- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Distinguishing the effects of altered morphology and size on visible-light-induced water oxidation activity and photoelectrochemical performance of BaTaO2N crystal structures
摘要： Factors, including crystallinity, morphology, size, preferential orientation, growth, composition, porosity, surface area, etc., can directly influence the optical, charge-separation, charge-transfer and water oxidation and reduction properties of particle-based photocatalysts. Therefore, these factors must be considered when designing high-performance particle-based photocatalysts for solar water splitting. Here, a flux growth method was applied to alter the morphology and size of the Ba5Ta4O15 precursor oxide crystals using BaCl2, KCl, RbCl, CsCl, KCl+BaCl2 and K2SO4 at different solute concentrations, and the impact of nitridation with and without KCl flux was studied. Specifically, the effects of altered morphology and size on the visible-light-induced water oxidation activity and photoelectrochemical performance of the BaTaO2N crystal structures were investigated. Upon nitridation, the samples became porous due to the lattice shrinkage caused by the replacement of 3 O2? with 2 N3? in the anionic network. The BaTaO2N crystal structures obtained by nitridation without KCl flux show higher surface areas than do their counterparts prepared by nitridation with KCl flux because of the formation of porous networks. All samples exhibited a high anodic photocurrent upon nitridation without KCl flux compared with that of the samples obtained by nitridation with KCl flux. The findings demonstrate that it is important to specifically engineer photocatalytic crystals to reach their maximum potential in solar water splitting.
关键词： Water splitting,Visible light,Flux growth,Crystal size,Morphology,BaTaO2N
更新于2025-11-19 16:51:07
-
Design and characterization of the non-uniform solar flux distribution measurement system
摘要： It is important to accurately measure the solar flux distribution on the heated surface for the utilization of solar energy. To this end, in this paper a new measurement system was proposed to measure the solar flux distribution of the absorber tube surface by taking advantage of the end loss effect. The new measurement system does not disturb the collected lights path and influence the operation of the solar collector. The solar flux distribution at different angles can be measured with a few number of heat flux gage by rotating the proposed solar flux measurement system. Compared with existing measurement techniques, the proposed solar flux measurement system has distinct advantages such as simple structure, flexible and reliable operation and easy application. An experimental platform was designed and constructed, and the solar flux distributions on the outer surface of the absorber under different conditions are measured. The feasibility and effectiveness of the proposed measurement method are validated by comparing the experiment results and the numerical simulation results.
关键词： solar flux distribution,solar flux measurement system,parabolic trough solar collector,experimental investigation
更新于2025-09-23 15:23:52
-
[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
-
A study of the effects of ullage during the burning of horizontal PMMA and MMA surfaces
摘要： Experimental and numerical investigations of burning of horizontal surfaces of poly methyl methacrylate and methyl methacrylate are presented. A burner used in this study allows for the fuel surface to be oriented horizontally at a given distance from the burner rim. One of the aims of this study is to understand the effects of ullage (distance between burner rim and fuel surface) on the burning rate of the fuel and the flame structure. In the case of poly methyl methacrylate, the surface at an initial ullage regresses during its burning, and in the case of methyl methacrylate, the pool level is maintained at the given ullage by supplying the fuel at the rate of its burning. Careful repeatable measurements of temperature and species fields are carried out. These reveal the structure of a small‐scale pool flame established over a polymeric fluid such as methyl methacrylate, and such data are scarce in literature. In order to complement the experimental results, fire dynamics simulator is employed to simulate the experimental cases. Flame structure and flow field in the gas phase have been presented and discussed. As the ullage increases, the burning rate decreases. This trend is explained using surface convective heat flux results.
关键词： fire dynamics simulator (FDS),convective heat flux,burning rate,poly methyl methacrylate (PMMA),flame structure,ullage
更新于2025-09-23 15:23:52
-
Combined effects of unsteady wake and free-stream turbulence on turbine blade film cooling with laid-back fan-shaped holes using PSP technique
摘要： Detailed film cooling effectiveness distribution for a gas turbine blade under the effects of unsteady wakes and oncoming free-stream turbulence intensities was obtained using pressure sensitive paint (PSP) technique. Tests were performed on a linear cascade at Reynolds number of 3.85 × 10^5 based on the blade chord at cascade exit. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The test blade has three rows of compound angled cylindrical film holes at the leading edge, five rows of laid-back fan-shaped holes on the pressure surface and three rows of laid-back fan-shaped holes on the suction surface. The wake Strouhal number was varied from 0 to 0.36 and three mass flux ratios were determined. The oncoming free-stream turbulence intensities are 2.7% and 26.9%, respectively. Results show that the effect of the mass flux ratio on the film cooling effectiveness decreases under the high turbulence intensity and unsteady wake conditions. In most regions of the blade surface, the film cooling effectiveness decreases with the increase of wake Strouhal number, and the free-stream turbulence superimposed on the unsteady wake reduces the film cooling effectiveness further. The effect of the unsteady wake decreases under the high free-stream turbulence conditions.
关键词： Turbulence intensity,Film cooling effectiveness,PSP,Wake,Mass flux ratio,Turbine blade,Strouhal number,Laid-back fan-shaped hole
更新于2025-09-23 15:23:52
-
Real-time estimation of time-dependent imposed heat flux in graded index media by KF-RLSE algorithm
摘要： Due to the large computational time caused by complex computational process of the existing inversion algorithm, real-time reconstruction of high-magnitude time-dependent heat flux in graded index media is quite challenging. In this study, based on hybrid technology of the Kalman filter and recursive least-square estimator (KF-RLSE), the real time reconstructed high-magnitude time-varying heat flux on graded index media surface, and the measurement information comes from the opposite side of the media. The ideal participating media, which is assumed to be isotropic scattering, constant thermophysical properties, and opaque and diffuse gray boundary, is employed to verify the reliability and validity of the proposed. All the reconstruction results show that the KF-RLSE algorithm can effectively reconstruct the boundary heat flux regardless of the positive or negative gradient of the refractive index. When the refractive index of each position increases or reduces, the transient heat flux on the surface can still be predicted effectively and acceptably. Furthermore, effects of different parameters on the accuracy and stability of the estimated results are also investigated. The reconstructed results show that the time-dependent heat flux can still be effectively reconstructed even when the measurement noise does not match its covariance. Meanwhile, the accuracy of the reconstruction results improves with the decrease of measurement noise covariance when the measurement noise distribution is fixed in a curtain range.
关键词： Recursive least squares estimator,Inverse radiation-conduction problem,Time-dependent heat flux,Graded index media,Kalman filter
更新于2025-09-23 15:23:52
-
Superdomain structure and high conductivity at the vertices in the (111)-oriented epitaxial tetragonal Pb(Zr,Ti)O3 thin film
摘要： Recently, in ferroelectric materials, there have been many experimental efforts to find out more intriguing topological objects and their functionalities, such as conduction property. Here we investigated ferroelectric domain structures and related topological defects in the (111)-oriented epitaxial tetragonal PbZr0.35Ti0.65O3 thin film. Systematic piezoresponse force microscopy measurements revealed that the field-induced polarization switching can form thermodynamically stable superdomain structures composed of nano-sized stripe sub-domains. Within such superdomain structures, we observed the exotic equilateral triangular in-plane flux-closure domains composed of three stripe domain bundles with 120/120/120 degrees of separation. The conductive-atomic force microscopy measurements under vacuum showed that some vertices have significantly higher conductivity compared to other surrounding regions. This work highlights electric field-driven polarization switching and unique crystallographic symmetry (here, three-fold rotational symmetry) can generate exotic ferroelectric domain structures and functional topological defects, such as conductive vertices.
关键词： Vertex,Ferroelectric,Superdomain,Flux-closure domain,Piezoresponse force microscopy,Conductive-atomic force microscopy
更新于2025-09-23 15:23:52
-
[IEEE 2018 24rd International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Stockholm, Sweden (2018.9.26-2018.9.28)] 2018 24rd International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Structural analysis and modelling of packaged light emitting devices by thermal transient measurements at multiple boundaries
摘要： The paper presents a comprehensive methodology for modeling the electrical, optical, and thermal domains of high-power LEDs, focusing on the XPE2 type from Cree. It introduces optimization algorithms (OPT1 and OPT2) to extract parameters such as series resistance (RS), ideality factor (m), and saturation current (I0) from forward voltage (VF) measurements. A quadratic model for radiant voltage (Vrad) is developed to describe the optical output, and thermal modeling is addressed through structure functions derived from transient thermal measurements. The approach enables accurate prediction of LED performance across varying currents and temperatures, with applications in thermal management and design optimization.
关键词： ideality factor,thermal management,structure function,LED modeling,radiant flux,forward voltage,saturation current,series resistance
更新于2025-09-23 15:23:52
-
Effects of flux pinning on the DC characteristics of meander-shaped superconducting quantum interference filters with flux concentrator
摘要： Superconducting quantum interference filters, or SQIFs, are a promising class of highly sensitive magnetometers benefiting from a highly peaked and symmetric magnetic response at zero-input flux. They can be used in magnetometry, e.g., in wideband applications. A simple solution to increase further their sensitivity is to add a superconducting flux concentrator (SFC) to their design. Using the ion irradiation process, we designed a meander-shaped SQIF enhanced with an SFC. The SFC improved the SQIF transfer factor by a factor of 8.4. However, high temperature superconducting (HTSc) devices are vulnerable to flux pinning, which can severely hinder their response. On the one hand, HTSc technologies alleviate the burden of cryogenics. On the other hand, applications that use SFCs in noisy and unshielded environments will become possible only if a better understanding of how this flux impacts the device's properties is achieved. We studied the relationship between the field present during the cooling process of the SQIF antenna (thereafter called 'cooling field') and the evolution of its DC response. We developed a simple and phenomenological model and were able to reproduce the degradation of the SQIF response. This work demonstrates the usability of SFC-enhanced SQIFs based on ion irradiated junctions in rather harsh conditions, in particular, an unshielded environment, and also gives an insight into the implications that such conditions cause on the application of SFCs in general.
关键词： ion irradiation,flux pinning,magnetometry,flux concentrator,superconducting quantum interference filters
更新于2025-09-23 15:22:29
-
[IEEE 2018 IEEE International Students' Conference on Electrical, Electronics and Computer Science (SCEECS) - Bhopal (2018.2.24-2018.2.25)] 2018 IEEE International Students' Conference on Electrical, Electronics and Computer Science (SCEECS) - Solar Power Based Three-Level Neutral Clamped Inverter Fed DTFC-SVM of an IM Drive
摘要： This paper presents a solar power based three-level neutral clamped inverter (3LNCI) fed induction motor drive (IMD) with space vector modulation based direct torque and flux control (DTFC-SVM) for the water pumping applications. Due to the robustness and the flexible operating characteristics, induction motor is most suitable for water pump system. A DC/DC boost converter along with perturb and observe method of maximum power point tracking (MPPT) control technique is employed to draw sophisticated power from the solar photovoltaic (PV) array. The DTFC-SVM of an IMD using 3LNCI is proposed for improving performance and reducing the ripple contents of torque, flux and stator currents. The proposed method is simulated in MATLAB/SIMULINK environment and simulated results are presented under various operating conditions.
关键词： photovoltaic array,space vector modulation,induction motor drive,three-level diode clamped inverter,Direct torque and flux control
更新于2025-09-23 15:22:29