Chaowei Yuan

Cognitive impairment is common but often overlooked in patients with inflammatory demyelinating diseases such as multiple sclerosis and neuromyelitis optica spectrum disorder. The conventional assessments may fail to detect subtle deficits and require substantial time and expertise. We collected neuropsychological scores and real-time handwriting data across nine drawing tasks and tasks from the Symbol Digit Modalities Test in 93 patients. Temporal, pressure, and kinematic features were extracted, and machine learning classifiers were trained using five-fold cross-validation with bootstrap confidence intervals. The response timing and pen pressure metrics correlated significantly with global cognitive scores (|r| = 0.30–0.37, p < 0.01). A support vector machine using eight selected features achieved an area under the receiver-operating characteristic curve (AUC) of 0.910, and a streamlined five-feature variant maintained an equivalent performance (AUC = 0.921) while reducing the assessment time by 35%. These results indicate that digital handwriting metrics can complement the standard screening by capturing fine motor and temporal characteristics overlooked in conventional testing. Validation in larger, disease-balanced, and longitudinal cohorts is needed to confirm their clinical utility.

Breakage and damage of fiber optic cable fibers seriously affect the normal operation of fiber optic networks and it is important to quickly and accurately determine the type and location of faults when they occur. The advantages of wavelet transform in singular signal detection and signal filtering are used to analyze Optical Time Domain Reflectometer (OTDR) curve signal and the fault detection method of fiber communication link with no relay and large span in high altitude area is given, which realizes the accurate detection and location of optical fiber communication link fault events under strong noise. The theoretical analysis is basically consistent with the experimental data. The accuracy of optical fiber fault location has been greatly improved in performance. The method has been directly applied to the field detection of ultra-long optical fiber links in high altitude areas, which has certain significance for the future real-time monitoring of optical fiber cables.

Channel estimation is crucial in millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems, especially with a few training sequences. To solve the problem of uplink channel estimation in mmWave massive MIMO systems, a PARAFAC-based algorithm is proposed for joint estimation of multiuser channels. The orthogonal frequency divisional multiplexing (OFDM) technique is exploited to combat the frequency selective fading channels. In this paper, the received signal at the base station (BS) is formulated as a third-order parallel factor (PARAFAC) tensor, and then a low-complexity algorithm is designed for fast estimation of the factor matrices related to channel parameters, thus leading to joint estimation of multiuser channel parameters via one-dimensional search. Moreover, the Cramér–Rao Bound (CRB) results for multiuser channel parameters are derived for evaluation. Theorical analysis and numerical results reveal that the algorithm performs well with a few training sequences. Compared with existing algorithms, the proposed algorithm has clear advantages both in estimation accuracy and computational complexity.

Up to now, there have been no complete theoretical researches and field experiment reports on the fiber fusion loss at high altitude. Therefore, we have conducted an exploratory study on the fiber splicing loss at high altitude, and firstly analyze the influence of mode field diameter mismatch, axial offset, angle tilt or end face gap affected by high altitude on splice loss, and then discuss the influence of fusion-splicing parameters on splice loss. Besides, a mathematical model for reducing the splicing loss of single-mode fiber at high altitude is established by combining the effects of temperature, humidity, oxygen content, atmospheric pressure, gale and gravity. We have conducted repeated field fusion experiments in different altitude areas (53, 2980, 4000, 4200, 4300, 5020, and 5200 m) more than once, hence obtaining a large number of field experimental data, making a deep comparison between typical “plain” area and typical “high altitude” area. The splice loss of most fusion points achieved successfully has been reduced by at least 0.07 dB. The simulation results are basically consistent with the theoretical analysis. Ultimately, the method proposed has been directly applied to on-site splicing engineering in high altitude environment and achieves good results.

Splicing loss of optical fibers has always been the focus of attention in engineering. With the construction of communication networks in high altitude areas, more attention has been paid to the fusion of optical fibers in high altitude areas. A mathematical model of single-mode optical fibers splice loss affected by altitude is established in this paper. The model takes the splice loss caused by the mismatch in mode field diameters (MFD), angular misalignment and lateral misalignment into account, as well as the influence of atmospheric pressure on splicing angular misalignment. Fiber fusion experiments are carried out at different altitudes. The proposed model validated by the experimental results and can be used as a reference to future research on the splice loss of single-mode fibers in plateau areas.

Performances of cellular networks over {\kappa}-{\mu} shadowed fading with long-term shadowing has been studied in the existing literature. However, the impact of {\kappa}-{\mu} shadowed fading with instantaneous shadowing on performances of cellular networks is unknown. Therefore, this letter analyzes the downlink coverage probability of a Poisson network with double shadowed fading which is composed of a large-scale fading of lognormal distribution and {\kappa}-{\mu} shadowed fading with integer fading parameters. The closest base station association rule without shadowing is considered. For analytical tractability, the double shadowed fading is approximated as a weighted sum of {\kappa}-{\mu} shadowed distributions based on the Gaussian-Hermit quadrature. As a main theoretical result, a closed-form expression for the downlink coverage probability of a Poisson network under double shadowed fading for the desired signal and arbitrary fading for the interfering signals is successfully derived. Numerical simulations reveal that the double shadowed fading provides a pessimistic coverage on a Poisson network compared with the long-term shadowing which is incorporated into cell selection.

针对传统交替最小二乘算法存在的收敛缓慢问题，本文在多用户上行放大转发中继系统中基于Levenberg Marquardt（LM）算法，提出了一种能够快速收敛的信道估计方法，实现了用户-中继信道和中继-基站信道的独立估计.在基站，通过对中继多次放大转发的信号进行建模，构造出具有平行因子结构的三维信号张量模型，并采用LM算法对该模型进行拟合，从而得到系统中两跳链路的信道状态信息.理论分析与仿真结果表明，与已有二线性交替最小二乘方法相比，所提方法具有近乎相同的估计精度；当中继放大因子矩阵为随机矩阵或者包含近似共线性相关列时，所提方法具有更快的收敛速度.