Energy Conservation Rule Research Articles

Hierarchical characterization of thermoelectric performance in copper-based chalcogenide CsCu3S2: Unveiling the role of anharmonic lattice dynamics

Fundamental understanding of anharmonic lattice dynamics and heat conductance physics in crystalline compounds is critical for the development of thermoelectric energy conversion devices. Herein, we thoroughly investigate the microscopic mechanisms of thermal transport in CsCu3S2 by coupling the self-consistent phonon (SCP) theory with the linearized Wigner transport equation (LWTE). We explicitly consider both phonon energy shifts and broadening arising from both cubic and quartic anharmonicities, as well as diagonal/non-diagonal terms of heat flux operators in thermal conductivity. Our findings show that the strong anharmonicity of CsCu3S2 primarily arises from the presence of p-d anti-bonding hybridization between Cu and S atoms, coupled with the random oscillations of Cs atoms. Notably, the competition between phonon hardening described by the loop diagram and softening induced by the bubble diagram significantly influences particle-like propagation, predominantly reflected in group velocity and energy-conservation rule. Additionally, the electrical transport properties are determined by employing the precise momentum relaxation-time approximation (MRTA). At high temperatures, the thermoelectric performance of p-type CsCu3S2 reaches its optimum theoretical value of 0.94 along the in-plane direction based on advanced phonon renormalization theory. In striking contrast, the harmonic approximation theory significantly overestimates the thermoelectric efficiency at the same temperatures, rendering it an impractical expectation. Conversely, the first-order renormalization approach leads to a serious underestimation of the thermoelectric properties due to the over-correction of phonon energy. Our study not only reveals the pivotal role of anharmonic lattice dynamics in accurately assessing thermoelectric properties but also underscores the potential thermoelectric applications for novel copper-based chalcogenides.

Long wave absorption by a dual purpose Helmholtz resonance OWC breakwater

In this paper, a novel hybrid breakwater-WEC system consisting of a Helmholtz-resonance oscillating water column (OWC) caisson array and a perforated wall is proposed to attenuate long waves. The principle of Helmholtz-resonance OWC is analogous to the acoustic Helmholtz resonator for noise reduction. A semi-analytical model was developed based on potential flow theory using the matching eigenfunction method to investigate wave interaction with the OWC-breakwater system. The velocity singularity at the tip of the wall is resolved using the Galerkin method to improve the model convergence. The semi-analytical model of the present wave-air-structure interaction problem is verified using Haskind relation and energy conservation rule. Furthermore, we validate the model using numerical and experimental data in terms of wave reflection and wave power absorption. Hydrodynamic characteristics of the proposed hybrid breakwater-WEC system and the influence of key geometrical and wave parameters were investigated. Theoretical results indicate that long waves can be effectively absorbed by the OWC caisson through Helmholtz resonance for both normal and oblique waves. The resonance frequency of OWC varies with the chamber wall draft and chamber width in the along-shore direction. It was found that installing a perforated wall in front of the OWC array could broaden the frequency bandwidth of significant wave attenuation. The along-shore length of each OWC chamber ( 2l ) and the incident wave angle ( θ ) are identified as the key parameters that affect the hydrodynamic performance of the system at high frequency range due to the along-shore sloshing of water column, but have a relatively minor effect on long waves attenuation. The present OWC-breakwater system demonstrates advantage and superior performance over conventional rubble mound breakwaters and breakwaters of multiple perforated walls in attenuating long waves. The findings of this paper provide guidance for a novel design of breakwaters for absorbing long waves. • Novel Helmholtz-resonance OWC breakwater with a perforated wall is proposed to absorb longer waves．. • Semi-analytical model of wave interaction with OWC array with perforated wall is developed and validated．. • Present hybrid OWC-breakwater system is more effective in absorbing long waves than conventional breakwaters. • Significant effect of incident wave angle on wave reflection is observed at higher frequency range but not at low frequency range.

Development and Application of Smart Home Energy Management System Based on Wireless Network Technology

In order to solve the problem of integration of home energy management system and wireless network technology, the author proposes the development and application of a smart home energy management system based on wireless network technology. Divide the NB-IoT into different simulation levels, simulate the physical layer of the NB-IoT, and according to the household energy conservation rules, calculate the household energy distribution parameters, convert the intelligent control signal into a signal constellation point, calculate the deviation value of the control command corresponding to the energy equipment, build an intelligent control simulation algorithm, and finally complete the simulation of the intelligent control system. Experimental results show the following: The simulation method in the intelligent home language input terminal control system is based on the Internet of Things, the average time of simulating the test point of energy equipment is about 4.9 s, the required simulation time is long, and in the intelligent control system of the mobile road tunnel lighting vehicle, the simulation time required by the designed simulation method is about 6.8 s, and the simulation time is the longest. The average time of the method proposed by the author to simulate the energy distribution instruction is about 3.3 s. Conclusion. The application prospect of a smart home energy management system based on wireless network technology is very broad.

Analytical Prototype Functions for Flux Linkage Approximation in Synchronous Machines

Physically motivated and analytical prototype functions are proposed to approximate the nonlinear flux linkages of nonlinear synchronous machines (SMs) in general; and reluctance synchronous machines (RSMs) and interior permanent magnet synchronous machines (IPMSMs) in particular. Such analytical functions obviate the need of huge lookup tables (LUTs) and are beneficial for optimal operation management and nonlinear control of such machines. The proposed flux linkage prototype functions are capable of mimicking the nonlinear self-axis and cross-coupling saturation effects of SMs. Moreover, the differentiable prototype functions allow to easily derive analytical expressions for the differential inductances by simple differentiation of the analytical flux linkage prototype functions. In total, two types of flux linkage prototype functions are developed. The first flux linkage approximation is rather simple and obeys the energy conservation rule for “symmetric” flux linkages of RSMs. With the gained knowledge, the second type of prototype functions is derived in order to achieve approximation flexibility necessary for SMs with permanent (or electrical) excitation with “unsymmetric” flux linkages due to the excitation offset. All proposed flux linkage prototype functions are continuously differentiable, obey the energy conservation rule and, as fitting results show, achieve a (very) high approximation accuracy over the whole operation range.

Coupling potential-forced network flow analysis based on potential energy conservation rules and network flow method

An integrated energy system that uses various networks to transfer electrical power, natural gas, heating, and cooling energy has been applied widely in recent decades. Heating energy flow is a typical coupling network flow consisting of pressure flow and thermal energy flow. It will be attractive to develop a similar network flow method for analyzing the general energy networks, including coupling network flows. In this work, two thermodynamic state properties in the energy networking transmission process, pressure, and temperature are proved as fundamental physical potentials in the network transmission process. It is found that the potential energy is conserved at the mixing node, and the generic network flow can be classified as fundamental potential-forced network flows or decoupled as the combination of potential-forced network flows. By comparing the transmission speed differences between different potentials, the unilateral continuity problem is found in the coupling network flows. The directional nodal potential method (DNPM) for modeling potential-forced network flows that capture the physical characteristics of pipeline transmission and nodal mixing for networking transmission is developed. The results show that the DNPM can unify modeling and analyzing all 3 types of typical potential-forced network flows, then directly obtain the state properties at the mixing nodal. These are instantiated in analyzing districted thermal energy networks. The case study on district heating networks shows that the unilateral continuity problem at the mixing node for coupling network flows can be well solved. The number of equations of the presented DNPM is 7 less than the traditional BFM, and 3 iterations less than BFM, which show the ability of effective formulation and solution. The present work gives researchers an efficient method of formulating, analyzing, and optimizing energy networks.

Theoretical Analysis of a Mathematical Relation between Driving Pressures in Membrane-Based Desalting Processes.

Osmotic and hydraulic pressures are both indispensable for operating membrane-based desalting processes, such as forward osmosis (FO), pressure-retarded osmosis (PRO), and reverse osmosis (RO). However, a clear relation between these driving pressures has not thus far been identified; hence, the effect of change in driving pressures on systems has not yet been sufficiently analyzed. In this context, this study formulates an actual mathematical relation between the driving pressures of membrane-based desalting processes by taking into consideration the presence of energy loss in each driving pressure. To do so, this study defines the pseudo-driving pressures representing the water transport direction of a system and the similarity coefficients that quantify the energy conservation rule. Consequently, this study finds three other theoretical constraints that are required to operate membrane-based desalting processes. Furthermore, along with the features of the similarity coefficients, this study diagnoses the commercial advantage of RO over FO/PRO and suggests desirable optimization sequences applicable to each process. Since this study provides researchers with guidelines regarding optimization sequences between membrane parameters and operational parameters for membrane-based desalting processes, it is expected that detailed optimization strategies for the processes could be established.

The utilisation of useful ambient energy in residential dwellings to improve thermal comfort and reduce energy consumption

Energy consumption in the housing sector, is significantly high and continues to escalate. Urbanisation due to population growth and migration from rural areas to cities are two main reasons for this rising demand. With the uncertainty in the energy market and the increasing awareness of the impact of fossil fuels on the environment, research work in efficient building design has gained momentum. Energy conservation guidelines in many countries have become mandatory. Howerver, more emphasis has been given to commercial, institutional, governmental and industrial buildings, which commonly employ more efficient HVAC systems than those deployed in houses. Thus, the push towards energy conservation in the residential sector is less noticeable. This is further compounded with the absence of will power to enforce the same energy conservation rules as the case with other sectors. In this paper five passive cooling and heating strategies have been reviewed (passive building design, night ventilation, nocturnal cooling, PCM (Phase Change Material) and IEC (Indirect Evaporative Cooling), solar thermal energy). The aim is to evaluate how to implement them better in a cost-effective way in existing and new houses. The literature review confirmed the need for further investigation of energy efficient HVAC systems with passives strategies solutions for contemporary residential dwellings is required to make a meaningful impact on the energy map of this sector. Also, the viability of an easy to deploy and configure HVAC system for retrofit and new applications for more benefits of these passive strategies either individually or in a hybrid configuration needs to be explored.

The standard dynamic energy budget model has no plausible alternatives

During its 40 years of development, the assumptions of the Dynamic Energy Budget (deb) theory for metabolic organisation turned out hard to replace. To understand this, a reasoning is here presented for why its standard model has no alternatives with a comparable level of simplicity and will never have them. Energy and mass conservation rules are essential to quantify the eco-physiological development of an individual organism thermodynamically. These rules strongly constrain the mathematical modelling of this development. In combination with consistency with a small set of stylised empirical facts, the freedom of modelling the skeleton of the model is reduced to a single one: the standard deb model. This skeleton can, however, be extended in many different ways to capture particular ‘details’. The key-message of this paper is that the more simple metabolic models become, the more constraining are consistency conditions.

InSe as a case between 3D and 2D layered crystals for excitons

InSe is a promising material in many aspects where the role of excitons is decisive. Here we report the sequential appearance in its luminescence of the exciton, the biexciton, and the P-band of the exciton-exciton scattering while the excitation power increases. The strict energy and momentum conservation rules of the P-band are used to reexamine the exciton binding energy. The new value ≥20 meV is markedly higher than the currently accepted one (14 meV), being however well consistent with the robustness of the excitons up to room temperature. A peak controlled by the Sommerfeld factor is found near the bandgap (~1.36 eV). Our findings supported by theoretical calculations taking into account the anisotropic material parameters question the pure three-dimensional character of the exciton in InSe, assumed up to now. The refined character and parameters of the exciton are of paramount importance for the successful application of InSe in nanophotonics.

Peak intrinsic thermal conductivity in non-metallic solids and new interpretation of experimental data for argon

The inelastic nature of 3-phonon processes is investigated within the framework of perturbation theory and linearized Boltzmann transport equation (BTE). By considering the energy conservation rule governing this type of interaction in a statistical average sense, the impact of different forms of the regularized energy-conserving Dirac delta function on 3-phonon scattering rates was evaluated. Strikingly, adopting Lorentz distribution, in accordance with the shape of eigenenergy broadening of phonon normal modes due to the leading term of crystal anharmonicity, was found to play a critical role in activating umklapp processes at low temperature, leading to intrinsic lattice thermal conductivity peak at finite temperature for perfect crystal. This characteristic behavior, unique to the Lorentzian, lays foundation for developing adjustable-parameter-free computational models for reliable prediction of the finite lattice conductivity at low temperature, even in the absence of extrinsic scattering processes (e.g., by crystal imperfections and boundary). An iterative solution scheme for BTE was used to compute the intrinsic thermal conductivity of solid argon over the entire temperature range (2–80 K). For the first time, the experimentally observed T2 behavior in the low temperature, T, limit and the peak temperature (∼8 K) were successfully recovered, in addition to the classical high temperature T−1 behavior above 20 K by the sole use of 3-phonon processes. The good agreement with experiment indicates that phonon–phonon interactions dominate over the entire temperature range in argon, contrary to previous hypotheses that the subpeak regime is dominated by phonon-defect scattering. Anisotropy in thermal conductivity of single crystal at low temperature due to phonon focusing was observed. In addition, argon conductivity is underestimated by an order of magnitude in single mode relaxation time approximation, where the collective nature of phonon mode relaxation is ignored.

An investigation on the thermal and energy performance of living wall system in Shanghai area

In order to analyze thermal and energy performance of living wall system in Shanghai area, a coupled heat and moisture transfer model is developed and validated by filed experiments. The measurement results prove that living wall has a better thermal performance than corresponding common wall in summer and winter. And an energy balance analysis is conducted to elucidate the difference of heat transfer mechanism between living wall and common wall. Based on the model, the impact of orientation on thermal performance of living wall is simulated and analyzed in summer and winter. Furthermore, additional equivalent thermal resistance is calculated to evaluate the average thermal performance of living wall according to the long-term simulation results of both walls. It's found that the additional equivalent thermal resistance of living wall in summer is obviously higher than that in winter. Finally, a sensitivity test is carried out to distinguish the significant factors that affect long-term thermal performance of living wall, including plant parameters, substrate parameters, structure layer parameters, indoor condition, weather parameters and irrigation frequency. The model in the paper helps to optimize the design of living wall to get a better thermal benefit and judge whether living wall satisfies the local rule of energy conservation.

Reflection and transmission of plane wave through fluid layer of finite width sandwiched between two monoclinic elastic half-spaces

This paper studies the reflection and transmission of a plane wave through a fluid layer of finite width sandwiched between two dissimilar monoclinic elastic half-spaces. Closed-form expressions for the phase velocity of quasi-waves (qP and qSV) have been obtained. The reflection/transmission coefficients and energy divisions have been procured for all the reflected and transmitted waves in terms of phase velocity, propagation vector, elastic constants and width of the layer. It has been noticed that these epitomes depend not only upon the incident angle and width of the layer, but also on the character of incident wave. Energy proportions have been calculated numerically to validate the rule of energy conservation at different angles of incidence. Graphical representation has been performed to demonstrate the analytical findings.

Nonconstant ponderomotive energy in above-threshold ionization by intense short laser pulses

We analyze the contribution of the quiver kinetic energy acquired by an electron in an oscillating electric field of a short laser pulse to the energy balance in atomic ionization processes. Due to the time dependence of this additional kinetic energy, a temporal average is assumed to preserve a stationary energy conservation rule, which is used to predict the position of the energy peaks observed in the photoelectron (PE) spectra. For a plane wave and a flattop pulse, the mean value of the quiver energy over the whole pulse leads to the concept of ponderomotive energy ${U}_{p}$. However, for a short pulse with a fast changing intensity, the stationary approximation loses its validity. We check these concepts by studying first the PE spectrum within the semiclassical model (SCM) for multiple-step pulses. The SCM offers the possibility to establish a connection between emission times and the PE spectrum in the energy domain. We show that PE substructures stem from ionization at different times mapping the pulse envelope. We also analyze the PE spectrum for a realistic sine-squared envelope within the Coulomb-Volkov and ab initio calculations solving the time-dependent Schr\odinger equation. We found that the electron emission amplitudes produced at different times interfere with each other producing, in this way, a new additional pattern that modulates the above-threshold ionization (ATI) peaks.

Strong excitation of emitters in an impedance matched cavity: the area theorem, π-pulse and self-induced transparency

I theoretically study the behavior of strong pulses exciting emitters inside a cavity. The ensemble is supposed to be inhomogeneously broadened and the cavity matched finding application in quantum storage of optical or RF photons. My analysis is based on energy and pulse area conservation rules predicting important distortions for specific areas. It is well supported by numerical simulations. I propose a qualitative interpretation in terms of slow-light. The analogy with the free space situation is remarkable.

Quantum Mechanical Analysis of the Compton Scattering Based on Electron Wave Model

A theoretical analysis is proposed to investigate the Compton scattering as well as the inverse Compton scattering. In this analysis, the incident and scattered electromagnetic (EM) waves are classically described using Maxwell's equations, while the interacting electron is represented quantum mechanically by a wavepacket with a finite spreading length. The density matrix formalism is introduced to analyze the interaction between the electron wave and the EM field in a quantum mechanical manner. The interaction mechanism is caused by the effective coupling between EM and electron waves satisfying the energy and momentum conservation rules. The effects of the electron relaxation time due to Coulomb collisions among electrons, as well as the finite spreading size of an electron, are newly considered. Expressions for the radiated power of the scattered wave are derived for Compton and inverse Compton scattering.

Magnetic ejection of submilimeter-sized diamagnetic grains observed in a chamber-type drop shaft

Mass dependence of magnetically induced translation is examined for submilimeter-sized diamagnetic grain, which is floated in a diffused gas medium of 70 Pa by the use of microgravity μG condition. Here the grains are ejected from field-center of a pole-piece magnetic circuit by field-gradient force in a direction of decreasing field; maximum field-intensity at initial point is about 0.6T. It was deduced from an energy conservation rule that magnetic potential of the grain at initial position was partially converted to kinetic energy during translation. Therefore, observed velocity was expected to be independent to mass of particle; this is because magnetic potential is proportional to mass of particle. In a given field distribution, the velocity was uniquely determined by intrinsic magnetic susceptibility χ DIA of material. We report here that the magnetic ejection in μ G condition is realized for sub-mm sized crystals of bismuth, graphite and magnesia. The χ DIA values obtained from the ejection agreed fairly well with the published values for the three materials. The mass-independent property of translation was examined by observing the translation of two bismuth grains with different sizes. A chamber-type drop shaft having a height of 1.5 m was introduced to produce the μ G condition. By the use of this drop shaft, study of field-induced motion of a single diamagnetic particle becomes possible in an ordinary laboratory.

Improved x-ray reflectivity calculations for rough surfaces and interfaces

We have investigated the fact that the calculated x-ray reflectivity based on the Parratt formalism, coupled with the use of the Nevot-Croce representation of roughness, show a strange phenomenon where the amplitude of the oscillation due to interference effects increases for a rougher surface. Here, we propose that the strange result has its origin in a currently used equation due to a serious mistake in which the Fresnel transmission coefficient in the reflectivity equation is increased at a rough interface, and the increase in the transmission coefficient completely overpowers any decrease in the value of the reflection coefficient because of a lack of consideration of diffuse scattering. The mistake in Nevot and Croce's treatment originates in the fact that the modified Fresnel coefficients were calculated based on the theory which contains the x-ray energy conservation rule at surface and interface. In their discussion, the transmission coefficients were replaced approximately by the reflection coefficients by the ignoring diffuse scattering term at the rough interface, and according to the principle of conservation energy at the rough interface also. The errors of transmittance without the modification cannot be ignored. It is meaningless to try to precisely match the numerical result based on a wrong calculating formula even to details of the reflectivity profile of the experimental result. Thus, because Nevot and Croce's treatment of the Parratt formalism contains a fundamental mistake regardless of the size of roughness, this approach needs to be corrected. In the present study, we present a new accurate formalism that corrects this mistake, and thereby derive an accurate analysis of the x-ray reflectivity from a multilayer surface, taking into account the effect of roughness-induced diffuse scattering. The calculated reflectivity obtained by the use of this accurate reflectivity equation gives a physically reasonable result, and should enable the structure of buried interfaces to be analyzed more accurately.

Long-lived states of antiprotonic lithiump¯Li+produced inp¯+ Li collisions

Antiproton capture by lithium atoms ($\overline{p}+\mathrm{Li}\ensuremath{\rightarrow}\overline{p}{\mathrm{Li}}^{+}+e$) is investigated at collision energies from $0.01$ to 10 eV by using a semiclassical (also know as quantum-classical hybrid) method, in which the radial distance between the antiproton and the Li${}^{+}$ ion is treated as a classical variable, and the other degrees of freedom are described by quantum mechanics. Analyzing the wave packet of the emitted electrons and making use of the energy conservation rule enable us to calculate the state distribution of the produced antiprotonic lithium $\overline{p}{\mathrm{Li}}^{+}$ atoms and also to distinguish between the capture and ionization ($\ensuremath{\rightarrow}\overline{p}+{\mathrm{Li}}^{+}+e$) channels at collisional energies above the ionization threshold. This method is tested for the capture of negative muons by hydrogen atoms, which was rigorously investigated in previous quantum mechanical studies. Most of the $\overline{p}{\mathrm{Li}}^{+}$ atoms produced in $\overline{p}+\mathrm{Li}$ are found to be sufficiently stable against Auger decays and are experimentally observable as long-lived states. The present system bears close similarities to the system of $\overline{p}+\mathrm{He}(2S)$. It is therefore expected that long-lived antiprotonic helium $\overline{p}{\mathrm{He}}^{+}$ atoms can be efficiently produced in the $\overline{p}$ capture by metastable He($2\phantom{\rule{0.16em}{0ex}}{}^{3}S$) atoms.

Comparative Study of FVM and FEM Using Rectangular Element in Heat Conduction Problems for Conductive Materials

This paper established the mathematic model of plane transient temperature field using the Finite Volume Method according to the energy conservation rule, it clearly interprets the actual physical meaning of fundamental formula in the calculus of variations. The computational domains were subdivided by rectangular elements and the contributing formula was obtained from the elements to respective dots. Comparing the results with FEM results showed that they have same coefficient except the coefficient of time change. This paper analyzed the reason of the different results between FEM and FVM. In addition, the actual problem of two-dimensional temperature field of thermal calculations is resolved by the new arithmetic of FVM and the FEM. Comparing FVM results with the theoretical solution and FEM result shows that the FVM is more approximate to the theoretical solution than the FEM. The new arithmetic of FVM not only can simplify the process of establish equation and make the meaning of formula understandable but also can ensure the calculation accuracy. What’s more, it can extend widely the applied range of the FVM on the problem of temperature field, and has great application value on solving complicated technological problems.

The Electrostatic Tangential Resistance of the MEMS Moving Plate with Bumps Considering the Edge Effects

Friction force is present in most microelectromechanical systems (MEMS), since they have a large ratio of surface area to their volume. To improve the performance and reliability of MEMS devices, it is necessary to fully understand the effect of friction which exists in the majority of MEMS. For the MEMS’s moving plate with bumps, the model of electrostatic tangential force is established based on the rule of energy conservation, and it is further revised considering the edge effects by the conformal mapping method. Three types of the electrostatic tangential resistance of the MEMS’s moving plate with bumps, which are the unrevised theoretical value and revised theoretical value considering the edge effects and simulation value, were compared. The effects of the applied voltage, the rate of all micro bumps projective area to the moving plate area, and the relative surface roughness are investigated, and the electrostatic tangential resistance between two charged moving plates with respect to each other is analyzed. It is found that the three types of the electrostatic tangential resistance will be increased with the increase of the applied voltage. The revised analytic results considering the edge effects are larger than the ones not revised, and the former are close to results of ANSYS simulation.