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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Tattoo Inks EM Characterization for MRI Interaction Evaluation
摘要： The lack of knowledge about the safety implications of tattooed individuals subjected to Magnetic Resonance Imaging (MRI) may, sometimes, lead to an exaggerate reaction from physicians such as the avoidance of the exam for tattooed patients. To explore the actual risks, in this work, the magnetic and electrical properties of five different tattoo inks have been measured to investigate their interaction with the MRI electromagnetic (EM) fields. Results highlight that the magnetic and electrical behaviour strongly depend on the type of analyzed ink. Magnetic measurements also reveal a different response between the ink solutions and the relative pigments.
关键词： Magnetic Resonance Imaging,electrochemical impedance,magnetization measurements,tattoo ink,Electrical conductivity,tattoo pigment
更新于2025-09-23 15:23:52
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Modeling of Radiative Properties of Polystyrene Foams Containing IR-Opacifiers
摘要： The addition of opacifiers in foams considerably reduces the radiative thermal conductivity and consequently enhances the insulation performance of the foams. In this work two different methods were developed to calculate the spectral specific extinction coefficient of opacified extruded polystyrene (XPS) foam material. Cell morphology and thermal conductivity of two identical XPS-foams, one opacified with 3 wt% carbon black as opacifier and one without opacifier, were thoroughly characterized. The experimental results were in a good agreement with the theoretical results obtained from two different computing techniques. These methods allow a good prediction of the specific extinction coefficient of arbitrary opacified foam material.
关键词： Radiative transfer,Radiative thermal conductivity,Complex refractive index,Extinction coefficient,Porous materials,Opacifiers
更新于2025-09-23 15:23:52
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In-situ synthesis of mullite-SiCw composite ceramics in Li2O-Al2O3-SiO2 ternary system for solar heat transmission pipeline
摘要： Nano-SiC whiskers (nano-SiCw) were in-situ synthesized in Li2O-Al2O3-SiO2 ternary system for preparing highly densified mullite-SiCw composite ceramics used for solar heat transmission pipeline. Mechanisms on the in-situ synthesis of nano-SiCw in the ternary system were investigated and the impact of nano-SiCw on the performances of the composites had been studied. Results showed that the growth processes of nano-SiC whiskers in Li2O-Al2O3-SiO2 ternary system were dominated by liquid-solid (LS) mechanism and the Li2CO3 additive could improve the SiCw yield through increasing the content of liquid phase and lowering the liquid viscosity. Sample BS3 (with 2.22 wt% Li2CO3 additive) sintered at 1440 °C obtained the highest SiC content of 47.9%. Nano-SiC whiskers with a diameter of 20e30 nm were interlocking with rod-like mullite crystals to improve the mechanical properties of the composites, and sample BS1 sintered at 1420 °C showed the highest bending strength of 115.4 MPa. The in-situ synthesized SiCw also shew significant effects on improving the thermophysical properties of the composites and sample BS1 exhibited a 3.6 times higher thermal conductivity than that of blank sample B1 without the introduction of nano-SiCw.
关键词： Li2O-Al2O3-SiO2 ternary system,Thermal conductivity,Mullite-SiCw composite ceramics,Solar heat transmission pipeline,SiC whiskers
更新于2025-09-23 15:23:52
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On the Singular Effects in the Relativistic Landau Levels in Graphene with a Disclination
摘要： The effect of a pseudo Aharonov-Bohm (AB) magnetic field generated by a disclination on a two-dimensional electron gas in graphene is addressed in the continuum limit within the geometric approach. The influence of the coupling between the spinor fields and the singular conical curvature is investigated, which shows that singularities have pronounced impact in the Hall conductivity. Moreover, the degeneracy related to the Dirac valleys is broken for negative values of the angular momentum quantum numbers, ?, including ? = 0. In this case, a Hall plateau develops at the null filling factor. Obtaining the Hall conductivity by summing over the positive and the negative ?'s, the null Landau level is recovered and the plateau at the null filling factor disappears. In any case, the standard plateaus, which are seen in a flat graphene are not obtained with these curvature and singular effects.
关键词： Elastic deformations,Graphene,Landau Levels,Hall conductivity
更新于2025-09-23 15:22:29
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Structural, optical, and dielectric properties of Cu, Ni-doped Zn ferrites
摘要： Ferrite nanocomposites with the composition Cu0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe2O4 were prepared by co-precipitation method. The effect of dopant to spinel ferrite ZnFe2O4 on the structural, morphological, optical, and dielectric properties of the as-prepared Cu-Zn and Ni-Zn ferrites were investigated. The structural, elemental, and optical properties conducted by using X-ray diffraction (XRD) technique with Cu/Kα radiation, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), Raman spectroscopy, and UV–Vis reflectance spectroscopy. For the electrical properties of the Cu-Zn and Ni-Zn ferrites, a real part of the dielectric constant and AC conductivity have been investigated with a frequency range of 20 Hz to 10 MHz at different temperature for each sample. The substitutions of Cu and Ni into the ZnFe2O4 nanocomposites crystal size calculated 20.36 nm for Cu-Zn ferrite and 10.95 nm for Ni-Zn ferrite. Also, the energy band gap of Cu-Zn ferrite is 2.6 eV and Ni-Zn ferrite is 2.83 eV. These results show that the energy band gap is increased when the crystal size is reduced by the substitution of Ni into the Zn ferrite. The dielectric constant and AC conductivity of Cu-Zn ferrite is bigger than the Ni-Zn ferrite at low frequencies. This situation is related to the structural parameters. Also, the AC conductivity increases with an increasing frequency and temperature.
关键词： AC conductivity,Co-precipitation,Cu-Zn ferrites,Dielectric constant,Ni-Zn ferrites
更新于2025-09-23 15:22:29
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Effect of Nb-doping on the structural and electrical properties of Ba0.97La0.02Ti1-xNb4x/5O3 ceramics at room temperature synthesized by molten-salt method
摘要： We, herein, report on the structural and electrical properties of Ba0,97La0.02Ti1-xNb4x/5O3 ceramics prepared by the molten-salt method. The XRD patterns of the samples at room temperature showed a single perovskite phase having a tetragonal structure with a P4/mmm space group. The electrical properties were studied by complex impedance spectroscopy in the frequency range (1–107Hz) at room temperature. The real and imaginary parts of impedance decreased with increasing Nb concentration. The complex impedance plot exhibited a single impedance semicircle for each compound, identified over the high and medium frequencies followed by a linear section, at low frequency, is explained by Warburg’s element. The study of the normalization curves of impedance and electrical modulus showed a mismatch of both peaks, which suggests the presence of short-range motion of charge carriers. The electrical conductivity decreased with increasing niobium amount and the experimental data were fitted using Jonscher’s universal power law. The exponent n is slightly superior to 1, indicating that the hopping occurs between neighboring sites.
关键词： molten-salt,conductivity,Ba0.97La0.02Ti1-xNb4x/5O3,EIS spectrum,impedance spectroscopy,Warburg element
更新于2025-09-23 15:22:29
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Optoelectronic properties of transparent conducting silver beta alumina and indium doped silver beta alumina thin films prepared by multi source vacuum evaporation method
摘要： The present study reports the optoelectronic properties of crystalline transparent conducting silver beta alumina (AgAl11O17) and indium doped silver beta alumina (AgAl11O17:In) thin films. In contrast to the p-type conductivity of the delafossite AgAlO2, both the hexagonal crystalline AgAl11O17 and AgAl11O17:In are n-type as confirmed by hot probe, hall effect and thermoelectric measurements. The variation in electrical conductivity (10-5-10-2 S/cm) and activation energy are correlated with carrier concentration and mobility. The films exhibit a wide direct band gap of ~3.93 ±0.02eV and transparency upto~62%.
关键词： Transparent conducting oxides,Thin films,Electrical conductivity,Optical properties
更新于2025-09-23 15:22:29
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Highly Hydrophobic Conducting Nanocomposites Based on a Fluoropolymer with Carbon Nanotubes
摘要： A procedure was suggested for preparing highly hydrophobic conducting coatings based on fluoropolymers with carbon nanotubes of two types: Taunit-MD and carbon nanotubes functionalized with alkyl groups. The surface resistance, contact angle, sliding angle, and surface roughness were measured; structural features of the nanocomposites were studied. The properties of the coatings obtained depend on the concentration and type of the carbon nanotubes used. Introduction of functionalized carbon nanotubes into a fluoropolymer matrix allows preparation of coatings with higher values of the sliding angle and electrical resistance. The contact angle and sliding angle depend on the surface roughness and structure in different fashions.
关键词： carbon nanotubes,electrical conductivity,surface roughness,hydrophobicity,nanocomposites
更新于2025-09-23 15:22:29
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A UV-Responsive Multifunctional Photoelectric Device Based on Discotic Columnar Nanostructures and Molecular Motors
摘要： Orientation control of ordered materials would not only produce new physical phenomenon but also facilitate the development of fancy devices. Discotic liquid crystals (DLCs) form 1D charge transport pathway by self-organizing into columnar nanostructures via π–π stacking. However, controlling the electrical properties in such nanostructures with some direct and instant way is a formidable task for their high viscosity and insensitivity to external stimuli. Herein, the arbitrary control over electrical conductivity of such columnar nanostructures is achieved with UV light by incorporating DLCs with molecular motors. Highly ordered DLC microstripe arrays are generated on desired substrate through a capillary bridge dewetting strategy. The conductivity of the microstripes could be continuously modulated by 365 nm light due to the influence of molecular motion under UV irradiation on the electron orbital overlap of columnar nanostructures. This is so because the disorder degree of the DLC molecules is associated with the intensity of UV light and the doping concentration of molecular motors. Moreover, the device shows memory effect and reversible conductivity change. The DLC microstripe arrays are very promising for the applications in UV detectors, memory devices, optical switches, and so on.
关键词： discotic liquid crystals,tunable conductivity,molecular motors,overcrowded alkenes,optical switches
更新于2025-09-23 15:22:29
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Analysis of a multistage solar thermal energy accumulator
摘要： The present work evaluates the effect of using two paraffin wax with different solidification points as PCM, stored in soda cans and sequentially distributed, on the discharge efficiency of solar thermal energy accumulators in laboratory and prototype scales. The discharge efficiency ranges found were [74 %, 92 %] and [49 %, 61 %] for the laboratory and prototype scale models respectively. Greater efficiency values were obtained in both accumulators when the first rows of soda cans exposed to the incoming air was filled with the PCM of lower solidification point (41 °C) and the last row with PCM of higher solidification point (56 °C). Numerical solution of the mathematical modeling allowed to predict the outlet air temperature which compared with experimental data. Bigger discrepancies with the simulation results were obtained in the prototype scale accumulator due to the variability of the environmental conditions. As conclusion we stated that it is possible to enhance the discharge efficiency of a solar energy accumulator by using two PCM with different solidification points. The implemented mathematical model allowed to predict the time evolution of the air temperature at the accumulators outlet. Row order and paraffin wax type allow to adjust the energy discharge rate depending on the application type.
关键词： Paraffin wax,Solar energy,Heat exchanger,Thermal conductivity
更新于2025-09-23 15:22:29