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Analysis of the Magnetic Properties of RFe₁₁Ti and RFe₁₁TiH (R=Tb,Ho)
S. W. Xu,Y. Yan,H. M. Jin,X. F. Wang,W. Q. Wang,F. Su 한국자기학회 2003 Journal of Magnetics Vol.8 No.4
The values of crystalline-electric-field parameters A㎚ for RFe₁₁TiHx (R=Tb,Ho) (x=0,1) are obtained by fitting calculations to the magnetization curves along the crystal axes at 4.2 K and higher temperatures. The insertion of H element in RFe₁₁Ti significantly affects CEF parameters A㎚. By using exchange field 2μ_BHex derived by inelastic neutron scattering and fitted A㎚, the calculations reproduce the experimental curves well.
A New Method for Tracking Meddies by Satellite Altimetry
Ienna, F.,Jo, Y.-H.,Yan, X.-H. AMERICAN METEOROLOGICAL SOCIETY 2014 Journal of atmospheric and oceanic technology Vol.31 No.6
Subsurface coherent vortices in the North Atlantic, whose saline water originates from the Mediterranean Sea and which are known as Mediterranean eddies (meddies), have been of particular interest to physical oceanographers since their discovery, especially for their salt and heat transport properties into the North Atlantic Ocean. Many studies in the past have been successful in observing and studying the typical properties of meddies by probing them with in situ techniques. The use of remote sensing techniques would offer a much cheaper and easier alternative for studying these phenomena, but only a few past studies have been able to study meddies by remote sensing, and a reliable method for observing them remotely remains elusive. This research presents a new way of locating and tracking meddies in the North Atlantic Ocean using satellite altimeter data. The method presented in this research makes use of ensemble empirical mode decomposition (EEMD) as a means to isolate the surface expressions of meddies on the ocean surface and separates them from any other surface constituents, allowing robust meddies to be consistently tracked by satellite. One such meddy is successfully tracked over a 6-month time period (2 November 2005 to 17 May 2006). Results of the satellite tracking method are verified using expendable bathythermographs (XBT).
Efficiency Enhancement of mm-Wave Power Amplifiers Using Envelope Tracking
Yan, J J,Presti, C D,Kimball, D F,Young-Pyo Hong,Chin Hsia,Asbeck, P M,Schellenberg, J IEEE 2011 IEEE microwave and wireless components letters Vol.21 No.3
<P>This letter presents a 44 GHz GaAs MMIC-based power amplifier (PA) which uses envelope tracking (ET) techniques for efficiency enhancement. Digital pre-distortion (DPD) is also employed to achieve high linearity. For a 7.6 dB PAPR 64QAM 20 MHz bandwidth signal (data rate 120 Mb/s) at an output power of 23.8 dBm, the measured EVM was 2.0% and ACPR1 was better than -40 dBc. Power efficiency enhancement of more than 5.7 times for the final MMIC stage (from 1.22% to 7%) was measured, using an external drain modulator. To the authors' best knowledge, this is the first time envelope tracking has been applied to PAs in the millimeter wave regime.</P>
On the fatigue performance of Aluminum alloy 2024 scarfed lap joints
Yan, W.Z.,Gao, H.S.,Yuan, X.,Wang, F.S.,Yue, Z.F. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.1
A series of fatigue test were carried out on scarfed lap joints (SLJ) using in airfoil siding to explore the effect of structural details, such as rows of rivets, lap angles, on its fatigue performance. Finite element (FE) analysis was employed to explore the effect of lap angle on load transfer and the stress evolution around the rivet hole. At last, the fatigue lives were predicted by nominal stress approach and critical plane approach. Both of the test results and predicted results showed that fatigue life of SLJ was remarkably increased after introducing lap angle into the faying surface. Specimen with the lap angle of $1.68^{\circ}$ exhibits the best fatigue performance in the present study.
Design of a 4-W Envelope Tracking Power Amplifier With More Than One Octave Carrier Bandwidth
Yan, J. J.,Chin Hsia,Kimball, D. F.,Asbeck, P. M. IEEE 2012 IEEE journal of solid-state circuits Vol.47 No.10
<P>This paper presents a high-efficiency broadband envelope-tracking power amplifier with operation at carrier frequencies from 500 to 1750 MHz. The RF power amplifier (RFPA) is provided by a single-chip gallium-nitride (GaN) integrated circuit (IC) whose design included a broadband output match achieved by operating directly into a load resistance of 50 Ω and broadband input match achieved using a feedback network. Under single-tone excitation, the Class-AB GaN PA IC provides output power above 12 W with greater than 50% drain efficiency and more than 10-dB gain at 40-V drain bias. When placed in envelope tracking configuration, using a representative WCDMA modulated signal with 4-MHz bandwidth and 6.6-dB peak-to-average power ratio, the ET PA achieved 4 W of average output power at its peak average drain efficiency of 31% at 752 MHz (including the power dissipation of the envelope modulator). The RFPA individually was measured to have an average drain efficiency of 58.5% for the WCDMA signal. Across the 500-1750-MHz band, using the WCDMA signal, greater than 25% average drain efficiency with more than 10 dB of gain was measured.</P>
Response of plasma rotation to resonant magnetic perturbations in J-TEXT tokamak
Yan, W,Chen, Z Y,Huang, D W,Hu, Q M,Shi, Y J,Ding, Y H,Cheng, Z F,Yang, Z J,Pan, X M,Lee, S G,Tong, R H,Wei, Y N,Dong, Y B IOP 2018 Plasma physics and controlled fusion Vol.60 No.3
<P>The response of plasma toroidal rotation to the external resonant magnetic perturbations (RMP) has been investigated in Joint Texas Experimental Tokamak (J-TEXT) ohmic heating plasmas. For the J-TEXT’s plasmas without the application of RMP, the core toroidal rotation is in the counter-current direction while the edge rotation is near zero or slightly in the co-current direction. Both static RMP experiments and rotating RMP experiments have been applied to investigate the plasma toroidal rotation. The core toroidal rotation decreases to lower level with static RMP. At the same time, the edge rotation can spin to more than 20 km s<SUP>−1</SUP> in co-current direction. On the other hand, the core plasma rotation can be slowed down or be accelerated with the rotating RMP. When the rotating RMP frequency is higher than mode frequency, the plasma rotation can be accelerated to the rotating RMP frequency. The plasma confinement is improved with high frequency rotating RMP. The plasma rotation is decelerated to the rotating RMP frequency when the rotating RMP frequency is lower than the mode frequency. The plasma confinement also degrades with low frequency rotating RMP.</P>