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eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Osman Darici ◽  
Arthur D Kuo

The simple task of walking up a sidewalk curb is actually a dynamic prediction task. The curb is a disturbance that could cause a loss of momentum if not anticipated and compensated for. It might be possible to adjust momentum sufficiently to ensure undisturbed time of arrival, but there are infinite possible ways to do so. Much of steady, level gait is determined by energy economy, which should be at least as important with terrain disturbances. It is, however, unknown whether economy also governs walking up a curb, and whether anticipation helps. Here we show that humans compensate with an anticipatory pattern of forward speed adjustments, predicted by a criterion of minimizing mechanical energy input. The strategy is mechanistically predicted by optimal control for a simple model of bipedal walking dynamics, with each leg's push-off work as input. Optimization predicts a tri-phasic trajectory of speed (and thus momentum) adjustments, including an anticipatory phase. In experiment, human subjects ascend an artificial curb with the predicted tri-phasic trajectory, which approximately conserves overall walking speed relative to undisturbed flat ground. The trajectory involves speeding up in a few steps before the curb, losing considerable momentum from ascending it, and then regaining speed in a few steps thereafter. Descending the curb entails a nearly opposite, but still anticipatory, speed fluctuation trajectory, in agreement with model predictions that speed fluctuation amplitudes should scale linearly with curb height. The fluctuation amplitudes also decrease slightly with faster average speeds, also as predicted by model. Humans can reason about the dynamics of walking to plan anticipatory and economical control, even with a sidewalk curb in the way.


2022 ◽  
Vol 153 ◽  
pp. 111739
Author(s):  
Ekaterina Rhodes ◽  
Aaron Hoyle ◽  
Madeleine McPherson ◽  
Kira Craig

2021 ◽  
Author(s):  
Lin Li ◽  
Biswanath Das ◽  
Ahibur Rahaman ◽  
Andrey Shatskiy ◽  
Fei Ye ◽  
...  

Electrochemical water splitting constitutes one of the most promising strategies for converting water into hydrogen-based fuels, and this technology is predicted to play a key role in our transition towards a carbon-neutral energy economy. To enable the design of cost-effective electrolysis cells based on this technology, new and more efficient anodes with augmented water splitting activity and stability will be required. Herein, we report an active molecular Ru-based catalyst for electrochemically-driven water oxidation and two simple methods for preparing anodes by attaching this catalyst onto multi-walled carbon nanotubes. The anodes modified with the molecular catalyst were characterized by a broad toolbox of microscopy and spectroscope techniques, and interestingly no RuO2 formation was detected during electrocatalysis over 4 h. These results demonstrate that the herein presented strategy can be used to prepare anodes that rival the performance of state-of-the-art metal oxide anodes.


Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 16
Author(s):  
Tomas Karpavicius ◽  
Tomas Balezentis

Energy policy affects the functioning of the economic and financial systems of countries worldwide. This paper provides a theoretical overview of the economy–energy nexus and discusses the particular cases of the energy policy dynamics amid the sustainability goals. This paper integrates multiple perspectives on the energy–economy nexus, with a particular focus on the energy trilemma, 4As of energy security and PESTEL approach. This allows the development of a comprehensive framework for the analysis of energy security and the sustainability interaction. A review of manifestations of the different dimensions of energy security and sustainability is carried out to identify the most topical facets of the issue. Then, the cases of the selected European Union countries (Ireland, Greece, Denmark and Lithuania) are presented to highlight the effects and features of the recent energy policy changes there. Indeed, these countries apply a PSO levy mechanism on electricity tariffs and are diverse in their geopolitical situation, economic development, geographical situation and energy dependency level. The analysis of the situations of such different countries applying the PSO levy mechanism makes it possible to perform a broader and more in-depth assessment and comparison of electricity tariff regulations. Thus, the developed theoretical model is applied to identify the major outcomes of the energy policy regimes (with a focus on tariff regulation) in the selected countries.


2021 ◽  
Vol 11 (24) ◽  
pp. 12137
Author(s):  
Fei-Xue Wang ◽  
Qian Peng ◽  
Xin-Liang Zang ◽  
Qi-Fan Xue

Adaptive cruise control (ACC), as a driver assistant system for vehicles, not only relieves the burden of drivers, but also improves driving safety. This paper takes the intelligent pure electric city bus as the research platform, presenting a novel ACC control strategy that could comprehensively address issues of tracking capability, driving safety, energy saving, and driving comfort during vehicle following. A hierarchical control architecture is utilized in this paper. The lower controller is based on the nonlinear vehicle dynamics model and adjusts vehicle acceleration with consideration to the changes of bus mass and road slope by extended Kalman filter (EKF). The upper controller adapts Model Predictive Control (MPC) theory to solve the multi-objective optimal problem in ACC process. Cost functions are developed to balance the tracking distance, driving safety, energy consumption, and driving comfort. The simulations and Hardware-in-the-Loop (HIL) test are implemented; results show that the proposed control strategy ensured the driving safety and tracking ability of the bus, and reduced the vehicle’s maximum impact to 5 m/s3 and the State of Charge (SoC) consumption by 10%. Vehicle comfort and energy economy are improved obviously.


2021 ◽  
Vol 13 (23) ◽  
pp. 13412
Author(s):  
Zhiyu Fang ◽  
Ling Jiang ◽  
Zhong Fang

Due to the different focus of policies in different regions, China’s energy efficiency has been unstable in recent years. The changing focus of policies at the same time has also impacted the energy system, and therefore, it is very important to explore the impact of China’s new energy policy on its oil and gas energy efficiency. The practical significance of this research is to integrate three policy intervention factors: incentive economic policy intervention, government financial intervention, and mandatory policy intervention. Through the regression of the Stochastic Frontier Approach model, the influence of these policy intervention factors on the efficiency evaluation of decision-making units is eliminated. We calculate the environmental pollution index as an undesired output to measure the efficiency of policy intervention in the green economy of China’s oil and gas energy, use Luenberger model to explore total factor productivity, and find the main reasons that affect the productivity of the green energy economy. The results show that China’s oil and gas energy construction is currently in the stage of scale economy, but the heavy dependence of China’s energy consumption on foreign imports leads to difficulties and urgency in the present stage of technological progress. After excluding the factors of policy intervention, China’s overall energy is in a slightly insufficient policy environment, and energy efficiency is in an unbalanced state.


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