Reducing PAPR of SC-FDMA Signals through Simple Amplitude Predistortion

Yujie Xia,Jinwei Ji 한국전자통신연구원 2015 ETRI Journal Vol.37 No.5

A novel peak-to-average power ratio (PAPR) reduction method is proposed for single-carrier frequency-division multiple access (SC-FDMA) signals. The proposed method deliberately distorts the amplitude values of a few of the complex modulated symbols that cause peaks beyond a predetermined threshold in the samples of the output signal. The method then marks the location indices of the distorted symbols by using a pilot block at the transmitter without transmitting side information. At the receiver, the method is then able to recover the distorted amplitude values through the marked location indices. Computer simulation results show that when compared to conventional SC-FDMA signals, the proposed scheme can effectively reduce the PAPR of SC-FDMA signals with asymptotically consistent bit error rate (BER) performance.

EXISTENCE OF THREE POSITIVE PERIODIC SOLUTIONS OF NEUTRAL IMPULSIVE FUNCTIONAL DIFFERENTIAL EQUATIONS

Yuji Liu,Jianye Xia 한국전산응용수학회 2010 Journal of applied mathematics & informatics Vol.28 No.1

This paper is concerned with the neutral impulsive functional differential equations [수식]Sufficient conditions for the existence of at least three positive T−periodic solution are established. Our results generalize and improve the known ones. Some examples are presented to illustrate the main results.

Positive periodic solutions of impulsive functional differential equations

Yuji Liu,Jianye Xia,Weigao Ge 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.19 No.1-2

We study the existence and nonexistence of positive periodic solutions of a non-autonomous functional differential equation with impulses. The equations we study may be of delay, advance or mixed type functional differential equations and the impulses may cause the existence of positive periodic solutions. The methods employed are fixed-point index theorem, Leray-Schauder degree, and upper and lower solutions. The results obtained are new, and some examples are given to illustrate our main results.

Inter-Turn Short Circuit Fault Detection of PMSM Based on Wavelet Packet Energy Spectrum and CEEMDAN-HT

Xia Yankun,Li Xinyang,Luo Yujie 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3

Due to prolonged high load operation, the insulation performance of the stator winding coil in a permanent magnet synchronous motor (PMSM) tends to deteriorate, resulting in an inter-turn short circuit. At this time, there will be signifcant changes in the stator winding current and motor vibration intensity. In view of this phenomenon, a more accurate and complete detection method is proposed. In this study, wavelet packet transform (WPT) is combined with energy spectrum to process the current signal of PMSM, and the main fault features of the current signal are obtained. Then, complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) is combined with Hilbert transform (HT) to form a CEEMDAN-HT nonlinear signal analysis method. Firstly, the vibration signal is decomposed using the CEEMDAN algorithm to obtain a series of intrinsic mode functions (IMFs), and the variance contribution rate in principal component analysis (PCA) is applied to discriminate the IMFs containing fault feature information. Then, HT is used to process the IMF with high contribution rate, and the time, instantaneous frequency and amplitude are presented using a three-dimensional joint time–frequency diagram to obtain the main fault features of the vibration signal. Finally, a short-circuit fault simulation is built using ANSYS fnite element software, and a short-circuit fault experiment is built. By comparing and analyzing the results of fnite element simulation and experiment, the accuracy of the method proposed in this study is verifed.

EXISTENCE OF THREE POSITIVE PERIODIC SOLUTIONS OF NEUTRAL IMPULSIVE FUNCTIONAL DIFFERENTIAL EQUATIONS

Liu, Yuji,Xia, Jianye The Korean Society for Computational and Applied M 2010 Journal of applied mathematics & informatics Vol.28 No.1

This paper is concerned with the neutral impulsive functional differential equations $$\{{x'(t)\;+\;a(t)x(t)\;=\;f(t,\;x(t\;-\;\tau(t),\;x'(t\;-\;\delta(t))),\;a.e.\;t\;{\in}\;R, \atop {\Delta}x(t_k)\;=\;b_kx(t_k),\;k\;{\in}\;Z.$$ Sufficient conditions for the existence of at least three positive T-periodic solution are established. Our results generalize and improve the known ones. Some examples are presented to illustrate the main results.

POSITIVE PERIODIC SOLUTIONS OF IMPULSIVE FUNCTIONAL DIFFERENTIAL EQUATIONS

LIU, YUJI,XIA, JIANYE,GE, WEIGAO 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.19 No.1

We study the existence and nonexistence of positive periodic solutions of a non-autonomous functional differential equation with impulses. The equations we study may be of delay, advance or mixed type functional differential equations and the impulses may cause the existence of positive periodic solutions. The methods employed are fixed-point index theorem, Leray-Schauder degree, and upper and lower solutions. The results obtained are new, and some examples are given to illustrate our main results.

Cyclic Shift Based Tone Reservation PAPR Reduction Scheme with Embedding Side Information for FBMC-OQAM Systems

( Yongpeng Shi ),( Yujie Xia ),( Ya Gao ),( Jianhua Cui ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.8

The tone reservation (TR) scheme is an attractive method to reduce peak-to-average power ratio (PAPR) in the filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) systems. However, the high PAPR of FBMC signal will severely degrades system performance. To address this issue, a cyclic shift based TR (CS-TR) scheme with embedding side information (SI) is proposed to reduce the PAPR of FBMC signals. At the transmitter, four candidate signals are first generated based on cyclic shift of the output of inverse discrete Fourier transform (IDFT), and the SI of the selected signal with minimum peak power among the four candidate signals is embedded in sparse symbols with quadrature phase-shift keying constellation. Then, the TR weighted by optimal scaling factor is employed to further reduce PAPR of the selected signal. At the receiver, a reliable SI detector is presented by determining the phase rotation of SI embedding symbols, and the transmitted data blocks can be correctly demodulated according to the detected SI. Simulation results show that the proposed scheme significantly outperforms the existing TR schemes in both PAPR reduction and bit error rate (BER) performances. In addition, the proposed scheme with detected SI can achieve the same BER performance compared to the one with perfect SI.

Blood lipids and all-cause mortality among old people: the Chinese Longitudinal Healthy Longevity Survey 2008-2018

Wang Rongxi,Yu Xiaoyue,Wang Zhiqiang,Liu Yujie,Chen Hui,Liu Shangbin,XU CHENG,Chen Yingjie,Xia Danni,Ge Xin,Chang Ruijie,Xu Gang,Xiang Mi,Wang Ying,Shen Tian,Hu Fan,Cai Yong 한국역학회 2022 Epidemiology and Health Vol.44 No.-

OBJECTIVES: Proper blood lipid levels are essential for survival in older adults, but inconsistent relationships have been reported between blood lipids and all-cause mortality in the elderly. METHODS: This retrospective longitudinal study analyzed data from 1,067 Chinese older adults enrolled in the Chinese Longitudinal Healthy Longevity Survey collected in 2008 and followed up until death or December 31, 2018. The outcome was allcause mortality. Multivariate Cox regression analyses were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with stratification by age (60-80, 80-100, or ≥ 100 years) for further analysis. The survival probability according to lipid profile quartiles was calculated using Kaplan-Meier curves and the log-rank test. RESULTS: The participants’ mean age was 84.84 years, and 57.0% were female. In total, 578 individuals died, and 277 were lost to follow-up. The mean total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were higher among those who died than among those who survived. Participants in the second HDL-C quartile and the highest LDL-C and triglyceride (TG) quartiles had 28% higher, 23% lower, and 49% lower risks of all-cause mortality, respectively. After further adjustment, the associations remained except for HDL-C, and additional associations were observed between all-cause mortality and the third TC and LDL-C quartiles and the second TG quartile (HR, 1.44; 95% CI, 1.01 to 2.06; HR, 0.68; 95% CI, 0.49 to 0.94; HR, 0.79; 95% CI, 0.62 to 0.99, respectively). CONCLUSIONS: Older adults should maintain an LDL-C level of 1.91-2.47 mmol/L and a TG level of no less than 1.66 mmol/L.

Structural and magnetic properties of M-type Sr0.1Ca0.4La0.5Fe12O19 ferrites: The effects of CoxFe3-xO4 in precursor

Xiubin Zhao,Shuang Zhang,Jinsong Li,Ailin Xia,Yujie Yang 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.1

M-type ferrite Sr0.1Ca0.4La0.5Fe12O19 magnetic powders doped with CoxFe3-xO4 (0 ≤ x ≤ 1.25) in precursors were prepared bya ceramics process. The structure of specimens were examined by using an X-ray diffractometer. Only the magnetoplumbitephase was found in the specimens with the cobalt content (x) from 0.25 to 1.25 in precursor. The specimens exhibited a typicalhexagonal M-type structure and the particles in specimens were uniformly distributed in size. The specimen with x=1.25 hadthe maximum saturation magnetization of 67.48 emu/g, while the residual magnetization and the coercivity of the specimenwith x=1.00 reached the maximum value of 31.83 emu/g and 1270 Oe, respectively.

Inter-server Computation Offloading and Resource Allocation in Multi-drone Aided Space-Air-Ground Integrated IoT Networks

Yongpeng Shi,Junjie Zhang,Ya Gao,Yujie Xia 한국통신학회 2022 Journal of communications and networks Vol.24 No.3

Combining mobile edge computing (MEC), themulti-drone aided space-air-ground integrated Internet of things(SAG-IoT) networks can provide ground IoT devices (GIDs) highqualitywireless access and computing services. However, the diversetasks, moving drones, and limited network resources revealgreat challenges for the task offloading and resource allocationscheme exploitation. Especially, given the restricted computationresources, how to make full use of available applications deployedon MEC servers (MECSs) to compute various types of tasks, iseven an important issue. To the best of our knowledge, it is anentirely new problem since most existing works in this line assumethat all types of applications can be deployed on one MECS so asto process various offloaded tasks. Toward this end, we presentthis paper to investigate inter-server computation offloading, resourceallocation, and drone deployment to minimize the overallcomputation overhead of all GIDs. An iteratively optimizationalgorithm is proposed which alternately utilizes heuristic greedyand successive convex approximation methods. Simulation resultsverify that, for different GID numbers, optimization schemes, andcomputing models, our devised schemes can not only significantlyreduce the overall computation overhead but also achieve optimaldecisions of computation offloading, spectrum allocation, anddrone deployment.