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Projector-based renormalization approach to electron-hole-photon systems in their nonequilibrium steady state
摘要： We present an extended version of the projector-based renormalization method that can be used to address not only equilibrium but also nonequilibrium situations in coupled fermion-boson systems. The theory is applied to interacting electrons, holes, and photons in a semiconductor microcavity, where the loss of cavity photons into vacuum is of particular importance. The method incorporates correlation and fluctuation processes beyond mean-field theory in a wide parameter range of detuning, Coulomb interaction, light-matter coupling, and damping, even in the case when the number of quasiparticle excitations is large. This enables the description of exciton and polariton formation and their possible condensation through spontaneous phase symmetry breaking by analyzing the ground-state, steady-state, and spectral properties of a rather generic electron-hole-photon Hamiltonian, which also includes the coupling to two fermionic baths and a free-space photon reservoir. Thereby, the steady-state behavior of the system is obtained by evaluating expectation values in the long-time limit by means of the Mori-Zwanzig projection technique. Tracking and tracing different order parameters, the fully renormalized single-particle spectra and the steady-state luminescence, we demonstrate the Bose-Einstein condensation of excitons and polaritons and its smooth transition when the excitation density is increased.
关键词： exciton condensation,nonequilibrium steady state,semiconductor microcavity,projector-based renormalization method,electron-hole-photon systems,Bose-Einstein condensation,polariton condensation
更新于2025-09-23 15:23:52
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Surface chemical states of gold nanoparticles prepared using the solution-plasma method in a CsCl aqueous solution
摘要： In this study, gold nanoparticles (AuNPs) prepared in a 5 mM CsCl aqueous solution using the solution‐plasma method are characterized via transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy with synchrotron radiation (SR‐XPS). The particle diameter is measured over the process time via TEM. During the solution‐plasma process, small particles of 2.1 to 2.2‐nm diameter are generated in the CsCl aqueous solution; these particles then enlarge via Ostwald ripening over time until they reach an equilibrium size of ~13 nm after 36 days. In addition, the surface chemical states of the AuNPs are characterized at different depths via SR‐XPS. The SR‐XPS measurements obtained using incident X‐ray energy (hν) of 945.0 eV revealed that Cs─Au, Cl─Au, and Cs─Cl─Au bonds are present 1.2 nm below the surface. The measurements obtained at an incident X‐ray energy of 2515.0 eV showed that Cs─Cl─Au bonding is also present 2.5 nm below the surface, indicating that Cs and Cl strongly interact with Au. The TEM and SR‐XPS measurements revealed that 2 processes occur cyclically during the growth process via Ostwald ripening: (i) the Cs and Cl in the aqueous solution adsorb on the AuNP surface and (ii) Au atoms subsequently bond to the AuNPs surface.
关键词： solution‐plasma method,TEM,gold nanoparticles,XPS,surface chemical states
更新于2025-09-23 15:23:52
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - A Novel Vacuum Interruption Contact Design for High Current DC Vacuum Circuit Breaker
摘要： The vacuum interruption contact structure affect the insulation and breaking performance of DC vacuum circuit breaker directly. A novel vacuum interruption contact system with axial magnetic field (AMF)-double transversal magnetic field (TMF) is investigated for high current interruption in DC vacuum circuit breaker in this paper. It consists of one AMF cup-shaped contact and two concentric TMF contacts, which the internal contact is a disk-shaped structure and the external contact is a cup-shaped structure. The so-called novel TMF-TMF-AMF contact structure has the merits of having a very high axial magnetic flux density at large current condition, and producing rotation Lorentz force for metal vapor arc caused during interruption process. Its performance is compared with that of traditional TMF contact, traditional AMF contact and TMF-AMF contacts using three-dimensional finite-element method and the comparison results verify the validity of this proposed interruption contact structure design.
关键词： Lorentz force,vacuum interruption,finite element method,Axial magnetic flux density,metal vapor arc
更新于2025-09-23 15:23:52
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Graphene oxide-based zirconium oxide nanocomposite for enhanced visible light-driven photocatalytic activity
摘要： In the present investigation, an efficient visible light-active, graphene oxide-based zirconium oxide nanocomposite (GO–ZrO2) has been synthesized by co-precipitation method. The synthesized photocatalyst was characterized by XRD, FTIR, FE-SEM, EDS, TEM, TGA, PL, UV-DRS and BET surface area analysis. The characterization results illustrate the homogeneous dispersion of ZrO2 nanoparticles in the GO–ZrO2 nanocomposite with excellent harmony between GO and ZrO2 nanoparticles. The photocatalytic efficiency of the synthesized GO–ZrO2 nanocomposite was evaluated by photodegradation of hazardous, water-soluble rhodamine B and methylene blue dyes under visible light irradiation. The 90% photocatalytic degradation of rhodamine B dye (with initial conc. 30 mg/L) was observed in 105 min of visible light irradiation, while 99.23% of methylene blue (with initial conc. 100 mg/L) dyes degradation was observed in just 60 min using 25 mg/100 ml dose of GO–ZrO2 nanocomposite as a photocatalyst. The mechanistic investigation using scavengers suggest that the superoxide (O2·?) is the most reactive species involved in the photodegradation of organic dyes. The synthesized photocatalyst GO–ZrO2 nanocomposite also exhibits excellent thermal stability and reusability.
关键词： Methylene blue,Rhodamine B,Photocatalytic activity,Zirconium oxide,Graphene oxide,Visible light,Co-precipitation method
更新于2025-09-23 15:23:52
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Statistical validation of utility of head-mounted display projection-based experimental impression evaluation for sequential streetscapes
摘要： This study compared the impression structure of streetscapes gained from field experiments with that from head-mounted display virtual reality experiments. The results were as follows: (1) the field experiment experience had a slight influence on the impressions reported from the head-mounted display experiment; (2) few items exhibited significant differences in impression values for the two experiments; (3) the impression structure comprised three factors—'Openness,' 'Balance,' and 'Activity'—in both experiments, and (4) no significant difference appeared between the two experiments relative to the subscale scores of these three factors. These results show that head-mounted display experiments can substitute field experiments.
关键词： semantic differential method,virtual reality,Impression evaluation,omnidirectional camera,head-mounted display
更新于2025-09-23 15:23:52
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A direct method to calculate second-order two-dimensional terahertz spectroscopy in frequency-domain based on classical theory
摘要： Previous theoretical researches on the two-dimensional terahertz spectroscopy (2DTS), which are conducted via inef?ciently time-consuming numerical simulation, deal with only single-mode system. To overcome the limitations, we derive a classical-theory-based analytical solution which is applicable to multi-modes system. Three typical weak sources of nonlinearities are introduced. The ?ndings suggest that the analytical results correspond well with those obtained by the traditional numerical simulation. Thus the study provides a more ef?cient and practical method to directly calculate 2DTS, and, in a broader sense, sheds new light on the theory of 2DTS.
关键词： terahertz,two-dimensional spectroscopy,classical method
更新于2025-09-23 15:23:52
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Performance Evaluation of Short Parabolic Trough Collectors Integrated with a Small-Scale Solar Power and Heating System
摘要： An investigation is presented on the performance of a small-scale solar power and heating system with short parabolic trough collectors (PTCs). The steady-state model of the short PTCs is evaluated with outside experiments. The model mainly contains the heat loss of the receiver, the peak optical efficiency and the incident angle factor consisting of incident angle modifier and end loss. It is found that the end loss effect is essential in this model when the length of the PTCs is less than 48 m, especially in the winter. The standard deviation of the steady-state model is 1.4%. Moreover, the potential energy efficiency ratio of the solar power and heating system is considerably larger than the coefficient of performance (COP) of general air-source heat pumps, and increases with the decrease of the condensation temperature. An overall system efficiency of 49% can be reached. Lastly, the existence of a water storage tank improves the flexibility of heating the building, and the volume of the water storage tank decreases with the increase of the heating water temperature.
关键词： practical operating characteristics,parabolic trough solar collector,thermal performance,testing method,small-scale
更新于2025-09-23 15:23:52
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Consideration of the Impact of the Environmental Conditions when Designing Heat-Receiving Systems of the Solar Cylindrical Parabolic Modules
摘要： The aerohydrodynamic and heat exchange characteristics in the cylindrical heat receiver of a solar cylindrical parabolic concentrating module are investigated. The mathematical model is based on the Navier-Stokes equation system for a laminar flow in a channel. The model is implemented using the control volume method. The created computer algorithm allows carrying out parametric studies and revealing the most rational geometric, dynamic, and power parameters of the process. The proposed model describes the general physical outlines of the heat exchange in a cylindrical heat receiver which allows estimating the influence of the environment—wind velocity, ambient temperature, etc.—on it.
关键词： cylindrical heat receiver,rational geometric, dynamic, and power parameters,solar cylindrical parabolic module,wind velocity,Navier-Stokes equation system,ambient temperature,control volume method
更新于2025-09-23 15:23:52
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Structural and Superconducting Properties of Thermal Treatment-Synthesised Bulk YBa2Cu3O7?δ Superconductor: Effect of Addition of SnO2 Nanoparticles
摘要： YBa2Cu3O7?δ (Y-123) bulk superconductors with the addition of (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt.%) SnO2 nanoparticles were synthesised via a thermal treatment method. The in?uence of SnO2 addition on the superconducting properties by means of critical temperature, Tc, AC susceptibility, phase formation and microstructures, including its elemental composition analysis, were studied. Sharp superconducting transition, ?Tc, and diamagnetic transition were obtained for all SnO2-added samples. It was observed that sample x = 0.4 with a Y-123 phase percentage of 95.8% gives the highest Tc, smallest ?Tc, and the sharpest diamagnetic transition in the normalised susceptibility curves. The microstructure also showed an excess of Sn precipitates on the sample’s surface at x = 0.8 and above. As such, the best superconducting properties were observed at x = 0.4 SnO2 addition inside the Y-123 host sample.
关键词： YBa2Cu3O7?δ,bulk superconductor,additions,SnO2,thermal treatment method
更新于2025-09-23 15:23:52
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Analogous Anti-Ferroelectricity in Y2O3-Coated (Pb0.92Sr0.05La0.02)(Zr0.7Sn0.25Ti0.05)O3 Ceramics and Their Energy-Storage Performance
摘要： Antiferroelectric analogous (Pb0.92Sr0.05La0.02)(Zr0.7Sn0.25Ti0.05)O3 (PSLZSnT) ceramics were prepared by the solid-state sintering method by introducing a Y2O3-coating via the self-combustion method. The synthesized Y2O3-doped PSLZSnT ceramics present pseudo-cubic structure and rather uniform microstructural morphology accompanied by relatively small grain size. Excellent energy-storage performance is obtained in the Y2O3-doped PSLZSnT ceramics, in which the value of the energy-storage density presents a linearly increasing trend within the electric field measurement range. Such excellent performance is considered as relating to the rather pure perovskite structure, high relative density accompanied by relatively small grain size, and the antiferroelectric-like polarization-electric field behavior.
关键词： oxide doping,self-combustion method,energy-storage density,perovskite structure,PSLZSnT antiferroelectric-like ceramics
更新于2025-09-23 15:23:52