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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Development of a Specialized Hydrostatic Comparator for the Accurate Density Determination of Natural Silicon Spheres: A Novel Method for a Primary Realization of the Unit Kilogram
摘要： A novel method to primary realize the soon-to-be redefined unit of mass, kilogram, is presented. The new approach will accurately relate the Planck constant to spheres manufactured from natural silicon. Therefore, the precisely known isotopical composition of a 28Si sphere will be transferred to a sphere made of natural silicon with a relative uncertainty of 3 x 10-8. To achieve this objective, the concept of a newly developed hydrostatic comparator, which combines the Archimedes principle with a magnetic suspension coupling, is discussed. This combination allows to improve the major uncertainty contribution of this type of instrument — the temperature stability.
关键词： silicon spheres,magnetic suspension coupling,Avogadro constant,hydrostatic weighing,Planck constant,kilogram
更新于2025-09-10 09:29:36
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Hydrostatic and uniaxial effects in InGaN/GaN quantum wells
摘要： We calculate strains, polarizations, and electric fields in InGaN/GaN quantum wells (lattice matched to GaN) under the influence of hydrostatic and uniaxial (along the c-axis) pressure. We calculate the confinement energies for electrons and holes, and we derive simple expressions for the transition energies and their pressure derivatives. We include the changes of the dielectric constant with pressure. The results seem compatible with the experimental data.
关键词： confinement energies,transition energies,uniaxial pressure,electric fields,strain,InGaN/GaN quantum wells,polarization,hydrostatic pressure
更新于2025-09-10 09:29:36
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A Novel Temperature-Insensitive Hydrostatic Liquid Level Sensor Using Chirped FBG
摘要： A novel half-bonded chirped fibre Bragg grating (CFBG) on a natural rubber diaphragm has been proposed to enhance the sensitivity and to compensate the temperature effects of a hydrostatic liquid level sensor. This innovative fabrication method resulted in the narrowing of the bandwidth with the hydrostatic pressure sensitivity recorded at -253 pm/kPa and water column sensitivity at -0.0253 nm/cm. The bandwidth modulation measurement was insensitive to temperature variations, when compared to centre wavelength modulation measurement. Furthermore, the proposed hydrostatic liquid level sensor is compatible with low cost photodetector.
关键词： temperature compensation,liquid level,hydrostatic pressure,Chirped fibre Bragg grating
更新于2025-09-09 09:28:46
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Two-dimensional semimetal in HgTe quantum well under hydrostatic pressure
摘要： We report results of systematic measurements of charge transport properties of the 20.5-nm-wide HgTe-based quantum well in perpendicular magnetic ?eld, performed under hydrostatic pressures up to 15.1 kbar. At ambient pressure, transport is well described by the two-band semiclassical model. In contrast, at elevated pressure, we observed nonmonotonic pressure dependence of resistivity at the “charge neutrality point.” For pressures lower than ≈9 kbar, resistivity grows with pressure, in accord with expectations from the band structure calculations and the model incorporating effects of disorder on transport in two-dimensional (2D) semimetals with indirect band overlap. For higher pressures, the resistivity saturates and starts decreasing upon further increase of pressure. Above ≈14 kbar the resistance value and the magnetoresistance character sharply change, which may indicate signi?cant change of electronic structure due to new electronic phase formation or some structural transitions. The data also reveal strong in?uence of disorder on transport in 2D electron-hole system with a small band overlap.
关键词： HgTe quantum well,charge transport,hydrostatic pressure,magnetoresistance,two-dimensional semimetal
更新于2025-09-04 15:30:14
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The Effects of Hydrostatic Pressure on the Surface Plasmon Resonance of Gold Nanocrystals
摘要： The surface plasmon resonances of gold nanospheres and nanorods have been measured as a function of hydrostatic pressure up to 17 GPa in methanol-ethanol 4:1 solvent and up to 10 GPa in paraffin. Both the sphere resonance and the longitudinal rod resonance exhibit redshifts while the transverse rod mode shows an extremely weak redshift or blueshift depending on the nanorod aspect ratio. Solidification of the solvent around 11 GPa causes some aggregation of the particles, readily identified through broadening of the SP band and further redshifting. Loading and unloading cycles show only minimal hysteresis in the spectra if the pressure remains below 11 GPa. The surface plasmon shifts are the result of two competing effects. Compression of the conduction electrons in the metals increases the bulk plasma frequency, which causes a blueshift. However, the increase in the solvent density under hydrostatic load leads to an increase in the solvent refractive index, which in turn leads to a redshift. We find that after accounting for the solvent contribution, we can spectroscopically determine the bulk modulus of the gold nanoparticles with a precision of 10%. The value obtained of K0 = 190 GPa is significantly higher than the value for bulk gold (167 GPa). Furthermore, we show that pressure-induced solidification causes a significant broadening and anomalous shift of the surface plasmon band that we attribute to aggregation and nanorod deformation.
关键词： optical absorption,refractive index,hydrostatic pressure,surface plasmon resonance,bulk modulus,gold nanoparticles
更新于2025-09-04 15:30:14