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2022 ◽  
Vol 238 ◽  
pp. 111948
Dong Seok Jeon ◽  
Gyu Jin Hwang ◽  
Hye Jin Jang ◽  
Nam Il Kim

Lubricants ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 12
Yuechang Wang ◽  
Abdullah Azam ◽  
Gaolong Zhang ◽  
Abdel Dorgham ◽  
Ying Liu ◽  

Experimental results have confirmed that parallel rough surfaces can be separated by a full fluid film. However, such a lift-off effect is not expected by the traditional Reynolds theory. This paper proposes a deterministic mixed lubrication model to understand the mechanism of the lift-off effect. The proposed model considered the interaction between asperities and the micro-elastohydrodynamic lubrication (micro-EHL) at asperities within parallel rough surfaces for the first time. The proposed model is verified by predicting the measured Stribeck curve taken from literature and experiments conducted in this work. The simulation results highlight that the micro-EHL effect at the asperity scale is critical in building load-carrying capacity between parallel rough surfaces. Finally, the drawbacks of the proposed model are addressed and the directions of future research are pointed out.

2022 ◽  
pp. 2111920
Weigao Sun ◽  
Lingfei Ji ◽  
Zhenyuan Lin ◽  
Jincan Zheng ◽  
Zhiyong Wang ◽  

2022 ◽  
Vol 12 (2) ◽  
pp. 820
Seungwan Woo ◽  
Geunhwan Ryu ◽  
Taesoo Kim ◽  
Namgi Hong ◽  
Jae-Hoon Han ◽  

We demonstrate, for the first time, GaAs thin film solar cells epitaxially grown on a Si substrate using a metal wafer bonding and epitaxial lift-off process. A relatively thin 2.1 μm GaAs buffer layer was first grown on Si as a virtual substrate, and a threading dislocation density of 1.8 × 107 cm−2 was achieved via two In0.1Ga0.9As strained insertion layers and 6× thermal cycle annealing. An inverted p-on-n GaAs solar cell structure grown on the GaAs/Si virtual substrate showed homogenous photoluminescence peak intensities throughout the 2″ wafer. We show a 10.6% efficient GaAs thin film solar cell without anti-reflection coatings and compare it to nominally identical upright structure solar cells grown on GaAs and Si. This work paves the way for large-scale and low-cost wafer-bonded III-V multi-junction solar cells.

Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 614
Haowen Wang ◽  
Jiangbo Huang ◽  
Longhuan Liu ◽  
Shanqiang Qin ◽  
Zhihong Fu

The pulsed eddy current (PEC) inspection is considered a versatile non-destructive evaluation technique, and it is widely used in metal thickness quantifications for structural health monitoring and target recognition. However, for non-ferromagnetic conductors covered with non-uniform thick insulating layers, there are still deficiencies in the current schemes. The main purpose of this study is to find an effective feature, to measure wall thinning under the large lift-off variations, and further expand application of the PEC technology. Therefore, a novel method named the dynamic apparent time constant (D-ATC) is proposed based on the coil-coupling model. It associates the dynamic behavior of the induced eddy current with the geometric dimensions of the non-ferromagnetic metallic component by the time and amplitude features of the D-ATC curve. Numeral calculations and experiments show that the time signature is immune to large lift-off variations.

Wenjin Qin ◽  
Dengbiao Lu ◽  
Lihui Xu

Abstract In this research, n-dodecane and JW are selected as single and multi-component surrogate fuel of aviation kerosene to study the Jet-A spray combustion characteristics. The spray combustion phenomena are simulated using large eddy simulation coupled with detailed chemical reaction mechanism. Proper orthogonal decomposition method is applied to analyze the flow field characteristics, and the instantaneous velocity field are decomposed into four parts, namely the mean field, coherent field, transition field and turbulent field, respectively. The four subfields have their own characteristics. In terms of different fuels, JW has a higher intensity of coherent structures and local vortices than n-dodecane, which promotes the fuel-air mixing and improves the combustion characteristics, and the soot formation is significantly reduced. In addition, with the increase of initial temperature, the combustion is more intense, the ignition delay time is advanced, the flame lift-off length is reduced, and soot formation is increased accordingly.

2022 ◽  
Christopher B. Reuter ◽  
Tanvir I. Farouk ◽  
Steven G. Tuttle
Jet Fuel ◽  
Lift Off ◽  

Sensors ◽  
2022 ◽  
Vol 22 (1) ◽  
pp. 326
Darko Vasić ◽  
Ivan Rep ◽  
Dorijan Špikić ◽  
Matija Kekelj

Computationally fast electromagnetic models of eddy current sensors are required in model-based measurements, machine interpretation approaches or in the sensor design phase. If a sensor geometry allows it, the analytical approach to the modeling has significant advantages in comparison to numerical methods, most notably less demanding implementation and faster computation. In this paper, we studied an eddy current sensor consisting of a transmitter coil with a finitely long I ferrite core, which was screened with a finitely thick magnetic shield. The sensor was placed above a conductive and magnetic half-layer. We used vector magnetic potential formulation of the problem with a truncated region eigenfunction expansion, and obtained expressions for the transmitter coil impedance and magnetic potential in all subdomains. The modeling results are in excellent agreement with the results using the finite element method. The model was also compared with the impedance measurement in the frequency range from 5 kHz to 100 kHz and the agreement is within 3% for the resistance change due to the presence of the half-layer and 1% for the inductance change. The presented model can be used for measurement of properties of metallic objects, sensor lift-off or nonconductive coating thickness.

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 201
Ruochen Huang ◽  
Mingyang Lu ◽  
Ziqi Chen ◽  
Wuliang Yin

Alternating current field measurement (ACFM) testing is one of the promising techniques in the field of non-destructive testing with advantages of the non-contact capability and the reduction of lift-off effects. In this paper, a novel crack detection approach was proposed to reduce the effect of the angled crack (cack orientation) by using rotated ACFM techniques. The sensor probe is composed of an excitation coil and two receiving coils. Two receiving coils are orthogonally placed in the center of the excitation coil where the magnetic field is measured. It was found that the change of the x component and the peak value of the z component of the magnetic field when the sensor probe rotates around a crack followed a sine wave shape. A customized accelerated finite element method solver programmed in MATLAB was adopted to simulate the performance of the designed sensor probe which could significantly improve the computation efficiency due to the small crack perturbation. The experiments were also carried out to validate the simulations. It was found that the ratio between the z and x components of the magnetic field remained stable under various rotation angles. It showed the potential to estimate the depth of the crack from the ratio detected by combining the magnetic fields from both receiving coils (i.e., the x and z components of the magnetic field) using the rotated ACFM technique.

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