Analysis of electromagnetic properties of superconducting suspension system for gravity measurement
A type of superconducting suspension system for gravity measurement was introduced, and the principle and feasibility was discussed. System modeling and simulation analysis was carried out by ANSOFT, and optimization of structural position was finally completed. Analysis shows that, the system was exceptionally stable with a magnetic force gradient small enough to observe gravity changes. For systems with a superconducting sphere weighed of 15 g, the gravity measurement accuracy could reach 1 nano-Gal.
Numerical simulation of AC losses in superconducting gravimeter
The annual drift of μGal level is an important indicator of superconducting gravimeters, which helps geophysicists to clarify the weak geophysical signals. In this paper, a finite element simulation model of the superconducting gravimeter sensor is developed based on the H formulation for evaluating the contribution of the excitation AC losses and the AC losses under operating conditions to the superconducting gravimeter’s drift. The model combines the H formulation and the heat transfer module of COMSOL Multiphysics software to calculate the AC losses of the superconducting gravimeter’s test mass and obtain the distribution images of the test mass’s temperature due to the AC losses-induced heating. The overall temperature rise of the test mass is obtained by assuming that it heats up uniformly and thus combines the temperature dependence factor (10 μGal mK−1) of the superconducting gravimeter to derive the instrument drift induced by AC losses. Then, the long-term drift due to excitation losses can reach 0.847 μGal yr−1, while the operating losses can be 0.45 μGal yr−1 or even less, according to the simulation. In addition, this paper discusses the effects of the parameters (index number, critical electric field, and critical current density) in the E–J power law introduced by the H formulation on the AC loss evaluation. It is concluded that the AC losses are sensitive to the critical current density, and increasing the test mass’s critical current density helps enhance the stability of the superconducting gravimeter.
Mineral element analyses of various tropical forages in Guatemala and their relationship to soil concentrations
Determination de la composition minerale de differents fourrages dans 3 regions d'elevage du Guatemala et etude des relations entre la chimie des sols et la composition minerale des fourrages