A novel wearable device to deliver unconstrained, unpredictable slip perturbations during gait

Abstract Background Task-specific perturbation training is a widely studied means of fall prevention, utilizing techniques that induce slips or slip-like perturbations during gait. Though effective, these methods only simulate narrow ranges within the larger space of possible slipping conditions encountered in daily life. Here we describe and test a novel, wearable apparatus designed to address these limitations and simulate a diverse range of slipping disturbances. Methods The device consists of wireless triggering and detachable outsole components that provide adequate friction with the floor when secured to the wearer’s foot, but suddenly create a low-friction surface underfoot upon release. “Benchtop” tests were carried out to quantify device triggering characteristics (i.e. cutting temperature, release delay) and the resulting friction reduction. The device was also tested on six healthy young adults (3 female, age 23 ± 2.4 years), who walked with and without the device to observe how gait kinematics and spatiotemporal parameters were influenced, then performed 12 walking trials ending with a slip delivered by the device. Each participant also completed a survey to obtain opinions on device safety, device comfort, slip realism, and slip difficulty. A linear mixed effects analysis was employed to compare subject spatiotemporal parameters with and without the apparatus, as well as correlation coefficients and root mean square errors (RMSE) to assess the impact of the device on lower limb gait kinematics. Slip onset phases, distances, directions, velocities, and recovery step locations were also calculated. Results This device rapidly diminishes available friction from static coefficients of 0.48 to 0.07, albeit after a substantial delay (0.482 ± 0.181 s) between signal reception and outsole release. Strong correlations (R > 0.93) and small RMSE between gait kinematics with and without the device indicate minimal effects on natural gait patterns, however some spatiotemporal parameters were significantly impacted. A diverse range of slip perturbations and recovery steps were successfully elicited by the device. Conclusions Our results highlight the efficacy and utility of a wearable slipping device to deliver diverse slip conditions. Such an apparatus enables the study of unconstrained slips administered across the gait cycle, as well as during different locomotor behaviors like turning, negotiating slopes, and level changes.

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Assessment of a generalizable methodology to assess learning from manikin-based simulation technology*

Journal of Chiropractic Education ◽

10.7899/jce-13-31 ◽

2014 ◽

Vol 28 (1) ◽

pp. 16-20 ◽

Cited By ~ 7

Author(s):

Dominic A. Giuliano ◽

Marion McGregor

Keyword(s):

Learning Outcomes ◽

Intraclass Correlation ◽

Correlation Coefficients ◽

Wisdom Of Crowds ◽

Diverse Range ◽

Intraclass Correlation Coefficients ◽

Significant Difference ◽

Assessment Procedures ◽

The Impact

Objective This study combined a learning outcomes-based checklist and salient characteristics derived from wisdom-of-crowds theory to test whether differing groups of judges (diversity maximized versus expertise maximized) would be able to appropriately assess videotaped, manikin-based simulation scenarios. Methods Two groups of 3 judges scored 9 videos of interns managing a simulated cardiac event. The first group had a diverse range of knowledge of simulation procedures, while the second group was more homogeneous in their knowledge and had greater simulation expertise. All judges viewed 3 types of videos (predebriefing, postdebriefing, and 6 month follow-up) in a blinded fashion and provided their scores independently. Intraclass correlation coefficients (ICCs) were used to assess the reliability of judges as related to group membership. Scores from each group of judges were averaged to determine the impact of group on scores. Results Results revealed strong ICCs for both groups of judges (diverse, 0.89; expert, 0.97), with the diverse group of judges having a much wider 95% confidence interval for the ICC. Analysis of variance of the average checklist scores indicated no significant difference between the 2 groups of judges for any of the types of videotapes assessed (F = 0.72, p = .4094). There was, however, a statistically significant difference between the types of videos (F = 14.39, p = .0004), with higher scores at the postdebrief and 6-month follow-up time periods. Conclusions Results obtained in this study provide optimism for assessment procedures in simulation using learning outcomes-based checklists and a small panel of judges.

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Limits to the Impact of Empirical Correction on Simulation of the Water Cycle

Journal of Hydrometeorology ◽

10.1175/2011jhm1348.1 ◽

2011 ◽

Vol 12 (4) ◽

pp. 650-662

Author(s):

Paul A. Dirmeyer ◽

Timothy DelSole ◽

Mei Zhao

Keyword(s):

Moisture Transport ◽

Climate Model ◽

Water Cycle ◽

Correlation Coefficients ◽

Correction Method ◽

Boreal Summer ◽

Model Errors ◽

Empirical Correction ◽

The Impact ◽

Mean Square Errors

Abstract Empirical correction is applied to wind, temperature, and soil moisture fields in a climate model to assess its impact on simulation of the water cycle during boreal summer. The empirical correction method is based on the biases in model forecasts only as a function of the time of year. Corrections are applied to the prognostic equations as an extra nudging term. Mean fields of evaporation, precipitation, moisture transport, and recycling ratio are all improved, even though humidity fields were not corrected. Simulation of the patterns of surface evaporation supplying rainfall at locations over land is also improved for most locations. There is also improvement in the simulation of evaporation and possibly rainfall, as measured by anomaly correlation coefficients and root-mean-square errors of the time series of monthly anomalies. However, monthly anomalies of other water cycle fields such as moisture transport and recycling ratio were not improved. Like any statistical adjustment, empirical correction does not address the cause of model errors, but it does provide a net improvement to the simulation of the water cycle. It can, however, be used to diagnose the sources of error in the model. Since corrections are only applied to prognostic variables, shortcomings due to physical parameterizations in the model are not remedied.

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The Oxford Handbook of Adult Cognitive Disorders

10.1093/oxfordhb/9780190664121.001.0001 ◽

2019 ◽

Keyword(s):

Cognitive Impairment ◽

Cognitive Function ◽

Neurodevelopmental Disorders ◽

Brain Aging ◽

Cognitive Disorders ◽

Diverse Range ◽

Medical Specialties ◽

Psychiatric Illnesses ◽

Medical Disorders ◽

The Impact

The prevalence of cognitive impairment caused by neurodegenerative diseases and other neurologic disorders associated with aging is expected to rise dramatically between now and year 2050, when the population of Americans aged 65 or older will nearly double. Cognitive impairment also commonly occurs in other neurologic conditions, as well as in non-neurologic medical disorders (and their treatments), idiopathic psychiatric illnesses, and adult neurodevelopmental disorders. Cognitive impairment can thus infiltrate all aspects of healthcare, making it necessary for clinicians and clinical researchers to have an integrated knowledge of the spectrum of adult cognitive disorders. The Oxford Handbook of Adult Cognitive Disorders is meant to serve as an up-to-date, scholarly, and comprehensive volume covering most diseases, conditions, and injuries resulting in impairments in cognitive function in adults. Topics covered include normal cognitive and brain aging, the impact of medical disorders (e.g., cardiovascular, liver, pulmonary) and psychiatric illnesses (e.g., depression and bipolar disorder) on cognitive function, adult neurodevelopmental disorders (e.g., Down Syndrome, Attention Deficit/Hyperactivity Disorder), as well as the various neurological conditions (e.g., Alzheimer’s disease, chronic traumatic encephalopathy, concussion). A section of the Handbook is also dedicated to unique perspectives and special considerations for the clinicians and clinical researchers, covering topics such as cognitive reserve, genetics, diversity, and neuroethics. The target audience of this Handbook includes: (1) clinicians, particularly psychologists, neuropsychologists, neurologists (including behavioral and cognitive neurologists), geriatricians, and psychiatrists (including neuropsychiatrists), who provide clinical care and management for adults with a diverse range of cognitive disorders; (2) clinical researchers who investigate cognitive outcomes and functioning in adult populations; and (3) graduate level students and post-doctoral trainees studying psychology, clinical neuroscience, and various medical specialties.

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Estimating Water Vapor Using Signals from Microwave Links below 25 GHz

Remote Sensing ◽

10.3390/rs13081409 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1409

Author(s):

Kun Song ◽

Xichuan Liu ◽

Taichang Gao ◽

Peng Zhang

Keyword(s):

Water Vapor ◽

Weather Forecasting ◽

Water Cycle ◽

Correlation Coefficients ◽

Support Vector ◽

Vapor Density ◽

Measurement Resolution ◽

Sensing Model ◽

Numerical Weather Forecasting ◽

Mean Square Errors

Water vapor is a key element in both the greenhouse effect and the water cycle. However, water vapor has not been well studied due to the limitations of conventional monitoring instruments. Recently, estimating rain rate by the rain-induced attenuation of commercial microwave links (MLs) has been proven to be a feasible method. Similar to rainfall, water vapor also attenuates the energy of MLs. Thus, MLs also have the potential of estimating water vapor. This study proposes a method to estimate water vapor density by using the received signal level (RSL) of MLs at 15, 18, and 23 GHz, which is the first attempt to estimate water vapor by MLs below 20 GHz. This method trains a sensing model with prior RSL data and water vapor density by the support vector machine, and the model can directly estimate the water vapor density from the RSLs without preprocessing. The results show that the measurement resolution of the proposed method is less than 1 g/m3. The correlation coefficients between automatic weather stations and MLs range from 0.72 to 0.81, and the root mean square errors range from 1.57 to 2.31 g/m3. With the large availability of signal measurements from communications operators, this method has the potential of providing refined data on water vapor density, which can contribute to research on the atmospheric boundary layer and numerical weather forecasting.

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Validity of Inertial Sensors for Assessing Balance Kinematics and Mobility during Treadmill-Based Perturbation and Dance Training

Sensors ◽

10.3390/s21093065 ◽

2021 ◽

Vol 21 (9) ◽

pp. 3065

Author(s):

Ernest Kwesi Ofori ◽

Shuaijie Wang ◽

Tanvi Bhatt

Keyword(s):

Concurrent Validity ◽

Inertial Sensors ◽

Intraclass Correlation ◽

Correlation Coefficients ◽

Human Motion ◽

Intraclass Correlation Coefficients ◽

Dance Training ◽

Silver Standard ◽

Mean Square Errors ◽

Reactive Balance

Inertial sensors (IS) enable the kinematic analysis of human motion with fewer logistical limitations than the silver standard optoelectronic motion capture (MOCAP) system. However, there are no data on the validity of IS for perturbation training and during the performance of dance. The aim of this present study was to determine the concurrent validity of IS in the analysis of kinematic data during slip and trip-like perturbations and during the performance of dance. Seven IS and the MOCAP system were simultaneously used to capture the reactive response and dance movements of fifteen healthy young participants (Age: 18–35 years). Bland Altman (BA) plots, root mean square errors (RMSE), Pearson’s correlation coefficients (R), and intraclass correlation coefficients (ICC) were used to compare kinematic variables of interest between the two systems for absolute equivalency and accuracy. Limits of agreements (LOA) of the BA plots ranged from −0.23 to 0.56 and −0.21 to 0.43 for slip and trip stability variables, respectively. The RMSE for slip and trip stabilities were from 0.11 to 0.20 and 0.11 to 0.16, respectively. For the joint mobility in dance, LOA varied from −6.98–18.54, while RMSE ranged from 1.90 to 13.06. Comparison of IS and optoelectronic MOCAP system for reactive balance and body segmental kinematics revealed that R varied from 0.59 to 0.81 and from 0.47 to 0.85 while ICC was from 0.50 to 0.72 and 0.45 to 0.84 respectively for slip–trip perturbations and dance. Results of moderate to high concurrent validity of IS and MOCAP systems. These results were consistent with results from similar studies. This suggests that IS are valid tools to quantitatively analyze reactive balance and mobility kinematics during slip–trip perturbation and the performance of dance at any location outside, including the laboratory, clinical and home settings.

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Synchronization in 5G networks: a hybrid Bayesian approach toward clock offset/skew estimation and its impact on localization

EURASIP Journal on Wireless Communications and Networking ◽

10.1186/s13638-021-01963-x ◽

2021 ◽

Vol 2021 (1) ◽

Author(s):

Meysam Goodarzi ◽

Darko Cvetkovski ◽

Nebojsa Maletic ◽

Jesús Gutiérrez ◽

Eckhard Grass

Keyword(s):

Bayesian Approach ◽

Large Scale ◽

Hybrid Approach ◽

Position Estimation ◽

5G Networks ◽

Clock Skew ◽

Depth Analysis ◽

The Impact ◽

Mean Square Errors ◽

Clock Offset

AbstractClock synchronization has always been a major challenge when designing wireless networks. This work focuses on tackling the time synchronization problem in 5G networks by adopting a hybrid Bayesian approach for clock offset and skew estimation. Furthermore, we provide an in-depth analysis of the impact of the proposed approach on a synchronization-sensitive service, i.e., localization. Specifically, we expose the substantial benefit of belief propagation (BP) running on factor graphs (FGs) in achieving precise network-wide synchronization. Moreover, we take advantage of Bayesian recursive filtering (BRF) to mitigate the time-stamping error in pairwise synchronization. Finally, we reveal the merit of hybrid synchronization by dividing a large-scale network into local synchronization domains and applying the most suitable synchronization algorithm (BP- or BRF-based) on each domain. The performance of the hybrid approach is then evaluated in terms of the root mean square errors (RMSEs) of the clock offset, clock skew, and the position estimation. According to the simulations, in spite of the simplifications in the hybrid approach, RMSEs of clock offset, clock skew, and position estimation remain below 10 ns, 1 ppm, and 1.5 m, respectively.

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Experimental Investigation on Improving Electromechanical Impedance Based Damage Detection by Temperature Compensation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.569-570.1132 ◽

2013 ◽

Vol 569-570 ◽

pp. 1132-1139 ◽

Cited By ~ 10

Author(s):

Thomas Siebel ◽

Mihail Lilov

Keyword(s):

Damage Detection ◽

Structural Damage ◽

Temperature Compensation ◽

Impact Damage ◽

Correlation Coefficients ◽

Electromechanical Impedance ◽

Reinforced Plastic ◽

Influence Of Temperature On ◽

Compensation Approach ◽

The Impact

The sensitivity of the electromechanical impedance to structural damage under varying temperature is investigated in this paper. An approach based on maximizing cross-correlation coefficients is used to compensate temperature effects. The experiments are carried out on an air plane conform carbon fiber reinforced plastic (CFRP) panel (500mm x 500mm x 5mm) instrumented with 26 piezoelectric transducers of two different sizes. In a first step, the panel is stepwise subjected to temperatures between-50 °C and 100 °C. The influence of varying temperatures on the measured impedances and the capability of the temperature compensation approach are analyzed. Next, the sensitivity to a 200 J impact damage is analyzed and it is set in relation to the influence of a temperature change. It becomes apparent the impact of the transducer size and location on the quality of the damage detection. The results further indicate a significant influence of temperature on the measured spectra. However, applying the temperature compensation algorithm can reduce the temperature effect at the same time increasing the transducer sensitivity within its measuring area. The paper concludes with a discussion about the trade-off between the sensing area, where damage should be detected, and the temperature range, in which damage within this area can reliably be detected.

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Assessing the Skills of a Seasonal Forecast of Chlorophyll in the Global Pelagic Oceans

Remote Sensing ◽

10.3390/rs13061051 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1051

Author(s):

Cecile S. Rousseaux ◽

Watson W. Gregg ◽

Lesley Ott

Keyword(s):

Ocean Circulation ◽

North Atlantic ◽

Harmful Algal Blooms ◽

Algal Blooms ◽

Chlorophyll Concentration ◽

Correlation Coefficients ◽

Global Scale ◽

Seasonal Forecasts ◽

Mean Square Errors ◽

Satellite Chlorophyll

While forecasts of atmospheric variables, and to a lesser degree ocean circulation, are relatively common, the forecast of biogeochemical conditions is still in its infancy. Using a dynamical ocean biogeochemical forecast forced by seasonal forecasts of atmospheric and physical ocean variables, we produce seasonal predictions of chlorophyll concentration at the global scale. Results show significant Anomaly Correlation Coefficients (ACCs) for the majority of regions (11 out of the 12 regions for the 1-month lead forecast). Root mean square errors are smaller (<0.05 µg chlorophyll (chl) L−1) in the Equatorial regions compared to the higher latitudes (range from 0.05 up to 0.13 µg chl L−1). The forecast for all regions except three (North Atlantic, South Pacific and North Indian) are within the Semi-Interquartile Range of the satellite chlorophyll concentration (Suomi-National Polar-orbiting Partnership (NPP), 27.9%). This suggests the potential for skillful global biogeochemical forecasts on seasonal timescales of chlorophyll, primary production and harmful algal blooms that could support fisheries management and other applications.

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Surfactant and Friction Reducer Interaction in High Salinity Slickwater Fracturing

10.2118/205284-ms ◽

2022 ◽

Author(s):

Abdelrahman Kotb ◽

Tariq Almubarak ◽

Hisham A. Nasr-El-Din

Keyword(s):

Ethylene Oxide ◽

Produced Water ◽

High Salinity ◽

Environmental Benefits ◽

Friction Reduction ◽

Water Salinity ◽

Ethylene Oxide Chain ◽

Chain Lengths ◽

The Impact ◽

Slickwater Fracturing

Abstract Slickwater fracturing has been phenomenally successful in unconventional shale formations due to their unique geomechanical properties. Nevertheless, these treatments consume large volumes of water. On average, hydraulic fracturing treatments use up to 13,000,000 gallons of water in unconventional wells. In an effort to reduce the use of freshwater, research has focused on developing friction reducers (FR) that can be used in high salinity brines such as seawater and produced water. However, commonly used friction reducers precipitate in high salinity brine, lose their friction reduction properties, and cause severe formation damage to the proppant pack. Consequently, this work proposes the use of common surfactants to aid the FR system and achieve salt tolerance at water salinity up to 230,000 ppm. This paper will (a) evaluate five surfactants for use in high salinity FR systems, (b) evaluate the rheological properties of these systems, and (c) evaluate the damage generated from using these systems. Four types of tests were conducted to analyze the performance of the new FR at high salinity brine. These are (a) rheology, (b) static proppant settling, (c) breakability, and (d) coreflood tests. Surfactants with ethylene oxide chain lengths ranging from 6 to 12 were incorporated in the tests. Rheology tests were done at temperatures up to 150°F to evaluate the FR at shear rates between 40-1000 s-1. Proppant settling tests were performed to investigate the proppant carrying capacity of the new FR system. Breakability and coreflood tests were conducted to study the potential damage caused by the proposed systems. Rheology tests showed that using surfactants with high ethylene oxide chain length (>8) improved the performance of the FR at water salinity up to 230,000 ppm. Anionic surfactants performed better than cationic surfactants in improving FR performance. The ammonium persulfate was used as a breaker and showed effectiveness with the proposed formula. Finally, the retained permeability after 12 hours of injecting the FR was over 95%. This shows that after using this system, the productivity of the formation is minimally affected by the new FR system. This research provides the first guide on studying the impact of using different ethylene oxide chain lengths of surfactants in developing new FR systems that can perform well in a high salinity environment. Given the economic and environmental benefits of reusing produced water, this new system can save costs that were previously spent on water treatments.

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A Novel Gemini Cationic Viscoelastic Surfactant-Based Fluid for High Temperature Well Stimulation Applications

10.2118/206297-ms ◽

2021 ◽

Author(s):

Dawn Friesen ◽

Brian Seymour ◽

Aaron Sanders

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Chain Length ◽

Surfactant Concentration ◽

Gemini Surfactant ◽

Alkyl Chain ◽

Friction Reduction ◽

Fluid Viscosity ◽

Viscoelastic Surfactant ◽

The Impact

Abstract Viscoelastic surfactant (VES)-based fracturing fluids can reduce the risk of formation damage when compared with conventional polymer-based fracturing systems. However, many VES systems lose viscoelasticity rapidly under high-temperature conditions, leading to high fluid leakoff and problems in proppant placement. A gemini cationic VES-based system offering thermal stability above 250°F and its efficiency in friction reduction is presented in this paper. Rheology measurements were conducted on viscoelastic cationic gemini surfactant fluids as a function of temperature (70 – 300°F) and surfactant concentration. The length of surfactant alkyl chain was varied to investigate the impact of surfactant chain length on VES fluid viscosity at elevated temperatures. The effect of flow rate on friction reduction capability of the surfactant fluid was measured on a friction flow loop. Foam rheology measurements were conducted to evaluate the VES fluid's ability to maintain high temperature viscosity with reduced surfactant concentration. A gemini cationic surfactant was used to prepare a viscoelastic surfactant system that could maintain viscosity over 50 cP at a shear rate of 100 s−1up to at least 250°F. With this system, viscoelastic gel viscosity was maintained without degradation for over 18 hours at 250°F, and the fluid showed rapid shear recovery throughout. Decreasing the average alkyl chain length on the surfactant reduced the maximum working temperature of the resulting viscoelastic gel and showed the critical influence of surfactant structure on the resulting fluid performance. The presence of elongated, worm-like micelles in the fluid provided polymer-like friction reduction even at low surfactant concentrations, with friction reduction of over 70% observed during pumping (relative to fresh water) up to a critical Reynolds number. Energized fluids could also be formulated with the gemini surfactant to give foam fluids suitable for hydraulic fracturing or wellbore cleanouts. The resulting viscoelastic surfactant foams had viscosities over 50 cP up to at least 300°F with both nitrogen and carbon dioxide as the gas phase. The information presented in this paper is important for various field applications where thermal stability of the treatment fluid is essential. This will hopefully expand the use of VES-based systems as an alternative to conventional polymer systems in oilfield applications where a less damaging viscosified fluid system is required.

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