- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
The Impact of Peltier Effect on the Temperature Field During Spark Plasma Sintering of Thermoelectric Materials
摘要： We report about the modelling of spark plasma sintering of a line of thermoelectric materials. A significant difference of sintering temperature DTs from 15 K to 110 K was found in the samples studied. The Peltier effect on the graphite-thermoelectric interfaces results in such temperature difference. The rise of sintering temperature leads to the DTs increase. DTs in the vertical direction is 2–3 times higher than in the radial one. Electric insulation modelled in the horizontal graphite–thermoelectric interfaces reduced DTs in all the types of numerically studied samples by 59–92%.
关键词： spark plasma sintering,FEM,SPS,Thermoelectrics,finite elements simulation
更新于2025-09-23 15:22:29
-
[IEEE 2018 IEEE 6th Workshop on Advances in Information, Electronic and Electrical Engineering (AIEEE) - Vilnius, Lithuania (2018.11.8-2018.11.10)] 2018 IEEE 6th Workshop on Advances in Information, Electronic and Electrical Engineering (AIEEE) - 18-pulse Rectifier with Electronic Phase Shifting with Autotransformer in Inverter and Rectifier Mode
摘要： To reduce harmonic distortion of the input current, multipulse rectifiers are used. They require the presence of phase-shifting transformers or autotransformers. Elimination of electromagnetic phase-shifting devices while maintaining small harmonic distortion of the input current and obtaining a power factor close to unity is possible with the use of electronic phase shift. The electronic phase shift is realized by means of the rectifier itself: the introduction of positive and negative control angles in the pairs of rectifiers’ modules. At present, 12-pulse rectifiers with electronic phase shift are known. Unlike classic rectifiers, they do not use phase-shifting transformers and have a unit power factor. Increasing of the rectifier’s pulse makes it possible to improve the harmonic composition of the input current. The use of the principle of electronic phase shift in 18-pulse rectifier leads to different levels of constant voltage at the output of the rectifiers. In this case, to equalize the currents of rectifiers’ modules, one can use both an increase the voltage at the input of rectifiers operating with large control angles and a decrease the input voltage of the rectifiers operating with smaller control angles. The principles of constructing of matching autotransformers for the 18-pulse rectifier with an electronic phase shift are considered in the article. Comparison of 18-pulse rectifiers with use of step-up and step-down autotransformers is made. Data on the installed capacity of autotransformers, power losses are obtained. The results of thermophysical modeling are presented. When comparing the parameters of the matching magnetic elements, it can be concluded that it is more appropriate to use a step-down autotransformer.
关键词： pulse-width modulation,magnetic elements,electronic phase shifting,rectifiers,power factor
更新于2025-09-23 15:22:29
-
Rare Earth Element || Optimisation of Parameters for Spectroscopic Analysis of Rare Earth Elements in Sediment Samples
摘要： The rapid demand for rare earth elements (REEs) in recent years due to increased use in various technological applications, agriculture, etc. has led to increased pollution and prevalence of REEs in the environment. Therefore, monitoring for REEs in the aquatic environment has become essential including the risk assessment to aquatic organisms. Since direct determination of REEs in sediment samples prove difficult at times, due to low concentrations available and complex matric effects, separation and enrichment steps are sometimes used. In this work, various REEs were determined employing wet acid digestion and lithium metaborate fusion in our optimised analytical technique. A com-parison of the two analytical techniques was also made. The results obtained from the optimised ICP-OES radial view technique were in 5% agreement with the ICP-MS results from the same samples. The accuracy of the method was checked with the geological ref-erence material GRE-03 and found to be in reasonable agreement. We demonstrated that there is a consistent relationship between the signals of the REEs and nebuliser gas flow rates, plasma power and pump speed. The detection limits for all the REEs ranged from 0.06 mg L-1 Yb to 2.5 mg L-1 Sm using the ICP-OES fusion technique.
关键词： spectroscopy optimization,rare earths elements,fusion digestion and sediment,lithium metaborate
更新于2025-09-23 15:21:21
-
Luminescent nanomaterials for droplet tracking in a microfluidic trapping array
摘要： The use of high-throughput multiplexed screening platforms has attracted significant interest in the field of on-site disease detection and diagnostics for their capability to simultaneously interrogate single-cell responses across different populations. However, many of the current approaches are limited by the spectral overlap between tracking materials (e.g., organic dyes) and commonly used fluorophores/biochemical stains, thus restraining their applications in multiplexed studies. This work demonstrates that the downconversion emission spectra offered by rare earth (RE)-doped β-hexagonal NaYF4 nanoparticles (NPs) can be exploited to address this spectral overlap issue. Compared to organic dyes and other tracking materials where the excitation and emission is separated by tens of nanometers, RE elements have a large gap between excitation and emission which results in their spectral independence from the organic dyes. As a proof of concept, two differently doped NaYF4 NPs (europium: Eu3+, and terbium: Tb3+) were employed on a fluorescent microscopy-based droplet microfluidic trapping array to test their feasibility as spectrally independent droplet trackers. The luminescence tracking properties of Eu3+-doped (red emission) and Tb3+-doped (green emission) NPs were successfully characterized by co-encapsulating with genetically modified cancer cell lines expressing green or red fluorescent proteins (GFP and RFP) in addition to a mixed population of live and dead cells stained with ethidium homodimer. Detailed quantification of the luminescent and fluorescent signals was performed to confirm no overlap between each of the NPs and between NPs and cells. Thus, the spectral independence of Eu3+-doped and Tb3+-doped NPs with each other and with common fluorophores highlights the potential application of this novel technique in multiplexed systems, where many such luminescent NPs (other doped and co-doped NPs) can be used to simultaneously track different input conditions on the same platform.
关键词： Rare earth elements,Single-cell analysis,Nanoparticles,Microfluidics,high-throughput screening
更新于2025-09-23 15:21:21
-
Nature-Inspired Quasicrystal SRG Using Fibonacci Sequences in Photo-Reconfiguration on Azo Polymer Films
摘要： In this study, we present the fabrication route of quasicrystal surface relief grating (SRG) of azopolymer. Based on photo-reconfigurable azobenzene property, various morphologies of grating patterns were inscribed on azopolymer thin-films by two-beam coupling light interference lithography (LIL) process. Multiplexing the LIL with different rotation sequence on azopolymers resulted in unusual surface structures including quasicrystal-like SRGs with Fibonacci sequences in rotational LIL. We investigated the effect of rotation sequence on the grating patterns by atomic force microscope, revealing that rotation sequence is a critical parameter determining surface structures of azopolymer films.
关键词： holographic optical elements,diffraction gratings,optical fabrication
更新于2025-09-23 15:21:21
-
Hopping parameters for tunnel coupling in 2D materials
摘要： Using Bardeen’s approach and orbital wave functions obtained by the algorithm of Herman and Skillman, we calculated interatomic matrix elements for tunnel interaction between the atoms from the set of B, C, N, Si, P, S, Ti, V, Se, Mo, Te and W, which constitute many 2D materials. In a wide range of interatomic distances, these values are approximated by simple functions with a small set of parameters. The results are presented in reference tables. These results will be useful for describing different tunnel phenomena in low-dimensional materials using the tight-binding approach.
关键词： tunnel coupling,2D materials,interatomic matrix elements,Bardeen’s approach,tight-binding approach
更新于2025-09-23 15:21:21
-
Compact antipodal Vivaldi antenna with rectangular slots and shaping of flare to cover 6 to 18 GHz
摘要： The compact antipodal Vivaldi antenna (AVA) with regular rectangular slots in the taper region is presented in this paper intended for electronic warfare applications. The antenna has a simple configuration with compact size. Micro strip line feeding is employed. The rectangular slots at regular intervals and terminal elliptical shaping of taper on top and bottom layers of antenna substrate enhance impedance bandwidth. The slot loading in the taper portion also enhances the gain. The novel feature of this antenna is its small aperture size which is 25 mm. Small aperture size is required for array applications to avoid grating lobes and element pattern nulls. A return loss of less than ?10 dB (VSWR <2.0) is obtained over 6 to 18 GHz. The antenna is designed using Ansoft HFSS software and the same is implemented in hardware. Return loss, radiation patterns, and gain have been measured and results reported.
关键词： Electronic Warfare,Printed antennas,Array elements
更新于2025-09-23 15:21:21
-
[IEEE 2020 Systems of Signals Generating and Processing in the Field of on Board Communications - Moscow, Russia (2020.3.19-2020.3.20)] 2020 Systems of Signals Generating and Processing in the Field of on Board Communications - Synthesis of Waveguide-Optical Analog-to-Digital Converter for Ultra-High Speed Systems of Information Processing
摘要： The possibility of synthesis of ultra-high speed of waveguide-optical analog-to-digital converter (further - ADC) providing conversion of analog information into digital in gigahertz range is considered. The functional scheme of the technologically well- waveguide-optical ADC developed optical elements is given, the principle of operation is described in detail. The possibility of increasing the speed of the ADC to potentially possible for optical data processing schemes is shown.
关键词： optical bistable elements,waveguide-optical analog-to-digital converter,optical waveguides,integrated optics
更新于2025-09-23 15:21:01
-
Investigation of temperature stability of ITO films characteristics
摘要： The paper represents research of thermal stability of optical and electro-physical parameters of ITO films deposited using various techniques. Variation of optical and electro-physical parameters was recorded using spectroscopy, and Hall’s and four-probe measurements. The best thermal stability was demonstrated by ITO films deposited by metal target sputtering In(90%)/Sn(10%) in mixture of gases O2 (25%) + Ar (75%) with further annealing in air atmosphere. This enables to apply this technique for production of thin film transparent resistive elements capable to heat the translucent structures up to 100?С without deterioration of their parameters.
关键词： thermal stability,transparent heating elements,magnetron sputtering,ITO films
更新于2025-09-23 15:21:01
-
Anion-Substituted Garnets Ca3Mn2 – x(Ni, Co)xVyGe3 – yO12 (x = 0, 1; y = 0, 1, 2): Preparation and Characterization
摘要： Garnets with the structure similar to that of Ca3Mn2Ge3O12 have been prepared with simultaneous substitutions of Ge4+ by V5+ in tetrahedra and of Mn3+ by Ni2+ or Co2+ in octahedra. X-ray photoelectron spectroscopy (XPS) proved the absence of V4+ in tetrahedra of the lattice of the compounds prepared and determined the valences of elements in octahedral sites. The increasing d-cation size in octahedra is accompanied by an increase in unit cell volume regardless of the composition of tetrahedra (VyGe3 – y)O12. The electrical conductivity of Ca3Mn2 – x(Ni, Co)xVyGe3 – yO12 (x = 0, 1; y = 0, 1, 2) garnet ceramic samples and the calculated bandgap widths make it possible to classify them with medium-gap semiconductors.
关键词： garnet,crystallographic radius,tetrahedron,electrical conductivity,octahedron,bandgap width,d elements
更新于2025-09-23 15:21:01