Article
Automation & Control Systems
Qichun Zhang, Jianhua Zhang, Hong Wang
Summary: This article presents a new minimum entropy control algorithm for stochastic nonlinear systems subjected to non-Gaussian noises. A new representation of the system stochastic properties is given using the cumulant-generating function based on the moment-generating function. Based on system output and control input samples, a time-variant linear model is identified and the minimum entropy optimization is transformed to system stabilization. An optimal control strategy is developed to achieve randomness attenuation and the boundedness of the controlled system output is analyzed.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2023)
Article
Chemistry, Physical
Sami Alajlouni, Albert Beardo, Lluc Sendra, Amirkoushyar Ziabari, Javier Bafaluy, Juan Camacho, Yi Xuan, F. Xavier Alvarez, Ali Shakouri
Summary: Thermoreflectance thermal imaging was used to measure the temperature field generated by nanostructured heat sources on a silicon substrate with different geometrical configurations. The traditional Fourier's law analysis failed as sizes decreased, and did not account for the geometry of the heat source. A hydrodynamic heat transport model successfully explained the observed temperature fields, highlighting differences in behavior between Silicon and InGaAs.
Article
Acoustics
Murat Sen, Orhan cakar
Summary: In many mechanical systems, different structural elements or subsystems produced by different producers are often combined to create a whole coupled system. This study presents a method for structural coupling of mechanical systems based on the Sherman-Morrison formula, which is known for solving mathematical inverse problems of modified matrices. The method is practical for real mechanical engineering applications as it only uses the frequency response functions of the coupling coordinates of the subsystems, eliminating the need for matrix inversion in calculations.
JOURNAL OF VIBRATION AND CONTROL
(2023)
Article
Thermodynamics
Jianfei Wei, Silong Zhang, Xingyu Zhou, Cheng Cheng, Jiang Qin, Oskar J. Haidn
Summary: This study investigates the coupling effects of near-wall flow and chemistry on the wall heat load in a methane combustion chamber. The results show that considering chemistry effects reduces the deviation of the wall heat load compared to experimental data. The influence of the coupled wall function is limited to the near-wall region.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Chuang Zhang, Songze Chen, Zhaoli Guo
Summary: Heat conduction in solid materials can exhibit fluid dynamics behavior when normal scattering dominates phonon transport, leading to the prediction of heat vortices with frequency-independent relaxation time in the hydrodynamic regime. This phenomenon can also appear in other regimes such as the ballistic regime, with differences in vortex sizes and critical values observed. The study provides insights into the wider window of heat vortices in different regimes and their characteristics in different material structures.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Physics, Condensed Matter
A. Yu Panchenko, V. A. Kuzkin, I. E. Berinskii
Summary: This study investigates the evolution of initial temperature profiles in a two-dimensional isolated harmonic graphene lattice. Two heat transfer problems are examined using analytical and numerical methods. Results show that the amplitude of the temperature profile decreases and oscillates at short times, with negligible anisotropy. However, at large times, the anisotropy becomes significant and each atom has distinct temperatures corresponding to different motion directions.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Thermodynamics
Junjie Lv, Yushan Gao, Ping Jin, Yaqun Qi, Bingyang Liu, Ruizhi Li, Guobiao Cai
Summary: In this study, a simplified one-dimensional transient heat transfer model is introduced to predict the temperature changes during the startup and shutdown of a rocket engine. By analyzing convective heat transfer and heat conductance, a strategy for iterative solving of the model is proposed and the accuracy of the model is verified through experiments.
APPLIED THERMAL ENGINEERING
(2023)
Article
Mathematics
Dmitry Kruchinin, Vladimir Kruchinin, Yuriy Shablya
Summary: This paper explores methods for deriving explicit formulas for coefficients of generating functions by utilizing powers of generating functions. The concept of compositae is generalized to bivariate generating functions, and basic operations are defined to obtain explicit formulas for compositae and coefficients of bivariate generating functions. The presented mathematical apparatus can be utilized to solve various problems related to the theory of generating functions.
Article
Thermodynamics
Yuxi Li, Longcang Shu, Rui Xiao, Yuezan Tao, Shuyao Niu, Zhe Wang
Summary: Groundwater heat pump (GWHP) systems provide geothermal energy utilization, with the aboveground part being relatively mature in design and construction. However, the underground part lacks sufficient development. The experimental results show that the structure of the pumping-recharge well has an impact on the heat transfer characteristics of GWHP systems, with the length and distance between screens affecting the pumping water temperature and thermal breakthrough time. The study suggests that the differences between the length of pumping and recharge well screens and the distance between them must be considered in the design of GWHP systems to improve heat transfer efficiency.
ENERGY CONVERSION AND MANAGEMENT
(2021)
Article
Mechanics
Jia-Hong Zheng, Zheng Zhong
Summary: A novel theoretical framework is proposed in this paper, decomposing internal energy into free internal energy and dissipation energy, and establishing dual-complementary variational principles with two energy functionals. The framework treats all variables as independent, and well-known variational principles can be derived from it, demonstrating its universality and adaptability.
Article
Physics, Multidisciplinary
Renwen Yu, Shanhui Fan
Summary: In this study, we demonstrate that the spatial coherence of thermal radiation can be manipulated in time-modulated photonic systems supporting surface polaritons. We develop a fluctuational electrodynamics formalism to calculate the cross-spectral density tensor of emitted thermal electromagnetic fields in the near-field regime. Our calculations indicate that time-modulation enables the transfer of spatial coherence between different frequencies and the possibility of correlations between different frequency components, which are unique to time-modulated systems. We also show that the decay rate of optical emitters can be controlled in the proximity of such structures, opening up avenues for coherence control in thermal radiation, dynamical thermal imaging, energy transfer manipulation, near-field radiative cooling, and the engineering of spontaneous emission rates.
PHYSICAL REVIEW LETTERS
(2023)
Article
Thermodynamics
Peng Xu, Tao Zhou, Zhongguang Fu, Shang Mao, Juan Chen, Yi Jiang
Summary: This study investigated the flow and heat transfer of lead-bismuth eutectic and supercritical carbon dioxide in a double D-type straight channel printed circuit heat exchanger using numerical simulations. The results revealed that the overall heat transfer coefficient was strongly influenced by the mass flux and temperature difference, and reducing the tube diameter and wall thickness improved the overall heat transfer efficiency.
APPLIED THERMAL ENGINEERING
(2023)
Article
Mechanics
Ming-Gen Li, Jing-Dong Bao
Summary: Research shows that under a Hamiltonian thermostat, particles controlled by a logarithmic-oscillator thermostat moving in an external logarithmic potential exhibit an inversion in scaling exponents for the mean-squared displacement, with a significant dependence on λ. This continuous reduction of the scaling exponent is crucial in quantitatively evaluating all diffusive processes.
JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT
(2021)
Article
Green & Sustainable Science & Technology
R. Yildirim, A. Akyuz, K. Kumas, A. Gungor
Summary: The study conducted theoretical-experimental and life cycle climate performance analyses of the gravity-assisted heat pipe filled with R513A. It investigated the heat carried by the heat pipe and the internal heat transfer coefficients of the evaporator and condenser. The results showed that as the temperature set value increased, so did the heat transferred by the heat pipe. The study also found that direct emissions, mainly due to leaks of the working fluid, accounted for 82.22% of the total emissions.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2023)
Article
Thermodynamics
Xuguang Yang, Jinqi Hu, Yuanhong Fan, Chunhua Min, Kun Wang
Summary: This study investigates the coupling effects and optimization methods in the heat dissipation of ribbed channels. Through the establishment of a movable experimental facility and CFD solutions based on the conjugate gradient method, the research identifies the key factors affecting heat dissipation and obtains optimal structural parameters for L-shaped, V-shaped, and W-shaped ribs. Experimental and numerical results demonstrate that the longitudinal vortices coupling with transverse secondary flows play a significant role in heat dissipation, and the optimal ribs can greatly improve the Nusselt number compared to smooth channels.
APPLIED THERMAL ENGINEERING
(2023)
Article
Physics, Applied
Ke Wang, Xiansong Xu, Yuan Cheng, Min Zhang, Jian-Sheng Wang, Hai Wang, Gang Zhang
Summary: Using density functional theory calculations, we investigated the spin-wave spectrum and magnon-phonon interaction in the CGT monolayer. The MPI in the CGT monolayer exhibits weak in-plane isotropy and a strong wave vector dependence. The temperature increase from 5K to 55K leads to a 4 times decrease in the magnon relaxation time, emphasizing the significance of MPI in the spin dynamics of the ferromagnetic CGT monolayer.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
Xuefei Liu, Zhaofu Zhang, Zhao Ding, Bing Lv, Zijiang Luo, Jian-Sheng Wang, Zhibin Gao
Summary: A study using first principles method systematically predicted the anisotropic electronic and mechanical properties of 2D As2S3, showing a significantly higher Young's modulus ratio along two axes compared to black phosphorous. These findings provide valuable insights for the realization of flexible orientation-dependent nano-devices.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Multidisciplinary
Jian-Sheng Wang
Summary: The article recalls the impression of Professor Dietrich Stauffer during the author's postdoc at HLRZ, and discusses the application of the theory of soft phonons with quartic nonlinear interactions in the phase transition of BaTiO3 crystal.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2021)
Article
Physics, Multidisciplinary
Huanan Li, Shixiong Yin, Emanuele Galiffi, Andrea Alu
Summary: This study reveals the role of temporal interfaces in non-Hermitian physics, introducing the dual of PT symmetry for temporal boundaries. It unveils unexplored interference mechanisms enabling extreme energy manipulation, and provides new scenarios for time-switched metamaterials, connecting them with the opportunities offered by non-Hermitian phenomena.
PHYSICAL REVIEW LETTERS
(2021)
Article
Optics
Zi-Lan Deng, Feng-Jun Li, Huanan Li, Xiangping Li, Andrea Alu
Summary: Coupled resonances in non-Hermitian systems can be used to achieve extreme control over diffraction orders and tailor the overall spectral response, enabling control over singular features.
LASER & PHOTONICS REVIEWS
(2022)
Article
Physics, Multidisciplinary
Huanan Li, Shixiong Yin, Andrea Alu
Summary: This study demonstrates nonreciprocity for temporal boundaries by showing Faraday polarization rotation in a magnetoplasma with abruptly switched material properties. The findings open new opportunities for time metamaterials and wave engineering.
PHYSICAL REVIEW LETTERS
(2022)
Article
Thermodynamics
Yong-Mei Zhang, Mauro Antezza, Jian-Sheng Wang
Summary: The presence of interlayer interactions in twisted bilayer graphene (TBG) enhances several characteristics, including the optical and electronic properties. A series of double magic angles have been theoretically investigated in TBG. The thermal radiation from TBG can be tuned to the far infrared range by changing twist angles.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Physics, Applied
Huan He, Sihao Zhang, Jiwei Qi, Fang Bo, Huanan Li
Summary: Researchers have introduced nonreciprocal photonic time-crystals (NPTCs) by periodically switching the material properties of a spatially homogeneous magnetoplasma medium in time, enabling temporal Faraday rotation in both momentum bands and (partial) bandgaps. By combining the bandgaps of the NPTCs, the temporal Faraday effect can be utilized to create a unidirectional wave amplifier through energy extraction from modulation.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Hangbo Zhou, Gang Zhang, Jian-Sheng Wang, Yong-Wei Zhang
Summary: We investigate the anharmonic phonon scattering across a weakly interacting interface and find that the contribution from anharmonic three-phonon scatterings can be described by a temperature-dependent Landauer formula. Surprisingly, in the weak coupling limit, the transmission due to anharmonic phonon scattering increases indefinitely with temperature, which is not the case for two-phonon processes. We further reveal that anharmonic effects dominate over harmonic processes even at room temperature in real heterogeneous interfaces, emphasizing the importance of anharmonicity in weakly interacting systems.
Article
Physics, Multidisciplinary
Huanan Li, Shixiong Yin, Huan He, Jingjun Xu, Andrea Alu, Boris Shapiro
Summary: Time metamaterials, including anisotropic photonic time crystals, have shown promising potential for wave manipulation. In this study, we investigate the unique wave dynamics of an anisotropic photonic time crystal formed by a periodically changing anisotropic medium. We demonstrate that a stationary charge embedded in the time crystal emits radiation, contrary to isotropic photonic time crystals, and its momentum distribution is controlled by the time crystal's band structure. This work expands the functionalities of time metamaterials and opens up new possibilities for radiation generation and control, with implications in classical and quantum applications.
PHYSICAL REVIEW LETTERS
(2023)
Review
Physics, Multidisciplinary
Jian-Sheng Wang, Jiebin Peng, Zu-Quan Zhang, Yong-Mei Zhang, Tao Zhu
Summary: This article discusses the description and modeling of transport phenomena in electron systems coupled via scalar or vector photons. It is divided into three parts: scalar photons (Coulomb interactions), transverse photons (described by vector potentials), and the phi = 0 or temporal gauge, which is a complete theory of electrodynamics. The nonequilibrium Green's function (NEGF) formalism is used as a tool to study steady-state transport, with the advantage of going beyond fluctuational electrodynamics (FE) due to its generality. Several examples are provided, including heat transfer between graphene sheets, light emission from a double quantum dot, and emission of energy, momentum, and angular momentum from a graphene nanoribbon. All calculations are based on a generalization of the Meir-Wingreen formula, with materials properties represented by photon self-energy and coupled with the Keldysh equation and the solution to the Dyson equation.
FRONTIERS OF PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Yong-Mei Zhang, Tao Zhu, Zu-Quan Zhang, Jian-Sheng Wang
Summary: We have developed a general microscopic theory for the transfer of energy, momentum, and angular momentum mediated by photons. Using the nonequilibrium Green's function method, we have proposed a unified formalism for describing the energy emitted, force experienced, and torque experienced by objects due to fluctuating electromagnetic fields. Our theory does not rely on the assumption of local thermal equilibrium and is applicable to arbitrary objects and non-reciprocal environments. By applying our theory to transport problems of graphene edges, we have demonstrated its capability and shown results that go beyond the predictive ability of conventional theories.
Review
Optics
Emanuele Galiffi, Romain Tirole, Shixiong Yin, Huanan Li, Stefano Vezzoli, Paloma A. Huidobro, Mario G. Silveirinha, Riccardo Sapienza, Andrea Alu, J. B. Pendry
Summary: This review comprehensively discusses the recent progress of time modulation in photonic metamaterials, including temporal switching, photonic time-crystals, and spatiotemporal modulation. It also reviews and provides perspectives on the applications of time modulation in nonreciprocity, synthetic motion, giant anisotropy, etc.
ADVANCED PHOTONICS
(2022)
Article
Materials Science, Multidisciplinary
Tao Zhu, Jian-Sheng Wang
Summary: A general microscopic first-principles method was presented to study Coulomb-interaction-mediated heat transfer in the near field, focusing on screened Coulomb potential and spectrum function of polarizability. Using single-layer graphene as an example, it was found that heat flux saturates at the extreme near field and differs from the 1/d dependence of local response functions.
Article
Materials Science, Multidisciplinary
Tianqi Deng, Gang Wu, Wen Shi, Zicong Marvin Wong, Jian-Sheng Wang, Shuo-Wang Yang
Summary: Researchers developed a new ab initio formalism for dipolar electron-phonon interactions in 2D materials, finding that out-of-plane dipoles contribute to the behavior of interactions. The study showed that the Frohlich model is inadequate for 2D materials and that a correct long-wavelength interaction is essential for reliable predictions.
