How does using an assistive device affect the energetic cost of walking?5 answersUsing an assistive device can reduce the energetic cost of walking. A study by Antonellis et al. found that applying a constant forward force at the center of mass can reduce the metabolic rate of walking by 48% in healthy participants. Guzelbulut et al. developed a computational method to determine the optimal location and stiffness of assistive walking systems, which resulted in an 8.8% reduction in total positive joint energy. Panizzolo et al. demonstrated that a passive exoskeleton applying a low torque to the hip flexors can reduce the metabolic cost of walking by 4.2% in older adults. Gordon et al. used a human-in-the-loop methodology to optimize assistive torques provided by a powered hip exoskeleton, resulting in greater reductions to metabolic cost compared to generic controllers. Another study by Panizzolo et al. showed that a passive wearable assistive device applying a torque to the hip joint can reduce the net metabolic power of walking by 3.3% in older adults.

How i can calculate energy levels ?5 answersEnergy levels can be calculated using various methods depending on the quantum system being studied. One approach is to solve an eigenvalue problem involving a differential equation in quasiposition space. Another method involves using the tensor-operator formalism and graphical methods to compute moments and enter them into a distribution function of a statistical model. Additionally, the calculation of energy levels can be done using semiclassical methods, such as the calculation of the dynamical zeta function via the Riemann-Siegel relations. It has also been shown that Feynman's way of doing quantum mechanics can be helpful in calculating atomic ground states. Furthermore, a method under the effective mass approximation has been proposed for calculating energy levels in quantum wells, quantum wires, and quantum dots of arbitrary materials.

How to calculate the cost of greeen hydrogen production?3 answersThe cost of green hydrogen production can be calculated using various methods and factors. One approach is to use thermodynamic analysis and exergy-based cost formation. Another method involves analyzing the price of renewable hydrogen production in a stand-alone photovoltaic plant, taking into account the price of electricity and the utilization rate of the connected electrolyzer. Additionally, a Monte Carlo simulation approach can be used to compare different configurations of hydrogen production from geothermal and solar energy sources, considering parameters such as the internal rate of return and the levelized cost of hydrogen. The cost of hydrogen production is influenced by factors such as the temperature and mass flow rate of the geothermal fluid, as well as the investment costs of electrolysis. By considering these factors and utilizing appropriate analysis methods, the cost of green hydrogen production can be accurately calculated.

How to calculate MVA?2 answersMVA can be calculated using different methods depending on the context. In the case of OTC derivatives, MVA can be defined as the liability-side discounted expected margin profile. Another approach involves using an extended partial differential equation to derive an all-in fair value, which can be decomposed into coherent CVA, FVA, and MVA components. For pricing equity derivatives with CVA, a marked branching diffusion algorithm can be used, which includes stochastic interest rate models. In the field of echocardiography, the mitral valve area (MVA) can be assessed using a simple echo-Doppler method that takes into account the mitral flow volume, transmitral mean flow velocity, and diastolic filling time. For large-scale capacitance calculations, an integral equation formulation with a new representation for charge distributions can be used, resulting in a significant reduction in problem size and faster computation of the capacitance matrix.

How the cost of living is measured?2 answersThe cost of living is measured using various methods and approaches. One approach is to use the consumer price index (CPI), which measures changes in the prices of a fixed basket of goods and services. However, the CPI may overstate the true increases in the cost of living due to conceptual differences and measurement issues. Another approach is to develop comprehensive measures that take into account differences in consumption patterns and lifestyles among cities. Econometric models can be used to derive cost-of-living indexes for individual households and aggregate consumer behavior. These models incorporate measures of individual welfare and normative criteria for evaluating transfers among individuals. Additionally, cost-of-living indexes can be calculated for specific groups of consuming units with common demographic characteristics. It is important to note that there may be differences in cost-of-living measures depending on the theoretical design, data collection, and sampling methods used.

How do I measure physical activity?5 answersZur Messung der körperlichen Aktivität können Gesundheitsdienstleister Fragebögen und/oder Bewegungssensoren verwenden, um das aktuelle Aktivitätsniveau des Patienten zu beurteilen. Bei Fragebögen beantworten Patienten eine Reihe von Fragen zu Art und Umfang der in der Vergangenheit ausgeübten Aktivitäten, während Bewegungssensoren Körperbewegungen in Echtzeit aufzeichnen. Statistische Regressionsmodelle können auf Fragebogen- und Bewegungssensordaten angewendet werden, um Kilokalorien abzuschätzen, was einen Hinweis auf den Kalorienverbrauch gibt. Für genauere Messungen des Energieverbrauchs kann die Methode des doppelt markierten Isotopenwassers verwendet werden, obwohl sie kostspielig und in klinischen Umgebungen außerhalb der Forschung nicht praktikabel ist. Objektive Methoden wie direkte Beobachtung und Beschleunigungsmesser ermöglichen genauere Messungen der körperlichen Aktivität, während subjektive Ansätze wie Logs, Interviews und Umfragen praktischer, aber aufgrund von Erinnerungsfehlern naturgemäß ungenauer sind. Letztlich sollte die Wahl des Messinstruments von den Forschungsfragen, dem Fachwissen, den Ressourcen und den verfügbaren Mitteln abhängen.