Standard Accelerometer Research Articles

Effects of a Wearable-Based Intervention on the Hemiparetic Upper Limb in Persons With Stroke: A Randomized Controlled Trial.

Wearables have emerged as a transformative rehabilitation tool to provide self-directed training in the home. Objective. In this study, we examined the efficacy of a novel wearable device, "Smart Reminder" (SR), to provide home-based telerehabilitation for hemiparetic upper limb (UL) training in persons with stroke. Forty stroke survivors from community support groups were randomized (stratified by the period after stroke onset and impairment severity) to either the SR group or the sham device group. Participants received either 20 hours of telerehabilitation using the SR device or training with pictorial handouts and a sham device over 4 weeks. In addition, all participants wore a standard accelerometer for 3 hours each day, 5 times a week, outside the prescribed training. Participants were assessed by a masked assessor at baseline, post-intervention (week 4), and follow-up (week 8). The outcome measures included Fugl-Meyer Assessment for Upper Extremity (FMA-UE), Action Research Arm Test, Motor Activity Log, muscle strength, active range of motion and amount of movement of the UL, and compliance rate of training. The SR group improved substantially in their FMA-UE scores after treatment (mean difference = 2.05, P = .036) compared to the sham group. Also, adherence to the training using the SR device was significantly higher, 97%, than the sham group, 82.3% (P = .038). The 4-week telerehabilitation program using a "SR" device demonstrated potential efficacy in improving FMA-UE scores of the hemiparetic upper limb. However, it did not significantly enhance the performance of the affected limb in daily activities. The trial was registered on ClinicalTrial.gov (URL: http://www.clinicaltrials.gov) with the identifier NCT05877183.

Low movement, deep-learned sitting patterns, and sedentary behavior in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE).

Sedentary behavior (SB) has both movement and postural components, but most SB research has only assessed low movement, especially in children. The purpose of this study was to compare estimates and health associations of SB when derived from a standard accelerometer cut-point, a novel sitting detection technique (CNN Hip Accelerometer Posture for Children; CHAP-Child), and both combined. Data were from the International Study of Childhood Obesity, Lifestyle, and the Environment (ISCOLE). Participants were 6103 children (mean ± SD age 10.4 ± 0.56 years) from 12 countries who wore an ActiGraph GT3X+ accelerometer on the right hip for approximately one week. We calculated SB time, mean SB bout duration, and SB breaks using a cut-point (SBmovement), CHAP-Child (SBposture), and both methods combined (SBcombined). Mixed effects regression was used to test associations of SB variables with pediatric obesity variables (waist circumference, body fat percentage, and body mass index z-score). After adjusting for MVPA, SBposture showed several significant obesity associations favoring lower mean SB bout duration (b = 0.251-0.449; all p < 0.001) and higher SB breaks (b = -0.005--0.052; all p < 0.001). Lower total SB was unexpectedly related to greater obesity (b = -0.077--0.649; p from <0.001-0.02). For mean SB bout duration and SB breaks, more associations were observed for SBposture (n = 5) than for SBmovement (n = 3) or SBcombined (n = 1), and tended to have larger magnitude as well. Using traditional measures of low movement as a surrogate for SB may lead to underestimated or undetected adverse associations between SB and obesity. CHAP-Child allows assessment of sitting posture using hip-worn accelerometers. Ongoing work is needed to understand how low movement and posture are related to one another, as well as their potential health implications.

Damage Localization in a Steel Truss Bridge Using Influence Lines Identified from Vehicle-Induced Acceleration

In the last few decades, structural health monitoring (SHM) has proven a helpful tool to support the maintenance and management of civil infrastructure. However, typical measurement networks are expensive and require considerable initial efforts. The user-friendliness and interpretability of the outcome of SHM systems are crucial factors in motivating infrastructure owners and decision-makers to sustain their costs. For this reason, simple algorithms that provide structural parameters with direct physical interpretability for professionals familiar with the typical quantities involved in structural engineering are still the most used in field applications. This paper proposes an original method to identify curvature influence lines of bridges and viaducts only using the structural acceleration response induced by vehicular loads. Acceleration time histories collected at sparse locations through standard accelerometers are employed. In contrast to SHM approaches based on modal parameters, the proposed method does not need strict synchronization, thus being suitable for wireless and low-cost monitoring solutions. Identified influence lines are used to define a spatially dense damage indicator for accurate localization of structural anomalies with a clear physical meaning. Experimental results obtained for a steel truss bridge analyzed in different damage conditions prove the efficacy of the proposed method for situations where modal-based approaches may fail.

Integrating flexibility-based curvature with quasi-static features induced by traffic loads for high-resolution damage localization in bridges

Curvature is one of the most popular damage-sensitive features in vibration-based structural health monitoring applications, typically calculated from identified modal features. While the relevant strategic or historical importance of bridges may justify dense sensor networks, a limited budget is generally assigned to monitor “minor” viaducts, thus involving inexpensive devices or extremely sparse sensing solutions. Modal parameters can only be obtained at instrumented locations. Thereby, damage assessment methods based on identified features typically have a low spatial resolution, especially when using low-cost monitoring setups with a modest number of sensing devices. This paper proposes an original identification method for the curvature of bridges based on sparse acceleration measurements that can be collected using standard accelerometers. The raw acceleration signal is processed through a particular filter bank that extracts dynamic and quasi-static signal components. The first components are employed to identify modal parameters, from which sparse yet robust estimates of the structural curvature are retrieved. On the other hand, the quasi-static acceleration generated by the structural deflection induced by traffic load is used to identify the curvature influence lines of the bridge, which are fused with modal estimates using a Kalman filter. The state variable of the analyzed system, representing a dense curvature profile of the structure subjected to concentrated loads, can be used as a damage-sensitive feature for high-resolution damage localization. The method is applied to a steel truss bridge subject to different damage configurations.

Concurrent validity, test-retest reliability, and sensitivity of a PostureRite system measurement on dynamic postural sway and risk of fall in cerebral palsy.

Accurately diagnosing dynamic postural sway (DPS) is essential for effective and sustainable intervention in children with cerebral palsy (CP). We developed an accurate, inexpensive, and wearable DPS measurement system to measure DPS accurately and consistently during walking and functional activities of daily living. We investigated the validity and reliability of this PostureRite system in children with CP, and the link between PostureRite and clinical measures including gross motor function measure (GMFM), pediatric balance scale (PBS), and fall efficacy scale (FES). Twenty-one participants were categorized as follows: 11 healthy adults (3 females, mean age, 25.00±1.00 years) and 10 children with CP (mean age, 11.10±6.28 years). We determined the concurrent validity of PostureRite by comparing DPS data to the gold standard accelerometer measurement results. We determined test-retest reliability by measuring DPS data on three occasions at 2-h intervals. We assessed PostureRite measurement sensitivity to ascertain differences between healthy children and children with CP DPS measurements. Random and mixed intraclass correlation coefficients (ICC2,k and ICC3,k) were obtained; an independent T-test was performed (P < 0.05). Concurrent validity analysis showed a good relationship between the gold standard accelerometer and PostureRite (ICC2,k = 0.973, P < 0.05). Test-retest reliability demonstrated a good relationship across the three repeated measures of the DPS data (ICC3,k = 0.816-0.924, P < 0.05). Independent T-test revealed a significant difference in DPS data between healthy adults and children with CP (P < 0.05). We developed a portable, wireless, and affordable PostureRite system to measure DPS during gross motor function associated with daily activity and participation, and established the concurrent validity, test-retest reliability as sensitivity, and clinical relevance by comparing the DPS obtained from the participants with and without CP.

PO-686-01 ASSOCIATION OF CLOSED-LOOP STIMULATION VERSUS ACCELEROMETER-BASED RATE ADAPTIVE PACING ON PHYSICAL ACTIVITY AND OUTCOMES IN PATIENTS WITH CARDIOVASCULAR IMPLANTABLE ELECTRONIC DEVICES

Patients with sinus node dysfunction benefit from atrial pacing with rate-adaptive pacing. An alternative to the standard accelerometer (XL), closed-loop stimulation (CLS) relies on intracardiac impedance measurements to allow for a more physiological response to all forms of stimulation. We aimed to evaluate and compare the baseline characteristics, remote monitoring serial data, and long-term outcomes between CLS and XL among three cohorts: 1) dual-chamber pacemaker (DC-PM); 2) dual-chamber implantable cardiac defibrillator (DC-ICD); and 3) cardiac resynchronization therapy (CRT). We used the Biotronik CERTITUDE remote monitoring database, including all Medicare insured patients aged ≥ 65 years with a device programmed to XL or CLS. Remote monitoring data was collected and compared across the cohorts with high arrhythmia burden defined as greater than the median, while chronic conditions and long-term outcomes were obtained via linkage to Medicare claims data. A total of 6,085 patients (mean baseline atrial pacing percentage 63.7%, SD ± 28.8) were included and stratified into respective three respective cohorts: DC-PM (4,346 CLS and 524 XL), DC-ICD (CLS 290 and XL 168), and CRT (CLS 383 and XL 374). Prior stroke and no obesity were predictors of CLS in the DC-PM cohort, while atrial fibrillation was a predictor for XL in the DC-ICD cohort. After multivariable adjustment using a backward selection model, as compared to XL, those with CLS were observed to have 0.5% greater levels of physical activity in the DC-PM cohort (mean 9.3% vs. mean 8.7%, p=0.01), 2.2% lower in the DC-ICD cohort (p<0.001), 1.1% lower in the CRT cohort (p<0.001). There was a significantly lower risk of atrial arrhythmias (OR 0.56, 95% CI 0.39 - 0.81, p = 0.002) and lower PVC burden (OR 0.66, 95% CI 0.47 - 0.93, p=0.02) with CLS as compared to XL in the DC-PM, while no differences were observed in the other cohorts. There were no significant differences between CLS and XL in any cohort with respect to 1-year outcomes linked to Medicare including all-cause hospitalization, cardiac hospitalization, and stroke. As compared to XL, those programmed to CLS had modestly higher physical activity levels and lower risk of high atrial arrhythmias and PVC burden in those with a DC-PM as compared to XL.

Fiber optic jerk sensor.

Jerk is directly related to a physical mutation process of structural damage and human comfort. A fiber optic jerk sensor (FOJS) based on a fiber optic differentiating Mach-Zehnder interferometer is proposed. It can directly measure jerk by demodulating the phase of interference light, which avoids the high-frequency noise interference caused by differentiating the acceleration. The sensing theory and sensor design are given in detail. The experimental and theoretical results agree, demonstrating that the FOJS has a high sensitivity, an ultralow phase noise floor, a wide measuring range, and good linearity. The impact test shows that the FOJS can directly measure jerk and has good consistency with a standard piezoelectric accelerometer. The FOJS has potential applications in earthquake engineering, comfort evaluations, and railway design. This is the first time that directly measuring jerk with an optical sensor is reported.

Using In-Vehicle Monitoring Data to Assess Road Conditions of Traffic Flows

Developments in adaptive systems for maintenance and repair of automotive vehicles set the task of monitoring the conditions of their operation. One of the main factors determining these conditions is the type of road surface.The article describes the results of identification of the type (and condition) of the road surface obtained by theoretical and experimental methods based on the analysis of vertical accelerations recorded on the vehicle body.The purpose of research was to provide a possibility of continuous monitoring of the type of road surface on which a vehicle is driving, with the subsequent application of the obtained data to correct maintenance intervals. The results of experiments have shown the dependence of the vertical acceleration of the body on the micro-profile of the road surface. The described experimentally obtained profiles of vertical accelerations refer to different types of road surface in different conditions. For quantitative assessment, it is proposed to calculate the average level of accelerations as an integral average over a certain time interval.The results of the experiments have allowed to substantiate the empirical dependence of the average level of accelerations on speed of a vehicle. Based on this dependence, a method is proposed for recalculating the current values of the average levels of accelerations obtained at different speeds into values adjusted to the base speed to ensure the possibility of their comparison.It is shown that based on the values of average acceleration levels obtained through operation monitoring regarding a previously known type of road surface, it is possible to determine its condition. A short algorithm is formulated for practical implementation and assessment of road conditions of traffic flows. As for hardware, it is proposed not to equip a vehicle with additional sensors but to use operational standard accelerometers as part of in-vehicle emergency call systems, e.g., ERA-GLONASS equipment units.

Realization and performance evaluation of a machine tool vibration monitoring module by multiple MEMS accelerometer integrations

The quality of machined products is largely dependent on the status of machines in various aspects. Vibration status monitoring is a fundamental step for reliability evaluation, machine fault diagnosis, and prognosis. For achieving such a task, miniature low-cost but effective sensors such as MEMS accelerometers should be used. However, due to the nature of machine tool characteristics, both high sensitivity and bandwidth are required and this imposes a challenging constraint on current MEMS devices. In this work, a tri-axial module by integrating three types and totally five MEMS accelerometers is designed and realized as the first step to realize the measurement module for machine tool applications. The performance of the module has been validated by a piezoelectric accelerometer, and the result indicated that the outputs of the proposed design essentially agree with those obtained by the standard piezoelectric accelerometer very well. Finally, the module has been applied on both a five-axis milling machine and a six-axis robot arms for detecting the process-induced vibration for demonstrating its possible applications in both abnormal condition monitoring and machine prognosis. In the near future, the performance will be improved by reducing noise and the size would be further reduced for fitting into critical location of machine tools.

Validity of Tools to Measure Physical Activity in Older Adults Following Total Knee Arthroplasty.

Few validated tools exist for measuring physical activity following total knee arthroplasty (TKA) despite the importance of returning to sufficient levels of physical activity post-TKA to achieve health benefits. This study examined the validity of two clinical measures-the Fitbit, a commercially available personal activity monitor, and the Community Healthy Activities Model Program for Seniors (CHAMPS), a self-report questionnaire-compared with a reference standard accelerometer, the SenseWearTM Armband (SWA). At 6-month post-TKA, 47 participants wore the Fitbit and SWA for 4 days and then completed the CHAMPS. Moderate-to-good correlation was observed between the Fitbit and SWA for steps (intraclass correlation coefficient [ICC] = .79), energy expenditure (ICC = .78), and energy expenditure <3 METS (ICC = .79). Poor-to-moderate correlation was observed between the CHAMPS and SWA (ICC = .43) with the questionnaire reporting lower daily energy expenditures than the SWA. Results showed that Fitbit may be a reasonable measurement tool to measure steps and energy expenditures in older adults following TKA.

Smartphone Accelerometry: A Smart and Reliable Measurement of Real-Life Physical Activity in Multiple Sclerosis and Healthy Individuals.

Background: Mobility impairment is common in persons with multiple sclerosis (pwMS) and can be assessed with clinical tests and surveys that have restricted ecological validity. Commercial research-based accelerometers are considered to be more valuable as they measure real-life mobility. Smartphone accelerometry might be an easily accessible alternative.Objective: To explore smartphone accelerometry in comparison to clinical tests, surveys, and a wrist-worn ActiGraph in pwMS and controls.Methods: Sixty-seven pwMS and 70 matched controls underwent mobility tests and surveys. Real-life data were collected with a smartphone and an ActiGraph over 7 days. We explored different smartphone metrics in a technical validation course and computed afterward correlation between ActiGraph (steps per minute), smartphone accelerometry (variance of vector magnitude), clinical tests, and surveys. We also determined the ability to separate between patients and controls as well as between different disability groups.Results: Based on the technical validation, we found the variance of the vector magnitude as a reliable estimate to discriminate wear time and no wear-time of the smartphone. Due to a further association with different activity levels, it was selected for real-life analyses. In the cross-sectional study, ActiGraph correlated moderately (r = 0.43, p < 0.05) with the smartphone but less with clinical tests (rho between |0.211| and |0.337|). Smartphone data showed stronger correlations with age (rho = −0.487) and clinical tests (rho between |0.565| and |0.605|). ActiGraph only differed between pwMS and controls (p < 0.001) but not between disability groups. At the same time, the smartphone showed differences between pwMS and controls, between RRMS and PP-/SPMS, and between participants with/without ambulatory impairment (all p < 0.001).Conclusions: Smartphone accelerometry provides better estimates of mobility and disability than a wrist-worn standard accelerometer in a free-living context for both controls and pwMS. Given the fact that no additional device is needed, smartphone accelerometry might be a convenient outcome of real-life ambulation in healthy individuals and chronic diseases such as MS.

Effect of closed loop stimulation versus accelerometer on outcomes with cardiac resynchronization therapy: the CLASS trial.

Chronotropic incompetence (CI) in patients with heart failure is common and associated with impaired exercise intolerance and adverse outcomes. This study sought to determine the effects of closed loop stimulation (CLS) rate-adaptive pacing on functional capacity in patients with heart failure with reduced ejection fraction (HFrEF) and CI implanted with cardiac resynchronization therapy (CRT) devices. A randomized, blinded, cross-over designed trial enrolled patients with HFrEF and CI implanted with a Biotronik CRT-D to complete a quality of life questionnaire, 6-min walk distance (6MWD), and cardiopulmonary exercise testing after two programmed periods: 1-week period of CLS and 1-week period of standard accelerometer (DDDR). Nine patients (6 males, mean age 71.4years, 7 with New York Heart Association Class III, mean ejection fraction 39 ± 8%) were enrolled. Quality of life trended higher in CLS as compared to DDDR (550.8 ± 123.9 vs 489.3 ± 164.9, p= 0.06). There were no differences between CLS and DDDR in 6MWD (293.1 ± 90.2m vs 315.1 ± 95.5m, p= 0.52), peak heart rate (HR) 110.7 ± 14.7bpm vs 109.7bpm ± 14.1, p= 0.67), or peak VO2 (12.3 ± 4.9ml/kg/min vs 12.9 ± 5.9, p= 0.47). As tests were submaximal as indicated by low respiratory exchange ratios (0.98 ± 0.11 vs 1.0 ± 0.8, p= 0.35), VE/VCO2 slope also showed no difference between CLS and DDDR (35.8 ± 5.6 vs 35.4 ± 5.7, p= 0.65). Five patients (56%) preferred CLS programming (p= 1.0). In patients with HFrEF and CI implanted with a CRT-D, peak HR, peak VO2, and 6MWD were equivalent, while there was a trend toward improved quality of life in CLS as compared to DDDR. URL: https://www.clinicaltrials.gov . Unique identifier: NCT02693262.

Predicting vertical ground reaction force during running using novel piezoresponsive sensors and accelerometry

ABSTRACT Running is a common exercise with numerous health benefits. Vertical ground reaction force (vGRF) influences running injury risk and running performance. Measurement of vGRF during running is now primarily constrained to a laboratory setting. The purpose of this study was to evaluate a new approach to measuring vGRF during running. This approach can be used outside of the laboratory and involves running shoes instrumented with novel piezoresponsive sensors and a standard accelerometer. Thirty-one individuals ran at three different speeds on a force-instrumented treadmill while wearing the instrumented running shoes. vGRF was predicted using data collected from the instrumented shoes, and predicted vGRF were compared to vGRF measured via the treadmill. Per cent error of the resulting predictions varied depending upon the predicted vGRF characteristic. Per cent error was relatively low for predicted vGRF impulse (2–7%), active peak vGRF (3–7%), and ground contact time (3–6%), but relatively high for predicted vGRF load rates (22–29%). These errors should decrease with future iterations of the instrumented shoes and collection of additional data from a more diverse sample. The novel technology described herein might become a feasible way to collect large amounts of vGRF data outside of the traditional biomechanics laboratory.

Ricochet quantification using a multiple sensor approach

This study investigates the ricochet behaviour of three different small-arms projectile types using a novel ricochet measuring device. The results can be used to estimate the danger potential of ricochets on shooting ranges.A ricochet is the change of direction and velocity of a projectile after impacting an oblique surface. This impact produces strong vibrations on a rigid plate.During this impact, flexural waves travel radially outwards from the point of impact. These waves are used to determine the properties of the impactor with accelerometers situated on the target surface. With the use of two measurement plates, one can produce a ricochet and detect the velocity at the same time.Accelerometers are suitable for accurate momentum measurements of single impacts. However, depending upon strike velocity and the impact angle, a ricochet can separate in multiple fragments after being deflected. From the operational safety perspective, these fragments need to be detected, as well. The approach of a coupled sensor concept was chosen to solve this problem.Thermographic sensors were additionally used to visualise the heat which is produced after penetrating a rubber layer pasted in front of the steel target plate. With this approach one was able to detect the position of impact. The investigations showed that the measurement system performance is better with a multiple sensor design, which includes accelerometers for the velocity, impact strength and partly the position measurement, while the thermographic sensor was used for the position measurement and partly the momentum measurement.The investigated ammunition showed plausible fragmentation behaviour, and the results can already be used to estimate the danger potential of different ammunition types. Frangible projectiles fragment to small particles already after being deflected under a small angle. However, Full Metal Jacket projectiles with or without a steel core do not fragment under angles which are less than 5°.The objective of the paper is to demonstrate the possibility of measuring the complex ricochet mechanics of small projectiles using standard accelerometers with the adequate signal processing approach. This measuring system is supported by an off the shelf thermographic camera.

Final report on key comparison EURAMET.AUV.V-K2

This final report describes the results obtained in a key comparison of primary vibration calibration facilities. Two piezoelectric standard accelerometers (one single-ended as well one back-to-back type) were calibrated first at Central Office of Measures (GUM), acting as pilot and linking laboratory, and Bulgarian Institute for Metrology (BIM). The results of the BIM obtained in this comparison were linked to the CCAUV.V-K2 key comparison through the joint participation of the GUM. The degrees of equivalence were computed for BIM with respect to the CCAUV.V-K2 key comparison reference value.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Combining strain and acceleration measurements for random force estimation via Kalman filtering on a cantilevered structure

Several engineering applications demand in-operation dynamic forces exerted on structural components to be modeled, however there are cases in which both phenomenological and empirical estimations are more uncertain than admissible. Although direct input measurements would be the first option to solve this lack, in many instances an appropriate and feasible instrumentation is hard to be accomplished due to reduced space, especial environment conditions (e.g. submerged structures), etc. leaving a gap for new methods to be explored. Virtual sensing represents a solution for determining forces when direct measurements are not feasible or present important technical challenges. In this context, augmented-state Kalman Filter (AKF) based techniques have recently been introduced in the field of force estimation. This technique consists in adding the unknown inputs (or input parameters) to the normal state vector of the mechanical system, which usually comprises only displacement and velocity states, and estimate the augmented-state vector in a Kalman Filter scheme. One of the challenges behind a successful AKF implementation is stability, as estimates based on acceleration tend to deviate with time. Dummy measurements have been used in the past as a means to guarantee stability. In this work, online dynamic strain measurements are used in that sense and the ability of the AKF for estimating a point force random in time, is successfully evaluated. In order to validate this procedure, the present experimental approach features a cantilevered structure, instrumented with standard accelerometers and dynamic strain sensors, excited with a known force. A force sensor is used to directly measure the input force for further comparisons, which show good agreement both in time and frequency domain.

2016 Central Italy Earthquakes: comparison between GPS signals and low-cost distributed MEMS arrays

Abstract. Modern seismic ground-motion sensors have reached an excellent performance quality in terms of dynamic range and bandwidth resolution. The weakest point in the recording of seismic events remains spatial sampling and spatial resolution, due to the limited number of installed sensors. A significant improvement in spatial resolution can be achieved by the use of non-conventional motion sensors, such as low-cost distributed sensors arrays or positioning systems, capable of increasing the density of classical seismic recording networks. In this perspective, we adopted micro-electro mechanical system (MEMS) sensors to integrate the use of standard accelerometers for moderate-to-strong seismic events. In addition, we analyse high-rate distributed positioning system data that also record soil motion. In this paper, we present data from the 2016 Central Italy earthquakes as recorded by a spatially dense prototype MEMS array installed in the proximity of the epicentral area, and we compare the results to the signal of local 1s GPS stations. We discuss advantages and limitations of this joint approach, reaching the conclusion that such low-cost sensors and the use of high rate GPS signal could be an effective choice for integrate the spatial density of stations providing strong-motion parameters.

Capturing sleep\u2013wake cycles by using day-to-day smartphone touchscreen interactions

Body movements drop with sleep, and this behavioural signature is widely exploited to infer sleep duration. However, a reduction in body movements may also occur in periods of intense cognitive activity, and the ubiquitous use of smartphones may capture these wakeful periods otherwise hidden in the standard measures of sleep. Here, we continuously captured the gross body movements using standard wrist-worn accelerometers to quantify sleep (actigraphy) and logged the timing of the day-to-day touchscreen events (‘tappigraphy’). Using these measures, we addressed how the gross body movements overlap with the cognitively engaging digital behaviour (from n = 79 individuals, accumulating ~1400 nights). We find that smartphone use was distributed across a broad spectrum of physical activity levels, but consistently peaked at rest. We estimated the putative sleep onset and wake-up times from the actigraphy data to find that these times were well correlated to the estimates from tappigraphy (R2 = 0.9 for sleep-onset time and wake-up time). However, actigraphy overestimated sleep as virtually all of the users used their phones during the putative sleep period. Interestingly, the probability of touches remained greater than zero for ~2 h after the putative sleep onset, and ~2 h before the putative wake-up time. Our findings suggest that touchscreen interactions are widely integrated into modern sleeping habits—surrounding both sleep onset and waking-up periods—yielding a new approach to measuring sleep. Smartphone interactions can be leveraged to update the behavioural signatures of sleep with these peculiarities of modern digital behaviour.

Key comparison in the field of acceleration on low intensity shock sensitivity

This is the final report for CIPM key comparison CCAUV.V-K4 in the area of 'vibration' (quantity of acceleration). The aim of this comparison was to measure the voltage shock sensitivity of an accelerometer measuring chain including a standard accelerometer with a charge amplifier and the charge shock sensitivity of an accelerometer at different peak acceleration values with associated pulse durations. Nine Metrology Institutes from five RMOs have participated in the comparison with National Institute of Metrology, P.R. China as pilot lab and National Metrology Institute of Japan as co-pilot lab. For voltage shock sensitivity, all the participating laboratories provided their calibration results, which were all consistent within their declared expanded uncertainties. All participants contributed to the KCRVs calculated for six peak acceleration comparison values. For charge shock sensitivity, one participant failed to contribute to the calculation of the KCRV at 5 000 m/s2 and two participating laboratories were not consistent within their declared expanded uncertainties at a total of five peak acceleration comparison values. Further improvements of their calibration devices and uncertainty evaluations will provide more accurate and reliable measurement results in the future.KEY WORDS FOR SEARCHKey comparison; shock acceleration; low intensity shockMain textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

MEMS accelerometers for mechanical vibrations analysis: a comprehensive review with applications

In this paper, the use of MEMS accelerometers for measuring mechanical vibrations is presented. Also a wide review of the literature is performed by presenting the uses of the MEMS accelerometers in a great number of applications. These sensors are known for their low prices, low power consumption and low sizes, which enhance their use in applications such as energy harvesters, monitoring processes and for educational purposes. In order to propose these sensors for measuring vibrations, a complete evaluation of the MEMS accelerometers was performed by measuring amplitudes and frequencies of oscillations and comparing their dynamic characteristics with other accelerometers with higher precision. Moreover, two experiments were conducted: In the first one, the measurements of the amplitude given by a MEMS and a standard accelerometer while being excited with sinusoidal waves with different frequencies using a vibration exciter were taken and compared. For the second experiment, three MEMS sensors and a piezoelectric accelerometer were used to measure the accelerations of a 3-DOF shear-building excited by an unbalanced DC motor. The signals obtained were compared in the time and frequency domains; for the last case, the wavelet transform, the wavelet coherence and the power spectrum density were used.