Net Energy Flow Research Articles

Quantum torque on a non-reciprocal body out of thermal equilibrium and induced by a magnetic field of arbitrary strength

AbstractA stationary body that is out of thermal equilibrium with its environment, and for which the electric susceptibility is non-reciprocal, experiences a quantum torque. This arises from the spatially non-symmetric electrical response of the body to its interaction with the non-equilibrium thermal fluctuations of the electromagnetic field: the non-equilibrium nature of the thermal field fluctuations results in a net energy flow through the body, and the spatially non-symmetric nature of the electrical response of the body to its interaction with these field fluctuations causes that energy flow to be transformed into a rotational motion. We establish an exact, closed-form, analytical expression for this torque in the case that the environment is the vacuum and the material of the body is described by a damped oscillator model, where the non-reciprocal nature of the electric susceptibility is induced by an external magnetic field, as for magneto-optical media. We also generalise this expression to the context in which the body is slowly rotating. By exploring the high-temperature expansion of the torque, we are able to identify the separate contributions from the continuous spectral distribution of the non-reciprocal electric susceptibility, and from the resonance modes. In particular, we find that the torque persists in the limiting case of zero damping parameter, due to the contribution of the resonance modes. We also consider the low-temperature expansion of the torque. This work extends our previous consideration of this model to an external magnetic field of arbitrary strength, thereby including non-linear magnetic field effects.

An investigation on Stirling approximation and entropy

The Stirling approximation is a mathematical formula developed by James Stirling in the early 18th century, which estimates the value of factorials for large numbers. The formula has had a significant impact on many fields of study, including being used to estimate the entropy of a system. Entropy is a fundamental concept in thermodynamics that describes the degree of disorder or randomness in a system which refers to the number of ways in which the systems particles can be arranged. The flow of entropy is a concept that describes the direction and rate of change of entropy in a system. Mechanical and thermal equilibrium is when no net flow of energy between the systems so that the systems do not undergo any further changes in their state. Joule expansion involves the expansion of a gas in a container with a movable piston. In this process, the gas expands into a larger volume, and as a result, either temperature or pressure changes. The Stirling approximation can be used to estimate the change in entropy of the gas during this process and can be used to calculate the amount of work done by the gas. This essay summarizes the importance of the Stirling approximation and finds that it is a fundamental calculation method for explaining and solving thermodynamics-related problems which can be used in various subtopics and fields. It is not only a calculation method in mathematics but also a key factor in further developing physics research.

Atmospheric heat transport is governed by meridional gradients in surface evaporation in modern-day earth-like climates

Evaporation adds moisture to the atmosphere, while condensation removes it. Condensation also adds thermal energy to the atmosphere, which must be removed from the atmosphere by radiative cooling. As a result of these two processes, there is a net flow of energy driven by surface evaporation adding energy and radiative cooling removing energy from the atmosphere. Here, we calculate the implied heat transport of this process to find the atmospheric heat transport in balance with the surface evaporation. In modern-day Earth-like climates, evaporation varies strongly between the equator and the poles, while the net radiative cooling in the atmosphere is nearly meridionally uniform, and as a consequence, the heat transport governed by evaporation is similar to the total poleward heat transport of the atmosphere. This analysis is free from cancellations between moist and dry static energy transports, which greatly simplifies the interpretation of atmospheric heat transport and its relationship to the diabatic heating and cooling that governs the atmospheric heat transport. We further demonstrate, using a hierarchy of models, that much of the response of atmospheric heat transport to perturbations, including increasing CO2 concentrations, can be understood from the distribution of evaporation changes. These findings suggest that meridional gradients in surface evaporation govern atmospheric heat transport and its changes.

Irreversible energy extraction from negative-temperature two-dimensional turbulence.

The formation and transition of patterns of two-dimensional turbulent flows observed in various geophysical systems are commonly explained in terms of statistical mechanics. Different from ordinary systems, for a two-dimensional flow, the absolute temperature defined for a statistical equilibrium can take negative values. In a state of negative temperature, the second law of thermodynamics predicts that energy in microscopic fluctuations is irreversibly converted to a macroscopic form. This study explores the possibility of this one-way energy conversion in a two-dimensional flow using a basic conceptual model. We consider an inviscid incompressible fluid contained in a bounded domain, the shape of which is distorted by an externally imposed force. Unlike the usual fixed boundary cases, the flow energy within the domain is exchanged with the external system via pressure work through the moving lateral boundary. Concurrently, the flow field remains constrained by vorticity conservation. Beginning from a state of Kraichnan's grand-canonical ensemble, when the domain shape is distorted from one shape to another in a finite time, the Jarzynski equality is established. This equality states that, on average, the direction of a net energy flow through the boundary during a cycle of domain distortion changes with the sign of the initial temperature of the system. Numerical experiments are carried out to verify this theoretical argument and to investigate the parameter dependence of the energy exchange rate.

Ion Behavior at Shocklets: A Case Study of MMS Observations

AbstractThe existence of shocklets, a kind of solitary structure, has been demonstrated in the Earth's foreshock regions for decades. Their formation and evolution are believed to be controlled by ions. However, the detailed behavior of ions at them has not been well investigated observationally yet. Here, we investigate a shocklet observed by the Magnetospheric Multiscale mission in the Earth's foreshock. Analysis of ion observations reveals that the solar wind (SW) ions are bunched in gyrophase space when interacting with the whistler precursor of the shocklet, suggesting the occurrence of cyclotron resonance between them. A more detailed examination suggests that the cyclotron resonance induces a net energy flow from the whistler precursor to the SW ions. Thus, the observations presented here indicate that the cyclotron resonance between shocklet whistler precursors and the SW ions could provide a mechanism for shocklet dissipation and SW ion energization.

Soil energetics: A unifying framework to quantify soil functionality

AbstractMassive quantities of energy flow through soils during a year. Emerging views indicate that when supplied with abundant energy, soil biology acts as a self‐organizing system as soil microbes forge their habitats into a porous, well‐aggregated structure with high functionality. The flow of energy to power these self‐organizing processes has not been accounted for in present soil models, which concentrate on static pools of soil organic matter (SOM) and carbon and their relationship to soil functionality. To address this, we introduce a new conceptual energetics framework that quantifies the net energy flows within a soil control volume (CV) using a suite of energetic components including mechanical, biogeochemical, and hydrological processes. This framework is presented at a conceptual level and can be expanded to more granular levels with further study. To assess its present capabilities, management systems of conventional‐till (CT) and no‐till (NT) corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations and a grassland system (GS) were evaluated using the model. Net energy fluxes over a growing season were found to be negative for the CT, net zero for NT, and positive for GS. The energetics framework shows it can provide a first‐order assessment of soil health and advise which management practices provide adequate supplies of energy to soil biology to effectively enhance soil functionality.

Segment power analysis of collegiate softball hitting

ABSTRACT The primary aim of this investigation was to describe the energy flow through the kinetic chain during softball hitting using a segmental power analysis. Twenty-three NCAA Division I collegiate softball athletes (20.4 ± 1.7 yr; 166.7 ± 22.0 cm; 74.9 ± 15.9 kg) performed three maximum effort swings off a stationary tee placed in the middle of the strike zone. Pelvis, trunk, humerus, forearm and hand segment powers were integrated across four phases of the softball swing (load, stride, acceleration, and follow-through). The load and stride phases had low segment energy inflow and outflow values as well as net segment energy flow for all body segments compared to subsequent phases of the swing. The acceleration phase showed large trunk inflow values relative to the pelvis. There was also descriptively larger front compared to back-side upper extremity inflow. Finally, the follow-through phase showed primarily energy outflow for the upper extremity segments likely attributed to slowing down rotation.

Hip Range of Motion and Strength and Energy Flow During Windmill Softball Pitching.

Inadequate hip range of motion (ROM) and isometric strength (ISO) may interfere with energy flow through the kinetic chain and result in increased injury susceptibility. To examine the relationship of hip ROM and ISO with energy flow through the trunk and pitching-arm segments during the windmill softball pitch in youth athletes. A subsequent purpose was to examine the relationship between energy flow and pitch speed. Descriptive laboratory study. University research laboratory. A sample of 29 youth softball pitchers (age = 11.2 ± 1.3 years, height = 155.0 ± 10.4 cm, mass = 53.2 ± 12.6 kg). Bilateral hip internal-rotation and external-rotation (ER) ROM and ISO were measured. Net energy outflow and peak rates of energy outflow from the distal ends of the trunk, humerus, and forearm were calculated for the acceleration phase of the windmill softball pitch, and pitch speed was measured. Regression analysis revealed an effect of drive-hip ER ISO on the net energy flow out of the distal ends of the trunk (P = .045) and humerus (P = .002). Specifically, increased drive-hip ER ISO was associated with increased net energy outflow from the trunk to the humerus and from the humerus to the forearm. No significant effects of hip ROM or other hip ISO measures were observed. Additionally, pitchers who achieved higher peak rates of distal outflow tended to achieve higher pitch speeds. An association was present between drive-hip ER ISO and the net energy flow out of the distal ends of the trunk and humerus during the acceleration phase of the windmill softball pitch, emphasizing the importance of hip and lower body strength in executing the whole-body windmill pitch. Overall, energy-flow analysis is an interesting new way to analyze pitching mechanics and will aid in furthering our understanding of performance and injury risk in windmill softball pitching.

Effects of Hip Range of Motion and Isometric Strength on Energy Flow during Windmill Softball Pitching.

Inadequate hip range of motion (ROM) and isometric strength (ISO) may interfere with energy flow through the kinetic chain and result in increased injury susceptibility. To examine the relationship of hip ROM and ISO with energy flow through the trunk and pitching arm segments during the windmill softball pitch in youth athletes. A subsequent purpose was to examine the relationship between energy flow and pitch speed. Descriptive laboratory study. University research laboratory. A sample of 29 youth softball pitchers (11.2±1.3 yrs.; 155.0±10.4 cm; 53.2±12.6 kg). Bilateral hip internal rotation (IR) and external rotation (ER) ROM and ISO were measured. Net energy outflow and peak rates of energy outflow from the distal ends of the trunk, humerus, and forearm were calculated for the acceleration phase of the windmill softball pitch, and pitch speed was measured. Regression analysis revealed a significant effect of drive hip ER ISO on the net energy flow out of the distal ends of the trunk (p=0.045) and humerus (p=0.002). Specifically, increased drive hip ER ISO was associated with increased net energy outflow from the trunk to the humerus and from the humerus to the forearm. No significant effects of hip ROM or other hip ISO measures were observed. Additionally, pitchers who achieved higher peak rates of distal outflow tended to also achieve higher pitch speeds. There is an association between drive hip ER ISO and the net energy flow out of the distal ends of the trunk and humerus during the acceleration phase of the windmill softball pitch, emphasizing the importance of hip and lower body strength in the execution of the whole-body windmill pitch. Overall, energy flow analysis is an interesting new way to analyze pitching mechanics and will aid in further understanding of performance and injury risk in windmill softball pitching.

Nonequilibrium thermodynamics of quantum friction

Thermodynamic principles are often deceptively simple and yet surprisingly powerful. We show how a simple rule, such as the net flow of energy in and out of a moving atom under nonequilibrium steady state condition, can expose the shortcomings of many popular theories of quantum friction. Our thermodynamic approach provides a conceptual framework in guiding atom-optical experiments, thereby highlighting the importance of fluctuation-dissipation relations and long-time correlations between subsystems. Our results introduce consistency conditions for (numerical) models of nonequilibrium dynamics of open quantum systems.

Comments on “A New Derivation of the Law of the Junctions”

Contribution: This brief comment highlights some crucial assumptions behind the “law of the junction” that are overlooked by the above paper and argues that the proposed derivation is not actually a “new” derivation at all. Background: The “law of the junction” is one of the most significant and useful results within the field of solid-state devices. The above paper is likely to confuse readers, particularly those who are undergraduate electrical engineering students studying semiconductor device physics for the first time. This is especially so because of the abstract nature of the underlying quantum mechanics framework and solid-state physics models (subjects which the typical student at that level lacks a substantial background in) as well as the plethora of tedious equations in the curriculum. Research Questions: What core physical concepts are essential to a fundamental yet intuitive understanding of the law of the junction? Methodology: Several key features of how semiconductor junctions behave under bias are explained. References to well-known textbooks are provided where appropriate. Findings: The above paper’s primary mistake is its assertion that its derivation does not rely on the assumption of thermal equilibrium. However, the law of the junction is equivalent to a calculation of depletion-edge minority carrier concentrations using Maxwell–Boltzmann statistics—a distribution which only holds under thermal equilibrium conditions. More rigorously, in a nondegenerate semiconductor, Fermi–Dirac statistics (which governs electrons) reduces to Boltzmann statistics only when the electrochemical potential is spatially uniform, a condition equivalent to having no net flow of thermal energy—the very definition of thermal equilibrium.

Nutrient management impacts on net ecosystem carbon budget and energy flow nexus in intensively cultivated cropland ecosystems of north-western India

Nutrient management has led to unprecedented increase in crop production, but with significant carbon (C) trade-off that has close nexus with energy flow. We quantified the impacts of nutrient management on emission of greenhouse gases, net ecosystem C budget (NECB) and energy flow in three cropland ecosystems (rice–wheat, maize–wheat and cotton–wheat). Carbon dioxide (CO2) and nitrous oxide (N2O) emissions were significantly (p < 0.05) higher in rice than cotton, while maize ecosystem was in-between. The greenhouse gas intensity was significantly higher for rice–wheat (by 0.2 kg CO2e kg−1 grain) and maize–wheat (by 0.1 kg CO2e kg−1 grain), compared with cotton–wheat. The higher carbon emission ratio for maize–wheat (9.59) and rice–wheat (8.07) suggested their higher potential to fix C per unit loss, compared with cotton–wheat (7.03). Atmospheric CO2 assimilated into net primary production (NPP) totalled 14.1 ± 0.18, 11.5 ± 0.13 and 9.7 ± 0.13 Mg C ha−1 for rice–wheat, maize–wheat and cotton–wheat ecosystems, respectively. With an estimated net ecosystem exchange of 9.5 ± 0.29, 5.8 ± 0.19 and 2.7 ± 0.23 Mg C ha−1, respectively, for three ecosystems, rice–wheat (2427 kg C ha−1 year−1) had significantly higher NECB, compared with maize–wheat (27.1 kg C ha−1 year−1) and cotton–wheat (− 3834 kg C ha−1 year−1). Rice–wheat had significantly higher C addition in soil organic carbon (SOC) pool, compared with other two ecosystems. Conversely, cotton–wheat had depletion of SOC pool (− 817 kg C ha−1). Although the three ecosystems did not differ significantly for fertilizer-related energy input (EI), energy output (EO), energy ratio (ER) and net energy gain were significantly higher for cotton–wheat, compared with other ecosystems.

Thermal biology and growth of bison (Bison bison) along the Great Plains: examining four theories of endotherm body size

AbstractBody size of bison (Bison bison) declines with rising global temperature across the fossil record and rising annual temperatures across the Great Plains, but what are the underlying drivers? Body size depends on growth, which depends on maximizing net energy and nutrient flows for the production of tissues at seasonal scales across the range of the species. We measured thermoregulation costs of body surface temperature (°C) and heat exchanges (W and W/m2) of 350 adult and 345 adolescent Bison from 19 herds in summer and winter along the Great Plains from Saskatchewan (52° N) to Texas (30° N). At the smallest scale, daily body surface temperature increased with solar radiation and decreased with relative humidity and wind speed, which is consistent with Kooijman’s dynamic energy budget theory. Total surface heat transfer (W) increased with body mass (kg) at an exponent of 0.63 ± 0.03, which is consistent with Schmidt‐Nielsen’s principle of surface‐area‐to‐volume ratios (b = 0.67). On an annual scale, growth (kg/yr) of adolescent Bison decreased with increasing total surface heat transfer (W) during summer, which supports Speakman and Król’s heat dissipation limit theory. On the largest scale, heat flux was weakly related to latitude in summer and winter for adolescent Bison, which provides support for Bergmann’s rule and suggests a role for local primary production along the Great Plains. Cooler summers are more optimal for Bison growth because of reduced heat loads during the growing season. Rising temperatures are likely to constrain body size and productivity of Bison and other large endotherms in North America.

Mechanical Stabilization of Nanoscale Conductors by Plasmon Oscillations.

External driving of the Fermion reservoirs interacting with a nanoscale charge-conductor is shown to enhance its mechanical stability during resonant tunneling. This counterintuitive cooling effect is predicted despite the net energy flow into the device. Field-induced plasmon oscillations stir the energy distribution of charge carriers near the reservoir’s chemical potentials into a nonequilibrium state with favored transport of low-energy electrons. Consequently, excess heating of mechanical degrees of freedom in the conductor is suppressed. We demonstrate and analyze this effect for a generic model of mechanical instability in nanoelectronic devices, covering a broad range of parameters. Plasmon-induced stabilization is suggested as a feasible strategy to confront a major problem of current-induced heating and breakdown of nanoscale systems operating far from equilibrium.

Optimal Sizing of Renewable Microgrid for Flow Shop Systems under Island Operations

This paper addresses a critical question pertaining to manufacturing sustainability: is it economically viable to implement an island microgrid to power a flow shop system under power demand and supply uncertainty? Though many studies on microgrid sizing are available, the majority assume the microgrid is interconnected with main grid. This paper aims to size wind turbine, photovoltaic and battery storage to energize a multi-stage flow shop system in island mode. A mixed-integer, non-linear programming model is formulated to optimize the renewable portfolio and capacity with the goal of minimizing the levelized cost of energy. The island microgrid is tested in three locations with diverse climate profiles. The results show that net zero energy flow shop production is economically feasible in the areas where the average wind speed exceed 8 m/s at 80-meter tower height, or the battery cost drops below $100,000/MWh. Sensitivity analyses are further carried out with respect to installation cost, demand response program, production scalability, and weather seasonality.

Instabilities of Nonconservative Fluid-Loaded Systems

Nonlinear bifurcations and instabilities of autonomous nonconservative systems, mainly involving the fluid loading of a solid or structure, are reviewed and described in this accessible, pictorial overview. In contrast to the earlier papers in this series (focusing on the instability of elastic deformable systems, and low-order periodically-forced mechanical systems), we focus on a handful of case studies in which the loss of stability is primarily driven by nonconservative forces, i.e. path-dependent forces not associated with a potential. Many systems involving fluid-structure interaction can lose stability under changing conditions in which there is a net flow of energy from the fluid to the structure, sometimes resulting in growing oscillatory behavior. Again, the generic manifestations of instability typically occur within the framework of bifurcation theory. Progression is from simple local bifurcations to more complex global events, and all are related to instructive and intriguing applications. Hopf bifurcations are presented in the context of the galloping and flutter of cables and pipes. Next, Neimark bifurcations appear in aircraft applications involving the free-play fluttering of aerofoils and the wing rock of the Harrier jump-jet. Turning to ships in wind and waves, a homoclinic saddle connection governs the surging and surf-riding of a vessel in stern seas, while an omega flow explosion can compromise the course-keeping of a passenger ferry in a side wind. Recent work on the dynamic step-buckling of a spherical shell illustrates the role of a center manifold, and the paper ends with a careful study of dissipation-generated instabilities, drawing on the historical struggles to understand the evolution of spinning liquid planets.

Enhanced radial energy transport induced by radially curved Alfvén eigenmode wavefronts

Radially curved Alfvén eigenmode wavefronts as observed on the electron cyclotron emission imaging diagnostic indicate that the modes are associated with a net radial energy flow. This energy flow is due to a radial mismatch in the location of the drive and damping of the mode. Energy transport is created by an enhanced parallel fluctuating magnetic field that is generated by the radial wavefront curvature.

Volumetric reconstruction of acoustic energy flows in a reverberation room.

This study examines the spatial and directional properties of net energy flows in a reverberation chamber. Based on measurements with a spherical array, a method is proposed to estimate the flows of acoustic energy in the volume surrounding the array. The proposed method is used to examine the steady state, early decay, and late decay of the sound field in a reverberation room (both empty and with an absorber on the floor). The results show that the approach is successful in characterizing the spatio-spectral and spatio-temporal properties of power flows in reverberant sound fields, constituting a valuable analysis tool.

A Bioenergetic Framework for Assessing Soil Organic Matter Persistence

The emerging view of soil organic matter (SOM) persistence asserts that SOM exists as a continuum of organic material, continuously processed by the decomposer community from large biopolymers to small monomers and with increasing oxidation and solubility, protected from decomposition through mineral aggregation and adsorption. Microbial community and ecosystem dynamics regulate the exchange of both nutrients and carbon between the soil and the atmosphere through the mineralization of SOM. Because these ecosystem dynamics are driven by net energy flows, analysis of SOM bioenergetics can provide complementary constraints to SOM models as well as insight into the fundamental conundrum of why thermodynamically unstable organic matter persists in soil. Microbial substrate preference has been shown to depend on the energy status of the potential substrates in terms of energy required and energy returned. Here we propose a framework for assessing the persistence of SOM utilizing thermally determined activation energy (Ea) and energy density (ED), tested on a suite of soils that have undergone alteration in field or laboratory experiments designed to isolate persistent SOM. Comparison of these energetic parameters in this framework will determine whether a chemical or physical change during SOM decomposition resulted in a change in its environmental persistence. An expanded framework of bioenergetics changes during SOM formation, decomposition, and stabilization is proposed as persistent SOM is characterized by decreased ED and Ea, relative to the bulk SOM.

Relations between work and entropy production for general information-driven, finite-state engines

We consider a system model of a general finite-state machine (ratchet) that simultaneously interacts with three kinds of reservoirs: a heat reservoir, a work reservoir, and an information reservoir, the latter being taken to be a running digital tape whose symbols interact sequentially with the machine. As has been shown in earlier work, this finite-state machine can act as a demon (with memory), which creates a net flow of energy from the heat reservoir into the work reservoir (thus extracting useful work) at the price of increasing the entropy of the information reservoir. Under very few assumptions, we propose a simple derivation of a family of inequalities that relate the work extraction with the entropy production. These inequalities can be seen as either upper bounds on the extractable work or as lower bounds on the entropy production, depending on the point of view. Many of these bounds are relatively easy to calculate and they are tight in the sense that equality can be approached arbitrarily closely. In their basic forms, these inequalities are applicable to any finite number of cycles (and not only asymptotically), and for a general input information sequence (possibly correlated), which is not necessarily assumed even stationary. Several known results are obtained as special cases.