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A Theoretical Extension of AH FDTD Method and Applications in Various Physical Fields
摘要： In this paper we extended the Associated Hermite (AH) FDTD method theoretically and used it to analyze various physical fields, which are electromagnetic field, acoustic field and heat-transfer field. The AH differential transformation operator is developed theoretically as a basic element for setting a time-frequency bridge, where several common operators such as differential, second-order differential and integral linear operator, etc. on the concept of signal processing and analyzing can be expediently transformed, which leads to a unified and much simpler derivation to construct the previous AH FDTD formula. Therefore, it gives a reconsideration for AH FDTD to calculate a more general or even arbitrary liner physic field problems, which are focused on the commonly partial differential equations. Finally, based on the time-frequency bridge theory, we adopted several examples for verification from the formula derivation to numerical validation in electromagnetic field, acoustic field and heat-transfer field, respectively.
关键词： Acoustic,Heat-transfer,Associated Hermite,Finite difference time domain (FDTD)
更新于2025-09-23 15:22:29
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Experimental Study on the Cogeneration Performance of Roll-bond-PVT Heat Pump System with Single Stage Compression During Summer
摘要： Photovoltaic thermal (PVT) heat pump technology refers to the integration of photovoltaic and solar heat pump, representing the deep exploitation and utilization of solar energy. In this paper, roll-bond-PVT heat pump (RB-PVTHP) system with single stage compression is proposed and investigated experimentally. The roll-bond-PVT (RB-PVT) unit is introduced in detail which is combined with the photovoltaic module and single-sided roll-bond evaporation heat exchanger laminating together. The designed experimental system consists of 4 pieces of RB-PVT units, 1HP heat pump unit and 150L heat storage tank, which is also equipped with various monitoring sensors to explore the system operating characteristics. Then the performance evaluation method of the unit and system is proposed. The experimental investigation on the cogeneration performance of the system in northern China during summer is carried out simultaneously, in terms of the thermal efficiency, electrical efficiency, thermal-based overall efficiency of the unit and heating COP of the system. The operating characteristics monitoring results show that the system works in a long-term stable condition during the daytime with considerable cogeneration performance. The detailed performance parameters have been given in this paper. This study demonstrates that the RB-PVTHP system has the large-scale practically feasible application value in northern China.
关键词： Single-sided roll-bond evaporator,PVT,Cogeneration performance evaluation,Roll-bond-PVT heat pump
更新于2025-09-23 15:21:21
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Comparison of holographic setups used in heat and mass transfer measurement
摘要： The authors of the paper deal with measurement of heat and mass transfer for several years and they have frequently used few techniqes for measurement of refractive index distribution based on holographic interferometry. Some of the well known techniques have been modified some and some new ones developped. Every technique could be applied with success in different type of meassurement and obviously every one has set of properties making them unique. We decided to digest few different basic techniques and describe its properties in this paper with the aim to help the reader select the proper one for their measurement. The list of techniques and its properties is not comprehensive but schould serve as a basic orientation in the field.
关键词： holographic interferometry,refractive index distribution,heat and mass transfer,measurement techniques
更新于2025-09-23 15:21:21
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - On the Contribution of Thermally Generated Surface Plasmon-Polaritons to Heat Radiation of Metal Objects
摘要： We present theoretical and experimental evaluations of the thermally generated surface plasmon polaritons (TSPPs) contribution to heat radiation of metal objects. It is found that this contribution is significant only for the edges of such objects flat facets observed at sliding angles to the facets planes and it is p-polarized. The analytical model for calculation the spectrum and the integral intensity of the entire set of TSPPs arriving to the edge of their sources line has been developed. In contrast to thermal radiation, intensity of TSPPs is proportional to the third rather than fourth degree of temperature, while the TSPP spectrum is shifted towards low frequencies relative to the thermal radiation spectrum.
关键词： thermally generated surface plasmon polaritons,metal objects,heat radiation,p-polarized,analytical model
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Effect of thermal pre-treatment on thermionic emission current stability from carbon nanotube forests
摘要： Carbon nanotube forests have great potential as efficient thermionic electron emitters due to a highly localized optical heating effect (“Heat Trap”). In past experiments, we observed a rapid decay in the emission current. In this work, we demonstrate that a relatively stable emission current can be achieved if the nanotube forest is pre-heated to 300 °C for 4 hours priors to electron emission. We attribute this improved current stability to the removal of reactant species, such as water trapped within the nanotube forest network.
关键词： Heat Trap,outgassing,lifetime,Carbon nanotubes,current stability,cathode,thermionic emission
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - The role of lateral confinement in the localized heating of thermionic emitters based on carbon nanotube forests
摘要： When vertically aligned carbon nanotube arrays (CNT forests) are heated by optical, electrical, or any other means, heat confinement (i.e. in perpendicular to the CNTs’ axes), which stems from the anisotropic structure of the forest, is expected to play an important role. It has been found that, in spite of being primarily conductive along the CNTs’ axes, focusing a laser beam on the sidewall of a CNT forest can lead to a highly localized hot region—an effect known as “Heat Trap”—and efficient thermionic emission. This unusual heat confinement phenomenon has applications where the spread of heat has to be minimized, but electrical conduction in energy conversion (e.g. vacuum thermionics and thermoelectrics). However, despite its strong scientific and practical importance, the existence and role of the lateral heat confinement in the Heat Trap effect have so far been elusive. In this work, for the first time, by using a rotating elliptical laser beam, we directly observe the existence of lateral heat confinement and its corresponding effects on the unusual temperature rise during the Heat Trap effect.
关键词： lateral heat confinement,thermal anisotropicity,carbon nanotube forest,thermionic electron emitter,vacuum nanoelectronics,optical heating
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Mechanism of non-saturated field electron emission from gated p-type Si tips
摘要： Gated p-type Si tip arrays with the same gate area (AG) but various tip numbers (Ntip) were investigated to clarify the mechanism of non-saturated electron emission. It was found that the Ntip/AG ratio determines the current increasing rate (dI/dVG) of the non-saturated emission. A surface depletion/inversion dominated electron supply model that considered the local Joule heat effect was proposed to interpret the variation of the increasing rate of the non-saturated current. Less emitter in an array would lead to a higher average current on each tip, and thereby much local Joule heat to induce a stronger non-saturated emission. This work clarifies the mechanism of non-saturated emission from gated p-type emitters, and shows that the current increasing rate can be modified by changing the Ntip/AG ratio. The findings are crucial for designing reliable and controllable Si-based electron sources.
关键词： electron supply,vacuum electronic devices,p-type field electron emitter,Joule heat
更新于2025-09-23 15:21:21
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[Energy, Environment, and Sustainability] Advances in Solar Energy Research || Techno-Economic Potential of Large-Scale Solar Deployment in the US
摘要： PV system generates electricity with minimum environmental impact reduces than conventional greenhouse gas emission and consequently reduces the effects of global warming. In late of 2014, the Indian government announced an ambitious target of 100 GW installation capacity of solar PV systems by 2022. Since then, India has achieved notable progress towards this goal and has installed 20 GW cumulative solar capacity with 9.6 GW in 2017 alone. Based on the 2015 MIT Energy Initiative, by 2050, a major fraction of the world’s electric power will come from solar sources. However, this poses many technical and economic challenges on the electrical infrastructure. In this chapter, we focus on the US case, by studying the technical and economic potentials of large-scale deployment of the most commonly recognized types of solar; photovoltiac (PV) and concentrated solar power (CSP) at different locations in the US. The technical potential is assessed based on grid interconnection topologies, and solar system performance. The economic potential is evaluated based on several metrics such as the levelized avoided cost of energy (LACE) and levelized cost of electricity (LCOE), and the possibility of integration into the electricity markets. The economic potential also covers the subsidies, taxes, policies, and incentives for large-scale solar deployment. Two simulation case studies are implemented on two large-scale solar PV and CSP projects at different locations in the US to evaluate their techno-economic potentials.
关键词： Concentrated solar power,Heat transfer fluid,NPV,LCOE,Thermal energy storage,Photovoltaic system,LACE,Payback period,Mounting system
更新于2025-09-23 15:21:21
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Structural transformations and spectroscopic properties of Ni-doped magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2 for broadband near-IR light emission
摘要： Ni:MgAl2O4 spinel shows a reversible random Ni2t site redistribution with increasing temperature. With the aim of determining the influence of the structure evolution induced by heat-treatment on the nature of luminescence centers in NiO-doped spinel-based magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2, the detailed spectroscopic study of the initial glass during its heat-treatments at increasing and decreasing temperatures has been performed and accompanied by an XRD analysis and Raman spectroscopy. The initial glass was X-ray amorphous. Its optical spectrum is mainly formed by absorption of [5]Ni2t sites with a small amount of [4]Ni2t ones. Crystals of the nucleating catalyst, ZrTiO4, about 4 nm in size, appear during heat-treatment at 800 °C, while the absorption spectrum of Ni2t ions remains near unchanged. At 850 °C, spinel crystals with size of about 6 nm precipitate, which is accompanied by a broadband luminescence in the near-IR centered at 1330 nm with a bandwidth of 380 nm. At 950 °C, there is a slight reduction in intensity of absorption bands attributed to [6]Ni2t site redistribution with increasing temperature. A decrease in the amount of the [6]Ni2t luminescent centers is not accompanied by a decrease in the luminescence intensity because of the increased size of spinel crystals. Additional low-temperature heat-treatment does not lead to a redistribution between [6]Ni2t sites in spinel crystals in favor of [6]Ni2t ones. An increase of the luminescence intensity after low-temperature heat-treatment is associated with additional spinel crystallization.
关键词： Glass-ceramics,Luminescence,Spinel,Heat-treatment,Nickel,Absorption
更新于2025-09-23 15:21:21
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nanoparticles
摘要： We report changes on the magnetic behavior of the Heavy-Fermion ferromagnetic YbNi2 alloy when reducing the size of the particles to the nanometer scale by high-energy ball milling. The milling process induces a reduction on the particle size of the bulk alloy down to 10 (2) nm and a lattice strain of 1.8 (2)%, for 30 h of milling time, as calculated from the x-ray diffraction data. The ferromagnetic transition at TC =10.5 K in the bulk alloy tends to disappear whereas other magnetic transitions arise at lower temperatures with the milling process. The AC magnetic susceptibility of the 30 h milled sample shows a frequency independent peak at 3 K, in a wide range of frequencies, consistent neither with superparamagnetic nor simple freezing of the magnetic moments, and as expected for a ferromagnetic behavior. However, from the specific heat measurements in the 30 h milled sample, a peak at 3.6 K is shifted respect to that observed in the AC magnetic susceptibility, as found in spin glasses. Additionally, the specific heat on nanometric samples show reduced magnetic contributions respect to the bulk alloy with ?cmax around 0.45 J/molK. The results are explained by the influence of magnetic inhomogeneities and disorder of the alloys enhanced by the milling process in the ensemble of nanoparticles.
关键词： Specific heat,Ferromagnetic,Spin glass,Magnetic properties,Yb alloys
更新于2025-09-23 15:21:21