arXiv subjects

Jianfeng Sun

Publications and source records attributed to Jianfeng Sun.

6 recordsLinked to original sources

arXiv2026

Notes on Liouville-type theorems for the 3D stationary Navier-Stokes equations

In \cite{CV23}, Chamorro and Vergara-Hermosilla established several Liouville-type theorems to the Navier-Stokes equations in the framework of the variable Lebesgue spaces. These results may allow the variable exponent $p(\cdot)$ beyond the range of $[3,\frac{9}{2}]$ in some non-negligible regions in $\mathbb{R}^3$. In this paper we find two new non-negligible regions, in which the Liouville-type theorems still hold under some assumptions imposed on $p(\cdot)$ in these regions. Our results can be regarded as the generalization of the results in \cite{CV23}.

math.AP↗

arXiv2025

First-Principle Modeling Framework of Boost Converter Dynamics for Precise Energy Conversions in Space

Boost converters are essential for modern electrification and intelligent technologies. However, conventional Boost converter models relying on steady-state assumptions fail to accurately predict transient behaviors during input voltage and load fluctuations, which cause significant output voltage overshoots and instability, resulting in failures of electrical systems, thereby restricting their use in space. This study introduces a first-principle modeling framework that derives precise dynamic equations for Boost converters by incorporating non-ideal component coupling. As compared to the most accurate existing Boost converter model, the proposed models reduce steady-state and dynamic-state errors between experimental and simulated output voltages by factors of 11.0 (from 20.9% to 1.9%) and 15.4 (from 77.1% to 5.0%) under input voltage variations, and by factors of 10.2 (from 15.3% to 1.5%) and 35.1 (from 42.1% to 1.2%) under load changes, respectively. Consequently, a reliable Boost converter is accordingly designed and on-orbit deployed for precise energy conversions.

eess.SY↗

arXiv2021

All-fiber photonic lantern multimode optical receiver with coherent adaptive optics beam combining

A multimode optical receiver for free space optical communications (FSOC) based on a photonic lantern and adaptive optics coherent beam combining (CBC) of the lantern's single-mode outputs is proposed and demonstrated for the first time. The use of optical coherent combining in fiber serves to increase the signal to noise ratio compared to similar receivers based on electrically combined signals, and represents an all-fiber approach to low-order adaptive optics. This optical receiver is demonstrated using a photonic lantern with three outputs, fibre couplers and active phase locking, and further investigated under atmospheric conditions with and without turbulence.

physics.optics↗

arXiv2020

Free-Space Optical Communication Using Non-mode-Selective Photonic Lantern Based Coherent Receiver

A free-space optical communication system using non-mode-selective photonic lantern (PL) based coherent receiver is studied. Based on the simulation of photon distribution, the power distribution at the single-mode fiber end of the PL is quantitatively described as a truncated Gaussian distribution over a simplex. The signal-to-noise ratios (SNRs) for the communication system using PL based receiver are analyzed using different combining techniques, including selection combining (SC), equal-gain combining (EGC), and maximal-ratio combining (MRC). The integral solution, series lower bound solution and asymptotic solution are presented for bit-error rate (BER) of PL based receiver, single-mode fiber receiver and multimode fiber receiver over the Gamma-Gamma atmosphere turbulence channels. We demonstrate that the power distribution of the PL has no effect on the SNR and BER performance of the PL based receiver when MRC is used; and it only has limited influence when EGC is used. However, the power distribution of the PL can greatly affect the BER performance when SC is used. Besides, the SNR gains of the PL based receiver using EGC over single-mode fiber receiver and multimode fiber receiver are numerically studied under different imperfect device parameters; and the scope of application of the communication system is further provided.

eess.SP↗

arXiv2019

Fiber-optic joint time and frequency transfer with the same wavelength

Optical fiber links have demonstrated their ability to transfer the ultra-stable clock signals. In this paper we propose and demonstrate a new scheme to transfer both time and radio frequency with the same wavelength based on coherent demodulation technique. Time signal is encoded as a binary phase-shift keying (BPSK) to the optical carrier using electro optic modulator (EOM) by phase modulation and makes sure the frequency signal free from interference with single pulse. The phase changes caused by the fluctuations of the transfer links are actively cancelled at local site by optical delay lines. Radio frequency with 1GHz and time signal with one pulse per second (1PPS) transmitted over a 110km fiber spools are obtained. The experimental results demonstrate that frequency instabilities of 1.7E-14 at 1s and 5.9E-17 at 104s. Moreover, time interval transfer of 1PPS signal reaches sub-ps stability after 1000s. This scheme offers advantages with respect to reduce the channel in fiber network, and can keep time and frequency signal independent of each other.

eess.SP↗

arXiv2017

Reducing the uncertainty in the forest volume-to-biomass relationship built from limited field plots

The method of biomass estimation based on a volume-to-biomass relationship has been applied in estimating forest biomass conventionally through the mean volume (m3 ha-1). However, few studies have been reported concerning the verification of the volume-biomass equations regressed using field data. The possible bias may result from the volume measurements and extrapolations from sample plots to stands or a unit area. This paper addresses (i) how to verify the volume-biomass equations, and (ii) how to reduce the bias while building these equations. This paper presents an applicable method for verifying the field data using reasonable wood densities, restricting the error in field data processing based on limited field plots, and achieving a better understanding of the uncertainty in building those equations. The verified and improved volume-biomass equations are more reliable and will help to estimate forest carbon sequestration and carbon balance at any large scale.

stat.AP↗