Removing energy with an exoskeleton reduces the metabolic cost of walking

Science ◽  
2021 ◽  
Vol 372 (6545) ◽  
pp. 957-960
Author(s):  
Michael Shepertycky ◽  
Sarah Burton ◽  
Andrew Dickson ◽  
Yan-Fei Liu ◽  
Qingguo Li
Keyword(s):  
Kinetic Energy ◽  
Cost Reduction ◽  
Gait Cycle ◽  
Electrical Power ◽  
Metabolic Cost ◽  
Healthy Male ◽  
Efficient Manner ◽  
Highly Efficient ◽  
Metabolic Expenditure

Evolutionary pressures have led humans to walk in a highly efficient manner that conserves energy, making it difficult for exoskeletons to reduce the metabolic cost of walking. Despite the challenge, some exoskeletons have managed to lessen the metabolic expenditure of walking, either by adding or storing and returning energy. We show that the use of an exoskeleton that strategically removes kinetic energy during the swing period of the gait cycle reduces the metabolic cost of walking by 2.5 ± 0.8% for healthy male users while converting the removed energy into 0.25 ± 0.02 watts of electrical power. By comparing two loading profiles, we demonstrate that the timing and magnitude of energy removal are vital for successful metabolic cost reduction.

scholarly journals A secure and highly efficient first-order masking scheme for AES linear operations

Cybersecurity ◽  
2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jingdian Ming ◽  
Yongbin Zhou ◽  
Huizhong Li ◽  
Qian Zhang
Keyword(s):  
Cost Reduction ◽  
Provable Security ◽  
State Of The Art ◽  
Side Channel ◽  
First Order ◽  
Highly Efficient ◽  
Non Linear ◽  
Device Independence ◽  
Practical Implications ◽  
Provably Secure

AbstractDue to its provable security and remarkable device-independence, masking has been widely accepted as a noteworthy algorithmic-level countermeasure against side-channel attacks. However, relatively high cost of masking severely limits its applicability. Considering the high tackling complexity of non-linear operations, most masked AES implementations focus on the security and cost reduction of masked S-boxes. In this paper, we focus on linear operations, which seems to be underestimated, on the contrary. Specifically, we discover some security flaws and redundant processes in popular first-order masked AES linear operations, and pinpoint the underlying root causes. Then we propose a provably secure and highly efficient masking scheme for AES linear operations. In order to show its practical implications, we replace the linear operations of state-of-the-art first-order AES masking schemes with our proposal, while keeping their original non-linear operations unchanged. We implement four newly combined masking schemes on an Intel Core i7-4790 CPU, and the results show they are roughly 20% faster than those original ones. Then we select one masked implementation named RSMv2 due to its popularity, and investigate its security and efficiency on an AVR ATMega163 processor and four different FPGA devices. The results show that no exploitable first-order side-channel leakages are detected. Moreover, compared with original masked AES implementations, our combined approach is nearly 25% faster on the AVR processor, and at least 70% more efficient on four FPGA devices.

scholarly journals ATM: Promoter of Metabolic “Cost” Reduction and “Savings” Usage during Hypoxia through mTORC1 Regulation

2010 ◽  
Vol 40 (4) ◽  
pp. 501-502 ◽  
Author(s):  
Sang Gyun Kim ◽  
Andrew Y. Choo ◽  
John Blenis
Keyword(s):  
Cost Reduction ◽  
Metabolic Cost

scholarly journals Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

1999 ◽  
Vol 86 (1) ◽  
pp. 383-390 ◽  
Author(s):  
Timothy M. Griffin ◽  
Neil A. Tolani ◽  
Rodger Kram
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Gravitational Potential Energy ◽  
Reduced Gravity

Walking humans conserve mechanical and, presumably, metabolic energy with an inverted pendulum-like exchange of gravitational potential energy and horizontal kinetic energy. Walking in simulated reduced gravity involves a relatively high metabolic cost, suggesting that the inverted-pendulum mechanism is disrupted because of a mismatch of potential and kinetic energy. We tested this hypothesis by measuring the fluctuations and exchange of mechanical energy of the center of mass at different combinations of velocity and simulated reduced gravity. Subjects walked with smaller fluctuations in horizontal velocity in lower gravity, such that the ratio of horizontal kinetic to gravitational potential energy fluctuations remained constant over a fourfold change in gravity. The amount of exchange, or percent recovery, at 1.00 m/s was not significantly different at 1.00, 0.75, and 0.50 G (average 64.4%), although it decreased to 48% at 0.25 G. As a result, the amount of work performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

scholarly journals Stereocontrolled total synthesis of (+)-vinblastine

2003 ◽  
Vol 75 (1) ◽  
pp. 29-38 ◽  
Author(s):  
Satoshi Yokoshima ◽  
T. Ueda ◽  
S. Kobayashi ◽  
A. Sato ◽  
Takeshi Kuboyama ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Coupling Reaction ◽  
Radical Cyclization ◽  
Critical Coupling ◽  
Efficient Manner ◽  
Complete Control ◽  
Highly Efficient ◽  
Indole Synthesis

Stereocontrolled total synthesis of (+)-vinblastine (1) has been achieved using a novel radical-mediated indole synthesis developed in our laboratories. The isothiocyanate 18, prepared readily from quinoline 17, underwent a facile addition of the malonate anion to give 19. The o-alkenylthioanilide 19 was then converted to indole 20 by radical cyclization and protection. (−)-Vindoline (2) was prepared from this key intermediate 20 in a highly efficient manner. The indole core of the 11-membered intermediate 3 was constructed similarly from quinoline. The critical coupling reaction between 2 and the chloroindolenine derived from 3 proceeded with complete control of stereochemistry to give the desired product 66 in 97 % yield, which could be successfully converted to (+)-vinblastine (1).

scholarly journals Energy expenditure of trans-tibial amputees during ambulation at self-selected pace

1994 ◽  
Vol 18 (2) ◽  
pp. 84-91 ◽  
Author(s):  
R. S. Gailey ◽  
M. A. Wenger ◽  
M. Raya ◽  
N. Kirk ◽  
K. Erbs ◽  
...  
Keyword(s):  
Heart Rate ◽  
Steady State ◽  
Energy Expenditure ◽  
Energy Cost ◽  
Metabolic Cost ◽  
The Self ◽  
Healthy Male ◽  
Subject Pool

The purpose of this investigation was two-fold: 1) to compare the metabolic cost (VO2), heart rate (HR), and self-selected speed of ambulation of trans-tibial amputees (TTAs) with those of non-amputee subjects; and 2) to determine whether a correlation exists between either stump length or prosthesis mass and the energy cost of ambulation at the self-selected ambulation pace of TTAs. Subjects were thirty-nine healthy male non-vascular TTAs between the ages of 22 and 75 years (mean ± sd = 47 ± 16). All had regularly used their prosthesis for longer than six months and were independent of assistive ambulation devices. Twenty-one healthy non-amputee males aged 27–47 years (31 ± 6) served as controls. Subjects ambulated at a self-selected pace over an indoor course, with steady-state VO2, HR, and ambulation speed averaged across minutes seven, eight and nine of walking. Results showed that HR and VO2 for TTAs were 16% greater, and the ambulation pace 11% slower than the non-amputee controls. Significant correlations were not observed between stump length or prosthesis mass and the energy cost of ambulation. However, when the TTA subject pool was stratified on the basis of long and short stump length, the former sustained significantly lower steady-state VO2 and HR than the latter while walking at comparable pace. These data indicate that stump length may influence the metabolic cost of ambulation in TTAs.

Activity Patterns and Energetics of the Moth, Hyalophora Cecropia

1970 ◽  
Vol 53 (3) ◽  
pp. 611-627
Author(s):  
JAMES L. HANEGAN ◽  
JAMES EDWARD HEATH
Keyword(s):  
Activity Patterns ◽  
Balance Sheet ◽  
Adult Life ◽  
Metabolic Cost ◽  
Hormonal Control ◽  
Energetic Cost ◽  
Air Temperatures ◽  
Hyalophora Cecropia ◽  
Metabolic Expenditure ◽  
Maintenance Metabolism

1. The time of activity and the duration of active periods (flight) of moths of the species Hyalophora cecropia has been determined by monitoring thoracic temperature. 2. The metabolic cost of flight per day and per adult life has been determined directly by measuring O2 consumption and indirectly by analysis of cooling curves of individual moths. 3. An energy balance sheet has been derived which gives the metabolic cost of flight and maintenance (during torpor) over the insect's adult life. 4. The metabolic stores mobilized for daily activity appear to be fixed and independent of air temperature. This mobilization of fat stores may be under hormonal control. 5. It is metabolically more expensive for moths to be active at low air temperatures. The number and duration of active periods at low air temperatures is reduced, but, the metabolic expenditure for activity is equal to that of animals held at higher air temperatures. 6. Females have a smaller total energy reserve than males. The number of active periods per day is not significantly different between the sexes at any given temperature, but in females the active periods are significantly shorter in duration. 7. The flight speed has been determined, and estimates of the flight range per day and per adult life have been calculated. 8. The ecology of H. cecropia has been discussed with respect to the timing and duration of active periods, the range and speed of flight, and the energetic cost of flight and maintenance metabolism.

Develop a Flexible Regenerative Exoskeleton to Assist Walking

2018 ◽  
Author(s):  
Longhan Xie ◽  
Xiaodong Li
Keyword(s):  
Kinetic Energy ◽  
Human Body ◽  
Lower Limb ◽  
Metabolic Cost ◽  
Lower Limbs ◽  
Metabolic Energy ◽  
Lower Limb Exoskeleton ◽  
Negative Work ◽  
Lower Limb Muscles ◽  
Assisting Device

During walking, human lower limbs accelerate and decelerate alternately, during which period the human body does positive and negative work, respectively. Muscles provide power to all motions and cost metabolic energy both in accelerating and decelerating the lower limbs. In this work, the lower-limb biomechanics of walking was analyzed and it revealed that if the negative work performed during deceleration can be harnessed using some assisting device to then assist the acceleration movement of the lower limb, the total metabolic cost of the human body during walking can be reduced. A flexible lower-limb exoskeleton was then proposed; it is worn in parallel to the lower limbs to assist human walking without consuming external power. The flexible exoskeleton consists of elastic and damping components that are similar to physiological structure of a human lower limb. When worn on the lower limb, the exoskeleton can partly replace the function of the lower limb muscles and scavenge kinetic energy during lower limb deceleration to assist the acceleration movement. Besides, the generator in the exoskeleton, serving as a damping component, can harvest kinetic energy to produce electricity. A prototype of the flexible exoskeleton was developed, and experiments were carried out to validate the analysis. The experiments showed that the exoskeleton could reduce the metabolic cost by 3.12% at the walking speed of 4.5 km/h.

Numerical Simulation of Convective-Radiative Heat Transfer in a Solar Chimney

2014 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Gianluca Tartaglione
Keyword(s):  
Kinetic Energy ◽  
Electrical Power ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Three Dimensional Model ◽  
Solar Chimney ◽  
Ansys Fluent ◽  
Heating And Cooling ◽  
Air Stream

Solar chimney is a new method to produce electrical power. It employs solar radiation to raise the temperature of the air and the buoyancy of warm air to accelerate the air stream flowing through the system. By converting thermal energy into the kinetic energy of air movement, solar chimneys have a number of different applications such as ventilation, passive solar heating and cooling of buildings, solar-energy drying, and power generation. Moreover, it can be employed as an energy conversion system from solar to mechanical. A component, such as a turbine or piezoelectric component, set in the path of the air current, converts the kinetic energy of the flowing air into electricity. In this paper, a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The chimney is 4.0 m high, 1.5 m wide whereas the thickness is 0.20 m for the vertical parallel walls configuration and at the inlet 0.34 m and at the outlet 0.20 m for convergent configuration. The chimney consists of a converging channel with one vertical wall and one inclined of 2°. The analysis is carried out on a three-dimensional model in airflow and the governing equations are given in terms of k-ε turbulence model. The problem is solved by means of the commercial code Ansys-Fluent. The numerical analysis was intended to examine the effect of the solar chimney’s height and spacing. Further, comparison between radiative and non-radiative model is examined and discussed. Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles for a uniform wall heat flux on the vertical wall equal to 300 W/m2. Thermal and fluid dynamics behaviors are evaluated in order to have some indications to improve the energy efficiency of the system.

Optimizing the Electrical Power in an Energy Harvesting System

2015 ◽  
Vol 25 (12) ◽  
pp. 1550171 ◽  
Author(s):  
Mattia Coccolo ◽  
Grzegorz Litak ◽  
Jesús M. Seoane ◽  
Miguel A. F. Sanjuán
Keyword(s):  
Energy Harvesting ◽  
Kinetic Energy ◽  
High Frequency ◽  
Energy Harvester ◽  
Electrical Power ◽  
Low Frequency ◽  
Electrical Energy ◽  
Resonance Phenomenon ◽  
Vibrational Resonance ◽  
Energy Harvesting System

In this paper, we study the vibrational resonance (VR) phenomenon as a useful mechanism for energy harvesting purposes. A system, driven by a low frequency and a high frequency forcing, can give birth to the vibrational resonance phenomenon, when the two forcing amplitudes resonate and a maximum in amplitude is reached. We apply this idea to a bistable oscillator that can convert environmental kinetic energy into electrical energy, that is, an energy harvester. Normally, the VR phenomenon is studied in terms of the forcing amplitudes or of the frequencies, that are not always easy to adjust and change. Here, we study the VR generated by tuning another parameter that is possible to manipulate when the forcing values depend on the environmental conditions. We have investigated the dependence of the maximum response due to the VR for small and large variations in the forcing amplitudes and frequencies. Besides, we have plotted color coded figures in the space of the two forcing amplitudes, in which it is possible to appreciate different patterns in the electrical power generated by the system. These patterns provide useful information on the forcing amplitudes in order to produce the optimal electrical power.

Picking Vanished Proteins from the Void: How to Collect and Ship/Share Extremely Dilute Proteins in a Reproducible and Highly Efficient Manner

2014 ◽  
Vol 86 (15) ◽  
pp. 7421-7427 ◽  
Author(s):  
Florian Bonn ◽  
Jürgen Bartel ◽  
Knut Büttner ◽  
Michael Hecker ◽  
Andreas Otto ◽  
...  
Keyword(s):  
Efficient Manner ◽  
Highly Efficient
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