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Introduction: The aim of the study was to compare the impact of 6 weeks plyometric intervention training (PIT) and speed intervention training (SIT) on the stimulation of speed abilities (indicators) of soccer players. Methods: Research group was uniformly divided to experimental sample 1 (n=7, graduated PIT) and experimental sample 2 (n=7, graduated SIT). The indicators of linear running speed were measured by 5m, 10m, 30m sprinting. 5-10-5 test was used to measure indicators of running speed with changes of direction, where the following have been recorded: (5-0-5L) 5m left side sprint from the start, change of direction, 5m sprint (5-0-5L); 5m sprint from the start, change of direction, 10m sprint, change of direction and 5m left side sprint to the finish (5-10-5L); 5m right side sprint from the start, change of direction, 5m sprint (5-0-5R); 5m sprint from the start, change of direction, 10m sprint, change of direction and 5m right side sprint to the finish (5-10-5R). Results: Intergroup comparisons of pretest-posttest (PRE-POST) differences between PIT and SIT have not revealed significant difference (p>0.05) in any of the speed indicators tests. In two indicators of linear speed, we observed PRE-POST differences with a medium effect in favour of SIT (5m; 10m) in one indicator (30m) in favour of PIT. In two indicators of speed with changes of direction PRE-POST differences with a large effect (5-10-5L; 5-0-5R) have been noted in favour of SIT. In two other indicators (5-0-5L; 5-10-5R) PRE-POST differences between PIT and SIT have been noted without any difference effect. Conclusion: The results of the pilot study revealed a positive effect of both PIT and SIT on the stimulation of the speed abilities of soccer players and indicate tendencies in favour of SIT, which is needed to be verified with larger research samples. [ABSTRACT FROM AUTHOR]

A ten-year complete seismological database is evaluated in the present work. These data are provided for events with magnitude ML -1.0, which have occurred in Eastern Greece and, more specifically, in Kos Island. Several selection criteria are applied and, hence, a catalog of the seismological records is compiled. Detailed big data (seismological, tide gauge, geodetic stations, accelerometers, etc.) of this region are used and processed in this work. The database consists of approximately 35,000 three-component broadband seismograms from 1198 digitally recorded events. It covers the last ten years of measurements, including records from the 20 July 2017, ML 6.2, Kos Island, Greece event. The seismological communities can either use this database to conduct new research or improve already existing seismic hazard studies in the region. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to determine 1) the test-retest reliability of adult accelerometer measured physical activity, and 2) how data processing decisions affect physical activity levels and test-retest reliability. Methods: 143 people wore the ActiGraph accelerometer for 2 7-day periods, 1 to 4 weeks apart. Five algorithms, varying nonwear criteria (20 vs. 60 min of 0 counts) and minimum wear requirements (6 vs. 10 hrs/day for ≥ 4 days) and a separate algorithm requiring ≥ 3 counts per min and ≥ 2 hours per day, were used to process the accelerometer data. Results: Processing the accelerometer data with different algorithms resulted in different levels of counts per day, sedentary, and moderate-to-vigorous physical activity. Reliability correlations were very good to excellent (ICC = 0.70-0.90) for almost all algorithms and there were no significant differences between physical activity measures at Time 1 and Time 2. Conclusions: This paper presents the first assessment of test-retest reliability of the Actigraph over separate administrations in free-living subjects. The ActiGraph was highly reliable in measuring activity over a 7-day period in natural settings but data were sensitive to the algorithms used to process them. [ABSTRACT FROM AUTHOR]

Background: The Kenz Lifecorder EX (KL) is a relatively new, moderately priced, user friendly accelerometer that tracks step counts and time spent in various intensity classifications. Thus, the KL is an attractive instrument for researchers and the public. However, there is limited research comparing the KL's output to other accelerometers during free-living conditions. Therefore the purpose of this study was to compare KL versus ActiGraph (AG) outputs of step counts and time spent in various intensity classifications during free-living conditions. Methods: Ten men and 10 women volunteers wore an AG (right side) and 2 KL (right side: KL-R vs. left side: KL-L) accelerometers on their waistline during waking hours for one day. Results: KL-R vs. KL-L yielded similar physical activity (PA) output. The AG recorded fewer steps compared with KL-L (P = .002) but was similar to the KL-R. The KL-R and KL-L yielded lower estimates of accumulated time spent in moderate PA compared with most AG intensity derivations (P < .003). There were no differences between KL-R and KL-L vs. the AG for time spent in vigorous PA. Conclusions: The KL provides similar estimates of step counts and time spent in vigorous PA compared with established AG intensity derivations. [ABSTRACT FROM AUTHOR]

Background: The purpose of the present investigation was to examine the relationship between age and the intensity of the daily physical activity in men and women, aged 18 to 69 years. Methods: A total 507 volunteers continuously wore a pedometer with a uni-axial accelerometer (Lifecorder, Kenz, Japan) for 7 days, to determine the number of steps (steps/ day) as well as the time spent in physical activity (minutes/day) at light (below 3 METs), moderate (3 to 6 METs), and vigorous (above 6 METs) intensities, respectively. All procedures carried out in the present investigation were conducted from 1999 to 2000 in Japan. Results: The time spent in moderate to vigorous intensity physical activity significantly decreased with aging (P < 0.01). In contrast, the middle- to older-aged individuals spent a longer time in light intensity physical activity in comparison with the younger individuals (P < 0.05). Furthermore, these age-associated differences of physical activity were also significant, even though the number of steps did not differ significantly. Conclusions: These results indicate that the intensity of daily physical activity decreases with increasing age regardless of the amount of daily physical activity. [ABSTRACT FROM AUTHOR]

The article discusses the comparison of two sets of accelerometer cut-off points for calculating moderate-to-vigorous physical activity. It was revealed that accelerometer are becoming more widely used in the assessment of physical activity in children, and converting the output in minimum of moderate to vigorous physical activity (MVPA) requires the use of age-specific cut-off point definitions.

The primary aim of this study was to test the validity of two accelerometers, CSA/MTI WAM-7164 and Actiwatch(r), against direct observation of physical activity using the Children's Physical Activity Form (CPAF). CSA/MTI WAM-7164 and Actiwatch accelerometers simultaneously measured activity during structured-play classes in 3- to 4-year olds. Accelerometry output was synchronized to CPAF assessments of physical activity in 78 children. Rank order correlations between accelerometry and direct observation evaluated the ability of the accelerometers to assess total physical activity. Within-child minute-to-minute correlations were calculated between accelerometry output and direct observation. For total physical activity, CSA/MTI output was significantly correlated with CPAF (r = .72, p < .001), but output from the Actiwatch was not (r = .16, p > .05). [ABSTRACT FROM AUTHOR]

Highlights • Impact of speed fluctuation on cepstrum is studied. • A time quefrency representation is used for non-stationary signal analysis. • Synthetic signals are used to explain theoretical results. • This time quefrency representation is used on Surveillance 8 contest data. Abstract This paper deals with the influence of speed fluctuations (non-stationary signal) on the cepstrum. After presenting the cepstrum classic properties, the cepstrum of multiple echoes with a period shift is computed. Examples help to interpret the form of the cepstrum. These shifts could be located in the cepstrum as peaks. Next, a discussion about quefrency resolution is made. It is shown that a low quefrency resolution could produce a fusion of cepstrum peaks (positive and negative). In order to take account of speed evolution of the signal a time-quefrency representation is proposed. Synthetic signal is used to show how to interpret this representation. Finally, illustrations on time quefrency representation were made by using gear signals by SAFRAN from the Surveillance 8 contest. [ABSTRACT FROM AUTHOR]

This paper describes an approach for characterizing the dynamic behavior of the vehicle/track interaction at railway crossings. In the approach, we integrate in situ axle box acceleration (ABA) measurements with roving-accelerometer hammer tests to evaluate the influence of train speed, train moving direction (facing and trailing directions), sensor position (leading and rear wheels of a bogie), and the natural response of track structure on ABA signals. The analysis of data from multiple sensors contributes to the following findings: the major frequency bands of the vertical ABA are related to the natural frequencies of the crossing; thus, these ABA frequency bands are not greatly affected by variations in train speed, moving direction, and sensor position. The vibration energy concentrated at the major ABA frequency bands increases at higher train speeds, along the facing moving direction and from the leading wheel. The crossing rails vibrate as a combination of bending and torsion rather than solely bending at the major ABA frequency bands, since the vibrations of the wing rails are not synchronized. These results help enhance our understanding of the vehicle/track interaction at crossings and can be used to improve the dynamic response-based system for monitoring the condition of crossings. [ABSTRACT FROM AUTHOR]

Summary: The goal of this paper is to show how nonparametric statistics can be used to solve some chance constrained optimization and optimal control problems. We use the kernel density estimation method to approximate the probability density function of a random variable with unknown distribution from a relatively small sample. We then show how this technique can be applied and implemented for a class of problems including the Goddard problem and the trajectory optimization of an Ariane five‐like launcher. [ABSTRACT FROM AUTHOR]

Objective: Distance estimation in pedestrian dead reckoning is acquired using vector norm of accelerations, which results in positive values. However, anteroposterior acceleration is negative when a step is taken backward, which must be detected for accurate localization. This paper proposes a novel approach for the detection of walking direction, which uses a dominant trend duration. Methods: The approach evaluates anteroposterior acceleration out of a foot-worn accelerometer for temporal dominance of acceleration trends during swing phase of the walk. The approach is tested for forward and backward walks with speed variations on a straight path as well as for forward walk at normal speed on a turning path. To validate the detection accuracy, success rates per participant per walk trial are calculated and then overall success rate for all the trials are reported. Moreover, metrics precision, recall and F1 scores are calculated for detection reliability in both directions. Results: Overall 98 ± 2% detection accuracy is achieved on linear path considering both directions and all speed variations, whereas 93 ± 7% on turning path including left and right turns. In comparison with the state-of-the-art bidirectional detection approach, the proposed approach delivers accurate detection with speed variations without requiring prior training and relies on a single sensory feature. Conclusion: Dominant trend duration is a novel and reliable feature to detect directional changes during communal walk with speed variation. Significance: The approach can be employed in different contexts, such as enabling pedestrian localization approaches to accommodate back stepping or any application that requires knowledge of changing directions while walking. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

High-resolution accelerometers have commonly used an electrostatic force-feedback sigma-delta closed-loop. In order to improve the resolution of the accelerometers, high-order noise shaping filters has been used. However, it is difficult to trade off between the stability and the noise shaping ability to design high-order sigma-delta closed-loop, especially with the high-Q acceleration sensors. In this paper, a pseudo electrostatic spring constant is proposed based on the electrostatic force-feedback sigma-delta closed-loop accelerometer. It uses to adjust the resonant frequency of the system transfer function to achieve a lower noise level in the signal band, and this adjustment is outside the closed-loop without influence on the stability of the closed-loop system. The concept of the pseudo electrostatic spring constant, the system analysis and simulation are presented. The integrated measurement system is implemented on the PCB. The system noise floor can achieve about 160 ng/√Hz after the adjustment by using the optimal pseudo electrostatic spring constant. The experimental results confirm the theoretical analysis and simulation results. [ABSTRACT FROM AUTHOR]

A dual-band, fiber-optic, photon time-of-flight instrument was developed. Its design was optimized for measuring the velocity of visible photons emanating from relatively dim astronomical sources (apparent magnitude m > 12), such as distant galaxies and quasars. We report the first direct photon group velocity measurements for extragalactic objects. The photon group velocity is found to be 3.00±0.03×108 m s-1 and is invariant, within experimental error, over the range of redshifts measured (0 ≤ z ≤ 1.33). This measurement provides additional validation of general relativity and is consistent with the Friedmann-Lemaître-Robertson-Walker and hyperbolic anti-de Sitter metrics but not with the elliptical de Sitter metric. [ABSTRACT FROM AUTHOR]

The micro-accelerometers are devices used to measure acceleration. They are implemented in applications such as tilt-control in spacecraft, inertial navigation, oil exploration, etc. These applications require high operating frequency and displacement sensitivity. But getting both high parameter values at the same time is difficult, because there are physical relationships, for each one, where the mass is involved. When the mass is reduced, the operating frequency is high, but the displacement sensitivity decreases and vice versa. The implementation of Displacement-amplifying Compliant Mechanism (DaCM) supports to this dependence decreases. In this paper the displacement sensitivity and operation frequency of a Conventional Capacitive Accelerometer are shown (CCA). A Capacitive Accelerometer with Extended Beams (CAEB) is also presented, which improves displacement sensitivity compared with CCA, and finally the implementation of DACM's in the aforementioned devices was also carried out. All analyzed cases were developed considering the in-plane mode. The Matlab code used to calculate displacement sensitivity and operating frequency relationship is given in Appendix A. [ABSTRACT FROM AUTHOR]

Road condition monitoring is a generally complex task, either involving slow and tedious visual surface examination or using expensive specialized equipment operated by qualified personnel. The aim of this paper is to explore a faster and cheaper method of monitoring road condition, by implementing a distributed system that can use existing Android smartphones. The system records sensor data (accelerometer and GPS) locally and allows users to upload the data to the server at their convenience. The web application component offers an easy to use interface for detailed examination of all the uploaded data by displaying entire routes over a diverse selection of map types. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel positioning solution for land vehicles which is highly reliable and cost-efficient. The proposed positioning system fuses information from the MEMS-based reduced inertial sensor system (RISS) which consists of one vertical gyroscope and two horizontal accelerometers, low-cost GPS, and supplementary sensors and sources. First, pitch and roll angle are accurately estimated based on a vehicle kinematic model. Meanwhile, the negative effect of the uncertain nonlinear drift of MEMS inertial sensors is eliminated by an H8 filter. Further, a distributed-dual-H8 filtering (DDHF) mechanism is adopted to address the uncertain nonlinear drift of the MEMS-RISS and make full use of the supplementary sensors and sources. The DDHF is composed of a main H8 filter (MHF) and an auxiliary H8 filter (AHF). Finally, a generalized regression neural network (GRNN) module with good approximation capability is specially designed for the MEMS-RISS. A hybrid methodology which combines the GRNN module and the AHF is utilized to compensate for RISS position errors during GPS outages. To verify the effectiveness of the proposed solution, road-test experiments with various scenarios were performed. The experimental results illustrate that the proposed system can achieve accurate and reliable positioning for land vehicles. [ABSTRACT FROM AUTHOR]

Recently the use of Inertial Measurement Units (IMU's) has been extended to several applications in human activity. In running, several studies show the possibility of using IMU's to measure different indicators of speed and foot strike. However, few studies describe the repeatability of those indicators. In this context, the aim of this study is to analyse the intra and inter test repeatability of several temporal and spectral indicators using an IMU under constant running conditions. Accelerations were measured using three IMU's mounted on the trunk near the lumbar, the right tibia and the dorsal surface of the right shoe above the metatarsals. The subject follows two different protocols to realize the intra test and the inter test repeatability of eight different parameters: root mean square (RMS) values of acceleration, kurtosis, total energy, median frequency, mechanical stiffness, mean stride duration, contact and flying duration. For all parameters the mean, standard deviation and coefficient of variation were computed for each set of test. The coefficient of variation was lower than 5% for both test for all parameters except kurtosis and the median frequency. Parameters with acceptable value at constant conditions of surface and speed can be used as an indicator to compare several conditions, such as the influence of speed, surface or anthropometry of the subjects. [ABSTRACT FROM AUTHOR]

This paper will report some of the findings from a trial which recorded accelerometer data from six elite level swimmers (three female and three male, varying primary event stroke and distance) over the course of a regular 15 week training block. Measurements from a head-mounted accelerometer are used to determine when the athlete is swimming, marking of turning points (and therefore distance and lap-time measurements), and is processed by frequency analysis to determine stroke-rate. Comparison with video where available, and with training plans and literature where not, have proven this method to be accurate and reliable for determining these performance metrics. The primary objective of this project was to develop a low-cost, simple and highly usable system for use in swim coaching, feedback from elite coaches has indicated that development of this could be an extremely useful addition to their training regime. [ABSTRACT FROM AUTHOR]

The accuracy of the conservative force-models is not clear and the new space accelerometers provide a unique opportunity for their validation. In this paper, the conservative-force model deficiencies are investigated via Principal Component Analysis (PCA) using 4 years of GRACE measurements (2006–2009). The deficiencies are assessed by comparing the accelerometer readouts with the differences between the conservative force-model and the precise orbit accelerations. Within this scheme, the spatiotemporal data analysis is synthesized in a time-series of grids whose latitudinal and longitudinal variations are respectively influenced by the half orbital period and the equatorial orbit shift. With maximum amplitude of 50 nm/s 2 , the mean map shows a positive overestimation in Canada and Brazil and negative in Greenland. Explaining the 74% of the variability, the two first pairs of PCA modes show un-modeled patterns with amplitudes maxima of 80 nm/s 2 and 50 nm/s 2 . Their periodic behavior and wave-length of degree-6 and degree-11s spherical harmonics strongly suggest an additional modeling and improvement. As for the long-term variations, our results show a latitudinal variation of 15 nm/s 2 maximum amplitude correlated with the day-night periods. Performing a combined analysis of ascending and descending orbits, a trend of 3 nm/s 2 yr in the Indian Ocean is also observed. Our new approach for orbital force-models validation can be considered crucial for the current state-of-the-art of precise orbit determination (POD) and Time–Varying Gravity (TVG) modeling. [ABSTRACT FROM AUTHOR]

In order to set integrated procedures involving geotechnical and structural aspects finalized to buildings diagnostics, uncertainty aspects are discussed concerning three-axis accelerometers and inclinometers for a distributed sensor network. This network allows to operate in a selective manner, preferring the most critical situations. To this aim, the main aspects affecting the measurement uncertainty of sensors to be used for building diagnostic should be known. As the firstly step of the uncertainty evaluation procedure, we focused on the calibration of sensors used for the task. The requirement of low cost and complexity of sensors and test benches was considered. Experimental results show that satisfactory calibration accuracy could be achieved, also for the low frequency range, 0–10 Hz. Systematic errors are minimized and main parameters affecting uncertainty are identified, such as: the motion positioning of the accelerometer with respect to the vertical axis, the imposed motion law, the parameter used as the reference and, finally, the real radial positioning of the sensor. Requirements to be satisfied by the sensor are also analysed. [ABSTRACT FROM AUTHOR]

This paper presents a new approach for the fabrication of a three-axis capacitive MEMS accelerometer that is capable of differentially sensing the acceleration in all three orthogonal axes. For the first time in literature, differential sensing for the out of plane direction is achieved by defining a movable sensing electrode on the structural layer of the SOI wafer that is sandwiched between two stationary electrodes defined on the glass substrate and the handle layer of the SOI wafer enabling the differential sensing. In this approach, individual lateral and vertical axis accelerometers are fabricated in the same die on an SOI wafer which is anodically bonded to a glass substrate. [ABSTRACT FROM AUTHOR]

Let a network with edge weights, a set of point-to-point transportation requests and a factor $$\alpha $$ be given. Our goal is to design a subnetwork of given length along which transportation costs are reduced by $$\alpha $$ . This reduces the costs of the network traffic which will choose to use edges of the new subnetwork if this is the more efficient option. Our goal is to design the subnetwork in such a way that the worst-case cost of all routing requests is minimized. The problem occurs in many applications, among others in transportation networks, in backbone, information, communication, or electricity networks. We classify the problem according to the types of the given network and of the network to be established. We are able to clarify the complexity status in all considered cases. It turns out that finding an optimal subtree in a tree already is NP-hard. We therefore further investigate this case and propose results and a solution approach. [ABSTRACT FROM AUTHOR]

Changing the position of the Center of Gravity (CoG) for an aerial vehicle is a challenging part in navigation, and control of such vehicles. In this paper, an all-accelerometers-based inertial measurement unit is presented, with a proposed method for on-line estimation of the position of the CoG. The accelerometers' readings are used to find and correct the vehicle's angular velocity and acceleration using an Extended Kalman Filter. Next, the accelerometers' readings along with the estimated angular velocity and acceleration are used in an identification scheme to estimate the position of the CoG and the vehicle's linear acceleration. The estimated position of the CoG and motion measurements can then be used to update the control rules to achieve better trim conditions for the air vehicle. [ABSTRACT FROM AUTHOR]

In Annex H.5, the Guide to the Evaluation of Uncertainty in Measurement (GUM) [1] recognizes the necessity to analyze certain types of experiments by applying random effects ANOVA models. These belong to the more general family of linear mixed models that we focus on in the current paper. Extending the short introduction provided by the GUM, our aim is to show that the more general, linear mixed models cover a wider range of situations occurring in practice and can be beneficial when employed in data analysis of long-term repeated experiments. Namely, we point out their potential as an aid in establishing an uncertainty budget and as means for gaining more insight into the measurement process. We also comment on computational issues and to make the explanations less abstract, we illustrate all the concepts with the help of a measurement campaign conducted in order to challenge the uncertainty budget in calibration of accelerometers. [ABSTRACT FROM AUTHOR]

Accelerometer-based combustion sensing in diesel engines has the potential of providing feedback for combustion control to reduce fuel consumption and engine emissions at a lower cost than in-cylinder pressure sensors. In this work, triaxial block-mounted accelerometers were used to measure the engine vibration, and pressure transducers were installed to measure the in-cylinder pressure. The in-cylinder pressure can be further utilized to compute combustion metrics, including the apparent heat release rate (AHR). Engine tests were conducted for various speeds, torques, and start of injections, on a 9L in-line six-cylinder diesel engine equipped with a common rail high pressure injection system. The relationship between engine block acceleration and AHR was modeled using a radial basis function neural network (RBFNN). By inputting the accelerometer signal to the fixed network, AHR and other combustion metrics were estimated. As the primary concern for radial basis network training is the hidden layer weight vector selection, two algorithms for weight vector selection (modified Gram-Schmidt orthogonalization and principal component analysis) were evaluated by examining the robustness of the resulting network. One-third of the conducted tests were utilized to train the network. The network was then applied to estimate the AHR for the remaining validation tests which were not used to train the network. Comparisons were made based on the combustion metrics estimation results and the selection efficiency among the two weight vector selection methods and the random selection method. Moreover, the capability concerning the network's tolerance for additive noise was also investigated. Results confirmed that the modified Gram-Schmidt method achieved much more accurately estimated combustion metrics with the highest efficiency. On the basis of this study, a real-time closed-loop control strategy was proposed with the feedback provided based on the application of the trained RBFNN. [ABSTRACT FROM AUTHOR]

Objectives: This study evaluated the degree and rate of implant stability development for photofunctionalized dental implants in humans. Materials and Methods: Thirtythree implants (7 patients) placed in the maxilla and immediate loaded were evaluated. Photofunctionalization was performed by treating implants with ultraviolet for 15 minutes immediately before placement. Implant stability was assessed by measuring the implant stability quotient (ISQ) weekly starting from implant placement up to 3 months. Osseointegration speed index (OSI), defined as ISQ increase per month, was also evaluated. Results: The average ISQ for photofunctionalized implants at week 6 was 78.0, which was considerably higher than the average ISQ of 66.1, reported in literature for various asreceived implants after a longer healing time of 2 to 6 months. No stability dip was observed for photofunctionalized implants regardless of the initial ISQ values. The OSI for photofunctionalized implants was 6.3 and 3.1 when their initial ISQ was 65 to 70 and 71 to 75, respectively, whereas the OSI values for asreceived implants calculated from literature ranged from -3.0 to 1.17 with an average of -0.10. Conclusions: Photofunctionalization accelerated and enhanced osseointegration of dental implants, providing novel and practical avenues for further advancement in implant therapy. [ABSTRACT FROM AUTHOR]

We present results from a vertical array of accelerometers that was recently installed in Bishkek (Kyrgyzstan) with the long-term aim of recording strong motion data. Taking advantage of recordings of a Mb 4.7 earthquake that occurred 40 km from the array site during the installation phase, we provide results of some preliminary data analysis. First, estimates of the S-wave velocity and Qs structure are deduced by the inversion of the deconvolved wavefield between the sensors in the borehole. Furthermore, the application of the nonstationary ray decomposition Kinoshita (Earth Planets Space 61:1297-1312, ) allowed at least three reflectors in the shallow velocity structure below the array to be identified. The complex nature of the wavefield (with up-going, down-going waves, and converted phases) due to the coarse, unconsolidated subsoil structure is highlighted by means of numerical simulations of ground motion. [ABSTRACT FROM AUTHOR]

Objective The 'single-item measure' was developed as a short self-report tool for assessing physical activity. The aim of this study was to test the criterion validity of the single-item measure against accelerometry. Design Participants (n=66, 65% female, age: 39±11 years) wore an accelerometer (ActiGraph GT3X) over a 7-day period and on day 8, completed the single-item measure. The number of days of ⩾30 min of accelerometer-determined moderate to vigorous intensity physical activity (MVPA) were calculated using two approaches; first by including all minutes of MVPA and second by including only MVPA accumulated in bouts of ⩾10 min (counts/min ⩾1952). Associations between the single-item measure and accelerometer were examined using Spearman correlations and 95% limits of agreement. Percent agreement and κ statistic were used to assess agreement between the tools in classifying participants as sufficiently/insufficiently active. Results Correlations between the number of days of ⩾30 min MVPA recorded by the single-item and accelerometer ranged from 0.46 to 0.57. Participants underreported their activity on the single-item measure (-1.59 days) when compared with all objectively measured MVPA, but stronger congruence was observed when compared with MVPA accumulated in bouts of ⩾10 min (0.38 days). Overall agreement between the single-item and accelerometry in classifying participants as sufficiently/insufficiently active was 58% (k=0.23, 95% CI 0.05 to 0.41) when including all MVPA and 76% (k=0.39, 95% CI 0.14 to 0.64) when including activity undertaken in bouts of ⩾10 min. Conclusions The single-item measure is a valid screening tool to determine whether respondents are sufficiently active to benefit their health. [ABSTRACT FROM AUTHOR]

The article deals with pneumatic muscle MAS-20-200N-AA-MC-O, its dynamic properties and positioning accuracy as well as overviews experimental and theoretical works. The paper introduces the diagrams of vibration acceleration, discusses displacement dependence on pressure and load and presents a diagram of speed dependence on operating pressure. Vibroacceleration has been measured employing two accelerometers. Measurements have been carried out in three mutually perpendicular directions: x, y and z. The most important one is direction z, because this way the muscle performs a valuable displacement along the axis of the muscle, since this direction is the movement of the working muscle. [ABSTRACT FROM AUTHOR]

Introduction: Animal travel speed is an ecologically significant parameter, with implications for the study of energetics and animal behaviour. It is also necessary for the calculation of animal paths by dead-reckoning. Dead-reckoning uses heading and speed to calculate an animal's path through its environment on a fine scale. It is often used in aquatic environments, where transmission telemetry is difficult. However, its adoption for tracking terrestrial animals is limited by our ability to measure speed accurately on a fine scale. Recently, tri-axial accelerometers have shown promise for estimating speed, but their accuracy appears affected by changes in substrate and surface gradients. The purpose of the present study was to evaluate four metrics of acceleration; Overall dynamic body acceleration (ODBA), vectorial dynamic body acceleration (VDBA), acceleration peak frequency and acceleration peak amplitude, as proxies for speed over hard, soft and inclined surfaces, using humans as a model species. Results: A general linear model (GLM) showed a significant difference in the relationships between the metrics and speed depending on substrate or surface gradient. When the data from all surface types were considered together, VeDBA had the highest coefficient of determination. Conclusions: All of the metrics showed some variation in their relationship with speed according to the surface type. This indicates that changes in the substrate or surface gradient during locomotion by animals would produce errors in speed estimates, and also in dead-reckoned tracks if they were calculated from speeds based entirely on a priori calibrations. However, we describe a method by which the relationship between acceleration metrics and speed can be corrected ad hoc, until tracks accord with periodic ground truthed positions, obtained via a secondary means (e.g. VHF or GPS telemetry). In this way, dead-reckoning provides a means to obtain fine scale movement data for terrestrial animals, without the need for additional data on substrate or gradient. [ABSTRACT FROM AUTHOR]

Two large explosions were recorded by a dense array of strong-motion accelerometers and rotational seismometers in northeastern Taiwan associated with a Taiwan Integrated Geodynamics Research long-range refraction experiment. The objective of this experiment was to test the response of the experimental eentec rotational seismometers against calculated array rotations. Computed array rotation rates are seen to have little variation across the array, but point rotation rate measurements obtained from individual rotational seismometers show significant deviations with each other and with the array rotation rates in the ranges of 3-5 Hz and, especially, 3-50 Hz. A cross-correlation method was used to compare array-computed rotation rates and point rotation rate measurements in the frequency band of 3-5 Hz with the result that the absolute value of the normalized maximum correlation coefficient for each station set varied from 0.45 to 0.97 with an average of 0.84. Amplitude differences of the point rotation rate measurements are seen to be factors of 0.2 to 1.8 times the array rotations as well. It is not likely that the differences seen in the point and array-computed rotation rates are due to nonlinear or heterogeneous site conditions under each array element since these effects should also be seen in the acceleration data used to determine rotation rate. A rigorous method for accurately calibrating rotation rate instruments is needed to understand their response in the field. [ABSTRACT FROM AUTHOR]

We investigate rotational motions derived from measurements by arrays of translational seismometers-hereafter called array-derived rotations (ADRs)-and compare these to measurements made by a commercially available point rotation sensor (eentec™ R-1™). We focus on two aspects of the array problem: (1) the requisite conditions for calculating an ADR well and (2) the effect of array configuration on the result. Our data set consists of translational accelerations and rotation rates recorded by an array of Kinemetrics™ EpiSensor™ accelerometers and two R-1™ rotational sensors in the TAIPEI 101 building in Taipei, Taiwan. Our results indicate that (1) array configuration affects the accuracy of ADRs about orthogonal components in horizontal plane, (2) coherence between two point rotation measurements (two R-1™) can determine the maximum frequency of translations viably used for the calculating ADRs, and (3) the performance of the R-1™ is adequate, at least above a frequency of 0.12 Hz (periods shorter than 8 s). We also discuss deriving strain from the same array. [ABSTRACT FROM AUTHOR]

Self-selected walking speed is an important measure of ambulation ability used in various clinical gait experiments. Inertial sensors, i.e., accelerometers and gyroscopes, have been gradually introduced to estimate walking speed. This research area has attracted a lot of attention for the past two decades, and the trend is continuing due to the improvement of performance and decrease in cost of the miniature inertial sensors. With the intention of understanding the state of the art of current development in this area, a systematic review on the exiting methods was done in the following electronic engines/databases: PubMed, ISI Web of Knowledge, SportDiscus and IEEE Xplore. Sixteen journal articles and papers in proceedings focusing on inertial sensor based walking speed estimation were fully reviewed. The existing methods were categorized by sensor specification, sensor attachment location, experimental design, and walking speed estimation algorithm. [ABSTRACT FROM AUTHOR]

Abstract: The working principles of a new kind of accelerometer that allows tilt angle to be measured separately from linear acceleration are presented here. This device could have relevant applications for creating inertial platforms and where an inertial suspension for test masses is needed, as it is the case of interferometric gravitational wave detectors. [Copyright &y& Elsevier]

Background: Most accelerometers are worn around the waist (hip or lower back) to assess habitual physical activity. Wrist-worn accelerometers may be an alternative to the waist-worn monitors and may improve compliance in studies with prolonged wear. The aim of this study was to validate the Vivago® Wrist-Worn Accelerometer at various intensities of physical activity (PA) in adults. Methods: Twenty-one healthy adults aged 20-34 years were recruited for the study. Accelerometer data and oxygen uptake (VO2) were measured at sedentary, light, moderate and vigorous levels of PA. Results: Activity categories and accelerometer counts were: sedentary, 0-15 counts·min-1; light, 16-40 counts·min-1; moderate, 41-85 counts·min-1; and vigorous activity, > 85 counts·min-1. ANOVA repeated measures was used to determine the relationship between accelerometry data output and oxygen consumption (r = .89; p < .001). The Bland and Altman method showed good agreement in the assessment of energy expenditure between the indirect calorimetry and the data obtained by the accelerometer. Conclusions: Results of the study suggest that the Vivago® wrist-worn accelerometer is a valid measure of PA at varying levels of intensity. The study has also defined threshold values at 4 intensities and hence te Vivago® accelerometer may be used to quantify PA in free living conditions among adults. This device has possible application in treating a variety of important health concerns. [ABSTRACT FROM AUTHOR]

Abstract: A cantilever based optical accelerometer with enhanced performance characteristics has been proposed. The sensitivity of the accelerometer has efficiently been enhanced by about twice as compared to the conventional design by tailoring the effective distance between the sensor axis to the neutral axis of the cantilever. The sensitivity enhancement has been done without affecting the characteristic resonant frequency of the system. A sensitivity of about 450pm/g is achieved for a specific cantilever-mass arrangement. The architecture requires much simpler design as compared to optical accelerometers based on similar working principle and having sensitivities of this order. [Copyright &y& Elsevier]

Abstract: In this paper, the effect of the package die adhesive and package shell on the performances of silicon based MEMS high-g accelerometers was reported. Using Raman spectroscopy, the residual stress caused by different package die adhesive thickness and different package shell material was characterized. It can be concluded from the testing results that: with thicker die adhesive, the residual stress increment was much smaller; the piezoresistance variation caused by this residual stress was much smaller; and the temperature shift of the output voltage was much smaller. Comparing with the ceramic package, the stainless steel package has bigger sensitivity and bigger anti-overload ability. [Copyright &y& Elsevier]

This study aimed to quantify the intra-and inter-instrument reliability of the Actiwatch 4 accelerometer (AW4) in a mechanical setting. Twenty seven AW4 were attached to an isokinetic dynamometer and subjected to angular acceleration for 30 min at 50 deg/sec representing moderate intensity (MPA condition) and 200 deg/sec representing vigorous intensity (VPA condition), with a repeat trial conducted. Reliability was assessed using coefficient of variation (CV), absolute percent error (APE), and intraclass correlation coefficients (ICC). Mean AW4 activity counts displayed acceptable reliability according to CV in both conditions (ConMPA: CVintra = 4.6%, APEintra = 6.6%, CVinter = 6.4%, APEinter = 5.2%; ConVPA: CVintra = 3.9%, APEintra = 5.6%, CVinter = 5.9%, APEinter = 4.7%). When counts were re-categorised into minutes of MPA and VPA, lower CV values were observed (ConMPA: CVintra = 3.2%, APEintra = 4.5%, CVinter = 4.3%, APEinter = 3.2%; ConVPA: CVintra = 0.0%, APEintra = 0.0%, CVinter = 0.0%, APEinter = 0.0%). When activity counts were re-categorised as minutes of MVPA, excellent reliability was observed (CVintra, APEintra, CVinter, and APEinter = 0.0%) in both conditions. Mean AW4 activity counts exhibit reliability statistics comparable to other accelerometers. Reliability is improved when activity counts are re-categorised as time spent in MPA and VPA, with greatest reliability obtained when counts are recategorised as time spent in MVPA. As MVPA is the subcomponent of physical activity most associated with health benefits it would appear that the AW4 is reliable for measuring time spent in this health enhancing intensity category, at least from testing in a mechanical laboratory setting. [ABSTRACT FROM AUTHOR]

In this paper we extend our previous work concerning the regulation of the contact force in active train pantographs with wire-actuators. In particular, we suggest a second-order sliding mode based control scheme that avoids the direct measurement of the contact force, which is quite unpractical in real applications. The idea is to estimate the contact force using the measured displacements of the upper and lower pantograph frames. Unlike the contact force, the frames displacements can be measured accurately and reliably in practice. The estimation method, based on the algebraic observability theory, entails the use of real-time sliding-mode differentiators. It makes use explicitly of the mechanical characteristics of the upper frame only. The considered second-order sliding mode control scheme also includes proper linear compensating cascade filters devoted to cope with the de-stabilizing effects of the resonant wire actuator. We show that such a control scheme can be effectively combined with the given contact force estimation method. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [ABSTRACT FROM AUTHOR]

The article discusses a research that quantifies skill development in junior elite hockey players using stick-mounted accelerometers to record hit events and the timing between each hit. The results of the study suggest that the modified Chapman ball control test is a good measure of stick speed and ball control. Also, the more experienced players had much higher Chapman scores, and hit times were significantly faster than that recorded in the other drills.

Abstract: Speed indicator devices (SIDs) are vehicle activated signs displaying the real-time speeds of passing vehicles. They are part of the array of road safety measures for managing speeds on local authority roads in the United Kingdom. This paper documents an evaluation of the effectiveness of SIDs that was carried out in South London in 2008. SIDs were installed at 10 sites in South London for periods of between one and three weeks. The overall effect of the SIDs being installed was a reduction in vehicle speeds of 1.4mph and a significant reduction in the proportion of vehicles exceeding the speed limit. The research also investigated the distance over which the SIDs are effective and the effect on vehicle speeds once the SID is removed. The results showed that a speed reduction occurred over a distance of up to 400m and that once the SID is removed then, in general, the mean vehicle speeds returned to pre-SID levels by the end of the first week. [Copyright &y& Elsevier]

This article demonstrates the feasibility of optimizing the choice of known measurement circuits using as a criterion the minimum value of a functional of the square of the difference between the ideal conversion function of the circuit being studied and a conversion function that includes the effect of parasitic semiconductor structures. Modelling confirms a reduction in the effect of parasitic MIS structures in measurement circuits based on pulsed charge balancing. [ABSTRACT FROM AUTHOR]