scholarly journals Idealized walking and running gaits minimize work

2007 ◽  
Vol 463 (2086) ◽  
pp. 2429-2446 ◽  
Author(s):  
Manoj Srinivasan ◽  
Andy Ruina
Keyword(s):  
Numerical Optimization ◽  
Phase Plane ◽  
Step Length ◽  
Metabolic Energy ◽  
One Dimensional ◽  
High Speeds ◽  
Locomotor Patterns ◽  
Positive Work ◽  
Selection Of ◽  
Trajectory Problem

Even though human legs allow a wide repertoire of movements, when people travel by foot they mostly use one of two locomotor patterns, namely, walking and running. The selection of these two gaits from the plethora of options might be because walking and running require less metabolic energy than other more unusual gaits. We addressed this possibility previously using numerical optimization of a minimal mathematical model of a biped. We had found that, for a given step-length, the two classical descriptions of walking and running, ‘inverted pendulum walking’ and ‘impulsive running’, do indeed minimize the amount of positive work required at low and high speeds respectively. Here, for the case of small step-lengths, we establish the previous results analytically. First, we simplify the two-dimensional particle trajectory problem to a one-dimensional ‘elevator’ problem. Then we use elementary geometric arguments on the resulting phase plane to show optimality of the two gaits: walking at low speeds and running at high speeds.

Selection of one-dimensional sedimentation: models for on-line use

1995 ◽  
Vol 31 (2) ◽  
pp. 193-204 ◽  
Author(s):  
Koen Grijspeerdt ◽  
Peter Vanrolleghem ◽  
Willy Verstraete
Keyword(s):  
Steady State ◽  
Selection Criteria ◽  
Data Sets ◽  
Concentration Profiles ◽  
A Posteriori ◽  
One Dimensional ◽  
On Line ◽  
Dynamic Concentration ◽  
Selection Of ◽  
Modelling Task

A comparative study of several recently proposed one-dimensional sedimentation models has been made. This has been achieved by fitting these models to steady-state and dynamic concentration profiles obtained in a down-scaled secondary decanter. The models were evaluated with several a posteriori model selection criteria. Since the purpose of the modelling task is to do on-line simulations, the calculation time was used as one of the selection criteria. Finally, the practical identifiability of the models for the available data sets was also investigated. It could be concluded that the model of Takács et al. (1991) gave the most reliable results.

A short ethnography of twenty-first century consumers: On retail rage and one-dimensionality

2021 ◽  
pp. 146954052110396
Author(s):  
Kevin P. Bingham
Keyword(s):  
Consumer Culture ◽  
Retail Trade ◽  
First Century ◽  
One Dimensional ◽  
Unique Position ◽  
Material Goods ◽  
Twenty First Century ◽  
Selection Of ◽  
Sociological Interpretation ◽  
The Way

This article begins with two central ideas – that feelings of rage appear to be on the increase in present modernity and that one of the main sources of rage is directly linked to consumer culture and the retail experience it fosters. Although retail trade allows twenty-first century individuals to spend their money on material goods and experiences which provide structure and a sense of meaning and belonging, what it also causes is ambivalence, insecurity and anxiety. These are formidable feelings that cause irritation, frustration and anger to gradually fester until it accumulates into something violent that distorts the way an individual thinks, acts and treats other people. With these points in mind, what this article provides is a thorough sociological interpretation of twenty-first century retail rage. Veering away from existing interpretations of rage by drawing on Herbert Marcuse’s analysis and image of a one-dimensional society, what this article explores is the idea that retail experiences turn people into individuals who are bound and controlled by a consumer duty. As I contend, based on my unique position as a researcher turned retail worker, it is this administered, one-dimensional kind of lifestyle that cultivates rage. To support my argument and understand more comprehensively how and why retail breeds frustration and anger, I use a selection of narrative episodes to unpack three key sources of consumer rage in the twenty-first century. These sources have been labelled instantaneity, performativity and unfulfillment.

scholarly journals Understanding Uncertainty and Risk in Management

2020 ◽  
Vol 12 (1) ◽  
pp. 12-35
Author(s):  
Piotr Jedynak ◽  
Sylwia Bąk
Keyword(s):  
Value Added ◽  
Research Process ◽  
Main Method ◽  
Proper Understanding ◽  
Organization Management ◽  
One Dimensional ◽  
Modern Management ◽  
Research Findings ◽  
Selection Of

AbstractObjective: The purpose of this text is to identify approaches to defining and subsequently reviewing the definitions of uncertainty and risk as interdisciplinary terms which are of key importance in modern management.Methodology: The work is theoretical. The main method used in the research process was the analysis of scientific literature. A one-dimensional logical classification method was also used, in order to categorize approaches to defining uncertainty and risk, satisfying the exhaustive and mutually exclusive criteria in the selection of categories of approaches.Findings: The main results of the work are: 1) identification of approaches to defining uncertainty and risk, 2) interdisciplinary review of definitions of uncertainty and risk indicating the criteria to distinguish between the two, and 3) determination of the meaning of the terms uncertainty and risk in modern management.Value Added: Considering the approaches to defining uncertainty and risk taken from many fields and disciplines of science, this text is a compendium of theoretical knowledge for the proper understanding and meaning of these concepts in management.Recommendations: The research findings can have implications for both management theory as well as the practice of organization management.

Numerical Optimization of Rotor-Bearing Systems

1989 ◽  
Author(s):  
J. P. Sadler ◽  
K. E. Rouch ◽  
A. S. Rani
Keyword(s):  
Numerical Optimization ◽  
Dynamic Performance ◽  
Optimal Designs ◽  
Design Parameters ◽  
Finite Element Program ◽  
Optimum Placement ◽  
Rotor Bearing ◽  
Element Program ◽  
Programming Techniques ◽  
Selection Of

Abstract Nonlinear programming techniques are combined with a finite element program for dynamic analysis of rotor-bearing systems. The resulting program provides the means for obtaining optimal designs for improved dynamic performance of a rotor through the automated selection of various design parameters of the rotor-bearing system. Both constrained and unconstrained optimizations are considered. Illustrative examples are presented for the case of optimum placement of critical speeds.

scholarly journals The Relationship Between Gait Symmetry and Metabolic Demand in Individuals With Unilateral Transfemoral Amputation: A Preliminary Study

2019 ◽  
Vol 184 (7-8) ◽  
pp. e281-e287
Author(s):  
Caitlin E Mahon ◽  
Benjamin J Darter ◽  
Christopher L Dearth ◽  
Brad D Hendershot
Keyword(s):  
Energy Expenditure ◽  
Case Series ◽  
Step Length ◽  
Metabolic Energy ◽  
Metabolic Power ◽  
Transfemoral Amputation ◽  
Preliminary Study ◽  
Spatial Asymmetries ◽  
Metabolic Energy Expenditure ◽  
The Relationship

Abstract Introduction Temporal-spatial symmetry allows for optimal metabolic economy in unimpaired human gait. The gait of individuals with unilateral transfemoral amputation is characterized by temporal-spatial asymmetries and greater metabolic energy expenditure. The objective of this study was to determine whether temporal-spatial asymmetries account for greater metabolic energy expenditure in individuals with unilateral transfemoral amputation. Materials and Methods The relationship between temporal-spatial gait asymmetry and metabolic economy (metabolic power normalized by walking speed) was retrospectively examined in eighteen individuals with transfemoral amputation walking at a self-selected velocity overground. Pearson’s product-moment correlations were used to assess the relationship between: (1) step time symmetry and metabolic economy and (2) step length symmetry and metabolic economy. The retrospective analysis of this data was approved by the Walter Reed National Military Medical Center Institutional Review Board and all individuals provided written consent. Additional insights on this relationship are presented through a case series describing the temporal-spatial and metabolic responses of two individuals with transfemoral amputation who completed a split-belt treadmill walking test. Results For the cohort of individuals, there was no significant relationship between metabolic economy and either step time asymmetry or step length asymmetry. However, the case series showed a positive relationship between step length asymmetry and metabolic power as participants adapted to split-belt treadmill walking. Conclusion There is mixed evidence for the relationship between temporal-spatial asymmetries and metabolic energy expenditure. This preliminary study may suggest optimal metabolic energy expenditure in individuals with transfemoral amputation occurs at an individualized level of symmetry and resultant deviations incur a metabolic penalty. The results of this study support the idea that addressing only temporal-spatial gait asymmetries in individuals with transfemoral amputation through rehabilitation may not improve metabolic economy. Nevertheless, future prospective research is necessary to confirm these results and implications for clinical practice.

scholarly journals Mobile robot path planning using an improved ant colony optimization

2018 ◽  
Vol 15 (3) ◽  
pp. 172988141877467 ◽  
Author(s):  
Khaled Akka ◽  
Farid Khaber
Keyword(s):  
Path Planning ◽  
Mobile Robot ◽  
Ant Colony Algorithm ◽  
Search Space ◽  
Step Length ◽  
Ant Colony ◽  
Dynamic Adjustment ◽  
Feedback Information ◽  
Intelligent Optimization Algorithm ◽  
Selection Of

Ant colony algorithm is an intelligent optimization algorithm that is widely used in path planning for mobile robot due to its advantages, such as good feedback information, strong robustness and better distributed computing. However, it has some problems such as the slow convergence and the prematurity. This article introduces an improved ant colony algorithm that uses a stimulating probability to help the ant in its selection of the next grid and employs new heuristic information based on the principle of unlimited step length to expand the vision field and to increase the visibility accuracy; and also the improved algorithm adopts new pheromone updating rule and dynamic adjustment of the evaporation rate to accelerate the convergence speed and to enlarge the search space. Simulation results prove that the proposed algorithm overcomes the shortcomings of the conventional algorithms.

Influence of Unsteady Effects on Air Venting in Pressure Die Casting

2001 ◽  
Vol 123 (4) ◽  
pp. 884-892 ◽  
Author(s):  
J. Herna´ndez ◽  
J. Lo´pez ◽  
F. Faura
Keyword(s):  
Method Of Characteristics ◽  
Die Casting ◽  
Operating Conditions ◽  
Filling Process ◽  
Air Mass ◽  
One Dimensional ◽  
Trapped Air ◽  
Unsteady Effects ◽  
Pressure Die Casting ◽  
Selection Of

The influence of unsteady effects on the evacuation of air through vents in pressure die casting processes is analyzed. A model is proposed which considers the air flow as one-dimensional and adiabatic, and which retains friction effects. Venting conditions for wide ranges of the relevant dimensionless parameters are analyzed for both atmospheric and vacuum venting systems. The model is solved numerically using the method of characteristics and its results are compared with those obtained for quasi-steady models. It is shown that wide ranges of operating conditions can exist in practical situations, for which unsteady effects, neglected in previous models, are important and must be taken into account to determine the air mass entrapped at the end of the filling process. The selection of parameters which will reduce the amount of trapped air and thus porosity in manufactured parts is also discussed.

Sign in / Sign up

Export Citation Format

Share Document