168 resultados para OUTER HELIOSHEATH
Resumo:
Simple geometries which are possible alternatives for the Orbitrap are studied in this paper. We have taken up for numerical investigation two segmented-electrode structures, ORB1 and ORB2, to mimic the electric field of the Orbitrap. In the ORB1, the inner spindle-like electrode and the outer barrel-like electrode of the Orbitrap have been replaced by 35 rings and 35 discs of fixed radii, respectively. In this structure two segmented end cap electrodes have been added. In this geometry, different potentials are applied to the different electrodes keeping top-bottom symmetry intact. In the second geometry, ORB2, the inner and outer electrodes of the Orbitrap were replaced by an approximate step structure which follows the profile of the Orbitrap electrodes. In the present study 45 steps have been used. In the ORB2, like the Orbitrap, the inner electrode is held at a negative potential and the outer electrode is at ground potential. For the purpose of comparing the performance of ORB1 and ORB2 with that of the Orbitrap, the following studies have been undertaken: (1) variation of electric potential, (2) computation of ion trajectories, (3) simulation of image currents. These studies have been carried out using both 2D and 3D Boundary Element Method (BEM), the 3D BEM was developed specifically for this study. It has been seen in these investigations that ORB1 and ORB2 have performance similar to that of the Orbitrap, with the performance of the ORB1 being seen to be marginally superior to that of the ORB2. It has been shown that with proper optimization, geometries containing far fewer electrodes can be used as mass analyzers. A novel technique of optimization of the electric field has been proposed with the objective of minimizing the dependence of axial frequency of ion motion on the initial position of an ion. The results on the optimization of 9 and 15 segmented-electrode traps having the same design as ORB1 show that it can provide accurate mass analysis. (C) 2015 Elsevier B.V. All rights reserved.
Resumo:
Simple geometries which are possible alternatives for the Orbitrap are studied in this paper. We have taken up for numerical investigation two segmented-electrode structures, ORB1 and ORB2, to mimic the electric field of the Orbitrap. In the ORB1, the inner spindle-like electrode and the outer barrel-like electrode of the Orbitrap have been replaced by 35 rings and 35 discs of fixed radii, respectively. In this structure two segmented end cap electrodes have been added. In this geometry, different potentials are applied to the different electrodes keeping top-bottom symmetry intact. In the second geometry, ORB2, the inner and outer electrodes of the Orbitrap were replaced by an approximate step structure which follows the profile of the Orbitrap electrodes. In the present study 45 steps have been used. In the ORB2, like the Orbitrap, the inner electrode is held at a negative potential and the outer electrode is at ground potential. For the purpose of comparing the performance of ORB1 and ORB2 with that of the Orbitrap, the following studies have been undertaken: (1) variation of electric potential, (2) computation of ion trajectories, (3) simulation of image currents. These studies have been carried out using both 2D and 3D Boundary Element Method (BEM), the 3D BEM was developed specifically for this study. It has been seen in these investigations that ORB1 and ORB2 have performance similar to that of the Orbitrap, with the performance of the ORB1 being seen to be marginally superior to that of the ORB2. It has been shown that with proper optimization, geometries containing far fewer electrodes can be used as mass analyzers. A novel technique of optimization of the electric field has been proposed with the objective of minimizing the dependence of axial frequency of ion motion on the initial position of an ion. The results on the optimization of 9 and 15 segmented-electrode traps having the same design as ORB1 show that it can provide accurate mass analysis. (C) 2015 Elsevier B.V. All rights reserved.
Resumo:
Plasma electrolytic oxidation coatings were produced on AM50 Mg alloy in alkaline phosphate based electrolyte with montmorillonite clay additives employing current densities of 30, 60, and 120 mA/cm(2). The effect of current density on the microstructure and corrosion properties of the coating was investigated. The clay additives got melted and reactively incorporated into the coating forming an amorphous phase, at all the current densities. However, the coating was predominantly amorphous only at 30 mA/cm(2) and with increasing current density, increasing fractions of crystalline phases were formed. Higher current densities resulted in increased thickness of the coating, but reduced the compactness of the coatings. Electrochemical impedance spectroscopy tests in 0.5 wt.% (0.08 M) and 3.5 wt.% (0.6 M) NaCl solution revealed that the coatings processed at 30 mA/cm(2) exhibited a relatively better initial corrosion resistance owing to its relatively defect-free barrier layer and compactness of the coating. However, the presence of amorphous phases in significant amounts and lack of MgO in the coating resulted in increased rate of dissolution of the coatings and degradation of corrosion resistance. Coatings produced at higher current densities exhibited initial inferior corrosion resistance due to a more defective barrier layer and increased porosity in pore band and outer porous layer. However, the increased amount of crystalline phases and an increased amount of MgO, which resisted dissolution, counterbalanced the negative effects of defective barrier and increased porosity resulting in a relatively lower rate of the degradation of the corrosion resistance. Thus, the corrosion resistance of all the coatings continuously decreased with time and became similar after prolonged immersion in NaCl solution. Increasing current density, therefore, did not prove to be beneficial for the improvement of the corrosion performance of the PEO coatings. (C) 2016 Elsevier B.V. All rights reserved.
