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| 1 | Proportional Fairness-Based Energy-Efficient Power Allocation in Downlink MIMO-NOMA Systems with Statistical CSI显示文摘In this paper, proportional fairness(PF)-based energy-efficient power allocation is studied for multiple-input multiple-output(MIMO) non-orthogonal multiple access(NOMA) systems. In our schemes, statistical channel state information(CSI) is utilized for perfect CSI is impossible to achieve in practice. PF is used to balance the transmission efficiency and user fairness. Energy efficiency(EE) is formulated under basic data rate requirements and maximum transmitting power constraints. Due to the non-convex nature of EE, a two-step algorithm is proposed to obtain sub-optimal solution with a low complexity. Firstly, power allocation is determined by golden section search for fixed power. Secondly total transmitting power is determined by fractional programming method in the feasible regions. Compared to the performance of MIMO-NOMA without PF constraint, fairness is obtained at expense of decreasing of EE. | Yonghai Lin Zhen Yang Haiyan Guo | 2019 | China Communications2019，16，12： | 5 |
| 2 | Evaluation of the geopotential value W_0^(LVD) of China显示文摘Estimation of the zero-height geopotential value W_0^(LVD) for the CVD(China Vertical Datum) plays a fundamental role in the connection of traditional height reference systems into a global height system.Estimation the W_0^(LVD) of China is based on the computation of the mean geopotential offset between the value W_0= 62636856.0 m^2 s^(-2), selected as reference in this study, and the unknown geopotential value W_0^(LVD). This estimation is based on the combination of ellipsoidal heights, levelled heights(referring to the CVD), and some physical parameters, such as geopotential values, gravity values, and geoid undulations.The geoid undulations derived from the GGM(Global Geopotential Models). This combination is performed through three approaches: The first one is based on the theory of Molodensky, and the second one compares levelled heights and geopotential values derived from the GGMs, while the third one analyses the differences between GPS/Levelling and GGMs geoid undulations. The approaches are evaluated at 65 benchmarks(BMs) covered around Qingdao where the tide gauge is used to observe the local mean sea level of China. The results from three approaches are very similar. Furthermore, the W_0^(LVD)determined for the China local vertical datum was 62636852.9462 m^2 s^(-2), indicates a bias of about3.0538 m^2/s^(-2) compared to the conventional value of 62636856.0 m^2 s^(-2). | Lin He Yonghai Chu Nan Yu | 2017 | Geodesy and Geodynamics2017，8，6： | 1 |
| 3 | Hard nanocrystalline gold materials prepared via high-pressure phase transformation显示文摘As one of the important materials,nanocrystalline Au(n-Au)has gained numerous interests in recent decades owing to its unique properties and promising applications.However,most of the current n-Au thin films are supported on substrates,limiting the study on their mechanical properties and applications.Therefore,it is urgently desired to develop a new strategy to prepare nAu materials with superior mechanical strength and hardness.Here,a hard n-Au material with an average grain size of~40 nm is prepared by cold-forging of the unique Au nanoribbons(NRBs)with unconventional 4H phase under high pressure.Systematic characterizations reveal the phase transformation from 4H to face-centered cubic(fcc)phase during the cold compression.Impressively,the compressive yield strength and Vickers hardness(HV)of the prepared n-Au material reach~140.2 MPa and~1.0 GPa,which are 4.2 and 2.2 times of the microcrystalline Au foil,respectively.This work demonstrates that the combination of high-pressure cold-forging and the in-situ 4H-to-fcc phase transformation can effectively inhibit the grain growth in the obtained n-Au materials,leading to the formation of novel hard n-Au materials.Our strategy opens up a new avenue for the preparation of nanocrystalline metals with superior mechanical property. | Chenlong Xie Wenxin Niu Penghui Li Yiyao Ge Jiawei Liu Zhanxi Fan Xiaoxiao Liu Ye Chen Ming Zhou Zihe Li Mengdong Ma Yonghai Yue Jing Wang Li Zhu Kun Luo Yang Zhang Yingju Wu Lin Wang Bo Xu Hua Zhang Zhisheng Zhao Yongjun Tian | 2022 | Nano Research2022，15，7： | 0 |
| 4 | Ambipolar tribotronic transistor of MoTe_(2)显示文摘Two-dimensional(2D)tribotronic devices have been successfully involved in electromechanical modulation for channel conductance and applied in intelligent sensing system,touch screen,and logic gates.Ambipolar transistors and corresponding complementary inverters based on one type of semiconductors are highly promising due to the facile fabrication process and readily tunable polarity.Here,we demonstrate an ambipolar tribotronic transistor of molybdenum ditelluride(MoTe_(2)),which shows typical ambipolar transport properties modulated by triboelectric potential.It is comprised of a MoTe_(2)transistor and a lateral sliding triboelectric nanogenerator(TENG).The induced triboelectric potential by Maxwell’s displacement current(a driving force for TENG)can readily modulate the transport properties of both electrons and holes in MoTe_(2)channel and effectively drive the transistor.High performance tribotronic properties have been achieved,including low cutoff current below 1 pA·μm^(−1)and high current on/off ratio of~103 for holes and electrons dominated transports.The working mechanism on how to achieve tribotronic ambipolarity is discussed in detail.A complementary tribotronic inverter based on single flake of MoTe_(2)is also demonstrated with low power consumption and high stability.This work presents an active approach to efficiently modulate semiconductor devices and logic circuits based on 2D materials through external mechanical signal,which has great potential in human–machine interaction,intelligent sensor,and other wearable devices. | Yonghai Li Jinran Yu Yichen Wei Yifei Wang Liuqi Cheng Zhenyu Feng Ya Yang Zhong Lin Wang Qijun Sun | 2023 | Nano Research2023，16，9： | 0 |
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