Energy Transfer Model Research Articles

Gray-box model-based predictive control of Czochralski process

The present study proposes a gray-box (GB) model-based predictive control method to produce high-quality 300 mm silicon ingots in the commercial Czochralski (CZ) process. The GB model consists of an energy transfer, hydrodynamic, and geometrical model and a statistical model, predicts three controlled variables, i.e., crystal radius, growth rate, and melt position, and represents the time-varying and nonlinear characteristics of the CZ process. Solving an optimization problem with the GB model requires heavy computational load; therefore, the proposed method derives the prediction model by successive linearization of the GB model to compute optimal manipulated variables in several seconds. The proposed method was compared with the conventional method using PID controllers in disturbance rejection performance through control simulations. The results have demonstrated that the integral absolute error (IAE) of the proposed method was reduced by 60% on average and 89% at maximum even when a plant-model mismatch exists.

Spectral and time-resolved photoluminescence of human platelets doped with platinum nanoparticles.

This paper describes a detailed study of spectral and time-resolved photoprocesses in human platelets and their complexes with platinum (Pt) nanoparticles (NPs). Fluorescence, quantum yield, and platelet amino acid lifetime changes in the presence and without femtosecond ablated platinum NPs have been studied. Fluorescence spectroscopy analysis of main fluorescent amino acids and their residues (tyrosine (Tyr), tryptophan (Trp), and phenylalanine (Phe)) belonging to the platelet membrane have been performed. The possibility of energy transfer between Pt NPs and the platelet membrane has been revealed. Förster Resonance Energy Transfer (FRET) model was used to perform the quantitative evaluation of energy transfer parameters. The prospects of Pt NPs usage deals with quenching-based sensing for pathology’s based on platelet conformations as cardiovascular diseases have been demonstrated.

Cluster density slopes from dark matter–baryons energy transfer

In this paper, we extend previous works on the relation between mass and the inner slope in dark matter density profiles. We calculate that relation in the mass range going from dwarf galaxies to cluster of galaxies. This was done thanks to a modeling of energy transfer via SN and AGN feedback, as well as via dynamical friction of baryon clumps. We show that, in the mass range above galaxy masses (Groups and clusters), the inner slope-mass relation changes its trend. It flattens (towards less cuspy profile) around masses corresponding to groups of galaxies and steepens again for large galaxy cluster masses. The flattening is produced by the AGN outflows (AGN feedback). The one-$ \sigma$ scatter on $\alpha$ is approximately constant in all the mass range ($\Delta\alpha\simeq 0.3$). This is the first paper extending the inner density profile slope-mass relationship to clusters of galaxies, accounting for the role of baryons. The result can be used to obtain a complete density profile, also taking baryons into account. Such kind of density profile was previously only available for galaxies.

Peeling graphite layer by layer reveals the charge exchange dynamics of ions inside a solid

Over seventy years ago, Niels Bohr described how the charge state of an atomic ion moving through a solid changes dynamically as a result of electron capture and loss processes, eventually resulting in an equilibrium charge state. Although obvious, this process has so far eluded direct experimental observation. By peeling a solid, such as graphite, layer by layer, and studying the transmission of highly charged ions through single-, bi- and trilayer graphene, we can now observe dynamical changes in ion charge states with monolayer precision. In addition we present a first-principles approach based on the virtual photon model for interparticle energy transfer to corroborate our findings. Our model that uses a Gaussian shaped dynamic polarisability rather than a spatial delta function is a major step in providing a self-consistent description for interparticle de-excitation processes at the limit of small separations.

Research on Energy Transmission Mechanism of the Electro-Hydraulic Servo Pump Control System

The electro-hydraulic servo pump control system (EHSPCS) is a volume control system that uses a permanent magnet synchronous motor (PMSM) with a fixed displacement pump to directly drive and control the hydraulic cylinder. The energy transmission law of the system is very complicated due to the transformation of electrical, mechanical and hydraulic energy as well as other energy fields, and qualitative analysis of the energy transfer efficiency is difficult. Energy transfer analysis of the EHSPCS under different working conditions and loads is proposed in this paper. First, the energy flow transfer mechanism was analyzed, and the mathematical and energy transfer models of the key components of the system were established to explore the energy characteristic state transition rule. Second, a power bond diagram model was built, its state equation and state matrix were deduced, and a system simulation model was built. Finally, combined with the EHSPCS experimental platform, simulation experiments were carried out on the dynamic position following and steady-state position holding conditions of the system, and the variation rules of the power of each energy characteristic state and the system energy transfer efficiency under different loads were obtained. The research results provide a foundation for the study of power matching and energy-saving mechanism of the EHSPCS.

Liquid metal with solvents for CO2 capture

AbstractCarbon dioxide (CO2) capture is an essential method for emission control. In CO2 capture, although with the promising advantage of industrial application, chemical absorption meets the challenge of substantial energy consumption. Thus, an advanced solvent with liquid metal GaInSn/PANI/TEMPO has been first developed to reduce the energy consumption. The intensified thermoelectric effect between GaInSn/PANI/TEMPO has the potential to enhance the CO2 desorption. Density functional theory (DFT) model and spherical mass transfer and energy transfer model in the nanoscale are developed to study the mass and energy transfer in CO2 and GaInSn/PANI/TEMPO. The CO2 fraction, electron density, and velocity in the nanodomain are studied. The symmetrical electron density zone is identified for the thermoelectric effect. The mass transfer coefficient is increased by twofolds. The thermoelectric conversion amount reaches 32.6–44.8% and the energy consumption is reduced to 1.07 GJ t−1. The CO2 desorption is finally proven to occur at temperature below 339 K. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Discovering nonlinear resonances through physics-informed machine learning

For an ensemble of nonlinear systems that model, for instance, molecules or photonic systems, we propose a method that finds efficiently the configuration that has prescribed transfer properties. Specifically, we use physics-informed machine learning (PIML) techniques to find the parameters for the efficient transfer of an electron (or photon) to a targeted state in a nonlinear dimer. We create a machine learning model containing two variables, χ D and χ A , representing the nonlinear terms in the donor and acceptor target system states. We then introduce a data-free physics-informed loss function as 1.0 − P j , where P j is the probability, the electron being in the targeted state, j . By minimizing the loss function, we maximize the occupation probability to the targeted state. The method recovers known results in the targeted energy transfer (TET) model, and it is then applied to a more complex system with an additional intermediate state. In this trimer configuration, the PIML approach discovers desired resonant paths from the donor to acceptor units. The proposed PIML method is general and may be used in the chemical design of molecular complexes or engineering design of quantum or photonic systems.

Numerical study on impact energy transfer and rock damage mechanism in percussive drilling based on high temperature hard rocks

Percussive drilling is suitable for fragmentation of high temperature hard rocks in geothermal wells. In actual geothermal drilling, the heat exchange will occur between the low temperature drilling fluid and the high temperature rocks. This heat transfer effects can cause thermal stress in rocks. High temperature environment and thermal stress will cause rock damage. Therefore, when analyzing percussive drilling based on high temperature rock, the high temperature and heat transfer need to be considered. This article focuses on the effects of mechanical percussion-heat transfer couplings on impact stress wave propagation, energy transfer efficiency and rock damage in percussive drilling. At first, the physical model for mechanical percussion-heat transfer coupled process was built. And then the heat transfer model, fully coupled thermal stress calculation method, temperature-dependent plasticity damage model for rocks, and impact energy transfer model were introduced. Finally, the mechanical percussion-heat transfer coupled process were simulated. The main findings show that the high temperature effect will reduce the impact energy transfer efficiency. However, it can also reduce the rock strength, which contributes to the generation of rock tensile damage in percussive drilling. The heat exchange between low temperature drilling fluid and the high temperature rock will cause the tensile thermal stress in rocks. This tensile thermal stress can induce rock tensile damage, which will improve the impact energy transfer efficiency in percussive drilling. As the control group, the rocks being heated will reduce the energy transfer efficiency in percussion drilling. When the input impact energy (less than 102 J under the present simulation conditions) is small, the impact energy transfer efficiency of stinger teeth is greater than that of hemispherical teeth. And when the input impact energy is large, the impact energy transfer efficiency of hemispherical teeth is greater than that of stinger teeth. The key findings of this study are expected to provide some theoretical guidance for high-efficiency fragmentation of high temperature hard rocks in percussive drilling.

Energy and exergy study on indirect evaporative cooler used in exhaust air heat recovery

Indirect evaporative cooler (IEC) applied as an exhaust air heat recovery component for fresh air pre-cooling in air-conditioned zone, which successfully extends its application range to hot and humid areas. To explore more effective application method of the heat recovery IEC, an energy and exergy transfer model for IEC operating as a heat recovery devices was proposed in this study. The thermal performance and exergy transfer characteristics of three basic types of IECs: cross-flow, counter-flow, and parallel-flow IECs were numerically investigated. The results show that the irreversible heat transfer in the primary air channels and the irreversible mass transfer in the secondary air channels are the main causes of exergy loss. These two factors account for more than 90% of the total exergy destruction in all the three types of IECs. To alleviate this situation and improve the energy efficiency of the IEC, two two-stage modified heat recovery systems which combine IEC with sensible heat exchanger and energy recovery exchanger were proposed and numerical analyzed. The simulation results show that, for the modified systems, the exergy transfer efficiency is increased by 104.6% and 131.7%, while the heat transfer capacity is increased by 47.6% and 48.5%, respectively.

Modeling and application of Czochralski silicon single crystal growth process using hybrid model of data-driven and mechanism-based methodologies

Czochralski (Cz) silicon single crystal growth process is a large delay, nonlinear dynamic time-varying system with complex physicochemical reactions, multi-field and multi-phase coupling, and its modeling and control has always been a problem in the automatic control field. In this paper, a hybrid modeling method based on the data-driven model and mechanism model is proposed, and applied to the Cz silicon crystal growth process modeling. Firstly, to simplify the model complexity and improve the model accuracy, the crystal growth process model is divided into the energy transfer model and a hydrodynamic and geometric model. Here, a Hammerstein–Wiener model based on a long short-term memory network (LSTM-Hammerstein–Wiener) is established for the energy transfer process with multiple heat transfer links and hysteresis effect. Further, a novel robust LSTM-Hammerstein–Wiener model is proposed by introducing the M-estimation method, which avoids the effect of the outliers on model robustness. Secondly, the proposed robust LSTM-Hammerstein–Wiener is combined with the hydrodynamic and geometric model to obtain the hybrid model between the heater power and the crystal diameter. Meanwhile, the crystal diameter error compensation model is established to reduce the unmodeled dynamics of the mechanism model, thereby improving the accuracy of the hybrid model. Besides, the proposed hybrid model is applied to the model-free adaptive control of silicon single crystal diameter. Finally, various data experiment results based on actual operating data verify the effectiveness of the proposed hybrid model.

Partial Energy Transfer Model of Lamb Waves Scattering in Materially Isotropic Waveguides

The scattering phenomena of the fundamental antisymmetric Lamb wave mode with a horizontal notch enabling the partial energy transfer (PET) option is addressed in this paper. The PET functionality for a given waveguide is realized using the material interface. The energy scattering coefficients are identified using two methods, namely, a hybrid approach, which utilizes the finite element method (FEM) and the general orthogonality relation, and the semi-analytical approach, which combines the modal expansion technique with the orthogonal property of Lamb waves. Using the stress and displacement continuity conditions on the present (sub)waveguide interfaces, one can explicitly derive the global scattering matrix, which allows detailed analysis of the scattering process across the considered interfaces. Both methods are then adopted on a simple representation of a surface breaking crack in the form of a vertical notch, of which a certain section enables not only the reflection of the incident energy, but also its nonzero transfer. The presented results show very good conformity between both utilized approaches, thus leading to further development of an alternative technique.

CO2 capture intensified by solvents with metal hydride

Carbon dioxide capture significantly helps achieve the carbon neutral goal. Chemical absorption of CO2 by the solvent meets the bottleneck of the high energy consumption. An advanced solvent of CuH/PANI/TEMPO has been developed to reduce the energy consumption. The metal hydride CuH decomposes into the Cu atom to intensify the thermoelectric effect between PANI and TEMPO. The strong thermoelectric effect has the potential to enhance the CO2 desorption. DFT model and mass and energy transfer model in the nano-scale are developed accurately to quantify the system of CO2 and CuH/PANI/TEMPO. The CO2 fraction, electron density and velocity in the nano-domain are studied. It is found that the symmetrical electron density zone is produced. The mass transfer coefficient is improved by 2.15 times with 4.65 × 10−6 m/s and the energy consumption is reduced to 1.02GJ/tCO2. The thermoelectric conversion accounts for 31.4%–43.5% of the overall energy transfer.

Transient performance of a nanowire-based near-field thermophotovoltaic system

• A transient model of the near-field thermophotovoltaics is constructed. • Heating mode beneficial to the system’s thermal stability is proposed. • Start-up power consumption as a new evaluation index is proposed. Great improvement has been made in the optimization on the near-field thermophotovoltaic system at the steady state, whereas system safety evaluation under near-field thermal radiation and transient output performance considering the energy consumption of the cooling device are lacking. Therefore, it is important to extend the investigation on the system to the transient state. Based on the law of energy conservation and theory of near-field radiative heat transfer, a transient energy transfer model of a W nanowire-based near-field TPV system considering the energy consumption of the cooling device was established. The heating process of each component in the system was explored, and the effects of the input power density and cooling medium’s velocity on system performances were analyzed. Moreover, a new evaluation index named the start-up power consumption was proposed to characterize the start-up performance of the system. The results show that based on the common working conditions, the maximum heating rate of the emitter in the transient process is up to 1500 K/s, which makes a serious threat to the experimental safety of the system. However, only the maximal operating temperature of 1752 K can be obtained according to the steady-state model and this temperature is within safe range, indicating the shortcomings of the steady-state model. The maximum heating rate of the emitter can be reduced to 304 K/s by adopting a progressive heating mode with a power supply rate of 20 W/cm 2 /s, showing that the safety operation of the system can be ensured. The highest cell efficiency occurs at the transient moment due to the increasing cell temperature. Increasing the cooling medium’s velocity is expected to maintain the highest cell efficiency until the steady state to improve the net system efficiency. However, the system needs external energy in the start-up stage because the cell is insufficient to produce enough electricity to drive the cooling device during this time, and the start-up power consumption of the system increases sharply with the increasing velocity of the cooling medium, which can be as high as 23405.9 W/m 2 . By comprehensively considering the net system efficiency and start-up power consumption, the alternative velocity was determined as 4 m/s. It can be seen that the transient energy transfer model of the near-field TPV system can be used to better guide the experimental safety design and comprehensively evaluate the system performance compared with the steady-state model.

Electrochemiluminescence resonance energy transfer system fabricated by quantum state complexes for cardiac troponin I detection

Electrochemiluminescence resonance energy transfer (ECL-RET) as an energy transfer model is used to explain signal quenching or enhancement phenomena. Establishing this model requires specific conditions including efficient electrochemiluminescence (ECL) emitters and energy donors with highly overlapping spectra and sufficient distance to complete the energy transfer. In this work, a novel ECL-based biosensor was proposed by utilizing graphene quantum dots (GQDs)-coupled gold nanoclusters (Au NCs) nanocomposites supported on a well-ordered Co3O4 nanoarrays (NAs) sensing substrate as signal labels. The as-synthesized Au NCs with controllable size by using glutathione as ligand showed stable ECL signal in triethylamine (TEA) aqueous solution. After coupling with GQDs, the obtained quantum state complexes (Au NCs-GQDs) are compact in space relation, and benefiting from resonance energy transfer and synergetic effect, thus producing higher ECL response. The prepared Co3O4 NAs exhibit consistent density orientation, which can not only work as an ideal substrate for capturing more immune molecules, but also act as a conductor to accelerate electron transport. This rational designed biosensor has been constructed for detecting cardiac troponin I (cTnI), a pivotal biomarker of acute myocardial infarction (AMI). Under optimal conditions, the biosensor showed a good ECL response of cTnI with a satisfactory linear range from 500 fg/mL to 20 ng/mL and an ultralow limit of detection of 354.2 fg/mL. With the excellent repeatability and stability, this method provides a clue for the expansion of the enhance-type ECL-RET model.

Transport Characteristics of the Near-Surface Layer of the Nucleus of Comet 67P/Churyumov–Gerasimenko

The paper considers the free molecular flow of gas through the dusty porous surface layer of a comet nucleus. The study is based on computer models of generation of a porous medium and Knudsen gas diffusion. We consider various types of homogeneous and heterogeneous layers constructed from nonintersecting spheres, including layers that contain microcracks or inner cavities. Using the test-particle method, we quantitatively estimate the free path distribution function, layer permeability, and effective kinetic characteristics of sublimation products passing through a nonisothermal porous layer. In addition, in this approach, we consider the volumetric absorption of visible solar radiation in the near-surface absorbing layer. Simple approximation expressions are obtained for all the transport characteristics under study, which makes it possible to estimate the characteristics with sufficient accuracy for practical applications in the physics of comets. The results will be used to construct new consistent models of energy transfer in the near-surface layer of a comet nucleus and, first of all, to analyze the results of the observations of comet 67P/Churyumov‒Gerasimenko.

Excitation energy transfer model for Ne-CO2 and Ne-N2 mixtures

The excited states of neon are capable of ionizing the CO2 and N2 molecules through Penning energy transfer mechanisms. Probability of such additional ionizations can be calculated from the measured gas gain fits. In the present work, Penning ionization processes for Ne-CO2 and Ne-N2 mixtures have been investigated with a newly developed model. The decreases in the transfer rates observed at high molecular gas concentrations indicate the existence of a remarkably interesting transfer mechanism for the excited neon atoms.

Effect of varying the TD-lc-DFTB range-separation parameter on charge and energy transfer in a model pentacene/buckminsterfullerene heterojunction.

Atomistic modeling of energy and charge transfer at the heterojunction of organic solar cells is an active field with many remaining outstanding questions owing, in part, to the difficulties in performing reliable photodynamics calculations on very large systems. One approach to being able to overcome these difficulties is to design and apply an appropriate simplified method. Density-functional tight binding (DFTB) has become a popular form of approximate density-functional theory based on a minimal valence basis set and neglect of all but two center integrals. We report the results of our tests of a recent long-range correction (lc) [A. Humeniuk and R. Mitrić, J. Chem. Phys. 143, 134120 (2015)] for time-dependent (TD) lc-DFTB by carrying out TD-lc-DFTB fewest switches surface hopping calculations of energy and charge transfer times using the relatively new DFTBABY [A. Humeniuk and R. Mitrić, Comput. Phys. Commun. 221, 174 (2017)] program. An advantage of this method is the ability to run enough trajectories to get meaningful ensemble averages. Our interest in the present work is less in determining exact energy and charge transfer rates than in understanding how the results of these calculations vary with the value of the range-separation parameter (Rlc = 1/μ) for a model organic solar cell heterojunction consisting of a gas-phase van der Waals complex P/F made up of a single pentacene (P) molecule together with a single buckminsterfullerene (F) molecule. The default value of Rlc = 3.03 a0 is found to be much too small as neither energy nor charge transfer is observed until Rlc ≈ 10 a0. Tests at a single geometry show that the best agreement with high-quality ab initio spectra is obtained in the limit of no lc (i.e., very large Rlc). A plot of energy and charge transfer rates as a function of Rlc is provided, which suggests that a value of Rlc ≈ 15 a0 yields the typical literature (condensed-phase) charge transfer time of about 100 fs. However, energy and charge transfer times become as high as ∼300 fs for Rlc ≈ 25 a0. A closer examination of the charge transfer process P*/F → P+/F- shows that the initial electron transfer is accompanied by a partial delocalization of the P hole onto F, which then relocalizes back onto P, consistent with a polaron-like picture in which the nuclei relax to stabilize the resultant redistribution of charges.

Оценка терморадиационного режима рабочего места крановщика в целях обоснованного выбора климатической системы кабины металлургического крана

The tendency of increasing of radiation sources power in metallurgy leads to an increase in the level of thermal radiation at the crane operator workplaces. The state of their health is characterized by a decrease in physical performance, the occurrence of colds, and occupational diseases of the cardiovascular and respiratory systems. Therefore, it is necessary to evaluate the thermal radiation regime of the crane operator workplace for further justification of the choice of the method and means of thermal protection. To assess the thermal irradiation of the metallurgical crane cabin, along with the method of building the thermal irradiation plot, the finite element method was used which was integrated into the automated software package ANSYS, into its plug-in Fluid Flow (Fluent) designed to build models of convective energy transfer by a liquid or gas flow. Flow turbulence is described by the Shear Stress Transport (SST) model. The article examines the thermal radiation situation in the steelmaking shop, which determines the choice of means to ensure an optimal microclimate at the crane operator workplace. It was revealed that the thermal radiation and the temperature of the railings of the metallurgical crane cabin significantly exceed the maximum permissible level, as a result of which it became impossible to choose a climate system that provides for a comfortable air temperature inside the cabin. To reduce the thermal load on the designed climate system, thermal protection elements are introduced into the design of the metallurgical crane cabin, such as a heat-reflecting screen of the floor and side wall and double glazing of the front wall. Then a high-temperature industrial air conditioner was selected, the efficiency of which was confirmed by the results of computer simulation. Thus, for a reasonable choice of the climate system of a metallurgical crane cabin, it is required to have rational combination of the methods and means of thermal protection used at the equipment design stage.

Research on Runoff Simulations Using Deep-Learning Methods

Runoff simulations are of great significance to the planning management of water resources. Here, we discussed the influence of the model component, model parameters and model input on runoff modeling, taking Hanjiang River Basin as the research area. Convolution kernel and attention mechanism were introduced into an LSTM network, and a new data-driven model Conv-TALSTM was developed. The model parameters were analyzed based on the Conv-TALSTM, and the results suggested that the optimal parameters were greatly affected by the correlation between the input data and output data. We compared the performance of Conv-TALSTM and variant models (TALSTM, Conv-LSTM, LSTM), and found that Conv-TALSTM can reproduce high flow more accurately. Moreover, the results were comparable when the model was trained with meteorological or hydrological variables, whereas the peak values with hydrological data were closer to the observations. When the two datasets were combined, the performance of the model was better. Additionally, Conv-TALSTM was also compared with an ANN (artificial neural network) and Wetspa (a distributed model for Water and Energy Transfer between Soil, Plants and Atmosphere), which verified the advantages of Conv-TALSTM in peak simulations. This study provides a direction for improving the accuracy, simplifying model structure and shortening calculation time in runoff simulations.

Radiative energy transfer model for finite anisotropic plates

This study aims to extend the radiative energy transfer method (RETM) to anisotropic plates loaded by transverse point force at high frequencies. The flexural wave field of a medium is represented by energy density and intensity. The energy variables are superposed by incoherent rays emitted by actual source in the analyzed domain and fictitious sources on the domain boundary. By applying Fermat’s principle, we theoretically prove that ray paths are straight lines for rays traveling in unbounded homogeneous anisotropic media. The kernel functions of the energy transfer in the domain are derived by considering the energy balance at the loading point. To represent the radiative intensity in a free field, we define a directivity function, which can be determined by the stationary phase approximation of the far field solution. The diffuse reflection of rays at free boundaries leads to a Fredholm integral equation, from which the fictitious sources are determined. Numerical examples show that the energy flow fields and energy distributions of typical anisotropic plates are well predicted by the proposed approach.