Ab Initio Study of Single-and Double-Electron Capture Processes in Collisions of He^(2+) Ions and Ne Atoms

The single-and double-electron capture(SEC, DEC) processes of He^(2+) ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selective SEC and DEC cross sections are presented in the energy region of 2 eV/u to 20 keV/u. Results show that the dominant reaction channel is Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s) in the considered energy region due to strong couplings with the initial state Ne(2s^(2)2p^(6)^(1)S) + He^(2+) around the internuclear distance of 4.6 a.u. In our calculations, the SEC cross sections decrease initially and then increase whereby, the minimum point is around 0.38 keV/u with the increase of collision energies. After considering the effects of the electron translation factor(ETF), the SEC cross sections are increased by 15%–25% nearby the energy region of keV/u and agree better with the available results. The DEC cross sections are smaller than those of SEC because of the larger energy gaps and no strong couplings with the initial state. Due to the Demkov-type couplings between DEC channel Ne^(2+)(2s^(2)2p^(4)^(1)S) + He(1s^(2)) and the dominating SEC channel Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s), the DEC cross sections increase with increasing impact energies. Good consistency can also be found between the present DEC and the experimental measurements in the overlapping energy region.

Rotor Position Estimation for Single-and Dual-Three-Phase Permanent Magnet Synchronous Machines Based on Third Harmonic Back-EMF under Imbalanced Situation

In this paper,an improved rotor position estimation strategy based on third harmonic back-EMF for single-and dual-three-phase permanent magnet synchronous machines(PMSMs)under imbalanced situation is proposed.Due to the imbalanced machine impedance,back-EMF or sensing resistor network,the measured triplen harmonic back-EMF will contain certain fundamental component distortion which may severely deteriorate the performance of rotor position estimation.With the aid of the fundamental component compensator,this distortion can be significantly compensated,and the rotor position estimation error can be minimized considerably.The proposed strategy has been implemented on a dSPACE platform with a prototype of dual-three-phase PMSM with serious imbalanced parameters,and operate at single-and dual-three-phase conditions.The experimental results prove that the proposed strategy can significantly improve the steady-state and dynamic performance of rotor position estimation under imbalanced situation.

An Efficient GCD-Based Cancelable Biometric Algorithm for Single and Multiple Biometrics

Cancelable biometrics are required in most remote access applications that need an authentication stage such as the cloud and Internet of Things(IoT)networks.The objective of using cancelable biometrics is to save the original ones from hacking attempts.A generalized algorithm to generate cancelable templates that is applicable on both single and multiple biometrics is proposed in this paper to be considered for cloud and IoT applications.The original biometric is blurred with two co-prime operators.Hence,it can be recovered as the Greatest Common Divisor(GCD)between its two blurred versions.Minimal changes if induced in the biometric image prior to processing with co-prime operators prevents the recovery of the original biometric image through a GCD operation.Hence,the ability to change cancelable templates is guaranteed,since the owner of the biometric can pre-determine and manage the minimal change induced in the biometric image.Furthermore,we test the utility of the proposed algorithm in the single-and multi-biometric scenarios.The multi-biometric scenario depends on compressing face,fingerprint,iris,and palm print images,simultaneously,to generate the cancelable templates.Evaluation metrics such as Equal Error Rate(EER)and Area and Receiver Operator Characteristic curve(AROC)are considered.Simulation results on single-and multi-biometric scenarios show high AROC values up to 99.59%,and low EER values down to 0.04%.

Effect of radio frequency bias on plasma characteristics of inductively coupled argon discharge based on fluid simulations

t A fluid model is employed to investigate the effect of radio frequency bias on the behavior of an argon inductively coupled plasma(ICP).In particular,the effects of ICP source power,single-frequency bias power,and dual-frequency bias power on the characteristics of ICP are simulated at a fixed pressure of 30 mTorr(1 Torr=1.33322×102 Pa).When the bias frequency is fixed at 27.12 MHz,the two-dimensional(2D)plasma density profile is significantly affected by the bias power at low ICP source power(e.g.,50 W),whereas it is weakly affected by the bias power at higher ICP source power(e.g.,100 W).When dual-frequency(27.12 MHz/2.26 MHz)bias is applied and the sum of bias powers is fixed at 500 W,a pronounced increase in the maximum argon ion density is observed with the increase of the bias power ratio in the absence of ICP source power.As the ratio of 27.12-MHz/2.26-MHz bias power decreases from 500 W/0 W to 0 W/500 W with the ICP source power fixed at 50 W,the plasma density profiles smoothly shifts from edge-high to center-high,and the effect of bias power on the plasma distribution becomes weaker with the bias power ratio decreasing.Besides,the axial ion flux at the substrate surface is characterized by a maximum at the edge of the substrate.When the ICP source power is higher,the 2D plasma density profiles,as well as the spatiotemporal and radial distributions of ion flux at the substrate surface are characterized by a peak in the reactor center,and the distributions of plasma parameters are negligibly affected by the dual-frequency bias power ratio.

Characteristics of pressure drop for singlephase and two-phase flow across sudden contraction in microtubes

Single-phase and gas-liquid two-phase pressure drops caused by a sudden con-traction in microtubes were experimentally investigated at room temperature and atmospheric pressure,using nitrogen and water. The experimental results on pressure drop with a novel measurement method,the tiny gaps on the tubes,were used to characterize the sudden contraction pressure drop for tube diameters from 850 to 330 μm. The ranges of the gas and liquid superficial velocity were 2.55―322.08 and 0.98―9.78 m/s in the smaller tube respectively. In single-phase flow experiments,the contraction loss coefficients were larger than the experimental results from conventional tubes in the laminar flow. While in the turbulent flow,the contraction loss coefficients were slightly smaller than those from conventional tubes and predicted well by Kc=0.5×(1-σ2)0.75. In two-phase flow experiments,the slip flow model with a velocity slip ratio S=(ρL/ρG)1/3 showed a good prediction that reveals the occurrence of velocity slip. An empirical correlation for two-phase flow pressure drops caused by the sudden contraction was developed based on the proposed contraction loss coefficients correlation for single-phase flow and Mar-tinelli factor.

Improvement of predictions of petrophysical transport behavior using three-dimensional finite volume element model with micro-CT images

Due to the intricate structure of porous media, the macroscopic petrophysical transport properties such as the permeability and the saturation used for the reservoir prediction also show a very complex nature and are difficult to obtain. Thus, a better understanding of the influence of the rock structure on the petrophysical transport properties is important. In this paper, we present a universal finite volume element modeling approach to reconstruct the three dimensional pore models from the micro-CT images based on the commercial software Mimics and ICEM, prior to the pore network model based on some basic assumptions. Moreover, tetra finite volume elements are piled up to realize the geometry reconstruction and the meshing process. Compared with the former methods, this process avoids the tremendously large storage requirement for the reconstructed porous geometry and the failures of meshing these complex polygon geometries, and at the same time improves the predictions of petrophysical transport behaviors. The model is tested on two Berea sandstones, four sandstone samples, two carbonate samples, and one Synthetic Silica. Single- and two phase flow simulations are conducted based on the Navier-Stokes equations in the Fluent software. Good agreements are obtained on both the network structures and predicted single- and two- phase transport properties against benchmark experimental data.