Mechanisms Of Energy Flow Research Articles

Simplified Weather-Related Building Energy Disaggregation and Change-Point Regression: Heating and Cooling Energy Use Perspective

End-use consumption provides more detailed information than total consumption and reveals the mechanism of energy flow through a given building. Specifically, for weather-sensitive energy end-uses, it enables the prioritization and selection of heating and cooling areas requiring investigation and actions. One of the major barriers to acquiring such heating and cooling information for small- and medium-sized buildings or low-income households is the high cost related to submetering and maintenance. The end-use data, especially for heating and cooling end-uses, of such-sized buildings are a national blind spot. In this study, to alleviate this measurement cost problem, two weather-sensitive energy disaggregation methods were examined: the simplified weather-related energy disaggregation (SED) and change-point regression (CPR) methods. The first is a nonparametric approach based on heuristics, whereas the second is a parametric approach. A comparative analysis (one-way ANOVA, correlation analysis, and individual comparison) was performed to explore the disaggregation results regarding heating and cooling energy perspectives using a measurement dataset (MEA) from eleven office buildings. The ANOVA results revealed that there was no significant difference between the three groups (SED, CPR, and MEA); rather strong correlation was observed (r > 0.95). Furthermore, an analysis of the building-level comparison showed that the more distinct the seasonal usage in the monthly consumption pattern, the lower the estimation error. Thus, the two approaches appropriately estimated the amount of heating and cooling used compared with the measurement dataset and demonstrated the possibility of mutual complements.

Biopotential changes of acupuncture points by acupuncture stimulation

BackgroundThe energy flow at acupuncture point is important for understanding the mechanism of acupuncture treatment. However, there are few studies on energy at acupuncture point, and related studies have limitation in explaining the energy flow in all meridians. Thus, we aimed to understand the properties of electrical energy at acupuncture point in twelve meridians by measuring the biopotential at acupuncture and non-acupuncture points. MethodsFor each meridian, twenty subjects were participated, and biopotential was measured at five transport points and their adjacent non-acupuncture points. In each subject, both ‘non-stimulation’ and ‘stimulation’ experiments were conducted in random order. The data were analyzed in two parts: biopotential variability and biopotential difference between acupuncture and non-acupuncture points. ResultsThe biopotential variability at acupuncture point was increased by acupuncture stimulation, and it was related to the activation of Qi flow by acupuncture stimulation. The biopotential difference between acupuncture and non-acupuncture points was formed in the direction related to the Qi flow theory, and this biopotential difference tended to decrease by acupuncture stimulation. ConclusionThe study on biopotential can provide a foundation for research on energy flow mechanism of acupuncture stimulation, and it is expected to overcome limitation of qualitative explanation in traditional medicine.

Economic-emission dispatch problem in integrated electricity and heat system considering multi-energy demand response and carbon capture Technologies

To combat global warming caused by excessive CO2 emissions, it is critical to achieving low-carbon economic operation of integrated electricity and heat systems (IEHS). Thermal power plants with carbon capture systems can significantly reduce the spread of carbon emissions, thus effectively reducing the overall carbon footprint. Meanwhile, the development and utilization of renewable energy sources, such as wind power, can effectively limit overall carbon emissions. Hence, this paper proposes a multi-objective optimization scheme incorporating carbon capture power plants (CCPP) and multi-energy demand response (MEDR), considering the uncertainties of the system for the economic-emission dispatch problem in IEHS. First, the energy flow mechanism and analysis of the wind power abandonment of the IEHS are presented. Then, the low-carbon mechanisms of the MEDR and CCPP are investigated. The uncertainties of the system are described by a membership function to ensure the reserve requirements. A weight setting method based on the improved analytic hierarchy process method is proposed, in which the multi-objective function is transformed into a single-objective function. The case studies were tested on an improved IEEE-30 bus power system and a 6-bus district heating system. The results demonstrate the effectiveness of the proposed method in reducing carbon emissions and improving wind power consumption.

Energy Relaxation and Electron-Phonon Coupling in Laser-Excited Metals.

The rate of energy transfer between electrons and phonons is investigated by a first-principles framework for electron temperatures up to = 50,000 K while considering the lattice at ground state. Two typical but differently complex metals are investigated: aluminum and copper. In order to reasonably take the electronic excitation effect into account, we adopt finite temperature density functional theory and linear response to determine the electron temperature-dependent Eliashberg function and electron density of states. Of the three branch-dependent electron–phonon coupling strengths, the longitudinal acoustic mode plays a dominant role in the electron–phonon coupling for aluminum for all temperatures considered here, but for copper it only dominates above an electron temperature of = 40,000 K. The second moment of the Eliashberg function and the electron phonon coupling constant at room temperature K show good agreement with other results. For increasing electron temperatures, we show the limits of the approximation for the Eliashberg function. Our present work provides a rich perspective on the phonon dynamics and this will help to improve insight into the underlying mechanism of energy flow in ultra-fast laser–metal interaction.

Nutrition and sulfur.

Sulfur is unusual in that it is a mineral that may be taken into the body in both inorganic and organic combinations. It has been available within the environment throughout the development of lifeforms and as such has become integrated into virtually every aspect of biochemical function. It is essential for the nature and maintenance of structure, assists in communication within the organism, is vital as a catalytic assistant in intermediary metabolism and the mechanism of energy flow as well as being involved in internal defense against potentially damaging reactive species and invading foreign chemicals. Recent studies have suggested extended roles for sulfur-containing molecules within living systems. As such, questions have been raised as to whether or not humans are receiving sufficient sulfur within their diet. Sulfur appears to have been the "poor relation" with regards to mineral nutrition. This may be because of difficulties encountered over its multifarious functions, the many chemical guises in which it may be ingested and its complex biochemical interconversions once taken into the body. No established daily requirements have been determined, unlike many minerals, although suggestions have been proposed. Owing to its widespread distribution within dietary components its intake has almost been taken for granted. In the majority of individuals partaking of a balanced diet the supply is deemed adequate, but those opting for specialized or restrictive diets may experience occasional and low-level shortages. In these instances, the careful use of sulfur supplements may be of benefit.

Interplay between Near-Field Radiative Coupling and Space-Charge Effects in a Microgap Thermionic Energy Converter under Fixed Heat Input

We investigate the performance of a micro gap vacuum thermionic energy converter considering the loss mechanisms due to the space charge effect and interelectrode radiative heat transfer. The dependencies of the space charge effect and near-field radiative heat exchange on the interelectrode distance are derived based on established theories. The electrode temperatures are determined by solving the steady-state energy balance equations in a numerical, iterative process and considering a constant energy flux input to the emitter. The resultant behaviour of the different mechanisms of energy flow from the electrodes is studied for a wide range of interelectrode distances, which provides new insights into the device operation. The maximum efficiency of the converter is obtained by optimizing the operating voltage and interelectrode distance. Considering the interplay between space charge and near-field radiative heat transfer, an optimal range is determined for the interelectrode distance. The optimal value of the distance and the lower limit of this range are found to be significantly higher than previously reported, where constant electrode temperatures had been assumed.

Playing with Power: Mechanisms of Energy Flow in Organismal Movement.

Across multiple evolutionary clades and size scales, organismal movement requires controlling the flow of energy through the body to enhance certain functions. Whether energy is released or absorbed by the organism, proper function hinges on the ability to manipulate both where and when energy is transferred. For example, both power amplification and power attenuation rely on the use of springs for the intermediate storage of energy between the body and the environment; but variation in function is the result of the path and timing of energy flow. In this symposium, we have invited speakers that demonstrate the diversity of mechanisms used to control the flow of energy through the body and into the environment. By bringing together researchers investigating movements in the context of power and energy flow, the major goal of this symposium is to facilitate fresh perspectives on the unifying mechanical themes of energy transfer in organismal movement.

Numerical evaluation of compatibility between comfort and energy recovery based on energy flow mechanism inside electromagnetic active suspension

The vibration energy of suspension system transformed from the driving kinetic energy has significant influence on vehicle performance during the driving process. Therefore, the analysis of energy flow mechanism inside the active suspension system is of great significance for the research of vehicle ride comfort and system energy recovery. In this paper, different control strategies for electromagnetic active suspension are designed based on the system energy flow mechanism, so that the compatibility between ride comfort and energy recovery efficiency is achieved under different road conditions. In this mechanism, not only the energy transmission path inside suspension system is considered, but also the vibration energy induced by road roughness is investigated. Subsequently, overall system performance under different strategies and the corresponding energy flow are analyzed, and comprehensive correlation coefficient γ is proposed to further evaluate performance varying. Furthermore, hardware-in-the-loop experiment is also implemented to verify corresponding control strategy and the results demonstrate that the proposed strategies have advantages over traditional strategies with single performance optimization, which can reduce system energy consumption by at least 14.51% and recover 2.45% extra energy while outputting active force, and meanwhile the ride comfort improvement rate can reach at least 13.75% when energy is regenerated.

Coherence in carotenoid-to-chlorophyll energy transfer

The subtle details of the mechanism of energy flow from carotenoids to chlorophylls in biological light-harvesting complexes are still not fully understood, especially in the ultrafast regime. Here we focus on the antenna complex peridinin–chlorophyll a–protein (PCP), known for its remarkable efficiency of excitation energy transfer from carotenoids—peridinins—to chlorophylls. PCP solutions are studied by means of 2D electronic spectroscopy in different experimental conditions. Together with a global kinetic analysis and multiscale quantum chemical calculations, these data allow us to comprehensively address the contribution of the potential pathways of energy flow in PCP. These data support dominant energy transfer from peridinin S2 to chlorophyll Qy state via an ultrafast coherent mechanism. The coherent superposition of the two states is functional to drive population to the final acceptor state, adding an important piece of information in the quest for connections between coherent phenomena and biological functions.

Dynamical tunneling versus fast diffusion for a non-convex Hamiltonian.

This paper attempts to resolve the issue of the nature of the 0.01-0.1 cm(-1) peak splittings observed in high-resolution IR spectra of polyatomic molecules. One hypothesis is that these splittings are caused by dynamical tunneling, a quantum-mechanical phenomenon whereby energy flows between two disconnected regions of phase-space across dynamical barriers. However, a competing classical mechanism for energy flow is Arnol'd diffusion, which connects different regions of phase-space by a resonance network known as the Arnol'd web. The speed of diffusion is bounded by the Nekhoroshev theorem, which guarantees stability on exponentially long time scales if the Hamiltonian is steep. Here we consider a non-convex Hamiltonian that contains the characteristics of a molecular Hamiltonian, but does not satisfy the Nekhoroshev theorem. The diffusion along the Arnol'd web is expected to be fast for a non-convex Hamiltonian. While fast diffusion is an unlikely competitor for longtime energy flow in molecules, we show how dynamical tunneling dominates compared to fast diffusion in the nearly integrable regime for a non-convex Hamiltonian, as well as present a new kind of dynamical tunneling.

Diffusion mechanism of energy flow in multi-heat-source synthesis of SiC

Through the experiments and the numerical simulation of temperature field in multi-heat-source synthesis SiC furnace, in order to research the feature point in multi-heat-source synthesis furnace, the variation law of heat flux was studied and the multi-directional energy flow diffusion mechanism was revealed. The results show that, due to the shielding action between the heat-source and the superposition effect of thermal fields, the insulating effect is best in multi-heat-source synthesis furnace. The heat emission effect is good outside the common area between heat-sources, but the heat storage is poor. Compared with the synthesis furnace that heat source is parallelly arranged, the furnace of stereoscopic arrangement has a more obvious heat stacking effect and better heat preservation effect, but the air permeability of heat source connecting regions is worse. In the case with the same ingredients, the resistance to thermal diffusion and mass diffusion is higher in heat source connecting regions.

A General control mechanism of energy flow in the excited state of polyenic biochromophores

Quantum dynamics in photobiology is a highly controversial subject of modern research. In particular, the role of low-frequency vibrational coherence of biochromophores has been intensely discussed. Coherent control of polyenic chromophores, like carotenoids and retinoids, has been showing that the manipulation of such low frequency coherences may play a crucial role in the evolution of excited population and therefore in the efficiency of photosynthesis. However, no precise control mechanism has been derived. In order to clarify this open question, we combined quantum dynamical modelling with a sensitive experimental technique, namely Pump-Degenerate Four Wave Mixing (Pump-DFWM). In this work we investigate in detail the internal conversion channel of beta-carotene, an important polyenic chromophore, under multipulse excitation and focus on the role of the non-adiabatic coupling between excited-state potentials and the internal energy loss. Our control mechanism is based on the interference between wavepackets in the excited state, which leads to a transient evolution of the vibrational population dependent on the relative phase between excitation sub-pulses. Such a transient evolution can affect the branching ratio between competing channels in the excited state. Therefore, our results are able to rationalize pulse shapes found in a whole class of coherent control experiments involving polyenic biochromophores, like in light harvesting complexes and in bacteriorhodopsin.

Vibrational energy transport in the presence of intrasite vibrational energy redistribution

The mechanism of vibrational energy flow is studied in a regime where a diffusion equation is likely to break down, i.e., on length scales of a few chemical bonds and time scales of a few picoseconds. This situation occurs, for example, during photochemical reactions in protein environment. To that end, a toy model is introduced that on the one hand mimics the vibrational normal mode distribution of proteins, and on the other hand is small enough to numerically time propagate the system fully quantum mechanically. Comparing classical and quantum-mechanical results, the question is addressed to what extent the classical nature of the molecular dynamics simulations (which would be the only choice for the modeling of a real molecular system) affects the vibrational energy flow mechanism. Small differences are found which are due to the different ways classical and quantum mechanics distribute thermal energy over vibrational modes. In either case, a ballistic and a diffusive phase can be identified. For these small length and time scales, the latter is governed by intrasite vibrational energy redistribution, since vibrational energy does not necessarily thermalize completely within individual peptide units. Overall, the model suggests a picture that unifies many of the observations made recently in experiments.

Optimal design of nanoplasmonic materials using genetic algorithms as a multiparameter optimization tool

An optimal control approach based on multiple parameter genetic algorithms is applied to the design of plasmonic nanoconstructs with predetermined optical properties and functionalities. We first develop nanoscale metallic lenses that focus an incident plane wave onto a prespecified, spatially confined spot. Our results illustrate the mechanism of energy flow through wires and cavities. Next we design a periodic array of silver particles to modify the polarization of an incident, linearly polarized plane wave in a desired fashion while localizing the light in space. The results provide insight into the structural features that determine the birefringence properties of metal nanoparticles and their arrays. Of the variety of potential applications that may be envisioned, we note the design of nanoscale light sources with controllable coherence and polarization properties that could serve for coherent control of molecular, electronic, or electromechanical dynamics in the nanoscale.

Visualization of Excitonic Structure in the Fenna-Matthews-Olson Photosynthetic Complex by Polarization-Dependent Two-Dimensional Electronic Spectroscopy

Photosynthetic light-harvesting proceeds by the collection and highly efficient transfer of energy through a network of pigment-protein complexes. Interchromophore electronic couplings and interactions between pigments and the surrounding protein determine energy levels of excitonic states, and dictate the mechanism of energy flow. The excitonic structure (orientation of excitonic transition dipoles) of pigment-protein complexes is generally deduced indirectly from x-ray crystallography, in combination with predictions of transition energies and couplings in the chromophore site basis. We demonstrate that coarse-grained, excitonic, structural information in the form of projection angles between transition dipole moments can be obtained from the polarization-dependent, two-dimensional electronic spectroscopy of an isotropic sample, particularly when the nonrephasing or free polarization decay signal, rather than the photon echo signal, is considered. This method provides an experimental link between atomic and electronic structure, and accesses dynamical information with femtosecond time resolution. In an investigation of the Fenna-Matthews-Olson complex from green sulfur bacteria, the energy transfer connecting two particular exciton states in the protein was isolated as the primary contributor to a crosspeak in the nonrephasing two-dimensional spectrum at 400 femtoseconds under a specific sequence of polarized excitation pulses. The results suggest the possibility of designing experiments using combinations of tailored polarization sequences to separate and monitor individual relaxation pathways.

Extinction and the optical theorem Part II Multiple particles

The extinction due to a group of identical particles in a fixed orientation is studied. An analytical description based on the Maxwell volume integral equation is presented, describing the interference energy flow due to a group of noninteracting identical particles. As compared to a single particle, the effect of multiple particles is shown to narrow the angular region around the forward direction over which the dominant contribution to the group's extinction cross section occurs. The extinction due to a group of fully interacting nonspherical particles is studied using the discrete dipole approximation. Interparticle interactions are found not to change the essential character of the interference-based energy flow mechanism that describes extinction.

Wave energy in surface layers for energy-based damage evaluation

Seismic wave energy in surface layers is calculated based on vertical array records at four sites during the 1995 Hyogo-ken Nambu earthquake by assuming vertical propagation of SH waves. The upward energy generally tends to decrease as it goes up from the base layer to the ground surface particularly in soft soil sites. Theoretical study on 1D multi-layers model to investigate the basic energy flow mechanism indicates that the energy at the ground surface can be smaller on softer soils due to high soil damping during strong shaking even if resonance effect is considered. A simple calculation for a shear-vibrating structure resting on foundation ground shows that induced strain in the structure is directly related to the energy or the energy flux of surface layers. Hence, a general perception that soft soil sites tend to suffer heavier damage than stiff sites should be explained not by greater incident energy but by other reasons such as degree of resonance. Furthermore, it is recommended that not only acceleration or velocity but also S-wave velocity should be specified at a layer where a design seismic motion is given, so that the seismic wave energy can clearly be quantified in seismic design practice.

Approaches for biological and biomimetic energy conversion

This article highlights areas of research at the interface of nanotechnology, the physical sciences, and biology that are related to energy conversion: specifically, those related to photovoltaic applications. Although much ongoing work is seeking to understand basic processes of photosynthesis and chemical conversion, such as light harvesting, electron transfer, and ion transport, application of this knowledge to the development of fully synthetic and/or hybrid devices is still in its infancy. To develop systems that produce energy in an efficient manner, it is important both to understand the biological mechanisms of energy flow for optimization of primary structure and to appreciate the roles of architecture and assembly. Whether devices are completely synthetic and mimic biological processes or devices use natural biomolecules, much of the research for future power systems will happen at the intersection of disciplines.

Two Dimensional Electronic Spectroscopy of Molecular Complexes

AbstractTwo dimensional (2D) heterodyne‐detected electronic photon echo spectroscopy is introduced and described. We give an intuitive description of the origin and information content of 2D electronic spectra, focusing on molecular complexes. We identify two important quantities—the transition dipole term, and the transition frequency cross correlation function that controls the appearance of 2D electronic spectra.We also show how the transition frequency cross correlation function controls the rate of exciton relaxation. These concepts are illustrated with experimental data on the seven bacteriochlorophyll FMO complex of a green sulfur bacterium, showing how the pathways and mechanisms of energy flow can be elucidated by combining 2D spectra with theoretical modeling.

Simulating Energy Flow in Biomolecules: Application to Tuna Cytochrome c

By constructing a continuity equation of energy flow, one can utilize results from a molecular dynamics simulation to calculate the energy flux or flow in different parts of a biomolecule. Such calculations can yield useful insights into the pathways of energy flow in biomolecules. The method was first tested on a small system of a cluster of 13 argon atoms and then applied to the study of the pathways of energy flow after a tuna ferrocytochrome c molecule was oxidized. Initially, energy propagated faster along the direction perpendicular to the heme plane. This was due to an efficient through-bond mechanism, because the heme iron in cytochrome c was covalently bonded to a cysteine and a histidine. For the oxidation of cytochrome c, electrostatic interactions also facilitated a long-range through-space mechanism of energy flow. As a result, polar or charged groups that were further away from the oxidation site could receive energy earlier than nonpolar groups closer to the site. Another bridging mechanism facilitating efficient long-range responses to cytochrome c oxidation involved the coupling of far-off atoms with atoms that were nearer to, and interacted directly with, the oxidation site. The different characteristics of these energy transfer mechanisms defied a simple correlation between the time that the excess energy of the oxidation site first dissipated to an atom and the distance of the atom from the oxidation site. For tuna cytochrome c, all of the atoms of the protein had sensed the effects of the oxidation within ∼40 fs. For the length scale of energy transfer considered in this study, the speed of the energy propagation in the protein was on the order of 10 5 m/s.