Optimal Estimation of Anthropometric Parameters for Quantifying Multisegment Trunk Kinetics

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Alireza Noamani ◽  
Albert H. Vette ◽  
Richard Preuss ◽  
Milos R. Popovic ◽  
Hossein Rouhani
Keyword(s):  
Inverse Dynamics ◽  
Center Of Pressure ◽  
Initial Guess ◽  
Joint Moment ◽  
Body Motion ◽  
Top Down ◽  
Joint Moments ◽  
Anthropometric Parameters ◽  
Bottom Up ◽  
The Difference

Kinetics assessment of the human head-arms-trunk (HAT) complex via a multisegment model is a useful tool for objective clinical evaluation of several pathological conditions. Inaccuracies in body segment parameters (BSPs) are a major source of uncertainty in the estimation of the joint moments associated with the multisegment HAT. Given the large intersubject variability, there is currently no comprehensive database for the estimation of BSPs for the HAT. We propose a nonlinear, multistep, optimization-based, noninvasive method for estimating individual-specific BSPs and calculating joint moments in a multisegment HAT model. Eleven nondisabled individuals participated in a trunk-bending experiment and their body motion was recorded using cameras and a force plate. A seven-segment model of the HAT was reconstructed for each participant. An initial guess of the BSPs was obtained by individual-specific scaling of the BSPs calculated from the male visible human (MVH) images. The intersegmental moments were calculated using both bottom-up and top-down inverse dynamics approaches. Our proposed method adjusted the scaled BSPs and center of pressure (COP) offsets to estimate optimal individual-specific BSPs that minimize the difference between the moments obtained by top-down and bottom-up inverse dynamics approaches. Our results indicate that the proposed method reduced the error in the net joint moment estimation (defined as the difference between the net joint moment calculated via bottom-up and top-down approaches) by 79.3% (median among participants). Our proposed method enables an optimized estimation of individual-specific BSPs and, consequently, a less erroneous assessment of the three-dimensional (3D) kinetics of a multisegment HAT model.

Influence of Center of Pressure Estimation Errors on 3D Inverse Dynamics Solutions During Gait at Different Velocities

2013 ◽  
Vol 29 (6) ◽  
pp. 790-797 ◽  
Author(s):  
Franklin Camargo-Junior ◽  
Marko Ackermann ◽  
Jefferson F. Loss ◽  
Isabel C.N. Sacco
Keyword(s):  
Reference Frames ◽  
Inverse Dynamics ◽  
Center Of Pressure ◽  
Joint Moment ◽  
Gait Velocity ◽  
Joint Moments ◽  
Absolute Moment ◽  
Estimation Errors ◽  
Knee Abduction ◽  
The Absolute

The aim of this study was to investigate the effect of errors in the location of the center of pressure (5 and 10 mm) on lower limb joint moment uncertainties at different gait velocities (1.0, 1.5, and 2.0 m/s). Our hypotheses were that the absolute joint moment uncertainties would be gradually reduced from distal to proximal joints and from higher to lower velocities. Joint moments of five healthy young adults were calculated by inverse dynamics using the bottom-up approach, depending on which estimate the uncertainty propagated. Results indicated that there is a linear relationship between errors in center of pressure and joint moment uncertainties. The absolute moment peak uncertainties expressed on the anatomic reference frames decreased from distal to proximal joints, confirming our first hypothesis, except for the abduction moments. There was an increase in moment uncertainty (up to 0.04 N m/kg for the 10 mm error in the center of pressure) from the lower to higher gait velocity, confirming our second hypothesis, although, once again, not for hip or knee abduction. Finally, depending on the plane of movement and the joint, relative uncertainties experienced variation (between 5 and 31%), and the knee joint moments were the most affected.

scholarly journals Bottom-up versus top-down factor investing: an alpha forecasting perspective

2020 ◽  
Author(s):  
Martin Zurek ◽  
Lars Heinrich
Keyword(s):  
Interaction Effects ◽  
Informational Content ◽  
Firm Characteristics ◽  
Recent Discussion ◽  
High Concentration ◽  
Top Down ◽  
Bottom Up ◽  
Factor Investing ◽  
Significant Performance ◽  
The Difference

AbstractIn a recent discussion about efficient ways to combine multiple firm characteristics into a multifactor portfolio, a distinction was made between the bottom-up and top-down approach. Both approaches integrate characteristics with equal weights and ignore interaction effects from differences in informational content and correlations between the firm characteristics. The authors complement the bottom-up approach for the missing interaction effects by implementing a linear alpha forecasting framework. Bottom-up versus top-down factor investing is typically discussed using the assumption that all characteristics are equally priced, but the pricing impact of different firm characteristics can vary tremendously. The alpha forecasting perspective provides a theoretical motivation for factor investing and helps to compare the bottom-up and top-down approach with regard to the difference of informational content and interaction effects between firm characteristics. Taking into account the difference in informational content between firm characteristics leads to significant performance improvement in factor models with a high concentration of informational content. Equally weighted characteristics result in related performance irrespective of whether the bottom-up or top-down approach is applied.

scholarly journals Trends and inter-annual variability of methane emissions derived from 1979-1993 global CTM simulations

2003 ◽  
Vol 3 (1) ◽  
pp. 73-88 ◽  
Author(s):  
F. Dentener ◽  
M. van Weele ◽  
M. Krol ◽  
S. Houweling ◽  
P. van Velthoven
Keyword(s):  
Transport Model ◽  
Meteorological Data ◽  
Stratospheric Ozone ◽  
Methane Emissions ◽  
Anthropogenic Emission ◽  
Top Down ◽  
Bottom Up ◽  
Annual Variability ◽  
The Difference ◽  
Ozone Precursor

Abstract. The trend and interannual variability of methane sources are derived from multi-annual simulations of tropospheric photochemistry using a 3-D global chemistry-transport model. Our semi-inverse analysis uses the fifteen years (1979--1993) re-analysis of ECMWF meteorological data and annually varying emissions including photo-chemistry, in conjunction with observed CH4 concentration distributions and trends derived from the NOAA-CMDL surface stations. Dividing the world in four zonal regions (45--90 N, 0--45 N, 0--45 S, 45--90 S) we find good agreement in each region between (top-down) calculated emission trends from model simulations and (bottom-up) estimated anthropogenic emission trends based on the EDGAR global anthropogenic emission database, which amounts for the period 1979--1993 2.7 Tg CH4 yr-1. Also the top-down determined total global methane emission compares well with the total of the bottom-up estimates. We use the difference between the bottom-up and top-down determined emission trends to calculate residual emissions. These residual emissions represent the inter-annual variability of the methane emissions. Simulations have been performed in which the year-to-year meteorology, the emissions of ozone precursor gases, and the stratospheric ozone column distribution are either varied, or kept constant. In studies of methane trends it is most important to include the trends and variability of the oxidant fields. The analyses reveals that the variability of the emissions is of the order of 8Tg CH4 yr-1, and likely related to wetland emissions and/or biomass burning.

scholarly journals The effect of stride length on lower extremity joint kinetics at various gait speeds

2018 ◽  
Author(s):  
Robert L. McGrath ◽  
Melissa L. Ziegler ◽  
Margaret Pires-Fernandes ◽  
Brian A. Knarr ◽  
Jill S. Higginson ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Gait Speed ◽  
Stride Length ◽  
Inverse Dynamics ◽  
Sagittal Plane ◽  
Gait Training ◽  
Joint Moment ◽  
Joint Moments ◽  
Joint Kinetics ◽  
Trailing Limb Angle

AbstractRobot-assisted training is a promising tool under development for improving walking function based on repetitive goal-oriented task practice. The challenges in developing the controllers for gait training devices that promote desired changes in gait is complicated by the limited understanding of the human response to robotic input. A possible method of controller formulation can be based on the principle of bio-inspiration, where a robot is controlled to apply the change in joint moment applied by human subjects when they achieve a gait feature of interest. However, it is currently unclear how lower extremity joint moments are modulated by even basic gaitspatio-temporal parameters.In this study, we investigated how sagittal plane joint moments are affected by a factorial modulation of two important gait parameters: gait speed and stride length. We present the findings obtained from 20 healthy control subjects walking at various treadmill-imposed speeds and instructed to modulate stride length utilizing real-time visual feedback. Implementing a continuum analysis of inverse-dynamics derived joint moment profiles, we extracted the effects of gait speed and stride length on joint moment throughout the gait cycle. Moreover, we utilized a torque pulse approximation analysis to determine the timing and amplitude of torque pulses that approximate the difference in joint moment profiles between stride length conditions, at all gait speed conditions.Our results show that gait speed has a significant effect on the moment profiles in all joints considered, while stride length has more localized effects, with the main effect observed on the knee moment during stance, and smaller effects observed for the hip joint moment during swing and ankle moment during the loading response. Moreover, our study demonstrated that trailing limb angle, a parameter of interest in programs targeting propulsion at push-off, was significantly correlated with stride length. As such, our study has generated assistance strategies based on pulses of torque suitable for implementation via a wearable exoskeleton with the objective of modulating stride length, and other correlated variables such as trailing limb angle.

Bottom-up rather than top-down: evidence from Middle Eastern and North African educational institutions

2020 ◽  
Vol 32 (4) ◽  
pp. 671-690
Author(s):  
Osama Mah'd
Keyword(s):  
North Africa ◽  
Middle Eastern ◽  
Educational Institutions ◽  
North African ◽  
Top Down ◽  
Bottom Up ◽  
Managerial Performance ◽  
Content Type ◽  
Significant Difference ◽  
The Difference

PurposeEducational institutions in the Middle East and North Africa (MENA) are striving for better resource management and finance. The bottom-up budgeting approach plays an important role in motivating executives' performance. The main aim of this paper is to discover whether there is a significant difference between bottom-up and a top-down approaches to budgeting in terms of managers' performance.Design/methodology/approachQuestionnaires were distributed to 453 university executives in 21 MENA educational institutions. The Kruskal–Wallis test was utilized to test the difference between the three groups (bottom-up, top-down and consultative approaches). Further analysis was conducted to test the difference between the two groups using the Mann–Whitney test.FindingsThe results show that there is a significant difference between a bottom-up and top-down approach in terms of managerial performance. The study's findings indicate that the bottom-up approach to budgeting leads to higher performance indicators than a top-down approach to budgeting.Originality/valueThe current study contributes to the research as it increases awareness of budgeting approaches that are used in higher education institutions, specifically in terms of the effect of these differences on executives' performance.

A Conceptual Tool Kit

2021 ◽  
pp. 31-86
Author(s):  
James V. Wertsch
Keyword(s):  
National Identity ◽  
Narrative Analysis ◽  
Empirical Studies ◽  
Top Down ◽  
Conceptual Tool ◽  
Bottom Up ◽  
National Memory ◽  
Narrative Truth ◽  
Individual Memory ◽  
The Difference

The chapter begins with a section on methods and forms of evidence that outlines the difference between top-down and bottom-up analyses of national memory and notes that the latter will be given more emphasis in this book than is the case in many studies of national identity and memory. The section also argues that by understanding how narrative tools can “co-author” individuals’ speaking and thinking, it is possible to avoid misguided notions of “primordialism” that are part of the rhetorical claims of nationalists. The next section examines the sense in which national memory is memory and argues for the need to focus on remembering individuals as members of groups. This involves a review of ideas from figures such as Maurice Halbwachs and Frederic Bartlett on collective and individual memory. This is followed by a section on “Flashbulb Memories as Memory in the Group,” which uses a body of literature in psychology to develop a conceptually grounded notion of national memory that includes the observation that Bartlett’s notion of schema underpins much of the entire discussion. The next section, on “symbolic mediation,” reviews the origins of this idea in the writings of several European and Russian scholars and goes into the case of literacy as an illustration as outlined in empirical studies by Luria and Vygotsky. It then poses an analogous line of reasoning for narratives as symbolic mediation. This includes a discussion of the “inner logic” of narrative tools, “narrative truth,” and two levels of narrative analysis (“specific narratives” and “narrative templates”).

scholarly journals Phytoplankton competition during the spring bloom in four Plankton Functional Type Models

2012 ◽  
Vol 9 (12) ◽  
pp. 18083-18129 ◽  
Author(s):  
T. Hashioka ◽  
M. Vogt ◽  
Y. Yamanaka ◽  
C. Le Quéré ◽  
E. T. Buitenhuis ◽  
...  
Keyword(s):  
Phytoplankton Biomass ◽  
Spring Bloom ◽  
Marine Ecosystems ◽  
Grazing Pressure ◽  
Similar Degree ◽  
Functional Type ◽  
Top Down ◽  
Bottom Up ◽  
The North ◽  
The Difference

Abstract. We investigated the mechanisms of phytoplankton competition during the spring bloom, one of the most dramatic seasonal events in lower-trophic level ecosystems, in four state-of-the-art Plankton Functional Type (PFTs) models: PISCES, NEMURO, PlankTOM5 and CCSM-BEC. In particular, we investigated the relative importance of different ecophysiological processes on the determination of the community structure, focusing both on the bottom-up and the top-down controls. The models reasonably reproduced the observed global distribution and seasonal variation of phytoplankton biomass. The fraction of diatoms with respect to the total phytoplankton biomass increases with the magnitude of the spring bloom in all models. However, the governing mechanisms differ between models, despite the fact that current PFT models represent ecophysiological processes using the same types of parameterizations. The increasing trend in the percentage of diatoms with increasing bloom magnitude is mainly caused by a stronger nutrient dependence of photosynthesis for diatoms compared to nanophytoplankton (bottom-up control). The difference in the maximum photosynthesis rate plays an important role in NEMURO and PlankTOM5 and determines the absolute values of the percentage of diatoms during the bloom. In CCSM-BEC, the light dependency of photosynthesis plays an important role in the North Atlantic and the Southern Ocean. The grazing pressure by zooplankton (top-down control), however, strongly contributes to the dominance of diatoms in PISCES and CCSM-BEC. The regional differences in the percentage of diatoms in PlankTOM5 are mainly determined by top-down control. These differences in the mechanisms suggest that the response of marine ecosystems to climate change could significantly differ among models, even if the present-day ecosystem is reproduced to a similar degree of confidence. For further understanding of plankton competition and for the prediction of future change in marine ecosystems, it is important to understand the relative differences in each physiological rate and life history rate in the bottom-up and the top-down controls between PFTs.

Leg Dominance May Not Be a Predictor of Asymmetry in Peak Joint Moments and Ground Reaction Forces During Sit-to-Stand Movements

2014 ◽  
Vol 30 (1) ◽  
pp. 179-183 ◽  
Author(s):  
Jonathon S. Schofield ◽  
Eric Parent ◽  
Justin Lewicke ◽  
Jason P. Carey ◽  
Marwan El-Rich ◽  
...  
Keyword(s):  
Lower Limb ◽  
Inverse Dynamics ◽  
Bilateral Symmetry ◽  
Joint Moment ◽  
Ground Reaction Forces ◽  
Joint Moments ◽  
Sit To Stand ◽  
Reaction Forces ◽  
Three Body ◽  
Leg Dominance

Sit-to-stand transfer is a common prerequisite for many daily tasks. Literature often assumes symmetric behavior across the left and right side. Although this assumption of bilateral symmetry is prominent, few studies have validated this supposition. This pilot study uniquely quantifies peak joint moments and ground reaction forces (GRFs), using a Euclidian norm approach, to evaluate bilateral symmetry and its relation to lower limb motor-dominance during sit to stand in ten healthy males. Peak joint moments and GRFs were determined using a motion capture system and inverse dynamics. This analysis included joint moment contributions from all three body planes (sagittal, coronal, and axial) as well as vertical and shearing GRFs. A paired, one-tailedttest was used, suggesting asymmetrical joint moment development in all three lower extremity joints as well as GRFs (P< .05). Furthermore, using an unpaired two-tailedttest, asymmetry developed during these movements does not appear to be predictable by participants’ lower limb motor-dominance (P< .025). Consequently, when evaluating sit-to-stand it is suggested the effects of asymmetry be considered in the interpretation of data. The absence of a relationship between dominance and asymmetry prevents the suggestion that one side can be tested to infer behavior of the contralateral.

COMPARING METHODS FOR 3D INVERSE DYNAMICS ANALYSIS OF SQUAT LIFTING USING A FULL BODY LINKED SEGMENT MODEL

2020 ◽  
Vol 20 (03) ◽  
pp. 2050004
Author(s):  
IMAN VAHDAT ◽  
MOHAMAD PARNIANPOUR ◽  
FARHAD TABATABAI GHOMSHEH ◽  
NIMA TOOSIZADEH ◽  
ALI TANBAKOOSAZ
Keyword(s):  
Inverse Dynamics ◽  
Three Dimensional ◽  
Dynamics Analysis ◽  
Joint Moments ◽  
Bottom Up ◽  
Mean Values ◽  
Segment Model ◽  
Squat Lifting ◽  
Inverse Dynamics Analysis ◽  
Full Body

Objective: The main objective of this study was to assess the accuracy of bottom-up solution for three-dimensional (3D) inverse dynamics analysis of squat lifting using a 3D full body linked segment model. Least squares solution was used in this study as reference for assessment of the accuracy of bottom-up solution. Findings of this study may clarify how much the bottom-up solution can be reliable for calculating the joint kinetics in 3D inverse dynamics problems. Methods: Ten healthy males volunteered to perform squat lifting of a box with a load of one-tenth of their body weights. The joint moments were calculated using 110 reflective passive markers (46 anatomical markers and 64 tracking markers) and a 3D full body linked segment model. Ground reaction forces and kinematics data were recorded using a Vicon system with two parallel Kistler force plates. Three-dimensional Newton–Euler equations of motion with bottom-up and least squares solutions were applied to calculate joint moments. The peak and mean values of the joint moments were determined to check the quantitative differences as well as the time-to-peak value of the moment curves was determined to check the temporal differences between the two inverse dynamics solutions. Results: Significant differences (all [Formula: see text]-values [Formula: see text]) between the two inverse dynamics solutions were detected for the peak values of the hip (right and left sides) and L5–S1 joint moments in the lateral anatomical direction as well significant differences (all [Formula: see text]-values [Formula: see text]) were detected for the peak and mean values of the L5–S1 joint moment in all anatomical directions. Moreover, small differences (all RMSEs [Formula: see text]%) were detected between the two inverse dynamic solutions for the calculated lower body joint moments. Conclusions: The findings of this study clarified the disadvantages of the straightforward solutions and demonstrated that the bottom-up solution may not be accurate for more distal measures from the force plate (for hip and S1–L5) but it may be accurate for more proximal joints (ankle and knee) in 3D inverse dynamics analysis.

scholarly journals Trends and inter-annual variability of methane emissions derived from 1979-1993 global CTM simulations

2002 ◽  
Vol 2 (2) ◽  
pp. 249-287 ◽  
Author(s):  
F. Dentener ◽  
M. van Weele ◽  
M. Krol ◽  
S. Houweling ◽  
P. van Velthoven
Keyword(s):  
Transport Model ◽  
Meteorological Data ◽  
Stratospheric Ozone ◽  
Regional Scale ◽  
Methane Emissions ◽  
Anthropogenic Emission ◽  
Top Down ◽  
Bottom Up ◽  
Annual Variability ◽  
The Difference

Abstract. The trend and interannual variability of methane sources are derived from multi-annual simulations of tropospheric photochemistry using a 3D global chemistry-transport model. Our semi-inverse analysis uses the fifteen years (1979 -1993) re-analysis of ECMWF meteorological data and annually varying including photo-chemistry, in conjunction with observed CH4 concentration distributions and trends derived from the NOAA-CMDL surface stations. Dividing the world in four zonal regions, (45-90 N, 0-45 N, 0-45 S; 45-90 S) we find good agreement in each region between (top-down) calculated emission trends from model simulations and (bottom-up) estimated anthropogenic emission trends based on the EDGAR global anthropogenic emission database, which amounts for the period 1979 -1993 2.7 Tg CH4 yr -1. Also the top-down determined total global methane emission compares well with the total of the bottom-up estimates. We use the difference between the bottom-up and top-down determined emission trends to calculate residual emissions. These residual emissions represent the inter-annual variability of the methane emissions. Simulations have been performed in which the year-to-year meteorology, the emissions of ozone precursor gases, and the stratospheric ozone column distribution are either varied, or kept constant. The analyses reveals that the variability of the emissions is of the order of 8 Tg CH4 yr -1, and most likely related to mid- and low-latitude wetland emissions and/or biomass burning. Indeed, a weak correlation is found between the residual emissions and regional scale temperatures.

Sign in / Sign up

Export Citation Format

Share Document