carey D.

2010-01-01

The caudal aspect of the parabrachial nucleus (PBN) contains neurons responsive to whole body, periodic rotational stimulation in alert monkeys. This study characterizes the angular and linear motion-sensitive response properties of PBN unit responses during off-vertical axis rotation (OVAR) and position trapezoid stimulation. The OVAR responses displayed a constant firing component which varied from the firing rate at rest. Nearly two-thirds of the units also modulated their discharges with respect to head orientation (re: gravity) during constant velocity OVAR stimulation. The modulated response magnitudes were equal during ipsilateral and contralateral OVARs, indicative of a one-dimensional accelerometer. These response orientations during OVAR divided the units into three spatially tuned populations, with peak modulation responses centered in the ipsilateral ear down, contralateral anterior semicircular canal down, and occiput down orientations. Because the orientation of the OVAR modulation response was opposite in polarity to the orientation of the static tilt component of responses to position trapezoids for the majority of units, the linear acceleration responses were divided into colinear dynamic linear and static tilt components. The orientations of these unit responses formed two distinct population response axes: (1) units with an interaural linear response axis and (2) units with an ipsilateral anterior semicircular canal-contralateral posterior semicircular canal plane linear response axis. The angular rotation sensitivity of these units is in a head-vertical plane that either contains the linear acceleration response axis or is perpendicular to the linear acceleration axis. Hence, these units behave like head-based (‘strap-down’) inertial guidance sensors. Because the PBN contributes to sensory and interoceptive processing, it is suggested that vestibulo-recipient caudal PBN units may detect potentially dangerous anomalies in control of postural stability during locomotion. In particular, these signals may contribute to the range of affective and emotional responses that include panic associated with falling, malaise associated with motion sickness and mal-de-debarquement, and comorbid balance and anxiety disorders. PMID:20039027

Calibrating accelerometer sensor on android phone with Accelerograph TDL 303 QS for earthquake online recorder

NASA Astrophysics Data System (ADS)

Riantana, R.; Darsono, D.; Triyono, A.; Azimut, H. B.

2016-11-01

Calibration of the android censor was done by placing the device in a mounting at side of accelerograph TDL 303 QS that will be a means of comparison. Leveling of both devices was set same, so that the state of the device can be assumed same anyway. Then applied vibrations in order to have the maximum amplitude value of both censor, so it can be found equality of the coefficient of proportionality both of them. The results on both devices obtain the Peak Ground Acceleration (PGA) as follows, on the x axis (EW) android censor is obtained PGA -2.4478145 gal than at TDL 303 QS obtained PGA -2.5504 gal, the y-axis (NS) on the censor android obtained PGA 3.0066964 gal than at TDL 303 QS obtained PGA 3.2073 gal, the z-axis (UD) on the android censor obtained PGA -14.0702377 gal than at TDL 303 QS obtained PGA -13.2927 gal, A correction value for android accelerometer censor is ± 0.1 gal for the x-axis (EW), ± 0.2 gal for the y-axis (NS), and ± 0.7 gal for the z-axis (UD).

Validation of a method to measure the vector fidelity of triaxial vector sensors

NASA Astrophysics Data System (ADS)

De Freitas, J. M.

2018-06-01

A method to measure the misalignment angles and vector fidelity of a mutually orthogonal arrangement of triaxial accelerometers has been validated by introducing known misalignments into the measurement procedure. The method is based on the excitation of all three accelerometers in equal measure and the determination of the second order responsivity tensor as a metric. The sensor axis misalignment angles measured using a sensor rotation technique as a reference were 1.49°  ±  0.05°, 0.63°  ±  0.02°, and 0.78°  ±  0.04°. The resolution of the new approach against the reference was 0.03° with an accuracy of 0.2° and maximum deviation of 0.4°. An ellipticity tensor β that characterises the extent to which a triaxial system preserves the input polarisation state purity was introduced. In a careful laboratory arrangement, up to 98% input polarisation state purity was shown to be maintained. It is recommended that documentation on commercial and research grade high-precision triaxial sensor systems should give the responsivity matrix . This technique will improve the range of vector fidelity measurement tools for triaxial accelerometers and other vector sensors such as magnetometers, gyroscopes and acoustic vector sensors.

Analysis of pendulum period with an iPod touch/iPhone

NASA Astrophysics Data System (ADS)

Briggle, Justin

2013-05-01

We describe the use of Apple’s iPod touch/iPhone, acting as the pendulum bob, as a means of measuring pendulum period, making use of the device’s three-axis digital accelerometer and the freely available SPARKvue app from PASCO scientific. The method can be readily incorporated into an introductory physics laboratory experiment. Moreover, the principles described may be carried out with any number of smartphone devices containing an integrated accelerometer and paired with an appropriate application for collecting and sending accelerometer data as a comma-separated value file.

Composite Bending Box Section Modal Vibration Fault Detection

NASA Technical Reports Server (NTRS)

Werlink, Rudy

2002-01-01

One of the primary concerns with Composite construction in critical structures such as wings and stabilizers is that hidden faults and cracks can develop operationally. In the real world, catastrophic sudden failure can result from these undetected faults in composite structures. Vibration data incorporating a broad frequency modal approach, could detect significant changes prior to failure. The purpose of this report is to investigate the usefulness of frequency mode testing before and after bending and torsion loading on a composite bending Box Test section. This test article is representative of construction techniques being developed for the recent NASA Blended Wing Body Low Speed Vehicle Project. The Box section represents the construction technique on the proposed blended wing aircraft. Modal testing using an impact hammer provides an frequency fingerprint before and after bending and torsional loading. If a significant structural discontinuity develops, the vibration response is expected to change. The limitations of the data will be evaluated for future use as a non-destructive in-situ method of assessing hidden damage in similarly constructed composite wing assemblies. Modal vibration fault detection sensitivity to band-width, location and axis will be investigated. Do the sensor accelerometers need to be near the fault and or in the same axis? The response data used in this report was recorded at 17 locations using tri-axial accelerometers. The modal tests were conducted following 5 independent loading conditions before load to failure and 2 following load to failure over a period of 6 weeks. Redundant data was used to minimize effects from uncontrolled variables which could lead to incorrect interpretations. It will be shown that vibrational modes detected failure at many locations when skin de-bonding failures occurred near the center section. Important considerations are the axis selected and frequency range.

Classification accuracies of physical activities using smartphone motion sensors.

PubMed

Wu, Wanmin; Dasgupta, Sanjoy; Ramirez, Ernesto E; Peterson, Carlyn; Norman, Gregory J

2012-10-05

Over the past few years, the world has witnessed an unprecedented growth in smartphone use. With sensors such as accelerometers and gyroscopes on board, smartphones have the potential to enhance our understanding of health behavior, in particular physical activity or the lack thereof. However, reliable and valid activity measurement using only a smartphone in situ has not been realized. To examine the validity of the iPod Touch (Apple, Inc.) and particularly to understand the value of using gyroscopes for classifying types of physical activity, with the goal of creating a measurement and feedback system that easily integrates into individuals' daily living. We collected accelerometer and gyroscope data for 16 participants on 13 activities with an iPod Touch, a device that has essentially the same sensors and computing platform as an iPhone. The 13 activities were sitting, walking, jogging, and going upstairs and downstairs at different paces. We extracted time and frequency features, including mean and variance of acceleration and gyroscope on each axis, vector magnitude of acceleration, and fast Fourier transform magnitude for each axis of acceleration. Different classifiers were compared using the Waikato Environment for Knowledge Analysis (WEKA) toolkit, including C4.5 (J48) decision tree, multilayer perception, naive Bayes, logistic, k-nearest neighbor (kNN), and meta-algorithms such as boosting and bagging. The 10-fold cross-validation protocol was used. Overall, the kNN classifier achieved the best accuracies: 52.3%-79.4% for up and down stair walking, 91.7% for jogging, 90.1%-94.1% for walking on a level ground, and 100% for sitting. A 2-second sliding window size with a 1-second overlap worked the best. Adding gyroscope measurements proved to be more beneficial than relying solely on accelerometer readings for all activities (with improvement ranging from 3.1% to 13.4%). Common categories of physical activity and sedentary behavior (walking, jogging, and sitting) can be recognized with high accuracies using both the accelerometer and gyroscope onboard the iPod touch or iPhone. This suggests the potential of developing just-in-time classification and feedback tools on smartphones.

Self Diagnostic Accelerometer Ground Testing on a C-17 Aircraft Engine

NASA Technical Reports Server (NTRS)

Tokars, Roger P.; Lekki, John D.

2013-01-01

The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. Sensor system malfunction is a significant contributor to propulsion in flight shutdowns (IFSD) which can lead to aircraft accidents when the issue is compounded with an inappropriate crew response. The development of the SDA is important for both reducing the IFSD rate, and hence reducing the rate at which this component failure type can put an aircraft in jeopardy, and also as a critical enabling technology for future automated malfunction diagnostic systems. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to making vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. In an effort toward demonstrating the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The two SDA attachment conditions used were fully tight and loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first time the robustness of the SDA in an engine environment characterized by high vibration levels.

Self diagnostic accelerometer ground testing on a C-17 aircraft engine

NASA Astrophysics Data System (ADS)

Tokars, Roger P.; Lekki, John D.

The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. Sensor system malfunction is a significant contributor to propulsion in flight shutdowns (IFSD) which can lead to aircraft accidents when the issue is compounded with an inappropriate crew response. The development of the SDA is important for both reducing the IFSD rate, and hence reducing the rate at which this component failure type can put an aircraft in jeopardy, and also as a critical enabling technology for future automated malfunction diagnostic systems. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to making vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. In an effort toward demonstrating the SDA's flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The two SDA attachment conditions used were fully tight and loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first time the robustness of the SDA in an engine environment characterized by high vibration levels.

Characterizing coarse bedload transport during floods with RFID and accelerometer tracers, in-stream RFID antennas and HEC-RAS modeling

NASA Astrophysics Data System (ADS)

Olinde, L.; Johnson, J. P.

2013-12-01

By monitoring the transport timing and distances of tracer grains in a steep mountains stream, we collected data that can constrain numerical bedload transport models considered for these systems. We captured bedload activity during a weeks-spanning snowmelt period in Reynolds Creek, Idaho by deploying Radio Frequency Identification (RFID) and accelerometer embedded tracers with in-stream stationary RFID antennas. During transport events, RFID dataloggers recorded the times when tracers passed over stationary antennas. The accelerometer tracers also logged x, y, z-axis accelerations every 10 minutes to identify times of motion and rest. After snowmelt flows receded, we found tracers with mobile antennas and surveyed their positions. We know the timing and tracer locations when accelerometer tracers were initially entrained, passed stationary antennas, and were finally deposited at the surveyed locations. The fraction of moving accelerometers over time correlates well with discharge. Comparisons of the transported tracer fraction between rising and falling limbs over multiple flood peaks suggest that some degree of clockwise hysteresis persisted during the snowmelt period. Additionally, we apply accelerometer transport durations and displacement distances to calculate virtual velocities over full tracer path lengths and over lengths between initial locations to stationary antennas as well as between stationary antennas to final positions. The accelerometer-based virtual velocities are significantly faster than those estimated from traditional tracer methods that estimate bedload transport durations by assuming threshold flow conditions. We also subsample the motion data to calculate how virtual velocities change over the measurement intervals. Regressions of these relations are in turn used to extrapolate virtual velocities at smaller sampling timescales. Minimum hop lengths are also evaluated for each accelerometer tracer. Finally, flow conditions during the snowmelt hydrograph are modeled over the 11 kilometers of surveyed stream by utilizing 1m airborne LiDAR and HEC-GeoRAS. Cross-sectional HEC-RAS results are used to estimate the spatial distribution of longitudinal shear velocities over the observed discharges. At final accelerometer tracer positions, we analyze the HEC-RAS generated flow conditions for each disentrainment discharge magnitude. The techniques developed here have the potential to link individual grain characteristics during floods to a range of time and length scales.

Physical Activity Assessment with the ActiGraph GT3X and Doubly Labeled Water.

PubMed

Chomistek, Andrea K; Yuan, Changzheng; Matthews, Charles E; Troiano, Richard P; Bowles, Heather R; Rood, Jennifer; Barnett, Junaidah B; Willett, Walter C; Rimm, Eric B; Bassett, David R

2017-09-01

To compare the degree to which four accelerometer metrics-total activity counts per day (TAC per day), steps per day (steps per day), physical activity energy expenditure (PAEE) (kcal·kg·d), and moderate- to vigorous-intensity physical activity (MVPA) (min·d)-were correlated with PAEE measured by doubly labeled water (DLW). Additionally, accelerometer metrics based on vertical axis counts and triaxial counts were compared. This analysis included 684 women and 611 men age 43 to 83 yr. Participants wore the Actigraph GT3X on the hip for 7 d twice during the study and the average of the two measurements was used. Each participant also completed one DLW measurement, with a subset having a repeat. PAEE was estimated by subtracting resting metabolic rate and the thermic effect of food from total daily energy expenditure estimated by DLW. Partial Spearman correlations were used to estimate associations between PAEE and each accelerometer metric. Correlations between the accelerometer metrics and DLW-determined PAEE were higher for triaxial counts than vertical axis counts. After adjusting for weight, age, accelerometer wear time, and fat free mass, the correlation between TAC per day based on triaxial counts and DLW-determined PAEE was 0.44 in women and 0.41 in men. Correlations for steps per day and accelerometer-estimated PAEE with DLW-determined PAEE were similar. After adjustment for within-person variation in DLW-determined PAEE, the correlations for TAC per day increased to 0.61 and 0.49, respectively. Correlations between MVPA and DLW-determined PAEE were lower, particularly for modified bouts of ≥10 min. Accelerometer measures that represent total activity volume, including TAC per day, steps per day, and PAEE, were more highly correlated with DLW-determined PAEE than MVPA using traditional thresholds and should be considered by researchers seeking to reduce accelerometer data to a single metric.

Recent developments in seismic seabed oil reservoir monitoring applications using fibre-optic sensing networks

NASA Astrophysics Data System (ADS)

De Freitas, J. M.

2011-05-01

This review looks at recent developments in seismic seabed oil reservoir monitoring techniques using fibre-optic sensing networks. After a brief introduction covering the background and scope of the review, the following section focuses on state-of-the-art fibre-optic hydrophones and accelerometers used for seismic applications. Related metrology aspects of the sensor such as measurement of sensitivity, noise and cross-axis performance are addressed. The third section focuses on interrogation systems. Two main phase-based competing systems have emerged over the past two decades for seismic applications, with a third technique showing much promise; these have been compared in terms of general performance.

A new microcomputer-based safety and life support system for solitary-living elderly people.

PubMed

Miyauchi, Kosuke; Yonezawa, Yoshiharu; Maki, Hiromichi; Ogawa, Hidekuni; Hahn, Allen W; Caldwell, W Morton

2003-01-01

A new safety and life support system has been developed to detect emergency situations of solitary-living elderly persons. The system employs a dual axis accelerometer, two low-power active filters, a low-power 8-bit single chip microcomputer and a personal handy phone. Body movements due to walking, running and posture changes are detected by the dual axis accelerometer and sent to the microcomputer. If the patient is in an inactive state for 5 minutes after falling, or for 64 minutes without previously falling, then the system automatically alarms the emergency situation, via the personal handy phone, to the patient's family, the fire station or the hospital.

Artifact Noise Removal Techniques on Seismocardiogram Using Two Tri-Axial Accelerometers

PubMed Central

Luu, Loc; Dinh, Anh

2018-01-01

The aim of this study is on the investigation of motion noise removal techniques using two-accelerometer sensor system and various placements of the sensors on gentle movement and walking of the patients. A Wi-Fi based data acquisition system and a framework on Matlab are developed to collect and process data while the subjects are in motion. The tests include eight volunteers who have no record of heart disease. The walking and running data on the subjects are analyzed to find the minimal-noise bandwidth of the SCG signal. This bandwidth is used to design filters in the motion noise removal techniques and peak signal detection. There are two main techniques of combining signals from the two sensors to mitigate the motion artifact: analog processing and digital processing. The analog processing comprises analog circuits performing adding or subtracting functions and bandpass filter to remove artifact noises before entering the data acquisition system. The digital processing processes all the data using combinations of total acceleration and z-axis only acceleration. The two techniques are tested on three placements of accelerometer sensors including horizontal, vertical, and diagonal on gentle motion and walking. In general, the total acceleration and z-axis acceleration are the best techniques to deal with gentle motion on all sensor placements which improve average systolic signal-noise-ratio (SNR) around 2 times and average diastolic SNR around 3 times comparing to traditional methods using only one accelerometer. With walking motion, ADDER and z-axis acceleration are the best techniques on all placements of the sensors on the body which enhance about 7 times of average systolic SNR and about 11 times of average diastolic SNR comparing to only one accelerometer method. Among the sensor placements, the performance of horizontal placement of the sensors is outstanding comparing with other positions on all motions. PMID:29614821

Three Three-Axis IEPE Accelerometers on the Inner Liner of a Tire for Finding the Tire-Road Friction Potential Indicators.

PubMed

Niskanen, Arto; Tuononen, Ari J

2015-08-05

Direct tire-road contact friction estimation is essential for future autonomous cars and active safety systems. Friction estimation methods have been proposed earlier for driving conditions in the presence of a slip angle or slip ratio. However, the estimation of the friction from a freely-rolling tire is still an unsolved topic. Knowing the existing friction potential would be beneficial since vehicle control systems could be adjusted before any remarkable tire force has been produced. Since accelerometers are well-known and robust, and thus a promising sensor type for intelligent tires, this study uses three three-axis IEPE accelerometers on the inner liner of a tire to detect friction potential indicators on two equally smooth surfaces with different friction levels. The equal roughness was chosen for both surfaces in order to study the friction phenomena by neglecting the effect of surface texture on vibrations. The acceleration data before the contact is used to differentiate the two friction levels between the tire and the road. In addition, the contact lengths from the three accelerometers are used to validate the acceleration data. A method to differentiate the friction levels on the basis of the acceleration signal is also introduced.

Three Three-Axis IEPE Accelerometers on the Inner Liner of a Tire for Finding the Tire-Road Friction Potential Indicators †

PubMed Central

Niskanen, Arto; Tuononen, Ari J.

2015-01-01

Direct tire-road contact friction estimation is essential for future autonomous cars and active safety systems. Friction estimation methods have been proposed earlier for driving conditions in the presence of a slip angle or slip ratio. However, the estimation of the friction from a freely-rolling tire is still an unsolved topic. Knowing the existing friction potential would be beneficial since vehicle control systems could be adjusted before any remarkable tire force has been produced. Since accelerometers are well-known and robust, and thus a promising sensor type for intelligent tires, this study uses three three-axis IEPE accelerometers on the inner liner of a tire to detect friction potential indicators on two equally smooth surfaces with different friction levels. The equal roughness was chosen for both surfaces in order to study the friction phenomena by neglecting the effect of surface texture on vibrations. The acceleration data before the contact is used to differentiate the two friction levels between the tire and the road. In addition, the contact lengths from the three accelerometers are used to validate the acceleration data. A method to differentiate the friction levels on the basis of the acceleration signal is also introduced. PMID:26251914

Vibration measurements of the Daniel K. Inouye Solar Telescope mount, Coudé rotator, and enclosure assemblies

NASA Astrophysics Data System (ADS)

McBride, William R.; McBride, Daniel R.

2016-08-01

The Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, with a 4-meter off-axis primary mirror and 16 meter rotating Coudé laboratory within the telescope pier. The off-axis design requires a mount similar to an 8-meter on-axis telescope. Both the telescope mount and the Coudé laboratory utilize a roller bearing technology in place of the more commonly used hydrostatic bearings. The telescope enclosure utilizes a crawler mechanism for the altitude axis. As these mechanisms have not previously been used in a telescope, understanding the vibration characteristics and the potential impact on the telescope image is important. This paper presents the methodology used to perform jitter measurements of the enclosure and the mount bearings and servo system in a high-noise environment utilizing seismic accelerometers and high dynamic-range data acquisition equipment, along with digital signal processing (DSP) techniques. Data acquisition and signal processing were implemented in MATLAB. In the factory acceptance testing of the telescope mount, multiple accelerometers were strategically located to capture the six axes-of-motion of the primary and secondary mirror dummies. The optical sensitivity analysis was used to map these mirror mount displacements and rotations into units of image motion on the focal plane. Similarly, tests were done with the Coudé rotator, treating the entire rotating instrument lab as a rigid body. Testing was performed by recording accelerometer data while the telescope control system performed tracking operations typical of various observing scenarios. The analysis of the accelerometer data utilized noise-averaging fast Fourier transform (FFT) routines, spectrograms, and periodograms. To achieve adequate dynamic range at frequencies as low as 3Hz, the use of special filters and advanced windowing functions were necessary. Numerous identical automated tests were compared to identify and select the data sets with the lowest level of external interference. Similar testing was performed on the telescope enclosure during the factory test campaign. The vibration of the enclosure altitude and azimuth mechanisms were characterized. This paper details jitter tests using accelerometers placed in locations that allowed the motion of the assemblies to be measured while the control system performed various moves typical of on-sky observations. The measurements were converted into the rigid body motion of the structures and mapped into image motion using the telescope's optical sensitivity analysis.

Development of a system for measurement and analysis of tremor using a three-axis accelerometer.

PubMed

Mamorita, N; Iizuka, T; Takeuchi, A; Shirataka, M; Ikeda, N

2009-01-01

The aim of the study was to develop a low-cost and compact system for analysis of tremor using a three-axis accelerometer (the Wii Remote (Nintendo)). To analyze tremor, we hypothesized that the influence of gravitational acceleration should be separated from that of movement. This hypothesis was tested experimentally and we also attempted to record and analyze tremor using our system in a clinical ward. A system for tremor measurement and analysis was developed using the three-axis accelerometer built into the Wii Remote. The frequency and amplitude of mechanical oscillation were calculated using methods for frequency analysis of the axis of largest variance and an estimation of tremor amplitude. The system consists of a program for measurement and analysis of Wii Remote acceleration (Tremor Analyzer), a Wii Remote, a Bluetooth USB adapter and a Web camera. The Tremor Analyzer has a GUI (graphical user interface) that is divided into five seg- ments. The sampling period of the analyzer is 30 msec. To confirm the hypothesis, mechanical oscillations were fed to the Wii Remote. The peak frequency of the power spectrum and the frequency of the oscillation generator were in good agreement, except at 1 Hz (0.01 G) and 2 Hz (0.02 G). With a change in the sum of squares of the three axes from 1.0 to 1.8 (G), the estimated and generated amplitude (0.3 cm) were in close agreement. This system using a Wii Remote is capable of analyzing frequency and estimated amplitude of tremor between 3 Hz and 15 Hz.

ACCELEROMETER

DOEpatents

Pope, K.E.

1958-11-25

A device, commonly known as an accelerometer, is described which may be utllized for measuring acceleratlon with high sensitivity and accuracy tbroughout a relatively wlde range of values. In general, the accelerometer consists of an assembly, including an electric motor stator and a mass element located away from the axis of rotation of the stator, rotatably mounted on a support, and an electric motor rotor positioned within the stator and rotatable thereln. An electrlcal switching circuit controlled by the movement of the stator lntermittently energizes the rotor winding and retards move ment of the stator, and a centrifugal switch is rotatable with the rotor to operate upon attainment of a predetermined rotor rotational velocity.

Development of a Superconducting Six-Axis Accelerometer

DTIC Science & Technology

1989-07-01

COW tH + R"( rkw rRk . (2.35) Recognizing that the components of the Levi - Civita tensor must remain the same in all Cartesian coordinate systems, this...Dynamics of a Rigid Body in a RuLating Accelerated Reference Frame ........ .................................. 10 2.2.3 Accelerometer Equations of Motion...in the Type-I region where currents are more stable. All the parts fit inside a 10.16 cm titanium cube. Two problems were encountered with this

Inertia-Wheel Vibration-Damping System

NASA Technical Reports Server (NTRS)

Fedor, Joseph V.

1990-01-01

Proposed electromechanical system would damp vibrations in large, flexible structure. In active vibration-damping system motors and reaction wheels at tips of appendages apply reaction torques in response to signals from accelerometers. Velocity signal for vibrations about one axis processes into control signal to oppose each of n vibrational modes. Various modes suppressed one at a time. Intended primarily for use in spacecraft that has large, flexible solar panels and science-instrument truss assembly, embodies principle of control interesting in its own right and adaptable to terrestrial structures, vehicles, and instrument platforms.

Innovative self-calibration method for accelerometer scale factor of the missile-borne RINS with fiber optic gyro.

PubMed

Zhang, Qian; Wang, Lei; Liu, Zengjun; Zhang, Yiming

2016-09-19

The calibration of an inertial measurement unit (IMU) is a key technique to improve the preciseness of the inertial navigation system (INS) for missile, especially for the calibration of accelerometer scale factor. Traditional calibration method is generally based on the high accuracy turntable, however, it leads to expensive costs and the calibration results are not suitable to the actual operating environment. In the wake of developments in multi-axis rotational INS (RINS) with optical inertial sensors, self-calibration is utilized as an effective way to calibrate IMU on missile and the calibration results are more accurate in practical application. However, the introduction of multi-axis RINS causes additional calibration errors, including non-orthogonality errors of mechanical processing and non-horizontal errors of operating environment, it means that the multi-axis gimbals could not be regarded as a high accuracy turntable. As for its application on missiles, in this paper, after analyzing the relationship between the calibration error of accelerometer scale factor and non-orthogonality and non-horizontal angles, an innovative calibration procedure using the signals of fiber optic gyro and photoelectric encoder is proposed. The laboratory and vehicle experiment results validate the theory and prove that the proposed method relaxes the orthogonality requirement of rotation axes and eliminates the strict application condition of the system.

Implementation of accelerometer sensor module and fall detection monitoring system based on wireless sensor network.

PubMed

Lee, Youngbum; Kim, Jinkwon; Son, Muntak; Lee, Myoungho

2007-01-01

This research implements wireless accelerometer sensor module and algorithm to determine wearer's posture, activity and fall. Wireless accelerometer sensor module uses ADXL202, 2-axis accelerometer sensor (Analog Device). And using wireless RF module, this module measures accelerometer signal and shows the signal at ;Acceloger' viewer program in PC. ADL algorithm determines posture, activity and fall that activity is determined by AC component of accelerometer signal and posture is determined by DC component of accelerometer signal. Those activity and posture include standing, sitting, lying, walking, running, etc. By the experiment for 30 subjects, the performance of implemented algorithm was assessed, and detection rate for postures, motions and subjects was calculated. Lastly, using wireless sensor network in experimental space, subject's postures, motions and fall monitoring system was implemented. By the simulation experiment for 30 subjects, 4 kinds of activity, 3 times, fall detection rate was calculated. In conclusion, this system can be application to patients and elders for activity monitoring and fall detection and also sports athletes' exercise measurement and pattern analysis. And it can be expected to common person's exercise training and just plaything for entertainment.

State Derivation of a 12-Axis Gyroscope-Free Inertial Measurement Unit

PubMed Central

Lu, Jau-Ching; Lin, Pei-Chun

2011-01-01

The derivation of linear acceleration, angular acceleration, and angular velocity states from a 12-axis gyroscope-free inertial measurement unit that utilizes four 3-axis accelerometer measurements at four distinct locations is reported. Particularly, a new algorithm which derives the angular velocity from its quadratic form and derivative form based on the context-based interacting multiple model is demonstrated. The performance of the system was evaluated under arbitrary 3-dimensional motion. PMID:22163791

Online Robot Dead Reckoning Localization Using Maximum Relative Entropy Optimization With Model Constraints

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

Urniezius, Renaldas

2011-03-14

The principle of Maximum relative Entropy optimization was analyzed for dead reckoning localization of a rigid body when observation data of two attached accelerometers was collected. Model constraints were derived from the relationships between the sensors. The experiment's results confirmed that accelerometers each axis' noise can be successfully filtered utilizing dependency between channels and the dependency between time series data. Dependency between channels was used for a priori calculation, and a posteriori distribution was derived utilizing dependency between time series data. There was revisited data of autocalibration experiment by removing the initial assumption that instantaneous rotation axis of a rigidmore » body was known. Performance results confirmed that such an approach could be used for online dead reckoning localization.« less

Determination of thermally induced effects and design guidelines of optomechanical accelerometers

NASA Astrophysics Data System (ADS)

Lu, Qianbo; Bai, Jian; Wang, Kaiwei; Jiao, Xufen; Han, Dandan; Chen, Peiwen; Liu, Dong; Yang, Yongying; Yang, Guoguang

2017-11-01

Thermal effects, including thermally induced deformation and warm up time, are ubiquitous problems for sensors, especially for inertial measurement units such as accelerometers. Optomechanical accelerometers, which contain light sources that can be regarded as heat sources, involve a different thermal phenomenon in terms of their specific optical readout, and the phenomenon has not been investigated systematically. This paper proposes a model to evaluate the temperature difference, rise time and thermally induced deformation of optomechanical accelerometers, and then constructs design guidelines which can diminish these thermal effects without compromising other mechanical performances, based on the analysis of the interplay of thermal and mechanical performances. In the model, the irradiation of the micromachined structure of a laser source is considered a dominant factor. The experimental data obtained using a prototype of an optomechanical accelerometer approximately confirm the validity of the model for the rise time and response tendency. Moreover, design guidelines that adopt suspensions with a flat cross-section and a short length are demonstrated with reference to the analysis. The guidelines can reduce the thermally induced deformation and rise time or achieve higher mechanical performances with similar thermal effects, which paves the way for the design of temperature-tolerant and robust, high-performance devices.

Satellite accelerometer measurements of neutral density and winds during geomagnetic storms

NASA Technical Reports Server (NTRS)

Marcos, F. A.; Forbes, J. M.

1986-01-01

A new thermospheric wind measurement technique is reported which is based on a Satellite Electrostatic Triaxial Accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in-track, cross-track and radial directions. Data obtained during two time periods are presented. The first data set describes cross-track winds measured between 170 and 210 km during a 5-day period (25 to 29 March 1979) of mostly high geomagnetic activity. In the second data set, cross-track winds and neutral densities from SETA and exospheric temperatures from the Millstone Hill incoherent scatter radar are examined during an isolated magnetic substorm occurring on 21 March 1979. A polar thermospheric wind circulation consisting of a two cell horizontal convection pattern is reflected in both sets of cross-track acceleration measurements. The density response is highly asymmetric with respect to its day/night behavior. Latitude structures of the density response at successive times following the substorm peak suggest the equatorward propagation of a disturbance with a phase speed between 300 and 600 m/s. A deep depression in the density at high latitudes (less than 70 deg) is evident in conjunction with this phenomenon. The more efficient propagation of the disturbance to lower latitudes during the night is probably due to the midnight surge effect.

Three-Axis Superconducting Gravity Gradiometer

NASA Technical Reports Server (NTRS)

Paik, Ho Jung

1987-01-01

Gravity gradients measured even on accelerating platforms. Three-axis superconducting gravity gradiometer based on flux quantization and Meissner effect in superconductors and employs superconducting quantum interference device as amplifier. Incorporates several magnetically levitated proof masses. Gradiometer design integrates accelerometers for operation in differential mode. Principal use in commercial instruments for measurement of Earth-gravity gradients in geo-physical surveying and exploration for oil.

Dynamic Fluid in a Porous Transducer-Based Angular Accelerometer

PubMed Central

Cheng, Siyuan; Fu, Mengyin; Wang, Meiling; Ming, Li; Fu, Huijin; Wang, Tonglei

2017-01-01

This paper presents a theoretical model of the dynamics of liquid flow in an angular accelerometer comprising a porous transducer in a circular tube of liquid. Wave speed and dynamic permeability of the transducer are considered to describe the relation between angular acceleration and the differential pressure on the transducer. The permeability and streaming potential coupling coefficient of the transducer are determined in the experiments, and special prototypes are utilized to validate the theoretical model in both the frequency and time domains. The model is applied to analyze the influence of structural parameters on the frequency response and the transient response of the fluidic system. It is shown that the radius of the circular tube and the wave speed affect the low frequency gain, as well as the bandwidth of the sensor. The hydrodynamic resistance of the transducer and the cross-section radius of the circular tube can be used to control the transient performance. The proposed model provides the basic techniques to achieve the optimization of the angular accelerometer together with the methodology to control the wave speed and the hydrodynamic resistance of the transducer. PMID:28230793

3. Credit WCT. Original 4"x5" black and white negative is ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. Credit WCT. Original 4"x5" black and white negative is housed in the JPL Archives, Pasadena, California. This view of the vibrator shows a large mounted ATS (Advanced Technology Satellite) motor. Accelerometer instrumentation has been added. JPL caption reads "C-210E Vibration Exciter ATS Accelerometer Installation on Q4TX AXIS" (JPL negative no. 384-5848B, 31 March 1966). - Jet Propulsion Laboratory Edwards Facility, Test Stand G, Edwards Air Force Base, Boron, Kern County, CA

Quantifying functional mobility progress for chronic disease management.

PubMed

Boyle, Justin; Karunanithi, Mohan; Wark, Tim; Chan, Wilbur; Colavitti, Christine

2006-01-01

A method for quantifying improvements in functional mobility is presented based on patient-worn accelerometer devices. For patients with cardiovascular, respiratory, or other chronic disease, increasing the amount of functional mobility is a large component of rehabilitation programs. We have conducted an observational trial on the use of accelerometers for quantifying mobility improvements in a small group of chronic disease patients (n=15, 48 - 86 yrs). Cognitive impairments precluded complex instrumentation of patients, and movement data was obtained from a single 2-axis accelerometer device worn at the hip. In our trial, movement data collected from accelerometer devices was classified into Lying vs Sitting/Standing vs Walking/Activity movements. This classification enabled the amount of walking to be quantified and graphically presented to clinicians and carers for feedback on exercise efficacy. Presenting long term trends in this data to patients also provides valuable feedback for self managed care and assisting with compliance.

GEOSTEP: A gravitation experiment in Earth-orbiting satellite to test the Equivalence Principle

NASA Astrophysics Data System (ADS)

Bonneville, R.

2003-10-01

Testing the Equivalence Principle has been recognized by the scientific community as a short-term prime objective for fundamental physics in space. In 1994, a Phase 0/A study of the GEOSTEP mission has been initiated by CNES in order to design a space experiment to test the Equivalence Principle to an accuracy of 10 -17, with the constraint to be compatible with the small versatile platform PROTEUS under study. The GEOSTEP payload comprises a set of four differential accelerometers placed at cryogenic temperature on board a drag-free, 3-axis stabilized satellite in low-Earth orbit. Each accelerometer contains a pair of test masses A-A, A-B, A-C, B-C (inner mass - outer mass) made of three different materials A, B, C with decreasing densities. The accelerometer concept is the fully electrostatic levitation and read-out device proposed by ONERA, called SAGE (Space Accelerometer for Gravitation Experiment). The drag-free and attitude control system (DFACS) is monitored by the common-mode data of the accelerometers along their three axes, while the possible violation signal is detected by the differential-mode data along the longitudinal sensitive axis. The cryostat is a single chamber supercritical Helium dewar designed by CEA. Helium boiling off from the dewar feeds a set of proportional gas thrusters performing the DFACS. Error analysis and data processing preparation is managed by OCA/CERGA. The satellite will be on a 6 am - 6 pm near-polar, near-circular, Sun-synchronous orbit, at an altitude of 600 to 900 km, depending on the atmospheric density at the time of launch. GEOSTEP could be launched in 2002; the nominal mission duration is at least four months.

Wearable Accelerometers in High Performance Jet Aircraft.

PubMed

Rice, G Merrill; VanBrunt, Thomas B; Snider, Dallas H; Hoyt, Robert E

2016-02-01

Wearable accelerometers have become ubiquitous in the fields of exercise physiology and ambulatory hospital settings. However, these devices have yet to be validated in extreme operational environments. The objective of this study was to correlate the gravitational forces (G forces) detected by wearable accelerometers with the G forces detected by high performance aircraft. We compared the in-flight G forces detected by the two commercially available portable accelerometers to the F/A-18 Carrier Aircraft Inertial Navigation System (CAINS-2) during 20 flights performed by the Navy's Flight Demonstration Squadron (Blue Angels). Postflight questionnaires were also used to assess the perception of distractibility during flight. Of the 20 flights analyzed, 10 complete in-flight comparisons were made, accounting for 25,700 s of correlation between the CAINS-2 and the two tested accelerometers. Both accelerometers had strong correlations with that of the F/A-18 Gz axis, averaging r = 0.92 and r = 0.93, respectively, over 10 flights. Comparison of both portable accelerometer's average vector magnitude to each other yielded an average correlation of r = 0.93. Both accelerometers were found to be minimally distracting. These results suggest the use of wearable accelerometers is a valid means of detecting G forces during high performance aircraft flight. Future studies using this surrogate method of detecting accelerative forces combined with physiological information may yield valuable in-flight normative data that heretofore has been technically difficult to obtain and hence holds the promise of opening the door for a new golden age of aeromedical research.

Active damping of spacecraft structural appendage vibrations

NASA Technical Reports Server (NTRS)

Fedor, Joseph V. (Inventor)

1990-01-01

An active vibration damper system, for bending in two orthogonal directions and torsion, in each of three mutually perpendicular axes is located at the extremities of the flexible appendages of a space platform. The system components for each axis includes: an accelerometer, filtering and signal processing apparatus, and a DC motor-inertia wheel torquer. The motor torquer, when driven by a voltage proportional to the relative vibration tip velocity, produces a reaction torque for opposing and therefore damping a specific modal velocity of vibration. The relative tip velocity is obtained by integrating the difference between the signal output from the accelerometer located at the end of the appendage with the output of a usually carried accelerometer located on a relatively rigid body portion of the space platform. A selector switch, with sequential stepping logic or highest modal vibration energy logic, steps to another modal tip velocity channel and receives a signal voltage to damp another vibration mode. In this manner, several vibration modes can be damped with a single sensor/actuator pair. When a three axis damper is located on each of the major appendages of the platform, then all of the system vibration modes can be effectively damped.

Design of electrostatically levitated micromachined rotational gyroscope based on UV-LIGA technology

NASA Astrophysics Data System (ADS)

Cui, Feng; Chen, Wenyuan; Su, Yufeng; Zhang, Weiping; Zhao, Xiaolin

2004-12-01

The prevailing micromachined vibratory gyroscope typically has a proof mass connected to the substrate by a mechanical suspension system, which makes it face a tough challenge to achieve tactical or inertial grade performance levels. With a levitated rotor as the proof mass, a micromachined rotational gyroscope will potentially have higher performance than vibratory gyroscope. Besides working as a moment rebalance dual-axis gyroscope, the micromachined rotational gyroscope based on a levitated rotor can simultaneously work as a force balance tri-axis accelerometer. Micromachined rotational gyroscope based on an electrostatically levitated silicon micromachined rotor has been notably developed. In this paper, factors in designing a rotational gyro/accelerometer based on an electrostatically levitated disc-like rotor, including gyroscopic action of micro rotor, methods of stable levitation, micro displacement detection and control, rotation drive and speed control, vacuum packaging and microfabrication, are comprehensively considered. Hence a design of rotational gyro/accelerometer with an electroforming nickel rotor employing low cost UV-LIGA technology is presented. In this design, a wheel-like flat rotor is proposed and its basic dimensions, diameter and thickness, are estimated according to the required loading capability. Finally, its micromachining methods based on UV-LIGA technology and assembly technology are discussed.

Instrument for Analysis of Greenland's Glacier Mills

NASA Technical Reports Server (NTRS)

Behar, Alberto E.; Matthews, Jaret B.; Tran, Hung B.; Steffen, Konrad; McGrath, Dan; Phillips, Thomas; Elliot, Andrew; OHern, Sean; Lutz, Colin; Martin, Sujita;

Cross-axis adaptation of torsional components in the yaw-axis vestibulo-ocular reflex

NASA Technical Reports Server (NTRS)

Trillenberg, P.; Shelhamer, M.; Roberts, D. C.; Zee, D. S.

2003-01-01

The three pairs of semicircular canals within the labyrinth are not perfectly aligned with the pulling directions of the six extraocular muscles. Therefore, for a given head movement, the vestibulo-ocular reflex (VOR) depends upon central neural mechanisms that couple the canals to the muscles with the appropriate functional gains in order to generate a response that rotates the eye the correct amount and around the correct axis. A consequence of these neural connections is a cross-axis adaptive capability, which can be stimulated experimentally when head rotation is around one axis and visual motion about another. From this visual-vestibular conflict the brain infers that the slow-phase eye movement is rotating around the wrong axis. We explored the capability of human cross-axis adaptation, using a short-term training paradigm, to determine if torsional eye movements could be elicited by yaw (horizontal) head rotation (where torsion is normally inappropriate). We applied yaw sinusoidal head rotation (+/-10 degrees, 0.33 Hz) and measured eye movement responses in the dark, and before and after adaptation. The adaptation paradigm lasted 45-60 min, and consisted of the identical head motion, coupled with a moving visual scene that required one of several types of eye movements: (1) torsion alone (-Roll); (2) horizontal/torsional, head right/CW torsion (Yaw-Roll); (3) horizontal/torsional, head right/CCW torsion (Yaw+Roll); (4) horizontal, vertical, torsional combined (Yaw+Pitch-Roll); and (5) horizontal and vertical together (Yaw+Pitch). The largest and most significant changes in torsional amplitude occurred in the Yaw-Roll and Yaw+Roll conditions. We conclude that short-term, cross-axis adaptation of torsion is possible but constrained by the complexity of the adaptation task: smaller torsional components are produced if more than one cross-coupling component is required. In contrast, vertical cross-axis components can be easily trained to occur with yaw head movements.

Seeing It All: Evaluating Supervised Machine Learning Methods for the Classification of Diverse Otariid Behaviours

PubMed Central

Slip, David J.; Hocking, David P.; Harcourt, Robert G.

2016-01-01

Constructing activity budgets for marine animals when they are at sea and cannot be directly observed is challenging, but recent advances in bio-logging technology offer solutions to this problem. Accelerometers can potentially identify a wide range of behaviours for animals based on unique patterns of acceleration. However, when analysing data derived from accelerometers, there are many statistical techniques available which when applied to different data sets produce different classification accuracies. We investigated a selection of supervised machine learning methods for interpreting behavioural data from captive otariids (fur seals and sea lions). We conducted controlled experiments with 12 seals, where their behaviours were filmed while they were wearing 3-axis accelerometers. From video we identified 26 behaviours that could be grouped into one of four categories (foraging, resting, travelling and grooming) representing key behaviour states for wild seals. We used data from 10 seals to train four predictive classification models: stochastic gradient boosting (GBM), random forests, support vector machine using four different kernels and a baseline model: penalised logistic regression. We then took the best parameters from each model and cross-validated the results on the two seals unseen so far. We also investigated the influence of feature statistics (describing some characteristic of the seal), testing the models both with and without these. Cross-validation accuracies were lower than training accuracy, but the SVM with a polynomial kernel was still able to classify seal behaviour with high accuracy (>70%). Adding feature statistics improved accuracies across all models tested. Most categories of behaviour -resting, grooming and feeding—were all predicted with reasonable accuracy (52–81%) by the SVM while travelling was poorly categorised (31–41%). These results show that model selection is important when classifying behaviour and that by using animal characteristics we can strengthen the overall accuracy. PMID:28002450

Apparent mass matrix of standing subjects exposed to multi-axial whole-body vibration.

PubMed

Tarabini, Marco; Solbiati, Stefano; Saggin, Bortolino; Scaccabarozzi, Diego

2016-08-01

This paper describes the experimental characterisation of the apparent mass matrix of eight male subjects in standing position and the identification of nonlinearities under both mono-axial and dual-axis whole-body vibration. The nonlinear behaviour of the response was studied using the conditioned response techniques considering models of increasing complexity. Results showed that the cross-axis terms are comparable to the diagonal terms. The contribution of the nonlinear effects are minor and can be endorsed to the change of modal parameters during the tests. The nonlinearity generated by the vibration magnitude is more evident in the subject response, since magnitude-dependent effects in the population are overlaid by the scatter in the subjects' biometric data. The biodynamic response is influenced by the addition of a secondary vibration axis and, in case of dual-axis vibrations, the overall magnitude has a marginal contribution. Practitioner Summary: We have measured both the diagonal and cross-axis elements of the apparent mass matrix. The effect of nonlinearities and the simultaneous presence of vibration along two axes are smaller than the inter-subject variability.

Prediction of energy expenditure and physical activity in preschoolers.

PubMed

Butte, Nancy F; Wong, William W; Lee, Jong Soo; Adolph, Anne L; Puyau, Maurice R; Zakeri, Issa F

2014-06-01

Accurate, nonintrusive, and feasible methods are needed to predict energy expenditure (EE) and physical activity (PA) levels in preschoolers. Herein, we validated cross-sectional time series (CSTS) and multivariate adaptive regression splines (MARS) models based on accelerometry and heart rate (HR) for the prediction of EE using room calorimetry and doubly labeled water (DLW) and established accelerometry cut points for PA levels. Fifty preschoolers, mean ± SD age of 4.5 ± 0.8 yr, participated in room calorimetry for minute-by-minute measurements of EE, accelerometer counts (AC) (Actiheart and ActiGraph GT3X+), and HR (Actiheart). Free-living 105 children, ages 4.6 ± 0.9 yr, completed the 7-d DLW procedure while wearing the devices. AC cut points for PA levels were established using smoothing splines and receiver operating characteristic curves. On the basis of calorimetry, mean percent errors for EE were -2.9% ± 10.8% and -1.1% ± 7.4% for CSTS models and -1.9% ± 9.6% and 1.3% ± 8.1% for MARS models using the Actiheart and ActiGraph+HR devices, respectively. On the basis of DLW, mean percent errors were -0.5% ± 9.7% and 4.1% ± 8.5% for CSTS models and 3.2% ± 10.1% and 7.5% ± 10.0% for MARS models using the Actiheart and ActiGraph+HR devices, respectively. Applying activity EE thresholds, final accelerometer cut points were determined: 41, 449, and 1297 cpm for Actiheart x-axis; 820, 3908, and 6112 cpm for ActiGraph vector magnitude; and 240, 2120, and 4450 cpm for ActiGraph x-axis for sedentary/light, light/moderate, and moderate/vigorous PA (MVPA), respectively. On the basis of confusion matrices, correctly classified rates were 81%-83% for sedentary PA, 58%-64% for light PA, and 62%-73% for MVPA. The lack of bias and acceptable limits of agreement affirms the validity of the CSTS and MARS models for the prediction of EE in preschool-aged children. Accelerometer cut points are satisfactory for the classification of sedentary, light, and moderate/vigorous levels of PA in preschoolers.

A microcomputer-based daily living activity recording system.

PubMed

Matsuoka, Shingo; Yonezawa, Yoshiharu; Maki, Hiromichi; Ogawa, Hidekuni; Hahn, Allen W; Thayer, Julian F; Caldwell, W Morton

2003-01-01

A new daily living activity recording system has been developed for monitoring health conditions and living patterns, such as respiration, posture, activity/rest ratios and general activity level. The system employs a piezoelectric sensor, a dual axis accelerometer, two low-power active filters, a low-power 8-bit single chip microcomputer and a 128 MB compact flash memory. The piezoelectric sensor, whose electrical polarization voltage is produced by mechanical strain, detects body movements. Its high-frequency output components reflect body movements produced by walking and running activities, while the low frequency components are mainly respiratory. The dual axis accelerometer detects, from body X and Y tilt angles, whether the patient is standing, sitting or lying down (prone, supine, left side or right side). The detected respiratory, behavior and posture signals are stored by the compact flash memory. After recording, these data are downloaded to a desktop computer and analyzed.

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

PubMed Central

Cui, Feng; Liu, Wu; Chen, Wenyuan; Zhang, Weiping; Wu, Xiaosheng

2011-01-01

A micromachined electrostatically suspended six-axis accelerometer, with a square plate as proof mass housed by a top stator and bottom stator, is presented. The device structure and related techniques concerning its operating principles, such as calculation of capacitances and electrostatic forces/moments, detection and levitation control of the proof mass, acceleration measurement, and structural parameters design, are described. Hybrid MEMS manufacturing techniques, including surface micromachining fabrication of thin film electrodes and interconnections, integration fabrication of thick nickel structures about 500 μm using UV-LIGA by successful removal of SU-8 photoresist mold, DRIE of silicon proof mass in thickness of 450 μm, microassembly and solder bonding, were employed to fabricate this prototype microdevice. A levitation experiment system for the fabricated microaccelerometer chip is introduced, and levitation results show that fast initial levitation within 10 ms and stable full suspension of the proof mass have been successfully demonstrated. PMID:22247662

Simple and robust resistive dual-axis accelerometer using a liquid metal droplet

NASA Astrophysics Data System (ADS)

Huh, Myoung; Won, Dong-Joon; Kim, Joong Gil; Kim, Joonwon

2017-12-01

This paper presents a novel dual-axis accelerometer that consists of a liquid metal droplet in a cone-shaped channel and an electrode layer with four Nichrome electrodes. The sensor uses the advantages of the liquid metal droplet (i.e., high surface tension, electrical conductivity, high density, and deformability). The cone-shaped channel imposes a restoring force on the liquid metal droplet. We conducted simulation tests to determine the appropriate design specifications of the cone-shaped channel. Surface modifications to the channel enhanced the nonwetting performance of the liquid metal droplet. The performances of the sensor were analyzed by a tilting test. When the acceleration was applied along the axial direction, the device showed 6 kΩ/g of sensitivity and negligible crosstalk between the X- and Y-axes. In a diagonal direction test, the device showed 4 kΩ/g of sensitivity.

Laboratory demonstrations of superconducting gravity and inertial sensors for space and airborne gravity measurements

NASA Technical Reports Server (NTRS)

Paik, Ho J.; Canavan, Edgar R.; Kong, Qin; Moody, M. V.

1992-01-01

The paper describes the superconducting gravity gradiometers (SGGs) and superconducting accelerometers being developed at the University of Maryland, which take advantage of many exotic properties of superconductivity to obtain the required low noise, high stability, and large dynamic range. Results of laboratory demonstrations of some of these instruments are presented together with the design and operating principles. Particular attention is given to the three-axis Model II SGG and a six-axis superconducting accelerometer model (Model I SSA). Model II SGG, after a residual common-mode balance, exhibited a noise level of 0.05/sq rt Hz above 0.1 Hz and a 1/f-squared noise below 0.1 Hz. All six channels of Model I SSA operated simultaneously with linear and angular acceleration noise levels of 3 x 10 exp -10 g(E)/sq rt Hz and 5 x 10 exp -8 rad/sec per sec per sq rt Hz, respectively.

Mechanical design of a single-axis monolithic accelerometer for advanced seismic attenuation systems

NASA Astrophysics Data System (ADS)

Bertolini, Alessandro; DeSalvo, Riccardo; Fidecaro, Francesco; Francesconi, Mario; Marka, Szabolcs; Sannibale, Virginio; Simonetti, Duccio; Takamori, Akiteru; Tariq, Hareem

2006-01-01

The design and mechanics for a new very-low noise low frequency horizontal accelerometer is presented. The sensor has been designed to be integrated in an advanced seismic isolation system for interferometric gravitational wave detectors. The motion of a small monolithic folded-pendulum (FP) is monitored by a high resolution capacitance displacement sensor; a feedback force actuator keeps the mass at the equilibrium position. The feedback signal is proportional to the ground acceleration in the frequency range 0-150 Hz. The very high mechanical quality factor, Q≃3000 at a resonant frequency of 0.5 Hz, reduces the Brownian motion of the proof mass of the accelerometer below the resolution of the displacement sensor. This scheme enables the accelerometer to detect the inertial displacement of a platform with a root-mean-square noise less than 1 nm, integrated over the frequency band from 0.01 to 150 Hz. The FP geometry, combined with the monolithic design, allows the accelerometer to be extremely directional. A vertical-horizontal coupling ranging better than 10-3 has been achieved. A detailed account of the design and construction of the accelerometer is reported here. The instrument is fully ultra-high vacuum compatible and has been tested and approved for integration in seismic attenuation system of japanese TAMA 300 gravitational wave detector. The monolithic design also makes the accelerometer suitable for cryogenic operation.

Physical activity and sedentary behavior during pregnancy and postpartum, measured using hip and wrist-worn accelerometers.

PubMed

Hesketh, Kathryn R; Evenson, Kelly R; Stroo, Marissa; Clancy, Shayna M; Østbye, Truls; Benjamin-Neelon, Sara E

2018-06-01

Physical activity in pregnancy and postpartum is beneficial to mothers and infants. To advance knowledge of objective physical activity measurement during these periods, this study compares hip to wrist accelerometer compliance; assesses convergent validity (correlation) between hip- and wrist-worn accelerometry; and assesses change in physical activity from pregnancy to postpartum. We recruited women during pregnancy ( n  = 100; 2014-2015), asking them to wear hip and wrist accelerometers for 7 days during Trimester 2 (T2), Trimester 3 (T3), and 3-, 6-, 9- and 12-months postpartum. We assessed average wear-time and correlations (axis-specific counts/minute, vector magnitude counts/day and step counts/day) at T2, T3, and postpartum. Compliance was higher for wrist-worn accelerometers. Hip and wrist accelerometers showed moderate to high correlations (Pearson's r 0.59 to 0.84). Hip-measured sedentary and active time differed little between T2 and T3. Moderate-to-vigorous physical activity decreased at T3 and remained low postpartum. Light physical activity increased and sedentary time decreased throughout the postpartum period. Wrist accelerometers may be preferable during pregnancy and appear comparable to hip accelerometers. As physical activity declines during later pregnancy and may not rebound post birth, support for re-engaging in physical activity earlier in the postpartum period may benefit women.

Accelerometer-Based Method for Extracting Respiratory and Cardiac Gating Information for Dual Gating during Nuclear Medicine Imaging

PubMed Central

Pänkäälä, Mikko; Paasio, Ari

2014-01-01

Both respiratory and cardiac motions reduce the quality and consistency of medical imaging specifically in nuclear medicine imaging. Motion artifacts can be eliminated by gating the image acquisition based on the respiratory phase and cardiac contractions throughout the medical imaging procedure. Electrocardiography (ECG), 3-axis accelerometer, and respiration belt data were processed and analyzed from ten healthy volunteers. Seismocardiography (SCG) is a noninvasive accelerometer-based method that measures accelerations caused by respiration and myocardial movements. This study was conducted to investigate the feasibility of the accelerometer-based method in dual gating technique. The SCG provides accelerometer-derived respiratory (ADR) data and accurate information about quiescent phases within the cardiac cycle. The correct information about the status of ventricles and atria helps us to create an improved estimate for quiescent phases within a cardiac cycle. The correlation of ADR signals with the reference respiration belt was investigated using Pearson correlation. High linear correlation was observed between accelerometer-based measurement and reference measurement methods (ECG and Respiration belt). Above all, due to the simplicity of the proposed method, the technique has high potential to be applied in dual gating in clinical cardiac positron emission tomography (PET) to obtain motion-free images in the future. PMID:25120563

Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge.

PubMed

Guan, W; Meng, X F; Dong, X M

2014-12-01

Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

Evaluation of Thermo-Mechanical Stability of COTS Dual-Axis MEMS Accelerometers for Space Applications

NASA Technical Reports Server (NTRS)

Sharma, Ashok K.; Teverovksy, Alexander; Day, John H. (Technical Monitor)

2000-01-01

Microelectromechanical systems in MEMS is one of the fastest growing technologies in microelectronics, and is of great interest for military and aerospace applications. Accelerometers are the earliest and most developed representatives of MEMS. First demonstrated in 1979, micromachined accelerometers were used in automobile industry for air bag crash- sensing applications since 1990. In 1999, N4EMS accelerometers were used in NASA-JPL Mars Microprobe. The most developed accelerometers for airbag crash- sensing are rated for a full range of +/- 50 G. The range of sensitivity for accelerometers required for military or aerospace applications is much larger, varying from 20,000 G (to measure acceleration during gun and ballistic munition launches), and to 10(exp -6) G, when used as guidance sensors (to measure attitude and position of a spacecraft). The presence of moving parts on the surface of chip is specific to MEMS, and particularly, to accelerometers. This characteristic brings new reliability issues to micromachined accelerometers, including cyclic fatigue cracking of polysilicon cantilevers and springs, mechanical stresses that are caused by packaging and contamination in the internal cavity of the package. Studies of fatigue cracks initiation and growth in polysilicon showed that the fatigue damage may influence MEMS device performance, and the presence of water vapor significantly enhances crack initiation and growth. Environmentally induced failures, particularly, failures due to thermal cycling and mechanical shock are considered as one of major reliability concerns in MEMS. These environmental conditions are also critical for space applications of the parts. For example, the Mars pathfinder mission had experienced 80 mechanical shock events during the pyrotechnic separation processes.

Design and Analysis of a Novel Fully Decoupled Tri-axis Linear Vibratory Gyroscope with Matched Modes.

PubMed

Xia, Dunzhu; Kong, Lun; Gao, Haiyu

2015-07-13

We present in this paper a novel fully decoupled silicon micromachined tri-axis linear vibratory gyroscope. The proposed gyroscope structure is highly symmetrical and can be limited to an area of about 8.5 mm × 8.5 mm. It can differentially detect three axes' angular velocities at the same time. By elaborately arranging different beams, anchors and sensing frames, the drive and sense modes are fully decoupled from each other. Moreover, the quadrature error correction and frequency tuning functions are taken into consideration in the structure design for all the sense modes. Since there exists an unwanted in-plane rotational mode, theoretical analysis is implemented to eliminate it. To accelerate the mode matching process, the particle swam optimization (PSO) algorithm is adopted and a frequency split of 149 Hz is first achieved by this method. Then, after two steps of manual adjustment of the springs' dimensions, the frequency gap is further decreased to 3 Hz. With the help of the finite element method (FEM) software ANSYS, the natural frequencies of drive, yaw, and pitch/roll modes are found to be 14,017 Hz, 14,018 Hz and 14,020 Hz, respectively. The cross-axis effect and scale factor of each mode are also simulated. All the simulation results are in good accordance with the theoretical analysis, which means the design is effective and worthy of further investigation on the integration of tri-axis accelerometers on the same single chip to form an inertial measurement unit.

Comprehensive Testing of ASL-Owned Accelerometers

NASA Astrophysics Data System (ADS)

Evans, J. R.; Hutt, C. R.; Ringler, A. T.; de la Torre, T.

2011-12-01

The Albuquerque Seismological Laboratory (ASL) of the U.S. Geological Survey (USGS) has undertaken detailed testing of several commercial, off-the-shelf accelerometers to characterize production-standard examples of each instrument. The models tested are the Geotech PA-23, Guralp CMG-5TC, Kinemetrics ES-T (Episensor), Nanometrics Titan (sensor only), and RefTek RT-147-01/3. All are ±4 g accelerometers excepting the CMG-5TC at ±2 g (self noise could be depressed relative to 4-g variant). For dynamic tests, all were recorded on Quanterra Q330 (24-bit) or Q330HR (26-bit) recorders; for static tests high-precision multimeters were used (generally Agilent 3458A 81/2-digit or 34401A 61/2-digit). We also used a translational shake table (Anorad LW10-18-P-E-A-A-B-0) to input controlled test motions. We performed the tests described by Hutt et al. (2010; U.S. Geol. Surv. Open File Rep., 2009-1295, http://pubs.usgs.gov/of/2009/1295/) for these strong-motion sensors (Section 7, Recommended Testing for Strong Motion Acceleration Sensors). These recommended tests result from a public/private effort called "GST2" (the second Guidelines for Seismometer Testing workshop) and represent a consensus of experts in government, academia, and industry (a secondary goal of this work is vetting the tests in this consensus document). The recommended accelerometer tests are: 7.1 Power Demand (Start-up and Steady-State) 7.2 Static Sensitivity, Offset, and Linearity 7.3 Frequency Response and Bandwidth 7.4 Clip Level 7.5 Self Noise and Operating Range 7.6 Distortion 7.7 Orientation (Case to Actual) and Orthogonally 7.8 Translational Cross-Axis Sensitivity 7.9 Temperature Effects (Sensitivity and Offset) 7.10 Power Supply Voltage and Voltage-Noise Effects (Offset and Sensitivity) 7.11 Double Integration (Band-Limited Displacement Square Wave) To the degree the tests and analyses have progressed at this writing, the results are generally good but have revealed a number of issues needing attention. A complete set of test results will be provided at the conference. For example, median self noise of all units is within ANSS guidelines but some are as quiet as ~12 dB below the guidelines, while sensitivities of all but one (malfunctioning) channel are within the 1% guideline, and the orientations of axes relative to instrument cases are nearly all within the 1° guideline. (Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.)

Q-Flex Accelerometer Thermal Performance Study

DTIC Science & Technology

1976-09-01

change which has a significantly long time constant. This newly acquired knowledge strongly suggests elastic meterial property changes, probably due to...hinge axis reference to proof mass center of gravity and rim lands plane). In similar fashion, the Invar excitation rings serve as pickoff

Development of an Inertial Measurement Unit for Unmanned Aerial Vehicles

DTIC Science & Technology

2011-02-01

Tri-axis accelerometers Dual Angular rate gyros Micro-Controller board Battery Rubber isolation stands wireless comunication module (XBee...University. Special thanks to Mr. Jesse McAvoy & Mr. Laith Sahawneh for all the support and valuable scientific contributions. gxk gyk gzk gxb

Three 3-axis accelerometers fixed inside the tyre for studying contact patch deformations in wet conditions

NASA Astrophysics Data System (ADS)

Niskanen, Arto J.; Tuononen, Ari J.

2014-05-01

The tyre-road contact area was studied visually by means of a high-speed camera and three accelerometers fixed to the inner liner of the tyre carcass. Both methods show a distorted contact area in wet conditions, but interesting differences appeared. First, the contact area in full aquaplaning seems strongly distorted on a glass plate when subjected to visual inspection, while the accelerometers indicate a more even hydrodynamic aquaplaning contact length (CL) across the tyre width. Secondly, the acceleration sensors predict the clear shortening of the CL of the tyre before the critical aquaplaning speed. It can be concluded that the visual contact area and shape are heavily dependent on the transparency of the liquid and smoothness of the glass. Meanwhile, the tyre sensors can provide a CL estimate on any road surface imaginable.

Development of a High Precision Displacement Measurement System by Fusing a Low Cost RTK-GPS Sensor and a Force Feedback Accelerometer for Infrastructure Monitoring.

PubMed

Koo, Gunhee; Kim, Kiyoung; Chung, Jun Yeon; Choi, Jaemook; Kwon, Nam-Yeol; Kang, Doo-Young; Sohn, Hoon

2017-11-28

A displacement measurement system fusing a low cost real-time kinematic global positioning system (RTK-GPS) receiver and a force feedback accelerometer is proposed for infrastructure monitoring. The proposed system is composed of a sensor module, a base module and a computation module. The sensor module consists of a RTK-GPS rover and a force feedback accelerometer, and is installed on a target structure like conventional RTK-GPS sensors. The base module is placed on a rigid ground away from the target structure similar to conventional RTK-GPS bases, and transmits observation messages to the sensor module. Then, the initial acceleration, velocity and displacement responses measured by the sensor module are transmitted to the computation module located at a central monitoring facility. Finally, high precision and high sampling rate displacement, velocity, and acceleration are estimated by fusing the acceleration from the accelerometer, the velocity from the GPS rover, and the displacement from RTK-GPS. Note that the proposed displacement measurement system can measure 3-axis acceleration, velocity as well as displacement in real time. In terms of displacement, the proposed measurement system can estimate dynamic and pseudo-static displacement with a root-mean-square error of 2 mm and a sampling rate of up to 100 Hz. The performance of the proposed system is validated under sinusoidal, random and steady-state vibrations. Field tests were performed on the Yeongjong Grand Bridge and Yi Sun-sin Bridge in Korea, and the Xihoumen Bridge in China to compare the performance of the proposed system with a commercial RTK-GPS sensor and other data fusion techniques.

Digital active material processing platform effort (DAMPER), SBIR phase 2

NASA Technical Reports Server (NTRS)

Blackburn, John; Smith, Dennis

1992-01-01

Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

Digital active material processing platform effort (DAMPER), SBIR phase 2

NASA Astrophysics Data System (ADS)

Blackburn, John; Smith, Dennis

1992-11-01

Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

Real-time seismic monitoring of the integrated cape girardeau bridge array and recorded earthquake response

USGS Publications Warehouse

Celebi, M.

2006-01-01

This paper introduces the state of the art, real-time and broad-band seismic monitoring network implemented for the 1206 m [3956 ft] long, cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (MO), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811-1812 New Madrid earthquakes. The bridge was designed for a strong earthquake (magnitude 7.5 or greater) during the design life of the bridge. The monitoring network comprises a total of 84 channels of accelerometers deployed on the superstructure, pier foundations and at surface and downhole free-field arrays of the bridge. The paper also presents the high quality response data obtained from the network. Such data is aimed to be used by the owner, researchers and engineers to assess the performance of the bridge, to check design parameters, including the comparison of dynamic characteristics with actual response, and to better design future similar bridges. Preliminary analyses of ambient and low amplitude small earthquake data reveal specific response characteristics of the bridge and the free-field. There is evidence of coherent tower, cable, deck interaction that sometimes results in amplified ambient motions. Motions at the lowest tri-axial downhole accelerometers on both MO and IL sides are practically free from any feedback from the bridge. Motions at the mid-level and surface downhole accelerometers are influenced significantly by feedback due to amplified ambient motions of the bridge. Copyright ASCE 2006.

Is questionnaire-based sitting time inaccurate and can it be improved? A cross-sectional investigation using accelerometer-based sitting time

PubMed Central

Gupta, Nidhi; Christiansen, Caroline Stordal; Hanisch, Christiana; Bay, Hans; Burr, Hermann; Holtermann, Andreas

2017-01-01

Objectives To investigate the differences between a questionnaire-based and accelerometer-based sitting time, and develop a model for improving the accuracy of questionnaire-based sitting time for predicting accelerometer-based sitting time. Methods 183 workers in a cross-sectional study reported sitting time per day using a single question during the measurement period, and wore 2 Actigraph GT3X+ accelerometers on the thigh and trunk for 1–4 working days to determine their actual sitting time per day using the validated Acti4 software. Least squares regression models were fitted with questionnaire-based siting time and other self-reported predictors to predict accelerometer-based sitting time. Results Questionnaire-based and accelerometer-based average sitting times were ≈272 and ≈476 min/day, respectively. A low Pearson correlation (r=0.32), high mean bias (204.1 min) and wide limits of agreement (549.8 to −139.7 min) between questionnaire-based and accelerometer-based sitting time were found. The prediction model based on questionnaire-based sitting explained 10% of the variance in accelerometer-based sitting time. Inclusion of 9 self-reported predictors in the model increased the explained variance to 41%, with 10% optimism using a resampling bootstrap validation. Based on a split validation analysis, the developed prediction model on ≈75% of the workers (n=132) reduced the mean and the SD of the difference between questionnaire-based and accelerometer-based sitting time by 64% and 42%, respectively, in the remaining 25% of the workers. Conclusions This study indicates that questionnaire-based sitting time has low validity and that a prediction model can be one solution to materially improve the precision of questionnaire-based sitting time. PMID:28093433

Application of Accelerometer Data to Mars Odyssey Aerobraking and Atmospheric Modeling

NASA Technical Reports Server (NTRS)

Tolson, R. H.; Keating, G. M.; George, B. E.; Escalera, P. E.; Werner, M. R.; Dwyer, A. M.; Hanna, J. L.

2002-01-01

Aerobraking was an enabling technology for the Mars Odyssey mission even though it involved risk due primarily to the variability of the Mars upper atmosphere. Consequently, numerous analyses based on various data types were performed during operations to reduce these risk and among these data were measurements from spacecraft accelerometers. This paper reports on the use of accelerometer data for determining atmospheric density during Odyssey aerobraking operations. Acceleration was measured along three orthogonal axes, although only data from the component along the axis nominally into the flow was used during operations. For a one second count time, the RMS noise level varied from 0.07 to 0.5 mm/s2 permitting density recovery to between 0.15 and 1.1 kg per cu km or about 2% of the mean density at periapsis during aerobraking. Accelerometer data were analyzed in near real time to provide estimates of density at periapsis, maximum density, density scale height, latitudinal gradient, longitudinal wave variations and location of the polar vortex. Summaries are given of the aerobraking phase of the mission, the accelerometer data analysis methods and operational procedures, some applications to determining thermospheric properties, and some remaining issues on interpretation of the data. Pre-flight estimates of natural variability based on Mars Global Surveyor accelerometer measurements proved reliable in the mid-latitudes, but overestimated the variability inside the polar vortex.

Predicting Chinese Children and Youth's Energy Expenditure Using ActiGraph Accelerometers: A Calibration and Cross-Validation Study

ERIC Educational Resources Information Center

Zhu, Zheng; Chen, Peijie; Zhuang, Jie

2013-01-01

Purpose: The purpose of this study was to develop and cross-validate an equation based on ActiGraph accelerometer GT3X output to predict children and youth's energy expenditure (EE) of physical activity (PA). Method: Participants were 367 Chinese children and youth (179 boys and 188 girls, aged 9 to 17 years old) who wore 1 ActiGraph GT3X…

A daily living activity remote monitoring system for solitary elderly people.

PubMed

Maki, Hiromichi; Ogawa, Hidekuni; Matsuoka, Shingo; Yonezawa, Yoshiharu; Caldwell, W Morton

2011-01-01

A daily living activity remote monitoring system has been developed for supporting solitary elderly people. The monitoring system consists of a tri-axis accelerometer, six low-power active filters, a low-power 8-bit microcontroller (MC), a 1GB SD memory card (SDMC) and a 2.4 GHz low transmitting power mobile phone (PHS). The tri-axis accelerometer attached to the subject's chest can simultaneously measure dynamic and static acceleration forces produced by heart sound, respiration, posture and behavior. The heart rate, respiration rate, activity, posture and behavior are detected from the dynamic and static acceleration forces. These data are stored in the SD. The MC sends the data to the server computer every hour. The server computer stores the data and makes a graphic chart from the data. When the caregiver calls from his/her mobile phone to the server computer, the server computer sends the graphical chart via the PHS. The caregiver's mobile phone displays the chart to the monitor graphically.

Airborne optical tracking control system design study

NASA Astrophysics Data System (ADS)

1992-09-01

The Kestrel LOS Tracking Program involves the development of a computer and algorithms for use in passive tracking of airborne targets from a high altitude balloon platform. The computer receivers track error signals from a video tracker connected to one of the imaging sensors. In addition, an on-board IRU (gyro), accelerometers, a magnetometer, and a two-axis inclinometer provide inputs which are used for initial acquisitions and course and fine tracking. Signals received by the control processor from the video tracker, IRU, accelerometers, magnetometer, and inclinometer are utilized by the control processor to generate drive signals for the payload azimuth drive, the Gimballed Mirror System (GMS), and the Fast Steering Mirror (FSM). The hardware which will be procured under the LOS tracking activity is the Controls Processor (CP), the IRU, and the FSM. The performance specifications for the GMS and the payload canister azimuth driver are established by the LOS tracking design team in an effort to achieve a tracking jitter of less than 3 micro-rad, 1 sigma for one axis.

A brief test of the Hewlett-Packard MEMS seismic accelerometer

USGS Publications Warehouse

Homeijer, Brian D.; Milligan, Donald J.; Hutt, Charles R.

2014-01-01

Testing was performed on a prototype of Hewlett-Packard (HP) Micro-Electro-Mechanical Systems (MEMS) seismic accelerometer at the U.S. Geological Survey’s Albuquerque Seismological Laboratory. This prototype was built using discrete electronic components. The self-noise level was measured during low seismic background conditions and found to be 9.8 ng/√Hz at periods below 0.2 s (frequencies above 5 Hz). The six-second microseism noise was also discernible. The HP MEMS accelerometer was compared to a Geotech Model GS-13 reference seismometer during seismic noise and signal levels well above the self-noise of the accelerometer. Matching power spectral densities (corrected for accelerometer and seismometer responses to represent true ground motion) indicated that the HP MEMS accelerometer has a flat (constant) response to acceleration from 0.0125 Hz to at least 62.5 Hz. Tilt calibrations of the HP MEMS accelerometer verified that the flat response to acceleration extends to 0 Hz. Future development of the HP MEMS accelerometer includes replacing the discreet electronic boards with a low power application-specific integrated circuit (ASIC) and increasing the dynamic range of the sensor to detect strong motion signals above one gravitational acceleration, while maintaining the self-noise observed during these tests.

Studying rotational dynamics with a smartphone—accelerometer versus gyroscope

NASA Astrophysics Data System (ADS)

Braskén, Mats; Pörn, Ray

2017-07-01

The wide-spread availability of smartphones makes them a valuable addition to the measurement equipment of both the physics classroom and the instructional physics laboratory, encouraging an active interaction between measurements and modeling activities. Two useful sensors, available in most modern smartphones and tablets, are the 3-axis acceleration sensor and the 3-axis gyroscope. We explore the strengths and weaknesses of each type of sensor and use them to study the rotational dynamics of objects rotating about a fixed axis. Care has to be taken when interpreting acceleration sensor data, and in some cases the gyroscope will allow for rotational measurements not easily replicated using the acceleration sensor.

A method to align the coordinate system of accelerometers to the axes of a human body: The depitch algorithm.

PubMed

Gietzelt, Matthias; Schnabel, Stephan; Wolf, Klaus-Hendrik; Büsching, Felix; Song, Bianying; Rust, Stefan; Marschollek, Michael

2012-05-01

One of the key problems in accelerometry based gait analyses is that it may not be possible to attach an accelerometer to the lower trunk so that its axes are perfectly aligned to the axes of the subject. In this paper we will present an algorithm that was designed to virtually align the axes of the accelerometer to the axes of the subject during walking sections. This algorithm is based on a physically reasonable approach and built for measurements in unsupervised settings, where the test persons are applying the sensors by themselves. For evaluation purposes we conducted a study with 6 healthy subjects and measured their gait with a manually aligned and a skewed accelerometer attached to the subject's lower trunk. After applying the algorithm the intra-axis correlation of both sensors was on average 0.89±0.1 with a mean absolute error of 0.05g. We concluded that the algorithm was able to adjust the skewed sensor node virtually to the coordinate system of the subject. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Physical Activity and Adiposity Markers at Older Ages: Accelerometer Vs Questionnaire Data

PubMed Central

Sabia, Séverine; Cogranne, Pol; van Hees, Vincent T.; Bell, Joshua A.; Elbaz, Alexis; Kivimaki, Mika; Singh-Manoux, Archana

2015-01-01

Objective Physical activity is critically important for successful aging, but its effect on adiposity markers at older ages is unclear as much of the evidence comes from self-reported data on physical activity. We assessed the associations of questionnaire-assessed and accelerometer-assessed physical activity with adiposity markers in older adults. Design/Setting/Participants This was a cross-sectional study on 3940 participants (age range 60-83 years) of the Whitehall II study who completed a 20-item physical activity questionnaire and wore a wrist-mounted accelerometer for 9 days in 2012 and 2013. Measurements Total physical activity was estimated using metabolic equivalent hours/week for the questionnaire and mean acceleration for the accelerometer. Time spent in moderate-and-vigorous physical activity (MVPA) was also assessed by questionnaire and accelerometer. Adiposity assessment included body mass index, waist circumference, and fat mass index. Fat mass index was calculated as fat mass/height² (kg/m²), with fat mass estimated using bioimpedance. Results Greater total physical activity was associated with lower adiposity for all adiposity markers in a dose-response manner. In men, the strength of this association was 2.4 to 2.8 times stronger with the accelerometer than with questionnaire data. In women, it was 1.9 to 2.3 times stronger. For MVPA, questionnaire data in men suggested no further benefit for adiposity markers past 1 hour/week of activity. This was not the case for accelerometer-assessed MVPA where, for example, compared with men undertaking <1 hour/week of accelerometer-assessed MVPA, waist circumference was 3.06 (95% confidence interval 2.06–4.06) cm lower in those performing MVPA 1–2.5 hours/week, 4.69 (3.47–5.91) cm lower in those undertaking 2.5–4 hours/week, and 7.11 (5.93–8.29) cm lower in those performing ≥4 hours/week. Conclusions The association of physical activity with adiposity markers in older adults was stronger when physical activity was assessed by accelerometer compared with questionnaire, suggesting that physical activity might be more important for adiposity than previously estimated. PMID:25752539

Automated Detection of Stereotypical Motor Movements

ERIC Educational Resources Information Center

Goodwin, Matthew S.; Intille, Stephen S.; Albinali, Fahd; Velicer, Wayne F.

2011-01-01

To overcome problems with traditional methods for measuring stereotypical motor movements in persons with Autism Spectrum Disorders (ASD), we evaluated the use of wireless three-axis accelerometers and pattern recognition algorithms to automatically detect body rocking and hand flapping in children with ASD. Findings revealed that, on average,…

Application of inertial instruments for DSN antenna pointing and tracking

NASA Technical Reports Server (NTRS)

Eldred, D. B.; Nerheim, N. M.; Holmes, K. G.

1990-01-01

The feasibility of using inertial instruments to determine the pointing attitude of the NASA Deep Space Network antennas is examined. The objective is to obtain 1 mdeg pointing knowledge in both blind pointing and tracking modes to facilitate operation of the Deep Space Network 70 m antennas at 32 GHz. A measurement system employing accelerometers, an inclinometer, and optical gyroscopes is proposed. The initial pointing attitude is established by determining the direction of the local gravity vector using the accelerometers and the inclinometer, and the Earth's spin axis using the gyroscopes. Pointing during long-term tracking is maintained by integrating the gyroscope rates and augmenting these measurements with knowledge of the local gravity vector. A minimum-variance estimator is used to combine measurements to obtain the antenna pointing attitude. A key feature of the algorithm is its ability to recalibrate accelerometer parameters during operation. A survey of available inertial instrument technologies is also given.

Low-cost, efficient wireless intelligent sensors (LEWIS) measuring real-time reference-free dynamic displacements

NASA Astrophysics Data System (ADS)

Ozdagli, A. I.; Liu, B.; Moreu, F.

2018-07-01

According to railroad managers, displacement of railroad bridges under service loads is an important parameter in the condition assessment and performance evaluation. However, measuring bridge responses in the field is often costly and labor-intensive. This paper proposes a low-cost, efficient wireless intelligent sensor (LEWIS) platform that can compute in real-time the dynamic transverse displacements of railroad bridges under service loads. This sensing platform drives on an open-source Arduino ecosystem and combines low-cost microcontrollers with affordable accelerometers and wireless transmission modules. The proposed LEWIS system is designed to reconstruct dynamic displacements from acceleration measurements onboard, eliminating the need for offline post-processing, and to transmit the data in real-time to a base station where the inspector at the bridge can see the displacements while the train is crossing, or to a remote office if so desired by internet. Researchers validated the effectiveness of the new LEWIS by conducting a series of laboratory experiments. A shake table setup simulated transverse bridge displacements measured on the field and excited the proposed platform, a commercially available wired expensive accelerometer, and reference LVDT displacement sensor. The responses obtained from the wireless system were compared to the displacements reconstructed from commercial accelerometer readings and the reference LVDT. The results of the laboratory experiments demonstrate that the proposed system is capable of reconstructing transverse displacements of railroad bridges under revenue service traffic accurately and transmitting the data in real-time wirelessly. In conclusion, the platform presented in this paper can be used in the performance assessment of railroad bridge network cost-effectively and accurately. Future work includes collecting real-time reference-free displacements of one railroad bridge in Colorado under train crossings to further prove LEWIS' suitability for engineering applications.

The impact of accelerometer wear location on the relationship between step counts and arterial stiffness in adults treated for hypertension and diabetes.

PubMed

Cooke, Alexandra B; Daskalopoulou, Stella S; Dasgupta, Kaberi

2018-04-01

Accelerometer placement at the wrist is convenient and increasingly adopted despite less accurate physical activity (PA) measurement than with waist placement. Capitalizing on a study that started with wrist placement and shifted to waist placement, we compared associations between PA measures derived from different accelerometer locations with a responsive arterial health indicator, carotid-femoral pulse wave velocity (cfPWV). Cross-sectional study. We previously demonstrated an inverse association between waist-worn pedometer-assessed step counts (Yamax SW-200, 7 days) and cfPWV (-0.20m/s, 95% CI -0.28, -0.12 per 1000 step/day increment) in 366 adults. Participants concurrently wore accelerometers (ActiGraph GT3X+), most at the waist but the first 46 at the wrist. We matched this subgroup with participants from the 'waist accelerometer' group (sex, age, and pedometer-assessed steps/day) and assessed associations with cfPWV (applanation tonometry, Sphygmocor) separately in each subgroup through linear regression models. Compared to the waist group, wrist group participants had higher step counts (mean difference 3980 steps/day; 95% CI 2517, 5443), energy expenditure (967kcal/day, 95% CI 755, 1179), and moderate-to-vigorous-PA (138min; 95% CI 114, 162). Accelerometer-assessed step counts (waist) suggested an association with cfPWV (-0.28m/s, 95% CI -0.58, 0.01); but no relationship was apparent with wrist-assessed steps (0.02m/s, 95% CI -0.24, 0.27). Waist but not wrist ActiGraph PA measures signal associations between PA and cfPWV. We urge researchers to consider the importance of wear location choice on relationships with health indicators. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

International Conference on the Mechanical Technology of Inertial Devices, University of Newcastle-upon-Tyne, England, Apr. 7-9, 1987, Proceedings

NASA Astrophysics Data System (ADS)

Various papers on the mechanical technology of inertial devices are presented. The topics addressed include: development of a directional gyroscope for remotely piloted vehicles and similar applications; a two-degree-of-freedom gyroscope with frictionless inner and outer gimbal pickoffs; oscillogyro design, manufacture, and performance; development of miniature two-axis rate gyroscope; mechanical design aspects of the electrostatically suspended gyroscope; role of gas-lubricated bearings in current and future sensors; development of a new microporous retainer material for precision ball bearings; design study for a high-stability, large-centrifuge test bed; evaluation of a two-axis rate gyro; operating principles of a two-axis angular rate transducer; and nutation frequency analysis. Also considered are: triaxial laser gyro; mechanical design considerations for a ring laser gyro dither mechanism; environmental considerations in the design of fiberoptic gyroscopes; manufacturing aspects of some critical high-precision mechanical components of inertial devices; dynamics and control of a gyroscopic force measurement system; high precision and high performance motion systems; use of multiple acceleration references to obtain high precision centrifuge data at low cost; gyro testing and evaluation at the Communications Research Centre; review of the mechanical design and development of a high-performance accelerometer; and silicon microengineering for accelerometers.

Minimized Bolus-Type Wireless Sensor Node with a Built-In Three-Axis Acceleration Meter for Monitoring a Cow’s Rumen Conditions

PubMed Central

Nogami, Hirofumi; Arai, Shozo; Okada, Hironao; Zhan, Lan; Itoh, Toshihiro

2017-01-01

Monitoring rumen conditions in cows is important because a dysfunctional rumen system may cause death. Sub-acute ruminal acidosis (SARA) is a typical disease in cows, and is characterized by repeated periods of low ruminal pH. SARA is regarded as a trigger for rumen atony, rumenitis, and abomasal displacement, which may cause death. In previous studies, rumen conditions were evaluated by wireless sensor nodes with pH measurement capability. The primary advantage of the pH sensor is its ability to continuously measure ruminal pH. However, these sensor nodes have short lifetimes since they are limited by the finite volume of the internal liquid of the reference electrode. Mimicking rumen atony, we attempt to evaluate the rumen condition using wireless sensor nodes with three-axis accelerometers. The theoretical life span of such sensor nodes depends mainly on the transmission frequency of acceleration data and the size of the battery, and the proposed sensor nodes are 30.0 mm in diameter and 70.0 mm in length and have a life span of over 600 days. Using the sensor nodes, we compare the rumen motility of the force transducer measurement with the three-axis accelerometer data. As a result, we can detect discriminative movement of rumen atony. PMID:28346374

Minimized Bolus-Type Wireless Sensor Node with a Built-In Three-Axis Acceleration Meter for Monitoring a Cow's Rumen Conditions.

PubMed

Nogami, Hirofumi; Arai, Shozo; Okada, Hironao; Zhan, Lan; Itoh, Toshihiro

2017-03-27

Monitoring rumen conditions in cows is important because a dysfunctional rumen system may cause death. Sub-acute ruminal acidosis (SARA) is a typical disease in cows, and is characterized by repeated periods of low ruminal pH. SARA is regarded as a trigger for rumen atony, rumenitis, and abomasal displacement, which may cause death. In previous studies, rumen conditions were evaluated by wireless sensor nodes with pH measurement capability. The primary advantage of the pH sensor is its ability to continuously measure ruminal pH. However, these sensor nodes have short lifetimes since they are limited by the finite volume of the internal liquid of the reference electrode. Mimicking rumen atony, we attempt to evaluate the rumen condition using wireless sensor nodes with three-axis accelerometers. The theoretical life span of such sensor nodes depends mainly on the transmission frequency of acceleration data and the size of the battery, and the proposed sensor nodes are 30.0 mm in diameter and 70.0 mm in length and have a life span of over 600 days. Using the sensor nodes, we compare the rumen motility of the force transducer measurement with the three-axis accelerometer data. As a result, we can detect discriminative movement of rumen atony.

The effectiveness of wrist guards for reducing wrist and elbow accelerations resulting from simulated forward falls.

PubMed

Burkhart, Timothy A; Andrews, David M

2010-08-01

The effectiveness of wrist guards and modifying elbow posture for reducing impact-induced accelerations at the wrist and elbow, for the purpose of decreasing upper extremity injury risk during forward fall arrest, has not yet been documented in living people. A seated human pendulum was used to simulate the impact conditions consistent with landing on outstretched arms during a forward fall. Accelerometers measured the wrist and elbow response characteristics of 28 subjects following impacts with and without a wrist guard, and with elbows straight or slightly bent. Overall, the wrist guard was very effective, with significant reductions in peak accelerations at the elbow in the axial and off-axis directions, and in the off-axis direction at the wrist by almost 50%. The effect of elbow posture as an intervention strategy was mixed; a change in magnitude and direction of the acceleration response was documented at the elbow, while there was little effect at the wrist. Unique evidence was presented in support of wrist guard use in activities like in-line skating where impacts to the hands are common. The elbow response clearly shows that more proximal anatomical structures also need to be monitored when assessing the effectiveness of injury prevention strategies.

A Physics Road Rally

ERIC Educational Resources Information Center

Ilyes, Mark A.; Ortman-Link, Whitney

2009-01-01

Our school recently acquired Vernier's Wireless Dynamics Sensor System (WDSS). The WDSS consists of a three-axis accelerometer, altimeter, and force sensor that has the ability to remotely collect data for later transfer to a computer. While our primary purpose for acquiring the WDSS was to enhance our amusement park physics experiments, we…

Complete Tri-Axis Magnetometer Calibration with a Gyro Auxiliary

PubMed Central

Yang, Deng; You, Zheng; Li, Bin; Duan, Wenrui; Yuan, Binwen

2017-01-01

Magnetometers combined with inertial sensors are widely used for orientation estimation, and calibrations are necessary to achieve high accuracy. This paper presents a complete tri-axis magnetometer calibration algorithm with a gyro auxiliary. The magnetic distortions and sensor errors, including the misalignment error between the magnetometer and assembled platform, are compensated after calibration. With the gyro auxiliary, the magnetometer linear interpolation outputs are calculated, and the error parameters are evaluated under linear operations of magnetometer interpolation outputs. The simulation and experiment are performed to illustrate the efficiency of the algorithm. After calibration, the heading errors calculated by magnetometers are reduced to 0.5° (1σ). This calibration algorithm can also be applied to tri-axis accelerometers whose error model is similar to tri-axis magnetometers. PMID:28587115

Is questionnaire-based sitting time inaccurate and can it be improved? A cross-sectional investigation using accelerometer-based sitting time.

PubMed

Gupta, Nidhi; Christiansen, Caroline Stordal; Hanisch, Christiana; Bay, Hans; Burr, Hermann; Holtermann, Andreas

2017-01-16

To investigate the differences between a questionnaire-based and accelerometer-based sitting time, and develop a model for improving the accuracy of questionnaire-based sitting time for predicting accelerometer-based sitting time. 183 workers in a cross-sectional study reported sitting time per day using a single question during the measurement period, and wore 2 Actigraph GT3X+ accelerometers on the thigh and trunk for 1-4 working days to determine their actual sitting time per day using the validated Acti4 software. Least squares regression models were fitted with questionnaire-based siting time and other self-reported predictors to predict accelerometer-based sitting time. Questionnaire-based and accelerometer-based average sitting times were ≈272 and ≈476 min/day, respectively. A low Pearson correlation (r=0.32), high mean bias (204.1 min) and wide limits of agreement (549.8 to -139.7 min) between questionnaire-based and accelerometer-based sitting time were found. The prediction model based on questionnaire-based sitting explained 10% of the variance in accelerometer-based sitting time. Inclusion of 9 self-reported predictors in the model increased the explained variance to 41%, with 10% optimism using a resampling bootstrap validation. Based on a split validation analysis, the developed prediction model on ≈75% of the workers (n=132) reduced the mean and the SD of the difference between questionnaire-based and accelerometer-based sitting time by 64% and 42%, respectively, in the remaining 25% of the workers. This study indicates that questionnaire-based sitting time has low validity and that a prediction model can be one solution to materially improve the precision of questionnaire-based sitting time. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

A Wireless Accelerometer-Based Body Posture Stability Detection System and Its Application for Meditation Practitioners

PubMed Central

Chang, Kang-Ming; Chen, Sih-Huei; Lee, Hsin-Yi; Ching, Congo Tak-Shing; Huang, Chun-Lung

2012-01-01

The practice of meditation has become an interesting research issue in recent decades. Meditation is known to be beneficial for health improvement and illness reduction and many studies on meditation have been made, from both the physiological and psychological points of view. It is a fundamental requirement of meditation practice to be able to sit without body motion. In this study, a novel body motion monitoring and estimation system has been developed. A wireless tri-axis accelerometer is used to measure body motion. Both a mean and maximum motion index is derived from the square summation of three axes. Two experiments were conducted in this study. The first experiment was to investigate the motion index baseline among three leg-crossing postures. The second experiment was to observe posture dynamics for thirty minute’s meditation. Twenty-six subjects participated in the experiments. In one experiment, thirteen subjects were recruited from an experienced meditation group (meditation experience > 3 years); and the other thirteen subjects were beginners (meditation experience < 1 years). There was a significant posture stability difference between both groups in terms of either mean or maximum parameters (p < 0.05), according to the results of the experiment. Results from another experiment showed that the motion index is different for various postures, such as full-lotus < half-lotus < non-lotus. PMID:23250281

Diagonalizing controller for a superconducting six-axis accelerometer

NASA Astrophysics Data System (ADS)

Bachrach, B.; Canavan, E. R.; Levine, W. S.

A relatively simple MIMO (multiple input, multiple output) controller which converts an instrument with a nondiagonally dominant transfer function matrix into a strongly diagonally dominant device is developed. The instrument, which uses inductance bridges to sense the position of a magnetically levitated superconducting mass, has very lightly damped resonances and fairly strong cross coupling. By taking advantage of the particular structure of the instrument's transfer function matrix, it is possible to develop a relatively simple controller which achieves the desired decoupling. This controller consists of two parts. The first part cancels the nondiagonal terms of the open-loop transfer function matrix, while the second part is simply a set of SISO (single input, single output) controllers. The stability of the closed-loop system is studied using Rosenbrock's INA (inverse Nyguist array) technique, which produces a simple set of conditions guaranteeing stability. Simulation of the closed-loop system indicates that it should easily achieve its performance goals.

Using the Wiimote in Introductory Physics Experiments

ERIC Educational Resources Information Center

Ochoa, Romulo; Rooney, Frank G.; Somers, William J.

2011-01-01

The Wii is a very popular gaming console. An important component of its appeal is the ease of use of its remote controller, popularly known as a Wiimote. This simple-looking but powerful device has a three-axis accelerometer and communicates with the console via Bluetooth protocol. We present two experiments that demonstrate the feasibility of…

Developmental Test of the Honeywell Laser Inertial Navigation System (LINS)

DTIC Science & Technology

1975-11-01

The ISA contains three Systron Donner 4841F-10 single axis accelerometers and three Honeywell GG1300- AEOI laser gyros in an orthogonal strapdown...DIAG.1,kM AN.D PHYSICAL CHARACTERISTICS The GG1300- AEOI laser gyro, shown schematically in Figure 2, has the following performance goals which were

Longitudinal, lateral and transverse axes of forearm muscles influence the crosstalk in the mechanomyographic signals during isometric wrist postures.

PubMed

Islam, Md Anamul; Sundaraj, Kenneth; Ahmad, R Badlishah; Sundaraj, Sebastian; Ahamed, Nizam Uddin; Ali, Md Asraf

2014-01-01

In mechanomyography (MMG), crosstalk refers to the contamination of the signal from the muscle of interest by the signal from another muscle or muscle group that is in close proximity. The aim of the present study was two-fold: i) to quantify the level of crosstalk in the mechanomyographic (MMG) signals from the longitudinal (Lo), lateral (La) and transverse (Tr) axes of the extensor digitorum (ED), extensor carpi ulnaris (ECU) and flexor carpi ulnaris (FCU) muscles during isometric wrist flexion (WF) and extension (WE), radial (RD) and ulnar (UD) deviations; and ii) to analyze whether the three-directional MMG signals influence the level of crosstalk between the muscle groups during these wrist postures. Twenty, healthy right-handed men (mean ± SD: age = 26.7±3.83 y; height = 174.47±6.3 cm; mass = 72.79±14.36 kg) participated in this study. During each wrist posture, the MMG signals propagated through the axes of the muscles were detected using three separate tri-axial accelerometers. The x-axis, y-axis, and z-axis of the sensor were placed in the Lo, La, and Tr directions with respect to muscle fibers. The peak cross-correlations were used to quantify the proportion of crosstalk between the different muscle groups. The average level of crosstalk in the MMG signals generated by the muscle groups ranged from: 34.28-69.69% for the Lo axis, 27.32-52.55% for the La axis and 11.38-25.55% for the Tr axis for all participants and their wrist postures. The Tr axes between the muscle groups showed significantly smaller crosstalk values for all wrist postures [F (2, 38) = 14-63, p<0.05, η2 = 0.416-0.769]. The results may be applied in the field of human movement research, especially for the examination of muscle mechanics during various types of the wrist postures.

Validation of heart rate extraction through an iPhone accelerometer.

PubMed

Kwon, Sungjun; Lee, Jeongsu; Chung, Gih Sung; Park, Kwang Suk

2011-01-01

Ubiquitous medical technology may provide advanced utility for evaluating the status of the patient beyond the clinical environment. The iPhone provides the capacity to measure the heart rate, as the iPhone consists of a 3-axis accelerometer that is sufficiently sensitive to perceive tiny body movements caused by heart pumping. In this preliminary study, an iPhone was tested and evaluated as the reliable heart rate extractor to use for medical purpose by comparing with reference electrocardiogram. By comparing the extracted heart rate from acquired acceleration data with the extracted one from ECG reference signal, iPhone functioning as the reliable heart rate extractor has demonstrated sufficient accuracy and consistency.

Slice&Dice: Recognizing Food Preparation Activities Using Embedded Accelerometers

NASA Astrophysics Data System (ADS)

Pham, Cuong; Olivier, Patrick

Within the context of an endeavor to provide situated support for people with cognitive impairments in the kitchen, we developed and evaluated classifiers for recognizing 11 actions involved in food preparation. Data was collected from 20 lay subjects using four specially designed kitchen utensils incorporating embedded 3-axis accelerometers. Subjects were asked to prepare a mixed salad in our laboratory-based instrumented kitchen environment. Video of each subject's food preparation activities were independently annotated by three different coders. Several classifiers were trained and tested using these features. With an overall accuracy of 82.9% our investigation demonstrated that a broad set of food preparation actions can be reliably recognized using sensors embedded in kitchen utensils.

Eutectic-based wafer-level-packaging technique for piezoresistive MEMS accelerometers and bond characterization using molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Aono, T.; Kazama, A.; Okada, R.; Iwasaki, T.; Isono, Y.

2018-03-01

We developed a eutectic-based wafer-level-packaging (WLP) technique for piezoresistive micro-electromechanical systems (MEMS) accelerometers on the basis of molecular dynamics analyses and shear tests of WLP accelerometers. The bonding conditions were experimentally and analytically determined to realize a high shear strength without solder material atoms diffusing to adhesion layers. Molecular dynamics (MD) simulations and energy dispersive x-ray (EDX) spectrometry done after the shear tests clarified the eutectic reaction of the solder materials used in this research. Energy relaxation calculations in MD showed that the diffusion of solder material atoms into the adhesive layer was promoted at a higher temperature. Tensile creep MD simulations also suggested that the local potential energy in a solder material model determined the fracture points of the model. These numerical results were supported by the shear tests and EDX analyses for WLP accelerometers. Consequently, a bonding load of 9.8 kN and temperature of 300 °C were found to be rational conditions because the shear strength was sufficient to endure the polishing process after the WLP process and there was little diffusion of solder material atoms to the adhesion layer. Also, eutectic-bonding-based WLP was effective for controlling the attenuation of the accelerometers by determining the thickness of electroplated solder materials that played the role of a cavity between the accelerometers and lids. If the gap distance between the two was less than 6.2 µm, the signal gains for x- and z-axis acceleration were less than 20 dB even at the resonance frequency due to air-damping.

An Enhanced Method to Estimate Heart Rate from Seismocardiography via Ensemble Averaging of Body Movements at Six Degrees of Freedom.

PubMed

Lee, Hyunwoo; Lee, Hana; Whang, Mincheol

2018-01-15

Continuous cardiac monitoring has been developed to evaluate cardiac activity outside of clinical environments due to the advancement of novel instruments. Seismocardiography (SCG) is one of the vital components that could develop such a monitoring system. Although SCG has been presented with a lower accuracy, this novel cardiac indicator has been steadily proposed over traditional methods such as electrocardiography (ECG). Thus, it is necessary to develop an enhanced method by combining the significant cardiac indicators. In this study, the six-axis signals of accelerometer and gyroscope were measured and integrated by the L2 normalization and multi-dimensional kineticardiography (MKCG) approaches, respectively. The waveforms of accelerometer and gyroscope were standardized and combined via ensemble averaging, and the heart rate was calculated from the dominant frequency. Thirty participants (15 females) were asked to stand or sit in relaxed and aroused conditions. Their SCG was measured during the task. As a result, proposed method showed higher accuracy than traditional SCG methods in all measurement conditions. The three main contributions are as follows: (1) the ensemble averaging enhanced heart rate estimation with the benefits of the six-axis signals; (2) the proposed method was compared with the previous SCG method that employs fewer-axis; and (3) the method was tested in various measurement conditions for a more practical application.

OARE flight maneuvers and calibration measurements on STS-58

NASA Technical Reports Server (NTRS)

Blanchard, Robert C.; Nicholson, John Y.; Ritter, James R.; Larman, Kevin T.

1994-01-01

The Orbital Acceleration Research Experiment (OARE), which has flown on STS-40, STS-50, and STS-58, contains a three axis accelerometer with a single, nonpendulous, electrostatically suspended proofmass which can resolve accelerations to the nano-g level. The experiment also contains a full calibration station to permit in situ bias and scale factor calibration. This on-orbit calibration capability eliminates the large uncertainty of ground-based calibrations encountered with accelerometers flown in the past on the orbiter, thus providing absolute acceleration measurement accuracy heretofore unachievable. This is the first time accelerometer scale factor measurements have been performed on orbit. A detailed analysis of the calibration process is given along with results of the calibration factors from the on-orbit OARE flight measurements on STS-58. In addition, the analysis of OARE flight maneuver data used to validate the scale factor measurements in the sensor's most sensitive range is also presented. Estimates on calibration uncertainties are discussed. This provides bounds on the STS-58 absolute acceleration measurements for future applications.

Accuracy improvement in a calibration test bench for accelerometers by a vision system

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

D’Emilia, Giulio, E-mail: giulio.demilia@univaq.it; Di Gasbarro, David, E-mail: david.digasbarro@graduate.univaq.it; Gaspari, Antonella, E-mail: antonella.gaspari@graduate.univaq.it

2016-06-28

A procedure is described in this paper for the accuracy improvement of calibration of low-cost accelerometers in a prototype rotary test bench, driven by a brushless servo-motor and operating in a low frequency range of vibrations (0 to 5 Hz). Vibration measurements by a vision system based on a low frequency camera have been carried out, in order to reduce the uncertainty of the real acceleration evaluation at the installation point of the sensor to be calibrated. A preliminary test device has been realized and operated in order to evaluate the metrological performances of the vision system, showing a satisfactory behaviormore » if the uncertainty measurement is taken into account. A combination of suitable settings of the control parameters of the motion control system and of the information gained by the vision system allowed to fit the information about the reference acceleration at the installation point to the needs of the procedure for static and dynamic calibration of three-axis accelerometers.« less

Magnetospheric Multiscale (MMS) Mission Attitude Ground System Design

NASA Technical Reports Server (NTRS)

Sedlak, Joseph E.; Superfin, Emil; Raymond, Juan C.

2010-01-01

This paper describes the attitude ground system (AGS) design to be used for support of the Magnetospheric MultiScale (MMS) mission. The AGS exists as one component of the mission operations control center. It has responsibility for validating the onboard attitude and accelerometer bias estimates, calibrating the attitude sensors and the spacecraft inertia tensor, and generating a definitive attitude history for use by the science teams. NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland is responsible for developing the MMS spacecraft, for the overall management of the MMS mission, and for mission operations. MMS is scheduled for launch in 2014 for a planned two-year mission. The MMS mission consists of four identical spacecraft flying in a tetrahedral formation in an eccentric Earth orbit. The relatively tight formation, ranging from 10 to 400 km, will provide coordinated observations giving insight into small-scale magnetic field reconnection processes. By varying the size of the tetrahedron and the orbital semi-major axis and eccentricity, and making use of the changing solar phase, this geometry allows for the study of both bow shock and magnetotail plasma physics, including acceleration, reconnection, and turbulence. The mission divides into two phases for science; these phases will have orbit dimensions of 1.2 x 12 Earth radii in the first phase and 1.2x25 Earth radii in the second in order to study the dayside magnetopause and the nightside magnetotail, respectively. The orbital periods are roughly one day and three days for the two mission phases. Each of the four MMS spacecraft will be spin stabilized at 3 revolutions per minute (rpm), with the spin axis oriented near the ecliptic north pole but tipped approximately 2.5 deg towards the Sun line. The main body of each spacecraft will be an eight-sided platform with diameter of 3.4 m and height of 1.2 m. Several booms are attached to this central core: two axial booms of 14.9 m length, two radial magnetometer booms of 5 m length, and four radial wire booms of 60 m length. Attitude and orbit control will use a set of axial and radial thrusters. A four-head star tracker and a slit-type digital Sun sensor (DSS) provide input for attitude determination. In addition, an accelerometer will be used for closed-loop orbit maneuver control. The primary AGS product will be a daily definitive attitude history. Due to power limitations, the star tracker and accelerometer data will not be available at all times. However, tracker data from at least 10 percent of each orbit and continuous DSS data will be provided. An extended Kalman filter (EKF) will be used to estimate the three-axis attitude (i.e., spin axis orientation and spin phase) and rotation rate for all times when the tracker data is valid. For other times, the attitude is generated by assuming a constant angular momentum vector in the inertial frame. The DSS sun pulse will provide a timing signal to maintain an accurate spin phase. There will be times when the Sun is occulted and DSS data is not available. If this occurs at the start or end of a definitive attitude product, then the spin phase will be extrapolated using the mean rate determined by the EKF.

Magnetospheric Multiscale (MMS) Mission Attitude Ground System Design

NASA Technical Reports Server (NTRS)

Sedlak, Joseph E.; Superfin, Emil; Raymond, Juan C.

2011-01-01

This paper describes the attitude ground system (AGS) design to be used for support of the Magnetospheric MultiScale (MMS) mission. The AGS exists as one component of the mission operations control center. It has responsibility for validating the onboard attitude and accelerometer bias estimates, calibrating the attitude sensors and the spacecraft inertia tensor, and generating a definitive attitude history for use by the science teams. NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland is responsible for developing the MMS spacecraft, for the overall management of the MMS mission, and for mission operations. MMS is scheduled for launch in 2014 for a planned two-year mission. The MMS mission consists of four identical spacecraft flying in a tetrahedral formation in an eccentric Earth orbit. The relatively tight formation, ranging from 10 to 400 km, will provide coordinated observations giving insight into small-scale magnetic field reconnection processes. By varying the size of the tetrahedron and the orbital semi-major axis and eccentricity, and making use of the changing solar phase, this geometry allows for the study of both bow shock and magnetotail plasma physics, including acceleration, reconnection, and turbulence. The mission divides into two phases for science; these phases will have orbit dimensions of l.2xl2 Earth radii in the first phase and l.2x25 Earth radii in the second in order to study the dayside magnetopause and the nightside magnetotail, respectively. The orbital periods are roughly one day and three days for the two mission phases. Each of the four MMS spacecraft will be spin stabilized at 3 revolutions per minute (rpm), with the spin axis oriented near the ecliptic north pole but tipped approximately 2.5 deg towards the Sun line. The main body of each spacecraft will be an eight-sided platform with diameter of 3.4 m and height of 1.2 m. Several booms are attached to this central core: two axial booms of 14.9 m length, two radial magnetometer booms of 5 m length, and four radial -wire booms of 60 m length. Attitude and orbit control will use a set of axial and radial thrusters. A four-head star tracker and a slit-type digital Sun sensor (DSS) provide input for attitude determination. In addition, an accelerometer will be· used for closed-loop orbit maneuver control. The primary AGS product will be a daily definitive attitude history. Due to power limitations; the star tracker and accelerometer data will not be available at all times. However, tracker data from at least 10 percent of each orbit and continuous DSS data will be provided. An extended Kalman filter (EKF) will be used to estimate the three-axis attitude (i.e., spin axis orientation and spin phase) and rotation rate for all times when the tracker data is valid. For other times, the attitude is generated by assuming a constant angular momentum vector in the inertial frame. The DSS sun pulse will provide a timing signal to maintain an accurate spin phase. There will be times when the Sun is occulted and DSS data is not available. If this occurs at the start or end of a definitive attitude product, then the spin phase will be extrapolated using the mean rate determined by the EKF.

Implementation of an iPhone wireless accelerometer application for the quantification of reflex response.

PubMed

LeMoyne, Robert; Mastroianni, Timothy; Grundfest, Warren; Nishikawa, Kiisa

2013-01-01

The patellar tendon reflex represents an inherent aspect of the standard neurological evaluation. The features of the reflex response provide initial perspective regarding the status of the nervous system. An iPhone wireless accelerometer application integrated with a potential energy impact pendulum attached to a reflex hammer has been successfully developed, tested, and evaluated for quantifying the patellar tendon reflex. The iPhone functions as a wireless accelerometer platform. The wide coverage range of the iPhone enables the quantification of reflex response samples in rural and remote settings. The iPhone has the capacity to transmit the reflex response acceleration waveform by wireless transmission through email. Automated post-processing of the acceleration waveform provides feature extraction of the maximum acceleration of the reflex response ascertained after evoking the patellar tendon reflex. The iPhone wireless accelerometer application demonstrated the utility of the smartphone as a biomedical device, while providing accurate and consistent quantification of the reflex response.

From GeoSTEP to MidiSTEP: a small satellite experiment to test the equivalence principle

NASA Astrophysics Data System (ADS)

Bonneville, R.

1996-11-01

Testing the equivalence principle (EP) has been recognized by the scientific community as a short term prime objective for fundamental physics in space. In 1994 a phase 0/A study of the GeoSTEP mission was initiated by CNES in order to design a space experiment to test the EP at the accuracy of 0264-9381/13/11A/020/img1, with the concern to be compatible with the small versatile platform `PROTEUS' under study. The GeoSTEP payload includes a set of four differential accelerometers placed at cryogenic temperature on board a drag-free, three-axis stabilized satellite in low-Earth orbit. Each accelerometer contains a pair of test masses A - A, A - B, A - C, B - C (inner mass - outer mass) made of three different materials A, B, C with decreasing densities. The accelerometer concept is the fully electrostatic levitation and read-out device proposed by ONERA (`SAGE'). The drag-free and attitude control system (DFACS) is monitored by the common mode data of the accelerometers along their three axes, while the expected violation signal is detected by the differential mode data along the longitudinal sensitive axis. The cryostat is a single chamber supercritical helium dewar designed by CEA. Helium boiling off from the dewar feeds a set of proportional gas thrusters performing the DFCAS. Error analysis and data processing preparation is managed by OCA/CERGA. The satellite will be on a 6 am - 6 pm near polar, near circular, Sun-synchronous orbit, at an altitude of 600 to 900 km, depending upon the atmosphere density at the launch date. The mission will last at least 4 months and could be launched in 2002. A descoped, room-temperature version of the project using electric thrusters (FEEPs) and called MidiSTEP has also been considered.

Characterization of a nine-meter sensor-equipped wind turbine blade using a laser measuring device

USDA-ARS?s Scientific Manuscript database

A nine-meter turbine blade was prepared for an experiment to examine the movement and fatigue patterns during operation on a 115 kW turbine. The blade, equipped with surface mounted fiber optic strain gauges, foil strain gauges, single, and triple axis accelerometers was placed on a calibration fixt...

MEMSlab: A Practical MEMS Course for the Fabrication, Packaging, and Testing of a Single-Axis Accelerometer

ERIC Educational Resources Information Center

Grundbacher, R.; Hoetzel, J. E.; Hierold, C.

2009-01-01

A microelectro-mechanical systems (MEMS) laboratory course (MEMSlab) in the Mechanical and Process Engineering Department at the Swiss Federal Institute of Technology (ETH Zurich), is presented. The course has been taught for four years and has been attended primarily by Master's students from mechanical and electrical engineering; since fall…

Flywheels Would Compensate for Rotor Imbalance

NASA Technical Reports Server (NTRS)

Hrastar, J. A. S.

1982-01-01

Spinning flywheels within rotor can null imbalance forces in rotor. Flywheels axes are perpendicular to each other and to rotor axis. Feedback signals from accelerometers or strain gages in platform control flywheel speeds and rotation directions. Concept should be useful for compensating rotating bodies on Earth. For example, may be applied to large industrial centrifuge, particularly if balance changes during operation.

Cross-sectional time series and multivariate adaptive regression splines models using accelerometry and heart rate predict energy expenditure of preschoolers

USDA-ARS?s Scientific Manuscript database

Prediction equations of energy expenditure (EE) using accelerometers and miniaturized heart rate (HR) monitors have been developed in older children and adults but not in preschool-aged children. Because the relationships between accelerometer counts (ACs), HR, and EE are confounded by growth and ma...

Evaluation of Thermal Protection Tile Transmissibility for Ground Vibration Test

NASA Technical Reports Server (NTRS)

Chung, Y. T.; Fowler, Samuel B.; Lo, Wenso; Towner, Robert

2005-01-01

Transmissibility analyses and tests were conducted on a composite panel with thermal protection system foams to evaluate the quality of the measured frequency response functions. Both the analysis and the test results indicate that the vehicle dynamic responses are fully transmitted to the accelerometers mounted on the thermal protection system in the normal direction below a certain frequency. In addition, the in-plane motions of the accelerometer mounted on the top surface of the thermal protection system behave more actively than those on the composite panel due to the geometric offset of the accelerometer from the panel in the test set-up. The transmissibility tests and analyses show that the frequency response functions measured from the accelerometers mounted on the TPS will provide accurate vehicle responses below 120 Hz for frequency and mode shape identification. By confirming that accurate dynamic responses below a given frequency can be obtained, this study increases the confidence needed for conducting the modal testing, model correlation, and model updating for a vehicle installed with TPS. '

An ECG electrode-mounted heart rate, respiratory rhythm, posture and behavior recording system.

PubMed

Yoshimura, Takahiro; Yonezawa, Yoshiharu; Maki, Hiromichi; Ogawa, Hidekuni; Ninomiya, Ishio; Morton Caldwell, W

2004-01-01

R-R interval, respiration rhythm, posture and behavior recording system has been developed for monitoring a patient's cardiovascular regulatory system in daily life. The recording system consists of three ECG chest electrodes, a variable gain instrumentation amplifier, a dual axis accelerometer, a low power 8-bit single-chip microcomputer and a 1024 KB EEPROM. The complete system is mounted on the chest electrodes. R-R interval and respiration rhythm are calculated by the R waves detected from the ECG. Posture and behavior such as walking and running are detected from the body movements recorded by the accelerometer. The detected data are stored by the EEPROM and, after recording, are downloaded to a desktop computer for analysis.

Simplified design of diaphragm-based fiber optic extrinsic Fabry-Perot accelerometer

NASA Astrophysics Data System (ADS)

Wang, Zhaogang; Zhang, Wentao; Han, Jing; Huang, Wenzhu; Li, Fang

2014-11-01

A fiber optic Fabry-Perot accelerometer (FOFPA) with diaphragm-mass-collimator (DMC) gathered structure is presented. This design makes the structure more compacts and the manufacturing process more controllable. The operation principle based on Fabry-Perot interference is described. Several tests using intensity demodulation scheme which can control the working point of FOFPA were carried out. Experimental results show that: axis sensitivity of the proposed FOFPA is 36.07 dB (re: 0 dB=1 V/g) with a fluctuation less than 0.9 dB in a frequency bandwidth of 10-125 Hz, the resonant frequency is about 350 Hz, measurement range is about 70 dB@100 Hz. which are much close to theoretical values

Global gravity survey by an orbiting gravity gradiometer

NASA Technical Reports Server (NTRS)

Paik, Ho Jung; Leung, Jurn-Sun; Morgan, Samuel H.; Parker, Joseph

1988-01-01

The scientific aims, design, and mission profile of the Superconducting Gravity Gradiometer Mission (SGGM), a NASA spacecraft mission proposed for the late 1990s, are discussed and illustrated with drawings and diagrams. SGGM would complement the two other planned gravimetry missions, GRM and Aristoteles, and would provide gravitational-field measurements with accuracy 2-3 mGal in 55 x 55-km blocks. The principal instruments are a (1) three-axis superconducting gravity gradiometer with intrinsic sensitivity 100 microeotvos/sq rt Hz, (2) a six-axis superconducting accelerometer with sensitivity 100 fg(E)/sq rt Hz linear and 10 prad/sec squared sq rt Hz angular, and (3) a six-axis shaker for active control of the platform. Consideration is given to the error budget and platform requirements, the orbit selection criteria, and the spacecraft design.

Obstacle Detection using Binocular Stereo Vision in Trajectory Planning for Quadcopter Navigation

NASA Astrophysics Data System (ADS)

Bugayong, Albert; Ramos, Manuel, Jr.

2018-02-01

Quadcopters are one of the most versatile unmanned aerial vehicles due to its vertical take-off and landing as well as hovering capabilities. This research uses the Sum of Absolute Differences (SAD) block matching algorithm for stereo vision. A complementary filter was used in sensor fusion to combine obtained quadcopter orientation data from the accelerometer and the gyroscope. PID control was implemented for the motor control and VFH+ algorithm was implemented for trajectory planning. Results show that the quadcopter was able to consistently actuate itself in the roll, yaw and z-axis during obstacle avoidance but was however found to be inconsistent in the pitch axis during forward and backward maneuvers due to the significant noise present in the pitch axis angle outputs compared to the roll and yaw axes.

Dual-axis high-data-rate atom interferometer via cold ensemble exchange

DOE PAGES

Rakholia, Akash V.; McGuinness, Hayden J.; Biedermann, Grant W.

2014-11-24

We demonstrate a dual-axis accelerometer and gyroscope atom interferometer, which can form the building blocks of a six-axis inertial measurement unit. By recapturing the atoms after the interferometer sequence, we maintain a large atom number at high data rates of 50 to 100 measurements per second. Two cold ensembles are formed in trap zones located a few centimeters apart and are launched toward one another. During their ballistic trajectory, they are interrogated with a stimulated Raman sequence, detected, and recaptured in the opposing trap zone. As a result, we achieve sensitivities at μg/ √Hz and μrad/s/ √Hz levels, making thismore » a compelling prospect for expanding the use of atom interferometer inertial sensors beyond benign laboratory environments.« less

Lumbar joint torque estimation based on simplified motion measurement using multiple inertial sensors.

PubMed

Miyajima, Saori; Tanaka, Takayuki; Imamura, Yumeko; Kusaka, Takashi

2015-01-01

We estimate lumbar torque based on motion measurement using only three inertial sensors. First, human motion is measured by a 6-axis motion tracking device that combines a 3-axis accelerometer and a 3-axis gyroscope placed on the shank, thigh, and back. Next, the lumbar joint torque during the motion is estimated by kinematic musculoskeletal simulation. The conventional method for estimating joint torque uses full body motion data measured by an optical motion capture system. However, in this research, joint torque is estimated by using only three link angles of the body, thigh, and shank. The utility of our method was verified by experiments. We measured motion of bendung knee and waist simultaneously. As the result, we were able to estimate the lumbar joint torque from measured motion.

Analysis of Pendulum Period with an iPod Touch/iPhone

ERIC Educational Resources Information Center

Briggle, Justin

2013-01-01

We describe the use of Apple's iPod touch/iPhone, acting as the pendulum bob, as a means of measuring pendulum period, making use of the device's three-axis digital accelerometer and the freely available SPARKvue app from PASCO scientific. The method can be readily incorporated into an introductory physics laboratory experiment.…

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.

Identifying Active Travel Behaviors in Challenging Environments Using GPS, Accelerometers, and Machine Learning Algorithms.

PubMed

Ellis, Katherine; Godbole, Suneeta; Marshall, Simon; Lanckriet, Gert; Staudenmayer, John; Kerr, Jacqueline

2014-01-01

Active travel is an important area in physical activity research, but objective measurement of active travel is still difficult. Automated methods to measure travel behaviors will improve research in this area. In this paper, we present a supervised machine learning method for transportation mode prediction from global positioning system (GPS) and accelerometer data. We collected a dataset of about 150 h of GPS and accelerometer data from two research assistants following a protocol of prescribed trips consisting of five activities: bicycling, riding in a vehicle, walking, sitting, and standing. We extracted 49 features from 1-min windows of this data. We compared the performance of several machine learning algorithms and chose a random forest algorithm to classify the transportation mode. We used a moving average output filter to smooth the output predictions over time. The random forest algorithm achieved 89.8% cross-validated accuracy on this dataset. Adding the moving average filter to smooth output predictions increased the cross-validated accuracy to 91.9%. Machine learning methods are a viable approach for automating measurement of active travel, particularly for measuring travel activities that traditional accelerometer data processing methods misclassify, such as bicycling and vehicle travel.

ITAG: A fine-scale measurement platform to inform organismal response to a changing ocean

NASA Astrophysics Data System (ADS)

Katija, K.; Shorter, K. A.; Mooney, T. A.; Mann, D.; Wang, A. Z.; Sonnichsen, F. N.

2016-02-01

Soft-bodied marine invertebrates comprise a keystone component of ocean ecosystems, however we know little of their behaviors and physiological responses within their natural habitat. Quantifying ocean conditions and measuring an organisms' response to the physical environment is vital to understanding organismal responses to a changing ocean. However, we face technological limitations when attempting to quantify the physical and environmental conditions that organisms encounter at spatial and temporal scales of an individual organism. Here we describe a novel, eco-sensor tag (the ITAG) that has 3-axis accelerometer, 3-axis magnetometer, pressure, temperature, and light sensors. Current and future efforts involve miniaturizing and integrating O2 and salinity sensors to the ITAG. The tagging package is designed to be neutrally buoyant, and after a prescribed time, the electronics separate from a weighted base and floats to the surface. Tags were deployed on five jellyfish (Aurelia aurita) and eight squid (Loligo forbesi) in laboratory conditions for up to 24 hr. Using concurrent video and tag data, movement signatures for specific behaviors were identified. Based on these laboratory trials, we found that squid activity level changed in response to ambient light conditions, which can inform trade-offs between behavior and energy expenditure in captive and wild animals. The ITAG opens the door for lab and field-based measurements of behavior, physiology, and concurrent environmental parameters that not only inform interactions in a changing ocean, but also provides a novel platform by which characterization of the environment can be conducted at fine spatial and temporal scales.

Accelerometer-determined physical activity and the cardiovascular response to mental stress in children.

PubMed

Spartano, Nicole L; Heffernan, Kevin S; Dumas, Amy K; Gump, Brooks B

2017-01-01

Cardiovascular reactivity has been associated with future hypertension and cardiovascular mortality. Higher physical activity (PA) has been associated with lower cardiovascular reactivity in adults, but little data is available in children. The purpose of this study was to examine the relationship between PA and cardiovascular reactivity to mental stress in children. Cross-sectional study. This study sample included children from the Oswego Lead Study (n=79, 46% female, 9-11 years old). Impedance cardiography was performed while children participated in a stress response protocol. Children were also asked to wear Actigraph accelerometers on their wrists for 3 days to measure intensity and duration of PA and sedentary time. In multivariable models, moderate to vigorous (MV) PA was associated with lower body mass index (BMI) percentile and lower total peripheral resistance (TPR) response to stress (beta=-0.025, p=0.02; beta=-0.009, p=0.05). After additional adjustment for BMI, MVPA was also associated with lower diastolic blood pressure response to stress (beta=-0.01, p=0.03). Total PA and sedentary time were not associated with BMI or cardiovascular responses to stress. A modest, inverse relation of PA to vascular reactivity to mental stress was observed in children. These data provide confirmatory evidence that the promotion of PA recommendations for children are important for cardiovascular health. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Towards Integrated Marmara Strong Motion Network

NASA Astrophysics Data System (ADS)

Durukal, E.; Erdik, M.; Safak, E.; Ansal, A.; Ozel, O.; Alcik, H.; Mert, A.; Kafadar, N.; Korkmaz, A.; Kurtulus, A.

2009-04-01

Istanbul has a 65% chance of having a magnitude 7 or above earthquake within the next 30 years. As part of the preparations for the future earthquake, strong motion networks have been installed in and around Istanbul. The Marmara Strong Motion Network, operated by the Department of Earthquake Engineering of Kandilli Observatory and Earthquake Research Institute, encompasses permanent systems outlined below. It is envisaged that the networks will be run by a single entity responsible for technical management and maintanence, as well as for data management, archiving and dissemination through dedicated web-based interfaces. • Istanbul Earthquake Rapid Response and Early Warning System - IERREWS (one hundred 18-bit accelerometers for rapid response; ten 24-bit accelerometers for early warning) • IGDAŞ Gas Shutoff Network (100 accelerometers to be installed in 2010 and integrated with IERREWS) • Structural Monitoring Arrays - Fatih Sultan Mehmet Suspension Bridge (1200m-long suspension bridge across the Bosphorus, five 3-component accelerometers + GPS sensors) - Hagia Sophia Array (1500-year-old historical edifice, 9 accelerometers) - Süleymaniye Mosque Array (450-year-old historical edifice,9 accelerometers) - Fatih Mosque Array (237-year-old historical edifice, 9 accelerometers) - Kanyon Building Array (high-rise office building, 5 accelerometers) - Isbank Tower Array (high-rise office building, 5 accelerometers) - ENRON Array (power generation facility, 4 acelerometers) - Mihrimah Sultan Mosque Array (450-year-old historical edifice,9 accelerometers + tiltmeters, to be installed in 2009) - Sultanahmet Mosque Array, (390-year-old historical edifice, 9 accelerometers + tiltmeters, to be installed in 2009) • Special Arrays - Atakoy Vertical Array (four 3-component accelerometers at 25, 50, 75, and 150 m depths) - Marmara Tube Tunnel (1400 m long submerged tunnel, 128 ch. accelerometric data, 24 ch. strain data, to be installed in 2010) - Air-Force Academy Array (72 ch. dense accelerometric array to be installed in 2010) - Gemlik Array (a dense basin array of 8 stations, to be installed in 2010) The objectives of these systems and networks are: (1) to produce rapid earthquake intensity, damage and loss assessment information after an earthquake (in the case of IERREWS), (2) to monitor conditions of structural systems, (3) to develop real-time data processing, analysis, and damage detection and location tools (in the case of structural networks) after an extreme event, (4) to assess spatial properties of strong ground motion and ground strain, and to characterise basin response (in the case of special arrays), (5) to investigate site response and wave propagation (in the case of vertical array). Ground motion data obtained from these strong motion networks have and are being used for investigations of attenuation, spatial variation (coherence), simulation benchmarking, source modeling, site response, seismic microzonation, system identification and structural model verification and structural health control. In addition to the systems and networks outlined above there are two temporary networks: KIMNET - a dense urban noise and microtremor network consisting of 50 broadband stations expected to be operational in mid 2009, and SOSEWIN - a 20-station, self-organizing structural integrated array at Ataköy in Istanbul.

Estimation of daily energy expenditure in pregnant and non-pregnant women using a wrist-worn tri-axial accelerometer.

PubMed

van Hees, Vincent T; Renström, Frida; Wright, Antony; Gradmark, Anna; Catt, Michael; Chen, Kong Y; Löf, Marie; Bluck, Les; Pomeroy, Jeremy; Wareham, Nicholas J; Ekelund, Ulf; Brage, Søren; Franks, Paul W

2011-01-01

Few studies have compared the validity of objective measures of physical activity energy expenditure (PAEE) in pregnant and non-pregnant women. PAEE is commonly estimated with accelerometers attached to the hip or waist, but little is known about the validity and participant acceptability of wrist attachment. The objectives of the current study were to assess the validity of a simple summary measure derived from a wrist-worn accelerometer (GENEA, Unilever Discover, UK) to estimate PAEE in pregnant and non-pregnant women, and to evaluate participant acceptability. Non-pregnant (N = 73) and pregnant (N = 35) Swedish women (aged 20-35 yrs) wore the accelerometer on their wrist for 10 days during which total energy expenditure (TEE) was assessed using doubly-labelled water. PAEE was calculated as 0.9×TEE-REE. British participants (N = 99; aged 22-65 yrs) wore accelerometers on their non-dominant wrist and hip for seven days and were asked to score the acceptability of monitor placement (scored 1 [least] through 10 [most] acceptable). There was no significant correlation between body weight and PAEE. In non-pregnant women, acceleration explained 24% of the variation in PAEE, which decreased to 19% in leave-one-out cross-validation. In pregnant women, acceleration explained 11% of the variation in PAEE, which was not significant in leave-one-out cross-validation. Median (IQR) acceptability of wrist and hip placement was 9(8-10) and 9(7-10), respectively; there was a within-individual difference of 0.47 (p<.001). A simple summary measure derived from a wrist-worn tri-axial accelerometer adds significantly to the prediction of energy expenditure in non-pregnant women and is scored acceptable by participants.

Investigation of Electrostatic Accelerometer in HUST for Space Science Missions

NASA Astrophysics Data System (ADS)

Bai, Yanzheng; Hu, Ming; Li, Gui; Liu, Li; Qu, Shaobo; Wu, Shuchao; Zhou, Zebing

2014-05-01

High-precision electrostatic accelerometers are significant payload in CHAMP, GRACE and GOCE gravity missions to measure the non-gravitational forces. In our group, space electrostatic accelerometer and inertial sensor based on the capacitive sensors and electrostatic control technique has been investigated for space science research in China such as testing of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, satellite Earth's field recovery and so on. In our group, a capacitive position sensor with a resolution of 10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are developed. 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. Meanwhile, high voltage suspension and free fall methods are applied to verify the function of electrostatic accelerometer. Last, the engineering model of electrostatic accelerometer has been developed and tested successfully in space and preliminary results are present.

Accelerometer telemetry system

NASA Technical Reports Server (NTRS)

Konigsberg, E. (Inventor)

1976-01-01

An accelerometer telemetry system incorporated in a finger ring is used for monitoring the motor responses of a subject. The system includes an accelerometer, battery, and transmitter and provides information to a remote receiver regarding hand movements of a subject wearing the ring, without the constraints of wires. Possible applications include the detection of fatigue from the hand movements of the wearer.

Reusable Rapid Prototyped Blunt Impact Simulator

DTIC Science & Technology

2016-08-01

for a nonclassical gun experimental application. 15. SUBJECT TERMS rapid prototype, additive manufacturing, reusable projectile, 3-axis accelerometer... gun -launched applications.1,2 SLS technology uses a bed of powdered material that is introduced to a laser. The laser is controlled by a computer to...in creating internal gun -hardened electronics for a variety of high-g applications, GTB developed an internal electronics package containing a COTS

Results of the Quasi-Steady Acceleration Environment from the STS-62 Missions

NASA Technical Reports Server (NTRS)

Matisak, Brian; French, Larry; DeLombard, Richard; Wagar, William

1995-01-01

One of the clear benefits of conducting scientific research in space is to take advantage of the reduced acceleration environment. Many accelerometer packages have proven to accurately measure the acceleration environment at frequency levels above one Hz. However, for particular classes of experiments the quality of science returns is a direct function of the extremely low frequency (less than 0.01 Hz), quasi-steady acceleration environment. One class particularly interested in this acceleration regime is the group of crystal growth experimenters. These scientists are primarily interested in knowing the resultant quasi-steady acceleration vector at their respective crystal growth locations. The objective of many of these scientists is to minimize the amount of convective flow acting in a direction perpendicular to the growth axis of the crystal. Convective flow within the crystal can be induced by the direction and magnitude of the quasi-steady acceleration vector. Convective flows acting perpendicular to the growth axis of the crystal can cause nonuniformity within the crystal, thus reducing the quality of the results. The Orbital Acceleration Research Experiment (OARE), an accelerometer package hardmounted to the bottom of the payload bay of the orbiter Columbia (OV-102), has the capability of monitoring and recording the quasi-steady acceleration environment. This paper will describe the components that make up the on-orbit quasi-steady acceleration environment, detail how results from the OARE device were achieved, and compare modelled acceleration results with actual on-orbit OARE results from the STS-62 and STS-65 flights. A summary of the results will be provided along with possible recommendations of how to combine modelled and realtime quasi-steady accelerometer data for future Shuttle flights.

Quasi-Static Calibration Method of a High-g Accelerometer

PubMed Central

Wang, Yan; Fan, Jinbiao; Zu, Jing; Xu, Peng

2017-01-01

To solve the problem of resonance during quasi-static calibration of high-g accelerometers, we deduce the relationship between the minimum excitation pulse width and the resonant frequency of the calibrated accelerometer according to the second-order mathematical model of the accelerometer, and improve the quasi-static calibration theory. We establish a quasi-static calibration testing system, which uses a gas gun to generate high-g acceleration signals, and apply a laser interferometer to reproduce the impact acceleration. These signals are used to drive the calibrated accelerometer. By comparing the excitation acceleration signal and the output responses of the calibrated accelerometer to the excitation signals, the impact sensitivity of the calibrated accelerometer is obtained. As indicated by the calibration test results, this calibration system produces excitation acceleration signals with a pulse width of less than 1000 μs, and realize the quasi-static calibration of high-g accelerometers with a resonant frequency above 20 kHz when the calibration error was 3%. PMID:28230743

The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer

PubMed Central

Shi, Yunbo; Yang, Zhicai; Ma, Zongmin; Cao, Huiliang; Kou, Zhiwei; Zhi, Dan; Chen, Yanxiang; Feng, Hengzhen; Liu, Jun

2016-01-01

Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method. PMID:27338383

An Attachable Electromagnetic Energy Harvester Driven Wireless Sensing System Demonstrating Milling-Processes and Cutter-Wear/Breakage-Condition Monitoring.

PubMed

Chung, Tien-Kan; Yeh, Po-Chen; Lee, Hao; Lin, Cheng-Mao; Tseng, Chia-Yung; Lo, Wen-Tuan; Wang, Chieh-Min; Wang, Wen-Chin; Tu, Chi-Jen; Tasi, Pei-Yuan; Chang, Jui-Wen

2016-02-23

An attachable electromagnetic-energy-harvester driven wireless vibration-sensing system for monitoring milling-processes and cutter-wear/breakage-conditions is demonstrated. The system includes an electromagnetic energy harvester, three single-axis Micro Electro-Mechanical Systems (MEMS) accelerometers, a wireless chip module, and corresponding circuits. The harvester consisting of magnets with a coil uses electromagnetic induction to harness mechanical energy produced by the rotating spindle in milling processes and consequently convert the harnessed energy to electrical output. The electrical output is rectified by the rectification circuit to power the accelerometers and wireless chip module. The harvester, circuits, accelerometer, and wireless chip are integrated as an energy-harvester driven wireless vibration-sensing system. Therefore, this completes a self-powered wireless vibration sensing system. For system testing, a numerical-controlled machining tool with various milling processes is used. According to the test results, the system is fully self-powered and able to successfully sense vibration in the milling processes. Furthermore, by analyzing the vibration signals (i.e., through analyzing the electrical outputs of the accelerometers), criteria are successfully established for the system for real-time accurate simulations of the milling-processes and cutter-conditions (such as cutter-wear conditions and cutter-breaking occurrence). Due to these results, our approach can be applied to most milling and other machining machines in factories to realize more smart machining technologies.

An Attachable Electromagnetic Energy Harvester Driven Wireless Sensing System Demonstrating Milling-Processes and Cutter-Wear/Breakage-Condition Monitoring

PubMed Central

Chung, Tien-Kan; Yeh, Po-Chen; Lee, Hao; Lin, Cheng-Mao; Tseng, Chia-Yung; Lo, Wen-Tuan; Wang, Chieh-Min; Wang, Wen-Chin; Tu, Chi-Jen; Tasi, Pei-Yuan; Chang, Jui-Wen

2016-01-01

An attachable electromagnetic-energy-harvester driven wireless vibration-sensing system for monitoring milling-processes and cutter-wear/breakage-conditions is demonstrated. The system includes an electromagnetic energy harvester, three single-axis Micro Electro-Mechanical Systems (MEMS) accelerometers, a wireless chip module, and corresponding circuits. The harvester consisting of magnets with a coil uses electromagnetic induction to harness mechanical energy produced by the rotating spindle in milling processes and consequently convert the harnessed energy to electrical output. The electrical output is rectified by the rectification circuit to power the accelerometers and wireless chip module. The harvester, circuits, accelerometer, and wireless chip are integrated as an energy-harvester driven wireless vibration-sensing system. Therefore, this completes a self-powered wireless vibration sensing system. For system testing, a numerical-controlled machining tool with various milling processes is used. According to the test results, the system is fully self-powered and able to successfully sense vibration in the milling processes. Furthermore, by analyzing the vibration signals (i.e., through analyzing the electrical outputs of the accelerometers), criteria are successfully established for the system for real-time accurate simulations of the milling-processes and cutter-conditions (such as cutter-wear conditions and cutter-breaking occurrence). Due to these results, our approach can be applied to most milling and other machining machines in factories to realize more smart machining technologies. PMID:26907297

An all-silicon single-wafer micro-g accelerometer with a combined surface and bulk micromachining process

NASA Technical Reports Server (NTRS)

Yazdi, N.; Najafi, K.

2000-01-01

This paper reports an all-silicon fully symmetrical z-axis micro-g accelerometer that is fabricated on a single-silicon wafer using a combined surface and bulk fabrication process. The microaccelerometer has high device sensitivity, low noise, and low/controllable damping that are the key factors for attaining micro g and sub-micro g resolution in capacitive accelerometers. The microfabrication process produces a large proof mass by using the whole wafer thickness and a large sense capacitance by utilizing a thin sacrificial layer. The sense/feedback electrodes are formed by a deposited 2-3 microns polysilicon film with embedded 25-35 microns-thick vertical stiffeners. These electrodes, while thin, are made very stiff by the thick embedded stiffeners so that force rebalancing of the proof mass becomes possible. The polysilicon electrodes are patterned to create damping holes. The microaccelerometers are batch-fabricated, packaged, and tested successfully. A device with a 2-mm x 1-mm proof mass and a full bridge support has a measured sensitivity of 2 pF/g. The measured sensitivity of a 4-mm x 1-mm accelerometer with a cantilever support is 19.4 pF/g. The calculated noise floor of these devices at atmosphere are 0.23 micro g/sqrt(Hz) and 0.16 micro g/sqrt(Hz), respectively.

Identifying Active Travel Behaviors in Challenging Environments Using GPS, Accelerometers, and Machine Learning Algorithms

PubMed Central

Ellis, Katherine; Godbole, Suneeta; Marshall, Simon; Lanckriet, Gert; Staudenmayer, John; Kerr, Jacqueline

2014-01-01

Background: Active travel is an important area in physical activity research, but objective measurement of active travel is still difficult. Automated methods to measure travel behaviors will improve research in this area. In this paper, we present a supervised machine learning method for transportation mode prediction from global positioning system (GPS) and accelerometer data. Methods: We collected a dataset of about 150 h of GPS and accelerometer data from two research assistants following a protocol of prescribed trips consisting of five activities: bicycling, riding in a vehicle, walking, sitting, and standing. We extracted 49 features from 1-min windows of this data. We compared the performance of several machine learning algorithms and chose a random forest algorithm to classify the transportation mode. We used a moving average output filter to smooth the output predictions over time. Results: The random forest algorithm achieved 89.8% cross-validated accuracy on this dataset. Adding the moving average filter to smooth output predictions increased the cross-validated accuracy to 91.9%. Conclusion: Machine learning methods are a viable approach for automating measurement of active travel, particularly for measuring travel activities that traditional accelerometer data processing methods misclassify, such as bicycling and vehicle travel. PMID:24795875

Accelerometer having integral fault null

NASA Astrophysics Data System (ADS)

Bozeman, Richard J., Jr.

1995-08-01

An improved accelerometer is introduced. It comprises a transducer responsive to vibration in machinery which produces an electrical signal related to the magnitude and frequency of the vibration; and a decoding circuit responsive to the transducer signal which produces a first fault signal to produce a second fault signal in which ground shift effects are nullified.

Accelerometer having integral fault null

NASA Technical Reports Server (NTRS)

Bozeman, Richard J., Jr. (Inventor)

1995-01-01

An improved accelerometer is introduced. It comprises a transducer responsive to vibration in machinery which produces an electrical signal related to the magnitude and frequency of the vibration; and a decoding circuit responsive to the transducer signal which produces a first fault signal to produce a second fault signal in which ground shift effects are nullified.

Superconducting techniques for gravity survey and inertial navigation

NASA Technical Reports Server (NTRS)

Chan, H. A.; Moody, M. V.; Paik, H. J.; Parke, J. W.

1985-01-01

A three-axis gravity gradiometer is developed, in which the magnetic fields produced by persistent currents are modulated by motions of superconducting proof masses. The common-acceleration-induced errors are compensated for by a six-axis superconducting accelerometer with a single magnetically levitated proof mass, linear acceleration resolution of 4 x 10 to the -12th m/(s exp 2 Hz exp 1/2), and angular acceleration resolution of 3 x 10 to the -11th rad/(s exp 2 Hz exp 1/2). The testing of a prototype gradiometer revealed that the environment-induced noise limits the noise floor to 7 x 10 to the -10th/(s exp 2 Hz exp 1/2).

Instrumentation Research and Support Services.

DTIC Science & Technology

1985-09-30

of a sensitive 3-axis 47 accelerometer within an ejectable instrumented sphere, has permitted a simple "Piggy- back" experimental program, in which a...45 3.3.3 Experimental PC M Ranging Test Flight.................... 46 3.3.4 C N2 Support Services .................................. 47 *3.4...led to the development of automated testing under control of a microcomputer, which per’iits elaborate sampling and analysis with hard-copy printout

Magnetic field `flyby' measurement using a smartphone's magnetometer and accelerometer simultaneously

NASA Astrophysics Data System (ADS)

Monteiro, Martín; Stari, Cecilia; Cabeza, Cecilia; Marti, Arturo C.

2017-12-01

The spatial dependence of magnetic fields in simple configurations is a common topic in introductory electromagnetism lessons, both in high school and in university courses. In typical experiments, magnetic fields and distances are obtained taking point-by-point values using a Hall sensor and a ruler, respectively. Here, we show how to take advantage of the smartphone capabilities to get simultaneous measures with the built-in accelerometer and magnetometer and to obtain the spatial dependence of magnetic fields. We consider a simple setup consisting of a smartphone mounted on a track whose direction coincides with the axis of a coil. While the smartphone is moving on the track, both the magnetic field and the distance from the center of the coil (integrated numerically from the acceleration values) are simultaneously obtained. This methodology can easily be extended to more complicated setups.

Attitude determination of planetary exploration rovers using solar panels characteristics and accelerometer

NASA Astrophysics Data System (ADS)

Ishida, Takayuki; Takahashi, Masaki

2014-12-01

In this study, we propose a new attitude determination system, which we call Irradiance-based Attitude Determination (IRAD). IRAD employs the characteristics and geometry of solar panels. First, the sun vector is estimated using data from solar panels including current, voltage, temperature, and the normal vectors of each solar panel. Because these values are obtained using internal sensors, it is easy for rovers to provide redundancy for IRAD. The normal vectors are used to apply to various shapes of rovers. Second, using the gravity vector obtained from an accelerometer, the attitude of a rover is estimated using a three-axis attitude determination method. The effectiveness of IRAD is verified through numerical simulations and experiments that show IRAD can estimate all the attitude angles (roll, pitch, and yaw) within a few degrees of accuracy, which is adequate for planetary explorations.

Vibration Analysis of the Space Shuttle External Tank Cable Tray Flight Data With and Without PAL Ramp

NASA Technical Reports Server (NTRS)

Walker, Bruce E.; Panda, Jayanta; Sutliff, Daniel L.

2008-01-01

External Tank Cable Tray vibration data for three successive Space Shuttle flights were analyzed to assess response to buffet and the effect of removal of the Protuberance Air Loads (PAL) ramp. Waveform integration, spectral analysis, cross-correlation analysis and wavelet analysis were employed to estimate vibration modes and temporal development of vibration motion from a sparse array of accelerometers and an on-board system that acquired 16 channels of data for approximately the first 2 min of each flight. The flight data indicated that PAL ramp removal had minimal effect on the fluctuating loads on the cable tray. The measured vibration frequencies and modes agreed well with predicted structural response.

Vibration Analysis of the Space Shuttle External Tank Cable Tray Flight Data with and without PAL Ramp

NASA Technical Reports Server (NTRS)

Walker, B. E.; Panda, B. E.; Sutliff, D. L.

2008-01-01

External Tank Cable Tray vibration data for three successive Space Shuttle flights were analyzed to assess response to buffet and the effect of removal of the Protuberance Air Loads (PAL) ramp. Waveform integration, spectral analysis, cross-correlation analysis and wavelet analysis were employed to estimate vibration modes and temporal development of vibration motion from a sparse array of accelerometers and an on-board system that acquired 16 channels of data for approximately the first two minutes of each flight. The flight data indicated that PAL ramp removal had minimal effect on the fluctuating loads on the cable tray. The measured vibration frequencies and modes agreed well with predicted structural response.

Superconducting six-axis accelerometer

NASA Technical Reports Server (NTRS)

Paik, H. J.

1990-01-01

A new superconducting accelerometer, capable of measuring both linear and angular accelerations, is under development at the University of Maryland. A single superconducting proof mass is magnetically levitated against gravity or any other proof force. Its relative positions and orientations with respect to the platform are monitored by six superconducting inductance bridges sharing a single amplifier, called the Superconducting Quantum Interference Device (SQUID). The six degrees of freedom, the three linear acceleration components and the three angular acceleration components, of the platform are measured simultaneously. In order to improve the linearity and the dynamic range of the instrument, the demodulated outputs of the SQUID are fed back to appropriate levitation coils so that the proof mass remains at the null position for all six inductance bridges. The expected intrinsic noise of the instrument is 4 x 10(exp -12)m s(exp -2) Hz(exp -1/2) for linear acceleration and 3 x 10(exp -11) rad s(exp -2) Hz(exp -1/2) for angular acceleration in 1-g environment. In 0-g, the linear acceleration sensitivity of the superconducting accelerometer could be improved by two orders of magnitude. The design and the operating principle of a laboratory prototype of the new instrument is discussed.

Associations of Accelerometer-Measured and Self-Reported Sedentary Time With Leukocyte Telomere Length in Older Women

PubMed Central

Shadyab, Aladdin H.; Macera, Caroline A.; Shaffer, Richard A.; Jain, Sonia; Gallo, Linda C.; LaMonte, Michael J.; Reiner, Alexander P.; Kooperberg, Charles; Carty, Cara L.; Di, Chongzhi; Manini, Todd M.; Hou, Lifang; LaCroix, Andrea Z.

2017-01-01

Abstract Few studies have assessed the association of sedentary time with leukocyte telomere length (LTL). In a cross-sectional study conducted in 2012–2013, we examined associations of accelerometer-measured and self-reported sedentary time with LTL in a sample of 1,481 older white and African-American women from the Women's Health Initiative and determined whether associations varied by level of moderate- to vigorous-intensity physical activity (MVPA). The association between sedentary time and LTL was evaluated using multiple linear regression models. Women were aged 79.2 (standard deviation, 6.7) years, on average. Self-reported sedentary time was not associated with LTL. In a model adjusting for demographic characteristics, lifestyle behaviors, and health-related factors, among women at or below the median level of accelerometer-measured MVPA, those in the highest quartile of accelerometer-measured sedentary time had significantly shorter LTL than those in the lowest quartile, with an average difference of 170 base pairs (95% confidence interval: 4, 340). Accelerometer-measured sedentary time was not associated with LTL in women above the median level of MVPA. Findings suggest that, on the basis of accelerometer measurements, higher sedentary time may be associated with shorter LTL among less physically active women. PMID:28100466

System identification of a tied arch bridge using reference-based wireless sensor networks

NASA Astrophysics Data System (ADS)

Hietbrink, Colby; Whelan, Matthew J.

2012-04-01

Vibration-based methods of structural health monitoring are generally founded on the principle that localized damage to a structure would exhibit changes within the global dynamic response. Upon this basis, accelerometers provide a unique health monitoring strategy in that a distributed network of sensors provides the technical feasibility to isolate the onset of damage without requiring that any sensor be located exactly on or in close proximity to the damage. While in theory this may be sufficient, practical experience has shown significant improvement in the application of damage diagnostic routines when mode shapes characterized by strongly localized behavior of specific elements are captured by the instrumentation array. In traditional applications, this presents a challenge since the cost and complexity of cable-based systems often effectively limits the number of instrumented locations thereby constraining the modal parameter extraction to only global modal responses. The advent of the low-cost RF chip transceiver with wireless networking capabilities has afforded a means by which a substantial number of output locations can be measured through referencebased testing using large-scale wireless sensor networks. In the current study, this approach was applied to the Prairie du Chien Bridge over the Mississippi River to extract operational mode shapes with high spatial reconstruction, including strongly localized modes. The tied arch bridge was instrumented at over 230 locations with single-axis accelerometers conditioned and acquired over a high-rate lossless wireless sensor network with simultaneous sampling capabilities. Acquisition of the dynamic response of the web plates of the arch rib was specifically targeted within the instrumentation array for diagnostic purposes. Reference-based operational modal analysis of the full structure through data-driven stochastic subspace identification is presented alongside finite element analysis results for confirmation of modal parameter plausibility. Particular emphasis is placed on the identification and reconstruction of modal response with large contribution from the arch rib web plates.

The effect of single engine fixed wing air transport on rate-responsive pacemakers.

PubMed

De Rotte, A A; Van Der Kemp, P

1999-09-01

Insufficient information exists about the safety of patients with accelerometer-based rate-responsive pacemakers in air transport by general aviation aircraft. The response in pacing rate of two types of accelerometer-based rate-responsive pacemakers with data logging capabilities was studied during test flights with single engine fixed wing aircraft. Results were compared with the rate-response of these pacemakers during transportation by car and were also interpreted in respect to physiological heart rate response of aircrew during flights in single engine fixed wing aircraft. In addition, a continuous accelerometer readout was recorded during a turbulent phase of flight. This recording was used for a pacemaker-simulator experiment with maximal sensitive motion-sensor settings. Only a minor increase in pacing rate due to aircraft motion could be demonstrated during all phases of flight at all altitudes with the pacemakers programmed in the normal mode. This increase was of the same magnitude as induced during transport by car and would be of negligible influence on the performance of the individual pacemaker patient equipped with such a pacemaker. Moreover, simultaneous Holter monitoring of the pilots during these flights showed a similar rate-response in natural heart rate compared with the increase in pacing rate induced by aircraft motion in accelerometer-based rate-responsive pacemakers. No sensor-mediated pacemaker tachycardia was seen during any of these recordings. However, a 15% increase in pacing rate was induced by severe air turbulence. Programming the maximal sensitivity of the motion sensor into the pacemaker could, on the other hand, induce a significant increase in pacing rate as was demonstrated by the simulation experiments. These results seem to rule out potentially dangerous or adverse effects from motional or vibrational influences during transport in single engine fixed wing aircraft on accelerometer-based rate-responsive pacemakers with normal activity sensor settings.

Using cross correlations of turbulent flow-induced ambient vibrations to estimate the structural impulse response. Application to structural health monitoring.

PubMed

Sabra, Karim G; Winkel, Eric S; Bourgoyne, Dwayne A; Elbing, Brian R; Ceccio, Steve L; Perlin, Marc; Dowling, David R

2007-04-01

It has been demonstrated theoretically and experimentally that an estimate of the impulse response (or Green's function) between two receivers can be obtained from the cross correlation of diffuse wave fields at these two receivers in various environments and frequency ranges: ultrasonics, civil engineering, underwater acoustics, and seismology. This result provides a means for structural monitoring using ambient structure-borne noise only, without the use of active sources. This paper presents experimental results obtained from flow-induced random vibration data recorded by pairs of accelerometers mounted within a flat plate or hydrofoil in the test section of the U.S. Navy's William B. Morgan Large Cavitation Channel. The experiments were conducted at high Reynolds number (Re > 50 million) with the primary excitation source being turbulent boundary layer pressure fluctuations on the upper and lower surfaces of the plate or foil. Identical deterministic time signatures emerge from the noise cross-correlation function computed via robust and simple processing of noise measured on different days by a pair of passive sensors. These time signatures are used to determine and/or monitor the structural response of the test models from a few hundred to a few thousand Hertz.

Comfort food is comforting to those most stressed: evidence of the chronic stress response network in high stress women.

PubMed

Tomiyama, A Janet; Dallman, Mary F; Epel, Elissa S

2011-11-01

Chronically stressed rodents who are allowed to eat calorie-dense "comfort" food develop greater mesenteric fat, which in turn dampens hypothalamic-pituitary-adrenocortical (HPA) axis activity. We tested whether similar relations exist in humans, at least cross-sectionally. Fifty-nine healthy premenopausal women were exposed to a standard laboratory stressor to examine HPA response to acute stress and underwent diurnal saliva sampling for basal cortisol and response to dexamethasone administration. Based on perceived stress scores, women were divided into extreme quartiles of low versus high stress categories. We found as hypothesized that the high stress group had significantly greater BMI and sagittal diameter, and reported greater emotional eating. In response to acute lab stressor, the high stress group showed a blunted cortisol response, lower diurnal cortisol levels, and greater suppression in response to dexamethasone. These cross-sectional findings support the animal model, which suggests that long-term adaptation to chronic stress in the face of dense calories result in greater visceral fat accumulation (via ingestion of calorie-dense food), which in turn modulates HPA axis response, resulting in lower cortisol levels. Copyright © 2011 Elsevier Ltd. All rights reserved.

Interactive Design and Development of Real Arm Movements for Application in Rehabilitation

NASA Astrophysics Data System (ADS)

Rosman, Rafidah; Hadi, Muhammad Zaidan Abdul; Abu Bakar, Nurulliyana

2018-03-01

An interactive real arm movements for application in rehabilitation is designed and developed. The aim is to encourage hand paralysis patients performing their physical therapy by introducing games application in replacing conventional hand therapy module and methods. In this project, the accelerometer is used for tracking the orientation of the arm. As the arm moves, the values from x, y and z axis from the accelerometer changes and are being read by the Analog Inputs of the Arduino Board. After being read by the Analog Inputs of the Arduino Board, the 3D model moves as well. Solidworks software was used to modeled the hand in which the data is then transferred to Matlab/Simulink using SimMechanicalLink from Mathworks. Lastly, the sensor glove was programmed to work as a controller of games application in hand rehabilitation thus makes it an enjoyable therapy process.

An Improved Fast Self-Calibration Method for Hybrid Inertial Navigation System under Stationary Condition

PubMed Central

Liu, Bingqi; Wei, Shihui; Su, Guohua; Wang, Jiping; Lu, Jiazhen

2018-01-01

The navigation accuracy of the inertial navigation system (INS) can be greatly improved when the inertial measurement unit (IMU) is effectively calibrated and compensated, such as gyro drifts and accelerometer biases. To reduce the requirement for turntable precision in the classical calibration method, a continuous dynamic self-calibration method based on a three-axis rotating frame for the hybrid inertial navigation system is presented. First, by selecting a suitable IMU frame, the error models of accelerometers and gyros are established. Then, by taking the navigation errors during rolling as the observations, the overall twenty-one error parameters of hybrid inertial navigation system (HINS) are identified based on the calculation of the intermediate parameter. The actual experiment verifies that the method can identify all error parameters of HINS and this method has equivalent accuracy to the classical calibration on a high-precision turntable. In addition, this method is rapid, simple and feasible. PMID:29695041

An Improved Fast Self-Calibration Method for Hybrid Inertial Navigation System under Stationary Condition.

PubMed

Liu, Bingqi; Wei, Shihui; Su, Guohua; Wang, Jiping; Lu, Jiazhen

2018-04-24

The navigation accuracy of the inertial navigation system (INS) can be greatly improved when the inertial measurement unit (IMU) is effectively calibrated and compensated, such as gyro drifts and accelerometer biases. To reduce the requirement for turntable precision in the classical calibration method, a continuous dynamic self-calibration method based on a three-axis rotating frame for the hybrid inertial navigation system is presented. First, by selecting a suitable IMU frame, the error models of accelerometers and gyros are established. Then, by taking the navigation errors during rolling as the observations, the overall twenty-one error parameters of hybrid inertial navigation system (HINS) are identified based on the calculation of the intermediate parameter. The actual experiment verifies that the method can identify all error parameters of HINS and this method has equivalent accuracy to the classical calibration on a high-precision turntable. In addition, this method is rapid, simple and feasible.

The microgravity environment of the Space Shuttle Columbia payload bay during STS-32

NASA Technical Reports Server (NTRS)

Dunbar, Bonnie J.; Giesecke, Robert L.; Thomas, Donald A.

1991-01-01

Over 11 hours of three-axis microgravity accelerometer data were successfully measured in the payload bay of Space Shuttle Columbia as part of the Microgravity Disturbances Experiment on STS-32. These data were measured using the High Resolution Accelerometer Package and the Aerodynamic Coefficient Identification Package which were mounted on the Orbiter keel in the aft payload bay. Data were recorded during specific mission events such as Orbiter quiescent periods, crew exercise on the treadmill, and numerous Orbiter engine burns. Orbiter background levels were measured in the 10(exp -5) G range, treadmill operations in the 10(exp -3) G range, and the Orbiter engine burns in the 10(exp -2) G range. Induced acceleration levels resulting from the SYNCOM satellite deploy were in the 10 (exp -2) G range, and operations during the pre-entry Flight Control System checkout were in the 10(exp -2) to 10(exp -1) G range.

Sonic Hedgehog switches on Wnt/planar cell polarity signaling in commissural axon growth cones by reducing levels of Shisa2

PubMed Central

Onishi, Keisuke

2017-01-01

Commissural axons switch on responsiveness to Wnt attraction during midline crossing and turn anteriorly only after exiting the floor plate. We report here that Sonic Hedgehog (Shh)-Smoothened signaling downregulates Shisa2, which inhibits the glycosylation and cell surface presentation of Frizzled3 in rodent commissural axon growth cones. Constitutive Shisa2 expression causes randomized turning of post-crossing commissural axons along the anterior–posterior (A–P) axis. Loss of Shisa2 led to precocious anterior turning of commissural axons before or during midline crossing. Post-crossing commissural axon turning is completely randomized along the A–P axis when Wntless, which is essential for Wnt secretion, is conditionally knocked out in the floor plate. This regulatory link between Shh and planar cell polarity (PCP) signaling may also occur in other developmental processes. PMID:28885142

Associations between physical behaviour patterns and levels of depressive symptoms, anxiety and well-being in middle-aged adults: a cross-sectional study using isotemporal substitution models

PubMed Central

Dillon, Christina B; McMahon, Elaine; O’Regan, Grace; Perry, Ivan J

2018-01-01

Objective To examine the compositional effects of physical behaviour on mental health. Design Cross-sectional study. Setting A population-representative random sample (Mitchelstown cohort) was recruited from a large primary care centre in Mitchelstown, County Cork, Ireland. Participants In total 3807 potential participants were selected from the practice list. Following exclusion of duplicates, deaths and ineligibles, 3043 were invited to participate and of these, 2047 (49.2% men) completed the questionnaire and physical examination components of the baseline assessment during the study period (April 2010 and May 2011). Accelerometers were introduced into the study in January 2011. Of the 745 participants seen between January and May of 2011, 475 (44.6% men) subjects (response rate 64%) agreed to participate and of these 397 (46.1% men) had valid accelerometer data. Primary and secondary outcome measures Participants wore the wrist GENEActiv accelerometer for 7 consecutive days. Data were summarised into 60 s epochs and activity categorised as sedentary behaviour, light or moderate-to-vigorous physical activity (MVPA). Levels of depressive and anxiety symptoms were assessed using the Centre for Epidemiologic Studies Depression scale and the Hospital Anxiety and Depression Scale. Well-being was assessed using the WHO-5 well-being scale. Results In adjusted isotemporal models, a 30 min increase in light activity per day was associated with a significant decrease in levels of anxiety symptoms (B=−0.34; 95% CI −0.64 to −0.04) and a significant increase in levels of well-being (B=0.58; 95% CI 0.05 to 1.11). No statistically significant associations were observed between any physical behaviour and depressive symptoms or when sedentary behaviour was substituted with MVPA (P>0.05). Conclusion Although based on a cross-sectional study, the findings suggest that substituting light activity for sedentary behaviour may have positive associations with symptoms of anxiety and reported well-being among middle-aged adults. PMID:29358436

Associations between physical behaviour patterns and levels of depressive symptoms, anxiety and well-being in middle-aged adults: a cross-sectional study using isotemporal substitution models.

PubMed

Dillon, Christina B; McMahon, Elaine; O'Regan, Grace; Perry, Ivan J

2018-01-21

To examine the compositional effects of physical behaviour on mental health. Cross-sectional study. A population-representative random sample (Mitchelstown cohort) was recruited from a large primary care centre in Mitchelstown, County Cork, Ireland. In total 3807 potential participants were selected from the practice list. Following exclusion of duplicates, deaths and ineligibles, 3043 were invited to participate and of these, 2047 (49.2% men) completed the questionnaire and physical examination components of the baseline assessment during the study period (April 2010 and May 2011). Accelerometers were introduced into the study in January 2011. Of the 745 participants seen between January and May of 2011, 475 (44.6% men) subjects (response rate 64%) agreed to participate and of these 397 (46.1% men) had valid accelerometer data. Participants wore the wrist GENEActiv accelerometer for 7 consecutive days. Data were summarised into 60 s epochs and activity categorised as sedentary behaviour, light or moderate-to-vigorous physical activity (MVPA). Levels of depressive and anxiety symptoms were assessed using the Centre for Epidemiologic Studies Depression scale and the Hospital Anxiety and Depression Scale. Well-being was assessed using the WHO-5 well-being scale. In adjusted isotemporal models, a 30 min increase in light activity per day was associated with a significant decrease in levels of anxiety symptoms (B=-0.34; 95% CI -0.64 to -0.04) and a significant increase in levels of well-being (B=0.58; 95% CI 0.05 to 1.11). No statistically significant associations were observed between any physical behaviour and depressive symptoms or when sedentary behaviour was substituted with MVPA (P>0.05). Although based on a cross-sectional study, the findings suggest that substituting light activity for sedentary behaviour may have positive associations with symptoms of anxiety and reported well-being among middle-aged adults. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Increasing physician activity with treadmill desks.

PubMed

Thompson, Warren G; Koepp, Gabriel A; Levine, James A

2014-01-01

Prolonged sitting has been shown to increase mortality and obesity. We sought to determine whether physicians would use a treadmill desk, increase their daily physical activity and lose weight. 20 overweight and obese physicians aged 25 to 70 with Body Mass Index > 25. Participants used a treadmill desk, a triaxial accelerometer, and received exercise counseling in a randomized, cross-over trial over 24 weeks. Group 1 received exercise counseling, accelerometer feedback, and a treadmill desk for 12 weeks and then accelerometer only for 12 weeks. Group 2 received an accelerometer without feedback for 12 weeks followed by exercise counseling, accelerometer feedback, and the treadmill desk for 12 weeks. Daily physical activity increased while using the treadmill desk compared to not using the desk by 197 kcal per day (p=0.003). The difference in weight during the two 12 week periods was 1.85 kg (p=0.03). Percent body fat was 1.9% lower while using the treadmill desk (p=0.02). There were no differences in metabolic or well-being measures. This study suggests that physicians will use a treadmill desk, that it does increase their activity, and that it may help with weight loss. Further studies are warranted.

A Novel Model-Based Driving Behavior Recognition System Using Motion Sensors.

PubMed

Wu, Minglin; Zhang, Sheng; Dong, Yuhan

2016-10-20

In this article, a novel driving behavior recognition system based on a specific physical model and motion sensory data is developed to promote traffic safety. Based on the theory of rigid body kinematics, we build a specific physical model to reveal the data change rule during the vehicle moving process. In this work, we adopt a nine-axis motion sensor including a three-axis accelerometer, a three-axis gyroscope and a three-axis magnetometer, and apply a Kalman filter for noise elimination and an adaptive time window for data extraction. Based on the feature extraction guided by the built physical model, various classifiers are accomplished to recognize different driving behaviors. Leveraging the system, normal driving behaviors (such as accelerating, braking, lane changing and turning with caution) and aggressive driving behaviors (such as accelerating, braking, lane changing and turning with a sudden) can be classified with a high accuracy of 93.25%. Compared with traditional driving behavior recognition methods using machine learning only, the proposed system possesses a solid theoretical basis, performs better and has good prospects.

A Novel Model-Based Driving Behavior Recognition System Using Motion Sensors

PubMed Central

Wu, Minglin; Zhang, Sheng; Dong, Yuhan

2016-01-01

In this article, a novel driving behavior recognition system based on a specific physical model and motion sensory data is developed to promote traffic safety. Based on the theory of rigid body kinematics, we build a specific physical model to reveal the data change rule during the vehicle moving process. In this work, we adopt a nine-axis motion sensor including a three-axis accelerometer, a three-axis gyroscope and a three-axis magnetometer, and apply a Kalman filter for noise elimination and an adaptive time window for data extraction. Based on the feature extraction guided by the built physical model, various classifiers are accomplished to recognize different driving behaviors. Leveraging the system, normal driving behaviors (such as accelerating, braking, lane changing and turning with caution) and aggressive driving behaviors (such as accelerating, braking, lane changing and turning with a sudden) can be classified with a high accuracy of 93.25%. Compared with traditional driving behavior recognition methods using machine learning only, the proposed system possesses a solid theoretical basis, performs better and has good prospects. PMID:27775625

Comparison of lung sound transducers using a bioacoustic transducer testing system.

PubMed

Kraman, Steve S; Wodicka, George R; Pressler, Gary A; Pasterkamp, Hans

2006-08-01

Sensors used for lung sound research are generally designed by the investigators or adapted from devices used in related fields. Their relative characteristics have never been defined. We employed an artificial chest wall with a viscoelastic surface and a white noise signal generator as a stable source of sound to compare the frequency response and pulse waveform reproduction of a selection of devices used for lung sound research. We used spectral estimation techniques to determine frequency response and cross-correlation of pulses to determine pulse shape fidelity. The sensors evaluated were the Siemens EMT 25 C accelerometer (Siemens); PPG 201 accelerometer (PPG); Sony ECM-T150 electret condenser microphone with air coupler (air coupler; with cylindrical air chambers of 5-, 10-, and 15-mm diameter and conical air chamber of 10-mm diameter); Littman classic stethoscope head (Littman) connected to an electret condenser microphone; and the Andries Tek (Andries) electronic stethoscope. We found that the size and shape of the air coupler chamber to have no important effect on the detected sound. The Siemens, air coupler, and Littman performed similarly with relatively flat frequency responses from 200 to 1,200 Hz. The PPG had the broadest frequency response, with useful sensitivity extending to 4,000 Hz. The Andries' frequency response was the poorest above 1,000 Hz. Accuracy in reproducing pulses roughly corresponded with the high-frequency sensitivity of the sensors. We conclude that there are important differences among commonly used lung sound sensors that have to be defined to allow the comparison of data from different laboratories.

Model-Scale Experiment of the Seakeeping Performance for R/V Melville, Model 5720

DTIC Science & Technology

2012-07-01

Angle 1 Y None Deg Sensor Bourns Rotary Potentiometer 6574S-1-103 NA 39596 KVH Sin 2 Y None volts Sensor KVH Fluxgate Compass C-100...NA Deg Sensor KVH Calc Heading NA N None DegM Calculated KVH Fluxgate Compass C-100 39449 Bow Tracker Sensor Bottom NA N None...3DM-3XI combined three axis of angular rate gyros, accelerometers, and magnetometers to provide various combinations of gyro stabilized Euler

MetalMapper: A Multi-Sensor TEM System for UXO Detection and Classification

DTIC Science & Technology

2011-02-01

accelerometer  to  measure  pitch  and  roll  angles  and  a  3-­axis   fluxgate   magnetometer  that  provides   reference  heading  to  magnetic...investigations  included  a   magnetometer  transect  survey   and   an   EMI   survey   over   a   larger   area   to   assist   in   selecting   a

Precision Orbit Derived Atmospheric Density: Development and Performance

NASA Astrophysics Data System (ADS)

McLaughlin, C.; Hiatt, A.; Lechtenberg, T.; Fattig, E.; Mehta, P.

2012-09-01

Precision orbit ephemerides (POE) are used to estimate atmospheric density along the orbits of CHAMP (Challenging Minisatellite Payload) and GRACE (Gravity Recovery and Climate Experiment). The densities are calibrated against accelerometer derived densities and considering ballistic coefficient estimation results. The 14-hour density solutions are stitched together using a linear weighted blending technique to obtain continuous solutions over the entire mission life of CHAMP and through 2011 for GRACE. POE derived densities outperform the High Accuracy Satellite Drag Model (HASDM), Jacchia 71 model, and NRLMSISE-2000 model densities when comparing cross correlation and RMS with accelerometer derived densities. Drag is the largest error source for estimating and predicting orbits for low Earth orbit satellites. This is one of the major areas that should be addressed to improve overall space surveillance capabilities; in particular, catalog maintenance. Generally, density is the largest error source in satellite drag calculations and current empirical density models such as Jacchia 71 and NRLMSISE-2000 have significant errors. Dynamic calibration of the atmosphere (DCA) has provided measurable improvements to the empirical density models and accelerometer derived densities of extremely high precision are available for a few satellites. However, DCA generally relies on observations of limited accuracy and accelerometer derived densities are extremely limited in terms of measurement coverage at any given time. The goal of this research is to provide an additional data source using satellites that have precision orbits available using Global Positioning System measurements and/or satellite laser ranging. These measurements strike a balance between the global coverage provided by DCA and the precise measurements of accelerometers. The temporal resolution of the POE derived density estimates is around 20-30 minutes, which is significantly worse than that of accelerometer derived density estimates. However, major variations in density are observed in the POE derived densities. These POE derived densities in combination with other data sources can be assimilated into physics based general circulation models of the thermosphere and ionosphere with the possibility of providing improved density forecasts for satellite drag analysis. POE derived density estimates were initially developed using CHAMP and GRACE data so comparisons could be made with accelerometer derived density estimates. This paper presents the results of the most extensive calibration of POE derived densities compared to accelerometer derived densities and provides the reasoning for selecting certain parameters in the estimation process. The factors taken into account for these selections are the cross correlation and RMS performance compared to the accelerometer derived densities and the output of the ballistic coefficient estimation that occurs simultaneously with the density estimation. This paper also presents the complete data set of CHAMP and GRACE results and shows that the POE derived densities match the accelerometer densities better than empirical models or DCA. This paves the way to expand the POE derived densities to include other satellites with quality GPS and/or satellite laser ranging observations.

Combined GPS and seismic monitoring of a 12-story structure in a region of induced seismicity in Oklahoma

NASA Astrophysics Data System (ADS)

Haase, J. S.; Soliman, M.; Kim, H.; Jaiswal, P.; Saunders, J. K.; Vernon, F.; Zhang, W.

2017-12-01

This work focuses on quantifying ground motions and their effects in Oklahoma near the location of the 2016 Mw 5.8 Pawnee earthquake, where seismicity has been increasing due to wastewater injection related to oil and natural gas production. Much of the building inventory in Oklahoma was constructed before the increase in seismicity and before the implementation of earthquake design and detailing provisions for reinforced concrete (RC) structures. We will use combined GPS/seismic monitoring techniques to measure ground motion in the field and the response of structures to this ground motion. Several Oklahoma State University buildings experienced damage due to the Pawnee earthquake. The USGS Shake Map product estimated peak ground acceleration (PGA) ranging from 0.12g to 0.15g at campus locations. We are deploying a high-rate GPS sensor and accelerometer on the roof and another accelerometer at ground level of a 12-story RC structure and at selected field sites in order to collect ambient noise data and nearby seismicity. The longer period recording characteristics of the GPS/seismic system are particularly well adapted to monitoring these large structures in the event of a significant earthquake. Gross characteristics of the structural system are described, which consists of RC columns and RC slabs in all stories. We conducted a preliminary structural analysis including modal analysis and response spectrum analysis based on a finite element (FE) simulation, which indicated that the period associated with the first X-axis bending, first torsional, and first Y-axis bending modes are 2.2 s, 2.1 s, and 1.8 s, respectively. Next, a preliminary analysis was conducted to estimate the range of expected deformation at the roof level for various earthquake excitations. The earthquake analysis shows a maximum roof displacement of 5 and 7 cm in the horizontal directions resulting from earthquake loads with PGA of 0.2g, well above the noise level of the combined GPS/seismic displacements. Another earthquake comparable to the Pawnee earthquake should be well recorded by the system. Recordings of ambient vibration data collected to date describing noise characteristics and measurement error levels will be presented. Any recordings of seismic motions will be discussed, should a significant event occur.

Modeling the Interaction between Fluid Pressure and Faulting in an Earthquake Swarm at Long Valley Caldera

NASA Astrophysics Data System (ADS)

Haase, J. S.; Soliman, M.; Kim, H.; Jaiswal, P.; Saunders, J. K.; Vernon, F.; Zhang, W.

2016-12-01

This work focuses on quantifying ground motions and their effects in Oklahoma near the location of the 2016 Mw 5.8 Pawnee earthquake, where seismicity has been increasing due to wastewater injection related to oil and natural gas production. Much of the building inventory in Oklahoma was constructed before the increase in seismicity and before the implementation of earthquake design and detailing provisions for reinforced concrete (RC) structures. We will use combined GPS/seismic monitoring techniques to measure ground motion in the field and the response of structures to this ground motion. Several Oklahoma State University buildings experienced damage due to the Pawnee earthquake. The USGS Shake Map product estimated peak ground acceleration (PGA) ranging from 0.12g to 0.15g at campus locations. We are deploying a high-rate GPS sensor and accelerometer on the roof and another accelerometer at ground level of a 12-story RC structure and at selected field sites in order to collect ambient noise data and nearby seismicity. The longer period recording characteristics of the GPS/seismic system are particularly well adapted to monitoring these large structures in the event of a significant earthquake. Gross characteristics of the structural system are described, which consists of RC columns and RC slabs in all stories. We conducted a preliminary structural analysis including modal analysis and response spectrum analysis based on a finite element (FE) simulation, which indicated that the period associated with the first X-axis bending, first torsional, and first Y-axis bending modes are 2.2 s, 2.1 s, and 1.8 s, respectively. Next, a preliminary analysis was conducted to estimate the range of expected deformation at the roof level for various earthquake excitations. The earthquake analysis shows a maximum roof displacement of 5 and 7 cm in the horizontal directions resulting from earthquake loads with PGA of 0.2g, well above the noise level of the combined GPS/seismic displacements. Another earthquake comparable to the Pawnee earthquake should be well recorded by the system. Recordings of ambient vibration data collected to date describing noise characteristics and measurement error levels will be presented. Any recordings of seismic motions will be discussed, should a significant event occur.

Experimental investigation and damage assessment in a post tensioned concrete beam

NASA Astrophysics Data System (ADS)

Limongelli, Maria; Siegert, Dominique; Merliot, Erick; Waeytens, Julien; Bourquin, Frederic; Vidal, Roland; Le Corvec, Veronique; Guegen, Ivan; Cottineau, Louis-Marie

2017-04-01

This paper presents the results of an experimental campaign carried out on a prestressed concrete beam in the realm of the project SIPRIS (Systèmes Intelligents pour la Prévention des Risques Structurels), aimed to develop intelligent systems for the prevention of structural risk related to the aging of large infrastructures. The specimen was tested in several configurations aimed to re-produce several different phases of the 'life' of the beam: in the original undamaged state, under an increasing loss of tension in the cables, during and after cracking induced by a point load, after a strengthening intervention, after new cracking of the 'repaired' beam. Damage was introduced in a controlled way by means of three-point static bending tests. The transverse point loads were ap-plied at several different sections along the beam axis. Before and after each static test, the dy-namical response of the beam was measured under sine-sweep and impact tests by an extensive set of accelerometers deployed along the beam axis. The availability of both static and dynamic tests allows to investigate and compare their effectiveness to detect damages in the tensioned beam and to reliably identify the evolution of damage. The paper discusses the tests program and some results relevant to the dynamic characterization of the beam in the different phases.

Directional abnormalities of vestibular and optokinetic responses in cerebellar disease

NASA Technical Reports Server (NTRS)

Walker, M. F.; Zee, D. S.; Shelhamer, M. J. (Principal Investigator)

1999-01-01

Directional abnormalities of vestibular and optokinetic responses in patients with cerebellar degeneration are reported. Three-axis magnetic search-coil recordings of the eye and head were performed in eight cerebellar patients. Among these patients, examples of directional cross-coupling were found during (1) high-frequency, high-acceleration head thrusts; (2) constant-velocity chair rotations with the head fixed; (3) constant-velocity optokinetic stimulation; and (4) following repetitive head shaking. Cross-coupling during horizontal head thrusts consisted of an inappropriate upward eye-velocity component. In some patients, sustained constant-velocity yaw-axis chair rotations produced a mixed horizontal-torsional nystagmus and/or an increase in the baseline vertical slow-phase velocity. Following horizontal head shaking, some patients showed an increase in the slow-phase velocity of their downbeat nystagmus. These various forms of cross-coupling did not necessarily occur to the same degree in a given patient; this suggests that different mechanisms may be responsible. It is suggested that cross-coupling during head thrusts may reflect a loss of calibration of brainstem connections involved in the direct vestibular pathways, perhaps due to dysfunction of the flocculus. Cross-coupling during constant-velocity rotations and following head shaking may result from a misorientation of the angular eye-velocity vector in the velocity-storage system. Finally, responses to horizontal optokinetic stimulation included an inappropriate torsional component in some patients. This suggests that the underlying organization of horizontal optokinetic tracking is in labyrinthine coordinates. The findings are also consistent with prior animal-lesion studies that have shown a role for the vestibulocerebellum in the control of the direction of the VOR.

Should Physical Activity Recommendations for South Asian Adults Be Ethnicity-Specific? Evidence from a Cross-Sectional Study of South Asian and White European Men and Women.

PubMed

Iliodromiti, Stamatina; Ghouri, Nazim; Celis-Morales, Carlos A; Sattar, Naveed; Lumsden, Mary Ann; Gill, Jason M R

2016-01-01

International public health guidelines recommend that adults undertake at least 150 min.week-1 of moderate-intensity physical activity. However, the underpinning evidence has largely been obtained from studies of populations of white European descent. It is unclear whether these recommendations are appropriate for other ethnic groups, particularly South Asians, who have greater cardio-metabolic risk than white Europeans. The objective of our study was to determine the level of moderate-intensity physical activity required in South Asians adults to confer a similar cardio-metabolic risk profile to that observed in Europeans of similar age and body mass index (BMI) undertaking the currently recommended levels of 150 min.week-1. 148 South Asians and 163 white Europeans aged 18 to 70 years were recruited. Physical activity was measured objectively via vertical axis accelerations from hip-worn accelerometers. Factor analysis was used to summarize the measured risk biomarkers into a single underlying latent "factor" describing overall cardio-metabolic risk. Sex did not modify the association between physical activity and the cardio-metabolic risk factor, so data for both sexes were combined and models adjusted for age, sex, BMI and accelerometer wear time. We estimated that South Asian adults needed to undertake 232 (95% Confidence interval: 200 to 268) min.week-1 in order to obtain the same cardio-metabolic risk factor score as a white European undertaking 150 minutes of moderate-equivalent physical activity per week. The present findings suggest that South Asian men and women need to undertake ~230 minutes of moderate intensity physical activity per week. This equates to South Asians undertaking an extra 10-15 minutes of moderate intensity physical activity per day on top of existing recommendations.

Method and apparatus for characterizing and enhancing the dynamic performance of machine tools

DOEpatents

Barkman, William E; Babelay, Jr., Edwin F

2013-12-17

Disclosed are various systems and methods for assessing and improving the capability of a machine tool. The disclosure applies to machine tools having at least one slide configured to move along a motion axis. Various patterns of dynamic excitation commands are employed to drive the one or more slides, typically involving repetitive short distance displacements. A quantification of a measurable merit of machine tool response to the one or more patterns of dynamic excitation commands is typically derived for the machine tool. Examples of measurable merits of machine tool performance include dynamic one axis positional accuracy of the machine tool, dynamic cross-axis stability of the machine tool, and dynamic multi-axis positional accuracy of the machine tool.

A calibration protocol for population-specific accelerometer cut-points in children.

PubMed

Mackintosh, Kelly A; Fairclough, Stuart J; Stratton, Gareth; Ridgers, Nicola D

2012-01-01

To test a field-based protocol using intermittent activities representative of children's physical activity behaviours, to generate behaviourally valid, population-specific accelerometer cut-points for sedentary behaviour, moderate, and vigorous physical activity. Twenty-eight children (46% boys) aged 10-11 years wore a hip-mounted uniaxial GT1M ActiGraph and engaged in 6 activities representative of children's play. A validated direct observation protocol was used as the criterion measure of physical activity. Receiver Operating Characteristics (ROC) curve analyses were conducted with four semi-structured activities to determine the accelerometer cut-points. To examine classification differences, cut-points were cross-validated with free-play and DVD viewing activities. Cut-points of ≤ 372, >2160 and >4806 counts • min(-1) representing sedentary, moderate and vigorous intensity thresholds, respectively, provided the optimal balance between the related needs for sensitivity (accurately detecting activity) and specificity (limiting misclassification of the activity). Cross-validation data demonstrated that these values yielded the best overall kappa scores (0.97; 0.71; 0.62), and a high classification agreement (98.6%; 89.0%; 87.2%), respectively. Specificity values of 96-97% showed that the developed cut-points accurately detected physical activity, and sensitivity values (89-99%) indicated that minutes of activity were seldom incorrectly classified as inactivity. The development of an inexpensive and replicable field-based protocol to generate behaviourally valid and population-specific accelerometer cut-points may improve the classification of physical activity levels in children, which could enhance subsequent intervention and observational studies.

Superconducting gravity gradiometer and a test of inverse square law

NASA Technical Reports Server (NTRS)

Moody, M. V.; Paik, Ho Jung

1989-01-01

The equivalence principle prohibits the distinction of gravity from acceleration by a local measurement. However, by making a differential measurement of acceleration over a baseline, platform accelerations can be cancelled and gravity gradients detected. In an in-line superconducting gravity gradiometer, this differencing is accomplished with two spring-mass accelerometers in which the proof masses are confined to motion in a single degree of freedom and are coupled together by superconducting circuits. Platform motions appear as common mode accelerations and are cancelled by adjusting the ratio of two persistent currents in the sensing circuit. The sensing circuit is connected to a commercial SQUID amplifier to sense changes in the persistent currents generated by differential accelerations, i.e., gravity gradients. A three-axis gravity gradiometer is formed by mounting six accelerometers on the faces of a precision cube, with the accelerometers on opposite faces of the cube forming one of three in-line gradiometers. A dedicated satellite mission for mapping the earth's gravity field is an important one. Additional scientific goals are a test of the inverse square law to a part in 10(exp 10) at 100 km, and a test of the Lense-Thirring effect by detecting the relativistic gravity magnetic terms in the gravity gradient tensor for the earth.

Classifying prosthetic use via accelerometry in persons with transtibial amputations.

PubMed

Redfield, Morgan T; Cagle, John C; Hafner, Brian J; Sanders, Joan E

2013-01-01

Knowledge of how persons with amputation use their prostheses and how this use changes over time may facilitate effective rehabilitation practices and enhance understanding of prosthesis functionality. Perpetual monitoring and classification of prosthesis use may also increase the health and quality of life for prosthetic users. Existing monitoring and classification systems are often limited in that they require the subject to manipulate the sensor (e.g., attach, remove, or reset a sensor), record data over relatively short time periods, and/or classify a limited number of activities and body postures of interest. In this study, a commercially available three-axis accelerometer (ActiLife ActiGraph GT3X+) was used to characterize the activities and body postures of individuals with transtibial amputation. Accelerometers were mounted on prosthetic pylons of 10 persons with transtibial amputation as they performed a preset routine of actions. Accelerometer data was postprocessed using a binary decision tree to identify when the prosthesis was being worn and to classify periods of use as movement (i.e., leg motion such as walking or stair climbing), standing (i.e., standing upright with limited leg motion), or sitting (i.e., seated with limited leg motion). Classifications were compared to visual observation by study researchers. The classifier achieved a mean +/- standard deviation accuracy of 96.6% +/- 3.0%.

Classifying Prosthetic Use via Accelerometry in Persons with Trans-Tibial Amputations

PubMed Central

Redfield, Morgan T.; Cagle, John C.; Hafner, Brian J.; Sanders, Joan E.

2014-01-01

Knowledge of how persons with amputation use their prostheses and how this use changes over time may facilitate effective rehabilitation practices and enhance understanding of prosthesis functionality. Perpetual monitoring and classification of prosthesis use may also increase the health and quality of life for prosthetic users. Existing monitoring and classification systems are often limited in that they require the subject to manipulate the sensor (e.g., attach, remove, or reset a sensor), record data over relatively short time periods, and/or classify a limited number of activities and body postures of interest. In this study, a commercially-available three-axis accelerometer (ActiLife ActiGraph GT3X+) was used to characterize the activities and body postures of individuals with trans-tibial amputation. Accelerometers were mounted on prosthetic pylons of ten persons with trans-tibial amputation as they performed a preset routine of actions. Accelerometer data was post-processed using a Binary Decision Tree to identify when the prosthesis was being worn and to classify periods of use as movement (i.e., leg motion like walking or stair climbing), standing (i.e., standing upright with limited leg motion), or sitting (i.e., seated with limited leg motion). Classifications were compared to visual observation by study researchers. The classifier achieved a mean accuracy of 96.6% (SD=3.0%). PMID:24458961

On-Orbit Gradiometry with the scientific instrument of the French Space Mission MICROSCOPE

NASA Astrophysics Data System (ADS)

Foulon, B.; Baghi, Q.; Panet, I.; Rodrigues, M.; Metris, G.; Touboul, P.

2017-12-01

The MICROSCOPE mission is fully dedicated to the in-orbit test of the universality of free fall, the so-called Weak Equivalence Principle (WEP). Based on a CNES Myriade microsatellite launched on the 25th of April 2016, MICROSCOPE is a CNES-ESA-ONERA-CNRS-OCA mission, the scientific objective of which is to test of the Equivalence Principle with an extraordinary accuracy at the level of 10-15. The measurement will be obtained from the T-SAGE (Twin Space Accelerometer for Gravitational Experimentation) instrument constituted by two ultrasensitive differential accelerometers. One differential electrostatic accelerometer, labeled SU-EP, contains, at its center, two proof masses made of Titanium and Platinum and is used for the test. The twin accelerometer, labeled SU-REF, contains two Platinum proof masses and is used as a reference instrument. Separated by a 17 cm-length arm, they are embarked in a very stable and soft environment on board a satellite equipped with a drag-free control system and orbiting on a sun synchronous circular orbit at 710 km above the Earth. In addition to the WEP test, this configuration can be interesting for various applications, and one of the proposed ideas is to use MICROSCOPE data for the measurement of Earth's gravitational gradient. Considering the gradiometer formed by the inner Platinum proof-masses of the two differential accelerometers and the arm along the Y-axis of the instrument which is perpendicular to the orbital plane, possibly 3 components of the gradient can be measured: Txy, Tyy and Tzy. Preliminary studies suggest that the errors can be lower than 10mE. Taking advantage of its higher altitude with respect to GOCE, the low frequency signature of Earth's potential seen by MICROSCOPE could provide an additional observable in gradiometry to discriminate between different models describing the large scales of the mass distribution in the Earth's deep mantle. The poster will shortly present the MICROSCOPE mission configuration. It will detail the actual in-flight performances of the accelerometers and of the attitude and position control, in order to evaluate the gradiometer error budget according to the satellite pointing mode configuration.

Characterization of a 21-Story Reinforced Building in the Valley of Mexico Using MEMS Accelerometers.

NASA Astrophysics Data System (ADS)

Husker, A. L.; Dominguez, L. A.; Becerril, A.; Espejo, L.; Cochran, E. S.

2014-12-01

Low cost MEMS accelerometers are becoming increasingly higher resolution making them useful in strong motion studies. Here we present a building response analysis in the lakebed zone of the Valley of Mexico. The Valley of Mexico represents one of the highest seismic risk locations in the world and incorporates Mexico City and part of Mexico State. More than 20 million people live there and it is the political and economic center of Mexico. In addition the valley has very high site effects with amplifications 100 - 500 times that of sites outside of the basin (Singh et al., 1988; Singh et al., 1995). We instrumented a 21-story building with MEMS accelerometers as part of the Quake Catcher Network or Red Atrapa Sismos as it is called in Mexico. The building known as the Centro Cultural de Tlateloco is located in an important historical and political area as well as a zone with some of the highest amplifications in the Valley of Mexico that had some of the worst destruction after the 1985 M8.1 Michoacan earthquake. During the earthquake most of the buildings that failed were between 7 - 18 stories tall. The peak accelerations near Tlateloco were at periods of 2 seconds. Since the earthquake the building has been retrofitted with N-S crossing supports to help withstand another earthquake. We present the measurements of frequencies and amplifications between floors for the length of the building.

Analysis of accelerations measured during full-scale tank car impact tests

DOT National Transportation Integrated Search

2007-04-01

Tank car impact responses were investigated using accelerometers mounted at various locations on a tank car. Several tests were run with both a full and an empty tank car, and varying the tank car impact speed. The data from the accelerometers went t...

Angle Measurement System (AMS) for Establishing Model Pitch and Roll Zero, and Performing Single Axis Angle Comparisons

NASA Technical Reports Server (NTRS)

Crawford, Bradley L.

2007-01-01

The angle measurement system (AMS) developed at NASA Langley Research Center (LaRC) is a system for many uses. It was originally developed to check taper fits in the wind tunnel model support system. The system was further developed to measure simultaneous pitch and roll angles using 3 orthogonally mounted accelerometers (3-axis). This 3-axis arrangement is used as a transfer standard from the calibration standard to the wind tunnel facility. It is generally used to establish model pitch and roll zero and performs the in-situ calibration on model attitude devices. The AMS originally used a laptop computer running DOS based software but has recently been upgraded to operate in a windows environment. Other improvements have also been made to the software to enhance its accuracy and add features. This paper will discuss the accuracy and calibration methodologies used in this system and some of the features that have contributed to its popularity.

Design, Fabrication and Characterization of a MEMS-Based Three-Dimensional Electric Field Sensor with Low Cross-Axis Coupling Interference

PubMed Central

Ling, Biyun; Peng, Chunrong; Ren, Ren; Chu, Zhaozhi; Zhang, Zhouwei; Lei, Hucheng; Xia, Shanhong

2018-01-01

One of the major concerns in the development of three-dimensional (3D) electric field sensors (EFSs) is their susceptibility to cross-axis coupling interference. The output signal for each sensing axis of a 3D EFS is often coupled by electric field components from the two other orthogonal sensing axes. In this paper, a one-dimensional (1D) electric field sensor chip (EFSC) with low cross-axis coupling interference is presented. It is designed to be symmetrical, forming a pair of in-plane symmetrically-located sensing structures. Using a difference circuit, the 1D EFSC is capable of sensing parallel electric fields along symmetrical structures and eliminating cross-axis coupling interference, which is contrast to previously reported 1D EFSCs designed for perpendicular electric field component measurement. Thus, a 3D EFS with low cross-axis coupling interference can be realized using three proposed 1D EFSCs. This 3D EFS has the advantages of low cross-axis coupling interference, small size, and high integration. The testing and calibration systems of the proposed 3D EFS were developed. Experimental results show that in the range of 0–120 kV/m, cross-axis sensitivities are within 5.48%, and the total measurement errors of this 3D EFS are within 6.16%. PMID:29543744

MovAid- a novel device for advanced rehabilitation monitoring.

PubMed

Gupta, Prashant; Verma, Piyush; Gupta, Rakesh; Verma, Bhawna

2015-08-01

The present article introduces a new device "MovAid" which helps to measure and monitor rehabilitation. It has two main components- "MovAid device" and the "MovAid Smart Phone Application". The device connects wirelessly to the MovAid smart phone application via Bluetooth. It has electronic sensors to measure three important parameters of the patient- Angle of Joint Bent, Lift from the ground and Orientation of the limb. A mono-axis flex sensor to measure the degree of joint bent and a 3-axis accelerometer and gyroscope to measure the orientation of the limb and lift from the ground have been used. MovAid system bridges the gap between caretakers and patients, empowering both in ways never thought of before, by providing detailed and accurate data on every move.

Power-Factor and Torque Calculation under Consideration of Cross Saturation of the Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

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

Lee, Seong T; Burress, Timothy A; Tolbert, Leon M

2009-01-01

This paper introduces a new method for calculating the power factor and output torque by considering the cross saturation between direct-axis (d-axis) and quadrature-axis (q-axis) of an interior permanent magnet synchronous motor (IPMSM). The conventional two-axis IPMSM model is modified to include the cross saturation effect by adding the cross-coupled inductance terms. This paper also contains the new method of calculating the cross-coupled inductance values as well as self-inductance values in d- and q-axes. The analyzed motor is a high-speed brushless field excitation machine that offers high torque per ampere per core length at low speed and weakened flux atmore » high speed, which was developed for the traction motor of a hybrid electric vehicle. The conventional two-axis IPMSM model was modified to include the cross-saturation effect by adding the cross-coupled inductance terms Ldq and Lqd. By the advantage of the excited structure of the experimental IPMSM, the analyzing works were performed under two conditions, the highest and lowest excited conditions. Therefore, it is possible to investigate the cross-saturation effect when a machine has higher magnetic flux from its rotor. The following is a summary of conclusions that may be drawn from this work: (1) Considering cross saturation of an IPMSM offers more accurate expected values of motor parameters in output torque calculation, especially when negative d-axis current is high; (2) A less saturated synchronous machine could be more affected by the cross-coupled saturation effect; (3) Both cross-coupled inductances, L{sub qd} and L{sub dq}, are mainly governed by d-axis current rather than q-axis current; (4) The modified torque equation, can be used for the dynamic model of an IPMSM for developing a better control model or control strategy; and (5) It is possible that the brushless field excitation structure has a common magnetic flux path on both d- and q-axis, and as a result, the reluctance torque of the machine could be reduced.« less

Accelerometry in persons with multiple sclerosis: measurement of physical activity or walking mobility?

PubMed

Weikert, Madeline; Motl, Robert W; Suh, Yoojin; McAuley, Edward; Wynn, Daniel

2010-03-15

Motion sensors such as accelerometers have been recognized as an ideal measure of physical activity in persons with MS. This study examined the hypothesis that accelerometer movement counts represent a measure of both physical activity and walking mobility in individuals with MS. The sample included 269 individuals with a definite diagnosis of relapsing-remitting MS who completed the Godin Leisure-Time Exercise Questionnaire (GLTEQ), International Physical Activity Questionnaire (IPAQ), Multiple Sclerosis Walking Scale-12 (MSWS-12), Patient Determined Disease Steps (PDDS), and then wore an ActiGraph accelerometer for 7days. The data were analyzed using bivariate correlation and confirmatory factor analysis. The results indicated that (a) the GLTEQ and IPAQ scores were strongly correlated and loaded significantly on a physical activity latent variable, (b) the MSWS-12 and PDDS scores strongly correlated and loaded significantly on a walking mobility latent variable, and (c) the accelerometer movement counts correlated similarly with the scores from the four self-report questionnaires and cross-loaded on both physical activity and walking mobility latent variables. Our data suggest that accelerometers are measuring both physical activity and walking mobility in persons with MS, whereas self-report instruments are measuring either physical activity or walking mobility in this population.

Measuring moderate-intensity walking in older adults using the ActiGraph accelerometer.

PubMed

Barnett, Anthony; van den Hoek, Daniel; Barnett, David; Cerin, Ester

2016-12-08

Accelerometry is the method of choice for objectively assessing physical activity in older adults. Many studies have used an accelerometer count cut point corresponding to 3 metabolic equivalents (METs) derived in young adults during treadmill walking and running with a resting metabolic rate (RMR) assumed at 3.5 mL · kg -1  · min -1 (corresponding to 1 MET). RMR is lower in older adults; therefore, their 3 MET level occurs at a lower absolute energy expenditure making the cut point derived from young adults inappropriate for this population. The few studies determining older adult specific moderate-to-vigorous intensity physical activity (MVPA) cut points had methodological limitations, such as not measuring RMR and using treadmill walking. This study determined a MVPA hip-worn accelerometer cut point for older adults using measured RMR and overground walking. Following determination of RMR, 45 older adults (mean age 70.2 ± 7 years, range 60-87.6 years) undertook an outdoor, overground walking protocol with accelerometer count and energy expenditure determined at five walking speeds. Mean RMR was 2.8 ± 0.6 mL · kg -1  · min -1 . The MVPA cut points (95% CI) determined using linear mixed models were: vertical axis 1013 (734, 1292) counts · min -1 ; vector magnitude 1924 (1657, 2192) counts · min -1 ; and walking speed 2.5 (2.2, 2.8) km · hr -1 . High levels of inter-individual variability in cut points were found. These MVPA accelerometer and speed cut points for walking, the most popular physical activity in older adults, were lower than those for younger adults. Using cut points determined in younger adults for older adult population studies is likely to underestimate time spent engaged in MVPA. In addition, prescription of walking speed based on the adult cut point is likely to result in older adults working at a higher intensity than intended.

Identifying physical activity type in manual wheelchair users with spinal cord injury by means of accelerometers.

PubMed

García-Massó, X; Serra-Añó, P; Gonzalez, L M; Ye-Lin, Y; Prats-Boluda, G; Garcia-Casado, J

2015-10-01

This was a cross-sectional study. The main objective of this study was to develop and test classification algorithms based on machine learning using accelerometers to identify the activity type performed by manual wheelchair users with spinal cord injury (SCI). The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia. A total of 20 volunteers were asked to perform 10 physical activities, lying down, body transfers, moving items, mopping, working on a computer, watching TV, arm-ergometer exercises, passive propulsion, slow propulsion and fast propulsion, while fitted with four accelerometers placed on both wrists, chest and waist. The activities were grouped into five categories: sedentary, locomotion, housework, body transfers and moderate physical activity. Different machine learning algorithms were used to develop individual and group activity classifiers from the acceleration data for different combinations of number and position of the accelerometers. We found that although the accuracy of the classifiers for individual activities was moderate (55-72%), with higher values for a greater number of accelerometers, grouped activities were correctly classified in a high percentage of cases (83.2-93.6%). With only two accelerometers and the quadratic discriminant analysis algorithm we achieved a reasonably accurate group activity recognition system (>90%). Such a system with the minimum of intervention would be a valuable tool for studying physical activity in individuals with SCI.

Stress-induced sensitization: the hypothalamic-pituitary-adrenal axis and beyond.

PubMed

Belda, Xavier; Fuentes, Silvia; Daviu, Nuria; Nadal, Roser; Armario, Antonio

2015-01-01

Exposure to certain acute and chronic stressors results in an immediate behavioral and physiological response to the situation followed by a period of days when cross-sensitization to further novel stressors is observed. Cross-sensitization affects to different behavioral and physiological systems, more particularly to the hypothalamus-pituitary-adrenal (HPA) axis. It appears that the nature of the initial (triggering) stressor plays a major role, HPA cross-sensitization being more widely observed with systemic or high-intensity emotional stressors. Less important appears to be the nature of the novel (challenging) stressor, although HPA cross-sensitization is better observed with short duration (5-15 min) challenging stressors. In some studies with acute immune stressors, HPA sensitization appears to develop over time (incubation), but most results indicate a strong initial sensitization that progressively declines over the days. Sensitization can affect other physiological system (i.e. plasma catecholamines, brain monoamines), but it is not a general phenomenon. When studied concurrently, behavioral sensitization appears to persist longer than that of the HPA axis, a finding of interest regarding long-term consequences of traumatic stress. In many cases, behavioral and physiological consequences of prior stress can only be observed following imposition of a new stressor, suggesting long-term latent effects of the initial exposure.

Analysis of posture and eye movement responses to Coriolis stimulation under 1 G and microgravity conditions.

PubMed

Sekine, Motoki; Takahashi, Masahiro; Iida, Masahiro

2009-12-20

To detect the effect of microgravity on vestibular responses, we conducted Coriolis stimulation experiments at 1 G and μ G. Five men with vision occluded were asked to tilt their head forward while rotating at 100 degrees/sec. Postural changes were recorded by a 3D linear accelerometer, and the distance of upper body movement was derived from recordings of linear acceleration. Eye movements were recorded by a CCD camera. For a second period after commencing head tilt, the upper body moved 10 cm in the direction of inertia input at 1 G, but it moved to the opposite direction at μ G, i.e., 4 cm in the direction of inertia force. Nystagmus peak slow-phase velocity immediately after head tilt and its attenuation process did not differ between 1 G and μ G. The strength of movement sensation and the severity of motion sickness were far weaker at μ G than at 1 G. It was concluded that inertia input is valid to induce postural and sensation responses only when the external reference is given Z axis by gravity. Vestibular ocular response may be maintained at μ G because the head reference is valid even after the external reference becomes arbitrary.

The symphonic structure of childhood stress reactivity: Patterns of sympathetic, parasympathetic, and adrenocortical responses to psychological challenge

PubMed Central

Quas, Jodi A.; Yim, Ilona S.; Oberlander, Tim F.; Nordstokke, David; Essex, Marilyn J.; Armstrong, Jeffrey M.; Bush, Nicole; Obradović, Jelena; Boyce, W. Thomas

2015-01-01

Despite widespread recognition that the physiological systems underlying stress reactivity are well coordinated at a neurobiological level, surprisingly little empirical attention has been given to delineating precisely how the systems actually interact with one another when confronted with stress. We examined cross-system response proclivities in anticipation of and following standardized laboratory challenges in 664 4- to 14-year-olds from four independent studies. In each study, measures of stress reactivity within both the locus coeruleus-norepinephrine system (i.e., the sympathetic and parasympathetic branches of the autonomic nervous system) and the corticotrophin releasing hormone system (i.e., the hypothalamic-pituitary-adrenal axis) were collected. Latent profile analyses revealed six distinctive patterns that recurred across the samples: moderate reactivity (average cross-system activation; 52%-80% of children across samples), parasympathetic-specific reactivity (2%-36%), anticipatory arousal (4%-9%), multisystem reactivity (7%—14%), hypothalamic-pituitary-adrenal axis specific reactivity (6%-7%), and underarousal (0%-2%). Groups meaningfully differed in socioeconomic status, family adversity, and age. Results highlight the sample-level reliability of children’s neuroendocrine responses to stress and suggest important cross-system regularities that are linked to development and prior experiences and may have implications for subsequent physical and mental morbidity. PMID:24909883

Critical features of acute stress-induced cross-sensitization identified through the hypothalamic-pituitary-adrenal axis output.

PubMed

Belda, Xavier; Nadal, Roser; Armario, Antonio

2016-08-11

Stress-induced sensitization represents a process whereby prior exposure to severe stressors leaves animals or humans in a hyper-responsive state to further stressors. Indeed, this phenomenon is assumed to be the basis of certain stress-associated pathologies, including post-traumatic stress disorder and psychosis. One biological system particularly prone to sensitization is the hypothalamic-pituitary-adrenal (HPA) axis, the prototypic stress system. It is well established that under certain conditions, prior exposure of animals to acute and chronic (triggering) stressors enhances HPA responses to novel (heterotypic) stressors on subsequent days (e.g. raised plasma ACTH and corticosterone levels). However, such changes remain somewhat controversial and thus, the present study aimed to identify the critical characteristics of the triggering and challenging stressors that affect acute stress-induced HPA cross-sensitization in adult rats. We found that HPA cross-sensitization is markedly influenced by the intensity of the triggering stressor, whereas the length of exposure mainly affects its persistence. Importantly, HPA sensitization is more evident with mild than strong challenging stressors, and it may remain unnoticed if exposure to the challenging stressor is prolonged beyond 15 min. We speculate that heterotypic HPA sensitization might have developed to optimize biologically adaptive responses to further brief stressors.

Critical features of acute stress-induced cross-sensitization identified through the hypothalamic-pituitary-adrenal axis output

PubMed Central

Belda, Xavier; Nadal, Roser; Armario, Antonio

2016-01-01

Stress-induced sensitization represents a process whereby prior exposure to severe stressors leaves animals or humans in a hyper-responsive state to further stressors. Indeed, this phenomenon is assumed to be the basis of certain stress-associated pathologies, including post-traumatic stress disorder and psychosis. One biological system particularly prone to sensitization is the hypothalamic-pituitary-adrenal (HPA) axis, the prototypic stress system. It is well established that under certain conditions, prior exposure of animals to acute and chronic (triggering) stressors enhances HPA responses to novel (heterotypic) stressors on subsequent days (e.g. raised plasma ACTH and corticosterone levels). However, such changes remain somewhat controversial and thus, the present study aimed to identify the critical characteristics of the triggering and challenging stressors that affect acute stress-induced HPA cross-sensitization in adult rats. We found that HPA cross-sensitization is markedly influenced by the intensity of the triggering stressor, whereas the length of exposure mainly affects its persistence. Importantly, HPA sensitization is more evident with mild than strong challenging stressors, and it may remain unnoticed if exposure to the challenging stressor is prolonged beyond 15 min. We speculate that heterotypic HPA sensitization might have developed to optimize biologically adaptive responses to further brief stressors. PMID:27511270

Criterion validity of the Physical Activity Questionnaire for Schoolchildren (PAQ-S) in assessing physical activity levels: the Healthy Growth Study.

PubMed

Manios, Y; Androutsos, O; Moschonis, G; Birbilis, M; Maragkopoulou, K; Giannopoulou, A; Argyri, E; Kourlaba, G

2013-10-01

The aim of this paper was to evaluate the criterion validity of the Physical Activity Questionnaire for Schoolchildren (PAQ-S). The current study is a subcohort of the Healthy Growth Study, a large-scale cross-sectional study. 202 schoolchildren aged 9-13 years from Greece completed the PAQ-S and wore an accelerometer for 4 consecutive days. Time spent moderate (MPA), moderate to vigorous (MVPA) and vigorous (VPA) physical activity was calculated based on PAQ-S and accelerometer data. The average time spent on MPA and MVPA as derived from PAQ-S and from accelerometers were significantly moderately correlated (r=0.462, P<0.001 and r=0.483, P<0.001, respectively). No significant correlation was detected between PAQ-S and accelerometer-measured time spent performing VPA (rho=0.150, P=0.057). Intraclass Correlation Coefficient (ICC) indicated a moderate agreement between PAQ-S and accelerometer in estimating MPA (ICC=0.592, P<0.001) and MVPA (ICC=0.581, P<0.001). Bland-Altman analysis revealed a small mean difference (the "bias"), between the two methods, in estimating MPA, although this difference was found to be significantly higher than zero ("bias"=27.4% of the accelerometer-measured mean score, P=0.006). On the other hand, Bland-Altman analysis revealed a large mean difference in estimating MVPA and VPA ("bias"=84.2% and 357% of the accelerometer-measured mean score for MVPA and VPA, respectively and P<0.001). The high correlation coefficient between the average and difference values between all physical activity scores derived from accelerometers and PAQ-S, indicate a systematic overestimation of physical activity time with increasing physical activity for PAQ-S. The validity of PAQ-S for the estimation of MPA and MVPA was found to be slightly similar self-reported measures for schoolchildren. Therefore, this questionnaire could be used as a tool for physical activity assessment in large population studies.

Sedentary Time and Physical Activity Surveillance Through Accelerometer Pooling in Four European Countries.

PubMed

Loyen, Anne; Clarke-Cornwell, Alexandra M; Anderssen, Sigmund A; Hagströmer, Maria; Sardinha, Luís B; Sundquist, Kristina; Ekelund, Ulf; Steene-Johannessen, Jostein; Baptista, Fátima; Hansen, Bjørge H; Wijndaele, Katrien; Brage, Søren; Lakerveld, Jeroen; Brug, Johannes; van der Ploeg, Hidde P

2017-07-01

The objective of this study was to pool, harmonise and re-analyse national accelerometer data from adults in four European countries in order to describe population levels of sedentary time and physical inactivity. Five cross-sectional studies were included from England, Portugal, Norway and Sweden. ActiGraph accelerometer count data were centrally processed using the same algorithms. Multivariable logistic regression analyses were conducted to study the associations of sedentary time and physical inactivity with sex, age, weight status and educational level, in both the pooled sample and the separate study samples. Data from 9509 participants were used. On average, participants were sedentary for 530 min/day, and accumulated 36 min/day of moderate to vigorous intensity physical activity. Twenty-three percent accumulated more than 10 h of sedentary time/day, and 72% did not meet the physical activity recommendations. Nine percent of all participants were classified as high sedentary and low active. Participants from Norway showed the highest levels of sedentary time, while participants from England were the least physically active. Age and weight status were positively associated with sedentary time and not meeting the physical activity recommendations. Men and higher-educated people were more likely to be highly sedentary, while women and lower-educated people were more likely to be inactive. We found high levels of sedentary time and physical inactivity in four European countries. Older people and obese people were most likely to display these behaviours and thus deserve special attention in interventions and policy planning. In order to monitor these behaviours, accelerometer-based cross-European surveillance is recommended.

Power-Factor Calculation under Consideration of Cross Saturation of the Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

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

Lee, Seong T; Burress, Timothy A; Hsu, John S

2009-01-01

This paper introduces a new method for calculating the power factor with consideration of the cross saturation between the direct-axis (d-axis) and the quadrature-axis (q-axis) of an interior permanent magnet synchronous motor (IPMSM). The conventional two-axis IPMSM model is modified to include the cross-saturation effect by adding the cross-coupled inductance terms. This paper also contains the new method of calculating the cross-coupled inductance values as well as self-inductance values in d- and q-axes. The analyzed motor is a high-speed brushless field excitation machine that offers high torque per ampere per core length at low speed and weakened flux at highmore » speed, which was developed for the traction motor of a hybrid electric vehicle.« less

Gimbaled multispectral imaging system and method

DOEpatents

Brown, Kevin H.; Crollett, Seferino; Henson, Tammy D.; Napier, Matthew; Stromberg, Peter G.

2016-01-26

A gimbaled multispectral imaging system and method is described herein. In an general embodiment, the gimbaled multispectral imaging system has a cross support that defines a first gimbal axis and a second gimbal axis, wherein the cross support is rotatable about the first gimbal axis. The gimbaled multispectral imaging system comprises a telescope that fixed to an upper end of the cross support, such that rotation of the cross support about the first gimbal axis causes the tilt of the telescope to alter. The gimbaled multispectral imaging system includes optics that facilitate on-gimbal detection of visible light and off-gimbal detection of infrared light.

Citizen sensors for SHM: use of accelerometer data from smartphones.

PubMed

Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

2015-01-29

Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications.

A Review of Microgravity Levels on Ten OARE Shuttle Missions

NASA Technical Reports Server (NTRS)

McPherson, Kevin M.

1998-01-01

The Orbital Acceleration Research Experiment (OARE) is an accelerometer package with nano-g sensitivity and on-orbit bias calibration capabilities. The OARE consists of a three axis miniature electrostatic accelerometer (MESA), a full in-flight bias and scale factor calibration station, and an on-board microprocessor for experiment control and data storage. Originally designed to measure and record the aerodynamic acceleration environment of the NASA Space Shuttles during re-entry, the OARE has been used on ten shuttle missions to measure the quasi-steady acceleration environment (<1 Hz) of the Orbiter while in low-Earth orbit. The effects on the quasi-steady acceleration environment from Orbiter systems, Orbiter attitude, Orbiter altitude, and crew activity are well understood as a result of these ten shuttle missions. This knowledge of the quasi-steady acceleration realm has direct application to understanding the quasi-steady acceleration environment expected for the International Space Station (ISS). This paper will summarize the more salient aspects of this quasi-steady acceleration knowledge base.

Failure detection and isolation investigation for strapdown skew redundant tetrad laser gyro inertial sensor arrays

NASA Technical Reports Server (NTRS)

Eberlein, A. J.; Lahm, T. G.

1976-01-01

The degree to which flight-critical failures in a strapdown laser gyro tetrad sensor assembly can be isolated in short-haul aircraft after a failure occurrence has been detected by the skewed sensor failure-detection voting logic is investigated along with the degree to which a failure in the tetrad computer can be detected and isolated at the computer level, assuming a dual-redundant computer configuration. The tetrad system was mechanized with two two-axis inertial navigation channels (INCs), each containing two gyro/accelerometer axes, computer, control circuitry, and input/output circuitry. Gyro/accelerometer data is crossfed between the two INCs to enable each computer to independently perform the navigation task. Computer calculations are synchronized between the computers so that calculated quantities are identical and may be compared. Fail-safe performance (identification of the first failure) is accomplished with a probability approaching 100 percent of the time, while fail-operational performance (identification and isolation of the first failure) is achieved 93 to 96 percent of the time.

Phase Space Dissimilarity Measures for Structural Health Monitoring

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

Bubacz, Jacob A; Chmielewski, Hana T; Pape, Alexander E

A novel method for structural health monitoring (SHM), known as the Phase Space Dissimilarity Measures (PSDM) approach, is proposed and developed. The patented PSDM approach has already been developed and demonstrated for a variety of equipment and biomedical applications. Here, we investigate SHM of bridges via analysis of time serial accelerometer measurements. This work has four aspects. The first is algorithm scalability, which was found to scale linearly from one processing core to four cores. Second, the same data are analyzed to determine how the use of the PSDM approach affects sensor placement. We found that a relatively low-density placementmore » sufficiently captures the dynamics of the structure. Third, the same data are analyzed by unique combinations of accelerometer axes (vertical, longitudinal, and lateral with respect to the bridge) to determine how the choice of axes affects the analysis. The vertical axis is found to provide satisfactory SHM data. Fourth, statistical methods were investigated to validate the PSDM approach for this application, yielding statistically significant results.« less

Satellite borne gravity gradiometer study

NASA Technical Reports Server (NTRS)

Metzger, E.; Jircitano, A.; Affleck, C.

1976-01-01

Gravity gradiometry is recognized to be a very difficult instrumentation problem because extremely small differential acceleration levels have to be measured, 0.1 EU corresponds to an acceleration of 10 to the minus 11th power g at two points 1 meter apart. A feasibility model of a gravity gradiometer is being developed for airborne applications using four modified versions of the proven Model VII accelerometers mounted on a slowly rotating fixture. Gravity gradients are being measured to 1.07 EU in a vertical rotation axis orientation. Equally significant are the outstanding operational characteristics such as fast reaction time, low temperature coefficients and high degree of bias stability over long periods of time. The rotating accelerometer gravity gradiometer approach and its present status is discussed and it is the foundation for the orbital gravity gradiometer analyzed. The performance levels achieved in a 1 g environment of the earth and under relatively high seismic disturbances, lend the orbital gravity gradiometer a high confidence level of success.

Electrostatically Levitated Ring-Shaped Rotational-Gyro/Accelerometer

NASA Astrophysics Data System (ADS)

Murakoshi, Takao; Endo, Yasuo; Fukatsu, Keisuke; Nakamura, Sigeru; Esashi, Masayoshi

2003-04-01

This paper reports an electrostatically levitated inertia measurement system which is based on the principle of a rotational gyro. The device has several advantages: the levitation of the rotor in a vacuum eliminates mechanical friction resulting in high sensitivity; the position control for the levitation allows accelerations to be sensed in the tri-axis; and the fabrication of the device by a micromachining technique has the cost advantages afforded by miniaturization. Latest measurements yield a noise floor of the gyro and that of the accelerometer as low as 0.15 deg/h1/2 and 30 μG/Hz1/2, respectively. This performance is achieved by a new sensor design. To further improve of the previous device, a ring-shaped structure is designed and fabricated by deep reactive ion etching using inductively coupled plasma. The rotor levitation is performed with capacitive detection and electrostatic actuation. Multiaxis closed-loop control is realized by differential capacitance sensing and frequency multiplying. The rotation of the micro gyro is based on the principle of a planar variable capacitance motor.

Experimental investigations of the large deflection capabilities of a compliant parallel mechanism actuated by shape memory alloy wires

NASA Astrophysics Data System (ADS)

Sreekumar, M.; Nagarajan, T.; Singaperumal, M.

2008-12-01

This experimental study investigates the coupled effect of the force developed by the shape memory alloy (SMA) actuators and the force required for the large deflection of an elastica member in a compliant parallel mechanism. The compliant mechanism developed in house consists of a moving platform mounted on a superelastic pillar and three SMA wire actuators to manipulate the platform. A three-axis MEMS accelerometer has been mounted on the moving platform to measure its tilt angle. Three miniature force sensors have been designed and fabricated out of cantilever beams, each mounted with a pair of strain gauges, to measure the force developed by the respective actuators. The force sensors are highly sensitive and cost effective compared to commercially available miniature force sensors. Calibration of the force sensors has been accomplished with known weights, and for the three-axis MEMS accelerometer a rotary base has been considered which is usually used in optical applications. The calibration curves obtained, with R-squared values between 0.9997 and 1.0, show that both the tilt and force sensors considered are most appropriate for the respective applications. The mechanism fixed with the sensors and the drivers for the SMA actuators is integrated with a National Instrument's data acquisition system. The experimental results have been compared with the analytical results and it was found that the relative error is less than 2%. This is a preliminary study in the development of a mechanism for eye prosthesis and similar applications.

Visualizing Flutter Mechanism as Traveling Wave Through Animation of Simulation Results for the Semi-Span Super-Sonic Transport Wind-Tunnel Model

NASA Technical Reports Server (NTRS)

Christhilf, David M.

2014-01-01

It has long been recognized that frequency and phasing of structural modes in the presence of airflow play a fundamental role in the occurrence of flutter. Animation of simulation results for the long, slender Semi-Span Super-Sonic Transport (S4T) wind-tunnel model demonstrates that, for the case of mass-ballasted nacelles, the flutter mode can be described as a traveling wave propagating downstream. Such a characterization provides certain insights, such as (1) describing the means by which energy is transferred from the airflow to the structure, (2) identifying airspeed as an upper limit for speed of wave propagation, (3) providing an interpretation for a companion mode that coalesces in frequency with the flutter mode but becomes very well damped, (4) providing an explanation for bursts of response to uniform turbulence, and (5) providing an explanation for loss of low frequency (lead) phase margin with increases in dynamic pressure (at constant Mach number) for feedback systems that use sensors located upstream from active control surfaces. Results from simulation animation, simplified modeling, and wind-tunnel testing are presented for comparison. The simulation animation was generated using double time-integration in Simulink of vertical accelerometer signals distributed over wing and fuselage, along with time histories for actuated control surfaces. Crossing points for a zero-elevation reference plane were tracked along a network of lines connecting the accelerometer locations. Accelerometer signals were used in preference to modal displacement state variables in anticipation that the technique could be used to animate motion of the actual wind-tunnel model using data acquired during testing. Double integration of wind-tunnel accelerometer signals introduced severe drift even with removal of both position and rate biases such that the technique does not currently work. Using wind-tunnel data to drive a Kalman filter based upon fitting coefficients to analytical mode shapes might provide a better means to animate the wind tunnel data.

Atomic References for Measuring Small Accelerations

NASA Technical Reports Server (NTRS)

Maleki, Lute; Yu, Nan

2009-01-01

Accelerometer systems that would combine the best features of both conventional (e.g., mechanical) accelerometers and atom interferometer accelerometers (AIAs) have been proposed. These systems are intended mainly for use in scientific research aboard spacecraft but may also be useful on Earth in special military, geological, and civil-engineering applications. Conventional accelerometers can be sensitive, can have high dynamic range, and can have high frequency response, but they lack accuracy and long-term stability. AIAs have low frequency response, but they offer high sensitivity, and high accuracy for measuring small accelerations. In a system according to the proposal, a conventional accelerometer would be used to perform short-term measurements of higher-frequency components of acceleration, while an AIA would be used to provide consistent calibration of, and correction of errors in, the measurements of the conventional accelerometer in the lower-frequency range over the long term. A brief description of an AIA is prerequisite to a meaningful description of a system according to the proposal. An AIA includes a retroreflector next to one end of a cell that contains a cold cloud of atoms in an ultrahigh vacuum. The atoms in the cloud are in free fall. The retroreflector is mounted on the object, the acceleration of which is to be measured. Raman laser beams are directed through the cell from the end opposite the retroreflector, then pass back through the cell after striking the retroreflector. The Raman laser beams together with the cold atoms measure the relative acceleration, through the readout of the AIA, between the cold atoms and the retroreflector.

Mixing Characteristics of Elliptical Jet Control with Crosswire

NASA Astrophysics Data System (ADS)

Manigandan, S.; Vijayaraja, K.

2018-02-01

The aerodynamic mixing efficiency of elliptical sonic jet flow with the effect of crosswire is studied computationally and experimentally at different range of nozzle pressure ratio with different orientation along the minor axis of the exit. The cross wire of different orientation is found to reduce the strength of the shock wave formation. Due to the presence of crosswire the pitot pressure oscillation is reduced fast, which weakens the shock cell structure. When the cross wire is placed at center position we see high mixing along the major axis. Similarly, when the cross wire is placed at ¼ and ¾ position we see high mixing promotion along minor axis. It also proves, as the position of the cross wire decreased along minor axis there will be increase in the mixing ratio. In addition to that we also found that, jet spread is high in major axis compared to minor axis due to bifurcation of jet along upstream

Application of Roll-Isolated Inertial Measurement Units to the Instrumentation of Spinning Vehicles

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

BEADER,MARK E.

Roll-isolated inertial measurement units are developed at Sandia for use in the instrumentation, guidance, and control of rapidly spinning vehicles. Roll-isolation is accomplished by supporting the inertial instrument cluster (gyros and accelerometers) on a single gimbal, the axis of which is parallel to the vehicle's spin axis. A rotary motor on the gimbal is driven by a servo loop to null the roll gyro output, thus inertially stabilizing the gimbal and instrument cluster while the vehicle spins around it. Roll-isolation prevents saturation of the roll gyro by the high vehicle spin rate, and vastly reduces measurement errors arising from gyromore » scale factor and alignment uncertainties. Nine versions of Sandia-developed roll-isolated inertial measurement units have been flown on a total of 27 flight tests since 1972.« less

Are context-specific measures of parental-reported physical activity and sedentary behaviour associated with accelerometer data in 2-9-year-old European children?

PubMed

Verbestel, Vera; De Henauw, Stefaan; Bammann, Karin; Barba, Gianvincenzo; Hadjigeorgiou, Charalambos; Eiben, Gabriele; Konstabel, Kenn; Kovács, Eva; Pitsiladis, Yannis; Reisch, Lucia; Santaliestra-Pasías, Alba M; Maes, Lea; De Bourdeaudhuij, Ilse

2015-04-01

The aim of the present study was to investigate if context-specific measures of parental-reported physical activity and sedentary behaviour are associated with objectively measured physical activity and sedentary time in children. Cross-sectional study. Seven European countries taking part in the IDEFICS (Identification and Prevention of Dietary- and Lifestyle-induced Health Effects in Children and Infants) study. Data were analysed from 2-9-year-old children (n 5982) who provided both parental-reported and accelerometer-derived physical activity/sedentary behaviour measures. Parents reported their children's daily screen-time, weekly sports participation and daily outdoor playtime by means of the Outdoor Playtime Checklist (OPC) and Outdoor Playtime Recall Questions (OPRQ). Sports participation, OPC- and OPRQ-derived outdoor play were positively associated with accelerometer-derived physical activity. Television viewing and computer use were positively associated with accelerometer-derived sedentary time. All parental-reported measures that were significantly associated with accelerometer outcomes explained only a minor part of the variance in accelerometer-derived physical activity or sedentary time. Parental-reported measures of physical activity and sedentary behaviour are not useful as a proxy for 2-9-year-old children's physical activity and sedentary time. Findings do not preclude the use of context-specific measures but imply that conclusions should be limited to the context-specific behaviours that are actually measured. Depending on the aim of the study, future research should carefully consider the choice of measurements, including the use of subjective or objective measures of the behaviour of interest or a combination of both.

Effects of variables upon pyrotechnically induced shock response spectra

NASA Technical Reports Server (NTRS)

Smith, J. L.

1986-01-01

Throughout the aerospace industry, large variations of 50 percent (6 dB) or more are continually noted for linear shaped charge (LSC) generated shock response spectra (SRS) from flight data (from the exact same location on different flights) and from plate tests (side by side measurements on the same test). A research program was developed to investigate causes of these large SRS variations. A series of ball drop calibration tests to verify calibration of accelerometers and a series of plate tests to investigate charge and assembly variables were performed. The resulting data were analyzed to determine if and to what degree manufacturing and assembly variables, distance from the shock source, data acquisition instrumentation, and shock energy propagation affect the SRS. LSC variables consisted of coreload, standoff, and apex angle. The assembly variable was the torque on the LSC holder. Other variables were distance from source of accelerometers, accelerometer mounting methods, and joint effects. Results indicated that LSC variables did not affect SRS as long as the plate was severed. Accelerometers mounted on mounting blocks showed significantly lower levels above 5000 Hz. Lap joints did not affect SRS levels. The test plate was mounted in an almost free-free state; therefore, distance from the source did not affect the SRS. Several varieties and brands of accelerometers were used, and all but one demonstrated very large variations in SRS.

Identification and compensation of the temperature influences in a miniature three-axial accelerometer based on the least squares method

NASA Astrophysics Data System (ADS)

Grigorie, Teodor Lucian; Corcau, Ileana Jenica; Tudosie, Alexandru Nicolae

2017-06-01

The paper presents a way to obtain an intelligent miniaturized three-axial accelerometric sensor, based on the on-line estimation and compensation of the sensor errors generated by the environmental temperature variation. Taking into account that this error's value is a strongly nonlinear complex function of the values of environmental temperature and of the acceleration exciting the sensor, its correction may not be done off-line and it requires the presence of an additional temperature sensor. The proposed identification methodology for the error model is based on the least square method which process off-line the numerical values obtained from the accelerometer experimental testing for different values of acceleration applied to its axes of sensitivity and for different values of operating temperature. A final analysis of the error level after the compensation highlights the best variant for the matrix in the error model. In the sections of the paper are shown the results of the experimental testing of the accelerometer on all the three sensitivity axes, the identification of the error models on each axis by using the least square method, and the validation of the obtained models with experimental values. For all of the three detection channels was obtained a reduction by almost two orders of magnitude of the acceleration absolute maximum error due to environmental temperature variation.

In vitro attenuation of impact shock in equine digits.

PubMed

Lanovaz, J L; Clayton, H M; Watson, L G

1998-09-01

This study was designed to test the impact characteristics of the equine digit in vitro with the objective of providing a better understanding of the role of the digital structures in the attenuation of impact shock. Uni-axial accelerometers were mounted on cadaver digits on the distolateral hoof wall, the proximolateral hoof wall, the dorsal surface of the second phalanx, and the mid-lateral first phalanx. The hoof-mounted accelerometers were aligned with the hoof tubules while the bone-mounted accelerometers were oriented along the longitudinal axis of the bone. Each digit was mounted in a test apparatus designed to simulate impact of the hoof with the ground during locomotion. The digits were subjected to 3 impact trials against a barrier at each of 3 vertical impact velocities that simulated a forward trotting velocity in the range of 2.67 to 4.46 m/s. The impact deceleration tended to increase with impact velocity. Attenuation of the impact shock by the digital tissues resulted in a reduction in impact decleration in the more proximal measuring locations. The interphalangeal joints appeared to play a larger role in amplitude attenuation than the hoof wall or the soft tissue structures within the hoof wall. The signal frequency data showed that the soft tissues within the hoof acted as a 'lowpass' filter, attenuating the higher deceleration frequencies. The hoof wall and the interphalangeal joints showed little frequency attenuation.

Vibration analysis of the sulky accessory for a commercial walk-behind lawn mower to determine operator comfort and health.

PubMed

Thrailkill, Elizabeth A; Lowndes, Bethany R; Hallbeck, M Susan

2013-01-01

A sulky is a single-wheeled platform attachment on which the operator of a commercial walk-behind lawn mower rides while standing. The effects of sulky vibration on operator comfort and health have not been investigated. In this study, tri-axial accelerometers measured sulky vibration during mower use by two commercial mowers on varied terrain and 12 volunteer mowers over a controlled course. The accelerometer data were processed according to methods established in ISO 2631. Results indicate the mean frequency-weighted root mean square (RMS) acceleration sums fall into the 'very uncomfortable' range for vibration of standing persons (1.9 ± 0.48 m s⁻²). Additionally, vibration dose values indicated that the mean vibration dosages exceeded the daily exposure limit values established in Directive 2002 /44/EC (z-axis A(8) value of 1.30 ± 34 m s⁻²; VDV(exp) value of 28.1 ± 6.25 m s⁻¹·⁷⁵). This information suggests that modifications including vibration damping should be added to the sulky to reduce rider discomfort and health risks. This study investigated the effects of vibration during use of a commercial lawn mowing sulky. Findings from accelerometer data suggest that the vibration experienced by sulky operators is significant enough to cause discomfort and health risks which may lead to personnel turnover or long-term effects for the operator.

Validity and reliability of the G-Cog device for kinematic measurements.

PubMed

Chiementin, X; Crequy, S; Bertucci, W

2013-11-01

The aim of this study was to test the validity and the reliability of the G-Cog which is a new BMX powermeter allowing for the measurements of the acceleration on X-Y-Z axis (250 Hz) at the BMX rear wheel. These measurements allow computing lateral, angular, linear acceleration, angular, linear velocity and the distance. Mechanical measurements at submaximal intensities in standardized laboratory conditions and during maximal exercises in the field conditions were performed to analyse the reliability of the G-Cog accelerometers. The performances were evaluated in comparison with an industrial accelerometer and with 2 powermeters, the SRM and PowerTap. Our results in laboratory conditions show that the G-Cog measurements have low value of variation coefficient (CV=2.35%). These results suggest that the G-cog accelerometers measurements are reproducible. The ratio limits of agreement of the rear hub angular velocity differences between the SRM and the G-Cog were 1.010 × ÷ 1.024 (95%CI=0.986-1.034) and between PowerTap and G-Cog were 0.993 × ÷ 1.019 (95%CI=0.974-1.012). In conclusion, our results suggest that the G-Cog angular velocity measurements are valid and reliable compared with SRM and PowerTap and could be used to analyse the kinematics during BMX actual conditions. © Georg Thieme Verlag KG Stuttgart · New York.

The development and testing of a novel cross axis wind turbine

NASA Astrophysics Data System (ADS)

Chong, W. T.; Muzammil, W. K.; Gwani, M.; Wong, K. H.; Fazlizan, A.; Wang, C. T.; Poh, S. C.

2016-06-01

A novel cross axis wind turbine (CAWT) which comprises of a cross axis blades arrangement was presented and investigated experimentally. The CAWT is a new type of wind turbine that extracts wind energy from airflow coming from the horizontal and vertical directions. The wind turbine consists of three vertical blades and six horizontal blades arranged in a cross axis orientation. Hubs in the middle of the CAWT link the horizontal and vertical blades through connectors to form the CAWT. The study used a 45° deflector to guide the oncoming airflow upward (vertical wind direction). The results from the study showed that the CAWT produced significant improvements in power output and rotational speed performance compared to a conventional straight-bladed vertical axis wind turbine (VAWT).

Characterization of the Hypothalamic-Pituitary-Adrenal-Axis in Familial Longevity under Resting Conditions.

PubMed

Jansen, Steffy W; Roelfsema, Ferdinand; Akintola, Abimbola A; Oei, Nicole Y; Cobbaert, Christa M; Ballieux, Bart E; van der Grond, Jeroen; Westendorp, Rudi G; Pijl, Hanno; van Heemst, Diana

2015-01-01

The hypothalamic-pituitary-adrenal (HPA)-axis is the most important neuro-endocrine stress response system of our body which is of critical importance for survival. Disturbances in HPA-axis activity have been associated with adverse metabolic and cognitive changes. Humans enriched for longevity have less metabolic and cognitive disturbances and therefore diminished activity of the HPA axis may be a potential candidate mechanism underlying healthy familial longevity. Here, we compared 24-h plasma ACTH and serum cortisol concentration profiles and different aspects of the regulation of the HPA-axis in offspring from long-lived siblings, who are enriched for familial longevity and age-matched controls. Case-control study within the Leiden Longevity study cohort consisting of 20 middle-aged offspring of nonagenarian siblings (offspring) together with 18 partners (controls). During 24 h, venous blood was sampled every 10 minutes for determination of circulatory ACTH and cortisol concentrations. Deconvolution analysis, cross approximate entropy analysis and ACTH-cortisol-dose response modeling were used to assess, respectively, ACTH and cortisol secretion parameters, feedforward and feedback synchrony and adrenal gland ACTH responsivity. Mean (95% Confidence Interval) basal ACTH secretion was higher in male offspring compared to male controls (645 (324-1286) ngl/L/24 h versus 240 (120-477) ng/L/24 h, P = 0.05). Other ACTH and cortisol secretion parameters did not differ between offspring and controls. In addition, no significant differences in feedforward and feedback synchrony and adrenal gland ACTH responsivity were observed between groups. These results suggest that familial longevity is not associated with major differences in HPA-axis activity under resting conditions, although modest, sex-specific differences may exist between groups that might be clinically relevant.

Urinary Estrogen Metabolites, Active and Sedentary Behaviors, and Breast Cancer Risk

Cancer.gov

A cross-sectional study of approximately 600 postmenopausal controls in the Breast Cancer Case-Control Study in Poland to assess urinary estrogen metabolites in relation to accelerometer-based measures of active and sedentary behaviors

Improved Satellite-Monitored Radio Tags for Large Whales: Dependable ARGOS Location-Only Tags and a GPS-Linked ARGOS Tag Reveal 3-Dimensional Body-Orientation and Surface Movements

DTIC Science & Technology

2013-09-30

funded tags have been used on a variety of projects: western gray whales in Russia, Pacific Coast Feeding Group (PCFG) gray whales, and sperm whales...provide an accurate, long duration, depiction of underwater dive behavior and especially to examine sperm whale foraging behavior. The data will be...an acoustic dosimeter. Eleven GPS/TDR tags containing three axis accelerometers were deployed on sperm whales in the Gulf of Mexico in July/Aug

Relative performance of several inexpensive accelerometers

USGS Publications Warehouse

Evans, John R.; Rogers, John A.

1995-01-01

We examined the performance of several low-cost accelerometers for highly cost-driven applications in recording earthquake strong motion. We anticipate applications for such sensors in providing the lifeline and emergency-response communities with an immediate, comprehensive picture of the extent and characteristics of likely damage. We also foresee their use as 'filler' instruments sited between research-grade instruments to provide spatially detailed and near-field records of large earthquakes (on the order of 1000 stations at 600-m intervals in San Fernando Valley, population 1.2 million, for example). The latter applications would provide greatly improved attenuation relationships for building codes and design, the first examples of mainshock information (that is, potentially nonlinear regime) for microzonation, and a suite of records for structural engineers. We also foresee possible applications in monitoring structural inter-story drift during earthquakes, possibly leading to local and remote alarm functions as well as design criteria. This effort appears to be the first of its type at the USGS. It is spurred by rapid advances in sensor technology and the recognition of potential non-classical applications. In this report, we estimate sensor noise spectra, relative transfer functions and cross-axis sensitivity of six inexpensive sensors. We tested three micromachined ('silicon-chip') sensors in addition to classical force-balance and piezoelectric examples. This sample of devices is meant to be representative, not comprehensive. Sensor noise spectra were estimated by recording system output with the sensor mounted on a pneumatically supported 545-kg optical-bench isolation table. This isolation table appears to limit ground motion to below our system noise level. These noise estimates include noise introduced by signal-conditioning circuitry, the analog-to-digital converter (ADC), and noise induced in connecting wiring by ambient electromagnetic fields in our suburban laboratory. These latter sources are believed to dominate sensor noise in the quieter sensors we tested. Transfer functions were obtained relative to a research grade force-balance accelerometer (a Kinemetrics TM FBA-11) by shaking the sensors simultaneously on the same shake table and taking spectral ratios with the output of the FBA- 11. This reference sensor is said to have 120 db dynamic range (-+20 bits, though we only digitized it at 16 bits resolution and drove it with relatively small signals). We did not test temperature sensitivity, which is thought to be a significant issue at least for the silicon devices. Though these tests were not designed to be definitive (our anticipated applications do not demand research-grade precision), our tests do appear to have been successful in estimating relative transfer functions from about 0.3 to 50 Hz. Most sensors performed adequately in this range, with essentially fiat relative transfer functions. Noise tests appear to measure sensor noise well for the noisier (generally less expensive) instruments from about 0.1 to 50 Hz.

Comparison of FRF measurements and mode shapes determined using optically image based, laser, and accelerometer measurements

NASA Astrophysics Data System (ADS)

Warren, Christopher; Niezrecki, Christopher; Avitabile, Peter; Pingle, Pawan

2011-08-01

Today, accelerometers and laser Doppler vibrometers are widely accepted as valid measurement tools for structural dynamic measurements. However, limitations of these transducers prevent the accurate measurement of some phenomena. For example, accelerometers typically measure motion at a limited number of discrete points and can mass load a structure. Scanning laser vibrometers have a very wide frequency range and can measure many points without mass-loading, but are sensitive to large displacements and can have lengthy acquisition times due to sequential measurements. Image-based stereo-photogrammetry techniques provide additional measurement capabilities that compliment the current array of measurement systems by providing an alternative that favors high-displacement and low-frequency vibrations typically difficult to measure with accelerometers and laser vibrometers. Within this paper, digital image correlation, three-dimensional (3D) point-tracking, 3D laser vibrometry, and accelerometer measurements are all used to measure the dynamics of a structure to compare each of the techniques. Each approach has its benefits and drawbacks, so comparative measurements are made using these approaches to show some of the strengths and weaknesses of each technique. Additionally, the displacements determined using 3D point-tracking are used to calculate frequency response functions, from which mode shapes are extracted. The image-based frequency response functions (FRFs) are compared to those obtained by collocated accelerometers. Extracted mode shapes are then compared to those of a previously validated finite element model (FEM) of the test structure and are shown to have excellent agreement between the FEM and the conventional measurement approaches when compared using the Modal Assurance Criterion (MAC) and Pseudo-Orthogonality Check (POC).

Accelerometer Method and Apparatus for Integral Display and Control Functions

NASA Technical Reports Server (NTRS)

Bozeman, Richard J., Jr. (Inventor)

1996-01-01

Method and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. Art accelerometer package having integral display and control functions is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine conditions over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase in amplitude over a selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated.

Accelerometer Method and Apparatus for Integral Display and Control Functions

NASA Technical Reports Server (NTRS)

Bozeman, Richard J., Jr. (Inventor)

1998-01-01

Method and apparatus for detecting mechanical vibrations and outputting a signal in response thereto is discussed. An accelerometer package having integral display and control functions is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine conditions over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase in amplitude over a selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated.

A method based on multi-sensor data fusion for fault detection of planetary gearboxes.

PubMed

Lei, Yaguo; Lin, Jing; He, Zhengjia; Kong, Detong

2012-01-01

Studies on fault detection and diagnosis of planetary gearboxes are quite limited compared with those of fixed-axis gearboxes. Different from fixed-axis gearboxes, planetary gearboxes exhibit unique behaviors, which invalidate fault diagnosis methods that work well for fixed-axis gearboxes. It is a fact that for systems as complex as planetary gearboxes, multiple sensors mounted on different locations provide complementary information on the health condition of the systems. On this basis, a fault detection method based on multi-sensor data fusion is introduced in this paper. In this method, two features developed for planetary gearboxes are used to characterize the gear health conditions, and an adaptive neuro-fuzzy inference system (ANFIS) is utilized to fuse all features from different sensors. In order to demonstrate the effectiveness of the proposed method, experiments are carried out on a planetary gearbox test rig, on which multiple accelerometers are mounted for data collection. The comparisons between the proposed method and the methods based on individual sensors show that the former achieves much higher accuracies in detecting planetary gearbox faults.

Citizen Sensors for SHM: Use of Accelerometer Data from Smartphones

PubMed Central

Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

2015-01-01

Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications. PMID:25643056

Use of smartphones and portable media devices for quantifying human movement characteristics of gait, tendon reflex response, and Parkinson's disease hand tremor.

PubMed

LeMoyne, Robert; Mastroianni, Timothy

2015-01-01

Smartphones and portable media devices are both equipped with sensor components, such as accelerometers. A software application enables these devices to function as a robust wireless accelerometer platform. The recorded accelerometer waveform can be transmitted wireless as an e-mail attachment through connectivity to the Internet. The implication of such devices as a wireless accelerometer platform is the experimental and post-processing locations can be placed anywhere in the world. Gait was quantified by mounting a smartphone or portable media device proximal to the lateral malleolus of the ankle joint. Attributes of the gait cycle were quantified with a considerable accuracy and reliability. The patellar tendon reflex response was quantified by using the device in tandem with a potential energy impact pendulum to evoke the patellar tendon reflex. The acceleration waveform maximum acceleration feature of the reflex response displayed considerable accuracy and reliability. By mounting the smartphone or portable media device to the dorsum of the hand through a glove, Parkinson's disease hand tremor was quantified and contrasted with significance to a non-Parkinson's disease steady hand control. With the methods advocated in this chapter, any aspect of human movement may be quantified through smartphones or portable media devices and post-processed anywhere in the world. These wearable devices are anticipated to substantially impact the biomedical and healthcare industry.

Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters: Part II

PubMed Central

Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg Y.; Fernández, Eduardo

2010-01-01

In this paper, the fast least-mean-squares (LMS) algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The response of the accelerometer under test was corrupted by process and measurement noise, and the signal processing stage was carried out by using both conventional filtering, which was already shown in a previous paper, and optimal adaptive filtering. The adaptive filtering process relied on the LMS adaptive filtering family, which has shown to have very good convergence and robustness properties, and here a comparative analysis between the results of the application of the conventional LMS algorithm and the fast LMS algorithm to solve a real-life filtering problem was carried out. In short, in this paper the piezoresistive accelerometer was tested for a multi-frequency acceleration excitation. Due to the kind of test conducted in this paper, the use of conventional filtering was discarded and the choice of one adaptive filter over the other was based on the signal-to-noise ratio improvement and the convergence rate. PMID:22315579

Ngram time series model to predict activity type and energy cost from wrist, hip and ankle accelerometers: implications of age

PubMed Central

Strath, Scott J; Kate, Rohit J; Keenan, Kevin G; Welch, Whitney A; Swartz, Ann M

2016-01-01

To develop and test time series single site and multi-site placement models, we used wrist, hip and ankle processed accelerometer data to estimate energy cost and type of physical activity in adults. Ninety-nine subjects in three age groups (18–39, 40–64, 65 + years) performed 11 activities while wearing three triaxial accelereometers: one each on the non-dominant wrist, hip, and ankle. During each activity net oxygen cost (METs) was assessed. The time series of accelerometer signals were represented in terms of uniformly discretized values called bins. Support Vector Machine was used for activity classification with bins and every pair of bins used as features. Bagged decision tree regression was used for net metabolic cost prediction. To evaluate model performance we employed the jackknife leave-one-out cross validation method. Single accelerometer and multi-accelerometer site model estimates across and within age group revealed similar accuracy, with a bias range of −0.03 to 0.01 METs, bias percent of −0.8 to 0.3%, and a rMSE range of 0.81–1.04 METs. Multi-site accelerometer location models improved activity type classification over single site location models from a low of 69.3% to a maximum of 92.8% accuracy. For each accelerometer site location model, or combined site location model, percent accuracy classification decreased as a function of age group, or when young age groups models were generalized to older age groups. Specific age group models on average performed better than when all age groups were combined. A time series computation show promising results for predicting energy cost and activity type. Differences in prediction across age group, a lack of generalizability across age groups, and that age group specific models perform better than when all ages are combined needs to be considered as analytic calibration procedures to detect energy cost and type are further developed. PMID:26449155

Superconducting gravity gradiometer mission. Volume 1: Study team executive summary

NASA Technical Reports Server (NTRS)

Morgan, Samuel H. (Editor); Paik, Ho Jung (Editor)

1989-01-01

An executive summary is presented based upon the scientific and engineering studies and developments performed or directed by a Study Team composed of various Federal and University activities involved with the development of a three-axis Superconducting Gravity Gradiometer integrated with a six-axis superconducting accelerometer. This instrument is being developed for a future orbital mission to make precise global gravity measurements. The scientific justification and requirements for such a mission are discussed. This includes geophysics, the primary mission objective, as well as secondary objectives, such as navigation and tests of fundamental laws of physics, i.e., a null test of the inverse square law of gravitation and tests of general relativity. The instrument design and status along with mission analysis, engineering assessments, and preliminary spacecraft concepts are discussed. In addition, critical spacecraft systems and required technology advancements are examined. The mission requirements and an engineering assessment of a precursor flight test of the instrument are discussed.

A Measuring System for Well Logging Attitude and a Method of Sensor Calibration

PubMed Central

Ren, Yong; Wang, Yangdong; Wang, Mijian; Wu, Sheng; Wei, Biao

2014-01-01

This paper proposes an approach for measuring the azimuth angle and tilt angle of underground drilling tools with a MEMS three-axis accelerometer and a three-axis fluxgate sensor. A mathematical model of well logging attitude angle is deduced based on combining space coordinate transformations and algebraic equations. In addition, a system implementation plan of the inclinometer is given in this paper, which features low cost, small volume and integration. Aiming at the sensor and assembly errors, this paper analyses the sources of errors, and establishes two mathematical models of errors and calculates related parameters to achieve sensor calibration. The results show that this scheme can obtain a stable and high precision azimuth angle and tilt angle of drilling tools, with the deviation of the former less than ±1.4° and the deviation of the latter less than ±0.1°. PMID:24859028

A measuring system for well logging attitude and a method of sensor calibration.

PubMed

Ren, Yong; Wang, Yangdong; Wang, Mijian; Wu, Sheng; Wei, Biao

2014-05-23

This paper proposes an approach for measuring the azimuth angle and tilt angle of underground drilling tools with a MEMS three-axis accelerometer and a three-axis fluxgate sensor. A mathematical model of well logging attitude angle is deduced based on combining space coordinate transformations and algebraic equations. In addition, a system implementation plan of the inclinometer is given in this paper, which features low cost, small volume and integration. Aiming at the sensor and assembly errors, this paper analyses the sources of errors, and establishes two mathematical models of errors and calculates related parameters to achieve sensor calibration. The results show that this scheme can obtain a stable and high precision azimuth angle and tilt angle of drilling tools, with the deviation of the former less than ±1.4° and the deviation of the latter less than ±0.1°.

Superconducting gravity gradiometer mission. Volume 2: Study team technical report

NASA Technical Reports Server (NTRS)

Morgan, Samuel H. (Editor); Paik, Ho Jung (Editor)

1988-01-01

Scientific and engineering studies and developments performed or directed by a Study Team composed of various Federal and University activities involved with the development of a three-axis superconducting gravity gradiometer integrated with a six-axis superconducting accelerometer are examined. This instrument is being developed for a future orbital mission to make precise global gravity measurements. The scientific justification and requirements for such a mission are discussed. This includes geophysics, the primary mission objective, as well as secondary objective, such as navigation and feats of fundamental laws of physics, i.e., a null test of the inverse square law of gravitation and tests of general relativity. The instrument design and status along with mission analysis, engineering assessments, and preliminary spacecraft concepts are discussed. In addition, critical spacecraft systems and required technology advancements are examined. The mission requirements and an engineering assessment of a precursor flight test of the instrument are discussed.

Self-calibration method of the inner lever-arm parameters for a tri-axis RINS

NASA Astrophysics Data System (ADS)

Song, Tianxiao; Li, Kui; Sui, Jie; Liu, Zengjun; Liu, Juncheng

2017-11-01

A rotational inertial navigation system (RINS) could improve navigation performance by modulating the inertial sensor errors with rotatable gimbals. When an inertial measurement unit (IMU) rotates, the deviations between the accelerometer-sensitive points and the IMU center will lead to an inner lever-arm effect. In this paper, a self-calibration method of the inner lever-arm parameters for a tri-axis RINS is proposed. A novel rotation scheme with variable angular rate rotation is designed to motivate the velocity errors caused by the inner lever-arm effect. By extending all inner lever-arm parameters as filter states, a Kalman filter with velocity errors as measurement is established to achieve the calibration. The accuracy and feasibility of the proposed method are illustrated by both simulations and experiments. The final results indicate that the inner lever-arm effect is significantly restrained after compensation by the calibration results.

Impaired chronotropic response to physical activities in heart failure patients.

PubMed

Shen, Hong; Zhao, Jianrong; Zhou, Xiaohong; Li, Jingbo; Wan, Qing; Huang, Jing; Li, Hui; Wu, Liqun; Yang, Shungang; Wang, Ping

2017-05-25

While exercise-based cardiac rehabilitation has a beneficial effect on heart failure hospitalization and mortality, it is limited by the presence of chronotropic incompetence (CI) in some patients. This study explored the feasibility of using wearable devices to assess impaired chronotropic response in heart failure patients. Forty patients with heart failure (left ventricular ejection fraction, LVEF: 44.6 ± 5.8; age: 54.4 ± 11.7) received ECG Holter and accelerometer to monitor heart rate (HR) and physical activities during symptom-limited treadmill exercise testing, 6-min hall walk (6MHW), and 24-h daily living. CI was defined as maximal HR during peak exercise testing failing to reach 70% of age-predicted maximal HR (APMHR, 220 - age). The correlation between HR and physical activities in Holter-accelerometer recording was analyzed. Of 40 enrolled patients, 26 were able to perform treadmill exercise testing. Based on exercise test reports, 13 (50%) of 26 patients did not achieve at least 70% of APMHR (CI patients). CI patients achieved a lower % APMHR (62.0 ± 6.3%) than non-CI patients who achieved 72.0 ± 1.2% of APMHR (P < 0.0001). When Holter-accelerometer recording was used to assess chronotropic response, the percent APMHR achieved during 6MHW and physical activities was significantly lower in CI patients than in non-CI patients. CI patients had a significantly shorter 6MHW distance and less physical activity intensity than non-CI patients. The study found impaired chronotropic response in 50% of heart failure patients who took treadmill exercise testing. The wearable Holter-accelerometer recording could help to identify impaired chronotropic response to physical activities in heart failure patients. ClinicalTrials.gov ID NCT02358603 . Registered 16 May 2014.

Microelectromechanical accelerometer with resonance-cancelling control circuit including an idle state

DOEpatents

Chu, Dahlon D.; Thelen, Jr., Donald C.; Campbell, David V.

2001-01-01

A digital feedback control circuit is disclosed for use in an accelerometer (e.g. a microelectromechanical accelerometer). The digital feedback control circuit, which periodically re-centers a proof mass in response to a sensed acceleration, is based on a sigma-delta (.SIGMA..DELTA.) configuration that includes a notch filter (e.g. a digital switched-capacitor filter) for rejecting signals due to mechanical resonances of the proof mass and further includes a comparator (e.g. a three-level comparator). The comparator generates one of three possible feedback states, with two of the feedback states acting to re-center the proof mass when that is needed, and with a third feedback state being an "idle" state which does not act to move the proof mass when no re-centering is needed. Additionally, the digital feedback control system includes an auto-zero trim capability for calibration of the accelerometer for accurate sensing of acceleration. The digital feedback control circuit can be fabricated using complementary metal-oxide semiconductor (CMOS) technology, bi-CMOS technology or bipolar technology and used in single- and dual-proof-mass accelerometers.

Small-scale seismic inversion using surface waves extracted from noise cross correlation.

PubMed

Gouédard, Pierre; Roux, Philippe; Campillo, Michel

2008-03-01

Green's functions can be retrieved between receivers from the correlation of ambient seismic noise or with an appropriate set of randomly distributed sources. This principle is demonstrated in small-scale geophysics using noise sources generated by human steps during a 10-min walk in the alignment of a 14-m-long accelerometer line array. The time-domain correlation of the records yields two surface wave modes extracted from the Green's function between each pair of accelerometers. A frequency-wave-number Fourier analysis yields each mode contribution and their dispersion curve. These dispersion curves are then inverted to provide the one-dimensional shear velocity of the near surface.

Development of a superconducting position sensor for the Satellite Test of the Equivalence Principle

NASA Astrophysics Data System (ADS)

Clavier, Odile Helene

The Satellite Test of the Equivalence Principle (STEP) is a joint NASA/ESA mission that proposes to measure the differential acceleration of two cylindrical test masses orbiting the earth in a drag-free satellite to a precision of 10-18 g. Such an experiment would conceptually reproduce Galileo's tower of Pisa experiment with a much longer time of fall and greatly reduced disturbances. The superconducting test masses are constrained in all degrees of freedom except their axial direction (the sensitive axis) using superconducting bearings. The STEP accelerometer measures the differential position of the masses in their sensitive direction using superconducting inductive pickup coils coupled to an extremely sensitive magnetometer called a DC-SQUID (Superconducting Quantum Interference Device). Position sensor development involves the design, manufacture and calibration of pickup coils that will meet the acceleration sensitivity requirement. Acceleration sensitivity depends on both the displacement sensitivity and stiffness of the position sensor. The stiffness must kept small while maintaining stability of the accelerometer. Using a model for the inductance of the pickup coils versus displacement of the test masses, a computer simulation calculates the sensitivity and stiffness of the accelerometer in its axial direction. This simulation produced a design of pickup coils for the four STEP accelerometers. Manufacture of the pickup coils involves standard photolithography techniques modified for superconducting thin-films. A single-turn pickup coil was manufactured and produced a successful superconducting coil using thin-film Niobium. A low-temperature apparatus was developed with a precision position sensor to measure the displacement of a superconducting plate (acting as a mock test mass) facing the coil. The position sensor was designed to detect five degrees of freedom so that coupling could be taken into account when measuring the translation of the plate relative to the coil. The inductance was measured using a DC-SQUID coupled to the pickup coil. The experimental results agree with the model used in the simulation thereby validating the concept used for the design. The STEP program now has the confidence necessary to design and manufacture a position sensor for the flight accelerometer.

Feasibility of Frequency-Modulated Wireless Transmission for a Multi-Purpose MEMS-Based Accelerometer

PubMed Central

Sabato, Alessandro; Feng, Maria Q.

2014-01-01

Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy—especially at very low frequencies—have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline. PMID:25198003

Feasibility of frequency-modulated wireless transmission for a multi-purpose MEMS-based accelerometer.

PubMed

Sabato, Alessandro; Feng, Maria Q

2014-09-05

Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy--especially at very low frequencies--have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline.

Attitude determination with three-axis accelerometer for emergency atmospheric entry

NASA Technical Reports Server (NTRS)

Garcia-Llama, Eduardo (Inventor)

2012-01-01

Two algorithms are disclosed that, with the use of a 3-axis accelerometer, will be able to determine the angles of attack, sideslip and roll of a capsule-type spacecraft prior to entry (at very high altitudes, where the atmospheric density is still very low) and during entry. The invention relates to emergency situations in which no reliable attitude and attitude rate are available. Provided that the spacecraft would not attempt a guided entry without reliable attitude information, the objective of the entry system in such case would be to attempt a safe ballistic entry. A ballistic entry requires three controlled phases to be executed in sequence: First, cancel initial rates in case the spacecraft is tumbling; second, maneuver the capsule to a heat-shield-forward attitude, preferably to the trim attitude, to counteract the heat rate and heat load build up; and third, impart a ballistic bank or roll rate to null the average lift vector in order to prevent prolonged lift down situations. Being able to know the attitude, hence the attitude rate, will allow the control system (nominal or backup, automatic or manual) to cancel any initial angular rates. Also, since a heat-shield forward attitude and the trim attitude can be specified in terms of the angles of attack and sideslip, being able to determine the current attitude in terms of these angles will allow the control system to maneuver the vehicle to the desired attitude. Finally, being able to determine the roll angle will allow for the control of the roll ballistic rate during entry.

Falls classification using tri-axial accelerometers during the five-times-sit-to-stand test.

PubMed

Doheny, Emer P; Walsh, Cathal; Foran, Timothy; Greene, Barry R; Fan, Chie Wei; Cunningham, Clodagh; Kenny, Rose Anne

2013-09-01

The five-times-sit-to-stand test (FTSS) is an established assessment of lower limb strength, balance dysfunction and falls risk. Clinically, the time taken to complete the task is recorded with longer times indicating increased falls risk. Quantifying the movement using tri-axial accelerometers may provide a more objective and potentially more accurate falls risk estimate. 39 older adults, 19 with a history of falls, performed four repetitions of the FTSS in their homes. A tri-axial accelerometer was attached to the lateral thigh and used to identify each sit-stand-sit phase and sit-stand and stand-sit transitions. A second tri-axial accelerometer, attached to the sternum, captured torso acceleration. The mean and variation of the root-mean-squared amplitude, jerk and spectral edge frequency of the acceleration during each section of the assessment were examined. The test-retest reliability of each feature was examined using intra-class correlation analysis, ICC(2,k). A model was developed to classify participants according to falls status. Only features with ICC>0.7 were considered during feature selection. Sequential forward feature selection within leave-one-out cross-validation resulted in a model including four reliable accelerometer-derived features, providing 74.4% classification accuracy, 80.0% specificity and 68.7% sensitivity. An alternative model using FTSS time alone resulted in significantly reduced classification performance. Results suggest that the described methodology could provide a robust and accurate falls risk assessment. Copyright © 2013 Elsevier B.V. All rights reserved.

Time Periods of Unusual Density Behavior Observed by GRACE and CHAMP

NASA Astrophysics Data System (ADS)

McLaughlin, C. A.; Fattig, E.; Mysore Krishna, D.; Locke, T.; Mehta, P. M.

2011-12-01

Time periods of low cross correlation between precision orbit ephemeris (POE) derived density and accelerometer density for CHAMP and GRACE are examined. In particular, the cross correlation for GRACE dropped from typical values near 0.9 to much lower values and then returned to typical over the time period of late October to late December of 2005. This time period includes a maneuver where GRACE-A and GRACE-B swapped positions. However, the drop in cross correlation begins and reaches its low point before the maneuvers begin. In addition, the densities were found using GRACE-A, but GRACE-B did most of the maneuvering. The time period is characterized by high frequency variations in accelerometer density of the same magnitude as the daylight to eclipse variations over the course of an orbit. However, the daylight to eclipse variations are particularly small during this time period because the orbit plane is near the terminator. Additionally, the difference between the accelerometer and POE derived densities are not unusually large during this time period. This implies the variations are not unusual, just more significant when the orbit plane is near terminator. Cyclical variations in correlation of the POE derived densities with accelerometer derived densities are seen for both GRACE and CHAMP, but the magnitude of the variations are much larger for GRACE, possibly because of the higher altitude of GRACE. The cycles seem to be phased so that low correlations occur with low beta angle when the orbit plane is near the terminator. The low correlation is possibly caused by the lower amplitude of the daylight to eclipse signal making higher frequency variations relatively more important. However, another possible explanation is terminator waves in density that propagate to the thermosphere from lower in the atmosphere. These waves have been observed in CHAMP accelerometer data and global circulation model simulations. Further investigation is needed to see if the variations correspond to terminator waves or if they represent typical high frequency signal from another source that is more apparent when the orbit plane is near the terminator. 1. C. A. McLaughlin, E. Fattig, D. Mysore Krishna, and P. M. Mehta, "Time Periods of Anomalous Density for GRACE and CHAMP," AAS/AIAA Astrodynamics Specialists Conference, AAS 11-613, Girdwood, AK, August 2011. 2. C. A. McLaughlin, A. Hiatt, and T. Lechtenberg, "Calibrating Precision Orbit Derived Total Density," Journal of Spacecraft and Rockets, Vol. 48, No. 1, January-February 2011, pp. 166-174.

A four-axis hand controller for helicopter flight control

NASA Technical Reports Server (NTRS)

Demaio, Joe

1993-01-01

A proof-of-concept hand controller for controlling lateral and longitudinal cyclic pitch, collective pitch and tail rotor thrust was developed. The purpose of the work was to address problems of operator fatigue, poor proprioceptive feedback and cross-coupling of axes associated with many four-axis controller designs. The present design is an attempt to reduce cross-coupling to a level that can be controlled with breakout force, rather than to eliminate it entirely. The cascaded design placed lateral and longitudinal cyclic in their normal configuration. Tail rotor thrust was placed atop the cyclic controller. A left/right twisting motion with the wrist made the control input. The axis of rotation was canted outboard (clockwise) to minimize cross-coupling with the cyclic pitch axis. The collective control was a twist grip, like a motorcycle throttle. Measurement of the amount of cross-coupling involved in pure, single-axis inputs showed cross coupling under 10 percent of full deflection for all axes. This small amount of cross-coupling could be further reduced with better damping and force gradient control. Fatigue was not found to be a problem, and proprioceptive feedback was adequate for all flight tasks executed.

Quantification of Trunk Postural Stability Using Convex Polyhedron of the Time-Series Accelerometer Data

PubMed Central

Melecky, Roman; Socha, Vladimir; Kutilek, Patrik; Hanakova, Lenka; Takac, Peter; Schlenker, Jakub; Svoboda, Zdenek

2016-01-01

Techniques to quantify postural stability usually rely on the evaluation of only two variables, that is, two coordinates of COP. However, by using three variables, that is, three components of acceleration vector, it is possible to describe human movement more precisely. For this purpose, a single three-axis accelerometer was used, making it possible to evaluate 3D movement by use of a novel method, convex polyhedron (CP), together with a traditional method, based on area of the confidence ellipse (ACE). Ten patients (Pts) with cerebellar ataxia and eleven healthy individuals of control group (CG) participated in the study. The results show a significant increase of volume of the CP (CPV) in Pts or CG standing on foam surface with eyes open (EO) and eyes closed (EC) after the EC phase. Significant difference between Pts and CG was found in all cases as well. Correlation coefficient indicates strong correlation between the CPV and ACE in most cases of patient examinations, thus confirming the possibility of quantification of postural instability by the introduced method of CPV. PMID:27195465

Quantification of Trunk Postural Stability Using Convex Polyhedron of the Time-Series Accelerometer Data.

PubMed

Melecky, Roman; Socha, Vladimir; Kutilek, Patrik; Hanakova, Lenka; Takac, Peter; Schlenker, Jakub; Svoboda, Zdenek

2016-01-01

Techniques to quantify postural stability usually rely on the evaluation of only two variables, that is, two coordinates of COP. However, by using three variables, that is, three components of acceleration vector, it is possible to describe human movement more precisely. For this purpose, a single three-axis accelerometer was used, making it possible to evaluate 3D movement by use of a novel method, convex polyhedron (CP), together with a traditional method, based on area of the confidence ellipse (ACE). Ten patients (Pts) with cerebellar ataxia and eleven healthy individuals of control group (CG) participated in the study. The results show a significant increase of volume of the CP (CPV) in Pts or CG standing on foam surface with eyes open (EO) and eyes closed (EC) after the EC phase. Significant difference between Pts and CG was found in all cases as well. Correlation coefficient indicates strong correlation between the CPV and ACE in most cases of patient examinations, thus confirming the possibility of quantification of postural instability by the introduced method of CPV.

Use of Accelerometer Activity Monitors to Detect Changes in Pruritic Behaviors: Interim Clinical Data on 6 Dogs

PubMed Central

Thompson, Robin J.; Mickelsen, Scott L.; Smith, Spencer C.; Alvarenga, Isabella C.; Gross, Kathy L.

2018-01-01

Veterinarians and pet owners have limited ability to assess pruritic behaviors in dogs. This pilot study assessed the capacity of the Vetrax® triaxial accelerometer to measure these behaviors in six dogs with pruritus likely due to environmental allergens. Dogs wore the activity monitor for two weeks while consuming their usual pet food (baseline), then for eight weeks while consuming a veterinary-exclusive pet food for dogs with suspected non-food-related skin conditions (Hill’s Prescription Diet® Derm DefenseTM Canine dry food). Veterinarians and owners completed questionnaires during baseline, phase 1 (days 1–28) and phase 2 (days 29–56) without knowledge of the activity data. Continuous 3-axis accelerometer data was processed using proprietary behavior recognition algorithms and analyzed using general linear mixed models with false discovery rate-adjusted p values. Veterinarian-assessed overall clinical signs of pruritus were significantly predicted by scratching (β 0.176, p = 0.008), head shaking (β 0.197, p < 0.001) and sleep quality (β −0.154, p < 0.001), while owner-assessed quality of life was significantly predicted by scratching (β −0.103, p = 0.013) and head shaking (β −0.146, p < 0.001). Among dogs exhibiting pruritus signs eating the veterinary-exclusive food, the Vetrax® sensor provided an objective assessment of clinically relevant pruritic behaviors that agreed with owner and veterinarian reports. PMID:29337903

Acoustic emission studies of large advanced composite rocket motor cases.

NASA Technical Reports Server (NTRS)

Robinson, E. Y.

1973-01-01

Acoustic emission (AE) patterns were measured during pressure testing of advanced composite rocket motor cases made of boron/epoxy and graphite/epoxy. Both accelerometers and high frequency AE transducers were used, and both frequency spectrum and amplitude distribution were studied. The AE patterns suggest that precursor emission might be used in certain cases to anticipate failure. The technique of hold-cycle AE monitoring was also evaluated and could become a valuable decision gate for test continuation/termination. Data presented show similarity of accelerometers and AE transducer responses despite the different frequency response, and suggest that structural AE phenomena are broadband.

LANDSAT-D MSS/TM tuned orbital jitter analysis model LDS900

NASA Technical Reports Server (NTRS)

Pollak, T. E.

1981-01-01

The final LANDSAT-D orbital dynamic math model (LSD900), comprised of all test validated substructures, was used to evaluate the jitter response of the MSS/TM experiments. A dynamic forced response analysis was performed at both the MSS and TM locations on all structural modes considered (thru 200 Hz). The analysis determined the roll angular response of the MSS/TM experiments to improve excitation generated by component operation. Cross axis and cross experiment responses were also calculated. The excitations were analytically represented by seven and nine term Fourier series approximations, for the MSS and TM experiment respectively, which enabled linear harmonic solution techniques to be applied to response calculations. Single worst case jitter was estimated by variations of the eigenvalue spectrum of model LSD 900. The probability of any worst case mode occurrence was investigated.

Investigation of Gearbox Vibration Transmission Paths on Gear Condition Indicator Performance

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Islam, AKM Anwarul; Feldman, Jason; Larsen, Chris

2013-01-01

Helicopter health monitoring systems use vibration signatures generated from damaged components to identify transmission faults. For damaged gears, these signatures relate to changes in dynamics due to the meshing of the damaged tooth. These signatures, referred to as condition indicators (CI), can perform differently when measured on different systems, such as a component test rig, or a full-scale transmission test stand, or an aircraft. These differences can result from dissimilarities in systems design and environment under dynamic operating conditions. The static structure can also filter the response between the vibration source and the accelerometer, when the accelerometer is installed on the housing. To assess the utility of static vibration transfer paths for predicting gear CI performance, measurements were taken on the NASA Glenn Spiral Bevel Gear Fatigue Test Rig. The vibration measurements were taken to determine the effect of torque, accelerometer location and gearbox design on accelerometer response. Measurements were taken at the housing and compared while impacting the gear set near mesh. These impacts were made at gear mesh to simulate gear meshing dynamics. Data measured on a helicopter gearbox installed in a static fixture were also compared to the test rig. The behavior of the structure under static conditions was also compared to CI values calculated under dynamic conditions. Results indicate that static vibration transfer path measurements can provide some insight into spiral bevel gear CI performance by identifying structural characteristics unique to each system that can affect specific CI response.

Evaluation of the MyWellness Key accelerometer.

PubMed

Herrmann, S D; Hart, T L; Lee, C D; Ainsworth, B E

2011-02-01

to examine the concurrent validity of the Technogym MyWellness Key accelerometer against objective and subjective physical activity (PA) measures. randomised, cross-sectional design with two phases. The laboratory phase compared the MyWellness Key with the ActiGraph GT1M and the Yamax SW200 Digiwalker pedometer during graded treadmill walking, increasing speed each minute. The free-living phase compared the MyWellness Key with the ActiGraph, Digiwalker, Bouchard Activity cord (BAR) and Global Physical Activity Questionnaire (GPAQ) for seven continuous days. Data were analysed using Spearman rank-order correlation coefficients for all comparisons. laboratory and free-living phases. sixteen participants randomly stratified from 41 eligible respondents by sex (n=8 men; n=8 women) and PA levels (n=4 low, n=8 middle and n=4 high active). there was a strong association between the MyWellness Key and the ActiGraph accelerometer during controlled graded treadmill walking (r=0.91, p<0.01) and in free-living settings (r=0.73-0.76 for light to vigorous PA, respectively, p<0.01). No associations were observed between the MyWellness Key and the BAR and GPAQ (p>0.05). the MyWellness Key has a high concurrent validity with the ActiGraph accelerometer to detect PA in both controlled laboratory and free-living settings.

Vehicle longitudinal velocity estimation during the braking process using unknown input Kalman filter

NASA Astrophysics Data System (ADS)

Moaveni, Bijan; Khosravi Roqaye Abad, Mahdi; Nasiri, Sayyad

2015-10-01

In this paper, vehicle longitudinal velocity during the braking process is estimated by measuring the wheels speed. Here, a new algorithm based on the unknown input Kalman filter is developed to estimate the vehicle longitudinal velocity with a minimum mean square error and without using the value of braking torque in the estimation procedure. The stability and convergence of the filter are analysed and proved. Effectiveness of the method is shown by designing a real experiment and comparing the estimation result with actual longitudinal velocity computing from a three-axis accelerometer output.

Balloon-Borne, High Altitude Gravimetry: The Flight of DUCKY Ia (11 October 1983)

DTIC Science & Technology

1985-12-31

three rate gyros, three-axis magnetometer and two tiltmeters ) combined with ground tracking (X, Y and Z position and velocity) will allow fqX_.,ep ar a...2.3 Sensors 9 2.3.1 Vibrating String Accelerometer (VSA) 9 2.3.1.1 Mechanical Liyout of’ System 10 2.3.i.2 VSA System Description i0 2.3.1.3 Method for...Block Diagram 11 2.2 A Sketch of the VSA Sensor 12 3.1 A Photograph of the Payload, Named DUCKY Ia, Just After Transport to the Launch Site 22 3.2 A

Conceptual Approach for Precise Relative Positioning with Miniaturized GPS Loggers and Experimental Results

DTIC Science & Technology

2010-03-01

readily met by standard single frequency GPS receiver modules as used in car navigation systems or latest generation cell phones. However...different strategies can now be applied as shown in Figure 5. btbξ SPP bξδ iξ itbiβ (a) Over-all solution btbξ SPP bξδ iξ it nn ,1−β 1− nt1 −nξ nξ nt (b... cells . The mass of the complete logging unit did not exceed 100 g. Some receivers additionally featured 3 axis MEMS accelerometers. Mounting on the

Using the Wiimote in Introductory Physics Experiments

NASA Astrophysics Data System (ADS)

Ochoa, Romulo; Rooney, Frank G.; Somers, William J.

2011-01-01

The Wii is a very popular gaming console. An important component of its appeal is the ease of use of its remote controller, popularly known as a Wiimote. This simple-looking but powerful device has a three-axis accelerometer and communicates with the console via Bluetooth protocol. We present two experiments that demonstrate the feasibility of using the Wiimote in introductory physics experiments. The linear dependence of centripetal acceleration on the radial distance at constant angular velocity is verified and compared with data obtained using photogate timers. A second application to simple harmonic oscillators tests the capabilities of the Wiimote to measure variable accelerations.

Nonlinear dual-axis biodynamic response of the semi-supine human body during longitudinal horizontal whole-body vibration

NASA Astrophysics Data System (ADS)

Huang, Ya; Griffin, Michael J.

2008-04-01

The resonance frequencies in frequency response functions of the human body (e.g. apparent mass and transmissibility) decrease with increasing vibration magnitude. This nonlinear biodynamic response is found with various sitting and standing postures requiring postural control. The present study measured the apparent mass of the body in a relaxed semi-supine posture with two types of longitudinal horizontal vibration (in the z-axis of the semi-supine body): (i) continuous random excitation (0.25-20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75 and 1.0 ms -2 rms); (ii) intermittent random excitation (0.25-20 Hz) alternately at 0.25 and 1.0 ms -2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 3.7 to 2.4 Hz as the vibration magnitude increased from 0.125 to 1.0 ms -2 rms. A nonlinear response was apparent in both the horizontal ( z-axis) apparent mass and the vertical ( x-axis) cross-axis apparent mass. With intermittent random vibration, as the vibration magnitude increased from 0.25 to 1.0 ms -2 rms, the median resonance frequency of the apparent mass decreased from 3.2 to 2.5 Hz whereas, with continuous random vibration over the same range of magnitudes, the resonance frequency decreased from 3.4 to 2.4 Hz. The median change in the resonance frequency (between 0.25 and 1.0 ms -2 rms) was 0.6 Hz with the intermittent random vibration and 0.9 Hz with the continuous random vibration. With intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration at the same magnitudes. The responses were consistent with passive thixotropy being a primary cause of nonlinear biodynamic responses to whole-body vibration, although reflex activity of the muscles may also have an influence.

Human occupants in low-speed frontal sled tests: effects of pre-impact bracing on chest compression, reaction forces, and subject acceleration.

PubMed

Kemper, Andrew R; Beeman, Stephanie M; Madigan, Michael L; Duma, Stefan M

2014-01-01

The purpose of this study was to investigate the effects of pre-impact bracing on the chest compression, reaction forces, and accelerations experienced by human occupants during low-speed frontal sled tests. A total of twenty low-speed frontal sled tests, ten low severity (∼2.5g, Δv=5 kph) and ten medium severity (∼5g, Δv=10 kph), were performed on five 50th-percentile male human volunteers. Each volunteer was exposed to two impulses at each severity, one relaxed and the other braced prior to the impulse. A 59-channel chestband, aligned at the nipple line, was used to quantify the chest contour and anterior-posterior sternum deflection. Three-axis accelerometer cubes were attached to the sternum, 7th cervical vertebra, and sacrum of each subject. In addition, three linear accelerometers and a three-axis angular rate sensor were mounted to a metal mouthpiece worn by each subject. Seatbelt tension load cells were attached to the retractor, shoulder, and lap portions of the standard three-point driver-side seatbelt. In addition, multi-axis load cells were mounted to each interface between the subject and the test buck to quantify reaction forces. For relaxed tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, all belt forces, and three resultant reaction forces (right foot, seatpan, and seatback). For braced tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, and two resultant reaction forces (right foot and seatpan). Bracing did not have a significant effect on the occupant accelerations during the low severity tests, but did result in a significant decrease in peak resultant sacrum linear acceleration during the medium severity tests. Bracing was also found to significantly reduce peak shoulder and retractor belt forces for both test severities, and peak lap belt force for the medium test severity. In contrast, bracing resulted in a significant increase in the peak resultant reaction force for the right foot and steering column at both test severities. Chest compression due to belt loading was observed for all relaxed subjects at both test severities, and was found to increase significantly with increasing severity. Conversely, chest compression due to belt loading was essentially eliminated during the braced tests for all but one subject, who sustained minor chest compression due to belt loading during the medium severity braced test. Overall, the data from this study illustrate that muscle activation has a significant effect on the biomechanical response of human occupants in low-speed frontal impacts.

Water Landing Characteristics of a Reentry Capsule

NASA Technical Reports Server (NTRS)

1958-01-01

Experimental and theoretical investigations have been made to determine the water-landing characteristics of a conical-shaped reentry capsule having a segment of a sphere as the bottom. For the experimental portion of the investigation, a 1/12-scale model capsule and a full-scale capsule were tested for nominal flight paths of 65 deg and 90 deg (vertical), a range of contact attitudes from -30 deg to 30 deg, and a full-scale vertical velocity of 30 feet per second at contact. Accelerations were measured by accelerometers installed at the centers of gravity of the model and full-scale capsules. For the model test the accelerations were measured along the X-axis (roll) and Z-axis (yaw) and for the full-scale test they were measured along the X-axis (roll), Y-axis (pitch), and Z-axis (yaw). Motions and displacements of the capsules that occurred after contact were determined from high-speed motion pictures. The theoretical investigation was conducted to determine the accelerations that might occur along the X-axis when the capsule contacted the water from a 90 deg flight path at a 0 deg attitude. Assuming a rigid body, computations were made from equations obtained by utilizing the principle of the conservation of momentum. The agreement among data obtained from the model test, the full-scale test, and the theory was very good. The accelerations along the X-axis, for a vertical flight path and 0 deg attitude, were in the order of 40g. For a 65 deg flight path and 0 deg attitude, the accelerations along the X-axis were in the order of 50g. Changes in contact attitude, in either the positive or negative direction from 0 deg attitude, considerably reduced the magnitude of the accelerations measured along the X-axis. Accelerations measured along the Y- and Z-axes were relatively small at all test conditions.

Water-Landing Characteristics of a Reentry Capsule

NASA Technical Reports Server (NTRS)

McGehee, John R.; Hathaway, Melvin E.; Vaughan, Victor L., Jr.

1959-01-01

Experimental and theoretical investigations have been made to determine the water-landing characteristics of a conical-shaped reentry capsule having a segment of a sphere as the bottom. For the experimental portion of the investigation, a 1/12-scale model capsule and a full-scale capsule were tested for nominal flight paths of 65 deg and 90 deg (vertical), a range of contact attitudes from -30 deg to 30 deg, and a full-scale vertical velocity of 30 feet per second at contact. Accelerations were measured by accelerometers installed at the centers of gravity of the model and full-scale capsules. For the model test the accelerations were measured along the X-axis (roll) and Z-axis (yaw) and for the full-scale test they were measured along the X-axis (roll), Y-axis (pitch), and Z-axis (yaw). Motions and displacements of the capsules that occurred after contact were determined from high-speed motion pictures. The theoretical investigation was conducted to determine the accelerations that might occur along the X-axis when the capsule contacted the water from a 90 deg flight path at a 0 deg attitude. Assuming a rigid body, computations were made from equations obtained by utilizing the principle of the conservation of momentum. The agreement among data obtained from the model test, the full-scale test, and the theory was very good. The accelerations along the X-axis, for a vertical flight path and 0 deg attitude, were in the order of 40g. For a 65 deg flight path and 0 deg attitude, the accelerations along the X-axis were in the order of 50g. Changes in contact attitude, in either the positive or negative direction from 0 deg attitude, considerably reduced the magnitude of the accelerations measured along the X-axis. Accelerations measured along the Y- and Z-axes were relatively small at all test conditions.

Integrated model reference adaptive control and time-varying angular rate estimation for micro-machined gyroscopes

NASA Astrophysics Data System (ADS)

Tsai, Nan-Chyuan; Sue, Chung-Yang

2010-02-01

Owing to the imposed but undesired accelerations such as quadrature error and cross-axis perturbation, the micro-machined gyroscope would not be unconditionally retained at resonant mode. Once the preset resonance is not sustained, the performance of the micro-gyroscope is accordingly degraded. In this article, a direct model reference adaptive control loop which is integrated with a modified disturbance estimating observer (MDEO) is proposed to guarantee the resonant oscillations at drive mode and counterbalance the undesired disturbance mainly caused by quadrature error and cross-axis perturbation. The parameters of controller are on-line innovated by the dynamic error between the MDEO output and expected response. In addition, Lyapunov stability theory is employed to examine the stability of the closed-loop control system. Finally, the efficacy of numerical evaluation on the exerted time-varying angular rate, which is to be detected and measured by the gyroscope, is verified by intensive simulations.

Luman/CREB3 recruitment factor regulates glucocorticoid receptor activity and is essential for prolactin-mediated maternal instinct.

PubMed

Martyn, Amanda C; Choleris, Elena; Gillis, Daniel J; Armstrong, John N; Amor, Talya R; McCluggage, Adam R R; Turner, Patricia V; Liang, Genqing; Cai, Kimberly; Lu, Ray

2012-12-01

The hypothalamic-pituitary-adrenal (HPA) axis is a major part of the neuroendocrine system in animal responses to stress. It is known that the HPA axis is attenuated at parturition to prevent detrimental effects of glucocorticoid secretion including inhibition of lactation and maternal responsiveness. Luman/CREB3 recruitment factor (LRF) was identified as a negative regulator of CREB3 which is involved in the endoplasmic reticulum stress response. Here, we report a LRF gene knockout mouse line that has a severe maternal behavioral defect. LRF(-/-) females lacked the instinct to tend pups; 80% of their litters died within 24 h, while most pups survived if cross-fostered. Prolactin levels were significantly repressed in lactating LRF(-/-) dams, with glucocorticoid receptor (GR) signaling markedly augmented. In cell culture, LRF repressed transcriptional activity of GR and promoted its protein degradation. LRF was found to colocalize with the known GR repressor, RIP140/NRIP1, which inhibits the activity by GR within specific nuclear punctates that are similar to LRF nuclear bodies. Furthermore, administration of prolactin or the GR antagonist RU486 restored maternal responses in mutant females. We thus postulate that LRF plays a critical role in the attenuation of the HPA axis through repression of glucocorticoid stress signaling during parturition and the postpartum period.

Accelerometer-determined physical activity level among government employees in Penang, Malaysia.

PubMed

Hazizi, A S; Aina, Mardiah B; Mohd, Nasir M T; Zaitun, Y; Hamid, Jan J M; Tabata, I

2012-04-01

A cross-sectional study was carried out to investigate accelerometer-determined physical activity level of 233 Malay government employees (104 men, 129 women) working in the Federal Government Building Penang, Malaysia. Body weight, height, waist and hip circumference, body fat percentage and blood pressure were measured for each respondent. All the respondents were asked to wear an accelerometer for 3 days. Body mass index (BMI) and waist-hip ratio (WHR) were calculated using a standard formulas. Fasting blood sample was obtained to determine the lipid profile and glucose levels of the respondents. Based on the accelerometer-determined physical activity level, almost 65% of the respondents were categorised as sedentary. Approximately 50.2% of the respondents were overweight or obese. There were negative but significant relationships between body mass index (BMI) (r = -0.353, p < 0.05), body fat percentage (r = -0.394, p < 0.05), waist circumference (WC) (r = -0.198, p < 0.05) and physical activity level. Sedentary individuals had a higher risk than moderate to active individuals of having a BMI more than or equal to 25 kg/m2 (OR = 2.80, 95% CI 1.55-5.05), an-risk classified WC (OR = 1.79, 95% CI 1.01-3.20), and a body fat percentage classified as unhealthy (OR = 3.01, 95% CI 1.41-6.44). The results of this study suggest that accelerometer-determined physical activity level is a significant factor associated with obesity in this study. The high prevalence of physical inactivity and obesity found among respondents of this study indicate a need for implementing intervention programmes among this population.

Cognitive function and the agreement between self-reported and accelerometer-accessed physical activity.

PubMed

Herbolsheimer, Florian; Riepe, Matthias W; Peter, Richard

2018-02-21

Numerous studies have reported weak or moderate correlations between self-reported and accelerometer-assessed physical activity. One explanation is that self-reported physical activity might be biased by demographic, cognitive or other factors. Cognitive function is one factor that could be associated with either overreporting or underreporting of daily physical activity. Difficulties in remembering past physical activities might result in recall bias. Thus, the current study examines whether the cognitive function is associated with differences between self-reported and accelerometer-assessed physical activity. Cross-sectional data from the population-based Activity and Function in the Elderly in Ulm study (ActiFE) were used. A total of 1172 community-dwelling older adults (aged 65-90 years) wore a uniaxial accelerometer (activPAL unit) for a week. Additionally, self-reported physical activity was assessed using the LASA Physical Activity Questionnaire (LAPAQ). Cognitive function was measured with four items (immediate memory, delayed memory, recognition memory, and semantic fluency) from the Consortium to Establish a Registry for Alzheimer's Disease Total Score (CERAD-TS). Mean differences of self-reported and accelerometer-assessed physical activity (MPA) were associated with cognitive function in men (r s  = -.12, p = .002) but not in women. Sex-stratified multiple linear regression analyses showed that MPA declined with high cognitive function in men (β = -.13; p = .015). Results suggest that self-reported physical activity should be interpreted with caution in older populations, as cognitive function was one factor that explained the differences between objective and subjective physical activity measurements.

Dielectric waveguide with transverse index variation that support a zero group velocity mode at a non-zero longitudinal wavevector

DOEpatents

Ibanescu, Mihai; Joannopoious, John D.; Fink, Yoel; Johnson, Steven G.; Fan, Shanhui

2005-06-21

Optical components including a laser based on a dielectric waveguide extending along a waveguide axis and having a refractive index cross-section perpendicular to the waveguide axis, the refractive index cross-section supporting an electromagnetic mode having a zero group velocity for a non-zero wavevector along the waveguide axis.

Quaternion-Based Unscented Kalman Filter for Accurate Indoor Heading Estimation Using Wearable Multi-Sensor System

PubMed Central

Yuan, Xuebing; Yu, Shuai; Zhang, Shengzhi; Wang, Guoping; Liu, Sheng

2015-01-01

Inertial navigation based on micro-electromechanical system (MEMS) inertial measurement units (IMUs) has attracted numerous researchers due to its high reliability and independence. The heading estimation, as one of the most important parts of inertial navigation, has been a research focus in this field. Heading estimation using magnetometers is perturbed by magnetic disturbances, such as indoor concrete structures and electronic equipment. The MEMS gyroscope is also used for heading estimation. However, the accuracy of gyroscope is unreliable with time. In this paper, a wearable multi-sensor system has been designed to obtain the high-accuracy indoor heading estimation, according to a quaternion-based unscented Kalman filter (UKF) algorithm. The proposed multi-sensor system including one three-axis accelerometer, three single-axis gyroscopes, one three-axis magnetometer and one microprocessor minimizes the size and cost. The wearable multi-sensor system was fixed on waist of pedestrian and the quadrotor unmanned aerial vehicle (UAV) for heading estimation experiments in our college building. The results show that the mean heading estimation errors are less 10° and 5° to multi-sensor system fixed on waist of pedestrian and the quadrotor UAV, respectively, compared to the reference path. PMID:25961384

A Simple Accelerometer Calibrator

NASA Astrophysics Data System (ADS)

Salam, R. A.; Islamy, M. R. F.; Munir, M. M.; Latief, H.; Irsyam, M.; Khairurrijal

2016-08-01

High possibility of earthquake could lead to the high number of victims caused by it. It also can cause other hazards such as tsunami, landslide, etc. In that case it requires a system that can examine the earthquake occurrence. Some possible system to detect earthquake is by creating a vibration sensor system using accelerometer. However, the output of the system is usually put in the form of acceleration data. Therefore, a calibrator system for accelerometer to sense the vibration is needed. In this study, a simple accelerometer calibrator has been developed using 12 V DC motor, optocoupler, Liquid Crystal Display (LCD) and AVR 328 microcontroller as controller system. The system uses the Pulse Wave Modulation (PWM) form microcontroller to control the motor rotational speed as response to vibration frequency. The frequency of vibration was read by optocoupler and then those data was used as feedback to the system. The results show that the systems could control the rotational speed and the vibration frequencies in accordance with the defined PWM.

Summary Report of Mission Acceleration Measurements for STS-73, Launched October 20, 1995

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.; DeLombard, Richard

1996-01-01

The microgravity environment of the Space Shuttle Columbia was measured during the STS-73 mission using accelerometers from five different instruments: the Orbital Acceleration Research Experiment, the Space Acceleration Measurement System, the Three-dimensional Microgravity Accelerometer, the Microgravity Measuring Device, and Suppression of Transient Accelerations by Levitation Evaluation System. The Microgravity Analysis Workstation quasi-steady environment calculation and comparison of this calculation with Orbital Acceleration Research Experiment data was used to assess how appropriate a planned attitude was expected to be for one Crystal Growth Facility experiment sample. The microgravity environment related to several different Orbiter, crew, and experiment operations is presented and interpreted in this report. Data are examined to show the effects of vernier reaction control system jet firings for Orbiter attitude control. This is compared to examples of data when no thrusters were firing, when the primary reaction control system jets were used for attitude control, and when single vernier jets were fired for test purposes. In general, vernier jets, when used for attitude control, cause accelerations in the 3 x 10(exp -4) g to 7 x 10(exp -4) g range. Primary jets used in this manner cause accelerations in the 0.01 to 0.025 g range. Other significant disturbance sources characterized are water dump operations, with Y(sub b) axis acceleration deviations of about 1 x 10(exp -6) g; payload bay door opening motion, with Y(sub o) and Z(sub o) axis accelerations of frequency 0.4 Hz; and probable Glovebox fan operations with notable frequency components at 20, 38, 43, 48, and 53 Hz. The STS-73 microgravity environment is comparable to the environments measured on earlier microgravity science missions.

Modal testing of a rotating wind turbine

NASA Astrophysics Data System (ADS)

Carne, T. G.; Nord, A. R.

1982-11-01

A testing technique was developed to measure the modes of vibration of a rotating vertical-axis wind turbine. This technique was applied to the Sandia Two-Meter Turbine, where the changes in individual modal frequencies as a function of the rotational speed were tracked from 0 rpm (parked) to 600 rpm. During rotational testing, the structural response was measured using a combination of strain gages and accelerometers, passing the signals through slip rings. Excitation of the turbine structure was provided by a scheme which suddenly released a pretensioned cable, thus plucking the turbine as it was rotating at a set speed. In addition to calculating the real modes of the parked turbine, the modes of the rotating turbine were also determined at several rotational speeds. The modes of the rotating system proved to be complex due to centrifugal and Coriolis effects. The modal data for the parked turbine were used to update a finite-element model. Also, the measured modal parameters for the rotating turbine were compared to the analytical results, thus verifying the analytical procedures used to incorporate the effects of the rotating coordinate system.

Wellbore inertial directional surveying system

DOEpatents

Andreas, R.D.; Heck, G.M.; Kohler, S.M.; Watts, A.C.

1982-09-08

A wellbore inertial directional surveying system for providing a complete directional survey of an oil or gas well borehole to determine the displacement in all three directions of the borehole path relative to the well head at the surface. The information generated by the present invention is especially useful when numerous wells are drilled to different geographical targets from a single offshore platform. Accurate knowledge of the path of the borehole allows proper well spacing and provides assurance that target formations are reached. The tool is lowered down into a borehole on an electrical cable. A computer positioned on the surface communicates with the tool via the cable. The tool contains a sensor block which is supported on a single gimbal, the rotation axis of which is aligned with the cylinder axis of the tool and, correspondingly, the borehole. The gyroscope measurement of the sensor block rotation is used in a null-seeking servo loop which essentially prevents rotation of the sensor block about the gimbal axis. Angular rates of the sensor block about axes which are perpendicular to te gimbal axis are measured by gyroscopes in a manner similar to a strapped-down arrangement. Three accelerometers provide acceleration information as the tool is lowered within the borehole. The uphole computer derives position information based upon acceleration information and angular rate information. Kalman estimation techniques are used to compensate for system errors. 25 figures.

Wellbore inertial directional surveying system

DOEpatents

Andreas, Ronald D.; Heck, G. Michael; Kohler, Stewart M.; Watts, Alfred C.

1991-01-01

A wellbore inertial directional surveying system for providing a complete directional survey of an oil or gas well borehole to determine the displacement in all three directions of the borehole path relative to the well head at the surface. The information generated by the present invention is especially useful when numerous wells are drilled to different geographical targets from a single off-shore platform. Accurate knowledge of the path of the borehole allows proper well spacing and provides assurance that target formations are reached. The tool is lowered down into a borehole on the electrical cable. A computer positioned on the surface communicates with the tool via the cable. The tool contains a sensor block which is supported on a single gimbal, the rotation axis of which is aligned with the cylinder axis of the tool and, correspondingly, the borehole. The gyroscope measurement of the sensor block rotation is used in a null-seeking servo loop which essentially prevents rotation of the sensor block aboutthe gimbal axis. Angular rates of the sensor block about axes which are perpendicular to the gimbal axis are measured by gyroscopes in a manner similar to a strapped-down arrangement. Three accelerometers provide acceleration information as the tool is lowered within the borehole. The uphole computer derives position information based upon acceleration information and anular rate information. Kalman estimation techniques are used to compensate for system errors.

Study protocol of physical activity and sedentary behaviour measurement among schoolchildren by accelerometry--cross-sectional survey as part of the ENERGY-project.

PubMed

Yıldırım, Mine; Verloigne, Maïté; de Bourdeaudhuij, Ilse; Androutsos, Odysseas; Manios, Yannis; Felso, Regina; Kovács, Éva; Doessegger, Alain; Bringolf-Isler, Bettina; te Velde, Saskia J; Brug, Johannes; Chinapaw, Mai J M

2011-03-25

Physical activity and sedentary behaviour among children should be measured accurately in order to investigate their relationship with health. Accelerometry provides objective and accurate measurement of body movement, which can be converted to meaningful behavioural outcomes. The aim of this study was to evaluate the best evidence for the decisions on data collection and data processing with accelerometers among children resulting in a standardized protocol for use in the participating countries. This cross-sectional accelerometer study was conducted as part of the European ENERGY-project that aimed to produce an obesity prevention intervention among schoolchildren. Five countries, namely Belgium, Greece, Hungary, Switzerland and the Netherlands participated in the accelerometer study. We used three different Actigraph models--Actitrainers (triaxial), GT3Xs and GT1Ms. Children wore the device for six consecutive days including two weekend days. We selected an epoch length of 15 seconds. Accelerometers were placed at children's waist at the right side of the body in an elastic belt. In total, 1082 children participated in the study (mean age = 11.7 ± 0.75 y, 51% girls). Non-wearing time was calculated as periods of more than 20 minutes of consecutive zero counts. The minimum daily wearing time was set to 10 hours for weekdays and 8 hours for weekend days. The inclusion criterion for further analysis was having at least three valid weekdays and one valid weekend day. We selected a cut-point (count per minute (cpm)) of <100 cpm for sedentary behaviour, <3000 cpm for light, <5200 cpm for moderate, and >5200 cpm for vigorous physical activity. We also created time filters for school-time during data cleaning in order to explore school-time physical activity and sedentary behaviour patterns in particular. This paper describes the decisions for data collection and processing. Use of standardized protocols would ease future use of accelerometry and the comparability of results between studies.

International study of objectively measured physical activity and sedentary time with body mass index and obesity: IPEN adult study.

PubMed

Van Dyck, D; Cerin, E; De Bourdeaudhuij, I; Hinckson, E; Reis, R S; Davey, R; Sarmiento, O L; Mitas, J; Troelsen, J; MacFarlane, D; Salvo, D; Aguinaga-Ontoso, I; Owen, N; Cain, K L; Sallis, J F

2015-02-01

Physical activity (PA) has been consistently implicated in the etiology of obesity, whereas recent evidence on the importance of sedentary time remains inconsistent. Understanding of dose-response associations of PA and sedentary time with overweight and obesity in adults can be improved with large-scale studies using objective measures of PA and sedentary time. The purpose of this study was to examine the strength, direction and shape of dose-response associations of accelerometer-based PA and sedentary time with body mass index (BMI) and weight status in 10 countries, and the moderating effects of study site and gender. Data from the International Physical activity and the Environment Network (IPEN) Adult study were used. IPEN Adult is an observational multi-country cross-sectional study, and 12 sites in 10 countries are included. Participants wore an accelerometer for seven consecutive days, completed a socio-demographic questionnaire and reported height and weight. In total, 5712 adults (18-65 years) were included in the analyses. Generalized additive mixed models, conducted in R, were used to estimate the strength and shape of the associations. A curvilinear relationship of accelerometer-based moderate-to-vigorous PA and total counts per minute with BMI and the probability of being overweight/obese was identified. The associations were negative, but weakened at higher levels of moderate-to-vigorous PA (>50 min per day) and higher counts per minute. No associations between sedentary time and weight outcomes were found. Complex site- and gender-specific findings were revealed for BMI, but not for weight status. On the basis of these results, the current Institute of Medicine recommendation of 60 min per day of moderate-to-vigorous PA to prevent weight gain in normal-weight adults was supported. No relationship between sedentary time and the weight outcomes was present, calling for further examination. If moderator findings are confirmed, the relationship between PA and BMI may be country- and gender-dependent, which could have important implications for country-specific health guidelines.

International Study of Objectively-measured Physical Activity and Sedentary Time with Body Mass Index and Obesity: IPEN Adult Study

PubMed Central

Van Dyck, Delfien; Cerin, Ester; De Bourdeaudhuij, Ilse; Hinckson, Erica; Reis, Rodrigo S; Davey, Rachel; Sarmiento, Olga Lucia; Mitas, Josef; Troelsen, Jens; MacFarlane, Duncan; Salvo, Deborah; Aguinaga-Ontoso, Ines; Owen, Neville; Cain, Kelli L; Sallis, James F

2014-01-01

Background Physical activity (PA) has been consistently implicated in the etiology of obesity, while recent evidence on the importance of sedentary time remains inconsistent. Understanding of dose-response associations of PA and sedentary time with overweight and obesity in adults can be improved with large-scale studies using objective measures of PA and sedentary time. The purpose of this study was to examine the strength, direction and shape of dose-response associations of accelerometer-based PA and sedentary time with BMI and weight status in 10 countries, and the moderating effects of study site and gender. Methods Data from the International Physical activity and the Environment Network (IPEN) Adult study were used. IPEN Adult is an observational multi-country cross-sectional study, and 12 sites in 10 countries are included. Participants wore an accelerometer for seven consecutive days, completed a socio-demographic questionnaire and reported height and weight. In total, 5712 adults (18–65 years) were included in the analyses. Generalized additive mixed models, conducted in R, were used to estimate the strength and shape of the associations. Results A curvilinear relationship of accelerometer-based moderate-to-vigorous PA and total counts/minute with BMI and the probability of being overweight/obese was identified. The associations were negative, but weakened at higher levels of moderate-to-vigorous PA (>50 min/day) and higher counts/minute. No associations between sedentary time and weight outcomes were found. Complex site- and gender-specific findings were revealed for BMI, but not for weight status. Conclusions Based on these results, the current Institute of Medicine recommendation of 60 minutes/day of moderate-to-vigorous PA to prevent weight gain in normal-weight adults was supported. No relationship between sedentary time and the weight outcomes was present, calling for further examination. If moderator findings are confirmed, the relationship between PA and BMI may be country- and gender-dependent, which could have important implications for country-specific health guidelines. PMID:24984753

Nonlinear dual-axis biodynamic response of the semi-supine human body during vertical whole-body vibration

NASA Astrophysics Data System (ADS)

Huang, Ya; Griffin, Michael J.

2008-04-01

Nonlinear biodynamic responses are evident in many studies of the apparent masses of sitting and standing subjects in static postures that require muscle activity for postural control. In the present study, 12 male subjects adopted a relaxed semi-supine posture assumed to involve less muscle activity than during static sitting and standing. The supine subjects were exposed to two types of vertical vibration (in the x-axis of the semi-supine body): (i) continuous random vibration (0.25-20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75, and 1.0 m s -2 rms); (ii) intermittent random vibration (0.25-20 Hz) alternately at 0.25 and 1.0 m s -2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 10.35 to 7.32 Hz as the vibration magnitude increased from 0.125 to 1.0 m s -2 rms. This nonlinear response was apparent in both the vertical ( x-axis) apparent mass and in the horizontal ( z-axis) cross-axis apparent mass. As the vibration magnitude increased from 0.25 to 1.0 m s -2 rms, the median resonance frequency of the apparent mass with intermittent random vibration decreased from 9.28 to 8.06 Hz whereas, over the same range of magnitudes with continuous random vibration, the resonance frequency decreased from 9.62 to 7.81 Hz. The median change in the resonance frequency (between 0.25 and 1.0 m s -2 rms) was 1.37 Hz with the intermittent random vibration and 1.71 with the continuous random vibration. With the intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration of the same magnitudes. The response was typical of thixotropy that may be a primary cause of the nonlinear biodynamic responses to whole-body vibration.

What are the associations between neighbourhood walkability and sedentary time in New Zealand adults? The URBAN cross-sectional study.

PubMed

Hinckson, Erica; Cerin, Ester; Mavoa, Surzanne; Smith, Melody; Badland, Hannah; Witten, Karen; Kearns, Robin; Schofield, Grant

2017-10-22

We estimated associations between objectively determined neighbourhood 'walkability' attributes and accelerometer-derived sedentary time (ST) by sex, city or type of day. A cross-sectional study. The URBAN (Understanding the Relationship between Activity and Neighbourhoods) study was conducted in 48 neighbourhoods across four cities in New Zealand (August 2008 to October 2010). The response rate was 41% (2029 recruited participants/5007 eligible households approached). In total, 1762 participants (aged 41.4±12.1, mean±SD) met the data inclusion criteria and were included in analyses. The exposure variables were geographical information system (GIS) measures of neighbourhood walkability (ie, street connectivity, residential density, land-use mix, retail footprint area ratio) for street network buffers of 500 m and 1000 m around residential addresses. Participants wore an accelerometer for 7 days. The outcome measure was average daily minutes of ST. Data were available from 1762 participants (aged 41.4±12.1 years; 58% women). No significant main effects of GIS-based neighbourhood walkability measures were found with ST. Retail footprint area ratio was negatively associated with sedentary time in women, significant only for 500 m residential buffers. An increase of 1 decile in street connectivity was significantly associated with a decrease of over 5 min of ST per day in Christchurch residents for both residential buffers. Neighbourhoods with proximal retail and higher street connectivity seem to be associated with less ST. These effects were sex and city specific. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Systematic Calibration for Ultra-High Accuracy Inertial Measurement Units.

PubMed

Cai, Qingzhong; Yang, Gongliu; Song, Ningfang; Liu, Yiliang

2016-06-22

An inertial navigation system (INS) has been widely used in challenging GPS environments. With the rapid development of modern physics, an atomic gyroscope will come into use in the near future with a predicted accuracy of 5 × 10(-6)°/h or better. However, existing calibration methods and devices can not satisfy the accuracy requirements of future ultra-high accuracy inertial sensors. In this paper, an improved calibration model is established by introducing gyro g-sensitivity errors, accelerometer cross-coupling errors and lever arm errors. A systematic calibration method is proposed based on a 51-state Kalman filter and smoother. Simulation results show that the proposed calibration method can realize the estimation of all the parameters using a common dual-axis turntable. Laboratory and sailing tests prove that the position accuracy in a five-day inertial navigation can be improved about 8% by the proposed calibration method. The accuracy can be improved at least 20% when the position accuracy of the atomic gyro INS can reach a level of 0.1 nautical miles/5 d. Compared with the existing calibration methods, the proposed method, with more error sources and high order small error parameters calibrated for ultra-high accuracy inertial measurement units (IMUs) using common turntables, has a great application potential in future atomic gyro INSs.

Gyro and Accelerometer Based Navigation System for a Mobile Autonomous Robot.

DTIC Science & Technology

1985-12-02

special thanks goes to our thesis advisor Dr. Matthew Kabrisky for having the confidence to turn us loose on this project. Additionally, we would...Wordmaster Word Processor 1 Wordstar Word Processor 1 Virtual Devices Robo A 6802 Cross Assembler 1 Modem 720 Communication Program 1 CP/M Operating

Cation-induced folding of alginate-bearing bilayer gels: an unusual example of spontaneous folding along the long axis.

PubMed

Athas, Jasmin C; Nguyen, Catherine P; Kummar, Shailaa; Raghavan, Srinivasa R

2018-04-04

The spontaneous folding of flat gel films into tubes is an interesting example of self-assembly. Typically, a rectangular film folds along its short axis when forming a tube; folding along the long axis has been seen only in rare instances when the film is constrained. Here, we report a case where the same free-swelling gel film folds along either its long or short axis depending on the concentration of a solute. Our gels are sandwiches (bilayers) of two layers: a passive layer of cross-linked N,N'-dimethylyacrylamide (DMAA) and an active layer of cross-linked DMAA that also contains chains of the biopolymer alginate. Multivalent cations like Ca2+ and Cu2+ induce these bilayer gels to fold into tubes. The folding occurs instantly when a flat film of the gel is introduced into a solution of these cations. The likely cause for folding is that the active layer stiffens and shrinks (because the alginate chains in it get cross-linked by the cations) whereas the passive layer is unaffected. The resulting mismatch in swelling degree between the two layers creates internal stresses that drive folding. Cations that are incapable of cross-linking alginate, such as Na+ and Mg2+, do not induce gel folding. Moreover, the striking aspect is the direction of folding. When the Ca2+ concentration is high (100 mM or higher), the gels fold along their long axis, whereas when the Ca2+ concentration is low (40 to 80 mM), the gels fold along their short axis. We hypothesize that the folding axis is dictated by the inhomogeneous nature of alginate-cation cross-linking, i.e., that the edges get cross-linked before the faces of the gel. At high Ca2+ concentration, the stiffer edges constrain the folding; in turn, the gel folds such that the longer edges are deformed less, which explains the folding along the long axis. At low Ca2+ concentration, the edges and the faces of the gel are more similar in their degree of cross-linking; therefore, the gel folds along its short axis. An analogy can be made to natural structures (such as leaves and seed pods) where stiff elements provide the directionality for folding.

Identification of biomechanical nonlinearity in whole-body vibration using a reverse path multi-input-single-output method

NASA Astrophysics Data System (ADS)

Huang, Ya; Ferguson, Neil S.

2018-04-01

The study implements a classic signal analysis technique, typically applied to structural dynamics, to examine the nonlinear characteristics seen in the apparent mass of a recumbent person during whole-body horizontal random vibration. The nonlinearity in the present context refers to the amount of 'output' that is not correlated or coherent to the 'input', usually indicated by values of the coherence function that are less than unity. The analysis is based on the longitudinal horizontal inline and vertical cross-axis apparent mass of twelve human subjects exposed to 0.25-20 Hz random acceleration vibration at 0.125 and 1.0 ms-2 r.m.s. The conditioned reverse path frequency response functions (FRF) reveal that the uncorrelated 'linear' relationship between physical input (acceleration) and outputs (inline and cross-axis forces) has much greater variation around the primary resonance frequency between 0.5 and 5 Hz. By reversing the input and outputs of the physical system, it is possible to assemble additional mathematical inputs from the physical output forces and mathematical constructs (e.g. square root of inline force). Depending on the specific construct, this can improve the summed multiple coherence at frequencies where the response magnitude is low. In the present case this is between 6 and 20 Hz. The statistical measures of the response force time histories of each of the twelve subjects indicate that there are potential anatomical 'end-stops' for the sprung mass in the inline axis. No previous study has applied this reverse path multi-input-single-output approach to human vibration kinematic and kinetic data before. The implementation demonstrated in the present study will allow new and existing data to be examined using this different analytical tool.

Microelectromechanical systems (MEMS) sensors based on lead zirconate titanate (PZT) films

NASA Astrophysics Data System (ADS)

Wang, Li-Peng

2001-12-01

In this thesis, modeling, fabrication and testing of microelectromechanical systems (MEMS) accelerometers based on piezoelectric lead zirconate titanate (PZT) films are investigated. Three different types of structures, cantilever beam, trampoline, and annular diaphragm, are studied. It demonstrates the high-performance, miniaturate, mass-production-compatible, and potentially circuitry-integratable piezoelectric-type PZT MEMS devices. Theoretical models of the cantilever-beam and trampoline accelerometers are derived via structural dynamics and the constitutive equations of piezoelectricity. The time-dependent transverse vibration equations, mode shapes, resonant frequencies, and sensitivities of the accelerometers are calculated through the models. Optimization of the silicon and PZT thickness is achieved with considering the effects of the structural dynamics, the material properties, and manufacturability for different accelerometer specifications. This work is the first demonstration of the fabrication of bulk-micromachined accelerometers combining a deep-trench reactive ion etching (DRIE) release strategy and thick piezoelectric PZT films deposited using a sol-gel method. Processing challenges which are overcome included materials compatibility, metallization, processing of thick layers, double-side processing, deep-trench silicon etching, post-etch cleaning and process integration. In addition, the processed PZT films are characterized by dielectric, ferroelectric (polarization electric-field hysteresis), and piezoelectric measurements and no adverse effects are found. Dynamic frequency response and impedance resonance measurements are performed to ascertain the performance of the MEMS accelerometers. The results show high sensitivities and broad frequency ranges of the piezoelectric-type PZT MEMS accelerometers; the sensitivities range from 0.1 to 7.6 pC/g for resonant frequencies ranging from 44.3 kHz to 3.7 kHz. The sensitivities were compared to theoretical values and a reasonable agreement (˜36% difference) is obtained.

Watch-Dog: Detecting Self-Harming Activities From Wrist Worn Accelerometers.

PubMed

Bharti, Pratool; Panwar, Anurag; Gopalakrishna, Ganesh; Chellappan, Sriram

2018-05-01

In a 2012 survey, in the United States alone, there were more than 35 000 reported suicides with approximately 1800 of being psychiatric inpatients. Recent Centers for Disease Control and Prevention (CDC) reports indicate an upward trend in these numbers. In psychiatric facilities, staff perform intermittent or continuous observation of patients manually in order to prevent such tragedies, but studies show that they are insufficient, and also consume staff time and resources. In this paper, we present the Watch-Dog system, to address the problem of detecting self-harming activities when attempted by in-patients in clinical settings. Watch-Dog comprises of three key components-Data sensed by tiny accelerometer sensors worn on wrists of subjects; an efficient algorithm to classify whether a user is active versus dormant (i.e., performing a physical activity versus not performing any activity); and a novel decision selection algorithm based on random forests and continuity indices for fine grained activity classification. With data acquired from 11 subjects performing a series of activities (both self-harming and otherwise), Watch-Dog achieves a classification accuracy of , , and for same-user 10-fold cross-validation, cross-user 10-fold cross-validation, and cross-user leave-one-out evaluation, respectively. We believe that the problem addressed in this paper is practical, important, and timely. We also believe that our proposed system is practically deployable, and related discussions are provided in this paper.

Are physical activity studies in Hispanics meeting reporting guidelines for continuous monitoring technology? A systematic review.

PubMed

Layne, Charles S; Parker, Nathan H; Soltero, Erica G; Rosales Chavez, José; O'Connor, Daniel P; Gallagher, Martina R; Lee, Rebecca E

2015-09-18

Continuous monitoring technologies such as accelerometers and pedometers are the gold standard for physical activity (PA) measurement. However, inconsistencies in use, analysis, and reporting limit the understanding of dose-response relationships involving PA and the ability to make comparisons across studies and population subgroups. These issues are particularly detrimental to the study of PA across different ethnicities with different PA habits. This systematic review examined the inclusion of published guidelines involving data collection, processing, and reporting among articles using accelerometers or pedometers in Hispanic or Latino populations. English (PubMed; EbscoHost) and Spanish (SCIELO; Biblioteca Virtual en Salud) articles published between 2000 and 2013 using accelerometers or pedometers to measure PA among Hispanics or Latinos were identified through systematic literature searches. Of the 253 abstracts which were initially reviewed, 57 met eligibility criteria (44 accelerometer, 13 pedometer). Articles were coded and reviewed to evaluate compliance with recommended guidelines (N = 20), and the percentage of accelerometer and pedometer articles following each guideline were computed and reported. On average, 57.1 % of accelerometer and 62.2 % of pedometer articles reported each recommended guideline for data collection. Device manufacturer and model were reported most frequently, and provision of instructions for device wear in Spanish was reported least frequently. On average, 29.6 % of accelerometer articles reported each guideline for data processing. Definitions of an acceptable day for inclusion in analyses were reported most frequently, and definitions of an acceptable hour for inclusion in analyses were reported least frequently. On average, 18.8 % of accelerometer and 85.7 % of pedometer articles included each guideline for data reporting. Accelerometer articles most frequently included average number of valid days and least frequently included percentage of wear time. Inclusion of standard collection and reporting procedures in studies using continuous monitoring devices in Hispanic or Latino population is generally low. Lack of reporting consistency in continuous monitoring studies limits researchers' ability to compare studies or draw meaningful conclusions concerning amounts, quality, and benefits of PA among Hispanic or Latino populations. Reporting data collection, computation, and decision-making standards should be required. Improved interpretability would allow practitioners and researchers to apply scientific findings to promote PA.

Validation of Accelerometer Prediction Equations in Children with Chronic Disease.

PubMed

Stephens, Samantha; Takken, Tim; Esliger, Dale W; Pullenayegum, Eleanor; Beyene, Joseph; Tremblay, Mark; Schneiderman, Jane; Biggar, Doug; Longmuir, Pat; McCrindle, Brian; Abad, Audrey; Ignas, Dan; Van Der Net, Janjaap; Feldman, Brian

2016-02-01

The purpose of this study was to assess the criterion validity of existing accelerometer-based energy expenditure (EE) prediction equations among children with chronic conditions, and to develop new prediction equations. Children with congenital heart disease (CHD), cystic fibrosis (CF), dermatomyositis (JDM), juvenile arthritis (JA), inherited muscle disease (IMD), and hemophilia (HE) completed 7 tasks while EE was measured using indirect calorimetry with counts determined by accelerometer. Agreement between predicted EE and measured EE was assessed. Disease-specific equations and cut points were developed and cross-validated. In total, 196 subjects participated. One participant dropped out before testing due to time constraints, while 15 CHD, 32 CF, 31 JDM, 31 JA, 30 IMD, 28 HE, and 29 healthy controls completed the study. Agreement between predicted and measured EE varied across disease group and ranged from (ICC) .13-.46. Disease-specific prediction equations exhibited a range of results (ICC .62-.88) (SE 0.45-0.78). In conclusion, poor agreement was demonstrated using current prediction equations in children with chronic conditions. Disease-specific equations and cut points were developed.

Passive cyclic pitch control for horizontal axis wind turbines

NASA Technical Reports Server (NTRS)

Bottrell, G. W.

1981-01-01

A flexible rotor concept, called the balanced pitch rotor, is described. The system provides passive adjustment of cyclic pitch in response to unbalanced pitching moments across the rotor disk. Various applications are described and performance predictions are made for wind shear and cross wind operating conditions. Comparisons with the teetered hub are made and significant cost savings are predicted.

Research on Robot Pose Control Technology Based on Kinematics Analysis Model

NASA Astrophysics Data System (ADS)

Liu, Dalong; Xu, Lijuan

2018-01-01

In order to improve the attitude stability of the robot, proposes an attitude control method of robot based on kinematics analysis model, solve the robot walking posture transformation, grasping and controlling the motion planning problem of robot kinematics. In Cartesian space analytical model, using three axis accelerometer, magnetometer and the three axis gyroscope for the combination of attitude measurement, the gyroscope data from Calman filter, using the four element method for robot attitude angle, according to the centroid of the moving parts of the robot corresponding to obtain stability inertia parameters, using random sampling RRT motion planning method, accurate operation to any position control of space robot, to ensure the end effector along a prescribed trajectory the implementation of attitude control. The accurate positioning of the experiment is taken using MT-R robot as the research object, the test robot. The simulation results show that the proposed method has better robustness, and higher positioning accuracy, and it improves the reliability and safety of robot operation.

Validity and reliability of the International Physical Activity Questionnaire among adults in Mexico.

PubMed

Medina, Catalina; Barquera, Simón; Janssen, Ian

2013-07-01

To determine the test-retest reliability and validity of the Spanish version of the short-form International Physical Activity Questionnaire (IPAQ) among adults in Mexico. This was a cross-sectional study of a convenience sample of 267 adult factory workers in Mexico City. Participants were 19 - 68 years of age; 48% were female. Participants wore an accelerometer for 9 consecutive days and were administered the Spanish version of the short form IPAQ on two occasions (IPAQ1 and IPAQ2, separated by 9 days). The relation and differences between moderate-to-vigorous physical activity (MVPA) measures obtained from IPAQ1, IPAQ2, and the accelerometer were determined using correlations, linear regression, and paired t-tests. IPAQ1 and IPAQ2 measures of MVPA were significantly correlated to each other (r = 0.55, P < 0.01). However, MVPA was 44 ± 408 minutes/week lower in IPAQ1 than in IPAQ2, although this difference did not reach statistical significance (P = 0.08). The (min/week) measures from IPAQ1 and IPAQ2 were only modestly correlated with the accelerometer measures (r = 0.26 and r = 0.31, P < 0.01), and by comparison to accelerometer measures, MVPA values were higher when based on IPAQ1 (174 ± 357 min/week, P < 0.01) than for IPAQ2 (135 ± 360 min/week, P < 0.01). The percentage of participants who were classified as physically inactive according to the World Health Organization guidelines was 18.0% in IPAQ1, 25.1% in IPAQ2, and 28.2% based on the accelerometer. Similar to what has been observed in other populations, the short form IPAQ has a modest reliability and poor validity for assessing MVPA among Mexican adults.

Step-Count Accuracy of 3 Motion Sensors for Older and Frail Medical Inpatients.

PubMed

McCullagh, Ruth; Dillon, Christina; O'Connell, Ann Marie; Horgan, N Frances; Timmons, Suzanne

2017-02-01

To measure the step-count accuracy of an ankle-worn accelerometer, a thigh-worn accelerometer, and a pedometer in older and frail inpatients. Cross-sectional design study. Research room within a hospital. Convenience sample of inpatients (N=32; age, ≥65 years) who were able to walk 20m independently with or without a walking aid. Patients completed a 40-minute program of predetermined tasks while wearing the 3 motion sensors simultaneously. Video recording of the procedure provided the criterion measurement of step count. Mean percentage errors were calculated for all tasks, for slow versus fast walkers, for independent walkers versus walking-aid users, and over shorter versus longer distances. The intraclass correlation was calculated, and accuracy was graphically displayed by Bland-Altman plots. Thirty-two patients (mean age, 78.1±7.8y) completed the study. Fifteen (47%) were women, and 17 (51%) used walking aids. Their median speed was .46m/s (interquartile range [IQR], .36-.66m/s). The ankle-worn accelerometer overestimated steps (median error, 1% [IQR, -3% to 13%]). The other motion sensors underestimated steps (median error, 40% [IQR, -51% to -35%] and 38% [IQR -93% to -27%], respectively). The ankle-worn accelerometer proved to be more accurate over longer distances (median error, 3% [IQR, 0%-9%]) than over shorter distances (median error, 10% [IQR, -23% to 9%]). The ankle-worn accelerometer gave the most accurate step-count measurement and was most accurate over longer distances. Neither of the other motion sensors had acceptable margins of error. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Reliability and validity of two multidimensional self-reported physical activity questionnaires in people with chronic low back pain.

PubMed

Carvalho, Flávia A; Morelhão, Priscila K; Franco, Marcia R; Maher, Chris G; Smeets, Rob J E M; Oliveira, Crystian B; Freitas Júnior, Ismael F; Pinto, Rafael Z

2017-02-01

Although there is some evidence for reliability and validity of self-report physical activity (PA) questionnaires in the general adult population, it is unclear whether we can assume similar measurement properties in people with chronic low back pain (LBP). To determine the test-retest reliability of the International Physical Activity Questionnaire (IPAQ) long-version and the Baecke Physical Activity Questionnaire (BPAQ) and their criterion-related validity against data derived from accelerometers in patients with chronic LBP. Cross-sectional study. Patients with non-specific chronic LBP were recruited. Each participant attended the clinic twice (one week interval) and completed self-report PA. Accelerometer measures >7 days included time spent in moderate-and-vigorous physical activity, steps/day, counts/minute, and vector magnitude counts/minute. Intraclass Correlation Coefficients (ICC) and Bland and Altman method were used to determine reliability and spearman rho correlation were used for criterion-related validity. A total of 73 patients were included in our analyses. The reliability analyses revealed that the BPAQ and its subscales have moderate to excellent reliability (ICC 2,1 : 0.61 to 0.81), whereas IPAQ and most IPAQ domains (except walking) showed poor reliability (ICC 2,1 : 0.20 to 0.40). The Bland and Altman method revealed larger discrepancies for the IPAQ. For the validity analysis, questionnaire and accelerometer measures showed at best fair correlation (rho < 0.37). Although the BPAQ showed better reliability than the IPAQ long-version, both questionnaires did not demonstrate acceptable validity against accelerometer data. These findings suggest that questionnaire and accelerometer PA measures should not be used interchangeably in this population. Copyright © 2016 Elsevier Ltd. All rights reserved.

FPGA-based fused smart-sensor for tool-wear area quantitative estimation in CNC machine inserts.

PubMed

Trejo-Hernandez, Miguel; Osornio-Rios, Roque Alfredo; de Jesus Romero-Troncoso, Rene; Rodriguez-Donate, Carlos; Dominguez-Gonzalez, Aurelio; Herrera-Ruiz, Gilberto

2010-01-01

Manufacturing processes are of great relevance nowadays, when there is a constant claim for better productivity with high quality at low cost. The contribution of this work is the development of a fused smart-sensor, based on FPGA to improve the online quantitative estimation of flank-wear area in CNC machine inserts from the information provided by two primary sensors: the monitoring current output of a servoamplifier, and a 3-axis accelerometer. Results from experimentation show that the fusion of both parameters makes it possible to obtain three times better accuracy when compared with the accuracy obtained from current and vibration signals, individually used.

Multi-Parameter Wireless Monitoring and Telecommand of a Rocket Payload: Design and Implementation

NASA Astrophysics Data System (ADS)

Pamungkas, Arga C.; Putra, Alma A.; Puspitaningayu, Pradini; Fransisca, Yulia; Widodo, Arif

2018-04-01

A rocket system generally consists of two parts, the rocket motor and the payload. The payload system is built of several sensors such as accelerometer, gyroscope, magnetometer, and also a surveillance camera. These sensors are used to monitor the rocket in a three-dimensional axis which determine its attitude. Additionally, the payload must be able to perform image capturing in a certain distance using telecommand. This article is intended to describe the design and also the implementation of a rocket payload which has attitude monitoring and telecommand ability from the ground control station using a long-range wireless module Digi XBee Pro 900 HP.

The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind-magnetosphere-ionosphere coupling

NASA Astrophysics Data System (ADS)

Cnossen, Ingrid; Wiltberger, Michael; Ouellette, Jeremy E.

2012-11-01

The angle μ between the geomagnetic dipole axis and the geocentric solar magnetospheric (GSM) z axis, sometimes called the “dipole tilt,” varies as a function of UT and season. Observations have shown that the cross-polar cap potential tends to maximize near the equinoxes, when on average μ = 0, with smaller values observed near the solstices. This is similar to the well-known semiannual variation in geomagnetic activity. We use numerical model simulations to investigate the role of two possible mechanisms that may be responsible for the influence of μ on the magnetosphere-ionosphere system: variations in the coupling efficiency between the solar wind and the magnetosphere and variations in the ionospheric conductance over the polar caps. Under southward interplanetary magnetic field (IMF) conditions, variations in ionospheric conductance at high magnetic latitudes are responsible for 10-30% of the variations in the cross-polar cap potential associated with μ, but variations in solar wind-magnetosphere coupling are more important and responsible for 70-90%. Variations in viscous processes contribute slightly to this, but variations in the reconnection rate with μ are the dominant cause. The variation in the reconnection rate is primarily the result of a variation in the length of the section of the separator line along which relatively strong reconnection occurs. Changes in solar wind-magnetosphere coupling also affect the field-aligned currents, but these are influenced as well by variations in the conductance associated with variations in μ, more so than the cross-polar cap potential. This may be the case for geomagnetic activity too.

Dynamical response of the Galileo Galilei on the ground rotor to test the equivalence principle: Theory, simulation, and experiment. II. The rejection of common mode forces

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

Comandi, G.L.; Toncelli, R.; Chiofalo, M.L.

'Galileo Galilei on the ground' (GGG) is a fast rotating differential accelerometer designed to test the equivalence principle (EP). Its sensitivity to differential effects, such as the effect of an EP violation, depends crucially on the capability of the accelerometer to reject all effects acting in common mode. By applying the theoretical and simulation methods reported in Part I of this work, and tested therein against experimental data, we predict the occurrence of an enhanced common mode rejection of the GGG accelerometer. We demonstrate that the best rejection of common mode disturbances can be tuned in a controlled way bymore » varying the spin frequency of the GGG rotor.« less

Dynamic Docking Test System (DDTS) active table frequency response test results. [Apollo Soyuz Test Project

NASA Technical Reports Server (NTRS)

Gates, R. M.

1974-01-01

Results are presented of the frequency response test performed on the dynamic docking test system (DDTS) active table. Sinusoidal displacement commands were applied to the table and the dynamic response determined from measured actuator responses and accelerometers mounted to the table and one actuator.

Acceleration ground test program to verify GAS payload No. 559 structure/support avionics and experiment structural integrity

NASA Technical Reports Server (NTRS)

Cassanto, John M.; Cassanto, Valerie A.

1988-01-01

Acceleration ground tests were conducted on the Get Away Special (GAS) payload 559 to verify the structural integrity of the structure/support avionics and two of the planned three flight experiments. The ITA (Integrated Test Area) Standardized Experiment Module (ISEM) structure was modified to accommodate the experiments for payload 559. The ISEM avionics consisted of a heavy duty sliver zinc power supply, three orthogonal-mounted low range microgravity accelerometers, a tri-axis high range accelerometer, a solid state recorder/programmer sequencer, and pressure and temperature sensors. The tests were conducted using the Gravitational Plant Physiology Laboratory Centrifuge of the University City Science Center in Philadelphia, PA. The launch-powered flight steady state acceleration profile of the shuttle was simulated from lift-off through jettison of the External Tank (3.0 g's). Additional tests were conducted at twice the nominal powered flight acceleration levels (6 g's) and an over-test condition of four times the powered flight loads to 12.6 g's. The present test program has demonstrated the value of conducting ground tests to verify GAS payload experiment integrity and operation before flying on the shuttle.

Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters

PubMed Central

Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg; Fernández, Eduardo

2010-01-01

In this paper, the least-mean-squares (LMS) algorithm was used to eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications. This kind of accelerometer is designed to be easily mounted in hard to reach places on vehicles under test, and they usually feature ranges from 50 to 2,000 g (where is the gravitational acceleration, 9.81 m/s2) and frequency responses to 3,000 Hz or higher, with DC response, durable cables, reliable performance and relatively low cost. However, here we show that the response of the sensor under test had a lot of noise and we carried out the signal processing stage by using both conventional and optimal adaptive filtering. Usually, designers have to build their specific analog and digital signal processing circuits, and this fact increases considerably the cost of the entire sensor system and the results are not always satisfactory, because the relevant signal is sometimes buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency band. Thus, in order to deal with this problem, here we used the LMS adaptive filtering algorithm and compare it with others based on the kind of filters that are typically used for automotive applications. The experimental results are satisfactory. PMID:22315542

Luman/CREB3 Recruitment Factor Regulates Glucocorticoid Receptor Activity and Is Essential for Prolactin-Mediated Maternal Instinct

PubMed Central

Martyn, Amanda C.; Choleris, Elena; Gillis, Daniel J.; Armstrong, John N.; Amor, Talya R.; McCluggage, Adam R. R.; Turner, Patricia V.; Liang, Genqing; Cai, Kimberly

2012-01-01

The hypothalamic-pituitary-adrenal (HPA) axis is a major part of the neuroendocrine system in animal responses to stress. It is known that the HPA axis is attenuated at parturition to prevent detrimental effects of glucocorticoid secretion including inhibition of lactation and maternal responsiveness. Luman/CREB3 recruitment factor (LRF) was identified as a negative regulator of CREB3 which is involved in the endoplasmic reticulum stress response. Here, we report a LRF gene knockout mouse line that has a severe maternal behavioral defect. LRF−/− females lacked the instinct to tend pups; 80% of their litters died within 24 h, while most pups survived if cross-fostered. Prolactin levels were significantly repressed in lactating LRF−/− dams, with glucocorticoid receptor (GR) signaling markedly augmented. In cell culture, LRF repressed transcriptional activity of GR and promoted its protein degradation. LRF was found to colocalize with the known GR repressor, RIP140/NRIP1, which inhibits the activity by GR within specific nuclear punctates that are similar to LRF nuclear bodies. Furthermore, administration of prolactin or the GR antagonist RU486 restored maternal responses in mutant females. We thus postulate that LRF plays a critical role in the attenuation of the HPA axis through repression of glucocorticoid stress signaling during parturition and the postpartum period. PMID:23071095

Mapping the Diagnosis Axis of an Interface Terminology to the NANDA International Taxonomy

PubMed Central

Juvé Udina, Maria-Eulàlia; Gonzalez Samartino, Maribel; Matud Calvo, Cristina

2012-01-01

Background. Nursing terminologies are designed to support nursing practice but, as with any other clinical tool, they should be evaluated. Cross-mapping is a formal method for examining the validity of the existing controlled vocabularies. Objectives. The study aims to assess the inclusiveness and expressiveness of the nursing diagnosis axis of a newly implemented interface terminology by cross-mapping with the NANDA-I taxonomy. Design/Methods. The study applied a descriptive design, using a cross-sectional, bidirectional mapping strategy. The sample included 728 concepts from both vocabularies. Concept cross-mapping was carried out to identify one-to-one, negative, and hierarchical connections. The analysis was conducted using descriptive statistics. Results. Agreement of the raters' mapping achieved 97%. More than 60% of the nursing diagnosis concepts in the NANDA-I taxonomy were mapped to concepts in the diagnosis axis of the new interface terminology; 71.1% were reversely mapped. Conclusions. Main results for outcome measures suggest that the diagnosis axis of this interface terminology meets the validity criterion of cross-mapping when mapped from and to the NANDA-I taxonomy. PMID:22830046

Mapping the Diagnosis Axis of an Interface Terminology to the NANDA International Taxonomy.

PubMed

Juvé Udina, Maria-Eulàlia; Gonzalez Samartino, Maribel; Matud Calvo, Cristina

2012-01-01

Background. Nursing terminologies are designed to support nursing practice but, as with any other clinical tool, they should be evaluated. Cross-mapping is a formal method for examining the validity of the existing controlled vocabularies. Objectives. The study aims to assess the inclusiveness and expressiveness of the nursing diagnosis axis of a newly implemented interface terminology by cross-mapping with the NANDA-I taxonomy. Design/Methods. The study applied a descriptive design, using a cross-sectional, bidirectional mapping strategy. The sample included 728 concepts from both vocabularies. Concept cross-mapping was carried out to identify one-to-one, negative, and hierarchical connections. The analysis was conducted using descriptive statistics. Results. Agreement of the raters' mapping achieved 97%. More than 60% of the nursing diagnosis concepts in the NANDA-I taxonomy were mapped to concepts in the diagnosis axis of the new interface terminology; 71.1% were reversely mapped. Conclusions. Main results for outcome measures suggest that the diagnosis axis of this interface terminology meets the validity criterion of cross-mapping when mapped from and to the NANDA-I taxonomy.

Traveling Atmospheric Disturbances (TADs) in the thermosphere inferred from accelerometer data at three altitudes

NASA Astrophysics Data System (ADS)

Bruinsma, Sean; Forbes, Jeffrey

2010-05-01

Densities derived from accelerometer measurements on the GRACE, CHAMP and Air Force/SETA satellites near 490, 390, and 220 km, respectively, are used to elucidate global-scale characteristics of traveling atmospheric disturbances. The accelerometers on the CHAMP and GRACE satellites have made it possible to accumulate near-continuous records of thermosphere density between about 320 and 490 km since May 2001, and July 2002, respectively. They have recorded the response to virtually every significant geomagnetic storm during this period. CHAMP and GRACE are in (near) polar and quasi-circular orbits, sampling 24 hr local time approximately every 4 and 5 months, respectively. These capabilities offer unique opportunities to study the temporal and latitudinal responses of the thermosphere to geomagnetic disturbances. The Air Force/SETA accelerometer data have also been processed, but the analysis is more complicated due to data gaps. Significant and unambiguous TAD activity in the observed response of the thermosphere was detected for about 25 events with CHAMP and GRACE, and less than 10 with SETA. The atmospheric variability is evaluated by de-trending the data, allowing the extraction of specific ranges in horizontal scale, and analyzing density "residuals". The scale of the perturbation is decisive for its lifetime and relative amplitude. Sometimes the disturbances represent wave-like structures propagating far from the source, and these so-called ‘TADs' were detected and described for the May 2003 storm for the first time. Some TADs traveled over the pole into the opposite hemisphere; this was found in both CHAMP and GRACE data. Most TADs propagate equatorward, but poleward propagating TADs have on occasion been detected too. The estimated speeds and amplitudes of the observed TADs, and their dependence on altitude and solar and geomagnetic activity in particular, will be presented in this poster.

Male and female WorldSID and post mortem human subject responses in full-scale vehicle tests.

PubMed

Yoganandan, Narayan; Humm, John; Pintar, Frank; Rhule, Heather; Moorhouse, Kevin; Suntay, Brian; Stricklin, Jim; Rudd, Rodney; Craig, Matthew

2017-05-29

This study compares the responses of male and female WorldSID dummies with post mortem human subject (PMHS) responses in full-scale vehicle tests. Tests were conducted according to the FMVSS-214 protocols and using the U.S. Side Impact New Car Assessment Program change in velocity to match PMHS experiments, published earlier. Moving deformable barrier (MDB) tests were conducted with the male and female surrogates in the left front and left rear seats. Pole tests were performed with the male surrogate in the left front seat. Three-point belt restraints were used. Sedan-type vehicles were used from the same manufacturer with side airbags. The PMHS head was instrumented with a pyramid-shaped nine-axis accelerometer package, with angular velocity transducers on the head. Accelerometers and angular velocity transducers were secured to T1, T6, and T12 spinous processes and sacrum. Three chest bands were secured around the upper, middle, and lower thoraces. Dummy instrumentation included five infrared telescoping rods for assessment of chest compression (IR-TRACC) and a chest band at the first abdomen rib, head angular velocity transducer, and head, T1, T4, T12, and pelvis accelerometers. Morphological responses of the kinematics of the head, thoracic spine, and pelvis matched in both surrogates for each pair. The peak magnitudes of the torso accelerations were lower for the dummy than for the biological surrogate. The brain rotational injury criterion (BrIC) response was the highest in the male dummy for the MDB test and PMHS. The probability of AIS3+ injuries, based on the head injury criterion, ranged from 3% to 13% for the PMHS and from 3% to 21% for the dummy from all tests. The BrIC-based metrics ranged from 0 to 21% for the biological and 0 to 48% for the dummy surrogates. The deflection profiles from the IR-TRACC sensors were unimodal. The maximum deflections from the chest band placed on the first abdominal rib were 31.7 mm and 25.4 mm for the male and female dummies in the MDB test, and 37.4 mm for the male dummy in the pole test. The maximum deflections computed from the chest band contours at a gauge equivalent to the IR-TRACC location were 25.9 mm and 14.8 mm for the male and female dummies in the MDB test, and 37.4 mm for the male dummy in the pole test. Other data (static vehicle deformation profiles, accelerations histories of different body regions, and chest band contours for the dummy and PMHS) are given in the appendix. This is the first study to compare the responses of PMHS and male and female dummies in MDB and pole tests, done using the same recent model year vehicles with side airbag and head curtain restraints. The differences between the dummy and PMHS torso accelerations suggest the need for design improvements in the WorldSID dummy. The translation-based metrics suggest low probability of head injury. As the dummy internal sensor underrecorded the peak deflection, multipoint displacement measures are therefore needed for a more accurate quantification of deflection to improve the safety assessment of occupants.

Screening of inorganic gases released from firework-rockets by a gas chromatography/whistle-accelerometer method.

PubMed

Chen, Kuan-Fu; Wu, Hui-Hsin; Lin, Chien-Hung; Lin, Cheng-Huang

2013-08-30

The use of an accelerometer for detecting inorganic gases in gas chromatography (GC) is described. A milli-whistle was connected to the outlet of the GC capillary and was used instead of a classical GC detector. When the GC carrier gases and the sample gases pass through the milli-whistle, a sound is produced, leading to vibrational changes, which can be recorded using an accelerometer. Inorganic gases, including SO2, N2 and CO2, which are released from traditional Chinese firework-rockets at relatively high levels as the result of burning the propellant and explosive material inside could be rapidly determined using the GC/whistle-accelerometer system. The method described herein is safe, the instrumentation is compact and has potential to be modified so as to be portable for use in the field. It also can be used in conjunction with FID (flame ionization detector) or TCD (thermal conductivity detector), in which either no response for FID (CO2, N2, NO2, SO2, etc.) or helium gas is needed for TCD, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Water Stress Impacts Tree-Atmosphere Interaction in the Amazon

NASA Astrophysics Data System (ADS)

van Emmerik, T. H. M.; Steele-Dunne, S. C.; Gentine, P.; Oliveira, R. S.; Van De Giesen, N.

2017-12-01

Land-atmosphere interactions depend on momentum exchange from the atmosphere to the canopy, which depends on the tree drag coefficient. It is known that the drag coefficient, and thus tree-atmosphere interaction, can vary strongly within a canopy. Yet, only few measurements are available to study the variation of tree-atmosphere interaction in time and space, and in response to vegetation water stress. Recent work [1] demonstrated how accelerometers can be used to study tree properties and responses. For this study, accelerometers were used to derive a measure of tree-atmosphere interaction for 19 individual trees of seven different species in the Brazilian Amazon. This study demonstrates that under field conditions, tree-atmosphere interaction can vary considerably in time and space. The five month measurement period included the transitioning from the wet to the dry season. We demonstrate that increased tree water deficit, measured with dendrometers, is related to observed changes in tree-atmosphere interaction, which is hypothesized to be caused by water stress induced changes in tree mass. References [1]. van Emmerik, T.; Steele-Dunne, S.; Hut, R.; Gentine, P.; Guerin, M.; Oliveira, R.S.; Wagner, J.; Selker, J.; van de Giesen, N. Measuring Tree Properties and Responses Using Low-Cost Accelerometers. Sensors 2017, 17, 1098.

Aligned Carbon Nanotube Tape for Sensor Applications

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.

2013-01-01

For this effort, will concentrate on three applications: Vibration Gyroscope utilizes piezoelectric properties of the tape and Coriolis effect Accelerometer utilizes the piezoresistive property Strain Gauge utilizes piezoresistive property Accelerometer and Strain Gauge can also utilize piezoelectric effect Test piezoelectric properties using facilities at the Microfabrication Laboratory (AMRDEC) . Enhance piezoelectric effect using polyvinylidine fluoride and P(VDF ]TrFE) which is readily polarizable .Spray matrix solution while winding fiber; Sandwich of CNT tape and PVDF film (DOE .Two Level) . Construct and test prototype vibration gyroscope . Construct and test prototype accelerometer using cantilever design . Test strain sensitivity of CNT tape against industrial strain gauge . Embed CNT tape in composite samples as well as on surface and test to failure (4 ]point bend) A piezoelectric device exhibits an electrical response from a mechanical applied stress. . A piezoelectric device has both capacitance and resistance properties in which by applying an electric field from a waveform will exert a mechanical stress that can be monitored for a response. . The typical waveform applied is a sinusoidal waveform of a defined voltage for a defined period. The defined voltage is driven from 0 volts to the positive defined volts then back to 0 and driven to negative defined volts then back to 0. . Example. Vmax set to 10V and period set to 10 ms. . Voltage will start at zero, go to 10 volts, return to zero, go to ]10 volts and return to zero during 10 ms. . Applying this electrical field to a DUT, the capacitance response and resistance response can be observed. CNT tape is easier to manufacture and cheaper than micromachining silicon or other ceramic piezoelectric used in gyroscopes and accelerometers CNT tape properties can be modified during manufacture for specific application CNT tape has enhanced mechanical and thermal properties in addition to unique electrical properties CNT tape as a strain gauge in Structural Health Monitoring will provide an excellent material to embed within composite structures

Discharge cell for optogalvanic spectroscopy having orthogonal relationship between the probe laser and discharge axis

NASA Technical Reports Server (NTRS)

Webster, C. R. (Inventor)

1986-01-01

A method and apparatus for an optogalvanic spectroscopy system are disclosed. Orthogonal geometry exists between the axis of a laser probe beam and the axis of a discharge created by a pair of spaced apart and longituduinally aligned high voltage electrodes. The electrodes are movable to permit adjustment of the location of a point in the discharge which is to irradiated by a laser beam crossing the discharge region. The cell dimensions are selected so that the cross section of the discharge region is substantly comparable in size to the cross section of the laser beam passing orthogonally through the discharge region.

Dynamic response of NASA Rotor Test Apparatus and Sikorsky S-76 hub mounted in the 80- by 120-Foot Wind Tunnel

NASA Technical Reports Server (NTRS)

Peterson, Randall L.; Hoque, Muhammed S.

1994-01-01

A shake test was conducted in the 80- by 120-Foot Wind Tunnel at NASA Ames Research Center, using the NASA Ames Rotor Test Apparatus (RTA) and the Sikorsky S-76 rotor hub. The primary objective of this shake test was to determine the modal properties of the RTA, the S-76 rotor hub, and the model support system installed in the wind tunnel. Random excitation was applied at the rotor hub, and vibration responses were measured using accelerometers mounted at various critical locations on the model and the model support system. Transfer functions were computed using the load cell data and the accelerometer responses. The transfer function data were used to compute the system modal parameters with the aid of modal analysis software.

The Application of Satellite Borne Accelerometer Data to the Study of Upper Atmosphere

NASA Astrophysics Data System (ADS)

Wang, H. B.

2010-10-01

The thesis studies some issues on the upper atmosphere based on the accelerometer data of CHAMP and GRACE-A/B satellites (Reigber et al. 2001, Tapley et al. 2004). The total atmospheric densities from 2002 to 2008 are computed from accelerometer measurements. Then the accuracies of three empirical density models such as CIRA72, DTM94 and NRLMSISE00 are evaluated. It shows that the mean errors of these models are about 22%, 26% and 27%, respectively. All of them underestimated the densities. For the years of Solar maximum (2002-2003), the models' errors exceed 30%, while for the years of Solar minimum (2007-2008), the errors are less than 15%. Three characteristics of density variation are studied, such as diurnal variation, seasonal variation and semi-annual variation. The results are: (1) The diurnal-amplitude in low-latitude region is about 1.3 at 470 km and 0.8 at 370 km. (2) The seasonal-amplitude is about 0.6 in the 60 degree region and 0.3 in the 30 degree region. (3) The semi-annual variation is related to the solar radiation. The stronger the radiation is, the greater the semi-annual-amplitude is. For example, it is about 0.32 with strong solar radiation and 0.20 with weak solar radiation. The effects of various solar indices on the model accuracy are also studied. It is shown that E10.7 could reduce the mean errors of models about 20%, and S10, Mg10, Y10 could reduce the standard deviations of models about 5%. To study the density response to magnetic storms, 52 storm events from 2003 to 2007 (ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/KP_AP) are chosen as examples. It is deduced that the index Dst is more suitable to describe the density variation than index Ap. The first response of density during the storm is very fast. In about 15 minutes after the storm onset, the density around the north and south poles would enhance about 40%~70%. However, the disturbance would take 2~6 hours to travel to the equator region. It is also found that the density response has seasonal difference and day-night difference. Concretely, the response in the summer hemisphere is stronger than that in the winter hemisphere, while the response in the dayside is greater than that in nightside. After the storm ends, the density would take 12~36 hours to recover to the level during the quiet time. The King-Hele method is applied to study the long-term variation of CHAMP inclination and estimate the angular velocity of atmosphere rotation. It is about 1.9 at CHAMP's height (the unit is the velocity of the earth rotation). On the other hand, the cross-track measurement of the accelerometer is used to study rotation velocity in detail. It is deduced that the velocity is about 1.8 at 370 km and 1.0 at 470 km, which is a little larger than the result in King-Hele (1971). A periodic variation of the velocity, which is about 130~160 days, is also found. The reason has not been discovered so far.

NASA Studies Lightning Storms Using High-Flying, Uninhabited Vehicle

NASA Technical Reports Server (NTRS)

2002-01-01

A NASA team studying the causes of electrical storms and their effects on our home planet achieved a milestone on August 21, 2002, completing the study's longest-duration research flight and monitoring four thunderstorms in succession. Based at the Naval Air Station Key West, Florida, researchers with the Altus Cumulus Electrification Study (ACES) used the Altus II remotely-piloted aircraft to study thunderstorms in the Atlantic Ocean off Key West and the west of the Everglades. Data obtained through sensors mounted to the aircraft will allow researchers in ACES to gauge elements such as lightning activity and the electrical environment in and around storms. By learning more about individual storms, scientists hope to better understand the global water and energy cycle, as well as climate variability. Contained in one portion of the aircraft is a three-axis magnetic search coil, which measures the AC magnetic field; a three-axis electric field change sensor; an accelerometer; and a three-axis magnetometer, which measures the DC magnetic field. With dual goals of gathering weather data safely and testing the adaptability of the uninhabited aircraft, the ACES study is a collaboration among the Marshall Space Flight Center, the University of Alabama in Huntsville, NASA's Goddard Space Flight Center in Greenbelt, Maryland, Pernsylvania State University in University Park, and General Atomics Aeronautical Systems, Inc.

Earth Science

NASA Image and Video Library

2002-08-01

A NASA team studying the causes of electrical storms and their effects on our home planet achieved a milestone on August 21, 2002, completing the study's longest-duration research flight and monitoring four thunderstorms in succession. Based at the Naval Air Station Key West, Florida, researchers with the Altus Cumulus Electrification Study (ACES) used the Altus II remotely-piloted aircraft to study thunderstorms in the Atlantic Ocean off Key West and the west of the Everglades. Data obtained through sensors mounted to the aircraft will allow researchers in ACES to gauge elements such as lightning activity and the electrical environment in and around storms. By learning more about individual storms, scientists hope to better understand the global water and energy cycle, as well as climate variability. Contained in one portion of the aircraft is a three-axis magnetic search coil, which measures the AC magnetic field; a three-axis electric field change sensor; an accelerometer; and a three-axis magnetometer, which measures the DC magnetic field. With dual goals of gathering weather data safely and testing the adaptability of the uninhabited aircraft, the ACES study is a collaboration among the Marshall Space Flight Center, the University of Alabama in Huntsville, NASA's Goddard Space Flight Center in Greenbelt, Maryland, Pernsylvania State University in University Park, and General Atomics Aeronautical Systems, Inc.

Designing on-Board Data Handling for EDF (Electric Ducted Fan) Rocket

NASA Astrophysics Data System (ADS)

Mulyana, A.; Faiz, L. A. A.

2018-02-01

The EDF (Electric Ducted Fan) rocket to launch requires a system of monitoring, tracking and controlling to allow the rocket to glide properly. One of the important components in the rocket is OBDH (On-Board Data Handling) which serves as a medium to perform commands and data processing. However, TTC (Telemetry, Tracking, and Command) are required to communicate between GCS (Ground Control Station) and OBDH on EDF rockets. So the design control system of EDF rockets and GCS for telemetry and telecommand needs to be made. In the design of integrated OBDH controller uses a lot of electronics modules, to know the behavior of rocket used IMU sensor (Inertial Measurement Unit) in which consist of 3-axis gyroscope sensor and Accelerometer 3-axis. To do tracking using GPS, compass sensor as a determinant of the direction of the rocket as well as a reference point on the z-axis of gyroscope sensor processing and used barometer sensors to measure the height of the rocket at the time of glide. The data can be known in real-time by sending data through radio modules at 2.4 GHz frequency using XBee-Pro S2B to GCS. By using windows filter, noises can be reduced, and it used to guarantee monitoring and controlling system can work properly.

VO2 estimation using 6-axis motion sensor with sports activity classification.

PubMed

Nagata, Takashi; Nakamura, Naoteru; Miyatake, Masato; Yuuki, Akira; Yomo, Hiroyuki; Kawabata, Takashi; Hara, Shinsuke

2016-08-01

In this paper, we focus on oxygen consumption (VO2) estimation using 6-axis motion sensor (3-axis accelerometer and 3-axis gyroscope) for people playing sports with diverse intensities. The VO2 estimated with a small motion sensor can be used to calculate the energy expenditure, however, its accuracy depends on the intensities of various types of activities. In order to achieve high accuracy over a wide range of intensities, we employ an estimation framework that first classifies activities with a simple machine-learning based classification algorithm. We prepare different coefficients of linear regression model for different types of activities, which are determined with training data obtained by experiments. The best-suited model is used for each type of activity when VO2 is estimated. The accuracy of the employed framework depends on the trade-off between the degradation due to classification errors and improvement brought by applying separate, optimum model to VO2 estimation. Taking this trade-off into account, we evaluate the accuracy of the employed estimation framework by using a set of experimental data consisting of VO2 and motion data of people with a wide range of intensities of exercises, which were measured by a VO2 meter and motion sensor, respectively. Our numerical results show that the employed framework can improve the estimation accuracy in comparison to a reference method that uses a common regression model for all types of activities.

A spaceborne superconducting gravity gradiometer for mapping the earth's gravity field

NASA Technical Reports Server (NTRS)

Paik, H. J.

1981-01-01

The principles of a satellite gravity gradiometer system which measures all five independent components of the gravity gradient tensor with a sensitivity of 0.001 E/Hz to the 1/2 power or better, are analyzed, and the status of development of the system is reviewed. The superconducting gravity gradiometer uses sensitive superconducting accelerometers, each of which are composed of a weakly suspended superconducting proof mass, a superconducting magnetic transducer, and a low-noise superconducting magnetometer. The magnetic field produced by the transducer coils is modulated by the motion of the proof mass and detected by the magnetometer. A combination of two or four of such accelerometers with proper relative orientation of sensitive axes results in an in-line or a cross component gravity gradiometer.

Environmental factors associated with long-term changes in chlorophyll concentration in the Sacramento-San Joaquin delta and Suisun Bay, California

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

Lehman, P.W.

Long-term changes in chlorophyll concentration were predicted from environmental variables using Box-Jenkins transfer function models for the Sacramento and San Joaquin rivers and Suisun Bay. The indication that oceanic phytoplankton biomass for the California regions is associated with climatic phenomena produced by El Nino and the Southern Oscillation (ENSO) was one of several factors used to standardize the dataset. Data used for the analyses were collected continuously on a semimonthly or monthly basis over the 17-yr period between 1971 and 1987. Groups of highly correlated environmental variables were summarized along three environmental axes using principal component analysis. The first environmentalmore » axis summarized river flow and specific conductance. The second environmental axis summarized water transparency and the third environmental axis summarized air and water temperature. Chlorophyll concentration was significantly cross-correlated with environmental axes and individual environmental variables. Transfer function models developed to describe changes in chlorophyll concentration over time were characterized by lag responses and described between 41% and 51% of the data variation. Significant cross-correlations between environmental axes and the California climate index (CA SLP) were used to develop a conceptual model of the link between regional climate and estuarine production. 50 refs., 5 figs.« less

Validity and Reliability of Gait and Postural Control Analysis Using the Tri-axial Accelerometer of the iPod Touch.

PubMed

Kosse, Nienke M; Caljouw, Simone; Vervoort, Danique; Vuillerme, Nicolas; Lamoth, Claudine J C

2015-08-01

Accelerometer-based assessments can identify elderly with an increased fall risk and monitor interventions. Smart devices, like the iPod Touch, with built-in accelerometers are promising for clinical gait and posture assessments due to easy use and cost-effectiveness. The aim of the present study was to establish the validity and reliability of the iPod Touch for gait and posture assessment. Sixty healthy participants (aged 18-75 years) were measured with an iPod Touch and stand-alone accelerometer while they walked under single- and dual-task conditions, and while standing in parallel and semi-tandem stance with eyes open, eyes closed and when performing a dual task. Cross-correlation values (CCV) showed high correspondence of anterior-posterior and medio-lateral signal patterns (CCV's ≥ 0.88). Validity of gait parameters (foot contacts, index of harmonicity, and amplitude variability) and standing posture parameters [root mean square of accelerations, median power frequency (MPF) and sway area] as indicated by intra-class correlation (ICC) was high (ICC = 0.85-0.99) and test-retest reliability was good (ICC = 0.81-0.97), except for MPF (ICC = 0.59-0.87). Overall, the iPod Touch obtained valid and reliable measures of gait and postural control in healthy adults of all ages under different conditions. Additionally, smart devices have the potential to be used for clinical gait and posture assessments.

Mechanical Anisotropy of Rat Aortic Smooth Muscle Cells Decreases with Their Contraction

NASA Astrophysics Data System (ADS)

Nagayama, Kazuaki; Matsumoto, Takeo

Tensile properties of smooth muscle cells freshly isolated from rat thoracic aortas (FSMCs) in their major and minor axes were measured using a laboratory-made micro tensile tester. The relationship between the tension applied to a cell and its elongation was obtained in untreated cells and those treated with 10-5M serotonin to induce contraction. An initial stiffness of untreated FSMCs, normalized by their initial cross-sectional area perpendicular to the stretch direction, was significantly higher in the major axis (14.8±4.3kPa, mean±SEM, n=5) than the minor axis (2.8±1.0kPa, n=5). The stiffness increased significantly in response to the contraction, but the increase was much higher in the minor axis (59.0±9.4kPa, n=4) than in the major (88.1±13.3kPa, n=4). The difference between the two directions was insignificant in the contracted state. Observations of the morphology of actin filaments with a confocal laser scanning microscope in untreated FSMCs revealed that they were long fibers running almost parallel to the major axis, while those in contracted cells showed an aggregated structure without a preferential direction. These results may indicate that anisotropy in untreated FSMCs is caused by the anisotropic alignment of their actin filaments, and that such anisotropy disappears in response to actin filament reorganization caused by the contraction.

A joint modeling and estimation method for multivariate longitudinal data with mixed types of responses to analyze physical activity data generated by accelerometers.

PubMed

Li, Haocheng; Zhang, Yukun; Carroll, Raymond J; Keadle, Sarah Kozey; Sampson, Joshua N; Matthews, Charles E

2017-11-10

A mixed effect model is proposed to jointly analyze multivariate longitudinal data with continuous, proportion, count, and binary responses. The association of the variables is modeled through the correlation of random effects. We use a quasi-likelihood type approximation for nonlinear variables and transform the proposed model into a multivariate linear mixed model framework for estimation and inference. Via an extension to the EM approach, an efficient algorithm is developed to fit the model. The method is applied to physical activity data, which uses a wearable accelerometer device to measure daily movement and energy expenditure information. Our approach is also evaluated by a simulation study. Copyright © 2017 John Wiley & Sons, Ltd.

WearSense: Detecting Autism Stereotypic Behaviors through Smartwatches

PubMed Central

Amiri, Amir Mohammad; Peltier, Nicholas; Goldberg, Cody; Sun, Yan; Nathan, Anoo; Hiremath, Shivayogi V.; Mankodiya, Kunal

2017-01-01

Autism is a complex developmental disorder that affects approximately 1 in 68 children (according to the recent survey conducted by the Centers for Disease Control and Prevention—CDC) in the U.S., and has become the fastest growing category of special education. Each student with autism comes with her or his own unique needs and an array of behaviors and habits that can be severe and which interfere with everyday tasks. Autism is associated with intellectual disability, impairments in social skills, and physical health issues such as sleep and abdominal disturbances. We have designed an Internet-of-Things (IoT) framework named WearSense that leverages the sensing capabilities of modern smartwatches to detect stereotypic behaviors in children with autism. In this work, we present a study that used the inbuilt accelerometer of a smartwatch to detect three behaviors, including hand flapping, painting, and sibbing that are commonly observed in children with autism. In this feasibility study, we recruited 14 subjects to record the accelerometer data from the smartwatch worn on the wrist. The processing part extracts 34 different features in each dimension of the three-axis accelerometer, resulting in 102 features. Using and comparing various classification techniques revealed that an ensemble of 40 decision trees has the best accuracy of around 94.6%. This accuracy shows the quality of the data collected from the smartwatch and feature extraction methods used in this study. The recognition of these behaviors by using a smartwatch would be helpful in monitoring individuals with autistic behaviors, since the smartwatch can send the data to the cloud for comprehensive analysis and also to help parents, caregivers, and clinicians make informed decisions. PMID:28264474

Nintendo Wii assessment of Hoehn and Yahr score with Parkinson's disease tremor.

PubMed

Koçer, Abdulkadir; Oktay, Ayse Betul

2016-01-01

Diagnosis of Parkinson's Disease (PD) by analyzing the resting tremor were much studied by using different accelerometer based methods, however the quantitative assessment of Hoehn and Yahr Scale (HYS) score with a machine learning based system has not been previously addressed. In this study, we aimed to propose a system to automatically assess the HYS score of patients with PD. The system was evaluated and tested on a dataset containing 55 subjects where 35 of them were patients and 20 of them were healthy controls. The resting tremor data were gathered with the 3 axis accelerometer of the Nintendo Wii (Wiimote). The clinical disability of the PD was graded from 1 to 5 by the HYS and tremor was recorded twice from the more affected side in each patient and from the dominant extremity in each control for a 60 seconds period. The HYS scores were learned with Support Vector Machines (SVM) from the features of the tremor data. Thirty-two of the subjects with PD were classified correctly and 18 of the normal subjects were also classified correctly by our system. The system had average 0.89 accuracy rate (Range: 81-100% changing according to grading by HYS). We compared quantitative measurements of hand tremor in PD patients, with staging of PD based on accelerometer data gathered using the Wii sensor. Our results showed that the machine learning based system with simple features could be helpful for diagnosis of PD and estimate HYS score. We believed that this portable and easy-to-use Wii sensor measure might also be applicable in the continuous monitoring of the resting tremor with small modifications in routine clinical use.

A multi-sensor monitoring system of human physiology and daily activities.

PubMed

Doherty, Sean T; Oh, Paul

2012-04-01

To present the design and pilot test results of a continuous multi-sensor monitoring system of real-world physiological conditions and daily life (activities, travel, exercise, and food consumption), culminating in a Web-based graphical decision-support interface. The system includes a set of wearable sensors wirelessly connected to a "smartphone" with a continuously running software application that compresses and transmits the data to a central server. Sensors include a Global Positioning System (GPS) receiver, electrocardiogram (ECG), three-axis accelerometer, and continuous blood glucose monitor. A food/medicine diary and prompted recall activity diary were also used. The pilot test involved 40 type 2 diabetic patients monitored over a 72-h period. All but three subjects were successfully monitored for the full study period. Smartphones proved to be an effective hub for managing multiple streams of data but required attention to data compression and battery consumption issues. ECG, accelerometer, and blood glucose devices performed adequately as long as subjects wore them. GPS tracking for a full day was feasible, although significant efforts are needed to impute missing data. Activity detection algorithms were successful in identifying activities and trip modes but could benefit by incorporating accelerometer data. The prompted recall diary was an effective tool for augmenting algorithm results, although subjects reported some difficulties with it. The food and medicine diary was completed fully, although end times and medicine dosages were occasionally missing. The unique combination of sensors holds promise for increasing accuracy and reducing burden associated with collecting individual-level activity and physiological data under real-world conditions, but significant data processing issues remain. Such data will provide new opportunities to explore the impacts of human geography and daily lifestyle on health at a fine spatial/temporal scale.

A high and low noise model for strong motion accelerometers

NASA Astrophysics Data System (ADS)

Clinton, J. F.; Cauzzi, C.; Olivieri, M.

2010-12-01

We present reference noise models for high-quality strong motion accelerometer installations. We use continuous accelerometer data acquired by the Swiss Seismological Service (SED) since 2006 and other international high-quality accelerometer network data to derive very broadband (50Hz-100s) high and low noise models. The proposed noise models are compared to the Peterson (1993) low and high noise models designed for broadband seismometers; the datalogger self-noise; background noise levels at existing Swiss strong motion stations; and typical earthquake signals recorded in Switzerland and worldwide. The standard strong motion station operated by the SED consists of a Kinemetrics Episensor (2g clip level; flat acceleration response from 200 Hz to DC; <155dB dynamic range) coupled with a 24-bit Nanometrics Taurus datalogger. The proposed noise models are based on power spectral density (PSD) noise levels for each strong motion station computed via PQLX (McNamara and Buland, 2004) from several years of continuous recording. The 'Accelerometer Low Noise Model', ALNM, is dominated by instrument noise from the sensor and datalogger. The 'Accelerometer High Noise Model', AHNM, reflects 1) at high frequencies the acceptable site noise in urban areas, 2) at mid-periods the peak microseismal energy, as determined by the Peterson High Noise Model and 3) at long periods the maximum noise observed from well insulated sensor / datalogger systems placed in vault quality sites. At all frequencies, there is at least one order of magnitude between the ALNM and the AHNM; at high frequencies (> 1Hz) this extends to 2 orders of magnitude. This study provides remarkable confirmation of the capability of modern strong motion accelerometers to record low-amplitude ground motions with seismic observation quality. In particular, an accelerometric station operating at the ALNM is capable of recording the full spectrum of near source earthquakes, out to 100 km, down to M2. Of particular interest for the SED, this study provides acceptable noise limits for candidate sites for the on-going Strong Motion Network modernisation.

Investigation into the cross-correlation of salivary cortisol and alpha-amylase responses to psychological stress.

PubMed

Engert, Veronika; Vogel, Susanne; Efanov, Simona I; Duchesne, Annie; Corbo, Vincent; Ali, Nida; Pruessner, Jens C

2011-10-01

Stress is a multidimensional construct. To accurately represent stress physiology, multiple stress measures across multiple stress-related systems should be assessed. However, associations may be masked given that different systems underlie different time courses. Salivary cortisol and alpha-amylase (sAA) are reliable biological stress markers of the sympathetic nervous system (SNS) and the hypothalamus pituitary adrenal (HPA) axis, respectively. Studies examining the link between sAA and cortisol levels in response to stress have produced inconsistent results. Here, we investigated whether the covariance of stress-induced sAA and cortisol release is dependent on the distinct temporal dynamics of the two stress markers. A total of 50 male participants were exposed to a psychological laboratory stressor with high frequency (2-min interval) saliva sampling in two independent studies. Synchronized time series of sAA and cortisol measures before, during and after stress induction were obtained. Cross-correlation analysis was applied to test for the association of sAA and cortisol levels at various stages relative to the onset of the stressor. Positive and negative cross-correlations between lagged pairs of sAA and cortisol measures were found in both studies. The strongest correlation was found for sAA preceding cortisol release by 13.5 min (r = .27, p < .001). With a smaller effect size cortisol also significantly preceded sAA by 13.5 min (r = -.16, p < .001). We suggest that sAA and cortisol stress responses are reliably associated at various time lags throughout a stressful situation. As a possible connection site between HPA axis and SNS that may underlie sAA-cortisol associations, we discuss CRF neurons of the hypothalamus involved in sympathetic regulation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Moderating effects of age, gender and education on the associations of perceived neighborhood environment attributes with accelerometer-based physical activity: the IPEN Adult study Moderating effects of age, gender and education on the associations of perceived neighborhood environment attributes with accelerometer-based physical activity: the IPEN Adult study

PubMed Central

Van Dyck, Delfien; Cerin, Ester; De Bourdeaudhuij, Ilse; Salvo, Deborah; Christiansen, Lars B; Macfarlane, Duncan; Owen, Neville; Mitas, Josef; Troelsen, Jens; Aguinaga-Ontoso, Ines; Davey, Rachel; Reis, Rodrigo; Sarmiento, Olga L; Schofield, Grant; Conway, Terry L; Sallis, James F

2015-01-01

The study's purpose was to examine age, gender, and education as potential moderators of the associations of perceived neighborhood environment variables with accelerometer-based moderate-to-vigorous physical activity (MVPA). Data were from 7273 adults from 16 sites (11 countries) that were part of a coordinated multi-country cross-sectional study. Age moderated the associations of perceived crime safety, and perceiving no major physical barriers to walking, with MVPA: positive associations were only found in older adults. Perceived land use mix-access was linearly (positive) associated with MVPA in men, and curvilinearly in women. Perceived crime safety was related to MVPA only in women. No moderating relationships were found for education. Overall the associations of adults’ perceptions of environmental attributes with MVPA were largely independent of the socio-demographic factors examined. These findings are encouraging, suggesting that efforts to optimize the perceived built and social environment may act in a socially-equitable manner to facilitate MVPA. PMID:26454247

Cloverleaf microgyroscope with electrostatic alignment and tuning

NASA Technical Reports Server (NTRS)

Challoner, A. Dorian (Inventor); Gutierrez, Roman C. (Inventor); Tang, Tony K. (Inventor)

2007-01-01

A micro-gyroscope (10) having closed loop output operation by a control voltage (V.sub.ty), that is demodulated by a drive axis (x-axis) signal V.sub.thx of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis) V.sub.thy.about.0. Closed loop drive axis torque, V.sub.tx maintains a constant drive axis amplitude signal, V.sub.thx. The present invention provides independent alignment and tuning of the micro-gyroscope by using separate electrodes and electrostatic bias voltages to adjust alignment and tuning. A quadrature amplitude signal, or cross-axis transfer function peak amplitude is used to detect misalignment that is corrected to zero by an electrostatic bias voltage adjustment. The cross-axis transfer function is either V.sub.thy/V.sub.ty or V.sub.tnx/V.sub.tx. A quadrature signal noise level, or difference in natural frequencies estimated from measurements of the transfer functions is used to detect residual mistuning, that is corrected to zero by a second electrostatic bias voltage adjustment.

FPGA-Based Fused Smart-Sensor for Tool-Wear Area Quantitative Estimation in CNC Machine Inserts

PubMed Central

Trejo-Hernandez, Miguel; Osornio-Rios, Roque Alfredo; de Jesus Romero-Troncoso, Rene; Rodriguez-Donate, Carlos; Dominguez-Gonzalez, Aurelio; Herrera-Ruiz, Gilberto

2010-01-01

Manufacturing processes are of great relevance nowadays, when there is a constant claim for better productivity with high quality at low cost. The contribution of this work is the development of a fused smart-sensor, based on FPGA to improve the online quantitative estimation of flank-wear area in CNC machine inserts from the information provided by two primary sensors: the monitoring current output of a servoamplifier, and a 3-axis accelerometer. Results from experimentation show that the fusion of both parameters makes it possible to obtain three times better accuracy when compared with the accuracy obtained from current and vibration signals, individually used. PMID:22319304

MEMS inertial sensors with integral rotation means.

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

Kohler, Stewart M.

The state-of-the-art of inertial micro-sensors (gyroscopes and accelerometers) has advanced to the point where they are displacing the more traditional sensors in many size, power, and/or cost-sensitive applications. A factor limiting the range of application of inertial micro-sensors has been their relatively poor bias stability. The incorporation of an integral sensitive axis rotation capability would enable bias mitigation through proven techniques such as indexing, and foster the use of inertial micro-sensors in more accuracy-sensitive applications. Fabricating the integral rotation mechanism in MEMS technology would minimize the penalties associated with incorporation of this capability, and preserve the inherent advantages of inertialmore » micro-sensors.« less

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.

Evaluation of electrolytic tilt sensors for measuring model angle of attack in wind tunnel tests

NASA Technical Reports Server (NTRS)

Wong, Douglas T.

1992-01-01

The results of a laboratory evaluation of electrolytic tilt sensors as potential candidates for measuring model attitude or angle of attack in wind tunnel tests are presented. The performance of eight electrolytic tilt sensors was compared with that of typical servo accelerometers used for angle-of-attack measurements. The areas evaluated included linearity, hysteresis, repeatability, temperature characteristics, roll-on-pitch interaction, sensitivity to lead-wire resistance, step response time, and rectification. Among the sensors being evaluated, the Spectron model RG-37 electrolytic tilt sensors have the highest overall accuracy in terms of linearity, hysteresis, repeatability, temperature sensitivity, and roll sensitivity. A comparison of the sensors with the servo accelerometers revealed that the accuracy of the RG-37 sensors was on the average about one order of magnitude worse. Even though a comparison indicates that the cost of each tilt sensor is about one-third the cost of each servo accelerometer, the sensors are considered unsuitable for angle-of-attack measurements. However, the potential exists for other applications such as wind tunnel wall-attitude measurements where the errors resulting from roll interaction, vibration, and response time are less and sensor temperature can be controlled.

Detailed analysis of Honeywell In-Space Accelerometer data - STS-32. [crystal microstructure response to different types of residual acceleration

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.; Alexander, J. I. D.; Schoess, Jeff

1993-01-01

The Honeywell In-Space Accelerometer (HISA) system collected data in the mid-deck area of the Shuttle Columbia during the flight of STS-32, January 1990. The resulting data were to be used to investigate the response of crystal microstructure to different types of residual acceleration. The HISA is designed to detect and record transient and oscillatory accelerations. The sampling and electronics package stored averaged accelerations over two sampling periods; two sampling rates were available: 1 Hz and 50 Hz. Analysis of the HISA data followed the CMMR Acceleration Data Processing Guide, considering in-house computer modelling of a float-zone indium crystal growth experiment. Characteristic examples of HISA data showing the response to the primary reaction control system, Orbiter Maneuvering System operations, and crew treadmill activity are presented. Various orbiter structural modes are excited by these and other activities.

Dynamic response characteristics of two transport models tested in the National Transonic Facility

NASA Technical Reports Server (NTRS)

Young, Clarence P., Jr.

1993-01-01

This paper documents recent experiences with measuring the dynamic response characteristics of a commercial transport and a military transport model during full scale Reynolds number tests in the National Transonic Facility. Both models were limited in angle of attack while testing at full scale Reynolds number and cruise Mach number due to pitch or stall buffet response. Roll buffet (wing buzz) was observed for both models at certain Mach numbers while testing at high Reynolds number. Roll buffet was more severe and more repeatable for the military transport model at cruise Mach number. Miniature strain-gage type accelerometers were used for the first time for obtaining dynamic data as a part of the continuing development of miniature dynamic measurements instrumentation for cryogenic applications. This paper presents the results of vibration measurements obtained for both the commercial and military transport models and documents the experience gained in the use of miniature strain gage type accelerometers.

Associations of objectively measured physical activity with daily mood ratings and psychophysiological stress responses in women.

PubMed

Poole, Lydia; Steptoe, Andrew; Wawrzyniak, Andrew J; Bostock, Sophie; Mitchell, Ellen S; Hamer, Mark

2011-08-01

The aim of this study was to examine associations of objectively measured physical activity with daily mood ratings and psychophysiological stress responses. We recruited 40 healthy females (aged 28.7 ± 6.1 yrs) who completed a once-a-day mood rating scale for 7 days, along with a 7-day assessment of physical activity using accelerometers and psychophysiological stress testing. The findings suggest that levels of physical activity as measured using an accelerometer are associated with both depressive symptoms over the past 2 weeks (CES-D) (r = - .33, p = .038) and with daily positive emotional style (r = .49, p = .001). The relationship between physical activity and positive emotional style remained after controlling for age, body mass index, and negative emotional style (t = 3.31, p = .002). Physical activity was not related to any psychophysiological stress responses. Copyright © 2011 Society for Psychophysiological Research.

Purification of Proteins From Cell-Culture Medium or Cell-Lysate by High-Speed Counter-Current Chromatography Using Cross-Axis Coil Planet Centrifuge

PubMed Central

Shibusawa, Yoichi; Ito, Yoichiro

2014-01-01

This review describes protein purifications from cell culture medium or cell-lysate by high speed counter-current chromatography using the cross-axis coil planet centrifuge. Purifications were performed using aqueous two phase systems composed of polyethylene glycols and dextrans. PMID:25360182

Targeted vertical cross-sectional imaging with handheld near-infrared dual axes confocal fluorescence endomicroscope.

PubMed

Qiu, Zhen; Liu, Zhongyao; Duan, Xiyu; Khondee, Supang; Joshi, Bishnu; Mandella, Michael J; Oldham, Kenn; Kurabayashi, Katsuo; Wang, Thomas D

2013-02-01

We demonstrate vertical cross-sectional (XZ-plane) images of near-infrared (NIR) fluorescence with a handheld dual axes confocal endomicroscope that reveals specific binding of a Cy5.5-labeled peptide to pre-malignant colonic mucosa. This view is perpendicular to the tissue surface, and is similar to that used by pathologists. The scan head is 10 mm in outer diameter (OD), and integrates a one dimensional (1-D) microelectromechanical systems (MEMS) X-axis scanner and a bulky lead zirconate titanate (PZT) based Z-axis actuator. The microscope images in a raster-scanning pattern with a ±6 degrees (mechanical) scan angle at ~3 kHz in the X-axis (fast) and up to 10 Hz (0-400 μm) in the Z-axis (slow). Vertical cross-sectional fluorescence images are collected with a transverse and axial resolution of 4 and 5 μm, respectively, over a field-of-view of 800 μm (width) × 400 μm (depth). NIR vertical cross-sectional fluorescence images of fresh mouse colonic mucosa demonstrate histology-like imaging performance with this miniature instrument.

Targeted vertical cross-sectional imaging with handheld near-infrared dual axes confocal fluorescence endomicroscope

PubMed Central

Qiu, Zhen; Liu, Zhongyao; Duan, Xiyu; Khondee, Supang; Joshi, Bishnu; Mandella, Michael J.; Oldham, Kenn; Kurabayashi, Katsuo; Wang, Thomas D.

2013-01-01

We demonstrate vertical cross-sectional (XZ-plane) images of near-infrared (NIR) fluorescence with a handheld dual axes confocal endomicroscope that reveals specific binding of a Cy5.5-labeled peptide to pre-malignant colonic mucosa. This view is perpendicular to the tissue surface, and is similar to that used by pathologists. The scan head is 10 mm in outer diameter (OD), and integrates a one dimensional (1-D) microelectromechanical systems (MEMS) X-axis scanner and a bulky lead zirconate titanate (PZT) based Z-axis actuator. The microscope images in a raster-scanning pattern with a ±6 degrees (mechanical) scan angle at ~3 kHz in the X-axis (fast) and up to 10 Hz (0–400 μm) in the Z-axis (slow). Vertical cross-sectional fluorescence images are collected with a transverse and axial resolution of 4 and 5 μm, respectively, over a field-of-view of 800 μm (width) × 400 μm (depth). NIR vertical cross-sectional fluorescence images of fresh mouse colonic mucosa demonstrate histology-like imaging performance with this miniature instrument. PMID:23412564

The SRS-Viewer: A Software Tool for Displaying and Evaluation of Pyroshock Data

NASA Astrophysics Data System (ADS)

Eberl, Stefan

2014-06-01

For the evaluation of the success of a pyroshock, the time domain and the corresponding Shock-Response- Spectra (SRS) have to be considered. The SRS-Viewer is an IABG developed software tool [1] to read data in Universal File format (*.unv) and either display or plot for each accelerometer the time domain, corresponding SRS and the specified Reference-SRS with tolerances in the background.The software calculates the "Average (AVG)", "Maximum (MAX)" and "Minimum (MIN)" SRS of any selection of accelerometers. A statistical analysis calculates the percentages of measured SRS above the specified Reference-SRS level and the percentage within the tolerance bands for comparison with the specified success criteria.Overlay plots of single accelerometers of different test runs enable to monitor the repeatability of the shock input and the integrity of the specimen. Furthermore the difference between the shock on a mass-dummy and the real test unit can be examined.

Using accelerometers to determine the calling behavior of tagged baleen whales.

PubMed

Goldbogen, J A; Stimpert, A K; DeRuiter, S L; Calambokidis, J; Friedlaender, A S; Schorr, G S; Moretti, D J; Tyack, P L; Southall, B L

2014-07-15

Low-frequency acoustic signals generated by baleen whales can propagate over vast distances, making the assignment of calls to specific individuals problematic. Here, we report the novel use of acoustic recording tags equipped with high-resolution accelerometers to detect vibrations from the surface of two tagged fin whales that directly match the timing of recorded acoustic signals. A tag deployed on a buoy in the vicinity of calling fin whales and a recording from a tag that had just fallen off a whale were able to detect calls acoustically but did not record corresponding accelerometer signals that were measured on calling individuals. Across the hundreds of calls measured on two tagged fin whales, the accelerometer response was generally anisotropic across all three axes, appeared to depend on tag placement and increased with the level of received sound. These data demonstrate that high-sample rate accelerometry can provide important insights into the acoustic behavior of baleen whales that communicate at low frequencies. This method helps identify vocalizing whales, which in turn enables the quantification of call rates, a fundamental component of models used to estimate baleen whale abundance and distribution from passive acoustic monitoring. © 2014. Published by The Company of Biologists Ltd.

Integrated monitoring of wind plant systems

NASA Astrophysics Data System (ADS)

Whelan, Matthew J.; Janoyan, Kerop D.; Qiu, Tong

2008-03-01

Wind power is a renewable source of energy that is quickly gaining acceptance by many. Advanced sensor technologies have currently focused solely on improving wind turbine rotor aerodynamics and increasing of the efficiency of the blade design and concentration. Alternatively, potential improvements in wind plant efficiency may be realized through reduction of reactionary losses of kinetic energy to the structural and substructural systems supporting the turbine mechanics. Investigation of the complete dynamic structural response of the wind plant is proposed using a large-scale, high-rate wireless sensor network. The wireless network enables sensors to be placed across the sizable structure, including the rotating blades, without consideration of cabling issues and the economic burden associated with large spools of measurement cables. A large array of multi-axis accelerometers is utilized to evaluate the modal properties of the system as well as individual members and would enable long-term structural condition monitoring of the wind turbine as well. Additionally, environmental parameters, including wind speed, temperature, and humidity, are wirelessly collected for correlation. Such a wireless system could be integrated with electrical monitoring sensors and actuators and incorporated into a remote multi-turbine centralized plant monitoring and control system.

Orbital Manuvering System Design and Performance For the Magnetosperic Multiscale Constellation

NASA Technical Reports Server (NTRS)

Queen, Steven Z.; Chai, Dean J.; Placanica, Sam

2013-01-01

The Magnetospheric Multiscale (MMS) mission, launched on March 13, 2015, is the fourth mission of NASA's Solar Terrestrial Probe program. The MMS mission consists of four identically instrumented observatories that function as a constellation to provide the first definitive study of magnetic reconnection in space. Since it is frequently desirable to isolate electric and magnetic field sensors from stray effects caused by the spacecraft's core-body, the suite of instruments on MMS includes six radial and two axial instrument-booms with deployed lengths ranging from 5-60 meters (see Figure 1). The observatory is spin-stabilized about its positive z-axis with a nominal rate slightly above 3 rev/min (RPM). The spin is also used to maintain tension in the four radial wire-booms. Each observatory's Attitude Control System (ACS) consists of digital sun sensors, star cameras, accelerometers, and mono-propellant hydrazine thrusters-responsible for orbital adjustments, attitude control, and spin adjustments. The sections that follow describe performance requirements, the hardware and algorithms used for 6-DOF estimation, and then similarly for 6-DOF control. The paper concludes with maneuver performance based on both simulated and on-orbit telem.

iFall: an Android application for fall monitoring and response.

PubMed

Sposaro, Frank; Tyson, Gary

2009-01-01

Injuries due to falls are among the leading causes of hospitalization in elderly persons, often resulting in a rapid decline in quality of life or death. Rapid response can improve the patients outcome, but this is often lacking when the injured person lives alone and the nature of the injury complicates calling for help. This paper presents an alert system for fall detection using common commercially available electronic devices to both detect the fall and alert authorities. We use an Android-based smart phone with an integrated tri-axial accelerometer. Data from the accelerometer is evaluated with several threshold based algorithms and position data to determine a fall. The threshold is adaptive based on user provided parameters such as: height, weight, and level of activity. The algorithm adapts to unique movements that a phone experiences as opposed to similar systems which require users to mount accelerometers to their chest or trunk. If a fall is suspected a notification is raised requiring the user's response. If the user does not respond, the system alerts pre-specified social contacts with an informational message via SMS. If a contact responds the system commits an audible notification, automatically connects, and enables the speakerphone. If a social contact confirms a fall, an appropriate emergency service is alerted. Our system provides a realizable, cost effective solution to fall detection using a simple graphical interface while not overwhelming the user with uncomfortable sensors.

[Polar and non polar notations of refraction].

PubMed

Touzeau, O; Gaujoux, T; Costantini, E; Borderie, V; Laroche, L

2010-01-01

Refraction can be expressed by four polar notations which correspond to four different combinations of spherical or cylindrical lenses. Conventional expressions of refraction (plus and minus cylinder notation) are described by sphere, cylinder, and axis. In the plus cylinder notation, the axis visualizes the most powerful meridian. The axis usually corresponds to the bow tie axis in curvature maps. Plus cylinder notation is also valuable for all relaxing procedures (i.e., selective suture ablation, arcuate keratotomy, etc.). In the cross-cylinder notation, two orthogonal cylinders can describe (without the sphere component) the actual refraction of both the principal meridians. This notation must be made before performing the vertex calculation. Using an association of a Jackson cross-cylinder and a spherical equivalent, refraction can be broken down into two pure components: astigmatism and sphere. All polar notations of refraction may perfectly characterize a single refraction but are not suitable for statistical analysis, which requires nonpolar expression. After doubling the axis, a rectangular projection breaks down the Jackson cross-cylinder, which has a polar axis, into two Jackson cross-cylinders on the 0 degrees /90 degrees and 45 degrees /135 degrees axis. This procedure results in the loss of the directional nature of the data. Refraction can be written in a nonpolar notation by three rectangular coordinates (x,y,z), which can also represent the spherocylinder by one point in a dioptric space. These three independent (orthogonal) variables have a concrete optical significance: a spherical component, a direct/inverse (WTR/ATR) component, and an oblique component of the astigmatism. Finally, nonpolar notations are useful for statistical analysis and graphical representation of refraction. Copyright (c) 2009 Elsevier Masson SAS. All rights reserved.

Investigation on a fiber optic accelerometer based on FBG-FP interferometer

NASA Astrophysics Data System (ADS)

Lin, Chongyu; Luo, Hong; Xiong, Shuidong; Li, Haitao

2014-12-01

A fiber optic accelerometer based on fiber Bragg grating Fabry-Perot (FBG-FP) interferometer is presented. The sensor is a FBG-FP cavity which is formed with two weak fiber Bragg gratings (FBGs) in a single-mode fiber. The reflectivity of the two FBGs is 9.42% and 7.74% respectively, and the fiber between them is 10 meters long. An optical demodulation system was set up to analyze the reflected light of FBG-FP cavity. Acceleration signals of different frequencies and intensities were demodulated correctly and stably by the system. Based on analyzing the optical spectrum of weak FBG based FBG-FP cavity, we got the equivalent length of FBG-FP cavity. We used a path-matching Michelson interferometer (MI) to demodulate the acceleration signal. The visibility of the interference fringe we got was 41%~42% while the theory limit was 50%. This indicated that the difference of interferometer's two arms and the equivalent length of FBG-FP cavity were matched well. Phase generated carrier (PGC) technology was used to eliminate phase fading caused by random phase shift and Faraday rotation mirrors (FRMs) were used to eliminate polarization-induced phase fading. The accelerometer used a compliant cylinder design and its' sensitivity and frequency response were analyzed and simulated based on elastic mechanics. Experiment result showed that the accelerometer had a flat frequency response over the frequency range of 31-630Hz. The sensitivity was about 31dB (0dB=1rad/g) with fluctuation less than 1.5dB.

Thermospheric density estimation and responses to the March 2013 geomagnetic storm from GRACE GPS-determined precise orbits

NASA Astrophysics Data System (ADS)

Calabia, Andres; Jin, Shuanggen

2017-02-01

The thermospheric mass density variations and the thermosphere-ionosphere coupling during geomagnetic storms are not clear due to lack of observables and large uncertainty in the models. Although accelerometers on-board Low-Orbit-Earth (LEO) satellites can measure non-gravitational accelerations and derive thermospheric mass density variations with unprecedented details, their measurements are not always available (e.g., for the March 2013 geomagnetic storm). In order to cover accelerometer data gaps of Gravity Recovery and Climate Experiment (GRACE), we estimate thermospheric mass densities from numerical derivation of GRACE determined precise orbit ephemeris (POE) for the period 2011-2016. Our results show good correlation with accelerometer-based mass densities, and a better estimation than the NRLMSISE00 empirical model. Furthermore, we statistically analyze the differences to accelerometer-based densities, and study the March 2013 geomagnetic storm response. The thermospheric density enhancements at the polar regions on 17 March 2013 are clearly represented by POE-based measurements. Although our results show density variations better correlate with Dst and k-derived geomagnetic indices, the auroral electroject activity index AE as well as the merging electric field Em picture better agreement at high latitude for the March 2013 geomagnetic storm. On the other side, low-latitude variations are better represented with the Dst index. With the increasing resolution and accuracy of Precise Orbit Determination (POD) products and LEO satellites, the straightforward technique of determining non-gravitational accelerations and thermospheric mass densities through numerical differentiation of POE promises potentially good applications for the upper atmosphere research community.

The influence of gravitoinertial force level on oculomotor and perceptual responses to sudden stop stimulation

NASA Technical Reports Server (NTRS)

Dizio, Paul; Lackner, James R.; Evanoff, John N.

1987-01-01

The goal of this investigation was to determine whether the vestibular response to vertical, z-axis body rotation in the dark is influenced by the magnitude of gravitoinertial force. The parameters measured were the nystagmus and the duration of illusory self-motion elicited in blindfolded subjects by cessation of such rotation during the free-fall, high, and terrestrial force phases of parabolic flight maneuvers. The pattern of findings is consistent with the responses that were observed earlier to constant levels of Coriolis cross-coupled stimulation during parabolic flight maneuvers both in terms of the mode of nystagmus suppression and the effect of G-level.

Accelerometer-based physical activity levels among Mexican adults and their relation with sociodemographic characteristics and BMI: a cross-sectional study.

PubMed

Salvo, Deborah; Torres, Catalina; Villa, Umberto; Rivera, Juan A; Sarmiento, Olga L; Reis, Rodrigo S; Pratt, Michael

2015-06-20

The objectives of this study were to describe the accelerometer based total and bout-specific PA levels for a representative sample of adults from Cuernavaca, Mexico, and to examine the relationships with sociodemographic characteristics and BMI status. Cross sectional study of adults from Cuernavaca, Mexico (2011, n = 677). Participants wore Actigraph GT3X accelerometers for seven days and sociodemographic data was collected through a survey. Weight and height were objectively measured. Total minutes/week of moderate-to-vigorous PA (MVPA) and of MVPA occurring within bouts of at least ten minutes were obtained. Intensity-specific (moderate and vigorous) total PA and bouted-PA was also obtained. The relation of each PA variable with sex, age, socioeconomic status, education, marital status and BMI status was assessed using unadjusted and adjusted linear models. The mean total MVPA among adults from Cuernavaca was 221.3 ± 10.0 (median = 178.3 min/week). Average MVPA within bouts was 65.8 ± 4.7 min/week (median = 30.0 min/week). 9.7 % of total MVPA occurred within bouts. Significant associations were found for total and bout-specific MVPA with being male (positive) and owning a motor vehicle (negative). Additional associations were found for intensity-specific PA outcomes. Mexican adults were more active during weekdays than weekends, suggesting that PA may be more strongly driven by necessity (transport) than by choice (leisure). This is the first study to objectively measure PA for a representative sample of Mexican adults in an urban setting. The sociodemographic correlates vary from those known from high income countries, stressing the need for more correlate studies from lower-to-middle income countries.

Longitudinal associations between sports participation, body composition and physical activity from childhood to adolescence

PubMed Central

Basterfield, Laura; Reilly, Jessica K.; Pearce, Mark S.; Parkinson, Kathryn N.; Adamson, Ashley J.; Reilly, John J.; Vella, Stewart A.

2015-01-01

Objectives Several important research questions have been addressed: (1) What are the cross-sectional associations between sports club participation, objectively measured physical activity, and adiposity? (2) Do measures of physical activity and adiposity predict subsequent sports club participation? (3) Does sports club participation predict subsequent measures of physical activity and adiposity? and (4) Do changes in sports club participation predict changes in objective measures of physical activity and adiposity? Design Longitudinal and cross-sectional. Methods Data from the Gateshead Millennium Study birth cohort (n = 609 at age 7 years) were analysed for associations between adiposity, sports club participation and accelerometer-measured physical activity from ages 7y to 9y to 12y. Results Seventy-two per cent of 9 year olds and 63% of 12 year olds took part in a sports club. Sports club participation was significantly associated with overall accelerometer-measured physical activity at 12y (coefficient = 0.0.09; 95% CI: 0.01–0.16) but not 9y. An inverse relationship between fat mass (estimated from bioelectric impedance) and sport club participation, and between fat mass and accelerometer-measured physical activity was observed at 12y, but not 9y. Sports club participation at 9y was highly predictive of participation at 12y. Sports club participation was significantly associated with socioeconomic status; fewer children from poorer areas took part. Conclusions Sports club participation in adolescence may be associated with decreased levels of adiposity. Furthermore, the potential benefits of sports club participation for adiposity are likely generated from continuous participation in sports, rather than any long-term protective effects. PMID:24704422

Inertial sensor-based smoother for gait analysis.

PubMed

Suh, Young Soo

2014-12-17

An off-line smoother algorithm is proposed to estimate foot motion using an inertial sensor unit (three-axis gyroscopes and accelerometers) attached to a shoe. The smoother gives more accurate foot motion estimation than filter-based algorithms by using all of the sensor data instead of using the current sensor data. The algorithm consists of two parts. In the first part, a Kalman filter is used to obtain initial foot motion estimation. In the second part, the error in the initial estimation is compensated using a smoother, where the problem is formulated in the quadratic optimization problem. An efficient solution of the quadratic optimization problem is given using the sparse structure. Through experiments, it is shown that the proposed algorithm can estimate foot motion more accurately than a filter-based algorithm with reasonable computation time. In particular, there is significant improvement in the foot motion estimation when the foot is moving off the floor: the z-axis position error squared sum (total time: 3.47 s) when the foot is in the air is 0.0807 m2 (Kalman filter) and 0.0020 m2 (the proposed smoother).

Accelerative Forces Associated with Routine Inhouse Transportation of Rodent Cages

PubMed Central

Hurst, Keriann; Litwak, Kenneth N

2012-01-01

Transportation of rodents has repeatedly been demonstrated to potentially affect research outcomes. In addition, rapid acceleration and deceleration have marked physiologic effects. The current study determined the accelerative forces associated with common types of animal transportation within the institution and means of reducing these effects. A rodent-sized (24 g) accelerometer was placed in a standard polycarbonate mouse cage, which then was hand-carried or loaded onto a plastic, small metal, or large metal cart. The cage then moved along a set path that included several flooring types and obstacles. Accelerative forces within the mouse cage varied by as much as 35 m/s2 in as little as 1 s, primarily along the vertical axis (Z-axis). Measured acceleration was greatest with the plastic cart and lowest during hand-carrying. The placement of a towel under the cage dampened in-cage acceleration due to cart use by more than 50%, whereas a similarly located underpad had no significant effect. These data document that small rodents typically are exposed to considerable motion during transportation. The resulting physical and physiologic effects could affect study outcomes. PMID:23312081

Comparison between the robo-horse and real horse movements for hippotherapy.

PubMed

Park, Ji H; Shurtleff, Timothy; Engsberg, Jack; Rafferty, Sandy; You, Joshua Y; You, Isaac Y; You, Sung H

2014-01-01

While the novel robotic hippotherapy system has gradually gained clinical application for therapeutic intervention on postural and locomotor control in individuals with neurological or musculoskeletal impairments, the system's validity and reliability for the robotic hippotherapy system has not been well established. The objective of the current study was to investigate the validity and test-retest reliability of the robotic hippotherapy system by comparing with real horse movements. The 3-axis accelerometer sensors attached on the robotic and real horse saddles were used to collect 3-dimensional acceleration data at a preferred walking velocity. Linear regression analysis showed an excellent correlation in the time-to-peak acceleration (TPA) (R(2)=0.997), but little correlation in X-axis acceleration between the real and robotic horses (R(2)=0.177), thus confirming consistent time control and a certain degree of variability between the robotic and real horse movements. The mean resultant accelerations for a real horse and robotic horse were 3.22 m/s(2) and 0.67 m/s(2), respectively, accounting for almost five times greater acceleration in the real horse than the robotic horse.

Kinematic properties of the helicopter in coordinated turns

NASA Technical Reports Server (NTRS)

Chen, R. T. N.; Jeske, J. A.

1981-01-01

A study on the kinematic relationship of the variables of helicopter motion in steady, coordinated turns involving inherent sideslip is described. A set of exact kinematic equations which govern a steady coordinated helical turn about an Earth referenced vertical axis is developed. A precise definition for the load factor parameter that best characterizes a coordinated turn is proposed. Formulas are developed which relate the aircraft angular rates and pitch and roll attitudes to the turn parameters, angle of attack, and inherent sideslip. A steep, coordinated helical turn at extreme angles of attack with inherent sideslip is of primary interest. The bank angle of the aircraft can differ markedly from the tilt angle of the normal load factor. The normal load factor can also differ substantially from the accelerometer reading along the vertical body axis of the aircraft. Sideslip has a strong influence on the pitch attitude and roll rate of the helicopter. Pitch rate is independent of angle of attack in a coordinated turn and in the absence of sideslip, angular rates about the stability axes are independent of the aerodynamic characteristics of the aircraft.

Longitudinal wearable tremor measurement system with activity recognition algorithms for upper limb tremor.

PubMed

Jeonghee Kim; Parnell, Claire; Wichmann, Thomas; DeWeerth, Stephen P

2016-08-01

Assessments of tremor characteristics by movement disorder physicians are usually done at single time points in clinic settings, so that the description of the tremor does not take into account the dependence of the tremor on specific behavioral situations. Moreover, treatment-induced changes in tremor or behavior cannot be quantitatively tracked for extended periods of time. We developed a wearable tremor measurement system with tremor and activity recognition algorithms for long-term upper limb behavior tracking, to characterize tremor characteristics and treatment effects in their daily lives. In this pilot study, we collected sensor data of arm movement from three healthy participants using a wrist device that included a 3-axis accelerometer and a 3-axis gyroscope, and classified tremor and activities within scenario tasks which resembled real life situations. Our results show that the system was able to classify the tremor and activities with 89.71% and 74.48% accuracies during the scenario tasks. From this results, we expect to expand our tremor and activity measurement in longer time period.

Magnetically Actuated Propellant Orientation Experiment, Controlling Fluid Motion With Magnetic Fields in a Low-Gravity Environment

NASA Technical Reports Server (NTRS)

Martin, J. J.; Holt, J. B.

2000-01-01

This report details the results of a series of fluid motion experiments to investigate the use of magnets to orient fluids in a low-gravity environment. The fluid of interest for this project was liquid oxygen (LO2) since it exhibits a paramagnetic behavior (is attracted to magnetic fields). However, due to safety and handling concerns, a water-based ferromagnetic mixture (produced by Ferrofluidics Corporation) was selected to simplify procedures. Three ferromagnetic fluid mixture strengths and a nonmagnetic water baseline were tested using three different initial fluid positions with respect to the magnet. Experiment accelerometer data were used with a modified computational fluid dynamics code termed CFX-4 (by AEA Technologies) to predict fluid motion. These predictions compared favorably with experiment video data, verifying the code's ability to predict fluid motion with and without magnetic influences. Additional predictions were generated for LO2 with the same test conditions and geometries used in the testing. Test hardware consisted of a cylindrical Plexiglas tank (6-in. bore with 10-in. length), a 6,000-G rare Earth magnet (10-in. ring), three-axis accelerometer package, and a video recorder system. All tests were conducted aboard the NASA Reduced-Gravity Workshop, a KC-135A aircraft.

In-Flight Vibration Environment of the NASA F-15B Flight Test Fixture

NASA Technical Reports Server (NTRS)

Corda, Stephen; Franz, Russell J.; Blanton, James N.; Vachon, M. Jake; DeBoer, James B.

2002-01-01

Flight vibration data are analyzed for the NASA F-15B/Flight Test Fixture II test bed. Understanding the in-flight vibration environment benefits design and integration of experiments on the test bed. The power spectral density (PSD) of accelerometer flight data is analyzed to quantify the in-flight vibration environment from a frequency of 15 Hz to 1325 Hz. These accelerometer data are analyzed for typical flight conditions and maneuvers. The vibration data are compared to flight-qualification random vibration test standards. The PSD levels in the lateral axis generally are greater than in the longitudinal and vertical axes and decrease with increasing frequency. At frequencies less than approximately 40 Hz, the highest PSD levels occur during takeoff and landing. Peaks in the PSD data for the test fixture occur at approximately 65, 85, 105-110, 200, 500, and 1000 Hz. The pitch-pulse and 2-g turn maneuvers produce PSD peaks at 115 Hz. For cruise conditions, the PSD level of the 85-Hz peak is greatest for transonic flight at Mach 0.9. From 400 Hz to 1325 Hz, the takeoff phase has the highest random vibration levels. The flight-measured vibration levels generally are substantially lower than the random vibration test curve.

Estimating Energy Expenditure with ActiGraph GT9X Inertial Measurement Unit.

PubMed

Hibbing, Paul R; Lamunion, Samuel R; Kaplan, Andrew S; Crouter, Scott E

2018-05-01

The purpose of this study was to explore whether gyroscope and magnetometer data from the ActiGraph GT9X improved accelerometer-based predictions of energy expenditure (EE). Thirty participants (mean ± SD: age, 23.0 ± 2.3 yr; body mass index, 25.2 ± 3.9 kg·m) volunteered to complete the study. Participants wore five GT9X monitors (right hip, both wrists, and both ankles) while performing 10 activities ranging from rest to running. A Cosmed K4b was worn during the trial, as a criterion measure of EE (30-s averages) expressed in METs. Triaxial accelerometer data (80 Hz) were converted to milli-G using Euclidean norm minus one (ENMO; 1-s epochs). Gyroscope data (100 Hz) were expressed as a vector magnitude (GVM) in degrees per second (1-s epochs) and magnetometer data (100 Hz) were expressed as direction changes per 5 s. Minutes 4-6 of each activity were used for analysis. Three two-regression algorithms were developed for each wear location: 1) ENMO, 2) ENMO and GVM, and 3) ENMO, GVM, and direction changes. Leave-one-participant-out cross-validation was used to evaluate the root mean square error (RMSE) and mean absolute percent error (MAPE) of each algorithm. Adding gyroscope to accelerometer-only algorithms resulted in RMSE reductions between 0.0 METs (right wrist) and 0.17 METs (right ankle), and MAPE reductions between 0.1% (right wrist) and 6.0% (hip). When direction changes were added, RMSE changed by ≤0.03 METs and MAPE by ≤0.21%. The combined use of gyroscope and accelerometer at the hip and ankles improved individual-level prediction of EE compared with accelerometer only. For the wrists, adding gyroscope produced negligible changes. The magnetometer did not meaningfully improve estimates for any algorithms.

A model for the response of vertical axis wind turbines to turbulent flow: Parts 1 and 2

NASA Astrophysics Data System (ADS)

Malcolm, D. R.

1988-07-01

This report describes a project intended to incorporate the effects of atmospheric turbulence into the structural response of Darrieus rotor, vertical axis wind turbines. The basis of the technique is the generation of a suitable time series of wind velocities, which are passed through a double multiple streamtube aerodynamic representation of the rotor. The aerodynamic loads are decomposed into components of the real eigenvectors of the rotor and subsequently into full-power and cross-spectral densities. These modal spectra are submitted as input to a modified NASTRAN random load analysis and the power spectra of selected responses are obtained. This procedure appears to be successful. Results at zero turbulence agree with alternative solutions, and when turbulence is included, the predicted stress spectra for the Indal 6400 rotor are in good agreement with field data. The model predicts that the effect of turbulence on harmonic frequency peaks and on all lead-lag bending will not be great. However, it appears that only 11 percent turbulence intensity can almost double the rms of cyclic flatwise blade bending.

BMI Group-Related Differences in Physical Fitness and Physical Activity in Preschool-Age Children: A Cross-Sectional Analysis

ERIC Educational Resources Information Center

Niederer, Iris; Kriemler, Susi; Zahner, Lukas; Burgi, Flavia; Ebenegger, Vincent; Marques- Vidal, Pedro; Puder, Jardena J.

2012-01-01

In the Ballabeina study, we investigated age- and BMI-group-related differences in aerobic fitness (20 m shuttle run), agility (obstacle course), dynamic (balance beam) and static balance (balance platform), and physical activity (PA, accelerometers) in 613 children (M age = 5.1 years, SD = 0.6). Normal weight (NW) children performed better than…

Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests

PubMed Central

Kim, Hyun Chan; Song, Sangho; Kim, Jaehwan

2016-01-01

This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm2, thus fitting the 1.8 × 1.8 mm2 haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices. PMID:27649184

Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization

NASA Technical Reports Server (NTRS)

Greem. David; DuToit, Cornelis

2013-01-01

The goal of this work was to improve off-axis cross-polarization performance and ease of assembly of a circularly polarized microwave antenna element. To ease assembly, the initial design requirement of Hexweb support for the internal circuit part, as well as the radiating disks, was eliminated. There is a need for different plating techniques to improve soldering. It was also desirable to change the design to eliminate soldering as well as the need to use the Hexweb support. Thus, a technique was developed to build the feed without using solder, solving the lathing and soldering issue. Internal parts were strengthened by adding curvature to eliminate Hexweb support, and in the process, the new geometries of the internal parts opened the way for improving the off-axis cross-polarization performance as well. The radiating disks curvatures were increased for increased strength, but it was found that this also improved crosspolarization. Optimization of the curvatures leads to very low off-axis cross-polarization. The feed circuit was curved into a cylinder for improved strength, eliminating Hexweb support. An aperture coupling feed mechanism eliminated the need for feed pins to the disks, which would have required soldering. The aperture coupling technique also improves cross-polarization performance by effectively exciting the radiating disks very close to the antenna s central axis of symmetry. Because of the shape of the parts, it allowed for an all-aluminum design bolted together and assembled with no solder needed. The advantage of a solderless design is that the reliability is higher, with no single-point failure (solder), and no need for special plating techniques in order to solder the unit together. The shapes (curved or round) make for a more robust build without extra support materials, as well as improved offaxis cross-polarization.

The effectiveness of front fork systems at damping accelerations during isolated aspects specific to cross-country mountain biking.

PubMed

Macdermid, Paul W; Miller, Matthew C; Fink, Philip W; Stannard, Stephen R

2017-11-01

Cross-country mountain bike suspension reportedly enhances comfort and performance through reduced vibration and impact exposure. This study analysed the effectiveness of three different front fork systems at damping accelerations during the crossing of three isolated obstacles (stairs, drop, and root). One participant completed three trials on six separate occasions in a randomised order using rigid, air-sprung, and carbon leaf-sprung forks. Performance was determined by time to cross obstacles, while triaxial accelerometers quantified impact exposure and damping response. Results identified significant main effect of fork type for performance time (p < 0.05). The air-sprung and leaf-sprung forks were significantly slower than the rigid forks for the stairs (p < 0.05), while air-sprung suspension was slower than the rigid for the root protocol (p < 0.05). There were no differences for the drop protocol (p < 0.05). Rigid forks reduced overall exposure (p < 0.05), specifically at the handlebars for the stairs and drop trials. More detailed analysis presented smaller vertical accelerations at the handlebar for air-sprung and leaf-sprung forks on the stairs (p < 0.05), and drop (p < 0.05) but not the root. As such, it appears that the suspension systems tested were ineffective at reducing overall impact exposure at the handlebar during isolated aspects of cross-country terrain features which may be influenced to a larger extent by rider technique.

Advances in Field Deployable Instrumented Particles for the Study of Alluvial Transport Mechanisms

NASA Astrophysics Data System (ADS)

Dillon, B.; Strom, K.

2017-12-01

Advances in microelectromechanical systems (MEMs) in the past decade have lead to the development of various instrumented or "smart" particles for use in the study of alluvial transport. The goal of many of these devices is to collect data on the interaction between hydrodynamic turbulence and individual sediment particles. Studying this interaction provides a basis to better understand entrainment and deposition processes which leads to better predictive morphologic and transport models. In collecting data on these processes, researchers seek to capture the time history of the forces incident on the particle and the particle's reaction. Many methods have been employed to capture this data - miniaturized pressure traps, accelerometers, gyroscopes, MEMs pressure transducers, and cantilevered load cells. However no system to date has been able to capture the pressure forces incident on the particle and its reaction while remaining mobile and of a size and density comparable to most gravels. Advances in the development, deployment, and use of waterproofed laboratory instrumentation have led our research group to develop such a particle. This particle has been used in both laboratory settings and large-scale fluvial environments (coupled with a field-deployable PIV system) to capture data on turbulent erosion processes. This system advances the practice in several ways: 1) It is, at present, the smallest (⌀ 19mm) instrumented erodible particle reported in the literature. 2) It contains novel developments in pressure sensing technology which allow the inclusion of six pressure ports, a 3-axis accelerometer, and a 1-axis gyroscope - all of which can be recorded simultaneously. 3) It expands the researcher's abilities to gather data on phenomena that, previously, have mandated the use of a laboratory scale model. The use of this system has generated observations of the so-called very large scale motions (VLSMs) in a reach of the Virginia section of the New River. Their effects on erosional processes are presented.

Squeeze-Film Air Damping of a Five-Axis Electrostatic Bearing for Rotary Micromotors

PubMed Central

Wang, Shunyue; Han, Fengtian; Sun, Boqian; Li, Haixia

2017-01-01

Air-film damping, which dominates over other losses, plays a significant role in the dynamic response of many micro-fabricated devices with a movable mass suspended by various bearing mechanisms. Modeling the damping characteristics accurately will be greatly helpful to the bearing design, control, and test in various micromotor devices. This paper presents the simulated and experimental squeeze-film air damping results of an electrostatic bearing for use in a rotary high-speed micromotor. It is shown that the boundary condition to solve the three-dimensional Reynolds equation, which governs the squeeze-film damping in the air gap between the rotor and its surrounding stator sealed in a three-layer evacuated cavity, behaves with strong cross-axis coupling characteristics. To accurately characterize the damping effect, a set of multiphysics finite-element simulations are performed by computing both the rotor velocity and the distribution of the viscous damping force acting on the rotor. The damping characteristics varying with several key structure parameters are simulated and discussed to optimize the device structure for desirable rotor dynamics. An electrical measurement method is also proposed and applied to validate the numerical results of the damping coefficients experimentally. Given that the frequency response of the electric bearing is critically dependent on the damping coefficients at atmospheric pressure, a solution to the air-film damping measurement problem is presented by taking approximate curve fitting of multi-axis experimental frequency responses. The measured squeeze-film damping coefficients for the five-axis electric bearing agrees well with the numerical solutions. This indicates that numerical multiphysics simulation is an effective method to accurately examine the air-film damping effect for complex device geometry and arbitrary boundary condition. The accurate damping coefficients obtained by FEM simulation will greatly simplify the design of the five-axis bearing control system and facilitate the initial suspension test of the rotor for various micromotor devices. PMID:28505089

Squeeze-Film Air Damping of a Five-Axis Electrostatic Bearing for Rotary Micromotors.

PubMed

Wang, Shunyue; Han, Fengtian; Sun, Boqian; Li, Haixia

2017-05-13

Air-film damping, which dominates over other losses, plays a significant role in the dynamic response of many micro-fabricated devices with a movable mass suspended by various bearing mechanisms. Modeling the damping characteristics accurately will be greatly helpful to the bearing design, control, and test in various micromotor devices. This paper presents the simulated and experimental squeeze-film air damping results of an electrostatic bearing for use in a rotary high-speed micromotor. It is shown that the boundary condition to solve the three-dimensional Reynolds equation, which governs the squeeze-film damping in the air gap between the rotor and its surrounding stator sealed in a three-layer evacuated cavity, behaves with strong cross-axis coupling characteristics. To accurately characterize the damping effect, a set of multiphysics finite-element simulations are performed by computing both the rotor velocity and the distribution of the viscous damping force acting on the rotor. The damping characteristics varying with several key structure parameters are simulated and discussed to optimize the device structure for desirable rotor dynamics. An electrical measurement method is also proposed and applied to validate the numerical results of the damping coefficients experimentally. Given that the frequency response of the electric bearing is critically dependent on the damping coefficients at atmospheric pressure, a solution to the air-film damping measurement problem is presented by taking approximate curve fitting of multi-axis experimental frequency responses. The measured squeeze-film damping coefficients for the five-axis electric bearing agrees well with the numerical solutions. This indicates that numerical multiphysics simulation is an effective method to accurately examine the air-film damping effect for complex device geometry and arbitrary boundary condition. The accurate damping coefficients obtained by FEM simulation will greatly simplify the design of the five-axis bearing control system and facilitate the initial suspension test of the rotor for various micromotor devices.

Material mechanical characterization method for multiple strains and strain rates

DOEpatents

Erdmand, III, Donald L.; Kunc, Vlastimil; Simunovic, Srdjan; Wang, Yanli

2016-01-19

A specimen for measuring a material under multiple strains and strain rates. The specimen including a body having first and second ends and a gage region disposed between the first and second ends, wherein the body has a central, longitudinal axis passing through the first and second ends. The gage region includes a first gage section and a second gage section, wherein the first gage section defines a first cross-sectional area that is defined by a first plane that extends through the first gage section and is perpendicular to the central, longitudinal axis. The second gage section defines a second cross-sectional area that is defined by a second plane that extends through the second gage section and is perpendicular to the central, longitudinal axis and wherein the first cross-sectional area is different in size than the second cross-sectional area.

Fast Estimation of Strains for Cross-Beams Six-Axis Force/Torque Sensors by Mechanical Modeling

PubMed Central

Ma, Junqing; Song, Aiguo

2013-01-01

Strain distributions are crucial criteria of cross-beams six-axis force/torque sensors. The conventional method for calculating the criteria is to utilize Finite Element Analysis (FEA) to get numerical solutions. This paper aims to obtain analytical solutions of strains under the effect of external force/torque in each dimension. Genetic mechanical models for cross-beams six-axis force/torque sensors are proposed, in which deformable cross elastic beams and compliant beams are modeled as quasi-static Timoshenko beam. A detailed description of model assumptions, model idealizations, application scope and model establishment is presented. The results are validated by both numerical FEA simulations and calibration experiments, and test results are found to be compatible with each other for a wide range of geometric properties. The proposed analytical solutions are demonstrated to be an accurate estimation algorithm with higher efficiency. PMID:23686144

Transect studies on pine forests along parallel 52° north, 12-32° east and along a pollution gradient in Poland: general assumptions

Treesearch

Alicja Breymeyer

1998-01-01

The responses of pine forest to changing climate and environmental chemistry were studied along two transects following the pollution and continentality gradients in Poland. One axis begins on the western border of Poland, crosses the country along the 52nd parallel, and ends on the eastern border of Poland in the area of Bialowieza National Park, Biosphere Reserve....

Tightly-coupled real-time analysis of GPS and accelerometer data for translational and rotational ground motions and application to earthquake and tsunami early warning

NASA Astrophysics Data System (ADS)

Geng, J.; Bock, Y.; Melgar, D.; Hasse, J.; Crowell, B. W.

2013-12-01

High-rate GPS can play an important role in earthquake early warning (EEW) systems for large (>M6) events by providing permanent displacements immediately as they are achieved, to be used in source inversions that can be repeatedly updated as more information becomes available. This is most valuable to implement at a site very near the potential source rupture, where broadband seismometers are likely to clip, and accelerometer data cannot be objectively integrated to produce reliable displacements in real time. At present, more than 525 real-time GPS stations have been established in western North America, which are being integrated into EEW systems. Our analysis technique relies on a tightly-coupled combination of GPS and accelerometer data, an extension of precise point positioning with ambiguity resolution (PPP-AR). We operate a PPP service based on North American stations available through the IGS and UNAVCO/PBO. The service provides real-time satellite clock and fractional-cycle bias products that allow us to position individual client stations in the zone of deformation. The service reference stations are chosen to be further than 200 km from the primary zones of tectonic deformation in the western U.S. to avoid contamination of the satellite products during a large seismic event. At client stations, accelerometer data are applied as tight constraints on the positions between epochs in PPP-AR, which improves cycle-slip repair and rapid ambiguity resolution after GPS outages. Furthermore, we estimate site displacements, seismic velocities, and coseismic ground tilts to facilitate the analysis of ground motion characteristics and the inversion for source mechanisms. The seismogeodetic displacement and velocity waveforms preserves the detection of P wave arrivals, and provides P-wave arrival displacement that is key new information for EEW. Our innovative solution method for coseismic tilts mitigates an error source that has continually plagued strong motion data analysis, and has a resolution of about 0.01 degrees. At present, there are few collocations of GPS and accelerometers in western North America (the exception being the BARD network in northern California) so we have developed a cost-effective way to upgrade existing real-time GPS stations with low-cost MEMS accelerometers; fifteen PBO and SCIGN stations in southern California have already been upgraded. We demonstrate our method of recovering broadband displacement and tilt waveforms using 13 experiments from the single-axis George E. Brown Jr. Network for Earthquake Engineering Simulation Large High-Performance Outdoor Shake Table at the University of California San Diego. Then we apply the method to data from the 2010 Mw 7.2 El Mayor-Cucapah earthquake and the 2011 Mw 9.0 Tohoku-oki earthquake to illustrate the improvement over standard base-line correction acceleration techniques and to demonstrate the order of magnitude of tilt errors present in typical observations.

A methodology to leverage cross-sectional accelerometry to capture weather's influence in active living research.

PubMed

Katapally, Tarun R; Rainham, Daniel; Muhajarine, Nazeem

2016-06-27

While active living interventions focus on modifying urban design and built environment, weather variation, a phenomenon that perennially interacts with these environmental factors, is consistently underexplored. This study's objective is to develop a methodology to link weather data with existing cross-sectional accelerometry data in capturing weather variation. Saskatoon's neighbourhoods were classified into grid-pattern, fractured grid-pattern and curvilinear neighbourhoods. Thereafter, 137 Actical accelerometers were used to derive moderate to vigorous physical activity (MVPA) and sedentary behaviour (SB) data from 455 children in 25 sequential one-week cycles between April and June, 2010. This sequential deployment was necessary to overcome the difference in the ratio between the sample size and the number of accelerometers. A data linkage methodology was developed, where each accelerometry cycle was matched with localized (Saskatoon-specific) weather patterns derived from Environment Canada. Statistical analyses were conducted to depict the influence of urban design on MVPA and SB after factoring in localized weather patterns. Integration of cross-sectional accelerometry with localized weather patterns allowed the capture of weather variation during a single seasonal transition. Overall, during the transition from spring to summer in Saskatoon, MVPA increased and SB decreased during warmer days. After factoring in localized weather, a recurring observation was that children residing in fractured grid-pattern neighbourhoods accumulated significantly lower MVPA and higher SB. The proposed methodology could be utilized to link globally available cross-sectional accelerometry data with place-specific weather data to understand how built and social environmental factors interact with varying weather patterns in influencing active living.

Dual axis operation of a micromachined rate gyroscope

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

Juneau, T.; Pisano, A.P.; Smith, J.

Since micromachining technology has raised the prospect of fabricating high performance sensors without the associated high cost and large size, many researchers have investigated micromachined rate gyroscopes. The vast majority of research has focused on single input axis rate gyroscopes, but this paper presents work on a dual input axis micromachined rate gyroscope. The key to successful simultaneous dual axis operation is the quad symmetry of the circular oscillating rotor design. Untuned gyroscopes with mismatched modes yielded random walk as low as 10{degrees}/{radical}hour with cross sensitivity ranging from 6% to 16%. Mode frequency matching via electrostatic tuning allowed performance bettermore » than 2{degrees}/{radical}hour, but at the expense of excessive cross sensitivity.« less

Current Measurements and Overwash Monitoring Using Tilt Current Meters in Three Coastal Environments

NASA Astrophysics Data System (ADS)

Lowell, N. S.; Sherwood, C. R.; Decarlo, T. M.; Grant, J. R.

2014-12-01

Tilt Current Meters (TCMs) provide accurate, cost effective measurements of near-bottom current velocities. Many studies in coastal environments require current measurements, which are frequently made with Acoustic Doppler Profilers (ADPs). ADPs are expensive, however, and may not be suitable for locations where there is significant risk of damage, loss, or theft or where a large spatial array of measurements is required. TCMs, by contrast, are smaller, less expensive, and easier to deploy. This study tested TCMs in three sites to determine their suitability for use in research applications. TCMs are based on the drag-tilt principle, where the instrument tilts in response to current. The meter consists of a buoyant float with an onboard accelerometer, three-axis tilt sensor, three-axis magnetometer (compass), and a data logger. Current measurements are derived by post processing the tilt and compass values and converting them to velocity using empirical calibration data. Large data-storage capacity (4 GB) and low power requirements allow long deployments (many months) at high sample rates (16 Hz). We demonstrate the utility of TCM current measurements on a reef at Dongsha Atoll in the South China Sea, and in Vineyard Sound off Cape Cod, where the TCM performance was evaluated against ADP measurements. We have also used the TCM to record waves during an overwash event on a Cape Cod barrier beach during a winter storm. The TCM recorded waves as they came through the overwash channel, and the data were in agreement with the water-level record used as a reference. These tests demonstrate that TCMs may be used in a variety of near shore environments and have the potential to significantly increase the density of meters in future studies were current measurements are required.

Statistical analysis of road-vehicle-driver interaction as an enabler to designing behavioural models

NASA Astrophysics Data System (ADS)

Chakravarty, T.; Chowdhury, A.; Ghose, A.; Bhaumik, C.; Balamuralidhar, P.

2014-03-01

Telematics form an important technology enabler for intelligent transportation systems. By deploying on-board diagnostic devices, the signatures of vehicle vibration along with its location and time are recorded. Detailed analyses of the collected signatures offer deep insights into the state of the objects under study. Towards that objective, we carried out experiments by deploying telematics device in one of the office bus that ferries employees to office and back. Data is being collected from 3-axis accelerometer, GPS, speed and the time for all the journeys. In this paper, we present initial results of the above exercise by applying statistical methods to derive information through systematic analysis of the data collected over four months. It is demonstrated that the higher order derivative of the measured Z axis acceleration samples display the properties Weibull distribution when the time axis is replaced by the amplitude of such processed acceleration data. Such an observation offers us a method to predict future behaviour where deviations from prediction are classified as context-based aberrations or progressive degradation of the system. In addition we capture the relationship between speed of the vehicle and median of the jerk energy samples using regression analysis. Such results offer an opportunity to develop a robust method to model road-vehicle interaction thereby enabling us to predict such like driving behaviour and condition based maintenance etc.

Accelerometer-based wireless body area network to estimate intensity of therapy in post-acute rehabilitation

PubMed Central

Choquette, Stéphane; Hamel, Mathieu; Boissy, Patrick

2008-01-01

Background It has been suggested that there is a dose-response relationship between the amount of therapy and functional recovery in post-acute rehabilitation care. To this day, only the total time of therapy has been investigated as a potential determinant of this dose-response relationship because of methodological and measurement challenges. The primary objective of this study was to compare time and motion measures during real life physical therapy with estimates of active time (i.e. the time during which a patient is active physically) obtained with a wireless body area network (WBAN) of 3D accelerometer modules positioned at the hip, wrist and ankle. The secondary objective was to assess the differences in estimates of active time when using a single accelerometer module positioned at the hip. Methods Five patients (77.4 ± 5.2 y) with 4 different admission diagnoses (stroke, lower limb fracture, amputation and immobilization syndrome) were recruited in a post-acute rehabilitation center and observed during their physical therapy sessions throughout their stay. Active time was recorded by a trained observer using a continuous time and motion analysis program running on a Tablet-PC. Two WBAN configurations were used: 1) three accelerometer modules located at the hip, wrist and ankle (M3) and 2) one accelerometer located at the hip (M1). Acceleration signals from the WBANs were synchronized with the observations. Estimates of active time were computed based on the temporal density of the acceleration signals. Results A total of 62 physical therapy sessions were observed. Strong associations were found between WBANs estimates of active time and time and motion measures of active time. For the combined sessions, the intraclass correlation coefficient (ICC) was 0.93 (P ≤ 0.001) for M3 and 0.79 (P ≤ 0.001) for M1. The mean percentage of differences between observation measures and estimates from the WBAN of active time was -8.7% ± 2.0% using data from M3 and -16.4% ± 10.4% using data from M1. Conclusion WBANs estimates of active time compare favorably with results from observation-based time and motion measures. While the investigation on the association between active time and outcomes of rehabilitation needs to be studied in a larger scale study, the use of an accelerometer-based WBAN to measure active time is a promising approach that offers a better overall precision than methods relying on work sampling. Depending on the accuracy needed, the use of a single accelerometer module positioned on the hip may still be an interesting alternative to using multiple modules. PMID:18764954

Precision grip responses to unexpected rotational perturbations scale with axis of rotation.

PubMed

De Gregorio, Michael; Santos, Veronica J

2013-04-05

It has been established that rapid, pulse-like increases in precision grip forces ("catch-up responses") are elicited by unexpected translational perturbations and that response latency and strength scale according to the direction of linear slip relative to the hand as well as gravity. To determine if catch-up responses are elicited by unexpected rotational perturbations and are strength-, axis-, and/or direction-dependent, we imposed step torque loads about each of two axes which were defined relative to the subject's hand: the distal-proximal axis away from and towards the subject's palm, and the grip axis which connects the two fingertips. Precision grip responses were dominated initially by passive mechanics and then by active, unimodal catch-up responses. First dorsal interosseous activity, marking the start of the catch-up response, began 71-89 ms after the onset of perturbation. The onset latency, shape, and duration (217-231 ms) of the catch-up response were not affected by the axis, direction, or magnitude of the rotational perturbation, while strength was scaled by axis of rotation and slip conditions. Rotations about the grip axis that tilted the object away from the palm and induced rotational slip elicited stronger catch-up responses than rotations about the distal-proximal axis that twisted the object between the digits. To our knowledge, this study is the first to investigate grip responses to unexpected torque loads and to show characteristic, yet axis-dependent, catch-up responses for conditions other than pure linear slip. Copyright © 2013 Elsevier Ltd. All rights reserved.

Do different data analytic approaches generate discrepant findings when measuring mother-infant HPA axis attunement?

PubMed

Bernard, Nicola K; Kashy, Deborah A; Levendosky, Alytia A; Bogat, G Anne; Lonstein, Joseph S

2017-03-01

Attunement between mothers and infants in their hypothalamic-pituitary-adrenal (HPA) axis responsiveness to acute stressors is thought to benefit the child's emerging physiological and behavioral self-regulation, as well as their socioemotional development. However, there is no universally accepted definition of attunement in the literature, which appears to have resulted in inconsistent statistical analyses for determining its presence or absence, and contributed to discrepant results. We used a series of data analytic approaches, some previously used in the attunement literature and others not, to evaluate the attunement between 182 women and their 1-year-old infants in their HPA axis responsivity to acute stress. Cortisol was measured in saliva samples taken from mothers and infants before and twice after a naturalistic laboratory stressor (infant arm restraint). The results of the data analytic approaches were mixed, with some analyses suggesting attunement while others did not. The strengths and weaknesses of each statistical approach are discussed, and an analysis using a cross-lagged model that considered both time and interactions between mother and infant appeared the most appropriate. Greater consensus in the field about the conceptualization and analysis of physiological attunement would be valuable in order to advance our understanding of this phenomenon. © 2016 Wiley Periodicals, Inc.

Theoretical performance of cross-wind axis turbines with results for a catenary vertical axis configuration

NASA Technical Reports Server (NTRS)

Muraca, R. J.; Stephens, M. V.; Dagenhart, J. R.

1975-01-01

A general analysis capable of predicting performance characteristics of cross-wind axis turbines was developed, including the effects of airfoil geometry, support struts, blade aspect ratio, windmill solidity, blade interference and curved flow. The results were compared with available wind tunnel results for a catenary blade shape. A theoretical performance curve for an aerodynamically efficient straight blade configuration was also presented. In addition, a linearized analytical solution applicable for straight configurations was developed. A listing of the computer program developed for numerical solutions of the general performance equations is included in the appendix.

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

Giunta, G.; Belouettar, S.

In this paper, the static response of three-dimensional beams made of functionally graded materials is investigated through a family of hierarchical one-dimensional finite elements. A wide variety of elements is proposed differing by the kinematic formulation and the number of nodes per elements along the beam axis. Elements’ stiffness matrix and load vector are derived in a unified nuclear form that does not depend upon the a priori expansion order over the cross-section nor the finite element approximation along the beam axis. Results are validated towards three-dimensional finite element models as well as equivalent Navier-type analytical solutions. The numerical investigationsmore » show that accurate and efficient solutions (when compared with full three-dimensional FEM solutions) can be obtained by the proposed family of hierarchical one-dimensional elements’ family.« less

The contribution of walking to work to adult physical activity levels: a cross sectional study.

PubMed

Audrey, Suzanne; Procter, Sunita; Cooper, Ashley R

2014-03-11

To objectively examine the contribution to adult physical activity levels of walking to work. Employees (n = 103; 36.3 ± 11.7 years) at 17 workplaces in south-west England, who lived within 2 miles (3.2 km) of their workplace, wore Actigraph accelerometers for seven days during waking hours and carried GPS receivers during the commute to and from work. Physical activity volume (accelerometer counts per minute (cpm)) and intensity (minutes of moderate to vigorous physical activity (MVPA)) were computed overall and during the walk to work. Total weekday physical activity was 45% higher in participants who walked to work compared to those travelling by car (524.6. ± 170.4 vs 364.6 ± 138.4 cpm) and MVPA almost 60% higher (78.1 ± 24.9 vs 49.8 ± 25.2 minutes per day). No differences were seen in weekend physical activity, and sedentary time did not differ between the groups. Combined accelerometer and GPS data showed that walking to work contributed 47.3% of total weekday MVPA. Walking to work was associated with overall higher levels of physical activity in young and middle-aged adults. These data provide preliminary evidence to underpin the need for interventions to increase active commuting, specifically walking, in adults.

The Relationship Between Time of Day of Physical Activity and Obesity in Older Women.

PubMed

Chomistek, Andrea K; Shiroma, Eric J; Lee, I-Min

2016-04-01

Physical activity is important for maintaining healthy weight. The time of day when exercise is performed-a highly discretionary aspect of behavior-may impact weight control, but evidence is limited. Thus, we examined the association between the timing of physical activity and obesity risk in women. A cross-sectional analysis was conducted among 7157 Women's Health Study participants who participated in an ancillary study begun in 2011 that is measuring physical activity using accelerometers. The exposure was percentage of total accelerometer counts accumulated before 12:00 noon and the outcome was obesity. Mean (±SD) BMI among participants was 26.1 (±4.9) kg/m2 and 1322 women were obese. The mean activity counts per day was 203,870 (±95,811) of which a mean 47.1% (±11.5%) were recorded in the morning. In multivariable-adjusted models, women who recorded < 39% (lowest quartile) of accelerometer counts before 12:00 noon had a 26% higher odds of being obese, compared with those recording ≥ 54% (highest quartile) of counts before noon (Ptrend = 0.02). These study findings-that women who are less active during morning hours may be at higher risk of obesity-if confirmed can provide a novel strategy to help combat the important health problem of obesity.

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.

Health Benefits of Light-Intensity Physical Activity: A Systematic Review of Accelerometer Data of the National Health and Nutrition Examination Survey (NHANES).

PubMed

Füzéki, Eszter; Engeroff, Tobias; Banzer, Winfried

2017-09-01

The health effects of light-intensity physical activity (PA) are not well known today. We conducted a systematic review to assess the association of accelerometer-measured light-intensity PA with modifiable health outcomes in adults and older adults. A systematic literature search up to March 2016 was performed in the PubMed, EMBASE, Web of Science and Google Scholar electronic databases, without language limitations, for studies of modifiable health outcomes in adults and older adults in the National Health and Nutrition Examination Survey accelerometer dataset. Overall, 37 cross-sectional studies and three longitudinal studies were included in the analysis, with considerable variation observed between the studies with regard to their operationalization of light-intensity PA. Light-intensity PA was found to be beneficially associated with obesity, markers of lipid and glucose metabolism, and mortality. Few data were available on musculoskeletal outcomes and results were mixed. Observational evidence that light-intensity PA can confer health benefits is accumulating. Currently inactive or insufficiently active people should be encouraged to engage in PA of any intensity. If longitudinal and intervention studies corroborate our findings, the revision of PA recommendations to include light-intensity activities, at least for currently inactive populations, might be warranted.

A pelvic motion driven electrical stimulator for drop-foot treatment.

PubMed

Chen, Shih-Wei; Chen, Shih-Ching; Chen, Chiun-Fan; Lai, Jin-Shin; Kuo, Te-Son

2009-01-01

Foot switches operating with force sensitive resistors placed in the shoe sole were considered as an effective way for driving FES assisted walking systems in gait restoration. However, the reliability and durability of the foot switches run down after a certain number of steps. As an alternative for foot switches, a simple, portable, and easy to handle motion driven electrical stimulator (ES) is provided for drop foot treatment. The device is equipped with a single tri-axis accelerometer worn on the pelvis, a commercial dual channel electrical stimulator, and a controller unit. By monitoring the pelvic rotation and acceleration during a walking cycle, the events including heel strike and toe off of each step is thereby predicted by a post-processing neural network model.

Dynamic motion modes of high temperature superconducting maglev on a 45-m long ring test line

NASA Astrophysics Data System (ADS)

Lei, W. Y.; Qian, N.; Zheng, J.; Jin, L. W.; Zhang, Y.; Deng, Z. G.

2017-10-01

With the development of high temperature superconducting (HTS) maglev, studies on the running stability have become more and more significant to ensure the operation safety. An experimental HTS maglev vehicle was tested on a 45-m long ring test line under the speed from 4 km/h to 20 km/h. The lateral and vertical acceleration signals of each cryostat were collected by tri-axis accelerometers in real time. By analyzing the phase relationship of acceleration signals on the four cryostats, several typical motion modes of the HTS maglev vehicle, including lateral, yaw, pitch and heave motions were observed. This experimental finding is important for the next improvement of the HTS maglev system.

Improved Signal Processing Technique Leads to More Robust Self Diagnostic Accelerometer System

NASA Technical Reports Server (NTRS)

Tokars, Roger; Lekki, John; Jaros, Dave; Riggs, Terrence; Evans, Kenneth P.

2010-01-01

The self diagnostic accelerometer (SDA) is a sensor system designed to actively monitor the health of an accelerometer. In this case an accelerometer is considered healthy if it can be determined that it is operating correctly and its measurements may be relied upon. The SDA system accomplishes this by actively monitoring the accelerometer for a variety of failure conditions including accelerometer structural damage, an electrical open circuit, and most importantly accelerometer detachment. In recent testing of the SDA system in emulated engine operating conditions it has been found that a more robust signal processing technique was necessary. An improved accelerometer diagnostic technique and test results of the SDA system utilizing this technique are presented here. Furthermore, the real time, autonomous capability of the SDA system to concurrently compensate for effects from real operating conditions such as temperature changes and mechanical noise, while monitoring the condition of the accelerometer health and attachment, will be demonstrated.

A Novel Inexpensive Use of Smartphone Technology for Ecological Momentary Assessment in Middle-Aged Women.

PubMed

Ehlers, Diane K; Huberty, Jennifer; Buman, Matthew; Hooker, Steven; Todd, Michael; de Vreede, Gert-Jan

2016-03-01

Commercially available mobile and Internet technologies present a promising opportunity to feasibly conduct ecological momentary assessment (EMA). The purpose of this study was to describe a novel EMA protocol administered on middle-aged women's smartphones via text messaging and mobile Internet. Women (N = 9; mean age = 46.2 ± 8.2 y) received 35 text message prompts to a mobile survey assessing activity, self-worth, and self-efficacy over 14 days. Prompts were scheduled and surveys were administered using commercial, Internet-based programs. Prompting was tailored to each woman's daily wake/sleep schedule. Women concurrently wore a wrist-worn accelerometer. Feasibility was assessed via survey completion, accelerometer wear, participant feedback, and researcher notes. Of 315 prompted surveys, 287 responses were valid (91.1%). Average completion time was 1.52 ± 1.03 minutes. One participant's activity data were excluded due to accelerometer malfunction, resulting in complete data from 8 participants (n = 252 [80.0%] valid observations). Women reported the survey was easily and quickly read/completed. However, most thought the accelerometer was inconvenient. High completion rates and perceived usability suggest capitalizing on widely available technology and tailoring prompting schedules may optimize EMA in middle-aged women. However, researchers may need to carefully select objective monitors to maintain data validity while limiting participant burden.

Single-accelerometer-based daily physical activity classification.

PubMed

Long, Xi; Yin, Bin; Aarts, Ronald M

2009-01-01

In this study, a single tri-axial accelerometer placed on the waist was used to record the acceleration data for human physical activity classification. The data collection involved 24 subjects performing daily real-life activities in a naturalistic environment without researchers' intervention. For the purpose of assessing customers' daily energy expenditure, walking, running, cycling, driving, and sports were chosen as target activities for classification. This study compared a Bayesian classification with that of a Decision Tree based approach. A Bayes classifier has the advantage to be more extensible, requiring little effort in classifier retraining and software update upon further expansion or modification of the target activities. Principal components analysis was applied to remove the correlation among features and to reduce the feature vector dimension. Experiments using leave-one-subject-out and 10-fold cross validation protocols revealed a classification accuracy of approximately 80%, which was comparable with that obtained by a Decision Tree classifier.

Acquisition and Analysis of Dynamic Responses of a Historic Pedestrian Bridge using Video Image Processing

NASA Astrophysics Data System (ADS)

O'Byrne, Michael; Ghosh, Bidisha; Schoefs, Franck; O'Donnell, Deirdre; Wright, Robert; Pakrashi, Vikram

2015-07-01

Video based tracking is capable of analysing bridge vibrations that are characterised by large amplitudes and low frequencies. This paper presents the use of video images and associated image processing techniques to obtain the dynamic response of a pedestrian suspension bridge in Cork, Ireland. This historic structure is one of the four suspension bridges in Ireland and is notable for its dynamic nature. A video camera is mounted on the river-bank and the dynamic responses of the bridge have been measured from the video images. The dynamic response is assessed without the need of a reflector on the bridge and in the presence of various forms of luminous complexities in the video image scenes. Vertical deformations of the bridge were measured in this regard. The video image tracking for the measurement of dynamic responses of the bridge were based on correlating patches in time-lagged scenes in video images and utilisinga zero mean normalised cross correlation (ZNCC) metric. The bridge was excited by designed pedestrian movement and by individual cyclists traversing the bridge. The time series data of dynamic displacement responses of the bridge were analysedto obtain the frequency domain response. Frequencies obtained from video analysis were checked against accelerometer data from the bridge obtained while carrying out the same set of experiments used for video image based recognition.

Modelling resonances of the standing body exposed to vertical whole-body vibration: Effects of posture

NASA Astrophysics Data System (ADS)

Subashi, G. H. M. J.; Matsumoto, Y.; Griffin, M. J.

2008-10-01

Lumped parameter mathematical models representing anatomical parts of the human body have been developed to represent body motions associated with resonances of the vertical apparent mass and the fore-and-aft cross-axis apparent mass of the human body standing in five different postures: 'upright', 'lordotic', 'anterior lean', 'knees bent', and 'knees more bent'. The inertial and geometric parameters of the models were determined from published anthropometric data. Stiffness and damping parameters were obtained by comparing model responses with experimental data obtained previously. The principal resonance of the vertical apparent mass, and the first peak in the fore-and-aft cross-axis apparent mass, of the standing body in an upright posture (at 5-6 Hz) corresponded to vertical motion of the viscera in phase with the vertical motion of the entire body due to deformation of the tissues at the soles of the feet, with pitch motion of the pelvis out of phase with pitch motion of the upper body above the pelvis. Upward motion of the body was in phase with the forward pitch motion of the pelvis. Changing the posture of the upper body had minor effects on the mode associated with the principal resonances of the apparent mass and cross-axis apparent mass, but the mode changed significantly with bending of the legs. In legs-bent postures, the principal resonance (at about 3 Hz) was attributed to bending of the legs coupled with pitch motion of the pelvis in phase with pitch motion of the upper body. In this mode, extension of the legs was in phase with the forward pitch motion of the upper body and the upward vertical motion of the viscera.

Induced strain actuation of composite beams and rotor blades with embedded piezoceramic elements

NASA Astrophysics Data System (ADS)

Chen, Peter C.; Chopra, Inderjit

1996-02-01

The objective of this research is to develop a dynamically-scaled (Froude scale) helicopter rotor blade with embedded piezoceramic elements as sensors and actuators to control blade vibrations. A 6 ft diameter 2-bladed bearingless rotor model was built where each blade is embedded with banks of piezoelectric actuators at 0964-1726/5/1/005/img1 degree angles with respect to the beam axis on the top and bottom surfaces. A twist distribution along the blade span is achieved through in-phase excitation of the top and bottom actuators at equal potentials, while a bending distribution is achieved through out-of-phase excitation. In order to fix design variables and to optimize blade performance, a uniform strain beam theory is formulated to analytically predict the static bending and torsional response of composite rectangular beams with embedded piezoelectric actuators. Parameters such as bond thicknesses, actuator skew angle and actuator spacing are investigated by experiments and then validated by theory. The static bending and torsional response of the rotor blades is experimentally measured and correlated with theory. Dynamic torsional and bending responses are experimentally determined for frequencies from 2 - 120 Hz to assess the viability of a vibration reduction system based on piezo-actuation of blade twist. To assess the performance of the piezo-actuators in rotation, hover tests were conducted where accelerometers embedded in the blades were used to resolve the tip twist amplitudes. Although the magnitudes of blade twist attained in this experiment were small, it is expected that future models can be built with improved performance.

Ridge-crossing mantle plumes and gaps in tracks

NASA Astrophysics Data System (ADS)

Sleep, Norman H.

2002-12-01

Hot spot tracks approach, cross, and leave ridge axes. The complications of this process make it difficult to determine the track followed by a plume and the evolution of its vigor. When a plume is sufficiently near the ridge axis, buoyant plume material flows along the base of the lithosphere toward the axis, forming an on-axis hot spot. The track of the on-axis hot spot is a symmetric V on both plates and an unreliable indication of the path followed by the plume. Aseismic ridges form more or less along flowlines from a plume to a ridge axis when channels form at the base of the lithosphere. A dynamic effect is that off-axis hot spots appear to shut off at the time that an on-axis hot spot becomes active along an axis-approaching track. This produces a gap in the obvious track and a jump of the hot spot to the ridge axis. The gap results from the effects of ponded plume material on intraplate (membrane) stress. Membrane tension lets dikes ascend efficiently to produce obvious tracks of edifices. An off-axis hot spot shuts down when the plume is sufficiently near the ridge axis that plume material flows there, putting the nearby lithosphere above the plume into compression, preventing dikes. In addition, the off-axis thickness of plume material, which produces membrane tension, decreases as the slope of the base of the lithosphere increases beneath young lithosphere. Slow spreading rates favor gaps produced in this way. Gaps are observed near both fast and slow ridges.

The application of image processing in the measurement for three-light-axis parallelity of laser ranger

NASA Astrophysics Data System (ADS)

Wang, Yang; Wang, Qianqian

2008-12-01

When laser ranger is transported or used in field operations, the transmitting axis, receiving axis and aiming axis may be not parallel. The nonparallelism of the three-light-axis will affect the range-measuring ability or make laser ranger not be operated exactly. So testing and adjusting the three-light-axis parallelity in the production and maintenance of laser ranger is important to ensure using laser ranger reliably. The paper proposes a new measurement method using digital image processing based on the comparison of some common measurement methods for the three-light-axis parallelity. It uses large aperture off-axis paraboloid reflector to get the images of laser spot and white light cross line, and then process the images on LabVIEW platform. The center of white light cross line can be achieved by the matching arithmetic in LABVIEW DLL. And the center of laser spot can be achieved by gradation transformation, binarization and area filter in turn. The software system can set CCD, detect the off-axis paraboloid reflector, measure the parallelity of transmitting axis and aiming axis and control the attenuation device. The hardware system selects SAA7111A, a programmable vedio decoding chip, to perform A/D conversion. FIFO (first-in first-out) is selected as buffer.USB bus is used to transmit data to PC. The three-light-axis parallelity can be achieved according to the position bias between them. The device based on this method has been already used. The application proves this method has high precision, speediness and automatization.

Accelerometer method and apparatus for integral display and control functions

NASA Astrophysics Data System (ADS)

Bozeman, Richard J., Jr.

1992-06-01

Vibration analysis has been used for years to provide a determination of the proper functioning of different types of machinery, including rotating machinery and rocket engines. A determination of a malfunction, if detected at a relatively early stage in its development, will allow changes in operating mode or a sequenced shutdown of the machinery prior to a total failure. Such preventative measures result in less extensive and/or less expensive repairs, and can also prevent a sometimes catastrophic failure of equipment. Standard vibration analyzers are generally rather complex, expensive, and of limited portability. They also usually result in displays and controls being located remotely from the machinery being monitored. Consequently, a need exists for improvements in accelerometer electronic display and control functions which are more suitable for operation directly on machines and which are not so expensive and complex. The invention includes methods and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. The apparatus includes an accelerometer package having integral display and control functions. The accelerometer package is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine condition over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase over the selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated. The benefits of a vibration recording and monitoring system with controls and displays readily mountable on the machinery being monitored and having capabilities described will be appreciated by those working in the art.

Accelerometer method and apparatus for integral display and control functions

NASA Technical Reports Server (NTRS)

Bozeman, Richard J., Jr. (Inventor)

1992-01-01

Vibration analysis has been used for years to provide a determination of the proper functioning of different types of machinery, including rotating machinery and rocket engines. A determination of a malfunction, if detected at a relatively early stage in its development, will allow changes in operating mode or a sequenced shutdown of the machinery prior to a total failure. Such preventative measures result in less extensive and/or less expensive repairs, and can also prevent a sometimes catastrophic failure of equipment. Standard vibration analyzers are generally rather complex, expensive, and of limited portability. They also usually result in displays and controls being located remotely from the machinery being monitored. Consequently, a need exists for improvements in accelerometer electronic display and control functions which are more suitable for operation directly on machines and which are not so expensive and complex. The invention includes methods and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. The apparatus includes an accelerometer package having integral display and control functions. The accelerometer package is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine condition over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase over the selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated. The benefits of a vibration recording and monitoring system with controls and displays readily mountable on the machinery being monitored and having capabilities described will be appreciated by those working in the art.

Experimental analysis of synchronization and dynamics in an automobile as a complex system

NASA Astrophysics Data System (ADS)

González-Cruz, C. A.; Jáuregui-Correa, J. C.; López-Cajún, C.; Sen, M.; Domínguez-González, A.

2015-08-01

A complex system is composed of many interacting elements, and its behavior, as a whole, can be quite different from that of the individual elements. An automobile is an example of a common mechanical system composed of a large number of individual elements. These elements are connected through soft and hard linkages that transmit motion to each other. This paper proposes a variety of analytical tools to study experimental data from complex systems using two elements of an automobile as an example. Accelerometer measurements were taken from two elements within an automobile: the door and the dashboard. Two types of data were collected: response to impact loading, and response to road excitation of the automobile driven at different speeds. The signals were processed via Fourier and wavelet transforms, cross-correlation coefficients, Hilbert transform, and Kuramoto order parameters. A new parameter, called the order-deficit parameter, is introduced. Considerable, but not complete, synchronization can be found between the accelerations measured at these two locations in the automobile, and the degree of synchronization is quantified using the order-deficit parameter.

An analytic model of the in-line and cross-axis apparent mass of the seated human body exposed to vertical vibration with and without a backrest

NASA Astrophysics Data System (ADS)

Zheng, Guangtai; Qiu, Yi; Griffin, Michael J.

2011-12-01

During vertical excitation of the seated human body there are vertical and fore-and-aft forces at the seat that are influenced by contact with a backrest, so it is desirable to take into account the effect of a backrest when developing models of the seated human body. Initially, a seven degree-of-freedom multi-body dynamic model was developed for the human body sitting with an upright posture unsupported by a backrest and exposed to vertical vibration. The model was optimized to fit the vertical apparent mass and the fore-and-aft cross-axis apparent mass measured on a seat. The model was then extended by the addition of vertical and fore-and-aft reaction forces to the upper lumbar spine to model the interaction between the human body and a backrest. By minimizing the least square error between experimental data and the analytical solution of the apparent masses on the seat and at the back, the human body model was able to represent both the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and at the back. Parameter sensitivity studies showed that the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and the backrest were all highly sensitive to the axial stiffness of the tissue beneath the pelvis. Pitch motion of the upper-body contributed to the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat. The apparent mass at the back was more sensitive to the stiffness and damping of the lower back than the properties of the upper back.

Video and accelerometer-based motion analysis for automated surgical skills assessment.

PubMed

Zia, Aneeq; Sharma, Yachna; Bettadapura, Vinay; Sarin, Eric L; Essa, Irfan

2018-03-01

Basic surgical skills of suturing and knot tying are an essential part of medical training. Having an automated system for surgical skills assessment could help save experts time and improve training efficiency. There have been some recent attempts at automated surgical skills assessment using either video analysis or acceleration data. In this paper, we present a novel approach for automated assessment of OSATS-like surgical skills and provide an analysis of different features on multi-modal data (video and accelerometer data). We conduct a large study for basic surgical skill assessment on a dataset that contained video and accelerometer data for suturing and knot-tying tasks. We introduce "entropy-based" features-approximate entropy and cross-approximate entropy, which quantify the amount of predictability and regularity of fluctuations in time series data. The proposed features are compared to existing methods of Sequential Motion Texture, Discrete Cosine Transform and Discrete Fourier Transform, for surgical skills assessment. We report average performance of different features across all applicable OSATS-like criteria for suturing and knot-tying tasks. Our analysis shows that the proposed entropy-based features outperform previous state-of-the-art methods using video data, achieving average classification accuracies of 95.1 and 92.2% for suturing and knot tying, respectively. For accelerometer data, our method performs better for suturing achieving 86.8% average accuracy. We also show that fusion of video and acceleration features can improve overall performance for skill assessment. Automated surgical skills assessment can be achieved with high accuracy using the proposed entropy features. Such a system can significantly improve the efficiency of surgical training in medical schools and teaching hospitals.

Associations between accelerometer-derived physical activity and regional adiposity in young men and women.

PubMed

Smith, H A; Storti, K L; Arena, V C; Kriska, A M; Gabriel, K K Pettee; Sutton-Tyrrell, K; Hames, K C; Conroy, M B

2013-06-01

Empirical evidence supports an inverse relationship between physical activity (PA) and adiposity, but studies using detailed measures of both are scarce. The relationship between regional adiposity and accelerometer-derived PA in men and women are described. Cross-sectional analysis included 253 participants from a weight loss study limited to ages 20-45 years and BMI 25-39.9 kg m(-2) . PA data were collected with accelerometers and expressed as total accelerometer counts and average amount of time per day accumulated in different intensity levels [sedentary, light-, and moderate-to-vigorous intensity PA (MVPA)]. Accumulation of time spent above 100 counts was expressed as total active time. Computed tomography (CT) was used to measure abdominal and adipose tissue (AT). Multivariate linear regression analyses were used to assess the relationship between regional adiposity (dependent variable) and the various PA levels (independent variable), and were executed separately for men and women, adjusting for wear time, age, race, education, and BMI. Among males, light activity was inversely associated with total AT (β = -0.19; P = 0.02) as well as visceral AT (VAT) (β = -0.30; P = 0.03). Among females sedentary time was positively associated with VAT (β = 0.11; P = 0.04) and total active time was inversely associated with VAT (β = -0.12; P = 0.04). Findings from this study suggest that PA intensity level may influence regional adiposity differently in men and women. Additional research is needed in larger samples to clarify the difference in these associations by sex, create recommendations for the frequency, duration and intensity of PA needed to target fat deposits, and determine if these recommendations should differ by sex. Copyright © 2013 The Obesity Society.

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study.

PubMed

Meinert, Ilka; Brown, Niklas; Alt, Wilfried

2016-01-01

Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill) on oscillations at the Achilles tendon. Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running). Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01) with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition. Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs.

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study

PubMed Central

Meinert, Ilka; Brown, Niklas; Alt, Wilfried

2016-01-01

Background Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill) on oscillations at the Achilles tendon. Methods Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running). Results Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01) with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition. Conclusion Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs. PMID:27010929

Blood pressure circadian pattern and physical exercise assessment by accelerometer and 7-day physical activity recall scale.

PubMed

García-Ortiz, Luis; Recio-Rodríguez, José I; Puig-Ribera, Anna; Lema-Bartolomé, Jorge; Ibáñez-Jalón, Elisa; González-Viejo, Natividad; Guenaga-Saenz, Nahia; Agudo-Conde, Cristina; Patino-Alonso, Maria C; Gomez-Marcos, Manuel A

2014-05-01

The relationship between regular physical activity, measured objectively and by self-report, and the circadian pattern of 24-hour ambulatory arterial blood pressure (BP) has not been clarified. We performed a cross-sectional study in a cohort of healthy patients. We included 1,345 patients from the EVIDENT study (mean age 55 ± 14 years; 59.3% women). Physical activity was assessed using the 7-day physical activity recall (PAR) questionnaire (metabolic equivalents (MET)/hour/week) and the Actigraph GT3X accelerometer (counts/minute) for 7 days; ambulatory arterial BP was measured with a radial tonometer (B-pro device). The dipper-pattern patients showed a higher level of activity than nondipper patients, as assessed by accelerometer and 7-day PAR. Physical activity measures correlated positively with the percent drop in systolic BP (SBP; ρ = 0.19 to 0.11; P < 0.01) and negatively with the systolic and diastolic sleep to wake ratios (ρ = -0.10 to -0.18; P < 0.01) and heart rate (ρ = -0.13; P < 0.01). In logistic regression, considering the circadian pattern (1, dipper; 0, nondipper) as the dependent variable, the odds ratio of the third tertile of counts/minute was 1.79 (95% confidence interval [CI], 1.35-2.38; P < 0.01) and of MET/hour/week was 1.33 (95% CI, 1.01-1.75; P = 0.04) after adjustment for confounding variables. Physical activity, as evaluated by both the accelerometer and the 7-day PAR, was associated with a more marked nocturnal BP dip and, accordingly, a lower SBP and diastolic BP sleep to wake ratio. Clinical Trials.gov Identifier: NCT01083082.

Equating accelerometer estimates among youth: the Rosetta Stone 2

PubMed Central

Brazendale, Keith; Beets, Michael W.; Bornstein, Daniel B.; Moore, Justin B.; Pate, Russell R.; Weaver, Robert G.; Falck, Ryan S.; Chandler, Jessica L.; Andersen, Lars B.; Anderssen, Sigmund A.; Cardon, Greet; Cooper, Ashley; Davey, Rachel; Froberg, Karsten; Hallal, Pedro C.; Janz, Kathleen F.; Kordas, Katarzyna; Kriemler, Susi; Puder, Jardena J.; Reilly, John J.; Salmon, Jo; Sardinha, Luis B.; Timperio, Anna; van Sluijs, Esther MF

2017-01-01

Objectives Different accelerometer cutpoints used by different researchers often yields vastly different estimates of moderate-to-vigorous intensity physical activity (MVPA). This is recognized as cutpoint non-equivalence (CNE), which reduces the ability to accurately compare youth MVPA across studies. The objective of this research is to develop a cutpoint conversion system that standardizes minutes of MVPA for six different sets of published cutpoints. Design Secondary data analysis Methods Data from the International Children’s Accelerometer Database (ICAD; Spring 2014) consisting of 43,112 Actigraph accelerometer data files from 21 worldwide studies (children 3-18 years, 61.5% female) were used to develop prediction equations for six sets of published cutpoints. Linear and non-linear modeling, using a leave one out cross-validation technique, was employed to develop equations to convert MVPA from one set of cutpoints into another. Bland Altman plots illustrate the agreement between actual MVPA and predicted MVPA values. Results Across the total sample, mean MVPA ranged from 29.7 MVPA min.d-1 (Puyau) to 126.1 MVPA min.d-1 (Freedson 3 METs). Across conversion equations, median absolute percent error was 12.6% (range: 1.3 to 30.1) and the proportion of variance explained ranged from 66.7% to 99.8%. Mean difference for the best performing prediction equation (VC from EV) was -0.110 min.d-1 (limits of agreement (LOA), -2.623 to 2.402). The mean difference for the worst performing prediction equation (FR3 from PY) was 34.76 min.d-1 (LOA, -60.392 to 129.910). Conclusions For six different sets of published cutpoints, the use of this equating system can assist individuals attempting to synthesize the growing body of literature on Actigraph, accelerometry-derived MVPA. PMID:25747468

Analysis of Accelerometer Data from a Woven Inflatable Creep Burst Test

NASA Technical Reports Server (NTRS)

James, George H.; Grygier, Michael; Selig, Molly M.

2015-01-01

Accelerometers were used to montor an inflatable test article during a creep test to failure. The test article experienced impulse events that were classified based on the response of the sensors and their time-dependent manifestation. These impulse events required specialized techniques to process the structural dynamics data. However, certain phenomena were defined as worthy of additional study. An assessment of one phenomena (a frequency near 1000Hz) showed a time dependent frequency and an amplitude that increased significantly near the end of the test. Hence, these observations are expected to drive future understanding of and utility in inflatable space structures.

Measurement of the inclusive νμ charged current cross section on iron and hydrocarbon in the T2K on-axis neutrino beam

NASA Astrophysics Data System (ADS)

Abe, K.; Adam, J.; Aihara, H.; Akiri, T.; Andreopoulos, C.; Aoki, S.; Ariga, A.; Assylbekov, S.; Autiero, D.; Barbi, M.; Barker, G. J.; Barr, G.; Bass, M.; Batkiewicz, M.; Bay, F.; Berardi, V.; Berger, B. E.; Berkman, S.; Bhadra, S.; Blaszczyk, F. d. M.; Blondel, A.; Bojechko, C.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Buchanan, N.; Calland, R. G.; Caravaca Rodríguez, J.; Cartwright, S. L.; Castillo, R.; Catanesi, M. G.; Cervera, A.; Cherdack, D.; Christodoulou, G.; Clifton, A.; Coleman, J.; Coleman, S. J.; Collazuol, G.; Connolly, K.; Cremonesi, L.; Dabrowska, A.; Danko, I.; Das, R.; Davis, S.; de Perio, P.; De Rosa, G.; Dealtry, T.; Dennis, S. R.; Densham, C.; Dewhurst, D.; Di Lodovico, F.; Di Luise, S.; Drapier, O.; Duboyski, T.; Duffy, K.; Dumarchez, J.; Dytman, S.; Dziewiecki, M.; Emery-Schrenk, S.; Ereditato, A.; Escudero, L.; Finch, A. J.; Friend, M.; Fujii, Y.; Fukuda, Y.; Furmanski, A. P.; Galymov, V.; Giffin, S.; Giganti, C.; Gilje, K.; Goeldi, D.; Golan, T.; Gonin, M.; Grant, N.; Gudin, D.; Hadley, D. R.; Haesler, A.; Haigh, M. D.; Hamilton, P.; Hansen, D.; Hara, T.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayato, Y.; Hearty, C.; Helmer, R. L.; Hierholzer, M.; Hignight, J.; Hillairet, A.; Himmel, A.; Hiraki, T.; Hirota, S.; Holeczek, J.; Horikawa, S.; Huang, K.; Ichikawa, A. K.; Ieki, K.; Ieva, M.; Ikeda, M.; Imber, J.; Insler, J.; Irvine, T. J.; Ishida, T.; Ishii, T.; Iwai, E.; Iwamoto, K.; Iyogi, K.; Izmaylov, A.; Jacob, A.; Jamieson, B.; Johnson, R. A.; Jo, J. H.; Jonsson, P.; Jung, C. K.; Kabirnezhad, M.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Kanazawa, Y.; Karlen, D.; Karpikov, I.; Katori, T.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kielczewska, D.; Kikawa, T.; Kilinski, A.; Kim, J.; Kisiel, J.; Kitching, P.; Kobayashi, T.; Koch, L.; Kolaceke, A.; Konaka, A.; Kormos, L. L.; Korzenev, A.; Koseki, K.; Koshio, Y.; Kreslo, I.; Kropp, W.; Kubo, H.; Kudenko, Y.; Kurjata, R.; Kutter, T.; Lagoda, J.; Laihem, K.; Lamont, I.; Larkin, E.; Laveder, M.; Lawe, M.; Lazos, M.; Lindner, T.; Lister, C.; Litchfield, R. P.; Longhin, A.; Ludovici, L.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Marino, A. D.; Marteau, J.; Martin, J. F.; Martynenko, S.; Maruyama, T.; Matveev, V.; Mavrokoridis, K.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Metelko, C.; Mijakowski, P.; Miller, C. A.; Minamino, A.; Mineev, O.; Missert, A.; Miura, M.; Moriyama, S.; Mueller, Th. A.; Murakami, A.; Murdoch, M.; Murphy, S.; Myslik, J.; Nakadaira, T.; Nakahata, M.; Nakamura, K.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Nielsen, C.; Nirkko, M.; Nishikawa, K.; Nishimura, Y.; O'Keeffe, H. M.; Ohta, R.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Otani, M.; Owen, R. A.; Oyama, Y.; Palladino, V.; Palomino, J. L.; Paolone, V.; Payne, D.; Perevozchikov, O.; Perkin, J. D.; Petrov, Y.; Pickard, L.; Pinzon Guerra, E. S.; Pistillo, C.; Plonski, P.; Poplawska, E.; Popov, B.; Posiadala, M.; Poutissou, J.-M.; Poutissou, R.; Przewlocki, P.; Quilain, B.; Radicioni, E.; Ratoff, P. N.; Ravonel, M.; Rayner, M. A. M.; Redij, A.; Reeves, M.; Reinherz-Aronis, E.; Retiere, F.; Rodrigues, P. A.; Rojas, P.; Rondio, E.; Roth, S.; Rubbia, A.; Ruterbories, D.; Sacco, R.; Sakashita, K.; Sánchez, F.; Sato, F.; Scantamburlo, E.; Scholberg, K.; Schoppmann, S.; Schwehr, J.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shiozawa, M.; Short, S.; Shustrov, Y.; Sinclair, P.; Smith, B.; Smy, M.; Sobczyk, J. T.; Sobel, H.; Sorel, M.; Southwell, L.; Stamoulis, P.; Steinmann, J.; Still, B.; Suda, Y.; Suzuki, A.; Suzuki, K.; Suzuki, S. Y.; Suzuki, Y.; Szeglowski, T.; Tacik, R.; Tada, M.; Takahashi, S.; Takeda, A.; Takeuchi, Y.; Tanaka, H. K.; Tanaka, H. A.; Tanaka, M. M.; Terhorst, D.; Terri, R.; Thompson, L. F.; Thorley, A.; Tobayama, S.; Toki, W.; Tomura, T.; Totsuka, Y.; Touramanis, C.; Tsukamoto, T.; Tzanov, M.; Uchida, Y.; Vacheret, A.; Vagins, M.; Vasseur, G.; Wachala, T.; Waldron, A. V.; Walter, C. W.; Wark, D.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilkes, R. J.; Wilking, M. J.; Wilkinson, C.; Williamson, Z.; Wilson, J. R.; Wilson, R. J.; Wongjirad, T.; Yamada, Y.; Yamamoto, K.; Yanagisawa, C.; Yano, T.; Yen, S.; Yershov, N.; Yokoyama, M.; Yuan, T.; Yu, M.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; Żmuda, J.; T2K Collaboration

2014-09-01

We report a measurement of the νμ inclusive charged current cross sections on iron and hydrocarbon in the Tokai-to-Kamioka (T2K) on-axis neutrino beam. The measured inclusive charged current cross sections on iron and hydrocarbon averaged over the T2K on-axis flux with a mean neutrino energy of 1.51 GeV are (1.444±0.002(stat)-0.157+0.189(syst))×10-38 cm2/nucleon and (1.379±0.009(stat)-0.147+0.178(syst))×10-38 cm2/nucleon, respectively, and their cross-section ratio is 1.047±0.007(stat)±0.035(syst). These results agree well with the predictions of the neutrino interaction model, and thus we checked the correct treatment of the nuclear effect for iron and hydrocarbon targets in the model within the measurement precisions.

Accelerometer-based physical activity in a large observational cohort--study protocol and design of the activity and function of the elderly in Ulm (ActiFE Ulm) study.

PubMed

Denkinger, Michael D; Franke, Sebastian; Rapp, Kilian; Weinmayr, Gudrun; Duran-Tauleria, Enric; Nikolaus, Thorsten; Peter, Richard

2010-07-27

A large number of studies have demonstrated a positive effect of increased physical activity (PA) on various health outcomes. In all large geriatric studies, however, PA has only been assessed by interview-based instruments which are all subject to substantial bias. This may represent one reason why associations of PA with geriatric syndromes such as falls show controversial results. The general aim of the Active-Ulm study was to determine the association of accelerometer-based physical activity with different health-related parameters, and to study the influence of this standardized objective measure of physical activity on health- and disability-related parameters in a longitudinal setting. We have set up an observational cohort study in 1500 community dwelling older persons (65 to 90 years) stratified by age and sex. Addresses have been obtained from the local residents registration offices. The study is carried out jointly with the IMCA--Respiratory Health Survey in the Elderly implemented in the context of the European project IMCA II. The study has a cross-sectional part (1) which focuses on PA and disability and two longitudinal parts (2) and (3). The primary information for part (2) is a prospective 1 year falls calendar including assessment of medication change. Part (3) will be performed about 36 months following baseline. Primary variables of interest include disability, PA, falls and cognitive function. Baseline recruitment has started in March 2009 and will be finished in April 2010.All participants are visited three times within one week, either at home or in the study center. Assessments included interviews on quality of life, diagnosed diseases, common risk factors as well as novel cognitive tests and established tests of physical functioning. PA is measured using an accelerometer-based sensor device, carried continuously over a one week period and accompanied by a prospective activity diary. The assessment of PA using a high standard accelerometer-based device is feasible in a large population-based study. The results obtained from cross-sectional and longitudinal analyses will shed light on important associations between PA and various outcomes and may provide information for specific interventions in older people.

Miniaturized accelerometer made with ZnO nanowires

NASA Astrophysics Data System (ADS)

Song, Sangho; Kim, Jeong Woong; Kim, Hyun Chan; Yun, Youngmin; Kim, Jaehwan

2017-04-01

Miniaturized accelerometer is required in many applications, such as, robotics, haptic devices, gyroscopes, simulators and mobile devices. ZnO is an essential semiconductor material with wide direct band gap, thermal stability and piezoelectricity. Especially, well aligned ZnO nanowire is appropriate for piezoelectric applications since it can produce high electrical signal under mechanical load. To miniaturize accelerometer, an aligned ZnO nanowire is adopted to implement active piezoelectric layer of the accelerometer and copper is chosen for the head mass. To grow ZnO nanowire on the copper head mass, hydrothermal synthesis is conducted and the effect of ZnO nanowire length on the accelerometer performance is investigated. Refresh hydrothermal synthesis can increase the length of ZnO nanowire. The performance of the fabricated ZnO accelerometers is compared with a commercial accelerometer. Sensitivity and linearity of the fabricated accelerometers are investigated.

A novel accelerometer-based method to describe day-to-day exposure to potentially osteogenic vertical impacts in older adults: findings from a multi-cohort study.

PubMed

Hannam, K; Deere, K C; Hartley, A; Clark, E M; Coulson, J; Ireland, A; Moss, C; Edwards, M H; Dennison, E; Gaysin, T; Cooper, R; Wong, A; McPhee, J S; Cooper, C; Kuh, D; Tobias, J H

2017-03-01

This observational study assessed vertical impacts experienced in older adults as part of their day-to-day physical activity using accelerometry and questionnaire data. Population-based older adults experienced very limited high-impact activity. The accelerometry method utilised appeared to be valid based on comparisons between different cohorts and with self-reported activity. We aimed to validate a novel method for evaluating day-to-day higher impact weight-bearing physical activity (PA) in older adults, thought to be important in protecting against osteoporosis, by comparing results between four cohorts varying in age and activity levels, and with self-reported PA levels. Participants were from three population-based cohorts, MRC National Survey of Health and Development (NSHD), Hertfordshire Cohort Study (HCS) and Cohort for Skeletal Health in Bristol and Avon (COSHIBA), and the Master Athlete Cohort (MAC). Y-axis peaks (reflecting the vertical when an individual is upright) from a triaxial accelerometer (sampling frequency 50 Hz, range 0-16 g) worn at the waist for 7 days were classified as low (0.5-1.0 g), medium (1.0-1.5 g) or higher (≥1.5 g) impacts. There were a median of 90, 41 and 39 higher impacts/week in NSHD (age 69.5), COSHIBA (age 76.8) and HCS (age 78.5) participants, respectively (total n = 1512). In contrast, MAC participants (age 68.5) had a median of 14,322 higher impacts/week. In the three population cohorts combined, based on comparison of beta coefficients, moderate-high-impact activities as assessed by PA questionnaire were suggestive of stronger association with higher impacts from accelerometers (0.25 [0.17, 0.34]), compared with medium (0.18 [0.09, 0.27]) and low impacts (0.13 [0.07,0.19]) (beta coefficient, with 95 % CI). Likewise in MAC, reported moderate-high-impact activities showed a stronger association with higher impacts (0.26 [0.14, 0.37]), compared with medium (0.14 [0.05, 0.22]) and low impacts (0.03 [-0.02, 0.08]). Our new accelerometer method appears to provide valid measures of higher vertical impacts in older adults. Results obtained from the three population-based cohorts indicate that older adults generally experience very limited higher impact weight-bearing PA.

Test of the Equivalence Principle in an Einstein Elevator

NASA Technical Reports Server (NTRS)

Shapiro, Irwin I.; Glashow, S.; Lorenzini, E. C.; Cosmo, M. L.; Cheimets, P. N.; Finkelstein, N.; Schneps, M.

2004-01-01

The scientific goal of the experiment is to test the equality of gravitational and inertial mass (i.e., to test the Principle of Equivalence) by measuring the independence of the rate of fall of bodies from their compositions. The measurement is accomplished by measuring the relative displacement (or equivalently acceleration) of two falling bodies of different materials which are the proof masses of a differential accelerometer spinning about an horizontal axis to modulate a possible violation signal. A non-zero differential acceleration appearing at the signal frequency will indicate a violation of the Equivalence Principle. The goal of the experiment is to measure the Eotvos ratio og/g (differential acceleration/common acceleration) with a targeted accuracy that is about two orders of magnitude better than the state of the art (presently at several parts in 10(exp 13). The analyses carried out during this first grant year have focused on: (1) evaluation of possible shapes for the proof masses to meet the requirements on the higher-order mass moment disturbances generated by the falling capsule; (2) dynamics of the instrument package and differential acceleration measurement in the presence of errors and imperfections; (3) computation of the inertia characteristic of the instrument package that enable a separation of the signal from the dynamics-related noise; (4) a revised thermal analysis of the instrument package in light of the new conceptual design of the cryostat; (5) the development of a dynamic and control model of the capsule attached to the gondola and balloon to define the requirements for the leveling mechanism (6) a conceptual design of the leveling mechanism that keeps the capsule aligned before release from the balloon; and (7) a new conceptual design of the customized cryostat and a preliminary valuation of its cost. The project also involves an international cooperation with the Institute of Space Physics (IFSI) in Rome, Italy. The group at IFSI is in charge of prototyping the differential accelerometer and carrying out precursor laboratory measurements. During this grant year, our partners analyzed and then designed a new prototype of differential accelerometer that has several characteristics in common with the flight accelerometer at this point of the instrument development. The highlights of these activities are documented in a section of this report.

Measuring older adults' sedentary time: reliability, validity, and responsiveness.

PubMed

Gardiner, Paul A; Clark, Bronwyn K; Healy, Genevieve N; Eakin, Elizabeth G; Winkler, Elisabeth A H; Owen, Neville

2011-11-01

With evidence that prolonged sitting has deleterious health consequences, decreasing sedentary time is a potentially important preventive health target. High-quality measures, particularly for use with older adults, who are the most sedentary population group, are needed to evaluate the effect of sedentary behavior interventions. We examined the reliability, validity, and responsiveness to change of a self-report sedentary behavior questionnaire that assessed time spent in behaviors common among older adults: watching television, computer use, reading, socializing, transport and hobbies, and a summary measure (total sedentary time). In the context of a sedentary behavior intervention, nonworking older adults (n = 48, age = 73 ± 8 yr (mean ± SD)) completed the questionnaire on three occasions during a 2-wk period (7 d between administrations) and wore an accelerometer (ActiGraph model GT1M) for two periods of 6 d. Test-retest reliability (for the individual items and the summary measure) and validity (self-reported total sedentary time compared with accelerometer-derived sedentary time) were assessed during the 1-wk preintervention period, using Spearman (ρ) correlations and 95% confidence intervals (CI). Responsiveness to change after the intervention was assessed using the responsiveness statistic (RS). Test-retest reliability was excellent for television viewing time (ρ (95% CI) = 0.78 (0.63-0.89)), computer use (ρ (95% CI) = 0.90 (0.83-0.94)), and reading (ρ (95% CI) = 0.77 (0.62-0.86)); acceptable for hobbies (ρ (95% CI) = 0.61 (0.39-0.76)); and poor for socializing and transport (ρ < 0.45). Total sedentary time had acceptable test-retest reliability (ρ (95% CI) = 0.52 (0.27-0.70)) and validity (ρ (95% CI) = 0.30 (0.02-0.54)). Self-report total sedentary time was similarly responsive to change (RS = 0.47) as accelerometer-derived sedentary time (RS = 0.39). The summary measure of total sedentary time has good repeatability and modest validity and is sufficiently responsive to change suggesting that it is suitable for use in interventions with older adults.

Transference of 3D accelerations during cross country mountain biking.

PubMed

Macdermid, Paul W; Fink, Philip W; Stannard, Stephen R

2014-06-03

Investigations into the work demands of Olympic format cross country mountain biking suggest an incongruent relationship between work done and physiological strain experienced by participants. A likely but unsubstantiated cause is the extra work demand of muscle damping of terrain/surface induced vibrations. The purpose of this study was to describe the relationship between vibration mechanics and their interaction with terrain, bicycle and rider during a race pace effort on a cross country mountain bike track, on both 26″ and 29″ wheels. Participants completed one lap of a cross country track using 26″ and 29″ wheels, at race pace. Power, cadence, speed, heart rate and geographical position were sampled and logged every second for control purposes. Tri-axial accelerometers located on the bicycle and rider, recorded accelerations (128Hz) and were used to quantify vibrations experienced during the whole lap and over terrain sections (uphill and downhill). While there were no differences in power output (p=0.3062) and heart rate (p=0.8423), time to complete the lap was significantly (p=0.0061) faster on the 29″ wheels despite increased vibrations in the larger wheels (p=0.0020). Overall accelerometer data (RMS) showed location differences (p<0.0001), specifically between the point of interface of bike-body compared to those experienced at the lower back and head. The reduction in accelerations at both the lower back and head are imperative for injury prevention and demonstrates an additional non-propulsive, muscular, challenge to riding. Stress was greatest during downhill sections as acceleration differences between locations were greater when compared to uphill sections, and thus possibly prevent the recovery processes that may occur during non-propulsive load. Copyright © 2014 Elsevier Ltd. All rights reserved.

Wide-field-of-view millimeter-wave telescope design with ultra-low cross-polarization

NASA Astrophysics Data System (ADS)

Bernacki, Bruce E.; Kelly, James F.; Sheen, David; Hatchell, Brian; Valdez, Patrick; Tedeschi, Jonathan; Hall, Thomas; McMakin, Douglas

2012-06-01

As millimeter-wave arrays become available, off-axis imaging performance of the fore optics increases in importance due to the relatively large physical extent of the arrays. Typically, simple optical telescope designs are adapted to millimeter-wave imaging but single-mirror spherical or classic conic designs cannot deliver adequate image quality except near the optical axis. Since millimeter-wave designs are quasi-optical, optical ray tracing and commercial design software can be used to optimize designs to improve off-axis imaging as well as minimize cross-polarization. Methods that obey the Dragone-Mizuguchi condition for the design of reflective millimeter-wave telescopes with low cross-polarization also provide additional degrees of freedom that offer larger fields of view than possible with single-reflector designs. Dragone's graphical design method does not lend itself readily to computer-based optical design approaches, but subsequent authors expanded on Dragone's geometric design approach with analytic expressions that describe the location, shape, off-axis height and tilt of the telescope elements that satisfy Dragone's design rules and can be used as a first-order design for subsequent computer-based design and optimization. We investigate two design variants that obey the Dragone-Mizuguchi conditions that exhibit ultra-low cross-polarization and a large diffraction-limited field of view well suited to millimeter-wave imaging arrays.

Attitude Ground System (AGS) For The Magnetospheric Multi-Scale (MMS) Mission

NASA Technical Reports Server (NTRS)

Raymond, Juan C.; Sedlak, Joseph E.; Vint, Babak

2015-01-01

The Magnetospheric Multiscale (MMS) mission is a Solar-Terrestrial Probe mission consisting of four identically instrumented spin-stabilized spacecraft flying in an adjustable pyramid-like formation around the Earth. The formation of the MMS spacecraft allows for three-dimensional study of the phenomenon of magnetic reconnection, which is the primary objective of the mission. The MMS spacecraft were launched early on March 13, 2015 GMT. Due to the challenging and very constricted attitude and orbit requirements for performing the science, as well as the need to maintain the spacecraft formation, multiple ground functionalities were designed to support the mission. These functionalities were incorporated into a ground system known as the Attitude Ground System (AGS). Various AGS configurations have been used widely to support a variety of three-axis-stabilized and spin-stabilized spacecraft missions within the NASA Goddard Space Flight Center (GSFC). The original MMS operational concept required the AGS to perform highly accurate predictions of the effects of environmental disturbances on the spacecraft orientation and to plan the attitude maneuvers necessary to stay within the science attitude tolerance. The orbit adjustment requirements for formation control drove the need also to perform calibrations that have never been done before in support of NASA GSFC missions. The MMS mission required support analysts to provide fast and accurately calibrated values of the inertia tensor, center of mass, and accelerometer bias for each MMS spacecraft. During early design of the AGS functionalities, a Kalman filter for estimating the attitude, body rates, center of mass, and accelerometer bias, using only star tracker and accelerometer measurements, was heavily analyzed. A set of six distinct filters was evaluated and considered for estimating the spacecraft attitude and body rates using star tracker data only. Four of the six filters are closely related and were compared during support of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Space Technology-5 (ST-5) missions. These analyses exposed high dependency and sensitivity on the knowledge of the spacecraft inertia tensor for both body rates and accelerometer bias estimation. The conclusion of the analysis led to the design of an inertia tensor calibration technique using only star tracker data. The second most important result of the analysis was the design of two separate Kalman filters to estimate the spacecraft attitude and body rates and the accelerometer bias instead of a single combined filter. In this paper, the calibration results of the mass properties, as well as the performance of the spacecraft attitude and body rates filters using flight data are presented and compared against the mission requirements.

Light-intensity physical activity is associated with insulin resistance in elderly Japanese women independent of moderate-to vigorous-intensity physical activity.

PubMed

Gando, Yuko; Murakami, Haruka; Kawakami, Ryoko; Tanaka, Noriko; Sanada, Kiyoshi; Tabata, Izumi; Higuchi, Mitsuru; Miyachi, Motohiko

2014-02-01

It is unclear whether light physical activity is beneficially associated with insulin resistance, similar to moderate and/or vigorous physical activity. This cross-sectional study was performed to determine the relationship between the amount of light physical activity, as determined with a triaxial accelerometer, and insulin resistance. A total of 807 healthy men and women participated in this study. Physical activity was measured using a triaxial accelerometer worn for 28 days and summarized as light intensity (1.1-2.9 METs) or moderate to vigorous intensity (≥ 3.0 METs). Insulin resistance was evaluated by HOMA_R (FPG [mg/dL] × IRI [μU/mL]/405). The daily time spent in light physical activity was inversely associated with HOMA_R (r = -0.173, P < 0.05). After adjustment for confounders, the association between light physical activity and HOMA_R remained statistically significant (β = -0.119, P < .05). Light physical activity remained significantly associated with HOMA_R following further adjustment for moderate to vigorous intensity activity (β = -0.125, P < .05). Similar results were observed when light physical activity was modeled as quartiles, especially in elderly women. These cross-sectional data suggest that light-intensity physical activity is beneficially associated with insulin resistance in elderly Japanese women.

Objectively Measured Sedentary Behavior, Obesity, and Psychological Well-Being: A Cross-Sectional Study of Japanese Schoolchildren.

PubMed

Ishii, Kaori; Shibata, Ai; Adachi, Minoru; Mano, Yoshiyuki; Oka, Koichiro

2017-04-01

Sedentary behaviors (SB) are associated with health indicators; however, there are currently very few studies that have examined these associations, especially in conjunction with psychological factors, in children. The current study examined the independent relationship between objectively assessed SB, and indicators of obesity and psychological well-being, among Japanese children. A total of 967 elementary-school children completed a cross-sectional survey. SB was measured with accelerometers for 7 consecutive days. Psychological well-being data (eg, anxiety and behavior problems) were collected via a self-report questionnaire. To determine the relationship of SB with degree of obesity and psychological well-being, linear regression analyses were conducted to relate the indicators of obesity and psychological well-being on SB, adjusted by gender, grade, percentage of moderate-to-vigorous physical activity per day, duration spent wearing the accelerometer, and degree of obesity. SB was significantly related to behavioral/emotional problems (β = .280, P = .010, R 2 = .015). There was a statistically significant relationship between SB and anxiety (β = .206, P = .059, R 2 = .007). No significant association with degree of obesity was found. Excess SB relates higher levels of behavioral/emotional problems and anxiety. These results can inspire the development of interventions that promote well-being and enhance psychological health, by focusing on SB in Japanese children.

Ensemble Methods for Classification of Physical Activities from Wrist Accelerometry.

PubMed

Chowdhury, Alok Kumar; Tjondronegoro, Dian; Chandran, Vinod; Trost, Stewart G

2017-09-01

To investigate whether the use of ensemble learning algorithms improve physical activity recognition accuracy compared to the single classifier algorithms, and to compare the classification accuracy achieved by three conventional ensemble machine learning methods (bagging, boosting, random forest) and a custom ensemble model comprising four algorithms commonly used for activity recognition (binary decision tree, k nearest neighbor, support vector machine, and neural network). The study used three independent data sets that included wrist-worn accelerometer data. For each data set, a four-step classification framework consisting of data preprocessing, feature extraction, normalization and feature selection, and classifier training and testing was implemented. For the custom ensemble, decisions from the single classifiers were aggregated using three decision fusion methods: weighted majority vote, naïve Bayes combination, and behavior knowledge space combination. Classifiers were cross-validated using leave-one subject out cross-validation and compared on the basis of average F1 scores. In all three data sets, ensemble learning methods consistently outperformed the individual classifiers. Among the conventional ensemble methods, random forest models provided consistently high activity recognition; however, the custom ensemble model using weighted majority voting demonstrated the highest classification accuracy in two of the three data sets. Combining multiple individual classifiers using conventional or custom ensemble learning methods can improve activity recognition accuracy from wrist-worn accelerometer data.

Three-dimensional ballistocardiography and respiratory motion in sustained microgravity

NASA Technical Reports Server (NTRS)

Prisk, G. K.; Verhaeghe, S.; Padeken, D.; Hamacher, H.; Paiva, M.; West, J. B. (Principal Investigator)

2001-01-01

BACKGROUND: We measured the three-dimensional ballistocardiogram (BCG) in a free-floating subject in sustained microgravity during spaceflight to test the usefulness of such measurements for future non-invasive monitoring of cardiac function, and to examine the effects of respiratory movement on the BCG in three axes. METHODS: Acceleration was measured using a three-axis accelerometer fastened to the lumbar region of the subject while simultaneous recordings of ECG, and respiratory motion via impedance plethysmography were also made. Data were recorded during a 146-s period of inactivity on the part of the subject during which time there was no contact with the spacecraft. RESULTS: Total body motion due to respiratory activity was consistent with that calculated from the known action of the diaphragm and conservation of momentum. The accelerations due to cardiac activity, ensemble averaged over the R-R interval, were greatest along the head-to-foot axis. Maximum amplitude of the HIJK complex of the BCG generated by ventricular ejection was greatest in the head to foot axis (approximately 70 x 10(-3) m x s(-2)), but there were also substantial accelerations along the dorsoventral axis of up to 43 10(-3) m x s(-2), that are not measured interrestrial two-dimensional studies. The amplitude of the BCG was strongly affected by lung volume, with accelerations being reduced 50 to 70% between end-inspiration and end-expiration. CONCLUSIONS: These data suggest a greatly reduced transmission of the cardiac motion to the body at end-expiration (FRC) than at higher lung volumes. The BCG might be further developed as a non-invasive means of monitoring parameters such as stroke volume in microgravity.

The GH-IGF-I response to typical field sports practices in adolescent athletes: a summary.

PubMed

Eliakim, Alon; Cooper, Dan M; Nemet, Dan

2014-11-01

The present study compares previous reports on the effect of "real-life" typical field individual (i.e., cross-country running and wrestling--representing combat versus noncombat sports) and team sports (i.e., volleyball and water polo-representing water and land team sports) training on GH and IGF-1, the main growth factors of the GH→IGF axis, in male and female late pubertal athletes. Cross-country running practice and volleyball practice in both males and females were associated with significant increases of circulating GH levels, while none of the practices led to a significant increase in IGF-I levels. The magnitude (percent change) of the GH response to the different practices was determined mainly by preexercise GH levels. There was no difference in the training-associated GH response between individual and team sports practices. The GH response to the different typical practices was not influenced by the practice-associated lactate change. Further studies are needed to better understand the effect of real-life typical training in prepubertal and adolescent athletes and their role in exercise adaptations.

Performance improvement of miniaturized ZnO nanowire accelerometer fabricated by refresh hydrothermal synthesis

PubMed Central

Song, Sangho; Kim, Hyun Chan; Kim, Jung Woong; Kim, Debora

2017-01-01

Miniaturized accelerometers are necessary for evaluating the performance of small devices, such as haptics, robotics and simulators. In this study, we fabricated miniaturized accelerometers using well-aligned ZnO nanowires. The layer of ZnO nanowires is used for active piezoelectric layer of the accelerometer, and copper was chosen as a head mass. Seedless and refresh hydrothermal synthesis methods were conducted to grow ZnO nanowires on the copper substrate and the effect of ZnO nanowire length on the accelerometer performance was investigated. The refresh hydrothermal synthesis exhibits longer ZnO nanowires, 12 µm, than the seedless hydrothermal synthesis, 6 µm. Performance of the fabricated accelerometers was verified by comparing with a commercial accelerometer. The sensitivity of the fabricated accelerometer by the refresh hydrothermal synthesis is shown to be 37.7 pA g−1, which is about 30 times larger than the previous result. PMID:28989760

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation.

PubMed

Tie, Junbo; Cao, Juliang; Chang, Lubing; Cai, Shaokun; Wu, Meiping; Lian, Junxiang

2018-03-16

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method.

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation

PubMed Central

Cao, Juliang; Cai, Shaokun; Wu, Meiping; Lian, Junxiang

2018-01-01

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method. PMID:29547552

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems.

PubMed

Seyed Moosavi, Seyed Mohsen; Moaveni, Bijan; Moshiri, Behzad; Arvan, Mohammad Reza

2018-02-27

The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors.

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems

PubMed Central

Seyed Moosavi, Seyed Mohsen; Moshiri, Behzad; Arvan, Mohammad Reza

2018-01-01

The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors. PMID:29495434

Hypothalamic-pituitary-adrenal and hypothalamic-pituitary-gonadal axes: sex differences in regulation of stress responsivity.

PubMed

Oyola, Mario G; Handa, Robert J

2017-09-01

Gonadal hormones play a key role in the establishment, activation, and regulation of the hypothalamic-pituitary-adrenal (HPA) axis. By influencing the response and sensitivity to releasing factors, neurotransmitters, and hormones, gonadal steroids help orchestrate the gain of the HPA axis to fine-tune the levels of stress hormones in the general circulation. From early life to adulthood, gonadal steroids can differentially affect the HPA axis, resulting in sex differences in the responsivity of this axis. The HPA axis influences many physiological functions making an organism's response to changes in the environment appropriate for its reproductive status. Although the acute HPA response to stressors is a beneficial response, constant activation of this circuitry by chronic or traumatic stressful episodes may lead to a dysregulation of the HPA axis and cause pathology. Compared to males, female mice and rats show a more robust HPA axis response, as a result of circulating estradiol levels which elevate stress hormone levels during non-threatening situations, and during and after stressors. Fluctuating levels of gonadal steroids in females across the estrous cycle are a major factor contributing to sex differences in the robustness of HPA activity in females compared to males. Moreover, gonadal steroids may also contribute to epigenetic and organizational influences on the HPA axis even before puberty. Correspondingly, crosstalk between the hypothalamic-pituitary-gonadal (HPG) and HPA axes could lead to abnormalities of stress responses. In humans, a dysregulated stress response is one of the most common symptoms seen across many neuropsychiatric disorders, and as a result, such interactions may exacerbate peripheral pathologies. In this review, we discuss the HPA and HPG axes and review how gonadal steroids interact with the HPA axis to regulate the stress circuitry during all stages in life.

Hypothalamic–pituitary–adrenal and hypothalamic–pituitary–gonadal axes: sex differences in regulation of stress responsivity

PubMed Central

Oyola, Mario G.; Handa, Robert J.

2018-01-01

Gonadal hormones play a key role in the establishment, activation, and regulation of the hypothalamic–pituitary–adrenal (HPA) axis. By influencing the response and sensitivity to releasing factors, neurotransmitters, and hormones, gonadal steroids help orchestrate the gain of the HPA axis to fine-tune the levels of stress hormones in the general circulation. From early life to adulthood, gonadal steroids can differentially affect the HPA axis, resulting in sex differences in the responsivity of this axis. The HPA axis influences many physiological functions making an organism’s response to changes in the environment appropriate for its reproductive status. Although the acute HPA response to stressors is a beneficial response, constant activation of this circuitry by chronic or traumatic stressful episodes may lead to a dysregulation of the HPA axis and cause pathology. Compared to males, female mice and rats show a more robust HPA axis response, as a result of circulating estradiol levels which elevate stress hormone levels during non-threatening situations, and during and after stressors. Fluctuating levels of gonadal steroids in females across the estrous cycle are a major factor contributing to sex differences in the robustness of HPA activity in females compared to males. Moreover, gonadal steroids may also contribute to epigenetic and organizational influences on the HPA axis even before puberty. Correspondingly, crosstalk between the hypothalamic–pituitary–gonadal (HPG) and HPA axes could lead to abnormalities of stress responses. In humans, a dysregulated stress response is one of the most common symptoms seen across many neuropsychiatric disorders, and as a result, such interactions may exacerbate peripheral pathologies. In this review, we discuss the HPA and HPG axes and review how gonadal steroids interact with the HPA axis to regulate the stress circuitry during all stages in life. PMID:28859530

Detection of atrial fibrillation with seismocardiography.

PubMed

Pankaala, Mikko; Koivisto, Tero; Lahdenoja, Olli; Kiviniemi, Tuomas; Saraste, Antti; Vasankari, Tuija; Airaksinen, Juhani

2016-08-01

In this paper we study the feasibility of seismocardiography (SCG) for the detection of Atrial Fibrillation (AF). In this preclinical study, data acquired from one patient having paroxysmal AF (no other heart diseases) is used to introduce specific changes in SCG signal due to AF. Observed changes and phenomena create a foundation for the development of SCG-based AF detection algorithms. SCG data was recorded from the sternum of an AF patient in dorso-ventral direction while at rest in a supine position using a three-axis high precision MEMS accelerometer simultaneously with a one-lead ECG. In contrast to ECG, the magnitude of beats registered with SCG varies considerably from beat to beat during AF. We show that the magnitude of the beats is not random but is in relation to beat intervals. It is shown that extra indicators for detecting AF become available when SCG data is combined with electrocardiographical (ECG) data; there is a certain behavior in the electromechanical delay characteristic of the AF. It is discussed how all this information can be taken advantage of in the detection of AF. Today electrocardiography (ECG) is the primary method for diagnosing arrhythmias, but there is a growing need for simpler and more convenient method for detecting asymptomatic AF. Given the very small dimensions of modern MEMS accelerometers (2mm×2mm), a reliable MEMS based measurement may provide totally new venues for arrhythmia detection.

Vector Acoustics, Vector Sensors, and 3D Underwater Imaging

NASA Astrophysics Data System (ADS)

Lindwall, D.

2007-12-01

Vector acoustic data has two more dimensions of information than pressure data and may allow for 3D underwater imaging with much less data than with hydrophone data. The vector acoustic sensors measures the particle motions due to passing sound waves and, in conjunction with a collocated hydrophone, the direction of travel of the sound waves. When using a controlled source with known source and sensor locations, the reflection points of the sound field can be determined with a simple trigonometric calculation. I demonstrate this concept with an experiment that used an accelerometer based vector acoustic sensor in a water tank with a short-pulse source and passive scattering targets. The sensor consists of a three-axis accelerometer and a matched hydrophone. The sound source was a standard transducer driven by a short 7 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. Several floats were placed in the tank as acoustic targets at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Without resorting to the usual methods of seismic imaging, which in this case is only two dimensional and relied entirely on the use of a synthetic source aperture, the two targets, the tank walls, the tank bottom, and the water surface were imaged. A directional ambiguity inherent to vector sensors is removed by using collocated hydrophone data. Although this experiment was in a very simple environment, it suggests that 3-D seismic surveys may be achieved with vector sensors using the same logistics as a 2-D survey that uses conventional hydrophones. This work was supported by the Office of Naval Research, program element 61153N.

Managing piezoelectric sensor jitter: kinematic position tracking applications

NASA Astrophysics Data System (ADS)

Khomo, Malome T.

2016-02-01

Piezo-acoustic distance tracking sensors have challenges of reporting true distance readings. Challenges include directional anisotropy signal loss in transmission power and in receiver sensitivity, distance-related attenuation of signal and the phase shifts that result in jittery values, some preceding, and others succeeding the expected distance readings. There also exist signal time losses arising from dead time associated with processor latency, with carrier signal pulse length and with voltage rise-time delays in pulse detection. Together these factors cause distance under-reporting, and more critically, makes each reported value uncertain, which is unacceptable in distance-critical applications. Piezo-inertial accelerometers have equivalent if not more severe challenges in tri-axial configurations, for instance where a rotational tilt may happen under linear accelerative force. In the absence of tensor component adaptation to change of orientation, signal is lost until the next axial sensor detects it. Study paper focusses on piezo-acoustic transducers UCD1007 and 400SR160 (40kHz), used in a face-to-face configuration over a 600mm range. Within that range 10 successive phase shift wave fronts were identified, but it took 15 reconstructed wave fronts to uniquely identify a continuous end-to-end jitter-free and slippage-free kinematic data stream from the jittery sensor data. The additional 5 degrees of freedom were consumed by the 5-stage filter applied. The technique has remarkable combinatorial and projective geometry implications for digital sensor design. It is possible for the procedure to be applicable in 3-axis accelerometers and adapted into firmware for truly kinematic device driver interfaces so long as the reporting rates are matched with the user interface refresh rates. It is shown that acoustic transducer sensors require phase loop locking for kinematic continuity whereas gravimetric accelerometers demand better measurement time consistence in sensor values for induced kinematic phase locking.

Activity classification using the GENEA: optimum sampling frequency and number of axes.

PubMed

Zhang, Shaoyan; Murray, Peter; Zillmer, Ruediger; Eston, Roger G; Catt, Michael; Rowlands, Alex V

2012-11-01

The GENEA shows high accuracy for classification of sedentary, household, walking, and running activities when sampling at 80 Hz on three axes. It is not known whether it is possible to decrease this sampling frequency and/or the number of axes without detriment to classification accuracy. The purpose of this study was to compare the classification rate of activities on the basis of data from a single axis, two axes, and three axes, with sampling rates ranging from 5 to 80 Hz. Sixty participants (age, 49.4 yr (6.5 yr); BMI, 24.6 kg·m (3.4 kg·m)) completed 10-12 semistructured activities in the laboratory and outdoor environment while wearing a GENEA accelerometer on the right wrist. We analyzed data from single axis, dual axes, and three axes at sampling rates of 5, 10, 20, 40, and 80 Hz. Mathematical models based on features extracted from mean, SD, fast Fourier transform, and wavelet decomposition were built, which combined one of the numbers of axes with one of the sampling rates to classify activities into sedentary, household, walking, and running. Classification accuracy was high irrespective of the number of axes for data collected at 80 Hz (96.93% ± 0.97%), 40 Hz (97.4% ± 0.73%), 20 Hz (96.86% ± 1.12%), and 10 Hz (97.01% ± 1.01%) but dropped for data collected at 5 Hz (94.98% ± 1.36%). Sampling frequencies >10 Hz and/or more than one axis of measurement were not associated with greater classification accuracy. Lower sampling rates and measurement of a single axis would result in a lower data load, longer battery life, and higher efficiency of data processing. Further research should investigate whether a lower sampling rate and a single axis affects classification accuracy when considering a wider range of activities.

The High-latitude Electric Potential Disparity and Hemispheric Differences in the Upper Thermospheric Neutral Wind Circulation

NASA Astrophysics Data System (ADS)

Foerster, M.; Haaland, S.; Cnossen, I.

2014-12-01

We present statistical studies of both the high-latitude ionospheric potential pattern deduced from long-term observations of the Cluster Electron Drift Instrument (EDI) and upper thermospheric neutral wind circulation patterns in the Northern (NH) and Southern Hemisphere (SH) obtained from accelerometers on board of low-Earth orbiting satellites like CHAMP during about the same time interval. The cross-polar cap potential difference during southward IMF conditions appears to be on average slightly (~7%) larger in the SH compared with the NH, while the neutral wind magnitude and vorticity amplitude are mostly larger in the NH than in the SH, especially during high solar activity conditions. We attribute such behaviour to peculiarities of the hemispheres due to the non-dipolar portions of Earth's main magnetic field that constitute substantial differences between the geomagnetic field configurations of both hemispheres. They cause in particular different magnetic field flux densities in the opposite polar regions and different offsets of the invariant poles with respect to the rotation axis of the Earth. The pole is presently displaced almost twice the distance in the SH compared to the NH, which has substantial implications for the coupled magnetosphere-ionosphere-thermosphere system under the influence of external drivers. To analyse this behaviour, we have run several numerical simulations using the first-principle Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model under various seasonal conditions. The survey of both the numerical simulation results and the observations confirm prominent asymmetries between the two hemispheres for these parameters.

Multi-sensor Array for High Altitude Balloon Missions to the Stratosphere

NASA Astrophysics Data System (ADS)

Davis, Tim; McClurg, Bryce; Sohl, John

2008-10-01

We have designed and built a microprocessor controlled and expandable multi-sensor array for data collection on near space missions. Weber State University has started a high altitude research balloon program called HARBOR. This array has been designed to data log a base set of measurements for every flight and has room for six guest instruments. The base measurements are absolute pressure, on-board temperature, 3-axis accelerometer for attitude measurement, and 2-axis compensated magnetic compass. The system also contains a real time clock and circuitry for logging data directly to a USB memory stick. In typical operation the measurements will be cycled through in sequence and saved to the memory stick along with the clock's time stamp. The microprocessor can be reprogrammed to adapt to guest experiments with either analog or digital interfacing. This system will fly with every mission and will provide backup data collection for other instrumentation for which the primary task is measuring atmospheric pressure and temperature. The attitude data will be used to determine the orientation of the onboard camera systems to aid in identifying features in the images. This will make these images easier to use for any future GIS (geographic information system) remote sensing missions.

Fused smart sensor network for multi-axis forward kinematics estimation in industrial robots.

PubMed

Rodriguez-Donate, Carlos; Osornio-Rios, Roque Alfredo; Rivera-Guillen, Jesus Rooney; Romero-Troncoso, Rene de Jesus

2011-01-01

Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that decrease the accuracy of the robot position and orientation. To overcome those problems, several sensor fusion methods have been proposed but at expenses of high-computational load, which avoids the online measurement of the joint's angular position and the online forward kinematics estimation. The contribution of this work is to propose a fused smart sensor network to estimate the forward kinematics of an industrial robot. The developed smart processor uses Kalman filters to filter and to fuse the information of the sensor network. Two primary sensors are used: an optical encoder, and a 3-axis accelerometer. In order to obtain the position and orientation of each joint online a field-programmable gate array (FPGA) is used in the hardware implementation taking advantage of the parallel computation capabilities and reconfigurability of this device. With the aim of evaluating the smart sensor network performance, three real-operation-oriented paths are executed and monitored in a 6-degree of freedom robot.

Stereo Photogrammetry Measurements of the Position and Attitude of a Nozzle-Plume/Shock-Wave Interaction Model in the NASA Ames 9- by 7-Ft Supersonic Wind Tunnel

NASA Technical Reports Server (NTRS)

Schairer, Edward T.; Kushner, Laura K.; Drain, Bethany A.; Heineck, James T.; Durston, Donald A.

2017-01-01

Stereo photogrammetry was used to measure the position and attitude of a slender body of revolution during nozzle-plume/shock-wave interaction tests in the NASA Ames 9- by 7-Ft Supersonic Wind Tunnel. The model support system was designed to allow the model to be placed at many locations in the test section relative to a pressure rail on one sidewall. It included a streamwise traverse as well as a thin blade that offset the model axis from the sting axis. With these features the support system was more flexible than usual resulting in higher-than-usual uncertainty in the position and attitude of the model. Also contributing to this uncertainty were the absence of a balance, so corrections for sting deflections could not be applied, and the wings-vertical orientation of the model, which precluded using a gravity-based accelerometer to measure pitch angle. Therefore, stereo photogrammetry was chosen to provide independent measures of the model position and orientation. This paper describes the photogrammetry system and presents selected results from the test.

A compensation method of lever arm effect for tri-axis hybrid inertial navigation system based on fiber optic gyro

NASA Astrophysics Data System (ADS)

Liu, Zengjun; Wang, Lei; Li, Kui; Gao, Jiaxin

2017-05-01

Hybrid inertial navigation system (HINS) is a new kind of inertial navigation system (INS), which combines advantages of platform INS, strap-down INS and rotational INS. HINS has a physical platform to isolate the angular motion as platform INS does, HINS also uses strap-down attitude algorithms and applies rotation modulation technique. Tri-axis HINS has three gimbals to isolate the angular motion in the dynamic base, in which way the system can reduce the effects of angular motion and improve the positioning precision. However, the angular motion will affect the compensation of some error parameters, especially for the lever arm effect. The lever arm effect caused by position errors between the accelerometers and rotation center cannot be ignored due to the rapid rotation of inertial measurement unit (IMU) and it will cause fluctuation and stage in velocity in HINS. The influences of angular motion on the lever arm effect compensation are analyzed firstly in this paper, and then the compensation method of lever arm effect based on the photoelectric encoders in dynamic base is proposed. Results of experiments on turntable show that after compensation, the fluctuations and stages in velocity curve disappear.

An Arduino-Based Resonant Cradle Design with Infant Cries Recognition

PubMed Central

Chao, Chun-Tang; Wang, Chia-Wei; Chiou, Juing-Shian; Wang, Chi-Jo

2015-01-01

This paper proposes a resonant electric cradle design with infant cries recognition, employing an Arduino UNO as the core processor. For most commercially available electric cradles, the drive motor is closely combined with the bearing on the top, resulting in a lot of energy consumption. In this proposal, a ball bearing design was adopted and the driving force is under the cradle to increase the distance from the object to fulcrum and torque. The sensors are designed to detect the oscillation state, and then the force is driven at the critical time to achieve the maximum output response while saving energy according to the principle of resonance. As for the driving forces, the winding power and motors are carefully placed under the cradle. The sensors, including the three-axis accelerometer and infrared sensor, are tested and applied under swinging amplitude control. In addition, infant cry recognition technology was incorporated in the design to further develop its functionality, which is a rare feature in this kind of hardware. The proposed nonlinear operator of fundamental frequency (f0) analysis is able to identify different types of infant cries. In conclusion, this paper proposes an energy-saving electric cradle with infant cries recognition and the experimental results demonstrate the effectiveness of this approach. PMID:26247947

An Arduino-Based Resonant Cradle Design with Infant Cries Recognition.

PubMed

Chao, Chun-Tang; Wang, Chia-Wei; Chiou, Juing-Shian; Wang, Chi-Jo

2015-08-03

This paper proposes a resonant electric cradle design with infant cries recognition, employing an Arduino UNO as the core processor. For most commercially available electric cradles, the drive motor is closely combined with the bearing on the top, resulting in a lot of energy consumption. In this proposal, a ball bearing design was adopted and the driving force is under the cradle to increase the distance from the object to fulcrum and torque. The sensors are designed to detect the oscillation state, and then the force is driven at the critical time to achieve the maximum output response while saving energy according to the principle of resonance. As for the driving forces, the winding power and motors are carefully placed under the cradle. The sensors, including the three-axis accelerometer and infrared sensor, are tested and applied under swinging amplitude control. In addition, infant cry recognition technology was incorporated in the design to further develop its functionality, which is a rare feature in this kind of hardware. The proposed nonlinear operator of fundamental frequency (f0) analysis is able to identify different types of infant cries. In conclusion, this paper proposes an energy-saving electric cradle with infant cries recognition and the experimental results demonstrate the effectiveness of this approach.

Improved Electromechanical Infrared Sensor

NASA Technical Reports Server (NTRS)

Kenny, Thomas W.; Kaiser, William J.

1994-01-01

Proposed electromechanical infrared detector improved version of device described in "Micromachined Electron-Tunneling Infrared Detectors" (NPO-18413). Fabrication easier, and undesired sensitivity to acceleration reduced. In devices, diaphragms and other components made of micromachined silicon, and displacements of diaphragms measured by electron tunneling displacement transducer {see "Micromachined Tunneling Accelerometer" (NPO-18513)}. Improved version offers enhanced frequency response and less spurious response to acceleration.

Design and implementation of a micromechanical silicon resonant accelerometer.

PubMed

Huang, Libin; Yang, Hui; Gao, Yang; Zhao, Liye; Liang, Jinxing

2013-11-19

The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG) technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C.

The location of the tibial accelerometer does influence impact acceleration parameters during running.

PubMed

Lucas-Cuevas, Angel Gabriel; Encarnación-Martínez, Alberto; Camacho-García, Andrés; Llana-Belloch, Salvador; Pérez-Soriano, Pedro

2017-09-01

Tibial accelerations have been associated with a number of running injuries. However, studies attaching the tibial accelerometer on the proximal section are as numerous as those attaching the accelerometer on the distal section. This study aimed to investigate whether accelerometer location influences acceleration parameters commonly reported in running literature. To fulfil this purpose, 30 athletes ran at 2.22, 2.78 and 3.33 m · s -1 with three accelerometers attached with double-sided tape and tightened to the participants' tolerance on the forehead, the proximal section of the tibia and the distal section of the tibia. Time-domain (peak acceleration, shock attenuation) and frequency-domain parameters (peak frequency, peak power, signal magnitude and shock attenuation in both the low and high frequency ranges) were calculated for each of the tibial locations. The distal accelerometer registered greater tibial acceleration peak and shock attenuation compared to the proximal accelerometer. With respect to the frequency-domain analysis, the distal accelerometer provided greater values of all the low-frequency parameters, whereas no difference was observed for the high-frequency parameters. These findings suggest that the location of the tibial accelerometer does influence the acceleration signal parameters, and thus, researchers should carefully consider the location they choose to place the accelerometer so that equivalent comparisons across studies can be made.

Simultaneous Observations of TADs in GOCE, CHAMP and GRACE Density Data Compared with CTIPe

NASA Astrophysics Data System (ADS)

Bruinsma, S. L.; Fedrizzi, M.

2012-12-01

The accelerometers on the CHAMP and GRACE satellites have made it possible to accumulate near-continuous records of thermosphere density between about 300 and 490 km since May 2001, and July 2002, respectively. Since November 2009, a third gravity field satellite mission, ESA's GOCE, is in a very low and near heliosynchronous dawn-dusk orbit at about 270 km. The spacecraft is actively maintained at that constant altitude using an ion propulsion engine that compensates the aerodynamic drag in the flight direction. The thrust level, combined with accelerometer and satellite attitude data, is used to compute atmospheric densities and cross-track winds. The response of the thermosphere to geomagnetic disturbances, i.e., space weather, has been extensively studied using the exceptional datasets of CHAMP and GRACE. Thanks to GOCE we now have a third excellent data set for these studies. In this presentation we will show the observed density and its variability for the geomagnetic storm of 5 April 2010, and compare it with predictions along the orbits obtained from a self-consistent physics-based coupled model of the thermosphere, ionosphere, plasmasphere and electrodynamics (CTIPe). For this storm, the CHAMP and GOCE orbit planes were perpendicular (12/24 Local Solar Time, and 6/18 LST, respectively) and the altitude difference was only approximately 30 km. The GRACE densities are at a much higher altitude of about 475 km. Wave-like features are revealed or enhanced after filtering of the densities and calculation of relative density variations. Traveling Atmospheric Disturbances are observed in the data, and the model's fidelity in reproducing the waves is evaluated.

MEMS capacitive accelerometer-based middle ear microphone.

PubMed

Young, Darrin J; Zurcher, Mark A; Semaan, Maroun; Megerian, Cliff A; Ko, Wen H

2012-12-01

The design, implementation, and characterization of a microelectromechanical systems (MEMS) capacitive accelerometer-based middle ear microphone are presented in this paper. The microphone is intended for middle ear hearing aids as well as future fully implantable cochlear prosthesis. Human temporal bones acoustic response characterization results are used to derive the accelerometer design requirements. The prototype accelerometer is fabricated in a commercial silicon-on-insulator (SOI) MEMS process. The sensor occupies a sensing area of 1 mm × 1 mm with a chip area of 2 mm × 2.4 mm and is interfaced with a custom-designed low-noise electronic IC chip over a flexible substrate. The packaged sensor unit occupies an area of 2.5 mm × 6.2 mm with a weight of 25 mg. The sensor unit attached to umbo can detect a sound pressure level (SPL) of 60 dB at 500 Hz, 35 dB at 2 kHz, and 57 dB at 8 kHz. An improved sound detection limit of 34-dB SPL at 150 Hz and 24-dB SPL at 500 Hz can be expected by employing start-of-the-art MEMS fabrication technology, which results in an articulation index of approximately 0.76. Further micro/nanofabrication technology advancement is needed to enhance the microphone sensitivity for improved understanding of normal conversational speech.

Rigid Body Modes Influence On Microvibration Analysis-Application To Swarm

NASA Astrophysics Data System (ADS)

Laduree, G.; Fransen, S.; Baldesi, G.; Pflieger, I.

2012-07-01

Microvibrations are defined as low level mechanical disturbances affecting payload performance, generated by mobile parts or mechanism operating on-board the spacecraft, like momentum or reaction wheels, pointing mechanism, cryo-coolers or thrusters. The disturbances caused by these sources are transmitted through the spacecraft structure and excite modes of that structure or elements of the payload impacting its performance (e.g. Line of sight rotations inducing some image quality degradation). The dynamic interaction between these three elements (noise source, spacecraft structure and sensitive receiver) makes the microvibration prediction a delicate problem. Microvibration sources are generally of concern in the frequency range from a few Hz to 1000 Hz. However, in some specific cases, high stability at lower frequencies might be requested. This is the case of the SWARM mission, whose objectives are to provide the best ever survey of the geomagnetic field and its temporal evolution as well as supplementary information for studying the interaction of the magnetic field with other physical quantities describing the Earth system (e.g. ocean circulation). Among its instruments, SWARM is embarking a very sensitive 6-axis accelerometer in the low frequency range (10-8 m/s2 or rad/s2 between 10-4 and 0.1 Hz) located at its Centre of Gravity and an Absolute Scalar Magnetometer located at the tip of a boom far from the spacecraft body. The ASM performs its measurements by rotating an alternative magnetic field around its main axis thanks to a piezo-electric motor. This repeated disturbance might generate some pollution of the accelerometer science data. The objective of this work is to focus on the interaction of the rigid body mode calculation method with the elastic contribution of the normal modes excited by the noise source frequency content. It has indeed been reported in the past that NASTRAN Lanczos rigid body modes may lead to inaccurate rigid-body accelerations affecting steady state responses due to numerical roundoffs coming from the coupled mode shape extraction method and from the associated non numerical zeros frequencies. Geometric rigid body modes are usually the preferred solution for dynamic transient analysis but are not retained by NASTRAN when the chosen eigensolver is Lanczos, even using a SUPORT card. The SWARM microvibration problem described above has been considered as a benchmark case for various codes (NASTRAN, PERMAS, DCAP - multi-body software) and methods (direct or modal transients). A specific DMAP in NASTRAN has been written to overcome the limitation imposed by the Lanczos method and considerations on the conditioning of the FEM are discussed. An assessment on the accuracy of the different rigid body modes calculation methods is finally proposed.

An enhanced inertial navigation system based on a low-cost IMU and laser scanner

NASA Astrophysics Data System (ADS)

Kim, Hyung-Soon; Baeg, Seung-Ho; Yang, Kwang-Woong; Cho, Kuk; Park, Sangdeok

2012-06-01

This paper describes an enhanced fusion method for an Inertial Navigation System (INS) based on a 3-axis accelerometer sensor, a 3-axis gyroscope sensor and a laser scanner. In GPS-denied environments, indoor or dense forests, a pure INS odometry is available for estimating the trajectory of a human or robot. However it has a critical implementation problem: a drift error of velocity, position and heading angles. Commonly the problem can be solved by fusing visual landmarks, a magnetometer or radio beacons. These methods are not robust in diverse environments: darkness, fog or sunlight, an unstable magnetic field and an environmental obstacle. We propose to overcome the drift problem using an Iterative Closest Point (ICP) scan matching algorithm with a laser scanner. This system consists of three parts. The first is the INS. It estimates attitude, velocity, position based on a 6-axis Inertial Measurement Unit (IMU) with both 'Heuristic Reduction of Gyro Drift' (HRGD) and 'Heuristic Reduction of Velocity Drift' (HRVD) methods. A frame-to-frame ICP matching algorithm for estimating position and attitude by laser scan data is the second. The third is an extended kalman filter method for multi-sensor data fusing: INS and Laser Range Finder (LRF). The proposed method is simple and robust in diverse environments, so we could reduce the drift error efficiently. We confirm the result comparing an odometry of the experimental result with ICP and LRF aided-INS in a long corridor.

Mechanisms and factors involved in hip injuries during frontal crashes.

PubMed

Yoganandan, N; Pintar, F A; Gennarelli, T A; Maltese, M R; Eppinger, R H

2001-11-01

This study was conducted to collect data and gain insights relative to the mechanisms and factors involved in hip injuries during frontal crashes and to study the tolerance of hip injuries from this type of loading. Unembalmed human cadavers were seated on a standard automotive seat (reinforced) and subjected to knee impact test to each lower extremity. Varying combinations of flexion and adduction/abduction were used for initial alignment conditions and pre-positioning. Accelerometers were fixed to the iliac wings and twelfth thoracic vertebral spinous process. A 23.4-kg padded pendulum impacted the knee at velocities ranging from 4.3 to 7.6 m/s. The impacting direction was along the anteroposterior axis, i.e., the global X-axis, in the body-fixed coordinate system. A load cell on the front of the pendulum recorded the impact force. Peak impact forces ranged from 2,450 to 10,950 N. The rate of loading ranged from 123 to 7,664 N/msec. The impulse values ranged from 12.4 to 31.9 Nsec. Injuries were not apparent in three tests. Eight tests resulted in trauma. Fractures involving the pelvis including the acetabulum and proximal femur occurred in five out of the eight tests, and distal femoral bone fracture occurred in one test. These results underscore the importance of leg pre-positioning and the orientation of the impacting axis to produce specific types of trauma to the pelvic region of the lower extremity.

The interaction of BDNF Val66Met, PTSD, and child abuse on psychophysiological reactivity and HPA axis function in a sample of Gulf War Veterans.

PubMed

Young, Dmitri A; Neylan, Thomas C; O'Donovan, Aoife; Metzler, Thomas; Richards, Anne; Ross, Jessica A; Inslicht, Sabra S

2018-08-01

While the BDNF Val66Met polymorphism has been linked to various psychological disorders, limited focus has been on its relationship to posttraumatic stress disorder (PTSD) and early traumas such as child abuse. Therefore, we assessed whether Val66Met was associated with fear potentiated psychophysiological response and HPA axis dysfunction and whether PTSD status or child abuse history moderated these outcomes in a sample of Veterans. 226 and 173 participants engaged in a fear potentiated acoustic startle paradigm and a dexamethasone suppression test (DST) respectively. Fear conditions included no, ambiguous, and high threat conditions. Psychophysiological response measures included electromyogram (EMG), skin conductance response (SCR), and heart rate. The Clinician Administered PTSD Scale (CAPS) and the Trauma History Questionnaire (THQ) were used to assess PTSD status and child abuse history respectively. Met allele carriers exhibited greater SCR magnitudes in the no and ambiguous threat conditions (p < 0.01 and p < 0.05 respectively). Met carriers with PTSD exhibited greater physiological response magnitudes in the ambiguous (SCR, p < 0.001) and high threat conditions (SCR and heart rate, both p ≤ 0.005). Met carrier survivors of child abuse exhibited blunted heart rate magnitudes in the high threat condition (p < 0.01). Met allele carries with PTSD also exhibited greater percent cortisol suppression (p < 0.005). Limitations included small sample size and the cross-sectional nature of the data. The Val66met may impact PTSD susceptibility differentially via enhanced threat sensitivity and HPA axis dysregulation. Child abuse may moderate Val66Met's impact on threat reactivity. Future research should explore how neuronal mechanisms might mediate this risk. Published by Elsevier B.V.

Objectively Measured Physical Activity in European Adults: Cross-Sectional Findings from the Food4Me Study.

PubMed

Marsaux, Cyril F M; Celis-Morales, Carlos; Hoonhout, Jettie; Claassen, Arjan; Goris, Annelies; Forster, Hannah; Fallaize, Rosalind; Macready, Anna L; Navas-Carretero, Santiago; Kolossa, Silvia; Walsh, Marianne C; Lambrinou, Christina-Paulina; Manios, Yannis; Godlewska, Magdalena; Traczyk, Iwona; Lovegrove, Julie A; Martinez, J Alfredo; Daniel, Hannelore; Gibney, Mike; Mathers, John C; Saris, Wim H M

2016-01-01

Comparisons of objectively measured physical activity (PA) between residents of European countries measured concurrently with the same protocol are lacking. We aimed to compare PA between the seven European countries involved in the Food4Me Study, using accelerometer data collected remotely via the Internet. Of the 1607 participants recruited, 1287 (539 men and 748 women) provided at least 3 weekdays and 2 weekend days of valid accelerometer data (TracmorD) at baseline and were included in the present analyses. Men were significantly more active than women (physical activity level = 1.74 vs. 1.70, p < 0.001). Time spent in light PA and moderate PA differed significantly between countries but only for women. Adherence to the World Health Organization recommendation to accumulate at least 150 min of moderate-equivalent PA weekly was similar between countries for men (range: 54-65%) but differed significantly between countries for women (range: 26-49%). Prevalence estimates decreased substantially for men and women in all seven countries when PA guidelines were defined as achieving 30 min of moderate and vigorous PA per day. We were able to obtain valid accelerometer data in real time via the Internet from 80% of participants. Although our estimates are higher compared with data from Sweden, Norway, Portugal and the US, there is room for improvement in PA for all countries involved in the Food4Me Study.

Drivers Are More Physically Active Than Non-Drivers in Older Adults.

PubMed

Amagasa, Shiho; Fukushima, Noritoshi; Kikuchi, Hiroyuki; Takamiya, Tomoko; Odagiri, Yuko; Oka, Koichiro; Inoue, Shigeru

2018-05-28

Car use has been identified as sedentary behavior, although it may enhance mobility, particularly in the older population. This cross-sectional study aimed to compare the time spent in objectively determined sedentary behavior (SB) and physical activity (PA) between older drivers and non-drivers. Four hundred and fifty Japanese older adults (74.3 ± 2.9 years) who had valid accelerometer data were included. They were asked to respond to a questionnaire and wear an accelerometer (HJA-350IT, Omron Healthcare) on their waist for 7 consecutive days in 2015. To compare activity time between drivers and non-drivers, we calculated estimated means using analysis of covariance, adjusting for sociodemographic, physical, and psychological factors and accelerometer wear time. Compared to non-drivers, drivers engaged in more light-intensity PA (LPA) (drivers: 325.0 vs. non-drivers: 289.0 min/day) and moderate-to-vigorous PA (drivers: 37.5 vs. non-drivers: 30.0 min/day) and less SB (drivers: 493.4 vs. non-drivers: 535.9 min/day) (all p < 0.05). After stratification by age, sex, and residential area, larger effect of driving on PA time was found in older-older adults, in men, and in rural residents. Older drivers were found to be more physically active than non-drivers, suggesting more access to outdoor activities or expanding social network.

The validation of a self-report measure and physical activity of Australian Aboriginal and Torres Strait Islander and non-Indigenous rural children.

PubMed

Gwynn, Josephine D; Hardy, Louise L; Wiggers, John H; Smith, Wayne T; D'Este, Catherine A; Turner, Nicole; Cochrane, Janine; Barker, Daniel J; Attia, John R

2010-07-01

To validate a self-report measure of physical activity for both Australian Aboriginal and Torres Strait Islander and non-Indigenous rural children, and to describe their physical activity participation. In this cross-sectional study, 84 Aboriginal and Torres Strait Islander and 146 non-Indigenous children aged 10-12 years old completed the Many Rivers Physical Activity Recall Questionnaire (MRPARQ), a modified version of the Adolescent Physical Activity Recall Questionnaire (APARQ). A sub-group (n=86) wore an accelerometer for seven consecutive days in order to validate the instrument. Pearson and Intra Class Correlation coefficients between the survey and acceleromtery for weekdays only are 0.31 and 0.16, respectively, for Aboriginal and Torres Strait Islander children, and 0.38 and 0.31, respectively, for non-Indigenous children, and demonstrate a modest (p<0.05) correlation. Self-reported MVPA for Aboriginal and Torres Strait Islander children is between 162 and 172 minutes/day, and is 125 minutes by accelerometer; for non-Indigenous children MVPA is between 123 and 149 minutes (survey) and 107 minutes (accelerometer). Australian Aboriginal and Torres Strait Islander children's self-report of physical activity is at least as valid as non-Indigenous children, given culturally appropriate support; they tend to be more active than non-Indigenous children. The MRPARQ can be administered with Aboriginal and Torres Strait Islander and non-Indigenous children.

levels and sociodemographic correlates of accelerometer-based physical activity in Irish children: a cross-sectional study.

PubMed

Li, Xia; Kearney, Patricia M; Keane, Eimear; Harrington, Janas M; Fitzgerald, Anthony P

2017-06-01

The aim of this study was to explore levels and sociodemographic correlates of physical activity (PA) over 1 week using accelerometer data. Accelerometer data was collected over 1 week from 1075 8-11-year-old children in the cross-sectional Cork Children's Lifestyle Study. Threshold values were used to categorise activity intensity as sedentary, light, moderate or vigorous. Questionnaires collected data on demographic factors. Smoothed curves were used to display minute by minute variations. Binomial regression was used to identify factors correlated with the probability of meeting WHO 60 min moderate to vigorous PA guidelines. Overall, 830 children (mean (SD) age: 9.9(0.7) years, 56.3% boys) were included. From the binomial multiple regression analysis, boys were found more likely to meet guidelines (probability ratio 1.17, 95% CI 1.06 to 1.28) than girls. Older children were less likely to meet guidelines than younger children (probability ratio 0.91, CI 0.87 to 0.95). Normal weight children were more likely than overweight and obese children to meet guidelines (probability ratio 1.25, CI 1.16 to 1.34). Children in urban areas were more likely to meet guidelines than those in rural areas (probability ratio 1.19, CI 1.07 to 1.33). Longer daylight length days were associated with greater probability of meeting guidelines compared to shorter daylight length days. PA levels differed by individual factors including age, gender and weight status as well as by environmental factors including residence and daylight length. Less than one-quarter of children (26.8% boys, 16.2% girls) meet guidelines. Effective intervention policies are urgently needed to increase PA. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Refining Time-Activity Classification of Human Subjects Using the Global Positioning System.

PubMed

Hu, Maogui; Li, Wei; Li, Lianfa; Houston, Douglas; Wu, Jun

2016-01-01

Detailed spatial location information is important in accurately estimating personal exposure to air pollution. Global Position System (GPS) has been widely used in tracking personal paths and activities. Previous researchers have developed time-activity classification models based on GPS data, most of them were developed for specific regions. An adaptive model for time-location classification can be widely applied to air pollution studies that use GPS to track individual level time-activity patterns. Time-activity data were collected for seven days using GPS loggers and accelerometers from thirteen adult participants from Southern California under free living conditions. We developed an automated model based on random forests to classify major time-activity patterns (i.e. indoor, outdoor-static, outdoor-walking, and in-vehicle travel). Sensitivity analysis was conducted to examine the contribution of the accelerometer data and the supplemental spatial data (i.e. roadway and tax parcel data) to the accuracy of time-activity classification. Our model was evaluated using both leave-one-fold-out and leave-one-subject-out methods. Maximum speeds in averaging time intervals of 7 and 5 minutes, and distance to primary highways with limited access were found to be the three most important variables in the classification model. Leave-one-fold-out cross-validation showed an overall accuracy of 99.71%. Sensitivities varied from 84.62% (outdoor walking) to 99.90% (indoor). Specificities varied from 96.33% (indoor) to 99.98% (outdoor static). The exclusion of accelerometer and ambient light sensor variables caused a slight loss in sensitivity for outdoor walking, but little loss in overall accuracy. However, leave-one-subject-out cross-validation showed considerable loss in sensitivity for outdoor static and outdoor walking conditions. The random forests classification model can achieve high accuracy for the four major time-activity categories. The model also performed well with just GPS, road and tax parcel data. However, caution is warranted when generalizing the model developed from a small number of subjects to other populations.

Validation and Comparison of Accelerometers Worn on the Hip, Thigh, and Wrists for Measuring Physical Activity and Sedentary Behavior.

PubMed

Montoye, Alexander H K; Pivarnik, James M; Mudd, Lanay M; Biswas, Subir; Pfeiffer, Karin A

2016-01-01

Recent evidence suggests that physical activity (PA) and sedentary behavior (SB) exert independent effects on health. Therefore, measurement methods that can accurately assess both constructs are needed. To compare the accuracy of accelerometers placed on the hip, thigh, and wrists, coupled with machine learning models, for measurement of PA intensity category (SB, light-intensity PA [LPA], and moderate- to vigorous-intensity PA [MVPA]) and breaks in SB. Forty young adults (21 female; age 22.0 ± 4.2 years) participated in a 90-minute semi-structured protocol, performing 13 activities (three sedentary, 10 non-sedentary) for 3-10 minutes each. Participants chose activity order, duration, and intensity. Direct observation (DO) was used as a criterion measure of PA intensity category, and transitions from SB to a non-sedentary activity were breaks in SB. Participants wore four accelerometers (right hip, right thigh, and both wrists), and a machine learning model was created for each accelerometer to predict PA intensity category. Sensitivity and specificity for PA intensity category classification were calculated and compared across accelerometers using repeated measures analysis of variance, and the number of breaks in SB was compared using repeated measures analysis of variance. Sensitivity and specificity values for the thigh-worn accelerometer were higher than for wrist- or hip-worn accelerometers, > 99% for all PA intensity categories. Sensitivity and specificity for the hip-worn accelerometer were 87-95% and 93-97%. The left wrist-worn accelerometer had sensitivities and specificities of > 97% for SB and LPA and 91-95% for MVPA, whereas the right wrist-worn accelerometer had sensitivities and specificities of 93-99% for SB and LPA but 67-84% for MVPA. The thigh-worn accelerometer had high accuracy for breaks in SB; all other accelerometers overestimated breaks in SB. Coupled with machine learning modeling, the thigh-worn accelerometer should be considered when objectively assessing PA and SB.

Compact Circuit Preprocesses Accelerometer Output

NASA Technical Reports Server (NTRS)

Bozeman, Richard J., Jr.

1993-01-01

Compact electronic circuit transfers dc power to, and preprocesses ac output of, accelerometer and associated preamplifier. Incorporated into accelerometer case during initial fabrication or retrofit onto commercial accelerometer. Made of commercial integrated circuits and other conventional components; made smaller by use of micrologic and surface-mount technology.

Tool enables proper mating of accelerometer and cable connector

NASA Technical Reports Server (NTRS)

Steed, C. N.

1966-01-01

Tool supports accelerometer in axial alignment with an accelerometer cable connector and permits tightening of the accelerometer to the cable connector with a torque wrench. This is done without damaging the components or permitting them to work loose under sustained, high-level vibrations.

Self-noise models of five commercial strong-motion accelerometers

USGS Publications Warehouse

Ringler, Adam; Evans, John R.; Hutt, Charles R.

2015-01-01

To better characterize the noise of a number of commonly deployed accelerometers in a standardized way, we conducted noise measurements on five different models of strong‐motion accelerometers. Our study was limited to traditional accelerometers (Fig. 1) and is in no way exhaustive.

Hypothalamic-pituitary-adrenal axis response to acute psychosocial stress: Effects of biological sex and circulating sex hormones

PubMed Central

Stephens, Mary Ann C.; Mahon, Pamela B.; McCaul, Mary E.; Wand, Gary S.

2016-01-01

Summary Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis influences the risk for developing stress-related disorders. Sex-dependent differences in the HPA axis stress response are believed to contribute to the different prevalence rates of stress-related disorders found in men and women. However, studies examining the HPA axis stress response have shown mixed support for sex differences, and the role of endogenous sex hormones on HPA axis response has not been adequately examined in humans. This study utilized the largest sample size to date to analyze the effects of biological sex and sex hormones on HPA axis social stress responses. Healthy, 18- to 30- year-old community volunteers (N=282) completed the Trier Social Stress Test (TSST), a widely used and well-validated stress-induction laboratory procedure. All women (n=135) were tested during the follicular phase of their menstrual cycle (when progesterone levels are most similar to men). Adrenocorticotropic hormone (ACTH) and cortisol measures were collected at multiple points throughout pre- and post-TSST. Testosterone and progesterone (in men) and progesterone and estradiol (in women) were determined pre-TSST. Following the TSST, men had greater ACTH and cortisol levels than women. Men had steeper baseline-to-peak and peak-to-end ACTH and cortisol response slopes than women; there was a trend for more cortisol responders among men than women. Testosterone negatively correlated with salivary cortisol response in men, while progesterone negatively correlated with ACTH and cortisol responses in women. These data confirm that men show more robust activation of the HPA axis response to the TSST than do women in the follicular phase of the menstrual cycle. Testosterone results suggest an inhibitory effect on HPA axis reactivity in men. Progesterone results suggest an inhibitory effect on HPA axis reactivity in women. Future work is needed to explain why men mount a greater ACTH and cortisol response to the TSST than do women during the follicular phase of the menstrual cycle. PMID:26773400

New Matching Method for Accelerometers in Gravity Gradiometer

PubMed Central

Wei, Hongwei; Wu, Meiping; Cao, Juliang

2017-01-01

The gravity gradiometer is widely used in mineral prospecting, including in the exploration of mineral, oil and gas deposits. The mismatch of accelerometers adversely affects the measuring precision of rotating accelerometer-based gravity gradiometers. Several strategies have been investigated to address the imbalance of accelerometers in gradiometers. These strategies, however, complicate gradiometer structures because feedback loops and re-designed accelerometers are needed in these strategies. In this paper, we present a novel matching method, which is based on a new configuration of accelerometers in a gravity gradiometer. In the new configuration, an angle was introduced between the measurement direction of the accelerometer and the spin direction. With the introduced angle, accelerometers could measure the centrifugal acceleration generated by the rotating disc. Matching was realized by updating the scale factors of the accelerometers with the help of centrifugal acceleration. Further simulation computations showed that after adopting the new matching method, signal-to-noise ratio improved from −41 dB to 22 dB. Compared with other matching methods, our method is more flexible and costs less. The matching accuracy of this new method is similar to that of other methods. Our method provides a new idea for matching methods in gravity gradiometer measurement. PMID:28757584

Helicopter flight dynamics simulation with a time-accurate free-vortex wake model

NASA Astrophysics Data System (ADS)

Ribera, Maria

This dissertation describes the implementation and validation of a coupled rotor-fuselage simulation model with a time-accurate free-vortex wake model capable of capturing the response to maneuvers of arbitrary amplitude. The resulting model has been used to analyze different flight conditions, including both steady and transient maneuvers. The flight dynamics model is based on a system of coupled nonlinear rotor-fuselage differential equations in first-order, state-space form. The rotor model includes flexible blades, with coupled flap-lag-torsion dynamics and swept tips; the rigid body dynamics are modeled with the non-linear Euler equations. The free wake models the rotor flow field by tracking the vortices released at the blade tips. Their behavior is described by the equations of vorticity transport, which is approximated using finite differences, and solved using a time-accurate numerical scheme. The flight dynamics model can be solved as a system of non-linear algebraic trim equations to determine the steady state solution, or integrated in time in response to pilot-applied controls. This study also implements new approaches to reduce the prohibitive computational costs associated with such complex models without losing accuracy. The mathematical model was validated for trim conditions in level flight, turns, climbs and descents. The results obtained correlate well with flight test data, both in level flight as well as turning and climbing and descending flight. The swept tip model was also found to improve the trim predictions, particularly at high speed. The behavior of the rigid body and the rotor blade dynamics were also studied and related to the aerodynamic load distributions obtained with the free wake induced velocities. The model was also validated in a lateral maneuver from hover. The results show improvements in the on-axis prediction, and indicate a possible relation between the off-axis prediction and the lack of rotor-body interaction aerodynamics. The swept blade model improves both the on-axis and off-axis response. An axial descent though the vortex ring state was simulated. As theǒrtex ring" goes through the rotor, the unsteady loads produce large attitude changes, unsteady flapping, fluctuating thrust and an increase in power required. A roll reversal maneuver was found useful in understanding the cross-couplings effects found in rotorcraft, specifically the effect of the aerodynamic loading on the rotor orientation and the off-axis response.

Launcher Dynamic Data Acquisition

DTIC Science & Technology

2012-07-31

K PR Pressure PR Pressure PR Accelerometer PR Accelerometer PR Accelerometer PR Pressure PR Pressure IEPE Microphone IEPE ...transducers, displacement potentiometers, or Integrated Electronics Piezoelectric ( IEPE ) microphones and accelerometers. The characteristics of these...Engineering Units HCl hydrogen chloride HVAC heating ventilation and cooling Hz hertz IEC International Electrotechnical Commission IEPE

Design and Implementation of a Micromechanical Silicon Resonant Accelerometer

PubMed Central

Huang, Libin; Yang, Hui; Gao, Yang; Zhao, Liye; Liang, Jinxing

2013-01-01

The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG) technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C. PMID:24256978

AF-Geospace User’s Manual Version 2.5.1 and Version 2.51P

DTIC Science & Technology

2012-08-01

system of the grid. The choices are: GEOC: Geocentric coordinate system: The Z axis is aligned with the north rotational pole, the X axis pierces...the Greenwich Meridian on the equator (0 o Long, 0 o Lat), and the Y axis is minus the cross-product of X and Z. GSM: Geocentric solar magnetospheric...handed system and is positive towards dusk. GEI: Geocentric equatorial inertial coordinate system: The Z axis is the same as for the geocentric

Calibration and comparison of accelerometer cut points in preschool children.

PubMed

van Cauwenberghe, Eveline; Labarque, Valery; Trost, Stewart G; de Bourdeaudhuij, Ilse; Cardon, Greet

2011-06-01

The present study aimed to develop accelerometer cut points to classify physical activities (PA) by intensity in preschoolers and to investigate discrepancies in PA levels when applying various accelerometer cut points. To calibrate the accelerometer, 18 preschoolers (5.8 ± 0.4 years) performed eleven structured activities and one free play session while wearing a GT1M ActiGraph accelerometer using 15 s epochs. The structured activities were chosen based on the direct observation system Children's Activity Rating Scale (CARS) while the criterion measure of PA intensity during free play was provided using a second-by-second observation protocol (modified CARS). Receiver Operating Characteristic (ROC) curve analyses were used to determine the accelerometer cut points. To examine the classification differences, accelerometer data of four consecutive days from 114 preschoolers (5.5 ± 0.3 years) were classified by intensity according to previously published and the newly developed accelerometer cut points. Differences in predicted PA levels were evaluated using repeated measures ANOVA and Chi Square test. Cut points were identified at 373 counts/15 s for light (sensitivity: 86%; specificity: 91%; Area under ROC curve: 0.95), 585 counts/15 s for moderate (87%; 82%; 0.91) and 881 counts/15 s for vigorous PA (88%; 91%; 0.94). Further, applying various accelerometer cut points to the same data resulted in statistically and biologically significant differences in PA. Accelerometer cut points were developed with good discriminatory power for differentiating between PA levels in preschoolers and the choice of accelerometer cut points can result in large discrepancies.

Design and realization of photoelectric instrument binocular optical axis parallelism calibration system

NASA Astrophysics Data System (ADS)

Ying, Jia-ju; Chen, Yu-dan; Liu, Jie; Wu, Dong-sheng; Lu, Jun

2016-10-01

The maladjustment of photoelectric instrument binocular optical axis parallelism will affect the observe effect directly. A binocular optical axis parallelism digital calibration system is designed. On the basis of the principle of optical axis binocular photoelectric instrument calibration, the scheme of system is designed, and the binocular optical axis parallelism digital calibration system is realized, which include four modules: multiband parallel light tube, optical axis translation, image acquisition system and software system. According to the different characteristics of thermal infrared imager and low-light-level night viewer, different algorithms is used to localize the center of the cross reticle. And the binocular optical axis parallelism calibration is realized for calibrating low-light-level night viewer and thermal infrared imager.

Assessment of Differing Definitions of Accelerometer Nonwear Time

ERIC Educational Resources Information Center

Evenson, Kelly R.; Terry, James W., Jr.

2009-01-01

Measuring physical activity with objective tools, such as accelerometers, is becoming more common. Accelerometers measure acceleration multiple times within a given frequency and summarize this as a count over a pre-specified time period or epoch. The resultant count represents acceleration over the epoch length. Accelerometers eliminate biases…

Effects of Cross-axis Wind Jet Events on the Northern Red Sea Circulation

NASA Astrophysics Data System (ADS)

Menezes, V. V.; Bower, A. S.; Farrar, J. T.

2016-12-01

Despite its small size, the Red Sea has a complex circulation. There are boundary currents in both sides of the basin, a meridional overturning circulation, water mass formation in the northern part and an intense eddy activity. This complex pattern is driven by strong air-sea interactions. The Red Sea has one of the largest evaporation rates of the global oceans (2m/yr), an intricate and seasonally varying wind pattern. The winds blowing over the Northern Rea Sea (NRS, north of 20N) are predominantly southeastward along the main axis all year round; in the southern, they reverse seasonally due to the monsoonal regime. Although the winds are mostly along-axis in the NRS, several works have shown that sometimes during the boreal winter, the winds blow in a cross-axis direction. The westward winds from Saudi Arabia bring relatively cold dry air and dust from the desert, enhancing heat loss and evaporation off the Red Sea. These wind-jet events may contribute to increased eddy activity and are a trigger for water mass formation. Despite that, our knowledge about the cross-axis winds and their effect on NRS circulation is still incipient. In the present work we analyze 10-years of Quikscat scatterometer winds and altimetric sea surface height anomalies, together with 2-yrs of mooring data, to characterize the westward wind jet events and their impacts on the circulation. We show that the cross-axis winds are, indeed, an important component of the wind regime, explaining 11% of wind variability of the NRS (well-described by a 2nd EOF mode). The westward events occur predominantly in the winter, preferentially in January (about 15 events in 10-years) and have a mean duration of 4-5 days, with a maximum of 12 days (north of 22N). There are around 6 events per year, but in 2002-2003 and 2007-2008, twice more events were detected. The westward wind events are found to strongly modify the wind stress curl, causing a distinct positive/negative curl pattern along the main axis. This pattern enhances the eddy activity and impacts the NRS circulation.

A Self-Diagnostic System for the M6 Accelerometer

NASA Technical Reports Server (NTRS)

Flanagan, Patrick M.; Lekki, John

2001-01-01

The design of a Self-Diagnostic (SD) accelerometer system for the Space Shuttle Main Engine is presented. This retrofit system connects diagnostic electronic hardware and software to the current M6 accelerometer system. This paper discusses the general operation of the M6 accelerometer SD system and procedures for developing and evaluating the SD system. Signal processing techniques using M6 accelerometer diagnostic data are explained. Test results include diagnostic data responding to changing ambient temperature, mounting torque and base mounting impedance.

Does cross-generational epigenetic inheritance contribute to cultural continuity?

PubMed Central

Pembrey, Marcus E

2018-01-01

Abstract Human studies of cross-generational epigenetic inheritance have to consider confounding by social patterning down the generations, often referred to as ‘cultural inheritance’. This raises the question to what extent is ‘cultural inheritance’ itself epigenetically mediated rather than just learnt. Human studies of non-genetic inheritance have demonstrated that, beyond foetal life, experiences occurring in mid-childhood before puberty are the most likely to be associated with cross-generational responses in the next generation(s). It is proposed that cultural continuity is played out along the axis, or ‘payoff’, between responsiveness and stability. During the formative years of childhood a stable family and/or home permits small children to explore and thereby learn. To counter disruptions to this family home ideal, cultural institutions such as local schools, religious centres and market places emerged to provide ongoing stability, holding the received wisdom of the past in an accessible state. This cultural support allows the growing child to freely indulge their responsiveness. Some of these prepubertal experiences induce epigenetic responses that also transfer molecular signals to the gametes through which they contribute to the conception of future offspring. In parallel co-evolution with growing cultural support for increasing responsiveness, ‘runaway’ responsiveness is countered by the positive selection of genetic variants that dampen responsiveness. Testing these ideas within longitudinal multigenerational cohorts will need information on ancestors/parents’ own communities and experiences (Exposome scans) linked to ongoing Phenome scans on grandchildren; coupled with epigenome analysis, metastable epialleles and DNA methylation age. Interactions with genetic variants affecting responsiveness should help inform the broad hypothesis. PMID:29732169

Does cross-generational epigenetic inheritance contribute to cultural continuity?

PubMed

Pembrey, Marcus E

2018-04-01

Human studies of cross-generational epigenetic inheritance have to consider confounding by social patterning down the generations, often referred to as 'cultural inheritance'. This raises the question to what extent is 'cultural inheritance' itself epigenetically mediated rather than just learnt. Human studies of non-genetic inheritance have demonstrated that, beyond foetal life, experiences occurring in mid-childhood before puberty are the most likely to be associated with cross-generational responses in the next generation(s). It is proposed that cultural continuity is played out along the axis, or 'payoff', between responsiveness and stability. During the formative years of childhood a stable family and/or home permits small children to explore and thereby learn. To counter disruptions to this family home ideal, cultural institutions such as local schools, religious centres and market places emerged to provide ongoing stability, holding the received wisdom of the past in an accessible state. This cultural support allows the growing child to freely indulge their responsiveness. Some of these prepubertal experiences induce epigenetic responses that also transfer molecular signals to the gametes through which they contribute to the conception of future offspring. In parallel co-evolution with growing cultural support for increasing responsiveness, 'runaway' responsiveness is countered by the positive selection of genetic variants that dampen responsiveness. Testing these ideas within longitudinal multigenerational cohorts will need information on ancestors/parents' own communities and experiences (Exposome scans) linked to ongoing Phenome scans on grandchildren; coupled with epigenome analysis, metastable epialleles and DNA methylation age. Interactions with genetic variants affecting responsiveness should help inform the broad hypothesis.

Objective vs. self-reported physical activity and sedentary time: effects of measurement method on relationships with risk biomarkers.

PubMed

Celis-Morales, Carlos A; Perez-Bravo, Francisco; Ibañez, Luis; Salas, Carlos; Bailey, Mark E S; Gill, Jason M R

2012-01-01

Imprecise measurement of physical activity variables might attenuate estimates of the beneficial effects of activity on health-related outcomes. We aimed to compare the cardiometabolic risk factor dose-response relationships for physical activity and sedentary behaviour between accelerometer- and questionnaire-based activity measures. Physical activity and sedentary behaviour were assessed in 317 adults by 7-day accelerometry and International Physical Activity Questionnaire (IPAQ). Fasting blood was taken to determine insulin, glucose, triglyceride and total, LDL and HDL cholesterol concentrations and homeostasis model-estimated insulin resistance (HOMA(IR)). Waist circumference, BMI, body fat percentage and blood pressure were also measured. For both accelerometer-derived sedentary time (<100 counts.min(-1)) and IPAQ-reported sitting time significant positive (negative for HDL cholesterol) relationships were observed with all measured risk factors--i.e. increased sedentary behaviour was associated with increased risk (all p ≤ 0.01). However, for HOMA(IR) and insulin the regression coefficients were >50% lower for the IPAQ-reported compared to the accelerometer-derived measure (p<0.0001 for both interactions). The relationships for moderate-to-vigorous physical activity (MVPA) and risk factors were less strong than those observed for sedentary behaviours, but significant negative relationships were observed for both accelerometer and IPAQ MVPA measures with glucose, and insulin and HOMA(IR) values (all p<0.05). For accelerometer-derived MVPA only, additional negative relationships were seen with triglyceride, total cholesterol and LDL cholesterol concentrations, BMI, waist circumference and percentage body fat, and a positive relationship was evident with HDL cholesterol (p = 0.0002). Regression coefficients for HOMA(IR), insulin and triglyceride were 43-50% lower for the IPAQ-reported compared to the accelerometer-derived MVPA measure (all p≤0.01). Using the IPAQ to determine sitting time and MVPA reveals some, but not all, relationships between these activity measures and metabolic and vascular disease risk factors. Using this self-report method to quantify activity can therefore underestimate the strength of some relationships with risk factors.

Locations of Joint Physical Activity in Parent-Child Pairs Based on Accelerometer and GPS Monitoring

PubMed Central

Dunton, Genevieve Fridlund; Liao, Yue; Almanza, Estela; Jerrett, Micheal; Spruijt-Metz, Donna; Pentz, Mary Ann

2012-01-01

Background Parental factors may play an important role in influencing children’s physical activity levels. Purpose This cross-sectional study sought to describe the locations of joint physical activity among parents and children. Methods Parent-child pairs (N = 291) wore an Actigraph GT2M accelerometer and GlobalSat BT-335 Global Positioning Systems (GPS) device over the same 7-day period. Children were ages 8–14 years. Joint behavior was defined by a linear separation distance of less than 50m between parent and child. Land use classifications were assigned to GPS data points. Results Joint physical activity was spread across residential locations (35%), and commercial venues (24%), and open spaces/parks (20%). Obese children and parents performed less joint physical activity in open spaces/parks than under/normal weight children and parents (p’s < .01). Conclusions Understanding where joint parent-child physical activity naturally occurs may inform location-based interventions to promote these behaviors. PMID:23011914

Orientation-dependent fiber-optic accelerometer based on grating inscription over fiber cladding.

PubMed

Rong, Qiangzhou; Qiao, Xueguang; Guo, Tuan; Bao, Weijia; Su, Dan; Yang, Hangzhou

2014-12-01

An orientation-sensitive fiber-optic accelerometer based on grating inscription over fiber cladding has been demonstrated. The sensor probe comprises a compact structure in which a short section of thin-core fiber (TCF) stub containing a "cladding" fiber Bragg grating (FBG) is spliced to another single-mode fiber (SMF) without any lateral offset. A femtosecond laser side-illumination technique was utilized to ensure that the grating inscription remains close to the core-cladding interface of the TCF. The core mode and the cladding mode of the TCF are coupled at the core-mismatch junction, and two well-defined resonances in reflection appear from the downstream FBG, in which the cladding resonance exhibits a strong polarization and bending dependence due to the asymmetrical distribution of the cladding FBG along the fiber cross section. Strong orientation dependence of the vibration (acceleration) measurement has been achieved by power detection of the cladding resonance. Meanwhile, the unwanted power fluctuations and temperature perturbations can be referenced out by monitoring the fundamental core resonance.

Identification of bearing faults using time domain zero-crossings

NASA Astrophysics Data System (ADS)

William, P. E.; Hoffman, M. W.

2011-11-01

In this paper, zero-crossing characteristic features are employed for early detection and identification of single point bearing defects in rotating machinery. As a result of bearing defects, characteristic defect frequencies appear in the machine vibration signal, normally requiring spectral analysis or envelope analysis to identify the defect type. Zero-crossing features are extracted directly from the time domain vibration signal using only the duration between successive zero-crossing intervals and do not require estimation of the rotational frequency. The features are a time domain representation of the composite vibration signature in the spectral domain. Features are normalized by the length of the observation window and classification is performed using a multilayer feedforward neural network. The model was evaluated on vibration data recorded using an accelerometer mounted on an induction motor housing subjected to a number of single point defects with different severity levels.

Single nucleotide polymorphisms in the growth hormone - insulin like growth factor axis in straight bred and crossbred Angus, Brahman, and Romosinuano heifers: population genetic analyses and association of genotypes

USDA-ARS?s Scientific Manuscript database

The growth endocrine axis influences reproduction. Objectives of this study were to evaluate population genetic characteristics of SNP genotypes within genes of the GH and IGF axis in straightbred and diallel-crossed Angus, Brahman and Romosinuano heifers (n = 650) and to test the associations of th...

Dual Accelerometer Usage Strategy for Onboard Space Navigation

NASA Technical Reports Server (NTRS)

Zanetti, Renato; D'Souza, Chris

2012-01-01

This work introduces a dual accelerometer usage strategy for onboard space navigation. In the proposed algorithm the accelerometer is used to propagate the state when its value exceeds a threshold and it is used to estimate its errors otherwise. Numerical examples and comparison to other accelerometer usage schemes are presented to validate the proposed approach.

Accelerometer-measured dose-response for physical activity, sedentary time, and mortality in US adults.

PubMed

Matthews, Charles E; Keadle, Sarah Kozey; Troiano, Richard P; Kahle, Lisa; Koster, Annemarie; Brychta, Robert; Van Domelen, Dane; Caserotti, Paolo; Chen, Kong Y; Harris, Tamara B; Berrigan, David

2016-11-01

Moderate-to-vigorous-intensity physical activity is recommended to maintain and improve health, but the mortality benefits of light activity and risk for sedentary time remain uncertain. Using accelerometer-based measures, we 1) described the mortality dose-response for sedentary time and light- and moderate-to-vigorous-intensity activity using restricted cubic splines, and 2) estimated the mortality benefits associated with replacing sedentary time with physical activity, accounting for total activity. US adults (n = 4840) from NHANES (2003-2006) wore an accelerometer for ≤7 d and were followed prospectively for mortality. Proportional hazards models were used to estimate adjusted HRs and 95% CIs for mortality associations with time spent sedentary and in light- and moderate-to-vigorous-intensity physical activity. Splines were used to graphically present behavior-mortality relation. Isotemporal models estimated replacement associations for sedentary time, and separate models were fit for low- (<5.8 h total activity/d) and high-active participants to account for nonlinear associations. Over a mean of 6.6 y, 700 deaths occurred. Compared with less-sedentary adults (6 sedentary h/d), those who spent 10 sedentary h/d had 29% greater risk (HR: 1.29; 95% CI: 1.1, 1.5). Compared with those who did less light activity (3 h/d), those who did 5 h of light activity/d had 23% lower risk (HR: 0.77; 95% CI: 0.6, 1.0). There was no association with mortality for sedentary time or light or moderate-to-vigorous activity in highly active adults. In less-active adults, replacing 1 h of sedentary time with either light- or moderate-to-vigorous-intensity activity was associated with 18% and 42% lower mortality, respectively. Health promotion efforts for physical activity have mostly focused on moderate-to-vigorous activity. However, our findings derived from accelerometer-based measurements suggest that increasing light-intensity activity and reducing sedentary time are also important, particularly for inactive adults. © 2016 American Society for Nutrition.

Intermittent inflations recorded by broadband seismometers prior to caldera formation at Miyake-jima volcano in 2000

NASA Astrophysics Data System (ADS)

Kobayashi, Tomokazu; Ohminato, Takao; Ida, Yoshiaki; Fujita, Eisuke

2012-12-01

Very-long-period (VLP) pulses with widths of 20 s on velocity seismograms were observed during volcanic activity at Miyake-jima Volcano, Japan in 2000. The VLP events occurred repeatedly during a few days prior to caldera formation and essentially vanished following the onset of caldera collapse. Waveform inversions of the pulse-like signals point to a source offset 3.5 km beneath and 1 km south of the summit. A candidate for the source mechanism is the inflation of an elliptical cylinder with axis tilted 20-30° from vertical and major axis of the elliptical cross section oriented northeast-southwest. The inferred mechanism appears consistent with a step-like pressurization of a magma reservoir impacted by a falling rock mass in response to gravitational instability. The repeated occurrences of the rock collapses lead to the caldera formation at Miyake-jima.

Neonatal vaginal irritation results in long-term visceral and somatic hypersensitivity and increased hypothalamic–pituitary–adrenal axis output in female mice

PubMed Central

Pierce, Angela N.; Zhang, Zhen; Fuentes, Isabella M.; Wang, Ruipeng; Ryals, Janelle M.; Christianson, Julie A.

2015-01-01

Abstract Experiencing early life stress or injury increases a woman's likelihood of developing vulvodynia and concomitant dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis. To investigate the outcome of neonatal vaginal irritation (NVI), female mouse pups were administered intravaginal zymosan on postnatal days 8 and 10 and were assessed as adults for vaginal hypersensitivity by measuring the visceromotor response to vaginal balloon distension (VBD). Western blotting and calcium imaging were performed to measure transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) in the vagina and innervating primary sensory neurons. Serum corticosterone (CORT), mast cell degranulation, and corticotropin-releasing factor receptor 1 (CRF1) expression were measured as indicators of peripheral HPA axis activation. Colorectal and hind paw sensitivity were measured to determine cross-sensitization resulting from NVI. Adult NVI mice had significantly larger visceromotor response during VBD than naive mice. TRPA1 protein expression was significantly elevated in the vagina, and calcium transients evoked by mustard oil (TRPA1 ligand) or capsaicin (TRPV1 ligand) were significantly decreased in dorsal root ganglion from NVI mice, despite displaying increased depolarization-evoked calcium transients. Serum CORT, vaginal mast cell degranulation, and CRF1 protein expression were all significantly increased in NVI mice, as were colorectal and hind paw mechanical and thermal sensitivity. Neonatal treatment with a CRF1 antagonist, NBI 35965, immediately before zymosan administration largely attenuated many of the effects of NVI. These results suggest that NVI produces chronic hypersensitivity of the vagina, as well as of adjacent visceral and distant somatic structures, driven in part by increased HPA axis activation. PMID:26098441

The analysis of temperature effect and temperature compensation of MOEMS accelerometer based on a grating interferometric cavity

NASA Astrophysics Data System (ADS)

Han, Dandan; Bai, Jian; Lu, Qianbo; Lou, Shuqi; Jiao, Xufen; Yang, Guoguang

2016-08-01

There is a temperature drift of an accelerometer attributed to the temperature variation, which would adversely influence the output performance. In this paper, a quantitative analysis of the temperature effect and the temperature compensation of a MOEMS accelerometer, which is composed of a grating interferometric cavity and a micromachined sensing chip, are proposed. A finite-element-method (FEM) approach is applied in this work to simulate the deformation of the sensing chip of the MOEMS accelerometer at different temperature from -20°C to 70°C. The deformation results in the variation of the distance between the grating and the sensing chip of the MOEMS accelerometer, modulating the output intensities finally. A static temperature model is set up to describe the temperature characteristics of the accelerometer through the simulation results and the temperature compensation is put forward based on the temperature model, which can improve the output performance of the accelerometer. This model is permitted to estimate the temperature effect of this type accelerometer, which contains a micromachined sensing chip. Comparison of the output intensities with and without temperature compensation indicates that the temperature compensation can improve the stability of the output intensities of the MOEMS accelerometer based on a grating interferometric cavity.

Using tri-axial accelerometers to identify wild polar bear behaviors

USGS Publications Warehouse

Pagano, Anthony M.; Rode, Karyn D.; Cutting, A.; Owen, M.A.; Jensen, S.; Ware, J.V.; Robbins, C.T.; Durner, George M.; Atwood, Todd C.; Obbard, M.E.; Middel, K.R.; Thiemann, G.W.; Williams, T.M.

2017-01-01

Tri-axial accelerometers have been used to remotely identify the behaviors of a wide range of taxa. Assigning behaviors to accelerometer data often involves the use of captive animals or surrogate species, as their accelerometer signatures are generally assumed to be similar to those of their wild counterparts. However, this has rarely been tested. Validated accelerometer data are needed for polar bears Ursus maritimus to understand how habitat conditions may influence behavior and energy demands. We used accelerometer and water conductivity data to remotely distinguish 10 polar bear behaviors. We calibrated accelerometer and conductivity data collected from collars with behaviors observed from video-recorded captive polar bears and brown bears U. arctos, and with video from camera collars deployed on free-ranging polar bears on sea ice and on land. We used random forest models to predict behaviors and found strong ability to discriminate the most common wild polar bear behaviors using a combination of accelerometer and conductivity sensor data from captive or wild polar bears. In contrast, models using data from captive brown bears failed to reliably distinguish most active behaviors in wild polar bears. Our ability to discriminate behavior was greatest when species- and habitat-specific data from wild individuals were used to train models. Data from captive individuals may be suitable for calibrating accelerometers, but may provide reduced ability to discriminate some behaviors. The accelerometer calibrations developed here provide a method to quantify polar bear behaviors to evaluate the impacts of declines in Arctic sea ice.

Optimal accelerometer placement on a robot arm for pose estimation

NASA Astrophysics Data System (ADS)

Wijayasinghe, Indika B.; Sanford, Joseph D.; Abubakar, Shamsudeen; Saadatzi, Mohammad Nasser; Das, Sumit K.; Popa, Dan O.

2017-05-01

The performance of robots to carry out tasks depends in part on the sensor information they can utilize. Usually, robots are fitted with angle joint encoders that are used to estimate the position and orientation (or the pose) of its end-effector. However, there are numerous situations, such as in legged locomotion, mobile manipulation, or prosthetics, where such joint sensors may not be present at every, or any joint. In this paper we study the use of inertial sensors, in particular accelerometers, placed on the robot that can be used to estimate the robot pose. Studying accelerometer placement on a robot involves many parameters that affect the performance of the intended positioning task. Parameters such as the number of accelerometers, their size, geometric placement and Signal-to-Noise Ratio (SNR) are included in our study of their effects for robot pose estimation. Due to the ubiquitous availability of inexpensive accelerometers, we investigated pose estimation gains resulting from using increasingly large numbers of sensors. Monte-Carlo simulations are performed with a two-link robot arm to obtain the expected value of an estimation error metric for different accelerometer configurations, which are then compared for optimization. Results show that, with a fixed SNR model, the pose estimation error decreases with increasing number of accelerometers, whereas for a SNR model that scales inversely to the accelerometer footprint, the pose estimation error increases with the number of accelerometers. It is also shown that the optimal placement of the accelerometers depends on the method used for pose estimation. The findings suggest that an integration-based method favors placement of accelerometers at the extremities of the robot links, whereas a kinematic-constraints-based method favors a more uniformly distributed placement along the robot links.

Comparison of Physical Activity Adult Questionnaire results with accelerometer data.

PubMed

Garriguet, Didier; Tremblay, Sylvain; Colley, Rachel C

2015-07-01

Discrepancies between self-reported and objectively measured physical activity are well-known. For the purpose of validation, this study compares a new self-reported physical activity questionnaire with an existing one and with accelerometer data. Data collected at one site of the Canadian Health Measures Survey in 2013 were used for this validation study. The International Physical Activity Questionnaire (IPAQ) was administered to respondents during the household interview, and the new Physical Activity for Adults Questionnaire (PAAQ) was administered during a subsequent visit to a mobile examination centre (MEC). At the MEC, respondents were given an accelerometer to wear for seven days. The analysis pertains to 112 respondents aged 18 to 79 who wore the accelerometer for 10 or more hours on at least four days. Moderate-to-vigorous physical activity (MVPA) measured by accelerometer had higher correlation with data from the PAAQ (r = 0.44) than with data from the IPAQ (r = 0.20). The differences between accelerometer and PAAQ data were greater based on accelerometer-measured physical activity accumulated in 10-minute bouts (30-minute difference in MVPA) than on all minutes (9-minute difference). The percentages of respondents meeting the Canadian Physical Activity Guidelines were 90% based on self-reported IPAQ minutes, 70% based on all accelerometer MVPA minutes, 29% based on accelerometer MVPA minutes accumulated in 10-minute bouts, and 61% based on self-reported PAAQ minutes. The PAAQ demonstrated reasonable validity against the accelerometer criterion. Based on correlations and absolute differences between daily minutes of MVPA and the percentages of respondents meeting the Canadian Physical Activity Guidelines, PAAQ results were closer to accelerometer data than were the IPAQ results for the study sample and previous Statistics Canada self-reported questionnaire findings.

Accelerometer-based measures in physical activity surveillance: current practices and issues.

PubMed

Pedišić, Željko; Bauman, Adrian

2015-02-01

Self-reports of physical activity (PA) have been the mainstay of measurement in most non-communicable disease (NCD) surveillance systems. To these, other measures are added to summate to a comprehensive PA surveillance system. Recently, some national NCD surveillance systems have started using accelerometers as a measure of PA. The purpose of this paper was specifically to appraise the suitability and role of accelerometers for population-level PA surveillance. A thorough literature search was conducted to examine aspects of the generalisability, reliability, validity, comprehensiveness and between-study comparability of accelerometer estimates, and to gauge the simplicity, cost-effectiveness, adaptability and sustainability of their use in NCD surveillance. Accelerometer data collected in PA surveillance systems may not provide estimates that are generalisable to the target population. Accelerometer-based estimates have adequate reliability for PA surveillance, but there are still several issues associated with their validity. Accelerometer-based prevalence estimates are largely dependent on the investigators' choice of intensity cut-off points. Maintaining standardised accelerometer data collections in long-term PA surveillance systems is difficult, which may cause discontinuity in time-trend data. The use of accelerometers does not necessarily produce useful between-study and international comparisons due to lack of standardisation of data collection and processing methods. To conclude, it appears that accelerometers still have limitations regarding generalisability, validity, comprehensiveness, simplicity, affordability, adaptability, between-study comparability and sustainability. Therefore, given the current evidence, it seems that the widespread adoption of accelerometers specifically for large-scale PA surveillance systems may be premature. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

ACCELEROMETERS IN FLOW FIELDS: A STRUCTURAL ANALYSIS OF THE CHOPPED DUMMY INPILE TUBE

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

Howard, T. K.; Marcum, W. R.; Latimer, G. D.

2016-06-01

Four tests characterizing the structural response of the Chopped-Dummy In-Pile tube (CDIPT) experiment design were measured in the Hydro-Mechanical Fuel Test Facility (HMFTF). Four different test configurations were tried. These configurations tested the pressure drop and flow impact of various plate configurations and flow control orifices to be used later at different reactor power levels. Accelerometers were placed on the test vehicle and flow simulation housing. A total of five accelerometers were used with one on the top and bottom of the flow simulator and vehicle, and one on the outside of the flow simulator. Data were collected at amore » series of flow rates for 5 seconds each at an acquisition rate of 2 kHz for a Nyquist frequency of 1 kHz. The data were then analyzed using a Fast Fourier Transform (FFT) algorithm. The results show very coherent vibrations of the CDIPT experiment on the order of 50 Hz in frequency and 0.01 m/s2 in magnitude. The coherent vibrations, although small in magnitude pose a potential design problem if the frequencies coincide with the natural frequency of the fueled plates or test vehicle. The accelerometer data was integrated and combined to create a 3D trace of the experiment during the test. The merits of this data as well as further anomalies and artifacts are also discussed as well as their relation to the instrumentation and experiment design.« less

The dynamic contributions of the otolith organs to human ocular torsion

NASA Technical Reports Server (NTRS)

Merfeld, D. M.; Teiwes, W.; Clarke, A. H.; Scherer, H.; Young, L. R.

1996-01-01

We measured human ocular torsion (OT) monocularly (using video) and binocularly (using search coils) while sinusoidally accelerating (0.7 g) five human subjects along an earth-horizontal axis at five frequencies (0.35, 0.4, 0.5, 0.75, and 1.0 Hz). The compensatory nature of OT was investigated by changing the relative orientation of the dynamic (linear acceleration) and static (gravitational) cues. Four subject orientations were investigated: (1) Y-upright-acceleration along the interaural (y) axis while upright; (2) Y-supine-acceleration along the y-axis while supine; (3) Z-RED-acceleration along the dorsoventral (z) axis with right ear down; (4) Z-supine-acceleration along the z-axis while supine. Linear acceleration in the Y-upright, Y-supine and Z-RED orientations elicited conjugate OT. The smaller response in the Z-supine orientation appeared disconjugate. The amplitude of the response decreased and the phase lag increased with increasing frequency for each orientation. This frequency dependence does not match the frequency response of the regular or irregular afferent otolith neurons; therefore the response dynamics cannot be explained by simple peripheral mechanisms. The Y-upright responses were larger than the Y-supine responses (P < 0.05). This difference indicates that OT must be more complicated than a simple low-pass filtered response to interaural shear force, since the dynamic shear force along the interaural axis was identical in these two orientations. The Y-supine responses were, in turn, larger than the Z-RED responses (P < 0.01). Interestingly, the vector sum of the Y-supine responses plus Z-RED responses was not significantly different (P = 0.99) from the Y-upright responses. This suggests that, in this frequency range, the conjugate OT response during Y-upright stimulation might be composed of two components: (1) a response to shear force along the y-axis (as in Y-supine stimulation), and (2) a response to roll tilt of gravitoinertial force (as in Z-RED stimulation).

Magnetization reversal dynamics in Co nanowires with competing magnetic anisotropies

NASA Astrophysics Data System (ADS)

Pal, Semanti; Saha, Susmita; Polley, Debanjan; Barman, Anjan

2011-12-01

We present the magnetization reversal dynamics of Co nanowires with competing magnetic anisotropies. The aspect ratio ( R) of the nanowires is varied between 2.5 and 60, and we observe a cross-over of the directions of the magnetic easy and hard axes at R=6.8. Micromagnetic simulations qualitatively reproduce the observed cross-over and give detailed insight into the reversal mechanisms associated with the cross-over. The reversal mechanism for a field applied along the long axis of the nanowire exhibits a quasi-coherent rotation mode and a corkscrew-like mode, respectively, above and below the cross-over, with the formation of a Bloch domain near the cross-over region. For a field applied along the short axis, the reversal occurs by nucleation and propagation of reversed domains from the two ends of the nanowires for very high values of the aspect ratio down to the cross-over region, but it transforms into quasi-coherent rotation mode for smaller aspect ratios (below the cross-over region).